High-Index Plastic Lens Dyeing With Vacuum Sublimation Control
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Solution Overview
Problem
Existing methods for dyeing plastic lenses with high refractive indices, such as those above 1.7, often result in uneven dyeing due to pigment crystallization and temperature variations, especially when using sublimation dyes without surfactants, leading to non-uniform color distribution.
Innovation Solution
A process involving coating a substrate with a sublimation dye ink at 60° C or lower, reducing the water content to 50% or less, and sublimating the dye under vacuum conditions to ensure uniform dye attachment and permeation into the lens, while controlling temperature and vacuum levels to prevent pigment crystallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a sublimation dye ink with high water content is used for coating the substrate, then the coating process is easier and the ink spreads better, but the water content varies greatly during coating leading to non-uniform dyeing
Solution Approach 1:
The substrate is pre-heated to 60°C or lower before coating, and the water content in the ink is reduced to 50% by mass or less beforehand. This preliminary preparation ensures that during the coating process, the ink maintains consistent properties and water evaporates uniformly, preventing the variation in water content per dot that occurs with high water content inks.
2Ease of manufacture
If the water content in the sublimation dye ink is high, then the ink is more fluid and easier to apply, but pigment crystallization occurs on the lens surface causing uneven dying
Solution Approach 1:
The water content in the sublimation dye ink is changed from high (greater than 50% by mass) to low (50% by mass or less). This parameter change maintains sufficient fluidity for easy application while preventing pigment crystallization on the lens surface during sublimation, thereby achieving uniform color distribution.
3Device complexity
If sublimation dyeing is performed without controlling water content, then the process is simpler, but temperature variations cause non-uniform dyeing
Solution Approach 1:
The water content in the ink is reduced to 50% by mass or less before the sublimation dyeing process. This preliminary action eliminates the need for complex temperature control measures during dyeing, as the reduced water content prevents excessive evaporation and temperature fluctuations, thereby achieving uniform dyeing with a simpler process.
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 process allows for uniform, high-density dyeing of plastic lenses with refractive indices between 1.7 and 1.8 without unevenness, ensuring consistent color distribution and optical quality.
Implementation Method 1
sublimating the sublimation dye in the ink comprising a sublimation dye coating the substrate by heating the substrate obtained after Step (2) under a degree of vacuum of 1×104 Pa or smaller to dye the plastic lens
Implementation Method 2
decreasing content of water in the ink comprising sublimation dye coating the substrate to 50% by mass or less of the entire ink
Data Source
AI summary
A process which enables a plastic lenses having a refractive index of 1.7 or greater and, in particular, plastic lenses having a refractive index of 1.7 to 1.8 to be dyed uniformly to a great density without unevenness, which is, specifically, a process for producing a dyed plastic lens which comprises conducting following steps (1), (2) and (3) in this order: Step (1): a step comprising coating a substrate at 60° C. or lower with an ink comprising a sublimation dye; Step (2): a step comprising decreasing content of water in the ink comprising sublimation dye coating the substrate to 50% by mass or less of the entire ink; and Step (3): a step comprising, after placing a plastic lens in a manner such that a face for dying of the lens and a face of the substrate coated with the ink comprising a sublimation dye face each other, sublimating the sublimation dye in the ink comprising a sublimation dye coating the substrate by heating the substrate obtained after Step (2) under a degree of vacuum of about 1×104 Pa or smaller to dye the plastic lens.