|LCD computer monitors|
|Saturday, 19 August 2006|
A LCD monitor is a display apparatus capable of visually changing an optical characteristic of a liquid crystal by varying a molecular arrangement by applying a voltage to a liquid crystal. An LCD monitor generally includes a liquid crystal panel on which a picture is displayed and has such a construction that the liquid crystal panel is mounted in a space defined by the front and rear cases of the monitor. The LCD display unit's front and rear housings are assembled into a single housing containing both an LCD and a printed circuit board (PCB). A LCD monitor is a light receiving type display apparatus capable of changing an optical characteristic a liquid crystal cell based on a change of a molecular arrangement by applying a voltage to a liquid crystal. A light source, usually located behind the display's liquid crystal panel, emits light which must pass through the panel out towards the user. A LCD monitor comprises a cover casing forming an outer appearance, the LCD assembly accommodated in the cover casing. The cover casing comprises a front casing and a rear casing. The liquid crystal display panel is encased in the monitor housing allowing for protection of the display panel and other electronic components of the monitor. Because of high displaying quality and small size, LCD monitors have been selected by lots of customers as displaying devices for computers. A LCD monitor is generally installed on an adjusting support. The support is manually adjusted by a user, which is inconvenient for the user to operate by hand.
Liquid crystal displays utilize such variations in optical properties to display an image. Liquid crystal displays apply an electric power to liquid crystal having a specific molecular configuration to vary the molecular arrangement of liquid crystal. The variation in the molecular configuration of liquid crystal causes a variation in optical properties such as birefringence, optical rotary power, dichroism, light scattering. A liquid crystal is a fluid having optical/dielectric anisotropy. When it is used for a liquid crystal display (LCD), it changes a phase difference of light depending on the voltage applied to a cell. The variation in the molecular configuration of liquid crystal causes a variation in optical properties such as birefringence, optical rotary power, dichroism, light scattering. Typical examples of LCD modes are DS (dynamic scattering) mode, TN (twisted nematic) mode, STN (supertwisted nematic) mode, IPS (in-plane switching) mode, OCB (optically compensated bend) mode, and VA (vertical alignment) mode. A liquid crystal display device comprises a liquid crystal display panel, an illuminating device for visualizing latent images electronically formed in the liquid crystal display panel, and an optically compensating sheet disposed between the liquid crystal display panel and the illuminating device. These components can be assembled as an integral unit which is capable of being mounted into a notebook personal computer or a liquid crystal display monitor.
Various types of liquid crystal devices are developed. They include a reflective liquid crystal device, a transmissive type liquid crystal device, and a transflective liquid crystal device. The reflective liquid crystal device displays an image by reflecting ambient light through a liquid crystal by reflecting means provided in the device. In the transmissive/transmission type liquid crystal display, light emitted from a light source provided in the device is passed through a liquid crystal and output to the outside thereby forming an image. The transflective liquid crystal displays are capable of switching its displaying mode between reflective and transmissive modes. A reflective type LCD comprises a reflector, instead of a backlight, to reflect ambient light. Reflective LCD devices include TN (twisted nematic) mode devices and STN (super twisted nematic) mode devices. Reflective liquid crystal devices can operate with very low power consumption because they need no light source. The transmissive LCD device using the back light as a light source is relatively heavy and voluminous due to the back light, but it is widely used since it does not use an exterior light source and displays an image independently from the exterior light source. The reflective liquid crystal display has a drawback that it is extremely deteriorated in visibility when it is used in a dark place, resulting in the decrease in the reflection light to be used for displaying. While the transmission type liquid crystal display has a problem that it is deteriorated in visibility when used under bright circumstances such as fine weather. In the transflective liquid crystal device, an image is displayed in the transmissive mode using a light source when used in a dark environment. The transflective liquid crystal display requires light to be incident on the liquid crystal layer through a region with a transmission function in the transmission mode. The transflective liquid crystal display has been developed which combines a transmission display mode and a reflection display mode.
The LCD device is largely classified into a TN (twisted nematic) type and a STN (super-twisted nematic) type displays. The liquid crystal display device is, according to the driving method, classified into an active matrix display type, which uses a switching device and a TN liquid crystal, and a passive matrix type, which uses an STN liquid crystal. Today, TN (twisted nematic) liquid crystal display devices are in wide use. The STN type LCD devices are a little poor in picture quality and response speed. The active matrix display method is used in a TFT-LCD and drives an LCD by using a thin film transistor (TFT) as a switch. The passive matrix display method does not use any transistor and does not require a complex circuit. The active matrix type can be classified into a type which uses three-terminal elements, such as a thin-film transistor (TFT), as switching elements, and a type which uses two-terminal elements such as a thin-film diode (TFD). Currently, the mainstream LCD is a TFT (thin film transistor) LCD, which is an active matrix type. A TFT-LCD panel includes a top substrate, a bottom substrate, and liquid crystal materials filled between the top substrate and the bottom substrate. TFT-LCD display panel utilizes a matrix of TFTs in conjunction with other electrical elements, such as capacitors and bonding pads, as switches for driving liquid crystal pixels to produce brilliant images. TFT-LCD is divided into amorphous silicon TFT LCD (a-Si TFT-LCD) and polycrystalline silicon TFT LCD (poly-Si TFT-LCD). The LCD devices of the TFT and TFD (thin film diode) types are characterized by excellent picture quality and response speed and have been widely used in lap top computers, liquid crystal monitor, or liquid crystal television receivers.