JP2008233403A - Antireflection film and optical component having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer antireflection film which is capable of obtaining a reflectivity of ≤1% at a wavelength of 400 to 800 nm by a multilayer having the same optical film thickness and layer constitution for substrates different by refractive indexes, and an optical component having the same. <P>SOLUTION: The antireflection film has first to seventh layers laminated on a substrate in order from the substrate side, and the first, third, and fifth layers are high-refractive index layers having refractive indexes of 2 to 2.45 at a wavelength of 400 to 800 nm, and the second, fourth, and sixth layers are low-refractive index layers having refractive indexes of 1.35 to 1.7 at a wavelength of 400 to 800 nm, and the seventh layer is an extralow-refractive index layer having a refractive index of 1.05 to 1.3 at a wavelength of 400 to 800 nm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an antireflection film and an optical component having the antireflection film, and more specifically, a refractive index of a lens, a prism, a diffraction element, or the like mounted on an optical device such as a television camera, a video camera, a digital camera, an in-vehicle camera, a microscope, or a telescope. The present invention relates to an antireflection film capable of obtaining a high antireflection effect by a multilayer film having the same optical film thickness even on different substrates, and an optical component having the same.

  A high-performance zoom lens widely used in photographic cameras, broadcast cameras, and the like has a lens barrel configuration of a lens group composed of a large number (10 to 40 lenses). A dielectric film having a large or small refractive index different from the refractive index of the substrate is combined on the surface of the optical component such as a lens, and the optical film thickness of each dielectric film is set to 1 / 2λ or 1 / Antireflection treatment by a multilayer film using interference effect is performed at 4λ. In recent years, astronomical telescopes, security cameras, vehicle-mounted cameras, and the like that use the visible to near-infrared wavelength range have also been required to significantly improve ghosts and flares by reducing the reflectance in that wavelength range.

A general antireflection film has a structure of about 1 to 3 layers, and its reflectance is about 0.5%. When such an antireflection film is applied to a lens barrel group consisting of 20 lenses, the number of lens surfaces is 40, so the transmittance is calculated as 0.995 ⁴⁰ ≈ 82%, and the reflection loss is about 18%. Will occur. In addition, flare and ghost are generated due to multiple reflection within or between lenses, and optical characteristics such as contrast are significantly deteriorated. In addition, in an optical pickup or the like, a serious problem such as laser light interference occurs.

  In order to solve such problems, an antireflection treatment using an antireflection film composed of more layers is effective. For example, Japanese Patent Application Laid-Open No. 10-20102 (Patent Document 1) discloses an antireflection treatment with a seven-layer structure. A membrane is disclosed. It is described that this antireflection film is improved to reflect about 0.3% in the visible wavelength band. Such an antireflection film is optimized so that the reflectance is minimized by adjusting the optical film thickness of each layer in accordance with the refractive index of the substrate. That is, when an antireflection film is formed on substrates having different refractive indexes, in order to obtain optimum antireflection properties, it is necessary to form each layer with a different film thickness depending on the refractive index of the substrate. When each layer is formed with the same optical film thickness on substrates having different refractive indexes, a good antireflection effect cannot be obtained. Therefore, the multilayer film must be formed under different conditions depending on the type of substrate, and the production efficiency is very poor.

In order to obtain an antireflection film that does not depend on the refractive index of the substrate, Non-Patent Document 1 reports an antireflection film in which a multilayer film of 8 to 23 layers is formed on a substrate having a refractive index of 1.48 to 1.75. It describes that a reflectance of 1% or less can be obtained at 400 to 800 nm. However, when the multilayer film described in Non-Patent Document 1 is formed on a substrate having a refractive index of 1.95, the maximum reflectance at a wavelength of 400 to 800 nm greatly exceeds 1%.
Japanese Patent Laid-Open No. 10-20102 JA Dobrowolski and Brian T. Sullivan, "Universal antireflection coatings for substrates for the visible spectral region", Applied Optics 35, 4993-4997 (1996)

  Accordingly, an object of the present invention is to provide a multilayer antireflection film having the same optical film thickness and layer structure and capable of obtaining a reflectance of 1% or less at a wavelength of 400 to 800 nm even for substrates having different refractive indexes. It is providing the optical component which has.

  As a result of diligent research in view of the above problems, the present inventors have found that an antireflection effect having less dependency on the refractive index of the substrate can be obtained by the antireflection film having the following seven-layer structure, and arrived at the present invention. did.

  That is, the antireflection film of the present invention is an antireflection film obtained by laminating a first layer to a seventh layer in order from the substrate side on a substrate, and the first layer, The third layer and the fifth layer are high refractive index layers having a refractive index of 2 to 2.45, and the second layer, the fourth layer, and the sixth layer are low refractive index layers having a refractive index of 1.35 to 1.7. The seventh layer is an ultra-low refractive index film having a refractive index of 1.05 to 1.3.

  The optical thickness of the first layer is preferably 7 to 39 nm, the optical thickness of the second layer is preferably 35 to 65 nm, and the optical thickness of the third layer is 22 to 75. The optical thickness of the fourth layer is preferably 47 to 102 nm, the optical thickness of the fifth layer is preferably 1 to 59 nm, and the sixth layer has an optical thickness of 47 to 102 nm. The optical film thickness is preferably 50 to 165 nm, and the optical film thickness of the seventh layer is preferably 121 to 141 nm.

The high refractive index layer is at least one selected from the group consisting of Ta ₂ O ₅ , TiO ₂ , Nb ₂ O ₅ , ZrO ₂ , HfO ₂ , CeO ₂ , SnO ₂ , In ₂ O ₃ , ZnO and ZnS. Preferably, it is a layer made of a material, and the low refractive index layer is preferably a layer made of at least one material selected from the group consisting of MgF ₂ , SiO ₂ , Al ₂ O ₃ and a fluororesin, The ultra low refractive index layer is preferably a porous layer made of at least one material selected from the group consisting of MgF ₂ , SiO ₂ , Al ₂ O ₃ and a fluororesin.

  The antireflection film of the present invention preferably has an antireflection effect having a reflectance of 1% or less over a wavelength range of 400 to 800 nm.

  The optical component of the present invention has the antireflection film. The optical component of the present invention is characterized in that the substrate has a refractive index of 1.45 to 1.95 at a wavelength of 400 to 800 nm.

  Even when a substrate having a different refractive index (especially a refractive index of 1.45 to 1.95) is used by the antireflection film comprising seven layers of the present invention, the antireflection of a reflectance of 1% or less in the wavelength region of 400 to 800 nm. An optical component having an effect can be obtained. Since the antireflection film of the present invention has almost no difference in antireflection performance due to the refractive index of the substrate, it is possible to apply an antireflection film having the same layer structure to different types of optical components. For this reason, it becomes possible to manufacture various optical materials at a time without switching the film forming conditions due to the difference in the refractive index of the substrate, thereby improving the production efficiency. Further, it can be suitably used for an optical element in which materials having significantly different refractive indexes such as a photonic crystal material are combined, and a high antireflection effect can be obtained.

[1] Antireflection film
(1) Configuration As shown in FIG. 1, the antireflection film of the present invention is formed by laminating thin films from the first layer to the seventh layer having a predetermined refractive index on the surface of the substrate 3. That is, the antireflection film of the present invention is a high refractive index layer having a refractive index of 2 to 2.45 at a wavelength of 400 to 800 nm, the first layer 101, the third layer 103, the fifth layer 105, and a refractive index of 1.35. The second layer 102, the fourth layer 104, and the sixth layer 106, which are low refractive index layers of .about.1.7, and the seventh layer 107, which is an ultra low refractive index layer of refractive indexes 1.05 to 1.3, are formed on the substrate 3. Have on. The refractive index of the high refractive index layer is preferably 2.05 to 2.40, more preferably 2.10 to 2.40, and the refractive index of the low refractive index layer is preferably 1.36 to 1.67, more preferably 1.37 to 1.48, and is extremely low. The refractive index of the refractive index layer is preferably 1.06 to 1.25, more preferably 1.07 to 1.23. The reflectance in the wavelength region of 400 to 800 nm is preferably 1% or less.

  In order to obtain a good antireflection effect at a wavelength of 400 to 800 nm, the optical thickness of the first layer is 7 to 39 nm, the optical thickness of the second layer is 35 to 65 nm, The optical thickness of the third layer is 22 to 75 nm, the optical thickness of the fourth layer is 47 to 102 nm, the optical thickness of the fifth layer is 1 to 59 nm, Preferably, the optical thickness of the layer is 50 to 165 nm, the optical thickness of the seventh layer is 121 to 141 nm, the optical thickness of the first layer is 10 to 36 nm, The optical thickness of the second layer is 38 to 62 nm, the optical thickness of the third layer is 25 to 72 nm, the optical thickness of the fourth layer is 50 to 99 nm, and the fifth layer More preferably, the optical thickness of the sixth layer is 4 to 56 nm, the optical thickness of the sixth layer is 53 to 162 nm, and the optical thickness of the seventh layer is 124 to 138 nm. The optical film thickness is a product (n × d) of the refractive index (n) and the physical film thickness (d) of the thin film.

(2) Material As a material constituting each layer, for example, Al ₂ O ₃ , TiO ₂ , ZrO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , CeO ₂ , Yb ₂ O ₃ , HfO ₂ , Nd ₂ O ₃ , Pr ₆ O ₁₁ , La ₂ O ₃ , Er ₂ O ₃ , CdO, Eu ₂ O ₃ , NiO, Cr ₂ O ₃ , SnO ₂ , Sb ₂ O ₃ , ZnO, ZnS, Sb ₂ S ₃ , CdS, AlN , SiO ₂ , MgF ₂ , AlF ₃ , BaF ₂ , CaF ₂ , LiF, NaF, SrF ₂ , In ₂ O ₃ , Y ₂ O ₃ , MgO, CeF ₃ , YF ₃ , DyF ₃ and fluororesin.

High refractive index layers with a refractive index of 2 to 2.45 are Ta ₂ O ₅ , TiO ₂ , Nb ₂ O ₅ , ZrO ₂ , HfO ₂ , CeO ₂ , SnO ₂ , In ₂ O ₃ , ZnO, Y ₂ O ₃ , ZnS and It is preferably made of at least one material selected from the group consisting of La ₂ O ₃ . At least one material low refractive index layer with a refractive index from 1.35 to 1.7 is selected from _{MgF 2, SiO 2, Al 2} O 3, MgO, group consisting of _{CeF 3, YF 3, DyF 3} , AlF 3 and fluororesin Preferably it consists of. Ultra-low refractive index layer with a refractive index 1.05 to 1.3 is _{MgF 2, SiO 2, Al 2} O 3 and is preferably a porous comprising at least one material selected from the group consisting of fluorine resin. The porous pore diameter is preferably 0.01 to 0.5 μm, and the porosity is preferably 20 to 80%.

  Examples of the fluororesin include ethylene tetrafluoride resin (PTFE), methylene trifluoride chloride resin (PCTFE), vinyl fluoride resin (PVF), ethylene tetrafluoride-hexafluoropropylene copolymer (FEP), and fluorine. Vinylidene chloride resin (PVDF) and the like are preferable.

(3) Method of forming antireflection film Each layer of the antireflection film (each layer constituting the antireflection film) can be formed by an existing method, for example, vacuum deposition, ion-assisted deposition, or ion plating. , Sputtering, chemical vapor deposition (CVD) and other vapor deposition methods (dry plating methods), wet plating methods, dip coating methods, ultrasonic mist coating methods, spin coating methods, spray coating methods and inkjet coating methods. It is done. For the vapor deposition method, for example, the methods described in JP-A-2001-59172 and JP-A-2001-81548 can be used, and the ultrasonic mist coating method is described in Japanese Patent No. 3159780. The method currently used can be used. In particular, it is preferable to use a vacuum deposition method, an ion assist deposition method, an ion plating method, a sputtering method, a dip coating method, an ultrasonic mist coating method, a spray coating method, and a spin coating method. Although all layers of the antireflection film may be formed by the same method, an optimum method may be selected and used for each layer.

[2] Substrate Examples of the substrate 3 include lenses, prisms, filters, optical fibers, and cathode ray tubes. Constituent materials of the substrate 3 include various inorganic materials such as optical glass, synthetic quartz, crystal, alumina crystal, LiNbO ₃ crystal, KTP crystal, YAG crystal, BBO crystal, LBO crystal, acrylic resin, polycarbonate resin, poly Various resin materials such as arylate resin, polyolefin resin, polyethylene resin, and polyester resin can be used.

  The substrate 3 preferably has a refractive index of 1.45 to 1.95 at a wavelength of 400 to 800 nm, more preferably 1.47 to 1.93. In such a range, even when a plurality of substrates 3 having different refractive indexes are used, a high antireflection effect can be obtained without changing the layer configuration of the antireflection film.

[3] Optical component By applying the antireflection film of the present invention to the above-described substrate, an optical component having an antireflection effect with a reflectance of 1% or less in a wide band of 400 to 800 nm can be obtained. The optical component of the present invention is suitable for a lens, a prism, a diffraction element, and the like mounted on an optical device such as a television camera, a video camera, a digital camera, an in-vehicle camera, a microscope, and a telescope.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
(1) Preparation of organic-modified silica-containing sol 5.21 g of tetraethoxysilane and 4.38 g of ethanol were mixed at room temperature, 0.4 g of 0.01 N hydrochloric acid was added, and the mixture was stirred for 90 minutes. After 44.35 g of ethanol and 0.5 g of 0.02 N aqueous ammonia were added and stirred for 46 hours, the temperature was raised to 60 ° C. and aged for 46 hours to obtain wet silica gel. The dispersion medium of silica gel was replaced with ethanol by repeating decantation, and the dispersion medium was further replaced with ethanol from hexane by decantation. A hexane solution of trimethylchlorosilane (concentration 5% by volume) was added to the silica gel, and the mixture was stirred for 30 hours to organically modify the silicon oxide terminal. The obtained organically modified silica gel was washed with hexane, adjusted to 1% by mass, and subjected to ultrasonic treatment (20 kHz, 500 W, 5 minutes) to obtain an organically modified silica sol.

(2) Layer formation Optical glass FK5 (nd = 1.487), BK6 (nd = 1.532), BaF10 (nd = 1.670), LaF2 (nd = 1.744), LaSF08 (nd = 1.883) and SFS1 (nd = 1.923) flat plate A high refractive index layer made of Nb ₂ O ₅ (nd = 2.25) and SiO ₂ (nd = 1.48) with an optical film thickness and layer structure as shown in Table 1 on a substrate (diameter 25 mm, thickness 1.0 mm). ) Was formed by a sputtering method. When the above-mentioned organic modified silica sol was applied to each substrate after sputtering by spin coating and dried at room temperature, gel shrinkage and springback occurred, and a porosity of 45% was formed. By baking this at 180 ° C. for 2 hours, an ultralow refractive index layer made of hydrophobic silica airgel (nd = 1.13) was formed, and the antireflection film of the present invention was obtained. The 5 ° incident spectral reflection characteristics are shown in Figs. 2-1 to 2-6.

  From the spectral reflection characteristics shown in FIGS. 2-1 to 2-6, the antireflection film of the present invention can reduce the reflectance to 1% or less in the wavelength range of 400 to 800 nm on a substrate having a refractive index of 1.487 to 1.923. I understood.

Example 2
Optical film thickness and layer structure as shown in Table 2 on a flat plate (diameter 25 mm, thickness 1.0 mm) of optical glass FK5 (nd = 1.487), LaF2 (nd = 1.744) and SFS1 (nd = 1.923) Thus, a high refractive index layer made of Ta ₂ O ₅ (nd = 2.20) and a low refractive index layer made of MgF ₂ (nd = 1.38) were formed by an ion plate method. Each substrate after the ion plate was baked at 160 ° C. for 2 hours, and the optical film thickness was changed as shown in Table 2 in the same manner as in Example 1 except that it was made of a superficial silica airgel layer (nd = 1.11). A low refractive index layer was formed to obtain an antireflection film of the present invention. The 5 ° incident spectral reflection characteristics are shown in Figs. 3-1 to 3-3.

  From the spectral reflection characteristics shown in FIGS. 3-1 to 3-3, the antireflection film of the present invention can reduce the reflectance to 1% or less in a wavelength range of 400 to 800 nm on a substrate having a refractive index of 1.487 to 1.923. I understood.

Example 3
Optical film thickness and layer structure as shown in Table 3 on optical glass FK5 (nd = 1.487), LaF2 (nd = 1.744) and SFS1 (nd = 1.923) flat plate (diameter 25 mm, thickness 1.0 mm) Thus, a high refractive index layer made of TiO ₂ (nd = 2.40) and a low refractive index layer made of MgF ₂ (nd = 1.38) were formed by vacuum deposition. Each substrate after vacuum deposition was composed of a hydrophobic silica airgel layer (nd = 1.15) in the same manner as in Example 1 except that the substrate was baked at 300 ° C. for 2 hours and the optical film thickness was changed as shown in Table 3. An ultra-low refractive index layer was formed to obtain an antireflection film of the present invention. The 5 ° incidence spectral reflection characteristics are shown in Figs. 4-1 to 4-3.

  From the spectral reflection characteristics shown in FIGS. 4-1 to 4-3, the antireflection film of the present invention can reduce the reflectance to 1% or less in a wavelength range of 400 to 800 nm on a substrate having a refractive index of 1.487 to 1.923. I understood.

Comparative Example 1
The optical film thickness of each layer having the refractive index shown in Table 4-1 with respect to the substrate having a refractive index of 1.45 was optimized by optical thin film calculation simulation so that the reflectance becomes the smallest in the wavelength range of 400 to 700 nm. The optical film thickness results are shown in Table 4-1, and the 5 ° incident spectral reflection characteristics are shown in FIG. 5-1.

Comparative Examples 2 and 3
Optimization was performed on the substrate having a refractive index of 1.70 and the substrate having a refractive index of 1.95 in the same manner as in Comparative Example 1 (Comparative Examples 2 and 3, respectively). The optical film thickness results are shown in Table 4-2 and Table 4-3, respectively, and the 5 ° incident spectral reflection characteristics are shown in FIGS. 5-2 and 5-3, respectively.

Comparative Examples 4 and 5
With respect to the substrate having a refractive index of 1.70 and the substrate having a refractive index of 1.95, an antireflection film having the same optical film thickness as that of Comparative Example 1 (Comparative Examples 4 and 5 respectively) is incident at 5 ° by optical thin film calculation simulation. Spectral reflection characteristics were obtained. The results are shown in FIGS. 5-4 and 5-5, respectively.

  By optimizing the optical film thickness of each layer so that the reflectance is minimized with respect to substrates having different refractive indexes, an antireflection film having a low reflectance (less than 1%) at a wavelength of 400 to 700 nm was obtained. (Comparative Examples 1-3). At this time, the optical film thickness of each layer was optimized depending on the refractive index of the substrate. However, when the optical film thickness (Table 4-1) optimized with the substrate refractive index of 1.45 (Comparative Example 1) is used as it is on a substrate with a refractive index of 1.70 or 1.95, it is shown in Figure 5-4 (Comparison As shown in Example 4) and FIG. 5-5 (Comparative Example 5), it was found that the antireflection performance at a wavelength of 400 to 700 nm was extremely inferior, and the reflectance exceeded 1% depending on the wavelength.

Comparative Example 6
With reference to JA Dobrowolski and Brian T. Sullivan, Applied Optics 35, 4993-4997 (1996) (Non-Patent Document 1), optical glass FK5 (nd = 1.487), LaF2 (nd = 1.744) and SFS1 (nd = 1.923) On a flat plate (diameter: 25 mm, thickness: 1.0 mm), ZnS (nd = 2.40) as a high refractive index layer and MgF ₂ ( nd = 1.38) was formed by vacuum deposition. In Non-Patent Document 1, the thickness of each layer is described as a physical film thickness, but Table 5 shows values converted into optical film thicknesses. The 5 ° incident spectral reflection characteristics are shown in FIGS. 6-1 to 6-3, respectively.

Comparative Example 7
With reference to JA Dobrowolski and Brian T. Sullivan, Applied Optics 35, 4993-4997 (1996) (Non-Patent Document 1), optical glass FK5 (nd = 1.487), LaF2 (nd = 1.744) and SFS1 (nd = 1.923) On a flat plate (diameter 25 mm, thickness 1.0 mm), ZnS (nd = 2.40) as the high refractive index layer and MgF ₂ (nd = 1.38) was formed by vacuum evaporation. In Non-Patent Document 1, the thickness of each layer is described as a physical film thickness, but Table 6 shows values converted into optical film thicknesses. The 5 ° incidence spectral reflection characteristics are shown in Figs. 7-1 to 7-3, respectively.

  Examples 1 to 3 (FIGS. 2-1 to 2-6, FIGS. 3-1 to 3-3, FIGS. 4-1 to 4-3) and Comparative Examples 6 and 7 (FIGS. 6-1 to 6-3, FIG. As is clear from comparison of 7-1 to 7-3), Examples 1 to 3 of the present invention have a refractive index of 1.487 to 1.923, although the number of layers is smaller than those of Comparative Examples 6 and 7. The substrate also has a low reflectance, and an excellent antireflection effect was obtained. In particular, when the optical glass SFS1 (nd = 1.923) having a high refractive index was used as the substrate, the effect of the antireflection film of the present invention was remarkable.

It is sectional drawing which shows the antireflection film of this invention formed in the surface of a board | substrate. 6 is a graph showing spectral reflectance of an antireflection film of Example 1 with respect to a substrate of FK5 (nd = 1.487). 6 is a graph showing the spectral reflectance with respect to the substrate of BK6 (nd = 1.532) of the antireflection film of Example 1. It is a graph showing the spectral reflectance with respect to the board | substrate of BaF10 (nd = 1.670) of the antireflection film of Example 1. 3 is a graph showing spectral reflectance of an antireflection film of Example 1 with respect to a substrate of LaF2 (nd = 1.744). 4 is a graph showing spectral reflectance of an antireflection film of Example 1 with respect to a LaSF08 (nd = 1.883) substrate. 4 is a graph showing spectral reflectance of an antireflection film of Example 1 with respect to a substrate of SFS1 (nd = 1.923). It is a graph showing the spectral reflectance with respect to the board | substrate of FK5 (nd = 1.487) of the antireflection film of Example 2. It is a graph showing the spectral reflectance with respect to the board | substrate of LaF2 (nd = 1.744) of the antireflection film of Example 2. It is a graph showing the spectral reflectance with respect to the board | substrate of SFS1 (nd = 1.923) of the antireflection film of Example 2. It is a graph showing the spectral reflectance with respect to the board | substrate of FK5 (nd = 1.487) of the antireflection film of Example 3. It is a graph showing the spectral reflectance with respect to the board | substrate of LaF2 (nd = 1.744) of the antireflection film of Example 3. It is a graph showing the spectral reflectance with respect to the board | substrate of SFS1 (nd = 1.923) of the antireflection film of Example 3. It is a graph showing the spectral reflectance with respect to the board | substrate of nd = 1.45 of the antireflection film of the comparative example 1. It is a graph showing the spectral reflectance with respect to the board | substrate of nd = 1.70 of the antireflection film of the comparative example 2. It is a graph showing the spectral reflectance with respect to the board | substrate of nd = 1.95 of the antireflection film of the comparative example 3. It is a graph showing the spectral reflectance with respect to the board | substrate of nd = 1.70 of the antireflection film of the comparative example 4. It is a graph showing the spectral reflectance with respect to the board | substrate of nd = 1.95 of the antireflection film of the comparative example 5. It is a graph showing the spectral reflectance with respect to the board | substrate of FK5 (nd = 1.487) of the antireflection film of the comparative example 6. It is a graph showing the spectral reflectance with respect to the board | substrate of LaF2 (nd = 1.744) of the antireflection film of the comparative example 6. It is a graph showing the spectral reflectance with respect to the board | substrate of SFS1 (nd = 1.923) of the antireflection film of the comparative example 6. It is a graph showing the spectral reflectance with respect to the board | substrate of FK5 (nd = 1.487) of the antireflection film of the comparative example 7. 10 is a graph showing the spectral reflectance with respect to the substrate of LaF2 (nd = 1.744) of the antireflection film of Comparative Example 7. It is a graph showing the spectral reflectance with respect to the board | substrate of SFS1 (nd = 1.923) of the antireflection film of the comparative example 7.

Explanation of symbols

1 Antireflection film
101 1st layer
102 2nd layer
103 3rd layer
104 4th layer
105 5th layer
106 6th layer
107 7th layer 3 substrate

Claims (6)

An antireflection film formed by laminating a first layer to a seventh layer in order from the substrate side on a substrate, at a wavelength of 400 to 800 nm,
The first layer, the third layer, and the fifth layer are high refractive index layers having a refractive index of 2 to 2.45,
The second layer, the fourth layer, and the sixth layer are low refractive index layers having a refractive index of 1.35 to 1.7;
The antireflection film, wherein the seventh layer is an ultra-low refractive index layer having a refractive index of 1.05 to 1.3. The antireflection film according to claim 1,
The optical thickness of the first layer is 7 to 39 nm,
The optical thickness of the second layer is 35 to 65 nm,
The optical thickness of the third layer is 22 to 75 nm,
The optical thickness of the fourth layer is 47 to 102 nm,
The optical thickness of the fifth layer is 1 to 59 nm,
The optical thickness of the sixth layer is 50 to 165 nm,
An antireflection film, wherein the seventh layer has an optical film thickness of 121 to 141 nm. 3. The antireflective film according to claim 1, wherein the high refractive index layer is Ta ₂ O ₅ , TiO ₂ , Nb ₂ O ₅ , ZrO ₂ , HfO ₂ , CeO ₂ , SnO ₂ , In ₂ O ₃ , ZnO. And at least one material selected from the group consisting of ZnS, wherein the low refractive index layer is at least one selected from the group consisting of MgF ₂ , SiO ₂ , Al ₂ O ₃ and a fluororesin. A layer made of a material, wherein the ultra-low refractive index layer is a porous layer made of at least one material selected from the group consisting of MgF ₂ , SiO ₂ , Al ₂ O ₃ and a fluororesin. Anti-reflective coating.   The antireflection film according to any one of claims 1 to 3, wherein the antireflection film has an antireflection effect having a reflectance of 1% or less over a wavelength range of 400 to 800 nm.   An optical component comprising the antireflection film according to claim 1.   6. The optical component according to claim 5, wherein a refractive index of the substrate at a wavelength of 400 to 800 nm is 1.45 to 1.95.

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