JPS6222122B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an antireflection coating for plastic optical components used in optical systems such as projection televisions, video cameras, and still cameras. Conventional configurations and their problems Traditionally, inorganic glass has been widely used for optical parts such as lenses, but in recent years plastics have become popular as they are lightweight, easy to process, and suitable for mass production. It has come to be used as a material for optical parts. However, plastic optical parts such as plastic lenses have the same disadvantage as inorganic glass in that they reflect a large amount of light on their surfaces, and they also have the disadvantage that their surfaces are easily scratched and have poor durability. In order to eliminate such drawbacks, it is necessary to prevent surface reflection by forming an antireflection film similar to the antireflection film formed on the surface of inorganic glass on the surface of the plastic optical component, and It is well known in the general art to harden the surface of an optical component to improve its durability by forming some kind of hardened thin film on the surface of the optical component. Hereinafter, a conventional antireflection coating for plastic optical components will be explained with reference to the drawings. Figure 1 is a diagram showing a structure in which an antireflection film similar to the antireflection film formed on the surface of inorganic glass is formed on the surface of a plastic optical component. This is an anti-reflection film made of magnesium chloride (MgF ₂ ). The anti-reflection film 2 is generally formed by a vacuum deposition method, but since plastic has a low flow temperature and thermal deformation temperature, and there is also the problem of gases released from inside the plastic, the film is deposited on an inorganic glass substrate. It is not possible to form a strong deposited film by heating the substrate (usually 200°C to 400°C) as in the case of forming. For this purpose, the antireflection film 2 was conventionally formed on the surface of the plastic optical component 1 at a low temperature of 50 to 60°C, but the antireflection film formed at this low temperature has poor adhesion to the plastic surface. It was bad and had low durability. In order to improve adhesion and durability, methods of heating plastic optical components to 60°C to 80°C and methods of forming antireflection films using RF ion plating methods, etc., have been used. Cracks may occur in the antireflection film produced by the above method, which may cause problems that are undesirable for improving durability. In addition, these methods keep the formation conditions of the antireflection film constant, and
It is difficult to maintain a constant state of the plastic surface, and it is not suitable for mass production. Next, referring to FIG. 2, an explanation will be given of an antireflection film in which a hardened thin film is formed on the surface of a plastic optical component. 3 is a thermosetting organic thin film or a hardened glass thin film that has good adhesion to the optical component 1 made of plastic. In this case, to form a thermosetting organic thin film, the organic thin film is usually formed with a thickness of 1 to 4 μm by coating or dipping, but since it is difficult to maintain a constant film thickness, the optical component 1 There is a risk of deteriorating the surface accuracy.
Furthermore, when a hardened thin film of glass is formed by vapor deposition, it is necessary to deposit a thick film, which causes the problem that cracks are likely to occur in the hardened thin glass film. Further, since the anti-reflection film 2 is present on the cured thin film 3, the durability of the anti-reflection film 2 itself suffers from the same problems as in the conventional example. As described above, conventional antireflection coatings for plastic optical components have had the problem of poor adhesion to the plastic surface and poor durability. OBJECTS OF THE INVENTION An object of the present invention is to provide an antireflection coating for plastic optical components that has excellent adhesion to plastic surfaces and durability, and is suitable for mass production. Structure of the Invention The antireflection coating for a plastic optical component of the present invention has a three-layer structure that is deposited on the surface of the plastic optical component in order from the surface side to the air side, consisting of a first layer, a second layer, and a third layer. The first layer is made of silicon dioxide (SiO ₂ ), the second layer is made of magnesium fluoride (MgF 2 ), and the third layer is made of magnesium fluoride (MgF ₂ ). is characterized in that it is made of silicon dioxide (SiO ₂ ), and the first layer, second layer, and third layer are formed while the plastic optical component is maintained at a temperature of 60° C. or lower. . This makes it possible to obtain an antireflection film that has excellent adhesion to the plastic surface and durability, and is suitable for mass production. DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 shows a structural diagram of the antireflection coating of the plastic optical component of the present invention. In FIG. 3, 4 is a first layer made of silicon dioxide, 5 is a second layer made of magnesium fluoride, and 6 is a third layer made of silicon dioxide. As shown in Table 1.

[Table] In addition, each layer was formed by a vacuum evaporation method while the plastic optical component was maintained at 60°C or lower. The tests conducted to compare the durability of the anti-reflective film of the above embodiment of the present invention and the conventional anti-reflective film were as follows: (1) Humidity test (temperature of 40°C, relative humidity of 95% (2) Heat resistance test (Leave for 1000 hours in a high temperature atmosphere of 85℃), (3) Thermal shock test (Leave it in a high temperature atmosphere of -30℃, 70℃ alternately) The conventional anti-reflective film for comparison was one of the conventional examples mentioned above, in which an anti-reflective film of magnesium fluoride was vacuum-deposited on the surface of a plastic optical component. It was formed to a thickness of approximately 1000 Å by
It has the structure shown in FIG. The results of the durability test are shown in Table 2.

[Table] As can be seen from Table 2 above, the antireflection film of the present invention is superior in durability to the conventional antireflection film. Figure 4 is a diagram comparing the spectral reflectance.
a is a plastic optical component without anti-reflection coating;
b shows the spectral reflectance of a plastic optical component having a conventional antireflection film, and c shows the spectral reflectance of a plastic optical component having an antireflection film according to an embodiment of the present invention. As can be seen from the figure, the spectral characteristics were almost the same as those of the conventional example, and the adhesion to the plastic surface was also excellent. Furthermore, in the conventional example, cracks sometimes occurred during the formation of the antireflection film, but in the embodiments of the present invention, the antireflection film was always stable. In addition, in the above embodiment, each film thickness was set as shown in Table 1, but the film thickness is not particularly limited to the above values, and may be changed according to the design wavelength. Any structure may be used as long as it has a structure as shown in FIG. Effects of the Invention As is clear from the above explanation, the antireflection coating of the plastic optical component of the present invention has three layers: a first layer made of silicon dioxide, a second layer made of magnesium fluoride, and a third layer made of silicon dioxide. By adopting a three-layer structure, the durability of the anti-reflection film is improved and the occurrence of cracks is prevented, which has the effect of eliminating the drawbacks of the conventional example. Furthermore, the antireflection coating for plastic optical components of the present invention is suitable for mass production, and therefore has great practical value.

[Brief explanation of the drawing]

1 and 2 are diagrams showing the structure of an antireflection film of a conventional plastic optical component, and FIG. 3 is a diagram showing the structure of an antireflection film of a plastic optical component in an embodiment of the present invention. FIG. 4 is a diagram showing the spectral reflectance of the present invention and conventional plastic optical components. 1...Plastic optical component, 2...Antireflection film, 3...Thermosetting organic thin film or hardened glass thin film, 4, 6... Thin film made of silicon dioxide, 5... Thin film made of magnesium fluoride.

Claims (1)

[Claims] 1. An antireflection film is formed on the surface of a plastic optical component by forming a vapor deposited film having a three-layer structure of a first layer, a second layer, and a third layer in order from the surface side to the air side. The first layer is made of silicon dioxide (SiO ₂ ), the second layer is made of magnesium fluoride (MgF ₂ ), and the third layer is made of silicon dioxide (SiO ₂ ). An anti-reflection coating for plastic optical parts characterized by: 2. The plastic optical component according to claim 1, wherein the first layer, second layer, and third layer are formed by maintaining a plastic optical component at 60° C. or lower. Anti-reflection coating for parts.