JP2003021702A - Antireflection film and optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antireflection film having a high reflectance in both of the UV region and the visible region. SOLUTION: The antireflection film is applied onto a substrate consisting of quartz or fluorite. The first, third, fifth and seventh layers from the substrate side are formed of an HfO2 film, and the second, fourth and sixth layers are formed of an SiO2 or an MgF2 film, and the eighth layer is formed of a MgF2 film. It is characterized in that the optical film thickness nd of each layer ranges, with respect to the reference wavelength λ, (0.15 to 0.25)×λ/4 for the first layer, (0.39 to 0.52)×λ/4 for the second layer, (0.31 to 0.41)×λ/4 for the third layer, (0.21 to 0.34)×λ/4 for the fourth layer, (2.3 to 3.0)×λ/4for the fifth layer, (0.27 to 0.43)×λ/4 for the sixth layer, (0.20 to 0.27)×λ/4 for the seventh layer, and (1.0 to 1.2)×λ/4 for the eighth layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antireflection film applied to an optical element used in the ultraviolet and visible regions, and an optical element formed with this antireflection film.

[0002]

2. Description of the Related Art An antireflection film is provided on the surface of optical elements such as lenses and prisms. By providing the antireflection film, it is possible to improve the transmittance of the entire optical system formed by the optical elements, and particularly to suppress the reflection in the visible range to improve the visibility. In the case of optical equipment used in the visible range or a narrower wavelength range,
The antireflection film was also sufficient if it could reduce the reflectance in a specific narrow wavelength range.

However, in recent years, an optical device for use in a wider wavelength band has appeared, and an optical element used therefor also requires an antireflection film having an antireflection property in such a wavelength band. It's coming. An antireflection film in a wide wavelength range is disclosed in, for example, Japanese Patent Publication No. 27116.
No. 97. In the present invention, a low reflectance of 0.8% or less is realized in a wide band from the visible region to the infrared region by using an eight-layer structure using three kinds of materials such as TiO ₂ , SiO ₂ , and MgF ₂ as a vapor deposition material. is doing.

[0004]

By the way, recently, in addition to the visible region and the infrared region, high antireflection performance is required in the ultraviolet region as well. For example, in the field of microscopes, in order to obtain a higher resolution, a light source with a short wavelength, particularly deep ultraviolet light with a wavelength of 248 nm, has been observed, and therefore, the optical element used also reflects in such a wavelength range. Preventive performance is required.

However, the above-described conventional antireflection film uses TiO ₂ which has strong light absorption in the wavelength range of 400 nm or less, and has a problem that it cannot be used in the ultraviolet range.

The present invention has been made in consideration of such problems, and an antireflection film having high antireflection performance in both the ultraviolet region and the visible region around 248 nm and such an antireflection film. It is intended to provide an optical element provided with.

[0007]

In order to solve the above-mentioned problems, the antireflection film of the invention of claim 1 has a thickness of 243 nm to 25 nm.
The reflectance is 1.5% or less in the wavelength range of 3 nm and 400 nm to 700 nm.

According to the antireflection film of the present invention, 248 nm
It has a high antireflection effect in the surrounding deep ultraviolet region and visible region.

The antireflection film of the invention of claim 2 is an antireflection film provided on a substrate made of quartz or fluorite.
Counting from the substrate side, HfO ₂ is in the first, third, fifth, and seventh layers, SiO ₂ or MgF ₂ is in the _second , fourth, sixth layers, and M is in the eighth layer.
gF ₂ is formed, and the optical thickness nd of each layer is (0.15 to 0.15) with respect to the reference wavelength λ.
0.25) × λ / 4, the second layer is (0.39 to 0.52)
× λ / 4, the third layer is (0.31 to 0.41) × λ / 4,
The fourth layer is (0.21 to 0.34) × λ / 4, the fifth layer is (2.3 to 3.0) × λ / 4, and the sixth layer is (0.27 to 0.34).
0.43) × λ / 4, the seventh layer is (0.20 to 0.27)
× λ / 4, and the eighth layer is (1.0 to 1.2) × λ / 4.

In the present invention, quartz or a substrate material is used.
Is fluorite and HfO which is a film forming material _Two, SiO_Two, Mg
F_TwoIs in the UV to visible range around 248 nm.
It is a material with almost no light absorption, and these are the films mentioned above.
The thick anti-reflection coating is used in the ultraviolet region around 248 nm.
And has a high antireflection effect in the visible range. Anti-reflection
The film formation method includes vacuum deposition method, sputtering method, and ion deposition method.
The plating method is not particularly limited.

The optical element of the invention of claim 3 is characterized in that the antireflection film of claim 1 or 2 is provided on a substrate.

According to this optical element, since it has a high transmittance in the deep ultraviolet region and the visible region around 248 nm, when this optical element is used in an optical system of an optical device,
High-resolution observation with a 48 nm light source and visual observation with visible light are possible with the same optical system, and thus can be versatile. The shape of the optical element is not particularly limited, such as a flat plate shape, a lens shape, and a prism shape.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <Embodiment 1> In this embodiment, a fluorite lens is used as a substrate, and a reference wavelength λ is set to 3
When the thickness is 50 nm, counting from the substrate side as shown in Table 1, reflection of a film structure using HfO ₂ for the first, third, fifth, seventh layer and MgF ₂ for the _second , fourth, sixth, eighth layer The prevention film was formed.

The spectral reflectance of this antireflection film is shown in FIG. As shown in FIG. 1, from the ultraviolet region of 243 nm to 2
53 nm and 400 nm to 700 nm in the visible range
In this range, the reflectance is 1% or less, and the antireflection performance is extremely good.

Further, the transmittance of the fluorite lens to which the antireflection film is not applied is 92%, but the transmittance of the lens as an optical element in which the antireflection film of this embodiment is applied to both sides is Approximately 99% in the range of 243 nm to 253 nm in the ultraviolet range and 400 nm to 700 nm in the visible range
And was extremely good.

Table 1 shows Modification 1 and Modification 2 in which the optical thickness of each layer is different from that of the present embodiment. These modifications also have the same effects as those of the present embodiment. Has been obtained.

[0017]

[Table 1]

<Embodiment 2> In this embodiment, a quartz lens is used as a substrate and a reference wavelength λ is 350 nm.
As shown in Table 2, counting from the substrate side,
HfO ₂ is on the fifth and seventh layers, and SiO is on the second, fourth and sixth layers
₂ , an antireflection film having a film structure using MgF ₂ was formed as the eighth layer.

The spectral reflectance of this antireflection film is shown in FIG. As shown in FIG. 2, from 243 nm in the ultraviolet region to 2
53 nm and 400 nm to 700 nm in the visible range
In this range, the reflectance is 1% or less and the antireflection performance is extremely good.

Further, the transmittance of the quartz lens not provided with the antireflection film is 92%, but the transmittance of the lens as an optical element having the antireflection film on both sides according to this embodiment is ultraviolet. Approximately 99% in the range of 243 nm to 253 nm and the visible range of 400 nm to 700 nm
And was extremely good.

Table 2 shows Modifications 3 to 6 in which the optical film thicknesses of the layers are different from those of the present embodiment. These modifications also have the same effects as those of the present embodiment. Has been obtained.

[0022]

[Table 2]

[0023]

As described above, according to the inventions of claims 1 and 2, it is possible to obtain a high antireflection effect in the ultraviolet region and the visible region around 248 nm.

According to the invention of claim 3, it is possible to have a high transmittance in the deep ultraviolet region and the visible region around 248 nm. Therefore, high-resolution observation with a 248 nm light source and visual observation with visible light are possible with the same optical system.

[Brief description of drawings]

FIG. 1 is a characteristic diagram of spectral reflectance according to the first embodiment.

FIG. 2 is a characteristic diagram of spectral reflectance according to the second embodiment.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takeshi Deguchi             2-43 Hatagaya, Shibuya-ku, Tokyo Ori             Inside Npus Optical Industry Co., Ltd. (72) Inventor Nobuyoshi Toyohara             2-43 Hatagaya, Shibuya-ku, Tokyo Ori             Inside Npus Optical Industry Co., Ltd. (72) Inventor Ken Kawamata             2-43 Hatagaya, Shibuya-ku, Tokyo Ori             Inside Npus Optical Industry Co., Ltd. (72) Inventor Tadashi Watanabe             2-43 Hatagaya, Shibuya-ku, Tokyo Ori             Inside Npus Optical Industry Co., Ltd. F term (reference) 2K009 AA09 BB01 CC03 CC06 DD03                       DD04 DD07                 4G059 AA11 AC04 EA01 EA05 EA09                       EB02

Claims (3)

[Claims] 1. 243 nm-253 nm and 400 n
An antireflection film having a reflectance of 1.5% or less in a wavelength range of m to 700 nm. 2. An antireflection film provided on a substrate made of quartz or fluorite, the first, third, and third counted from the substrate side.
HfO ₂ is formed on the fifth and seventh layers, SiO ₂ or MgF ₂ is formed on the _second , fourth, and sixth layers, and MgF ₂ is formed on the eighth layer, and the optical film thickness nd of each layer is the reference wavelength λ. On the other hand, the first layer is (0.15-0.25) × λ / 4, the second layer is (0.39-0.52) × λ / 4, and the third layer is (0.3
1 to 0.41) × λ / 4, the fourth layer is (0.21 to 0.3)
4) × λ / 4, the fifth layer is (2.3 to 3.0) × λ / 4,
The sixth layer is (0.27 to 0.43) × λ / 4, the seventh layer is (0.20 to 0.27) × λ / 4, and the eighth layer is (1.0 to
1.2) × λ / 4, which is an antireflection film. 3. An optical element comprising a substrate having the antireflection film according to claim 1 or 2.