Optical Filters

Abstract

The present invention pertains to an optical filter that comprises: a base material including a resin film that contains a dye that absorbs near-infrared light; and a first thin film laminated structure and a second thin film laminated structure that limit the passage of near-infrared light. The first thin film laminated structure includes at least two dielectric multilayer films and is laminated on one main surface side of the base material, as an outermost layer. The second thin film laminated structure includes at least one dielectric multilayer film and is laminated on the other main surface side of the base material, as the outermost layer. The first thin film laminated structure fulfills specified optical characteristics (i–1A) and (i–1B). The second thin film laminated structure fulfills specified optical characteristics (i–2A).

Description

[Technical Field]

[0001] The present invention relates to optical filters. [Background technology]

[0002] In order to reproduce color tones well and obtain clear images, imaging devices using solid-state imaging elements use optical filters that transmit light in the visible range (hereinafter also referred to as "visible light") and block light in the near-infrared wavelength range (hereinafter also referred to as "near-infrared light").

[0003] Such optical filters include various types, such as a reflective filter in which dielectric thin films with different refractive indices are alternately stacked on one or both sides of a transparent substrate (dielectric multilayer film), and the filter utilizes optical interference to reflect light that is to be blocked.

[0004] Optical filters that block near-infrared light are required to block a wide wavelength range from 750 to 1200 nm, but it is technically difficult to cover this range with a single type of multilayer film. Therefore, it is known to use a combination of multiple dielectric multilayer films with different near-infrared light reflection ranges (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2007-183525 Summary of the Invention [Problem to be solved by the invention]

[0006] In dielectric multilayer films, ripples, or large changes in transmittance, occur due to interference caused by reflected light at the interfaces of each layer depending on the number of layers stacked in the multilayer film, and it is known that these ripples tend to occur more strongly the greater the angle of incidence of light.

[0007] When a dielectric multilayer film is combined to block a wide range of light in the near-infrared region, as in the optical filter described in Patent Document 1, there is a risk that ripples in the visible light region will not cancel each other out and will be amplified.

[0008] Furthermore, the dielectric multilayer film constituting the thin film laminated structure has so-called incident angle dependency, in which the light transmission characteristics shift to the shorter wavelength side as the incident angle of light increases. Therefore, in the near-infrared light region near the border with the visible light region, where the transmittance of the multilayer film changes abruptly, there is a risk that the reflection characteristics will deteriorate under high incident angle conditions.

[0009] The present invention aims to provide an optical filter that has high transmittance for visible light and high blocking ability for near-infrared light, and that suppresses the generation of ripples in the visible light region and the decrease in blocking ability in the near-infrared light region even at high angles of incidence. [Means for solving the problem]

[0010] In the present invention, a thin film laminate structure is used in which two or more multilayer films are combined by shifting the near-infrared light reflection regions so that ripples in the visible light region are canceled out. However, in such a structure, gaps are generated where the near-infrared light reflection regions of each multilayer film overlap, making light leakage more likely, and this is particularly likely at high incident angles due to the incidence angle dependence of the dielectric multilayer film. Therefore, it has been discovered that the above problem can be solved by further providing a thin film laminate structure that reflects light in the wavelength region where light leakage occurs and by using a dye that absorbs light in that wavelength region. That is, the present invention provides an optical filter having the following configuration. [1] A substrate, a first thin film stack structure and a second thin film stack structure that limit the transmission of light in the near infrared wavelength range; An optical filter comprising: the substrate includes a resin film containing a dye that absorbs light in the near-infrared wavelength region; 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 base material, 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 base material, The first thin film stack structure satisfies the following optical properties (i-1A) and (i-1B), The second thin film stack structure satisfies the following optical property (i-2A): Optical filters. (i-1A) Maximum transmittance of 5% or more at wavelengths of 850nm to 950nm at an incident angle of 40° (i-1B) Maximum reflectance of 8% or less at wavelengths of 450nm to 600nm at an incident angle of 40° (i-2A) Average reflectance of 25% to 60% at wavelengths of 850nm to 950nm at an incident angle of 40° [2] The optical filter according to [1], wherein the resin film satisfies all of the following optical properties (ii-1) to (ii-3): (ii-1) The average internal transmittance at wavelengths of 850 nm to 950 nm at an incident angle of 0° is 60 to 90% (ii-2) Average internal transmittance of 60-90% at wavelengths of 850nm to 950nm at an incident angle of 30° (ii-3) The average internal transmittance at wavelengths of 850 nm to 950 nm at an incident angle of 40° is 60 to 90% [3] The optical filter according to [1] or [2], wherein the resin film further satisfies the following optical characteristic (ii-4): (ii-4) The average internal transmittance at wavelengths of 660 nm to 730 nm at an incident angle of 30° is 10% or less [4] The optical filter according to any one of [1] to [3], wherein the second thin film laminated structure is laminated on the surface of the resin film. [5] The optical filter according to any one of [1] to [4], wherein the resin film further satisfies the following optical characteristic (ii-5): (ii-5) The average internal transmittance of the wavelength of 450 to 600 nm at an incident angle of 0° is 70% or more [6] An optical filter described in any one of [1] to [5], wherein the second thin film stack structure has a dielectric multilayer film in which TiO2 and SiO2 are alternately stacked, and the film ratio shown in 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] The optical filter according to any one of [1] to [6], wherein the resin film contains a polyimide resin. [8] The optical filter according to any one of [1] to [7], which satisfies all of the following optical properties (iii-1) to (iii-5): (iii-1) Average transmittance at an incident angle of 0° in the wavelength range of 400 to 600 nm is 70% or more (iii-2) Average reflectance at wavelengths of 450 to 600 nm at an incident angle of 40° is 5% or less (iii-3) The average reflectance at an incident angle of 5° in the wavelength range of 450 to 600 nm is 3% or less (iii-4) The maximum transmittance at an incident angle of 40° in the wavelength range of 700 to 900 nm is 15% or less (iii-5) Average transmittance at wavelengths of 1000 to 1100 nm at an incident angle of 40° is 5% or less [Effects of the Invention]

[0011] According to the present invention, an optical filter can be provided which has high transmittance for visible light and high blocking ability for near-infrared light, and which suppresses the generation of ripples in the visible light region and the decrease in blocking ability in the near-infrared light region even at high angles of incidence. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating an example of an optical filter according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically illustrating an example of an optical filter according to an embodiment. [Figure 3] FIG. 3 is a cross-sectional view schematically illustrating an example of an optical filter according to an embodiment. [Figure 4] FIG. 4 is a diagram showing the spectral transmittance curve of the first thin film laminated structure 1-4. [Figure 5] FIG. 5 is a diagram showing the spectral reflectance curve of the first thin film laminated structure 1-4. [Figure 6]FIG. 6 is a diagram showing the spectral transmittance curve of the first thin film laminated structure 1-5. [Figure 7] FIG. 7 is a diagram showing the spectral reflectance curve of the first thin film laminated structure 1-5. [Figure 8] FIG. 8 is a diagram showing the spectral transmittance curve of the second thin film laminated structure 2-1. [Figure 9] FIG. 9 is a diagram showing the spectral reflectance curve of the second thin film laminated structure 2-1. [Figure 10] FIG. 10 is a diagram showing the spectral transmittance curve of the second thin film laminated structure 2-2. [Figure 11] FIG. 11 is a diagram showing the spectral reflectance curve of the second thin film laminated structure 2-2. [Figure 12] FIG. 12 is a diagram showing the spectral transmittance curve of the optical filter of Example 3-1. [Figure 13] FIG. 13 is a diagram showing the spectral transmittance curve of the optical filter of Example 3-2. [Figure 14] FIG. 14 is a diagram showing the spectral transmittance curve of the optical filter of Example 3-3. [Figure 15] FIG. 15 is a diagram showing the spectral transmittance curve of the optical filter of Example 3-4. [Figure 16] FIG. 16 is a diagram showing the spectral transmittance curve of the optical filter of Example 3-5. [Figure 17] FIG. 17 is a diagram showing the spectral transmittance curve of the optical filter of Example 3-6. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described. In this specification, the near-infrared absorbing dye may be abbreviated as "NIR dye." In this specification, a compound represented by formula (I) is referred to as compound (I). The same applies to compounds represented by other formulas. A dye consisting of compound (I) is also referred to as dye (I), and the same applies to other dyes. Furthermore, a group represented by formula (I) is also referred to as group (I), and the same applies to groups represented by other formulas.

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

[0015] In this specification, the internal transmittance is the transmittance obtained by subtracting the influence of interface reflection from the measured transmittance, as expressed by the formula {measured transmittance / (100-reflectance)}×100. In this specification, the transmittance of a substrate and the transmittance of a resin film, including a resin containing a dye, are all "internal transmittance" even when they are referred to as "transmittance." On the other hand, the transmittance of an optical filter having a dielectric multilayer film is an actually measured transmittance.

[0016] In this specification, for example, a transmittance of 90% or more in a specific wavelength range means that the transmittance is not less than 90% across the entire wavelength range, i.e., the minimum transmittance is 90% or more across the wavelength range. Similarly, for example, a transmittance of 1% or less in a specific wavelength range means that the transmittance is not more than 1% across the entire wavelength range, i.e., the maximum transmittance is 1% or less across the wavelength range. The same applies to internal transmittance. The average transmittance and average internal transmittance in a specific wavelength range are the arithmetic mean of the transmittance and internal transmittance per 1 nm in the wavelength range. The optical properties can be measured using a UV-visible spectrophotometer. In this specification, the use of "to" to indicate a range of values ​​includes the upper and lower limits.

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

[0018] The first thin film stack structure is a composite of two or more dielectric multilayer films, and the near-infrared light reflection region is shifted so that the ripples in the visible light region of each multilayer film cancel each other out. Meanwhile, the first thin film stack structure exhibits light leakage in a predetermined near-infrared wavelength region, specifically, the wavelength region of 850 nm to 950 nm. This light leakage is blocked by the reflective properties of the second thin film stack structure and the absorption properties of the dye contained in the resin film, thereby achieving high visible light transmittance, high near-infrared light blocking properties, and reduced ripple in the visible light region for the entire optical filter. Furthermore, because dyes exhibit absorption properties independent of incident angle dependence, using a dye that absorbs near-infrared light can compensate for the reduced near-infrared light blocking properties of the multilayer film due to the incident angle dependence of the multilayer film.

[0019] An example of the configuration of the present filter will be described with reference to the drawings. Figures 1 to 3 are cross-sectional views that schematically show an example of an optical filter according to an embodiment.

[0020] The optical filter 1 shown in Fig. 1 has a first thin film stacked structure 31 on one main surface of a substrate 10 and a second thin film stacked structure 32 on the other main surface. In Fig. 1, the first thin film stacked structure 31 has a dielectric multilayer film 31A and a dielectric multilayer film 31B. The substrate 10 also has a support 11 and a resin film 12 stacked on one main surface of the support.

[0021] The optical filter 1 shown in FIG. 2 is an example in which the substrate 10 is made of a resin film 12 without a support.

[0022] The optical filter 1 shown in FIG. 3 is an example in which the first thin film stack structure 31 has a dielectric multilayer film 31A, a dielectric multilayer film 31B, and a dielectric multilayer film 31C.

[0023] <Thin film laminated structure> The optical filter of the present invention has a first thin film stack structure and a second thin film stack structure that limit the transmission of light in the near-infrared wavelength region, and each thin film stack structure is stacked as an outermost layer on both main surface sides of a substrate.

[0024] The first thin film stack 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 wavelengths of 850 nm to 950 nm at an incident angle of 40° 850-950(40deg)MAX is 5% or more (i-1B) Maximum reflectance R at wavelengths of 450 nm to 600 nm at an incident angle of 40° 450-600(40deg)MAX is less than 8%

[0025] The first thin film laminate structure is designed by shifting the near-infrared light reflection region so that the ripples in the visible light region of two or more dielectric multilayer films cancel each other out, resulting in light leakage in the near-infrared wavelength region. The optical characteristic (i-1A) indicates the wavelength region where light leakage occurs and the level at which light leakage is acceptable. T 850-950(40deg)MAX is more preferably 6% or more, and is preferably 30% or less, more preferably 20% or less.

[0026] By satisfying the optical characteristic (i-1B), it means that the reflectance in the visible light region is low. This means that it exhibits good transmittance in the visible light region. 450-600(40deg)MAX is more preferably 7% or less.

[0027] The first thin film laminated structure preferably further satisfies the following optical property (i-1C). (i-1C) Average reflectance R at wavelengths of 1000 nm to 1100 nm at an incident angle of 40° 1000-1100(40deg)AVE More than 95% Satisfying the optical property (i-1C) means that the film is excellent in blocking light, particularly light of 1000 nm to 1100 nm in the near-infrared light region.

[0028] The second thin film stack includes at least one dielectric multilayer film. The second thin film stack structure satisfies the following optical property (i-2A). (i-2A) Average reflectance R at wavelengths of 850 nm to 950 nm at an incident angle of 40° 850-950(40deg)AVE25% to 60% By satisfying the optical characteristic (i-2A), it is possible to block light that could not be blocked due to light leakage from the first thin film laminated structure, by the reflection characteristics of the second thin film laminated structure. 850-950(40deg)AVE When R is 25% or more, light leakage occurring in the first thin film laminated structure can be effectively blocked. 850-950(40deg)AVE By keeping the R value at 60% or less, it is possible to prevent the physical thickness of the dielectric multilayer film from becoming excessively thick. 850-950(40deg)AVE is preferably 30% to 55%.

[0029] It is preferable that the second thin film laminated structure further satisfies the following optical property (i-2B). (i-2B) Average transmittance T at wavelengths of 450 nm to 600 nm at an incident angle of 0° 450-600(0deg)AVE Over 80% By satisfying the optical characteristic (i-2B), it is possible to obtain high visible light transmittance as an optical filter. 450-600(0deg)AVE is preferably 90% or more.

[0030] The second thin film stack structure preferably further satisfies the following optical property (i-2C). (i-2C) Average reflectance R at wavelengths of 1000 nm to 1100 nm at an incident angle of 40° 1000-1100(40deg)AVE 25% to 60% Satisfying the optical property (i-2C) means that the film is excellent in blocking light, particularly light in the 1000 nm to 1100 nm range, in the near-infrared light region.

[0031] The first thin film stack structure and the second thin film stack structure are configured to limit transmission of a desired wavelength range using a dielectric multilayer film. The dielectric multilayer film is a film with optical functionality obtained by alternately stacking a selection of dielectric films with low refractive index (low refractive index film), dielectric films with medium refractive index (medium refractive index film), and dielectric films with high refractive index (high refractive index film). Depending on the design, it is possible to utilize optical interference to achieve the function of transmitting light in a specific wavelength range or controlling the light transmission limit. Note that a low refractive index, a high refractive index, or a medium refractive index means having a high or low refractive index relative to the refractive index of the adjacent layer, or a refractive index intermediate therebetween.

[0032] The high refractive index film is a film having a refractive index of preferably 1.9 or more, more preferably 1.9 to 2.6 at a wavelength of 500 nm. Examples of materials for the high refractive index film include Ta2O5, TiO2, and Nb2O5. Of these, TiO2 is preferred from the standpoints of film formability, reproducibility in refractive index, etc., and stability.

[0033] The medium refractive index film is a film having a refractive index at a wavelength of 500 nm of preferably 1.5 to 2.1, more preferably 1.8 to 2.0. Examples of materials for the medium refractive index film include Al2O3, Y2O3, and ZrO2. Of these, Al2O3, ZrO2, or a mixed material containing these two materials are preferred from the standpoint of stability, etc.

[0034] The low refractive index film is a film having a refractive index of preferably 1.8 or less, more preferably 1.3 to 1.6 at a wavelength of 500 nm. Examples of materials for the low refractive index film include SiO2, MgF2, SiO x N y In terms of reproducibility, stability, economy, etc. in film formation, SiO2 is preferred.

[0035] The second thin film laminated structure is a multilayer film in which TiO2 and SiO2 are alternately laminated, and the film ratio shown in the following formula is preferably 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) This configuration allows the second thin film laminate structure to achieve reflection characteristics at wavelengths of 850 to 950 nm, specifically, a reflectance of 25 to 60% at an incident angle of 40°. The film ratio is more preferably 0.55 or more, and even more preferably 0.60 to 0.70. The physical film thickness can be measured using a stylus-type surface profiler (Dektak150, manufactured by ULVAC, Inc.).

[0036] When the thin film laminated structure is constructed by alternately laminating thin films of different refractive indexes, the number of layers depends on the optical properties of the dielectric multilayer film, but the total number of thin film layers is preferably 50 to 150. If the total number of layers is 50 or more, the blocking performance for wavelengths of 800 nm to 1000 nm is sufficient. On the other hand, if the total number of layers is 150 or less, the takt time during production of the optical filter is not long and warping of the optical filter due to the dielectric multilayer film is unlikely to occur, which is not preferable. Furthermore, from the viewpoint of obtaining high near-infrared shading performance, the total number of layers in the first thin film laminate structure is preferably 20 to 150, and more preferably 20 to 50. From the viewpoint of mass productivity, the total number of layers in the second thin film laminate structure is preferably 50 or less, and more preferably less than 20.

[0037] The physical film thickness of the thin film laminated structure is preferably thinner from the viewpoint of making the optical filter thinner, while still satisfying the above-mentioned preferable number of layers. The physical film thickness of the first thin film laminate structure is preferably 3 μm or more from the viewpoint of obtaining the desired optical characteristics, and is preferably 15 μm or less from the viewpoint of suppressing warping of the optical filter. The film thickness of the second thin film laminate structure is preferably less than 3 μm, more preferably less than 2.5 μm, from the viewpoint of suppressing wrinkling of the resin layer.

[0038] The first thin film laminated structure and the second thin film laminated structure may be laminated on either main surface of the substrate, but it is preferable that the second thin film laminated structure be laminated on the surface of the resin film of the substrate. The second thin film laminated structure, which has fewer dielectric multilayer films, has a smaller number of layers than the first thin film laminated structure. The resin film in contact with the thin film laminated structure is subjected to stronger stress as the number of thin film layers increases. If the stress from the thin film laminated structure is strong, wrinkles will occur in the resin film when the resin softens due to heat during assembly processes such as reflow, causing problems with appearance quality. By laminating the film laminated structure with a smaller number of layers on the surface of the resin film, the resin film is subjected to less stress and wrinkles are suppressed, which is preferable.

[0039] The thin film laminated structure can be formed by dry film formation processes such as IAD (Ion Assisted Deposition) vapor deposition, CVD, sputtering, and vacuum deposition, or wet film formation processes such as spraying and dipping.

[0040] <Base material> In the optical filter of the present invention, the substrate has a resin film containing a dye (IR) that absorbs light in the near-infrared wavelength range and a resin. The absorption properties of the dye (IR) can block light leakage in the near-infrared wavelength range that occurs in the first thin film laminate structure. Furthermore, the absorption properties of the dye (IR) can compensate for the decrease in the near-infrared light blocking ability caused by the incident angle dependency 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 wavelengths of 850 nm to 950 nm at an incident angle of 0° 850-950(0deg)AVE 60-90% (ii-2) Average internal transmittance T at wavelengths of 850 nm to 950 nm at an incident angle of 30° 850-950(30deg)AVE 60-90% (ii-3) Average internal transmittance T at wavelengths of 850 nm to 950 nm at an incident angle of 40° 850-950(40deg)AVE 60-90%

[0042] By satisfying the optical properties (ii-1) to (ii-3), it means that light can be blocked by the absorption properties of the dye (IR) under incident angle conditions and in a wavelength range where light leakage occurs in the first thin film laminate structure.

[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] It is preferable that the resin film further satisfies the following optical property (ii-4). (ii-4) Average internal transmittance T at wavelengths of 660 nm to 730 nm at an incident angle of 30° 660-730(30deg)AVE is less than 10% The wavelength range of 660nm to 730nm is close to the border with the visible light region within the near-infrared light region, and is a region where the reflectivity at high angles of incidence (oblique incidence shift) is likely to decrease due to the incidence angle dependency of the dielectric multilayer film. By satisfying the optical property (ii-4), it means that the absorption properties of the dye can block the near-infrared light that is not fully reflected by the dielectric multilayer film. 660-730(30deg)AVE is more preferably 20% or less.

[0045] It is preferable that the resin film further satisfies the following optical property (ii-5). (ii-5) Average internal transmittance T for wavelengths from 450 to 600 nm at an incident angle of 0° 450-600(0deg)AVE Over 70% By satisfying the optical property (ii-5), the resin film has high visible light transmittance. 450-600(0deg)AVE is more preferably 60% or more.

[0046] As the dye (IR) that absorbs light in the near-infrared wavelength region, a dye that has a maximum absorption wavelength in the range of 570 to 950 nm in the resin that constitutes the resin film is preferred. By using such a dye, near-infrared light can be effectively blocked.

[0047] Examples of the dye (IR) include squarylium dyes, cyanine dyes, phthalocyanine dyes, naphthalocyanine dyes, dithiol metal complex dyes, azo dyes, polymethine dyes, phthalide dyes, naphthoquinone dyes, anthraquinone dyes, indophenol dyes, pyrylium dyes, thiopyrylium dyes, croconium dyes, tetradehydrocholine dyes, triphenylmethane dyes, aminium dyes, and diimonium dyes. Among these, squarylium dyes and cyanine dyes are preferred from the viewpoint of spectral characteristics, and phthalocyanine dyes are preferred from the viewpoint of durability. The dye (IR) may consist of one type of compound, or may contain two or more types of compounds.

[0048] The content of the NIR dye (IR) in the resin film is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 15 parts by mass, per 100 parts by mass of the resin. When two or more compounds are combined, the above content is the total of the respective compounds.

[0049] The resin film may contain other dyes, such as ultraviolet light absorbing dyes, to the extent that the effects of the present invention are not impaired. Examples of ultraviolet light absorbing dyes include oxazole dyes, merocyanine dyes, cyanine dyes, naphthalimide dyes, oxadiazole dyes, oxazine dyes, oxazolidine dyes, naphthalic acid dyes, styryl dyes, anthracene dyes, cyclic carbonyl dyes, triazole dyes, etc. Among these, merocyanine dyes are particularly preferred.

[0050] The substrate in the present filter may have a single-layer structure or a multi-layer structure, and the material of the substrate is not particularly limited and may be an organic or inorganic material as long as it is a transparent material that transmits visible light. When the substrate has a single layer structure, it is preferable that the substrate is a resin substrate made of a resin film containing a resin and an NIR dye (IR). When the substrate has a multi-layer structure, a composite substrate is preferred in which a resin film containing an NIR dye (IR) is laminated on at least one main surface of the support, and the support is preferably made of a transparent resin or a transparent inorganic material.

[0051] The resin is not limited as long as it is a transparent resin, and one or more transparent resins selected from polyester resin, acrylic resin, epoxy resin, enethiol resin, polycarbonate resin, polyether resin, polyarylate resin, polysulfone resin, polyethersulfone resin, polyparaphenylene resin, polyarylene ether phosphine oxide resin, polyamide resin, polyimide resin, polyamideimide resin, polyolefin resin, cyclic olefin resin, polyurethane resin, polystyrene resin, etc. These resins may be used alone or in combination of two or more. Among these, polyimide resins are preferred because they have excellent dye solubility, little absorption on the UV side, a high glass transition temperature (Tg), and excellent adhesion to the support and the dielectric multilayer film.

[0052] When a plurality of compounds are used as the NIR dye (IR) or other dyes, they may be contained in the same resin film, or may be contained in separate resin films.

[0053] As the transparent inorganic material, glass or crystalline material is preferred. Examples of glass that can be used for the support include absorption-type glass (near-infrared absorbing glass) containing copper ions in fluorophosphate glass or phosphate glass, soda-lime glass, borosilicate glass, alkali-free glass, and quartz glass. As the glass, phosphate glass and fluorophosphate glass are preferred from the viewpoint of absorbing infrared light (especially 900 to 1200 nm). Note that "phosphate glass" also includes silicophosphate glass, in which part of the glass skeleton is composed of SiO2.

[0054] The glass may be chemically strengthened glass obtained by ion exchange at a temperature equal to or lower than the glass transition point to exchange alkali metal ions (e.g., Li ions, Na ions) having a small ionic radius present on the main surface of the glass plate with alkali ions having a larger ionic radius (e.g., Na ions or K ions for Li ions, and K ions for Na ions).

[0055] Examples of crystalline materials that can be used for the support include birefringent crystals such as quartz, lithium niobate, and sapphire.

[0056] As the support, inorganic materials are preferred, and glass and sapphire are particularly preferred, from the viewpoint of shape stability related to long-term reliability of optical properties, mechanical properties, etc., and ease of handling during filter production.

[0057] The resin film can be formed by dissolving or dispersing the dye (IR), resin or resin raw material components, and other components blended as needed in a solvent to prepare a coating solution, applying the coating solution to a support, drying, and optionally curing. The support may be the support included in the filter, or a peelable support used only when forming the resin film. The solvent may be a dispersion medium or a solvent capable of stably dispersing the dye (IR).

[0058] The coating liquid may also contain a surfactant to prevent voids caused by microbubbles, depressions caused by the adhesion of foreign matter, and repellency during the drying process. For example, the coating liquid can be applied by dip coating, cast coating, or spin coating. After the coating liquid is applied to a support, a resin film is formed by drying. When the coating liquid contains raw materials for a transparent resin, it is further subjected to a curing treatment such as thermal curing or photocuring.

[0059] The resin film can also be produced in a film form by extrusion molding. When the substrate has a single-layer structure (resin substrate) consisting of a resin film containing the dye (IR), the resin film can be used as is as the substrate. When the substrate has a multi-layer structure (composite substrate) having a support and a resin film containing the dye (IR) laminated on at least one main surface of the support, the substrate can be produced by laminating this film on the support and integrating them by thermocompression bonding or the like.

[0060] The optical filter may have one resin film layer or two or more resin films. When the optical filter has two or more resin films, the layers may have the same or different configurations.

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

[0062] The shape of the substrate is not particularly limited, and may be a block, plate, or film. Furthermore, the thickness of the substrate is preferably 300 μm or less from the viewpoints of reducing warpage during the formation of the dielectric multilayer film and reducing the height of the optical element. When the substrate is a resin substrate made of a resin film, the thickness is preferably 50 to 300 μm, and when the substrate is a composite substrate comprising a support and a resin film, the thickness is preferably 50 to 300 μm.

[0063] <Optical filters (optical characteristics)> The optical filter of the present invention having the above configuration preferably satisfies all of the following optical properties (iii-1) to (iii-5). (iii-1) Average transmittance T at wavelengths of 400 to 600 nm at an incident angle of 0° 400-600(0deg)AVE Over 70% (iii-2) Average reflectance R at wavelengths of 450 to 600 nm at an incident angle of 40°450-600(40deg)AVE is 5% or less (iii-3) Average reflectance R at wavelengths of 450 to 600 nm at an incident angle of 5° 450-600(5deg)AVE is less than 3% (iii-4) Maximum transmittance T at wavelengths of 700 to 900 nm at an incident angle of 40° 700-900(40deg)MAX is 15% or less (iii-5) Average transmittance T at wavelengths of 1000 to 1100 nm at an incident angle of 40° 1000-1100(40deg)AVE is 5% or less

[0064] The optical filter of the present invention, which satisfies all of the optical properties (iii-1) to (iii-5), has high transmittance for visible light and high blocking properties for near-infrared light, and is an optical filter in which ripples in the visible light region are suppressed even at high angles of incidence.

[0065] By satisfying the optical property (iii-1), it means that the film has excellent transmittance in the visible light region with wavelengths of 400 to 600 nm. 400-600(0deg)AVE is preferably 72% or more.

[0066] Satisfying the optical characteristic (iii-2) means that the ripple is small in the visible light region with wavelengths of 450 to 600 nm. 450-600(40deg)AVE is preferably 4% or less.

[0067] Satisfying the optical characteristic (iii-3) means that the ripple is small in the visible light range. 450-600(5deg)AVE is preferably 2.5% or less.

[0068] By satisfying the optical property (iii-4), it means that the film has excellent blocking properties for the near-infrared light region of 700 to 900 nm even at high angles of incidence. 700-900(40deg)MAX is preferably 14% or less.

[0069] By satisfying the optical property (iii-5), it means that the film has excellent blocking properties for the near-infrared light region of 1000 to 1100 nm even at high angles of incidence. 1000-1100(40deg)AVE is preferably 4.5% or less.

[0070] The optical filter of the present invention preferably further satisfies the following optical property (iii-6). (iii-6) Maximum transmittance T at wavelengths of 850 nm to 950 nm at an incident angle of 40° 850-950(40deg)MAX is 20% or less By satisfying the optical property (iii-6), it is meant that the light leakage allowed in the first thin film laminate structure is blocked by the optical filter. 850-950(40deg)MAX is preferably 15% or less.

[0071] When the optical filter of the present invention is used in an imaging device such as a digital still camera, it can provide an imaging device with excellent color reproducibility. Such an imaging device includes a solid-state 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, by being disposed between the imaging lens and the solid-state imaging element, or by being directly attached to the solid-state imaging element, imaging lens, etc. of the imaging device via an adhesive layer. [Example]

[0072] Next, the present invention will be explained more specifically with reference to examples. Each optical property was verified using optical thin film simulation software (TFCalc, manufactured by Software Spectra, Inc.) In this application, the refractive index of each film at a wavelength of 500 nm was used as a representative value, but the simulation was performed taking into account the wavelength dependency of the refractive index. In addition, unless the incident angle is specifically stated, the optical characteristics are values ​​simulated at an incident angle of 0 degrees (perpendicular to the main surface of the optical filter).

[0073] The dyes used in each example are as follows: Compound 1 (cyanine compound): Synthesized based on Dyes and pigments 73 (2007) 344-352. Compound 2 (squarylium dye): synthesized based on the specifications of U.S. Patent Application Publication No. 2014 / 0061505 and WO 2014 / 088063. Compound 3 (merocyanine compound): Synthesized with reference to Japanese Patent No. 6504176.

[0074] [ka]

[0075] <Example 1-1: Resin film> A polyimide resin (C-3G30G manufactured by Mitsubishi Gas Chemical Company, Ltd.) was dissolved in an organic solvent (cyclohexanone) at a concentration of 10% by mass. To the polyimide resin solution prepared above, 0.05 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, and the mixture was stirred for 2 hours while heating to 50° C. The dye-containing resin solution was applied to a glass substrate (alkali glass, D263 manufactured by Schott) using a spin coater, and thoroughly dried by heating to obtain a resin film (coated film) with a thickness of 5 μm.

[0076] <Example 1-2: Resin film> A 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] For each resin film, the transmission and reflection spectra were measured using a spectrophotometer at a wavelength range of 350 nm to 1200 nm at an angle of 5° relative to the incident direction. The obtained spectral transmittance curves and spectral reflectance curves were used to calculate the spectral internal transmittance curve, which was normalized so that the transmittance at the maximum absorption wavelength was 10%. Internal transmittance (%)=Transmittance / (100-Reflectance)*100 The optical properties are shown in Table 1 below. It should be noted that Examples 1-1 and 1-2 are reference examples.

[0078] <Example 2-1: Thin film laminated structure 1-1> We designed thin film stack structure 1-1 by combining three types of dielectric multilayer films, each with different numbers of layers and physical thicknesses, each consisting of alternately stacked TiO2, SiO2, and ZrO2 films. The numbers of layers and physical thicknesses are shown in Table 1 below.

[0079] <Example 2-2: Thin film laminated structure 1-2> We designed thin film stack structure 1-2 by combining two types of dielectric multilayer films, each with alternating TiO2 and SiO2 layers, and differing in the number of layers and physical thickness. The number of layers and physical thickness of each are shown in Table 1 below.

[0080] <Example 2-3: Thin film laminated structure 1-3> A thin film stacked structure 1-3 was designed in the same manner as in Example 2-2, except that the number of stacked TiO2 films and SiO2 films and the physical film thickness were as shown in Table 1 below.

[0081] <Example 2-4: Thin film laminated structure 1-4> A thin film stacked structure 1-4 was designed in the same manner as in Example 2-2, except that the number of stacked TiO2 films and SiO2 films and the physical film thickness were as shown in Table 1 below.

[0082] <Example 2-5: Thin film laminated structure 1-5> With reference to Example 4 of JP 2007-183525 A, we designed a thin film laminate structure 1-5 consisting of a dielectric multilayer film in which TiO films, LaO films, and AlO films were alternately laminated. The number of layers is shown in Table 1 below.

[0083] <Example 2-6: Thin film laminated structure 2-1> We designed a thin film laminated structure 2-1 consisting of a dielectric multilayer film in which TiO2 and SiO2 films were alternately laminated. The number of layers and physical film thickness are shown in Table 1 below.

[0084] <Example 2-7: Thin film laminated structure 2-2> A thin film laminated structure 2-1 was designed, which was made of a dielectric multilayer film in which TiO2 films and SiO2 films were alternately laminated, with reference to the description in Example 4 of Japanese Patent Application Laid-Open No. 2007-183525. The number of layers is shown in Table 1 below.

[0085] The optical properties of the thin film laminated structures 1-1 to 1-5 and the optical properties of the thin film laminated structures 2-1 to 2-2 are shown in Table 1 below. 4 to 11 show the spectral transmittance curves and the spectral reflectance curves of the thin film laminated structures 1-4 and 1-5 and the thin film laminated structures 2-1 and 2-2, respectively. Examples 2-1 to 2-7 are reference examples.

[0086] <Example 3-1: Optical filter> The resin film of Example 1-1 and thin film laminate structure 2-1 were laminated on one main surface of a glass substrate (alkali glass, D263 manufactured by Schott), and thin film laminate structure 1-1 was laminated on the other main surface to obtain an optical filter.

[0087] <Example 3-2: Optical filter> An optical filter was obtained in the same manner as in Example 3-1, except that the thin film laminated structure 1-1 was replaced with the thin film laminated structure 1-2.

[0088] <Example 3-3: Optical filter> An optical filter was obtained in the same manner as in Example 3-1, except that the thin film laminated structure 1-1 was replaced with the thin film laminated structure 1-3.

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

[0090] <Example 3-5: Optical filter> An optical filter was obtained in the same manner as in Example 3-1, except that the thin film laminated structure 1-1 was replaced with the thin film laminated structure 1-4.

[0091] <Example 3-6: Optical filter> Referring to Example 4 of JP 2007-183525 A, a thin film stacked structure 2-2 was laminated on one main surface of a glass substrate, and a thin film stacked structure 1-5 was laminated on the other main surface to obtain an optical filter.

[0092] The optical characteristics of each of the obtained optical filters were measured using a spectrophotometer at incident angles of 0° and 40°, and at incident angle of 5°. The optical characteristics are shown in the table below. The spectral transmittance curves of the optical filters 3-1 to 3-6 are shown in FIGS. 12 to 17, respectively. Examples 3-1 to 3-5 are working examples, and Example 3-6 is a comparative example.

[0093] Furthermore, the optical filter was evaluated for wrinkles by the following method. For the wrinkle evaluation, the optical filter was heated in an electric furnace set to 160°C for 10 minutes, then removed from the furnace and cooled to room temperature. The center of the optical filter was then observed under an optical microscope to check for the presence or absence of wrinkles. If the optical filter had wrinkles that were visible to the eye, it was marked with an X, and if there were no wrinkles that were visible to the eye, it was marked with an O. The results are shown in Table 1.

[0094] [Table 1]

[0095] The above results show that optical filters 3-1 to 3-5 have high transmittance for visible light and high blocking ability for near-infrared light, suppress the generation of ripples in the visible light region at high incident angles, and also suppress the decrease in blocking ability for near-infrared light at high incident angles.Furthermore, the generation of wrinkles in the resin film was also suppressed. On the other hand, optical filter 3-6, which used two types of multilayer film and did not use any dye, exhibited ripples in the visible light range at high incident angles, and the transmission characteristics shifted at high incident angles, resulting in a decrease in blocking ability in the near-infrared light range.

[0096] Although the present invention has been described in detail and with reference to specific embodiments, 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 present invention. This application is based on a Japanese patent application (Patent Application No. 2020-217100) filed on December 25, 2020, the contents of which are incorporated herein by reference. [Industrial Applicability]

[0097] The optical filter of the present invention has excellent visible light transmittance and good near-infrared light blocking properties, in which the decrease in near-infrared light blocking properties at high incident angles is suppressed, and is useful for applications in information acquisition devices, such as cameras and sensors for transportation aircraft, which have been increasingly sophisticated in recent years. [Explanation of symbols]

[0098] 1...optical filter, 10...substrate, 11...support, 12...resin film, 31...first thin film laminated structure, 31A, 31B, 31C...dielectric multilayer film, 32...second thin film laminated structure

Claims

1. A substrate; a first thin film stack structure and a second thin film stack structure that limit the transmission of light in the near infrared wavelength range; An optical filter comprising: the substrate includes a resin film containing a dye that absorbs light in the near-infrared wavelength region; 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 base material, 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 base material, The first thin film stack structure satisfies the following optical properties (i-1A) and (i-1B), The second thin film stack structure satisfies the following optical property (i-2A): the second thin film laminated structure is laminated on the surface of the resin film; Optical filters. (i-1A) Maximum transmittance at wavelengths of 850 nm to 950 nm at an incident angle of 40° is 5% or more (i-1B) The maximum reflectance at a wavelength of 450 nm to 600 nm at an incident angle of 40° is 8% or less (i-2A) Average reflectance of 25% to 60% at wavelengths of 850 nm to 950 nm at an incident angle of 40°

2. 2. The optical filter according to 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° in the wavelength range of 850 nm to 950 nm is 60 to 90%. (ii-2) Average internal transmittance at an incident angle of 30° in the wavelength range of 850 nm to 950 nm is 60 to 90% (ii-3) The average internal transmittance at an incident angle of 40° in the wavelength range of 850 nm to 950 nm is 60 to 90%.

3. 3. The optical filter according to claim 1, wherein the resin film further satisfies the following optical property (ii-4): (ii-4) The average internal transmittance at an incident angle of 30° in the wavelength range of 660 nm to 730 nm is 10% or less.

4. 4. The optical filter according to claim 1, wherein the resin film further satisfies the following optical characteristic (ii-5): (ii-5) The average internal transmittance at an incident angle of 0° for wavelengths of 450 to 600 nm is 70% or more.

5. The second thin film stack structure is TiO ２ and SiO ２ 5. The optical filter according to claim 1, further comprising a dielectric multilayer film in which the layers are alternately stacked, and wherein the film ratio represented by the following formula is 0.50 or more: Film ratio (physical film thickness) = SiO ２ Total physical film thickness / (TiO ２ Total physical film thickness + SiO ２ total physical thickness)

6. 6. The optical filter according to claim 1, wherein the resin film contains a polyimide resin.

7. 7. The optical filter according to claim 1, which satisfies all of the following optical properties (iii-1) to (iii-5): (iii-1) Average transmittance at an incident angle of 0° in the wavelength range of 400 to 600 nm is 70% or more (iii-2) The average reflectance at an incident angle of 40° in the wavelength range of 450 to 600 nm is 5% or less. (iii-3) The average reflectance at an incident angle of 5° in the wavelength range of 450 to 600 nm is 3% or less. (iii-4) The maximum transmittance at an incident angle of 40° in the wavelength range of 700 to 900 nm is 15% or less. (iii-5) Average transmittance at an incident angle of 40° in the wavelength range of 1000 to 1100 nm is 5% or less

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