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Introduction to photochromic lenses and how to choose the right photochromic lenses

Posting time:2023-01-28 05:53:40

Introduction to photochromic lenses and how to choose the right photochromic lenses

I. What are photochromic lenses

Ordinary optical glasses are colorless and transparent. Sunglasses are suitable for blocking strong light and UV rays outdoors, but are not suitable for use in low-light environments indoors. The above two types of lenses are only suitable for use in specific environments, and the photochromic lens achieves the effect of both. Color-changing lenses, as the name suggests, are lenses that can change color in different environments. The lenses are colorless and transparent indoors, and can be used as ordinary optical glasses. Color-changing lenses show different colors in different scenarios.

Second, the use occasions and people of color-changing lenses

Each lens has a specific usage scene. It takes a certain amount of time to fade, and the visual effect is not good during the discoloration and fading, so the color-changing lenses are not one-shot, but also have specific use occasions and groups of people. 1. People who are sensitive to sunlight, people who are often outdoors, and people who are unwilling to switch back and forth between ordinary glasses and sunglasses are suitable for using color-changing lenses. 2. It is not recommended to wear color-changing lenses for customers who often go indoors and outdoors, because the color-changing lenses take a certain amount of time to change color and fade, especially when the lens is dark in color, and the objects in the room will be very dark. 3. The effect of using photochromic lenses when driving is not ideal, because the windshield of the car filters out most of the ultraviolet rays, and the lens discoloration effect is not very good.

III. Principle of color-changing lens

According to the principle of reversible reaction of light-color interconversion, the color-changing lens contains silver halide (silver chloride, silver bromide) and catalyst copper oxide microcrystalline particles, which can be used in ultraviolet light. Under irradiation, silver halide decomposes into silver and bromine, and decomposes the tiny grains of silver, which darkens the lens and reduces the light transmittance; when entering the dark indoor environment, the ultraviolet rays are reduced, and silver can catalyze the action of halogen and copper oxide. In the next step, the silver halide is regenerated, and the lens returns to a colorless and transparent state.

Four. Classification of color-changing lenses

1. According to color classification, color-changing lenses can be divided into gray color-changing lenses and brown color-changing lenses according to color. Gray lenses can effectively reduce the intensity of light without affecting the contrast of object colors, and are more suitable for men to wear; brown tones are softer, more comfortable for vision, and less prone to eye fatigue, which is more suitable for women to wear. 2. According to the production process, the photochromic lenses can be divided into two types: substrate photochromic lenses (referred to as "basic change") and film-layer photochromic lenses (referred to as "film change"). (1) The characteristic of the fundamental change technology is that the color-changing dye is evenly mixed with the raw material of the lens, and the molded lens with color-changing ability is obtained after the monomer is cured by casting molding, that is, the entire lens material participates in the color change. (2) Coated lenses are specially treated in the lens coating process. For example, spiropyran compounds are used for high-speed spin coating on the surface of the lens. According to the intensity of light and ultraviolet rays, the inversion of the molecular structure itself is used. Opening and closing realizes the effect of passing or blocking light, and the lens film layer is involved in the color change, and the lens base material does not change color. 3. Advantages and disadvantages of base change and film change (1) Advantages and disadvantages of base change Advantages: ① The entire lens substrate is full of color-changing agent, the lens has a long time to change color, and is more resistant to high temperature than film change. ②The price of base-change lenses is low, which is suitable for mass consumption. Disadvantages: ① The height of the lens (above 600 degrees) is uneven, and the color of the center is light and the color of the periphery is dark. ②There are fewer discolored products, mainly concentrated in the refractive index of 1.56 and 1.60. (2) Advantages and disadvantages of film change Advantages: ① Rapid and uniform discoloration. ②It will not be limited by materials, 1.56, 1.61, 1.67, 1.74, etc. can be processed into film variable lenses. Disadvantages: complex process and high price. 5. How to evaluate the quality of photochromic lenses, the quality of photochromic lenses can be comprehensively considered from five aspects: color changing speed, fading speed, color changing depth, initial transmittance, and durability. 1. The time it takes for the color-changing lens to change from the initial colorless and transparent state to the darkest state, the sooner the better. 2. Fading speed The time it takes for the lens to go from the darkest state to the initial colorless and transparent state, the sooner the better, if the speed is too slow, it will feel darker for a period of time from the outdoors to the indoors, which will affect the comfort. 3. The color changing depth lens can achieve the deepest color state. The color changing depth is not only affected by materials and processes, but also related to the ambient temperature. In summer, the temperature is high, the color changing speed is fast, and the color is lighter; in winter, the temperature is low, the color changing speed is slow, and the color will change. very deep. 4. The initial transmittance refers to the transmittance of the lens before discoloration. The higher the transmittance, the more transparent the lens, and the higher the transmittance, the better. 5. Durability The effect of photochromic lenses is photochromic molecules, which may fail after multiple reactions, resulting in a decrease in the color changing effect. Generally, the photochromic lenses can be used for 2-3 years. 6. How to choose photochromic lenses As mentioned above, the quality of photochromic lenses can be comprehensively considered from five aspects, but it is difficult for ordinary consumers to do so. So what should consumers do if they need to buy photochromic lenses, and how to choose the right one? Color-changing lenses? 1. Choose base change or film change. The speed of base change is slower than that of film, but the price of base change is lower than that of film. If it is within 400 degrees, you can choose base change or film change. Above 400 degrees, it is recommended to choose film change. Membrane change is recommended for anisometropia of 200 degrees and above. 2. Choose domestic brands or foreign brands. The mainstream foreign brands of color-changing lenses are Essilor, Zeiss, Heuer, Transitions, Rodenstock, etc. The mainstream brands of domestic color-changing lenses are Wanxin, Mingyue, and Quanzhen Optics. The quality ratio of foreign color-changing lenses It is good in China, but the price is more expensive than that of domestic color-changing films. Consumers can choose the corresponding brand according to their own economic conditions. 7. Summary After reading the above, what you need to know about color-changing lenses is the following: 1. Color-changing lenses are divided into basic and film changes. The time of basic change is slower than that of film change, but the price is lower than that of film change. 2. Within 400 degrees, you can choose the basic transformation or the film transformation. Above 400 degrees, it is recommended to choose the membrane transformation, and choose the corresponding refractive index according to the degree. 3. Ultraviolet rays are the main factor causing the discoloration of photochromic lenses. Outdoor ultraviolet rays are strong and indoor ultraviolet rays are weak. 4. If the economic situation is not very good, you can choose domestic brands, local tyrants are free.

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