1. Field of the Invention
The present invention relates to the fabrication of a liquid crystal display panel and, more particularly, to a dispenser for fabricating a liquid crystal display panel.
2. Description of the Related Art
In a liquid crystal display device, data signals corresponding to picture information are individually supplied to liquid crystal cells arranged in a matrix. The light transmittance of each liquid crystal cell is controlled to display a desired picture. The liquid crystal display device includes a liquid crystal display panel having the liquid crystal display cells and a driver integrated circuit (IC) for driving the liquid crystal cells. The liquid crystal display panel also has a color filter substrate and a thin film transistor array substrate facing each other with a liquid crystal layer positioned between the color filter substrate and the thin film transistor array substrate.
Data lines and gate lines are formed on the thin film transistor array substrate of the liquid crystal display panel. The data lines and the gate lines cross at right angles, thereby defining the liquid crystal cells adjacent to each of the crossings. The data lines transmit a data signal supplied from the data driver integrated circuit to the liquid crystal cells. The gate lines transmit a scan signal supplied from the gate driver integrated circuit to the liquid crystal cells. The gate driver integrated circuit sequentially supplies scan signals to the gate lines so that the liquid crystal cells arranged in the matrix can be sequentially selected line by line. A data signal is supplied to the selected one of the data lines of liquid crystal cells from the data driver integrated circuit.
A common electrode and a pixel electrode system are respectively formed on the inner side of the color filter substrate and the inner side of the thin film transistor array substrate. An electric field is applied across the liquid crystal layer using the common electrode and the pixel electrode. More specifically, the pixel electrode is formed in each liquid crystal cell on the thin film transistor array substrate. The common electrode is integrally formed over the entire surface of the color filter substrate. Therefore, by controlling a voltage applied to the pixel electrode when a voltage is applied to the common electrode, light transmittance of the individual liquid crystal cells can be controlled. To control the voltage applied to the pixel electrode of liquid crystal cells, thin film transistors used as switching devices are formed so that each correspond to a liquid crystal cell.
Elements of a related art liquid crystal display device will now be described. FIG. 1 is a plan view of the unit liquid crystal display panel having a thin film transistor array substrate and a color filter substrate according to the related art.
As shown in FIG. 1, the liquid crystal display panel 100 includes an image display portion 113 where the liquid crystal cells are arranged in a matrix, a gate pad portion 114 connected to the gate lines of the image display portion 113, and a data pad portion 115 connected to the data lines. The gate pad portion 114 and the data pad portion 115 are formed along an edge region of the thin film transistor array substrate 101 that does not overlap the color filter substrate 102. The gate pad portion 114 supplies a scan signal from the gate driver integrated circuit to the gate lines of the image display portion 113, and the data pad portion 115 supplies image information from the data driver integrated circuit to the data lines of the image display portion 113.
Data lines to which image information is applied and gate lines to which a scan signal is applied are provided on the thin film transistor array substrate 101. The data lines and the gate lines cross each other. Additionally, a thin film transistor for switching the liquid crystal cells is provided at each crossing of the data lines and the gate lines. Pixel electrodes for driving the liquid crystal cells connected to the thin film transistors are provided on the thin film transistor array substrate 101. A passivation film protecting the thin film transistors is formed on the entire surface of the thin film transistor array substrate 101.
Color filters in the cell regions of the color filter substrate 102 are separated by the black matrix. A common transparent electrode is provided on the color filter substrate 102. The thin film transistor array substrate 101 and the color filter substrate 102 are attached to each other by a seal pattern 116 formed along an outer edge of the image display portion 113. Here, a cell gap is maintained uniformly by a spacer between the thin film transistor array substrate 101 and the color filter substrate 102.
In fabricating the liquid crystal display panel, a method for simultaneously forming a multiple liquid crystal display panels on a large-scale mother substrate is typically used. Thus, this method requires a process for separating the liquid crystal display panels from the large-scale mother substrate by cutting and processing the mother substrate having the plurality of liquid crystal display panels formed thereon. After a liquid crystal display panel is separated from the large-scale mother substrate, liquid crystal is injected through a liquid crystal injection opening to form a liquid crystal layer in the cell gap which separates the thin film transistor array substrate 101 and the color filter substrate 102. Then, the liquid crystal injection opening is sealed.
To fabricate a liquid crystal display panel, the following processes are generally required. First, the thin film transistor array substrate 101 and the color filter substrate 102 are separately fabricated on the first and second mother substrates. The first and second mother substrates are attached so that a uniform cell gap is maintained therebetween. The attached first and second mother substrates are cut into unit panels. Then, liquid crystal is injected to the cell gap between the thin film transistor array substrate 101 and the color filter substrate 102.
A process of forming the seal pattern 116 along an outer edge of the image display portion 113 is required to attach the thin film transistor array substrate 101 and the color filter substrate 102. The related art seal pattern forming method will now be described. FIGS. 2A and 2B illustrate a screen printing method to form a seal pattern.
As shown in FIGS. 2A and 2B, a screen mask 206 is provided with a pattern so that a seal pattern forming region is selectively exposed. A rubber squeegee 208 for selectively supplying a sealant 203 to the substrate 200 through the screen mask 206 is used to form the seal pattern 216. Thus, the seal pattern 216 is formed along an outer edge of the image display portion 213 of the substrate 200, and a liquid crystal injection opening 204 is formed at one side. The opening 204 is for injecting liquid crystal into the cell gap between the thin film transistor array substrate 101 and the color filter substrate 102. The seal pattern 216 prevents the leakage of the liquid crystal.
In general, the screen printing method includes applying the sealant 203 on the screen mask 206 having a seal pattern forming region patterned thereon, forming the seal pattern 216 on the substrate 200 through printing with the rubber squeegee 208, drying the seal pattern 216 by evaporating a solvent contained in the seal pattern 216, and leveling the seal pattern 216. The screen printing method is widely used because it has the advantage of processing ease. However, it has the disadvantage of wasting sealant. More particularly, sealant is wasted because sealant is applied over the entire surface of the screen mask 206 and then the seal pattern is printed with the rubber squeegee 208. As a result, excess sealant material, which is not printed, is discarded. In the case of fabricating a large-scale liquid crystal display panel, more sealant is consumed, thereby increasing a unit cost of the liquid crystal display device. In addition, the screen printing method has another disadvantage in that a rubbed alignment layer (not shown) formed on the substrate 200 is degraded as a result of the screen mask 206 being brought into contact with the substrate 200. The degradation of the rubbed alignment layer degrades picture quality of the liquid crystal display device.
Therefore, to overcome the shortcomings of the screen printing method, a seal dispensing method has been proposed. FIG. 3 is an exemplary view of a dispensing method for forming a seal pattern in accordance with the related art.
As shown in FIG. 3, while a table 310 with a substrate 300 loaded thereon is moved in forward/backward and left/right directions, a seal pattern 316 is formed along an outer edge of an image display portion 410 of the substrate 300 by applying a certain pressure to sealant in a syringe 301. In this seal dispensing method, since the sealant is selectively supplied to the region where the seal pattern 316 is to be formed, sealant consumption can be reduced. In addition, since the syringe is not in contact with the alignment layer (not shown) of the image display portion 410 of the substrate 300, the rubbed alignment layer is not damaged, and thus, the picture quality of the liquid crystal display device is not degraded.
When forming the seal pattern 316 on the substrate 300 loaded on the table 310 using the syringe 301, a technique is required to precisely control a gap between the substrate 300 and the syringe 301. That is, if the substrate 300 and the syringe 301 are too close together as compared to a desired gap, the seal pattern 316 formed on the substrate 300 widens and becomes low in height. Conversely, if the substrate 300 and the syringe 301 are too separated as compared to the desired gap, the seal pattern 316 formed on the substrate 300 narrows, and there may be a broken portion resulting in a defective liquid crystal display device.
In addition, if the sealant filled in the syringe 301 is completely used up, the seal pattern 316 may have a broken portion or the seal pattern 316 may not be formed. In this case, the syringe 301 should be replaced with another syringe 301 filled with the sealant before it is completely used up. At this time, however, the gap between the substrate 300 and the syringe 301 varies depending on how the syringe 301 is set into and combined with a holder (not shown). Thus, the gap between the substrate 300 and the syringe 301 should be reset each time the syringe 301 is replaced with a new one. Replacement of the syringe 301 frequently occurs in the actual manufacturing of products. Therefore, a technique for setting the gap between the substrate 300 and the syringe 301 within a short time is also required.
In addition, simultaneous formation of the plurality of image display portions 410 on the substrate 300 can improve a yield of the liquid crystal display panel. As shown in FIG. 4, in a related art dispenser for a liquid crystal display panel, a plurality of image display portions 410A-410F are formed on a substrate 400, and sealant is discharged from a plurality of dispensing units 430A-430C aligned and fixed at a support 420, to form a plurality of seal patterns 440A-440F along an outer edge of the image display portions 410A-420F formed on the substrate 400. The plurality of dispensing units 430A-430C respectively include syringes 431A-431C each having a nozzle at one end portion thereof to supply sealant to the substrate 400. Though not shown in FIG. 4, the plurality of dispensing units 430A-430C individually include a gap controller to control a gap between the substrate 400 and the syringes 431A-431C.
Thus, the related art dispenser and dispensing method of the liquid crystal display panel has a problem due to the restriction of space taken by the syringes 431 A-431 C and the gap controllers, which are individually provided for the plurality of dispensing units 430A-430C, it is impossible to form the seal patterns 440A-440F for a small liquid crystal display panel. In other words, if the liquid crystal display panel is too small, the seal patterns 440A-440F can not be formed due to interference between the dispensing units 430A-430C respectively having the syringes 431A-431C and the gap controllers.