Intelligent ring outer surface color decoration method and titanium alloy intelligent ring

Abstract

The application discloses a color decoration method for an outer surface of an intelligent ring and a titanium alloy intelligent ring, and the method comprises the following steps: after cleaning and activating a ring shell, a titanium transition layer is deposited, and a high-hardness diamond-like carbon film bottom layer is magnetron sputtered; the carbon film bottom layer is activated by oxygen plasma, oxygen-containing functional groups are introduced, and the water contact angle is reduced to the hydrophilic range; ultraviolet curing ink containing nano alumina oxide particles and inorganic coloring pigments is coated, and a nano ceramic color layer is obtained through ultraviolet curing. Oxygen plasma activation is used to introduce oxygen-containing functional groups on the surface of the diamond-like carbon film to form a chemical bonding interface, so that the problem that the surface of the diamond-like carbon film layer is difficult to color is solved, and color diversification decoration and diamond-like abrasion resistance protection are simultaneously realized.

Description

Technical Field

[0001] This application relates to the field of wearable device technology, and in particular to a method for color decoration on the outer surface of a smart ring and a titanium alloy smart ring. Background Technology

[0002] A smart ring is a miniaturized wearable electronic device worn on the finger. It can realize a variety of functions such as health indicator monitoring, sports data tracking, and near-field communication interaction. With its core advantages of small size, imperceptible wearing, and high portability, it has become one of the wearable categories with great growth potential in the consumer electronics field.

[0003] In daily use, the outer surface of a smart ring serves as the direct carrier of the product's appearance, and its color and decorative effects have a significant impact on consumers' visual perception and purchasing decisions. As the consumer market matures and users' aesthetic standards rise, consumer demand for the color of smart rings has evolved from a single metallic color to a widespread expectation for diverse and personalized colors. Whether a product can offer a rich selection of colors has become one of the key factors influencing its market competitiveness.

[0004] However, in actual industrial production, existing surface coloring processes for smart ring casings made of titanium alloy all have varying degrees of limitations in achieving the desired colors. Some processes can only present a limited range of colors, making it difficult to meet consumers' demands for vibrant hues and diverse colors; while other processes can achieve a wider range of colors, they still face many challenges in terms of color uniformity, batch consistency, or color durability. Summary of the Invention

[0005] This application provides a method for color decoration on the outer surface of a smart ring and a titanium alloy smart ring. By constructing a chemically bonded laminated structure of a diamond-like carbon film substrate and a nano-ceramic color layer, the technical problem of achieving both color diversity and high hardness and wear resistance is solved.

[0006] The first aspect of this application provides a method for color decoration on the outer surface of a smart ring, the method comprising:

[0007] The outer surface of the ring casing is cleaned and activated to obtain a base surface layer; A titanium transition layer is deposited on the surface of the substrate, and a diamond-like carbon film underlayer is deposited on the titanium transition layer using a magnetron sputtering process. The surface of the diamond-like carbon film substrate is subjected to oxygen plasma activation treatment, and oxygen-containing functional groups are introduced on the surface of the diamond-like carbon film substrate, so that the water contact angle of the treated diamond-like carbon film substrate surface is reduced to below a preset angle. An uncured colored coating is obtained by coating the surface of the diamond-like carbon film substrate with an ultraviolet-cured ink containing nano-alumina particles and inorganic coloring pigments. The colored coating is subjected to ultraviolet light curing treatment to obtain a nano-ceramic colored layer.

[0008] Optionally, the step of performing oxygen plasma activation treatment on the surface of the diamond-like carbon film substrate to introduce oxygen-containing functional groups on the surface of the diamond-like carbon film substrate includes: The ring shell with the diamond-like carbon film deposited on it is placed in a plasma processing chamber, and the chamber is evacuated and oxygen is introduced. Radio frequency power is applied to the oxygen in the cavity to excite it, thereby generating oxygen plasma; The surface of the diamond-like carbon film substrate is exposed to the oxygen plasma for surface bombardment treatment, which causes the carbon-hydrogen bonds on the surface to break. Based on the chemical reaction between oxygen plasma and the surface, oxygen-containing functional groups are introduced into the surface of the diamond-like carbon film substrate.

[0009] Optionally, the pretreatment of cleaning and activation on the outer surface of the ring casing to obtain a base surface layer includes: The ring casing was ultrasonically cleaned sequentially using acetone, anhydrous ethanol, and deionized water. After cleaning and drying, the ring shell is bombarded with an argon ion beam under vacuum conditions to remove the original oxide layer and make the surface roughness Ra not exceed 0.05 μm.

[0010] Optionally, the step of depositing a titanium transition layer on the surface of the substrate, and depositing a diamond-like carbon film underlayer on the titanium transition layer using a magnetron sputtering process, includes: The pretreated ring shell is placed under vacuum conditions, and a titanium transition layer is pre-deposited on the surface layer of the substrate by magnetron sputtering. The ring casing after depositing the titanium transition layer is placed in a hydrogen-containing atmosphere, and a diamond-like carbon film is deposited on the surface of the titanium transition layer. The content of diamond phase carbon in the diamond-like carbon film is controlled to a preset ratio.

[0011] Optionally, coating the surface of the diamond-like carbon film substrate with a UV-curable ink containing nano-alumina particles and inorganic coloring pigments to obtain an uncured colored coating includes: Nano-alumina particles, inorganic coloring pigments, and UV-curable resin system are mixed and then dispersed to obtain UV-curable ink. The UV-curable ink is transferred to a printing device to print and coat the activated diamond-like carbon film substrate surface to form an uncured colored coating.

[0012] Optionally, the inorganic coloring pigment is selected from one or more combinations of iron oxide red, cobalt blue, chromium oxide green, titanium dioxide, and carbon black.

[0013] Optionally, the printing coating process includes: The activated diamond-like carbon film substrate is subjected to multiple overprinting processes using a screen printing plate with gradient dots to obtain a multi-layered coating structure; wherein, between two adjacent printings, the previous layer of coating is pre-cured to achieve a semi-cured state. After all the overprinting is completed, the multilayer coatings are subjected to the ultraviolet curing treatment together, so that the unreacted functional groups at the interface of adjacent coatings cross-link and interpenetrate, and form a chemically bonded interlayer interface based on the cross-linking and interpenetration.

[0014] A second aspect of this application provides a titanium alloy smart ring, including a ring housing, the outer surface of which has a multilayer decorative coating prepared by the color decoration method described above.

[0015] Optionally, the multilayer decorative coating comprises, from the inside out: a substrate surface layer, a titanium transition layer, a diamond-like carbon film underlayer, and a nano-ceramic colored layer formed by curing with ultraviolet light-curing ink; The diamond-like carbon film substrate and the nano-ceramic colored layer have an oxygen-containing functional group chemical bonding interface introduced through oxygen plasma activation treatment.

[0016] Optionally, the substrate surface layer is an activated surface formed by cleaning and ion beam bombardment, and its roughness Ra does not exceed 0.05 μm; The thickness of the titanium transition layer is 50~100nm; The thickness of the diamond-like carbon film substrate is 1~3μm; The thickness of the nano-ceramic colored layer is 5~15μm.

[0017] As can be seen from the above technical solutions, this application has the following advantages: By systematically integrating processes such as titanium transition layer deposition, diamond-like carbon film preparation, oxygen plasma activation treatment, nano-ceramic color layer coating, and ultraviolet curing, a layered structure with specific interlayer chemical bonding relationships is constructed on the surface of the ring casing. Specifically, this invention utilizes oxygen plasma activation treatment to actively introduce oxygen-containing functional groups onto the surface of the diamond-like carbon film, transforming it from a hydrophobic and inert state into a hydrophilic interface with chemical bonding capabilities. Simultaneously, ultraviolet-curable ink containing nano-alumina particles and inorganic coloring pigments is coated onto the activated surface and cured under ultraviolet light to form a nano-ceramic color layer. This results in a strong chemical bond between the color layer and the diamond-like carbon film, rather than a simple physical stacking. Based on this, the diamond-like carbon film undertakes the core protective function of resisting external friction and scratches, while the nano-ceramic color layer undertakes the function of diverse color decoration across the entire color gamut. In the layered structure, functions complement each other and interfaces synergize, ensuring that the technical effect produced by the entire solution is not a simple summation of the effects of each step. Ultimately, a diversified color decoration effect and diamond-like wear-resistant protection effect are simultaneously achieved on the outer surface of the titanium alloy smart ring. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart illustrating an embodiment of the method for color decoration of the outer surface of a smart ring provided in this application; Figure 2 A schematic flowchart of an embodiment of the method for color decoration of the outer surface of a smart ring provided in this application, which introduces oxygen-containing functional groups on the surface of a diamond-like carbon film substrate; Figure 3 A schematic flowchart of an embodiment of the method for color decoration of the outer surface of a smart ring provided in this application, wherein a titanium transition layer is deposited on a substrate surface layer; Figure 4 A schematic flowchart of an embodiment of the method for color decoration of the outer surface of a smart ring provided in this application, which involves coating an uncured colored coating with UV-curable ink on the surface of a diamond-like carbon film substrate; Figure 5 A schematic diagram of the structure of the layered decorative coating of the titanium alloy smart ring provided in this application. Detailed Implementation

[0020] This application provides a method for color decoration of the outer surface of a smart ring and a titanium alloy smart ring, which can be widely used for surface decoration and protective treatment of various smart ring products. For example, fashion consumer-grade smart rings can achieve rich colors across the entire color gamut and fine patterns such as gradients and logos by flexibly adjusting inorganic coloring pigments. Health monitoring smart rings can meet the wear resistance and safety requirements for long-term wear by leveraging the good biocompatibility of each layer of materials and a synergistic protective system. High-end customized smart rings can achieve high-precision personalized decoration and obtain a high-end texture similar to ceramic or enamel through screen printing. In addition, this solution can also be extended to small wearable devices with titanium alloy shells, such as smart watch bezels, watch strap buckles, and smart bracelet casings.

[0021] Please see Figure 1 , Figure 1 A flowchart illustrating an embodiment of the method for color decoration of the outer surface of a smart ring provided in this application, the embodiment including: S101. Clean and activate the outer surface of the ring case to obtain the base surface layer; The ring casing undergoes multi-stage ultrasonic cleaning to remove residual cutting fluid, grease, and particulate contaminants from the manufacturing process. Specifically, after the ring casing is precision machined, various contaminants introduced during the manufacturing process inevitably adhere to its outer surface, mainly including residual cutting coolant, grease, metal shavings, dust particles, and fingerprints.

[0022] A three-stage progressive ultrasonic cleaning scheme is adopted. Specifically, the first stage uses acetone as the cleaning medium. Acetone has excellent dissolving ability for oily organic contaminants, effectively removing processing oil and grease residues adhering to the shell surface. The ring shell is completely immersed in the acetone solution and placed in an ultrasonic cleaning tank. The micro-jets generated by the ultrasonic cavitation effect powerfully scour the shell surface, causing contaminants to be rapidly peeled off and dissolved in the cleaning solution. The second stage uses anhydrous ethanol as the cleaning medium. Anhydrous ethanol can effectively dissolve and remove any acetone and some polar organic contaminants that may remain on the surface after the first stage cleaning, while being non-corrosive to the shell surface, ensuring that the base material is not damaged. The third stage uses deionized water as the cleaning medium for a final rinsing of the shell, thoroughly removing any trace solutes and ionic impurities that may remain on the surface after the first two stages of organic solvent cleaning, ensuring that the surface cleanliness meets the requirements of subsequent processes. After the three-stage cleaning is completed, the shell surface is thoroughly dried with high-purity inert gas to avoid water residue from adversely affecting subsequent vacuum processing.

[0023] Although the cleaning process removes macroscopic contaminants from the surface, a loose and uneven primary oxide layer naturally forms on the surface of titanium alloy materials during processing and storage. The presence of this oxide layer significantly reduces the surface energy of the substrate, hindering the formation of a tight metallurgical bond between the subsequently deposited film and the base metal. Therefore, it is necessary to effectively remove this primary oxide layer by ion beam bombardment.

[0024] After drying, the ring casing is transferred to a vacuum chamber, which is then evacuated to a preset high vacuum level to eliminate any interference from residual gas. High-purity argon gas is introduced into the chamber as the working gas, and after adjusting to a suitable working pressure, a bias voltage is applied to the chamber. This causes high-energy argon ions generated by the ionization of argon atoms to accelerate and bombard the casing surface under the influence of an electric field. The high-energy argon ions produce a physical sputtering etching effect on the surface, peeling away the original loose primary oxide layer on the titanium alloy surface layer by layer, exposing the fresh metal surface with high chemical activity underneath. At the same time, ion bombardment can also form a uniform micro-nano-scale rough morphology on the surface, increasing the effective surface area and ensuring that the surface roughness Ra does not exceed 0.05 μm. After this treatment, the casing surface becomes the substrate surface layer.

[0025] S102. Deposit a titanium transition layer on the surface of the substrate, and deposit a diamond-like carbon film underlayer on the titanium transition layer using a magnetron sputtering process. A titanium transition layer and a diamond-like carbon (DLC) film underlayer were sequentially deposited using magnetron sputtering. The pretreated ring casing was placed in the vacuum chamber of a magnetron sputtering apparatus, and a pure titanium transition layer was sputtered onto the substrate surface under an inert atmosphere using a high-purity titanium target as the sputtering source. This titanium transition layer serves as a stress buffer and bonding reinforcement layer between the titanium alloy substrate and the DLC film, effectively alleviating the interfacial stress caused by lattice mismatch and differences in thermal expansion coefficients between the two materials, thereby significantly improving the overall adhesion of the film layers.

[0026] After the titanium transition layer is deposited, the sputtering target is switched to a graphite target as the carbon source, and reactive sputtering is performed in a hydrogen-containing atmosphere to deposit a diamond-like carbon film underlayer on the titanium transition layer. During the deposition process, parameters such as sputtering power, working gas pressure, and hydrogen flow rate are adjusted to control the bonding state of carbon atoms during deposition, ensuring that the diamond phase carbon content in the film reaches a preset ratio, thereby endowing the film with ultra-high diamond-like hardness. The obtained diamond-like carbon film underlayer can achieve a microhardness of over HV2000, providing a solid and wear-resistant protective foundation for the outer surface of the ring.

[0027] S103. The surface of the diamond-like carbon film substrate is activated by oxygen plasma to introduce oxygen-containing functional groups into the surface of the diamond-like carbon film substrate, so that the water contact angle of the treated diamond-like carbon film substrate surface is reduced to below the preset angle. To address the inherent chemical inertness and poor wettability of the diamond-like carbon (DLC) film substrate, oxygen plasma was used for surface activation modification. The ring casing with the deposited DLC film substrate was placed in a plasma treatment chamber. After evacuating the chamber, high-purity oxygen was introduced as the working gas. Radio frequency power was applied to the oxygen in the chamber to excite it, generating oxygen plasma containing active oxygen particles.

[0028] The surface of a diamond-like carbon film substrate is exposed to an oxygen plasma atmosphere. Active oxygen particles bombard the surface, breaking the carbon-hydrogen bonds and introducing oxygen-containing functional groups, primarily hydroxyl and carboxyl groups, onto the carbon atom sites. By controlling parameters such as treatment time, radio frequency power, and oxygen flow rate, a certain density of these introduced oxygen-containing functional groups is achieved. After this treatment, the surface properties of the diamond-like carbon film substrate undergo a significant transformation: its water contact angle decreases to below a predetermined angle (e.g., 30°), and the surface changes from a hydrophobic and inert state to a hydrophilic and active state. These oxygen-containing functional groups on the activated surface provide chemical bonding sites for the subsequently coated nanoceramic color layer, forming a strong chemical bond between the two, rather than simple physical adsorption.

[0029] S104. Coat the surface of the diamond-like carbon film substrate with an ultraviolet-curable ink containing nano-alumina particles and inorganic coloring pigments to obtain an uncured colored coating. To formulate UV-curable inks, nano-alumina particles, inorganic coloring pigments, and a UV-curable resin system are thoroughly mixed and then ground and dispersed to a predetermined fineness to obtain uniformly dispersed UV-curable inks. The particle size of the nano-alumina particles can be controlled within the range of 20–50 nm, and their mass fraction in the ink can be 15%–25%. This particle size range and addition amount ensure that the nanoparticles are uniformly dispersed in the resin matrix and exert a significant reinforcing effect after curing. Inorganic coloring pigments can be selected according to the target color effect; for example, iron oxide red for red, cobalt blue for blue, chromium oxide green for green, titanium dioxide for white, and carbon black for black. Multiple pigments can also be combined to create the desired hue.

[0030] The prepared UV-curable ink is transferred to a printing device, and the ink is uniformly coated onto the surface of the diamond-like carbon film substrate after oxygen plasma activation treatment by means of screen printing, forming a wet film coating of a preset thickness.

[0031] S105. The colored coating is cured with ultraviolet light to obtain a nano-ceramic colored layer.

[0032] The uncured colored coating was cured by ultraviolet (UV) irradiation. The ring casing coated with the ink was placed in an area irradiated by a UV light source, and the coating was irradiated with UV light within a preset wavelength range. Under the action of UV light, the photoinitiator molecules in the ink absorbed the UV light energy and broke down, generating active free radicals. These free radicals rapidly initiated the opening of acrylate double bonds in the resin matrix and reactive diluent, resulting in a chain polymerization and cross-linking reaction. Within tens of seconds, the coating system rapidly transformed from a low-viscosity liquid wet film into a highly cross-linked three-dimensional network structure solid dry film.

[0033] During the curing process, the nano-alumina particles are irreversibly anchored within a dense cross-linked network, forming a polymer composite structure reinforced with nano-ceramic particles. This gives the coating ceramic-like high hardness and excellent scratch resistance. Inorganic pigment particles are also uniformly coated and locked within the cross-linked network, preventing migration, aggregation, or detachment during use and ensuring long-term color stability and uniformity of the coating. Simultaneously, at the interface between the coating and the diamond-like carbon film substrate, the active functional groups in the resin system and the oxygen-containing functional groups introduced on the activated surface complete chemical bonding during photocuring. This creates a strong chemical bond between the nano-ceramic color layer and the diamond-like carbon film substrate, rather than simple physical adhesion. Upon completion of curing, a nano-ceramic color layer with a chemically bonded interface to the diamond-like carbon film substrate is obtained.

[0034] In this embodiment, by systematically integrating processes such as titanium transition layer deposition, diamond-like carbon film underlayer preparation, oxygen plasma activation treatment, nano-ceramic color layer coating, and ultraviolet curing, a layered structure with interlayer chemical bonding is constructed on the surface of the ring casing, thereby overcoming the functional limitations of a single technical means. Specifically, the diamond-like carbon film underlayer serves as the core wear-resistant barrier, while the nano-ceramic color layer serves as the color decoration carrier. The two play their respective roles and complement each other in the layered structure. The oxygen plasma activation treatment introduces oxygen-containing functional groups on the surface of the diamond-like carbon film, transforming the originally hydrophobic and inert interface into a chemically bonded active interface, forming a strong chemical bond between the color layer and the wear-resistant layer, ensuring the integrity of the layered structure, and achieving a synergistic effect of diversified color decoration and diamond-like grade wear-resistant protection.

[0035] The surface of the diamond-like carbon film substrate is activated by oxygen plasma to introduce oxygen-containing functional groups onto the surface of the diamond-like carbon film substrate. (See also...) Figure 2 , Figure 2 A schematic flowchart illustrating an embodiment of the method for color decoration of the outer surface of a smart ring provided in this application, which involves introducing oxygen-containing functional groups on the surface of a diamond-like carbon film substrate, includes: S201. Place the ring shell with the diamond-like carbon film deposited on it in the plasma treatment chamber, evacuate the chamber and introduce oxygen. The ring casing, with its diamond-like carbon film underlayer deposited, is removed from the magnetron sputtering equipment and transferred to the cavity of a plasma processing unit. This plasma processing cavity typically employs a parallel-plate electrode structure or an inductively coupled structure, and includes a stage for placing the sample. The stage can be grounded or biased. The ring casing is placed on the stage, and the cavity door is closed, ensuring a tight seal.

[0036] The cavity is evacuated to remove air and residual moisture. The vacuum pump unit is then activated to raise the cavity's base vacuum to a preset level, typically requiring a high vacuum range, to ensure the purity of the working gas during subsequent processing and to prevent impurities such as nitrogen and water vapor in the air from adversely affecting the plasma treatment effect. During the evacuation process, residual air molecules and water molecules adhering to the cavity walls and sample surfaces are gradually removed.

[0037] Once the vacuum level in the chamber reaches the preset value, high-purity oxygen is introduced into the chamber as the working gas. The oxygen purity is typically required to be above 99% to minimize interference from impurity gases on the surface chemical reaction. The oxygen flow rate is precisely adjusted using a gas flow controller to achieve and maintain a stable working pressure within the chamber. The selection of the working pressure must balance the ignition stability of the plasma and the density of active particles. Too low a pressure makes it difficult to maintain a stable glow discharge, while too high a pressure will shorten the mean free path of the active particles, reducing their bombardment efficiency and modification effect on the surface.

[0038] S202. Apply radio frequency power to the oxygen in the cavity to excite it and generate oxygen plasma; After a stable oxygen atmosphere is established within the cavity, radio frequency power is applied to the electrodes to excite the oxygen to produce a glow discharge, forming oxygen plasma. Under the influence of an alternating electric field, free electrons within the cavity are accelerated and gain kinetic energy. High-energy electrons collide inelasticly with oxygen molecules, triggering a series of complex physicochemical processes: electron collisions ionize oxygen molecules, producing oxygen ions and secondary electrons; electron collisions also dissociate oxygen molecules, producing oxygen atoms; some oxygen atoms and molecules further interact with high-energy electrons, forming excited-state oxygen molecules and oxygen free radicals, among other reactive particles. These processes occur and reach dynamic equilibrium in a very short time, forming an oxygen plasma within the cavity composed of electrons, oxygen ions, oxygen atoms, oxygen free radicals, excited-state oxygen molecules, and neutral oxygen molecules. During glow discharge, a pale purple or pale blue luminescence is visible within the cavity, indicating the establishment of a stable plasma.

[0039] S203. Expose the surface of the diamond-like carbon film substrate to oxygen plasma for surface bombardment treatment to break the carbon-hydrogen bonds on the surface. The surface of a ring shell with a deposited diamond-like carbon (DLC) film underlayer was fully exposed to an established oxygen plasma environment, and the surface was bombarded by active particles in the plasma. Under the influence of the electric field of the plasma sheath, the active particles in the oxygen plasma gained kinetic energy and continuously bombarded the surface of the DLC film underlayer. Specifically, the high-energy oxygen ions and oxygen atoms exerted a physical bombardment effect on the surface, with kinetic energy sufficient to break the original carbon-hydrogen bonds and some carbon-carbon single bonds on the DLC film surface. During the deposition process, a certain amount of carbon-hydrogen bonds inevitably remain on the surface of the DLC film, which is one of the main reasons for the surface's hydrophobic and inert nature. Under the continuous bombardment of the active particles, hydrogen atoms in the surface carbon-hydrogen bonds are preferentially stripped, generating a large number of highly reactive dangling bonds on the carbon framework, placing the surface carbon atoms in a metastable state of unsaturated coordination.

[0040] S204. Based on the chemical reaction between oxygen plasma and the surface, oxygen-containing functional groups are introduced into the surface of the bottom layer of diamond-like carbon film.

[0041] By utilizing the chemical reaction between the generated dangling bonds and reactive oxygen particles in the oxygen plasma, oxygen-containing functional groups are generated in situ on the surface of the diamond-like carbon film, thus completing the surface chemical modification. In the oxygen plasma environment, the numerous carbon dangling bonds generated after the surface carbon-hydrogen bonds break are in a highly reactive metastable state. These dangling bonds rapidly react with the abundant oxygen atoms and oxygen free radicals in the plasma. Depending on the reaction conditions and local chemical environment, carbon dangling bonds can combine with a single oxygen atom to form a hydroxyl group, or combine with two oxygen atoms or form a double bond with a single oxygen atom to form a carboxyl group. In addition, small amounts of carbonyl and ester functional groups may also be generated on the surface. Among these functional groups, hydroxyl and carboxyl groups, with their strong polarity and chemical reactivity, are the most crucial for improving surface wettability and providing chemical bonding sites.

[0042] With the gradual introduction of oxygen-containing functional groups into the surface, the chemical composition and physical properties of the diamond-like carbon film's underlying surface undergo a fundamental transformation. Chemically, the carbon content of the surface layer decreases while the oxygen content significantly increases, and characteristic signal peaks corresponding to these oxygen-containing functional groups can be detected using surface analysis techniques such as X-ray photoelectron spectroscopy. Physically, the surface transforms from a nonpolar hydrophobic state to a polar hydrophilic state, providing abundant chemical bonding sites for components such as the resin matrix and silane coupling agent in the subsequently coated UV-curable ink system. This allows the nano-ceramic color layer to form strong covalent or hydrogen bond chemical connections with the diamond-like carbon film's underlying surface.

[0043] In this embodiment, by sequentially connecting four sub-steps—establishing a pure oxygen environment through vacuuming, generating oxygen plasma through radio frequency excitation, breaking carbon-hydrogen bonds on the surface by bombarding with active particles, and introducing oxygen-containing functional groups through the reaction of dangling bonds with active oxygen—a controllable transformation of the bottom surface of the diamond-like carbon film from hydrophobic and inert to hydrophilic and active is achieved, effectively solving the problem that the surface of the diamond-like carbon film layer is difficult to form a firm adhesion with other coatings.

[0044] A titanium transition layer is deposited on the substrate surface, and a diamond-like carbon film is deposited on top of the titanium transition layer using a magnetron sputtering process. (See also...) Figure 3 , Figure 3 A schematic flowchart of an embodiment of the method for color decoration of the outer surface of a smart ring provided in this application, wherein a titanium transition layer is deposited on a substrate surface layer, the embodiment including: S301. Place the pretreated ring shell under vacuum conditions and pre-deposit a titanium transition layer on the substrate surface layer using a magnetron sputtering process. The ring shell, which has undergone cleaning and activation pretreatment, is fixed in the vacuum chamber of the magnetron sputtering equipment. After closing the chamber door, the vacuum pump unit is started to evacuate the chamber to a preset high vacuum range, thereby reducing the interference of residual gas on the purity of the film. Once the background vacuum reaches the preset value, high-purity argon gas is introduced into the chamber as the sputtering working gas and adjusted to a suitable working pressure.

[0045] A high-purity titanium target was selected as the sputtering source. A DC negative bias voltage was applied to the back of the titanium target, causing argon atoms near the target surface to undergo glow discharge, generating a high density of argon ions. Under the influence of the negative bias electric field, the argon ions bombarded the titanium target surface at high speed, sputtering titanium atoms from the target surface through physical momentum transfer. The magnetic field set on the back of the titanium target formed a confinement magnetic field parallel to the target surface near the target surface, causing secondary electrons to undergo helical motion near the target surface, lengthening the electron motion path, and improving argon ion yield and sputtering efficiency. The sputtered titanium atoms flew in a vacuum environment and deposited on the substrate surface layer of the ring shell, layer by layer, to form a continuous and dense titanium transition layer film.

[0046] S302. Place the ring shell after depositing the titanium transition layer in a hydrogen atmosphere, deposit a diamond-like carbon film underlayer on the surface of the titanium transition layer, and control the content of diamond phase carbon in the diamond-like carbon film underlayer to a preset ratio.

[0047] After the titanium transition layer is deposited, a mixture of high-purity argon and high-purity hydrogen is introduced into the chamber as the working gas. Argon primarily performs the sputtering function, while hydrogen acts as the reactant gas, participating in the chemical regulation of the film deposition process. A high-purity graphite target is selected as the carbon source sputtering target. A negative bias is applied to the back of the graphite target, inducing glow discharge near the target surface. Argon ions bombard the graphite target surface, sputtering carbon atoms. The sputtered carbon atoms are deposited on the surface of the titanium transition layer, gradually forming a diamond-like carbon film underlayer.

[0048] During deposition, carbon atoms can form two different bonding states: sp² hybrid bonds correspond to the graphitic carbon structure, which is softer and has poor wear resistance; sp³ hybrid bonds correspond to the diamond carbon structure, which has a tetrahedral three-dimensional network, giving the film extremely high hardness. The role of hydrogen in the mixed gas is to selectively control these two carbon bonding modes. In the plasma environment, hydrogen molecules are dissociated into active hydrogen particles, which preferentially etch sp² hybrid carbon. That is, the reaction rate of active hydrogen with graphitic carbon atoms is significantly higher than its reaction rate with diamond carbon atoms, thus selectively removing the graphitic carbon structure already formed in the film while having little impact on the diamond carbon structure. By reasonably controlling process parameters such as sputtering power, argon to hydrogen flow ratio, working pressure, and substrate bias, the diamond carbon content in the bottom layer of the diamond-like carbon film can be controlled within a preset ratio range, enabling the film microhardness to reach HV2000 or higher.

[0049] In this embodiment, a two-step magnetron sputtering process, first depositing a titanium transition layer and then depositing a diamond-like carbon (DLC) film underlayer, achieves a synergistic improvement in interfacial bonding strength and surface wear resistance. The introduction of the titanium transition layer effectively solves the interfacial stress problem caused by the difference in material properties between the DLC film and the titanium alloy substrate. Its metallurgical compatibility with the substrate forms a strong bond, preventing film cracking or peeling. During the deposition of the DLC film underlayer, hydrogen gas is introduced into the argon atmosphere. The selective etching effect of active hydrogen particles on sp² hybrid carbon allows the high-hardness sp³ hybrid carbon structure to be fully preserved, thereby obtaining a wear-resistant protective layer and providing diamond-like carbon-level protection for the outer surface of the ring.

[0050] A UV-curable ink containing nano-alumina particles and inorganic coloring pigments is coated onto the surface of a diamond-like carbon film substrate to obtain an uncured colored coating. (See also...) Figure 4 , Figure 4 A schematic flowchart of an embodiment of the method for color decoration of the outer surface of a smart ring provided in this application, which involves coating an ultraviolet-cured ink onto the surface of a diamond-like carbon film substrate to form an uncured colored coating, is shown. This embodiment includes: S401. Nano-alumina particles, inorganic coloring pigments and UV-curable resin system are mixed and treated, and then ground and dispersed to obtain UV-curable ink; Nano-alumina particles, inorganic coloring pigments, and UV-curable resin system are mixed in a preset ratio. After thorough stirring, the mixture is ground and dispersed to ensure that each component is uniformly dispersed in the resin system, resulting in a uniform and stable UV-curable ink.

[0051] Nano-alumina particles, acting as reinforcing fillers, significantly improve the surface hardness and scratch resistance of the colored layer after curing. Inorganic coloring pigments impart the target color to the coating and can be selected according to decorative needs; for example, iron oxide red produces red, cobalt blue produces blue, chromium oxide green produces green, titanium oxide white produces white, and carbon black produces black. Different pigments can be mixed in any proportion to create a rich variety of intermediate shades. The UV-curable resin system includes components such as a resin matrix, reactive diluent, and photoinitiator. After grinding, the solid particles in the ink are refined to a preset fineness and uniformly dispersed.

[0052] S402. Transfer UV-curable ink to a printing device and print it onto the surface of the activated diamond-like carbon film substrate to form an uncured colored coating.

[0053] The prepared UV-curable ink was transferred to a printing apparatus. The ring casing, after being activated by oxygen plasma, was fixed at the printing station. The ink was then uniformly coated onto the surface of the diamond-like carbon film substrate using screen printing. During the coating process, the polar functional groups in the resin matrix and reactive diluent of the ink interacted with the oxygen-containing functional groups such as hydroxyl and carboxyl groups introduced onto the activated surface, laying the molecular-level contact foundation for the formation of strong chemical bonds during the curing stage. After coating, a uniform, consistent uncured colored coating was obtained.

[0054] To further enrich the decorative effect, the printing and coating process can employ a multi-color gradient effect using a multi-overprinting technique. Specifically, a screen printing plate with gradient dots is used to repeatedly overprint the activated diamond-like carbon film substrate, resulting in a multi-layered coating structure. Between adjacent prints, the previous layer is pre-cured to a semi-cured state, preventing color crosstalk caused by interlayer dissolution while preserving unreacted active functional groups on the surface. After all overprints are completed, the multi-layer coatings are simultaneously subjected to UV curing, causing unreacted functional groups at the interfaces of adjacent coatings to cross-link and interpenetrate, forming chemically bonded interlayer interfaces and ensuring strong bonding between each color sublayer.

[0055] In this embodiment, ink is prepared by mixing and grinding nano-alumina particles, inorganic coloring pigments, and a UV-curable resin system. This ink is then screen-printed onto the surface of a diamond-like carbon film substrate activated by oxygen plasma, achieving functional integration of the ink formulation and interfacial synergy in the coating process. Specifically, the nano-alumina particles are uniformly anchored in the cross-linked network after curing, enhancing the surface hardness of the colored layer. The flexible selection and formulation of inorganic coloring pigments endow the coating with rich color expression capabilities. Furthermore, the polar functional groups of the resin matrix and reactive diluent in the ink pre-bond with the oxygen-containing functional groups introduced from the activated surface during the coating process, laying the foundation for the formation of chemically bonded interfaces during the curing stage. In addition, through multiple overprinting and pre-curing processes, multi-color gradient decorative effects can be achieved. Unreacted functional groups at adjacent coating interfaces undergo cross-linking and interpenetration during final curing to form chemical bonds, ensuring the robustness of the multi-layer coating structure.

[0056] This application also provides a titanium alloy smart ring, including a ring housing, the outer surface of which has a multilayer decorative coating prepared by the color decoration method of any of the above embodiments.

[0057] Please see Figure 5 , Figure 5 This is a schematic diagram of the structure of the multilayer decorative coating of the titanium alloy smart ring provided in this application. The multilayer decorative coating, from the inside out, includes: a substrate surface layer 501, a titanium transition layer 502, a diamond-like carbon film underlayer 503, and a nano-ceramic color layer 504 formed by UV-curing ink. The diamond-like carbon film underlayer 503 and the nano-ceramic color layer 504 have a chemically bonded interface of oxygen-containing functional groups introduced through oxygen plasma activation treatment.

[0058] In the multilayer decorative coating, the substrate surface layer 501 is an activated surface formed by cleaning and ion beam bombardment, with a roughness Ra not exceeding 0.05 μm. A titanium transition layer 502, with a thickness of 50-100 nm, is disposed above the substrate surface layer 501. It serves as a stress buffer and bonding reinforcement layer between the titanium alloy substrate and the diamond-like carbon film underlayer 503. Due to its metallurgical compatibility with the substrate (both are titanium-based materials), it achieves a strong interfacial bond, while effectively alleviating interfacial stress caused by differences in thermal expansion coefficients and lattice mismatch between the carbon film and the metal substrate. The diamond-like carbon film underlayer 503, with a thickness of 1-3 μm, is disposed above the titanium transition layer 502 and has a microhardness exceeding HV2000, providing diamond-like carbon-level core wear-resistant protection for the outer surface of the ring. A nano-ceramic colored layer 504, with a thickness of 5-15 μm, is disposed on top of a diamond-like carbon film substrate 503. It is formed by coating and UV-curing an ink containing nano-alumina particles and inorganic pigments, providing the ring's outer surface with the desired diverse color decorative effects. The total thickness of the entire multilayer decorative coating does not exceed 18 μm. A chemical bonding interface of oxygen-containing functional groups, introduced through oxygen plasma activation treatment, exists between the diamond-like carbon film substrate 503 and the nano-ceramic colored layer 504. This interface ensures the integrity and stability of the multilayer structure during long-term use.

Claims

1. A method for color decoration on the outer surface of a smart ring, characterized in that, The method includes: The outer surface of the ring casing is cleaned and activated to obtain a base surface layer; A titanium transition layer is deposited on the surface of the substrate, and a diamond-like carbon film underlayer is deposited on the titanium transition layer using a magnetron sputtering process. The surface of the diamond-like carbon film substrate is subjected to oxygen plasma activation treatment, and oxygen-containing functional groups are introduced on the surface of the diamond-like carbon film substrate, so that the water contact angle of the treated diamond-like carbon film substrate surface is reduced to below a preset angle. An uncured colored coating is obtained by coating the surface of the diamond-like carbon film substrate with an ultraviolet-cured ink containing nano-alumina particles and inorganic coloring pigments. The colored coating is subjected to ultraviolet light curing treatment to obtain a nano-ceramic colored layer.

2. The color decoration method according to claim 1, characterized in that, The oxygen plasma activation treatment of the surface of the diamond-like carbon film substrate, which introduces oxygen-containing functional groups onto the surface of the diamond-like carbon film substrate, includes: The ring shell with the diamond-like carbon film deposited on it is placed in a plasma processing chamber, and the chamber is evacuated and oxygen is introduced. Radio frequency power is applied to the oxygen in the cavity to excite it, thereby generating oxygen plasma; The surface of the diamond-like carbon film substrate is exposed to the oxygen plasma for surface bombardment treatment, which causes the carbon-hydrogen bonds on the surface to break. Based on the chemical reaction between oxygen plasma and the surface, oxygen-containing functional groups are introduced into the surface of the diamond-like carbon film substrate.

3. The color decoration method according to claim 1, characterized in that, The process of cleaning and activating the outer surface of the ring casing to obtain a base surface layer includes: The ring casing was ultrasonically cleaned sequentially using acetone, anhydrous ethanol, and deionized water. After cleaning and drying, the ring shell is bombarded with an argon ion beam under vacuum conditions to remove the original oxide layer and make the surface roughness Ra not exceed 0.05 μm.

4. The color decoration method according to claim 1, characterized in that, The process of depositing a titanium transition layer on the surface of the substrate, and depositing a diamond-like carbon film underlayer on the titanium transition layer using a magnetron sputtering process, includes: The pretreated ring shell is placed under vacuum conditions, and a titanium transition layer is pre-deposited on the surface layer of the substrate by magnetron sputtering. The ring casing after depositing the titanium transition layer is placed in a hydrogen-containing atmosphere, and a diamond-like carbon film is deposited on the surface of the titanium transition layer. The content of diamond phase carbon in the diamond-like carbon film is controlled to a preset ratio.

5. The color decoration method according to claim 1, characterized in that, The process of coating the surface of the diamond-like carbon film substrate with a UV-curable ink containing nano-alumina particles and inorganic coloring pigments to obtain an uncured colored coating includes: Nano-alumina particles, inorganic coloring pigments, and UV-curable resin system are mixed and then dispersed to obtain UV-curable ink. The UV-curable ink is transferred to a printing device to print and coat the activated diamond-like carbon film substrate surface to form an uncured colored coating.

6. The color decoration method according to claim 5, characterized in that, The inorganic coloring pigment is selected from one or more combinations of iron oxide red, cobalt blue, chromium oxide green, titanium dioxide, and carbon black.

7. The color decoration method according to claim 5, characterized in that, The printing coating process includes: The activated diamond-like carbon film substrate is subjected to multiple overprinting processes using a screen printing plate with gradient dots to obtain a multi-layered coating structure; wherein, between two adjacent printings, the previous layer of coating is pre-cured to achieve a semi-cured state. After all the overprinting is completed, the multilayer coatings are subjected to the ultraviolet curing treatment together, so that the unreacted functional groups at the interface of adjacent coatings cross-link and interpenetrate, and form a chemically bonded interlayer interface based on the cross-linking and interpenetration.

8. A titanium alloy smart ring, comprising a ring casing, characterized in that, The outer surface of the ring casing has a multilayer decorative coating prepared by any one of the color decoration methods according to claims 1 to 7.

9. The titanium alloy smart ring according to claim 8, characterized in that, The multilayer decorative coating, from the inside out, includes: a substrate surface layer, a titanium transition layer, a diamond-like carbon film bottom layer, and a nano-ceramic colored layer formed by UV-curable ink; The diamond-like carbon film substrate and the nano-ceramic colored layer have an oxygen-containing functional group chemical bonding interface introduced through oxygen plasma activation treatment.

10. The titanium alloy smart ring according to claim 9, characterized in that, The substrate surface layer is an activated surface formed by cleaning and ion beam bombardment, and its roughness Ra does not exceed 0.05 μm; The thickness of the titanium transition layer is 50~100nm; The thickness of the diamond-like carbon film substrate is 1~3μm; The thickness of the nano-ceramic colored layer is 5~15μm.

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