Color television display

This is not a comprehensive listing of all of the phosphors investigated. The most important part for a color-television display is the brightness produced at the "Daylight" color, i.e.- the niumlnant-C color... 

The design of a color-television display panel that uses the twisted nematic phenomena and polycrystalline thin-film transistors (TFT s)... 

Green emitting (544 nm) phosphor for display screens and color televisions at high current densities better than other green phosphors... 

G.3.3.3 Liquid Crystal Displays (LCDs). Liquid crystalline polymers, first intro-dnced in Section 1.3.6.3, are ntilized for a different type of computer and television display, the liquid crystal display (LCD). Most of today s laptop computers and handheld devices ntilize color flat panel displays where the light transmission from the... 

The number of devices required to multiplex a monochromic television display of moderate resolution is enormous, about 100,000, and color schemes triple this number (see, e.g., Uchida etal., 1982,1983). To succeed, therefore, a specific technology must demonstrate not only that individual elements meet the (very modest) electrical requirements but also that active matrices, with gate counts comparable to the largest intergrated circuits produced, can be fabricated with acceptable yields. 

Traditionally, yttrium has had many of the same uses as the rare earth elements. For example, it has been used in phosphors. A phosphor is a material that gives off light when struck by electrons. The color of the light produced depends on the elements of which the phosphor is made. Yttrium phosphors have long been used in color television sets and in computer monitors. They have also been used in specialized fluorescent lights and newer plat-panel displays. In 2007, approximately 89 percent of all the yttrium consumed in the United States was used for the manufacture of lamp and cathode ray phosphors. Another 10 percent was used in ceramics. 

Clusters of three phosphors are used for each dot in a color television or computer display screen. Commonly used phosphors for this purpose are europium-activated yttrium orthovanadate, YVO4, for the red color, silver-activated zinc sulfide for blue, and copper-activated zinc sulfide for green. 

The cathode ray tubes are scanned in a raster like a television picture. Each scan line is modulated into a series of dots called picture elements (abbreviated to pixels or pels) and each character is built up from these pixels. It soon became possible to manipulate the pixels individually so that as well as characters, dots, lines and shapes could be displayed on the screen. Microcomputers are now available with graphics capabilities rivalling those found on mainframe systems, but at a fraction of the cost. Clearly, more memory locations have to be put aside for graphics displays. For example, compare the text (character) display of the IBM Color/Graphics display with its high-resolution monochrome graphics mode. The 80-character mode puts 25 rows of 80 characters on the screen. Each character is stored in two bytes - one for the character itself and one for its attributes , that is, colour. 

Of the displays that can be used for color-television, the PDP panel outperforms aU of its competitors. The screen is brighter, resulting in superior contrast for high definition display. 

The shadow-mask CRT is the workhorse of the video display industry. Used in the majority of color video displays since the introduction of color television in the early 1950s, the shadow-mask technique has been refined to yield greater performance and lower manufacturing cost. 

In color television, the image is reproduced by selective excitation of three RE-phosphors (blue, green, and red) deposited on the internal face of the screen by a highly powerful electron beam originating from a metal electrode (cathode). Such an excitation technique is termed Cathode Ray Tube (CRT) technology. It is estimated that over 80% of the total worldwide display phosphor market will be utilized in the CRT industry (TVs and desktop PC monitors). 

Donor and acceptor levels are the active centers in most phosphors, as in zinc sulfide [1314-98-3] ZnS, containing an activator such as Cu and various co-activators. Phosphors are coated onto the inside of fluorescent lamps to convert the intense ultraviolet and blue from the mercury emissions into lower energy light to provide a color balance closer to daylight as in Figure 11. Phosphors can also be stimulated directly by electricity as in the Destriau effect in electroluminescent panels and by an electron beam as in the cathodoluminescence used in television and cathode ray display tubes and in (usually blue) vacuum-fluorescence alphanumeric displays. 

Liquid crystal display systems have been increasingly used in electro-optical devices such as digital watches, calculators, televisions, instmment panels, and displays of various kinds of electronic equipment, ie, lap-top computers and word processors. The dominant reason for thek success is thek extremely low power consumption. Furthermore, the Hquid crystal display systems have been remarkably improved in recent years, and today they have high resolution (more than 300,000 pixels) and full color capabiUty almost equivalent to those of a cathode ray tube. 

The upper end of the display market requires full color capability, whether the intended use is for video games, television, computer monitors or graphical design. 

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