EIZO, which occupies a leading position in high-end LCD, thinks that IPS panel has better consistency and more details, which is suitable for ultra-high gray scale and fine display requirements. Therefore, printing and medical displays, especially medical displays, can only use IPS panel products, and the gray level of those displays for diagnosis and treatment should exceed 1000, otherwise problems will easily occur. At this time, the advantages of IPS panel are very obvious, and they require the interference between pixels to be minimized.
Since EIZO greatly appreciates this, it is necessary for us to take a closer look at the difference between IPS panel and general panel, especially its old rival VA panel. IPS panel and VA panel are two technologies to make up for the defects of TN panel, which improve the viewing angle and color reproduction. Especially TN panel, the liquid crystal molecules are oriented in advance, and the liquid crystal molecules are twisted step by step, forming the deflection of the optical path. Because the thickness difference of liquid crystal molecules has more obvious influence on the optical characteristics when the power is off, TN panel first orients the molecules, and then controls the pixels by changing the arrangement of some molecules by energizing. However, due to the orientation in advance, the efficiency is not as good as that of electric field self-orientation, and the manual orientation can not guarantee enough accuracy, which leads to the failure to guarantee the level of TN panel and greatly affects the contrast. Even when power is applied, the polaroid glass of the vertical panel of liquid crystal molecules may cause light leakage, because it is not absolute. The orientation film used in this technology does not consider the viewing angle, and the viewing angle of TN panel is greatly limited. IPS and VA adopt different strategies.
In fact, the VA panel also has traces of imitating IPS. They orient the liquid crystal molecules vertically in advance, but this vertical orientation can't solve the problem of light deflection, and even if deflection is realized, it can't improve the viewing angle and contrast. This brings great manufacturing difficulty to panel technology. On the one hand, it is necessary to deflect the liquid crystal molecules as close as possible to the horizontal state, on the other hand, it is necessary to give the liquid crystal molecules a tangential force to realize the deflection of the liquid crystal molecules. Its electrode arrangement is different from that of ordinary IPS, and there must be an intersection angle, so that an electrode can both deflect and distort liquid crystal molecules. In order to solve this problem, VA panel adopts an interesting technology, which divides a pixel into two parts, each part is aimed at different directions, so that they use a conical electrode in the middle of the pixel and a corresponding conical electrode on the opposite glass substrate. The electrodes are not on the same plane, but have an included angle, which determines the twist angle of liquid crystal molecules. After the electrode is energized, the light can be deflected to the electric field and twisted at the same time, so that the light can pass through the front polarizer of the panel. From the technical root, VA is exactly the same as IPS, and VA is more complex and fragile, which is probably the real reason for the difference between soft and hard panels. Because the VA panel has two deflections, the deflection process will become longer and the deflection amount will be difficult to control. The strength of the electric field determines the number of molecules biased towards the electrode and the number of twisted molecules, and controls the brightness of the pixel from two aspects. However, because there are two processes, the number of molecular deflection and torsion is not absolutely linear with the electric field, so the brightness unevenness of the screen is greater than that of the IPS panel. When the screen is dynamic, when the deflection and torsion are different, there will be obvious smear in the color-connected area or strange grating phenomenon at the boundary, which is caused by the fact that the two do not reach the maximum at the same time. This feature of VA panel also determines that VA panel cannot control light leakage. In the process of deflection and distortion of liquid crystal molecules, the light will be directed in an inappropriate direction, and the intensity will gradually change, resulting in color drift in the moving picture, and the eyes seem to become a part of the smear. This is necessary for VA panel to solve the problem of viewing angle. Moreover, the conical electrode occupies a part of the space, and some molecules do not deflect when the screen is bright, forming a dark area, so the uniformity of the screen will also be affected.
The genius of IPS panel is that the liquid crystal molecules are not oriented in the light transmission mode in advance, but in the light transmission mode, so that the light transmission amount is determined by the electrode perpendicular to the orientation direction of the liquid crystal molecules. The higher the voltage, the more molecules twist, thus achieving accurate control of light. It only controls one deflection angle of IPS panel liquid crystal, and the number of deflection molecules can be approximately proportional to the voltage, so the hierarchical control of the panel is easier to realize.