Dark black decorative coating with enhanced heat resistance

Abstract

The invention relates to a coating comprising at least a light-absorbing metal oxide and / or nitrogen oxide dark black layer deposited directly on the surface of a part to be coated. In another embodiment, a deep black layer is deposited on a metal adhesion promoting layer followed by a hard optically transparent nitrogen oxide layer. The coating may be deposited by reactive magnetron sputtering and exhibit enhanced heat resistance at temperatures in excess of 400 DEG C.

Description

Technical Field

[0001] The present invention relates to a deep black coating that exhibits enhanced heat resistance at high temperatures. Background Art

[0002] Recently, coatings with a decorative deep black appearance (also known as deep black coatings) have become popular in decorative coloring coatings, especially in consumer goods fields such as jewelry, watches, mobile phones, bathroom facilities, and medical devices. According to the International Commission on Illumination (CIE) standard CIE 1976 L*a*b* color space, a surface is considered a deep black surface if it exhibits L* < 40, most preferably L* < 35, and a and b values close to 0, where the L* value represents perceived brightness and a* and b* represent the colors seen by the human eye. The CIE 1976 L*a*b* color space based on D65 standard illumination and d / 8° (i.e., diffuse illumination, measured at 8°) is used as a reference.

[0003] In addition to the aesthetic appearance of the coating, these decorative coatings also have additional functional properties such as high hardness, enhanced scratch and abrasion resistance, and chemical and corrosion resistance.

[0004] German Patent Application No. DE3639469A1 describes a hard material layer with a decorative black appearance that also has high wear resistance. This hard material layer includes a first layer composed of elements from Groups IVa and Va of the periodic table, a second layer containing nitrides of the elements of the first layer, a third layer containing carbides of the same elements, and a covering layer composed of a hard carbon layer, where the carbide crystals of the same elements are embedded in this covering layer.

[0005] Diamond-like carbon (DLC) layers with a black appearance and high hardness are known. However, traditional DLC layers have a neutral gray value represented by the brightness L*, which is in the range above 40.

[0006] U.S. Patent Application Publication No. 2016 / 0002792A1 describes a method for manufacturing a wear-resistant layer with a deep black appearance for decorative use. This hard material layer includes a diamond-like carbon (DLC) layer with a hardness of at least 10 GPa and a refractive index of n DLC>2.1. An independent gradient layer is disposed above the DLC layer, wherein the thickness of the gradient layer is at least 300 nm. This gradient layer has a gradually decreasing density, and the refractive index also decreases accordingly, thereby forming a refractive index gradient. Among them, the average refractive index within 30 nm of the interface close to the DLC layer is greater than or equal to 2.0, while within 30 nm of the outer surface opposite to the DLC layer, the average refractive index of the gradient layer determined by averaging does not exceed 1.85. Through the refractive index gradient generated by the gradient layer, the gradient layer functions as an antireflection layer. The chemical composition of the gradient layer is mainly different from that of the DLC layer in terms of hydrogen content.

[0007] The US patent application with publication number 2016 / 0053371A1 describes an ornament, which includes a substrate and a black hard coating film formed on the substrate and containing diamond-like carbon (DLC), wherein the hydrogen content on the surface of the black hard coating film far from the substrate is higher than that on the surface of the black hard coating film close to the substrate. The hydrogen content on the surface of the black hard coating film far from the substrate is 30.0 to 70.0 atomic %. The article with the coating can be a watch, a necklace, a pendant, a brooch or glasses. The black hard coating film contains a gradient layer containing diamond-like carbon. The hydrogen content of the gradient layer increases along the direction away from the substrate. Similar to US20160002792A1, with the gradient distribution of hydrogen content, the gradient layer functions as an antireflection layer.

[0008] The above coatings all use DLC layers. A known disadvantage of DLC layers is that their thermal stability only lasts up to about 350 °C, and graphitization occurs at temperatures higher than this. When heated to such temperatures, the optical and mechanical properties of the DLC layer will undergo irreversible changes. In some applications, it is desired that the components coated with decorative coatings can withstand temperature exposure above 400 °C, and the optical properties of the coatings do not change enough to cause the color of the coatings to be perceptible to the naked eye.

[0009] This application provides a hard deep black appearance coating whose optical properties hardly or completely do not change at high temperatures. Summary of the Invention

[0010] Provide a coating deposited on a substrate. The coating adopts a multi-layer design and at least includes a light-absorbing deep black gradient layer directly deposited on the surface of the part to be coated or a metal adhesion-promoting layer, followed by a hard optically transparent layer deposited thereon. The "hard layer" described herein refers to a layer with a coating hardness higher than 15 GPa. The "optically transparent" described herein means that the material has a high transmittance coefficient (close to 100%) for light with an energy distribution in the infrared, visible, and ultraviolet wavelength ranges.

[0011] The above coating also includes a deep black layer that can be a metal oxide and / or a nitride oxide.

[0012] In the above-mentioned coating, the deep black metal oxide and / or nitride layer has an L* < 40.

[0013] In the above-mentioned coating, the deep black metal oxide and / or nitride layer contains one or more metals, one or more rare earth metals, one or more metalloids, or one or more alkaline earth metals.

[0014] In the above-mentioned coating, the one or more metals include Al, Ti, Cr, Ni, Nb, V, Fe, Mo, Ta, W, or Hf; the one or more rare earth metals include Y, Ce, Gd, or Er; the one or more metalloids include Si, C, or B; and the one or more alkaline earth metals include Mg, Ca, Sr, or Be.

[0015] In the above-mentioned coating, the metal concentration in the deep black metal oxide and / or nitride layer decreases, and the concentration of oxygen or an oxygen-nitrogen combination increases, measured from the substrate.

[0016] In the above-mentioned coating, the deep black metal oxide and / or nitride layer is Me1 x Rx, where 0.05 < x < 0.5, and R is a non-metallic element containing oxygen and / or an oxygen-nitrogen combination.

[0017] In the above-mentioned coating, the oxygen-nitrogen ratio of the deep black nitride layer is fixed and greater than or equal to 0.4.

[0018] In the above-mentioned coating, the thickness of the deep black metal oxide and / or nitride layer is greater than 0.1 μm.

[0019] In the above-mentioned coating, the thickness of the deep black metal oxide and / or nitride layer is greater than 0.3 μm.

[0020] In the above-mentioned coating, the thickness of the deep black metal oxide and / or nitride layer is greater than 0.5 μm.

[0021] The above-mentioned coating further includes an optically transparent nitride layer deposited on the deep black metal oxide and / or nitride layer.

[0022] In the above-mentioned coating, the optically transparent nitride layer contains one or more metals, one or more rare earth metals, one or more metalloids, or one or more alkaline earth metals.

[0023] In the above-mentioned coating, the one or more metals include Al, Ti, Cr, Ni, Nb, V, Fe, Mo, Ta, W, or Hf; the one or more rare earth metals include Y, Ce, Gd, or Er; the one or more metalloids include Si, C, or B; and the one or more alkaline earth metals include Mg, Ca, Sr, or Be.

[0024] In the above-mentioned coating, the optically transparent nitrogen oxide layer is a single layer, with a metal content between 0.4 and 0.5, an oxygen content between 0.05 and 0.1, and a nitrogen content between 0.4 and 0.45.

[0025] In the above-mentioned coating, the thickness of the optically transparent nitrogen oxide layer is greater than 0.3 μm.

[0026] In the above-mentioned coating, the thickness of the optically transparent nitrogen oxide layer is greater than 0.5 μm.

[0027] In the above-mentioned coating, the thickness of the optically transparent nitrogen oxide layer is greater than 1.0 μm.

[0028] In the above-mentioned coating, the hardness of the optically transparent nitrogen oxide layer is greater than 12 GPa.

[0029] In the above-mentioned coating, the hardness of the optically transparent nitrogen oxide layer is greater than 15 GPa.

[0030] In the above-mentioned coating, the hardness of the optically transparent nitrogen oxide layer is greater than 20 GPa.

[0031] In the above-mentioned coating, the thickness of the metal adhesion promoting layer is greater than 0.3 μm.

[0032] In the above-mentioned coating, the metal element is similar to the metal element used for the deep black metal oxide and / or nitrogen oxide layer and the optically transparent nitrogen oxide layer.

[0033] There is also provided a method for depositing a coating on a substrate. The method includes the following steps: achieving closed-loop control of the reactive gas in the coating chamber to directly deposit the deep black metal oxide and / or nitrogen oxide layer onto the substrate, or directly depositing it onto the adhesion promoting means (such as the metal adhesion promoting layer) as the case may be; maintaining the conditions achieved during the above step for a predetermined period of time to deposit the optically transparent nitrogen oxide layer on the deep black metal oxide and / or nitrogen oxide layer.

[0034] In the above method, before implementing the above step, it further includes the following steps: solvent cleaning the substrate; placing the substrate in the coating chamber; evacuating the coating chamber; performing plasma etching on the substrate; and exposing the substrate to a bipolar power supply to form an adhesion layer on the substrate. Description of the Drawings

[0035] Figure 1 A schematic diagram of the coating chamber that can be used in the present invention is provided.

[0036] Figure 2 The color characteristics of the AlON-based coating including the metal-based adhesion layer and the light-absorbing deep black layer according to an embodiment of the present invention are shown.

[0037] Figure 3Shows the color characteristics of an AlON-based coating comprising a metal-based adhesion layer, a light-absorbing deep black layer, and a hard optically transparent layer according to a second embodiment of the present invention.

[0038] Figure 4 Provides a comparison between the deep black coating of the present invention and the deep black coatings of the prior art, and shows the changes in each coating after annealing in air at 500 °C for 24 hours.

[0039] Figure 5 Provides a comparison between the deep black coating of the present invention and the deep black coatings of the prior art, and graphically shows the change in coating hardness with annealing temperature. Detailed Description

[0040] The present invention can provide a method for depositing a multi-layer coating, the multi-layer coating comprising a light-absorbing deep black layer 20 (see Figure 2 ) directly deposited onto a substrate 10 to be coated. Figure 1 See

[0041] See Figure 2 , the light-absorbing deep black layer 20 can include, but is not limited to, metal oxides (M-O) or oxynitrides (M-O-N). It is contemplated that the light-absorbing deep black layer 20 can comprise a single metal element or a composite metal oxide containing a mixture of multiple metals. In some embodiments, the light-absorbing deep black layer 20 can comprise a bimetallic composition (M1 x M2 y O z ), a trimetallic composition (M1 w M2 x M3 y O z ), a tetrametallic composition (M1 v M2 w M3 x M4 y O z ), a pentametallic composition (M1 u M2 v M3 w M4 x M5 y O z ), etc. In each of the above light-absorbing deep black layers 20, the variables u, v, w, x, y, z can be positive integers or decimal values. In certain examples, the values of u, v, w, x, y, z can range from about 0.02 to about 1.0.

[0042] In an alternative embodiment, it is contemplated that the light-absorbing metal oxide deep black layer 20 may comprise one or more metals including, but not limited to, Al, Ti, Cr, Ni, Nb, V, Fe, Mo, Ta, W, Hf, and / or one or more rare earth metals such as Y, Ce, Gd, Er, and / or one or more metalloids such as Si, C, B, and / or one or more alkaline earth metals such as Mg, Ca, Sr, Be. In some embodiments, the light-absorbing deep black layer 20 may be Al-O, Al-Si-O, Al-Cr-O, Al-Ti-O-N, Al-Mg-O, Al-Ca-O, Al-Mn-O, Al-Zn-O, Al-Ta-O, Al-W-O, Al-Mo-O, Al-Mn-O, Si-O, Si-Mg-O, Si-Ca-O, Ti-O, Nb-Ti-O, Ti-Mg-O, Ti-Ca-O, Ni-O, Ni-Ca-O, Ni-Mg-O.

[0043] In an alternative embodiment, the light-absorbing deep black layer 20 may comprise a single metal element or a complex metal oxynitride containing a mixture of multiple metals. In some embodiments, the light-absorbing deep black layer 20 may comprise a bimetallic component (M1 w M2 x O y N z ), a trimetallic component (M1 v M2 w M3 x O y N z ), a tetrametallic component (M1 u M2 v M3 w M4 x O y N z ), a pentametallic component (M1 t M2 u M3 v M4 w M5 x O y N z ), etc. In each of the above light-absorbing deep black layers 20, the variables t, v, w, x, y, z may be positive integers or decimal values. In certain examples, the values of t, v, w, x, y, z may range from about 0.05 to about 0.6.

[0044] In one embodiment, the light-absorbing metal oxide deep black layer 20 may comprise one or more metals including, but not limited to, Al, Ti, Cr, Ni, Nb, V, Fe, Mo, Ta, W, Hf, and / or one or more rare earth metals such as Y, Ce, Gd, Er, and / or one or more metalloids such as Si, C, B, and / or one or more alkaline earth metals such as Mg, Ca, Sr, Be. In some embodiments, the light-absorbing deep black layer 20 may be Al-O-N, Al-Si-O-N, Al-Cr-O-N, Al-Ti-O-N, Al-Mg-O-N, Al-Ca-O-N, Al-Mn-O-N, Al-Zn-O-N, Al-Ta-O-N, Al-W-O-N, Al-Mo-O-N, Si-O-N, Si-Mg-O-N, Si-Ca-O-N, Ti-O-N, Nb-Ti-O-N, Ti-Mg-O-N, Ti-Ca-O-N, Ni-O-N, Ni-Ca-O-N, Ni-Mg-O-N.

[0045] According to the present invention, the light-absorbing deep black layer 20 may be formed as a gradient layer having a decreasing metal concentration and an increasing concentration of oxygen or an oxygen-nitrogen combination with increasing distance from the substrate. To this end, the absorption layer 20 may be the compound Me 1x Rx, where x is preferably adjusted such that 0.05 < x < 0.5, and R represents a non-metallic element (which may be oxygen or an oxygen-nitrogen combination) for producing a sub-oxide material or a sub-nitride oxide material to obtain unique absorption properties. The inventors have unexpectedly found that for a nitride oxide light-absorbing deep black layer, the oxygen-nitrogen ratio within the gradient layer should be fixed and have a value of at least 0.4 or higher, meaning that oxygen accounts for 40% of the non-metallic elements.

[0046] The present invention for depositing the deep black layer 20 on the substrate 10 will now be described. Figure 1 A schematic view of a coating chamber useful for the present invention is provided. It is contemplated that the light-absorbing deep black layer 20 may be deposited by reactive magnetron sputtering (dual high-power pulsed magnetron sputtering (HiPIMS), direct current (DC), etc.), where the discharge voltage is regulated by feedback control of a reactive gas (oxygen or an oxygen-nitrogen combination). The inventors have unexpectedly found that a smooth and controllable transition from a pure metal to a metal oxide (or metal nitride oxide) is the preferred way to obtain a light-absorbing deep black layer. The regulation of the oxygen-nitrogen ratio in the coating is achieved by appropriately adjusting the ratio of the reactive gases (here O2 and N2) injected into the vacuum chamber by a feedback controller.

[0047] The thickness of the expected light-absorbing deep black layer 20 can be greater than 0.1 μm, preferably greater than 0.3 μm, and most preferably greater than 0.5 μm. It is also expected that the deep black value L* of the obtained light-absorbing deep black layer 20 can be between 30 and 40 (according to the CIE 1976 L*a*b* color space based on the D65 standard light illumination).

[0048] According to another embodiment, the present invention can directly deposit the hard optically transparent layer 30 onto the deep black layer when the deep black layer is directly deposited onto the substrate or deposited on the metal adhesion promoting layer. The term "optically transparent" means that the material has a high transmittance coefficient (close to 100%) for light with an energy distribution in the infrared, visible, and ultraviolet wavelength ranges. Similar to the light-absorbing deep black layer 20, the hard optically transparent layer 30 can contain a single metal element or can be a composite metal oxynitride containing a mixture of multiple metals. In some embodiments, the light-absorbing deep black layer 30 can comprise a bimetallic component (M1 w M2 x O y N z ), a trimetallic component (M1 v M2 w M3 x O y N z ), a tetrametallic component (M1 u M2 v M3 w M4 x O y N z ), a pentametallic component (M1 t M2 u M3 v M4 w M5 x O y N z ), etc. In each of the above light-absorbing deep black layers 30, the variables t, v, w, x, y, z can be positive integers or decimal values.

[0049] According to one embodiment, the hard optically transparent layer 30 can be a single layer with a constant metal content and a constant oxygen and nitrogen content. The metal content can be between 0.4 and 0.5, the oxygen content can be between 0.05 and 0.1, and the nitrogen content can be between 0.4 and 0.45. The inventors unexpectedly found that the hard optically transparent layer 30 is preferably oxygen-deficient relative to nitrogen to form a hard layer.

[0050] Similar to the light-absorbing dark layer 20, the hard optically transparent layer 30 can be deposited by reactive magnetron sputtering (dual high-power pulsed magnetron sputtering (HiPIMS), direct current (DC), etc.). The thickness of the hard optically transparent layer 30 can be greater than 0.3 μm, preferably greater than 0.5 μm, and most preferably greater than 1.0 μm. The minimum preferred hardness of the hard optically transparent layer 30 can be not less than 12 GPa, preferably not less than 15 GPa, and more preferably not less than 20 GPa.

[0051] The following is an example of coating a substrate with the coatings detailed above.

[0052] Example

[0053] In this example, an AlON (aluminum oxynitride) coating is deposited by reactive magnetron sputtering. A metal-based adhesion layer, a light-absorbing dark layer 20, and a hard transparent AlON 30 are deposited. The following steps are performed to form the functional dark coating:

[0054] Step 1: Tungsten carbide (WC) and alumina (Al2O3) substrates are solvent-cleaned and loaded onto a dual-axis rotating planetary vacuum system.

[0055] Step 2: The vacuum chamber is evacuated to a low pressure range of 10E-5 mbar.

[0056] Step 3: The substrates are subjected to argon plasma etching for 10 minutes using a radio frequency substrate bias.

[0057] Step 4: The working pressure is then adjusted to 5.0E-3 mbar and the argon gas flow is adjusted to 25 PSccm.

[0058] Step 5: Bipolar power is applied to an unbalanced 6-inch circular planar aluminum target at 5 kW for 3 minutes to form an aluminum adhesion layer.

[0059] Step 6: According to the present invention, a closed-loop control of the reactive gases P2 and N2 is then achieved in a manner of adjusting the reactive gas process by means of a discharge voltage regulator to form the light-absorbing dark layer 20. The ratio of P2 to N2 is set to 0.2:0.8, i.e., 20% of the total reactive gas flow injected into the vacuum system is P2 and 80% is N2. The software control of the vacuum system allows the user to program a ramp function while maintaining a fixed P2 / N2 ratio. The reactive gases are then slowly varied over a period of 20 minutes such that the cathode voltage steadily decreases from the pure metal state to the final set fully nitroxide film state. At this point, the O2 / N2 gas ratio is adjusted to 0.1:0.9 to obtain the optimal stoichiometry of the nitroxide top layer.

[0060] Step 7: The above conditions are then maintained until the hard transparent top layer 30 of the coating reaches the desired thickness.

[0061] The resulting coating includes a 0.3-μm thick pure aluminum layer, a 0.5-μm thick light-absorbing dark black layer 20, and a 4.0-μm thick hard transparent AlON layer 30. A Konica-Minolt CN-2600d spectrophotometer was used to compare the coating characteristics and visual appearance of the two coatings. According to the CIE 1976 L*a*b* color space, the AlON-based coating containing the metal adhesion layer and the light-absorbing dark black layer 30 (see Figure 2 ) has color characteristics of L* 33, a* -0.84, and b* -0.1, with a dark black appearance characteristic. It is worth noting that the coating characteristics are independent of the substrate material, indicating that the coating appearance can be adapted to any type of substrate material. This is ideal in the decorative industry.

[0062] It is worth noting that the color characteristics of the second coating containing the hard top optical transparent layer 30 are similar, with L* 35, a* -0.04, and b* -0.75, also having a dark black appearance characteristic (according to the CIE 1976 L*a*b* color space), see Figure 3 . This is because the top layer has antireflective and transparent optical functions. The spectrophotometer can also provide the reflection behavior of the two selected coatings, as shown in the reflectance spectrum versus wavelength of the bottom graph in Figure 2 and 3 . It can be seen that the light reflection percentage of both coatings is very low, meeting the expectations of a dark black appearance surface.

[0063] In addition, the mechanical properties of the two coatings were compared. Although the two coatings show the same color appearance, the AlON coating without the hard transparent top layer 30 has a lower hardness, less than 10 GPa (see Figure 2 ). On the other hand, adding the hard transparent top layer 30 significantly improves the mechanical properties of the coating, with a measured hardness of 22 GPa (see Figure 3 ). In summary, the deposition of the hard transparent top layer 30 does not affect the optical effect of the coating, but instead enhances the mechanical properties of the decorative coating.

[0064] The two selected dark black coatings, namely the DLC-based coating and the (present invention) AlON-based coating, were deposited on cemented carbide and annealed at 500 °C for 24 hours (see Figure 4 and 5 ). The prior art DLC dark black coating peeled off after high-temperature exposure, and the surface was exposed to oxidation. However, no visual or optical changes were observed in the dark black coating of the present invention. Its color characteristics remained unchanged, and even after 24 hours of high-temperature exposure, the L* value was still 35.

[0065] In addition, the hardness of both coatings as a function of the annealing temperature was also monitored. For the prior art DLC-based deep black coating, a hardness decrease was observed between 250 °C and 400 °C, indicating a graphitization effect. Above this annealing temperature, the coating peeled off, as previously described. In contrast, the deep black coating of the present invention showed no change in mechanical properties at 500 °C, demonstrating excellent mechanical property stability and confirming the enhanced heat resistance of the deep black coating of the present invention.

[0066] The present invention has been described with reference to the above embodiments. Modifications and variations may occur to others upon reading and understanding the specification. Embodiments incorporating one or more aspects of the present invention are intended to include all such modifications and variations insofar as they fall within the scope of the appended claims and their equivalents.

Claims

1. A coating deposited on a substrate, the coating comprising: A deep black metal oxide and / or oxynitride layer, which is directly deposited on the substrate or deposited on a metal adhesion promoting layer, Followed by a hard optically transparent oxynitride layer.

2. The coating according to claim 1, wherein The deep black metal oxide and / or oxynitride layer has an L* < 40.

3. The coating according to claim 1, wherein The deep black metal oxide and / or oxynitride layer contains one or more metals or one or more rare earth metals or one or more metalloids or one or more alkaline earth metals.

4. The coating according to claim 3, wherein The one or more metals include Al, Ti, Cr, Ni, Nb, V, Fe, Mo, Ta, W or Hf, the one or more rare earth metals include Y, Ce, Gd or Er, the one or more metalloids include Si, C or B, and the one or more alkaline earth metals include Mg, Ca, Sr or Be.

5. The coating according to claim 1, wherein The deep black metal oxide and / or oxynitride layer has an increasing concentration of oxygen or oxygen-nitrogen combination and a decreasing metal concentration measured from the substrate.

6. The coating according to claim 5, wherein, The deep black metal oxide and / or oxynitride layer is Me1- x Rx, where 0.05 < x < 0.5 and R is a non-metallic element containing oxygen and / or an oxygen-nitrogen combination.

7. The coating according to claim 5, wherein In the deep black oxynitride layer, the oxygen-nitrogen ratio is fixed and greater than or equal to 0.

4.

8. The coating according to claim 1, wherein, The thickness of the deep black metal oxide and / or oxynitride layer is greater than 0.1 μm.

9. The coating according to claim 1, wherein, The thickness of the deep black metal oxide and / or oxynitride layer is greater than 0.3 μm.

10. The coating according to claim 1, wherein, The thickness of the deep black metal oxide and / or oxynitride layer is greater than 0.5 μm.

11. The coating according to claim 1, further comprising an optically transparent oxynitride layer deposited on the deep black metal oxide and / or oxynitride layer.

12. The coating according to claim 11, wherein, The optically transparent oxynitride layer contains one or more metals or one or more rare earth metals or one or more metalloids or one or more alkaline earth metals.

13. The coating according to claim 12, wherein, The one or more metals include Al, Ti, Cr, Ni, Nb, V, Fe, Mo, Ta, W or Hf, the one or more rare earth metals include Y, Ce, Gd or Er, the one or more metalloids include Si, C or B, and the one or more alkaline earth metals include Mg, Ca, Sr or Be.

14. The coating according to claim 11, wherein, The optically transparent oxynitride layer is a single layer, with a metal content between 0.4 and 0.5, an oxygen content between 0.05 and 0.1, and a nitrogen content between 0.4 and 0.

45.

15. The coating according to claim 11, wherein, The thickness of the optically transparent oxynitride layer is greater than 0.3 μm.

16. The coating according to claim 11, wherein, The thickness of the optically transparent oxynitride layer is greater than 0.5 μm.

17. The coating according to claim 11, wherein, The thickness of the optically transparent oxynitride layer is greater than 1.0 μm.

18. The coating according to claim 11, wherein, The hardness of the optically transparent oxynitride layer is greater than 12 GPa.

19. The coating according to claim 11, wherein, The hardness of the optically transparent oxynitride layer is greater than 15 GPa.

20. The coating according to claim 11, wherein The hardness of the optically transparent oxynitride layer is greater than 20 GPa.

21. A method for depositing a deep black coating on a substrate, comprising the following steps: Implementing closed-loop control of reactive gases in a coating chamber to directly deposit a deep black metal oxide and / or oxynitride layer on the substrate; And Maintaining the conditions achieved in the above step for a predetermined time to deposit an optically transparent oxynitride layer on the deep black metal oxide and / or oxynitride layer.

22. The method according to claim 21, wherein, Before implementing the above steps, the following steps are further included: Solvent cleaning the substrate; Place the substrate in a coating chamber; Vacuum the coating chamber; Perform plasma etching on the substrate; and Expose the substrate to bipolar power to form an adhesion layer on the substrate.

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