Optical filter

Abstract

The present application relates to an optical filter provided with a substrate including a resin film containing a pigment that absorbs near-infrared light, and a first thin film laminated structure and a second thin film laminated structure that limit transmission of near-infrared light, wherein the first thin film laminated structure includes at least two dielectric multilayer films and is laminated as an outermost layer on one main surface side of the substrate, the second thin film laminated structure includes at least one dielectric multilayer film and is laminated as an outermost layer on the other main surface side of the substrate, the first thin film laminated structure satisfies specific optical properties (i-1A) and (i-1B), and the second thin film laminated structure satisfies specific optical properties (i-2A).

Description

Technical Field

[0001] This invention relates to optical filters. Background Technology

[0002] In imaging devices that use solid-state imaging elements, optical filters are used to transmit light in the visible region (hereinafter also referred to as "visible light") while blocking light in the near-infrared wavelength region (hereinafter also referred to as "near-infrared light") in order to reproduce tones well and obtain vivid images.

[0003] Examples of such optical filters include reflective filters that use light interference to reflect the light to be blocked by alternately stacking dielectric thin films with different refractive indices (dielectric multilayer films) on one or both sides of a transparent substrate.

[0004] Optical filters that block near-infrared light need to block a wide wavelength region of 750–1200 nm, but it is technically difficult to cover this filter with a single multilayer film. Therefore, it is known to use a combination of multiple dielectric multilayer films with different near-infrared light reflection regions (Patent Document 1). Existing technical documents Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2007-183525 Summary of the Invention The technical problem that the invention aims to solve

[0006] It is known that in dielectric multilayer films, as the number of layers changes, the interference caused by reflected light at the interfaces of each layer leads to a sharp change in transmittance, generating so-called ripples. The larger the incident angle of light, the more easily and strongly these ripples are generated.

[0007] As with the optical filter described in Patent Document 1 above, when a dielectric multilayer film is composited to provide wide-range shielding in the near-infrared region, the ripple in the visible light region may not only not be eliminated, but may even be amplified.

[0008] Furthermore, the dielectric multilayer films constituting the thin film stack structure may exhibit incident angle dependence; that is, the larger the incident angle of light, the more the light transmission characteristics shift towards the shorter wavelength side. Therefore, in the near-infrared region near the boundary of the visible light region where the transmittance of the multilayer film changes drastically, the reflectivity may decrease under high incident angle conditions.

[0009] The purpose of this invention is to provide an optical filter that has high transmittance of visible light and high shielding properties of near-infrared light, and can suppress ripple generation in the visible light region and reduce shielding properties in the near-infrared light region even at high incident angles. Technical solutions adopted to solve technical problems

[0010] This invention employs a thin-film stacked structure composed of two or more multilayer films, which shifts the near-infrared light reflection region to eliminate ripple in the visible light region. However, in this structure, gaps arise at the overlap of the near-infrared light reflection regions of each multilayer film, easily leading to light leakage, which is particularly prone to occur at high incident angles due to the incident angle dependence of the dielectric multilayer film. Therefore, the inventors discovered that the above-mentioned problem can be solved by further equipping the thin-film stacked structure with light reflecting in the wavelength region where light leakage occurs and by using a pigment that absorbs light in that wavelength region. That is, the present invention provides an optical filter having the following configuration. [1] An optical filter comprising: Substrate, and A first thin-film stacked structure and a second thin-film stacked structure that restrict the transmission of light in the near-infrared wavelength region. The substrate comprises a resin film containing pigments that absorb light in the near-infrared wavelength region. The first thin-film laminate structure comprises at least two dielectric multilayer films and is laminated as the outermost layer on one main surface of the substrate. The second thin film laminate structure comprises at least one dielectric multilayer film and is laminated as the outermost layer on another main surface of the substrate. The first thin film stacked structure satisfies the following optical properties (i-1A) and (i-1B), The second thin film stack structure satisfies the following optical properties (i-2A): (i-1A) The maximum transmittance at an incident angle of 40° and a wavelength of 850nm to 950nm is above 5%; (i-1B) The maximum reflectivity at an incident angle of 40° and wavelengths of 450nm to 600nm is below 8%; (i-2A) The average reflectance at an incident angle of 40° and wavelengths of 850nm to 950nm is 25% to 60%. [2] The optical filter as described in [1], wherein the resin film satisfies all of the following optical properties (ii-1) to (ii-3): (ii-1) The average internal transmittance at an incident angle of 0° and a wavelength of 850 nm to 950 nm is 60% to 90%. (ii-2) The average internal transmittance at an incident angle of 30° and a wavelength of 850 nm to 950 nm is 60 to 90%. (ii-3) The average internal transmittance at an incident angle of 40° and wavelengths of 850 nm to 950 nm is 60% to 90%. [3] An optical filter as described in [1] or [2], wherein the resin film further satisfies the following optical properties (ii-4): (ii-4) The average internal transmittance at an incident angle of 30° and wavelengths of 660nm to 730nm is less than 10%. [4] An optical filter as described in any one of [1] to [3], wherein the second thin film stacked structure is stacked on the surface of the resin film. [5] An optical filter as described in any one of [1] to [4], wherein the resin film further satisfies the following optical properties (ii-5): (ii-5) The average internal transmittance at an incident angle of 0° and a wavelength of 450–600 nm is above 70%. [6] An optical filter as described in any one of [1] to [5], wherein the second thin film stacked structure has a dielectric multilayer film formed by alternating layers of TiO2 and SiO2, and the film ratio represented by the following formula is 0.50 or more: Film ratio (physical film thickness) = total physical film thickness of SiO2 / (total physical film thickness of TiO2 + total physical film thickness of SiO2). [7] An optical filter as described in any one of [1] to [6], comprising a polyimide resin. [8] An optical filter as described in any one of [1] to [7], which satisfies all of the following optical properties (iii-1) to (iii-5): (iii-1) The average transmittance at an incident angle of 0° and a wavelength of 400–600 nm is above 70%; (iii-2) The average reflectivity at an incident angle of 40° and a wavelength of 450–600 nm is less than 5%; (iii-3) The average reflectivity at an incident angle of 5° and a wavelength of 450–600 nm is less than 3%; (iii-4) The maximum transmittance at an incident angle of 40° and a wavelength of 700–900 nm is less than 15%; (iii-5) The average transmittance at an incident angle of 40° and a wavelength of 1000-1100nm is less than 5%. Invention Effects

[0011] According to the present invention, an optical filter is provided that has high transmittance to visible light and high shielding properties to near-infrared light, and can suppress ripple generation in the visible light region and decrease shielding properties in the near-infrared light region even at high incident angles. Attached Figure Description

[0012] Figure 1The image shown is a schematic cross-sectional view of an example of an optical filter according to one embodiment. Figure 2 The image shown is a schematic cross-sectional view of an example of an optical filter according to one embodiment. Figure 3 The image shown is a schematic cross-sectional view of an example of an optical filter according to one embodiment. Figure 4 The figure shows the spectral transmittance curves of the first thin film stack structure 1-4. Figure 5 The image shows the spectral reflectance curves of the first thin film stacked structure 1-4. Figure 6 The image shows the spectral transmittance curves of the first thin film stack structure 1-5. Figure 7 The image shows the spectral reflectance curves of the first thin film stacked structure 1-5. Figure 8 The figure shows the spectral transmittance curve of the second thin film stack structure 2-1. Figure 9 The figure shows the spectral reflectance curve of the second thin film stacked structure 2-1. Figure 10 The figure shows the spectral transmittance curve of the second thin film stack structure 2-2. Figure 11 The figure shows the spectral reflectance curve of the second thin film stack structure 2-2. Figure 12 The figure shows the spectral transmittance curve of the optical filter in Example 3-1. Figure 13 The figure shows the spectral transmittance curve of the optical filter in Example 3-2. Figure 14 The figure shows the spectral transmittance curve of the optical filter in Example 3-3. Figure 15 The figure shows the spectral transmittance curve of the optical filter in Example 3-4. Figure 16 The figure shows the spectral transmittance curve of the optical filter in Example 3-5. Figure 17 The figure shows the spectral transmittance curve of the optical filter in Example 3-6. Detailed Implementation

[0013] The embodiments of the present invention will now be described. In this manual, near-infrared absorbing pigments are sometimes abbreviated as "NIR pigments". In this specification, the compound represented by formula (I) is referred to as compound (I). The same applies to compounds represented by other formulas. The pigment composed of compound (I) is also referred to as pigment (I), and the same applies to other pigments. In addition, the group represented by formula (I) is also denoted as group (I), and the same applies to groups represented by other formulas.

[0014] In this specification, "restricted light transmission" means that the light transmittance is less than 5% when light of a specified wavelength is incident at an angle of 0 degrees (perpendicular incidence).

[0015] In this specification, internal transmittance refers to the transmittance obtained by subtracting the effect of interface reflection from the measured transmittance, as expressed by the formula {measured transmittance / (100-reflectance)}×100. In this specification, the transmittance of the substrate, including the transmittance of the resin film when the resin contains pigments, is referred to as "internal transmittance" even when described as such. The transmittance of the optical filter having a dielectric multilayer film is the measured transmittance.

[0016] In this specification, "transmittance of 90% or more for a specific wavelength region" means that the transmittance of the entire wavelength region is not less than 90%, i.e., the minimum transmittance of that wavelength region is 90% or more. Similarly, "transmittance of 1% or less for a specific wavelength region" means that the transmittance of the entire wavelength region is not greater than 1%, i.e., the maximum transmittance of that wavelength region is 1% or less. The same applies to internal transmittance. The average transmittance and average internal transmittance of a specific wavelength region are the sum of the transmittance and internal transmittance per 1 nm of that wavelength region. Optical properties can be measured using a UV-Vis spectrophotometer. In this specification, the "~" sign indicating a numerical range includes both the upper and lower limits.

[0017] <Optical Filters> The optical filter of the present invention comprises a substrate and two thin-film stacked structures that restrict the transmission of light in the near-infrared wavelength region. The substrate includes a resin film containing a pigment that absorbs light in the near-infrared wavelength region. The first thin-film stacked structure comprises at least two dielectric multilayer films and is stacked as the outermost layer on one main surface of the substrate, and the second thin-film stacked structure comprises at least one dielectric multilayer film and is stacked as the outermost layer on the other main surface of the substrate. That is, the optical filter of the present invention comprises at least three dielectric multilayer films. The first and second thin-film stacked structures respectively satisfy specific optical characteristics described later.

[0018] The first thin-film stacked structure is a composite of two or more dielectric multilayer films, which shifts the near-infrared light reflection region to eliminate ripple in the visible light region of each multilayer film. On the other hand, the first thin-film stacked structure experiences light leakage in a defined near-infrared wavelength region, specifically 850 nm to 950 nm. By utilizing the reflective properties of the second thin-film stacked structure and the absorption properties of the pigment contained in the resin film to block this light leakage, high visible light transmittance, high near-infrared light shielding, and reduced ripple in the visible light region are achieved for the overall optical filter. Furthermore, since the pigment can exert its absorption properties independently of the incident angle, by using a pigment that absorbs near-infrared light, the decrease in near-infrared light shielding caused by the incident angle dependence of the multilayer film can be compensated for.

[0019] The configuration example of this filter will be described using the accompanying drawings. Figures 1-3 The image shown is a schematic cross-sectional view of an example of an optical filter according to one embodiment.

[0020] Figure 1 The optical filter 1 shown has a first thin film stack structure 31 on one main surface of the substrate 10 and a second thin film stack structure 32 on the other main surface. Figure 1 In the first thin film laminate structure 31, there are dielectric multilayer films 31A and 31B. In addition, the substrate 10 also has a support 11 and a resin film 12 laminated on one main side of the support.

[0021] Figure 2 The optical filter 1 shown is an example where the substrate 10 does not have a support and is made of a resin film 12.

[0022] Figure 3 The optical filter 1 shown is an example of a first thin film stacked structure 31 having a dielectric multilayer film 31A, a dielectric multilayer film 31B and a dielectric multilayer film 31C.

[0023] <Thin Film Stacked Structure> The optical filter of the present invention has a first thin film stack structure and a second thin film stack structure that restrict the transmission of light in the near-infrared wavelength region, and each thin film stack structure is stacked as the outermost layer on two main surfaces of the substrate.

[0024] The first thin film stack structure is a composite having at least two dielectric multilayer films. The first thin film stack structure satisfies the following optical properties (i-1A) and (i-1B). (i-1A) Maximum transmittance T at an incident angle of 40° and wavelengths of 850nm to 950nm 850-950(40deg)MAX Above 5% (i-1B) Maximum reflectivity R at an incident angle of 40° and wavelengths of 450nm to 600nm 450-600(40deg)MAX Below 8%

[0025] The first thin-film stack structure is designed to shift the near-infrared light-reflecting region to eliminate ripple in the visible light region of two or more dielectric multilayer films. As a result, light leakage occurs in the near-infrared wavelength region. Optical properties (i-1A) indicate the wavelength region where light leakage occurs and the permissible degree of leakage. T 850-950(40deg)MAX More preferably, it is 6% or more; furthermore, it is preferably 30% or less; and even more preferably, it is 20% or less.

[0026] Meeting the optical characteristic (i-1B) indicates low reflectivity in the visible light region. This results in good transmittance in the visible light region. R 450-600(40deg)MAX More preferably, it should be below 7%.

[0027] The first thin film stack structure is further preferably satisfied with the following optical properties (i-1C). (i-1C) Average reflectance R at an incident angle of 40° and wavelengths of 1000nm to 1100nm 1000-1100(40deg)AVE Above 95% Satisfying optical properties (i-1C) indicates excellent shielding performance in the near-infrared region, particularly in the 1000nm–1100nm range.

[0028] The second thin film stack structure comprises at least one dielectric multilayer film. The second thin film stack structure satisfies the following optical properties (i-2A). (i-2A) Average reflectance R at an incident angle of 40° and wavelengths of 850nm to 950nm 850-950(40deg)AVE 25% to 60% Satisfying the optical properties (i-2A) means that the light that cannot be blocked due to light leakage from the first thin film stack can be blocked by the reflective properties of the second thin film stack. R 850-950(40deg)AVE At concentrations above 25%, it can effectively block light leakage occurring in the first thin-film stacked structure, while R 850-950(40deg)AVE At concentrations below 60%, it is possible to suppress the excessive physical thickness of dielectric multilayer films. 850-950(40deg)AVE Preferably, it is 30% to 55%.

[0029] The second thin film stack structure is further preferably designed to satisfy the following optical properties (i-2B). (i-2B) Average transmittance T at an incident angle of 0° and wavelengths of 450 nm to 600 nm 450-600(0deg)AVE Over 80% The optical properties satisfying (i-2B) indicate that high visible light transmittance can be achieved as an optical filter.450-600(0deg)AVE The preferred ratio is above 90%.

[0030] The second thin film stack structure is further preferably designed to satisfy the following optical properties (i-2C). (i-2C) Average reflectance R at an incident angle of 40° and wavelengths of 1000nm to 1100nm 1000-1100(40deg)AVE 25% to 60% Satisfying the optical properties (i-2C) indicates excellent shielding performance in the near-infrared region, particularly in the 1000nm–1100nm range.

[0031] The first and second thin-film stacked structures are constructed using dielectric multilayer films to limit the transmission of light within a desired wavelength range. The dielectric multilayer film is an optically functional film obtained by selecting and alternately stacking low-refractive-index dielectric films (low-refractive-index films), medium-refractive-index dielectric films (medium-refractive-index films), and high-refractive-index dielectric films (high-refractive-index films). Through design, it is possible to utilize light interference to transmit light in a specific wavelength range or to control the transmission limitation of light. Furthermore, low-refractive-index, high-refractive-index, and medium-refractive-index refer to high and low refractive indices relative to adjacent layers, as well as intermediate refractive indices.

[0032] The high refractive index film is preferably a film with a refractive index of 1.9 or higher, more preferably 1.9 to 2.6, at a wavelength of 500 nm. Examples of materials for high refractive index films include Ta2O5, TiO2, and Nb2O5. Among these, TiO2 is preferred considering factors such as film formation properties, reproducibility of refractive index, and stability.

[0033] The intermediate refractive index film is preferably a film with a refractive index of 1.5 to 2.1, more preferably 1.8 to 2.0, at a wavelength of 500 nm. Examples of materials for intermediate refractive index films include Al2O3, Y2O3, and ZrO2. Among these, considering stability and other factors, Al2O3, ZrO2, or a mixture of these two materials are preferred.

[0034] The low-refractive-index film is preferably a film with a refractive index of 1.8 or less, more preferably 1.3 to 1.6, at a wavelength of 500 nm. Examples of materials for low-refractive-index films include SiO2, MgF2, and SiO2. x N y Considering factors such as reproducibility, stability, and economy of film formation, SiO2 is preferred.

[0035] The second thin film stacked structure is a multilayer film composed of alternating layers of TiO2 and SiO2, and the film ratio represented by the following formula is preferably above 0.50. Film ratio (physical film thickness) = total physical film thickness of SiO2 / (total physical film thickness of TiO2 + total physical film thickness of SiO2). With this configuration, the second thin-film laminate structure can achieve reflectivity of 850–950 nm, specifically a reflectivity of 25–60% at an incident angle of 40°. A film ratio of 0.55 or higher is more preferable, and 0.60–0.70 is even more preferable. Furthermore, the physical film thickness can be measured using a stylus-type surface shape measuring instrument (Dektak150, manufactured by Vacuum Corporation).

[0036] When a thin-film laminated structure is composed of alternating layers of thin films with different refractive indices, the number of layers depends on the optical properties of the dielectric multilayer film. However, the total number of layers is preferably 50 to 150. If the total number of layers is 50 or more, the blocking performance at wavelengths of 800 nm to 1000 nm is sufficient. If the total number of layers is less than 150, the cycle time for fabricating the optical filter is short, and warping of the optical filter caused by the dielectric multilayer film is less likely to occur, which is therefore preferable. Furthermore, from the viewpoint of obtaining high light-shielding performance in the near-infrared region, the total number of layers in the first thin film laminate structure is preferably 20 to 150, more preferably 20 to 50. From the viewpoint of mass production, the total number of layers in the second thin film laminate structure is preferably 50 or less, more preferably less than 20.

[0037] As for the physical film thickness of the thin film stacked structure, under the premise of satisfying the above-mentioned preferred number of stacks, from the viewpoint of making the optical filter thinner, thinness is preferred. The physical film thickness of the first thin film stack structure is preferably 3 μm or more from the viewpoint of obtaining the desired optical properties, and preferably 15 μm or less from the viewpoint of suppressing the warping of the optical filter. The film thickness of the second thin film stack structure is preferably less than 3 μm from the viewpoint of suppressing the formation of wrinkles in the resin layer, and more preferably less than 2.5 μm.

[0038] The first and second thin-film laminates can be laminated on any main surface of the substrate, but the second thin-film laminate is preferably laminated on the surface of the resin film of the substrate. The second thin-film laminate, with fewer dielectric multilayers, has a smaller number of layers than the first thin-film laminate. The resin film in contact with the thin-film laminate experiences stronger stress as the number of film layers increases. When the stress from the thin-film laminate is high, heat during assembly processes such as reflow can cause the resin film to wrinkle when the resin softens, resulting in appearance quality problems. By laminating a thin-film laminate with a smaller number of layers onto the surface of the resin film, the stress on the resin film is reduced, and wrinkle formation can be suppressed, making this method preferable.

[0039] Thin film stacked structures can be formed using dry film deposition processes such as IAD (ion-assisted deposition), CVD, sputtering, and vacuum evaporation, or wet film deposition processes such as spraying and immersion.

[0040] <Substrate> In the optical filter of the present invention, the substrate has a resin film comprising a pigment (IR) that absorbs light in the near-infrared wavelength region and a resin. Utilizing the absorption characteristics of the pigment (IR), light leakage in the near-infrared wavelength region occurring at the first thin film stack structure can be blocked. Furthermore, utilizing the absorption characteristics of the pigment (IR), the pigment can compensate for the decrease in near-infrared light shielding caused by the incident angle dependence of the multilayer film.

[0041] The resin film preferably satisfies all of the following optical properties (ii-1) to (ii-3). (ii-1) Average internal transmittance T at an incident angle of 0° and wavelengths of 850 nm to 950 nm 850-950(0deg)AVE 60-90% (ii-2) Average internal transmittance T at an incident angle of 30° and wavelengths of 850 nm to 950 nm 850-950(30deg)AVE 60-90% (ii-3) Average internal transmittance T at an incident angle of 40° and wavelengths of 850nm to 950nm 850-950(40deg)AVE 60-90%

[0042] Satisfying optical properties (ii-1) to (ii-3) means that under the incident angle condition where light leakage occurs at the first thin film stack structure and in the wavelength region, the absorption characteristics of the pigment (IR) can still be used for light blocking.

[0043] T 850-950(0deg)AVE More preferably, it is 70% to 90%. T 850-950(30deg)AVE More preferably, it is 70% to 90%. T 850-950(40deg)AVE More preferably, it is 70% to 90%.

[0044] The resin film preferably further satisfies the following optical properties (ii-4). (ii-4) Average internal transmittance T at an incident angle of 30° and wavelengths of 660nm to 730nm 660-730(30deg)AVE Below 10% The wavelength range of 660 nm to 730 nm is a region in the near-infrared light region that is close to the boundary with the visible light region. This region is prone to a decrease in reflectivity at high incident angles (oblique incident displacement) due to the incident angle dependence of dielectric multilayer films. Satisfying optical properties (ii-4) means that the absorption characteristics of pigments can be used to block near-infrared light that cannot be completely reflected by dielectric multilayer films. 660-730(30deg)AVE More preferably, it should be below 20%.

[0045] The resin film preferably further satisfies the following optical properties (ii-5). (ii-5) Average internal transmittance T at an incident angle of 0° and wavelengths of 450–600 nm 450-600(0deg)AVE Above 70% Meeting optical property (ii-5) indicates that the resin film has high visible light transmittance. 450-600(0deg)AVE More preferably, it should be above 60%.

[0046] As a pigment that absorbs light in the near-infrared wavelength region (IR), it is preferable to use a pigment in the resin constituting the resin film that has the maximum absorption wavelength in the 570–950 nm range. Using such a pigment can effectively block near-infrared light.

[0047] Examples of pigments (IR) include squaric acid cyanine pigments, anthocyanin pigments, phthalocyanine pigments, naphthyl phthalocyanine pigments, dithiol metal complex pigments, azo pigments, polymethystyl pigments, phthalophthalic acid pigments, naphthoquinone pigments, anthraquinone pigments, indophenol pigments, pyranonium pigments, thiopyranonium pigments, ketone acid pigments, tetradehydrocholine pigments, triphenylmethane pigments, imine pigments, and diimine pigments. From the perspective of spectroscopic properties, succinic acid pigment and anthocyanin pigment are preferred, while from the perspective of durability, phthalocyanine pigment is preferred. Furthermore, as a pigment (IR), it can be composed of one compound or contain two or more compounds.

[0048] The content of NIR pigment (IR) in the resin film is preferably 0.1 to 30 parts by weight, more preferably 0.1 to 15 parts by weight, relative to 100 parts by weight of the resin. Furthermore, when two or more compounds are combined, the above content refers to the sum of the contents of each compound.

[0049] Without impairing the effects of the present invention, the resin film may also contain other pigments, such as ultraviolet light absorbing pigments. Examples of ultraviolet-absorbing pigments include oxazole pigments, anthocyanins, naphthalimide pigments, oxadiazole pigments, oxazine pigments, oxazolidinyl pigments, naphthalenedicarboxylic acid pigments, styryl pigments, anthracene pigments, cyclic carbonyl pigments, and triazole pigments. Among these, anthocyanins are particularly preferred.

[0050] The substrate of this filter can be a single-layer structure or a multi-layer structure. Furthermore, the material used as the substrate can be any transparent material that transmits visible light; it can be organic or inorganic, with no particular limitations. When the substrate has a single-layer structure, a resin substrate composed of a resin film containing resin and NIR pigment (IR) is preferred. When the substrate has a multilayer structure, it is preferable to have a composite substrate formed by laminating a resin film containing NIR pigment (IR) on at least one main surface of the support. In this case, the support is preferably made of transparent resin or transparent inorganic material.

[0051] As for the resin, there are no particular limitations as long as it is a transparent resin. One or more transparent resins selected from polyester resin, acrylic resin, epoxy resin, ethimide resin, polycarbonate resin, polyether resin, polyacrylate resin, polysulfone resin, polyethersulfone resin, poly(p-phenylene) resin, polyaryl 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 can be used alone or in mixtures of two or more. Among these factors, polyimide resin is preferred due to its excellent pigment solubility, low UV absorption, high glass transition temperature (Tg), and excellent adhesion to the support or dielectric multilayer film.

[0052] When using multiple compounds as NIR pigments (IR) or other pigments, these compounds may be contained in the same resin film or in different resin films.

[0053] As a transparent inorganic material, glass or crystalline materials are preferred. Examples of glasses that can be used as supports include copper-containing absorbing glasses (near-infrared absorbing glasses) such as fluorophosphate glasses or phosphate glasses, soda-lime glass, borosilicate glass, alkali-free glass, and quartz glass. From the viewpoint of being able to absorb infrared light (especially 900–1200 nm), phosphate glasses and fluorophosphate glasses are preferred as glass. In addition, "phosphate glasses" also include silicate phosphate glasses in which a portion of the glass framework is composed of SiO2.

[0054] As a type of glass, chemically strengthened glass can be used, which is obtained by exchanging alkali metal ions with small ionic radii (such as Li ions and Na ions) present on the main surface of the glass plate with alkali metal ions with large ionic radii (such as exchanging Na ions or K ions for Li ions, and exchanging K ions for Na ions) at a temperature below the glass transition temperature.

[0055] Examples of crystalline materials that can be used as supports include quartz, lithium niobate, and sapphire, among other multi-refractive crystals.

[0056] As a support, inorganic materials are preferred from the perspective of shape stability related to long-term reliability such as optical and mechanical properties, as well as from the perspective of operability when manufacturing filters. Glass and sapphire are particularly preferred.

[0057] The resin film is formed by dissolving or dispersing pigments (IR), resin or resin raw material components, and other components as needed, in a solvent to prepare a coating solution, which is then coated onto a support, dried, and cured as needed. The support can be the support included in this filter, or it can be a peelable support used only during the formation of the resin film. Furthermore, the solvent can be any dispersant that can stably disperse the resin or a solvent that can dissolve it.

[0058] Furthermore, the coating liquid may contain surfactants to improve pores caused by tiny bubbles, depressions caused by the adhesion of foreign matter, and small holes in the drying process. Furthermore, the coating liquid can be applied using methods such as dip coating, mold coating, or spin coating. A resin film is formed by applying the coating liquid onto a support and then allowing it to dry. In addition, if the coating liquid contains a transparent resin component, further curing treatments such as thermosetting or photocuring are performed.

[0059] Furthermore, resin films can also be manufactured into a film shape by extrusion molding. When the substrate is a single-layer structure (resin substrate) consisting of a resin film containing pigment (IR), the resin film can be used directly as the substrate. When the substrate is a multilayer structure (composite substrate) having a support and a resin film containing pigment (IR) laminated on at least one main surface of the support, the substrate can be manufactured by laminating the film onto the support and integrating it through heat pressing or the like.

[0060] Resin film can be one layer or two or more layers in an optical filter. When there are two or more layers, the layers can have the same composition or different compositions.

[0061] The thickness of the resin film is preferably 20 to 150 μm when the substrate is a single-layer structure (resin substrate) consisting of a resin film containing pigment (IR). When the substrate is a multilayer structure (composite substrate) having a support and a resin film containing pigment (IR) laminated on at least one main surface of the support, the thickness of the resin film is preferably 0.3 to 20 μm. Furthermore, when the optical filter has two or more resin films, the total thickness of each resin film is preferably within the above range.

[0062] The shape of the substrate is not particularly limited; it can be block-shaped, plate-shaped, or film-shaped. Furthermore, from the viewpoint of reducing warpage during the formation of dielectric multilayer films and minimizing the height of optical components, the thickness of the substrate is preferably 300 μm or less. In the case of a resin substrate composed of a resin film, it is preferably 50 to 300 μm. In the case of a composite substrate having a support and a resin film, it is preferably 50 to 300 μm.

[0063] <Optical Filters (Optical Properties)> The optical filter of the present invention configured as described above preferably satisfies all of the following optical characteristics (iii-1) to (iii-5). (iii-1) Average transmittance T at an incident angle of 0° and wavelengths of 400–600 nm 400-600(0deg)AVE Above 70% (iii-2) Average reflectance R at an incident angle of 40° and wavelengths of 450–600 nm 450-600(40deg)AVE Below 5% (iii-3) Average reflectance R at an incident angle of 5° and wavelengths of 450–600 nm 450-600(5deg)AVE Below 3% (iii-4) Maximum transmittance T at an incident angle of 40° and wavelengths of 700–900 nm 700-900(40deg)MAX Below 15% (iii-5) Average transmittance T at an incident angle of 40° and wavelengths of 1000–1100 nm 1000-1100(40deg)AVE Below 5%

[0064] The optical filter of the present invention, which satisfies all of the optical characteristics (iii-1) to (iii-5), is an optical filter that has high transmittance of visible light and high shielding of near-infrared light, and suppresses ripple in the visible light region even at high incident angles.

[0065] Satisfying optical property (iii-1) indicates excellent transmittance in the visible light region of 400–600 nm. 400-600(0deg)AVE The preferred ratio is above 72%.

[0066] Satisfying optical characteristic (iii-2) means having low ripple in the visible light region with wavelengths of 450–600 nm. R 450-600(40deg)AVE Preferably below 4%.

[0067] Satisfying optical characteristic (iii-3) indicates low ripple in the visible light region. R 450-600(5deg)AVE Preferably below 2.5%.

[0068] Meeting optical property (iii-4) indicates excellent shielding performance even at high incident angles in the near-infrared region of 700–900 nm. 700-900(40deg)MAXPreferably below 14%.

[0069] Satisfying optical properties (iii-5) indicates excellent shielding performance even at high incident angles in the near-infrared region of 1000–1100 nm. 1000-1100(40deg)AVE Preferably below 4.5%.

[0070] The optical filter of the present invention preferably further satisfies the following optical properties (iii-6). (iii-6) Maximum transmittance T at an incident angle of 40° and wavelengths of 850 nm to 950 nm 850-950(40deg)MAX Below 20% Satisfying optical property (iii-6) means that the permissible light leakage at the first thin film stack structure is blocked by the optical filter. T 850-950(40deg)MAX Preferably below 15%.

[0071] When the optical filter of the present invention is used, for example, in imaging devices such as digital cameras, it can provide an imaging device with excellent color reproduction. This imaging device includes a solid imaging element, an imaging lens, and the optical filter of the present invention. The optical filter of the present invention can be used, for example, disposed between the imaging lens and the solid imaging element, or directly adhered to the solid imaging element, imaging lens, etc., of the imaging device via an adhesive layer. Example

[0072] The present invention will be further described in detail below through examples. Each optical property was verified using optical thin film simulation software (TFCalc, Software Spectra). This application uses the refractive index of each film at a wavelength of 500 nm as a representative value, but simulations were performed to take into account the wavelength dependence of the refractive index. In addition, unless otherwise specified, the optical characteristics are simulated values ​​at an incident angle of 0 degrees (perpendicular to the main surface of the optical filter).

[0073] The pigments used in each case are as follows. Compound 1 (cyanide compound): synthesized according to Dyes and pigments 73 (2007) 344-352. Compound 2 (squamousine pigment): synthesized according to the description in U.S. Patent Application Publication No. 2014 / 0061505 and International Publication No. 2014 / 088063. Compound 3 (partial cyanide compound): synthesized with reference to Japanese Patent No. 6504176.

[0074]

Chemistry 1

[0075] <Example 1-1: Resin Film> The polyimide resin (C-3G30G manufactured by Mitsubishi Gas Chemical Co., Ltd.) was dissolved in an organic solvent (cyclohexanone) at a concentration of 10% by mass. Add 0.05 parts by weight of compound 1, 2.76 parts by weight of compound 2, and 11.7 parts by weight of compound 3 relative to 100 parts by weight of the resin to the above-prepared polyimide resin solution, heat to 50°C, and stir for 2 hours. Spin-coat the pigmented resin solution onto a glass substrate (alkali glass, Schott AG D263), and heat thoroughly to dry to obtain a resin film (coated film) with a thickness of 5 μm.

[0076] <Example 1-2: Resin Film> The resin film was obtained in the same manner as in Example 1-1, except that 0.44 parts by mass of compound 1, 2.76 parts by mass of compound 2, and 11.7 parts by mass of compound 3 were added relative to 100 parts by mass of the resin.

[0077] Transmission and reflection spectrometry of each resin film were measured using a spectrophotometer within the wavelength range of 350 nm to 1200 nm at an incident direction of 5 degrees relative to the incident direction. The internal transmittance curves were calculated using the obtained transmittance and reflectance curves, and the results were standardized to a transmittance of 10% at the maximum absorption wavelength. Internal transmittance (%) = transmittance / (100 - reflectance) * 100 The optical properties are shown in Table 1, which is described later. In addition, Examples 1-1 and 1-2 are for reference only.

[0078] <Example 2-1: Thin Film Laminated Structure 1-1> A thin film stack structure 1-1 was designed by combining three dielectric multilayer films with different stack numbers and physical film thicknesses, consisting of alternating layers of TiO2, SiO2, and ZrO2 films. The stack numbers and physical film thicknesses are shown in Table 1 below.

[0079] <Example 2-2: Thin Film Laminated Structure 1-2> Two dielectric multilayer films with different stack numbers and physical film thicknesses, formed by alternating layers of TiO2 and SiO2 films, were designed to create thin film stack structures 1-2. The stack numbers and physical film thicknesses are shown in Table 1 below.

[0080] <Example 2-3: Thin Film Laminated Structure 1-3> Except for the number of TiO2 and SiO2 films and their physical film thicknesses as shown in Table 1 below, thin film stack structures 1-3 were designed in the same manner as in Example 2-2.

[0081] <Example 2-4: Thin Film Laminated Structure 1-4> Except for the number of TiO2 and SiO2 films and their physical film thicknesses as shown in Table 1 below, thin film stack structures 1-4 were designed in the same manner as in Example 2-2.

[0082] <Example 2-5: Thin Film Laminated Structure 1-5> Referring to Example 4 of Japanese Patent Application Publication No. 2007-183525, thin film stacked structures 1-5, consisting of alternating layers of TiO2, La2O3, and Al2O3 films, were designed. The number of each layer is shown in Table 1 described later.

[0083] <Example 2-6: Thin Film Laminated Structure 2-1> A thin film stack structure consisting of alternating TiO2 and SiO2 films and composed of dielectric multilayer films was designed 2-1. The number of layers and physical film thickness are shown in Table 1 below.

[0084] <Example 2-2: Thin Film Laminated Structure 2-2> Referring to Example 4 of Japanese Patent Application Publication No. 2007-183525, a thin film stacked structure 2-1 composed of alternating TiO2 and SiO2 films and made up of dielectric multilayer films was designed. The number of layers is shown in Table 1 described later.

[0085] The optical properties of thin film laminates 1-1 to 1-5 and thin film laminates 2-1 to 2-2 are shown in Table 1 below. Furthermore, the spectral transmittance and spectral reflectance curves of thin film laminates 1-4, 1-5 and thin film laminates 2-1, 2-2 are shown in the figures. Figures 4-11 . In addition, Examples 2-1 to 2-7 are for reference.

[0086] <Example 3-1: Optical Filters> An optical filter is obtained by stacking the resin film and thin film laminate structure 2-1 of Example 1-1 on one main surface of a glass substrate (alkali glass, D263 manufactured by Schott AG) and stacking the thin film laminate structure 1-1 on the other main surface.

[0087] <Example 3-2: Optical Filters> Except for replacing the thin film stacked structure 1-1 with the thin film stacked structure 1-2, an optical filter was obtained in the same manner as in Example 3-1.

[0088] <Example 3-3: Optical Filters> Except for replacing the thin film stacked structure 1-1 with the thin film stacked structure 1-3, an optical filter was obtained in the same manner as in Example 3-1.

[0089] <Example 3-4: Optical Filters> Except for replacing the thin film laminate structure 1-1 with the thin film laminate structure 1-3 and replacing the resin film of Example 1-1 with the resin film of Example 1-2, the optical filter was obtained in the same manner as in Example 3-1.

[0090] <Example 3-5: Optical Filters> Except for replacing the thin film stacked structure 1-1 with the thin film stacked structure 1-4, an optical filter was obtained in the same manner as in Example 3-1.

[0091] <Example 3-6: Optical Filters> Referring to Example 4 of Japanese Patent Application Publication No. 2007-183525, a thin film laminate structure 2-2 is laminated on one main surface of a glass substrate, and a thin film laminate structure 1-5 is laminated on the other main surface to obtain an optical filter.

[0092] For each optical filter obtained, the transmission spectral density at incident directions of 0deg and 40deg was measured using a spectrophotometer, and the reflection spectral density at incident direction of 5deg was also measured. The optical properties are shown in the table below. Furthermore, the spectral transmittance curves of optical filters 3-1 to 3-6 are shown in the figure. Figures 12-17 . In addition, Examples 3-1 to 3-5 are examples, and Example 3-6 is a comparative example.

[0093] In addition, the wrinkles of the optical filter were evaluated using the following method. The wrinkle evaluation involves placing the optical filter in an electric furnace set at 160°C and heating it for 10 minutes. After removing it from the furnace, it is allowed to cool to room temperature. Next, the central part of the optical filter is observed using an optical microscope to confirm the presence or absence of wrinkles. Cases with visually identifiable wrinkles are marked as ×, and cases without visually identifiable wrinkles are marked as 0. The results are shown in Table 1.

[0094] [Table 1] Table 1

[0095] The results above show that optical filters 3-1 to 3-5 have high transmittance of visible light and high shielding properties for near-infrared light. Ripple generation in the visible light region at high incident angles is suppressed, and the decrease in shielding properties in the near-infrared light region at high incident angles is also suppressed. Consequently, wrinkle generation in the resin film is also suppressed. On the other hand, the optical filters 3-6, which are two types of multilayer films and do not use pigments in combination, produce ripples in the visible light region at high incident angles. In addition, the transmission characteristics shift at high incident angles, resulting in a decrease in the shielding properties in the near-infrared region.

[0096] The present invention has been described in detail or with reference to specific embodiments; however, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2020-217100, filed on December 25, 2020, the contents of which are incorporated herein by reference. Industrial applications

[0097] The optical filter of this invention exhibits excellent visible light transmittance and suppresses the decrease in near-infrared light shielding at high incident angles. It can be used in information acquisition devices such as cameras or sensors for transport aircraft, where high performance has been continuously developing in recent years. Symbol Explanation

[0098] 1…Optical filter, 10…Substrate, 11…Support, 12…Resin film, 31…First thin film laminate, 31A, 31B, 31C…Dielectric multilayer film, 32…Second thin film laminate

Claims

1. An optical filter comprising: Substrate, and A first thin-film stacked structure and a second thin-film stacked structure that restrict the transmission of light in the near-infrared wavelength region. in, The substrate comprises a resin film containing pigments that absorb light in the near-infrared wavelength region. The first thin-film laminate structure comprises at least two dielectric multilayer films and is laminated as the outermost layer on one main surface of the substrate. The second thin film laminate structure comprises at least one dielectric multilayer film and is laminated as the outermost layer on another main surface of the substrate. The second thin film laminate structure is stacked on the surface of the resin film. The first thin film stacked structure satisfies the following optical properties (i-1A) and (i-1B), The second thin film stack structure satisfies the following optical properties (i-2A): (i-1A) The maximum transmittance at an incident angle of 40° and a wavelength of 850nm to 950nm is above 5%; (i-1B) The maximum reflectivity at an incident angle of 40° and wavelengths of 450nm to 600nm is below 8%; (i-2A) The average reflectance at an incident angle of 40° and wavelengths of 850nm to 950nm is 25% to 60%.

2. The optical filter as described in claim 1, wherein, The resin film satisfies all of the following optical properties (ii-1) to (ii-3): (ii-1) The average internal transmittance at an incident angle of 0° and a wavelength of 850 nm to 950 nm is 60% to 90%. (ii-2) The average internal transmittance at an incident angle of 30° and a wavelength of 850 nm to 950 nm is 60 to 90%. (ii-3) The average internal transmittance at an incident angle of 40° and wavelengths of 850 nm to 950 nm is 60% to 90%.

3. The optical filter as described in claim 1 or claim 2, wherein, The resin film further satisfies the following optical properties (ii-4): (ii-4) The average internal transmittance at an incident angle of 30° and wavelengths of 660nm to 730nm is less than 10%.

4. The optical filter as claimed in claim 1 or claim 2, wherein, The resin film further satisfies the following optical properties (ii-5): (ii-5) The average internal transmittance at an incident angle of 0° and a wavelength of 450–600 nm is above 70%.

5. The optical filter as claimed in claim 1 or claim 2, wherein, The second thin film stacked structure has a dielectric multilayer film formed by alternating layers of TiO2 and SiO2, and the film ratio represented by the following formula is greater than 0.50: Film ratio (physical film thickness) = total physical film thickness of SiO2 / (total physical film thickness of TiO2 + total physical film thickness of SiO2).

6. The optical filter as claimed in claim 1 or claim 2, wherein, The resin film comprises a polyimide resin.

7. The optical filter as described in claim 1 or claim 2, which satisfies all of the following optical properties (iii-1) to (iii-5): (iii-1) The average transmittance at an incident angle of 0° and a wavelength of 400–600 nm is above 70%; (iii-2) The average reflectivity at an incident angle of 40° and a wavelength of 450–600 nm is less than 5%; (iii-3) The average reflectivity at an incident angle of 5° and a wavelength of 450–600 nm is less than 3%; (iii-4) The maximum transmittance at an incident angle of 40° and a wavelength of 700–900 nm is less than 15%; (iii-5) The average transmittance at an incident angle of 40° and a wavelength of 1000-1100nm is less than 5%.

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