Factors influencing the color-changing speed of color-changing sunglasses

The color-changing speed of color-changing sunglasses is mainly affected by factors such as the intensity of ultraviolet rays, temperature, and the hardness of the lenses:

Intensity of ultraviolet rays

Photochromic lenses are made by adding a « photochromic agent » to the lens. The photochromic agent changes color rapidly according to the intensity of ultraviolet rays in the light. When the ultraviolet rays are strong, the color change rate is fast. When ultraviolet rays are weak, the rate of color change is slow. People in different regions wearing the same type of photochromic lenses may have different color-changing speeds, which is because the intensity of ultraviolet rays varies from place to place.

Temperature

Temperature has a significant influence on the color-changing speed of photochromic lenses. At present, the resin photochromic lenses on the market are particularly sensitive to temperature. When the temperature is high, the color change and fading speed of the lenses is fast, but the depth of color change is shallow. When the temperature is low, the rate of color change and fading of the lenses both slow down, and the depth of color change increases. For instance, in the high-temperature environment of summer, the depth of color change of photochromic lenses is shallow. Only the shading rate of visible light decreases, but the blocking rate of ultraviolet light does not decrease, and the protective effect does not decline. In a colder environment, the color-changing speed of photochromic glasses may slow down, or even fail to reach the expected color depth, which may affect the user’s visual experience under rapidly changing light conditions.

Lens hardness

The hardness of the lens also affects the rate of color change. Generally speaking, the higher the hardness of the lens, the slower the rate of color change. The lower the hardness of the lens, the faster it changes color. However, it is not the case that the lower the hardness of the lens, the better. Lenses made of overly soft materials often have a shorter service life, are more fragile and prone to deformation, and are also likely to break during the processing of the lens.