JPH052101A - Optical component - Google Patents

Abstract

PURPOSE:To provide an optical component which has superior reflection prevention characteristics and high transmissivity characteristics over the entire area of visible light, specially to light in a 400-450nm wavelength range and also has small variation in the accuracy of the surface. CONSTITUTION:A reflection preventive film consisting of a laminate film of five-layered constitution is formed on the surface and the refractive index ni and optical film thickness nidi of an (i)th layer (i: counted from a medium like air to the substrate surface) constituting the laminate film are as mentioned below. Here, lambda0 is set wavelength. Namely, 0.24lambda0<=n1d1<=0.26lambda0, and 1.37<=n1<=1.40; 0.52lambda0<=n2d2<=0.56lambda0 and 1.90<=n2<=2.30; 0.10lambda0<=n3d3<=0.15lambda0 and 1.37<=n3<=1.47; 0.05lambda0<=n4d4<=0.12lambda0 and 1.80<=n4<=2.30; and 0.08lambda0<=n5d5<=0.18lambda0 and 1.37<=n5<=1.40.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical component, and more particularly to an optical component having an antireflection film composed of a laminated film having a five-layer structure formed on the surface.

[0002]

2. Description of the Related Art On the surface of an optical component, about 4 to 8% of the incident light amount is reflected due to the refractive index of the optical component. This phenomenon not only reduces the amount of light transmitted to the inside, but also causes ghost and flare when such an optical component is used as a projection lens of a camera or the like. As the simplest example for reducing this surface reflection, an optical component in which a single layer film made of magnesium fluoride is formed on the surface is widely known. For example, this single layer film is formed on the surface. The surface reflectance of a glass plate having a refractive index of 1.52 is reduced to about 1.2%.

However, the means for forming this monolayer film on the surface cannot obtain an effective antireflection effect in the entire visible light region (400 nm to 700 nm). Therefore, a means for forming a laminated film on the surface has been devised. The basic structure of such a laminated film is, for example, a low refractive index layer having an optical film thickness of 0.25λ ₀ as the first layer and an optical film thickness of 0.50 as the second layer when counted from a medium such as air.
high refractive index layer of lambda _0, the third layer in constituted by a total of three layers of the intermediate refractive index layer having an optical thickness of 0.25 [lambda ₀ (hereinafter referred to as "basic three-layer") stacked film, the basic three-layer structure There is known a laminated film including a total of four layers (hereinafter referred to as “basic four-layer configuration”) in which an intermediate refractive index layer having an optical film thickness of 0.25λ ₀ is further provided as a fourth layer. According to the laminated film having such a configuration, it is possible to obtain a reflectance of 1% or less over the entire visible light region in calculation.

However, for the low refractive index layer and the high refractive index layer, there are film materials satisfying the condition of the refractive index, but film materials suitable for satisfying the condition of the intermediate refractive index layer are currently known. Therefore, the above basic three-layer structure cannot be realized by a laminated film of three layers, and the same applies to the basic four-layer structure. Therefore, as a method often used,
There is a three-layer equivalent film method. In this method, a layer made of a film material having an arbitrary refractive index n _M is alternated with a layer made of a film material having a refractive index n _H larger than n _M and a layer made of a film material having a refractive index n _L smaller than n _M. It is based on the principle that it can be replaced by three layers.

At present, many structures are proposed as an antireflection film composed of a laminated film, but most of them use the principle of the three-layer equivalent film method for the intermediate refractive index layer in the basic three-layer structure and the basic four-layer structure. 5 to 7 layers in total, which have been replaced.

[0006]

However, the optical component having the antireflection film made of the laminated film having these structures has the following problems. Phenomenon in which the refractive index of the film material of each layer differs depending on the incident wavelength (hereinafter referred to as "refractive index dispersion phenomenon"), and phenomenon in which the refractive index changes in the same layer in the thickness direction (hereinafter referred to as "film non-uniformity phenomenon") .) And the like, it does not have good antireflection properties over the entire visible light region, and the reflectance rapidly increases in the short wavelength region (400 nm to 450 nm) of visible light. Further, when an antireflection film made of a laminated film is formed, in order to obtain antireflection properties in the entire wavelength range of visible light, a high refractive index material with a refractive index of around 2.0 is used to obtain an optical film thickness of about 0.5λ ₀ . Constructing thick layers becomes essential. However, when the antireflection film is formed of such a thick layer of a high refractive index material, light in the short wavelength region of visible light is easily absorbed, and the amount of transmitted light is reduced. Therefore, it is not possible to obtain the desired amount of transmitted light in the short wavelength region of visible light, and when a large number of such optical components are used as photographing lenses of a camera, the amount of transmitted light in the short wavelength region (blue) decreases. However, the color balance is lost, which is not preferable for color reproduction. The film stress of each layer constituting the laminated film causes a warp on the surface and changes the surface accuracy.

The present invention has been made based on the above circumstances, and a first object of the present invention is to have good antireflection properties over the entire visible light range, and particularly 400 to 450.
An object of the present invention is to provide an optical component having an excellent antireflection property of light in the wavelength region of nm.

A second object of the present invention is to provide an optical component having a high transmittance characteristic with a small light amount loss due to absorption or scattering of light in the short wavelength region of visible light.

A third object of the present invention is to provide an optical component in which a change in surface accuracy due to film stress is small and warpage or the like does not occur.

[0010]

[Here, i (i: i = 1 to 5) is counted from a medium such as air toward the underlying surface. Further, λ ₀ indicates the set wavelength. ]

The film material forming the second and fourth layers is a metal oxide or metal oxide selected from the group consisting of tantalum oxide, a mixture of titanium oxide and zirconium oxide, and a mixture of titanium oxide and praseodymium oxide. It is preferably a mixture of substances.

Further, the film material forming the third layer is preferably silicon oxide.

[0013]

By forming an antireflection film composed of a laminated film having a five-layer structure on the surface and defining the refractive index and the optical film thickness in each layer within a specific range, it will be clear from Examples and Comparative Examples described later. As described above, it has excellent antireflection properties in the entire visible light region, and particularly has excellent antireflection properties in the wavelength region of 400 to 450 nm.

By using a specific metal oxide or a mixture of specific metal oxides as the film material forming the second layer and the fourth layer, the amount of light such as absorption and scattering of light in the short wavelength region of visible light is obtained. The loss is small and the transmittance is high.

By using, as the film material forming the third layer, silicon oxide whose film stress direction is opposite to that of the film material forming the other layers, the film stress generated in the other layers can be relaxed. Therefore, the change in surface accuracy is small, and warpage or the like does not occur.

<Film Material in Each Layer> Examples of the film material constituting the first layer and the fifth layer include magnesium fluoride, aluminum oxide, silicon oxide and the like, which have particularly stable optical characteristics. Magnesium fluoride is preferable because it has excellent wear resistance and moisture resistance. Examples of the film material forming the second layer and the fourth layer include zirconium oxide, tantalum oxide, a mixture of titanium oxide and zirconium oxide, a mixture of titanium oxide and praseodymium oxide, and the like. A mixture of tantalum oxide, a mixture of titanium oxide and zirconium oxide, and a mixture of titanium oxide and praseodymium oxide are preferable because they have a small light loss such as scattering and have a high transmittance characteristic. Examples of the film material forming the third layer include magnesium fluoride, aluminum oxide, silicon oxide, and the like. In particular, silicon oxide is preferable because it has an effect of relieving film stress generated in other layers.

[0017]

Examples 1 to 5 On each glass substrate having a different refractive index, an antireflection film made of a laminated film was formed according to the film material and the optical film thickness shown in Table 1 to manufacture an optical component.

[0018]

[Table 1]

In Table 1, the value of _x in MgF _x , SiO _x , ZrO _x and TiO _x is within the range of 1 ≦ x ≦ 2. Further, λ ₀ is the set wavelength, and the set wavelength λ ₀ is 5
It was set to 10 nm. * 1: In the mixture of titanium oxide (TiO _x ) and zirconium oxide (ZrO _x ) forming the second layer and the fourth layer, the value of the refractive index with respect to the light having the wavelength λ substantially conforms to the following formula. n ₂ or n ₄ = 2.031 + 23.28 / (λ-217)

<Method of forming laminated film> Each of the washed glass substrates is set in a vacuum vapor deposition apparatus and heated until the surface temperature of the glass substrate reaches about 300 ° C., and the degree of vacuum is 1.0 × 10 ^−5.
After evacuation to mbar, vacuum deposition was started. In addition, in the second layer, the third layer, and the fourth layer, while introducing oxygen gas as a reaction gas, the vacuum degree is 1.5 × 10 ⁻⁵ mbar.
Vacuum deposition was performed. The optical film thickness in each layer is
It was performed by controlling the reflectance on the monitor glass based on the optical film thickness monitoring method.

<Antireflection Property> FIG. 1 shows the spectral reflectance property of each optical component produced in Examples 1 to 5 above.
~ Shown in FIG. From these spectral reflectance characteristics, it is understood that it shows good antireflection characteristics over the entire visible light range (400 nm to 700 nm), and particularly in the wavelength range of 400 to 450 nm. .

<Transmittance characteristics> An antireflection film having the same structure as in Example 1 was formed on a glass substrate made of a glass material "BK7" which does not absorb light in the short wavelength region of visible light, and the wavelength was 400 nm.
When (T + R) was measured from the reflectance R and the transmittance T for the light, it was almost 100%, and it was confirmed that no light quantity loss such as absorption or scattering of light occurred in the inside of each layer and the boundary surface of the layers. confirmed.

In this embodiment, the optical film thickness is 0.5λ _0.
The second layer is composed of the high refractive index material layer described above, but since a mixture of titanium oxide and zirconium oxide is used as the film material, light quantity loss such as absorption and scattering of light occurs even in the short wavelength region. Does not happen.

As the film materials for the second and fourth layers, Table 2
An optical component having the same configuration as in Example 1 was prepared except that the various metal oxides shown in 1 were used, and the optical loss amount at λ = 400 nm was measured. The results are shown in Table 2.

[0025]

[Table 2] From the results in Table 2, it was found that all metal oxides (mixtures) were second
It is suitable as a film material for the fourth layer and the fourth layer, and particularly when a mixture of titanium oxide and zirconium oxide is used,
It is understood that the transmittance characteristics in the short wavelength region are excellent. Further, an optical component having the same configuration as in Example 1 was prepared except that a mixture of titanium oxide and praseodymium oxide was used as the film material for the second and fourth layers, and λ
When the amount of light loss at 400 nm was measured, the amount of light loss was 0%.

<Surface Accuracy> Instead of the glass substrate, an antireflection film made of the same laminated film as in Example 1 was formed on the surfaces of various lenses having different shapes and an ultrathin filter having a thickness of 0.5 mm. The surface accuracy of various lenses and filters before and after the formation of the antireflection film is measured by the Zygo interferometer "MAR".
K-II ”(manufactured by Zygo), the change in surface accuracy was λ / 10 or less, and good results without warpage were obtained. On the other hand, for comparison, when magnesium fluoride was used as the film material of the first layer, the third layer, and the fifth layer, the change in surface accuracy of each lens and filter was measured and found to be λ / 5 or more. From the above, by using silicon oxide as the film material of the third layer, the film stress generated in other layers can be relaxed, the change in surface accuracy can be made small, and warpage can be prevented. .

Example 6 On each glass substrate having a different refractive index, an antireflection film made of a laminated film was formed according to the film material and the optical film thickness shown in Table 3 to manufacture an optical component.

[0028]

[Table 3]

In Table 3, MgF _x , SiO _x and Ta _x
The value of x in O _Y is within the range of 1 ≦ x ≦ 2, and T
The value of _Y in a _x O _Y is within the range of 2.5 ≦ Y ≦ 5. Further, λ ₀ is the set wavelength, and the set wavelength λ ₀ is 510
nm. * 2: Tantalum oxide (T
a _x O _Y ), the value of the refractive index with respect to the light having the wavelength λ substantially follows the following formula. n ₂ or n ₄ = 2.094 + 10.08 / (λ−320)

Example 7 On each glass substrate having a different refractive index, an antireflection film consisting of a laminated film was formed according to the film material and the optical film thickness shown in Table 4 to prepare an optical component.

[0031]

[Table 4]

In Table 4, the value of x in MgF _x , SiO _x , TiO _x and Pr _x O _Z is within the range of 1 ≦ x ≦ 2, and the value of _Z in Pr _x O _Z is 1.5 ≦ x ≦. It is within the range of 4. Further, λ ₀ is the set wavelength, and the set wavelength λ
₀ was 510 nm. * 3: In titanium oxide (TiO _x ) and praseodymium oxide (Pr _x O _Z ) forming the second layer and the fourth layer, the value of the refractive index with respect to the light having the wavelength λ substantially conforms to the following formula. n ₂ or n ₄ = 2.045 + 5.162 / (λ-355)

Spectral reflectance characteristics of the optical components produced in Examples 6 to 7 are shown in FIGS. From these spectral reflectance characteristics, this example also shows good antireflection characteristics over the entire visible light range (400 nm to 700 nm), and particularly good antireflection characteristics in the wavelength range of 400 to 450 nm. It is understood that

<Comparative Example> Comparative Examples 1 and 2 Glass substrates having different refractive indexes (Examples 3 and 5)
On the same glass substrate as used in (1), an antireflection film composed of a laminated film was formed according to the film material and the optical film thickness shown in Table 5 to manufacture an optical component. The laminated film in this example is
It is generally used as a multi-coat material for optical parts, and has a four-layer structure in which the third layer (intermediate refractive index layer) of the basic three-layer structure is replaced by the three-layer equivalent film method.

[0035]

[Table 5]

In Table 5, MgF _x , ZrO _x and TiO
The value of _x in x is within the range of 1 ≦ x ≦ 2. Further, λ ₀ is a set wavelength, and the set wavelength λ ₀ is 510 nm. * 1: In the mixture of titanium oxide (TiO _x ) and zirconium oxide (ZrO _x ) forming the second layer and the fourth layer, the value of the refractive index with respect to the light having the wavelength λ substantially conforms to the following formula. n ₂ or n ₄ = 2.031 + 23.28 / (λ-217)

Spectral reflectance characteristics of the optical components produced in Comparative Example 1 and Comparative Example 2 are shown in FIGS. From these spectral reflectance characteristics, it is understood that the wavelength region where the reflectance is low is narrower than that in FIGS. 3 and 5, and the reflectance of light is particularly large in the wavelength region of 400 to 450 nm. To be done. It is considered that this is due to the dispersion phenomenon of the refractive index and the inhomogeneity phenomenon of the film in the high refractive index layer having a refractive index of around 2.0.

In the optical component of this embodiment, the antireflection film made of a laminated film having a five-layer structure is formed on the surface, and the refractive index and the optical film thickness of each layer are set within specific ranges.
Has good anti-reflection properties over the entire visible light range,
In particular, it has excellent antireflection properties for light in the wavelength range of 400 to 450 nm.

As the film material forming the second layer and the fourth layer, a specific metal oxide (Example 6) or a mixture of specific metal oxides (Examples 1 to 5 and Example 7) is used. Therefore, the light amount loss such as absorption and scattering of light in the short wavelength region of visible light is small, and high transmittance characteristics are obtained.

Further, since silicon oxide whose film stress direction is opposite to that of the film material forming the other layers is used as the film material forming the third layer, the film stress generated in the other layers is relaxed. The surface precision can be changed with a small change.

[0041]

According to the invention of claim 1, it has a good antireflection property in the entire visible light region, and particularly has an excellent light antireflection property in the wavelength region of 400 to 450 nm.

According to the second aspect of the present invention, a light amount loss such as absorption and scattering of light in the short wavelength region of visible light is small, and a high transmittance characteristic is obtained.

According to the third aspect of the invention, the change in surface accuracy is small, and warpage or the like does not occur.

By using the optical component of the present invention for a projection lens of a camera or the like, the reflectance is small over the entire visible light region and the transmittance is high, and ghost and flare are not generated, and color reproduction is extremely high. Done exactly.

[Brief description of drawings]

FIG. 1 is a curve diagram showing a spectral reflectance characteristic of an optical component of Example 1.

FIG. 2 is a curve diagram showing a spectral reflectance characteristic of an optical component of Example 2.

FIG. 3 is a curve diagram showing a spectral reflectance characteristic of an optical component of Example 3.

FIG. 4 is a curve diagram showing a spectral reflectance characteristic of an optical component of Example 4.

FIG. 5 is a curve diagram showing a spectral reflectance characteristic of an optical component of Example 5.

FIG. 6 is a curve diagram showing a spectral reflectance characteristic of an optical component of Example 6.

FIG. 7 is a curve diagram showing a spectral reflectance characteristic of an optical component of Example 7.

8 is a curve diagram showing the spectral reflectance characteristics of the optical component of Comparative Example 1. FIG.

FIG. 9 is a curve diagram showing a spectral reflectance characteristic of an optical component of Comparative Example 2.

Claims (3)

[Claims] 1. An antireflection film comprising a laminated film having a five-layer structure is formed on the surface, and a refractive index n _i and an optical film thickness n _i d _{i of an i-} th layer constituting the laminated film are within the following ranges. An optical component characterized by being present. 0.24λ ₀ ≤ n ₁ d ₁ ≤ 0.26λ ₀ 1.37 ≤ n ₁ ≤ 1.40 0.52λ ₀ ≤ n ₂ d ₂ ≤ 0.56λ ₀ 1.90 ≤ n ₂ ≤ 2.30 0.10 λ ₀ ≤ n ₃ d ₃ ≤ 0.15λ ₀ 1.37 ≤ n ₃ ≦ 1.47 0.05λ ₀ ≦ n ₄ d ₄ ≦ 0.12λ ₀ 1.80 ≦ n ₄ ≦ 2.30 0.08λ ₀ ≦ n ₅ d ₅ ≦ 0.18λ ₀ 1.37 ≦ n ₅ ≦ 1.40 [where i (i: i = 1 to 5) are counted from a medium such as air toward the underlying surface. Further, λ ₀ indicates the set wavelength. ] 2. A metal oxide or a metal oxide selected from the group consisting of tantalum oxide, a mixture of titanium oxide and zirconium oxide, and a mixture of titanium oxide and praseodymium oxide, as the film material forming the second and fourth layers. The optical component according to claim 1, which is a mixture of materials. 3. The optical component according to claim 1, wherein the film material forming the third layer is silicon oxide.