Optical filter and imaging device

Abstract

Provided is an optical filter comprising a glass substrate, wherein: a first barrier layer, a resin layer, and a first multilayer film are disposed on a first main surface of the glass substrate in order from the glass substrate; a second barrier layer and a second multilayer film are disposed on a second main surface of the glass substrate in order from the glass substrate; the glass substrate is a phosphate glass comprising an infrared absorber; the first barrier layer and the second barrier layer each independently comprise at least 80 mol % of an oxide of at least one metal selected from the group consisting of titanium (Ti), niobium (Nb), tantalum (Ta), and hafnium (Hf); and the first multilayer film and the second multilayer film are each independently constituted by a plurality of dielectric layers.

Description

Optical filter and imaging device

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

[0002] Imaging devices such as in-vehicle cameras and smartphone cameras are equipped with solid-state imaging elements (such as CCDs and CMOS). However, solid-state imaging elements have a higher sensitivity to infrared light than human vision. Therefore, to make the image captured by the solid-state imaging element closer to human vision sensitivity, an optical filter is also installed in the imaging device.

[0003] International Publication No. WO 2014 / 030628 International Publication No. WO 2023 / 282187

[0004] High-precision optical filters are required to have (1) high transmittance in the visible light region, (2) high light blocking properties in the infrared region, and (3) optical properties that do not change depending on the angle of incidence of light.

[0005] In this regard, Patent Document 1 describes an optical filter having a CuO-containing fluorophosphates glass substrate. The CuO-containing fluorophosphates glass substrate has the function of absorbing infrared rays to a certain extent. Therefore, it discloses that an optical filter having the above-mentioned effects (1) to (3) can be provided by combining a CuO-containing fluorophosphates glass substrate, a dye-containing layer, and an infrared reflective film.

[0006] However, according to the inventors of the present application, it is understood that even with the optical filter described in Patent Document 1, it is difficult to say that the effects of (2) and (3) above are sufficient.

[0007] On the other hand, Patent Document 2 describes an optical filter in which phosphate glass is used as a glass substrate instead of fluorophosphate glass. CuO-containing phosphate glass has a higher infrared absorption function than CuO-containing fluorophosphate glass. Therefore, it is disclosed that by using such a phosphate glass substrate, a filter with significantly higher light-blocking properties in the infrared region can be obtained.

[0008] However, according to the experience of the present inventors, phosphate glass has a problem in that it is prone to elution when it comes into contact with moisture. Therefore, in an optical filter using phosphate glass as the glass substrate, the glass substrate deteriorates over time, which can cause a problem of reduced filter characteristics.

[0009] The present invention has been made in view of the above background, and an object of the present invention is to provide an optical filter that has significantly high light-blocking properties in the infrared region and that has significantly improved water resistance.

[0010] The present invention provides an optical filter including a glass substrate, wherein the glass substrate has a first main surface and a second main surface facing each other, a first barrier layer, a resin layer, and a first multilayer film are disposed on the first main surface of the glass substrate in order of proximity to the glass substrate, and a second barrier layer and a second multilayer film are disposed on the second main surface of the glass substrate in order of proximity to the glass substrate, the glass substrate is phosphate glass containing an infrared absorber, the first barrier layer and the second barrier layer each independently contain an oxide of at least one metal selected from the group consisting of titanium (Ti), niobium (Nb), tantalum (Ta), and hafnium (Hf) in a proportion of 80 mol % or more, the resin layer contains a near-infrared absorbing dye having a maximum absorption wavelength in the range of 700 nm to 800 nm, and the first multilayer film and the second multilayer film each independently comprise a plurality of dielectric layers.

[0011] The present invention can provide an optical filter that has significantly high light-blocking properties in the infrared region and significantly improved water resistance.

[0012] FIG. 1 is a cross-sectional view schematically showing an example of the configuration of an optical filter according to one embodiment of the present invention; FIG. 2 is a cross-sectional view schematically showing an example of the configuration of an optical filter according to another embodiment of the present invention; FIG. 3 is a flow chart schematically showing an example of a method for manufacturing an optical filter according to one embodiment of the present invention; FIG. 4 is a diagram showing an example of the optical characteristics of a glass substrate included in an optical filter according to one embodiment of the present invention; FIG. 5 is a graph showing an example of the optical characteristics (transmittance) of an optical filter according to one embodiment of the present invention; FIG. 6 is a graph showing an example of the optical characteristics (reflectance measured on the side of the second multilayer film) of an optical filter according to one embodiment of the present invention; and FIG. 7 is a graph showing an example of the optical characteristics (reflectance measured on the side of the first multilayer film) of an optical filter according to one embodiment of the present invention.

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] As described above, the optical filter described in Patent Document 1 still has a problem in that it is difficult to say that the effects of (2) and (3) described above are sufficient. Furthermore, an optical filter using phosphate glass as a substrate instead of fluorophosphate glass may have a problem in terms of environmental resistance due to its low resistance to moisture.

[0015] Under these circumstances, the inventors of the present invention have carried out extensive research and development and have discovered an optical filter that has significantly high light-blocking properties in the infrared region and significantly improved water resistance.

[0016] That is, one embodiment of the present invention provides an optical filter including a glass substrate, wherein the glass substrate has a first main surface and a second main surface facing each other, a first barrier layer, a resin layer, and a first multilayer film are disposed on the first main surface of the glass substrate in this order from the side closest to the glass substrate, and a second barrier layer and a second multilayer film are disposed on the second main surface of the glass substrate in this order from the side closest to the glass substrate, the glass substrate is phosphate glass containing an infrared absorber, the first barrier layer and the second barrier layer each independently contain an oxide of at least one metal selected from the group consisting of titanium (Ti), niobium (Nb), tantalum (Ta), and hafnium (Hf), the resin layer contains a near-infrared absorbing dye having a maximum absorption wavelength in the range of 700 nm to 800 nm, and the first multilayer film and the second multilayer film each independently are composed of a plurality of dielectric layers.

[0017] In an optical filter according to one embodiment of the present invention, phosphate glass containing an infrared absorbing agent is used as the glass substrate.

[0018] Therefore, the optical filter according to one embodiment of the present invention can achieve higher infrared absorption characteristics than conventional optical filters using phosphate glass substrates.

[0019] In an optical filter according to one embodiment of the present invention, a first barrier layer and a second barrier layer are provided on a first main surface and a second main surface of the phosphate glass, respectively, and the first barrier layer and the second barrier layer each independently contain an oxide of at least one metal selected from the group consisting of titanium (Ti), niobium (Nb), tantalum (Ta), and hafnium (Hf) in a proportion of 80 mol % or more.

[0020] In the optical filter according to one embodiment of the present invention, the first barrier layer and the second barrier layer, which have such moisture protection properties, are disposed on both main surfaces of the glass substrate, thereby improving the environmental resistance of the glass substrate to the outside world. Therefore, in the optical filter according to one embodiment of the present invention, although phosphate glass is used as the glass substrate, the problem of elution of the glass substrate is significantly suppressed, and stable characteristics can be exhibited over a long period of time.

[0021] In one embodiment of the present invention, the first and second main surfaces of the glass substrate are covered with a first barrier layer and a second barrier layer, respectively, and it is not necessary to provide the oxide on the end surfaces of the glass substrate.

[0022] This is because the proportion of the edge surface to the total surface area of ​​the glass substrate is sufficiently low, and the problem of glass elution can be suppressed by covering the main surface, which occupies most of the surface area of ​​the glass substrate, with the above-mentioned barrier layer.

[0023] (Optical Filter According to an Embodiment of the Present Invention) Hereinafter, an optical filter according to an embodiment of the present invention will be described in more detail with reference to FIG.

[0024] FIG. 1 is a schematic cross-sectional view of the configuration of an optical filter according to one embodiment of the present invention.

[0025] As shown in FIG. 1, an optical filter 100 according to one embodiment of the present invention (hereinafter referred to as a “first optical filter”) has a glass substrate 110 having a first major surface 112 and a second major surface 114 facing each other.

[0026] The glass substrate 110 is made of phosphate glass containing an infrared absorbing agent. ２ O ５ The term "substantially free of fluorine atoms" refers to glass containing 40 mol % or more of F and substantially free of fluorine atoms. Here, "substantially free of fluorine atoms" means that, when the content of component elements other than F in the glass is taken as 100 mass %, and the content of F in the glass is expressed as an exclusive percentage, the content of F is less than 3 mass % in exclusive percentage.

[0027] On the first main surface 112 side of the glass substrate 110, a first barrier layer 120, a resin layer 140, and a first multilayer film 150 are arranged in order from the side closest to the glass substrate 110. On the second main surface 114 side of the glass substrate 110, a second barrier layer 130 and a second multilayer film 160 are arranged in order from the side closest to the glass substrate 110.

[0028] The first multilayer film 150 and the second multilayer film 150 are each composed of a plurality of dielectric layers. The resin layer 140 contains a near-infrared absorbing dye having a maximum absorption wavelength in the range of 700 nm to 800 nm.

[0029] The first barrier layer 120 and the second barrier layer 130 each independently comprise an oxide of at least one metal selected from the group consisting of titanium (Ti), niobium (Nb), tantalum (Ta), and hafnium (Hf).

[0030] As described above, the glass substrate 110 made of phosphate glass tends to dissolve relatively easily when it comes into contact with moisture in the environment.

[0031] However, in the first optical filter 100, the first and second major surfaces 112, 114 of the glass substrate 110 are protected with first and second barrier layers 120, 130, respectively, which comprise the materials described above.

[0032] Therefore, in the first optical filter 100, the problem of the glass substrate 110 reacting with external moisture and being dissolved can be significantly suppressed.

[0033] Furthermore, in the first optical filter 100, phosphate glass, which has high infrared absorption properties, is used instead of fluorophosphate glass as the glass substrate 110. Therefore, the first optical filter 100 can exhibit significantly high light blocking properties in the infrared region.

[0034] (Regarding each component included in the optical filter according to one embodiment of the present invention) Next, each component constituting the optical filter according to one embodiment of the present invention will be described in more detail. For clarity, the components will be described using the first optical filter 100 shown in FIG. 1 as an example. Therefore, the reference numerals shown in FIG. 1 will be used to represent each component.

[0035] (Glass Substrate 110) The glass substrate 110 used in the optical filter according to one embodiment of the present invention will be described below. In the description of the glass substrate, the content and total content of each component are expressed as mole percentages based on oxides, unless otherwise specified.

[0036] The glass substrate 110 is made of phosphate glass containing an infrared absorbing agent. The infrared absorbing agent is selected from CuO or FeO in order to obtain excellent infrared absorbing ability. ２ O ３ is preferred, but other components may also be used.

[0037] For example, the glass substrate 110 may contain the following components in mole percentages on an oxide basis: 40% to 75% P ２ O ５ , 10% to 30% Al ２ O ３ , 2% to 30% CuO, 0.1% to 30% R (1) ２ O, where R(1) is at least one element selected from the group consisting of Li, Na, K, Rb, and Cs, and 0-30% R(2)O, where R(2) is at least one element selected from the group consisting of Ca, Mg, Ba, Sr, and Zn, and is substantially free of F.

[0038] P ２ O ５ is the main component that forms glass and is a component that enhances the near-infrared ray blocking properties. ２ O ５If the content is 40% or more, the effect is sufficiently obtained, and if it is 75% or less, problems such as glass instability and reduced weather resistance are unlikely to occur. Therefore, the content is preferably 40 to 75%, more preferably 45 to 73%, even more preferably 47 to 71%, still more preferably 50 to 69%, and most preferably 55 to 67%.

[0039] Al ２ O ３ is the main component that forms glass and is a component that increases the strength of the glass. ２ O ３ If the content of Al is 10% or more, the effect is sufficiently obtained, and if it is 30% or less, problems such as glass instability and reduced near-infrared cutoff are unlikely to occur. Therefore, the content is preferably 10 to 30%, more preferably 11 to 29%, even more preferably 12 to 28%, still more preferably 13 to 27%, and most preferably 14 to 26%. ２ O ３ If the content is 14% or more, the weather resistance of the glass can be improved.

[0040] R ２ O (However, R ２ O is Li ２ O, Na ２ O.K. ２ O, Rb ２ O, and Cs ２ O) are components for lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, stabilizing the glass, etc. ２ The total amount of O (ΣR ２ If O) is 0.1% or more, the effect is sufficiently obtained, and if it is 30% or less, the glass is less likely to become unstable, which is preferable. Therefore, the O content is preferably 0.1 to 30%, more preferably 0.4 to 27%, even more preferably 0.7 to 24%, still more preferably 1.0 to 21%, and most preferably 1.3 to 18%.

[0041] Li ２O is a component that lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, stabilizes the glass, etc. ２ The content of O is preferably 0 to 20%. ２ If the O content is 20% or less, problems such as glass instability and a decrease in near-infrared blocking properties are unlikely to occur, which is preferable. The O content is more preferably 0 to 15%, even more preferably 0 to 10%, still more preferably 0 to 5%, and most preferably Li ２ It contains substantially no O.

[0042] Here, "substantially not containing a specific component" means that the component is not intentionally added, and does not exclude the inclusion of the component to an extent that does not affect the desired properties and is unavoidably mixed in from raw materials, etc.

[0043] Na ２ O is a component that lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, and stabilizes the glass. ２ The content of O is preferably 0 to 20%. ２ If the O content is 20% or less, the glass is less likely to become unstable, which is preferable, and the O content is more preferably 0.5 to 17%, even more preferably 1 to 14%, and even more preferably 1.5 to 11%.

[0044] K ２ O is a component that has the effect of lowering the melting temperature of the glass and the liquidus temperature of the glass. ２ The O content is preferably 0 to 20%. ２ If the O content is 20% or less, the glass is less likely to become unstable, which is preferable, and the O content is more preferably 1 to 18%, even more preferably 2 to 15%, and even more preferably 3 to 13%.

[0045] Rb ２ O is a component that 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 20%. ２If the O content is 20% or less, the glass is less likely to become unstable, which is preferable, and the O content is more preferably 0.5 to 18%, even more preferably 1 to 16%, and even more preferably 2 to 14%.

[0046] Cs ２ O is a component that 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 20%. ２ If the O content is 20% or less, the glass is less likely to become unstable, which is preferable, and the O content is more preferably 0.5 to 18%, even more preferably 1 to 16%, and even more preferably 2 to 14%.

[0047] 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 ＋ The hydration reaction caused by the ion exchange of ions is inhibited, and the weather resistance of the glass is improved. 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 12 to 25%. ２ If the total amount of O exceeds 12%, the effect can be sufficiently obtained, and if it is 25% or less, problems such as instability of the glass, deterioration of the near-infrared cutoff property, and deterioration of the strength of the glass are unlikely to occur, which is preferable. ２O is preferably 12 to 25%, more preferably 13 to 24%, even more preferably 14 to 25%, even more preferably 15 to 26%, and most preferably 16 to 24%.

[0048] R'O (where R'O is one or more components selected from CaO, MgO, BaO, SrO, and ZnO) is a component that lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, stabilizes the glass, and increases the strength of the glass. The total amount of R'O (ΣR'O) is preferably 0 to 30%. A total amount of R'O of 30% or less is preferred because problems such as glass instability, reduced near-infrared blocking ability, reduced short-wavelength infrared transmittance, and reduced glass strength are less likely to occur. The amount is more preferably 0 to 25%, and even more preferably 0 to 20%. The amount is even more preferably 0 to 15%, and even more preferably 0 to 10%.

[0049] The glass of this embodiment preferably contains substantially no divalent cations other than Cu, for the reasons described below.

[0050] When the glass of the present embodiment contains CuO, Cu ２＋ Light absorption in the near-infrared region is cut off by ions. ２－ Cu split by the electric field of ions ２＋ This occurs due to electron transitions between the d orbitals of the ions. The splitting of the d orbitals occurs in Cu ２＋ O present around the ion ２－ This is promoted by reducing the symmetry of the ion. For example, O ２－ When positive ions are present around an ion, the electric field of the positive ions causes the ２－ Ions are attracted and O ２－ The symmetry of the ions decreases. As a result, the splitting of d orbitals is promoted, and light absorption occurs due to electronic transitions between the split d orbitals, weakening the light absorption ability in the near-infrared region and strengthening the light absorption ability in the short-wavelength infrared region. Since the strength of the electric field of a cation increases with the valence of the ion, adding an oxide containing a divalent cation other than Cu to glass may reduce the near-infrared blocking ability and reduce the transmittance of short-wavelength infrared light.

[0051] CaO is a component that lowers the melting temperature of glass, lowers the liquidus temperature of glass, stabilizes glass, and increases the strength of glass. The CaO content is preferably 0 to 20%. A CaO content of 20% or less is preferred because it is less likely to cause problems such as glass instability, reduced near-infrared blocking properties, and reduced transmittance of short-wavelength infrared rays. The CaO content is more preferably 0 to 15%, even more preferably 0 to 10%, and even more preferably 0 to 5%. Most preferably, the glass contains substantially no CaO.

[0052] MgO is a component that lowers the melting temperature of glass, lowers the liquidus temperature of glass, stabilizes glass, and increases the strength of glass. The MgO content is preferably 0 to 20%. An MgO content of 20% or less is preferred because it is less likely to cause problems such as glass instability, reduced near-infrared blocking properties, and reduced transmittance of short-wavelength infrared rays. The content is more preferably 0 to 15%, even more preferably 0 to 10%, and even more preferably 0 to 5%. Most preferably, the glass is substantially free of MgO.

[0053] BaO is a component that lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, stabilizes the glass, and so on. The BaO content is preferably 0 to 20%. A BaO content of 20% or less is preferable because it is less likely to cause problems such as glass instability, reduced near-infrared blocking properties, and reduced transmittance of short-wavelength infrared rays. The BaO content is more preferably 0 to 15%, even more preferably 0 to 10%, and even more preferably 0 to 5%. The BaO content may be 0.1% or more. Most preferably, BaO is substantially not contained.

[0054] SrO is a component that lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, stabilizes the glass, and so on. The SrO content is preferably 0 to 20%. If the SrO content is 20% or less, problems such as glass instability, reduced near-infrared blocking properties, and reduced transmittance of short-wavelength infrared rays are unlikely to occur, which is preferable. The SrO content is more preferably 0 to 15%, and even more preferably 0 to 10%. Most preferably, the glass is substantially free of SrO.

[0055] ZnO has the effect of lowering the melting temperature of glass, lowering the liquidus temperature of glass, etc. The ZnO content is preferably 0 to 20%. A ZnO content of 20% or less is preferable because problems such as deterioration of the melting point of the glass, deterioration of the near-infrared blocking ability, and deterioration of the transmittance of short-wavelength infrared rays are unlikely to occur. The ZnO content is more preferably 0 to 15%, even more preferably 0 to 10%, and even more preferably 0 to 5%. Most preferably, ZnO is substantially not contained.

[0056] CuO is a component for blocking near-infrared rays. The CuO content is preferably 2 to 30%. A CuO content of 2% or more provides sufficient effects, while a CuO content of 30% or less is preferable because problems such as reduced transmittance in the visible light range and reduced transmittance in the short-wavelength infrared range are unlikely to occur. It is more preferably 4 to 25%, even more preferably 5 to 19%, and even more preferably 6 to 20%. Furthermore, it is even more preferably 8% or more. In particular, when the glass contains substantially no divalent cations other than Cu, a CuO content of 8% or more can further enhance the near-infrared blocking properties and the short-wavelength infrared transmittance. It is more preferably 10 to 18%, and most preferably 11 to 18%.

[0057] Fe ２ O ３ is a component for blocking near-infrared rays. ２ O ３ The content of Fe is preferably 0.1% or more and 35% or less. ２ O ３ If the content is less than 0.1%, the above effect cannot be obtained sufficiently, ２ O ３If the content of Fe is 35% or more, the transmittance of light in the visible region decreases, which is not preferable. ２ O ３ The content is preferably 1 to 35%, more preferably 2 to 35%, even more preferably 3 to 35%, still more preferably 4 to 35%, particularly preferably 5 to 35%, and most preferably 6 to 35%.

[0058] B ２ O ３ may be contained in an amount of 15% or less to stabilize the glass. ２ O ３ If the content of B is 15% or less, problems such as deterioration of the weather resistance of the glass, deterioration of the near-infrared cutoff property, and deterioration of the transmittance of short-wavelength infrared rays are unlikely to occur, and therefore it is preferable. It is preferably 13% or less, more preferably 11% or less, even more preferably 9% or less, still more preferably 7% or less, and most preferably B ２ O ３ It is substantially free of

[0059] In the glass of this embodiment, F is an effective component for improving weather resistance, but is an environmentally hazardous substance and may reduce near-infrared blocking properties, so the glass does not substantially contain F. Here, "substantially not containing F" 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 % as an exclusive percentage.

[0060] In the glass of this embodiment, 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 , Nb ２ O ５may be contained in a range of 5% or less to improve the weather resistance of the glass. If the content of these components is 5% or less, problems such as a decrease in near-infrared blocking ability and a decrease in transmittance of short-wavelength infrared rays are unlikely to occur, which is preferable. The content is preferably 4% or less, more preferably 3% or less, even more preferably 2% or less, and even more preferably 1% or less.

[0061] The thickness of the phosphate glass is preferably 3 mm or less, more preferably 2 mm or less, and even more preferably 1 mm or less, from the viewpoint of ease of optical design when incorporating it into a camera module, and is preferably 0.1 mm or more from the viewpoint of element strength and the need to obtain desired optical characteristics.

[0062] Furthermore, when converted into a thickness of 0.29 mm, the glass substrate 110 has the following average transmittance T in the wavelength range of 440 nm to 500 nm at an incident angle of 0°: ｇ（ｖ）ａｖｅ (ii) the transmittance T at a wavelength of 800 nm is 70% or more; ｇ（８００） (iii) the transmittance T at a wavelength of 1000 nm is 7% or less; ｇ（１０００） (iv) the transmittance T at a wavelength of 1200 nm is 7% or less; ｇ（１２００） The spectral characteristic may be such that T ｇ（ｖ）ａｖｅ is more preferably 75% or more, and even more preferably 80% or more. ｇ（８００） is more preferably 5% or less, and even more preferably 3% or less. ｇ（１０００） is more preferably 5% or less, and even more preferably 3% or less. ｇ（１２００） is more preferably 15% or less, and even more preferably 10% or less.

[0063] (First Barrier Layer 120 and Second Barrier Layer 130) The first barrier layer 120 and the second barrier layer 130 are provided to protect the glass substrate 110 from the outside. That is, the glass substrate 110 made of phosphate glass tends to dissolve when exposed to moisture in the outside. However, by covering the main surfaces 112, 114 of the glass substrate 110 with the first barrier layer 120 and the second barrier layer 130, respectively, such dissolution can be significantly suppressed.

[0064] As described above, the first barrier layer 120 and the second barrier layer 130 contain 80 mol % or more, preferably 90 mol % or more, more preferably 95 mol % or more, and particularly preferably 100 mol % of an oxide of at least one metal selected from the group consisting of titanium (Ti), niobium (Nb), tantalum (Ta), and hafnium (Hf).

[0065] For example, resin materials are not preferable as materials for the first barrier layer 120 and the second barrier layer 130 because they have a lower ability to prevent moisture penetration than inorganic materials.

[0066] Furthermore, the first barrier layer 120 preferably contains 80 mol % or more of an oxide of at least one metal selected from the group consisting of titanium (Ti), niobium (Nb), tantalum (Ta), and hafnium (Hf) from the viewpoint of improving adhesion to the glass substrate 110. The second barrier layer 130 also preferably satisfies the above-mentioned requirements from the viewpoint of improving adhesion to the glass substrate 110.

[0067] Here, the first barrier layer 120 and the second barrier layer 130 may contain 80 mol % or more of an oxide of at least one metal selected from the group consisting of titanium (Ti), niobium (Nb), tantalum (Ta), and hafnium (Hf) alone, or may contain 80 mol % or more of two or more materials in total.

[0068] Furthermore, the first barrier layer 120 and the second barrier layer 130 may contain materials other than metal oxides of titanium (Ti), niobium (Nb), tantalum (Ta), and hafnium (Hf) as long as they satisfy the above requirements and do not impair moisture resistance. For example, from the viewpoint of adjusting the refractive index of the first barrier layer 120 and the second barrier layer 130, they may contain oxides of silicon (Si). On the other hand, layers containing silicon (Si) may reduce adhesion to the glass substrate, so it is preferable to avoid containing silicon (Si) as much as possible. Furthermore, from the viewpoint of improving the water resistance of the optical filter, it is preferable to avoid containing materials other than metal oxides of aluminum (Al), titanium (Ti), niobium (Nb), tantalum (Ta), and hafnium (Hf).

[0069] The first barrier layer 120 and the second barrier layer 130 do not necessarily have to be made of the same material.

[0070] However, it is preferable that both the first barrier layer 120 and the second barrier layer 130 be made of titanium oxide, since a titanium oxide barrier film is a particularly effective protective barrier against moisture.

[0071] There are no particular limitations on the method for forming the first barrier layer 120 and the second barrier layer 130. The first barrier layer 120 and the second barrier layer 130 may be formed by, for example, a sputtering method, a vapor deposition method, or the like.

[0072] The thickness of the first barrier layer 120 and the second barrier layer 130 is not particularly limited, but is preferably 10 nm or more from the viewpoint of improving the water resistance of the optical filter.

[0073] (First Multilayer Film 150) The first multilayer film 150 has a role of adjusting the optical characteristics of the first optical filter 100. For example, the first multilayer film 150 may function as an "anti-reflection film."

[0074] In this application, the term "antireflection film" refers to a layer configured so that when light is incident at an incident angle of 5° onto the surface of the optical filter on which the antireflection film is laminated, the maximum reflectance of light having a wavelength between 450 nm and 1200 nm on the surface is 45% or less.

[0075] The first multilayer film 150 is made of a dielectric multilayer film, and may be configured as a stack of alternating high refractive index layers and low refractive index layers.

[0076] Among these, the high refractive index layer may be selected from, for example, titania and alumina, and the low refractive index layer may be selected from, for example, silica and magnesium fluoride.

[0077] The thickness of the first multilayer film 150 is, but is not limited to, in the range of 0.1 μm to 3 μm, for example.

[0078] (Second Multilayer Film 160) The second multilayer film 160 cooperates with the second barrier layer 130 to adjust the optical properties of the first optical filter 100. For example, the second multilayer film may cooperate with the second barrier layer 130 to function as an "anti-reflection film."

[0079] The second multilayer film 160 may be formed by laminating the same materials as the first multilayer film 150 in the same manner.

[0080] The thickness of the second multilayer film 160 is, but is not limited to, in the range of 0.1 μm to 5 μm, for example.

[0081] (Resin Layer 140) The resin layer 140 contains a resin and a dye that absorbs near-infrared rays.

[0082] Such a dye may be selected from, for example, a squarylium dye, a phthalocyanine dye, and a cyanine dye. It may also be selected from at least one dye selected from the group consisting of a cyanine dye, a phthalocyanine dye, a squarylium dye, a naphthalocyanine dye, and a diimonium dye. Among these, squarylium dyes and cyanine dyes are preferred.

[0083] The resin layer 140 may also contain two types of near-infrared absorbing dyes.

[0084] In this case, the first near-infrared absorbing dye may have a maximum absorption wavelength in the range of 700 to 730 nm, and / or the second near-infrared absorbing dye may have a maximum absorption wavelength in the range of 740 to 800 nm.

[0085] The content of the near-infrared absorbing dye contained in the resin layer 140 is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, relative to 100 parts by mass of the resin. When two or more types of compounds are combined, the above content is the total of the respective compounds.

[0086] The resin layer 140 may contain other dyes, such as ultraviolet light absorbing dyes, as long as the effects of the present invention are not impaired.

[0087] Examples of ultraviolet light absorbing dyes include oxazole dyes, merocyanine dyes, cyanine dyes, naphthalimide dyes, oxadiazole dyes, oxazine dyes, oxazolidine dyes, naphthalic acid dyes, styryl dyes, anthracene dyes, cyclic carbonyl dyes, and triazole dyes. Among these, merocyanine dyes are particularly preferred. Furthermore, one type may be used alone, or two or more types may be used in combination.

[0088] The resin that forms the resin layer 140 is not particularly limited as long as it is transparent.

[0089] The resin may be selected from, for example, 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, polystyrene resin, etc. These resins may be used alone or in combination of two or more.

[0090] From the viewpoint of the spectral characteristics, glass transition temperature (Tg), and adhesiveness of the resin layer 140, the resin is preferably selected from polyimide resin, polycarbonate resin, polyester resin, and acrylic resin.

[0091] (First Optical Filter 100) The first optical filter 100 has the following characteristics: (I) an average transmittance T ｔ（ｖ）ａｖｅ１ is 70% or more, and the average transmittance T ｔ（ｖ）ａｖｅ２ (II) The wavelength λ at which the transmittance becomes 10% at an incident angle θ = 0° is ｔ（ｔ＝１０）１ is in the range of 600 nm to 700 nm, and (III) the wavelength λ when the transmittance is 10% at an incident angle θ = 60° ｔ（ｔ＝１０）２ and the λ ｔ（ｔ＝１０）１ The difference △λ ｔ (IV) the average transmittance T at wavelengths of 750 nm to 1000 nm at an incident angle θ = 0° is 12 nm or less (absolute value); ｔ（ｉ）ａｖｅ１ is 4% or less, and the average transmittance T ｔ（ｉ）ａｖｅ２ The optical characteristic may be such that the difference is 4% or less.

[0092] Here, T ｔ（ｖ）ａｖｅ１ is more preferably 75% or more, even more preferably 80% or more, even more preferably 85% or more, and particularly preferably 90% or more. ｔ（ｖ）ａｖｅ２ is more preferably 70% or more, even more preferably 75% or more, and even more preferably 80% or more. ｔ（ｔ＝１０）１ is more preferably in the range of 630 nm to 700 nm, and even more preferably in the range of 650 nm to 700 nm. ｔ It is more preferable that the absolute value of T is 10 nm or less. ｔ（ｉ）ａｖｅ１ is more preferably 2% or less, and even more preferably 1% or less. ｔ（ｉ）ａｖｅ２ is more preferably 2% or less, and even more preferably 1% or less.

[0093] Furthermore, when light is incident on the first optical filter 100 from the side of the second multilayer film 160, (V) the maximum reflectance R in the wavelength range of 450 nm to 950 nm at an incident angle θ=5° is ｔ２ｍａｘ１ (VI) the maximum reflectance R in the wavelength range of 450 nm to 950 nm at an incident angle θ of 60° ｔ２ｍａｘ２ The optical characteristic may be such that R is 15% or less. ｔ２ｍａｘ１ is more preferably 8% or less, and even more preferably 6% or less. ｔ２ｍａｘ２ is more preferably 13% or less, and even more preferably 12% or less.

[0094] Furthermore, when light is incident on the first optical filter 100 from the side of the first multilayer film 150, (VII) the maximum reflectance R in the wavelength range of 450 nm to 950 nm at an incident angle θ=5° is ｔ１ｍａｘ１ (VIII) The maximum reflectance R in the wavelength range of 450 nm to 950 nm at an incident angle θ of 60° is ｔ１ｍａｘ２ is 35% or less.

[0095] By having the optical filter have the optical characteristics, for example, when reflected light from the sensor side is incident on the optical filter, the reflection can be suppressed on the optical filter side, and therefore unnecessary light can be prevented from entering the sensor. ｔ１ｍａｘ１ is more preferably 25% or less, even more preferably 15% or less, and even more preferably 10% or less. ｔ１ｍａｘ２ is more preferably 25% or less, even more preferably 22% or less, and even more preferably 20% or less.

[0096] Furthermore, the first optical filter 100 has an average transmittance T ｔ（ｖ）ａｖｅ１ and average transmittance T ｔ（ｖ）ａｖｅ２ The absolute value of the difference △T ｔ（ｖ）ａｖｅ The optical characteristic may be such that ΔT is 10% or less. ｔ（ｖ）ａｖｅ is more preferably 8% or less, even more preferably 15% or less, and even more preferably 7% or less.

[0097] In the first optical filter 100, phosphate glass, which has high infrared absorption properties, is used instead of fluorophosphate glass for the glass substrate 110, and therefore, in order to obtain the above-described optical properties, it is not necessarily necessary to use an infrared reflective film on the side of the second main surface 114 of the glass substrate 110. In this application, the term "infrared reflective film" refers to a layer configured to have a wavelength band with a width of 100 nm or more, in which the reflectance is 80% or more at an incident angle θ of 5° for light having a wavelength between 750 nm and 1200 nm.

[0098] The optical filter described in the aforementioned Patent Document 1 requires the use of an infrared reflective film to enhance the infrared blocking function in the infrared region. However, when an infrared reflective film is used, an "angle dependency problem" can occur, in which the optical characteristics change depending on the angle of incidence of light.

[0099] In contrast, it is not necessary to use an infrared reflective film in the first optical filter 100. For example, the second multilayer film 160 may be configured as an anti-reflection film in cooperation with the second barrier layer 130. In this case, the first optical filter 100 can be provided with the optical properties (V) and (VI) described above, thereby significantly reducing the "angle dependency problem."

[0100] (Optical Filter According to Another Embodiment of the Present Invention) Next, with reference to FIG. 2, the configuration of an optical filter according to another embodiment of the present invention will be described.

[0101] FIG. 2 is a schematic cross-sectional view of the configuration of an optical filter according to another embodiment of the present invention.

[0102] 2, an optical filter 200 according to another embodiment of the present invention (hereinafter referred to as the "second optical filter") has a configuration similar to that of the above-described first optical filter 100. Therefore, in the second optical filter 200, parts that are similar to those of the first optical filter 100 are designated by reference numerals that are 100 larger than the reference numerals shown in FIG.

[0103] For example, the first optical filter 200 includes a glass substrate 210 , a first barrier layer 220 , a second barrier layer 230 , a resin layer 240 , a first multilayer film 250 , and a second multilayer film 260 .

[0104] However, unlike the first optical filter 100, the second optical filter 200 further includes a third multilayer film 270 between the first barrier layer 220 and the resin layer 240 on the side of the first main surface 212 of the glass substrate 210.

[0105] The third multilayer film 270 is composed of multiple dielectric layers. For example, the third multilayer film 270 may be configured as a stack of alternating high refractive index layers and low refractive index layers.

[0106] The glass substrate 210 of the second optical filter 200 is also made of phosphate glass containing an infrared absorbing agent, so that the second optical filter 200 can exhibit significantly high light blocking properties in the infrared region.

[0107] Also in the second optical filter 200, a first barrier layer 220 is disposed on a first main surface 212 of a glass substrate 210, and a second barrier layer 230 is disposed on a second main surface 214. Furthermore, the first barrier layer 220 and the second barrier layer 230 are made of the above-mentioned materials.

[0108] Therefore, in the second optical filter 200 as well, the problem of the glass substrate 210 reacting with external moisture and being dissolved can be significantly suppressed.

[0109] Here, in the second optical filter 200, in a portion 280 from the first barrier layer 220 to the third multilayer film 270 (hereinafter also referred to as a "laminated portion"), X expressed by the following formula (1): X(%)={A / (B-C)}×100 (Formula (1)) may be 35% or more.

[0110] In equation (1), A (nm) is the total thickness of the dielectric layers contained in the laminated portion 280 that have a QWOT of less than 2 and a refractive index of 1.9 or less when each layer contained in the laminated portion 280 is evaluated using the QWOT represented by the following equation (2): QWOT = (thickness of the target layer / 550 nm) x 4 x refractive index at a wavelength of 550 nm Equation (2) B (nm) is the total thickness of the laminated portion 280, and C (nm) is the total thickness of the layers in the laminated portion 280 that have a QWOT of 2 or more.

[0111] When the laminated portion 280 is configured in this manner, the influence of undesirable reflection behavior at the interface between the first barrier layer 220 and the resin layer 240 can be suppressed, making it possible to obtain an optical filter with better spectral characteristics. By suppressing the above-mentioned reflection behavior, for example, the maximum reflectance of light incident from the first multilayer film 250 side shown as optical characteristics (VII) and (VII) of the optical filter can be suppressed. As described above, by suppressing the maximum reflectance of light incident from the first multilayer film 250 side, it is possible to suppress the intrusion of unnecessary light into the optical filter.

[0112] In particular, from the viewpoint of improving the water resistance of the optical filter and preventing film deformation when the glass surface is altered, it is preferable that the laminated portion 280 has a thickness of 0.2 μm or more, more preferably 0.5 μm or more, even more preferably 1.0 μm or more, and even more preferably 1.5 μm or more.

[0113] The laminated portion 180 is SiO ２ In the case where the laminated portion 180 has a layer made of the above, X' represented by the following formula (3): X'(%)={A' / (B'-C')}×100 (Formula (3)) may be 35% or more. X(%) is more preferably 50% or more, and even more preferably 70% or more.

[0114] In the formula (3), A' (nm) is the SiO layer having a thickness of 180 nm or less in the laminated portion 180. ２B' (nm) is the total thickness of the stacked portion 180; and C' (nm) is the thickness of the SiO layer having a thickness greater than 180 nm in the stacked portion 180. ２ is the total thickness of the layers.

[0115] (Method for manufacturing an optical filter according to one embodiment of the present invention) Next, an example of a method for manufacturing an optical filter according to one embodiment of the present invention will be described with reference to Fig. 3. Fig. 3 is a flow chart schematically showing an example of a method for manufacturing an optical filter according to one embodiment of the present invention.

[0116] As shown in FIG. 3 , a method for manufacturing an optical filter according to one embodiment of the present invention (hereinafter referred to as the “first method”) includes the steps of: preparing a glass substrate having predetermined dimensions (step S110); providing a first barrier layer on a first main surface of the glass substrate and providing a second barrier layer on a second main surface thereof (step S120); and providing a resin layer and a first multilayer film on the first barrier layer and providing a second multilayer film on the second barrier layer (step S130).

[0117] Each step will be described below.

[0118] The manufacturing method will be described below using the first optical filter 100 as an example, and the reference numerals shown in FIG.

[0119] (Step S110) First, a glass substrate is prepared. As described above, the glass substrate 110 has a first main surface 112 and a second main surface 114, and is made of phosphate glass containing an absorbent.

[0120] (Step S120) Next, the first barrier layer 120 is provided on the first main surface 112 of the glass substrate 110, and the second barrier layer 130 is provided on the second main surface 214 thereof.

[0121] The first barrier layer 120 and the second barrier layer 130 (collectively referred to herein as "barrier layers") may be the same material or different materials, for example, both barriers may be composed of titanium dioxide.

[0122] The method for forming the barrier layer is not particularly limited, and the barrier layer may be formed by, for example, a vapor deposition method or a sputtering method.

[0123] (Step S130) Thereafter, components necessary for the first optical filter 100 are sequentially formed on the glass substrate 110. Specifically, the resin layer 140 and the first multilayer film 150 are sequentially formed on the first barrier layer 120, and the second multilayer film 160 is formed on the second barrier layer 130.

[0124] As described above, the first multilayer film 150 is formed by alternately depositing high refractive index films and low refractive index films, and may function as an anti-reflection film.

[0125] There are no particular limitations on the method for forming the first multilayer film 150. For example, a general film formation method such as sputtering may be used.

[0126] The resin layer 140 is formed from, for example, a resin solution containing a dye.

[0127] The resin solution may be prepared by dissolving a dye in a solution containing a resin and an organic solvent, etc. The dye may include an infrared absorbing dye and an ultraviolet absorbing dye as described above.

[0128] Next, a resin solution is applied onto the first barrier layer 120 by a coating method such as spin coating. Thereafter, the applied film is dried to form the resin layer 140.

[0129] Thereafter, a second multilayer film 160 is formed on the resin layer 140 .

[0130] The second multilayer film 160 can be formed by the same method as the first multilayer film 150. The second multilayer film 160 may function as an anti-reflection film.

[0131] Through the above steps, the first optical filter 100 can be manufactured.

[0132] It should be noted that the above method is merely an example, and it will be apparent to those skilled in the art that the first optical filter 100 may be manufactured by other manufacturing methods.

[0133] For example, in a first method, barrier layers 120, 130 are formed on both major surfaces 112, 114 of glass substrate 110 in step S120, and then the remaining layers are applied in step S130.

[0134] Alternatively, however, the second barrier layer 130 and the second multilayer film 160 may be formed on the second main surface 114 of the glass substrate 110, and then the necessary layers may be formed in sequence on the first main surface 112 of the glass substrate 110. Alternatively, conversely, all the necessary layers may be formed on the first main surface 112 of the glass substrate 110, and then the necessary layers may be formed in sequence on the second main surface 114 of the glass substrate 110.

[0135] Furthermore, when manufacturing the second optical filter 200, in step S130 of the first method described above, the third multilayer film 270 is provided before the resin layer 140 is provided on the first barrier layer 120. Thereafter, the resin layer 240 and the first multilayer film 250 may be provided in this order on the third multilayer film 270.

[0136] In addition, various modifications are possible.

[0137] An optical filter according to an embodiment of the present invention can be applied to an imaging device such as a digital still camera, etc. In such an imaging device, good color reproducibility can be provided.

[0138] An imaging device including an optical filter according to an embodiment of the present invention may further include a solid-state imaging element and an imaging lens, and the optical filter may be disposed, for example, between the imaging lens and the solid-state imaging element. Also, the optical filter according to an embodiment of the present invention may be directly attached to the solid-state imaging element and / or the imaging lens of the imaging device via, for example, an adhesive layer.

[0139] (Preliminary Test 1) In order to evaluate the effects of the first and second barrier layers used in the optical filter according to one embodiment of the present invention, the following Experiments 1 to 5 were carried out.

[0140] (Experiment 1) A glass substrate having a first main surface and a second main surface covered with a barrier layer was prepared by the following method.

[0141] First, a glass substrate measuring 5 mm long, 5 mm wide, and 0.29 mm thick was prepared. The glass substrate was made of phosphate glass having the composition shown in "Glass A" in Table 1 below.

[0142] The optical characteristics of the glass substrate used are shown as curve A in Figure 4. The column for Glass A in Table 2 below shows the parameters corresponding to the above (i) to (iv), calculated from the measured optical characteristics.

[0143] Next, a first barrier layer was formed on the first main surface of the glass substrate by vapor deposition. The first barrier layer was a titania layer with a thickness of 143 nm.

[0144] Similarly, a second barrier layer was formed on the second main surface of the glass substrate, the second barrier layer being a titania layer with a thickness of 143 nm.

[0145] Next, a high-temperature, high-humidity test was carried out for 100 hours and 250 hours using the glass substrates coated with the first and second barrier layers (hereinafter referred to as "coated substrates") at a temperature of 85°C and a relative humidity of 85%.

[0146] (Experiment 2) An experiment similar to Experiment 1 was carried out.

[0147] However, in this experiment 2, tantalum oxide layers were used as the first and second barrier layers.

[0148] (Experiment 3) An experiment similar to Experiment 1 was carried out.

[0149] However, in this experiment 3, alumina layers were used as the first and second barrier layers.

[0150] (Experiment 4) An experiment similar to Experiment 1 was carried out.

[0151] However, in this experiment 4, silica layers were used as the first and second barrier layers.

[0152] (Experiment 5) An experiment similar to Experiment 1 was carried out.

[0153] However, in Experiment 5, zirconia layers were used as the first and second barrier layers.

[0154] (Evaluation) After each experiment, the coated substrate was taken out and the following barrier property evaluation was carried out using a microscope.

[0155] The coated substrate is observed from the first main surface side using a microscope. The distance from the nearest edge surface to the most eroded point inside the first main surface of the glass substrate is measured. If the measured distance is less than 150 μm, the barrier property is judged as "A (very good)." If the distance is 150 μm to 200 μm, the barrier property is judged as "B (good)." If the distance is more than 200 μm, the barrier property is judged as "C (poor)."

[0156] Table 3 below summarizes the results of each experiment.

[0157] These results show that the use of alumina, silica, and zirconia as barrier layers does not significantly suppress glass leaching. On the other hand, the use of titania or tantalum oxide as a barrier layer significantly suppressed glass leaching. In particular, the use of titania as a barrier layer was found to suppress glass leaching for a longer period of time.

[0158] (Preliminary Test 2) Next, the following Experiments 10 and 11 were carried out to evaluate the effect of the third multilayer film (see FIG. 2) used in the optical filter according to one embodiment of the present invention.

[0159] (Experiment 10) A glass substrate having both main surfaces covered with a barrier layer and a multilayer film was prepared by the following method.

[0160] First, a glass substrate measuring 5 mm long, 5 mm wide, and 0.29 mm thick was prepared. The glass substrate was made of phosphate glass having the composition shown in "Glass A" in Table 1 above.

[0161] Next, a first barrier layer and a multilayer film A were successively formed on the first main surface of the glass substrate by vapor deposition.

[0162] The first barrier layer was a titania layer having a thickness of 11.49 nm, and the multilayer film A was an alternating layer of silica and titania.

[0163] Table 4 below shows the layer structure of multilayer film A.

[0164] In Table 4, the layer numbers are listed in ascending order from the barrier layer (note that the same notation is used in the tables showing the configurations of multilayer films described later). The total thickness of the first barrier layer and multilayer film A is approximately 1645 nm.

[0165] Similarly, a second barrier layer (titania layer: thickness 11.49 nm) and multilayer film A were successively formed by vapor deposition on the second main surface of the glass substrate, with the total thickness of the second barrier layer and multilayer film A being approximately 1645 nm.

[0166] This resulted in a test sample (hereinafter referred to as "Sample 1").

[0167] (Experiment 11) A test sample (hereinafter referred to as "Sample 2") was prepared in the same manner as in Experiment 10.

[0168] However, in this experiment 11, the multilayer film used was multilayer film B having the layer structure shown in Table 5 below. On either side of the glass substrate, the total thickness of the barrier layer and multilayer film B was about 645 nm.

[0169] (Evaluation) Sample 1 and Sample 2 were used to carry out the high temperature and high humidity test described above.

[0170] Table 6 below summarizes the results obtained for Sample 1 and Sample 2.

[0171] In Table 6, "A" to "C" correspond to the evaluation criteria used in the above-mentioned preliminary test 1.

[0172] These results show that no significant elution occurred in the glass substrate in any of the samples. In particular, Sample 1 exhibited a better anti-glass elution effect. This is presumably because the multilayer film A used in Sample 1 was thicker than the multilayer film B used in Sample 2, and therefore the glass elution suppression effect of the barrier layer was combined with the elution suppression effect of the multilayer film A.

[0173] Examples of the present invention will be described below. In the following description, Examples 1 to 9 are examples, and Example 10 is a reference example.

[0174] Example 1 An optical filter was produced by the following method.

[0175] First, a second barrier layer and a second multilayer film (anti-reflection film) were formed on the second main surface of the glass substrate by the same method as that shown in Experiment 10 above.

[0176] For the glass substrate, phosphate glass having the composition shown in "Glass A" in Table 1 above was used.

[0177] The second barrier layer was made of titania with a thickness of 12 nm, and the second multilayer film was made of alternating layers of silica and titania.

[0178] Table 7 below shows the configuration of the second multilayer film.

[0179] Next, a first barrier layer and a third multilayer film were formed on the first main surface side of the glass substrate.

[0180] The first barrier layer was made of titania and had a thickness of 12 nm. The third multilayer film was made of alternating layers of silica and titania. The total thickness of the first barrier layer and the third multilayer film was 2154 nm.

[0181] The column for "Configuration I-1" in Table 8 below shows the configuration of the third multilayer film.

[0182] Next, a resin layer was formed on the third multilayer film by the following method.

[0183] First, a liquid for a resin layer was prepared as follows.

[0184] A polyimide resin (C3G30G, refractive index 1.59; manufactured by Mitsubishi Gas Chemical Company, Inc.) was dissolved in γ-butyrolactone (GBL):cyclohexanone = 1:1 (mass ratio) to prepare a solution with a resin concentration of 8.5 mass %.

[0185] Next, Compound A, Compound B, and Compound C were added as dyes to this diluted solution, and the mixture was stirred at 50° C. for 2 hours to dissolve, thereby preparing a liquid for the resin layer.

[0186] The amounts of Compound A, Compound B, and Compound C added were 3.99 mass %, 2.25 mass %, and 6.89 mass %, respectively, relative to the resin content.

[0187] Table 9 below summarizes the specifications of Compound A, Compound B, and Compound C.

[0188] Compound A, Compound B, and Compound C each have the following general formula:

[0189]

[0190]

[0191] Next, a resin layer liquid was spin-coated onto the third multilayer film, with a target thickness of 1 μm, and then dried to form a resin layer.

[0192] Next, a first multilayer film (anti-reflection film) was formed on the resin layer.

[0193] Table 10 below shows the configuration of the first multilayer film.

[0194] This resulted in an optical filter, which will be referred to as "optical filter 1."

[0195] Example 2 An optical filter was fabricated in the same manner as in Example 1. However, in Example 2, the thickness of the first barrier layer was set to 15.89 nm, and the configuration of the third multilayer film was changed from that in Example 1.

[0196] The column for Structure I-2 in Table 8 above shows the structure of the third multilayer film used in Example 2.

[0197] This resulted in an optical filter, which will be referred to as "optical filter 2."

[0198] Example 3 An optical filter was fabricated in the same manner as in Example 1. However, in Example 3, the thickness of the first barrier layer was set to 17.54 nm, and the configuration of the third multilayer film was changed from that in Example 1.

[0199] The column for Structure I-3 in Table 8 above shows the structure of the third multilayer film used in Example 3.

[0200] This resulted in the production of an optical filter, which will be referred to as "optical filter 3."

[0201] Example 4 An optical filter was produced in the same manner as in Example 1. However, in Example 4, the thickness of the first barrier layer was set to 15.24 nm, and the configuration of the third multilayer film was changed from that in Example 1.

[0202] The column for Structure I-4 in Table 8 above shows the structure of the third multilayer film used in Example 4.

[0203] This resulted in the production of an optical filter, which will be referred to as "optical filter 4."

[0204] Example 5 An optical filter was fabricated in the same manner as in Example 1. However, in Example 5, the thickness of the first barrier layer was set to 13.25 nm, and the configuration of the third multilayer film was changed from that in Example 1.

[0205] The column for Structure I-5 in Table 8 above shows the structure of the third multilayer film used in Example 5.

[0206] As a result, an optical filter was obtained, which will be referred to as "optical filter 5."

[0207] (Example 6) An optical filter was produced in the same manner as in Example 1. However, in this Example 6, phosphate glass having the composition shown in "Glass B" in Table 1 above was used as the glass substrate. Curve B in FIG. 4 above shows the optical characteristics of Glass B. In addition, the column for Glass B in Table 2 above shows various parameters calculated from the measured optical characteristics.

[0208] Thereafter, the same steps as in Example 1 were followed to produce an optical filter.

[0209] Hereinafter, the obtained optical filter will be referred to as "optical filter 6."

[0210] (Example 7) An optical filter was produced in the same manner as in Example 1. However, in Example 7, phosphate glass having the composition shown in "Glass C" in Table 1 was used as the glass substrate. Curve C in FIG. 4 shows the optical characteristics of Glass C. The column for Glass C in Table 2 shows various parameters calculated from the measured optical characteristics.

[0211] Thereafter, the same steps as in Example 1 were followed to produce an optical filter.

[0212] Hereinafter, the obtained optical filter will be referred to as "optical filter 7."

[0213] (Example 8) An optical filter was produced in the same manner as in Example 1. However, in this Example 8, phosphate glass having the composition shown in "Glass D" in Table 1 was used as the glass substrate. Curve D in FIG. 4 shows the optical characteristics of Glass D. In addition, the column for Glass D in Table 2 shows various parameters calculated from the measured optical characteristics.

[0214] Thereafter, the same steps as in Example 1 were followed to produce an optical filter.

[0215] Hereinafter, the obtained optical filter will be referred to as "optical filter 8."

[0216] (Example 9) An optical filter was produced in the same manner as in Example 1. However, in this Example 9, phosphate glass having the composition shown in "Glass E" in Table 1 was used as the glass substrate. Curve E in FIG. 4 shows the optical characteristics of Glass E. In addition, the column for Glass E in Table 2 shows various parameters calculated from the measured optical characteristics.

[0217] Thereafter, the same steps as in Example 1 were followed to produce an optical filter.

[0218] Hereinafter, the obtained optical filter will be referred to as "optical filter 9."

[0219] (Example 10) An optical filter was produced by the same method as in Example 1. However, in Example 10, fluorophosphate glass having the composition shown in "Glass F" in Table 1 was used as the glass substrate. Curve F in FIG. 4 shows the optical characteristics of Glass F. In addition, the column for Glass F in Table 2 shows various parameters calculated from the measured optical characteristics.

[0220] Thereafter, the same steps as in Example 1 were followed to produce an optical filter.

[0221] Hereinafter, the obtained optical filter will be referred to as "optical filter 10."

[0222] Table 11 below shows the configuration of each optical filter, the value of X determined as described above, and so on.

[0223] (Evaluation) The following evaluations were carried out using each optical filter.

[0224] (Evaluation of Durability) The above-described high temperature and high humidity test was carried out using each optical filter for 250 hours.

[0225] As a result of observation after the test, almost no elution from the glass substrate was observed in any of the optical filters, and therefore, all of the filters were rated "A" on the above-mentioned scale.

[0226] (Evaluation of Optical Properties) The optical properties of each optical filter were evaluated using an ultraviolet-visible-near-infrared spectrophotometer (UH4150, manufactured by Hitachi High-Tech Science Corporation).

[0227] In measuring the transmittance, light was incident on the first multilayer film side of each optical filter.

[0228] Fig. 5 shows an example of a transmittance profile obtained for the optical filter 1. In Fig. 5, the horizontal axis represents wavelength and the vertical axis represents transmittance. Fig. 5 also shows results at incident angles θ = 0° and θ = 60°.

[0229] As shown in Figure 5, it can be seen that the incidence angle θ of the optical filter 1 has almost no effect on the transmittance profile. That is, in the visible light region, high transmittance was obtained regardless of the incidence angle θ. Furthermore, even when the incidence angle θ was changed, the region where the transmittance dropped sharply did not change much. Furthermore, it was found that low transmittance was shown in the infrared region regardless of the incidence angle θ.

[0230] Fig. 6 shows an example of a reflectance profile obtained in the optical filter 1 for light incident from the second multilayer film side. In Fig. 6, the horizontal axis represents wavelength and the vertical axis represents reflectance. Fig. 6 also shows results for incident angles θ = 5° and θ = 60°.

[0231] Fig. 7 shows an example of a reflectance profile obtained in the optical filter 1 for light incident from the first multilayer film side. In Fig. 7, the horizontal axis represents wavelength and the vertical axis represents reflectance. Fig. 7 also shows results for incident angles θ = 5° and θ = 60°.

[0232] As shown in FIGS. 6 and 7, it can be seen that the optical filter 1 significantly suppresses reflection of infrared rays in the infrared region, even though no infrared reflective film is provided.

[0233] Table 12 below shows a summary of the parameters related to the spectral characteristics measured for each optical filter.

[0234] As shown in Table 12, it was confirmed that optical filters 1 to 9 had sufficiently high transmittance in the visible light region. It was also confirmed that optical filters 1 to 9 sufficiently blocked light in the infrared region. It was also found that optical filters 1 to 9 did not change their optical characteristics much even when the angle of incidence θ was changed.

[0235] (Aspects of the Invention) The present invention includes the following aspects.

[0236] (Aspect 1) An optical filter including a glass substrate, wherein the glass substrate has a first main surface and a second main surface opposing each other, a first barrier layer, a resin layer, and a first multilayer film are disposed on the first main surface of the glass substrate in order of proximity to the glass substrate, and a second barrier layer and a second multilayer film are disposed on the second main surface of the glass substrate in order of proximity to the glass substrate, the glass substrate is phosphate glass containing an infrared absorber, the first barrier layer and the second barrier layer each independently contain an oxide of at least one metal selected from the group consisting of titanium (Ti), niobium (Nb), tantalum (Ta), and hafnium (Hf) in a proportion of 80 mol % or more, the resin layer contains a near-infrared absorbing dye having a maximum absorption wavelength in the range of 700 nm to 800 nm, and the first multilayer film and the second multilayer film each independently comprise a plurality of dielectric layers.

[0237] (Aspect 2) The optical filter according to aspect 1, further comprising a third multilayer film between the first barrier layer and the resin layer and composed of a plurality of dielectric layers, wherein X, expressed by the following formula (1), for a portion including the first barrier layer and the third multilayer film combined is 35% or more: X (%) = {A / (B-C)} x 100 (1) where A (nm) is the total thickness of the dielectric layers included in the portion, which have a QWOT of less than 2 and a refractive index of 1.9 or less, when each layer included in the portion is evaluated using a QWOT expressed by the following formula (2), QWOT = (thickness of target layer / 550 nm) x 4 x refractive index at a wavelength of 550 nm (2) where B (nm) is the total thickness of the portion, and C (nm) is the total thickness of the layers in the portion, which have a QWOT of 2 or more.

[0238] (Aspect 3) The optical filter has: (I) an average transmittance T at wavelengths of 440 nm to 500 nm at an incident angle θ=0°; ｔ（ｖ）ａｖｅ１ is 70% or more, and the average transmittance T ｔ（ｖ）ａｖｅ２(II) The wavelength λ at which the transmittance becomes 10% at an incident angle θ = 0° is ｔ（ｔ＝１０）１ is in the range of 600 nm to 700 nm, and (III) the wavelength λ when the transmittance is 10% at an incident angle θ = 60° ｔ（ｔ＝１０）２ and the λ ｔ（ｔ＝１０）１ The difference △λ ｔ (IV) the average transmittance T at wavelengths of 750 nm to 1000 nm at an incident angle θ = 0° is 12 nm or less (absolute value); ｔ（ｉ）ａｖｅ１ is 4% or less, and the average transmittance T ｔ（ｉ）ａｖｅ２ 3. The optical filter according to aspect 1 or 2, having a spectral characteristic in which:

[0239] (Aspect 4) When light is incident from the second multilayer film side, the optical filter has: (V) a maximum reflectance R in the wavelength range of 450 nm to 950 nm at an incident angle θ of 5°; ｔ２ｍａｘ１ (VI) The maximum reflectance R in the wavelength range of 450 nm to 950 nm at an incident angle θ of 60° ｔ２ｍａｘ２ 4. The optical filter according to any one of aspects 1 to 3, having optical properties in which:

[0240] (Aspect 5) When light is incident from the first multilayer film side, the optical filter has the following: (VII) a maximum reflectance R in the wavelength range of 450 nm to 950 nm at an incident angle θ of 5°. ｔ１ｍａｘ１ (VIII) The maximum reflectance R in the wavelength range of 450 nm to 950 nm at an incident angle θ of 60° ｔ１ｍａｘ２ 5. The optical filter according to any one of aspects 1 to 4, having optical properties in which:

[0241] (Aspect 6) The optical filter has: (IX) the average transmittance T ｔ（ｖ）ａｖｅ１ and the average transmittance T ｔ（ｖ）ａｖｅ２ The absolute value of the difference △T ｔ（ｖ）ａｖｅ 4. The optical filter according to aspect 3, having optical properties such that

[0242] (Aspect 7) The optical filter according to any one of aspects 1 to 6, wherein the first barrier layer and the second barrier layer are made of an oxide of Ti.

[0243] (Aspect 8) The optical filter according to any one of aspects 1 to 7, wherein the first barrier layer and the third multilayer film have a total thickness of 1.0 μm or more.

[0244] (Aspect 9) The glass substrate has the following composition in mass percentage based on oxides: ２ O ５ ;40%~75%, Al ２ O ３ 9. The optical filter according to any one of claims 1 to 8, comprising: 10% to 30% CuO; 2% to 30% CuO; a total amount of alkali metal components; 0.1% to 30% Alkaline earth metal components; 0 to 30% Alkaline earth metal components; and being substantially free of F.

[0245] (Aspect 10) The glass substrate has, when converted into a thickness of 0.29 mm, at an incident angle of 0°, (i) an average transmittance T in the wavelength range of 440 nm to 500 nm ｇ（ｖ）ａｖｅ (ii) the transmittance T at a wavelength of 800 nm is 70% or more; ｇ（８００） (iii) the transmittance T at a wavelength of 1000 nm is 7% or less; ｇ（１０００） (iv) the transmittance T at a wavelength of 1200 nm is 7% or less; ｇ（１２００） 10. The optical filter according to any one of aspects 1 to 9, having a spectral characteristic in which .gtoreq..gtoreq..gtoreq.20%.

[0246] (Aspect 11) An imaging device including the optical filter according to any one of aspects 1 to 10.

[0247] This application claims priority based on Japanese Patent Application No. 2023-135099, filed on August 23, 2023, the entire contents of which are incorporated herein by reference.

[0248] REFERENCE SIGNS LIST 100 First optical filter 110 Glass substrate 112 First main surface 114 Second main surface 120 First barrier layer 130 Second barrier layer 140 Resin layer 150 First multilayer film 160 Second multilayer film 200 Second optical filter 210 Glass substrate 212 First main surface 214 Second main surface 220 First barrier layer 230 Second barrier layer 240 Resin layer 250 First multilayer film 260 Second multilayer film 270 Third multilayer film 280 Laminated portion

Claims

1. An optical filter including a glass substrate, the glass substrate having a first main surface and a second main surface opposed to each other, a first barrier layer, a resin layer, and a first multilayer film disposed on the first main surface of the glass substrate in the order of proximity to the glass substrate, and a second barrier layer and a second multilayer film disposed on the second main surface of the glass substrate in the order of proximity to the glass substrate, the glass substrate being a phosphate glass containing an infrared absorbing agent, the first barrier layer and the second barrier layer each independently containing an oxide of at least one metal selected from the group consisting of titanium (Ti), niobium (Nb), tantalum (Ta), and hafnium (Hf) in a proportion of 80 mol % or more, the resin layer containing a near-infrared absorbing dye having a maximum absorption wavelength in the range of 700 nm to 800 nm, and the first multilayer film and the second multilayer film each independently being composed of a plurality of dielectric layers.

2. The optical filter according to claim 1, further comprising a third multilayer film composed of a plurality of dielectric layers between the first barrier layer and the resin layer, wherein X represented by the following formula (1) is 35% or more for a portion including the first barrier layer and the third multilayer film: X (%) = {A / (B-C)} x 100 (1) where A (nm) is the total thickness of the dielectric layers included in the portion, which have a QWOT of less than 2 and a refractive index of 1.9 or less, when each layer included in the portion is evaluated using a QWOT represented by the following formula (2), QWOT = (thickness of target layer / 550 nm) x 4 x refractive index at a wavelength of 550 nm (2) where B (nm) is the total thickness of the portion, and C (nm) is the total thickness of the layers in the portion, which have a QWOT of 2 or more.

3. The optical filter has the following characteristics: (I) At an incident angle θ = 0°, the average transmittance T ｔ（ｖ）ａｖｅ１ is 70% or more, and the average transmittance T ｔ（ｖ）ａｖｅ２ is 65% or more; (II) the wavelength λ at which the transmittance is 10% at an incident angle θ = 0° ｔ（ｔ＝１０）１ is in the range of 600 nm to 700 nm, and (III) the wavelength λ at which the transmittance is 10% at an incident angle θ = 60° ｔ（ｔ＝１０）２ and the λ ｔ（ｔ＝１０）１ Difference △λ ｔ (IV) the average transmittance T at wavelengths of 750 nm to 1000 nm at an incident angle θ of 0° is 12 nm or less (absolute value); ｔ（ｉ）ａｖｅ１ is 4% or less, and the average transmittance T ｔ（ｉ）ａｖｅ２ The optical filter according to claim 1 , having a spectral characteristic of 4% or less.

4. When light is incident on the optical filter from the side of the second multilayer film, (V) the maximum reflectance R in the wavelength range of 450 nm to 950 nm at an incident angle θ = 5° ｔ２ｍａｘ１ is 10% or less, (VI) the maximum reflectance R in the wavelength range of 450 nm to 950 nm at an incident angle θ of 60° ｔ２ｍａｘ２ The optical filter according to claim 1 , having optical properties in which:

5. When light is incident on the optical filter from the side of the first multilayer film, (VII) the maximum reflectance R in the wavelength range of 450 nm to 950 nm at an incident angle θ = 5° ｔ１ｍａｘ１ is 35% or less; (VIII) The maximum reflectance R in the wavelength range of 450 nm to 950 nm at an incident angle θ of 60° ｔ１ｍａｘ２ The optical filter according to claim 1 , having optical properties in which:

6. The optical filter has: (IX) the average transmittance T ｔ（ｖ）ａｖｅ１ and the average transmittance T ｔ（ｖ）ａｖｅ２ The absolute value of the difference △T ｔ（ｖ）ａｖｅ The optical filter according to claim 3 , having optical characteristics such that 7. The optical filter according to claim 1 or 2, wherein the first barrier layer and the second barrier layer are made of an oxide of Ti.

8. The optical filter according to claim 2, wherein the first barrier layer and the third multilayer film have a total thickness of 1.0 μm or more.

9. The glass substrate has the following composition, in terms of mass percentage based on oxide: ２ O ５ ;40%~75%, Al ２ O ３ 3. The optical filter according to claim 1, comprising: 10% to 30% CuO; 2% to 30% total amount of alkali metal components; 0.1% to 30% total amount of alkaline earth metal components; and substantially no F.

10. The glass substrate, when converted to a thickness of 0.29 mm, has the following average transmittance T in the wavelength range of 440 nm to 500 nm at an incident angle of 0°: ｇ（ｖ）ａｖｅ (ii) the transmittance T at a wavelength of 800 nm is 70% or more; ｇ（８００） (iii) the transmittance T at a wavelength of 1000 nm is 7% or less; ｇ（１０００） (iv) the transmittance T at a wavelength of 1200 nm is 7% or less; ｇ（１２００） The optical filter according to claim 1 , having a spectral characteristic of 20% or less.

11. An imaging device equipped with the optical filter according to claim 1.

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