gas plasma display screens factory

A plasma display panel (PDP) is a type of flat panel display that uses small cells containing plasma: ionized gas that responds to electric fields. Plasma televisions were the first large (over 32 inches diagonal) flat panel displays to be released to the public.

Until about 2007, plasma displays were commonly used in large televisions (30 inches (76 cm) and larger). By 2013, they had lost nearly all market share due to competition from low-cost LCDs and more expensive but high-contrast OLED flat-panel displays. Manufacturing of plasma displays for the United States retail market ended in 2014,

Plasma displays are bright (1,000 lux or higher for the display module), have a wide color gamut, and can be produced in fairly large sizes—up to 3.8 metres (150 in) diagonally. They had a very low luminance "dark-room" black level compared with the lighter grey of the unilluminated parts of an LCD screen. (As plasma panels are locally lit and do not require a back light, blacks are blacker on plasma and grayer on LCD"s.)LED-backlit LCD televisions have been developed to reduce this distinction. The display panel itself is about 6 cm (2.4 in) thick, generally allowing the device"s total thickness (including electronics) to be less than 10 cm (3.9 in). Power consumption varies greatly with picture content, with bright scenes drawing significantly more power than darker ones – this is also true for CRTs as well as modern LCDs where LED backlight brightness is adjusted dynamically. The plasma that illuminates the screen can reach a temperature of at least 1200 °C (2200 °F). Typical power consumption is 400 watts for a 127 cm (50 in) screen. Most screens are set to "vivid" mode by default in the factory (which maximizes the brightness and raises the contrast so the image on the screen looks good under the extremely bright lights that are common in big box stores), which draws at least twice the power (around 500–700 watts) of a "home" setting of less extreme brightness.

Plasma screens are made out of glass, which may result in glare on the screen from nearby light sources. Plasma display panels cannot be economically manufactured in screen sizes smaller than 82 centimetres (32 in).enhanced-definition televisions (EDTV) this small, even fewer have made 32 inch plasma HDTVs. With the trend toward large-screen television technology, the 32 inch screen size is rapidly disappearing. Though considered bulky and thick compared with their LCD counterparts, some sets such as Panasonic"s Z1 and Samsung"s B860 series are as slim as 2.5 cm (1 in) thick making them comparable to LCDs in this respect.

Wider viewing angles than those of LCD; images do not suffer from degradation at less than straight ahead angles like LCDs. LCDs using IPS technology have the widest angles, but they do not equal the range of plasma primarily due to "IPS glow", a generally whitish haze that appears due to the nature of the IPS pixel design.

Less visible motion blur, thanks in large part to very high refresh rates and a faster response time, contributing to superior performance when displaying content with significant amounts of rapid motion such as auto racing, hockey, baseball, etc.

Earlier generation displays were more susceptible to screen burn-in and image retention. Recent models have a pixel orbiter that moves the entire picture slower than is noticeable to the human eye, which reduces the effect of burn-in but does not prevent it.

Due to the bistable nature of the color and intensity generating method, some people will notice that plasma displays have a shimmering or flickering effect with a number of hues, intensities and dither patterns.

Earlier generation displays (circa 2006 and prior) had phosphors that lost luminosity over time, resulting in gradual decline of absolute image brightness. Newer models have advertised lifespans exceeding 100,000 hours (11 years), far longer than older CRTs.

Uses more electrical power, on average, than an LCD TV using a LED backlight. Older CCFL backlights for LCD panels used quite a bit more power, and older plasma TVs used quite a bit more power than recent models.

Fixed-pixel displays such as plasma TVs scale the video image of each incoming signal to the native resolution of the display panel. The most common native resolutions for plasma display panels are 852×480 (EDTV), 1,366×768 and 1920×1080 (HDTV). As a result, picture quality varies depending on the performance of the video scaling processor and the upscaling and downscaling algorithms used by each display manufacturer.

Early plasma televisions were enhanced-definition (ED) with a native resolution of 840×480 (discontinued) or 852×480 and down-scaled their incoming high-definition video signals to match their native display resolutions.

The following ED resolutions were common prior to the introduction of HD displays, but have long been phased out in favor of HD displays, as well as because the overall pixel count in ED displays is lower than the pixel count on SD PAL displays (852×480 vs 720×576, respectively).

Early high-definition (HD) plasma displays had a resolution of 1024x1024 and were alternate lighting of surfaces (ALiS) panels made by Fujitsu and Hitachi.

Later HDTV plasma televisions usually have a resolution of 1,024×768 found on many 42 inch plasma screens, 1280×768 and 1,366×768 found on 50 in, 60 in, and 65 in plasma screens, or 1920×1080 found on plasma screen sizes from 42 inch to 103 inch. These displays are usually progressive displays, with non-square pixels, and will up-scale and de-interlace their incoming standard-definition signals to match their native display resolutions. 1024×768 resolution requires that 720p content be downscaled in one direction and upscaled in the other.

Ionized gases such as the ones shown here are confined to millions of tiny individual compartments across the face of a plasma display, to collectively form a visual image.

A panel of a plasma display typically comprises millions of tiny compartments in between two panels of glass. These compartments, or "bulbs" or "cells", hold a mixture of noble gases and a minuscule amount of another gas (e.g., mercury vapor). Just as in the fluorescent lamps over an office desk, when a high voltage is applied across the cell, the gas in the cells forms a plasma. With flow of electricity (electrons), some of the electrons strike mercury particles as the electrons move through the plasma, momentarily increasing the energy level of the atom until the excess energy is shed. Mercury sheds the energy as ultraviolet (UV) photons. The UV photons then strike phosphor that is painted on the inside of the cell. When the UV photon strikes a phosphor molecule, it momentarily raises the energy level of an outer orbit electron in the phosphor molecule, moving the electron from a stable to an unstable state; the electron then sheds the excess energy as a photon at a lower energy level than UV light; the lower energy photons are mostly in the infrared range but about 40% are in the visible light range. Thus the input energy is converted to mostly infrared but also as visible light. The screen heats up to between 30 and 41 °C (86 and 106 °F) during operation. Depending on the phosphors used, different colors of visible light can be achieved. Each pixel in a plasma display is made up of three cells comprising the primary colors of visible light. Varying the voltage of the signals to the cells thus allows different perceived colors.

The long electrodes are stripes of electrically conducting material that also lies between the glass plates in front of and behind the cells. The "address electrodes" sit behind the cells, along the rear glass plate, and can be opaque. The transparent display electrodes are mounted in front of the cell, along the front glass plate. As can be seen in the illustration, the electrodes are covered by an insulating protective layer.

Control circuitry charges the electrodes that cross paths at a cell, creating a voltage difference between front and back. Some of the atoms in the gas of a cell then lose electrons and become ionized, which creates an electrically conducting plasma of atoms, free electrons, and ions. The collisions of the flowing electrons in the plasma with the inert gas atoms leads to light emission; such light-emitting plasmas are known as glow discharges.

Relative spectral power of red, green and blue phosphors of a common plasma display. The units of spectral power are simply raw sensor values (with a linear response at specific wavelengths).

In a monochrome plasma panel, the gas is mostly neon, and the color is the characteristic orange of a neon-filled lamp (or sign). Once a glow discharge has been initiated in a cell, it can be maintained by applying a low-level voltage between all the horizontal and vertical electrodes–even after the ionizing voltage is removed. To erase a cell all voltage is removed from a pair of electrodes. This type of panel has inherent memory. A small amount of nitrogen is added to the neon to increase hysteresis.phosphor. The ultraviolet photons emitted by the plasma excite these phosphors, which give off visible light with colors determined by the phosphor materials. This aspect is comparable to fluorescent lamps and to the neon signs that use colored phosphors.

Every pixel is made up of three separate subpixel cells, each with different colored phosphors. One subpixel has a red light phosphor, one subpixel has a green light phosphor and one subpixel has a blue light phosphor. These colors blend together to create the overall color of the pixel, the same as a triad of a shadow mask CRT or color LCD. Plasma panels use pulse-width modulation (PWM) to control brightness: by varying the pulses of current flowing through the different cells thousands of times per second, the control system can increase or decrease the intensity of each subpixel color to create billions of different combinations of red, green and blue. In this way, the control system can produce most of the visible colors. Plasma displays use the same phosphors as CRTs, which accounts for the extremely accurate color reproduction when viewing television or computer video images (which use an RGB color system designed for CRT displays).

Plasma displays are different from liquid crystal displays (LCDs), another lightweight flat-screen display using very different technology. LCDs may use one or two large fluorescent lamps as a backlight source, but the different colors are controlled by LCD units, which in effect behave as gates that allow or block light through red, green, or blue filters on the front of the LCD panel.

To produce light, the cells need to be driven at a relatively high voltage (~300 volts) and the pressure of the gases inside the cell needs to be low (~500 torr).

Contrast ratio is the difference between the brightest and darkest parts of an image, measured in discrete steps, at any given moment. Generally, the higher the contrast ratio, the more realistic the image is (though the "realism" of an image depends on many factors including color accuracy, luminance linearity, and spatial linearity). Contrast ratios for plasma displays are often advertised as high as 5,000,000:1.organic light-emitting diode. Although there are no industry-wide guidelines for reporting contrast ratio, most manufacturers follow either the ANSI standard or perform a full-on-full-off test. The ANSI standard uses a checkered test pattern whereby the darkest blacks and the lightest whites are simultaneously measured, yielding the most accurate "real-world" ratings. In contrast, a full-on-full-off test measures the ratio using a pure black screen and a pure white screen, which gives higher values but does not represent a typical viewing scenario. Some displays, using many different technologies, have some "leakage" of light, through either optical or electronic means, from lit pixels to adjacent pixels so that dark pixels that are near bright ones appear less dark than they do during a full-off display. Manufacturers can further artificially improve the reported contrast ratio by increasing the contrast and brightness settings to achieve the highest test values. However, a contrast ratio generated by this method is misleading, as content would be essentially unwatchable at such settings.

Each cell on a plasma display must be precharged before it is lit, otherwise the cell would not respond quickly enough. Precharging normally increases power consumption, so energy recovery mechanisms may be in place to avoid an increase in power consumption.LED illumination can automatically reduce the backlighting on darker scenes, though this method cannot be used in high-contrast scenes, leaving some light showing from black parts of an image with bright parts, such as (at the extreme) a solid black screen with one fine intense bright line. This is called a "halo" effect which has been minimized on newer LED-backlit LCDs with local dimming. Edgelit models cannot compete with this as the light is reflected via a light guide to distribute the light behind the panel.

Image burn-in occurs on CRTs and plasma panels when the same picture is displayed for long periods. This causes the phosphors to overheat, losing some of their luminosity and producing a "shadow" image that is visible with the power off. Burn-in is especially a problem on plasma panels because they run hotter than CRTs. Early plasma televisions were plagued by burn-in, making it impossible to use video games or anything else that displayed static images.

Plasma displays also exhibit another image retention issue which is sometimes confused with screen burn-in damage. In this mode, when a group of pixels are run at high brightness (when displaying white, for example) for an extended period, a charge build-up in the pixel structure occurs and a ghost image can be seen. However, unlike burn-in, this charge build-up is transient and self-corrects after the image condition that caused the effect has been removed and a long enough period has passed (with the display either off or on).

Plasma manufacturers have tried various ways of reducing burn-in such as using gray pillarboxes, pixel orbiters and image washing routines, but none to date have eliminated the problem and all plasma manufacturers continue to exclude burn-in from their warranties.

The first practical plasma video display was co-invented in 1964 at the University of Illinois at Urbana–Champaign by Donald Bitzer, H. Gene Slottow, and graduate student Robert Willson for the PLATO computer system.Owens-Illinois were very popular in the early 1970s because they were rugged and needed neither memory nor circuitry to refresh the images.CRT displays cheaper than the $2500 USD 512 × 512 PLATO plasma displays.

Burroughs Corporation, a maker of adding machines and computers, developed the Panaplex display in the early 1970s. The Panaplex display, generically referred to as a gas-discharge or gas-plasma display,seven-segment display for use in adding machines. They became popular for their bright orange luminous look and found nearly ubiquitous use throughout the late 1970s and into the 1990s in cash registers, calculators, pinball machines, aircraft avionics such as radios, navigational instruments, and stormscopes; test equipment such as frequency counters and multimeters; and generally anything that previously used nixie tube or numitron displays with a high digit-count. These displays were eventually replaced by LEDs because of their low current-draw and module-flexibility, but are still found in some applications where their high brightness is desired, such as pinball machines and avionics.

In 1983, IBM introduced a 19-inch (48 cm) orange-on-black monochrome display (Model 3290 Information Panel) which was able to show up to four simultaneous IBM 3270 terminal sessions. By the end of the decade, orange monochrome plasma displays were used in a number of high-end AC-powered portable computers, such as the Compaq Portable 386 (1987) and the IBM P75 (1990). Plasma displays had a better contrast ratio, viewability angle, and less motion blur than the LCDs that were available at the time, and were used until the introduction of active-matrix color LCD displays in 1992.

Due to heavy competition from monochrome LCDs used in laptops and the high costs of plasma display technology, in 1987 IBM planned to shut down its factory in Kingston, New York, the largest plasma plant in the world, in favor of manufacturing mainframe computers, which would have left development to Japanese companies.Larry F. Weber, a University of Illinois ECE PhD (in plasma display research) and staff scientist working at CERL (home of the PLATO System), co-founded Plasmaco with Stephen Globus and IBM plant manager James Kehoe, and bought the plant from IBM for US$50,000. Weber stayed in Urbana as CTO until 1990, then moved to upstate New York to work at Plasmaco.

In 1992, Fujitsu introduced the world"s first 21-inch (53 cm) full-color display. It was based on technology created at the University of Illinois at Urbana–Champaign and NHK Science & Technology Research Laboratories.

In 1994, Weber demonstrated a color plasma display at an industry convention in San Jose. Panasonic Corporation began a joint development project with Plasmaco, which led in 1996 to the purchase of Plasmaco, its color AC technology, and its American factory for US$26 million.

In 1995, Fujitsu introduced the first 42-inch (107 cm) plasma display panel;Philips introduced the first large commercially available flat-panel TV, using the Fujitsu panels. It was available at four Sears locations in the US for $14,999, including in-home installation. Pioneer also began selling plasma televisions that year, and other manufacturers followed. By the year 2000 prices had dropped to $10,000.

In the year 2000, the first 60-inch plasma display was developed by Plasmaco. Panasonic was also reported to have developed a process to make plasma displays using ordinary window glass instead of the much more expensive "high strain point" glass.

In late 2006, analysts noted that LCDs had overtaken plasmas, particularly in the 40-inch (100 cm) and above segment where plasma had previously gained market share.

Until the early 2000s, plasma displays were the most popular choice for HDTV flat panel display as they had many benefits over LCDs. Beyond plasma"s deeper blacks, increased contrast, faster response time, greater color spectrum, and wider viewing angle; they were also much bigger than LCDs, and it was believed that LCDs were suited only to smaller sized televisions. However, improvements in VLSI fabrication narrowed the technological gap. The increased size, lower weight, falling prices, and often lower electrical power consumption of LCDs made them competitive with plasma television sets.

Screen sizes have increased since the introduction of plasma displays. The largest plasma video display in the world at the 2008 Consumer Electronics Show in Las Vegas, Nevada, was a 150-inch (380 cm) unit manufactured by Matsushita Electric Industrial (Panasonic) standing 6 ft (180 cm) tall by 11 ft (330 cm) wide.

At the 2010 Consumer Electronics Show in Las Vegas, Panasonic introduced their 152" 2160p 3D plasma. In 2010, Panasonic shipped 19.1 million plasma TV panels.

Panasonic was the biggest plasma display manufacturer until 2013, when it decided to discontinue plasma production. In the following months, Samsung and LG also ceased production of plasma sets. Panasonic, Samsung and LG were the last plasma manufacturers for the U.S. retail market.

Plasma displays were once the creme-de-la-creme of television technology. With deep blacks and great colour, they could rival CRTs at a time when a lot of the LCD technology at the time was often seen as less than inspiring. But did the plasma display ever have a real future?

Consider some technological almost-greats of the last few decades, just in the field of film and TV. Anyone have a plasma display on the wall at home? No? There was a time when the writing was on the wall for CRT displays and the writing did not say “TFT-LCD”. It said “plasma display panel”. Plasma displays are made, quite literally, of tiny cells full of ionised gas. Early types were filled with neon which glowed the characteristic red-orange when a high voltage was applied, creating the bright orange flat panel displays found in early 90s laptops.

This image reveals the structure of the Pioneer PDP-V402 plasma display panel. There"s a mesh over the front of the matrix of cells to provide electrical conductivity and not great fill factor

Full-colour plasma displays are filled with a gas mix including mercury which, as in a fluorescent tube, emits ultraviolet radiation when excited. The UV light excites coloured phosphors which glow with colour performance very much like that of a CRT. Crucially, if we turn the power off to a particular cell, it is thoroughly and completely off and the light output can be zero. That means that plasma displays can achieve almost OLED-like black levels. Many don’t, as a consequence of less-than-ideal electronics, but the performance was a bit better than most LCDs.

The problem was, it wasn’t a lot better than the best LCDs, because LCD was a maturing technology. Plasma as a full-colour display dates back perhaps to a 21-inch Fujitsu panel in 1992, though they didn’t become consumer products until the late 90s and they didn’t become really practical until a few years after that. Conversely, researchers at Westinghouse created the term “active matrix” in the 1970s to describe what would become TFT-LCD. In the end, manufacturing techniques for big TFT-LCD panels improved enough to outsell plasma in the mid-2000s.

Large plasma displays were being shown at the big shows as recently as ten years ago, but, in the end, they were a technology that was quite literally outshone by a more experienced incumbent.

Images of the Pioneer PDP-V402 plasma display panel appear courtesy of the people at Rarevision LLC, whose enthusiasm for retro technology is exemplified in the VHS Camcorder application.

This mixture of gases is inert and harmless. That issue of light applied an electric current which turns it into plasma, a fluid ionized whose atoms have lost one or more of their electrons and are electrically neutral, so that the freed electrons form a cloud autour. The gas is contained in cells, corresponding to the (phosphors) sub-pixels. Each cell is addressed by an electrode line and a column electrode;

RMW0MAEB–In a 2000 NASA image, the Hubble Space Telescope took this photograph of the Eskimo Nebula that displays gas clouds so complex they are not fully understood. In 1787, astronomer William Herschel discovered the Eskimo Nebula, which from the ground resembles a person"s head surrounded by a parka hood. The Eskimo Nebula is a planetary nebula, a glowing shell of gas and plasma formed by certain types of stars at the end of their lives. The outer disk contains unusual light-year long orange filaments. (UPI Photo/Andrew Fruchter/NASA)

PLATO. This is one of Bitzer"s own illustrations of his invention from his original patent, which was filed in 1966 and eventually granted in 1971. Like my illustration above, you can see that the screen consists of multiple, gas-filled display "minicells" (the orange blobs in the central blue section). In front and behind this are two sets of electrodes, one running horizontally and the other vertically. Each gas minicell ("blob") in the screen can be fired by energizing the appropriate pair of electrodes either side. Since each minicell can only be either on or off, this screen can display monochrome pictures but not color ones.

Artwork: Bitzer"s original plasma display. From US Patent 3,559,190: Gaseous display and memory apparatus by Donald Bitzer et al, University of Illinois, courtesy of US Patent and Trademark Office.

in 2014 when first Panasonic and then Samsung (which, between them, made about three quarters of all plasma sets) abandoned the technology and better-funded, more-innovative rival technologies (LCDs and OLEDs (organic LEDs)) took over.

Technology trends in backplane technology are driving higher gas demand in display manufacturing. Specific gas requirements of process blocks are discussed, and various supply modes are reviewed.

Since its initial communalization in the 1990s, active matrix thin-film-transistor (TFT) displays have become an essential and indispensable part of modern living. They are much more than just televisions and smartphones; they are the primary communication and information portals for our day-to- day life: watches (wearables), appliances, advertising, signage, automobiles and more.

There are many similarities in the display TFT manufacturing and semiconductor device manufacturing such as the process steps (deposition, etch, cleaning, and doping), the type of gases used in these steps, and the fact that both display and semiconductor manufacturing both heavily use gases.

However, there are technology drivers and manufacturing challenges that differentiate the two. For semiconductor device manufacturing, there are technology limitations in making the device increasingly smaller. For display manufacturing, the challenge is primarily maintaining the uniformity of glass as consumers drive the demand for larger and thinner displays.

While semiconductor wafer size has maxed because of the challenges of making smaller features uniformly across the surface of the wafer, the size of the display mother glass has grown from 0.1m x 0.1m with 1.1mm thickness to 3m x 3m with 0.5mm thickness over the past 20 years due to consumer demands for larger, lighter, and more cost-effective devices.

As the display mother glass area gets bigger and bigger,so does the equipment used in the display manufacturing process and the volume of gases required. In addition, the consumer’s desire for a better viewing experience such as more vivid color, higher resolution, and lower power consumption has also driven display manufacturers to develop and commercialize active matrix organic light emitting displays (AMOLED).

In general, there are two types of displays in the market today: active matrix liquid crystal display (AMLCD) and AMOLED. In its simplicity, the fundamental components required to make up the display are the same for AMLCD and AMOLED. There are four layers of a display device (FIGURE 1): a light source, switches that are the thin-film-transistor and where the gases are mainly used, a shutter to control the color selection, and the RGB (red, green, blue) color filter.

The thin-film-transistors used for display are 2D transitional transistors, which are similar to bulk CMOS before FinFET. For the active matrix display, there is one transistor for each pixel to drive the individual RGB within the pixel. As the resolution of the display grows, the transistor size also reduces, but not to the sub-micron scale of semiconductor devices. For the 325 PPI density, the transistor size is approximately 0.0001 mm2 and for the 4K TV with 80 PPI density, the transistor size is approximately 0.001 mm2.

Technology trends TFT-LCD (thin-film-transistor liquid-crystal display) is the baseline technology. MO / White OLED (organic light emitting diode) is used for larger screens. LTPS / AMOLED is used for small / medium screens. The challenges for OLED are the effect of < 1 micron particles on yield, much higher cost compared to a-Si due to increased mask steps, and moisture impact to yield for the OLED step.

Although AMLCD displays are still dominant in the market today, AMOLED displays are growing quickly. Currently about 25% of smartphones are made with AMOLED displays and this is expected to grow to ~40% by 2021. OLED televisions are also growing rapidly, enjoying double digit growth rate year over year. Based on IHS data, the revenue for display panels with AMOLED technol- ogies is expected to have a CAGR of 18.9% in the next five years while the AMLCD display revenue will have a -2.8% CAGR for the same period with the total display panel revenue CAGR of 2.5%. With the rapid growth of AMOLED display panels, the panel makers have accel- erated their investment in the equipment to produce AMOLED panels.

There are three types of thin-film-transistor devices for display: amorphous silicon (a-Si), low temperature polysilicon (LTPS), and metal oxide (MO), also known as transparent amorphous oxide semiconductor (TAOS). AMLCD panels typically use a-Si for lower-resolution displays and TVs while high-resolution displays use LTPS transistors, but this use is mainly limited to small and medium displays due to its higher costs and scalability limitations. AMOLED panels use LTPS and MO transistors where MO devices are typically used for TV and large displays (FIGURE 3).

This shift in technology also requires a change in the gases used in production of AMOLED panels as compared with the AMLCD panels. As shown in FIGURE 4, display manufacturing today uses a wide variety of gases.

These gases can be categorized into two types: Electronic Specialty gases (ESGs) and Electronic Bulk gases (EBGs) (FIGURE 5). Electronic Specialty gases such as silane, nitrogen trifluoride, fluorine (on-site generation), sulfur hexafluoride, ammonia, and phosphine mixtures make up 52% of the gases used in the manufacture of the displays while the Electronic Bulk gases–nitrogen, hydrogen, helium, oxygen, carbon dioxide, and argon – make up the remaining 48% of the gases used in the display manufacturing.

The key ga susage driver in the manufacturing of displays is PECVD (plasma-enhanced chemical vapor deposition), which accounts for 75% of the ESG spending, while dry etch is driving helium usage. LTPS and MO transistor production is driving nitrous oxide usage. The ESG usage for MO transistor production differs from what is shown in FIGURE 4: nitrous oxide makes up 63% of gas spend, nitrogen trifluoride 26%, silane 7%, and sulfur hexafluoride and ammonia together around 4%. Laser gases are used not only for lithography, but also for excimer laser annealing application in LTPS.

Silane: SiH4 is one of the most critical molecules in display manufacturing. It is used in conjunction with ammonia (NH3) to create the silicon nitride layer for a-Si transistor, with nitrogen (N2) to form the pre excimer laser anneal a-Si for the LTPS transistor, or with nitrous oxide (N2O) to form the silicon oxide layer of MO transistor.

Nitrogen trifluoride: NF3 is the single largest electronic material from spend and volume standpoint for a-Si and LTPS display production while being surpassed by N2O for MO production. NF3 is used for cleaning the PECVD chambers. This gas requires scalability to get the cost advantage necessary for the highly competitive market.

Nitrous oxide: Used in both LTPS and MO display production, N2O has surpassed NF3 to become the largest electronic material from spend and volume standpoint for MO production. N2O is a regional and localized product due to its low cost, making long supply chains with high logistic costs unfeasible. Averaging approximately 2 kg per 5.5 m2 of mother glass area, it requires around 240 tons per month for a typical 120K per month capacity generation 8.5 MO display production. The largest N2O compressed gas trailer can only deliver six tons of N2O each time and thus it becomes both costly and risky

Nitrogen: For a typical large display fab, N2 demand can be as high as 50,000 Nm3/hour, so an on-site generator, such as the Linde SPECTRA-N® 50,000, is a cost-effective solution that has the added benefit of an 8% reduction in CO2 (carbon dioxide) footprint over conventional nitrogen plants.

Helium: H2 is used for cooling the glass during and after processing. Manufacturers are looking at ways to decrease the usage of helium because of cost and availability issues due it being a non-renewable gas.

N2 On-site generators: Nitrogen is the largest consumed gas at the fab, and is required to be available before the first tools are brought to the fab. Like major semiconductor fabs, large display fabs require very large amounts of nitrogen, which can only be economically supplied by on-site plants.

Compressed gas truck trailers: Other large volume gases like hydrogen and helium are supplied over longer distances in truck or ISO-sized tanks as compressed gases.

Individual packages: Specialty gases are supplied in individual packages. For higher volume materials like silane and nitrogen trifluoride, these can be supplied in large ISO packages holding up to 10 tons. Materials with smaller requirements are packaged in standard gas cylinders.

Blended gases: Laser gases and dopants are supplied as blends of several different gases. Both the accuracy and precision of the blended products are important to maintain the display device fabrication operating within acceptable parameters.

In-fab distribution: Gas supply does not end with the delivery or production of the material of the fab. Rather, the materials are further regulated with additional filtration, purification, and on-line analysis before delivery to individual production tools.

The consumer demand for displays that offer increas- ingly vivid color, higher resolution, and lower power consumption will challenge display makers to step up the technologies they employ and to develop newer displays such as flexible and transparent displays. The transistors to support these new displays will either be LTPS and / or MO, which means the gases currently being used in these processes will continue to grow. Considering the current a-Si display production, the gas consumption per area of the glass will increase by 25% for LTPS and ~ 50% for MO productions.

To facilitate these increasing demands, display manufacturers must partner with gas suppliers to identify which can meet their technology needs, globally source electronic materials to provide customers with stable and cost- effective gas solutions, develop local sources of electronic materials, improve productivity, reduce carbon footprint, and increase energy efficiency through on-site gas plants. This is particularly true for the burgeoning China display manufacturing market, which will benefit from investing in on-site bulk gas plants and collaboration with global materials suppliers with local production facilities for high-purity gas and chemical manufacturing.

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Kojima T, Toyonaga R, Sakai T, Tajima T, Sega S, Kuriyama T, Koike J, Murakami H (1979) Sixteen-inch gas-discharge display panel with 2-lines-at-a-time-driving. Proc SID 20:153

The present invention generally relates to a plasma display panel (PDP) for displaying characters or images through utilization of gas discharge and more particularly, to a plasma display device which includes a means for efficiently dissipating heat produced by the plasma display panel, and its manufacturing method.

Recently, plasma display devices acting as flat, thin and light display units having large screens are used for information terminals such as portable computers and their applicable field is expanding due to their clear display and their wide angle of field of view. In a plasma display device, a plasma display panel is formed by front and rear glass plates bonded to each other, and gas for electrical discharge is contained in a minute gap between the glass plates. Ultraviolet rays produced by electrical discharge in the gas are irradiated to phosphor on the rear glass plate such that display of light emission from the phosphor is performed. Hence, the plasma display device as a whole reaches rather high temperature through repetition of electrical discharge in the gas.

In a plasma display device, as display luminance of a plasma display panel is raised further, more heat is produced by the plasma display panel, so that the temperature of the plasma display panel rises and thus, display performance of the plasma display panel deteriorates. To actuate the plasma display panel for a long time will result in, for example, a drop in reliability of a driver circuit for driving the plasma display panel and therefore, is not preferable for performance and properties of the plasma display panel. Meanwhile, if a state in which a large difference in temperature exists in a plane of the plasma display panel continues for a long time, glass forming the plasma display panel is distorted, thereby resulting in fracture of the glass.

Therefore, in order to lower the temperature of the plasma display panel in operation and lessen distortion of the glass leading to its fracture, difference in temperature in the plane of the plasma display panel should be reduced and performance and quality of the plasma display device should be upgraded. As one of such countermeasures in a known plasma display device, a pair of draft fans 92 are provided on a rear face of a plasma display panel 91 through spacers 93 as shown in FIG. 1 and blow wind to the plasma display panel 91 as shown by the arrow A in FIG. 2 so as to lower temperature of the plasma display panel 91.

In case the plasma display panel 91 is installed in parallel with a vertical plane, temperature is distributed in a plane of the plasma display panel 91 as shown in FIG. 3 by natural convection of heat and thus, temperature difference between a high-temperature portion and a low-temperature portion reaches 10 plus several °C. Meanwhile, temperature difference in the plane of the plasma display panel 91 increases according to a pattern of an image displayed on the plasma display panel 91. For example, if a state in which a small bright image (bright display) is present in a dark background (dark display) as shown in FIG. 4 continues for a long time, temperature difference between the bright image and the dark background increases considerably, so that glass forming the plasma display panel 91 is distorted, thus resulting in fracture of the plasma display panel 91. Especially, if temperature difference in the plane of the plasma display panel 91 reaches 20° C. or more, there is a great risk of fracture of the plasma display panel 91.

In the conventional plasma display device provided with the draft fans 92, temperature of the plasma display panel 91 can be lowered but such a problem arises that it is difficult to reduce temperature difference in the plane of the plasma display panel 91. Furthermore, the prior art plasma display device has such drawbacks that noise of motors for the draft fans 92 is annoying, electric power is required to be supplied for driving the motors for the draft fans 92, the plasma display device as a whole becomes large due to the need for providing space for mounting the motors for the draft fans 92 and dust sucked together with external air into a casing of the plasma display device by the draft fans 92 stains the interior of the casing.

Meanwhile, in a known plasma display device, in order to lower the temperature of a plasma display panel in operation and upgrade performance and quality of the plasma display device as a whole, it is effective to attach a chassis member to a rear face of the plasma display panel. In this case, it is important that the plasma display panel and the chassis member are brought into close contact with each other.

Accordingly, an essential object of the present invention is to provide, with a view to eliminating the above mentioned disadvantages of prior art, a plasma display device in which even when luminance of a plasma display panel is raised, the temperature of the plasma display panel is kept low and high display quality is secured by lessening temperature difference in a plane of the plasma display panel.

In order to accomplish this object of the present invention, a plasma display device according to the present invention comprises: a plasma display panel; a chassis member which is disposed substantially in parallel with the plasma display panel; and a thermally conductive medium which is interposed between the plasma display panel and the chassis member.

It is preferable that the thermally conductive medium is provided so as to be brought into substantially close contact with the plasma display panel and the chassis member.

It is also preferable that the thermally conductive medium has a two-layer construction having first and second mediums brought into substantially close contact with the plasma display panel and the chassis member, respectively, such that not only does the first medium have a coefficient of thermal conductivity higher than that of the second medium but the second medium also function as a cushioning medium.

By the above described arrangements of the plasma display device of the present invention, since heat in a plane of the plasma display panel in operation is conducted to the chassis member through the thermally conductive medium so as to be dissipated into the air, temperature in the plane of the plasma display panel can be lowered and temperature difference in the plane of the plasma display panel can be lessened.

Furthermore, close contact of the thermally conductive medium with the plasma display panel and the chassis member can be enhanced by eliminating warpage of the plasma display panel and the chassis member and impact applied to the plasma display device from outside can be mitigated by the second medium functioning also as the cushioning medium.

FIG. 3 is a schematic view showing temperature distribution in a plane of a plasma display panel of the prior art plasma display device of FIG. 1 (already referred to);

Referring now to the drawings, FIGS. 5 and 6 show a plasma display device K1 according to a first embodiment of the present invention. The plasma display device K1 includes a plasma display panel 1, a thermally conductive medium 2 and a chassis member 3 acting as a heat dissipating member. Projections 4 for effecting heat dissipation efficiently are provided on the chassis member 3. The thermally conductive medium 2 is adapted to not only lessen temperature difference in a plane of the plasma display panel 1 but lower the temperature of the plasma display panel 1 by transferring heat of the plasma display panel 1 to the chassis member 3 efficiently and dissipating heat from the chassis member 3 into the air. Meanwhile, if the thermally conductive medium 2 is made of soft material in a gel state, the thermally conductive medium 2 acts also as a cushioning medium so as to protect the plasma display panel 1 from external impact.

In this embodiment, a 26-inch type plasma display panel is used as the plasma display panel 1. The thermally conductive medium 2 having a thickness of 1 to 5 mm and formed by a silicone sheet in a gel state and the chassis member 3 made of aluminum are sequentially attached to a whole rear face of the plasma display panel 1. When white display was performed on a whole face of the plasma display panel 1 by an electric power of 120 W, the temperature of the plasma display panel 1 dropped about 25° C. in comparison with a case in which both the thermally conductive medium 2 and the chassis member 3 are not attached to the plasma display panel 1. The thermally conductive medium 2 may be formed by a rubber sheet in place of the silicone sheet.

Meanwhile, since the plasma display panel 1 and the chassis member 3 have slight warpage, it is preferable that the thermally conductive medium 2 has higher flexibility so as to bring the thermally conductive medium 2 into close contact with the plasma display panel 1 and the chassis member 3 such that not only is heat conduction from the plasma display panel 1 to the chassis member 3 improved but the plasma display panel 1 is protected from external impact by the thermally conductive medium. In order to effectively reduce temperature difference in the plane of the plasma display panel 1 and lower the temperature of the plasma display panel 1, the thermally conductive medium 2 has a higher coefficient of thermal conductivity preferably. However, if material having a high coefficient of thermal conductivity is used for making the thermally conductive medium 2, content of metal in the material is high and thus, elasticity and flexibility of the thermally conductive medium 2 drop. Thus, in FIG. 7 showing a plasma display device K2 according to a second embodiment of the present invention, the thermally conductive medium 2 has a two-layer construction including first and second mediums 6 and 7. The first medium 6 is formed by a metal sheet or a carbon sheet having a high coefficient of thermal conductivity, while the second medium 7 is formed by a flexible silicone sheet in a gel state or the like having a standard coefficient of thermal conductivity. Flexibility is imparted to the first medium 6 by reducing the thickness of the first medium 6 to 0.1 to 0.5 mm. Temperature difference in the plane of the plasma display panel 1, which is caused by heat produced in the plasma display panel 1, is lessened by the first medium 6. Heat transferred to the first medium 6 is transferred to the chassis member 3 by the second medium 7 efficiently and then, is dissipated from the chassis member 3 into the air. Meanwhile, since the thermally conductive medium 2 has elasticity, vibrations and impact applied from outside to the plasma display panel 1 are mitigated by the thermally conductive medium 2, so that fracture of the plasma display panel 1 is prevented effectively and close contact of the thermally conductive medium 2 with the plasma display panel 1 and the chassis member 3 is enhanced and heat conduction from the plasma display panel 1 to the chassis member 3 is performed efficiently.

In the plasma display device K2, a carbon sheet having a coefficient of thermal conductivity of 800 to 1000 W/m°C. and a thickness of 0.1 to 0.5 mm is employed as the first medium 6, while a silicone sheet in a gel state, which has a coefficient of thermal conductivity of 1 to 5 W/m°C. and a thickness of 1 to 5 mm, is employed as the second medium 7. By using this thermally conductive medium 2, a bright image is displayed at a central portion of the plasma display panel 1 against dark background as shown in FIG. 4. At this time, the solid line 8 in FIG. 8 shows characteristics of temperature distribution along the line X--X (FIG. 4) of the plasma display panel 1 of the plasma display device K2. On the other hand, the broken line 9 in FIG. 8 shows characteristics of temperature distribution along the line X--X of the plasma display panel 1 of the plasma display device K1. Heat in the plane of the plasma display panel 1 in the characteristics of the solid line 8 for the plasma display device K2 is diffused more sufficiently from the central portion of the plasma display panel 1 towards opposite end portions of the plasma display panel 1 than that in the characteristics of the broken line 9 for the plasma display device K1. As a result, temperature difference in the plane of the plasma display panel 1 of the plasma display device K2 is reduced conspicuously in comparison with that of the plasma display device K1. This is because the carbon sheet acting as the first medium 6 has the coefficient of thermal conductivity of 800 to 1000 W/m°C. in a direction of its face. Although the coefficient of thermal conductivity of the carbon sheet acting as the first medium 6 is lower in the direction of its thickness than in the direction of its face, heat is efficiently transferred in the direction of the thickness from the plasma display panel 1 to the chassis member 3 by making the carbon sheet thin as described above.

In the plasma display devices K2 and K1, since temperature difference in the plane of the plasma display panel 1 is less than 20° C. as is apparent from the lines 8 and 9 of FIG. 8, fracture of the plasma display panel 1 can be prevented.

As is clear from the foregoing description of the first and second embodiments of the present invention, since the thermally conductive medium is provided between the plasma display panel and the chassis member, not only is the temperature of the plasma display panel in operation lowered but temperature difference in the plane of the plasma display panel is lessened, so that a highly reliable plasma display device can be obtained. Furthermore, since the hitherto required draft fans are not employed, noise of motors of the draft fans is eliminated and electric power for driving the motors of the draft fans and space for mounting the motors of the draft fans are not necessary.

FIG. 9 shows a plasma display device K3 according to a third embodiment of the present invention. In the plasma display device K3, a groove 13 is formed at a rectangular peripheral edge of the chassis member 3 and a cushioning medium 14 is fitted into the groove 13. The thermally conductive medium 2 is provided in a region enclosed by the cushioning medium 14 such that the cushioning medium 14 is brought into substantially close contact with the thermally conductive medium 2.

Hereinafter, a manufacturing method of the plasma display device K3 is described. As shown in FIG. 10, the groove 13 is formed at the rectangular peripheral edge of the chassis member 3 and has, for example, a width W of 5.5 mm and a depth H of 2 mm. The cushioning medium 14 having a rectangularly annular shape as shown in FIG. 11 is fitted into this groove 13 such that a predetermined region is enclosed by the cushioning medium 14 as shown in FIGS. 12 and 13. For example, the cushioning medium 14 has a width of 5 mm and a height of 4 mm.

The solid thermally conductive medium 2 obtained by curing the liquid silicone resin as described above has a thickness of 2 mm. By attaching the plasma display panel 1 to the thermally conductive medium 2, the plasma display device K3 is obtained.

In the above described manufacturing method of the plasma display device K3, since bubbles do not penetrate in between the thermally conductive medium 2 and the chassis member 3, the plasma display device K3 having excellent heat conductivity and heat dissipation property can be obtained.

FIG. 15 shows a plasma display device K4 according to a fourth embodiment of the present invention. It should be noted that the plasma display device K4 is identical with the plasma display device K1. In the plasma display device K4, the thermally conductive medium 2 is provided on the chassis member 3 and the plasma display panel 1 is provided so as to be brought into substantially close contact with the thermally conductive medium 2.

Hereinafter, a manufacturing method of the plasma display device K4 is described. A rectangularly annular frame mold 16 shown in FIG. 17 is secured to the chassis member 3 shown in FIG. 16 such that a region enclosed by the frame mold 16 is defined as shown in FIGS. 18 and 19. For example, the frame mold 16 has a width of 5 mm and a height of 2 mm. Subsequently, as shown in FIG. 20, paste of the thermally conductive medium 2 is injected into the region enclosed by the frame mold 16 and then, is cured so as to obtain the solid thermally conductive medium 2. At this time, the thermally conductive medium 2 has a thickness of 1 to 5 mm, preferably, about 2 mm. Thereafter, the frame mold 16 is removed from the chassis member 3 and the plasma display panel 1 is attached to the thermally conductive medium 2. As a result, the plasma display device K4 is obtained.

In the manufacturing method of the plasma display device K4, since bubbles do not penetrate in between the thermally conductive medium 2 and the chassis member 3, the plasma display device K4 having excellent thermal conductivity and heat dissipation property can be obtained.

Meanwhile, in the above described third and fourth embodiments of the present invention, the thermally conductive medium 2 may be made of soft material in a gel state, so that the thermally conductive medium 2 acts also as a cushioning medium so as to protect the plasma display panel 1 from external impact.

As is clear from the foregoing description of the third and fourth embodiments of the present invention, since the thermally conductive medium is provided between the plasma display panel and the chassis member, temperature of the plasma display panel in operation is lowered and thus, the highly reliable plasma display device can be obtained. Furthermore, in the manufacturing methods of the plasma display devices according to the third and fourth embodiments of the present invention, it is possible to obtain the plasma display device having excellent heat conductivity and heat dissipation property, in which close contact of the thermally conductive medium with the plasma display panel and the chassis member is enhanced.

FIG. 21 shows a plasma display device K5 according to a fifth embodiment of the present invention. The plasma display device K5 includes a casing 22 and an internal unit 36 accommodated in the casing 22. The casing 22 is formed by assembling a front casing 24 and a rear casing 26 with each other. A plurality of vent holes 28 and 30 are formed in a lateral direction of the arrow a at upper and lower portions of the front casing 24, respectively and a light transmitting portion 32 made of glass or the like is provided on a front face of the front casing 24. Likewise, a plurality of the vent holes 28 and 30 are formed in the lateral direction at upper and lower portions of the rear casing 26, respectively.

The internal unit 36 includes a chassis member 38, a plasma display panel 42 mounted on a front face 56 of the chassis member 38 by L-shaped angle plates 40, a thermally conductive medium 44 formed by a silicone sheet or the like and interposed between the chassis member 38 and the plasma display panel 42 and a plurality of circuit boards 46 supported on a rear face 50 of the chassis member 38. The thermally conductive medium 44 is provided for efficiently transferring heat of the plasma display panel 42 to the chassis member 38. Meanwhile, the circuit boards 46 are provided for driving and controlling light emission of the plasma display panel 42.

The plasma display panel 42 is constituted by a front panel and a rear panel. As will be seen from FIG. 5, the front panel has a lateral side longer than that of the rear panel and a vertical side shorter than that of the rear panel and thus, the front and rear panels have portions in which the front and rear panels do not overlap each other. Although not specifically shown, terminals connected to electrodes in the plasma display panel 42 are formed at these nonoverlapping portions of the front and rear panels. A plurality of filmy wires (not shown) each having a female connector at its distal end are contact bonded to the terminals. The female connectors are, respectively, connected to male connectors (not shown) provided at an edge of each of the circuit boards 46. Consequently, each of the circuit boards 46 is electrically connected to the plasma display panel 42.

As shown in FIG. 22, the fins 52 at an upper central region 54 of the rear face 50 of the chassis member 38 are projected further from the rear face 50 than the fins 52 at the remaining region of the rear face 50 of the chassis member 38 for the following reason. Namely, the temperature of the chassis member 38 is raised by heat transferred from the plasma display panel 42 to the chassis member 38 via the thermally conductive medium 44. However, temperature distribution of the chassis member 38 is not uniform and the temperature of an upper portion of the chassis member 38 is higher than that of the remaining portion of the chassis member 38. Therefore, on the basis of this finding, heat dissipation efficiency of the upper central region 54 of the rear face 50 of the chassis member 38 is made larger than that of the remaining region of the rear face 50 of the chassis member 38.

The angle plates 40 are provided for four sides of the rectangular plasma display panel 42, respectively so as to clamp the plasma display panel 42 and the thermally conductive medium 44 to the chassis member 38 by screwing bolts 60 into the threaded holes of the bosses 58 through bolt holes of the angle plates 40 as shown in FIGS. 21 and 23. Each of the angle plates 40 is formed by plate portions 40a and 40b intersecting with each other substantially orthogonally. The plate portion 40a is brought into pressing contact with a peripheral edge of a front face of the plasma display panel 42 through a cushioning member 62 made of foamed material such that the plasma display panel 42 is secured to the front face 56 of the chassis member 38 via the thermally conductive medium 44.

Meanwhile, the plate portion 40b of the angle plate 40 extends along each of four outer peripheral surfaces 64. A number of the above mentioned filmy wires (not shown) for electrically connecting the circuit boards 46 and the plasma display panel 42 are present between the plate portions 40b and the outer peripheral surfaces 64 of the chassis member 38. Therefore, when an operator mounts the assembled internal unit 36 in the rear casing 26 by gripping an edge of the assembled internal unit 36, the plate portions 40b serve to protect the filmy wires so as to prevent damage to the filmy wires.

In the plasma display device K5 of the above described arrangement, when display is performed by light emission of the plasma display panel 42, the temperature of the plasma display panel 42 is raised by heat produced by electrical discharge in the plasma display panel 42. Heat produced in the plasma display panel 42 is transferred to the chassis member 38 through the thermally conductive medium 44 and is efficiently dissipated from the fins 52 molded integrally with the chassis member 38. Air heated in the casing 22 by this heat dissipation is discharged outwardly from the vent holes 28 of the upper portion of the casing 22, while air at room temperature flows into the casing 22 from the vent holes 30 of the lower portion of the casing 22. The plasma display panel 42 and the circuit boards 46 are cooled by this natural convection. On the supposition that a maximum room temperature is 40° C., it was found by experiments conducted by the inventors of this application that the temperature in the casing 22 can be maintained at not more than a permissible highest temperature which is equal to a sum of 40° C. and room temperature.

Since the fins 52 are molded integrally with the chassis member 38 for supporting the plasma display panel 42 such that the chassis member 38 acts also as a heat dissipating member as described above, it is possible to obtain an unforced cooling construction in which air in the casing 22 is subjected to natural convection so as to cool the interior of the casing 22. Therefore, since exhaust fans for forcibly discharging air in the casing 22 outwardly so as to forcibly cool the interior of the casing 22 are not required, such problems as noise and failure of the exhaust fans and suction of dust due to forced exhaust can be eliminated and production cost can be reduced.

Meanwhile, in the plasma display device K5, the unforced cooling construction in which the exhaust fans are eliminated is employed as described above. However, in the plasma display device K5, the exhaust fan may also be provided as an auxiliary for natural convection of air so as to promote flow of air in the casing 22. In this case, since the number of the installed exhaust fans can be reduced in comparison with prior art plasma display devices, the above described drawbacks of the prior art plasma display devices can be mitigated.

FIG. 24 shows a plasma display device K5" which is a modification of the plasma display device K5. In the plasma display device K5", an auxiliary heat dissipating member 65 is additionally provided on the fins 52 at the upper central region 54 of the rear face 50 of the chassis member 38 so as to further raise heat dissipation efficiency of the fins 52 at the upper central region 54 of the chassis member 38. The auxiliary heat dissipating member 65 is formed by a metal plate 65a bent into a substantially U-shaped configuration and a metal plate assembly 65b having a checked pattern and fixed to an inside of the metal plate 65a. A plurality of square space regions 66 are defined in the auxiliary heat dissipating member 65 so as to extend vertically in the same manner as the fins 52. Each of the space regions 66 is not restricted to the square shape but may have any other shape. Experiments conducted by the inventors of this application showed that if the auxiliary heat dissipating member 65 is provided, the temperature of the chassis member 38 further drops 10° C. as compared with a case in which the auxiliary heat dissipating member 65 is not provided. Therefore, in the case of a plasma display device employing a DC type plasma display panel, in which the quantity of heat produced in the DC plasma display panel is larger than that of an AC type plasma display panel, it is especially preferable that the auxiliary heat dissipating member 65 is additionally provided.

As is clear from the foregoing description of the fifth embodiment of the present invention, heat transferred from the plasma display panel to the chassis member can be dissipated efficiently by the fins molded integrally with the chassis member. Air in the casing, which has been heated by this heat dissipati