Optical member, translucent member unit, imaging device, and method for manufacturing optical member

Abstract

Provided is an optical member comprising a hydrophilic layer including photocatalyst particles, a translucent member, and a reflection layer located between the hydrophilic layer and the translucent member and reflecting, to the hydrophilic layer, light having a wavelength in a range of 300-400 nm transmitted through the hydrophilic layer, wherein the average reflectance of light having a wavelength in the range of the optical member is 16% or more.

Description

Optical member, light-transmitting member unit, imaging device, and method for manufacturing optical member

[0001] The present disclosure relates to an optical member, a light-transmissive member unit, an imaging device, and a method for manufacturing an optical member.

[0002] In the conventional hydrophilic member disclosed in Patent Document 1, a photocatalytic layer (hydrophilic layer) containing titanium dioxide particles and a silicon dioxide binder and an underlayer containing silicon dioxide are formed on a substrate.

[0003] Patent Publication No. 2020-116897

[0004] In the above-mentioned conventional technology, the hydrophilicity is lower in an environment with little sunlight than in an environment with a lot of sunlight.

[0005] The technology disclosed herein has been developed in consideration of the above facts, and aims to provide an optical element, a light-transmitting element unit, an imaging device, and a method for manufacturing an optical element that can increase the photocatalytic effect related to the expression of hydrophilicity even in environments with little sunlight compared to conventional techniques.

[0006] In order to achieve the above-mentioned object, the optical element of a first aspect of the technology of the present disclosure is an optical element comprising a hydrophilic layer containing photocatalytic particles, a translucent member, and a reflective layer located between the hydrophilic layer and the translucent member, which reflects light having a wavelength in the range of 300 nm to 400 nm that has passed through the hydrophilic layer back to the hydrophilic layer, wherein the average reflectance of the optical element for light having a wavelength in the range is 16% or more.

[0007] A second aspect is a method for manufacturing an optical element, which includes forming a hydrophilic layer containing photocatalytic particles and forming a reflective layer, wherein the reflective layer is located between the hydrophilic layer and a translucent element, reflects light having a wavelength in the range of 300 nm or more and 400 nm or less that has passed through the hydrophilic layer back to the hydrophilic layer, and the average reflectance of the optical element for light of the wavelengths is 16% or more.

[0008] The technology of the present disclosure can increase the photocatalytic effect related to the development of hydrophilicity even in environments with little sunlight, compared to conventional technologies.

[0009] FIG. 1 is a schematic diagram showing an example of an imaging device according to the present embodiment. FIG. 2 is a schematic diagram showing an example of an optical member according to the present embodiment. FIG. 3 is a diagram showing an example of a manufacturing method for an optical member 100, illustrating the formation of a low-refractive-index layer. FIG. 4 is a diagram showing an example of a manufacturing method for an optical member 100, illustrating the formation of a low-refractive-index layer on a light-transmitting member. FIG. 5 is a diagram showing an example of a manufacturing method for an optical member 100, illustrating the formation of multiple alternating low-refractive-index layers and high-refractive-index layers. FIG. 6 is a diagram showing an example of a manufacturing method for an optical member 100, illustrating the supply of a hydrophilic material from a nozzle to a reflective layer. FIG. 7 is a diagram showing an example of a manufacturing method for an optical member 100, illustrating the rotation of a light-transmitting member and a reflective layer until the hydrophilic material reaches a predetermined thickness. FIG. 8 is a table showing the film thickness (nm) of the hydrophilic layer, the number and film thickness (nm) of the reflection adjustment layer (reflective layer), the optical properties of the optical members, and evaluations of the optical members in Examples 1 to 4 and Comparative Examples 1 and 2. FIG. 9 is a graph showing the reflectance (%) at each wavelength (Wavelength (nm)) from 300 nm to 700 nm in Examples 1 and 4 and Comparative Example 1. FIG. 10 is a graph showing the static contact angle in the hydrophilic layer in Example 1. FIG. 11 is a graph showing the static contact angle in the hydrophilic layer in Example 4. FIG. 12 is a graph showing the static contact angle in the hydrophilic layer in Comparative Example 1.

[0010] Hereinafter, embodiments of the technology of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and descriptions thereof will not be repeated. The dimensions, shapes, and dimensional relationships between components in the drawings are not necessarily identical to the actual dimensions, shapes, and dimensional relationships between components. In particular, the thickness ratios and curvatures of the reflective layer, hydrophilic layer, and translucent member in the drawings may differ significantly from those in reality.

[0011] In this specification, "thickness" refers to the length of an optical member in the optical axis direction. The "outside" of an optical member refers to the direction from the light-transmitting member toward the hydrophilic layer. The "inside" of an optical member refers to the direction from the hydrophilic layer toward the light-transmitting member.

[0012] 1 is a schematic diagram showing an example of an imaging device 1000 according to this embodiment. As shown in Fig. 1, the imaging device 1000 includes a light-transmitting member unit 200 including a plurality of light-transmitting members arranged in the optical axis direction, and an imaging section 300 that captures an image of light passing through the light-transmitting member unit 200.

[0013] The light-transmitting member unit 200 includes a plurality of light-transmitting members made of resin or glass. The light-transmitting member unit 200 includes the optical member 100 on the most object side (outside).

[0014] The optical member 100 according to this embodiment is used in a light-transmitting member unit 200 that is used outdoors. Specifically, the imaging device 1000 according to this embodiment is an in-vehicle camera for monitoring the surroundings of a vehicle. The in-vehicle camera may be a front camera attached to a windshield. Alternatively, the in-vehicle camera may be a back camera attached to a back glass or a side camera attached to a side glass.

[0015] Fig. 2 is a schematic diagram showing an example of an optical member 100 according to this embodiment. Fig. 2 is a schematic diagram of the optical member 100, which differs in shape and the like from the optical member 100 shown in Fig. 1. As shown in Fig. 2, the optical member 100 includes a light-transmitting member 10 and a laminate member 2030 formed on the light-transmitting member 10.

[0016] The laminated member 2030 includes a reflective layer 20 located on a translucent member 10, and a hydrophilic layer 30 located on the reflective layer 20 and containing photocatalytic particles. The hydrophilic layer 30, reflective layer 20, and translucent member 10 are arranged in this order from the light incident side. The reflective layer 20 prevents reflection of light in the visible range and reflects light in the ultraviolet range to the hydrophilic layer 30. Therefore, the reflective layer 20 also functions as a reflection adjustment layer. Hereinafter, the reflective layer 20 may also be referred to as the reflection adjustment layer 20. Specifically, the reflective layer 20 reflects light with a wavelength of 300 nm or more and 400 nm or less to the hydrophilic layer 30. The optical member 100 has an average reflectance of 16% or more for light with a wavelength of 300 nm or more and 400 nm or less. The average reflectance of the optical member 100 for light in the above wavelength range is 16% or more, more preferably 25% or more, and even more preferably 53% or more. If the average reflectance of the optical element 100 for light of wavelengths in the above range is 16% or more, the hydrophilic layer 30 has a hydrophilic recovery function; if the average reflectance is 25%, the hydrophilic recovery function is good; and if the average reflectance is 53%, the hydrophilic recovery function is even better.

[0017] The reflectance of the optical member 100 for light having a wavelength in the range of 400 nm to 700 nm is 3% or less.

[0018] <Light-Transmitting Member> The light-transmitting member 10 has light-transmitting properties. That is, the light-transmitting member 10 transmits visible light. The light-transmitting member 10 may be transparent or translucent. The light-transmitting member 10 contains, for example, glass or synthetic resin as a main component. In the present embodiment, the light-transmitting member 10 contains glass as a main component.

[0019] The light-transmitting member 10 functions as, for example, a lens (specifically, for example, a biconvex lens, a biconcave lens, a plano-convex lens, a plano-concave lens, a convex meniscus lens, or a concave meniscus lens). In this specification, when the light-transmitting member 10 is a lens, the lens surface of the light-transmitting member 10 may be spherical or aspherical. The radius of curvature of the lens surface of the light-transmitting member 10 is preferably 9 mm or more and 16 mm or less.

[0020] <Hydrophilic Layer> The hydrophilic layer 30 covers the light-transmitting member 10. Specifically, the hydrophilic layer 30 is disposed on the reflective layer 20. The hydrophilic layer 30 has hydrophilic properties.

[0021] The thickness of the hydrophilic layer 30 is preferably 20 nm to 200 nm, more preferably 30 nm to 100 nm. If the thickness of the hydrophilic layer 30 is less than 20 nm, the hydrophilicity recovery function tends to be insufficient. If the thickness of the hydrophilic layer 30 is more than 200 nm, the transmittance to visible light tends to be insufficient.

[0022] In the present specification, "thickness" may be determined using a stylus-type step gauge. Specifically, a sharp needle is traced across the surface to measure the step between areas with and without a layer (film). Steps are measured at three arbitrary locations, and the average value of the step differences at the three locations is taken as the "thickness."

[0023] The hydrophilic layer 30 includes a plurality of photocatalyst particles. The photocatalyst particles have a photocatalytic function. For example, when the optical element 100 is used for a long period of time, dirt accumulates on the optical element 100, reducing the hydrophilic function. When the optical element 100 is irradiated with sunlight, the photocatalytic reaction caused by the photocatalyst particles decomposes the dirt, thereby restoring the hydrophilic property.

[0024] In the optical member 100 according to this embodiment, when the contact angle exceeds 45.0°, the integrated ultraviolet light amount is 1000 mJ / cm ２ When the optical member 100 is irradiated with ultraviolet light under the conditions described above, the contact angle is preferably less than 45.0°, and more preferably less than 30.0°.

[0025] Examples of photocatalytic particles include particles of titanium oxide, strontium titanate, zinc oxide, silicon carbide, gallium phosphate, cadmium sulfide, cadmium selenide, and molybdenum trisulfide, but titanium oxide particles are preferred in terms of photocatalytic function. Specifically, the photocatalytic particles are, for example, primary or secondary particles of titanium dioxide. In particular, the hydrophilic layer 30 preferably contains secondary particles formed by agglomeration of multiple primary particles of titanium dioxide.

[0026] Examples of titanium dioxide include anatase type titanium dioxide, rutile type titanium dioxide, and brookite type titanium dioxide. From the viewpoint of photocatalytic activity, anatase type titanium dioxide is preferred.

[0027] The hydrophilic layer 30 preferably further contains tetraethoxysilane and silicon dioxide, which results in further improved abrasion resistance of the optical member 100.

[0028] <Reflective Layer> The reflective layer 20 is disposed below the hydrophilic layer 30. The reflective layer 20 covers the light-transmitting member 10. The reflective layer 20 is disposed between the light-transmitting member 10 and the hydrophilic layer 30.

[0029] The reflective layer 20 has a multilayer structure. Specifically, the reflective layer 20 includes low-refractive index layers and high-refractive index layers alternately stacked along the thickness direction (optical axis direction). The refractive index of the low-refractive index layers is lower than the refractive index of the high-refractive index layers. The refractive index of the low-refractive index layers is, for example, 1.80 or less. The refractive index of the high-refractive index layers is, for example, greater than 1.80.

[0030] For example, the refractive index of the low refractive index layer is preferably 1.30 or more and 1.80 or less, and more preferably 1.40 or more and 1.60 or less. When the refractive index of the low refractive index layer is 1.30 or more and 1.80 or less, the reflectance of the optical member 100 for light having a wavelength in the range of 400 nm or more and 700 nm or less is further reduced. The low refractive index layer may be made of, for example, SiO ２ , Al ２ O ３ , MgF ２ It is preferable that the compound contains SiO ２ It is more preferred that the compound contains:

[0031] The refractive index of the high refractive index layer may be higher than that of the low refractive index layer. For example, the refractive index of the high refractive index layer is preferably 1.80 or more and 3.00 or less, and more preferably 2.00 or more and 2.80 or less. When the refractive index of the high refractive index layer is 1.80 or more and 3.00 or less, the reflectance of the optical member 100 for light having a wavelength in the range of 400 nm or more and 700 nm or less is further reduced. The high refractive index layer may be, for example, Si ３ N ４ , ZrO ２, TiO ２ , Ti ３ O ５ , Ta ２ O ５ , In ２ O ３ , CeO ２ and Nb ２ O ５ It is preferable that the alloy contains Si. ３ N ４ It is more preferred that the compound contains:

[0032] The thickness of the reflective layer 20 is at least 5 times the thickness of the hydrophilic layer 30. From the viewpoint of productivity, the thickness of the reflective layer 20 is preferably 100 times or less the thickness of the hydrophilic layer 30. That is, the thickness of the reflective layer 20 is preferably 5 times or more and 100 times or less the thickness of the hydrophilic layer 30. The total film thickness of the reflective layer 20 is preferably 20 nm or more and 2000 nm or less, and more preferably 200 nm or more and 750 nm or less. If the total film thickness of the reflective layer 20 is less than 20 nm, a sufficient anti-reflection effect tends to be insufficient. If the total film thickness of the reflective layer 20 exceeds 2000 nm, film formation takes a long time, and the productivity of the optical element 100 tends to decrease. Furthermore, if the total film thickness exceeds 2000 nm, the production cost of the optical element 100 tends to increase.

[0033] The thickness of one low refractive index layer is, for example, 5.0 nm or more and 200.0 nm or less, and the thickness of one high refractive index layer is, for example, 5.0 nm or more and 200.0 nm or less.

[0034] 1 and 2 , in this embodiment, the thickness of the reflective layer 20 is five times or more the thickness of the hydrophilic layer 30, and therefore it is possible to suppress reflection of incident light by the hydrophilic layer 30 and the light-transmitting member 10. Specifically, by including the reflective layer 20, the optical member 100 suppresses reflection of light attempting to enter the light-transmitting member 10 from the reflective layer 20 by the surface on the reflective layer 20 side.

[0035] The reflective layer 20 has low refractive index layers and high refractive index layers alternately stacked along the thickness direction (optical axis direction), thereby achieving the effect of multilayer film interference.

[0036] As will be described in detail later, the reflective layer 20 is formed by alternately stacking low refractive index layers and high refractive index layers. ３ N ４ The content of SiO in the low refractive index material is 95 mass % or more. ２ The content of is 95 mass % or more. Each of the low refractive index layer and the high refractive index layer is formed by sputtering. Therefore, the Vickers hardness of the reflective layer 20 is 400 HV or more. This can improve the durability of the reflective layer 20. As a result, the durability of the optical member 100 can be improved.

[0037] A coating layer may be disposed on the reflective layer 20. The coating layer may contain particles of titanium oxide.

[0038] (Method for Manufacturing Optical Element) Next, an example of a method for manufacturing the optical element 100 according to the present embodiment will be described with reference to FIGS. 3 to 7 . The method for manufacturing the optical element 100 includes forming a reflective layer 20 on a light-transmitting element 10, and forming a hydrophilic layer 30 containing photocatalytic particles on the reflective layer 20 formed on the light-transmitting element 10. Specifically, the method includes a <preparation step>, a <reflective layer formation step>, a <coating step>, and a <drying step>. By carrying out this manufacturing method, a reflective layer 20 is manufactured that reflects light having a wavelength in the range of 300 nm to 400 nm that has passed through the hydrophilic layer 30 back to the hydrophilic layer 30, and an optical element 100 is manufactured that has an average reflectance of 16% or more for light of that wavelength.

[0039] <Preparation Step> Prepare the light-transmitting member 10. The light-transmitting member 10 contains, for example, glass (or synthetic resin) as a main component.

[0040] <Reflective Layer Forming Step> The reflective layer 20 is formed on the light-transmitting member 10 by alternately stacking low refractive index layers and high refractive index layers.

[0041] The number of alternating low refractive index layers and high refractive index layers in the reflective layer 20 and the thickness of each low refractive index layer and each high refractive index layer are both predetermined so that the reflective layer 20 reflects light with wavelengths in the range of 300 nm or more and 400 nm or less that has passed through the hydrophilic layer 30 back to the hydrophilic layer 30, and the average reflectance of light with those wavelengths in the optical element 100 is 16% or more.

[0042] In addition, both the number of alternating low-refractive index layers and high-refractive index layers in the reflective layer 20 and the thickness of each low-refractive index layer and each high-refractive index layer are predetermined so that the reflectance of light in the wavelength range of 400 nm or more and 700 nm or less in the optical element 100 is 3% or less.

[0043] This will be explained in detail below.

[0044] A low refractive index material and a high refractive index material are prepared.

[0045] The low refractive index material is, for example, SiO ２ , Al ２ O ３ , MgF ２ It is preferable that the compound contains SiO ２ It is more preferable that the low refractive index material contains SiO. ２ The content of is preferably 95% by mass or more. The low refractive index material is preferably formed by vapor deposition or sputtering.

[0046] The high refractive index material is, for example, Si ３ N ４ , ZrO ２ , TiO ２ , Ti ３ O ５ , Ta ２ O ５ , In ２ O ３ , CeO ２ and Nb ２ O ５ It is preferable that the compound contains Si. ３ N ４ It is more preferable that the high refractive index material contains Si. ３ N ４The content of is preferably 95% by mass or more. The high refractive index material is preferably formed by vapor deposition or sputtering.

[0047] As shown in FIG. 3, a transparent member 10 is coated with, for example, SiO ２ was deposited to form a SiO ２ The low refractive index layer 20L1 is formed.

[0048] Next, in the same manner as in FIG. 3, for example, Si is sputtered on the low refractive index layer 20L1. ３ N ４ As shown in FIG. ３ N ４ The high refractive index layer 20H1 is formed.

[0049] Next, similarly to the above, a plurality of low-refractive index layers and a plurality of high-refractive index layers are alternately stacked. As shown in Fig. 5, a high-refractive index layer 20H1 is formed on the low-refractive index layer 20L1. Next, a low-refractive index layer 20L2 is formed on the high-refractive index layer 20H1. Next, a high-refractive index layer 20H2 is formed on the low-refractive index layer 20L2. The above process is repeated a plurality of times. Finally, a low-refractive index layer 20Ln is formed.

[0050] In the reflective layer forming step, each low refractive index layer and each high refractive index layer are formed to the predetermined thickness, and the low refractive index layers and the high refractive index layers are alternately stacked to a predetermined number of layers, thereby producing the reflective layer 20 that reflects light having a wavelength in the range of 300 nm to 400 nm that has passed through the hydrophilic layer 30 back to the hydrophilic layer 30.

[0051] When a coating layer is disposed on the reflective layer 20 as described above, the coating agent is applied to the surface of the reflective layer 20 by the following methods: spin coating, roll coating, and bar coating, as well as dip coating and spray coating.

[0052] <Coating Step> The hydrophilic layer 30 is formed (for example, coated) on the reflective layer 20 formed on the light-transmitting member 10 using a hydrophilic material.

[0053] The hydrophilic material contains a plurality of primary particles of photocatalyst particles, and the average particle size of the primary particles of the photocatalyst particles is preferably 5 nm or more and 20 nm or less.

[0054] The hydrophilic material preferably further contains a solvent. The solvent is preferably an aqueous solvent. The aqueous solvent contains water and an additive. Examples of the additive include an organic acid, an alcohol compound, or ammonia. Examples of the organic acid include nitric acid, formic acid, acetic acid, propionic acid, succinic acid, citric acid, or malic acid. Examples of the alcohol compound include methanol, ethanol, isopropyl alcohol, n-propyl alcohol, or butanol.

[0055] The content of the solvent in the hydrophilic material is preferably 50.0% by mass or more and 99.9% by mass or less. By having the content of the solvent be 50.0% by mass or more and 99.9% by mass or less, coating can be easily performed.

[0056] A wet process is preferred as a method for applying the hydrophilic material. Examples of wet processes include spin coating, roll coating, bar coating, dip coating, spray coating, and a combination of two or more of these (e.g., dip spin coating). Preferred wet processes are spin coating, dip coating, and dip spin coating.

[0057] 6 and 7 are diagrams showing an example of how a hydrophilic material is applied to the reflective layer 20 by spin coating, with Fig. 6 showing how a hydrophilic material 30L is supplied from a nozzle 30N to the reflective layer 20, and Fig. 7 showing how the light-transmitting member 10 and the reflective layer 20 are rotated. As shown in Fig. 6, the hydrophilic material 30L is supplied from the nozzle 30N to the reflective layer 20, and as shown in Fig. 7, the light-transmitting member 10 and the reflective layer 20 are rotated until the hydrophilic material reaches a predetermined thickness.

[0058] In this manner, the hydrophilic layer 30 is formed on the reflective layer 20 formed on the light-transmitting member 10 .

[0059] Silica particles may be added to the hydrophilic layer 30. Even if silica particles are added, the thickness of the silica particles is very small compared to the thickness of the hydrophilic layer 30. Therefore, even if silica particles are added, the hydrophilic layer 30 remains a single layer.

[0060] <Drying Step> The hydrophilic material is dried to form the hydrophilic layer 30. The hydrophilic layer 30 preferably contains secondary particles formed by aggregation of a plurality of primary particles of photocatalyst particles.

[0061] It is preferable to heat-treat the coated hydrophilic material. Heat treatment promotes the removal of the solvent in the hydrophilic material. Heating conditions can be, for example, a treatment temperature of 60°C to 200°C and a treatment time of 10 minutes to 2 hours.

[0062] By carrying out the manufacturing method of the optical element 100 described above, an optical element 100 having an average reflectance of 16% or more for light having a wavelength in the range of 300 nm to 400 nm is manufactured. As a result, when the contact angle exceeds 45.0°, the integrated ultraviolet light amount is 1000 mJ / cm. ２ When the optical member 100 is irradiated with ultraviolet light under the condition of (a) and (b), the contact angle becomes less than 45.0°.

[0063] As described above, the optical element 100 includes the light-transmitting element 10, the reflective layer 20 located on the light-transmitting element 10, and the hydrophilic layer 30 containing photocatalytic particles located on the reflective layer 20. As described above, in order to manufacture the optical element 100 having an average reflectance of 16% or more for light with a wavelength in the range of 300 nm to 400 nm, the number of alternately stacked low-refractive index layers and high-refractive index layers of the reflective layer 20 and the thickness of each of the low-refractive index layers and high-refractive index layers are mainly adjusted.

[0064] (Operation) Light enters the imaging device 1000 from the optical member 100 side, which is arranged on the outermost side of the light-transmitting member unit 200. The light that enters the light-transmitting member unit 200 passes through the hydrophilic layer 30 of the optical member 100, the reflective layer 20, and the light-transmitting member 10, in that order.

[0065] The hydrophilic layer 30 contains photocatalytic particles and is hydrophilic, and when water splashes on the hydrophilic layer 30 on which light is incident, the water spreads and forms a water film on the surface of the hydrophilic layer 30 on the object side, floating and washing away dirt adhering to the surface.

[0066] Light that has passed through the hydrophilic layer 30 is incident on the reflective layer 20. The reflectance of the optical element 100 for light in the visible region, specifically, light with a wavelength in the range of 400 nm to 700 nm, is 3% or less. Therefore, in the optical element 100, reflection of light in the visible region out of the light that has entered the reflective layer 20 is prevented, and the light in the visible region passes through the reflective layer 20 and then passes through the light-transmissive member 10 and other light-transmissive members of the light-transmissive member unit 200. The imaging unit 300 captures an image of the light in the visible region that has passed through the light-transmissive member unit 200 in this manner.

[0067] However, in the case of the above-mentioned hydrophilic members of the prior art, the hydrophilic properties are lower in an environment with little sunlight than in an environment with a lot of sunlight, making it difficult to lift and wash away dirt adhering to the surface of the hydrophilic member.

[0068] Here, even in an environment with little sunlight, light with a wavelength of 300 nm or more and 400 nm or less is incident on the light-transmitting member unit 200 .

[0069] Therefore, in this embodiment, the optical member 100 is manufactured with an average reflectance of 16% or more in the range of 300 nm to 400 nm, so that light with wavelengths in this range is reflected by the hydrophilic layer 30.

[0070] Therefore, not only the light incident from the outside to the inside of the light-transmitting member unit 200 (specifically, the hydrophilic layer 30), but also the light in the above wavelength range reflected from the reflective layer 20 onto the hydrophilic layer 30 increases the photocatalytic effect related to the development of hydrophilicity in the hydrophilic layer 30. Therefore, dirt adhering to the surface of the hydrophilic layer 30 is more easily floated and washed away than in the prior art.

[0071] (Effects) As described above, the optical element, translucent member unit, imaging device, and method for manufacturing an optical element according to the present embodiment can enhance the photocatalytic effect related to the development of hydrophilicity, even in environments with little sunlight, compared to the prior art. More specifically, the present embodiment increases the average reflectance of light with wavelengths of 300 nm or more and 400 nm or less in the optical element 100 compared to the prior art. As a result, the present embodiment allows light from outside the translucent member unit 200 and light that has passed through the hydrophilic layer 30 and been reflected by the reflective layer 20 to be incident on the hydrophilic layer 30. In this way, the present embodiment allows more light to be incident on the hydrophilic layer 30 than the prior art, thereby enhancing the photocatalytic reaction caused by the photocatalyst particles compared to the prior art. As a result, the present embodiment can accelerate the recovery rate of hydrophilicity under ultraviolet light compared to the prior art.

[0072] Incidentally, if the maximum value of the reflectance of the optical member 100 in the wavelength region of 400 nm or more and 700 nm or less is greater than 3%, glare is likely to occur on the surface of the optical member 100. In this regard, in the present embodiment, the reflectance of the optical member 100 in the wavelength region of 400 nm or more and 700 nm or less is 3% or less, so that reflection of light with wavelengths in the visible region can be suppressed and glare on the surface of the optical member can be reduced.

[0073] In this embodiment, the reflective layer 20 having a Vickers hardness of 400 HV or more is provided between the hydrophilic layer 30 and the light-transmitting member 10, thereby improving the scratch resistance of the entire optical member 100. In this embodiment, the reflective layer 20 has low refractive index layers and high refractive index layers alternately stacked along the thickness direction (optical axis direction), thereby achieving the effect of multilayer film interference.

[0074] In this embodiment, the light-transmitting member unit 200 includes the optical member 100 closest to the object, and therefore, a light-transmitting member unit that is hydrophilic and has excellent optical performance can be provided. Furthermore, damage to the optical member 100 inside the light-transmitting member unit caused by ultraviolet light, such as yellowing of the light-transmitting member if the light-transmitting member is made of resin, can be reduced.

[0075] The embodiments of the technology of the present disclosure have been described above with reference to the drawings. However, these embodiments are merely examples of the present disclosure, and the technology of the present disclosure is not limited to the above embodiments and can be implemented in various forms without departing from the spirit and scope of the present disclosure. The drawings mainly show each component in a schematic manner for ease of understanding, and the thickness, length, number, etc. of each component shown in the drawings may differ from the actual ones due to the convenience of creating the drawings. Furthermore, the materials, shapes, dimensions, etc. of each component shown in the above embodiments are merely examples and are not particularly limited, and various modifications are possible within a scope that does not substantially deviate from the effects of the present disclosure. The configuration of the embodiments may be appropriately modified within a scope that does not deviate from the technical concept of the present disclosure. Furthermore, the embodiments may be implemented in combination within the scope of possibility.

[0076] Next, Examples 1 to 4 will be described in comparison with Comparative Examples 1 and 2. Note that the technology of the present disclosure is not limited to the scope of Examples 1 to 4.

[0077] In Examples 1 to 4 and Comparative Example 1, the optical members were configured with a hydrophilic layer, a reflection adjustment layer (reflective layer), and a lens. In Comparative Example 2, the optical members were configured with a hydrophilic layer and a lens. Each of the hydrophilic layers in Examples 1 to Comparative Example 2 was coated by a wet process spin coating method.

[0078] Fig. 8 is a table showing the film thickness (nm) of the hydrophilic layer, the number of layers and film thickness (nm) of the reflection adjustment layer (reflective layer), the optical characteristics of the optical members, and the evaluation of the optical members in Examples 1 to 4 and Comparative Examples 1 and 2. Fig. 9 is a graph showing the reflectance (%) at each wavelength (Wavelength (nm)) from 300 nm to 700 nm in Examples 1 and 4 and Comparative Example 1.

[0079] The film thickness (nm) of the hydrophilic layer, the number of layers and film thickness (nm) of the reflection adjustment layer (reflective layer), the optical characteristics of the optical members, and the evaluation of the optical members in Examples 1 to 4 and Comparative Examples 1 and 2 are as shown in FIG. 8.

[0080] The optical properties include, first, the average reflectance of light having a wavelength in the range of 300 nm or more and 400 nm or less, and the average reflectance in Examples 1 to 4 was 16% or more, the average reflectance in Examples 1 to 3 was 25% or more, and the average reflectance in Example 3 was 53%. The average reflectances in Comparative Examples 1 and 2 were 3.2% and 5.0%, respectively.

[0081] The second optical characteristic is the maximum reflectance of light having a wavelength in the range of 400 nm to 700 nm, and the maximum reflectance of Examples 1 to 4 is 3% or less, more specifically, 1.8% or less, the maximum reflectance of Examples 1 to 3 is 1.7% or less, and the maximum reflectance of Example 3 is 1.0% or less. The maximum reflectances of Comparative Examples 1 and 2 are 2.7% and 8.0%, respectively.

[0082] The optical member is formed so that the average reflectance of light having a wavelength in the range of 300 nm to 400 nm that has passed through the hydrophilic layer is 16% or more, and the reflectance of light having a wavelength in the range of 400 nm to 700 nm that has passed through the hydrophilic layer is 3% or less. Therefore, as shown in Figure 9, the reflectance of each wavelength from 300 nm to 400 nm in Examples 1 and 4 is greater than the reflectance of each wavelength from 400 nm to 700 nm.

[0083] In contrast to this, in Comparative Example 1, the change in reflectance at each wavelength over the range of 300 nm to 700 nm is not large compared to Examples 1 and 4.

[0084] The first evaluation was whether or not the subject was reflected in the image. Specifically, the optical element was placed in a sunny outdoor environment, and the degree of reflection was visually confirmed and evaluated according to the following evaluation criteria.

[0085] In Figure 8, the case where the reflection on the lens surface was not visible to the naked eye was marked with "◯", and the case where the reflection on the lens surface was clearly visible to the naked eye was marked with "X".

[0086] As described above, if the maximum reflectance of an optical element in the wavelength region of 400 nm or more and 700 nm or less is greater than 3%, glare is likely to occur on the surface of the optical element. In Examples 1 to 4 and Comparative Example 1, the maximum reflectance in the above wavelength region is less than 3%. Therefore, in Examples 1 to 4 and Comparative Example 1, the evaluation of glare is good (i.e., not visible to the naked eye). However, in Comparative Example 2, the maximum reflectance in the above wavelength region is greater than 3%, specifically 8.0%. Therefore, the evaluation of glare is bad (i.e., clearly visible to the naked eye).

[0087] The second evaluation is the hydrophilicity recovery function. Specifically, the optical element is placed in a thermo-hygrostat at a humidity of 85% and a temperature of 85°C for 250 hours, and then exposed to an integrated ultraviolet light dose of 1000 mJ / cm. ２ The optical component was irradiated with ultraviolet light under the conditions of: Pure water was dropped onto the hydrophilic layer, and the static contact angle was measured at the end point of the dropped pure water droplet using an automatic contact angle meter ("DMo-601" manufactured by Kyowa Interface Science Co., Ltd.) with the surface of the hydrophilic layer as the reference. Based on the static contact angle after ultraviolet light irradiation, the hydrophilicity recovery function was ranked according to the following criteria.

[0088] In Fig. 8, the pure water contact angle of less than 30° is indicated as "◯", the pure water contact angle of 30° or more and less than 45° is indicated as "△", and the pure water contact angle of 45° or more is indicated as "X".

[0089] In Examples 1 to 3, the hydrophilicity recovery function was evaluated as ◯ (i.e., the pure water contact angle was less than 30°). In Example 4, the hydrophilicity recovery function was evaluated as △ (i.e., the pure water contact angle was 30° or more and less than 45°). As in Examples 1 to 4, when the average reflectance of the reflective layer 20 for light in the wavelength range of 400 nm to 700 nm is 16% or more, the hydrophilicity recovery function of the hydrophilic layer 30 is confirmed. When the average reflectance is 25%, as in Examples 1 to 3, the hydrophilicity recovery function is good. When the average reflectance is 53%, as in Example 3, the hydrophilicity recovery function is even better. However, in Comparative Examples 1 and 2, the average reflectance is less than 16% (3.2%, 5.0%), so the hydrophilicity recovery function is not confirmed, and the hydrophilicity recovery function is evaluated as × (the pure water contact angle is 45° or more).

[0090] The hydrophilic recovery function will be explained in detail.

[0091] Fig. 10 is a diagram showing the static contact angle θn1 of the hydrophilic layer 30N1 in Example 1. As shown in Fig. 10, the static contact angle θn1 of the hydrophilic layer 30N1 in Example 1 is 30°. The hydrophilicity recovery function was evaluated as good.

[0092] Fig. 11 is a diagram showing the static contact angle θn4 of the hydrophilic layer 30N4 in Example 4. As shown in Fig. 11, the static contact angle θn4 of the hydrophilic layer 30N4 in Example 4 is 40°. The hydrophilicity recovery function was evaluated as fair.

[0093] Fig. 12 is a diagram showing the static contact angle θt1 of the hydrophilic layer 30T1 in Comparative Example 1. As shown in Fig. 12, the static contact angle θt1 of the hydrophilic layer 30T1 in Comparative Example 1 is 50°. The hydrophilicity recovery function was evaluated as ×.

[0094] (Modifications) (First Modification) The method for manufacturing the optical member 100 according to the above-described embodiment includes forming a reflective layer 20 on the light-transmitting member 10, and forming a hydrophilic layer 30 containing photocatalytic particles on the reflective layer 20 formed on the light-transmitting member 10. The technology of the present disclosure is not limited to this. Specifically, it is as follows.

[0095] The light-transmitting member 10 is attached to one surface of a resin film having an adhesive layer on the one surface, and the laminated member 2030 is formed on the other surface of the resin film. Note that the light-transmitting member 10 may be attached to one surface of the resin film and then the laminated member 2030 may be formed on the other surface of the resin film, or the light-transmitting member 10 may be attached to one surface of the resin film after the laminated member 2030 is formed on the other surface of the resin film.

[0096] (Second Modification) When the light-transmitting member 10 of the optical member 100 is a resin lens, a hard coat layer may be provided. Specifically, the hard coat layer may be provided at least either firstly between the hydrophilic layer 30 and the reflective layer 20, or secondly between the light-transmitting member 10 and the reflective layer 20.

[0097] (Third Modification) The imaging device 1000 according to this embodiment is an in-vehicle camera (a front camera, a rear camera, or a side camera). The technology of the present disclosure is not limited to this, and the imaging device may be a surveillance camera attached to a windowpane of a building, etc.

[0098] In light of the above disclosure, the following remarks are proposed:

[0099] (Supplementary Note 1) An optical element comprising: a hydrophilic layer containing photocatalytic particles; a translucent member; and a reflective layer located between the hydrophilic layer and the translucent member, which reflects light having a wavelength in the range of 300 nm to 400 nm that has passed through the hydrophilic layer back to the hydrophilic layer, wherein the optical element has an average reflectance of 16% or more for light having a wavelength in the range.

[0100] (Supplementary Note 2) The optical member according to Supplementary Note 1, wherein the optical member has a reflectance of 3% or less for light having a wavelength in the range of 400 nm or more and 700 nm or less.

[0101] (Supplementary Note 3) The optical member according to Supplementary Note 1 or Supplementary Note 2, wherein the reflective layer has a Vickers hardness of 400 HV or more.

[0102] (Supplementary Note 4) The optical member according to any one of Supplementary Notes 1 to 3, wherein the reflective layer has a multilayer structure.

[0103] (Supplementary Note 5) The optical member according to Supplementary Note 4, wherein the reflective layer includes low refractive index layers and high refractive index layers alternately stacked along the optical axis direction.

[0104] (Supplementary Note 6) The optical member according to Supplementary Note 5, wherein the refractive index of the low refractive index layer is 1.80 or less.

[0105] (Supplementary Note 7) The optical member according to Supplementary Note 5 or Supplementary Note 6, wherein the refractive index of the high refractive index layer is greater than 1.80.

[0106] (Supplementary Note 8) A light-transmitting member unit including a plurality of light-transmitting members arranged side by side in an optical axis direction, the light-transmitting member unit including the optical member according to Supplementary Note 1, wherein the hydrophilic layer, the reflective layer, and the light-transmitting members are arranged in this order from the light incident side.

[0107] (Supplementary Note 9) An imaging device comprising: the light-transmitting member unit according to Supplementary Note 8; and an imaging section that images light transmitted through the light-transmitting member unit.

[0108] (Appendix 10) A method for manufacturing an optical element, comprising: forming a hydrophilic layer containing photocatalytic particles; and forming a reflective layer, wherein the reflective layer is located between the hydrophilic layer and a translucent member, and reflects light having a wavelength in the range of 300 nm to 400 nm that has passed through the hydrophilic layer back to the hydrophilic layer, and the average reflectance of the optical element for light of the wavelengths is 16% or more.

[0109] (Supplementary Note 11) The method for manufacturing an optical member according to Supplementary Note 10, further comprising: forming the reflective layer on the light-transmitting member; and forming the hydrophilic layer on the reflective layer formed on the light-transmitting member.

[0110] (Appendix 12) The method for manufacturing an optical member according to appendix 10 or appendix 11, wherein the reflective layer is formed by forming a multilayer structure, and the number of layers constituting the reflective layer and the thickness of each layer are determined so that the average reflectance of the optical member for light in the wavelength range is 16% or more.

[0111] 1000 Imaging device 200 Light-transmitting member unit 300 Imaging section 100 Optical member 10 Light-transmitting member 2030 Laminated member 30 Hydrophilic layer 20 Reflective layer 20L1 Low refractive index layer 20H1 High refractive index layer 20L2 Low refractive index layer 20H2 High refractive index layer 20Ln Low refractive index layer

Claims

1. An optical element comprising: a hydrophilic layer containing photocatalytic particles; a translucent member; and a reflective layer located between the hydrophilic layer and the translucent member, which reflects light having a wavelength in the range of 300 nm to 400 nm that has passed through the hydrophilic layer back to the hydrophilic layer, wherein the average reflectance of the optical element for light having a wavelength in the range is 16% or more.

2. The optical element according to claim 1, wherein the reflectance of said optical element for light having a wavelength in the range of 400 nm to 700 nm is 3% or less.

3. The optical member according to claim 1, wherein the reflective layer has a Vickers hardness of 400 HV or more.

4. The optical element according to claim 1, wherein the reflective layer has a multi-layer structure.

5. The optical element according to claim 4, wherein the reflective layer comprises low refractive index layers and high refractive index layers alternately stacked along the optical axis direction.

6. The optical member according to claim 5, wherein the refractive index of the low refractive index layer is 1.80 or less.

7. The optical element according to claim 5, wherein the refractive index of the high refractive index layer is greater than 1.

80.

8. A light-transmitting member unit comprising a plurality of light-transmitting members arranged side by side in the optical axis direction, the light-transmitting member unit including the optical member according to claim 1, wherein the hydrophilic layer, the reflective layer, and the light-transmitting members are arranged in this order from the light incident side.

9. An imaging device comprising: the light-transmitting member unit according to claim 8; and an imaging section that captures an image of light passing through the light-transmitting member unit.

10. A method for manufacturing an optical element, comprising: forming a hydrophilic layer containing photocatalytic particles; and forming a reflective layer, wherein the reflective layer is located between the hydrophilic layer and a translucent member, and reflects light having a wavelength in the range of 300 nm to 400 nm that has passed through the hydrophilic layer back to the hydrophilic layer, and the average reflectance of the optical element for light of the wavelengths is 16% or more.

11. The method for manufacturing an optical member according to claim 10, wherein the reflective layer is formed on the light-transmitting member, and the hydrophilic layer is formed on the reflective layer formed on the light-transmitting member.

12. A method for manufacturing an optical element according to claim 10, wherein the reflective layer is formed by forming a multilayer structure, and the number of layers constituting the reflective layer and the thickness of each layer are determined so that the average reflectance of the optical element for light in the wavelength range is 16% or more.

Images