Optical element and imaging device

Abstract

Provided is an optical element that can exhibit an excellent weathering resistance despite having a glass substrate comprising a phosphate glass or a fluorophosphate glass. The optical element is characterized by the disposition, on at least one main surface of a glass substrate comprising a phosphate glass or a fluorophosphate glass, of a weathering-resistant protective film having a monolayer structure that contains the Si atom and in addition at least one selection from the Ti atom, Zr atom, and Al atom, wherein the proportion of the total number of Ti, Zr, and Al atoms in the total number of the Si, Ti, Zr, and Al atoms exceeds 20.0 atomic% and is not more than 75.0 atomic%.

Description

Optical element and imaging device

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

[0002] In imaging devices using solid-state imaging elements such as CCD or CMOS image sensors mounted on digital still cameras (DSCs) such as compact digital cameras and digital single-lens reflex cameras, in order to reproduce color tones well and obtain clear images, an infrared cut filter (IRCF (InfraRed Cut Filter)) that transmits visible light and blocks ultraviolet light and near-infrared light is used (see, for example, Patent Document 1 (JP 2014-148567 A)).

[0003] 1A and 1B are schematic diagrams of camera modules constituting a DSC, with Fig. 1A being a schematic diagram of a camera module for a compact digital camera mounted on a smartphone or the like, and Fig. 1B being a schematic diagram of a camera module for a digital single-lens reflex camera. In the camera module shown in Fig. 1A, ultraviolet and near-infrared light from light transmitted through a lens L is selectively reflected by an infrared cut filter (IRCF) 1, and only light in the visible light range that matches the human visual sensitivity is selectively introduced into the module and captured into an image sensor IC. Similarly, in the camera module shown in Fig. 1B, ultraviolet and near-infrared light from light transmitted through the lens L is selectively reflected by the infrared cut filter (IRCF) 1, and alpha rays are removed by a cover glass CG while preventing dust from entering, and only light in the visible light range that matches the human visual sensitivity is selectively introduced into the module and captured into the image sensor IC.

[0004] An absorbing glass substrate that absorbs ultraviolet light and near-infrared light is used as the constituent substrate of the infrared cut filter (IRCF), and an anti-reflection film (AR film) is provided on the underside (light exit surface side) of the glass substrate, or an absorbing resin film that absorbs ultraviolet light or near-infrared light and an anti-reflection film (AR film) are sequentially provided on the underside (light exit surface side) of the glass substrate, thereby effectively reducing ultraviolet light and near-infrared light in the incident light while transmitting only light in the visible light range downward with high incidence characteristics.

[0005] Japanese Patent Application Laid-Open No. 2014-148567

[0006] However, the inventors have conducted studies and found that phosphate-based glass, fluorophosphate-based glass, or the like is usually used as a constituent material of the absorbing glass substrate that absorbs the above-mentioned ultraviolet light or near-infrared light, and that these glasses are prone to glass burning under high temperature and high humidity conditions, and that such glass burning changes the optical properties and makes it easy for an anti-reflection film or the like provided on the surface of the glass substrate to peel off.

[0007] Under these circumstances, an object of the present invention is to provide an optical element that can exhibit excellent weather resistance despite having a glass substrate made of phosphate-based glass or fluorophosphate-based glass, and to provide an imaging device that includes such an optical element.

[0008] As a result of intensive research conducted by the present inventors in order to achieve the above-mentioned object, they have found that the above-mentioned technical problems can be solved by an optical element comprising a glass substrate made of phosphate-based glass or fluorophosphate-based glass, and a weather-resistant protective film having a single-layer structure provided on at least one main surface thereof, the weather-resistant protective film containing Si atoms and one or more atoms selected from Ti atoms, Zr atoms, and Al atoms, wherein the proportion of the total number of Ti atoms, Zr atoms, and Al atoms to the total number of Si atoms, Ti atoms, Zr atoms, and Al atoms is more than 20.0 atomic % and not more than 75.0 atomic %, and they have completed the present invention based on this finding.

[0009] That is, the present invention provides: (1) an optical element comprising a glass substrate made of phosphate glass or fluorophosphate glass, and a weather-resistant protective film having a single-layer structure provided on at least one main surface thereof, the weather-resistant protective film containing Si atoms and one or more atoms selected from Ti atoms, Zr atoms, and Al atoms, and the proportion of the total number of Ti atoms, Zr atoms, and Al atoms to the total number of Si atoms, Ti atoms, Zr atoms, and Al atoms is more than 20.0 atomic % and not more than 75.0 atomic %; (2) the optical element according to (1) above, in which the Si atoms and the one or more atoms selected from Ti atoms, Zr atoms, and Al atoms constituting the weather-resistant protective film are bonded in a three-dimensional network form by chemical bonds via oxygen atoms between atoms of the same kind or between atoms of different kinds; (3) The optical element according to (1) or (2) above, wherein the weather-resistant protective film contains 8.3 to 27.5 atomic % of Si atoms, 6.6 to 28.5 atomic % of one or more selected from Ti atoms, Zr atoms, and Al atoms, and 61.9 to 66.6 atomic % of oxygen atoms; (4) The optical element according to any one of (1) to (3) above, wherein the weather-resistant protective film contains a reaction product of one or more silicon compounds selected from (I) alkoxysilanes, alkoxysilane derivatives, or oligomers of one or more polymers thereof, and one or more polyvalent metal compounds selected from (IIa) alkoxytitaniums, alkoxytitanium derivatives, or oligomers of one or more polymers thereof, (IIb) alkoxyzirconiums, alkoxyzirconium derivatives, or oligomers of one or more polymers thereof, and (IIc) alkoxyaluminums, alkoxyaluminum derivatives, or oligomers of one or more polymers thereof; (5) A glass substrate made of phosphate glass or fluorophosphate glass is provided on at least one main surface thereof with a compound represented by the following general formula (i): Si(OR １ ) (OR ２ ) (OR ３ ) (OR ４ ) (i) (However, R １ , R ２ , R ３ and R ４are linear or branched hydrocarbon groups having 1 to 10 carbon atoms, and may be the same or different from each other.) and an alkoxysilane represented by the following general formula (iia): Ti(OR ５ ) (OR ６ )(OR ７ )(OR ８ ) (iia) (However, R ５ , R ６ , R ７ and R ８ are linear or branched hydrocarbon groups having 1 to 10 carbon atoms, and may be the same or different from each other. ), Zr(OR ９ ) (OR １０ )(OR １１ )(OR １２ ) (iib) (However, R ９ , R １０ , R １１ and R １２ are linear or branched hydrocarbon groups having 1 to 10 carbon atoms, and may be the same or different from each other.) and a group represented by the following general formula (iic): Al(OR １３ ) (OR １４ )(OR １５ ) (ii c) (However, R １３ , R １４ and R １５are straight-chain or branched-chain hydrocarbon groups having 1 to 10 carbon atoms, and may be the same or different. (6) The optical element according to any one of the above (1) to (4), which is provided with a weather-resistant protective film containing a hydrolysis and dehydration condensation product of 25.0 mol % or more and less than 80.0 mol % of the alkoxysilane represented by general formula (i) and one or more metal alkoxides selected from general formulas (iia) to (iic), when the total content of the alkoxysilane represented by general formula (i) and one or more metal alkoxides selected from general formulas (iia) to (iic) is taken as 100.0 mol %; (7) The optical element according to any one of the above (1) to (6), wherein the weather-resistant protective film contains a hydrolysis and dehydration condensation product of 25.0 mol % or more and less than 80.0 mol % of the alkoxysilane represented by general formula (i) and more than 20.0 mol % and not more than 75.0 mol % of one or more metal alkoxides selected from general formulas (iia) to (iic); (8) The optical element according to any one of (1) to (7) above, in which a resin film or an anti-reflection film is further provided on the weather-resistant protective film; (9) The optical element according to any one of (1) to (7) above, in which a resin film and an anti-reflection film are further provided in this order on the weather-resistant protective film, or an anti-reflection film and a resin film are further provided in this order; (10) The optical element according to any one of (1) to (9) above, in which the optical element is an optical filter; (11) An imaging device characterized by having the optical element according to any one of (1) to (9) above as an optical filter, together with a solid-state imaging element and an imaging lens.

[0010] According to the present invention, it is possible to provide an optical element that can exhibit excellent weather resistance despite having a glass substrate made of phosphate-based glass or fluorophosphate-based glass, and it is also possible to provide an imaging device that includes such an optical element.

[0011] 1(a) is a schematic explanatory diagram of a camera module related to a compact digital camera, and FIG. 1(b) is a schematic explanatory diagram of a camera module related to a digital single-lens reflex camera. It is a schematic explanatory diagram showing an example of an optical element according to the present invention. It is a schematic explanatory diagram showing an example of an optical element according to the present invention.

[0012] The optical element according to the present invention is characterized in that it comprises a glass substrate made of phosphate glass or fluorophosphate glass, and a weather-resistant protective film having a single-layer structure provided on at least one main surface thereof, the weather-resistant protective film containing Si atoms and one or more atoms selected from Ti atoms, Zr atoms, and Al atoms, wherein the ratio of the total number of Ti atoms, Zr atoms, and Al atoms to the total number of Si atoms, Ti atoms, Zr atoms, and Al atoms is more than 20.0 atomic % and not more than 75.0 atomic %. The optical element according to the present invention will now be described.

[0013] [Glass Substrate] The optical element according to the present invention has a glass substrate made of phosphate glass or fluorophosphate glass.

[0014] In the optical element according to the present invention, the glass substrate preferably has a thickness of 0.01 to 1.50 mm, more preferably 0.01 to 0.70 mm, and even more preferably 0.01 to 0.30 mm. By having the thickness of the glass substrate within the above range, it is possible to easily achieve a thin optical element.

[0015] In the optical element according to the present invention, the glass substrate is made of phosphate glass or fluorophosphate glass.

[0016] The phosphate-based glass in the present invention is a glass containing P and O as essential components and other optional components, and one containing CuO is particularly preferred. The inclusion of CuO in the phosphate-based glass allows for more effective absorption of near-infrared light. Examples of other optional components in the phosphate-based glass include Ca, Mg, Sr, Ba, Li, Na, K, and Cs.

[0017] The fluorophosphate glass in the present invention is a glass containing P, O, and F as essential components and other optional components, and one containing CuO is particularly preferred. When the fluorophosphate glass contains CuO, it can absorb near-infrared light more effectively. Examples of other optional components in the fluorophosphate glass include Ca, Mg, Sr, Ba, Li, Na, K, and Cs.

[0018] The phosphate-based glass may be: ２ O ５ More than 0 mass% and 70 mass% or less, Al ２ O ３ 0 to 40% by mass of BaO, 0 to 40% by mass of CuO.

[0019] The phosphate-based glass may be: ２ O ５ 20-60% by mass, Al ２ O ３ More preferably, the composition contains 0 to 10 mass % of BaO, 0 to 10 mass % of CuO.

[0020] The phosphate-based glass may be: ２ O ５ 20-60% by mass, Al ２ O ３ More preferably, the composition contains 1 to 10 mass % of BaO, 1 to 10 mass % of CuO.

[0021] The fluorophosphate glass may be: ２ O ５ More than 0 mass% and 70 mass% or less, Al ２ O ３ 0 to 40% by mass of BaO, 0 to 40% by mass of CuO, and more preferably, more than 0% by mass but not more than 40% by mass of fluoride.

[0022] The fluorophosphate glass may be: ２ O ５ 20-60% by mass, Al ２ O３ More preferably, the composition contains 0 to 10 mass % of BaO, 0 to 10 mass % of CuO, and further contains 1 to 30 mass % of fluoride.

[0023] The fluorophosphate glass may be: ２ O ５ 20-60% by mass, Al ２ O ３ More preferably, the composition contains 1 to 10 mass % of BaO, 1 to 10 mass % of CuO, and further contains 2 to 30 mass % of fluoride.

[0024] The fluoride may be MgF ２ , CaF ２ , SrF ２ One or more selected from the following may be mentioned.

[0025] In the optical element according to the present invention, the glass substrate is preferably an absorbing glass substrate that absorbs ultraviolet light or near-infrared light. In the present application, the absorbing glass substrate refers to a glass substrate used to absorb only ultraviolet light, only near-infrared light, or both ultraviolet and near-infrared light, and specifically refers to glass that, when irradiated with light containing ultraviolet light (wavelength range of 200 to 400 nm) and visible light (wavelength range of more than 400 nm and not more than 2500 nm), selectively absorbs only ultraviolet light (wavelength range of 200 to 400 nm), only near-infrared light (wavelength range of 700 to 2500 nm), or both ultraviolet and near-infrared light, and selectively transmits light in a wavelength range of more than 400 nm and less than 700 nm.

[0026] The optical element according to the present invention is characterized in that a weather-resistant protective film having a single layer structure is provided on at least one main surface of the glass substrate. The weather-resistant protective film may include one containing, in addition to Si atoms, one or more atoms selected from Ti, Zr, Al, Mg, P, Ca, Y, Hf, Nb, Ta, W, Zn, Ga, In, and La. Among these, the optical element according to the present invention employs one containing, in addition to Si atoms, one or more atoms selected from Ti, Zr, and Al. In the optical element according to the present invention, the weather-resistant protective film may include, in addition to Si atoms, one or more atoms selected from Ti, Zr, and Al, and may further include one or more atoms selected from Mg, P, Ca, Y, Hf, Nb, Ta, W, Zn, Ga, In, and La.

[0027] In the optical element according to the present invention, the weather-resistant protective film may include, as will be described later, a hydrolysis and dehydration condensation product of an oligomer made of an alkoxide of each metal, a derivative thereof, or a polymer of one or more of these. In the optical element according to the present invention, when the weather-resistant protective film contains, in addition to Si atoms, one or more atoms selected from Ti atoms, Zr atoms, and Al atoms, and further contains one or more atoms selected from Mg atoms, P atoms, Ca atoms, Y atoms, Hf atoms, Nb atoms, Ta atoms, W atoms, Zn atoms, Ga atoms, In atoms, and La atoms, the weather-resistant protective film may be made of yttrium aluminum i-propoxide (Y[Al(O-i-C ３ H ７ ) ４ ] ３ ) may also contain a hydrolysis and dehydration condensation product of a composite metal alkoxide containing a plurality of metals.

[0028] In the optical element according to the present invention, the weather-resistant protective film has a single-layer structure containing Si atoms as well as one or more atoms selected from Ti atoms, Zr atoms, and Al atoms. In this application, the single-layer structure refers to a layer structure that is identified as being made of materials having the same composition from the measurement image (image contrast) or elemental analysis results obtained when measured using a scanning transmission electron microscope-energy dispersive X-ray spectrometer (STEM-EDX) under the following conditions: <Measurement conditions> Scanning transmission electron microscope: ARM200F manufactured by JEOL Ltd. Energy dispersive X-ray spectrometer: JED-2300T manufactured by JEOL Ltd. Sample preparation: Focused ion beam processing (FIB) Acceleration voltage: 200 kV Elemental analysis: EDX mapping (resolution: 256 x 256)

[0029] In the optical element according to the present invention, the thickness of the weather-resistant protective film is preferably 1000 nm or less, more preferably 10 to 500 nm, and even more preferably 30 to 300 nm. Having a thickness of 1000 nm or less makes it easier to suppress the occurrence of unevenness during the formation of the weather-resistant protective film (during heating), and makes it easier to make the film surface of the weather-resistant protective film uniform. Furthermore, when the thickness of the weather-resistant protective film is 10 nm or more, the weather-resistant protective film is more likely to exhibit sufficient bonding strength, making it easier to improve the mechanical strength of the optical element.

[0030] In the present application, the thickness of the weather-resistant protective film refers to the arithmetic average value when the thickness of the weather-resistant protective film is measured at 50 points in a measurement image (image contrast) of the cross section of the optical element obtained by measurement using the STEM-EDX.

[0031] In the optical element according to the present invention, the weather-resistant protective film contains, in addition to Si atoms, one or more atoms selected from Ti atoms, Zr atoms, and Al atoms. The one or more atoms selected from Ti atoms, Zr atoms, and Al atoms contained in the weather-resistant protective film together with Si atoms are preferably Al atoms or Ti atoms, and more preferably Al atoms.

[0032] In the weather-resistant protective film constituting the optical element according to the present invention, the proportion α (atomic %) of the total number of Ti atoms, Zr atoms and Al atoms to the total number of Si atoms, Ti atoms, Zr atoms and Al atoms (total atomic number) is preferably more than 20.0 atomic % and not more than 75.0 atomic %, more preferably 22.5 to 70.0 atomic %, and even more preferably 25.0 to 65.0 atomic %.

[0033] In this application, the ratio α (atomic %) of the total number of Ti atoms, Zr atoms, and Al atoms to the total number (total number of atoms) of Si atoms, Ti atoms, Zr atoms, and Al atoms that make up the weather-resistant protective film is a value calculated by the following method: (1) STEM-EDX measurement of the optical element is performed under the measurement conditions described above to obtain STEM-EDX lines (EDX-ray (K-line) detection intensity lines in the depth direction of each element that makes up the optical element). (2) In the region that makes up the weather-resistant protective film, the integrated EDX-ray intensity XSi of Si atoms, the integrated EDX-ray intensity XTi of Ti atoms, the integrated EDX-ray intensity XZr of Zr atoms, and the integrated EDX-ray intensity XAl of Al atoms are each determined. (3) The value obtained by multiplying each EDX-ray integrated intensity obtained in (2) by a k-factor (a correction coefficient that depends on the accelerating voltage and detection efficiency and differs depending on the atomic number. For convenience, the k-factor of Si atoms will be referred to as KSi, the k-factor of Ti atoms as KTi, the k-factor of Zr atoms as KZr, and the k-factor of Al atoms as KAl) can be considered to correspond to the weight ratio of each constituent element. Therefore, for example, the weight percentage ATi (wt%) of Ti atoms constituting the weather-resistant protective film can be calculated using the following formula: (4) Furthermore, the value obtained by multiplying the integrated EDX-ray intensity X of each atom by the k-factor and dividing the result by the atomic weight M of each element can be considered to correspond to the ratio of the number of atoms of each constituent element. Therefore, if the atomic weight of a Si atom is MSi, the atomic weight of a Ti atom is MTi, the atomic weight of a Zr atom is MZr, and the atomic weight of an Al atom is MAl, then the atomic percentage αTi (atomic %) of the number of Ti atoms constituting the weather-resistant protective film can be calculated by the following formula: The atomic percentage α (atomic %) of the total number of Ti atoms, Zr atoms, and Al atoms that make up the weather-resistant protective film can be calculated using the following formula. For example, if a weather-resistant protective film contains Si atoms and Ti atoms but does not contain Zr atoms or Al atoms, the atomic percentage α (atomic %) of the total number of Ti atoms, Zr atoms, and Al atoms that make up the weather-resistant protective film can be calculated using the following formula. In this application, K Ｓｉ = 1.000, K Ｔｉ = 1.033, K Ｚｒ = 5.696, K Ａｌ = 1.050.

[0034] In the optical element according to the present invention, the proportion of the total number of Si atoms, Ti atoms, Zr atoms, and Al atoms to the total number of metal atoms constituting the weather-resistant protective film is preferably 70.0 to 100.0 atomic%, more preferably 80.0 to 100.0 atomic%, and even more preferably 90.0 to 100.0 atomic%. In the present application, the proportion (atomic %) of the total number of Si atoms, Ti atoms, Zr atoms, and Al atoms to the total number of metal atoms constituting the weather-resistant protective film also refers to a value calculated in the same manner as the proportion α (atomic %) of the total number of Ti atoms, Zr atoms, and Al atoms to the total number (total number of atoms) of Si atoms, Ti atoms, Zr atoms, and Al atoms constituting the weather-resistant protective film. In the optical element according to the present invention, the metal atoms constituting the weather-resistant protective film preferably include only one or more atoms selected from Ti atoms, Zr atoms, and Al atoms, in addition to Si atoms.

[0035] In the optical element according to the present invention, it is preferable that the Si atoms and one or more atoms selected from Ti atoms, Zr atoms, and Al atoms constituting the weather-resistant protective film are bonded in a three-dimensional network pattern by chemical bonds between the same atoms or between different atoms via oxygen atoms.

[0036] Here, the expression "atoms of the same kind are chemically bonded via an oxygen atom" means that atoms of the same kind (Si atoms and Si atoms, Ti atoms and Ti atoms, Zr atoms and Zr atoms, or Al atoms and Al atoms) are chemically bonded via an oxygen atom. For example, in the case of Si atoms, this means that adjacent Si atoms form a chemical bond represented by -Si-O-Si- via an oxygen atom.

[0037] Furthermore, the expression "different atoms are chemically bonded via an oxygen atom" means that different atoms (Si and Ti atoms, Si and Zr atoms, Si and Al atoms, Ti and Zr atoms, Ti and Al atoms, or Zr and Al atoms) are chemically bonded via an oxygen atom. For example, when the different atoms are Si and Ti atoms, this means that adjacent Si and Ti atoms form a chemical bond represented by -Si-O-Ti- via an oxygen atom.

[0038] The phrase "Si atoms and one or more selected from Ti atoms, Zr atoms, and Al atoms are bonded in a three-dimensional network pattern by chemical bonds via oxygen atoms between the same atoms or different atoms" means that adjacent metal atoms form chemical bonds via oxygen atoms, and the metal atoms are bonded in an infinite number of ways in a network pattern in three dimensions. In the optical element according to the present invention, the weather-resistant protective film can include, as will be described later, a hydrolysis and dehydration condensation product of an alkoxide of each metal, a derivative thereof, or an oligomer composed of one or more polymers thereof. Such a hydrolysis and dehydration condensation product can easily form a structure in which the Si atoms and one or more selected from Ti atoms, Zr atoms, and Al atoms are bonded in a three-dimensional network pattern by chemical bonds via oxygen atoms between the same atoms or different atoms.

[0039] In the optical element according to the present invention, the weather-resistant protective film is made up of Si atoms and one or more atoms selected from Ti atoms, Zr atoms, and Al atoms, and the Si atoms and the one or more atoms selected from Ti atoms, Zr atoms, and Al atoms, which are bonded in a three-dimensional network pattern by chemical bonds between the same atoms or between different atoms via oxygen atoms. This state can be confirmed by vibrational spectroscopy (infrared spectroscopy, Raman spectroscopy).

[0040] In the optical element according to the present invention, the weather-resistant protective film contains, as essential components, Si atoms and one or more atoms selected from Ti atoms, Zr atoms, and Al atoms. In the optical element according to the present invention, when the weather-resistant protective film is in a state in which multiple atoms of the same type or different types are three-dimensionally bonded together by chemical bonds via oxygen atoms, the weather-resistant protective film preferably contains 8.3 to 27.5 atomic %, more preferably 13.3 to 26.8 atomic %, and even more preferably 16.6 to 26.0 atomic % of Si atoms. In the optical element according to the present invention, the weather-resistant protective film preferably contains 6.6 to 28.5 atomic %, more preferably 7.5 to 22.2 atomic %, and even more preferably 8.3 to 18.1 atomic % of one or more atoms selected from Ti atoms, Zr atoms, and Al atoms. In the optical element according to the present invention, the weather-resistant protective film preferably contains 61.9 to 66.6 atomic % of oxygen atoms, more preferably 62.9 to 66.6 atomic %, and even more preferably 63.6 to 66.6 atomic %.

[0041] In this application, the content of Si atoms and the content of one or more atoms selected from Ti atoms, Zr atoms, and Al atoms constituting the weather-resistant protective film refer to values ​​measured by ICP (Inductively Coupled Plasma) spectroscopy, and the content of oxygen atoms constituting the weather-resistant protective film refer to values ​​measured by inorganic elemental analysis.

[0042] In the optical element according to the present invention, the weather-resistant protective film preferably contains a hydrolysis / dehydration condensation product of one or more selected from (I) an oligomer of an alkoxysilane, an alkoxysilane derivative, or a polymer of one or more of these, and (IIa) an oligomer of an alkoxytitanium, an alkoxytitanium derivative, or a polymer of one or more of these, (IIb) an oligomer of an alkoxyaluminum, an alkoxyaluminum derivative, or a polymer of one or more of these, and (IIc) an oligomer of an alkoxyaluminum, an alkoxyaluminum derivative, or a polymer of one or more of these.

[0043] Examples of alkoxysilanes that are used as raw materials for the weather-resistant protective film include one or more selected from tetramethyl silicate, tetraethyl silicate, tetrapropyl silicate, and tetrabutyl silicate. When reactivity is taken into consideration, one or more selected from tetramethyl silicate and tetraethyl silicate are preferred.

[0044] The alkoxysilane derivatives used as raw materials for the weather-resistant protective film are preferably compounds derived from alkoxysilanes in which functional groups other than alkoxy groups have been introduced as some or all of the substituents, and which have functional groups that can react with hydroxyl groups on the surface of the glass substrate, with each other, or with other components that make up the weather-resistant protective film during hydrolysis and dehydration condensation reactions to form bonds. Specific examples of such compounds include the following:

[0045] (Those in which the functional group is an alkyl group) Methyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, n-propyltriethoxysilane, n-hexyltriethoxysilane, and the like.

[0046] (Those in which the functional group is an aromatic group (phenyl group)) Phenyltrimethoxysilane, phenyltriethoxysilane, etc.

[0047] (Those in which the functional group is a vinyl group) Vinyltrimethoxysilane, vinyltriethoxysilane, etc.

[0048] (Those in which the functional group is an epoxy group) 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, etc.

[0049] (Those in which the functional group is a styryl group) p-styryltrimethoxysilane, etc.

[0050] (Those in which the functional group is a methacryl group) 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, etc.

[0051] (Those in which the functional group is an acrylic group) 3-acryloxypropyltrimethoxysilane, etc.

[0052] (Those in which the functional group is an amino group) 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and the like.

[0053] (Those in which the functional group is a ureido group) Tris-(trimethoxysilylpropyl) isocyanurate, etc.

[0054] (Those in which the functional group is a mercapto group) 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, etc.

[0055] (Those in which the functional group is an isocyanate group) 3-isocyanatepropyltriethoxysilane, tetraisocyanatesilane, monomethyltriisocyanatesilane, etc.

[0056] (Those with halogen functional groups) Silicon tetrachloride, etc.

[0057] Examples of oligomers made from one or more polymers selected from alkoxysilanes and alkoxysilane derivatives that serve as raw materials for the weather-resistant protective film include oligomers made from a polymer of a monomer made from one or more of the above-mentioned alkoxysilanes, oligomers made from a polymer of a monomer made from one or more of the above-mentioned alkoxysilane derivatives, and oligomers made from a polymer of a monomer made from one or more of the above-mentioned alkoxysilanes and a monomer made from one or more of the above-mentioned alkoxysilane derivatives.

[0058] Examples of the alkoxytitanium that can be used as a raw material for the weather-resistant protective film include one or more selected from titanium (IV) tetramethoxide, titanium (IV) tetraethoxide, titanium (IV) tetra-iso-propoxide, titanium (IV) tetra-n-butoxide, and the like.

[0059] The alkoxytitanium derivatives used as raw materials for the weather-resistant protective film are preferably compounds derived from alkoxytitanium in which functional groups other than alkoxy groups have been introduced as some or all of the substituents, and which have functional groups that can react with hydroxyl groups on the surface of the glass substrate, with each other, or with other components that make up the weather-resistant protective film during hydrolysis and dehydration condensation reactions to form bonds.

[0060] Specific examples of the alkoxy titanium derivative include one or more selected from titanium diisopropoxybis(acetylacetonate), titanium diisopropoxybis(ethylacetoacetate), titanium octylene glycolate, titanium tetraacetylacetonate, titanium diisopropoxybis(triethanolaminate), titanyl chloride, titanium tetrachloride, and the like.

[0061] Examples of oligomers comprising one or more polymers selected from alkoxytitaniums and alkoxytitanium derivatives, which are raw materials for the weather-resistant protective film, include oligomers comprising a polymer of monomers comprising one or more of the above-mentioned alkoxytitaniums, oligomers comprising a polymer of monomers comprising one or more of the above-mentioned alkoxytitanium derivatives, and oligomers comprising a polymer of a monomer comprising one or more of the above-mentioned alkoxytitaniums and a monomer comprising one or more of the above-mentioned alkoxytitanium derivatives.

[0062] Examples of the alkoxyzirconium that is the raw material for the weather-resistant protective film include one or more compounds selected from zirconium(IV) tetramethoxide, zirconium(IV) tetraethoxide, zirconium(IV) tetra-n-propoxide, zirconium(IV) tetra-i-propoxide, zirconium(IV) tetra-n-butoxide, and the like.

[0063] The alkoxyzirconium derivative used as a raw material for the weather-resistant protective film is preferably a compound derived from alkoxyzirconium in which functional groups other than alkoxy groups have been introduced as some or all of the substituents, and which has functional groups that can react with hydroxyl groups on the surface of the glass substrate, with each other, or with other components that make up the weather-resistant protective film during hydrolysis and dehydration condensation reactions to form bonds.

[0064] Specific examples of the alkoxyzirconium derivative include one or more selected from zirconium tributoxymonoacetylacetonate, zirconium dibutoxybis(ethylacetoacetate), (isopropoxy)tris(dipivaloylmethanato)zirconium, and the like.

[0065] Examples of oligomers made from a polymer of one or more types selected from alkoxyzirconium and alkoxyzirconium derivatives, which are raw materials for the weather-resistant protective film, include oligomers made from a polymer of monomers made from one or more of the above-mentioned alkoxyzirconium types, oligomers made from a polymer of monomers made from one or more of the above-mentioned alkoxyzirconium derivatives, and oligomers made from a polymer of a monomer made from one or more of the above-mentioned alkoxyzirconium types and a monomer made from one or more of the above-mentioned alkoxyzirconium derivatives.

[0066] Examples of the alkoxyaluminum that is the raw material for the weather-resistant protective film include one or more compounds selected from aluminum(III) trimethoxide, aluminum(III) triethoxide, aluminum(III) tri-n-propoxide, aluminum tri-i-propoxide, aluminum(III) tri-sec-butoxide, aluminum(III) di-i-propylate mono-sec-butylate, and the like.

[0067] The alkoxyaluminum derivatives used as raw materials for the weather-resistant protective film are preferably compounds derived from alkoxyaluminum in which functional groups other than alkoxy groups have been introduced as some or all of the substituents, and which contain functional groups that can react with hydroxyl groups on the surface of the glass substrate, with each other, or with other components that make up the weather-resistant protective film during hydrolysis and dehydration condensation reactions to form bonds.

[0068] Specific examples of the alkoxyaluminum derivative include one or more selected from aluminum ethylacetoacetate diisopropylate, aluminum alkylacetoacetate diisopropylate, aluminum tris(acetylacetonate), aluminum tris(ethylacetoacetate), aluminum monoacetylacetonate bis(ethylacetoacetate), cyclic aluminum oxide stearate, and cyclic aluminum oxide octylate.

[0069] Examples of oligomers comprising a polymer of one or more types selected from alkoxyaluminums and alkoxyaluminum derivatives, which are used as raw materials for the weather-resistant protective film, include oligomers comprising a polymer of monomers comprising one or more of the above-mentioned alkoxyaluminums, oligomers comprising a polymer of monomers comprising one or more of the above-mentioned alkoxyaluminum derivatives, and oligomers comprising a polymer of monomers comprising one or more of the above-mentioned alkoxyaluminums and monomers comprising one or more of the above-mentioned alkoxyaluminum derivatives.

[0070] In the optical element according to the present invention, the weather-resistant protective film is preferably a reaction product of 25.0 mol % or more and less than 80.0 mol % of the silicon compound (I) with more than 20.0 mol % and 75.0 mol % or less of one or more metal alkoxides selected from the general formulae (IIa) to (IIc), when the total content of the silicon compound (I) and one or more polyvalent metal compounds selected from the general formulae (IIa) to (IIc) is taken as 100.0 mol %, and It is more preferable that the (I) silicon compound is a reaction product of 30.0 mol % to 77.5 mol % with 22.5 mol % to 70.0 mol % of one or more metal alkoxides selected from the general formulae (IIa) to (IIc) above, and it is even more preferable that the (I) silicon compound is a reaction product of 35.0 mol % to 75.0 mol % with 25.0 mol % to 65.0 mol % of one or more metal alkoxides selected from the general formulae (IIa) to (IIc) above.

[0071] More specifically, the optical element according to the present invention comprises a glass substrate made of phosphate glass or fluorophosphate glass, and a compound represented by the following general formula (i): Si(OR １ ) (OR ２ ) (OR ３ ) (OR ４ ) (i) (However, R １ , R ２ , R ３ and R ４are linear or branched hydrocarbon groups having 1 to 10 carbon atoms, and may be the same or different from each other.) and an alkoxysilane represented by the following general formula (iia): Ti(OR ５ ) (OR ６ )(OR ７ )(OR ８ ) (iia) (However, R ５ , R ６ , R ７ and R ８ are linear or branched hydrocarbon groups having 1 to 10 carbon atoms, and may be the same or different from each other. ), Zr(OR ９ ) (OR １０ )(OR １１ )(OR １２ ) (iib) (However, R ９ , R １０ , R １１ and R １２ are linear or branched hydrocarbon groups having 1 to 10 carbon atoms, and may be the same or different from each other.) and a group represented by the following general formula (iic): Al(OR １３ ) (OR １４ )(OR １５ ) (ii c) (However, R １３ , R １４ and R １５ are linear or branched hydrocarbon groups having 1 to 10 carbon atoms, and may be the same or different from each other.

[0072] General formula (i) Si(OR １ ) (OR ２ ) (OR ３ ) (OR ４ ) (i) In the compound represented by the formula: １ , R ２ , R ３ and R ４is a linear or branched hydrocarbon group having 1 to 10 carbon atoms, preferably a linear or branched hydrocarbon group having 1 to 4 carbon atoms, and more preferably a linear or branched hydrocarbon group having 1 to 3 carbon atoms.

[0073] R １ , R ２ , R ３ and R ４ Specific examples of R include those selected from linear, branched, and cyclic hydrocarbon groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups. １ , R ２ , R ３ and R ４ may be the same or different from each other.

[0074] In the optical element according to the present invention, R １ , R ２ , R ３ and R ４ When the number of carbon atoms is within the above range, it becomes easier to maintain a suitable reaction rate between the alkoxysilane and the metal alkoxide, and it becomes easier to carry out a more uniform reaction.

[0075] General formula (iia) Ti(OR ５ )(OR ６ )(OR ７ )(OR ８ ), titanium alkoxides represented by the general formula (iib) Zr(OR ９ ) (OR １０ )(OR １１ )(OR １２ ) and zirconium alkoxides represented by the general formula (ii) Al(OR １３ ) (OR １４ )(OR １５ In the aluminum alkoxide represented by the formula ５ ~R １５ (R ５ , R ６ , R ７ , R ８ , R ９ , R １０ , R １１ , R１２ , R １３ , R １４ and R １５ ) is a linear or branched hydrocarbon group having 1 to 10 carbon atoms, preferably a linear or branched hydrocarbon group having 2 to 9 carbon atoms, and more preferably a linear or branched hydrocarbon group having 3 to 8 carbon atoms.

[0076] R ５ , R ６ , R ７ , R ８ , R ９ , R １０ , R １１ , R １２ , R １３ , R １４ or R １５ Specific examples of R include those selected from linear, branched, and cyclic hydrocarbon groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups. ５ , R ６ , R ７ , R ８ , R ９ , R １０ , R １１ , R １２ , R １３ , R １４ and R １５ may be the same as or different from each other.

[0077] In the optical element according to the present invention, R ５ , R ６ , R ７ , R ８ , R ９ , R １０ , R １１ , R １２ , R １３ , R １４ and R １５ When the number of carbon atoms is 2 or more, the stability of the metal alkoxide against moisture can be effectively improved, and when the number of carbon atoms is 9 or less, an increase in the viscosity of the metal alkoxide can be suppressed, and the handleability can be effectively improved.

[0078] General formula (i) Si(OR １ ) (OR ２ ) (OR ３ ) (OR ４ Alkoxysilanes represented by the general formula (i) can easily produce compounds having reactive silanol groups (Si-OH groups) by hydrolysis. When alkoxysilanes represented by the general formula (i) are partially hydrolyzed, the reaction proceeds, for example, as follows: Si(OR １ ) (OR ２ ) (OR ３ ) (OR ４ ) + H ２ O → Si(OR １ ) (OR ２ ) (OR ３ )OH+R ４ OH Furthermore, when all the alkoxy groups of the alkoxysilane represented by the general formula (i) are hydrolyzed, the reaction proceeds as follows to form silanol Si(OH) ４ Generate Si(OR １ ) (OR ２ ) (OR ３ ) (OR ４ ) + 4H ２ O → Si(OH) ４ +R １ OH+R ２ OH+R ３ OH+R ４ OH

[0079] General formula (iia) Ti(OR ５ )(OR ６ )(OR ７ )(OR ８ ), titanium alkoxides represented by the general formula (iib) Zr(OR ９ ) (OR １０ )(OR １１ )(OR １２ ) and zirconium alkoxides represented by the general formula (ii) Al(OR １３ ) (OR １４ )(OR １５ ) also easily produces a compound having a hydroxyl group by hydrolysis.

[0080] Then, by subjecting a hydrolyzate of an alkoxysilane represented by the general formula (i) above and a hydrolyzate of one or more metal alkoxides selected from the group consisting of a titanium alkoxide represented by the general formula (iia) above, a zirconium alkoxide represented by the general formula (iib) above, and an aluminum alkoxide represented by the general formula (iic) above, to a dehydration condensation reaction, at least some of these components bond to each other, or the alkoxysilane hydrolyzates or the metal alkoxides bond to each other, thereby forming a weather-resistant protective film. Furthermore, when the dehydration condensation reaction is carried out on a glass substrate, at least some of the hydrolyzates of the above components react with hydroxyl groups on the surface of the glass substrate, thereby being able to bond firmly to the glass substrate.

[0081] In the optical element according to the present invention, the weather-resistant protective film preferably contains a hydrolysis / dehydration condensate of 25.0 mol % or more and less than 80.0 mol % of the alkoxysilane represented by general formula (i) (or a partial hydrolyzate thereof) and more than 20.0 mol % and 75.0 mol % or less of one or more metal alkoxides selected from general formulas (iia) to (iic), where the total content of the alkoxysilane represented by general formula (i) and one or more metal alkoxides selected from general formulas (iia) to (iic) is taken as 100.0 mol %, and It is more preferable that the alkoxysilane (or partial hydrolysate thereof) represented by the general formula (i) above contains a hydrolysis / dehydration condensation product of 30.0 mol % to 77.5 mol % of an alkoxysilane (or partial hydrolysate thereof) represented by the general formula (i) above with 22.5 mol % to 70.0 mol % of one or more metal alkoxides selected from the general formulas (iia) to (iic) above, and it is even more preferable that the alkoxysilane (or partial hydrolysate thereof) represented by the general formula (i) above contains a hydrolysis / dehydration condensation product of 35.0 mol % to 75.0 mol % of an alkoxysilane (or partial hydrolysate thereof) represented by the general formula (i) above with 25.0 mol % to 65.0 mol % of one or more metal alkoxides selected from the general formulas (iia) to (iic) above.

[0082] In the optical element according to the present invention, the mixing ratio of the alkoxysilane (or partial hydrolyzate thereof) represented by the general formula (i) above and one or more metal alkoxides selected from the general formulae (iia) to (iic) above is each within the above range, so that a weather-resistant protective film exhibiting the desired properties can be easily formed.

[0083] In the optical element according to the present invention, the weather-resistant protective film is formed by partially hydrolyzing the alkoxysilane represented by the general formula (i) (Si(OR １ ) (OR ２ ) (OR ３ The alkoxysilane represented by the general formula (i) and the metal alkoxide represented by the general formula (iia) to (iic) are preferably hydrolyzed and dehydrated condensed with one or more metal alkoxides selected from the general formulas (iia) to (iic) as described above. As described above, the alkoxysilane represented by the general formula (i) and the metal alkoxide represented by the general formulas (iia) to (iic) undergo hydrolysis in the presence of water to form silanol Si(OH) ４ and the corresponding metal hydroxides. Here, the metal alkoxides (alkoxides of Ti, Zr, or Al) represented by the above general formulas (iia) to (iic) have significantly higher reactivity with water than the alkoxysilanes represented by general formula (i). In the presence of water, they immediately produce metal hydroxides derived from the metal alkoxides represented by the above general formulas (iia) to (iic), and a precipitate easily forms in the subsequent polycondensation reaction, making it difficult for homogeneous hydrolysis and polymerization reactions to occur. In particular, when attempting to form a weather-resistant protective film using a coating liquid containing a larger amount of the metal alkoxides (alkoxides of Ti, Zr, and Al) represented by the above general formulas (iia) to (iic) than the alkoxysilanes represented by general formula (i), it is difficult to form a homogeneous coating liquid or coating film (weather-resistant protective film) due to the difference in reactivity. Therefore, it is possible to prepare a coating liquid containing a metal alkoxide (alkoxide of Ti, Zr, or Al) represented by the above general formulas (iia) to (iic) in advance, which is partially hydrolyzed (Si(OR １ ) (OR ２ ) (OR ３A homogeneous hydrolysis and dehydration-condensation reaction can be easily carried out by mixing a partial hydrolyzate of alkoxysilane represented by general formula (i) above with one or more metal alkoxides selected from the compounds represented by general formulas (iia) to (iic) to form a homogeneous coating solution, which is then hydrolyzed and dehydration-condensed. As a result of this homogeneous reaction, not only do hydrolyzates of alkoxysilane represented by general formula (i) bond together through a dehydration-condensation reaction, or hydrolyzates of metal alkoxides represented by general formulas (iia) to (iic) bond together through a dehydration-condensation reaction, but also, the hydrolyzate of alkoxysilane represented by general formula (i) and the hydrolyzate of one or more metal alkoxides selected from the compounds represented by general formulas (iia) to (iic) above undergo a dehydration-condensation reaction, whereby at least some of these components bond together to form bonds such as Si—O—Al bonds, Si—O—Ti bonds, and Si—O—Zr bonds, thereby easily forming the desired weather-resistant protective film.

[0084] In the optical element according to the present invention, it is preferable that the alkoxysilane represented by the general formula (i) (or a partial hydrolyzate thereof) and one or more metal alkoxides selected from the general formulae (iia) to (iic) are stirred for a predetermined period of time in the presence of a catalyst and an appropriate solvent to form a mixed liquid (coating liquid).

[0085] In the optical element according to the present invention, the catalyst may be one or more acids selected from hydrochloric acid, nitric acid, acetic acid, etc., or one or more bases selected from ammonia, sodium hydroxide, etc., in order to promote the sol-gel reaction (hydrolysis reaction, polycondensation reaction).

[0086] In the optical element according to the present invention, the solvent is not particularly limited as long as it can ultimately form a homogeneous coating solution, and examples of the solvent include one or more selected from alcohols such as methanol, ethanol, n-propanol, iso-propanol, and n-butanol, and alkoxy alcohols such as 2-methoxyethanol and 2-ethoxyethanol.

[0087] In the optical element according to the present invention, when the alkoxysilane represented by the general formula (i) (or a partial hydrolyzate thereof) is mixed with one or more metal alkoxides selected from the general formulae (iia) to (iic), a solvent or a stabilizer for the metal alkoxide can be used. Examples of the stabilizer include one or more selected from β-diketones such as acetylacetone and ethyl acetoacetate, alkanolamines such as monoethanolamine, diethanolamine and triethanolamine, and glycols such as ethylene glycol, propylene glycol and diethylene glycol.

[0088] In the optical element according to the present invention, the alkoxysilane represented by the general formula (i) (or a partial hydrolyzate thereof) and one or more metal alkoxides selected from the general formulae (iia) to (iic) are preferably mixed at a temperature of 0 to 200°C, more preferably at a temperature of 10 to 175°C, and even more preferably at a temperature of 15 to 150°C.

[0089] In the optical element of the present invention, the alkoxysilane (or partial hydrolyzate thereof) represented by the general formula (i) above and one or more metal alkoxides selected from the general formulae (iia) to (iic) above are preferably stirred and mixed for 1 minute to 24 hours to form a mixed liquid, more preferably stirred and mixed for 1 minute to 12 hours to form a mixed liquid, and even more preferably stirred and mixed for 1 minute to 6 minutes to form a mixed liquid.

[0090] The alkoxysilane represented by the general formula (i) (or a partial hydrolyzate thereof) and one or more metal alkoxides selected from the general formulae (iia) to (iic) are usually subjected to a hydrolysis and dehydration condensation reaction in the coexistence of the catalyst and solvent used at the time of mixing.

[0091] In the above hydrolysis and dehydration condensation reaction, it is preferable to use a mixed liquid containing the catalyst and solvent used when mixing the alkoxysilane represented by general formula (i) (or a partial hydrolyzate thereof) with one or more metal alkoxides selected from the general formulae (iia) to (iic) as a coating liquid (weather-resistant protective film-forming liquid).

[0092] That is, it is preferable that a desired amount of a coating liquid (weather-resistant protective film-forming liquid) made from the above-mentioned mixed liquid is applied to at least one main surface of a glass substrate made of phosphate-based glass or fluorophosphate-based glass, and then the resulting substrate is heated (baked) at a predetermined temperature for a certain period of time, whereby a metal element M (Si, Ti, Zr, Al, etc.) in the coating liquid (weather-resistant protective film-forming liquid) and a constituent element M' (a semimetallic or semiconductor element or metal element such as P, Si, Ge, As, Se, Sn, Sb, Te, Bi, etc.) in the glass substrate undergo a dehydration condensation reaction, a dealcoholization condensation reaction, or the like, to form a metalloxane bond M-O-M and / or a M-O-M' bond.

[0093] The method for applying the coating liquid is not particularly limited, and can be appropriately selected from spin coating (spin method), nozzle flow method, spray method, dipping method, roll method, brush coating, and the like.

[0094] The heating temperature when the desired amount of the coating liquid is applied to at least one main surface of the glass substrate and then heated is not particularly limited as long as it is equal to or higher than the temperature at which the solvent constituting the coating liquid volatilizes and equal to or lower than the glass transition point of the glass substrate, and is suitably, for example, 100 to 500° C. Furthermore, the heating time when the desired amount of the coating liquid is applied to at least one main surface of the glass substrate and then heated is preferably 1 minute to 24 hours, more preferably 3 minutes to 12 hours, and even more preferably 5 minutes to 6 hours.

[0095] After applying a desired amount of the coating liquid to at least one main surface of a glass substrate, the higher the heating temperature when heating, the easier it is to form a weather-resistant protective film with excellent weather resistance improving effects, but for example, heating at a temperature above the glass transition temperature of the glass substrate makes the glass more likely to soften. Furthermore, the longer the heating time during the hydrolysis and dehydration condensation reaction, the easier it is to form a weather-resistant protective film with excellent weather resistance improving effects, but if the heating time is too long, it becomes difficult to perform efficient heat treatment.

[0096] It is believed that the hydrolysis / dehydration condensation product obtained by the above reaction not only bonds the alkoxysilane represented by general formula (i) above and one or more metal alkoxides selected from general formulae (iia) to (iic) above to each other, but also forms a coating film in which they are firmly bonded to the glass substrate, and that such a coating film functions as a protective film (weather-resistant protective film) that can highly inhibit burning of the glass substrate even under high temperature and high humidity conditions.

[0097] The alkoxysilane (or its partial hydrolyzate) represented by the general formula (i) is used on a glass substrate made of phosphate glass or fluorophosphate glass, and the alkoxysilane is subjected to hydrolysis and dehydration condensation polymerization to form SiO ２ When a film is formed, SiO ２ Si-O-P bonds are formed between the film and the glass substrate. ２Although the film is inherently highly weather-resistant, the Si-O-P bond formed between the film and the glass substrate has poor water resistance and is easily hydrolyzed to Si-OH in the presence of water, thereby losing its bonding strength with the glass substrate. On the other hand, when a metal oxide film is formed on a glass substrate made of phosphate glass or fluorophosphate glass by hydrolysis and dehydration condensation polymerization of a metal alkoxide represented by any of the general formulas (iia) to (iic), a Ti-O-P bond, a Zr-O-P bond, or an Al-O-P bond is formed between the metal oxide film and the glass substrate. These bonds are highly water-resistant and resistant to hydrolysis, so that the bonding strength with the glass substrate can be easily maintained. For this reason, it is believed that a weather-resistant protective film with excellent weather resistance can be easily formed by combining an alkoxysilane represented by the general formula (i) (or a partial hydrolyzate thereof) with one or more metal alkoxides selected from the general formulas (iia) to (iic) and then subjecting the resulting mixture to hydrolysis and dehydration condensation.

[0098] The metal alkoxide to be combined with the alkoxysilane (or partial hydrolyzate thereof) represented by the general formula (i) above is preferably an alkoxyaluminum represented by the general formula (ii) above. The phosphorus atom (P) constituting phosphate glass or fluorophosphate glass has a structure bonded to three bridging oxygen atoms (-O-) and one non-bridging oxygen atom (=O) as shown below, and among these, the non-bridging oxygen atom (=O) does not form a glass mesh structure, loosening the glass structure, and is therefore considered to have low water resistance. On the other hand, in phosphate-based glass or fluorophosphate-based glass, Al has a tetracoordinated structure or a hexacoordinated structure, and among these, Al in the tetracoordinated structure acts to transform non-bridging oxygen (=O) of P into bridging oxygen (-O-), so that all oxygen atoms bonded to P become bridging oxygen (-O-), forming a dense glass mesh structure, and the glass structure is strengthened, which is thought to improve water resistance in particular.

[0099] In the optical element according to the present invention, the thickness of the weather-resistant protective film is preferably 1 nm to 5 μm, more preferably 10 nm to 2 μm, and even more preferably 20 nm to 1 μm. In this application, the thickness of the weather-resistant protective film refers to a value measured with a spectroscopic ellipsometer (M-20000V-Te manufactured by J.A. Woollam Co.) for thicknesses of 1 μm or less, and a value measured with a stylus-type ultra-precision roughness and film thickness measuring instrument (Dektak 6M manufactured by Veeco Co.) for thicknesses of more than 1 μm.

[0100] The optical element according to the present invention comprises a glass substrate made of phosphate glass or fluorophosphate glass, and a weather-resistant protective film having a single layer structure provided on at least one main surface of the glass substrate. That is, examples of the optical element according to the present invention include: (1) an optical element 1, as shown in Fig. 2(a), in which a weather-resistant protective film P is provided on one main surface of a glass substrate G made of phosphate glass or fluorophosphate glass; and (2) an optical element 1, as shown in Fig. 2(b), in which weather-resistant protective films P, P are provided on both main surfaces of a glass substrate G made of phosphate glass or fluorophosphate glass.

[0101] Furthermore, an example of the optical element according to the present invention is one in which a resin film or an anti-reflection film is further provided on the weather-resistant protective film.

[0102] Specifically, examples include: (3) an optical element 1 in which a weather-resistant protective film P is provided on one main surface of a glass substrate G made of phosphate-based glass or fluorophosphate-based glass, as exemplified in FIG. 3( a), and an anti-reflection film AR is further provided on the weather-resistant protective film P; and (4) an optical element 1 in which a weather-resistant protective film P is provided on one main surface of a glass substrate G made of phosphate-based glass or fluorophosphate-based glass, and a resin film R is further provided on the weather-resistant protective film P, as exemplified in FIG. 3( b).

[0103] Furthermore, examples of the optical element according to the present invention include an optical element in which a resin film and an anti-reflection film are further provided in this order on the weather-resistant protective film, or an optical element in which an anti-reflection film and a resin film are further provided in this order.

[0104] Specifically, examples include: (5) an optical element 1 in which a weather-resistant protective film P is provided on one main surface of a glass substrate G made of phosphate-based glass or fluorophosphate-based glass, and a resin film R and an anti-reflection film AR are further provided in this order on the weather-resistant protective film P, as exemplified in FIG. 3( c ); and (6) an optical element 1 in which a weather-resistant protective film P is provided on one main surface of a glass substrate G made of phosphate-based glass or fluorophosphate-based glass, and an anti-reflection film AR and a resin film R are further provided in this order on the weather-resistant protective film P, as exemplified in FIG. 3( d ).

[0105] In each optical element 1 shown in FIGS. 2 and 3, it is preferable that the upper main surface of the glass substrate P shown in each figure is the light incident surface when disposed, and the lower main surface of the glass substrate P is the light exit surface when disposed.

[0106] In the optical element 1 shown in Figures 3(a) to 3(d), the upper main surface of the glass substrate G (the main surface opposite to the side on which the weather-resistant protective film P is provided) may have: (7) no film formed thereon (as exemplified in Figures 3(a) to 3(d)), (8) a weather-resistant protective film P may be further provided thereon, (9) a resin film R or a weather-resistant protective film AR may be further provided thereon, with or without a weather-resistant protective film P interposed therebetween, (10) a resin film R and an anti-reflection film AR may be further provided thereon in this order, with or without a weather-resistant protective film P interposed therebetween, or (11) an anti-reflection film AR and a resin film R may be further provided thereon in this order, with or without a weather-resistant protective film P interposed therebetween.

[0107] In each of the above-mentioned aspects, examples of the resin film include an absorptive resin film that absorbs ultraviolet light or near-infrared light, a reflection-amplifying film, a protective film for preventing glass from burning, a strengthening film for improving the strength of glass, a water-repellent film, etc. Examples of the absorptive resin film that absorbs ultraviolet light or near-infrared light include one that contains a near-infrared absorbing dye and a transparent resin, and one in which the near-infrared absorbing dye is uniformly dissolved or dispersed in the transparent resin is preferred.

[0108] As the near-infrared absorbing dye constituting the absorbing resin film, conventionally known dyes can be used, and one or more selected from cyanine dyes, polymethine dyes, squarylium dyes, porphyrin dyes, metal dithiol complex dyes, phthalocyanine dyes, diimonium dyes, and inorganic oxide particles are preferred, and one or more selected from squarylium dyes, cyanine dyes, and phthalocyanine dyes are more preferred.

[0109] As the resin constituting the resin film, conventionally known transparent resins can be used, and examples thereof include one or more selected from acrylic resins, epoxy resins, ene-thiol resins, polycarbonate resins, polyether resins, polyarylate resins, polysulfone resins, polyethersulfone resins, polyparaphenylene resins, polyarylene ether phosphine oxide resins, polyimide resins, polyamideimide resins, polyolefin resins, cyclic olefin resins, and polyester resins.

[0110] From the viewpoints of transparency, solubility of the near-infrared absorbing dye in the transparent resin, and heat resistance, the transparent resin is preferably one having a high glass transition point (Tg), and specifically, one or more selected from polyester resin, polycarbonate resin, polyethersulfone resin, polyarylate resin, polyimide resin, and epoxy resin are preferred, and one or more selected from polyester resin and polyimide resin are more preferred. As the polyester resin, one or more selected from polyethylene terephthalate resin and polyethylene naphthalate resin are preferred.

[0111] In addition to the near-infrared absorbing dye and transparent resin, the resin film may further contain optional components such as a color correction dye, a leveling agent, an antistatic agent, a heat stabilizer, a light stabilizer, an antioxidant, a dispersant, a flame retardant, a lubricant, and a plasticizer, as long as the effects of the present invention are not impaired.

[0112] The resin film can be formed, for example, by dissolving or dispersing a pigment, a transparent resin, and further optional ingredients in a solvent to prepare a resin film-forming liquid, which is then applied, dried, and, if necessary, cured.

[0113] The resin film forming liquid may contain a known surfactant such as a cationic, anionic or nonionic surfactant.

[0114] The resin film-forming liquid can be applied by one or more coating methods selected from dip coating, cast coating, spray coating, spin coating, nozzle flow coating, roll coating, and the like.

[0115] The resin film can be formed by applying the resin film-forming liquid onto a substrate and then drying it.

[0116] In each of the above-described embodiments, the anti-reflection film is preferably MgF ２ A single layer film using a low refractive index material such as SiO ２ etc., and TiO as a high refractive index material. ２ Multilayer film using SiO ２ The porous film may be one or more selected from a porous film composed of fine particles and a binder.

[0117] The anti-reflection film can be formed by any method selected from gas phase methods such as vapor deposition, sputtering, and CVD, and liquid phase methods such as dip coating, cast coating, spray coating, spin coating, nozzle flow coating, and roll coating.

[0118] Examples of optical elements according to the present invention include optical filters such as infrared cut filters (IRCF), as well as lenses, prisms, diffraction gratings, substrates, and the like that constitute various optical devices.

[0119] According to the present invention, it is possible to provide an optical element that can exhibit excellent weather resistance despite having a glass substrate made of phosphate glass or fluorophosphate glass.

[0120] Next, an imaging device according to the present invention will be described. The imaging device according to the present invention is characterized by having an optical element according to the present invention as an optical filter, in addition to a solid-state imaging element and an imaging lens. Examples of the solid-state imaging element include image sensors such as a CCD (Charge-Coupled Device) sensor and a CMOS (Complementary Metal Oxide Semiconductor) sensor.

[0121] An example of the configuration of an imaging device according to the present invention is a camera module as illustrated in Fig. 1. Fig. 1(a) is a schematic explanatory diagram of a camera module for a compact digital camera mounted on a smartphone or the like. The camera module shown in Fig. 1(a) has one lens L (or lenses L1...Ln, where n is an integer greater than or equal to 1), an optical filter 1 made of the optical element according to the present invention, and an image sensor IC. Fig. 1(b) is a schematic explanatory diagram of a camera module for a digital single-lens reflex camera. The camera module shown in Fig. 1(b) has a lens L, an optical filter 1 made of the optical element according to the present invention, a cover glass CG, and an image sensor IC.

[0122] According to the present invention, it is possible to provide an imaging device having, as an optical filter, an optical element that can exhibit excellent weather resistance despite having a glass substrate made of phosphate glass or fluorophosphate glass.

[0123] The present invention will be further explained below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0124] (Example 1) 1. Preparation of Coating Solution (1) 4.2 g of 2.0 N (mol / L) HCl aqueous solution, 10.4 g of 2-propanol, and 17.8 g of 2-methoxyethanol were weighed and mixed in a sealed container. (2) Tetraethyl orthosilicate (Si(OC ２ H ５ ) ４ (3) 24.4 g of aluminum (III) tri-sec-butoxide (Al(OC ４ H ９ ) ３ ) was added, and the mixture was heated under reflux for 1.5 hours, after which heating was discontinued and the mixture was cooled to approximately room temperature. (4) A mixed solution of 21.1 g of 2.0 N HCl aqueous solution and 194.0 g of 2-methoxyethanol was added to the container with stirring, and the mixture was mixed for 10 minutes in a sealed container at room temperature to obtain a transparent, homogeneous coating liquid (coating liquid composition). The obtained coating liquid corresponds to a mixture of 42.9 mol % of tetraethyl orthosilicate and 57.1 mol % of aluminum (III) tri-sec-butoxide, where the total amount of tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide added is taken as 100 mol %. The solids concentration of the obtained coating liquid, i.e., the ratio of tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide to SiO in the coating liquid, was also calculated. ２ and Al ２ O ３ The total content of tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide in the coating solution was 5% by weight when converted into tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide.

[0125] 2. Formation of a coating film (1) The coating solution obtained in 1. was applied to one main surface of an absorbent glass substrate made of phosphate-based glass (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) at a concentration of 10 μL / cm using a spin coater. ２ The glass substrate on which the coating liquid was applied was then placed on a hot plate heated to 135°C, heated for 3 minutes, and then allowed to cool naturally. (2) Thereafter, the coating liquid was applied at a rate of 10 μL / cm onto the main surface opposite to the main surface on which the coating liquid was applied. ２The coating solution was applied by dropping the coating solution onto the glass substrate so that the coating solution was applied to the glass substrate. Next, the glass substrate coated with the coating solution was placed on a hot plate heated to 200°C and heated for 10 minutes. (3) Thereafter, the absorbent glass substrate, to which the coating solution had been applied and which had been heat-treated on both main surfaces, was heat-treated at 280°C for 10 minutes in a muffle furnace. The heat treatments (1) to (3) above caused dehydration condensation between hydroxyl groups on the glass substrate surface and hydroxyl groups of components constituting the coating solution, or between hydroxyl groups of components constituting the coating solution, thereby producing a glass substrate (optical filter 1) having a protective film of a single layer structure on each of both main surfaces. In the protective film, the proportion of Al atoms in the total number of Al atoms and Si atoms was 57.1 atomic %, and the proportion of Si atoms in the total number of Al atoms and Si atoms was 42.9 atomic %. In addition, in the protective film, the Al atoms and Si atoms were each replaced with Al atoms. ２ O ３ and SiO ２ When converted to Al ２ O ３ and SiO ２ Al in the total amount of ２ O ３ The proportion of Al is 40.0 mol%. ２ O ３ and SiO ２ SiO in the total amount ２ The proportion of is 60.0 mol%.

[0126] (Example 2) 1. Preparation of Coating Solution (1) 3.1 g of 0.5 N (mol / L) HCl aqueous solution, 10.4 g of 2-propanol, and 13.2 g of 2-methoxyethanol were weighed and mixed in a sealed container. (2) Tetraethyl orthosilicate (Si(OC ２ H ５ ) ４ (3) 36.0 g of titanium (IV) tetra-n-butoxide (Ti(OC ４ H ９ ) ４(4) A mixed solution of 30.1 g of 0.5 N aqueous HCl, 82.8 g of 2-propanol, and 104.8 g of 2-methoxyethanol was added to the container with stirring, and the mixture was mixed at room temperature in a sealed container for 30 minutes, yielding a transparent, homogeneous coating liquid (coating liquid composition). The resulting coating liquid corresponds to a mixture of 75.0 mol % of tetraethyl orthosilicate and 25.0 mol % of titanium(IV) tetra-n-butoxide, where the total amount of tetraethyl orthosilicate and titanium(IV) tetra-n-butoxide added is taken as 100 mol %. The solids concentration of the resulting coating liquid, i.e., the percentage of tetraethyl orthosilicate and titanium(IV) tetra-n-butoxide in the coating liquid that are each converted to SiO ２ and TiO ２ The total content of tetraethyl orthosilicate and titanium (IV) tetra-n-butoxide in the coating solution was 5% by weight when converted into the total amount of tetraethyl orthosilicate and titanium (IV) tetra-n-butoxide.

[0127] 2. Formation of Coating Film Using the obtained coating solution, a glass substrate (optical filter 2) having a protective film of a single layer structure on each of the two main surfaces of a glass substrate (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) made of phosphate glass was produced in the same manner as in Example 1. In the protective film, the ratio of Ti atoms to the total number of Ti atoms and Si atoms was 25.0 atomic %, and the ratio of Si atoms to the total number of Ti atoms and Si atoms was 75.0 atomic %. In the protective film, the Ti atoms and Si atoms were each replaced with TiO ２ and SiO ２ When converted to TiO ２ and SiO ２ TiO in the total amount ２ The ratio of TiO ２ and SiO ２ SiO in the total amount ２ The proportion of was 75.0 mol %.

[0128] (Example 3) 1. Preparation of Coating Solution (1) 4.8 g of a 1.0 N (mol / L) HCl aqueous solution and 20.2 g of 2-methoxyethanol were weighed and mixed in a sealed container. (2) Tetraethyl orthosilicate (Si(OC ２ H ５ ) ４ (3) 27.7 g of zirconium (IV) tetra-n-butoxide (Zr(OC ４ H ９ ) ４ 25.7 g of an 85% n-butanol solution of 22.6 g of 1.0 N HCl aqueous solution and 199.0 g of 2-methoxyethanol were added to the container with stirring, and the mixture was mixed at room temperature in a sealed container for 30 minutes, yielding a transparent, homogeneous coating liquid (coating liquid composition). The resulting coating liquid corresponds to a mixture of 70.0 mol % of tetraethyl orthosilicate and 30.0 mol % of zirconium(IV) tetra-n-butoxide, where the total amount of tetraethyl orthosilicate and zirconium(IV) tetra-n-butoxide added is taken as 100 mol %. The solids concentration of the resulting coating liquid, i.e., the ratio of tetraethyl orthosilicate and zirconium(IV) tetra-n-butoxide in the coating liquid to SiO , was also calculated. ２ and ZrO ２ The total content of tetraethyl orthosilicate and zirconium (IV) tetra-n-butoxide in the coating solution was 5% by weight when calculated as the total weight of the coating solution.

[0129] 2. Formation of Coating Film Using the obtained coating solution, a glass substrate (optical filter 3) having a protective film of a single layer structure on each of the two main surfaces of a glass substrate (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) made of phosphate glass was produced in the same manner as in Example 1. In the protective film, the ratio of Zr atoms to the total number of Zr atoms and Si atoms was 30.0 atomic %, and the ratio of Si atoms to the total number of Zr atoms and Si atoms was 70.0 atomic %. In the protective film, zirconium atoms and Si atoms were each replaced with ZrO ２ and SiO２ When converted to ZrO ２ and SiO ２ ZrO in the total amount of ２ The ratio of ZrO is 30.0 mol%. ２ and SiO ２ SiO in the total amount ２ The proportion of is 70.0 mol%.

[0130] (Example 4) 1. Preparation of coating solution In "1. Preparation of coating solution" (2) of Example 1, tetraethyl orthosilicate (Si(OC ２ H ５ ) ４ 36.0 g of tetraethyl orthosilicate (Si(OC ２ H ５ ) ４ ) 21.6 g and methyltriethoxysilane (CH ３ Si(OC ２ H ５ ) ３ A transparent, homogeneous coating liquid (coating liquid composition) was obtained in the same manner as in Example 1, except that 12.3 g of tetraethyl orthosilicate, methyltriethoxysilane, and titanium(IV) tetra-n-butoxide were used. The obtained coating liquid corresponds to a mixture of 75.0 mol % in total of tetraethyl orthosilicate and methyltriethoxysilane and 25.0 mol % of titanium(IV) tetra-n-butoxide, when the total amount of the added tetraethyl orthosilicate, methyltriethoxysilane, and titanium(IV) tetra-n-butoxide is taken as 100 mol %. The solids concentration of the obtained coating liquid, i.e., the ratio of tetraethyl orthosilicate and methyltriethoxysilane to SiO ２ Titanium (IV) tetra-n-butoxide is converted to TiO ２ The total content of tetraethyl orthosilicate, methyltriethoxysilane and titanium (IV) tetra-n-butoxide in the coating liquid was 5% by weight when converted into the total amount of tetraethyl orthosilicate, methyltriethoxysilane and titanium (IV) tetra-n-butoxide.

[0131] 2. Formation of Coating Film Using the obtained coating solution, a glass substrate (optical filter 4) having a protective film of a single layer structure on each of the two main surfaces of a glass substrate (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) made of phosphate glass was produced in the same manner as in Example 1. In the protective film, the proportion of Ti atoms in the total number of Ti atoms and Si atoms was 25.0 atomic %, and the proportion of Si atoms in the total number of Ti atoms and Si atoms was 75.0 atomic %. In the protective film, the Ti atoms and Si atoms were each replaced with TiO ２ and SiO ２ When converted to TiO ２ and SiO ２ TiO in the total amount ２ The ratio of TiO ２ and SiO ２ SiO in the total amount ２ The proportion of is 75.0 mol %.

[0132] (Example 5) 1. Preparation of coating solution In "1. Preparation of coating solution" (3) of Example 1, titanium (IV) tetra-n-butoxide (Ti(OC ４ H ９ ) ４ ) 19.6 g, instead of titanium (IV) tetra-n-butoxide (Ti(OC ４ H ９ ) ４ A transparent, homogeneous coating liquid (coating liquid composition) was obtained in the same manner as in Example 1, except that 14.0 g of the tetramer of titanium(IV) tetra-n-butoxide was used. The obtained coating liquid corresponds to a mixture of 75.0 mol % of tetraethyl orthosilicate and 25.0 mol % of the tetramer of titanium(IV) tetra-n-butoxide, where the total amount of tetraethyl orthosilicate and the tetramer of titanium(IV) tetra-n-butoxide added is taken as 100 mol %. The solids concentration of the obtained coating liquid, i.e., the ratio of the tetraethyl orthosilicate and the tetramer of titanium(IV) tetra-n-butoxide in the coating liquid to SiO ２ and TiO ２The total content of tetraethyl orthosilicate and the tetramer of titanium (IV) tetra-n-butoxide in the coating solution was 5% by weight when converted into tetraethyl orthosilicate.

[0133] 2. Formation of Coating Film Using the obtained coating solution, a glass substrate (optical filter 5) having a protective film of a single layer structure on each of the two main surfaces of a glass substrate (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) made of phosphate glass was produced in the same manner as in Example 1. In the protective film, the proportion of Ti atoms in the total number of Ti atoms and Si atoms was 25.0 atomic %, and the proportion of Si atoms in the total number of Ti atoms and Si atoms was 75.0 atomic %. In the protective film, the Ti atoms and Si atoms were each replaced with TiO ２ and SiO ２ When converted to TiO ２ and SiO ２ TiO in the total amount ２ The ratio of TiO ２ and SiO ２ SiO in the total amount ２ The proportion of is 75.0 mol %.

[0134] (Example 6) 1. Preparation of Coating Solution In "1. Preparation of Coating Solution" (2) of Example 1, 30.2 g of tetraethyl orthosilicate was used instead of 36.0 g of tetraethyl orthosilicate, and in "1. Preparation of Coating Solution" (3) of Example 1, titanium (IV) tetra-n-butoxide (Ti(OC ４ H ９ ) ４ ) 19.6 g, instead of titanium (IV) tetra-n-butoxide (Ti(OC ４ H ９ ) ４A transparent, homogeneous coating liquid (coating liquid composition) was obtained in the same manner as in Example 1, except that 10.6 g of tetraethyl orthosilicate and 14.0 g of an 85% n-butanol solution of zirconium(IV) tetra-n-butoxide were used. The obtained coating liquid corresponds to a mixture of 70.0 mol % of tetraethyl orthosilicate, 15.0 mol % of titanium(IV) tetra-n-butoxide, and 15.0 mol % of zirconium(IV) tetra-n-butoxide, where the total amount of tetraethyl orthosilicate, titanium(IV) tetra-n-butoxide, and zirconium(IV) tetra-n-butoxide added is taken as 100 mol %. The solids concentration of the obtained coating liquid, i.e., the ratio of tetraethyl orthosilicate to SiO ２ Titanium (IV) tetra-n-butoxide is converted to TiO ２ and converting zirconium (IV) tetra-n-butoxide to ZrO ２ The total content of tetraethyl orthosilicate, titanium (IV) tetra-n-butoxide and zirconium (IV) tetra-n-butoxide in the coating liquid was 5% by weight when converted into the total amount of tetraethyl orthosilicate, titanium (IV) tetra-n-butoxide and zirconium (IV) tetra-n-butoxide.

[0135] 2. Formation of Coating Film Using the obtained coating solution, a glass substrate (optical filter 6) having a single-layer protective film on each of the main surfaces of a glass substrate (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) made of phosphate glass was prepared in the same manner as in Example 1. In the protective film, the proportion of Ti atoms in the total number of Ti atoms, Zr atoms, and Si atoms was 15.0 atomic %, the proportion of Zr atoms in the total number of Ti atoms, Zr atoms, and Si atoms was 15.0 atomic %, and the proportion of Si atoms in the total number of Ti atoms, Zr atoms, and Si atoms was 70.0 atomic %. In addition, in the protective film, the Ti atoms, Zr atoms, and Si atoms were each replaced with TiO ２ , ZrO ２ and SiO ２ When converted to TiO ２ , ZrO ２ and SiO ２ TiO in the total amount ２ The ratio of TiO２ , ZrO ２ and SiO ２ ZrO in the total amount of ２ The ratio of TiO ２ , ZrO ２ and SiO ２ SiO in the total amount ２ The proportion of is 70.0 mol%.

[0136] (Example 7) 1. Preparation of Coating Solution In "1. Preparation of Coating Solution" (2) of Example 1, 27.6 g of tetraethyl orthosilicate was used instead of 36.0 g of tetraethyl orthosilicate, and in "1. Preparation of Coating Solution" (3) of Example 1, titanium (IV) tetra-n-butoxide (Ti(OC ４ H ９ ) ４ ) 19.6 g, instead of titanium (IV) tetra-n-butoxide (Ti(OC ４ H ９ ) ４ A transparent, homogeneous coating liquid (coating liquid composition) was obtained in the same manner as in Example 1, except that 30.0 g of tetraethyl orthosilicate and titanium(IV) tetra-n-butoxide were used. The obtained coating liquid corresponds to a mixture of 60.0 mol % of tetraethyl orthosilicate and 40.0 mol % of titanium(IV) tetra-n-butoxide, where the total amount of tetraethyl orthosilicate and titanium(IV) tetra-n-butoxide added is taken as 100 mol %. The solids concentration of the obtained coating liquid, i.e., the ratio of tetraethyl orthosilicate and titanium(IV) tetra-n-butoxide in the coating liquid to SiO ２ and TiO ２ The total content of tetraethyl orthosilicate and titanium (IV) tetra-n-butoxide in the coating solution was 5% by weight when converted into the total amount of tetraethyl orthosilicate and titanium (IV) tetra-n-butoxide.

[0137] 2. Formation of Coating Film Using the obtained coating solution, a glass substrate (optical filter 7) having a protective film of a single layer structure on each of the two main surfaces of a glass substrate (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) made of phosphate glass was produced in the same manner as in Example 1. In the protective film, the proportion of Ti atoms in the total number of Ti atoms and Si atoms was 40.0 atomic %, and the proportion of Si atoms in the total number of Ti atoms and Si atoms was 60.0 atomic %. In the protective film, the Ti atoms and Si atoms were each replaced with TiO ２ and SiO ２ When converted to TiO ２ and SiO ２ TiO in the total amount ２ The ratio of TiO ２ and SiO ２ SiO in the total amount ２ The proportion of is 60.0 mol%.

[0138] (Example 8) 1. Preparation of Coating Solution In "1. Preparation of Coating Solution" (2) of Example 1, 22.3 g of tetraethyl orthosilicate was used instead of 36.0 g of tetraethyl orthosilicate, and in "1. Preparation of Coating Solution" (3) of Example 1, titanium (IV) tetra-n-butoxide (Ti(OC ４ H ９ ) ４ ) 19.6 g, instead of titanium (IV) tetra-n-butoxide (Ti(OC ４ H ９ ) ４ A transparent, homogeneous coating liquid (coating liquid composition) was obtained in the same manner as in Example 1, except that 36.5 g of tetraethyl orthosilicate and titanium(IV) tetra-n-butoxide were used. The obtained coating liquid corresponds to a mixture of 50.0 mol % of tetraethyl orthosilicate and 50.0 mol % of titanium(IV) tetra-n-butoxide, where the total amount of tetraethyl orthosilicate and titanium(IV) tetra-n-butoxide added is taken as 100 mol %. The solids concentration of the obtained coating liquid, i.e., the ratio of tetraethyl orthosilicate and titanium(IV) tetra-n-butoxide in the coating liquid to SiO ２ and TiO ２The total content of tetraethyl orthosilicate and titanium (IV) tetra-n-butoxide in the coating solution was 5% by weight when converted into the total amount of tetraethyl orthosilicate and titanium (IV) tetra-n-butoxide.

[0139] 2. Formation of Coating Film Using the obtained coating solution, a glass substrate (optical filter 8) having a protective film of a single layer structure on each of the two main surfaces of a glass substrate (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) made of phosphate glass was produced in the same manner as in Example 1. In the protective film, the proportion of Ti atoms in the total number of Ti atoms and Si atoms was 50.0 atomic %, and the proportion of Si atoms in the total number of Ti atoms and Si atoms was 50.0 atomic %. In the protective film, the Ti atoms and Si atoms were each replaced with TiO ２ and SiO ２ When converted to TiO ２ and SiO ２ TiO in the total amount ２ The ratio of TiO ２ and SiO ２ SiO in the total amount ２ The proportion of is 50.0 mol%.

[0140] Example 9 1. Preparation of Coating Liquid A transparent, homogeneous coating liquid (coating liquid composition) was obtained in the same manner as in Example 2, except that 17.0 g of tetraethyl orthosilicate was used instead of 27.7 g of tetraethyl orthosilicate in "1. Preparation of Coating Liquid" (2) of Example 2, and 36.9 g of an 85% butanol solution of zirconium(IV) tetra-n-butoxide was used instead of 25.7 g of an 85% butanol solution of zirconium(IV) tetra-n-butoxide in "1. Preparation of Coating Liquid" (3) of Example 2. The obtained coating liquid corresponds to a mixture of 50.0 mol % of tetraethyl orthosilicate and 50.0 mol % of zirconium(IV) tetra-n-butoxide, where the total amount of tetraethyl orthosilicate and zirconium(IV) tetra-n-butoxide added is taken as 100 mol %. The solids concentration of the obtained coating solution, that is, the concentration of tetraethyl orthosilicate and zirconium (IV) tetra-n-butoxide in the coating solution was determined by the following formula:２ and ZrO ２ The total content of tetraethyl orthosilicate and zirconium (IV) tetra-n-butoxide in the coating solution was 5% by weight when calculated as the total weight of the coating solution.

[0141] 2. Formation of Coating Film Using the obtained coating solution, a glass substrate (optical filter 9) having a protective film of a single layer structure on each of the two main surfaces of a glass substrate (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) made of phosphate glass was produced in the same manner as in Example 1. In the protective film, the ratio of Zr atoms to the total number of Zr atoms and Si atoms was 50.0 atomic %, and the ratio of Si atoms to the total number of Zr atoms and Si atoms was 50.0 atomic %. In the protective film, the Zr atoms and Si atoms were each replaced with ZrO ２ and SiO ２ When converted to ZrO ２ and SiO ２ ZrO in the total amount of ２ The ratio of ZrO is 50.0 mol%. ２ and SiO ２ SiO in the total amount ２ The proportion of is 50.0 mol%.

[0142] Example 10 1. Preparation of Coating Liquid A transparent, homogeneous coating liquid (coating liquid composition) was obtained in the same manner as in Example 3, except that 36.5 g of tetraethyl orthosilicate was used instead of 36.0 g of tetraethyl orthosilicate in "1. Preparation of Coating Liquid" (2) of Example 3, and 21.6 g of aluminum (III) tri-sec-butoxide was used instead of 38.5 g of aluminum (III) tri-sec-butoxide in "1. Preparation of Coating Liquid" (3) of Example 3. The obtained coating liquid corresponds to a mixture of 66.7 mol % of tetraethyl orthosilicate and 33.3 mol % of aluminum (III) tri-sec-butoxide, where the total amount of tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide added is taken as 100 mol %. The solid content of the resulting coating solution, that is, the concentration of tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide in the coating solution was determined by the following formula: ２ and Al ２ O ３ The total content of tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide in the coating solution was 5% by weight when converted into tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide.

[0143] 2. Formation of Coating Film Using the obtained coating liquid, a glass substrate (optical filter 10) having a protective film of a single layer structure on each of the two main surfaces of a glass substrate (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) made of phosphate glass was produced in the same manner as in Example 1. In the protective film, the ratio of Al atoms to the total number of Al atoms and Si atoms was 33.3 atomic %, and the ratio of Si atoms to the total number of Al atoms and Si atoms was 66.7 atomic %. In addition, in the protective film, the Al atoms and Si atoms were each replaced with Al atoms. ２ O ３ and SiO ２ When converted to Al ２ O ３ and SiO ２ Al in the total amount of ２ O ３ The proportion of Al is 20.0 mol%. ２ O ３and SiO ２ SiO in the total amount ２ The proportion of is 80.0 mol %.

[0144] Comparative Example 1 In this example, a comparative optical filter 1 was prepared without forming a coating film on the glass substrate made of phosphate glass (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) used in Example 1.

[0145] (Comparative Example 2) 1. Preparation of Coating Solution In "1. Preparation of Coating Solution" (2) of Example 1, 45.3 g of tetraethyl orthosilicate was used instead of 36.0 g of tetraethyl orthosilicate, and in "1. Preparation of Coating Solution" (3) of Example 1, titanium (IV) tetra-n-butoxide (Ti(OC ４ H ９ ) ４ ) 19.6 g, instead of titanium (IV) tetra-n-butoxide (Ti(OC ４ H ９ ) ４ A transparent, homogeneous coating liquid (coating liquid composition) was obtained in the same manner as in Example 1, except that 8.2 g of tetraethyl orthosilicate and titanium(IV) tetra-n-butoxide were used. The obtained coating liquid corresponds to a mixture of 90.0 mol % of tetraethyl orthosilicate and 10.0 mol % of titanium(IV) tetra-n-butoxide, where the total amount of tetraethyl orthosilicate and titanium(IV) tetra-n-butoxide added is taken as 100 mol %. The solids concentration of the obtained coating liquid, i.e., the ratio of tetraethyl orthosilicate and titanium(IV) tetra-n-butoxide in the coating liquid to SiO ２ and TiO ２ The total content of tetraethyl orthosilicate and titanium (IV) tetra-n-butoxide in the coating solution was 5% by weight when converted into the total amount of tetraethyl orthosilicate and titanium (IV) tetra-n-butoxide.

[0146] 2. Formation of Coating Film Using the obtained coating solution, a glass substrate (comparative optical filter 2) having a protective film of a single layer structure on each of the two main surfaces of a glass substrate (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) made of phosphate glass was produced in the same manner as in Example 1. In the protective film, the proportion of Ti atoms in the total number of Ti atoms and Si atoms was 10.0 atomic %, and the proportion of Si atoms in the total number of Ti atoms and Si atoms was 90.0 atomic %. In the protective film, the Ti atoms and Si atoms were each replaced with TiO ２ and TiO when converted to SiO ２ and SiO ２ TiO in the total amount ２ The ratio of TiO ２ and SiO ２ SiO in the total amount ２ The proportion of is 90.0 mol %.

[0147] Comparative Example 3 1. Preparation of Coating Solution In "1. Preparation of Coating Solution" (2) of Example 1, 40.2 g of tetraethyl orthosilicate was used instead of 36.0 g of tetraethyl orthosilicate, and in "1. Preparation of Coating Solution" (3) of Example 1, titanium (IV) tetra-n-butoxide (Ti(OC ４ H ９ ) ４ ) 19.6 g, instead of titanium (IV) tetra-n-butoxide (Ti(OC ４ H ９ ) ４ A transparent, homogeneous coating liquid (coating liquid composition) was obtained in the same manner as in Example 1, except that 14.5 g of tetraethyl orthosilicate and titanium(IV) tetra-n-butoxide were used. The obtained coating liquid corresponds to a mixture of 82.0 mol % of tetraethyl orthosilicate and 18.0 mol % of titanium(IV) tetra-n-butoxide, where the total amount of tetraethyl orthosilicate and titanium(IV) tetra-n-butoxide added is taken as 100 mol %. The solids concentration of the obtained coating liquid, i.e., the ratio of tetraethyl orthosilicate and titanium(IV) tetra-n-butoxide in the coating liquid to SiO ２ and TiO ２The total content of tetraethyl orthosilicate and titanium (IV) tetra-n-butoxide in the coating solution was 5% by weight when converted into the total amount of tetraethyl orthosilicate and titanium (IV) tetra-n-butoxide.

[0148] 2. Formation of Coating Film Using the obtained coating solution, a glass substrate (comparative optical filter 3) having a protective film of a single layer structure on each of the two main surfaces of a glass substrate (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) made of phosphate glass was produced in the same manner as in Example 1. In the protective film, the proportion of Ti atoms in the total number of Ti atoms and Si atoms was 18.0 atomic %, and the proportion of Si atoms in the total number of Ti atoms and Si atoms was 82.0 atomic %. In the protective film, the Ti atoms and Si atoms were each replaced with TiO ２ and SiO ２ When converted to TiO ２ and SiO ２ TiO in the total amount ２ The proportion of TiO ２ and SiO ２ SiO in the total amount ２ The proportion of is 82.0 mol%.

[0149] <Weather Resistance Evaluation> The weather resistance of the optical filters obtained in the above Examples and Comparative Examples was evaluated based on the degree of cloudiness indicated by the haze value shown below. (Evaluation Method) (1) Weather Resistance Life 1 A test piece cut out from each optical filter was exposed to an environment at a temperature of 65°C and a relative humidity of 90% in a thermo-humidistat chamber, and the appearance of the surface on which the weather-resistant protective film was provided was visually observed and the cloudiness (haze value) was measured using a haze meter 10 hours, 20 hours, 30 hours, 40 hours, 50 hours, 75 hours, 100 hours, 150 hours, 200 hours, 250 hours, 300 hours, 350 hours, 400 hours, 500 hours, 750 hours, and 1000 hours after the start of exposure. Based on the definition that the haze value at which an optical filter becomes cloudy and begins to interfere with use is a haze value of 0.2, the exposure time measured immediately before the exposure time at which the haze value first reached 0.2 or greater was defined as the limit time at which the haze value reached 0.2 or less. This limit time was defined as the weather resistance life (limit time at which weather resistance is demonstrated). The exposure time associated with this weather resistance life was calculated. (For example, if the haze value first exceeded 0.2 500 hours after the start of exposure, the weather resistance life of the optical filter was 400 hours.) If the haze value was less than 0.2 1000 hours after the start of exposure, the exposure time associated with the weather resistance life was calculated as 1000 hours. (2) Weather Resistance Life 2: The weather resistance life was determined by evaluating test pieces cut from each optical filter in the same manner as in (1) Weather Resistance Life 1, except that they were exposed to a temperature of 85°C and a relative humidity of 85% in a thermo-hygrostat. The results for each example and comparative example are shown in Table 1.

[0150]

[0151] Example 11 1. Preparation of Coating Liquid A transparent, homogeneous coating liquid (coating liquid composition) was obtained in the same manner as in Example 1, except that 30.1 g of tetraethyl orthosilicate was used instead of 24.4 g of tetraethyl orthosilicate in "1. Preparation of Coating Liquid" (2) of Example 1, and 30.5 g of aluminum (III) tri-sec-butoxide was used instead of 38.5 g of aluminum (III) tri-sec-butoxide in "1. Preparation of Coating Liquid" (3) of Example 1. The obtained coating liquid corresponds to a mixture of 53.8 mol % of tetraethyl orthosilicate and 46.2 mol % of aluminum (III) tri-sec-butoxide, where the total amount of tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide added is taken as 100 mol %. The solid content of the resulting coating solution, that is, the concentration of tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide in the coating solution was determined by the following formula: ２ and Al ２ O ３ The total content of tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide in the coating solution was 5% by weight when converted into tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide.

[0152] 2. Formation of Coating Film Using the obtained coating liquid, a glass substrate (optical filter 11) having a protective film of a single layer structure on each of the two main surfaces of a glass substrate (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) made of phosphate glass was produced in the same manner as in Example 1. In the protective film, the ratio of Al atoms to the total number of Al atoms and Si atoms was 46.2 atomic %, and the ratio of Si atoms to the total number of Al atoms and Si atoms was 53.8 atomic %. In addition, in the protective film, the Al atoms and Si atoms were each replaced with Al atoms. ２ O ３ and SiO ２ When converted to Al ２ O ３ and SiO ２ Al in the total amount of ２ O ３ The proportion of Al is 30.0 mol%. ２ O ３and SiO ２ SiO in the total amount ２ The proportion of is 70.0 mol%.

[0153] <Confirmation of Chemical Bonds (Al—O—Si Bonds)> (1) 13.5 g of the coating liquid prepared in 1 above was poured into a polymethylpentene Petri dish with an inner diameter of 85 mm and a depth of 15 mm, and the dish was then covered and left in a thermostatic bath at an internal temperature of 60°C to gel and dry to obtain a plate-shaped sample with a thickness of 0.5 mm. (2) The plate-shaped sample obtained in (1) was heat-treated in a muffle furnace at 280°C for 10 minutes to obtain a measurement sample. (3) Using a micro FT-IR (Digital Lab Excalibur+UMA600), FT-IR measurement of the measurement sample obtained in (2) was performed under the following measurement conditions. (Measurement Conditions) Measurement mode: Transmission mode Measurement area: 500 to 1000 cm －１ Number of integration: 128 times Resolution: 4cm －１ Scan speed: 5 kHz (4) As a result of the FT-IR measurement according to (3) above, 555 cm －１ , 852 cm －１ , 911 cm －１ An absorption peak was observed. J Sol-Gel Sci Technol (2010) 56:47-52, NP Damayanti, "Preparation of Superhydrophobic PET fabric from Al2O3-SiO 2 According to "High Contact Angle Surface from Low Contact Angle Material: A Geometrical Approach to Create a High Contact Angle Surface from a Low Contact Angle Material," when FT-IR was measured, an absorption peak due to Si-O-Al bonds was observed at 557 cm －１ 、 850 cm －１ and 902 cm －１(See Fig. 4 and the right column on page 51 of the above document.) In the measurement sample used in this measurement, all of the absorption peaks corresponding to the above absorption peaks were detected by the above FT-IR measurement, and it was therefore confirmed that the Si atoms and Al atoms constituting the coating film constituting the optical filter 11 obtained in this example form chemical bonds (Si-O-Al bonds) between the Si atoms and Al atoms via oxygen bonds.

[0154] Example 12 1. Preparation of Coating Liquid A transparent, homogeneous coating liquid (coating liquid composition) was obtained in the same manner as in Example 1, except that 33.2 g of tetraethyl orthosilicate was used instead of 24.4 g of tetraethyl orthosilicate in "1. Preparation of Coating Liquid" (2) of Example 1, and 26.2 g of aluminum(III) tri-sec-butoxide was used instead of 38.5 g of aluminum(III) tri-sec-butoxide in "1. Preparation of Coating Liquid" (3) of Example 1. The obtained coating liquid corresponds to a mixture of 60.0 mol % of tetraethyl orthosilicate and 40.0 mol % of aluminum(III) tri-sec-butoxide, where the total amount of tetraethyl orthosilicate and aluminum(III) tri-sec-butoxide added is taken as 100 mol %. The solid content of the resulting coating solution, that is, the concentration of tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide in the coating solution was determined by the following formula: ２ and Al ２ O ３The total content of tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide in the coating solution was 5% by weight when converted to tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide. 2. Formation of Coating Film Using the obtained coating solution, a glass substrate (optical filter 12) was produced in the same manner as in Example 1, having a protective film of a single layer structure on each of the two main surfaces of a glass substrate (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) made of phosphate-based glass. In the protective film, the ratio of Al atoms to the total number of Al atoms and Si atoms was 40.0 atomic %, and the ratio of Si atoms to the total number of Al atoms and Si atoms was 60.0 atomic %. In addition, in the protective film, the Al atoms and Si atoms were each replaced with Al atoms. ２ O ３ and SiO ２ When converted to Al ２ O ３ and SiO ２ Al in the total amount of ２ O ３ The proportion of Al is 25.0 mol%. ２ O ３ and SiO ２ SiO in the total amount ２ The proportion of is 75.0 mol %.

[0155] Example 13 1. Preparation of Coating Liquid A transparent, homogeneous coating liquid (coating liquid composition) was obtained in the same manner as in Example 1, except that 19.3 g of tetraethyl orthosilicate was used instead of 24.4 g of tetraethyl orthosilicate in "1. Preparation of Coating Liquid" (2) of Example 1, and 45.6 g of aluminum (III) tri-sec-butoxide was used instead of 38.5 g of aluminum (III) tri-sec-butoxide in "1. Preparation of Coating Liquid" (3) of Example 1. The obtained coating liquid corresponds to a mixture of 33.3 mol % of tetraethyl orthosilicate and 66.7 mol % of aluminum (III) tri-sec-butoxide, where the total amount of tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide added is taken as 100 mol %. The solid content of the resulting coating solution, that is, the concentration of tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide in the coating solution was determined by the following formula: ２ and Al ２ O ３ The total content of tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide in the coating solution was 5% by weight, calculated as a percentage of the total content of tetraethyl orthosilicate and aluminum (III) tri-sec-butoxide. 2. Formation of Coating Film Using the obtained coating solution, a glass substrate (optical filter 13) was produced in the same manner as in Example 1, having a protective film of a single layer structure on each of the two main surfaces of a glass substrate (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) made of phosphate-based glass. In the protective film, the proportion of Al atoms in the total number of Al atoms and Si atoms was 66.7 atomic %, and the proportion of Si atoms in the total number of Al atoms and Si atoms was 33.3 atomic %. In addition, in the protective film, the Al atoms and Si atoms were each replaced with Al atoms. ２ O ３ and SiO ２ When converted to Al ２ O ３ and SiO ２ Al in the total amount of ２ O ３ The proportion of Al is 50.0 mol%. ２ O ３ and SiO ２SiO in the total amount ２ The proportion of is 50.0 mol%.

[0156] (Comparative Example 4) 1. Preparation of Coating Liquid A transparent, homogeneous coating liquid (coating liquid composition) was obtained in the same manner as in Example 1, except that 52.0 g of tetraethyl orthosilicate was used instead of 24.4 g of tetraethyl orthosilicate in "1. Preparation of Coating Liquid" (2) of Example 1, and aluminum (III) tri-sec-butoxide was not used in "1. Preparation of Coating Liquid" (3) of Example 1. The obtained coating liquid corresponds to 100.0 mol % tetraethyl orthosilicate. In addition, the solids concentration of the obtained coating liquid, that is, the ratio of tetraethyl orthosilicate to SiO ２ The content of tetraethyl orthosilicate in the coating solution was 5% by weight when converted to tetraethyl orthosilicate. 2. Formation of Coating Film Using the obtained coating solution, a glass substrate (comparative optical filter 4) was prepared in the same manner as in Example 1, having a protective film of a single layer structure on each of the two main surfaces of a glass substrate (CM500 manufactured by HOYA Corporation, thickness 0.59 mm) made of phosphate glass. In the protective film, the proportion of Si atoms in the total number of Si atoms was 100.0 atomic %. In addition, in the protective film, Si atoms were replaced with SiO ２ When converted to SiO ２ The proportion of is 100.0 mol%.

[0157] <Confirmation of Chemical Bonds (Al—O—Si Bonds)> In the same manner as in Example 10, a measurement sample was prepared using the coating liquid prepared in 1 above, and the obtained measurement sample was subjected to FT-IR measurement. As described above, when the FT-IR measurement was performed, an absorption peak due to the Si—O—Al bond was observed at 557 cm －１ , 850 cm －１ and 902 cm －１ However, no absorption peak was detected in the above wavelength range in the measurement sample used in this measurement. Therefore, it was confirmed that in the coating film constituting the comparative optical filter 4 obtained in this comparative example, no chemical bond (Si-O-Al bond) was formed between Si atoms and Al atoms via an oxygen bond.

[0158] <Weather Resistance Evaluation> The optical filters obtained in the above Examples and Comparative Examples were evaluated for weather resistance using the haze value (cloudiness) according to the above-mentioned "Weather Resistance Life 1" and "Weather Resistance Life 2." The results for each Example and Comparative Example are shown in Table 2.

[0159]

[0160] Tables 1 and 2 show that the optical filters obtained in Examples 1 to 13 were each provided with a weather-resistant protective film having a single-layer structure on the surface of an absorbing glass substrate made of phosphate glass, the weather-resistant protective film containing Si atoms and one or more atoms selected from Ti, Zr, and Al, and in which the proportion of the total number of Ti, Zr, and Al atoms to the total number of Si, Ti, Zr, and Al atoms was greater than 20.0 atomic % and not greater than 75.0 atomic %. As a result, the weather-resistant lifetimes (weather-resistant lifetime 1 and weather-resistant lifetime 2), defined by the limit time at which the haze value reached 0.2 or less, were sufficiently long, ranging from 200 hours (200 hours) to 1,000 hours (1,000 hours), and visual observation showed that the surface maintained a homogeneous and transparent state throughout the weather-resistant lifetime, demonstrating excellent weather resistance. Furthermore, from the results of Example 11 and the like, it was considered that the optical filters obtained in the above Examples have a specific structure in which Si atoms and one or more atoms selected from Ti atoms, Zr atoms, and Al atoms that constitute the weather-resistant protective film are bonded in a three-dimensional network pattern by chemical bonds between atoms of the same kind or between atoms of different kinds via oxygen atoms, and therefore can exhibit excellent weather resistance.

[0161] On the other hand, Table 1 shows that the optical filter obtained in Comparative Example 1, which did not have a protective film on the surface of the absorbing glass substrate made of phosphate-based glass, had a haze value exceeding 0.2 after 10 hours or 5 hours of exposure in a thermo-humidistat chamber, and visual observation revealed that the surface had deliquesced, become sticky, and deteriorated, indicating that the filter had poor weather resistance. Table 1 also shows that the optical filter obtained in Comparative Example 2, which had a weather-resistant protective film on the surface of the absorbing glass substrate made of phosphate-based glass, had a ratio of Ti atoms to the total number of Si atoms and Ti atoms outside the specified range, indicating that the weather resistance life, defined as the limit time for maintaining a haze value of 0.2 or less, was short at 50 hours (50 hours) or 10 hours (10 hours), indicating that the filter had poor weather resistance. In addition, Table 1 shows that the optical filter obtained in Comparative Example 3 has a weather-resistant protective film formed on the surface of an absorbing glass substrate made of phosphate glass, and the ratio of the number of Ti atoms to the total number of Si and Ti atoms is outside the specified range, so the weather-resistant life, defined as the limit time for maintaining a haze value of 0.2 or less, is short at 150 hours (150 hours) or 40 hours (40 hours), and is therefore poor in weather resistance.From the results of Comparative Example 4, it can be seen that the optical filters obtained in each of the above Comparative Examples do not use a weather-resistant protective film having a specific structure in which Si atoms and one or more atoms selected from Ti atoms, Zr atoms, and Al atoms are bonded in a three-dimensional network shape by chemical bonds via oxygen atoms between atoms of the same type or between atoms of different types.

[0162] 1 Optical element, optical filter or infrared cut filter (IRCF) L Lens CG Cover glass IC Image sensor G Glass substrate P Weather-resistant protective film AR Anti-reflection film R Resin film

Claims

1. On at least one main surface of a glass substrate made of phosphate glass or fluorophosphate glass, Contains at least one selected from Ti atoms, Zr atoms and Al atoms together with Si atoms, a ratio of the total number of Ti atoms, Zr atoms and Al atoms to the total number of Si atoms, Ti atoms, Zr atoms and Al atoms is 25.0 atomic % or more and 75.0 atomic % or less. A weather-resistant protective film having a single layer structure is provided. An optical element characterized by:

2. 2. The optical element according to claim 1, wherein the weather-resistant protective film is made up of Si atoms and one or more atoms selected from Ti atoms, Zr atoms, and Al atoms, which are bonded in a three-dimensional network pattern by chemical bonds between the same atoms or between different atoms via oxygen atoms.

3. 2. The optical element according to claim 1, wherein the weather-resistant protective film contains 8.3 to 27.5 atomic % of Si atoms, 6.6 to 28.5 atomic % of one or more atoms selected from Ti atoms, Zr atoms and Al atoms, and 61.9 to 66.6 atomic % of oxygen atoms.

4. The weather-resistant protective film is (I) one or more silicon compounds selected from alkoxysilanes, alkoxysilane derivatives, and oligomers of one or more of these polymers; (IIa) an alkoxytitanium, an alkoxytitanium derivative, or an oligomer comprising one or more of these polymers; (IIb) an oligomer consisting of an alkoxyzirconium, an alkoxyzirconium derivative, or a polymer of one or more of these; and (IIc) Alkoxyaluminum, alkoxyaluminum derivatives, or oligomers consisting of polymers of one or more of these. and one or more polyvalent metal compounds selected from The optical element according to claim 1 .

5. A glass substrate made of phosphate glass or fluorophosphate glass is provided on at least one main surface thereof with a compound represented by the following general formula (i): Si(OR 1 )(OR 2 ) (OR 3 ) (OR 4 ) (i) (However, R 1 , R 2 , R 3 and R 4 are linear or branched hydrocarbon groups having 1 to 10 carbon atoms, and may be the same or different. and an alkoxysilane represented by the following general formula (iia): Ti(OR 5 )(OR 6 )(OR 7 )(OR 8 ) (iia) (However, R 5 , R 6 , R 7 and R 8 are linear or branched hydrocarbon groups having 1 to 10 carbon atoms, and may be the same or different from each other. The following general formula (iib): Zr(OR 9 )(OR 10 )(OR 11 )(OR 12 ) (iib) (However, R 9 , R 10 , R 11 and R 12 are linear or branched hydrocarbon groups having 1 to 10 carbon atoms, and may be the same or different from each other.) and the following general formula (iic): Al(OR 13 )(OR 14 )(OR 15 ) (iic) (However, R 13 , R 14 and R 15 are linear or branched hydrocarbon groups having 1 to 10 carbon atoms, and may be the same or different. and a weather-resistant protective film containing a hydrolysis / dehydration condensation product with at least one metal alkoxide selected from the group consisting of The optical element according to claim 1 .

6. When the total content of the alkoxysilane represented by the general formula (i) and the one or more metal alkoxides selected from the general formulas (iia) to (iic) is taken as 100.0 mol %, the weather-resistant protective film has The optical element according to claim 5, comprising a hydrolysis / dehydration condensation product of 25.0 mol % or more and 75.0 mol % or less of an alkoxysilane represented by the general formula (i) and 25.0 mol % or more and 75.0 mol % or less of one or more metal alkoxides selected from the general formulae (iia) to (iic).

7. 2. The optical element according to claim 1, wherein the glass substrate is an absorbing glass substrate that absorbs ultraviolet light or near infrared light.

8. 2. The optical element according to claim 1, further comprising a resin film or an anti-reflection film provided on the weather-resistant protective film.

9. 2. The optical element according to claim 1, wherein a resin film and an anti-reflection film are further provided in this order on the weather-resistant protective film, or an anti-reflection film and a resin film are further provided in this order.

10. 10. The optical element according to claim 1, wherein the optical element is an optical filter.

11. 10. An imaging device comprising an optical element according to claim 1 as an optical filter, together with a solid-state imaging element and an imaging lens.