LCD bonding machine and method for fabricating LCD by using the same

A bonding machine for fabricating an liquid crystal display (LCD) panel to which a liquid crystal dropping method been performed includes a bonding chamber of a one pieced body for carrying out bonding of substrates, at least two or more than two air extraction tubes in communication with an interior space of the bonding chamber, and at least two vacuum means respectively connected to the air extraction tubes each for generating an air suction power to evacuate the bonding chamber. A method for fabricating an LCD panel by using the bonding machine includes loading a first substrate onto which liquid crystal has been dropped and a second substrate having sealant coated thereon into a bonding chamber, evacuating the bonding chamber, bonding the first and second substrates, applying varying bonding pressure, and unloading the bonded first and second substrates.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display (LCD), and more particularly, to an LCD bonding apparatus and method for fabricating an LCD incorporating a liquid crystal dispensing method applied thereto.

2. Discussion of the Related Art

In general, recent developments in the information communication field have increased demand for various types of display devices. In response to this demand, various flat panel displays such as liquid crystal display (LCD), plasma display panel (PDP), electro luminescent display (ELD), and vacuum fluorescent display (VFD) have been developed, some of which have been employed as displays in various products.

The LCDs have been used most widely as mobile displays. The LCD has replaced the CRT (Cathode Ray Tube) because of features and advantages including excellent picture quality, light weight, thin profile, and low power consumption. In addition to the mobile type LCDs, such as a display for notebook computer, LCDs have been developed for computer monitors and televisions to receive and display broadcasting signals.

Despite various technical developments in the LCD technology with applications in different fields, research in enhancing the picture quality of the LCD as a display has been in some respects lacking as compared to the features and advantages of the LCD. Therefore, to use the LCD in various fields as a general display, the key to developing the LCD lies on whether the LCD can provide a high quality picture, such as high resolution, high luminance, and large sized screen, while still maintaining light weight, thin profile, and low power consumption.

An LCD device includes a liquid crystal panel for displaying a picture and a driving part for providing a driving signal to the liquid crystal panel. The liquid crystal panel has first and second glass substrates bonded together with a gap between the substrates. A liquid crystal layer is formed by injecting liquid crystal into the gap between the first and second glass substrates.

On the first glass substrate (a TFT array substrate, for example), there are a plurality of gate lines arranged in a first direction at fixed intervals, a plurality of data lines arranged in a second direction perpendicular to the gate lines at fixed intervals, a plurality of pixel electrodes in respective pixel regions defined by the gate lines and the data lines in a matrix, and a plurality of thin film transistors switchable in response to a signal from the gate lines for transmission of a signal from the data line to the pixel electrodes.

The second glass substrate (a color filter substrate) has a black matrix layer for shielding light from areas excluding the pixel regions, red (R), green (G), blue (B) color filter layers, and a common electrode for implementing a picture.

The foregoing first and second substrates have a gap between them which is maintained by spacers. The first and second substrates are bonded to each other by a sealant. The seal has a liquid crystal injection inlet through which liquid crystal is injected after the two substrates are bonded and sealed.

After the individual liquid crystal panels are cut, the space between the two bonded substrates of each LCD panel is evacuated and the liquid crystal injection inlet is dipped in a liquid crystal bath, so that the liquid crystal is injected into the space by a capillary tube phenomenon. Once the liquid crystal is injected into the space between the two substrates the liquid crystal injection inlet is sealed by a sealant.

However, the related art method for fabricating an LCD having liquid crystal injected therein has the following problems. First, the related art method has poor productivity because the dipping of the liquid crystal in a liquid crystal bath while the space between the two substrates are maintained at a vacuum and the unit panels are cut into individual pieces for injection of the liquid crystal takes much time. Second, the liquid crystal injection, for a large LCD in particular, may cause imperfect filling of the liquid crystal in the panel, which may result in a defective panel. Third, the complicated and lengthy fabrication process requires the use of many liquid crystal injection devices, which occupies a large portion of space.

Accordingly, a method for fabricating an LCD by using a liquid crystal dropping method has been under research recently. Japanese Patent Application Nos. H11-89612, and H11-172903, and Japanese Laid-Open Patent Publication No. 2000-147528 disclose the following liquid crystal dropping method.

FIGS. 1A-1Dillustrate a related art bonding machine having the liquid crystal dropping method applied thereto.FIG. 2illustrates a perspective view showing a state of operation of key parts of substrate receiving means in a related art bonding machine, schematically.

The related art LCD bonding machine (e.g., substrate assembler) is provided with a frame10, stage parts21and22, a sealant outlet (not shown), a liquid crystal dropping part30, chamber parts31and32, chamber moving means, substrate receiving means, stage moving means, and evacuating means.

The stage parts include an upper stage21and a lower stage22. The sealant outlet and the liquid crystal dropping part30are fitted to the outside of the frame10.

The chamber parts include an upper chamber unit31and a lower chamber unit32. The upper chamber unit31has a vacuum valve23and a hose24connected thereto for evacuating the chamber parts, and a gas purge valve80and a gas tube81for turning the chamber parts from a vacuum state to an atmospheric pressure state.

The chamber moving means has a driving motor40for selective movement of the lower chamber unit32. That is movement of the lower chamber unit32to a location (S2) where the bonding may occur or to a location (S1) where the coating of the sealant and dropping of the liquid crystal may occur.

The substrate receiving means for temporarily receiving opposite diagonal positions of the second substrate52and when the interior of the chamber is in vacuum and is attached and fixed to the upper stage21.

The substrate receiving means has a rotatable shaft61passing from the outside chamber unit31to the interior of chamber unit31. A rotation actuator63fixed to the outside of an upper part of the chamber unit31, one end of the rotating shaft61, for selective rotation of the rotating shaft61, an elevating actuator64fixed to an outside of an upper part of the chamber unit31for selective elevation of the rotating shaft61, and a supporting plate62formed as one unit with the rotating shaft61at the other end thereof for selective supporting of comers of the substrate.

The stage moving means has a shaft71, a housing72, a linear guide73, a motor74, a ball screw75, and a nut housing76. That is, the upper stage21is supported on the shaft71and the shaft is fixed to the housing72. The housing72is fitted to the frame10by the linear guide73. The upper stage21is moved up/down by the motor74fixed to a bracket77on frame10. In this instance, the ball screw75and the nut housing76transmit a driving power, and the nut housing76is connected to the housing72through a load gauge78.

The steps of a method for fabricating an LCD by using the foregoing related art bonding machine will be explained following an order of the fabrication process in detail.

Referring toFIG. 1A, the second substrate52in a carrier is placed on the lower stage by a robot arm90. Next, the second substrate52is moved toward the upper stage21by the driving motor40positioned in the chamber moving means.

Referring toFIG. 1B, the upper stage21biases the second substrate52by vacuum. Next, the lower chamber unit32, having the lower stage22, is moved to location (S1) for coating sealant and dropping liquid crystal by driving the driving motor40.

Then, referring toFIG. 1C, the first substrate51is placed on the lower stage22by the robot arm90and connected to the lower stage22by vacuum.

Referring toFIG. 1D, after the sealant coating and the liquid crystal dropping have been applied to the first substrate51by the sealant outlet and the liquid crystal dropping part30, the chamber moving means40moves the lower chamber unit32to location (S2).

Next, the chamber moving means40unites the chamber units31and32, thereby, enclosing a space where the stages21and22are placed so that the space can be evacuated with the vacuum valve23and the hose24.

Since the vacuum of the space becomes higher than the vacuum applied to the upper stage21, which holds the second substrate52. Temporary safekeeping of the second substrate52is required before the space is fully evacuated in order to prevent the second substrate52from falling and/or breaking.

The elevating actuator64is driven to move the rotating shaft51toward the under side of the upper stage. In addition, the rotating actuator63is driven to rotate the rotating shaft61for placing a supporting plate62on two corners of the second substrate52connected to the upper stage21via a vacuum.

The stage moving means moves the upper stage21down to a location close to a height of the supporting plate62in which the substrate receiving means is located and releases the vacuum that holds the second substrate52, in order to place the second substrate52on the supporting plates62as shown in FIG.2.

When the chamber is fully evacuated, the second substrate52is held to the upper stage21by static electricity applied thereto. Subsequently, the rotating actuator63and the elevating actuator64are driven, bringing the supporting plates62and the rotating shaft61to their original positions where the bonding will not be interfered with.

Under the vacuum state the motor74is driven to move down the upper stage21thereby pressing the substrates51and52together.

In this instance, a preset pressure is applied as required for bonding by controlling the motor74with reference to pressure signals. That is, feed back pressure signals are used to ensure appropriate application of pressures. The load gauge78serves as a load cell (pressure application sensor).

FIGS. 3A-3Fschematically illustrate sections showing the steps of a related art method for fabricating an LCD having the liquid crystal dropping method disclosed in Japanese laid-open patent publication No. 2000-147528 applied thereto.

Referring toFIG. 3A, ultra violet (UV) sealant1is coated on a first glass substrate3having thin film transistor arrays formed thereon to a thickness of approximately 30 μm. The liquid crystal2is dropped on an inner side of the UV sealant1where there is a thin film transistor array. No liquid crystal injection inlet is provided in the sealant1.

The first glass substrate3in a vacuum chamber is mounted on a table4, which is movable in a horizontal direction. A first vacuum channel5holds the entire bottom surface of the glass substrate3.

Referring toFIG. 3B, the entire bottom surface of the second glass substrate6having the color filter arrays formed thereon is held by vacuum channels of7and the vacuum chamber is closed and evacuated. The second table is moved down in a vertical direction until a gap between the first and second glass substrate3and6is 1 mm. Table4with the first glass substrate3is moved in a horizontal direction to pre-align the first and second glass substrates3and6.

Referring toFIG. 3C, the second table is moved down until the second glass substrate6comes into contact with the liquid crystal2and/or the sealant1.

Referring toFIG. 3D, table4with the first glass substrate3is moved in a horizontal direction to align the first and second glass substrates3and6.

Referring toFIG. 3E, the second table is moved down in a vertical direction until the second glass substrate6comes into contact with the sealant1. In addition, the second table is pressed down until a gap between the second glass substrate6and the first glass substrate3becomes approximately 5 μm.

Referring toFIG. 3F, the bonded first and second glass substrates,3and6respectively, are taken out of the vacuum chamber and a UV ray is applied to the sealant in order to harden the sealant1, thereby completing the fabrication of the LCD.

The foregoing related art vacuum bonding machine and method for fabricating an LCD having the liquid crystal dropping method applied thereto has the following problems.

First, the use of only one vacuum means creates difficulty in adjusting the evacuation rate. In particular, it is desirable that the interior of the chamber is evacuated faster in order to reduce the fabrication time period. However, the use of a vacuum means that can form a high vacuum (e.g., generating a high air suction power) causes defective amount of liquid crystal on the substrate, thereby causing a defective product. That is, the volatility of the liquid crystal becomes greater as the vacuum becomes higher. For example, a rapid evacuation of the interior of the bonding chamber may cause more violent volatilization, thereby creating a defective liquid crystal amount on the substrate.

Second, the use of a vacuum pump that forms a low air suction power for solving the foregoing problem requires a large amount of time for evacuating the interior of the chamber.

Third, rapid introduction of air into the process chamber when the vacuum state is changed may lead the upper or lower stage to become stuck to one of the substrates. This affects the atmospheric state bonding of the substrates significantly and may cause defective bonding.

Fourth, defective sealing between the lower chamber unit and the upper chamber unit when the two pieces are united can occur as a result of the two-pieced chamber parts. In particular, difficulty arises in forming a tight seal and may create vacuum leaks, which can prevent the desired degree of bonding due to difficulty in obtaining a high vacuum in the interior of the chamber.

Fifth, the supporting of corner parts of the substrate by the substrate receiving means may cause bending or warping of the substrate when the substrate is large and/or may cause the substrate to break and fall down from the substrate receiving means.

Sixth, the sealant coating and liquid crystal dropping on the same substrate require a lengthy fabrication time period before the two substrates are bonded.

Seventh, as the sealant is coated and the liquid crystal is dropped on the first substrate, no progress is made for the second substrate. Thereby, resulting in an imbalance of fabrication processes between the first and second substrates creating an ineffective operation of the production line.

Eighth, the first substrate has the sealant and liquid crystal applied, therefore, it can not be subjected to cleaning by ultra-sonic cleaning (USC). Therefore, particles can not be removed as the USC is not applied, and this may cause defective contact of the sealant in the bonding process.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a liquid crystal display (LCD) bonding machine and a method for fabricating a liquid crystal display having liquid crystal applied thereto using the same that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.

An advantage of the present invention is to provide an LCD bonding machine and a method for fabricating an LCD having the liquid crystal applied thereto using the same, which reduces a fabrication time of the LCD and increases the efficiency to improve productivity

To achieve these and other advantages, and in accordance with the purpose of the present invention as embodied and broadly described, the LCD bonding machines include a bonding chamber of a one pieced body for carrying out bonding of substrates, at least two or more than two air extraction tubes in communication with an interior space of the bonding chamber, and at least two vacuum means respectively connected to each air extraction tubes for generating an air suction power to evacuate the bonding chamber.

In one aspect of the present invention, at least one of the vacuum means includes a Turbo Molecular Pump (TMP) for generating a greater air suction power than the other vacuum means, for example a dry pump.

In the present aspect of the invention, the other vacuum means includes a plurality, e.g., four, dry pumps that may be paired into two sets, wherein each of the pairs may be connected to one of the air extraction tubes. Additionally, the TMP of present aspect of the invention has an evacuation rate of, for example, 0.1-5.0 kl/min and the dry pump has an evacuation rate of, for example, 10-30 kl/min.

In another aspect of the present invention, the bonding chamber includes a vent tube in communication with the bonding chamber for supplying air or gas and gas supply means connected in correspondence to vent tube of the bonding chamber for respectively supplying air or gas at different pressures.

The gas supplying means may include a gas charge part having gas, such as air or gas, stored therein for turning a pressure within the bonding chamber from a vacuum state into an atmospheric pressure state and a valve for selectively opening and shutting the vent tube. The gas supplying means may further include a driving pump for forced pumping of the air or gas stored in the gas charge part into the bonding chamber.

In yet another aspect of the present invention, a method for fabricating an LCD includes steps of loading a first substrate having liquid crystal applied thereon, and a second substrate having a sealant coated thereon, into a bonding chamber; evacuating the bonding chamber; bonding the first and second substrates using varied bonding pressures; and unloading the bonded first and second substrates.

In the present aspect of the invention, the loading step may include holding the second substrate to an upper stage provided within the bonding chamber, and holding the first substrate to a lower stage also provided within the bonding chamber, for example, using electrostatic charge (ESC).

In the present aspect of the invention, the step of evacuating the bonding chamber may include two stages. Accordingly, the step of evacuating the bonding chamber may include a first evacuation step carried out after the first and second substrates are arranged on the lower and upper stages, respectively, and a second evacuation step carried out after a substrate receiver is moved below the second substrate.

In the present aspect of the invention, the step of unloading the first and second substrates may be carried out when the bonding chamber pressure is below 50 Pa and may further include the steps of the holding the bonded first and second substrates using the upper stage, moving the upper stage upwards, and loading an unbonded first or second substrate and unloading the bonded substrates held to the upper stage.

The method for fabricating LCDs may further include the step of venting the bonding chamber to thereby apply pressure to the bonded substrates.

In one aspect of the present invention, the method for fabricating LCDs may further include a step of spreading liquid crystal, for example toward the seal, before or after the step of unloading the bonded first and second substrates. The step of liquid crystal spreading may be carried out for a period of time, for example, at least 10 minutes.

In further aspect of the present invention, a method for fabricating LCDs uses bonding machines having an upper stage and a lower stage, respectively, arranged in upper and lower spaces of the bonding chamber; a turbo molecular pump (TMP) and dry pumps, vent means, and substrate receiving means. The method includes the steps of loading a second substrate having sealant coated thereon and a first substrate having liquid crystal dispensed thereon; putting the dry pump into operation for a first evacuation of the bonding chamber; moving the substrate receiving means for supporting the second substrate; putting the TMP into operation for a second evacuation of the bonding chamber; moving the upper and lower stages for bonding the first and second substrates; and putting vent means into operation to vent the bonding chamber for application of a pressure to the bonded substrates. The step of putting vent means into operation for venting the bonding chamber and applying pressure to the bonded substrates may include two stages.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to an embodiment of the present invention, examples of which are illustrated in the accompanying drawings.

FIGS. 4A-9Billustrate sections of liquid crystal display (LCD) vacuum bonding machines for performing the liquid crystal dispensing method of the present invention. The figures illustrate the method in an order of a process.

As noted in the aforementioned drawings, the bonding machines of the present invention include a bonding chamber110, a stage part, a stage moving device, and vacuum means.

The bonding chamber110is designed as a one piece unit and has an interior designed to selectively be in a vacuum state or an atmospheric pressure state. The bonding chamber110also includes a bonding chamber entrance111to allow for ingress and egress of a first substrate510and a second substrate520, into or out of the bonding chamber110.

The bonding chamber110may also include at least one air outlet112,113, and114connected to one side thereof for extracting air from the interior of the bonding chamber110by a vacuum means; and a vent pipe or tube115corresponding to a vent hole in the bonding chamber110connected to one side thereof for introducing air or any suitable gas into the bonding chamber110for sustaining the bonding chamber110at atmospheric pressure.

The air outlets112,113, and114include electronically controlled valves112a,113a, and114a, respectively, for selective opening and shutting of tube lines.

The bonding chamber entrance111may include a door111a(not shown) for sealing the bonding chamber entrance111. The door111amay be a general sliding or rotating type door, or suitable type of device that can close an opening. In one aspect of the present invention, the sliding or rotating type door may include a sealing member for sealing a gap between the door111aand the bonding chamber entrance111, thereby allowing an appropriate vacuum state the detail of which is not shown in the drawing.

The stage parts may be provided in the upper and lower spaces of the bonding chamber110. They may face each other and include an upper stage121and a lower stage122for securing the substrates510and520introduced into the bonding chamber110.

The upper and lower stages121and122, respectively, may include at least one electrostatic chuck (ESC)121aprovided at opposing surfaces of the upper and lower stages. The upper electrostatic chuck121aelectrostatically holds the second substrate520to the upper stage121, and the lower electrostatic chuck122aelectrostatically holds the first substrate520to the lower stage122. In addition, the upper and lower stages121and122may also include a plurality of vacuum channels121bformed therethrough. The vacuum channels enable the substrates510and520to be arranged on the upper stage121and the lower stage122, respectively.

Although the present embodiment suggests that at least two electrostatic chucks121amay be utilized, pairs of electrostatic chucks having DC voltages of opposite polarities may also be formed to electrostatically hold the substrates to their respective stages. Alternatively, single electrostatic chucks having DC voltages of opposite polarities applied thereto may also provide the electrostatic charge to provide required holding power.

In one aspect of the present invention, the plurality of vacuum channels121bmay be formed in a center portion and/or along the circumference of the electrostatic chucks121aand may be connected to single or multiple tubes121c. The vacuum channels121btransmit a vacuum force generated by a vacuum pump123connected to the upper stage121.

The lower stage122may include at least one electrostatic chucks122aon a top surface of the lower stage to provide electrostatic power for holding the substrate, and at least one vacuum channel (not shown) for holding the substrate by vacuum.

The electrostatic chuck and the vacuum channel may or may not be identical to the vacuum channels of the upper stage121. The arrangement of the electrostatic chuck and the vacuum channels be determined by taking into account the overall fabrication processes of the substrates and/or each liquid crystal coating regions.

The stage moving device includes a moving shaft131for selective up and down movement of the upper stage121, a rotating shaft131for selective left and right rotation of the lower stage122, and driving motors133and134fitted to the interior or exterior of the chamber110, that are coupled to the stages121and122via shafts, respectively.

The stage moving device is not limited to a system in which the upper stage121is movable only in the up and down directions, and the lower stage122is rotatable only in the left and right directions. Rather, the upper stage121may be made to be rotatable in left and right directions, and the lower stage may be made to be movable in up and down directions when the upper stage121is provided with a separate rotating shaft (not shown). In addition, the upper stage and lower stage122are provided with a separate moving shaft (not shown) for rotation of the upper stage and lower stage122and for up and down directional movement of the lower stage122.

The vacuum means is connected to the air outlets112-114on the bonding chamber110for extracting air from the interior of the bonding chamber110, and includes at least more than two units, and preferably five units.

At least one of the vacuum means is a Turbo Molecular Pump (TMP)210that has a higher air suction capability compared to other vacuum means, and the rest of the vacuum means are dry pumps220. In particular, there may be one TMP210and four dry pumps220.

Of the three air outlets112,113, and114in total connected to the bonding chamber110, one air outlet (“a first air outlet”)112is connected to the TMP210, and the remaining two air outlets113(“a second air outlet”) and114(“a third air outlet”) are connected to two pairs of the dry pumps, respectively.

Moreover, there may be five air outlets so that one of the air outlets is connected to the TMP210and the other four outlets are connected to the other four dry pumps, respectively.

Along with this, the present invention suggests making a system by connecting gas supplying means300that regulates the amount of air or gas supplied to the vent pipe115and is connected to the bonding chamber110.

The gas supplying means300includes a gas charge part310, having air or gas storage therein, to sustain the atmospheric pressure in the bonding chamber110, and a valve320for selective opening and shutting of the vent pipe115as required.

Moreover, the present invention can make a system inclusive of a pump for forced pumping of the air or gas charged in the gas charge part310to the vent tube115by a selective pressure. That is, the system for sustaining the interior of the bonding chamber at the atmospheric pressure is not limited to the valve, only.

However, since the air or gas can infiltrate into the bonding chamber110by itself through a minute gap as the interior of bonding chamber110is at a vacuum, the forced pumping may not be necessarily used. According, the present invention suggests a system with the valve320applied thereto for selectively opening and shutting the vent tube115as much as required instead of the pump.

Moreover, if the vacuum of the bonding chamber becomes greater than the vacuum applied to the stages during evacuation of the bonding chamber110, when the stages121and122, respectively have the first and second glass substrates held respectively thereto, the stages to lose vacuum holding power and the second glass substrate can fall off the upper stage and drop onto the first glass substrate. To prevent this event from occurring, a substrate receiving means400is provided to the bonding chamber for supporting the substrate to the upper stage121. In this instance, the substrate receiving means400supports a central part of the substrate of the non-active region, rather than supporting only the comer parts of the substrate.

It is noted thatFIGS. 4A,5A,6A,7A,8A and9A show one embodiment andFIGS. 4B,5B,6B,7B,8B and9B show another embodiment. In particular, the vent300, the dry pumps220and the TMP210are in different locations inFIGS. 4B,5B,6B,7B,8B and9B to show that different locations can be used for such elements. For example,FIGS. 4B,5B,6B,7B,8B and9B show the vent300at the top of the bonding chamber110, the dry pumps220at the bottom of the bonding chamber110, and the TMP210at the side of the bonding chamber110, whereasFIGS. 4A,5A,6A,7A,8A and9A show the vent300at the side of the bonding chamber110, the dry pumps220at the side of the bonding chamber110, and the TMP210at the top of the bonding chamber110. Other permutations of different suitable locations for these elements are contemplated in the present invention.

For example,FIGS. 12 and 13show multiple vent holes115aat the top of the bonding chamber whileFIGS. 14 and 15show multiple vent holes115aat all sides of the bonding chamber. The plurality of vent holes may be formed at the top of the bonding chamber. The plurality of vent holes may be formed at the top, bottom and sides of the bonding chamber. At least two of said vent holes may be formed at the top of the bonding chamber, at least one of the vent holes may be formed at least at one side of the bonding chamber, and at least two of the vent holes may be formed at the bottom of the bonding chamber. The plurality of vent holes may be formed at the top surface and the side surface of the bonding chamber. The plurality of vent holes may be formed at the top surface and the bottom surface of the bonding chamber. The top surface may have at least two vent holes and the side surface may have at least two vent holes.

FIGS. 10A-10Eillustrate sections showing the steps of a method for fabricating an LCD in accordance with an embodiment of the present invention.FIG. 11illustrates a flow chart showing the steps of a method for fabricating LCDs having the liquid crystal dispensing method applied thereto in accordance with an embodiment of the present invention. Next, the method for fabricating LCDs by using the bonding machines of the foregoing present invention will be explained, with reference toFIGS. 10A-10E, and4A-9B.

The method for fabricating LCDs includes the steps of loading the two substrates into the vacuum bonding chamber, evacuating the bonding chamber, bonding the two substrates, venting the bonding chamber for uniform application of pressure to the bonded substrates, and unloading the pressed two substrates from the vacuum bonding chamber.

Referring toFIG. 10A, liquid crystal12is dropped onto a first glass substrate510and sealant14is coated on a second substrate520. Before loading the substrates into the bonding chamber, the second glass substrate520having the sealant14coated thereon may be cleaned by Ultra Sonic Cleaner (USC), thereby enabling the removal particles formed during the previous processes. The USC is possible as the second glass substrate520has no liquid crystal dropped thereon.

One of the first and second substrates is a substrate having the thin film transistor arrays formed thereon, and the other substrate is a substrate having the color filter layers formed thereon. In this invention, the liquid crystal dropping and the sealant coating may be made applied to only one of the first and second substrates. Only positioning of the substrate having the liquid crystal dropped thereon on the lower stage, and the other substrate on the upper stage is required.

Referring toFIGS. 4A,4B, or10B, schematically illustrating the loading step, the second glass substrate520having the sealant14coated thereon is held to the upper stage121by vacuum. The second glass substrate520with sealant coated thereon is positioned faced down (31S) on the upper stage121. The first glass substrate510having the liquid crystal12dispensed thereon is held to the lower stage122by vacuum (32S). At this time the vacuum bonding chamber110is at an atmospheric pressure state.

The second glass substrate520having the sealant14coated thereon is held by a loader of a robot (not shown) with the face on which the sealant14is coated facing down and brought into the vacuum bonding chamber110. In this state, the upper stage121in the vacuum bonding chamber110is moved down, and the lower stage holding the second glass substrate520may be moved up. In addition, instead of a vacuum holding the upper and lower substrates, the electrostatic chuck may be used for one substrate or both simultaneously.

Next, the loader of the robot is moved out of the vacuum bonding chamber110, and the first glass substrate510having the liquid crystal12dropped thereon is placed over the lower stage122in the vacuum bonding chamber110by the loader of the robot, so that the lower stage122vacuum channels hold the first substrate510. When respective loading of the substrates510and520on the stages121and122are finished, the door in the bonding chamber entrance111is closed in order to seal the interior of the bonding chamber110. It is preferable that the second substrate520having the sealant coated thereon be loaded on the upper stage121first and that the first substrate510having the liquid crystal dropped thereon loaded on the lower stage122second. This is because if the first substrate510is loaded first and the second substrate520is loaded second, foreign matter may fall onto the first substrate510when the second substrate520is loaded.

The evacuation step is progressed in two stages. That is, after the substrates510and520are held to the upper and lower stages121and122, respectively, and the chamber door is closed a first evacuation is started. After bringing the substrate receiver400below the upper stage121and placing down the second substrate520held to the upper stage121on the substrate receiver400, or bringing the upper stage121and the substrate receiver400to be at a certain distance from the upper stage121holds the substrate. Next, a second evacuation of the vacuum bonding chamber is conducted. In this instance, the second evacuation is made faster than the first evacuation, and the first evacuation is made such that the vacuum in the vacuum bonding chamber is not higher than the vacuum channel force of the upper stage.

Without dividing the evacuation into first and second stages, the evacuation of the bonding chamber110may be started at a fixed rate, and the substrate receiver400may be brought below the upper stage during the evacuation. It is required that the substrate receiver400is brought below the upper stage121before the vacuum in the vacuum bonding chamber becomes higher than the vacuum holding force in upper stage121.

That is, dry pumps220in the vacuum means are put into operation for evacuation of the bonding chamber110through the second and third air outlets113and114and are operated at 10-30 Kl/min (preferably, 23 Kl/min). For example, the valves113aand114aon the second and third air outlets113and114are opened during the first evacuation.

It should be noted that if the vacuum force in the bonding chamber110becomes higher than the vacuum force that holds the substrate520to the upper stage121(i.e., the interior of the bonding chamber110reaches a higher vacuum force than in the vacuum channels), then the substrate520held to the upper stage520may drop from the upper stage121.

Referring toFIGS. 5A and 5B, in order to prevent the substrate520from dropping and/or being broken, a substrate receiving means400temporarily receives the substrate520held to the upper stage121(33S). The substrate receiving means400moves during the slow evacuation before the bonding chamber110reaches to a high vacuum. The substrate receiver400is contacted with the second substrate520by the following method.

For example, after the second substrate520and the substrate receiver400are brought closer together by either moving the upper stage121down or moving the substrate receiver400up or both, the second substrate520is placed down on the substrate receiving means400by releasing the vacuum channel force of the upper stage121.

Thus, the second glass substrate520held to the upper stage may be arranged on the substrate receiver400before evacuating the vacuum bonding chamber, or the upper stage having the second glass substrate held thereto and the substrate receiver may be brought to be at a certain distance so that the second glass substrate520is arranged on the substrate receiver400from the upper stage121during the evacuation of the chamber. Moreover, other means for fastening the substrates may additionally be provided as there may be an occurrence of airflow in the chamber at the initial stage, which can shake the substrates when the evacuation of the vacuum bonding chamber is started.

The step of evacuating the bonding chamber110is not necessarily carried out after the bonding chamber entrance111is closed by the door111a.

Considering an initial evacuation that is slow, the bonding chamber entrance111may be closed during the evacuation.

Moreover, the movement of the substrate receiving means400to a location for receiving the second substrate520is not necessarily required until the bonding chamber110reaches a high vacuum, but the movement of the substrate receiving means400can made before the evacuation of the bonding chamber. However, for enhancing the fabrication process efficiency, it is preferable that the substrate receiving means400is moved during the evacuation of the bonding chamber110.

Then, referring toFIGS. 6A and 6B, when the vacuum of the bonding chamber110reaches a pressure of approximately 50 Pa (preferably below 13 Pa) by the continuous evacuation of the dry pumps220, the substrate520is held to the upper stage121and is supported on the substrate receiving means400. Next, the valve112ais opened to open the first air extraction tube112and the TMP210is put into operation, for the second evacuation (34S).

In this instance, the TMP210evacuates the bonding chamber110through the first air extraction tube112rapidly at a rate of approx. 0.1-5 Kl/min (preferably, 1.1 Kl/min).

However, the operation of TMP210and the dry pumps220is not limited to performing the rapid evacuation of the chamber at a particular time. For example, it is not limited to the time when the substrate520held to the upper stage121and supported on the substrate receiving means400. That is, a driving control may be utilized to reach the high vacuum by selective regulation of the valves112a,113a, and114a, fitted on the air outlets112,113, and114.

When the vacuum of the bonding chamber110reaches a desired pressure range, the foregoing steps are conducted. For example, when the vacuum of the bonding chamber110reaches a pressure below 0.01 Pa (preferably, 0.67 Pa), the operation of the TMP is stopped. In this instance, the valve112afitted to the first air outlet112closes the first air outlet112.

The vacuum within the vacuum bonding chamber10may have a pressure in a range of about 1.0×10−3Pa to 1 Pa for in-plane switching (IPS) mode liquid crystal display devices, and about 1.1×10−3Pa to 102Pa for twisted nematic (TN) mode liquid crystal display devices.

Evacuation of the vacuum bonding chamber may be carried out in two stages, thereby preventing deformation or shaking of the substrates in the vacuum bonding chamber that may be caused by rapid evacuation of the vacuum bonding chamber.

Once the vacuum bonding chamber110is evacuated to a preset vacuum pressure, the upper and lower stages121and122bias the first and second glass substrates510and520, respectively by electrostatic chuck (35S) and the substrate receiver400is brought to the home position (36S). That is, the second substrate520is temporarily supported on the substrate receiving means400and is held at the upper stage121, and the first substrate510on the lower stage122is held at the lower stage122.

Using electrostatic charge, the first and second substrates may be fixed to their respective stages by applying negative/positive DC voltages to two or more plate electrodes formed at the stages. When the negative/positive voltages are applied to the plate electrodes, a coulomb force is generated between the conductive layer (e.g., transparent electrodes, common electrodes, pixel electrodes, etc.) formed on the substrate and the stage. When the conductive layer formed on the substrate faces the stage, approximately 0.1-1 KV is applied to the plate electrodes. When the substrate contains no conductive layer formed facing the stage, approximately 3-4 KV is applied to the plate electrodes. An elastic sheet may be optionally provided to the upper stage.

Referring toFIGS. 10C,10D,7A and7B, after the two glass substrates510and520are held by their respective stages121and122by electrostatic charge, the two stages are moved into proximity such that the two glass substrates may be bonded (37S). The first and second glass substrates are pressed by moving either the upper stage121or the lower stage122in a vertical direction, while varying speeds and pressures at different stage locations. Until the time the liquid crystal12on the first glass substrate510and the second glass substrate520come into contact, or until the time the first glass substrate510and the sealant14on the second glass substrate520come into contact, the stages may be moved at a fixed speed or fixed pressure and the pressure may be incrementally increased from the time of contact to a final pressure. After the load cell fitted to a shaft of the movable stages senses contact, the glass substrates are pressed together with increasing pressures. For example, at contact the substrates are pressed at a pressure of about 0.1 ton; at an intermediate stage they are pressed to a pressure of about 0.3 ton; at an end stage they are pressed to a pressure of about 0.4 ton at an end stage; and finally they are pressed to a pressure of about pressure of 0.5 ton at the final stage (see FIG.10D).

Although it is illustrated that the upper stage presses down onto the substrate by means of one shaft, a plurality of shafts may independently apply and control pressure using an individual load cell. If the lower stage and the upper stage are not leveled or fail to press down uniformly, any number of predetermined shafts may be pressed at a lower or higher pressure in order to obtain a uniform bonding of the seal.

Referring toFIG. 10E, after the foregoing process bonds the two substrates and after the electrostatic charge has been turned off to the upper and lower stages, the upper stage121is moved up in order to separate the upper stage121from the bonded two glass substrates510and520.

Next, referring toFIGS. 8A and 8B, the vent pipe115is opened to the required degree via the valve320at an initial stage. Then, referring toFIGS. 9A and 9B, the vent pipe115is opened fully in order to pressurize the bonding chamber110slowly. The pressure difference in the bonding chamber110during the slow pressurization of the bonding chamber causes a pressure to be applied to the two substrates. Since the chamber is at the atmospheric pressure and the space between the bonded substrates is at a vacuum, thus the two substrates are subjected to a uniform application of pressure.

Although only one vent300is shown, multiple vents, for example, may positioned at any location on the chamber. For example, referring toFIG. 8B, the vent may be positioned at the top of the chamber.

Then, the bonded substrates are unloaded (38S). That is, after the door111a in the bonding chamber110is operated to open the bonding chamber entrance111, the bonded first and second glass substrates510and520are unloaded by using the loader on the robot directly, or after the upper stage holds and moves up the first and second stages121.

To shorten the fabrication time period, one of the first and second glass substrates to be bonded in the next bonding process may be loaded onto an empty stage while the fixed first and second glass substrates are unloaded. For example, after the second glass substrate520to be bonded in the next bonding process is brought to the upper stage121via the loader and held to the upper stage by vacuum, the bonded first and second glass substrates on the lower stage122may be unloaded. Alternatively, after the upper stage121lifts the bonded first and second glass substrates, the loader may load the first glass substrate510to be bonded on the lower stage and the bonded first and second glass substrates may be unloaded.

A liquid crystal spreading process may optionally be added before the process of unloading the bonded substrates in which the liquid crystal between the fixed substrates may be spread toward the sealant. Alternatively, a liquid crystal spreading process may be carried out to evenly spread the liquid crystal toward the sealant when the liquid crystal does not adequately spread after the unloading. The liquid crystal spreading process may be carried out for more than 10 minutes under atmospheric pressure or in a vacuum.

As has been explained the LCD bonding machines and the method for fabricating LCDs have the following advantages.

First, the LCD bonding machines of the present invention includes at least two different vacuum pumps, which have different vacuum powers. For example, a TMP and dry pumps that allow a smooth evacuation of the bonding chamber thereby preventing damage to the liquid crystal panel.

Second, the step by step evacuation of the bonding chamber permits operation of other parts required during the steps of evacuation are made at the same time, thereby improving efficiencies in the fabrication process.

Third, the availability of two staged evacuations from a low vacuum pressure to a high vacuum pressure without generating excessive air suction pressures prevents deformation caused by rapid evacuation and defective distribution of the liquid crystal in the substrates.

Fourth, the availability of gradual introduction of air or gas into the bonding chamber for sustaining the atmospheric pressure in the process of turning the bonding chamber into the atmospheric pressure prevents defective bonding of the substrates.

Fifth, the one-piece bonding chamber is favorable for obtaining a high vacuum in the bonding chamber. That is, it minimizes or eliminates leaks that may be present in the two-piece bonding chamber.

Sixth, the dispensing the liquid crystal on the first substrate and coating of the sealant on the second substrate reduces the fabrication time.

Seventh, dispensing liquid crystal onto the first substrate and coating sealant on the second substrate permits a balanced progression of the fabrication processes to the first and second substrates, thereby making effective use of the production line.

Eighth, not dropping liquid crystal on the second substrate permits the sealant minimizes contamination of particles on the second substrate because it can be cleaned by USC just prior to bonding.

Ninth, since the bonding chamber is evacuated after the substrate receiving means supports a central portion of the substrate prevents falling and breakage of the substrate even if the substrate is of large size.

Tenth, sensing the time during which the two substrates come into contact and varying the pressure in bonding the two substrates minimizes damage made by the liquid crystal to the orientation film.

Eleventh, since the upper stage presses the substrate down by means of a plurality of shafts, each of which is capable of applying pressure independently, uniform bonding of the sealant can be achieved by independently applying a lower or higher pressure by predetermined shafts when the lower stage and the upper stage are not level or fail to bond to the sealant uniformly.

Twelfth, simultaneous loading and unloading of the glass substrates shortens the fabrication time.

Thirteenth, inclusion of a liquid crystal spreading process shortens the LCD fabrication time.