DE19636970A1 - Anti-reflection optical multilayer coating - Google Patents

Abstract

An optical multilayer coating, exhibiting wide band especially high anti-reflection and light transmission or especially high anti-reflection at a given light transmission, comprises a layer stack of high and low refractive index layers, at least two high refractive index layers being immediately adjacent one another. Also claimed is a method of producing the above coating, in which the individual layers are produced by cathodic sputtering, especially reactive sputter deposition.

Description

The invention relates to an optically acting Layer covering, consisting of one on substrates arranged multilayer system, the Layer system a high anti-reflective effect and has a high light transmission or a high he anti-reflective effect with a given light transmission sion owns.

Such anti-reflective layers are preferred on transparent in the visible light spectrum Substrates, in particular glass panes brings which z. B. for protection from paintings or for use in showcases or as a shop rear windows can be used.

From DE 41 17 257 a layer system is be knows which on a transparent substrate is applied and a high anti-reflective effect  having. This is based on DE 39 42 990 Layer system consists essentially of alternately applied to the substrate Metal oxide and nitride layers. According to the DE 41 17 257 produced layer systems are sufficient required high transmittance over the entire optically acting light wave range and the demands for an inexpensive manufacturer not anymore. especially the proposed there, made of TiO₂ layer can only be done with a high level of manufacturing effort in correspondingly expensive manufacturing processes per duz because the sputtering rate of TiO₂ in there coating process used about 5 times is smaller than that for low refractive index SiO₂.

The object of the present invention is a Generic layer system and its manufacture specify the disadvantages avoids the layer systems mentioned at the beginning and the requirements that are required today look at the anti-reflective effect, contrast hung and inexpensive manufacture of today Layers met.

At the same time, the requirements for this should be met created that only a small number of Single layers to build up a multi-layer sy stems is needed.

This object is achieved by a Features of the main claim layer system fulfilled. A method of making egg  Nes layer system according to the invention with the Proposed features proposed in claim 7.

A layer system according to the invention consists of a plurality of individual layers forming a coating, which are successively applied to a light-transparent substrate, preferably by means of a vacuum-assisted coating process, a sequence of high-index and low-index layers being provided, in which at least two high-index layers are connected to one another issue. The refractive indices of these two mutually adjacent, high-index layers differ by a minimum of 0.1 and a maximum of 0.4, preferably a maximum of 0.3. The low refractive index layers exist e.g. B. from Al₂O₃, MgF₂ or silicon dioxide. The high refractive index layers consist of a metal oxide, preferably of titanium dioxide, or of a metal nitride, preferably of a compound of the type TiO _x N _y , the refractive index n _{L of} the TiO _x N _{y being} chosen for the indices x and _y Layer is adjustable. As an alternative to such high-refractive-index layers made from TiO _x N _y , it is easily seen that doped TiO₂ layers are used who who are doped with Al₂O₃ and / or SiO₂. Instead of SiO₂ as a doping material, MgF₂ or AlO₃ is proposed. Suitable material for the production of the high refractive index layers is suggested in diumtinoxy, known under the abbreviation ITO. As an alternative to the layers made of ITO, high-index layers consisting of one of the compounds: ZnO, SnO₂, ZrO₂, Ta₂O₅ or Si₃N₄ are provided.

As a substrate material, glass is preferably proposed, which has a refractive index n _G of 1.46 n _G 1.6. It is intended to produce the layer systems according to the invention by means of a cathode sputtering process. The process chamber pressures for layer production are in the range of 1 × 10 ^-3 P 8 × 10 ^-3 mbar. The coatings are preferably applied to the substrate by means of a reactive sputtering process, the process gas consisting of a mixture of noble gas, preferably argon and a reactive gas, preferably consisting of nitrogen and / or oxygen.

An essential advantage of a layer system according to the invention is that the overall thickness is smaller in comparison to conventionally produced layer systems or, for the same total thickness, it is less reflective. A conventional four-layer anti-reflective coating, e.g. B. has a layer sequence and individual layer thickness as follows: glass | TiO₂, 15 nm | SiO₂, 30 nm | TiO₂, 110 nm | SiO₂, 90 nm | has a total thickness of 245 nm. An anti-reflective layer system according to the invention, consisting of five individual layers, in which the third individual layer consists of two individual layers consisting of | TiO₂, 48 nm | TiO _x N _y , 63 nm | there is a total layer thickness of 246 nm, the layer system according to the invention having an overall thickness of 246 nm over the entire visible wavelength range showing an advantageously lower reflection than the aforementioned four-layer system.

As specified in subclaims 3 and 4, respectively summarizes an inventive layer system z. B. five individual layers, successively on one Substrate using a cathode sputtering process be applied according to claim 7.

The use of TiO _x N _y (see claim 4) as a high-index layer material, the refractive index n _L can be adjusted by the relative oxygen to nitrogen proportions during the reactive sputtering process.

Further advantageous features of the invention are in the further subclaims 2, 5 and 6 ben.

Below are particularly advantageous in the Figures shown embodiments be wrote.

Show it:

Fig. 1 reflectance curves depending on the light wavelength λ for the layer system shown in Fig 2a or Fig 2b according to the prior art, Kur ve, a, and after a first embodiment, curve b;

2a shows a cross section of a four-A zelschichten existing on a substrate adjacent layer system according to the prior art.

Figure 2b shows a cross section through a fiction, according best of five individual layers Hendes, layer system according to a first embodiment.

Fig. 3 shows a measured and a calculated Re flexionsgradkurve depending on the incident light wavelength λ of a layer system consisting of five individual layers according to a second exemplary embodiment from depending on the light wavelength;

Fig. 4 is a cross-sectional view of a layer system consisting of five individual layers according to the second embodiment;

Fig. 5 is a reflectance curve for the layer system shown in Figure 6a according to the prior art and a third embodiment shown in Fig. 6b, for example, depending on the light wave length λ.

FIG. 6a shows a cross section of a conventional, consisting of four individual layers applied on a substrate layer systems according to the prior art;

FIG. 6b is a cross section through a fiction, according best of five individual layers Henden, layer system according to the third embodiment;

Fig. 7 is a graph of the reflectance in Figure 8a layer system shown in the prior art and 8b shown Ausführungsbei fourth game in dependence of the light wave length λ in Fig..;

Figure 8a is a cross section of a four-A zelschichten existing on a substrate adjacent the layer system according to the prior art.

Fig. 8b shows a cross section through a fiction, according best of five individual layers Henden layer system according to the fourth embodiment.

The layer systems according to the invention shown in FIGS. 2b, 4, 6b, 8b consist of five individual layers 6 , 8 , 9 , 11 , 13 applied to a substrate 4 by means of a vacuum-assisted coating method; 16 , 18 , 19 , 21 , 22 ; 26 , 28 , 29 , 31 , 33 ; 36 , 38 , 39 , 41 , 43 .

In the following four embodiments of the Layer systems according to the invention presented.

example 1

The layer system 2 of the first embodiment (see FIG. 2b) is constructed as follows:

• On the substrate 4 , a vitreous body, a first optically acting, high-index layer 6 is applied, which consists of TiO₂ and has a layer thickness of 15 nm,
• - The second, optically effective layer 8 consists of a 30 nm thick SiO₂ layer,
• - The third, optically effective layer 9 consists of a highly refractive TiO₂ layer and has a layer thickness of 48 nm and a refraction coefficient of 2.5,
• - The fourth, optically effective layer 11 consists of a highly refractive TiO _x N _y layer, which has a layer thickness of 63 nm and
• - The fifth, optically effective layer 13 consists of a low-refractive SiO₂ layer, which has a layer thickness of 90 mm.

The third layer 9 together with the fourth layer 11 forms a high-index double layer, each of which has an effective refractive index of 2.5 and 2.35. The refraction coefficient for the double layer of layer 9 can be adjusted by the relative proportions of gas in the reaction gases of oxygen and nitrogen during the reactive sputter coating process to produce the TiO _x N _y layer. The wavelength-dependent reflectance of the layer system 2 shown in FIG. 2b is shown in FIG. 1 by the curve course b. The reflection curve a determined with the model shown in Fig. 2a, with a union herkömm layer system shows on the interest Wellenlängenbe reaching an overall higher reflection than the cure ve b.

In the following, the reflectance R and the transmittance T of the curve profiles for R (λ) shown in FIG. 1 are compared in Table 1 with certain wavelengths over an extended wavelength range from 288 nm to 2478 nm.

Table 1

(to Fig. 1)

Example 2

The layer system of the second embodiment shown in FIG. 4 is constructed as follows:

• - The first, brought up directly on the substrate 4 layer 16 consists of an ITO compound and has a layer thickness d 1 of 19 d 1 21, nm preferably of 20 nm;
• - The second, optically active layer 18 consists of a low-refractive SiO₂ layer, in a layer thickness of 21 d₁ 23 nm, preferably 22 nm se;
• - The third, optically effective layer consists of high refractive index TiO₂ in a layer thickness of 44  d₁ 46 nm, preferably 45 nm;
• - The fourth, optically effective layer 21 consists of a highly refractive TiO _x N _y compound with a layer thickness of 62 d₁ 64 nm, preferably 63 nm;
• - The fifth, optically active layer 22 consists of a SiO₂ compound and has a layer thickness of 89 d₁ 91 nm, preferably of 90 nm.

The reflection values measured with the layer system 15 shown in FIG. 4 are represented by the curve c shown in FIG. 3. Comparative calculations, which were calculated on the basis of the layer parameters defined by the layer system 15 shown in FIG. 4, such as the refraction coefficient and the layer thicknesses, give the reflection curves shown by the curve curve d in FIG. 3 curve as Function of the incident light wave length λ.

The reflectance and transmittance values shown in FIG. 3 are shown in Table 2a, respectively. listed in Table 2b as a function of the light wavelength λ.

Table 2a

(c Fig. 3, curve)

Table 2b

(d to Fig. 3, curve)

Example 3

The layer system of the third embodiment shown in FIG. 6b is constructed as follows:

• The first layer 26 applied directly to the substrate 4 , a glass body, consists of a TiO _x N _y compound as a high-index layer material, and has a layer thickness of 18 nm,
• - The second layer 28 applied to the first layer 26 consists of SiO₂ as a low-index material with a layer thickness of 27 nm,
• - The third, optically active layer 29 is highly refractive and consists of a 58 nm thick TiO₂ layer with a refractive index of 2.5,
• - a fourth, optically active layer 31 is made of a TiO _x N _y, single layer of high refractive index having a refractive index of 2.35 provided, and has a layer thickness of 55 nm,
• - As the fifth layer, an 89 nm thick layer 33 made of SiO₂ is provided.

A layer system 24 which corresponds to the prior art and is shown in FIG. 6a consists of four individual layers ( 26 , 28 , 30 , 32 ) and has a layer thickness of 247 nm which is almost identical to the layer system 25 shown in FIG. 6b. Deviating from the layer system 25 shown in FIG. 6b, instead of the double layer 29 , 31 formed in this, a single layer 30 consisting of highly refractive TiO₂ is provided, which has a layer thickness of 110 nm.

The reflection values on which curve e and curve f (see FIG. 5) are based are compared in Table 3 with the associated light wavelengths λ.

The curve values e show the prior art values of the layer system 24 shown in FIG. 2a.

Table 3

(to Fig. 5)

The comparison of the reflection curves e and f shown in FIG. 5 as a function of wavelength shows that the reflection values of the layer system 25 , which correspond to the curve profile f, lie clearly within the entire visible wavelength range below the corresponding reflection values of the layer system 24 , which curve e are reproduced.

Example 4

The layer system 35 of the fourth exemplary embodiment shown in FIG. 8b has a total of five layers and is constructed as follows:

• - The first layer 36 is a 32 nm thick indium tin oxide (ITO), a refractive index of 2.0 having high refractive index layer on which a
• second, a low-refractive SiO₂ layer 38 is applied, which has a layer thickness of 23 nm and a refractive index of 1.46,
• - As a third, optically effective layer 39 , a 45 nm thick TiO₂ layer is provided, which has a refractive index of 2.5, on which cher
• a fourth layer 41 , consisting of TiO _x N _y , is applied with a layer thickness of 63 nm and has a refractive index of 2.35;
• - The final fifth layer 43 is a 90 nm thick, made of SiO₂ applied layer, which has a refractive index of 1.46.

The reflection values obtained with the layer system 35 depending on the wavelength are shown in the diagram shown in FIG. 7 by curve h. The reflection values obtained with a conventional layer system 34 , shown in FIG. 8a and represented by curve g, are in the short-wave, ie in the range from 370-425 nm and in the long-wave, ie <650 nm wavelength range, clearly above those with the five-layer system according to the invention 35 reflection values obtained from curve h. The layer system 34 differs from the layer system 35 in that here the double layer, 39 , 41 is replaced by a single, but much thicker layer 40 , which has a single layer thickness of 108 nm.

The reflectance values R of the curve g and the Curve h are wavelength dependent in Table 4 ne give up the associated transmittance values T. listed.

Table 4

(to Fig. 7)

The layer systems with which the transmission and reflection values mentioned above in Examples 1 to 4 were achieved were produced by the method described below. In a reactive gas atmosphere of approx. 5 × 10 ^-3 mbar, depending on the optical layer to be deposited, titanium, zirconium, silicon or aluminum, zinc, tin, tantalum or silicon was selected as the target material. Using noble gas with admixture of a reactive gas, such as. B. an O₂ / N₂ gas mixture, was sputtered from the target surface under sputtering target substance material, which is on the substrate 4 to be coated as a chemical compound, such as. B. ZrN or TiO _x N _y , precipitates and forms as a closed ge layer. Due to the temporal sequence of the sputtering process on different target materials, individual layers composed of compounds composed of different chemical elements are successively built up to form a layer system 2 , 15 , 25 , 35 which has the optically acting properties mentioned, in particular with a low degree of reflection having.

Reference list

1 covering, layer system
2 covering, layer system
4 substrate
6 first layer
8 second layer
9 third layer
10 third layer
11 fourth shift
12 fourth shift
13 fifth shift
15 covering, layer system
16 first layer
18 second layer
19 third shift
21 fourth shift
22 fifth shift
24 covering, layer system
25 covering, layer system
26 first layer
28 second layer
29 third shift
30 third shift
31 fourth shift
32 fourth shift
33 fifth shift
34 covering, layer system
35 covering, layer system
36 first shift
38 second layer
39 third shift
40 third shift
41 fourth shift
42 fourth shift
43 fifth shift
a Reflectance curve for layer system 1
b reflectance curve for layer system 2
c measured reflectance curve for layer system
d reflectance curve for layer system 24
e Reflectivity curve for layer system 25
f reflectance curve for layer system 34
g reflectance curve for layer system 35 .

Claims (7)

1. covering, consisting of an optically active layer system for substrates, the broadband layer system in particular having a high antireflection effect and in particular a high light transmission or having a high antireflection effect for a given light transmission, characterized in that the layer system ( 2 , 15 , 25 , 35 ) a layer sequence of mutually abutting the optically high-index and low-index single layers, at least two high-index layers ( 9 , 11 ; 19 , 21 ; 29 , 31 ; 39 , 41 ) immediately following one another. 2. Rubber according to claim 1, characterized net that the refractive indices of each other adjacent, high refractive index layers a value of minimum 0.1 and maximum 0.4 differentiate. 3. Covering according to claim 1 and / or 2, characterized in that the layer system ( 2 , 15 , 25 , 35 ) at least 5 individual layers ( 6 , 8 , 9 , 11 , 13 ; 16 , 18 , 19 , 21 , 22nd ; 26 , 28 , 29 , 31 , 33 ; 36 , 38 , 39 , 41 , 43 ), a first, preferably highly refractive layer ( 6 ; 16 ; 26 ; 36 ) being arranged on the substrate ( 4 ) thereon followed by a preferably low-refractive second layer ( 8 ; 18 ; 28 ; 38 ), followed by a third, preferably high-refractive layer ( 9 ; 19 ; 29 ; 39 ), followed by a fourth, preferably high-refractive layer ( 11 ; 21 ; 31 ; 41 ) is arranged, on which a fifth layer ( 13 ; 22 ; 33 ; 43 ), preferably consisting of material that is broken down, is arranged. 4. Covering according to at least one of claims 1 to 3, characterized in that the high refractive index layers ( 6 , 9 , 11 ; 16 , 19 , 21 ; 26 , 29 , 31 ) made of a titanium oxide, preferably titanium dioxide, or TiO _x N _y and that the low-index layers consist of a silicon oxide, preferably of silicon dioxide or of MgF₂ or Al₂O₃. 5. Covering according to at least one of claims 1 to 4, characterized in that one of the successive high-index double layers ( 9 , 11 ; 19 , 21 ; 29 , 31 ; 39 , 41 ) consists of TiO _x N _y or titanium dioxide, which is doped with a material with low refractive index, preferably with Al₂O₃ or SiO₂ or MgF₂. 6. Covering according to at least one of claims 1 to 5, characterized in that the first layer ( 6 , 16 , 26 , 36 ) consists of one / one of the following compounds, namely ZnO, SnO₂, ZrO₂, Ta₂O₅, Si₃N₄, Indium tin oxide. 7. A method for producing a covering according to at least one of claims 1 to 6, characterized in that the individual layers ( 6 , 8 , 9 , 10 , 11 , 12 ; 16 , 18 , 19 , 21 , 22 ; 26 , 28 , 29 , 30 , 31 , 32 , 33 ; 36 , 38 , 40 , 41 , 42 , 43 ) by means of a cathode sputtering process, in particular by means of a reactive sputter coating process.