Different Types of Photochromic Lens
Different Types of Photochromic Lens
In the previous article, we introduced the characteristics, advantages and disadvantages of Photochromic Lenses. So what are the specific types of photochromic lenses? In this article, we will introduce the specific types of photochromic lenses and their characteristics.
Types of photochromic lens:
In term of production technique, there are basically two types of photochromic lenses: By material, and by coating. And there’ re two of coating: spin coating and dipping coating.
Nowadays, the popular photochromic lens by material is mainly 1.56 index, available with single vision, bifocal and multi-focal.
While the photochromic lenses made by coating have more choices, such as 1.499/1.56/1.61/1.67/1.74/PC.
Material photochromic
Principle:
The photochromic material is evenly distributed inside the lens substrate (such as resin or glass) and changes color through a chemical reaction stimulated by ultraviolet light.
Feature:
Uniform color change-the color changes from the inside to the outside.
Slow color change-Color change and fading time is relatively long (especially fading).
Long life- the color-changing material is embedded in the base material and is not easily worn out.
Dark base color-May have a slight base color (such as light gray or light brown) when not discolored.
Applicable scenarios-General color change needs, suitable for users who are not sensitive to the base color.
Spin coating photochromic
Principle:
The liquid photochromic material is evenly applied to the surface of the lens through high-speed rotation, and then solidified to form a photochromic film layer.
Feature:
Faster color change-thin film layer, quick reaction to ultraviolet rays.
Lighter base color-Closer to transparent when not discolored.
Wear resistance depends on coating-Hard coating protection is required, otherwise it is easy to scratch.
Lower cost- The process is relatively simple.
Dipping coating photochromic
Principle:
The lens is immersed in a solution containing photochromic material, and the photochromic molecules penetrate into the surface of the lens through ion exchange, so as to coat the lens with a photochromic layer on both sides.
Feature:
Better color uniformity-deeper molecular penetration.
Stronger durability-the color-changing layer is more tightly bonded to the substrate.
Complex process-higher cost, more common in high-end lenses.
Excellent base color control-nearly colorless.
Lighter base color-Closer to transparent when not discolored.
Wear resistance depends on coating-Hard coating protection is required, otherwise it is easy to scratch.
Lower cost- The process is relatively simple.
Feature:
Better color uniformity-deeper molecular penetration.
Stronger durability-the color-changing layer is more tightly bonded to the substrate.
Complex process-higher cost, more common in high-end lenses.
Excellent base color control-nearly colorless.
How to choose?
Pursuing cost-effectiveness and durability: choose material photochromic.
Require Fast color change and light base color: choosespin coating or dipping coating.
High-end demand (such as driving lenses): dipping coating is preferred because of its better color change performance and transparency.
