JPS63131101A - Multi-layered antireflection film - Google Patents

Abstract

PURPOSE:To increase the speed of film formation by forming at least either of high refractive index film layers of two layers having different refractive indices by reactive sputtering. CONSTITUTION:The 1st high refractive index film 12, the 1st low refractive index film 13, the 2nd high refractive index film consisting of the 1st film-like body 14a and 2nd film-like 14b and the 2nd low refractive index film 15 are successively formed on a transparent substrate 11 consisting of glass, etc., and having a large area. The film 14a is formed by using the reactive sputtering to 1.9-2.2 refractive index and the film 14b is formed by the same method to 2.2-2.5 refractive index. The use of Ta2O5, ZrO2 and In2O3 for the film 14a and the use of TiO2 for the film 14b are preferable. The forming speed of the films is increased by forming the film 14a consisting of the material having the higher sputtering rate to the larger thickness and the film 14b consisting of the material having the lower sputtering rate to the smaller thickness in the above-mentioned manner. In addition, the films having the larger area are formed uniformly at the lower cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a multilayer antireflection film formed on a transparent substrate in order to reduce light reflection on the surface of the transparent substrate. Therefore, it is ideal for application to the face of cathode ray tubes used in television receivers and other anti-reflection devices placed in front of the face.

[Summary of the invention]

In the present invention, a first high refractive index film, a first low refractive index film, a second high refractive index film, and a second low refractive index film are sequentially arranged on a transparent substrate in the direction away from the transparent substrate. In the laminated multilayer antireflection film, at least one of the first and second high refractive index films is combined with a first film-like body having a high refractive index formed using reactive sputtering, and a first film-like body having a high refractive index formed using reactive sputtering. By laminating a second film-like body with a higher refractive index than the first film-like body, it has high throughput, high uniformity, and excellent spectral reflectance characteristics at low cost. This makes it possible to provide a multilayer anti-reflection coating with a large area.

[Conventional technology]

In general, optical equipment such as cameras and binoculars uses a transparent material called a coating material on the surface of the glass substrate of the lens to eliminate phenomena such as flare and ghosting, and to improve image contrast and sharpness. An anti-reflection coating is deposited. As is well known, the antireflection film increases transmittance by reducing light reflection on the surface of a transparent substrate such as a glass substrate.

Such anti-reflection films are formed not only on small-area objects such as lenses as mentioned above, but also on large-area objects.
For example, the above-mentioned antireflection film is also formed on the face of a cathode ray tube used in a television receiver or the like, and on the surface of an explosion-proof glass plate placed in front of the face.

Antireflection films that have been commonly used include single-layer, two-layer, and three-layer structures. Among these, the single-layer antireflection film, which has the simplest structure, has an antireflection effect only for a single wavelength. However, since the normally used glass substrate has a refractive index of about ng-1.52, a transparent material that makes the reflectance zero, that is, a refractive index n that is the amplitude condition of the reflected light, is used.
Since there is no low refractive index film that satisfies , = 2 = 1.23,
Residual reflections occur.

The two-layer antireflection film has a structure in which a high refractive index film is interposed between a glass substrate and a low refractive index film.

According to this two-layer antireflection film, the apparent refractive index of the glass substrate can be increased due to the interposition of the high refractive index film, so the selection range of materials for the low refractive index film is expanded and the residual reflection described above is eliminated. However, in the case of this two-layer anti-reflection coating, the anti-reflection effect is limited to a single wavelength and a narrow wavelength region around it.

The three-layer antireflection film is effective in expanding the wavelength range of antireflection. That is, by creating a structure in which a film with an intermediate refractive index is interposed between the high refractive index film and the glass substrate in the case of a two-layer structure, the reflectance can be reduced to zero or It can be made extremely small.

In addition, when creating a three-layer structure like this, the refractive index and film thickness of each transparent material making up each film can be varied over a wide range to obtain the desired antireflection effect, allowing for greater freedom in design. It is possible to improve the degree of

Here, in the case of a two-layer or more multilayer structure,
Since no systematic method has been established for setting the refractive index and film thickness of each transparent material, the reflected light is generally set using a vector method that treats reflected light as a vector, or a complicated matrix method. This is done through trial and error in order to satisfy the phase and amplitude conditions as desired.

By the way, the wavelength range of visible light (wavelength; 400 to 700μ)
The antireflection effect for (m) cannot be sufficiently obtained with a three-layer structure. In order to meet this requirement, a four-layer structure has been developed in which the medium refractive index film of the three-layer structure is further replaced with a high refractive index film and a low refractive index film (in order from the glass substrate side). In this case as well, the refractive index and film thickness of each transparent material are of course determined by trial and error based on the vector method as described above, but in general, in order to obtain the desired spectral reflectance characteristics, The high refractive index film and the low refractive index film are made thin, and the high refractive index film and low refractive index film thereon are made thick.

By adopting such a four-layer structure, the number of boundary surfaces between the films increases, and light interference becomes stronger, so that a substantially good antireflection effect can be obtained over the entire visible light range. Moreover, according to this four-layer antireflection film, the degree of freedom in design can be further increased.

Next, the configuration and spectral reflectance characteristics of a conventional four-layer antireflection film and a four-layer antireflection film in a reference example of the present invention will be described with reference to FIGS. 3 to 5.

First, FIG. 3 shows a conventional four-layer antireflection film, in which Mgh, a typical low refractive index film material, is shown.
(Magnesium fluoride Hn=1.38) is used. Due to its characteristics, the formation method for MgFt is generally limited to vacuum evaporation, so from a practical standpoint, the glass substrate on which the antireflection film is formed is also limited to a small area. There is a problem.

In the figure, 11 is a glass substrate (n=1.52), 12 is ZrO□ (zirconium oxide; n=2.
13 is a first high refractive index film made of MgFt with a film thickness of 310 mm; 14 is a film with a film thickness of 1
A second high refractive index film consisting of 320 Zr0t, also 1
5 is a second low refractive index film made of Mgh with a film thickness of 940 nm.

FIG. 5a shows the spectral reflectance characteristics of the conventional example shown in FIG. 3 configured as described above.

As is clear from the figure, this conventional example sufficiently satisfies the MIL standard indicated by the shaded area and has excellent characteristics over almost the entire wavelength range of visible light.

Here, the first and second high refractive index films and 2.14
In addition to the above-mentioned Zr0t, the material may include vacuum evaporation of TazOs (tantalum oxide Hn = 2.15), Pr1e (praseodymium oxide: n = 2.20), TiOx (titanium oxide; n = 2.35), etc. Transparent materials suitable for reactive DC sputtering can be used.

Next, FIG. 4 shows a 4Ji antireflection film in a reference example of the present invention. In this case, a large-area glass substrate is used, and a high refractive index film and a low refractive index film are each made of a reactive material. It is formed using DC sputtering.

Note that a typical material for a low refractive index film suitable for reactive DC sputtering is 5iOz (silicon oxide: n=1.455), and the refractive index of this SiO□ is n=1.455. 455, which is relatively large for a low refractive index film, and n is suitable for combination as a material for a high refractive index film.
-2.3 to 2.5 must be used. For this reason,
In this reference example, a four-layer antireflection film is formed using TiOx (titanium oxide; n=2.35), which is a transparent material that has a refractive index in the above range and is suitable for reactive DC sputtering.

In FIG. 4, 11 is a glass substrate, 12.13 is a first high refractive index film made of Ti01 with a thickness of 110 mm, and a first low refractive index film made of SiO2 with a thickness of 360 mm,
Further, reference numeral 14.15 denotes a second high refractive index film made of Ti01 with a thickness of 1120 nm and a second low refractive index film made of SiO□ with a thickness of 900 nm.

In the case of this large-area reference example shown in FIG. 4, the spectral reflectance characteristics, as shown in b in FIG. 5, are comparable to the above-mentioned conventional example shown in FIG. M in case
It fully complies with IL standards.

Here, as the first and second low refractive index films 13.15, in addition to the above SiO□ alone, a transparent material mainly composed of SiO□ suitable for reactive DC sputtering can be used. As the 1 and 2nd high refractive index films and 2.14, in addition to the above TiO□ alone, TiO2 as a main component and a transparent material suitable for similar sputtering can be appropriately used.

[Problem that the invention seeks to solve]

However, in the above-mentioned conventional example shown in FIG. 3, since MgF is used for the low refractive index film, it is generally necessary to rely on a vacuum evaporation method to form this low refractive index film. For this reason, there is a problem in that it is not possible to increase the area of the antireflection film, and the range of its application is limited to small area objects such as lenses.

In addition, in the case of the above-mentioned reference example shown in FIG. 4, since the reactive DC sputtering method is used, a large area can be achieved.
Although it can be applied to large glass substrates (for example, anti-reflection plates placed in front of cathode ray tubes), there are technical limitations during production. IgF.

Since this is not used, problems arise due to this.

That is, the refractive index of 5iOz is n = 1.455, which is relatively large for a low refractive index film, so it is necessary to use TiO□, which has a relatively high refractive index, as a material for a high refractive index film.
Since the reactive DC sputtering rate of g is low, it is necessary to form the second high refractive index film and 4 particularly thick, resulting in extremely low productivity and high costs. Ta.

In addition to TiOz, ZrO2,
It is also possible to use TazQs, PrbO□, etc., but these Zr0z, Ta205, Pr, 0. has a refractive index of 2.2 or less, so in the four-layer antireflection film shown in FIG.
a, 0. In the case of another reference example of the present invention using , the spectral reflectance characteristics are as shown in FIG. And in this case,
As is clear from the figure, there is a wavelength range that has little margin or cannot meet the MIL standard (C
) occurs, deteriorating the spectral reflectance characteristics.

In addition, in the case of the above-mentioned another reference example whose spectral reflectance characteristics are shown in FIG. 6, the first and second high refractive index films and 2.1
The film thicknesses of TazOs used as 4 are 140 and 1130, respectively, and the first and second low refractive index films 1
3.15 The film thickness of SiO□ used as 270 people,
and 850 people.

The present invention has been made in view of the above-mentioned problems, and can be applied to large-area transparent substrates from a practical standpoint.
An object of the present invention is to provide a multilayer antireflection film that can uniformly and efficiently form a high refractive index film and a low refractive index film.

[Means to solve the problem]

The present invention relates to an antireflection film formed on a transparent substrate such as a glass substrate or a synthetic resin substrate in order to reduce light reflection on the surface of the substrate, the invention comprising a first high refractive index film, a first high refractive index film, and a second high refractive index film. It is composed of a multilayer structure consisting of a first low refractive index film, a second high refractive index film, and a second low refractive index film, and these films are arranged on a transparent substrate in the above-described order in the direction away from the transparent substrate. In the sequentially formed multilayer antireflection films, at least one of the first and second high refractive index films includes a first film-like body having a high refractive index formed using reactive sputtering; The present invention relates to a multilayer antireflection film characterized in that it is constructed by laminating a second film-like material having a higher refractive index than the first film-like material.

According to the present invention configured as above, the first film-like body having a relatively lower refractive index among the first and second film-like bodies constituting at least one high refractive index film Since it is formed using reactive sputtering, it is possible to increase the sputtering rate, and therefore the throughput can be improved. Furthermore, in addition to the first film-like body formed by the above-mentioned reactive sputtering, the at least one high-refractive-index film is provided with a second film-like body having a higher refractive index than the first film-like body, which provides excellent spectroscopic properties. Reflectance characteristics can be obtained.

In the present invention, one of the first and second high refractive index films is configured to be sufficiently thicker than the other, and only one of the high refractive index films is separated from the first and second film-like bodies. Becomes,
Further, the first film-like body is configured to be sufficiently thicker than the second film-like body, and is located immediately outside the high refractive index film of one of the first and second low refractive index films. It is preferable that the low refractive index film is sufficiently thicker than the other low refractive index film. And by configuring it like this,
Throughput can be further improved, and even more excellent spectral reflectance characteristics can be obtained.

In addition, as for the reactive sputtering for forming the first film-like body, particularly when using Ta5ks alone or a substance containing Ta5ks as a main component, the sputtering rate should be high. Preferably, reactive direct current sputtering is used.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.

In FIG. 1, 11 is a large-area glass substrate (n=1.
52), 12.13 has a film thickness of 75 people.
The first high refractive index film consists of i0z (n = 2.35) and SiOg (n = 1.455) with a film thickness of 395 mm.
A first low refractive index film consisting of these films 12.1
3 functions to change the apparent refractive index of the glass substrate 11. In addition, 14a has a film thickness of 1015 people TazOs (
The first film-like body 14b is made of TiO□ with a thickness of 180 mm, and these first and second film-like bodies 14a and 14b A second high refractive index film is configured. Furthermore, 15 is 960
This is a second low refractive index film made of human Stow.

In this five-layer antireflection film, the above film 12.13.14
The transparent materials constituting a, 14b, and 15 are selected so as to satisfy the desired phase and amplitude conditions of the reflected light in order to have zero or extremely low reflectance in the visible light wavelength range, and are Each thickness is set.

In addition, when manufacturing the above five-layer antireflection film, a reactive magnetron sputtering method was used to produce 85% Ar-15
Pressure 5 x 10 with %0□ mixed gas as atmospheric gas
Reactive direct current swaying is carried out under the condition of -3 Torr.

The first film-like body 14a in the second high refractive index film, which is the thickest in this 5jQ2-TiQz 78gOs-based five-layer film and requires the longest sputtering time, is made of Ta and O. Since the sputtering rate of Ta20g is high, the time required for sputtering TazOs is about 5 minutes. On the other hand, the entire second high refractive index film is made of TiO
In the case of □ (SiO2-TiO□ system structure, which is the same as the above-mentioned reference example shown in FIG. 4), the same structure as that of this example is used as described above (because the sputtering rate of TiOg is low, Even if it is formed under the manufacturing conditions, the time required for sputtering the second high refractive index film Ti0z is about 27 minutes.

In this way, according to this embodiment, the first film-like body 14a made of ↑atog with a high sputtering rate is made thick, and the second film-like body 14b made of TiO2 with a low sputtering rate is made thin. Since they constitute the second high refractive index film, the respective films 12, 13, 14a,
When manufacturing this five-layer anti-reflection film using an in-line sputtering device that can form 14b and 15 in an assembly line, the formation speed of these five films as a whole is
Compared to the overall formation speed of the four films 12, 13, 14, and 15 of the 5tO1-TiOg-based four-layer antireflection film shown in the figure, the formation speed can be approximately five times or more.

FIG. 2 shows the Sing Ti0z-
This figure shows the spectral reflectance characteristics of a Ta, OS-based five-layer antireflection film. As is clear from the figure, the five-layer anti-reflection film in this example fully complies with the MIL standard indicated by the shaded area, and also has excellent characteristics over almost the entire wavelength range of visible light. There is.

In the above embodiment, in order to obtain spectral reflectance characteristics that meet the MIL standard, the first high refractive index film 13 made of TiO and the first low refractive index film 13 made of 75±10 and 5iOt are required. The second group consisted of 395±20 people, Ta, 05
The first film-like body 14a of the high refractive index film is 1015±10 people, and the second film-like body 1 of the second high refractive index film is made of TiO2.
4b is 180±IO, and the second low refractive index film is 5iOz
Although each film thickness can be increased so that 15 is in the range of 960±20 people, it goes without saying that the present invention is not necessarily limited to the above range.

Further, the first film-like body 14a of the second high refractive index film made of TazOs and the second film-like body 14a of the second high refractive index film made of TiO2
Almost the same effect could be obtained even if the film-like body 14b was turned upside down;
A second film-like body 14 with a higher refractive index consisting of e. It has been found that when b is on the second low refractive index film 15 side, better spectral reflectance characteristics are obtained.

Also a set of membranes 12.13 and membranes 14a, 14b.

Almost the same effect could be obtained by turning the membranes 12.1 and 15 upside down; however, as in the above example,
It has been found that the spectral reflectance characteristics are better when the group No. 3 is on the glass substrate 11 side.

Furthermore, although TiO□ was used as the first high refractive index film and 2, other transparent materials having a refractive index of 2.2 to 2.5, or Taz05, Zr0z, Inz03 (indium oxide; n = 2. 00), 5nOz (tin oxide; n=2.00), Pr60++s 5bzOt
(antimony oxide; n=1.95), Nd, 0
A transparent material such as neodymium oxide No. 3 (neodymium oxide; n = 1.90) alone or a mixture thereof having a refractive index preferably in the range of 1.9 to 2.2 can be used. Further, the film thickness can be appropriately set depending on the material selected.

Moreover, as the first film-like body 14a of the second high refractive index film, in addition to the above-mentioned Ta2O, Zr0z, Inz03.5nO
z, Pr60th, 5b203, Nd2O, 1, etc. alone or a mixture thereof, and the refractive index is preferably 1.9
A transparent material having a sputtering rate in the range of 2.2 to 2.2 and higher than that of the second film-like body 14b of the second high refractive index film can be used. Furthermore, the second high refractive index film
As the film-like body 14b, in addition to the above-mentioned TiO□, other transparent materials having a refractive index of preferably 2.2 to 2.5 can be used. In this case, the first and second membrane bodies 14a
, 14b have a different thickness than the first high refractive index film and 2.
As in the case of , it can be set appropriately depending on the material selected.

Furthermore, as the first low refractive index film 13, the above-mentioned 5iO
In addition to z, ^j2zo+ (aluminum oxide; n = 1
．． 64) alone, a mixture thereof, or a transparent material containing one or both of these as main components, preferably having a refractive index in the range of 1.44 to 1.65, can be used. Further, as the second low refractive index film 15, S
In addition to iO□ alone, mixtures of SiO□ and A/z (h),
Alternatively, a transparent material containing 5ift as a main component and having a refractive index preferably in the range of 1644 to 1.50 can be appropriately selected and used.

〔Effect of the invention〕

As described above in detail, according to the present invention, a large-area multilayer anti-reflection film with excellent spectral reflectance characteristics can be provided with high throughput, high uniformity, and at low cost.
Therefore, it is extremely practical.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a part of a multilayer antireflection coating according to an embodiment of the present invention, FIG. 2 is a spectral reflectance characteristic diagram of the multilayer antireflection coating shown in FIG. 1, and FIG. 3 is a multilayer of a conventional example. FIG. 4 is a partial cross-sectional view showing a multilayer anti-reflection film in a reference example of the present invention; FIG. 5 is a partial cross-sectional view showing the conventional example shown in FIG. 3 and the reference example shown in FIG. 4. 6 is a spectral reflectance characteristic diagram of Si in another reference example of the present invention.
FIG. 2 is a spectral reflectance characteristic diagram of an n, -Ta, OS multilayer antireflection film. In addition, in the symbols used in the drawings, 11-・-・・・・・・Glass substrate (transparent substrate)
12--.--.---First high refractive index film and 3-.--.--1--.First low refractive index film 14a ...--...--First membrane-like body 14
b.
...----------This is the second low refractive index film.

Claims (1)

[Claims] 1. An anti-reflection film formed on a transparent substrate to reduce light reflection on the surface of the transparent substrate, comprising a first high refractive index film, a first low refractive film A multi-layer structure consisting of a high refractive index film, a second high refractive index film, and a second low refractive index film, and these films are sequentially laminated on a transparent substrate in the above-mentioned order in the direction away from the transparent substrate. In the multilayer antireflection film, at least one of the first and second high refractive index films includes a first film-like body having a high refractive index formed using reactive sputtering, and the first film-like body having a high refractive index formed using reactive sputtering. A multilayer antireflection film characterized in that it is constructed by laminating a second film-like body having a higher refractive index than the film-like body. 2. Claim 1, wherein the first film-like body has a refractive index of 1.9 to 2.2, and the second film-like body has a refractive index of 2.2 to 2.5. Multilayer anti-reflective coating as described. 3. The multilayer antireflection film according to claim 1, wherein the first and second low refractive index films each have a refractive index of 1.44 to 1.50. 4. The refractive index of the first low refractive index film is 1.50 to 1.6.
5, and the refractive index of the second low refractive index film is 1.44 to 1.44.
1.50. The multilayer antireflection film according to claim 1, which has an anti-reflection coating of 1.50. 5. The multilayer antireflection film according to claim 1, wherein only the second high refractive index film is constructed by laminating the first film-like body and the second film-like body. 6. The multilayer antireflection film according to claim 5, wherein the first high refractive index film has a refractive index of 1.9 to 2.2. 7. The multilayer antireflection film according to claim 1, wherein the first high refractive index film has a refractive index of 2.2 to 2.5. 8. As the first film-like body, Ta_2O_5, ZrO
_2, In_2O_3, SnO_2, Pr_6O_1_
1. The multilayer antireflection film according to claim 1, characterized in that any one of Sb_2O_3, Nd_2O_3, or a mixture thereof is used, and TiO_2 is used as the second film-like body. 9. As the first low refractive index film, SiO_2, Al_
5. The multilayer antireflection film according to claim 3 or 4, characterized in that the multilayer antireflection film uses a substance containing either 2O_3 alone, a mixture thereof, or one or both of these as a main component. 10. As the second low refractive index film, SiO_2, a mixture of SiO_2 and Al_2O_3, or S
The multilayer antireflection film according to claim 4, characterized in that a substance containing iO_2 as a main component is used.