Optical filter and imaging device

Abstract

This invention provides an optical filter having high infrared absorption ability and excellent adhesion between layers, and an imaging device including the optical filter and excellent in durability.　An optical filter (100) comprises, in the stated order, a glass substrate (10), a dielectric film (20), and a layer (30) with dips and bumps. The glass substrate (10) is phosphate glass or fluorophosphate glass.

Description

Optical filter and imaging device

[0001] The present disclosure relates to an optical filter and an imaging device.

[0002] In optical filters that cut infrared rays, the use of glass with higher infrared absorption capacity has been studied in order to suppress oblique incidence characteristics. For example, Patent Document 1 discloses phosphate glass with high infrared absorption capacity.

[0003] WO 2023 / 190090

[0004] Glass with infrared absorption capabilities, such as phosphate glass, has issues with water resistance compared to general glass. One known example of an optical filter is one in which a dielectric (multilayer) film is laminated on a glass substrate. However, when a dielectric film is provided on a glass substrate that has issues with water resistance, there is a risk that the dielectric film may peel off depending on the environment.

[0005] In view of the above problems, an object of the present disclosure is to provide an optical filter having high infrared absorption ability and excellent adhesion between layers, and an imaging device having such an optical filter and excellent durability.

[0006] The present disclosure includes the following aspects: [1] An optical filter comprising a glass substrate, a dielectric film, and a concave-convex layer in this order, the glass substrate being made of phosphate glass or fluorophosphate glass. [2] The optical filter according to [1], wherein the thickness of the dielectric film is 30 nm to 250 nm. [3] The dielectric film is made of SiO ２ , MgF ２ , TiO ２ , Nb ２ O ５ , Ta ２ O ５ , or ZrO ２ [4] The optical filter according to any one of [1] to [3], wherein the dielectric film is a dielectric multilayer film. [5] The layer of the dielectric film adjacent to the glass substrate is TiO ２ , Nb ２ O ５ , Ta ２ O５ , or ZrO ２ The optical filter according to any one of [1] to [4], which is mainly composed of [1]. [6] The optical filter according to any one of [1] to [5], wherein the concave-convex layer contains one or more elements selected from Al, Mg, and Zn. [7] The optical filter according to any one of [1] to [6], wherein the glass substrate is phosphate glass. [8] The optical filter according to any one of [1] to [7], further comprising a second dielectric film on the main surface of the glass substrate opposite to the surface on which the dielectric film is provided. [9] The optical filter according to [8], wherein the second dielectric film is a dielectric multilayer film.

[10] The optical filter according to [8] or [9], further comprising a second concave-convex layer on the second dielectric film.

[11] The optical filter according to

[10] , further comprising a resin film between the second dielectric film and the second concave-convex layer, the resin film containing a near-infrared absorbing dye.

[12] The optical filter according to

[11] , further comprising a third dielectric film between the resin film and the second concave-convex layer.

[13] The optical filter according to any one of [1] to

[12] , further comprising a resin film on a main surface of the glass substrate opposite to the surface on which the dielectric film is provided, the resin film containing a near-infrared absorbing dye.

[14] The optical filter according to

[13] , further comprising a second uneven layer on the resin film.

[15] The optical filter according to

[14] , further comprising a second dielectric film between the resin film and the second uneven layer.

[16] An imaging device comprising the optical filter according to any one of [1] to

[15] .

[0007] The present disclosure provides an optical filter having high infrared absorption capability and excellent adhesion between layers, and an imaging device having the optical filter and excellent durability.

[0008] FIG. 1 is a schematic cross-sectional view showing an example of an optical filter of the present embodiment. FIG. 2 is a schematic cross-sectional view showing another example of an optical filter of the present embodiment. FIG. 3 is a schematic cross-sectional view showing another example of an optical filter of the present embodiment. FIG. 4 is a schematic cross-sectional view showing another example of an optical filter of the present embodiment. FIG. 5 is a schematic cross-sectional view showing another example of an optical filter of the present embodiment. FIG. 6 is a schematic cross-sectional view showing another example of an optical filter of the present embodiment. FIG. 7 is a schematic cross-sectional view showing another example of an optical filter of the present embodiment.

[0009] Hereinafter, embodiments of the invention will be described with reference to the drawings. In each embodiment, identical components are designated by the same reference numerals, and their description will be omitted or simplified. For clarity, the following description and drawings may be simplified as appropriate, and the scale of each component may differ significantly. For clarity, one direction of the object's main surface may be referred to as the X-axis, one direction of the object's main surface perpendicular to the X-axis as the Y-axis, and the normal direction of the object's main surface as the Z-axis. The XY plane may be a curved surface. Furthermore, terms used in this specification that specify shape, geometric conditions, and their degree, such as "parallel," "perpendicular," "orthogonal," and "identical," are not limited to their strict meanings and are interpreted to include a range within which similar functionality can be expected. Unless otherwise specified, "to" indicating a numerical range includes the numerical values ​​before and after it as the upper and lower limits. In numerical ranges described in stages in this specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described herein, the upper or lower limit of the numerical range may be replaced with a value shown in the Examples. In this specification, the term "dielectric film" collectively refers to a single dielectric film (also referred to as a dielectric monolayer film) and a dielectric multilayer film. In this specification, the term "oblique incidence characteristics" refers to the incidence angle dependence of the spectral transmittance of an optical filter. In this specification, the term "near-infrared" refers to light with a wavelength of 750 nm to 1200 nm. In this specification, the term "short-wavelength infrared" refers to light with a wavelength of 1200 nm to 1600 nm. In this specification, the term "substantially free" of a specific component means that the component is not intentionally added, and does not exclude the inclusion of a component to an extent that is unavoidably mixed in from raw materials, etc., and does not affect the intended properties. Unless otherwise specified, "substantially free" means that the content of the target component is 0.1% by mass or less.

[0010] 1 is a schematic cross-sectional view showing an example of an optical filter according to the present embodiment. The optical filter 100 according to the present embodiment includes a glass substrate 10, a dielectric film 20, and a concave-convex layer 30 in this order, and may further include other layers.

[0011] In an optical filter in which a dielectric multilayer film is laminated on a glass substrate, when a substrate with poor water resistance, such as phosphate glass, is used, peeling of the dielectric film tends to occur more easily as the thickness of the dielectric film increases. The optical filter of this embodiment is provided with an anti-reflection concave-convex layer, eliminating the need for an anti-reflection dielectric film. This allows the thickness of the dielectric film to be kept small while simultaneously achieving infrared blocking performance and suppressing oblique incidence characteristics. This also prevents peeling of the dielectric film, resulting in an optical filter with excellent durability. Below, each component that can constitute the optical filter will be described.

[0012] <Glass Substrate> The optical filter of this embodiment uses phosphate glass or fluorophosphate glass as the glass substrate. This specific glass substrate allows for the production of an optical filter with excellent infrared absorption performance.

[0013] Phosphate glass is P in mole percent on an oxide basis. ２ O ５ The term "substantially free of fluorine atoms" means that, when the content of component elements other than F contained in the glass is taken as 100 mass %, and the content of F contained in the glass is expressed as an exclusive percentage, the content of F is less than 3 mass %. Fluorophosphate glass is a glass containing 40% or more of P in mass %. ５＋ Contains 20% or more of F － The term "glass" refers to a glass containing 3% or more of the above.

[0014] (Phosphate Glass) In this embodiment, the phosphate glass (hereinafter also referred to as phosphate glass A) preferably has the following composition expressed in mass % on an oxide basis: ２ O ５ : 40 to 80% Al ２ O ３ : 5 to 20% ΣR２ O: 0.5-20% (R ２ O is Li ２ O, Na ２ O.K. ２ O, Rb ２ O, and Cs ２ one or more components selected from O, ΣR ２ O is R ２ ΣR′O: 0 to 15% (R′O is one or more components selected from CaO, MgO, BaO, SrO, and ZnO, and ΣR′O is the total amount of R′O), CuO: 4 to 40%. Furthermore, other oxides may be contained within the above composition range.

[0015] In this embodiment, the phosphate glass (hereinafter also referred to as phosphate glass B) may have the following composition expressed in mass % on an oxide basis: ２ O ５ : 40 to 80% Al ２ O ３ : 5 to 20% ΣR ２ O: 0.5-20% (R ２ O is Li ２ O, Na ２ O.K. ２ O, Rb ２ O, and Cs ２ one or more components selected from O, ΣR ２ O is R ２ ΣR'O: 0 to 15% (R'O is one or more components selected from CaO, MgO, BaO, SrO, and ZnO, and ΣR'O is the total amount of R'O), CuO: 4 to 20%. Furthermore, other oxides may be contained within the above composition ranges. Below, each component that may be contained in the phosphate glass will be explained. Unless otherwise specified, the content is expressed in mass % based on the oxide. Furthermore, unless otherwise specified, the preferred content of each oxide in the phosphate glass A and the phosphate glass B is the same.

[0016] P ２ O ５ is the main component that forms the glass and is a component that enhances the near-infrared ray blocking property. ２ O ５The content of P is 40% or more, preferably 50% or more. ２ O ５ The content of P is preferably 80% or less. ２ O ５ The content is preferably 50 to 80%, more preferably 52 to 78%, even more preferably 54 to 77%, still more preferably 56 to 76%, and most preferably 60 to 75%.

[0017] Phosphate glass is made of Al to increase the strength of the glass. ２ O ３ From the viewpoint of the stability of the glass and the near-infrared ray blocking property, it is preferable that the glass contains 5% or more of Al. ２ O ３ In order to achieve both the strength of the glass and the near-infrared ray blocking property, Al is preferably 20% or less. ２ O ３ The content of Al is preferably 5 to 20%, more preferably 6 to 18%, even more preferably 7 to 17%, still more preferably 8 to 17%, and most preferably 9 to 16.5%. ２ O ３ When the content is 9% or more, the weather resistance of the glass can be improved.

[0018] The phosphate glass is Li ２ O, Na ２ O.K. ２ O, Rb ２ O, and Cs ２ One or more components selected from O (R ２ It is preferable that the content of R is 0.5 to 20%. ２ By including 0.5% or more of O in total, the melting temperature and liquidus temperature of the glass are lowered, and the ease of processing the glass is improved. ２ The total content of O is preferably 20% or less from the viewpoint of the stability of the glass. ２The total content of O is preferably 0.5 to 20%, more preferably 1 to 20%, even more preferably 2 to 20%, still more preferably 3 to 20%, and most preferably 4 to 20%.

[0019] The above Li ２ O has the effects of lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, and stabilizing the glass. ２ The content of O is preferably 0 to 15%. From the viewpoint of the stability of the glass and excellent near-infrared cutoff properties, Li ２ The content of O is preferably 15% or less, more preferably 0 to 8%, even more preferably 0 to 7%, even more preferably 0 to 6%, and most preferably Li ２ It does not substantially contain O. ２ O has the effects of lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, and stabilizing the glass. ２ The content of O is preferably 0 to 15%. ２ The O content is preferably 15% or less, more preferably 0.5 to 14%, even more preferably 1 to 13%, and even more preferably 2 to 13%. ２ O has the effect of lowering the melting temperature of the glass and the liquidus temperature of the glass. ２ The content of O is preferably 0 to 15%. ２ The content of O is preferably 15% or less, more preferably 0.5 to 14%, even more preferably 1 to 13%, and even more preferably 2 to 13%. ２ O has the effects of lowering the melting temperature of the glass and lowering the liquidus temperature of the glass. ２ The content of O is preferably 0 to 15%. ２ The O content is preferably 15% or less, more preferably 0.5 to 14%, even more preferably 1 to 13%, and even more preferably 2 to 13%. ２O has the effect of lowering the melting temperature of the glass and the liquidus temperature of the glass. ２ The content of O is preferably 0 to 15%. ２ The O content is preferably 15% or less, more preferably 0.5 to 14%, even more preferably 1 to 13%, and even more preferably 2 to 13%.

[0020] In addition, the above R ２ The alkali metal components represented by O produce a mixed alkali effect in the glass by adding two or more of each component at the same time, and R ＋ The mobility of ions is reduced, so that when the glass comes into contact with water, the H ＋ Ions and R in glass ＋ This inhibits the hydration reaction caused by the ion exchange of ions, thereby improving the weather resistance of the glass. ２ O, Na ２ O.K. ２ O, Rb ２ O, and Cs ２ In this case, it is preferable that the compound contains two or more components selected from R ２ O (However, R ２ O is Li ２ O, Na ２ O.K. ２ O, Rb ２ O, and Cs ２ O) total amount (ΣR ２ O) is preferably 7 to 18% (but not including 7%). ２ If the total amount of O exceeds 7%, the weather resistance of the glass is improved. ２ If the total amount of O is 18% or less, the stability and strength of the glass are excellent, and the near-infrared blocking properties are also excellent. ２ Among these, O is preferably more than 7% and 18% or less, more preferably 7.5 to 17%, even more preferably 8 to 16%, still more preferably 8.5% to 15%, and most preferably 9 to 14%.

[0021] The phosphate glass preferably contains 0 to 15% of one or more components (R'O) selected from CaO, MgO, BaO, SrO, and ZnO. The inclusion of R'O lowers the melting temperature and liquidus temperature of the glass, improving the ease of glass processability. On the other hand, the total content of R'O is preferably 15% or less, more preferably 0 to 13%, and even more preferably 0 to 11%, from the viewpoint of improving the stability, strength, and near-infrared cutoff properties of the glass. It is even more preferably 0 to 9%, even more preferably 0 to 8%, and most preferably substantially free of R'O. The CaO has the effects of lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, stabilizing the glass, and increasing the strength of the glass. The CaO content is preferably 0 to 10%. From the viewpoint of improving the stability, strength, and near-infrared blocking properties of the glass, the CaO content is preferably 10% or less, more preferably 0 to 8%, even more preferably 0 to 6%, and even more preferably 0 to 5%. Most preferably, CaO is substantially not contained. The MgO has effects such as lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, stabilizing the glass, and increasing the strength of the glass. The MgO content is preferably 0 to 15%. From the viewpoint of improving the stability, strength, and near-infrared blocking properties of the glass, the MgO content is preferably 15% or less, more preferably 0 to 13%, even more preferably 0 to 10%, and even more preferably 0 to 9%. Most preferably, MgO is substantially not contained. The BaO has effects such as lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, and stabilizing the glass. From the viewpoint of improving the stability and strength of the glass, as well as the near-infrared cutoff properties, the BaO content is preferably 10% or less, more preferably 0 to 8%, even more preferably 0 to 6%, and even more preferably 0 to 5%. The BaO content may be 0.1% or more. Most preferably, BaO is substantially not contained. The SrO has the effects of lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, stabilizing the glass, and the like.From the viewpoint of improving the stability, strength, and near-infrared blocking properties of the glass, the SrO content is preferably 0 to 10%, more preferably 0 to 8%, and even more preferably 0 to 7%. Most preferably, SrO is substantially not contained. The ZnO has the effects of lowering the melting temperature of the glass and lowering the liquidus temperature of the glass. From the viewpoint of improving the stability, strength, and near-infrared blocking properties of the glass, the ZnO content is preferably 0 to 15%, more preferably 0 to 13%, even more preferably 0 to 10%, and even more preferably 0 to 9%. Most preferably, ZnO is substantially not contained.

[0022] From the viewpoint of near-infrared ray blocking performance, the phosphate glass (phosphate glass A) preferably contains CuO. From the viewpoint of near-infrared ray blocking performance, the CuO content is preferably 4% or more. From the viewpoint of excellent visible light transmittance, the CuO content is preferably 40% or less. From the viewpoint of achieving both near-infrared ray blocking performance and visible light transmittance, the CuO content is more preferably 4 to 30%, even more preferably 5 to 30%, still more preferably 6 to 30%, and particularly preferably 7 to 30% (but excluding 7%). In particular, when the glass does not substantially contain divalent cations other than Cu, a CuO content of more than 7% can further improve near-infrared ray blocking performance and short-wavelength infrared ray transmittance.

[0023] The phosphate glass (phosphate glass B) preferably contains CuO from the viewpoint of near-infrared blocking performance. From the viewpoint of near-infrared blocking performance, the CuO content is preferably 4% or more. From the viewpoint of excellent visible light transmittance, the CuO content is preferably 20% or less. From the viewpoint of achieving both near-infrared blocking performance and visible light transmittance, the CuO content is more preferably 4 to 19.5%, even more preferably 5 to 19%, even more preferably 6 to 18.5%, even more preferably more than 7%, and most preferably 7 to 18% (but excluding 7%). In particular, when the glass is substantially free of divalent cations other than Cu, a CuO content of more than 7% can further improve near-infrared blocking performance and short-wavelength infrared transmittance.

[0024] Phosphate glass contains B to stabilize the glass. ２ O ３ In view of the excellent weather resistance and near-infrared cutoff properties of the glass, B ２ O ３ The content of is preferably 9% or less, more preferably 8% or less, even more preferably 7% or less, still more preferably 6% or less, and most preferably B ２ O ３ Phosphate glass contains substantially no SiO ２ , GeO ２ , ZrO ２ , SnO ２ , TiO ２ , CeO ２ , W.O. ３ , Y ２ O ３ , La ２ O ３ , Gd ２ O ３ , Yb ２ O ３ , and Nb ２ O ５In view of near-infrared ray blocking performance, the total content of these components is preferably 5% or less, more preferably 4% or less, even more preferably 3% or less, still more preferably 2% or less, and particularly preferably 1% or less.

[0025] Phosphate glass is made of MoO ３ MoO ３ Phosphate glass containing MoO has increased transmittance of light with wavelengths of 400 nm to 540 nm. ３ The content of MoO is preferably 0.01% or more from the viewpoint of improving the transmittance of visible light. ３ The content is more preferably 0.02% to 9%, even more preferably 0.03% to 8%, even more preferably 0.04% to 7%, and most preferably 0.05% to 6%.

[0026] Phosphate glass contains Fe in order to suppress the decrease in transmittance of visible light on the short wavelength side. ２ O ３ , Cr ２ O ３ , Bi ２ O ３ , NiO, V ２ O ５ , MoO ３ , MnO ２ It is preferable that the phosphate glass contains substantially no Fe and CoO. In order to prevent a decrease in the near-infrared ray blocking property, it is preferable that the phosphate glass contains substantially no F.

[0027] The thickness of the glass substrate may be adjusted appropriately depending on the application, and is, for example, 3 mm or less. From the viewpoint of weight reduction, the thickness of the glass substrate is preferably 2 mm or less, more preferably 1 mm or less, further preferably 0.5 mm or less, and particularly preferably 0.3 mm or less. On the other hand, from the viewpoint of strength of the optical filter, the thickness of the glass substrate is preferably 0.05 mm or more.

[0028] <Dielectric Film> In this embodiment, the dielectric film not only imparts the desired optical properties but also protects the glass substrate from moisture, suppressing elution, and protecting the uneven layer from acidic substances that may be generated if the glass substrate is eluted. The dielectric film may be, for example, a dielectric multilayer film in which low-refractive index dielectric films (low-refractive index films) and high-refractive index dielectric films (high-refractive index films) are alternately stacked, or a single layer film made of a low-refractive index film or a high-refractive index film. From the viewpoints of protecting the uneven layer and adhesion, a multilayer film is preferred. Here, the high-refractive index film preferably has a refractive index of 1.6 or more, more preferably 2.2 to 2.5. The low-refractive index film preferably has a refractive index of less than 1.6, more preferably 1.45 or more and less than 1.55.

[0029] When the dielectric film is a multilayer film, the multilayer film may be designed to have desired optical properties. However, as described above, the optical filter according to this embodiment has a concave-convex layer, and therefore can exhibit anti-reflection function without imparting optical properties to the multilayer film.

[0030] The material of the dielectric film is preferably any of oxides, nitrides, and fluorides of metals and silicon. In addition to materials that are transparent over a wide wavelength range, materials that absorb light in specific wavelength ranges, such as infrared or ultraviolet, may also be used.

[0031] The dielectric film is made of SiO from the viewpoint of protecting the glass substrate and the uneven layer and providing good adhesion. ２ , MgF ２ , TiO ２ , Nb ２ O ５ , Ta ２ O ５ , or ZrO ２ In order to further improve adhesion, the dielectric film 20 preferably includes a layer adjacent to the glass substrate 10 that is composed mainly of TiO ２ , Nb ２ O ５ , Ta ２ O ５ , or ZrO ２Here, the term "main component" means that the component is contained in a total amount of 80 at % or more per one dielectric film layer.

[0032] When the dielectric film is a multilayer film, the total number of layers (number of films) of the dielectric multilayer film is preferably 10 layers or less, more preferably 7 layers or less, and even more preferably 5 layers or less, in order to suppress peeling of the dielectric film due to accumulation of stress.

[0033] The thickness of the dielectric film (total thickness in the case of a multilayer film) is preferably 30 to 250 nm, more preferably 50 to 220 nm, even more preferably 80 to 200 nm, and particularly preferably 90 to 190 nm, from the viewpoint of preventing peeling.

[0034] The dielectric film can be formed by, for example, a vacuum film-forming process such as CVD, sputtering, or vacuum deposition, or a wet film-forming process such as spraying or dipping.

[0035] <Uneven Layer> In this embodiment, the uneven layer 30 has anti-reflection properties. The uneven layer 30 may have a structure in which the refractive index continuously decreases from the dielectric film 20 interface toward the air interface. The uneven layer 30 preferably has an average reflectance of 2% or less when visible light having a wavelength of 400 to 600 nm is incident from the uneven surface side (the -Z side in FIG. 1 ) at an incident angle of 0°. Furthermore, the uneven layer 30 preferably has a fine uneven structure in which the pitch between convex portions (see P in FIG. 1 ) is 400 nm or less, preferably 200 nm or less. Furthermore, the average height of the convex portions is preferably 400 nm or less, more preferably 200 to 350 nm.

[0036] The uneven layer 30 may be formed on a filter (dielectric film) or may be formed using, for example, a commercially available moth-eye filter. Examples of the formation method include attaching a film on which a moth-eye is formed, creating a resin structure by nanoimprinting, or forming a SiO ２Examples of suitable methods include etching a low-refractive index film such as aluminum oxide, magnesium oxide, zinc oxide, or an alloy thereof. In particular, a film containing an oxide of aluminum, magnesium oxide, zinc oxide, or an alloy thereof can be formed by a known film-forming method (such as a vacuum deposition method or a sol-gel method), and the film can be treated with water vapor or hot water to convert the surface layer into boehmite (hydroxide), thereby forming the uneven layer 30. The uneven layer formed by this method contains one or more elements selected from aluminum, magnesium, and zinc, and typically also contains hydrogen and oxygen. When an alumina film is formed, the resulting uneven layer contains aluminum oxide hydroxide (AlO(OH)), and the effective refractive index on the air interface side is approximately 1, while the refractive index at the interface on the dielectric film 20 side is in the range of 1.35 to 1.58.

[0037] The optical filter of this embodiment may have other configurations to impart further optical properties, etc., depending on the application, etc. Each layer that is optionally provided will be described below.

[0038] <Second Dielectric Film> As shown in the example of FIG. 2 , the optical filter 100 may further include a second dielectric film 40 on the main surface of the glass substrate 10 opposite to the surface on which the first dielectric film 20 is provided. The second dielectric film 40 may be a near-infrared reflective dielectric film or an anti-reflective dielectric film. The second dielectric film may be a dielectric multilayer film in which the low refractive index film and the high refractive index film are alternately stacked, or may be a single-layer film made of a low refractive index film or a high refractive index film. Specific examples of the low refractive index film and the high refractive index film are as described above, and various optical properties can be imparted to the optical filter by adjusting the thickness of each film.

[0039] In terms of adhesion, the layer of the second dielectric film adjacent to the glass substrate 10 is TiO ２ , Nb ２ O ５ , Ta ２ O ５ , or ZrO ２The second dielectric film is preferably a dielectric multilayer film from the viewpoint of preventing peeling. The total number of layers (number of films) in the dielectric multilayer film is preferably 10 or less, more preferably 7 or less, and even more preferably 5 or less. The thickness of the second dielectric film is preferably 30 to 250 nm, more preferably 50 to 220 nm, and even more preferably 80 to 200 nm, from the viewpoint of preventing peeling.

[0040] <Second Concave-Convex Layer> As shown in the example of Fig. 3, the optical filter 100 may further have a second concave-convex layer 50 on the second dielectric film 40. The second concave-convex layer 50 may have the same configuration as the first concave-convex layer 30. The edges of the optical filter 100 may not be covered with the second concave-convex layer 50. By not covering the edges of the optical filter 100 with the second concave-convex layer 50, detachment of the microstructure from the edges can be suppressed, and handling such as holding or adhering the edges can be facilitated.

[0041] <Resin Film> As shown in the example of FIG. 4, the optical filter 100 may have, for example, a resin film 60 between the second dielectric film 40 and the second concave-convex layer 50 .

[0042] The resin constituting the resin film 60 is preferably transparent. Examples of such resins include polyester resin, acrylic resin, epoxy resin, ene-thiol resin, polycarbonate resin, polyether resin, polyarylate resin, polysulfone resin, polyethersulfone resin, polyparaphenylene resin, polyarylene ether phosphine oxide resin, polyamide resin, polyimide resin, polyamideimide resin, polyolefin resin, cyclic olefin resin, polyurethane resin, and polystyrene resin. The resin may be one type, or two or more types may be mixed.

[0043] Among these, polyimide resin, polycarbonate resin, polyester resin, or acrylic resin is preferable from the viewpoint of the spectral characteristics, glass transition temperature (Tg), and adhesion of the resin film 60. The glass transition temperature (Tg) of the resin is preferably 200° C. or higher from the viewpoint of heat resistance.

[0044] In order to improve the infrared blocking performance, the resin film 60 preferably contains a near-infrared absorbing dye, such as a squarylium dye, a phthalocyanine dye, or a cyanine dye.

[0045] The thickness of the resin film 60 is sufficient to be 10 μm or less, and preferably 3 μm to 10 μm. If the resin film is 10 μm or less, the haze value can be reduced, and an optical filter with excellent infrared blocking performance can be obtained while maintaining image clarity.

[0046] 6 to 8, the resin film 60 may be provided on the main surface of the glass substrate 10 opposite to the dielectric film 20. Various functional layers and a glass protective film (not shown) may further be provided between the glass substrate and the resin film 60.

[0047] <Other Layer Configurations> As shown in the example of FIG. 5, the optical filter 100 of this embodiment may include a third dielectric film 70 between the resin layer and the second uneven layer 50. Furthermore, as shown in the examples of FIGS. 7 and 8, the optical filter 100 of FIG. 6 may further include a second uneven layer 50 or a second dielectric film 40 on the resin film 60. Each of these layers (films) may have the same configuration as the first uneven layer and first dielectric film 20 described above. A preferred layer configuration of the optical filter of this embodiment is shown below. Note that the description "A layer / B layer / C layer..." indicates that layers are stacked in the order of A layer, B layer, C layer... from the side where the optical sensor is mainly arranged. (1) Glass substrate / dielectric film / concave-convex layer (2) Second dielectric film / glass substrate / first dielectric film / concave-convex layer (3) Second concave-convex layer / second dielectric film / glass substrate / first dielectric film / first concave-convex layer (4) Second concave-convex layer / resin film / second dielectric film / glass substrate / first dielectric film / first concave-convex layer (5) Second concave-convex layer / third dielectric film / resin film / second dielectric film / glass substrate / first dielectric film / first concave-convex layer (6) Third dielectric film / resin film / second dielectric film / glass substrate / first dielectric film / first concave-convex layer (7) Resin film ( / functional layer) / glass substrate / dielectric film / concave-convex layer (8) Second concave-convex layer / resin film ( / functional layer) / glass substrate / dielectric film / first concave-convex layer (9) Second concave-convex layer / second dielectric film / resin film ( / functional layer) / glass substrate / first dielectric film / first concave-convex layer (10) Second dielectric film / resin film ( / functional layer) / glass substrate / first dielectric film / first uneven layer.

[0048] The optical filter according to the present embodiment is capable of achieving both high levels of infrared blocking performance and suppression of oblique incidence characteristics, and is also excellent in durability. This optical filter is useful as an optical filter for an imaging device, and can provide an imaging device with excellent color reproducibility.

[0049] [Imaging Device] The imaging device according to this embodiment is characterized by including the optical filter of this embodiment. The imaging device includes at least a solid-state imaging element and the optical filter of this embodiment, and may further include an imaging lens, etc. The optical filter may be disposed, for example, on the optical path between the imaging lens and the solid-state imaging element, or may be directly attached to the solid-state imaging element, imaging lens, etc. of the imaging device via an adhesive layer.

[0050] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. Examples 1 to 3 are examples, and Example 4 is a comparative example.

[0051] [Example 1: Production of optical filter] As a substrate, a phosphate glass substrate having the following composition and a thickness of 0.2 mm was prepared. <Composition of phosphate glass (unit: oxide mass %)> P ２ O ５ :68.73%, Al ２ O ３ :11.36%, Na ２ O: 3.16%, K ２ O: 9.06%, CuO: 7.68%

[0052] On one main surface of the phosphate glass, a dielectric film having the layer structure shown in Table 1 was formed by reactive sputtering. The layer numbers are 1, 2, 3, etc. in order of proximity to the glass substrate.

[0053] Next, a concave-convex layer was formed on the dielectric film. Specifically, a 50 nm alumina film was first formed by reactive sputtering, and the alumina film was then immersed in hot water (pure water) at 60°C for 30 minutes to form a concave-convex layer. This resulted in the optical filter of Example 1.

[0054] [Examples 2 to 4: Production of optical filters] In Examples 2 and 3, optical filters were produced in the same manner as in Example 1, except that the layer structure of the dielectric film was changed as shown in Table 1. In Example 4, an optical filter was produced in the same manner as in Example 1, except that the layer structure of the dielectric film was changed as shown in Table 1 and no uneven layer was formed.

[0055]

[0056] [Evaluation] <Reflectance> The regular reflectance of the concave-convex layer side of each optical filter (dielectric film side in Example 4) was measured, and the average reflectance in the wavelength range of 400 to 600 nm was calculated. The results are shown in Table 2.

[0057] <Durability Evaluation> Each optical filter was left to stand for 50 hours in an environment of 85°C and 85% humidity, and then the optical filter was observed and evaluated according to the following evaluation criteria. The results are shown in Table 2. △, ○, and ◎ indicate practical use. (Main surface evaluation criteria) ×: Large wrinkled peeling was observed throughout. △: Defects of about 100 μm or less were observed. ○: No defects were observed. (Edge evaluation) ×: Large wrinkled film lifting was observed. △: Film lifting of about 100 μm from the edge was observed throughout. ○: Film lifting of about 100 μm from the edge was observed in parts. ◎: No film lifting was observed.

[0058]

[0059] As shown in Table 2, the optical filters of Examples 1 to 3, which include a concave-convex layer, can reduce the thickness of the dielectric film while suppressing the average reflectance. This has been shown to significantly improve the adhesion between the glass and the dielectric film under high temperature and high humidity conditions. This is thought to be because the force exerted on the interface by the dielectric film as a whole is alleviated by being able to reduce the thickness of the dielectric film. As such, the optical filter according to the present embodiment has been shown to have excellent infrared blocking performance as well as excellent durability.

[0060] This application claims priority based on Japanese Patent Application No. 2024-72472, filed April 26, 2024, the disclosure of which is incorporated herein in its entirety by reference.

[0061] REFERENCE SIGNS 10 Glass substrate 20 (First) dielectric film 30 (First) concave-convex layer 40 Second dielectric film 50 Second concave-convex layer 60 Resin film 70 Third dielectric film 100 Optical filter

Claims

1. An optical filter comprising a glass substrate, a dielectric film, and a concave-convex layer in this order, wherein the glass substrate is made of phosphate glass or fluorophosphate glass.

2. The optical filter according to claim 1, wherein the thickness of the dielectric film is 30 nm to 250 nm.

3. The dielectric film is made of SiO ２ , MgF ２ , TiO ２ , Nb ２ O ５ , Ta ２ O ５ , or ZrO ２ The optical filter according to claim 1 , comprising a layer mainly composed of 4. The optical filter according to claim 1, wherein the dielectric film is a dielectric multilayer film.

5. The layer of the dielectric film adjacent to the glass substrate is TiO ２ , Nb ２ O ５ , Ta ２ O ５ , or ZrO ２ The optical filter according to claim 1 , wherein the main component is 6. The optical filter according to claim 1, wherein the uneven layer contains one or more elements selected from Al, Mg, and Zn.

7. The optical filter according to claim 1, wherein the glass substrate is phosphate glass.

8. The optical filter according to claim 1, further comprising a second dielectric film on the main surface of said glass substrate opposite to the surface on which said dielectric film is provided.

9. The optical filter according to claim 8, wherein the second dielectric film is a dielectric multilayer film.

10. The optical filter according to claim 8, further comprising a second uneven layer on said second dielectric film.

11. The optical filter according to claim 10, further comprising a resin film between said second dielectric film and said second uneven layer, said resin film containing a near-infrared absorbing dye.

12. The optical filter according to claim 11, further comprising a third dielectric film between the resin film and the second concave-convex layer.

13. The optical filter according to claim 1, further comprising a resin film on the main surface of the glass substrate opposite to the surface on which the dielectric film is provided, the resin film containing a near-infrared absorbing dye.

14. The optical filter according to claim 13, further comprising a second uneven layer on the resin film.

15. The optical filter according to claim 14, further comprising a second dielectric film between the resin film and the second concave-convex layer.

16. An imaging device comprising an optical filter according to any one of claims 1 to 15.

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