Optical element, optical system, optical apparatus, display apparatus, and image pickup apparatus

Abstract

To provide an optical element in which a resin layer is integrated between two base materials via an adhesive layer and which can reduce or prevent deterioration in optical characteristics due to a temperature difference.SOLUTION: The optical device includes a first base material, a first adhesive layer, a resin layer having a reflective property, a second adhesive layer, and a second base material, wherein the first base material, the first adhesive layer, the resin layer, the second adhesive layer, and the second base material are laminated in this order, and the optical device satisfies the following formula (1-1) when an average thickness of the first adhesive layer is T1, a Young's modulus of the first adhesive layer is E1, an average thickness of the second adhesive layer is T2, and a Young's modulus of the second adhesive layer is E2: 1.1 * T1 / E1 ≤ T2 / E2 (1-1) SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an optical element, an optical system, an optical instrument, a display device, and an imaging device. [Background technology]

[0002] Head-mounted displays (HMDs) are used in various fields, such as virtual reality (VR), augmented reality (AR), and mixed reality (MR). HMDs have an optical system that focuses images displayed on a display panel at the user's eye position. To improve the sense of immersion, realism, and comfort, HMDs are expected to have high image quality, a wide angle of view, and be compact and lightweight. To achieve this, HMDs employ a folding optical system that folds the optical path using circularly polarized light and a transmissive / reflective layer.

[0003] In recent years, attempts have been made to apply folding optical systems to imaging optical systems such as camera lenses, thereby improving the image quality of camera lenses and making them smaller and lighter.

[0004] Such folded optical systems require a reflective polarizing layer, which transmits light of a certain polarization direction and reflects light of a polarization direction perpendicular to the transmitted light. Patent Document 1 discloses an optical element in which a reflective polarizing layer is integrated with a substrate. Because a reflective polarizing layer is thin and easily deformed when used alone, integrating it with a substrate allows the required surface shape to be maintained. Patent Document 1 also discloses an optical element in which a reflective polarizing layer is sandwiched and integrated between two substrates. Because reflective polarizing layers are primarily made of resin, they are prone to shape changes due to temperature changes and water absorption. By sandwiching and integrating the reflective polarizing layer between two substrates, shape changes of the reflective polarizing layer due to temperature changes and water absorption can be suppressed.

[0005] Furthermore, to improve the image quality of display devices and imaging devices, the surface shape of optical elements needs to be smooth and have small shape error. In particular, when a reflective surface in an optical system, such as a reflective polarizing layer, is used, it is strongly required that the surface be smooth and have small shape error. Patent Document 2 discloses an optical element in which a reflective polarizing layer is integrated with a substrate via an adhesive layer with a thickness of less than 20 micrometers in order to obtain a smooth reflective polarizing layer with small shape error. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2021-500606 [Patent Document 2] Japanese Patent Application Publication No. 2023-159337 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the case of an optical element such as that described in Patent Document 2, in which a reflective polarizing layer is sandwiched and integrated between two substrates, the optical properties can be significantly degraded due to temperature differences that occur when the device is in use or when the environmental temperature of the device changes.

[0008] The present invention aims to provide an optical element in which a resin layer is integrated between two substrates via an adhesive layer, and which can reduce or prevent deterioration of optical properties due to temperature differences. [Means for solving the problem]

[0009] According to one aspect of the present invention, there is provided an optical element having a first substrate, a first adhesive layer, a resin layer having reflective properties, a second adhesive layer, and a second substrate, wherein the first substrate, the first adhesive layer, the resin layer, the second adhesive layer, and the second substrate are laminated in this order, and wherein when the average thickness of the first adhesive layer is T1, the Young's modulus of the first adhesive layer is E1, the average thickness of the second adhesive layer is T2, and the Young's modulus of the second adhesive layer is E2, the following formula (1-1) is satisfied: 1.1×T1 / E1≦T2 / E2…(1-1)

[0010] According to another aspect of the present invention, there is provided an optical element having a first substrate, a first adhesive layer, a first resin layer having reflective properties, a second adhesive layer, a second resin layer, a third adhesive layer, and a second substrate, wherein the first substrate, the first adhesive layer, the first resin layer, the second adhesive layer, the second resin layer, the third adhesive layer, and the second substrate are stacked in this order, and wherein, when the average thickness of the first adhesive layer is T1, the Young's modulus of the first adhesive layer is E1, the average thickness of the second adhesive layer is T2, the Young's modulus of the second adhesive layer is E2, the average thickness of the third adhesive layer is T3, and the Young's modulus of the third adhesive layer is E3, the optical element satisfies the following formula (2-1) or the following formula (3-1). 1.1×T1 / E1≦T2 / E2…(2-1) 1.1×T1 / E1≦T3 / E3…(3-1)

[0011] According to another aspect of the present invention, there is provided an optical element having a first substrate made of glass, a first adhesive layer, a resin layer having reflective properties, a second adhesive layer, and a second substrate made of glass, wherein the first substrate, the first adhesive layer, the resin layer, the second adhesive layer, and the second substrate are laminated in this order, and wherein when the average thickness of the first adhesive layer is T1, the Young's modulus of the first adhesive layer is E1, the average thickness of the second adhesive layer is T2, and the Young's modulus of the second adhesive layer is E2, the following equation is satisfied: 1.1×T1 / E1≦T2 / E2 [Effects of the Invention]

[0012] According to the present invention, in an optical element in which a resin layer is integrated between two base materials via an adhesive layer, deterioration of optical properties due to temperature differences can be reduced or prevented. [Brief explanation of the drawings]

[0013] [Figure 1A] FIG. 1 is a plan view showing an optical element according to a first embodiment of the present invention. [Figure 1B] 1 is a cross-sectional view showing an optical element according to a first embodiment of the present invention. [Figure 2A] 5A and 5B are plan views showing other examples of the planar shape of the optical element according to the first embodiment of the present invention. [Figure 2B] 5A and 5B are plan views showing other examples of the planar shape of the optical element according to the first embodiment of the present invention. [Figure 3] FIG. 1 is an enlarged cross-sectional view showing an optical element according to a first embodiment of the present invention. [Figure 4] FIG. 1 is an enlarged cross-sectional view showing an optical element according to a first embodiment of the present invention. [Figure 5] 1 is a cross-sectional view showing a display device according to a first embodiment of the present invention. [Figure 6] 1 is a cross-sectional view showing an imaging device according to a first embodiment of the present invention. [Figure 7A] 1 is a cross-sectional view showing an optical element according to a first embodiment of the present invention. [Figure 7B] 1 is a cross-sectional view showing an optical element according to a first embodiment of the present invention. [Figure 8] FIG. 10 is a cross-sectional view showing an optical element with a comparative configuration. [Figure 9] FIG. 5 is a schematic cross-sectional view showing a display device according to a second embodiment of the present invention. [Figure 10] FIG. 10 is a schematic cross-sectional view showing an imaging device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] [First embodiment] An optical element, a display device, and an imaging device according to a first embodiment of the present invention will be described with reference to FIGS. 1A to 7B. First, the configuration of the optical element according to this embodiment will be described with reference to Figures 1A to 4. Figure 1A is a plan view showing an optical element 10 according to this embodiment, illustrating the shape of the optical element 10 in a plan view as viewed in the optical axis direction. Figure 1B is a cross-sectional view showing the optical element 10 according to this embodiment, illustrating a cross section taken along line XX' in Figure 1A. Figures 2A and 2B are plan views each showing another example of the planar shape of the optical element 10 according to this embodiment. Figures 3 and 4 are enlarged cross-sectional views each showing an enlarged region A indicated by a dashed rectangle in Figure 1B.

[0015] As shown in Fig. 1A, the shape of optical element 10 according to this embodiment in a plan view in the optical axis direction is, for example, a circle. The shape of optical element 10 in a plan view may be a partial circle as shown in Fig. 2A or an ellipse as shown in Fig. 2B, and is not limited to a specific shape. The shape of optical element 10 in a plan view in the optical axis direction can be selected appropriately in consideration of, for example, small size and weight reduction, design of the device, etc., in addition to a circle.

[0016] As shown in Fig. 1B, the optical element 10 according to this embodiment has a substrate 1, which is a base body, and a substrate 5, which is also a base body. The substrate 1 and the substrate 5 are disposed so as to face each other. Figs. 3 and 4 show examples of the cross-sectional structure of a region A in the optical element 10, including the layer configuration between the substrate 1 and the substrate 5, which are disposed so as to face each other.

[0017] 3, the optical element 10 according to this embodiment has an adhesive layer 2, a resin layer 3, and an adhesive layer 4 laminated between a substrate 1 and a substrate 5 in this order from the substrate 1 side to the substrate 5 side, and has a configuration in which the resin layer 3 is sandwiched between the substrate 1 and the substrate 5 via the adhesive layers 2 and 4, forming an integrated structure. In other words, the optical element 10 has a configuration in which the substrate 1, the adhesive layer 2, the resin layer 3, the adhesive layer 4, and the substrate 5 are laminated in this order and integrated. The resin layer 3 is a resin layer having an optical function, as will be described later.

[0018] It should be noted that the resin layer having an optical function in the optical element 10 is not limited to a single layer, such as the resin layer 3. The optical element 10 may have two or more resin layers having an optical function. For example, when the optical element 10 has two resin layers having an optical function, as shown in FIG. 4, the optical element 10 has an adhesive layer 2, a resin layer 3, an adhesive layer 4, a resin layer 6, and an adhesive layer 7 laminated between the substrate 1 and the substrate 5 in this order from the substrate 1 side to the substrate 5 side. In this case, the optical element 10 has a configuration in which the substrate 1, the adhesive layer 2, the resin layer 3, the adhesive layer 4, the resin layer 6, the adhesive layer 7, and the substrate 5 are laminated in this order and integrated together. The resin layer 3 and the resin layer 6 are each a resin layer having an optical function.

[0019] The optical element 10 according to this embodiment is used in optical devices such as a head-mounted display (HMD), a digital camera, a video camera, etc. Figures 5 and 6 are cross-sectional views showing examples of optical devices in which the optical element 10 is used.

[0020] FIG. 5 is a cross-sectional view showing an example of a display device 104, such as an HMD, in which the optical element 10 is used. As shown in FIG. 5, the display device 104 includes a display optical system 100 and a display panel 101. The display optical system 100 includes an optical element 10, an optical element 102, and an optical element 103. The optical elements 102, 103, and 10 are arranged side by side between the display panel 101 that displays an image and a display side of the display panel 101 that is located on the side of a user's eye 20 that views the image. The display optical system 100 has a function of focusing an image displayed on the display panel 101 onto the user's eye 20 through the optical elements 102, 103, and 10. The number of optical elements in the display optical system 100 may be one or more as long as it satisfies the required functions. 5 indicates an optical path in the folded optical system of the display optical system 100, which is folded by optical functional surfaces such as a reflective polarizing layer, a retardation layer, and a transmissive reflective layer provided in the display optical system 100. Each optical functional surface is disposed on the surface of any optical element or inside the optical element.

[0021] FIG. 6 is a cross-sectional view showing an example of an imaging device 204, such as a digital camera or video camera, that uses the optical element 10. As shown in FIG. 6, the imaging device 204 includes an imaging optical system 200 and an image sensor 201, which is an imaging element. The imaging optical system 200 includes an optical element 10, an optical element 203, and an optical element 202. The optical elements 202, 203, and 10 are arranged side by side between the image sensor 201, which receives light from a subject and captures an image of the subject, and the imaging side of the imaging device 204, which is located on the subject side. The imaging optical system 200 has a function of forming an image on the image sensor 201 via the optical element 10, the optical element 203, and the optical element 202. The image sensor 201 receives light from the subject that has passed through the imaging optical system 200 and been imaged, and generates an image signal for forming an image. The imaging optical system 200 may include one or more optical elements as long as they satisfy the required functions. 6 indicates an optical path in the folded optical system of the imaging optical system 200, which is folded by optical functional surfaces such as a reflective polarizing layer, a retardation layer, and a transmissive reflective layer provided in the imaging optical system 200. Each optical functional surface is disposed on the surface of any optical element or inside the optical element.

[0022] In this way, the optical element 10 according to this embodiment can be included in an optical system that is arranged between a sensor, such as an image sensor 201, into which light from an object such as a subject is incident, and the object. In such an optical system, the optical element 10 reflects light once by the resin layer 3, which has reflective properties, before the light reaches the sensor.

[0023] Next, the substrates 1 and 5, the resin layers 3 and 6, and the adhesive layers 4 and 7 in the optical element 10 according to this embodiment will be described in detail. Note that the optical element 10 may have a similar resin layer in addition to the resin layers 3 and 6, and may have a similar adhesive layer in addition to the adhesive layers 4 and 7.

[0024] The substrate 1 and the substrate 5 each have, for example, a parallel plate shape with flat surfaces on both sides as shown in FIG. 1B. The substrate 1 and the substrate 5 each have the function of maintaining the shape of the optical element 10. The shapes of the substrate 1 and the substrate 5 may be flat, convex spherical, concave spherical, aspherical, or a combination thereof. At least one of the substrate 1 and the substrate 5 may have a function as a lens, specifically, it may have a function of converging incident light like a convex lens, or a function of diffusing incident light like a concave lens.

[0025] Furthermore, the materials constituting the substrate 1 and the substrate 5 are not particularly limited as long as they are transparent materials that are transmissive to light such as visible light that is the target of the optical element 10. Note that "transparent" means that the transmittance of the light that is the target of the optical element 10 is a predetermined value or more, for example, 10% or more, and specifically means that the transmittance of light with a wavelength in the range of 420 nm to 700 nm is 10% or more. For example, the materials constituting the substrate 1 and the substrate 5 are selected from glass, resin, ceramic, etc.

[0026] Furthermore, it is preferable that the substrates 1 and 5 have high bending rigidity in order to maintain the shape of the optical element 10. For this reason, it is preferable that the thicknesses of the substrates 1 and 5 are set to be sufficiently thicker than the other resin layers and adhesive layers that constitute the optical element 10. Specifically, the thicknesses of the substrates 1 and 5 are each preferably 0.5 mm or greater, and more preferably 1.0 mm or greater. If the thickness is less than 0.5 mm, the optical element 10 will be significantly deformed by the force used to fix the optical element 10 to the optical device and by its own weight, making it difficult to maintain the shape of the optical element 10 with high precision.

[0027] Furthermore, the Young's modulus of the substrate 1 and the substrate 5 is preferably equal to or higher than that of other resin layers and adhesive layers constituting the optical element 10. Specifically, the Young's modulus of the substrate 1 and the substrate 5 is preferably 0.5 GPa or more and 300 GPa or less.

[0028] The resin layer 3 and the resin layer 6 are layers having an optical function, and are selected from layers having an optical function such as a reflective polarizing layer, an absorptive polarizing layer, a retardation layer, and a transflective layer. The resin layer serving as the layer having an optical function in the optical element 10 may be a single layer, the resin layer 3, as shown in Fig. 3, or may be two layers, the resin layer 3 and the resin layer 6, as shown in Fig. 4, or may be a multiple layer of three or more layers. At least one resin layer 3 included in the optical element 10 has a reflective property that reflects incident light.

[0029] The reflective polarizing layer is a layer that transmits incident light with a certain polarization direction and reflects light with a polarization direction perpendicular to the transmitted light. Examples of the reflective polarizing layer that can be used include a wire grid film (product name "WGF") manufactured by Asahi Kasei Corporation and a laminated reflective polarizing film (product name "IQPE") manufactured by 3M.

[0030] The absorbing polarizing layer transmits incident light of a certain polarization direction and absorbs light of a polarization direction perpendicular to that direction. Examples of the absorbing polarizing layer include a polarizing film manufactured by Nippon Kayaku Co., Ltd. (product name: "ACE") and a dye-based polarizing film manufactured by the same company (product name: "GHC").

[0031] The retardation layer is a layer that changes the polarization direction of incident light by a certain amount. Examples of the retardation layer that can be used include a polymer film retardation film manufactured by Nippon Kayaku Co., Ltd. (product name "WA-140T") and a retardation film manufactured by Colorlink Japan Co., Ltd. (product name "CP3").

[0032] The transflective layer is a layer that separates incident light into transmitted light and reflected light at a certain ratio, and can be, for example, a half mirror.

[0033] The resin layer 3 having a reflective property is not particularly limited, but is preferably a reflective polarizing layer or a transflective layer, which are layers having a reflective property, among the layers having the above-mentioned optical functions. Furthermore, when the optical element 10 shown in Fig. 4 has two layers, the resin layer 3 and the resin layer 6, it is not particularly limited, but it is preferable that the resin layer 6 be a resin layer having a transmissive property for light that the optical element 10 targets.

[0034] Specifically, for example, the resin layer 3 can be a reflective polarizing layer, and the resin layer 6 can be a retardation layer. Alternatively, for example, the resin layer 3 can be a transmissive reflective layer, and the resin layer 6 can be a retardation layer. In these cases, the optical element 10 can be used as one element constituting a folded optical system. In these cases, another resin layer functioning as an absorbing polarizing layer may be further provided between the resin layer 6 and the substrate 5 via an adhesive layer. When the resin layer 3 is a reflective polarizing layer, the optical element 10 functions as a reflective polarizing optical element.

[0035] The thicknesses of the resin layers 3 and 6 are set appropriately to a thickness that allows them to exhibit their optical functions. However, it is preferable that the thicknesses of the resin layers 3 and 6 are set sufficiently thinner than the thicknesses of the substrates 1 and 5 so as not to significantly affect the shape of the optical element 10. Specifically, the thicknesses of the resin layers 3 and 6 are each preferably 10 μm or more and 300 μm or less, and more preferably 20 μm or more and 200 μm or less.

[0036] Furthermore, the Young's modulus of the resin layer 3 and the resin layer 6 is preferably equal to or lower than that of the substrate 1 and the substrate 5, respectively, so as not to significantly affect the shape of the optical element 10. Furthermore, the Young's modulus of the resin layer 3 and the resin layer 6 is preferably equal to or higher than that of the adhesive layer 2, the adhesive layer 4, and the adhesive layer 7, respectively, so as not to deform the surface shapes of the resin layer 3 and the resin layer 6, respectively. Specifically, the Young's modulus of the resin layer 3 and the resin layer 6 is preferably 2 MPa or more and 10 GPa or less.

[0037] Adhesive layer 2, adhesive layer 4, and adhesive layer 7 have the function of adhering and integrating the components sandwiching the layers. Specifically, adhesive layer 2 adheres and integrates substrate 1 and resin layer 3. Adhesive layer 4 adheres and integrates resin layer 3 and resin layer 6. Adhesive layer 7 adheres and integrates resin layer 6 and substrate 5.

[0038] Furthermore, the materials constituting adhesive layer 2, adhesive layer 4, and adhesive layer 7 are not particularly limited as long as they are transparent materials that are transmissive to light such as visible light that is the target of optical element 10. However, from the viewpoint of ease of manufacturing, it is preferable that the materials constituting adhesive layer 2, adhesive layer 4, and adhesive layer 7 are each a photocurable resin or a thermosetting resin.

[0039] Furthermore, the thicknesses of adhesive layer 2, adhesive layer 4, and adhesive layer 7 are each set appropriately within the configuration of optical element 10 depending on the performance, size, shape, etc. of optical element 10. Specifically, the thicknesses of adhesive layer 2, adhesive layer 4, and adhesive layer 7 are each preferably 1 μm or more and 100 μm or less, and more preferably 3 μm or more and 50 μm or less.

[0040] Furthermore, the Young's moduli of adhesive layer 2, adhesive layer 4, and adhesive layer 7 are preferably equal to or lower than the Young's moduli of substrate 1 and substrate 5 so as not to significantly affect the shape of optical element 10. Furthermore, the Young's moduli of adhesive layer 2, adhesive layer 4, and adhesive layer 7 are preferably equal to or lower than the Young's modulus of resin layer 3 so as not to deform the surface shape of at least resin layer 3, which has reflective properties, out of resin layer 3 and resin layer 6. Specifically, the Young's moduli of adhesive layer 2, adhesive layer 4, and adhesive layer 7 are preferably each equal to or lower than the Young's modulus of resin layer 3 so as not to deform the surface shape of at least resin layer 3, which has reflective properties. Specifically, the Young's moduli of adhesive layer 2, adhesive layer 4, and adhesive layer 7 are each preferably 0.01 MPa or more and 3 GPa or less.

[0041] The thicknesses of adhesive layer 2, adhesive layer 4, and adhesive layer 7 can be measured by cutting optical element 10 and measuring the cross-sectional shape using, for example, an image measuring device manufactured by Nikon Corporation (product name "NEXIV"). The thickness can be calculated as an average thickness, which is the average of measurements taken at multiple locations on optical element 10. The Young's modulus of adhesive layer 2, adhesive layer 4, and adhesive layer 7 can be measured by peeling off the surface of the adhesive layer on optical element 10 and using, for example, a nanoindenter manufactured by Agilent Technologies (product name "NanoIndenter G-200"). The Young's modulus can be calculated as an average Young's modulus, which is the average of measurements taken at multiple locations on the adhesive layer on optical element 10.

[0042] A transparent inorganic film may be provided on the surfaces of the substrate 1 and the substrate 5. Transparent inorganic films may also be provided between the substrate 1 and the adhesive layer 2, between the adhesive layer 2 and the resin layer 3, between the resin layer 3 and the adhesive layer 4, between the adhesive layer 4 and the substrate 5, between the adhesive layer 4 and the resin layer 6, between the resin layer 6 and the adhesive layer 7, and between the adhesive layer 7 and the substrate 5. Transparent inorganic films may be provided on all or any of these surfaces and between the layers. For example, a transparent inorganic film may be provided on the top surface of the substrate 1, which faces the substrate 5, and the adhesive layer 2 and the resin layer 3 may be sequentially provided on the substrate 1 via the transparent inorganic film. In this case, the transparent inorganic film is a thin film made of a transparent inorganic material that is transparent to light, such as visible light, that is the target of the optical element 10.

[0043] The inorganic materials for the transparent inorganic film include aluminum oxide (Al2O3), silicon oxide (SiO2, SiO), and titanium oxide (TiO x ), tantalum oxide (TaO x ), niobium oxide (NbO x) are examples. The transparent inorganic film can be provided by various film formation methods such as vacuum deposition and sputtering. The provision of the transparent inorganic film can improve the adhesion between layers and suppress reflection due to refractive index differences at interfaces. The thickness of the transparent inorganic film is appropriately set depending on its function, and specifically, for example, is 10 nm or more and 1000 nm or less.

[0044] Here, the average thickness of adhesive layer 2 is T1, the Young's modulus of adhesive layer 2 is E1, the average thickness of adhesive layer 4 is T2, and the Young's modulus of adhesive layer 4 is E2. In the configuration shown in FIG. 3, optical element 10 according to this embodiment is configured to satisfy the following formula (1-1), and preferably the following formula (1-2). 1.1× T1 / E1≦ T2 / E2…Formula (1-1) 1.8× T1 / E1≦ T2 / E2…Formula (1-2)

[0045] Generally, when the thickness of an adhesive layer is T and the Young's modulus of the adhesive layer is E, the value T / E obtained by dividing the thickness T by the Young's modulus E is an empirical index indicating the susceptibility of the adhesive layer to local deformation. The adhesive layer is set to a thickness of approximately 1 μm or more and 100 μm or less and has very low bending rigidity relative to the substrate. Therefore, the adhesive layer has little effect on overall deformation of the optical element, such as warping. On the other hand, when a local compressive or tensile force is applied to the adhesive layer, the adhesive layer itself undergoes local compressive or elongated deformation. In this case, if the thickness of the adhesive layer is, for example, twice the standard, it will deform by approximately twice the standard, and if the Young's modulus of the adhesive layer is, for example, twice the standard, it will deform by approximately half the standard. In other words, the larger the value T / E obtained by dividing the thickness T of the adhesive layer by the Young's modulus E, the greater the amount of deformation when the same force is applied. Equations (1-1) and (1-2) mean that the index of ease of deformation of adhesive layer 4 is 1.1 times or more, preferably 1.8 times or more, of the index of ease of deformation of adhesive layer 2, meaning that adhesive layer 2 is relatively difficult to deform and adhesive layer 4 is relatively easy to deform.

[0046] In conventional optical elements, such as those described in Patent Document 2, which sandwich a reflective polarizing layer between two substrates, the optical properties of the optical element can deteriorate significantly during use or when the ambient temperature of the device changes, resulting in significant degradation of image quality in devices such as display devices and imaging devices. This occurs when a temperature difference occurs between the two substrates of the integrated optical element. For example, when using an HMD, heat is transferred to the optical element from the display panel, other electronic components, and the wearer. Furthermore, when the ambient temperature changes, such as when the device is taken from indoors to outdoors, a temperature difference occurs as the device adjusts to the ambient temperature. This temperature difference causes a difference in the amount of expansion between the two substrates, causing the edge of the substrate with the greater expansion to warp toward the substrate with the smaller expansion. This warping changes the surface shape of the optical element, particularly the surface shape of the reflective polarizing layer. This change in the surface shape of the optical element degrades the optical properties of the optical element, resulting in degradation of image quality in devices such as display devices and imaging devices.

[0047] Thus, when an apparatus using the optical element 10 is used or when the ambient temperature of the apparatus changes, a temperature difference occurs in the optical element 10, and the difference in the amount of expansion between the substrate 1 and the substrate 5 causes deformation such as warping in the optical element 10, which can result in deterioration of the optical performance. The resin layer 3 is a layer that has an optical function, and it is important not to deform the resin layer 3 in order to prevent deterioration of the optical performance of the optical element 10. In particular, because the resin layer 3 has reflective properties, not deforming the resin layer 3 is extremely important in reducing or preventing deterioration of the optical performance.

[0048] In the configuration shown in FIG. 3, the resin layer 3 is adhered and fixed to the surface of the substrate 1 via the adhesive layer 2, but the adhesive layer 2 is relatively less likely to deform than the adhesive layer 4. This allows the resin layer 3 to accurately conform to the surface shape of the substrate 1. On the other hand, the resin layer 3 is adhered and fixed to the surface of the substrate 5 via the adhesive layer 4, but the adhesive layer 4 is relatively more likely to deform than the adhesive layer 2. This allows the adhesive layer 4 to flexibly deform to conform to the surface shape of the substrate 5.

[0049] In the optical element 10 according to this embodiment, the adhesive layer 4 is relatively more easily deformed than the adhesive layer 2, so deformation of the resin layer 3 can be suppressed or prevented even when a temperature difference occurs. The mechanism by which deformation of the resin layer 3 is suppressed or prevented in the optical element 10 according to this embodiment will be described with reference to FIGS. 7A to 8. FIG. 7A is a cross-sectional view showing deformation of the optical element 10 according to this embodiment when a temperature difference causes the diameter of the substrate 5 to become larger relative to the diameter of the substrate 1. FIG. 7B is a cross-sectional view showing deformation of the optical element 10 according to this embodiment when a temperature difference causes the diameter of the substrate 5 to become smaller relative to the diameter of the substrate 1. FIG. 8 is a cross-sectional view showing deformation of the optical element 10 when the adhesive layer 4 is as difficult to deform as the adhesive layer 2. FIGS. 7A to 8 correspond to the cross-sectional views shown in FIGS. 1B and 3, respectively.

[0050] For example, if the diameter of substrate 5 becomes larger relative to the diameter of substrate 1 due to a temperature difference, resin layer 3 follows the surface shape of substrate 1 via adhesive layer 2, which is relatively resistant to deformation. Meanwhile, resin layer 3 is adhered and fixed to substrate 5 via adhesive layer 4, which is relatively easy to deform. Therefore, as shown in FIG. 7A, adhesive layer 4 deforms to match the difference in shape between resin layer 3 and substrate 5, thereby reducing or preventing deformation such as warping of resin layer 3. Similarly, if the diameter of substrate 5 becomes smaller relative to the diameter of substrate 1, adhesive layer 4 deforms to match the difference in shape between resin layer 3 and substrate 5, thereby reducing or preventing deformation such as warping of resin layer 3, as shown in FIG. 7B. As such, according to this embodiment, deformation of the resin layer 3 having reflective properties can be reduced or prevented when the device is in use or when the ambient temperature changes, and deterioration of the optical properties of the optical element 10 can be reduced or prevented.

[0051] From the viewpoint of sufficiently reducing or preventing deformation of the resin layer 3, the average thickness T1 of the adhesive layer 2 can be set preferably in the range of 3 μm to 20 μm, and the Young's modulus E1 of the adhesive layer 2 can be set preferably in the range of 1 MPa to 100 MPa. From the same viewpoint, the average thickness T2 of the adhesive layer 4 can be set preferably in the range of 3 μm to 100 μm, and the Young's modulus E2 of the adhesive layer 4 can be set preferably in the range of 0.1 MPa to 100 MPa.

[0052] 8, if adhesive layer 4 is as difficult to deform as adhesive layer 2, adhesive layer 2 and adhesive layer 4 cannot deform locally, causing deformation such as warping of substrate 1 and substrate 5, which in turn deforms resin layer 3. As a result, it becomes difficult to reduce or prevent deterioration of the optical properties of optical element 10.

[0053] As described above, the optical element 10 can also have a configuration in which the substrate 1, adhesive layer 2, resin layer 3, adhesive layer 4, resin layer 6, adhesive layer 7, and substrate 5 shown in FIG. 4 are laminated in this order and integrated. In this case, the adhesive layer 7 can be configured similarly to the adhesive layer 4. Here, the average thickness of the adhesive layer 7 is further defined as T3, and the Young's modulus of the adhesive layer 7 is defined as E3. When having the configuration shown in FIG. 4, the optical element 10 can be configured to satisfy the following formula (2-1) or (3-1), and preferably to satisfy the following formula (2-2) or (3-2). 1.1× T1 / E1≦ T2 / E2…Formula (2-1) 1.8× T1 / E1≦ T2 / E2…Formula (2-2) 1.1× T1 / E1≦ T3 / E3…Formula (3-1) 1.8× T1 / E1≦ T3 / E3…Formula (3-2)

[0054] When the above relationship is satisfied, first, adhesive layer 2 is sufficiently resistant to deformation relative to adhesive layer 4 or adhesive layer 7, allowing resin layer 3 to accurately conform to the surface shape of substrate 1. Furthermore, adhesive layer 4 or adhesive layer 7 is sufficiently resistant to deformation relative to adhesive layer 2, allowing adhesive layer 4 or adhesive layer 7 to deform to conform to the difference in shape between resin layer 3 and substrate 5, thereby reducing or preventing deformation, such as warping, of resin layer 3. Additionally, resin layer 6 can also deform to conform to the difference in shape between resin layer 3 and substrate 5. When resin layer 6 is a transmissive layer without reflective properties, deformation of resin layer 6 does not significantly affect the optical properties of optical element 10. This deformation of resin layer 6 can more reliably reduce or prevent deformation, such as warping, of resin layer 3. Thus, even when optical element 10 has the configuration shown in FIG. 4 , deformation of resin layer 3, which has reflective properties, can be reduced or prevented, thereby reducing or preventing deterioration of the optical properties of optical element 10.

[0055] In the optical element 10 according to this embodiment, the resin layer 3 is a layer having reflective properties such as a reflective polarizing layer or a transmissive reflective layer, and therefore is more effective in reducing or preventing deterioration of optical properties.

[0056] In optical devices, light passes through an optical element and is transmitted or reflected by several interfaces with different refractive indices to form an image on the observer's eye, an image sensor, or the like. If there is a shape error in the surface shape of this interface, an optical path difference occurs, degrading the optical characteristics of the optical element 10. Here, if the interface is a transmissive surface, the optical characteristics degrade in proportion to the difference in refractive index between the two layers that make up the interface. On the other hand, if the interface is a reflective surface, the optical characteristics degrade in proportion to twice the difference between the refractive index of the layer on the reflective side and the refractive index of vacuum.

[0057] Considering the interface between a resin layer and an adhesive layer used in optical element 10 according to this embodiment, for example, let us assume that the refractive index of the resin layer is 1.54 and the refractive index of the adhesive layer is 1.50. In this case, the effect of shape error at the interface between the resin layer and the adhesive layer on the optical properties is approximately 25 times greater in the case of a reflective surface than in the case of a transmissive surface, as shown in the following equation (4): (1.50-1.00)×2 / (1.54-1.50)=25 …Equation (4)

[0058] Therefore, when the resin layer 3 is a layer having reflective properties such as a reflective polarizing layer or a transmissive reflective layer, the deformation of the resin layer 3 has a very large effect on the optical properties, and reducing or preventing the deformation of the resin layer 3 has a greater effect of reducing or preventing deterioration of the optical properties of the optical element 10.

[0059] From the viewpoint of fully achieving the effect of reducing or preventing deterioration of the optical properties of the optical element 10, it is preferable that the average thickness of the adhesive layer 2 be 20 μm or less. When the adhesive layer 2 is sufficiently thin, the resin layer 3 can be made to more accurately conform to the surface shape of the substrate 1. Furthermore, when the adhesive layer 2 is sufficiently thin, deformation of the adhesive layer 2 itself due to temperature changes is small, and deformation of the resin layer 3 can be sufficiently reduced or prevented.

[0060] Furthermore, the substrate 1 and the substrate 5 may be made of materials having the same or different linear expansion coefficients. However, materials having different linear expansion coefficients are more effective in reducing or preventing deterioration of the optical properties of the optical element 10. If the substrate 1 and the substrate 5 are made of materials having the same linear expansion coefficients, a temperature difference between the substrate 1 and the substrate 5 will cause a difference in the amount of expansion between the two, resulting in deformation such as warping of the optical element 10. On the other hand, if the substrates 1 and 5 are made of materials having the same linear expansion coefficients, no difference in the amount of expansion will occur even if the temperature rises or falls in the absence of a temperature difference, and deformation such as warping will not occur in the optical element 10. However, if the substrate 1 and the substrate 5 are made of materials having different linear expansion coefficients, a difference in the amount of expansion will occur between the two when the temperature rises or falls even in the absence of a temperature difference, resulting in deformation such as warping of the optical element 10. Even if such deformation occurs, according to this embodiment, the deformation of the resin layer 3 will be reduced or prevented, thereby reducing or preventing deterioration of the optical properties of the optical element 10.

[0061] The method for manufacturing the optical element 10 according to this embodiment is not particularly limited, and for example, techniques such as film lamination, bonding, resin layer molding, and insert molding can be used alone or in combination to manufacture the optical element 10. As an example, the following describes the case where the optical element 10 shown in FIG. 3 is manufactured using a manufacturing method for the optical element 10 that combines film lamination and bonding techniques.

[0062] First, prepare the substrates 1 and 5, a resin film that will become the resin layer 3, and an adhesive that will become the adhesive layer 2 and the adhesive layer 4. As the adhesive, a photocurable adhesive, a thermosetting adhesive, a two-component adhesive, a pressure-sensitive adhesive, etc. can be used, but a photocurable adhesive is preferably used because of ease of production. Furthermore, the adhesive that will become the adhesive layer 2 and the adhesive layer 4 may be the same or different.

[0063] Next, a liquid adhesive that will become the adhesive layer 2 is dispensed onto the substrate 1. Next, a resin film that will become the resin layer 3 is brought into contact with the adhesive, and the adhesive sandwiched between the substrate 1 and the resin film is spread thinly. Methods for spreading the adhesive include, for example, squeegeeing using a spatula or roller, applying pressure by pressing a support member against the back of the film, and applying pressure using a pressure difference caused by compressed gas or reduced pressure. Here, the adhesive may be in sheet form rather than liquid form and attached to the substrate 1. The adhesive is then cured by means of ultraviolet irradiation, heating, or the like, to obtain an intermediate element in which the substrate 1 and the resin film are laminated and integrated via the adhesive.

[0064] Next, a liquid adhesive that will become the adhesive layer 4 is dispensed onto the surface of the intermediate element facing the resin film. Then, another substrate 5 is brought into contact with the adhesive, and the adhesive is pressed and spread thinly. The same method as described above can be used to press and spread the adhesive. The adhesive is then cured by means of ultraviolet irradiation, heating, or the like, and the substrate 5 is provided on the surface of the intermediate element facing the resin film via the adhesive. In this way, an optical element 10 can be manufactured in which the substrate 1, adhesive layer 2, resin layer 3, adhesive layer 4, and substrate 5 are laminated and integrated.

[0065] Contrary to the case of manufacturing from the substrate 1 side described above, an intermediate element can be obtained in which the substrate 5 and the resin film are laminated together via an adhesive, and then the substrate 1 can be placed on the resin film side of the intermediate element via an adhesive, and the optical element 10 can be manufactured from the substrate 5 side.

[0066] [Example] Next, the optical element 10 according to the first embodiment will be specifically described using examples.

[0067] Example 1 A description will be given of an optical element 10 and a method for manufacturing the optical element 10 according to Example 1. In Example 1, an optical element 10 having the shape shown in Figures 1A, 1B and 4 was manufactured.

[0068] In Example 1, first, a glass plate (S-BSL7 manufactured by Ohara Inc.) was prepared as the substrate 1. The substrate 1 had an outer diameter of 46 mm, a thickness of 2.0 mm, and a parallel plate shape with optically mirrored surfaces on both sides. Next, a glass plate (manufactured by Ohara Inc., product name "S-BSL7") was prepared as the substrate 5. The substrate 5 had an outer diameter of 50 mm, a thickness of 2.0 mm, and a parallel plate shape with optically mirrored surfaces on both sides. Next, an ultraviolet-curable adhesive (manufactured by Kyoritsu Chemical Industries Co., Ltd., product name "OP-1055H") was prepared to form the adhesive layer 2. The Young's modulus of the adhesive layer when this adhesive was cured was 9.3 MPa. Next, an ultraviolet-curable adhesive (manufactured by Kyoritsu Chemical Industries Co., Ltd., product name "WR-3970") to form the adhesive layers 4 and 7 was prepared. The Young's modulus of the adhesive when this adhesive was cured was 0.2 MPa. Next, a laminated reflective polarizing film (manufactured by 3M, product name "IQPE") was prepared as the resin film to form the resin layer 3. This resin film had an outer diameter of φ46 mm and a thickness of 60 μm. Next, a retardation film (manufactured by Color Link Japan, product name "CP3") was prepared as the resin film to become the resin layer 6. This resin film had an outer diameter of φ46 mm and a thickness of 200 μm.

[0069] Next, 20 μl of adhesive that would become adhesive layer 2 was dispensed onto substrate 1 using a precision dispenser. Next, a resin film that would become resin layer 3 was brought into contact with the adhesive from above, and a parallel flat plate glass for pressure application weighing 3 kg was placed on top and left to stand for 180 seconds. Thereafter, the parallel flat plate glass for pressure application was removed, and ultraviolet light with a wavelength of 365 nm was applied from above the resin film at 10 mW / cm. 2 The adhesive was cured by irradiation for 300 seconds at an intensity of 1000 ppm, to obtain a first intermediate element.

[0070] Next, 20 μl of adhesive that would become adhesive layer 4 was dispensed onto the resin film side of the first intermediate element using a precision dispenser. Next, the resin film that would become resin layer 6 was brought into contact with the adhesive from above, and a parallel plate glass for pressure application weighing 3 kg was placed on top and left to stand for 180 seconds. Thereafter, the parallel plate glass for pressure application was removed, and ultraviolet light with a wavelength of 365 nm and a beam of 10 mW / cm was applied from above the resin film. 2 The adhesive was cured by irradiation for 300 seconds at an intensity of 1000 ppm, to obtain a second intermediate element.

[0071] Next, 100 μl of adhesive that would become adhesive layer 7 was dispensed onto the resin film side surface of the second intermediate element using a precision dispenser. Next, substrate 5 was brought into contact with the adhesive from above, and a parallel plate glass for pressure application weighing 200 g was placed on top of it and left to stand for 60 seconds. Thereafter, the parallel plate glass for pressure application was removed, and ultraviolet light with a wavelength of 365 nm and a beam of 10 mW / cm was applied from above substrate 5. 2 The adhesive was cured by irradiation for 300 seconds at an intensity of 1000 nm, and the optical element 10 according to Example 1 was obtained.

[0072] The optical element 10 according to Example 1 manufactured as described above was evaluated by measuring the change in the reflected wavefront with respect to changes in environmental temperature. The reason for evaluating the optical element 10 by measuring the change in the reflected wavefront with respect to changes in environmental temperature is that changes in the reflected wavefront of the optical element 10 have a significant effect on the optical characteristics of the optical device. To evaluate the optical element 10, the optical element 10 was first placed in a housing simulating an optical device and left undisturbed in an environment at 20°C for at least three hours, after which the reflected wavefront was measured using an interferometer manufactured by ZYGO Corporation under the product name "VerifireAT." This measurement result was used as a reference reflected wavefront for the optical element 10 at room temperature with no temperature difference. Next, the optical element 10 placed in the housing was left undisturbed in an environment at -10°C for three hours. Thereafter, the optical element 10 was left undisturbed in an environment at 20°C for 10 minutes, and the reflected wavefront was measured. The difference between this measurement result and the reference reflected wavefront was analyzed, and this difference was used as the reflected wavefront change in the optical element 10.

[0073] In evaluating the optical element 10, when the change in the reflected wavefront was less than 100 nm, there was no significant effect on the optical characteristics, and so it was rated as very good, A. When the change in the reflected wavefront was 100 nm or more but less than 200 nm, there was no problem with the optical performance, and so it was rated as good, B. When the change in the reflected wavefront was 200 nm or more, the degradation of the optical characteristics was not negligible, and so it was rated as poor, C.

[0074] When the optical element 10 according to Example 1 was evaluated using the above evaluation method, the change in the reflected wavefront was 40 nm, and therefore it was evaluated as A.

[0075] Next, the average thicknesses of adhesive layer 2, adhesive layer 4, and adhesive layer 7 were measured for the optical element 10 according to Example 1. First, the optical element 10 was cut using a diamond wire saw to obtain the cross section shown in FIG. 1B. Next, the cut cross section was polished. The cross-sectional shape was then observed using a Nikon Corporation image measuring instrument "NEXIV," and the thicknesses of adhesive layer 2, adhesive layer 4, and adhesive layer 7 were measured. The average thicknesses of adhesive layer 2, adhesive layer 4, and adhesive layer 7 were calculated from the average thicknesses of five locations on the cross section of the adhesive layer: one location at the center, two locations 10 mm outward from the center, and two locations 20 mm outward from the center. As a result, for the optical element 10 according to Example 1, the average thickness of adhesive layer 2 was 6 μm, the average thickness of adhesive layer 4 was 6 μm, and the average thickness of adhesive layer 7 was 30 μm.

[0076] Example 2 In Example 2, an ultraviolet-curing adhesive (manufactured by Kyoritsu Chemical Industry Co., Ltd., product name "OP-1055H") was used as the adhesive for the adhesive layers 4 and 7. In the step of forming the adhesive layer 7, 40 μl of the adhesive for the adhesive layer 7 was dispensed onto the resin film side surface of the second intermediate element using a precision dispenser. Next, the substrate 5 was brought into contact with the adhesive from above, and a parallel flat glass for pressure application weighing 3 kg was placed on top and left to stand for 60 seconds. Except for these points, the optical element 10 according to Example 2 was manufactured in the same manner as in Example 1.

[0077] The change in the reflected wavefront due to the change in the environmental temperature was measured for the optical element 10 according to Example 2 in the same manner as in Example 1. The change in the reflected wavefront was 70 nm, and the optical element was evaluated as A.

[0078] Furthermore, for the optical element 10 according to Example 2, the average thicknesses of the adhesive layer 2, adhesive layer 4, and adhesive layer 7 were measured in the same manner as in Example 1. As a result, for the optical element 10 according to Example 2, the average thickness of the adhesive layer 2 was 6 μm, the average thickness of the adhesive layer 4 was 6 μm, and the average thickness of the adhesive layer 7 was 11 μm.

[0079] Example 3 In Example 3, in the step of forming adhesive layer 2, 50 μl of adhesive to become adhesive layer 2 was dispensed onto substrate 1 using a precision dispenser. Next, a resin film to become resin layer 3 was brought into contact with the adhesive from above, and a parallel flat plate glass for pressure application weighing 200 g was placed on top and left to stand for 180 seconds. Furthermore, in the step of forming adhesive layer 7, 100 μl of adhesive to become adhesive layer 7 was dispensed onto the resin film side surface of the second intermediate element using a precision dispenser. Next, substrate 5 was brought into contact with the adhesive from above, and a parallel flat plate glass for pressure application weighing 200 g was placed on top and left to stand for 60 seconds. Except for these points, the optical element 10 of Example 3 was manufactured in the same manner as in Example 2.

[0080] The change in the reflected wavefront due to the change in the environmental temperature was measured for the optical element 10 according to Example 3 in the same manner as in Example 1. The change in the reflected wavefront was 80 nm, and the optical element was evaluated as A.

[0081] Furthermore, for the optical element 10 according to Example 3, the average thicknesses of the adhesive layer 2, adhesive layer 4, and adhesive layer 7 were measured in the same manner as in Example 1. As a result, for the optical element 10 according to Example 3, the average thickness of the adhesive layer 2 was 18 μm, the average thickness of the adhesive layer 4 was 6 μm, and the average thickness of the adhesive layer 7 was 32 μm.

[0082] Example 4 In Example 4, an ultraviolet-curing adhesive (manufactured by Kyoritsu Chemical Industry Co., Ltd., product name "OP-1903R") was used as the adhesive for the adhesive layers 4 and 7. When this adhesive was cured, the Young's modulus of the adhesive layer was 0.4 MPa. In addition, in the step of forming the adhesive layer 7, 20 μl of the adhesive for the adhesive layer 7 was dispensed onto the surface of the second intermediate element facing the resin film using a precision dispenser. Next, the substrate 5 was brought into contact with the adhesive from above, and a parallel flat glass for pressure application weighing 3 kg was placed on top and left to stand for 180 seconds. Except for these points, the optical element 10 according to Example 4 was manufactured in the same manner as in Example 2.

[0083] The change in the reflected wavefront due to the change in the environmental temperature was measured for the optical element 10 according to Example 4 in the same manner as in Example 1. The change in the reflected wavefront was 70 nm, and the optical element was evaluated as A.

[0084] Furthermore, for the optical element 10 according to Example 4, the average thicknesses of the adhesive layer 2, adhesive layer 4, and adhesive layer 7 were measured in the same manner as in Example 1. As a result, for the optical element 10 according to Example 4, the average thickness of the adhesive layer 2 was 6 μm, the average thickness of the adhesive layer 4 was 6 μm, and the average thickness of the adhesive layer 7 was 6 μm.

[0085] Example 5 In Example 5, in the step of forming adhesive layer 2, 100 μl of adhesive to become adhesive layer 2 was dispensed onto substrate 1 using a precision dispenser. Next, a resin film to become resin layer 3 was brought into contact with the adhesive from above, and a parallel flat plate glass for pressure application weighing 200 g was placed on top and left to stand for 60 seconds. Furthermore, in the step of forming adhesive layer 7, 200 μl of adhesive to become adhesive layer 7 was dispensed onto the surface of the second intermediate element facing the resin film using a precision dispenser. Next, substrate 5 was brought into contact with the adhesive from above, and a parallel flat plate glass for pressure application weighing 200 g was placed on top and left to stand for 10 seconds. Except for these points, the optical element 10 according to Example 5 was manufactured in the same manner as in Example 2.

[0086] The change in the reflected wavefront due to the change in the environmental temperature was measured for the optical element 10 according to Example 5 in the same manner as in Example 1. The change in the reflected wavefront was 130 nm, and therefore the optical element was evaluated as B.

[0087] Furthermore, for the optical element 10 according to Example 5, the average thicknesses of the adhesive layer 2, adhesive layer 4, and adhesive layer 7 were measured in the same manner as in Example 1. As a result, for the optical element 10 according to Example 5, the average thickness of the adhesive layer 2 was 30 μm, the average thickness of the adhesive layer 4 was 6 μm, and the average thickness of the adhesive layer 7 was 60 μm.

[0088] Example 6 In Example 6, the optical element 10 was manufactured without forming the resin layer 6 and the adhesive layer 7. In the step of forming the adhesive layer 4, 100 μl of adhesive to become the adhesive layer 4 was dispensed onto the resin film side surface of the first intermediate element using a precision dispenser. Next, the substrate 5 was brought into contact with the adhesive from above, and a parallel flat glass for pressure application weighing 200 g was placed on top and left to stand for 60 seconds. Except for these points, the optical element 10 according to Example 6 was manufactured in the same manner as in Example 1.

[0089] The change in the reflected wavefront due to the change in the environmental temperature was measured for the optical element 10 according to Example 6 in the same manner as in Example 1. The change in the reflected wavefront was 70 nm, and the optical element was evaluated as A.

[0090] Furthermore, for the optical element 10 according to Example 6, the average thicknesses of the adhesive layer 2 and the adhesive layer 4 were measured in the same manner as in Example 1. As a result, for the optical element 10 according to Example 6, the average thickness of the adhesive layer 2 was 6 μm, and the average thickness of the adhesive layer 4 was 30 μm.

[0091] Example 7 In Example 7, an optical element 10 was manufactured without forming a resin layer 6 or an adhesive layer 7. In the step of forming adhesive layer 2, 50 μl of adhesive to become adhesive layer 2 was dispensed onto substrate 1 using a precision dispenser. Next, a resin film to become resin layer 3 was brought into contact with the adhesive from above, and a parallel flat plate glass for pressure application weighing 200 g was placed on top and left to stand for 180 seconds. In the step of forming adhesive layer 4, 100 μl of adhesive to become adhesive layer 4 was dispensed onto the resin film side surface of the first intermediate element using a precision dispenser. Next, substrate 5 was brought into contact with the adhesive from above, and a parallel flat plate glass for pressure application weighing 200 g was placed on top and left to stand for 60 seconds. Except for these points, the optical element 10 of Example 7 was manufactured in the same manner as in Example 2.

[0092] The change in the reflected wavefront due to the change in the environmental temperature was measured for the optical element 10 according to Example 7 in the same manner as in Example 1. The change in the reflected wavefront was 90 nm, and the optical element was evaluated as A.

[0093] Furthermore, for the optical element 10 according to Example 7, the average thicknesses of the adhesive layer 2 and the adhesive layer 4 were measured in the same manner as in Example 1. As a result, for the optical element 10 according to Example 7, the average thickness of the adhesive layer 2 was 18 μm, and the average thickness of the adhesive layer 4 was 32 μm.

[0094] Example 8 In Example 8, an optical element 10 was manufactured without forming a resin layer 6 or an adhesive layer 7. An ultraviolet-curing adhesive (manufactured by Kyoritsu Chemical Industry Co., Ltd., product name "OP-1903R") was used as the adhesive that would become the adhesive layer 4. In addition, in the process of forming the adhesive layer 4, 20 μl of the adhesive that would become the adhesive layer 4 was dispensed using a precision dispenser onto the surface of the first intermediate element facing the resin film. Next, the substrate 5 was brought into contact with the adhesive from above, and a 3 kg weight parallel flat glass for pressure application was placed on top and left to stand for 180 seconds. Except for these points, the optical element 10 according to Example 8 was manufactured in the same manner as in Example 6.

[0095] The change in the reflected wavefront due to the change in the environmental temperature was measured for the optical element 10 according to Example 8 in the same manner as in Example 1. The change in the reflected wavefront was 90 nm, and therefore the optical element was evaluated as A.

[0096] Furthermore, for the optical element 10 according to Example 8, the average thicknesses of the adhesive layer 2 and the adhesive layer 4 were measured in the same manner as in Example 1. As a result, for the optical element 10 according to Example 8, the average thickness of the adhesive layer 2 was 6 μm, and the average thickness of the adhesive layer 4 was 6 μm.

[0097] Example 9 In Example 9, an optical element 10 was manufactured without forming a resin layer 6 or an adhesive layer 7. In the step of forming adhesive layer 2, 30 μl of adhesive to become adhesive layer 2 was dispensed onto substrate 1 using a precision dispenser. Next, a resin film to become resin layer 3 was brought into contact with the adhesive from above, and a parallel flat plate glass for pressure application weighing 3 kg was placed on top and left to stand for 120 seconds. In the step of forming adhesive layer 4, 33 μl of adhesive to become adhesive layer 4 was dispensed onto the resin film side surface of the first intermediate element using a precision dispenser. Next, substrate 5 was brought into contact with the adhesive from above, and a parallel flat plate glass for pressure application weighing 3 kg was placed on top and left to stand for 110 seconds. Except for these points, the optical element 10 of Example 9 was manufactured in the same manner as in Example 7.

[0098] The change in the reflected wavefront due to the change in the environmental temperature was measured for the optical element 10 according to Example 9 in the same manner as in Example 1. The change in the reflected wavefront was 190 nm, and therefore the optical element was evaluated as B.

[0099] Furthermore, for the optical element 10 according to Example 6, the average thicknesses of the adhesive layer 2 and the adhesive layer 4 were measured in the same manner as in Example 1. As a result, for the optical element 10 according to Example 6, the average thickness of the adhesive layer 2 was 9 μm, and the average thickness of the adhesive layer 4 was 10 μm.

[0100] (Comparative Example 1) In Comparative Example 1, in the step of forming the adhesive layer 7, 20 μl of adhesive to become the adhesive layer 7 was dispensed onto the resin film side surface of the second intermediate element using a precision dispenser. Next, the substrate 5 was brought into contact with the adhesive from above, and a parallel flat glass plate for pressure application weighing 3 kg was placed on top and left to stand for 180 seconds. Except for these points, the optical element 10 according to Comparative Example 1 was manufactured in the same manner as in Example 2.

[0101] The change in the reflected wavefront due to the change in the environmental temperature was measured for the optical element 10 according to Comparative Example 1 in the same manner as in Example 1. The change in the reflected wavefront was 220 nm, and therefore the optical element was evaluated as C.

[0102] Furthermore, for the optical element 10 according to Comparative Example 1, the average thicknesses of adhesive layer 2, adhesive layer 4, and adhesive layer 7 were measured in the same manner as in Example 1. As a result, for the optical element 10 according to Comparative Example 1, the average thickness of adhesive layer 2 was 6 μm, the average thickness of adhesive layer 4 was 6 μm, and the average thickness of adhesive layer 7 was 6 μm.

[0103] (Comparative Example 2) In Comparative Example 2, an optical element 10 was manufactured without forming a resin layer 6 or an adhesive layer 7. In the step of forming adhesive layer 2, 20 μl of adhesive to become adhesive layer 2 was dispensed onto substrate 1 using a precision dispenser. Next, a resin film to become resin layer 3 was brought into contact with the adhesive from above, and a parallel flat plate glass for pressure application weighing 3 kg was placed on top and left to stand for 180 seconds. In the step of forming adhesive layer 4, 20 μl of adhesive to become adhesive layer 4 was dispensed onto the resin film side surface of the first intermediate element using a precision dispenser. Next, substrate 5 was brought into contact with the adhesive from above, and a parallel flat plate glass for pressure application weighing 3 kg was placed on top and left to stand for 180 seconds. Except for these points, the optical element 10 according to Comparative Example 2 was manufactured in the same manner as in Example 2.

[0104] The change in the reflected wavefront due to the change in the environmental temperature was measured for the optical element 10 according to Comparative Example 2 in the same manner as in Example 1. The change in the reflected wavefront was 240 nm, and therefore the optical element was evaluated as C.

[0105] Furthermore, for the optical element 10 according to Comparative Example 2, the average thicknesses of the adhesive layer 2 and the adhesive layer 4 were measured in the same manner as in Example 1. As a result, for the optical element 10 according to Comparative Example 2, the average thickness of the adhesive layer 2 was 6 μm, and the average thickness of the adhesive layer 4 was 6 μm.

[0106] The evaluation results for Examples 1 to 9 and Comparative Examples 1 and 2 are shown in Table 1 below along with various numerical values. Note that Examples 1 to 5 show the value of (T3 / E3) / (T1 / E1), and Examples 6 to 9 and Comparative Example 2 show the value of (T2 / E2) / (T1 / E1). Comparative Example 1 shows the values ​​of (T2 / E2) / (T1 / E1) and (T3 / E3) / (T1 / E1), which are the same value.

[0107] As is clear from Table 1, the optical elements 10 according to Examples 1 to 9 can reduce the change in the reflected wavefront when the environmental temperature changes, and can reduce or prevent the deterioration of the optical characteristics.

[0108] [Table 1]

[0109] [Second embodiment] The optical element 10 according to the first embodiment can be applied to various devices and apparatuses such as optical equipment, display devices, imaging devices, etc. In the second embodiment, an optical equipment will be described as a specific application example of the optical element 10 according to the first embodiment.

[0110] (optical equipment) Specific application examples of the optical element 10 according to the first embodiment include lenses constituting optical devices (display optical systems) for head-mounted displays and liquid crystal projectors, lenses constituting optical devices (photography optical systems) for cameras and video cameras, etc. These optical systems are composed of at least one optical element arranged in a housing, and the optical element 10 according to the first embodiment can be used for at least one of these optical elements.

[0111] (display device) FIG. 9 is a schematic cross-sectional view showing the configuration of a head-mounted display 107, which is an example of a preferred embodiment of a display device using the optical element 10 according to the first embodiment.

[0112] 9, the head-mounted display 107 has a housing 105, a wearing device 106, display optical systems 100 for the left and right eyes, and display panels 101 for the left and right eyes. Each display optical system 100 and each display panel 101 is provided inside the housing 105. The head-mounted display 107 is worn on the user's head by the wearing device 106 so that the display optical systems 100 for the left and right eyes and the display panels 101 are positioned corresponding to the user's left and right eyes, respectively.

[0113] Each display optical system 100 is disposed relative to a corresponding display panel 101 and includes an optical element 102, an optical element 103, and the optical element 10 according to the first embodiment. The display panel 101 is a display unit such as an organic electroluminescence panel or a liquid crystal panel, and displays an image for the corresponding left or right eye. The optical elements 102, 103, and 10 in the display optical system 100 are used to focus image light emitted from the display panel 101 at the position of the user's eye 20. As described above with reference to FIG. 5 , the display optical system 100 is a folded optical system in which the optical path is folded by optical functional surfaces, such as a reflective polarizing layer, a retardation layer, and a transmissive reflective layer, included in the display optical system 100. Depending on the design of the head-mounted display 107, the display optical system 100 may include a transmissive optical element such as a convex lens or a concave lens, a polarizing beam splitter (PBS), a half mirror, a polarizing plate, a retardation plate, or other optical path-changing optical elements. The optical element 10, together with the optical elements 102 and 103, constitutes an optical system that guides image light, which is light emitted from the display panel 101, to the user's eye 20, and functions as at least one of the optical elements in the optical system.

[0114] Although the display device has been described here using a head-mounted display, the optical element 10 can also be used in a projector or the like.

[0115] (imaging device) 10 is a schematic diagram showing the configuration of a digital camera 209, which is an example of a preferred embodiment of an imaging device using the optical element 10 according to the first embodiment. In Fig. 10, a camera body 208 and a lens barrel 205, which is an optical device, are coupled together, but the lens barrel 205 may be a so-called interchangeable lens that is detachable from the camera body 208, or may be fixed to the camera body 208.

[0116] Light from a subject passes through an imaging optical system 200, which is composed of multiple optical elements arranged on an optical axis within a housing of a lens barrel 205, and is focused on an image sensor 201, which is an imaging element, and captured. The image captured by the image sensor 201 is stored in a memory within a camera body 208 and displayed on an electronic viewfinder 206 or a monitor 207, allowing a user to check the image. Each optical element is movably supported relative to the outer barrel of the lens barrel 205 for focusing and zooming. As described above with reference to FIG. 6 , the imaging optical system 200 is a folded optical system in which the optical path is folded by optical functional surfaces, such as a reflective polarizing layer, a retardation layer, and a transflective layer, contained within the imaging optical system 200. The optical element 10, together with optical elements 202 and 203, constitutes an optical system that guides light from a subject to the image sensor 201 and functions as at least one of the optical elements in the optical system.

[0117] The disclosure of this embodiment includes the following configurations and methods. (Configuration 1) a first substrate; a first adhesive layer; a resin layer having reflective properties; a second adhesive layer; and a second substrate; the first substrate, the first adhesive layer, the resin layer, the second adhesive layer, and the second substrate are laminated in this order; An optical element characterized by satisfying the following formula (1-1), where T1 is the average thickness of the first adhesive layer, E1 is the Young's modulus of the first adhesive layer, T2 is the average thickness of the second adhesive layer, and E2 is the Young's modulus of the second adhesive layer. 1.1×T1 / E1≦T2 / E2…(1-1) (Configuration 2) The optical element according to configuration 1, wherein the following formula (1-2) is satisfied: 1.8×T1 / E1≦T2 / E2…(1-2) (Configuration 3) The resin layer is a reflective polarizing layer. 3. The optical element according to configuration 1 or 2. (Configuration 4) a first substrate; a first adhesive layer; a first resin layer having reflective properties; a second adhesive layer; and a second resin layer; a third adhesive layer; and a second substrate; the first base material, the first adhesive layer, the first resin layer, the second adhesive layer, the second resin layer, the third adhesive layer, and the second base material are laminated in this order; An optical element characterized by satisfying the following formula (2-1) or (3-1), when the average thickness of the first adhesive layer is T1, the Young's modulus of the first adhesive layer is E1, the average thickness of the second adhesive layer is T2, the Young's modulus of the second adhesive layer is E2, the average thickness of the third adhesive layer is T3, and the Young's modulus of the third adhesive layer is E3. 1.1×T1 / E1≦T2 / E2…(2-1) 1.1×T1 / E1≦T3 / E3…(3-1) (Configuration 5) The optical element according to configuration 4, wherein the following formula (2-2) or (3-2) is satisfied: 1.8×T1 / E1≦T2 / E2…(2-2) 1.8×T1 / E1≦T3 / E3…(3-2) (Configuration 6) the first resin layer is a reflective polarizing layer, The second resin layer is a retardation layer. 6. The optical element according to configuration 4 or 5, (Configuration 7) The T1 is 20 μm or less 7. The optical element according to any one of configurations 1 to 6. (Configuration 8) The first base material and the second base material are made of materials having different linear expansion coefficients. 8. The optical element according to any one of configurations 1 to 7, wherein: (Configuration 9) The material of the first substrate and the second substrate is glass. 10. The optical element according to any one of configurations 1 to 9. (Configuration 10) At least one of the first substrate and the second substrate functions as a lens. 11. The optical element according to any one of configurations 1 to 10. (Configuration 11) An optical system disposed between a sensor on which light from an object is incident and the object, The optical element according to any one of configurations 1 to 10 is included; The optical element reflects the light once before it reaches the sensor. An optical system characterized by: (Configuration 12) 11. An optical device comprising a housing and an optical system having at least one optical element disposed within the housing, wherein at least one of the optical elements is the optical element described in any one of configurations 1 to 10. (Configuration 13) A display device having a housing, an optical system having at least one optical element arranged in the housing, and a display unit that emits light guided by the optical system, wherein at least one of the optical elements is the optical element described in any one of configurations 1 to 10. (Configuration 14) An imaging device having a housing, an optical system having at least one optical element arranged in the housing, and an imaging element that receives light that has passed through the optical system, wherein at least one of the optical elements is the optical element described in any one of configurations 1 to 10. [Explanation of symbols]

[0118] 1 Base material 2 Adhesive layer 3 Resin layer 4 Adhesive layer 5 Base material 6 Resin layer 7 Adhesive layer 10 Optical Elements 100 Display optical system 101 Display Panel 102 Optical Elements 103 Optical Elements 104 Display device 105 Case 106 Wearing equipment 107 Head-mounted display 200 Imaging Optical System 201 Image Sensor 202 Optical Elements 203 Optical Elements 204 Imaging device 205 Lens barrel 206 Electronic Viewfinder 207 Monitor 208 Camera body 209 Digital Camera

Claims

1. a first substrate; a first adhesive layer; a resin layer having reflective properties; a second adhesive layer; and a second substrate; the first substrate, the first adhesive layer, the resin layer, the second adhesive layer, and the second substrate are laminated in this order; The average thickness of the first adhesive layer is T １ , the Young's modulus of the first adhesive layer is E １ , the average thickness of the second adhesive layer is T ２ , the Young's modulus of the second adhesive layer is E ２ When the above formula is set, the optical element satisfies the following formula (1-1): 1.1×T １ / E １ ≦T ２ / E ２ …(1-1)

2. 2. The optical element according to claim 1, wherein the following formula (1-2) is satisfied: 1.8×T １ / E １ ≦T ２ / E ２ …(1-2)

3. The resin layer is a reflective polarizing layer.

3. The optical element according to claim 1 or 2.

4. a first substrate; a first adhesive layer; a first resin layer having reflective properties; a second adhesive layer; and a second resin layer; a third adhesive layer; and a second substrate; the first base material, the first adhesive layer, the first resin layer, the second adhesive layer, the second resin layer, the third adhesive layer, and the second base material are laminated in this order; The average thickness of the first adhesive layer is T １ , the Young's modulus of the first adhesive layer is E １ , the average thickness of the second adhesive layer is T ２ , the Young's modulus of the second adhesive layer is E ２ , the average thickness of the third adhesive layer is T ３ , the Young's modulus of the third adhesive layer is E ３ and the optical element satisfies the following formula (2-1) or (3-1): 1.1×T １ / E １ ≦T ２ / E ２ …(2-1) 1.1×T １ / E １ ≦T ３ / E ３ …(3-1)

5. 5. The optical element according to claim 4, wherein the following formula (2-2) or (3-2) is satisfied: 1.8×T １ / E １ ≦T ２ / E ２ …(2-2) 1.8×T １ / E １ ≦T ３ / E ３ …(3-2)

6. the first resin layer is a reflective polarizing layer, The second resin layer is a retardation layer.

6. The optical element according to claim 4 or 5.

7. The T1 is 20 μm or less 5. The optical element according to claim 1 or 4.

8. The first base material and the second base material are made of materials having different linear expansion coefficients.

5. The optical element according to claim 1 or 4.

9. The material of the first substrate and the second substrate is glass.

5. The optical element according to claim 1 or 4.

10. At least one of the first substrate and the second substrate functions as a lens.

5. The optical element according to claim 1 or 4.

11. An optical system disposed between a sensor on which light from an object is incident and the object, The optical element according to claim 1 or 4, The optical element reflects the light once before it reaches the sensor. An optical system characterized by:

12. 10. An optical device comprising a housing and an optical system having at least one optical element disposed within the housing, wherein at least one of the optical elements is the optical element according to claim 1 or 4.

13. 10. A display device comprising: a housing; an optical system having at least one optical element disposed within the housing; and a display unit that emits light guided by the optical system, wherein at least one of the optical elements is the optical element according to claim 1 or 4.

14. 10. An imaging device comprising: a housing; an optical system having at least one optical element disposed within the housing; and an imaging element that receives light that has passed through the optical system, wherein at least one of the optical elements is the optical element according to claim 1 or 4.

Images