Manufacturing method for optical system for head mounted display

Abstract

The problem addressed by the present invention is to provide a method for manufacturing an optical system for a head-mounted display that allows realization of a head-mounted display that prevents unexpected blurring and bleeding and that is excellent in a sense of immersion. The problem is solved by a method for manufacturing an optical system for a head-mounted display, the method including a bonding step, which is a manufacturing step for a laminate formed by laminating a plurality of optical members and in which a plurality of optical members are bonded and fixed by laminating one optical member on a surface of another optical member, wherein the bonding step includes a step for applying a bonding layer forming composition to one optical member, a step for applying a bonding layer forming composition to another optical member, and a step for using a nip roller to laminate the one optical member and the another optical member such that the bonding layer forming compositions face each other.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an optical system for a head-mounted display. [Background technology]

[0002] Head-up displays (HUDs) and head-mounted displays (HMDs) have been proposed as means of providing virtual reality (VR), augmented reality (AR), and mixed reality (MR) to viewers. Head-mounted displays, which are relatively small and easy to carry and wear, are expected to become multifunctional devices that can replace smartphones and tablets.

[0003] Head-mounted displays that use a magnifying optical system using lenses have been realized as head-mounted displays that are binocular, have excellent three-dimensional reproduction capabilities, and can be realized with a relatively simple configuration (for example, Patent Document 1). In particular, high-end models combine high-resolution display elements with laminated lenses to achieve an unprecedented user experience.

[0004] However, when laminated lenses used in cameras, binoculars, etc. are used as lenses, there is little aberration and distortion, and natural images can be provided to the user, but they are heavy and bulky, placing a great physical burden on the user. On the other hand, using a single lens or a Fresnel lens made of plastic makes the device small and lightweight (for example, Patent Document 2), but this can cause aberrations and distortions in the image, and the resolution that can be achieved can be dissatisfactory, which could impair the user's sense of immersion. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-145488 [Patent Document 2] JP 2017-211475 A Summary of the Invention [Problem to be solved by the invention]

[0006] The inventors have investigated optical systems using a catadioptric system known as a pancake lens or a birdbath-type beam splitter as a means of achieving both a sense of immersion and minimal physical strain on the user. However, even with properly assembled optical systems, when viewing displayed images, they have observed phenomena such as blurred edges of bright images placed against a dark background and the appearance of scattered rays of light in unexpected locations. This phenomenon cannot be explained by theories of geometric optics such as aberration and image plane distortion, but it significantly impairs the user's sense of immersion.

[0007] Therefore, an object of the present invention is to provide a method for manufacturing a head-mounted display that can obtain an optical system for a head-mounted display that is free from unexpected blurring and bleeding and that can realize a head-mounted display with excellent immersion. [Means for solving the problem]

[0008] As a result of efforts to solve the above-mentioned problems, the inventors have found that the above-mentioned problems can be solved by the following configuration. That is, the present invention is as follows.

[0009] [1] A method for manufacturing an optical system for a head-mounted display, comprising at least a step of manufacturing a laminate and a step of assembling the optical system for a head-mounted display, The laminate manufacturing process is a process for manufacturing a laminate formed by stacking a plurality of optical members constituting an optical system for a head-mounted display, and includes at least an adhesion process of laminating one optical member on a surface of another optical member to bond and fix the plurality of optical members, The method for manufacturing an optical system for a head-mounted display includes the steps of: applying an adhesive layer-forming composition to one optical element; applying an adhesive layer-forming composition to another optical element; and laminating the one optical element and the other optical element with the adhesive layer-forming compositions facing each other using nip rollers. [2] The manufacturing process of the laminate includes two or more optical elements having a coating-type optical functional layer formed on a support, and the optical elements having the coating-type optical functional layer are adjacent to each other in the laminate, and a laminate is manufactured by laminating three or more optical elements, A laminate is produced by applying an adhesive layer-forming composition to the optical functional layers of two optical members having coating-type optical functional layers and performing an adhesion step, and stacking the two optical members. Then, a laminate formed by stacking two optical elements and another optical element are used, and an adhesive layer forming composition is applied to one of the optical elements of the laminate formed by stacking two optical elements, and the adhesive process is performed again, in accordance with the method for manufacturing an optical system for a head-mounted display described in [1]. [3] The support is a temporary support, the optical functional layer is formed by applying a liquid crystal composition onto a temporary support, The method for manufacturing an optical system for a head-mounted display according to [2], wherein an operation of removing the temporary support is carried out in the manufacturing process of the laminate. [4] The method for manufacturing an optical system for a head-mounted display according to [3], wherein each of the liquid crystal compositions contains a surfactant. [5] The method for producing an optical system for a head-mounted display according to any one of [1] to [4], wherein a laminate including a polarizer is produced in the laminate production step. [6] The method for manufacturing an optical system for a head-mounted display according to any one of [1] to [5], further comprising a three-dimensional molding step. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a manufacturing method for an optical system for a head-mounted display that is free from unexpected blurring and bleeding and that can realize a head-mounted display that provides an excellent sense of immersion. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a conceptual diagram of an optical system for a head-mounted display including a preferred embodiment of a pancake lens optical system. [Figure 2] FIG. 2 is a conceptual diagram showing an example of a birdbath optical system. [Figure 3] FIG. 3 is a conceptual diagram for explaining the step of performing activation treatment while the optical member is in close contact with a cooled roll. [Figure 4] FIG. 4 is a conceptual diagram for explaining the lamination process. [Figure 5] 5(a) to 5(c) are conceptual diagrams for explaining an example of the arrangement of knurling. [Figure 6] 6(a) to 6(c) are conceptual diagrams for explaining an example of the arrangement of knurling. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below with reference to embodiments. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after it as the lower and upper limits. Furthermore, with regard to angles, "perpendicular" and "parallel" refer to a range of ±10° of the exact angle, and "same" and "different" angles can be determined based on whether the difference is less than 5°. In this specification, "visible light" refers to 380 to 780 nm. In this specification, unless otherwise specified, the measurement wavelength is 550 nm. Next, the terms used in this specification will be explained.

[0013] <Re(λ)、Rth(λ)> The in-plane retardation Re(λ) and the thickness direction retardation Re(λ) are values ​​measured using an AxoScan OPMF-1 (manufactured by Optoscience) with light of a measurement wavelength, where λ is the measurement wavelength, and unless otherwise specified, the wavelength λ is 550 nm. Specifically, by inputting the average refractive index ((Nx+Ny+Nz) / 3) and film thickness (d (μm)) into the AxoScan OPMF-1, Slow axis direction (°) Re(λ)=R0(λ) Rth(λ)=((nx+ny) / 2-nz)×d is calculated. Note that R0(λ) is displayed as a numerical value calculated by AxoScan OPMF-1, but it means Re(λ).

[0014] [Optical system for head-mounted displays] The optical system for a head mounted display manufactured by the manufacturing method of the present invention includes at least a display element, various optical members (a laminate of optical members) described later, and a frame for fixing the respective optical members. The optical system for a head-mounted display according to the present invention performs one or more of magnification, reduction and reflection on the image light emitted from the display element, and also performs one or more of refraction, absorption and polarization conversion as necessary, so that the light reaches the observer's eyeball, thereby allowing the observer to recognize the image.

[0015] [Pancake lens optical system] One preferred embodiment of the optical system for a head-mounted display manufactured by the manufacturing method of the present invention is a catadioptric optical system called a pancake lens. A preferred example of a pancake lens optical system is a configuration having, in order from the display element side, a half mirror and a reflective polarizer. This pancake lens optical system can function as a lens by curving the half mirror, the reflective polarizer, or both. Alternatively, the half mirror or the reflective polarizer may be flat and may further include another lens element to achieve the same function. Although there is no specific name for this type of catadioptric system, for convenience, this specification will refer to it as a pancake lens optical system. Pancake lens optical systems have small aberrations and little image plane distortion, yet are far lighter and more compact than systems combining multiple lenses, which reduces the physical burden on the user. Such optical systems are described in, for example, Japanese Patent Application Laid-Open Nos. 8-327940, 2000-180785, 2003-504663, and 2018-508800.

[0016] FIG. 1 shows a conceptual diagram of an optical system for a head-mounted display including a preferred embodiment of a pancake lens system. The head mounted display 15 is made up of a display element 30, a linear polarizer 32, and a pancake lens optical system 20. The exit pupil 50 is the position where the user's eye 45 is positioned.

[0017] Although shown as separate from the display element 30, the linear polarizer 32 may be part of the display element 30. Light emitted from the display element 30 exits through the linear polarizer 32, thereby providing light of one polarization.

[0018] The pancake lens optical system 20 includes a half mirror 34 and a polarizing mirror 38. In Fig. 1, the half mirror 34 is disposed on the display element 30 side, and the polarizing mirror 38 is disposed on the user's eye 45 side. The polarizing mirror 38 is the reflective polarizer described above.

[0019] One or more surfaces of the half mirror 34 and the polarizing mirror 38 may be shaped to correct for field curvature. One or more surfaces of the half mirror 34 can have a variety of shapes, such as spherical concave (e.g., a portion of a sphere), spherical convex, rotationally symmetric aspheric, freeform, and any other shape that reduces field curvature. In some embodiments, the shape of one or more surfaces of the half mirror 34 and the polarizing mirror 38 can be configured to further correct for other forms of optical aberration. Also, in some embodiments, one or more optical elements in the pancake lens optical system 20 may have one or more coatings, such as anti-reflective coatings, to reduce ghost images and enhance contrast. In addition, although the half mirror 34 and the polarizing mirror 38 are both depicted as curved surfaces in the figure, at least one or both of these may be made flat and combined with a refractive lens element (not shown) to correct field curvature and aberration.

[0020] The half mirror 34 may include a wave plate surface 33 and a mirror surface 35 . Waveplate surface 33 is a quarter-wave plate that shifts the polarization of incident light. The quarter-wave plate has a slow axis. The quarter-wave plate can convert linearly polarized light incident from the user side or the display element side into circularly polarized light by positioning the slow axis at 45° to the linearly polarized light incident from the user side or the display element side. The rotation direction (polarization rotation direction) of the circularly polarized light can be controlled by the tilt direction of the slow axis. Alternatively, the quarter-wave plate converts circularly polarized light that may be incident from the user side or the display element side into linearly polarized light. The polarization direction of the linearly polarized light can be controlled by appropriately positioning the rotation direction of the incident circularly polarized light and the slow axis of the quarter-wave plate. The mirror surface 35 is a half mirror configured to reflect a portion of the incident light. For example, the mirror surface 35 can be configured to transmit 50% of the incident light and reflect 50% of the incident light. The mirror surface 35 may also be a reflective polarizer.

[0021] Polarizing mirror 38 includes a waveplate surface 37 and a reflective polarizer surface 39 . The wave plate surface 37 is a quarter wave plate. The reflective polarizer surface 39 is a half mirror configured to reflect (polarization-block) light of a first polarization and transmit light of a second polarization that is orthogonal to the first polarization. For example, the reflective polarizer surface 39 can be configured to reflect light linearly polarized in the x direction and transmit light linearly polarized in the y direction that is orthogonal to the x direction.

[0022] It is preferable that the light emitted from the display element 30 is either linearly polarized light in the first direction or becomes linearly polarized light in the first direction after passing through the linear polarizer 32. As an example, the linearly polarized light emitted from the display element 30 and transmitted through the linear polarizer 32 is incident on the wave plate surface 33 of the half mirror 34 and becomes circularly polarized light. A part of the circularly polarized light transmitted through the wave plate surface 33 of the half mirror 34 is transmitted through the mirror surface 35 of the half mirror 34 . This circularly polarized light is transmitted through the wave plate surface 37 of the polarizing mirror 38 and converted into linearly polarized light in the first direction. The reflective polarizer surface 39 of the polarizing mirror 38 reflects this linearly polarized light because the first direction is perpendicular to the polarization axis (transmission axis) of the reflective polarizer surface 39. The linearly polarized light in the first direction reflected by the polarizing mirror 38 is converted by the wave plate surface 37 into circularly polarized light. This circularly polarized light is incident on the mirror surface 35 of the half mirror 34. A part of the circularly polarized light is reflected by the mirror surface 35 and becomes circularly polarized light in the opposite rotation direction. The circularly polarized light reflected by mirror surface 35 is transmitted through wave plate surface 37. Here, the circularly polarized light has its rotation direction reversed upon reflection by mirror surface 35, and therefore, by transmitting through wave plate surface 37, it becomes linearly polarized light in a second direction that is perpendicular to the first direction. The second direction is aligned with the polarization axis of the reflective polarizer surface 39. Thus, light linearly polarized in the second direction is transmitted through the reflective polarizer surface 39 and enters the user's eye 45 (exit pupil 50). Therefore, according to the pancake lens optical system 20, the image (light) emitted (projected) by the display element 30 can be made to travel back and forth between the half mirror 34 and the polarizing mirror 38, thereby lengthening the optical path length and displaying a virtual image with a sense of perspective.

[0023] The polarizing mirror 38 may be a circularly polarized reflective polarizer using cholesteric liquid crystal, instead of the one including the linearly reflective polarizer surface and the wave plate surface described above. 1, polarizing mirror 38 only needs to have reflective polarizer surface 39, and wave plate surface 37 can be omitted. This is advantageous in that simplifying the pancake lens optical system reduces the probability of optical defects occurring and makes it possible to avoid unexpected blurring and bleeding.

[0024] As light passes through the polarizing mirror 38, polarization components other than the polarization that matches the polarizing mirror 38 may leak out, which is perceived by the user as ghost images or reduced contrast. Since this phenomenon is caused by imperfect polarization selectivity of the polarizing mirror 38, an absorptive polarizer may be provided on the user side of the polarizing mirror 38 in order to remove unintended polarization components. If the reflective polarizer surface 39 of the polarizing mirror 38 has linear polarization selectivity, it is preferable to align the transmission axis of the absorptive polarizer with the linear polarization axis of the light transmitted through the polarizing mirror. Furthermore, if the reflective polarizer surface 39 of the polarizing mirror 38 has circular polarization selectivity, it is preferable to provide a quarter-wave plate between the reflective polarizer surface 39 and the absorptive polarizer to convert the light to linear polarization and align the transmission axis of the absorptive polarizer.

[0025] [Birdbath type optical system] Another preferred embodiment of the optical system for a head-mounted display manufactured by the manufacturing method of the present invention is a reflective optical system called a birdbath type. As an example of a preferred birdbath-type optical system, the optical system shown in Figure 2 has been proposed. This type of optical system does not require heavy and bulky elements such as display elements and lenses to be placed in front of the observer, so even if it is equipped with a somewhat heavy optical system with low aberration and distortion, depending on the design, it can reduce the physical burden on the user. In addition, because it does not require the placement of opaque optical elements such as display elements in front of the observer, it has the advantage of being applicable to augmented reality (AR), which superimposes virtual images on the real field of view.

[0026] An example of a preferred embodiment of the birdbath optical system will be described with reference to FIG. 2, head-mounted display 205 is mounted on a user's head 210. As shown, head-mounted display 205 comprises a frame 215 containing a display element 220 that generates an image for presentation to a user. In addition to display element 220, a linear polarizer 225, a beam splitter 230, a first reflecting mirror 235, and a second reflecting mirror 240 are disposed within frame 215. For simplicity, FIG. 2 illustrates the arrangement of each optical member in the optical system for the left eye, and the path of display light in the optical system for the right eye.

[0027] The light (display image) generated by the display element 220 is converted by the linear polarizer 225 into linearly polarized light in a first polarization direction. A lens (not shown) and other optical members may be provided on the display element 220 side or the opposite side of the linear polarizer 225. The linear polarizer 225 may be integrated with the display element 220, or may be laminated with a lens or other optical members.

[0028] The beam splitter 230 has a transmission axis arranged to transmit the linearly polarized light produced by the linear polarizer 225. The beam splitter 230 is typically a linear polarization separation type beam splitter, and has a transmission axis and a reflection axis that is orthogonal to the transmission axis. The light transmitted through the beam splitter 230 is incident on the first reflecting mirror 235. A quarter-wave plate (not shown) is provided on the incident surface side of the first reflecting mirror 235. In the first reflecting mirror 235, the linearly polarized light passes through the quarter-wave plate and is converted into circularly polarized light, and is then reflected by the reflecting surface, whereby the rotation direction of the circularly polarized light is reversed. This circularly polarized light is then incident on the quarter-wave plate again. As a result, linearly polarized light that is orthogonal to the incident linearly polarized light is output from the first reflecting mirror 235.

[0029] The linearly polarized light incident on the beam splitter 230 from the first reflecting mirror 235 is linearly polarized light that is perpendicular to the transmission axis of the beam splitter 230 , and therefore most of it is reflected and directed toward the second reflecting mirror 240 . Similar to the first reflecting mirror 235, the second reflecting mirror 240 also has a quarter-wave plate (not shown) provided on the incident surface side. In the second reflecting mirror 240, the linearly polarized light passes through the quarter-wave plate and is converted into circularly polarized light. The circularly polarized light is then reflected by the reflecting surface, whereby the rotation direction of the circularly polarized light is reversed. This circularly polarized light is then incident on the quarter-wave plate again. As a result, the second reflecting mirror 240 also emits linearly polarized light that is orthogonal to the incident linearly polarized light. The linearly polarized light incident on the beam splitter 230 from the second reflecting mirror 240 is aligned with the transmission axis of the beam splitter 230. Therefore, most of the linearly polarized light incident on the beam splitter 230 is transmitted, proceeds toward the observer, and is recognized as an image. In addition, such a birdbath optical system can also extend the optical path length by sending the image (light) emitted (projected) by the display element 220 back and forth along an optical path consisting of the first mirror 235, the beam splitter 230, and the second reflecting mirror 240, thereby displaying a virtual image with a sense of perspective.

[0030] Although first reflecting mirror 235 and second reflecting mirror 240 are both depicted as flat surfaces in FIG. 2, one or more shapes of first reflecting mirror 235 and second reflecting mirror 240 may be shaped to correct for field curvature. The surface of the first reflecting mirror 235 and / or the second reflecting mirror 240 can be formed as a spherical concave (e.g., a portion of a sphere), a spherical convex, a rotationally symmetric aspheric, a freeform surface, or any other shape that reduces field curvature, etc. In some embodiments, the shape of first reflecting mirror 235 and / or first reflecting mirror 240 may be configured to further correct for other forms of optical aberrations. Also, in some embodiments, one or more optical elements in the birdbath optical system may have one or more coatings, such as anti-reflective coatings, to reduce ghost images and enhance contrast. Furthermore, by combining with a refractive lens element (not shown), field curvature and aberration may be corrected. The refractive lens element may be provided on one or more of the following: on the optical path from the display element 220 to the beam splitter 230; on the optical path from the beam splitter 230 to the first reflecting mirror 235; on the optical path from the beam splitter 230 to the second reflecting mirror 240; and on the optical path from the beam splitter 230 to the user. A refractive lens element may also be provided together with the vision correction lens 250.

[0031] The birdbath optical system may be a system that uses circularly polarized light instead of linearly polarized light. That is, a configuration is used in which a circularly polarized light-selective beam splitter 230 is used and polarizer 225 is used as a circularly polarized light output polarizer. In such a configuration, first reflecting mirror 235 and second reflecting mirror 240 may be simple mirror surfaces, which is preferable in terms of simplifying the configuration. An example of such a circularly polarized light selective beam splitter 230 is a beam splitter 230 using a cholesteric liquid crystal, similar to the polarizing mirror 38 of the pancake type optical system described above.

[0032] {Optical components for head-mounted displays} In this specification, the above-mentioned polarizers, half mirrors, wave plates, reflective polarizers, reflective mirrors, beam splitters, transparent optical members (not shown), and functional coatings such as anti-reflection coatings are collectively referred to as optical members for head-mounted displays. Each of these will be described in detail below.

[0033] (half mirror) The half mirror is an optical element that is partially reflective at least for a specific wavelength, and more preferably is partially reflective over a broad band. Such a half-mirror can be made of any suitable partially reflective material. For example, it can be constructed by coating a thin layer of metal on a transparent substrate. Examples of metals include silver and aluminum. The half-mirror can also be formed by depositing a thin dielectric coating or a combination of a metal coating and a dielectric coating on the surface of the transparent substrate. Suitable examples of the half mirror include a multilayer polymer film reflector, a multilayer polymer reflective polarizer, and a reflective wire grid polarizer. Examples of the multilayer polymer film reflector include ESR Film (product name) from 3M and Picassus Film (product name) from Toray. Examples of the multilayer polymer reflective polarizer include APF and DBEF from 3M.

[0034] The half mirror can have an average optical reflectance of at least 30% at a plurality of desired or predetermined wavelengths, which can be visible light (380-780 nm), the infrared wavelength range, the ultraviolet wavelength range, or any combination of visible light, infrared wavelengths, and ultraviolet wavelengths. In one embodiment, the desired or predetermined wavelengths may be a narrow wavelength range or narrow wavelength ranges, and the partial reflector may be a notch reflector having at least one reflection band with a full width at half maximum of 100 nm or less, or 50 nm or less. The average light reflectance can be determined by averaging the reflectance over the desired or predetermined wavelengths. Similarly, the average light transmittance can be determined by averaging the transmittance over the desired or predetermined wavelengths. These partial reflectors can have average light reflectances and average light transmittances in the range of 30-70%, or 40-60%, respectively, at the desired or predetermined wavelengths.

[0035] (wave plate) A wave plate is an optical element used to control the phase of incident polarized light. The wavelength plate is preferably a quarter-wave plate. A quarter-wave plate is a retardation plate that shifts the phase of incident polarized light by λ / 4. This action allows the quarter-wave plate to convert linearly polarized light into circularly polarized light and vice versa.

[0036] The quarter-wave plate used in the present invention may be a single-layer type composed of one optically anisotropic layer, or a laminated type wavelength plate composed of a stack of two or more optically anisotropic layers, each having a plurality of different slow axes. The optically anisotropic layer is made of a material capable of exhibiting optical anisotropy. Known examples of such materials include inorganic anisotropic crystalline materials, birefringent polymers, cured polymerizable liquid crystal compositions, lyotropic liquid crystals, and structural birefringent materials. The retardation layer may also be a triacetyl cellulose retardation layer, a polymer carbonate retardation layer, or a cycloolefin retardation layer. In other words, the retardation layer is an "optically anisotropic layer that exhibits retardation."

[0037] It is preferable that the wave plate has a phase shifting effect that is approximately uniform over a wide band. Such a wave plate is known as a broadband wave plate, and in particular, a quarter-wave plate is also referred to as a broadband quarter-wave plate. For a single-layer one that acts as a broadband quarter-wave plate, a material with a wavelength dispersion of refractive index having so-called inverse wavelength dispersion property is used. Here, the inverse wavelength dispersion property means that the in-plane phase difference Re(λ) of the quarter-wave plate satisfies Re(450) < Re(550) ≦ Re(650). Also, it may be a laminated type that acts as a broadband quarter-wave plate. In the above in-plane phase difference Re(λ), λ represents the wavelength [nm]. Specific examples of such a laminated quarter-wave plate include those described in International Publication No. 2013 / 137464, International Publication No. 2016 / 158300, Japanese Unexamined Patent Application Publication No. 2014-209219, Japanese Unexamined Patent Application Publication No. 2014-209220, International Publication No. 2014 / 157079, Japanese Unexamined Patent Application Publication No. 2019-215416, International Publication No. 2016 / 158300, and International Publication No. 2019 / 160044, etc., and are exemplified and preferably used.

[0038] The optical anisotropy of the wave plate is not particularly limited, and a positive A plate (for three-dimensional refractive index, nx > ny = nz), a negative A plate (the same, nz = nx > ny), a positive B plate with a positive Rth (the same, nz > nx > ny), a B plate with a negative Rth (the same, nx > ny > nz), and a wave plate showing a relationship of three-dimensional refractive index of nx > nz > ny can be used. Here, the three-dimensional refractive indices nx, ny, and nz refer to the three-dimensional refractive indices nx, ny, and nz measured by the above-mentioned AxoScan OPMF-1. Examples of materials for forming a positive A plate include rod-shaped liquid crystal materials and birefringent polymer materials with positive intrinsic birefringence. On the other hand, examples of materials for forming a negative A plate include discotic liquid crystal materials and birefringent polymer materials with negative intrinsic birefringence. B plates with positive Rth and B plates with negative Rth can be obtained by adjusting the manufacturing conditions of the above-mentioned materials. Specific examples of wave plates whose three-dimensional refractive indexes satisfy the relationship nx>nz>ny include those described in JP 2017-107177 A and JP 2006-215142 A, and these are preferably used.

[0039] The wave plate may be combined with an optical compensation layer in addition to the wave plate. For example, a C-plate can be combined to compensate for the change in the refractive index ellipsoid of the wave plate for incident light from an oblique direction. The C-plate here is a plate that is used to compensate for the change in the refractive index ellipsoid of the wave plate for incident light from an oblique direction. The C-plate ... used to compensate for the change in the refractive index ellips<nz(ポジティブCプレート)、または、nx=ny> nz (negative C plate).

[0040] The above example is merely one of the preferred embodiments, and various known wave plates and optical compensation layers thereof can be applied within the scope of the present invention.

[0041] (reflective polarizer) A reflective polarizer is an optical component that specularly reflects one polarized light component of light incident from the front and transmits the other polarized light component (orthogonal polarized light component). The polarized light reflected and transmitted may be linearly polarized or circularly polarized. For example, one polarized light component is linearly polarized in one direction, and the other polarized light component is linearly polarized in the orthogonal direction. Alternatively, one polarized light component is right-handed circularly polarized light, and the other polarized light component is left-handed circularly polarized light. Examples of reflective polarizers that can selectively reflect linearly polarized light include a film formed by stretching a layer containing two types of polymers, and a wire grid polarizer, as described in JP 2011-053705 A. From the viewpoint of brightness, a film formed by stretching a layer containing a polymer is preferred. Commercially available products that can be used include a reflective polarizer (product name: APF) manufactured by 3M and a wire grid polarizer (product name: WGF) manufactured by Asahi Kasei Corporation. As a reflective polarizer having selective reflectivity for circularly polarized light, a circularly polarized selective reflective polarizer in which a liquid crystal compound is fixed in a cholesteric orientation is preferred. In other words, as a reflective polarizer having selective reflectivity for circularly polarized light, a circularly polarized selective reflective polarizer having a cholesteric liquid crystal layer in which a cholesteric liquid crystal phase is fixed is preferred. Suitable examples of such circularly polarized selective reflective polarizers include those described in, for example, JP 2004-333671 A, JP 2006-078617 A, JP 2011-133707 A, JP 2012-008576 A, JP 2012-013963 A, JP 2012-018228 A, JP 2012-032759 A, JP 2017-097217 A, JP 2018-173565 A, and JP 2020-060627 A.

[0042] A cholesteric liquid crystal layer is generally formed using a liquid crystal composition containing a liquid crystal compound, a chiral agent for helically aligning the liquid crystal compound, a polymerization initiator, and the like. The cholesteric liquid crystal layer is formed by applying the liquid crystal composition to the surface of an alignment film, helically orienting the liquid crystal compound by heating or the like, and then polymerizing the liquid crystal compound by irradiating it with ultraviolet light or the like to form a liquid crystal polymer, thereby hardening the composition.

[0043] As the liquid crystal composition described above, the compositions described in the above-mentioned patent publications in which preferred circularly polarized light selective reflection polarizers are described can be used. It is also preferable to add an adhesion improver to the liquid crystal composition, assuming that it will be bonded to other optical components. It is also preferable to add a surfactant to the liquid crystal composition to prevent uneven application. As additives that function as both an adhesion improver and a surfactant, fluorine-based surfactants having reactive groups and silicone-based surfactants having reactive groups are preferred. Preferred reactive groups include N-methylolamine groups, epoxy groups, and acrylate groups. Commercially available products of these can also be used, such as BYK-UV3505 (manufactured by BYK Japan), an acrylic group-modified polydimethylsiloxane.

[0044] The reflective polarizer may further be combined with an optical compensation layer. One preferred function of the optical compensation layer is to transmit or reflect light incident from an oblique direction with the same selectivity as that of light incident from the front. As an optical compensation layer that exhibits such a function, a C plate, which is exemplified as the optical compensation layer of the wave plate, is preferably used.

[0045] (Absorptive polarizer) An absorptive polarizer is an optical element that transmits only one polarized light of light incident from the front and absorbs the other polarized light. While absorptive linear polarizers that transmit and absorb linearly polarized light are the most well-known, other absorptive polarizers may also be used as long as they do not deviate from the spirit of the present invention. The following will describe in detail an absorptive linear polarizer as an absorptive polarizer.

[0046] Examples of absorptive polarizers include polyvinyl alcohol films, hydrophilic polymer films that have been uniaxially stretched after adsorbing a dichroic substance such as iodine or a dichroic dye, and polyene-based oriented films. Examples of hydrophilic polymer films include partially formalized polyvinyl alcohol films and partially saponified ethylene-vinyl acetate copolymer films. Examples of polyene-based oriented films include dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. Furthermore, as the absorptive linear polarizer, one in which a dichroic dye or pigment is dissolved or dispersed in a lyotropic liquid crystal or a thermotropic liquid crystal, etc., and the uniaxially oriented and fixed orientation is also suitably used.

[0047] The absorptive polarizer is preferably a thin one having a thickness of 10 μm or less. From the viewpoint of thinning, the thickness of the absorptive polarizer is preferably 1 to 7 μm. Such a thin absorptive polarizer has excellent durability due to minimal thickness unevenness and minimal dimensional change, and is also advantageous in that it can be made thinner when used as a laminate of optical components. Furthermore, the thinness of the absorptive polarizer allows for easy removal of foreign matter, air bubbles, and the like, if trapped during the manufacturing process, and allows for the provision of only a good absorptive polarizer free of foreign matter and air bubbles in subsequent processes. Therefore, the absorptive polarizer is particularly suitable as an optical component for a head-mounted display optical system that provides a high level of immersion and suppresses unexpected blurring and bleeding.

[0048] Among thin absorptive polarizers, examples of those that use a polyvinyl alcohol resin and a dichroic substance such as iodine and a dichroic dye include thin polarizing films described in JP-A-51-069644, JP-A-2000-338329, WO 2010 / 100917, PCT / JP2010 / 001460, JP-A-2014-059328, and JP-A-2012-073563. These thin absorptive polarizing films can be obtained by a manufacturing method including a step of stretching a polyvinyl alcohol-based resin layer and a resin substrate for stretching in a laminate state, and a step of dyeing the laminate. In the following description, the polyvinyl alcohol-based resin is also referred to as a PVA-based resin. With this manufacturing method, even if the PVA-based resin layer is thin, it can be stretched without problems such as breakage due to stretching because it is supported by the resin substrate for stretching.

[0049] From the viewpoint of functionality, it is preferable that the absorptive polarizer has a high degree of polarization and the transmittance of the transmission axis is as high as possible. Therefore, it is preferable that the polarizer has optical properties of a single transmittance of 42.0% or more and a polarization degree of 99.95% or more. In particular, when the polarizer has a thickness of 7 μm or less, when the single transmittance is T and the polarization degree is P, the following relationship is satisfied: P>−(10 0.929T-42.4 It is preferable that the optical characteristics satisfy the conditions of P≧99.9 (provided that T≧42.3) and P≧99.9 (provided that T≧42.3).

[0050] (beam splitter) A beam splitter is an optical element that creates a correct optical path by transmitting or reflecting light rays incident from various directions. As the beam splitter, the optical components described above as reflective polarizers among the optical components for head-mounted displays are preferably used. In particular, in a birdbath optical system as shown in Fig. 2, the incident polarized light and the transmitted or reflected polarized light are oblique to the reflective polarizer, so it is preferable to design the optical system to be suitable for oblique light rays.

[0051] (Reflective mirror) The reflecting mirror is an optical element that is reflective to at least a specific wavelength. It is more preferable that the reflective mirror has reflectivity over a broadband. Any material can be used for such a reflective mirror. For example, such a reflective mirror can be formed by coating a thin layer of metal on a metallic mirror surface or a transparent substrate. Examples of metals include silver and aluminum. The reflective mirror can also be formed by depositing a thin dielectric coating on the surface of a transparent substrate, or by depositing a combination of a metal coating and a dielectric coating. In addition, as the reflective mirror, a multilayer polymer film reflector, a multilayer polymer reflective polarizer, a reflective wire grid polarizer, etc. can also be suitably used. Examples of multilayer polymer film reflectors include ESR Film (product name) from 3M and Picass Film (product name) from Toray Industries, Inc. In addition, examples of multilayer polymer reflective polarizers include APF and DBEF from 3M.

[0052] It is preferable that the reflectance of the reflecting mirror is high. For example, the reflectance of the first reflecting mirror 235 of the birdbath optical system described above is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. However, when used for augmented reality (AR), the second reflecting mirror 240 can be made selectively reflective, in which case the above-mentioned half mirror may be used. For measuring the reflectance, please refer to the explanation of the half mirror described above.

[0053] (Other optical components) In addition to the optical components described above, the optical system for a head mounted display may include, as necessary, optical components such as lenses, shutters, apertures, filters, etc. These optical components may be passive, or may be variable or movable (active) by electrical or mechanical control.

[0054] (frame) The frame is an optical member that fixes the relative positions of the various optical members and the display element described above and maintains optical precision. The frame can be made of known materials, such as metal, ceramic, glass, resin, fabric, and wood. The frame may also be made of a composite material. Ceramics and resins are preferred because they are lightweight, have excellent rigidity, and are easy to process, and resins are particularly preferred because of their cost.

[0055] The display element and all optical members may be fixed to a single frame, but a head-mounted display may also be constructed by combining multiple sub-frames in which some of the optical members are joined and fixed together. In particular, it is preferable that the frame adjacent to the area through which the display light passes has a light-absorbing interior in order to prevent diffuse reflection of light, suppress unexpected blurring and smearing, and realize a highly immersive head-mounted display. Furthermore, when a head-mounted display is constructed by combining multiple sub-frames, it is preferable to seal or adhere the sub-frames together to prevent external light from entering the optical system and to prevent foreign matter from entering from the external environment. This makes it possible to suppress unexpected blurring and bleeding, and to realize a head-mounted display that provides a high level of immersion.

[0056] (Adhesive layer) As described above, the polarizing mirror 38 in the pancake lens optical system 20 shown in Fig. 1 is configured by laminating a wave plate (wave plate surface 37) and a reflective polarizer (reflective polarizer surface 39). Also, a quarter-wave plate (not shown) is provided on the incident surface side of the first reflecting mirror 235 shown in Fig. 2. In this way, the components that make up the optical system for a head-mounted display may be configured by stacking multiple optical components. In the following description, such a stack of multiple optical components will also be referred to as a "laminate." To manufacture this laminate, an adhesive layer can be provided between the optical members. The adhesive layer can be rephrased as a layer having the function of physically bonding the plurality of optical members together. As such an adhesive layer, various commonly available adhesives can be used, the details of which will be described later in the description of the method for producing the laminate.

[0057] {Method of manufacturing an optical system for a head-mounted display} In one preferred embodiment, such an optical system for a head-mounted display can be manufactured by carrying out the steps described below in order. i) Optical component manufacturing process ii) Laminate manufacturing process iii) 3D molding process iv) Assembly process of optical systems for head-mounted displays In one embodiment, it is preferable to perform all of these steps in the stated order, but some of the steps may be omitted depending on the combination of optical members used, the design of the optical system for a head-mounted display, etc. However, the method for manufacturing an optical system for a head-mounted display of the present invention includes at least a step of manufacturing a laminate and a step of assembling the optical system for a head-mounted display. Furthermore, one or more of these steps may be repeated as necessary. The manufacturing method for an optical system for a head-mounted display of the present invention is not limited to manufacturing a finished product (final product) of an optical system that constitutes a head-mounted display. In other words, the manufacturing method for an optical system for a head-mounted display of the present invention may be, for example, a method for manufacturing an optical system such as a unit (assembly) that constitutes a part of the optical system of a head-mounted display, as long as it includes a manufacturing process of a laminate and a process of assembling the optical system for a head-mounted display.

[0058] [Optical component manufacturing process] The manufacturing process of the optical members is a manufacturing process of each of the optical members described above that constitute the optical system for a head-mounted display. The manufacturing process for optical components can use known methods depending on the optical component. For manufacturing, a sheet-by-sheet process can be used, or a roll-to-roll process can be used to manufacture long optical components. In the following explanation, the "roll-to-roll process" will also be referred to as "RtoR." From the viewpoints of not only the productivity and quality stability of the optical component itself, but also the productivity and quality stability of the laminate described below, and the quality stability of the resulting optical system, it is preferable to manufacture optical components to which RtoR can be applied using RtoR. In the method for manufacturing an optical system for a head-mounted display of the present invention, various commercially available optical members may be used without performing the manufacturing process of the optical members.

[0059] [Laminate manufacturing process] In the laminate manufacturing process, a laminate is manufactured by combining a plurality of optical members that constitute the optical system for a head-mounted display. In other words, in the laminate manufacturing process, a laminate is manufactured by stacking a plurality of optical members that constitute the optical system for a head-mounted display. By manufacturing the laminate in advance using the laminate manufacturing process, the "three-dimensional molding process" and "assembly process of the optical system for head-mounted displays" described below can be carried out efficiently. Furthermore, by laminating adjacent optical elements with an adhesive layer to form a laminate, gaps between the optical elements can be eliminated, unlike when the individual optical elements are provided independently. As a result, even if foreign matter, such as dust, gets into the optical system, it can be prevented from getting between the optical elements. Considering this point, it is preferable to adopt a configuration using a laminate to suppress unexpected blurring and bleeding caused by foreign matter getting between the optical elements and realize a head-mounted display with a superior immersive feeling. In the manufacturing method of the optical system for a head-mounted display of the present invention, the manufacturing process of the laminate is not limited to laminating a single optical element with another single optical element. That is, in the manufacturing method of the present invention, the manufacturing process of the laminate also includes laminating a laminate with a single optical element and laminating another laminate. Furthermore, when laminating another laminate with another laminate, the number of optical elements stacked in each laminate may be the same or different.

[0060] The optical members constituting the laminate can be combined in various ways depending on the configuration of the optical system for a head-mounted display to be manufactured. The laminate may have the following structure, for example. ·(Linear polarizer) / (Adhesive layer) / (Linear reflective polarizer) / (Adhesive layer) / (1 / 4 wavelength plate) (Linear polarizer) / (Adhesive layer) / (1 / 4 wave plate) / (Adhesive layer) / (Circular reflective polarizer) ·(1 / 4 wavelength plate) / (adhesive layer) / (linear polarizer) / (adhesive layer) / (linear reflective polarizer) / (adhesive layer) / (1 / 4 wavelength plate) (Anti-reflection film) / (Adhesive layer) / (Linear polarizer) / (Adhesive layer) / (Linear reflective polarizer) / (Adhesive layer) / (1 / 4 wave plate) (Anti-reflection film) / (Adhesive layer) / (Linear polarizer) / (Adhesive layer) / (1 / 4 wave plate) / (Adhesive layer) / (Circularly polarized reflective polarizer) Examples of optical components that make up these laminates include a stretched PVA polarizer as a linear polarizer, a multilayer polymer stretched reflective polarizer as a linear reflective polarizer, and a cholesteric liquid crystal layer as a circularly polarized reflective polarizer.

[0061] When the laminate is a long product in which each of the constituent optical members is manufactured by roll-to-roll, it is preferable to carry out the manufacturing process by roll-to-roll from the viewpoint of productivity and uniformity of quality. The laminate manufacturing process described below is based on roll-to-roll manufacturing unless otherwise specified. However, the laminate manufacturing process of the present invention does not necessarily have to be roll-to-roll, and may be a sheet-by-sheet process using cut-sheet optical members (laminates) without departing from the spirit of the invention. Each treatment (operation) performed in the manufacturing process of the laminate will be explained below.

[0062] (Activation treatment of optical component surfaces) Prior to bonding the optical members that constitute the laminate, the surfaces of the optical members may be subjected to an activation treatment. In the following description, the activation treatment applied to the surfaces of the optical members is also referred to as "surface treatment." Examples of activation treatment methods include gas phase treatments such as corona discharge treatment, plasma treatment, glow discharge treatment, ozone treatment, and atmospheric pressure CVD treatment, chemical treatments such as itro treatment, saponification treatment, and solvent treatment, and film formation treatments such as vapor deposition and sputtering. Among these, gas phase treatments such as corona treatment, plasma treatment, glow discharge treatment, ozone treatment, and atmospheric pressure CVD treatment are preferred because they can be carried out under atmospheric pressure and as a dry process.

[0063] In these surface treatments, compounds in the atmosphere or contained in the materials being treated may be decomposed to produce oxalates and the like. These products may deposit on the treated optical element, causing defects in appearance. Furthermore, uneven application of the adhesive layer-forming composition due to these deposits may also result in defects in appearance. These defects in appearance tend to increase as the effectiveness of the activation treatment increases. These defects in appearance may cause unexpected blurring and bleeding in head-up displays.

[0064] In order to suppress such defects in appearance while enhancing the effect of the surface treatment, it is preferable to cool the optical member (laminate) before performing the surface treatment. The cooling of the optical member may be performed before the surface treatment, while performing the surface treatment, or both may be performed in combination. It is preferable to cool the optical member at least while performing the surface treatment. When performing surface treatment such as corona discharge treatment, the surface to be treated is heated due to discharge irradiation, etc. By suppressing the heating of the optical component during treatment, it is possible to increase the effect of the surface treatment while suppressing defects in appearance. The temperature of the optical member during the surface treatment is not limited and may be set appropriately depending on the surface treatment method. The temperature of the optical member during the surface treatment is preferably 80°C or less, more preferably 50°C or less, and even more preferably 30°C or less. There are no limitations on the method for cooling the optical member, and various known methods can be used depending on the surface treatment method, the timing of cooling, etc. Examples include a method of cooling the surface treatment atmosphere, a method of passing (storing) the optical member through a cooled space, a method of blowing cold air onto the optical member, and a method of cooling a member that comes into contact with the optical member, such as a conveying roller.

[0065] A preferred method for cooling an optical element to be surface-treated is to carry out the surface treatment while conveying the optical element in close contact with a cooled roller (drum, can). In other words, a preferred method for surface-treating an optical element is to carry out the surface treatment while wrapping the optical element around a cooled roller. The cooled roller has a high specific heat and thermal conductivity compared to air, allowing the optical element to be cooled efficiently. This makes it possible to precisely control the temperature of the optical element during the surface-treatment process, thereby enhancing and stably suppressing the appearance defects described below. Therefore, it is particularly preferred to carry out the surface treatment while conveying the optical element in close contact with a cooled roller. The steps for carrying out such processing will be explained using the conceptual diagram of FIG. While the optical element 301 is conveyed along the roller 302 disposed between the two guide rollers 321 and 322, the optical element 301 is subjected to surface treatment by the treatment means 304 disposed at a position opposite the roller 302. During this process, the surface treatment of the optical element 301 is performed while the roller 302 is cooled. For example, in the case of corona discharge treatment, in Fig. 3, roller 302 acts as a dielectric (earth) roll, and a corona discharge electrode is used as treatment means 304 to perform corona discharge treatment while cooling roller 302. Corona discharge treatment can be performed at atmospheric pressure, and atmospheric pressure corona discharge treatment in which the treatment atmosphere indicated by reference numeral 305 is atmospheric is preferred. 3, roller 302 acts as a dielectric (earthed) roller, and a plasma excitation electrode is used as processing means 304, and plasma processing is performed in the presence of plasma gas. Plasma processing can be performed at atmospheric pressure, and the processing atmosphere indicated by reference numeral 305 can be an atmospheric (air) atmosphere containing N2, O2, Ar, etc. Atmospheric pressure plasma processing is preferred, in which atmospheric air can be used as the plasma gas.

[0066] As a method for cooling the roller 302, various known methods can be used, such as blowing cold air onto the roller, contacting the roller with a cooling roller, or incorporating a cooling means such as a Peltier element. A preferred example is a method of cooling roller 302 by circulating a cooled refrigerant through a path passing through roller 302 . Generally, when performing surface treatment such as corona discharge treatment, the surface of the roller and the material to be treated, such as an optical element, generate heat due to discharge irradiation, etc., and rise to approximately 80 to 100°C. Because the optical element is transported while being in close contact with the outer circumferential surface of roller 302, the temperature of the optical element becomes approximately the same as the surface temperature of the roller. In other words, by cooling roller 302, the optical element is also cooled, and as a result, appearance defects on the optical element can be prevented. In the present invention, there is no limitation on the surface temperature of the roller 302 to be cooled, but it is preferably 80° C. or less, more preferably 50° C. or less, and even more preferably 30° C. or less. When water is passed through the roller 302 as a refrigerant, there is no limitation on the water temperature, but an example is about 20 to 30° C.

[0067] It is also a preferred embodiment to provide an easy-adhesion layer in advance on the adhesion surface of the optical member.

[0068] (Adhesion of multiple optical components) In the manufacturing process of the laminate, an adhesion step is carried out in which a plurality of optical members are adhered and fixed by laminating another optical member on the surface of one optical member. The bonding process involves applying an adhesive layer-forming composition to the surface of one optical element, applying an adhesive layer-forming composition to the surface of another optical element, and then laminating the other optical element onto the surface of the first optical element with a nip roller while the adhesive layer-forming compositions are facing each other, thereby bonding and fixing the one optical element to the other optical element, thereby producing a laminate. As described above, in the manufacturing method of the optical system for a head-mounted display of the present invention, the manufacturing process of the laminate includes not only manufacturing a laminate by stacking a single optical element with another single optical element, but also manufacturing a laminate by stacking a laminate with a single optical element, and manufacturing a laminate by stacking another laminate with another laminate. When laminating a laminate and a single optical member, for example, the adhesive layer-forming composition may be applied to the surface of the single optical member as one optical member, and the adhesive layer-forming composition may be applied to the surface of one layer of the optical member constituting the laminate as the other optical member, and the other optical member may be laminated on the surface of the one optical member using a nip roller. In this case, the one optical member and the other optical member may be reversed. When laminating laminates, one layer of an optical element constituting one laminate is treated as one optical element and a composition for forming an adhesive layer is applied to the surface, and one layer of an optical element constituting the other laminate is treated as the other optical element and a composition for forming an adhesive layer is applied to the surface, and the other optical element is laminated onto the surface of one optical element using a nip roller. The adhesive layer-forming composition becomes an adhesive layer that bonds optical members together. The adhesive layer-forming composition can be an aqueous adhesive, an active energy ray-curable adhesive, a pressure-sensitive adhesive, a hot-melt adhesive, etc. If the optical member itself has adhesive properties, or if the optical member itself has acquired adhesive properties through the surface treatment of the optical member surface described above, an adhesive layer may not necessarily be provided, and another optical member may be laminated on the surface of one optical member using a nip roller.

[0069] <Water-based adhesive> Examples of water-based adhesives include vinyl polymer-based, gelatin-based, vinyl latex-based, polyurethane-based, isocyanate-based, polyester-based, and epoxy-based adhesives. An adhesive layer made of such an aqueous adhesive can be formed as a coated and dried layer of an aqueous solution that is a composition for forming an adhesive layer, etc. An adhesive layer made of an aqueous adhesive is particularly suitable for bonding a polarizer containing a dichroic dye in a stretched polyvinyl alcohol film, an optical member having a hydrophilic surface such as saponified triacetyl cellulose, and an optical member that has been hydrophilized by surface treatment, because it can form a thin and strong adhesive layer. When preparing the aqueous solution (adhesive layer-forming composition), additives such as a light absorber and a polarizer durability improver, a crosslinking agent, a crosslinking catalyst, and the like may be added as needed.

[0070] As the aqueous adhesive, it is preferable to use an adhesive containing a vinyl polymer. As the vinyl polymer, a polyvinyl alcohol-based resin is preferable. As the polyvinyl alcohol-based resin, an adhesive containing a polyvinyl alcohol-based resin having an acetoacetyl group is more preferable in terms of improving durability. In addition, as a crosslinking agent that can be blended with the polyvinyl alcohol-based resin, a compound having at least two functional groups reactive with the polyvinyl alcohol-based resin can be preferably used. Examples of such compounds include boric acid and borax, carboxylic acid compounds, alkyldiamines, isocyanates, epoxies, monoaldehydes, dialdehydes, amino-formaldehyde resins, and salts of divalent or trivalent metals and their oxides.

[0071] (pressure-sensitive adhesive) Pressure-sensitive adhesives are primarily made of adhesives, and various types of adhesives can be used, including rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, urethane-based adhesives, vinyl alkyl ether-based adhesives, polyvinylpyrrolidone-based adhesives, polyacrylamide-based adhesives, and cellulose-based adhesives. Depending on the type of adhesive used, an adhesive base polymer is selected. Among these pressure-sensitive adhesives, acrylic pressure-sensitive adhesives are preferably used because they have excellent optical transparency, exhibit appropriate adhesive properties such as wettability, cohesion, and adhesion, and are excellent in weather resistance and heat resistance.

[0072] In a preferred embodiment, the storage modulus G' of the adhesive layer made of the pressure-sensitive adhesive at 25°C is, for example, 1.0 × 10 4 ~1.0×10 6 The storage modulus can be determined, for example, by dynamic viscoelasticity measurement. If the adhesive layer made of the pressure-sensitive adhesive has these properties, it is less likely to develop dents from foreign matter or orange peel marks caused by tight winding of the rolled material during roll-to-roll processing, and it also prevents the adhesive from adhering to the processed surface during cutting and milling, as described below. By preventing dents from foreign matter and orange peel marks, it is possible to prevent unexpected blurring and bleeding, which are thought to be caused by these.

[0073] The adhesive preferably has a gel fraction of 70 to 90% and a holding power (HA) of 200 μm or less at 23° C. as measured by the following evaluation method. Here, the holding strength (HA) represents the width of deviation from the glass plate before and after the load is applied when an upper 10 x 10 mm portion of a 10 x 30 mm optical film is attached to the unprimed surface of a PET film (Cosmoshine A4100, manufactured by Toyobo) via an adhesive layer with a pressing force of 2 kg, autoclaved for 15 minutes at 50°C and 5 atmospheres, left at room temperature for 1 hour, and then a load of 500 g is applied to the lower end of the optical film and left for 1 hour. When the gel fraction of the adhesive is within the above range, adhesion of glue to the cut surface can be further reduced and peeling under aging conditions with humidity and heat can be made less likely. Furthermore, when the holding strength (HA) is within the above range, adhesion of glue to the cut surface can be further reduced, and the adhesive adhering to the cut surface can be prevented from transferring to the surface of the optical element or laminate, which can cause unexpected blurring and bleeding during the assembly process of the optical system for a head-mounted display.

[0074] The adhesive has a storage modulus of 7.0 × 10 at -40°C. 7 It is preferably at least 10 Pa. When the storage modulus of the pressure-sensitive adhesive at -40°C is within this range, nanocracks occurring in adjacent members can be reduced, and unexpected blurring, bleeding, and the like can be suppressed. The term "nanocracks" used here refers to small cracks that occur only on the surface of a component, as opposed to visible fractures such as breaks or perforations. Resin materials have a smooth and continuous surface immediately after film formation, but when the material is subjected to bending or shear stress, tiny cracks can form on the surface. While these cracks are difficult to see with the naked eye, if numerous cracks appear on the surface of a resin material, they can cause diffraction and interference of light rays within the optical system of a head-mounted display, resulting in unexpected blurring and bleeding. The storage modulus of the adhesive at -40°C is 7.0×10 7If the pressure-sensitive adhesive layer has a compressive strength of 100 Pa or more, it is believed that even if the laminate is subjected to an impact or strong shear, the pressure-sensitive adhesive layer will absorb the impact and shear, thereby suppressing the occurrence of nanocracks on the surfaces of adjacent members. Storage modulus at -40°C is 7.0×10 7 An adhesive having a surface tension of Pa or more can be preferably used when the adjacent component is an optical component made of a brittle material such as polyvinyl alcohol, polymethyl methacrylate, triacetyl cellulose, and polycarbonate, and when the adjacent component is an optical component made of a cross-linked cured film of a polymerizable liquid crystal compound, a polymerizable monomer, or the like. Storage modulus at -40°C is 7.0×10 7 Pressure-sensitive adhesives having a surface tension of Pa or more can be particularly preferably used when optical components such as polarizing plates using stretched polyvinyl alcohol films, retardation films made of stretched polymethyl methacrylate, triacetyl cellulose, polycarbonate, etc., and optical components consisting of liquid crystal layers whose orientation is fixed in a smectic phase or a nematic phase with a high degree of orientation are laminated to other optical components via the pressure-sensitive adhesive.

[0075] (Active energy ray curing adhesive) The active energy ray-curable adhesive is an adhesive that undergoes curing by active energy rays such as electron beams and ultraviolet rays, and can be used in the form of, for example, an electron beam-curable adhesive, an ultraviolet ray-curable adhesive, etc. Examples of the active energy ray-curable adhesive include a photocationic polymerization type adhesive and a photoradical polymerization type adhesive. Active energy ray-curable adhesives are preferably used because they can be widely applied to optical members made of various materials by appropriately designing the components and process.

[0076] Examples of photoradical polymerization type active energy ray curable adhesives include compositions containing a compound having a (meth)acryloyl group and / or a compound having a vinyl group as a curable component, and further containing an active energy ray sensitive radical polymerization initiator. The curable component may be either monofunctional or di- or higher functional. These curable components can be used alone or in combination of two or more. As these curable components, for example, compounds having a (meth)acryloyl group are suitable. When a radical polymerizable compound is used as an active energy ray-curable adhesive, a polymerization initiator is appropriately selected depending on the active energy ray. When the adhesive is cured by irradiation with ultraviolet light or visible light, a polymerization initiator that is cleaved by ultraviolet light or visible light is used. Examples of such polymerization initiators include benzophenone-based compounds, aromatic ketone compounds, acetophenone-based compounds, aromatic ketal-based compounds, aromatic sulfonyl chloride-based compounds, and thioxanthone-based compounds.

[0077] Furthermore, examples of photocationic polymerization type active energy ray curable adhesives include compositions containing, as a curable component, a compound having an epoxy group or an oxetanyl group, and further containing an active energy ray sensitive cationic polymerization initiator. The compound having an epoxy group is not particularly limited as long as it has at least two epoxy groups in the molecule, and various commonly known curable epoxy compounds can be used. Preferred examples of the epoxy compound include a compound having at least two epoxy groups and at least one aromatic ring in the molecule, and a compound having at least two epoxy groups in the molecule, at least one of which is formed between two adjacent carbon atoms constituting an alicyclic ring. When a cationic polymerizable compound is used as an active energy ray-curable adhesive, a cationic polymerization initiator is blended into the adhesive. This cationic polymerization initiator generates cationic species or Lewis acids when irradiated with active energy rays such as visible light, ultraviolet light, or electron beams, and initiates a polymerization reaction with the epoxy group of the cationic polymerizable compound. Examples of the cationic polymerization initiator that can be used include photoacid generators and photobase generators.

[0078] These active energy ray curable adhesives generally undergo shrinkage upon curing. Such shrinkage causes minute distortions on the surface of the optical component, which may result in unexpected blurring and bleeding in the optical system for a head-mounted display. Therefore, the cure shrinkage rate of the active energy ray-curable adhesive is preferably less than 3%. The cure shrinkage rate can be calculated by measuring the specific gravity α of the adhesive layer-forming composition before curing (resin liquid) and the specific gravity β of the adhesive layer-forming composition after curing (solid) using an electronic hydrometer (e.g., SD-200L manufactured by MIRAGE Co., Ltd.), and applying the values ​​α and β to the following formula. Curing shrinkage rate (%)=[(β-α) / β]×100 As such a low-shrinkage active energy ray-curable adhesive, a photocationic polymerization type active energy ray-curable adhesive is preferred. Furthermore, among the photoradical polymerization type active energy ray-curable adhesives, low-shrinkage adhesives are preferred, such as those containing polyalkylene-modified (meth)acrylate compounds, polyurethane-modified (meth)acrylate compounds, isocyanuric group-containing polyalkylene-modified (meth)acrylates, and those containing polyfunctional acrylate oligomers.

[0079] Refractive index n of active energy ray curing adhesive at a wavelength of 589 nm a The absolute value of the difference between the refractive index of the adjacent optical member at a wavelength of 589 nm is preferably less than 0.05, and more preferably less than 0.04. If the adjacent optical element has optical anisotropy and has a slow axis and a fast axis, the refractive index n of the optical element in the slow axis direction at a wavelength of 589 nm is e , the refractive index n at a wavelength of 589 nm in the fast axis direction o About n e >n a >n o In addition, it is preferable that the refractive index n e and refractive index n a The absolute value of the difference between the refractive index and the refractive index n o and refractive index n a and the absolute value of the difference between them is preferably less than 0.05, and more preferably less than 0.04. This reduces the difference in refractive index between the adhesive layer and the optical member, reducing the reflection at the interface, which in turn reduces the interference between the reflected light between the layers and prevents unexpected blurring and bleeding. The refractive index of the active energy ray-curable adhesive can be adjusted by mixing a polymerizable compound having multiple aromatic rings, a polymerizable compound containing sulfur atoms in its structure, a metal chelate compound, and high refractive index inorganic nanoparticles into the adhesive composition.

[0080] Specific examples of photoradical polymerization type active energy ray curable adhesives include those described in JP 2019-147865 A, JP 2017-193634 A, JP 2017-193633 A, and JP 2014-132092 A.

[0081] Specific examples of photocationically polymerizable active energy ray-curable adhesives include those described in JP-A-2020-56988, JP-A-2019-79065, JP-A-2018-41079, and JP-A-2017-122883.

[0082] Various additives may be added to the adhesive layer-forming composition containing such an adhesive, which will become the adhesive layer, as needed. Examples of the additives include UV (ultraviolet) absorbers, adhesion improvers, antioxidants, polarizer durability improvers, tackifiers, and plasticizers. Particularly preferred adhesion improvers include silane coupling agents, boronic acid compounds, hydroxyl group-containing compounds, and urethane group-containing compounds. These additives preferably contain a polymerizable group that is copolymerizable with the polymerizable compound that constitutes the adhesive. An adhesive layer containing an adhesion improver does not experience lifting or peeling of the adhesive layer even after long-term use. Therefore, by using an adhesive layer containing an adhesion improver, it is possible to provide a head-mounted display with a high level of immersion, in which unexpected blurring and bleeding that are presumed to be caused by lifting or peeling of the adhesive layer are suppressed.

[0083] Air bubbles trapped in the composition during preparation (liquid preparation) and application may remain in the adhesive layer, creating small voids. If such voids are present in the optical system for a head-mounted display, they can cause unexpected blurring and bleeding, so it is preferable to remove them during the process of forming the adhesive layer. Therefore, it is preferable to add a bubble inhibitor to the adhesive layer-forming composition.

[0084] The bubble inhibitor is a compound that can reduce the surface tension of the adhesive layer-forming composition when blended therein, thereby having the effect of reducing bubbles between the adhesive layer-forming composition and the adherends to be bonded. Examples of bubble inhibitors that can be used for adhesive layer-forming compositions containing active energy ray-curable adhesives and adhesive layer-forming compositions containing pressure-sensitive adhesives include silicone-based bubble inhibitors having a polysiloxane skeleton such as polydimethylsiloxane, (meth)acrylic-based bubble inhibitors having a (meth)acrylic skeleton formed by polymerizing (meth)acrylic esters, etc., polyether-based bubble inhibitors formed by polymerizing vinyl ethers, cyclic ethers, etc., and fluorine-based bubble inhibitors consisting of fluorine-based compounds having perfluoroalkyl groups, which have the effect of reducing the surface tension when added to the adhesive layer-forming composition.

[0085] For the purpose of improving the adhesiveness when a bubble suppressor is added, the bubble suppressor is preferably a compound having a reactive group. Examples of the reactive group include polymerizable functional groups. Specific examples of the polymerizable functional group include radically polymerizable functional groups having an ethylenic double bond, such as (meth)acryloyl groups, vinyl groups, and allyl groups, epoxy groups such as glycidyl groups, oxetane groups, vinyl ether groups, cyclic ether groups, cyclic thioether groups, and cationic polymerizable functional groups such as lactone groups. From the viewpoint of reactivity in the adhesive layer-forming composition, bubble suppressors having a double bond as a reactive group are preferred, and bubble suppressors having a (meth)acryloyl group are more preferred.

[0086] In consideration of the bubble suppression effect and the adhesiveness improving effect, among the above-mentioned bubble suppressors, fluorine-based bubble suppressors and silicone-based bubble suppressors are preferred, and silicone-based bubble suppressors are particularly preferred. Furthermore, among the bubble suppressors, in consideration of the adhesiveness of the adhesive layer, those containing a urethane bond or an isocyanurate ring structure in the main chain skeleton or side chain are preferred. As the silicone-based foam inhibitor, commercially available products can also be suitably used, for example, "BYK-UV3505" (manufactured by BYK Japan), which is an acrylic group-modified polydimethylsiloxane.

[0087] In order to achieve both the adhesive strength of the resulting adhesive layer and the effect of reducing lamination bubbles, the content of the bubble inhibitor is preferably 0.01 to 0.6% by weight when the total amount of the adhesive layer-forming composition is taken as 100% by weight.

[0088] The adhesive layer-forming composition may be prepared by a known method. Here, from the viewpoint of solving the problem of the present invention, which is to suppress the occurrence of unexpected blurring and bleeding in head-up displays, it is necessary to take great care to prevent foreign matter, air bubbles, etc. from being mixed into the composition for forming the adhesive layer. For example, when the adhesive layer-forming composition has a high viscosity, it is preferable to use a static mixer or an in-line mixer instead of a method using a rotating stirring blade in order to prevent air bubbles from being entrained during stirring during preparation. In consideration of this point, it is preferable to remove foreign matter and air bubbles (defoaming treatment) from the adhesive layer-forming composition after preparation. Various known means can be used to remove foreign matter from the adhesive layer-forming composition. Specific means for removing foreign matter include filtering the adhesive layer-forming composition after preparation. The mesh size of the filter used can be selected appropriately, but is preferably 10 μm or less, more preferably 5 μm or less. Various known filter materials can be used, but sintered filters and metal mesh filters are preferred from the viewpoint of durability. Commercially available filters may be used. In addition, various known means can be used to remove bubbles from the adhesive layer-forming composition. Examples of methods for removing bubbles from the adhesive layer-forming composition include a method using reduced pressure (vacuum degassing), a method using pressure, a method using a degassing pump, a method using centrifugal force, a method using ultrasonic vibration, degassing filtration, and a combination of these. Suitable examples of specific means for removing bubbles from the adhesive layer-forming composition include removing bubbles using centrifugal force and removing bubbles using ultrasonic vibration. If necessary, such removal of foreign matter and / or air bubbles may be carried out during the preparation of the adhesive layer-forming composition.

[0089] In the manufacturing method of the optical system for a head-mounted display of the present invention, the adhesion process in the manufacturing process of the laminate includes a step of applying (coating) an adhesive layer-forming composition to the surface of one optical element, and a step of laminating this optical element with another optical element. As mentioned above, in the manufacturing method of the present invention, the one optical element and / or the other optical element in the bonding step included in the manufacturing process of the laminate may not only be a single optical element, but may also be one optical element layer constituting a laminate in which multiple optical elements are stacked. The step of applying the adhesive layer-forming composition to the surface of one optical member is preferably carried out by roll-to-roll. A more preferred example is a method in which the adhesive layer-forming composition is continuously applied to a long optical member while the long optical member is fed in the longitudinal direction by a conveying device, and then the long optical member is laminated with another optical member. When an active energy ray-curable adhesive is used, after laminating one optical element with another optical element, a process can be provided in which the adhesive layer-forming composition is cured by irradiating with active energy rays and / or heating while transporting the laminate.

[0090] The optical member to be laminated on the one optical member described above is subjected to a step of applying a second adhesive layer-forming composition prior to lamination. The one optical member and the other optical member are laminated with the adhesive layer-forming compositions facing each other. When two optical members are laminated, adhesive layer-forming compositions are applied to the surfaces of both optical members, and then the adhesive layer-forming compositions are laminated so that they face each other. This not only removes any foreign matter present on the optical members together with excess liquid, but also quickly spreads the adhesive layer-forming compositions between the optical members during lamination, preventing air bubbles from getting caught in. As a result, an adhesive layer is formed that prevents foreign matter and air bubbles that can cause unexpected blurring and bleeding, and a uniform laminated state of the optical members can be achieved. The second adhesive layer-forming composition used here may be the same as or different from the adhesive layer-forming composition applied to the optical component described above, but a combination that is compatible with each other is preferred. The two optical members are laminated using nip rollers, which allows for more efficient control of the thickness of the adhesive layer in the laminate and more efficient removal of air bubbles from the adhesive layer.

[0091] There are no limitations on the coating thickness of the adhesive composition, and it may be set appropriately depending on the expected thickness of the adhesive layer, the viscosity and / or physical properties of the adhesive composition, the influence of shear forces applied from a coater, nip rollers, etc., and film thickness changes and / or shrinkage due to curing, aging, etc. The coating thickness of the adhesive composition is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm, and even more preferably 0.8 to 3 μm. There are also no limitations on the gap between the nip roller and the opposing roll, and the nip pressure of the nip roller, and these may be set appropriately depending on the expected thickness of the adhesive layer, the thickness of the optical member (laminate), the viscoelasticity of the adhesive layer and its constituent members, the material and surface hardness of the nip roller used, etc. Typically, it is preferable that the gap between the nip roller and the opposing roll is set to about 1.0 to 1.4 times the expected total thickness of the adhesive layer.

[0092] The above-mentioned lamination process will be explained with reference to Fig. 4. Note that Fig. 4 is a conceptual diagram and does not limit the present invention in terms of the apparatus or process. The surfaces of the transported first optical member 401 and second optical member 402 are each provided (applied) with adhesive layer-forming composition 403 by coater 410. As described above, first optical member 401 and / or second optical member 402 may not only be single-layer optical members, but may also be optical members constituting one layer (an end portion in the stacking direction) of a laminate in which a plurality of optical members are stacked. The first optical element 401 and the second optical element 402, each having the adhesive layer-forming composition 403 applied thereto, are laminated and bonded together by a nip roller 409, and if necessary, are exposed to light and / or heated by means not shown to form a bonded laminate. As described above, adhesive layer-forming composition 403 is applied to both first optical element 401 and second optical element 402, and then laminated with nip roller 409 with adhesive layer-forming composition 430 facing each other. During lamination, the adhesive layer-forming compositions quickly wet and spread across each other, removing any foreign matter present on the optical elements together with excess liquid, and further scraping out any air bubbles contained in the adhesive layer-forming composition. Furthermore, by adjusting the nip pressure of the nip roller 409, unevenness in the thickness of the adhesive layer can be suppressed, making it possible to produce a laminate that can be used to fabricate optical systems for head-mounted displays in which unexpected blurring and bleeding, etc., which are thought to be caused by uneven layer thickness, are suppressed.

[0093] Another preferred method is to transfer a layer of the adhesive layer-forming composition coated on a temporary support to one optical member, then remove the temporary support while leaving only the layer of the adhesive layer-forming composition, and laminate the other optical member to which the adhesive layer-forming composition has been applied onto the surface of the exposed layer of the adhesive layer-forming composition by pressing with a nip roller. In this case, the other optical member may also have a layer of the adhesive layer-forming composition similarly transferred thereto. The layer of the adhesive layer-forming composition transferred onto the optical member may be an uncured coating film or a semi-cured layer of the adhesive layer-forming composition. Such a transfer process is particularly suitable for use with a pressure-sensitive adhesive.

[0094] In applying the adhesive layer-forming composition to the surface of such an optical member, various known methods, i.e., coating methods (coating devices), can be used. The coating method may be appropriately selected depending on the viscosity of the adhesive layer-forming composition, the desired thickness of the adhesive layer, etc. Examples of the coating device include a reverse coater, a gravure coater (direct, reverse, offset, etc.), a bar reverse coater, a roll coater, a die coater, a bar coater, a rod coater, an edge coater, and an air knife coater. The coating method used in these coating devices is to form a fixed amount of liquid film on the optical element by using surface tension, a fixed gap formed between the coater (coating device) and the optical element, or external force. Among these, a preferred example is a coating method in which an external force is applied to a liquid film to remove excess liquid and obtain a predetermined coating thickness. This coating method is preferable in that foreign matter and air bubbles contained in the coating liquid are scraped out together with the excess liquid, thereby forming an adhesive layer that can be used to construct an optical system for a head-mounted display that can display images without unexpected blurring or bleeding. Specific examples include gravure roll coating, forward roll coating, air knife coating, and rod / bar coating. Among these, in terms of foreign matter removal accuracy and coating film thickness uniformity, in the present invention, gravure roll coating using a gravure roll is preferred as the coating method for the adhesive layer-forming composition, and among these, reverse gravure roll coating is particularly preferred.

[0095] Various patterns can be formed on the surface of the gravure roll, such as a honeycomb mesh pattern, a trapezoidal pattern, a lattice pattern, a pyramidal pattern, a diagonal line pattern, etc. In order to effectively prevent appearance defects from occurring in the final optical component, the pattern formed on the surface of the gravure roll is preferably a honeycomb mesh pattern. In the case of a honeycomb mesh pattern, the cell volume is set to 1 to 5 cm in order to improve the surface accuracy of the coating surface after the adhesive layer-forming composition is applied. 3 / m2 is preferable, 2 to 3 cm 3 / m 2 is more preferable. Similarly, in order to improve the surface precision of the coating surface after coating the adhesive layer-forming composition, the number of cell lines per inch of the roll is preferably 200 to 3000 lines / inch. Furthermore, the ratio of the rotation speed of the gravure roll to the traveling speed of the first optical member 401 and the second optical member 403 is preferably 100 to 300%. Furthermore, the frequency of air bubbles getting trapped in the coating film varies depending on the cell opening rate of the gravure roll. Taking this into consideration, the cell opening rate is preferably 7 to 55%, more preferably 10 to 50%, and even more preferably 15 to 40%. The cell opening rate [%] is calculated using the formula: (cell depth / cell opening width) x 100. The reason for the correlation between air bubbles getting trapped in the coating film and the cell opening rate is unclear, but as mentioned above, suppressing air bubbles getting trapped in the coating film has the effect of suppressing unexpected blurring and bleeding.

[0096] In the method for manufacturing an optical system for a head-mounted display of the present invention, the laminate produced in the laminate manufacturing step may be a laminate of three or more layers of optical members. In this case, the bonding process is carried out as described above to produce a laminate in which two layers of optical elements are stacked, and then the bonding process is carried out again to stack another layer of optical element on one of the optical elements of this laminate to produce a laminate in which three layers of optical elements are stacked. When preparing a laminate having four layers of optical members, the laminate having three layers of optical members prepared as described above and a single optical member are used to perform the bonding process again to prepare a laminate having four layers of optical members. Alternatively, two laminates having two layers of optical members as described above may be prepared, and the two laminates may be used to perform the bonding process again to prepare a laminate having four layers of optical members. A laminate in which five or more optical members are laminated may be produced in accordance with the above method. In the following description, a "laminate in which two optical members are laminated" or the like is also simply referred to as a "two-layer laminate." Furthermore, "performing a bonding step" is also simply referred to as "laminating."

[0097] Here, when manufacturing a laminate of three or more layers, where two or more optical components have coated optical functional layers formed on a support, and two of these are adjacent in the laminate, it is preferable to manufacture the laminate as follows. First, an adhesive layer-forming composition is applied to the optical functional layers of two adjacent optical members in a laminate of three or more layers to be produced, with the adhesive layer-forming composition, i.e., the optical functional layers, facing each other to produce a two-layer laminate. Then, in the laminate of three or more layers to be produced, an optical member adjacent to the two-layer laminate produced is laminated. In the production of this three or more layer laminate, when the third layer optical member has a polymer film (polymer layer, resin layer), it is preferable to laminate the polymer film facing the two-layer laminate. That is, it is preferable to laminate the polymer film facing the support. The polymer film also includes the support. Furthermore, when two optical elements each having a coating-type optical functional layer are formed on a temporary support, and both temporary supports are removed during the manufacturing process of the laminate, it is preferable to first laminate the two optical elements each having an optical functional layer formed on a temporary support, then remove one of the temporary supports, laminate a third optical element on the optical functional layer, and then remove the remaining other temporary support. In the present invention, when an optical functional layer is formed on a support (temporary support), the optical element also includes the support, and when the temporary support is removed after laminating the optical element, the optical element is the part from which the temporary support has been removed, for example, only the optical functional layer. The above-mentioned operation is particularly preferable when the coating-type optical functional layer is formed by coating a liquid crystal composition on a support (temporary support).

[0098] Coating-type optical functional layers (optical components) may contain surfactants to reduce unevenness in film thickness due to coating. In particular, optical functional layers (liquid crystal films (liquid crystal layers)) formed by coating a liquid crystal composition on a support often use liquid crystal compositions containing surfactants to achieve high optical performance even in thin films. Such surfactants are unevenly distributed on the surface of the optical functional layer, reducing the surface energy. Therefore, when a commonly used adhesive layer-forming composition is applied, the adhesive layer may have poor wettability, resulting in unevenness and defects. A laminate having an adhesive layer with such unevenness and defects may cause unexpected blurring and bleeding in the optical system for a head-mounted display. This phenomenon can occur not only with coated optical functional layers, but also when two surfaces with significantly different surface energies are bonded together.

[0099] In contrast, for example, coating-type optical members formed from liquid crystal compositions have similar surface energies, and therefore, by using a composition for forming an adhesive layer that has wettability suitable for a surface with low surface energy, a strong adhesive layer can be formed without unevenness, defects, and the like. As a result, a laminate can be obtained that can be used to fabricate an optical system for a head-mounted display in which unexpected blurring and bleeding are suppressed.

[0100] That is, in the manufacturing method of the optical system for a head-mounted display of the present invention, it is preferable that the optical elements to be laminated in the manufacturing process (adhesion process) of the laminate are laminated with surfaces made of similar materials facing each other. Materials for forming optical members that constitute the optical system for a head-mounted display can be broadly divided into two categories: polymer films (resin films, polymer layers, resin layers) and liquid crystal films (liquid crystal layers). Therefore, in the manufacturing process (adhesion process) of the laminate, it is preferable to laminate the two optical members with the polymer films facing each other or with the liquid crystal films facing each other.

[0101] Examples of optical members (optical functional layers) formed from polymer films include retardation layers (retardation films), absorptive polarizers, and reflective polarizers. Examples of the retardation layer formed of a polymer film include the above-mentioned triacetyl cellulose retardation layer, polycarbonate retardation layer, and cycloolefin retardation layer. Examples of absorptive polarizers formed from polymer films include those obtained by uniaxially stretching hydrophilic polymer films such as the above-mentioned polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films, after adsorbing a dichroic substance such as a dichroic dye and iodine, as well as polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. Further, examples of reflective polarizers formed from polymer films include the above-mentioned reflective polarizer formed by stretching a layer containing two types of polymers as described in JP-A-2011-053705, and a wire grid polarizer. In an optical member in which an optically anisotropic layer such as the above-mentioned retardation layer and a liquid crystal film described later are formed on a support, the support is also usually formed of a polymer film.

[0102] On the other hand, examples of optical members (optical functional layers) formed from liquid crystal films include retardation layers (retardation films), absorptive polarizers, and reflective polarizers. Examples of retardation layers formed by liquid crystal films include the twisted retardation layers described in WO 2013 / 137464, WO 2016 / 158300, and JP 2014-209219, the reverse dispersion liquid crystal retardation layers described in JP 2014-209220, WO 2014 / 157079, and JP 2019-215416, and the retardation layers described in WO 2016 / 158300 and WO 2019 / 160044, etc. In addition, the vertical alignment layer of rod-shaped liquid crystal constituting the above-mentioned positive C plate is also exemplified as a retardation layer formed by a liquid crystal film. Examples of absorptive polarizers formed from liquid crystal films include those obtained by dissolving or dispersing a dichroic dye or pigment in the above-mentioned lyotropic liquid crystal or thermotropic liquid crystal, uniaxially aligning the dye or pigment, and fixing the alignment. Also, lyotropic liquid crystal compounds themselves have the properties of dichroic dyes, and those obtained by fixing or curing such compounds in an oriented state are preferably used. Furthermore, examples of reflective polarizers formed by liquid crystal films include the above-mentioned circularly polarized selective reflective polarizers in which cholesteric orientation is fixed.

[0103] As described above, the optical member of the present invention also includes an optical member obtained by forming an optical function layer on a temporary support and then peeling off the temporary support. When this optical functional layer is a liquid crystal film, the surface from which the temporary support has been removed, i.e., the surface opposite the air interface, has a small decrease in surface energy due to the small uneven distribution of surfactant, even though it is a liquid crystal film, and its properties are similar to those of a polymer film. Therefore, even if the optical member is a liquid crystal film, it is preferable to treat it as a polymer film when another optical member is laminated on the surface from which the temporary support has been removed.

[0104] For example, when laminating an optical element having a reflective polarizer (cholesteric liquid crystal layer) made of a liquid crystal film on a support and an optical element having a retardation layer made of a liquid crystal film on a support, it is preferable to prepare the laminate with the reflective polarizer and the retardation layer facing each other or with the supports facing each other. In contrast, when a reflective polarizer (cholesteric liquid crystal layer) made of a liquid crystal film is formed on a temporary support, and then the temporary support is peeled off to laminate an optical element with the temporary support peeled surface of the reflective polarizer exposed and an optical element formed of a polymer film, it is preferable to prepare a laminate by facing the temporary support peeled surface of the reflective polarizer to one of the surfaces of the optical element formed of the polymer film. Furthermore, when a reflective polarizer (cholesteric liquid crystal layer) made of a liquid crystal film is formed on a temporary support, and then the temporary support is peeled off to laminate an optical element with the temporary support peeled surface of the reflective polarizer exposed, and an optical element made of a support and a liquid crystal film, it is preferable to prepare a laminate by facing the temporary support peeled surface of the reflective polarizer to the support, or by peeling the support from the liquid crystal film and facing the support peeled surface of the liquid crystal film to the temporary support peeled surface of the reflective polarizer.

[0105] As described above, such an adhesion step (an adhesion step for adhering and fixing a plurality of optical members) can be suitably repeated to form a desired laminate. The laminate obtained in this manner, preferably a long roll-to-roll laminate, has little entrapment of foreign matter, air bubbles, etc., and therefore when incorporated into an optical system for a head-mounted display as described below, it is possible to construct a head-mounted display that provides a high level of immersion without unexpected blurring, bleeding, etc. Also, as described above, a laminate in which multiple laminates are integrated may be manufactured by bonding the laminates together.

[0106] In producing the laminate, a surface protective film may be provided to protect the surface of the outermost optical member. By providing a surface protection film, it is possible to prevent damage to the surface of the optical component located on the outermost surface of the laminate and the adhesion of foreign matter, and it is possible to provide an optical system for a head-mounted display that provides a highly immersive head-mounted display without unexpected blurring or bleeding.

[0107] The surface protection film typically has a substrate and a pressure-sensitive adhesive layer. Examples of materials for forming the substrate include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof.Preferred examples include ester resins (particularly polyethylene terephthalate resins) and polypropylene resins. Such a material is unlikely to deform even when tension is applied during transportation and / or lamination, and when subjected to the three-dimensional molding described below, it easily conforms to the shape by heating and does not interfere with the molding of the optical component and laminate. In the following description, the adhesive layer provided on the surface protection film is also referred to as a PF adhesive layer, in order to distinguish it from the adhesive as a pressure-sensitive adhesive layer.

[0108] The PF pressure-sensitive adhesive layer may have any appropriate configuration. Specific examples 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 having the desired properties according to the purpose. The storage modulus G' of the PF adhesive layer at 25°C is, for example, 0.5 × 10 6 ~3.0×10 6When the storage modulus is within this range, a surface protection film having an excellent balance between adhesiveness and releasability can be obtained. In addition, adhesion of glue to the edge surface can be suppressed during the cutting and edge cutting processes described below.

[0109] The surface of the surface protection film opposite to the surface on which the PF pressure-sensitive adhesive is applied is preferably subjected to an anti-blocking treatment to prevent unexpected adhesion (blocking) that occurs when the film comes into contact with an adjacent laminate in the form of a roll. Examples of anti-blocking treatments include surface roughening treatment and the formation of an anti-blocking layer. Furthermore, contact between the laminates may be suppressed by knurling, which will be described later.

[0110] In the manufacturing process of a laminate, particularly when manufacturing a laminate by roll-to-roll, the tightness of the wound laminate may cause dents on the manufactured laminate due to foreign matter that has been caught in it, scratches due to friction, and blocking due to long-term pressure bonding. In order to prevent such defects due to tight winding, it is preferable to provide knurling on the laminate to prevent contact between optical elements that come into contact with each other when wound, thereby performing knurling treatment.

[0111] There is no particular limitation on the location of the knurling, as long as it is provided on a part of the surface of the optical member. An example of the arrangement of knurling will be described below, but the position of the knurling is not limited to the form described below. For example, as shown in the widthwise cross-sectional view of Figure 5(a), of the first optical member 501 and the second optical member 502 that constitute the laminate 510, knurling 505 can be provided on the surface of the second optical member 502. 5(b), when the adhesive layer 503 and the second optical member 502 have good shape conformability, the unevenness caused by the knurling 505 previously provided on the first optical member 501 is transferred to the second optical member 502, forming the convex portions 507. The convex portions 507 can also be knurled. 5(c), knurling 505 may be provided on the surface of the first optical member 501 opposite to the second optical member 502.

[0112] There are no particular limitations on the arrangement of the in-plane knurling in a long laminate, but it is preferable to provide it in an area that will not interfere with processing in subsequent steps. For example, as shown in the top view of the optical member in Figure 6(a), knurling 605 can be provided in a strip-like shape parallel to the longitudinal direction (X direction) in a region near the end of the laminate 601 in the width direction (Y direction). As shown in Figure 6(b), the knurling 605 may be provided intermittently in the longitudinal direction. Alternatively, as shown in Figure 6(c), the knurling 605 may be provided intermittently in the width direction.

[0113] There is no limitation on the method for forming the knurling, and various known methods can be used. Examples of such methods include direct coating methods such as die coating, slit coating, curtain coating, gravure printing, screen printing, and reverse coating using a gravure plate, as well as non-contact methods such as dispenser methods and inkjet methods. Embossing methods such as embossing using a heated embossing roll and laser embossing using laser irradiation can also be used. The cross-sectional shape of the knurling is not limited, and various shapes can be used. Examples of the cross-sectional shape of the knurling include a truncated cone, a truncated prism, a cylinder, a prism, a cone, a pyramid, and a dome. A shape with a curvature at the apex is preferred because it has little effect on the opposing back surface of the laminate. There is no limitation on the height of the knurling, but it is preferably 0.5 to 20 μm, more preferably 0.5 to 12 μm, and even more preferably 0.5 to 7 μm.

[0114] It is preferable to detect and mark defects in the optical members to be laminated in the laminate manufacturing process (adhesion process) and / or the laminate obtained by the laminate manufacturing process (adhesion process). The term "defects" refers to non-uniformities in the surface, such as foreign matter and bubbles mixed in the layer, as well as cissing and orientation defects in the coating film. The various means described above can suppress the occurrence of defects in the manufacturing method of the present invention. However, by detecting and marking unexpected defects and defects that are already present in components, it becomes possible to completely remove defective areas and defective products during the sheet separation process or final product inspection, as described below. As a result, it is possible to obtain an optical system for a head-mounted display that is free from unexpected blurring and bleeding and that can realize a head-mounted display that provides an excellent sense of immersion.

[0115] Defect detection is preferably performed in-line using RtoR. Preferred examples of the detection method include optical means and non-contact detection means using electromagnetic waves, and optical means are more preferred in terms of accuracy and amount of information. Optical means include methods using visible light and methods using invisible light such as near-infrared light, and can be selected depending on the defect to be detected. As an optical means, a method of directly detecting defects illuminated by a light source using an imaging device is well known. Other methods that can be used include a method of highlighting and detecting defective areas using polarized light, and a method of detecting defective areas using the reflection, diffraction, and interference of light irradiated from a light source by defects. Also available are methods of detecting defective areas by combining multiple imaging elements and analyzing the differences between images captured by each imaging element, or by analyzing the differences between images captured using a time difference. In particular, when detecting defects caused by cissing of a layer or defects caused by minute irregularities on the surface, it is particularly preferable to position the light source and / or the image sensor at an angle to the running web, as this emphasizes the effects of polarization and the effects of reflection, diffraction, interference, etc., making it possible to effectively detect even very small defects. Specific examples include methods described in JP 2019-70617 A, JP 2019-23587 A, JP 2018-84431 A, JP 2017-68106 A, JP 2015-14570 A, JP 2005-351825 A, and republished 2016 / 194874 A.

[0116] Defect marking is also preferably done in-line using RtoR. The marking may be made directly at the defective portion, may be made so as to surround the defective portion, may be made on the same roll but at a location distant from the defective portion, or may be made using a recording medium provided separately from the roll. In particular, when defect detection and marking are performed on each member constituting the laminate, it is preferable that the marking be made on the same roll but at a location distant from the defective portion, or be made using a recording medium provided separately from the roll, in order to prevent surface defects that may be unnecessarily caused by the marking.

[0117] Known marking methods can be used, such as inkjet marking, thermal transfer marking, stamping, and laser marking. Methods described in JP-A-2018-146579, JP-A-2009-80131, and JP-A-2005-114624 are also suitable.

[0118] It is preferable to perform defect detection and marking on either the optical element to be laminated in the laminate manufacturing process (adhesion process) or the laminate obtained by the laminate manufacturing process (adhesion process), and it is more preferable to perform defect detection and marking on both. Preferred examples of defects to be detected and marked include foreign matter and bubbles mixed in a layer, repelling of a coating film, and fine irregularities formed on a surface, etc. For the above-mentioned reflective polarizer, quarter-wave plate, and absorptive polarizer, it is also preferred to detect regions showing abnormal orientation (orientation defects). When the reflective polarizer, quarter-wave plate, and absorptive polarizer are the transfer-type optical elements described above, if markings are made on the release substrate side of the optical element, the markings will be lost during transfer. Therefore, if defect markings are made on the release substrate side of the transfer-type optical element, it is preferable to read the markings once during transfer and then print the markings again on the optical element to which the transfer is to be made, in accordance with the read defect area. This reduces the load required for detection and allows the laminate to be manufactured while maintaining information on detected defects.

[0119] When the laminate manufacturing process is carried out using roll-to-roll, the manufactured long laminate is appropriately wound up in a roll on a core and sent to the next process. The long laminate may be cut to a predetermined width with a blade or the like before or after being wound around the core, and then unwound again to form a long laminate having the desired width before being wound up. Alternatively, the laminate may be further cut in the longitudinal direction to form sheets (cut sheets) before being subjected to the next process. There are no limitations on the cutting method, and mechanical cutting methods such as punching, Thomson blade punching, plotter, and water jet may be used, or separation and removal may be performed by laser cutting. At this time, by cutting so that the above-mentioned defective marking portion is not included in the product area, it is possible to obtain only non-defective products that are free from defects from the laminate cut into sheets.

[0120] The laminate cut into sheets can be shaped by cutting the outer surface to improve the processing accuracy in the subsequent three-dimensional forming process and at the same time remove foreign matter and adhesive (glue) adhering to the edge. The outer surface can be cut using an end mill with a twisted blade. When cutting, it is preferable to perform cutting on a workpiece in which a large number of rectangularly cut sheet-like laminates are stacked, from the viewpoint of productivity and processing accuracy.

[0121] {3D molding process} By three-dimensionally molding the laminate manufactured by the laminate manufacturing process, it is possible to form it into a shape that corrects either field curvature or various aberrations, or both. There are no limitations on the shape of the three-dimensionally molded laminate, and various shapes can be used depending on the configuration and shape of the optical system for a head-mounted display in which the laminate is incorporated. Examples of the shape of the three-dimensionally molded laminate include a spherical concave shape (e.g., a part of a sphere), a spherical convex shape, a rotationally symmetric aspherical surface, and a free-form surface shape.

[0122] Such a three-dimensional molding step may be carried out by a known method. Examples of molding methods that can be used in the three-dimensional molding process include insert molding, simultaneous injection molding, blow molding, gas injection molding, stretch molding, vacuum molding, and pressure molding. A preferred molding method is the three-dimensional overlay method (TOM). can be applied.

[0123] In the three-dimensional molding process, an excess portion is provided in addition to the portion that will become the molded product to prevent the molded body from shifting position and to make it easier to remove the molded product from the mold after molding. Since this excess portion is not necessary when assembling the optical system for a head-mounted display, it is preferable to separate and remove it as appropriate after the three-dimensional molding process. The excess portion may be separated and removed by mechanical punching, such as punching, Thomson blade punching, plotter, or water jet, or by laser cutting. Furthermore, when carrying out the three-dimensional molding process, an edge may be added to the edge of the molding die, and the stress generated during molding may be used to half-cut or notch the boundary with the excess portion, thereby facilitating separation and removal.

[0124] {Assembly process of optical systems for head-mounted displays} The assembly process of the optical system for a head-mounted display is a process in which the laminate manufactured in the laminate manufacturing process and molded in the three-dimensional molding process as needed is adhered to or fitted into a frame, etc. When this process fixes the relative positions of each element that makes up the optical system for a head-mounted display as designed, the head-mounted display becomes ready to allow the user to view images. [Example]

[0125] Examples of the present invention are described below, but the present invention is not limited to these. Unless otherwise specified, processing was performed by roll-to-roll. (Production Example 1: Production of polarizer) First, a laminate consisting of an amorphous PET substrate and a 9 μm-thick PVA layer was formed on it, and a stretched laminate was produced by in-air auxiliary stretching at a stretching temperature of 130°C. The stretched laminate was then dyed to produce a dyed laminate. The dyed laminate was then stretched in boric acid water at a stretching temperature of 65°C to a total stretch ratio of 5.94, producing a laminated optical film including a 5 μm-thick PVA layer stretched integrally with the amorphous PET substrate. This two-stage stretching process resulted in a laminated optical film containing a 5 μm-thick PVA layer, which constitutes a thin polarizer in which the PVA molecules in the PVA layer formed on the amorphous PET substrate are highly oriented, and the iodine absorbed by dyeing is highly oriented in one direction as a polyiodine ion complex. The moisture content of the PVA layer acting as a thin polarizer was 10% by mass.

[0126] (Production Example 2: Production of polarizing film having a transparent protective film on one side) On a continuous line, a laminated optical film containing a 5 μm thick PVA layer was produced using a gravure roll coating method equipped with a gravure roll. The prepared adhesive layer forming composition A described below was applied to the PVA side at an initial thickness of 760 nm to continuously form a first coating film. Meanwhile, on another continuous line, a gravure roll coating method equipped with a gravure roll was used to apply the following adhesive layer forming composition B to the bonding surface of a 25 μm thick triacetyl cellulose film (Konica Minolta: KC2UA) to an initial thickness of 1500 nm to continuously form a second coating film. The ratio of the thickness of the first coating film to the thickness of the second coating film (thickness ratio) was initially set to 0.507 (760 nm / 1500 nm).

[0127] Next, using a nip roller, the bonding surface of the laminated optical film on which the first coating film had been formed and the bonding surface of the transparent protective film on which the second coating film had been formed were bonded together to form an uncured adhesive layer. Thereafter, visible light was irradiated from the side of the laminated transparent protective film using an active energy ray irradiation device to bond the polarizer and the transparent protective film via the adhesive layer, and the film was further dried with hot air at 70°C for 3 minutes, and the amorphous PET substrate was peeled off to obtain a polarized film having a transparent protective film on one side of the polarizer.

[0128] <Preparation of Adhesive Layer-Forming Composition A> 90 parts by mass of acryloylmorpholine (manufactured by Kojin Co., Ltd., trade name "ACMO", SP value: 22.9), 1 part by mass of 3-acrylamidophenylboronic acid (manufactured by Junsei Chemical Co., Ltd.), and 9 parts by mass of hydroxyethylacrylamide (manufactured by Kojin Co., Ltd., trade name "HEAA") were mixed and stirred at 25°C for 30 minutes. Thereafter, the composition was pressure filtered through a 5 μm mesh sintered metal filter and further subjected to centrifugal degassing treatment to prepare a composition A for forming an adhesive layer.

[0129] <Preparation of Adhesive Layer-Forming Composition B> 45 parts by mass of acryloylmorpholine (manufactured by Kojin Co., Ltd., trade name "ACMO", SP value: 22.9), 41 parts by mass of 1,9-nonanediol diacrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Acrylate 1.9ND-A"), 10 parts by mass of an acrylic oligomer obtained by polymerizing a (meth)acrylic monomer (manufactured by Toagosei Co., Ltd., trade name "ARUFON UG4010"), 1.5 parts by mass of a photopolymerization initiator diethylthioxanthone (manufactured by Nippon Kayaku Co., Ltd., trade name "KAYACURE DETX-S"), and 2.5 parts by mass of a photopolymerization initiator 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (manufactured by BASF, trade name "IRGACURE907") were mixed and stirred at 50°C for 1 hour. Thereafter, the composition was pressure filtered through a 5 μm mesh sintered metal filter and further subjected to centrifugal degassing treatment to prepare composition B for forming an adhesive layer.

[0130] (Manufacturing Example 3: Manufacturing of a quarter wave plate) <Preparation of Liquid Crystal Composition Solution A> Liquid crystal composition solution A was prepared by mixing 100 parts by mass of a photopolymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (manufactured by BASF, trade name "Paliocolor LC242"), 0.5 parts by mass of a surfactant (manufactured by BYK-Chemie, trade name "BYK-361"), 3 parts by mass of a photopolymerization initiator (manufactured by BASF, "Irgacure 907"), and 200 parts by mass of toluene.

[0131] <Formation of Liquid Crystal Alignment Solidified Layer A> The surface of a polyethylene terephthalate (PET) film (38 μm thick) was rubbed with a rubbing cloth to perform an alignment treatment, with the orientation direction set at 15° from the longitudinal direction of the web when it was attached to the polarizing plate, as viewed from the coating layer side. Liquid crystal composition solution A was applied to this alignment-treated surface using a bar coater, and the liquid crystal compound was aligned by drying under heat at 90° C. for 2 minutes. The liquid crystal layer thus formed was irradiated with 1 mJ / cm using a metal halide lamp. 2The liquid crystal layer was cured by irradiating it with light of 1000 kJ / cm 2 , thereby forming a liquid crystal alignment solidified layer A on the PET film. The liquid crystal alignment fixed layer A had a thickness of 2.5 μm and an in-plane retardation Re(550) of 270 nm. Furthermore, the liquid crystal alignment fixed layer A had a refractive index profile of nx>ny=nz.

[0132] <Formation of Liquid Crystal Alignment Solidified Layer B> A liquid crystal alignment solidified layer B was formed on a PET film in the same manner as above, except that the coating thickness was changed and the orientation treatment direction was set to be 75° from the longitudinal direction of the web when viewed from the substrate side. The liquid crystal alignment fixed layer B had a thickness of 1.5 μm and an in-plane retardation Re(550) of 140 nm. Furthermore, the liquid crystal alignment fixed layer B had a refractive index profile of nx>ny=nz.

[0133] (Manufacturing Example 4: Manufacturing of a quarter wave plate) The adhesive layer-forming composition C prepared below was applied to the surface of each of the liquid crystal alignment solidified layer A and the liquid crystal alignment solidified layer B obtained above using a reverse gravure coater. Next, the coated films of the adhesive layer-forming composition C were laminated using nip rollers so that they faced each other, and then visible light was irradiated onto both sides using an active energy ray irradiation device to harden the adhesive layer-forming composition C. Thereafter, the PET film on the liquid crystal alignment solidified layer A side was peeled off from the obtained laminate to expose the liquid crystal alignment solidified layer A. By laminating the liquid crystal alignment solidified layer A and the second alignment solidified liquid crystal layer B in this configuration, a laminate having the function of a broadband quarter wave plate was produced.

[0134] <Preparation of Adhesive Layer-Forming Composition C> The active energy ray-curable components were 54.5 wt% of 1,9-nonanediol diacrylate, 10 wt% of hydroxyethyl acrylamide, and 30 wt% of acryloylmorpholine, the reactive group-containing bubble inhibitor "BYK-UV3570" manufactured by BYK was used at 0.5 wt%, and the polymerization initiators were 3 wt% of IRGACURE 907 and 2 wt% of KAYACURE DETX-S, and the mixture was stirred for 3 hours. Thereafter, the composition was pressure filtered through a 5 μm mesh sintered metal filter, and further subjected to centrifugal degassing treatment, to obtain a composition C for forming an adhesive layer.

[0135] (Production Example 5: Production of a circular polarizing plate having a broadband 1 / 4 plate) The adhesive layer-forming composition A was applied to the polarizer surface of the polarizing film having the transparent protective film obtained above, and the adhesive layer-forming composition B was applied to the exposed surface of the liquid crystal alignment solidified layer A of the broadband quarter-wave plate using a gravure roll, and then the films were laminated using nip rollers, and then exposed to visible light using an active energy ray irradiation device to form an adhesive layer. After this, the PET film on the second liquid crystal alignment solidified layer B side was peeled off to produce a circular polarizer with a layer structure of (broadband 1 / 4 plate) / (adhesive layer) / (polarizer) / (adhesive layer) / (transparent protective film). As described above, the wideband 1 / 4 plate is a laminate of the liquid crystal alignment solidified layer A, the adhesive layer, and the liquid crystal alignment solidified layer B.

[0136] (Production Example 6: Production of selective reflection film having cholesteric alignment) The surface of a polyethylene terephthalate (PET) film (thickness: 38 μm) was rubbed with a rubbing cloth to perform an alignment treatment. The following polymerizable liquid crystal composition 3 was applied to the rubbed surface of the PET film using a #5 wire bar to form an uncured liquid crystal composition layer on the support, which was then dried by heating at 100°C for 3 minutes in a hot air dryer. Next, the dried liquid crystal composition layer was exposed to an integrated illuminance of 1500 mJ / cm 2The liquid crystal composition layer was cured by irradiating it with ultraviolet light of 1000 kJ / cm 2 , thereby forming a liquid crystal composition cured layer R fixed in a cholesteric alignment. The obtained liquid crystal composition cured layer R was red in color.

[0137] ---------------------------------------------------------------------------------- (Polymerizable liquid crystal composition 3) ---------------------------------------------------------------------------------- 85.1 parts by mass of the following liquid crystal compound (Z-1) 5.3 parts by mass of the following compound (Z-2) Polymerization initiator (Irgacure 379, manufactured by BASF) 5.8 parts by mass Surfactant (S-420, manufactured by AGC Seimi Chemical Co., Ltd.) 0.2 parts by mass Chiral agent (LC-756, manufactured by BASF) 0.8 parts by mass 1,3-dioxolane 51 parts by mass Cyclopentanone 34 parts by mass ----------------------------------------------------------------------------------

[0138] Liquid crystal compound (Z-1) [ka]

[0139] Compound (Z-2) [ka]

[0140] A cured liquid crystal composition layer V that reflected blue light and a cured liquid crystal composition layer G that reflected green light were formed in the same manner as above, except for adjusting the amount of chiral agent added to the polymerizable liquid crystal composition 3. The light reflected by these cured liquid crystal composition layers was circularly polarized light, and the rotation direction of the circularly polarized light was the same.

[0141] (Production Example 7: Production of circularly polarized reflective polarizer) A laminate having the cured liquid crystal composition layers R and G laminated thereon was obtained in the same manner as in Production Example 4, except that the liquid crystal alignment solidified layer A in Production Example 4 was replaced with the above-described cured liquid crystal composition layer R, and the liquid crystal alignment solidified layer B in Production Example 4 was replaced with the above-described cured liquid crystal composition layer G. After lamination, the PET film on the side of the cured liquid crystal composition layer G was peeled off and removed.

[0142] Furthermore, a pressure-sensitive adhesive layer with a separator (thickness: 20 μm) was attached to the surface of the cured liquid crystal composition layer V, and the surface of the pressure-sensitive adhesive layer revealed by removing the separator was attached to the exposed surface of the cured liquid crystal composition layer G in the laminate prepared above using a nip roller to form a laminate. After aging for 24 hours, the PET film on the liquid crystal composition cured layer V side was removed to obtain a cholesteric liquid crystal layer laminate (circularly polarized reflective polarizer) having red, green, and blue reflection bands.

[0143] (Production Example 8: Production of a laminate for a pancake lens optical system) Using the circular polarizer obtained in Production Example 5 and the circularly polarized reflective polarizer obtained in Production Example 7, a laminate for a pancake lens optical system was produced in the same manner as Production Example 4, such that the surface of the circular polarizer facing the aligned liquid crystal solidified layer B faced the surface of the circularly polarized reflective polarizer facing the liquid crystal composition cured layer V. The laminate for the pancake lens optical system obtained above was long and had the following layer structure: transparent protective film / adhesive layer / polarizer / adhesive layer / liquid crystal alignment solidified layer A / adhesive layer / liquid crystal alignment solidified layer B / adhesive layer / liquid crystal composition cured layer V / sticky layer / liquid crystal composition cured layer G / adhesive layer / liquid crystal composition cured layer R / PET film. As described above, in this laminate, "liquid crystal alignment solidified layer A / adhesive layer / liquid crystal alignment solidified layer B" constitutes a broadband quarter-wave plate. Furthermore, "cured liquid crystal composition layer V / adhesive layer / cured liquid crystal composition layer G / adhesive layer / cured liquid crystal composition layer R" constitutes a circularly polarized reflective polarizer that supports the full colors of red, green, and blue. Furthermore, the polarizer and the broadband quarter-wave plate constitute a circular polarizing plate.

[0144] (Manufacturing example 9: Three-dimensional molding process) The resulting long laminate for the pancake lens optical system was cut into a piece approximately 6 cm square, and the end faces were end-milled to form it into an accurate 6 cm square. The laminate for the pancake lens optical system, processed into a sheet, was set in a spherical crown-shaped mold with a diameter of 50 mm and a depth of 5 mm, heated to 150°C with an infrared heater, and then molded by vacuum molding. The portions other than the spherical crown-shaped molded body were separated and removed from the obtained three-dimensional molded body using a Thomson cutter to obtain a three-dimensional molded body, in which the liquid crystal composition cured layer R side was the convex side and the transparent protective film side was the concave side.

[0145] (Manufacturing Example 10: Fabrication of pancake lens optical system and head-mounted display) The three-dimensional molded body produced in Production Example 9 was fixed to one end of a cylindrical subframe with a hot melt adhesive. A separately molded convex half mirror was set at the other end to create a pancake lens optical system. Furthermore, a head-mounted display was created by placing and fixing an LCD display with a circular polarizer on its surface to emit circularly polarized light and the prepared pancake lens optical system in a frame, and adjusting it so that an appropriate image was displayed on the exit pupil.

[0146] (evaluation) The displayed image was a black and white checkered pattern, and the fineness of the pattern was varied. The images displayed on the head-mounted display were visually evaluated. No unexpected blurring or bleeding of the pattern was observed, and no noticeable light beams were observed in the black display area, even when the fineness of the pattern was varied. Two similar pancake lens systems were prepared, and evaluation images for stereoscopic viewing were divided into one for the left eye and one for the right eye. When these images were observed with each eye, a display with an excellent sense of immersion was achieved. [Industrial Applicability]

[0147] The present invention can be suitably used in the manufacture of head-mounted displays and the like. [Explanation of symbols]

[0148] 15,205 Head-Mounted Display 20 Pancake lens optical system 30,220 display elements 32,225 Linear Polarizer 33,37 Wave plate surface 34 Half Mirror 35 Mirror surface 38 Polarized Mirror 39 Reflective polarizer surface 45 eyes 50 Exit pupil 210 heads 215 frames 230 Beam Splitter 235 First Reflecting Mirror 240 Second Reflecting Mirror 250 Vision Correction Lenses 301 Optical components 321,322 Guide roller 302 Laura 304 Processing means 305 Processing atmosphere 401,501 First optical member 402,502 Second optical element 403 Composition for forming adhesive layer 409 Nip Roller 410 Coater 503 Adhesive layer 505,605 Knurling 507 Convex 510,601 Laminate

Claims

1. A method for manufacturing an optical system for a head-mounted display, the method including at least a step of manufacturing a laminate and a step of assembling the optical system for a head-mounted display, the manufacturing process of the laminate is a process for manufacturing a laminate formed by stacking a plurality of optical members constituting the optical system for a head mounted display, and includes at least an adhesion process of adhering and fixing the plurality of optical members by stacking one of the optical members on a surface of another of the optical members; the bonding step includes a step of applying an adhesive layer-forming composition to the one optical member, a step of applying an adhesive layer-forming composition to the other optical member, and a step of laminating the one optical member and the other optical member with the adhesive layer-forming composition facing each other using nip rollers, the manufacturing step of the laminate includes manufacturing a laminate in which three or more optical members are stacked, the optical members having coating-type optical functional layers formed on a support, and the optical members having the coating-type optical functional layers are adjacent in the laminate, the adhesive layer-forming composition is applied to the optical functional layers of two optical members each having the coating-type optical functional layer, and the bonding step is performed to produce a laminate in which two of the optical members are stacked; Then, using a laminate formed by stacking the two optical elements and a third-layer optical element having a coating-type optical functional layer formed on a support, the adhesive layer-forming composition is applied to the optical functional layer of the third-layer optical element and to the support of one of the optical elements in the laminate formed by stacking the two optical elements, and the adhesive process is performed again with the optical functional layer of the third-layer optical element facing the support of one of the optical elements in the laminate formed by stacking the two optical elements, in a method for manufacturing an optical system for a head-mounted display.

2. The method for manufacturing an optical system for a head-mounted display according to claim 1 , wherein the laminate manufacturing step includes manufacturing a laminate including a polarizer.

3. The method for manufacturing an optical system for a head mounted display according to claim 1 or 2, further comprising a three-dimensional molding step of three-dimensionally molding the laminate manufactured in the laminate manufacturing step.

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