JPH0772306A - Optical thin film and its formation - Google Patents

Abstract

PURPOSE:To realize the optical thin film which is formable at a high speed even without heating and has a high adhesion property and scratch resistance. CONSTITUTION:A first layer 1a is deposited by a cluster ion beam method on the surface 2a of a substrate 2 and a second layer 1b is deposited by using an evaporating source by electron gun heating thereon. Further, a third layer 1c is deposited on the surface of the second layer 1b by the cluster ion beam method. The film thicknesses of the first layer 1a and the third layer 1c are respectively 90Angstrom and the film thickness of the second layer 1b is 730Angstrom . All these layers are deposited without heating the substrate 2. The second layer 1b is formed at a high speed by the film forming method by electron gun heating, by which the film forming speed over the entire part of the optical thin film is improved.

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 such as an antireflection film used for optical parts such as lenses, filters and polarizers, and a film forming method thereof.

[0002]

2. Description of the Related Art Optical thin films such as antireflection films, selective transmission films and reflection enhancing films provided on the surfaces of optical components such as lenses, filters and polarizers are generally formed by vacuum deposition. When the optical component is made of glass, it is easy to obtain a high-quality optical thin film with good adhesion by heating the surface of the optical component to about 300 ° C. In the case of optical parts made of plastics, whose applications are expanding due to easy improvement of cost performance and cost reduction, it is necessary to form a film without heating on the surface of the optical parts. There was a tendency for the adhesiveness and scratch resistance of the obtained optical thin film to be insufficient. Therefore, it is desired to develop a film forming method capable of obtaining an optical thin film having sufficient adhesion and scratch resistance even without heating.

Recently, even if the optical component is made of glass, it is desired to form an optical thin film without heating in order to save the time required for heating and cooling.

As described above, the following techniques have been developed as conventional techniques for forming an optical thin film without heating the substrate of an optical component.

(1) A multilayer film using a metal oxide containing tantalum, zirconium and yttrium as a high refractive index material (see Japanese Patent Laid-Open No. 2-291502).

(2) An antireflection film using a sublimable evaporation material and magnesium fluoride (see JP-A-3-209201).

(3) A cluster ion beam method in which vaporized particles are clustered (lumped atomic group), ionized, accelerated by an electric field and incident on a substrate (Japanese Patent Publication No. 54-959).
No. 2). This method uses MgF ₂ , SiO ₂ , A
In order to obtain a good-quality optical thin film with little absorption from evaporation materials such as l ₂ O _3, there is a restriction that the film formation rate must be 1-2 Å / s or less, and in order to obtain a predetermined vapor pressure. In the case of evaporation materials that must be heated to a relatively high temperature, such as ZrO ₂ , TiO ₂ , Ta ₂ O _5, etc., the film formation rate must be further reduced, for example, 1 Å / s or less. Attention has been paid to this method as a method for forming an optical component having a sufficiently high adhesion and excellent scratch resistance even if the substrate is formed without heating.

[0008]

However, according to the above-mentioned conventional techniques, the methods (1) and (2) limit the material of the optical thin film, and therefore the degree of freedom in design is small. It was found that the hardness of the optical thin film was lower than that in the case where the substrate was heated, and the scratch resistance was insufficient. Further, the method (3) has a drawback in that the film forming rate is limited to be low as a whole as described above, so that the productivity is extremely low and therefore the cost is high.

The present invention has been made in view of the above problems of the prior art, and an optical thin film which can be formed at a high speed without heating and has high adhesion and scratch resistance, and the film formation thereof. It is intended to provide a method.

[0010]

In order to achieve the above object, the optical thin film of the present invention comprises a first layer deposited on the surface of a substrate by the cluster ion beam method and a layer other than the cluster ion beam method. Second deposited by membrane method
And a third layer deposited by the cluster ion beam method on the second layer.

The film thickness of the first layer is preferably 50 Å or more.

The thickness of the third layer is preferably 90 Å or more.

[0013]

Since the first layer that adheres to the surface of the substrate is deposited by the cluster ion beam method, the adhesion to the substrate is extremely high, and the third layer is also deposited by the cluster ion beam method. Therefore, it has excellent scratch resistance. In addition, the second layer is deposited by a deposition method using an evaporation source such as electron gun heating or resistance heating, which has a faster deposition rate than the cluster ion beam method, to increase the deposition rate of the entire thin film and improve productivity. Can be improved.

[0014]

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

First Embodiment FIG. 1 is a schematic sectional view showing the present embodiment. The optical thin film 1 of this embodiment has an optical film thickness nd = 125 nm, that is,
It is an antireflection film having a so-called λ / 4 optical film thickness, which has a minimum reflectance at a design wavelength λ ₀ = 500 nm, and has a wavelength of 500 nm.
First layer 1a made of MgF ₂ deposited by the known cluster ion beam method on the surface 2a of the substrate 2 which is a glass base having a refractive index of 1.52 for the above-mentioned light, and the known electron gun heating thereon. M deposited by the vacuum deposition method such as
It comprises a second layer 1b made of gF ₂ and a third layer 1c made of MgF ₂ deposited thereon in the same manner as the first layer 1a. The film thickness of each of the first layer 1a and the third layer 1c is 90.
Å, the refractive index for light with a wavelength of 500 nm is 1.37, the film thickness of the second layer 1b is 730 Å, and the refractive index for light with a wavelength of 500 nm is 1.39, both of which are for heating the substrate 2. It was formed without a film.

The film forming apparatus for forming the optical thin film 1 is, as shown in FIG. 2, a substrate holder 12 arranged on an upper portion of a vacuum chamber 11 having an exhaust port 11a, and a driving device (not shown) for rotating the substrate holder 12. And MgF disposed under the vacuum chamber 11.
Has first and second evaporation sources 13 and 14 of the _2, vaporized particles generated from the first evaporation source 13, after being clustered by the cluster generating device 13a, it is ionized by an ionization device 13b, ionized The vaporized particles (hereinafter, referred to as “cluster ion beam”) thus generated are accelerated by the acceleration electrode 13c and are applied to the substrate 2 held by the substrate holder 12.

The second evaporation source 14 is an electron gun 14a.
Is heated and vaporized by the to generate vaporized particles toward the substrate 2. Between the first and second evaporation sources 13 and 14 and the substrate holder 12, there are first and second shutters 15 and 1 for blocking evaporated particles generated from the evaporation sources 13 and 14, respectively.
6 is provided, and by opening and closing the shutters 15 and 16, the evaporation particles generated from the evaporation sources 13 and 14 can be irradiated onto the substrate 2 alternately or simultaneously. Further, in the vicinity of the substrate holder 12, a film thickness monitor 1 for monitoring the film thickness of a thin film deposited on the surface 2 a of the substrate 2.
7 are provided.

The optical thin film 1 is formed as follows.

First, the substrate 2 is held by the substrate holder 12 and the inside of the vacuum chamber 11 is depressurized to about 1 × 10 ^-6 Torr to heat and vaporize the first evaporation source 13 to generate evaporated particles of MgF ₂ . Clustered and ionized as described above,
The obtained cluster ion beam is accelerated at an accelerating voltage of 1.0 kV to irradiate the substrate 2 to deposit the first layer 1a of MgF _{2 on} the surface 2a. During the film formation of the first layer 1a, the temperature of the first evaporation source 13 is controlled so that the film formation rate becomes 2Å / sec, and when the film thickness reaches 90Å, the first shutter 15 is closed.

Next, the second evaporation source 14 is heated by the electron gun 14a to generate evaporated particles of MgF ₂ ,
The shutter 16 is opened to apply the second layer 1b. The film forming rate at this time is controlled to 10 Å / sec. When the film thickness of the second layer 1b reaches 730Å, the second shutter 16 is closed and the first shutter 15 is opened, and the third layer 1c is deposited in the same manner as the first layer 1a, and the film thickness is 90Å. When it reaches, the first shutter 15 is closed. The first to third layers 1a to 1c are formed without heating the substrate 2.

The optical thin film of this embodiment has anti-reflection properties and durability such as adhesion to the substrate which are almost the same as those of the optical thin film formed by a known method while heating the substrate, and Since most of the film thickness is formed by a vacuum vapor deposition method or the like by electron gun heating, which has a high film formation speed, the overall film formation speed is high and the productivity is extremely high.

Comparative Example For comparison, while heating the same substrate as in this example at 300 ° C., an evaporation source of MgF ₂ was heated and vaporized by an electron gun to form an optical thin film having an optical film thickness of 125 nm.

Spectral reflectances of the optical thin film of this example and the optical thin film of the comparative example were measured, and a quality evaluation test was carried out by the method described below. Adhesion and scratch resistance to the substrate immediately after film formation and high temperature and high humidity conditions After the durability test, the adhesion and scratch resistance were examined. 3 and 4 show the spectral reflectances of the optical thin film of this example and the optical thin film of the comparative example, respectively, and Table 1 shows the results of the quality evaluation test.

[0024]

[Table 1] Experimental Example Optical thin film samples 1 to 9 in which the film thicknesses of the first layer and the third layer were changed in the range of 30 to 200 nm were produced in the same manner as in the first example. A quality evaluation test was conducted. The film thicknesses of the first layer and the third layer of each sample are shown in Table 2, and the results of the quality evaluation test are shown in Table 3.

[0025]

[Table 2]

[0026]

[Table 3] From Table 3, it can be seen that Sample 1 in which the film thickness of the first layer is 30Å has insufficient adhesion after the durability test, and that the film thickness of the first layer is preferably 50Å or more. Further, regarding scratch resistance, since it is easy for scratches to occur in Samples 5 and 6 in which the thickness of the third layer is 30Å and 50Å, it is understood that the thickness of the third layer is preferably 90Å or more.

Second Embodiment Using the film forming apparatus of FIG. 2, first, only the shutter 15 is opened, and a first layer of MgF ₂ is formed on the glass substrate, which is the same substrate as in the first embodiment, by the cluster ion beam method. Membrane
When the film thickness reaches 90 Å, the second shutter 16 is opened without closing the first shutter 15, and the second layer is formed by mixing which is a combination of the cluster ion beam method and the vacuum vapor deposition method using electron gun heating. The thickness of the second layer is 730
When it reaches Å, the second shutter 16 is closed and the third layer is formed only by the cluster ion beam method.

In the present embodiment, the strength of the boundary surface between each of the first and third layers and the second layer can be improved by using the second layer as the mixing layer. The spectral reflectance of the optical thin film of this embodiment is almost the same as that of the first embodiment,
Also, the result of the quality evaluation test was as good as the optical thin film of the first embodiment.

Third Embodiment A SiO ₂ thin film, a TiO ₂ thin film, and an Al ₂ O ₃ thin film were formed on a glass substrate, which is the same substrate as in the first embodiment, by the same method as in the first embodiment. By forming the film, a three-layer antireflection film was produced.

Table 4 shows the refractive index of the first to third layers of each thin film with respect to light having a wavelength of 500 nm, the optical film thickness, the film forming speed, and the acceleration voltage of the film forming process of the first and third layers by the cluster ion beam method. It was as shown in. When forming each thin film, oxygen gas was introduced into the film forming chamber to adjust the pressure to 1 × 10 ⁻⁴ T.
orr, and the evaporation source of the cluster ion beam during the formation of the SiO ₂ and TiO ₂ thin films is set to Si.
O, TiO, other than this, SiO ₂ , TiO ₂ , Al
₂ O ₃ was used as the evaporation source. As shown in FIG. 5, the optical thin film of this example had a good antireflection property against light in a wide wavelength range, and the result of the above-mentioned quality evaluation test was also very good.

[0031]

[Table 4] Fourth Embodiment A MgF ₂ thin film and a ZrO ₂ thin film are alternately formed on a glass substrate, which is the same substrate as in the first embodiment, by the same method as in the first embodiment. A trimming edge filter was produced. The refractive index of the first to third layers of each thin film for light having a wavelength of 500 nm, the optical film thickness,
Table 5 shows the film forming speed and the acceleration voltage of the film forming process of the first layer and the third layer by the cluster ion beam method.

[0032]

[Table 5] During the formation of the ZrO ₂ thin film, oxygen gas was introduced into the film formation chamber to maintain the pressure at 1 × 10 ⁻⁴ Torr, and the MgF ₂
At the time of forming the thin film of 1 × 10 ⁻⁶ Tor as in the first embodiment.
Controlled to r.

FIG. 6 shows the spectral transmittance of the red trimming edge filter of this embodiment. The result of the above-mentioned quality evaluation test was extremely good, and when the spectral transmittance was examined again after the durability test, the half-value wavelength change shown in FIG. It turned out to be an edge filter.

The method of the above quality evaluation test was as follows.

(Adhesion) After the cellophane tape having a width of 18 mm was firmly attached to the surface of the optical thin film, the peeling angle was about 9
The test of rapid peeling at 0 ° was repeated 10 times, and then the presence or absence of peeling of the optical thin film was examined.

(Scratch resistance) The optical thin film was rubbed with steel wool # 1000 at a pressure of about 100 g / cm ² for 50 times,
The scratch resistance was visually evaluated. The judgment criteria are as follows.

A: Almost no scratches B: There are scratches but the transparency does not change C: Many scratches and it looks cloudy (high temperature and high humidity endurance experiment) Temperature 70 ° C. Humidity 250% for 250 hours It was left to stand and the above-mentioned adhesion and scratch resistance tests were conducted.

[0038]

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

It is possible to realize an optical thin film which has high productivity even without heating and which is excellent in adhesion to a substrate and scratch resistance. As a result, the adhesion, scratch resistance and productivity of the optical thin film provided on the surface of the plastic optical component can be improved. Further, it facilitates simplification of the manufacturing process of the optical thin film provided on the surface of the optical component made of glass, which helps reduce the manufacturing cost.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a first embodiment.

FIG. 2 is an explanatory diagram illustrating a film forming apparatus for forming an optical thin film according to this embodiment.

FIG. 3 is a graph showing the spectral reflectance of the first example.

FIG. 4 is a graph showing a spectral reflectance of a comparative example.

FIG. 5 is a graph showing the spectral reflectance of the third example.

FIG. 6 is a graph showing the spectral transmittance of the fourth example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical thin film 1a 1st layer 1b 2nd layer 1c 3rd layer 2 Substrate 11 Vacuum chamber 12 Substrate holder 13,14 Evaporation source 13a Cluster generator 13b Ionizer 14a Electron gun 15,16 Shutter

Claims (6)

[Claims] 1. A first layer deposited on the surface of a substrate by a cluster ion beam method, a second layer deposited thereon by a film forming method other than the cluster ion beam method, and a second layer on the second layer An optical thin film comprising a third layer deposited by the cluster ion beam method. 2. A first layer deposited on the surface of a substrate by the cluster ion beam method, a second layer deposited thereon by a combination of the cluster ion beam method and another film forming method, and the first layer. An optical thin film consisting of a third layer deposited on the two layers by the cluster ion beam method. 3. The optical thin film according to claim 1, wherein the thickness of the first layer is 50 Å or more. 4. The optical thin film according to claim 1, wherein the thickness of the third layer is 90 Å or more. 5. A step of depositing a first layer on the surface of a substrate by a cluster ion beam method, and a step of depositing a second layer on the deposited first layer by a film forming method other than the cluster ion beam method.
A step of depositing a layer and a step of depositing a third layer on the deposited second layer by a cluster ion beam method, wherein all the steps are performed without heating the substrate. Method for forming optical thin film. 6. A method comprising depositing a first layer on the surface of a substrate by a cluster ion beam method, and combining the cluster ion beam method on the deposited first layer with another film forming method. A step of depositing a layer and a step of depositing a third layer on the deposited second layer by a cluster ion beam method, wherein all the steps are performed without heating the substrate. Method for forming optical thin film.