Polymeric Substrate Gradient Tinting Using UV Photodegradation
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Solution Overview
Problem
Current methods for tinting polymeric substrates, such as polycarbonate lenses, fail to achieve gradient tints effectively, either using aggressive solvents, complex apparatus, or limited gradient types, and often compromise the substrate's surface or safety.
Innovation Solution
A method involving UV photodegradation of the substrate surface to create a gradient thickness layer, followed by dyeing with a dyeing agent, allowing for linear or geometrical gradient tinting without aggressive solvents or complex equipment, and maintaining the substrate's properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If uniform UV irradiation is applied to the substrate surface, then the substrate can be photodegraded and dyed, but the result is uniform colour across the entire surface rather than gradient tint
Solution Approach 1:
The patent applies local quality by creating a gradient thickness photodegraded layer where different regions of the substrate surface have different layer thicknesses. This is achieved by controlling UV irradiation exposure time or intensity across the substrate surface, resulting in varying degrees of photodegradation that allow differential dye absorption and create gradient tint effects.
Solution Approach 2:
The patent employs preliminary action by first photodegrading the substrate surface to create a gradient thickness layer before applying the dye. This pre-treatment modifies the substrate surface properties in advance, creating regions with different dye receptivity that will produce the desired gradient tint when exposed to the dyeing agent.
2Manufacturing precision
If impregnating solvents are used to achieve gradient tint by varying contact time, then linear gradient can be obtained, but the method uses aggressive solvents that are unsafe and not suitable for ophthalmic application
Solution Approach 1:
The patent converts the harmful effect of aggressive solvents into a beneficial photodegradation process using UV irradiation. Instead of using chemical solvents that attack and potentially damage the substrate, the method uses controlled UV light to create a gradient thickness photodegraded layer that safely enables gradient dye absorption without the safety concerns of aggressive chemical solvents.
Solution Approach 2:
The patent changes the fundamental parameter from chemical solvent-based gradient control to physical UV irradiation-based gradient control. By varying UV exposure parameters (time, intensity, wavelength) across the substrate surface, the method achieves gradient tint without requiring impregnating solvents, thereby eliminating solvent safety issues while maintaining gradient precision.
3Manufacturing precision
If the substrate is gradually immersed and withdrawn from dying bath, then linear gradient in tint density is obtained, but annular gradient cannot be achieved
Solution Approach 1:
The patent transitions from one-dimensional linear gradient control (through immersion/withdrawal) to two-dimensional gradient control by applying UV irradiation across the substrate surface in different spatial patterns. This allows annular, radial, or other complex gradient patterns to be created by controlling the spatial distribution of UV exposure, enabling multiple gradient types with the same basic apparatus.
4Manufacturing precision
If heating furnace is used to diffuse dye into lens with varying temperature, then gradient imbibition is achieved, but the method is difficult to carry out and does not produce regular tint gradient
Solution Approach 1:
The patent replaces the complex thermal field control system (heating furnace with varying temperature zones) with a simpler optical field control system (UV irradiation source with controllable exposure). This substitution simplifies the manufacturing process while achieving more regular and predictable gradient patterns, as UV exposure can be more precisely controlled spatially and temporally compared to thermal diffusion.
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
The method enables stable, time-resistant gradient tinting on polymeric substrates, including polycarbonate lenses, with linear or geometrical gradients, ensuring the substrate's integrity and safety, and is adaptable for various polymeric materials.
Implementation Method 1
irradiating a least one face of the substrate with UV radiation causing the surface of the substrate to be photodegraded over a determined thickness
Implementation Method 2
contacting the irradiated face of the substrate with a colouring agent so as to diffuse the colouring agent in the entire thickness of the photodegraded surface layer of the substrate
Data Source
Figure 1~2
Figure 3~4c
Figure 5a~5c2
AI summary
A method for dyeing a transparent article made of a polymeric substrate with gradient tint comprising: a) a first step of photodegrading the polymeric substrate (1) of the transparent article, by irradiation (3) of at least one first surface of the article to UV radiations to produce a gradiently photodegraded surface layer of the polymeric substrate, and b) a second step of dyeing said first face of the article with a dyeing agent so as to diffuse said dyeing agent into the gradiently photodegraded surface layer of the polymeric substrate.