Film coating method of high-transmittance and high-hardness film layer for wearable cover plate and film layer thereof

Abstract

The invention relates to the technical field of film coating, in particular to a film coating method of a high-transmittance and high-hardness film layer for a wearable cover plate and the film layer thereof. The invention discloses a coating method of a high-transmittance and high-hardness film layer for a wearable cover plate, and CO2 gas is used as sputtering gas to bombard a target material and sputter C atoms to be deposited on a substrate. According to the film coating method, the CO2 gas is adopted to replace traditional Ar gas for target material bombardment, radio frequency plasma assistance and H2 addition are combined, the proportion of carbon atoms of an SP3 structure in the deposition process is effectively increased, film coating and etching are conducted at the same time, carbon atoms of an SP2 structure are oxidized and etched away, and therefore the proportion of the SP3 structure in the DLC film layer is increased.

Description

Technical Field

[0001] The present application relates to the technical field of coating, and in particular to a coating method and a film layer of a high-transmittance and high-hardness film layer for a wearable cover. Background Art

[0002] In the current wearable device market, the cover plate is a key component for protecting the screen and enhancing the user experience, and its performance requirements are increasing. In particular, traditional coating technology has been unable to meet market demand in terms of high transparency, high hardness, and good wear resistance. At present, DLC (diamond-like carbon) superhard film has become a research hotspot due to its excellent hardness and wear resistance. However, the existing DLC ​​coating technology still faces many challenges in achieving high hardness and large-area coating.

[0003] First of all, although arc source deposition of DLC film can obtain a higher SP3 carbon content and thus have excellent hardness, this technology has significant difficulties in large-area coating and is usually limited to small-scale applications of 8 to 12 inches, which makes it difficult to meet the needs of large-size wearable covers.

[0004] Secondly, although chemical vapor deposition (CVD) technology can achieve DLC coating on large-area substrates, its process requires high temperature conditions. Even with the assistance of RF plasma, the temperature must be maintained at around 700°C. Such high temperature conditions not only increase energy consumption, but also limit its application in conventional consumer electronic products, because the substrate materials of many wearable devices cannot withstand such high temperatures.

[0005] Finally, as a DLC coating solution more suitable for consumer electronic products, sputtering coating machine can achieve large-area coating at a relatively low temperature (less than 200°C), but its traditional process mostly uses Ar gas to bombard the target material, resulting in a low proportion of carbon atoms in the SP3 structure in the generated DLC film, large overall absorption of the film, and insufficient hardness. In addition, due to the presence of C atoms, the light transmittance of the film is also affected to a certain extent, making it difficult to meet the needs of high-transparency cover plates.

[0006] In summary, the existing DLC ​​coating technology has obvious technical bottlenecks in achieving high hardness, large area, high transparency and low temperature coating. Therefore, developing a new DLC coating method that can overcome these defects is of great significance for improving the performance of wearable covers and meeting market demand.

[0007] To this end, the present application provides a coating method for a high-transmittance and high-hardness film layer for a wearable cover plate and a film layer thereof Summary of the invention

[0008] In order to overcome the shortcomings of the prior art, the present application provides a coating method and film layer of a high-transmittance and high-hardness film layer for a wearable cover. By using CO2 gas instead of traditional Ar gas for target bombardment, and combining radio frequency plasma assistance and the addition of H2, the proportion of SP3 structure carbon atoms in the deposition process is effectively increased, thereby achieving simultaneous coating and etching, so that the carbon atoms in the SP2 structure are oxidized and etched away, thereby increasing the proportion of SP3 structure in the DLC film layer.

[0009] The technical solution adopted by this application to solve its technical problem is:

[0010] On the one hand, the present application provides a coating method for a high-transmittance and high-hardness film layer for a wearable cover plate, using CO2 gas as a sputtering gas to bombard a target material and sputter out C atoms to be deposited on a substrate.

[0011] In some embodiments, CO2 gas is introduced into the coating chamber to excite the CO2 gas to decompose and generate C and O elements, and the C element bombards the target material to sputter out C atoms that are deposited on the substrate;

[0012] The O element reacts with the C atoms on the substrate to generate CO;

[0013] The mixed gas of CO and CO2 etches the substrate.

[0014] In some embodiments, the CO2 gas is used for coating for 3000-8000 seconds.

[0015] In some embodiments, the vacuum degree of the CO2 gas during coating is ≥10 -3 pa.

[0016] In some embodiments, the temperature of the CO2 gas during film coating is less than 200°C.

[0017] In some embodiments, the CO 2 gas is used instead of the Ar gas to bombard the target.

[0018] In some embodiments, the target power is 3-8 kW, the ion source auxiliary power is 1-5 kW, and the CO2 flow rate is 100-250 sccm.

[0019] In some embodiments, when the CO2 gas bombards the target, H2 is also added for bombardment, and the flow rate of H2 is 0-100 sccm.

[0020] On the other hand, the present application provides a film layer, including a film layer formed by the above-mentioned coating method.

[0021] In some embodiments, the membrane layer has a transmittance greater than 90%.

[0022] The beneficial effects of this application are:

[0023] 1. The coating method described in the present application uses CO2 gas instead of traditional Ar gas for target bombardment, and combines RF plasma assistance and the addition of H2 to effectively increase the proportion of SP3 structure carbon atoms during the deposition process, thereby achieving simultaneous etching while coating, so that the carbon atoms of the SP2 structure are oxidized and etched away, thereby increasing the proportion of SP3 structure in the DLC film layer.

[0024] 2. The film layer described in the present application optimizes the process parameters in the preparation method so that the transmittance of the prepared DLC superhard film layer at a wavelength of 550nm is greater than 90%, meeting the demand for high transmittance.

[0025] 3. The film layer described in the present application can meet the condition that a Mohs 6 pen can move 40 mm at a 45° angle based on glass without any visible scratches when the pen tip is placed at a 750 g load, indicating that the film layer has a relatively high hardness.

[0026] 4. The coating method described in this application allows the entire coating process to be achieved at a low temperature of less than 200°C, which is of great significance for the application of conventional consumer products and can avoid the impact of high temperature on the performance of substrate materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present application is further described below in conjunction with the accompanying drawings and embodiments.

[0028] Figure 1 Schematic diagram of hardness test of the film layer described in this application. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the concept, specific structure and technical effects of the present application in combination with the embodiments and drawings, so as to fully understand the purpose, characteristics and effects of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of them. Based on the embodiments of the present application, other embodiments obtained by technicians in this field without creative work are all within the scope of protection of the present application. In addition, all the connection / connection relationships involved in the patent do not simply refer to the direct connection of components, but refer to the formation of a better connection structure by adding or reducing connection accessories according to the specific implementation situation. The various technical features created in this application can be combined interactively without conflicting with each other.

[0030] Terminology explanation:

[0031] DLC (Diamond-Like Carbon) Superhard Coating: DLC is a diamond-like carbon film that has similar hardness, wear resistance, chemical stability and thermal stability to natural diamond, but the cost is much lower than natural diamond. It is widely used in various surface coating fields that require high hardness and high wear resistance.

[0032] Arc source: In coating technology, arc source refers to a device that generates high-temperature plasma through arc discharge, which is used to bombard the target material and sputter out the desired substance. Arc source coating technology can usually achieve higher hardness and purity, but large-area coating is more difficult.

[0033] Chemical vapor deposition (CVD): Chemical vapor deposition is a process in which gaseous substances react chemically on a solid surface to form solid deposits. In DLC coating, CVD technology requires high temperature conditions to promote carbon atoms to form a DLC film layer on the substrate surface.

[0034] Sputtering machine: A sputtering machine is a device that uses high-energy particles (such as ions or electrons) to bombard a target material, so that atoms or molecules on the surface of the target material are sputtered out and deposited on the substrate. Sputtering coating technology has the advantages of large area, low temperature and high hardness, and is particularly suitable for consumer electronic products.

[0035] SP2 hybridization refers to the mixing of one s orbital and two p orbitals of a carbon atom to form three equivalent hybrid orbitals, namely sp 2 Hybridized orbitals. This type of hybridization usually occurs when carbon atoms form double bonds, such as the carbon-carbon double bonds in graphite, graphene, and some organic compounds. In SP2 hybridization, the three hybrid orbitals of a carbon atom form σ bonds with three other atoms (usually hydrogen atoms or other carbon atoms), while the remaining p orbital is perpendicular to the plane of the three σ bonds to form a π bond. This structure enables SP2 hybridized carbon atoms to form a relatively flat layered structure, such as the layered arrangement of graphite, with lower hardness and higher conductivity.

[0036] SP3 hybridization, unlike SP2 hybridization, refers to the mixing of one s orbital and three p orbitals of a carbon atom to form four equivalent hybrid orbitals, namely sp 3 Hybridized orbitals. This type of hybridization usually occurs when a carbon atom forms four single bonds, such as the carbon-carbon single bond or carbon-hydrogen bond in diamond and some organic compounds. In SP3 hybridization, the four hybrid orbitals of a carbon atom form σ bonds with four other atoms (usually hydrogen atoms or other carbon atoms), and there are no remaining p orbitals to form π bonds. This structure enables SP3 hybridized carbon atoms to form a three-dimensional network structure, such as the tetrahedral structure in diamond, which has higher hardness and lower conductivity.

[0037] Application of SP2 hybridization and SP3 hybridization in DLC film:

[0038] In DLC (diamond-like carbon) films, carbon atoms can exist in two hybrid forms: SP2 and SP3. The performance of DLC films, especially their hardness and wear resistance, depends largely on the proportion of carbon atoms with SP3 structure. The diamond structure formed by SP3 hybridized carbon atoms is the key to the high hardness of DLC films. However, traditional DLC coating technology often finds it difficult to obtain a high proportion of SP3 structure carbon atoms during the preparation process, resulting in limited hardness and wear resistance of the film.

[0039] ICP (Inductively Coupled Plasma) bombardment: ICP bombardment is a technology that uses plasma generated by inductive coupling to bombard the substrate surface. In DLC coating, ICP bombardment can promote the transformation of C atoms into SP3 structure and improve the hardness and wear resistance of the DLC film.

[0040] Transmittance: Transmittance refers to the ratio of the intensity of transmitted light to the intensity of incident light after light passes through the material. In DLC coating technology, high transmittance means that the coated cover can maintain a high light transmittance without affecting the display effect.

[0041] Mohs hardness: Mohs hardness is a measure of the hardness of a material, determined by a scratch test. In DLC coating technology, Mohs hardness is often used to evaluate the wear resistance and hardness of the DLC film.

[0042] Ar gas: Ar gas is an inert gas, which is often used as a sputtering gas in the sputtering coating process. However, in the technical solution of the present invention, in order to improve the SP3 structure ratio and performance of the DLC film, CO2 gas is used instead of Ar gas for sputtering coating.

[0043] Vacuum degree: During the coating process, the coating chamber and the preparation chamber need to reach a certain vacuum degree to reduce the interference of gas molecules on the coating process and improve the coating quality and stability. -1 Pa" and "10 -3 Pa” represents the vacuum level that the preparation chamber and the coating chamber need to reach before coating.

[0044] Target power and gas flow: Target power refers to the amount of energy received by the target during the sputtering coating process, which directly affects the sputtering efficiency and coating rate. Gas flow refers to the flow of gas (such as Ar gas) used in the sputtering process, which affects the composition of the sputtering product and the coating quality.

[0045] The existing DLC ​​coating technology has obvious technical bottlenecks in achieving high hardness, large area, high transparency and low-temperature coating. The present application provides a coating method for a high-transmittance and high-hardness film layer for a wearable cover, using CO2 gas as a sputtering gas to bombard the target material and sputter out C atoms to be deposited on the substrate; that is, the CO2 gas is used instead of Ar gas to bombard the target material.

[0046] In the traditional method, the C atoms sputtered by bombarding the target with Ar gas can partially convert the carbon atoms of SP2 structure into carbon atoms of SP3 structure under the assistance of radio frequency plasma, but the conversion efficiency is limited, resulting in a low proportion of SP3 structure in the film layer. Carbon atoms of SP3 structure are the key to the high hardness of DLC (diamond-like carbon) film layer. Therefore, in the present application, the CO2 gas replaces the Ar gas to bombard the target material, and the CO2 gas is introduced into the coating chamber to stimulate the decomposition of CO2 gas to produce C and O elements. The C element bombards the target material to sputter C atoms deposited on the substrate; the O element reacts with the C atoms on the substrate to generate CO; the mixed gas of CO and CO2 "etches" away some of the C atoms of SP2 structure; CO2 gas replaces the Ar gas to bombard the target material, which increases the proportion of carbon atoms of SP3 structure in the film layer, thereby improving the hardness and wear resistance of the film layer.

[0047] In some embodiments, the time for the CO2 gas to perform the coating is 3000-8000 seconds, and the vacuum degree of the CO2 gas during the coating is ≥10 -3 pa, the temperature of CO2 gas during coating is less than 200℃.

[0048] Specifically, in the present application, the coating time is selected to be 3000-8000 seconds in order to ensure that the DLC film layer can form a complete and uniform coating on the substrate; too short a coating time may result in an incomplete film layer and affect performance; while too long a time may increase costs and introduce unnecessary process complexity.

[0049] Vacuum degree ≥10 -3 The coating is carried out under pa. The high vacuum degree can significantly reduce the number of gas molecules and impurities in the coating chamber, thereby reducing the impurity contamination in the DLC film layer and improving the purity and performance of the film layer. Moreover, the high vacuum environment is conducive to the uniform deposition of C atoms and the transformation of SP2 to SP3 structure, thereby obtaining a more dense, uniform and high-performance DLC film layer.

[0050] The temperature of CO2 gas coating is less than 200℃. The low temperature coating condition reduces the thermal stress on the substrate and reduces the risk of substrate deformation or performance degradation caused by high temperature treatment. At the same time, low temperature treatment also broadens the application scope of coating technology, making it applicable to more types of substrates and products.

[0051] In some embodiments, the target power is 3-8kw, the ion source auxiliary power is 1-5kw, and the CO2 flow rate is 100-250sccm.

[0052] Specifically, the power of the target material is 3-8kw, which can improve the energy transfer efficiency during the sputtering process, so that more C atoms are sputtered out, thereby increasing the coating rate and film thickness.

[0053] The auxiliary power of the ion source is 1-5kw. The increase of the auxiliary power of the ion source can provide more ion energy, promote the rearrangement and combination of C atoms on the substrate, and is conducive to the formation of more SP3 structures, thereby improving the hardness and density of the film layer.

[0054] Specifically, the ion source is a kind of equipment hardware that uses a 13.6MHz frequency radio frequency to excite the gas in the vacuum chamber to form a stable plasma in the vacuum. The working gases include common argon, oxygen, nitrogen, etc., while CO2 and other gases are rarely used. In this application, when the ion source is assisted, the power is 1-5kw, and the flow rate of argon is 50sccm. The addition of argon is mainly to assist the excitation of the ion source and make the ion source work stably. The bond energy of argon is low and it is easy to be opened into argon atoms by radio frequency. If Ar gas is not used, the ion source is easy to be unstable.

[0055] As a sputtering gas, the flow rate of CO directly affects the sputtering rate of the target and the gas atmosphere during the coating process. The flow rate of CO2 is 100-250sccm, which can maintain a stable coating rate while promoting the effective deposition of C atoms and the formation of SP3 structure.

[0056] In some embodiments, when the CO2 gas bombards the target, H2 is also added for bombardment, and the flow rate of H2 is 0-100 sccm.

[0057] Specifically, during the coating process, the addition of H can utilize its reducing property to help convert some carbon atoms in the SP2 structure into carbon atoms in the SP3 structure, because H can react with carbon atoms in the SP2 structure to form a more stable SP3 structure. In the present application, by adjusting the flow rate of H, the chemical reaction during the coating process can be finely controlled, thereby optimizing the structure and properties of the DLC film layer, such as hardness, transmittance, etc.

[0058] The coating method described in the present application is further described through the following embodiments and comparative examples;

[0059] Example 1

[0060] A coating method for a high-transmittance and high-hardness film layer for a wearable cover plate comprises the following steps:

[0061] Step 1, the glass substrate is fixed on the fixture;

[0062] Before coating, the glass substrate must be cleaned to ensure that there is no oil, dust or other impurities on the surface of the substrate to avoid affecting the coating quality. The cleaning process can be done by ultrasonic cleaning or chemical cleaning. Then, the cleaned substrate is fixed on a special fixture to ensure stability during the coating process.

[0063] Step 2: Put the fixture into the transport cart;

[0064] Step 3: Place the fixture's transport cart into the coating preparation chamber;

[0065] Step 4: Prepare the chamber and evacuate it to 6.0*10 -1 Pa;

[0066] Step 5, punch the doors of the preparation chamber and the coating chamber, and exchange the fixture of the preparation chamber with the fixture of the coating chamber;

[0067] Step 6: After the exchange is completed, close the doors of the preparation chamber and the coating chamber;

[0068] Step 7: Evacuate the coating chamber to 10 -3 Vacuum above Pa.

[0069] Step 8: The carbon target starts working, the coating time is 3000s, and the DLC deposition is completed;

[0070] CO2 gas is introduced into the coating chamber to generate C and O elements by exciting the decomposition of CO2 gas. The C element is used to bombard the target material to sputter out C atoms deposited on the substrate, while the O element reacts with the C atoms on the substrate to generate CO. The mixed gas of CO and CO2 etches the substrate to remove the carbon atoms of the SP2 structure.

[0071] The target power is 3kw, the ion source auxiliary power is 1kw, the CO2 flow rate is 100sccm, and the operating temperature is 150℃.

[0072] Step 9: Release the vacuum in the prepared cavity and return it to normal pressure;

[0073] After the coating is completed, the CO2 gas supply system is turned off and the coating chamber is deflated to restore the inside of the chamber to normal pressure.

[0074] Step 10, taking out the coated glass substrate;

[0075] Open the door of the coating chamber, remove the coated substrate from the fixture, and carry out subsequent inspection and testing.

[0076] Example 2

[0077] A coating method for a high-transmittance and high-hardness film layer for a wearable cover plate comprises the following steps:

[0078] In step 8, the coating time is 8000s, the target power is 8kw, the ion source auxiliary power is 5kw, the CO2 flow rate is 250sccm, and the operating temperature is 180°C.

[0079] The remaining conditions are the same as those in Example 1.

[0080] Example 3

[0081] A coating method for a high-transmittance and high-hardness film layer for a wearable cover comprises the following steps:

[0082] In step 8, the coating time is 500 s, the target power is 5 kW, the ion source auxiliary power is 2 kW, the CO2 flow rate is 200 sccm, and the operating temperature is 160°C.

[0083] The remaining conditions are the same as those in Example 1.

[0084] Example 4

[0085] A coating method for a high-transmittance and high-hardness film layer for a wearable cover comprises the following steps:

[0086] In step 8, the coating time is 3000s, the target power is 2kw, the ion source auxiliary power is 2kw, the CO2 flow rate is 130sccm, the H2 flow rate is 100sccm, and the operating temperature is 170°C.

[0087] The remaining conditions are the same as those in Example 1.

[0088] Example 5

[0089] A coating method for a high-transmittance and high-hardness film layer for a wearable cover plate comprises the following steps:

[0090] In step 8, the coating time is 400 s, the target power is 6 kW, the ion source auxiliary power is 5 kW, the CO2 flow rate is 150 sccm, the H2 flow rate is 50 sccm, and the operating temperature is 150°C.

[0091] The remaining conditions are the same as those in Example 1.

[0092] Comparative Example 1

[0093] A coating method for a film layer of a wearable cover plate comprises the following steps:

[0094] In step 8, the coating time is 3000s, the target power is 3kw, the ion source auxiliary power is 1kw, the argon flow rate is 1000ccm, and the working temperature is 150°C.

[0095] The remaining conditions are the same as those in Example 1.

[0096] The coated glass substrates prepared in Examples 1-5 and Comparative Example 1 were subjected to the following performance tests, and the test results are summarized in the following Table 1;

[0097] Performance testing:

[0098] 1. Hardness test, such as Figure 1 As shown, use a Mohs 6 pen, under a load of 750g, place the pen tip at 45° based on the glass, move 40mm*10 times, and observe the scratches on the glass surface.

[0099] 2. Transmittance test: detect the transmittance under light with a wavelength of 550nm.

[0100] Table 1

[0101]

[0102]

[0103] The above is a specific description of the preferred implementation of the present application, but the invention of the present application is not limited to the described embodiments. Technical personnel familiar with the field can also make various equivalent modifications or substitutions without violating the spirit of the present application. These equivalent modifications or substitutions are all included in the scope defined by the claims of the present application.

Claims

1. A coating method for a high-transmittance and high-hardness film layer for a wearable cover, characterized in that: CO2 gas is used as the sputtering gas to bombard the target and sputter out C atoms which are deposited on the substrate.

2. The coating method according to claim 1, characterized in that: CO2 gas is introduced into the coating chamber to stimulate the decomposition of CO2 gas to produce C and O elements. The C element bombards the target material to sputter out C atoms that are deposited on the substrate. The O element reacts with the C atoms on the substrate to generate CO; The mixed gas of CO and CO2 etches the substrate.

3. The coating method according to claim 1, characterized in that: The CO2 gas coating time is 3000-8000 seconds.

4. The coating method according to claim 1, characterized in that: The vacuum degree of the CO2 gas during coating is ≥10 -3 pa.

5. The coating method according to claim 1, characterized in that: The temperature of the CO2 gas during coating is less than 200°C.

6. The coating method according to claim 1, characterized in that: The CO2 gas is used instead of the Ar gas to bombard the target material.

7. The coating method according to claim 1, characterized in that: The power of the target material is 3-8kw, the power of the ion source auxiliary is 1-5kw, and the flow rate of CO2 is 100-250sccm.

8. The coating method according to claim 1, characterized in that: When the CO2 gas bombards the target material, H2 is also added for bombardment, and the flow rate of H2 is 0-100 sccm.

9. A film layer, characterized in that A film layer formed by the coating method according to any one of claims 1 to 8.

10. The film layer according to claim 9, characterized in that: The film layer has a transmittance greater than 90%.

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