DOUBLE-LAYER SYSTEM COMPRISING A PARTIALLY ABSORBING LAYER, AND METHOD AND SPUTTER TARGET FOR PRODUCING SAID LAYER

Abstract

A double-layer system includes a metal layer facing away from a viewer and a coating facing the viewer. In order to make the layer system production process as simple as possible and to provide a sputter deposition method that dispenses entirely with the use of reactive gases in the sputtering atmosphere or requires only a small amount thereof, the coating is in the form of an optically partially absorbing layer which has an absorption coefficient kappa of less than 0.7 at a wavelength of 550 nm and a thickness ranging from 30 to 55 nm.

Claims

1.-23. (canceled)

24. A double-layer system comprising: a metal layer facing away from a viewer; and a top layer facing the viewer, wherein the top layer is configured as an optically partially absorbing layer which has a thickness in the range of 30-55 nm and an absorption coefficient kappa of less than 0.7 at a wavelength of 550 nm.

25. The double-layer system according to claim 24, wherein the absorption coefficient kappa is in the range between 0.4 and 0.69.

26. The double-layer system according to claim 24, wherein the partially absorbing layer has a refractive index in the range of 2.6 to 2.95.

27. The double-layer system according to claim 24, wherein the optically partially absorbing layer is in contact with a transparent substrate, the refractive index n of which is in the range of 1.4 to 2.0, and wherein an effective visual reflection R.sub.v,eff is less than 5% for the viewer looking onto the transparent substrate.

28. The double-layer system according to claim 24, wherein the optically partially absorbing layer is in contact with a transparent medium, the refractive index n of which is in the range of 0.7 to 1.4, and wherein an effective visual reflection R.sub.v,eff is less than 7% for the viewer looking through the transparent medium onto the optically partially absorbing layer.

29. The double-layer system according to claim 24, wherein the color of reflecting light in the CIE L*a*b* color space determined according to EN ISO 11664-4 is in the range 2<a*<6 and 9<b*<5.

30. The double-layer system according to claim 24, wherein the optically partially absorbing layer comprises an oxide or oxynitride layer material with a substoichiometric oxygen content and an optional metal amount which contains a first metal Me1 and a second metal Me2, and wherein the first metal Me1 has a higher oxygen affinity than the second metal Me2.

31. The double-layer system according to claim 30, wherein the layer material contains the second metal Me1 in a metallic phase, as substoichiometric oxide and/or substoichiometric oxynitride, and wherein the second metal Me2 is selected from a group 2 consisting of Mo, W and mixtures of said substances.

32. The double-layer system according to claim 30, wherein if the substoichiometrically existing oxygen on the whole is arithmetically ascribed to a fully oxidic phase, a proportion in the range of 10-20 vol. % is obtained in the layer material for the second metal Me2 in metallic phase.

33. The double-layer system according to claim 30, wherein the layer material contains the first metal Me1 in oxide or oxynitride phase, and wherein the first metal Me1 is selected from a group 1 consisting of zinc, tin, indium and mixtures of said substances.

34. The double-layer system according to claim 33, wherein the proportion of the metal Me1 is in the range of 0-50 vol. %, preferably in the range of 2-45 vol. %, and particularly preferably in the range of 5-40 vol. %.

35. The double-layer system according to claim 30, wherein the layer material contains a third metal Me3 which is present as oxide, substoichiometric oxide or substoichiometric oxynitride, and wherein the third metal Me3 is selected from a group 3 consisting of oxides or oxynitrides of niobium, hafnium, titanium, tantalum, vanadium, yttrium, zirconium, aluminum and mixtures of said substances.

36. The double-layer system according to claim 24, wherein the metal layer consists of a metal selected from the group Al, Ag, Cu, Mo, Ni, Ti and alloys thereof.

37. The double-layer system according to claim 24, wherein the optically partially absorbing layer is X-ray amorphous.

38. Method for producing an optically partially absorbing layer of the double-layer system according to claim 24, wherein by DC or MF sputtering of a sputter target in a sputtering atmosphere containing a noble gas and optionally a reactive gas in the form of oxygen and/or nitrogen, a light-absorbing top layer is deposited by using a sputter target consisting of a target material of substoichiometric oxide or a substoichiometric oxynitride with a first degree of oxygen deficiency, in such a manner that it is obtained from a layer material of substoichiometric oxide or a substoichiometric oxynitride with a second degree of oxygen deficiency that differs from the first degree of oxygen deficiency by not more than+/25% (based on the first degree of oxygen deficiency), and wherein an optically partially absorbing layer is deposited as the top layer, the layer thickness of which is adjusted to a value in the range of 30 to 35 nm and the absorption coefficient kappa of which at a wavelength of 550 nm is adjusted to less than 0.7.

39. Method according to claim 38, wherein the absorption coefficient kappa is adjusted to a value in the range of 0.4-0.69.

40. Sputter target for producing the optically partially absorbing layer of a double-layer system according to claim 24, comprising a target material which contains a first metal Me1 and a second metal Me2, wherein the first metal Me1 is selected from the group 1 consisting of tin, zinc, indium and mixtures of said substances, wherein the first metal Me1 is present in the form of an oxide, oxynitride, substoichiometric oxide or substoichiometric oxynitride, and wherein the second metal Me2 is selected from the group 2 consisting of Mo, W and alloys of said substances that contain at least 50 wt. % of said metals.

41. Sputter target according to claim 40, wherein the material contains a third metal Me3 selected from the group 3 consisting of niobium, hafnium, titanium, tantalum, vanadium, yttrium, zirconium, aluminum and mixtures of said substances, which is present as an oxide, substoichiometric oxide or substoichiometric oxynitride.

42. Sputter target according to claim 41, wherein the content of oxides, substoichiometric oxides or oxynitrides of group 3 is in the range of 0 to 50 vol. %, preferably in the range of 10 to 45 vol. %, and particularly preferably in the range of 25 to 40 vol. %.

43. Sputter target according to claim 40, wherein the metals of group 2 are contained in an amount between 10 and 20 vol. %.

44. Sputter target according to claim 40, wherein the target material has a density of more than 95% of the theoretical density and a content of impurities of less than 500 wt. ppm, and wherein a reduction degree which is obtained in the oxidic target material arithmetically as a proportion of the second metal Me2 in metallic phase in the range of 10-20 vol. % if the substoichiometrically existing oxygen on the whole is ascribed to a fully oxidic phase.

45. Sputter target according to claim 40, wherein it is present as a sinter product of powder with a d50 value of less than 100 m, and wherein the second metal Me2 is present as a powder with a d50 value of less than 50 m, preferably less than 10 m.

46. Sputter target according to claim 40, wherein the target material comprises a homogeneous composition of the substances forming the same, such that the composition of five samples of 1 g each has a standard deviation of each of the substances of less than5%, based on the maximum content of the substance, and a homogeneous reduction degree, such that the reduction degree of five samples of 1 g each has a standard deviation in the reduction degree of less than5%.

Description

EMBODIMENT

[0089] The invention will now be explained in more detail with reference to a patent drawing and an embodiment. In detail,

[0090] FIG. 1 is a schematic representation of the layer system according to the invention in one embodiment in contact with a substrate of dielectric solid in a cross section,

[0091] FIG. 2 is an electron micrograph of a partially absorbing layer according to the invention,

[0092] FIG. 3 shows the spectral curve of the reflection of the layer system glass/S1 (42.5 nm) Mo(40 nm),

[0093] FIG. 4 shows the spectral curve of the reflection of the layer system glass/S2 (42.5 nm)/Mo(40 nm),

[0094] FIG. 5 shows the spectral curve of the reflection of the layer system glass/S1 (40 nm)/Cu(100 nm),

[0095] FIG. 6 shows the spectral curve of the reflection of the layer system glass/S2 (35 nm)/Cu(100 nm),

[0096] FIG. 7 shows the spectral curve of the reflection of the layer system air/S3 (33 nm) Mo(130 nm),

[0097] FIG. 8 shows the spectral curve of the reflection of the layer system air/S3 (40 nm)/Al(130 nm),

[0098] FIG. 9 shows the spectral curve of the reflection of the layer system air/S3 (40 nm)/Cu(250 nm), and

[0099] FIG. 10 shows the spectral curve of the reflection of the layer system air/S3 (50 nm)/Mo(30 nm).

[0100] FIG. 1 schematically shows a layer system 1 consisting of two layers A, B according to the invention. The first layer is a partially absorbing layer A sputtered onto a transparent glass plate 3, which is in contact with a metal layer B. The partially absorbing layer consists of a layer material of a base component K1 of oxide of a first metal Me1 and of a metallic blackening component K2 of metallic phase or a partially oxidized phase of a second metal Me2. Optionally, an additional component K3 is contained that is present as an oxide of a third metal Me3. The layer system is almost opaque for a viewer with viewing direction from the glass plate 3 and almost black at the same time.

[0101] A plurality of these double-layer systems with the outlined structure was produced, and the properties thereof were measured. The respective compositions and properties are indicated in Table 1 and Table 2.

[0102] FIG. 2 shows an electron micrograph of a partially absorbing layer according to Example S2 described in more detail below (see Table 1, line 2). No metal deposits can be seen. This result is also confirmed by an X-ray measurement. In a corresponding X-ray diffraction diagram, no concrete diffraction lines are visible; the layer is X-ray amorphous.

[0103] Measuring Methods

[0104] Layer Thickness Measurement

[0105] The layer thickness measurement was carried out with a stylus-type profilometer (Ambios Technology XP-200). For the preparation of the sample a part of the substrate was covered with a Kapton tape. The correspondingly covered area was not sputtered. After removal of the cover the layer thickness was determined on the created step between coated and uncoated area.

[0106] Instrument calibration to 10 m on supplied standard. The measurement was repeated at 10 different places of the sample and the average value was formed.

[0107] Absorption Coefficient Kappa

[0108] The absorption coefficient is a measure of the weakening of electromagnetic radiation in material and was determined with a spectrometer (Perkin Elmer Lambda900/950). The transmission and reflection measurement values are here integrally determined on the layers in the wavelength range 380-780 nm in 10 nm step size.

[0109] The transmission and reflection values obtained were read into the software of the company Woollam M2000 and the refractive indices and absorption coefficients were calculated. As reference, the measuring instrument was calibrated to an uncoated substrate.

[0110] Reflection Rv

[0111] Reflection R.sub.v,eff was measured as directed reflection. Diffusely reflecting light is not taken into account (i.e. no integrating sphere). For the measurement the spectrometer Perkin Elmer Lambda35 was used. Calibration is carried out by way of an Al sample of known reflection, which has been calibrated by the producer.

[0112] Visual reflection R.sub.v, is here understood to be the reflection standardized to eye sensitivity, which is calculated from the total reflection of the layer system. If the reflection measurement is here carried out through a transparent medium, such as a glass substrate or air, the reflection on the surface of this transparent medium is deducted from the total reflection for determining the effective reflection R.sub.v,eff. 4% (reflection on the glass surface) were therefore deducted in the table values.

[0113] Color Value Measurements

[0114] The color of the composition, e.g. after application of the composition in a layer structure, is defined by the color values in the CIE L*a*b* color space according to the international standard EN ISO 11664-4. Color value measurements were carried out with a Konica Minolta Spectrophotometer CM-700d (of Konica Minolta Sensing Europe B.V.) in the CIE L*a*b* color space system. After calibration with supplied black and white reference (black hole and a white ceramic plate), the measurements were carried out. The spectrophotometer was here placed on a dry and burned layer. 5 measurements each were carried out, and the arithmetic mean was formed subsequently.

[0115] Determination of the Particle Size

[0116] The particle size of the powders used was determined by way of laser diffraction and with the instrument CLIAS 990. The sample was dispersed in distilled water and 0.1 Ma % sodium pyrophosphate by ultrasound for 30 s and subsequently measured. The Fraunhofer method was used for evaluation. The d50 value was here determined based on the volume of the particles that marks the particle size at which 50% of the particles are smaller than that value.

[0117] Determination of the Reduction Degree

[0118] Samples were taken from the targets and an exactly weighted amount was dissolved in suitable acids such as HCl and HF. These solutions were analyzed by way of ICP OES and the content of metals was determined. The theoretical weight of the fully oxidic sample was calculated from the metal contents determined in this way, the corresponding amount (MOxygen stoichiometric) of stoichiometric oxygen of the respectively most stable oxide (such as e.g. ZnO, Nb.sub.2O.sub.5, TiO.sub.2, MoO.sub.3, W.sub.2O.sub.3, Al.sub.2O.sub.3, Ta.sub.2O.sub.5) being added to the respective metal weight for this purpose. The difference (delta M) with respect to the real weight of the sample then represents the oxygen deficiency of the sample that can be converted into a reduction degree R: R[%)=100delta M/MOxygen stoichiometric.

[0119] Emission Spectrometric Analysis (ICP-OES)

[0120] An emission spectrometer Varian Vista-MPX and ICP expert software (of the company Varian Inc.) was used. First of all, two calibration samples are respectively produced for the metals from standard solutions with known metal content (e.g. 1000 mg/l) in aqua regia matrix (concentrated hydrochloric acid and concentrated nitric acid in the ratio 3:1). The parameters of the ICP device were: [0121] Power: 1.25 kW [0122] Plasma gas: 15.0 l/min (argon) [0123] Auxiliary gas: 1.50 l/min (argon) [0124] Atomizer gas pressure: 220 kPa (argon) [0125] Repetition: 20 s [0126] Stabilization time: 45 s [0127] Observation height: 10 mm [0128] Sucking of sample: 45 s [0129] Flushing time: 10 s [0130] Pump rate: 20 rpm [0131] Repetitions: 3

[0132] For the measurement of a sample: 0.10+/0.02 g of the sample is mixed with 3 ml nitric acid and 9 ml hydrochloric acid, as indicated above, and solubilized in a microwave (company: Anton Paar, instrument: Multivave 3000) at 800-1200 W within 60 min. The solubilized sample is transferred with 50 vol. % hydrochloric acid into a 100 ml flask and used for measurement.

[0133] Determination of the Density and Method for Determining the Theoretical Density

[0134] The density is determined according to the so-called buoyancy method. To this end a sample is weighed in air and in water and the volume is measured with a caliper rule (accuracy 0.2 mm). The relative density in % is the measured density/theoretical density100. The theoretical densities are taken from tables of standard references.

[0135] Determination and Definition of X-Ray Amorphous

[0136] The samples were irradiated by a two circle goniometer Stadi P of the company Stoe in transmission mode with X-rays CuK alpha 1 between 2 theta 10-105, step size 0.03, and the diffraction diagrams were evaluated. The missing regularity of the lattice plane spacings leads to a diffuse scattering of the X-ray radiation and to broad distinct halos; no sharp diffraction lines or reflections can be detected. The material of the sample is X-ray amorphous.

[0137] Conversion into vol. %

[0138] mmass; Vvolume

[0139] density, theo.=mass/volume

[0140] volume %=mass.sub.n/density.sub.n/(mass.sub.1/density.sub.1+mass.sub.n/density.sub.n)

[0141] Preparation of the Sputter Target

[0142] Starting from powder mixtures according to the components listed in Table 1 (in vol. %) planar, round sputter targets were produced via hot pressing with a diameter of 75 mm. To this end powder components of purity 3N5 and of a mean particle size of less than 100 m were mixed on a roller block. For the metal component (blackening component K2) powders with a particularly small mean particle size of less than 50 m and less than 10 m, respectively, were also selectively used. For the generation of the base component K1 and the additional component K3 stoichiometric oxides were used. On account of the metal content of component K2, sufficiently electrically conductive targets with a specific conductivity of<1 *cm were nevertheless obtained. As an alternative, it is possible to use, as far as available, and instead of the fully oxidic additional component K3, also niobium oxide, hafnium oxide, titanium oxide, vanadium oxide, yttrium oxide, zirconium oxide and/or aluminum oxide, also slightly substoichiometric oxides with an oxygen deficiency of a few percent up to 20%. This oxygen deficiency must then be taken into account in the calculation of the total metal content and the reduction degree, respectively.

[0143] The sputter targets obtained were analyzed for their homogeneity in that 5 samples of 1 g each were taken at any desired sites and were measured with respect to chemical composition and reduction degree. Depending on the mixture, the composition of the components varied by 3% to 5% relatively, and the reduction degree by +4 to +5% relatively.

[0144] It has been found that the target surface was the smoother and a stable sputter rate was adjusted the faster the finer the selected grains were. Especially the particle size of the metal component was here important. From this viewpoint a fine metal powder with a mean particle size<10 m must be preferred. An excessively fine powder (<0.5 m), however, makes handling more complicated again.

[0145] Preparation of Layers for Performing Etching Tests

[0146] Of these sputter targets, layers with a thickness of 125 nm were deposited by DC sputtering in a sputtering atmosphere of argon on glass substrates (Samples 1 to 9) and on a metal electrode (Samples 10 to 12), respectively.

[0147] The sputter parameters were here as follows:

[0148] Residual gas pressure: 2*10.sup.6 mbar

[0149] Process pressure: 3*10.sup.3 mbar at 200 sccm argon

[0150] Specific cathode powder: 5 W/cm2

[0151] The layers obtained in this way were optically measured (Table 1). Moreover, the etch rate was determined on these layers in that the etch duration was determined, starting from which the full optical transparence of the layer is visually detectable.

TABLE-US-00001 TABLE 1 Refractive index, absorption and etch rate of partially absorbing layers Optical Composition properties Etch (in vol. %) n K rate No ZnO Nb.sub.2O.sub.5 TiO.sub.2 Mo (550 nm) (550 nm) (nm/s) Rem. 1 47 40 0 13 2.66 0.6 0.3 S 1 2 54 30 0 16 2.71 0.67 2.1 S 2 3 60 20 0 20 2.91 0.59 8.5 4 70 5 0 25 2.77 0.48 9.4 i) 5 80 0 0 20 2.27 0.64 50 ii) 6 47 0 40 13 2.64 0.61 0.5 7 60 0 20 20 2.92 0.52 10 8 33 50 0 13 2.68 0.67 0.1 iii) 9 25 50 0 25 3.0 1.19 0.4 iv) 10 53 34 0 13 2.69 0.57 0.7 11 84 0 0 16 2.64 0.59 30 12 35 40 0 25 3.04 1.0 0.42 v) Layers etched with Al etchant: 13 81 3 0 16 2.75 0.59 25 14 77 7 0 16 2.66 0.65 4.5 15 62 12 0 16 2.69 0.67 0.95 16 77 0 7 16 2.69 0.68 5.9 17 58 0 12 16 2.70 0.69 0.55 i) Deposition of the layer with 2.5% oxygen addition to the sputter gas Ar. ii) Since no slowly etching additional component K3 was here added, the etch rate for the used etchant is much too high. With weaker etchants it is here however possible to work on condition that these weaker etchants are also sufficient for etching the underlying metal layer. This may for instance be the case with a metal layer of Al. iii) Due to the high amount of the slowly etching additional component Nb.sub.2O.sub.5 a slow etch rate is obtained. iv) Comparative example: Due to the high amount of the blackening component Mo an excessively high absorption coefficient is obtained. The refractive index is also unfavorably high. The corresponding layer properties are listed in Table 2. This also yields a considerably deteriorated visual reflection. v) Comparative example: Due to the high amount of the blackening component Mo one obtains an excessively high absorption coefficient and an unfavorably high refractive index (and thus an excessively high visual reflection R.sub.v).

[0152] The oxygen deficiency of the layers (the reduction degree) is substantially given by the content of Mo metal. During the sputtering process the reduction degree will change only insignificantly. This is however not true for Sample 4 where the sputtering atmosphere has been mixed with small amounts of oxygen during deposition of the partially absorbing layer. As a consequence, a part of the Mo metal contained in the target or of corresponding substoichiometric oxides is additionally oxidized. This reduces the metal content (oxygen deficiency) in the layer in comparison with sputtering in pure Ar atmosphere and thus reduces the absorption kappa.

[0153] The oxygen deficiency of all layers, with the exception of the layers of Samples 9 and 12, is in the range of 30-65% of the stoichiometric oxygen content. This oxygen deficiency leadsif the substoichiometrically existing oxygen content on the whole is arithmetically ascribed to a fully oxidic phaseto a metallic phase with an amount in the range of 10-20 vol. %. As for Samples 9 and 12, the reduction degree is higher than 55% of the stoichiometric oxygen content.

[0154] For etching a commercial copper etchant was used on the basis of H.sub.2O.sub.2. However, the above layers are also etchable at room temperature with an etchant consisting of H.sub.2O=785 ml+H.sub.2O.sub.2=215 ml+30 g K.sub.2S.sub.2O.sub.5+15 g H.sub.5F.sub.2N, wherein other values then tend to follow for the etch rate. The slightly different etch rates obtained, depending on the respective etchants, can easily be compensated by varying the ratio of base component K1 (for example ZnO) to additional component K3 (for instance Nb.sub.2O.sub.5 or TiO.sub.2). To a certain extent the content of metallic blackening component K2 (for instance Mo or W) can also be varied for this purpose. It must however be taken into account that this will also have an impact on absorption.

[0155] The following composition was used as a further etchant for etching Al: CH.sub.3COOH 10%+H.sub.3PO.sub.4 71%+HNO.sub.3 1.8%+deionized H.sub.2O (temperature: 41 C.).

[0156] Depending on the amount of the layer components, etch rates in the range of 0.2 nm/s to 10 nm/s are obtained for the partially absorbing layer according to the invention. These are values of good practical usability.

[0157] Preparation of Layer Systems with Partially Absorbing Layers

[0158] Examples 1 to 4 are listed hereinafter for layer systems according to the invention.

[0159] These layer systems are distinguished by a partially absorbing layer which at a wavelength of around 550 nm has an absorption coefficient kappa<0.7, preferably in the range of 0.4-0.69. Moreover, these layers have an effective visual reflection R.sub.v,eff<5%, preferably<2%. The reflection measurement was carried out through the glass substrate (reference numeral 3 in FIG. 1). Therefore, for the determination of the effective reflection R.sub.v,eff of the double layer system, the reflection of 4% on the glass surface has to be deducted from the total reflection. Also other transparent media such as e.g. transparent sheets represent advantageous intermediate layers between the partially absorbing layer and air.

[0160] These media normally have a refractive index of 1.4 to 2.0 (at a measurement wavelength of 550 nm).

[0161] The layers were produced as follows:

[0162] A partially absorbing layer A was deposited on the glass substrate 3 by way of pure DC argon sputtering and the above-indicated parameters. The sputter targets were here used, as listed in Table 2 (Samples A to K) and Table 3 (Sample O).

[0163] Subsequently, and without interruption of the vacuum, the metal layer B was then deposited. The thickness of the partially absorbing layer A was each time optimized in a few tests with the aim to obtain an effective reflection as low as possible and also to maintain a neutral color at the same time. Corresponding layer thicknesses were in the range of 30-55 nm. It has been found that the partially absorbing layers produced in this way are distinguished by a neutral color. In the reflected light proportion the following is applicable to the coordinates a*, b* in the CIE L*a*b system:

2<a*<6; 9<b*<5.

[0164] In the following Examples 1 to 4 the partially absorbing layers S1 and S2 according to Table 1 were integrated into different layer systems and their reflection behaviors and color values were determined (the sample designations refer to Table 2; the figures respectively preceding the components are concentration data in vol. %).

[0165] The diagrams for explaining the samples according to FIGS. 3 to 10 respectively show the curve of the visual reflection R in [%] over the wavelength range in [nm] of about 380 nm to 780 nm. In curves 5-10, the measurements were taken against air and thus R.sub.v=R.sub.v,eff. In the tables the layers were measured on glass, and 4% (reflection on the glass surface) were therefore deducted.

EXAMPLE 1

Sample A

[0166] Partially absorbing layer S1: 40 Nb.sub.2O.sub.5 47 ZnO, 13 Mo

[0167] Layer system: glass/S1 (thickness: 42.5 nm)/Mo (thickness: 40 nm)

[0168] FIG. 3 shows for this layer system the curve of the reflection R in [%] over the wavelength range in [nm] of about 380 nm to 780 nm. The reflection shows a minimum (including reflection on the glass substrate) at a wavelength of around 550 nm with a reflection value of about 5.2%. This yields an effective visual reflection R.sub.v,eff of 1.2% after deduction of the reflection on the surface of the glass substrate. This yielded a*=2.5; b*=3.1 for the color values.

EXAMPLE 2

Sample B

[0169] Partially absorbing layer S2: 30 Nb.sub.2O.sub.5, 54 ZnO, 16 Mo [0170] Layer system: glass/S2 (45 nm)/Mo (40 nm)

[0171] FIG. 4 shows a minimum (including reflection on the glass substrate) for this layer system at a wavelength of around 550 nm with a reflection value of about 6.6%. This yields an effective visual reflection R.sub.v,eff of 2.6% after deduction of the reflection on the surface of the glass substrate.

[0172] This yielded for the color values: a*=3.0; b*=4.1

EXAMPLE 3

Sample D

[0173] Partially absorbing layer S1: 40 Nb.sub.2O.sub.5, 47 ZnO, 13 Mo [0174] Layer system: glass/S1 (40 nm)/Cu (100 nm)

[0175] FIG. 5 shows for this layer system that the reflection in the wavelength range of about 529 to 600 nm has a wide minimum with a reflection value of about Rv=7.7% (including reflection from the glass substrate). This yields an effective visual reflection R.sub.v,eff of about 3.7% after deduction of the reflection on the surface of the glass substrate.

[0176] This yielded for the color values: a*=0.1; b*=7.3

EXAMPLE 4

Sample E

[0177] Partially absorbing layer S2: 30 Nb.sub.2O.sub.5, 54 ZnO, 16 Mo [0178] Layer system: glass/S2 (35 nm)/Cu (100 nm)

[0179] The curve of the reflection R according to FIG. 6 shows for this layer system a minimum at a wavelength of about 590 nm with a reflection value of about Rv=5.2%, including reflection from the glass substrate. This yields an effective visual reflection R.sub.v,eff of about 1.2% after deduction of the reflection on the surface of the glass substrate.

[0180] This yielded for the color values: a*=4.1; b*=8.1

[0181] The above Examples 1 to 4 describe layer systems in which the partially absorbing layer is in contact with a transparent substrate. In the layer systems according to the invention, the partially absorbing layer, however, may also be in contact with a fluid medium having a refractive index n<2, as for instance air, nitrogen, or a liquid. This, however, will then yield, depending on the refractive index of the medium which is in direct contact with the partially absorbing layer, reflection values that are about 5-10% higher than in the measurement against a glass substrate. The lower the refractive index of the fluid medium, the higher is the resulting reflection. It may here be of advantage to deposit also a low-refractive dielectric layer at the side of the partially absorbing layer that is facing the viewer, for instance a standard anti-reflective layer. As shown by the following Examples 5 to 7, good blackening values of metal layers are however also achievable when the reflection is viewed against air (instead of a glass substrate).

[0182] The metal layer which must be blackened is positioned behind the partially absorbing layer, as viewed by the viewer, so that the reflection measurement is directly performed on the partially absorbing layer.

[0183] This layer systems are distinguished by a partially absorbing layer which at a wavelength of about 550 nm has an absorption coefficient kappa<0.7, preferably in the range of 0.4-0.69. Moreover, these layers have an effective visual reflection R.sub.v,eff <7%, preferably<3%.

[0184] The layers of Examples 5 to 7 were produced as follows:

[0185] With the help of a standard sputtering process a metal layer B was first deposited on a glass substrate. Thereupon, without interruption of the vacuum, a partially absorbing layer (hereinafter respectively called S3) was deposited with the help of pure DC argon sputtering and the parameters indicated in Table 1. The sputter targets were here used, as listed in Table 2 (Samples L to N).

EXAMPLE 5

Sample N

[0186] Partially absorbing layer S3 34 Nb.sub.2O.sub.5, 53 ZnO, 13 Mo [0187] Layer system: glass/Mo (30 nm)/S3 (43 nm)

[0188] FIG. 7 shows for this layer system a curve of the reflection with a minimum of about 1.8% (including reflection on the surface of the partially absorbing layer S3). This yields an effective visual reflection R.sub.v,eff of 1.8%.

EXAMPLE 6

Sample M

[0189] Partially absorbing layer S3 84 ZnO, 16 Mo [0190] Layer system: glass/Al (130 nm)/S3 (40 nm)

[0191] FIG. 8 shows for this layer system the curve of reflection R in [%]. At a wavelength of about 550 m with a reflection value of about R=0.4% it shows a minimum (including reflection on the surface of the partially absorbing layer S3). This yields an effective visual reflection R.sub.v,eff of 2.1%.

EXAMPLE 7

Sample L

[0192] Partially absorbing layer S3 84 ZnO, 16 Mo

[0193] Layer system: glass/Cu (250 nm)/S3 (40 nm) [0194] Layer thickness 40 nm; Rv=3.7%

[0195] The curve of the reflection R in [%] for this layer system according to FIG. 9 shows a minimum (including reflection on the surface of the partially absorbing layer S3) at a reflection value of about R=2% at a wavelength of 550 nm. This yields an effective visual reflection R.sub.v,eff of 3.7.

COMPARATIVE EXAMPLE TABLE 3

Sample P

[0196] Partially absorbing layer S3 40 Nb.sub.2O.sub.5, 35 ZnO, 25 Mo [0197] Layer system: glass/Mo (30 nm)/S3 (50 nm) [0198] Rv=23%

[0199] The curve of the reflection R (in %) for this layer system is shown in FIG. 10. Thus the reflection at a wavelength of about 630 nm shows a minimum with a reflection value of about R=22.7%. This high reflectivity of the partially absorbing layer S3 against air is based on its high absorption kappa.

[0200] The following Table 2 gives further examples of target compositions according to the invention and of partially absorbing layers produced therefrom.

[0201] The following Table 2 lists optical characteristics (effective visual reflection R.sub.v,eff and CIE L*a*b color a*, b* (as far as measured) for partially absorbing layers S1 of different compositions in combination with different metal layers of thickness d. The two last columns indicate the coordinates a* and b* according to the CIE L*a*b system.

TABLE-US-00002 TABLE 2 Composition, thickness and optical characteristics of layer systems Thick- Metal Target composition ness S layer/ R.sub.v, eff No (vol. %) (nm) d (nm) (%) a* b* A ZnO Nb.sub.2O.sub.5 Mo 42.5 Mo/40 1.2 2.5 3.1 47 40 13 B ZnO Nb.sub.2O.sub.5 Mo 45 Mo/40 2.6 3.0 4.1 54 30 16 C ZnO Nb.sub.2O.sub.5 Mo 43 Mo/50 0.8 2.7 3.5 51 35 14 D ZnO Nb.sub.2O.sub.5 Mo 40 Cu/100 3.7 0.1 7.3 47 40 13 E ZnO Nb.sub.2O.sub.5 Mo 35 Cu/100 1.2 4.8 8.1 54 30 16 F ZnO Nb.sub.2O.sub.5 Mo 40 W/100 1.0 2.9 3.3 80 0 20 G ZnO Nb.sub.2O.sub.5 W 42.5 Mo/50 0.9 3.0 3.6 61 25 14 H ZnO TiO.sub.2 Mo 40 Mo/40 1.1 4.2 3.0 47 40 13 I ZnO TiO.sub.2 Mo 35 Cu/80 3.2 0.5 6.8 60 20 20 J ZnO TiO.sub.2 W 40 Mo/40 1.2 3.4 3.8 61 20 19 K SnO.sub.2 Nb.sub.2O.sub.5 Mo 44 Cu/50 1.4 0.5 6.9 50 35 15 L ZnO Nb.sub.2O.sub.5 Mo 40 Cu/250 3.7 not not 84 0 16 spec. spec. M ZnO Nb.sub.2O.sub.5 Mo 40 Al/130 2.1 not not 84 0 16 spec. spec. N ZnO Nb.sub.2O.sub.5 Mo 43 Mo/30 1.8 5.7 5.1 53 34 13 not spec. = not specified

[0202] Table 3 gives comparative examples that illustrate the negative impact of an excessively high absorption coefficient on the visual reflection of the layer system.

TABLE-US-00003 TABLE 3 Comparative Examples Thick- Metal Target composition ness S layer/ R.sub.v, eff No (vol. %) (nm) d (nm) (%) a* b* O ZnO Nb.sub.2O.sub.5 Mo 40 Mo/50 8.2 0.2 2.6 25 50 25 P ZnO Nb.sub.2O.sub.5 Mo 40 Mo/40 23 1.36 1.67 35 40 25

[0203] Sample O is a comparative example of a layer system as in Samples A to K, where the reflection for a partially absorbing layer in contact with a glass substrate is determined. The composition of the partially absorbing layer corresponds to Sample No. 9 of Table 1.

[0204] The layer system of Sample P is a comparative example of a layer system as in Samples L to N with a partially absorbing layer in contact with air. The composition of the partially absorbing layer corresponds to Sample No. 12 of Table 1.