Liquid crystal display device and method of fabricating the same

A liquid crystal display device and a method of fabricating the same are disclosed in the present invention. The liquid crystal display device includes a first substrate having a thin film transistor array and a common line with a UV-ray irradiation path passing UV-rays, a second substrate having a color filter array, a sealant between the first and second substrates over the common line, and a liquid crystal layer between the first and second substrates.

This application claims the benefit of the Korean Patent Application No. P2001-083219 filed on Dec. 22, 2001, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device, and more particularly, to a liquid crystal display device and a method of fabricating the same. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for facilitating hardening of a photo-hardening sealant without modifying a black matrix layer pattern or increasing a size of the substrate.

2. Discussion of the Related Art

Generally, a liquid crystal display device has characteristics, such as low-voltage driving, low power consumption, full-color implementation, thin and compact size, and the like. Thus, it has been widely used for calculators, notebook computers, electronic watches, computer monitors, aircraft gauges, personal mobile terminals, and mobile phones.

Screens of liquid crystal display devices are becoming wider and larger in size. When a wide-screen liquid crystal display is fabricated by a liquid crystal injection method, it takes too much time. For this reason, a liquid crystal dropping method has been widely used to form a liquid crystal layer. The liquid crystal dropping method includes the steps of dropping liquid crystals on a substrate before bonding two substrates, forming a photo-hardening sealant, bonding the substrates, and hardening the sealant.

The photo-hardening sealant includes a photo-hardening sealant, which becomes a radical when UV-ray is applied thereto, and a single solution type sealant mixed with acrylate polymerized by the photo-hardening sealant. Hence, in order to harden the photo-hardening sealant, a portion where the sealant is disposed is exposed to UV-ray.

Moreover, the liquid crystal dropping method uses a column spacer attached to the substrate instead of a ball spacer dispersed on the substrate to obtain a uniform cell thickness.

A liquid crystal display device and a method of fabricating the same are explained by referring to the attached drawings as follows.

FIG. 1Aillustrates a layout of a thin film transistor array substrate for a related art liquid crystal display device.FIG. 1Billustrates a cross-sectional view taken along line IB—IB inFIG. 1A.

As shown inFIG. 1A, a plurality of gate and data lines80and90are formed on an active area120of a thin film transistor array substrate100to cross each other and define a plurality of pixel areas. A pixel electrode112is formed at each of the pixel areas. And, a plurality of thin film transistors (not shown) are formed at each intersection between the gate and data lines80and90and apply signals of the data lines90to the pixel electrodes112by being turned on/off through signals of the gate lines80, respectively.

A common line140is formed at the circumference of the active area120to provide a common electrode on a color filter array substrate (not shown) with a common voltage. And, a plurality of silver (Ag) dots (not shown) are formed at the common line140for electrical connections to the common electrode on the color filter array substrate.

Moreover, a column spacer105is formed on the gate or data line80or90to maintain a uniform cell gap. And, a photo-hardening sealant110is formed at the circumference of the active area120to surround the active area120for bonding the thin film array substrate and the color filter array substrate to each other. In this case, the photo-hardening sealant110is partially formed on the common line140.

Hence, in order to bond the substrates with the photo-hardening sealant110and to fix the photo-hardening sealant110thereto, UV-ray is applied from the color filter array substrate side or a thermo-hardening sealant is used instead of the photo-hardening sealant.

When the UV-ray is applied from the thin film transistor array substrate side, the UV-ray cannot be applied to the photo-hardening sealant110on the common line140, thereby degrading the adhesion since the photo-hardening sealant110is not hardened completely.

InFIG. 1B, an insulating layer141to form a gate insulating layer and a passivation layer is formed on the common line140, and the photo-hardening sealant110is deposited on the insulating layer141. Since the insulating layer141is transparent, the UV-ray is transmitted. However, since the common line140is opaque, the UV-ray is cut off by the common line140. Hence, the photo-hardening sealant110cannot be hardened by the UV-ray, thereby weakening the adhesion.

A related art method of fabricating a liquid crystal display device using a liquid crystal dropping method is explained in detail as follows.

FIGS. 2A to 2Gillustrate layouts and cross-sectional views of a related art fabricating process of a liquid crystal display device.

In the method of fabricating a liquid crystal display device using a liquid crystal dropping method, a plurality of liquid crystal display panel is designed on a mother substrate. More specifically, a plurality of liquid crystal display panels are designed on the mother substrate to form a thin film transistor array and a color filter array on each of the corresponding substrates. Liquid crystals are dispensed on the substrate. A sealant is deposited on the substrate, and the substrates are bonded to each other. The bonded substrates are then cut into a plurality of unit liquid crystal display panels. A plurality of the liquid crystal display panels designed on a single substrate will be explained in the following descriptions.

Although not shown inFIG. 2A, a plurality of gate and data lines are arranged on a first substrate100to cross each other and define a plurality of pixel areas. A pixel electrode (not shown) is formed on each of the pixel areas. A plurality of thin film transistors (not shown) are formed at each intersection between the gate and data lines to apply signals of the data lines to the pixel electrodes by being turned on/off through signals of the gate lines. A common line (not shown) is formed on the first substrate100to supply a common electrode with a common voltage. Herein, a plurality of liquid crystal display panels99are arranged on the first substrate100.

Subsequently, a plurality of silver (Ag) dots101are formed on the common line of each of the liquid crystal display panels99to be electrically connected thereto.

As shown inFIG. 2B, liquid crystals103for the size of each liquid crystal display panel99is dropped on each of the liquid crystal display panels99of the first substrate100.

As shown inFIG. 2C, a photo-hardening sealant110is deposited at the circumference of each liquid crystal display panel99of the first substrate100.

As shown inFIG. 2D, a plurality of column spacers105are formed on a second substrate having a black matrix layer (not shown), a color filter layer (not shown), and a common electrode (not shown) formed thereon. And, the second substrate150is turned over to be placed over the first substrate100.

Namely, the overturned second substrate150is fixed to an upper stage170, which enables movement in the Z-axis direction (i.e., vertical direction), of a bonding machine having a controllable vacuum chamber. And, the first substrate100is fixed to a lower stage160, which enables movement in the XY-axes direction (i.e., horizontal direction), of the bonding machine.

As shown inFIG. 2E, the first substrate100fixed to the lower stage160and the second substrate150fixed to the upper stage170are aligned. Then, the inside of the bonding machine is pumped down to have a desired vacuum condition. Hence, the first and second substrates100and150are bonded to each other. The first and second substrates100and150do not contact each other so as to form a first gap between the substrates100and150.

As shown inFIG. 2F, after both of the substrates are bonded to have the first gap, a gas or air is injected into the bonding machine under a vacuum condition to provide the inner space of the bonding machine with the atmospheric pressure. Since the space between the bonded substrates is in a vacuum state and the surrounding is in the atmospheric pressure, both of the substrates are pressurized by a difference between the pressure within the gap between the first and second substrates and the atmospheric pressure. In this case, both of the substrates are pressurized to have a cell gap by the column spacers105. Hence, the liquid crystals103are spread between the substrates to form a liquid crystal layer103a.

As shown inFIG. 2G, UV-ray is applied from the side of the second substrate150to harden the photo-hardening sealant110.

However, the related art liquid crystal display device and the method of fabricating the same have the following problems or disadvantages.

Since the common line on the first substrate blocks the UV-ray, the UV-ray should be applied to the first substrate from the upper side instead of the lower side.

Furthermore, when the UV-ray is applied from the upper side of the substrate, either a pattern of the black matrix layer is modified or the size of the substrate is increased, thereby misaligning the sealant from the black matrix layer.

SUMMARY OF THE INVENTION

Another object of the present invention is to provide a liquid crystal display device and a method of fabricating the same that facilitate hardening of the photo-hardening sealant without modifying the black matrix layer pattern or increasing the size of the substrate.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a liquid crystal display device includes a first substrate having a thin film transistor array and a common line with a UV-ray irradiation path passing UV-rays, a second substrate having a color filter array, a sealant between the first and second substrates over the common line, and a liquid crystal layer between the first and second substrates.

In another aspect of the present invention, a method of fabricating a liquid crystal display device includes forming a thin film transistor array on an active area of a first substrate and a metal pattern as a UV-ray irradiation path passing UV-rays at a circumference of the active area, forming a color filter array on a second substrate, forming a sealant at the periphery of the active area of one of the first and second substrates to pass the UV-ray irradiation path, bonding the first and second substrates to each other after overturning the second substrate to dispose over the first substrate, and applying UV-ray to the photo-hardening sealant from a side of the first substrate through the UV-ray irradiation path to harden the sealant.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to the illustrated embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

FIG. 3illustrates a cross-sectional view of a TN type liquid crystal display device according to the present invention.

As shown inFIG. 3, a gate line349, a gate electrode309, and a common line440of a thin film transistor are formed on a first substrate300. A gate insulating layer320is formed on the entire surface of the first substrate300. The common line440supplies a common electrode with a common voltage and provides a UV-ray irradiation path through which UV-ray is applied to harden a sealant.

A semiconductor layer315is formed on the gate insulating layer320over the gate electrode309. A data line330having source and drain electrodes316and317is formed at both sides of the semiconductor layer315. Herein, when the source and drain electrodes316and317are formed over the gate line349, a storage electrode may be formed to provide a storage capacitor.

A passivation layer325is formed on the entire surface including the source and drain electrodes316and317to provide a contact hole on the drain electrode316. A pixel electrode314is formed on the passivation layer325in the pixel area to be connected to the drain electrode316. A first alignment layer331is formed on the entire surface including the pixel electrode314.

On a second substrate350, a black matrix321is formed on a surface facing into the first substrate300to prevent a light leakage from a portion excluding the pixel area. And, a R/G/B color filter layer322is embedded in the black matrix321.

A common electrode326is formed on the entire surface of the substrate including the color filter layer322. A column spacer305is formed over the black matrix321. A second alignment layer335is formed on the entire surface of the substrate including the column spacer305. A photo-hardening sealant410is formed between the first and second substrates300and350on the edge portion of the liquid crystal display panel. And, liquid crystals are formed between the first and second substrates300and350in the liquid crystal display panel area. At this point, the photo-hardening sealant410is formed over the common line440having a UV-ray irradiation path.

The above-explained structure, wherein the photo-hardening sealant410is formed on the common line440having a UV-ray irradiation path, may be applied to various modes of liquid crystal display devices, such as vertical alignment (VA) mode, optically compensated birefringence (OCB) mode, ferroelectric liquid crystal (FLC) mode, reflective mode, horizontal electric field mode, and TN mode.

FIG. 4Aillustrates a layout of a thin film transistor array substrate for a liquid crystal display device according to the present invention.FIG. 4Billustrates a cross-sectional view taken along line IVB-IVB inFIG. 4A.

As shown inFIG. 4A, a plurality of gate and data lines349and330are formed on an active area420of a thin film transistor array substrate400to cross each other, thereby defining a plurality of pixel areas. A pixel electrode412is formed on each of the pixel areas. A plurality of thin film transistors (not shown) are formed at each intersection between the gate and data lines349and330to apply signals of the data lines330to the pixel electrodes412by being turned on/off through signals of the gate lines349.

A common line440is formed at the circumference of the active area420to provide a common electrode on a color filter array substrate (not shown) with a common voltage. And, a plurality of silver (Ag) dots (not shown) are formed at the common line440for electrical connection to the common electrode on the color filter array substrate.

Moreover, a column spacer405is formed on the gate line349or the data line330to maintain a uniform cell gap. And, a photo-hardening sealant410is formed at the circumference of the active area420to surround the active area420in order to bond the thin film array substrate and the color filter array substrate to each other. At this point, the photo-hardening sealant410is partially formed on the common line440. The column spacer405and the photo-hardening sealant410may be formed on a second substrate450as a color filter array substrate instead of the first substrate400, which acts as a thin film transistor array substrate. A path442through which UV-ray444is applied is formed in the common line440. Alternatively, the common line440may be constructed with a plurality of lines each having a fine width to pass the UV-ray444(cf. magnified view inFIG. 4A). Furthermore, the path442can also be constructed with a plurality of circles or polygons formed along a portion on which the photo-hardening sealant410is formed.

Hence, after the bonding of both substrates by the photo-hardening sealant410, the UV-ray can be applied to both of the substrates from the backside of the thin film transistor array substrate400instead of the side of the color filter array substrate.

InFIG. 4B, an insulating layer441for a gate insulating layer or a passivation layer is formed on the common line pattern440, and the photo-hardening sealant410is deposited on the insulating layer441. Even if the common line pattern440is opaque cutting off the UV-ray, a path442is formed in the common line pattern440to pass sufficient UV-ray through to harden the photo-hardening sealant110. In this case, the path for UV-ray irradiation has an opening part having an opening ratio of at least about 50%.

The photo-hardening sealant410may be shrunk during the hardening process. Hence, a thermo-hardening sealant may be added to the photo-hardening sealant.

A method of fabricating a liquid crystal display device using a liquid crystal dropping method according to the present invention is explained in detail as follows.

FIGS. 5A to 5Gillustrate layouts and cross-sectional views of a fabricating process of a liquid crystal display device according to the present invention.

As mentioned in the foregoing descriptions, more than one liquid crystal display panel is designed on a mother substrate. Thus, a plurality of liquid crystal display panels are designed on two substrates to form a thin film transistor array and a color filter array on the substrates, respectively. Liquid crystals are dropped on one of the substrates. A sealant is formed on one of the substrates, and both of the substrates are bonded to each other. The bonded substrates are then cut into a plurality of unit liquid crystal display panels.

InFIG. 5A, a plurality of gate and data lines (not shown) are arranged on a first substrate400to cross each other and define a plurality of pixel areas. A pixel electrode (not shown) is formed on each of the pixel areas. A plurality of thin film transistors (not shown) are formed at each intersection between the gate and data lines to apply signals of the data lines to the pixel electrodes by being turned on/off through signals of the gate lines. A common line (not shown) is formed on the first substrate400to supply a common electrode with a common voltage. Herein, a plurality of liquid crystal display panels399are arranged on the first substrate400, and the common line includes a UV-ray irradiation path, as described inFIGS. 4A and 4B.

Subsequently, a plurality of silver (Ag) dots401are formed on the common line of each liquid crystal display panel399to be electrically connected to the common line.

As shown inFIG. 5B, liquid crystals403for the size of each liquid crystal display panel399are dropped on each corresponding liquid crystal display panel399of the first substrate400.

As shown inFIG. 5C, a photo-hardening sealant410is deposited at the circumference of each liquid crystal display panel399of the first substrate400. The photo-hardening sealant410may also be deposited on a second substrate450.

As shown inFIG. 5D, a plurality of column spacers405are formed on the second substrate450having a black matrix layer (not shown), a color filter layer (not shown), and a common electrode (not shown). The second substrate450is turned over to be placed over the first substrate400. The column spacers405may also be formed on the first substrate400.

The overturned second substrate450fixed to an upper stage470, which enables movement in the Z-axis direction (i.e., vertical direction), of a bonding machine having a controllable vacuum chamber. The first substrate400is fixed to a lower stage460, which enables movement in the XY-axes direction (i.e., horizontal direction), of the bonding machine.

As shown inFIG. 5E, the first substrate400fixed to the lower stage460and the second substrate450fixed to the upper stage470are aligned. Then, the inside of the bonding machine is pumped down to have a desired vacuum condition. Subsequently, the first and second substrates400and450are bonded to each other. At this point, the first and second substrates400and450do not entirely contact each other, so as to form a first gap between the substrates400and450.

As shown inFIG. 5F, after both of the substrates are bonded to have the first gap, a gas or air is injected in the bonding machine under a vacuum condition to make an inner space of the bonding machine have the atmospheric pressure. Since the space between both of the substrates bonded through the sealant is in a vacuum condition and the surrounding is in atmospheric pressure, both of the substrates are pressurized by a difference between the pressure within the gap between the first and second substrates and the atmospheric pressure. In this case, both of the substrates are pressurized to have a cell gap by the column spacers405. Hence, the liquid crystals403are uniformly spread between the substrates to become a liquid crystal layer403a.

As shown inFIG. 5G, the bonded substrates are placed on a transparent quartz stage480. UV-ray is then applied from the side of the first substrate400to the photo-hardening sealant410to be hardened.

In the above-described embodiment of the present invention, the liquid crystals403are dropped on the first substrate400only. The photo-hardening sealant410, the silver (Ag) dots401, and the column spacers405may be formed on either the first substrate or the second substrate.

Accordingly, the liquid crystal display device and the method of fabricating the same according to the present invention have the following effects or advantages.

The UV-ray irradiation path is formed in the common line formed on the thin film transistor array substrate, thereby hardening the sealant by applying the UV-ray from the backside of the thin film transistor array substrate.

Moreover, since the sealant can be hardened by forming the UV-ray irradiation path in the common line of the thin film transistor array substrate, a substrate size does not have to be increased.