Lens portion, laminate, display element, method for manufacturing the display element, and display method.

Abstract

To provide a lens component that enables lighter weight and higher resolution for VR goggles. [Solution] The lens portion according to an embodiment of the present invention is a lens portion used in a display system that displays an image to a user, and comprises: a reflective portion that reflects light emitted forward from the display surface of a display element representing an image, and that has passed through a polarizing member and a first λ / 4 member, and includes a reflective polarizing member and an absorbing polarizing member disposed in front of the reflective polarizing member; a first lens portion disposed in the optical path between the display element and the reflective portion; a half mirror disposed between the display element and the first lens portion, which transmits light emitted from the display element and reflects the light reflected by the reflective portion toward the reflective portion; and a second λ / 4 member disposed in the optical path between the half mirror and the reflective portion, wherein the thickness of the absorbing polarizing film constituting the absorbing polarizing member is 8 μm or less.

Description

[Technical Field]

[0001] The present invention relates to a lens portion, a laminate, a display element, a method for manufacturing a display element, and a display method. [Background technology]

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

[0003] In recent years, new applications for image display devices have been developed. For example, goggles with displays for realizing Virtual Reality (VR) (VR goggles) are beginning to be commercialized. As VR goggles are being considered for use in various situations, there is a demand for lighter weight and higher resolution. Lighter weight can be achieved, for example, by making the lenses used in VR goggles thinner. On the other hand, there is also a demand for the development of optical materials suitable for display systems using thin lenses. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-103286 [Overview of the project] [Problems that the invention aims to solve]

[0005] In view of the above, the primary objective of the present invention is to provide a lens part that can achieve lighter weight and higher resolution for VR goggles. [Means for solving the problem]

[0006] 1. The lens portion according to an embodiment of the present invention is a lens portion used in a display system that displays an image to a user, and comprises: a reflective portion that reflects light emitted forward from the display surface of a display element representing an image, and that has passed through a polarizing member and a first λ / 4 member, and includes a reflective polarizing member and an absorbing polarizing member disposed in front of the reflective polarizing member; a first lens portion disposed in the optical path between the display element and the reflective portion; a half mirror disposed between the display element and the first lens portion, which transmits light emitted from the display element and reflects the light reflected by the reflective portion toward the reflective portion; and a second λ / 4 member disposed in the optical path between the half mirror and the reflective portion, wherein the thickness of the absorbing polarizing film constituting the absorbing polarizing member is 8 μm or less. 2. In the lens portion described in item 1 above, the reflection axis of the reflective polarizing member and the absorption axis of the absorptive polarizing member may be arranged parallel to each other. 3. In the lens portion described in 1 or 2 above, the first lens portion and the half mirror may be integrated. 4. In the lens portion described in any of items 1 to 3 above, the lens portion may include a second lens portion positioned in front of the reflecting portion. 5. In the lens portion described in any of items 1 to 4 above, the angle between the absorption axis of the polarizing member included in the display element and the slow axis of the first λ / 4 member may be 40° to 50°, and the angle between the absorption axis of the polarizing member included in the display element and the slow axis of the second λ / 4 member may be 40° to 50°. 6. In the lens portion described in any of items 1 to 5 above, the ratio of the thickness of the absorbing polarizing film to the thickness of the reflective polarizing member may be 15% or less.

[0007] 7. The laminate according to an embodiment of the present invention is used in the reflective portion of the lens portion described in any of 1 to 6 above, and comprises the reflective polarizing member and the absorptive polarizing member. 8. In the laminate described in item 7 above, the reflective polarizing member and the absorptive polarizing member may be laminated with an adhesive layer in between.

[0008] 9. The display body according to an embodiment of the present invention has a lens portion as described in any of 1 to 6 above. 10. A method for manufacturing a display body according to an embodiment of the present invention, a method for manufacturing a display body having a lens portion as described in any of 1 to 6 above.

[0009] 11. A display method according to an embodiment of the present invention comprises the steps of: passing light representing an image emitted through a polarizing member and a first λ / 4 member through a half mirror and a first lens portion; passing the light that has passed through the half mirror and the first lens portion through a second λ / 4 member; reflecting the light that has passed through the second λ / 4 member toward the half mirror with a reflective portion including a reflective polarizing member; making the light reflected by the reflective portion and the half mirror permeable to the reflective polarizing member of the reflective portion by the second λ / 4 member; and passing the light that has passed through the reflective polarizing member through an absorbing polarizing member, wherein the thickness of the absorbing polarizing film constituting the absorbing polarizing member is 8 μm or less.

[0010] 12. A method for manufacturing an absorption polarizing film for a lens portion according to an embodiment of the present invention includes forming a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin on one side of a long thermoplastic resin substrate to form a laminate, and subjecting the laminate to the following in this order: air-assisted stretching, dyeing, underwater stretching, and drying shrinkage by heating while conveying in the longitudinal direction to shrink by 2% or more in the width direction. 13. In the manufacturing method described in item 12 above, the content of the halogenated compound in the polyvinyl alcohol-based resin layer is 5 to 20 parts by weight per 100 parts by weight of the polyvinyl alcohol-based resin. 14. In the manufacturing method described in item 12 or 13 above, the stretching ratio in the aerial auxiliary stretching treatment is 2.0 times or more. 15. In the manufacturing method described in any of items 12 to 14 above, the drying shrinkage treatment step is a step of heating using a heating roll. 16. In the manufacturing method according to 15 above, the temperature of the heating roll is 60°C to 120°C, and the shrinkage rate in the width direction of the laminate due to the drying shrinkage treatment is 2% or more.

Advantages of the Invention

[0011] According to the lens unit according to the embodiment of the present invention, weight reduction and high definition of the VR goggles can be achieved.

Brief Description of the Drawings

[0012] [Figure 1] It is a schematic diagram showing the schematic configuration of a display system according to one embodiment of the present invention. [Figure 2] It is a schematic cross-sectional view showing an example of a laminate used for the reflection part of the display system shown in FIG. 1. [Figure 3] It is a schematic perspective view showing an example of a multilayer structure included in a reflective polarizing film. [Figure 4] It is a schematic diagram showing an example of a drying shrinkage treatment using a heating roll. [Figure 5] It is an observation photograph showing optical unevenness.

Modes for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. Also, for the purpose of making the description clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part as compared with the embodiments, but this is merely an example and does not limit the interpretation of the present invention.

[0014] (Definition of Terms and Symbols) The definitions of the terms and symbols in this specification are as follows. (1) Refractive Index (nx, ny, nz) "nx" is the refractive index in the direction in which the refractive index in the plane is maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane phase difference measured with light of wavelength λnm at 23°C. For example, "Re(550)" is the in-plane phase difference measured with light of wavelength 550nm at 23°C. Re(λ) can be calculated using the formula: Re(λ) = (nx - ny) × d, where d (nm) is the thickness of the layer (film). (3) Phase difference in the thickness direction (Rth) "Rth(λ)" is the phase difference in the thickness direction measured with light of wavelength λnm at 23°C. For example, "Rth(550)" is the phase difference in the thickness direction measured with light of wavelength 550nm at 23°C. Rth(λ) can be calculated using the formula: Rth(λ) = (nx - nz) × d, where d (nm) is the thickness of the layer (film). (4) Nz coefficient The Nz coefficient is calculated using the formula Nz = Rth / Re. (5)Angle In this specification, when an angle is referred to, it encompasses both clockwise and counterclockwise directions with respect to the reference direction. Therefore, for example, "45°" means ±45°.

[0015] Figure 1 is a schematic diagram showing the general configuration of a display system according to one embodiment of the present invention. Figure 1 schematically illustrates the arrangement and shape of each component of the display system 2. The display system 2 comprises a display element 12, a reflector 14, a first lens 16, a half mirror 18, a first phase difference member 20, a second phase difference member 22, and a second lens 24. The reflector 14 is positioned in front of the display element 12 on the display surface 12a side and can reflect light emitted from the display element 12. The first lens 16 is positioned in the optical path between the display element 12 and the reflector 14, and the half mirror 18 is positioned between the display element 12 and the first lens 16. The first phase difference member 20 is positioned in the optical path between the display element 12 and the half mirror 18, and the second phase difference member 22 is positioned in the optical path between the half mirror 18 and the reflector 14.

[0016] The components positioned in front of the half-mirror (in the illustrated example, the half-mirror 18, the first lens section 16, the second phase difference member 22, the reflecting section 14, and the second lens section 24) are sometimes collectively referred to as the lens section (lens section 4).

[0017] The display element 12 is, for example, a liquid crystal display or an organic EL display, and has a display surface 12a for displaying an image. Light emitted from the display surface 12a passes through a polarizing member (typically a polarizing film) that may be included in the display element 12, and is emitted as first linearly polarized light.

[0018] The first phase difference member 20 is a λ / 4 member capable of converting a first linearly polarized light incident on the first phase difference member 20 into a first circularly polarized light (hereinafter, the first phase difference member may be referred to as the first λ / 4 member). The first phase difference member 20 may be provided integrally with the display element 12.

[0019] The half-mirror 18 transmits light emitted from the display element 12 and reflects the light reflected by the reflecting part 14 back towards the reflecting part 14. The half-mirror 18 is integrally provided with the first lens part 16.

[0020] The second phase difference member 22 is a λ / 4 member that can transmit light reflected by the reflecting portion 14 and the half mirror 18 through the reflecting portion 14, which includes a reflective polarizing member (hereinafter, the second phase difference member may be referred to as the second λ / 4 member). The second phase difference member 22 may be provided integrally with the first lens portion 16, or it may be provided integrally with the reflective polarizing member included in the reflecting portion 14.

[0021] The first circularly polarized light emitted from the first λ / 4 member 20 passes through the half mirror 18 and the first lens portion 16 and is converted into a second linearly polarized light by the second λ / 4 member 22. The second linearly polarized light emitted from the second λ / 4 member 22 is reflected towards the half mirror 18 without passing through the reflective polarizing member included in the reflecting portion 14. At this time, the polarization direction of the second linearly polarized light incident on the reflective polarizing member included in the reflecting portion 14 is in the same direction as the reflection axis of the reflective polarizing member. Therefore, the second linearly polarized light incident on the reflecting portion is reflected by the reflective polarizing member.

[0022] The second linearly polarized light reflected by the reflecting section 14 is converted into a second circularly polarized light by the second λ / 4 member 22, and the second circularly polarized light emitted from the second λ / 4 member 22 passes through the first lens section 16 and is reflected by the half mirror 18. The second circularly polarized light reflected by the half mirror 18 passes through the first lens section 16 and is converted into a third linearly polarized light by the second λ / 4 member 22. The third linearly polarized light is transmitted through the reflective polarizing member included in the reflecting section 14. At this time, the polarization direction of the third linearly polarized light incident on the reflective polarizing member included in the reflecting section 14 is in the same direction as the transmission axis of the reflective polarizing member. Therefore, the third linearly polarized light incident on the reflecting section 14 is transmitted through the reflective polarizing member.

[0023] Light that has passed through the reflective section 14 passes through the second lens section 24 and enters the user's eye 26.

[0024] For example, the absorption axis of the polarizing member included in the display element 12 and the reflection axis of the reflective polarizing member included in the reflection section 14 may be arranged substantially parallel to each other or substantially orthogonal to each other. The angle between the absorption axis of the polarizing member included in the display element 12 and the lagging axis of the first phase difference member 20 may be, for example, 40° to 50°, but may also be 42° to 48°, or approximately 45°. The angle between the absorption axis of the polarizing member included in the display element 12 and the lagging axis of the second phase difference member 22 may be, for example, 40° to 50°, but may also be 42° to 48°, or approximately 45°.

[0025] The in-plane phase difference Re(550) of the first phase difference member 20 is, for example, 100 nm to 190 nm, but may also be 110 nm to 180 nm, 130 nm to 160 nm, or 135 nm to 155 nm.

[0026] The first phase difference member 20 preferably exhibits an inverse dispersion wavelength characteristic in which the phase difference value increases with the wavelength of the measured light. The Re(450) / Re(550) of the first phase difference member 20 is, for example, 0.75 or more and less than 1, and may be 0.8 or more and 0.95 or less.

[0027] The in-plane phase difference Re(550) of the second phase difference member 22 is, for example, 100 nm to 190 nm, but may also be 110 nm to 180 nm, 130 nm to 160 nm, or 135 nm to 155 nm.

[0028] The second phase difference member 22 preferably exhibits an inverse dispersion wavelength characteristic in which the phase difference value increases with the wavelength of the measured light. The Re(450) / Re(550) of the second phase difference member 22 is, for example, 0.75 or more and less than 1, and may be 0.8 or more and 0.95 or less.

[0029] Each phase difference member is formed from any suitable material. For example, it may be a resin film (typically a stretched film) or it may be formed from a liquid crystal compound. If the phase difference member is a resin film, its thickness is, for example, 10 μm to 100 μm.

[0030] Examples of resins included in the above-mentioned resin film include polycarbonate resins, polyester carbonate resins, polyester resins, polyvinyl acetal resins, polyarylate resins, cyclic olefin resins, cellulose resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, and acrylic resins. These resins may be used individually or in combination (e.g., blended, copolymerized). For example, a resin film containing a polycarbonate resin or a polyester carbonate resin (hereinafter sometimes simply referred to as a polycarbonate resin) can be suitably used. By using such a resin, for example, the above-mentioned inverse dispersion wavelength characteristics can be obtained.

[0031] Any suitable polycarbonate resin can be used as the above-mentioned polycarbonate resin. For example, the polycarbonate resin includes structural units derived from fluorene-based dihydroxy compounds, structural units derived from isosorbide-based dihydroxy compounds, and structural units derived from at least one dihydroxy compound selected from the group consisting of alicyclic diols, alicyclic dimethanol, di, tri, or polyethylene glycol, and alkylene glycol or spiroglycol. Preferably, the polycarbonate resin includes structural units derived from fluorene-based dihydroxy compounds, structural units derived from isosorbide-based dihydroxy compounds, structural units derived from alicyclic dimethanol, and / or structural units derived from di, tri, or polyethylene glycol; more preferably, it includes structural units derived from fluorene-based dihydroxy compounds, structural units derived from isosorbide-based dihydroxy compounds, and structural units derived from di, tri, or polyethylene glycol. The polycarbonate resin may optionally include structural units derived from other dihydroxy compounds. Further details regarding polycarbonate resins suitably used for phase difference members and methods for forming phase difference members are described, for example, in Japanese Patent Publication No. 2014-10291, Japanese Patent Publication No. 2014-26266, Japanese Patent Publication No. 2015-212816, Japanese Patent Publication No. 2015-212817, and Japanese Patent Publication No. 2015-212818, and the descriptions in these publications are incorporated herein by reference.

[0032] An absorptive polarizing member may be provided in front of the reflective polarizing member. Typically, the absorptive polarizing member can be provided between the reflective polarizing member and the second lens portion 24. The reflection axis of the reflective polarizing member and the absorption axis of the absorptive polarizing member may be arranged substantially parallel to each other, and the transmission axis of the reflective polarizing member and the transmission axis of the absorptive polarizing member may be arranged substantially parallel to each other. The absorptive polarizing member may be included in the reflective portion 14. If the reflective portion 14 includes the absorptive polarizing member, the reflective portion 14 may include a laminate having the reflective polarizing member and the absorptive polarizing member.

[0033] Figure 2 is a schematic cross-sectional view showing an example of a laminate used in the reflective portion of the display system shown in Figure 1. The laminate 30 has a reflective polarizing member 32 and an absorptive polarizing member 34, and the reflective polarizing member 32 and the absorptive polarizing member 34 are laminated together via an adhesive layer 36. By using the adhesive layer, the reflective polarizing member 32 and the absorptive polarizing member 34 are fixed together, and misalignment of the axial arrangement between the reflective axis and the absorptive axis (transmission axis and transmission axis) can be prevented. In addition, adverse effects due to the air layer that may be formed between the reflective polarizing member 32 and the absorptive polarizing member 34 can be suppressed. The adhesive layer 36 may be formed of an adhesive or a tack. The thickness of the adhesive layer 36 is, for example, 0.05 μm to 30 μm, preferably 3 μm to 20 μm, and more preferably 5 μm to 15 μm. Although not shown, a second phase difference member 22 may be integrally provided with the reflective polarizing member 32, so the laminate 30 may have a second phase difference member 22. In this case, the second phase difference member 22 can be laminated onto the reflective polarizing member 32 via an adhesive layer.

[0034] The above-described reflective polarizing member transmits polarized light parallel to its transmission axis (typically linearly polarized light) while maintaining its polarization state, and reflects light in other polarization states. Typically, the reflective polarizing member is composed of a multilayer film (sometimes referred to as a reflective polarizing film). In this case, the thickness of the reflective polarizing member is, for example, 10 μm to 150 μm, preferably 20 μm to 100 μm, and more preferably 30 μm to 60 μm.

[0035] Figure 3 is a schematic perspective view showing an example of a multilayer structure included in a reflective polarizing film. The multilayer structure 32a alternates between layers A, which have birefringence, and layers B, which have substantially no birefringence. The total number of layers constituting the multilayer structure may be 50 to 1000. For example, the refractive index nx in the x-axis direction of layer A is greater than the refractive index ny in the y-axis direction, and the refractive index nx in the x-axis direction and the refractive index ny in the y-axis direction of layer B are substantially the same, so the refractive index difference between layer A and layer B is large in the x-axis direction and substantially zero in the y-axis direction. As a result, the x-axis direction can be the reflection axis and the y-axis direction can be the transmission axis. The refractive index difference between layer A and layer B in the x-axis direction is preferably 0.2 to 0.3.

[0036] The above-mentioned layer A is typically composed of a material that exhibits birefringence upon stretching. Examples of such materials include naphthalenedicarboxylic acid polyester (e.g., polyethylene naphthalate), polycarbonate, and acrylic resins (e.g., polymethyl methacrylate). The above-mentioned layer B is typically composed of a material that does not substantially exhibit birefringence upon stretching. Examples of such materials include a copolyester of naphthalenedicarboxylic acid and terephthalic acid. The above multilayer structure can be formed by a combination of co-extrusion and stretching. For example, the materials constituting layer A and layer B are extruded and then multilayered (e.g., using a multiplier). The resulting multilayer laminate is then stretched. The x-axis direction in the illustrated example may correspond to the stretching direction.

[0037] Examples of commercially available reflective polarizing films include the product names "DBEF" and "APF" from 3M, and "APCF" from Nitto Denko.

[0038] The orthogonal transmittance (Tc) of the reflective polarizing member (reflective polarizing film) may be, for example, 0.01% to 3%. The single-element transmittance (Ts) of the reflective polarizing member (reflective polarizing film) may be, for example, 43% to 49%, preferably 45% to 47%. The degree of polarization (P) of the reflective polarizing member (reflective polarizing film) may be, for example, 92% to 99.99%.

[0039] The above single-element transmittance (Ts) is typically measured using a UV-Vis spectrophotometer. The above polarization degree (P) is typically measured using a UV-Vis spectrophotometer and calculated using the following formula based on the parallel transmittance (Tp) and orthogonal transmittance (Tc) obtained after luminous efficiency correction. Ts, Tp, and Tc are Y values ​​obtained by measuring with a 2-degree field of view (C light source) according to JIS Z8701 and correcting for luminous efficiency. Polarization degree (P)={(Tp-Tc) / (Tp+Tc)} 1 / 2 ×100

[0040] The above-mentioned absorption-type polarizing member may typically include a resin film containing a dichroic substance (sometimes referred to as an absorption-type polarizing film or simply a polarizing film). Preferably, it includes a polyvinyl alcohol (PVA) film containing iodine. The thickness of the absorption-type polarizing film is preferably 1 μm to 8 μm, more preferably 7 μm or less, and even more preferably 5 μm or less. By using an absorption-type polarizing film of such thickness, shrinkage that may occur due to environmental changes (e.g., temperature changes) can be suppressed, and excellent display characteristics can be maintained. Specifically, in the above-mentioned display system, even slight shrinkage of the member can cause image distortion, so by using an absorption-type polarizing film of such thickness, distortion of the displayed image can be suppressed very well.

[0041] The ratio of the thickness of the absorbing polarizing film to the thickness of the reflective polarizing member is preferably 15% or less, and more preferably 10% or less. The ratio of the thickness of the absorbing polarizing film to the sum of the thicknesses of the second phase difference member, the reflective polarizing member, and the absorbing polarizing member is preferably 10% or less, and more preferably 5% or less.

[0042] The orthogonal transmittance (Tc) of the absorbing polarizing member (absorbing polarizing film) is preferably 0.5% or less, more preferably 0.1% or less, and even more preferably 0.05% or less. The single-element transmittance (Ts) of the absorbing polarizing member (absorbing polarizing film) is, for example, 41.0% to 45.0%, and preferably 42.0% or more. The degree of polarization (P) of the absorbing polarizing member (absorbing polarizing film) is, for example, 99.0% to 99.997%, and preferably 99.9% or more. By combining an absorbing polarizing member with a reflective polarizing member, excellent display characteristics can be achieved. For example, the user's perception of afterimages (ghosting) can be suppressed.

[0043] One embodiment of the method for producing the above-described absorption polarizing film includes forming a polyvinyl alcohol-based resin layer (PVA-based resin layer) containing a halogenated compound and a polyvinyl alcohol-based resin (PVA-based resin) on one side of a long thermoplastic resin substrate to form a laminate, and subjecting the laminate to the following in order: air-assisted stretching, dyeing, underwater stretching, and drying shrinkage by heating while conveying in the longitudinal direction to shrink by 2% or more in the width direction. The halogenated compound content in the PVA-based resin layer is preferably 5 to 20 parts by weight per 100 parts by weight of the PVA-based resin. The stretching ratio in the air-assisted stretching is preferably 2.0 times or more. The drying shrinkage is preferably performed using a heated roll, and the temperature of the heated roll is preferably 60°C to 120°C. The shrinkage rate in the width direction of the laminate due to the drying shrinkage is preferably 2% or more. By fabricating a laminate containing a PVA-based resin layer containing a halide, performing multi-stage stretching of the laminate including aerial assisted stretching and underwater stretching, and then heating the stretched laminate with a heated roll, a polarizing film with excellent optical properties (typically single-layer transmittance and polarization degree) and suppressed variations in optical properties can be obtained. Specifically, by using a heated roll in the drying shrinkage process, the laminate can be uniformly shrunk throughout the entire laminate while being transported. This not only improves the optical properties of the resulting polarizing film but also enables the stable production of polarizing films with excellent optical properties and suppresses variations in the optical properties of the polarizing film (especially single-layer transmittance).

[0044] Any suitable method can be used to produce a laminate of a thermoplastic resin substrate and a PVA-based resin layer. Preferably, a coating solution containing a halogenated compound and a PVA-based resin is applied to the surface of the thermoplastic resin substrate and dried to form a PVA-based resin layer on the thermoplastic resin substrate. As described above, the halogenated compound content in the PVA-based resin layer is preferably 5 to 20 parts by weight per 100 parts by weight of the PVA-based resin.

[0045] Any suitable method can be used to apply the coating solution. Examples include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, knife coating (comma coating, etc.). The application and drying temperature of the above coating solution is preferably 50°C or higher.

[0046] The thickness of the PVA resin layer is preferably 3 μm to 40 μm, and more preferably 3 μm to 20 μm.

[0047] Before forming the PVA resin layer, the thermoplastic resin substrate may be subjected to surface treatment (e.g., corona treatment), or an easy-adhesion layer may be formed on the thermoplastic resin substrate. By performing such treatments, the adhesion between the thermoplastic resin substrate and the PVA resin layer can be improved.

[0048] The thickness of the thermoplastic resin substrate is preferably 20 μm to 300 μm, more preferably 50 μm to 200 μm. If it is less than 20 μm, it may be difficult to form the PVA-based resin layer. If it exceeds 300 μm, for example, in the underwater stretching treatment described later, it may take a long time for the thermoplastic resin substrate to absorb water and may require an excessive load for stretching.

[0049] The thermoplastic resin substrate preferably has a water absorption rate of 0.2% or more, and more preferably 0.3% or more. The thermoplastic resin substrate can absorb water, and the water acts as a plasticizer, causing plasticization. As a result, the tensile stress can be significantly reduced, and it can be stretched to a high magnification. On the other hand, the water absorption rate of the thermoplastic resin substrate is preferably 3.0% or less, and more preferably 1.0% or less. By using such a thermoplastic resin substrate, it is possible to prevent problems such as a significant decrease in the dimensional stability of the thermoplastic resin substrate during manufacturing, which can lead to deterioration of the appearance of the resulting polarizing film. It is also possible to prevent the substrate from breaking during underwater stretching, or the PVA-based resin layer from peeling off from the thermoplastic resin substrate. The water absorption rate of the thermoplastic resin substrate can be adjusted, for example, by introducing a modifying group into the constituent material. The water absorption rate is a value determined in accordance with JIS K 7209.

[0050] The glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 120°C or lower. By using such a thermoplastic resin substrate, it is possible to sufficiently ensure the stretchability of the laminate while suppressing the crystallization of the PVA-based resin layer. Furthermore, considering the plasticization of the thermoplastic resin substrate by water and the ability to stretch it in water, it is more preferable that the Tg is 100°C or lower, and even more preferably 90°C or lower. On the other hand, the glass transition temperature of the thermoplastic resin substrate is preferably 60°C or higher. By using such a thermoplastic resin substrate, when applying and drying the coating solution containing the PVA-based resin, it is possible to prevent defects such as deformation of the thermoplastic resin substrate (e.g., the occurrence of unevenness, sagging, wrinkles, etc.) and to produce a well-made laminate. In addition, the stretching of the PVA-based resin layer can be performed well at a suitable temperature (e.g., around 60°C). The glass transition temperature of the thermoplastic resin substrate can be adjusted, for example, by introducing a modifying group into the constituent material or by heating with a crystallizing material. The glass transition temperature (Tg) is a value determined in accordance with JIS K 7121.

[0051] Any suitable thermoplastic resin can be used as the constituent material of the thermoplastic resin substrate. Examples of thermoplastic resins 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. Among these, norbornene resins and amorphous polyethylene terephthalate resins are preferred.

[0052] In one embodiment, amorphous (non-crystallized) polyethylene terephthalate resin is preferably used. Among these, amorphous (less crystallized) polyethylene terephthalate resin is particularly preferred. Specific examples of amorphous polyethylene terephthalate resins include copolymers further containing isophthalic acid and / or cyclohexanedicarboxylic acid as the dicarboxylic acid, and copolymers further containing cyclohexanedimethanol or diethylene glycol as the glycol.

[0053] In a preferred embodiment, the thermoplastic resin substrate is composed of a polyethylene terephthalate resin having isophthalic acid units. Such a thermoplastic resin substrate has excellent stretchability and crystallization during stretching can be suppressed. This is thought to be due to the introduction of isophthalic acid units, which imparts significant bending to the main chain. The polyethylene terephthalate resin has terephthalic acid units and ethylene glycol units. The content of isophthalic acid units is preferably 0.1 mol% or more, more preferably 1.0 mol% or more, relative to the total of all repeating units. This is because a thermoplastic resin substrate with excellent stretchability can be obtained. On the other hand, the content of isophthalic acid units is preferably 20 mol% or less, more preferably 10 mol% or less, relative to the total of all repeating units. By setting the content to such a ratio, the degree of crystallinity can be increased well in the drying shrinkage treatment described later.

[0054] The thermoplastic resin substrate may be stretched beforehand (before forming the PVA-based resin layer). In one embodiment, the thermoplastic resin substrate is stretched in the transverse direction. The transverse direction is preferably perpendicular to the stretching direction of the laminate described later. In this specification, "perpendicular" also includes substantially perpendicular. Here, "substantially perpendicular" includes the case where the angle is 90°±5.0°, preferably 90°±3.0°, and more preferably 90°±1.0°.

[0055] The stretching temperature of the thermoplastic resin substrate is preferably between Tg-10°C and Tg+50°C relative to the glass transition temperature (Tg). The stretching ratio of the thermoplastic resin substrate is preferably between 1.5 and 3.0 times.

[0056] Any suitable method can be used to stretch the thermoplastic resin substrate. Specifically, it may be fixed-end stretching or free-end stretching. The stretching method may be dry or wet. Stretching of the thermoplastic resin substrate may be carried out in one stage or in multiple stages. In the case of multiple stages, the stretching ratio mentioned above is the product of the stretching ratios of each stage.

[0057] The coating solution contains a halogenated compound and a PVA-based resin, as described above. Typically, the coating solution is a solution obtained by dissolving the halogenated compound and the PVA-based resin in a solvent. Examples of solvents include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These can be used individually or in combination of two or more. Among these, water is preferred. The concentration of the PVA-based resin in the solution is preferably 3 to 20 parts by weight per 100 parts by weight of the solvent. Such a resin concentration allows for the formation of a uniform coating film that adheres closely to the thermoplastic resin substrate. The halogenated compound content in the coating solution is preferably 5 to 20 parts by weight per 100 parts by weight of the PVA-based resin.

[0058] Additives may be added to the coating solution. Examples of additives include plasticizers and surfactants. Examples of plasticizers include polyhydric alcohols such as ethylene glycol and glycerin. Examples of surfactants include nonionic surfactants. These may be used to further improve the uniformity, dyeability, and stretchability of the resulting PVA-based resin layer.

[0059] Any suitable resin can be used as the PVA-based resin mentioned above. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymers can be used. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymers are obtained by saponifying ethylene-vinyl acetate copolymers. The degree of saponification of PVA-based resins is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The degree of saponification can be determined in accordance with JIS K 6726-1994. By using a PVA-based resin with such a degree of saponification, a polarizing film with excellent durability can be obtained. If the degree of saponification is too high, there is a risk of gelation.

[0060] The average degree of polymerization of PVA resins can be appropriately selected depending on the purpose. The average degree of polymerization is typically 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average degree of polymerization can be determined in accordance with JIS K 6726-1994.

[0061] Any suitable halide can be used as the above-mentioned halide. Examples include iodide and sodium chloride. Examples of iodide include potassium iodide, sodium iodide, and lithium iodide. Among these, potassium iodide is preferred.

[0062] The amount of halogen in the coating solution is preferably 5 to 20 parts by weight per 100 parts by weight of PVA resin, and more preferably 10 to 15 parts by weight per 100 parts by weight of PVA resin. If the amount of halogen per 100 parts by weight of PVA resin exceeds 20 parts by weight, the halogen may bleed out, and the resulting polarizing film may become cloudy.

[0063] Generally, stretching a PVA-based resin layer increases the orientation of polyvinyl alcohol molecules within the PVA-based resin. However, immersing the stretched PVA-based resin layer in a water-containing liquid can disrupt the orientation of the polyvinyl alcohol molecules, potentially reducing their degree of orientation. This tendency to decrease orientation is particularly pronounced when stretching a laminate of a thermoplastic resin and a PVA-based resin layer in boric acid water, especially when stretching the laminate at a relatively high temperature in boric acid water to stabilize the stretching of the thermoplastic resin. For example, while stretching a PVA film alone in boric acid water is typically performed at 60°C, stretching a laminate of A-PET (thermoplastic resin substrate) and a PVA-based resin layer is performed at a much higher temperature of around 70°C. In this case, the orientation of the PVA in the initial stages of stretching may decrease before it increases due to water stretching. In contrast, by fabricating a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin substrate, and performing high-temperature stretching (auxiliary stretching) in air before stretching the laminate in boric acid water, the crystallization of the PVA-based resin in the PVA-based resin layer of the laminate after auxiliary stretching can be promoted. As a result, when the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide. This can improve the optical properties of the polarizing film obtained through processing steps that involve immersing the laminate in a liquid, such as dyeing and water stretching.

[0064] In particular, to obtain high optical properties, a two-stage stretching method combining dry stretching (auxiliary stretching) and stretching in boric acid water is selected. By introducing auxiliary stretching, as in two-stage stretching, it is possible to stretch the thermoplastic resin substrate while suppressing crystallization, solving the problem of reduced stretchability due to excessive crystallization of the thermoplastic resin substrate during subsequent stretching in boric acid water, and enabling stretching of the laminate to a higher magnification. Furthermore, when coating a PVA-based resin onto a thermoplastic resin substrate, it is necessary to lower the coating temperature compared to coating a PVA-based resin onto a normal metal drum in order to suppress the influence of the glass transition temperature of the thermoplastic resin substrate. As a result, the crystallization of the PVA-based resin becomes relatively low, which can lead to the problem of not being able to obtain sufficient optical properties. In contrast, by introducing auxiliary stretching, it is possible to increase the crystallinity of the PVA-based resin even when coating a thermoplastic resin, making it possible to achieve high optical properties. Furthermore, by simultaneously enhancing the orientation of the PVA resin beforehand, it is possible to prevent problems such as a decrease in the orientation or dissolution of the PVA resin when it is immersed in water during subsequent dyeing and stretching processes, thereby achieving high optical properties.

[0065] The stretching method for aerial assisted stretching may be fixed-end stretching (for example, stretching using a tenter stretcher) or free-end stretching (for example, uniaxial stretching by passing the laminate between rolls with different peripheral speeds), but free-end stretching may be actively adopted in order to obtain high optical properties. In one embodiment, the aerial stretching process includes a heated roll stretching step in which the laminate is stretched by the difference in peripheral speed between heated rolls while being transported in its longitudinal direction. Typically, the aerial stretching process includes a zone stretching step and a heated roll stretching step. The order of the zone stretching step and the heated roll stretching step is not limited, and the zone stretching step may be performed first, or the heated roll stretching step may be performed first. The zone stretching step may be omitted. In one embodiment, the zone stretching step and the heated roll stretching step are performed in this order. In another embodiment, the film is stretched by gripping the film end in a tenter stretcher and widening the distance between tenters in the flow direction (the widening of the distance between tenters becomes the stretching ratio). At this time, the distance between tenters in the width direction (perpendicular to the flow direction) is set to be arbitrarily close. Preferably, it can be set to be closer to the free-end stretching ratio in the flow direction. In the case of free-end stretching, the shrinkage rate in the width direction = (1 / stretching ratio) 1 / 2 It is calculated as follows.

[0066] Aerial assisted stretching may be performed in one stage or in multiple stages. When performed in multiple stages, the stretching ratio is the product of the stretching ratios of each stage. Preferably, the stretching direction in aerial assisted stretching is substantially the same as the stretching direction in underwater stretching.

[0067] The stretching ratio in aerial assisted stretching is preferably 2.0 to 3.5 times. When aerial assisted stretching and underwater stretching are combined, the maximum stretching ratio is preferably 5.0 times or more, more preferably 5.5 times or more, and even more preferably 6.0 times or more, relative to the original length of the laminate. In this specification, "maximum stretching ratio" refers to the stretching ratio immediately before the laminate breaks, and is defined as a value 0.2 lower than the stretching ratio at which the laminate breaks, which is determined separately.

[0068] The stretching temperature of the air-assisted stretching can be set to any appropriate value according to the forming material of the thermoplastic resin substrate, the stretching method, etc. The stretching temperature is preferably equal to or higher than the glass transition temperature (Tg) of the thermoplastic resin substrate, more preferably equal to or higher than the glass transition temperature (Tg) of the thermoplastic resin substrate + 10°C, and particularly preferably equal to or higher than Tg + 15°C. On the other hand, the upper limit of the stretching temperature is preferably 170°C. By stretching at such a temperature, the crystallization of the PVA-based resin can be suppressed from proceeding rapidly, and the defects caused by such crystallization (for example, hindering the orientation of the PVA-based resin layer by stretching) can be suppressed. The crystallization index of the PVA-based resin after the air-assisted stretching is preferably 1.3 to 1.8, and more preferably 1.4 to 1.7. The crystallization index of the PVA-based resin can be measured by the ATR method using a Fourier transform infrared spectrophotometer. Specifically, the measurement is carried out using polarized light as the measurement light, and the crystallization index is calculated according to the following formula using the intensities at 1141 cm -1 and 1440 cm -1 . Crystallization index = (I C / I R ) However, I C : The intensity at 1141 cm -1 when the measurement light is incident and measured I R : The intensity at 1440 cm -1 when the measurement light is incident and measured .

[0069] ( If necessary, after the air-assisted stretching treatment and before the underwater stretching treatment and the dyeing treatment, an insolubilization treatment is performed. The above insolubilization treatment is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By performing the insolubilization treatment, water resistance can be imparted to the PVA-based resin layer, and the orientation degradation of PVA when immersed in water can be prevented. The concentration of the aqueous boric acid solution is preferably 1 part by weight to 4 parts by weight with respect to 100 parts by weight of water. The liquid temperature of the insolubilization bath (aqueous boric acid solution) is preferably 20°C to 50°C.

[0070] The above dyeing process is typically carried out by dyeing a PVA-based resin layer with iodine. Specifically, it is carried out by adsorbing iodine onto the PVA-based resin layer. Examples of such adsorption methods include immersing the PVA-based resin layer (laminated structure) in a dyeing solution containing iodine, coating the PVA-based resin layer with the dyeing solution, or spraying the dyeing solution onto the PVA-based resin layer. Preferably, the laminate is immersed in the dyeing solution (dyeing bath) because iodine can be adsorbed well in this method.

[0071] The above-mentioned dyeing solution is preferably an iodine aqueous solution. The amount of iodine is preferably 0.05 to 0.5 parts by weight per 100 parts by weight of water. To increase the solubility of iodine in water, it is preferable to add iodide to the iodine aqueous solution. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Among these, potassium iodide is preferred. The amount of iodide is preferably 0.1 to 10 parts by weight, more preferably 0.3 to 5 parts by weight, per 100 parts by weight of water. The temperature of the dyeing solution during dyeing is preferably 20°C to 50°C to suppress the dissolution of the PVA resin. When immersing a PVA-based resin layer in a dyeing solution, the immersion time is preferably 5 seconds to 5 minutes, and more preferably 30 seconds to 90 seconds, in order to ensure the permeability of the PVA-based resin layer.

[0072] The staining conditions (concentration, liquid temperature, immersion time) can be set so that the transmittance and polarization degree of the final polarizing film fall within the above-mentioned range. Preferably, such staining conditions involve using an iodine aqueous solution as the staining solution, with a ratio of iodine to potassium iodide content in the iodine aqueous solution of 1:5 to 1:20. Preferably, the ratio of iodine to potassium iodide content in the iodine aqueous solution is 1:5 to 1:10. This makes it possible to obtain a polarizing film having the optical properties described above.

[0073] When a dyeing treatment is performed immediately after a treatment in which a laminate is immersed in a treatment bath containing boric acid (typically an immobilization treatment), the boric acid contained in the treatment bath may mix with the dyeing bath, causing the boric acid concentration in the dyeing bath to change over time, which may result in unstable dyeing properties. To suppress such instability in dyeing properties, the upper limit of the boric acid concentration in the dyeing bath is adjusted to preferably 4 parts by weight, more preferably 2 parts by weight, per 100 parts by weight of water. On the other hand, the lower limit of the boric acid concentration in the dyeing bath is preferably 0.1 parts by weight, more preferably 0.2 parts by weight, and even more preferably 0.5 parts by weight, per 100 parts by weight of water. In one embodiment, the dyeing treatment is performed using a dyeing bath that has been pre-mixed with boric acid. This can reduce the rate of change in boric acid concentration when the boric acid in the treatment bath is mixed with the dyeing bath. The amount of boric acid added to the dyeing bath beforehand (i.e., the amount of boric acid not derived from the above treatment bath) is preferably 0.1 to 2 parts by weight, and more preferably 0.5 to 1.5 parts by weight, per 100 parts by weight of water.

[0074] If necessary, a crosslinking treatment is performed after the dyeing treatment and before the underwater stretching treatment. Typically, the above crosslinking treatment is performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By applying the crosslinking treatment, water resistance is imparted to the PVA-based resin layer, and a decrease in the orientation of PVA when immersed in high-temperature water during subsequent underwater stretching can be prevented. The concentration of the aqueous boric acid solution is preferably 1 to 5 parts by weight per 100 parts by weight of water. Furthermore, when the crosslinking treatment is performed after the above dyeing treatment, it is preferable to further add iodide. By adding iodide, the elution of iodine adsorbed on the PVA-based resin layer can be suppressed. The amount of iodide added is preferably 1 to 5 parts by weight per 100 parts by weight of water. Specific examples of iodide are as described above. The liquid temperature of the crosslinking bath (aqueous boric acid solution) is preferably 20°C to 50°C.

[0075] Underwater stretching is performed by immersing the laminate in a stretching bath. Underwater stretching allows stretching at a temperature lower than the glass transition temperature (typically around 80°C) of the thermoplastic resin substrate or PVA-based resin layer, enabling high-magnification stretching of the PVA-based resin layer while suppressing its crystallization. As a result, polarizing films with excellent optical properties can be manufactured.

[0076] Any suitable method can be used to stretch the laminate. Specifically, it may be fixed-end stretching or free-end stretching (for example, uniaxial stretching by passing the laminate between rolls with different peripheral speeds). Preferably, free-end stretching is selected. The stretching of the laminate may be carried out in one stage or in multiple stages. In the case of multiple stages, the stretching ratio of the laminate (maximum stretching ratio), which will be described later, is the product of the stretching ratios of each stage.

[0077] Stretching in water is preferably carried out by immersing the laminate in an aqueous boric acid solution (boric acid water stretching). By using an aqueous boric acid solution as the stretching bath, the PVA resin layer can be given rigidity to withstand the tension applied during stretching and water resistance that prevents it from dissolving in water. Specifically, boric acid can generate tetrahydroxyborate anions in the aqueous solution and crosslink with the PVA resin by hydrogen bonding. As a result, the PVA resin layer can be given rigidity and water resistance, allowing for good stretching and the production of a polarizing film with excellent optical properties.

[0078] The above-mentioned aqueous boric acid solution is preferably obtained by dissolving boric acid and / or a borate in water, which is the solvent. The boric acid concentration is preferably 1 to 10 parts by weight, more preferably 3.5 to 7 parts by weight, and particularly preferably 4 to 6 parts by weight, per 100 parts by weight of water. By setting the boric acid concentration to 1 part by weight or more, the dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizing film with higher properties can be produced. In addition to boric acid or a borate, aqueous solutions obtained by dissolving boron compounds such as borax, glyoxal, glutaraldehyde, etc., in a solvent can also be used.

[0079] Preferably, iodide is added to the stretching bath (boric acid aqueous solution). By adding iodide, the elution of iodine adsorbed on the PVA resin layer can be suppressed. Specific examples of iodide are as described above. The concentration of iodide is preferably 0.05 to 15 parts by weight, more preferably 0.5 to 8 parts by weight, per 100 parts by weight of water.

[0080] The stretching temperature (liquid temperature of the stretching bath) is preferably 40°C to 85°C, more preferably 60°C to 75°C. At such temperatures, high-magnification stretching is possible while suppressing the dissolution of the PVA-based resin layer. Specifically, as described above, the glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 60°C or higher in relation to the formation of the PVA-based resin layer. In this case, if the stretching temperature falls below 40°C, even considering the plasticization of the thermoplastic resin substrate by water, good stretching may not be possible. On the other hand, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer becomes, which may prevent the acquisition of excellent optical properties. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

[0081] The stretching ratio by underwater stretching is preferably 1.5 times or more, more preferably 3.0 times or more. The total stretching ratio of the laminate is preferably 5.0 times or more, and even more preferably 5.5 times or more, relative to the original length of the laminate. By achieving such high stretching ratios, it is possible to manufacture polarizing films with extremely excellent optical properties. Such high stretching ratios can be achieved by employing an underwater stretching method (boric acid underwater stretching).

[0082] The above drying shrinkage treatment may be performed by zone heating, which involves heating the entire zone, or by heating the conveying rolls (using so-called heated rolls) (heated roll drying method). Preferably, both methods are used. By drying using heated rolls, heat curling of the laminate can be efficiently suppressed, and a polarizing film with excellent appearance can be manufactured. Specifically, by drying the laminate while it is aligned with the heated rolls, the crystallization of the thermoplastic resin substrate can be efficiently promoted, increasing the degree of crystallinity, and even at relatively low drying temperatures, the degree of crystallinity of the thermoplastic resin substrate can be increased well. As a result, the rigidity of the thermoplastic resin substrate increases, making it able to withstand the shrinkage of the PVA-based resin layer due to drying, and curling is suppressed. Furthermore, by using heated rolls, the laminate can be dried while maintaining a flat state, so not only curling but also wrinkles can be suppressed. At this time, the optical properties of the laminate can be improved by shrinking it in the width direction through the drying shrinkage treatment. This is because the orientation of PVA and PVA / iodine complex can be effectively increased. The shrinkage rate in the width direction of the laminate due to the drying shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, and particularly preferably 4% to 6%. By using heated rolls, the laminate can be continuously shrunk in the width direction while being transported, thereby achieving high productivity.

[0083] Figure 4 is a schematic diagram showing an example of a drying shrinkage process. In the drying shrinkage process, the laminate 200 is dried while being transported by transport rolls R1 to R6 heated to a predetermined temperature and guide rolls G1 to G4. In the illustrated example, the transport rolls R1 to R6 are arranged to continuously heat the PVA resin layer surface and the thermoplastic resin substrate surface alternately, but for example, the transport rolls R1 to R6 may be arranged to continuously heat only one side of the laminate 200 (for example, the thermoplastic resin substrate surface).

[0084] Drying conditions can be controlled by adjusting the heating temperature of the conveying rolls (temperature of the heating rolls), the number of heating rolls, and the contact time with the heating rolls. The heating roll temperature is preferably 60°C to 120°C, more preferably 65°C to 100°C, and particularly preferably 70°C to 80°C. This effectively increases the crystallinity of the thermoplastic resin, effectively suppresses curling, and provides the laminate with extremely excellent durability. The heating roll temperature can be measured using a contact thermometer. In the illustrated example, six conveying rolls are provided, but there are no particular restrictions on the number of conveying rolls as long as there are multiples. Typically, 2 to 40 conveying rolls are provided, preferably 4 to 30. The contact time between the laminate and the heating rolls (total contact time) is preferably 1 second to 300 seconds, more preferably 1 to 20 seconds, and even more preferably 1 to 10 seconds.

[0085] The heating rolls may be installed inside a heating furnace (e.g., an oven) or in a normal production line (at room temperature). Preferably, they are installed inside a heating furnace equipped with a blowing mechanism. By using heating roll drying in combination with hot air drying, abrupt temperature changes between the heating rolls can be suppressed, and shrinkage in the width direction can be easily controlled. The temperature for hot air drying is preferably 30°C to 100°C. The hot air drying time is preferably 1 second to 300 seconds. The wind speed of the hot air is preferably about 10 m / s to 30 m / s. This wind speed is the wind speed inside the heating furnace and can be measured with a mini-vane type digital anemometer.

[0086] Preferably, a washing treatment is performed after the underwater stretching treatment and before the drying shrinkage treatment. Typically, the above washing treatment is carried out by immersing the PVA-based resin layer in an aqueous potassium iodide solution. [Examples]

[0087] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The thickness is a value measured by the measurement method described below. <thickness> Thicknesses of 10 μm or less were measured using a scanning electron microscope (JEOL Ltd., product name "JSM-7100F"). Thicknesses exceeding 10 μm were measured using a digital micrometer (Anritsu Corporation, product name "KC-351C").

[0088] [Example 1] As the thermoplastic resin substrate, an amorphous isophthalic copolymer polyethylene terephthalate film (thickness: 100 μm) in a long length, with a water absorption rate of 0.75% and a Tg of approximately 75°C was used. One side of the resin substrate was subjected to corona treatment. A PVA aqueous solution (coating solution) was prepared by dissolving 100 parts by weight of a PVA-based resin, which was prepared by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Mitsubishi Chemical Corporation, trade name "Gosenex Z410") in a 9:1 ratio, with 13 parts by weight of potassium iodide. A PVA aqueous solution was applied to the corona-treated surface of a resin substrate and dried at 60°C to form a 13 μm thick PVA-based resin layer, thereby creating a laminate. The resulting laminate was uniaxially stretched 2.4 times in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds in an oven at 130°C (air-assisted stretching). Next, the laminate was immersed for 30 seconds in an insolubilization bath at a liquid temperature of 40°C (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) (insolubilization treatment). Next, the polarizing film was immersed for 60 seconds in a staining bath at a liquid temperature of 30°C (an iodine aqueous solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with 100 parts by weight of water) while adjusting the concentration so that the final polarizing film's single-element transmittance (Ts) was 43.0% (staining treatment). Next, the material was immersed for 30 seconds in a crosslinking bath at a liquid temperature of 40°C (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water) (crosslinking treatment). Subsequently, the laminate was immersed in a boric acid aqueous solution (boric acid concentration 4% by weight, potassium iodide concentration 5% by weight) at a liquid temperature of 70°C, and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds to achieve a total stretch ratio of 5.5 times (underwater stretching treatment). Subsequently, the laminate was immersed in a washing bath at a liquid temperature of 20°C (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) (washing treatment). Subsequently, the laminate was dried in an oven maintained at 90°C while being brought into contact with a SUS (stainless steel) heated roll with a surface temperature maintained at 75°C for approximately 2 seconds (drying shrinkage treatment). The shrinkage rate in the width direction of the laminate due to the drying shrinkage treatment was 5.2%. In this way, a polarizing film (absorption polarizing film) with a thickness of 5 μm was formed on the resin substrate.

[0089] A 25 μm thick cycloolefin resin film was bonded to the surface of the obtained polarizing film (the polarizing film side of the laminate) via an ultraviolet-curing adhesive as a protective layer. Specifically, the adhesive layer was coated to a thickness of approximately 1 μm after curing, and bonded using a roll press. Then, UV light was irradiated from the cycloolefin resin film side to cure the adhesive. Next, the resin substrate was peeled off to obtain a polarizing film (absorbent polarizing film) having a cycloolefin resin film / absorbent polarizing film structure.

[0090] [Example 2] A polarizing film containing a 7 μm thick polarizing film was obtained in the same manner as in Example 1, except that a PVA-based resin layer with a thickness of 18 μm was formed on a resin substrate.

[0091] [Comparative Example 1] A 12 μm thick polarizing film (absorption polarizing film) was fabricated by uniaxially stretching a 30 μm thick polyvinyl alcohol (PVA) resin film (manufactured by Kuraray, product name "PE3000") in the longitudinal direction using a roll stretching machine to 5.9 times its length, while simultaneously applying swelling, dyeing, crosslinking, and washing treatments in that order, and finally drying treatment. The above swelling treatment involved stretching the material 2.2 times while treating it with pure water at 20°C. Next, the dyeing treatment involved stretching the material 1.4 times while treating it in an aqueous solution at 30°C with an iodine-to-potassium iodide weight ratio of 1:7, where the iodine concentration was adjusted so that the resulting polarizing film had a single-layer transmittance of 45.0%. Next, the crosslinking treatment was performed in two stages. In the first stage, the material was stretched 1.2 times while treating it in an aqueous solution of boric acid and potassium iodide at 40°C. The boric acid content of the aqueous solution for the first stage of crosslinking was 5.0% by weight, and the potassium iodide content was 3.0% by weight. In the second stage of crosslinking, the material was stretched 1.6 times while treating it in an aqueous solution of boric acid and potassium iodide at 65°C. The boric acid content of the aqueous solution for the second stage of crosslinking was 4.3% by weight, and the potassium iodide content was 5.0% by weight. Next, the washing treatment was performed with an aqueous potassium iodide solution at 20°C. The potassium iodide content of the washing solution was 2.6% by weight. Finally, the polarizing film was obtained by drying at 70°C for 5 minutes.

[0092] A 25 μm thick cycloolefin resin film was laminated to the obtained polarizing film as a protective layer using a 3% aqueous solution of PVA-based adhesive (Mitsubishi Chemical Corporation, product name "Gosenor Z200") to obtain a polarizing film.

[0093] [Comparative Example 2] A polarizing film containing a polarizing film with a thickness of 17 μm was obtained in the same manner as in Comparative Example 1, except that a PVA-based resin film with a thickness of 45 μm was used.

[0094] [Comparative Example 3] A polarizing film containing a polarizing film with a thickness of 23 μm was obtained in the same manner as in Comparative Example 1, except that a PVA-based resin film with a thickness of 60 μm was used.

[0095] [Comparative Example 4] A polarizing film containing a polarizing film with a thickness of 30 μm was obtained in the same manner as in Comparative Example 1, except that a PVA-based resin film with a thickness of 75 μm was used.

[0096] The following evaluations were conducted on the examples and comparative examples. The evaluation results are summarized in Table 1. <Rating> 1. Dimensional change rate (%) Test specimens measuring 100 mm x 100 mm were cut from the obtained polarizing film along the stretching direction and the direction perpendicular thereto, and bonded to a glass plate via a 20 μm thick acrylic adhesive layer. These were then heated in an 80°C oven for 500 hours, and the size was measured before and after heating, and the dimensional change rate before and after heating was calculated. 2. Shrinkage stress (N / 4mm) Test specimens measuring 20 mm x 4 mm were cut from the obtained polarizing film (before the protective film was laminated) along the stretching direction and the direction perpendicular to it, and then set in a TMA analyzer (Hitachi High-Tech Science Corporation, "TMA7100E"). While maintaining this state, the specimens were heated at 50°C for 30 minutes, and the shrinkage stress generated from the test specimens was measured. 3. Optical unevenness The obtained polarizing film was cut to a size of 200 mm x 150 mm, and the resulting sample, bonded to a glass plate via a 20 μm acrylic adhesive layer, was placed in an 80°C heating test machine for 120 hours. Afterwards, another standard polarizing plate (Nitto Denko Corporation, "CRT1794") was superimposed on the removed sample so that their absorption axes were perpendicular to each other, and this was placed on a backlight. In this state, the uniformity within the surface was checked.

[0097] [Table 1]

[0098] In the comparative example, optical unevenness (particularly at the corners) was observed, as shown in Figure 5.

[0099] The present invention is not limited to the embodiments described above, and various modifications are possible. For example, the configurations shown in the embodiments above can be replaced with configurations that are substantially the same, configurations that produce the same effects, or configurations that can achieve the same purpose. [Industrial applicability]

[0100] The lens portion according to an embodiment of the present invention can be used, for example, in a display device such as VR goggles. [Explanation of Symbols]

[0101] 2 Display System 4. Lens section 12 Display elements 14 Reflector 16 First lens section 18 Half Mirror 20 First phase difference member 22 Second phase difference member 24 Second lens section 30-layer structure 32 Reflective polarizing member 34 Absorbing polarizing element 36 Adhesive layer

Claims

1. A reflective member used in the lens portion of VR goggles, which reflects light incident on the lens portion, The reflective member is a laminate including a reflective polarizing member and an absorbing polarizing member positioned in front of the reflective polarizing member. The thickness of the absorbing polarizing film constituting the absorbing polarizing member is 8 μm or less. Reflective material.

2. The VR goggles are based on a display system in which light emitted forward from the display surface of an image-representing display element is transmitted through the lens to display an image to the user. The reflective member according to claim 1, wherein the light is reflected twice by the lens portion to display an image to the user.

3. The reflective member according to claim 2, wherein one of the two reflections in the lens portion is a reflection in the reflective member.

4. The reflective member according to claim 1, wherein the reflective polarizing member and the absorptive polarizing member are laminated with an adhesive layer in between.

5. The reflective member according to claim 1, wherein the reflection axis of the reflective polarizing member and the absorption axis of the absorptive polarizing member are arranged parallel to each other.

Images