DE2049738C3 - Multi-layer anti-reflective coating for visible light - Google Patents

Description

Satisfy conditions:

The invention relates to an anti-reflective coating • hiharcs light for optical glasses with a S'funSdex of at least 1.7, consisting of three ς-Sen "of which the first, to the medium (Luftj SUiCtitea, _{a Brec} H ,, _{ng? In} dex of about

fe'HieWan ^ _Ό . ^ _a . Quarter of the

£ :, "| length of the anechoic area * on \ ™ 5SS, M3n« IuninuorW (MgF ₂ ).

^we '' HJ _inscribed j _e, the invention also hi a Werteren J _{"sjchtbares UCHT optical Glascr}

Amiretlew ^ _{b SINDEX} less than or greater than 1.7, ^'m jS four layers, the first of which, the adjacent layer also a _{d of about} 1.39 and an optical thickness J ^ K _V ^iertel the center shafts ength of refle-Jf ⁿ JJJ, _e " _Breich it has and made of magnesium fluoride

^ JgJJJJtht

^
from

known Antireflex.onsbelag is made of MgF ₂ an optical thickness e of the central wavelength (Xs) of the _range . Furthermore, it is known for glasses with a high refractive index to be 'en'sp.ege'. _{htbe | ag to be provided} . its top one

e, nen ° PP _{ine As / 4 thick} Mgh layer .st and

Sd "ch ^l * JS layer has a thickness of λ ^ / 2 has, its." ,, _"langenber calibration. for the anti-reflective coating dalJaer - ^^ _{bejter wj} . _{d One such}

However, anti-reflective is for one entire visible area

where n denotes the refractive index of the substrate and / J _{2 denotes} that of the second layer

2. Anti-reflective coating for visible light for optical glasses with a refractive index less than 1.6 or greater than 1.7 consisting of four layers, the first of which is adjacent to the medium (air); Layer has a refractive index ve about 1.39 and an optical thickness of a quarter of the central wavelength of the reflection-free area and consists of magnesium fluoride (MgF ₂ ), characterized in that the second, third and fourth layers each have an optical thickness equal to the halo central wavelength, that the second layer adjacent to the first layer has a refractive cortex of about 2.0 to about 2.1 and is made up of a substance. those made from titanium oxide (TiO ₂ ). ZirkonoKid (ZrO ₂ ), ^ onumox.d (ThO.) And cerium oxide (CeO ₂ ) is selected. that the fourth, for Subs rat adjacent layer has a refractive index of about 13 owns and composed of lanthanum oxide (La ₂ O), is. that the third, between second and fourth J ^"r .Jl ^e _be known to use three H'F _{nnch me} hr individual layers of the antireflection coating. Thus, ^ ^1" "J ⁰ J ₈ ^ ₂ 47 385, and 31 85 020 (GB-PS 9 78 471) from aeii u three-layer anti-reflective coverings

/ ΐ, -λ, / 4-λ. , -λ, / 4-Lutt unsealing glass or substrate). Furthermore ^ / Vt ₁ , _r ner suggested instead of the thickness of hai M-. · _Adjacent layer of a substrate

A / 4 iur α anti-reflective coating one thickness

such · dreiscnwmg

^from "^ ⁴ ^ ^to _{n three-notch anti-fire} coverings

With «open w _pressure not yet for the

b _a L · range possible, and the despatches are _particularly bad for glasses with an S of more than 1.7. Additionally. £ te _t required refraction indexes of the ^^ layers often with chemically or Zw ^ gje resistant layering mate-

Group is selected and that the refractive indices of the substrate and the third layer are different from each other and have the following relationship fulfill) .

O, 85 / ö <n _i <U5 / fe,

woriti ^ and ^ ₃ mean the refractive index of the third layer.

Antireflective coatings known one way or another

IMViIiUU ₆ ... w ... satisfy. So hatred

a four-layer anti-reflective coating of the structure Ug-XjA -KJA - XJTkJA - Luft

brought in the proposal, while the GB-PS 9 9163Sun & to describe the CH-PS 475 £ ö6s vierscjiichtige antireflective coatings'", at $ epen all interlayers far dijnner _ati: M # 5ind subheadings genört the _& pT-PS i 42463 _R. di ^ e'ui% n / kntifeflexiorisbejag from a "y \ ta W utfädtytjlßir layers of only zvyei materials 6s in alternifefendef filing sequence bescfi ^ ibt, the use of very thin layers (i.e. layers that are substantially thin ?; s's Λ / 4) ! .T. but SeimiengksitSB firmly 4 & measurement such less

Layer thicknesses and in compliance with the in individual cases exactly the desired thickness values. Be that as it may, these well-known four-layer anti-reflective coatings permit but also not an anti-reflective coating in the entire visible range (4000 to 7000 A) and often do not resort to too much stable layer materials.

Anti-reflective coverings are generally designed using the following methods:

). Observation method based on the analysis conditions,

2. graphical approximation, as in the case of the Double and triple layer anti-reflective coverings by A.F. Turner or using the Vector system or a Smith's diagram and

3, numerical calculation using the design parameters such as refractive index, optical Thickness of the layer, etc.

However, these methods are for reflection suppression only fully effective if this is in comparatively narrow spectral ranges of a respective desired central wavelength λ should happen. They fail, however, when the reflection is visible as a whole Area should be suppressed.

The object of the invention is therefore, by modifying the methods described above, a to create three or four-layer anti-reflective coating with an MgF2 layer as the top layer, which is in the to suppress the reflectivity to values smaller than 0.2 to 0.3% in the entire visible area. does not work with ultra thin layers, is chemically and physically stable and also allows glasses with a refractive index of more than 17 to be anti-reflective.

D'.e inventive solution to this problem is for the three-layer and four-layer anti-reflective flooring of the type described in the introduction in the characterizing part of the claims! and 2 respectively.

The selection made according to the invention of the thickness and materials of the individual layers of the Antireflection coating is achieved that with good chemical and physical resistance Reflex suppression is possible in the entire visible range to values less than 0.2 to C3%, and in the case of the three-layer anti-reflective coating for optical glasses with a refractive index greater than 1.7 and in the case of the four-layer anti-reflective coating not only for glasses with a refractive index of 1.7 and above, but also for glasses with a refractive index less than 1.6. ! m principle is that according to the invention Four-layer covering from the three-layer covering according to the invention resulted from the fact that between the substrate and a fourth layer of the type specified in claim 2 has been added to the three-layer covering.

The two embodiments of the invention are detailed below with reference to the drawing described. F.s shows

F i g. 1 the spectral reflectivity of the first embodiment of the invention in comparison to known two-layer covering, F i g. 2 shows the structure of the first embodiment,

3 shows a vector diagram to illustrate the reflectivity at 400 μm and 700 μm of the second embodiment of the invention and its structure, ⁶ p

F i g. 4 the spectral reflectivity of the second embodiment,
5 shows the structure of the two embodiments.

First embodiment

To (Jos reflectivity in next to the range from 400 to about 630 μπι lying areas in the known double-layer covering (see dashed curve in Fig. 1) to improve, according to the invention

/ ν-λί / 2-

air

Here, an MgF2 layer with an optical thickness of As / 4 is provided for the first layer (adjacent to the air), and a TiCV or ZrOa layer with a thickness of XJ2 and a refractive index of 2.0 to 2 for the second layer , 1, further for the third layer an AbOj or CeFj layer with an optical thickness of % J2 and a refractive index of 1.6 and finally the condition for the refractive index of the glass

ie rig is greater than 1.7 (n _g => refractive index of the glass, Π2 = refractive index of the / wide layer).

The clearly better reflectivity R (K) is shown by the solid curve in FIG. 1, while the dashed curve shows the reflectivity of the known / white layer bag. F i g. 2 inclines the structure.

Second embodiment

The second embodiment is an anti-reflective coating following structure:

n _g - λ / 2 - λ / 2 - λ / 2 - λ / 4 - air

which is obtained for the still further improvement of the first embodiment, in order to keep the reflectivity R in the entire visible range less than 0.3% and this also for substrate glasses with a refractive index less than 1.6. The reflectivities at 400 and 700 μm) are shown in FIG. 3 reproduced on the basis of a vector diagram. In this case, as shown in FIG. 3, a layer of an optical thickness of XJ2 and a refractive index of 2.0 to 2.1 and a layer of an optical thickness of 3/2 K and a refractive index of 1.5 are required to compensate for the layer of an optical thickness of KJ2 in order to keep the reflectivity in the areas adjacent to 400 and 700 (im less than 03% zr. According to the invention, the first layer adjacent to the air is an optical Aj / 4 thick MgF2 layer; the second layer is a A layer of an optical thickness of KJ2 made of T1O2, ZrC> 2, ThOj, CeO3, etc.; the third layer is a layer of an optical thickness of Aj / 2, a refractive index of 1.6, and is made of Al ₂ O ₁ , MgO, CeFj, etc. ; and finally the fourth layer is a La2O ₃ layer with an optical thickness of Λ / 2, which is in contact with the glass, where

\ (n _g -n _} ) / ni \ <0, i5

, with Λ3 = refractive index of the third layer) and n _g < 1.6 or> 1.7 apply, so that the reflectivity R can be kept below 0.3% in the entire visible range. The reflectivity of the embodiment is shown in FIG. 4 and their structure in FIG. 5 shown.

For this purpose 3 sheets of drawings

Claims (1)

Patent claims: \ ' ! .Antireflective coating for visible light for optical ■ glasses with a refractive index of at least. 1.7, consisting of three layers, of which the first layer, which is adjacent to the medium (air), is one / Refractive index of about 1.39 and an optical 'Covered by a quarter of the centreJ waviness of the , reflection-free area and made of magnesia ^ umfluorid (MgF ₂ ) consists, characterized - / characterized that the /. width, to the first rail - adjacent layer and the third, to the substrate r adjacent layer of the anti-reflective coating "each" an optical thickness of half the central wave > 5 ί 'length that the second layer has a * ^, refractive index of about 2.0 to 2.1 and is made up of your substance, that of the titanium oxide (TiO ₂ ). Zirconium oxide (ZrO ₂ ). Thoriumox.d (ThO ₂ ) and cerium oxide (CeO ₂ ) existing group is selected. that the third layer has a refractive index of about 1.6 and is made up of one substance. di · from that of aluminum oxide (Al ₂ O ₃ ). Magnesium Oxide (MgO) and Cerfluond (CeF ₃ ) is selected, and that the refractive indices of the substrate and the second layer are different from each other and the following