JP2021096392A - Optical element with antireflection film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element with an antireflection film and an optical system provided with an antireflection film which suppresses the generation of vibration due to a local increase or decrease of the reflectance and uniformly reduces the reflectance in an ultra-wide band from 400 nm to 1800 nm. , And a method of manufacturing an optical element. In order to achieve this object, the optical element with an antireflection film according to the present invention is an optical element with an antireflection film provided with an antireflection film at least on an optically effective region, and the antireflection film is It is composed of an inorganic base layer 21 composed of a plurality of layers and a low refractive index layer 22 provided on the surface of the inorganic base layer. When the incident angle of light is 0 degrees, the wavelength width is in the range of 400 nm to 1800 nm every 1 nm. The standard deviation σ of the reflectance measured in 1 is larger than 0.05% and smaller than 0.15%. [Selection diagram] Fig. 1

Description

The present invention relates to an optical element, an optical element and an optical system provided with an antireflection film having excellent antireflection characteristics for light rays in a wide wavelength range from the visible region to the near infrared region, and a method for manufacturing the optical element. ..

A spectrum camera capable of acquiring wavelength information in an ultra-wide band by spectroscopic technology can acquire detailed wavelength information in addition to an image as compared with an RGB camera. From the obtained wavelength information, it is possible to discriminate fine color information, and it is possible to visualize differences and states of physical properties that are difficult for the human eye to identify. Furthermore, it is also possible to identify and discriminate the composition of a substance from the wavelength information in the near infrared region. Due to these characteristics, spectrum cameras are widely used in fields such as food, agriculture, industry, and medicine for the purpose of inspection and measurement.

When an ultra-wide band from the visible region to the near infrared region is imaged using such a spectrum camera, the spectral transmittance characteristic with respect to the wavelength of the camera lens has a great influence on the acquired image and wavelength information. The main factors that determine the spectral transmittance characteristics are the optical characteristics of the lens base material constituting the camera lens, the number of lenses, and the characteristics of the antireflection film formed on the lens surface. Among them, the reflectance characteristic of the antireflection film with respect to the wavelength is one of the factors having a great influence on the wavelength information.

The antireflection film corresponding to an ultra-wide band from the visible region to the near infrared region is composed of a multilayer film in which a plurality of dielectric thin films are laminated. Therefore, in the reflectance characteristic, a phenomenon that the reflectance locally increases or decreases with respect to the wavelength and vibrates easily occurs. The vibration due to the local increase or decrease of the reflectance appears as the vibration of the spectral transmittance characteristic and affects the wavelength information. As described above, the antireflection film is required to suppress the generation of vibration due to the local increase / decrease of the reflectance in the ultra-wideband wavelength band and uniformly reduce the reflectance.

Therefore, in Patent Document 1, as an antireflection film having antireflection characteristics from the visible region to the near infrared region, a high refractive index material and a low refractive index material are alternately laminated, and the refractive index is 1. An antireflection film having a low refractive index material layer of 1 or more and 1.3 or less is disclosed.

JP-A-2017-76081

However, the reflectance characteristics of the antireflection film disclosed in Patent Document 1 have an incident angle in the wavelength range of 400 nm to 1800 nm, according to a simulation performed according to the configuration described in Example 1 of Patent Document 1. Regarding the reflectance characteristics at 0 °, the difference between the maximum value and the minimum value is about 10.5%, and the standard deviation is as large as 0.78%. When an ultra-wideband spectral image such as 400 nm to 1800 nm is continuously imaged using a camera lens on which such an antireflection film is formed, the acquired image and wavelength information may be significantly affected. is there.

The present invention presents an optical element and optical system with an antireflection film provided with an antireflection film that suppresses the occurrence of vibration due to a local increase or decrease in reflectance and uniformly reduces the reflectance in an ultra-wide band from 400 nm to 1800 nm, and optics. It is an object of the present invention to provide a method for manufacturing an element.

Therefore, in order to achieve the above-mentioned object, as a result of diligent research, the following invention was conceived.

Optical element with antireflection film: The optical element with antireflection film according to the present invention is an optical element with antireflection film provided with an antireflection film on at least the optically effective region of the surface of the base material, and the antireflection film is It is composed of an inorganic base layer composed of a plurality of layers and a low refractive index layer provided on the surface of the inorganic base layer, and when the incident angle of light is 0 degrees, in the wavelength range of 400 nm to 1800 nm, every 1 nm of wavelength width. The standard deviation σ of the measured reflectance is larger than 0.05% and smaller than 0.15%.

Method for manufacturing an optical element with an antireflection film: The method for manufacturing an optical element with an antireflection film according to the present invention is for manufacturing an optical element with an antireflection film having an antireflection film on at least an optically effective region on the surface of the base material. In the method, among the antireflection films provided on the optically effective regions on both sides of the base material, the first step of forming an inorganic base layer on the optically effective region and at least the low refractive index layer are described. It is characterized by having a second step of simultaneously forming both sides of the base material on the surface of the inorganic base layer.

The optical element with an antireflection film according to the present invention has low reflectance in the wavelength range of 400 nm to 1800 nm, and when the incident angle of light is 0 degrees, the standard deviation σ of the reflectance measured for each wavelength width of 1 nm. Is greater than 0.05% and less than 0.15%, providing uniform low reflectance characteristics over ultra-wideband wavelengths in the range of 400 nm to 1800 nm.

Further, the method for manufacturing an optical element with an antireflection film according to the present invention enables uniform film formation even with a concave lens having a small radius of curvature, suppresses the occurrence of color unevenness, and optics with an antireflection film according to the present invention. Provides stable manufacture of elements.

It is sectional drawing which shows the optical element which concerns on Example 1 to Example 9 and Comparative Example 3 to Comparative Example 4. It is sectional drawing which shows an example of the optical element which concerns on this invention. It is a schematic diagram which shows the layer structure of the antireflection film of this embodiment. It is a schematic diagram (a) which shows the structure of hollow silica which is a constituent material of a low refractive index layer, and the schematic diagram (b) which shows the structure of a low refractive index layer. It is sectional drawing which shows the optical element which concerns on Comparative Examples 1 and 2. It is sectional drawing which shows the optical element which concerns on Comparative Examples 5-6. It is a figure which shows the reflectance characteristic of the antireflection film of Example 1. It is a figure which shows the reflectance characteristic of the antireflection film of Example 2. It is a figure which shows the reflectance characteristic of the antireflection film of Example 3. It is a figure which shows the reflectance characteristic of the antireflection film of Example 4. It is a figure which shows the reflectance characteristic of the antireflection film of Example 5. It is a figure which shows the reflectance characteristic of the antireflection film of Example 6. It is a figure which shows the reflectance characteristic of the antireflection film of Example 7. It is a figure which shows the reflectance characteristic of the antireflection film of Example 8. It is a figure which shows the reflectance characteristic of the antireflection film of Example 9. It is a figure which shows the reflectance characteristic of the antireflection film of the comparative example 1. FIG. It is a figure which shows the reflectance characteristic of the antireflection film of the comparative example 2. It is a figure which shows the reflectance characteristic of the antireflection film of the comparative example 3. It is a figure which shows the reflectance characteristic of the antireflection film of the comparative example 4. It is a figure which shows the reflectance characteristic of the antireflection film of the central part and the peripheral part of Example 1. FIG. It is a figure which shows the reflectance characteristic of the antireflection film of the central part and the peripheral part of the comparative example 6. It is a figure which shows the transmittance characteristic of the optical element of Example 1. FIG. It is a figure which shows the transmittance characteristic of the optical element of the comparative example 1. FIG. It is a figure which shows the transmittance characteristic of the optical element of the comparative example 5. It is a figure which shows the transmittance characteristic of the optical element of Example 1 (assuming an optical system of 10 elements). It is a figure which shows the transmittance characteristic of the optical element of the comparative example 1 (assuming an optical system of 10 elements). It is a figure which shows the transmittance characteristic of the optical element (assuming the optical system of 10 elements) of the comparative example 5.

Hereinafter, embodiments of the optical element with an antireflection film according to the present invention will be described.

A. Embodiments in the structure of an optical element with an antireflection film In the present invention, the optical element is not particularly limited, and various elements such as a lens, a filter, and a mirror can be used. As an example of the optical element of the present embodiment, FIG. 2 shows the optical element 10 according to the present invention, which is a meniscus lens. The optical element 10 is made of a base material 11, and the base material 11 may be made of glass or plastic, and the material is not particularly limited as long as it is formed by using an optical material. .. The base material 11 includes an optically effective region 12 and an optically effective region 13 through which an effective light flux contributing to image formation is passed, and a broken line O indicates a central axis of curvature of the optical element 10. Further, a non-optical effective region 14 is provided on the outer peripheral portion of the base material 11.

Here, the optically effective region 12 and the optically effective region 13 refer to regions of the optical surface of the optical element 10 where the maximum diameter of the optical path when the above-mentioned effective luminous flux is passed intersects with the optical surface. On the other hand, the non-optically effective region 14 is a region generally referred to as an edge surface or an edge portion. The non-optical effective region 14 may be coated with a light-shielding paint (ink) that prevents internal reflection. The shapes and ranges of the optically effective regions 12 and 13 and the non-optical effective regions 14 shown in FIG. 2 are merely examples, and the optically effective regions are according to the optical characteristics of the optical element 10 and its specific shape and the like. The shape, range, etc. of the non-optical effective region are appropriately changed.

A-1. Antireflection film First, the antireflection film will be described. When a light beam enters the interface between two media with different refractive indexes, reflected light is generated. Taking advantage of this property, thin films with different refractive indexes are formed on the base material, and by utilizing the interference caused by the reflected light generated at the interface, the one having the effect of suppressing the reflected light is antireflection. It is a membrane. FIG. 3 is a schematic view showing the layer structure of the antireflection film 20 formed on the base material 11 in the optical element 10 of the present embodiment. The antireflection film 20 has a multilayer structure composed of an inorganic base layer 21 composed of a plurality of layers and a low refractive index layer 22 formed on the surface of the inorganic base layer 21. Further, as shown in FIG. 3, a functional layer 23 may be further provided on the surface of the low refractive index layer 22.

A-2. Inorganic Underlayer of Antireflection Film The inorganic underlayer 21 of the antireflection film 20 is composed of a plurality of layers having different refractive indexes at the interface thereof. The reflected light is suppressed by utilizing the interference caused by the reflected light generated at the interface between the two media having different refractive indexes. The inorganic base layer 21 in the antireflection film 20 can achieve a predetermined low reflectance characteristic under conditions such as various wavelength bands and incident angles by forming the inorganic base layer 21 with a plurality of layers. Here, the inorganic base layer 21 of the antireflection film according to the present invention is preferably 8 layers or more. When the inorganic base layer 21 is less than 8 layers, the standard deviation σ of the reflectance measured for each wavelength width of 1 nm is larger than 0.15% in the wavelength range of 400 nm to 1800 nm when the incident angle of light is 0 degrees. Therefore, the difference between the maximum value and the minimum value of the reflectance is 0.7% or more. When the inorganic base layer 21 is 8 layers or more, vibration due to a local increase or decrease in reflectance can be reduced at a wavelength of 400 nm to 1800 nm.

Further, the material of the inorganic base layer 21 of the antireflection film 20 according to the present invention is preferably either a simple substance of oxides of titanium, tantalum, zirconium, niobium, hafnium, aluminum and silicon, or a mixture thereof. ..

A-3. Low refractive index layer of antireflection film Next, the low refractive index layer 22 will be described. The low refractive index layer 22 functions as an antireflection film that suppresses the reflection of incident light due to the optical interference action. The low refractive index layer 22 is, for example, a layer in which a low refractive index material having voids in particles such as hollow silica particles and porous silica (nanoporous silica) is bound by a binder, or a refractive index within the above range. It can be a layer made of a material to have. In the present invention, it is particularly preferable that the low refractive index layer 22 is a hollow silica layer in which hollow silica particles are bound to each other by a binder (binding material). Hereinafter, assuming that the low refractive index layer 22 is a hollow silica layer, the configuration of the low refractive index layer 22 is shown in a schematic diagram showing the structure of the hollow silica particles which are the constituent materials of the low refractive index layer 22 in FIG. A) and a schematic diagram (b) showing the configuration of the low refractive index layer 22 will be specifically described.

(A) Hollow silica particles 221
First, the hollow silica particles 221 will be described. In the present invention, the hollow silica particles 221 refer to primary silica particles having a core-shell structure (balloon structure) having a hollow portion in an outer shell made of silica. Further, the primary particles refer to those in which the silica particles are not aggregated with other particles. Specifically, as schematically shown in FIG. 4A, silica particles composed of an outer shell portion 221a made of silica and a hollow portion 221b completely surrounded by the outer shell portion 221a. Point to. By adopting hollow silica particles 221 having this core-shell structure as the main material as the layer constituent material of the low refractive index layer 22, the refractive index of the low refractive index layer 22 is higher than that of silica itself (1.48). It can be reduced. Further, when compared with the porous silica layer composed of the aggregate of the porous silica having many pores in the silica particles, in the present invention, the hollow portion 221b is completely surrounded by the outer shell portion 221a. Since hollow silica is used, the strength of the silica particles themselves is high, and a film having excellent durability can be obtained. Further, since the liquid or the like does not enter the inside of the hollow silica particles 221, there is no possibility that the hollow portion 221b inside the silica is filled with the resin material or the like even when the film is formed by the wet film forming method. That is, it is possible to maintain the porosity of the material itself and prevent the refractive index from increasing.

Here, the average particle size of the hollow silica particles 221 is preferably 5 nm or more and 100 nm or less. If it is less than 5 nm, it becomes difficult to provide the void portion 223 other than the hollow portion 221b of the hollow silica particles 221 in the low refractive index layer 22. On the other hand, when the average particle size of the hollow silica particles 221 exceeds 100 nm, light scattering occurs due to an increase in haze. When light scattering occurs, the antireflection film 20 using the hollow silica particles 221 cannot satisfy the antireflection performance required for the image pickup device, which is not preferable. Further, when the average particle size of the hollow silica particles 221 exceeds 100 nm, it becomes extremely difficult to precisely control the physical film thickness of the low refractive index layer 22 in units of several nm. If the film thickness of the low refractive index layer 22 varies, the antireflection performance of the antireflection film 20 may vary, which is not preferable.

(B) Binder 222
Next, the binder 222 will be described. As shown in FIG. 4B, the low refractive index layer 22 is formed on the surface of the inorganic base layer 21, and the hollow silica particles 221 are bound to each other by the binder 222. Here, it is preferable that the outer surface of the hollow silica particles 221 is coated with the binder 222, and the hollow silica particles 221 are bound to each other by the binder 222 covering the outer surface of the hollow silica particles 221.

The binder 222 is preferably made of a resin material or a metal alkoxide. Examples of the resin material constituting the binder 222 include epoxy resin, fluororesin, silicone resin, polyethylene resin, polypropylene resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, acrylic resin, and polyamide resin. , Polyacetal resin, polycarbonate resin, modified polyphenylene ether resin, polybutylene terephthalate resin, polyethylene terephthalate resin, cyclic polyolefin resin, liquid crystal polymer and the like, or monomer compounds thereof. These resin materials are preferably compounds that are UV curable, room temperature curable, or thermosetting.

(C) Void portion 223
In the present invention, it is preferable that the low refractive index layer 22 is provided with the void portion 223 between the silica particles 221 bonded to each other as shown in FIG. 4 (b). In the low refractive index layer 22, the hollow portion 221b existing inside the hollow silica particles 221 and the void portion 223 surrounded by the binder 222 are provided between the hollow silica particles 221 to form the inside of the low refractive index layer 22. By increasing the refractive index of the low refractive index layer 22, the refractive index of the low refractive index layer 22 can be made even lower than the refractive index of the silica itself, and a layer having higher antireflection performance can be obtained. Further, as in the present embodiment, the hollow silica particles 221 are bound to each other via the binder 222 that covers the outer surface of the hollow silica particles 221 without filling the void portion 223 with a binder or the like. The adhesion between the hollow silica particles 221 can be improved, and the adhesion between the individual hollow silica particles 221 and the inorganic base layer 21 can be improved. Further, since the hollow silica particles 221 themselves are surrounded by the outer shell portion 221a made of silica, the layer has excellent scratch resistance and durability even if the outer surface of the low refractive index layer 22 is not covered with a resin or the like. can do.

(D) Volume Ratio of Hollow Silica Particles 221 and Binder 222 Here, the volume occupied by the hollow silica particles 221 and the binder 222 in the low refractive index layer 22 is preferably 30% by volume or more and 99% by volume or less. .. The volume occupied by the hollow silica particles 221 referred to here is the entire hollow silica sphere including the outer shell portion 221a of the hollow silica particles 221 and the hollow portion 221b surrounded by the outer shell portion 221a in the low refractive index layer 22. Means a product. When the volume occupied by the hollow silica particles 221 and the binder 222 in the low refractive index layer 22 is less than 30% by volume, the durability and scratch resistance of the low refractive index layer 22 are lowered, which is not preferable. On the other hand, when the volume occupied by the hollow silica particles 221 in the low refractive index layer 22 exceeds 99% by volume, the volume of the above-mentioned void portion 223 in the low refractive index layer becomes small, and the refractive index of the low refractive index layer 22 is desired. It does not reach the characteristics. From the viewpoint of further lowering the refractive index of the low refractive index layer 22, the volume occupied by the hollow silica particles 221 in the low refractive index layer 22 is more preferably 90% by volume or less.

A-4. Functional layer Next, the functional layer 23 will be described. The optical element 10 according to the present invention can be provided with a functional layer 23 on the surface of the low refractive index layer 22. FIG. 3 shows a state in which the functional layer 23 is provided on the surface of the low refractive index layer 22. Here, the functional layer 23 is a transparent ultrathin film that does not optically affect the antireflection performance of the low refractive index layer 22, and refers to a layer having various functions. For example, the surface of the low refractive index layer 22 has hardness, scratch resistance, heat resistance, weather resistance, solvent resistance, water repellency, oil repellency, antifogging property, hydrophilicity, and resistance to the surface of the low refractive index layer 22. A functional layer 23 having various functions such as improvement of antifouling property and conductivity can be provided.

The functional layer 23 preferably has a physical film thickness of 0.1 nm or more and 30 nm or less. If the physical film thickness is less than 0.1 nm, even if the functional layer 23 is provided, the function required for the functional layer 23 cannot be exhibited, which is not preferable. Further, when the physical film thickness exceeds 30 nm, the antireflection property of the low refractive index layer 22 may be optically affected, which is not preferable.

As the material constituting the functional layer 23, a transparent material having a refractive index of 1.30 or more and 2.35 or less can be used. If the material has a refractive index within the range and is transparent, an appropriate material may be appropriately selected according to the function to be imparted to the surface of the antireflection film. For example, as a transparent inorganic material having a refractive index within the range, SiO _x N _y , SiO ₂ , SiO _x , Al ₂ O ₃ , _{a mixture of ZrO 2} and TiO ₂ , a mixture of La ₂ O ₃ and TiO ₂ , SnO ₂ , ZrO ₂ , a mixture of _{La 2} O ₃ and Al ₂ O _{3 , Pr 2} O ₅ , ITO (indium tin oxide), AZO (aluminum zinc oxide) and the like. Further, DLC (diamond dry carbon), HMDSO (hexamethyldisiloxane), epoxy-based resin, acrylic-based resin (particularly PMMA resin (polymethylmethacrylate resin), fluorine-based resin and the like can be used. Further, various hard coating agents containing these materials may be used. In forming the functional layer 23, an appropriate film forming method can be appropriately adopted depending on the material and the film thickness.

When the functional layer 23 is provided on the surface of the low refractive index layer 22, the total physical film thickness of the physical film thickness of the low refractive index layer 22 and the physical film thickness of the functional layer 23 may be 100 nm or more and 180 nm or less. preferable. If it exceeds this range, the antireflection effect of the low refractive index layer 22 may be reduced, which is not preferable.

A-5. Optical element with antireflection film FIG. 1 shows a cross-sectional view of an optical element provided with the antireflection film of the present embodiment. An inorganic base layer 21 composed of a plurality of layers is formed in the optically effective region 12 and the optically effective region 13 of the base material 11. A low refractive index layer 22 is formed on the surface of the inorganic base layer and the non-optically effective region 14. Since the antireflection film of the present embodiment is provided in the optically effective region, an optical element having a low reflectance at a wavelength of 400 nm to 1800 nm and vibration due to a local increase or decrease in the reflectance can be obtained.

B. Embodiment B-1 in the characteristics of the optical element with antireflection film. Inorganic Underlayer As described above, the inorganic underlayer 21 in the antireflection film 20 is composed of a plurality of layers having different refractive indexes at the interface thereof. _{Here, when the refractive index of the material having the highest refractive index is n H} and the refractive index of the material having the lowest refractive index is n _L among the materials of the inorganic base layer 21 of the antireflection film according to the present invention, It is preferable to satisfy 0.5 ≦ n _H − n _{L ≦ 0.9.} When n _H − n _L is less than 0.5, or when n _H − n _L exceeds 0.9, low reflectance characteristics and high transmittance characteristics cannot be obtained in an ultra-wide wavelength region, and low reflectance characteristics and high transmittance characteristics cannot be obtained. The standard deviation σ of the reflectance of the optical element with the antireflection film is larger than 0.15%, the difference between the maximum value and the minimum value of the reflectance is 0.7% or more, and the reflectance is locally increased or decreased. The generation of vibration increases. By satisfying 0.5 ≤ n _H -n _L ≤ 0.9, low reflection characteristics and high transmittance characteristics can be obtained even in an ultra-wide band having a wavelength from 400 nm to 1800 nm.

B-2. Low Refractive Index Layer As described above, the low refractive index layer 22 is formed on the surface of the inorganic base layer 21. Here, the low refractive index layer 22 of the antireflection film according to the present invention preferably has a refractive index n of more than 1.10 and less than 1.25, and the film thickness of the low refractive index layer 22 is adjusted. When d, it is preferable to satisfy 125 <n × d <200. However, the unit of d is "nm". When the refractive index n is 1.10 or less, the porosity in the low refractive index layer 22 using the hollow silica particles becomes too high, and the durability of the low refractive index layer 22 decreases, which is preferable. Absent. On the other hand, when it is 1.25 or more, the antireflection performance is deteriorated. Further, when n × d is 125 or less, or n × d is 200 or more, a low reflectance characteristic with an average reflectance of 0.5% or less cannot be obtained in the wavelength range of 400 nm to 1800 nm. When the refractive index n is larger than 1.10 and smaller than 1.25, and the film thickness is d, if 125 <n × d <200, the reflectance is low at wavelengths of 400 nm to 1800 nm. Vibration due to local increase / decrease in reflectance can be reduced.

When the refractive index of the low refractive index layer 22 is small, the void ratio in the layer becomes too high in the low refractive index layer 22 made of hollow silica particles, and the durability of the low refractive index layer 22 deteriorates. Therefore, the refractive index n of the low refractive index layer 22 is more preferably larger than 1.15 and smaller than 1.25, and when the film thickness of the low refractive index layer is d, 130 ≦ n × d ≦ It is more preferable to satisfy 190.

B-3. Functional layer The functional layer 23 preferably has a refractive index of 1.30 or more and 2.35 or less and a physical film thickness of 0.1 nm or more and 30 nm or less. If the refractive index of the functional layer 23 is 1.30 or more and 2.35 or less and the physical film thickness is 0.1 nm or more and 30 nm or less, the optical effect on the antireflection effect of the low refractive index layer 22 is exerted. It can be ignored. If the refractive index exceeds the above range, the antireflection characteristics of the low refractive index layer 22 may be optically affected.

B-4. Reflectance of Optical Element with Antireflection Film The antireflection film according to the present invention formed in the optically effective region 12 and the optically effective region 13 is provided on the surface of the inorganic base layer 21 composed of a plurality of layers and the surface of the inorganic base layer 21. It is composed of a low refractive index layer 22. Here, when the incident angle of light is 0 degrees, the standard deviation σ of the reflectance of the optical element with an antireflection film measured for each wavelength width of 1 nm in the wavelength range of 400 nm to 1800 nm is greater than 0.01%. It is preferably less than .15%. When the standard deviation of the reflectance is 0.15% or more, the variation of the reflectance at each wavelength is large, which may greatly affect the acquired image and wavelength information. When the standard deviation of the reflectance is 0.01% or less, the film formation is difficult. When the standard deviation σ of the reflectance is larger than 0.01% and smaller than 0.15%, the variation distribution of the reflectance is suppressed to be small, and the reflectance can be uniformly reduced.

Considering the formation of a stable antireflection film in the film forming process, the standard deviation σ of the reflectance of the optical element with the antireflection film measured for each wavelength width of 1 nm in the wavelength range of 400 nm to 1800 nm is 0.05. More preferably than 0.15% and less than 0.15%.

Further, the antireflection film according to the present invention formed in the optically effective region 12 and the optically effective region 13 preferably has a difference between the maximum value and the minimum value of the reflectance of 0.7% or less. If the difference between the maximum and minimum reflectance values is greater than 0.7%, the reflectance will increase or decrease locally, which may significantly affect the acquired image and wavelength information. .. When the difference between the maximum value and the minimum value of the reflectance is 0.7% or less, the reflectance does not increase or decrease locally, and a uniform reflectance distribution characteristic can be obtained.

Further, the antireflection film according to the present invention formed in the optically effective region 12 and the optically effective region 13 is said to prevent reflection when the incident angle of light rays from 400 nm to 1800 nm with respect to the antireflection film is 0 degrees or more and 15 degrees or less. It is preferable that the reflectance of the optical element with a film is 1.0% or less, and the reflectance when the incident angle is 30 ° or more and 45 ° or less is 3.5% or less. When the incident angle is 0 degrees or more and 15 degrees or less, the reflectance is greater than 1.0%, and when the incident angle is 30 ° or more and 45 ° or less, the reflectance is greater than 3.5%. Is high and the transmittance is low, which may greatly affect the acquired image and wavelength information. When the incident angle is 0 degrees or more and 15 degrees or less, the reflectance is 1.0% or less, and when the incident angle is 30 ° or more and 45 ° or less, the reflectance is 3.5% or less, so that the reflection is low. It is a rate, and the transmittance is increased to improve the accuracy of the acquired image and wavelength information.

C. Embodiment in an optical system provided with an optical element with an antireflection film However, the above-described embodiment is one aspect of the present invention, and of course, it can be appropriately changed as long as the gist of the present invention is not deviated. For example, in the above embodiment, the concave meniscus lens shown in FIG. 2 has been described as an example, but the shape of the optical element 10 according to the present invention is not limited to the concave meniscus lens, and the convex meniscus lens is of course. , Biconvex lens, biconcave lens, plano-convex lens, plano-concave lens, aspherical lens, bonded lens bonded with adhesive, free curved lens, prism, etc. It's not a thing. That is, it can be suitably applied to the various optical elements 10 listed above.

In general, an optical system is a combination of the various optical elements 10 described above that generate an image of an object by utilizing the properties of light such as reflection and refraction. Here, the optical element with an antireflection film according to the present invention has a low reflectance over a wavelength of 400 nm to 1800 nm, and can reduce vibration due to a local increase or decrease in the reflectance. Therefore, it is particularly preferable that the present invention is applied not only to an optical element 10 used alone such as a single lens, but also to an optical element 10 incorporated in an optical system that acquires images and wavelength information over a wavelength of 400 nm to 1800 nm.

D. Embodiment in the method of manufacturing an optical element with an antireflection film An embodiment of a method of manufacturing an optical element with an antireflection film according to the present invention will be described. In the method for manufacturing an optical element with an antireflection film according to the present invention, among the antireflection films provided on the optically effective regions on both sides of the base material 11, the inorganic base layer 21 is placed on the optically effective region 12 and the optically effective region 13. It has a first step of forming a film and a second step of simultaneously forming the low refractive index layer 22 on the surface of at least the inorganic base layer 21 on both sides of the base material 11.

D-1. First Step The first step of forming the inorganic base layer 21 of the antireflection film according to the present invention is a vacuum vapor deposition method, a sputtering method, an ion plating method, an ion beam deposition method, or an ion beam deposition method classified as physical vapor deposition. , It is preferable to carry out by the atomic layer deposition method classified into chemical vapor deposition and the plasma CVD method.

D-2. Second Step The second step of forming the low refractive index layer 22 of the antireflection film according to the present invention is a step of simultaneously forming both sides of the base material 11 including the non-optical effective region 14, and is a dip coating method. It is preferable to do so. By forming a film by the dip coating method, the non-optical effective region 14 of the base material 11 and both sides of the optically effective region 12 and the optically effective region 13 can be formed at the same time, and both sides can be formed at the same time. , The film-formed antireflection film on both sides becomes a uniform film without defects such as color unevenness. Further, the thickness of the low refractive index layer 22 provided on one of the antireflection films formed on both sides of the base material 11 is d1 (nm), and the thickness of the low refractive index layer 22 provided on the other side is d2. When (nm), the low refractive index layer 22 can be formed within ± 1% of the deviation of d1 and d2 with respect to the average value dm (nm) of these two film thicknesses. The film formation quality of the antireflection film formed on both sides can be made uniform, and vibration due to a local increase or decrease in the refractive index can be reduced.

Here, as a second step, when a film is formed by using the spin coating method, the film thickness of a concave lens having a small radius of curvature becomes thicker toward the peripheral portion, and the reflection characteristics differ between the peripheral portion and the central portion. Color unevenness may occur. In film formation using such a spin coating method, it is difficult to sufficiently reduce the difference between the maximum value and the minimum value and the standard deviation in the reflectance characteristics in an ultra-wide band. A lens having a non-uniform film thickness in the plane is excellent in the antireflection effect in the central portion in terms of reflectance characteristics in an ultra-wideband, but the antireflection effect in the peripheral portion is inferior to that in the central portion. ..

Further, the spin coating method is a film forming method for each side. When the low refractive index layer is formed on both sides of the lens in order to improve the transmittance, the spin coating method has scratches on the low refractive index layer previously formed when the lens is attached to the spin coater or when the film is formed. There is a high possibility that damage will occur due to sticking or peeling, and dirt will occur due to the coating solution wrapping around the back surface. Therefore, it is not preferable to use the spin coating method as the second step.

Next, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples.

[Examples 1 and 2]
Table 1 shows the configurations of the antireflection films of Examples 1 and 2. As the base material 11 of Example 1, a lens made of optical glass having a refractive index of 1.448 at a wavelength of 550 nm was used. As the base material 11 of Example 2, a lens made of optical glass having a refractive index of 2.118 at a wavelength of 550 nm was used. Then, in the optically effective regions 12 and 13 of the base material 11, an inorganic base layer 21 having a multilayer structure from the first layer to the 16th layer was provided by a sputtering method using _{Nb 2} O ₅ and SiO _{2 as materials.} Subsequently, the surface of the inorganic base layer 21 is subjected to RIE treatment (reactive ion etching treatment) with oxygen to improve the wettability of the surface of the inorganic base layer 21, and then the surface of the inorganic base layer 21 has a low refractive index. The rate layer 22 was formed. In the film formation of the low refractive index layer 22, a coating prepared by stirring, dissolving, and preparing hollow silica particles having a particle size of about 60 nm and an acrylic resin as a binder component in a solvent containing propylene glycol monomethyl ether and propylene glycol as main components. Using the working solution, a film was formed simultaneously in the optically effective regions 12 and 13 by the dip coating method. Then, the coating film formed as described above was heated at 180 ° C. for 1 hour in a clean oven. As a result, a low refractive index layer 22 formed by binding hollow silica particles with an acrylic resin (binder) was obtained. The low refractive index layer 22 was adjusted so that the refractive index at a wavelength of 550 nm was 1.23 and the film thickness was 143 nm. As described above, the optical elements of the modes shown in FIG. 1 in Examples 1 and 2 were produced.

[Examples 3 to 9]
Table 2 shows the configurations of the antireflection films of Examples 3 to 9. As the base material 11 of Examples 4 to 6, a lens made of optical glass having a refractive index of 1.448 at a wavelength of 550 nm was used. As the base materials 11 of Examples 3 and 7 to 9, a lens made of optical glass having a refractive index of 2.118 at a wavelength of 550 nm was used. Then, an inorganic base layer 21 having a multilayer film structure was provided in the optically effective regions 12 and 13 of the base material 11 _{by a sputtering method using Nb 2} O ₅ and SiO _{2 as materials.} Subsequently, the surface of the inorganic base layer 21 is subjected to RIE treatment (reactive ion etching treatment) with oxygen to improve the wettability of the surface of the inorganic base layer 21, and then the surface of the inorganic base layer 21 has a low refractive index. The rate layer 22 was formed. In the film formation of the low refractive index layer 22, a coating prepared by stirring, dissolving, and preparing hollow silica particles having a particle size of about 60 nm and an acrylic resin as a binder component in a solvent containing propylene glycol monomethyl ether and propylene glycol as main components. Using the working solution, a film was formed simultaneously in the optically effective regions 12 and 13 by the dip coating method. Then, the coating film formed as described above was heated in a clean oven at 180 ° C. for 1 hour to prepare the film. As a result, a low refractive index layer 22 formed by binding hollow silica particles with an acrylic resin (binder) was obtained. As described above, the optical elements having the form shown in FIG. 1 in Examples 3 to 9 were produced.

[Comparative Examples 1 and 2]
Table 3 shows the configurations of the antireflection films of Comparative Example 1 and Comparative Example 2. As the base material 11 of Comparative Example 1, a lens made of optical glass having a refractive index of 1.448 at the same wavelength of 550 nm as in Example 1 was used. As the base material 11 of Comparative Example 2, a lens made of optical glass having a refractive index of 2.118 at the same wavelength of 550 nm as in Example 2 was used. Then, an inorganic base layer 21 having a multilayer film structure was provided in the optically effective regions 12 and 13 of the base material 11 _{by a sputtering method using Nb 2} O ₅ and SiO _{2 as materials.} Next, in the low refractive index layers 22 of Comparative Examples 1 and ₂ , MgF 2 was formed into the optically effective regions 12 and 13 by a vacuum vapor deposition method. The low refractive index layer 22 had a refractive index of 1.38 at a wavelength of 550 nm. As described above, the optical elements having the form shown in FIG. 5 in Comparative Example 1 and Comparative Example 2 were produced.

[Comparative Examples 3 and 4]
Table 4 shows the configurations of the antireflection films of Examples 3 and 4. As the base material 11 of Comparative Example 3, a lens made of optical glass having the same shape as that of Example 1 and having a refractive index of 1.448 at a wavelength of 550 nm was used. As the base material 11 of Comparative Example 4, a lens made of optical glass having the same shape as that of Example 2 and having a refractive index of 2.118 at a wavelength of 550 nm was used. The inorganic base layer 21 was formed into optically effective regions 12 and 13 by a vacuum vapor deposition method using _{AL 2} O _{3 and OH-5 (a mixture of ZrO 2} and TiO ₂ ) manufactured by Canon Optron Co., Ltd. as materials. The low refractive index layer 22 is a coating liquid prepared by stirring, dissolving, and preparing hollow silica particles having a particle size of about 60 nm and an acrylic resin as a binder component in a solvent containing propylene glycol monomethyl ether and propylene glycol as main components. Was formed into the optically effective regions 12 and 13 at the same time by the dip coating method. Then, the coating film formed as described above was heated in a clean oven at 180 ° C. for 1 hour to prepare the film. As a result, a low refractive index layer 22 formed by binding hollow silica particles with an acrylic resin (binder) was obtained. The low refractive index layer 22 was adjusted so that the refractive index at a wavelength of 550 nm was 1.23 and the film thickness was 143 nm. As described above, the optical elements having the form shown in FIG. 1 in Comparative Example 3 and Comparative Example 4 were produced.

[Comparative Example 5]
As the base material 11 of Comparative Example 5, a lens made of optical glass having a refractive index of 1.448 at the same wavelength of 550 nm as in Example 1 was used. First, an antireflection film of the inorganic base layer 21 and the low refractive index phase 22 described in Comparative Example 1 was formed on the optically effective region 12. Subsequently, the inorganic base layer 21 described in Example 1 was formed into a film on the optically effective region 13 by a sputtering method, and then masking treatment was performed on the optically effective region 12. Next, the low refractive index layer 22 was formed into the optically effective region 13 by the dip coating method in the same manner as in Example 1. Then, the coating film formed as described above was heated at 180 ° C. for 1 hour in a clean oven. After firing in a clean oven, the masking applied to the optically effective region 12 was peeled off. As described above, the optical element having the form shown in FIG. 6 in Comparative Example 5 was produced.

[Comparative Example 6]
As the base material 11 of Comparative Example 6, a lens made of optical glass having a refractive index of 1.448 at the same wavelength of 550 nm as in Example 1 was used. First, an antireflection film of the inorganic base layer 21 and the low refractive index phase 22 described in Comparative Example 1 was formed on the optically effective region 12. Subsequently, the inorganic base layer 21 described in Example 1 was formed on the optically effective region 13 by a sputtering method. Next, using the coating liquid for the low refractive index layer adjusted under the conditions described in Example 1, the low refractive index layer 22 was applied to the optically effective region 13 by the spin coating method using a commercially available spin coater. The film was formed so that the thickness was 143 nm. Then, the coating film formed as described above was heated at 180 ° C. for 1 hour in a clean oven. As described above, the optical element having the form shown in FIG. 5 in Comparative Example 6 was produced.

[Evaluation]
1. 1. Antireflection characteristics The antireflection characteristics of the antireflection films obtained in Examples 1 to 9 and the antireflection films of Comparative Examples 1 to 4 were evaluated. For the reflectance, the angle of incidence of the light beam on the antireflection film was set to 0 degrees, 15 degrees, 30 degrees, and 45 degrees using a reflectance measuring device, and the reflectance was measured in the wavelength range of 400 nm to 1800 nm at each incident angle. .. The results of Examples 1 and 2 are shown in FIGS. 7 to 8, the results of Examples 3 to 9 are shown in FIGS. 9 to 15, the results of Comparative Examples 1 and 2 are shown in FIGS. 16 to 17, and the results of Comparative Examples 3 to 4 are shown in FIGS. The results of the above are shown in FIGS. 18 to 19, respectively. In each figure, the reflectance when the incident angle is 0 degrees is a solid line, the reflectance when the incident angle is 15 degrees is a dotted line, the reflectance when the incident angle is 30 degrees is a broken line, and the reflectance is 45 degrees. The reflectance of each is indicated by a single point chain line. The evaluation results of each Example and Comparative Example will be described below.

1-1. Reflectance evaluation results in Examples 1 and 2 From FIGS. 7 and 8, the reflectances in Examples 1 and 2 are in the wavelength range of 400 nm to 1800 nm when the incident angles are 0 degrees and 15 degrees. It was found to be 0.6% or less and 3.0% or less when the incident angles were 30 degrees and 45 degrees. From this result, in the optical elements with antireflection films of Examples 1 and 2, the antireflection film 20 according to the present invention is applied to at least both sides of the optical effective area (optical effective area 12 and optical effective area 13). It was clarified that high antireflection performance was obtained by preparing for.

1-2. Reflectance evaluation results in Examples 3 to 9 From FIGS. 9 to 15, the reflectance in Examples 3 to 9 is 1.0% in the wavelength range of 400 nm to 1800 nm when the incident angle is 0 degrees and 15 degrees. Below, it was found to be 3.5% or less when the incident angles were 30 degrees and 45 degrees. From this result, in the optical element with the antireflection film of Examples 3 to 9, the antireflection film 20 according to the present invention is provided on at least both sides of the optical effective region (optical effective region 12 and optical effective region 13) of the optical element. As a result, it became clear that high antireflection performance was obtained.

Further, in Example 3, the inorganic base layer 21 has an eight-layer multilayer film structure. Even in this case, since the above-mentioned reflectance result is obtained, if the inorganic base layer of the antireflection film according to the present application is 8 layers or more, high antireflection performance can be obtained in the wavelength range of 400 nm to 1800 nm. It became clear.

1-3. Reflectance evaluation results in Comparative Example 1 and Comparative Example From FIGS. 16 and 17, the reflectance in Comparative Example 1 and Comparative Example 2 is in the wavelength range of 400 nm to 1800 nm when the incident angles are 0 degrees and 15 degrees. It was found to be 2.5% or less and 5.0% or less when the incident angles were 30 degrees and 45 degrees. From this result, it was clarified that the optical elements with antireflection films of Comparative Example 1 and Comparative Example 2 were inferior in antireflection performance as compared with Examples 1 to 9.

Here, the antireflection film produced in Comparative Examples 1 and 2 and the antireflection film produced in Examples 1 and 2 are made of the same material as the inorganic base layer 21, but have a low refractive index. The refractive index of the rate layer 22 is different. The low refractive index layer 22 in Comparative Example 1 and Comparative Example 2 is formed _{by forming a film of MgF 2} (magnesium fluoride) having a refractive index of 1.38 by a vacuum vapor deposition method. Therefore, it has been found that the low refractive index layer 22 in which MgF ₂ is deposited by the vacuum vapor deposition method cannot obtain low reflection of light rays having a wide incident angle in the wavelength range of 400 nm to 1800 nm.

Further, from FIGS. 10 to 15 which are the evaluation results of Examples 4 to 9, it is clear that these optical elements with an antireflection film have high antireflection performance. The refractive index of the low refractive index layer 22 of Examples 4 and 7 was 1.15, and the refractive index of the low refractive index layer 22 of Examples 6 and 9 was 1.25. Therefore, based on the evaluation results of Examples 1 and 2, Examples 4 to 9 and Comparative Example 1 and Comparative Example 2 described above, the refractive index of the low refractive index layer 22 of the antireflection film according to the present application. Is more than 1.10 and less than 1.25, and when the film thickness of the low refractive index layer is d, it is preferable that 125 <n × d <200 ”is satisfied, and“ 1. It has become clear that it is more preferable that it is larger than 15 and smaller than 1.25, and that 130 ≦ n × d ≦ 190 ”is satisfied.

1-4. Reflectance evaluation results in Comparative Examples 3 and 4 From FIGS. 18 and 19, the reflectances in Comparative Examples 3 and 4 are in the wavelength range of 400 nm to 1800 nm when the incident angles are 0 degrees and 15 degrees. It was found to be 3.5% or less and 6.5% or less when the incident angles were 30 degrees and 45 degrees. From this result, it was clarified that the optical elements with antireflection films of Comparative Examples 3 and 4 were inferior in antireflection performance as compared with Examples 1 to 9.

Here, in the antireflection film prepared in Comparative Examples 3 and 4, and the antireflection film prepared in Examples 1 and 2, the low refractive index layer 22 has the same configuration (material, refractive index and physical film). (Thickness), but the materials constituting the inorganic base layer 21 are different. In the materials constituting the inorganic base layer 21 in Comparative Example 3 and Comparative Example 4, the difference between _{the refractive index n H of the material having the highest refractive index and n L} of the refractive index of the material having the lowest refractive index was 0.47. .. That is, in the material constituting the inorganic base layer 21, when _{the difference between the refractive index n H} of the material having the highest refractive index and the refractive index n _L of the material having the lowest refractive index is 0.47 or less, the wavelength range is 400 nm to 1800 nm. Therefore, it was found that it is not possible to obtain low-refractive index characteristics for light rays with a wide incident angle. On the other hand, the difference between the refractive index of the material having the highest refractive index and the refractive index of the material having the lowest refractive index in the inorganic base layer in Examples 1 and 2 was 0.84.

Therefore, from the above results, the difference between _{the refractive index n H} of the material having the highest refractive index and the refractive index n _L of the material having the lowest refractive index of the inorganic base layer 21 of the antireflection film according to the present application is 0.5. It became clear that ≦ n _H − n _L ≦ 0.9 is preferable.

2. Comparison of antireflection characteristics of antireflection film composed of low refractive index layers by different film formation methods In the antireflection film in the optically effective region 13 of Example 1 and Comparative Example 6, the inorganic base layer 21 has the same configuration (material, refractive index). And the physical film thickness), the low refractive index layer 22 is formed by forming the same coating liquid by different methods. Specifically, Example 1 uses the dip coating method, and Comparative Example 6 uses the spin coating method as the film forming method. Here, the reflectance characteristics of the antireflection film formed on the optically effective region 13 of Example 1 and Comparative Example 6 were evaluated.

The reflectance measurement points in the optically effective region 13 were set at two points, the central position of the optical element 10 and the semi-open angle position. Here, the open angle is an angle formed by a straight line connecting the center of curvature of the optically effective region to the effective diameter end of the optically effective region, and the semi-open angle means an angle halved of the open angle. The opening angle of the optical element 10 which is an example of the present embodiment is 120 degrees, and the half opening angle is 60 degrees. The angle of incidence of the light beam on the antireflection film at the measurement point was set to 0 degrees, and the reflectance was measured using a reflectance measuring device in the wavelength range of 400 nm to 1800 nm. The results of the optical element manufactured in Example 1 are shown in FIG. 20, and the results of the optical element manufactured in Comparative Example 6 are shown in FIG. 21. Further, in each figure, the reflectance at the center position of the optical element 10 is shown by a solid line, and the reflectance at the half-open angle position of the optical element 10 is shown by a dotted line. The evaluation results will be described below.

From FIG. 20, it was found that the reflectance at the center position and the half-open angle position of the optical element 10 produced in Example 1 was 0.7% or less in the wavelength range of 400 nm to 1800 nm. From this result, it was clarified that the low refractive index layer 22 was uniformly formed in the optically effective region 13 of the antireflection film formed on the optically effective region 13 of Example 1 by the dip coating method. It was.

Next, from FIG. 21, the reflectance at the center position of the optical element 10 produced in Comparative Example 6 was 0.7% or less in the wavelength range of 400 nm to 1800 nm. However, the reflectance at the half-open angle position was 3% or more at 400 nm and 1% or more at 700 nm to 1800 nm, and it was found that the antireflection performance was inferior. That is, it was clarified that the film thickness of the low refractive index layer 22 formed on the optically effective region 13 of Comparative Example 6 by the spin coating method varies. From this result, it was clarified that the dip coating method is preferable and the spin coating method is not preferable in the coating liquid film forming method described in Example 1 in the low refractive index layer 22 of the antireflection film.

3. 3. Vibration characteristics due to local increase / decrease in reflectance The wavelength characteristics of the reflectance R of the antireflection film are uniform with small and uniform vibration due to local increase / decrease in reflectance in the wavelength range of 400 nm to 1800 nm, and the average value of reflectance. It is desirable that the standard deviation is low and the standard deviation is small. Therefore, based on FIGS. 7 to 19 of the evaluation results in Examples 1 to 9 and Comparative Examples 1 to 4, the average reflectance Rm, standard deviation σ, and maximum value Rmax of the reflectance R in the wavelength range of 400 nm to 1800 nm. , The difference between the minimum value Rmin, the maximum value Rmax and the minimum value Rmin was obtained and evaluated. The reflectance R was measured from 400 nm to 1800 nm for each wavelength width of 1 nm (N = 1401).

Table 5 shows the wavelength characteristics of the reflectance R in Examples 1 to 9 and Comparative Examples 1 to 4 with an average reflectance Rm of 400 nm to 1800 nm, a standard deviation σ, a maximum value Rmax, a minimum value Rmin, and a maximum value Rmax. The result of finding the difference of the value Rmin and the result of evaluating these five parameters are shown. The evaluation criteria in this example are that the average reflectance Rm is 0.5% or less, the standard deviation σ is 0.15% or less, and the difference between the maximum value Rmax and the minimum value Rmin is 0.7% or less. It was considered preferable (indicated by "○" in Table 5).

As shown in Table 5, the antireflection films of Examples 1 to 9 have high antireflection performance with an average reflectance of 0.5% or less in the wavelength range of 400 nm to 1800 nm, and the standard deviation of the reflectance is Since it was 0.15% or less and the difference between the maximum value and the minimum value of the reflectance was 0.7% or less, it was found that the evaluation criteria were satisfied. On the other hand, in Comparative Examples 1 to 4, the average reflectance is 1.0% or more, the standard deviation of the reflectance is 0.2% or more, and the difference between the maximum value and the minimum value of the reflectance is 1%. From the above, it was found that the evaluation criteria were not satisfied.

Therefore, from the above results, the optical element with an antireflection film according to the present application has high antireflection performance in the wavelength range of 400 nm to 1800 nm, and vibration due to a local increase or decrease in reflectance is also suppressed. It became clear.

4. Transmittance Characteristics The optical system of various optical devices is generally composed of a plurality of optical elements. As the number of optical elements in the optical system increases, the light reflection loss also increases. Therefore, in an optical system composed of a plurality of optical elements, it is necessary to improve the amount of transmitted light of the optical system in order to acquire a minute difference in image and wavelength information in an ultra-wide band such as 400 nm to 1800 nm. is there. Therefore, the transmittances of the optical elements produced in Example 1 and the optical elements produced in Comparative Examples 1 and 5 were evaluated.

A spectrophotometer U4100 manufactured by Hitachi High-Technologies Corporation was used for measuring the transmittance. The transmittance was measured from 400 nm to 1800 nm for each wavelength width of 1 nm (N = 1401), with the angle of incidence of the light beam on the optical element as 0 degree.

4-1. Transmittance Characteristics of Optical Elements Table 6 shows the average transmittance Tm and standard deviation σ of 400 nm to 1800 nm for the transmittance T of the optical element manufactured in Example 1 and the optical elements manufactured in Comparative Example 1 and Comparative Example 5. , The result of obtaining the difference between the maximum value Tmax, the minimum value Tmin, the maximum value Tmax and the minimum value Tmin, and the result of evaluating these five parameters are shown. As the evaluation criteria in this example, it is preferable that the average transmittance Tm is 99.0% or more, the standard deviation σ is 0.30% or less, and the difference between the maximum value Tmax and the minimum value Tmin is 1.5% or less. (Indicated by "○" in Table 6).

The measurement result of the transmittance of the optical element produced in Example 1 is shown in FIG. From Table 6 and FIG. 22, the optical element of Example 1 has an average transmittance of 99.0% or more in the wavelength range of 400 nm to 1800 nm, a standard deviation of the transmittance of 0.3% or less, and a maximum value of the transmittance. Since the difference between the minimum values was 1.5% or less, it was found that the evaluation criteria were satisfied. Therefore, it has been clarified that the optical element with an antireflection film according to the present invention has high transmittance characteristics.

Next, the measurement result of the transmittance of the optical element produced in Comparative Example 1 is shown in FIG. From Table 6 and FIG. 23, the optical element of Comparative Example 1 has an average transmittance of 99.0% or less in the wavelength range of 400 nm to 1800 nm, a standard deviation of the transmittance of 0.3% or more, and the maximum transmittance. Since the difference between the value and the minimum value was 1.5% or more, it was found that the evaluation criteria were not satisfied. _{Therefore, it was clarified that the optical element with the antireflection film in which MgF 2} was formed as the low refractive index layer 22 in the optically effective regions 12 and 13 by the vacuum vapor deposition method was inferior in transmittance.

Next, the measurement result of the transmittance of the optical element produced in Comparative Example 5 is shown in FIG. From Table 6 and FIG. 24, the optical element of Comparative Example 5 has an average transmittance of 99.0% or less in the wavelength range of 400 nm to 1800 nm, a standard deviation of the transmittance of 0.3% or more, and the maximum transmittance. Since the difference between the value and the minimum value was 1.5% or more, it was found that the evaluation criteria were not satisfied. Therefore, the optical element with the antireflection film having the antireflection film of Comparative Example 1 formed on the optically effective region 12 and the antireflection film of Example 1 formed on the optically effective region 13 has inferior transmittance. It became clear that there was.

Based on the above, the optical element with an antireflection film according to the present invention includes the antireflection film 20 according to the present invention on at least both sides of the optical effective region (optical effective region 12 and optical effective region 13). It was clarified that it has high transmittance characteristics.

4-2. Transmittance Characteristics in an Optical System Consisting of a plurality of Optical Elements Next, the transmittance when the optical elements manufactured in Example 1 and the optical elements manufactured in Comparative Examples 1 and 5 are used in an optical system having 10 elements. The rate was calculated by simulation using the transmittance result measured by the spectrophotometer U4100.

Table 7 shows the average transmittance of 400 to 1800 nm for the transmittance T when the optical element manufactured in Example 1 and the optical elements manufactured in Comparative Example 1 and Comparative Example 5 are used in an optical system having a 10-element configuration. The result of finding the difference between Tm, the standard deviation σ, the maximum value Tmax, the minimum value Tmin, the maximum value Tmax and the minimum value Tmin, and the result of evaluating these five parameters are shown. As the evaluation criteria in this example, it is preferable that the average transmittance Tm is 90.0% or more, the standard deviation σ is 3.00% or less, and the difference between the maximum value Tmax and the minimum value Tmin is 10.0% or less. (Indicated by "○" in Table 7).

FIG. 25 shows the transmittance simulation results in the case of an optical system having 10 optical elements manufactured in Example 1. From Table 7 and FIG. 25, even if the number of optical elements of Example 1 is used in a configuration of 10, the average transmittance is 90.0% or more in the wavelength range of 400 to 1800 nm, and the standard deviation of the transmittance is 3. Since it was 0% or less and the difference between the maximum value and the minimum value of the transmittance was 10.0% or less, it was found that the evaluation criteria were satisfied. Therefore, it has been clarified that the optical system having 10 optical elements with an antireflection film according to the present invention has high transmittance characteristics.

FIG. 26 shows the transmittance simulation result in the case of an optical system having 10 optical elements manufactured in Comparative Example 1. From Table 7 and FIG. 26, when the number of optical elements of Comparative Example 1 is used in a configuration of 10, the average transmittance is 85.0% or less in the wavelength range of 400 to 1800 nm, and the standard deviation of the transmittance is 3.0%. As described above, the difference between the maximum value and the minimum value of the transmittance was 10.0% or more, and it was found that the evaluation criteria were not satisfied. Therefore, it is clear that the optical system having 10 optical elements with antireflection films formed by forming _{MgF 2} as the low refractive index layer 22 in the optically effective regions 12 and 13 by the vacuum vapor deposition method is inferior in transmittance. It became.

FIG. 27 shows the transmittance simulation result when the optical element manufactured in Comparative Example 5 is used in an optical system having a 10-element configuration. From Table 7 and FIG. 27, when the number of optical elements of Comparative Example 5 is used in a configuration of 10, the average transmittance is 90.0% or less in the wavelength range of 400 to 1800 nm, and the standard deviation of the transmittance is 3.0%. As described above, the difference between the maximum value and the minimum value of the transmittance was 10.0% or more, and it was found that the evaluation criteria were not satisfied. Therefore, the optical effective region 12 is formed with the antireflection film of Comparative Example 1, and the optically effective region 13 is formed with 10 optical elements with an antireflection film formed with the antireflection film of Example 1. The system was found to be inferior in permeability.

From the above, in the optical element with an antireflection film according to the present invention, the antireflection film 20 according to the present invention is provided on at least both sides of the optical effective region (optical effective region 12 and optical effective region 13) of the optical element. As a result, it was clarified that the optical system having 10 optical elements has high transmittance characteristics. Further, it has been clarified that the optical element with an antireflection film according to the present invention has a high transmittance in the wavelength range of 400 nm to 1800 nm and also suppresses vibration due to a local increase or decrease in the transmittance. ..

The optical element with an antireflection film according to the present invention has an effect of suppressing the generation of vibration due to a local increase or decrease in reflectance in an ultra-wide spectrum of 400 nm to 1800 nm and uniformly reducing the reflectance, and thus has an ultra-wide band. It can be suitably used for an optical device such as a spectrum camera that captures a wavelength band.

10 Optical element (lens)
11 Base material 12 Optical effective area 13 Optical effective area 14 Non-optical effective area 20 Antireflection film 21 Inorganic base layer 22 Low refractive index layer 23 Functional layer 30 Magnesium fluoride (MgF2) layer 221 Hollow silica particles 221a Outer shell 221b Hollow Part 222 Binder 223 Void part

Claims (15)

An optical element with an antireflection film having an antireflection film on at least an optically effective region on the surface of the base material.
The antireflection film is composed of an inorganic base layer composed of a plurality of layers and a low refractive index layer provided on the surface of the inorganic base layer.
When the incident angle of light is 0 degrees, the standard deviation σ of the reflectance measured for each wavelength width of 1 nm is larger than 0.05% and smaller than 0.15% in the wavelength range of 400 nm to 1800 nm. Optical element with antireflection film. The optical element according to claim 1, wherein the inorganic base layer is composed of eight or more layers. The first or second aspect, wherein the material of the inorganic base layer is either a simple substance of oxides of titanium, tantalum, zirconium, niobium, hafnium, aluminum and silicon, or a mixture thereof. Optical element with anti-reflection film. In the low refractive index layer, hollow silica particles having a balloon structure including an outer shell portion made of silica and a hollow portion surrounded by the outer shell portion are bound by a binder, and the hollow silica particles are described. The optical element with an antireflection film according to any one of claims 1 to 3, wherein the layer has voids other than the hollow portion, and the average particle size of the hollow silica particles is 5 nm or more and 100 nm or less. .. The optical element with an antireflection film according to claim 4, wherein the binder is made of a resin material or a metal alkoxide. The optical element with an antireflection film according to any one of claims 1 to 5, wherein the antireflection film is provided with a functional layer on the surface of the low refractive index layer. When the refractive index of the material having the highest refractive index is n _H and the refractive index of the material having the lowest refractive index is n _L among the materials forming the layer constituting the inorganic base layer, the following equation 1 is used. The optical element with an antireflection film according to any one of claims 1 to 6.
0.5 ≤ n _H -n _L ≤ 0.9 ... (1) The low refractive index layer has a refractive index n of greater than 1.10 and less than 1.25.
The optical element with an antireflection film according to any one of claims 1 to 7, which satisfies the following formula 2 when the film thickness is d.
125 <n x d <200 ... (2)
However, the unit of d is "nm". The optical element with an antireflection film according to any one of claims 1 to 8, wherein the difference between the maximum value and the minimum value of the reflectance is 0.7% or less in the wavelength range of 400 nm to 1800 nm. The invention according to any one of claims 1 to 9, wherein when the angle of incidence of light rays at a wavelength of 400 nm to 1800 nm with respect to the antireflection film is 0 degrees or more and 15 degrees or less, the reflectance is 1.0% or less. Optical element with antireflection film. The invention according to any one of claims 1 to 10, wherein when the angle of incidence of light rays at a wavelength of 400 nm to 1800 nm with respect to the antireflection film is 30 ° or more and 45 ° or less, the reflectance is 3.5% or less. Optical element with antireflection film. An optical system comprising the optical element with an antireflection film according to any one of claims 1 to 11. A method for manufacturing an optical element with an antireflection film, which comprises an antireflection film on at least an optically effective region on the surface of the base material.
Of the antireflection films provided on the optically effective regions on both sides of the substrate,
The first step of forming an inorganic base layer on the optically effective region, and
A second step of simultaneously forming a low refractive index layer on the surface of at least the inorganic base layer on both sides of the base material,
A method for manufacturing an optical element with an antireflection film. The method for manufacturing an optical element with an antireflection film according to claim 13, wherein the first step is a vacuum deposition method, a sputtering method, or an atomic layer deposition method. The second step is the method for manufacturing an optical element with an antireflection film according to claim 13 or 14, which uses a dip coating method.

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