JPH0763903A - Optical thin film of plastic optical parts and its film formation - Google Patents

Abstract

PURPOSE:To realize an optical thin film of plastic optical parts having excellent optical characteristics and sufficient mechanical strength and durability. CONSTITUTION:An under coat film of SiOx (1<=x<=12) is formed on a substrate W consisting of PMMA by heating SiO to evaporate in an evaporating source by resistance heating. The pressure in a vacuum chamber 1 is then reduced to 8X10<-6>Torr and the vapor of MgF2 is generated from a cluster ion beam evaporating source 3 to form the MgF2 film having, for example, an optical film thickness of 130nm. The substrate W is not heated during the formation of the under coat and the MgF2 film. The MgF2 film formed by a cluster ion beam vapor deposition method has an excellent antireflection characteristic and has a high packing rate and, therefore, the mechanical strength, such as adhesion property, wear resistance and solvent resistance, and durability are sufficient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical thin film of a plastic optical component such as an antireflection film for preventing surface reflection of a plastic lens or mirror, and a film forming method thereof.

[0002]

2. Description of the Related Art Optical parts such as plastic lenses and mirrors have been widely used in recent years because they can significantly reduce weight and cost compared with inorganic glass, and various plastic materials are used for this purpose. Things are being developed.
Similar to the optical component made of inorganic glass, the plastic optical component needs to be provided with an optical thin film such as an antireflection film composed of various single layer films or various multilayer films. For the anti-reflection film of the optical parts made of inorganic glass, the substrate is 200 ° C.
Films are often formed by heating to 0 ° C. However, if the plastic optical parts are heated to a high temperature, they may be deformed by heat and their optical characteristics may be deteriorated. I can't. Also, when an optical thin film such as an antireflection film or a highly reflective film is formed without heating the substrate by the vacuum vapor deposition method, the mechanical strength and durability such as the adhesion of the film, abrasion resistance, solvent resistance, etc. Run out. Therefore, in order to form an optical thin film excellent in mechanical strength and durability without heating the base of the plastic optical component to a high temperature,
Various measures have been taken to reduce the temperature of the substrate during film formation to 50
It not ° C. and method for controlled between 80 ° C., it is proposed to adopt the RF ion plating method, SiO _2, Z
In the case of an antireflection film containing an oxide such as rO ₂ or Al ₂ O ₃ as a main component, some effects have been confirmed.

On the other hand, recently, optical thin films such as antireflection films and high reflection films have been developed which have improved optical properties such as antireflection properties by using MgF ₂ as a low refractive index material. The MgF ₂ film generally has a very low filling rate, and it is not possible to obtain sufficient mechanical strength and durability by controlling the substrate to a relatively low temperature or employing the ion plating method as described above. Therefore, in order to improve the filling rate of the MgF ₂ film, the degree of vacuum in the film forming chamber is set to 1 × 1.
Although a method of applying a high vacuum of 0 ^-6 Torr or more has been developed (see Japanese Patent Laid-Open No. 2-298252), the adhesiveness is slightly improved by reducing the amount of residual water and impurities on the surface of the substrate. However, it was found that the wear resistance was insufficient, and it was found that the filling rate of the MgF ₂ film could not be greatly improved even under a high vacuum of 1 × 10 ⁻⁶ Torr or more.

Further, in order to supplement the softness of the base body of the plastic optical part, an undercoat of silicon oxide SiOx is provided between the base body and the optical thin film such as an antireflection film or a high reflection film to make the plastic optical part A method of strengthening the surface hardness has also been developed (see Japanese Patent Laid-Open No. 53-306). This method can be expected to be particularly effective when the thickness of the optical thin film is small. Even when the filling rate of the optical thin film is high and therefore the hardness is sufficient, the adhesion and the like tend to be insufficient without the SiOx undercoat.

[0005]

However, according to the above-mentioned conventional technique, as described above, M as a low refractive index material is used.
In the case of an antireflection film or the like using gF ₂ , if the film is formed without heating the substrate to a high temperature, the filling rate of MgF ₂ will be insufficient, so that sufficient adhesion, abrasion resistance, solvent resistance, etc. It is impossible to obtain an optical thin film having mechanical strength and durability.

The present invention has been made in view of the above problems of the prior art, and has at least one layer of MgF ₂
An optical thin film having a film, and an object thereof is to provide an optical thin film of a plastic optical component having sufficient mechanical strength and durability even if it is formed without heating and a film forming method thereof. Is.

[0007]

In order to achieve the above object, the optical thin film of the plastic optical component of the present invention is made of SiOx (1≤1) provided on the surface of a plastic substrate.
x ≦ 2) undercoat and an optical thin film laminated thereon, wherein the optical thin film is at least one layer of MgF ₂
It has a film, and the MgF ₂ film is formed by a cluster ion beam vapor deposition method.

The optical thin film is preferably an antireflection film.

[0009]

Since the optical thin film has at least one MgF ₂ film, the optical properties of the optical thin film are significantly improved. In addition, even if the substrate is not heated, the MgF ₂ film is formed by the cluster ion beam deposition method. Since it is formed into a film, its filling rate is sufficiently high, and therefore, there is no fear that mechanical strength and durability are insufficient. Further, since the undercoat of SiOx is provided, the softness of the plastic substrate is compensated for, and an antireflection film, which is an optical thin film of a plastic optical component, having excellent mechanical strength and durability can be obtained.

[0010]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of a film forming apparatus used in the film forming method of the present invention, which is a vacuum chamber 1 having an exhaust port 1a, and a dome-shaped substrate holder 2 arranged above the vacuum chamber 1.
And a cluster ion beam evaporation source 3, a resistance heating evaporation source 4, and an electron gun heating evaporation source 5, which are respectively arranged at the bottom of the vacuum chamber 1, and the substrate holder 2 has a plurality of substrates at equal intervals in the circumferential direction. It holds W and is rotated by a rotating mechanism (not shown). Further, a crystal monitor 6 for monitoring the evaporation rate is arranged at a position close to the outer peripheral edge of the substrate holder 2, and an optical monitor 7 for monitoring the film thickness of a thin film to be formed is further provided at the rotation center of the substrate holder 2. It is provided.

(First Embodiment) A substrate, which is a plastic substrate made of polymethylmethacrylate (PMMA), is held by a substrate holder 2 and the vacuum chamber 1 is set to 2 × 10 ^-6 T.
After reducing the pressure to orr or less, oxygen is introduced from an atmosphere adjusting line (not shown), and silicon monoxide SiO is heated and evaporated by the resistance heating evaporation source 4 to obtain a silicon oxide SiOx (1 ≦ x ≦ 2) having an optical film thickness of 300 nm. Of undercoat was deposited. Then, vapor of magnesium fluoride MgF ₂ was generated by the cluster ion beam evaporation source 3, and a MgF ₂ film which was an optical thin film having an optical film thickness of 130 nm was formed by the cluster ion beam vapor deposition method. The substrate was not heated (room temperature) during the above film forming process. The conditions for forming the MgF ₂ film by the cluster ion beam evaporation method are as follows: the temperature of the crucible heating of the cluster ion beam evaporation source 3 is 2000 ° C. or less, the acceleration voltage is 2 kV or less, the ionization voltage is 400 V or less, the ionization current is 400 mA or less, and the vacuum chamber 1 is used. Vacuum degree of 8 ×
Samples 1 to 5 were prepared by controlling the pressure to 10 ^-6 Torr or less and changing the content within this range as shown in Table 1.

[0013]

[Table 1] As a result of measuring the spectral characteristics of reflectance for Samples 1 to 5, calculating the refractive index and the absorptance at wavelengths of 500 nm and 400 nm, and examining the adhesion, abrasion resistance, and solvent resistance immediately after film formation and after the durability test. Is shown in Table 2.

[0014]

[Table 2] Mechanical property evaluation: ○: Good in all samples △: Inferior in some samples ×: Inferior in most of samples Mechanical properties after 500 hours endurance test at 70 ° C and 85% humidity in parentheses It is the result of the evaluation.

From this table, it can be seen that the reflectance of this embodiment is extremely excellent in all points.

The method of evaluating mechanical properties was as follows. As for the adhesive force, a cellophane tape was adhered and peeled off, and a peeled body of the film was confirmed. Abrasion resistance is 500 with Silbon paper
A load of gf was applied and it was confirmed whether there were 50 reciprocating scratches. Regarding the solvent resistance, the presence of a 50 reciprocating scratch was confirmed by impregnating sillbon paper with an alcohol + ether solvent and applying a load of 500 gf.

Further, FIG. 2 shows the spectral characteristics of the reflectance of Sample 2. The other samples were almost the same. It can be seen from FIG. 2 that the antireflection film of this example has a reflectance of 2.5% or less in the visible range and has sufficient antireflection properties.

(Comparative Example) For comparison, Sample 6 was prepared by controlling a part of the film forming conditions of the MgF ₂ film to a value exceeding the above range as shown in Table 3 in the same process as in the first embodiment. 9 to 9 and a MgF ₂ film was formed by a conventional vacuum evaporation method to prepare Sample 10.

[0019]

[Table 3] That is, sample 6 has an ionization voltage of 500 V and an ionization current of 450 mA, samples 7 and 8 have acceleration voltages of 3 kV and 5 kV, respectively, and sample 9 has an acceleration voltage of 5 kV, an ionization current of 350 mA, and a vacuum degree of a vacuum chamber. The control was performed at 9 × 10 ⁻⁶ Torr, and the remaining film forming conditions were controlled in substantially the same manner as in the samples 1 to 5 of the first embodiment.

First for each sample 6 to 10 of the comparative example
Table 4 shows the results obtained by calculating the refractive index and the absorptance in the same manner as in the examples and examining the adhesion, abrasion resistance and solvent resistance immediately after film formation and after the durability test.

[0021]

[Table 4] As can be seen from Table 4, if the acceleration voltage is 5 kV or less, the ionization voltage is 500 V or less, the ionization current is 500 mA or less, and the vacuum degree of the vacuum chamber is 1 × 10 ⁻⁵ Torr or less, absorption, adhesion, and abrasion resistance are higher than those in the conventional example. However, in order to obtain a high quality antireflection film in all respects, it is desirable to limit the film forming conditions of the cluster ion beam vapor deposition method to the above range.

According to this embodiment, when an antireflection film consisting of an SiO ₂ undercoat and a MgF ₂ film is formed on the surface of a plastic optical component, the MgF ₂ film is formed even if the substrate is not heated. By carrying out the film by the cluster ion beam deposition method, the filling rate thereof can be strengthened, and the mechanical strength and durability of the antireflection film such as adhesion, abrasion resistance and solvent resistance can be greatly improved.

(Second Embodiment) Using the film forming apparatus of FIG. 1, SiOx is formed on the substrate which is the base of PMMA in the same manner as in the first embodiment.
Of undercoat of Titanium oxide T
A four-layer antireflection film, which is an optical thin film, was manufactured by alternately laminating the iO ₂ film and the MgF ₂ film, and this was designated as Sample 11.
Each MgF ₂ film is formed by a cluster ion beam vapor deposition method, and the film forming conditions are the same as those of Sample 2 shown in Table 1. Each TiO ₂ film is formed by the resistance heating evaporation source 4 or the electron gun. A film was formed using the heating evaporation source 5. The substrate was not heated (room temperature) during the formation of the undercoat, each MgF ₂ film, and each TiO ₂ film. Also, the same 4
A multilayer antireflection film, in which a SiO ₂ film was laminated instead of the MgF ₂ film closest to the undercoat, was produced, and this was used as Sample 12. In addition, in the same film forming process, MgF ₂
A four-layer antireflection film which does not include any film and uses a SiO ₂ film in place of the film was manufactured, and this was used as Sample 13. Each Si
The conditions for forming the O ₂ film were the same as those for the undercoat. Undercoat and 4 for each of Samples 11-13
The optical film thickness of each layer of the layer antireflection film is as shown in Table 5.

[0024]

[Table 5] 3 to 5 are graphs showing the spectral characteristics of the reflectances of Samples 11 to 13, respectively. As can be seen from these, the average reflectance in the visible region of Samples 11 and 12 is 0.2% or less. , Again, adhesion,
The results of examining the abrasion resistance and the solvent resistance by the same method as described above were all good. Sample 13 was similar to Samples 11 and 12 in terms of adhesion, abrasion resistance and solvent resistance, but as can be seen from FIG.
The reflectance is higher than that of, and the antireflection property is insufficient.
It is considered that this is because the four-layer antireflection film does not include the MgF ₂ film.

According to this embodiment, when an antireflection film composed of a multilayer film including an SiO ₂ undercoat and a MgF ₂ film is formed on the surface of a plastic optical component, the plastic substrate is not heated. Also, the filling rate is enhanced by forming the MgF ₂ film by the cluster ion beam vapor deposition method, and the adhesion, abrasion resistance,
Mechanical strength such as solvent resistance and durability can be significantly improved.

When the optical film thickness of the SiO ₂ undercoat is 50 nm or less, the mechanical strength generally decreases, and when the antireflection film is a multilayer film,
Experiments have shown that cracks tend to occur when the optical film thickness of the undercoat exceeds 800 nm.

[0027]

Since the present invention is constructed as described above, it has the following effects.

It is possible to realize an optical thin film of a plastic optical component having excellent optical characteristics and having sufficient mechanical strength and durability.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating a film forming apparatus used in a film forming method according to a first embodiment and a second embodiment.

FIG. 2 is a graph showing a spectral characteristic of reflectance of Sample 2 of the first example.

FIG. 3 is a graph showing the spectral characteristics of reflectance of Sample 11 of the second example.

FIG. 4 is a graph showing a spectral characteristic of reflectance of a sample 12 of the second example.

FIG. 5 is a graph showing spectral characteristics of reflectance of Sample 13 of the second example.

[Explanation of symbols]

 1 vacuum chamber 2 substrate holder 3 cluster ion beam evaporation source 4 resistance heating evaporation source 5 electron gun heating evaporation source

Claims (5)

[Claims] 1. A and undercoat of SiOx provided on the surface of the plastic substrate (1 ≦ x ≦ 2), consists of an optical thin film deposited thereon, MgF ₂ of the optical thin film is at least one layer An optical thin film for a plastic optical component, which has a film, and the MgF ₂ film is formed by a cluster ion beam vapor deposition method. 2. The optical thin film according to claim 1, wherein the optical thin film is an antireflection film. 3. The optical thin film of a plastic optical component according to claim 1, wherein the optical film thickness of the undercoat is within a range of 50 nm to 800 nm. 4. SiOx on the surface of a plastic substrate
(1 ≦ x ≦ 2) forming an undercoat, and at least one layer of MgF ₂ on the formed undercoat.
An optical process for a plastic optical component, comprising laminating optical thin films having a film, wherein the substrate is not heated during each process, and the MgF ₂ film is formed by a cluster ion beam deposition method. Thin film forming method. 5. The MgF ₂ film is formed by using a crucible heating temperature of a cluster ion beam evaporation source of 2000 ° C. or less, an acceleration voltage of 2 kV or less, an ionization voltage of 400 V or less, an ionization current of 400 mA or less, and a vacuum degree of 8 × 10 ⁻⁶ Torr or less. 5. The method for forming an optical thin film of a plastic optical component according to claim 4, wherein the film forming condition is performed.