JP2023041346A - Anti-reflection coating, optical fiber, optical component, and method for manufacturing anti-reflection coating - Google Patents

Abstract

An object of the present invention is to provide an anti-reflection coating that can be manufactured at low cost and has a wide band and low reflectance regardless of variations in optical film thickness and refractive index. SOLUTION: Nine layers of optical thin films (11 to 19) are laminated on a surface 2 of a substrate 1 having a refractive index of 1.44 or more and 1.47 or less. , the 5th, 7th and 9th layers are made of SiO2 with a refractive index of 1.45±0.01 with respect to the design center wavelength, the 2nd, 4th, 6th and 8th layers are made of Ta2O5 with a refractive index of 2.10±0.10, The optical film thickness ndk of the k-th layer is 100 nm ≤ nd1 ≤ 700 nm, 100 nm ≤ nd2 ≤ 165 nm, 100 nm ≤ nd3 ≤ 260 nm, 100 nm ≤ nd4 ≤ 700 nm, 100 nm ≤ nd5 ≤ 700 nm, 100 nm ≤ nd6 ≤ 700 nm, 100 nm ≤ nd7 ≤ 700 nm , 100 nm≦nd8≦700 nm, 100 nm≦nd9≦700 nm, and the reflectance in the wavelength band of 1260 nm to 1625 nm is 0.2% or less. [Selection drawing] Fig. 2

Description

TECHNICAL FIELD The present invention relates to an antireflection coating, an optical fiber, an optical component, and a method for manufacturing an antireflection coating.

A well-known anti-reflection film consisting of a dielectric multilayer film consists of two types of dielectric thin films with different refractive indices (hereinafter sometimes referred to as "optical thin films") on the surface of a base material (optical fiber, glass substrate, etc.). It is laminated alternately.

An antireflection film is provided on the end surface of an optical fiber for the purpose of reducing insertion loss and preventing stray light in, for example, products using optical fibers (fiber assembly products: hereinafter referred to as FA products). As the anti-reflection film formed on the end face of the optical fiber, considering the durability, optical thin films using SiO ₂ which is a low refractive index material and Ta ₂ O ₅ which is a high refractive index material are alternately laminated. is well known.

In conventional antireflection films for optical fibers, the wavelength band to be antireflection (hereinafter sometimes referred to as "antireflection band") is about 100 nm, and the number of dielectric multilayer films is 4 to 5. Met. However, in recent years, an antireflection film with a wider antireflection band has been desired, and Patent Document 1 below discloses an antireflection film having nine layers. In addition, Non-Patent Document 1 below describes an outline of a vapor deposition apparatus (IAD) using an ion beam assisted vapor deposition technique related to the present invention.

Japanese Patent No. 3741692

Shincron Co., Ltd., "4. Various film formation methods of physical vapor deposition (PVD)", [online], [searched on July 15, 2021], Internet <URL: https://www.shincron.co. jp/technical/device4-1.html＞

As described above, the antireflection film is required to have a low reflectance (eg, 0.2%) for light in a wide antireflection band (eg, 1260 nm to 1625 nm). Although the antireflection film described in Patent Literature 1 has such characteristics, when mass productivity as an industrial product is taken into consideration, the manufacturing cost is high and the characteristics may vary.

Specifically, the optical characteristics of the optical thin film that constitutes each layer of the dielectric multilayer film that serves as an antireflection film are obtained by multiplying the refractive index n of the film material by the physical film thickness (physical film thickness) d of the thin film. It is determined by the optical film thickness (also referred to as optical film thickness, hereinafter “optical film thickness”) nd. Then, the optical thin film of each layer is formed using a film forming device such as a sputtering device or a vapor deposition device.

A sputtering apparatus is capable of forming a uniform film, and the film forming speed can be controlled with high accuracy by controlling the applied power and the film forming process time, but the film forming speed is slower than other film forming apparatuses. In addition, the sputtering apparatus itself is more expensive than the vapor deposition apparatus, and it is necessary to strictly control the targets. Therefore, when mass-producing industrial products such as optical fibers with anti-reflection coatings, the vapor deposition method is used as the film-forming method because the cost of the equipment itself is low, and mass productivity and low film-forming temperatures can be achieved at the same time. is desirable.

On the other hand, the vapor deposition apparatus has a problem that the optical thin film formed has a variation in the refractive index, and the characteristics are not stable. There are two types of variations in the refractive index. The first variation is a large variation depending on the apparatus, and variations occur between different vapor deposition apparatuses or depending on the position of the substrate within the vacuum chamber of the same vapor deposition apparatus. For example, the refractive index of _SiO2, which is a low refractive index material, may vary by a maximum of about 0.02, and the refractive index of _Ta2O5 , _a high refractive index material, may vary by a maximum of about 0.2. As for this type of variation, although the degree of variation is stabilized between batches, it is necessary to individually adjust the target value of the film thickness of the optical thin film for each vapor deposition apparatus.

The second type of variation is a small refractive index variation that occurs during the manufacturing process. This depends on the contamination of the vapor deposition apparatus and the numerical values of the loaded workpieces (for example, variations in the refractive index of the base material, etc.). To deal with this kind of variation, the film forming process is terminated when the set optical film thickness is reached while measuring the refractive index n and the optical film thickness nd using an optical film thickness meter. It is necessary to adopt a control method. However, in the film thickness control method using an optical film thickness meter, there is a problem that the refractive index cannot be measured when the optical film thickness is 100 nm or less, and it is difficult to correct the dispersion of the refractive index. The antireflection film described in Patent Document 1 includes a layer having an optical thickness of less than 100 nm.

FIG. 1 shows the optical characteristics of the anti-reflection film described in Patent Document 1 when variations occurring in the manufacturing process are taken into consideration. FIG. 1 shows the reflectance of the antireflection film described in Patent Document 1 using SiO ₂ and Ta ₂ O ₅ as film materials (see Patent Document 1, Table 3) obtained by simulation. Spectral characteristics are shown. In the figure, the simulation result of the optical characteristics based on the design value (R-Design) and the simulation result of the optical characteristics when there is variation in the refractive index, the one when the error from the design value is the maximum (R-Design). -Max) are shown. As shown in FIG. 1, the simulation result (R-Max) corresponding to the properties of the actually manufactured antireflection film deviates from the design value properties (R-Design). In other words, even if the design meets the specifications (reflectance of 0.2% or less in the wavelength band of 1260 nm to 1625 nm in the figure), some anti-reflection coatings that are actually manufactured do not meet the specifications. become. Therefore, if an antireflection film is produced by a vapor deposition apparatus, the yield may decrease. If the yield decreases, the manufacturing cost increases, and the benefit of cost reduction by a vapor deposition apparatus that excels in mass productivity cannot be obtained.

Therefore, the present invention provides an antireflection film that can reduce manufacturing costs and has low reflectance over a wide band even if there are variations in the optical film thickness and refractive index during manufacturing, and an optical fiber having the antireflection film formed on the end face. An object of the present invention is to provide an optical component having the optical fiber and a method for forming an antireflection film.

One aspect of the present invention for achieving the above object is nine layers of optical thin films laminated on the surface of a substrate having a refractive index of 1.44 or more and 1.47 or less with respect to a medium having a refractive index of 1. An antireflection film consisting of

With the layer in contact with the surface of the substrate as the first layer, the first, third, fifth, seventh and ninth layers made of SiO ₂ having a refractive index of 1.45 ± 0.01 with respect to the design center wavelength, and the design center wavelength 2nd, 4th, 6th and 8th layers made of Ta ₂ O ₅ with a refractive index of 2.10 ± 0.10 for
If k is a natural number from 1 to 9 and the optical film thickness of the k-th layer is nd _k ,
100 nm≦nd ₁ ≦700 nm,
100 nm≦nd ₂ ≦165 nm,
100 nm≦nd ₃ ≦260 nm,
100 nm≦nd ₄ ≦700 nm,
100 nm≦nd ₅ ≦700 nm,
100 nm≦nd ₆ ≦700 nm,
100 nm≦nd ₇ ≦700 nm,
100 nm≦nd ₈ ≦700 nm,
100 nm≦nd ₉ ≦700 nm,
and
The reflectance is 0.2% or less in the wavelength band of 1260 nm or more and 1625 nm or less.
It is used as an antireflection film.
100 nm≦nd ₁ ≦150 nm,
100 nm≦nd ₂ ≦165 nm,
100 nm≦nd ₃ ≦260 nm,
100 nm≦nd ₄ ≦500 nm,
100 nm≦nd ₅ ≦400 nm,
100 nm≦nd ₆ ≦260 nm,
100 nm≦nd ₇ ≦260 nm,
350 nm≦nd ₈ ≦650 nm,
300 nm≦nd ₉ ≦400 nm,
It is good also as an antireflection film.
The scope of the present invention also includes an optical fiber having the antireflection film on its end face, and an optical component incorporating the optical fiber.

A method for producing an antireflection film having a reflectance of 0.2% or less in a wavelength band of 1260 nm or more and 1625 nm or less is also an aspect of the present invention.
a film formation step of forming the antireflection film consisting of nine layers of optical thin films on the surface of a substrate having a refractive index of 1.44 or more and 1.47 or less with respect to a medium having a refractive index of 1 by a vapor deposition method; including
In the film formation step, the optical thin film in contact with the surface of the substrate is used as a first layer, and the first, third, fifth, seventh, and second layers are made of SiO ₂ having a refractive index of 1.45±0.01 with respect to the design center wavelength. The 9th layer and the 2nd, 4th, 6th and 8th layers made of Ta ₂ O ₅ having a refractive index of 2.10±0.10 with respect to the design center wavelength were arranged based on the design values of the respective optical film thicknesses. sequentially forming from the 1st layer to the 9th layer,
The design value nd _k of the optical film thickness of the k-th layer when k is a natural number from 1 to 9,
100 nm≦nd ₁ ≦700 nm,
100 nm≦nd ₂ ≦165 nm,
100 nm≦nd ₃ ≦260 nm,
100 nm≦nd ₄ ≦700 nm,
100 nm≦nd ₅ ≦700 nm,
100 nm≦nd ₆ ≦700 nm,
100 nm≦nd ₇ ≦700 nm,
100 nm≦nd ₈ ≦700 nm,
100 nm≦nd ₉ ≦700 nm,
to be
A method for producing an antireflection film.

In the film forming step, the design value nd _k of the optical film thickness is
100 nm≦nd ₁ ≦150 nm,
100 nm≦nd ₂ ≦165 nm,
100 nm≦nd ₃ ≦260 nm,
100 nm≦nd ₄ ≦500 nm,
100 nm≦nd ₅ ≦400 nm,
100 nm≦nd ₆ ≦260 nm,
100 nm≦nd ₇ ≦260 nm,
350 nm≦nd ₈ ≦650 nm,
300 nm≦nd ₉ ≦400 nm,
It is good also as a manufacturing method of the antireflection film which makes it.

According to the present invention, an anti-reflection coating that can reduce the manufacturing cost and has a low reflectance over a wide band even if there are variations in the optical film thickness and refractive index during manufacturing, and an optical fiber with the anti-reflection coating formed on the end face. , an optical component having the optical fiber, and a method of forming an antireflection coating are provided. Other effects will be clarified in the following description.

FIG. 2 is a diagram showing optical characteristics obtained by simulation based on design values and optical characteristics when variations occurring in the manufacturing process are taken into consideration for the antireflection film described in Patent Document 1; It is a figure which shows the structure of the antireflection film which concerns on an Example. FIG. 10 is a diagram showing optical characteristics obtained by simulation based on design values and optical characteristics when variations occurring in the manufacturing process are taken into account for antireflection films according to examples. FIG. 5 is a diagram showing measurement results of optical properties of antireflection films according to examples.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

=== Optical Simulation ===
As is well known, the optical properties of an antireflection film made of a dielectric multilayer film can be specified with high accuracy by simulation based on Fresnel's law without actually measuring the antireflection film that has been produced. Then, if each layer constituting the antireflection film is manufactured according to the conditions (optical film thickness, refractive index, etc.) given in the simulation, the optical properties of the manufactured antireflection film are similar to those obtained by the simulation. It reflects the characteristics.

However, as described above, the above conditions vary during the manufacturing process of the antireflection film. In particular, when an optical thin film having an optical thickness of less than 100 nm is produced using a vapor deposition apparatus that controls the thickness using an optical thickness gauge, the variation is large. Therefore, unless variations in conditions in the manufacturing process are taken into account, the properties of an actually manufactured antireflection film deviate from the properties obtained by simulation.

=== Example ===
An antireflection film according to an embodiment is formed on the surface of a substrate. Examples of base materials include glass substrates and optical fibers. FIG. 2 shows a schematic structure of the antireflection film 10 according to the example. The antireflection film 10 illustrated in FIG. 2 uses the optical fiber 1 as a base material, and is formed on the end face 2 of the optical fiber 1, which is the surface of the base material. The dielectric multilayer film constituting the antireflection film 10 is formed from the layer in contact with the end face 2 of the optical fiber 1 as the first layer to the outermost layer, the ninth layer in contact with the air, and the first layer is an optical thin film made of SiO ₂ . 11, the second layer is an optical thin film 12 made of Ta ₂ O ₅ , and thereafter, layers of optical thin films ( 13 to 19 ) made of SiO ₂ and Ta ₂ O ₅ are alternated toward the optical thin film 19 of the ninth layer. It is laminated to In the drawing, the optical thin films (11, 13, 15, 17, 19) made of SiO ₂ are indicated by halftone hatching, and the optical thin films (12, 14, 16, 18) made of Ta ₂ O ₅ ) are indicated by diagonal hatching.

The antireflection film 10 according to the embodiment satisfies desired specifications even if there are variations in various conditions that determine optical characteristics during the manufacturing process. Here, the specification is set such that the reflectance is 0.2% or less in the wavelength band of 1260 nm to 1625 nm. Then, in order to satisfy the above specifications, the antireflection film 10 according to the embodiment is based on the optical simulation described above. The thickness is set appropriately.

In the simulation, it is assumed that an optical fiber is used as a base material and the antireflection film 10 is formed on the end surface of the optical fiber by using a vapor deposition method, and the lower limit of the optical film thickness of the optical thin films (11 to 19) of each layer is set to 100 nm or more. set to Considering the refractive index of the core and cladding of the optical fiber in air (in a medium with a refractive index of 1), the refractive index of the substrate was set to 1.44 to 1.47. Furthermore, since the refractive index of the optical thin film at the design center wavelength may vary between deposition apparatuses or depending on the position of the substrate in the vacuum chamber of the deposition apparatus, in the simulation, _SiO2 at the design center wavelength of 1450 nm The refractive index is in the range of 1.45±0.01, the refractive index of Ta ₂ O ₅ is in the range of 2.10±0.10, and the difference between the refractive index n1 of SiO ₂ and the refractive index n2 of Ta ₂ O ₅ is As a combination, (n1, n2) = (1.44, 2.00), (1.44, 2.20), (1.46, 2 . 00), (1.46, 2.20). Then, under the setting related to the upper and lower limits of the optical film thickness and the setting related to the dispersion of the refractive index, the anti-reflection that satisfies the specification that the reflectance is 0.2% or less in the anti-reflection band of 1260 nm to 1625 nm The optical film thickness of each layer in the film was obtained by simulation. Table 1 below shows an example of simulation results satisfying the above specifications under the above settings.

Table 1 shows the optical film thickness of each layer at the center wavelength λ=1450 nm when the refractive index of the substrate is 1.45. In addition, in Table 1, the optical film thickness of the first layer that is first laminated on the substrate is uniformly set to 125 nm in order to make it easier to understand the increasing and decreasing tendency of the optical film thickness of two specific adjacent layers. Also shown are the simulation results (samples a to h) when the optical film thickness of the second layer is 100 nm or 165 nm, and the simulation result (sample i) when the optical thin film of the second layer is 170 nm. ing.

As shown in Table 1, when comparing the samples (ae, bf, cg, dh) with the same combination of refractive indices of SiO ₂ and Ta ₂ O ₅ , the second layer and the third layer It can be confirmed that as one of the optical film thicknesses of the layers increases, the other tends to decrease. In addition, in sample i in which the optical film thickness of the second layer is 170 nm, which is larger than 165 nm, the optical film thickness of the third layer is 103 nm, which is close to the lower limit (100 nm) desired for manufacturing. is the lower limit of 100 nm. That is, there is a possibility that the anti-reflection film designed with the optical film thickness of each layer as that of sample i may fail to meet the specifications when actually manufactured. In other words, it can be easily assumed that an antireflection film satisfying the above specifications can be obtained at least if the optical film thickness of each layer is within the numerical range of any one of samples a to h. Therefore, in order to obtain an antireflection film that satisfies the above specifications, the optical film thickness of the second layer should be 100 nm or more and 165 nm or less, and the optical film thickness of the third layer should be 100 nm as the lower limit. 260 nm may be set as the upper limit. For other layers, the lower limit of the optical film thickness should be 100 nm. Regarding the upper limit of the optical film thickness of other layers, there is a possibility that when a high-power laser beam is incident on a layer with a thick optical film thickness, the laser beam will be absorbed in that layer and the film material will be destroyed. Considering the possibility that a thick layer may separate from the underlying layer and the film formation time will be long, it is not possible to increase the thickness blindly, so the maximum optical film thickness in Table 1 (sample g, 8th layer, 635 nm) to 700 nm. Of course, an optical thin film having an optical thickness of about 700 nm can be stably formed using a vapor deposition apparatus.

Furthermore, in order to more reliably obtain an antireflection film that satisfies the above specifications, based on the simulation results in Table 1, while setting the optical film thicknesses of the second and third layers within the above numerical ranges, for example, The optical film thickness of one layer is set to a uniform average film thickness of 125 nm shown in Table 1 with a lower limit of 100 nm, and the numerical range of the optical film thickness of each of the 4th to 9th layers shown in Table 1. Just do it. That is, when the optical film thickness of the k-th optical thin film is _ndk , where k is a natural number of 1 to 9, 100 nm≦nd ₁ ≦150 nm, 100 nm≦nd ₂ ≦165 nm, 100 nm≦nd ₃ ≦260 nm, 100 nm≦nd ₄ ≦500 nm, 100 nm≦nd ₅ ≦400 nm, 100 nm≦nd ₆ ≦260 nm, 100 nm≦nd ₇ ≦260 nm, 350 nm≦nd ₈ ≦650 nm, and 300 nm≦nd ₉ ≦400 nm.

Here, in order to verify the above simulation results, IAD (MIC- 1350DSN, manufactured by Syncron Co., Ltd.).

FIG. 3 shows the results of simulations of the optical properties of the antireflection coatings shown in Table 2. In FIG. FIG. 3 shows the simulation results (R-Design) of the optical characteristics of the antireflection film based on the design values shown in Table 2 and the simulation results of the optical characteristics of the antireflection film when there is variation in the refractive index. The value (R-Max) when the error from the value is maximum is shown. In the simulation based on the design values, the refractive index of the substrate is set to 1.45, the refractive index of _SiO2 is set to _1.45 , and the refractive index of _Ta2O5 is set to 2.10. According to the simulation results shown in FIG. 3, the anti-reflection film according to the example has the above specifications (wavelength band of 1260 nm to 1625 nm) even if the refractive index varies from the design value in the manufacturing process. reflectance of 0.2% or less).

FIG. 4 shows the optical properties of an antireflection film actually produced based on the design values shown in Table 2. As shown in FIG. In Fig. 4, the optical characteristics of the antireflection coating formed on the base material placed at three different heights in the vacuum chamber of the IAD were measured using a spectrophotometer (U-4100, manufactured by Hitachi High-Tech Science Co., Ltd.). Measured results are shown. FIG. 4 shows the simulation results (R-Design) based on the design values also shown in FIG. The spectral characteristics of the reflectance of the film (R-UP), the antireflection film (R-Down) formed at the lowest position, and the antireflection film (R-Center) formed at the intermediate position thereof are shown. ing. Then, as shown in FIG. 4, the antireflection films (R-UP, R-Down, R-Center) actually manufactured by setting the design values in Table 2 to the IAD all meet the above specifications. It was confirmed that the requirements were met.

As described above, the antireflection films according to the examples are formed by sequentially forming the first to ninth layers using a vapor deposition apparatus such as IAD, and when forming each layer, the optical film thickness of each layer is determined by the vapor deposition apparatus. It should be set so that it becomes a numerical range. Also, even if the actual optical film thickness deviates from the set value depending on the position of the base material between devices or within the device, the manufactured antireflection film satisfies the specifications as shown in FIG. . In other words, the antireflection films according to the examples, which are manufactured so that the optical film thickness of each layer falls within the numerical range described above, satisfy the specifications.

===Other Examples===
An optical fiber having an antireflection film formed on an end surface according to the embodiment is used, for example, on the output side of various optical components (optical demultiplexer/multiplexer, wavelength selection filter, etc.) installed in an optical communication network. , the light incident on the optical component can be emitted with extremely low loss. In addition, it is possible to suppress the generation of return light that is reflected into the optical component from the end face of the optical fiber on the output side, so that stray light that becomes noise in the optical component can be effectively suppressed.

Of course, the antireflection film according to the embodiment can be applied not only to optical fibers but also to appropriate devices such as infrared sensors and displays.

Although the anti-reflection films according to the above examples were produced using an IAD, they may of course be produced using a vapor deposition apparatus using a resistance heating method, a high-frequency induction heating method, or the like.

1 base material (optical fiber), 2 surface of base material (end surface of optical fiber),
10 antireflection film, 11, 13, 15, 17, 19 optical thin film made of _SiO2 ,
Optical thin film made of 12, 14, 16, 18 Ta ₂ O ₅

Claims (6)

An antireflection film composed of nine layers of optical thin films laminated on the surface of a substrate having a refractive index of 1.44 or more and 1.47 or less with respect to a medium having a refractive index of 1,
With the layer in contact with the surface of the substrate as the first layer, the first, third, fifth, seventh and ninth layers made of SiO ₂ having a refractive index of 1.45 ± 0.01 with respect to the design center wavelength, and the design center wavelength 2nd, 4th, 6th and 8th layers made of Ta ₂ O ₅ with a refractive index of 2.10 ± 0.10 for
If k is a natural number from 1 to 9 and the optical film thickness of the k-th layer is nd _k ,
100 nm≦nd ₁ ≦700 nm,
100 nm≦nd ₂ ≦165 nm,
100 nm≦nd ₃ ≦260 nm,
100 nm≦nd ₄ ≦700 nm,
100 nm≦nd ₅ ≦700 nm,
100 nm≦nd ₆ ≦700 nm,
100 nm≦nd ₇ ≦700 nm,
100 nm≦nd ₈ ≦700 nm,
100 nm≦nd ₉ ≦700 nm,
and
The reflectance is 0.2% or less in the wavelength band of 1260 nm or more and 1625 nm or less.
Anti-reflective coating. The antireflection film according to claim 1,
100 nm≦nd ₁ ≦150 nm,
100 nm≦nd ₂ ≦165 nm,
100 nm≦nd ₃ ≦260 nm,
100 nm≦nd ₄ ≦500 nm,
100 nm≦nd ₅ ≦400 nm,
100 nm≦nd ₆ ≦260 nm,
100 nm≦nd ₇ ≦260 nm,
350 nm≦nd ₈ ≦650 nm,
300 nm≦nd ₉ ≦400 nm,
is
Anti-reflective coating. An optical fiber having the antireflection film according to claim 1 or 2 on its end face. An optical component in which the optical fiber according to claim 3 is incorporated. A method for producing an antireflection film having a reflectance of 0.2% or less in a wavelength band of 1260 nm or more and 1625 nm or less,
a film formation step of forming the antireflection film consisting of nine layers of optical thin films on the surface of a substrate having a refractive index of 1.44 or more and 1.47 or less with respect to a medium having a refractive index of 1 by a vapor deposition method; including
In the film formation step, the optical thin film in contact with the surface of the substrate is used as a first layer, and the first, third, fifth, seventh, and second layers are made of SiO ₂ having a refractive index of 1.45±0.01 with respect to the design center wavelength. The 9th layer and the 2nd, 4th, 6th and 8th layers made of Ta ₂ O ₅ having a refractive index of 2.10±0.10 with respect to the design center wavelength were arranged based on the design values of the respective optical film thicknesses. sequentially forming from the 1st layer to the 9th layer,
The design value nd _k of the optical film thickness of the k-th layer when k is a natural number from 1 to 9,
100 nm≦nd ₁ ≦700 nm,
100 nm≦nd ₂ ≦165 nm,
100 nm≦nd ₃ ≦260 nm,
100 nm≦nd ₄ ≦700 nm,
100 nm≦nd ₅ ≦700 nm,
100 nm≦nd ₆ ≦700 nm,
100 nm≦nd ₇ ≦700 nm,
100 nm≦nd ₈ ≦700 nm,
100 nm≦nd ₉ ≦700 nm,
to be
A method for producing an antireflection film. A method for producing an antireflection film according to claim 5,
In the film forming step, the design value nd _k of the optical film thickness is
100 nm≦nd ₁ ≦150 nm,
100 nm≦nd ₂ ≦165 nm,
100 nm≦nd ₃ ≦260 nm,
100 nm≦nd ₄ ≦500 nm,
100 nm≦nd ₅ ≦400 nm,
100 nm≦nd ₆ ≦260 nm,
100 nm≦nd ₇ ≦260 nm,
350 nm≦nd ₈ ≦650 nm,
300 nm≦nd ₉ ≦400 nm,
to be
A method for producing an antireflection film.

Images