The shadow mask is one of two major technologies used to manufacture cathode ray tube (CRT) televisions and computer displays that produce color images (the other is aperture grille). Tiny holes in a metal plate separate the colored phosphors in the layer behind the front glass of the screen. The holes are placed in a manner ensuring that electrons from each of the tube's three cathode guns reach only the appropriately-colored phosphors on the display. All three beams pass through the same holes in the mask, but the angle of approach is different for each gun. The spacing of the holes, the spacing of the phosphors, and the placement of the guns is arranged so that for example the blue gun only has an unobstructed path to blue phosphors. The red, green, and blue phosphors for each pixel are generally arranged in a triangular shape (sometimes called a "triad"). All early color televisions and the majority of computer monitors, past and present, use shadow mask technology. Cathode ray tube employing electromagnetic focus and deflection Cutaway rendering of a color CRT The cathode ray tube or CRT, invented by Karl Ferdinand Braun, is the display device that was traditionally used in most computer displays, video monitors, televisions, radar displays and oscilloscopes. ... Nineteen inch (48 cm) CRT computer monitor A computer display, monitor or screen is a computer peripheral device capable of showing characters and/or still or moving images generated by a computer and processed by a graphics card. ... Color is an important part of the visual arts. ... An aperture grille is one of two major technologies used to manufacture cathode ray tube (CRT) televisions and computer displays; the other is shadow mask. ... A phosphor is a substance that can exhibit the phenomenon of fluorescence (glowing during absorption of radiation of another kind) or phosphorescence (sustained glowing without further stimulus). ... Properties The electron is a fundamental subatomic particle that carries a negative electric charge. ... Red is any of a number of similar colors at the lowest frequencies of light discernible by the human eye. ... Green is any of a number of similar colors. ... Blue is any of a number of similar colors. ... A pixel (pix, 1932 abbreviation of pictures, coined by Variety headline writers + element) is one of the many tiny dots that make up the representation of a picture in a computers memory. ... A triangle is one of the basic shapes of geometry: a two-dimensional figure with three vertices and three sides which are straight line segments. ... For other meanings see Triad (disambiguation). ...

Shadow mask CRT close-up

Traditionally, shadow masks have been made of materials which temperature variations cause to expand and contract to the point of affecting performance. The energy the shadow mask absorbs from the electron gun in normal operation causes it to heat up and expand, which leads to blurred or discolored (see doming) images. The invar shadow mask, which is composed of the nickel-iron alloy invar, expands and contracts much less than other materials in response to temperature changes. This property allows displays made with this technology to provide a clearer, more accurate picture. It also reduces the amount of long-term stress and damage to the shadow mask that can result from repeated expand/contract cycles, thus increasing the display's life expectancy. Image File history File links Shadow_mask. ... Image File history File links Shadow_mask. ... Doming is a defect found on some CRT televisions in which parts of the shadow mask become heated. ... Invar, also called FeNi36, is an alloy of iron (64%) and nickel (36%) with some carbon and chromium. ...

While many long have considered aperture grille technology to produce superior images, advances in shadow mask and hybrid technologies since the 1990s have made purchasing decisions more a matter of personal choice or specific application. The arrival of inexpensive liquid crystal display (LCD) monitors and other flat-screen designs now challenges both aperture grille and shadow mask CRTs' long reign as the technology behind the screens we look at. The 1990s decade refers to the years from 1990 to 1999, inclusive. ... Reflective twisted nematic liquid crystal display. ...

See also

• Dot pitch

Dot pitch (sometimes called line pitch or phosphor pitch) is a specification for a computer display that describes the distance between phosphor dots (sub-pixels) or LCD cells of the same color on the inside of a display screen. ...

External links

• What is a shadow mask?
• azom.com: Invar – Nickel Iron Alloy
• Illustration