Principle, Structure, Advantages and Disadvantages of Plasma Display Screen

Plasma display panel (plasma for short) is also known as plasma display. It is a flat display screen. Light is emitted from ions between two glasses to phosphorus. The emitted gas has no mercury component, but is a mixture of inert gases neon and xenon. This gas is harmless. The plasma display is very bright (1000 LX or more), can display more colors, and can also produce a large area display screen, with a maximum diagonal of 381 cm (150 inches). The contrast of plasma display screen is also high, creating an all black effect, which is especially suitable for watching movies. The thickness of the display screen is only 6 cm (2.5 inches). Together with other circuit boards, the thickness is only 10 cm.

Structure and composition of plasma display screenThe panel of the ion screen is mainly composed of two parts. One is the front process close to the user's surface, including glass substrate, transparent electrode, bus electrode, transparent inductor layer and MgO thin film.The other is the rear process, which includes a phosphor layer, a barrier rib, a lower plate transparent inductor layer, an address electrode and a glass substrate. Therefore, the phosphor responsible for luminescence is not on the side close to the user, but on the inner part.

Since the control circuit must be clamped between the front panel process and the rear panel process, during the panel combination process, the front and rear panels need to be accurately aligned and matched with the control circuit to ensure that there is no problem in lighting. In this step, it will be found that the LCD panel needs a backlight module, but the PDP does not, because it belongs to self illumination.Only the panel is not enough, because there is also a high-voltage drive circuit, which can meet the basic needs of the screen with different control circuits. If you buy a plasma TV, most of them will be equipped with an exclusive TV box, because whether it is image input or tuner, most of them are designed in the TV box. Therefore, a complete plasma TV includes a plasma screen and a TV box.Structure of plasma screen discharge unit (sub-pixel)

On the CRT display screen, the bright spots of pixels are generated; The image signal is generated by bombarding the screen phosphor with an electron beam controlled by the cathode of the CRT; Finally, the image is formed under the action of scanning. Bright spots of pixels generated by plasma screen; The image signal passes through the address electrode (d) of the plasma screen discharge unit; Controlling the discharge of the discharge unit to excite the phosphor inside the discharge unit to emit light; Generating luminance pixels; final; A large number of pixels with certain brightness form an image under the arrangement of matrix circuit.

Although CRT screen and plasma screen are composed of images controlled by image signal, the way and principle of phosphor producing bright spots; But very different. Fig. 1 is a cross-sectional structure of a primary color pixel (sub-pixel) three electrode AC plasma discharge tube.

Figure 1 is a cross-sectional view of the plasma screen. The part marked "emitted light" in the figure is the front of the screen. Between the two "isolation walls" below is a monochrome discharge chamber, which is filled with mixed inert gas under certain pressure; The lower part of the cavity is coated with phosphor (the structure of the green discharge cavity is shown in the figure), the upper part is provided with "X electrode" and "Y electrode", the lower part is "address electrode", and the surface of the electrode is coated with an insulating electrolyte layer (black edge line). "X electrode" and "Y electrode" apply sustain discharge voltage (the waveform is AC square wave, the amplitude is slightly lower than the trigger voltage amplitude; make the X and Y electrodes in critical discharge state); "Address electrode" applies control discharge pulse (the control discharge pulse is the processed image signal, which passes through the address electrode; ignites the inert gas between X and Y electrodes in critical state to generate discharge); Under the action of electric field; The gas inside the cavity ionizes to produce discharge; The discharge produces a large amount of ultraviolet light with a wavelength of 147nm (nm); The ultraviolet ray shoots the phosphor at the lower part of the cavity; Phosphors emit light under the excitation of ultraviolet light; Light is emitted from the front of the screen (the glass on the front is also a protective layer against ultraviolet rays). Same as CRT picture tube; A pixel is composed of three monochromatic emitters emitting red, green and blue (R, G and b). This monochromatic emitter is called "sub-pixel", as shown in Fig. 1; It is a green sub-pixel structure, with discharge chambers of blue and red sub-pixels on both sides.

Fig. 2 is a cross-sectional structure of a plurality of R, G and B primary color plasma discharge tubes arranged together.

In the previous section, we talked about the discharge unit - sub-pixel, which constitutes the plasma screen; In fact, it is a small "fluorescent tube". More specifically, it is a "cold cathode fluorescent tube" (now the backlight tube of LCD screen is also a cold cathode fluorescent tube, but it is only large). To make this "cold cathode fluorescent tube" with the size of pixels under the control of image signal; It is extremely difficult to produce brightness with corresponding light and shade changes. To solve many complex problems in principle and technology. Achieved today; This is the crystallization of the development of science and technology and electronic technology.

Characteristics of plasma display screenCompared with direct viewing CRT color TV:PDP displays are smaller, lighter, and free of X-ray radiation.

Since the structure of each light-emitting unit of PDP is exactly the same, there will be no geometric deformation of the image of the picture tube.The brightness of PDP screen is very uniform - there are no bright and dark areas; The brightness of the traditional picture tube - the brightness of the center of the screen is always higher than that of the surrounding areas.PDP will not be affected by magnetic field and has better environmental adaptability.

There is no focusing problem on the PDP screen. Therefore, the problem of poor focusing or defocus in some areas of the picture tube can be solved, and the color drift of the picture tube will not occur.The flat surface completely improves the distortion and color purity change at the corners of the large screen. With high brightness, large viewing angle, full-color and high contrast, the PDP image is clearer, the color is brighter and the effect is more ideal, which makes the traditional TV amazing.Compared with LCD:

The PDP display brightness is high, and the screen brightness is up to 150lux, so you can enjoy the video program of Dali picture in a bright environment.Good color restoration and rich gray, which can provide a particularly bright, uniform and smooth picture.PDP has a wide field of vision, and the viewing angle of PDP is as high as 160 degrees. When ordinary TV is viewed at a place greater than 160 degrees, the picture has been seriously distorted, while the viewing angle of LCD is only about 40 degrees, which is incomparable with the effect of PDP.

Fast response to rapidly changing images. In addition, the flat and thin appearance of PDP also makes its advantages more obvious.Principle of plasma display screen1. The basic working principle of plasma screen is similar to that of CRT and fluorescent lamp. Basically, the plasma screen is formed by arranging a plurality of small discharge spaces. Each small discharge space is called a cell, and each cell is responsible for one of the three colors of red, green and blue (RGB). Therefore, the multi tone colors we see are mixed by mixing the primary colors of three cells with different proportions, and this color mixing method, It is similar to the color mixing method used in LCD screen.

2. The architecture of each cell uses the working principle similar to fluorescent lamp. In other words, you can think of it as a compact ultraviolet fluorescent lamp, which uses dissociated inert mixtures of helium (he), neon (NE), xenon (Xe) and so on. When high voltage electricity passes through, it will release electric energy, trigger the gas in the cell, generate gas discharge and emit ultraviolet light.3. After the cell is stimulated by high pressure to produce ultraviolet light, the ultraviolet light is used to stimulate the red, green and blue phosphors on the coated glass, so as to produce the required three primary colors of red, green and blue. By controlling different cells to emit ultraviolet light of different intensities, three primary colors with different brightness can be generated, and then a variety of colors can be formed.4. Because the plasma screen stimulates phosphorous luminescence through ultraviolet light, it belongs to self luminescence like CRT, which is different from the passive luminescence of LCD screen. Therefore, its luminous brightness, color brightness and screen reaction speed are similar to CRT, so you will find that the brightness of PDP can often exceed 700nits, However, the brightness of LCD can not reach more than 500nits until later products.

Advantages of plasma display screen1. PDP does not need to be viewed in a relatively dark environment, and there is no problem of viewing angle. The best picture quality can be viewed at any position under any ambient light.2. The panel is large in size and thin in thickness.

3. PDP is composed of each light-emitting monomer, so it is particularly clear and distinct. Unlike CRT, it will have some visual and sensory uncomfortable problems, such as ambiguity, non concentration of RGB three primary colors, picture distortion and flicker.4. The electromagnetic wave radiation of plasma is only 1 / 100 to 1 / 1000 of that of CRT TV.5. It can be made into a wide screen.

Different from the liquid crystal or projection light-emitting principle, each pixel of the plasma display can emit light by itself (active self illumination), so it presents a softer picture and can reach a viewing angle of about 170 degrees. In addition, the response time of each pixel is short, the color saturation is high, and it is suitable for large-scale development. Plasma TV is also a new technology that is very close to and can surpass image tube TV in overall image quality performance. In addition, it has the characteristics of no radiation and no external magnetic interference, which is very conducive to the adjacent setting of family viewing or theater speakers. For example, Panasonic's "Viera" series has launched a 150 inch plasma TV, and pioneer has also launched a "pure vision" plasma TV with an ultra-high color saturation of about 107% over the NTSC standard color gamut.

Disadvantages of plasma display screen1. When viewing in a bright environment, the brightness is slightly inferior to the LCD. When the still picture is displayed for a long time, it is easy to produce residual shadow during picture switching. It consumes quite a lot of power, and it is easy to generate high heat during display. Heat dissipation must be considered. Due to material and structural constraints, plasma displays cannot develop to a small size below 20 inches, which is the biggest weakness in market competition.

2. According to the above shortcomings, three major plasma display manufacturers in Japan: Panasonic PDP, Fujitsu Hitachi PDP and pioneer PDP have spent many years to continuously improve. The most significant aspect is the power consumption. The power consumption in the average display time including moving and static images has been reduced to even lower than that of LCD. This improved technology is based on the luminous characteristics, so that the PDP can use less power consumption when displaying dark color; On the contrary, the LCD still uses the backlight module with the same power to provide a fixed intensity light source, so the total power consumption may exceed that of the PDP.

3. The service life of plasma display screen is short