TW202026678A - Optical filter and near-infrared cut filter wherein the optical filter includes a substrate, an optical multilayer film, an integrated layer, and an absorption layer - Google Patents

Abstract

The subject of the present invention is to provide an optical filter and a near-infrared cut filter having excellent optical characteristics. The optical filter includes a substrate, an optical multilayer film provided on the substrate, an integrated layer provided on the optical multilayer film, and an absorption layer provided on the integrated layer. The absorption layer includes a transparent matrix having an infrared absorbing component. The integrated layer can suppress a change of a transmittance intensity caused by the absorption layer.

Description

Optical filter and near infrared cut filter

The present invention relates to an optical filter used in an optical machine. In particular, it relates to a visual sensitivity correction filter used in solid-state imaging devices such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) used in digital cameras or video cameras. Near infrared cut filter.

Compared with the visibility characteristics of human beings, the spectral sensitivity of solid-state imaging elements such as CCD or CMOS used in digital cameras or video cameras has stronger sensitivity to near-infrared light. For this reason, a visual sensitivity correction filter is generally used to make the spectral sensitivity of the solid-state imaging elements meet the human visibility characteristics.

Regarding the visual sensitivity correction filter, Patent Document 1 discloses a near-infrared cut filter glass in which Cu ²⁺ ions are present in glass such as fluorophosphate glass or phosphate glass to adjust spectral characteristics.

In addition, there is a known near-infrared cut filter with excellent characteristics. In order to be able to sensitively and accurately determine the wavelength range to be transmitted, a multi-layer alternate laminated layer is provided on the surface of the above-mentioned near-infrared cut filter with high refraction. The optical multilayer film of the high refractive index layer and the low refractive index layer efficiently transmits wavelengths in the visible region (400 to 600 nm) and sensitively cuts off wavelengths in the near infrared region (700 nm) (for example, refer to Patent Document 2). In addition, in order to suppress reflection on the surface of the glass substrate and improve transmittance, sometimes an anti-reflection film is provided on the surface of the near-infrared cut filter glass.

In the case of a near-infrared cut filter, for example, an optical multilayer film is alternately laminated on a glass substrate with high refractive index layers composed of titanium oxide, tantalum oxide, niobium oxide, etc., and low refractive index layers composed of silicon oxide, etc. In addition, by appropriately setting the constituent materials, thickness, and number of layers of the high refractive index layer and the low refractive index layer, light interference can be used to selectively transmit light.

In addition, as a near-infrared cut filter that has high transparency in the visible light region and excellent blocking performance in the near-infrared region, the literature has proposed a substrate with a resin absorption layer containing an infrared-absorbing pigment or pigment and optical Multi-layer optical filters (for example, refer to Patent Documents 3 and 4).

Prior art literature Patent literature Patent Document 1: Japanese Patent Laid-Open No. 06-16451 Patent Document 2: Japanese Patent Laid-Open No. 02-213803 Patent Document 3: Japanese Patent Laid-Open No. 2006-301489 Patent Document 4: International Publication No. 2014/030628

Problems to be solved by the invention The optical filters described in Patent Document 3 and Patent Document 4 have excellent optical characteristics. However, the inventors of the present invention have found that the configuration of providing a resin layer on the optical multilayer film has a problem of adversely affecting the optical properties. When a resin layer is provided on a substrate or an optical multilayer film, wet coating methods such as spin coating, dipping, and printing are generally used. Compared with the thickness of the optical multilayer film, the thickness of the resin layer formed by these methods is quite thick, most of which is less than tens of μm, especially the film thickness of the number of images less than μm. Similar, and become a layer with optical interference characteristics. At this time, in the case where a resin layer is formed on the optical multilayer film, in particular, the optical characteristics may be unexpectedly affected. That is to say, it is well known that, compared with the thickness accuracy of optical multilayer films, the uniformity or lot-to-lot variation of the resin layer formed by the wet coating method is large, especially when the optical multilayer film When the resin layer is present, the optical characteristics designed by the interference of the optical multilayer film may be severely deteriorated due to the existence of the resin layer. Moreover, when the film thickness of the resin layer is deliberately changed in order to obtain the desired optical characteristics, the optical multilayer film must be redesigned every time depending on the situation, and there is also a problem that the degree of freedom of design is small.

The present invention was made in view of the above-mentioned problems, and its object is to provide an optical filter and a near-infrared cut filter having excellent optical characteristics.

Means to solve the problem In order to solve the above problems and achieve the objective, the optical filter of the present disclosure includes a substrate, an optical multilayer film provided on the substrate, an integrated layer provided on the optical multilayer film, and an absorption layer provided on the integrated layer, And the absorption layer has a transparent matrix containing near-infrared absorption components; the integration layer can suppress the transmittance intensity fluctuation caused by the absorption layer.

The aforementioned integration layer is preferably composed of a multilayer high refractive index film with a high refractive index and a low refractive index film with a lower refractive index than the aforementioned high refractive index film, or a single-layer intermediate refractive index film; the aforementioned high refractive index film The refractive index of the film at a wavelength of 500 nm is 1.8 or more, the refractive index of the aforementioned low refractive index film at a wavelength of 500 nm is less than 1.6, and the refractive index of the aforementioned medium refractive index film at a wavelength of 500 nm is 1.6 or more and less than 1.8.

When the center wavelength in the case where the center of the optical multilayer film on the wavelength as designed, so that the film of high refractive index QWOT and let Q _H is the QWOT of low refractive index film is Q _L, the integration layer is suitably from The aforementioned substrate side has a three-layer structure of (aQ _L bQ _H cQ _L ), wherein a and c are 0.2 or more and less than 0.5, b is 0.07 or more and less than 0.5, and b<a.

It is preferable to further have an auxiliary integration layer provided on the absorption layer, and the auxiliary integration layer can suppress the incident light in the visible wavelength band from being reflected by the absorption layer.

The thickness of the aforementioned absorption layer is preferably 100 nm or more and 5000 nm or less.

The aforementioned substrate is preferably any one of white board glass, blue glass and resin.

The average transmittance of light in the visible wavelength band of the aforementioned optical multilayer film is 80% or more, and the average transmittance of light in the near-infrared wavelength band is 10% or less.

In order to solve the above-mentioned problems and achieve the objective, the near-infrared cut filter of the present disclosure preferably has the aforementioned optical filter.

Invention effect According to the present invention, an optical filter and a near-infrared cut filter having excellent optical characteristics can be provided.

Hereinafter, the preferred embodiment of the present invention will be described in detail with reference to the attached drawings. In addition, the present invention is not limited by this embodiment, and when there are multiple embodiments, it also includes a combination of each embodiment.

Fig. 1 is a schematic cross-sectional view of the imaging device of this embodiment. As shown in FIG. 1, the imaging device 10 of this embodiment has a housing 12, a lens 14, an optical filter 16, and an imaging element 18. The housing 12 is a member that holds the lens 14, the optical filter 16, and the imaging element 18. The lens 14, the optical filter 16 and the imaging element 18 are arranged in the housing 12 in order from the side where the light L enters. The light L incident from the lens 14 passes through the optical filter 16 and enters the imaging element 18. The optical filter 16 shields light in a predetermined wavelength band of the light L incident from the lens 14 and at the same time transmits light in an unshielded wavelength band to enter the imaging element 18. In this embodiment, the optical filter 16 functions as a near-infrared cut filter that transmits light in the visible wavelength band while shielding light in the near-infrared wavelength band. The imaging element 18 converts the incident light through the optical filter 16 into an electrical signal, and outputs it as an image signal. The camera device 10 obtains image signals in the manner described above to photograph the object. In addition, the imaging element 18 is, for example, a solid-state imaging element such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor). The configuration of the imaging device 10 in FIG. 1 is an example, and the imaging device 10 may be configured such that the light L incident from the lens passes through the optical filter 16 and enters the imaging element 18.

Fig. 2 is a schematic cross-sectional view of the optical filter of this embodiment. As shown in FIG. 2, the optical filter 16 has a substrate 20, an optical multilayer film 22, an integration layer 24, an absorption layer 26, an auxiliary integration layer 28 and a back layer 30. The optical multilayer film 22 is provided on the surface 20 a of the substrate 20. In other words, the surface 20a can also be referred to as a main surface of the substrate 20. The integration layer 24 is provided on the surface 22 a of the optical multilayer film 22. The surface 22a is the surface of the optical multilayer film 22 on the opposite side of the substrate 20. In other words, it can also be referred to as a main surface of the optical multilayer film 22. The absorption layer 26 is provided on the surface 24 a of the integration layer 24. The surface 24a is the surface of the integration layer 24 on the opposite side of the optical multilayer film 22. In other words, it can also be referred to as a main surface of the integration layer 24. The auxiliary integration layer 28 is provided on the surface 26 a of the absorption layer 26. The surface 26a is the surface of the absorption layer 26 on the opposite side of the integration layer 24. In other words, it can also be referred to as a main surface of the absorption layer 26. The auxiliary integration layer 28 has no other layer laminated on the surface 28a on the side opposite to the absorption layer 26, so it can be said that it is exposed to the outside. That is, the surface 28a of the auxiliary integration layer 28 can be said to be an air side surface in contact with air. In other words, the surface 28a can also be referred to as a main surface of the auxiliary integration layer 28.

The back layer 30 is provided on the surface 20 b of the substrate 20. The surface 20b is a surface on the opposite side to the surface 20a. In other words, it can also be called the other main surface of the substrate 20. Furthermore, when the surface of the back layer 30 on the side opposite to the substrate 20 is set to 30a, this surface can be said to be a surface on the air side that is in contact with air.

As shown in FIGS. 1 and 2, the optical filter 16 is provided in the imaging device 10 in such a manner that the auxiliary alignment layer 28 of the auxiliary alignment layer 28 and the back layer 30 becomes the incident light L side (the lens 14 side). That is, in the optical filter 16, the auxiliary integration layer 28, the absorption layer 26, the integration layer 24, the optical multilayer film 22, the substrate 20 and the back layer 30 are laminated in this order from the incident side of the light L. In addition, the optical filter 16 may be arranged such that the back layer 30 faces the incident light L side (the lens 14 side). If the optical filter 16 is arranged in the above-mentioned manner, when the absorption layer 26 has a pigment or a pigment with near-infrared absorption characteristics, the influence of internal random reflection light reflected on the surface of the imaging element 18 can be more effectively suppressed.

The optical filter 16 is formed by laminating each layer in the order described above. The structure of each layer of the optical filter 16 is specifically described below.

(Substrate) The substrate 20 is a plate-shaped member that can transmit light in the wavelength band of the visible region. The visible wavelength band generally refers to light above 380nm and below 780nm. For example, when considering the use of optical filters as a visual sensitivity correction filter for solid-state imaging elements, 420nm~650nm (that is, above 420nm and below 650nm) is often considered Visible region, and regard 700nm above and below 400nm as near-infrared light and ultraviolet light respectively and listed as the object of blocking. However, this depends on the wavelength dependence of the visibility of the human eye and the visual sensitivity of the solid-state image sensor, and the color reproduction method used to construct the image. Therefore, a single definition cannot be adopted. Therefore, consideration should be taken as a reference. For example, for optical filters used for visual sensitivity correction filters, the transmittance of the most important green area (generally between 500nm and 560nm) in image composition should be above 80%.

The light in the near-infrared region wavelength band of the substrate 20 should preferably be low. The near-infrared region wavelength band generally refers to the light of 750nm~1.4μm, in this manual it refers to 700nm~1000nm. As mentioned above, the sensitivity characteristics of the solid-state imaging element, especially the visibility characteristics of 700 nm or more, are greater than that of the human eye. Therefore, when the optical filter 16 is used as a visual sensitivity correction filter, it is suitable to use a blue filter that can transmit visible light and absorb near-infrared light as a substrate. At this time, the average transmittance of the substrate 20 in the wavelength range of 700 nm to 1000 nm is preferably 20% or less. However, if the transmittance of wavelength 700~1000nm is low, the transmittance of visible light tends to decrease. Therefore, optical multilayer films such as infrared cut filters described later are generally used in combination.

The substrate 20 is preferably glass or resin. For the substrate 20, it is required to support the strength of the optical multilayer film or the absorption layer. Generally, glass has the required strength and excellent weather resistance, so it is suitable. As for the resin, the ring is excellent in strength, transparency, and weather resistance. Olefin resin etc. are preferable. When a resin is used as the substrate 20, the resin itself may contain pigments and the like contained in the absorption layer described later.

In addition, when the substrate 20 is made of glass, it is preferable to use white glass or blue glass as the glass. High-transparency silicate glass is often used for whiteboard glass, and borosilicate glass with a low content of alkali components is preferable from the viewpoint of weather resistance. In addition, it is also preferable to use glass with a low iron content, which is the cause of reduced visible light transmittance or solarization. Blue glass is a glass that has a wide range of absorption characteristics in the wavelength region of the near infrared region. Specifically, copper-containing fluorophosphate glass has good weather resistance, can transmit visible light, and has high near-infrared light absorption, so it is suitable. In addition, copper-containing phosphoric acid glass based on phosphoric acid glass containing no fluorine component has high near-infrared light absorption and is therefore suitable.

For example, fluorophosphoric acid glass is preferably: P ⁵⁺ : 25~50%, Al ³⁺ : 5~20%, R ⁺ : 20~40% expressed in cation% (However, R ⁺ means Li ⁺ , Na ⁺ And the total amount of K ⁺ ), ^R'2+ : 10~30% (However, ^R'2+ represents the total amount of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ ), Cu ²⁺ : 0.1~15%, Sb ³⁺ : 0~1% and containing O ^2- : 30~90%, F ^- : 10~70% glass in anion %. The fluorophosphoric acid glass of the above composition has excellent weather resistance and contains a copper component, so it has spectral characteristics suitable for near-infrared cut filter glass. In addition to the above composition, fluorophosphoric acid-based glass can also be used, for example, Japanese Patent Laid-Open No. 3-83834, Japanese Patent Laid-Open No. 6-16451, Japanese Patent Laid-Open No. 8-253341, and Japanese Patent Laid-Open The composition range disclosed in 2004-83290 or Japanese Patent Laid-Open No. 2011-132077 or the glass described in the examples. Phosphoric acid glass, for example, should contain P ₂ O ₅ : 50~75%, Al ₂ O ₃ : 5~22%, R ₂ O: 0.5~20% expressed in mole% (However, R ₂ O means Li The total amount of ₂ O, Na ₂ O and K ₂ O), R'O: 0.1~25% (However, R'O represents the total amount of MgO, CaO, SrO, BaO and ZnO), CuO: 0.1~15% Glass. The phosphoric acid-based glass of the above composition has high near-infrared absorption energy and has spectral characteristics suitable for near-infrared cut filter glass. In addition to the above-mentioned composition, the phosphoric acid-based glass may also be used, for example, Japanese Patent Laid-Open No. 2010-8908, Japanese Patent Laid-Open No. 2011-121792, Japanese Patent Laid-Open No. 2012-224491, and Japanese Patent Laid-Open 2015. The composition range disclosed in -13773 bulletin or the glass described in the examples.

In order to obtain the glass substrate 20, glass raw materials are blended and melted so as to have the aforementioned desired glass composition, and then the melted glass is formed. Then, after the outer shape is processed into a predetermined size to produce a glass substrate, the surface of the glass substrate is lapping, followed by precision polishing, to obtain a substrate 20. In addition, in order to obtain the optical filter 16, an optical multilayer film 22, an integration layer 24, an absorption layer 26, and an auxiliary integration layer 28 will be sequentially formed on the surface 20a of the substrate 20 prepared in the manner described above, and placed on the surface of the substrate 20 20b forms the back layer 30. Then, it is cut into a predetermined product size by a known method (scribing, cutting, laser cutting, etc.).

From the viewpoint of making the optical filter 16 thinner, the thickness of the substrate 20 is preferably 0.3 mm or less, preferably 0.22 mm or less, more preferably 0.18 mm or less, and most preferably 0.15 mm or less. In addition, from the viewpoint of suppressing processing cost and suppressing strength reduction, the thickness of the substrate 20 is preferably 0.025 mm or more, preferably 0.03 mm or more, and more preferably 0.05 mm or more.

(Optical multilayer film) The optical multilayer film 22 is a layer having predetermined optical characteristics. In this embodiment, it is configured to transmit light in the visible wavelength band and suppress the transmission of light in the near-infrared region wavelength. For example, the optical multilayer film 22 suppresses the transmission of light with wavelengths in the near infrared region by reflecting light with wavelengths in the near infrared region. That is, the optical multilayer film 22 is an infrared shielding film (InfraRed Cut Filter film, also referred to as IRCF film). The average transmittance of light in the visible wavelength band of the optical multilayer film 22 is 80% or more, and more preferably 100% or less. In addition, the average transmittance of light of wavelengths in the near infrared region of the optical multilayer film 22 is 10% or less, and more preferably 0% or more.

For the optical multilayer film 22 having the above-mentioned function, for example, a laminated film in which films with different refractive indexes are laminated can be used. The optical multilayer film 22 is constructed in the manner described above, which can reflect light of wavelengths in the near-infrared region and transmit light of wavelengths in the visible region by light interference. The optical multilayer film 22 is configured by alternately arranging a high refractive index film 22A and a low refractive index film 22B with a low refractive index film 22A and a low refractive index film 22A, for example. For the high refractive index film 22A, for example, at least one metal oxide film selected from ZrO ₂ , Nb ₂ O ₅ , TiO ₂ and Ta ₂ O ₅ can be used. For the low refractive index film 22B, for example, SiO ₂ or the like can be used. The film thickness and the number of layers of the high refractive index film 22A and the low refractive index film 22B can be appropriately set according to the optical characteristics required of the optical multilayer film 22.

The optical multilayer film 22 can be formed on the surface 20a of the substrate 20 by using a sputtering method or an ion-assisted evaporation method. Compared with the film formed by the evaporation method without ion assist, the film formed by the sputtering method or the ion assisted evaporation method has very little change in the spectral characteristics under high temperature and high humidity, and it can achieve substantially no spectrum. The advantages of the change-free film. In addition, the films formed by these methods are dense and high in hardness, so they are not easy to scratch, and they are also easy to handle in the assembly process of parts. Therefore, the film forming method of the optical multilayer film of the near-infrared cut filter that can be used as the visual sensitivity correction filter of the image sensor is quite suitable.

In addition, the optical multilayer film 22 may also be formed by a vacuum evaporation method without ion assistance. When this vapor deposition method is used, the device cost is low, and the manufacturing cost can be suppressed. In addition, it is possible to obtain a film with little foreign matter and the like adhesion when the optical multilayer film 22 is formed. That is, the method of forming the optical multilayer film 22 is not limited to a sputtering method, an ion-assisted vapor deposition method, etc., and any method may be used.

(Absorbing layer) Before describing the integration layer 24, the absorption layer 26 will be described first. The absorbing layer 26 is a layer composed of a transparent substrate containing a near-infrared absorbing component. The "transparency" of the transparent substrate means that it is transmissive to light in the visible wavelength band.

The transparent matrix of the absorption layer 26 is preferably resin or inorganic material. When the transparent matrix is a resin, the resin may be, for example, acrylic resin, epoxy resin, en-thiol resin, polycarbonate resin, polyether resin, polyarylate resin, polyether resin, and polyether resin. Resin, polyparaphenylene resin, polyester resin, polyimide resin, polyimide resin, polyolefin resin, cyclic olefin resin, etc. In particular, the resin having a high glass transition temperature (Tg) is preferably one or more selected from polyester resins, polycarbonate resins, polyether ether resins, polyarylate resins, polyimide resins, and epoxy resins. In addition, the resin that becomes the transparent matrix is preferably one or more selected from polyester resins and polyimide resins, and polyimide resins are particularly preferred. The polyester resin is preferably polyethylene terephthalate resin, polyethylene naphthalate resin, and the like. In addition, when the transparent substrate of the absorption layer 26 is an inorganic material, the inorganic material is preferably a silicon oxide film, for example.

In addition, the near-infrared absorption component contained in the absorption layer 26 is composed of an absorber that can absorb light in the near-infrared region wavelength band. The absorption layer 26 is formed by uniformly dissolving or dispersing an absorbent in a transparent substrate to contain a near-infrared absorbing component in the transparent substrate, and can transmit light in the visible wavelength band and simultaneously absorb light in the near-infrared wavelength band. For example, the absorption maximum wavelength of the absorbent when it is dissolved or dispersed in a transparent substrate is preferably 600nm or more and 1200nm or less, preferably 600nm or more and 1000nm or less, and 600nm or more and 850nm or less. The absorbent may also be a pigment that can absorb light of wavelengths in the near infrared region. If the pigment is a pigment (A), the pigment (A) can include: diimmonium series, cyanine series, phthalocyanine series, naphthalocyanine series, dithiol metal complex series, azo series , Aluminum series, polymethine series, phthalide, naphthoquinone series, anthraquinone series, indophenol series, pyrylium series, thiopyrylium series, squarylium Pigments such as croconium, tetradehydrocholine, triphenylmethane, aluminum, etc. In addition, for example, the absorber may also be an inorganic pigment that can absorb light in the near-infrared region. Examples of inorganic pigments include: A _1/n CuPO ₄ (However, A is selected from alkali metals (Li, Na, K, Rb, Cs), alkaline earth metals (Mg, Ca, Sr, Ba) and NH ₄ constitutes one or more kinds of the group, and, a 1, a is an alkaline earth metal n is 2 near-infrared) absorption of particles or crystallites containing tungsten oxide microparticles NH ₄ or an alkali metal when n is Wait.

In addition, when the transparent substrate of the absorption layer 26 is resin, the transparent substrate that has been uniformly dissolved or dispersed with the absorbent is coated on the surface 24a of the integration layer 24 by spin coating and dip coating (dipping) coating methods, and The transparent substrate is cured by heat, ultraviolet light, or the like to form the absorption layer 26. In addition, when the transparent substrate of the absorption layer 26 is an inorganic material, for example, a sol-gel method can be used to form the absorption layer 26. That is, the absorbent is uniformly dissolved or dispersed in a solution that can become a transparent base material, and then the solution is applied to the surface 24a of the integration layer 24 to solize the solution and gel the sol to form the absorption layer 26.

In addition, in this embodiment, the absorption layer 26 is a single layer, but it may be composed of multiple layers. When the thickness of the absorption layer 26 is composed of a single layer or a multilayer, it is preferably 100 nm or more and 5000 nm or less. Setting the thickness to 5000 nm or less can prevent the degradation of the optical characteristics caused by the uneven film thickness of the absorption layer 26 from becoming too large. In addition, setting the thickness to 100 nm or more can suppress the absorption energy of the absorption layer 26, that is, suppress the extinction coefficient from becoming too high, suppress the rapid rise of the refractive index, and suppress the influence of moire from increasing. In addition, if the thickness is less than 100nm, in addition to the difficulty of coating and other film formation, if the near-infrared absorption and other characteristics are taken into account, the increase in the extinction coefficient k will greatly increase the refractive index n value, which may be disadvantageous in film design. . In addition, when the thickness exceeds 5000 nm, the total thickness of the optical filter increases, and the ratio of resin with lower weather resistance increases, which may cause deterioration of weather resistance, which is not suitable.

唑系、部花青素系、花青系、萘二甲醯亞胺系、

二唑系、

系、

唑啶系、萘二甲酸系、苯乙烯基系、蒽系、環狀羰基系、三唑系等色素。In addition, the absorption layer 26 may contain an ultraviolet absorbing component. The ultraviolet absorbing component may be composed of, for example, an ultraviolet absorber capable of absorbing light in the wavelength band of the ultraviolet region. By uniformly dissolving or dispersing the ultraviolet absorber in a transparent matrix, the absorbing layer 26 contains ultraviolet absorbing components. The ultraviolet absorber preferably has an absorption maximum wavelength of 360 nm or more and 415 nm or less when uniformly dissolved or dispersed in a transparent substrate. The ultraviolet absorber is, for example, a pigment that can absorb light in the wavelength band of the ultraviolet region. When the pigment that can absorb light in the ultraviolet wavelength band is the pigment (U), the pigment (U) can be mentioned

Azole series, merocyanidin series, cyanine series, naphthalimide series,

Diazole series,

system,

Zolidine-based, naphthalenedicarboxylic acid-based, styryl-based, anthracene-based, cyclic carbonyl-based, and triazole-based dyes.

(Integration layer, auxiliary integration layer) The integration layer 24 and the auxiliary integration layer 28 are easier to understand together, so the functions and effects of them are explained below.

The integration layer 24 and the auxiliary integration layer 28 are respectively a ripple adjustment layer for suppressing the film thickness dependency of the absorption layer 26 as an interference film. As described separately, the absorption layer 26 may vary in film thickness during the forming step or the like. The integration layer 24 is capable of suppressing the change in film thickness from affecting the optical characteristics of the optical filter.

First, the idea of suppressing the change in transmittance intensity caused by the absorption layer 26 by the integration layer 24 will be explained.

The components from the absorption layer 26 to the substrate 20 are composed in the order of the substrate 20, the optical multilayer film 22, the integration layer 24, and the absorption layer 26. Here, if the absorption layer 26 is regarded as the incident medium, it is the order of the substrate 20, the optical multilayer film 22, the integration layer 24, and the incident medium (absorption layer 26). For example, when the incident medium is air, it is very general The composition of the optical film is the same. The incident medium is generally believed to have an infinite existence on the light incident side, and in this view, it is a concept of no thickness. In addition, the calculation of optical interference is usually based on the premise that the incident medium is infinitely thick, so the extinction coefficient k value of the absorption characteristic is regarded as zero.

In the above configuration, in order to minimize the reflectance in the visible region of the spectral waveform produced by the optical multilayer film 22, and to suppress the so-called reflection ripples, transmission ripples and other waveform fluctuations, in the past, a so-called For the film of the corrugation adjustment layer, the integration layer 24 performs the same function as the corrugation adjustment layer. That is, the integration layer 24 is a ripple adjustment layer when the absorption layer 26 is used as an incident medium. In addition, the moiré adjustment mentioned here refers to suppressing the intensity variation of the optical characteristics in the visible wavelength band caused by the change in the film thickness of the absorption layer 26.

The visible region reflectance of the spectral waveform produced by the optical multilayer film 22 is preferably 2% or less, and preferably 1% or less. If it is this reflectance, it is also possible to limit the intensity variation in the spectral characteristics of the so-called ripple.

In addition, regarding the incident angle, the optical filter 16 in actual use is used in the atmosphere or in a vacuum. Therefore, the incident angle when air is used as the medium is adjusted to conform to Snell’s law. Incident angle on the media side.

Similarly, the auxiliary integration layer 28 regards the absorption layer 26 as a substrate, and in order to minimize the reflectivity of the visible area when the substrate (absorption layer 26), auxiliary integration layer 28, and incident medium (air) are formed A ripple adjustment layer that suppresses the so-called reflection ripples and transmission ripples. However, in the above case, there is only the auxiliary integration layer 28, so it will be configured as a layer to minimize the reflectivity, and the smallest unit for this purpose is an anti-reflection film Therefore, the auxiliary alignment layer 28 may be an anti-reflection film when it is configured as a substrate (absorption layer 26), auxiliary alignment layer 28, and incident medium (air). Of course, as long as the reflectance in the visible area is the least and the ripple is suppressed, it can also be a band pass filter such as an infrared cut filter, etc. However, if the purpose of the present invention is considered, the minimum film thickness and number of layers The anti-reflective film is most suitable.

When the absorption layer 26 is regarded as a substrate and constituted as a substrate (absorption layer 26), an auxiliary integration layer 28, and an incident medium (air), the reflectance of the visible area is preferably 2% or less and 1% or less in terms of measurement standards Better. As long as under this condition, the intensity variation in the spectral characteristics of the so-called ripple can also be restricted.

The substrate can be calculated by considering the absorption-related extinction coefficient k as zero in the calculation of optical interference, and the thickness of the substrate can be considered as infinite in the optical interference. That is, like the incident medium, there is no film thickness dependence in the interference design of the optical film.

When the optical filter 16 is considered based on the absorption layer 26, the structure from the absorption layer 26 to the air side in FIG. 1 is designed to use the absorption layer 26 as the substrate, and the absorption layer 26 to the substrate 20 side is designed The absorbing layer 26 is used as the incident medium. Therefore, even when all the components (substrate 20, optical multilayer film 22, integration layer 24, absorption layer 26, auxiliary integration layer 28, air (incident medium)) are combined, the thickness dependence of absorption layer 26 is still very small In terms of this result, even if the film thickness of the absorption layer 26 varies greatly due to the coating step, etc., the adverse effects as an optical interference film can still be suppressed. In order to maintain the state of minimizing the reflectance and waviness of the visible area in the state where all the components are combined, the integration layer 24 is preferably a three-layer structure or a single-layer intermediate refractive index film described later.

In addition, as long as the structure is designed as described above, even if there is no auxiliary integration layer, the effect of suppressing the influence of the optical characteristics of the optical filter caused by the variation of the film thickness of the absorption layer 26 which is the object of the present invention can be obtained. This is because the absorption layer 26 is a resin layer, and its surface reflectance is relatively low. However, in order to obtain better optical properties, an auxiliary integration layer is necessary.

In the present embodiment, the integration layer 24 is constituted by a three-layer or more laminated film in which a high refractive index film 24A and a low refractive index film 24B are alternately laminated. As mentioned above, the integration layer 24 functions as a ripple adjustment layer of the optical multilayer film 22, so the film thickness depends on the structure of the optical multilayer film 22. Considering the main purpose of the optical filter 16, for example, the optical multilayer film 22 is an infrared cut filter. Generally, the optical design of the optical multilayer film 22 makes the optical film thickness QWOT of the high refractive index film H and the optical film thickness QWOT of the low refractive index film L, basically the repetition of (HL)^n constitute. In addition, (HL)^n represents a configuration in which the high refractive index film 24A and the low refractive index film 24B are repeated n times in this order. In addition, the high refractive index films 24A laminated at this time may have different optical film thicknesses. This is the same in the low refractive index film 24B. The integration layer 24 in the repetitive structure of the optical multilayer film 22 must be composed of a thinner film than the optical film thickness of the basic repetitive structure (HL) ^n near the side of the integration layer 24, and it is better to be described later (aQ _L bQ _H cQ _L ) three-layer structure. In addition, the film material of the integration layer 24 constructed in the above-mentioned manner is preferably the same as that of the optical multilayer film 22 during the manufacturing process, and the optical film thickness does not need to be the same film material as long as the above conditions are satisfied.

In addition to the above, the structure of the integration layer 24 can also be composed of an intermediate refractive index film, in which case the number of film layers can be reduced. The intermediate refractive index film is a three-layer structure of a thinner high refractive index film and a low refractive index film based on the idea of an equivalent film, so it can exhibit optical properties close to the above-mentioned three-layer integrated layer 24. However, the equivalent film conditions are different from those of the above-mentioned three-layer structure, so the performance is slightly inferior, but it can exhibit the characteristics of the integrated layer 24 to the extent that there is no problem in actual use.

In addition, the refractive index of the high refractive index film at a wavelength of 500nm is 1.8 or more and less than 3, the refractive index of the low refractive index film at a wavelength of 500nm should preferably be 1.4 or more and less than 1.6, and the refractive index of the intermediate refractive index film at a wavelength of 500nm Preferably it is 1.6 or more and less than 1.8. The present invention is based on the premise that the absorption layer 26 is arranged on the optical multilayer film 22. Therefore, the optical characteristics of the optical filter 16 as an interference multilayer film are basically determined by the optical multilayer film 22. The film material and refractive index of the integrated layer 24 are determined by the optical multilayer film 22. Therefore, the above-mentioned range of refractive index is also applicable to the optical multilayer film 22. The above-mentioned designation of the refractive index is based on, for example, the manufacturing requirements for the production of infrared cut filters. Condition depends.

The composition of the integration layer 24 is described in further detail. As previously explained, the integration layer 24 functions as a ripple adjustment layer for the optical multilayer film 22 under specific conditions. Therefore, the center wavelength of QWOT (Quarter-wave Optical Thickness) in the optical film thickness is determined according to the center wavelength of the optical multilayer film 22 in the film design. Specifically, when the optical multilayer film 22 is an infrared cut filter, the center wavelength of the wavelength band cut by the infrared cut filter becomes the center wavelength of the QWOT of the integration layer 24. In addition, when there are many wavelength bands cut by the infrared cut filter, the center wavelength of the wavelength band close to the integration layer 24 side is selected. Moreover, the center wavelength of the QWOT of the integration layer 24 should fall between 700 nm and 1400 nm.

Here, let the QWOT (Quarter-wave Optical Thickness) of the high refractive index film 24A be Q _H , and let the QWOT of the low refractive index film 24B be Q _L. At this time, the integration layer 24 is preferably composed of three layers (aQ _L bQ _H cQ _L ) from the substrate 20 side (the optical multilayer film 22 side) to the absorption layer 26 side. Here, a, b, and c are the coefficients of each basic unit, indicating that the physical film thickness of the film in each basic unit is several times the QWOT. Therefore, aQ _L , bQ _H , and cQ _L mean the optical film thickness of each film. That is, the film of the integration layer 24 closest to the substrate 20 (the optical multilayer film 22 side) is the low refractive index film 24B, and its optical film thickness is aQ _L. Furthermore, the film of the integration layer 24 on the absorption layer 26 side of the low-refractive-index film 24B closest to the substrate 20 is the high-refractive-index film 24A, and its optical film thickness is bQ _H. Next, the film provided on the absorption layer 26 side of the high refractive index film 24A of the integration layer 24 is the low refractive index film 24B, and its optical film thickness is cQ _L. In this embodiment, the alignment layer 24 is composed of three layers, and therefore the low refractive index film 24B provided on the absorption layer 26 side of the high refractive index film 24A is the film provided closest to the absorption layer 26 side. In addition, when the integration layer 24 is composed of three layers of (aQ _L bQ _H cQ _L ), a, b, and c use the high refractive index film 24A and the low refractive index film 24B of the center wavelength of the stop band of the optical multilayer film 22 Calculate each refractive index.

Here, a and c are 0.2 or more and less than 0.5, b is 0.07 or more and less than 0.5, and b<a is preferable. With a, b, and c being the numerical range, the integration layer 24 can suppress the dependence of the film thickness of the absorbing layer 26 from contributing to the reflectance of the visible region and suppress moire.

However, if the integration layer 24 is configured to suppress light interference in the visible wavelength band caused by the absorption layer 26, it is not necessary to provide a high refractive index film 24A between the two low refractive index films 24B as described above. In addition, the optical film thickness of the high refractive index film 24A and the low refractive index film 24B does not need to be in the above-mentioned relationship. For example, the integration layer 24 may have a three-layer structure in which a low-refractive-index film 24B is provided between two high-refractive-index films 24A. In addition, the integration layer 24 may be, for example, a high-refractive-index film 24A and a low-refractive-index film 24B alternately laminated in a total of four or more layers, or a total of two layers may be laminated. In addition, the integration layer 24 may be composed of a single layer having an intermediate refractive index of a predetermined refractive index, that is, a single layer of the aforementioned intermediate refractive index film. The intermediate refractive index is, for example, a value between the refractive index of the high refractive index film 24A and the refractive index of the low refractive index film 24B described above.

In addition, when the substrate 20, the optical multilayer film 22, the integration layer 24, the absorption layer 26, and the auxiliary integration layer 28 are sequentially laminated, and the auxiliary integration layer 28 is exposed to the air, the integration layer 24 is preferably configured to suppress the incidence from the air side. The integration layer 28 and the visible wavelength band of the light penetrating the substrate 20 generate ripples.

In addition, for the high refractive index film 24A, for example, at least one metal oxide film selected from ZrO ₂ , Nb ₂ O ₅ , TiO ₂ and Ta ₂ O ₅ can be used. In addition, for the low refractive index film 24B, for example, SiO ₂ or the like can be used. Preferably, the high refractive index film 24A and the high refractive index film 22A of the optical multilayer film 22 are made of the same material, and the low refractive index film 24B and the low refractive index film 22B of the optical multilayer film 22 are made of the same material. With the same material, it can be easily laminated. However, the high refractive index film 24A and the high refractive index film 22A may be different materials, and the low refractive index film 24B and the low refractive index film 22B may also be different materials.

The integration layer 24 can also be formed on the surface 22a of the optical multilayer film 22 in the same way as the optical multilayer film 22 is formed. That is, the integration layer 24 may be formed using, for example, a sputtering method, an ion-assisted vapor deposition method, a vacuum vapor deposition method, or the like.

(Auxiliary Integration Layer) The auxiliary integration layer 28 is a layer that suppresses the light that has entered the visible wavelength band of the auxiliary integration layer 28 from being reflected by the absorption layer 26 (the interface between the auxiliary integration layer 28 and the absorption layer 26). That is, the auxiliary integration layer 28 is an anti-reflection film (Anti-Reflection film, also known as AR film) having an anti-reflection function. In this embodiment, the auxiliary integration layer 28 is an optical multilayer film formed by laminating a plurality of films having different refractive indexes. That is, the auxiliary integration layer 28 is a laminated film in which a high refractive index film and a low refractive index film with a high refractive index film and a low refractive index film are alternately arranged, for example. For the high refractive index film, for example, at least one metal oxide film selected from ZrO ₂ , Nb ₂ O ₅ , TiO ₂ and Ta ₂ O ₅ can be used. For the low refractive index film, for example, SiO ₂ can be used. The film thickness or the number of layers of the high refractive index film and the low refractive index film can be appropriately set according to the optical characteristics required for the auxiliary integration layer 28. The auxiliary integration layer 28 can also be formed on the surface 26a of the absorption layer 26 in the same way as the optical multilayer film 22 is formed. That is, the auxiliary integration layer 28 may be formed using, for example, a sputtering method, an ion-assisted vapor deposition method, a vacuum vapor deposition method, or the like. In addition, the auxiliary integration layer 28 is not limited to the above-mentioned multilayer film as long as it has an anti-reflection function, and may be a single-layer structure, and may be an infrared cut filter, an ultraviolet cut filter, or the like. Moreover, the optical filter 16 may not be provided with the auxiliary integration layer 28.

(Back layer) The back layer 30 is provided to complement the optical characteristics of the optical filter 16 composed of the substrate 20 and the optical multilayer film 22 provided on the substrate 20, the integration layer 24, the absorption layer 26, and the auxiliary integration layer 28 . Therefore, the back layer 30 may have the same structure as the optical multilayer film 22, the integration layer 24, the absorption layer 26, and the auxiliary integration layer 28, or may be composed of only the optical multilayer film, or may not be provided. When the optical filter 16 is used as an optical filter for an imaging device, the back layer 30 is assumed to be an infrared cut filter or an anti-reflection film. When the back layer 30 is composed of an optical multilayer film, for example, a multilayer film in which a high refractive index film and a low refractive index film with a high refractive index film and a low refractive index film are alternately arranged in multiple layers can be used. For the high refractive index film, for example, at least one metal oxide film selected from ZrO ₂ , Nb ₂ O ₅ , TiO ₂ and Ta ₂ O ₅ can be used. For the low refractive index film, for example, SiO ₂ can be used. The film thickness or the number of layers of the high refractive index film and the low refractive index film can be appropriately set according to the optical characteristics required for the back layer 30. The back layer 30 can also be formed on the surface 20b of the substrate 20 in the same way as the optical multilayer film 22 is formed. That is, the back layer 30 may be formed using, for example, a sputtering method, an ion-assisted vapor deposition method, a vacuum vapor deposition method, or the like. In addition, as long as the back layer 30 has an anti-reflection function, it is not limited to the above-mentioned multilayer film, and may be formed of a single layer.

The optical filter 16 adopts the above configuration. Fig. 3 is a schematic diagram showing an example of the state of reflected light. FIG. 3 shows the difference between the reflected light state of the optical filter 16x of the comparative example and the optical filter 16 of this embodiment. As shown in FIG. 3, the optical filter 16x of the comparative example is laminated in the order of the substrate 20x, the absorption layer 26x, and the optical multilayer film 22x. That is, in the comparative example, the optical multilayer film 22x is positioned closer to the incident light L1x side than the absorption layer 26x. At this time, the unwanted wavelength light in the incident light L1x is reflected on the surface of the optical multilayer film 22x as the reflected light L2x. The reflected light L2x exists in the housing of the imaging device as stray light, for example, and may be incident on the optical filter 16x again. At this time, if the stray light enters the optical filter 16x at a wide angle, the stray light cannot be reflected by the oblique characteristic of the optical multilayer film 22X, and there is a concern that it may penetrate the optical filter 16x and reach the imaging element. In this case, the light will be recognized as noise in the camera image, which may reduce the image quality of the camera image.

On the other hand, in the optical filter 16 of the present embodiment, the absorption layer 26 is positioned closer to the incident light L1 than the optical multilayer film 22. In addition, in FIG. 3, for convenience of description, the auxiliary integration layer 28 and the back layer 30 are omitted. As shown in FIG. 3, the incident light L1 incident on the optical filter 16 will enter the absorption layer 26, and the unwanted wavelength light in the incident light L1 will be absorbed by the absorption layer 26. In addition, the unwanted wavelength light not absorbed by the absorption layer 26 will be reflected on the surface of the optical multilayer film 22. The light reflected on the surface of the optical multilayer film 22 will enter the absorbing layer 26 again and be absorbed by the absorbing layer 26, and only the light not absorbed by the absorbing layer 26 will be emitted into the housing of the imaging device as reflected light L2. In other words, the reflected light L2 transmits through the absorption layer 26 twice, and therefore is absorbed in the second transmission, so that the intensity drops lower than the reflected light L2x. Therefore, according to the optical filter 16 of this embodiment, even if the stray light reaches the imaging element, the intensity of the stray light is reduced, so the influence on the captured image can be reduced, and the deterioration of the image quality of the captured image can be suppressed. In other words, the optical filter 16 of the present embodiment suppresses the decrease in optical characteristics by reducing the intensity of stray light.

However, when the absorption layer 26 is arranged on the side of the incident light L1 relative to the optical multilayer film 22, as described above, the transmittance ripple of the optical multilayer film 22 becomes obvious, and the optical characteristics of the optical filter 16 may be lowered. In contrast, the optical filter 16 of the present embodiment suppresses the interference of light in the visible wavelength band caused by the absorption layer 26 by the integration layer 24, and suppresses the transmittance ripple of the optical multilayer film 22, thereby suppressing optical The optical characteristics of the filter 16 are reduced.

As described above, the optical filter 16 of this embodiment includes: a substrate 20, an optical multilayer film 22 provided on the substrate 20, an integration layer 24 provided on the optical multilayer film 22, and an absorption layer provided on the integration layer 24 26, and the absorption layer 26 has a transparent matrix containing infrared absorption components. The integration layer 24 is configured to suppress changes in transmittance intensity due to the absorption layer 26. According to the optical filter 16, it is possible to suppress the degradation of the optical characteristics of the optical filter 16 by reducing the intensity of stray light and simultaneously suppressing the light interference in the visible wavelength band caused by the absorption layer 26.

(Example 1) Next, Example 1 will be described. In Example 1, regarding the optical filter 16 of this embodiment, the film thickness (thickness) of the absorption layer 26 was changed to simulate the transmittance. Table 1 describes the structure of each layer of the optical filter 16 of Example 1. As shown in Table 1, in Example 1, the high refractive index film of the auxiliary integration layer 28 is TiO ₂ , and the low refractive index film of the auxiliary integration layer 28 is SiO ₂ , and the high refractive index of the integration layer 24 The high refractive index film 22A of the film 24A and the optical multilayer film 22 is set to ZrO ₂ , and the low refractive index film 24B of the integration layer 24 and the low refractive index film 22B of the optical multilayer film 22 are set to SiO ₂ . At a wavelength of 500 nm, the refractive index of TiO ₂ is 2.467, the refractive index of SiO ₂ is 1.483, and the refractive index of ZrO ₂ is 2.058. In addition, in Example 1, the optical multilayer film 22, the integration layer 24, and the auxiliary integration layer 28 are configured as shown in Table 1, and the film thickness of the absorption layer 26 is changed in the range of 700 nm to 1400 nm to simulate In this way, the spectral transmittance of the optical filter 16 is calculated. That is, for the optical filter 16 having the configuration in Table 1, the transmittance of the light emitted from the substrate 20 after the light enters the auxiliary integration layer 28 at each film thickness of the absorption layer 26 is calculated in a simulated manner. In addition, as shown in Table 1, the integration layer 24 of Example 1 has a three-layer structure of (aQ _L bQ _H cQ _L ). In Table 1, the optical multilayer film is on the substrate 20 side, and the auxiliary integration layer is on the air side. In Example 1, the designed center wavelength of the optical multilayer film 22 is 930 nm, a is 0.313, b is 0.131, and c is 0.412. In addition, each coefficient is calculated using the refractive index (ZrO ₂ : 2.025, SiO ₂ : 1.467) of the high refractive index film 24A and the low refractive index film 24B of the integration layer 24 at a wavelength of 930 nm. In addition, TFCalc (manufactured by Software Spectra Corporation) was used for the simulation soft system for calculating the spectral transmittance. The substrate 20 and the absorption layer 26 are calculated under the condition of no light absorption. The calculation of optical interference is to consider the absorption coefficient k as zero.

[Table 1]

On the other hand, Table 2 shows the composition of each layer of the optical filter of Comparative Example 1. In Table 2, the optical multilayer film is on the substrate 20 side, and the auxiliary integration layer is on the air side. The optical filter of Comparative Example 1 is different from Example 1 in that it does not have an integrated layer 24. Regarding Comparative Example 1, as in Example 1, after changing the film thickness of the absorption layer 26 in the range of 700 nm to 1400 nm, the spectral transmittance of the optical filter 16 was calculated by simulation.

[Table 2]

4 is a graph showing the value of the spectral transmittance of each film thickness of Example 1. FIG. 5 is a graph showing the value of the spectral transmittance of each film thickness of Comparative Example 1. FIG. The horizontal axis of FIGS. 4 and 5 is the wavelength, and the vertical axis is the spectral transmittance of the optical filter 16. FIGS. 4 and 5 respectively show the calculation results of the transmittance of the optical filter 16 of each thickness of the absorption layer 26 for each wavelength light of 350 nm to 1200 nm. As shown in Figures 4 and 5, compared to Comparative Example 1, in Example 1, in particular, the incident light has a wavelength of 450 nm or more and 750 nm or less (more specifically, 450 nm or more and 650 nm or less). Compared with the change of the film thickness of the absorbing layer 26, the value of the spectral transmittance of the optical filter changes less, and moire is suppressed. After confirming in detail the change in the spectral transmittance of the optical filter 16 when the film thickness of the absorption layer 26 is changed, the maximum transmittance and the minimum transmittance in the visible wavelength band (wavelength above 450nm and below 650nm) The difference is 0.66% or more and 0.89% or less in Example 1, while in Comparative Example 1, it is 2.60% or more and 7.66% or less.

(Example 2, Example 3) Next, Example 2 and Example 3 will be described. In Example 2, regarding the optical filter 16 of this embodiment, the film thickness (thickness) of the absorption layer 26 was changed to simulate the transmittance. Table 3 describes the structure of each layer of the optical filter 16 of Example 2. In Table 3, the optical multilayer film is on the substrate 20 side, and the auxiliary integration layer is on the air side. As shown in Table 3, the structure of the auxiliary integration layer 28 in the second embodiment is substantially the same as that of the first embodiment. On the other hand, the integration layer 24 is different from Example 1 in that a single layer of Al ₂ O ₃ is used as a medium refractive index film. At a wavelength of 500 nm, the refractive index of Al ₂ O ₃ is 1.617. In addition, in Example 2, the optical multilayer film 22, the integration layer 24, and the auxiliary integration layer 28 are configured as shown in Table 3, and the film thickness of the absorption layer 26 is changed in the range of 700 nm to 1400 nm to simulate In this way, the spectral transmittance of the optical filter 16 is calculated. That is, for the optical filter 16 with the configuration in Table 3, using the same simulation software and conditions as in Example 1, the film thickness of the absorption layer 26 is simulated by calculating the light incident from the auxiliary integration layer 28 and emitted from the substrate 20 The transmittance of light.

[table 3]

In Example 3, regarding the optical filter 16 of this embodiment, the film thickness (thickness) of the absorption layer 26 was changed to simulate the spectral transmittance. Table 4 lists the structure of each layer of the optical filter 16 of Example 3. In Table 4, the optical multilayer film is on the substrate 20 side, and the absorption layer is on the air side. As shown in Table 4, the structure of the integration layer 24 in Example 3 is substantially the same as that of Example 1. In Example 3, the designed center wavelength of the optical multilayer film 22 is 930 nm, a is 0.313, b is 0.131, and c is 0.412. In addition, each coefficient is calculated using the refractive index (ZrO ₂ : 2.025, SiO ₂ : 1.467) of the high refractive index film 24A and the low refractive index film 24B of the integration layer 24 at a wavelength of 930 nm. On the other hand, the third embodiment is different from the first embodiment in that the auxiliary integration layer 28 is not provided. In addition, in Example 3, the optical multilayer film 22 and the integration layer 24 are configured as shown in Table 4, and the film thickness of the absorption layer 26 is changed in the range of 700 nm to 1400 nm, and then the optical filter is calculated by simulation. The spectral transmittance of 16. That is, for the optical filter 16 with the configuration in Table 4, using the same simulation software and conditions as in Example 1, the light emitted from the substrate 20 after the light enters the absorption layer 26 is calculated in a simulation method for each film thickness of the absorption layer 26 The transmittance.

[Table 4]

On the other hand, Table 5 shows the composition of each layer of the optical filter of Comparative Example 2. In Table 5, the optical multilayer film is on the substrate 20 side, and the absorption layer is on the air side. The optical filter of Comparative Example 2 is different from Example 1 in that it does not have the integration layer 24 and the auxiliary integration layer 28. Regarding Comparative Example 2, as in Example 1, after changing the film thickness of the absorption layer 26, the spectral transmittance of the optical filter 16 was calculated by simulation.

[table 5]

6 is a graph showing the value of the spectral transmittance of each film thickness of Example 2. FIG. 7 is a graph showing the value of the spectral transmittance of each film thickness of Example 3. FIG. 8 is a graph showing the value of the spectral transmittance of each film thickness of Comparative Example 2. The horizontal axis of FIGS. 6 to 8 is the wavelength, and the vertical axis is the spectral transmittance of the optical filter 16. FIGS. 6 to 8 show the calculation results of the spectral transmittance of the optical filter 16 for each thickness of the absorption layer 26 for each wavelength light of 350 nm to 1200 nm. As shown in FIGS. 6 to 8, compared with each comparative example, in Example 2 and Example 3, in particular, the wavelength of the incident light is 450 nm or more and 750 nm or less (more specifically, 450 nm or more and 650 nm or less) Within the range of light of all wavelengths, the value of transmittance varies little, and moire is suppressed. On the other hand, in Comparative Example 2, it can be seen that, in particular, with respect to the variation of the film thickness (thickness) of the absorption layer 26, the value of the transmittance varies greatly, and moire occurs. In addition, after confirming in detail the change in the spectral transmittance of the optical filter 16 when the film thickness of the absorbing layer 26 is changed, the maximum transmittance and the minimum transmittance in the visible wavelength band (here, the wavelength is 450nm or more and 650nm or less) The difference is 1.27% or more and 2.38% or less in Example 2, and 3.11% or more and 4.72% or less in Example 3, while in Comparative Example 2, it is 1.34% or more and 17.97% or less.

The embodiment of the present invention has been described above, but the embodiment is not limited by the content of the embodiment. In addition, the aforementioned constituent elements include those that can be easily imagined by a person familiar with the art, those that are substantially the same, and those that are so-called equal. In addition, the aforementioned constituent elements can be appropriately combined. In addition, various omissions, substitutions, or changes of constituent elements can be made without departing from the spirit of the foregoing embodiment.

10: Camera device 12: Shell 14: lens 16,16x: optical filter 18: Camera element 20, 20x: substrate 20a, 20b, 22a, 24a, 26a, 28a, 30a: surface 22, 22x: Optical multilayer film 22A, 24A: High refractive index film 22B, 24B: low refractive index film 24: Integration layer 26, 26x: absorption layer 28: auxiliary integration layer 30: back layer L: light L1, L1x: incident light L2, L2x: reflected light

Fig. 1 is a schematic cross-sectional view of the imaging device of this embodiment. Fig. 2 is a schematic cross-sectional view of the optical filter of this embodiment. Fig. 3 is a schematic diagram showing an example of the state of reflected light. 4 is a graph showing the transmittance value of each film thickness of Example 1. FIG. 5 is a graph showing the transmittance value of each film thickness of Comparative Example 1. FIG. 6 is a graph showing the transmittance value of each film thickness of Example 2. FIG. 7 is a graph showing the transmittance values of each film thickness of Example 3. FIG. FIG. 8 is a graph showing the transmittance value of each film thickness of Comparative Example 2. FIG.

16: optical filter

20: substrate

20a, 20b, 22a, 24a, 26a, 28a, 30a: surface

22: Optical multilayer film

22A, 24A: High refractive index film

22B, 24B: low refractive index film

24: Integration layer

26: Absorption layer

28: auxiliary integration layer

30: back layer

L: light

Claims (8)

An optical filter characterized by: Substrate, Optical multilayer film on the aforementioned substrate, The integrated layer provided on the aforementioned optical multilayer film, and The absorption layer provided on the aforementioned integration layer, and the absorption layer has a transparent matrix containing near-infrared absorption components; The integration layer can suppress changes in transmittance intensity caused by the absorption layer. The optical filter of claim 1, wherein the integrated layer is composed of a multilayer high refractive index film with a high refractive index and a low refractive index film with a lower refractive index than the high refractive index film, or in a single layer Refractive index film composition; The high refractive index film has a refractive index of 1.8 or more at a wavelength of 500 nm, the low refractive index film has a refractive index of less than 1.6 at a wavelength of 500 nm, and the medium refractive index film has a refractive index of 1.6 or more and less than 1.8 at a wavelength of 500 nm. The optical filter 2 of the requested item, in the case in which the optical multilayer film in the center of the design wavelength as a center wavelength, so that the film of high refractive index QWOT and let Q _H is the QWOT of low refractive index film is For Q _L , the integration layer is composed of three layers (aQ _L bQ _H cQ _L ) from the substrate side, where a and c are 0.2 or more and less than 0.5, b is 0.07 or more and less than 0.5, and b< a. For example, the optical filter of any one of claim 1 to claim 3, which further has an auxiliary integration layer provided on the aforementioned absorption layer, and the auxiliary integration layer can suppress the incident light in the visible wavelength band from being absorbed by the aforementioned absorption layer reflection. Such as the optical filter of any one of claim 1 to claim 4, wherein the thickness of the aforementioned absorption layer is 100 nm or more and 5000 nm or less. Such as the optical filter of any one of claim 1 to claim 5, wherein the aforementioned substrate is any one of white glass, blue glass, and resin. The optical filter according to any one of claim 1 to claim 6, wherein the average transmittance of light in the visible wavelength band of the optical multilayer film is 80% or more, and the average transmittance of light in the near infrared region wavelength band Less than 10%. A near-infrared cut-off filter having an optical filter as in any one of claim 1 to claim 7.

Images