LCD

The abbreviation of LCD in English is Liquid Crystal Display, which is a kind of flat display. The liquid crystal display uses a liquid crystal solution in two pieces of polarized material, and when the current passes through the liquid, the crystal is rearranged to achieve the purpose of imaging.

(1) Physical characteristics of liquid crystal (LCD)

The physical properties of liquid crystal are: when it is energized, it is turned on and the arrangement becomes orderly, making it easy for light to pass; when it is not energized, the arrangement is chaotic, preventing light from passing. Let the liquid crystal block or allow light to penetrate like a gate. Technically speaking, the LCD panel contains two very delicate soda-free glass materials, called Substrates, with a layer of liquid crystal in between. When the light beam passes through this layer of liquid crystal, the liquid crystal itself will stand in rows or twist in an irregular shape, thus blocking or allowing the light beam to pass smoothly. Most liquid crystals are organic compounds, composed of long rod-shaped molecules. In the natural state, the long axes of these rod-shaped molecules are roughly parallel. Pour the liquid crystal into a well-machined slotted plane, and the liquid crystal molecules will be arranged along the grooves, so if the grooves are very parallel, the molecules are also completely parallel.

(2) Principle of Monochrome Liquid Crystal (LCD) Display

LCD technology is to pour liquid crystal between two planes lined with fine grooves. The grooves on these two planes are perpendicular to each other (intersect at 90 degrees). In other words, if the molecules on one plane are aligned north-south, the molecules on the other plane are aligned east-west, and the molecules between the two planes are forced into a 90-degree twisted state. Since the light travels along the direction of the arrangement of the molecules, the light is also twisted 90 degrees when passing through the liquid crystal. But when a voltage is applied to the liquid crystal, the molecules will rearrange vertically, so that the light can be directed out without any twisting.

LCD relies on polarization filters (plates) and light itself. Natural light diverges randomly in all directions. The polarization filter is actually a series of increasingly thinner parallel lines. These lines form a net, blocking all light that is not parallel to these lines. The line of the polarization filter is exactly perpendicular to the first one, so it can completely block those polarized light. Only when the lines of the two filters are completely parallel, or the light itself has been twisted to match the second polarized filter, the light can penetrate.

LCD is composed of two polarized filters that are perpendicular to each other, so under normal circumstances, all light that attempts to penetrate should be blocked. However, because the two filters are filled with twisted liquid crystals, after the light passes through the first filter, it will be twisted 90 degrees by the liquid crystal molecules, and finally pass through the second filter. On the other hand, if a voltage is applied to the liquid crystal, the molecules will rearrange and be completely parallel, so that the light is no longer twisted, so it happens to be blocked by the second filter. In short, the light is blocked when power is applied, and the light is emitted when the power is not applied.

From the perspective of the structure of the liquid crystal display, whether it is a notebook computer or a desktop system, the LCD display used is a layered structure composed of different parts. The LCD consists of two glass plates with a thickness of about 1 mm, separated by a uniform interval of 5 μm containing liquid crystal (LC) materials. Because the liquid crystal material itself does not emit light, there are lamps on both sides of the display screen as the light source, and there is a backlight plate (or even light plate) and reflective film on the back of the liquid crystal display. The backlight plate is composed of fluorescent material Can emit light, its main function is to provide a uniform background light source. The light emitted by the backlight enters the liquid crystal layer containing thousands of crystal droplets after passing through the first polarization filter layer. The crystal droplets in the liquid crystal layer are all contained in a small cell structure, and one or more cells constitute a pixel on the screen. There are transparent electrodes between the glass plate and the liquid crystal material. The electrodes are divided into rows and columns. At the intersection of the rows and columns, the optical rotation state of the liquid crystal is changed by changing the voltage. The liquid crystal material acts like a small light valve. Around the liquid crystal material are the control circuit part and the drive circuit part. When the electrodes in the LCD generate an electric field, the liquid crystal molecules will be twisted, so that the light passing through it will be refracted regularly, and then filtered by the second layer of filter layer and displayed on the screen.