Optical filter and imaging device

Abstract

To provide an optical filter which effectively blocks ultraviolet and infrared rays, exhibits a high transmittance for visible light, stably maintains the transmission properties even when the angle of incidence varies, and is free from problems like ripples and petal flares, and to provide uses thereof.SOLUTION: An optical filter is provided, comprising an infrared absorbing substrate containing copper, a first dielectric film formed on a first surface of the infrared absorbing substrate, the first dielectric film including a structure consisting of repetitively laminated first and second sub-layers having different refractive indices, and a second dielectric film formed on a second surface of the infrared absorbing substrate, the second dielectric film including a structure consisting of repetitively laminated third and fourth sub-layers having different refractive indices, where a sum of a value (V1) of V represented by a formula 1 for the first dielectric film and a value (V2) of V for the second dielectric film is in a range of 50 to 75, and a ratio V2 / V1 is in a range of 3 to 7, and where the shortest wavelength corresponding to 50% reflectance in a wavelength range of 600-900 nm is 720 nm or greater, or nonexistent for the first or second dielectric film.SELECTED DRAWING: Figure 18

Description

[Technical field]

[0001] The present disclosure relates to an optical filter and an imaging device. [Background technology]

[0002] Optical filters are used in imaging devices that use CCD (Charge-Coupled Device) and CMOS (Complementary Metal-Oxide-Semiconductor) image sensors, etc. These optical filters are used to obtain good color reproducibility and clear images, and are also called near-infrared cut filters.

[0003] Many characteristics are required for such optical filters.

[0004] The optical filter must effectively block light in the ultraviolet and infrared regions and transmit visible light with high transmittance, and therefore must have abrupt and sharp changes in transmittance at the boundaries between the ultraviolet and visible light and between the infrared and visible light to be blocked.

[0005] It is necessary for an optical filter to maintain the above-mentioned transmission and blocking characteristics even when the angle of incidence changes. With the development of wide-angle cameras and the like, such characteristics have become more important, and the need for optical filters that maintain the transmission and blocking characteristics even at a wider angle of incidence has increased.

[0006] It is also necessary for the optical filter to suppress a phenomenon called ripple. Ripple is a phenomenon in which a periodic variation in transmittance occurs in the visible light region, and a phenomenon in which the actual transmittance in a certain region is periodically observed to be larger or smaller than the average transmittance of the corresponding region. The imaging device senses the visible light transmitted through the optical filter using sensors for RGB (Red, Green, Blue). The sensitivity of each RGB sensor is adjusted taking into account the average transmittance by wavelength, but if ripple occurs, fluctuations occur in the light recognized by the sensor, resulting in a decrease in color reproducibility. Such a ripple phenomenon can generate an area (a so-called bunk area) where the transmittance drops instantaneously in the visible light region, which induces a ghost phenomenon, and such a ghost phenomenon also reduces color reproducibility.

[0007] Recently, a phenomenon called petal flare has become a problem. The petal flare phenomenon refers to the phenomenon in which red lines that cannot be seen with the naked eye appear in a photograph when photographing a light source, and is called petal flare because the red lines often have a petal-like shape based on the light source. The frequency of petal flare is increasing as the sensitivity of sensors included in imaging devices increases and the transmittance of optical filters is increased to obtain clearer photographs.

[0008] Known optical filters include those that use an absorption layer containing an absorbent and / or a reflection layer that is a dielectric film. By using a dielectric film, it is possible to block light in the ultraviolet and / or infrared regions. However, the dielectric film has a characteristic that the transmittance curve changes (shifts) depending on the angle of incidence. Therefore, in order to compensate for the shortcomings of the dielectric film, optical filters are also known that use an absorption layer containing a near-infrared absorbing dye whose transmittance has a small dependency on the angle of incidence.

[0009] There are also optical filters that use infrared absorbing glass (also called blue glass) as a substrate, which has near-infrared absorbing properties. Infrared absorbing glass is a glass filter in which CuO or the like is added to glass so that it selectively absorbs light in the near-infrared wavelength range.

[0010] However, since infrared absorbing glass also exhibits some absorption characteristics in the visible light region, there is a problem in that the transmittance of visible light is also reduced.

[0011] Obtaining an optical filter that exhibits desired blocking and transmission characteristics, but does not shift in transmission characteristics with angle of incidence, and does not produce ripples, petal flare, etc., is a difficult problem. Summary of the Invention [Problem to be solved by the invention]

[0012] The present disclosure aims to provide an optical filter and its use. The present disclosure aims to provide an optical filter that effectively blocks ultraviolet and infrared rays and exhibits high transmittance for visible light, and its use. The present disclosure aims to provide an optical filter in which the above-mentioned transmission characteristics are stably maintained even when the angle of incidence varies, and its use. The present disclosure aims to provide an optical filter that does not have problems such as ripples and petal flare, and its use. [Means for solving the problem]

[0013] Among the physical properties mentioned in this specification, those whose results are affected by the measurement temperature are measured at room temperature, unless otherwise specified.

[0014] The term "room temperature" refers to a natural temperature that is neither heated nor cooled, and means, for example, any temperature within the range of 10° C. to 30° C., such as a temperature of about 23° C. or about 25° C. In addition, the unit of temperature in this specification is Celsius (° C.) unless otherwise specified.

[0015] Among the physical properties mentioned in this specification, those whose results are affected by the measurement pressure are the results measured at normal pressure, unless otherwise specified.

[0016] The term "normal pressure" refers to the natural pressure without pressure increase or decrease, and generally means atmospheric pressure of about 740mmHg to 780mmHg.

[0017] In the present specification, when a physical property is affected by the measurement humidity, the physical property is measured at room temperature and / or pressure at natural humidity without any special adjustment.

[0018] When an optical property (eg, refractive index) referred to in this disclosure is a property that varies with wavelength, the optical property is for light with a wavelength of 520 nm, unless otherwise specified.

[0019] In this disclosure, the term "transmittance" or "reflectance" means the actual transmittance (measured transmittance) or actual reflectance (measured reflectance) observed at a specific wavelength, unless otherwise specified.

[0020] Furthermore, the terms "transmittance" and "reflectance" used herein refer to transmittance and reflectance based on an incident angle of 0 degrees, unless otherwise specified.

[0021] In the present disclosure, unless otherwise specified, the term "average transmittance" refers to the result of measuring the transmittance at each wavelength while increasing the wavelength by 1 nm from the shortest wavelength in a given wavelength range, and then calculating the arithmetic average of the measured transmittance. For example, the average transmittance within a wavelength range of 350 nm to 360 nm is the arithmetic average of the transmittances measured at wavelengths of 350 nm, 351 nm, 352 nm, 353 nm, 354 nm, 355 nm, 356 nm, 357 nm, 358 nm, 359 nm, and 360 nm.

[0022] The term "maximum transmittance" as used herein refers to the maximum transmittance measured at each wavelength, starting from the shortest wavelength in a given wavelength range and increasing the wavelength by 1 nm. For example, the maximum transmittance in the wavelength range of 350 nm to 360 nm is the highest transmittance measured at wavelengths of 350 nm, 351 nm, 352 nm, 353 nm, 354 nm, 355 nm, 356 nm, 357 nm, 358 nm, 359 nm, and 360 nm.

[0023] In this disclosure, the term "average reflectance" refers to the result of measuring the reflectance at each wavelength in a given wavelength range, starting from the shortest wavelength and increasing the wavelength by 1 nm, and then calculating the arithmetic average of the measured reflectances, unless otherwise specified. For example, the average reflectance within a wavelength range of 350 nm to 360 nm is the arithmetic average of the reflectances measured at wavelengths of 350 nm, 351 nm, 352 nm, 353 nm, 354 nm, 355 nm, 356 nm, 357 nm, 358 nm, 359 nm, and 360 nm.

[0024] The term "maximum reflectance" as used herein refers to the maximum reflectance measured at each wavelength, starting from the shortest wavelength in a given wavelength range and increasing the wavelength by 1 nm. For example, the maximum reflectance in the wavelength range of 350 nm to 360 nm is the highest reflectance measured at wavelengths of 350 nm, 351 nm, 352 nm, 353 nm, 354 nm, 355 nm, 356 nm, 357 nm, 358 nm, 359 nm, and 360 nm.

[0025] In this specification, the term "incident angle" refers to an angle based on the normal to the surface to be evaluated. For example, the transmittance of an optical filter at an incident angle of 0 degrees means the transmittance of light incident in a direction substantially parallel to the normal to the surface of the optical filter. For example, an incident angle of 40 degrees is a value for incident light that forms an angle of substantially 40 degrees with the normal in a clockwise or counterclockwise direction. This definition of the incident angle is also applied to other characteristics such as transmittance.

[0026] The optical filter of the present disclosure 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 implement a visible light transmission band with high transmittance.

[0027] The optical filter of the present disclosure may include a transparent substrate, and a so-called infrared absorbing substrate may be applied as the transparent substrate. The infrared absorbing substrate is a substrate that exhibits absorption characteristics in at least a part of the infrared region. A representative example of the infrared absorbing substrate is so-called blue glass, which exhibits the above characteristics by containing copper. Such an infrared absorbing substrate is useful in constructing an optical filter that blocks light in the infrared region, but is disadvantageous in terms of ensuring high transmittance in the visible light region due to the absorption characteristics. In the present disclosure, an infrared absorbing substrate is selected and combined with a specific dielectric film to provide an optical filter that efficiently blocks light in the desired ultraviolet and infrared regions and exhibits high transmittance characteristics in the visible light region.

[0028] The infrared absorbing substrate may have an average transmittance of 75% or more in the range of 425 nm to 560 nm. In other examples, the average transmittance may be in the range of 77% or more, 79% or more, 81% or more, 83% or more, 85% or more, 87% or more, 89% or more, or 91% or more, and / or in the range of 98% or less, 96% or less, 94% or less, or 92% or less.

[0029] The infrared absorbing substrate may have a maximum transmittance of 80% or more in the range of 425 nm to 560 nm. In other examples, the maximum transmittance may be in the range of 82% or more, 84% or more, 86% or more, 88% or more, 90% or more, or 92% or more, and / or in the range of 100% or less, 98% or less, 96% or less, or 94% or less.

[0030] The infrared absorbing substrate may have an average transmittance of 75% or more in the range of 350 nm to 390 nm. In other examples, the average transmittance may be in the range of 77% or more, 79% or more, or 81% or more, and / or in the range of 98% or less, 96% or less, 94% or less, 92% or less, 90% or less, 88% or less, 86% or less, or 84% or less.

[0031] The infrared absorbing substrate may have a maximum transmittance of 80% or more in the range of 350 nm to 390 nm. In other examples, the maximum transmittance may be in the range of 82% or more, 84% or more, or 86% or more, and / or in the range of 100% or less, 98% or less, 96% or less, 94% or less, 92% or less, 90% or less, or 88% or less.

[0032] The infrared absorbing substrate may have a transmittance of 30% or less at a wavelength of 700 nm. In other examples, the transmittance may be about 28% or less, 26% or less, 24% or less, 22% or less, 20% or less, 18% or less, 16% or less, 14% or less, or 12% or less, or about 0% or more, 2% or more, 4% or more, 6% or more, 8% or more, 10% or more, or 12% or more.

[0033] The infrared absorbing substrate may have an average transmittance of 10% or less in the range of 700 nm to 800 nm. In other examples, the average transmittance may be in the range of 0% or more, 0.5% or more, 1% or more, 1.5% or more, 2% or more, 2.5% or more, 3% or more, or 3.5% or more, and / or in the range of 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, or 4% or less.

[0034] The infrared absorbing substrate may have a maximum transmittance of 20% or less in the range of 700 nm to 800 nm. The maximum transmittance may be in the range of 0% or more, 2% or more, 6% or more, 8% or more, 10% or more, or 12% or more, and / or in the range of 19% or less, 18% or less, 17% or less, 16% or less, 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, or 10% or less.

[0035] The infrared absorbing substrate may have an average transmittance of 5% or less in the range of 800 nm to 1000 nm. The average transmittance may be further adjusted within the range of 0% or more, 0.1% or more, 0.2% or more, or 0.3% or more, and / or 4.8% or less, 4.6% or less, 4.4% or less, 4.2% or less, 4.0% or less, 3.8% or less, 3.6% or less, 3.4% or less, 3.2% or less, 3.0% or less, 2.8% or less, 2.6% or less, 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, or 0.6% or less.

[0036] The infrared absorbing substrate may have a maximum transmittance of 5% or less in the range of 800 nm to 1000 nm. The maximum transmittance may be in the range of 0% or more, 0.2% or more, 0.4% or more, or 0.6% or more, and / or 4.8% or less, 4.6% or less, 4.4% or less, 4.2% or less, 4.0% or less, 3.8% or less, 3.6% or less, 3.4% or less, 3.2% or less, 3.0% or less, 2.8% or less, 2.6% or less, 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, or 0.6% or less.

[0037] The infrared absorbing substrate may have an average transmittance of 10% or less in the range of 1000 nm to 1200 nm. In other examples, the average transmittance may be adjusted within a range of 0% or more, 0.5% or more, 1% or more, or 1.5% or more, and / or 9.5% or less, 9% or less, 8.5% or less, 8% or less, 7.5% or less, 7% or less, 6.5% or less, 6% or less, 5.5% or less, 5% or less, 4.5% or less, 4% or less, 3.5% or less, 3% or less, 2.5% or less, or 2% or less.

[0038] The infrared absorbing substrate may have a transmission band showing a maximum transmittance of 10% or less in the range of 1000 nm to 1200 nm. In other examples, the maximum transmittance may be in the range of 0% or more, 0.5% or more, 1% or more, 1.5% or more, 2% or more, 2.5% or more, 3% or more, or 3.5% or more, and / or in the range of 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, or 4% or less.

[0039] An infrared absorbing substrate having the above characteristics can be combined with the dielectric film of the present disclosure to form the desired optical filter.

[0040] As such a substrate, a substrate known as so-called infrared absorbing glass can be used. Such glass is an absorbing glass manufactured by adding CuO or the like to fluorophosphate glass or phosphate glass. Therefore, as an example, in the present disclosure, a CuO-containing fluorophosphate glass substrate or a CuO-containing phosphate glass substrate may be used as the infrared absorbing substrate. The phosphate glass includes silicate phosphate glass in which a part of the glass skeleton is composed of SiO2. Such absorbing glass is well known, and for example, glass disclosed in Korean Patent Registration No. 10-2056613 and other commercially available absorbing glasses (for example, commercially available products from HOYA, SCHOTT, PTOT, etc.) can be used.

[0041] Such an infrared absorbing substrate includes copper. In the present disclosure, a substrate having a copper content in the range of 7% by weight to 30% by weight can be used. At this time, a method for measuring the copper content is summarized in the examples of the present specification. In other examples, the copper content may be about 8% by weight or more, 9% by weight or more, 10% by weight or more, 11% by weight or more, or 12% by weight or more, or about 28% by weight or less, 26% by weight or less, 24% by weight or less, 22% by weight or less, 20% by weight or less, 18% by weight or less, 16% by weight or less, 14% by weight or less, or 13% by weight or less. A substrate having such a copper content is likely to exhibit the above-mentioned optical properties, and can be combined with a dielectric film described later to form an optical filter with desired properties.

[0042] The thickness of the infrared absorbing substrate may be adjusted within a range of, for example, about 0.03 mm to 5 mm, but is not limited thereto.

[0043] The optical filter of the present disclosure may include dielectric films on both sides of the infrared absorbing substrate. For convenience, in the following description, one of the dielectric films formed on both sides of the infrared absorbing substrate may be referred to as a first dielectric film, and the other may be referred to as a second dielectric film.

[0044] The infrared absorbing substrate may include a first dielectric film formed on a first surface and a second dielectric film formed on a second surface, where the first surface refers to any one of the main surfaces of the infrared absorbing substrate, and the second surface refers to the other main surface of the infrared absorbing substrate opposite to the first surface.

[0045] FIG. 1 shows an exemplary structure of such an optical filter, in which the dielectric films 201 and 202 are formed on both sides of an infrared absorbing substrate 100 .

[0046] The first and second dielectric films may each have a multilayer structure including at least two sublayers having different refractive indices, and may include a multilayer structure in which the two sublayers are repeatedly stacked. For example, the first dielectric film may include a structure in which first and second sublayers having different refractive indices are repeatedly stacked, and the second dielectric film may include a structure in which third and fourth sublayers having different refractive indices are repeatedly stacked.

[0047] The first and second sublayers are sublayers that are differentiated by the difference in refractive index between them, and the third and fourth sublayers are also sublayers that are differentiated by the difference in refractive index between them. Therefore, as long as the first sublayer has a different refractive index from the second sublayer, the first sublayer may be made of the same material as the third or fourth sublayer, and this is also true for the second to fourth sublayers.

[0048] Typically, a dielectric film is a film formed by repeatedly stacking a dielectric material with a low refractive index and a dielectric material with a high refractive index, and is used to form a so-called IR reflective layer and an AR (anti-reflection) layer. In the present disclosure, such a known dielectric film for forming an IR reflective layer or an AR layer may be applied.

[0049] By adjusting the formation form of the dielectric film in relation to the infrared absorbing substrate, the desired optical filter can be provided.

[0050] For example, in the optical filter of the present disclosure, the sum (V1+V2) of the V value (V1) of the first dielectric film according to the following formula 1 and the V value (V2) of the second dielectric film according to the following formula 1 may be in the range of 50 to 75.

[0051]

number

[0052] In Equation 1, when checking the V value of the first dielectric film, R is the ratio (n1 / n2) of the refractive index (n1) of the sublayer having the higher refractive index among the first and second sublayers to the refractive index (n2) of the sublayer having the lower refractive index among the first and second sublayers, and when checking the V value of the second dielectric film, R is the ratio (n1 / n2) of the refractive index (n1) of the sublayer having the higher refractive index among the third and fourth sublayers to the refractive index (n2) of the sublayer having the lower refractive index among the third and fourth sublayers.

[0053] In Equation 1, n2 is the refractive index (n2) of the sublayer having the smaller refractive index among the first and second sublayers when checking the V value of the first dielectric film, and is the refractive index (n2) of the sublayer having the smaller refractive index among the third and fourth sublayers when checking the V value of the second dielectric film.

[0054] In formula 1, Cu is the content of copper contained in the infrared absorbing substrate.

[0055] In Equation 1, K is the total number of the first and second sublayers in the first dielectric film when checking the V value of the first dielectric film, and K is the total number of the third and fourth sublayers in the second dielectric film when checking the V value of the second dielectric film, and 2p is K-1.

[0056] The first and second sublayers for determining the V value of formula 1 are sublayers that form a repeated laminate structure of sublayers with different refractive indices in the first dielectric film, and the total number of layers of the first and second sublayers is at least 50% or more, 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, or 95% or more of the total number of layers of all the sublayers in the first dielectric film. There is no upper limit to the ratio of the total number of layers of the first and second sublayers, and it may be, for example, less than or equal to 100%. That is, the first dielectric film may include only the first and second sublayers, or may include other sublayers.

[0057] The third and fourth sublayers, which are used to determine the V value in formula 1, are sublayers that form a repeated laminate structure of sublayers with different refractive indices in the second dielectric film, and the total number of layers of the third and fourth sublayers is at least 50% or more, 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, or 95% or more of the total number of all sublayers in the second dielectric film. There is no upper limit to the ratio of the total number of layers of the third and fourth sublayers, and it may be, for example, less than or equal to 100%. That is, the first dielectric film may include only the third and fourth sublayers, or may include other sublayers.

[0058] In other examples, the sum of the V values ​​(V1+V2) may be 52 or more, 54 or more, 56 or more, 58 or more, 60 or more, or 61 or more, or may be 73 or less, 71 or less, 69 or less, 67 or less, 65 or less, or 63 or less.

[0059] In the optical filter, the ratio V2 / V1 of the V value (V2) of the second dielectric film to the V value (V1) of the first dielectric film may be within a range of 3 to 7. In other examples, the ratio V2 / V1 may be 3.5 or more, 4 or more, or 4.5 or more, or about 6.5 or less, 6 or less, 5.5 or less, or 5 or less.

[0060] A dielectric film formed to satisfy these conditions can provide an optical filter that exhibits the desired blocking and transmission characteristics by complementing or improving the insufficient properties of the infrared absorbing substrate and does not cause problems such as ripples and petal flare.

[0061] The value of V in Equation 1 is proportional to the difference in refractive index between the first and second sublayers or the third and fourth sublayers, the copper content in the substrate, and the total number of layers, i.e., the first and second sublayers or the third and fourth sublayers, and is inversely proportional to the refractive index of the sublayer with the lower refractive index among the first and second sublayers and the third and fourth sublayers.

[0062] The factors that affect the V value each affect the transmission and reflection characteristics of the individual components of the optical filter.

[0063] For example, as the copper content in the substrate increases, the substrate's absorption characteristics in the long wavelength region increase, and a sharper decrease in transmittance is observed from a wavelength of about 550 nm onwards. Therefore, while an increase in the copper content in the substrate is advantageous in terms of blocking light in the long wavelength region, the increased copper content reduces the durability of the substrate.

[0064] The difference in refractive index between the first and second sublayers (or the third and fourth sublayers), the total number of the first and second sublayers (or the third and fourth sublayers), and the refractive index of the sublayer with the lower refractive index among the first and second sublayers (or the third and fourth sublayers) affect the transmission and reflection characteristics of each dielectric film.

[0065] In the present disclosure, by combining the substrate and the dielectric film such that the sum of the V values ​​of the first and second dielectric films is within the range of 15 to 50 and the ratio of the V values, V2 / V1, is within the range of 4 to 12, it is possible to maximize the contribution of each element (substrate and dielectric film) within the optical filter to exhibiting the desired optical characteristics of the optical filter, and to eliminate the characteristics of any one element that may have a negative effect on the characteristics of the optical filter while complementing it with the other element.

[0066] As a result, the present disclosure provides an optical filter and its uses that effectively blocks ultraviolet and infrared rays, exhibits high transmittance for visible light, and stably maintains these characteristics even when the angle of incidence varies, does not cause problems such as ripple and petal flare, and has excellent durability.

[0067] For example, if the optical filter is configured so that the sum of the V values ​​of the first and second dielectric films is excessively large, problems may occur such as a decrease in the durability of the optical filter and / or a decrease in transmittance in the visible light range, or the optical filter may block usable long-wavelength light in the visible light range, reducing the light utilization efficiency.

[0068] If the optical filter is configured so that the sum of the V values ​​of the first and second dielectric films is excessively small, the efficiency of the optical filter in blocking light in the long wavelength region will decrease, and a local increase in transmittance may occur in some regions (e.g., the 700 nm to 800 nm region) within the long wavelength region that should be blocked.

[0069] If the ratio of the V values ​​of the first and second dielectric films becomes excessively small or large, problems such as a decrease in the durability of the optical filter and / or a decrease in transmittance in the visible light region may occur, or the optical filter may block usable long-wavelength light in the visible light region, reducing the light utilization efficiency.Furthermore, problems such as a decrease in the efficiency of the optical filter in blocking light in the long-wavelength region and / or a local increase in transmittance in some regions within the long-wavelength region (e.g., the 700 nm to 800 nm region) may occur.

[0070] In formula 1, the ratio (n1 / n2) of the refractive index (n1) of the layer with the higher refractive index among the first and second sublayers or the third and fourth sublayers to the refractive index (n2) of the layer with the lower refractive index may be in the range of about 1.4 to 2.0, for example. 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 about 1.95 or less, 1.9 or less, 1.85 or less, or 1.8 or less.

[0071] In formula 1, the refractive index (n1) of the layer having the higher refractive index among the first and second sublayers or the third and fourth sublayers may be in the range of about 1.8 to 3.5. In other examples, 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 about 3.3 or less, 3.1 or less, 2.9 or less, or 2.7 or less.

[0072] In formula 1, the refractive index (n2) of the layer having the lower refractive index among the first and second sublayers or the third and fourth sublayers may be in the range of about 1.1 to 1.7. In other examples, 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.

[0073] Cu in formula 1, i.e., the copper content contained in the infrared absorbing substrate, may be in the range of 7 wt% to 30 wt% as described above. When calculating the V value in formula 1, the copper content is substituted with only a number, ignoring the unit. That is, the V value in formula 1 may be dimensionless. Cu in formula 1 may be about 8 wt% or more, 9 wt% or more, 10 wt% or more, 11 wt% or more, or 12 wt% or more, or about 28 wt% or less, 26 wt% or less, 24 wt% or less, 22 wt% or less, 20 wt% or less, 18 wt% or less, 16 wt% or less, 14 wt% or less, or 13 wt% or less.

[0074] In the case of the first dielectric film, K, which determines 2p in Equation 1, i.e., the total number of layers of the first sublayer and the second sublayer (the number of layers of the first sublayer + the number of layers of the second sublayer), 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, or about 9 or less, and as another example, may be 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, or 9 or more. The first dielectric film may include a repeated stacked structure of the first and second sublayers, and therefore, in such a case, the number of layers of each of the first and second sublayers may be the same as each other, or any one of the layers may be about one or two layers more.

[0075] The total number of all sub-layers included in such a first dielectric film may be about 20 layers or less, 19 layers or less, 18 layers or less, 17 layers or less, 16 layers or less, 15 layers or less, 14 layers or less, 13 layers or less, 12 layers or less, 11 layers or less, 10 layers or less, or 9 layers or less, and as other examples, it may be 2 layers or more, 3 layers or more, 4 layers or more, 5 layers or more, 6 layers or more, 7 layers or more, 8 layers or more, or 9 layers or more.

[0076] In the case of the second dielectric film, K, which determines 2p in Equation 1, i.e., the total number of layers of the third and fourth sublayers (number of layers of the third sublayers + number of layers of the fourth sublayers), may be about 60 or less, 58 or less, 56 or less, 54 or less, 52 or less, 50 or less, 48 ​​or less, 46 or less, 44 or less, 42 or less, 40 or less, or about 39 or less, or about 10 or more, 12 or more, 13 or more, 14 or more, 16 or more, 18 or more, 20 or more, 22 or more, 24 or more, 26 or more, 28 or more, 30 or more, 32 or more, 34 or more, 36 or more, 38 or more, or about 39 or more. The second dielectric film may include a repeated stack structure of the third and fourth sublayers, and therefore in such a case, the number of layers of the third and fourth sublayers may be the same as each other, or any one of the layers may be about one or two layers more.

[0077] The total number of all sub-layers included in such a second dielectric film may be, for example, about 70 layers or less, 68 layers or less, 66 layers or less, 64 layers or less, 62 layers or less, 60 layers or less, 58 layers or less, 56 layers or less, 54 layers or less, 52 layers or less, 50 layers or less, 48 ​​layers or less, 46 layers or less, 44 layers or less, 42 layers or less, 40 layers or less, or 39 layers or less, or about 10 layers or more, 12 layers or more, 13 layers or more, 14 layers or more, 16 layers or more, 18 layers or more, 20 layers or more, 22 layers or more, 24 layers or more, 26 layers or more, 28 layers or more, 30 layers or more, 32 layers or more, 34 layers or more, 36 layers or more, 38 layers or more, or 39 layers or more.

[0078] The thickness of each of the first and second sub-layers in the first dielectric film may be adjusted according to the purpose, and may be within the range of about 1 nm to 200 nm. Other examples of the thickness include 3 nm or more, 5 nm or more, 7 nm or more, 9 nm or more, 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, 85 nm or more, 90 nm or more, or 95 nm or more, or 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, 15 nm or less, or 10 nm or less.

[0079] The average (arithmetic mean) thickness of the first sub-layer and the second sub-layer included in the first dielectric film may be within a range of about 10 nm to 100 nm, and may be, for example, 15 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, 35 nm or more, or 40 nm or more, or 95 nm or less, 90 nm or less, 85 nm or less, 80 nm or less, 75 nm or less, 70 nm or less, 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.

[0080] The first or second dielectric film may have a total thickness in the range of about 200 nm to 500 nm. In other examples, the thickness may be 220 nm or more, 240 nm or more, 260 nm or more, 280 nm or more, 300 nm or more, 320 nm or more, 340 nm or more, or 360 nm or more, or 480 nm or less, 460 nm or less, 440 nm or less, 420 nm or less, 400 nm or less, or 380 nm or less.

[0081] The first dielectric film may have a laminate structure including the first and second sublayers alternately, with one surface formed of the first sublayer and the other surface formed of the second sublayer. For example, the surface of the laminate structure of the first dielectric film facing the infrared absorbing substrate may be formed of the first sublayer or the second sublayer, and the opposite surface may be formed of the second sublayer or the first sublayer. However, such a laminate order may be changed.

[0082] The thickness of each of the second dielectric film, the third sub-layer, and the fourth sub-layer can be adjusted according to the purpose, and may be within a range of about 1 nm to 300 nm. Other examples of the thickness include 5 nm or more, 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, 85 nm or more, 90 nm or more, 95 nm or more, 100 nm or more, 105 nm or more, 110 nm or more, 115 nm or more, 120 nm or more, 125 nm or more, 130 nm or more, 135 nm or more, and the like. on the order of 140 nm or more, 145 nm or more, 150 nm or more, 155 nm or more, 160 nm or more, 165 nm or more, 170 nm or more, 175 nm or more, 180 nm or more, 185 nm or more, or 190 nm or more, or on the order of 290 nm or less, 280 nm or less, 270 nm or less, 260 nm or less, 250 nm or less, 240 nm or less, 230 nm or less, 220 nm or less, 210 nm or less, 200 nm or less, or 195 nm or less.

[0083] The average value (arithmetic mean) of the thickness of the third sub-layer and the fourth sub-layer included in the second dielectric film may be within a range of about 50 nm to 300 nm. The average value may be, for example, 55 nm or more, 60 nm or more, 75 nm or more, 80 nm or more, 95 nm or more, 100 nm or more, 105 nm or more, 110 nm or more, 115 nm or more, 120 nm or more, or 125 nm or more, or 290 nm or less, 280 nm or less, 270 nm or less, 260 nm or less, 250 nm or less, 240 nm or less, 230 nm or less, 220 nm or less, 210 nm or less, 200 nm or less, 190 nm or less, 180 nm or less, 170 nm or less, 160 nm or less, 150 nm or less, 140 nm or less, or 130 nm or less.

[0084] The second dielectric film may have a total thickness in the range of about 3000 nm to 7000 nm. In other examples, the thickness may be 3500 nm or more, 4000 nm or more, or 4500 nm or more, or 6500 nm or less, 6000 nm or less, 5500 nm or less, or 5000 nm or less.

[0085] In the second dielectric film, the third and fourth sublayers may be alternately stacked, and both surfaces of the second dielectric film may be formed of the same sublayer. For example, the third and fourth sublayers may be stacked with a layer having a high refractive index or a layer having a low refractive index. However, the stacking order may be changed.

[0086] The V value V1 of the first dielectric film according to Formula 1 may be, for example, in the range of 7 to 20. In other examples, V1 may be about 8 or more, 9 or more, or 10 or more, or about 19 or less, 18 or less, 17 or less, 16 or less, 15 or less, 14 or less, 13 or less, 12 or less, or 11 or less.

[0087] The V value V2 of the second dielectric film according to Formula 1 may be, for example, in the range of 40 to 70. In other examples, V2 may be about 42 or more, 44 or more, 46 or more, 48 or more, or 50 or more, or about 68 or less, 66 or less, 64 or less, 62 or less, 60 or less, 58 or less, 56 or less, 54 or less, 52 or less, or 51 or less.

[0088] The first and second dielectric films having the above characteristics can ensure the desired optical characteristics together with the infrared absorbing substrate.

[0089] The material for forming the first or second dielectric film, i.e., the material for forming each of the sub-layers, is not particularly limited, and known materials can be used. Usually, the low refractive index sub-layer is manufactured using SiO2 or Na5Al3F 14 For the manufacture of the high refractive index sub-layer, fluorides such as Na3AlF6 or MgF2 may be applied, and for the manufacture of the high refractive index sub-layer, TiO2, Ta2O5, Nb2O5, ZnS or ZnSe may be applied, but the materials applied in the present disclosure are not limited to the above.

[0090] To ensure a suitable effect, one of the first and second dielectric films may be a dielectric film having stronger reflective properties than the other one, for example, the second dielectric film may have higher reflective properties than the first dielectric film.

[0091] The first dielectric film may exhibit an average reflectance of 2% or less in the range of 425 nm to 560 nm. In other examples, the average reflectance may be in the range of 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, or 0.4% or more, and / or in the range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1% or less, 0.8% or less, 0.6% or less, or 0.4% or less.

[0092] The first dielectric film may exhibit a maximum reflectance of 2% or more in the range of 425 nm to 560 nm, and may, for example, be in the range of 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, or 0.5% or more, and / or in the range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1% or less, 0.8% or less, or 0.6% or less.

[0093] The first dielectric film may exhibit an average reflectance of 40% or less in the range of 350 nm to 390 nm. In other examples, the average reflectance may be in the range of 5% or more, 10% or more, 15% or more, or 20% or more, and / or in the range of 38% or less, 36% or less, 34% or less, 32% or less, 30% or less, 28% or less, 26% or less, 24% or less, 22% or less, or 21% or less.

[0094] The first dielectric film may exhibit a maximum reflectance of 60% or less in the range of 350 nm to 390 nm. In other examples, the maximum reflectance may be in the range of 5% or more, 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, or 40% or more, and / or in the range of 58% or less, 56% or less, 54% or less, 52% or less, 50% or less, 48% or less, 46% or less, 44% or less, or 42% or less.

[0095] The first dielectric film may use a substrate having a reflectance of 2% or less at a wavelength of 700 nm, and the reflectance may be about 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1% or less, 0.8% or less, 0.6% or less, or 0.4% or less, or 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, or 0.4% or more.

[0096] The first dielectric film may exhibit an average reflectance of 5% or less in a range of 700 nm to 800 nm. In other examples, the average reflectance may be in the range of 4.8% or less, 4.6% or less, 4.4% or less, 4.2% or less, 4% or less, 3.8% or less, 3.6% or less, 3.4% or less, 3.2% or less, 3% or less, 2.8% or less, 2.6% or less, 2.4% or less, 2.2% or less, 2% or less, 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1% or less, 0.8% or less, 0.6% or less, or 0.4% or less, and / or in the range of 0% or more, 0.1% or more, 0.2% or more, or 0.3% or more.

[0097] The first dielectric film may exhibit a maximum reflectance of 5% or less in a range of 700 nm to 800 nm. In other examples, the maximum reflectance may be in the range of 4.8% or less, 4.6% or less, 4.4% or less, 4.2% or less, 4% or less, 3.8% or less, 3.6% or less, 3.4% or less, 3.2% or less, 3% or less, 2.8% or less, 2.6% or less, 2.4% or less, 2.2% or less, 2% or less, 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1% or less, 0.8% or less, 0.6% or less, or 0.4% or less, and / or in the range of 0% or more, 0.1% or more, 0.2% or more, or 0.3% or more.

[0098] The first dielectric film may exhibit an average reflectance of 10% or less in a range of 800 nm to 1000 nm, and may be further adjusted to be within a range of 0% or more, 0.5% or more, 1% or more, 1.5% or more, 2% or more, or 2.4% or more, and / or within a range of 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, or 3% or less.

[0099] The first dielectric film may exhibit a maximum reflectance of 15% or less in a range of 800 nm to 1000 nm, and may, in other examples, be in a range of 0% or more, 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, or 5.5% or more, and / or in a range of 14% or less, 13% or less, 12% or less, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, or 6% or less.

[0100] The first dielectric film may exhibit an average reflectance of 15% or less in a range of 1000 nm to 1200 nm, and the average reflectance may be further adjusted within a range of 0% or more, 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, or 9.5% or more and / or within a range of 14% or less, 13% or less, 12% or less, 11% or less, or 10% or less.

[0101] The first dielectric film may exhibit a maximum reflectance of 20% or less in the range of 1000 nm to 1200 nm, and may, as another example, have a maximum reflectance of 0% or more, 2% or more, 4% or more, 6% or more, 8% or more, 10% or more, 12% or more, or 13% or more, and / or 18% or less, 16% or less, or 14% or less.

[0102] The second dielectric film may exhibit an average reflectance of 2% or less in the range of 425 nm to 560 nm, which may be, for example, 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, or 0.4% or more, and / or 1.5% or less, 1% or less, or 0.5% or less.

[0103] The second dielectric film may exhibit a maximum reflectance of 4% or less in the range of 425 nm to 560 nm, and may, in other examples, be in the range of 0% or more, 0.5% or more, 1% or more, 1.2% or more, or 1.4% or more, and / or in the range of 3.5% or less, 3% or less, 2.5% or less, or 2% or less.

[0104] The second dielectric film may exhibit an average reflectance of 75% or more in the range of 350 nm to 390 nm, and may alternatively have an average reflectance of 80% or more, 85% or more, 90% or more, or 94% or more, and / or 98% or less, 96% or less, or 95% or less.

[0105] The second dielectric film may exhibit a maximum reflectance of 80% or more in the range of 350 nm to 390 nm, and may alternatively have a maximum reflectance of 85% or more, 90% or more, or 95% or more, and / or 100% or less.

[0106] The second dielectric film may have a reflectance of 30% or less at a wavelength of 700 nm. Other examples of the reflectance may be about 28% or less, 26% or less, 24% or less, 22% or less, 20% or less, 18% or less, 16% or less, 14% or less, 12% or less, 10% or less, 8% or less, 6% or less, 4% or less, 2% or less, 1% or less, or 0.5% or less, or about 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, or 0.4% or more.

[0107] The second dielectric film may exhibit an average reflectance of 20% or more in a range of 700 nm to 800 nm, and the average reflectance may be in a range of 22% or more, 24% or more, 26% or more, 28% or more, 30% or more, 32% or more, 34% or more, 36% or more, 38% or more, 40% or more, 42% or more, or 44% or more, and / or in a range of 60% or less, 68% or less, 66% or less, 64% or less, 62% or less, 60% or less, 58% or less, 56% or less, 54% or less, 52% or less, 50% or less, 48% or less, 46% or less, or 45% or less.

[0108] The second dielectric film may exhibit a maximum reflectance of 80% or more in the range of 700 nm to 800 nm, and may be, for example, in the range of 82% or more, 84% or more, 86% or more, 88% or more, 90% or more, 92% or more, 94% or more, 96% or more, 98% or more, or 99% or more and / or in the range of 100% or less or less than 100%.

[0109] The second dielectric film may exhibit an average reflectance of 80% or more in a range of 800 nm to 1000 nm, and may, for example, be in the range of 82% or more, 84% or more, 86% or more, 88% or more, 90% or more, 92% or more, 94% or more, 96% or more, 98% or more, or 99% or more, and / or in the range of 100% or less, or less than 100%.

[0110] The second dielectric film may exhibit a maximum reflectance of 80% or more in the range of 800 nm to 1000 nm, and may, for example, be in the range of 82% or more, 84% or more, 86% or more, 88% or more, 90% or more, 92% or more, 94% or more, 96% or more, 98% or more, or 99% or more and / or in the range of 100% or less or less than 100%.

[0111] The second dielectric film may be a substrate exhibiting an average reflectance of 80% or more in the range of 1000 nm to 1200 nm. In other examples, the average reflectance may be in the range of 82% or more, 84% or more, 86% or more, 88% or more, 90% or more, 92% or more, 94% or more, 96% or more, 98% or more, or 99% or more, and / or in the range of 100% or less or less than 100%.

[0112] The second dielectric film may have a transmission band showing a maximum reflectance of 80% or more in the range of 1000 nm to 1200 nm, and the maximum reflectance may be in the range of 82% or more, 84% or more, 86% or more, 88% or more, 90% or more, 92% or more, 94% or more, 96% or more, 98% or more, or 99% or more and / or in the range of 100% or less or less than 100%.

[0113] The reflectance of the first or second dielectric film may be a value measured when each dielectric film is formed on a transparent substrate (D263, SCHOTT) or may be a value measured on an optical filter. That is, when the first dielectric film is the outermost part of the optical filter, the reflectance can be measured on the first dielectric film side of the optical filter, and the reflectance of the second dielectric film can be measured on the optical filter in the same manner.

[0114] In order to ensure appropriate optical filter characteristics, the reflection characteristics of the first dielectric film, the second dielectric film or the optical filter, particularly within the range of 600 nm to 900 nm, may be adjusted.

[0115] In one example, the shortest wavelength at which any one of the first dielectric film, the second dielectric film, and the optical filter, or any two or all of them show a reflectance of 50% within a wavelength range of 600 nm to 900 nm may be 720 nm or more, or the wavelength may not exist. In the latter case, the maximum transmittance is less than 50% within a wavelength range of 600 nm to 900 nm. In another example, the shortest wavelength at which the reflectance of 50% is shown may be 725 nm or more, 730 nm or more, 735 nm or more, 740 nm or more, 745 nm or more, 750 nm or more, or 754 nm or more, or may be 900 nm or less, 850 nm or less, 800 nm or less, 790 nm or less, 780 nm or less, 770 nm or less, or 760 nm or less.

[0116] In this case, any one of the first dielectric film, the second dielectric film and the optical filter, or any two or all of them may have an average reflectance of 80% or less in a wavelength range of 600 nm to 900 nm. In other examples, the average reflectance may be about 75% or less, 70% or less, 65% or less, 60% or less, 55% or less, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 5% or less, or 1% or less, or about 5% or more, 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, or 50% or more.

[0117] In the case where the first dielectric film, the second dielectric film and / or the optical filter does not have the shortest wavelength at which the first dielectric film, the second dielectric film and / or the optical filter exhibits a reflectance of 50% within the wavelength range of 600 nm to 900 nm, the maximum reflectance of the corresponding configuration within the wavelength range of 600 nm to 900 nm may be less than 50%. In other examples, the maximum reflectance may be about 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 5% or less, or 1% or less, or about 0.5% or more, 1% or more, 5% or more, 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, or 40% or more.

[0118] The reflectance of the first or second dielectric film is a value measured when each dielectric film is formed on a transparent substrate (SCHOTT, D263), and the reflection characteristics of the optical filter are values ​​measured on the surface of the optical filter on the side where the first dielectric film exists or the surface on the side where the second dielectric film exists.

[0119] Typically, the layers in an optical filter are relatively thin, and in the case of a substrate, the reflection characteristics are small or nonexistent, so the reflection characteristics measured on the surface where the first dielectric film is present and the reflection characteristics measured on the surface where the second dielectric film is present are approximately similar.

[0120] By controlling the reflection characteristics as described above, it is possible to prevent the so-called petal flare phenomenon. That is, one of the causes of the petal flare phenomenon may be the repeated reflection of near-infrared light within an imaging device equipped with an optical filter. In such a case, it is possible to prevent the petal flare phenomenon by controlling the reflection characteristics of the first and / or second dielectric films and / or the optical filter as described above.

[0121] The method for forming the dielectric film is not particularly limited, and may be formed, for example, by applying a known deposition method. In the industry, a method for controlling the reflection or transmission characteristics of the corresponding dielectric film by considering the deposition thickness of the sub-layer, the number of layers, etc. is known, and in the present disclosure, the first and second dielectric films exhibiting the above characteristics may be formed according to such a known method, and the reflectance of the surface of the optical filter on the second dielectric film side may also be adjusted by controlling the characteristics of the dielectric film.

[0122] The optical filter may include various optional additional layers as long as it basically includes the transparent substrate, the infrared absorbing substrate, and the dielectric film.

[0123] For example, the optical filter may further include an absorbing layer formed on one or both sides of the transparent substrate and / or the dielectric film. The absorbing layer is a light absorbing layer, for example, a layer that absorbs light within at least a part of a wavelength range of the infrared and / or ultraviolet regions. One or more such absorbing layers may be formed in the optical filter.

[0124] 2 to 4 are views showing the case where absorbing layers 300, 301, and 302 are formed on the optical filter of Fig. 1. As shown in Figs. 2 to 4, the absorbing layers may be formed in one or more layers between the infrared absorbing substrate 100 and the first and / or second dielectric films 201 and 202.

[0125] In one example, the absorbing layer may be an infrared absorbing layer and / or an ultraviolet absorbing layer. The absorbing layer may be a layer having both infrared absorbing and ultraviolet absorbing properties. Such a layer is usually a layer containing an absorbent (pigment, dye, etc.) and a transparent resin, and may be applied to realize a sharper transmittance band by cutting light in the near ultraviolet region and / or near infrared region.

[0126] In one example, the ultraviolet absorbing layer may be designed to exhibit an absorption maximum in a wavelength range of about 300 nm to 390 nm, and the infrared absorbing layer may be designed to exhibit an absorption maximum in a wavelength range of 600 nm to 800 nm.

[0127] In one example, when the light absorbing layer is a layer that simultaneously exhibits absorbency for ultraviolet rays and infrared rays, the light absorbing layer may be designed to simultaneously exhibit an absorption band in a wavelength region of about 300 nm to 390 nm and an absorption band in a wavelength region of 600 nm to 800 nm.

[0128] The infrared absorbing layer and the ultraviolet absorbing layer may be formed as one layer, or may be formed as separate layers. For example, one layer may be designed to show 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 show the respective absorption maxima. Also, multiple infrared absorbing layers and / or ultraviolet absorbing layers may be present.

[0129] Each absorbing layer may contain only one type of absorbing agent, or, if necessary, may contain two or more types of absorbing agents for appropriate filtering of infrared and / or ultraviolet radiation.

[0130] For example, the infrared absorbing layer may include at least a first absorbent having an absorption maximum wavelength in the range of 700 nm to 720 nm and a half width in the range of 50 nm to 60 nm; a second absorbent having an absorption maximum wavelength in the range of 730 nm to 750 nm and a half width in the range of 60 nm to 70 nm, and a third absorbent having an absorption maximum wavelength in the range of 760 nm to 780 nm and a half width in the range of 90 nm 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 nm to 350 nm and a second absorbent having an absorption maximum wavelength in the range of 360 nm to 370 nm.

[0131] The material and method of constructing the absorbing layer are not particularly limited, and known materials and methods of construction can be applied.

[0132] The absorbing layer is typically formed using a material in which an absorbing agent (such as a dye or pigment) that enables the layer to exhibit the desired absorption maximum is blended with a transparent resin.

[0133] For example, as the ultraviolet absorber, a known absorber that exhibits an absorption maximum in the wavelength region of about 300 nm to 390 nm can be used. Examples of such an absorber 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 A from HW Sands. Examples of suitable choke resistors 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, ADA7158; CRYSTALYN DLS 381B, DLS 381C, DLS 382A, DLS 386A, DLS 404A, DLS 405A, DLS 405C, and DLS 403A.

[0134] The infrared absorbing agent may be a suitable dye or pigment that exhibits an absorption maximum in the wavelength region of 600 nm to 800 nm, such as, but not limited to, a squarylium-based dye, a cyanine-based compound, a phthalocyanine-based compound, a naphthalocyanine-based compound, or a dithiol metal complex-based compound.

[0135] The transparent resin applied to 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.

[0136] The optical filter of the present disclosure as described above can exhibit excellent optical properties together with excellent durability.

[0137] For example, the optical filter may exhibit a transmission band with a T50% cut-on wavelength in the range of about 400 nm to 425 nm. The T50% cut-on wavelength is the shortest wavelength among the wavelengths showing 50% transmittance in the wavelength range of 350 nm to 425 nm. The wavelengths showing 50% transmittance may be one or more in the range of 400 nm to 425 nm, and if there is one, that wavelength, and if there are two or more, the shortest wavelength among them, is the T50% cut-on wavelength. The T50% cut-on wavelength may be additionally adjusted within the range of 402 nm or more, 404 nm or more, 406 nm or more, 408 nm or more, or 410 nm or more and / or within the range of 424 nm or less, 422 nm or less, 420 nm or less, 418 nm or less, 416 nm or less, 414 nm or less, 412 nm or less, or 410 nm or less.

[0138] The optical filter may exhibit a transmission band with a T50% cut off wavelength in the range of about 590 nm to 680 nm. The T50% cut off wavelength is the longest wavelength among the wavelengths showing 50% transmittance within the wavelength range of 560 nm to 700 nm. There may be one or more wavelengths showing 50% transmittance within the range of 560 nm to 700 nm, and if there is one, that wavelength is the T50% cut off wavelength, and if there are two or more, the longest wavelength is the T50% cut off wavelength. The T50% cut The off wavelength is within the range of 592nm or more, 594nm or more, 596nm or more, 598nm or more, 600nm or more, 602nm or more, 604nm or more, 606nm or more, 608nm or more, 610nm or more, 612nm or more, 614nm or more, 616nm or more, 618nm or more, 620nm or more, 622nm or more, 624nm or more or 626nm or more and / or 678nm or less, 676nm or less, 674nm or less, 672nm or more. nm or less, 670 nm or less, 668 nm or less, 666 nm or less, 664 nm or less, 662 nm or less, 660 nm or less, 658 nm or less, 656 nm or less, 654 nm or less, 652 nm or less, 650 nm or less, 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.

[0139] The optical filter may have a transmission band exhibiting an average transmittance of 75% or more within a range of 425 nm to 560 nm. In other examples, the average transmittance may be adjusted within a range of 77% or more, 79% or more, 81% or more, 83% or more, 85% or more, 87% or more, 89% or more, 91% or more, 92% or more, or 92.5% or more, and / or within a range of 98% or less, 96% or less, 94% or less, 93% or less, or 92.5% or less.

[0140] The optical filter of the present disclosure may have a transmission band exhibiting a maximum transmittance of 79% or more within the range of 425 nm to 560 nm, which may be adjusted within the range of 81% or more, 83% or more, 85% or more, 87% or more, 89% or more, 91% or more, 93% or more, or 95% or more and / or within the range of 100% or less, 98% or less, or 96% or less.

[0141] The optical filter of the present disclosure may have a transmission band exhibiting an average transmittance of 2% or less within the range of 350 nm to 390 nm. The average transmittance may be additionally adjusted within the range of 0% or more, 0.1% or more, or 0.2% or more, and / or 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, in other examples.

[0142] The optical filter of the present disclosure may have a transmission band exhibiting a maximum transmittance of 10% or less within the range of 300 nm to 390 nm. The maximum transmittance may be additionally adjusted within the range of 0% or more, 0.5% or more, 1% or more, 1.5% or more, 2% or more, or 2.5% or more, and / or 9.5% or less, 9% or less, 8.5% or less, 8% or less, 7.5% or less, 7% or less, 6.5% or less, 6% or less, 5.5% or less, 5% or less, 4.5% or less, 4% or less, 3.5% or less, or 3% or less, in other examples.

[0143] The optical filter of the present disclosure may have a transmittance of 2% or less at 700 nm wavelength, which may be further adjusted within the range of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, or 0.8% or more, and / or 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less, in other examples.

[0144] The optical filter of the present disclosure may have a transmission band exhibiting an average transmittance of 2% or less in the range of 700 nm to 800 nm. The average transmittance may be additionally adjusted within the range of 0% or more, 0.1% or more, 0.3% or more, 0.4% or more, or 0.5% or more, and / or 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, or 0.5% or less.

[0145] The optical filter of the present disclosure may have a transmission band exhibiting a maximum transmittance of 2% or less within the range of 700 nm to 800 nm, which may be further adjusted within the range of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, or 0.8% or more and / or 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less, in other examples.

[0146] The optical filter of the present disclosure may have a transmission band exhibiting an average transmittance of 2% or less in the range of 800 nm to 1000 nm. The average transmittance may be additionally adjusted within the range of 0% or more, 0.01% or more, 0.03% or more, 0.05% or more, 0.07% or more, or 0.09% or more, and / or 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, 0.15% or less, or 0.1% or less.

[0147] The optical filter of the present disclosure may have a transmission band exhibiting a maximum transmittance of 2% or less within the range of 800 nm to 1000 nm, which may be further adjusted within the range of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, or 0.8% or more, and / or 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, or 0.4% or less.

[0148] The optical filter of the present disclosure may have a transmission band exhibiting an average transmittance of 5% or less within the range of 1000 nm to 1200 nm. The average transmittance may be additionally adjusted within the range of 0% or more, 0.5% or more, 1% or more, or 1.5% or more, and / or 4.5% or less, 4% or less, 3.5% or less, 3% or less, 2.5% or less, 2% or less, 1.5% or less, 1% or less, 0.8% or less, 0.6% or less, 0.4% or less, or 0.3% or less.

[0149] The optical filter of the present disclosure may have a transmission band exhibiting a maximum transmittance of 5% or less within the range of 1000 nm to 1200 nm. The maximum transmittance may be additionally adjusted within the range of 0% or more, 0.5% or more, 1% or more, or 1.5% or more and / or 4.5% or less, 4% or less, 3.5% or less, 3% or less, 2.5% or less, 2% or less, 1.5% or less, 1% or less, 0.8% or less, 0.6% or less, 0.4% or less, or 0.3% or less.

[0150] The optical filter of the present disclosure may exhibit any one, any combination of two or more of the optical characteristics described above, or may suitably satisfy all of the optical characteristics described above.

[0151] In addition to the above-mentioned layers, various other layers may be added to the optical filter as necessary, as long as the desired effect is not impaired.

[0152] The present disclosure also relates to an imaging device including the optical filter, wherein the configuration of the imaging device and the application of the optical filter are not particularly limited, and known configurations and application methods may be used.

[0153] Furthermore, the use of the optical filter of the present disclosure is not limited to the imaging device, but can be applied to a variety of other uses requiring near-infrared blocking (for example, display devices such as PDPs). Effect of the Invention

[0154] The present disclosure can provide an optical filter and a use thereof. The present disclosure can provide an optical filter that effectively blocks ultraviolet and infrared rays and exhibits high transmittance for visible light, and a use thereof. The present disclosure can provide an optical filter in which the above-mentioned transmission characteristics are stably maintained even when the angle of incidence varies, and a use thereof. The present disclosure can provide an optical filter that does not have problems such as ripples and petal flare, and a use thereof. [Brief description of the drawings]

[0155] [Figure 1] 1 is a diagram illustrating an exemplary structure of an optical filter of the present disclosure. [Diagram 2] 1 is a diagram illustrating an exemplary structure of an optical filter of the present disclosure. [Diagram 3] 1 is a diagram illustrating an exemplary structure of an optical filter of the present disclosure. [Figure 4] 1 is a diagram illustrating an exemplary structure of an optical filter of the present disclosure. [Diagram 5] 1 shows a transmittance spectrum of an infrared absorbing substrate used in an example. [Figure 6] 1 shows the transmission spectrum of the dielectric film applied in the examples and comparative examples. [Figure 7] 1 shows the reflectance spectrum of the dielectric film applied in the examples and comparative examples. [Figure 8] 1 shows the transmission spectrum of the dielectric film applied in the examples and comparative examples. [Figure 9] 1 shows the reflectance spectrum of the dielectric film applied in the examples and comparative examples. [Figure 10] 13 is a transmittance spectrum of a transparent substrate used in a comparative example. [Figure 11] 13 is a transmittance spectrum of a transparent substrate used in a comparative example. [Figure 12] 1 shows the transmission spectrum of the dielectric film applied in the examples and comparative examples. [Figure 13]1 shows the reflectance spectrum of the dielectric film applied in the examples and comparative examples. [Figure 14] 1 shows the transmission spectrum of the dielectric film applied in the examples and comparative examples. [Figure 15] 1 shows the reflectance spectrum of the dielectric film applied in the examples and comparative examples. [Figure 16] 1 shows the transmission spectrum of the dielectric film applied in the examples and comparative examples. [Figure 17] 1 shows the reflectance spectrum of the dielectric film applied in the examples and comparative examples. [Figure 18] 1 shows a transmittance spectrum of an optical filter according to an embodiment of the present invention. [Figure 19] 13 is a transmittance spectrum of an optical filter of a comparative example. [Figure 20] 13 is a transmittance spectrum of an optical filter of a comparative example. [Figure 21] 13 is a transmittance spectrum of an optical filter of a comparative example. [Figure 22] 13 is a transmittance spectrum of an optical filter of a comparative example. [Figure 23] 13 is a transmittance spectrum of an optical filter of a comparative example. [Figure 24] 11 is a photograph for confirming the petal flare phenomenon when the optical filter of the embodiment is applied. [Diagram 25] 13 is a photograph for confirming the petal flare phenomenon when the optical filter of the comparative example is applied. [Figure 26] 13 is a photograph for confirming the petal flare phenomenon when the optical filter of the comparative example is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0156] Hereinafter, the optical filter of the present disclosure will be described in detail with reference to examples. However, the scope of the optical filter of the present disclosure is not limited to the following examples.

[0157] 1. Evaluation of transmittance or reflectance spectrum

[0158] The transmittance or reflectance spectrum was measured using a spectrophotometer (manufacturer: Perkinelmer, product name: Lambda750 spectrophotometer) for a specimen obtained by cutting the measurement object to 10 mm in width and 10 mm in length, respectively. The transmittance or reflectance spectrum was measured for each wavelength and incident angle according to the manual of the device. The specimen was positioned on a straight line between the measurement beam and detector of the spectrophotometer, and the incident angle of the measurement beam was changed from 0 degrees to 40 degrees to confirm the transmittance or reflectance spectrum. Unless otherwise specified, the results of the transmittance or reflectance spectrum in this embodiment are the results when the incident angle is 0 degrees. The incident angle of 0 degrees is a direction substantially parallel to the normal direction of the surface of the specimen.

[0159] The average transmittance or average reflectance within a given wavelength range in a transmittance or reflectance spectrum is the result of measuring the transmittance or reflectance at each wavelength while increasing the wavelength by 1 nm from the shortest wavelength in the wavelength range, and then calculating the arithmetic average of the measured transmittance or reflectance, and the maximum transmittance or maximum reflectance is the maximum transmittance or maximum reflectance among the transmittances or reflectances measured while increasing the wavelength by 1 nm. For example, the average transmittance within the wavelength range of 350 nm to 360 nm is the arithmetic average of the transmittances measured at wavelengths of 350 nm, 351 nm, 352 nm, 353 nm, 354 nm, 355 nm, 356 nm, 357 nm, 358 nm, 359 nm, and 360 nm, and the maximum transmittance within the wavelength range of 350 nm to 360 nm is the highest transmittance among the transmittances measured at wavelengths of 350 nm, 351 nm, 352 nm, 353 nm, 354 nm, 355 nm, 356 nm, 357 nm, 358 nm, 359 nm, and 360 nm.

[0160] 2. Evaluation of copper content

[0161] The copper content of the glass substrate was confirmed using an X-ray fluorescence analyzer (WD XRF, Wavelength Dispersive X-Ray Fluorescence Spectrometry). When the specimen (glass substrate) is irradiated with X-rays using this device, secondary X-rays characteristic of each element in the specimen are generated, and the device detects the secondary X-rays according to the wavelength of each element. The intensity of the secondary X-rays is proportional to the element content, so quantitative analysis can be performed based on the intensity of the secondary X-rays measured according to the wavelength of each element.

[0162] 3.Evaluation of refractive index

[0163] The refractive index of the dielectric film sub-layer was measured at 520 nm wavelength using a Wizz Optics M-2000 Ellipsometer instrument.

[0164] Production Example 1. Production of Absorbing Layer Material A

[0165] The absorbing layer material A was manufactured using an infrared absorbing agent 1 (triazine-based dye) having an absorption maximum in the range of about 340 nm to 390 nm, an infrared absorbing agent 2 (squarylium-based dye) having an absorption maximum wavelength in the range of about 700 nm to 720 nm and a full width at half maximum (FWHM) of about 50 nm to 60 nm, an infrared absorbing agent 3 (squarylium-based dye) having an absorption maximum wavelength in the range of about 730 nm to 750 nm and a full width at half maximum (FWHM) of about 60 nm to 70 nm, and an infrared absorbing agent 4 (squarylium-based dye) having an absorption maximum wavelength in the range of about 760 nm to 780 nm and a full width at half maximum (FWHM) of about 90 nm to 100 nm. The absorbing agents 1 to 4 were mixed with a binder resin to manufacture the absorbing layer material A. Cycloolefin polymer (COP) was used as the binder resin. Absorbent layer material A was prepared by mixing about 5 parts by weight of absorbent 1, about 0.1 parts by weight of absorbent 2, about 0.2 parts by weight of absorbent 3, and about 0.4 parts by weight of absorbent 4 with 100 parts by weight of the binder resin in toluene.

[0166] Manufacturing Example 2. Manufacturing of Absorbing Layer Material B

[0167] The absorbing layer material B was prepared by additionally blending an infrared absorbing agent 4 (a diimonium dye) having an absorption maximum wavelength of about 1050 nm to 1150 nm into the absorbing layer material A. During blending, the infrared absorbing agent 4 was added in a ratio of about 0.8 parts by weight based on 100 parts by weight of the solid content of the absorbing layer material A.

[0168] Example 1

[0169] As the infrared absorbing glass substrate, a phosphate-based infrared absorbing glass substrate (manufactured by HOYA) (thickness: about 0.21 mm) showing a transmittance spectrum as shown in FIG. 5 was used. The copper content measured for the infrared absorbing glass substrate was about 12.08 wt %. The spectral characteristics of the infrared absorbing glass substrate are summarized in Table 1 below. In Table 1 below, TMAX is the maximum transmittance in a corresponding wavelength range, and its unit is %, and TAVG is the average transmittance in a corresponding wavelength range, and its unit is %. In Table 1 below, T50% cut on is the shortest wavelength (unit: nm) showing 50% transmittance in a wavelength range of 350 nm to 425 nm, and T50% cut off is the longest wavelength (unit: nm) showing 50% transmittance in a wavelength range of 560 nm to 700 nm.

[0170] [Table 1]

[0171] The absorbing layer material A of Preparation Example 1 was applied to one surface of the infrared absorbing glass substrate, and heat-treated at 135°C for 2 hours to form an absorbing layer. The absorbing layer was formed to a thickness of about 3 μm. A first dielectric film was formed on the surface on which the absorbing layer was formed. The first dielectric film was formed by depositing a sub-layer using an ion-beam assisted deposition method. 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. In this method, a TiO2 layer (refractive index about 2.61) as a high refractive index layer and a SiO2 layer (refractive index about 1.46) as a low refractive index layer were alternately formed to form a first dielectric film. A total of nine high refractive index layers and low refractive index layers were formed as sub-layers. Specifically, a SiO2 layer (approximately 98.9 nm thick), a TiO2 layer (approximately 28.5 nm thick), a SiO2 layer (approximately 12 nm thick), a TiO2 layer (approximately 76.1 nm thick), a SiO2 layer (approximately 23.1 nm thick), a TiO2 layer (approximately 24.5 nm thick), a SiO2 layer (approximately 56.5 nm thick), a TiO2 layer (approximately 8.3 nm thick) and a SiO2 layer (approximately 44.3 nm thick) were sequentially formed on the absorbing layer to form the first dielectric film.

[0172] Such a first dielectric film is a dielectric film in which R (n1 / n2, n1 is the refractive index of TiO2 (about 2.61), n2 is the refractive index of SiO2 (about 1.46)) in the following formula 1 is about 1.79, n2 is about 1.46 (refractive index of SiO2 layer), K is 9, and 2p is 8. Since the copper content of the infrared absorbing glass substrate, Cu in the following formula 1, is about 12.08 wt %, when the first dielectric film is applied to the infrared absorbing glass substrate, the value of V in the following formula 1 is about 10.5.

[0173]

number

[0174] Figure 6 is a graph showing the transmittance of the first dielectric film formed in the above manner, and Figure 7 is a graph showing the reflectance of the first dielectric film. The transmittance and reflectance were measured after the first dielectric film was formed on a transparent substrate (SCHOTT, D263). In Figures 6 and 7, AR(9L)-0deg is the transmittance or reflectance at an incident angle of 0 degrees, AR(9L)-30deg is the transmittance or reflectance at an incident angle of 30 degrees, and AR(9L)-40deg is the transmittance or reflectance at an incident angle of 40 degrees.

[0175] The transmittance and reflectance characteristics in Figures 6 and 7 are summarized in Table 2 below. In Table 2 below, TMAX is the maximum transmittance or maximum reflectance in the corresponding wavelength region, and its unit is %, and TAVG is the average transmittance or average reflectance in the corresponding wavelength region, and its unit is %.

[0176] In Table 2 below, T50% cut on is the shortest wavelength (unit: nm) showing 50% transmittance or reflectance in the wavelength range of 350 nm to 425 nm, and T50% cut off is the shortest wavelength (unit: nm) showing 50% transmittance or reflectance in the wavelength range of 600 nm to 900 nm.

[0177] [Table 2]

[0178] Subsequently, a second dielectric film was formed on the surface of the infrared absorbing glass substrate opposite to the surface on which the first dielectric film was formed, to manufacture an optical filter. The second dielectric film was formed in the same manner as the first dielectric film. However, the second dielectric film had a total of 39 layers, with TiO2 layers (refractive index: about 2.61) as high refractive index layers and SiO2 layers (refractive index: about 1.46) as low refractive index layers alternately formed, and the thickness of each layer was adjusted as shown in Tables 3-1 and 3-2 below. In Tables 3-1 and 3-2 below, number 1 is the first layer formed on the infrared absorbing glass, and number 39 is the last layer formed.

[0179] [Table 3-1]

[0180] [Table 3-2]

[0181] Such a second dielectric film is a dielectric film in which R (n1 / n2, n1 is the refractive index of TiO2 (about 2.61), n2 is the refractive index of SiO2 (about 1.46)) in formula 1 is about 1.79, n2 is about 1.46 (refractive index of SiO2 layer), K is 39, and 2p is 38. Since the copper content of the infrared absorbing glass substrate, Cu in formula 1, is about 12.08 wt %, when the second dielectric film is applied to the infrared absorbing glass substrate, the V value in formula 1 is about 50.5.

[0182] Figure 8 is a graph showing the transmittance of the second dielectric film formed in the above manner, and Figure 9 is a graph showing the reflectance of the second dielectric film. The transmittance and reflectance were measured in the same manner as for the first dielectric film. In Figures 8 and 9, IR(39L)-0deg is the transmittance or reflectance at an incident angle of 0 degrees, IR(39L)-30deg is the transmittance or reflectance at an incident angle of 30 degrees, and IR(39L)-40deg is the transmittance or reflectance at an incident angle of 40 degrees.

[0183] The transmittance and reflectance characteristics of Figures 8 and 9 are summarized in Table 4 below. In Table 4 below, TMAX is the maximum transmittance or maximum reflectance in the corresponding wavelength region, and its unit is %, and TAVG is the average transmittance or average reflectance in the corresponding wavelength region, and its unit is %.

[0184] In Table 4 below, T50% cut on is the shortest wavelength (unit: nm) showing 50% transmittance or reflectance in the wavelength range of 350 nm to 425 nm, and T50% cut off is the shortest wavelength (unit: nm) showing 50% transmittance or reflectance in the wavelength range of 600 nm to 900 nm.

[0185] On the other hand, the shortest wavelength showing a reflectance of 50% within the 600 nm to 900 nm region measured on the first dielectric film side or the surface of the second dielectric film layer of the optical filter was about 755 nm.

[0186] [Table 4]

[0187] Comparative Example 1

[0188] An optical filter was manufactured in the same manner as in Example 1, except that a general transparent glass substrate with no absorption characteristics was used as the glass substrate. Figure 10 shows the transmittance spectrum of the transparent glass substrate used, and it can be seen from the figure that the substrate has no absorption characteristics. The shortest wavelength showing 50% reflectance within the 600nm to 900nm range measured on the first dielectric film side or the surface of the second dielectric film layer of the optical filter was about 755nm.

[0189] Comparative Example 2

[0190] An optical filter was manufactured in the same manner as in Comparative Example 1, except that the absorbing layer was formed using the absorbing layer material B of Manufacturing Example 2. The shortest wavelength showing 50% reflectance within the 600 nm to 900 nm region measured on the first dielectric film side or the surface of the second dielectric film layer of the optical filter was about 755 nm.

[0191] Comparative Example 3

[0192] As the infrared absorbing glass substrate, a phosphate-based infrared absorbing glass substrate (manufactured by HOYA) (thickness: about 0.21 mm) showing a transmittance spectrum as shown in FIG. 11 was used. The copper content measured for the infrared absorbing glass substrate was about 2.89 wt %. The spectral characteristics of the infrared absorbing glass substrate are summarized in Table 5 below. In Table 5 below, TMAX is the maximum transmittance in a corresponding wavelength range, and its unit is %, and TAVG is the average transmittance in a corresponding wavelength range, and its unit is %. In Table 5 below, T50% cut on is the shortest wavelength (unit: nm) showing 50% transmittance in a wavelength range of 350 nm to 425 nm, and T50% cut off is the longest wavelength (unit: nm) showing 50% transmittance in a wavelength range of 560 nm to 700 nm.

[0193] [Table 5]

[0194] In the case of the infrared absorbing glass substrate, the Cu content in formula 1 is about 2.89 wt %, so that in the case of the first dielectric film applied to the infrared absorbing glass substrate, the V value in formula 1 is about 5.5, and in the case of the second dielectric film, the V value in formula 1 is about 26.9. The shortest wavelength showing 50% reflectance within the 600 nm to 900 nm region measured on the first dielectric film side or the surface of the second dielectric film layer of the optical filter was about 755 nm.

[0195] Comparative Example 4

[0196] An optical filter was manufactured in the same manner as in Example 1, except that the first and second dielectric films were formed as follows.

[0197] The first dielectric film is made up of a total of 21 layers, with high refractive index TiO2 layers (refractive index approximately 2.61) and low refractive index SiO2 layers (refractive index approximately 1.46) alternately formed, and the thickness of each layer was adjusted as shown in Table 6 below. In Table 6 below, number 1 is the first layer formed on the infrared absorbing glass, and number 21 is the last layer formed.

[0198] [Table 6]

[0199] Such a first dielectric film is a dielectric film in which R (n1 / n2, n1 is the refractive index of TiO2 (about 2.61), n2 is the refractive index of SiO2 (about 1.46)) in formula 1 is about 1.79, n2 is about 1.46 (refractive index of SiO2 layer), K is 21, and 2p is 20. Since Cu in formula 1, which is the copper content of the infrared absorbing glass substrate, is about 12.08 wt %, when the first dielectric film is applied to the infrared absorbing glass substrate, the value of V in formula 1 is about 26.5.

[0200] Figure 12 is a graph showing the transmittance of the first dielectric film formed in the above manner, and Figure 13 is a graph showing the reflectance of the first dielectric film. The transmittance and reflectance of the first dielectric film were measured in the same manner as in Example 1. In Figures 12 and 13, AR(21L)-0deg is the transmittance or reflectance at an incident angle of 0 degrees, AR(21L)-30deg is the transmittance or reflectance at an incident angle of 30 degrees, and AR(21L)-40deg is the transmittance or reflectance at an incident angle of 40 degrees.

[0201] The transmittance and reflectance characteristics of Figures 12 and 13 are summarized in Table 7 below. In Table 7 below, TMAX is the maximum transmittance or maximum reflectance in the corresponding wavelength region, and its unit is %, and TAVG is the average transmittance or average reflectance in the corresponding wavelength region, and its unit is %.

[0202] In Table 7 below, T50% cut on is the shortest wavelength (unit: nm) showing 50% transmittance or reflectance in the wavelength range of 350 nm to 425 nm, and T50% cut off is the shortest wavelength (unit: nm) showing 50% transmittance or reflectance in the wavelength range of 600 nm to 900 nm.

[0203] [Table 7]

[0204] The second dielectric film was made up of a total of 22 layers, with high refractive index TiO2 layers (refractive index approximately 2.61) and low refractive index SiO2 layers (refractive index approximately 1.46) alternately formed, and the thickness of each layer was adjusted as shown in Table 8 below. In Table 8 below, number 1 is the first layer formed on the infrared absorbing glass, and number 22 is the last layer formed.

[0205] [Table 8]

[0206] Such a second dielectric film is a dielectric film in which R (n1 / n2, n1 is the refractive index of TiO2 (about 2.61), n2 is the refractive index of SiO2 (about 1.46)) in formula 1 is about 1.79, n2 is about 1.46 (refractive index of SiO2 layer), K is 22, and 2p is 21. Since Cu in formula 1, which is the copper content of the infrared absorbing glass substrate, is about 12.08 wt %, when the second dielectric film is applied to the infrared absorbing glass substrate, the V value in formula 1 is about 27.9.

[0207] Figure 14 is a graph showing the transmittance of the second dielectric film formed in the above manner, and Figure 15 is a graph showing the reflectance of the second dielectric film. The transmittance and reflectance were measured after the second dielectric film was formed on a transparent substrate that does not absorb or reflect light. In Figures 14 and 15, IR(22L)-0deg is the transmittance or reflectance at an incident angle of 0 degrees, IR(22L)-30deg is the transmittance or reflectance at an incident angle of 30 degrees, and IR(22L)-40deg is the transmittance or reflectance at an incident angle of 40 degrees.

[0208] The transmittance and reflectance characteristics of Figs. 14 and 15 are summarized in Table 9 below. In Table 9 below, TMAX is the maximum transmittance or maximum reflectance in the corresponding wavelength region, and its unit is %, and TAVG is the average transmittance or average reflectance in the corresponding wavelength region, and its unit is %. In Table 9 below, T50% cut on is the shortest wavelength (unit: nm) showing 50% transmittance or reflectance in the wavelength region of 350 nm to 425 nm, and T50% cut off is the longest wavelength (unit: nm) showing 50% transmittance or reflectance in the wavelength region of 600 nm to 900 nm. The shortest wavelength showing 50% reflectance in the 600 nm to 900 nm region measured on the first dielectric film side or the surface of the second dielectric film layer of the optical filter was about 755 nm.

[0209] [Table 9]

[0210] Comparative Example 5

[0211] An optical filter was manufactured in the same manner as in Example 1, except that the second dielectric film was formed as follows.

[0212] The second dielectric film is made up of a total of 38 layers, with high refractive index TiO2 layers (refractive index approximately 2.61) and low refractive index SiO2 layers (refractive index approximately 1.46) alternately formed, and the thickness of each layer was adjusted as shown in Tables 10-1 and 10-2 below. In Tables 10-1 and 10-2 below, number 1 is the first layer formed on the infrared absorbing glass, and number 38 is the last layer formed.

[0213] [Table 10-1]

[0214] [Table 10-2]

[0215] Such a second dielectric film is a dielectric film in which R (n1 / n2, n1 is the refractive index of TiO2 (about 2.61), n2 is the refractive index of SiO2 (about 1.46)) in formula 1 is about 1.79, n2 is about 1.46 (refractive index of SiO2 layer), K is 38, and 2p is 37. Since the copper content of the infrared absorbing glass substrate, Cu in formula 1, is about 12.08 wt %, when the second dielectric film is applied to the infrared absorbing glass substrate, the V value of formula 1 is about 49.2.

[0216] Figure 14 is a graph showing the transmittance of the second dielectric film formed in the above manner, and Figure 15 is a graph showing the reflectance of the second dielectric film. The transmittance and reflectance were measured after the second dielectric film was formed on a transparent substrate that does not absorb or reflect light. In Figures 14 and 15, IR(22L)-0deg is the transmittance or reflectance at an incident angle of 0 degrees, IR(22L)-30deg is the transmittance or reflectance at an incident angle of 30 degrees, and IR(22L)-40deg is the transmittance or reflectance at an incident angle of 40 degrees.

[0217] Figure 16 is a graph showing the transmittance of the second dielectric film formed in the above manner, and Figure 17 is a graph showing the reflectance of the second dielectric film. The transmittance and reflectance were measured in the same manner as in Example 1. In Figures 16 and 17, IR(38L)-0deg is the transmittance or reflectance at an incident angle of 0 degrees, IR(38L)-30deg is the transmittance or reflectance at an incident angle of 30 degrees, and IR(38L)-40deg is the transmittance or reflectance at an incident angle of 40 degrees.

[0218] The transmittance and reflectance characteristics of Figs. 16 and 17 are summarized in Table 11 below. In Table 11 below, TMAX is the maximum transmittance or maximum reflectance in the corresponding wavelength region, and its unit is %, and TAVG is the average transmittance or average reflectance in the corresponding wavelength region, and its unit is %. In Table 11, T50% cut on is the shortest wavelength (unit: nm) showing 50% transmittance or reflectance in the wavelength region of 350 nm to 425 nm, and T50% cut off is the shortest wavelength (unit: nm) showing 50% transmittance or reflectance in the wavelength region of 600 nm to 900 nm. The shortest wavelength showing 50% reflectance in the region of 600 nm to 900 nm measured on the first dielectric film side or the surface of the second dielectric film layer of the optical filter was about 712 nm.

[0219] [Table 11]

[0220] Test Example 1. Evaluation of transmittance spectrum

[0221] 18 to 23 show the transmittance spectra (based on an incident angle of 0 degrees) of the optical filter of Example 1 (FIG. 18) and the optical filters of Comparative Examples 1 to 5, respectively. The spectral characteristics of the optical filters are summarized in Table 12 below. In Table 12 below, TMAX is the maximum transmittance in a corresponding wavelength range, and its unit is %, and TAVG is the average transmittance in a corresponding wavelength range, and its unit is %. In Table 12 below, T50% cut on is the shortest wavelength (unit: nm) that shows a transmittance of 50% in the wavelength range of 350 nm to 425 nm, and T50% cut off is the longest wavelength (unit: nm) that shows a transmittance of 50% in the wavelength range of 560 nm to 700 nm.

[0222] [Table 12]

[0223] Comparing the transmittance spectra of the optical filters of Example 1 and Comparative Example 1 (FIGS. 18 and 19), it can be seen that in the case of Comparative Example 1, the T50% cut off wavelength is longer than that of Example 1, so that it does not exhibit an appropriate blocking effect against infrared rays, and also shows high transmittance in the long wavelength band of 700 nm or more, so that it cannot properly function as an optical filter.

[0224] The transmittance spectrum of the optical filter of Comparative Example 2 (FIG. 20) also shows that, like Comparative Example 1, it is unable to provide an appropriate blocking effect against infrared rays, and the transmittance in the visible light region in particular drops significantly.

[0225] Comparing the transmittance spectra of the optical filters of Example 1 and Comparative Example 3 (FIGS. 18 and 21), it can be seen that in the case of Comparative Example 3, the T50% cut-off wavelength is longer than that of Example 1, so that it does not exhibit an appropriate blocking effect against infrared rays, and also shows high transmittance in the long wavelength band of 700 nm or more, so that it cannot properly function as an optical filter.

[0226] Test Example 3.Petal Flare Evaluation

[0227] The light emission sources were photographed using imaging devices equipped with the optical filters of Example 1 and Comparative Examples 4 and 5. The results are shown in Figures 24 to 26 (Example 1: Figure 24, Comparative Example 4: Figure 25, Comparative Example 5: Figure 26).

[0228] Figures 24 to 26 are respectively a photograph of a light source (a halogen LED light source with a color temperature of 3100 K) taken with a rear camera equipped with the optical filter of Example 1 (Figure 24), a photograph of a subject (a halogen LED light source with a color temperature of 3100 K) taken with a rear camera equipped with the optical filter of Comparative Example 4 (Figure 25), and a photograph of a subject (a halogen LED light source with a color temperature of 3100 K) taken with a rear camera equipped with the optical filter of Comparative Example 5 (Figure 26).

[0229] During the photographing, the distance between the light source and the camera was set to approximately 50 cm, and photographing was carried out in a darkroom within a 1 m radius of the light source.

[0230] Comparing the figures, it can be seen that no particular defects were identified in the photographs taken with the imaging device using the optical filter of Example 1, but in the cases of Comparative Examples 4 and 5, red lines (Petal Flare phenomenon) that were not actually visible to the naked eye were observed in the photographs.

[0231] Quantitatively, the RGB values ​​for the darkroom were 11, 11, and 9, respectively, whereas the RGB values ​​at the point with the highest R value in the photograph of FIG. 24 were 39, 40, and 42, respectively.

[0232] Therefore, in the case of FIG. 24, the absolute values ​​of the difference between the R value and the G value and the difference between the R value and the B value at the point where the R value was the largest were about 1 and about 3, respectively.

[0233] On the other hand, in the photograph of FIG. 25, the RGB values ​​at the point where the R value was the largest were 81, 25, and 8, respectively.

[0234] Therefore, in the case of FIG. 25, the absolute values ​​of the difference between the R value and the G value and the difference between the R value and the B value at the point where the R value was the largest were approximately 56 and approximately 73, respectively.

[0235] On the other hand, in the photograph of FIG. 26, the RGB values ​​at the point where the R value was the largest were 136, 43, and 28, respectively.

[0236] Therefore, in the case of FIG. 26, the absolute values ​​of the difference between the R value and the G value and the difference between the R value and the B value at the point where the R value was the largest were approximately 93 and approximately 108, respectively.

[0237] These results indicate that the so-called petal flare did not occur in Figure 24, but the petal flare phenomenon occurred significantly in Figures 25 and 26. [Explanation of symbols]

[0238] 100: Infrared absorbing substrate 201: First dielectric film 202: second dielectric film 300, 301, 302: light absorbing layer

Claims

1. an infrared absorbing substrate containing copper; a first dielectric film formed on a first surface of the infrared absorbing substrate, the first dielectric film including a structure in which first and second sub-layers having refractive indices different from each other are repeatedly stacked; a second dielectric film formed on the second surface of the infrared absorbing substrate, the second dielectric film including a structure in which third and fourth sub-layers having refractive indices different from each other are repeatedly stacked; The V value (V １ ) and the V value of the second dielectric film according to the following formula 1 (V ２ ) Sum of (V １ +V ２ ) is in the range of 58 to 63; The V ２ V １ Ratio to V ２ / V １ is in the range of 4 to 6, The first or second dielectric film has a shortest wavelength at which it exhibits 50% reflectance within a wavelength range of 600 nm to 900 nm of 720 nm or more, or does not exist; The shortest wavelength showing 50% transmittance in the wavelength region of 350 nm to 425 nm is in the range of 400 nm to 425 nm, The longest wavelength showing 50% transmittance in the wavelength region of 560 nm to 700 nm is in the range of 590 nm to 680 nm, The maximum transmittance in the wavelength range of 700 nm to 800 nm is 2% or less, and the average transmittance in said wavelength range is 2% or less; An optical filter having a maximum transmittance of 2% or less in the wavelength range of 800 nm to 1000 nm and an average transmittance of 2% or less in said wavelength range: [0010] In Equation 1, R is the refractive index of the sublayer having the greater refractive index among the first and second sublayers (n １ The refractive index (n ２ ) to the ratio (n １ / n ２ ) or the refractive index of the sublayer having the greater refractive index (n １ The refractive index (n ２ ) to the ratio (n １ / n ２ ), where n ２ is the refractive index of the sublayer having the smaller refractive index among the first and second sublayers (n ２ ) or the refractive index of the sublayer having the smaller refractive index (n ２ ), Cu is the content of copper contained in the infrared absorbing substrate, K is the total number of the first and second sublayers in the first dielectric film or the total number of the third and fourth sublayers in the second dielectric film, and 2p is K-1.

2. 2. The optical filter of claim 1, wherein the copper content in the infrared absorbing substrate is in the range of 7% to 30% by weight.

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

4. 2. The optical filter according to claim 1, wherein the infrared absorbing substrate has a maximum transmittance of 20% or less in the wavelength region of 700 nm to 800 nm, and an average transmittance of 5% or less in said wavelength region.

5. 2. The optical filter according to claim 1, wherein the infrared absorbing substrate has a maximum transmittance of 2% or less in the wavelength region of 800 nm to 1000 nm, and an average transmittance of 2% or less in said wavelength region.

6. 2. The optical filter according to claim 1, wherein the infrared absorbing substrate has a maximum transmittance of 7% or less in the wavelength region of 1000 nm to 1200 nm, and an average transmittance of 5% or less in said wavelength region.

7. The V value of the first dielectric film according to Equation 1 (V １ 2. The optical filter of claim 1, wherein the n-th order number is in the range of 7 to 20.

8. 2. The optical filter according to claim 1, wherein the first dielectric film has a maximum reflectance of 5% or less within a wavelength range of 700 nm to 800 nm, and an average reflectance of 5% or less within said wavelength range.

9. 2. The optical filter according to claim 1, wherein the first dielectric film has a maximum reflectance of 15% or less within a wavelength range of 800 nm to 1000 nm, and an average reflectance of 10% or less within said wavelength range.

10. The V value of the second dielectric film according to Equation 1 (V ２ 2. The optical filter of claim 1, wherein the .lambda.-value is in the range of 40 to 70.

11. 2. The optical filter according to claim 1, wherein the second dielectric film has a maximum reflectance of 40% or more in a wavelength range of 700 nm to 800 nm, and an average reflectance of 20% or more in said wavelength range.

12. 2. The optical filter according to claim 1, wherein the second dielectric film has a maximum reflectance of 70% or more in a wavelength range of 800 nm to 1000 nm, and an average reflectance of 70% or more in said wavelength range.

13. 10. The optical filter of claim 1, further comprising a light absorbing layer on one or both sides of the infrared absorbing substrate.

14. 2. The optical filter of claim 1, wherein the first dielectric film has a thickness in the range of 200 nm to 500 nm.

15. 15. The optical filter of claim 14, wherein the thicknesses of the first and second sublayers are each in the range of 1 nm to 200 nm, and the average thickness of the first and second sublayers is in the range of 10 nm to 100 nm.

16. 2. The optical filter of claim 1, wherein the second dielectric film has a thickness in the range of 3000 nm to 7000 nm.

17. 17. The optical filter of claim 16, wherein the thicknesses of the third and fourth sublayers are each in the range of 1 nm to 300 nm, and the average thicknesses of the third and fourth sublayers are in the range of 50 nm to 300 nm.

18. An imaging device comprising the optical filter according to claim 1 .

Images