JP7493918B2 - Optical member with anti-reflection film and method for producing same - Google Patents

Description

The present invention relates to an optical component with an anti-reflection coating and a method for manufacturing the same.

It is common for optical components such as lenses to have an anti-reflection coating on their surfaces. For example, as described in Patent Document 1, the anti-reflection coating is formed by laminating multiple layers with different refractive indices. Patent Document 1 claims that by appropriately adjusting the refractive index of each layer, it is possible to further lower the refractive index from the visible light region to the near infrared region, and further widen the anti-reflection band.

JP 2004-163549 A

Patent Document 1 claims that the reflectance in the wavelength range of 380 nm to 980 nm can be reduced to 1% or less, but in recent years, there has been a demand to expand the anti-reflection function to a wavelength range of 1000 nm, and there are also strict requirements for the reliability of the coating in high temperatures and high humidity.

The present invention was made based on the above-mentioned awareness, and aims to provide an optical component with an anti-reflection coating that has excellent anti-reflection function in the wavelength range of 400 nm to 1000 nm and is highly reliable, as well as a manufacturing method thereof.

The present invention is an optical member with an antireflection film, in which an antireflection film is formed on a surface of a substrate, the substrate being a glass lens, the antireflection film being formed by alternately laminating low refractive index layers and high refractive index layers, the total number of the low refractive index layers and the high refractive index layers being 11 to 15 layers, the outermost layer of the antireflection film being a single layer of _MgF2 as the low refractive index layer , the low refractive index layers other than the outermost layer having a density of 2.158 g/cm3 ^or more and 2.174 g/cm3 ^or less, and a spectral reflectance in a wavelength range of 400 nm or more and 1000 nm or less being 1% or less .

In the present invention, the refractive index (wavelength 550 nm) of the low refractive index layer other than the outermost layer is preferably 1.4425 to 1.4525 .

In the present invention, the low refractive index layers other than the outermost surface layer are preferably formed of a single layer of SiO ₂ or a mixed layer containing SiO ₂ .

The present invention is a method for manufacturing an optical member with an antireflection film, which comprises alternately laminating low and high refractive index layers on a surface of a substrate to form an antireflection film, the substrate being a glass lens, the low refractive index layer being formed by deposition without using an ion-assisted deposition method, the high refractive index layer being formed by an ion-assisted deposition method, the total number of the low refractive index layers and the high refractive index layers being 11 to 15, the outermost layer of the antireflection film being formed of a single layer of _MgF2 as the low refractive index layer , the density of the low refractive index layer other than the outermost layer being adjusted to 2.158 g/cm3 or more and 2.174 g/cm3 or less, and ^the spectral ^reflectance in a wavelength range of 400 nm or more and 1000 nm or less being 1% or less.

In the present invention, the pressure during deposition of the low refractive index layers other than the outermost layer is preferably adjusted within the range of 1.5×10 ⁻² Pa to 3.2×10 ⁻² Pa.

In the present invention, it is preferable to use a simple substance of SiO ₂ or a mixture containing SiO ₂ as an evaporation material for the low refractive index layers other than the outermost layer .

According to the present invention, the spectral reflectance can be suppressed to 1% or less in the wavelength range of 400 nm to 1000 nm.

1 is a schematic diagram of an anti-reflection coated optical member according to an embodiment of the present invention. 1 is a partially enlarged schematic view of an antireflection-coated optical member according to an embodiment of the present invention. 1 is a graph showing the relationship between wavelength and spectral reflectance R for Examples 1 to 3 and a comparative example.

The following is a detailed description of an embodiment of the present invention (hereinafter, simply referred to as "this embodiment"). Note that in the following, "~" may be used, but this includes both the lower limit and the upper limit.

<Optical member with anti-reflection film>
As a result of extensive research into the antireflection function of antireflection-coated optical members, the inventors have developed an antireflection-coated optical member that has excellent antireflection function and high reliability in the wavelength range of 400 nm to 1000 nm by adjusting the density of the low refractive index layer. That is, the antireflection-coated optical member of this embodiment is characterized in that the antireflection film has a laminated structure of a low refractive index layer and a high refractive index layer, and the density of the low refractive index layer is 2.1 g/ ^cm3 or more and 2.2 g/ ^cm3 or less.

Figure 1 is a schematic diagram of an optical component with an anti-reflection coating according to this embodiment. The optical component with an anti-reflection coating 1 shown in Figure 1 is composed of a substrate 2 and an anti-reflection coating 3 formed on a surface 2a of the substrate 2.

The substrate 2 is made of glass, plastic, or the like, and is preferably made of glass. Although not particularly limited, the substrate 2 is, for example, a glass lens for a surveillance camera or an in-vehicle camera. The surface of the substrate 2 on which the anti-reflection film 3 is formed is, for example, aspheric. The substrate 2 in FIG. 1 is, for example, a meniscus lens with negative power, but it may also be a meniscus lens with positive power, or a biconvex lens or a biconcave lens, etc.

In FIG. 1, the anti-reflection coating 3 is formed on the surface 2a of the substrate 2, but it may be formed on both the surfaces 2a and 2b.
The anti-reflection film 3 will be described in more detail below.

<Anti-reflection coating>
As shown in FIG. 2 , the antireflection coating 3 of the present embodiment is formed by alternately laminating low refractive index layers 4 and high refractive index layers 5 from the surface (optical surface) of the substrate 2, with the uppermost layer being an outermost layer 6 that comes into contact with the outside air.

Each low-refractive index layer 4 has a lower refractive index than each high-refractive index layer 5. On the other hand, the high-refractive index layer 5 may have a higher refractive index than the substrate 2. In addition, the anti-reflection film 3 is adjusted so that it has a lower reflectance than the substrate 2 alone.

The density of the low refractive index layer 4 is 2.1 g/cm ³ or more and 2.2 g/cm ³ or less. If the density exceeds the upper limit of the density range, the desired low refractive index cannot be obtained (the refractive index becomes too high), and if the density is below the lower limit, the number of voids increases. If the number of voids increases too much, moisture enters the voids, affecting the properties of the film, or the adhesion of the film decreases due to the voids. In addition, the density of the low refractive index layer 4 is preferably 2.132 g/cm ³ or more and 2.199 g/cm ³ or less, more preferably 2.132 g/cm ³ or more and 2.191 g/cm ³ or less, and even more preferably 2.158 g/cm ³ or more and 2.174 g/cm ³ or less.

In this embodiment, as described below, when forming the low refractive index layer 4 by a vapor deposition method, the ion assisted deposition (IAD) method is not used. On the other hand, when forming the high refractive index layer 5 by a vapor deposition method, the ion assisted deposition method is used. This makes it possible to reduce the density of the low refractive index layer 4 to within the above range. Note that the density of the high refractive index layer 5 is higher when the ion assisted deposition method is used than when the ion assisted deposition method is not used.

In this embodiment, the low refractive index layer 4 can be adjusted to a relatively low density, thereby making it possible to reduce the refractive index of the low refractive index layer 4. Specifically, the refractive index of the low refractive index layer 4 (wavelength 550 nm) is 1.41 or more and 1.47 or less, preferably 1.4245 or more and 1.469 or less, more preferably 1.4245 or more and 1.464 or less, and even more preferably 1.4425 or more and 1.4525 or less.

In this way, by keeping the density and refractive index of the low refractive index layer 4 low within the above range, the spectral reflectance in the wavelength range of 400 nm to 1000 nm can be kept to 1% or less. In this embodiment, the spectral reflectance in the wavelength range of 410 nm to 430 nm can be kept to 0.8% or less. In this embodiment, the spectral reflectance in the wavelength range of 480 nm to 600 nm can preferably be kept to 0.5 or less, and further, the spectral reflectance in the wavelength range of 650 nm to 1000 nm can be kept to 0.8 or less.

In this embodiment, the total number of low-refractive index layers 4 and high-refractive index layers 5 is not limited, but is preferably about 9 to 19 layers, and more preferably 11 to 15 layers. By increasing the number of layers, the wavelength range in which the spectral reflectance is 1% or less can be expanded. However, it has been found from the experiment described below that if the low-refractive index layer 4 is formed using the ion-assisted deposition method, the wavelength range in which the spectral reflectance is 1% or less cannot be expanded to a wavelength of 1000 nm. Therefore, the inventors have succeeded in expanding the wavelength range in which the spectral reflectance is 1% or less to a wavelength of 1000 nm by forming the low-refractive index layer 4 without using the ion-assisted deposition method and reducing the density of the low-refractive index layer 4 compared to conventional methods.

In addition, in FIG. 1, a low refractive index layer 4 is used as the bottom layer that contacts the surface of the substrate 2, but the bottom layer can be appropriately selected from the viewpoint of adhesion to the substrate 2. In other words, it is optional whether or not to use a low refractive index layer 4 as the bottom layer.

Next, preferred materials for the low refractive index layer 4 and the high refractive index layer 5 will be described.
In this embodiment, the low refractive index layer 4 is preferably formed of a single layer of SiO ₂ or a mixed layer containing SiO _2. The materials of the multiple low refractive index layers 4 laminated on the antireflection film 3 may be the same or different.

In this embodiment, the high refractive index layer 5 is preferably formed of a single layer or a mixed layer containing two or more selected from ZrO _x (x is 1.5 to 2), TiO _x (x is 1 to 2), TaO _x (x is 2 to 2.5), and NbO _x (x is 2 to 2.5). It is preferable to use ZrO ₂ for ZrO _x , Ti ₃ O ₅ or Ti ₂ O ₅ for TiO _x , Ta ₂ O ₅ for TaO _x , and Nb ₂ O ₅ for NbO _x . The above metal oxides do not need to have a stoichiometric composition, as long as the composition ratio of oxygen is within the above range of x.

The materials of the multiple high refractive index layers 5 stacked within the anti-reflection film 3 may be the same or different.

In addition, in this embodiment, the outermost layer 6 of the anti-reflection film 3 is preferably a single layer of MgF ₂ , a single layer of SiO ₂ , or a mixed layer containing at least one of MgF ₂ and SiO _2. The outermost layer 6 is an adjustment layer for suppressing the reflectance of the anti-reflection film 3 in which the low refractive index layer 4 and the high refractive index layer 5 are laminated to within a predetermined value. That is, the outermost layer 6 is provided as the uppermost layer of the low refractive index layer 4 and the high refractive index layer 5, so that the reflectance can be optimized. For example, in a configuration in which SiO ₂ is used as the low refractive index layer 4 and Ta ₂ O ₅ is used as the high refractive index layer 5, it is preferable to use MgF ₂ for the outermost layer 6 from the viewpoint of adjusting the reflectance. As shown in Table 1 below, the refractive index of MgF ₂ can be lower than that of SiO ₂ .

The film density was calculated using the refractive index and density of the evaporation material according to the following formula (1).
Film density = (refractive index of film / refractive index of evaporating material) x theoretical density of evaporating material (1)

As shown in Table 1, the refractive index is _MgF2 < _SiO2 . In this embodiment, however, from the viewpoints of reliability and adhesion between each layer, it is preferable to use _SiO2 rather than _MgF2 for the low refractive index layer 4, and it is preferable to use _MgF2 for the outermost surface layer 6 as an adjustment layer for the reflectance of the antireflection film 3.

<Method of manufacturing an optical member with an anti-reflection film>
A method for producing the anti-reflection coated optical member of this embodiment shown in FIG. 2 will be described.
In this embodiment, the anti-reflection film 3 is formed by alternately laminating low refractive index layers 4 and high refractive index layers 5 on the surface of the substrate 2 .

At this time, the low refractive index layer 4 is formed by deposition without using the ion-assisted deposition method, and the high refractive index layer 5 is formed by the ion-assisted deposition method.

This allows the low refractive index layer 4 to be formed at a low density, and the high refractive index layer 5 to be formed at a high density. Here, "high density" and "low density" refer to the density of each layer compared with the application of the ion-assisted deposition method.

There is no limitation on the atmosphere in which the low refractive index layer 4 is deposited, but it is preferable to use, for example, an atmosphere of oxygen, argon, or nitrogen alone, or a mixture of these.

In this embodiment, the deposition pressure when depositing the low refractive index layer 4 is preferably adjusted in the range of 3×10 ⁻³ Pa to 8×10 ⁻² Pa. The deposition pressure is more preferably set to 3×10 ⁻³ Pa to 5.8×10 ⁻² Pa, even more preferably set to 7.8×10 ⁻³ Pa to 5.8×10 ⁻² Pa, and even more preferably set to 1.5×10 ⁻² Pa to 3.2×10 ⁻² Pa.

This allows the density of the formed low refractive index layer 4 to be 2.1 g/cm ³ or more and 2.2 g/cm ³ or less, preferably 2.132 g/cm ³ to 2.199 g/cm ³ , more preferably 2.132 g/cm ³ to 2.191 g/cm ³ , and even more preferably 2.158 g/cm ³ to 2.174 g/cm ³ .

In this embodiment, it is preferable to use, as the evaporation material of the low refractive index layer 4, a simple substance of SiO ₂ or a mixture containing SiO ₂ .

In this embodiment, it is preferable to use, as the evaporation material of the high refractive index layer 5, a single material selected from ZrO ₂ , Ti ₃ O ₅ , Ta ₂ O ₅ , and Nb ₂ O ₅ or a mixture containing two or more of them.

In the present embodiment, it is preferable to use a single material selected from _MgF2 and _SiO2 or a mixture containing two or more of them as the evaporation material of the outermost surface layer 6. It is preferable to select _MgF2 as the evaporation material of the outermost surface layer 6.

As described above, the optical member 1 with anti-reflection coating of this embodiment can reduce the density of the low refractive index layer 4, thereby lowering the refractive index. In this embodiment, the spectral reflectance can be suppressed to 1% or less in the wavelength range of 400 nm to 1000 nm. Furthermore, the optical member 1 with anti-reflection coating of this embodiment has excellent adhesion between the layers, and is less susceptible to peeling or cracking even in high temperature and high humidity environments, providing high reliability.

In addition, according to the manufacturing method of the optical component 1 with an anti-reflection film of this embodiment, by controlling whether or not to apply the ion-assisted deposition method when forming the low refractive index layer 4 and the high refractive index layer 5, it is possible to easily manufacture an optical component 1 with an anti-reflection film that has excellent anti-reflection function and high reliability.

In addition, in this embodiment, the low refractive index layer is formed without ion-assisted deposition, so the time the ion gun is used to form the anti-reflective coating 3 can be reduced, and the temperature change during film formation can be reduced. This makes it possible to reduce the variation in the light reflection characteristics of the formed anti-reflective coating 3.

Hereinafter, this embodiment will be described in more detail using examples and comparative examples. In the experiment, examples 1 to 3 and a comparative example shown below were produced.

[Examples 1 to 3]
In Examples 1 to 3, the materials shown in Table 2 below were used, and in the Comparative Example, the materials shown in Table 3 below were used, and antireflection coatings were obtained by depositing _SiO2 as a low refractive index layer, _Ta2O5 as a high refractive index layer, and _MgF2 as _an outermost surface layer, as shown in Tables 2 and 3. The substrate was a lens molded using BACD14 glass (manufactured by HOYA Corporation).

In Examples 1 to 3 shown in Table 2, the low refractive index layer was formed by vacuum deposition without ion-assisted deposition. As shown in Table 2, the density of _SiO2 was 2.191 g/ ^cm3 in Example 1, 2.158 g/ ^cm3 in Example ₂ , and 2.132 g/ ^cm3 in Example 3. The _deposition pressure in vacuum deposition to obtain these densities is shown in Table 4 below. As shown in Table 4, the density can be changed by changing the deposition pressure.

On the other hand, in the comparative example, _SiO2 was deposited by ion-assisted deposition. The data for "with IAD" shown in Table 4 applies to the comparative example.

The relationship between wavelength and reflectance was investigated using Examples 1 to 3 and the Comparative Example. The reflectance was measured using a microscope-type spectrometer (USPM-RUIII) manufactured by Olympus Corporation. In the experiment, the spectral reflectance of the incident light was measured with an incident angle of 0°.

Figure 3 is a graph showing the relationship between wavelength and reflectance in Examples 1 to 3 and the Comparative Example.

As shown in Figure 3, it was found that in Examples 1 to 3, the wavelength range of the spectral reflectance R of 1% or less can be expanded compared to the comparative example. Specifically, it was found that in the examples, the spectral reflectance can be made 1% or less in the wavelength range of 400 nm to 1000 nm. It was also found that in the examples, the spectral reflectance can be made 0.5 or less in the wavelength range of 480 nm to 600 nm, and further, the spectral reflectance can be made 0.8 or less in the wavelength range of 650 nm to 1000 nm.

Based on the experimental results in Table 4, the preferred film formation pressure, density, and refractive index were determined. That is, as shown in Table 4, when SiO ₂ is formed without ion-assisted deposition, if the film formation pressure is 8.2×10 ⁻² Pa, the density becomes quite small at 2.098, and it was found that voids are likely to occur in the low refractive index layer. Therefore, based on the experimental results in Table 4, the film formation pressure is set to 3×10 ⁻³ Pa to 8×10 ⁻² Pa, preferably 3×10 ⁻³ Pa to 5.8×10 ⁻² Pa, more preferably 7.8×10 ⁻³ Pa to 5.8×10 ⁻² Pa, and even more preferably 1.5×10 ⁻² Pa to 3.2×10 ⁻² Pa.

The density of the low refractive index layer is 2.1 g/cm ³ to 2.2 g/cm ³ , preferably 2.132 g/cm ³ to 2.199 g/cm ³ , more preferably 2.132 g/cm ³ to 2.191 g/cm ³ , and even more preferably 2.158 g/cm ³ to 2.174 g/cm ³ .

The refractive index of the low refractive index layer (wavelength 550 nm) is 1.41 to 1.47, preferably 1.4245 to 1.469, more preferably 1.4245 to 1.4640, and even more preferably 1.4425 to 1.4525.

In addition, it was found that, when SiO ₂ (low refractive index layer) is formed by ion-assisted deposition as in the comparative example, the substrate is heated by the radiant heat of the ion gun during film formation, and the temperature change during film formation becomes large. On the other hand, it was found that, when SiO ₂ (low refractive index layer) is formed without ion-assisted deposition as in this embodiment, the use time of the ion gun can be reduced, and therefore the temperature change during film formation can be reduced. It was found that, by reducing the temperature change during film formation as in this embodiment, the characteristic variation of the formed anti-reflection film can be reduced.

Next, a high temperature and humidity test was conducted using Example 2. The experimental conditions were a temperature of 60°, humidity of 90%, and an experimental time of 240 hours. After the test, no abnormalities in appearance such as peeling or cracks were observed. As a result, a highly reliable optical component with an anti-reflection film was obtained.

The optical member with anti-reflection coating of the present invention can be preferably applied to glass lenses for vehicle-mounted cameras, etc.

1: Optical member with anti-reflection film 2: Substrate 3: Anti-reflection film 4: Low refractive index layer 5: High refractive index layer 6: Outermost layer

Claims (6)

An anti-reflection-coated optical member having an anti-reflection film formed on a surface of a substrate,
The substrate is a glass lens,
The antireflection film is formed by alternately laminating low refractive index layers and high refractive index layers,
the total number of the low refractive index layers and the high refractive index layers is 11 to 15;
The outermost surface layer of the antireflection film is a single layer of _MgF2 as the low refractive index layer , and the low refractive index layer other than the outermost surface layer has a density of 2.158 g/cm3 ^or more and 2.174 g/cm3 ^or less;
An optical member with an anti-reflection film, characterized in that the spectral reflectance in the wavelength region of 400 nm or more and 1000 nm or less is 1% or less. 2. The optical member with an anti-reflection film according to claim 1, wherein the refractive index (wavelength 550 nm) of the low refractive index layer other than the outermost layer is 1.4425 to 1.4525 . 3. The optical member with an antireflection film according to claim 1, wherein the low refractive index layer other than the outermost layer is formed of a single layer of _SiO2 or a mixed layer containing _SiO2 . A method for producing an optical member with an antireflection film, comprising alternately laminating low refractive index layers and high refractive index layers on a surface of a substrate to form an antireflection film, the method comprising the steps of:
The substrate is a glass lens,
The low refractive index layer is formed by deposition without using an ion-assisted deposition method, and the high refractive index layer is formed by an ion-assisted deposition method;
The total number of the low refractive index layers and the high refractive index layers is 11 to 15,
The outermost surface layer of the antireflection film is formed of a single layer of _MgF2 as the low refractive index layer ,
The density of the low refractive index layer other than the outermost layer is adjusted to 2.158 g/ ^cm3 or more and 2.174 g/cm3 ^or less,
The spectral reflectance in the wavelength range of 400 nm to 1000 nm is 1% or less.
The present invention relates to a method for producing an optical member with an anti-reflection film. 5. The method for producing an anti-reflection coated optical member according to claim 4, wherein a deposition pressure during deposition of the low refractive index layers other than the outermost layer is adjusted in a range of 1.5×10 ⁻² Pa to 3.2×10 ⁻² Pa. 6. The method for producing an anti-reflection coated optical member according to claim 4, wherein a single material of _SiO2 or a mixture containing _SiO2 is used as an evaporation material for the low refractive index layer other than the outermost layer .

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