JPH05313001A - Reflection preventing film for plastic made optical part - Google Patents

Abstract

PURPOSE:To improve adhesion, durability and spectral characteristics by forming a reflection preventing film of a first layer made of an indium-tin oxide film, and a second and a third layers made of metallic oxides. CONSTITUTION:A first layer 2 formed of an indium-tin oxide film, and a second and a third layers 3, 4 formed of metallic oxides are provided in order from the surface of a plastic made optical part 1 to the air side. Oxygen is led in after exhausting a vacuum deposition tank, for instance, and the indium-tin oxide film with indium oxide and tin oxide added thereto is deposited as the first layer 2. Oxygen is then led in, and cerium oxide is deposited as the second layer 3. The lead-in of oxygen is then stopped, and a silicon dioxide film is deposited as the third layer 4. With this constitution, adhesion to the plastic made optical part 1 is improved by the transparent and conductive indium-tin oxide film of the first layer 2, which results in obtaining a reflection preventing film excellent in adhesion, durability and optical characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antireflection film for plastic optical components used in optical systems such as projection type television receivers, video cameras and still cameras.

[0002]

2. Description of the Related Art Conventionally, a large amount of inorganic glass has been used for optical parts such as lenses, but in recent years, plastics that are lightweight, easy to process and excellent in mass production have been used as materials for optical parts. Has become. However, a plastic optical component such as a plastic lens also has a drawback in that light reflection on the surface is large like the inorganic glass optical component. In order to eliminate this drawback,
It is known as a general technology to form an antireflection film on the surface of a plastic optical component like the inorganic glass optical component to prevent light reflection on the surface (for example, "design and molding technology of precision plastic optical lens"). And its problems "Trikeps Data Book No. 87, P6-1 to P6-4).

A conventional antireflection film of a plastic optical component will be described below with reference to the drawings together with a method of forming the same. The single-layer antireflection film is generally composed of a magnesium fluoride (MgF ₂ ) film, and its cross section is shown in FIG. 3, and an optical component made of acrylic resin (polymethylmethacrylate) having a refractive index of 1.49 ( The spectral reflection characteristic when the magnesium fluoride film 12 is formed on the surface of the optical component 11 is shown in FIG. 4D. The characteristic shown in (e) of FIG. 4 is a spectral reflection characteristic of an optical component (made of polymethylmethacrylate) having no antireflection film for comparison. The antireflection film such as the magnesium fluoride film 12 is usually formed by a vacuum deposition method, but recently, in order to improve the adhesion and durability between the antireflection film and the optical component, the optical component is heated to 60 ° C to 80 ° C. A method of heating and vacuum vapor deposition, and a method of forming using an RF ion plating method are used. The antireflection film shown in FIG. 3 uses one type of vapor deposition material, but two types use a silicon dioxide film and a magnesium fluoride film (JP-A-60-129701). (See Japanese Patent Laid-Open No. 63-172201) and the like using a cerium oxide film and a silicon oxide (SiO _x ) film.

As shown in FIG. 4, the reflection spectral characteristic (d) of the magnesium fluoride film 12 formed is 1.5% at the central wavelength of 520 nm, which is much better than that of (e).

[0005]

However, the above conventional structure has the following problems.

(1) Substrate heating (300 ° C. to 400 ° C.) performed when an antireflection film is formed on an inorganic glass substrate due to the fact that the plastic has a low flow temperature and heat distortion temperature and there is a problem of gas released from the inside of the plastic. ) Is not possible and a strong vapor-deposited film cannot be obtained, and an antireflection film is formed on the surface of a plastic optical component at a low temperature of 40 ° C. to 50 ° C. or less. The antireflection film formed at this low temperature. Has poor adhesion to the plastic surface and low durability.

(2) A plastic optical component is kept at 60 ° C.
The antireflection film formed by heating to 80 ° C. or using the RF ion plating method is likely to have cracks,
Further, it is difficult to keep the conditions during formation constant and the state of the plastic surface constant, which is not suitable for mass production.

(3) As shown in FIG. 4D, the antireflection film of the magnesium fluoride single layer film has a center wavelength (λ ₀ )
The residual reflectance is about 1.5%, which means that it does not have sufficient characteristics as an antireflection film. Further, the antireflection film using the magnesium fluoride film and the silicon dioxide film does not generate cracks and has relatively good durability, but the residual reflectance is about the same as that of the single-layer film, which is not sufficient characteristics. Further, an antireflection film using a cerium oxide film and a silicon monoxide film has a problem in stability of optical characteristics because the refractive index of the silicon monoxide film easily changes with time.

As described above, the conventional antireflection film has problems such as poor adhesion to the plastic surface, poor durability, insufficient optical properties as an antireflection film, and lack of stability in optical properties. I had.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide an antireflection film for plastic optical parts which is excellent in adhesion to plastic optical parts, durability and optical characteristics. To do.

[0011]

In order to achieve this object, an antireflection film for a plastic optical component of the present invention comprises an indium tin oxide film as a first layer in order from the surface of the plastic optical component to the air side. The second layer and the third layer are composed of a metal oxide film.

[0012]

With this structure, the transparent and conductive indium oxide / tin film of the first layer improves the adhesion to the plastic optical component, and as a result, the reflection excellent in the adhesion, durability and optical characteristics. A protective film can be obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an antireflection film of a plastic optical component according to an embodiment of the present invention, and FIGS. 2A to 2C show its spectral reflection characteristics. FIG. 2 also shows the characteristics of the conventional antireflection film (d) and the conventional antireflection film (e). In this embodiment, the optical component is made of acrylic resin (polymethylmethacrylate). In FIG. 1, 1 is an acrylic resin optical component, 2 is an indium tin oxide film, 3 is a cerium oxide film (may be a tantalum pentoxide film or a hafnium oxide film), and 4 is a silicon dioxide film.

(First Embodiment) The structure of the antireflection film of the first embodiment is as shown in (Table 1).

[0016]

[Table 1]

The conditions for forming each film are as follows. First
The layer of indium oxide / tin film is 1.0 × in the vacuum deposition tank.
10 oxygen 3 × 10 ^-5 Tor was evacuated to ^-5 Torr
up to 2 wt. % Optical film thickness of the indium tin oxide film doped λ _0/4 (λ ₀
= 520 nm) at a vapor deposition rate of about 2 to 3Å / sec. At this time, the indium oxide / tin film has a refractive index of 1.90. Then oxygen was introduced until 5 × 10 ^-5 Torr, the optical thickness of the cerium oxide film _{λ 0/4 (λ 0 =} 52
The thickness was 0 nm) and the deposition rate was about 5 to 8 Å / sec. The refractive index of the cerium oxide film at this time is 2.20. Then, the introduction of oxygen was stopped, and the vacuum degree was 1 × 10 ⁻⁵ Tor.
optical film thickness of the silicon dioxide film at _{r λ 0/4 (λ 0} = 520n
m) was formed at a vapor deposition rate of about 10Å / sec. The refractive index of the silicon dioxide film at this time is 1.46.

The spectral reflection characteristic of the first embodiment is shown in FIG. The reflectance was 0.2% or less at the center wavelength (λ ₀ = 520 nm), which was excellent as an antireflection film and excellent characteristics were obtained in a wide band.

(Second Embodiment) The structure of the antireflection film of the second embodiment is as shown in (Table 2).

[0020]

[Table 2]

The conditions for forming each film are as follows. First
The layer of indium oxide / tin film is 1.0 × in the vacuum deposition tank.
10 oxygen 3 × 10 ^-5 Tor was evacuated to ^-5 Torr
up to 3 wt. % Optical film thickness of the indium tin oxide film doped λ _0/4 (λ ₀
= 520 nm) at a vapor deposition rate of about 2 to 3Å / sec. At this time, the indium oxide / tin film has a refractive index of 1.85. Then oxygen was introduced until 5 × 10 ^-5 Torr, tantalum pentoxide film having an optical film thickness of _{λ 0/4 (λ 0 =} 5
The thickness was 20 nm) and the deposition rate was about 7 to 8Å / sec. At this time, the refractive index of the tantalum pentoxide film is 2.10.
Is. Then, the introduction of oxygen was stopped, and the degree of vacuum was 1 × 10 ^-5 T
optical film thickness of the silicon dioxide film _{orr λ 0/4 (λ 0} = 52
It was formed to a thickness of 0 nm) at a vapor deposition rate of about 10Å / sec. The refractive index of the silicon dioxide film at this time is 1.46.

The spectral reflection characteristic of the second embodiment is shown in FIG. 2 (b). The reflectance was 0.4% or less at the central wavelength (λ ₀ = 520 nm), which was excellent as an antireflection film and excellent characteristics were obtained in a wide band.

(Third Embodiment) The structure of the antireflection film of the third embodiment is as shown in (Table 3).

[0024]

[Table 3]

The conditions for forming each film are as follows. First
The layer of indium oxide / tin film is 1.0 × in the vacuum deposition tank.
10 oxygen 3 × 10 ^-5 Tor was evacuated to ^-5 Torr
up to 2 wt. % Optical film thickness of the indium tin oxide film doped λ _0/4 (λ ₀
= 520 nm) at a vapor deposition rate of about 2 to 3Å / sec. At this time, the indium oxide / tin film has a refractive index of 1.90. Then oxygen was introduced until 5 × 10 ^-5 Torr, the optical film thickness of the hafnium oxide film _{λ 0/4 (λ 0 =} 5
20 nm) with a vapor deposition rate of about 5 to 7Å / sec. At this time, the hafnium oxide film has a refractive index of 2.15.
Is. Then, the introduction of oxygen was stopped, and the degree of vacuum was 1 × 10 ^-5 T
optical film thickness of the silicon dioxide film _{orr λ 0/4 (λ 0} = 52
It was formed to a thickness of 0 nm) at a vapor deposition rate of about 10Å / sec. The refractive index of the silicon dioxide film at this time is 1.46.

The spectral reflection characteristics of the third embodiment are shown in FIG. 2 (c). The spectral reflection characteristics of the third embodiment were almost the same as those of the second embodiment. Center wavelength (λ ₀ = 520
nm), the reflectance was 0.4% or less, which was excellent as an antireflection film and excellent characteristics were obtained in a wide band.

The tests conducted to confirm the adhesion and durability of the antireflection films of the above-mentioned first to third embodiments are as follows.
(1) Peeling test (temperature 40 ° C, relative humidity 85%
After left in a high humidity atmosphere for 1000 hours, the adhesive tape is adhered to the surface of the plastic optical component and peeled off. ), (2) Humidity resistance test (temperature 40 ° C, relative humidity 95%
In a high-temperature and high-humidity atmosphere for 1000 hours), and (3) thermal shock test (temperatures of -30 ° C and 70 ° C in a low-temperature / high-temperature atmosphere for 30 minutes alternately for about 100 hours). The results of the adhesion / durability test are as shown in (Table 4).

[0028]

[Table 4]

As shown in (Table 4), each of the antireflection films of this example has excellent adhesion and durability. Further, conventionally, cracks were observed in some cases when the antireflection film was formed, but in this example, it was always stable. In the above embodiments, the respective film thicknesses are shown in (Table 1) to (Table 3), but the film thickness is not particularly limited to the above value and can be changed according to the design wavelength. Good.

[0030]

INDUSTRIAL APPLICABILITY As described above, the present invention has a three-layer structure including a first layer made of an indium tin oxide film, a second layer made of a metal oxide, and a third layer. It is possible to realize an excellent antireflection film for optical parts made of plastic, which has excellent adhesiveness with and improved durability of the antireflection film as well as excellent spectral characteristics and does not generate cracks.

[Brief description of drawings]

FIG. 1 is a sectional view of an antireflection film of a plastic optical component according to an embodiment of the present invention.

FIG. 2 is a spectral reflection characteristic diagram of the antireflection film.

FIG. 3 is a sectional view of an antireflection film of a conventional plastic optical component.

FIG. 4 is a spectral reflection characteristic diagram of the antireflection film.

[Explanation of symbols]

 1 Plastic Optical Components 2 Indium Oxide / Tin Film (First Layer) 3 Cerium Oxide Film (Metal Oxide Film; Second Layer) 4 Silicon Dioxide Film (Metal Oxide Film; Third Layer)

Claims (2)

[Claims] 1. An antireflection film for a plastic optical component, in which the first layer is an indium tin oxide film and the second and third layers are metal oxide films in order from the surface of the plastic optical component to the air side. 2. The antireflection film for a plastic optical component according to claim 1, wherein the second layer is a cerium oxide film, a tantalum oxide film or a hafnium oxide film, and the third layer is a silicon dioxide film.