JP3353931B2 - Optical thin film, optical component formed with this optical thin film, antireflection film, and plastic optical component formed with this antireflection film - Google Patents

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, an optical component having the optical thin film formed thereon, an antireflection film, and a plastic optical component having the antireflection film formed thereon.

[0002]

2. Description of the Related Art In recent years, plastic has been increasingly used in place of inorganic glass as a material for optical components such as lenses, mirrors, and prisms. The main reason for this is that it is lightweight and can be manufactured at low cost, and has the advantage of a large degree of freedom in shape. Also, due to these advantages, recently, they have been widely used for various components other than optical components.

However, parts made of these plastics are inferior in abrasion resistance and abrasion resistance as compared with glass or metal parts, and therefore have many practical problems unless some surface treatment is applied. In particular, when plastic is used as an optical component, it is necessary to form an optical thin film as in the case of optical glass.

As an optical multilayer film serving as an optical thin film of a plastic optical component, many optical multilayer films mainly related to an antireflection film have been proposed.
An antireflection film as disclosed in Japanese Patent Application Publication No. 01-001 is known. This is because SiO ₂ , ZrO ₂ + TiO ₂ , ZrO ₂ , SiO
Alternatively, it has a four-layer structure of SiO ₂ .

[0005]

In order to obtain an optical thin film for obtaining a sufficient antireflection effect over a wide wavelength range, it is necessary to combine a low refractive index material and a high refractive index material. As the high-refractive index substance, ZrO ₂ or TiO ₂ found in the above prior art is often used. However, ZrO ₂ , TiO _{2, and the} like have a high melting point, and in the same setting method of an apparatus as when an antireflection film is formed on a normal glass substrate, the plastic substrate is heated by the influence of radiant heat from the evaporation source, and the substrate is heated. The surface may be damaged to deteriorate the adhesion of the film, or the surface accuracy which is the most important for the optical component may be deteriorated. This is especially true for heat-sensitive acrylic resins (PM
This is remarkable when MA) is used for the substrate. As a countermeasure, a method of increasing the distance from the evaporation source to the substrate or providing a shielding plate between the evaporation source and the substrate to reduce the influence of radiant heat from the evaporation source can be considered.

However, all of the above-mentioned methods require a significant improvement in hardware, so that a conventional apparatus for forming an antireflection film on a glass substrate cannot be used as it is. Was. In addition, the above method inevitably requires a longer deposition time, which is not preferable in terms of productivity. Further, the conventional antireflection film has a drawback that it is vulnerable to a heat cycle and cracks easily occur.

The present invention has been made in view of the above-mentioned conventional problems, and can be easily formed with high productivity using a conventional apparatus, and yet has sufficient adhesion, and the surface accuracy of the substrate is not deteriorated. To provide an optical thin film having excellent durability, especially heat cycle resistance, an optical component formed with the optical thin film, particularly an antireflection film of a plastic optical component and a plastic optical component formed with the antireflection film. The purpose is to:

[0008]

In order to solve the above-mentioned problems, if a material having low radiant heat from the evaporation source can be used, it is necessary to modify the above-mentioned apparatus, to lower the productivity, to obtain a good adhesion, and to improve the adhesion. Problems such as deterioration of accuracy can be solved. As such a material, MoO ₃ , W
O ₃ and CeO ₂ can be cited. Mo
O ₃ and WO ₃ have hitherto hardly received much attention as materials for optical thin films. However, if they are completely oxidized, there is no problem of light absorption, and the refractive index is 1.85.
２．１2.1 (varies depending on the deposition conditions). Therefore, it is possible to use MoO ₃ and WO ₃ as high-refractive-index materials, and to form a broadband antireflection film as an optical thin film.

[0009] On the other hand, CeO2 has absorption on the short wavelength side in the visible region, and is therefore not preferably used as an antireflection film. In particular, application to an imaging system lens is unsuitable.

Therefore, an optical thin film according to a first aspect of the present invention comprises a Si oxide layer formed on a substrate of an optical component,
a layer containing at least one of MoO ₃ and WO ₃ formed on the oxide layer of i. Also,
An optical component according to a second aspect of the present invention is an optical component in which an optical thin film is formed on a substrate, wherein an Si oxide layer formed on the substrate and a MoO layer formed on the Si oxide layer are provided.
₃ and WO ₃ are those having a layer comprising at least one. Further, the antireflection film according to the third invention is characterized in that:
It has an oxide layer of Si of 2 nm or more formed on a substrate of a plastic optical component, and a layer containing at least one of MoO ₃ and WO ₃ formed on the oxide layer of Si. . A plastic optical component according to a fourth invention is a plastic optical component having an antireflection film formed on a substrate, wherein the plastic optical component is formed on the substrate.
a Si oxide layer having a thickness of at least nm and a layer formed on the Si oxide layer and containing at least one of MoO ₃ and WO ₃ .

Here, an optical thin film using MoO ₃ and WO ₃ , particularly an anti-reflection film, is formed on an optical component, particularly a plastic substrate. When the plastic substrate is viewed, the first layer is formed of MoO ₃ and WO ₃ . When used, there was a point that it was still vulnerable to a heat cycle and cracks were easily generated. Accordingly, the present invention provides a multilayer antireflection film formed on a substrate of a plastic optical component, wherein the first layer on the substrate side has an optical thickness nd.
Is an oxide layer of Si having a thickness of 2 nm or more.
It was configured to include at least one layer containing at least one of oO _{3 and} WO ₃ .

[0012] MoO _3, WO ₃ are those that can be used as a high refractive index material constituting an antireflection film made of an optical thin film, each about 2.0 refractive index of the case of forming without heating the substrate, 1.85. In addition, it has a lower melting point than conventional high refractive index materials such as ZrO ₂ and TiO ₂ ,
Further, since the substance has a very high vapor pressure, the energy to be added at the evaporation source can be set extremely low. As a result, without any hardware modifications
The radiant heat from the evaporation source can be kept low, and even if the substrate is a plastic substrate, deterioration of the adhesion of the film due to surface damage of the substrate and deterioration of the surface accuracy do not occur.

As described above, both MoO ₃ and WO ₃ have not received much attention in the past as materials for optical thin films. However, when completely oxidized, MoO ₃ and WO ₃ absorb light having a wavelength of 420 nm or more. And the absorption at 400 nm is slightly less than 2%.
There is no problem at all.

When the antireflection multilayer film is formed using MoO ₃ and WO ₃ , it is needless to say that it may be used as a mixture with another dielectric. MoO ₃ and WO ₃
Or a mixture of MoO ₃ and another dielectric, WO ₃
And other dielectrics, or a mixture of MoO ₃ , WO ₃ and other dielectrics can be used. In this case, it has been confirmed that heat cycle resistance and mechanical strength are particularly improved by mixing with SiO ₂ .

When vapor deposition is to be performed by an electron beam method using MoO ₃ or WO ₃ as a vapor deposition material, the electron beam is reflected and it is difficult to heat the vapor deposition material. However, reflection of an electron beam can be suppressed by mixing a small amount of another dielectric material with MoO ₃ and WO ₃ . As the mixture in this case, Al ₂ O ₃ , ZrO ₂ , Ta ₂ O ₅ , TiO _2, etc. can be used in addition to the above-mentioned SiO ₂ . When a mixture with these high-melting substances is used as a vapor deposition material, only MoO ₃ and WO ₃ are present in the vapor deposited film because the vapor pressure is significantly different. It is sufficient that the amount of the mixture added is 1% by weight or more. It should be noted that this vapor deposition material for an optical film is not limited to an antireflection film on a plastic substrate, but can be used in a wide range.

The plastic in the present invention is not particularly limited, and may be acrylic, polycarbonate, CR-39,
Including energy-curable resins. Further, the Si oxide layer may be any of those having a composition of SiO _x (x = 1 to 2). The reason why the optical thickness nd of the first layer is set to 2 nm or more is that if it is less than 2 nm, cracks occur in the heat cycle test. This point will be described in detail in Examples. Further, the second and subsequent high refractive index layers may be composed of only MoO ₃ or WO _3, or may be a mixture layer with another dielectric.

[0017]

Example 1 An anti-reflection film having the structure shown in Table 1 was formed. In other words, an acrylic resin having a refractive index n = 1.49 (P
MoO ₃ on a plastic substrate made of MMA)
And SiO ₂ are alternately laminated.

[0018]

[Table 1]

The antireflection film having the above structure was formed by using a vacuum deposition apparatus shown in FIG. Reference numeral 10 denotes a vacuum chamber, and a resistance heating evaporation source 11 is provided at a lower position in the vacuum chamber 10.
And an electron gun evaporation source 12 are arranged. 1
Reference numeral 3 denotes a resistance heating melting boat attached to the resistance heating evaporation source 11, and reference numeral 14 denotes a hearth liner of the electron gun evaporation source. At an upper position in the vacuum chamber 10, a rotating dome 15 which allows the substrate 1 to be mounted and is rotatable around an axis is provided. Reference numeral 16 denotes a vacuum exhaust pipe connected to a vacuum pump (not shown). The distance from the evaporation source to the substrate 1 is 52
0 mm. As can be seen from the above description, the present apparatus has no difference from the conventional apparatus for forming an antireflection film on a glass substrate.

A method for forming an antireflection film having the structure shown in Table 1 using the apparatus shown in FIG. 1 will be described below. MoO ₃ layer is MoO
Put the granulated ₃ into a Mo boat 13,
It was formed by a resistance heating method while introducing oxygen gas until the total pressure reached 2 × 10 ⁻⁴ Torr. The SiO ₂ layer is made of S
The granulated iO ₂ was put into a hearth liner 14 and formed by an electron beam method.

When the spectral reflectance of the antireflection film formed as described above was measured, it was as shown in FIG.
It had sufficient properties as an antireflection film on a plastic substrate. In addition, the result of the adhesion evaluation test by a peel test using a cellophane tape was also good. There was no change in the surface accuracy of the substrate.

In this embodiment, the O ₂ gas is introduced during the film formation in order to prevent MoO ₃ from dissociating and becoming oxygen-deficient and absorbing visible light. Similar results were obtained by using oxygen plasma or an oxygen ion beam.

[0023]

Example 2 An antireflection film having the structure shown in Table 2 was formed using the apparatus shown in FIG. 1 in exactly the same manner as in Example 1 except that a boat made of W was used with WO ₃ as a raw material. The spectral reflectance had sufficient characteristics as shown in FIG. 3, and the adhesion was good.

[0024]

[Table 2]

[0025]

Example 3 An anti-reflection film having the structure shown in Table 3 was formed using the apparatus shown in FIG. The second and fourth layers are made of MoO ₃
And WO ₃ powder were mixed at a weight ratio of 2: 1, and the resulting granules were placed in a Mo boat 13 and oxygen gas was supplied at a total pressure of 8%.
The film was formed by a resistance heating method while introducing the solution to a pressure of ^10-5 Torr.

[0026]

[Table 3]

The spectral reflectance had sufficient characteristics as shown in FIG. 4, and the adhesion was good. MoO ₃ and WO ₃
It is possible to adjust the refractive index by changing the mixing ratio with.

[0028]

Example 4 An antireflection film having the structure shown in Table 4 was formed using the apparatus shown in FIG. The first SiO layer was formed by placing a SiO raw material in a boat 13 made of Mo and introducing a oxygen gas by a resistance heating method. The second layer of MoO ₃ comprises 97 to 98% by weight of MoO ₃ powder and Al ₂ O ₃ powder 2
-3% by weight and solidified into a pellet was placed on a hearth liner 14 as a raw material and formed by an electron beam method. The third SiO ₂ layer was formed by placing the SiO ₂ granules on the hearth liner 14 and using an electron beam method.

[0029]

[Table 4]

The spectral reflectance of the antireflection film formed as described above had sufficient characteristics as shown in FIG. 5, and the adhesion was good.

In this embodiment, Al ₂ O is added to MoO _{3.
Since a} small amount of ₃ was used as a deposition material,
The evaporation material could be easily heated by the electron gun without reflecting the electron beam. The same effect was obtained when ZrO ₂ , Ta ₂ O ₅ , and TiO ₂ were mixed instead of Al ₂ O ₃ . Similar effects can be obtained with many other high melting point oxides.

[0032]

Embodiment 5 An anti-reflection film having the structure shown in Table 5 was formed.
That is, the surface of a plastic substrate made of polycarbonate resin (PC) having a refractive index n = 1.58
₂ and a mixture of MoO ₃ and SiO ₂ are alternately laminated.

The mixture layer of MoO ₃ and SiO ₂ was formed as follows. A mixture of MoO ₃ granules and SiO ₂ granules at a weight ratio of 4: 1 was used as a vapor deposition material. This was put in a hearth liner 14 and vapor-deposited by an electron beam method while introducing oxygen gas at 1 × 10 ⁻⁴ Torr.

[0034]

[Table 5]

The antireflection film formed as described above has a sufficient spectral reflectance as shown in FIG. 6, and has good adhesion. The antireflection film of this embodiment is made of MoO
_{Since 3} is mixed with SiO ₂ , it is particularly resistant to a heat cycle, and “1 hour at 20 ° C. → 1 hour at −40 ° C. → 1 hour at 20 ° C.
Even after repeating 20 cycles with “time → holding at 70 ° C. for 1 hour” as one cycle, there was no problem such as deterioration of adhesion and generation of cracks.

The mixing amount of SiO ₂ is 10% by weight or more,
The same effects as above can be obtained. By changing the mixing amount, it is possible to change the refractive index. In addition, WO
_It was also confirmed that the mixed film of ₃ and SiO ₂ was similarly excellent in durability such as heat cycle resistance.

[0037]

Example 6 An anti-reflection film having the structure shown in Table 6 was formed.
That is, an acrylic resin (PMM having a refractive index n = 1.49)
WO ₃ and Si on the surface of the plastic substrate made of A)
O ₂ and O ₂ are alternately stacked.

An antireflection film having the structure shown in Table 6 was formed using the apparatus shown in FIG. The WO ₃ layer was formed by heating the pelletized form with an electron gun. In addition, SiO ₂
The layer was formed by putting a granulated SiO ₂ into a hearth liner 14 and heating it with an electron gun.

[0039]

[Table 6]

When the spectral reflectance of the antireflection film formed as described above was measured, it was as shown in FIG. 7, and it was found that the antireflection film had sufficient characteristics as an antireflection film for a plastic substrate. In addition, the result of the adhesion evaluation test by a peel test using a cellophane tape was also good. There was no change in the surface accuracy of the substrate.

Further, a heat cycle test was performed on the antireflection film formed as described above. "20 ° C for 1 hour →
Even after repeating 20 cycles of “40 ° C. for 1 hour → 20 ° C. for 1 hour → 70 ° C. for 1 hour”, no problems such as deterioration of adhesion and generation of cracks occurred.

[0042]

[Embodiment 7] The first to fifth layers in Table 6 are exactly the same as those in the sixth embodiment. The first layer is eliminated, and the adhesion and heat resistance when the thickness of the first layer is changed. Table 7 summarizes the evaluation results of the cycleability. If there is no first layer of the SiO ₂ layer, since the cracks evident visually occurs on the entire surface, but is defective, the optical thickness of the SiO ₂ layer 5
If it is not less than nm, no crack will be generated. Si
When the optical film thickness of the O ₂ layer was 2 nm, the occurrence of cracks was not visually recognized, but the occurrence of cracks was confirmed by viewing with an optical microscope (× 50). However, this was at a level that did not cause any problem in optical characteristics. Thus, the first
It is desirable that the optical thickness of the _second SiO ₂ layer is at least 2 nm or more, preferably 5 nm or more. This is not limited to the present embodiment, and the same applies to other film configurations and other plastic substrates.

[0043]

[Table 7]

As described above, cracks are generated by the heat cycle test because the plastic substrate repeatedly expands and contracts during the test, whereas MoO ₃ and WO ₃ cannot follow them and the stress is large. It will eventually be destroyed. Since the first Si oxide layer has a function of relaxing this stress, it can be considered that the generation of cracks can be prevented.

[0045]

Example 8 An antireflection film having the structure shown in Table 8 was formed using the apparatus shown in FIG. The first SiO layer is made of SiO
The raw materials were placed in a Mo boat 13 and formed by a resistance heating method. WO _3rd layer of 2nd and 4th layer, S of 3rd and 5th layer
The iO ₂ layer was formed by heating with an electron gun as in Example 6. During the formation of the first to fifth layers, oxygen
× 10 ⁻⁴ Torr was introduced.

[0046]

[Table 8]

The spectral reflectance of the antireflection film thus formed had sufficient characteristics as shown in FIG. 8, and the adhesion was good. In addition, there was no generation of cracks and no deterioration in adhesion due to the heat cycle.

[0048]

Ninth Embodiment A similar experiment was conducted by replacing WO ₃ in Example 8 with MoO ₃ . As a result, the adhesiveness was excellent, and no crack was generated by the heat cycle.

[0049]

Embodiments 10 to 13 The above embodiments are examples of the reflection film on the acrylic resin substrate. Table 9 shows an example using another substrate. Each of them has good adhesiveness and does not generate cracks due to a heat cycle.

[0050]

[Table 9]

[0051]

As described above, according to the present invention, the layer containing MoO ₃ and WO ₃ is used as the high refractive index layer, so that the conventional vapor deposition apparatus can be removed from the evaporation source without any modification. The radiant heat can be suppressed low, and even if the substrate is a plastic substrate, the adhesion of the film is not deteriorated or the surface accuracy is not deteriorated due to surface damage. In addition, S
When the i-oxide layer is provided with an optical thickness of 2 nm or more, durability, particularly heat cycle resistance, is increased.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a vacuum evaporation apparatus used in an embodiment of the present invention.

FIG. 2 is a graph showing the spectral reflectance characteristics of the antireflection film of Example 1 of the present invention.

FIG. 3 is a graph showing a spectral reflectance characteristic of an antireflection film of Example 2 of the present invention.

FIG. 4 is a graph showing a spectral reflectance characteristic of an antireflection film of Example 3 of the present invention.

FIG. 5 is a graph showing the spectral reflectance characteristics of the antireflection film of Example 4 of the present invention.

FIG. 6 is a graph showing the spectral reflectance characteristics of the antireflection film of Example 5 of the present invention.

FIG. 7 is a graph showing the spectral reflectance characteristics of the antireflection film of Example 6 of the present invention.

FIG. 8 is a graph showing the spectral reflectance characteristics of the antireflection film of Example 8 of the present invention.

[Explanation of symbols]

 1 Substrate

Claims (4)

(57) [Claims] 1. An Si oxide layer formed on a substrate of an optical component, and MoO ₃ and WO formed on the Si oxide layer
_3. An optical thin film comprising: a layer containing at least one of ₃ . 2. An optical component having an optical thin film formed on a substrate, comprising: an Si oxide layer formed on the substrate; and MoO ₃ and WO formed on the Si oxide layer.
_3. An optical component, comprising: a layer containing at least one of the following: 3. An oxide layer of Si having a thickness of 2 nm or more formed on a substrate of a plastic optical component, and MoO ₃ and WO formed on the oxide layer of Si.
_3. An anti-reflection film for a plastic optical component, comprising: a layer containing at least one of ₃ . 4. A plastic optical component having an anti-reflection film formed on a substrate, comprising: an oxide layer of Si having a thickness of 2 nm or more formed on the substrate; and MoO ₃ formed on the oxide layer of Si. And WO
_3. A plastic optical component, comprising: a layer containing at least one of ₃ .