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91-426: In raster cathode-ray tube (CRT) displays, the blank level is usually supplied during this period to avoid painting the retrace line—see raster scan for details; signal sources such as television broadcasts do not supply image information during the blanking period. Digital displays usually will not display incoming data stream during the blanking interval even if present. The VBI was originally needed because of

182-431: A picture tube . CRTs have also been used as memory devices , in which case the screen is not intended to be visible to an observer. The term cathode ray was used to describe electron beams when they were first discovered, before it was understood that what was emitted from the cathode was a beam of electrons. In CRT TVs and computer monitors, the entire front area of the tube is scanned repeatedly and systematically in

273-401: 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

364-419: A voltage multiplier for the current delivered by the flyback. For the inner funnel coating, monochrome CRTs use aluminum while color CRTs use aquadag ; Some CRTs may use iron oxide on the inside. On the outside, most CRTs (but not all) use aquadag. Aquadag is an electrically conductive graphite-based paint. In color CRTs, the aquadag is sprayed onto the interior of the funnel whereas historically aquadag

455-441: 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

546-458: A CRT and limits its practical size (see § Size ). The funnel and neck glass comprise the remaining 30% and 5% respectively. The glass in the funnel can vary in thickness, to join the thin neck with the thick screen. Chemically or thermally tempered glass may be used to reduce the weight of the CRT glass. The outer conductive coating is connected to ground while the inner conductive coating

637-479: A CRT as a display device. The Braun tube became the foundation of 20th century TV. In 1908, Alan Archibald Campbell-Swinton , fellow of the Royal Society (UK), published a letter in the scientific journal Nature , in which he described how "distant electric vision" could be achieved by using a cathode-ray tube (or "Braun" tube) as both a transmitting and receiving device. He expanded on his vision in

728-406: A CRT can be measured by the screen's entire area (or face diagonal ) or alternatively by only its viewable area (or diagonal) that is coated by phosphor and surrounded by black edges. While the viewable area may be rectangular, the edges of the CRT may have a curvature (e.g. black stripe CRTs, first made by Toshiba in 1972) or the edges may be black and truly flat (e.g. Flatron CRTs), or

819-515: A CRT is related to its screen size. Usual deflection angles were 90° for computer monitor CRTs and small CRTs and 110° which was the standard in larger TV CRTs, with 120 or 125° being used in slim CRTs made since 2001–2005 in an attempt to compete with LCD TVs. Over time, deflection angles increased as they became practical, from 50° in 1938 to 110° in 1959, and 125° in the 2000s. 140° deflection CRTs were researched but never commercialized, as convergence problems were never resolved. The size of

910-440: A CRT is usually made up of three parts: A screen/faceplate/panel, a cone/funnel, and a neck. The joined screen, funnel and neck are known as the bulb or envelope. The neck is made from a glass tube while the funnel and screen are made by pouring and then pressing glass into a mold. The glass, known as CRT glass or TV glass, needs special properties to shield against x-rays while providing adequate light transmission in

1001-414: 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

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1092-529: A cross hatch pattern. CRT glass used to be made by dedicated companies such as AGC Inc. , O-I Glass , Samsung Corning Precision Materials, Corning Inc. , and Nippon Electric Glass ; others such as Videocon, Sony for the US market and Thomson made their own glass. The funnel and the neck are made of leaded potash-soda glass or lead silicate glass formulation to shield against x-rays generated by high voltage electrons as they decelerate after striking

1183-414: A fixed pattern called a raster . In color devices, an image is produced by controlling the intensity of each of three electron beams , one for each additive primary color (red, green, and blue) with a video signal as a reference. In modern CRT monitors and TVs the beams are bent by magnetic deflection , using a deflection yoke . Electrostatic deflection is commonly used in oscilloscopes. The tube

1274-454: A long blanking interval, and thin panel displays require none, but the standards were established when the delay was needed (and to allow the continued use of older equipment). Blanking of a CRT may not be perfect due to equipment faults or brightness set very high; in this case a white retrace line shows on the screen, often alternating between fairly steep diagonals from right to left and less-steep diagonals back from left to right, starting in

1365-600: A mainstay of display technology for decades, CRT-based computer monitors and TVs are now obsolete . Demand for CRT screens dropped in the late 2000s. Despite efforts from Samsung and LG to make CRTs competitive with their LCD and plasma counterparts, offering slimmer and cheaper models to compete with similarly sized and more expensive LCDs, CRTs eventually became obsolete and were relegated to developing markets and vintage enthusiasts once LCDs fell in price, with their lower bulk, weight and ability to be wall mounted coming as pluses. Some industries still use CRTs because it

1456-426: A metal funnel insulated with polyethylene instead of glass with conductive material. Others had ceramic or blown Pyrex instead of pressed glass funnels. Early CRTs did not have a dedicated anode cap connection; the funnel was the anode connection, so it was live during operation. The funnel is coated on the inside and outside with a conductive coating, making the funnel a capacitor, helping stabilize and filter

1547-423: 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

1638-435: 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

1729-464: A sheet of glass and the electrons were accelerated to a nearby sheet of glass with phosphors using an anode voltage. The electrons were not focused, making each subpixel essentially a flood beam CRT. They were never put into mass production as LCD technology was significantly cheaper, eliminating the market for such displays. The last large-scale manufacturer of (in this case, recycled) CRTs, Videocon , ceased in 2015. CRT TVs stopped being made around

1820-399: 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

1911-687: A speech given in London in 1911 and reported in The Times and the Journal of the Röntgen Society . The first cathode-ray tube to use a hot cathode was developed by John Bertrand Johnson (who gave his name to the term Johnson noise ) and Harry Weiner Weinhart of Western Electric , and became a commercial product in 1922. The introduction of hot cathodes allowed for lower acceleration anode voltages and higher electron beam currents, since

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2002-444: A target, such as the phosphor screen or shadow mask of a color CRT. The velocity of the electrons depends on the anode voltage of the CRT; the higher the voltage, the higher the speed. The amount of x-rays emitted by a CRT can also lowered by reducing the brightness of the image. Leaded glass is used because it is inexpensive, while also shielding heavily against x-rays, although some funnels may also contain barium. The screen

2093-419: A tradeoff between the two. It consists of a metal clip that expands on the inside of an anode button that is embedded on the funnel glass of the CRT. The connection is insulated by a silicone suction cup, possibly also using silicone grease to prevent corona discharge . Phosphorescent Phosphorescence is a type of photoluminescence related to fluorescence . When exposed to light (radiation) of

2184-467: A visible tear . This is especially true in video game systems, where the fixed frequency of the blanking period might also be used to derive in-game timing. On many consoles there is an extended blanking period, as the console opts to paint graphics on fewer lines than the television would natively allow, permitting its output to be surrounded by a border. On some very early machines such as the Atari 2600 ,

2275-412: Is a vacuum tube containing one or more electron guns , which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms on an oscilloscope , a frame of video on an analog television set (TV), digital raster graphics on a computer monitor , or other phenomena like radar targets. A CRT in a TV is commonly called

2366-444: Is a glass envelope which is heavy, fragile, and long from front screen face to rear end. Its interior must be close to a vacuum to prevent the emitted electrons from colliding with air molecules and scattering before they hit the tube's face. Thus, the interior is evacuated to less than a millionth of atmospheric pressure . As such, handling a CRT carries the risk of violent implosion that can hurl glass at great velocity. The face

2457-440: Is connected using the anode button/cap through a series of capacitors and diodes (a Cockcroft–Walton generator ) to the high voltage flyback transformer ; the inner coating is the anode of the CRT, which, together with an electrode in the electron gun, is also known as the final anode. The inner coating is connected to the electrode using springs. The electrode forms part of a bipotential lens. The capacitors and diodes serve as

2548-437: 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

2639-412: 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

2730-687: Is either too much effort, downtime, and/or cost to replace them, or there is no substitute available; a notable example is the airline industry. Planes such as the Boeing 747-400 and the Airbus A320 used CRT instruments in their glass cockpits instead of mechanical instruments. Airlines such as Lufthansa still use CRT technology, which also uses floppy disks for navigation updates. They are also used in some military equipment for similar reasons. As of 2022 , at least one company manufactures new CRTs for these markets. A popular consumer usage of CRTs

2821-399: Is for retrogaming . Some games are impossible to play without CRT display hardware. Light guns only work on CRTs because they depend on the progressive timing properties of CRTs. Another reason people use CRTs due to the natural blending of these displays. Some games designed for CRT displays exploit this, which allows them to look more aesthetically pleasing on these displays. The body of

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2912-510: Is gradually reduced. This means that flat-screen CRTs may not be completely flat on the inside. The glass used in CRTs arrives from the glass factory to the CRT factory as either separate screens and funnels with fused necks, for Color CRTs, or as bulbs made up of a fused screen, funnel and neck. There were several glass formulations for different types of CRTs, that were classified using codes specific to each glass manufacturer. The compositions of

3003-531: 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

3094-537: Is typically made of thick lead glass or special barium - strontium glass to be shatter-resistant and to block most X-ray emissions. This tube makes up most of the weight of CRT TVs and computer monitors. Since the early 2010s, CRTs have been superseded by flat-panel display technologies such as LCD , plasma display , and OLED displays which are cheaper to manufacture and run, as well as significantly lighter and thinner. Flat-panel displays can also be made in very large sizes whereas 40–45 inches (100–110 cm)

3185-419: Is usually instead made out of a special lead-free silicate glass formulation with barium and strontium to shield against x-rays, as it doesn't brown unlike glass containing lead. Another glass formulation uses 2–3% of lead on the screen. Alternatively zirconium can also be used on the screen in combination with barium, instead of lead. Monochrome CRTs may have a tinted barium-lead glass formulation in both

3276-475: The Aiken tube was invented. It was a CRT in a flat-panel display format with a single electron gun. Deflection was electrostatic and magnetic, but due to patent problems, it was never put into production. It was also envisioned as a head-up display in aircraft. By the time patent issues were solved, RCA had already invested heavily in conventional CRTs. 1968 marked the release of Sony Trinitron brand with

3367-486: The cathode (negative electrode) which could cast shadows on the glowing wall of the tube, indicating the rays were travelling in straight lines. In 1890, Arthur Schuster demonstrated cathode rays could be deflected by electric fields , and William Crookes showed they could be deflected by magnetic fields. In 1897, J. J. Thomson succeeded in measuring the mass-to-charge ratio of cathode rays, showing that they consisted of negatively charged particles smaller than atoms,

3458-484: 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

3549-407: 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

3640-421: The CRT cathode wears out due to cathode poisoning before browning becomes apparent. The glass formulation determines the highest possible anode voltage and hence the maximum possible CRT screen size. For color, maximum voltages are often 24–32 kV, while for monochrome it is usually 21 or 24.5 kV, limiting the size of monochrome CRTs to 21 inches, or ~1 kV per inch. The voltage needed depends on

3731-465: The CRT. In 1954, RCA produced some of the first color CRTs, the 15GP22 CRTs used in the CT-100 , the first color TV set to be mass produced . The first rectangular color CRTs were also made in 1954. However, the first rectangular color CRTs to be offered to the public were made in 1963. One of the challenges that had to be solved to produce the rectangular color CRT was convergence at the corners of

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3822-459: The CRT. In 1965, brighter rare earth phosphors began replacing dimmer and cadmium-containing red and green phosphors. Eventually blue phosphors were replaced as well. The size of CRTs increased over time, from 20 inches in 1938, to 21 inches in 1955, 25 inches by 1974, 30 inches by 1980, 35 inches by 1985, and 43 inches by 1989. However, experimental 31 inch CRTs were made as far back as 1938. In 1960,

3913-562: 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

4004-573: The VBI, where the recorder expects a constant level, to disrupt recording to videotapes. While digital video interconnects (such as DVI and HDMI) generally do have a "vertical blanking" part of the datastream, they are unable to carry closed caption text or most of the other items that, in analog TV interconnects, are transmitted during the "vertical blanking interval". This can lead to closed captioning § Digital television interoperability issues . Cathode-ray tube A cathode-ray tube ( CRT )

4095-408: The anode now only accelerated the electrons emitted by the hot cathode, and no longer had to have a very high voltage to induce electron emission from the cold cathode. In 1926, Kenjiro Takayanagi demonstrated a CRT TV receiver with a mechanical video camera that received images with a 40-line resolution. By 1927, he improved the resolution to 100 lines, which was unrivaled until 1931. By 1928, he

4186-441: The anode voltage of the CRT, and significantly reducing the amount of time needed to turn on a CRT. The stability provided by the coating solved problems inherent to early power supply designs, as they used vacuum tubes. Because the funnel is used as a capacitor, the glass used in the funnel must be an excellent electrical insulator ( dielectric ). The inner coating has a positive voltage (the anode voltage that can be several kV) while

4277-419: 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

4368-408: The center of the screen with a 546 nm wavelength light, and a 10.16mm thick screen. Transmittance goes down with increasing thickness. Standard transmittances for Color CRT screens are 86%, 73%, 57%, 46%, 42% and 30%. Lower transmittances are used to improve image contrast but they put more stress on the electron gun, requiring more power on the electron gun for a higher electron beam power to light

4459-1093: 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

4550-508: The first " subatomic particles ", which had already been named electrons by Irish physicist George Johnstone Stoney in 1891. The earliest version of the CRT was known as the "Braun tube", invented by the German physicist Ferdinand Braun in 1897. It was a cold-cathode diode , a modification of the Crookes tube with a phosphor -coated screen. Braun was the first to conceive the use of

4641-658: The first CRT with HD resolution, the Sony KW-3600HD, was released to the market. It is considered to be "historical material" by Japan's national museum. The Sony KWP-5500HD, an HD CRT projection TV, was released in 1992. In the mid-1990s, some 160 million CRTs were made per year. In the mid-2000s, Canon and Sony presented the surface-conduction electron-emitter display and field-emission displays , respectively. They both were flat-panel displays that had one (SED) or several (FED) electron emitters per subpixel in place of electron guns. The electron emitters were placed on

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4732-472: The first CRTs to last 1,000  hours of use, which was one of the factors that led to the widespread adoption of TV. The first commercially made electronic TV sets with cathode-ray tubes were manufactured by Telefunken in Germany in 1934. In 1947, the cathode-ray tube amusement device , the earliest known interactive electronic game as well as the first to incorporate a cathode-ray tube screen,

4823-467: The first manufacturers to stop CRT production was Hitachi in 2001, followed by Sony in Japan in 2004, Flat-panel displays dropped in price and started significantly displacing cathode-ray tubes in the 2000s. LCD monitor sales began exceeding those of CRTs in 2003–2004 and LCD TV sales started exceeding those of CRTs in some markets in 2005. Samsung SDI stopped CRT production in 2012. Despite being

4914-422: 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

5005-401: The furnace, to allow production of CRTs of several sizes. Only the glass used on the screen needs to have precise optical properties. The optical properties of the glass used on the screen affect color reproduction and purity in color CRTs. Transmittance, or how transparent the glass is, may be adjusted to be more transparent to certain colors (wavelengths) of light. Transmittance is measured at

5096-512: 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

5187-403: 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

5278-441: The inductive inertia of the magnetic coils which deflect the electron beam vertically in a CRT; the magnetic field, and hence the position being drawn, cannot change instantly. Additionally, the speed of older circuits was limited. For horizontal deflection, there is also a pause between successive lines, to allow the beam to return from right to left, called the horizontal blanking interval . Modern CRT circuitry does not require such

5369-568: The lower right of the display. In analog television systems the vertical blanking interval can be used for datacasting (to carry digital data), since nothing sent during the VBI is displayed on the screen; various test signals, VITC timecode , closed captioning , teletext , CGMS-A copy-protection indicators, and various data encoded by the XDS protocol (e.g., the content ratings for V-chip use) and other digital data can be sent during this time period. In U.S. analog broadcast television, line 19

5460-435: 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

5551-579: 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,

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5642-489: The melts were also specific to each manufacturer. Those optimized for high color purity and contrast were doped with Neodymium, while those for monochrome CRTs were tinted to differing levels, depending on the formulation used and had transmittances of 42% or 30%. Purity is ensuring that the correct colors are activated (for example, ensuring that red is displayed uniformly across the screen) while convergence ensures that images are not distorted. Convergence may be modified using

5733-589: The model KV-1310, which was based on Aperture Grille technology. It was acclaimed to have improved the output brightness. The Trinitron screen was identical with its upright cylindrical shape due to its unique triple cathode single gun construction. In 1987, flat-screen CRTs were developed by Zenith for computer monitors, reducing reflections and helping increase image contrast and brightness. Such CRTs were expensive, which limited their use to computer monitors. Attempts were made to produce flat-screen CRTs using inexpensive and widely available float glass . In 1990,

5824-403: 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,

5915-428: 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

6006-530: The outer coating is connected to ground. CRTs powered by more modern power supplies do not need to be connected to ground , due to the more robust design of modern power supplies. The value of the capacitor formed by the funnel is 5–10  nF , although at the voltage the anode is normally supplied with. The capacitor formed by the funnel can also suffer from dielectric absorption , similarly to other types of capacitors. Because of this CRTs have to be discharged before handling to prevent injury. The depth of

6097-401: 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

6188-406: 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

6279-443: The phosphors more brightly to compensate for the reduced transmittance. The transmittance must be uniform across the screen to ensure color purity. The radius (curvature) of screens has increased (grown less curved) over time, from 30 to 68 inches, ultimately evolving into completely flat screens, reducing reflections. The thickness of both curved and flat screens gradually increases from the center outwards, and with it, transmittance

6370-408: 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

6461-499: The programmer is in full control of video output and therefore may select their own blanking period, allowing arbitrarily few painted lines. On others such as the Nintendo Entertainment System , a predefined blanking period could be extended. Most consumer VCRs use the known black level of the vertical blanking pulse to set their recording levels. The Macrovision copy protection scheme inserts pulses in

6552-687: The same time. In 2012, Samsung SDI and several other major companies were fined by the European Commission for price fixing of TV cathode-ray tubes. The same occurred in 2015 in the US and in Canada in 2018. Worldwide sales of CRT computer monitors peaked in 2000, at 90 million units, while those of CRT TVs peaked in 2005 at 130 million units. Beginning in the late 1990s to the early 2000s, CRTs began to be replaced with LCDs, starting first with computer monitors smaller than 15 inches in size, largely because of their lower bulk. Among

6643-406: The screen and funnel, with a potash-soda lead glass in the neck; the potash-soda and barium-lead formulations have different thermal expansion coefficients. The glass used in the neck must be an excellent electrical insulator to contain the voltages used in the electron optics of the electron gun, such as focusing lenses. The lead in the glass causes it to brown (darken) with use due to x-rays, usually

6734-427: The screen may contain 12% of barium oxide , and 12% of strontium oxide . A typical CRT contains several kilograms of lead as lead oxide in the glass depending on its size; 12 inch CRTs contain 0.5 kg of lead in total while 32 inch CRTs contain up to 3 kg. Strontium oxide began being used in CRTs, its major application, in the 1970s. Before this, CRTs used lead on the faceplate. Some early CRTs used

6825-449: The screen or being very electrically insulating in the funnel and neck. The formulation that gives the glass its properties is also known as the melt. The glass is of very high quality, being almost contaminant and defect free. Most of the costs associated with glass production come from the energy used to melt the raw materials into glass. Glass furnaces for CRT glass production have several taps to allow molds to be replaced without stopping

6916-444: The size and type of CRT. Since the formulations are different, they must be compatible with one another, having similar thermal expansion coefficients. The screen may also have an anti-glare or anti-reflective coating, or be ground to prevent reflections. CRTs may also have an anti-static coating. The leaded glass in the funnels of CRTs may contain 21–25% of lead oxide (PbO), The neck may contain 30–40% of lead oxide, and

7007-437: 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,

7098-437: 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

7189-432: 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

7280-458: 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

7371-411: 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

7462-421: 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

7553-401: 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

7644-461: The viewable area may follow the curvature of the edges of the CRT (with or without black edges or curved edges). Small CRTs below 3 inches were made for handheld TVs such as the MTV-1 and viewfinders in camcorders. In these, there may be no black edges, that are however truly flat. Most of the weight of a CRT comes from the thick glass screen, which comprises 65% of the total weight of

7735-718: 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

7826-539: Was about the largest size of a CRT. A CRT works by electrically heating a tungsten coil which in turn heats a cathode in the rear of the CRT, causing it to emit electrons which are modulated and focused by electrodes. The electrons are steered by deflection coils or plates, and an anode accelerates them towards the phosphor -coated screen, which generates light when hit by the electrons. Cathode rays were discovered by Julius Plücker and Johann Wilhelm Hittorf . Hittorf observed that some unknown rays were emitted from

7917-421: Was created. From 1949 to the early 1960s, there was a shift from circular CRTs to rectangular CRTs, although the first rectangular CRTs were made in 1938 by Telefunken. While circular CRTs were the norm, European TV sets often blocked portions of the screen to make it appear somewhat rectangular while American sets often left the entire front of the CRT exposed or only blocked the upper and lower portions of

8008-541: 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

8099-428: Was painted into the interior of monochrome CRTs. The anode is used to accelerate the electrons towards the screen and also collects the secondary electrons that are emitted by the phosphor particles in the vacuum of the CRT. The anode cap connection in modern CRTs must be able to handle up to 55–60kV depending on the size and brightness of the CRT. Higher voltages allow for larger CRTs, higher image brightness, or

8190-417: Was reserved for a Ghost-canceling reference and line 21 was reserved for NABTS captioning data. The obsolete Teletext service contemplated the use of line 22 for data transmission. The pause between sending video data is sometimes used in real time computer graphics to modify the frame buffer , or to provide a time reference for when switching the source buffer for video output can happen without causing

8281-425: Was the first to transmit human faces in half-tones on a CRT display. In 1927, Philo Farnsworth created a TV prototype. The CRT was named in 1929 by inventor Vladimir K. Zworykin . He was subsequently hired by RCA , which was granted a trademark for the term "Kinescope", RCA's term for a CRT, in 1932; it voluntarily released the term to the public domain in 1950. In the 1930s, Allen B. DuMont made

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