Element in the highlighting of the clock hands. Luminous dials. Absorbing sun rays
"Let there be light!"
Backlights in hours - a necessary component of everyday life, without it it is already impossible to imagine a modern wristwatch. This is a reality where the quality of the backlight is everything.
Today, wristwatches often include electroluminescent backlight, but the backlight is gaining momentum from day to day tritium.
Backlight Indiglopresented by an American company Timex at 1992 year, is the best fit as an example electroluminescent backlight... We press the button, electricity is converted into light by applying a voltage of 100-200 volts to phosphorus atoms. Of course, a voltage converter (1: 100) plays a role here, without which it would be impossible to get even one hundred volts. Having received a charge, phosphorus atoms emit photons, and they illuminate the dial. The name itself "Indiglo" came from the word "Indigo"... It is in color indigo (a cross between blue and purple) the dial of the watch model of the family was illuminated Ironman... This series of watches became the first in the history of the company Timexequipped with backlight Indiglo.
The ubiquitous Japanese corporation Casio could not stay away, in 1995 responding to the invention of Americans with backlight Illuminator... Backlight Casio illuminator similar in design to the backlight Indiglo... In Japan, backlight Illuminator bears the name "Fox Fire".
Only the hands and markers of a given dial can be equipped with tritium backlightwhile an electroluminescent backlight illuminates the entire dial. But do not rush to jump to conclusions!
The use of tritium backlighting in dials is a much more complex process than installing an electroluminescent backlight. Tritium backlight does not require pressing buttons and does not use auxiliary energy sources - be it a clock battery or sunlight. Accordingly, such illumination does not affect the "vitality" reserve of the watch's energy carrier.
Tritium is a radioactive isotope of hydrogen used in thermonuclear weapons as a source of neutrons and fuel. "That's enough for me, leave the watch with such a backlight for yourself, and I'd rather choose a harmless electroluminescent backlight!" - you will think. And you will be wrong.
Tritium does not pose a radiation hazard, because it is enclosed in sealed containers made of borosilicate glass. But even if the dial of the watch suddenly cracked, and the sealed container with tritium was damaged, then nothing would threaten our health. The containers located on the watch dials contain a relatively small amount of tritium, which, if leaked, will have time to escape into the atmosphere without harmful consequences for humans. The most important thing is not to inhale or swallow tritium. Especially when the leak came from a large container.
Long service life without any recharging is the main trump card of tritium backlight. The tritium backlight can last as long as 25 years. During this time, the tritium in the containers will undergo radioactive beta decay, which forces the emerging electrons to act on the phosphor atoms. It is this process that gives a bright green glow to the hands and marks, which can help the owner of the watch under any circumstances.
By the way, tritium backlight can be represented by the most different colors, Not only green, but also dark blue, yellow, orange, red, white... In the watch industry, however, it is precisely green that is used, because the human eye perceives it as the brightest (intensity - 100%). The tritium backlight will lose half of its brightness in 12 years, and after 25 years of service, it "emaciates" by 80% brightness.
Strongly sought after by military and firefighters watches Traser are remarkable not only for their durability, but also for tritium illumination trigalight... A well-known company does not lag behind Luminox, which gives a 25-year guarantee for continuous operation of the tritium backlight in its watches.
The backlight is worthy of special mention SuperLumiNova... This system has declared itself in 1993 yearclearly identifying their positive properties... Backlight operation SuperLumiNova made possible by strontium aluminate, a substance applied to the hands and indexes of hour dials. System SuperLumiNova does not contain radioactive substances, which means it will not lose its quality over time, as it happens with tritium backlighting. For backlight SuperLumiNova periodic "meetings" with sunlight or artificial light are important, they charge the luminous coating of arrows and marks with the required energy.
Some watches not only have an advanced dial lighting system, but can also be used as an independent source of lighting. Men's watches are the best example of this.
Their dial is illuminated by a high-power LED for excellent readability in the dark. But as soon as we go beyond the edges of the dial, a flashlight built into the body reminds of itself, operating in three modes. With details of the clock lighting system Victorinox Swiss Army Night Vision can be found in a separate article.
The various lighting systems in watches today are able to meet the needs of many people. Practical electroluminescent light on the watch Timex, Casiocontributes to the appearance of attractive prices for the models of these companies. More complex tritium illumination awaits on watch dials Traser and Luminox.
Simplicity and affordability, or technical sophistication and innovation? The choice is yours!
Man has long sought to create technical utility. He also learned to measure time. However, even now he has not invented an ideal way to illuminate the hour hands in the dark. Most famous materialused by to illuminate the hour dial- luminescence. This function allows you to see the time on the dial in low light conditions. The fluorescent lighting method is also called "cold light". On clock hands a special coating is applied that glows in the dark. But in order to emit light in the dark, a watch with such a coating must stay for some time in bright light, then it is charged with energy and gives it up in the dark. Several types of luminescence :
- chemiluminescence;
- photoluminescence;
- radioluminescence.
Previously, photoluminescent and radio-luminescent methods were most often used to illuminate the watch dial. Radioluminescence occurs as a result of nuclear radiation. Before World War II, people did not understand the whole danger radiation... Even after learning the full risk of using radiation, some stores continued to sell watches with radium-treated dials.
Today remains popular photoluminescent coating... In this case, light energy comes from hard electromagnetic radiation. Such material absorbs light energy for a long time. Then it emits light much longer than it absorbed.
There is another substance that is used to illuminate the hour hands - tritium. Tritium is a radioactive isotope of hydrogen. Its radioactivity is almost completely absorbed by the glass of the dial. Tritium complies with international standards NIHS 97-10 and ISO 3157. These standards are designed to determine the minimum amount of luminescent material required to see the time on a watch dial in the dark. If tritium contains a high-quality luminescent substance, it can retain the emission of light for several years. The light intensity also depends on the volume of the coating and the thickness of the applied layer. Despite the low radioactivity of tritium, it still has not won one hundred percent confidence in people. Consumer concerns and the requirement of some countries to provide an environmental certificate are forcing watch manufacturers to look for new types of illumination of watch dials.
Japanese watchmakers recently started using completely new materials: LumiBright and LumiNova. Although they are of better quality, however, they are not able to maintain the ability to glow for a long time. Such an hour dial must be constantly recharged - kept under a bright light.
Today, the Swiss Association for Watchmaking (ASRH) is spending a lot of money on research to improve photoluminescence. However, so far, tritium is the best material to solve the problem of time indication in poor lighting conditions.
When choosing a watch, future owners will certainly look at what the mechanism is worth, what the case and glass are made of, what kind of material is the strap or bracelet. The question of which clock backlight is better arises less often. Meanwhile, the performance of this function is seriously different in the models of different watch brands. We will tell you which backlit watch is comfortable to wear every day in the city, which will illuminate your path on a camping trip, and which will pierce the water column with their powerful light when scuba diving.
Luminescent clock illumination
Back in the 19th century, Swiss craftsmen invented a way to preserve the readability of the dial of a pocket watch in the dark - the hands and indices were treated with a luminous substance, barium sulfide. Today, luminescent watch illumination is found in the collections of TAG Heuer, Breitling, Corum and other leaders in the watch industry. Manufacturers process indexes, hands and watch bezels with light-accumulating compounds.
Breitling Professional EVO Night Mission Aviator Watch Dial With Luminescent Markers
SuperLuminova
In 1993, the Japanese company Nemoto introduced a light-accumulating composition (phosphor) based on strontium aluminate. Prior to this, zinc sulfide served as the basis for phosphors. The novelty was ten times brighter and longer than its predecessors, in addition, it was non-toxic and economical - the pigment did not fade for years. The composition was named Luminova. The phosphor was “recharged” from contact with light waves 200-400 nm long, the initial color was green. In 1998, industrial production was launched, and in 2000, an improved version of SuperLuminova was released - one of the most popular clock lights today.
Cozy green glow
Twice as bright as the 1993 SuperLuminova, this illuminated watch is a favorite among divers. The dial markers, treated with a phosphor, are perfectly readable at any depth. A striking example is the TAG Heuer Aquaracer watch, which has already become a classic element of diving equipment. Faceted indexes and hands of the model are covered with white SuperLuminova. The glow time from the moment of contact with the light source is 6-12 hours. In this case, the watch will not go out at once - the backlight brightness will decrease evenly every hour. Watches with such illumination are suitable for deep diving and for a long evening walk.
LED clock
LED watches are popular for their convenience and their bright light. It is enough to press one button on the case and small LEDs located along the entire diameter will evenly illuminate the entire dial. In the famous G-Shock collection of the Japanese brand Casio, there are many models with LED-illumination, which are activated intuitively - in low light, just turn your hand and it will turn on itself.
Military robust GA700 Camo Series with non-edged lighting
Tritium (superheavy hydrogen) is a radioactive isotope of hydrogen that is actively used in the manufacture of nuclear weapons. Surely, such a characteristic sounds at least alarming, but fears are in vain - the radioactive element is securely enclosed in sealed containers made of borosilicate glass. Even if the container is damaged, the substance is not capable of causing harm to health due to its small amount. It is only important to remember that in no case should you swallow and inhale tritium!
Tritium flasks
If the LED backlight depends on a battery, and the light-accumulative backlight, although it lasts a long time, requires mandatory contact with the light source, the tritium backlight of the watch does not need external recharging and lasts about 25 years. This is due to the frequent use of tritium in the creation of night vision devices for the army, aviation and navy.
Trigalight
Trigalight (GTLS, trigalight) is a technology of self-activated tritium illumination of wristwatches, developed by the Swiss company Mb-microtec. The concern has been developing tritium light sources since 1968. The first wristwatch with a trigger of the Traser brand was released in 1991 by order of the US Department of Defense. The US Army has ordered 60,000 watches for units participating in Operation Desert Storm. The debut Traser P6500 Type 6 model was released until 2003.
Classic Milatari Traser Trigalight Watch
Today, Traser watches with tritium backlighting are worn by military personnel from 59 countries. Also, the brand has become a favorite among fans of extreme tourism.
Luminox watches
When choosing a model whose dial is readable in any light, pay attention to water resistance.
("KhiZh", 1977, №10)
Ivan was a miracle here.
“What,” he said, “for the shaitan:
There will be five caps for the light,
And there is no heat and smoke,
Eco miracle light!
P.P. Ershov. The Little Humpbacked Horse
Not everyone can imagine why the clock shines. More than once I had to explain - verbally and in writing - that no, the phosphorus element had nothing to do with it. The watch owes its light to phosphors - substances that can give off in the form of radiation an excess of energy that they received when excited, or, if you like, recharging, say, with visible light or ultraviolet rays. Quite often, the following question is asked: is this glow harmful to health? It tells about those phosphors that are applied to the dials and hands, what they are made of and how; it is briefly said about the hygienic side of the matter.
Absorbing sun rays
Many different phosphors are known to science and practitioners. For example, bioluminophores (the causative agent of energy is a biochemical reaction); electroluminophores, which begin to glow under the influence of an electric discharge; chemiluminophores excited by chemical reactions, and many others. In the watch industry, only a small part of them are used, namely photoluminophores and radio phosphors.
If the substance after excitation emits only billionths of a second, then such a glow is called fluorescence (the word comes from the name of fluorspar - fluorite; some varieties of it glow). When a substance emits rays of minutes, hours, days, then this phenomenon is called phosphorescence, and luminous materials are called phosphorus. Like the name of the chemical element, this word comes from the Greek "phosphoros" - luminiferous.
The term "phosphorus" in relation to luminescent substances appeared in the middle of the 17th century - after it was discovered that, after calcining, some minerals acquire the ability to absorb sunlight, and then emit them in the dark. In 1612, Galileo became interested in such minerals; he left us one of the first descriptions of phosphorescence, but he could not explain the reason for this strange phenomenon.
Another 250 years passed before the mystery of the glowing stones was solved ... In the seventies of the last century, the English company "Balmen" began the industrial production of Balmen's glowing paint. As it should be, its composition was the secret of the company. However, it was soon solved by the French chemist Verneuil. The scientist found that the basis of the paint is calcium sulphide, and it acquires the ability to glow due to an insignificant admixture of bismuth salts. These impurities are now called activators.
Trapped electrons
Luminophores, or crystalline phosphors, are composed of a base and an activator (for example, calcium sulphide and bismuth salts, as in Balmen's paint; many other combinations exist). However, not all of the phosphor has the ability to glow, but only some parts of it, the so-called luminescence centers, or phosphorescence centers. These are the places where there are violations in the crystal lattice of the base. This is how they arise: the mixture of base and activator is heat treated; then a strictly defined amount of impurity enters the base lattice and their joint crystallization occurs; where this happened, the crystal lattice is broken. By the way, it was found that the penetration of impurities is facilitated by low-melting salts - melts, therefore, in the manufacture of a phosphor, they are specially introduced into the reaction mass.
There are three energy zones in crystal phosphorus; they differ in the degree to which their energy levels are filled with electrons; hence the name of the bands: filled, or valence (I), forbidden (II), unfilled, or conduction band (III). The probability of electrons of an ideal crystal falling into zone II is negligible, therefore it is called forbidden. When special impurities - activators - are introduced into the lattice, the picture changes at the places where they enter the lattice: in zone II, new levels appear - luminescence centers (C) and traps (L), into which the phosphor electrons can be taken.
In fact, of course, there are no real traps here, it is just that an electron can remain in such an energy state for a rather long time even after the excitation of the crystal has ceased; the nature of this phenomenon is not yet fully understood. Under the influence of thermal vibrations of the lattice, electrons are gradually released from the traps, lose energy, and the phosphor glows. It was noticed that the duration of the afterglow is the longer, the lower the trap is located, that is, the more energy is required to release an electron.
Under the influence of visible light or ultraviolet rays, from collision with rapidly moving charged particles (for example, alpha or beta), the phosphor electrons are excited and move to higher energy levels. Returning then to their original state, the electrons emit excess energy in the form of light quanta. With the simple eye, we see not individual flashes, but a continuous stream of light, but through a magnifying glass one can also observe single scintillations, although the duration of each is about 0.00005 seconds.
Long-lived phosphors
Phosphors are divided into temporary and permanent. Think of Christmas tree decorations covered with luminescent paints. These paints contain short-lived phosphors ... Lamps are off. The toys glow brightly. But after a while they are no longer visible. If you turn on the light again and then turn it off, the toys light up again.
The basis of the luminous compositions of temporary action is made up of sulfur compounds of zinc, calcium, cadmium, strontium, barium. They are calcined with trace amounts of salts heavy metals: copper, manganese, bismuth. Some phosphors glow blue, others red, and others green.
For watches, phosphors are inconvenient, they do not glow for a long time (although earlier, and sometimes, unfortunately, even now, some enterprises still use such substances). The dials should be visible at least 10-12 hours after illumination. Among the luminophores of temporary action, such compositions are For example, strontium sulfide luminophore; it emits light for about 12 hours on a single charge. But this substance has a significant drawback: in the presence of moisture, hydrolysis of strontium sulfide occurs and hydrogen sulfide is released - an aggressive gas that corrodes the clock mechanism.
Luminophores are increasingly used in watchmaking. Such long-livers include radio phosphors. In addition to the usual base and activator, they also include an energy source - a radioactive substance. Luminescent mixtures of this kind do not need periodic illumination: the phosphor makes charged particles emitted by the radioactive additive work.
The watchmaking industry imposes strict requirements on radioactive additives. Initially, radium-220 compounds were introduced into the phosphors. But its half-life is 1500 years. The watch grew old, broke, and the dial continued to be a source of radioactive radiation. Later it became clear that in luminescent compositions tritium, promethium-147, carbon-14 are more acceptable as energy sources. They live for about 10 years. In addition, these substances emit soft beta rays, which is also very important.
The more radioactive substance is added to the phosphorescent mass, the brighter it glows. But the constant bombardment with charged particles does not pass without a trace for the phosphor itself. If there are too many particles and they carry too much energy, the phosphorus luminescence centers are quickly destroyed. They let the tenants into the house, and they destroyed it ... Therefore, those that emit beta rays are taken from radioactive substances: firstly, they destroy the phosphor less, and, secondly, they are almost completely absorbed by the watch case and glass.
Strict sanitary and hygienic requirements are imposed on phosphors. At one time, the amount of radioactive radiation from dials with a constant light mass was carefully measured, and doctors came to the conclusion that it is possible to wear watches with such phosphors, they do not pose a threat to health. However, the problems of industrial hazards have not been completely resolved: how to apply luminous compounds, while observing safety rules; what to do with waste; how to store large quantities of such watches. This led to the fact that in 1958 in the USSR, the production of watches with radioactive photomass was discontinued. Now, thanks to the efforts of technologists, chemists, doctors and engineers, special sections have been created where phosphors are prepared and applied; these areas meet all safety requirements.
Phosphor-whim
The phosphorescent mixture is a colorless crystalline powder, very delicate and capricious: the destruction of the crystal lattice or the appearance of impurities sharply reduces the brightness of its glow. And yet, the powder has to be subjected to some processing. At least in order to glue it to the dial.
The best thing would, of course, be to enclose the crystals in a transparent shell and attach them to the watch in this form. But this method is not always possible. This means that binders are needed: adhesives, varnishes. With their help, by the way, they not only keep the phosphor on the dial, but also protect it from the effects of atmospheric moisture, from mechanical damage and even from ultraviolet rays that can destroy the luminous coating.
Acrylic, vinyl and polystyrene varnishes are most often used in the watch industry; less often use tsaponlak or cellulose acetate; and special preference is given to dammar pack, it forms a durable transparent film impervious to ultraviolet rays.
The amount of binder added to the phosphor is usually very small, otherwise the varnish envelops the crystals and greatly reduces the brightness of their glow. The components are carefully mixed in glass or porcelain dishes, there can be no question of grinding the mixture. Prepare the composition immediately before application. The finished mixture is applied with a brush, pen, glass rod, syringe or using a printing machine.
Not so long ago in the foreign literature there were reports about another method of applying phosphorescent mixtures - about the method of precipitating them from electrolytes together with metals: nickel, silver, palladium, gold. A beautiful combined coating forms on the dial, it looks equally good in the light and in the dark.
Now the country's watch industry produces watches with dials coated with permanent phosphors in several versions, for example "Amphibia" for scuba divers. (In addition, they still make alarm clocks with dials on which luminescent paint is applied, but it does not fulfill its role well - after one and a half to two hours after recharging it no longer shines.) In the future, the range of watches with long-lived phosphors will expand, their production will increase ...
Candidate of Technical Sciences E. Ya.Besidovsky,
Research Institute of the Watch Industry
