JPH01167701A - Two-wavelength range reflection preventing film - Google Patents

Abstract

PURPOSE:To prevent reflection in an optional two-wavelength range by forming a 1st substrate refractive index adjusting layer and a 1st reflection preventing layer to wavelength lambda1 and interposing an unparticipant layer to the wavelength lambda1 at least one place. CONSTITUTION:When the refractive index of a substrate S is denoted as nsub, a two-layered reflection preventing film (V coat) needs to consist basically of the substrate refractive index adjusting layer with optical film thicknesses n1d1=lambda1/4 and n1=(nsub)<1/2>.n2 and the reflection preventing layer made of a material n2 with a low refractive index n2d2=lambda1/4 so as to preclude reflection of the wavelength lambda1 efficiently. When reflection is precluded in the two- wavelength range of lambda1 and lambda2, a lambda2 substrate refractive index adjusting layer and a lambda2 reflection preventing layer are only provided so as to preclude reflection of lambda2 without spoiling characteristics of the V coat to the lambda1. The unparticipant layer is constituted to an integral multiple of n1(lambda1/2) or/and n1(lambda1/4)-n2(lambda1/2)-n1(lambda1/4), and the refractive index of the unparticipant layer is selected corresponding to the substrate refractive index adjusting layer and reflection preventing layer.

Description

[Detailed Description of the Invention] Skin-exhibiting Tachishina beans! The present invention relates to a multilayer antireflection coating for three relatively separate wavelength regions, such as visible light and infrared light.

l Limb distortion Conventional anti-reflection coatings only prevent reflection in a single wavelength range.
For example, in a three-layer anti-reflection film in the visible range, reflection in the infrared range increases more than that of the substrate.

Therefore, there is no problem when the wavelength range used is a single wavelength range, but when two wavelength ranges, for example, visible and infrared ranges are used in the same optical system, ghosts and flares may occur, or the amount of light may be insufficient. On the other hand, the above three-layer antireflection coating is applied to the infrared region (e.g.
λ. -3750 nm), it becomes difficult to prevent reflection in the visible range. However, λ. /3,λ
. It is anti-reflection in the wavelength band of 15,...
Conventionally, such secondary, tertiary, etc. antireflection bands were used to prevent reflection in three wavelength ranges, but the wavelength ranges are λa/3 and λ as described above. It was limited to 15,..., and its use was severely restricted.

The present invention has been made in view of the above-mentioned problems of conventional antireflection films for three wavelength bands, and provides an antireflection film that can prevent reflection for any three wavelength bands. It is an object of the present invention to provide an antireflection film having a wide antireflection band for short wavelengths among the three wavelength bands.

The present invention is a multilayer film that is sequentially laminated on a substrate S, and is an antireflection film for two wavelengths, center wavelength λ1, λba, and <λ2. a refractive index adjusting layer and a first antireflection layer, between the substrate S and the first substrate refractive index adjustment layer, between the first substrate refractive index adjustment layer and the first antireflection layer, and between the first antireflection layer and the medium. The film has a structure in which a layer that does not participate in the wavelength λ is inserted at at least one location in the wavelength λ, and the structure of the layer that does not participate in the wavelength
Integer multiple of (λI/2), or n, (λt/4)-nz
(λI/2)-n, (λI/4), or a combination thereof, and the refractive index of the first non-participating layer is the same as that of the first substrate refractive index adjusting layer, A dual-wavelength anti-reflection film, characterized in that the refractive index of the non-participating layer is selected such that the first non-participating layer corresponds to the substrate refractive index adjusting layer and the anti-reflection layer with respect to λ2. It is.

Hara 1! The basic type of anti-reflection coating (V coat) is n5ub/n((λ,/4)−
It has a two-layer structure of ng(λ+/-4)/air. n2(
λ1/4), usually MgFz (n=1.38) is used, but at that time, n parts are n, y, /"ii" τ・
If n2 is set, the reflectance becomes 0 at the center wavelength λ1. ...
...(1) For example, BK7 (n=1.52)/1
．． 70(λ,/4)-1,38(λl/4)/a
In order to efficiently prevent reflection at ir (n n = 1), that is, at a certain wavelength λ, the optical film thicknesses n, d, -λI
/4, n, a substrate refractive index adjusting layer of mJ-π·n2, and n,
An antireflection layer of a low refractive index material n2 with dt=λ1/4 is required.

Usually, 81203 is used as the material for n, and MgF is used as the material for nz.

However, this two-layer antireflection coating (V coat) provides antireflection near λ, but at other wavelengths λ! (>A+)
In this case, the reflectance of the substrate itself is usually increased compared to that of the substrate itself without an antireflection coating. That is, in the long wavelength range, λ8〉〉λ,
If so, it will be almost the same as the substrate. In other words, the film thickness is so thin that it can be ignored in the long wavelength range.

On the other hand, regarding λt, if anti-reflection is performed with a coating, λg/3, λ815, λ! on the short wavelength side from the proverb λ! /
7,... are anti-reflection, but the band is very narrow.

In order to efficiently prevent reflection in the three wavelength ranges of λ and λ, it is necessary to use a λ substrate refractive index adjustment layer and a λ2 reflection layer to prevent reflection at λ8 without destroying the characteristics of the V coating at λ. A layer that does not impair the characteristics of λ1 (a layer that does not affect λ1), which may be provided as a prevention layer, is thin when λ8 is short and thick when λ8 is long, depending on the wavelength of λ.

A layer that does not participate in this λ is a layer with a refractive index naSn=, nc
na(λ1/2), ns(λ+/4) −n c(λ+
/2) -n m (λ1/4), etc. Since these become the characteristic matrix M of the film, it can be understood that they do not affect the characteristics at λ.

These groups of λ1-uninvolved layers are defined as (1), (If), (1
′) and (■′), any film having a combination of V-coats of λ1 becomes a V-coat of λ. Here, A: AjltOs(λ,/4) layer, M; M
gFz (λ1/4) layer is shown.

In order to further prevent reflection for λ2 in the configuration (3), the first half should be a λ22 substrate refractive index adjustment layer, and the second half should be a λ3 antireflection layer, that is, the refractive index of the film should be equivalent to the several layers in the first half. is Nl, the film thickness (film thickness) is DI, and the latter half is Nl.
* , Dz, then from (1), so that (1)
, (II), (■'), (■'), etc., the refractive index, the calendar number, or a combination thereof may be determined.

At this time, λ, uninvolved layer (1), (II), (■'),
In (■'), it is also possible to make the antireflection band at λ wider than that of the original V coating by including a band widening layer of n(λl/2).

λ1 substrate refractive index adjustment layer λ1 antireflection layer λ2 substrate refractive index adjustment layer λ2 antireflection layer (Description of related technology) First, the complex amplitude reflectance r at the interface between the glass substrate and air
As shown in Fig. 5, (rei δ) is expressed as the point 0 + (r = 0.20, δ = 180°). This is called Apfe1 display. Then, when a thin film is deposited on this glass substrate, the value of r changes.

For example, when Zn5i (n I = 2.30) is deposited, the optical thickness n, d increases, and the point 0x (r
= 0.39) and a radius of 0.02, and consider two-layer anti-reflection as a path from point P on the circumference to origin O. n5ub=1.52 substrate to n=1.38
using the first layer of λ. To make the residual reflection θ%,
n Sub = 1.52 as an equivalent film. It is known that setting it to -1,9 is sufficient. For that purpose, the 6th
As shown in the figure, a substance with n = 1.7 is λ. /4 vapor deposition, and further n=1.38 λ. It can be seen that it is sufficient to perform vapor deposition of /4. In addition, in FIG. 6, the dotted line 1O112 indicates the reflectance R=1%, 0.5% (7) area, and the mata point 114
．． 16.18 wavelength ratio ν=1.1, ν=1.2, ν=1
．． 3 is shown.

If a material with n = 1.7 cannot be obtained, as shown in Figure 6, a material with n > l, 7, such as ZrOg (
n-2,03) and a substance with n < 1.7, such as M
gF.

(n = 1.38) is equivalent to n = 1.7, 2.03 (phase film thickness: δ,) - 1,38 (phase film thickness:
62). This is a two-layer equivalent film (or a composite film), and together with a three-layer symmetrical equivalent film, it is an extremely effective method for obtaining a film equivalent to a single-layer film with a refractive index of nH<n<nL at a single wavelength. However, in this case, a technique is required to control the film thickness to λ.74 or less.

In the two-layer anti-reflection coating described above, the first half is 1.7 (λ
(1/4), 2.03 (δth) - 1,38 (δ2)
The layer called nswb' is for non-reflection in the latter 1.38 (λ./4) layer, that is, the refractive index of the substrate is made into an equivalent film.
It can be considered as a substrate refractive index adjustment layer for adjusting −1,38″=1.9.

These two-layer anti-reflection coatings (V coats) are single-wavelength anti-reflection coatings, and at wavelengths other than the center wavelength, the reflectance increases monotonically depending on the wavelength ratio, as shown by dotted lines 14, 16, and 18 in Figure 6. do.

Daikodan (1) Ultraviolet and visible dual-wavelength anti-reflection coating (λI-250n
s, λ3 proverb 633ns) A M This configuration is 1.50/Ns (λ!/4) Nz (λ18)/ai from condition (5) and at the same time due to a very rough calculation.
r... (6') should be satisfied, which is shown in Figure 1 as 1
04.

Strictly speaking, the N l (λ, /4) layer corresponds to the solid line 10 in FIG.
0■-■, the N bus 8/4) layer corresponds to the solid line ioo■-■, but for simplicity, the total optical film thickness (λ, /4) ×
Half of 6 (λI/4)X3, or 1.46 (λ1/4
)−1,90(λI/2) as N + (λt/4
), 1,46 (λt/4) 1.63(λ,
/4) -1,38(λI/4) part is Nx(λ!/4
). At this time, N t D t ” N t
D O (λ+/4) X 3 Proverbs 750/4 lq 63
3/4 (-λ8/4) ... (7) Dr Therefore, NI "il, 727 Nx 1=11.4
83 Therefore, (6') is 1. as shown by IO2.
50/1,727 (750 nm/4) - 1,483 (7
50nm/4)/air...Ql. However, strictly speaking, α・does not satisfy the condition (5), that is, n! =1.483, as shown by 106, it becomes nt-1,816 for n□, =1.50.

By the way, the condition (5) is only a condition for reflection O, but depending on the type of anti-reflection, the wavelength λ1- or λ8
There are also looser conditions such that the reflectance is ≦1%, or that it only needs to be lower than the reflection of the substrate itself. In addition, (6
) is shown as 102 in FIG. Further, the reflection characteristics of Ql are as shown in FIG. 2, and the reflectance at λ1 is 0.25%. This corresponds to the weighted mean of the refractive index. Strictly speaking, as mentioned above, the configuration (6) is 633n■, and the solid line 1 in Figure 1
It is an equivalent V coat like 00■～■～■.

From Figure 1, we find the solid line 104■〜■〜■
Approximately, NII=11.88 and Nz#1.50.

Anti-reflection in the visible and infrared dual wavelength range (Visible: λ1 = 430 ~ 6
50 nm, infrared: λg = 3.0 to 5.0 μm) The configuration of the edge is also at λ2, from the solid line 2000 to [phase] in Fig. 3.
It becomes an equivalent film such that ~0, and Nt=
It is approximated as 1.747, N, -1,420.・
・ ・ ・ ・ ・ ・ (11') If we consider the same as Example (1) as a rough approximation, the total optical film thickness is (
λl/4)X12 and the first half is 1.63(λI/4)
−2,03(λ,/2) −1,63(,11/4) −
1,46 (λI/2) is the λ2 substrate refractive index adjustment layer, the latter half 1.46 (λ, /2) - 1,38 (λ, /2) - 1,6
3(λl/4) −1,38(λ,/4) is considered to be the λ2 antireflection layer. At this time, N r D t = N t D t = (λI/
4) X6 = (550/4)X6- (33
00/4) two (3750/4) = (λt/4) Therefore,
N, = 1.675, Nz-1,433 Therefore, the approximation of aυ is 1.50/1.67, as shown at 206
5 (3300 nm/4) -1,433 (3300
ns/ 4) /air ・・−−・・・−・・Q
It will be 21. Strictly speaking, this does not satisfy the condition (5), but its reflection characteristics are as shown in FIG. 4, and it can be used practically as an antireflection film.

Note that the exact complex amplitude graph of αυ is shown as 202 in FIG.

[Brief explanation of the drawing]

1st WJ is a graph of complex amplitude reflectance according to Apfe1 display of the first embodiment of the present invention, FIG. 2 is a reflection characteristic diagram of the first embodiment, and FIG. 3 is a complex amplitude reflectance graph according to Apfe1 display of the second embodiment. FIG. 4 is a reflection characteristic diagram of the second embodiment, and FIGS. 5 and 6 are explanatory diagrams of complex reflectance graphs in Apfe1 display. 10...Graph showing a region with a reflectance of 1% 12...Graph 14 showing a region with a reflectance of 0.5%...Wavelength ratio 1.
1 16... Wavelength ratio 1.2 18... Wavelength ratio 1.3 100... Complex amplitude reflectance graph 200 of the first example
... Complex amplitude reflectance graph procedure correction document of the second example (
Method) 1. Display of the case 1986 Patent Application No. 326176
No. 2, Name of the invention Dual-wavelength anti-reflection coating 3, Relationship with the person making the amendment Applicant name: Tokyo Kogaku Kikai Co., Ltd. 4, Agent 6, Subject of the amendment All drawings 7, Contents of the amendment First stated in the application Engraving of the attached drawings

Claims (3)

[Claims] (1) A multilayer film that is sequentially laminated on a substrate S, and is an antireflection film for two wavelengths, center wavelengths λ_1 and λ_2 (λ_1<λ_2), which includes a first substrate refractive index adjusting layer for wavelength λ_1, and a first substrate refractive index adjusting layer for wavelength λ_1. It has an antireflection layer, and has a wavelength λ_1 at at least one location between the substrate S and the first substrate refractive index adjustment layer, between the first substrate refractive index adjustment layer and the first antireflection layer, and between the first antireflection layer and the medium. This is a film structure in which a non-participating layer is inserted, and the structure of the non-participating layer is an integral multiple of n(λ_1/2) or n_1(λ_1/4).
)-n_2(λ_1/2)-n_1(λ_1/4) or a combination thereof, and the refractive index of the first non-participating layer is the same as that of the first substrate refractive index adjusting layer, the first
A dual-wavelength antireflection device characterized in that the refractive index of the noninvolved layer is selected such that the antireflection layer and the first noninvolved layer correspond to the substrate refractive index adjusting layer and the antireflection layer with respect to λ_2. film. (2) The sum of the film thicknesses of the first substrate refractive index adjusting layer, the first antireflection layer, and the first non-involved layer is approximately equal to λ_2/2;
When these are divided into two with a film thickness of approximately λ_2/4, the weighted average of the refractive index of the film on the substrate side is N_1, and the weighted average of the refractive index of the other film is N_2, then N_1≒√(n_s_u_
The dual-wavelength antireflection film according to claim 1, wherein the dual-wavelength antireflection film is configured to have the following relationship: b).N_2. (3) Among the configurations of the first antireflection layer, n(λ_1/
2) film n(λ_1/4)-n'(λ_1/4) or n_1(λ_1/4)-n_2(λ_1/2)-n_
1 (λ_1/4) film as n_1, (λ_1/4)-n_
2(λ_1/2)-n'_1(λ_1/4).