JPS6381403A - Reflection reducing coating of plastic optical parts - Google Patents

Abstract

PURPOSE:To eliminate the change of refractive index with the lapse of time and to improve the adhesion of the coating to the substrate by forming a first layer consisting of SiO2, a second layer consisting of Al2O3, a third layer consisting of CeO2, and a fourth layer consisting of Al2O3, and a fifth layer consisting of CeO2, on the surface of the plastic optical parts, providing thus respectively specified refractive index and optical film thickness to each layer. CONSTITUTION:A first layer consisting of SiO2 to the outermost side contacting with air, a second layer consisting of Al2O3, a third layer consisting of CeO2, and a fourth layer consisting of Al2O3, and a fifth layer consisting of CeO2, are formed on the surface of a plastic optical parts, wherein following conditions as described by the formulas among n1 (the refractive index of the first layer), n2 (the refractive index of the second layer), n3 (the refractive index of the third layer), n4 (the refractive index of the fourth layer), n5 (the refractive index of the fifth layer), n1d1 (the optical film thickness of the first layer), n2d2 (the optical film thickness of the second layer), n3d3 (the optical film thickness of the third layer), n4d4 (the optical film thickness of the fourth layer), n5d5 (the optical film thickness of the fifth layer), and lambda0 (the designed principal wavelength), are satisfied. By this constitution, there is no fear of causing change of the refractive index with the lapse of time, and the adhesion of the reflection reducing coating to the substrate is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an antireflection film that has excellent adhesion to synthetic resin optical components.

The conventional antireflection film can obtain an antireflection effect by having a structure in which materials having different refractive indexes are laminated.

As for the structure of the anti-reflection film, there is a known technique in which silicon dioxide or silicon monoxide is interposed and the anti-reflection film is formed thereon (for example, Japanese Patent Application Laid-Open No. 55-101901, Japanese Patent Application Laid-open No. 6O-13070I). Public bulletin or Japanese Patent Application Publication No. 1986
-130704 publication or JP-A-60-13150
Publication No. 1, etc.).

Coating with a thin film such as silicon dioxide eliminates the disadvantage that the surfaces of synthetic resin optical parts are weak and easily scratched by mechanical scratches and solvents such as chemicals, and improves surface hardness and durability. This is for the purpose of achieving this goal.

However, since silicon dioxide has a refractive index almost equal to the refractive index of synthetic resin optical components, it does not play the role of providing an antireflection effect, but only exists as an intervening layer that improves the adhesion between the resin optical components and the antireflection coating. I haven't. Moreover, the intervening layer needs to have a certain thickness or more, and this film also causes problems such as a decrease in the efficiency of the antireflection effect and difficulty in maintaining the surface precision.

On the other hand, like silicon dioxide, -silicon oxide is utilized for its good adhesion to resin optical parts.

However, a problem exists in the instability of the reflectance characteristics.

Therefore, it is desired that the substance itself has an antireflection effect, is not subject to change over time, and has good adhesion to synthetic resin optical parts.

The technique disclosed in Japanese Patent Application Laid-Open No. 55-101901 uses silicon monoxide (SiO) or silicon dioxide (St) on the resin substrate side.
A glass layer (approximately 2 μm to 3 μm thick) consisting of ow) is prepared, and an antireflection film is coated on it. The glass layer needs to have a certain thickness. For example, when a glass layer is coated by a dipping method, it is difficult to control the film thickness, and it is difficult to maintain the surface precision of the optical member.
Problems such as lack of stability of reflectance characteristics arise.

JP-A-60-130701 or JP-A-60-1
30704 and JP-A-60-131501 disclose an antireflection film having a film made of silicon monoxide and silicon dioxide on a synthetic resin substrate.
- Since the refractive index of the silicon oxide film changes over time, there is a problem that the reflectance characteristics lack stability.

Problems to be Solved by the Invention As mentioned above, antireflection films containing a film made of silicon monoxide or silicon dioxide on a synthetic resin substrate have problems with the stability of surface reflectance (-due to silicon oxide). exists, and it is difficult to maintain surface accuracy (due to the necessity of a certain film thickness of silicon dioxide).

The present invention is based on the knowledge that cerium oxide has very good adhesion to synthetic resins such as acrylic resin, and that the effect can be obtained even if the film thickness of cerium oxide is thin. We have succeeded in producing an antireflection film that eliminates the above-mentioned drawbacks and has good adhesion and does not cause the problem of changes in reflectance over time.

Means for Solving the Problems The present invention provides a first layer of silicon dioxide (Sins), a second layer of aluminum oxide (A1*03), and a cerium oxide layer on the surface of the synthetic resin from the air side to the surface of the synthetic resin. (
The third layer consists of CeOJ, aluminum oxide (AIyO
The present invention relates to an antireflection film characterized in that it has a fourth layer consisting of s) and a fifth layer consisting of cerium oxide (CeO2).

Examples of synthetic resins that can be used in the present invention include resins commonly used for optical components, such as acrylic resin (PMMA),
Polycarbonate resin (PC), polystyrene resin (P
S), refractive index of ultraviolet (UV) curing resin, etc. 1.49 to 1
．． 58 is sufficient.

The fifth layer, cerium oxide, has a higher refractive index than the above resin! ,9
It is as large as 2 to 2.10 and can constitute a good antireflection film. In addition, cerium oxide has very good adhesion to resin,
Moreover, no change in refractive index occurs over time.

Even if the fifth layer has a thin film thickness (optical film thickness), good adhesion with the resin can be obtained and the film thickness is 0.05λ.

(λ. Two design dominant wavelengths) or more, 0.20λ. By adjusting as follows, reduction in reflectance can be achieved over a wide wavelength range of the entire visible light (400 to 700 nm).

The fourth layer of aluminum oxide has a layer with a lower refractive index (1.50 to 1.62) between the 5th and 3rd high refractive index layers made of cerium oxide. composition to increase the anti-reflection effect. Furthermore, aluminum oxide functions to improve the adhesion between the third and fifth layers of cerium oxide.

The third layer of cerium oxide is formed between the fourth layer of aluminum oxide and the second layer. The difference in refractive index provides an antireflection effect.

A second layer of aluminum oxide is formed intermediate the third layer of cerium oxide and the first layer of silicon dioxide. Aluminum oxide has a refractive index between those of cerium oxide and silicon dioxide (1.50 to 1.62), and constitutes an antireflection film, as well as a third layer of cerium oxide and a third layer of silicon dioxide. It works to improve the adhesion of the first layer.

The first layer made of silicon dioxide on the outermost surface takes advantage of the fact that the refractive index of silicon dioxide (1,47) is smaller than the refractive index of the second layer of aluminum oxide, and that silicon dioxide is hard. It constitutes an anti-reflection film and also functions as a surface protective layer.

The first to fifth layers can be provided by vacuum deposition. The thickness is the design dominant wavelength λ. The first layer is 0.20~
0.32λ. , the second ff is 0 to 0.10λ. , the third layer is 0.20 to 0.35λ. , 4th FJ is 0°02~0.1
0λ. , the fifth layer has a thickness of 0.05 to 0.20λ. Set it up so that Even if the fifth layer made of cerium oxide is thin, the antireflection film has very good adhesion.

The antireflection film of the present invention can be used for a variety of synthetic resin optical parts such as plastic lenses for video projectors, plastic lenses for cameras, and composite aspheric lenses.

This will be explained in more detail by giving examples.

Example Using the electron gun method, the ultimate vacuum level was 5 x 10'' without heating the acrylic resin optical parts to be vapor-deposited.
The antireflection films having the film configurations shown in Tables 1 to 5 were fabricated by vapor deposition at a vapor deposition rate of 0.5 nm and 7 seconds at Torr.

Table-1 (Membrane configuration 1) Table-2 (Membrane configuration 2) Table-3 (Membrane configuration 3) λ. = 510 nm; Incident angle θ-0° Table 4 (Film configuration 4) Table 5 (Film configuration 5) The reflectance characteristics of the antireflection coatings with film configurations 1 to 5 are shown in Figures 1 to 5.
It is shown in Figure 5.

As reliability tests for the antireflection films having the film configurations shown in Tables 1 to 5 above, an adhesion test, a chemical resistance test, and an environmental test were conducted.

Adhesion test After adhering the tape to the prepared anti-reflection film thin film surface,
The tape was peeled off perpendicularly from the surface and the state of peeling of the film was observed.

As a result of the adhesion test, no film peeling occurred.

Chemical Resistance Test The surface of the antireflection film prepared using paper and a lens cleaner impregnated with Freonsolve, alcohol, and ether solvents was wiped, but no abnormalities were observed in the film.

Environmental test (humidity resistance test): The prepared anti-reflection film was tested at a temperature of 50°C and a relative humidity of 95°C.
% environment for 500 hours, no abnormality was observed in the film.

(Thermal cycle test) The produced anti-reflection film was left in environments with temperatures of -30°C and +70°C for 1 hour each for 4 cycles.
No abnormality was observed in the membrane.

Effects of the Invention An antireflection film having a thin film of cerium oxide on a synthetic resin optical component substrate has an excellent antireflection effect, and there is no concern that the refractive index will change over time. In addition, since the antireflection film has very good adhesion to the substrate, peeling of the film is less likely to occur.

[Brief explanation of the drawing]

FIGS. 1 to 5 are diagrams showing the reflectance characteristics of the antireflection film of the present invention. $12!1 Figure 2 Kacho C1ml Yoi Figure 3 v, Figure 5

Claims (1)

[Claims] 1. On the synthetic resin surface, from the air side to the synthetic resin surface, a first layer consisting of silicon dioxide (SiO_2), a second layer consisting of aluminum oxide (Al_2O_3), and a second layer consisting of cerium oxide (CeO_2). Third layer, aluminum oxide (A
l_2O_3) and cerium oxide (C
An antireflection film characterized by having a fifth layer consisting of eO_2). 2. The antireflection film according to claim 1, further satisfying the following conditions: n_1=1.47 0.20λ_0≦n_1d_1≦0
．． 30λ_0 1.50≦n_2≦1.62 0<n_2d_2≦0.
10λ_0 1.92≦n_3≦2.10 0.20λ_0≦n_3
d_3≦0.35λ_0 1.50≦n_4≦1.62 0.02λ_0≦n_4
d_4≦0.10λ_0 1.92≦n_5≦2.10 0.05λ_0≦n_5
d_5≦0.20λ_0 However, here, n_1: refractive index of the first layer n_2: refractive index of the second layer n_3: refractive index of the third layer n_4: refractive index of the fourth layer n_5: refractive index of the fifth layer n_1d_1: Optical thickness of the first layer n_2d_2: Optical thickness of the second layer n_3d_3: Optical thickness of the third layer n_4d_4: Optical thickness of the fourth layer n_5d_5: Optical thickness of the fifth layer λ_0: Design dominant wavelength.