In-line system and a method for manufacturing a liquid crystal display

Disclosed is an in-line system and a method for manufacturing a liquid crystal display. The system includes a spacer-dispersing unit for dispersing spacers on one of two substrates of a mother glass, the mother glass having at least one liquid crystal cell; a sealant-applying unit for depositing a sealant on one of the two substrates; a liquid crystal depositing unit for depositing liquid crystal material on the substrate on which the sealant is deposited; and a substrate-attaching unit for receiving the two substrates from the sealant-applying unit or the liquid crystal depositing unit, then conjoining the substrates in a vacuum state. The method includes the steps of dispersing spacers on one of two substrates of a mother glass, the mother glass having at least one liquid crystal cell; depositing sealant on one of the two substrates; depositing liquid crystal material on the substrate where the sealant is deposited; and conjoining the substrates in a vacuum state to complete the manufacture of a liquid crystal panel.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a system and method for manufacturing liquid crystal displays.

(b) Description of the Related Art

A liquid crystal display (LCD) is structured having liquid crystal material injected between two substrates. The two substrates have electrodes formed on an inner surface thereof and are joined using a sealant. A plurality of spacers are provided between the substrates to maintain a predetermined cell gap. The liquid crystal material sandwiched between the substrates is dielectrically anisotropic such that, when a voltage of a different potential is applied to electrodes of the substrates to form an electric field, the alignment of liquid crystal molecules of the liquid crystal material is varied. Accordingly, the transmittance of incident light is controlled to enable the display of images.

To manufacture the LCD, orientation layers for orienting the liquid crystal molecules of the liquid crystal material are first provided on the substrates, and an orientation process is performed. Next, spacers are dispersed on one of the substrates, then the sealant is applied to outer edges of the substrates. The sealant is provided with a hole through which the liquid crystal material is to be injected. Following this step, the substrates are aligned then attached through a hot press process. Next, liquid crystal material is injected through the hole of the sealant, after which the hole is sealed.

In the LCD manufacturing process, a plurality of liquid crystal cells, each for producing a single LCD, are formed from a single mother glass. Before the injection of the liquid crystal material, the mother glass is divided into 4, 6 or 8 liquid crystal cells (but not yet cut into these divisions), after which the process is continued on the individual liquid crystal cells.

A serious drawback of the conventional LCD manufacturing process is that it is time-consuming. In particular, the injection of the liquid crystal material must be performed when the space between the substrates is kept vacuum. Both keeping vacuum while maintaining the cell gap, and injecting the liquid crystal material through the small injection hole require substantial amounts of time. Further, since the time required for each individual process may vary according to, for example, the drive method used for a particular LCD, and since there occurs a switch during production from processes performed on the mother glass to those performed on the individual liquid crystal cells, it becomes difficult to provide production equipment for the specific processes in an in-line configuration or to automate manufacture. This substantially limits the productivity improvement. Also, while injecting the liquid crystal material, the spacers become re-positioned by the forces generated from the flow of the liquid crystal material, thereby making it difficult to obtain a uniform cell gap.

SUMMARY OF THE INVENTION

The present invention has been made in an effort to solve the above problems.

It is an object of the present invention to provide an in-line system for manufacturing a liquid crystal display and a method for manufacturing liquid crystal displays.

It is another object of the present invention to simplify a method for manufacturing a liquid crystal display, and to minimize manufacturing costs and reduce the time required for manufacturing.

The in-line system comprises a spacer-dispersing unit for dispersing spacers on one of two substrates of a mother glass, the mother glass having at least one liquid crystal cell region; a sealant-applying unit for depositing a sealant on one of the two substrates; a liquid crystal depositing unit for depositing liquid crystal material on the substrate on which the sealant is deposited; and a substrate-attaching unit for receiving the two substrates from the sealant-applying unit or the liquid crystal depositing unit, then conjoining the substrates in a vacuum state to complete a liquid crystal display panel.

The method for manufacturing a liquid crystal display panel is also provided.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows a plan view of a liquid crystal panel produced using an in-line system according to a preferred embodiment of the present invention, andFIG. 2shows a sectional view taken along line II-II ofFIG. 1.

A liquid crystal panel100, which is made from a single mother glass that has undergone liquid crystal injection and substrate-attachment processes, includes a plurality of liquid crystal cells. For example, four liquid crystal cell regions111,121,131and141are formed in the liquid crystal panel100. The liquid crystal panel100includes insulation substrates110and120opposing each other and a liquid crystal layer130, which is formed of liquid crystal material injected between the substrates110and120. Spherical spacers140are mixed in with the liquid crystal layer130. The spacers140maintain a predetermined cell gap between the substrates110and120such that the substrates110and120are substantially parallel. Further, a sealant150is formed around edges of each liquid crystal cell such that the liquid crystal layer130is sealed between the substrates110and120. Spacers may also be mixed in with the sealant150.

As described above, the liquid crystal layer130is injected before the liquid crystal panel100is divided into liquid crystal cells. The liquid crystal cells are divided along cut lines a and b, and only after completing both liquid crystal injection and substrate-attachment processes.

Wiring for transmitting electrical signals such as scanning signals and image signals may be formed on the substrates110and120of the liquid crystal panel100. The wirings intersect to define pixel regions. Thin film transistors are formed as switching devices for controlling image signals. Pixel electrodes and a common electrode are laid to form an electric field to drive liquid crystal molecules of the liquid crystal material. And an RGB color filter is formed for displaying images.

FIG. 3shows a schematic block diagram of an in-line system for manufacturing liquid crystal displays according to a preferred embodiment of the present invention.

As shown in the drawing, an in-line system for manufacturing liquid crystal displays according to a preferred embodiment of the present invention includes a first loading unit1000, a spacer-dispersing unit2000, a sealant-applying unit3000, a sealant heat-treating unit4000, a liquid crystal depositing unit5000having a liquid crystal depositer5100, a substrate-combination unit6000, a second loading unit7000, a substrate-attaching unit8000, and an unloading unit9000. Provided between the first loading unit1000, the spacer-dispersing unit2000, the sealant-applying unit3000, the sealant heat-treating unit4000, the liquid crystal depositing unit5000, the substrate-combination unit6000, the substrate-attaching unit8000, and the unloading unit9000are in-line conveying units1110,1120,1130,1140,1150,1170and1180for conveying the substrates110and120from one process to the next. The second loading unit7000is connected to the substrate-combination unit6000through an in-line conveying unit1160. Since the substrates110and120are attached at the substrate-attaching unit8000in a vacuum state between the substrates110and120, the in-line conveying units1170and1180may include vacuum chamber connecting means.

Manufacturing a liquid crystal display using the in-line system above will now be described.

First, the substrate110, which is loaded on the first loading unit1000, is transported to the spacer-dispersing unit2000via the in-line conveying unit1110. The spacers140are dispersed at a predetermined density on an inner face of the substrate110at the spacer-dispersing unit2000. At this time, it is preferable that the spacers140be spherical or cylindrical and have a diameter that is 10-30% greater than the desired cell gap between the substrates110and120. Further, if the spacers140are simply dispersed without securing them to the substrate110, external shocks or vibrations during manufacture or the flow of the liquid crystal material may displace the spacers140from their intended positions. This results in a non-uniform cell gap between the substrates110and120. Accordingly, it is preferable that the spacers140are adhered to the substrate110after being dispersed.

With reference toFIG. 4A, according to the present invention, the spacers140are coated with an adhesive142, which is made from an epoxy group polymer. Next, infrared rays are irradiated onto the substrate100and the spacers140dispersed thereon such that the adhesive142on an upper portion of the spacers140melts down to fully surround a lower portion of the spacers140, as shown inFIG. 4B. Accordingly, the spacers140are fixed to their positions on the substrate110. Instead of dispersing the spacers140in this manner, it is possible to form the spacers140through a photolithography process. This may also include the formation of the spacers140in the sealant. Such an alternative process is particularly advantageous for large substrates.

Following the above, the substrate110is transported from the spacer-dispersing unit2000to the sealant-applying unit3000via the in-line conveying unit1120. The sealant150is deposited on the substrate110at the sealant-applying unit3000. The sealant150is formed in a closed configuration, that is, the sealant150does not include a liquid crystal injection hole as in the prior art. Also, the sealant150may formed of a heat-hardening material or an infrared ray-hardening material, and may include spacers for better maintaining the cell gap between the substrates110and120.

Since there is no liquid crystal injection hole formed in the sealant150, the amount of liquid crystal material provided between the substrates is difficult to control. Too much liquid crystal material leads to damage to the sealant.150, while an insufficient amount of liquid crystal material results in areas that are not fully filled with the liquid crystal material. To solve this problem, it is preferable that a buffer region(s) is formed in the sealant150such that liquid crystal material fully fills display portions and any excess liquid crystal material flows into the buffer region(s). With reference toFIG. 5A, at least one buffer region151is formed in the sealant150. When the amount of liquid crystal material provided to the substrate110surpasses that needed to fill a display region c, the excess liquid crystal material flows into the buffer region151. As another example, with reference toFIG. 5B, buffer regions152, which allow the inflow of excess liquid crystal material, are formed around a circumference of the display region c. It is preferable that the amount of liquid crystal material deposited during a subsequent liquid crystal depositing process is in excess of an amount needed to fill the display region c and less than a volume defined by the sealant150.

Next, the substrate110is transported from the sealant-applying unit3000to the sealant heat-treating unit4000by the in-line conveying unit1130. It is preferable that a reaction prevention layer is formed on a surface of the sealant150through an exposure or heat-treating process such that no reaction takes place between the liquid crystal layer130and the sealant150. For this purpose, it is preferable that an infrared ray-hardening material is used for the sealant150. During a first hardening process, the sealant150, with reference toFIG. 6A, is divided into a portion155that is hardened and is comprised of the reaction prevention layer, and a portion157that has not been hardened.

During an initial stage of a substrate-attachment process, which is to be performed at a later point in the production process, with reference toFIG. 6B, the reaction prevention layer of the portion155on the surface of the sealant150is pressed by the conjoining of the substrates110and120. Further, during a second hardening process with reference toFIG. 6C, infrared rays are irradiated onto the substrates110and120such that the sealant150is fully hardened, thereby completing the attachment of the substrates110and120.

Before the attachment of the substrates110and120, however, the substrate110is transported to the liquid crystal depositing unit5000from the sealant heat-treating unit4000via the in-line conveying unit1140. Next, using the liquid crystal depositer5100, predetermined amounts of the liquid crystal material are deposited such that the liquid crystal layer130is formed to correspond to the sizes of the liquid crystal cell regions111,121,131and141. As shown inFIG. 7A, the liquid crystal depositer5100may be a syringe-type device such that liquid crystal material132is provided in specific areas, that is, in the liquid crystal cell regions111,121,131and141. The liquid crystal depositer5100may also be a spray-type device, which includes a jig5110and a nozzle5120connected to the jig5110, which is able to provide the liquid crystal material132over an entire surface of the liquid crystal cell regions111,121,131and141as shown inFIG. 7B.

The syringe-type liquid crystal depositor device is advantageous when the liquid crystal panel100of the mother glass is produced into a single liquid crystal cell. With this configuration, it is preferable that the substrate110is rotated at approximately 30-60 rpm to reduce the time required to deposit the liquid crystal material132. However, the spray-type liquid crystal depositor has an advantage in adjusting the liquid crystal material132deposition. That is, the number of nozzles5120as well as an application length (d) may be controlled such that the spray-type liquid crystal depositor can be used for various sizes of liquid crystal cells.

In the prior art, liquid crystal material is injected into a liquid crystal injection hole while keeping each of the liquid crystal cells vacuum. However, according to the present invention, since the liquid crystal material132is either dispersed or deposited while the substrate110is being rotated, the manufacturing time is substantially reduced. Further, in the prior art, time periods for injecting liquid crystal are varied by the size of the liquid crystal cells or the material characteristics of the liquid crystal, which is selected typically depending on the drive method of liquid crystal molecules. Such variation in injection time significantly deters overall control of the production. In the present invention, on the other hand, the time for supplying the liquid crystal material132to the substrate110can be fixed regardless of liquid crystal cell size and characteristics of the liquid crystal material132because the liquid crystal material132is deposited or dispersed thereon.

Following the processes performed in the liquid crystal depositing unit5000, the substrate110is transported to the substrate-combination unit6000via the in-line conveying unit1150. At the same time, the substrate120loaded on the second loading unit7000is transported to the substrate-combination unit6000through the in-line conveying unit1160.

Next, the two substrates110and120are transported to the substrate-attaching unit8000, which is a vacuum chamber, via the in-line conveying unit1170. The substrates110and120are attached to one another in a vacuum state in the substrate-attaching unit8000, thereby completing the liquid crystal panel100. The substrate-attaching unit8000includes a first compression plate8100and a second compression plate8200, as shown inFIG. 3. The substrates110and120are mounted to the compression plates8100and8200, respectively, such that they are aligned in parallel. Next, the compression plates8100and8200apply a uniform force toward each other such that the substrates110and120are pressed together. As a result of this force, the spacers140(seeFIG. 2) dispersed on the substrate110(and provided in the sealant150in some cases) are deformed. Also resulting from the compression force, the liquid crystal material deposited on the substrate110is spread over the entire area of the liquid crystal cell regions111,121,131and141(seeFIG. 1) to form the liquid crystal layer130(seeFIG. 2).

Subsequently, after a force is applied by the compression plates8100and8200such that the desired gap is obtained between the substrates110and120, an exposure unit (not shown) is used to irradiate infrared rays onto the substrates110and120for a second hardening process such that the sealant150is fully hardened. Accordingly, the substrates110and120are conjoined as shown inFIG. 6. It is preferable that the substrates110and120be precisely aligned either during the process of compressing the substrates110and120or when performing the second hardening process. Also, it is preferable that an air pressurization method be used in order to apply an even pressure to the substrates110and120.

In order to mount the substrates110and120respectively to the first and second compression plates8100and8200, a point vacuum adhesion method or a planar vacuum adhesion method may be used. When the point vacuum adhesion method is used, with reference toFIGS. 8A,8B and8C, pipes8110mounted to the first and second compression plates8100and8200at areas corresponding to corner portions of the substrates110and120are pressed against the substrates110and120, then a vacuum is formed in an inside area8111of the pipes8110. Accordingly, the substrates110and120are attached to the8100and8200as long as the vacuum is maintained.

When the substrates are attached, center portions112and122respectively of the substrates110and120may become deformed as shown inFIG. 8B, making it difficult to align the substrates110and120precisely. To prevent this, it is preferable that a vacuum hole be formed in the compression plates8100and8200as shown inFIG. 8Cto keep the space between the compression plates8100and8200and the substrates110and120vacuum by pumping the air out therebetween.

If a planar vacuum adhesion method is used, with reference toFIGS. 9A and 9B, a planar suction mechanism8220is provided on the compression plates8100and8200. The planar suction mechanism8220includes a plurality of openings8221, which can be formed in a variety of shapes over the entire area of the planar suction mechanism8220. After contacting the planar suction mechanism8220to the substrates110and120, air is drawn inwardly through the openings8221to adhere the substrates110and120to the compression plates8100and8200. The planar vacuum adhesion method is preferred over the point vacuum adhesion method for a variety of reasons. The substrates110and120are supported over an entire area. It can be easily applied to a variety of sizes of substrates. It can prevent substrate deformation problems. Also it can attach the substrates110and120more rigidly to the compression plates8100and8200.

After the above step, the conjoined substrates110and120(i.e., the completed liquid crystal panel100) are transported to the unloading unit9000from the substrate-attaching unit8000through the in-line conveying unit1180. Next, the liquid crystal panel100is transported to a cutting unit (not shown) where the liquid crystal panel100is cut into portions corresponding to the liquid crystal cells111,121,131and141.

In the manufacturing method of the present invention described above, a vacuum must be formed in order to attach the substrates110and120to one another. The time required for forming the vacuum is greater than that needed to disperse the spacers140, deposit the sealant150or liquid crystal material, or in the actual conjoining of the substrates110and120. Overall productivity is reduced as a result. To solve this problem, a plurality of vacuum chambers may be used. Also, a method may be used that can minimize the occasions wherea vacuum must be formed. This will be described in detail with reference to the drawings.

FIGS. 10,11and12are views showing a structure of a substrate-attaching unit in an in-line system according to different embodiments of the present invention. Like reference numerals will be used for elements identical to those of the above embodiment.

First, with reference toFIG. 10, a substrate-attaching unit8000according to another embodiment includes first, second, third and fourth vacuum chambers8300,8400,8500and8600; connecting units8010,8020and8030, which interconnect the vacuum chambers8300,8400,8500and8600; a substrate-attaching vacuum chamber8700; and a connecting unit8040connecting the substrate-attaching vacuum chamber8700to the fourth vacuum chamber8600.

With this structure, the substrates110and120are moved in sequence through the first, second, third and fourth vacuum chambers8300,8400,8500and8600, which generate an increasingly higher vacuum, such that the substrates110and120arrive at the substrate-attaching vacuum chamber8700in a desired vacuum state. The substrates110and120are aligned and conjoined in the substrate-attaching vacuum chamber8700using the methods described previously. As a result, the vacuum chamber is not any more a bottleneck of the entire process in the in-line system, allowing the substrates110and120to keep moving through the system. This improves the productivity dramatically. Further, this structure can provide more prcise control because the number of vacuum chambers can be manipulated to correspond to a unit of time at each vacuum chamber that matches the time used in the other processes of the in-line system.

According to yet another embodiment, with reference toFIG. 11, a substrate-attaching unit8000includes, like the previous embodiment, first, second, third and fourth vacuum chambers8300,8400,8500and8600; and a substrate-attaching vacuum chamber8700. However, the first, second, third and fourth vacuum chambers8300,8400,8500and8600are provided in parallel and are connected to the substrate-combination unit6000via the connecting units1171,1172,1173and1174, respectively, and to the substrate-attaching vacuum chamber8700via the connecting units1191,1192,1193and1194, respectively.

With this structure, a desired vacuum state is formed in each of the vacuum chambers8300,8400,8500and8600, and the substrates110and120are supplied to the vacuum chambers8300,8400,8500and8600from the substrate-combination unit6000in sequence, then they are also supplied in sequence to the substrate-attaching vacuum chamber8700. Accordingly, sufficient time is provided for each of the vacuum chambers8300,8400,8500and8600to provide the desired vacuum state, thereby preventing any back-up in the in-line system. In this embodiment also, the number of vacuum chambers may be adjusted as needed.

Referring now toFIG. 12, a substrate-attaching unit8000can be structured to perform a variety of processes on the substrates110and120. That is, the substrate-attaching unit8000includes first and second compression plates8100and8200, which have at least one vacuum hole8900, and a support tube8800provided between the compression plates8100and8200, and which seals the space therebetween.

With this configuration, the substrates110and120are first attached to the inner faces of the compression plates8100and8200using the methods described with reference toFIGS. 8A,8B,8C or9A and9B, then air between the compression plates8100and8200is exhausted through the vacuum hole8900until a vacuum of 0.1 Torr or less is formed between the compression plates8100and8200. Next, the air within the support tube8800is slowly exhausted to decrease the interval between the compression plates8100and8200until the desired cell gap between the substrates110and120is obtained. Infrared rays are then irradiated onto the substrates110and120to harden the sealant150, thereby completing the liquid crystal panel100ofFIG. 1.

During the formation of a vacuum between the compression plates8100and8200by exhausting air from the vacuum hole8900, if the liquid crystal material132gathers at edges of the substrate110, an uneven cell gap between the substrates110and120may result. To solve this problem, it is preferable that a plurality of vacuum holes8900be provided in specific areas of the first and second compression plates8100and8200, and the air is pupmped out in sequence from the vacuum holes8900to create the vacuum state. The vacuum holes8900may be formed at corners of the compression plates8100and8200as shown inFIG. 13A, at center portions of side edges of the compression plates8100and8200as shown inFIG. 13B, or both at the corners and in center portions of the side edges of the compression plates8100and8200as shown inFIG. 13C. In addition, the vacuum holes8900may be formed as slits along sides of the compression plates8100and8200as shown inFIG. 13D, as slits around corners of the compression plates8100and8200as shown inFIG. 13E, or as slits both along the sides and the corners of the compression plates8100and8200with predetermined distances therebetween as shown inFIG. 13F.

When exhausting air through the vacuum holes8900to form the vacuum between the compression plates8100and8200, it is preferable that the vacuum holes8900be used in a sequence that is suitable for the viscosity of the liquid crystal material132. The vacuum holes8900described in the various shapes and positions above can be provided in both or only one of the compression plates8100and8200.

In the in-line system and manufacturing method of an LCD using the in-line system described above, the majority of the processes are performed on one of the substrates110and120, after which the substrates110and120are attached together. That is, the spacers are dispersed, the sealant is formed, and the liquid crystal material is deposited on only the substrate110. However, it is possible to disperse the spacers on one substrate then form the sealant and deposit the liquid crystal material on the other substrate. If this alternative method is used, the spacer-dispersing unit2000ofFIG. 3is connected between the second loading unit7000and the substrate-combination unit6000through in-line conveying units.

Further, the in-line system described above is designed with a single substrate-attaching unit8000having vacuum chambers. However, it is possible to provide a plurality of substrate-attaching units. This will be described in detail with reference toFIG. 14.

FIG. 14shows a schematic view of an in-line system having a plurality of substrate-attaching units according to another embodiment of the present invention.

As shown in the drawing, the in-line system includes (a) a substrate-combination unit6100that is provided with the first substrate110, on which are deposited the sealant150and the liquid crystal material132, and the second substrate120, on which the spacers140are dispersed; and (b) a plurality of substrate-attaching units8001,8002and8003, which are each provided with a pair of substrates110and120for assembly from the substrate-combination unit6100. The number of substrate-attaching units can be adjusted as needed. With this configuration, the in-line system can keep operating without delays due to the relatively slow processes involved in the substrate-attaching units.