What is the difference between anti-reflective lenses and regular lenses? Glasses with anti-reflective coating. The principle of operation of anti-glare glasses for a computer
An anti-reflective coating is a special coating applied that diffuses direct sunlight or a beam of bright artificial light, which serves to improve the quality of image perception. human eye and cutting off the high spectrum of light.
For mobile devices
In the bright sun, it is simply impossible to see what is written on the monitor of a tablet or smartphone. The reason is the intense reflection of the sun's beam, the appearance of glare. To combat this problem, there is a special anti-reflective film that is simply glued onto the display. mobile device. The film is quite inexpensive, and also protects the device from scratches and bumps.
Computer monitors and large LCD televisions use a built-in factory anti-reflective coating. It is a special multi-layer deposition on the monitor. The anti-reflective coating literally scatters sunlight or artificial light that hits the surface of the device and prevents glare.
For optics
The glasses also use an anti-reflective system. This system implemented on the basis of an anti-reflex coating that reflects glare and improves the quality of the lens. Anti-reflective coating works best in high-index lenses, as they reflect significantly more light than plastic lenses.
The use of anti-reflective coating in glasses allows, in addition to eliminating the effect of glare, also to increase visual acuity.
Technology has spread to Sunglasses. However, please note that it is impossible to stick or spray such protection on glasses, the application is carried out only by an industrial method in the vacuum placement of lenses in a special installation. The thickness of the anti-reflective coating layer is only 0.15 to 0.3 microns, and therefore the proposals to "upgrade" your "special coating" are nothing more than a hoax.
For the automotive industry
Anti-glare technology has also gained ground in the automotive industry. The same technology as in optics is used in the manufacture of windshields.
Such glasses have good color reproduction, scatter ultraviolet radiation, allow you to maintain high image clarity, scatter and block the reflections of the headlights of other vehicles.
Glass is produced by the method of magnetor-sputtering technology in industrial environment. Anti-reflective glass allows you to experience driving comfort in any situation. weather conditions and at any time of the day. True, such glass costs a little more than usual, but is it really worth saving on convenience and traffic safety?
Computers, smartphones, tablets have firmly entered life modern humanity. Though work, even a house, but a person most spends most of his time in front of a computer or laptop screen. At the same time, the natural desire of anyone will be to preserve vision and protect it as much as possible from the negative radiation that any monitor and screen generates.
What does a person want from a monitor or tablet screen? It must accurately reproduce colors, have no dead pixels and have a sufficient viewing angle. Good brightness will not hurt, so that there are no glare on the screen in the sun.
A good monitor should not create problems, especially for the eyes.
Most of the debate today revolves around several topics related to screens and vision:
- which screen is better - gloss or matte?
- Should I install anti-reflective film?
In dealing with these issues, many consumers forget that 90% of the quality of a good screen is the matrix. Therefore, the first question that should worry every consumer is which matrix to choose?
How does the quality of the matrix affect the laptop screen?
Main a sign of a good matrix directly for vision is the viewing angle. After determining the matrix, the following questions of convenience are already coming up, for some it is more convenient to work with a matte monitor, for others with a glossy one.
In total, there are three groups of matrices:
Liquid crystal matrix (TN) one of the cheapest and available matrices. She responds quickly, but her viewing angle leaves much to be desired. And yes, it distorts the colors a bit. Because for the view is not the most the best option, but its cheapness does its job.
The picture below clearly shows the viewing angle of the TN matrix and the IPS matrix. After that, there are no unnecessary questions about which laptop screen is better.
The best in terms of viewing angle and color quality is an IPS matrix. Based on it, LED monitors, etc. have already begun to develop. For vision, such matrices are the best, but they are also the most expensive. They are always used in professional monitors and screens. AT difficult conditions such a matrix has better readability. Bright light, sunny color do not distort the image.
The example below shows how much juicier and better colors on an IPS matrix. When working with such a laptop, the eyes will get tired much less.
Monitor with MDV-matrix has collected the advantages of the two previous matrices- he took the color reproduction from IPS, and the response speed from the TN + Film matrix. But such a matrix is not as dynamic as others. Perfect for artists and photographers who care about accurate color reproduction.
Highly detailed classification matrices is described at the following link - classes of matrices.
Gloss or matte - what do the eyes vote for?
It does not matter what the user owns, a tablet or laptop, whether he has a computer installed. The debate about which is better is still going on. At first glance, the matte surface of the screen seems more comfortable and pleasing to the human eye.
Matte virtues
Unlike a glossy surface, matte, first of all, does not glare in the sun. Since a laptop, like a tablet, a person can constantly carry with him, then his work on the street can be unlimited. A glossy surface in bright sunlight is extra way spoil not only vision, but also nerves.
But besides the reflection, there is also color reproduction and brightness. And here the matte screen begins to lose ground to gloss. If a laptop, like a tablet, has to be used everywhere, then you can choose a matte screen. Moreover, the laptop cover can always be adjusted to obtain the desired viewing angle.
The matrix is of great importance. If it is TN, then it is better to choose a glossy version. If IPS, then the matte screen will be the most comfortable for the eyes. Especially if the user often works with numbers and documents. The matte screen will strain your eyes less during many hours of such work.
glossy beauty
People are weak, and very often, when choosing a laptop, a person is guided not by common sense, but by beauty. And it is very good if beauty implies quality. In the case of glossy screens, only a good matrix can guarantee the quality of the screen.
The image on such screens seems brighter and more saturated, which seems to help the eyes rest more. But with such reflectivity, the screen with its glare is very tiring for the eyes. Moreover, on such a screen you can see every drop, mote, which also interferes with the eyes.
On the street with such a laptop or tablet is a complete torment. You need to look for a shadow, twist the lid of the laptop. From the sun glare, the eyes begin to hurt even more. With a good IPS matrix, this effect is slightly less, but it is not completely excluded.
True, in a room with ordinary electric lighting (and not behind the back of a person sitting behind a screen!) The viewing angle of such screens is much larger than that of matte ones. Yes, and the black color here is more accurate and deep..
For clarity, further on the link, a very good test of the operation of both types of screens on films, graphics and office applications is the battle of screens.
Anti-glare coating - saving and protecting the eyes?
Very often they sell laptops and tablets with an anti-glare coating already installed. But there are also anti-reflective films that are relevant not only for tablets. Is it worth it to spend money on buying a laptop with such a built-in option, or is it better to buy a film?
Below is an example of a peeling anti-reflective coating. And this is his main problem. It quickly becomes unusable, especially since few users wonder how to properly care for it. And then the monitor screen looks very impartial.
Anti-reflective films are much cheaper. And since any user will buy a protective film for the same tablet, there is no point in buying a tablet with such a coating. It is better to buy a film with such a coating. The task of the coating or film is to protect the screen from glare when exposed to sunlight or bright electric light. And the cover really helps. But the film beats him in this sense. It is much more comfortable for the eyes to work with such a film.
The coating is very quickly torn, cut and spoils the entire look of the laptop screen. Therefore, when buying a glossy laptop, it is better to immediately buy a protective anti-reflective film in the kit, it is more reliable and more convenient. Although over time, dust will begin to clog under it and it will have to be changed. Although the film makes the screen a little dimmer, it is also protective at the same time.
Protective anti-glare film
You can read about how to remove a spoiled coating from a laptop screen.
So that the user should always approach the choice consciously and familiarize himself with the topic at least minimally. And it doesn't matter what he will choose - a screen and a matrix or a tablet. The health of his eyes depends on this.
Neva Max coating is an innovative breakthrough of the team of researchers and developers of the famous French company BBGR. It has been specifically designed to prevent the formation of minor scratches that inevitably occur with daily wear of glasses.
The composition of the coating "Neva Max" introduced an additional exclusive layer that provides unsurpassed strength characteristics of the lens.
REINFORCING LAYER
Spectacle lenses made of polymeric materials resist mechanical damage well, which is the reason for the high safety when wearing glasses with polymer lenses. However, when worn, their relative disadvantage affects: they are quickly scratched due to the softness of the lens material. Scratches, of course, worsen not only the cosmetic, but also the optical properties of glasses and shorten their service life. To increase the resistance of the surface of organic lenses to scratches, you can use a hard coating on the lenses. Such a coating, without changing the optical qualities of the spectacle lens, increases the resistance of its surfaces to scratches.
Because minerals significantly more resistant to scratching than organic lenses, a thin layer of mineral material (quartz) was applied to the surface of the polymer lens. For the first time, quartz coatings appeared in the early 70s of the last century, but by the middle of the same decade it became clear that this was not best way out out of position. The quartz coating easily peeled off due to the low strength of the connection between the reinforcing layer and the polymer, in addition, the difference in the coefficients of thermal expansion - small for quartz and significant for the polymer base - had an effect. Therefore, even those small temperature differences that goggles are exposed to during everyday use, very quickly destroyed the quartz coating. In addition, scratches that appeared on the surface of the lens under strong mechanical stress had torn edges and were very noticeable.
The mechanism of destruction of a hardening quartz coating can be demonstrated by the example given: if a lens made of a polymeric material with a hardening coating on both surfaces is bent, then one surface of the lens experiences tension, and the other, compression - both coatings experience breaking stress.
The next invention turned out to be more successful - flexibility began to resist strength. An organosilicon compound, polysiloxane varnish, was applied to the surface of the lens. Polysiloxane lacquer has a high elasticity, thanks to which it creates a surface that is not damaged by contact with abrasive particles. After complete polymerization of the varnish, the surface of the spectacle lens becomes highly resistant to scratching. The high elasticity of the lacquer layer allows it to bend along with the lens material during temperature changes, while remaining firmly connected to its surface.
The process of hardening lenses consists of several stages. To ensure that the coating does not have defects, the room where the coating is applied is ensured by absolute cleanliness and complete dedusting of the air. It is very important to carefully prepare the lens surface. First, the lens surface is thoroughly cleaned by rinsing in baths with various detergents and degreasers. chemicals, then the lenses are washed in an ultrasonic bath. After that, the lenses are fixed in a special device that controls the coating process, and are immersed in a bath of liquid polysiloxane varnish.
Preservation of good optical properties of a spectacle lens on which a hardening coating is applied is possible only when the thickness of the coating is the same over the entire surface of the lens. The uniformity of the coating is ensured by maintaining a constant viscosity of the varnish and the speed of dipping and removing the lenses from the liquid varnish bath. This is monitored by high-precision computer-controlled measuring instruments. After being removed from the bath, the lenses are heated for three to four hours. The duration of heating depends on the material from which the lens is made. During this heat treatment the polymerization of the lacquer ends and the strength of the bond between the coating and the lens surface increases.
ENLIGHTENING OF OPTICAL LENSES
A ray of light passing through a transparent medium at some angle different indicators refraction, undergoes certain changes at the interface between the media. One part of the beam will pass inside the second medium, changing its direction. The other part will bounce off the interface, returning to the first medium. In this case, the ratio of transmitted and reflected light is not the same. The proportion of reflected light is mainly determined by the ratio of the refractive indices of the first and second medium and the angle of incidence of the light beam on the interface.
Thus, the surface of any transparent object with a refractive index different from that of air reflects some of the light falling on it. Spectacle lenses are no exception to this rule. The light reflected from the surfaces of spectacle lenses does not enter the eye, which means that it does not participate in the construction of the image on the retina. As a result, the image seen through the glasses is less bright and has less contrast.
But the loss of light is not the only trouble associated with reflection from a spectacle lens. Reflection of light also occurs when light exits the spectacle lens into the air, so the reflection can be multiple. The spectacle lens has a convex surface, that is, in its shape it resembles a curved mirror, which not only reflects, but also distorts the reflection. This distorted reflection is superimposed on the main image seen by the patient through glasses. Since the proportion of reflected light is small, the distorted image is usually very weak, it is practically not perceived by the patient. And yet this image makes it difficult for the eyes and hastens the onset of visual fatigue.
Reflections from the back of a spectacle lens are also a problem. Objects located behind the patient, reflected from the back surface of the lenses, may appear to be located in front of the eyes, disrupting the normal orientation in space. Reflections from spectacle lenses are especially troublesome if light sources enter the patient's field of vision. Due to their high brightness, they give bright reflections, which significantly complicate the work of the eyes. AT most drivers suffer from this phenomenon (blinding by the headlights of oncoming cars), people forced to work under artificial lighting and people working at video monitors.
The principle of operation of antireflection coatings is to create conditions for the interference of light rays incident on the lens and reflected from it. Interference occurs due to the deposition of one or more thin films of various thicknesses on the surface of the lens. transparent materials with different refractive indices. The thickness of the films is commensurate with the wavelength of light. The interference of light reflected from the front and rear boundaries of the antireflection films leads to mutual cancellation of the reflected light waves. The redistribution of the energy of the interfering rays enhances the intensity of the transmitted light. The effect of enlightenment will be maximum if, at an angle of incidence of the rays close to normal, the thickness of the thin film will be equal to an odd number of quarters of the wavelength of the light. Those. The fraction of light reflected by a lens can be significantly reduced by applying a special coating to both of its surfaces. In domestic terminology, such a coating is called an antireflection coating, in the English literature it is called an "anti-reflex" or "anti-reflective" coating that eliminates reflections and light glare. Yet more correct name it should be recognized as domestic - in addition to reducing reflection and eliminating glare on surfaces, the coating makes the lens more transparent, and the image obtained with its help is of higher quality.
We conclude that the anti-reflective coating allows the lens to transmit more light. About 7.8% of the light is reflected from both surfaces of the lens without anti-reflection coating with a refractive index of 1.5. A lens made of a material with a refractive index of 1.9 reflects 18% of the light. A high-quality anti-reflective coating can reduce reflected light to less than 1%. Thus, if there is an antireflection coating on the lens, more light is involved in the construction of the image on the retina, the image is brighter and more contrast. Subjectively, this is perceived by the patient as an increase in the clarity of the image seen through glasses with anti-reflective lenses. In addition, anti-reflective coatings prevent reflections from bright light sources located in front of and behind the patient. As a result, the blinding effect of light sources is significantly weakened, vision becomes more comfortable. Lenses with anti-reflective coatings also have cosmetic benefits. Since they do not reflect surrounding objects, the eyes of a person wearing glasses are clearly visible through them. This contributes to better visual contact when communicating. Due to the absence of reflections, the lenses look completely transparent, and glasses with coated lenses are almost invisible on the face.
Currently released spectacle lenses with one-, two-, three- and multilayer antireflection coatings. Coatings with multiple layers reduce the reflection of most waves across the entire visible spectrum, as well as rays that strike the lens at various angles. In general, the more layers in an AR coating, the more effective it is.
The color of the anti-reflective coating is visible in reflected light, so if the coating transmits red and Blue colour well, it looks green. If it is blue, then longer wavelengths (green, red, etc.) are transmitted. High performance coatings have a low residual reflection of neutral tones. A bright residual reflection is typical of low-quality, inefficient antireflection coatings. Since not all antireflection coatings equally suppress reflected light, the problem of assessing their quality arises. However, it is not possible to quantify the effectiveness of a coating visually or with instruments commonly found in an optical shop. In this matter, one has to rely on the reputation of the lens manufacturer and the information provided by the company.
The technology of applying antireflection coatings is quite complicated. The most common now are vacuum and chemical methods coatings. Chemical methods compared to vacuum methods, do not require expensive equipment and are more economical when obtaining the simplest types of coatings. Unfortunately, chemical methods do not allow applying antireflective coatings of proper quality to lenses. A highly effective coating can only be created in a vacuum chamber.
Since the coating possibilities are also determined by the properties of the lens material, for each material it is necessary to create its own coating and develop a separate technological process its application.
First, the lens surface is thoroughly cleaned by rinsing in several baths with various cleaning and degreasing chemicals, then washed in an ultrasonic bath. After that, the lenses on a special stand are placed in a sealed chamber of the installation, in which a vacuum is created. A substance heated to a vaporous state is supplied inside the installation, which, settling on the lens, forms the thinnest film. The film thickness is controlled by high-precision measuring devices. On top of the first layer, a second layer is applied, the material of which has a different refractive index. Layers of different thicknesses from materials with different refractive indices alternate. The thickness of the layers is selected, ensuring that the reflection from each layer boundary extinguishes the reflection of light of a certain wavelength from the surface of the lens.
To create a high-strength antireflection coating on the surface of glass lenses, the coating process is carried out at a temperature of about 250°C.
Polymer lenses should not be heated to such high temperatures, so they are coated at a temperature of 80-100°C. Before applying an antireflection coating to a polymer lens, the lens surface is coated with a layer of polysiloxane varnish, which acts as a hardening coating. The elastic lacquer layer prevents damage to the anti-reflective coating during the operation of glasses with anti-reflective lenses.
An anti-reflective coating must be present on lens surfaces with a refractive index greater than 1.5. In addition, the proportion of reflected light increases with oblique incidence of rays. If the light beam forms an angle of 45° with the normal to the surface of the spectacle lens, the reflection loss increases by a factor of 2. To reduce the reflection of oblique rays, multilayer antireflection coatings are also used.
In order for the patient to fully experience the benefits of coated spectacle optics, it is necessary to monitor the cleanliness of the lens surfaces. Proper care behind lenses with anti-reflective coatings will ensure the preservation of their properties for a long time. Lenses should be washed in cool water neutral detergent or use special “sprays” and wipes to clean the lenses. Do not wipe the lenses with paper, as the hard particles it contains can scratch the surface. Polymer lenses should not be subjected to sudden temperature changes and high temperatures (the temperature can reach 80 ° C in saunas, in summer in car interiors left in the sun. Temperature changes can adversely affect the strength of the anti-reflex coating.
WATER-REPELLENT COATINGS
Lenses with anti-reflective coatings allow the eyes to make better use of the light passing through spectacle glasses light, thereby improving the quality of vision. At the same time, a very unpleasant cosmetic defect - reflections from the glass surface - is eliminated. However, sometimes patients complain about the rapid contamination of the coated lenses, while noting that coated lenses when used in the same conditions, they almost do not get dirty. Do anti-reflective coatings really contribute to the rapid contamination of lenses? The answer to this question follows from the very principle of action of antireflection coatings. The most interesting thing is that the consequence of surface contamination clearly demonstrates how significantly the quality of optical surfaces, acquired during antireflection, increases.
The deposition of any substances on the surface of the antireflection coating (water, grease, dust) leads to the fact that in this place the negative interference, which weakens the reflection from the lens, does not occur. After all, the effect of enlightenment affects at a certain refractive index environment, in our case air. Therefore, pollution, replacing the air that is usually adjacent to the lens, deprives the contaminated areas of the surface of all useful properties given to them by enlightenment. As a result, the lens surface is divided into clean areas that have retained antireflex properties, and contaminated areas that do not have such properties. And now, against the background of an almost non-reflective enlightened surface, sections of the “ordinary”, as if not enlightened, lens become clearly visible. Of course, this phenomenon is reversible: washing the lenses completely restores their anti-reflex properties.
Why is the contamination of non-coated lenses not so noticeable? Because their surface is so reflective a large number of light, which against this background, the losses additionally introduced by pollution are almost imperceptible. Thus, both coated and non-coated lenses in the process of wearing glasses get dirty to the same extent. But contamination of coated lenses is more noticeable. And the more effective the anti-reflective coating, the more contaminants on its surface can be noticeable. But even this unpleasant property, albeit easily eliminated by washing, can be eliminated with the help of another one - a hydrophobic (water-repellent) coating applied over antireflection layers. By smoothing out microscopic irregularities on the lens surface, this coating makes it harder for dirt particles to attach to the lens surface. Right choice coating material can provide the following semi-fantastic phenomenon: water drops do not spread over the surface, but roll off the lens, leaving no wet trace behind. What is the reason for such an unusual behavior of water on the surface of the lens? A water drop is made up of individual water molecules. In this drop, the molecules are attracted with some force to each other. The surface of the lens is also molecules, the molecules of the substance that makes up the outermost layer of the lens. If the force of attraction between a molecule of the lens substance and a water molecule is greater than between two water molecules, the water drop will spread over the surface of the lens, tending to turn into thinnest layer one molecule of water thick, acquiring the appearance of a spot. This kind of interaction between liquid and solid called "wetting" or hydrophilicity - water wets the substance that makes up the outer layer of the lens. The force of attraction of water molecules by molecules of glasses and polymers of spectacle lenses more power attraction between water molecules. As a result, all lenses without hydrophobic coatings are wetted by water. Substances used for antireflection coatings are also wetted by water. Therefore, spectacle lenses with coatings and without anti-reflective coatings, without the protection of a water-repellent layer, will quickly become dirty. In the case when the force of attraction between two water molecules is greater than the force with which the lens surface attracts a water molecule, a drop of water tends to take spherical shape. The resulting water ball rolls off the surface without leaving a trace. This type of interaction between a lens and water is called "nonwetting" or hydrophobicity. If a layer of a hydrophobic substance is applied to the surface of a spectacle lens, water droplets can be removed by simply shaking the spectacles. At the same time, after their removal, no spots remain on the spectacle lens.
The wettability of a solid by a liquid is estimated by experts in terms of the contact angle. For non-wetting liquids this angle is obtuse, for wetting liquids it is acute. The larger the contact angle, the more pronounced the water-repellent properties of the hydrophobic coating. What does knowing the value of the contact angle give to the user of glasses? This allows him to compare the effectiveness of various hydrophobic coatings from different manufacturers spectacle lenses. best choice there will always be a coating characterized by the maximum value of the contact angle.
Substances used for hydrophobic (water-repellent) coatings belong to the group of alkylsilanes. Each alkylsilane molecule contains at least one SiO group, which provides a strong connection between the hydrophobic layer and the lens, as well as a hydrocarbon chain that endows the substance with hydrophobic properties. The thickness of the hydrophobic coating is very small. Usually it is no more than 1/10 of the thickness of one antireflection layer, that is, only a few molecules.
Spectacle lenses with hydrophobic coatings have significant advantages. They are more resistant to dirt and stay cleaner longer. This ensures that the user maintains good optical properties of the lenses while wearing glasses. The hydrophobic properties of the lens surface also greatly simplify the care of glasses: the lenses are easily cleaned by wiping with a special cloth. Their surface is easy to dry after washing, while the water does not leave stains on the lenses. Of course, the question arises - but this is about water, and fats, dust? Just a negative property of hydrophobic coatings is a high affinity for fats, which makes it more difficult to remove fatty contaminants from the lens surface. But not always. Many lens manufacturers have their own methods and compositions of coatings, including those with a water-dirt-repellent effect.
Each such coating has its own special name. Therefore, lenses with such a coating are more resistant to fatty contamination, and if necessary, they are easily cleaned of grease.
The technology for obtaining water-dirt-repellent is similar to the technology used for the enlightenment of spectacle lenses. Coating substances are converted into a vapor state. The resulting vapor in the vacuum chamber settles on the lenses, forming a very thin water and dirt-repellent layer.
Despite the economic crisis, the eyewear sector continues to grow, as evidenced by big number innovations from companies. Many world manufacturers of spectacle lenses began to offer coatings that have improved characteristics compared to previous versions of branded coatings, including higher antistatic properties that make spectacle optics products stronger and more durable.
Coatings are increasingly becoming an integral part of spectacle lenses, significantly increasing their consumer properties. Hard coatings protect the lens surface from scratches. Lenses with anti-reflective coatings not only look more aesthetically pleasing, but also provide the user with high quality vision and visual comfort.
Therefore, the technology of applying various coatings to spectacle lenses is being intensively developed, improving the optical and mechanical properties of lenses.
Currently, coatings are applied to both mineral and organic spectacle lenses. AT last years are becoming more and more common multifunctional coatings applied to the surface of organic spectacle lenses. They consist of a hardening, multi-layer antireflection and hydrophobic coating.
AR coating
An antireflective (“anti-reflex”, AR-coating, “anti-reflective”) coating is used to increase the transparency of a spectacle lens and reduce the reflection of light from its surfaces. When passing through a lens, light is partially absorbed and reflected from its surfaces due to different refractive indices of the lens material and the surrounding air. In this case, the reflected rays lead to the appearance of interfering reflections and reduce the clarity of the perception of the image.
The action of antireflection coatings is based on the phenomenon of interference of light waves, in which light rays cancel each other out. The residual reflection of light from the surface of a spectacle lens (residual reflex) depends on the quality of the applied coating and has its own characteristic color (green, blue, lilac, greenish-yellow, gold).
Spectacle lenses with high-quality anti-reflective coatings practically do not reflect the light falling on them. The residual reflection of such spectacle lenses is very weak and usually has greenish tint, or such lenses are absolutely transparent, i.e. achromatic.
However bright color residual reflection, according to many manufacturers, is not a disadvantage, but, on the contrary, makes such lenses attractive to a certain category of buyers.
If the antireflection coating consists of a single layer, the reduction in light transmission occurs only in one specific part of the spectrum. Therefore, to cover the entire spectrum visible light apply several coatings corresponding to different parts range.
An important property spectacle lenses is their ability to stay clean to maximize light transmission. This is especially important for spectacle lenses with anti-reflective coatings, which even a small amount of water or grease stains on the surface significantly impairs the effectiveness of the anti-reflective coating.
Therefore, users of such spectacle lenses often complain that their glasses are more dirty and harder to clean. In fact, pollution is simply much more noticeable on coated spectacle lenses.
Hydrophobic coating
To protect the lens surface from “sticking” of dust and grease particles, a hydrophobic coating is applied with the so-called “Lotus effect”, which has water and dirt repellent properties, as well as some antistatic effect, as a result of which polluting particles are less attracted to the lens.
Hydrophobic coating improves lens fogging resistance even when sharp drop temperatures
This coating makes the lens smoother, preventing water droplets from sticking, which increases its resistance to fogging even with sudden temperature changes (“anti-fog effect”).
At first glance, the perfectly flat surface of a spectacle lens under a microscope looks completely different - with peaks and dips that trap liquid drops. Very thin silicone films fill these irregularities, and there are no drop traps on the surface of the spectacle lens. Liquid easily rolls off the surface of the spectacle lens.
The hydrophobic coating also reduces surface tension. On water-repellent surfaces, a drop of water does not spread, thereby reducing the contact area with the surface. The hydrophobic properties of the surface characterize the contact angle between the surface of the spectacle lens and the drop at the point of contact. The larger the contact angle, the easier it is for water droplets to roll off it.
In recent years, new coatings based on fluorosilicone have appeared, in which the contact angle for water has increased to 112-115° (for a lotus leaf, for example, it is 180°), and for fat - up to 70°. This means that the surface of a spectacle lens with such coatings becomes not only highly hydrophobic, but also lipophobic; repulsive fat.
Hardening coatings
Highly refractive polymers and polycarbonate, which are currently the most popular in the production of eyeglass lenses, are softer than glass. Therefore, in the manufacture of organic spectacle lenses, hardening coatings are applied, which increase the resistance to abrasion of the lenses, i.e. increases the resistance of the spectacle lens to scratching.
To obtain hardening coatings, special varnishes are most often used, which are applied to a spectacle lens by immersion or centrifugation, followed by heating. A hardening coating is applied to both the outer and inside spectacle lenses and is often part of a multifunctional coating.
UV blocking coating
It's no secret that UV radiation is harmful to the eyes. Polymeric materials have a high degree of filtration ultraviolet radiation. Polycarbonate absorbs 98-100% of the radiation of the medium and long-wave energy components of the UV range, which are the most dangerous for eye structures.
Any of the specialized optical plastics has a much higher degree of UV filtration compared to optical glass!
The degree of protection of spectacle lenses in the UV region cannot be determined visually
The ability to filter out the potentially dangerous component of the solar spectrum is associated with the phenomena of absorption, polarization or reflection of the radiation flux. Special organic or inorganic materials are introduced into the composition of lenses (UV absorber, photochromic pigment) or applied as coatings to their surface.
The degree of protection of spectacle lenses in the UV region cannot be determined visually based on the shade or color of the lens, as well as the degree of darkening of the spectacle lenses. These absorbers do not change the color of the lenses, so a high-quality clear spectacle lens can absorb almost all eye-hazardous radiation.
Modern multifunctional coatings provide high quality of vision and comfort when wearing spectacle lenses, have a certain aesthetic value and ease of care for them. In addition, coatings significantly increase the life of glasses, which is important given the current high cost of branded spectacle lenses.
Now almost no medical spectacle lenses are made without special coatings, which significantly improve the quality of vision in glasses and the convenience of their use. One of the most popular and significant coatings for spectacle lenses is anti-reflective.
Why Apply Anti-Reflective Coating to Eyeglass Lenses
Anti-reflective coating has many advantages that improve image quality and enhance the comfort of wearing glasses. First of all, anti-reflective, or as it is also called anti-reflex, coating effectively eliminates glare and halos that occur on the front and back surfaces of spectacle lenses. Thus, in glasses with anti-reflective coating, the effect of blinding reflected light, for example, from car headlights, from snow and wet asphalt, or from car glass, is significantly less. Therefore, such a coating is especially important for. It is also necessarily applied to to eliminate glare from a computer monitor. Anti-reflex coating improves visual acuity in glasses while reducing stress eye muscles and provides visual comfort.
The anti-reflective coating also has an anti-reflective effect, that is, thanks to it, the lenses transmit up to 99.5% of the light and become almost completely transparent. This allows you to see better in bad weather and in dark time days.
Another advantage of anti-reflective coating is the elimination of the “shop window effect”. Spectacle lenses create a light reflection that blocks the user's eyes. This effect is visible to everyone around, and is also displayed in photographs. Therefore, glasses without anti-reflective coating often look unaesthetic.
Features of glasses with anti-reflective coating
If only one anti-reflective coating is applied to spectacle lenses, the lenses become more prone to scratches and fingerprints more often. However, now there are multifunctional coatings for glasses, which, in addition to the anti-reflective coating, also include a hydrophobic and hardening coating. Therefore, this lack of anti-reflective coating is easily eliminated.
