Optical filter and imaging device including the optical filter

Abstract

The present application provides an optical filter that can efficiently and accurately block ultraviolet light near the short-wavelength visible light region and infrared light near the long-wavelength visible light region, while obtaining a sharp visible light transmission band and minimizing ripples regardless of the incident angle. Even when a near-infrared absorbing glass is used as a substrate, the above properties can be maintained, and high visible light transmittance can be obtained.

Description

[Technical Field]

[0001] This application relates to optical filters. [Background technology]

[0002] In imaging devices that use imaging elements such as CCD and CMOS image sensors, optical filters that transmit visible light and block infrared light such as near-infrared light are used to obtain good color reproducibility and clear images. Such optical filters are also called near-infrared cut filters.

[0003] Such optical filters are required to exhibit a transmittance curve that transmits visible light while blocking ultraviolet and infrared light.

[0004] However, it is not easy to accurately block ultraviolet light in the short wavelength region of visible light and infrared light in the long wavelength region of visible light and obtain a transmittance curve with high transmittance for visible light.

[0005] Known optical filters include an absorption layer containing a near-infrared absorbing dye and a reflection layer containing a dielectric film that blocks light in the ultraviolet and infrared wavelength regions (see, for example, Patent Document 1). , Korean Patent Registration No. 10-2056613 ) Dielectric films have the property that their transmittance curves change (shift) depending on the angle of incidence. Therefore, in order to compensate for the shortcomings of the dielectric film, optical filters such as those disclosed in Patent Document 1 employ an absorption layer containing a near-infrared absorbing dye whose transmittance has little dependency on the angle of incidence. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Korean Patent Registration No. 10-2056613

[0007] Optical filters using near-infrared absorbing glass (also called blue glass) as a substrate, which itself has near-infrared absorbing properties, are also known. The near-infrared absorbing glass is a glass filter in which CuO or the like is added to a fluorophosphate glass or a phosphate glass so as to selectively absorb light in the near-infrared wavelength region. However, when using such near-infrared glass, it is difficult to obtain a sharp visible light transmittance band while accurately blocking ultraviolet light near the short wavelength region of visible light and infrared light in the long wavelength region of visible light. Furthermore, due to the characteristics of the near-infrared absorbing glass itself, it is difficult to obtain high transmittance within the visible light transmittance band.

[0008] On the other hand, conventional optical filters suffer from periodic fluctuations in transmittance (so-called ripple phenomenon) in the visible light transmission region.

[0009] The ripple phenomenon is a phenomenon in which the actual transmittance in a specific region periodically becomes larger and smaller than the average transmittance in that region.

[0010] An imaging device senses visible light that has passed through an optical filter using sensors for each of the red, green, and blue (RGB) colors. The sensitivity of each RGB sensor is adjusted based on the average transmittance of each wavelength, but if ripple occurs, fluctuations occur in the light perceived by the sensor, resulting in poor color reproducibility.

[0011] In addition, the ripple phenomenon can generate areas where the transmittance in the visible light region drops instantaneously (so-called bunk areas), which induces ghosting, and this ghosting also reduces color reproducibility.

[0012] In the prior art, in order to prevent the ripple or ghost phenomenon as described above, a method has been adopted in which the thickness of each sub-layer in a dielectric film composed of multiple sub-layers is varied by about 10%. However, this method alone is not effective in preventing the ripple phenomenon, and it is particularly difficult to prevent the ripple phenomenon that occurs depending on the incident angle.

[0013] Furthermore, the wavelength range of approximately 400 nm to 600 nm in the visible light range is where the ripple phenomenon due to the angle of incidence occurs most severely, but the prior art does not take such a wavelength range into consideration. Summary of the Invention [Problem to be solved by the invention]

[0014] The present application aims to provide an optical filter that can efficiently and accurately block ultraviolet light near the short-wavelength visible light region and infrared light near the long-wavelength visible light region, while achieving a sharp visible light transmission band and minimizing ripple regardless of the angle of incidence. Another object of the present application is to provide an optical filter that can achieve high visible light transmittance while maintaining the above properties even when a near-infrared absorbing glass is used as the substrate. [Means for solving the problem]

[0015] An optical filter according to one embodiment of the present application includes a transparent substrate and a dielectric film formed on one or both surfaces of the transparent substrate and consisting of two or more sub-layers, and has an incident angle 0 degree ripple value of 2.5% or less in a wavelength range of 450 nm to 560 nm. [Effects of the Invention]

[0016] The present application provides an optical filter that can efficiently and accurately block ultraviolet light near the short-wavelength visible light region and infrared light near the long-wavelength visible light region, while obtaining a sharp visible light transmission band and minimizing the ripple phenomenon regardless of the incident angle.

[0017] Furthermore, in the present application, even when near-infrared absorbing glass is used as the substrate, an optical filter can be provided that can ensure the above-mentioned properties and at the same time achieve high visible light transmittance. [Brief explanation of the drawings]

[0018] [Figure 1] 1A and 1B illustrate exemplary stacked structures of optical filters of the present application. [Figure 2] 1A and 1B illustrate exemplary stacked structures of optical filters of the present application. [Figure 3] 1A and 1B illustrate exemplary stacked structures of optical filters of the present application. [Figure 4] 1A and 1B illustrate exemplary stacked structures of optical filters of the present application. [Figure 5] 1A and 1B illustrate exemplary stacked structures of optical filters of the present application. [Figure 6] 1 shows the optical spectrum of a substrate used in an example. [Figure 7] 7 shows an optical spectrum when an ultraviolet absorbing layer is formed on the substrate of FIG. [Figure 8] 8 shows an optical spectrum when an infrared absorbing layer is formed in the structure of FIG. [Figure 9] 9 shows the optical spectrum of an optical filter in which a dielectric film is formed on the structure of FIG. [Figure 10] 1 shows the spectrum of the optical filter of the example depending on the angle of incidence. [Figure 11] 10 shows the spectrum of the optical filter of the comparative example depending on the angle of incidence. [Figure 12] 1 is a spectrum for confirming the ripple value of the optical filter of an example or a comparative example. [Figure 13] 1 is a spectrum for confirming the ripple value of the optical filter of an example or a comparative example. [Figure 14] 1 is a spectrum for confirming the ripple value of the optical filter of an example or a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0019] Of the physical properties referred to in this specification, those whose results are affected by the measurement temperature and / or measurement pressure are the results measured at room temperature and / or normal pressure, unless otherwise specified.

[0020] The term "room temperature" refers to a natural temperature that is not heated or cooled, and may be, for example, any temperature within the range of 10°C to 30°C, and means a temperature of about 23°C or about 25°C. Furthermore, in this specification, the unit of temperature is Celsius (°C) unless otherwise specified.

[0021] The term "normal pressure" refers to natural pressure without pressure or decompression, and generally refers to atmospheric pressure of about 1 atmosphere.

[0022] In the present specification, when a physical property is one whose measurement humidity affects the results, the physical property is measured at the natural humidity without any particular adjustment at room temperature and / or normal pressure.

[0023] When optical properties (eg, refractive index) referred to in this application are wavelength-dependent properties, unless otherwise specified, the optical properties are those obtained for light of 520 nm wavelength.

[0024] In this application, the term "transmittance" means the actual transmittance (measured transmittance) observed at a particular wavelength, unless otherwise specified.

[0025] In this application, unless otherwise specified, the term "average transmittance" refers to the sum of the wavelength-specific transmittances in a given wavelength range divided by the number of wavelengths (N). In this case, the wavelength-specific transmittance is calculated in 1 nm increments. For example, the average transmittance from 400 nm to 450 nm can be calculated by calculating the transmittances at 51 wavelength points from 400 nm to 450 nm, increasing the wavelength in 1 nm increments, such as 400 nm, 401 nm, and 402 nm, adding them up, and then dividing the sum by 51. Such average transmittances can usually be calculated using known transmittance measuring devices and software.

[0026] In this application, unless otherwise specified, the term "maximum transmittance" means the highest transmittance among the transmittances (actually measured transmittances) within a specific wavelength range.

[0027] In this specification, the incidence angle is an angle based on the normal to the surface to be evaluated. For example, the ripple value at an incidence angle of 0 degrees of an optical filter refers to the ripple value for light incident in a direction parallel to the normal to the surface of the optical filter, and the ripple value at an incidence angle of 40 degrees refers to the ripple value for light incident at an angle of 40 degrees clockwise or counterclockwise from the normal. This definition of the incidence angle also applies to other properties such as transmittance.

[0028] The optical filter of the present application can efficiently and accurately block ultraviolet light near the short wavelength visible light region and infrared light near the long wavelength visible light region, and can realize a visible light transmission band with high transmittance.

[0029] In this application, the term "visible light" means light in the range of approximately 400 to 700 nm.

[0030] In this application, the term "visible light transmission band" refers to a spectral characteristic that exhibits an average transmittance of approximately 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, or 90% or more in the visible light range. The upper limit of the average transmittance in the visible light range is not particularly limited. For example, the average transmittance may be approximately 100% or less, 95% or less, 90% or less, 85% or less, 80% or less, or 75% or less.

[0031] In this application, the term "Tn% cut on" means the shortest wavelength showing n% transmittance in the visible light transmission band, and Tn% cut off means the longest wavelength showing n% transmittance in the visible light transmission band. For example, T50% cut on means the shortest wavelength showing 50% transmittance in the visible light transmission band, and T50% cut off means the longest wavelength showing 50% transmittance in the visible light transmission band.

[0032] The optical filter of the present application may exhibit a transmission band with a T50% cut-on wavelength in the range of about 400 to 420 nm. The T50% cut-on wavelength of the visible light transmission band may be further adjusted within the range of 402 nm or more, 404 nm or more, 406 nm or more, or 408 nm or more, and / or within the range of 418 nm or less, 416 nm or less, 414 nm or less, 412 nm or less, or 410 nm or less.

[0033] The optical filter of the present application may exhibit a transmission band with a T50% cutoff wavelength in the range of about 610 to 650 nm. The T50% cutoff wavelength of the visible light transmission band may be further adjusted within the range of 612 nm or more, 614 nm or more, 616 nm or more, 618 nm or more, 620 nm or more, 622 nm or more, 624 nm or more, 626 nm or more, 628 nm or more, or 630 nm or more, and / or within the range of 648 nm or less, 646 nm or less, 644 nm or less, 642 nm or less, 640 nm or less, 638 nm or less, 636 nm or less, 634 nm or less, 632 nm or less, or 630 nm or less.

[0034] The optical filter of the present application may have a transmission band exhibiting an average transmittance of 85% or more within the range of 425 to 560 nm. In another example, the average transmittance can be adjusted within a range of 87% or more, 89% or more, 91% or more, or 93% or more, and / or within a range of 98% or less, 96% or less, 94% or less, 92% or less, 90% or less, or 88% or less.

[0035] The optical filter of the present application may have a transmission band exhibiting a maximum transmittance of 87% or more within the range of 425 to 560 nm. In another example, the maximum transmittance can be adjusted within a range of 89% or more, 91% or more, 93% or more, or 95% or more, and / or within a range of 100% or less, 98% or less, 96% or less, 94% or less, 92% or less, or 90% or less.

[0036] The optical filter of the present application may have a transmission band exhibiting an average transmittance of 2% or less within the range of 300 to 390 nm, which, in another example, can be further adjusted within a range of 0% or more, 0.1% or more, or 0.2% or more, and / or within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1.0% or less, 0.8% or less, 0.6% or less, 0.4% or less, 0.35% or less, or 0.3% or less.

[0037] The optical filter of the present application may have a transmission band exhibiting a maximum transmittance of 2% or less within the range of 300 to 390 nm, which, in another example, can be further adjusted within a range of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, or 0.8% or more and / or within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less.

[0038] The optical filter of the present application may have a transmittance of 2% or less at a wavelength of 700 nm, which, in another example, can be further adjusted within a range of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, or 0.8% or more, and / or within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less.

[0039] The optical filter of the present application may have a transmission band exhibiting an average transmittance of 2% or less in the range of 700 to 800 nm, which, in another example, can be further adjusted within a range of 0% or more, 0.1% or more, 0.3% or more, 0.4% or more, or 0.5% or more, and / or within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1.0% or less, 0.8% or less, or 0.6% or less.

[0040] The optical filter of the present application may have a transmission band exhibiting a maximum transmittance of 2% or less within the range of 700 to 800 nm, which, in another example, can be further adjusted within a range of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, or 0.8% or more and / or within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less.

[0041] The optical filter of the present application may have a transmission band exhibiting an average transmittance of 2% or less within the range of 800 to 1000 nm, which, in another example, can be further adjusted within a range of 0% or more, 0.1% or more, 0.3% or more, 0.4% or more, or 0.5% or more, and / or within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1.0% or less, 0.8% or less, or 0.6% or less.

[0042] The optical filter of the present application may have a transmission band exhibiting a maximum transmittance of 2% or less within the range of 800 to 1000 nm, which, in another example, can be further adjusted within a range of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, or 0.8% or more and / or within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less.

[0043] The optical filter of the present application may have a transmission band exhibiting an average transmittance of 5% or less within the range of 1000 to 1200 nm, which, in another example, can be further adjusted within a range of 0% or more, 0.5% or more, 1% or more, 1.5% or more, 2.0% or more, or 2.5% or more, and / or within a range of 4.5% or less, 4% or less, 3.5% or less, 3% or less, or 2.5% or less.

[0044] The optical filter of the present application may have a transmission band exhibiting a maximum transmittance of 10% or less within the range of 1000 to 1200 nm, which, in another example, can be further adjusted within a range of 0% or more, 1% or more, 2% or more, 3% or more, 4% or more, or 5% or more, and / or within a range of 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less.

[0045] The optical filter of the present application may have a transmittance of 10% or less at a wavelength of 1200 nm, which, in another example, can be further adjusted within a range of 1% or more, 2% or more, 3% or more, 4% or more, or 5% or more, and / or within a range of 9% or less, 8% or less, 7% or less, 6% or less, or 5.5% or less.

[0046] The optical filter of the present application has a low ripple value, and can maintain the low ripple value even when the angle of incidence varies.

[0047] In one example, the optical filter of the present application may have a ripple value of 2.5% or less in the wavelength region of 450 nm to 560 nm, with an incident angle of 0 degrees as the reference.

[0048] The term "ripple value" refers to the average transmittance T ave.i , i=1~n and actual transmittance T i , the difference between i=1~n = T diff.i =T i -T ave.i After calculating all (i=1~n), the maximum value of the difference Max(T diff.i ) and minimum value Min(T diff.i) is the value obtained by subtracting the value of the wavelength. The subscript i, which is determined in the range of 1 to n, is an ordinal number indicating the wavelength. For example, when checking the ripple value in the range of 450 nm to 560 nm, 450 nm is designated as the case where i is 1, and as the wavelength increases by 1 nm, i also increases by 1. In other words, 451 nm is designated as the case where i is 2, and 560 nm is designated as the case where i is 111. The ripple value is the R value determined by the following Equation 1. Meanwhile, the average transmittance in the process of determining the ripple value is calculated by a statistical analysis program Minitab The value was calculated using a cubic spline regression equation.

[0049] [Formula 1] R=Max(T diff.i )-Min(T diff.i )

[0050] In Equation 1, R is the ripple value, and Max(T diff.i ) is the maximum value of the difference between the average transmittance and the actual transmittance, and Min(T diff.i ) is the minimum value of the difference between the average transmittance and the actual transmittance.

[0051] The ripple value is calculated by a statistical analysis program. Minitab It can be calculated using a cubic spline regression equation.

[0052] In another example, the ripple value can be further adjusted within a range of about 2.4% or less, 2.3% or less, 2.2% or less, 2.1% or less, 2.0% or less, 1.9% or less, 1.8% or less, 1.7% or less, 1.6% or less, 1.5% or less, 1.4% or less, 1.3% or less, or 1.2% or less, and / or within a range of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, 0.8% or more, or 1% or more.

[0053] In the optical filter of the present application, the variation of the ripple value due to the angle of incidence is also almost non-existent or minimized. For example, in the optical filter of the present application, the ripple value R0 at an incident angle of 0 degrees and the ripple value R1 at an incident angle of 40 degrees are 0.05 and 0.15, respectively, in the wavelength range of 450 nm to 560 nm. 40 The difference between R0 and R 40 The absolute value of the difference may be in the range of 0% to 2.5%. In other examples, the absolute value of the difference may be in the range of about 2.4% or less, 2.2% or less, 2.0% or less, 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1.0% or less, 0.8% or less, 0.6% or less, 0.4% or less, 0.2% or less, 0.1% or less, 0.09% or less, 0.08% or less, 0.07% or less, 0.06% or less, 0.05% or less, or 0.04% or less.

[0054] The optical filter of the present application may exhibit any one or a combination of two or more of the above-mentioned optical properties, and preferably may satisfy all of the above-mentioned optical properties.

[0055] In one example, the optical filter of the present application includes a transparent substrate, and one or more layers selected from the group consisting of a dielectric film, an ultraviolet absorbing layer, and an infrared absorbing layer may be included on one or both sides of the transparent substrate. In this case, the dielectric film, the infrared absorbing layer, or the ultraviolet absorbing layer may be formed in two or more layers. By appropriately selecting and combining each of the layers, the optical characteristics including the above-mentioned ripple value can be achieved.

[0056] 1 and 2 show the structure of an exemplary optical filter, in which dielectric films 200, 201, 202 are formed on one or both surfaces of a transparent substrate 100. FIG.

[0057] The type of transparent substrate applied to the optical filter is not particularly limited, and any suitable type used in the construction of the optical filter can be selected and used.

[0058] The term "transparent substrate" refers to a substrate that has the property of transmitting visible light, for example, a substrate having an average transmittance of 70% or more in the wavelength range of about 425 to 560 nm. The average transmittance of the transparent substrate can be further adjusted within a range of 75% or more, 80% or more, or 85% or more, and / or 95% or less, or 90% or less.

[0059] As the transparent substrate, a substrate made of a variety of known materials can be used as long as it exhibits the above-mentioned transmittance and physical properties such as appropriate rigidity as a substrate. For example, a substrate made of an inorganic material such as glass or crystal, or an organic material such as resin can be used.

[0060] Examples of resin materials that can be used for the transparent substrate include, but are not limited to, polyesters such as PET (poly(ethylene terephthalate)) and PBT (poly(butylene terephthalate)), polyolefins such as polyethylene, polypropylene, and EVA (ethylene-vinyl acetate copolymer), norbornene polymers, acrylic polymers such as PMMA (poly(methyl methacrylate)), urethane polymers, vinyl chloride polymers, fluoropolymers, polycarbonate, polyvinyl butyral, polyvinyl alcohol, and polyimides.

[0061] Examples of glass materials that can be used for the transparent substrate include soda-lime glass, borosilicate glass, alkali-free glass, and quartz glass.

[0062] Crystalline materials that can be used for the transparent substrate include birefringent crystals such as quartz, lithium niobate, or sapphire.

[0063] The thickness of the transparent substrate can be adjusted within the range of, for example, about 0.03 mm to 5 mm, but is not limited to this.

[0064] The transparent substrate may be a glass known as near-infrared absorbing glass, which absorbs light in the near-infrared and / or near-ultraviolet regions. Such glass is known as an absorbing glass in which CuO or the like is added to fluorophosphate glass or phosphate glass. The phosphate glass has a structure in which part of the glass framework is composed of SiO2. silicic acid Phosphate glasses are also included.

[0065] When the absorbing glass is used as a transparent substrate, the transmittance of the absorbing glass in the near-infrared region can be reduced to 20% or less by adjusting the concentration of CuO and the thickness of the substrate. This improves the light-shielding properties against near-infrared light. Such absorbing glass is well known, and examples thereof include the glass disclosed in Korean Patent Registration No. 10-2056613 and other commercially available absorbing glasses (e.g., commercially available products from HOYA, SCHOTT, PTOT, etc.).

[0066] The dielectric film formed on one or both surfaces of the transparent substrate is one of the important components that allows the optical filter of the present application to exhibit the above-mentioned optical characteristics, particularly a low ripple value. The dielectric film may have a multilayer structure including at least a first sublayer and a second sublayer having different refractive indices. In one specific example, the first and second sublayers have different refractive indices, and the first sublayer may have a higher refractive index than the second sublayer. The dielectric film may have a structure in which the first and second sublayers are alternately stacked.

[0067] Typically, a dielectric film is a film formed by repeatedly laminating a low-refractive index dielectric material and a high-refractive index dielectric material, and is used to form so-called IR reflective layers and AR (anti-reflection) layers. However, the dielectric film of the present application is formed to ensure the above-mentioned optical properties, particularly a low ripple value. That is, in the present application, by adjusting the refractive index of each sublayer, the refractive index of the transparent substrate, and the number of sublayers, it is possible to ensure the above-mentioned optical properties, including the low ripple value. Therefore, excellent transmittance characteristics can be ensured even when a substrate with generally poor transmittance characteristics, such as near-infrared absorbing glass, is used.

[0068] Such a dielectric film of the present application differs from the dielectric films serving as the IR reflecting layer and the AR layer, and accordingly the actual layer configuration and the like differs.

[0069] For example, the dielectric film may be formed so that the V value of the dielectric film according to the following equation 2 is 17 or less.

[0070] [Formula 2] V=K×{[(n1 / n2) 2p ×(n1 2 / n s )-1] / [(n1 / n2) 2p ×(n1 2 / n s )+1]} 2

[0071] In Equation 2, n1 is the refractive index of the first sublayer, n2 is the refractive index of the second sublayer, and n s is the refractive index of the transparent substrate, K is the total number of first and second sublayers in the dielectric film, and p is a number that satisfies K=(2p+1).

[0072] V in Equation 2 is created based on an equation for determining the theoretical reflectance required for effectively blocking light that the IR reflective layer and AR layer are intended to block when designing the IR reflective layer and AR layer. As can be seen from the equation, when the first and second sub-layers are the same, the V value increases as the values ​​of K and p increase. Therefore, in conventional designs of IR reflective layers and AR layers, the number of layers, K, of the first and second sub-layers is set to a minimum of 20 or more to ensure the desired performance, and in this case, the V value is at least 20.

[0073] However, such a layer design does not contribute to ensuring optical properties such as a low ripple value, which is the objective of the present application.

[0074] That is, in order to achieve the object of the present application, the refractive index of each layer and the number of layers must be adjusted so that the value of V in the above formula 2 is 17 or less.

[0075] Although the reason is unclear, it is believed that the dielectric film that satisfies the above design, combined with the optical properties (e.g., refractive index) of the transparent substrate, induces an optical interference phenomenon that can increase the transmittance of the overall optical filter and ensure a low ripple value.

[0076] In Equation 2, the ratio n1 / n2 of the refractive index n1 of the first sublayer to the refractive index n2 of the second sublayer may be, for example, in the range of about 1.4 to 2.0. In other examples, the ratio may be 1.45 or more, 1.5 or more, 1.55 or more, 1.6 or more, 1.65 or more, 1.7 or more, or 1.75 or more, or 1.95 or less, 1.9 or less, 1.85 or less, or 1.8 or less. In Equation 2, the refractive index n1 of the first sublayer may be in the range of about 1.8 to 3.5.

[0077] In another example, the refractive index n1 may be 2.0 or more, 2.2 or more, 2.4 or more, 2.5 or more, or 2.55 or more, or may be 3.3 or less, 3.1 or less, 2.9 or less, or 2.7 or less.

[0078] In addition, in Equation 2, the refractive index n2 of the second sublayer may be in the range of about 1.1 to 1.7. In another example, the refractive index n2 may be 1.2 or more, 1.3 or more, or 1.4 or more, or about 1.65 or less, 1.6 or less, 1.55 or less, or 1.5 or less.

[0079] The first sublayer of the dielectric film may be defined as a layer having a refractive index within the range, and the second sublayer may be defined as a layer having a refractive index within the range or a ratio of the refractive index of the first sublayer to the refractive index within the range.

[0080] Equation 2 can be calculated for a structure including first and second sublayers that are alternately stacked. In this case, if two or more first sublayers have different refractive indices, or if two or more second sublayers have different refractive indices, the arithmetic mean value of the refractive indices of the first sublayers can be used as n1 in Equation 2, and the arithmetic mean value of the refractive indices of the second sublayers can be used as n2 in Equation 2.

[0081] In Equation 2, the refractive index of the first sublayer n1 and the refractive index of the transparent substrate n s The ratio n1 / n s In one example, the ratio may be in the range of about 1.4 to 2.0. In another example, the ratio may be 1.45 or more, 1.5 or more, 1.55 or more, 1.6 or more, or 1.65 or more, or about 1.95 or less, 1.9 or less, 1.85 or less, 1.8 or less, 1.75 or less, or 1.7 or less.

[0082] Taking into consideration the refractive index of the transparent substrate, an appropriate material can be selected so as to satisfy the above range.

[0083] In Equation 2, K, which determines p, i.e., the total number of layers of the first sublayers and the second sublayers (number of layers of the first sublayers + number of layers of the second sublayers), may be about 17 or less, 16 or less, 15 or less, 14 or less, 13 or less, 12 or less, 11 or less, 10 or less, 9 or less, or 8 or less, or in another example, 2 or more, 3 or more, 4 or more, 5 or more, or 6 or more. The dielectric film may include a repeated stack structure of the first and second sublayers, and therefore, in such a case, the number of layers of the first and second sublayers may be the same as each other, or one of the layers may be about one or two layers more.

[0084] The thickness of each of the first and second sublayers in the dielectric film can be adjusted depending on the purpose, but may be within a range of approximately 5 to 200 nm. In another example, the thickness may be approximately 10 nm or more, 15 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, 35 nm or more, 40 nm or more, 45 nm or more, 50 nm or more, 55 nm or more, 60 nm or more, 65 nm or more, 70 nm or more, 75 nm or more, or 85 nm or more, or approximately 190 nm or less, 180 nm or less, 170 nm or less, 160 nm or less, 150 nm or less, 140 nm or less, 130 nm or less, 120 nm or less, 110 nm or less, 100 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less, or 15 nm or less.

[0085] The average (arithmetic mean) thickness of the first sublayer and the second sublayer included in the dielectric film may be within a range of about 5 to 70 nm, and in another example, the average may be 10 nm or more, 15 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, or 35 nm or more, or about 65 nm or less, 60 nm or less, 55 nm or less, 50 nm or less, 45 nm or less, or 40 nm or less.

[0086] The dielectric film may include other sublayers in addition to the first and second sublayers, but even in this case, the thickness of the total sublayers must be controlled to approximately 15 layers or less, 14 layers or less, 13 layers or less, 12 layers or less, 11 layers or less, 10 layers or less, 9 layers or less, 8 layers or less, 7 layers or less, or 6 layers or less, and must be controlled to approximately 2 layers or more, 3 layers or more, 4 layers or more, 5 layers or more, or 6 layers or more.

[0087] Furthermore, even if the dielectric film includes other sublayers in addition to the first and second sublayers, the ratio of the total number of the first and second sublayers to the total number of sublayers must be 80% or more, 85% or more, 90% or more, or 95% or more, with the upper limit of this ratio being 100%.

[0088] Such a dielectric film may have a total thickness in the range of about 100 to 500 nm. In another example, the thickness may be 120 nm or more, 140 nm or more, 160 nm or more, 180 nm or more, or 200 nm or more, or 480 nm or less, 460 nm or less, 440 nm or less, 420 nm or less, 400 nm or less, 380 nm or less, 360 nm or less, 340 nm or less, 320 nm or less, 300 nm or less, 280 nm or less, 260 nm or less, 240 nm or less, or 220 nm or less.

[0089] One surface of the dielectric film including alternating first and second sublayers satisfying Formula 2 may be formed of the first sublayer, and the other surface may be formed of the second sublayer. For example, the surface of the dielectric film facing the transparent substrate may be formed of the first sublayer, and the opposite surface may be formed of the second sublayer. However, this stacking order may be changed.

[0090] By applying a dielectric film having the above-described characteristics, it is possible to ensure the desired optical characteristics, including a low ripple value. Such a dielectric film may be formed on only one side of the transparent substrate, but preferably on both sides. Furthermore, the optical filter may not include any other dielectric film other than the dielectric film having a V value of 17 or less in Equation 2. That is, when dielectric films are formed on both sides of the transparent substrate, it is preferable that the V values ​​of the dielectric films are each 17 or less.

[0091] The material for forming the dielectric film, i.e., the material for forming each of the sub-layers, is not particularly limited, and known materials can be used. Typically, low-refractive-index sub-layers are made of SiO2 or fluorides such as Na5Al3F14, Na3AlF6, or MgF2, and high-refractive-index sub-layers are made of TiO2, Ta2O5, Nb2O5, ZnS, or ZnSe, but the materials used in this application are not limited to these.

[0092] The method for forming the dielectric film as described above is not particularly limited, and for example, it can be formed by applying a known vapor deposition method.

[0093] The present application may also include an absorbing layer as an additional layer, such as an infrared absorbing layer and / or an ultraviolet absorbing layer. Such a layer typically contains an absorber (pigment, dye, etc.) and a transparent resin, and can be applied to cut light in the near ultraviolet and / or near infrared regions to achieve a sharper transmittance band.

[0094] In one example, the ultraviolet absorbing layer can be designed to exhibit an absorption maximum in the wavelength region of approximately 300 to 390 nm, and the infrared absorbing layer can be designed to exhibit an absorption maximum in the wavelength region of 600 to 800 nm.

[0095] The infrared absorbing layer and the ultraviolet absorbing layer may be formed as a single layer, or as separate layers. For example, a single layer may be designed to exhibit both the absorption maxima of the ultraviolet absorbing layer and the absorption maxima of the infrared absorbing layer, or two layers may be formed to exhibit the respective absorption maxima. Alternatively, multiple infrared absorbing layers and / or ultraviolet absorbing layers may be present.

[0096] 3 shows an example of the structure of an optical filter, in which an absorption layer 300 and a dielectric film 201 are formed on one surface of a substrate 100, and a further dielectric film 202 is formed on the other surface of the substrate. In this case, the absorption layer 300 may be the ultraviolet absorption layer, the infrared absorption layer, or an absorption layer that simultaneously exhibits the absorption maxima of both the ultraviolet absorption layer and the infrared absorption layer.

[0097] 4 and 5 show an example in which two absorption layers 301 and 302 are present, and one of the two absorption layers 301 and 302 may be an infrared absorption layer and the other may be an ultraviolet absorption layer.

[0098] However, the structure of the optical filter on which the absorbing layers are formed is not limited to the cases shown in FIGS. 3 to 5, and the number of absorbing layers and the stacking positions can be changed appropriately.

[0099] Each absorbing layer may contain only one type of absorber, or may contain two or more types of absorbers, if necessary, for appropriate filtering of infrared and / or ultraviolet radiation.

[0100] For example, the infrared absorbing layer may include at least a first absorbent having an absorption maximum wavelength in the range of 700 to 720 nm and a half width in the range of 50 to 60 nm; a second absorbent having an absorption maximum wavelength in the range of 730 to 750 nm and a half width in the range of 60 to 70 nm; and a third absorbent having an absorption maximum wavelength in the range of 760 to 780 nm and a half width in the range of 90 to 100 nm, and the ultraviolet absorbing layer may include at least a first absorbent having an absorption maximum wavelength in the range of 340 to 350 nm; and a second absorbent having an absorption maximum wavelength in the range of 360 to 370 nm.

[0101] The material and method of forming the absorbing layer are not particularly limited, and known materials and methods of forming the absorbing layer can be used.

[0102] Typically, the absorbing layer is formed using a material in which an absorbing agent (such as a dye or pigment) capable of exhibiting a desired absorption maximum is blended with a transparent resin.

[0103] In this case, for example, known absorbers that exhibit an absorption maximum in the wavelength region of about 300 to 390 nm can be used as the ultraviolet absorber. Examples of such absorbers include ABS 407 from Exiton; UV381A, UV381B, UV382A, UV386A, and VIS404A from QCR Solutions Corp; and ADA1225, ADA3209, ADA3216, ADA3217, ADA3218, ADA3230, ADA5205, ADA3217, ADA2055, ADA6798, ADA3102, ADA3204, ADA3210, ADA2041, ADA3201, ADA3202, ADA3215, ADA3219, ADA3225, and ADA404A from HW Sands. Examples of suitable MOSFETs include, but are not limited to, ADA3232, ADA4160, ADA5278, ADA5762, ADA6826, ADA7226, ADA4634, ADA3213, ADA3227, ADA5922, ADA5950, ADA6752, ADA7130, ADA8212, ADA2984, ADA2999, ADA3220, ADA3228, ADA3235, ADA3240, ADA3211, ADA3221, ADA5220, and ADA7158; and CRYSTALYN DLS 381B, DLS 381C, DLS 382A, DLS 386A, DLS 404A, DLS 405A, DLS 405C, and DLS 403A.

[0104] In addition, as the infrared absorber, a suitable dye or pigment that exhibits an absorption maximum in the wavelength region of 600 to 800 nm can be used, for example, squarylium-based dyes, cyanine-based compounds, phthalocyanine-based compounds, naphthalocyanine-based compounds, or dithiol metal complex-based compounds, but is not limited thereto.

[0105] In addition, the transparent resin used in the absorbing layer may be any known resin, for example, one or more of cyclic olefin resins, polyarylate resins, polysulfone resins, polyethersulfone resins, polyparaphenylene resins, polyarylene ether phosphine oxide resins, polyimide resins, polyetherimide resins, polyamideimide resins, acrylic resins, polycarbonate resins, polyethylene naphthalate resins, and various organic-inorganic hybrid resins.

[0106] In addition to the above-mentioned layers, the optical filter may include various other layers as needed, provided that the desired effect is not impaired.

[0107] The present application also relates to an optical filter including the near-infrared absorbing glass substrate, the ultraviolet absorbing layer, and the infrared absorbing layer. The above-described dielectric film may also be formed on this optical filter. This optical filter may exhibit at least one, two or more, or all of the above-described transmittance characteristics (visible light transmission bands).

[0108] For example, the optical filter may exhibit a visible light transmission band with an average transmittance of approximately 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, or 90% or more in the visible light region of the spectrum. The upper limit of the average transmittance in the visible light region is not particularly limited. For example, the average transmittance may be approximately 100% or less, 95% or less, 90% or less, 85% or less, 80% or less, or 75% or less.

[0109] The optical filter may also exhibit a transmission band with a T50% cut-on wavelength in the range of about 400 to 420 nm. The T50% cut-on wavelength of the visible light transmission band may be further adjusted within the range of 402 nm or more, 404 nm or more, 406 nm or more, or 408 nm or more, and / or within the range of 418 nm or less, 416 nm or less, 414 nm or less, 412 nm or less, or 410 nm or less.

[0110] The optical filter may also exhibit a transmission band with a T50% cutoff wavelength in the range of about 610 to 650 nm. The T50% cutoff wavelength of the visible light transmission band may be further adjusted within the range of 612 nm or more, 614 nm or more, 616 nm or more, 618 nm or more, 620 nm or more, 622 nm or more, 624 nm or more, 626 nm or more, 628 nm or more, or 630 nm or more, and / or within the range of 648 nm or less, 646 nm or less, 644 nm or less, 642 nm or less, 640 nm or less, 638 nm or less, 636 nm or less, 634 nm or less, 632 nm or less, or 630 nm or less.

[0111] The optical filter may also have a transmission band showing an average transmittance of 85% or more in the range of 425 to 560 nm. In another example, the average transmittance can be adjusted within a range of 87% or more, 89% or more, 91% or more, or 93% or more, and / or within a range of 98% or less, 96% or less, 94% or less, 92% or less, 90% or less, or 88% or less.

[0112] The optical filter may have a transmission band showing a maximum transmittance of 87% or more within the range of 425 to 560 nm. In another example, the maximum transmittance can be adjusted within a range of 89% or more, 91% or more, 93% or more, or 95% or more, and / or within a range of 100% or less, 98% or less, 96% or less, 94% or less, 92% or less, or 90% or less.

[0113] The optical filter may have a transmission band exhibiting an average transmittance of 2% or less in the range of 300 to 390 nm, which average transmittance can be further adjusted within a range of 0% or more, 0.1% or more, or 0.2% or more, and / or within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1.0% or less, 0.8% or less, 0.6% or less, 0.4% or less, 0.35% or less, or 0.3% or less.

[0114] The optical filter may have a transmission band exhibiting a maximum transmittance of 2% or less within the range of 300 to 390 nm, which can be further adjusted within a range of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, or 0.8% or more, and / or within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less.

[0115] The optical filter may have a transmittance of 2% or less at a wavelength of 700 nm, which may be further adjusted within a range of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, or 0.8% or more, and / or within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less.

[0116] The optical filter may have a transmission band exhibiting an average transmittance of 2% or less in the range of 700 to 800 nm, which may be further adjusted within a range of 0% or more, 0.1% or more, 0.3% or more, 0.4% or more, or 0.5% or more, and / or within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1.0% or less, 0.8% or less, or 0.6% or less.

[0117] The optical filter may have a transmission band showing a maximum transmittance of 2% or less in the range of 700 to 800 nm, which can be further adjusted within a range of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, or 0.8% or more, and / or within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less.

[0118] The optical filter may have a transmission band exhibiting an average transmittance of 2% or less in the range of 800 to 1000 nm, which may be further adjusted within a range of 0% or more, 0.1% or more, 0.3% or more, 0.4% or more, or 0.5% or more, and / or within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1.0% or less, 0.8% or less, or 0.6% or less.

[0119] The optical filter may have a transmission band exhibiting a maximum transmittance of 2% or less within the range of 800 to 1000 nm, which can be further adjusted within a range of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, or 0.8% or more, and / or within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less.

[0120] The optical filter may have a transmission band exhibiting an average transmittance of 5% or less in the range of 1000 to 1200 nm, which may be further adjusted within a range of 0% or more, 0.5% or more, 1% or more, 1.5% or more, 2.0% or more, or 2.5% or more, and / or within a range of 4.5% or less, 4% or less, 3.5% or less, 3% or less, or 2.5% or less.

[0121] The optical filter may have a transmission band exhibiting a maximum transmittance of 10% or less within the range of 1000 to 1200 nm, which can be further adjusted within a range of 0% or more, 1% or more, 2% or more, 3% or more, 4% or more, or 5% or more, and / or within a range of 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less.

[0122] The optical filter may have a transmittance of 10% or less at a wavelength of 1200 nm, which may be further adjusted within a range of 1% or more, 2% or more, 3% or more, 4% or more, or 5% or more, and / or within a range of 9% or less, 8% or less, 7% or less, 6% or less, or 5.5% or less.

[0123] The optical filter also has a low ripple value within the aforementioned range, and can maintain the low ripple value even when the angle of incidence varies.

[0124] That is, the ripple value at an incident angle of 0 degrees of the optical filter and the ripple value at an incident angle of 0 degrees and an incident angle of 40 degrees can be within the above-mentioned ranges.

[0125] As mentioned above, near-infrared absorbing glass (also called blue glass) itself exhibits absorption properties in the near-infrared region, but it is poor at accurately blocking ultraviolet light near the short wavelength region of visible light and infrared light in the long wavelength region of visible light, making it difficult to obtain a sharp visible light transmittance band.

[0126] However, by appropriately forming the ultraviolet absorbing layer and / or infrared absorbing layer described above in the present application, the above-mentioned excellent optical spectrum can be obtained even when the near-infrared absorbing glass is used.

[0127] In this case, the specific types of applicable infrared absorbing layer and / or ultraviolet absorbing layer are as described above.

[0128] The present application also relates to an imaging device including the optical filter. In this case, the configuration of the imaging device and the application of the optical filter are not particularly limited, and known configurations and application methods can be applied.

[0129] Furthermore, the use of the optical filter of the present application is not limited to the imaging device, but can be applied to a variety of other uses that require blocking of near-infrared rays (for example, display devices such as PDPs).

[0130] The present application will be specifically described below based on examples, but the scope of the present application is not limited to the following examples.

[0131] 1. Evaluation of transmittance spectrum The transmittance spectrum of a laminate (e.g., optical filter) comprising an infrared-absorbing glass (e.g., infrared-absorbing substrate) and an infrared-absorbing layer, an ultraviolet-absorbing layer, and / or a dielectric layer formed on the glass was measured using a spectrophotometer (manufacturer: Perkin-Elmer, product name: Lambda 750 Spectrophotometer) on test specimens obtained by cutting the infrared-absorbing glass to a fixed size (10 mm width, 10 mm length, and 0.2 mm thickness, respectively). The transmittance spectrum was measured for each wavelength and incident angle according to the equipment manual. The test specimen (e.g., infrared-absorbing glass) was positioned on a line between the measurement beam and the detector of the spectrophotometer, and the transmittance spectrum was measured while varying the incident angle of the measurement beam from 0° to 40°. Unless otherwise specified, the transmittance spectrum results in this example are those obtained when the incident angle is 0°, which is parallel to the surface normal of the test specimen.

[0132] 2.Evaluation of refractive index The refractive indices of the infrared absorbing glass and the dielectric sub-layer were measured for a wavelength of 520 nm by applying an ellipsometer (M-2000® Ellipsometer) device from Weeds Optics.

[0133] Manufacturing Example 1. Manufacturing of UV absorbing layer material The ultraviolet absorbing layer material was prepared by blending a triazine dye, which has an absorption maximum in the range of approximately 340 to 390 nm, with a binder resin. The binder resin used was PMMA (poly(methyl methacrylate)). The binder resin and absorbent were blended with cyclohexanone to prepare the material, and approximately 5 parts by weight of the dye was mixed with 100 parts by weight of the binder resin.

[0134] Production Example 2: Production of near-infrared absorbing layer material The near-infrared absorbing layer was manufactured using an infrared absorber 1 (squarylium-based dye) having an absorption maximum wavelength in the range of approximately 700 to 720 nm and a full width at half maximum (FWHM) of approximately 50 to 60 nm, an infrared absorber 2 (squarylium-based dye) having an absorption maximum wavelength in the range of approximately 730 to 750 nm and a full width at half maximum (FWHM) of approximately 60 to 70 nm, and an infrared absorber 3 (squarylium-based dye) having an absorption maximum wavelength in the range of approximately 760 to 780 nm and a full width at half maximum (FWHM) of approximately 90 to 100 nm.

[0135] The materials were prepared by blending the three infrared absorbers with a binder resin, which was a cycloolefin polymer (COP).

[0136] The materials were prepared by blending the binder resin and absorbent with toluene, with the blending ratios being 0.1 parts by weight of absorbent 1, 0.2 parts by weight of absorbent 2, and 0.4 parts by weight of absorbent 3 per 100 parts by weight of binder resin, respectively.

[0137] Example 1 For the substrate, near-infrared absorbing glass showing a transmittance spectrum as shown in Figure 6 was used. Near-infrared absorbing glass is glass that is given absorbing properties by adding a coloring component such as copper ions, and is also known as blue glass. In this example, a commercially available product from PTOT was used. The spectral characteristics of the near-infrared absorbing glass are summarized in Table 1 below.

[0138] The near-infrared absorbing glass had a refractive index of about 1.57.

[0139] First, a UV-absorbing layer was formed on one surface of the near-infrared absorbing glass using a UV-absorbing layer material. The UV-absorbing layer was formed to a thickness of about 3 μm by coating the material of Preparation Example 1 on the near-infrared absorbing glass and drying it in a furnace at 140°C for about 2 hours.

[0140] The transmittance spectrum with the UV absorbing layer formed is shown in Figure 7. As shown in Figure 7, it can be seen that the transmittance in the UV region (wavelength range of about 300 to 390 nm) is reduced to 1% or less by the formation of the UV absorbing layer, and the T50% cut-on wavelength of the visible light transmission band is shifted to a longer wavelength.

[0141] An infrared absorbing layer was formed on the UV absorbing layer using the infrared absorbing layer material of Preparation Example 2. The infrared absorbing layer was formed to a thickness of about 3.5 μm by drying the material of Preparation Example 2 in a furnace at 130°C for 2 hours. The transmittance spectrum of the formed infrared absorbing layer is shown in FIG. 8. As shown in FIG. 8, it can be seen that the transmittance in the infrared region (wavelength range of about 700 to 1000 nm) was reduced to less than 1% by the formation of the infrared absorbing layer, and the T50% cutoff wavelength of the visible light transmission band was shifted to a shorter wavelength.

[0142] A dielectric film was formed on the near-infrared absorbing glass on which the ultraviolet and infrared absorbing layers were formed. The dielectric film was formed by depositing a sub-layer using ion-beam assisted deposition. The vacuum and temperature conditions during deposition were 5.0E-5 Torr and 120°C, respectively, and the IBS (Ion Beam Sputtering) source voltage and current were set to 350V and 850mA. Using this method, a high-refractive-index TiO2 layer (refractive index approximately 2.61) and a low-refractive-index SiO2 layer (refractive index approximately 1.46) were alternately formed to form the dielectric film.

[0143] The high refractive index layer and low refractive index layer, which are sub-layers, form a total of six layers. Specifically, a TiO2 layer (thickness: approximately 12.4 nm), a SiO2 layer (thickness: approximately 30.3 nm), a TiO2 layer (thickness: approximately 43.7 nm), a SiO2 layer (thickness: approximately 13 nm), a TiO2 layer (thickness: approximately 30.4 nm), and a SiO2 layer (thickness: approximately 85.3 nm) were sequentially formed on the infrared absorption layer to form a dielectric film. Such a dielectric film has a refractive index of approximately 2.61 (the refractive index of the TiO2 layer) in the following formula 1, and n2 is approximately 1.46 (the refractive index of the SiO2 layer). s is about 1.57 (the refractive index of the near-infrared absorbing glass), and p is 2.5 (=(6-1) / 2), so that the V value is about 5.70.

[0144] [Formula 2] V=K×{[(n1 / n2) 2p ×(n1 2 / n s )-1] / [(n1 / n2) 2p ×(n1 2 / n s )+1]} 2

[0145] Next, a TiO2 layer (approximately 12.4 nm thick), an SiO2 layer (approximately 30.3 nm thick), a TiO2 layer (approximately 43.7 nm thick), an SiO2 layer (approximately 13 nm thick), a TiO2 layer (approximately 30.4 nm thick), and an SiO2 layer (approximately 85.3 nm thick) were sequentially formed on the same side of the near-infrared absorbing glass on which the infrared absorbing layer was not formed, thereby producing an optical filter with dielectric films on both sides and an SiO2 layer (approximately 85.3 nm thick) as the outermost layer.

[0146] The spectrum of the optical filter is shown in Figure 9. As shown in Figure 9, it can be seen that the visible light transmittance of the optical filter is higher than that of the near-infrared absorbing glass, and the T50% cut-off wavelength of the visible light transmission band is shifted to a longer wavelength.

[0147] Table 1 below summarizes the transmittance spectral characteristics of the near-infrared absorbing glass, the near-infrared absorbing glass on which an ultraviolet absorbing layer has been formed (filter A), filter A on which an infrared absorbing layer has been formed (filter B), and an optical filter in which a dielectric film with a V value of 5.70 level has been formed on both sides of filter B.

[0148] In Table 1 below, the unit of transmittance is %.

[0149] In Table 1 below, the average transmittance (Tave) is the sum of the transmittances for each wavelength in the corresponding wavelength range divided by the number of wavelengths (N), as described above, and the transmittances for each wavelength were calculated in 1 nm units.

[0150] [Table 1]

[0151] Comparative Example 1 An optical filter was manufactured in the same manner as in Example 1, except that dielectric films having high and low refractive indices were laminated on the infrared absorbing layer using the same ion-beam assisted deposition method as in the examples to form a total of 19 layers, and 22 dielectric film layers were formed using the same method on the near-infrared absorbing glass on which no infrared absorbing layer was formed. The dielectric film formed on the infrared absorbing layer was formed to exhibit so-called AR (anti-reflection) layer properties, which have visible light anti-reflection properties, and the dielectric film formed on the near-infrared absorbing glass was formed to exhibit so-called IR layer properties, which have infrared reflective properties.

[0152] The materials and thicknesses of the dielectric films having the IR and AR layer characteristics, as well as the lamination order, are as shown in Tables 2 and 3. As a result, the V value of the dielectric film having the IR layer characteristics is 21.9, and the V value of the dielectric film having the AR layer characteristics is about 18.9.

[0153] [Table 2]

[0154] [Table 3]

[0155] Test example 1. The transmittance spectra of the optical filters manufactured in the examples were evaluated at incident angles of 0 degrees, 30 degrees, and 40 degrees, and the results are shown in Figure 10. As can be seen from Figure 10, the optical filters of the examples showed almost the same spectrum regardless of the incident angle. In addition, there was essentially no shift in the T10% cut on and T10% cut off of the visible light transmission band depending on the incident angle.

[0156] Fig. 11 shows the transmittance spectra at incident angles of 0 degrees, 30 degrees, and 40 degrees for Comparative Example 1. As can be seen from Fig. 11, in the case of Comparative Example 1, the T10% cut-on of the visible light transmission band shifted by 5 nm or more depending on the incident angle.

[0157] Test example 2. FIG. 12 is an enlarged view of the transmittance spectrum within the wavelength range of 450 nm to 560 nm (incident angle 0 degrees) in order to confirm the ripple values ​​of the optical filters of the example and comparative example.

[0158] As is clear from the figure, in the case of the optical filter of Comparative Example 1, it is expected that the transmittance fluctuation with wavelength would be severe and a large ripple value would be exhibited, but in the optical filter of Example 1, such fluctuation was hardly observed.

[0159] 13 and 14 show enlarged average values ​​(solid lines) and actual measured values ​​(dots) of transmittance in the range of 450 to 560 nm (incident angle: 0 degrees) in order to confirm the ripple values ​​of Example 1 and Comparative Example 1, respectively, and the difference between Example 1 and Comparative Example 1 can be more clearly confirmed on the drawings.

[0160] For Example 1, the ripple value at an incident angle of 0 degrees was approximately 1.17%, and the ripple value at an incident angle of 40 degrees was approximately 1.20%. For Comparative Example 1, the ripple value at an incident angle of 0 degrees was approximately 2.40%, and the ripple value at an incident angle of 40 degrees was approximately 7.08%.

[0161] The average transmittance (average transmittance) for confirming the ripple value is calculated using a statistical analysis program. Minitab The value was calculated using a cubic spline regression equation.

Claims

1. a transparent substrate that is a near-infrared absorbing glass substrate; a dielectric film formed on one or both surfaces of the transparent substrate and consisting of two or more sub-layers; the dielectric film includes first and second sub-layers having different refractive indices and stacked alternately; The first sublayer and the second sublayer are formed so that a V value according to the following formula 2 is 17 or less, The average transmittance T calculated using a cubic spline regression equation in the wavelength range of 450 nm to 560 nm and at an incident angle of 0 degrees ａｖｅ．ｉ , i = 1 to n and the actual transmittance T ｉ , i = 1 to n = T ｄｉｆｆ．ｉ =T ｉ -T ａｖｅ．ｉ (i = 1 to n) for every 1 nm wavelength, and then the maximum value of the obtained difference Max (T ｄｉｆｆ．ｉ ) and the minimum value Min(T ｄｉｆｆ．ｉ An optical filter having a ripple value of 2.5% or less, which is calculated by subtracting the above-mentioned ripple value from the above-mentioned ripple value. [Formula 2] V=K×{[(n １ / n ２ ) ２ｐ ×(n １ ２ / n ｓ )-1] / [(n １ / n ２ ) ２ｐ ×(n １ ２ / n ｓ )+1]} ２ In Equation 2, n １ is the refractive index of the first sublayer, and n ２ is the refractive index of the second sublayer, and n １ >n ２ and n ｓ is the refractive index of the transparent substrate, K is the total number of first and second sublayers in the dielectric film, and p is a number that satisfies K=(2p+1).

2. Ripple value R at an incident angle of 0 degrees in the wavelength range of 450 nm to 560 nm ０ and the ripple value R at an incident angle of 40 degrees ４０ 2. The optical filter according to claim 1, wherein the absolute value of the difference between

3. 2. The optical filter according to claim 1, wherein the T50% cut-on wavelength is in the range of 400 to 420 nm, the T50% cut-off wavelength is in the range of 610 to 650 nm, and the optical filter has a transmission band showing an average transmittance of 85% or more in the wavelength range of 425 to 560 nm.

4. 4. The optical filter according to claim 3, wherein the maximum transmittance within the wavelength range of 425 to 560 nm is 87% or more.

5. 4. The optical filter according to claim 3, which exhibits an average transmittance and a maximum transmittance of 2% or less within a wavelength range of 300 to 390 nm.

6. 4. The optical filter according to claim 3, which has a transmittance of 2% or less at a wavelength of 700 nm, an average transmittance and a maximum transmittance of 2% or less within a wavelength range of 700 to 800 nm, an average transmittance and a maximum transmittance of 2% or less within a wavelength range of 800 to 1000 nm, an average transmittance of 5% or less and a maximum transmittance of 10% or less within a wavelength range of 1000 to 1200 nm, and a transmittance of 10% or less at a wavelength of 1200 nm.

7. 2. The optical filter according to claim 1, wherein the transparent substrate is a CuO-containing fluorophosphate glass substrate or a CuO-containing phosphate glass substrate.

8. The refractive index of the first sublayer, n １ and the refractive index of the second sublayer n ２ The ratio of n １ / n ２ 2. The optical filter according to claim 1, wherein the σ is in the range of 1.4 to 2.

0.

9. The refractive index of the first sublayer, n １ The optical filter according to claim 8, wherein is in the range of 1.8 to 3.

5.

10. The refractive index of the first sublayer, n １ and the refractive index of the transparent substrate n ｓ The ratio of n １ / n ｓ 2. The optical filter according to claim 1, wherein the σ is in the range of 1.4 to 2.

0.

11. 2. The optical filter according to claim 1, wherein K in formula 2 is 15 or less.

12. The optical filter of claim 1, wherein the thicknesses of the first and second sublayers are each in the range of 5 to 200 nm, and the average thickness of the first sublayer and the second sublayer included in the dielectric film is in the range of 5 to 70 nm.

13. 2. The optical filter according to claim 1, wherein the dielectric film has a thickness in the range of 100 to 500 nm.

14. 2. The optical filter according to claim 1, wherein the dielectric film is formed on both sides of the transparent substrate.

15. 10. The optical filter of claim 1, further comprising one or more layers selected from the group consisting of an infrared absorbing layer and an ultraviolet absorbing layer.

16. The dielectric film includes an ultraviolet absorbing layer and an infrared absorbing layer, a T50% cut-on wavelength in the range of 400 to 420 nm, a T50% cut-off wavelength in the range of 610 to 650 nm, and a transmission band showing an average transmittance of 85% or more in the wavelength range of 425 to 560 nm; exhibiting an average transmittance and a maximum transmittance of 2% or less within a wavelength range of 300 to 390 nm; 2. The optical filter according to claim 1, which has a transmittance of 2% or less at a wavelength of 700 nm, and an average transmittance and a maximum transmittance of 2% or less within the wavelength range of 700 to 800 nm.

17. The infrared absorbing layer is a first absorbent having an absorption maximum wavelength in the range of 700 to 720 nm and a half-width in the range of 50 to 60 nm; A second absorber having an absorption maximum wavelength in the range of 730 to 750 nm and a half-width in the range of 60 to 70 nm; and 17. The optical filter according to claim 16, comprising a third absorber having an absorption maximum wavelength in the range of 760 to 780 nm and a half-width in the range of 90 to 100 nm.

18. The ultraviolet absorbing layer is a first absorber having an absorption maximum wavelength in the range of 340 to 350 nm; and 17. The optical filter according to claim 16, comprising a second absorber having an absorption maximum wavelength in the range of 360 to 370 nm.

19. An imaging device comprising the optical filter of any one of claims 1 to 18.

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