MASS
Advantages
Photochromic agents are blended into the monomer raw materials during production, resulting in the agents being evenly distributed throughout the entire lens. This design delivers two key benefits: a long-lasting photochromic effect and high temperature resistance.
Disadvantages
Disadvantage A: Color Variation in High-Power Lenses
A color difference may occur between the center and edges of high-power lenses, with the discrepancy becoming more noticeable as the diopter increases.As is commonly known, the edge thickness of a lens differs significantly from its center thickness—this physical difference leads to the observed color variation. However, during spectacle fitting, lenses are cut and processed to use the central portion. For lenses with a power of 400 diopters or below, the color difference caused by photochromism is virtually unnoticeable in the final finished spectacles. Additionally, mass photochromic lenses manufactured via this process maintain excellent overall performance for up to two years.
Disadvantage B: Limited Product Range
The range of mass photochromic lens products is relatively narrow, with options primarily concentrated in lenses with refractive indices of 1.56 and 1.60.
SPIN
A. Single-Layer Surface Photochromic (Spin-Coating Photochromic Process)
This process involves spraying photochromic agents onto the coating of one side (Side A) of the lens. It is also known as "spray coating" or "spin coating," a technique widely adopted by international brands. A key feature of this method is its ultra-light base tint—closely resembling a "no-base tint" effect—resulting in an aesthetically pleasing appearance.
Advantages
Enables fast and uniform color change.
Disadvantages
The photochromic effect has a relatively short duration, especially in high temperatures, where the lens may even lose its ability to change color entirely. For instance, testing the lens in hot water: excessively high temperatures can cause permanent failure of the photochromic function, rendering the lens unusable.
B. Double-Layer Surface Photochromic
This process involves immersing the lens in a photochromic solution, allowing photochromic layers to form on both the inner and outer coatings of the lens. It ensures uniform color change across the lens surface.
Advantages
Delivers relatively fast and uniform color change.
Disadvantages
Poor adhesion of the photochromic layers to the lens surface (the coating is prone to peeling or wearing off over time).
Key Advantages of Surface Photochromic (SPIN) Lenses
No Material Restrictions for Wide Applicability
Surface photochromic lenses are not limited by lens materials or types. Whether for standard aspheric lenses, progressive lenses, blue-light blocking lenses, or lenses with refractive indices ranging from 1.499, 1.56, 1.61, 1.67 to 1.74, all can be processed into surface photochromic versions. This wide product range offers consumers extensive choices
More Uniform Tint for High-Power Lenses
Compared with conventional mass photochromic (MASS) lenses, surface photochromic lenses maintain a relatively more uniform color change when applied to high-power lenses—effectively addressing the color discrepancy issue that often occurs in high-diopter mass photochromic products.
Advances in Mass Photochromic (MASS) Lenses
With the rapid evolution of technology, modern mass photochromic lenses are now on par with surface photochromic counterparts in terms of color-changing speed and fading speed. For low to medium-power lenses, they deliver uniform color change and top-tier quality, while retaining their inherent advantage of a longer-lasting photochromic effect.
Post time: Sep-12-2025