JPS6022101A - Antireflection film for plastic optical parts - Google Patents

Abstract

PURPOSE:To obtain an antireflection film causing no cracking by forming the 1st layer of silicon dioxide and the 2nd layer of magnesium fluoride satisfying prescribed conditions on each surface of plastic optical parts. CONSTITUTION:The 1st layer 3 of silicon dioxide and the 2nd layer 2 of magnesium fluoride are formed on the surface of an optical lens 1 of polymethyl methacrylate so that the refractive indexes and the geometrical thicknesses satisfy two prescribed conditional equations. When the refractive indexes of the 1st and the 2nd layers are represented by N1, N2, and the geometrical thicknesses by d1, d2, the optical thicknesses N1d1, N2d2 of the 1st and the 2nd layers to a set standard wavelength lambda0 are regulated to 0.050lambda0<N1d1<0.520lambda0 and 0.125lambda0<N2d2<0.375lambda0. The 1st and the 2nd layers are formed by vacuum deposition at room temp.-100 deg.C.

Description

[Detailed description of the invention] [The purpose of dullness''] This invention, Grojeksindelevy,
It relates to anti-reflection coatings for plastic optical parts used in optical systems such as video cameras and still cameras, and its purpose is to have excellent durability and aging resistance, high hardness, and The purpose of the present invention is to provide an antireflection coating for plastic optical components that is suitable for mass production.

Inorganic glass has been widely used for optical components, but in recent years plastics have come to be used as materials for optical components because they are lightweight, easy to process, and suitable for mass production. . By the way, similar to inorganic glass, plastic optical components such as plastic lenses
c. Since light reflection on the surface is large and spectral transmission characteristics are poor, an antireflection film similar to the antireflection film formed on the surface of inorganic glass is formed on the surface of plastic.

Hereinafter, a conventional antireflection coating for plastic optical components will be explained with reference to FIG. In the figure, 1 is a plastic substrate, and 2 is an antireflection film made of magnesium fluoride (MfF). This anti-reflection film 2 is generally formed by a vacuum evaporation method, but since plastic has a low flow temperature and heat deformation temperature, it can be thermally deformed using methacrylic resin (Acrybella VH Mitsubishi Rayon L K, trade name). Temperature: 100°C, flow temperature: 170°C), vaporized onto an inorganic glass substrate.
Substrate heating such as when forming a deposit (usually 200°C to 4°C)
oo°C) cannot be carried out. For this reason, in the past, an anti-reflective film of magnesium fluoride was formed on the surface of plastic at a low temperature of 50 degrees Celsius or less, but the anti-reflective film formed at a low temperature of 30 degrees is extremely durable, heat resistant, and hard. low. Therefore, in order to improve durability, heat resistance, and hardness, there are methods of forming an antireflection film by heating the substrate to 50°C to 80°C and methods of forming an antireflection film using the RP ion blating method. However, in the antireflection film produced by these methods, a rack 4 may be formed over the entire antireflection film as shown in FIG. Such a rack is undesirable because it causes problems in durability, especially clouding and peeling of the antireflection film due to changes over time. Also,
These methods are not suitable for mass production because it is difficult to maintain uniform formation conditions for the antireflection film and to uniformly control the physical properties of the plastic surface.

The present invention is intended to solve the above-mentioned problems of the prior art. The object of the present invention is to provide an antireflection coating for plastic optical components.

[Structure of the Invention] The antireflection coating for a plastic optical component of the present invention includes a first layer made of silicon dioxide (SIO2) formed on the surface of the plastic optical component, and a fluoride film formed on the first layer. In the structure in which a second layer made of magnesium (Mnrt) is formed to constitute an antireflection film, the first layer
When the design standard wavelength of the layer and d1 is λ0, the optical thickness N1 dl of each layer and N, d are the design standard wavelength λ.

For o, o s oλ. <'N+ 't < CL 52
0λ00.125λo <Nt dt <α375λ.

The first layer and the second layer are characterized in that the temperature of the plastic optical component is within the range of 70°C to 70°C.
It is formed by vacuum evaporation in a state heated to 100° C. or by other methods.

In the present invention, the optical thickness N, dl of the first layer is o,
o s oλ0 <Mldt <o, s 20λ. The reason for this is to prevent cracks in the antireflection film and improve heat resistance, and the optical thickness of the first layer is o, osoλ. This is because cracks are likely to occur after the second layer is formed, and a thickness of 0.520λ0 or more is not preferable from the viewpoint of antireflection effect and shape variation of the optical component. Also, the optical thickness of the second layer n, 't is Q, 125λo <It d
l < α575λ. When providing an antireflection effect using the first and second layers, even if there is a variation in the antireflection properties due to a difference in the optical thickness of the first layer, the second layer's Optical film thickness from 0.125λ0 to 0.575λ0
This is because by selecting an appropriate value within the range of , it is possible to obtain an antireflection film with practically necessary characteristics. Note that the above numbers were confirmed through experiments.

[Effects of the Invention] In order to confirm the effects of the anti-reflection film of the present invention, an experiment was conducted to compare the characteristics of the anti-reflection film of the present invention and a conventional anti-reflection film according to the following two examples.

FIG. 3(a) shows a first embodiment of the present invention, and FIG. 3(b) shows a second embodiment. In the figure, 1 is an optical lens made of polymethyl methacrylate (PMMA) as a plastic optical component, and a first layer 3 of silicon dioxide and a second layer 2 of magnesium fluoride are formed on the surface as an antireflection film. has been done. The specific contents are shown in Tables 1 and 2 below. In addition, the design reference wavelength λ. is 560μ
In Example 1, the antireflection film was formed by a vacuum evaporation method while the optical lens was maintained at a temperature of around 75° C. in Example 1, and at room temperature in Example 2.

Table 1 (First Example) Table 2 (Second Example) This was carried out to compare the characteristics of the anti-reflection film of the present invention in the first example and the second example and the conventional anti-reflection film. The experiments were as follows: (1) Durability test (temperature 40℃, relative temperature 9 degrees)
Leave it in a high temperature, high humidity atmosphere for about 1000 hours, (
2) Heat resistance test (Raise the temperature by 10℃ from the initial temperature, leave it at a constant temperature for 2 hours, and then test the surface of the optical lens at a magnification of 2
(6) Lead fiber hardness test (, r■sK 54
In 00), a conventional antireflection film for comparison was a magnesium fluoride antireflection film formed on the surface of an optical lens made of polymethyl methacrylate by vacuum evaporation. The test results are shown in Table 3.

Stop [mi Z, 'L narrow, MW, and immediately at the point of the melon. In addition, in the conventional example, cracks sometimes occurred during the formation of the anti-reflection film, but in the embodiment of the present invention, the anti-reflection film was always stable. is PMMA having the anti-reflection film of the first embodiment $1! Optical lens, d is 1'MMA with antireflection film of the second embodiment
It shows the spectral reflectance of manufactured optical lenses. As can be seen from the figure, the spectral reflectance of the PMMA optical lens equipped with the antireflection film of the present invention is no inferior to that of the conventional example.
It is rather advantageous in terms of color tone improvement because it has sharp characteristics.

As mentioned above, in the present invention, the first silicon dioxide
Providing this layer improves the durability and heat resistance of plastic optical components having an antireflection film, and also prevents the occurrence of cracks, thereby having the effect of eliminating the drawbacks of the prior art. Furthermore, the present invention can be applied to plastic products other than the PMMA optical lenses shown in the examples, so its practical value is extremely high.

[Brief explanation of drawings]

Figure 1: Diagram showing the anti-reflection coating of the conventional plastic optical component Figure 2: Diagram showing the cracks that occurred in the anti-reflection coating of Figure 1 In the diagrams, (a) is the first example, (b) is the second example, No. 4N: Grafted plastic substrate ( Optical lens) 2... 2nd layer (magnesium fluoride) 5... 1st layer (silicon dioxide) 4... Crack

Claims (2)

[Claims] (1) A first layer made of silicon dioxide (SIO, ) is formed on the surface of a plastic optical component, and a second layer made of magnesium fluoride (MSV, ) is formed on the first layer. In the structure constituting an anti-reflection film, the first layer and the second layer have refractive indexes of N, , N, geometric thicknesses of dl and dl, and a design reference wavelength of 4,
The optical thickness Nl'1 and IJ,d of each layer are 0,050λ with respect to the design reference wavelength λ0. <N, d, (0,520λ00,1
Anti-reflection coating for plastic optical components, characterized in that it is within the range of 25λo(N, d!(0,375λ0) (2) The first layer and the second layer are made of plastic according to claim 1, wherein the first layer and the second layer are formed by holding a plastic optical component at a temperature of 70°C to 100°C. Anti-reflection coating for optical parts 0