Lens surface treatment process

Abstract

The invention discloses a lens surface treatment process which sequentially comprises the following steps: carrying out injection molding on polycarbonate plastic to obtain a lens; coating a first optical organic silicon hardening coating on the surface of the lens; performing optical vacuum coating on the lens with the first coating to form a coating layer; carrying out ion bombardment cleaning on the coating layer by using inert gas under vacuum / high vacuum, removing pollutants and generating an activated microstructure so as to improve the adhesive force of a subsequent coating; coating a second optical organic silicon hardening coating on the surface of the bombarded coating layer; and cooling to room temperature to obtain a finished product. The process breaks through the bottleneck that an organic silicon coating cannot be secondarily coated after traditional film coating, a composite protection system is formed, the abrasion resistance and firmness of a lens film layer are remarkably improved, the film layer is prevented from being abraded and faded, the problem of electrostatic reaction of a film coating layer and an electrostatic protection film is solved, the process is suitable for helmet lenses, goggles and the like, and the process is stable and easy to industrialize.

Description

Technical Field

[0001] This invention relates to the field of plastic optical element surface treatment technology, and particularly to a complete production line process for further improving the wear resistance and fading resistance of polycarbonate (PC) helmet lenses, goggles, ski goggles, and other lens surfaces after high-vacuum optical coating, and allowing for the coating of an organosilicon protective layer. Background Technology

[0002] In sports protection and outdoor work scenarios, polycarbonate (PC plastic) is often used as the core substrate for optical products such as helmet lenses, goggles, swimming goggles, and ski goggles. PC plastic has become the preferred material for these optical products due to its excellent impact resistance, lightweight, and light transmittance. However, it also has technical drawbacks such as low surface hardness, easy wear, and difficulty in achieving both "color diversity" and "durability" with a single surface treatment. These factors have driven the industry to continuously explore surface modification processes.

[0003] In existing technologies, to improve the abrasion resistance and adhesion of PC plastic lenses, the industry generally first coats the lens surface with an optical silicone hardening coating (commonly known as a "reinforced coating"). Utilizing the cross-linking and curing properties of silicone resin, a dense protective layer is formed on the lens surface, initially improving its scratch resistance. Building upon this, to meet users' demands for personalized lens colors and functionalities (such as light blocking and anti-glare), a thin film (such as titanium pentoxide, silicon dioxide, zirconium oxide, or silicon-aluminum mixtures) is further deposited on the surface of the optical silicone hardening coating using an optical vacuum coating process. This allows the lenses to exhibit diverse colors or specific optical properties. This combined process of "silicone hardening + optical vacuum coating" has become a standard industry practice.

[0004] However, the aforementioned conventional process has significant technical defects, which severely restrict the quality and user experience of the finished lenses. The specific problems are as follows: 1. Insufficient film adhesion and abrasion resistance: The adhesion between the film formed by optical vacuum coating and the underlying optical silicone hardening coating is limited, and the density of the coating layer itself is easily affected by trace impurities in the vacuum environment. As a result, the finished lens is very prone to film wear and peeling during daily use (such as wiping or slight impact), which in turn causes the lens color to fade or become distorted, greatly shortening the product's service life.

[0005] Poor compatibility with electrostatic protective film: To prevent lenses from being contaminated by dust and scratches during storage and transportation, the industry typically uses electrostatic protective film for packaging. However, in conventional processes, the surface of the film layer after optical vacuum coating has a large number of active groups, which are prone to electrostatic adsorption reactions when in contact with the electrostatic protective film. This not only damages the color uniformity of the film surface, but may also leave marks on the lens surface or remove part of the coating layer when the protective film is peeled off, resulting in product marks or even scrap.

[0006] The inability to perform secondary optical silicone hardening coating processing: If an attempt is made to solve the wear resistance problem of the coating layer by applying a secondary optical silicone hardening coating, the coating layer will not adhere effectively due to its smooth surface and the presence of trace oxides and mineral residues. The coating is prone to sagging, pinholes, or delamination after curing, ultimately failing to form an effective protective structure. This technical bottleneck makes it difficult for conventional processes to further improve the durability of the lens.

[0007] To address the aforementioned issues, the industry has attempted to improve film performance by optimizing the vacuum level of optical vacuum coating and adjusting the ratio of coating materials. However, none of these methods have addressed the core problem of insufficient adhesion between the coating surface and the secondary silicone coating. Other solutions have attempted to remove surface impurities using chemical cleaning processes under normal pressure after coating, but this environment easily leads to oxidation of the coating and cannot alter its surface microstructure, thus failing to provide an effective foundation for the secondary coating. Therefore, existing PC plastic lens surface treatment processes urgently need an innovative technological solution that can overcome these bottlenecks while also considering color diversity, high abrasion resistance, and packaging compatibility. Summary of the Invention

[0008] In view of the shortcomings of the prior art, the present invention provides a lens surface treatment process.

[0009] The technical solution adopted in this invention is: a lens surface treatment process, which includes the following steps in sequence: (a) Providing lenses: The required lens is obtained by injection molding using polycarbonate plastic as raw material; (b) First coating: A first layer of optical silicone hardening coating is applied to the surface of the lens; (c) Optical vacuum coating: Optical vacuum coating is performed on the lens with the first organosilicon hardened layer to form a coating layer on the lens surface; (d) Ion bombardment: Under the condition of maintaining vacuum or restoring high vacuum, the coating layer is cleaned by ion bombardment with inert gas to remove surface contaminants and generate activated microstructure, thereby improving surface hydrophilicity and the adhesion of subsequent coatings. (e) Secondary coating: A second optical silicone hardening coating is applied to the surface of the coating layer after ion bombardment cleaning; (f) Finished product: Cool to room temperature to obtain the finished lens.

[0010] Furthermore, the coating thickness is 3nm–10nm, and it is pre-dried at 60–70℃ for 2–10 min and then cured at 110–130℃ for 1.5–2.5 h to form a first organosilicon hardened layer.

[0011] Furthermore, in step (c), the optical vacuum coating is carried out in an environment with a vacuum degree ≤1.0×10-3Pa, where 5–10 optical thin films are deposited sequentially, with a total physical thickness of 400 nm–1.3 μm, to obtain a coating layer with predetermined spectral properties.

[0012] Furthermore, the inert gas in step (d) is Ar. + Ions, Ar + The ion bombardment step uses a Hall ion source or a Kaufman ion source, with bombardment energies of 200–1200 eV and beam current densities of 0.2–1.0 mA / cm². 2 .

[0013] Furthermore, the second optical silicone hardening coating has a thickness of 3 nm–10 nm, and is pre-dried again at 60–70°C for 2–10 min and then cured at 110–130°C for 1.5–2.5 h to form a second silicone protective layer.

[0014] Furthermore, the first and second optical silicone hardening coatings are silicone resin alcohol solutions of the same system, with a solid content controlled between 29wt% and 31wt%.

[0015] Furthermore, the optical vacuum coating is achieved using ion-assisted deposition or sputtering deposition, with a single-layer film thickness of 30nm-150nm.

[0016] Furthermore, the duration of ion bombardment in step (d) is 5–15 min, and the ion bombardment cleaning process is carried out in a vacuum environment with a vacuum degree of less than or equal to 5.0 × 10⁻³ Pa.

[0017] Furthermore, before applying the second layer of optical silicone hardening coating, the optical silicone coating stock solution for the optical silicone hardening coating is filtered using a 1μm or 2μm polypropylene pleated filter for at least 2 hours.

[0018] The beneficial effects of this invention are: 1. Significantly improves coating durability: Through the innovative combination of "ion bombardment after optical vacuum coating + secondary organosilicon coating", the problem of poor wear resistance and easy color peeling of traditional coating processes is solved, which greatly enhances the adhesion of the lens coating and significantly improves its scratch resistance and wear resistance in daily use, thus extending the product's service life.

[0019] 2. Solving the compatibility problem of electrostatic protective film: The secondary silicone coating forms a protective barrier on the surface of the coating layer, avoiding electrostatic reaction between the coating layer and the electrostatic protective film. This allows the electrostatic protective film to be safely attached to the lenses during storage and transportation, preventing damage to the film color and reducing the product scrap rate.

[0020] 3. Breakthrough in secondary coating technology bottleneck: Ion bombardment process in a vacuum environment can effectively remove oxides and mineral residues from the surface of the coating layer and increase surface roughness, laying the foundation for secondary silicone coating processing and breaking the limitation that traditional processes cannot apply a secondary silicone coating after coating.

[0021] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The present invention will be further described in detail below with reference to embodiments. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. This invention provides a lens surface treatment process.

[0024] Reference Figure 1 The lens surface treatment process includes the following steps in sequence: (a) Providing lenses: The required lens is obtained by injection molding using polycarbonate plastic as raw material; (b) First coating: A first layer of optical silicone hardening coating is applied to the surface of the lens; (c) Optical vacuum coating: Optical vacuum coating is performed on the lens with the first organosilicon hardened layer to form a coating layer on the lens surface; (d) Ion bombardment: Under the condition of maintaining vacuum or restoring high vacuum, the coating layer is cleaned by ion bombardment with inert gas to remove surface contaminants and generate activated microstructure, thereby improving surface hydrophilicity and the adhesion of subsequent coatings. (e) Secondary coating: A second optical silicone hardening coating is applied to the surface of the coating layer after ion bombardment cleaning; (f) Finished product: Cool to room temperature to obtain the finished lens.

[0025] The above technical solution uses polycarbonate (PC) plastic as the substrate and constructs a multi-layer protective structure through a complete process: "injection molding → initial optical silicone hardening coating → optical vacuum coating → inert gas ion bombardment under vacuum / high vacuum → secondary optical silicone hardening coating → cooling". The core principle is that ion bombardment, in a vacuum environment, utilizes the high-energy impact of inert gas ions to remove contaminants such as oxides and mineral residues from the coating surface. Simultaneously, it forms activated microstructures (such as micro-pits) on the film surface, overcoming the technical bottleneck of insufficient adhesion between the coating layer and the secondary coating in traditional processes, and achieving a continuous processing of "hardening-coating-re-hardening".

[0026] Breaking through the limitations of traditional processes where a second silicone coating cannot be applied after the initial coating, this invention forms a composite protective system of "double-layer silicone coating + intermediate coating layer." This significantly improves the surface abrasion resistance and coating adhesion of the lens, preventing wear and fading during daily use. It also solves the problem of electrostatic reaction between the coating layer and the electrostatic protective film, ensuring safe attachment of the protective film during lens storage and transportation, thus reducing product scrap rates. The process is compatible with PC plastic substrates and can be widely used in various optical products such as helmet lenses and goggles, demonstrating strong compatibility.

[0027] Specifically, the coating thickness is 3nm–10nm, and it is pre-dried at 60–70℃ for 2–10 min and then cured at 110–130℃ for 1.5–2.5 h to form the first organosilicon hardened layer.

[0028] By limiting the first layer of optical silicone hardening coating to a thickness of 3nm–10nm and a pre-drying time of 60–70℃ for 2–10 min followed by curing at 110–130℃ for 1.5–2.5 h, the cross-linking curing characteristics of silicone resin at specific temperatures are utilized: the pre-drying stage removes alcohol solvents from the coating to prevent bubbles and pinholes caused by rapid solvent evaporation during curing; the high-temperature curing stage promotes full cross-linking of resin molecules to form a dense and uniform film structure, while controlling the thickness within the range suitable for PC substrates to avoid cracking or decreased light transmittance caused by excessive coating thickness.

[0029] Specifically, in step (c), the optical vacuum coating is carried out in an environment with a vacuum degree ≤1.0×10-3Pa, where 5–10 optical thin films are deposited sequentially, with a total physical thickness of 400 nm–1.3 μm, to obtain a coating layer with predetermined spectral properties.

[0030] "Vacuum degree ≤ 1.0 × 10" -3In a high vacuum environment of "Pa", 5–10 layers of optical thin films (total physical thickness 400nm–1.3μm) are deposited. The high vacuum environment can reduce the interference of water vapor and oxygen in the air on the coating process and avoid defects such as oxidation and scattering in the film. The multilayer thin film achieves the predetermined spectral performance (such as transmittance and reflectance at a specific wavelength) by alternating deposition of different optical materials (such as high refractive index and low refractive index materials) using the principle of light interference, while controlling the total thickness within the range that adapts to the optical performance and structural stability.

[0031] Specifically, the inert gas in step (d) is Ar. + Ions, Ar + The ion bombardment step uses a Hall ion source or a Kaufman ion source, with bombardment energies of 200–1200 eV and beam current densities of 0.2–1.0 mA / cm². 2 .

[0032] The inert gas bombarded by ions is Ar. + "Ions" Independent Kaufman ion source; "Bombardment energy 200–1200 eV"; "Beam current density 0.2–1.0 mA / cm²" 2 ”:Ar + The ions are chemically inert, avoiding reaction with the coating layer. The Kaufman ion source can achieve focused ion beam scanning. Both methods can precisely control the ion energy and beam density. Too low an energy will not effectively remove contaminants and activate the surface, while too high an energy will easily damage the coating layer. Beam density control ensures uniform bombardment and avoids local over-etching.

[0033] Specifically, the second layer of optical silicone hardening coating has a thickness of 3 nm–10 nm, and is pre-dried again at 60–70°C for 2–10 min and then cured at 110–130°C for 1.5–2.5 h to form a second silicone protective layer.

[0034] The second coating uses the same "3nm–10nm thickness" and "pre-drying + curing" parameters as the first silicone coating layer, and utilizes the same silicone resin cross-linking curing mechanism: when the second coating is spread on the surface of the ion-bombarded activated coating layer, the resin molecules can combine with the activated groups (such as dangling bonds) on the surface of the coating layer. At the same time, by controlling the same temperature parameters, it is ensured that the second coating is tightly bonded to the intermediate coating layer and that the thickness matches that of the first layer, so as to avoid uneven stress and film cracking caused by the difference in thickness between the two layers.

[0035] Specifically, the first and second optical silicone hardening coatings are silicone resin alcohol solutions of the same system, with solid content controlled between 29wt% and 31wt%.

[0036] The first and second optical silicone hardening coatings are made of the same silicone resin alcohol solution with a solid content of 29wt%–31wt%. The same resin system ensures the chemical compatibility of the two coatings and avoids interfacial reactions caused by differences in composition. The solid content is controlled by adjusting the ratio of resin to alcohol solvent to ensure that the coating has a suitable viscosity (6–12cp) during coating, which can spread evenly (suitable for dip / coating processes) and form a film of a predetermined thickness after curing. This avoids the coating being too thick due to excessive solid content and too thin due to insufficient wear resistance due to excessive solid content.

[0037] Specifically, the optical vacuum coating is achieved by ion-assisted deposition or sputtering deposition, with a single-layer film thickness of 30nm-150nm.

[0038] The optical vacuum coating process is limited to "ion-assisted deposition / sputtering deposition": Ion-assisted deposition uses an ion beam to bombard the growing film layer during the coating process, making the atomic arrangement of the film layer more compact; sputtering deposition uses plasma to bombard the target material, making the target material atoms uniformly deposited on the substrate surface. Both methods can improve the film layer density and adhesion.

[0039] Specifically, the duration of ion bombardment in step (d) is 5–15 min, and the ion bombardment cleaning process is carried out in a vacuum environment with a vacuum degree of less than or equal to 5.0 × 10⁻³ Pa.

[0040] Ion bombardment duration 5–15 min, vacuum level better than 5.0 × 10⁻⁶. -3 Pa”: High vacuum environment reduces the interaction between gas molecules and Ar. + Ion collisions ensure that ions reach the surface of the coating layer with sufficient energy; if the bombardment time is too short, contaminants will not be completely removed and the surface activation will be insufficient, while if it is too long, it will easily lead to loss of coating layer thickness or excessive surface roughness; a duration of 5–15 minutes can achieve a balance between "thorough cleaning and activation" and "protection of coating layer integrity".

[0041] Specifically, the ion bombardment cleaning process employs either a DC glow discharge method or an independent ion source method.

[0042] Two specific methods for ion bombardment cleaning: DC glow discharge uses a mirror as a cathode to form a uniform plasma region in a vacuum chamber, Ar... + Ion bombardment of the lens surface from all directions is suitable for the simultaneous processing of multiple lenses in mass production; independent ion sources (such as Kaufman sources) extract a focused ion beam through a grid, which can achieve precise bombardment of the lens surface through a scanning mechanism, suitable for processing high-precision optical lenses (such as ski goggles and sports glasses). Both methods are based on the core principle of "high-energy ion bombardment," differing only in the ion generation and distribution methods, and are adapted to different production needs.

[0043] Specifically, before applying the second layer of optical silicone hardening coating, the optical silicone coating stock solution for the optical silicone hardening coating is filtered using a 1μm or 2μm polypropylene pleated filter for at least 2 hours.

[0044] Before applying the second silicone coating, the coating solution is filtered for at least 2 hours using a 1μm or 2μm polypropylene pleated filter cartridge. This utilizes the high-precision filtration characteristics of the polypropylene filter cartridge to intercept any tiny particles (such as undissolved resin particles or environmental dust) that may be present in the solution, preventing these particles from being applied to the coating surface and causing defects such as crystal points or scratches. The filtration time is no less than 2 hours to ensure that the solution is fully circulated and filtered, leaving no particle residue.

[0045] Helmet lens example 1: Step 1, PC Injection Molding: Using Sumitomo PC2200 resin, injection mold a 2 mm thick helmet visor. Film base film.

[0046] Step 2: Formulation of the first organosilicon hardening layer strengthening liquid: 30% methyltrimethoxysilane condensate wt%, isopropanol 70 wt%, solid content 30%.

[0047] Cleaning: 40℃ neutral detergent, ultrasonic for 60 s → 60℃ deionized water, ultrasonic for 60 s → isopropanol Rinse for 15 seconds → dry with nitrogen; Dip-coating lifting: lifting speed 30 cm / min, wet film thickness approximately 6 nm; Curing: Pre-baking at 70 ℃ for 5 min → curing at 120 ℃ for 2 h, dry film thickness 5 nm.

[0048] Step 3: Optical Vacuum Coating Equipment: Ion-assisted coating machine; Vacuum: Pumped to 5.0 × 10⁻⁶ using a mechanical pump and a molecular pump. -4 Pa; Ion cleaning: Ar + 800eV×10 min; Film system: 9-layer antireflection film system (alternating SiO2 / TiO2), controlled by optical monitoring extremum method. The total physical thickness is 850nm, and the reflectivity at 550nm is R≤0.5%.

[0049] Step 4: Ar + Ion bombardment activation, in the same vacuum chamber, maintained at 3.0 × 10⁻⁶. -3 Pa, Kauf Mann ion source 600 eV, beam current density 0.5 mA / cm² 2 After bombarding for 8 minutes, the water contact angle dropped to 22°.

[0050] Step 5: After breaking the vacuum of the second silicone protective layer, the lens is removed and immediately placed in the clean pre-coating chamber. (Cleanliness level 1000), using the same strengthening solution and parameters as in step 2, a second dip-coating and lifting process is employed, resulting in a dry film. Thickness 5nm, curing conditions same as step 2.

[0051] Step 6: Performance Testing (1) Adhesion: Cross-cut test ISO24090 grade; Peel force 5.4 N / 25 mm; (2) Abrasion resistance: 50 g of 0000# steel wool, after 100 round trips, ΔH = 0.3%; (3) Colorfastness: After applying the electrostatic protective film for 24 hours, it is quickly peeled off. Visual inspection shows no color transfer, and the color difference ΔE*ab=0.15. Example 2 (only the ion bombardment time was changed) The bombardment time in step 4 was changed to 5 minutes, and the rest remained the same as in Example 1. Peel force: 4.8 N / 25 mm, ΔH=0.45%, still meets the requirements.

[0052] Example 3 (Changing the thickness of the second silicone) Step 5: The lifting speed was changed to 20 cm / min, the dry film thickness was 3 nm, and the rest was the same as in Example 1.

[0053] Peel force 5.1 N / 25 mm, ΔH=0.35%.

[0054] Comparative Example 1 (No Ion Bombardment) Step 4 is omitted, and the second silicone is directly applied to the coating layer. The peel strength is only 1.2 N / 25 mm, and cracks appear after rubbing with your fingers 10 times.

[0055] Comparative Example 2 (without second organosilicon) Step 5 omitted; after wear resistance testing, ΔH = 1.8%; after removing the protective film, localized film peeling occurred. E*ab=1.05.

[0056] The above embodiments and comparative examples show that: only when Ar is introduced after coating... + Ion bombardment activation followed by coating with a second silicone layer is required to achieve a combination of high wear resistance, fade resistance, and the ability to apply an electrostatic protective film.

[0057] All processes of this invention can be completed in series on the basis of existing optical coating lines and hardened wire drawing lines, without the need for additional expensive equipment; the strengthening liquid and coating materials are commercially available, the process window is wide, and it is suitable for mass continuous production of helmet lenses, goggles, ski goggles, sports glasses, etc.

[0058] Please note to all technical personnel: Although the present invention has been described according to the specific embodiments above, the ideas of the present invention are not limited to this invention. Any modifications that utilize the ideas of the present invention will be included within the scope of protection of this patent.

Claims

1. A lens surface treatment process, characterized in that, The steps are as follows: (a) Providing lenses: The required lenses are obtained by injection molding from polycarbonate plastic. (b) First coating: A first layer of optical silicone hardening coating is applied to the surface of the lens; (c) Optical vacuum coating: optical vacuum coating is performed on the lens with the first organosilicon hardened layer. Empty coating, which forms a coating layer on the surface of the lens; (d) Ion bombardment: Under conditions of maintaining or restoring a high vacuum, inert gas is used to bombard the ion population. The coating layer is subjected to ion bombardment cleaning to remove surface contaminants and generate an activated microstructure. This improves the surface hydrophilicity and the adhesion of subsequent coatings; (e) Secondary coating: A second layer of silicone coating is applied to the surface of the ion-bombarded cleaned film. Hard coating; (f) Finished product: Cool to room temperature to obtain the finished lens.

2. The lens surface treatment process according to claim 1, characterized in that: The coating thickness is 3nm–10nm, and it is pre-dried at 60–70℃ for 2–10 min and then cured at 110–130℃ for 1.5–2.5 h to form the first organosilicon hardened layer.

3. The lens surface treatment process according to claim 1, characterized in that: In step (c), the optical vacuum coating is carried out in an environment with a vacuum degree ≤1.0×10-3Pa, where 5–10 optical thin films are deposited sequentially, with a total physical thickness of 400 nm–1.3 μm, in order to obtain a coating layer with predetermined spectral properties.

4. The lens surface treatment process according to claim 1, characterized in that: The inert gas in step (d) is Ar. + Ions, Ar + The ion bombardment step uses a Hall ion source or a Kaufman ion source, with bombardment energies of 200–1200 eV and beam current densities of 0.2–1.0 mA / cm². 2 .

5. The lens surface treatment process according to claim 1, characterized in that: The second layer of optical silicone hardening coating has a thickness of 3 nm–10 nm, and is pre-dried again at 60–70 °C for 2–10 min and then cured at 110–130 °C for 1.5–2.5 h to form a second silicone protective layer.

6. The lens surface treatment process according to claim 5, characterized in that: The first and second optical silicone hardening coatings are silicone resin alcohol solutions of the same system, with solid content controlled between 29wt% and 31wt%.

7. The lens surface treatment process according to claim 1, characterized in that: The optical vacuum coating is achieved by ion-assisted deposition or sputtering deposition, with a single-layer film thickness of 30nm-150nm.

8. The lens surface treatment process according to claim 1, characterized in that: The duration of ion bombardment in step (d) is 5–15 min, and the ion bombardment cleaning process is carried out in a vacuum environment with a vacuum degree of less than or equal to 5.0 × 10-3 Pa.

9. The lens surface treatment process according to claim 8, characterized in that: Before applying the second layer of optical silicone hardening coating, the optical silicone coating stock solution for the optical silicone hardening coating is filtered using a 1μm or 2μm polypropylene pleated filter for at least 2 hours.

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