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83-441: These types of phosphorescent pigments, often called lume , operate like a rechargeable light battery. After sufficient activation by sunlight, fluorescent, LED, UV (blacklight), incandescent and other light sources, they glow in the dark for hours. Electrons within the pigment are being "excited" by ultraviolet light exposure—the excitation wavelengths for strontium aluminate range from 200 to 450 nm electromagnetic radiation —to

166-468: A phosphor layer and filled with tritium gas before the containers are permanently sealed. They have the advantage of being self-powered and producing a consistent luminosity that does not gradually fade during the night. However, GTLS contain radioactive tritium gas that has a half-life of slightly over 12.3 years. Additionally, phosphor degradation will cause the brightness of a tritium container to drop by more during that period. The more tritium that

249-401: A substitutional defect occurs, while an interstitial defect occurs when a much smaller atom gets trapped in the "interstices", or the spaces between atoms. In contrast, amorphous materials have no "long-range order" (beyond the space of a few atoms in any direction), thus by definition are filled with defects. When a defect occurs, depending on the type and material, it can create a hole, or

332-441: A "trap". For example, a missing oxygen atom from a zinc oxide compound creates a hole in the lattice, surrounded by unbound zinc-atoms. This creates a net force or attraction that can be measured in electron-volts . When a high-energy photon strikes one of the zinc atoms, its electron absorbs the photon and is thrown out into a higher orbit. The electron may then enter the trap and be held in place (out of its normal orbit) by

415-414: A brighter yet short-lived emission, while lower temperatures produce a dimmer but longer-lasting glow. Temperatures that are too hot or cold, depending on the substance, may not allow the accumulation or release of energy at all. The ideal depth of trap for persistent phosphorescence at room temperature is typically between 0.6 and 0.7 electron-volts. If the phosphorescent quantum yield is high, that is, if

498-444: A charge-discharge cycle, the pigments theoretically retain their afterglow properties indefinitely. A reduction in light intensity only occurs very slowly, almost imperceptibly. This reduction increases with the degree of coloring of the pigments. Intensely colored types lose their intensity more quickly than neutral ones. High temperatures of up to several hundred degrees Celsius are not a problem. The only thing that needs to be avoided

581-555: A global manufacturer of phosphorescent pigments and other specialized phosphors – was founded by Kenzo Nemoto in December 1941 as a luminous paint processing company and has supplied and developed luminous paint to the watch and clock and aviation instruments industry since. Super-LumiNova is based on LumiNova branded pigments, invented in 1993 by the Nemoto staff members Yoshihiko Murayama, Nobuyoshi Takeuchi, Yasumitsu Aoki and Takashi Matsuzawa as

664-466: A higher energetic state and after the excitation source is removed, fall back to their normal energetic state by releasing the energy loss as visible light over a period of time. Although fading over time, appropriately thick applicated larger markings remain visible for dark adapted human eyes for the whole night. This Ultraviolet light exposure induced activation and subsequent light emission process can be repeated again and again. Nemoto & Co., Ltd. –

747-446: A person or object in front of a phosphorescent screen which temporarily captures the shadow. The screen or wall is painted with a glow-in-the-dark product that contains phosphorescent compounds. Publicly, these shadow walls can be found at certain science museums. Screen printing Screen printing is a printing technique where a mesh is used to transfer ink (or dye ) onto a substrate , except in areas made impermeable to

830-439: A preferred choice for large-scale production of printed electronic devices. While screen printing offers tremendous potential in printed electronics, it also faces certain challenges. Fine-line resolution, compatibility with advanced materials, and the need for precise registration pose ongoing research and development opportunities. However, continuous advancements in ink formulations, equipment, and process optimization are paving

913-777: A reputation bolstered by the publication of his 1937 booklet Technical Problems of the Artist: Technique of the Silkscreen Process. Guido Lengweiler has corrected this misunderstanding in his book, A History of Screen Printing , published in English in 2016. Outgrowths of these WPA poster shops, at least two New York City studios in wartime started decorating ceramic tiles with fire-on underglaze applied by silkscreen starting as early as 1939: Esteban Soriano and Harold Ambellan 's workshop called Designed Tiles . The Printers' National Environmental Assistance Center says, "Screenprinting

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996-406: A reservoir of ink. The operator lifts the screen to prevent contact with the substrate and then using a slight amount of downward force pulls the fill bar to the front of the screen. This effectively fills the mesh openings with ink and moves the ink reservoir to the front of the screen. The operator then uses a squeegee (rubber blade) to move the mesh down to the substrate and pushes the squeegee to

1079-437: A safe replacement for radium -based luminous paints . The invention was patented in 1994 by Nemoto & Co., Ltd. and licensed to other manufacturers and watch brands. In 1998 Nemoto & Co. established a join-venture with RC Tritec AG called LumiNova AG, Switzerland to manufacture 100 percent Swiss made afterglow pigments branded as Super-LumiNova. After that, the production of radioactive luminous compounds by RC Tritec AG

1162-423: A second after the illumination is switched off. Conversely, when the stored energy is due to persistent phosphorescence, an entirely different process occurs without a fluorescence precursor. When electrons become trapped within a defect in the atomic or molecular lattice, light is prevented from reemitting until the electron can escape. To escape, the electron needs a boost of thermal energy to help spring it out of

1245-435: A second) after the excitation radiation is removed, phosphorescent materials may continue to emit an afterglow ranging from a few microseconds to many hours after the excitation is removed. There are two separate mechanisms that may produce phosphorescence, called triplet phosphorescence (or simply phosphorescence) and persistent phosphorescence (or persistent luminescence ). Everyday examples of phosphorescent materials are

1328-399: A shorter wavelength, a phosphorescent substance will glow, absorbing the light and reemitting it at a longer wavelength. Unlike fluorescence, a phosphorescent material does not immediately reemit the radiation it absorbs. Instead, a phosphorescent material absorbs some of the radiation energy and reemits it for a much longer time after the radiation source is removed. In a general sense, there

1411-401: A time, so several screens can be used to produce a multi-coloured image or design. Traditionally, silk was used in the process. Currently, synthetic threads are commonly used. The most popular mesh in general use is made of polyester. There are special-use mesh materials of nylon and stainless steel available to the screen-printer. There are also different types of mesh size which will determine

1494-419: A variety of materials, such as textiles, ceramics, wood, paper, glass, metal, and plastic. As a result, screen printing is used in many different industries, including: In screen printing on wafer-based solar photovoltaic (PV) cells, the mesh and buses of silver are printed on the front; furthermore, the buses of silver are printed on the back. Subsequently, aluminum paste is dispensed over the whole surface of

1577-412: A water spray, leaving behind a clean area in the mesh with the identical shape as the desired image, which will allow passage of ink. It is a positive process. In fabric printing, the surface supporting the fabric to be printed (commonly referred to as a pallet) is coated with a wide 'pallet tape'. This serves to protect the 'pallet' from any unwanted ink leaking through the screen and potentially staining

1660-457: A widely adopted technique in the printing industry, has found its niche in the realm of printed electronics. Its versatility and ability to deposit thick layers of inks make it ideal for creating conductive tracks, sensors, and other electronic components. Furthermore, screen printing offers advantages such as high throughput, low production costs, and compatibility with a wide range of substrates, including flexible materials. These attributes make it

1743-430: Is a union between analog screen printing and traditional digital direct-to-garment printing, two of the most common textile embellishment technologies in use today. Essentially, digital hybrid screen printing is an automatic screen-printing press with a CMYK digital enhancement located on one of the screen print stations. Digital hybrid screen printing is capable of variable data options, creating endless customizations, with

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1826-453: Is arguably the most versatile of all printing processes. Since rudimentary screenprinting materials are so affordable and readily available, it has been used frequently in underground settings and subcultures , and the non-professional look of such DIY culture screenprints have become a significant cultural aesthetic seen on movie posters, record album covers, flyers, shirts, commercial fonts in advertising, in artwork and elsewhere. Credit

1909-437: Is created via a chemical reaction. The light emission tracks the kinetic progress of the underlying chemical reaction. The excited state will then transfer to a dye molecule, also known as a sensitizer or fluorophor , and subsequently fluoresce back to the ground state. Common pigments used in phosphorescent materials include zinc sulfide and strontium aluminate . Use of zinc sulfide for safety related products dates back to

1992-412: Is decoration. Stars made of glow-in-the-dark plastic are placed on walls, ceilings, or hanging from strings make a room look like the night sky. Other objects like figurines, cups, posters, lamp fixtures, toys and bracelet beads may also glow. Using blacklights makes these things glow brightly, common at raves , bedrooms, theme parks, and festivals. A shadow wall is created when a light flashes upon

2075-429: Is given to the artist Andy Warhol for popularising screen printing as an artistic technique. Warhol's silk screens include his 1962 Marilyn Diptych , which is a portrait of the actress Marilyn Monroe printed in bold colours. Warhol was supported in his production by master screen printer Michel Caza , a founding member of Fespa . Sister Mary Corita Kent gained international fame for her vibrant serigraphs during

2158-417: Is initially inserted in the container, the brighter it is to begin with, and the longer its useful life. This means the intensity of the tritium-powered light source will slowly fade, generally becoming too dim to be useful for dark adapted human eyes after 20 to 30 years. Phosphorescence Phosphorescence is a type of photoluminescence related to fluorescence . When exposed to light (radiation) of

2241-531: Is no distinct boundary between the emission times of fluorescence and phosphorescence (i.e.: if a substance glows under a black light it is generally considered fluorescent, and if it glows in the dark it is often simply called phosphorescent). In a modern, scientific sense, the phenomena can usually be classified by the three different mechanisms that produce the light, and the typical timescales during which those mechanisms emit light. Whereas fluorescent materials stop emitting light within nanoseconds (billionths of

2324-473: Is offered in three grade levels; Standard, A and X1. The initial brightness of these grades does not significantly vary, but the light intensity decay over time of the A and X1 grades is significantly reduced. This means the X1 grade takes the longest to become too dim to be useful for the human eye. Not all Super-LumiNova color variations are available in three grades. Due to the fact that no chemical change occurs after

2407-491: Is prolonged contact with water or high humidity, as this creates a hydroxide layer that negatively affects the light emission intensity. Besides being used in timepieces by industry and hobbyists, Super-LumiNova is also marketed for application on: Super-LumiNova granulated pigments are applied either by manual application, screen printing or pad printing . RC Tritec AG recommends up to 0.30 mm (0.012 in) application thickness in one or multiple layer(s). Over that,

2490-414: Is the only way to make high-build fully patterned printing/coating as a continuous process, and has been widely used for manufacturing textured wallpapers. Textile items printed with multi-coloured designs often use a wet on wet technique, or colours dried while on the press, while graphic items are allowed to dry between colours that are then printed with another screen and often in a different colour after

2573-621: The National Serigraph Society , including WPA artists Max Arthur Cohn , Anthony Velonis and Hyman Warsager , coined the word "serigraphy" in the 1930s to differentiate the artistic application of screen printing from the industrial use of the process. "Serigraphy" is a compound word formed from Latin "sēricum" (silk) and Greek "graphein" (to write or draw). Historians of the New York WPA poster shop give sole credit to Anthony Velonis for establishing Silkscreen methods used there,

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2656-509: The Song dynasty (960–1279 AD). It was then adapted by other Asian countries like Japan, and was further created using newer methods. Screen printing was largely introduced to Western Europe from Asia sometime in the late 18th century, but did not gain large acceptance or use in Europe until silk mesh was more available for trade from the east and a profitable outlet for the medium discovered. Early in

2739-411: The 'pallet' or transferring unwanted ink onto the next substrate. The pallet tape is also used to protect the pallet from the usage of glue that keeps the substrate adhered and in place on the pallet. Over time the pallet tape will become covered with lint which it then can be removed, discarded, and replaced by new pallet tape. Next, the screen and frame are lined with a tape to prevent ink from reaching

2822-448: The 1910s, several printers experimenting with photo-reactive chemicals used the well-known actinic light –activated cross linking or hardening traits of potassium, sodium or ammonium chromate and dichromate chemicals with glues and gelatin compounds. Roy Beck, Charles Peter and Edward Owens studied and experimented with chromic acid salt sensitized emulsions for photo-reactive stencils. This trio of developers would prove to revolutionize

2905-484: The 1930s. The development of strontium aluminate pigments in 1993 was spurred on by the need to find a substitute for glow-in-the-dark materials with high luminance and long phosphorescence, especially those that used promethium . This led to the discovery by Yasumitsu Aoki (Nemoto & Co.) of materials with luminance approximately 10 times greater than zinc sulfide and phosphorescence approximately 10 times longer. This has relegated most zinc sulfide based products to

2988-407: The 1950s and 1960s did advances in quantum electronics , spectroscopy , and lasers provide a measure to distinguish between the various processes that emit the light, although in common speech the distinctions are still often rather vague. In simple terms, phosphorescence is a process in which energy absorbed by a substance is released relatively slowly in the form of light. This is in some cases

3071-430: The 1960s and 1970s. Her works were rainbow coloured, contained words that were both political, and fostered peace and love and caring. American entrepreneur, artist and inventor Michael Vasilantone started to use, develop, and sell a rotatable multicolour garment screen printing machine in 1960. Vasilantone later filed for a patent on his invention in 1967 granted number 3,427,964 on 18 February 1969. The original machine

3154-548: The Greek suffix -φόρος ( -phoros ), meaning "to bear", combined with the Latin suffix -escentem , meaning "becoming of", "having a tendency towards", or "with the essence of". Thus, phosphorescence literally means "having a tendency to bear light". It was first recorded in 1766. The term phosphor had been used since the Middle Ages to describe minerals that glowed in the dark. One of

3237-650: The United States. Graphic screen-printing is widely used today to create mass- or large-batch produced graphics, such as posters or display stands. Full colour prints can be created by printing in CMYK (cyan, magenta, yellow and black). Screen printing lends itself well to printing on canvas. Andy Warhol , Arthur Okamura , Robert Rauschenberg , Roy Lichtenstein , Harry Gottlieb and many other artists have used screen printing as an expression of creativity and artistic vision. Another variation, digital hybrid screen printing,

3320-430: The added ability of screen print specific techniques. A screen is made of a piece of mesh stretched over a frame. The mesh could be made of a synthetic polymer , such as nylon , and a finer and smaller aperture for the mesh would be utilized for a design that requires a higher and more delicate degree of detail. For the mesh to be effective, it must be mounted on a frame and it must be under tension. The frame which holds

3403-452: The afterglow pigment can absorb and emit. After the green glowing and pale yellow-green in daylight appearing C3 (emission at 515 nm) variant, the blue-green glowing and in daylight white appearing BGW9 (emission at 485 nm, close to the turquoise wavelength) color variant is the second most effective variant regarding pure afterglow brightness. Different colors can however be chosen to optimize (perceived) light emission, dictated by

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3486-419: The attraction. To trigger the release of the energy, a random spike in thermal energy of sufficient magnitude is needed to boost the electron out of the trap and back into its normal orbit. Once in orbit, the electron's energy can drop back to normal (ground state) resulting in the release of a photon. The release of energy in this way is a completely random process, governed mostly by the average temperature of

3569-419: The back for passivation and surface reflection. One of the parameters that can vary and can be controlled in screen printing is the thickness of the print. This makes it useful for some of the techniques of printing solar cells, electronics etc. Solar wafers are becoming thinner and larger, so careful printing is required to maintain a lower breakage rate, though high throughput at the printing stage improves

3652-424: The commercial screen printing industry by introducing photo-imaged stencils to the industry, though the acceptance of this method would take many years. Commercial screen printing now uses sensitizers far safer and less toxic than bichromates. Currently, there are large selections of pre-sensitized and "user mixed" sensitized emulsion chemicals for creating photo-reactive stencils. A group of artists who later formed

3735-435: The copper and solder-stop layers ). Typical names for these service print overlays include tSilk / bSilk aka PLC / PLS or TSK / BSK ( EAGLE ), F.SilkS / B.SilkS ( KiCad ), PosiTop / PosiBot ( TARGET ), silkTop / silkBottom ( Fritzing ), SST / SSB ( OrCAD ), ST.PHO / SB.PHO ( PADS ), SEVS / SERS ( WEdirekt ) or GTO / GBO (Gerber and many others ). Screen printing,

3818-422: The edge of the screen and the frame. The type of tape used in for this purpose often depends upon the ink that is to be printed onto the substrate. More aggressive tapes are generally used for UV and water-based inks due to the inks' lower viscosities and greater tendency to creep underneath tape. The last process in the 'pre-press' is blocking out any unwanted 'pin-holes' in the emulsion. If these holes are left in

3901-409: The emulsion, the ink will continue through and leave unwanted marks. To block out these holes, materials such as tapes, speciality emulsions and 'block-out pens' may be used effectively. The screen is placed atop a substrate. Ink is placed on top of the screen, and a floodbar is used to push the ink through the holes in the mesh. The operator begins with the fill bar at the rear of the screen and behind

3984-1084: The excited triplet state, and, even if T 1 is formed, phosphorescence is most frequently outcompeted by non-radiative pathways. One strategy to enhance the ISC and phosphorescence is the incorporation of heavy atoms, which increase spin-orbit coupling (SOC). Additionally, the SOC (and therefore the ISC) can be promoted by coupling n-π* and π-π* transitions with different angular momenta, also known as Mostafa El-Sayed 's rule. Such transitions are typically exhibited by carbonyl or triazine derivatives, and most organic room-temperature phosphorescent (ORTP) materials incorporate such moieties. In turn, to inhibit competitive non-radiative deactivation pathways, including vibrational relaxation and oxygen quenching and triplet-triplet annihilations, organic phosphors have to be embedded in rigid matrices such as polymers, and molecular solids (crystals, covalent organic frameworks, and others). In 1974 Becky Schroeder

4067-422: The formation of a picture as the electron beam scans the screen, but fast enough to prevent the frames from blurring together. Even substances commonly associated with fluorescence may in fact be prone to phosphorescence, such as the liquid dyes found in highlighter pens, which is a common problem in liquid dye lasers . The onset of phosphorescence in this case can sometimes be reduced or delayed significantly by

4150-505: The glow-in-the-dark toys, stickers, paint, and clock dials that glow after being charged with a bright light such as in any normal reading or room light. Typically, the glow slowly fades out, sometimes within a few minutes or up to a few hours in a dark room. The study of phosphorescent materials led to the discovery of radioactive decay . The term phosphorescence comes from the Ancient Greek word φῶς ( phos ), meaning "light", and

4233-403: The ground state, and 1 the excited state). Transitions can also occur to higher energy levels, but the first excited state is denoted for simplicity. Solid materials typically come in two main types: crystalline and amorphous. In either case, a lattice or network of atoms and molecules form. In crystals, the lattice is a very neat, uniform assembly. However, nearly all crystals have defects in

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4316-595: The human eye luminous efficiency function variance. Maximal light emission around wavelengths of 555 nm ( green ) is important for obtaining optimal photopic vision using the eye cone cells for observation in – or just coming from – well-lit conditions. Maximal light emission around wavelengths of 498 nm ( cyan ) is important for obtaining optimal scotopic vision using the eye rod cells for observation in low-light conditions. Besides technical and human eye dictated reasons, esthetic or other reasons can also influence Super-LumiNova color choices. Super-LumiNova

4399-411: The ink by a blocking stencil . A blade or squeegee is moved across the screen in a "flood stroke" to fill the open mesh apertures with ink, and a reverse stroke then causes the screen to touch the substrate momentarily along a line of contact. This causes the ink to wet the substrate and be pulled out of the mesh apertures as the screen springs back after the blade has passed. One colour is printed at

4482-610: The late 1960s, radium was phased out and replaced with safer alternatives. Tritium was used on and the original Panerai Luminor dive watch Radiomir and almost all Swiss watches from 1960 to 1998 when it was banned. Tritium-based substances ceased to be used by Omega SA in 1997. In the 21st century, one radioluminescent alternative for afterglow pigments requiring radiation protection is being produced and used for watches and other uses. These are tritium -based devices called "gaseous tritium light source" ( GTLS ). GTLS are made using sturdy (often glass) containers internally coated with

4565-435: The material versus the "depth" of the trap, or how many electron-volts it exerts. A trap that has a depth of 2.0 electron-volts would require a great amount of thermal energy (very high temperature) to overcome the attraction, while at a depth of 0.1 electron-volts very little heat (very cold temperature) is needed for the trap to even hold an electron. Generally, higher temperatures cause a faster release of energy, resulting in

4648-579: The mechanism used for glow-in-the-dark materials which are "charged" by exposure to light. Unlike the relatively swift reactions in fluorescence, such as those seen in laser mediums like the common ruby , phosphorescent materials "store" absorbed energy for a longer time, as the processes required to reemit energy occur less often. However, timescale is still only a general distinction, as there are slow-emitting fluorescent materials, for example uranyl salts , and, likewise, some phosphorescent materials like zinc sulfide (in violet) are very fast. Scientifically,

4731-430: The mesh could be made of diverse materials, such as wood, metal, or aluminum, depending on the sophistication of the machine or the artisan procedure. The tension of the mesh may be checked by using a tensiometer; a common unit for the measurement of the tension of the mesh is Newton per centimeter (N/cm). A stencil is formed by blocking off parts of the screen in the negative image of the design to be printed; that is,

4814-425: The mixture for application on various surfaces. Alternatively, RC Tritec AG offers Lumicast pieces, which are highly concentrated luminous Super-LumiNova 3D-castings. According to RC Tritec AG these ceramic parts can be made in any customer desired shape and result in a higher light emission brightness when compared to the common application methods. Lumicast pieces can be glued or form fitted on various surfaces. By

4897-403: The most famous, but not the first, was Bolognian phosphor. Around 1604, Vincenzo Casciarolo discovered a " lapis solaris " near Bologna, Italy. Once heated in an oxygen-rich furnace , it thereafter absorbed sunlight and glowed in the dark. In 1677, Hennig Brand isolated a new element that glowed due to a chemiluminescent reaction when exposed to air, and named it " phosphorus ". In contrast,

4980-428: The novelty category. Strontium aluminate based pigments are now used in exit signs, pathway marking, and other safety related signage. Since both phosphorescence (transition from T 1 to S 0 ) and the generation of T 1 from an excited singlet state (e.g., S 1 ) via intersystem crossing (ISC) are spin-forbidden processes, most organic materials exhibit insignificant phosphorescence as they mostly fail to populate

5063-441: The open spaces are where the ink will appear on the substrate. Before printing occurs, the frame and screen must undergo the pre-press process, in which an emulsion is 'scooped' across the mesh. Once this emulsion has dried, it is selectively exposed to ultra-violet light, through a film printed with the required design. This hardens the emulsion in the exposed areas but leaves the unexposed parts soft. They are then washed away using

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5146-481: The outcome and look of the finished design on the material. The technique is used not only for garment printing but for printing on many other substances, including decals, clock and watch faces, balloons, and many other products. Advanced uses include laying down conductors and resistors in multi-layer circuits using thin ceramic layers as the substrate. Screen printing first appeared in a recognizable form in China during

5229-401: The phenomena are classified by the different mechanisms that produce the light, as materials that phosphoresce may be suitable for some purposes such as lighting, but may be completely unsuitable for others that require fluorescence, like lasers. Further blurring the lines, a substance may emit light by one, two, or all three mechanisms depending on the material and excitation conditions. When

5312-406: The phosphor coatings used in fluorescent lamps , where phosphorescence on the order of milliseconds or longer is useful for filling in the "off-time" between AC current cycles, helping to reduce "flicker". Phosphors with faster decay times are used in applications like the pixels excited by free electrons ( cathodoluminescence ) in cathode-ray tube television-sets , which are slow enough to allow

5395-408: The photons involved matches the available energy states and allowed transitions of the substrate. In the special case of phosphorescence, the electron which absorbed the photon (energy) undergoes an unusual intersystem crossing into an energy state of different (usually higher) spin multiplicity ( see term symbol ), usually a triplet state . As a result, the excited electron can become trapped in

5478-409: The product is re-aligned on the press. Most screens are ready for re-coating at this stage, but sometimes screens will have to undergo a further step in the reclaiming process called de-hazing. This additional step removes haze or "ghost images" left behind in the screen once the emulsion has been removed. Ghost images tend to faintly outline the open areas of previous stencils, hence the name. They are

5561-400: The rear of the screen. The ink that is in the mesh opening is pumped or squeezed by capillary action to the substrate in a controlled and prescribed amount, i.e. the wet ink deposit is proportional to the thickness of the mesh and or stencil. As the squeegee moves toward the rear of the screen the tension of the mesh pulls the mesh up away from the substrate (called snap-off) leaving the ink upon

5644-575: The result of ink residue trapped in the mesh, often in the knuckles of the mesh (the points where threads cross). A properly cleaned screen will not have any residual traces of the previous image apparent on its surface. A method of stenciling that has increased in popularity over the past years is the photo emulsion technique: Screen printing is more versatile than traditional printing techniques. The surface does not have to be printed under pressure, unlike etching or lithography , and it does not have to be planar. Different inks can be used to work with

5727-452: The squeegees, rotate and raise or lower pallets removing much of the manual labour from the task and use UV for instant image curing - resulting in significant reductions in operator fatigue as well as more consistent results. In electronic design automation , the silk screen is part of the layer stack of the printed circuit board (PCB), and the top and bottom sides are described in individual Gerber files like any other layers (such as

5810-437: The stacking sequence of these molecules and atoms. A vacancy defect , where an atom is simply missing from its place, leaving an empty "hole", is one type of defect. Sometimes atoms can move from place to place within the lattice, creating Schottky defects or Frenkel defects . Other defects can occur from impurities in the lattice. For example, when a normal atom is substituted by a different atom of much larger or smaller size,

5893-437: The stored energy becomes locked in by the spin of the atomic electrons , a triplet state can occur, slowing the emission of light, sometimes by several orders of magnitude. Because the atoms usually begin in a singlet state of spin, favoring fluorescence, these types of phosphors typically produce both types of emission during illumination, and then a dimmer afterglow of strictly phosphorescent light typically lasting less than

5976-432: The substance has a large number of traps of the correct depth, this substance will release a significant amount of light over a long period of time, creating a so-called "glow in the dark" material. Some examples of glow-in-the-dark materials do not glow by phosphorescence. For example, glow sticks glow due to a chemiluminescent process which is commonly mistaken for phosphorescence. In chemiluminescence, an excited state

6059-425: The substrate surface. There are three common types of screen printing presses: flat-bed, cylinder, and rotary. A development of screen printing with flat screens from 1963 was to wrap the screen around to form a tube, with the ink supply and squeegee inside the tube. The resulting roller rotates at the same speed as the web in a roll-to-roll machine. The benefits are high output rates and long rolls of product. This

6142-454: The term luminescence (from the Latin lumen for "light"), was coined by Eilhardt Wiedemann in 1888 as a term to refer to "light without heat", while "fluorescence" by Sir George Stokes in 1852, when he noticed that, when exposing a solution of quinine sulfate to light refracted through a prism , the solution glowed when exposed to the mysterious invisible-light (now known to be UV light) beyond

6225-1272: The throughput of the whole cell production line. To print multiple copies of the screen design on garments in an efficient manner, amateur and professional printers usually use a screen printing press, which is a colloquial term as most screen printing machines are vastly different from offset printing presses . Many companies offer simple to sophisticated printing presses. These presses come in one of three types, manual (also referred to as handbench), semi-automatic, and fully automatic. Most printing companies will use one or more semi-automatic or fully automatic machines with manual machines for small runs and sampling. Whilst manual screen printing can be done with carousels, handbenches (both of which are often referred to colloquially as presses) or even on to tables. Semi- and fully-automatic machines are broken into two main categories; flatbed printers (poster, art printing or other flat substrates) and carousels and oval machines (garments and other apparel, amongst other textiles). Both which are fundamentally similar in terms of automation but differ in areas such as physical footprint and upgrade paths. These machines are much faster and use either pneumatic pressure generated by air compressors or use electric motors to draw

6308-411: The trap and back into orbit around the atom. Only then can the atom emit a photon. Thus, persistent phosphorescence is highly dependent on the temperature of the material. Most photoluminescent events, in which a chemical substrate absorbs and then re-emits a photon of light, are fast, in the order of 10 nanoseconds . Light is absorbed and emitted at these fast time scales in cases where the energy of

6391-421: The triplet state with only "forbidden" transitions available to return to the lower energy singlet state. These transitions, although "forbidden", will still occur in quantum mechanics but are kinetically unfavored and thus progress at significantly slower time scales. Most phosphorescent compounds are still relatively fast emitters, with triplet decay-times in the order of milliseconds. Common examples include

6474-422: The ultraviolet light starts getting problems to effectively reach and activate the bottom of the deposited pigment, diminishing the returns for additional application thickness. The pigments and binders are produced separately, as there is no optimal binder for differing applications. This forces RC Tritec AG to offer many solvent and non-solvent based binder systems to maximally concentrate the granulated pigments in

6557-401: The use of triplet-quenching agents. S 0 + h ν → S 1 → T 1 → S 0 + h ν ′   {\displaystyle S_{0}+h\nu \to S_{1}\to T_{1}\to S_{0}+h\nu ^{\prime }\ } where S is a singlet and T a triplet whose subscripts denote states (0 is

6640-718: The violet end of the spectrum. Stokes formed the term from a combination of fluorspar and opalescence (preferring to use a mineral instead of a solution), albeit it was later discovered that fluorspar glows due to phosphorescence. There was much confusion between the meanings of these terms throughout the late nineteenth to mid-twentieth centuries. Whereas the term "fluorescence" tended to refer to luminescence that ceased immediately (by human-eye standards) when removed from excitation, "phosphorescence" referred to virtually any substance that glowed for appreciable periods in darkness, sometimes to include even chemiluminescence (which occasionally produced substantial amounts of heat). Only after

6723-458: Was completely stopped. According to RC Tritec AG the Swiss watch brands all use their Super-LumiNova pigments. Over time, RC Tritec AG developed other afterglow color variations than the original Nemoto & Co. C3 green and higher grades of afterglow pigments. Any other Super-LumiNova emission color offering than C3 is achieved by adding colorants that adsorb light and hence limit the amount of light

6806-541: Was given a US patent for her invention of the "Glow Sheet" which used phosphorescent lines under writing paper to help people write in low-light conditions. Glow in the dark material is added to the plastic blend used in injection molds to make some disc golf discs, which allow the game to be played at night. Often clock faces of watches are painted with phosphorescent colours. Therefore, they can be used in absolute dark environments for several hours after having been exposed to bright light. A common use of phosphorescence

6889-407: Was manufactured to print logos and team information on bowling garments, but was soon directed to the new fad of printing on T-shirts. The Vasilantone patent was licensed by multiple manufacturers and the resulting production and boom in printed T-shirts made this garment screen printing machine popular. Screen printing on garments currently accounts for over half of the screen printing activity in

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