Europaisches Patentamt 0101033 J European Patent Office Publication number: B1 Office europeen des brevets

EUROPEAN PATENT SPECIFICATION

08.11.89 Intel.4: G 02 B 1/10 Date of publication of patent specification:

Application number: 83107752.4 Date of filing: 05.08.83

Optical article having a conductive anti-reflection coating.

(§) Priority: 09.08.82 US 406302 Proprietor: OPTICAL COA1COATING LABORATORY, INC. 2789 Northpoint Parkway Date of publication of application: Santa Rosa, CA 95401 (US) 22.02.84 Bulletin 84/08 Inventor: Hahn, Robert E. Publication of the grant of the patent: 1657EICaminoWay 08.1 1.89 Bulletin 89/45 Santa Rosa California 95404 (US) Inventor: Jones, Thomas R. 2139 Saint John Court Designated Contracting States: Santa Rosa California 95401 (US) AT BE CH DE FR GB IT LI LU NL SE Inventor: Berning, Peter H. 1287 Bingtree Way Sebastopol California 95472 (US) References cited: BE-A- 560 087 DE-A-968248 Representative: von Fiiner, Alexander, Dr. et al US-A-2852415 Patentanwalte v. Fiiner, Ebbinghaus, Finck US-A-3 679 291 Mariahilfplatz2&3 CO US-A-3914516 D-8000 Miinchen 90 (DE) US-A-4313 647 vol. 7, 1974, CO APPLIED OPTICS, 13, no. July cited: New York, US; H. DUPOISOT References CO pages 1605-1609, GLASTECHNISCHE BERICHTE, vol. 53, 9, al.: lumiere interferentiels a larges no. o et "Pieges a 245-258, Frankfurt am Main, DE; bandes azimuthale et spectrale" 1980, pages H.J. GLASER: "Verfahren zur Beschichtung von 5 Fensterscheiben mit Sonnen- und Warmeschutzschichten" months from the publication of the mention of the grant of the European patent, any person may o Note- Within nine shall notice to the European Patent Office of opposition to the European patent granted. Notice of opposition give the fee has been be filed in a written reasoned statement. It shall not be deemed to have been filed until opposition convention). LU paid. (Art. 99(1 ) European patent Courier Press, Leamington Spa, England. EP 0 101 033 B1 Description new and improved conducting anti reflecting coat- ing. This invention relates to antireflection coatings In general it is an object of the present invention and more particularly to conductive antireflection to provide an optical article having a conductive coatings. 5 antireflection coating thereon. Antireflection coatings have found widespread Another object of the invention is to provide a application throughout the field of optics and coating of the above character in which the layer electro-optics where it is desirable or necessary to adjacent to the incident medium (air) is a layer of reduce the reflectance at any optical interface, as high index conducting material which is readily for example, air to glass. Application includes 10 accessible. camera lenses, copier platens, cover glasses for Another object of the invention is to provide a instruments glare reduction coatings on panels coating of the above character in which the for cathode ray tube and other display devices. various layers of the coating provide an optical Optical thin film coatings utilized for the various performance which closely approximates that of applications include single layer coatings, such as 15 their non-conducting counterparts. coatings formed of magnesium fluoride, two Other object of the invention is to provide an layer coatings characterized as V-coats to mini- optical article having a coating of the character mize reflectance at a single wavelength region, described which has both optical antireflection and multi-layer broad-band coatings such as properties and electrical conducting properties. those disclosed in United States Letters Patent 20 Another object of the invention is to provide an No. 3,185,020 that produce low reflectance over a article having a coating thereon of the above relatively broad wavelength region, as for character which has high transmission and low example, the visible spectrum. Transparent con- absorption. ductive coatings have also found widespread Another object of the invention is to provide an appications within recent years or wherever elec- 25 article having a coating thereon of the above trical conductivity and high optical transparency character which permits direct electrical contact are required. For such purposes films of indium to the conductive layer. tin oxide, cadmium stannate, tin antimony oxide Additional objects and features of the invention and others have been utilized in various displays, will appear from the following description in as for example, liquid crystal displays, visually 30 which preferred embodiments are set forth in transmitting window heating elements for aircraft conjunction with the accompanying drawings. windows, static bleed coatings and heat retaining Figure 1 is a cross-sectional view of an optical visible light transmitting coatings for lamp article having a conductive antireflection coating envelopes, etc. However, all presently known thereon incorporating the present invention. transparent conducting film materials have high 35 Figure 2 is a graph showing the performance of indices of refraction with values typically in the the coating shown in Figure 1. range of 1.8 to 2.2. Use of such materials having Figure 3 is a cross-sectional view of another high indices of refraction frequently leads to the optical article having a coating thereon incor- undesirable effect that films of these materials porating another embodiment of the present deposited on glass substrates increase visual 40 invention. reflectance which often reduces device or system Figure 4 is a graph showing the performance of performance. Also, because of the high index of the coating shown in Figure 2. refraction of transparent conductive materials, Figure 5 is a cross-sectional view of another the design of antireflection coatings with electri- optical article having a coating thereon incor- cal conductivity has been seriously constrained. 45 porating another embodiment of the present Presently available wide band anti-reflection coat- invention. ings with electrical conductivity employ either a Figure 6 is a cross-sectional view of still another half wave layer or part of a modified quarter wave optical article having a coating thereon incor- layer nearest the substrate of a conventional porating another embodiment of the present quarter wave-half wave-quarter wave design. 50 invention. Such designs have conductance values that are Figure 7 is a curve showing the performance of relatively high and relatively low respectively. The the coating shown in Figure 6. optical performance of such coatings is compar- In Figure 1, there is shown an optical article able to, but generally less efficient than, the non having a conductive antireflection coating conducting designs on which they are based. In 55 thereon incorporating the present invention. As addition, in order to use such conducting anti- shown, the optical article 10 consists of a suitable reflection coatings it has been necessary to make transparent substrate such as glass having an electrical contact to the conductive layer by index of refraction ranging from 1.5 to 2.0 and various methods such as by scratching through typically having an index of refraction of 1 .52. The the non-conducting layer, using masks to prevent 60 substrate 11 is provided with first and second overcoating the conducting layer or by providing optical surfaces 12 and 13. An antireflection coat- bus bars to provide the necessary physical con- ing 14 is carried by one of the surfaces 12 and 13 tact to the conducting layer. Such contact struc- of the substrate 11 as, for example, surface 13 as tures add to the complexity and costs of the shown in Figure 1. resulting product. There is therefore a need for a 65 The conducting antireflection coating 14 con- EP 0 101 033 B1 anti reflection sists of a layer 16 formed of a material. having a obtained from use of a conducting low index of refraction ranging from 1.35 to 1.46 coating 14 as shown in Figure 1 is shown in Figure for example, magnesium fluoride having an 2. In the coatings providing the curves in Figure 2, as, of index or refraction of 1.38. Typically, the layer of there have been added 4.5 nanometers con- low index material would have an optical thick- s ducting material to quarterwave layers at 550 (curve ness for use in the visible region of approximately nanometers (curve 21), 440 nanometers As be one-quarterwave for a design wavelength of 22) and 330 nanometers (curve 23). can of approximately 550 nanometers. A thin trans- seen from Figure 2, the addition of a thin layer the to parent conducting layer 17 also forms a part of conducting material shifts spectral curve low the coating 14 and overlies the layer of low index w slightly longer wavelengths but retains material. Because of the thickness of the thin reflectance comparable to a single layer of mag- transparent conducting layer 17, the thickness of nesium fluoride. In a nearly equivalent manner be reduced the layer 16 is slightly less than the conventional the magnesium fluoride layer can optical thickness for reasons herein- slightly in thickness to keep the reflectance mini- quarterwave the after explained. The thin transparent conducting w mum at the initial location. In any event, is the to layer 17 would have a suitable thickness ranging addition of a thin conducting layer key from 1.0 to 10.0 nanometers with the preferred retaining the essential characteristics of the thickness ranging from 4.0 to 6.0 nanometers. single-layer antireflection coating. It has been Materials found to be suitable for the thin trans- found that it would be unacceptable to place the parent conducting layer have been indium tin 20 thin transparent conducting layer over a mag- oxide, cadmium stannate and antimony oxide. nesium fluoride coating of conventional thickness of the The magnesium fluoride layer can be deposited in because this would shift the performance would be a conventional manner well known to those skil- coating upscale so that it no longer led in the art. The materials for making the thin centered well in the visible region and therefore it conducting layer also can be applied 25 would not have the appropriate anti reflective transparent of the in a conventional manner. For example, the properties. In order to shift the performance indium and tin metals can be placed in boats and coating downscale in order to provide a good decrease the evaporated in an oxygen atmosphere in a conven- visual appearance, it is necessary to tional coating chamber to condense on the sub- optical thickness of the magnesium fluoride layer strate. Sputtering and chemical vapor deposition 30 to make up for the addition of the optical thick- It can also be utilized to apply these materials. ness of the thin transparent conducting layer. The design concept which is utilized in connec- has been found that the minimum antireflectance tion with the design of the conductive anti-reflec- curve tends to be determined by the combined tion coating 14 is based on the premise that if a optical thickness of both the magnesium fluoride thin layer of non-absorbing material whose 35 layer and the thin transparent conducting layer. optical thickness is a small fraction of a Therefore in order to keep the combined optical wavelength is added to the design, relatively thickness substantially constant it is necessary to fluoride small changes will occur in the optical perform- reduce the thickness of the magnesium thickness of ance of the anti-reflection coating. In addition, it layer to compensate for the optical has been found that if the optical thickness of the 40 the thin transparent conducting layer. outermost layer of the initial design for the anti- In Figure 2, the conducting coating 14 providing reflection coating is reduced by approximately the curve 21, the thin transparent conducting 4.5000 the optical thickness of the added conducting layer 17 had a physical thickness of thickness layer, the resulting changes in optical perform- nanometers and a quarterwave optical fluoride ance are minimized. 45 of 36.00 nanometers and the magnesium The optical coating which is shown in Figure 1 layer 16 had a physical thickness of 99.6377 thickness can be characterized as a single layer antireflec- nanometers and a quarterwave optical thick- tion coating which typically is made by using a of 550.000 nanometers. The total physical film of quarterwave optical thickness as herein- ness of the coating 14 was 104.138 nanometers before described and having indices that are as 50 (.00410 mils). The optical coating 14 providing the of 4.5000 close as possible to the value curve 22 had a physical thickness nanometers and a 36.000 nanometer quarterwave optical thickness for the thin transparent conduct- ing layer 17 and a physical thickness of 79.7101 where Nf, No and Ns are the refractive indices of 55 and a quarterwave optical thickness of 440.000 the film, the incident medium and the substrate nanometers for the magnesium fluoride layer 16 of respectively. The most common example of this to provide a total physical coating thickness The coat- type of antireflection film is a quarterwave layer 84.210 nanometers (.00332 mils). optical of magnesium fluoride on a glass substrate as ing 14 providing the curve 23 had a physical shown in Figure 1. This single-layer coating has 60 thickness of 4.500 nanometers and a 36.000 been modified, as shown in Figure 1,to produce a nanometer quarterwave optical thickness for the conducting antireflection coating by adding a thin thin transparent conducting layer 17 and a physi- transparent conducting layer 17 described pre- cal thickness of 59.7826 and a quarterwave optical viously in connection with Figure 1. thickness of 330.000 nanometers for the mag- The spectral performance which can be 65 nesium fluoride layer 16 with a total physical EP 0 101 033 B1 6 thickness for the optical coating 14 being 64.283 have a thickness of approximatley 110 nanome- nanometers (.00253 mils). ters whereas the thin conducting layer can have a From the foregoing, it can be seen that the thin thickness ranging from 1.0 to 10.0 nanometers transparent conducting layer 17 had the same depending upon the desired characteristics. thickness in each of the three designs, shown in 5 The embodiment shown in Figure 1 is basically Figure 2 and that the magnesium fluoride layer a single layer antireflection coating whereas the thickness was varied. These three curves show embodiment shown in Figure 2 is basically a two that for a well-balanced design, it is desirable to layer antirefection coating. The graph shown in have a thickness of magnesium fluoride corre- Figure 4 shows the performance characteristics sponding to curve 22 so that the antireflection w for the two-layer design of the type described in coating is centered in the visible region for opti- Figure 3. Curves 36, 37, 38 and 39 are shown in mal performance. Figure 4. Curve 36 was formed by a conducting It has been found that the appropriate design antireflection coating 29 by forming the layer 31 technique is to select the thickness of the thin of indium tin oxide having an index of refraction transparent conducting layer and thereafter to is of 2.000 with a physical thickness of 28.4375 redesign the magnesium fluoride layer to com- nanometers and a quarterwave optical thickness pensate for the thickness of the thin transparent of 227.5 nanometers, by forming the low index conducting layer. The thickness of the thin trans- layer 32 of magnesium fluoride with a physical parent conducting layer 17 typically is selected on thickness of 111.8659 nanometers and a the basis of the sheet resistivity desired. As, for 20 quarterwave optical thickness of 617.5 nanome- example, in platen applications where it is desired ters and by forming the layer 33 of indium tin to bleed off any static charge, a sheet resistivity of oxide having an index of refraction of 2.000 and less than 1010 ohms/square is desirable. In addi- having a physical thickness of 1.2187 nanometers tion in selecting the thickness for the thin trans- • and a quarterwave optical thickness of 9.75 parent conducting layer 17, it is necessary to also 25 nanometers to provide a total physical thickness consider the durability, electrical stability, overall for the coating 29 of 141.522 nanometers (.00557 performance, and repeatability of making the mils). This design has typically been called a V- coating. Therefore, the ultimate objective is to coat which has been modified to include a con- increase the thickness of the thin transparent ductive outer layer. conducting layer to a sufficient amount without 30 The curve 37 was provided by a conductive substantially degrading the optical properties antireflection coating 29 in which the layer 31 was desired for the antireflection coating. As can be also formed of indium tin oxide having a physical appreciated, the tradeoff is between providing thickness of 385.00 nanometers with the layer 32 increased sheet conductivity against ultimately being formed of magnesium fluoride having a what will become unacceptable overall optical 35 physical thickness of 62.2735 nanometers with a performance. With such constraints, it is possible quarterwave optical thickness of 343.75 nanome- to provide a thin transparent conducting layer ters and with the outer layer 33 being formed of having a sheet resistivity as low as 300 ohms per indium tin oxide having a physical thickness of square. 22.343 nanometers to provide a coating of a total In Figure 3, there is shown an optical article 40 physical thickness of 132.742 nanometers (.00523 having an antireflection coating incorporating mils). This coating 29 can be characterized as a another embodiment of the invention which the two layer V-coat antireflection coating with a reflectance at a single or very narrow wavelength thicker outer transparent conducting layer. region can be made to approach zero reflectance. Curve 38 was produced by a coating 29 having The optical article 24 shown in Figure 3 consists of 45 a layer 31 of indium tin oxide having a physical a substrate 26 formed of a suitable material such thickness of 20.6250 nanometers and a as glass having the same characteristics as the quarterwave optical thickness of 165.00 nanome- substrate 11 for the embodiment shown in Figure ters and with the layer 32 formed of magnesium 1. It is also provided with optical surfaces 27 and fluoride having a physical thickness of 129.5290 28. An antireflection coating 29 is disposed on the 50 nanometers and a quarterwave optical thickness surface 28 and consists of a plurality of layers of 715.00 nanometers with the layer 33 being including layers 31, 32 and 33. Layer 31 which can omitted and with the coating 29 having a total be either conducting or nonconducting is dis- physical thickness of 150.15 nanometers (.00591 posed on the surface 28. For example, it can be mils). This coating 29 shown in curve 38 can be formed of a transparent conducting material such 55 characterized as a V-coat comparable to the V- as indium tin oxide having a high index of coat producing curve 36 without the outer indium refraction of 2.00 and an optical thickness of tin oxide layer as an overcoat. approximately 20 nanometers. A layer 32 is dis- A comparison of the curves 36 and 38 show the posed on the layer 31 and is formed of a low index difference in performance of the V-coat with and material such as magnesium fluoride having an 60 without a thin conductive layer on the outer index of refraction of 1.38. A thin transparent surface. Curves 36 and 37 show that there is a conducting layer 33 is disposed on the layer 32 negligible degradation of performance in the and is formed of a suitable material such as region of the reflectance minimum by adding the indium tin oxide having a high index refraction of conductive coating to the outer surface. 2.000. The magnesium fluoride layer can typically 65 Curve 36 shows the optical performance using EP 0 101 033 B1 8 the previously described design principles utilized 53. The coating 54 can be characterized as a in connection with the embodiment of the inven- conventional HEA coating such as the type tion shown in Figure 1 but utilizing the additional described in United States Letters Patent No. layer between the magnesium fluoride layer and 3,185,020 and 3,432,225 which has been modified the substrate and shows that the very thin con- 5 by the addition of a thin transparent conducting ducting layer on the outer surface does not layer. Thus the coating 54 is comprised of a layer appreciably degrade the performance of the anti- 56 formed of a high index material having an reflection coating and provides near zero reflect- index of refraction of approximately 2.0 to 2.1 and ance of a portion of the visible region. Curve 37 having a quarterwave optical thickness at 115 to shows that even when a thicker outer layer of to 130 nanometers. It is also comprised of a layer 57 conducting material is provided a substantially of a low index material such as magnesium zero reflectance is still obtained although the fluoride having a quarterwave optical thickness at reflectance is reduced over only a narrower 160 to 170 nanometers and another layer 58 waveJength region. However, the conducting formed of a high index material having an index layer is adjacent to the incident medium and is 15 of refraction of 2.0 to 2.1 and having approxi- available for direct electrical contact. In addition, mately a quarterwave optical thickness at 1070 its reasonable optical thickness results in a nanometers followed by another layer 59 formed reasonably low value of electrical resistance, i.e., of a material having a low index refraction such as less than 1000 ohms per square. magnesium fluoride and having an approximate Curve 39 shown in Figure 4 is a curve which is 20 quarterwave optical thickness of 425 nanometers produced by a coating of indium tin oxide only in the visible region. The layers 56 through 59 are with a thickness of approximately 250 Angstroms. designed in accordance with the teaching of This curve demonstrates that such a coating is United States Letters Patent No. 3,185,020 and very reflective and is not very useful for critical 3,432,225. applications where low reflectance is required. 25 The coating 54 is also comprised of the layer 61 Another embodiment of an optical article formed of a thin transparent conducting material having a conducting antireflection coating incor- 'such as indium tin oxide having a thickness porating the present invention is shown in Figure ranging from 1.0 to 10.0 nanometers and having a 5 which is similar to the design shown in Figure 3 thickness of preferably approximately 4.5 but which has been modified to make possible the 30 nanometers. In this embodiment of the invention use of thicker outer transparent conducting it can be seen that a conventional HEA coating layers. As shown in Figure 5, this optical article 40 has been modified with the addition of an consists of a substrate 41 of the type hereinbefore approximately 5.0 nanometer thick layer of described in connection with the previous indium tin oxide as the outer layer with an embodiments having optical surfaces 42 and 43 35 adjustment in the thickness of the magnesium and a conductive antireflection coating 44 dis- fluoride layer to compensate for the indium tin posed thereon. Coating 44 consists of a layer 46 oxide layer so as to maintain achromatic low which typically can be a transparent conducting reflectivity in the visible spectrum. In order to layer followed by a layer 47 of a low index obtain this compensation, the thickness of the material such as magnesium fluoride followed by 40 magnesium fluoride has been reduced from the a thicker transparent conducting layer 48 formed quarterwave optical thickness of 500 nanometers of a high index material such as indium tin oxide to approximately 425 nanometers. and having a thickness of 15.0 to 30.0 nanometers In Figure 7 curves 62, 63 and 64 are shown with a preferred thickness of 20.0 to 25.0 nanome- demonstrating the performance of a coating of ters. The transparent conducting layer 46 typically 45 the type shown in Figure 4. Curve 63 illustrates can have a physical thickness ranging from 25 to the calculated reflectance of a conventional HEA 60 nanometres with a preferred physical thick- broadband a nti reflection coating. Curve 62 illus- ness of 40 to 50 nanometers. The magnesium trates the same coating with the outer mag- fluoride layer 47 can have a thickness ranging nesium fluoride layer 59 being approximately 15 from 40 to 80 nanometers with a preferred physi- 50 percent thinner. By the addition of a thin layer of cal thickness of 55 to 70 nanometers. With such a indium tin oxide as an outer layer 61 having a thicker outer transparent conducting layer it has physical thickness of approximately 4.5 nanome- been found it is possible to obtain sheet ters the optical performance which is shown by resistances which are well below 1000 ohms per curve 64 is obtained. It can be seen this provides a square. Such highly conductive coatings find 55 conducting HEA coating whose optical perform- applications in cathode ray tube displays where ance is substantially similar to that of the noncon- some moderate amount of radio frequency inter- ducting HEA coating and permits direct contact to ference (RFI) shielding is required. the outer conducting layer. Increases in the thick- Another optical article 50 having a conductive ness of the conducting layer 61 leading to con- antireflection coating thereon incorporating the 60 comitant decreases in the thickness of the mag- present invention is shown in Figure 6 and con- nesium fluoride layer 59 leads to progressive sists of a substrate 51 of the type hereinbefore deterioration of the spectral performance of the described with the previous embodiments having coating until the performance becomes unaccept- optical surfaces 52 and 53 with a conducting able. antireflection coating 54 disposed on the surface 65 It should be appreciated that the design EP 0 101 033 B1 10 approach hereinbefore described in conjunction Claims with Figure 6 can be utilized with designs that utilize a conducting layer for the halfwave layer 1. A conductive antireflection coating (14) dis- 58. Modification of the outer magnesium fluoride posed on the surface of a substrate (11) having layer to accommodate an additional thin conduct- 5 first and second surfaces, characterized by said ing layer yields a broadband antireflection coat- conductive antireflection coating (14) having at ing permitting direct contact to one of the con- least one layer (16) of a low index material carried ducting layers while still having a high overall by said surface and a thin transparent conducting reflectance. Such coatings are useful for RFI layer (17) of a material having a high index of shielding applications. 10 refraction carried by said layer (16) of low index From the foregoing it can be seen that the material and providing an exposed surface to relatively thin conducting layers provided in each which a direct electrical contact can be made, said of the designs give sheet resistance levels that thin transparent conducting layer (17) having an can be adjusted from nearly infinite values to optical thickness ranging from 1.0 to 30.0 values of several thousand ohms per square. The 15 nanometers and wherein said layer (16) of low designs employing a thick halfwave layer of the index material has its design thickness reduced to narrow band modified two-layer coating herein- compensate for the thickness of the thin trans- before described have thicker conducting layers parent conducting layer (17) whereby the pro- and again can have sheet resistance values below vision of the thin conducting layer does not 100 ohms per square. However in all cases, 20 seriously degrade the optical performance of the increased conductance leads to a tradeoff with coating over that which could be obtained with- the optical performance. out the use of the thin transparent conducting The principle discovery in connection with the layer. present invention is that a certain portion of the 2. An article as in Claim 1 wherein said conduct- outermost magnesium fluoride layer can be 25 ing layer (17) has a thickness ranging from 1.0 to replaced by a high index layer with conducting 10.0 nanometers. properties without significant loss in reflection 3. An article as in Claim 1 wherein said thin performance provided: 1) the high index layer conducting layer (17) has a thickness ranging thickness has been confined to a suitable low from 4.0 to 6.0 nanometers. range of values and 2) the thickness of the outer 30 4. An article as in Claim 1 wherein said thin magnesium fluoride layer is appropriately conducting layer (17) has a thickness ranging reduced. from 20.0 to 25.0 nanometers. In general, use of the thin transparent conduct- 5. An article as in Claim 1 together with an ing coatings used in an anti-static applications additional layer (31, Fig. 3) of a material having a have suffered a maximum reflectance increase of 35 high index of refraction disposed between the only about 0.1 percent whereas the integrated first surface of the substrate and the layer (32) reflectance increases is substantially less than formed of a material having a low index material. this value. Moreover, the effective bandwidth is 6. An article as in claim 5 wherein said actually slightly increased over that which is additional layer (31) is formed of a transparent obtained with a conventional coating without the 40 conducting material. thin transparent conducting layer. Whereas, as 7. An article as in Claim 1 wherein said material pointed out earlier, failure to properly adjust the forming the thin transparent conducting layer is outer magnesium fluoride layer thickness down- selected from the materials of indium tin oxide, wardly results in a spectral curve with a definite cadmium stannate and tin antimony oxide. tilt-up at shorter wavelength and a subsequent 45 8. An article as in Claim 7 wherein said layer (16, loss of achromatic behavior. 32) formed of a material having a low index of The lower limit of the thin conducting layer refraction is formed of magnesium fluoride and thickness is dictated by questions of adequate wherein said thin transparent conducting layer is conductivity and stability of the same. The upper formed of indium tin oxide. limit thickness is set by what is deemed accept- so 9. An article as in Claim 1 together with at least able in terms of increased reflectance. Reason- two layers formed of a material having a low ably achromatic coating performance and be index of refraction and at least two layers formed maintained with the use of still thicker layers of of a material having a high index of refraction the material utilized for forming the thin trans- (Fig. 5, 6). parent conducting layer to a certain point at which 55 time reflectance levels will begin to rise con- Patentansprtiche siderably. In order to completely optimize the design common in certain applications, it is 1. Leitender Antireflexionsbelag (14), der auf necessary to make some concurring adjustments der Oberflache eines Substrats (11) angeordnet in all of the layers in the design and not neces- 60 ist, das eine erste und eine zweite Oberflache sarily just to the upper or outer magnesium aufweist, dadurch gekennzeichnet, daB der lei- fluoride layer. tende Antireflexionsbelag (14) wenigstens eine Schichf (16) aus einem Material mit niedrigem Index, die von der Oberflache getragen wird, und 65 eine dunne leitende transparente Schicht (17) aus 11 EP 0 101 033 B1 12 einem Material mit einem hohen Brechungsindex dispose sur la surface d'un substrat (11) ayant des aufweist, das von der Schicht (16) aus dem premiere et seconde surfaces, caracterise en ce Material mit niedrigem Index getragen wird und que ledit revetement anti-reflexion conducteur eine freiliegende Oberflache bildet, mit der ein (14) comporte au moins une couche (16) d'une direkter elektrischer Kontakt hergestellt werden 5 matiere a faible indice portee par ladite surface et kann, wobei die dunne transparente leitende une mince couche conductrice transparente (17) Schicht (17) eine optische Dicke im Bereich von d'une matiere ayant un indice de refraction eleve, 1,0 bis 30,0 nm aufweist und die Schicht (16) aus portee par ladite couche (16) de matiere a faible dem Material mit niedrigem Index eine derart indice et formant une surface exposee sur reduzierte Auslegungsdicke aufweist, daS die to laquelle un contact electrique direct peut. etre Dicke der dunnen transparenten leitenden Schicht realise, ladite mince couche conductrice transpa- (17) kompensiert wird, und das Vorhandensein rente (17) ayant une epaisseur optique allant de der dunnen leitenden Schicht die optische Lei- 1,0 a 30,0 nanometres, et ladite couche (16) de nomi- stung des Belags gegeniiber der Leistung nicht matiere a faible indice ayant une epaisseur ernsthaft verschlechtert, die ohne Einsatz der 15 nale reduite de facon a compenser I'epaisseur de dunnen transparenten leitenden Schicht erhalten la mince couche conductrice transparente (17) werden konnte. afin que la presence de la mince couche conduc- 2. Gegenstand nach Anspruch 1, bei welchem trice ne degrade par gravement le comportement die leitende Schicht (17) eine Dicke im Bereich optique du revetement par rapport au comporte- de von 1,0 bis 10,0 nm hat. 20 ment qui pourrait etre obtenu sans ('utilisation 3. Gegenstand nach Anspruch 1, bei welchem la mince couche conductrice transaparente. die dunne leitende Schicht (17) eine Dicke im 2. Article selon la revendication 1, dans lequel Bereich von 4,0 bis 6,0 nm hat. ladite couche conductrice (17) a une epaisseur 4. Gegenstand nach Anspruch 1, bei welchem allant de 1,0 a 10,0 nanometres. die dunne leitende Schicht (17) eine Dicke im 25 3. Article selon la revendication 1, dans lequel Bereich von 20,0 bis 25,0 nm hat. ladite mince couche conductrice (17) a une epais- 5. Gegenstand nach Anspruch 1, zusammen mit seur allant de 4,0 a 6,0 nanometres-. einer zusatzlichen Schicht (31, Fig. 3) eines Mate- 4. Article selon la revendication 1, dans lequel rials, mit einem hohen Brechungsindex, die ladite mince couche conductrice (17) a une epais- zwischen der ersten Oberflache des Substrats und 30 seur allant de 20,0 a 25,0 nanometres. der Schicht (32) angeordnet ist, die aus einem 5. Article selon la revendication 1, associe a une Material mit einem niedrigen Index ausgebildet couche supplementaire (31, figure 3) d'une ist. matiere ayant un indice de refraction eleve dispo- 6. Gegenstand nach Anspruch 5, bei welchem see entre la premiere surface du substrat et la die zusatzliche Schicht (31 ) aus einem transparen- 35 couche (32) formee d'une matiere ayant un faible ten leitenden Material ausgebildet ist. indice. 7. Gegenstand nach Anspruch 1, bei welchem 6. Article selon la revendication 5, dans lequel das Material, welches die dunne transparente ladite couche supplementaire (31) est formee leitende Schicht bildet, aus den Materialien d'une matiere conductrice transparente. Indiumzinnoxid, Cadmiumstannat und Zinnanti- 40 7. Article selon la revendication 1, dans lequel monoxid ausgewahlt wird. ladite matiere formant la mince couche conduc- 8. Gegenstand nach Anspruch 7, bei welchem trice transparente est choisie parmi les matieres die Schicht (16) 32) aus einem Material mit einem constitutes d'oxyde d'indium et d'etain, de stan- niedrigen Brechungsindex aus Magnesiumfluo- nate de cadmium et d'oyxde d'etain et d'anti- rid, und die dunne transparente leitende Schicht 45 moine. aus Indiumzinnoxid besteht. 8. Article selon la revendication 7, dans lequel 9. Gegenstand nach Anspruch 1 zusammen mit ladite couche (16, 32) formee d'une matiere ayant wenigstens 2 Schichten, die aus einem Material un faible indice de refraction est constitute de ausgebildet sind, das einen niedrigen Brechungs- fluorure de magnesium et dans lequel ladite index hat und mit wenigstens zwei Schichten, die so mince couche conductrice transparente est for- aus einem Material ausgebildet sind, das einen mee d'oxyde d'indium et d'etain. hohen Brechungsindex hat (Fig. 5, 6). 9. Article selon la revendication 1, en associa- tion avec au moins deux couches formees d'une Revendications matiere ayant un faible indice de refraction et au 55 moins deux couches formees d'une matiere ayant 1. Revetement anti-reflexion conducteur (14) un indice de refraction eleve (figures 5, 6).

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65 EP 0 101 033 B1

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FIG.— I

FIG.— 2

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FIG.— 5

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FIG.— 6

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400 ^63 700 WAVELENGTH (nm)

FIG.— 7