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Performance, identification and application of color-changing lenses

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A color-changing lens is a lens whose color changes with changes in external light. In sunlight, the lens can quickly turn dark, the transmittance of the lens is greatly reduced, the stronger the light, the darker the color of the lens; the weaker the light, the lighter the lens, when the lens is returned indoors The color of the lens can be quickly faded back to its original transparent state. At present, the color-changing lenses on the market are divided into two categories according to materials, one is a relatively traditional glass color-changing lens, and the other is a new resin color-changing lens that has been introduced to the market since the 1990s. The market is popular among China and the developed countries in the world, mainly resin-based color-changing lenses, while some developing countries in the Middle East, South America, and Africa still have a certain market for glass-chromic lenses. From the total amount of resin color changing lens is the mainstream of today's color-changing lenses, glass color-changing lenses are gradually withdrawing from the mainstream market due to their heavy weight and fragility.

 

Resin color-changing lenses can be divided into 1.039, 1.56, 1.60, PC and other color-changing lens series according to the refractive index of the materials used. Higher refractive index lenses are still under development. Among them, the 1.999 series of color-changing lenses mainly use the surface penetration method to infiltrate the color-changing dye into the lens. The color-changing lens has a small market share and is not widely used. Due to the high price of high-refractive-index ultra-thin color-changing lenses of 1.60 or more, the market has yet to be further expanded and cultivated. At present, the main color-changing lens varieties in the domestic market are 1.56 color-changing lenses. The main colors are gray and brown. In addition, colorful color-changing lenses (colors including yellow, orange, red, blue, green, purple, etc.) have recently become popular on the market. A polarizing lens and a two-color discoloration mirror combined with polarized light and color change. These special color-changing lenses are mainly used for driving mirrors and fashion mirrors.

 

1 main performance of color-changing lenses

 

1.1 In the absence of ultraviolet light, the transmittance of the lens is higher. The discoloration of the color-changing lens is mainly driven by the ultraviolet light in the environment, and the transmittance of visible light in the environment without ultraviolet rays can reach more than 84%. Generally used as vision correction, just like ordinary white lenses.

 

1.2 Under ultraviolet or sunlight, the lens has a blackout rate of at least 50%. In Europe, America, Japan and other developed countries and regions, the main varieties of color-changing lenses are gray and brown. Most of the two types of lenses have a blackout rate of more than 50% for visible light, and the most common variety has a light blocking rate of 70%. In the sun, the color-changing lens is used as a sunglasses. Of course, there are also types with a shading rate of less than 50%, but because of the limited shading, the use is of little significance.

 

1.3 UV-resistant color-changing lenses are added with a certain amount of UV absorbers in the production process, so the lens itself has anti-ultraviolet function, and the color-changing dye mainly relies on the absorption of ultraviolet light. Therefore, the UV-proof function of the color-changing lens is generally It is better. Generally, the internationally popular gray and tea-changing lenses have an ultraviolet absorption rate of more than 95% for 380 nm or less, and an ultraviolet absorption rate of more than 85% for 400 nm or less. In addition, at present, most color-changing lenses are used for multi-layer vacuum coating treatment and anti-electromagnetic treatment, so-called EMI coating treatment. The color-changing lens thus treated appears to be more transparent, and has an insulating effect on electromagnetic waves emitted by various electric appliances including computers.

 

1.4 Fast color change

 

The color change lens of the mature technology has a very fast discoloration speed. Generally, the lens is placed in the sun for more than 1 minute, and the transmittance of the lens can be reduced to more than 80% of the maximum value. When the lens was transferred from the sun into the room for 2 minutes, the transmittance of the lens returned to more than 60%. The discoloration speed of the lens is faster than the adaptation of the eye to the light.

 

1.5 Long service life

 

The service life of the color-changing lens consists of two parts, one part is the service life of the lens material itself, and the life requirement is the same as that of the ordinary resin lens; the life of the other part is determined by the life of the color-changing agent in the lens, and the validity of the color-changing agent is generally required. Must be greater than the life of the resin lens itself. The validity of the so-called color-changing agent refers to the reversible change performance of the color-changing agent repeatedly undergoing discoloration and fading under the irradiation of ultraviolet rays. If the color-changing agent does not change color, we say that the color-changing agent fails, and the life of the color-changing lens ends. It is. In general, mature color-changing lenses have a service life of more than a few years.

 

1.6 sensitive to temperature

 

At present, all the color-changing resin lenses are sensitive to temperature, that is, when the temperature is high, the color change and the color of the lens are fast, and the color change depth is shallow; when the temperature is low, the color change speed and the fading speed of the lens are slow, and the color depth is deepened. . This is why the color-changing lens does not change depth in summer as deep as winter. For the same pair of lenses, the depth of discoloration in the outdoors is deep in winter, and the fading speed in the room is slow. In summer, the color change speed is much faster, but the depth of color change is not as deep as winter. It should be noted here that the color change depth is shallow in summer, but the light blocking rate of visible light is lowered, but the blocking rate of ultraviolet light is not lowered, so the protective effect is not lowered. In completely dark conditions, the color-changing lens may not be tarnished to a colorless state, but once it is seen, the natural light lens can quickly fade back. The phenomenon that the color-changing lens has a shallow depth of discoloration under high temperature and climatic conditions is ubiquitous, and the current level of technology is not enough to completely solve this problem. However, different quality color-changing lenses are still quite different in this respect.

 

1.7 Color change speed is related to lens hardness

 

The color change speed of the lens has a certain relationship with the hardness. Generally speaking, the hardness of the lens is high and the color change speed is slow; the hardness of the lens is low and the color change speed is fast. The color change speed of the lens should be a good thing, but if the material of the lens is too soft, it will affect the service life of the lens, because the lens is too soft, the polymerization reaction is not complete enough, and it is prone to deformation after a long time.

 

2 Identification of color-changing lenses

 

The pros and cons of the color-changing lens are mainly determined by the color change speed of the lens and the service life of the color change agent. A good color-changing lens, its color change speed should be fast enough. The color change is too slow and the eyes will feel very uncomfortable, so the performance of the lens is poor. Of course, lenses that are too fast to change color are not necessarily good. Such lenses may fade in color at high temperatures and fail to block sunlight.

 

Another important feature of a color-changing lens is its useful life. A good color-changing lens should have a sufficiently long service life and should generally not be shorter than the life of the lens material itself. The poor performance of the lens is generally used for several months, and some even use only a few days of color will not change.

 

In addition, the color-changing lens must have a lighter background so that it has sufficient transparency in the room. Some lens lenses use cracks, deformations, etc. after a period of use, which indicates that the quality of the lens is not good. Other properties of the color-changing lens should be in accordance with the standards of the national or related industry of general optical lenses.

 

3 Main use of color-changing lenses Since the color-changing lenses have many of the above-mentioned excellent properties, the lenses have become a high-tech product that combines multiple functions. Its main uses include the following:

 

3.1 vision correction and sunshade mirror

 

The luminosity range of the color-changing resin lens on the market covers a variety of luminosity such as myopia, presbyopia, astigmatism, progressive multifocal and double light. Because of its high transmittance to visible light when it is in a transparent state, it can be used for vision. For correction. At the same time, it can be used as sunglasses in the sun, so it is very convenient to use one mirror. This is the biggest use of color lenses today.

 

It is important to emphasize that many people in the society, including some in the optical industry, still have different degrees of misunderstanding about the use of color-changing lenses. They believe that the color-changing lenses are only used in the summer hot season, mainly used as sunglasses, so the main sales season is summer. In fact, this kind of thinking is not comprehensive. In fact, the color-changing lenses are equally important to the eyes all year round, because the ultraviolet rays of the sun are strong all the year round, even if the ultraviolet rays around the noon in winter are harmful to the eyes. Wearing a color-changing mirror should be the most convenient and practical.

 

3.2 for protective glasses

 

Color-changing lenses can also be used in many special applications, such as making ski mirrors, field sandblasting, hiking, fishing, swimming and more. Because the intensity of ultraviolet rays in the snow, mountains, and water is much stronger than that of ordinary places, the damage to the eyes is particularly serious, and the people in these occasions must ensure that the eyes have sufficient clarity. The lens is just enough to meet these various requirements.

 

3.3 for fashion glasses

 

In addition to being used for shading, the colorful color-changing mirror and the two-color color-changing mirror have a strong beautification effect, so they are mostly used in fashion glasses, and the market prospect is extremely broad.

 

3.4 for driving mirrors

 

When driving a car, there is often strong light interference. If you wear a driving mirror with polarized light and photochromism, you can operate in various lighting conditions. It is worth noting that the selection of color-changing lenses with too shallow a color depth may not achieve the purpose of shading under high temperature conditions in summer. Therefore, it is recommended to select a color-changing sheet with a color-changing depth of 70% or more in summer, and vice versa. For color-changing lenses, it is best to choose a color-changing lens with a color change depth of more than 60% throughout the year. In addition, some specially designed color-changing mirrors are also used to correct eye diseases in some people.