cover lens related knowledge
Covers are available in glass and acrylic. The acrylic cover is cheap, has high transparency, and is easy to process, but the acrylic cover has low hardness and is easy to scratch. The glass cover is the most widely used, the glass cover has high strength, and can also be strengthened and surface treated. The OGS technology is formed by plating ITO on the glass cover lens.
cover lens enhancement
The theoretical strength of ordinary flat glass is greater than 10000MPa, but the actual test results are much worse, only 50~120MPa, because defects will appear during the processing of flat glass, among which microcracks have the greatest impact on the strength.
The process of glass strengthening is the process of eliminating microcracks. The main methods are chemical strengthening and physical strengthening.
chemical strengthening
The chemical toughening of glass refers to the interdiffusion and exchange of alkali metal ions in glass with alkali metal ions in molten salt at high temperature, generating compressive stress on the glass surface to prevent the expansion of cracks.
Physical Enhancement Technology
By heating the glass to a certain tempering initial test temperature (critical temperature), the two surfaces are quickly and evenly cooled, so that the glass surface forms a prestressed system, thereby improving the mechanical strength of the glass. It is the most widely used strengthening technology to make glass produce surface compressive stress and intermediate tensile stress balance system through heat treatment.
The test method of glass strength usually adopts four-axis bending test and small ball drop test. LCD panel also has four-axis bending test to ensure the strength of tft display.
IR transparent ink
IR ink can pass through infrared rays while shielding visible light and ultraviolet rays. Light with a wavelength of 900-1100nm in the infrared can pass through. IR ink also has a certain shielding ability, so that it can receive infrared rays and is more beautiful.
AG (anti-glare) process
Anti-glare is a treatment that creates a rough surface on the cover lens through an etching process or a spraying process. Compared with ordinary glass, it has a lower reflectance, thereby reducing the interference of ambient light and reducing the reflection of the screen. After using AG treatment, the product will have better readability in bright environments.
The cover lens without anti-glare treatment will reflect light and affect the display.
The anti-glare treated cover lens diffuses light.
Six Important Parameters of Anti-Glare
Hazz
Transmittance
Gloss
particle size
hardness
Wear-resistant
There are two ways to achieve anti-glare: surface etching process and spraying process.
The surface etching process is to etch out lines or pits on the smooth glass surface. This process has a long life and good effect, but the glass etching agent will pollute the environment and the cost is high.
The spraying process is to spray the agent on the surface of the glass, and heat to evaporate the solvent to form an uneven surface (picture on the left). The spraying process is simple and the price is relatively low.
Main components of spraying anti-glare
| Main components | proportion |
| silicon dioxide | 0-2% |
| Isopropyl alcohol | 80-90% |
| ethanol | 0-5% |
| water | 0-5% |
Manufacturing process of spraying anti-glare
Cover lens printing
Cover lens washing and drying
Cover lens preheating 120-150 ℃
AG spraying, and heat preservation of 100℃.
Heat curing at 200℃ for 60min.
Spray anti-glare performance
| item | Performance |
| Adhesion | 100 grid test: normal product (unboiled) → 5B Boil in boiling water for 3 hours → 5B |
| Gloss | 20GU-120GU |
| Transmittance | 92%-93% |
| pencil hardness test | After spraying: 7-9H |
AR (anti-reflection) process
Anti-reflection is the process of coating a specific thickness of film or coating on the surface of the protective mirror. Because the film is reflected back to the customer, its reflection on the surface is reduced by the cancellation of specific wavelengths of light. When light of a specific wavelength passes through an AR object, some of it is reflected back to the surface of the AR film (R1) and some of it is reflected to the surface of the cover (R2). Due to the thickness of the anti-reflection coating, the reflected wavelengths R1, R2 are reflected completely out of phase with each other and cancel each other out. As a result, consumers will see the brighter, sharper display rather than their own reflection.
AF/AS (Anti-fingerprint/Anti-smudge) process
This treatment reduces the shield’s ability to keep oils from getting into your fingers. Anti-fingerprint/anti-smudge treatment is done by vacuum decomposition or liquid chemical process. AF/AS processing does not completely remove fingerprints. It’s just an oleophobic layer that keeps the oil from your fingers from adhering.
No anti-fingerprint coating
Anti-fingerprint coating
Manufacturing process of spraying Anti-fingerprint/Anti-smudge
Cover lens ultrasonic washing and drying
Plasma clear and atmospheric pressure spraying
Heating, drying and curing.
Inspection and testing
Performance of spray anti-fingerprint coating
| test item | Spray anti-fingerprint coating |
| Water Contact Angle | 113° |
| Water Sliding Angle | 8° |
| Steel Wool Abrasion | 3000 Cycles |
| Rubber Eraser brasion | 3000 |
More Resources:
Chemically strengthened glass– Source: Wikipedia
Anti-reflective coating– Source: Wikipedia
