Optical filter

Abstract

The present application can provide an optical filter which can obtain a sharp visible light transmission band while effectively and accurately blocking ultraviolet light near a short wavelength visible light region and infrared light near a long wavelength visible light region, minimize a ripple phenomenon regardless of an incident angle, and obtain a high visible light transmittance while ensuring a characteristic even in a case where a near-infrared absorbing glass is used as a substrate.

Description

TECHNICAL FIELD

[0001] The present application relates to an optical filter. BACKGROUND

[0002] For an image capturing device using an image sensing component such as a CCD or CMOS image sensor, an optical filter that transmits visible light and blocks infrared light such as near-infrared light is used to obtain good color reproducibility and a clear image, and the optical filter is also called a near-infrared cut filter.

[0003] For such an optical filter, it is required to exhibit a transmittance curve that transmits visible light and blocks ultraviolet light and infrared light.

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

[0005] As a known optical filter, a reflection layer including an absorption layer containing a near-infrared absorbing dye and a dielectric film that blocks light in the ultraviolet and infrared wavelength regions is known (for example, Patent Document 1, Korean Patent Registration No. 10-2056613). The dielectric film has a characteristic that the transmittance curve varies (shifts) depending on the incident angle. Therefore, for the optical filter in Patent Document 1, an absorption layer containing a near-infrared absorbing dye having a small transmittance dependence on the incident angle is applied to compensate for the shortcomings of the dielectric film.

[0006] An optical filter using so-called near-infrared absorbing glass (also called blue glass) as a substrate that has near-infrared absorbing properties as is also known. Near-infrared absorbing glass is a glass filter in which CuO or the like is added to a fluorophosphate-based glass or a phosphate-based glass to selectively absorb light in the near-infrared wavelength region. However, in the case of applying such near-infrared glass, it is difficult to obtain a sharp visible light transmittance band by accurately blocking ultraviolet light in the vicinity of a short wavelength region of visible light and infrared light in a long wavelength region of visible light. In addition, due to the properties of the near-infrared absorbing glass as is, a high transmittance within the visible light transmittance band cannot be obtained.

[0007] On the other hand, in a conventional optical filter, a phenomenon in which periodic transmittance fluctuations occur in the visible light transmittance region (so-called ripple phenomenon) occurs.

[0008] The ripple phenomenon is a phenomenon in which an increase and a decrease in actual transmittance in a specific region with respect to the average transmittance of the corresponding region are periodically observed.

[0009] The image capturing device senses the visible light transmitted through the optical filter by a sensor for each corresponding RGB (red, green, blue) color. In the above case, the sensitivity of each sensor of RGB is adjusted in consideration of the average transmittance for each wavelength, and if the moire phenomenon occurs, the color reproducibility is deteriorated due to the fluctuation of light recognized by the sensor.

[0010] In addition, the moire phenomenon can generate a region (so-called bunk region) in which the transmittance of the visible light region momentarily decreases and thus causes a ghost phenomenon, and this ghost phenomenon also deteriorates the color reproducibility.

[0011] In the related art, in order to prevent the moire phenomenon or the ghost phenomenon as described above, a method of shifting the thickness of each sub-layer in a dielectric film mainly composed of a plurality of sub-layers by about 10% has been employed. It cannot effectively prevent the moire phenomenon, and in particular, it is difficult to prevent the moire phenomenon occurring with respect to the incident angle.

[0012] In addition, the region in which the moire phenomenon with respect to the incident angle is severe is a wavelength region of about 400 nm to 600 nm in the visible light region, and this wavelength region has not been considered in the related art. SUMMARY

[0013] TECHNICAL PROBLEM

[0014] An object of the present application is to provide an optical filter. In the present application, it is possible to obtain a sharp visible light transmittance band while effectively and accurately blocking ultraviolet light in the vicinity of a short wavelength visible light region and infrared light in the vicinity of a long wavelength visible light region, and it is possible to achieve one object of providing an optical filter capable of minimizing the moire phenomenon regardless of the incident angle. In addition, an object of the present application is to provide an optical filter capable of obtaining a high visible light transmittance while securing the above-described characteristics even when a near-infrared absorbing glass is applied as a substrate.

[0015] TECHNICAL SOLUTION

[0016] The optical filter according to the embodiment of the present application includes a transparent substrate and a dielectric film formed on one or both surfaces of the transparent substrate and having two or more sub-layers, and a moire value at an incident angle of 0° in a wavelength range of 450 nm to 560 nm is less than or equal to 2.5%.

[0017] TECHNICAL EFFECT

[0018] In the present application, it is possible to obtain a sharp visible light transmission band while effectively and accurately blocking ultraviolet light in the vicinity of the short wavelength visible light region and infrared light in the vicinity of the long wavelength visible light region, and to provide an optical filter that minimizes the ripple phenomenon regardless of the incident angle. Furthermore, in the present application, even when a near-infrared absorbing glass is applied as a substrate, it is possible to provide an optical filter that can ensure the above-described characteristics and obtain a high visible light transmittance. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figures 1 to 5 is a graph showing an exemplary stacked structure of the optical filter of the present application.

[0020] Figure 6 is a spectrum of a substrate applied in the embodiment.

[0021] Figure 7 is a spectrum when forming an ultraviolet absorbing layer on the substrate of Figure 6 .

[0022] Figure 8 is a spectrum when forming an infrared absorbing layer in the structure of Figure 7 .

[0023] Figure 9 is a spectrum of an optical filter in which a dielectric film is formed in the structure of Figure 8 .

[0024] Figure 10 is a spectrum with respect to the incident angle of the optical filter of the embodiment.

[0025] Figure 11 is a spectrum with respect to the incident angle of the optical filter of the comparative example.

[0026] Figures 12 to 14 is a spectrum for confirming the ripple value of the optical filter of the embodiment or the comparative example.

[0027] BEST MODE FOR CARRYING OUT THE INVENTION

[0028] For those physical properties mentioned in the present application that can affect the results of temperature and / or pressure, unless otherwise specified, are measured at room temperature and / or atmospheric pressure.

[0029] The term room temperature refers to a natural temperature without heating or lowering, for example, room temperature means any temperature in the range of 10°C to 30°C, a temperature of about 23°C, or a temperature of about 25°C. Furthermore, in the present specification, unless otherwise specified, the unit of temperature is degrees Celsius (°C).

[0030] The term atmospheric pressure refers to a natural pressure without pressurization or depressurization, and generally means about 1 atmosphere of atmospheric pressure.

[0031] In the case where the physical property measured is a property affected by humidity, the physical property is a physical property measured at natural humidity, which is not particularly controlled at room temperature and / or atmospheric pressure.

[0032] In the case where the optical property mentioned in the present application (e.g., refractive index) is a property that varies depending on wavelength, unless otherwise specified, the optical property is a result obtained for light having a wavelength of 520 nm.

[0033] In the present application, unless otherwise specified, the term transmittance means actual transmittance (measured transmittance) examined at a specific wavelength.

[0034] In the present application, unless otherwise specified, the term average transmittance refers to a value obtained by dividing the sum of transmittances for each wavelength in a corresponding wavelength segment by the number of wavelengths (N). In this case, the transmittance for each wavelength is obtained in units of 1 nm. For example, the average transmittance in 400 nm to 450 nm is obtained by first obtaining each transmittance at all 51 wavelength points while increasing by 1 nm from 400 nm to 450 nm (such as 400 nm, 401 nm, and 402 nm), summing the transmittances, and then dividing the summed transmittance by 51. Such average transmittance can be calculated by a commonly known transmittance measuring device or software.

[0035] In the present application, unless otherwise specified, the term maximum transmittance means the highest transmittance among transmittances (measured transmittances) in a specific wavelength range.

[0036] In the present application, the incident angle is an angle with reference to the normal of the surface to be evaluated. For example, the ripple value of an optical filter at an incident angle of 0° means a ripple value for light incident in a direction parallel to the normal of the surface of the optical filter, and the ripple value at an incident angle of 40° is a ripple value for incident light forming an angle of 40° in the clockwise or counterclockwise direction with respect to the normal of the surface of the optical filter. Such a definition of the incident angle is equally applicable to other properties, such as transmittance.

[0037] The optical filter of the present application can effectively and accurately block ultraviolet light in the vicinity of the short-wavelength visible light region and infrared light in the vicinity of the long-wavelength visible light region, and can achieve a visible light transmission band having a high transmittance.

[0038] In the present application, the term visible light means light in the range of approximately 400 nm to 700 nm.

[0039] In the present application, the term visible light transmission band refers to a characteristic of a spectrum that exhibits an average transmittance of about 60% or greater, 65% or greater, 70% or greater, 75% or greater, 80% or greater, 85% or greater, or 90% or greater in the visible light region. The upper limit of the average transmittance in the visible light region is not particularly limited. For example, the average transmittance can be about 100% or less, 95% or less, 90% or less, 85% or less, 80% or less, or 75% or less.

[0040] In the present application, the term Tn% cut-on means the shortest wavelength that exhibits n% transmittance in the visible light transmission band, while Tn% cut-off means the longest wavelength that exhibits n% transmittance in the visible light transmission band. For example, T50% cut-on can mean the shortest wavelength that indicates 50% transmittance in the visible light transmission band, while T50% cut-off can mean the longest wavelength that indicates 50% transmittance in the visible light transmission band.

[0041] The optical filter of the present application can exhibit a transmission band having a T50% cut-on wavelength in the range of about 400 nm to 420 nm. The T50% cut-on wavelength of the visible light transmission band can be in the range of 402 nm or greater, 404 nm or greater, 406 nm or greater, or 408 nm or greater, and / or further adjusted in the range of 418 nm or less, 416 nm or less, 414 nm or less, 412 nm or less, or 410 nm or less.

[0042] The optical filter of the present application can exhibit a transmission band having a T50% cut-off wavelength in the range of about 610 nm to 650 nm. The T50% cut-off wavelength of the visible light transmission band can be in the range of 612 nm or greater, 614 nm or greater, 616 nm or greater, 618 nm or greater, 620 nm or greater, 622 nm or greater, 624 nm or greater, 626 nm or greater, 628 nm or greater, or 630 nm or greater, and / or additionally adjusted in the range of 648 nm or less, 646 nm or less, 644 nm or less, 642 nm or less, 640 nm or less, 638 nm or less, 636 nm or less, 634 nm or less, 632 nm or less, or 630 nm or less.

[0043] The optical filter of the present application can have a transmission band that exhibits an average transmittance of 85% or greater in the range of 425 nm to 560 nm. In another example, the average transmittance can be in the range of 87% or greater, 89% or greater, 91% or greater, or 93% or greater, and / or adjusted in the range of 98% or less, 96% or less, 94% or less, 92% or less, 90% or less, or 88% or less.

[0044] The optical filter of the present application can have a transmission band exhibiting a maximum transmittance of 87% or greater in the range of 425 nm to 560 nm. In another example, the maximum transmittance can be in the range of 89% or greater, 91% or greater, 93% or greater, or 95% or greater, and / or further adjusted in the range of 100% or less, 98% or less, 96% or less, 94% or less, 92% or less, or 90% or less.

[0045] The optical filter of the present application can have a transmission band exhibiting an average transmittance of 2% or less in the range of 300 nm to 390 nm. In another example, the average transmittance can be in the range of 0% or greater, 0.1% or greater, or 0.2% or greater, and / or further adjusted in 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, 0.4% or less, 0.35% or less, or 0.3% or less.

[0046] The optical filter of the present application can have a transmission band exhibiting a maximum transmittance of 2% or less in the range of 300 nm to 390 nm. In another example, the maximum transmittance can be in the range of 0% or greater, 0.2% or greater, 0.4% or greater, 0.6% or greater, or 0.8% or greater, and / or further adjusted in the range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less.

[0047] The optical filter of the present application can have a transmission band exhibiting an average transmittance of 2% or less in the range of 700 nm to 800 nm. In another example, the average transmittance can be in the range of 0% or greater, 0.1% or greater, 0.3% or greater, 0.4% or greater, or 0.5% or greater, and / or further adjusted in 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, or 0.6% or less.

[0048] The optical filter of the present application can have a transmission band exhibiting an average transmittance of 2% or less in the range of 700 nm to 800 nm. In another example, the average transmittance can be in the range of 0% or greater, 0.1% or greater, 0.3% or greater, 0.4% or greater, or 0.5% or greater, and / or further adjusted in 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, or 0.6% or less.

[0049] The optical filter of the present application can have a transmission band exhibiting a maximum transmittance of 2% or less in the range of 700 nm to 800 nm. In another example, the maximum transmittance can be in 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 further adjusted in the range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less.

[0050] The optical filter of the present application can have a transmission band exhibiting an average transmittance of 2% or less in the range of 800 nm to 1000 nm. In another example, the average transmittance can be in the range of 0% or more, 0.1% or more, 0.3% or more, 0.4% or more, or 0.5% or more, and / or further adjusted in 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, or 0.6% or less.

[0051] The optical filter of the present application can have a transmission band exhibiting a maximum transmittance of 2% or less in the range of 800 nm to 1000 nm. In another example, the maximum transmittance can be in 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 further adjusted in the range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less.

[0052] The optical filter of the present application can have a transmission band exhibiting an average transmittance of 5% or less in the range of 1000 nm to 1200 nm. In another example, the average transmittance can be in the range of 0% or more, 0.5% or more, 1% or more, 1.5% or more, 2.0% or more, or 2.5% or more, and / or further adjusted in the range of 4.5% or less, 4% or less, 3.5% or less, 3% or less, or 2.5% or less.

[0053] The optical filter of the present application can have a transmission band exhibiting a maximum transmittance of 10% or less in the range of 1000 nm to 1200 nm. In another example, the maximum transmittance can be in the range of 0% or more, 1% or more, 2% or more, 3% or more, 4% or more, or 5% or more, and / or further adjusted in the range of 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less.

[0054] The optical filter of this application can have a transmittance of 10% or less at a wavelength of 1200 nm. In another example, the transmittance can be further adjusted in the range of 1% or more, 2% or more, 3% or more, 4% or more, or 5% or more, and / or in the range of 9% or less, 8% or less, 7% or less, 6% or less, or 5.5% or less.

[0055] The optical filter of this application can have a low ripple value and can maintain a low ripple value even when the incident angle changes.

[0056] In one example, the optical filter of this application can have a ripple value of 2.5% or less relative to an incident angle of 0° in the wavelength region of 450nm to 560nm.

[0057] The average transmittance (T) in the wavelength range (450 nm to 560 nm) was obtained. ave.i (i = 1 to n) and actual transmittance (T) i All differences between (i = 1 to n) (= T) diff.i =T i -T ave.i (i = 1 to n), then subtract the maximum value of the obtained difference (Max(T)). diff.i )) and minimum value (Min(T) diff.i Following this, the term ripple value is obtained. In the above, the subscript i, determined in the range from 1 to n, represents the wavelength number. For example, when examining ripple values ​​in the range of 450 nm to 560 nm, 450 nm is designated as the case where i is 1, and i also increases by 1 when the wavelength increases by 1 nm. That is, 451 nm is designated when i is 2, and 560 nm is designated when i is 111. The ripple value is the R value determined according to Equation 1 below. Meanwhile, in obtaining the ripple value, the average transmittance is calculated using a cubic spline regression equation using the Minitab tool (a statistical analysis program).

[0058] [Equation 1]

[0059] R = Max(T) diff.i )-Min(T diff.i )

[0060] In Equation 1, R is the ripple value, Max(T) diff.i ) is the maximum value among the differences between the average transmittance and the actual transmittance, and Min(T) diff.i () is the minimum value among the differences between the average transmittance and the actual transmittance.

[0061] The ripple value can be calculated using a Minitab tool (a statistical analysis program) according to a cubic spline regression equation.

[0062] In another example, the ripple value can be adjusted in a range of about 2.4% or less, 2.3% or less, 2.2% or less, 2.1% or less, 2.0% or less, 1.9% or less, 1.8% or less, 1.7% or less, 1.6% or less, 1.5% or less, 1.4% or less, 1.3% or less, or 1.2% or less, and / or in a range of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, 0.8% or more, or 1% or more.

[0063] For the optical filter in the present application, the change in the ripple value with respect to the incident angle is hardly or is minimized. For example, in the optical filter of the present application, the absolute value of the difference (R0-R 40 ) between the ripple value at an incident angle of 0° (R0) and the ripple value at an incident angle of 40° (R 40 ) in the wavelength range of 450 nm to 560 nm can be in a range of 0% to 2.5%. In another example, the absolute value of the difference can be in a range of about 2.4% or less, 2.2% or less, 2.0% or less, 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1.0% or less, 0.8% or less, 0.6% or less, 0.4% or less, 0.2% or less, 0.1% or less, 0.09% or less, 0.08% or less, 0.07% or less, 0.06% or less, 0.05% or less, or 0.04% or less.

[0064] The optical filter of the present application can exhibit any one of the above-described optical characteristics or a combination of two or more thereof, and can appropriately satisfy all of the above-described optical characteristics.

[0065] The optical filter of the present application can include more layers selected from the group consisting of a dielectric film, an ultraviolet absorption layer, and an infrared absorption layer on one or both surfaces of the transparent substrate. At this time, two or more of the dielectric film, the infrared absorption layer, or the ultraviolet absorption layer can be formed. By selecting and combining appropriate layers among the respective layers, optical properties including the above-described ripple value, etc. can be achieved.

[0066] Figure 1 and Figure 2 Exemplary structures of optical filters are disclosed, and they show cases in which dielectric films 200, 201, and 202 are formed on one or both surfaces of a transparent substrate 100.

[0067] The type of the transparent substrate to be applied to the optical filter is not particularly limited, and an appropriate type can be selected for use in the configuration of the optical filter.

[0068] The term transparent substrate refers to a substrate having a property of transmitting visible light, and for example, the transparent substrate can refer to a substrate having an average transmittance of 70% or more in a wavelength range of about 425 nm to 560 nm. The average transmittance of the transparent substrate can be further adjusted in a range of 75% or more, 80% or more, or 85% or more, and / or 95% or less, or 90% or less.

[0069] For the transparent substrate, a substrate made of various known materials can be applied as long as the substrate exhibits the above-described transmittance and exhibits physical properties such as appropriate rigidity as a substrate. For example, a substrate made of an inorganic material such as glass or quartz or an organic material such as resin can be used.

[0070] A polyester such as PET (poly(ethylene terephthalate)) or PBT (poly(butylene terephthalate)), polyethylene, polypropylene, or a polyolefin such as EVA (ethylene-vinyl acetate copolymer), a norbornene polymer, an acrylic polymer such as PMMA (polymethyl methacrylate), a polyurethane polymer, a vinyl chloride polymer, a fluorine-containing polymer, a polycarbonate, polyvinyl butyral, polyvinyl alcohol, or a polyimide can be exemplified as a resin material that can be used for the transparent substrate, but the present application is not limited thereto.

[0071] Soda-lime glass, borosilicate glass, alkali-free glass, quartz glass, and the like are mentioned as a glass material that can be used for the transparent substrate.

[0072] A crystal material that can be used for the transparent substrate includes quartz and birefringent crystals such as lithium niobate or sapphire, and the like.

[0073] The thickness of the transparent substrate can be adjusted in a range of, for example, about 0.03 mm to 5 mm, but is not limited thereto.

[0074] For the transparent substrate, a substrate that absorbs light in the near-infrared and / or near-ultraviolet region can be used as a glass called so-called near-infrared absorbing glass. Such a glass is called an absorbing type glass in which CuO or the like is added to a fluorophosphate-based glass or a phosphate-based glass, and in the phosphate-based glass, a silicon phosphate-based glass in which a part of the glass structure is composed of SiO2 can be included.

[0075] When the absorption-type glass is used as the transparent substrate, the transmittance of the absorption-type glass in the near-infrared region can be set to 20% or less by adjusting the addition concentration of CuO or the thickness of the substrate. Thus, the light-shielding property with respect to near-infrared light can be improved. Such an absorption-type glass is known, and for example, the glass disclosed in Korean Patent Registration No. 10-2056613 or other commercial absorption-type glasses (for example, commercial products such as Hoya, SCHOTT, and PTO T) can be used.

[0076] The dielectric film that can be formed on one or both surfaces of the transparent substrate is one of important components that enable the optical filter of the present application to exhibit the above-described optical properties, particularly, to exhibit a low ripple value. The dielectric film can have a multilayer structure including at least a first sub-layer and a second sub-layer having different refractive indices. In one embodiment, the first sub-layer and the second sub-layer can have different refractive indices, and the first sub-layer can have a higher refractive index than the second sub-layer. The dielectric film can include a structure in which the first sub-layer and the second sub-layer are alternately and repeatedly stacked.

[0077] In general, the dielectric film is a film that is repeatedly stacked by a dielectric material having a low refractive index and a dielectric material having a high refractive index, and is used to form a so-called infrared reflective layer and an AR (anti-reflective) layer. However, the dielectric film of the present application is formed to secure the above-described optical properties, particularly, a low ripple value. That is, in the present application, by adjusting the refractive index of each sub-layer, the refractive index of the transparent substrate, and the number of sub-layers, it is possible to secure optical properties including the above-described low ripple value, and basically, even when a substrate having poor transmittance characteristics, such as a near-infrared absorption glass, is applied, it is still possible to secure excellent transmittance characteristics.

[0078] The dielectric film of the present application is different from a dielectric film that is an infrared reflective layer and an anti-reflective layer, and thus, the actual layer configuration is also different.

[0079] For example, the dielectric film can be formed such that the V value according to Equation 2 below is 17 or less.

[0080] [Equation 2]

[0081] V = K x {[(n1 / n2) 2p ×(n1 2 / n s )-1] / [(n1 / n2) 2p ×(n1 2 / n s )+1]}) 2

[0082] In Equation 2, n1 is the refractive index of the first sub-layer, n2 is the refractive index of the second sub-layer, n sis a refractive index of the transparent substrate, K is the total number of layers of the first sub-layer and the second sub-layer in the dielectric film, and p is a number satisfying K = (2p + 1).

[0083] V in Equation 2 is written based on an equation for confirming a theoretical reflectance for effectively blocking light to be blocked by the infrared reflection layer when designing the infrared reflection layer and the anti-reflection layer. As confirmed by the equation, when the first sub-layer and the second sub-layer are the same, the value of V increases as the values of K and p increase. Therefore, when designing an existing infrared reflection layer or anti-reflection layer, the number of layers (K) of the first sub-layer and the second sub-layer is at least 20 or more to ensure the intended performance, and in this case, the V value indicates at least more than 20.

[0084] However, designing such a layer does not help to ensure optical properties such as a low ripple value as targeted in the present application.

[0085] That is, in order to achieve the object of the present application, it is necessary to adjust the refractive index and the number of layers of each layer so that the V value of Equation 2 is 17 or less.

[0086] Although the reason is not clear, the dielectric film satisfying the above design increases the transmittance of the entire optical filter in conjunction with the optical properties of the transparent substrate such as the refractive index, and thus it seems to cause a light interference phenomenon capable of ensuring a low ripple value.

[0087] In one example, in Equation 2, the ratio (n1 / n2) of the refractive index (n1) of the first sub-layer and the refractive index (n2) of the second sub-layer can be in the range of about 1.4 to 2.0. In another example, the ratio can be about 1.45 or more, 1.5 or more, 1.55 or more, 1.6 or more, 1.65 or more, 1.7 or more, or 1.75 or more, or 1.95 or less, 1.9 or less, 1.85 or less, or 1.8 or less.

[0088] In Equation 2, the refractive index (n1) of the first sub-layer can be in the range of about 1.8 to 3.5. In another example, the refractive index (n1) can be 2.0 or more, 2.2 or more, 2.4 or more, 2.5 or more, or 2.55 or more, or about 3.3 or less, 3.1 or less, 2.9 or less, or 2.7 or less.

[0089] Further, in Equation 2, the refractive index (n2) of the second sub-layer can be in the range of about 1.1 to 1.7. In another example, the refractive index (n2) can be 1.2 or more, 1.3 or more, or 1.4 or more, or 1.65 or less, 1.6 or less, 1.55 or less, or about 1.5 or less.

[0090] Among the sub-layers of the dielectric film, it can be defined that the first sub-layer is a layer having a refractive index in the above range, and the second sub-layer is a layer having a refractive index in the above range or a layer having a refractive index satisfying the refractive index ratio of the first sub-layer and in the above range.

[0091] Equation 2 can be calculated as where the structure in which the first sub-layer and the second sub-layer are alternately repeatedly stacked, and in the case where the refractive indices of the first sub-layers present in two or more layers are different from each other or the refractive indices of the second sub-layers present in two or more layers are different from each other, when the calculation is performed using Equation 2, the arithmetic mean of the refractive indices of the first sub-layers can be set as n1 in Equation 2, and the arithmetic mean of the refractive indices of the second sub-layers can be set as n2 in Equation 2.

[0092] In one example, in Equation 2, the ratio (n1 / n s ) of the refractive index (n1) of the first sub-layer and the refractive index (n s ) of the transparent substrate can be in the range of about 1.4 to 2.0. In another example, the ratio can be 1.45 or more, 1.5 or more, 1.55 or more, 1.6 or more, or 1.65 or more, or 1.95 or less, 1.9 or less, 1.85 or less, 1.8 or less, 1.75 or less, or 1.7 or less.

[0093] Considering the refractive index of the transparent substrate, an appropriate material can be selected so as to satisfy the above range.

[0094] In Equation 2, K, that is, the total number of layers of the first sub-layer and the second sub-layer (the number of layers of the first sub-layer + the number of layers of the second sub-layer) is determined to be 17 or less, 16 or less, 15 or less, 14 or less, 13 or less, 12 or less, 11 or less, 10 or less, 9 or less, or 8 or less, and in another example, K can be 2 or more, 3 or more, 4 or more, 5 or more, or 6 or more. The dielectric film can include a repeatedly stacked structure of the first sub-layer and the second sub-layer, and thus, in this case, the number of layers of each of the first sub-layer and the second sub-layer is the same as each other, or one layer can have one or two layers above the other layer.

[0095] The respective thicknesses of the first sub-layer and the second sub-layer in the dielectric film can be adjusted according to the purpose, but the thicknesses can be in the range of about 5 nm to 200 nm. In another example, the thickness is 10 nm or more, 15 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, 35 nm or more, 40 nm or more, 45 nm or more, 50 nm or more, 55 nm or more, 60 nm or more, 65 nm or more, 70 nm or more, 75 nm or more, or 85 nm or more, or 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.

[0096] The average (arithmetic mean) of the thickness of the first sub-layer and the thickness of the second sub-layer included in the dielectric film can be in the range of about 5 nm to 70 nm. In another example, the average can be 10 nm or more, 15 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, or 35 nm or more, or 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.

[0097] Although the dielectric film can include other sub-layers in addition to the first sub-layer and the second sub-layer, even in this case, it is necessary to control the thickness of the entire sub-layers to be 15 layers or less, 14 layers or less, 13 layers or less, 12 layers or less, 11 layers or less, 10 layers or less, 9 layers or less, 8 layers or less, 7 layers or less, or 6 layers or less, and it is also necessary to control the thickness of the entire sub-layers to be 2 layers or more, 3 layers or more, 4 layers or more, 5 layers or more, or 6 layers or more.

[0098] Further, even when the dielectric film includes other sub-layers in addition to the first sub-layer and the second sub-layer, it is necessary to make the ratio of the total number of the first sub-layer and the second sub-layer to the total number of the sub-layers 80% or more, 85% or more, 90% or more, or 95% or more, and the upper limit of the ratio is 100%.

[0099] Such a dielectric film can have a total thickness in the range of about 100 nm to 500 nm. In another example, the thickness can be in the range of 120 nm or more, 140 nm or more, 160 nm or more, 180 nm or more, or 200 nm or more, or in the range of 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.

[0100] For a dielectric film that includes the first sub-layer and the second sub-layer alternately and also satisfies Equation 2, the first sub-layer can be formed on one surface of the dielectric film, and the second sub-layer can be formed on the other surface. For example, the first sub-layer can be formed on the surface of the dielectric film facing the transparent substrate, and the second sub-layer can be formed on the opposite surface of the dielectric film. However, the order of stacking can be changed.

[0101] By applying a dielectric film having the above-described properties, optical properties including a desired low ripple value can be ensured. Such a dielectric film can be formed only on one surface of the transparent substrate, but can be formed on both surfaces of the transparent substrate depending on the situation. Furthermore, the optical filter can not include other dielectric films in addition to the dielectric film in which the V value in Equation 2 above is 17 or less. That is, when the dielectric film is formed on both surfaces of the transparent substrate, it is appropriate that the V value of the dielectric film is 17 or less, respectively.

[0102] The material of the dielectric film, that is, the kind of the material forming each of the sub-layers is not particularly limited, and known materials can be utilized. In general, for the preparation of a low refractive index sub-layer, a fluoride such as SiO2, Na5Al3F14, Na3AlF6, or MgF2is utilized, and for the preparation of a high refractive index sub-layer, TiO2, Ta2O5, Nb2O5, ZnS, or ZnSe can be utilized, but the materials utilized in the present application are not limited thereto. 13 F 14 , Na3AlF6, or MgF2, and for the preparation of a high refractive index sub-layer, TiO2, Ta2O5, Nb2O5, ZnS, or ZnSe can be utilized, but the materials utilized in the present application are not limited thereto.

[0103] The method of forming the dielectric film as described above is not particularly limited, and for example, can be formed by applying a known deposition method.

[0104] Furthermore, in the present application, the optical filter can include an absorption layer as an additional layer, and an infrared absorption layer and / or an ultraviolet absorption layer can be exemplified as the absorption layer. These layers are generally layers including an absorber (pigment, dye, etc.) and a transparent resin, and can be applied to achieve a sharper transmission band by cutting light in the near-ultraviolet region and / or the near-infrared region.

[0105] In one example, the ultraviolet absorption layer can be designed to exhibit an absorption maximum in a wavelength region of about 300 nm to 390 nm, and the infrared absorption layer can be designed to exhibit an absorption maximum in a wavelength region of 600 nm to 800 nm.

[0106] The infrared absorption layer and the ultraviolet absorption layer can be configured as one layer, or can be configured as separate layers, respectively. For example, one layer can be designed to exhibit both the absorption maximum of the ultraviolet absorption layer and the absorption maximum of the infrared absorption layer, or two layers exhibiting respective absorption maxima can be formed. In addition, there can also be a plurality of infrared absorption layers and / or ultraviolet absorption layers.

[0107] Figure 3 is a drawing showing an example of a structure in which the absorption layer 300 and the dielectric film 201 are formed on one surface of the substrate 100 and the additional dielectric film 202 is formed on the other surface of the substrate as an optical filter. In this case, the absorption layer 300 can be an ultraviolet absorption layer, an infrared absorption layer, or an absorption layer exhibiting absorption maxima of both the ultraviolet absorption layer and the infrared absorption layer.

[0108] Figure 4 and Figure 5 is an example in which two absorption layers 301 and 302 are present, and one of the two absorption layers 301, 302 can be an infrared absorption layer and the other can be an ultraviolet absorption layer.

[0109] However, the structure in which the absorption layer is formed of the optical filter is not limited to Figures 3 to 5 , and the number and stacking position of the absorption layers can be changed as appropriate.

[0110] Each absorption layer can contain only one kind of absorber, and two or more kinds of absorbers can be contained as necessary, so as to appropriately cut infrared light and / or ultraviolet light.

[0111] For example, the infrared absorption layer can include a first absorber having an absorption maximum wavelength in a range of 700 nm to 720 nm and a full width at half maximum in a range of 50 nm to 60 nm, a second absorber having an absorption maximum wavelength in a range of 730 nm to 750 nm and a full width at half maximum in a range of 60 nm to 70 nm, and a third absorber having an absorption maximum wavelength in a range of 760 nm to 780 nm and a full width at half maximum in a range of 90 nm to 100 nm. The ultraviolet absorption layer can include at least a first absorber having an absorption maximum wavelength in a range of 340 nm to 350 nm and a second absorber having an absorption maximum wavelength in a range of 360 nm to 370 nm.

[0112] The material constituting the absorption layer is not particularly limited, and known materials and constitution methods can be used.

[0113] Generally, the absorption layer is formed using a material in which an absorbent (dye or pigment, etc.) capable of exhibiting a desired absorption maximum is mixed with a transparent resin.

[0114] At this time, for example, a known absorbent exhibiting an absorption maximum in a wavelength region of about 300 nm to 390 nm can be applied as an ultraviolet absorbent, such as ABS407 manufactured by Exiton Co.; UV381A, UV381B, UV382A, UV386A, and VIS404A from QCR Solutions Corp.; ADA1225, ADA3209, ADA3216, ADA3217, ADA3218, ADA3230, ADA5205, ADA3217, ADA2055, ADA6798, ADA3102, ADA3204, ADA3210, ADA2041, ADA3201, ADA3202, ADA3215, ADA3219, ADA3225, ADA3232, ADA4160, ADA5278, ADA5762, ADA6826, ADA7226, ADA4634, ADA3213, ADA3227, ADA5922, ADA5950, ADA6752, ADA7130, ADA8212, ADA2984, ADA2999, ADA3220, ADA3228, ADA3235, ADA3240, ADA3211, ADA3221, ADA5220, ADA7158 from HW Sands Co.; and DLS 381B, DLS381C, DLS 382A, DLS 386A, DLS404A, DLS 405A, DLS 405C, DLS 403A from CRYSTALYN Co., but is not limited thereto.

[0115] A suitable dye or pigment exhibiting an absorption maximum in a wavelength region of 600 nm to 800 nm can be used as an infrared absorbent, and for example, a squarylium-based dye, a fluorion-based compound, a phthalocyanine-based compound, a naphthalocyanine-based compound, or a dithiol metal complex-based compound can be used, but is not limited thereto.

[0116] The transparent resin applied to the absorption layer can also use a known resin, for example, one or more of a cyclic olefin resin, a polyarylate resin, a polysulfone resin, a polyethersulfone resin, a poly-p-phenylene resin, a polyarylene ether phosphine oxide resin, a polyimide resin, a polyetherimide resin, a polyamideimide resin, an acrylic resin, a polycarbonate resin, a polyethylene naphthalate resin, and various organic-inorganic hybrid resins can be used.

[0117] In addition to the above-described layers, various necessary layers can be added to the optical filter within a range that does not impair the desired effects.

[0118] The present application also relates to an optical filter including a near-infrared absorbing glass substrate, an ultraviolet absorbing layer, and an infrared absorbing layer. The above-described dielectric film can also be formed in such an optical filter. Such an optical filter can exhibit at least any one, two or more, or all of the above-described transmission characteristics (visible light transmission band).

[0119] For example, the optical filter can also exhibit a visible light transmission band exhibiting an average transmittance of substantially 60% or greater, 65% or greater, 70% or greater, 75% or greater, 80% or greater, 85% or greater, or 90% or greater in the visible region of the spectrum. The upper limit of the average transmittance in the visible light region is not particularly limited. For example, the average transmittance can be about 100% or less, 95% or less, 90% or less, 85% or less, 80% or less, or 75% or less.

[0120] The optical filter can also exhibit a transmission band having a T50% onset wavelength in the range of about 400 nm to 420 nm. The T50% onset wavelength of the visible light transmission band can be adjusted in the range of 402 nm or greater, 404 nm or greater, 406 nm or greater, or 408 nm or greater, and / or further adjusted in the range of 418 nm or less, 416 nm or less, 414 nm or less, 412 nm or less, or 410 nm or less.

[0121] The optical filter can also exhibit a transmission band with a T50% cutoff wavelength in a range of about 610 nm to 650 nm. The T50% cutoff wavelength of the visible transmission band can be adjusted in a range of 612 nm or greater, 614 nm or greater, 616 nm or greater, 618 nm or greater, 620 nm or greater, 622 nm or greater, 624 nm or greater, 626 nm or greater, 628 nm or greater, or 630 nm or greater, and / or further adjusted in a range of 648 nm or less, 646 nm or less, 644 nm or less, 642 nm or less, 640 nm or less, 638 nm or less, 636 nm or less, 634 nm or less, 632 nm or less, or 630 nm or less.

[0122] The optical filter can also have a transmission band exhibiting an average transmittance of 85% or greater in a range of 425 nm to 560 nm. In another example, the average transmittance can be in a range of 87% or greater, 89% or greater, 91% or greater, or 93% or greater, and / or further adjusted in a range of 98% or less, 96% or less, 94% or less, 92% or less, 90% or less, or 88% or less.

[0123] The optical filter can have a transmission band exhibiting a maximum transmittance of 87% or greater in a range of 425 nm to 560 nm. In another example, the maximum transmittance can be in a range of 89% or greater, 91% or greater, 93% or greater, or 95% or greater, and / or further adjusted in a range of 100% or less, 98% or less, 96% or less, 94% or less, 92% or less, or 90% or less.

[0124] The optical filter can have a transmission band exhibiting an average transmittance of 2% or less in a range of 300 nm to 390 nm. In another example, the average transmittance can be adjusted in a range of 0% or greater, 0.1% or greater, or 0.2% or greater, and / or further adjusted in a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1.0% or less, 0.8% or less, 0.6% or less, 0.4% or less, 0.35% or less, or 0.3% or less.

[0125] The optical filter can have a transmission band exhibiting a maximum transmittance of 2% or less in a range of 300 nm to 390 nm. In another example, the maximum transmittance can be adjusted in a range of 0% or greater, 0.2% or greater, 0.4% or greater, 0.6% or greater, or 0.8% or greater, and / or further adjusted in a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less.

[0126] The optical filter can have a transmittance of 2% or less at a wavelength of 700 nm. In another example, the transmittance can be adjusted in a range of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, or 0.8% or more, and / or further adjusted in a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less.

[0127] The optical filter can have a transmittance band exhibiting an average transmittance of 2% or less in a range of 700 nm to 800 nm. In another example, the average transmittance can be adjusted in a range of 0% or more, 0.1% or more, 0.3% or more, 0.4% or more, or 0.5% or more, and / or further adjusted in a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1.0% or less, 0.8% or less, or 0.6% or less.

[0128] The optical filter can have a transmittance band exhibiting a maximum transmittance of 2% or less in a range of 700 nm to 800 nm. In another example, the maximum transmittance can be adjusted in a range of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, or 0.8% or more, and / or further adjusted in a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less.

[0129] The optical filter can have a transmittance band exhibiting an average transmittance of 2% or less in a range of 800 nm to 1000 nm. In another example, the average transmittance can be adjusted in a range of 0% or more, 0.1% or more, 0.3% or more, 0.4% or more, or 0.5% or more, and / or further adjusted in a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1.0% or less, 0.8% or less, or 0.6% or less.

[0130] The optical filter can have a transmittance band exhibiting a maximum transmittance of 2% or less in a range of 800 nm to 1000 nm. In another example, the maximum transmittance can be adjusted in a range of 0% or more, 0.2% or more, 0.4% or more, 0.6% or more, or 0.8% or more, and / or further adjusted in a range of 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less.

[0131] The optical filter can have a transmission band exhibiting an average transmittance of 5% or less in the range of 1000 nm to 1200 nm. In another example, the average transmittance can be adjusted in the range of 0% or more, 0.5% or more, 1% or more, 1.5% or more, 2.0% or more, or 2.5% or more, and / or further adjusted in the range of 4.5% or less, 4% or less, 3.5% or less, 3% or less, or 2.5% or less.

[0132] The optical filter can have a transmission band exhibiting a maximum transmittance of 10% or less in the range of 1000 nm to 1200 nm. In another example, the maximum transmittance can be adjusted in the range of 0% or more, 1% or more, 2% or more, 3% or more, 4% or more, or 5% or more, and / or further adjusted in the range of 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less.

[0133] The optical filter can have a transmittance of 10% or less at a wavelength of 1200 nm. In another example, the transmittance can be adjusted in the range of 1% or more, 2% or more, 3% or more, 4% or more, or 5% or more, and / or further adjusted in the range of 9% or less, 8% or less, 7% or less, 6% or less, or 5.5% or less.

[0134] The optical filter can have a ripple value in the above range, and can maintain a low ripple value even when the incident angle changes.

[0135] Accordingly, the ripple value at an incident angle of 0° of the optical filter, and the ripple value at an incident angle of 0° and the ripple value at an incident angle of 40° can be in the above range.

[0136] As described above, infrared-absorbing glass (so-called blue glass) exhibits an absorption characteristic with respect to the near-infrared region itself, but has a poor characteristic of accurately blocking ultraviolet light in the short-wavelength region of visible light and infrared light in the long-wavelength region of visible light, and thus it is difficult to obtain a sharp transmission band of visible light.

[0137] However, in the present application, by appropriately forming the above-described ultraviolet-absorbing layer and / or infrared-absorbing layer, it is possible to obtain the above-described excellent spectrum even when near-infrared-absorbing glass is applied.

[0138] The specific type of the infrared-absorbing layer and / or ultraviolet-absorbing layer that can be applied at this time is as described above.

[0139] The present application also relates to an image capturing device including the optical filter. In this case, the configuration method of the image capturing device or the application method of the optical filter is not particularly limited, and known configuration and application methods can be applied.

[0140] Further, the use of the optical filter of the present application is not limited to image capturing devices, and can be applied to other various applications requiring near-infrared cut (for example, display devices such as PDP, etc.).

[0141] Hereinafter, the present application will be described in detail by examples, but the scope of the present application is not limited by the following examples.

[0142] 1. Evaluation of transmission spectrum

[0143] The transmission spectrum of the infrared absorbing glass (infrared absorbing substrate) and the stack structure (optical filter, etc.) in which the infrared absorbing layer, the ultraviolet absorbing layer, and / or the dielectric film are formed on the glass was measured from a sample obtained by cutting the absorbing glass into a certain size (10 mm, 10 mm, and 0.2 mm in width, length, and thickness, respectively) using a spectrophotometer (manufacturer: Perkinelmer, product name: Lambda 750 spectrophotometer). According to the manual of the apparatus, the transmission spectrum was measured for each wavelength and incident angle. The sample (infrared absorbing glass, etc.) was placed on a straight line between the measurement beam and the detector of the spectrophotometer, and the transmission spectrum was checked while changing the incident angle of the measurement beam from 0° to 40°. Unless otherwise specified, the transmission spectrum result in this example is the result at an incident angle of 0°, and in this case, the incident angle 0° is a direction parallel to the surface normal direction of the sample.

[0144] 2. Evaluation of refractive index

[0145] The refractive index of the infrared absorbing glass and the intermediate layer was measured by using a Wiz Optics Ellipsometer (Ellipsometer) with respect to the wavelength of 520 nm.

[0146] Preparation Example 1: Preparation of ultraviolet absorbing layer material

[0147] The ultraviolet absorbing layer material was prepared by mixing a triazine-based dye exhibiting an absorption maximum in the range of about 340 nm to 390 nm with a binder resin. As the binder resin, polymethyl methacrylate (PMMA) binder was used. The material was prepared by mixing the binder resin and the absorber in cyclohexanone, and about 5 parts by weight of the dye was mixed with respect to 100 parts by weight of the binder resin.

[0148] Preparation Example 2: Preparation of near-infrared absorbing layer material

[0149] ​An infrared absorber (1) having an absorption maximum wavelength in the range of about 700 nm to 720 nm and having a full width at half maximum (FWHM) of about 50 nm to 60 nm, an infrared absorber (2) having an absorption maximum wavelength in the range of about 730 nm to 750 nm and a full width at half maximum (FWHM) of about 60 nm to 70 nm, and an infrared absorber (3) having an absorption maximum wavelength in the range of about 760 nm to 780 nm and having a full width at half maximum (FWHM) of about 90 nm to 100 nm were used as the absorber to prepare the near-infrared absorbing layer.

[0150] The above three types of infrared absorbers were mixed with a binder resin to prepare the material. A cyclo-olefin polymer (COP) was used as the binder resin.

[0151] The material was prepared by mixing the binder resin and the absorber with toluene, and the mixing ratio was 0.1 parts by weight, 0.2 parts by weight, and 0.4 parts by weight of the absorber (1), the absorber (2), and the absorber (3), respectively, with respect to 100 parts by weight of the binder resin.

[0152] Example 1

[0153] A near-infrared absorbing glass having a transmittance spectrum as shown in FIG. 1 was used as the substrate. The near-infrared absorbing glass is a glass imparted with an absorption property by including a coloring component such as a copper ion, and is also called blue glass, and a commercial product of PTOT Corporation was used in this example. The spectral characteristics of the near-infrared absorbing glass are summarized in Table 1 below. Figure 6 The near-infrared absorbing glass had a refractive index of about 1.57.

[0154] A near-infrared absorbing glass having a transmittance spectrum as shown in FIG. 1 was used as the substrate. The near-infrared absorbing glass is a glass imparted with an absorption property by including a coloring component such as a copper ion, and is also called blue glass, and a commercial product of PTOT Corporation was used in this example. The spectral characteristics of the near-infrared absorbing glass are summarized in Table 1 below.

[0155] The transmittance spectrum in the state where the ultraviolet absorbing layer was formed is shown in FIG. 2. As shown in FIG. 2, it was confirmed that the transmittance of the ultraviolet region (wavelength range of about 300 nm to 390 nm) formed by the ultraviolet absorbing layer was reduced to 1% or less, and the T50% opening wavelength of the visible light transmittance band was shifted to a longer wavelength.

[0156] Figure 7 The transmittance spectrum in the state where the ultraviolet absorbing layer was formed is shown in FIG. 2. As shown in FIG. 2, it was confirmed that the transmittance of the ultraviolet region (wavelength range of about 300 nm to 390 nm) formed by the ultraviolet absorbing layer was reduced to 1% or less, and the T50% opening wavelength of the visible light transmittance band was shifted to a longer wavelength. Figure 7

[0157] ​​An infrared absorbing layer was formed on the ultraviolet absorbing layer by using the infrared absorbing layer material of Production Example 2. The infrared absorbing layer having a thickness of about 3.5 micrometers was formed by drying the material of Production Example 2 in a hot oven at 130°C for 2 hours. The transmittance spectrum in the state where the infrared absorbing layer was formed is shown in Fig. 6. As shown in Fig. 6, it was confirmed that the transmittance of the infrared region (wavelength range of about 700 nm to 1000 nm) formed by the infrared absorbing layer was reduced to 1% or less, and the T50% cutoff wavelength of the visible light transmittance band was shifted to a shorter wavelength. Figure 8 Figure 8

[0158] A dielectric film was formed on the glass on which the ultraviolet absorbing layer and the infrared absorbing layer were formed. The dielectric film was formed by depositing sublayers in an ion-beam assisted deposition (IBAD) manner. The vacuum level and the temperature condition during deposition were set to 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, respectively. In the above-described manner, the dielectric film was formed by alternately depositing a TiO2layer (refractive index of about 2.61) - high refractive layer and a SiO2layer (refractive index of about 1.46) - low refractive layer.

[0159] A total of six high refractive layers and low refractive layers that become sublayers were formed, and specifically, a TiO2layer (thickness of about 12.4 nm), a SiO2layer (thickness of about 30.3 nm), a TiO2layer (thickness of about 43.7 nm), a SiO2layer (thickness of about 13 nm), a TiO2layer (thickness of about 30.4 nm), and a SiO2layer (thickness of about 85.3 nm) were sequentially formed on the infrared absorbing layer to form the dielectric film. In this dielectric film, nl of the following Equation 1 was about 2.61 (refractive index of the TiO2layer), n2 was about 1.46 (refractive index of the SiO2layer), and n s was about 1.57 (refractive index of the near-infrared absorbing glass), p was 2.5 (= (6 - 1) / 2), and V was about 5.70.

[0160] [Equation 2]

[0161] V = K x {[(nl / n2) 2p x (nl 2 / n s ) - 1] / [(nl / n2) 2p x (nl 2 / n s + 1]} 2

[0162] ​​As a next step, an optical filter was prepared to include a dielectric film present on both sides by sequentially forming a TiO2 layer (thickness of about 12.4 nm), a SiO2 layer (thickness of about 30.3 nm), a TiO2 layer (thickness of about 43.7 nm), and a SiO2 layer (thickness of about 13 nm), a TiO2 layer (thickness of about 30.4 nm), and a SiO2 layer (thickness of about 85.3 nm) on the surface of the near-infrared absorbing glass on which the infrared absorbing layer was not formed and thus the SiO2 layer (thickness of about 85.3 nm) was made as an outermost layer.

[0163] The spectrum of the optical filter was as shown in Figure 9 . As shown in Figure 9 , it can be seen that the visible light transmittance of the optical filter is higher than that of the near-infrared absorbing glass, and the T50% cutoff wavelength of the visible light transmittance band is shifted to a longer wavelength.

[0164] The following Table 1 shows a summary of the transmittance spectrum characteristics of the near-infrared absorbing glass, the near-infrared absorbing glass with an ultraviolet absorbing layer (filter A), the case where an infrared absorbing layer is formed on filter A (filter B), and the optical filter formed with a dielectric film having a V value of 5.70 on both sides of filter B. The unit of transmittance in the following Table 1 is %.

[0165] The average transmittance (T ave ) in the following Table 1 is a value obtained by dividing the sum of the transmittances for each wavelength in the corresponding wavelength segment by the number of wavelengths (N), as described above, and in this case, the transmittance for each wavelength is calculated in units of 1 nm.

[0166] [Table 1]

[0167]

[0168]

[0169] Comparative Example 1

[0170] An optical filter identical to that in Example 1 was prepared, and a dielectric film having a stack of 19 layers in total of high refractive index and low refractive index was formed on the infrared absorbing layer by ion beam assisted deposition in the same manner as in Example 1, except that 22 layers of the dielectric film were formed on the near-infrared absorbing glass on which the infrared absorbing layer was not formed in the same manner. The dielectric film formed on the infrared absorbing layer was to exhibit the properties of a so-called anti-reflection layer having visible light reflection preventing properties, and the dielectric film formed on the near-infrared absorbing glass was to exhibit the properties of a so-called infrared layer having infrared reflection properties.

[0171] The formation material and thickness of the dielectric films having the infrared layer characteristics and the anti-reflection layer characteristics, and the stacking order are shown in Table 2 and Table 3 below. Thus, the V value of the dielectric film having the infrared layer characteristics is 21.9, and the V value of the dielectric film having the anti-reflection layer characteristics is about 18.9.

[0172] Table 2

[0173]

[0174]

[0175] Table 3

[0176]

[0177]

[0178] Test Example 1

[0179] The transmittance spectrum of the optical filter prepared in the example was evaluated at an incident angle of 0°, 30°, and 40°, and the results are shown in FIG. 1. As can be seen from FIG. 1, the optical filter of the example exhibits almost the same spectrum regardless of the incident angle. In addition, the T10%onset and the T10%off of the visible light transmission band are not substantially shifted with respect to the incident angle. Figure 10 Figure 10 The transmittance spectrum of the optical filter prepared in the example was evaluated at an incident angle of 0°, 30°, and 40°, and the results are shown in FIG. 1. As can be seen from FIG. 1, the optical filter of the example exhibits almost the same spectrum regardless of the incident angle. In addition, the T10%onset and the T10%off of the visible light transmission band are not substantially shifted with respect to the incident angle.

[0180] Figure 11 The transmittance spectrum of the optical filter prepared in the example was evaluated at an incident angle of 0°, 30°, and 40°, and the results are shown in FIG. 1. As can be seen from FIG. 1, the optical filter of the example exhibits almost the same spectrum regardless of the incident angle. In addition, the T10%onset and the T10%off of the visible light transmission band are not substantially shifted with respect to the incident angle. Figure 11 Test Example 2

[0181]

[0182] Figure 12 The enlarged view of the transmittance spectrum at a wavelength in the range of 450 nm to 560 nm (incident angle 0°) to confirm the ripple value of the optical filters of the example and the comparative example.

[0183] As is clear from the figure, for the case of the optical filter of the comparative example 1, it can be expected that the transmittance fluctuation with respect to the wavelength occurs significantly, and thus exhibits a large ripple value, while in the optical filter of the example 1, almost no fluctuation is observed.

[0184] Figure 13 and Figure 14 ​​is an enlarged view of the average value (solid line) and measured values (dots) of transmittance in the range of 450 nm to 560 nm to confirm the ripple value (incident angle: 0°) of Example 1 and Comparative Example 1, respectively, and the difference between Example 1 and Comparative Example 1 can be more clearly identified in the graph.

[0185] For Example 1, the ripple value at an incident angle of 0° was about 1.17%, the ripple value at an incident angle of 40° was about 1.20%, and for Comparative Example 1, the ripple value at an incident angle of 0° was about 2.40%, and the ripple value at an incident angle of 40° was about 7.08%.

[0186] The average value of transmittance (average transmittance) used to confirm the ripple value was a value calculated using a regression equation of a cubic spline method using a Minitab tool (a statistical analysis program).

Claims

1. An optical filter, comprising: A transparent substrate, wherein the transparent substrate is a near-infrared absorbing glass substrate; as well as A dielectric film formed on one or both surfaces of a transparent substrate and comprising two or more sublayers, wherein the dielectric film comprises first and second sublayers with different refractive indices and alternately stacked, wherein the first and second sublayers are formed such that the value of V according to Equation 2 below is 17 or less, and wherein the average transmittance (T) at an incident angle of 0° in the wavelength range of 450 nm to 560 nm is... ave.i (i = 1 to n) and actual transmittance (T) i The difference between (i = 1 to n) is T diff.i =T i -T ave.i The maximum value of (i = 1 to n) (Max(T) diff.i Subtract the minimum value (Min(T)) diff.i The obtained ripple value is 2.5% or less. [Equation 2] V=K×{[(n1 / n2) 2p ×(n1 2 / n s )-1] / [(n1 / n2) 2p ×(n1 2 / n s )+1]} 2 Where n1 is the refractive index of the first sublayer, n2 is the refractive index of the second sublayer, and n s K is the refractive index of the transparent substrate, K is the total number of the first and second sublayers in the dielectric film, and p is the number in equation 2 that satisfies K = (2p + 1).

2. The optical filter according to claim 1, wherein, In the wavelength range of 450 nm to 560 nm, the ripple value (R0) at an incident angle of 0° and the ripple value (R...) at an incident angle of 40°... 40 The absolute value of the difference between them is in the range of 0 to 2.5%.

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

4. The optical filter according to claim 3, wherein, In the wavelength range of 425 nm to 560 nm, the average transmittance is 87% or greater.

5. The optical filter according to claim 3, wherein the optical filter has an average transmittance and a maximum transmittance of 2% or less in the wavelength range of 300 nm to 390 nm.

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

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

8. The optical filter according to claim 1, wherein, The ratio (n1 / n2) of the refractive index (n1) of the first sublayer to the refractive index (n2) of the second sublayer is in the range of 1.4 to 2.

0.

9. The optical filter according to claim 8, wherein, The refractive index (n1) of the first sublayer is in the range of 1.8 to 3.

5.

10. The optical filter according to claim 1, wherein, The refractive index (n1) of the first sublayer and the refractive index (n) of the transparent substrate s The ratio of (n1 / n) s It is in the range of 1.4 to 2.

0.

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

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

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

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

15. The optical filter according to claim 1, wherein the optical filter further comprises at least one layer selected from the group consisting of an infrared absorption layer and an ultraviolet absorption layer.

16. The optical filter according to claim 15, in, The ultraviolet absorption layer and / or the infrared absorption layer are formed on one or both sides of the transparent substrate, wherein the T50% turn-on wavelength is in the range of 400 nm to 420 nm, the T50% cut-off wavelength is in the range of 610 nm to 650 nm, wherein the optical filter has a transmission band exhibiting an average transmittance of 85% or greater in the wavelength range of 425 nm to 560 nm, and wherein the optical filter exhibits an average transmittance and maximum transmittance of 2% or less in the wavelength range of 300 nm to 390 nm and an average transmittance and maximum transmittance of 2% or less at a wavelength of 700 nm, and an average transmittance and maximum transmittance of 2% or less in the wavelength range of 700 nm to 800 nm.

17. The optical filter according to claim 16, wherein, The infrared absorption layer comprises: a first absorber having a maximum absorption wavelength in the range of 700 nm to 720 nm and a full width at half maximum (FWHM) in the range of 50 nm to 60 nm; a second absorber having a maximum absorption wavelength in the range of 730 nm to 750 nm and a full WHM in the range of 60 nm to 70 nm; and a third absorber having a maximum absorption wavelength in the range of 760 nm to 780 nm and a full WHM in the range of 90 nm to 100 nm.

18. The optical filter according to claim 16, wherein, The ultraviolet absorption layer includes a first absorber having a maximum absorption wavelength in the range of 340 nm to 350 nm and a second absorber having a maximum absorption wavelength in the range of 360 nm to 370 nm.

19. An image capturing device comprising the optical filter according to any one of claims 1 to 18.

Images