Optical device and method for manufacturing optical device

Abstract

An optical device comprises: a concavo-convex structure layer having a concavo-convex structure on its surface, the concavo-convex structure being either a plurality of convex portions or a plurality of concave portions arranged in a subwavelength period; a high refractive index layer composed of a material having a higher refractive index than the concavo-convex structure layer, located on the concavo-convex structure and having a surface that follows the shape of the concavo-convex structure; and a low refractive index layer composed of a material having a lower refractive index than the high refractive index layer, located on the high refractive index layer. The high refractive index layer includes a first grating high refractive index portion located at the bottom of the concavo-convex structure and forming a first subwavelength grating, and a second grating high refractive index portion located at the top of the concavo-convex structure and forming a second subwavelength grating. Either the concavo-convex structure layer or the low refractive index layer has absorptivity for light within a predetermined wavelength range, or the optical device comprises an additional layer having absorptivity for light within the predetermined wavelength range.

Description

Technical Field

[0001] The present invention relates to an optical device utilizing a waveguide mode resonance phenomenon and a method for manufacturing the optical device. Background Art

[0002] Optical devices that extract light within a specific wavelength range from incident light as transmitted light or reflected light are used as wavelength-selective filters, such as color filters that extract light of various colors, such as red, green, and blue, from incident light. For example, filters that transmit relatively more light within a specific wavelength range through the absorption of pigments such as pigments are widely used. On the other hand, optical devices that utilize the waveguide mode resonance phenomenon can be used as filters that can achieve higher wavelength selectivity than filters that utilize pigment absorption. This optical device includes a subwavelength grating, which is a diffraction grating with a period less than the wavelength of the light. When light is incident on this subwavelength grating, it causes resonance while propagating through multiple reflections of the specific wavelength range due to differences in refractive index with the surrounding light, and is strongly emitted as reflected light. Furthermore, light within the wavelength range of the incident light, excluding the wavelength range of the reflected light, is emitted from the optical device as transmitted light (for example, see Patent Documents 1 and 2).

[0003] Patent Document 1: Japanese Patent No. 5023324

[0004] Patent Document 2: Japanese Patent Application Laid-Open No. 2009-25558 Summary of the Invention

[0005] However, in order to expand the use of optical devices, it is preferable that the optical devices have a light shielding function in addition to the functions of selectively reflecting and transmitting light.

[0006] For example, LED displays using tiny LED elements are attracting attention as next-generation displays. One type of LED display is to irradiate light from an ultraviolet LED (UV-LED) element onto a wavelength conversion layer composed of a phosphor to excite the phosphor, thereby emitting colored light. Specifically, the wavelength conversion layer has: a sub-pixel area that emits red light; a sub-pixel area that emits green light; and a sub-pixel area that emits blue light. A plurality of LED elements are arranged in an arrangement corresponding to the arrangement of the sub-pixel areas, and the ultraviolet light emitted by each LED element is irradiated onto each sub-pixel area, thereby emitting light of various colors with intensities corresponding to the intensity of the ultraviolet light from each sub-pixel area. In this way, the display of color images on the LED display is achieved.

[0007] Here, a portion of the ultraviolet light emitted by the LED element passes through the wavelength conversion layer and leaks onto the surface of the LED display. To protect the eyes of viewers of the LED display, it is desirable to minimize the leakage of ultraviolet light from the LED display. If the optical device not only transmits colored light but also blocks ultraviolet light, the optical device can be used to suppress ultraviolet light leakage, thereby expanding its applications.

[0008] An object of the present disclosure is to provide an optical device having a light shielding function and a method for manufacturing the optical device.

[0009] In one embodiment, an optical device is provided. The optical device comprises: a concavo-convex structure layer having a concavo-convex structure on its surface, the concavo-convex structure being either a plurality of convex portions or a plurality of concave portions arranged in a subwavelength period; a high refractive index layer, located on the concavo-convex structure and having a surface that follows the shape of the concavo-convex structure, comprising a first grating high refractive index portion located at the bottom of the concavo-convex structure and forming a first subwavelength grating, and a second grating high refractive index portion located at the top of the concavo-convex structure and forming a second subwavelength grating, the layer being composed of a material having a higher refractive index than the concavo-convex structure layer; and a low refractive index layer, located on the high refractive index layer and composed of a material having a lower refractive index than the high refractive index layer. Either the concavo-convex structure layer or the low refractive index layer has absorptivity for light within a predetermined wavelength range, or the optical device comprises an additional layer having absorptivity for light within the predetermined wavelength range.

[0010] In another embodiment, a method for manufacturing an optical device is provided. The method comprises the following steps: a first step of forming a concavo-convex structure layer having a concavo-convex structure on its surface, the concavo-convex structure being composed of a first low-refractive-index material, the concavo-convex structure being either a plurality of convex portions or a plurality of concave portions arranged in a subwavelength period; a second step of forming a high-refractive-index layer composed of a high-refractive-index material having a higher refractive index than the first low-refractive-index material, the high-refractive-index layer comprising, along the surface of the concavo-convex structure layer, a first grating high-refractive-index portion located at the bottom of the concavo-convex structure forming a first subwavelength grating, and a second grating high-refractive-index portion located at the top of the concavo-convex structure forming a second subwavelength grating; and a third step of forming a low-refractive-index layer composed of a second low-refractive-index material having a lower refractive index than the high-refractive-index material on the high-refractive-index layer. Either the concavo-convex structure layer or the low-refractive-index layer has absorptivity for light within a predetermined wavelength range, or the method further comprises the step of forming an additional layer having absorptivity for light within the predetermined wavelength range. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1AThis is a diagram showing a cross-sectional structure of an optical device according to a first embodiment of the optical device. Figure 1B is a diagram showing a cross-sectional structure of a first grid region in accordance with a first embodiment of the optical device. Figure 1C This is a diagram showing a cross-sectional structure of an intermediate region in accordance with a first embodiment of the optical device. Figure 1D This is a diagram showing the cross-sectional structure of the second grating region in the first embodiment of the optical device.

[0012] Figure 2 It is a diagram showing a step of forming a concavo-convex structure layer in the method for manufacturing the optical device according to the first embodiment.

[0013] Figure 3 These are diagrams showing steps of forming a high refractive index layer in the method for manufacturing an optical device according to the first embodiment.

[0014] Figure 4 These are diagrams showing steps of forming a low-refractive-index layer in the method for manufacturing an optical device according to the first embodiment.

[0015] Figure 5 It is a diagram showing a cross-sectional structure of a modified example of the optical device according to the first embodiment.

[0016] Figure 6 It is a diagram showing a cross-sectional structure of a modified example of the optical device according to the first embodiment.

[0017] Figure 7 It is a diagram showing a planar structure of a display device including an optical filter to which the optical device according to the first embodiment is applied.

[0018] Figure 8 This is a diagram showing the operation of a display device including an optical filter to which the optical device according to the first embodiment is applied.

[0019] Figure 9 This is a diagram showing an example of a cross-sectional structure of an optical device according to a second embodiment of the optical device.

[0020] Figure 10 This is a diagram showing an example of a cross-sectional structure of an optical device according to a second embodiment of the optical device.

[0021] Figure 11 This is a diagram showing a state where concavo-convex structures face each other, in relation to the method for manufacturing an optical device according to the second embodiment.

[0022] Figure 12 This is a diagram showing a process of forming a embedding layer in the method for manufacturing an optical device according to the second embodiment.

[0023] Figure 13This is a diagram showing a part of the cross-sectional structure of an optical device according to a third embodiment of the optical device.

[0024] Figure 14A This is a diagram showing a cross-sectional structure of an optical device according to a fourth embodiment of the optical device. Figure 14B is a diagram showing the cross-sectional structure of the first grid region in accordance with the fourth embodiment of the optical device. Figure 14C This is a diagram showing the cross-sectional structure of the intermediate region in accordance with the fourth embodiment of the optical device. Figure 14D This is a diagram showing the cross-sectional structure of the second grating region in the fourth embodiment of the optical device.

[0025] Figure 15 It is a diagram showing a cross-sectional structure of a modified example of the optical device according to the first embodiment. DETAILED DESCRIPTION

[0026] (First embodiment)

[0027] Reference Figures 1A to 8 A first embodiment of an optical device and a method for manufacturing the optical device will be described. In this embodiment, an optical device having a function of shielding light in the ultraviolet region will be described as an example. The wavelength of light in the visible region is set to be greater than or equal to 400 nm and less than or equal to 800 nm, and the wavelength of light in the ultraviolet region is set to be greater than or equal to 300 nm and less than 400 nm.

[0028] [Overall structure of optical equipment]

[0029] like Figure 1A As shown, the optical device 10 includes a substrate 11, a first low-refractive-index region 12, a first grid region 13, an intermediate region 14, a second grid region 15, a second low-refractive-index region 16, and a top region 17. Each of these regions is layered and extended, with the first low-refractive-index region 12, the first grid region 13, the intermediate region 14, the second grid region 15, the second low-refractive-index region 16, and the top region 17 being arranged in order from a position close to the substrate 11. The direction in which the regions are arranged is a first direction, which is the thickness direction of the regions and the optical device 10. The side of the top region 17 relative to the substrate 11 is the surface side of the optical device 10, and the side of the substrate 11 relative to the top region 17 is the back side of the optical device 10. Figure 1B shows a cross section of the first grid region 13 perpendicular to the first direction, Figure 1C shows a cross section of the intermediate region 14 perpendicular to the first direction, Figure 1D A cross section of the second grid region 15 perpendicular to the first direction is shown.

[0030] The substrate 11 has a plate shape, and among the surfaces of the substrate 11, the surface located on the surface side of the optical device 10 is the surface of the substrate 11. The substrate 11 is made of a material that has no absorption wavelength in the wavelength range to be extracted by the optical device 10. For example, when light in the visible region is to be extracted as transmitted light, a substrate that is transparent to light in the visible region, such as a synthetic quartz substrate or a film made of a resin such as polyethylene terephthalate or polyethylene naphthalate, is used as the substrate 11.

[0031] The first low-refractive-index region 12 contacts the surface of the substrate 11 and extends uniformly along the surface of the substrate 11. The first grating region 13 includes a first grating high-refractive-index portion 13a and a first grating low-refractive-index portion 13b. When viewed from a position facing the surface of the substrate 11, that is, viewed along the first direction, the first grating high-refractive-index portion 13a and the first grating low-refractive-index portion 13b extend in a strip-like pattern along a second direction, which serves as a common direction, and are alternately arranged along a third direction, which is orthogonal to the second direction. The second and third directions are each orthogonal to the first direction.

[0032] The intermediate region 14 includes an intermediate high-refractive-index portion 14a, a first intermediate low-refractive-index portion 14b, and a second intermediate low-refractive-index portion 14c. When viewed along the first direction, these portions extend along the second direction. The first intermediate low-refractive-index portion 14b and the second intermediate low-refractive-index portion 14c are alternately arranged along the third direction, with the intermediate high-refractive-index portion 14a interposed therebetween. That is, the first intermediate low-refractive-index portion 14b, the intermediate high-refractive-index portion 14a, the second intermediate low-refractive-index portion 14c, and the intermediate high-refractive-index portion 14a are repeatedly arranged in this order along the third direction. The first intermediate low-refractive-index portion 14b is located on the first grating low-refractive-index portion 13b. The intermediate high-refractive-index portion 14a is located at the end of the first grating high-refractive-index portion 13a in the width direction, while the second intermediate low-refractive-index portion 14c is located at the center of the first grating high-refractive-index portion 13a in the width direction.

[0033] The second grating region 15 includes a second grating high-refractive-index portion 15a and a second grating low-refractive-index portion 15b. When viewed along the first direction, the second grating high-refractive-index portion 15a and the second grating low-refractive-index portion 15b extend in a strip-like pattern along the second direction and are alternately arranged along the third direction. That is, the high-refractive-index portions and the low-refractive-index portions in the two grating regions 13 and 15 are arranged in the same direction. The second grating high-refractive-index portion 15a is located on the first intermediate low-refractive-index portion 14b and the intermediate high-refractive-index portion 14a, while the second grating low-refractive-index portion 15b is located on the second intermediate low-refractive-index portion 14c.

[0034] The second low-refractive-index region 16 extends uniformly along the second grating region 15 on the side opposite to the intermediate region 14 relative to the second grating region 15. The top region 17 includes a first top low-refractive-index portion 17a and a second top low-refractive-index portion 17b. When viewed along the first direction, the first top low-refractive-index portion 17a and the second top low-refractive-index portion 17b extend in a strip-like pattern along the second direction and are alternately arranged along the third direction. The first top low-refractive-index portion 17a is located above the second grating high-refractive-index portion 15a across the second low-refractive-index region 16, while the second top low-refractive-index portion 17b is located above the second grating low-refractive-index portion 15b across the second low-refractive-index region 16.

[0035] In the aforementioned regions of the optical device 10, adjacent regions along the first direction are partially continuous. Specifically, the first low-refractive-index region 12 and the first grid low-refractive-index portion 13b are continuous with each other, and the first grid low-refractive-index portion 13b and the first intermediate low-refractive-index portion 14b are continuous with each other, and these portions are composed of the same material. Furthermore, the first grid high-refractive-index portion 13a and the intermediate high-refractive-index portion 14a are continuous with each other, and the intermediate high-refractive-index portion 14a and the second grid high-refractive-index portion 15a are continuous with each other, and these portions are composed of the same material. Furthermore, the second intermediate low-refractive-index portion 14c and the second grid low-refractive-index portion 15b are continuous with each other, the second grid low-refractive-index portion 15b is continuous with each other, and the second low-refractive-index region 16 is continuous with each other, and the second low-refractive-index region 16 and the first top low-refractive-index portion 17a are continuous with each other, and these portions are composed of the same material. Furthermore, the second top low-refractive-index portion 17b is filled with air.

[0036] That is, the optical device 10 can also be considered as a structure having the following components: a substrate 11; a concavo-convex structure layer 21, located on the substrate 11 and having a concavo-convex structure composed of a plurality of convex portions 21a on its surface; a high refractive index layer 22, disposed along the surface of the concavo-convex structure layer 21; and a low refractive index layer 23, disposed along the surface of the high refractive index layer 22. The plurality of convex portions 21a extend along the second direction and are arranged along the third direction. The high refractive index layer 22 has a surface that follows the concavo-convex shape of the concavo-convex structure layer 21, and the low refractive index layer 23 has a surface that follows the concavo-convex shape of the high refractive index layer 22.

[0037] The concavo-convex structure layer 21 is composed of the first low refractive index region 12, the first grid low refractive index portion 13b, and the first intermediate low refractive index portion 14b. The convex portion 21a is composed of the first grid low refractive index portion 13b and the first intermediate low refractive index portion 14b.

[0038] The high-refractive-index layer 22 is composed of a first grating high-refractive-index portion 13a, an intermediate high-refractive-index portion 14a, and a second grating high-refractive-index portion 15a. The first grating high-refractive-index portion 13a is located between the plurality of protrusions 21a, i.e., at the bottom of the concavo-convex structure of the concavo-convex structure layer 21. The intermediate high-refractive-index portion 14a contacts the side surfaces of the protrusions 21a and extends along the thickness direction of the intermediate region 14, connecting the ends of the first and second grating high-refractive-index portions 13a, 15a, which are adjacent to each other when viewed along the first direction. The second grating high-refractive-index portion 15a covers the top surfaces of the protrusions 21a, i.e., is located at the top of the concavo-convex structure of the concavo-convex structure layer 21.

[0039] The low-refractive-index layer 23 is composed of the second intermediate low-refractive-index portion 14c, the second grating low-refractive-index portion 15b, the second low-refractive-index region 16, and the first top low-refractive-index portion 17a. The low-refractive-index layer 23 has a shape in which the second intermediate low-refractive-index portion 14c and the second grating low-refractive-index portion 15b protrude from the second low-refractive-index region 16 toward the substrate 11, and the first top low-refractive-index portion 17a protrudes from the second low-refractive-index region 16 toward the side opposite to the substrate 11. The surface of the low-refractive-index layer 23 has concavities and convexities, and the second top low-refractive-index portion 17b corresponds to the concavities.

[0040] The refractive index of the material of the high refractive index layer 22 is greater than the refractive index of air, and greater than the refractive index of each of the materials of the concavo-convex structure layer 21 and the low refractive index layer 23. That is, the refractive index of each of the first grating high refractive index portion 13a, the intermediate high refractive index portion 14a, and the second grating high refractive index portion 15a is greater than the refractive index of each of the first low refractive index region 12, the first grating low refractive index portion 13b, the first intermediate low refractive index portion 14b, the second intermediate low refractive index portion 14c, the second grating low refractive index portion 15b, the second low refractive index region 16, the first top low refractive index portion 17a, and the second top low refractive index portion 17b.

[0041] The refractive index of the material of the concavo-convex structure layer 21 and the material of the low-refractive index layer 23 is greater than that of air. To properly generate the waveguide mode resonance phenomenon, it is preferable that the refractive index difference between the material of the concavo-convex structure layer 21 and the material of the low-refractive index layer 23 and the material of the high-refractive index layer 22 is large. The refractive index difference between each of these materials and the material of the high-refractive index layer 22 is preferably greater than the refractive index difference between the material of the concavo-convex structure layer 21 and the material of the low-refractive index layer 23. In addition, the refractive index of the material of the low-refractive index layer 23 adjacent to the air layer is preferably less than or equal to the refractive index of the material of the concavo-convex structure layer 21.

[0042] The concavo-convex structure layer 21, the high refractive index layer 22, and the low refractive index layer 23 are each composed of a material that does not have an absorption wavelength in the wavelength range to be extracted in the optical device 10. For example, when light in the visible region is extracted as transmitted light, the concavo-convex structure layer 21, the high refractive index layer 22, and the low refractive index layer 23 are each composed of a material that is transparent to light in the visible region. Furthermore, the low refractive index layer 23 is composed of a material that has an absorption wavelength in the ultraviolet region, that is, a material that absorbs ultraviolet light.

[0043] Specifically, the low-refractive-index material for the concavo-convex structure layer 21 may be an inorganic material such as synthetic quartz, or a resin material such as an ultraviolet-curable resin, a thermoplastic resin, or a thermosetting resin. Furthermore, the low-refractive-index material for the low-refractive-index layer 23 may be an epoxy resin, zinc oxide, or the like. Furthermore, the high-refractive-index material for the high-refractive-index layer 22 may be an inorganic compound material such as titanium oxide, niobium oxide, tantalum oxide, zirconium oxide, zinc sulfide, indium tin oxide, or aluminum nitride.

[0044] [The role of optical equipment]

[0045] The period of the grating structure of the first grating region 13, that is, the arrangement period of the first grating high-refractive-index portions 13a, is a first period P1, which is smaller than the wavelength of light incident on the optical device 10. Similarly, the period of the grating structure of the second grating region 15, that is, the arrangement period of the second grating high-refractive-index portions 15a, is a second period P2, which is smaller than the wavelength of light incident on the optical device 10. In other words, the first period P1 and the second period P2 are subwavelength periods, and the first grating region 13 and the second grating region 15 each include a subwavelength grating. Furthermore, the wavelength range of incident light targeted by the optical device 10 of this embodiment is within the ultraviolet and visible regions, that is, greater than or equal to 300 nm and less than or equal to 800 nm.

[0046] In optical device 10, the average refractive index of each region approximates the average of the refractive indices of the high and low refractive index regions, corresponding to the volume ratio of the high and low refractive index regions in each region. The proportion of intermediate high refractive index region 14a in intermediate region 14 is smaller than the proportion of first grating high refractive index region 13a in first grating region 13 and the proportion of second grating high refractive index region 15a in second grating region 15. Therefore, the average refractive index of intermediate region 14 is smaller than the average refractive index of first grating region 13 and the average refractive index of second grating region 15. That is, in optical device 10, the subwavelength gratings located in first grating region 13 and second grating region 15 have a structure embedded in the low refractive index region.

[0047] When light enters the optical device 10 from the front surface, the subwavelength grating of the second grating region 15 is embedded in a low-refractive-index region. Therefore, the second grating region 15 suppresses the emission of diffracted light toward the front surface, thereby causing a waveguide mode resonance phenomenon. Specifically, light within a specific wavelength range undergoes multiple reflections and propagates through the second grating region 15, causing resonance. The light within this specific wavelength range is then emitted toward the front surface of the optical device 10 as reflected light.

[0048] Light that passes through second grating region 15 and then intermediate region 14 enters first grating region 13. When light enters first grating region 13, the subwavelength gratings of first grating region 13 are embedded in a low-refractive-index region, causing waveguide mode resonance even in first grating region 13. Specifically, light within a specific wavelength range undergoes multiple reflections and propagates through first grating region 13, causing resonance. Light within this specific wavelength range is then emitted toward the front surface of optical device 10 as reflected light.

[0049] The light transmitted through the first grating region 13 is transmitted through the first low refractive index region 12 and the substrate 11 and is emitted toward the rear surface side of the optical device 10 .

[0050] When the incident light includes ultraviolet light, the ultraviolet light is absorbed by the low refractive index layer 23. That is, the ultraviolet light is absorbed by each region when passing through the top region 17, the second low refractive index region 16, the second grid region 15, and the intermediate region 14.

[0051] As a result, light in the wavelength range enhanced by second grating region 15 and light in the wavelength range enhanced by first grating region 13 are emitted toward the front surface of optical device 10. Furthermore, light transmitted through each region of optical device 10 is emitted toward the back surface of optical device 10 as transmitted light.

[0052] The low-refractive-index layer 23 has an absorptive property for ultraviolet light. Thus, even when the incident light of the optical device 10 includes ultraviolet light, it can suppress the presence of ultraviolet light in the light transmitted by the optical device 10. In other words, light in the visible region predominates in the light transmitted by the optical device 10. Furthermore, the reflected light from the optical device 10 may include ultraviolet light. For example, the wavelength range enhanced by the first and second grating regions 13 and 15 may be in the ultraviolet region, and the light reflected at the interface between these regions may include ultraviolet light.

[0053] The wavelength range enhanced in each grid region 13 , 15 can be adjusted according to the period of the subwavelength grid of each grid region 13 , 15 , the thickness T1 , T2 of each grid region 13 , 15 , and the materials of each layer of the concavo-convex structure layer 21 , the high refractive index layer 22 , and the low refractive index layer 23 .

[0054] Furthermore, as described above, in addition to the light in the wavelength range amplified by each grating region 13, 15, light caused by reflection and interference at various regions of optical device 10 may be emitted toward the surface side of optical device 10. Furthermore, this light includes wavelength ranges different from the wavelength range amplified by each grating region 13, 15. Therefore, if the intensity of the light in these different wavelength ranges emitted toward the surface side of optical device 10 is high, the wavelength selectivity of the reflected light emitted toward the surface side of optical device 10 decreases.

[0055] In the case where a higher wavelength selectivity of the reflected light is desired according to the purpose of the optical device 10, the top region 17 preferably has a function of suppressing light of a wavelength range different from the wavelength range enhanced in each grid region 13, 15 from being emitted toward the surface side of the optical device 10. In other words, the top region 17 is preferably configured to eliminate the light of the above-mentioned different wavelength range. Specifically, the top region 17 weakens the light of the above-mentioned different wavelength range by interference and reflects the light of the above-mentioned different wavelength range toward the back side, thereby reducing the intensity of the light of the above-mentioned different wavelength range emitted toward the surface side. The wavelength range of light eliminated by the top region 17 can be adjusted according to the thickness and average refractive index of the top region 17, in other words, can be adjusted according to the thickness and material of the low refractive index layer 23. That is, the thickness and material of the low refractive index layer 23 are selected in such a manner as to suppress light other than the wavelength range enhanced in each grid region 13, 15 from being emitted from the top region 17 toward the surface side.

[0056] Furthermore, the outermost surface of the optical device 10, i.e., the surface of the low-refractive-index layer 23, has irregularities, thereby suppressing surface reflections from the optical device 10 compared to a case where the outermost surface of the optical device 10 is flat. This also suppresses light in a wavelength range different from the wavelength range of light enhanced by each grating region 13, 15 from being emitted toward the surface side of the optical device 10. Consequently, the wavelength selectivity of light emitted toward the surface side of the optical device 10 can be improved.

[0057] When each subwavelength grating is composed of grating high refractive index portions 13a, 15a extending in a stripe shape in a single direction, light polarized in a specific direction determined by the arrangement of the subwavelength gratings undergoes multiple reflections in each grating region 13, 15, causing resonance and being emitted as reflected light. Therefore, the optical device 10 of the first embodiment can efficiently extract reflected light from incident light with uniform polarization.

[0058] Furthermore, if wavelength selectivity of reflected light is not important depending on the application of optical device 10 , top region 17 may not have the function of eliminating light in a wavelength range different from the wavelength range enhanced by each grating region 13 , 15 .

[0059] Alternatively, optical device 10 can be used so that light enters from the back side of optical device 10. In this case, light in the wavelength range enhanced by each grating region 13, 15 is also emitted as reflected light toward the back side of optical device 10. Furthermore, light transmitted through each region of optical device 10 is emitted as transmitted light toward the front side of optical device 10. To obtain ultraviolet light as reflected light enhanced by grating regions 13, 15, by allowing light to enter from the back side, the amount of ultraviolet light that enters grating regions 13, 15 before being absorbed by low-refractive-index layer 23 is increased, thereby increasing the amount of light contributing to resonance. It is difficult for low-refractive-index layer 23 to absorb all of the ultraviolet light contained in the incident light, and it is also difficult for grating regions 13 and 15 to resonate and reflect all of the ultraviolet light contained in the incident light. Therefore, by performing both absorption of ultraviolet light by low-refractive-index layer 23 and absorption of ultraviolet light by resonance of grating regions 13 and 15, it is possible to more reliably suppress ultraviolet light contained in the transmitted light of optical device 10. In other words, the ultraviolet light shielding function of optical device 10 is improved.

[0060] [Details of optical equipment]

[0061] Regarding the optical device 10 , the wavelength range of light causing resonance in the first grating region 13 and the wavelength range of light causing resonance in the second grating region 15 may be set according to the wavelength range of light to be extracted as reflected light or transmitted light.

[0062] For example, to obtain a narrower and more intense reflected light, that is, to further improve the wavelength selectivity of the reflected light, the closer the wavelength range of the light resonating in first grating region 13 and the wavelength range of the light resonating in second grating region 15 are, the better. When light of a specific wavelength range resonates in second grating region 15, and for example, when the difference in refractive index between second grating region 15 and intermediate region 14 is small, a portion of the light in the specific wavelength range leaks into intermediate region 14 each time it is reflected in second grating region 15. In this case, if the wavelength ranges of the light resonating in first grating region 13 and second grating region 15 are the same, the light in the specific wavelength range that leaks into intermediate region 14 will also enter first grating region 13, resonate, and be emitted as reflected light. Consequently, the wavelength selectivity of the reflected light emitted from optical device 10 is improved.

[0063] On the other hand, when the ultraviolet light absorptivity of the optical device 10 is prioritized over the wavelength selectivity of the reflected light, the material and thickness of the low refractive index layer 23 can be determined with priority given to the ultraviolet light absorptivity of the low refractive index layer 23 over the reduction of multiple reflection losses and the adjustment of the wavelength range of resonance in the second grating region 15. In this case, the wavelength range of light that causes resonance in the first grating region 13 and the wavelength range of light that causes resonance in the second grating region 15 may deviate.

[0064] The following describes a preferred structure for improving the wavelength selectivity of reflected light. In order to improve the wavelength selectivity of reflected light, that is, to make the wavelength range of light that causes resonance in the first grid area 13 and the second grid area 15 consistent, it is sufficient to make the optical film thickness, a parameter represented by the value obtained by multiplying the average refractive index and the film thickness, consistent in the first grid area 13 and the second grid area 15. That is, the closer the optical film thickness is in the first grid area 13 and the second grid area 15, the closer the wavelength range of light that causes resonance is, and the wavelength selectivity is improved. The inventors of the present application discovered through simulation the range of the ratio of the optical film thickness of the first grid area 13 and the second grid area 15 that achieves good wavelength selectivity for reflected light. The following describes the details.

[0065] The volume ratio of the first grating high refractive index portion 13a to the entire first grating region 13 is equal to the area ratio of the first grating high refractive index portion 13a to the entire first grating region 13 when viewed from above along the first direction. In other words, this area ratio is the area ratio of the first grating high refractive index portion 13a in a cross section that includes the first grating high refractive index portion 13a and is perpendicular to the thickness direction of the first grating high refractive index portion 13a. If the area of ​​the first grating high refractive index portion 13a varies depending on the position of the cross section, the area ratio of the first grating high refractive index portion 13a in the cross section where the area of ​​the first grating high refractive index portion 13a is the largest is used.

[0066] When the area ratio of the first grating high refractive index portion 13 a is represented by R1, the area ratio of the first grating low refractive index portion 13 b in the cross section is represented by 1-R1.

[0067] When the refractive index of the material of the high refractive index layer 22 is n1 and the refractive index of the material of the concavo-convex structure layer 21 is n2 (n1>n2), the average refractive index NA1 of the first grid region 13 is expressed by the following formula (1).

[0068] NA1=n1×R1+n2×(1-R1)…(1)

[0069] Furthermore, the optical film thickness OT1 of the first grating region 13 is expressed by the following formula (2) using the average refractive index NA1 and thickness T1 of the first grating region 13 .

[0070] OT1=T1×NA1

[0071] =T1×{n1×R1+n2×(1-R1)}…(2)

[0072] In second grating region 15, the period of the grating structure, i.e., second period P2, coincides with first period P1 of first grating region 13. However, when viewed along the first direction, the width of second grating high-refractive-index portion 15a of second grating region 15 is greater than the width of first grating low-refractive-index portion 13b of first grating region 13. Furthermore, the width of second grating low-refractive-index portion 15b is smaller than the width of first grating high-refractive-index portion 13a.

[0073] The volume ratio of the second grating high refractive index portion 15a to the entire second grating region 15 is equal to the area ratio of the second grating high refractive index portion 15a to the entire second grating region 15 when viewed from above along the first direction. In other words, this area ratio is the area ratio of the second grating high refractive index portion 15a in a cross section that includes the second grating high refractive index portion 15a and is perpendicular to the thickness direction of the second grating high refractive index portion 15a. If the area of ​​the second grating high refractive index portion 15a varies depending on the position of the cross section, the area ratio of the second grating high refractive index portion 15a in the cross section where the area of ​​the second grating high refractive index portion 15a is the largest is used.

[0074] When the area ratio of the second grating high refractive index portion 15 a is represented by R2, the area ratio of the second grating low refractive index portion 15 b in the cross section is represented by 1−R2.

[0075] When the refractive index of the material of the high refractive index layer 22 is n1 and the refractive index of the material of the low refractive index layer 23 is n3 (n1>n3), the average refractive index NA2 of the second grating region 15 is expressed by the following formula (3).

[0076] NA2=n1×R2+n3×(1-R2)…(3)

[0077] Furthermore, the optical film thickness OT2 of the second grating region 15 is expressed by the following formula (4) using the average refractive index NA2 and thickness T2 of the second grating region 15 .

[0078] OT2=T2×NA2

[0079] =T2×{n1×R2+n3×(1-R2)}…(4)

[0080] As the ratio (OT2 / OT1) of the optical film thickness OT2 of second grating region 15 to the optical film thickness OT1 of first grating region 13 approaches 1, the wavelength ranges of light causing resonance in first grating region 13 and second grating region 15 become closer. On the other hand, as this ratio deviates from 1, the wavelength ranges of light causing resonance in first grating region 13 and second grating region 15 differ. The inventors of the present application have confirmed that, in order to achieve high wavelength selectivity, the value of OT2 / OT1 is preferably greater than or equal to 0.5 and less than or equal to 2.0, and in order to achieve even higher wavelength selectivity, the value of OT2 / OT1 is preferably greater than or equal to 0.625 and less than or equal to 1.6.

[0081] If the value of OT2 / OT1 is 1.0, that is, the optical film thickness OT1 and the optical film thickness OT2 are equal, the wavelength range of light causing resonance in the first grating region 13 and the wavelength range of light causing resonance in the second grating region 15 will be consistent, and wavelength selectivity will be significantly improved. Therefore, it is preferable to select the materials of each layer so that the optical film thickness OT1 and the optical film thickness OT2 are consistent, and to set the thicknesses T1 and T2, as well as the width of the convex portions 21a of the concavo-convex structure layer 21. The smaller the refractive index difference between the material of the concavo-convex structure layer 21 and the material of the low-refractive-index layer 23, the easier it is to make the ratio of the optical film thickness OT2 to the optical film thickness OT1 close to 1.0.

[0082] For example, in order to make the area ratio R1 of the first grating high refractive index portion 13a and the area ratio R2 of the second grating high refractive index portion 15a close to each other, the width of the convex portion 21a can be set so that the area ratio of the first grating low refractive index portion 13b is smaller than the area ratio of the first grating high refractive index portion 13a in the first grating region 13, and the area ratio of the second grating high refractive index portion 15a is larger than the area ratio of the second grating low refractive index portion 15b in the second grating region 15. In this case, the area ratio R1 of the first grating high refractive index portion 13a and the area ratio R2 of the second grating high refractive index portion 15a are both greater than 0.5, and R1 + R2 is greater than 1.

[0083] By setting area ratios R1 and R2 to be greater than 0.5, the average refractive index of grille regions 13 and 15 increases compared to when area ratios R1 and R2 are less than or equal to 0.5. This increases the difference in average refractive index between each grille region 13 and 15 and its adjacent regions 12, 14, and 16. As a result, the loss from multiple reflections occurring in each grille region 13 and 15 is reduced, thereby increasing the intensity of reflected light emitted from grille regions 13 and 15.

[0084] The arrangement period of the first intermediate low refractive index portions 14b in the intermediate region 14, i.e., the third period P3, matches the first period P1 of the first grating region 13. When viewed along the first direction, the width of the first intermediate low refractive index portions 14b matches the width of the first grating low refractive index portions 13b.

[0085] The area ratio of the intermediate high refractive index portion 14a relative to the entire intermediate region 14, when viewed from above along the first direction, is preferably less than or equal to the difference between the area ratio of the second grating high refractive index portion 15a and the area ratio of the first grating low refractive index portion 13b. That is, when the area ratio of the intermediate high refractive index portion 14a is set to R3, R3 preferably satisfies the following equation (5). In other words, this area ratio is the area ratio of the intermediate high refractive index portion 14a in a cross-section that includes the intermediate high refractive index portion 14a and is perpendicular to its thickness direction. If the area of ​​the intermediate high refractive index portion 14a varies depending on the position of the cross-section, the area ratio of the intermediate high refractive index portion 14a in the cross-section where the area of ​​the intermediate high refractive index portion 14a is the largest is used.

[0086] R3≤R2-(1-R1)=R1+R2-1...(5)

[0087] When viewed along the first direction, the area of ​​the second grating high refractive index portion 15a coincides with the area of ​​the first intermediate low refractive index portion 14b and the intermediate high refractive index portion 14a, and the area ratio R3 of the intermediate high refractive index portion 14a coincides with the right side, i.e., R1 + R2 - 1. Furthermore, when the area of ​​the second grating high refractive index portion 15a is larger than the area of ​​the first intermediate low refractive index portion 14b and the intermediate high refractive index portion 14a, when viewed along the first direction, in other words, when the intermediate high refractive index portion 14a is located inward of the outer edge of the second grating high refractive index portion 15a, the area ratio R3 is less than R1 + R2 - 1.

[0088] As described above, in order to increase the intensity of the reflected light emitted from the grating regions 13 and 15 through the waveguide mode resonance phenomenon, it is preferable that the difference between the average refractive index of each grating region 13 and 15 and the average refractive index of the regions 12, 14, and 16 sandwiching the grating regions 13 and 15 be large. Therefore, the smaller the average refractive index of the intermediate region 14, the better. In other words, the smaller the area ratio of the intermediate high refractive index portion 14a, the better. If the structure satisfies the above formula (5), the width of the intermediate high refractive index portion 14a can be suppressed to a level that does not extend outward compared to the second grating high refractive index portion 15a, and thus the area ratio of the intermediate high refractive index portion 14a does not become too large. As a result, the intensity of the reflected light from each grating region 13 and 15 is improved.

[0089] To increase the intensity of the reflected light, the difference between the average refractive index of the first grating region 13 and the average refractive index of the first low-refractive-index region 12 and the average refractive index of the intermediate region 14 is preferably greater than 0.1. Similarly, the difference between the average refractive index of the second grating region 15 and the average refractive index of the intermediate region 14 and the average refractive index of the second low-refractive-index region 16 is preferably greater than 0.1.

[0090] Furthermore, the arrangement period of the first top low-refractive-index portions 17 a of the top region 17 also coincides with the first period P1 of the first grating region 13 .

[0091] [Method for manufacturing optical device]

[0092] Reference Figures 2 to 4 A method for manufacturing the optical device 10 will be described.

[0093] like Figure 2 As shown, first, a layer made of a low-refractive-index material is formed on the surface of a substrate 11, and a concavo-convex structure is formed on the surface of this layer, thereby forming a concavo-convex structure layer 21. The concavo-convex structure layer 21 includes a flat portion 21c extending along the substrate 11, and a plurality of convex portions 21a protruding from the flat portion 21c, and a plurality of concave portions 21b located between the convex portions 21a. The convex portions 21a and concave portions 21b extend in a stripe shape along the second direction.

[0094] The concavo-convex structure is formed using a known microfabrication technique such as nanoimprint lithography or dry etching. Of these, nanoimprint lithography is preferred because it can easily form fine convex portions 21a and concave portions 21b.

[0095] For example, when using an ultraviolet curable resin as a low-refractive index material and forming the concavo-convex structure layer 21 by a photo-nanoimprinting method, first, the ultraviolet curable resin is applied to the surface of the substrate 11. Next, a gravure having a concavo-convex reversed concavo-convex structure composed of the convex portions 21a and concave portions 21b to be formed, i.e., a synthetic quartz mold, is pressed against the surface of a coating layer composed of ultraviolet curable resin, and the coating layer and the gravure are irradiated with ultraviolet rays. Next, the gravure is demolded from the cured ultraviolet curable resin. As a result, the concavo-convex structure of the gravure is transferred to the ultraviolet curable resin to form the convex portions 21a and concave portions 21b, and a flat portion 21c is formed as a residual film composed of ultraviolet curable resin between the convex portions 21a and concave portions 21b and the substrate 11.

[0096] Next, if Figure 3As shown, a high-refractive-index layer 22 made of a high-refractive-index material is formed on the surface of the concavo-convex structure layer 21. The high-refractive-index layer 22 is formed using a known film-forming technique such as vacuum evaporation or sputtering. The thickness of the high-refractive-index layer 22 is less than the height of the convex portion 21a and is set based on the desired thickness T1 and thickness T2. For example, the thickness of the high-refractive-index layer 22 is greater than or equal to 10 nm and less than or equal to 500 nm.

[0097] When forming the high refractive index layer 22 using a physical vapor deposition method, such as vacuum evaporation or sputtering, the film is formed on the convex portions 21a of the concavo-convex structure layer 21, extending further than the convex portions 21a. Specifically, the width of the second grating high refractive index portion 15a is formed to be greater than the width of the convex portions 21a, namely, the first grating low refractive index portion 13b, and the first intermediate low refractive index portion 14b. Therefore, when using a physical vapor deposition method, even if the area ratio of the convex portions 21a to the concave portions 21b on the surface of the concavo-convex structure layer 21 is set to 1:1, the area ratio of the first grating high refractive index portion 13a to the second grating high refractive index portion 15a will still vary.

[0098] In addition, if the width of the second grating high refractive index portion 15a increases during film formation, it is difficult for particles of the vapor deposition material to adhere to the recess 21b, so sometimes the thickness T1 of the first grating high refractive index portion 13a and the thickness T2 of the second grating high refractive index portion 15a deviate.

[0099] In the case of improving the wavelength selectivity of the reflected light of the optical device 10, it is preferred to set the width of the convex portion 21a, that is, the area ratio of the convex portion 21a and the concave portion 21b in such a manner as to compensate for the deviation in area ratio and thickness caused by the expansion of the width of the second grating high refractive index portion 15a, and the ratio of the above-mentioned optical film thickness OT2 to the optical film thickness OT1 is greater than or equal to 0.5 and less than or equal to 2.0, and more preferably greater than or equal to 0.625 and less than or equal to 1.6.

[0100] Furthermore, when the high refractive index layer 22 is formed using a physical vapor growth method, the high refractive index material often adheres to the side surfaces of the convex portions 21a of the concavo-convex structure layer 21, making it difficult to avoid the formation of the intermediate high refractive index portion 14a. Therefore, as described above, by controlling the width of the intermediate high refractive index portion 14a so as to satisfy the above formula (5), it is possible to obtain a good intensity of reflected light from each grating region 13, 15, even though a manufacturing method for forming the intermediate high refractive index portion 14a is employed.

[0101] The width of the middle high refractive index portion 14a can be controlled by the film forming method and film forming conditions. For example, the angular dependence of the particle flying direction is different in vacuum evaporation and sputtering, so the width of the middle high refractive index portion 14a can be changed depending on which method is used. In addition, the width of the middle high refractive index portion 14a can be reduced by etching after forming the high refractive index layer 22.

[0102] Next, if Figure 4 As shown, a low refractive index layer 23 made of a low refractive index material is formed on the surface of the high refractive index layer 22. As a method for forming the low refractive index layer 23, a well-known film forming technology such as a vacuum evaporation method and a sputtering method is used. The thickness of the low refractive index layer 23 is, for example, greater than or equal to 10 nm and less than or equal to 500 nm.

[0103] In this embodiment, compared to a method in which the layer in contact with the grating region is used as a waveguide layer for waveguide mode resonance, precise control of the film thickness of the layer in contact with the grating region is not required. Specifically, when the optical device 10 is formed using nanoimprint lithography, the optical device 10 can be manufactured without requiring precise control of the film thickness of the residual film. Therefore, the optical device 10 can be manufactured easily.

[0104] Furthermore, the optical device 10 can be formed by combining a manufacturing method such as photo-nanoimprinting and vacuum deposition, and is therefore suitable for roll-to-roll manufacturing.

[0105] Furthermore, in the above-described manufacturing method, a thermosetting resin or a thermoplastic resin may be used instead of the ultraviolet curing resin to form the concavo-convex structure layer 21 by nanoimprinting. When a thermosetting resin is used, the ultraviolet irradiation can be replaced by heating, and when a thermoplastic resin is used, the ultraviolet irradiation can be replaced by heating and cooling.

[0106] [Modification]

[0107] The optical device 10 of the above-described embodiment can be modified in the following manner.

[0108] like Figure 5 As shown, the optical device 10 may not include the substrate 11. In this case, the concavo-convex structure layer 21 is formed by forming a concavo-convex structure on the surface of a plate-like body made of a low-refractive-index material. For example, a sheet made of a thermoplastic resin may be used, and the concavo-convex structure may be formed on the surface of the sheet. Alternatively, a substrate made of synthetic quartz may be used, and the concavo-convex structure may be formed on the surface of the substrate. Forming the concavo-convex structure on the synthetic quartz substrate can be accomplished using known techniques such as dry etching.

[0109] In addition, if Figure 6 As shown, the protrusions 21a can be formed directly on the surface of the substrate 11. That is, the concavo-convex structure layer 21 does not need to have the flat portion 21c continuous with the protrusions 21a. In this case, the protrusions 21a and the substrate 11 constitute the concavo-convex structure layer 21, and the area of ​​the substrate 11 in contact with the protrusions 21a functions as the first low refractive index region 12. This concavo-convex structure layer 21 can be formed, for example, by photolithography.

[0110] Alternatively, the low refractive index layer 23 can be formed using various coating methods. When the low refractive index layer 23 is formed using a coating method, soda glass can be used as the material for the low refractive index layer 23. However, in order to form the low refractive index layer 23 to follow the shape of the high refractive index layer 22, in other words, to appropriately form unevenness on the surface of the low refractive index layer 23, it is preferable to form the low refractive index layer 23 using a physical vapor deposition method. The unevenness of the low refractive index layer 23 makes it possible to adjust the average refractive index of the top region 17, thereby adjusting the wavelength eliminated by the top region 17 and suppressing surface reflection of the optical device 10.

[0111] Furthermore, if the function of the top region 17 is not important, the surface of the low refractive index layer 23 may be flat. In this case, the optical device 10 does not have the top region 17, i.e., the region of the low refractive index layer 23 corresponding to the surface unevenness, and the surface of the second low refractive index region 16 becomes the outermost surface of the optical device 10.

[0112] [Application examples of optical equipment]

[0113] As a specific application example of the optical device 10 , a description will be given of a mode in which the optical device 10 is used as an optical filter included in a display device.

[0114] like Figure 7 As shown, display device 100 includes a light source layer 110, a conversion layer 120, and a filter layer 130. Light source layer 110 includes multiple light-emitting sections 111. Light-emitting sections 111 include ultraviolet LED (UV-LED) elements that emit ultraviolet light. The UV-LED elements are formed to have a length and width of, for example, several tens of micrometers.

[0115] The conversion layer 120 includes multiple sub-pixel regions 121. These sub-pixel regions 121 include three types of pixel regions 121: a red sub-pixel region 121R, a green sub-pixel region 121G, and a blue sub-pixel region 121B. The red sub-pixel region 121R includes an inorganic phosphor that emits red light when excited by ultraviolet light, the green sub-pixel region 121G includes an inorganic phosphor that emits green light when excited by ultraviolet light, and the blue sub-pixel region 121B includes an inorganic phosphor that emits blue light when excited by ultraviolet light. In this embodiment, red light has an intensity peak within a wavelength range of 600 nm or greater and 700 nm or less, green light has an intensity peak within a wavelength range of 520 nm or greater and 580 nm or less, and blue light has an intensity peak within a wavelength range of 400 nm or greater and 500 nm or less.

[0116] exist Figure 7 , each sub-pixel region 121R, 121G, and 121B is shown individually, but the red sub-pixel region 121R, the green sub-pixel region 121G, and the blue sub-pixel region 121B are repeatedly arranged in a predetermined pattern. A unit area including the red sub-pixel region 121R, the green sub-pixel region 121G, and the blue sub-pixel region 121B is a pixel area. Adjacent sub-pixel regions 121 may be in contact, or a region dividing these regions may be provided between adjacent sub-pixel regions 121.

[0117] The plurality of light emitting sections 111 are arranged one by one with respect to each sub-pixel region 121R, 121G, and 121B. That is, one light emitting section 111 is arranged below one sub-pixel region 121 .

[0118] The filter layer 130 has multiple filter regions 131. The optical device 10 is applied to each filter region 131. The multiple filter regions 131 include three types of filter regions 131: a red filter region 131R, a green filter region 131G, and a blue filter region 131B. The red filter region 131R transmits red light, the green filter region 131G transmits green light, and the blue filter region 131B transmits blue light. The red filter region 131R is located above the red sub-pixel region 121R, the green filter region 131G is located above the green sub-pixel region 121G, and the blue filter region 131B is located above the blue sub-pixel region 121B. The side of the filter layer 130 opposite the conversion layer 120 is the surface side of the display device 100.

[0119] The red filter region 131R only needs to transmit at least red light within the visible range. For example, the red filter region 131R may transmit all visible light and reflect ultraviolet light, or may transmit red light and reflect green and blue light. Similarly, the green filter region 131G only needs to transmit at least green light within the visible range, and the blue filter region 131B only needs to transmit at least blue light within the visible range.

[0120] Therefore, the structures of the red filter regions 131R, green filter regions 131G, and blue filter regions 131B do not necessarily need to be different from each other. For example, the filter regions 131R, 131G, and 131B can have the same structure, each transmitting light in the entire visible range and reflecting light in the ultraviolet range. This structure makes it easier to form the filter layer 130 than if the red filter regions 131R, green filter regions 131G, and blue filter regions 131B had different structures.

[0121] The optical device 10 is applied to the filter region 131, for example, so that the substrate 11 faces the sub-pixel region 121. If the structures of the filter regions 131R, 131G, and 131B are identical, the plurality of filter regions 131 can be collectively formed through the same manufacturing process. Furthermore, even if the structures of the filter regions 131R, 131G, and 131B are different, if only the period of the sub-wavelength grating is changed to vary the wavelength ranges of reflected and transmitted light, the plurality of filter regions 131 can be collectively formed through the same manufacturing process by changing the period of the convex portions 21a when forming the convex portions 21a.

[0122] In the above case, the substrate 11, first low-refractive-index region 12, first grating region 13, intermediate region 14, second grating region 15, second low-refractive-index region 16, and top region 17 are each continuous between the plurality of filter regions 131. Specifically, the plurality of filter regions 131 comprise: a common substrate 11; a concavo-convex structure layer 21 that is continuous between the filter regions 131; a high-refractive-index layer 22 that is continuous between the filter regions 131; and a low-refractive-index layer 23 that is continuous between the filter regions 131. When the period of the subwavelength grating is varied, the concavo-convex structure layer 21 of the plurality of filter regions 131 can be formed simultaneously using, for example, nanoimprint lithography using a synthetic quartz mold with a varying concavo-convex period in the portions corresponding to the filter regions 131 of each color. Furthermore, the high-refractive-index layer 22 and the low-refractive-index layer 23 can also be formed simultaneously in the portions corresponding to the filter regions 131 of each color. This facilitates the formation of the plurality of filter regions 131.

[0123] like Figure 8As shown, each light-emitting section 111 emits ultraviolet light Io. The ultraviolet light Io emitted from the light-emitting section 111 enters the sub-pixel region 121 above the light-emitting section 111. As a result, red light Ir is emitted from the red sub-pixel region 121R, green light Ig is emitted from the green sub-pixel region 121G, and blue light Ib is emitted from the blue sub-pixel region 121B.

[0124] The red light Ir emitted from the red sub-pixel region 121R enters the red filter region 131R above the red sub-pixel region 121R. The red filter region 131R reflects light in a certain wavelength range while transmitting red light. Therefore, the red light Ir that enters the red filter region 131R passes through the red filter region 131R and is emitted toward the front surface of the display device 100.

[0125] Green light Ig emitted from the green sub-pixel region 121G enters the green filter region 131G above the green sub-pixel region 121G. The green filter region 131G reflects light in a certain wavelength range while transmitting green light. Therefore, the green light Ig entering the green filter region 131G passes through the green filter region 131G and is emitted toward the front surface of the display device 100.

[0126] Blue light Ib emitted from the blue sub-pixel region 121B enters the blue filter region 131B above the blue sub-pixel region 121B. The blue filter region 131B reflects light within a certain wavelength range while transmitting blue light. Therefore, the blue light Ib that enters the blue filter region 131B passes through the blue filter region 131B and is emitted toward the front surface of the display device 100.

[0127] The intensity of the ultraviolet light Io irradiated to each sub-pixel region 121 is controlled based on the image data input to the display device 100. This controls the intensities of the red, green, and blue light emitted from the sub-pixel region 121, thereby controlling the color visually recognized in the pixel region. As a result, an image corresponding to the image data is displayed on the display device 100. Using tiny ultraviolet LED elements, the display device 100 achieves high brightness, wide viewing angles, and high-definition image display.

[0128] Here, a portion of the ultraviolet light Io emitted from the light-emitting section 111 passes through the sub-pixel region 121. The ultraviolet light Iu thus transmitted through the sub-pixel region 121 enters the filter region 131. Because the filter region 131 has ultraviolet light absorptivity due to the low-refractive-index layer 23, the ultraviolet light Iu is absorbed by the filter region 131. As a result, the ultraviolet light can be prevented from leaking toward the front surface of the display device 100. Therefore, the ultraviolet light can be prevented from affecting external objects such as viewers.

[0129] Furthermore, if the filter region 131 reflects ultraviolet light through waveguide mode resonance, leakage of ultraviolet light toward the surface of the display device 100 can be more reliably suppressed. Furthermore, in this structure, a portion of the ultraviolet light transmitted through the sub-pixel region 121 is reflected by the filter region 131 and enters the sub-pixel region 121 below the filter region 131, contributing to the excitation of the inorganic phosphor. Consequently, the efficiency of generating colored light in the sub-pixel region 121 relative to the amount of light emitted by the light-emitting portion 111 can be improved.

[0130] In addition, the red filter region 131R transmits only red light in the visible range, the green filter region 131G transmits only green light in the visible range, and if the blue filter region 131B is a structure that transmits only blue light in the visible range, the vividness of the color emitted by the display device 100 is improved.

[0131] Furthermore, the use of the optical device 10 is not limited to being a filter for shielding ultraviolet light in the display device 100. If shielding ultraviolet light is desired, the optical device 10 can also be applied to wavelength selection filters used in devices that convert or decompose the color of light, or to displays affixed to items for anti-counterfeiting or decorative purposes.

[0132] As described above, according to the first embodiment, the following advantages can be obtained.

[0133] (1) Waveguide mode resonance occurs in the first and second grating regions 13 and 15, allowing the optical device 10 to selectively reflect and transmit light. Furthermore, since the low-refractive-index layer 23 absorbs light in the ultraviolet region, the optical device 10 has a light-shielding function in the ultraviolet region. Therefore, the optical device 10 can be used as an optical filter in devices such as the display device 100 that excites a phosphor using ultraviolet light, which require suppression of ultraviolet light leakage, thereby expanding the application of the optical device 10.

[0134] (2) If the wavelength range of the ultraviolet region is included in at least one of the wavelength range enhanced by the first grating region 13 and the wavelength range enhanced by the second grating region 15, it is possible to further suppress the inclusion of light in the ultraviolet region in the transmitted light of the optical device 10. In other words, the ultraviolet light shielding function of the optical device 10 can be further improved.

[0135] (3) The top region 17 has the function of eliminating light of a wavelength range different from the reflected light enhanced by the grating regions 13 and 15 and suppressing the emission of this light together with the reflected light. This can improve the wavelength selectivity of the reflected light of the optical device 10.

[0136] (4) The ratio of the optical film thickness OT2 of the second grating region 15 to the optical film thickness OT1 of the first grating region 13 is greater than or equal to 0.5 and less than or equal to 2.0, and more preferably greater than or equal to 0.625 and less than or equal to 1.6. This allows light in similar wavelength ranges, which are enhanced in the two grating regions 13 and 15, to be obtained as reflected light. Consequently, the wavelength selectivity of the reflected light of the optical device 10 can be improved.

[0137] (5) The area ratio R3 of the intermediate high refractive index portion 14a of the intermediate region 14 satisfies R3 ≤ R1 + R2 - 1, thereby reducing the width of the intermediate high refractive index portion 14a. This prevents the average refractive index of the intermediate region 14 from becoming excessively high. Consequently, the difference in average refractive index between the grating regions 13 and 15 and their adjacent regions is maintained to a good value, thereby improving the intensity of reflected light from each grating region 13 and 15, which is obtained through the waveguide mode resonance phenomenon.

[0138] In addition, when viewed from the direction along the first direction, if the second grating high refractive index portion 15a is a structure that extends to the outside of the intermediate high refractive index portion 14a, the width of the intermediate high refractive index portion 14a can be suppressed to a smaller value. Therefore, as described above, the intensity of the reflected light from each grating area 13, 15 becomes good.

[0139] (6) The optical device 10 is formed by forming a concavo-convex structure layer 21 made of a low-refractive-index material, forming a high-refractive-index layer 22 on the surface of the concavo-convex structure layer 21, and forming a low-refractive-index layer 23 on the surface of the high-refractive-index layer 22. According to this manufacturing method, the wavelength selectivity of the optical device 10 can be improved without requiring precise control of the film thickness of the layer in contact with the subwavelength grating, and thus the optical device 10 can be easily manufactured.

[0140] In addition, regarding the method of using a resin as a low-refractive-index material, pressing a gravure plate onto a coating layer composed of the resin, and forming the concavo-convex structure layer 21 by curing the resin, the concavo-convex structure layer 21 is formed by a nanoimprint method, so that a concavo-convex structure layer 21 having fine concavo-convexity can be appropriately and simply formed. In addition, if the method of forming the low-refractive-index layer 23 by a physical vapor growth method is used, a low-refractive-index layer 23 having a surface shape that follows the concavo-convex shape of the surface of the high-refractive-index layer 22 can be appropriately formed. In addition, when the physical vapor growth method is used for forming the high-refractive-index layer 22, the high-refractive-index layer 22 is formed in such a manner that the second grating high-refractive-index portion 15a extends to the outside of the intermediate high-refractive-index portion 14a when viewed from the direction along the first direction. According to this manufacturing method, although the intermediate high refractive index portion 14a is formed on the side surface of the convex portion 21a, the width of the intermediate high refractive index portion 14a can be suppressed small, so the intensity of the reflected light from each grid area 13, 15 becomes good.

[0141] (Second embodiment)

[0142] Reference Figures 9 to 12 , a second embodiment of an optical device and a method for manufacturing an optical device will be described. Hereinafter, the second embodiment will be described with a focus on the differences between the second embodiment and the first embodiment. Elements identical to those in the first embodiment will be denoted by the same reference numerals and their description will be omitted.

[0143] [Optical equipment]

[0144] Reference Figure 9 as well as Figure 10 , the optical device of the second embodiment is described. Figure 9 As shown, the optical device 30 of the second embodiment includes two structures, namely, resonance structures 31, which are composed of the first low-refractive-index region 12, the first grating region 13, the intermediate region 14, the second grating region 15, the second low-refractive-index region 16, and the top region 17 described in the first embodiment. However, the second top low-refractive-index portion 17b of the top region 17 is filled with a low-refractive-index material.

[0145] The two resonant structures 31, namely the first resonant structure 31A and the second resonant structure 31B, are adjacent in the first direction, and the two resonant structures 31A and 31B are sandwiched between two substrates 11. In other words, the optical device 30 of the second embodiment has a structure in which the two optical devices 10 of the first embodiment are joined so that the top regions 17 face each other. In other words, the optical device 30 of the second embodiment has a structure in which four subwavelength gratings are arranged at intervals in the first direction, and these subwavelength gratings are embedded in the low-refractive-index material. Furthermore, the side of the other substrate 11 relative to the one substrate 11 is the front side of the optical device 30, and the side of the one substrate 11 relative to the other substrate 11 is the back side of the optical device 30.

[0146] In the optical device 30, the grating elements of the first resonant structure 31A, namely, the grating high-refractive-index portions 13a, 15a and the grating low-refractive-index portions 13b, 15b, extend in the same direction as the grating elements of the second resonant structure 31B, namely, the grating high-refractive-index portions 13a, 15a and the grating low-refractive-index portions 13b, 15b. In other words, the subwavelength gratings of the first resonant structure 31A are arranged in the same direction as the subwavelength gratings of the second resonant structure 31B. Furthermore, the low-refractive-index portions and high-refractive-index portions of the intermediate region 14 and the top region 17 of each resonant structure 31 also extend in the same direction as the grating elements.

[0147] A boundary low-refractive-index region 18, extending uniformly along the top region 17 of the first resonance structure 31A and the top region 17 of the first resonance structure 31A, is located between the first resonance structure 31A and the second resonance structure 31B. The boundary low-refractive-index region 18 is continuous with the second top low-refractive-index portion 17b of the top region 17 of the first resonance structure 31A and the second top low-refractive-index portion 17b of the top region 17 of the second resonance structure 31B, respectively. The boundary low-refractive-index region 18 and the second top low-refractive-index portion 17b of each resonance structure 31 are made of the same material.

[0148] The structural period Pk, which is the period of arrangement of the convex portions 21a of the first resonant structure 31A, and the structural period Pk, which is the period of arrangement of the convex portions 21a of the second resonant structure 31B, can be expressed as follows: Figure 9 The same as shown, can also be Figure 10 The structural period Pk is identical to the first period P1 of the first grid region 13 .

[0149] When emphasis is placed on the high degree of wavelength selectivity of reflected light, in each of the first resonant structure 31A and the second resonant structure 31B, similarly to the first embodiment, the ratio of the optical film thickness OT2 of the second grating region 15 to the optical film thickness OT1 of the first grating region 13 is preferably greater than or equal to 0.5 and less than or equal to 2.0, and more preferably greater than or equal to 0.625 and less than or equal to 1.6.

[0150] [The role of optical equipment]

[0151] In a structure where the two resonant structures 31A and 31B have the same structural period Pk, fluctuations in the wavelength range of light causing resonance in the four grating regions 13 and 15 of the optical device 30 are reduced. Reflected light in the wavelength ranges enhanced by each of the four grating regions 13 and 15 is emitted from the optical device 30, resulting in a higher intensity of reflected light in a specific wavelength range compared to the optical device 10 of the first embodiment. In this case, if the ratio of the optical film thickness OT2 to the optical film thickness OT1 in the first resonant structure 31A and the second resonant structure 31B is consistent, fluctuations in the optical film thickness of the four grating regions 13 and 15 are reduced, and the wavelength ranges of light causing resonance in each grating region 13 and 15 become closer, thereby further improving the wavelength selectivity of the reflected light.

[0152] On the other hand, in a configuration where the two resonant structures 31A and 31B have different structural periods Pk, the wavelength range of light that resonates in the grating regions 13 and 15 of the first resonant structure 31A differs from the wavelength range of light that resonates in the grating regions 13 and 15 of the second resonant structure 31B. As a result, reflected light, including light in the wavelength range enhanced by the grating regions 13 and 15 of the first resonant structure 31A and light in the wavelength range enhanced by the grating regions 13 and 15 of the second resonant structure 31B, is emitted from the optical device 30. Furthermore, light incident on the optical device 30 that has passed through each of the resonant structures 31A and 31B and the boundary low-refractive-index region 18 is emitted as transmitted light from the optical device 30. Setting the structural period Pk of each resonant structure 31A and 31B allows the wavelength range of light reflected and enhanced by each resonant structure 31A and 31B to be set, thereby also adjusting the wavelength range of the transmitted light.

[0153] Thus, the optical device 30 of the second embodiment includes a plurality of resonant structures 31 each having two grating regions 13 and 15 , thereby increasing the degree of freedom in adjusting the wavelength range and intensity of reflected light and transmitted light.

[0154] Furthermore, the optical device 30 of the second embodiment includes two low-refractive-index layers 23 that absorb ultraviolet light. Ultraviolet light is absorbed by each of the two resonant structures 31A and 31B. Therefore, even when the incident light includes ultraviolet wavelengths, it is preferable to suppress the inclusion of ultraviolet light in the transmitted light of the optical device 30. In other words, the optical device 30 has an improved ultraviolet light shielding function compared to the first embodiment.

[0155] Furthermore, if the wavelength range of the ultraviolet region is included in the wavelength range where light is enhanced and reflected by the grating regions 13 and 15 , the ultraviolet light shielding function of the optical device 30 is improved.

[0156] Furthermore, similarly to the first embodiment, the top region 17 can suppress the emission of light in a wavelength range different from the wavelength range of light to be extracted from the light due to reflection or interference at a location further back than the top region 17 toward the front surface of the optical device 30. Specifically, the thickness and material of the low-refractive-index layer 23 and the material of the boundary low-refractive-index region 18 are preferably selected so that the top region 17 eliminates light outside the wavelength range enhanced by the grating regions 13 and 15.

[0157] [Method for manufacturing optical device]

[0158] Reference Figure 11 as well as Figure 12 The manufacturing method of the optical device 30 of the second embodiment is described. First, when manufacturing the optical device 30 of the second embodiment, the concavo-convex structure layer 21, the high refractive index layer 22, and the low refractive index layer 23 are sequentially formed on the substrate 11 in the same manner as in the first embodiment.

[0159] Then, if Figure 11 As shown, the structure composed of the substrate 11, the concavo-convex structure layer 21, the high refractive index layer 22 and the low refractive index layer 23, that is, two concavo-convex structures 32 are opposite to each other in such a manner that the low refractive index layer 23 faces each other, as shown in FIG. Figure 12 As shown, the region between the two concavo-convex structures 32 is filled with a low-refractive-index material, thereby bonding the concavo-convex structures 32. In this way, the optical device 30 is formed.

[0160] like Figure 12 As shown, the portion formed between the two concavo-convex structures 32 by embedding the low-refractive-index material is the embedding layer 24. The embedding layer 24 is composed of the second top low-refractive-index portion 17b of the top region 17 of the first resonant structure 31A, the second top low-refractive-index portion 17b of the top region 17 of the second resonant structure 31B, and the boundary low-refractive-index region 18.

[0161] The low-refractive-index material of the embedding layer 24 is a material having a lower refractive index than the high-refractive-index material of the high-refractive-index layer 22, and is preferably a resin material such as an ultraviolet-curable resin, a thermoplastic resin, or a thermosetting resin. For example, the embedding layer 24 may be formed of the same material as the concavo-convex structure layer 21. Various coating methods may be used to form the embedding layer 24.

[0162] Furthermore, when the two concavo-convex structures 32 are opposed to each other, the first top low-refractive-index portions 17a may face each other, or the first top low-refractive-index portion 17a of one concavo-convex structure 32 and the second top low-refractive-index portion 17b of the other concavo-convex structure 32 may face each other. Alternatively, the first top low-refractive-index portion 17a of one concavo-convex structure 32 may face a portion of the first top low-refractive-index portion 17a and a portion of the second top low-refractive-index portion 17b of the other concavo-convex structure 32.

[0163] For example, by joining two concave-convex structures 32 having the same period of the convex portions 21a, the optical device 30 can be formed in which the two resonant structures 31A and 31B have the same structural period Pk. Alternatively, by joining two concave-convex structures 32 having different periods of the convex portions 21a, the optical device 30 can be formed in which the two resonant structures 31A and 31B have different structural periods Pk.

[0164] In addition, the two resonant structures 31A and 31B may be arranged with the top regions 17 facing each other instead of being arranged with the top regions 17 facing each other. That is, the two concavo-convex structures 32 may be bonded with the low refractive index material with the substrates 11 facing each other.

[0165] Alternatively, the two resonant structures 31A and 31B may be arranged so that the top regions 17 of the respective resonant structures 31A and 31B face the surface side. In other words, the two concave-convex structures 32 may be bonded together using a low-refractive-index material so that the top region 17 of one concave-convex structure 32 faces the substrate 11 of the other concave-convex structure 32.

[0166] If the top region 17 is located on the outermost surface of the optical device 30 , the effect of suppressing surface reflection by the top region 17 can be obtained similarly to the first embodiment.

[0167] In addition, the optical device 30 may have three or more resonant structural portions 31 arranged in the first direction. The more resonant structural portions 31 the optical device 30 has, the higher the absorbency of the optical device 30 for light in the ultraviolet region. In a configuration in which the optical device 30 has a plurality of resonant structural portions 31, if the structural periods Pk of these resonant structural portions 31 are the same, the greater the number of resonant structural portions 31, the higher the intensity of the reflected light. In addition, the plurality of resonant structural portions 31 may also include resonant structural portions 31 having the same structural period Pk and resonant structural portions 31 having different structural periods Pk. According to such a structure, it is also possible to finely adjust the wavelength range of the reflected light and the transmitted light emitted from the optical device 30.

[0168] When manufacturing an optical device 30 having three or more resonant structure portions 31, the substrate 11 and the concavo-convex structure layer 21 can be formed of a material that allows the substrate 11 to be peeled off from the concavo-convex structure layer 21, and the substrate 11 can be peeled off when the concavo-convex structures 32 are stacked. For example, after two concavo-convex structures 32 are bonded together with a low-refractive-index material so that their top regions 17 face each other, one substrate 11 is peeled off, and the exposed concavo-convex structure layer 21 is further bonded to the other concavo-convex structure 32 via a low-refractive-index material. By repeating this process, an optical device 30 having six or more subwavelength gratings can be formed.

[0169] The optical device 30 of the second embodiment can be applied to an optical filter provided in a display device, etc., similarly to the application example shown in the first embodiment, or can be applied to a display body. As described above, according to the second embodiment, in addition to the advantages (1) to (6) of the first embodiment, the following advantages are also obtained.

[0170] (7) Since the optical device 30 has a plurality of resonant structures 31 arranged in the first direction, the optical device 30 includes four or more grating regions 13 and 15, thereby further improving the wavelength selectivity of the optical device 30 and increasing the degree of freedom in adjusting the wavelength ranges included in reflected light and transmitted light. Furthermore, since the optical device 30 includes two low-refractive-index layers 23, the optical device 30 has an improved ultraviolet light shielding function.

[0171] (8) If the structural period Pk is equal in the plurality of resonant structures 31, the fluctuation in the wavelength range of the light causing resonance in the grating regions 13 and 15 of each resonant structure 31 becomes smaller. Therefore, the wavelength selectivity of the reflected light is further improved. Furthermore, due to the configuration in which the ratio of the optical film thickness OT2 to the optical film thickness OT1 in the first resonant structure 31A and the second resonant structure 31B is consistent, the fluctuation in the optical film thickness in the four grating regions 13 and 15 becomes smaller, that is, the wavelength range of the light causing resonance in each grating region 13 and 15 becomes closer. Therefore, the wavelength selectivity of the reflected light is further improved.

[0172] (9) If the structural period Pk of the first resonant structure 31A and the structural period Pk of the second resonant structure 31B are different from each other, the wavelength range of light that resonates in each grating region 13, 15 of the first resonant structure 31A and the wavelength range of light that resonates in each grating region 13, 15 of the second resonant structure 31B will differ from each other. Therefore, the degree of freedom in adjusting the wavelength ranges of reflected light and transmitted light is increased.

[0173] (10) The optical device 30 is formed by facing two concavo-convex structures 32 and filling the region between the two concavo-convex structures 32 with a low refractive index material. This makes it possible to easily form the optical device 30 having a plurality of resonance structures 31 .

[0174] (Third embodiment)

[0175] Reference Figure 13 , a third embodiment of an optical device and a method for manufacturing an optical device is described. Compared with the second embodiment, the arrangement direction of the sub-wavelength gratings of the two resonant structure parts in the third embodiment is different. The following description focuses on the differences between the third embodiment and the second embodiment. For the same elements as the second embodiment, the same reference numerals are marked and their descriptions are omitted. In addition, Figure 13 This figure shows a part of an optical device. To facilitate understanding of the structure of the optical device, dots of different concentrations are added to the concavo-convex structure layer 21 , the high refractive index layer 22 , the low refractive index layer 23 , and the embedding layer 24 .

[0176] [Optical equipment]

[0177] like Figure 13As shown, the optical device 40 of the third embodiment has two resonant structures 31A and 31B adjacent to each other in the first direction, similar to the second embodiment. However, in the third embodiment, the directions in which the grating elements, namely, the grating high-refractive-index portions 13a and 15a and the grating low-refractive-index portions 13b and 15b, of the grating regions 13 and 15 of the first resonant structure 31A extend differ from the directions in which the grating elements of the grating regions 13 and 15 of the second resonant structure 31B extend. In other words, the sub-wavelength gratings of the first resonant structure 31A and the sub-wavelength gratings of the second resonant structure 31B are arranged in different directions.

[0178] The structural period Pk, which is the period of arrangement of the convex portions 21a of the first resonant structure 31A, is identical to the structural period P, which is the period of arrangement of the convex portions 21a of the second resonant structure 31B. When the degree of wavelength selectivity of reflected light is important, the ratio of the optical film thickness OT2 of the second grating region 15 to the optical film thickness OT1 of the first grating region 13 in each of the first resonant structure 31A and the second resonant structure 31B is preferably greater than or equal to 0.5 and less than or equal to 2.0, and more preferably greater than or equal to 0.625 and less than or equal to 1.6. Furthermore, the above ratios are preferably identical in the first resonant structure 31A and the second resonant structure 31B.

[0179] The high-refractive-index grating portions 13a, 15a and the low-refractive-index grating portions 13b, 15b of the first resonant structure 31A extend along the second direction and are aligned along the third direction. Meanwhile, the high-refractive-index grating portions 13a, 15a and the low-refractive-index grating portions 13b, 15b of the second resonant structure 31B extend along the third direction and are aligned along the second direction. That is, the direction in which the grating elements of the first resonant structure 31A extend is orthogonal to the direction in which the grating elements of the second resonant structure 31B extend. In other words, the angle formed by the arrangement direction of the sub-wavelength gratings of the first resonant structure 31A and the arrangement direction of the sub-wavelength gratings of the second resonant structure 31B is 90°.

[0180] [The role of optical equipment]

[0181] As described above, when a subwavelength grating is constructed from grating high refractive index portions 13a and 15a extending in a single direction in a strip-like pattern, light polarized in a specific direction undergoes multiple reflections in each grating region 13 and 15, causing resonance and being emitted as reflected light. This specific direction is determined by the arrangement direction of the subwavelength gratings. Because the arrangement directions of the subwavelength gratings differ between the first resonant structure 31A and the second resonant structure 31B, the polarization directions of the multiply reflected light differ between the grating regions 13 and 15 of the first resonant structure 31A and the grating regions 13 and 15 of the second resonant structure 31B. Therefore, according to the optical device 40 of the third embodiment, reflected light, including components polarized in various directions, is efficiently emitted, further improving the intensity of the reflected light.

[0182] [Method for manufacturing optical device]

[0183] The optical device 40 of the third embodiment is similar to the second embodiment, in that two concave-convex structures 32 are opposed to each other with their top regions 17 facing each other, and the region between the two concave-convex structures 32 is filled with a low-refractive-index material. Here, in the third embodiment, the concave-convex structures 32 are opposed to each other and bonded with the low-refractive-index material so that the direction in which the convex portions 21a of one concave-convex structure 32 extend is orthogonal to the direction in which the convex portions 21a of the other concave-convex structure 32 extend.

[0184] Furthermore, similarly to the second embodiment, the two resonance structures 31A and 31B may be arranged with the top regions 17 facing outward, or the top regions 17 of the resonance structures 31A and 31B may be arranged with the top regions 17 facing the front surface.

[0185] Alternatively, the optical device 40 may include three or more resonant structures 31 arranged in the first direction, wherein the plurality of resonant structures 31 may include resonant structures 31 in which the grating elements extend in different directions. The optical device 40 includes an even number, i.e., 2n (n is an integer greater than or equal to 3), of subwavelength gratings. The 2m-1th (m is an integer greater than or equal to 1 and less than or equal to n) and 2mth subwavelength gratings from the front or back side have the same arrangement direction and the same arrangement period. In other words, the optical device 40 has a structure in which pairs of subwavelength gratings having the same arrangement direction and arrangement period are arranged in the first direction, and these subwavelength gratings are embedded in a low-refractive-index material.

[0186] With this configuration, the polarization responsiveness of the optical device 40 can be adjusted by setting the arrangement direction of the subwavelength gratings of each resonant structure 31, setting the number of resonant structures 31 with the same subwavelength grating arrangement direction, and so on. Furthermore, the greater the number of resonant structures 31 an optical device 40 has, the higher the optical device 40's absorptivity for ultraviolet light. Furthermore, the plurality of resonant structures 31 can include resonant structures 31 with different subwavelength grating arrangement periods.

[0187] The optical device 40 of the third embodiment can be applied to a filter provided in a display device, etc., similar to the application example shown in the first embodiment, or can be applied to a display body. When the optical device 40 of the third embodiment is applied to incident light containing polarized light components in various directions, the effect of effectively emitting reflected light in accordance with polarization can be enhanced. On the other hand, when incident light with a uniform polarization direction is applied, the optical device 30 of the second embodiment is preferably applied.

[0188] As described above, according to the third embodiment, in addition to the advantages (1) to (6) of the first embodiment and (7), (8), and (10) of the second embodiment, the following advantages are obtained.

[0189] (11) The directions in which the grating elements of the first resonant structure 31A extend are different from the directions in which the grating elements of the second resonant structure 31B extend. Therefore, light polarized in different directions among the light included in the incident light resonates with the grating regions 13 and 15 of the first resonant structure 31A and the grating regions 13 and 15 of the second resonant structure 31B and is emitted from the respective resonant structures 31. Therefore, reflected light is efficiently emitted from the incident light including light components polarized in various directions.

[0190] (Fourth embodiment)

[0191] Reference Figures 14A to 14D A fourth embodiment of an optical device and a method for manufacturing the optical device will be described. The fourth embodiment differs from the first embodiment in the arrangement of the subwavelength gratings. The following description will focus on the differences between the fourth embodiment and the first embodiment. Elements identical to those in the first embodiment will be assigned the same reference numerals, and their description will be omitted.

[0192] like Figures 14A to 14D As shown, in the optical device 50 according to the fourth embodiment, the sub-wavelength grating has a two-dimensional grating arrangement.

[0193] In detail, Figure 14BAs shown, in the first grid region 13, a plurality of first grid low refractive index portions 13b are arranged in a two-dimensional grid pattern. The type of two-dimensional grid is not particularly limited, as long as the first grid low refractive index portions 13b are located at grid points of a grid formed by the intersection of two sets of parallel lines extending in different directions. For example, the two-dimensional grid formed by the first grid low refractive index portions 13b can be a square grid or a hexagonal grid. The period of the grid structure of the first grid region 13, i.e., the first period P1, is consistent in all directions in which the two-dimensional grid extends. The first grid high refractive index portion 13a is embedded between the plurality of first grid low refractive index portions 13b, forming a continuous high refractive index portion.

[0194] The shape of the first grating low refractive index portion 13b as viewed along the first direction is not particularly limited. For example, if the first grating low refractive index portion 13b is square, it is easy to set a predetermined area ratio for the average refractive index of the first grating region 13.

[0195] like Figure 14C As shown, in the intermediate region 14, a plurality of first intermediate low-refractive-index portions 14b are arranged in a two-dimensional grating pattern that is consistent with the first grating low-refractive-index portions 13b. The third period P3, the period of arrangement of the first intermediate low-refractive-index portions 14b in the intermediate region 14, is consistent with the first period P1 of the first grating region 13. When viewed along the first direction, the size of the first intermediate low-refractive-index portions 14b is consistent with that of the first grating low-refractive-index portions 13b.

[0196] When viewed from the direction along the first direction, the intermediate high refractive index portion 14a has a frame shape, surrounding the first intermediate low refractive index portions 14b one by one. The second intermediate low refractive index portion 14c is embedded between adjacent intermediate high refractive index portions 14a to form a continuous low refractive index portion.

[0197] like Figure 14D As shown, in the second grating region 15, a plurality of second grating high-refractive-index portions 15a are arranged in a two-dimensional grating pattern that matches the first grating low-refractive-index portions 13b. The second grating low-refractive-index portions 15b are embedded between the plurality of second grating high-refractive-index portions 15a, forming a single continuous low-refractive-index portion. The period of the grating structure of the second grating region 15, i.e., the second period P2, matches the first period P1 of the first grating region 13.

[0198] However, when viewed along the first direction, the second grating high-refractive-index portions 15a distributed throughout the second grating region 15 are larger than the first grating low-refractive-index portions 13b distributed throughout the first grating region 13. In other words, the width of the second grating high-refractive-index portions 15a is larger than the width of the first grating low-refractive-index portions 13b in both the second and third directions. Therefore, the width of the second grating low-refractive-index portions 15b is smaller than the width of the first grating high-refractive-index portions 13a. When viewed along the first direction, the second grating high-refractive-index portions 15a have a shape based on the shape of the first grating low-refractive-index portions 13b.

[0199] Furthermore, in apex region 17, multiple first apex low-refractive-index portions 17a are also arranged in a two-dimensional lattice pattern that matches the first grating low-refractive-index portions 13b. Furthermore, second apex low-refractive-index portions 17b are embedded between the multiple first apex low-refractive-index portions 17a, forming a single continuous low-refractive-index portion. The period of arrangement of the first apex low-refractive-index portions 17a in apex region 17 matches the first period P1 of first grating region 13.

[0200] In the optical device 50 of the fourth embodiment, a waveguide mode resonance phenomenon occurs due to the same principle as in the first embodiment, and light in the wavelength range enhanced by the first grating region 13 and light in the wavelength range enhanced by the second grating region 15 are emitted as reflected light. Furthermore, light in the ultraviolet region is absorbed by the low-refractive-index layer 23, and light that has passed through each region of the optical device 50 is emitted as transmitted light.

[0201] In the fourth embodiment, the optical film thickness OT1 of the first grating region 13 is calculated using the equation (2) shown in the first embodiment, and the optical film thickness OT2 of the second grating region 15 is calculated using the equation (4) shown in the first embodiment. Furthermore, as long as the ratio of the optical film thickness OT2 of the second grating region 15 to the optical film thickness OT1 of the first grating region 13 is greater than or equal to 0.5 and less than or equal to 2.0, and more preferably greater than or equal to 0.625 and less than or equal to 1.6, good wavelength selectivity for reflected light can be obtained in the optical device 50.

[0202] Furthermore, in the fourth embodiment, the area ratio R3 of the intermediate high refractive index portion 14a also preferably satisfies the formula (5) shown in the first embodiment. If formula (5) is satisfied, the width of the intermediate high refractive index portion 14a is suppressed so as not to extend beyond the outer side of the second grating high refractive index portion 15a, thereby preventing the area ratio of the intermediate high refractive index portion 14a from becoming excessively large. Consequently, the intensity of the reflected light from each grating region 13, 15 is improved.

[0203] As shown in the fourth embodiment, when the grating elements of a subwavelength grating are arranged in a two-dimensional grid pattern, light polarized in mutually different directions can be resonated separately along each direction in which the grating elements are arranged. Therefore, compared to the arrangement of the grating elements in only one direction, as shown in the first embodiment, incident light containing polarized light components in various directions can be efficiently reflected. Consequently, the intensity of the reflected light is further improved.

[0204] In particular, if the grid elements are arranged in a hexagonal grid shape, the directions of polarized light that can resonate in the grid area increase compared to when the grid elements are arranged in a square grid shape, so the reflected light can be emitted more efficiently for incident light containing polarized light components in various directions.

[0205] The optical device 50 of the fourth embodiment can be manufactured by changing the arrangement of the protrusions 21a in the manufacturing method of the optical device 10 of the first embodiment. Specifically, the concavo-convex structure layer 21 is formed by forming a concavo-convex structure in which a plurality of protrusions 21a are arranged in a two-dimensional grid shape. The plurality of protrusions 21a are separated from each other, and the concave portions 21b located between the protrusions 21a constitute a continuous concave portion. As shown in the fourth embodiment, if the protrusions 21a are arranged in a two-dimensional grid shape, the size and arrangement of the protrusions 21a are more flexible, so it is easy to make fine adjustments when setting the area ratio of the protrusions 21a and the concave portions 21b.

[0206] The various variations of the optical device 10 of the first embodiment can be applied to the optical device 50 of the fourth embodiment. Furthermore, the optical device 50 of the fourth embodiment can be applied to the second and third embodiments. That is, a plurality of optical devices 50 can be stacked along the first direction to form an optical device having four or more grating regions. In this case, in two or more resonant structure portions 31, the directions in which the grating elements of the subwavelength grating are arranged, in other words, the directions in which the two-dimensional gratings extend, can be the same or different. In a structure in which the two-dimensional gratings of the two resonant structure portions 31 extend in different directions, reflected light can be emitted corresponding to a greater number of directions for polarized light.

[0207] Furthermore, the period of the grating structure in each grating region 13 or 15 can be varied depending on the direction in which the two-dimensional grating extends. This structure allows the wavelength range that causes resonance to vary depending on the direction in which the two-dimensional grating extends, thereby adjusting the wavelength range included in the reflected light and the responsiveness to polarized light.

[0208] The concavo-convex structure of the concavo-convex structure layer 21 can be composed of a plurality of concave portions separated from each other, and a single convex portion continuous between the concave portions. In other words, the concavo-convex structure of the concavo-convex structure layer 21 can be formed by a plurality of concavo-convex elements, either convex or concave portions, separated from each other and arranged in a two-dimensional grid pattern.

[0209] Similar to the application example shown in the first embodiment, the optical device 50 of the fourth embodiment can be applied to an optical filter included in a display device or the like, or can be applied to a display body.

[0210] As described above, according to the fourth embodiment, in addition to the advantages (1) to (6) of the first embodiment, the following advantages can be obtained.

[0211] (12) The grid elements of the sub-wavelength grid are arranged in a two-dimensional grid shape, so the reflected light is efficiently emitted for incident light including polarization components in various directions.

[0212] (Variation)

[0213] The above-mentioned embodiments may be modified and implemented in the following manner.

[0214] If the layer is composed of a low-refractive index material, a layer different from the low-refractive index layer 23 may have ultraviolet light absorptivity. For example, the concavo-convex structure layer 21 or the substrate 11 may have ultraviolet light absorptivity. Furthermore, in the second and third embodiments, the embedding layer 24 may have ultraviolet light absorptivity. Such a layer having ultraviolet light absorptivity may be composed, for example, of a resin to which an ultraviolet absorber has been added.

[0215] When extracting light in the ultraviolet region as reflected light enhanced by the grating regions 13 and 15, it is sufficient to use an optical device in such a manner that the incident light enters the grating regions 13 and 15 from the side opposite to the layer having the ability to absorb light in the ultraviolet region. For example, when the concave-convex structure layer 21 or the substrate 11 has the ability to absorb light in the ultraviolet region, in the first and fourth embodiments, it is sufficient that light enters from the side where the top region 17 is located. In addition, in the second and third embodiments, it is sufficient that light enters from the side where the other of the two resonant structure portions 31 is located, as long as the concave-convex structure layer 21 or the substrate 11 of one of the two resonant structure portions 31 has the ability to absorb light in the ultraviolet region. In the case where the embedding layer 24 has the ability to absorb light in the ultraviolet region, light can be injected from either side.

[0216] If any one of the substrate 11, the concavo-convex structure layer 21, the low-refractive index layer 23, or the embedding layer 24 has ultraviolet light absorptivity, ultraviolet light absorptivity can be added to the layers required for an optical device that generates waveguide mode resonance in two or more grating regions. Therefore, compared to a case where the optical device does not have ultraviolet light absorptivity, an optical device with ultraviolet light shielding function can be formed without adding additional structural layers to the optical device, thereby suppressing any increase in the burden required to manufacture the optical device.

[0217] On the other hand, the optical device may have a layer having absorptivity for light in the ultraviolet region, in addition to the above-mentioned layers. Figure 15 As shown, the optical device 10 of the first embodiment can include an absorption layer 19 in contact with the substrate 11 on the side opposite to the concavo-convex structure layer 21 relative to the substrate 11. The absorption layer 19 has the ability to absorb light in the ultraviolet region. The absorption layer 19 is formed, for example, by various coating methods and is composed of a resin to which an ultraviolet absorber is added. In addition, in the case where the optical device has two resonant structures 31 as shown in the second and third embodiments, the absorption layer having the ability to absorb light in the ultraviolet region can be laminated on the substrate 11 in contact with one resonant structure 31.

[0218] In the above structure, when extracting ultraviolet light as reflected light enhanced by grille regions 13 , 15 , the incident light may be incident on grille regions 13 , 15 from the side opposite to the layer having ultraviolet light absorptivity.

[0219] If a structure that realizes the light shielding function of an optical device by providing a layer having a specific function of absorbing light in the ultraviolet region, such as the above-mentioned absorption layer 19, can provide the following advantages. Specifically, compared to a case where a layer having the ability to absorb light in the ultraviolet region also serves as a layer having other functions, such as a layer having the function of generating a waveguide mode resonance phenomenon, the material and film thickness of each layer can be appropriately selected according to each function.

[0220] As described above, it is sufficient that the constituent layers of the optical device include a layer having absorptivity for light in the ultraviolet region. The layer having absorptivity for light in the ultraviolet region has a higher absorptivity for ultraviolet light than the cured ultraviolet curable resin.

[0221] The structural layer of the aforementioned optical device only needs to have absorption properties within a specified wavelength range, and the wavelength range of absorption does not need to be in the ultraviolet region. An optical device having a layer that absorbs light within a specified wavelength range has the function of shielding light within that wavelength range. Therefore, it can be used as an optical filter installed in a device where shielding within that wavelength range is desired.

[0222] In each of the above embodiments, the intermediate region 14 of the optical device may not include the intermediate high refractive index portion 14a. That is, the intermediate region 14 may be composed of the first intermediate low refractive index portion 14b and the second intermediate low refractive index portion 14c. Depending on the manufacturing conditions of the high refractive index layer 22, an optical device without the intermediate high refractive index portion 14a, that is, without the high refractive index layer 22 formed on the side surfaces of the convex portion 21a, can be manufactured.

[0223] In an embodiment where the top region 17 is located on the outermost surface, a protective layer may be provided to cover the top region 17. In this case, the protective layer is made of a low-refractive-index material such as resin, and the recessed portion of the low-refractive-index layer 23 is filled with the protective layer. In other words, the second top low-refractive-index portion 17b is filled with a low-refractive-index material.

[0224] In the second and third embodiments, the space between the high-refractive-index layer 22 of the first resonance structure 31A and the high-refractive-index layer 22 of the second resonance structure 31B may be filled with a embedding layer 24 functioning as a low-refractive-index layer. In this case, the resonance structure 31 does not have a top region 17, and the second low-refractive-index region 16 of the first resonance structure 31A and the second low-refractive-index region 16 of the second resonance structure 31B are continuous, with no boundary between these regions.

Claims

1. An optical device, wherein: The optical device comprises: a concavo-convex structure layer having a concavo-convex structure on its surface, wherein the concavo-convex structure is either a plurality of convex portions or a plurality of concave portions arranged in a sub-wavelength period; a high refractive index layer, located on the concavo-convex structure and having a surface following the shape of the concavo-convex structure, comprising a first grating high refractive index portion located at the bottom of the concavo-convex structure and forming a first sub-wavelength grating, and a second grating high refractive index portion located at the top of the concavo-convex structure and forming a second sub-wavelength grating, the layer being made of a material having a higher refractive index than that of the concavo-convex structure layer; and a low refractive index layer, which is located on the high refractive index layer and is composed of a material with a lower refractive index than the high refractive index layer; Either the concavo-convex structure layer or the low refractive index layer has absorptivity for light in a predetermined wavelength range, or the optical device has an additional layer having absorptivity for light in the predetermined wavelength range. When the thickness of the first grating high refractive index portion is T1, the thickness of the second grating high refractive index portion is T2, the refractive index of the material of the high refractive index layer is n1, the refractive index of the material of the concavo-convex structure layer is n2, the refractive index of the material of the low refractive index layer is n3, the area ratio of the first grating high refractive index portion in a cross section that includes the first grating high refractive index portion and is perpendicular to the thickness direction thereof is R1, and the area ratio of the second grating high refractive index portion in a cross section that includes the second grating high refractive index portion and is perpendicular to the thickness direction thereof is R2, n1>n2、n1>n3、and R1+R2>1, The ratio of the second parameter represented by T2×{n1×R2+n3×(1−R2)} to the first parameter represented by T1×{n1×R1+n2×(1−R1)} is greater than or equal to 0.5 and less than or equal to 2.

0.

2. The optical device according to claim 1, wherein The light in the predetermined wavelength range is light in the ultraviolet region.

3. The optical device according to claim 2, wherein At least one of the reflected light enhanced and emitted by the waveguide mode resonance phenomenon in the region including the first grating high refractive index portion and the reflected light enhanced and emitted by the waveguide mode resonance phenomenon in the region including the second grating high refractive index portion includes light in the ultraviolet region.

4. The optical device according to any one of claims 1 to 3, wherein The low refractive index layer has absorptivity for light in the predetermined wavelength range.

5. The optical device according to any one of claims 1 to 3, wherein The concavo-convex structure layer has absorptivity for light in the predetermined wavelength range.

6. The optical device according to any one of claims 1 to 3, wherein The optical device comprises the additional layer, The additional layer is a base material that supports the concavo-convex structure layer.

7. The optical device according to any one of claims 1 to 3, wherein The optical device comprises: a substrate supporting the concavo-convex structure layer; and The additional layer, The additional layer is located on the opposite side of the concavo-convex structure layer with respect to the substrate.

8. The optical device according to any one of claims 1 to 3, wherein: The low refractive index layer has a surface that follows the concavoconvex shape of the surface of the high refractive index layer.

9. The optical device according to claim 1, wherein The high refractive index layer includes an intermediate high refractive index portion extending along the side surfaces of the plurality of convex portions or the plurality of concave portions between the first grating high refractive index portion and the second grating high refractive index portion. When the area ratio of the intermediate high refractive index portion in the cross section including the intermediate high refractive index portion and perpendicular to the thickness direction thereof is defined as R3, R3≦R1+R2−1 is satisfied.

10. The optical device according to any one of claims 1 to 3, wherein The portion including the concavo-convex structure layer, the high refractive index layer, and the low refractive index layer forms a resonant structure portion. The optical device comprises: a plurality of the resonance structures, which are arranged along the thickness direction of the resonance structure; and The additional layer, The additional layer fills the gap between the adjacent resonance structures and is made of a material having a lower refractive index than the high refractive index layer.

11. A method for manufacturing an optical device, wherein: The manufacturing method of the optical device comprises the following steps: In a first step, a concavo-convex structure layer is formed. The concavo-convex structure layer has a concavo-convex structure on its surface and is made of a first low-refractive index material. The concavo-convex structure is either a plurality of convex portions or a plurality of concave portions arranged in a subwavelength period. A second step is to form a high refractive index layer made of a high refractive index material having a higher refractive index than the first low refractive index material, wherein the high refractive index layer includes, along the surface of the concavo-convex structure layer, a first grating high refractive index portion located at the bottom of the concavo-convex structure and forming a first sub-wavelength grating, and a second grating high refractive index portion located at the top of the concavo-convex structure and forming a second sub-wavelength grating; as well as In a third step, a low refractive index layer made of a second low refractive index material having a lower refractive index than that of the high refractive index material is formed on the high refractive index layer. Either the concavo-convex structure layer or the low refractive index layer has absorptivity for light in a predetermined wavelength range, or the method includes the step of forming an additional layer having absorptivity for light in the predetermined wavelength range. When the thickness of the first grating high refractive index portion is T1, the thickness of the second grating high refractive index portion is T2, the refractive index of the material of the high refractive index layer is n1, the refractive index of the material of the concavo-convex structure layer is n2, the refractive index of the material of the low refractive index layer is n3, the area ratio of the first grating high refractive index portion in a cross section that includes the first grating high refractive index portion and is perpendicular to the thickness direction thereof is R1, and the area ratio of the second grating high refractive index portion in a cross section that includes the second grating high refractive index portion and is perpendicular to the thickness direction thereof is R2, n1>n2、n1>n3、and R1+R2>1, The ratio of the second parameter represented by T2×{n1×R2+n3×(1−R2)} to the first parameter represented by T1×{n1×R1+n2×(1−R1)} is greater than or equal to 0.5 and less than or equal to 2.0.

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