EP4055202A1

EP4055202A1 - Method for producing a coating

Info

Publication number: EP4055202A1
Application number: EP20803554.3A
Authority: EP
Inventors: Mathias Maier; Othmar Zueger
Original assignee: Oerlikon Surface Solutions AG Pfaeffikon
Current assignee: Oerlikon Surface Solutions AG Pfaeffikon
Priority date: 2019-11-07
Filing date: 2020-11-06
Publication date: 2022-09-14
Also published as: US20220389560A1; JP2023500927A; CN114651083A; WO2021089842A1; KR20220097462A

Abstract

The invention relates to a method for producing a coating for application to nonmetallic surfaces, comprising the steps of applying (120) a semiconductor material to a substrate in order to form a semiconductor material layer, and simultaneously or subsequently applying (140) metallic material or additional semiconductor material, wherein the metallic material or the additional semiconductor material is introduced into the semiconductor material layer in a targeted manner in order to adapt the optical properties of the coating.

Description

Process for producing a coating

Description

The present invention relates to a method for producing a coating for application to non-metallic surfaces and a coating for application to non-metallic surfaces.

Non-metallic surfaces, such as the surfaces of components made of plastics, are nowadays often provided with metallic thin-film coatings in order to change their appearance and / or to achieve other desired layer properties.

A desired metallic appearance of a component can be achieved, for example, with thin layers of a selected metal, the thickness of which does not have to be more than about 10 to 100 nm in order to make them indistinguishable in appearance from fully metallic components. Such metal layers can be applied using vacuum coating processes such as evaporation or sputtering processes.

However, most metal layers have a low transparency in large parts of the electromagnetic spectrum, which makes them unsuitable for some applications. For example, metal layers absorb or reflect electromagnetic waves strongly in frequency ranges between 76 - 77 GHz, which are of interest for use in radar technology, so that metal coatings are not suitable for such applications due to their low permeability in these areas.

It has been known for some time that such a desired metallic appearance can also be achieved with semiconducting thin layers, whereby these layers are largely transparent to electromagnetic waves due to their semiconducting properties and can therefore also be used, for example, for radar technology, capacitive sensors or the like. The metallic appearance of such layers results from the high refractive index n in the optical range, which leads to high reflection even with very thin layers. The use of semiconductor materials also has the advantage that the external color appearance has little dependency on the viewing angle, which is also the case when natural metal layers are used.

By choosing a suitable layer thickness and / or using a “thick” multilayer system, it is possible to achieve a certain range of metallic-looking, non-gray color tones.

Disadvantageously, however, the metallic-looking color shades that can be achieved in this way are restricted to a narrow range of color coordinates (for example CIE L ^* a ^* b ^* ). In addition, the use of thin optical interference layers made of semiconductor materials to produce a metallic exterior has the disadvantage that, due to the high refractive index and the low absorption, there are large differences between reflection minima and maxima in the optical range. This in turn causes an undesirable “glaring” color perception.

It is therefore the object of the present invention to at least partially overcome the aforementioned disadvantages of known coatings and processes for their production remedy. In particular, it is the object of the invention to provide a coating that has an appealing external appearance largely regardless of the viewing angle and can be used in a variety of ways, in particular also in the radar range.

The above object is achieved by a method with the features of the independent method claim and a coating according to claim 13. Further features and details of the invention emerge from the respective subclaims, the description and the drawings. Features and details that are described in connection with the method according to the invention naturally also apply in connection with the coating according to the invention and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is or can always be made to each other.

Here, the method according to the invention comprises the steps of applying a semiconductor material to a substrate to form a semiconductor material layer as well as simultaneous or subsequent application of metallic material or additional semiconductor material, wherein the metallic material or the additional semiconductor material for adapting the optical properties of the coating in a targeted manner in the semiconductor material layer is introduced.

A semiconductor material is preferably understood to mean a material composed of semiconductor ^{elements or semiconductor compounds, which in particular has an electrical conductivity between 10 4} S / cm and 10 ⁸ S / cm. An additional semiconductor material is preferably understood to mean a semiconductor material different from the semiconductor material for forming a semiconductor material layer, which is preferably only introduced for doping. According to the invention, a metal is preferably understood to mean a material composed of elemental metals. In the context of the invention, a substrate is understood in particular as a base or a base for a coating, such as a display, a body or the like. Targeted introduction of a metallic material into a semiconductor material layer can objectively include, in particular, selecting the quantity of the metallic material to be applied and / or the application area of the metallic material to be applied. The optical properties can also, in particular, be the absolute and / or relative reflectivity of the coating as a function of the wavelength in the optical range include. Likewise, the optical properties can relate to the transparency in other frequency ranges of the electromagnetic spectrum, such as in the radar range at 76-77 GHz, or contain the viewing angle dependence of the external appearance.

In order to be able to adapt the optical properties of a coating as precisely as possible, it can objectively advantageously be provided that the semiconductor material is added in the form of a pure substance, the semiconductor material preferably being formed from silicon or germanium or selenium or gallium arsenide. With a view to increasing the flexibility with regard to the adaptation of the optical properties of a coating, in particular the adaptation of various optical properties of a coating, it can also be advantageous if the semiconductor material is present as a mixture of different semiconductor materials, the semiconductor materials preferably silicon and / or germanium and / or selenium and / or gallium arsenide.

With regard to the most targeted adaptation of the optical properties of a coating, provision can also be made for the metallic material to be added in the form of a pure substance, the metallic material preferably being formed from chromium or molybdenum or aluminum or zirconium. With a view to increasing the flexibility with regard to the adaptation of the optical properties of the coating, it can also be advantageous if the metallic material is present as a mixture of different metals, the metals preferably chromium and / or molybdenum and / or aluminum and / or zirconium can include.

With regard to a particularly effective and targeted adaptation of the optical properties of a coating, it can also be provided that the metallic material to be applied and / or the amount of metallic material to be applied and / or the application area of the metallic material to be applied is at least partially based on the absorption coefficient k of the metallic material in the optical range is selected. In the context of the invention it has been recognized that the differences between reflection minima and reflection maxima of a coating are responsible for an undesirable “glaring” external appearance. In addition, it has been recognized within the scope of the invention that metals with a high absorption coefficient k the differences between reflection minima and Effectively minimize reflection maxima of a coating, which are responsible for the undesirable "glaring" external appearance. This is possible in particular because after light rays have entered the coating layer at the first interface of the coating layer due to the increased absorption of the

Coating layer (in the optical range), the reflection of the light rays at the second interface of the coating layer is significantly lower, which consequently the destructive and constructive interference at the first and second interface of the

Coating layer reduces reflected light rays and thus effectively minimizes the differences between reflection minima and reflection maxima of the coating. This leads in particular to preferred “softer” (less contrasting) color transitions. In the context of the invention, the optical range is understood to mean, in particular, the optical frequency range of the electromagnetic spectrum of the light in a range of approx. 350-750 nm. It is also conceivable that the selection of the metallic material to be applied and / or the selection of the amount of the metallic material to be applied and / or the selection of the application area of the metallic material to be applied is at least partially based on the electrical conductivity of the metallic material in the optical range, because this is at least partially related to the absorption coefficient k. In addition, it is also advantageous to select the metallic material to be applied and / or the selection of the amount of the metallic material to be applied and / or the selection of the application area of the metallic material to be applied at least partially in relation to the semiconductor material used, in particular in relation to the refractive index n to make the used semiconductor material dependent in the optical area. In the context of a structurally simple possibility of the most sensitive dosage possible when applying the layer materials, it can objectively advantageously be provided that the application of the semiconductor material and / or the application of the metallic material takes place via a thermal treatment, the thermal treatment preferably at a temperature of more than than 400 ° C, in particular at a temperature of more than 800 ° C. Alternatively, the “doping” could already be set on the “target”, for example.

It is particularly conceivable that the amount of applied metallic material and / or the proportion of applied metallic material in relation to the Sum of semiconductor material and metallic material takes place via a variation in the treatment time and / or a variation in the treatment temperature. Such an adjustment of the amount or the proportion of material to be applied is particularly advantageous in coating processes under vacuum conditions because a variation in the treatment temperature and treatment duration can be controlled in a simple manner from outside a coating chamber.

In the context of a structurally simple yet flexible and sensitive adjustable application of the coating materials, according to the invention it can advantageously be provided in particular that the application of the semiconductor material to the substrate takes place at least partially simultaneously with the application of a portion of metallic material, the semiconductor material to be applied and the one to be applied Metal are preferably premixed and / or mixed with one another during application. In the context of a simultaneous application of the semiconductor material and the metallic material, for example when using a sputtering method to apply the coating, either a semiconductor target alloyed with a suitable metal, such as a silicon target alloyed with chromium, or the metallic material (for example chromium) and the semiconductor material (for example silicon) can be applied from different targets as part of a co-sputtering process. Likewise, when using a vapor deposition process to apply the coating in a crucible or the like, a premixed material or an alloy of metallic material and semiconductor material could already be used or the materials could be vaporized separately at least partially from two crucibles at the same time.

With regard to the possible application processes, it is also conceivable that the application of the semiconductor material and the metallic material using a chemical and / or physical coating process, preferably a chemical vapor deposition process (CVD process) and / or a physical vapor deposition process (PVD Process), in particular a plasma-assisted chemical vapor deposition process (PA-CVD process) and / or high-power pulse magnetron sputtering (HIPIMS) and / or a cathodic arc deposition process and / or an electron beam-assisted physical vapor deposition Process (EB-PVD process) takes place. Furthermore, in order to modify the application conditions, especially in coating processes with ionization steps, it is conceivable that a negative bias voltage is applied to the substrate to be coated when the semiconductor material is applied (for example when using a direct voltage), the negative bias voltage being less than 200 V, preferably is less than 150 V, in particular less than 100 V. Alternatively, of course, the use of an alternating voltage is also conceivable.

In addition, within the framework of a controllable application of coating materials, it is conceivable that a protective gas is used when the semiconductor material is applied, the protective gas preferably being formed in the form of nitrogen and / or argon.

In order to achieve improved adhesion of the coating material on the substrate, provision can also be made that the substrate surface is pretreated before application of a semiconductor material to a substrate in order to bring about stronger adhesion of the semiconductor material layer on the substrate, the pretreatment in particular Can include application of an adhesive layer to the substrate surface, wherein the adhesive layer can be designed in particular in the form of a lacquer layer.

In order to integrate improved protection or additional properties into the coating in question, provision can advantageously also be made for a final application of a protective layer to take place after application of a semiconductor material and simultaneous or subsequent application of metallic material, the protective layer in particular in the form of a Lacquer layer is formed.

The invention also relates to a coating for application to non-metallic surfaces, in particular producible using a method described above. In this case, the coating comprises a semiconductor material layer with a proportion of metallic material or additional semiconductor material integrated within the semiconductor material layer. The coating according to the invention thus has the same advantages as have already been described in detail with regard to the method according to the invention. In the context of the formation of the thinnest possible layer thicknesses, it can objectively be provided in particular that the coating is in the form of a monolayer. A small layer thickness can be advantageous here not only for reasons of saving coating material, but also for reasons of saving process time for applying the coating.

In the context of the formation of the thinnest possible layer thicknesses, it is particularly conceivable that the coating has a layer thickness of less than 120 nm, preferably a layer thickness of less than 100 nm, in particular a layer thickness of less than 80 nm.

With regard to the simultaneous guarantee of a minimum layer thickness to ensure the necessary robustness, it is also conceivable that the coating has a layer thickness between 20 and 120 nm, preferably a layer thickness between 40 and 100 nm, in particular a layer thickness between 50 and 60 nm.

In the context of maintaining an advantageous transparency for large parts of the electromagnetic spectrum, for example in the range of 76-77 GHz and the associated applicability as a coating for radar applications or for capacitive sensors, it can also advantageously be provided that the metallic material is less than 50% by weight, preferably less than 25% by weight, in particular less than 10% by weight, is present in the coating. As the addition of metallic material increases, it is to be expected that the transparency of the coating will decrease in large parts of the electromagnetic spectrum, which is disadvantageous for some applications.

With a view to minimizing the differences between reflection minima and reflection maxima of the coating as effectively as possible, provision can advantageously be made for the coating to have an average absorption coefficient k in the optical range of> 2, preferably> 3, in particular> 4. Alternatively, instead of the mean absorption coefficient k in the optical range, the absorption coefficient k at a specific wavelength (for example 620 nm) could also be used. As already described above, large differences between reflection minima and reflection maxima of a coating layer lead to undesirable “glaring” color perceptions within the coating layer. For possible applications of the coating in question in radar technology, it is particularly advantageous if the coating is as transparent as possible in the frequency ranges used. It can therefore advantageously be provided that the coating has a transparency of> 80%, preferably> 90%, in particular> 95%, in a frequency range between 76 and 77 GFIz.

In order to be able to adapt the optical properties of a coating as precisely as possible, it can advantageously be provided that the semiconductor material is present in the form of a pure substance, the semiconductor material preferably being formed from silicon or germanium or selenium or gallium arsenide. With a view to increasing the flexibility with regard to the adaptation of the optical properties of a coating, in particular the adaptation of various optical properties of a coating, it can also be advantageous if the semiconductor material is present as a mixture of different semiconductor materials, the semiconductor materials preferably silicon and / or germanium and / or selenium and / or gallium arsenide.

With regard to the most targeted adaptation of the optical properties of a coating, provision can also be made for the metallic material to be in the form of a pure substance, the metallic material preferably being formed from chromium or molybdenum or aluminum or zirconium. With a view to increasing the flexibility with regard to the adaptation of the optical properties of the coating, it can also be advantageous if the metallic material is present as a mixture of different metals, the metals preferably chromium and / or molybdenum and / or aluminum and / or zirconium can include.

Further advantages, features and details of the invention emerge from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can each be essential to the invention individually or in any combination. Show it:

1a-c a schematic representation of a plot of the L value (a), the a value (b) and the b value (c) of an L ^* a ^* b color space as a function of the metal content of a coating according to the invention ,

2 shows a schematic representation of a plot of the reflection index (%) of various coatings in the wavelength range from 350 nm to 750 nm,

3 shows a schematic representation of a plot of the reflection index (%) of various coatings in the wavelength range from 350 nm to 750 nm,

4 shows a schematic representation of a plot of the L value (top), the a value (middle) and the b value (bottom) of an L ^* a ^* b color space as a function of the layer thickness of a coating according to the invention according to a first embodiment as well as a reference measurement,

5 shows a schematic representation of the individual steps of a method according to the invention for producing a coating for application to non-metallic surfaces.

FIGS. 1a-c show a schematic representation of a plot of the L value (FIG. 1a), the a value (FIG. 1b) and the b value (FIG. 1c) of an L ^* a ^* b color space as a function the metal content of a coating according to the invention.

As can be seen from FIGS. 1a-c, the L, a and b values of the L ^* a ^* b color space vary specifically depending on the composition of the coating according to the invention. The proportion of metal in the coating according to the invention is proportional to the evaporation power (in kW). Thus, the L value of a coating according to the invention initially decreases with increasing metal content, before it increases briefly at a value of approx. 0.5 kW and then decreases further with further addition of a metallic material. The a-value, on the other hand, increases steadily up to a value of approx. 0.5 kW, before it continuously decreases from a value of approx. 0.5 kW. On the other hand, the b-value decreases steadily after the first addition of a metallic material. From the plots according to FIGS. 1a-c it can therefore be seen that the optical properties of the coating according to the invention can be varied in a targeted manner by means of a targeted admixture or application of metallic material.

Fig. 2 shows a schematic representation of a plot of the reflection index (%) of various coatings in the wavelength range 350 nm to 750 nm, the coating 1 consists of pure silicon, whereas the coating 2 is a coating according to the invention with silicon and a low chromium content and the coating 3 represents a coating according to the invention with silicon and a high chromium content.

As can be seen from FIG. 2, the reflection index in the optical range from 350 to 750 nm is clearly dependent on the composition of the coating layer. The course of the reflection index of the three coatings 1-3 in the wavelength range 350 nm to 750 nm is basically similar, but the coating layer 1 (pure Si) shows the highest reflection index between 500 and 750 nm. The coating 2 (Si + little Cr), on the other hand, has a significantly lower reflection index between 500 and 750 nm, which is, however, even greater than that of the coating 3 (Si + a lot of Cr).

3 shows a schematic representation of a plot of the reflection index (%) of various coatings in the wavelength range 350 nm to 750 nm. The coating 1 'here consists of pure silicon, whereas the coating 2' is a coating according to the invention with silicon and a high germanium content ( Fall conductor material + doped additional fall conductor material, which is different from the fall conductor material for forming a fall conductor material layer) and the coating 3 'represents a coating according to the invention with silicon and a medium proportion of germanium and the coating 4' represents a coating with silicon and a low proportion of germanium.

As can be seen from FIG. 3, the reflection index in the optical range from 350 to 750 nm is clearly dependent on the composition of the coating layer. The course of the reflection index of the four coatings 1 '-4' in the wavelength range 350 nm to 750 nm is basically similar, but the coating layer 1 '(pure Si) shows the highest reflection index between 500 and 750 nm. The coating 2 '(Si + a lot of Ge) has a lower reflection index between 500 and 750 nm, but it is still is greater than that of the coatings 3 '(Si + medium proportion of Ge) and 4' (Si + low proportion of Ge).

4 shows a schematic representation of a plot of the L value (top), the a value (middle) and the b value (bottom) of an L ^* a ^* b color space as a function of the layer thickness of a coating according to the invention (circle) according to a first embodiment as well as a reference measurement (square),

As can be seen from FIG. 4, the reference measurements (pure Si) show in principle the same course with regard to the L, a and b values as the coating (Si + Cr), namely that the L value with increasing layer thickness decreases, the a-value increases with increasing layer thickness and the b-value initially remains constant with increasing layer thickness and then decreases slightly. However, it can be clearly seen that the L and a values, in particular the b values, are significantly higher for the pure semiconductor material and consequently achieve a sometimes undesirable, brighter color perception.

In this case, the method according to the invention initially comprises a first optional step of pretreatment 100 of the substrate surface in order to bring about stronger adhesion of the semiconductor material layer on the substrate. The pretreatment 100 can preferably include the application of an adhesive layer, wherein the adhesive layer can in particular be designed in the form of a lacquer layer.

Subsequently, according to the method according to the invention, a semiconductor material is applied 120 to a substrate to form a semiconductor material layer, and metallic material is applied 140, the metallic material being introduced into the semiconductor material layer in a targeted manner to adapt the optical properties of the coating. In this case, the application 140 of the metallic material can take place simultaneously or also subsequently to the application 120 of the semiconductor material.

In order to integrate improved protection or additional properties into the coating in question, an application 160 can then optionally be carried out Protective layer take place, wherein the protective layer can be formed in particular in the form of a paint layer or the like.

By means of the method according to the invention or the coating according to the invention, it is possible, in particular via a targeted introduction of a metallic material into a semiconductor layer, to generate a coating with an attractive metallic external appearance that can be used in a variety of ways, especially for radar applications or in the field of capacitive sensors and its appearance is at the same time largely independent of the viewing angle.

References

100 pretreatment of a substrate surface

120 applications of a semiconductor material

140 application of a metallic material 160 application of a protective layer

Claims

Patent claims

1. A method of producing a coating for application to non-metallic surfaces, comprising the steps of:

- Applications (120) of a semiconductor material on a substrate to form a semiconductor material layer,

- Simultaneous or subsequent application (140) of metallic material or additional semiconductor material, the metallic material or the additional semiconductor material being introduced into the semiconductor material layer in a targeted manner in order to adapt the optical properties of the coating.

2. The method according to claim 1, characterized in that the semiconductor material is added in the form of a pure substance, the semiconductor material preferably being formed from silicon or germanium or selenium or gallium arsenide.

3. The method according to claim 1 or 2, characterized in that the metallic material is added in the form of a pure substance, wherein the metallic material is preferably formed from chromium or molybdenum or aluminum or zirconium.

4. The method according to any one of the preceding claims, characterized in that the metallic material to be applied and / or the amount of metallic material to be applied and / or the application area of the metallic material to be applied is selected at least partially on the basis of the absorption coefficient k of the metallic material in the optical range .

5. The method according to any one of the preceding claims, characterized in that the application (120) of the semiconductor material and / or the application (140) of the metallic material takes place via a thermal treatment, the thermal treatment preferably at a temperature of more than 400 ° C, in particular at a temperature of more than 800 ° C.

6. The method according to any one of the preceding claims, characterized in that the amount of applied metallic material and / or the proportion of applied metallic material in relation to the sum of semiconductor material and metallic material over a variation of the treatment time and / or a variation of the treatment temperature he follows.

7. The method according to any one of the preceding claims, characterized in that the application (120) of the semiconductor material to the substrate at least partially takes place simultaneously with the application (140) of a portion of metallic material, the semiconductor material to be applied and the metal to be applied preferably premixed and / or are mixed with one another during application (120, 140).

8. The method according to any one of the preceding claims, characterized in that the application (120, 140) of the semiconductor material and the metallic material via a chemical and / or physical coating process, preferably via a CVD and / or PVD process, in particular via a PA -CVD and / or HIPIMS and / or a cathodic arc deposition process and / or an EB-PVD process is carried out.

9. The method according to any one of the preceding claims, characterized in that when the semiconductor material is applied (120), a negative bias voltage is applied to the substrate to be coated, the negative bias voltage being less than 200 V, preferably less than 150 V, in particular less than 100 V.

10. The method according to any one of the preceding claims, characterized in that a protective gas is used when applying (120) the semiconductor material, wherein the protective gas is preferably formed in the form of nitrogen and / or argon.

11. The method according to any one of the preceding claims, characterized in that prior to application (120) of a semiconductor material to a substrate, a pretreatment (100) of the substrate surface takes place in order to bring about a stronger adhesion of the semiconductor material layer on the substrate, wherein the pretreatment (100 ) preferably comprises the application of an adhesive layer, the adhesive layer being in particular in the form of a lacquer layer.

12. The method according to any one of the preceding claims, characterized in that after an application (120) of a semiconductor material and a simultaneous or subsequent application (140) of metallic material, a final application (160) of a protective layer takes place, the protective layer in particular in the form of a Lacquer layer is formed.

13. Coating for application to non-metallic surfaces, in particular producible by a method according to one of the preceding claims, comprising a semiconductor material layer with a proportion of metallic material or additional semiconductor material integrated within the semiconductor material layer.

14. Coating according to claim 13, characterized in that the coating is in the form of a monolayer.

15. Coating according to claim 13 or 14, characterized in that the coating has a layer thickness of less than 120 nm, preferably a layer thickness of less than 100 nm, in particular a layer thickness of less than 80 nm.

16. Coating according to one of the preceding claims, characterized in that the coating has a layer thickness between 20 and 120 nm, preferably a layer thickness between 40 and 100 nm, in particular a layer thickness between 50 and 60 nm.

17. Coating according to one of the preceding claims, characterized in that the metallic material is less than 50% by weight, preferably less than 25% by weight, in particular less than 10% by weight, in the coating.

18. Coating according to one of the preceding claims, characterized in that the coating has an average absorption coefficient k in the optical range of> 2, preferably> 3, in particular> 4.

19. Coating according to one of the preceding claims, characterized in that the coating has a transparency of> 80%, preferably> 90%, in particular> 95%, in a frequency range between 76 and 77 GHz.

20. Coating according to one of the preceding claims, characterized in that the semiconductor material is in the form of a pure substance, the semiconductor material preferably being formed from silicon or germanium or selenium or gallium arsenide.

21. Coating according to one of the preceding claims, characterized in that the metallic material is in the form of a pure substance, the metallic material preferably being formed from chromium or molybdenum or aluminum or zirconium.