KR20010047194A - Method for manufacturing an Antiferroelectric LCD panel - Google Patents

Abstract

PURPOSE: A method for manufacturing an antiferroelectric liquid crystal display panel is provided to increase directional force and preventing direction of the liquid crystal from being broken, and promptly return the liquid crystal to the original place. CONSTITUTION: Transparent electrodes(3a,3b) are formed on two transparent substrates(2). Each upper surface of the transparent substrates are coated with polyimide directing agent in a polyamic acid state and the polyimide directing agent is firstly plasticized for a predetermined time at the temperature of 70-80°C for evaporating a solvent. The polyimidized directing agent is rubbed firstly. The rubbed directing agent is secondarily platicized for a predetermined time at the temperature of 180-200°C for being polyimidized. The secondarily platicized directing agent is secondarily rubbed in the equal direction of the first rubbing. The transparent substrates are arranged so that the polyimide film maintain the fixed gaps, the edges are sealed, and liquid crystal is injected between the arranged polyimide films.

Description

Method for manufacturing an antiferroelectric liquid crystal display panel {Method for manufacturing an Antiferroelectric LCD panel}

According to the present invention, the antiferroelectric liquid crystal (AFLC) uses an antiferroelectric liquid crystal (AFLC), which is 500 times faster than the conventional dielectric anisotropy (TN) responsiveness, and the response of the liquid crystal is in the electric field direction. The present invention relates to a method of manufacturing a semi-ferroelectric liquid crystal display panel in which the viewing angle is close to the CRT, the gray scale display is possible, and the driving voltage is low, thereby enabling active driving by moving in the vertical direction.

Conventional AFLC alignment method (Japanese Patent Laid-Open No. 8-328047) uses a polyamic acid aligning agent or a conventional polymer aligning agent as a solvent in the alignment of liquid crystals as a solvent, and the solvent is coated at a high temperature in a state of being coated on a substrate in a solution state. Orientation is carried out by rubbing in a state of evaporating or dehydrating amic acid to polyimide. However, the antiferroelectric liquid crystal cell made by this method has a disadvantage in that the contrast is lowered and the display quality is lowered because the phase is broken by repeated driving. Also, the antiferroelectric liquid crystal cell is generally oriented by one rubbing, but in this case, the electro-optic is caused by the difference in the electric field between the upper and lower substrates according to the area difference of the interface between the liquid crystal and the alignment agent on the rubbing side and the non-rubbing side. Due to the influence of the characteristics, hysteresis occurs and causes flicker during driving.

The present invention has been made to solve the above problems, using a semi-ferroelectric liquid crystal, the response speed is fast, the viewing angle is wide, the image is not broken by repeated driving, hysteresis is generated significantly due to the electric field difference between the upper and lower substrates It is an object of the present invention to provide a method for manufacturing a shrinking antiferroelectric liquid crystal display panel.

1 is a vertical cross-sectional view showing the structure of a liquid crystal cell to which the method of manufacturing an antiferroelectric liquid crystal panel according to the present invention is applied,

FIG. 2 is a diagram illustrating a cone structure of liquid crystal molecules in the liquid crystal cell of FIG. 1.

<Description of the symbols for the main parts of the drawings>

1. Upper and lower polarizer 2. Upper and lower transparent substrate

3a, 3b. Upper and lower transparent electrodes 4. Upper and lower alignment layers

5. Thin Film Transistor 6. Spacer

7. Antiferroelectric Liquid Crystal

In order to achieve the above object, a method of manufacturing a semi-ferroelectric liquid crystal display panel according to the present invention includes the steps of: (a) forming transparent electrodes on a stripe on two transparent substrates; (B) applying a polyimide aligning agent to the upper surface of the transparent substrate on which the transparent electrodes are formed, respectively, in a polyamic phase, and then first baking at 70 to 80 ° C. for 10 minutes to evaporate the solvent; (C) first rubbing the polyimide aligning agent; (D) polyimidating the first rubbed alignment agent by secondary firing at 180 to 200 ° C. for 50 to 80 minutes; (E) secondary rubbing treatment of the secondary calcined alignment agent in the same direction as the rubbing direction during the primary rubbing treatment; And (f) arranging the two transparent substrates on which the alignment layer is formed by the second rubbing process so that the alignment layer maintains a constant interval, sealing the edges, and then injecting liquid crystal between the arranged alignment layers. It is characterized by.

Hereinafter, a method of manufacturing an antiferroelectric liquid crystal display panel according to the present invention will be described in detail with reference to the drawings.

The present invention produces liquid crystals using antiferroelectric liquid crystals having spontaneous polarization. The alignment of the antiferroelectric liquid crystals (AFLC) is a result of the image being broken by repeated driving, resulting in a decrease in contrast and deterioration of the display quality of the panel. By applying a new orientation method to prevent this from happening, this phase is prevented from breaking and the response speed is faster than the conventional method.

1 is a partial vertical cross-sectional view showing the structure of a ferroelectric liquid crystal panel manufactured by the method of manufacturing a ferroelectric liquid crystal display panel according to the present invention. As shown, the ferroelectric liquid crystal display panel includes two upper and lower polarizing plates 1 surrounding the outside of the liquid crystal cell, upper and lower transparent substrates 2 disposed opposite to each other, and opposite surfaces of the upper and lower transparent substrates 2, respectively. Intersections of the upper and lower transparent electrodes 3a and 3b arranged on the stripe in the crossing direction, the upper and lower alignment layers 4 and the upper and lower transparent electrodes 3a and 3b stacked on the substrate to cover the transparent electrodes 3a and 3b. A liquid crystal cell formed between the thin film transistor 5 and the upper and lower transparent substrates 2 to apply a voltage to the transparent electrodes to maintain a gap between the spacers 6 and the upper and lower alignment layers 4. It consists of the antiferroelectric liquid crystal 7 which exists.

The manufacturing method of the liquid crystal display panel of such a structure is as follows.

As shown in FIG. 2, in the manufacturing process of the liquid crystal display panel, a vertical alignment agent is coated on the opposite surface of the transparent substrate 2 on which upper and lower transparent electrodes 3a and 3b are formed, and then rubbed to perform alignment treatment. Then, the upper and lower transparent substrate 2 is made of a process for completing a vacuum injection empty cell. In this process, the alignment treatment is one of the most important processes that influence the performance of the liquid crystal display panel, and is performed by the following method.

That is, it is coated on the transparent substrate 2 in the state of the polyamic acid of the high mobility of the polymer as an alignment agent for liquid crystal alignment. After coating the solution containing this polyamic acid on the transparent substrate 2, the solvent is evaporated and removed over 70 minutes at 70-80 degreeC (primary baking). In this way, the surface of the coated substrate was first subjected to strong rubbing, which gave large curvature to the surface, followed by post-baking (secondary firing) at 180 to 200 ° C. for 50 to 80 minutes. After mid-ization, the surface of this substrate is subjected to a rubbing treatment again.

When the alignment is performed, the main body of the polymer is easily oriented in the rubbing direction on the high-mobility polyamic phase, thereby increasing the orientation force and making it difficult to break the alignment of the liquid crystal due to the large bend. Anchoring power on the ferroelectric liquid crystal becomes three-dimensional, so that the time for the liquid crystal to return to its original position is increased even when the electric field is applied and then removed. Moreover, the effect of general orientation can be acquired again by the secondary rubbing performed in the polyimide state. The first and second rubbing treatments are made in the same direction so that the angles are the same. If the directions of the first and second rubbing are different, this may cause the contrast to decrease.

In addition, the thickness of the cell at the time of manufacturing the liquid crystal cell greatly affects the electro-optical characteristics, the liquid crystal cell thickness is less than the helix structure of the anti-ferroelectric liquid crystal is a good alignment of the liquid crystal. Although the gap of a normal liquid crystal cell should maintain 2 micrometers or less, it is common to maintain 1.5-2.02 micrometers.

The liquid crystal is injected into the empty cell in which the alignment film oriented by the rubbing process is formed by vacuum or the like. The temperature at the time of injection should be performed in a temperature range in which the injected liquid crystal exhibits isotropy. When the injection is completed, the liquid crystal cell performs the alignment while gradually decreasing the temperature, but the alignment is not properly performed when the liquid crystal cell is rapidly cooled. In the case of the aligned cells, a liquid crystal display panel is manufactured by attaching a polarizing plate having the rubbing direction of the rubbed substrate as an optical axis, and attaching an analyzer in the vertical direction to the other substrate.

The operation principle of the antiferroelectric liquid crystal display panel manufactured by the above method is as follows.

When the electric field is applied to the liquid crystal cell of the liquid crystal display panel fabricated as described above, the liquid crystal molecules are X, Y in the cone of the liquid crystal perpendicular to the optical axis in the rubbing direction with respect to the upper and lower electric fields as shown in FIG. 2. It moves in the direction of. At this time, the angle moving from side to side changes in accordance with the cone angle in proportion to the magnitude of the voltage, thereby enabling gray scale display.

<Example 1>

The liquid crystal cell of Example 1 used a polyimide-based alignment agent synthesized for the present study as an alignment agent. First, the alignment agent was spin-coated on a transparent substrate on which one transparent electrode was formed, and then baked at 80 ° C. for 10 minutes, followed by a first rubbing treatment. Next, it was refired at 180 ° C. for 1 hour and subjected to second rubbing again. The other transparent electrode was spin-coated with an alignment agent and calcined at 80 ° C., followed by a first rubbing treatment, and refired at 180 ° C. for 1 hour to undergo a second rubbing treatment on the surface. The empty cell for vacuum injection was made using the upper and lower transparent electrodes thus made. At this time, in order to maintain the cell gap, the cell gap was maintained as a spacer of 1.6 μm and the thickness of the finished cell was maintained as 1.6 to 8 μm. After injecting the liquid crystal at 120 ℃ to the completed vacuum cell, the cooling was performed at a cooling rate of 2 ℃ per minute to orient. On the surface of the electrode subjected to the rubbing treatment, the optical axis of the polarizing plate and the optical axis of the liquid crystal were made to coincide with each other, and the polarizing plate was attached to the opposite electrode surface so that the optical axis was perpendicular to this. The electro-optical properties of the cell thus obtained did not decrease the contrast even after repeated driving, and the response speed was 250 µsec and the contrast was 200 or more. In addition, the viewing angle was 150 ° or more in the upper, lower, left and right directions on the basis of contrast 10: 1.

On the other hand, in Example 1, as a result of measuring the electro-optical characteristics of the cell prepared by one rubbing treatment after firing at 200 ° C., which is a conventional cell manufacturing method, the response speed was 330 μsec and the contrast was about 100.

As described above, the method of manufacturing the antiferroelectric liquid crystal display panel according to the present invention is a polyimide-based polymer with a high mobility of the polyimide-based polymer as an alignment agent in a polyamic acid state and in this state to remove the solvent around 70 ~ 80 ℃ After the first strong rubbing, the surface of the alignment agent is subjected to large bending, the polyamic acid is again polyimide at 180 to 200 ° C., and then the second rubbing is performed to perform the alignment treatment. When the alignment is performed, the main body of the polymer is easily oriented in the rubbing direction on the polyamic phase where the mobility of the polymer is high, thereby increasing the orientation force and making the liquid crystal's orientation difficult to be broken due to the large bend. On the curved surface, the anchoring power on the antiferroelectric liquid crystal becomes three-dimensional, so that the liquid crystal returns to its original position even if the electric field is applied and then removed. Moreover, the effect of general orientation can be acquired again by rubbing performed in the polyimide state.

Therefore, the liquid crystal cell of the liquid crystal display panel manufactured as described above has a faster response speed and higher contrast than that produced by the conventional AFLC cell manufacturing method. The reason for the improved electro-optical characteristics is that the primary rubbing performed in the state of polyamic acid, in which the hardness is not high when the alignment is performed, facilitates deep alignment bending and alignment of the main chain of the polymer, thereby facilitating the alignment of liquid crystals. The microstructure which can be formed is possible, and the orientation is stabilized by perfecting the micro orientation by the secondary rubbing.

In addition, the anti-ferroelectric liquid crystal display panel manufactured as described above uses a semi-ferroelectric liquid crystal having spontaneous polarization instead of conventional TN (twested nematic), which is 500 times or more than TN liquid crystal which responds with conventional dielectric anisotropy. The response speed is fast, and the response of the liquid crystal moves in the vertical direction with respect to the electric field direction of the vertical electrode, so that the viewing angle is close to the CRT. In addition, gray scale display is possible, and the driving voltage is low, thereby enabling active driving, and it is possible to prevent cracking of the liquid crystal phase due to repetitive driving.

Claims (3)

(A) forming transparent electrodes on the stripe on each of the two transparent substrates; (B) applying a polyimide aligning agent to the upper surface of the transparent substrate on which the transparent electrodes are formed, respectively, in a polyamic state, and then first baking at 70 to 80 ° C. for a predetermined time to evaporate the solvent; (C) first rubbing the polyimide aligning agent; (D) polyimidizing the first rubbed alignment agent by second baking at 180 to 200 ° C. for a predetermined time; (E) secondary rubbing treatment of the secondary calcined alignment agent in the same direction as the rubbing direction during the primary rubbing treatment; And (F) arranging the two transparent substrates on which the alignment layer is formed by the secondary rubbing process so that the alignment layer maintains a constant interval, sealing the edges, and then injecting liquid crystal between the aligned alignment layers; The manufacturing method of the antiferroelectric liquid crystal display panel characterized by including. The method of claim 1, In the step (b), the first firing is performed for 10 minutes. The method of claim 1, In the step (d), the secondary firing is performed for 50 to 80 minutes.