DE4117257A1 - Antireflective optical coating for glass substrates - comprising titanium nitride layer with over-stoichiometric nitrogen content - Google Patents

Abstract

A coating for substrates comprises an optically-active layer system with a high anti-reflection effect, according to the parent Patent. The substrate is transparent and pref. has a refractive index of 1.5-1.65. The coating comprises TiNx layers where x = 1-1.16 for at least one layer. USE/ADVANTAGE - The coating is used as an anti-reflection coating in optical equipment. The coating provides good anti-reflection properties, good contrast and optical brilliance, and increases the anti-static effect. The overall coating thickness is low, leading to low materials and mfg. costs.

Description

The invention relates to a covering consisting of a optically acting layer system, for substrates, wherein the layer system in particular a high anti-reflection effect has after main patent ... (patent application P 39 42 990.3).

There is a wide range of coating systems for Substrates, in particular for glass, the particular optical Fulfill functions. The present invention relates the genus of antireflection coatings, respectively Anti-reflective coating systems.

By the German patent application 36 29 996 is a Attachment unit for the cathode ray tube of monitors, TV sets and the like, consisting of a Glass pane, in particular a gray glass pane, a Front anti-reflection equipment and one rear absorption coating, wherein the Absorption coating metal atoms, known become.

In this German patent application is suggested that the absorption coating single layer of chrome,  built up of a chromium / nickel alloy or silicides and antistatic and grounded, as well as with a thickness is provided which the light transmission around the uncoated glass pane by about one Third lowers.

In the US Patent No. 38 54 796 is still a Coating proposed to reduce the To serve reflection. The coating should be for a Substrate, which is a plurality of Has layers. In the order starting at Substrate is the following arrangement in the US patent described: three groups of at least two Lambda / 4-layers, the successive layers of the first group have a refractive index that is below the refractive index of the substrate. The Layers of the second group have one increasing refractive index and the layers of the third Group have a refractive index below the Refractive index of the substrate. more details can be found in the cited US patent.

The state of the art still includes the US Patent 37 61 160th There will be a Broadband antireflection coating and substrates that coated with it are proposed. They point at least four layers for high index glass and at least six layers for low index glass on. Further details are the mentioned US-Script refer to.  

Furthermore, in US Patent 36 95 910 a Method of applying an antireflective coating described on a substrate. This coating exists from several individual layers. The procedure for the Application of the antireflection layers takes place under Vacuum, using electron beams. Further details are the aforementioned US patent refer to.

Furthermore, the prior art belongs to the US Pat. No. 3,829,197 which discloses an antireflection coating, which is designed as a multilayer system describes. This surface should be on a strong breaking substrate be attached. The shift system consists of five individual layers, which are mutually adapted, in terms of their refractive index and in Respect to their optical thickness. Through this adaptation should have a favorable antireflection curve with a broad, shallow, middle part can be achieved. Further Details of this proposal are those mentioned US Patent refer to.

The state of the art still includes the Swiss Patent 2 23 344. This document is concerned with a coating to reduce the surface reflection. The coating consists of at least three layers with different refractive indices. The reduction of Surface reflection should be according to this document by a certain selection of the refractive indices of the individual Layers are achieved.

The invention is based on the following tasks:
It will create conditions for the economic production of antireflective coatings for transparent substrates.

Transparent substrates are becoming more modern in a variety of ways Facilities and equipment needed. The manufacturers of this Equipment and devices make high demands Regard to the optical and other properties of these substrates.

The invention is intended to meet these stringent requirements in particular in terms of the anti-reflective coating, the increase in contrast and fulfill the increase in antistatic effect.

Furthermore, conditions are to be created for that only a small number of layers is needed. At the same time, the thicknesses of the individual layers should be small his. The invention continues to be the task Requirements for the use of cheaper To create materials.

With the invention, a concept is to be proposed, in the DC reactive with magnetron from the metal target can be sputtered.

The small number of layers of the layer system, the small thickness of the individual layers of the layer system, the selection of inexpensive feedstock and the Possibility of DC-reactive with magnetron from the metal target to sputter,  lead to a very economical production the antireflective layer systems according to the invention.

In itself, the use of metal layers for Antireflection systems known in principle. It has, however proved that the known metal layers for the daily routine is too soft.

It is therefore part of the task of present invention, a substitute for the known soft metal layers (Ag, Ni, ...). This Replacement should be hard and scratch resistant. He should on the one hand have a ceramic hardness, on the other hand, however also have the effect of a metal-like appearance.

The tasks are set by those in the main patent solved inventive measures described. In addition, it is suggested that the substrate is especially transparent and preferably one Refractive index of 1.5 to 1.65 has.

Furthermore, it is additionally proposed that, for at least one of TiN _x layer described in the main patent layer systems over-stoichiometric TiN _x is used with x in the range 1 to 1.16.

In a further additional embodiment it can be provided that all TiN _x layers of the layer systems described in the main patent have TiN _x with x in the range from 1 to 1.16.

Further details of the invention, the task and the advantages achieved are the following description several embodiments of the invention can be seen.

These embodiments will be described with reference to five figures explained.

FIGS. 1, 2 and 5 each show a layer system.

FIGS. 3 and 4 show transmission and reflection curves in percent over wavelengths in nm.

In the following, five exemplary embodiments are described below:
The substrate 1 is made of glass. The front side 2 of the substrate is the side of the substrate facing the viewer. The back 9 of the substrate is the side facing away from the viewer.

The layer applied to the front side of the substrate is referred to as the "first" layer 4 . In the direction of the viewer, the "second" layer 5 and the "third" layer 6 follow.

The layer system of the first embodiment is constructed as follows: (see FIG. 1)

• on the back of the substrate glass, an optically effective TiN _x layer 8 is attached,
• in the direction of the observer, the substrate follows glass 1 ,
• the first optically active layer 4 , which bears against the substrate, consists of SnO ₂ ,
• the second optically active layer 5 , which follows in the direction of the observer the first optically active layer, consists of TiN _x ,
• - The third optically active layer 6 , which follows in the direction of the viewer of the second optically active layer, consists of Al ₂ O ₃ .

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

• on the back of the substrate glass, an optically effective TiN _x layer 8 is attached,
• - in the direction of the observer follows the substrate: Glass,
• the first optically active layer 4 , which bears against the substrate, consists of SnO ₂ ,
• - It follows in the direction of the viewer a bonding agent layer 7 , consisting of NiCrO _x ,
• the second optically active layer 5 , which follows in the direction of the observer, consists of TiN _x ,
• - The third optically active layer 6 , which follows in the direction of the viewer of the second optically active layer, consists of Al ₂ O ₃ .

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

• on the back of the substrate glass, an optically effective TiN _x layer 8 is attached,
• in the direction of the observer, the substrate follows glass 1 ,
• the first optically active layer 4 , which bears against the substrate, consists of SnO ₂ ,
• - It follows in the direction of the viewer, a bonding agent layer 7 , consisting of NiCr suboxide,
• the second optically active layer 5 , which follows in the direction of the observer, consists of TiN _x ,
• - The third optically active layer 6 , which follows in the direction of the viewer of the second optically active layer, consists of SiO ₂ .

The layer system of the fourth embodiment is constructed as follows: (see FIG. 1)

• on the back of the substrate glass, an optically effective TiN _x layer 8 is attached,
• in the direction of the observer, the substrate follows glass 1 ,
• the first optically active layer 4 , which bears against the substrate, consists of NiCrO _x ; this layer 4 simultaneously acts as a primer layer,
• the second optically active layer 5 , which follows in the direction of the observer, consists of TiN _x ,
• - The third optically active layer 6 , which follows in the direction of the viewer of the second optically active layer, consists of SiO ₂ .

The layer system of the fifth embodiment is constructed as follows: (see FIG. 1)

• on the back of the substrate glass, an optically effective TiN _x layer 8 is attached,
• - in the direction of the observer follows the substrate: glass 1 ,
• the first optically active layer 4 , which bears against the substrate, consists of NiCrO _x ; this layer 4 simultaneously acts as a primer layer,
• the second optically active layer 5 , which follows in the direction of the observer, consists of TiN _x ,
• - The third optically active layer 6 , which follows in the direction of the viewer of the second optically active layer, consists of Al ₂ O ₃ .

As a substrate except mineral glass, float glass can also Plexiglas, transparent plastic layers, foils etc. are used.

In addition to the front side mirroring through the described, arranged in front of the front layer systems, a further surprisingly low overall reflection is achieved by the arranged on the back TiN _x layer. The basic idea of the invention allows for a multiplicity of exemplary embodiments or layer systems, which are characterized by the following materials and layer thicknesses.

"First" layer (reference numeral 4 ), a dielectric: metal oxide (SnO ₂ , ZrO ₂ , ZnO, Ta ₂ O ₅ , NiCrO _x , TiO ₂ , Sb ₂ O ₃ , In ₂ O ₃ ),
Layer thickness: 80 angstroms +/- 20%,
"Second" layer (reference numeral 5 ) nitride (TiN, ZrN) layer thickness: 130 angstroms +/- 20%,
"Third" layer (reference numeral 6 ) Dielectric: low-refractive materials, n less than 1.7, (SiO ₂ , Al ₂ O ₃ , AlSi oxide, NiSi oxide, MgO, MgF ₂ ) Optical thickness: 5550/4 Angstrom + / -10%
"Adhesive Layer" (Ref. 7 ): Ni, Cr, NiCr (80 wt% Ni, 20 wt% Cr) Layer Thickness: 10 Angstroms +/- 10%.

On the back 9 of the substrate is the "backside layer" (reference numeral 8 ) consisting of TiN _x , layer thickness: 40-150 Angstroms.

It goes without saying that such values for the respective layer thickness within the mentioned Layer thickness tolerances are chosen, which are the Interdependence of the individual layer thicknesses and the consider used materials to each other.

The following is the description of two examples of Layer systems in which the reflection and the Transmission in the visible wavelength range of the light were measured.

The measurement results are graphically illustrated by curves in FIGS. 3 and 4.

In describing the layer systems, the reference numerals of the description of Fig. 1 are used.

The layer system of the first example is constructed as follows:
Substrate: glass ( 1 ), thickness 2 mm, refractive index n = 1.52,
Layer ( 4 ) Material: SnO ₂ , thickness 90 Angstrom Refractive index n = 2.05,
Layer ( 5 ) Material: TiN _x , thickness 130 angstroms,
Layer ( 6 ) material: Al ₂ O ₃ , thickness 730 Angstrom refractive index n = 1.6,
Layer ( 8 ) Material: TiN _x , thickness 70 angstroms.

The designated in Fig. 2 with 7 adhesion promoter is not present in this embodiment.

For this layer system, the reflection in percent and measured the transmission in percent, for a wavelength range of 400 nm to 700 nm.

The following are the measurement results for the reflection and determined the transmission in a table Wavelengths faced:

As shown, the results of the measurements are graphically represented as curves in FIG . On the abscissa 10 of the coordinate system in Fig. 3, the wavelengths are entered in nm. On the left ordinate 11 of the coordinate system, the percentages for the reflection are entered. The percentages for the transmission are entered on the right-hand ordinate 12 of the coordinate system.

It can clearly be seen from the curves that the reflection curve 14 is extremely low in the core wavelength region of visible light. It is well below 1%. Thus, the desired high antireflection effect has been achieved in a surprisingly clear manner. In the same core wavelength range, the transmission curve 13 has relatively high values. The layer system of the second example is characterized as follows:
Substrate: glass, thickness 2 mm, refractive index n = 1.52,
Layer ( 4 ) Material: NiCr oxide, thickness 70 Angstrom Refractive index n = 2.1,
Layer ( 5 ) Material: TiN _x , thickness 130 angstroms,
Layer ( 6 ) Material: SiO ₂ , thickness 790 Angstrom Refractive index n = 1.5
Layer ( 8 ) Material: TiN _x , thickness 70 angstroms.

A separate adhesion promoter, see reference numeral 7 , is not present in this embodiment.

For this layer system, the reflection in percent and measured the transmission in percent, for a wavelength range of 400 nm to 700 nm.

The following are the measurement results for the reflection and determined the transmission in a table Wavelengths faced:  

As shown, the measurement results are graphically represented as curves in FIG . The abscissa and the ordinate carry the units of measurement described in connection with FIG .

From the reflection curve 16 it can be clearly seen that the reflection in the range of about 560 nm wavelength has a pronounced low point. Thus, the desired high antireflection effect has been achieved convincingly by this example. The transmission curve 15 has its maximum in the core region of visible light.

As regards the transmission curve 13 ( FIG. 3) and the transmission curve 15 ( FIG. 4), the following can basically be said:
Low transmission values of an auxiliary lens can be easily achieved by amplifying the light source, for. B. by turning the potentiometer on an LCD, be compensated.

The layer systems with which the above-commented transmission and reflection values were obtained were prepared by the method described below:
It was sputtered with magnetron in a reactive gas atmosphere.

Subsequently, in the left column, the sputtering material and in the right column the reactive sputter mixture stated:

SnO₂ Ar + O₂ SiO₂ Ar + O₂ Al₂O₃ Ar + O₂ TiN Ar + N₂ NiCr Ar + O₂

Pressure during sputtering: about 5 × 10 ^-3 mb.

Target material: Sn, Si, Ti, NiCr (80 weight percent Ni, 20% by weight Cr), Al.

On the front of the layer systems was a Sheet resistance of 150 ohms per square measured on the backside had a sheet resistance of 240 ohms measured per square. These are relatively small Surface resistances.

By grounding the surfaces, therefore, the static Charge reduced or even reversed. In order to the desired antistatic effect is achieved.  

FIG. 5 shows an exemplary embodiment of the system discussed above in the introduction to the description, consisting of two layers, on the front side 2 of the substrate 1 . The "first" applied to the substrate layer carries in the two-layer system of FIG. 5, the reference numeral 17th The viewer then follows the "second" layer 18 .

For the "first" layer 17 and the "second" layer 18 of the two-layer system of FIG. 5, those chemical composition data, layer thicknesses, refractive indices, and those combinations of data used for layers 5 and 6 of FIG. 1 and 2 have been described above and in the introduction to the description.

The alternative embodiments described for the layers 5 and 6 in the introduction to the description and in connection with FIGS. 1 and 2 also apply to the two-layer system, as for example in FIG. 5 with the "first" layer 17 and the "second" layer 18 is pictured.

In this case, the "first" layer 17 of the two-layer system of FIG. 5 corresponds to the layer 5 of the layer systems of FIGS. 1 and 2.

The "second" layer 18 of the two-layer system of FIG. 5 corresponds to the layer 6 of the layer systems of FIGS. 1 and 2.

The surface resistances of the two-layer system correspond to those of the systems according to FIGS. 1 and 2.

List of items

1 substrate, glass
2 front side
3 arrow, line of sight
4 "first" layer of FIGS. 1 and 2
5 "second" layer of FIGS. 1 and 2
6 "third" layer of FIGS. 1 and 2
7 adhesion promoter layer
8 backside layer
9 back side
10 abscissa
11 left ordinate
12 right ordinates
13 transmission curve
14 reflection curve
15 transmission curve
16 reflection curve
17 "first" layer of FIG. 5
18 "second" layer of FIG. 5

Claims (3)

1. covering, consisting of an optically acting layer system, for substrates, wherein the layer system in particular has a high antireflection effect, according to the main patent. , , (Patent Application P 39 42 990.3), characterized in that the substrate is in particular transparent and preferably has a refractive index of 1.5 to 1.65. 2. covering, in particular according to claim 1, consisting of an optically acting layer system, for substrates, wherein the layer system in particular has a high antireflection effect, according to the main patent. , , (Patent Application P 39 42 990.3), characterized in that for at least one TiN _x layer in particular superstoichiometric TiN _{x is used} with x in the range of 1 to 1.16. 3. Covering according to claim 1 and / or 2, characterized in that for all TiN _x layers superstoichiometric TiN _x with x in the range of 1 to 1.16 is used.