Optical laminate member and method for manufacturing optical laminate

Abstract

The present invention provides an optical laminate with high yield. This optical laminate member has a first optical functional layer with a thickness of 8 μm or less and a second optical functional layer with a thickness of 8 μm or less. The first and second optical functional layers are laminated with an adhesive layer interposed therebetween. The ratio of the thickness of the second optical functional layer to the thickness of the first optical functional layer is 0.25-4. The thickness of the adhesive layer is smaller than the thickness of each of the first and second optical functional layers.

Description

Optical laminated member and method for manufacturing optical laminated body

[0001] The present invention relates to an optical laminated member and a method for manufacturing an optical laminated body.

[0002] Image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices (e.g., organic EL display devices), are rapidly becoming popular. Optical components such as retardation components and polarizing components are generally used in image display devices to realize image display and improve image display performance (see, for example, Patent Document 1). These optical components can be integrated in advance and mounted on the image display device as an optical laminate.

[0003] In recent years, new applications of image display devices have been developed. For example, goggles with displays (VR goggles) for realizing virtual reality (VR) have begun to be commercialized.

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

[0005] As the applications of image display devices expand, the optical laminate may be composed of many optical components. In this case, depending on the method for laminating the components, the yield of the optical laminate may be significantly reduced.

[0006] In view of the above, a main object of the present invention is to provide an optical laminate with a high yield.

[0007] 1. An optical laminated member according to an embodiment of the present invention includes a first optical functional layer having a thickness of 8 μm or less and a second optical functional layer having a thickness of 8 μm or less, the first optical functional layer and the second optical functional layer being laminated via an adhesive layer, the ratio of the thickness of the second optical functional layer to the thickness of the first optical functional layer being 0.25 or more and 4 or less, the thickness of the adhesive layer being smaller than the thickness of the first optical functional layer, and the thickness of the adhesive layer being smaller than the thickness of the second optical functional layer. 2. In the optical laminated member described in 1 above, the end face of the adhesive layer may be flush with the end faces of the first optical functional layer and the second optical functional layer, or may be located inside the end faces of the first optical functional layer and the second optical functional layer. 3. The optical laminated member described in 1 or 2 above may have a tensile modulus of elasticity of 10 MPa to 25 MPa. 4. A method for manufacturing an optical laminate according to an embodiment of the present invention includes preparing an optical laminate member in which a first optical functional layer formed on a first substrate and a second optical functional layer formed on a second substrate are laminated via an adhesive layer; peeling at least one of the first substrate and the second substrate from the optical laminate member; and laminating another optical component on the surface exposed by peeling the substrate, wherein the thickness of the first optical functional layer is 8 μm or less, the thickness of the second optical functional layer is 8 μm or less, the ratio of the thickness of the second optical functional layer to the thickness of the first optical functional layer is 0.25 or more and 4 or less, the thickness of the adhesive layer is smaller than the thickness of the first optical functional layer, and the thickness of the adhesive layer is smaller than the thickness of the second optical functional layer.

[0008] According to the embodiment of the present invention, optical laminates can be provided with a high yield.

[0009] Fig. 3B is a schematic cross-sectional view showing an example of the general configuration of an optical laminated member according to a first embodiment of the present invention; Fig. 4 is a schematic cross-sectional view showing an example of the general configuration of an optical laminated member according to a second embodiment of the present invention; Fig. 5 is a diagram showing an example of a method of using an optical laminated member according to one embodiment of the present invention; Fig. 6 is a diagram continuing from Fig. 3A; Fig. 7 is a diagram continuing from Fig. 3B; Fig. 8 is a schematic diagram showing an example of the general configuration of an example of a display system for VR goggles; Fig. 9 is a schematic cross-sectional view showing an example of the details of an optical laminate; Fig. 10 is a schematic perspective view showing an example of a multilayer structure included in a reflective polarizing film;

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. In order to clarify the description, the drawings may schematically show the width, thickness, shape, etc. of each part compared to the embodiments, but these are merely examples and do not limit the interpretation of the present invention. Furthermore, in the drawings, the same or equivalent elements are given the same reference numerals, and redundant explanations may be omitted.

[0011] (Definition of Terms and Symbols) The definitions of terms and symbols used in this specification are as follows. (1) Refractive Index (nx, ny, nz) "nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the in-plane direction perpendicular to the slow axis (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. (2) In-Plane Retardation (Re) "Re(λ)" is the in-plane retardation measured with light having a wavelength of λ nm at 23°C. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) is calculated by the formula: Re(λ) = (nx - ny) × d, where d (nm) is the thickness of the layer (film). (3) Thickness Direction Retardation (Rth) "Rth(λ)" is the retardation in the thickness direction measured with light having a wavelength of λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction measured with light having a wavelength of 550 nm at 23°C. Rth(λ) is calculated by the formula: Rth(λ) = (nx - nz) x d, where d (nm) is the thickness of the layer (film). (4) Nz coefficient The Nz coefficient is calculated by Nz = Rth / Re. (5) Angle When an angle is mentioned in this specification, the angle includes both clockwise and counterclockwise angles relative to the reference direction. Therefore, for example, "45°" means ±45°.

[0012] [Optical Laminated Member] FIG. 1 is a schematic cross-sectional view showing the general configuration of an optical laminated member according to a first embodiment of the present invention.

[0013] The optical laminated member 1 has a first optical functional layer 31 and a second optical functional layer 32, which are laminated via an adhesive layer 40. Specifically, the first optical functional layer 31 and the second optical functional layer 32 are in direct contact with the adhesive layer 40. By using an optical laminated member 1 having such a configuration, it is possible to provide optical laminates with a high yield. The first optical functional layer 31 and the second optical functional layer 32 may each be a retardation layer (retardation member) or an absorptive polarizing film. The optical properties of the retardation member (e.g., refractive index characteristics, in-plane retardation, Nz coefficient, photoelastic coefficient) can be appropriately set depending on the purpose.

[0014] The optical laminate member 1 may be, for example, long and wound into a roll. Here, "long" refers to an elongated shape in which the length is sufficiently long relative to the width, for example, a long and thin shape in which the length is 10 times or more, preferably 20 times or more, relative to the width. Furthermore, for example, the optical laminate member 1 may be in the form of a sheet, and its planar shape may be, for example, rectangular or square.

[0015] In the optical laminated member 1, the thickness of the adhesive layer 40 is smaller than the thickness of the first optical functional layer 31. The thickness of the adhesive layer 40 is also smaller than the thickness of the second optical functional layer 32. The end faces of the adhesive layer 40 may be flush with the end faces of the first optical functional layer 31 and the second optical functional layer 32, or may be located more inward than the end faces of the first optical functional layer 31 and the second optical functional layer 32. With this configuration, when the optical laminated member is long, the substrate can be peeled off very well, as described below, and, for example, the optical laminated member has excellent roll transportability and can be wound into a roll.

[0016] The thickness of the first optical functional layer 31 and the thickness of the second optical functional layer 32 are each, for example, 8 μm or less, or may be 6 μm or less, 5 μm or less, or may be 4 μm or less. The thickness of the first optical functional layer 31 and the thickness of the second optical functional layer 32 are each, for example, 1 μm or more.

[0017] The absorptive polarizing film is typically composed of a film containing a dichroic substance such as iodine or an organic dye. The thickness of the absorptive polarizing film is, for example, 8 μm or less, and may be 6 μm or less, 5 μm or less, or 4 μm or less. On the other hand, the thickness of the absorptive polarizing film is, for example, 1 μm or more. The retardation member is typically composed of an oriented and solidified layer of a liquid crystal compound or a resin film. The thickness of the retardation member is, for example, 8 μm or less, and may be 6 μm or less, 5 μm or less, or 4 μm or less. On the other hand, the thickness of the retardation member is, for example, 1 μm or more.

[0018] The ratio of the thickness of the second optical functional layer 32 to the thickness of the first optical functional layer 31 is, for example, from 0.25 to 4, preferably from 0.4 to 2.5, and more preferably from 0.5 to 2. By laminating the first optical functional layer 31 and the second optical functional layer 32 having such thicknesses via the adhesive layer 40, excellent mechanical properties and ease of handling can be achieved.

[0019] When the optical laminated member 1 is a laminate of a retardation member and a retardation member, the ratio of the refractive index of the second optical functional layer 32 to the refractive index of the first optical functional layer 31 is preferably 0.9 or more and 1.1 or less. When the optical laminated member 1 is a laminate of a retardation member and a retardation member, the ratio of the transmittance of the second optical functional layer 32 to the transmittance of the first optical functional layer 31 is preferably 0.9 or more and 1.1 or less. When the optical laminated member 1 is a laminate of a retardation member and an absorptive polarizing film, the ratio of the transmittance of the retardation member to the transmittance of the absorptive polarizing film is preferably 1.7 or more and 2.7 or less.

[0020] When the optical laminated member 1 is a laminate of a retardation member and an absorptive polarizing film, and the retardation member has an optical axis (e.g., a slow axis), the optical axis of the retardation member and the optical axis of the absorptive polarizing film (e.g., an absorption axis, a transmission axis) can be aligned at any appropriate angle depending on the purpose, application, etc. When the retardation member included in the optical laminated member 1 is a λ / 4 member, the angle between the absorption axis of the absorptive polarizing film and the slow axis of the retardation member is, for example, 40° to 50°, or may be 42° to 48°, or may be approximately 45°. For example, in the optical laminated member 1, when natural light is incident perpendicularly on the main surface of the absorptive polarizing film, the ellipticity of light vertically emitted from the retardation member is preferably 0.5 or more. Furthermore, for example, when the retardation member included in the optical laminated member 1 is a λ / 2 member, the angle between the absorption axis or transmission axis of the absorptive polarizing film and the slow axis of the retardation member is, for example, 10° to 20°, or may be 12° to 18°, or may be approximately 15°. In the optical laminated member 1, it is preferable that the optical axis of the retardation member and the optical axis of the absorptive polarizing film are precisely aligned.

[0021] When the optical laminated member 1 is a laminate of a phase difference member and a phase difference member, one of which is a λ / 2 member and the other is a λ / 4 member, the angle between the slow axes is, for example, 50° to 70°, or may be 55° to 65°, or may be approximately 60°. In the optical laminated member 1, it is preferable that the optical axis of one phase difference member and the optical axis of the other phase difference member are precisely aligned.

[0022] In the optical laminated member 1, the ratio of the refractive index of the first optical functional layer 31 to the refractive index of the adhesive layer 40 is preferably 0.9 or more and 1.1 or less. In the optical laminated member 1, the ratio of the refractive index of the second optical functional layer 32 to the refractive index of the adhesive layer 40 is preferably 0.9 or more and 1.1 or less. In the optical laminated member 1, the ratio of the transmittance of the first optical functional layer 31 to the transmittance of the adhesive layer 40 is preferably 0.9 or more and 1.1 or less. In the optical laminated member 1, the ratio of the transmittance of the second optical functional layer 32 to the transmittance of the adhesive layer 40 is preferably 0.9 or more and 1.1 or less.

[0023] The tensile modulus of elasticity of the optical laminated member 1 (the tensile modulus of elasticity of the laminated portion from the first optical functional layer 31 to the second optical functional layer 32) is, for example, 10 MPa to 25 MPa.

[0024] The laminate smoothness of the optical laminated member 1 (the laminated portion laminate smoothness from the first optical functional layer 31 to the second optical functional layer 32) is preferably 0.6 arcmin or less, more preferably 0.5 arcmin or less. The laminate smoothness of the optical laminated member can be measured, for example, using a phase-shifting laser interferometer (manufactured by Zygo, product name "DynaFiz"). For example, the optical laminate is laminated on a microslide glass (manufactured by Matsunami Glass Industry Co., Ltd., product name "S200200") to prevent the inclusion of foreign matter, bubbles, and deformation lines, and degassed using a pressure degassing device (autoclave) to remove the influence of minute bubbles, and a measurement sample is obtained. Specifically, after degassing under conditions of 50 ° C, 0.5 MPa, and 30 minutes, the sample is allowed to cool at room temperature for 30 minutes or more to obtain a measurement sample. The sample is placed on a vibration-isolating measurement table, and a single-wavelength (633 nm) laser is used to interfere with a standard whose flatness is guaranteed, and the relative displacement within a predetermined area (a circle of 30 mm diameter) is measured. For analysis, the smoothness of the laminate (unit: arcmin) is defined as double the "Slope magnitude RMS" angle index obtained by extracting frequency values ​​from 0.1 / mm to 1 / mm (corresponding to 2σ).

[0025] FIG. 2 is a schematic cross-sectional view showing the overall configuration of an optical laminated member according to a second embodiment of the present invention. The optical laminated member 2 includes, in this order, a substrate (first substrate) 51, a first optical functional layer 31, an adhesive layer 40, a second optical functional layer 32, and a substrate (second substrate) 52. The second embodiment differs from the first embodiment in that the optical laminated member further includes a substrate 51 and a substrate 52. The substrate (first substrate) 51 may be a substrate used when forming the first optical functional layer 31. The substrate (second substrate) 52 may be a substrate used when forming the second optical functional layer 32. As described above, the first optical functional layer 31 and the second optical functional layer 32 may each be a retardation layer (retardation member) or an absorptive polarizing film.

[0026] <Absorptive Polarizing Film> The absorptive polarizing film is typically composed of a film containing a dichroic substance such as iodine or an organic dye. The crossed transmittance (Tc) of the absorptive polarizing film is preferably 0.5% or less, more preferably 0.1% or less, and even more preferably 0.05% or less. The single transmittance (Ts) of the absorptive polarizing film is, for example, 41.0% to 45.0%, and preferably 42.0% or more. The polarization degree (P) of the absorptive polarizing film is, for example, 99.0% to 99.997%, and preferably 99.8% or more.

[0027] For example, the absorptive polarizing film may be made of a resin film, and in this case, the absorptive polarizing film is preferably a polyvinyl alcohol (PVA) film containing iodine.

[0028] An example of a method for producing an absorptive polarizing film made of a resin film includes forming a polyvinyl alcohol-based resin layer (PVA-based resin layer) containing a polyvinyl alcohol-based resin (PVA-based resin) and a halide on one side of a long thermoplastic resin substrate to form a laminate, and subjecting the laminate to an auxiliary in-air stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in which the laminate is heated while being transported in the longitudinal direction to shrink the laminate by 2% or more in the width direction, in this order. The thickness of the resulting absorptive polarizing film can be controlled, for example, by adjusting the stretching ratio in the underwater stretching treatment.

[0029] The PVA-based resin layer is preferably formed by applying a coating liquid containing a PVA-based resin and a halide to a thermoplastic resin substrate and drying the coating liquid. The content of the halide 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 thickness of the PVA-based resin layer is preferably 3 to 40 μm, more preferably 3 to 20 μm.

[0030] Examples of the method for applying the coating liquid include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, knife coating (comma coating, etc.), etc. The temperature for applying and drying the coating liquid is preferably 50° C. or higher.

[0031] In order to improve the adhesion between the thermoplastic resin substrate and the PVA-based resin layer, the thermoplastic resin substrate may be subjected to a surface treatment such as a corona treatment before forming the PVA-based resin layer, or an easy-adhesion layer may be formed on the thermoplastic resin substrate.

[0032] The thickness of the thermoplastic resin substrate is preferably 20 μm to 300 μm, more preferably 50 μm to 200 μm. If the thickness is less than 20 μm, for example, it may be difficult to form a PVA-based resin layer. If the thickness is more than 300 μm, for example, in the underwater stretching treatment described below, it may take a long time for the thermoplastic resin substrate to absorb water, and an excessive load may be required for stretching.

[0033] The water absorption of the thermoplastic resin substrate is preferably 0.2% or more, more preferably 0.3% or more. The thermoplastic resin substrate can absorb water, which acts as a plasticizer to plasticize the substrate. As a result, the stretching stress can be significantly reduced, allowing the substrate to be stretched at a high ratio. On the other hand, the water absorption of the thermoplastic resin substrate is preferably 3.0% or less, more preferably 1.0% or less. Use of such a thermoplastic resin substrate can prevent problems such as a significant decrease in the dimensional stability of the substrate during production, resulting in poor appearance of the resulting absorptive polarizing film. Furthermore, it can prevent breakage of the substrate and peeling of the PVA-based resin layer from the substrate during underwater stretching. The water absorption of the thermoplastic resin substrate can be adjusted, for example, by introducing a modifying group into the constituent materials. The water absorption is a value determined in accordance with JIS K 7209.

[0034] The glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 120°C or lower. By using such a thermoplastic resin substrate, the stretchability of the laminate can be sufficiently ensured while suppressing crystallization of the PVA-based resin layer. Considering the plasticization of the thermoplastic resin substrate with water and the smooth underwater stretching, the Tg is more preferably 100°C or lower, and even more preferably 90°C or lower. On the other hand, the Tg of the thermoplastic resin substrate is preferably 60°C or higher. By using such a thermoplastic resin substrate, defects such as deformation of the substrate (e.g., the occurrence of unevenness, sagging, wrinkles, etc.) during the application and drying of the coating liquid can be prevented, allowing for the production of a satisfactory laminate. Furthermore, the PVA-based resin layer can be stretched at a suitable temperature (e.g., about 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 using a crystallizing material. The glass transition temperature (Tg) is a value determined in accordance with JIS K 7121.

[0035] 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 preferably used.

[0036] In one embodiment, an amorphous (non-crystallized) polyethylene terephthalate resin is preferably used. Among them, an amorphous (hard to crystallize) polyethylene terephthalate resin is preferably used. Specific examples of the amorphous polyethylene terephthalate resin include copolymers further containing isophthalic acid and / or cyclohexanedicarboxylic acid as a dicarboxylic acid, and copolymers further containing cyclohexanedimethanol or diethylene glycol as a glycol.

[0037] In a preferred embodiment, the thermoplastic resin substrate is composed of a polyethylene terephthalate resin having an isophthalic acid unit. Such a thermoplastic resin substrate has excellent stretchability and can suppress crystallization during stretching. This is thought to be due to the introduction of the isophthalic acid unit, which imparts a large curvature to the main chain. The polyethylene terephthalate resin has a terephthalic acid unit and an ethylene glycol unit. The content of the isophthalic acid unit is preferably 0.1 mol% or more, more preferably 1.0 mol% or more, based on the total of all repeating units. This is because a thermoplastic resin substrate with extremely excellent stretchability can be obtained. On the other hand, the content of the isophthalic acid unit is preferably 20 mol% or less, more preferably 10 mol% or less, based on the total of all repeating units. By setting such a content ratio, the crystallinity can be favorably increased during the drying shrinkage treatment described below.

[0038] The thermoplastic resin substrate may be stretched by any appropriate method before forming the PVA-based resin layer. For example, the long thermoplastic resin substrate may be stretched in the transverse direction. The transverse direction is preferably a direction approximately perpendicular to the stretching direction of the laminate described below. The stretching temperature of the thermoplastic resin substrate is preferably Tg-10°C to Tg+50°C relative to the glass transition temperature (Tg). The stretching ratio of the thermoplastic resin substrate is preferably 1.5 to 3.0 times.

[0039] As described above, the coating liquid may contain a PVA-based resin and a halide. The coating liquid may typically be a solution in which a PVA-based resin and a halide are dissolved in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. Among these, water is preferably used. The concentration of the PVA-based resin is preferably 3 to 20 parts by weight per 100 parts by weight of the solvent. The content of the halide in the coating liquid is preferably 5 to 20 parts by weight, more preferably 10 to 15 parts by weight, per 100 parts by weight of the PVA-based resin.

[0040] Examples of the PVA-based resin include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer is obtained by saponifying ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is, for example, 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The saponification degree can be determined in accordance with JIS K 6726-1994. The average polymerization degree of the PVA-based resin is, for example, 1,000 to 10,000, preferably 1,200 to 4,500, and more preferably 1,500 to 4,300. The average polymerization degree can be determined in accordance with JIS K 6726-1994. Examples of the halide include iodides such as potassium iodide, sodium iodide, and lithium iodide, and sodium chloride. Of these, potassium iodide is preferably used.

[0041] The coating liquid may contain additives. 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.

[0042] Stretching a PVA-based resin layer can increase the orientation of polyvinyl alcohol molecules in the PVA-based resin. However, immersing the stretched PVA-based resin layer in a liquid containing water can disrupt the orientation of the polyvinyl alcohol molecules, resulting in a decrease in the orientation. When a laminate of a thermoplastic resin and a PVA-based resin layer is stretched in boric acid water at a relatively high temperature to stabilize the stretching of the thermoplastic resin, the orientation tends to decrease significantly. In contrast, high-temperature stretching (auxiliary stretching) in air of a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin substrate before stretching in boric acid water can promote crystallization of the PVA-based resin in the PVA-based resin layer of the laminate after auxiliary stretching. As a result, when the PVA-based resin layer is immersed in a liquid, the disruption of the orientation of polyvinyl alcohol molecules and the decrease in the orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide. This can improve the optical properties of the absorptive polarizing film obtained by immersing the laminate in a liquid, such as through a dyeing treatment and an underwater stretching treatment.

[0043] To obtain high optical properties, a two-stage stretching method can be selected, combining in-air stretching (auxiliary stretching) and stretching in boric acid water. By introducing auxiliary stretching, stretching can be performed while suppressing crystallization of the thermoplastic resin substrate, thereby solving the problem of reduced stretchability due to excessive crystallization of the thermoplastic resin substrate during subsequent stretching in boric acid water, and allowing the laminate to be stretched at a high magnification. Furthermore, when a PVA-based resin is applied to a thermoplastic resin substrate, the application temperature must be lower than, for example, when the PVA-based resin is applied to a 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 is relatively low, which can lead to problems such as insufficient optical properties being obtained. In contrast, by introducing auxiliary stretching, it is possible to increase the crystallinity of the PVA-based resin, even when the PVA-based resin is applied to a thermoplastic resin, and high optical properties can be achieved. At the same time, by increasing the orientation of the PVA-based resin in advance, problems such as a decrease in the orientation of the PVA-based resin or dissolution when the PVA-based resin is immersed in water during subsequent dyeing or stretching treatments can be prevented, and high optical properties can be achieved.

[0044] The method of the auxiliary in-air stretching may be fixed-end stretching (e.g., a method of stretching using a tenter stretching machine) or free-end stretching (e.g., a method of uniaxially stretching a laminate by passing it between rolls having different peripheral speeds). From the viewpoint of obtaining high optical properties, free-end stretching is preferably used.

[0045] The draw ratio of the auxiliary in-air stretching is preferably 2.0 to 3.5. The auxiliary in-air stretching may be carried out in one stage or in multiple stages. When carried out in multiple stages, the draw ratio is the product of the draw ratios in each stage. The stretching direction in the auxiliary in-air stretching is preferably approximately the same as the stretching direction in the underwater stretching.

[0046] The stretching temperature for the auxiliary in-air stretching is preferably equal to or higher than the glass transition temperature (Tg) of the thermoplastic resin substrate, more preferably equal to or higher than Tg of the thermoplastic resin substrate + 10°C, and even more preferably equal to or higher than Tg of the thermoplastic resin substrate + 15°C. On the other hand, the upper limit of the stretching temperature is preferably 170°C. By stretching at such a temperature, rapid crystallization of the PVA-based resin can be suppressed, thereby suppressing defects due to crystallization (for example, preventing the orientation of the PVA-based resin layer due to stretching). The crystallization index of the PVA-based resin after the auxiliary in-air stretching is preferably 1.3 to 1.8, 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 performed using polarized light as the measurement light, and the crystallization index at 1141 cm of the obtained spectrum is measured. －１ and 1440 cm －１ The crystallization index is calculated using the intensity according to the following formula: Crystallization index = (I Ｃ / I Ｒ ) where I Ｃ is 1141 cm when measured with incident measuring light －１ is the intensity of I Ｒ is 1440 cm when measured with incident measuring light －１ is the strength.

[0047] After the auxiliary air-stretching treatment, an insolubilization treatment may be carried out before the underwater stretching treatment or the dyeing treatment. The insolubilization treatment is typically carried out by immersing the PVA-based resin layer in an aqueous boric acid solution. The insolubilization treatment imparts water resistance to the PVA-based resin layer, thereby preventing a decrease in the orientation of the PVA when immersed in water. The concentration of the aqueous boric acid solution used in the insolubilization treatment is preferably 1 to 4 parts by weight per 100 parts by weight of water. The liquid temperature of the insolubilization bath (aqueous boric acid solution) is preferably 20 to 50°C.

[0048] The dyeing treatment is typically carried out by dyeing the PVA-based resin layer with iodine. Specifically, the dyeing treatment is carried out by allowing the PVA-based resin layer to adsorb iodine. A preferred method for adsorbing iodine is to immerse the PVA-based resin layer (laminate) in a dye solution (dye bath) containing iodine.

[0049] The dye solution is preferably an aqueous iodine solution. In this case, the amount of iodine blended 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 blend an iodide into the aqueous iodine 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 preferably used. The amount of iodide blended 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 dye solution during dyeing is preferably 20 to 50°C to suppress dissolution of the PVA-based resin. When the PVA-based resin layer is immersed in the dye solution, the immersion time is preferably 5 seconds to 5 minutes, more preferably 30 seconds to 90 seconds, in order to ensure the transmittance of the PVA-based resin layer.

[0050] The dyeing conditions (concentration, solution temperature, and immersion time) can be set so that the single transmittance and polarization degree of the resulting absorptive polarizing film fall within the above-mentioned ranges. For example, the ratio of the iodine content to the potassium iodide content in the iodine aqueous solution used as the dyeing solution is preferably 1:5 to 1:20, and more preferably 1:5 to 1:10.

[0051] When a dyeing process is performed consecutively after a treatment (e.g., an insolubilization treatment) in which a laminate is immersed in a treatment bath containing boric acid, the boric acid contained in the treatment bath may be mixed into the dye bath, causing the boric acid concentration of the dye bath to change over time, resulting in unstable dyeability. To prevent this instability in dyeability, the upper limit of the boric acid concentration of the dye bath is preferably adjusted to 4 parts by weight, more preferably 2 parts by weight, per 100 parts by weight of water. Meanwhile, the lower limit of the boric acid concentration of the dye 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, a dye bath containing boric acid is used in advance. This can reduce the rate of change in boric acid concentration when the boric acid from the treatment bath is mixed into the dye bath. The amount of boric acid to be blended in advance into the dye bath (i.e., the content of boric acid not derived from the 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.

[0052] A crosslinking treatment may be performed after the dyeing treatment and before the underwater stretching treatment. The crosslinking treatment is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. The crosslinking treatment imparts water resistance to the PVA-based resin layer, thereby preventing a decrease in the orientation of the PVA when the layer is immersed in high-temperature water during the subsequent underwater stretching treatment. The concentration of the aqueous boric acid solution used in the crosslinking treatment is preferably 1 to 5 parts by weight per 100 parts by weight of water. Furthermore, when the crosslinking treatment is performed after the dyeing treatment, it is preferable to further incorporate an iodide. The incorporation of an iodide can suppress the elution of iodine adsorbed to the PVA-based resin layer. The amount of iodide incorporated is preferably 1 to 5 parts by weight per 100 parts by weight of water. Specific examples of iodides are as described above. The liquid temperature of the crosslinking bath (aqueous boric acid solution) is preferably 20 to 50°C.

[0053] The underwater stretching treatment is carried out by immersing the laminate in a stretching bath. Underwater stretching treatment allows stretching at a temperature lower than the glass transition temperatures (typically, about 80° C.) of the thermoplastic resin substrate and the PVA-based resin layer, and allows the PVA-based resin layer to be stretched while suppressing crystallization. As a result, a polarizing film having excellent optical properties can be produced.

[0054] Any appropriate method can be adopted as the stretching method for the laminate. Specifically, it may be fixed-end stretching or free-end stretching (for example, a method in which the laminate is uniaxially stretched by passing it 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. When it is carried out in multiple stages, the stretching ratio of the laminate described below is the product of the stretching ratios in each stage.

[0055] The underwater stretching is preferably performed by immersing the laminate in an aqueous boric acid solution (stretching in boric acid solution). Using an aqueous boric acid solution as a stretching bath can impart to the PVA-based resin layer rigidity sufficient to withstand the tension applied during stretching and water resistance sufficient to prevent dissolution in water. Specifically, boric acid generates tetrahydroxyborate anions in the aqueous solution, which can crosslink with the PVA-based resin through hydrogen bonding. As a result, the PVA-based resin layer is imparted with rigidity and water resistance, allowing for satisfactory stretching, and an absorptive polarizing film with excellent optical properties can be produced.

[0056] The boric acid aqueous solution is preferably obtained by dissolving boric acid and / or a borate in water as a solvent. The boric acid concentration is preferably 1 to 10 parts by weight, more preferably 2.5 to 7 parts by weight, and even more preferably 3 to 6 parts by weight, per 100 parts by weight of water. By adjusting the boric acid concentration to 1 part by weight or more, dissolution of the PVA-based resin layer can be effectively suppressed, allowing for the production of an absorptive polarizing film with even higher performance. In addition to boric acid or a borate, aqueous solutions obtained by dissolving boron compounds such as borax, glyoxal, glutaraldehyde, or the like in a solvent can also be used.

[0057] Preferably, an iodide is added to the stretching bath (boric acid aqueous solution). By adding an iodide, it is possible to suppress the elution of iodine adsorbed in the PVA-based resin layer. Specific examples of iodides are as described above. The concentration of the 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.

[0058] The stretching temperature (liquid temperature of the stretching bath) is preferably 40°C or higher, more preferably 60°C or higher. At such a temperature, good stretching can be achieved. 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 is lower than 40°C, good stretching may not be possible, even taking into account the plasticization of the thermoplastic resin substrate by water. On the other hand, the stretching temperature (liquid temperature of the stretching bath) is preferably 85°C or lower, more preferably 75°C or lower. The higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer, which may result in poor optical properties. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

[0059] In one embodiment, the stretching ratio in underwater stretching is preferably 1.0 to 2.2, more preferably 1.1 to 2.0, even more preferably 1.1 to 1.8, and particularly preferably 1.2 to 1.6. By setting the stretching ratio in underwater stretching within this range, it is possible to obtain, for example, a polarizing film in which breakage along the absorption axis direction is suppressed. The total stretching ratio of the laminate is preferably 3.0 to 4.5, more preferably 3.0 to 4.3, and even more preferably 3.0 to 4.0, times the original length of the laminate.

[0060] In one embodiment, the stretching ratio in 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 a high stretching ratio, an absorptive polarizing film with excellent optical properties can be produced. Such a high stretching ratio can be achieved by employing underwater stretching (stretching in boric acid water).

[0061] The drying shrinkage treatment may be performed by zone heating, which heats the entire zone, or by heating the transport rolls (using so-called heated rolls). Preferably, both methods are used. Drying using heated rolls efficiently suppresses heat curling of the laminate, resulting in the production of an absorptive polarizing film with excellent appearance. Specifically, drying the laminate while it is aligned with heated rolls efficiently promotes crystallization of the thermoplastic resin substrate, thereby increasing the crystallinity. Even at relatively low drying temperatures, the crystallinity of the thermoplastic resin substrate can be favorably increased. As a result, the rigidity of the thermoplastic resin substrate increases, enabling it to withstand shrinkage of the PVA-based resin layer due to drying, thereby suppressing curling. Furthermore, using heated rolls allows the laminate to be dried while maintaining a flat state, thereby suppressing not only curling but also wrinkling. In this case, 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 the PVA and the PVA / iodine complex can be effectively enhanced. The shrinkage rate of the laminate in the width direction due to the drying shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, and particularly preferably 4% to 6%. By using a heated roll, the laminate can be continuously shrunk in the width direction while being transported, thereby achieving high productivity.

[0062] For example, drying conditions can be controlled by adjusting the heating temperature of the transport rolls (temperature of the heating rolls), the number of heating rolls, the contact time with the heating rolls, etc. The temperature of the heating rolls is preferably 60°C to 120°C, more preferably 65°C to 100°C, and even more preferably 70°C to 80°C. This effectively increases the crystallinity of the thermoplastic resin, effectively suppressing curling and imparting excellent strength to the laminate. The temperature of the heating rolls can be measured using a contact thermometer. Typically, 2 to 40 transport rolls, preferably 4 to 30 rolls, are used. The contact time between the laminate and the heating rolls (total contact time) is preferably 1 to 300 seconds, more preferably 1 to 20 seconds, and even more preferably 1 to 10 seconds.

[0063] The heating rolls may be installed in a heating furnace (e.g., an oven) or in a normal production line (under room temperature). Preferably, they are installed in a heating furnace equipped with a blower. By using both heating roll drying and hot air drying, it is possible to suppress abrupt temperature changes between the heating rolls, and to easily control shrinkage in the width direction. The hot air drying temperature is preferably 30°C to 100°C. The hot air drying time is preferably 1 second to 300 seconds. The hot air speed is preferably about 10 m / s to 30 m / s. Note that this air speed is the air speed inside the heating furnace and can be measured using a mini-vane type digital anemometer.

[0064] Preferably, after the underwater stretching treatment and before the drying shrinkage treatment, a washing treatment is carried out by, for example, immersing the PVA-based resin layer in an aqueous potassium iodide solution.

[0065] <Retardation Member> As described above, the retardation member is typically composed of a liquid crystal compound alignment solidified layer or a resin film. The liquid crystal compound alignment solidified layer (hereinafter sometimes referred to as a liquid crystal alignment solidified layer) is a layer in which the liquid crystal compound is aligned in a predetermined direction within the layer, and the alignment state is fixed. Note that the "alignment solidified layer" is a concept that encompasses an alignment solidified layer obtained by curing a liquid crystal monomer, as described below.

[0066] In a retardation member that is a λ / 4 member or a λ / 2 member, rod-shaped liquid crystal compounds are typically aligned in the slow axis direction of the retardation member (homogeneous alignment). Examples of rod-shaped liquid crystal compounds include liquid crystal polymers and liquid crystal monomers. The liquid crystal compound is preferably polymerizable. If the liquid crystal compound is polymerizable, the alignment state of the liquid crystal compound can be fixed by aligning the liquid crystal compound and then polymerizing it.

[0067] The liquid crystal alignment solidified layer can be formed by performing an alignment treatment on the surface of a predetermined substrate, applying a coating liquid containing a liquid crystal compound to the surface to align the liquid crystal compound in a direction corresponding to the alignment treatment, and fixing the alignment state. Any appropriate alignment treatment can be used as the alignment treatment. Specific examples include mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment. Specific examples of mechanical alignment treatment include rubbing treatment and stretching treatment. Specific examples of physical alignment treatment include magnetic field alignment treatment and electric field alignment treatment. Specific examples of chemical alignment treatment include oblique vapor deposition and photoalignment treatment. Any appropriate treatment conditions can be used for the various alignment treatments depending on the purpose.

[0068] The alignment of liquid crystal compounds is achieved by treating them at a temperature at which they exhibit a liquid crystal phase depending on the type of liquid crystal compound. By performing such temperature treatment, the liquid crystal compounds assume a liquid crystal state and are aligned in accordance with the alignment treatment direction on the substrate surface.

[0069] In one embodiment, the alignment state is fixed by cooling the liquid crystal compound aligned as described above. When the liquid crystal compound is polymerizable or crosslinkable, the alignment state is fixed by subjecting the liquid crystal compound aligned as described above to a polymerization treatment or a crosslinking treatment.

[0070] Any suitable liquid crystal polymer and / or liquid crystal monomer can be used as the liquid crystal compound. The liquid crystal polymer and the liquid crystal monomer can be used alone or in combination. Specific examples of liquid crystal compounds and methods for producing a liquid crystal alignment solidified layer are described in, for example, JP 2006-163343 A, JP 2006-178389 A, and WO 2018 / 123551 A. The descriptions in these publications are incorporated herein by reference.

[0071] The retardation member may be, for example, a member whose refractive index characteristics exhibit the relationship nz > nx = ny (a so-called positive C plate). Here, "nx = ny" includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. The in-plane retardation Re(550) of the positive C plate is, for example, less than 10 nm.

[0072] A typical example of a material for the resin film constituting the positive C plate is a resin material having negative birefringence. A resin having negative birefringence is a resin that exhibits the property that, when uniaxially stretched, the refractive index in the direction perpendicular to the stretching direction is maximized. Examples of resins having negative birefringence include resins in which chemical bonds or functional groups with large polarization anisotropy, such as aromatic rings or carbonyl groups, are introduced into the side chain. Specific examples of resins having negative birefringence include acrylic resins, styrene resins, maleimide resins, modified polyolefin resins, fumaric acid ester resins, etc., and specific examples thereof can be found in JP 2021-076759 A, JP 2008-544304 A, JP 2008-544317 A, etc., for example. The above resin materials can be used alone or in combination of two or more.

[0073] The resin film constituting the positive C plate may further contain any appropriate additives as necessary. Specific examples of additives include plasticizers, heat stabilizers, light stabilizers, lubricants, antioxidants, UV absorbers, flame retardants, colorants, antistatic agents, compatibilizers, crosslinking agents, thickeners, etc. The type and content of the additives may be appropriately determined depending on the purpose. The content of the additives in the resin film is, for example, about 3% to 10% by weight.

[0074] In one embodiment, the resin material can be formed into a film and then used as a positive C plate as is. Specifically, the formed film can be used as a positive C plate as is without stretching. For example, when a resin solution containing the resin material is applied to a substrate (using a solution casting method) to form a film, stress occurs due to volume shrinkage when the resin solution dries on the substrate, and the polymer molecular chains tend to be oriented in the in-plane direction. When a resin material with high birefringence expression and negative intrinsic birefringence is used, a coating film with large thickness-direction birefringence can be formed on the substrate due to shrinkage during drying. The formed coating film can then be used as a positive C plate as is.

[0075] A preferred example of the alignment and solidification layer of a liquid crystal compound constituting the positive C plate is an alignment and solidification layer of a liquid crystal material fixed in homeotropic alignment. The liquid crystal material (liquid crystal compound) that can be homeotropically aligned may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of such liquid crystal compounds and methods for forming a positive C plate include the liquid crystal compounds and methods for forming the retardation layer described in paragraphs

[0020] to

[0028] of JP-A-2002-333642.

[0076] <Adhesive Layer> The form of the adhesive constituting the adhesive layer 40 is not particularly limited, and examples thereof include aqueous adhesives, solvent-based adhesives, hot-melt adhesives, and curing adhesives. Among these, aqueous adhesives or curing adhesives are preferably used because they allow the thickness of the adhesive layer to be reduced. The thickness of the adhesive layer is preferably 0.01 μm to 5 μm, more preferably 0.03 μm to 3 μm, and even more preferably 0.5 μm to 1.5 μm. The storage modulus of the adhesive layer at 25° C. is, for example, 1.0 MPa or more, and preferably 2.0 MPa to 1.0×10 ４ MPa.

[0077] As described above, a water-based adhesive is preferably used as the adhesive. By using a water-based adhesive, for example, the obtained optical laminate member can have excellent smoothness.

[0078] The aqueous adhesive preferably contains a PVA-based resin. From the viewpoint of adhesiveness, the average degree of polymerization of the PVA-based resin contained in the aqueous adhesive is preferably approximately 100 to 5,000, more preferably 1,000 to 4,000. From the viewpoint of adhesiveness, the average degree of saponification is preferably approximately 85 mol% to 100 mol%, more preferably 90 mol% to 100 mol%. The PVA-based resin preferably contains an acetoacetyl group, as this can provide excellent adhesion between the absorptive polarizing film and the retardation member. The acetoacetyl-group-containing PVA-based resin can be obtained, for example, by reacting a PVA-based resin with diketene using any method. The acetoacetyl-group modification degree of the acetoacetyl-group-containing PVA-based resin is, for example, 0.1 mol% or more, preferably 0.1 mol% to 40 mol%, more preferably 1 mol% to 20 mol%, and even more preferably 2 mol% to 7 mol%. The acetoacetyl-group modification degree can be measured by NMR.

[0079] The aqueous adhesive may contain any appropriate crosslinking agent. Examples of crosslinking agents include compounds having functional groups (e.g., methylol groups) reactive with the PVA-based resin. The aqueous adhesive may also contain a metal compound colloid. The metal compound colloid may be a dispersion of metal compound fine particles in a dispersion medium, which may be electrostatically stabilized due to mutual repulsion of like-charged particles of the fine particles, thereby providing permanent stability. The average particle diameter of the fine particles forming the metal compound colloid may be any appropriate value, as long as it does not adversely affect the optical properties of the absorptive polarizing film and the retardation member. The average particle diameter of the fine particles forming the metal compound colloid is, for example, 1 nm to 100 nm, preferably 1 nm to 50 nm. Such an average particle diameter allows the fine particles to be uniformly dispersed in the adhesive layer, ensuring adhesion while suppressing knicks. Here, "knicks" refers to localized irregularities that occur at the interface between the absorptive polarizing film and the retardation member.

[0080] As described above, the adhesive is preferably a curable adhesive that can be cured by a curing treatment (e.g., irradiation with active energy rays or heating). In this case, the adhesive layer 40 can be a cured layer of resin. The curable adhesive is preferably an ultraviolet curable adhesive.

[0081] The ultraviolet-curable adhesive contains a curable monomer such as a compound having a (meth)acryloyl group or a compound having a vinyl group. Preferably, a compound having a (meth)acryloyl group is used. Here, the (meth)acryloyl group refers to an acryloyl group and / or a methacryloyl group.

[0082] <Substrate> The thickness of the substrate is, for example, 10 μm to 80 μm, preferably 20 μm to 70 μm. The substrate can be composed of any appropriate film. Examples of materials that form the main component of the film constituting the substrate include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based resins such as polyethylene terephthalate (PET), polyvinyl alcohol-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyethersulfone-based resins, polysulfone-based resins, polystyrene-based resins, cycloolefin-based resins such as polynorbornene, polyolefin-based resins, (meth)acrylic resins, and acetate-based resins. For example, TAC film or PET film is preferably used as the substrate. Such films have the advantage of being less likely to deform during the optical functional layer formation process, and are less likely to suffer from defects such as dents and scratches when the optical functional layer formation material is applied and dried and then wound up. On the other hand, using a substrate that is less likely to deform tends to make it difficult to peel the substrate from the formed optical functional layer after the optical functional layer is formed. When the thickness of the optical functional layer is very thin, this tendency can become significant.

[0083] <Method of Use> The optical stack member according to the embodiment of the present invention can be combined with any suitable optical member and / or optical component.

[0084] 3A to 3C are diagrams illustrating an example of a method of using an optical stack according to one embodiment of the present invention.

[0085] 3A shows a state in which the second substrate 52 has been peeled off from the second optical functional layer 32 of the optical laminate member 2, exposing the surface 32a of the second optical functional layer 32. The second optical functional layer 32 can be formed by applying a material for forming the second optical functional layer 32 to the second substrate 52. The second optical functional layer 32 is fixed to the first optical functional layer 31 via the adhesive layer 40, so that the second substrate 52 can be easily peeled off from the second optical functional layer 32.

[0086] 3B shows a state in which a pressure-sensitive adhesive layer 41 for bonding the optical laminate member 1 to an optical member or optical component (not shown) is laminated on the second optical functional layer 32. Typically, the pressure-sensitive adhesive layer 41 is provided in advance on an optical film (e.g., a release liner) 53, and is laminated on the second optical functional layer 32 in this state.

[0087] 3C shows a state in which the first substrate 51 has been peeled off from the first optical functional layer 31, exposing the surface 31 a of the first optical functional layer 31. The first optical functional layer 31 can be formed by applying a material for forming the first optical functional layer 31 to the first substrate 51. Because the first optical functional layer 31 is fixed to the second optical functional layer 32 via the adhesive layer 40, the first substrate 51 can be easily peeled off from the first optical functional layer 31.

[0088] In the optical laminated member 2, the peel force F1 of the first substrate 51 relative to the first optical functional layer 31 is preferably greater than the peel force F2 of the second substrate 52 relative to the second optical functional layer 32, which peels from the optical laminated member 2 before the first substrate 51. The difference between these peel forces is, for example, 0.002 N / 50 mm to 0.2 N / 50 mm, and may be 0.02 N / 50 mm to 0.2 N / 50 mm. The ratio of the peel force F2 to the peel force F1 is, for example, 0.3 or more and less than 1, and may be 0.95 or less. The peel force F1 of the first substrate 51 relative to the first optical functional layer 31 is, for example, 0.05 N / 50 mm to 0.3 N / 50 mm, and may be 0.1 N / 50 mm or less.

[0089] Although not shown, after the first substrate 51 is peeled off from the first optical functional layer 31, an optical element or optical component may be laminated on the first optical functional layer 31. For example, another optical element may be laminated on the optical laminate member 1 to form an optical laminate. The optical laminate may be used in any appropriate display. For example, it may be suitably used in VR goggles.

[0090] FIG. 4 is a schematic diagram showing the general configuration of an example of a display system for VR goggles, and schematically illustrates the arrangement and shape of each component of the display system. The display system 10 includes a display element 12, a reflective polarizing element 14, a first lens unit 16, a half mirror 18, a first λ / 4 element 20, a second λ / 4 element 22, and a second lens unit 24. The reflective polarizing element 14 is disposed in front of the display surface 12a of the display element 12 and can reflect light emitted from the display element 12. The first lens unit 16 is disposed on the optical path between the display element 12 and the reflective polarizing element 14, and the half mirror 18 is disposed between the display element 12 and the first lens unit 16. The first λ / 4 element 20 is disposed on the optical path between the display element 12 and the half mirror 18, and the second λ / 4 element 22 is disposed on the optical path between the half mirror 18 and the reflective polarizing element 14.

[0091] The display element 12 is, for example, a liquid crystal display or an organic EL display, and has a display surface 12 a for displaying an image. The light emitted from the display surface 12 a passes through, for example, a polarizing member that may be included in the display element 12, and is converted into first linearly polarized light.

[0092] The first λ / 4 member 20 can convert the first linearly polarized light incident on the first λ / 4 member 20 into the first circularly polarized light. The first λ / 4 member 20 may be provided integrally with the display element 12.

[0093] The half mirror 18 transmits the light emitted from the display element 12 and reflects the light reflected by the reflective polarizing member 14 back toward the reflective polarizing member 14. The half mirror 18 is provided integrally with the first lens portion 16.

[0094] The second λ / 4 member 22 can transmit the light reflected by the reflective polarizing member 14 and the half mirror 18 through the reflective polarizing member 14. The second λ / 4 member 22 may be provided integrally with the first lens portion 16.

[0095] The first circularly polarized light output from the first λ / 4 member 20 passes through the half mirror 18 and the first lens portion 16, and is converted into the second linearly polarized light by the second λ / 4 member 22. The second linearly polarized light output from the second λ / 4 member 22 is reflected toward the half mirror 18 without passing through the reflective polarizing member 14. At this time, the polarization direction of the second linearly polarized light incident on the reflective polarizing member 14 is the same as the reflection axis of the reflective polarizing member 14. Therefore, the second linearly polarized light incident on the reflective polarizing member 14 is reflected by the reflective polarizing member 14.

[0096] The second linearly polarized light reflected by the reflective polarizing element 14 is converted into second circularly polarized light by the second λ / 4 element 22, and the second circularly polarized light emitted from the second λ / 4 element 22 passes through the first lens unit 16 and is reflected by the half mirror 18. The second circularly polarized light reflected by the half mirror 18 passes through the first lens unit 16 and is converted into third linearly polarized light by the second λ / 4 element 22. The third linearly polarized light is transmitted through the reflective polarizing element 14. At this time, the polarization direction of the third linearly polarized light incident on the reflective polarizing element 14 is the same direction as the transmission axis of the reflective polarizing element 14. Therefore, the third linearly polarized light incident on the reflective polarizing element 14 is transmitted through the reflective polarizing element 14.

[0097] The light transmitted through the reflective polarizing member 14 passes through the second lens portion 24 and enters the user's eye 26 .

[0098] The absorption axis of the polarizing member included in the display element 12 and the reflection axis of the reflective polarizing member 14 may be disposed approximately parallel to each other or approximately perpendicular to each other. The angle between the absorption axis of the polarizing member included in the display element 12 and the slow axis of the first λ / 4 member 20 is, for example, 40° to 50°, or may be 42° to 48°, or may be approximately 45°. The angle between the absorption axis of the polarizing member included in the display element 12 and the slow axis of the second λ / 4 member 22 is, for example, 40° to 50°, or may be 42° to 48°, or may be approximately 45°.

[0099] The in-plane retardation Re(550) of the first λ / 4 member 20 is, for example, 100 nm to 190 nm, or may be 110 nm to 180 nm, 130 nm to 160 nm, or 135 nm to 155 nm. The first λ / 4 member 20 preferably exhibits an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light. The Re(450) / Re(550) of the first λ / 4 member 20 may be, for example, 0.75 or more and less than 1, or 0.8 or more and 0.95 or less.

[0100] The in-plane retardation Re(550) of the second λ / 4 member 22 is, for example, 100 nm to 190 nm, or may be 110 nm to 180 nm, 130 nm to 160 nm, or 135 nm to 155 nm. The second λ / 4 member 22 preferably exhibits an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light. The Re(450) / Re(550) of the second λ / 4 member 22 may be, for example, 0.75 or more and less than 1, or 0.8 or more and 0.95 or less.

[0101] The optical laminate may include, for example, components that are included in the display system. Specifically, the optical laminate may include a phase difference component such as a λ / 4 component. The optical laminate may also include a polarizing component such as a reflective polarizing component or an absorptive polarizing film. The optical laminate may also include other components such as a protective component and an adhesive layer for integrating adjacent components. The thickness of the optical laminate may vary depending on, for example, the type and number of components included, but is, for example, 50 μm to 400 μm.

[0102] Fig. 5 is a schematic cross-sectional view showing an example of the details of an optical stack. The optical stack 3 includes a reflective polarizing element 14. The optical stack 3 further includes a positive C plate 31 and a third λ / 4 element 32 that can be disposed between the reflective polarizing element 14 and the second lens unit 24 in the display system 10. The optical stack 1 including the positive C plate 31 and the third λ / 4 element 32 is laminated in front of the reflective polarizing element 14 via an adhesive layer 41. In Fig. 5, the positive C plate 31 and the third λ / 4 element 32 are laminated below the reflective polarizing element 14.

[0103] The angle between the reflection axis of the reflective polarizing element 14 and the slow axis of the third λ / 4 element 32 is, for example, 40° to 50°, or may be 42° to 48°, or approximately 45°. By providing such an element, for example, in the display system 10, reflection of external light from the second lens unit 24 can be prevented. The in-plane retardation Re(550) of the third λ / 4 element 32 is, for example, 100 nm to 190 nm, 110 nm to 180 nm, 130 nm to 160 nm, or 135 nm to 155 nm. The third λ / 4 element 32 preferably exhibits an inverse dispersion wavelength characteristic in which the retardation value increases with the wavelength of the measurement light. The Re(450) / Re(550) of the third λ / 4 element is, for example, 0.75 or more but less than 1, or 0.8 or more but 0.95 or less.

[0104] The thickness direction retardation Rth(550) of the positive C plate 31 is preferably −20 nm to −300 nm, more preferably −40 nm to −250 nm, still more preferably −60 nm to −150 nm, and particularly preferably −70 nm to −110 nm.

[0105] The optical laminate 3 includes, for example, a pressure-sensitive adhesive layer 42 for integration with an adherend (for example, the second lens portion 24), and a release liner 54 is attached to the surface of the pressure-sensitive adhesive layer 42. For example, the pressure-sensitive adhesive layer 42 can be protected by the release liner 54.

[0106] As shown in Fig. 5, the optical laminate 3 may further include a protective member 33 that can be disposed behind the reflective polarizing member 14. In Fig. 5, the protective member 33 is laminated on the upper side of the reflective polarizing member 14. The protective member 33 is laminated on the reflective polarizing member 14 via an adhesive layer 43.

[0107] In the illustrated example, the optical laminate 3 includes a surface protection film 55 removably attached to the protective member 33. The surface protection film 55 may be peeled off before the optical laminate 3 is put into use (for example, before being laminated on the second lens portion 24) or during the manufacturing process of the final product (for example, VR goggles), or may be mounted directly on the final product.

[0108] The optical laminate 3 can be obtained by laminating a reflective polarizing member 14 and a protective member 33 on an optical laminate member 1, which is a laminated portion of a positive C plate 31, which is a retardation member, and a third λ / 4 member 32. The optical laminate 3 can be cut into a shape corresponding to the shape of the first lens unit or the second lens unit of the display system. For example, the optical laminate 3 can be cut into a shape such as a substantially ellipse or a substantially circle. The optical laminate 3 can then be provided integrally with the first lens unit or the second lens unit.

[0109] The refractive index characteristics of the λ / 4 member preferably exhibit the relationship nx>ny≧nz. Here, "ny=nz" includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, there may be cases where ny<nz, as long as the effects of the present invention are not impaired. The Nz coefficient of the λ / 4 member is preferably 0.9 to 3, more preferably 0.9 to 2.5, even more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3.

[0110] The first λ / 4 member 20 and the second λ / 4 member 22 may each be, for example, a liquid crystal alignment solidified layer or a stretched resin film.

[0111] The details of the liquid crystal alignment solidified layer constituting the λ / 4 member (phase difference member) are as described above. The thickness of the λ / 4 member constituted by the liquid crystal alignment solidified layer is, for example, 1 μm to 10 μm, preferably 1 μm to 8 μm, more preferably 1 μm to 6 μm, and even more preferably 1 μm to 4 μm.

[0112] Examples of resins contained in the resin film include polycarbonate resins, polyester carbonate resins, polyester resins, polyvinyl acetal resins, polyarylate resins, cyclic olefin resins, cellulose resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, and acrylic resins. These resins may be used alone or in combination. Examples of combination methods include blending and copolymerization. When the λ / 4 member exhibits reverse dispersion wavelength characteristics, a resin film containing a polycarbonate resin or a polyester carbonate resin (hereinafter sometimes simply referred to as a polycarbonate resin) can be suitably used.

[0113] Any suitable polycarbonate resin can be used as the polycarbonate resin. For example, the polycarbonate resin contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, and structural units derived from at least one dihydroxy compound selected from the group consisting of alicyclic diols, alicyclic dimethanols, di-, tri-, or polyethylene glycols, and alkylene glycols or spiroglycols. Preferably, the polycarbonate resin contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, structural units derived from an alicyclic dimethanol and / or structural units derived from di-, tri-, or polyethylene glycol; more preferably, it contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, and structural units derived from di-, tri-, or polyethylene glycol. The polycarbonate resin may contain structural units derived from other dihydroxy compounds as needed. Details of polycarbonate-based resins that can be suitably used for λ / 4 members and methods for forming λ / 4 members are described in, for example, JP 2014-10291 A, JP 2014-26266 A, JP 2015-212816 A, JP 2015-212817 A, and JP 2015-212818 A, and the descriptions in these publications are incorporated herein by reference.

[0114] The thickness of the λ / 4 member made of a stretched resin film is, for example, 10 μm to 100 μm, preferably 10 μm to 70 μm, and more preferably 20 μm to 60 μm.

[0115] The reflective polarizing element transmits light polarized parallel to its transmission axis (typically, linearly polarized light) while maintaining its polarization state, and can reflect light polarized in other states (typically, light polarized perpendicular to its transmission axis). The reflective polarizing element is typically composed of a film having a multilayer structure (sometimes referred to as a reflective polarizing film). In this case, the thickness of the reflective polarizing element is, for example, 10 μm to 150 μm, preferably 20 μm to 100 μm, and more preferably 30 μm to 60 μm.

[0116] FIG. 6 is a schematic perspective view showing an example of a multilayer structure included in a reflective polarizing film. The multilayer structure 14a has alternating birefringent layers A and substantially non-birefringent layers B. The total number of layers constituting the multilayer structure may be 50 to 1,000. 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 of layer B and the refractive index ny in the y-axis direction are substantially the same. 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.

[0117] The A layer is typically made of a material that exhibits birefringence upon stretching. Examples of such materials include naphthalenedicarboxylic acid polyesters (e.g., polyethylene naphthalate), polycarbonates, and acrylic resins (e.g., polymethyl methacrylate). The B layer is typically made of a material that does not substantially exhibit birefringence upon stretching. Examples of such materials include copolyesters of naphthalenedicarboxylic acid and terephthalic acid. The multilayer structure can be formed by a combination of coextrusion and stretching. For example, the materials constituting the A layer and the B layer 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.

[0118] Commercially available reflective polarizing films include, for example, "DBEF" and "APF" manufactured by 3M, and "APCF" manufactured by Nitto Denko Corporation.

[0119] The crossed transmittance (Tc) of the reflective polarizing element (reflective polarizing film) can be, for example, 0.001% to 3%. The single transmittance (Ts) of the reflective polarizing element (reflective polarizing film) can be, for example, 43% to 49%, preferably 45% to 47%. The polarization degree (P) of the reflective polarizing element (reflective polarizing film) can be, for example, 92% to 99.99%.

[0120] The crossed transmittance, single transmittance, and degree of polarization can be measured, for example, using an ultraviolet-visible spectrophotometer. The degree of polarization P can be calculated from the obtained Tp and Tc by measuring the single transmittance Ts, parallel transmittance Tp, and crossed transmittance Tc using an ultraviolet-visible spectrophotometer, using the following formula: Ts, Tp, and Tc are Y values ​​measured using a 2-degree visual field (C light source) according to JIS Z 8701 and corrected for visibility. Degree of polarization P (%) = {(Tp - Tc) / (Tp + Tc)} １／２ ×100

[0121] The protective member typically includes a substrate. The substrate can be composed of any appropriate film. Examples of materials that form the main component of the film that constitutes the substrate include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, polysulfone-based, polystyrene-based, cycloolefin-based resins such as polynorbornene, polyolefin-based, (meth)acrylic, and acetate-based resins. Here, (meth)acrylic refers to acrylic and / or methacrylic. The thickness of the substrate is preferably 5 μm to 80 μm, more preferably 10 μm to 50 μm, and even more preferably 15 μm to 40 μm.

[0122] The protective member is preferably composed of a laminated film having a substrate and a surface treatment layer formed on the substrate. The thickness of the laminated film is preferably 10 μm to 80 μm, more preferably 15 μm to 60 μm, and even more preferably 20 μm to 45 μm. The thickness of the surface treatment layer is preferably 0.5 μm to 10 μm, more preferably 1 μm to 7 μm, and even more preferably 2 μm to 5 μm.

[0123] The surface treatment layer typically includes a hard coat layer. The hard coat layer is typically formed by applying a hard coat layer-forming material to a substrate and curing the applied layer. The hard coat layer-forming material typically includes a curable compound as a layer-forming component. Examples of the curable compound's curing mechanism include heat curing and photocuring. Examples of the curable compound include monomers, oligomers, and prepolymers. Preferably, a polyfunctional monomer or oligomer is used as the curable compound. Examples of the polyfunctional monomer or oligomer include a monomer or oligomer having two or more (meth)acryloyl groups, a urethane (meth)acrylate or a urethane (meth)acrylate oligomer, an epoxy-based monomer or oligomer, and a silicone-based monomer or oligomer.

[0124] The thickness of the hard coat layer is preferably 0.5 μm to 10 μm, more preferably 1 μm to 7 μm, and even more preferably 2 μm to 5 μm.

[0125] The surface treatment layer preferably includes a functional layer. The functional layer preferably functions as an antireflection layer. In a preferred embodiment, the surface treatment layer includes the hard coat layer and the antireflection layer in this order from the substrate side. The thickness of the functional layer is preferably 0.05 μm to 10 μm, more preferably 0.1 μm to 5 μm, and even more preferably 0.1 μm to 2 μm.

[0126] The surface protection film typically comprises a laminate of a substrate film and a pressure-sensitive adhesive layer. Materials for forming the substrate film include polyester-based polymers such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT); cellulose-based polymers such as diacetyl cellulose and triacetyl cellulose; polycarbonate-based polymers; (meth)acrylic polymers such as polymethyl methacrylate; and cycloolefin-based polymers such as polynorbornene. These may be used alone or in combination of two or more. The thickness of the substrate film is preferably 15 μm to 70 μm, more preferably 20 μm to 60 μm, and even more preferably 25 μm to 50 μm. The thickness of the pressure-sensitive adhesive layer is, for example, 5 μm to 15 μm. Furthermore, a self-adhesive film may be used as the surface protection film.

[0127] The release liner may typically be made of any suitable plastic film. Specific examples of plastic films include polyethylene terephthalate (PET) film, polyethylene film, and polypropylene film. A plastic film whose surface is coated with a release agent is preferably used as the release liner. Examples of the release agent include silicone-based release agents, fluorine-based release agents, and long-chain alkyl acrylate-based release agents.

[0128] The thickness of the release liner is preferably 30 μm or more, more preferably 40 μm or more, and even more preferably 50 μm or more, and is, for example, 100 μm or less.

[0129] As shown in the figure, the components included in the optical laminate 3 can be integrated via an adhesive layer (e.g., a pressure-sensitive adhesive layer). The optical laminate 3 may also be integrally provided on the second lens portion of the display system via an adhesive layer (e.g., a pressure-sensitive adhesive layer). The adhesive layer may be formed of an adhesive or a pressure-sensitive adhesive. The thickness of the adhesive layer is, for example, 0.05 μm to 30 μm, preferably 0.5 μm to 20 μm, and more preferably 3 μm to 15 μm.

[0130] The pressure-sensitive adhesive layer can be composed of any appropriate pressure-sensitive adhesive. Specific examples include acrylic pressure-sensitive adhesives, rubber pressure-sensitive adhesives, silicone pressure-sensitive adhesives, polyester pressure-sensitive adhesives, urethane pressure-sensitive adhesives, epoxy pressure-sensitive adhesives, and polyether pressure-sensitive adhesives. By adjusting the type, number, combination, and compounding ratio of monomers forming the base resin of the pressure-sensitive adhesive, as well as the compounding amount of cross-linking agent, reaction temperature, reaction time, etc., a pressure-sensitive adhesive having desired properties according to the purpose can be prepared. The base resin of the pressure-sensitive adhesive may be used alone or in combination of two or more types. An acrylic resin is preferably used as the base resin. Specifically, the pressure-sensitive adhesive layer is preferably composed of an acrylic pressure-sensitive adhesive.

[0131] For example, the pressure-sensitive adhesive layer can be formed by applying a pressure-sensitive adhesive composition containing a base resin, additives such as a crosslinking agent, and a solvent, followed by drying. The pressure-sensitive adhesive composition may be applied directly to the adherend, or may be applied to a separately prepared substrate such as a base film (e.g., a release liner). Drying is typically performed by heating.

[0132] Although not shown, from the viewpoint of improving visibility, for example, the optical laminate 3 may further include an absorptive polarizing film that can be disposed between the reflective polarizing element 14 and the second lens portion 24. The reflection axis of the reflective polarizing element 14 and the absorption axis of the absorptive polarizing film can be disposed approximately parallel to each other, and the transmission axis of the reflective polarizing element 14 and the transmission axis of the absorptive polarizing film can be disposed approximately parallel to each other.

[0133] The present invention will be described in detail below using examples, but the present invention is not limited to these examples. The thickness, retardation value, refractive index, transmittance, and storage modulus were measured using the following measurement methods. Unless otherwise specified, "parts" and "%" are based on weight. <Thickness> Thicknesses of 10 μm or less were measured using a scanning electron microscope (manufactured by JEOL Ltd., product name "JSM-7100F"). Thicknesses exceeding 10 μm were measured using a digital micrometer (manufactured by Anritsu Corporation, product name "KC-351C"). <Retardation Value> Retardation values ​​at each wavelength at 23°C were measured using a Mueller matrix polarimeter (manufactured by Axometrics, product name "Axoscan"). <Refractive Index> A prism coupler (Model 2010 / M manufactured by Metricon) was used to measure the in-plane and thickness-direction refractive indices of the film or layer to be measured, and the average value was calculated to determine the refractive index (average refractive index). The measurement temperature was 23°C, and the measurement wavelengths were 407nm, 594nm, and 782nm. The refractive index at 550nm was calculated from the obtained measured values ​​and Cauchy's dispersion equation. <Transmittance> A transmittance spectrum was measured using a UV-visible spectrophotometer (LPF200, manufactured by Otsuka Electronics Co., Ltd.), and the transmittance at a wavelength of 550nm was read from the obtained spectrum. <Storage Modulus> The measurement object (for example, an adhesive layer and a pressure-sensitive adhesive layer) was molded to a thickness of 2mm by lamination. This molded product was punched into a disk shape with a diameter of 7.9mm to prepare a test specimen. This test specimen was sandwiched between parallel plates, and dynamic viscoelasticity measurement was performed under the following conditions using a dynamic viscoelasticity measuring device ("Advanced Rheometric Expansion System (ARES)" manufactured by Rheometric Scientific Co., Ltd.), and the storage modulus at 25°C was determined. (Measurement conditions) Deformation mode: torsion Measurement frequency: 1 Hz Measurement temperature: -40°C to +150°C Heating rate: 5°C / min

[0134] Example 1 (Preparation of λ / 4 Member) 55 parts of a compound represented by formula (I), 25 parts of a compound represented by formula (II), and 20 parts of a compound represented by formula (III) were added to 400 parts of cyclopentanone (CPN), heated to 60°C, and stirred to dissolve. After dissolution was confirmed, the mixture was returned to room temperature, and 3 parts of Irgacure 907 (manufactured by BASF Japan Ltd.), 0.2 parts of Megafac F-554 (manufactured by DIC Corporation), and 0.1 parts of p-methoxyphenol (MEHQ) were added and further stirred to obtain a solution. The solution was transparent and homogeneous. The resulting solution was filtered through a 0.20 μm membrane filter to obtain a polymerizable composition. The polyimide solution for the alignment film was applied to a 40 μm-thick TAC film (substrate) using a spin coating method, dried at 100°C for 10 minutes, and then baked at 200°C for 60 minutes to obtain a coating film. The resulting coating film was subjected to rubbing treatment using a commercially available rubbing device to form an alignment film. The polymerizable composition obtained above was applied to the alignment film side of the substrate by spin coating, and dried at 100°C for 2 minutes. After cooling the resulting coating film to room temperature, it was irradiated with 30 mW / cm using a high-pressure mercury lamp. ２ The film was irradiated with ultraviolet light at an intensity of 1000 nm for 30 seconds to obtain a 3 μm thick liquid crystal alignment solidified layer. The obtained liquid crystal alignment solidified layer had an in-plane retardation Re(550) of 130 nm, an Re(450) / Re(550) of 0.851, and exhibited reverse dispersion wavelength characteristics. The obtained liquid crystal alignment solidified layer also had a refractive index of 1.57 and a transmittance of 90.2%.

[0135]

[0136] (Formation of Positive C Plate 1) A liquid crystal coating solution was prepared by dissolving 20 parts by weight of a side-chain liquid crystal polymer represented by the following chemical formula (1) (the numbers 65 and 35 in the formula indicate the mole percentage of the monomer unit, and are conveniently expressed as a block polymer; weight-average molecular weight 5000), 80 parts by weight of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name Paliocolor LC242), and 5 parts by weight of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals: trade name Irgacure 907) in 200 parts by weight of cyclopentanone. The coating solution was then applied to a PET film (substrate) that had been subjected to vertical alignment treatment using a bar coater, and the liquid crystal was aligned by heating and drying at 80°C for 4 minutes. The liquid crystal layer was irradiated with ultraviolet light to harden it, thereby forming a positive C plate 1 on the substrate, which had a thickness of 4 μm, an Rth(550) of −100 nm, a refractive index of 1.62, and a transmittance of 88.8%.

[0137] (Preparation of adhesive) 20 parts by weight of acryloyl morpholine (manufactured by Kojin Co., Ltd., "ACMO (registered trademark)"), 50 parts by weight of unsaturated fatty acid hydroxyalkyl ester-modified ε-caprolactone (manufactured by Daicel Corporation, trade name "Placcel FA-1DDM"), 10 parts by weight of polyethylene glycol diacrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Acrylate 9EG-A"), 15 parts by weight of an acrylic polymer (manufactured by Toa Gosei Co., Ltd., "ARFON UP-1190"), 3 parts by weight of a photopolymerization initiator (manufactured by IGM Resins, trade name "Omnirad 907"), and 2 parts by weight of a photopolymerization initiator (manufactured by Nippon Kayaku Co., Ltd., trade name "KAYACURE DETX-S") were mixed to prepare an adhesive. The obtained adhesive was then exposed to a high-pressure mercury lamp with an integrated light intensity of 300 mJ / cm ２ The resulting adhesive layer, which was 1 μm thick and cured by irradiation with ultraviolet light, had a refractive index of 1.51, a transmittance of 92.0%, and a storage modulus of 2.6 MPa.

[0138] (Production of optical laminated member) The adhesive was applied to each of the λ / 4 member formed on the substrate and the positive C plate 1 formed on the substrate so that the thickness after curing was 0.4 μm, and the adhesives were bonded together. After that, a high-pressure mercury lamp was used to apply an integrated light amount of 300 mJ / cm ２ The adhesive was cured by irradiation with ultraviolet light of 1000 kJ / cm, and an optical laminated member was obtained.

[0139] Example 2 A retardation member was obtained in the same manner as in Example 1, except that the positive C plate 2 described below was used instead of the positive C plate 1.

[0140] (Formation of Positive C Plate 2) 48 parts by weight of hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "Metolose 60SH-50"), 15,601 parts by weight of distilled water, 8,161 parts by weight of diisopropyl fumarate, 240 parts by weight of 3-ethyl-3-oxetanylmethyl acrylate, and 45 parts by weight of t-butyl peroxypivalate as a polymerization initiator were placed in an autoclave equipped with a stirrer, a cooling tube, a nitrogen inlet tube, and a thermometer. Nitrogen bubbling was performed for 1 hour, and then the mixture was stirred at 49°C for 24 hours to carry out radical suspension polymerization. The mixture was then cooled to room temperature, and the suspension containing the produced polymer particles was centrifuged. The resulting polymer was washed twice with distilled water and twice with methanol, and then dried under reduced pressure to obtain a fumarate ester-based resin.

[0141] The obtained fumarate ester resin was dissolved in a toluene-methyl ethyl ketone mixed solution (toluene / methyl ethyl ketone 50% by weight / 50% by weight) to prepare a solution with a solids concentration of 20% by weight. Furthermore, 5 parts by weight of tributyl trimellitate as a plasticizer was added to 100 parts by weight of the fumarate ester resin to prepare a dope. A biaxially stretched polyethylene terephthalate film with a thickness of 75 μm and a width of 1,350 mm was prepared as a substrate. The substrate roll was set in the unwinding section of a film-forming device, and while the substrate was unwound and transported downstream, the dope was applied to the substrate to a film thickness of 4 μm after drying and dried at 140°C. In this way, a positive C plate 2 with an Rth(550) of -25 nm, a refractive index of 1.47, and a transmittance of 92.8% was formed on the substrate.

[0142] [Comparative Example 1 and Comparative Example 2] An optical laminated member was obtained in the same manner as in Example 1 and Example 2, except that the λ / 4 member formed on the substrate and the positive C plate formed on the substrate were bonded together using the following pressure-sensitive adhesive layer instead of the adhesive.

[0143] (Formation of Pressure-Sensitive Adhesive Layer) A four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser was charged with a monomer mixture containing 92 parts by weight of butyl acrylate, 2.9 parts by weight of acrylic acid, 0.1 parts by weight of 2-hydroxyethyl acrylate, and 5 parts by weight of N-acryloylmorpholine. Furthermore, 0.1 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator and 200 parts by weight of ethyl acetate were charged to 100 parts by weight of this monomer mixture. Nitrogen gas was introduced while gently stirring to replace the atmosphere in the flask with nitrogen, and the liquid temperature in the flask was maintained at around 55°C for 8 hours to carry out a polymerization reaction, thereby preparing an acrylic polymer solution with a weight-average molecular weight (Mw) of 1.78 million. The obtained acrylic polymer solution was coated and dried to form a pressure-sensitive adhesive layer having a thickness of 5 μm, a refractive index of 1.47, a transmittance of 92.8%, and a storage modulus of 0.11 MPa on a release liner.

[0144] [Comparative Example 3] (Production Example 1: Preparation of λ / 4 Member) 10 g of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF under the trade name "Paliocolor LC242") and 3 g of a photopolymerization initiator for the polymerizable liquid crystal compound (manufactured by BASF under the trade name "Irgacure 907") were dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid). The surface of a 40 μm thick TAC film was rubbed with a rubbing cloth to perform an alignment treatment. The liquid crystal coating liquid was applied to this alignment-treated surface using a bar coater, and the liquid crystal compound was aligned by heating and drying at 90°C for 2 minutes. The liquid crystal layer thus formed was then irradiated with 1 mJ / cm using a metal halide lamp. ２The liquid crystal layer was cured by irradiating the PET film with light, forming a retardation layer, which was a liquid crystal alignment solidified layer. The retardation layer had a thickness of 1.5 μm and an in-plane retardation Re(590) of 140 nm. Furthermore, the retardation layer exhibited a refractive index characteristic of nx>ny=nz. The retardation layer also had a refractive index of 1.59, a transmittance of 89.6%, and an Re(450) / Re(550) of 1.089, demonstrating positive dispersion wavelength characteristics.

[0145] (Production of λ / 2 member) A retardation layer having an in-plane retardation Re(590) of 270 nm was obtained in the same manner as in Production Example 1, except that the thickness of the retardation layer was 2.5 μm. The retardation layer exhibited a refractive index characteristic of nx>ny=nz. The refractive index of the retardation layer was 1.59, the transmittance was 89.6%, and Re(450) / Re(550) was 1.089, showing positive dispersion wavelength characteristics.

[0146] (Preparation of optical laminated member) The λ / 4 member formed on the substrate and the λ / 2 member formed on the substrate were bonded together using the pressure-sensitive adhesive layer so that the slow axes of the respective members were at an angle of 60° to obtain an optical laminated member.

[0147] <Evaluation> The peel strength of the substrates on both sides of the optical laminated members obtained in the Examples and Comparative Examples, and the tensile modulus of the laminated portion from which the substrates on both sides of the optical laminated members obtained in the Examples and Comparative Examples were peeled, were evaluated as follows. The evaluation results are shown in Tables 1 and 2. (1) Peel Strength Samples were cut from the obtained optical laminated members to a size of 50 mm wide and 150 mm long, and left in an environment of 23 ° C x 50% RH for 30 minutes or more. After that, the peel strength (N / 50 mm) was measured when peeled in the longitudinal direction at a peel rate of 300 mm / min and a peel angle of 180 ° using a universal tensile tester. Specifically, the peel strength of the substrate from the λ / 4 member and the positive C plate or λ / 2 member was measured. The measurements were performed in an environment of 23 ° C x 50% RH. Three measurement samples were prepared for each Example and Comparative Example, and the average values ​​of the obtained measurements are shown in the table below. (2) Tensile Modulus of Elasticity The measurement object was molded into a tensile test dumbbell with a parallel portion width of 10 mm and a length of 40 mm in accordance with JIS K 6734:2000. This was pulled in the longitudinal direction at a pulling rate of 300 mm / min using a tensile tester (Shimadzu Corporation, "Autograph AG-Xplus"), and the tensile modulus was calculated from the slope of the line at test forces of 10 N to 20 N in the obtained stress-strain curve. Measurements were performed in an environment of 23°C and a relative humidity of 50% RH. Three measurement samples were prepared for each example and comparative example, and the average values ​​of the obtained measurements are shown in the table below. In Table 1, "MD" and "TD" indicate directions at +45° and -45°, respectively, relative to the slow axis of the λ / 4 member. In Table 2, "MD" indicates a direction at +75° to the slow axis of the λ / 4 member and +15° to the slow axis of the λ / 2 member, and "TD" indicates a direction perpendicular to "MD".

[0148]

[0149]

[0150] The substrate (TAC film) could be successfully peeled from the optical laminated members obtained in Examples 1 and 2. The rate of peeling failure was 0%. Then, a 15 μm thick adhesive layer formed on a release liner (polyethylene terephthalate film treated with a silicone-based release agent, thickness 50 μm, manufactured by Mitsubishi Chemical Corporation, "Diafoil MHE50") could be laminated onto the release surface (λ / 4 member). Then, the other substrate (PET film) could be successfully peeled from the optical laminated member. The rate of peeling failure was 0%.

[0151] In contrast, when the substrate (TAC film) was peeled from the optical laminated members obtained in Comparative Examples 1 and 2, peeling defects occurred. The incidence of peeling defects was 20% in both Comparative Examples 1 and 2. Specifically, when the substrate (TAC film) was peeled from the λ / 4 member, the λ / 4 member (liquid crystal alignment solidified layer) was torn. Furthermore, a portion of the λ / 4 member (liquid crystal alignment solidified layer) was attached to the substrate. A 15 μm thick pressure-sensitive adhesive layer formed on a release liner (polyethylene terephthalate film treated with a silicone-based release agent, 50 μm thick, manufactured by Mitsubishi Chemical Corporation, "Diafoil MHE50") was then laminated onto the release surface (λ / 4 member). Then, when the other substrate (PET film) was peeled from the optical laminated member, peeling defects occurred. The incidence of peeling defects was 8% in both Comparative Examples 1 and 2. Specifically, when the substrate (PET film) was peeled from the positive C plate, the positive C plate was torn. In addition, a part of the positive C-plate was attached to the substrate.

[0152] In addition to the above examples and comparative examples, a 15 μm thick adhesive layer formed on a release liner (polyethylene terephthalate film treated with a silicone-based release agent, 50 μm thick, manufactured by Mitsubishi Chemical Corporation, "Diafoil MHE50") was first laminated onto the λ / 4 member formed on the substrate, and then a positive C-plate formed on the substrate was attempted to be laminated. When the substrate was peeled from the λ / 4 member, peeling failure occurred (peeling failure rate: 24%). Specifically, the λ / 4 member (liquid crystal alignment solidified layer) was torn when the substrate was peeled from the λ / 4 member. In addition, a part of the λ / 4 member (liquid crystal alignment solidified layer) was attached to the substrate.

[0153] Furthermore, when an optical element (polarizing element) was first laminated on the λ / 4 element formed on the substrate using the adhesive layer, and then a positive C plate formed on the substrate was attempted to be laminated, peeling failure occurred when peeling the substrate from the λ / 4 element (peeling failure rate: 12%). Specifically, the λ / 4 element (liquid crystal alignment solidified layer) was torn when peeling the substrate from the λ / 4 element.

[0154] In the optical laminated member obtained in Comparative Example 3, similar to Comparative Examples 1 and 2, poor peeling of the substrate occurred.

[0155] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the configurations shown in the above-described embodiment can be replaced with configurations that are substantially the same as those shown in the above-described embodiment, that have the same effects, or that can achieve the same purpose.

[0156] The optical laminate member according to the embodiment of the present invention can be used in a display such as, for example, VR goggles.

[0157] 1 Optical laminated member, 2 Optical laminated member, 3 Optical laminate, 10 Display system, 12 Display element, 14 Reflective polarizing member, 16 First lens portion, 18 Half mirror, 20 First λ / 4 member, 22 Second λ / 4 member, 24 Second lens portion, 26 User's eye, 31 First optical functional layer (positive C plate), 32 Second optical functional layer (third λ / 4 member), 33 Protective member, 40 Adhesive layer, 41 Pressure-sensitive adhesive layer, 42 Pressure-sensitive adhesive layer, 43 Pressure-sensitive adhesive layer, 51 Substrate (first substrate), 52 Substrate (second substrate), 53 Optical film (release liner), 54 Release liner, 55 Surface protective film.

Claims

1. An optical laminated member having a first optical functional layer having a thickness of 8 μm or less and a second optical functional layer having a thickness of 8 μm or less, wherein the first optical functional layer and the second optical functional layer are laminated via an adhesive layer, the ratio of the thickness of the second optical functional layer to the thickness of the first optical functional layer is 0.25 or more and 4 or less, the thickness of the adhesive layer is smaller than the thickness of the first optical functional layer, and the thickness of the adhesive layer is smaller than the thickness of the second optical functional layer.

2. An optical laminated member as described in claim 1, wherein the end face of the adhesive layer is flush with the end faces of the first optical functional layer and the second optical functional layer, or is located inside the end faces of the first optical functional layer and the second optical functional layer.

3. The optical laminated member according to claim 1, having a tensile modulus of elasticity of 10 MPa to 25 MPa.

4. A method for manufacturing an optical laminate, comprising: preparing an optical laminate member in which a first optical functional layer formed on a first substrate and a second optical functional layer formed on a second substrate are laminated via an adhesive layer; peeling at least one of the first substrate and the second substrate from the optical laminate member; and laminating another optical component on the surface exposed by peeling the substrate, wherein the thickness of the first optical functional layer is 8 μm or less, the thickness of the second optical functional layer is 8 μm or less, the ratio of the thickness of the second optical functional layer to the thickness of the first optical functional layer is 0.25 or more and 4 or less, the thickness of the adhesive layer is smaller than the thickness of the first optical functional layer, and the thickness of the adhesive layer is smaller than the thickness of the second optical functional layer.

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