Lens Coating Spatula Tilt Angle for Edge Adhesion Control
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Solution Overview
Problem
The existing methods for applying photochromic coatings to lenses often result in irregular thickness, optical distortion, and peeling issues due to the high viscosity of the coating solution, which adheres to the side and back surfaces, causing defects and requiring cumbersome post-treatment polishing.
Innovation Solution
A method involving a spatula tilted towards the center of the lens is used to remove excess photochromic coating solution before it reaches the edge, ensuring it doesn't adhere to the side or back surfaces, utilizing a photocurable coating solution with viscosity between 80 to 1000 centipoises and spreading it using a flexible film while rotating the lens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a photochromic coating solution with high viscosity (25 to 1000 centipoises) is used to ensure sufficient photochromic properties, then the coating can maintain a thickness of not less than 5 μm, but the coating solution adheres to the side and back surfaces of the lens, causing irregular thickness and optical distortion
Solution Approach 1:
The spatula is positioned to contact the outer circumferential edge portion of the lens before the coating solution reaches that area. This preliminary positioning allows the spatula to prevent the high-viscosity coating solution from adhering to the side and back surfaces before the problem occurs, thereby maintaining coating uniformity without requiring post-treatment polishing
Solution Approach 2:
The spatula acts as an intermediary tool between the coating solution application process and the lens. By being tilted at a specific angle (30 to 60 degrees) and positioned at the outer circumferential edge, the spatula intercepts and redirects the high-viscosity coating solution, preventing it from flowing onto areas where it would cause defects
2Reliability
If the coating solution is applied to ensure sufficient coverage and photochromic properties, then the coating thickness can be maintained at not less than 5 μm, but post-treatment polishing is required to remove defects, increasing manufacturing complexity and time
Solution Approach 1:
The spatula is positioned in advance to contact the lens edge before coating solution overflow occurs. This preliminary intervention prevents the formation of defects that would otherwise require post-treatment polishing, thereby simplifying the manufacturing process while maintaining coating quality
Solution Approach 2:
The spatula extracts or removes the excess coating solution from the system before it can adhere to the side and back surfaces of the lens. By taking out the problematic excess solution at the point of application, the need for subsequent removal processes like polishing is eliminated
3Manufacturing precision
If a tilted spatula is used to remove excess coating solution at the outer circumferential edge, then coating uniformity is improved and adhesion to side surfaces is prevented, but the device complexity increases
Solution Approach 1:
The spatula is positioned specifically at the outer circumferential edge portion of the lens, where the coating solution tends to overflow. The localized positioning at this critical area allows the spatula to effectively prevent adhesion to side surfaces without requiring complex mechanisms, as the intervention is focused only where needed
Solution Approach 2:
The spatula is tilted at an asymmetric angle (30 to 60 degrees) relative to the lens surface rather than being perpendicular. This asymmetric tilting creates an optimal geometry for intercepting the coating solution flow and directing it away from the side surfaces, improving effectiveness while using a simple angular adjustment
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach prevents the coating solution from adhering to the side and back surfaces, eliminating defects and the need for post-treatment polishing, resulting in high-quality lenses with uniform coatings and improved yield.
Implementation Method 1
forming a coating on the surface of the lens by the spin coating by injecting, onto the surface of the lens, a coating solution from a nozzle of a container containing the photochromic coating solution while rotating the lens
Implementation Method 2
The photocurable coating solution has a viscosity at 25°C of 80 to 1000 centipoises (cP)
Implementation Method 3
forming a coating by curing the photocurable coating solution by irradiating the lens coated with the photocurable coating solution that is spread thereon through the above step (C) with light
Implementation Method 4
A material that changes color depending upon the light can be represented by a photochromic material. The photochromic material reversibly varies the structure depending upon the incidence of ultraviolet rays
Data Source
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AI summary
A method of coating without permitting the coating solution to flow onto the side surfaces or the back surfaces of the lenses in the operation for applying the coating solution onto the lenses. A lens 15 is spin-coated with the coating solution having a particular viscosity. A side edge portion 121 of a spatula 119 is brought into contact with an upper edge portion of a side surface 15a of the lens 15 before the coating solution fed onto the surface of the lens arrives at the peripheral edge portion of the lens. The side edge portion 121 of the spatula 119 is so arranged that the upper end side of the spatula is tilted toward the center side of the lens 15 at an angle of 5 to 35 degrees with the vertical line as a reference. The coating solution applied onto the lens 15 that is rotating adheres onto the spatula 119 but does not adhere onto the side surface of the lens 15.