Optical element and optical film
阅读说明:本技术 光学元件以及光学薄膜 (Optical element and optical film ) 是由 川岸秀一朗 山下照夫 白石幸一郎 于 2018-04-13 设计创作,主要内容包括:本发明提供一种同时具有亲水性和防反射功能的光学薄膜。在作为光学薄膜的多层膜(102)中,最上层的膜是作为多孔膜的亲水性膜(111)。最上层的下一层的膜是作为致密膜的底膜(122)。亲水性膜(111)的气孔率为2%以上20%以下,亲水性膜(111)的物理膜厚为0.5nm以上20nm以下。底膜(122)的气孔率不足2%。(The invention provides an optical film having both hydrophilicity and antireflection function. In the multilayer film (102) as an optical thin film, the uppermost film is a hydrophilic film (111) as a porous film. The film of the lower layer of the uppermost layer is a base film (122) which is a dense film. The porosity of the hydrophilic film (111) is 2% to 20%, and the physical thickness of the hydrophilic film (111) is 0.5nm to 20 nm. The porosity of the primary coating (122) is less than 2%.)
1. An optical element, comprising:
an optical element body;
a multilayer film (optical film) formed on a surface of the optical element body;
in the optical film, a light-transmitting layer is formed on the surface of the optical film,
the uppermost film is a hydrophilic film as a porous film,
the film of the lower layer of the uppermost layer is a bottom film as a dense film,
the porosity of the hydrophilic film is 2% to 20%,
the physical film thickness of the hydrophilic film is 0.5nm to 20nm,
the porosity of the basement membrane is less than 2%.
2. The optical element of claim 1,
at least one of the hydrophilic film and the base film is SiO2、ZrO2、Al2O3、TiO2、Ti3O5、Ta2O5And Nb2O5A monomer of (1) or a mixed material including these.
3. The optical element of claim 2,
the hydrophilic film is SiO2And (3) a membrane.
4. The optical element according to claim 2 or 3,
the bottom film is SiO2And (3) a membrane.
5. The optical element according to any one of claims 1 to 3,
the hydrophilic film is a film formed by EB (electron beam) vapor deposition,
the base film is a film formed by IAD (ion assisted vapor deposition).
6. An optical film which is a multilayer film, wherein,
the uppermost film is a hydrophilic film as a porous film,
the film of the lower layer of the uppermost layer is a bottom film as a dense film,
the porosity of the hydrophilic film is 2% to 20%,
the physical film thickness of the hydrophilic film is 0.5nm to 20nm,
the porosity of the basement membrane is less than 2%.
Technical Field
The present disclosure relates generally to optical films.
Background
As an example of the optical element, there is an optical lens (for example, glass lens) mounted on a camera such as a still camera or a video camera. It is known that when photographing is performed in a state where water droplets (for example, mist) adhere to the lens surface, the quality of a photographed image deteriorates.
As a countermeasure for solving such a problem, a technique of forming a hydrophilic film on a camera lens disclosed in
Disclosure of Invention
(problems to be solved by the invention)
In general, an antireflection film is formed on a lens for a camera to improve transmittance and improve quality of a captured image. Accordingly, the technique disclosed in
However, if a hydrophilic film is simply formed on the antireflection film, sufficient hydrophilicity may not be obtained, or the refractive index of the antireflection film may change due to moisture absorption, thereby impairing the antireflection function (for example, reflectance characteristics may decrease). If the antireflection function is impaired, the quality of the captured image deteriorates, and specifically, at least one of an artifact and color shading is generated in the captured image. The quality deterioration of the captured image adversely affects the image processing. Particularly, it is a very serious problem for high-level image processing such as remote sensing processing and recognition processing (typically, processing for recognizing a person or an object) by an on-vehicle camera and a monitoring camera.
Such problems may also be present with optical films on optical elements other than optical lenses.
The optical thin film disclosed in
An object of one embodiment of the present invention is to provide an optical film having both hydrophilic and antireflection functions.
(means for solving the problems)
An optical film according to an embodiment of the present invention is a multilayer film. In the multilayer film, the uppermost film is a hydrophilic film as a porous film. The film of the lower layer of the uppermost layer is a base film as a dense film.
The porosity of the hydrophilic film is 2% to 20%, and the physical thickness of the hydrophilic film is 0.5nm to 20 nm. The porosity of the basement membrane is less than 2 percent.
(Effect of the invention)
According to an embodiment of the present invention, an optical film having both hydrophilic and antireflection functions can be provided.
Drawings
Fig. 1 shows a concept of a configuration of an optical lens according to an embodiment of the present invention.
Fig. 2 is a schematic view illustrating functions of the hydrophilic film and the base film.
Fig. 3 shows the structure of a multilayer film according to an embodiment of the present invention.
Fig. 4 shows an optical film forming system according to an embodiment of the present invention.
Fig. 5 shows the relationship between the difference in porosity of the primary film and the difference in the time-series change in contact angle of a water droplet adhering to the hydrophilic film.
Fig. 6 shows the structure of the multilayer film according to the comparative example in the experiment shown in fig. 5.
Fig. 7 shows the relationship between the physical film thickness of the hydrophilic film and the contact angle of a water droplet after a certain time from the dripping of the water droplet.
Fig. 8 shows first spectral reflectance characteristics and second spectral reflectance characteristics of the optical lens according to the embodiment.
Fig. 9 shows the structure of the multilayer film according to the comparative example in the experiment shown in fig. 8.
Fig. 10 shows a first modification of the configuration of the multilayer film.
Fig. 11 shows a second modification of the configuration of the multilayer film.
Fig. 12 shows a third modification of the structure of the multilayer film.
Detailed Description
Hereinafter, an optical lens according to several embodiments of the present invention will be described. The embodiments described below are not intended to limit the invention according to the scope of the claims, and the elements and combinations thereof described in the embodiments are not necessarily all necessary for the means for solving the technical problems of the invention.
Fig. 1 shows a concept of a configuration of an optical lens according to an embodiment of the present invention.
The
The
The
Fig. 2 is a schematic diagram illustrating functions of the
As described above, the
The
The flow before the
In a state where the
When the amount of water droplets adhering to the surface of the
However, as shown in fig. 2 (E) (for example, in a high humidity environment), when the amount of
As shown in fig. 2 (G), the
In addition, according to the present embodiment, the physical film thickness of the
In addition, according to the embodiment, as described above, the film underlying the
The material and physical film thickness of each film in the
Fig. 3 shows the structure of a
The
In embodiments, SiO formed by EB (Electron Beam) vapor deposition2The membrane is a hydrophilic membrane 111 (membrane 8). SiO formed by IAD (ion assisted vapor deposition)2The film is the bottom film 122 (film 7).
Fig. 4 shows an optical film forming system according to an embodiment.
The optical thin
IAD is a film formation method in which vapor deposition material molecules are pressed against a substrate by ionized gas molecules irradiated from an ion gun to the substrate. Therefore, it is considered that a dense film having no gap into which water molecules enter can be formed by IAD. Therefore, in the present embodiment, a film formed by IAD (e.g., SiO) is used as the underlying film 1222A film).
EB vapor deposition is a film formation method in which electrons are concentrated on a part of a vapor deposition material, bombarded, and evaporated by heating. Therefore, it is considered that the
The film formation method performed by the system shown in fig. 4 is an example of a preferable film formation method. The film forming method is not limited to the example shown in fig. 4. For example, the
The
FIG. 5 shows a base film (SiO)2Film) and the time-series change in the contact angle of a water droplet adhering to the
Here, a method of calculating the porosity will be described. First, the known refractive index of the material used for the hydrophilic film is represented by n, and the refractive index in vacuum of the hydrophilic film formed in this experiment is represented by n (v). The refractive index in vacuum is obtained by measuring the reflectance during film formation using an optical film thickness meter in a film formation chamber held in vacuum and converting the reflectance into the refractive index. The filling ratio of the hydrophilic membrane can be expressed as follows.
Filling factor (%) (% refractive index in vacuum/known refractive index (%)) × 100 (%)
Therefore, the porosity can be obtained as follows:
porosity (%) -filling ratio (%).
The physical film thickness was measured using a cross-sectional TEM image. The optical film thickness nd can be determined from the refractive index n × the physical film thickness d shown in the table. The refractive index of each layer is obtained by conversion from the reflectance of the film (corresponding to the refractive index of the film in the atmosphere). Specifically, the reflectance of the substrate taken out into the atmosphere was measured using a microscope type spectrometer (USPM-RU3) manufactured by olympus, and the reflectance was calculated by converting the reflectance into a refractive index. Further, the refractive index is a refractive index at a wavelength of 550 nm. The optical film thickness coefficient k is a coefficient at a
As is clear from FIG. 5, the porosity was 2.8% as compared with that of SiO2The film is a primary film and is made of SiO with porosity of 1.5%2A water droplet whose film is the base film spreads more rapidly (i.e., the contact angle becomes smaller in a shorter time).
The water droplet spreading speed depends on the physical film thickness of the
Fig. 7 shows the relationship between the physical film thickness of the
In the experiment, 0.8. mu.l of pure water was dropped onto the sample surface, and the contact angle θ after five seconds was determined.
According to fig. 7, the smaller the physical film thickness of the
According to FIG. 7, the physical film thickness of the
In addition, according to fig. 7, since the contact angle after a certain time from the start of dropping is less than 10 °, it can be said that the
Fig. 7 illustrates the trend.
In the embodiment, by reducing the physical film thickness of the
Fig. 8 shows a first spectral reflectance characteristic of the optical lens 100 (the physical film thickness of the
The spectral reflectance measured in the experiment of fig. 8 was measured using a microscope type spectrometer (USPM-RU3) manufactured by olympus.
Graph (a) shows spectral reflectance characteristics of the
The above description has been made of an embodiment of the present invention, and it is only an example for illustrating the present invention, and it is not intended to limit the scope of the present invention to the embodiment. That is, the present invention may be embodied in other various forms.
For example, at least one of the
The present invention can be applied to, for example, optical elements other than optical lenses, such as mirrors (reflective optical elements), optical filters, array-shaped optical elements (lens arrays, prism arrays), probe elements, diffraction-type optical elements, fresnel lenses, and the like. The surface of an optical element such as an optical lens (the surface on which an optical thin film is formed) may be spherical or aspherical.
For example, the base film may also serve as an antireflection film. That is, the multilayer film may be a hydrophilic film or a base film that also serves as an antireflection film. Such a multilayer film is suitable for a lens for a camera, which has lower performance than that of an in-vehicle camera or a monitoring camera, or an optical element in an environment where high antireflection performance is not required like a rear view mirror.
The structure of the multilayer film is not limited to the structure illustrated in fig. 3, and may be, for example, the structures illustrated in fig. 10, 11, and 12.
The application is based on a special application 2017-080463 applied on 4, 14 and 4 in 2017. The contents of which are incorporated herein in their entirety.
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