JP2002277606A - Antireflection film and optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antireflection film having a high antireflection effect in the wide wavelength band from ultraviolet region to visible region and further to infrared region. SOLUTION: The antireflection film is disposed on a substrate whose refractive index is in the range of 1.65-1.85, films of HfO2 , ZrO2 , Ta2 O5 , Y2 O3 or a mixture of these are deposited as the first, third and fifth layers of the antireflection film counted from the substrate side, films of SiO2 or MgF2 are deposited as the second and fourth layers and a film of MgF2 is deposited as the sixth layer. When standard wavelength is represented by λ, the optical thicknesses of the first, second, third, fourth, fifth and sixth layers are (0.36-0.47)×λ/4, (0.08-0.18)×λ/4, (1.11-1.22)×λ/4, (0.17-0.23)×λ/4, (0.45-0.46)×λ/4 and (0.80-1.20)×λ/4, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antireflection film which can be used in a wide wavelength range of ultraviolet, visible and infrared regions, and an optical element having the antireflection film.

[0002]

2. Description of the Related Art An antireflection film is provided on the surface of an optical element such as a lens or a prism. Its main purpose is to improve the transmittance of the entire optical system transposed by the optical element,
In particular, it is to improve the visibility by suppressing reflection in the visible region. Many conventional optical devices are used in the visible and narrower wavelength ranges, so it is sufficient if the antireflection film can also suppress reflection in the visible and narrower wavelength ranges. Had become.

In recent years, however, they have been used in a wider wavelength range.
Optical equipment is required, and the optical elements used for
It is necessary to apply an antireflection film in the wavelength range corresponding to
ing. Conventional anti-reflection coating in such a wide wavelength range
Is described in Japanese Patent No. 2711697.
This antireflection film is made of TiO as a deposition material.₂, Si
O ₂, MgF₂8-layer structure using three types of materials
0.8 wideband from visible to infrared
% Or less.

[0004]

In addition to the above visible and infrared bands, high antireflection performance has recently been required also in the ultraviolet region. For example, in the field of microscopes, the observation range is widened to the ultraviolet region in order to obtain higher resolution, and there is also a case where light in the infrared region is required for fluorescence detection and the like. As described above, in order to use an optical device in a wide wavelength range, it is required that an optical element also has a high transmittance in a wide band from an ultraviolet region to an infrared region.

However, in the above-described conventional antireflection film, Ti having a strong light absorption in a wavelength region of 400 nm or less is used.
Due to the use of O _2, there is a problem that can not be used in the ultraviolet region.

The present invention has been made in consideration of such conventional problems, and has an anti-reflection film having high anti-reflection performance in a wide band from the ultraviolet to the visible and further to the infrared. It is an object to provide an optical element provided with a film.

[0007]

In order to achieve the above object, the antireflection film according to the first aspect of the present invention has a refractive index of 1.65.
An antireflection film provided on a substrate in the range of from 1.85 to 1.85, wherein HfO ₂ ,
Any of ZrO ₂ , Ta ₂ O ₅ , Y ₂ O ₃ or a mixture thereof, SiO ₂ or MgF _{2 in the second and} fourth layers,
MgF ₂ is formed on each of the sixth layers, and the optical thickness of each layer when the reference wavelength is λ is (0.
36 to 0.47) × λ / 4, and the second layer is (0.08 to 0.
18) × λ / 4, the third layer is (1.11 to 1.22) × λ
/ 4, the fourth layer is (0.17 to 0.23) × λ / 4, the fifth layer
The layer is (0.45-0.46) × λ / 4, and the sixth layer is (0.
80 to 1.20) × λ / 4.

The antireflection film according to the second aspect of the present invention has a refractive index
Reflection provided on a substrate in the range of 1.42 to 1.65
The second, fourth and sixth layers counted from the substrate side.
fO ₂, ZrO₂, Ta₂O₅, Y₂O₃Any of
Is a mixture of these materials in the first, third, and fifth layers.₂Or
MgF₂But the seventh layer has MgF₂Are each deposited
The optical thickness of each layer when the reference wavelength is λ is
One layer is (0.05 to 2.44) × λ / 4, and the second layer is
(0.32-0.45) × λ / 4, the third layer is (0.29
.About.0.43) .times..lamda. / 4, and the fourth layer is (0.77 to 1.7).
2) × λ / 4, the fifth layer is (0.07 to 0.38) × λ /
4. The sixth layer is (0.48-0.70) × λ / 4, the seventh layer
Is (1.00 to 1.36) × λ / 4
Features.

The antireflection film according to the third aspect of the present invention is an antireflection film provided on a substrate having a refractive index in the range of 1.44 to 1.76. , 8,
HfO ₂ , ZrO ₂ , Ta ₂ O ₅ , Y ₂
Any of O ₃ or a mixture thereof is the first 1, 3, 5,
SiO ₂ or MgF ₂ is formed on each of the 7, 9, 11, and 13 layers, and the optical thickness of each layer when the reference wavelength is λ is (0.02 to 0.53 ) × λ /
4, the second layer is (0.06-0.44) × λ / 4, the third layer is (0.33-0.84) × λ / 4, and the fourth layer is (0.1
0 to 0.50) × λ / 4, and the fifth layer is (0.58 to 1.2)
0) × λ / 4, and the sixth layer is (0.04-0.21) × λ /
Fourth, the seventh layer is (0.55 to 1.14) × λ / 4, the eighth layer is (0.30 to 0.54) × λ / 4, and the ninth layer is (0.15
5 to 0.44) × λ / 4, and the tenth layer is (0.29 to 1.
25) × λ / 4, and the eleventh layer is (0.14-0.29) ×
λ / 4, the twelfth layer is (0.45-0.62) × λ / 4,
The thirteenth layer is characterized by (0.80 to 1.20) × λ / 4.

HfO ₂ , ZrO ₂ , Ta ₂ O ₅ , Y ₂ O used as the film-forming material according to the first to third aspects of the present invention.
₃ , SiO ₂ , and MgF ₂ all have low light absorption in a wide range from the ultraviolet region to the infrared region. Therefore, an antireflection film formed of these materials has a high antireflection effect in a wide wavelength range from the ultraviolet region to the infrared region. Have. Further, it is possible to selectively lower the reflectance in a specific wavelength range actually used or to lower the reflectance over a wide wavelength range according to the use condition.

The antireflection film according to the first aspect of the present invention has a thickness of 6
It has a layer structure, and the number of layers is smaller than in the past, and the manufacture is easy.

In the first aspect of the present invention, the substrate may have a refractive index in the range of 1.65 to 1.85.
In the invention of the third aspect, the refractive index may be in the range of 1.42 to 1.65, and in the third aspect of the invention, the refractive index may be in the range of 1.44 to 1.76. The material of the substrate may be a crystal material, plastic, or the like, in addition to glass. Further, the shape of the substrate can be applied to any shape such as a flat plate shape, a lens shape, and a prism shape. As a method of forming the anti-reflection film,
There is no particular limitation on the vacuum deposition method, the sputtering method, the ion plating method, and the like.

An optical element according to a fourth aspect of the present invention is the optical element according to the first aspect.
3. An anti-reflection film according to any one of 3) is provided on the substrate.

According to the optical element of the present invention, there is a high antireflection effect in a wide wavelength range from the ultraviolet to the infrared.
As a result, it is possible to have a high transmittance in a wide wavelength range. The material of the substrate may be a crystal material, plastic, or the like in addition to glass. Further, the substrate may have any shape such as a flat plate, a lens, a prism, and the like.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to embodiments. Embodiments 1 to 4 correspond to the invention of claim 1, Embodiments 5 to 11 correspond to the invention of claim 2, and Embodiments 12 to 14 correspond to the invention of claim 3. It is.

(Embodiment 1) In this embodiment, 3
4 shows an antireflection film having a reduced reflectance in a wavelength range of 50 nm to 500 nm and in a wavelength range of 750 nm to 800 nm. Depending on the optical device, the wavelengths actually used are often discrete, and this embodiment lowers the reflectance only in the wavelength region used in this way.

Using a glass lens having a refractive index of 1.65 as a substrate and a reference wavelength λ of 535 nm, as shown in Table 1, HfO _{2 is applied} to the first, third, and fifth layers, and HfO _{2 is applied} to the _second , fourth, and sixth layers. Formed an antireflection film having a configuration using MgF ₂ .

FIG. 1 shows the spectral reflectance of the antireflection film, which ranges from 350 nm, which is the target ultraviolet region, to 500 nm, which is the visible region, and from 750 nm, which is the infrared region, to 8 nm.
It has a reflectance of about 1% or less in the range of 00 nm, and has extremely good antireflection performance. Also, 1,3
Substantially the same antireflection performance could be obtained by using Y ₂ O ₃ instead of the fifth layer of HfO ₂ .

The transmittance of the lens not provided with the anti-reflection film is 88%, while the transmittance of the lens provided with the anti-reflection film of this embodiment on both sides is in the ultraviolet range.
In the range from 0 nm to 500 nm, which is a visible region, and the range from 750 nm to 800 nm, which is an infrared region, 98% or more was extremely good.

[0020]

[Table 1]

(Embodiment 2) In the first embodiment, the anti-reflection film for reducing the reflectance in two discrete wavelength ranges is shown. However, the anti-reflection film of this embodiment has a reflectance in a continuous wavelength range. Lower it.

A glass lens having a refractive index of 1.85 was used as a substrate, and a reference wavelength λ was 491 nm. As shown in Table 2, HfO ₂ was applied to the first, third, and fifth layers, and to the second, fourth, and sixth layers. Formed an antireflection film having a configuration using MgF ₂ .

FIG. 2 shows the spectral reflectance of the antireflection film, which is from 370 nm in the ultraviolet region to 760 n in the infrared region.
It has a reflectance of about 1% or less in a wide wavelength range up to m, and has extremely good antireflection performance.

The transmittance of the lens not provided with the anti-reflection film is about 82%, but the transmittance of the lens provided with the anti-reflection film of this embodiment on both sides is in the range of 370 nm to 760 nm. It was very good at 98% or more.

[0025]

[Table 2]

(Embodiment 3) A plastic lens having a refractive index of 1.74 is used as a substrate, and a reference wavelength λ is 508.
As shown in Table 3, the first, third and fifth layers were Ta ₂ O
₅ , SiO ₂ for the _second and fourth layers, and MgF ₂ for the sixth layer.
An antireflection film having a structure using was formed.

FIG. 3 shows the spectral reflectance of this antireflection film, which is from 350 nm in the ultraviolet region to 740 n in the infrared region.
It has a reflectance of about 1% or less in a wide wavelength range up to m, and has extremely good antireflection performance.

The first, third, and fifth layers of Ta₂O₅Instead of
And ZrO₂Or ZrO₂And Ta ₂O₅Mixtures with
Almost the same antireflection performance can be obtained even if
I was able to.

[0029]

[Table 3]

(Embodiment 4) A glass prism having a refractive index of 1.75 is used as a substrate, and a reference wavelength λ is 546 nm.
As shown in Table 4, an antireflection film having almost the same configuration as that of the second embodiment was formed.

FIG. 4 shows the spectral reflectance of the antireflection film, which is from 400 nm in the visible region to 870 n in the infrared region.
It has a reflectance of about 1% or less in a wide wavelength range of m, and has extremely good antireflection performance.

In this embodiment, the wavelength range having high antireflection performance can be shifted to the infrared region by shifting the reference wavelength to the longer wavelength side compared to the second embodiment.

[0033]

[Table 4]

(Embodiment 5) In this embodiment, 3
Range from 50 nm to 500 nm and 750 nm to 8
4 shows an antireflection film having a reduced reflectance in the range of 00 nm. Depending on the optical device, the wavelengths actually used are often discrete, and this embodiment is a mode in which the reflectance is reduced only in the wavelength range used in this way.

A glass lens having a refractive index of 1.43 was used as a substrate, and a reference wavelength λ was set to 480 nm. As shown in Table 5, HfO ₂ was used for the _second , fourth, and sixth layers, and 1, 3, 5, and 7 layers were used. An anti-reflection film using MgF ₂ was formed on the eyes.

FIG. 5 shows the spectral reflectance of the antireflection film, which is about 1% or less in the range from 350 nm, which is the target ultraviolet region, to 500 nm, which is the visible region, and the range of 750 nm to 800 nm, which is the infrared region. Reflectivity,
It has extremely good antireflection performance. Note that 2,
Almost the same antireflection performance could be obtained by using Y ₂ O ₃ instead of the fourth and sixth layers of HfO ₂ .

The transmittance of the lens not provided with the anti-reflection film is 88%, while the transmittance of the lens provided with the anti-reflection film of this embodiment on both sides is in the ultraviolet region.
In the range from 0 nm to 500 nm, which is a visible region, and the range from 750 nm to 800 nm, which is an infrared region, 98% or more was extremely good.

[0038]

[Table 5]

(Embodiment 6) In Embodiment 5, an anti-reflection film that reduces the reflectance in two discrete wavelength ranges has been described. In this embodiment, the reflectance is reduced in a continuous wavelength range. It is.

A glass lens having a refractive index of 1.62 was used as a substrate, and a reference wavelength λ was set to 480 nm. As shown in Table 6, HfO ₂ was used for the _second , fourth, and sixth layers, and 1, 3, 5, and 7 layers were used. An anti-reflection film using MgF ₂ was formed on the eyes.

FIG. 6 shows the spectral reflectance of the antireflection film, which is from 370 nm in the ultraviolet region to 830 n in the infrared region.
It has a reflectance of about 1% or less in a wide wavelength range up to m, and has extremely good antireflection performance.

The transmittance of the lens not provided with the anti-reflection film is about 82%, but the transmittance of the lens provided with the anti-reflection film of this embodiment on both sides is in the range of 370 nm to 760 nm. It was very good at 98% or more.

[0043]

[Table 6]

(Embodiment 7) In Embodiment 6, an antireflection film whose reflectance is lowered in a continuous wavelength range is shown. However, in this embodiment, the maximum reflectance is further lowered in this wavelength range. is there.

A glass lens having a refractive index of 1.62 was used as a substrate, and a reference wavelength λ was 500 nm. As shown in Table 7, HfO ₂ was added to the _second , fourth, and sixth layers, and An anti-reflection film using MgF ₂ was formed on the eyes.

FIG. 7 shows the spectral reflectance of the antireflection film, which is from 370 nm in the ultraviolet region to 830 n in the infrared region.
It has a reflectance of about 1% or less over a wide wavelength range up to m, and has extremely good antireflection performance.

The transmittance of the lens not provided with the anti-reflection film is about 82%, but the transmittance of the lens provided with the anti-reflection film of this embodiment on both sides is in the range of 370 nm to 760 nm. It was very good at 98% or more.

[0048]

[Table 7]

(Embodiment 8) A plastic lens having a refractive index of 1.52 is used as a substrate, and a reference wavelength λ is set to 520.
As shown in Table 8, the _2nd , 4th and 6th layers are Ta ₂ O
_5, the SiO ₂ to 1, 3, 5-layer, Mg is in the seventh layer
It was deposited antireflection film configuration using F _2.

FIG. 8 shows the spectral reflectance of this antireflection film, which is from 350 nm in the ultraviolet region to 800 n in the infrared region.
It has a reflectance of about 1% or less in a wide wavelength range up to m, and has extremely good antireflection performance.

Even if ZrO ₂ or a mixture of ZrO ₂ and Ta ₂ O ₅ is used instead of the _second, fourth and sixth layers of Ta ₂ O ₅ , substantially the same antireflection performance can be obtained. Was completed.

[0052]

[Table 8]

(Embodiment 9) A glass prism having a refractive index of 1.62 is used as a substrate, and a reference wavelength λ is 550 nm.
As shown in Table 9, an antireflection film having almost the same configuration as that of Embodiment 7 was formed.

FIG. 9 shows the spectral reflectance of this antireflection film, which is from 400 nm in the visible region to 870 n in the infrared region.
It has a reflectance of about 1% or less in a wide wavelength range of m, and has extremely good antireflection performance.

In this embodiment, the wavelength range having high antireflection performance can be shifted to the infrared region by shifting the reference wavelength to the longer wavelength side as compared with the seventh embodiment.

[0056]

[Table 9]

(Embodiment 10) In this embodiment, as in Embodiment 6, the reflectance is reduced in a continuous wavelength range.

Using a glass lens having a refractive index of 1.43 as a substrate and a reference wavelength λ of 475 nm, as shown in Table 10, the second, fourth and sixth layers were made of HfO ₂ and the first, third, fifth and seventh layers. An anti-reflection film using MgF ₂ was formed on the eyes.

FIG. 10 shows the spectral reflectance of the antireflection film, which ranges from 400 nm in the visible region to 830 n in the infrared region.
It has a reflectance of about 1% or less in a wide wavelength range up to m, and has extremely good antireflection performance.

The transmittance of the lens not provided with the anti-reflection film is 88%, while the transmittance of the lens provided with the anti-reflection film of this embodiment on both sides is from 400 nm to 7%.
It was extremely good at 98% or more in the range of 60 nm.

[0061]

[Table 10]

(Embodiment 11) In this embodiment,
Similar to Embodiment 5, an antireflection film having a reduced reflectance in the range of 350 nm to 500 nm and in the range of 750 nm to 800 nm is shown.

Using a glass lens having a refractive index of 1.57 as a substrate and a reference wavelength λ of 480 nm, as shown in Table 11, the second, fourth and sixth layers were made of HfO ₂ and the first, third, fifth and seventh layers were made. An anti-reflection film using MgF ₂ was formed on the eyes.

FIG. 11 shows the spectral reflectance of the anti-reflection film. The reflectance of the anti-reflection film is approximately 1% or less in the range of 350 to 500 nm, which is a target ultraviolet region, and in the range of 750 to 800 nm, which is an infrared region. And has very good antireflection performance.

The transmittance of the lens not provided with the anti-reflection film is about 82%, but the transmittance of the lens provided with the anti-reflection film of this embodiment on both sides is in the ultraviolet region.
In the range from 50 nm to 500 nm, which is a visible region, and the range from 750 nm to 800 nm, which is an infrared region, 98% or more was extremely good.

[0066]

[Table 11]

(Embodiment 12) In this embodiment,
3 shows an antireflection film having a reduced reflectance in the range of 370 nm to 570 nm and in the range of 750 nm to 830 nm.
Depending on the optical device, the wavelengths actually used are often discrete, and this embodiment is a mode in which the reflectance is reduced only in the wavelength range used in this way.

[0068] with a glass lens having a refractive index of 1.44 as the substrate, the reference wavelength λ as 520 nm, MgF ₂ in the 1,3,5,7,9,11,13-layer as shown in Table 12
On the second, fourth, sixth, eighth, tenth, and twelfth layers, an antireflection film having a configuration using HfO ₂ was formed.

FIG. 12 shows the spectral reflectance of the antireflection film, which is about 0.5% in the range of 370 nm to 570 nm in the visible region and 750 to 830 nm in the infrared region. It has the following reflectance, and has extremely good antireflection performance.

In this embodiment, 1, 3, 5, 7,
Instead of MgF ₂ of the ninth, eleventh, and thirteenth layers, SiO ₂ was used.
T instead of HfO ₂ on the _second , fourth, sixth, eighth, tenth and twelfth layers
be deposited using a ₂ O ₅ could be obtained almost the same antireflection performance.

The total transmittance of the lens group in which the antireflection film of this embodiment is applied to each surface of a plurality of lens groups having 16 air contact surfaces is from 370 nm in the ultraviolet region. In the range of 570 nm which is a visible region and the range of 750 nm to 830 nm which is an infrared region, 92% or more was extremely good.

[0072]

[Table 12]

(Embodiment 13) A glass lens having a refractive index of 1.52 is used as a substrate, and a reference wavelength λ is 570 nm.
As shown in Table 13, 1,3,5,7,9,11,1
An antireflection film having a configuration using MgF ₂ as the third layer and HfO ₂ as the ₂ , 4, 6, 8, 10, and 12 layers was formed.

FIG. 13 shows the spectral reflectance of the antireflection film, which is from 360 nm in the ultraviolet region to 550 n in the visible region.
m and 730 nm to 810 nm in the infrared region
In the range, the reflectance is about 0.5% or less, which is an extremely good antireflection property.

The total transmittance of the lens group in which the antireflection film of this embodiment is applied to each surface of a plurality of lens groups having 16 air contact surfaces is from 360 nm in the ultraviolet region. In the range of 550 nm, which is a visible region, and the range of 730 nm to 810 nm, which is an infrared region, 92% or more was extremely good.

[0076]

[Table 13]

(Embodiment 14) A glass lens having a refractive index of 1.76 is used as a substrate, and a reference wavelength λ is 580 nm.
As shown in Table 14, 1,3,5,7,9,11,1
An antireflection film having a configuration using MgF ₂ as the third layer and HfO ₂ as the ₂ , 4, 6, 8, 10, and 12 layers was formed.

FIG. 14 shows the spectral reflectance of the antireflection film, which is from 360 nm in the ultraviolet region to 560 n in the visible region.
m and the infrared range of 740 nm to 830 nm
In the range of approximately 0.5% or less, and has extremely good antireflection performance.

The total transmittance of the lens group in which the antireflection film of this embodiment is applied to each surface of a plurality of lens groups having 16 air contact surfaces is from 360 nm in the ultraviolet region. In the range of 560 nm, which is a visible region, and the range of 740 nm to 830 nm, which is an infrared region, 92% or more was extremely good.

[0080]

[Table 14]

[0081]

As described above, according to the antireflection film of the first to third aspects of the present invention, high antireflection performance can be obtained in a wide wavelength range from the ultraviolet region to the infrared region. In addition, an anti-reflection film whose reflectance is selectively reduced in a specific wavelength range actually used or an anti-reflection film whose reflectance is lowered over the entire wide wavelength range can be used according to the use situation.

According to the optical element of the fourth aspect of the present invention, a high antireflection effect can be obtained in a wide wavelength range from the ultraviolet region to the infrared region, and as a result, a high transmittance can be obtained in a wide wavelength range. it can

[Brief description of the drawings]

FIG. 1 is a characteristic diagram of a spectral reflectance of an antireflection film according to a first embodiment.

FIG. 2 is a characteristic diagram of a spectral reflectance of an antireflection film according to a second embodiment.

FIG. 3 is a characteristic diagram of a spectral reflectance of an antireflection film according to a third embodiment.

FIG. 4 is a characteristic diagram of spectral reflectance of an antireflection film according to a fourth embodiment.

FIG. 5 is a characteristic diagram of the spectral reflectance of the antireflection film according to the fifth embodiment.

FIG. 6 is a characteristic diagram of the spectral reflectance of the antireflection film according to the sixth embodiment.

FIG. 7 is a characteristic diagram of the spectral reflectance of the antireflection film according to the seventh embodiment.

FIG. 8 is a characteristic diagram of the spectral reflectance of the antireflection film according to the eighth embodiment.

FIG. 9 is a characteristic diagram of the spectral reflectance of the antireflection film according to the ninth embodiment.

FIG. 10 is a characteristic diagram of the spectral reflectance of the antireflection film according to the tenth embodiment.

FIG. 11 is a characteristic diagram of the spectral reflectance of the antireflection film according to the eleventh embodiment.

FIG. 12 is a characteristic diagram of the spectral reflectance of the antireflection film according to the twelfth embodiment.

FIG. 13 is a characteristic diagram of the spectral reflectance of the antireflection film according to the thirteenth embodiment.

FIG. 14 is a characteristic diagram of the spectral reflectance of the antireflection film according to the fourteenth embodiment.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tadashi Watanabe 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Industrial Co., Ltd. (72) Inventor Takeshi Exit 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd. (72) Nobuyoshi Toyohara 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Kogyo Co., Ltd. (72) Kunihiko Uzawa 2-43-2 Hatagaya, Shibuya-ku, Tokyo No. Olympus Optical Industrial Co., Ltd. F-term (reference) 2K009 AA09 BB02 BB11 CC03 CC06 4G059 AA11 AB11 AC04 EA01 EB03 GA02 GA04 GA12

Claims (4)

[Claims] 1. An antireflection film provided on a substrate having a refractive index in a range of 1.65 to 1.85, wherein HfO ₂ , ZrO ₂ , and Ta are formed on _first , _third , and fifth layers counted from the substrate side.
₂ O ₅ , Y ₂ O ₃ or a mixture thereof, SiO ₂ or MgF _{2 in the second and} fourth layers, and MgF ₂ in the sixth layer.
₂ are formed, and the optical thickness of each layer when the reference wavelength is λ is (0.36 to 0.4) for the first layer.
7) × λ / 4, the second layer is (0.08 to 0.18) × λ /
4, the third layer is (1.11 to 1.22) × λ / 4, the fourth layer is (0.17 to 0.23) × λ / 4, and the fifth layer is (0.4
5 to 0.46) × λ / 4, and the sixth layer is (0.80 to 1.2)
0) × λ / 4. 2. An antireflection film provided on a substrate having a refractive index in a range of 1.42 to 1.65, wherein HfO ₂ , ZrO ₂ , and Ta are formed on _second , fourth, and sixth layers counted from the substrate side.
₂ O ₅ , Y ₂ O ₃ or a mixture thereof, SiO ₂ or MgF ₂ in the first, third, fifth layers, and M in the seventh layer.
gF ₂ are respectively formed, the optical film thickness of each layer when a reference wavelength is lambda, the first layer (0.05-2.
44) × λ / 4, the second layer is (0.32-0.45) × λ
/ 4, the third layer is (0.29 to 0.43) × λ / 4, the fourth layer
The layer is (0.77 to 1.72) × λ / 4, and the fifth layer is (0.
07-0.38) × λ / 4, and the sixth layer is (0.48-0.
70) × λ / 4, and the seventh layer is (1.00 to 1.36) × λ
/ 4. 3. An antireflection film provided on a substrate having a refractive index in a range of 1.44 to 1.76, wherein HfO is added to the second, fourth, sixth, eighth, tenth and twelfth layers counted from the substrate side. ₂ , Zr
Any of O ₂ , Ta ₂ O ₅ , Y ₂ O ₃ or a mixture thereof is coated with SiO 1 in the first, third, fifth, seventh, ninth, eleventh and thirteenth layers.
₂ or MgF ₂ , and the first layer has an optical film thickness of (0.
02 to 0.53) × λ / 4, and the second layer is (0.06 to 0.5).
44) × λ / 4, the third layer is (0.33-0.84) × λ
/ 4, the fourth layer is (0.10 to 0.50) × λ / 4, the fifth layer
The layer is (0.58 to 1.20) × λ / 4, and the sixth layer is (0.
04-0.21) × λ / 4, and the seventh layer is (0.55-1.
14) × λ / 4, the eighth layer is (0.30-0.54) × λ
/ 4, the ninth layer is (0.15 to 0.44) × λ / 4,
The 0th layer is (0.29 to 1.25) × λ / 4, the eleventh layer is (0.14 to 0.29) × λ / 4, and the twelfth layer is (0.4
5 to 0.62) × λ / 4, and the thirteenth layer is (0.80 to 1.
20) An anti-reflection film characterized by xλ / 4. 4. An optical element, wherein the antireflection film according to claim 1 is provided on a substrate.