JP2021026163A - Optical member with antireflection film and method for manufacturing the same - Google Patents

Abstract

To provide an optical member with an antireflection film having excellent antireflection function in a wavelength region of 400 nm to 1000 nm as well as high reliability, and a method for manufacturing the optical member with an antireflection film.SOLUTION: An optical member with an antireflection film has an antireflection film (3) formed on a surface of a substrate (2) and is characterized in that: the antireflection film comprises low refractive index layers (4) and high refractive index layers (5) alternately laminated; and the low refractive index layer has a density of 2.1 g/cm3 or more and 2.2 g/cm3 or less. The refractive index (at a wavelength of 550 nm) of the low refractive index layer is preferably 1.41 to 1.47.SELECTED DRAWING: Figure 2

Description

The present invention relates to an optical member with an antireflection film and a method for manufacturing the same.

It is common practice to provide an antireflection film on the surface of optical components such as lenses. The antireflection film is formed by laminating a plurality of layers having different refractive indexes, for example, as described in Patent Document 1. Patent Document 1 states that by appropriately adjusting the refractive index of each layer, the refractive index in the visible light region to the near infrared region can be further lowered, and the antireflection band can be further widened.

Japanese Unexamined Patent Publication No. 2004-163549

Patent Document 1 states that the reflectance in the wavelength range of 380 nm to 980 nm can be reduced to 1% or less. However, due to recent needs, it is desired to widen the antireflection function to the wavelength range of 1000 nm, and the reliability of the coating such as high temperature and high humidity Is also strictly required.

The present invention has been made based on the above awareness of the problems, and is an optical member with an antireflection film having an excellent antireflection function and high reliability in a wavelength range of 400 nm to 1000 nm, and a method for manufacturing the same. The purpose is to provide.

The present invention is an optical member with an antireflection film in which an antireflection film is formed on the surface of a base material, and the antireflection film is obtained by alternately laminating low refractive index layers and high refractive index layers. The density of the low refractive index layer is 2.1 g / cm ³ or more and 2.2 g / cm ³ or less.

In the present invention, the refractive index (wavelength 550 nm) of the low refractive index layer is preferably 1.41 to 1.47.

In the present invention, the low refractive index layer is preferably formed of a mixed layer comprising a single layer or SiO ₂ in SiO _2.

In the present invention, the outermost surface layer of the antireflection film 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.

In the present invention, the spectral reflectance in the wavelength range of 400 nm or more and 1000 nm or less is preferably 1% or less.

The present invention is a method for manufacturing an optical member with an antireflection film, in which low refractive index layers and high refractive index layers are alternately laminated on the surface of a base material to form an antireflection film. It is preferable that the layer is formed by vapor deposition without using the ion-assisted vapor deposition method, and the high refractive index layer is formed by the ion-assisted vapor deposition method.

In the present invention, it is preferable to adjust the film forming pressure when forming the low refractive index layer in ^{the range of 3 × 10 -3} Pa or more and 8 × 10 ^{-2 Pa or less.}

In the present invention, as the evaporation material of the low refractive index layer, it is preferable to use a mixed material containing a simple substance or SiO ₂ in SiO _2.

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.

It is a schematic diagram of the optical member with an antireflection film of this embodiment. It is a partially enlarged schematic diagram of the optical member with an antireflection film of this embodiment. 3 is a graph showing the relationship between the wavelengths of Examples 1 to 3 and Comparative Examples and the spectral reflectance R.

Hereinafter, embodiments for carrying out the present invention (hereinafter, simply referred to as “the present embodiment”) will be described in detail. In the following, "~" may be used, but both the lower limit value and the upper limit value shall be included.

<Optical member with antireflection film>
As a result of diligent research on the antireflection function of the optical member with an antireflection film, the present inventors have an excellent antireflection function in the wavelength range of 400 nm to 1000 nm by adjusting the density of the low refractive index layer. At the same time, we have developed an optical member with an antireflection film with high reliability. That is, the optical member with an antireflection film of the present embodiment has an antireflection film having 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 / cm ³ or more. It is characterized by being 2.2 g / cm ^{3 or less.}

FIG. 1 is a schematic view of an optical member with an antireflection film of the present embodiment. The optical member 1 with an antireflection film shown in FIG. 1 includes a base material 2 and an antireflection film 3 formed on the surface 2a of the base material 2.

The base material 2 is glass, plastic, or the like, and is particularly preferably glass. Although not particularly limited, the base material 2 is, for example, a glass lens for a surveillance camera or an in-vehicle camera. Further, the surface of the base material 2 on which the antireflection film 3 is formed is, for example, an aspherical surface. The base material 2 in FIG. 1 is, for example, a meniscus lens having a negative power, but may be a meniscus lens having a positive power, a biconvex lens, a biconcave lens, or the like.

In FIG. 1, the antireflection film 3 is formed on the surface 2a of the base material 2, but may be formed on both the surfaces 2a and 2b.
Hereinafter, the antireflection film 3 will be described in more detail.

<Anti-reflective coating>
As shown in FIG. 2, in the antireflection film 3 of the present embodiment, the low refractive index layer 4 and the high refractive index layer 5 are alternately laminated from the surface (optical surface) of the base material 2, and the uppermost layer is formed. It is the outermost surface 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 be higher than the refractive index of the base material 2. Further, the antireflection film 3 is adjusted so that the reflectance is lower than that of the base material 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 upper limit of the density range is exceeded, the desired low refractive index cannot be obtained (the refractive index becomes too high), and if it is lower than the lower limit, the number of voids increases. If there are too many voids, water will enter the voids and affect the characteristics of the film, or the voids will reduce the adhesion of the film. The density of the low refractive index layer 4 is more it is preferably at most 2.132g / cm ³ or more 2.199g / cm ^3, is 2.132g / cm ³ or more 2.191g / cm ³ or less It is preferable that it is 2.158 g / cm ³ or more and 2.174 g / cm ³ or less.

In the present embodiment, as will be described later, when the low refractive index layer 4 is formed by the thin film deposition method, the ion assisted deposition (IAD) method is not used. On the other hand, when the high refractive index layer 5 is formed by the vapor deposition method, the ion-assisted vapor deposition method is used. Thereby, the density of the low refractive index layer 4 can be lowered within the above range. The density of the high refractive index layer 5 is higher by using the ion-assisted vapor deposition method than in the case where the ion-assisted vapor deposition method is not used.

In the present embodiment, the low refractive index layer 4 can be adjusted to a relatively low density, whereby the refractive index of the low refractive index layer 4 can be reduced. Specifically, the refractive index (wavelength 550 nm) of the low refractive index layer 4 is 1.41 or more and 1.47 or less, preferably 1.4245 or more and 1.469 or less, and more preferably 1. It is 4245 or more and 1.464 or less, and more preferably 1.4425 or more and 1.4525 or less.

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 or more and 1000 nm or less can be suppressed to 1% or less. In the present embodiment, the spectral reflectance at a wavelength of 410 nm to 430 nm can be set to 0.8% or less. Further, in the present embodiment, preferably, the spectral reflectance at a wavelength of 480 nm to 600 nm can be set to 0.5 or less, and the spectral reflectance at a wavelength of 650 nm to 1000 nm can be set to 0.8 or less. is there.

In the present embodiment, the total number of the low refractive index layer 4 and the high refractive index layer 5 is not limited, but it is preferably about 9 to 19 layers, and more preferably 11 to 15 layers. Is. By increasing the number of layers, the wavelength range in which the spectral reflectance is 1% or less can be widened, but when the low refractive index layer 4 is formed by the ion-assisted vapor deposition method, the spectral reflectance is 1% or less. It is known from the experiments described later that the wavelength range of the reflectance cannot be expanded to a wavelength of 1000 nm. Therefore, the present inventors have formed a film of the low refractive index layer 4 without using the ion-assisted vapor deposition method to reduce the density of the low refractive index layer 4 as compared with the conventional case, thereby achieving a spectral reflectance of 1% or less. We have succeeded in expanding the wavelength range to 1000 nm.

Further, in FIG. 1, the low refractive index layer 4 is used as the lowermost layer in contact with the surface of the base material 2, but the lowermost layer can be appropriately selected from the viewpoint of adhesion to the base material 2. That is, it is arbitrary whether or not the low refractive index layer 4 is used as the lowermost layer.

Next, preferable materials of the low refractive index layer 4 and the high refractive index layer 5 will be described.
In the present embodiment, the low refractive index layer 4 is preferably formed by mixing layer comprising a single layer or SiO ₂ in SiO _2. The materials of the plurality of low refractive index layers 4 laminated on the antireflection film 3 may be the same or different.

Further, in the present embodiment, the high refractive index layer 5 includes ZrO _x (x is 1.5 to 2), TiO _x (x is 1 to 2), and TaO _x (x is 2 to 2.5). , And NbO _x (x is 2 to 2.5), preferably a single layer or a mixed layer containing two or more kinds. It is preferable to use ZrO _{2 for} ZrO _x , Ti ₃ O ₅ and Ti ₂ O _{5 for} TiO _x , Ta ₂ O _{5 for} TaO _x , and Nb ₂ O ₅ for NbO _x. The above-mentioned metal oxide does not have to have a stoichiometric composition as long as the oxygen composition ratio is in the above-mentioned range of x.

The materials of the plurality of high refractive index layers 5 laminated in the antireflection film 3 may be the same or different.

Further, in the present embodiment, the outermost surface layer 6 of the antireflection 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 surface layer 6 is an adjusting layer for suppressing the reflectance of the antireflection film 3 in which the low refractive index layer 4 and the high refractive index layer 5 are laminated within a predetermined value. That is, the outermost surface layer 6 can be provided as the uppermost layer of the low refractive index layer 4 and the high refractive index layer 5, and 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 surface layer 6 from the viewpoint of adjusting the reflectance. is there. 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 following formula (1) using the refractive index and density of the evaporator.
Membrane density = (refractive index of film / refractive index of evaporator) x theoretical density of evaporator (1)

As shown in Table 1, the refractive index is MgF ₂ <SiO ₂ , but in the present embodiment, from the viewpoint of reliability and adhesion between layers, the low refractive index layer 4 has more SiO than _{MgF 2. 2 is preferably used, and MgF 2} is preferably used for the outermost surface layer 6 as the refractive index adjusting layer of the antireflection film 3.

<Manufacturing method of optical member with antireflection film>
A method of manufacturing the optical member with an antireflection film of the present embodiment shown in FIG. 2 will be described.
In the present embodiment, the low refractive index layer 4 and the high refractive index layer 5 are alternately laminated on the surface of the base material 2 to form the antireflection film 3.

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

As a result, the low refractive index layer 4 can be formed with a low density, and the high refractive index layer 5 can be formed with a high density. Here, the "high density" and the "low density" mean the densities compared in each layer depending on whether or not the ion-assisted vapor deposition method is applied.

Although the atmosphere when the low refractive index layer 4 is vapor-deposited is not limited, for example, oxygen, argon, nitrogen alone, or a mixed atmosphere thereof is preferable.

Further, in the present embodiment, it is preferable to adjust the film forming pressure when forming the low refractive index layer 4 in ^{the range of 3 × 10 -3} Pa to 8 × 10 ^{-2 Pa.} The film forming pressure ^{is more preferably 3 × 10 -3} Pa to 5.8 × 10 ^-2 Pa, and further preferably 7.8 × 10 ^-3 Pa to 5.8 × 10 ^{-2 Pa.} It is preferably 1.5 × 10 ^-2 Pa to 3.2 × 10 ^-2 Pa, even more preferably.

As a result, the density of the formed low refractive index layer 4 ^{is adjusted to 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. Can be 2.132 g / cm ^{3 to} 2.191 g / cm ³ , and more preferably 2.158 g / cm ^{3 to} 2.174 g / cm ³ .

In the present embodiment, as the evaporation material of the low refractive index layer 4, it is preferable to use a mixed material containing a simple substance or SiO ₂ in SiO _2.

Further, in the present embodiment, as the evaporation material of the high refractive index layer 5, a simple substance or a mixed material containing two or more kinds selected from _{ZrO 2} , Ti ₃ O ₅ , Ta ₂ O ₅ , and Nb ₂ O _{5 is used.} It is preferable to use it.

Further, in the present embodiment, as the evaporation material of the outermost surface layer 6, it is preferable to use a simple substance selected from _{MgF 2} and SiO _{2 or a mixed material containing two or more kinds.} It is preferable to select _{MgF 2} as the evaporation material of the outermost surface layer 6.

According to the optical member 1 with an antireflection film of the present embodiment described in detail above, the density of the low refractive index layer 4 can be lowered, and the refractive index can be lowered. Then, in the present embodiment, the spectral reflectance can be suppressed to 1% or less in the wavelength range of 400 nm to 1000 nm. Further, according to the optical member 1 with an antireflection film of the present embodiment, the adhesion of each layer is excellent, peeling and cracking are unlikely to occur even in a high temperature and high humidity environment, and high reliability can be obtained.

Further, according to the method for manufacturing the optical member 1 with an antireflection film of the present embodiment, it is possible to control whether or not the ion-assisted vapor deposition method is applied when the low refractive index layer 4 and the high refractive index layer 5 are formed. Therefore, it is possible to easily manufacture the optical member 1 with an antireflection film which has an excellent antireflection function and has high reliability.

Further, in the present embodiment, since the low refractive index layer is formed without ion-assisted vapor deposition, the use time of the ion gun can be reduced when forming the antireflection film 3, and therefore, during the film formation. The temperature change can be reduced. This makes it possible to reduce the variation in the light reflection characteristics of the film-formed antireflection film 3.

Hereinafter, the present embodiment will be described in more detail with reference to Examples and Comparative Examples. In the experiment, Examples 1 to 3 and Comparative Examples shown below were produced.

[Examples 1 to 3]
In Examples 1 to 3, the materials shown in Table 2 below are used, and in Comparative Examples, the materials shown in Table 3 below are used, and SiO ₂ shown in Tables 2 and 3 is used as a low refractive index layer, Ta ₂ O ₅ was formed as a high refractive index layer and MgF ₂ was formed as the outermost surface layer to obtain an antireflection film. The base material is a lens molded using BACD14 glass (manufactured by HOYA Corporation).

In Examples 1 to 3 shown in Table 2, when the low refractive index layer was formed, it was formed by a vacuum vapor deposition method without ion-assisted vapor deposition. As shown in Table 2, in Example 1, _{the density of SiO 2} was 2.191 g / cm ³ , in Example 2, _{the density of SiO 2} was 2.158 g / cm ³ , and in Example 3, SiO _{2 was used.} The density of was 2.132 g / cm ³ . The pressures during film formation in vacuum vapor deposition to obtain these densities are shown in Table 4 below. As shown in Table 4, the density can be changed by changing the film forming pressure.

On the other hand, in the comparative example, SiO ₂ was formed by an ion-assisted thin-film deposition method. The data “with IAD” shown in Table 4 is applied to the comparative example.

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

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

As shown in FIG. 3, it was found that in Examples 1 to 3, the wavelength range of the spectral reflectance R of 1% or less can be widened as compared with Comparative Examples. Specifically, in the examples, it was found that the spectral reflectance can be reduced to 1% or less in the wavelength range of 400 nm to 1000 nm. Further, in the examples, it was found that the spectral reflectance at a wavelength of 480 nm to 600 nm can be set to 0.5 or less, and the spectral reflectance at a wavelength of 650 nm to 1000 nm can be set to 0.8 or less.

Based on the experimental results in Table 4, preferable film formation pressure, density and refractive index were determined. That is, as shown in Table 4, when SiO ₂ is deposited without ion-assisted vapor deposition, the density becomes as small as 2.098 when the film forming pressure is 8.2 × 10 ^{-2 Pa.} It was found that pores are likely to occur in the low refractive index layer. Therefore, according to the experimental results in Table 4, the film forming pressure was set to 3 × 10 ^-3 Pa to 8 × 10 ^-2 Pa, preferably 3 × 10 ^-3 Pa to 5.8 × 10 ^{-2 Pa. preferably, 7.8 × 10 -3 Pa~5.8 × 10} -2 Pa, and more preferably, set to ^{1.5 × 10 -2 Pa~3.2 × 10 -2} Pa.

The density of the low refractive index layer ^is set to ^{2.1g / cm 3 ~2.2g / cm 3} , ^preferably, a ^{2.132g / cm 3 ~2.199g / cm 3} , more preferably, 2.132G It was set to / cm ^{3 to} 2.191 g / cm ^3, and more preferably 2.158 g / cm ^{3 to} 2.174 g / cm ³ .

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

_{Further, when the SiO 2} (low refractive index layer) is formed by the ion-assisted vapor deposition method as in the comparative example, the base material during the film formation is heated by the radiant heat of the ion gun, and the temperature changes during the film formation. Was found to increase. On the other hand, when the SiO ₂ (low refractive index layer) is formed without ion-assisted vapor deposition as in this embodiment, the usage time of the ion gun can be reduced, and therefore the temperature change during the film formation can be reduced. I found that I could make it smaller. It was found that the variation in the characteristics of the film-formed antireflection film can be reduced by reducing the temperature change during film formation as in this example.

Next, a high temperature and high humidity test was performed using Example 2. The experimental conditions were a temperature of 60 °, a humidity of 90%, and an experimental time of 240 hours. After the test, no abnormal appearance such as peeling or cracks was observed. As a result, a highly reliable optical member with an antireflection film could be obtained.

The optical member with an antireflection film of the present invention can be preferably applied to a glass lens for an in-vehicle camera or the like.

1: Optical member with antireflection film 2: Base material 3: Antireflection film 4: Low refractive index layer 5: High refractive index layer 6: Outermost surface layer

Claims (8)

An optical member with an antireflection film having an antireflection film formed on the surface of the base material.
In the antireflection film, low refractive index layers and high refractive index layers are alternately laminated.
An optical member with an antireflection film, wherein the density of the low refractive index layer is 2.1 g / cm ³ or more and 2.2 g / cm ^{3 or less.} The optical member with an antireflection film according to claim 1, wherein the refractive index (wavelength 550 nm) of the low refractive index layer is 1.41 to 1.47. The low refractive index layer, an antireflection film-coated optical member according to claim 1 or claim 2, characterized in that it is formed by the mixed layer containing a single-layer or SiO ₂ in SiO _2. Claims 1 to 3 are characterized in that the outermost surface layer of the antireflection film is _{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 optical member with an antireflection film according to any one of. The optical member with an antireflection film according to any one of claims 1 to 4, wherein the spectral reflectance in the wavelength range of 400 nm or more and 1000 nm or less is 1% or less. A method for manufacturing an optical member with an antireflection film, in which low refractive index layers and high refractive index layers are alternately laminated on the surface of a base material to form an antireflection film.
A method for manufacturing an optical member with an antireflection film, which comprises forming the low refractive index layer by vapor deposition without using the ion-assisted vapor deposition method and forming the high refractive index layer by the ion-assisted vapor deposition method. .. A method for manufacturing an optical member with an antireflection film, which comprises adjusting the film forming pressure at the time of forming the low refractive index layer in ^{the range of 3 × 10 -3} Pa or more and 8 × 10 ^{-2 Pa or less.} .. Examples evaporation material of the low refractive index layer, the manufacturing method of the antireflection film-coated optical element of claim 6 or claim 7, characterized by using a mixed material containing a simple substance or SiO ₂ in SiO _2.

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