Patent Application
20110217532
The present application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2010-50671 filed on Mar. 8, 2010; the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an optical component and a manufacturing method thereof.
2. Description of the Related Art
Substrates made of resin have come to be used more commonly in recent years to manufacture optical systems inexpensively and in large quantities. A substrate made of resin is less hard as compared to a substrate made of glass. Furthermore, an optical thin film such as an antireflective film formed on the resin substrate or a low-pass filter gets easily scratched. Therefore, it is necessary to improve a scratch resistance and a hardness of the optical thin film.
An optical member is proposed in Japanese Patent Application Laid-open No. 2009-199022 with a view to providing a solution to the above-described problem. The optical member is provided with a thin film of a low refractive index layer made of a film coating material made of SiO2 and Al2O3, that has an improved film density and excellent scratch resistance, without a hard coat layer that is normally used in a spectacle lens. To improve the film density, an ion assisted deposition method is used for forming the low refractive index layer.
An optical component according to an aspect of the present invention includes a multilayered optical thin film formed on a substrate. A critical load value of the optical thin film that includes at least one layer that is formed by a vacuum deposition method is greater than or equal to 30 mN. The critical load value is a value evaluated by a measurement method complying with JIS R3255 “Testing methods for adhesion of thin films on a glass substrate”.
A method of manufacturing an optical component according to another aspect of the present invention includes forming an optical thin film on a substrate. A critical load value of the optical thin film that includes at least one layer that is formed by a vacuum deposition method, is greater than or equal to 30 mN. The critical load value being a value evaluated by a measurement method complying with JIS R3255 “Testing methods for adhesion of thin films on a glass substrate”.
The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.
Exemplary embodiments of an optical component and a manufacturing method thereof according to the present invention are explained below in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below.
The optical component according to the present invention includes a multilayered optical thin film on a substrate. An antireflective film is explained as an example of the optical thin film. In the antireflective film formed of multiple layers, at least one layer is formed by a vacuum deposition method and a critical load value of this layer of the antireflective film is greater than or equal to 30 mN.
The value of the critical load is evaluated by a measurement method complying with JIS R3255 “Test methods for adhesion of thin films on a glass substrate”.
A structure of the antireflective film of the optical component according to Example 1 is given in Table 2. The antireflective film is formed of alternating Ta2O5 and SiO2 layers arranged in that order from a substrate side.
The antireflective film that serves as the optical thin film of multiple layers of a low refractive index material SiO2 and a high refractive index material Ta2O5 is formed on a surface of a resin substrate. The antireflective film has a four-layer structure with alternating Ta2O5 and SiO2 layers, the first layer on the substrate side being that of Ta2O5. The substrate is made of resin of polycarbonate series. A plasma gun is used to perform plasma irradiation during the deposition of the Ta2O5 and SiO2 layers of the antireflective film using a plasma assisted deposition method.
The low refractive index material SiO2 used in the present Example can be of any shape. It can be granular, sintered pellets, or molten ring. A mixture with Al2O3 can also be used as long as the main component is SiO2.
TiO2 or Nb2O5 can be used in place of Ta2O5 as a high refractive index material. Similar to the low refractive index material, the high refractive index material also can be of any shape.
The substrate has a dimension of 30 millimeter (mm)×30 mm×1.5 mm. The dimension of the substrate is the same in all the Examples described below.
In the antireflective film according to Example 1, a plasma gun is used to perform plasma irradiation during the deposition of at least one layer of the optical thin film of multiple layers using the plasma assisted deposition method.
The ion assisted deposition method can be used in place of the plasma assisted deposition method. In the ion assisted deposition method or the plasma assisted deposition method, parameters (for example, gas flow amount, irradiation time, and applied power) should preferably be controlled according to a constituent material of the layer being formed.
A method for measuring the critical load value is explained below. The critical load value is a value that corresponds to a scratch resistance of the optical thin film. Conditions when measuring the critical load value are shown in Table 1.
A diamond stylus is provided at a tip of a cantilever. Because an equivalent mass of the stylus is extremely small, minute variations on a surface of the thin film can be identified with a high sensitivity while scanning the thin film using the stylus. Vibrations of the stylus tip pass through the cantilever, and are converted into an electric signal inside a cartridge.
Direct current signals cannot be output from the cartridge carrying such a converted form of the vibrations. Therefore, the cartridge is forcibly horizontally excited to generate alternating current signals. Micro-vibrations of the stylus can be converted into an electric signal having a good sensitivity. A testing range is of the order of 1 mN to 1 Newton (N).
A diameter of the stylus tip can be selected from a range of 5 micrometers (μm) to 100 μm. Thus, there is a significant freedom in applying pressure on the surface of the thin film. An optimum diameter can be selected as the stylus diameter of a diamond indenter based on a measurement sample.
A method for measuring a Young's modulus is explained below. The Young's modulus is a value that corresponds to a hardness of the optical thin film. An indentation testing is performed for measuring the hardness. In the indentation testing, the load applied on the antireflective film and displacement of the antireflective film when the load is applied are measured. Specifically, application of the load and displacement due to application of load are measured with a high precision.
Particularly, according to a CSM method, that is, a so-called continuous stiffness measurement method, the hardness and an elastic modulus at each indentation depth can be continuously measured in a single push-in test.
A measurement procedure is explained below. A minute amount of AC signal is added to a load DC signal and a force is caused to micro-vibrate during indentation. Furthermore, a load amplitude and a displacement response amplitude/phase are measured according to a time, and a rigidity (stiffness) at each depth is measured continuously. A Berkovich diamond indenter that has a triangular pyramidal shape is used as the indenter. The indentation depth is targeted at approximately 30% of the film thickness.
As shown in Table 2, an antireflective film is formed of alternating SiO2 and TiO2 layers arranged in that order from the substrate side.
The plasma assisted deposition method is used only for forming the SiO2 layer of the antireflective film.
The antireflective film that serves as an optical thin film of multiple layers of a low refractive index material SiO2 and a high refractive index material TiO2 is deposited on the surface of the resin substrate. The antireflective film has a five-layer structure with alternating SiO2 and TiO2 layers, the first layer on the substrate side being that of SiO2. A plasma gun is used to perform plasma irradiation during the deposition of the SiO2 layer of the antireflective film using the plasma assisted deposition method.
The substrate is made of resin of cycloolefin series.
As shown in Table 2, an antireflective film has a seven-layer structure, and is formed of alternating SiO2 and TiO2 layers arranged in that order from the substrate side up to the sixth layer. The seventh layer is an MgF2 layer. The plasma assisted deposition method is used only for forming the SiO2 layer and the MgF2 layer of the antireflective film. The substrate is made of a resin of polycarbonate series.
As shown in Table 2, an antireflective film has a structure similar to that of Example 2. The antireflective film has a six-layer structure, the first layer being that of SiO that serves as an adhesive layer. A plasma gun is used to perform plasma irradiation during the deposition of the SiO2 layer of the antireflective film using the plasma assisted deposition method. The substrate is made of a resin of acrylic series.
An antireflective film of Comparative Example 1 has a four-layer structure that is similar to that of Example 1, and is formed using only a vapor deposition method.
An antireflective film of Comparative Example 2 has a five-layer structure that is similar to that of Example 2, and is formed using only the vapor deposition method.
An antireflective film of Comparative Example 3 has a seven-layer structure that is similar to that of Example 3, and is formed using only the vapor deposition method.
An antireflective film of Comparative Example 4 has a six-layer structure that is similar to that of Example 4, and is formed using only the vapor deposition method.
Values of the critical load and the Young's modulus are shown in Table 3 for each Example and Comparative Example.
In Examples 1 to 4, the critical load value of the antireflective film is greater by 70% or above relative to a critical load value of the substrate.
Furthermore, the Young's modulus of the antireflective film is greater than or equal to ten times a Young's modulus of the substrate.
The optical thin film described above should preferably be the outermost layer of the multilayered film.
The gas used in the plasma assisted deposition method used for forming the optical thin film can be of any type. It is desirable to form the optical thin film using the plasma assisted deposition method in which a mixture of oxygen gas and argon gas is used.
According to the present invention, an optical thin film is obtained that has an improved scratch resistance (critical load value) and a hardness (Young's modulus). As a result, a lightweight optical system can be formed inexpensively.
As described above, the optical thin film according to the present invention can make the optical system inexpensive and lightweight.
According to the present invention, a critical load value, that is, a scratch resistance of an optical thin film formed on a substrate can be improved.
Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-050671 | Mar 2010 | JP | national |
