JPH02163701A - Antireflection film of optical parts made of plastic - Google Patents

Abstract

PURPOSE:To improve adhesiveness and durability by using silicon dioxide to constitute the 1st and 3rd layers, which are formed by vapor deposition successively from a surface side to an air side on the surface of optical parts made of plastic, and using magnesium fluoride to constitute the 2nd layer. CONSTITUTION:The vapor deposited film of the 3-layered structure including the 1st layer 2 consisting of the silicon dioxide, the 2nd layer 3 consisting of the magnesium fluoride and the 3rd layer 4 consisting of the silicon dioxide are formed on the surface of the optical parts made of plastic from the surface side to the air side. The antireflection film having the excellent adhesiveness to the optical parts made of plastic and durability is formed in such a manner.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an antireflection coating for plastic optical components used in optical systems such as projector televisions, video cameras, and still cameras.

Conventional technology Traditionally, inorganic glass has been widely used for optical parts such as lenses, but in recent years, plastic has become the material for optical parts because it is lightweight, easy to process, and suitable for mass production. It has come to be used as. However, plastic optical parts such as plastic lenses have the disadvantage that, like inorganic glass, 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 form an antireflection film similar to inorganic glass on the surface of the plastic optical component to prevent reflection on the surface, and to form some kind of hardened thin film on the surface of the plastic optical component. Hardening the surface of the plastic optical component to improve its durability is known as -film technology.

(For example, "Design and molding technology of precision plastic optical lenses and their problems" Trikembus Report Collection Nα87P6-1~
P6-4) Hereinafter, a conventional antireflection film for plastic optical components will be explained with reference to the drawings. Figure 2 shows a structure in which a single layer film made of magnesium fluoride is formed, which is the same as the antireflection film formed on the surface of plastic optical components, and Figure 3 (b) shows its spectral reflection characteristics. FIG. 3(C) for comparison is a diagram showing the spectral reflection characteristics of the plastic optical component when no antireflection film is formed. In FIG. 2, 1 is a plastic optical component, and 3 is an antireflection film made of magnesium fluoride. The anti-reflection film 3 is usually formed by a vacuum one-layer method, but recently, in order to improve the adhesion and durability between the anti-reflection film and the surface of the plastic optical component, plastic optical components are coated at 60'C or higher. A method of forming an antireflection film using a method of heating to 80° C. and vacuum deposition, and a method of forming an antireflection film using an RF ion blating method has been used.

Next, referring to FIG. 3, 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.

5 is a thermosetting silicon-based hardened thin film that has good adhesion to the plastic optical component 1. In this case, the cured thin film is usually formed by coating or dipping for 1 to 4 hours.
Form a cured film of μ.

Problems to be Solved by the Invention In an example of forming an anti-reflective film made of magnesium fluoride using the vacuum evaporation method, which is a conventional example of the anti-reflective film forming method described above, the flow temperature and heat distortion temperature of the plastic are low, and ,
Since there is also the problem of gases released from inside the plastic, this is done when forming a vapor-deposited film on an inorganic glass substrate. Substrate heating (
However, anti-reflection films were formed on the surfaces of plastic optical components at low temperatures of 50 to 60 degrees Celsius or lower, as it was impossible to obtain a strong vapor deposition film.
The antireflection film formed at this low temperature has poor adhesion to the plastic surface and low durability. In addition, anti-reflection coatings formed by heating plastic optical components to 60°C to 80°C or using RF bio-ion blating are prone to cracking, and it is also important to keep the conditions constant during formation. It is difficult to maintain a constant state of the plastic surface, and it is not suitable for mass production.

Next, since it is difficult to control the film thickness by the above-mentioned method for forming a cured thin film, the surface precision of the optical component may be deteriorated because it is difficult to maintain the film thickness constant. Further, since it is necessary to increase the III thickness, there is a problem that cracks are likely to occur in the cured film during a heat resistance test.

Furthermore, since the antireflection film 3 is formed on the cured thin film 5, the durability of the antireflection film 3 itself is subject to 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.

In view of the above problems, the present invention provides an antireflection film that has excellent adhesion and durability to plastic optical components.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a method of vapor depositing a three-layer structure of a first layer, a second layer, and a third layer on the surface of a plastic optical component from the surface side to the air side. It has a structure in which an antireflection film is formed by forming a film, and the first and third layers are made of silica dioxide,
The second layer is made of magnesium fluoride, and the first layer and the second layer are made of magnesium fluoride.
The refractive index of the third layer is N, , N, , N3 . When the geometric film thicknesses are dI, dz, and d3, and the set reference wavelength is λo, the optical film thickness of each layer is 0.1λ with respect to the set reference wavelength.
o<NI・d, <0.15λo, 0.2λo<N!・
dt <0.25λo.

0.04λo<N,・d! The object of the present invention is to provide an antireflection film characterized in that the antireflection film has an antireflection value in the range of <0.06λo.

Function The present invention forms a three-layer anti-reflection film made of silica dioxide and magnesium fluoride on the surface of a plastic optical component, and controls the optical thickness of each film within the above range. This provides an antireflection coating for plastic optical components that has excellent adhesion and durability and is suitable for mass production.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the structure of the antireflection film of the plastic optical component of the present invention, and FIG. 3(a) shows an example of its spectral reflection characteristics. In FIG. 1, 1 is a plastic optical component, 2 and 4 are first and third layers made of cape dioxide,
3 is a second layer made of magnesium fluoride, and the specific contents of the present invention are as shown in Table 1.

Table 1 (λo” 400n1m) Each layer also has plastic optical components at 60°.
It was formed by a vacuum evaporation method while maintaining the temperature below C.

The tests conducted to compare the adhesion and durability of the above embodiments of the present invention and conventional antireflection films were as follows: (1) Adhesive tape peel test (temperature 40°C, relative humidity 85% high temperature/high temperature atmosphere) After leaving it inside for 1000 hours, stick the adhesive tape to the surface of the plastic optical component and peel it off.)
, (2) Humidity test (leaved for 1000 hours in a high-temperature atmosphere with a temperature of 40°C and relative humidity of 95%), (3) Heat resistance test (left in a high-temperature atmosphere with a temperature of 85°C for 1000 hours)
, (4) Thermal shock test (approximately 100 minutes left for 30 minutes alternately in low and high temperature atmospheres at temperatures of -30°C and 70"C)
A conventional anti-reflection film for comparison is a magnesium fluoride anti-reflection film on the surface of a plastic optical component, which is one of the conventional examples, by a vacuum evaporation method and has an optical film thickness of λo. /4 (λo"" 550nn+), and has the structure shown in FIG. The results of the adhesion/durability test are shown in Table 2.

As can be seen from Table 2 in Table 2 below, the antireflection film of the present invention is superior to conventional antireflection films in terms of adhesion, durability, and heat resistance.

Further, in the conventional example, cracks and cracks occurred during the formation of the antireflection film, but in the example of the present invention, the antireflection film was always stable. Regarding the spectral reflection characteristics, as can be seen from FIG. 3, the embodiment of the present invention has almost the same spectral characteristics as the conventional example.

Effects of the Invention As is clear from the above explanation, the antireflection coating of the plastic optical component of the present invention has a first coating made of a carbon dioxide cape.
The refractive index of the first layer, second layer, and third layer is N.
NZ, N3. When the geometric film thicknesses are d1, d2, and d3 and the set reference wavelength is λo, the optical thickness of each layer is 0.1 with respect to the set reference wavelength λo<N, -di <0.15
λo, 0.2λo<N2・dz<0.25λo, 0.
By controlling the range of 04λo<Nld3<0.06λo, the adhesion with the plastic optical parts is improved, the durability of the anti-reflection film is improved, and cracks are prevented from occurring, which improves the properties of the conventional example. It has the effect of eliminating defects. Furthermore, the antireflection film for plastic optical components of the present invention is suitable for mass production, and therefore has great practical value.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an antireflection coating for a plastic optical component of the present invention, Fig. 2 is a block diagram of a conventional antireflection coating for a plastic optical component, and Fig. 3 is a graph showing spectral reflection characteristics. FIG. 4 shows the structure of a conventional antireflection film in which a hardened thin film is formed on the surface of a plastic optical component and an antireflection film is formed thereon. 1...Plastic optical parts, 2.4...
...Thin film made of silica dioxide, 3...Thin film made of magnesium fluoride, 5... Thin film made of thermosetting silicone. Agent's name Patent attorney Shigetaka Awano Haka 1 List Figure 1 - Plastic comparison crime F! , 4-- Integrity by 2^9 Gui element et al. 3-%
Seima 2nd figure consisting of fjimazuosiu L

Claims (1)

[Scope of Claims] (1) A structure in which a three-layered vapor deposited film of a first layer, a second layer, and a third layer is formed on the surface of a plastic optical component in order from the surface side to the air side. An antireflection film for a plastic optical component, wherein the first layer and the third layer are made of silica dioxide, and the second layer is made of magnesium fluoride. (2) The refractive index of the first layer, second layer, and third layer is N_1, N_
2, N_3, When the geometric film thicknesses are d_1, d_2, d_3 and the set reference wavelength is λ_o, the optical film thicknesses of each layer N_1・d_1, N_2・d_2, N_3・d_3 are as follows with respect to the set reference wavelength. The antireflection coating for plastic optical parts according to claim 1, characterized in that the antireflection coating falls within the range of the following conditions. 0.10λ_o<N_1・d_1<0.15λ_o 0.20λ_o<N_2・d_2<0.25λ_o 0.04λ_o<N_1・d_3<0.06λ_o