Optical filter and imaging apparatus

Abstract

Provided is an optical filter that is composed of glass which is difficult to cut and that has sufficient bending strength. Also provided is an imaging apparatus. An optical filter (10) according to the present disclosure comprises, in the given order: a first dielectric multilayer film (200); a resin layer (210); a near-infrared absorbing glass (100); and a third dielectric multilayer film (230). The optical filter (10) has a coefficient of thermal expansion of 80×10-7 / K to 120×10-7 / K and a fracture toughness of 0.35 MPa۰√m to 0.55 MPa۰√m. The optical filter (10) further comprises: a first mirror surface layer (110) which is provided on the second resin layer (210) side and has a line roughness of 0.5 μm or less; a second mirror surface layer (120) which is provided on the third dielectric multilayer film (230) side and has a line roughness of 0.5 μm or less. The line roughness of a region B of a crack layer (130) is greater than the line roughness of a region A and a region C.

Description

Optical filters and imaging devices

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

[0002] From the perspective of matching the sensitivity of CMOS (Complementary Metal Oxide Semiconductor) sensors with that of the human eye, near-infrared cut filters (IR Cut Filters, IRCFs) are sometimes placed in the optical filter elements used in CMOS cameras. The optical filter element is formed by laser cutting a glass on which a near-infrared cut filter is placed to a predetermined size. Patent Document 1 discloses a technique for cutting an optical filter on which a near-infrared cut filter is placed using a laser.

[0003] Patent No. 6551404

[0004] Through repeated trials, the inventors discovered that by constructing an optical filter using glass with a thermal expansion coefficient smaller than a predetermined value and a fracture toughness value larger than a predetermined value, they could obtain an optical filter with high light shielding in the near-infrared region and less change in spectral characteristics depending on the angle of incident light. However, if the fracture toughness value is large, it is difficult to crack the glass with a laser. Also, if the thermal expansion coefficient is small, crack propagation is difficult. Therefore, optical filters constructed using glass with a thermal expansion coefficient smaller than a predetermined value and a fracture toughness value larger than a predetermined value were difficult to laser cut. Because optical filters that are difficult to cut require a large amount of energy during laser cutting, the glass is damaged by the laser, and large hackles tend to form on the cut surface. Therefore, there was a risk that the bending strength would be insufficient when laser cutting optical filters that are difficult to cut.

[0005] In view of the above issues, the object of the present invention is to provide an optical filter that is made of glass that is difficult to cut and has sufficient bending strength.

[0006] An optical filter and imaging device according to one aspect of this disclosure have the following configuration.

[0007] [1] An optical filter comprising a first dielectric multilayer film, a resin layer, a near-infrared absorbing glass, and a third dielectric multilayer film in this order, wherein the thermal expansion coefficient of the near-infrared absorbing glass is 80 × 10 －７ / K ~ 120 x 10 －７ The optical filter is such that the fracture toughness of the near-infrared absorbing glass is 0.35 MPa·√m to 0.55 MPa·√m, the end face of the near-infrared absorbing glass comprises a first mirrored layer, a cracked layer, and a second mirrored layer in that order, the first mirrored layer is provided on the resin layer side of the end face, the width of the first mirrored layer is 25% to 50% of the width of the end face, the line roughness of the first mirrored layer is 0.5 μm or less, the second mirrored layer is provided on the third dielectric multilayer side of the end face, the width of the second mirrored layer is 25% to 50% of the width of the end face, the line roughness of the second mirrored layer is 0.5 μm or less, and the cracked layer has three regions A, B, and C in that order from the first mirrored layer side, the line roughness of region B is greater than the line roughness of regions A and C.

[0008] [2] The optical filter according to [1], wherein the crack layer is divided into five regions Z, Y, X, W, and V in order from the first mirrored layer side, the linear roughness of regions X, Y, and Z increases in this order, and the linear roughness of regions X, W, and V increases in this order.

[0009] [3] The optical filter according to [1] or [2], wherein the roughness of the crack layer is 0.5 μm or more.

[0010] [4] The optical filter according to any one of [1] to [3], wherein the line roughness of region B is 0.5 μm to 1.5 μm, and the line roughness of region A and region C is 0.5 μm to 1.0 μm.

[0011] [5] The optical filter according to any one of [1] to [4], wherein the length of the hackle extending from the crack layer toward the first mirror layer or the second mirror layer is 30 μm or less from the edge of the crack layer.

[0012] [6] The reflectance at 1000 nm to 1100 nm of incident light from the side of the first dielectric multilayer film or from the side of the third dielectric multilayer film is at least one of 20% or less, and the optical filter according to any one of [1] to [5].

[0013] [7] Among the reflectances at 1000 nm to 1100 nm of incident light from the side of the first dielectric multilayer film or from the side of the third dielectric multilayer film, the incident light from the side with the lower reflectance reaches the near-infrared absorbing glass, and the optical filter according to any one of [1] to [6].

[0014] [8] Taking T0 as the transmittance at an incident angle of 0° and R5 as the reflectance on the side of the first dielectric multilayer film, the absorption rate at 1030 nm calculated by the following mathematical formula (1) is 80% or more, and the optical filter according to any one of [1] to [7].

[0015] [9] The near-infrared absorbing glass has a spectral transmittance at 1030 nm of 10% or less, and the optical filter according to any one of [1] to [8].

[0016]

[10] The near-infrared absorbing glass is phosphate glass, and the optical filter according to any one of [1] to [9].

[0017]

[11] The phosphate glass is expressed in mass% based on oxides, P ２ O ５ : 40% to 80%, Al ２ O ３ : 5% to 20%, ΣR ２ O: 0.5% to 20% (R ２ O is one or more components selected from Li ２ O, Na ２ O, K ２ O, Rb ２ O, and Cs ２ O, ΣR ２ O is R ２The optical filter according to

[10] , comprising: total amount of O), ΣR'O: 0% to 15% (R'O is one or more components selected from CaO, MgO, BaO, SrO, and ZnO, ΣR'O is the total amount of R'O), CuO: 4% to 20%.

[0018]

[12] An optical filter according to any one of [1] to

[11] , wherein in the range of 450 nm to 600 nm, the difference in transmittance between the case where the incident angle is 0° and the case where the incident angle is 60° is 13% or less, in both the case where the incident angle is 0° and the case where the incident angle is 60°, there is a wavelength between 600 nm and 700 nm at which the transmittance is 30%, the difference between the wavelength at which the transmittance is 30% when the incident angle is 0° and the wavelength at which the transmittance is 30% when the incident angle is 60° is 20 nm or less, and in the range of 750 nm to 1000 nm, the transmittance when the incident angle is 0° is 1% or less.

[0019]

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

[12] , comprising a second dielectric multilayer film between the resin layer and the near-infrared absorbing glass.

[0020]

[14] An imaging device equipped with an optical filter as described in any of [1] to

[13] .

[0021] The present invention provides an optical filter and imaging device that are constructed using glass that is difficult to cut and have sufficient bending strength.

[0022] This is a schematic diagram showing an example of the configuration of the end face of the optical filter according to Embodiment 1. This is an enlarged schematic diagram of the end face of the glass provided in the optical filter according to Embodiment 1. This is an enlarged schematic diagram of the crack layer. This is a graph showing the absorption rate of the optical filter according to Embodiment 1 when the wavelength of incident light is 1030 nm. This is a graph showing the spectral transmittance of the glass constituting the optical filter according to Embodiment 1. This is a graph showing the transmittance of the optical filter according to Embodiment 1 when the incident angle is 0° or 60°. This is an enlarged schematic diagram of the end face of the glass provided in the optical filter according to Embodiment 1.

[0023] Embodiments of the present invention will be described below with reference to the drawings. In each drawing, the same or corresponding elements are denoted by the same reference numerals, and redundant explanations are omitted as necessary for clarity of explanation. In this specification, the "~" indicating a numerical range includes the values ​​described before and after it as the lower and upper limits. In numerical ranges described stepwise in this specification, the upper or lower limit described in one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. In addition, in numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with the values ​​shown in the examples. In this specification, "grazing incidence characteristics" refers to the incidence angle dependence of the spectral transmittance in an optical filter. In this specification, "near-infrared" refers to light with a wavelength of 750 nm to 1200 nm. In this specification, "short-wavelength infrared" refers to light with a wavelength of 1200 nm to 1600 nm. In this specification, "substantially free of" a specific component means that it is not intentionally added, and does not mean that it excludes content that is inevitably mixed in from raw materials, etc., to an extent that does not affect the intended characteristics. Unless otherwise specified, "substantially absent" means that the content of the target ingredient is 0.1% by mass or less.

[0024] <Embodiment 1> First, the configuration of the optical filter 10 according to Embodiment 1 will be described with reference to Figure 1. Figure 1 is a schematic diagram showing the end face, or cross-section, of the optical filter 10, but some parts are hatched for explanatory purposes. The optical filter 10 is a glass element that has the function of cutting near-infrared rays. The optical filter 10 is suitable for cameras such as CMOS cameras, sensing equipment used in the VR / AR (Virtual Reality / Augmented Reality) field, etc. The optical filter 10 comprises at least a first dielectric multilayer film 200, a resin layer 210, a near-infrared absorbing glass 100, and a third dielectric multilayer film 230, and may further comprise a second dielectric multilayer film. In the example shown in Figure 1, the optical filter 10 comprises the first dielectric multilayer film 200, a resin layer 210, a second dielectric multilayer film 220, a near-infrared absorbing glass 100, and a third dielectric multilayer film 230 in this order. When the optical filter 10 is used in a CMOS camera, the sensor is placed on the side of the first dielectric multilayer film 200.

[0025] <First Dielectric Multilayer Film> The first dielectric multilayer film 200 may function as an anti-reflective film. The first dielectric multilayer film 200 is composed of a dielectric multilayer film in which dielectric films with different refractive indices are stacked, for example. More specifically, examples include a dielectric film with a low refractive index (low refractive index film), a dielectric film with a medium refractive index (medium refractive index film), and a dielectric film with a high refractive index (high refractive index film), and is composed of a dielectric multilayer film in which two or more of these are stacked.

[0026] The high refractive index film preferably has a refractive index of 1.6 or higher at a wavelength of 500 nm, more preferably 1.8 to 2.5, and particularly preferably 2.2 to 2.5. Examples of materials for the high refractive index film include Ta ２ O ５ , TiO ２ ,TiO,Nb ２ O ５ Other commercially available products include the OS50 (Ti) manufactured by Canon Optron Corporation. ３ O ５ ), OS10 (Ti ４ O ７ ), OA500 (Ta ２ O ５ and ZrO２ A mixture of OA600 (Ta ２ O ５ and TiO ２ Examples include mixtures of TiO. ２ It is preferable.

[0027] The medium refractive index film preferably has a refractive index of 1.6 or more and less than 2.2 at a wavelength of 500 nm. Examples of materials for the medium refractive index film include ZrO2 and Nb. ２ O ５ Al ２ O ３ , HfO ２ Also, the OM-4 and OM-6 (Al) sold by Canon Optron Corporation. ２ O ３ and ZrO ２ Examples include a mixture of ), OA-100, H4 and M2 (alumina antania) sold by Merck, etc. Of these, Al is chosen based on its film-forming properties, reproducibility in refractive index, stability, etc. ２ O ３ Compounds of the system and Al ２ O ３ and ZrO ２ A mixture of these is preferred.

[0028] The low refractive index film preferably has a refractive index of less than 1.6 at a wavelength of 500 nm, and more preferably 1.38 to 1.5. Examples of materials for the low refractive index film include SiO2. ２ SiO ｘ N ｙ MgF ２ These are some examples. Other commercially available products include Canon Optron's S4F and S5F (SiO ２ and Al ２ O ３ A mixture of these can be cited. Of these, in terms of reproducibility, stability, and economy in film formation, SiO ２ It is preferable.

[0029] The first dielectric multilayer film 200 has a total number of layers, preferably 40 or fewer, more preferably 30 or fewer, even more preferably 20 or fewer, and preferably 6 or more. The thickness (physical thickness) of the first dielectric multilayer film 200 is preferably 0.2 μm to 1.0 μm overall. For forming the first dielectric multilayer film 200, for example, vacuum deposition processes such as CVD, sputtering, and vacuum evaporation, or wet deposition processes such as spraying and dipping can be used.

[0030] <Resin Layer> The resin layer 210 contains a resin and a near-infrared absorbing dye. Here, "resin" refers to the resin that constitutes the resin layer.

[0031] As the near-infrared absorbing dye, a dye having a maximum absorption wavelength of 700 to 800 nm in the resin is preferred. By having a maximum absorption wavelength of 700 to 800 nm, the near-infrared light region around 700 nm, where near-infrared absorbing glass has somewhat weak light-shielding properties, can be shielded by the absorption characteristics of the dye.

[0032] Examples of near-infrared absorbing dyes include at least one selected from the group consisting of cyanine dyes, phthalocyanine dyes, squarylium dyes, naphthalocyanine dyes, and diimonium dyes, which can be used individually or in combination. Among these, squarylium dyes and cyanine dyes are preferred from the viewpoint of being able to absorb sharply in the 700-800 nm region and thus easily exhibit the effects of the present invention.

[0033] The content of the near-infrared absorbing dye in the resin layer is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, per 100 parts by mass of resin. When two or more compounds are combined, the above content is the sum of the individual compounds.

[0034] The resin layer may contain other dyes, such as ultraviolet light absorbing dyes, as long as they do not impair the effects of the present invention. Examples of ultraviolet light absorbing dyes include oxazole dyes, merocyanine dyes, cyanine dyes, naphthalimide dyes, oxadiazole dyes, oxazine dyes, oxazolidine dyes, naphthalic acid dyes, styryl dyes, anthracene dyes, cyclic carbonyl dyes, and triazole dyes. Among these, merocyanine dyes are particularly preferred. One type may be used alone, or two or more types may be used in combination.

[0035] The resin used in the resin layer 210 is not limited as long as it is a transparent resin, and one or more transparent resins selected from polyester resin, acrylic resin, epoxy resin, ene-thiol resin, polycarbonate resin, polyether resin, polyarylate resin, polysulfone resin, polyethersulfone resin, polyparaphenylene resin, polyarylene ether phosphine oxide resin, polyamide resin, polyimide resin, polyamide-imide resin, polyolefin resin, cyclic olefin resin, polyurethane resin, and polystyrene resin can be used. These resins may be used individually or in mixtures of two or more. From the viewpoint of spectral properties, glass transition temperature (Tg), and adhesion of the resin layer, one or more resins selected from polyimide resin, polycarbonate resin, polyester resin, and acrylic resin are preferred.

[0036] When multiple dyes are used, they may be contained in the same resin layer, or they may each be contained in a separate resin layer.

[0037] The resin layer can be formed by preparing a coating solution by dissolving or dispersing a dye, a resin or resin raw material component, and other components as needed in a solvent, coating this solution onto a support, drying it, and further curing it as needed. The support in this case may be near-infrared absorbing glass 100, or a releaseable support used only when forming the resin layer. The solvent may be any dispersion medium or solvent that can stably disperse or dissolve the components.

[0038] Furthermore, the coating solution may contain a surfactant to improve voids caused by minute bubbles, indentations caused by the adhesion of foreign matter, and repulsion during the drying process. In addition, methods such as immersion coating, cast coating, or spin coating can be used for applying the coating solution. After applying the above coating solution to the support, a resin layer is formed by drying. Furthermore, if the coating solution contains raw material components of a transparent resin, a curing treatment such as thermosetting or photocuring is performed.

[0039] Furthermore, the resin layer can also be manufactured in film form by extrusion molding. The obtained film-like resin layer can be laminated onto the near-infrared absorbing glass 100 and integrated by thermocompression bonding or the like to produce a base material.

[0040] The thickness of the resin layer is preferably 10 μm or less, more preferably 5 μm or less, from the viewpoint of in-plane film thickness distribution within the substrate after coating and appearance quality, and preferably 0.5 μm or more from the viewpoint of exhibiting desired spectral characteristics with an appropriate dye concentration.

[0041] <Second Dielectric Multilayer Film> The second dielectric multilayer film 220 may be constructed using the same materials as the first dielectric multilayer film 200, and examples of materials and formation methods will not be described. The second dielectric multilayer film 220 has a total number of layers, preferably 40 layers or less, more preferably 30 layers or less, even more preferably 20 layers or less, and also preferably 6 layers or more. The thickness (physical thickness) of the second dielectric multilayer film 220 is preferably 0.2 μm to 1.0 μm overall.

[0042] <Near-infrared absorbing glass> The thermal expansion coefficient of near-infrared absorbing glass 100 is 80 x 10 －７ / K ~ 120 x 10 －７ / K, preferably 115 × 10 －７ / K or less, more preferably 110 x 10 －７ It is less than or equal to / K, and particularly preferably 100 × 10 －７ It is less than or equal to / K, and preferably 85 × 10 －７ / K or higher, more preferably 90 x 10 －７The thermal expansion coefficient is 0.35 MPa·√m to 0.55 MPa·√m, preferably 0.50 MPa·√m or less, and more preferably 0.40 MPa·√m or more. The near-infrared absorbing glass 100 is not particularly limited as long as it satisfies the above-mentioned thermal expansion coefficient and fracture toughness value, and may be phosphoric acid glass or fluorine phosphoric acid glass. The thickness of the near-infrared absorbing glass 100 is not particularly limited, but from the viewpoint of miniaturization and weight reduction, a range of 0.1 mm to 1 mm is preferred, and a range of 0.1 mm to 0.5 mm is more preferred.

[0043] In this specification, "phosphate glass" refers to the P content of phosphate glass expressed in mol% based on oxides. ２ O ５ This refers to glass in which the content of P is 40 mol% or more, and the content of fluorine atoms in the phosphate glass is less than 3 mass% of the total content of other elemental components in the phosphate glass (100 mass%). Furthermore, "phthalic acid glass" refers to glass in which P is present in phthalic acid glass. ５＋ The content of is 20% by mass or more, and F in phthalic acid glass － The amount of F contained in phthalic acid glass － This refers to glass in which the content of all other constituent elements is 3% by mass or more, relative to 100% by mass.

[0044] The components that can constitute the phosphate glass used as the near-infrared absorbing glass 100, and their preferred contents, are described below. Unless otherwise specified in this specification, the content of each component and the total content are expressed in mass percent based on oxides. Furthermore, the transmittance of the glass in this embodiment includes the reflective properties of the glass surface (i.e., it is the external transmittance of the glass, not the internal transmittance of the glass).

[0045] P ２ O ５ P is the main component that forms glass and is an essential component for enhancing near-infrared ray blocking properties. ２ O ５If the content is 40% or more, the effect can be sufficiently obtained, and if it is 80% or less, problems such as glass instability are less likely to occur. For this reason, it is preferably 50% to 80%, more preferably 52% to 78%, even more preferably 54% to 77%, even more preferably 56% to 76%, and most preferably 60% to 75%.

[0046] Al ２ O ３ Al is the main component that forms glass and is used to increase the strength of the glass. ２ O ３ If the content is 5% or more, the effect can be obtained sufficiently, and if it is 20% or less, problems such as glass instability and reduced near-infrared cutting ability are less likely to occur. For this reason, it is preferably 5% to 20%, more preferably 6% to 18%, even more preferably 7% to 17%, even more preferably 8% to 17%, and most preferably 9% to 16.5%.

[0047] R ２ O (however, R ２ O is Li ２ O, Na ２ O, K ２ O, Rb ２ O, and Cs ２ One or more components selected from O are components that lower the melting temperature of the glass, lower the liquidus temperature of the glass, or stabilize the glass. ２ Total amount of O (ΣR ２ If O) is 0.5% or more, the effect can be sufficiently obtained, and if it is 20% or less, the glass is less likely to become unstable, which is preferable. Therefore, it is preferably 0.5% to 20%, more preferably 1% to 20%, even more preferably 2% to 20%, even more preferably 3% to 20%, and most preferably 4% to 20%.

[0048] Li ２ O is a component that lowers the melting temperature of glass, lowers the liquidus temperature of glass, and stabilizes glass. Li ２ The O content is preferably 0% to 15%. ２If the content of O is 15% or less, it is preferable because problems such as instability of the glass and reduction of near-infrared cut performance are less likely to occur. More preferably, it is 0% to 8%, still more preferably 0% to 7%, even more preferably 0% to 6%, and most preferably 0% to 5%.

[0049] Na ２ O is a component for lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, stabilizing the glass, etc. Na ２ The content of O is preferably 0% to 15%. Na ２ If the content of NaO is 15% or less, it is preferable because the glass is less likely to become unstable. More preferably, it is 0.5% to 14%, still more preferably 1% to 13%, and even more preferably 2% to 13%.

[0050] K ２ O is a component having effects such as lowering the melting temperature of the glass and lowering the liquidus temperature of the glass. K ２ As the content of KO, 0% to 15% is preferable. K ２ If the content of KO is 15% or less, it is preferable because the glass is less likely to become unstable. More preferably, it is 0.5% to 14%, still more preferably 1% to 13%, and even more preferably 2% to 13%.

[0051] Rb ２ O is a component having effects such as lowering the melting temperature of the glass and lowering the liquidus temperature of the glass. Rb ２ As the content of RbO, 0% to 15% is preferable. Rb ２ If the content of RbO is 15% or less, it is preferable because the glass is less likely to become unstable. More preferably, it is 0.5% to 14%, still more preferably 1% to 13%, and even more preferably 2% to 13%.

[0052] Cs ２ O is a component having effects such as lowering the melting temperature of the glass and lowering the liquidus temperature of the glass. Cs ２ As the content of CsO, 0% to 15% is preferable. Cs ２If the content of O is 15% or less, the glass is less likely to become unstable, which is preferable. More preferably, it is 0.5% to 14%, still more preferably 1% to 13%, and even more preferably 2% to 13%.

[0053] Also, the above R ２ The alkali metal component represented by O causes a mixed alkali effect in the glass when two or more of these components are added simultaneously, and the mobility of R ＋ ions decreases. As a result, when the glass comes into contact with water, the hydration reaction caused by the ion exchange between H ＋ ions in the water molecule and R ＋ ions in the glass is inhibited. Therefore, the phosphate glass constituting the optical filter according to Embodiment 1 preferably contains two or more components selected from Li ２ O, Na ２ O, K ２ O, Rb ２ O, and Cs ２ O. In this case, the total amount of R ２ O (however, R ２ O is Li ２ O, Na ２ O, K ２ O, Rb ２ O, and Cs ２ O) is preferably 7% to 18% (excluding 7%). If the total amount of R ２ O exceeds 7%, the effect can be sufficiently obtained, and if it is 18% or less, problems such as the glass becoming unstable, the near-infrared cut-off property deteriorating, and the strength of the glass decreasing are less likely to occur, which is preferable. Therefore, ΣR ２ O is preferably more than 7% and 18% or less, more preferably 7.5% to 17%, still more preferably 8% to 16%, even more preferably 8.5% to 15%, and most preferably 9% to 14%.

[0054] ​​R'O (where R'O is one or more components selected from CaO, MgO, BaO, SrO, and ZnO) is a component that lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, stabilizes the glass, and increases the strength of the glass. The total amount of R'O (ΣR'O) is preferably 0% to 15%. A total amount of R'O of 15% or less is preferable because it is less likely to cause problems such as glass instability, reduced near-infrared cut properties, and reduced strength of the glass. More preferably it is 0% to 13%, and even more preferably 0% to 11%. Even more preferably it is 0% to 9%, and even more preferably 0% to 8%.

[0055] CaO is a component that lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, stabilizes the glass, and increases the strength of the glass. The CaO content is preferably 0% to 10%. A CaO content of 10% or less is preferable because it is less likely to cause problems such as glass instability and a decrease in near-infrared ray blocking properties. More preferably it is 0% to 8%, even more preferably 0% to 6%, even more preferably 0% to 5%, and most preferably 0% to 4%.

[0056] MgO is a component that lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, stabilizes the glass, and increases the strength of the glass. The MgO content is preferably 0% to 15%. An MgO content of 15% or less is preferable because it is less likely to cause problems such as glass instability or a decrease in near-infrared ray blocking properties. More preferably it is 0% to 13%, even more preferably 0% to 10%, even more preferably 0% to 9%, and most preferably 0% to 8%.

[0057] BaO is a component that lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, and stabilizes the glass. The BaO content is preferably 0.1% to 10%. A BaO content of 10% or less is preferable because it is less likely to cause problems such as glass instability or a decrease in near-infrared ray blocking properties. More preferably 0% to 8%, even more preferably 0% to 6%, even more preferably 0% to 5%, and most preferably 0% to 4%.

[0058] SrO is a component that lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, and stabilizes the glass. The SrO content is preferably 0% to 10%. A SrO content of 10% or less is preferable because it is less likely to cause problems such as glass instability or a decrease in near-infrared ray blocking properties. More preferably it is 0% to 8%, even more preferably 0% to 7%, and most preferably 0% to 6%.

[0059] ZnO has effects such as lowering the melting temperature of the glass and lowering the liquidus temperature of the glass. The ZnO content is preferably 0% to 15%. A ZnO content of 15% or less is preferable because it is less likely to cause problems such as deterioration of the glass's solubility and a decrease in near-infrared ray blocking properties. More preferably 0% to 13%, even more preferably 0% to 10%, even more preferably 0% to 9%, and most preferably 0% to 8%.

[0060] Adding oxides containing divalent cations of elements other than Cu to glass may reduce near-infrared blocking properties and short-wavelength infrared transmittance. Therefore, it is preferable that the phosphoric acid glass used as near-infrared absorbing glass 100 substantially does not contain divalent cations of elements other than Cu. Examples of elements other than Cu include R' as mentioned above. Accordingly, it is preferable that ΣR'O is 0%. Furthermore, in this invention, substantially not containing a specific component means not intentionally adding it, and does not mean excluding content that is inevitably mixed in from raw materials, etc., to an extent that does not affect the desired properties.

[0061] CuO is an essential component for blocking near-infrared rays. A CuO content of more than 2.0% is sufficient to obtain the desired effect, while a content of 20% or less is preferable because it is less likely to cause problems such as the formation of devitrified foreign matter in the glass and a decrease in the transmittance of visible light. More preferably, the content is 4% to 19.5%, even more preferably 5% to 19%, even more preferably 6% to 18.5%, and most preferably 7% to 18% (however, 7% is not included).

[0062] <Third Dielectric Multilayer Film> The third dielectric multilayer film 230 may have functions such as reflecting near-infrared light or acting as an anti-reflective film. The third dielectric multilayer film 230 may be constructed using the same materials as the first dielectric multilayer film 200 and the second dielectric multilayer film 220, and examples of materials and examples of formation methods will not be described. The third dielectric multilayer film 230 has a total number of layers, preferably 110 layers or less, more preferably 80 layers or less, even more preferably 60 layers or less, and also preferably 10 layers or more, more preferably 20 layers or more, and even more preferably 30 layers or more. The thickness (physical thickness) of the third dielectric multilayer film 230 is preferably 1 μm to 6 μm overall.

[0063] Generally, if a large amount of near-infrared light is cut by reflection from a derivative multilayer film, the spectral characteristics tend to change significantly depending on the angle of incidence of light, i.e., the oblique incidence characteristics tend to deteriorate. Since the optical filter 10 absorbs near-infrared light to some extent with the resin layer 210 and the near-infrared absorbing glass 100, the amount of near-infrared reflection by the first, second, and third derivative multilayer films necessary to achieve the desired near-infrared cut is small. Therefore, the oblique incidence characteristics of the optical filter 10 are suppressed. In addition, since near-infrared cut is achieved by the above-described configuration, the optical filter 10 has high light-shielding properties in the near-infrared region. Thus, the optical filter 10 is an optical filter that achieves both high light-shielding properties in the near-infrared region and low oblique incidence characteristics. However, since the optical filter 10 uses near-infrared absorbing glass 100 with a thermal expansion coefficient smaller than a predetermined value and a fracture toughness value larger than a predetermined value, it is difficult to cut with a laser. The details of the cutting method and the shape of the cut surface of the optical filter 10 will be described below.

[0064] As shown in Figure 1, the radar cross-section, or end face, of the near-infrared absorbing glass 100 has a first mirrored layer 110, a cracked layer 130, and a second mirrored layer 120 in that order. The near-infrared absorbing glass 100 is cut by first creating a crack with a laser at the location corresponding to the cracked layer 130, and then pulling the cracked area with tape or the like.

[0065] The boundaries between the first mirrored layer 110, the cracked layer 130, and the second mirrored layer 120 are determined based on an image of the end face of the near-infrared absorbing glass 100. At the boundaries between the first mirrored layer 110, the cracked layer 130, and the second mirrored layer 120, multiple protrusions are observed in the direction of the main surface of the near-infrared absorbing glass 100 from the cracked layer 130 side as shown in Figure 1. The boundaries between the first mirrored layer 110, the cracked layer 130, and the second mirrored layer 120 can be determined as follows, depending on the position of the vertices of each protrusion.

[0066] Specifically, perpendicular lines are drawn to the main surface of the near-infrared absorbing glass 100 towards the vertices of each protrusion, and the average length of the obtained perpendicular lines, that is, the average distance between the main surface of the near-infrared absorbing glass 100 and the vertices of each protrusion, is obtained. Then, a straight line parallel to the main surface is drawn at a position separated from the main surface of the near-infrared absorbing glass 100 by the obtained average value, and this line forms the boundary between the first mirrored layer 110, the cracked layer 130, and the second mirrored layer 120. This straight line is obtained on one side of the main surface of the near-infrared absorbing glass 100 and on the other side of the main surface, and the distance between these straight lines is considered to be the cracked layer 130.

[0067] Multiple crack regions may be provided on the end face of the near-infrared absorbing glass 100. As shown in Figure 7, when multiple crack regions exist on the end face of the near-infrared absorbing glass, the width of the crack layer 130 is defined as the distance between the straight line on one side of the crack region closest to one side of the main surface of the near-infrared absorbing glass substrate and the straight line on the other side of the crack region closest to the other side.

[0068] Returning to Figure 1, the explanation continues. The first mirror-finish layer 110 is provided along the side of the near-infrared absorbing glass 100 that faces the second dielectric multilayer film 220. The width of the first mirror-finish layer 110 is 25% to 50% of the width, i.e., thickness, of the end face of the near-infrared absorbing glass 100. The line roughness Ra of the first mirror-finish layer 110 is 0.5 μm or less, preferably 0.4 μm or less.

[0069] Here, the linear roughness Ra of the first mirrored layer 110 is calculated based on the elevation information of the observation area obtained by focusing light emitted from a laser light source onto the glass end face and scanning the observation area of ​​the glass end face to acquire the amount of reflected light. Specifically, elevation information is acquired in a range of 1 mm or more in a direction parallel to the glass end face and perpendicular to it, including the entire first mirrored layer 110. Based on the acquired elevation information, the average linear roughness is obtained on at least one straight line that passes through the center of the first mirrored layer 110 and has a length of 10% to 100% of the length parallel to the end face of the range in which the elevation information was acquired, and the obtained value is taken as the linear roughness Ra of the first mirrored layer 110.

[0070] The second mirror-finish layer 120 is provided along the edge of the near-infrared absorbing glass 100 that faces the third dielectric multilayer film 230. The width of the second mirror-finish layer 120 is 25% to 50% of the width, i.e., thickness, of the end face of the near-infrared absorbing glass 100. The linear roughness Ra of the second mirror-finish layer 120 is 0.5 μm or less, preferably 0.4 μm or less. The linear roughness Ra of the second mirror-finish layer 120 is determined by the same method as the linear roughness Ra of the first mirror-finish layer 110.

[0071] The linear roughness Ra of the crack layer 130 is 0.5 μm to 1.5 μm, preferably 1.3 μm or less, more preferably 1.0 μm or less, and also preferably 0.7 μm or more. The crack layer 130 is the area where cracks are generated when the laser is irradiated during laser cutting. On the other hand, the first mirrored layer 110 and the second mirrored layer 120 are the areas that are cut by pulling the glass after laser irradiation. Here, the linear roughness Ra of the crack layer 130 is calculated based on the height information of the observation area obtained by focusing the light emitted from the laser light source onto the glass end face and scanning the observation area of ​​the glass end face to acquire the amount of reflected light.

[0072] Specifically, when crack regions are adjacent or overlap each other, height information is acquired in a direction parallel to the glass end face by 1 mm or more and in a direction perpendicular to it that includes the entire crack layer 130. Based on the acquired height information, the average line roughness is acquired along at least one straight line that passes through the center of the crack layer 130 and has a length of 10% to 100% of the length parallel to the end face of the area where the height information was acquired. The obtained value is defined as the line roughness Ra of the crack layer 130.

[0073] If the crack regions are spaced apart from each other, the boundary of the crack region identifies the crack region closest to the center of the crack layer 130, and elevation information is obtained for a range of 1 mm or more in a direction parallel to the glass end face and perpendicular to the entire crack region. Based on the obtained elevation information, the average line roughness is obtained along at least one straight line that passes through the center of the crack region and has a length of 10%-100% of the length parallel to the end face of the range in which the elevation information was obtained, and the obtained value is defined as the line roughness Ra of the crack layer 130.

[0074] When laser cutting the near-infrared absorbing glass 100, a crack layer 130 is formed by irradiating it with a laser in three or more passes. Here, "irradiating with a laser in three or more passes" means setting and irradiating at three or more laser irradiation points in the width direction of the glass. In other words, the crack layer 130 has three or more cracks in the width direction. Figure 2 is an enlarged schematic diagram of the end face of the near-infrared absorbing glass 100. As shown in Figure 2, the crack layer 130 has three crack regions A, B, and C from the side of the first mirrored layer 110. When cutting the glass with a laser in three passes, crack regions A, B, and C correspond to each pass. In the example shown in Figure 2, the three crack regions A, B, and C are adjacent to each other. However, the three crack regions A, B, and C may be arranged so as to be separated from each other, or they may be arranged so as to partially overlap.

[0075] Furthermore, crack regions A and C have a lower linear roughness Ra than crack region B. This relationship in linear roughness Ra can be achieved by irradiating crack regions A and C with a lower laser energy, and crack region B with a higher laser energy.

[0076] The laser energy acting on crack regions A and C is lower than the laser energy acting on crack region B. Therefore, cracks that occur in crack regions A and C are less likely to spread to areas where crack formation is not intended, and it is possible to suppress the extension of cracks to areas other than the crack layer 130, namely the first mirrored layer 110 and the second mirrored layer 120.

[0077] On the other hand, the laser energy acting on crack region B is higher than the laser energy acting on crack regions A and C. Therefore, it is possible to create a crack sufficient to cut the glass. Accordingly, by making the line roughness Ra of crack regions A and C smaller than that of crack region B, it is possible to create a crack sufficient to cut the glass while suppressing the extension of the crack to areas other than the crack layer 130.

[0078] Here, the locations of crack regions A, B, and C, and the linear roughness Ra of crack regions A, B, and C are determined as follows.

[0079] When crack regions are adjacent to or overlap each other as shown in Figures 1 and 7, the regions obtained by dividing the crack layer 130 into three parts in a direction parallel to the glass end face are designated as crack regions A, B, and C, respectively. The linear roughness Ra of each crack region A, B, and C is determined by acquiring height information in a range of 1 mm or more in a direction parallel to the glass end face and including the entire vertically symmetrical crack region, obtaining the average linear roughness along at least one straight line that passes through the center of the crack region and has a length of 10% to 100% of the length parallel to the end face of the range in which the height information was acquired, and setting the obtained value as the linear roughness Ra of each crack region A, B, and C.

[0080] If the crack regions are arranged so as to be separated from each other, and two layers of crack regions are observed, the three regions obtained by dividing the wider crack region in a direction parallel to the end face, and the other crack region, are designated as crack regions A, B, and C. The method for measuring the linear roughness Ra of crack regions A, B, and C is the same as described above.

[0081] If the crack regions are arranged so as to be separated from each other, and three or more crack regions are observed, select the three crack regions closest to the center of the crack layer 130, and designate them as crack regions A, B, and C. The method for measuring the linear roughness Ra of crack regions A, B, and C is the same as described above.

[0082] The linear roughness Ra of crack regions A and C may be approximately the same. The linear roughness Ra at the central position of crack region B is preferably 0.7 μm or more. Also, the linear roughness Ra at the central position when the crack layer 130 is divided into two in the glass width direction is preferably 0.5 μm to 1.5 μm. The linear roughness Ra at a position 3 μm inward from the main surface of the crack layer 130 on the second dielectric multilayer film 220 side is preferably 0.5 μm to 1.0 μm. The linear roughness Ra at a position 3 μm inward from the main surface of the crack layer 130 on the third dielectric multilayer film 230 side is preferably 0.5 μm to 1.0 μm.

[0083] The hackle 140 shown in Figure 2 is a streaky pattern extending from the surface of the cracked layer 130 toward the first mirrored layer 110 or the second mirrored layer 120. Here, the length of the hackle 140 is defined as the length from the boundary line between the cracked layer 130 and the mirrored layer 120 to the tip of the hackle 140. From the viewpoint of achieving sufficient bending strength, the length of the hackle 140 is preferably 30 μm or less, more preferably 25 μm or less, and particularly preferably 20 μm or less.

[0084] Figure 3 is an enlarged schematic diagram of the crack layer 130. Below, we consider the case where the crack layer 130 is divided into five regions Z, Y, X, W, and V from the first mirrored layer 110 side, as shown in Figure 3. As described above, in the crack layer 130, region B is irradiated with a laser with high output, and regions A and C are irradiated with a laser with low output. Therefore, the line roughness Ra in region Y is greater than that of region Z and less than that of region X. Also, the line roughness Ra in region W is greater than that of region V and less than that of region X.

[0085] The crack layer 130 may be formed, for example, by the glass fracturing after being irradiated with a laser for five passes. When the crack layer 130 is formed by irradiating with a laser for five passes, the five regions Z, Y, X, W, and V shown in Figure 3 correspond to each pass of the laser. In this case, the intensity of the laser output irradiated to each region is strongest in region X, moderate in regions Y and W, and weakest in regions Z and V.

[0086] The wavelength of the laser used during cutting is, for example, 1030 nm. Therefore, it is preferable that the optical filter 10 allows incident light with a wavelength of approximately 1000 nm to 1100 nm from either the first dielectric multilayer film 200 side or the third dielectric multilayer film 230 side to reach the near-infrared absorbing glass 100 for a predetermined amount of time. From this viewpoint, the reflectance in the range of 1000 nm to 1100 nm for incident light from either the first dielectric multilayer film 200 side or the third dielectric multilayer film 230 side is preferably 20% or less for at least one of them. Furthermore, it is preferable that the incident light from the side with the lower reflectance in the range of 1000 nm to 1100 nm for incident light from either the first dielectric multilayer film 200 side or the third dielectric multilayer film 230 side reaches the near-infrared absorbing glass 100.

[0087] Figure 4 is a graph showing the absorption rate of the optical filter 10 when the wavelength of incident light is 1030 nm. The absorption rate shown in Figure 4 is calculated by the following formula (1). In formula (1), T0 is the transmittance at an incident angle of 0°, and R5 is the reflectance on the first dielectric multilayer film 200 side.

[0088] The absorptivity shown in formula (1) corresponds to the absorption of the near-infrared absorbing glass 100 and the resin layer 210. From the viewpoint of providing sufficient near-infrared absorption characteristics to the optical filter 10, the absorptivity calculated by formula (1) is preferably 80% or more at 1030 nm.

[0089] Figure 5 is a graph showing the spectral transmittance of the near-infrared absorbing glass 100 when the incident angle of light is 0°. As shown in Figure 5, it is preferable that the transmittance of the near-infrared absorbing glass 100 is 10% or less at a wavelength of 1030 nm.

[0090] Figure 6 is a graph showing the transmittance of the optical filter 10 when the incident angle is 0° or 60°. The fact that the transmittance does not fluctuate significantly with respect to the incident angle means that the oblique incidence characteristics of the optical filter 10 are suppressed. As shown in Figure 6, in the wavelength range of 450 nm to 600 nm, the difference in transmittance between the incident angle at 0° and the incident angle at 60° is preferably 13% or less, more preferably 11% or less, and even more preferably 9% or less. Also, as shown in Figure 6, in both the incident angle at 0° and the incident angle at 60°, it is preferable that there is a wavelength between 600 nm and 700 nm at which the transmittance is 30%. Furthermore, the difference between the wavelength at which the transmittance is 30% when the incident angle is 0° and the wavelength at which the transmittance is 30% when the incident angle is 60° is preferably 20 nm or less, more preferably 17 nm or less, and even more preferably 15 nm or less. Furthermore, in the wavelength range of 750 nm to 1000 nm, the transmittance when the incident angle is 0° is preferably 1% or less, more preferably 0.5% or less, and even more preferably 0.1% or less, from the viewpoint of achieving a sufficient near-infrared cut effect. Furthermore, in the wavelength range of 450 nm to 600 nm, the transmittance when the incident angle is 0° is preferably 83% or more, more preferably 85% or more, and especially preferably 87% or more, from the viewpoint of sufficiently transmitting visible light. Furthermore, in the wavelength range of 450 nm to 600 nm, the transmittance when the incident angle is 60° is preferably 75% or more, more preferably 77% or more, and especially preferably 80% or more, from the viewpoint of suppressing oblique incidence characteristics.

[0091] Next, embodiments of the present invention will be described. Optical filters cut by laser irradiation were prepared using the following method.

[0092] <Optical Filter Element Configuration> The optical filter element used was one of elements 1 to 3 shown in Table 1 below.

[0093] <Procedure for Fabricating Optical Filter Elements> The procedure for fabricating elements 1 to 3 shown in Table 1 is as follows. First, a third dielectric multilayer film with the configuration shown in Table 1 was deposited onto the glass substrate by vapor deposition. Then, a second dielectric multilayer film with the configuration shown in Table 1 was deposited on the other side. A resin layer with the configuration shown in Table 1 was deposited on the second dielectric multilayer film by spin coating. Next, elements 1 to 3 were fabricated by depositing a first dielectric multilayer film with the configuration shown in Table 1 onto the resin surface.

[0094] <Details of the Resin Layers> Both resin layers 1 and 2 shown in Table 1 are polyimide resins, but they differ in the type and amount of dyes they contain. The composition of resin layers 1 and 2 is shown in Table 2 below. When creating optical filter elements 1 to 3, a resin dye solution was used. The resin dye solution was prepared by adding the first dye, the second dye, and the UV dye to a polyimide resin varnish (C3G30G) manufactured by Mitsubishi Gas Chemical Co., Ltd. in the types and amounts shown in Table 2 relative to the resin, and then diluting it with a diluent. As the diluent, a 1:1 weight ratio of γ-butyrolactone and cyclohexanone was used.

[0095] The chemical formula for dye 1 shown in Table 2 is shown in Chemical Formula 1 below. The maximum absorption wavelength of dye 1 is 752 nm.

[0096] The chemical formula for dye 2, shown in Table 2, is shown in Chemical Formula 2 below. The maximum absorption wavelength of dye 2 is 722 nm.

[0097] The chemical formula for dye 3 shown in Table 2 is represented by chemical formula 3 below. The maximum absorption wavelength of dye 3 is 708 nm.

[0098] The chemical formula for dye 4 shown in Table 2 is represented by chemical formula 4 below. The maximum absorption wavelength of dye 4 is 399 nm.

[0099] <Details of the glass composition> The compositions of phosphate glass 1, phosphate glass 2, and fluorphosphate glass shown in Table 1 are shown in Table 3 below.

[0100] <Procedure for Cutting Optical Filter Elements> Elements 1 to 3 shown in Table 1 were subjected to laser light irradiation onto a glass substrate using a Yb:KGW laser (center wavelength 1030 nm) as the laser light source. The laser output of each pass was selected to an appropriate level such that the crack layer did not reach the main surface of the glass substrate, and the average laser energy per pulse was 5 μJ to 30 μJ. The positions in which each pass generated cracks were selected so that the cracks overlapped. Each optical filter element cut in this manner was used as a sample for Examples 1 to 8. Table 4 shows the glass elements and number of passes used for the samples in Examples 1 to 8. Examples 1 to 3, 5 and 7 are examples, and Examples 4, 6 and 8 are comparative examples.

[0101] <Fracture Toughness and Thermal Expansion Coefficient> Fracture toughness and thermal expansion coefficient are properties inherent to the glass. In Examples 1 to 7 using phosphoric acid glass 1 and 2, the fracture toughness was 0.35 MPa·√m to 0.55 MPa·√m, and the thermal expansion coefficient was 80 × 10⁻⁶. －７ / K ~ 120 x 10 －７ Although it was within the range of / K, Example 8, which used phthalic acid glass, did not satisfy this condition.

[0102] <Method for Measuring Line Roughness> The line roughness Ra of each sample was measured using a Keyence VKX-3000 laser microscope. The height information of the observation area was acquired by scanning with a width of 10 to 200 μm in the height direction and a pitch of 0.1 nm. The line roughness Ra measurement function was used to measure the area parallel to the end face of the element by 1 mm or more, and perpendicular to it, including the mirror layer and the crack layer. The measurement results are summarized in Table 4. As shown in Table 4, in all of Examples 1 to 8, the Ra of the mirror layer was less than 0.5 μm, and the Ra of the crack layer was 0.5 μm or more. Furthermore, in Examples 1 to 3, 5, and 7 to 8, the line roughness Ra of region B was greater than that of regions A and C, but this was not the case in Examples 4 and 6.

[0103] <Resin Burrs> Resin burrs were measured using the optical microscope mode of a Keyence VKX-3000 laser microscope. For measuring resin burrs, any optical microscope with a length measurement function can be used. Here, resin burrs refer to the resin layer 210 protruding from the outer shape of the optical filter obtained after cutting. Specifically, by viewing the cut optical filter from above with the above microscope, if the resin layer protrudes from the outer shape of the optical filter, it is considered that resin burrs have occurred. The evaluation was based on the number of optical filters with resin burrs among 100 optical filters manufactured using the same procedure. A smaller number of resin burrs indicates that an optical filter with good dimensional accuracy and high appearance quality has been obtained.

[0104] The results are shown in Table 5 below. Resin burrs were evaluated as follows: less than 7 / 100 was excellent, 7 / 100 or more and less than 15 / 100 was good, and 15 / 100 or more was poor. Examples 1, 3-5, and 8 had excellent resin burrs. Examples 2 and 7 had good resin burrs. Example 6 had poor resin burrs.

[0105] <Four-Point Bending (4PB) Strength> The four-point bending strength was measured using an Imada Manufacturing SVZ-201F type tensile and compression testing machine SV SNZ-201F-50R03T. The four-point bending strength was evaluated as follows: 350 MPa or more is excellent, 300 to 350 MPa is good, and less than 300 MPa is poor. As shown in Table 5, the four-point bending strength was excellent in Examples 1 to 2 and 6. The four-point bending strength was good in Examples 3 to 5 and 7. The four-point bending strength was poor in Example 8.

[0106] <Hackle Length> Hackle length was measured using the optical microscope mode of a Keyence VKX-3000 laser microscope. For measuring hackle length, any optical microscope with a length measurement function may be used. Hackle length was evaluated as follows: 0 μm or more and less than 10 μm is excellent, 10 μm or more and less than 30 μm is good, and 30 μm or more is poor. As shown in Table 5, the hackle length was excellent in Examples 1 and 7. The hackle length was good in Examples 2 to 3 and 5. The hackle length was poor in Examples 4, 6 and 8.

[0107] <Other Characteristics, etc.> Table 6 summarizes the other characteristics of the samples for Examples 1 to 8. The linear roughness Ra of the five regions Z, Y, X, W, and V of the crack layer was small, medium, large, medium, small in Examples 1 to 3, 5, and 7, but this was not the case in Examples 4, 6, and 8. In addition, the linear roughness Ra at the center of region B was 0.7 μm or greater in all of Examples 1 to 8.

[0108] Table 6 shows the "Ra [μ] at each position within the crack layer," which, from left to right, represents the line roughness Ra at a position 3 μm from the main surface on the second dielectric multilayer side of the crack layer, the line roughness Ra at the center of the two-part division of the crack layer, and the line roughness Ra at a position 3 μm from the main surface on the third dielectric multilayer side of the crack layer.

[0109] The line roughness Ra at a position 3 μm from the main surface on the second dielectric multilayer side of the crack layer, and the line roughness Ra at a position 3 μm from the main surface on the third dielectric multilayer side of the crack layer, were evaluated with 0.5 to 1.0 μm being considered good. The line roughness Ra at the center of the two-part split in the crack layer was evaluated with 0.5 to 1.5 μm being considered good. In Examples 1 to 4 and 6 to 7, the line roughness Ra at each position was good, but in Examples 5 and 8 it was poor.

[0110] The reflectance of the optical filter elements in the wavelength range of 1000 to 1100 nm was 20% or less in all of Examples 1 to 8. Furthermore, the absorptance at a wavelength of 1030 nm, as expressed by the above formula (1), was 80% or more in all of Examples 1 to 8. The transmittance of the glass in the optical filter elements at a wavelength of 1030 nm was 10% or less in Examples 1 to 7, but this was not met in Example 8. Details of the "spectral characteristics" shown in Table 6 are shown in Table 7. The spectral characteristics shown in Table 7 are those of optical filter elements constructed using each of the glasses shown in Table 1.

[0111] As shown in Table 7, the difference in average transmittance in the wavelength range of 450-600 nm between the case of an incident angle of 0° and the case of an incident angle of 60° was 13% or less for elements 1 and 2, but not for element 3. For all elements 1, 2, and 3, there was a wavelength in the range of 600 nm to 700 nm at both the incident angle of 0° and the incident angle of 60° where the transmittance was 30%. For elements 1 and 2, the difference between the wavelength at which the transmittance was 30% at the incident angle of 0° and the wavelength at which the transmittance was 30% at the incident angle of 60° was 20 nm or less, but not for element 3. For all elements 1, 2, and 3, the transmittance at the incident angle of 0° in the range of 750 nm to 1000 nm was 1% or less. Based on these results, elements 1 and 2 were evaluated as satisfying the spectral characteristics, but element 3 was evaluated as not satisfying them.

[0112] Although the present invention has been described above in accordance with the above embodiments, the present invention is not limited to the configuration of the above embodiments, and of course includes various modifications, alterations, and combinations that can be made by a person skilled in the art within the scope of the claims of the present patent application.

[0113] This application claims priority based on Japanese Patent Application No. 2025-013344, filed on 29 January 2025, and incorporates all of its disclosures herein.

[0114] 10 Optical filter 100 Near-infrared absorbing glass 110 First mirror layer 120 Second mirror layer 130 Cracked layer 140 Huckle 200 First dielectric multilayer film 210 Resin layer 220 Second dielectric multilayer film 230 Third dielectric multilayer film

Claims

An optical filter comprising a first dielectric multilayer film, a resin layer, a near-infrared absorbing glass, and a third dielectric multilayer film in this order, The thermal expansion coefficient of the near-infrared absorbing glass is 80 × 10 －７ / K ~ 120 x 10 －７ / K is, The fracture toughness value of the aforementioned near-infrared absorbing glass is 0.35 MPa·√m to 0.55 MPa·√m. The end face of the near-infrared absorbing glass comprises a first mirrored layer, a cracked layer, and a second mirrored layer in this order. The first mirror-finish layer is provided on the resin layer side of the end face, The width of the first mirror-finish layer is 25% to 50% of the width of the end face. The line roughness of the first mirror-finish layer is 0.5 μm or less. The second mirror-finish layer is provided on the end face on the side of the third dielectric multilayer film, The width of the second mirror-finish layer is 25% to 50% of the width of the end face. The line roughness of the second mirror-finish layer is 0.5 μm or less. The crack layer has three regions A, B, and C in order from the first mirror-finish layer side, The line roughness in region B is greater than that of regions A and C. Optical filter. 　 If the crack layer is divided into five regions Z, Y, X, W, and V in order from the first mirror-finish layer side, the line roughness of regions X, Y, and Z increases in that order, and the line roughness of regions X, W, and V increases in that order. The optical filter according to claim 1. 　 The roughness of the crack layer is 0.5 μm or more. The optical filter according to claim 1 or 2. 　 The line roughness of region B is 0.5 μm to 1.5 μm. The line roughness of region A and region C is 0.5 μm to 1.0 μm. The optical filter according to claim 1 or 2. 　 The length of the hackle extending from the crack layer toward the first mirror layer or the second mirror layer is 30 μm or less from the edge of the crack layer. The optical filter according to claim 1 or 2. 　 The reflectance at 1000 nm to 1100 nm for incident light from either the first dielectric multilayer film side or the third dielectric multilayer film side is 20% or less for at least one of them. The optical filter according to claim 1 or 2. 　 Of the reflectances in the 1000 nm to 1100 nm range of incident light from the first dielectric multilayer film side or the third dielectric multilayer film side, the incident light from the side with the lower reflectance reaches the near-infrared absorbing glass. The optical filter according to claim 1 or 2. Let T0 be the transmittance at an incident angle of 0°, and R5 be the reflectance on the first dielectric multilayer film side. The absorption rate at 1030 nm, calculated by the following formula (1), is 80% or more. The optical filter according to claim 1 or 2. The near-infrared absorbing glass has a spectral transmittance of 10% or less at 1030 nm. The optical filter according to claim 1 or 2. 　 The aforementioned near-infrared absorbing glass is phosphoric acid glass. The optical filter according to claim 1 or 2. 　 The aforementioned phosphate glass is expressed in mass % based on oxides, P ２ O ５ :40%~80%、 Al ２ O ３ 50-200 ΣR ２ O: 0.5% to 20% (R ２ O is Li ２ O, Na ２ O, K ２ O, Rb ２ O, and Cs ２ O is one or more components selected from, ΣR ２ O is the total amount of R ２ O), ΣR'O: 0% to 15% (R'O is one or more components selected from CaO, MgO, BaO, SrO, and ZnO; ΣR'O is the total amount of R'O), CuO: 4% to 20%, The optical filter according to claim 10, including the following: 　 In the range of 450 nm to 600 nm, the difference in transmittance between an incident angle of 0° and an incident angle of 60° is 13% or less. In both cases, where the incident angle is 0° and where it is 60°, there is a wavelength between 600 nm and 700 nm at which the transmittance is 30%, and the difference between the wavelength at which the transmittance is 30% when the incident angle is 0° and the wavelength at which the transmittance is 30% when the incident angle is 60° is 20 nm or less. The transmittance is 1% or less at an incident angle of 0° in the range of 750 nm to 1000 nm. The optical filter according to claim 1 or 2. 　 A second dielectric multilayer film is provided between the resin layer and the near-infrared absorbing glass. The optical filter according to claim 1 or 2. 　 An imaging device comprising the optical filter described in claim 1 or 2.

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