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, is free from ripples and petal flares, and offers superior durability, 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 (V1+V2) of a value (V1) of V represented by a formula 1 below for the first dielectric film and a value (V2) of V represented by the formula 1 below for the second dielectric film is in a range of 15 to 50, and a ratio V2 / V1 of V2 to V1 is in a range of 4 to 12.SELECTED DRAWING: Figure 16

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) or CMOS (Complementary Metal-Oxide-Semiconductor) image sensors. These optical filters, also known as near-infrared cut filters, are used to obtain good color reproduction and clear images.

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

[0004] The optical filter must effectively block light in the ultraviolet and infrared regions while transmitting visible light with high transmittance. To achieve this, a sharp and abrupt change in transmittance is required at the boundary between the ultraviolet and visible light to be blocked and at the boundary between the infrared and visible light.

[0005] Optical filters must 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, these characteristics have become more important, and the need for optical filters that maintain their transmission and blocking characteristics even at wider angles of incidence has increased.

[0006] Optical filters must also suppress a phenomenon known as ripple. Ripple is a periodic fluctuation in transmittance in the visible light range, where the actual transmittance in a given region periodically increases or decreases compared to the average transmittance for that region. An imaging device senses the visible light that passes through an optical filter using sensors for red, green, and blue (RGB). The sensitivity of each RGB sensor is adjusted based on the average transmittance for each wavelength. However, if ripple occurs, fluctuations occur in the light recognized by the sensor, resulting in reduced color reproducibility. This ripple can create areas in the visible light range where transmittance momentarily drops (known as "bunk areas"), which can cause ghosting, which also reduces color reproducibility.

[0007] Recently, a phenomenon known as petal flare has become a problem. Petal flare refers to the phenomenon in which red lines, which are not visible to the naked eye, appear in photographs when photographing a light source. The red lines often resemble petals relative to the light source, hence the name petal flare. The frequency of petal flare is increasing as the sensitivity of sensors in imaging devices increases and optical filters are used with higher transmittance to obtain clearer photographs.

[0008] As the environments in which imaging devices are used become more diverse and the frequency of use under harsh conditions increases, optical filters are required to have excellent durability so as to maintain their optical characteristics even under harsh conditions.

[0009] Known optical filters include those that use an absorption layer containing an absorbent and / or a reflective layer that is a dielectric film. The application of a dielectric film can block light in the ultraviolet and / or infrared regions. However, dielectric films have the property that their transmittance curves change (shift) depending on the angle of incidence. Therefore, to compensate for the shortcomings of dielectric films, optical filters are also known that use an absorption layer containing a near-infrared absorbing dye, whose transmittance has little dependency on the angle of incidence.

[0010] Optical filters that use infrared-absorbing glass (also known as blue glass) as a substrate, which has near-infrared absorbing properties, are also known. Infrared-absorbing glass is a glass filter in which CuO or other elements are added to glass so that it selectively absorbs light in the near-infrared wavelength range.

[0011] However, infrared absorbing glass has a problem in that it also exhibits some absorption characteristics in the visible light region, resulting in a decrease in the transmittance of visible light. In addition, infrared absorbing glass generally does not have good durability under high temperature or high humidity conditions.

[0012] Therefore, it is difficult to obtain an optical filter that exhibits desired blocking and transmission characteristics, does not shift in transmission characteristics depending on the incident angle, does not generate ripples or petal flare, and has excellent durability. Summary of the Invention [Problem to be solved by the invention]

[0013] 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 that stably maintains the above-mentioned transmission characteristics even when the angle of incidence varies, and its use. The present disclosure aims to provide an optical filter that does not cause problems such as ripple and petal flare and has excellent durability, and its use. [Means for solving the problem]

[0014] 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.

[0015] In this specification, "room temperature" means a natural temperature that is neither heated nor cooled, and means, for example, any temperature within the range of 10°C to 30°C, or 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.

[0016] Among the physical properties mentioned in this specification, those whose results are affected by the measurement pressure are measured at normal pressure unless otherwise specified.

[0017] In this specification, "normal pressure" refers to the natural pressure without pressure increase or decrease, and generally means atmospheric pressure of approximately 740 mmHg to 780 mmHg.

[0018] In the present specification, when a physical property is affected by the measurement humidity, the corresponding physical property is measured at the natural humidity without any special adjustment under the conditions of room temperature and / or normal pressure.

[0019] When an optical property (eg, refractive index) referred to in this disclosure is a property that varies with wavelength, the optical property is a property for light with a wavelength of 520 nm, unless otherwise specified.

[0020] In this disclosure, the terms "transmittance" and "reflectance" refer to the actual transmittance (measured transmittance) or actual reflectance (measured reflectance) determined at a specific wavelength, unless otherwise specified.

[0021] In this specification, the terms "transmittance" and "reflectance" refer to transmittance or reflectance based on an incident angle of 0 degrees, unless otherwise specified.

[0022] Unless otherwise specified, the term "average transmittance" in this disclosure refers to the result of measuring the transmittance at each wavelength in a given wavelength range, increasing the wavelength by 1 nm from the shortest wavelength, and then calculating the arithmetic mean of the measured transmittances. For example, the average transmittance within a wavelength range of 350 nm to 360 nm is the arithmetic mean 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.

[0023] The term "maximum transmittance" as used herein refers to the maximum transmittance measured at wavelengths increasing in 1 nm increments from the shortest wavelength within a given wavelength range. For example, the maximum transmittance within a 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.

[0024] Unless otherwise specified, the term "average reflectance" in this disclosure 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 mean of the measured reflectances. For example, the average reflectance within the wavelength range of 350 nm to 360 nm is the arithmetic mean 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.

[0025] The term "maximum reflectance" as used herein refers to the maximum reflectance measured at wavelengths increasing in 1 nm increments from the shortest wavelength within a given wavelength range. For example, the maximum reflectance within a 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.

[0026] As used herein, the term "incident angle" refers to an angle relative to the normal to the surface being evaluated. For example, the transmittance or reflectance of an optical filter at an incident angle of 0 degrees refers to 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 refers to the value for incident light that forms a substantially 40-degree angle with the normal in a clockwise or counterclockwise direction. This definition of the incident angle also applies to other characteristics, such as transmittance or reflectance.

[0027] 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 realize a visible light transmission band with high transmittance.

[0028] The optical filter of the present disclosure may include a transparent substrate, and a so-called infrared-absorbing substrate may be used as the transparent substrate. The infrared-absorbing substrate is a substrate that exhibits absorption characteristics in at least a portion of the infrared region. So-called blue glass, which exhibits this characteristic by containing copper, is a typical example of the infrared-absorbing substrate. While such an infrared-absorbing substrate is useful for constructing an optical filter that blocks light in the infrared region, it is disadvantageous in terms of ensuring high transmittance in the visible light region due to its absorption characteristics, and also in terms of durability. In the present disclosure, by selecting an infrared-absorbing substrate and combining it with a specific dielectric film, an optical filter can be provided that efficiently blocks light in the desired ultraviolet and infrared regions, exhibits high transmittance characteristics in the visible light region, and has excellent durability.

[0029] The infrared absorbing substrate may have an average transmittance of 75% or more in the wavelength range of 425 nm to 560 nm. The average transmittance may be, for example, 77% or more, 79% or more, 81% or more, 83% or more, 85% or more, 87% or more, or 89% or more, and / or 98% or less, 96% or less, 94% or less, 92% or less, or 90% or less.

[0030] The infrared absorbing substrate may have a maximum transmittance of 80% or more in the wavelength range of 425 nm to 560 nm. The maximum transmittance may be, for example, 82% or more, 84% or more, 86% or more, 88% or more, or 90% or more, and / or 100% or less, 98% or less, 96% or less, 94% or less, 92% or less, or 90% or less.

[0031] The infrared absorbing substrate may have an average transmittance of 75% or more in the wavelength range of 350 nm to 390 nm. The average transmittance may be, for example, 77% or more, 79% or more, 81% or more, or 83% or more, and / or 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.

[0032] The infrared absorbing substrate may have a maximum transmittance of 80% or more in the wavelength range of 350 nm to 390 nm. The maximum transmittance may be, for example, 82% or more, 84% or more, 86% or more, or 87% or more, and / or 100% or less, 98% or less, 96% or less, 94% or less, 92% or less, 90% or less, or 88% or less.

[0033] The infrared absorbing substrate may have a transmittance of 10% to 45% at a wavelength of 700 nm. Other examples of the transmittance include 43% or less, 41% or less, 39% or less, 37% or less, 35% or less, 33% or less, 31% or less, or 29% or less, or 12% or more, 14% or more, 16% or more, 18% or more, 20% or more, 22% or more, 24% or more, 26% or more, or 28% or more.

[0034] The infrared absorbing substrate may have an average transmittance of 5% to 30% in the wavelength range of 700 to 800 nm. The average transmittance may be, for example, 7% or more, 9% or more, 11% or more, 13% or more, 15% or more, 15.5% or more, 16% or more, or 16.5% or more, and / or 28% or less, 26% or less, 24% or less, 22% or less, 20% or less, 18% or less, or 17% or less.

[0035] The infrared absorbing substrate may have a maximum transmittance of 10% to 45% in the wavelength range of 700 to 800 nm. The maximum transmittance may be, for example, 12% or more, 14% or more, 16% or more, 18% or more, 20% or more, 22% or more, 24% or more, 26% or more, or 28% or more, and / or 43% or less, 41% or less, 39% or less, 37% or less, 35% or less, 33% or less, 31% or less, or 29% or less.

[0036] The infrared absorbing substrate may have an average transmittance of 3% to 20% in the wavelength range of 800 nm to 1000 nm. In other examples, the average transmittance may be adjusted to 5% or more, 7% or more, 9% or more, or 11% or more, and / or 18% or less, 16% or less, 14% or less, or 12% or less.

[0037] The infrared absorbing substrate may have a maximum transmittance of 5% to 30% in the wavelength range of 800 nm to 1000 nm, and the maximum transmittance may be, for example, 7% or more, 9% or more, 11% or more, 13% or more, or 15% or more, and / or 28% or less, 26% or less, 24% or less, 22% or less, 20% or less, 18% or less, or 16% or less.

[0038] The infrared absorbing substrate may have an average transmittance of 10% to 50% in the wavelength range of 1000 nm to 1200 nm. The average transmittance may be adjusted to, for example, 12% or more, 14% or more, 16% or more, 18% or more, 20% or more, 22% or more, 24% or more, or 25% or more, and / or 48% or less, 46% or less, 44% or less, 42% or less, 40% or less, 38% or less, 36% or less, 34% or less, 32% or less, 30% or less, 28% or less, or 26% or less.

[0039] The infrared-absorbing substrate may have a transmission band exhibiting a maximum transmittance of 10% to 70% within the wavelength range of 1000 nm to 1200 nm. The maximum transmittance may be, for example, 12% 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, or 36% or more, and / or 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, 44% or less, 42% or less, 40% or less, 38% or less, or 37% or less.

[0040] The infrared absorbing substrate having the above characteristics can be combined with the dielectric film of the present disclosure to form the desired optical filter.

[0041] Such a substrate may be a substrate known as infrared absorbing glass. Such glass is an absorbing glass manufactured by adding CuO or the like to fluorophosphate glass or phosphate glass. Therefore, in one 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. Phosphate glass also includes silicate phosphate glass, in which part of the glass skeleton is composed of SiO2. Such absorbing glass is well known, and examples thereof include glasses disclosed in Korean Patent Registration No. 10-2056613 and other commercially available absorbing glasses (e.g., commercially available products from HOYA, SCHOTT, PTOT, etc.).

[0042] Such an infrared-absorbing substrate contains copper. In the present disclosure, a substrate having a copper content in the range of 1 wt% to 7 wt% may be used. A method for measuring the copper content is summarized in the Examples section of this specification. Other examples of the copper content include 1.5 wt% or more, 2 wt% or more, 2.5 wt% or more, 2.6 wt% or more, 2.7 wt% or more, or 2.8 wt% or more, or 6.5 wt% or less, 6 wt% or less, 5.5 wt% or less, 5 wt% or less, 4.5 wt% or less, 4 wt% or less, 3.5 wt% or less, 3 wt% or less, or 2.9 wt% or less. Substrates having such copper contents are likely to exhibit the optical properties described above and can be combined with the dielectric film described below to form optical filters with desired characteristics.

[0043] 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.

[0044] 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. In one example, of the two dielectric films, the dielectric film having a smaller V value (described below) may be referred to as the first dielectric film, and the dielectric film having a larger V value may be referred to as the second dielectric film.

[0045] A first dielectric film may be formed on a first surface of the infrared absorbing substrate, and a second dielectric film may be 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.

[0046] 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, respectively.

[0047] 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.

[0048] The first and second sublayers are sublayers distinguished by the difference in refractive index between them, and the third and fourth sublayers are also sublayers distinguished by the difference in refractive index between them. Therefore, as long as the first sublayer has a different refractive index from the second sublayer, it can be made of the same material as the third or fourth sublayer, and this also applies to the second to fourth sublayers.

[0049] The 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 also be applied.

[0050] By adjusting the formation form of the dielectric film in relation to the infrared absorbing substrate, the desired optical filter can be provided.

[0051] 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 15 to 50.

[0052]

number

[0053] In Equation 1, when determining the V value of the first dielectric film, R is the ratio (n1 / n2) of the refractive index (n1) of the sublayer with the higher refractive index among the first and second sublayers to the refractive index (n2) of the sublayer with the lower refractive index among the first and second sublayers, and when determining the V value of the second dielectric film, R is the ratio (n1 / n2) of the refractive index (n1) of the sublayer with the higher refractive index among the third and fourth sublayers to the refractive index (n2) of the sublayer with the lower refractive index among the third and fourth sublayers.

[0054] In Equation 1, n2 is the refractive index (n2) of the sublayer having the smaller refractive index out of 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 out of the third and fourth sublayers when checking the V value of the second dielectric film.

[0055] In formula 1, Cu is the content of copper (unit: wt %) contained in the infrared absorbing substrate.

[0056] 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.

[0057] The first and second sublayers, which determine the V value in Equation 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 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 all sublayers in the first dielectric film. There is no upper limit to the ratio of the total number of the first and second sublayers, and it can be, for example, less than or equal to 100%. That is, the first dielectric film may include only the first and second sublayers, or it may include other sublayers.

[0058] The third and fourth sublayers, which determine the V value in Equation 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 the third and fourth sublayers is at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95% 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 the third and fourth sublayers, and it can 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.

[0059] In other examples, the sum of the V values ​​(V1+V2) may be 17 or more, 19 or more, 21 or more, 23 or more, 25 or more, 27 or more, or 29 or more, or may be 48 or less, 46 or less, 44 or less, 42 or less, 40 or less, 38 or less, 36 or less, 34 or less, 32 or less, or 30 or less.

[0060] 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 4 to 12. In other examples, the ratio V2 / V1 may be 4.5 or more, 5 or more, 5.5 or more, 6 or more, 6.5 or more, 7 or more, or 7.5 or more, or 11.5 or less, 11 or less, 10.5 or less, 9.5 or less, 9 or less, 8.5 or less, or 8 or less.

[0061] The dielectric film formed to satisfy these conditions complements or improves the insufficient properties of the infrared absorbing substrate, exhibits the desired blocking and transmission properties, and does not cause problems such as ripples and petal flare, making it possible to provide an optical filter with excellent durability.

[0062] That is, 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.

[0063] The factors that affect the V value each affect the transmission and reflection characteristics of the individual components of the optical filter.

[0064] For example, as the copper content in the substrate increases, the substrate's absorption characteristics in the long wavelength region increase, resulting in a sharper decrease in transmittance from wavelengths around 550 nm. Therefore, while increasing 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.

[0065] In addition, the difference in refractive index between the first and second sublayers (or the third and fourth sublayers), the total number of layers between the first and second sublayers (or the third and fourth sublayers), and the refractive index of the sublayer with the lowest refractive index among the first and second sublayers (or the third and fourth sublayers) affect the transmission and reflection characteristics of each dielectric film.

[0066] In the present disclosure, by combining the substrate and the dielectric film so 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 individual 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 other elements.

[0067] As a result, the present disclosure provides an optical filter and its use that effectively blocks ultraviolet and infrared rays, exhibits high transmittance for visible light, and stably maintains these characteristics even when the angle of incidence fluctuates, does not cause problems such as ripple and petal flare, and has excellent durability.

[0068] 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 arise such as a decrease in the durability of the optical filter and / or a decrease in transmittance in the visible light region, or the optical filter may block usable long-wavelength light in the visible light region, reducing the light utilization efficiency.

[0069] Furthermore, 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 within the long wavelength region that should be blocked (e.g., the 700 nm to 800 nm region).

[0070] Furthermore, if the ratio of the V values ​​of the first and second dielectric films becomes excessively small or 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 region, or the optical filter may block usable light in the long wavelength visible light region, reducing the light utilization efficiency.Furthermore, problems may occur such as a decrease in the optical filter's efficiency 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).

[0071] In Formula 1, the ratio (n1 / n2) of the refractive index of the layer with the higher refractive index (n1) to the refractive index of the layer with the lower refractive index (n2) of the first and second sublayers or the third and fourth sublayers may be, for example, in the range of about 1.4 to 2.0. In other examples, the ratio may be 1.45 or more, 1.5 or more, 1.55 or more, 1.6 or more, 1.65 or more, 1.7 or more, or 1.75 or more, or about 1.95 or less, 1.9 or less, 1.85 or less, or 1.8 or less.

[0072] In Formula 1, the refractive index (n1) of the layer with 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 3.3 or less, 3.1 or less, 2.9 or less, or 2.7 or less.

[0073] In formula 1, the refractive index (n2) of the layer with 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.

[0074] As described above, Cu in Formula 1, i.e., the copper content in the infrared absorbing substrate, may be in the range of 1 wt % to 7 wt %. When calculating the V value in Formula 1, the copper content is substituted without regard to units. That is, the V value in Formula 1 may be dimensionless. For example, Cu in Formula 1 may be 1.5 wt % or more, 2 wt % or more, 2.5 wt % or more, 2.6 wt % or more, 2.7 wt % or more, or 2.8 wt % or more, or 6.5 wt % or less, 6 wt % or less, 5.5 wt % or less, 5 wt % or less, 4.5 wt % or less, 4 wt % or less, 3.5 wt % or less, 3 wt % or less, or 2.9 wt % or less.

[0075] In the case of the first dielectric film, K, which determines 2p in Equation 1, i.e., the total number of first and second sublayers (number of first sublayers + number of second sublayers), may be about 17 or less, 16 or less, 15 or less, 14 or less, 13 or less, 12 or less, 11 or less, 10 or less, 9 or less, 8 or less, 7 or less, or 6 or less, or as other examples, 2 or more, 3 or more, 4 or more, 5 or more, or 6 or more. The first dielectric film may include a repeated stack structure of the first and second sublayers, and therefore, in such a case, the number of layers of the first and second sublayers may be the same, or one of the layers may be one or two layers more.

[0076] The total number of all sub-layers included in such a first dielectric film may be approximately 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, 9 layers or less, 8 layers or less, 7 layers or less, or 6 layers or less, as other examples, 2 layers or more, 3 layers or more, 4 layers or more, 5 layers or more, or 6 layers or more.

[0077] In the case of the second dielectric film, K, which determines 2p in Equation 1, i.e., the total number of the third and fourth sublayers (number of third sublayers + number of 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 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, or 38 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, or one of the layers may be one or two layers more.

[0078] The total number of all sub-layers included in such a second dielectric film may be, for example, approximately 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 approximately 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, or 38 layers or more.

[0079] The thickness of each of the first and second sub-layers of the first dielectric film can be adjusted depending on the purpose, but may be in the range of approximately 5 nm to 200 nm. Other examples of the thickness include 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, 80 nm or more, or 85 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, or 15 nm or less.

[0080] The average (arithmetic mean) thickness of the first sub-layer and the second sub-layer included in the first dielectric film may be in the 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, or 35 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.

[0081] The first dielectric film may have a total thickness in the range of about 100 nm to 500 nm, which may be, for example, 120 nm or more, 140 nm or more, 160 nm or more, 180 nm or more, or 200 nm or more, or 480 nm or less, 460 nm or less, 440 nm or less, 420 nm or less, 400 nm or less, 380 nm or less, 360 nm or less, 340 nm or less, 320 nm or less, 300 nm or less, 280 nm or less, 260 nm or less, 240 nm or less, or 220 nm or less.

[0082] The first dielectric film may have a laminated 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 first dielectric film facing the infrared absorbing substrate in the laminated structure 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, this laminated order may be changed.

[0083] The thickness of each of the third and fourth sub-layers of the second dielectric film can be adjusted depending on the purpose, but may be in the range of approximately 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, 80 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, 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, 180 nm or more, 190 nm or more, 200 nm or more, 210 nm or more, 220 nm or more, 230 nm or more, 240 nm or more, 250 nm or more, 260 nm or more, 270 nm or more, 280 nm or more, 290 nm or more, 300 nm or more, 310 nm or more, 320 nm or more, 330 nm or more, 340 nm or more, 350 nm or more, 360 nm or more, 370 nm or more, 380 nm or more, 390 nm or more, 400 nm or more, 410 nm or more, 420 nm or more, 430 nm or more, It may be about 75 nm or more or about 180 nm or more, or about 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, 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.

[0084] The average (arithmetic mean) thickness of the third sublayer and the fourth sublayer included in the second dielectric film may be in the range of about 80 nm to 200 nm, and may be, for example, 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, or 120 nm or more, or 195 nm or less, 190 nm or less, 185 nm or less, 180 nm or less, 175 nm or less, 170 nm or less, 165 nm or less, 160 nm or less, 155 nm or less, 150 nm or less, 145 nm or less, 140 nm or less, 135 nm or less, 130 nm or less, or 125 nm or less.

[0085] The second dielectric film may have a total thickness of about 3000 nm to 6000 nm, and may be, for example, 3500 nm or more, 4000 nm or more, or 4500 nm or more, or 5500 nm or less, 5000 nm or less, or 4800 nm or less.

[0086] The second dielectric film may have a laminate structure including the third and fourth sublayers alternately, and both surfaces may be formed of the same sublayer. For example, the third and fourth sublayers may have a higher or lower refractive index, respectively, forming the both surfaces. However, the order of the layers may be changed.

[0087] The V value V1 of the first dielectric film according to Equation 1 may be, for example, in the range of 1 to 10. In other examples, V1 may be about 1.5 or more, 2 or more, 2.5 or more, or 3 or more, or about 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, or 4 or less.

[0088] The V value V2 of the second dielectric film according to Equation 1 may be, for example, in the range of 10 to 60. In other examples, V2 may be about 12 or more, 14 or more, 16 or more, 18 or more, 20 or more, 22 or more, 24 or more, or 26 or more, or about 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, 38 or less, 36 or less, 34 or less, 32 or less, 30 or less, 28 or less, or 27 or less.

[0089] The first and second dielectric films having the above characteristics can ensure the desired optical characteristics together with the infrared absorbing substrate.

[0090] 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. Generally, the low refractive index sub-layer is manufactured using SiO2 or Na5Al3F 14Fluorides such as Na3AlF6 or MgF2 may be applied to form the high refractive index sub-layer, and TiO2, Ta2O5, Nb2O5, ZnS or ZnSe may be applied to form the high refractive index sub-layer, but the materials applied in this disclosure are not limited to the above.

[0091] To ensure a proper effect, one of the first and second dielectric layers may have a higher reflectivity than the other, for example, the second dielectric layer may have a higher reflectivity than the first dielectric layer.

[0092] The first dielectric film may exhibit an average reflectance of 2% or less in the wavelength 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, or 0.2% or more, and / or 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, 0.4% or less, or 0.3% or less.

[0093] The first dielectric film may exhibit a maximum reflectance of 2% or less in the wavelength range of 425 nm to 560 nm. In other examples, the maximum reflectance may be in the range of 0% or more, 0.1% or more, 0.2% or more, or 0.3% 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.

[0094] The first dielectric film may exhibit an average reflectance of 30% or less in a wavelength range of 350 nm to 390 nm. The average reflectance may be, for example, 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, or 5.5% or more, and / or 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, or 6% or less.

[0095] The first dielectric film may exhibit a maximum reflectance of 40% or less in the range of 350 nm to 390 nm. In other examples, the maximum reflectance may be in the range of 2% or more, 4% or more, 6% or more, 8% or more, 10% or more, 12% or more, or 14% 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, 20% or less, 18% or less, 16% or less, or 15% or less.

[0096] The first dielectric film may have a reflectance of 10% or less at a wavelength of 700 nm. Other examples of the reflectance may include 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, or 2.5% or less, or 0% or more, 0.5% or more, 1% or more, 1.5% or more, or 2% or more.

[0097] The first dielectric film may exhibit an average reflectance of 10% or less in a range of 700 nm to 800 nm, and the average reflectance may be in the range of 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less, and / or 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, 3.5% or more, 4% or more, or 4.5% or more.

[0098] The first dielectric film may exhibit a maximum reflectance of 15% or less in the range of 700 nm to 800 nm, and the maximum reflectance may be in the range of 14% or less, 13% or less, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, or 7.5% or less, and / or in the range of 0% or more, 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, or 7% or more.

[0099] The first dielectric film may exhibit an average reflectance of 30% or less in a range of 800 nm to 1000 nm, and the average reflectance may be additionally adjusted within a range of 0% or more, 2% or more, 4% or more, 6% or more, 8% or more, 10% or more, or 12% or more, and / or within a range of 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 13% or less.

[0100] The first dielectric film may exhibit a maximum reflectance of 30% or less in a range of 800 nm to 1000 nm, and the maximum reflectance may be additionally adjusted within a range of 0% or more, 2% or more, 4% or more, 6% or more, 8% or more, 10% or more, 12% or more, 14% or more, or 16% or more, and / or within a range of 28% or less, 26% or less, 24% or less, 22% or less, 20% or less, 18% or less, 17% or less, or 16.5% or less.

[0101] The first dielectric film may exhibit an average reflectance of 30% or less in a wavelength range of 1000 nm to 1200 nm. In other examples, the average reflectance may be adjusted within a range of 0% or more, 2% or more, 4% or more, 6% or more, 8% or more, 10% or more, 12% or more, 14% or more, 16% or more, or 18% or more, and / or within a range of 28% or less, 26% or less, 24% or less, 22% or less, 20% or less, or 19% or less.

[0102] The first dielectric film may exhibit a maximum reflectance of 30% or less in a wavelength range of 1000 nm to 1200 nm, and the maximum reflectance may be adjusted to, for example, 0% or more, 2% or more, 4% or more, 6% or more, 8% or more, 10% or more, 12% or more, 14% or more, 16% or more, 18% or more, or 20% or more, and / or 28% or less, 26% or less, 24% or less, 22% or less, or 21% or less.

[0103] The first dielectric film may exhibit an average reflectance of 10% or less in a range of 600 nm to 900 nm, and the average reflectance may be in the range of 9% or less, 8% or less, 7% or less, 6% or less, or 5.5% or less, and / or 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, 3.5% or more, 4% or more, 4.5% or more, or 5% or more.

[0104] The first dielectric film may exhibit a maximum reflectance of 25% or less in a range of 600 nm to 900 nm. Other examples of the maximum reflectance may be in the range of 24% or less, 23% or less, 22% or less, 21% or less, 20% or less, 19% or less, 18% or less, 17% or less, 16% or less, 15% or less, 14% or less, or 13% or less, and / or in the 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, 10% or more, 11% or more, or 12% or more.

[0105] The second dielectric film may exhibit an average reflectance of 2% or less in the wavelength 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 1.5% or less, 1% or less, or 0.5% or less.

[0106] The second dielectric film may exhibit a maximum reflectance of 4% or less in the wavelength range of 425 nm to 560 nm. In other examples, the maximum reflectance may 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.

[0107] The second dielectric film may exhibit an average reflectance of 75% or more in the range of 350 nm to 390 nm, and the average reflectance may be, for example, 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.

[0108] The second dielectric film may exhibit a maximum reflectance of 80% or more in the range of 350 nm to 390 nm, and the maximum reflectance may be, for example, 85% or more, 90% or more, or 95% or more, and / or 100% or less.

[0109] The second dielectric film may have a reflectance of 30% or less at a wavelength of 700 nm. Other examples of the reflectance may include 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, or 1% or less, or 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, 0.6% or more, or 0.7% or more.

[0110] The second dielectric film may exhibit an average reflectance of 50% or more in a wavelength range of 700 nm to 800 nm. In other examples, the average reflectance may be in the range of 52% or more, 54% or more, 56% or more, 58% or more, 60% or more, 62% or more, 64% or more, 66% or more, 68% or more, 70% or more, 72% or more, 74% or more, 76% or more, 78% or more, 80% or more, 82% or more, 84% or more, or 86% or more, and / or in the range of 95% or less, 93% or less, 91% or less, 89% or less, or 87% or less.

[0111] The second dielectric film may exhibit a maximum reflectance of 50% or more in the range of 700 nm to 800 nm. In other examples, the maximum reflectance may be in the range of 52% or more, 54% or more, 56% or more, 58% or more, 60% or more, 62% or more, 64% or more, 66% or more, 68% or more, 70% or more, 72% or more, 74% or more, 76% or more, 78% or more, 80% or more, 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 exhibit an average reflectance of 80% or more in the range of 800 nm to 1000 nm, and the average reflectance may be, for example, 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 100% or less or less than 100%.

[0113] The second dielectric film may exhibit a maximum reflectance of 80% or more in the range of 800 nm to 1000 nm, and the maximum reflectance may be, for example, 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 100% or less or less than 100%.

[0114] 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. Other examples of the average reflectance may include 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 100% or less or less than 100%.

[0115] The second dielectric film may have a transmission band exhibiting a maximum reflectance of 80% or more in the range of 1000 nm to 1200 nm, and the maximum reflectance may be, for example, 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 100% or less or less than 100%.

[0116] The second dielectric film may have a longest wavelength in the wavelength range of 350 nm to 425 nm at which it exhibits 50% reflectance in the range of 400 nm to 426 nm. The longest wavelength may be, for example, 401 nm or more, 402 nm or more, 403 nm or more, 404 nm or more, 405 nm or more, 406 nm or more, 407 nm or more, 408 nm or more, 409 nm or more, 410 nm or more, 411 nm or more, 412 nm or more, 413 nm or more, or 414 nm or more, or 423 nm or less, 421 nm or less, 419 nm or less, 417 nm or less, or 415 nm or less.

[0117] The second dielectric film may exhibit an average reflectance of 80% or less in a wavelength range of 600 nm to 900 nm. The average reflectance may be, for example, 78% or less, 76% or less, 74% or less, 72% or less, 70% or less, 68% or less, 66% or less, 64% or less, or 63% or less, and / or 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 55% or more, or 60% or more.

[0118] The second dielectric film may exhibit a maximum reflectance of 50% or more in the range of 600 nm to 900 nm. In other examples, the maximum reflectance may be in the range of 52% or more, 54% or more, 56% or more, 58% or more, 60% or more, 62% or more, 64% or more, 66% or more, 68% or more, 70% or more, 72% or more, 74% or more, 76% or more, 78% or more, 80% or more, 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%.

[0119] The second dielectric film may have a shortest wavelength in the wavelength range of 600 nm to 900 nm at which it exhibits 50% reflectance in the range of 690 nm to 750 nm, and the longest wavelength may be, for example, 692 nm or more, 694 nm or more, 696 nm or more, 698 nm or more, 700 nm or more, 702 nm or more, 704 nm or more, 706 nm or more, 708 nm or more, 710 nm or more, or 712 nm or more, or 748 nm or less, 746 nm or less, 744 nm or less, 742 nm or less, 740 nm or less, 738 nm or less, 736 nm or less, 734 nm or less, 732 nm or less, 730 nm or less, 728 nm or less, 726 nm or less, 724 nm or less, 722 nm or less, 720 nm or less, 718 nm or less, 716 nm or less, 714 nm or less, or 713 nm or less.

[0120] In another example, the second dielectric film may not have a wavelength that exhibits 50% reflectance within a wavelength range of 600 nm to 900 nm, and in this case, the second dielectric film may have a maximum transmittance of less than 50% within the wavelength range of 600 nm to 900 nm.

[0121] The reflectance of the first or second dielectric film may be a value measured in a state where each dielectric film is formed on a transparent substrate (SCHOTT, D263), or may be a value measured on an optical filter.

[0122] That is, when the first dielectric film is located on the outermost side 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 also be measured on the optical filter using the same method.

[0123] In another example, the optical filter has an average reflectance of 70% or less in the wavelength region of 600 nm to 900 nm, and the shortest wavelength showing a reflectance of 50% within the wavelength region of 600 nm to 900 nm is in the range of 690 nm to 750 nm (first embodiment), or the maximum reflectance within the wavelength region of 600 nm to 900 nm may be less than 50% (second embodiment). The reflection characteristics of the optical filter may be measured on the surface of the optical filter on the side where the first dielectric film is formed or the surface on the side where the second dielectric film is formed.

[0124] In the first aspect, the average reflectance of the optical filter within the range of 600 nm to 900 nm may be, in other examples, within the range of 68% or less, 66% or less, 64% or less, or 63% or less, and / or within the range of 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 55% or more, or 60% or more.

[0125] In the first embodiment, the optical filter can exhibit a maximum reflectance of 50% or more in the range of 600 nm to 900 nm. Other examples of the maximum reflectance may include 52% or more, 54% or more, 56% or more, 58% or more, 60% or more, 62% or more, 64% or more, 66% or more, 68% or more, 70% or more, 72% or more, 74% or more, 76% or more, 78% or more, 80% or more, 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 100% or less or less than 100%.

[0126] In the first aspect, the optical filter may have a shortest wavelength within a wavelength range of 600 nm to 900 nm at which 50% reflectance is in the range of 690 nm to 750 nm. For example, the shortest wavelength may be 692 nm or more, 694 nm or more, 696 nm or more, 698 nm or more, 700 nm or more, 702 nm or more, 704 nm or more, 706 nm or more, 708 nm or more, 710 nm or more, or 712 nm or more, or 748 nm or less, 746 nm or less, 744 nm or less, 742 nm or less, 740 nm or less, 738 nm or less, 736 nm or less, 734 nm or less, 732 nm or less, 730 nm or less, 728 nm or less, 726 nm or less, 724 nm or less, 722 nm or less, 720 nm or less, 718 nm or less, 716 nm or less, 714 nm or less, or 713 nm or less.

[0127] In the second embodiment, the optical filter may have a maximum reflectance within a wavelength range of 600 nm to 900 nm of less than 50%, 48% or less, 46% or less, 44% or less, 42% or less, 40% or less, 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, 20% or less, 18% or less, 16% or less, or 14% or less, or may be 8% or more, 10% or more, 12% 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, or 30% or more.

[0128] The reflection characteristics of the optical filter in the wavelength range of 600 nm to 900 nm are measured on the surface of the optical filter where the first dielectric film is present or the surface where the second dielectric film is present. Typically, the layers present in an optical filter are relatively thin, and in the case of a substrate, 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.

[0129] 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 second dielectric film and / or the optical filter as described above.

[0130] The method for forming the dielectric film is not particularly limited, and may be, for example, a known deposition method. Methods for controlling the reflection and transmission characteristics of a corresponding dielectric film by taking into account the deposition thickness of a sub-layer, the number of layers, etc., are known in the art. In the present disclosure, the first and second dielectric films exhibiting the above characteristics may be formed according to such known methods, and the reflectance of the surface of the optical filter facing the second dielectric film may also be adjusted by controlling the characteristics of the dielectric film.

[0131] 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.

[0132] For example, the optical filter may further include an absorbing layer formed on one or both surfaces of the transparent substrate and / or dielectric film. The absorbing layer is a light absorbing layer, for example, a layer that absorbs light within at least a portion of the wavelength range of the infrared and / or ultraviolet regions. One or more such absorbing layers may be formed in the optical filter.

[0133] 2 to 4 are views showing the case where absorption layers 300, 301, and 302 are formed on the optical filter of Fig. 1. As shown in Figs. 2 to 4, one or more absorption layers may be formed between the infrared absorbing substrate 100 and the first and / or second dielectric films 201 and 202.

[0134] 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 that has both infrared absorbing and ultraviolet absorbing properties. Such a layer typically contains an absorber (pigment, dye, etc.) and a transparent resin, and may be applied to achieve a sharper transmittance band by cutting light in the near ultraviolet and / or near infrared regions.

[0135] 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.

[0136] In one example, when the light absorbing layer is a layer that simultaneously exhibits absorption properties for ultraviolet light and infrared light, the light absorbing layer may be designed to simultaneously exhibit an absorption band in a wavelength range of approximately 300 nm to 390 nm and an absorption band in a wavelength range of 600 nm to 800 nm.

[0137] The infrared absorbing layer and the ultraviolet absorbing layer may be formed as a single layer or as separate layers. For example, a single layer may be designed to exhibit both the absorption maxima of the ultraviolet absorbing layer and the absorption maxima of the infrared absorbing layer, or two layers may be formed to exhibit the respective absorption maxima. Furthermore, multiple infrared absorbing layers and / or ultraviolet absorbing layers may be present.

[0138] Each absorbing layer may contain only one type of absorber, or, if necessary, may contain two or more types of absorbers for appropriate filtering of infrared and / or ultraviolet radiation.

[0139] For example, the infrared absorbing layer may contain 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; and 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 the ultraviolet absorbing layer may contain at least an absorbent having an absorption maximum wavelength in the range of 340 nm to 390 nm.

[0140] The infrared and ultraviolet absorbing layer may be composed of one layer.

[0141] The material and method of forming the absorbing layer are not particularly limited, and known materials and methods of forming the absorbing layer can be used.

[0142] The absorbing layer is formed using a material in which an absorbing agent (such as a dye or pigment) that allows the desired absorption maximum to be exhibited is mixed with a transparent resin.

[0143] For example, known absorbers that exhibit an absorption maximum in the wavelength region of approximately 300 nm to 390 nm can be used as the ultraviolet absorber. Examples of such absorbers include ABS 407 from Exiton; UV381A, UV381B, UV382A, UV386A, and VIS404A from QCR Solutions Corp; and ADA1225, ADA3209, ADA3216, ADA3217, ADA3218, ADA3230, ADA5205, ADA3217, ADA2055, ADA6798, ADA3102, ADA3204, ADA3210, ADA2041, ADA3201, ADA3202, ADA3215, ADA3219, ADA3225, and ADA from HW Sands. Examples of suitable MOSFETs include, but are not limited to, ADA3232, ADA4160, ADA5278, ADA5762, ADA6826, ADA7226, ADA4634, ADA3213, ADA3227, ADA5922, ADA5950, ADA6752, ADA7130, ADA8212, ADA2984, ADA2999, ADA3220, ADA3228, ADA3235, ADA3240, ADA3211, ADA3221, ADA5220, and ADA7158; and CRYSTALYN DLS 381B, DLS 381C, DLS 382A, DLS 386A, DLS 404A, DLS 405A, DLS 405C, and DLS 403A.

[0144] The infrared absorber may also be an appropriate 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.

[0145] 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.

[0146] The optical filter of the present disclosure can exhibit excellent optical properties along with excellent durability.

[0147] For example, the optical filter may exhibit a transmission band with a T50% cut-on wavelength in the range of approximately 390 nm to 425 nm. The T50% cut-on wavelength is the shortest wavelength showing 50% transmittance within the wavelength range of 350 nm to 425 nm. There may be one or more wavelengths showing 50% transmittance within the range of 390 nm to 425 nm. If there is one, that wavelength is the T50% cut-on wavelength; if there are two or more, the shortest wavelength among them is the T50% cut-on wavelength. The T50% cut-on wavelength may be further adjusted within the range of 392 nm or more, 394 nm or more, 396 nm or more, 398 nm or more, 400 nm or more, 402 nm or more, 404 nm or more, 406 nm or more, 408 nm or more, 410 nm or more, 412 nm or more, or 414 nm or more, and / or within the range of 428 nm or less, 426 nm or less, 424 nm or less, 422 nm or less, 420 nm or less, 418 nm or less, 416 nm or less, or 414 nm or less.

[0148] The optical filter can 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 can 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 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 or 624nm or more and / or 678nm or less, 676nm or less, 674nm or less, 672nm or less, 670nm or less, 668nm or less The wavelength may be further adjusted within the ranges of 666nm or less, 664nm or less, 662nm or less, 660nm or less, 658nm or less, 656nm or less, 654nm or less, 652nm or less, 650nm or less, 648nm or less, 646nm or less, 644nm or less, 642nm or less, 640nm or less, 638nm or less, 636nm or less, 634nm or less, 632nm or less, 630nm or less, 628nm or less, 626nm or less, or 624nm or less.

[0149] The optical filter may have a transmission band exhibiting an average transmittance of 75% or more within the 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, 92% or less, or 91.5% or less.

[0150] 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, 94% or more, or 95% or more, and / or within the range of 100% or less, 98% or less, 96% or less, 95% or less, or 94.5% or less.

[0151] 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. In other examples, the average transmittance may be adjusted within a 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 within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1.0% or less, 0.8% or less, 0.6% or less, 0.55% or less, or 0.5% or less.

[0152] 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. In other examples, the maximum transmittance may be adjusted within a 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, 3.5% or more, or 4% or more, and / or within a range of 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.

[0153] The optical filter of the present disclosure may have a transmittance of 2% or less at a wavelength of 700 nm, which may be further adjusted within the ranges of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, 0.8% or more, 1% or more, or 1.2% 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.

[0154] 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. In other examples, the average transmittance may be adjusted within a range of 0% or more or 0.1% or more and / or within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1.0% or less, 0.8% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, or 0.15% or less.

[0155] The optical filter of the present disclosure may have a transmission band exhibiting a maximum transmittance of 5% 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, 0.8% or more, 1% or more, or 1.2% or more, and / or within the range of 4.5% or less, 4% or less, 3.5% or less, 3% or less, 2.5% or less, 2% or less, or 1.5% or less.

[0156] The optical filter of the present disclosure may have a transmission band exhibiting an average transmittance of 2% or less within the range of 800 nm to 1000 nm. In other examples, the average transmittance may be adjusted within a 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 within a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1.0% or less, 0.8% or less, 0.6% or less, 0.4% or less, 0.2% or less, 0.15% or less, or 0.1% or less.

[0157] 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 to 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 within the range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1.0% or less, 0.8% or less, 0.6% or less, or 0.4% or less.

[0158] 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, in other examples.

[0159] 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. In other examples, the maximum 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 within a range of 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.

[0160] The optical filter of the present disclosure may exhibit any one or a combination of two or more of the above optical characteristics, and may suitably satisfy all of the above-described optical characteristics.

[0161] The optical filter can exhibit excellent durability.

[0162] For example, the optical filter can stably maintain the optical properties even after being kept under high temperature and high humidity conditions for a long time.

[0163] Such durability can be confirmed by the following formula 2.

[0164] △T=100×(T f -T i ) / T i ...(Formula 2)

[0165] T in Equation 2 f is the optical characteristic of the optical filter after it has been maintained at a temperature of 85°C and a relative humidity of 85% for 120 hours, and T iis the optical characteristic of the optical filter before being maintained at the temperature and humidity.

[0166] For example, the optical filter is T in Equation 2. f is the T50% cut-on wavelength after being maintained at a temperature of 85°C and a relative humidity of 85% for 120 hours, and T i is the T50% cut-on wavelength before being maintained at a temperature of 85°C and a relative humidity of 85% for 120 hours, the absolute value of ΔT in Equation 2 may be 20% or less. In this case, the absolute value of ΔT may be, for example, 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, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less, or about 0% or more, 0.5% or more, 1% or more, 1.5% or more, or 2% or more.

[0167] For example, the optical filter is T in Equation 2. f is the T50% cut-off wavelength after being maintained at a temperature of 85°C and a relative humidity of 85% for 120 hours, and T i is the T50% cut-off wavelength before being maintained at a temperature of 85°C and a relative humidity of 85% for 120 hours, the absolute value of ΔT in Equation 2 may be 20% or less. In this case, the absolute value of ΔT may be, for example, 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, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less, or about 0% or more, 0.5% or more, 1% or more, 1.5% or more, or 2% or more.

[0168] For example, the optical filter is T in Equation 2. f is the average transmittance in the range of 425 nm to 560 nm of the optical filter after being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, and T iis the average transmittance in the wavelength range of 425 nm to 560 nm of the optical filter before being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, the absolute value of ΔT in Equation 2 may be 20% or less. In this case, the absolute value of ΔT may be, for example, 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, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less, or about 0% or more, 0.5% or more, 1% or more, 1.5% or more, or 2% or more.

[0169] For example, the optical filter is T in Equation 2. f is the maximum transmittance of the optical filter in the range of 425 nm to 560 nm after being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, and T i is the maximum transmittance in the wavelength range of 425 nm to 560 nm of the optical filter before being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, the absolute value of ΔT in Equation 2 may be 20% or less. In this case, the absolute value of ΔT may be, for example, 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, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less, or about 0% or more, 0.5% or more, 1% or more, 1.5% or more, or 2% or more.

[0170] For example, the optical filter is T in Equation 2. f is the average transmittance in the range of 350 nm to 390 nm of the optical filter after being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, and T iis the average transmittance in the range of 350 nm to 390 nm of the optical filter before being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, the absolute value of ΔT in Equation 2 may be 20% or less. In this case, the absolute value of ΔT may be, for example, 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, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less, or about 0% or more, 0.5% or more, 1% or more, 1.5% or more, or 2% or more.

[0171] For example, the optical filter is T in Equation 2. f is the maximum transmittance of the optical filter in the range of 350 nm to 390 nm after being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, and T i is the maximum transmittance in the wavelength range of 350 nm to 390 nm of the optical filter before being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, the absolute value of ΔT in Equation 2 may be 20% or less. In this case, the absolute value of ΔT may be, for example, 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, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less, or about 0% or more, 0.5% or more, 1% or more, 1.5% or more, or 2% or more.

[0172] For example, the optical filter is T in Equation 2. f is the transmittance of the optical filter at 700 nm after being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, and T iis the transmittance at 700 nm of the optical filter before being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, the absolute value of ΔT in Equation 2 may be 20% or less. In this case, the absolute value of ΔT may be, for example, 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, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less, or about 0% or more, 0.5% or more, 1% or more, 1.5% or more, or 2% or more.

[0173] For example, the optical filter is T in Equation 2. f is the average transmittance in the range of 700 nm to 800 nm of the optical filter after being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, and T i is the average transmittance in the range of 700 nm to 800 nm of the optical filter before being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, the absolute value of ΔT in Equation 2 may be 20% or less. In this case, the absolute value of ΔT may be, for example, 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, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less, or about 0% or more, 0.5% or more, 1% or more, 1.5% or more, or 2% or more.

[0174] For example, the optical filter is T in Equation 2. f is the maximum transmittance in the range of 700 nm to 800 nm of the optical filter after being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, and T iis the maximum transmittance in the range of 700 nm to 800 nm of the optical filter before being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, the absolute value of ΔT in Equation 2 may be 20% or less. In this case, the absolute value of ΔT may be, for example, 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, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less, or about 0% or more, 0.5% or more, 1% or more, 1.5% or more, or 2% or more.

[0175] For example, the optical filter is T in Equation 2. f is the average transmittance in the range of 800 nm to 1000 nm of the optical filter after being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, and T i is the average transmittance in the range of 800 nm to 1000 nm of the optical filter before being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, the absolute value of ΔT in Equation 2 may be 20% or less. In this case, the absolute value of ΔT may be, for example, 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, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less, or about 0% or more, 0.5% or more, 1% or more, 1.5% or more, or 2% or more.

[0176] For example, the optical filter is T in Equation 2. f is the maximum transmittance in the range of 800 nm to 1000 nm of the optical filter after being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, and T iis the maximum transmittance in the range of 800 nm to 1000 nm of the optical filter before being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, the absolute value of ΔT in Equation 2 may be 20% or less. In this case, the absolute value of ΔT may be, for example, 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, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less, or about 0% or more, 0.5% or more, 1% or more, 1.5% or more, or 2% or more.

[0177] For example, the optical filter is T in Equation 2. f is the average transmittance in the range of 1000 nm to 1200 nm of the optical filter after being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, and T i is the average transmittance in the range of 1000 nm to 1200 nm of the optical filter before being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, the absolute value of ΔT in Equation 2 may be 20% or less. In this case, the absolute value of ΔT may be, for example, 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, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less, or about 0% or more, 0.5% or more, 1% or more, 1.5% or more, or 2% or more.

[0178] For example, the optical filter is T in Equation 2. f is the maximum transmittance of the optical filter in the range of 1000 nm to 1200 nm after being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, and T iis the maximum transmittance in the range of 1000 nm to 1200 nm of the optical filter before being maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, the absolute value of ΔT in Equation 2 may be 20% or less. In this case, the absolute value of ΔT may be, for example, 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, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less, or about 0% or more, 0.5% or more, 1% or more, 1.5% or more, or 2% or more.

[0179] In addition to the above-mentioned layers, various other layers may be added as needed to the optical filter as long as the desired effect is not impaired.

[0180] The present disclosure also relates to an imaging device including the optical filter. In this case, the configuration of the imaging device and the application of the optical filter are not particularly limited, and known configurations and application methods can be applied.

[0181] 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 that require blocking of near-infrared rays (for example, display devices such as PDPs). [Effects of the Invention]

[0182] The present disclosure may provide an optical filter and a use thereof. The present disclosure may 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 may provide an optical filter that stably maintains the above-mentioned transmission characteristics even when the angle of incidence varies, and a use thereof. The present disclosure may provide an optical filter that is excellent in durability and does not cause problems such as ripples or petal flare, and a use thereof. [Brief explanation of the drawings]

[0183] [Figure 1]1 is a diagram illustrating an exemplary structure of an optical filter of the present disclosure. [Figure 2] 1 is a diagram illustrating an exemplary structure of an optical filter of the present disclosure. [Figure 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. [Figure 5] 1 shows the transmittance spectrum of an infrared absorbing substrate used in an example. [Figure 6] 1 shows the transmission spectra of the dielectric films 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 spectra of the dielectric films 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] 10 is a transmittance spectrum of a transparent substrate used in a comparative example. [Figure 11] 10 is a transmittance spectrum of a transparent substrate used in a comparative example. [Figure 12] 1 shows the reflectance spectrum of the dielectric film applied in the examples and comparative examples. [Figure 13] 1 shows the transmission spectra of the dielectric films applied in the examples and comparative examples. [Figure 14] 1 shows the reflectance spectrum of the dielectric film applied in the examples and comparative examples. [Figure 15] 1 is a transmittance spectrum of an optical filter according to an embodiment of the present invention. [Figure 16] 10 is a transmittance spectrum of an optical filter of a comparative example. [Figure 17] 10 is a transmittance spectrum of an optical filter of a comparative example. [Figure 18] 10 is a transmittance spectrum of an optical filter of a comparative example. [Figure 19] 10 is a transmittance spectrum of an optical filter of a comparative example. [Figure 20] 10 is a transmittance spectrum of an optical filter of a comparative example. [Figure 21] 1 shows transmittance spectra of the optical filter of the example before and after a durability test. [Figure 22] 10 shows transmittance spectra of the optical filter of the comparative example before and after a durability test. DETAILED DESCRIPTION OF THE INVENTION

[0184] The optical filter of the present disclosure will be specifically described below through examples, but the scope of the optical filter of the present disclosure is not limited by the following examples.

[0185] 1. Evaluation of transmittance or reflectance spectrum

[0186] The transmittance or reflectance was measured using a spectrophotometer (manufacturer: PerkinElmer, product name: Lambda 750 Spectrophotometer) on specimens obtained by cutting the measurement object to 10 mm in width and length, respectively. The transmittance or reflectance was measured for each wavelength and incident angle according to the instrument's manual. 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 check the transmittance or reflectance. Unless otherwise specified, the transmittance or reflectance results in this example are those obtained when the incident angle is 0 degrees. An incident angle of 0 degrees is a direction substantially parallel to the normal direction of the specimen surface.

[0187] Regarding transmittance or reflectance, the average transmittance or average reflectance within a predetermined wavelength range 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 mean 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.

[0188] 2. Evaluation of copper content

[0189] The copper content of the glass substrate was confirmed using a Wavelength Dispersive X-Ray Fluorescence Spectrometry (WD XRF). When the specimen (glass substrate) is irradiated with X-rays using this device, characteristic secondary X-rays are generated from the individual elements of the specimen, and the device detects these secondary X-rays at wavelengths specific to each element. The intensity of these 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 at the wavelengths specific to each element.

[0190] 3.Evaluation of refractive index

[0191] The refractive index of the dielectric film sublayer was measured at a wavelength of 520 nm using a Wizz Optics M-2000 Ellipsometer.

[0192] Production Example 1. Production of Absorbing Layer Material A

[0193] Absorbing layer material A was prepared using absorber 1 (triazine-based dye) with an absorption maximum in the range of approximately 340 nm to 390 nm, infrared absorber 2 (squarylium-based dye) with an absorption maximum wavelength in the range of approximately 700 nm to 720 nm and a full width at half maximum (FWHM) of approximately 50 nm to 60 nm, and infrared absorber 3 (squarylium-based dye) with an absorption maximum wavelength in the range of approximately 730 nm to 750 nm and a full width at half maximum (FWHM) of approximately 60 nm to 70 nm. Absorbing layer material A was prepared by blending absorbers 1 to 3 with a binder resin. COP (cycloolefin polymer) was used as the binder resin. When preparing absorbing layer material A, the binder resin, absorbers 1, 2, and 3 were blended in toluene at a weight ratio of 100:5:0.4:0.5 (binder resin:1:2:3).

[0194] Production Example 2: Production of Absorbing Layer Material B

[0195] Absorbing layer material B was prepared by additionally blending infrared absorber 4 (diimmonium dye) having an absorption maximum wavelength of approximately 1050 nm to 1150 nm to the absorbing layer material A. During blending, the infrared absorber 4 was added in a ratio of approximately 0.8 parts by weight relative to 100 parts by weight of the solid content of the absorbing layer material A.

[0196] Example 1

[0197] The infrared-absorbing glass substrate used was a phosphate-based infrared-absorbing glass substrate (manufactured by HOYA Corporation) (thickness: approximately 0.21 mm) that exhibits the transmittance spectrum shown in Figure 5. The measured copper content of the infrared-absorbing glass substrate was approximately 2.89 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 within a given wavelength range, expressed in %, and TAVG is the average transmittance within a given wavelength range, also expressed in %. In Table 1, T50% cut on is the shortest wavelength (unit: nm) that exhibits 50% transmittance within the wavelength range of 350 nm to 425 nm, and T50% cut off is the longest wavelength (unit: nm) that exhibits 50% transmittance within the wavelength range of 560 nm to 700 nm.

[0198] [Table 1]

[0199] The absorber layer material A of Preparation Example 1 was applied to one side of the infrared-absorbing glass substrate and heat-treated at 135°C for two hours to form an absorber layer. The absorber layer had a thickness of approximately 3 μm. A first dielectric film was formed on the surface on which the absorber 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 350 V and 850 mA. Using this method, a high-refractive-index TiO2 layer (refractive index approximately 2.61) and a low-refractive-index SiO2 layer (refractive index approximately 1.46) were alternately formed to form the first dielectric film. A total of six high-refractive-index and low-refractive-index sub-layers were formed.

[0200] The thickness of each layer was adjusted as shown in Table 2 below. In Table 2 below, number 1 is the first layer formed on the infrared absorbing glass, and number 6 is the last layer formed.

[0201] [Table 2]

[0202] The first dielectric film is a dielectric film in which R (=n1 / n2, where n1 is the refractive index of TiO2 (about 2.61) and 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 the SiO2 layer), K is 6, and 2p is 5. Since the copper content of the infrared absorbing glass substrate, Cu in the following formula 1, is about 2.89 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 3.4.

[0203]

number

[0204] Figure 6 is a transmittance graph of the first dielectric film, and Figure 7 is a reflectance graph 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(6L)-0deg is the transmittance or reflectance at an incident angle of 0 degrees, AR(6L)-30deg is the transmittance or reflectance at an incident angle of 30 degrees, and AR(6L)-40deg is the transmittance or reflectance at an incident angle of 40 degrees.

[0205] The transmittance and reflectance characteristics in Figures 6 and 7 are summarized in Table 3 below. In Table 3 below, TMAX is the maximum transmittance or maximum reflectance within the corresponding wavelength range, expressed in %, and TAVG is the average transmittance or average reflectance within the corresponding wavelength range, also expressed in %.

[0206] In Table 3 below, T50% cut on is the shortest wavelength (unit: nm) that shows 50% transmittance or reflectance within the wavelength range of 350 nm to 425 nm, and T50% cut off is the shortest wavelength (unit: nm) that shows 50% transmittance or reflectance within the wavelength range of 600 nm to 900 nm.

[0207] [Table 3]

[0208] An optical filter was manufactured by forming a second dielectric film on the side of the infrared-absorbing glass substrate opposite the side on which the first dielectric film was formed. The second dielectric film was formed in the same manner as the first dielectric film. However, the second dielectric film consisted of alternating high-refractive-index TiO2 layers (refractive index: approximately 2.61) and low-refractive-index SiO2 layers (refractive index: approximately 1.46) for a total of 38 layers, with the thickness of each layer adjusted as shown in Tables 4-1 and 4-2 below. In Tables 4-1 and 4-2 below, number 1 indicates the first layer formed on the infrared-absorbing glass, and number 38 indicates the last layer formed.

[0209] [Table 4-1]

[0210] [Table 4-2]

[0211] The 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 (the refractive index of the 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 2.89 wt %, when the second dielectric film is applied to the infrared absorbing glass substrate, the V value of Formula 1 is about 26.22.

[0212] Figure 8 is a graph showing the transmittance of the second dielectric film, and Figure 9 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 8 and 9, 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.

[0213] The transmittance and reflectance characteristics in Figures 8 and 9 are summarized in Table 5 below. In Table 5 below, TMAX is the maximum transmittance or maximum reflectance within the relevant wavelength range, expressed in %, and TAVG is the average transmittance or average reflectance within the relevant wavelength range, also expressed in %. In Table 5, T50% cut on is the shortest wavelength (unit: nm) that shows 50% transmittance or reflectance within the wavelength range of 350 nm to 425 nm, and T50% cut off is the shortest wavelength (unit: nm) that shows 50% transmittance or reflectance within the wavelength range of 600 nm to 900 nm.

[0214] [Table 5]

[0215] The average reflectance within the 600nm to 900nm range measured on the surface of the second dielectric film layer of the optical filter was approximately 62.3%, and the shortest wavelength showing 50% reflectance within the 600nm to 900nm range was approximately 712nm.

[0216] Comparative Example 1

[0217] An optical filter was fabricated in the same manner as in Example 1, except that a glass substrate that does not contain copper and has no absorption characteristics was used. 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. This glass substrate has 0 wt % Cu in Formula 1 above.

[0218] The average reflectance within the 600nm to 900nm range measured on the surface of the second dielectric film layer of the optical filter was approximately 62.3%, and the shortest wavelength showing 50% reflectance within the 600nm to 900nm range was approximately 712nm.

[0219] Comparative Example 2

[0220] An optical filter was manufactured in the same manner as in Comparative Example 1, except that the absorber layer was formed using absorber layer material B of Manufacturing Example 2. The average reflectance within the 600 nm to 900 nm range measured on the surface of the second dielectric film layer of the optical filter was about 62.3%, and the shortest wavelength showing 50% reflectance within the 600 nm to 900 nm range was about 712 nm.

[0221] Comparative Example 3

[0222] The infrared-absorbing glass substrate used was a phosphate-based infrared-absorbing glass substrate (manufactured by HOYA Corporation) (thickness: approximately 0.21 mm) that exhibits the transmittance spectrum shown in Figure 11. The measured copper content of the infrared-absorbing glass substrate was approximately 12.08 wt%. The spectral characteristics of the infrared-absorbing glass substrate are summarized in Table 6 below. In Table 6 below, TMAX is the maximum transmittance within a given wavelength range, expressed in %, and TAVG is the average transmittance within a given wavelength range, also expressed in %. In Table 6, T50% cut on is the shortest wavelength (unit: nm) that exhibits 50% transmittance within the wavelength range of 350 nm to 425 nm, and T50% cut off is the longest wavelength (unit: nm) that exhibits 50% transmittance within the wavelength range of 560 nm to 700 nm.

[0223] [Table 6]

[0224] In the case of the infrared absorbing glass substrate, the Cu content in Equation 1 was about 12.08 wt %, so the V value in Equation 1 for the first dielectric film applied to the infrared absorbing glass substrate was about 6.51, and the V value for the second dielectric film was about 49.21. The average reflectance within the 600nm to 900nm range measured on the surface of the second dielectric film layer of the optical filter was about 62.3%, and the shortest wavelength showing 50% reflectance within the 600nm to 900nm range was about 712nm.

[0225] Comparative Example 4

[0226] The infrared-absorbing glass substrate used was the same glass substrate as in Example 1. Absorbing layer material A from Preparation Example 1 was applied to one side 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 approximately 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 350 V and 850 mA. Using this method, a high-refractive-index TiO2 layer (refractive index approximately 2.61) and a low-refractive-index SiO2 layer (refractive index approximately 1.46) were alternately formed to form the first dielectric film. A total of 21 high-refractive-index and low-refractive-index sub-layers were formed.

[0227] The thickness of each layer was adjusted as shown in Table 7 below. In Table 7 below, number 1 is the first layer formed on the infrared absorbing glass, and number 21 is the last layer formed.

[0228] [Table 7]

[0229] The first dielectric film is a dielectric film in which R (=n1 / n2, where n1 is the refractive index of TiO2 (about 2.61) and 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 the SiO2 layer), K is 21, and 2p is 20. Since the copper content of the infrared absorbing glass substrate, Cu in the following formula 1, is about 2.89 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 14.1.

[0230]

number

[0231] Figure 12 is a graph showing the reflectance of the first dielectric film. The reflectance of the first dielectric film was measured using the same method as in the example. In Figure 12, AR(21L)-0deg is the reflectance at an incident angle of 0 degrees, AR(21L)-30deg is the reflectance at an incident angle of 30 degrees, and AR(21L)-40deg is the reflectance at an incident angle of 40 degrees.

[0232] The transmittance and reflectance characteristics in Figure 12 are summarized in Table 8 below. In Table 8 below, TMAX is the maximum reflectance in the corresponding wavelength range, and its unit is %, and TAVG is the average reflectance in the corresponding wavelength range, and its unit is %.

[0233] In Table 8 below, T50% cut on is the shortest wavelength (unit: nm) that shows 50% transmittance or reflectance within the wavelength range of 350 nm to 425 nm, and T50% cut off is the shortest wavelength (unit: nm) that shows 50% transmittance or reflectance within the wavelength range of 600 nm to 900 nm.

[0234] [Table 8]

[0235] An optical filter was manufactured by forming a second dielectric film on the side of the infrared-absorbing glass substrate opposite the side on which the first dielectric film was formed. The second dielectric film was formed in the same manner as the first dielectric film. However, the second dielectric film consisted of alternating high-refractive-index TiO2 layers (refractive index: approximately 2.61) and low-refractive-index SiO2 layers (refractive index: approximately 1.46) for a total of 19 layers, with the thickness of each layer adjusted as shown in Table 9 below. In Table 9 below, number 1 is the first layer formed on the infrared-absorbing glass, and number 19 is the last layer formed.

[0236] [Table 9]

[0237] The 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 (the refractive index of the SiO2 layer), K is 19, and 2p is 18. Since the copper content of the infrared absorbing glass substrate, Cu in Formula 1, is about 2.89 wt %, when the second dielectric film is applied to the infrared absorbing glass substrate, the value of V in Formula 1 is about 12.67.

[0238] Figure 13 is a transmittance graph of the second dielectric film, and Figure 14 is a reflectance graph of the second dielectric film. The transmittance and reflectance were measured in the same manner as in Example 1. In Figures 13 and 14, IR(19L)-0deg is the transmittance or reflectance at an incident angle of 0 degrees, IR(19L)-30deg is the transmittance or reflectance at an incident angle of 30 degrees, and IR(19L)-40deg is the transmittance or reflectance at an incident angle of 40 degrees.

[0239] The transmittance and reflectance characteristics of Figures 13 and 14 are summarized in Table 10 below. In Table 10 below, TMAX is the maximum transmittance or maximum reflectance within the relevant wavelength range, expressed in %, and TAVG is the average transmittance or average reflectance within the relevant wavelength range, also expressed in %. In Table 10, T50% cut on is the shortest wavelength (unit: nm) that shows 50% transmittance or reflectance within the wavelength range of 350 nm to 425 nm, and T50% cut off is the shortest wavelength (unit: nm) that shows 50% transmittance or reflectance within the wavelength range of 600 nm to 900 nm.

[0240] [Table 10]

[0241] The average reflectance within the 600nm to 900nm range measured on the surface of the second dielectric film layer of the optical filter was approximately 99%, and the shortest wavelength showing a reflectance of 50% within the 600nm to 900nm range was approximately 846nm.

[0242] Comparative Example 5

[0243] A filter was manufactured in the same manner as in Example 1, except that the second dielectric film formed in Comparative Example 4 was used as the second dielectric film.

[0244] Test Example 1: Evaluation of transmittance spectrum

[0245] 15 to 20 respectively show the transmittance spectra of the optical filter of Example 1 (FIG. 15) and the optical filters of Comparative Examples 1 to 5. In each figure, 0D means an incident angle of 0 degrees, 30D means an incident angle of 30 degrees, and 40D means an incident angle of 40 degrees.

[0246] The spectral characteristics of each optical filter are summarized in Table 11 below. In Table 11 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 11 below, T50% cut on is the shortest wavelength (unit: nm) that shows 50% transmittance in the wavelength range of 350 nm to 425 nm, and T50% cut off is the longest wavelength (unit: nm) that shows 50% transmittance in the wavelength range of 560 nm to 700 nm.

[0247] [Table 11]

[0248] Comparing the transmittance spectra of the optical filters of Example 1 and Comparative Example 1 (FIGS. 15 and 16), it can be seen that Comparative Example 1 does not exhibit an adequate blocking effect against infrared rays because the T50% cutoff wavelength is longer than that of Example 1, and it also exhibits high transmittance in the long wavelength band of 700 nm or more, so it cannot properly function as an optical filter.

[0249] The transmittance spectrum (Figure 17) of the optical filter of Comparative Example 2 also shows that, like Comparative Example 1, it is unable to exhibit an appropriate blocking effect against infrared rays, and that the transmittance in the visible light region in particular drops significantly.

[0250] Comparing the transmittance spectra of the optical filters of Example 1 and Comparative Example 3 (FIGS. 15 and 18), it can be predicted that in the case of Comparative Example 3, the T50% cut-off wavelength is excessively short compared to Example 1, resulting in a significant drop in the utilization efficiency of visible light in the long wavelength region.

[0251] In the case of the transmittance spectra of the optical filters of Comparative Examples 4 and 5 (Figures 19 and 20), both show an increase in transmittance in the wavelength region around 750 nm to 850 nm, indicating that the performance of the optical filters is not being properly demonstrated.

[0252] Test example 2: Durability evaluation

[0253] The optical filters of Example 1 and Comparative Example 3 were subjected to a durability test.

[0254] The durability test involves maintaining each optical filter at 85° C. and 85% relative humidity for 120 hours.

[0255] FIG. 21 shows the measurement results for the optical filter of Example 1, and FIG. 22 shows the measurement results for the optical filter of Comparative Example 3.

[0256] 21 and 22, the dotted lines represent the transmittance characteristics before being maintained at 85°C and 85% relative humidity for 120 hours (before durability in Table 12 below), and the red lines represent the transmittance characteristics after being maintained at 85°C and 85% relative humidity for 120 hours (after durability in Table 12 below).

[0257] [Table 12]

[0258] In Table 12, TMAX is the maximum transmittance in the wavelength range in %, and TAVG is the average transmittance in the wavelength range in %, and T50% cut on is the shortest wavelength (unit: nm) that shows 50% transmittance in the wavelength range of 350 nm to 425 nm, and T50% cut off is the longest wavelength (unit: nm) that shows 50% transmittance in the wavelength range of 560 nm to 700 nm.

[0259] From the results in Table 12, it can be seen that the optical filter of the present invention maintains its transmission characteristics almost unchanged even after the durability test, whereas in the case of Comparative Example 3, the transmittance in the visible light region drops significantly, and the T50% Cut on and T50% Cut off wavelengths also change significantly. [Explanation of symbols]

[0260] 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 the first surface of the infrared absorbing substrate, the first dielectric film including a structure in which first sub-layers 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 sub-layers and fourth sub-layers having refractive indices different from each other are repeatedly stacked; and a light absorbing layer provided on the first surface or the second surface of the infrared absorbing substrate, or on the first surface and the second surface of the infrared absorbing substrate; The V value (V １ ) and the V value (V ２ ) Sum of (V １ +V ２ ) is in the range of 15 to 50, The V ２ The above V １ Ratio V to ２ / V １ is in the range of 4 to 12, The copper content in the infrared absorbing substrate is in the range of 1 wt % to 7 wt %; the infrared absorbing substrate has a maximum transmittance in the range of 22% to 70% in the wavelength region of 1000 nm to 1200 nm; the first dielectric film has a thickness in the range of 100 nm to 500 nm; [Equation 1] According to the formula 1, １ When calculating the refractive index of the sublayer having a larger refractive index (n １ The refractive index (n ２ ) to the ratio (n １ / n ２ ) and n ２ is the refractive index of the sublayer having a smaller refractive index between the first sublayer and the second sublayer (n ２ ), Cu is the content of copper contained in the infrared absorbing substrate, K is the total number of the first sub-layers and the second sub-layers in the first dielectric film, and 2p is K-1; According to the formula 1, ２ When calculating the refractive index, R is the refractive index (n １ The refractive index (n ２ ) to the ratio (n １ / n ２ ) and n ２ is the refractive index of the sublayer having a smaller refractive index between the third sublayer and the fourth sublayer (n ２ ), where Cu is the copper content contained in the infrared absorbing substrate, K is the total number of the third sub-layer and the fourth sub-layer in the second dielectric film, and 2p is K-1.

2. 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.

3. 2. The optical filter according to claim 1, wherein the infrared absorbing substrate has a maximum transmittance in the range of 10% to 45% in a wavelength region of 700 nm to 800 nm, and an average transmittance in the wavelength region in the range of 5% to 30%.

4. 2. The optical filter according to claim 1, wherein the infrared absorbing substrate has a maximum transmittance in the range of 5% to 30% in a wavelength region of 800 nm to 1000 nm, and an average transmittance in the wavelength region in the range of 3% to 20%.

5. 2. The optical filter according to claim 1, wherein the infrared absorbing substrate has an average transmittance in the wavelength region of 1000 nm to 1200 nm within a range of 10% to 50%.

6. The V value (V １ 2. The optical filter of claim 1, wherein .gamma.

7. 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 700 nm to 800 nm, and an average reflectance of 10% or less within said wavelength range.

8. 2. The optical filter according to claim 1, wherein the first dielectric film has a maximum reflectance of 30% or less within a wavelength range of 800 nm to 1000 nm, and an average reflectance of 30% or less within said wavelength range.

9. The V value (V ２ 2. The optical filter according to claim 1, wherein the value of β is in the range of 10 to 60.

10. 2. The optical filter according to claim 1, wherein the second dielectric film has a maximum reflectance of 50% or more within a wavelength range of 700 nm to 800 nm, and an average reflectance of 50% or more within said wavelength range.

11. 2. The optical filter according to claim 1, wherein the second dielectric film has a maximum reflectance of 80% or more within a wavelength range of 800 nm to 1000 nm, and an average reflectance of 80% or more within said wavelength range.

12. 2. The optical filter according to claim 1, wherein the average reflectance in the wavelength region of 600 nm to 900 nm is 70% or less.

13. 2. The optical filter according to claim 1, wherein the shortest wavelength at which the filter exhibits 50% reflectance in the wavelength region of 600 nm to 900 nm is in the range of 690 nm to 750 nm.

14. 14. The optical filter of claim 13, wherein the thickness of the first sublayer and the second sublayer are each in the range of 5 nm to 200 nm, and the average thickness of the first sublayer and the second sublayer is in the range of 10 nm to 100 nm.

15. 2. The optical filter according to claim 1, wherein the second dielectric film has a thickness in the range of 3000 nm to 6000 nm.

16. 16. The optical filter of claim 15, wherein the thicknesses of the third sublayer and the fourth sublayer are each in the range of 1 nm to 300 nm, and the average thickness of the third sublayer and the fourth sublayer is in the range of 80 nm to 200 nm.

17. 2. The optical filter according to claim 1, wherein the shortest wavelength showing 50% transmittance within the wavelength region of 350 nm to 425 nm is within the range of 400 nm to 425 nm.

18. 2. The optical filter according to claim 1, wherein the longest wavelength at which 50% transmittance is exhibited within the wavelength region of 560 nm to 700 nm is within the range of 590 nm to 660 nm.

19. 2. The optical filter according to claim 1, wherein the absolute value of ΔTV in the following formula 2 is 20% or less: △T Ｖ =100×(T) Ｖ．ｆ -T Ｖ．ｉ ) / T Ｖ．ｉ ... (Formula 2) In the formula 2, the T Ｖ．ｆ is the average transmittance in the wavelength range of 425 nm to 560 nm after the optical filter is maintained at a temperature of 85° C. and a relative humidity of 85% for 120 hours, and T Ｖ．ｉ is the average transmittance of the optical filter in the wavelength range of 425 nm to 560 nm before being maintained at the temperature and relative humidity.

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

Images