JPH012004A - Ultra-narrowband optical multilayer film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to an optical multilayer film that selectively transmits or reflects light of a specific wavelength.

[Background technology]

The optical multilayer film 1 that selectively transmits or reflects light of a specific wavelength is a high refractive index thin film having a thickness of 1/4 of the wavelength (λ) of the target light, as shown in FIG. 7(a). H# and
It is formed by alternately stacking low refractive index thin films L# having the same thickness on the substrate 2.

However, in such an optical multilayer film, it is difficult to freely control characteristics such as bandwidth and reflectance.

Also, the bandwidth at the peak of the target wavelength is the 7th
Another problem is that it is not possible to obtain a wide and steep peak as shown in Figure (b). In particular, the bandwidth (half width)
It is nearly impossible to reduce the thickness to 150 nm or less with conventional optical multilayer films.

[Purpose of the invention]

This invention was made in view of the above circumstances, and
The object of the present invention is to provide an ultra-narrowband optical multilayer film in which the bandwidth and reflectance can be set over a wider range, and the bandwidth can be made narrower than ever before.

[Disclosure of the invention]

To achieve the above object, the present invention provides an optical multilayer film in which high refractive index thin films and low refractive index thin films are alternately laminated on the surface of a substrate, wherein the film thickness of the high refractive index thin film is that of the low refractive index thin film. The gist of this paper is an ultra-narrow band optical multilayer film characterized by having a strong selective optical property for light with a wavelength that is thicker than the average film thickness of the entire thin film and approximately twice the average film thickness of the entire thin film.

The present invention will be explained in detail below.

As shown in FIG. 1(a), the ultra-narrow band optical multilayer film 1 of the present invention has a high refractive index thin film 1 on the surface of the substrate 2. Although it is formed by alternately laminating H and low refractive index thin films, this point is the same as the conventional one.

Each thin film 14. As the material for L, the same compounds as conventional ones can be used.

For example, as the high refractive index thin film H, Ti0t-, Ce
Refractive index n of O□, ZrO*, ZnS % VzOs, etc.
A thin film made of a substance with a diameter of about 2.0 to 2.6 is used.

As a low refractive index thin film, CaFt-, MgFz, 5i
A thin film made of a material having a refractive index n of about 1.3 to 1.6, such as ft, Aim's, etc., is used.

If the combination of the above compounds and the thickness of each of the thin films H and L are selected as described below, it becomes possible to reflect or transmit light of the required wavelength.

The method of forming each of the thin films H and L as described above is not particularly limited in this invention, and the same method as usual may be employed.

For example, a physical vapor deposition method such as a vacuum evaporation method using resistance heating, an evaporation method using electron beam heating, a sputtering method, an ion blating method, or a chemical vapor deposition method such as a CVD method can be used.

In forming the Wl# film by these methods, the substrate may be heated above room temperature.

Generally, the higher the substrate temperature, the higher the hardness of the formed thin film and the better its durability. However, if the substrate temperature is too high, workability and productivity may deteriorate.

Therefore, the substrate temperature is preferably about room temperature to 350° C., although it depends on the type of thin film to be formed and its manufacturing method.

Further, in the present invention, a method may be adopted in which a solution of an organometallic compound that becomes the above-mentioned substance upon firing is applied to the surface of the substrate and then fired.

In the ultra-narrow band optical multilayer film of the present invention, of the double-groove films H and L as described above, the film thickness of the high refractive index thin film H is the low refractive index W/
#It is characterized by being thicker than the film thickness.

In this way, if the film thickness of the high refractive index thin film H is thicker than the film thickness of the low refractive index thin film, as shown in Figure 1(b), the absorption characteristic of λ/2 will change. A peak with extremely narrow bandwidth and strong selectivity is obtained at the position. The shape of the peak (bandwidth, intensity, etc.) varies depending on the combination of materials composing the double-groove films H and L, their film thickness ratio, number of layers, etc., but the peak shape (bandwidth, half-width) is about 50 to 60 nw+. , the transmittance is 10 to 30%, which is unprecedented, extremely selective, and steep.

Such a steep peak is due to the ripple-like component (ripple) that exists in the wavelength region shorter than the peak of wavelength λ in the conventional absorption characteristics shown in Figure 7(b). , one component is larger.

This phenomenon occurs because when the film thicknesses of both groove films H and L are different, the phase of the reflected waves generated at each interface changes, and the reflection of this λ/2 component is strengthened due to interference. It is thought that this will occur.

This phenomenon is affected by the film thickness ratio and material of both groove films, so it is difficult to calculate the generation wavelength strictly theoretically, but basically it is around twice the average value of all thin films, that is. , occurs at a component near half the wavelength (λ/2) of the conventionally termed peak of wavelength λ (component with a wavelength four times the average value of all thin films).

On the other hand, as shown in Fig. 1(b), the conventional peak at wavelength λ does not exist, but exists in the same way as before.
The ultra-narrow band optical multilayer film of this invention ultimately has two peaks.

As mentioned above, the shape of the peak at wavelength λ/2 (bandwidth, intensity, etc.) can be controlled in various ways depending on conditions such as the combination of materials constituting the double-groove films H and L, their film thickness ratio, and the number of layers. be able to.

For example, TiOx is used as the high refractive index thin film H, 5ift is used as the low refractive index thin film, the total number of layers is 10, the film thickness of the high refractive index thin film H is 350 nm, and the low refractive index thin film is If the film thickness is 250no+, the transmittance is 25
~30%, a peak with a bandwidth (half width) of 50 to 60 nm can be obtained at a wavelength of 600 nm.

As an example, in FIG. 2, TiOx is used as a high refractive index thin film H.
The following shows optical properties when the total number of layers is changed from 6 to 18 using 5ift as a low refractive index thin film. As shown in the figure, as the total number of layers is increased from 6, the transmittance of the peak at wavelength λ/2 (near -600 nm) is gradually decreased (increases the reflectance).
You will be able to do this. This can be more clearly understood by looking only at the transmittance at the peak apex, as shown in Fig. 4.

As mentioned above, the difference in thickness between the high refractive index thin film H and the low refractive index thin film H is an important factor in this invention. The ratio is not particularly limited as long as it is thicker than the film thickness, and it is effective up to the film thickness ratio of both groove films H:L=11. However, when the ratio H:L of both increases from around 3:l to more than that, on the contrary,
The characteristics will be similar to the conventional one in which both film thicknesses are the same. Therefore, the film thickness ratio H:L is 1.1=1~2
: It is preferable that it is within the range of l.

Also, the film thickness ratio H:L is within the above range, 1°1:1.
More preferably, the ratio is within the range of 1.5:1.

FIG. 3 shows the relationship between the film thickness ratio of both groove films H and L and optical characteristics. As shown in the figure, when both groove films HSL have the same thickness (1:1), no characteristic peak is observed at wavelength λ/2 (near 500 nm). Just like the components before and after it, there is only one ripple. On the other hand, in the ultra-narrow band optical multilayer film of the present invention in which the film thickness ratio of both is H:L=t, i:1, this λ/2 component grows rapidly and shows a steep peak. If the ratio of both film thicknesses is further increased,
The peak becomes even larger, and the transmittance at the apex becomes H:
When L=1.5:1, it becomes 20%. This can be more easily understood by looking at only the transmittance at the peak apex, as shown in Figure 5.

At this time, the bandwidth of the peak also widens as the peak becomes larger, but as shown in FIG. 3, the half-width still does not exceed 1100n. In other words, a steep peak is maintained.

The arrangement of the high refractive index thin film H and the low refractive index thin film H on the substrate is not particularly limited in this invention, but as shown in FIG. 6(a), the outermost layer is a low refractive index thin film, and the film thickness is It is preferable that the refractive index is approximately 1/2 that of other low refractive index thin films. This is because by arranging both grooves IQH and L in this manner, the spectral characteristics of the transmission band other than the peak can be made more flat, as shown in FIG. 6(b).

As described above, the ultra-narrowband optical multilayer film of the present invention can be used as a mirror (so-called gicchroic mirror) that transmits light of unnecessary wavelengths and reflects other necessary light, It can be used as a color temperature conversion filter for illumination, a filter for optical equipment, etc. that cuts light of different wavelengths.

Next, embodiments of the invention will be described.

(Example 1) A TiOx film with a thickness of 350 nm was used as the high refractive index thin film H.
A 5ins film with a thickness of 250nm is used as a low refractive index thin film.
After stacking 9 layers alternately, the top layer has a thickness of 12 mm to flatten the spectral characteristics of the transmission band.
A 5 nm thick 5ift film was laminated to obtain an ultra-narrow band optical multilayer film with the layer structure shown in Figure 6 (al). It had an extremely steep peak of 50r+ll+ (half width), and could be used as a monochromatic mirror.

(Example 2) When an ultra-narrow band optical multilayer film with the same layer structure as in Example 1 was used as a filter, the color temperature could be adjusted by removing only the green light component from the radiation component, and bright red light could be transmitted. was gotten.

〔Effect of the invention〕

The ultra-narrow band optical multilayer film of this invention is as described above,
It is an optical multilayer film in which a high refractive index Wi film and a low refractive index thin film are alternately laminated on the substrate surface, and the film thickness of the high refractive index thin film is thicker than the film thickness of the low refractive index thin film, and the average thickness of all the thin films is Because it has strong selective optical properties for light with a wavelength around twice the film thickness, it is possible to set the bandwidth and reflectance over a wider range, and it is also possible to narrow the bandwidth more than ever before. Become what you can.

[Brief explanation of drawings]

FIG. 1 (Al is a layer configuration diagram explaining an example of the layer configuration of the ultra-narrow band optical multilayer film of the present invention, FIG. 1(b) is a graph showing an example of the optical characteristics in this layer configuration, and FIG. 2 Figure 3 is a graph showing the relationship between the number of layers in a multilayer film and optical properties, Figure 3 is a graph showing the relationship between the film thickness ratio and optical properties of a thin film with both high and low refractive indexes, and Figure 4 is a graph showing the relationship between the number of layers in a multilayer film and its peak. Figure 5 is a graph showing the relationship between the transmittance at the peak and Figure 6 is a graph showing the relationship between the film thickness ratio and the transmittance at the peak. Layer structure diagram explaining the layer structure of an example with 1/2 of other low refractive index thin films, No. 6
Figure (b) is a graph showing an example of the optical characteristics of this layer configuration, Figure 7 (7k) is a layer configuration diagram explaining an example of the layer configuration of a conventional optical multilayer film, and Figure 7 (bl is a graph of this layer). This is a graph showing an example of the optical properties of the configuration. 2...Substrate H...High refractive index thin film L...Low refractive index thin ll11... Ultra-narrow band optical multilayer film Agent Patent attorney Matsumoto Takehiko Figure 1 (b) i length [nm] Figure 82 Figure 3 Length (front) Figure 4 Figure 5 JIIJl ratio (high/low) Figure 6 (b) Wavelength [nm] Figure 7 <a) (b) Yang Cho (n) Procedural amendment (spontaneous February 24, 1986)

Claims (5)

[Claims] (1) An optical multilayer film in which high refractive index thin films and low refractive index thin films are alternately laminated on the surface of a substrate, wherein the film thickness of the high refractive index thin film is thicker than the film thickness of the low refractive index thin film, and An ultra-narrow band optical multilayer film characterized by having strong selective optical properties for light having a wavelength approximately twice the average film thickness of the thin film. (2) The film thickness ratio H:L of the high refractive index thin film (H) and the low refractive index thin film (L) is within the range of 1.1:1 to 2:1. Ultra-narrowband optical multilayer film. (3) The ultra-narrow band optical multilayer film according to claim 1 or 2, wherein the outermost layer is a low refractive index thin film, and the film thickness is approximately 1/2 that of other low refractive index thin films. (4) Claim 1 used for a mirror that transmits light of unnecessary wavelengths and reflects light of necessary wavelengths.
The ultra-narrow band optical multilayer film according to any one of items 1 to 3. (5) The ultra-narrow band optical multilayer film according to any one of claims 1 to 3, which is used in a filter that cuts light of unnecessary wavelengths.