KR100756249B1 - apparatus for removing bubbles in liquid crystal - Google Patents

Abstract

The present invention relates to an apparatus used for defoaming of liquid crystals.

It is important to constantly discharge the air in the chamber during the defoaming of the liquid crystal, it is difficult to control accurately because the degree of opening and closing of the chamber outlet by using a manual valve in the general liquid crystal defoaming device. Therefore, when the air inside the chamber is discharged too rapidly, the bubbles existing in the liquid crystal are largely generated and the liquid crystal flows out of the liquid crystal tray.

In the present invention, by using an automatic pressure controller that automatically adjusts the opening and closing of the chamber outlet according to the vacuum degree of the vacuum gauge, by accurately controlling the air discharge in the chamber, by controlling the size of the generated bubbles small, the large bubbles are burst It is possible to prevent the liquid crystal spill on the liquid crystal tray caused.

Liquid crystal defoaming, bubble, defoaming time

Description

Apparatus for removing bubbles in liquid crystal             

1 is a cross-sectional view of a general liquid crystal display device.

2 is a flowchart illustrating a manufacturing process of a general liquid crystal cell.

3 is a view showing a conventional liquid crystal defoaming apparatus.

4 is a view showing a liquid crystal defoaming apparatus according to the present invention.

The present invention relates to an apparatus for manufacturing a liquid crystal display device, and more particularly, to a defoaming device for a liquid crystal.

Recently, with the rapid development of the information society, there is a need for a flat panel display having excellent characteristics such as thinning, light weight, and low power consumption. Among them, a liquid crystal display having excellent color reproducibility, etc. displays are actively being developed.

In general, a liquid crystal display device includes two substrates on which electrodes are formed so that the surfaces on which the two electrodes are formed face each other, inject a liquid crystal material between the two substrates, and apply a voltage to the two electrodes to generate an electric field. By moving the liquid crystal molecules, the image is expressed by the transmittance of light that varies accordingly.

Hereinafter, a structure of a general liquid crystal display device will be described with reference to the accompanying drawings.

1 is a cross-sectional view of a general liquid crystal display.

As shown in FIG. 1, a gate electrode 21 made of a conductive material such as a metal is formed on a transparent first substrate 10, and a silicon nitride film (SiN _x ) or a silicon oxide film (SiO ₂ ) is formed thereon. The gate insulating film 30 covers the gate electrode 21. An active layer 41 made of amorphous silicon is formed on the gate insulating layer 30 on the gate electrode 21, and ohmic contact layers 51 and 52 made of amorphous silicon doped with impurities are formed thereon.

Source and drain electrodes 61 and 62 made of a conductive material such as a metal are formed on the ohmic contact layers 51 and 52, and the source and drain electrodes 61 and 62 together with the gate electrode 21 are thin film transistors. (T).

Although not shown, the gate electrode 21 is connected to the gate wiring, the source electrode 61 is connected to the data wiring, and the gate wiring and the data wiring are orthogonal to each other to define the pixel region.

Subsequently, a passivation layer 70 made of a silicon nitride film, a silicon oxide film, or an organic insulating layer is formed on the source and drain electrodes 61 and 62, and the passivation layer 70 has a contact hole 71 exposing the drain electrode 62. )

A pixel electrode 81 made of a transparent conductive material is formed in the pixel area above the passivation layer 70, and the pixel electrode 81 is connected to the drain electrode 62 through the contact hole 71.

On the other hand, the second substrate 90, which is spaced apart from the first substrate 10 at regular intervals and disposed above the first substrate 10, is disposed.

A black matrix 91 is formed below the second substrate 90. The black matrix 91 is positioned at a portion corresponding to the thin film transistor T. Although not illustrated, portions other than the pixel electrode 81 are also illustrated. Covering. A color filter 92 is formed below the black matrix 91. Three colors of red (R), green (G), and blue (B) are sequentially repeated. The color corresponds to one pixel area. Next, a common electrode 93 made of a transparent conductive material is formed under the color filter 92.

An alignment film (not shown) is formed on the pixel electrode 81 and the common electrode 93, respectively, and the liquid crystal layer 100 is injected between the two alignment films.

Such a liquid crystal display includes an array substrate manufacturing process for forming a thin film transistor and a pixel electrode, a color filter substrate manufacturing process for forming a color filter and a common electrode, bonding of the two substrates, injecting and encapsulating a liquid crystal material, and attaching a polarizing plate. It is formed by a liquid crystal cell process consisting of.                         

Hereinafter, the liquid crystal cell manufacturing process of the liquid crystal display device will be described in more detail with reference to FIG. 2.

2 is a flowchart illustrating a general liquid crystal cell manufacturing process.

First, a lower thin film transistor substrate including a thin film transistor and an upper color filter substrate including a color filter are prepared (st1).

The thin film transistor substrate is formed by repeating a process of depositing and patterning a thin film several times. The number of masks used in patterning of thin films represents the number of processes, and researches are being actively conducted to reduce manufacturing costs by reducing the number of masks. .

The color filter substrate is formed by sequentially forming a black matrix, a color filter of red (R), green (G), and blue (B) and a common electrode to prevent light leakage from occurring in portions other than the pixel region. The color filter is formed by a dyeing method, a printing method, a pigment dispersion method, an electrodeposition method, or the like. A common method currently used for forming a color filter is a pigment dispersion method.

The color filter substrate is formed by sequentially forming a black matrix, a color filter, and a common electrode. In addition to the manufacturing method described above, a color filter has recently been developed and used such as an inkjet method or a transfer method.

Subsequently, an alignment film for determining an initial arrangement direction of liquid crystal molecules is formed on each substrate (st2).

Formation of the alignment film consists of applying a polymer thin film and arranging the alignment film in a constant direction. In general, a polyimide-based organic material is mainly used for the alignment layer, and a rubbing method is used as a method of arranging the alignment layer. The rubbing method is to rub the alignment film in a certain direction by using a rubbing cloth, and has an advantage of easy alignment treatment, suitable for mass production, stable orientation, and easy control of the pretilt angle. However, since a defect caused by a rubbing cloth occurs, a photo-alignment method has recently been developed and used.

Next, a seal pattern is formed on one of the two substrates (st3), and the seal pattern is located outside the region where the image is represented, and forms a gap for injecting the liquid crystal and leaks the injected liquid crystal. Serves to prevent.

The seal pattern is formed by forming a thermosetting resin in a predetermined pattern, and a seal pattern forming method includes a screen printing method using a screen mask and a seal dispenser method using a dispenser. Currently, screen printing, which has a large process convenience, is mainly used. However, the screen mask is difficult to cope with defects caused by the contact between the mask and the alignment layer and the size of the substrate increases. .

Subsequently, in order to maintain a precise and uniform gap between the thin film transistor substrate and the color filter substrate, a spacer having a predetermined size is scattered on one of the two substrates (st4). The scattering method of the spacer can be divided into a wet spraying method in which the spacer is mixed by spraying alcohol and the like and a dry spraying method in which only the spacer is scattered. Since the liquid crystal display has a structure vulnerable to static electricity, the static elimination dispersion method is widely used.

Next, two substrates of the liquid crystal display, that is, the thin film transistor substrate and the color filter substrate are disposed, and the seal pattern is pressed and bonded (st5). At this time, the alignment layers of the substrates face each other, and the pixel electrodes and the color filters are disposed to correspond one-to-one.

Next, the two substrates are cut into respective cells and separated (st6). In general, the liquid crystal display may improve the manufacturing efficiency and reduce the manufacturing cost by forming a plurality of cells to be one liquid crystal display on a single substrate and separating the cells into individual cells.

The cell cutting process includes a scribe process of forming a cutting line on the surface of the glass substrate using a diamond pen having a hardness higher than that of the glass substrate, and a break process of applying a force to cut the glass substrate.

Next, the liquid crystal is injected between the alignment layers of the two substrates (st7). As the injection of the liquid crystal, a vacuum injection method using a pressure difference inside and outside the cell is mainly used. Here, when the liquid crystal is injected into the cell, bubbles may be formed inside the cell by minute air bubbles in the liquid crystal, which may cause a defect. Therefore, in order to prevent this, a defoaming process of removing bubbles by leaving the liquid crystal in vacuum for a long time is necessary.

When the injection of the liquid crystal is completed, the injection hole is sealed so that the liquid crystal does not flow out of the injection hole of the cell. In general, after applying the ultraviolet curable resin to the inlet using a dispenser, the inlet is prevented by irradiating with ultraviolet rays to cure.

Next, when the polarizers are attached to the outside of the liquid crystal cell formed in this manner, the driving circuits are connected to complete the liquid crystal display (st8).

In manufacturing the liquid crystal display device in such a manner, a device used for the defoaming process of the liquid crystal will be described below.

3 illustrates a vacuum apparatus used for the defoaming process of the liquid crystal, and as shown, the vacuum apparatus used for the defoaming of the liquid crystal includes a chamber 110 having an entrance 111 and an outlet 112 of a sample on one side. ), The liquid crystal tray 120 in which the liquid crystal is contained is located in the chamber 110. On the outer side of the chamber 110, vacuum gauges 130 and 140 for measuring the pressure inside the chamber 110 are located, and the vacuum gauges 130 and 140 respectively have a vacuum degree of a low vacuum region, The degree of vacuum in the high vacuum region is measured.

The outlet 112 of the chamber 110 is connected to a pumping system 150, and in the middle of the outlet 112, a valve 160 for opening and closing the outlet 112 by adjusting the handle 161 is provided. Located.

Degassing the liquid crystal using such a device is as follows.

First, the liquid crystal tray 120 containing the liquid crystal is loaded in the chamber 110 and blocks the inside and the outside of the chamber 110. Subsequently, the exhaust system 150 is operated and the air inside the chamber 110 is discharged through the valve 160 whose pre-opening and closing rate is adjusted, thereby gradually making the inside of the chamber 110 into a vacuum state.

In the chamber 110, the air is continuously discharged to become a vacuum state, and pressure difference occurs inside and outside of the liquid crystal, thereby removing bubbles contained in the liquid crystal. The pressure inside the chamber 110 is 40 pascals (Pa). Until this, open the valve 160 only about 15% and slowly deflate by slowly venting the air, and when less than 40 pascal, open the valve 160 completely until the pressure inside the chamber 110 becomes about 1 pascal. Defoaming.

By the way, the degree of air discharged inside the chamber 110 during the defoaming process should be appropriately adjusted. When the air discharge rate is too fast when the pressure inside the chamber 110 is 40 Pascal or more, bubbles may be generated largely and the liquid crystal may flow out of the liquid crystal tray 120. Accordingly, defects such as insufficient liquid crystal injection may occur during liquid crystal injection, and in particular, recently, high-speed response liquid crystals are required in liquid crystal displays, and since the liquid crystal has a low viscosity, it is unlikely that bubbles are generated during defoaming. Even higher.

The degree of air discharge is controlled by the degree of opening of the valve 160. In such a device, the degree of opening of the valve 160 is adjusted by turning the manual handle 161. There is a problem that is difficult to control.

The present invention has been made to solve the above-mentioned conventional problems, an object of the present invention is to provide a defoaming apparatus that can be quantitatively managed in the liquid crystal defoaming process.

Another object of the present invention is to provide a defoaming apparatus that can prevent the occurrence of defects due to bubbles during defoaming of the low viscosity liquid crystal.

Liquid crystal defoaming apparatus according to the present invention for achieving the above object comprises a chamber having an entrance and exit port of the liquid crystal tray, the outlet air is discharged; A vacuum gauge for measuring the degree of vacuum inside the chamber; An exhaust system connected to the discharge port and maintaining a degree of vacuum in the chamber; The flow of the liquid crystal in the liquid crystal tray is controlled by automatically adjusting the opening and closing degree of the outlet in two stages in a low vacuum state from atmospheric pressure to a defoaming reference pressure and in a high vacuum state below the reference pressure according to the degree of vacuum in the chamber. It consists of an automatic pressure controller, characterized in that to prevent.

Here, the vacuum gauge may be composed of a low vacuum gauge for measuring a low vacuum degree of 100 Pascal or more, and a high vacuum gauge for measuring a high vacuum of 1 pascal or less.

As described above, in the present invention, by automatically adjusting the opening and closing degree of the discharge port to accurately control the discharge of air in the chamber, it is possible to prevent the defect caused by the bubbles generated during the defoaming of the liquid crystal.

Hereinafter, a defoaming apparatus for a liquid crystal according to the present invention will be described in detail with reference to the accompanying FIG. 4. 4 shows a defoaming apparatus for liquid crystal.

As shown, the defoaming apparatus of the liquid crystal according to the present invention has a chamber 210 having an entrance 211 of the sample and an outlet 212 for discharging the air therein and defining a closed space on one side. The liquid crystal tray 220 in which the liquid crystal is contained is located inside 210. On the outer side of the chamber 210, there are vacuum gauges 230 and 240 for measuring the pressure inside the chamber 210. Since the pressure range is wide, one gauge does not know all the pressure inside the chamber 210. . Therefore, the vacuum gauges 230 and 240 which measure the vacuum degree for the low-electron area | region of 100 pascal or more and the vacuum degree for the high vacuum area of 1 pascal or less are used, respectively. The gauge for measuring the low vacuum area includes a thermocouple gauge (TC gauge) and a pirani gauge, and the gauge for specifying the high vacuum area is an ionization gauge.

The outlet 212 of the chamber 210 is connected to a pumping system 250, and an auto pressure controller 260 is positioned in the middle of the outlet 212.

Here, the exhaust system 250 is composed of a pump, which may be divided into a roughing pump, a high vacuum pump, and an ultra high vacuum pump according to an operating range. The rubbing pump is used when an operating range of 1 atm (101,325 pascals) to about 0.1 pascals is required, such as a mechanical pump, a booster pump, and a dry vacuum pump. High vacuum pumps are used when a range of 0.1 Pascals to 1 × 10 ^-6 Pascals is required, such as mechanical cryopumps, turbomolecular pumps, and oil diffusion pumps. The ultra-high vacuum pump is used when a range of 1 × 10 ⁻⁶ Pascal or less is required, and includes an ion pump and a getter pump. In general, a single pump cannot produce the required vacuum, so a combination of pumps in each of these vacuum ranges will produce the desired vacuum.

On the other hand, the automatic pressure controller 260 to adjust the opening and closing rate of the outlet 212, and includes a valve. The automatic pressure controller 260 is connected to the vacuum gauges 230 and 240, and is configured to automatically adjust the opening degree of the valve according to the pressure variation inside the chamber 210 when defoaming the liquid crystal. Therefore, since the control of the degassing time which the pressure inside the chamber 210 reaches to about 40 pascals is precisely performed, less bubbles are generated inside the liquid crystal and the liquid crystal can be prevented from flowing out of the liquid crystal tray 220. Moreover, even if defoaming of the high-speed response liquid crystal having a low viscosity can prevent defects from occurring.

The present invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit of the present invention.

In the liquid crystal defoaming apparatus according to the present invention, by controlling the discharge degree of the air in the chamber by the automatic pressure controller, it is possible to accurately control the defoaming process of the liquid crystal.

In addition, defects can be prevented by reducing the occurrence of liquid crystal bubbles during the defoaming of the liquid crystal and preventing the outflow of the liquid crystal.

Claims (4)

A chamber having an entrance and exit port of the liquid crystal tray and an outlet port through which air is discharged; A vacuum gauge for measuring the degree of vacuum inside the chamber; An exhaust system connected to the discharge port and maintaining a degree of vacuum in the chamber; The flow of the liquid crystal in the liquid crystal tray is controlled by automatically adjusting the opening and closing degree of the outlet in two stages in a low vacuum state from atmospheric pressure to a defoaming reference pressure and in a high vacuum state below the reference pressure according to the degree of vacuum in the chamber. Automatic pressure controller characterized in that Defoaming device of the liquid crystal comprising a. The method of claim 1, The vacuum gauge is a defoaming device for a liquid crystal comprising a low vacuum gauge for measuring a low vacuum of 100 Pascal or higher, and a high vacuum gauge for measuring a high vacuum of 1 pascal or lower. The method of claim 1, And a defoaming reference pressure of 40 pascals. The method of claim 1, The opening and closing degree of the second stage of the discharge port is divided into a first opening and closing degree and a second opening and closing degree, respectively, according to the low and high vacuum state, wherein the second opening and closing degree is greater than the first opening and closing degree.

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