JPH0585778A - Optical parts with antireflection film - Google Patents

Abstract

PURPOSE:To unnecessitate a polishing process for removing the yellowed or scratched part of the surface of the substrate of each of optical parts before forming an antireflection film on the surface of the substrate. CONSTITUTION:When an antireflection film is formed on the surface of the substrate of each of optical parts, the 1st layer of the antireflection film closest to the surface of the substrate is made of an SiOx film and the thickness nd is regulated to nd >=0.25lambda0. (lambda0 is designed wavelength). Since the yellowed or scratched part of the surface of the substrate can be made inconspicuous when the surface of the substrate is seen through the SiO2 film, a polishing process for removing the yellowed or scratched part can be omitted.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Generally, when light is incident on a boundary surface having a different refractive index, a part of the incident light is reflected according to the refractive index ratio on both sides of the boundary surface. Then, the larger the ratio of the refractive indices of the boundary surface, the larger the amount of light reflected by the boundary surface.
For example, since the optical glass used as an optical component has a refractive index in the range of about 1.5 to 1.8, when light enters from a medium such as air, 4 to 8% of the incident light is reflected.

This surface reflection phenomenon is not only a problem that the amount of light that passes through is reduced, but if such an optical component is used as it is for a camera lens or the like, it becomes a major cause of ghost and flare, and is a problem. Therefore, in order to reduce this surface reflection, a thin dielectric film having a wavelength order of light (generally a film thickness of 0.25 λ where λ is the wavelength of light) is provided on the surface of the optical component as an anti-reflection film. It is often practiced to reduce reflected light due to the interference effect of light inside. And as a high-performance antireflection film structure, 2
Many proposals have been made to realize low reflectance in a wide wavelength range by laminating several layers of dielectric films of various types or more.

[0004]

By the way, the surface of the optical glass used as the optical component may be burnt or scratched during the manufacturing process. For the burnt phenomenon, when the optical glass is left in the atmosphere, dew condensation of water drops on the glass surface or contact with water during the polishing process elutes the basic component in the glass to form a thin film. There are a blue burn phenomenon and a white burn phenomenon in which the eluted components cause some chemical reaction to deposit as white spot-like particles. And, the degree of occurrence of burns differs depending on the glass type, but it is SK system, La
Burns are likely to occur in the glass of SF type and SF type.

The cause of scratches on the glass surface is considered to be scratches caused by the presence of a relatively large abrasive during polishing, and the scratches generated during this polishing step are caused by the surface cleaning step. It is expected to be expanded. In particular, such a scratch is often generated in glass having low hardness. When an antireflection film having a conventional laminated structure is provided on the surface of the optical glass where such burns and scratches occur, the burns and scratches are more emphasized and visible, which often causes a problem in appearance. Therefore, in the conventional optical component having the antireflection film, it is necessary to remove the burns and scratches on the surface of the optical component substrate before forming the antireflection film, and the burns and scratches are removed using a relatively soft abrasive. A polishing process was required. Therefore, in the conventional production of an optical component having an antireflection film, a polishing process for removing burns and scratches, which is an essentially unnecessary process, is added, which causes a cost increase.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical component having an antireflection film which does not require a polishing step for removing a burn or a scratch on the surface of an optical component substrate. To do.

[0007]

Therefore, according to the present invention, an antireflection film is formed by laminating a plurality of dielectric films on the surface of a light-transmitting optical component substrate, and the antireflection film is closest to the substrate. The composition of the first layer close to that of silicon oxide (SiO _x , x: 1 ≦ x ≦
2), and the film thickness nd was set to 0.25λ ₀ ≦ nd (λ ₀ is a design wavelength).

The antireflection film is formed by laminating five layers of dielectric films, and the first layer, the second layer, the third layer, the fourth layer and the layers closer to the optical component substrate side in this order. When the fifth layer is used, the refractive indices n _{1 to} n ₅ and the film thickness n ₁ d of the first to fifth layers are set.
_{1 to} n ₅ d ₅ , 0.25λ ₀ ≦ n ₁ d ₁ ≦ 0.50λ ₀ , 1.45 ≦ n ₁ ≦ 1.47 0.03λ ₀ ≦ n ₂ d ₂ ≦ 0.07λ ₀ , 1.90 ≦ n ₂ ≦ 2.20 0.03λ ₀ ≦ n ₃ d ₃ ≦ 0.15λ ₀ , 1.36 ≦ n ₃ ≦ 1.65 0.45λ ₀ ≦ n ₄ d ₄ ≦ 0.54λ ₀ , 1.90 ≦ n ₄ ≦ 2.20 0.24λ ₀ ≦ n ₅ d ₅ ≦ 0.26λ ₀ , 1.36 ≦ n _It was set within the range of ₅ ≤ 1.40.

Further, the composition of the dielectric films of the second layer and the fourth layer is any one of a mixture of zirconium oxide and titanium oxide, a mixture of praseodymium oxide and titanium oxide, and tantalum oxide. The composition of the body film was any one of silicon oxide, magnesium fluoride and aluminum oxide, and the composition of the dielectric film of the fifth layer was magnesium fluoride.

[0010]

According to such a construction, the composition of the first layer closest to the optical substrate side of the antireflection film formed by laminating a plurality of dielectric films is silicon oxide (SiO _x , x: 1 ≦ x ≦ 2). ), And the film thickness nd is set to 0.25λ ₀ ≦ nd (λ ₀ is a design wavelength), even if there are burns or scratches on the surface of the optical component substrate, these become inconspicuous.

Further, the antireflection film is formed by laminating five layers of dielectric films, and the first one is arranged in order from the one closer to the optical component substrate side.
Layer 1, 2nd layer, 3rd layer, 4th layer and 5th layer
Refractive index of the layer-fifth layer n ₁ ~n ₅ and the thickness n ₁ d ₁ ~n ₅
d ₅ is 0.25λ ₀ ≦ n ₁ d ₁ ≦ 0.50λ ₀ , 1.45 ≦ n ₁ ≦ 1.47 0.03λ ₀ ≦ n ₂ d ₂ ≦ 0.07λ ₀ , 1.90 ≦ n ₂ ≦ 2.20 0.03λ ₀ ≦ n ₃ d ₃ ≤0.15 λ ₀ , 1.36 ≤ n ₃ ≤ 1.65 0.45 λ ₀ ≤ n ₄ d ₄ ≤ 0.54 λ ₀ , 1.90 ≤ n ₄ ≤ 2.20 0.24 λ ₀ ≤ n ₅ d ₅ ≤ 0.26 λ ₀ , 1.36 ≤ n ₅ ≤ 1.40 Within the range, light in the visible light range (wavelengths between 400 nm and 70 nm
(0 nm), it has an excellent antireflection property that its reflectance is stable at 1% or less.

Further, the composition of the dielectric films of the second layer and the fourth layer is any one of a mixture of zirconium oxide and titanium oxide, a mixture of praseodymium oxide and titanium oxide, and tantalum oxide. When the composition of the body film is any one of silicon oxide, magnesium fluoride and aluminum oxide and the composition of the dielectric film of the fifth layer is magnesium fluoride, the reflectance can be further reduced. The prevention performance can be improved.

[0013]

EXAMPLES Examples of the present invention will be described below. First, a comparison will be made between the case where a dielectric film of silicon oxide SiO _x (1 ≦ x ≦ 2) is provided on the surface of an optical component substrate having a burn or a scratch, and a conventional dielectric film. As the glass for the optical component substrate, select SK15, which is prone to burns and scratches,
A substrate sample is processed into a shape with a diameter of 30 mm and a thickness of 3 mm and subjected to pitch polishing. After washing this substrate sample with alcohol, ether, etc., it is stored at room temperature in a container with a relative humidity of 100% for 5 days. When the surface of the substrate sample after the high humidity storage was observed in this manner, white spots were observed, and fine scratches were observed during pitch polishing. Silicon oxide SiO _x (1 ≦ x ≦ 2), magnesium fluoride Mg was formed on the surface of the substrate sample where the whitening and scratches were generated.
_{F x (1 ≦ x ≦ 2} ) and OH-5 ((Ltd.) OPTRON product names, and titanium oxide mixtures zirconium oxide) observing a dielectric film formed by the surface of a suitable thickness for each composition did. The results are shown in Table 1.

The evaluation criteria of the surface condition of each sample in Table 1
Is A rank when no discoloration or scratches are observed.
Then, the surface condition before forming the dielectric film (after polishing and cleaning,
Left for 5 days at room temperature and 100% relative humidity)
A, depending on the degree of burns and scratches observed below.
It was set to 5 stages from E to E. Also, λ in the table₀Is the design wavelength,
λ ₀= 510 nm.

[0015]

[Table 1]

As is clear from Table 1, a SiO _x film having a film thickness of 0.25λ ₀ or more is better than the surface condition before film formation, and has the effect of making the effects of burns and scratches inconspicuous. I know there is. The observation result of the MgF _x film is the same as the surface state before the film formation, regardless of the film thickness. O
On the other hand, in the H-5 film, as the film thickness increases, the appearance deterioration such as burns and scratches is emphasized.

Therefore, by providing the SiO _x film having a film thickness of 0.25λ ₀ or more on the surface of the optical component substrate, it is possible to make the appearance deterioration such as scoring and scratches on the optical component substrate surface inconspicuous. It is possible to omit the polishing step for removing scratches and the like. Next, the antireflection effect of the antireflection film of the present invention will be described. BK as an optical component board
Using three kinds of optical glass of 7, SK15, LaK8,
Each is processed into a shape with a diameter of 30 mm and a thickness of 3 mm, the surface is pitch-polished, washed with alcohol, ether, etc., and then left at room temperature in an environment of 100% relative humidity for 5 days. Thereafter, different antireflection films of Examples 1 to 3 shown in Table 2 are formed on the surfaces of the three substrate samples.

As a method for forming a film, a vacuum vapor deposition method was used, a sample substrate was set in a vacuum chamber, heated to 300 ° C., and vapor deposition was started when the degree of vacuum reached 1.0 × 10 ⁻⁵ mbar. When the first layer, the second layer, and the fourth layer are deposited, a vacuum degree of 1.5 × 10 ⁻⁴ is used as a reaction gas in the vacuum chamber.
Deposition was carried out while introducing oxygen gas to mbar. Also,
The film thickness of each layer was adjusted by controlling the reflectance on the monitor glass based on the optical film thickness monitoring method.

[0019]

[Table 2]

The first layer to the fifth layer in Table 2 are the first layer, the second layer and the third layer in order from the layer closest to the optical component substrate side.
The layers were the fourth layer and the fifth layer. Then, the optical components of Examples 1 to 3 thus created were taken out into the atmosphere, the surface thereof was observed, and the surface condition was evaluated (same as the evaluation method in Table 1). The results are shown in Table 3.

[0021]

[Table 3]

Comparative Examples 1 and 2 in Table 3 are the same as Example 2,
The first layer of No. 3 is obtained by replacing SiO _{x with} MgF _x . As is clear from Table 3, SiO _{x is used} as the first layer.
In each of Examples 1 to 3 in which the film is provided, the evaluation of the surface state after the film formation is higher than that in the surface state before the film deposition, while each comparison in which the MgF _x film is provided as the first layer Examples 1 and 2
The evaluation of the surface state is the same as or lower than that of the above. By providing the SiO _x film as the first layer, it is possible to make the surface of the substrate inconspicuous such as burn and scratch.

Further, FIGS. 1 to 3 show the reflectance characteristics of the first to third embodiments. As is clear from FIGS.
In the region of 0 nm to 680 nm, the reflectance R is R ≦ 0.5%
And has high performance as a reflectance characteristic. In the present embodiment, the second layer and the fourth layer were made of a mixture of titanium oxide and zirconium oxide, and the third layer was made of MgF _x . However, the present invention is not limited to this, and the second layer and the fourth layer may be used. , A mixture of praseodymium oxide and titanium oxide or tantalum oxide may be used, and similar results could be obtained by using silicon oxide or aluminum oxide in the third layer.

[0024]

As described above, according to the present invention, the design wavelength λ is set as the first layer closest to the substrate side of the antireflection film.
_When it is set to ₀ , by providing an SiO _x film having a film thickness of 0.25λ ₀ or more, it is possible to make the burn-off and scratches on the substrate surface inconspicuous. The polishing step for removal can be omitted, the productivity can be improved, and the manufacturing cost of the optical component with the antireflection film can be reduced.

Further, the antireflection film has a laminated structure of 5 layers,
By specifying the composition, film thickness, and refractive index of each layer, it becomes possible to manufacture an optical component having a high-performance antireflection film having better reflectance characteristics than ever before.

[Brief description of drawings]

FIG. 1 is a diagram showing the reflectance characteristics of Example 1 shown in Table 2 of the optical component of the present invention.

FIG. 2 is a diagram showing reflectance characteristics of Example 2 shown in Table 2 above.

FIG. 3 is a diagram showing reflectance characteristics of Example 3 shown in Table 2 above.

Claims (3)

[Claims] 1. A plurality of light-transmitting optical component substrates are provided on a surface thereof.
An antireflection film is formed by laminating dielectric films, and the antireflection film is formed.
The composition of the first layer closest to the substrate side is silicon oxide (Si
O_x, X: 1 ≦ x ≦ 2) and the film thickness nd is 0.25λ
₀≦ nd (λ ₀Is the design wavelength)
An optical component having an anti-reflection film. 2. The antireflection film is formed by laminating 5 layers of dielectric films, and the first layer, the second layer, the third layer, the fourth layer, and the like in order from the side closer to the optical component substrate. When the fifth layer is used, the refractive index n _{1 to} n ₅ and the film thickness n ₁ d _{1 to} n of the first to fifth layers are set.
₅ d ₅ is 0.25λ ₀ ≤n ₁ d ₁ ≤0.50λ ₀ , 1.45 ≤n ₁ ≤1.47 0.03λ ₀ ≤n ₂ d ₂ ≤0.07λ ₀ , 1.90 ≤n ₂ ≤2.20 0.03λ ₀ ≤n ₃ d ₃ ≤0.15 λ ₀ , 1.36 ≤ n ₃ ≤ 1.65 0.45 λ ₀ ≤ n ₄ d ₄ ≤ 0.54 λ ₀ , 1.90 ≤ n ₄ ≤ 2.20 0.24 λ ₀ ≤ n ₅ d ₅ ≤ 0.26 λ ₀ , 1.36 ≤ n ₅ ≤ 1.40 The optical component having the antireflection film according to claim 1, wherein the optical component is within the range. 3. The composition of the second and fourth dielectric films is any one of a mixture of zirconium oxide and titanium oxide, a mixture of praseodymium oxide and titanium oxide, and tantalum oxide, and a dielectric film of the third layer is formed. The antireflection coating according to claim 2, wherein the composition of the body film is one of silicon oxide, magnesium fluoride and aluminum oxide, and the composition of the dielectric film of the fifth layer is magnesium fluoride. Optical component having a film.