JPH0442201A - Antireflecting film of plastic optical parts and formation thereof - Google Patents

Abstract

PURPOSE:To enhance the adhesive property to plastic optical parts and to improve the durability of the antireflecting film by forming this film into a three-layered structure of a 1st layer and 2nd layer consisting of hafnium oxide and a 3rd layer consisting of silicon dioxide and forming the film by introducing gaseous oxygen at the time of forming the 1st layer. CONSTITUTION:The vapor deposited films of the three-layered structure of the 1st layer and 2nd layers 2, 3 consisting of the hafnium oxide and the 3rd layer 4 consisting of the silicon dioxide are formed on the surface of a plastic lens 1 to constitute the antireflecting film. The gaseous oxygen is introduced and the hafnium oxide of the 1st layer 2 is formed in the oxidizing gaseous atmosphere at the time of forming this film, by which the refractive index of the hafnium oxide of the 1st layer 2 is so controlled as to be smaller than the refractive index of the hafnium oxide of the 2nd layer 3. The antireflecting film having the excellent adhesive property to the plastic optical parts, durability and optical characteristics is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention 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, and a method for forming the antireflection coating.

Conventional technology Traditionally, inorganic glass has been widely used for optical parts such as lenses, but in recent years, plastics have been used for optical parts such as lenses because they are lightweight, easy to process, and suitable for mass production. It has come to be used as a material for

However, like inorganic glass, optical components made of plastic also have the disadvantage of large reflection of light on their surfaces.

In order to eliminate this drawback, an antireflection film similar to that of inorganic glass is formed on the surface of plastic optical components. Antireflection coatings are typically formed by vacuum deposition.

Hereinafter, a conventional antireflection film for plastic optical components and a method for forming the same will be described with reference to the drawings. The single-layer anti-reflection coating is made of magnesium fluoride (MgFz), and its structure is shown in Figure 2.
7 in Figure 3 shows the spectral reflection characteristics when formed on the surface of a plastic lens made of acrylic resin (polymethyl methacrylate) with a refractive index of 1.49 as a plastic optical component.
Shown below.

For comparison, 8 in FIG. 3 is a diagram showing the spectral reflection characteristics of a plastic lens without an antireflection film formed thereon. In FIG. 2, 1 is a plastic lens, and 5 is an antireflection film made of magnesium fluoride. The antireflection film 5 is usually formed by a vacuum deposition method. This anti-reflection film uses one type of vapor deposition material, but there is also an anti-reflection film using only silicon monoxide (Sin) that uses one type of vapor deposition material (
USP No. 4497539). Among those using two types of vapor deposition materials, a three-layer structure using silicon dioxide (SiOz) and magnesium fluoride (Japanese Patent Laid-Open No. 6012
No. 9701) and an antireflection film with a two-layer structure of cerium oxide (CeO2) and silicon oxide (Sin) (Japanese Patent Laid-Open No. 631)
72201). Furthermore, silicon dioxide (Si
There is an anti-reflection film having a three-layer structure of aluminum oxide (A1203), aluminum oxide (A1203), and cerium oxide (Japanese Unexamined Patent Publication No. 81402/1983).

Problems to be Solved by the Invention In the conventional example of forming an anti-reflective film made of magnesium fluoride, the flow temperature and thermal deformation temperature of plastic are low, so the substrate heating required when forming an anti-reflective film on inorganic glass is difficult. (usually at 300″C to 400″C), a strong antireflection film cannot be formed. Therefore, an antireflection film is formed on the surface of a plastic optical component at a low temperature of 50 to 60°C or lower. However, the antireflection film formed at such a low temperature has low magnesium fluoride crystal content and is a very soft film that is easily damaged and has low durability. Therefore, recently, in order to improve the adhesion and durability between the anti-reflection film and the surface of plastic optical components, methods have been developed in which plastic optical components are heated to 60 to 80°C and vacuum deposited, and RF ion blating methods are used. A method of forming an antireflection film using However, in this method, the deposition conditions are delicately controlled, and the antireflection film is likely to crack during formation. It is difficult to maintain constant formation conditions and maintain a constant condition of the plastic surface so that the anti-reflective film does not develop cranks.
It is not suitable for mass production. Furthermore, polymethyl methacrylate (PM), which is often used as a material for optical components,
MA), diallyl glycol carbonate (CR39
) has a refractive index of 1.4.
As low as 9.1.50, magnesium fluoride (refraction heavy translation 1.
The single layer film of No. 38) had a residual reflectance of about 1.5%, as shown in 7 in FIG. 3, and did not have sufficient properties as an antireflection film. It has also been proposed in the past. - Regarding the three-layer antireflection film using only silicon oxide (USP No. 4,497,539), it is known that the refractive index of SiO, which is the vapor deposition material, changes greatly depending on the vapor deposition conditions, and the range is about 1.
50 to 1.90.

However, there is a problem in that the refractive index of SiO tends to change over time, and therefore the optical properties as an antireflection film are also unstable.

Three-layer anti-reflection coating of magnesium fluoride and silicon dioxide (
JP-A-60-129701) has a magnesium fluoride layer sandwiched between silicon dioxide layers, so no cracks occur (durability is also relatively good).

However, the residual reflectance is about the same as that of a single layer film, so it does not have sufficient characteristics.

Double-layer anti-reflection coating of cerium oxide and silicon oxide (Unexamined Japanese Patent Publication No. 6
3-172201) has a problem in the stability of optical properties because the refractive index of SiO, which is a thin film material, tends to change over time. Furthermore, an antireflection film (Japanese Patent Application Laid-open No. 81402/1983) using three or more types of vapor deposition substances increases manufacturing costs due to the necessity of material management. As mentioned above, conventional anti-reflection coatings for plastic optical components have problems such as poor adhesion to the plastic surface, poor durability, insufficient optical properties as an anti-reflection coating, and lack of stability in optical properties. , or that it was not suitable for mass production.

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

Means for Solving the Problems In order to solve the above problems, the present invention provides a first layer, a second layer, and a third layer on the surface of a plastic optical component in order from the surface side.
This is a structure in which an antireflection film is formed by forming a vapor deposited film with a three-layer structure, in which the first layer and the second layer are made of hafnium oxide, and the third layer is made of hafnium oxide.
A method for forming an anti-reflective film, characterized in that when forming the anti-reflective film with the three-layer structure, the first layer of hafnium oxide is formed in an oxygen gas atmosphere. It provides:

Function The present invention relates to an antireflection film formed on the surface of a plastic optical component, comprising a first layer, a second layer, and a third layer in order from the surface side.
The first and second layers are made of hafnium oxide, and the third layer is made of silicon dioxide.When forming the first layer of hafnium oxide, oxygen (
0°) The refractive index of the hafnium oxide in the first layer is controlled to be smaller than the refractive index of the hafnium oxide in the second layer by introducing gas and forming in an oxidizing gas atmosphere, and the Improves adhesion.

As a result, an antireflection film with excellent adhesion, durability, optical properties, and mass productivity can be obtained.

EXAMPLE Hereinafter, a reflective film for a plastic optical component according to an example of the present invention and a method for forming the same will be described with reference to the drawings. FIG. 1 is a block diagram (cross-sectional view) of an antireflection film for a plastic optical component according to the present invention, and 6 in FIG. 3 shows its spectral reflection characteristics. In this embodiment, the plastic optical component is a plastic lens made of acrylic resin (polymethyl methacrylate). In FIG. 1, 1 is a plastic lens, 2.3 is a first layer and a second layer made of hafnium oxide, and 4 is a third layer made of silicon dioxide.The specific contents of the present invention are shown in Table 1. That's right.

(Margin below) Table 1 (λ.-500n111) The conditions for forming each layer are as follows. The first layer has no vacuum layer, and after evacuating to 1.0X10-'Torr, oxygen gas is pumped to 5.0X10-'Toor to 1.0X10'.
Hafnium oxide is introduced up to the surface and the optical film thickness is λ by electron beam evaporation. /4 (λ.-500 nm) at a deposition rate of about 12 to 15 people/sec.

The refractive index of hafnium oxide at this time was 1.70.

Next, the introduction of oxygen gas was stopped and the vacuum level was 1.5X10-5T.
.

Hafnium oxide is deposited by electron beam evaporation to an optical thickness of λ below rr. /4 thickness and deposition rate, about 3 to 7 people/s
ec was formed. At this time, the refractive index of hafnium oxide is 2
．． It was 00. Next, silicon dioxide was deposited to an optical thickness λ using the same electron beam evaporation method.

The film was formed at a deposition rate of approximately 7 to 15 persons/sec to a thickness of 1/4 mm. The refractive index of silicon dioxide at this time was 1.46.

In order to confirm the adhesion and durability of the antireflection film of the example of the present invention, the following tests were conducted. (1) Peeling test: 1 in a high temperature and high humidity atmosphere with a temperature of 40°C and a relative humidity of 85%.
After being left for 1,000 hours, the adhesive tape was adhered to the surface of the plastic optical component and then peeled off.

(2) Humidity test: Leave in a high-temperature atmosphere at 40° C. and 95% relative humidity for 100 hours. (3) Thermal shock test: The test piece was left in low and high temperature atmospheres at temperatures of 30°C and 70'C for about 100 hours, alternately for 30 minutes each.

The test results are shown in Table 2.

As can be seen from Table 2, the antireflection film of the present invention has excellent adhesion and durability. Furthermore, in some cases in the past, the occurrence of cranking was observed during the formation of the antireflection film, but in the examples of the present invention, it was always stable. Regarding the spectral reflection characteristics, as can be seen from 6 in Figure 3, the center wavelength (λ.=
500 nm), the reflectance was 0.1% or less, and a reflectance of 1.0% or less was obtained in the band of approximately 425 to 610 nm.

In addition, in the above example, each film thickness was set as shown in Table 1, but the film thickness is not particularly limited to the above values,
It may be changed according to the design wavelength, and the structure may be as shown in FIG. 1.

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 3N layer consisting of the first and second layers made of hafnium oxide and the third layer made of silicon dioxide.
In addition, when forming the first hafnium oxide layer, oxygen gas is introduced in an oxygen atmosphere to improve adhesion to plastic optical components and improve the durability of the anti-reflection coating. In addition to improving the spectral reflection characteristics, it also prevents the occurrence of cracks and has the effect of eliminating the drawbacks of the conventional examples. 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 drawings]

FIG. 1 is a cross-sectional view of the structure of the antireflection film of the plastic optical component of the present invention, FIG. 2 is a structure diagram of the antireflection film of the conventional plastic optical component, and FIG. 3 is a graph showing the spectral reflection characteristics. . 1...Plastic lens, 2.3...
- Layer made of hafnium oxide, 4... Layer made of silicon dioxide, 5... Layer made of magnesium fluoride, 6... Layer of plastic lens in the embodiment of the present invention. Characteristics of anti-reflection film, 7...Characteristics of anti-reflection film of conventional plastic lenses (single layer film made of magnesium fluoride), 8...Plastic without anti-reflection film formed Lens characteristics.

Claims (1)

Scope of Claims: (1) An antireflection film formed on the surface of a plastic optical component, which has a three-layer structure of a first layer, a second layer, and a third layer in order from the surface side, An antireflection coating for a plastic optical component, characterized in that the first layer and the second layer are made of hafnium oxide (HfO_2), and the third layer is made of silicon dioxide (SiO_2). (2) The antireflection coating for a plastic optical component according to claim (1), wherein the first layer of hafnium oxide has a smaller refractive index than the second layer of hafnium oxide. (3) A method for forming an antireflection film for a plastic optical component, which comprises introducing oxygen gas when forming the first layer of hafnium oxide (HfO_2).