JPH04362922A - Manufacture of liquid crystal display element - Google Patents

Abstract

PURPOSE:To manufacture the liquid crystal display element which has extremely high reliability without leaving any air bubble in a cell in an injecting process for a liquid crystal composition. CONSTITUTION:An empty cell is formed by sealing the periphery of a couple of electrode substrates, arranged in parallel to each other, except an injection opening 11, and the liquid crystal composition is injected into the cell through the injection opening 11, which is sealed from outside to manufacture the liquid crystal display element. In this manufacture, the cell is applied with ultrasonic vibration energy to resonate after the pressure in the cell is reduced under a vacuum in a vacuum tank, gas which is adsorbed by the inner peripheral surface is thus completely discharged, and then the liquid crystal composition is injected into the cell. In another way, the cell is applied with the ultrasonic vibration energy in the vacuum tank to resonate, the gas adsorbed by the inner peripheral surface is completely discharged, and after the internal pressure in the cell is reduced under a vacuum, the liquid crystal composition is injected into the cell.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a liquid crystal display element, and more particularly to a method of manufacturing a liquid crystal display element with no residual bubbles and good characteristics.

0003

[Prior Art] In recent years, liquid crystal display devices have been used in televisions, word processors, etc., taking advantage of their light weight and low power consumption.
Many of them are now on the market as displays for personal computers and the like.

The structure of such a liquid crystal display element is shown in FIG. In the figure, numerals 1 and 2 indicate two glass substrates arranged parallel to each other, and transparent electrodes 3 and 4 are formed on their opposing surfaces, respectively, and on them are oriented glass substrates. Alignment films 5 and 6 are formed. In addition, a liquid crystal composition 7 is sandwiched between such electrode substrates in contact with alignment films 5 and 6, and these substrates are bonded together with an adhesive 8 such as an epoxy resin type, so that the inside is airtight. It is sealed.

Conventionally, the following method has been used to manufacture such a liquid crystal display element.

That is, first, transparent electrodes 3 and 4 are formed on the surfaces of two glass substrates 1 and 2, respectively, and then alignment films 5 and 6 that have been subjected to an alignment treatment are formed thereon to form electrode substrates. Form. Next, spherical or cylindrical particles having approximately the same diameter as the distance between the substrates are uniformly scattered on the surface of one electrode substrate (alignment film surface) as a spacer. Furthermore, an adhesive is applied to the periphery of the alignment film on the other electrode substrate. At this time, create a part of the periphery where no adhesive is applied,
This is an opening (injection port) for injecting a liquid crystal composition. Then, such two electrode substrates are stacked and uniformly pressed together to produce an empty cell.

Next, such a cell is placed in a vacuum chamber, and both the inside and outside of the cell are brought into a vacuum state using a vacuum suction device, and then the liquid crystal composition 7 is introduced into contact with the injection port, and in this state, the liquid crystal composition 7 is introduced into contact with the injection port. The outside of the cell (inside the vacuum chamber) is returned to atmospheric pressure or a pressurized state, creating a pressure difference between the inside and outside of the cell. A method is adopted in which the liquid crystal composition 7 is injected (press-fitted) into the cell from the injection port using this pressure difference, and then the injection port is sealed from the outside with an adhesive or the like.

[0008]

[Problems to be Solved by the Invention] However, in such conventional methods, a color filter (
CF), thin film transistor (TFT), etc., the inside of the cell could not be completely evacuated. In other words, gas is adsorbed in the forming parts of CF and TFT, and even if the inside of the vacuum chamber is vacuumed to a vacuum level of 3 x 10-3 torr for more than 6 hours, the adsorbed gas will not be completely exhausted to the outside of the cell. could not be removed. Therefore, for example, when a liquid crystal composition is injected and filled into a cell with an injection area of 220 x 180 mm, there is a problem that air bubbles remain on the side diagonal to the injection port.

The present invention has been made to solve these problems, and provides a method for manufacturing an extremely reliable liquid crystal display element without leaving any air bubbles inside the cell during the injection process of the liquid crystal composition. The purpose is to provide.

[Configuration of the invention]

[0011]

[Means for Solving the Problems] In the liquid crystal display element of the present invention, a pair of electrode substrates arranged parallel to each other are sealed around a pair of electrode substrates except for an injection port to form an empty cell. In the method for manufacturing a liquid crystal display element, in which the liquid crystal composition is injected and filled from the injection port, and the injection port is sealed from the outside, the inside of the cell is vacuum-depressurized in a vacuum chamber, and then ultrasonic waves are applied to the cell. It is characterized in that vibrational energy is applied to cause resonance, gas adsorbed on the inner peripheral surface is completely exhausted, and then the liquid crystal composition is injected and filled into the cell.

Another liquid crystal display element of the present invention has a pair of electrode substrates arranged parallel to each other, and the surroundings of the electrode substrates are sealed except for an injection port to form an empty cell. In a method for manufacturing a liquid crystal display element, in which the injection port is sealed from the outside after a liquid crystal composition is injected and filled, ultrasonic vibration energy is applied to the cell in a vacuum chamber to cause it to resonate, and the cell is adsorbed to the inner peripheral surface. The method is characterized in that after the gas is completely evacuated and the inside of the cell is vacuumed, a disturbance liquid crystal composition is injected and filled into the cell.

[0013]

[Function] In the method for manufacturing a liquid crystal display element of the present invention,
After the inside of the cell is evacuated, ultrasonic vibration energy generated from an ultrasonic oscillator is applied to the cell, and as a result, the cell resonates. In addition, ultrasonic vibration energy is applied to the cell in the vacuum chamber to cause it to resonate, completely evacuating the gas adsorbed on the inner peripheral surface, and reducing the pressure inside the cell to vacuum. This resonance significantly promotes the discharge of gas adsorbed on the mounting portions of CF, TFT, etc. inside the cell to the outside of the cell, and then the liquid crystal composition is injected and filled into the cell. Therefore, the inside of the cell can be completely evacuated in a shorter time than before, and no air bubbles remain inside the cell.

As described above, according to the manufacturing method of the present invention, not only productivity is improved, but also a liquid crystal display element with improved characteristics can be obtained.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the method for manufacturing a liquid crystal display element of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view for explaining the step of injecting a liquid crystal composition in an example of the present invention.

In the example, first transparent electrodes 3 and 4 made of ITO (indium-tin oxide) or the like are formed on the surfaces of two glass substrates 1 and 2, respectively, and then TFTs 9 are formed on the electrodes of each substrate. and CF10, respectively. Next, a polyimide film is formed on the TFT 9 and the CF 10, and then a rubbing process is performed to form alignment films 5 and 6. Next, a gap material (spacer) such as plastic beads is uniformly sprinkled on one surface (alignment film surface) of the electrode substrate thus obtained. Further, an adhesive such as an epoxy resin is applied to the peripheral portion of the alignment film on the other electrode substrate except for the injection port 11 for injecting the liquid crystal composition. Then, such two electrode substrates are stacked and evenly pressed together to produce a cell.

Next, the cell thus prepared was placed horizontally on the upper surface of the holding jig 13 to which the ultrasonic oscillator 12 was attached to the lower surface, and then the entire cell was placed in a vacuum suction device equipped with a vacuum suction device. It is placed in a vacuum chamber 14. And vacuum chamber 14
The inside of the cell is evacuated by vacuum suction to a vacuum level of 3 x 10-3 torr. Next, the ultrasonic oscillator 12 is output
It is operated at 600 (W) to oscillate ultrasonic waves with a frequency of 40 (kHz), causing the cells placed in contact with each other via the holding jig 13 to resonate. After the gas adsorbed by the TFT 9 and CF 10 forming portions in the cell is discharged to the outside, the ultrasonic oscillation is stopped. After injecting and filling the liquid crystal composition into the cell from the injection port 11, the inside of the vacuum chamber 14 is returned to atmospheric pressure, and an ultraviolet curing adhesive or the like is applied to the outside of the injection port 11 and cured. completely sealed.

According to the method of the embodiment configured as described above, the liquid crystal composition is injected after the gas adsorbed in the cell is completely discharged and removed, so that no air bubbles remain inside the cell. Never. Further, even when receiving ultrasonic energy, the cell and the liquid crystal composition are not heated and the characteristics are not impaired thereby, so that a liquid crystal display element with good characteristics can be obtained. Furthermore, the inside of the cell can be completely evacuated in a shorter time than in the past, resulting in improved productivity.

Note that the oscillation frequency of the ultrasonic oscillator 12 is
For example, the range of 28 to 42 (kHz) can be used, and the output can be selected in the range of 65 to 720 (W), but is not limited to the above range. Further, such an ultrasonic oscillator 12 is attached to a holding jig 1.
It is possible not only to attach it closely to the bottom surface of 3, but also to embed it inside. Furthermore, when the ultrasonic oscillator 12 is used continuously, the oscillator itself generates heat, which is undesirable. Therefore, it is preferable to operate the ultrasonic oscillator 12 intermittently and cool it appropriately. Furthermore, the method of the present invention can be applied to CF10 or TFT.
Similar effects can be obtained not only in the manufacture of liquid crystal display elements using ferroelectric liquid crystals, but also in the manufacture of elements using ferroelectric liquid crystals, which have only transparent electrodes 3 and 4 and a very thin cell thickness.

In addition to the above-described embodiments, the present invention also applies ultrasonic vibration energy to the cell in a vacuum chamber to cause it to resonate, completely evacuating the gas adsorbed on the inner peripheral surface, and evacuating the inside of the cell. Needless to say, the liquid crystal composition may be injected and filled into the cell after the pressure is reduced.

[0021]

As explained above, according to the present invention, the adsorbed gas inside the empty cell is completely and quickly exhausted by using ultrasonic vibration energy. The time can be significantly reduced. In addition, the time required to equalize the degree of vacuum in the cell with the degree of vacuum in the vacuum chamber can be reduced to 40% of the conventional time, dramatically improving productivity of liquid crystal display elements. can be done.

Furthermore, the ultrasonic vibration energy used in the present invention can degas the inside of the cell without heating the cell or the liquid crystal composition, and therefore does not cause deterioration of the characteristics of the cell or the liquid crystal composition.

Furthermore, bubbles do not occur between the electrode substrates, which has been a problem with conventional injection methods that utilize the pressure difference between the inside and outside of the cell, and this is highly effective in preventing the formation of voids at low temperatures in the cell.

[Brief explanation of drawings]

[Fig. 1] A cross-sectional view for explaining the injection process of a liquid crystal composition in an example of the present invention.

FIG. 2 is a cross-sectional view showing the structure of a conventional liquid crystal display element.

[Explanation of symbols]

1, 2...Glass substrate 3, 4...Transparent electrode 5, 6...Alignment film 7……Liquid crystal composition 8...Adhesive 9...TFT 10……CF 11……Inlet 12……Ultrasonic oscillator 13……Holding jig 14……Vacuum chamber.

Claims (2)

[Claims] 1. A pair of electrode substrates arranged parallel to each other are sealed except for an injection port to form an empty cell, and a liquid crystal composition is injected into the cell from the injection port. After that, in the method for manufacturing a liquid crystal display device in which the injection port is sealed from the outside, the inside of the cell is depressurized in a vacuum chamber, and then ultrasonic vibration energy is applied to the cell to cause it to resonate, so that the inner peripheral surface A method for manufacturing a liquid crystal display element, comprising completely exhausting the adsorbed gas, and then injecting and filling the liquid crystal composition into the cell. 2. A pair of electrode substrates arranged parallel to each other are sealed except for an injection port to form an empty cell, and a liquid crystal composition is injected into the cell from the injection port. After that, in the method for manufacturing a liquid crystal display device in which the injection port is sealed from the outside, ultrasonic vibration energy is applied to the cell in a vacuum chamber to cause it to resonate, and the gas adsorbed on the inner peripheral surface is completely exhausted; A method for manufacturing a liquid crystal display element, comprising: reducing the pressure inside the cell, and then injecting and filling the cell with a completely disordered liquid crystal composition.