Liquid crystal display and repairing method thereof

A liquid crystal display includes a plurality of data lines and a plurality of pixels arranged in a matrix, wherein the plurality of pixels include a first pixel and a second pixel, and each of the first pixel and the second pixel includes a first subpixel electrode and a second subpixel electrode, a first switching element, a second switching element, a third switching element, and a voltage-changing capacitor, wherein a first source electrode on the first switching element and a second source electrode on the second switching element from the first pixel are connected to a data line, the first source electrode and the second source electrode of the second pixel are disconnected from the plurality of data lines, and the two terminals of the voltage-changing capacitor of the second pixel are shorted to each other.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2009-0097443 filed in the Korean Intellectual Property Office on Oct. 13, 2009, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a liquid crystal display and a repairing method thereof.

(b) Description of the Related Art

One of the most widely used flat panel displays, a liquid crystal display (LCD) includes two display panels, each provided with field generating electrodes such as pixel electrodes and a common electrode, and a liquid crystal (LC) layer interposed there between. The LCD displays images by applying voltages to the field-generating electrodes on the display panel to generate an electric field across the LC layer. The electric field across the LC layer determines the orientation of LC molecules therein to adjust the polarization of incident light.

The liquid crystal layer includes a liquid crystal material having refractive anisotropy. Because of the refractive anisotropy of the liquid crystal material however, large differences in the color and the contrast ratio can occur between different viewing angles of the liquid crystal display, such that side visibility may be inferior to front visibility, thereby narrowing the viewing angle of the liquid crystal display. To solve this problem, a method has been proposed in which one pixel electrode is divided into two subpixel electrodes, and the two subpixel electrodes are applied with different voltages. Each subpixel electrode is connected to a thin film transistor as a three terminal element for switching the applied voltage.

However, in the process for manufacturing the liquid crystal display, deterioration of the channel of the thin film transistor can occur when impurities are introduced, or when the light used to form a photosensitive film for patterning a conductive layer is not suitably focused. Such deterioration can cause a subpixel electrode that is not to be applied with the data voltage, to be applied with the data voltage, such that the display quality deteriorates.

SUMMARY OF THE INVENTION

A liquid crystal display according to one aspect includes a plurality of data lines and a plurality of pixels arranged in a matrix, wherein the plurality of pixels include a first pixel and a second pixel, and each of the first pixel and the second pixel includes a first subpixel electrode and a second subpixel electrode, a first switching element including a first drain electrode connected to the first subpixel electrode and a first source electrode facing the first drain electrode, a second switching element including a second drain electrode connected to the second subpixel electrode and a second source electrode facing the second drain electrode, a third switching element including a third source electrode connected to the second drain electrode and a third drain electrode facing the third source electrode, and a voltage-changing capacitor including the third drain electrode and a common voltage line transmitting a common voltage as its two terminals, wherein the first source electrode and the second source electrode of the first pixel are connected to a data line of the plurality of data lines, the first source electrode and the second source electrode of the second pixel are disconnected from any of the plurality of data lines, and the two terminals of the voltage-changing capacitor of the second pixel are shorted to each other.

The liquid crystal display further includes a plurality of first gate lines, wherein one first gate line is connected to the first switching element and the second switching element of the first pixel and one first gate line is connected to the first switching element and the second switching element of the second pixel, and a plurality of second gate lines, wherein one second gate line is connected to the third switching element of the first pixel and one second gate line is connected to the third switching element of the second pixel.

The first subpixel electrode of the second pixel may be electrically connected to the first source electrode of the second pixel regardless of, that is, independently of, a gate signal of the first gate line.

The second subpixel electrode of the second pixel may be electrically connected to the second source electrode of the second pixel regardless of a gate signal of the first gate line.

The second gate line may be applied with a gate-off voltage Voff when the first gate line is applied with a gate-on voltage Von, and the first gate line may be applied with the gate-off voltage Voff when the second gate line is applied with the gate-on voltage Von.

In the first pixel, the voltages of the first subpixel electrode and the second subpixel electrode may be changed when the second gate line is applied with the gate-on voltage Von.

In the second pixel, the common voltage may be transmitted to the second subpixel electrode when the second gate line is applied with the gate-on voltage Von.

In the second subpixel, the first subpixel electrode may be electrically connected to the second subpixel electrode when the first gate line is applied with the gate-on voltage Von.

In the second subpixel, the second subpixel electrode may be applied with the common voltage when the second gate line is applied with the gate-on voltage Von.

In the second pixel, the common voltage may be transmitted to the second subpixel electrode.

The common voltage may be also transmitted to the first subpixel electrode in the second pixel.

A method for repairing a liquid crystal display according to one aspect is provided. The liquid crystal display including a plurality of data lines and a first pixel and a second pixel, wherein the first pixel and the second pixel respectively include a first subpixel electrode and a second subpixel electrode, a first switching element including a first drain electrode connected to the first subpixel electrode and a first source electrode facing the first drain electrode, a second switching element including a second drain electrode connected to the second subpixel electrode and a second source electrode facing the second drain electrode, a third switching element including a third source electrode connected to the second drain electrode and a third drain electrode facing the third source electrode, and a voltage-changing capacitor including the third drain electrode and a common voltage line transmitting a common voltage as its two terminals, the method including disconnecting the first source electrode and the second source electrode of the second pixel from any of the plurality of data lines, and shorting the two terminals of the voltage-changing capacitor in the second pixel.

The first source electrode and the second source electrode of the first pixel may be connected to a data line of the plurality of data lines.

The liquid crystal display may further include a plurality of first gate lines, wherein one first gate line is connected to the first switching element and the second switching element of the first pixel and one first gate line is connected to the first switching element and the second switching element of the second pixel, and a plurality of second gate lines, wherein one second gate line is connected to the third switching element of the first pixel and one second gate line is connected to the third switching element of the second.

The first subpixel electrode of the second pixel may be electrically connected to the first source electrode of the second pixel regardless of a gate signal of the first gate line.

The second subpixel electrode of the second pixel may be electrically connected to the second source electrode of the second pixel regardless of a gate signal of the first gate line.

The second gate line may be applied with the gate-off voltage Voff when the first gate line is applied with the gate-on voltage Von, and the first gate line may be applied with the gate-off voltage Voff when the second gate line is applied with the gate-on voltage Von.

In the first pixel, the voltages of the first subpixel electrode and the second subpixel electrode may be changed when the second gate line is applied with the gate-on voltage Von.

In the second pixel, the common voltage may be transmitted to the second subpixel electrode when the second gate line is applied with the gate-on voltage Von.

In the second pixel, the first subpixel electrode may be electrically connected to the second subpixel electrode when the first gate line is applied with the gate-on voltage Von.

In the second pixel, the first subpixel electrode may also be applied with the common voltage when the second gate line is also applied with the gate-on voltage Von.

In the second pixel, the common voltage may be transmitted to the second subpixel electrode.

The common voltage may also be transmitted to the first subpixel electrode in the second pixel.

At least one of the disconnecting of the first source electrode and the second source electrode of the second pixel from any of the plurality of data lines and the shorting of the two terminals of the voltage-changing capacitor in the second pixel may comprise using a laser.

DESCRIPTION OF REFERENCE NUMERALS INDICATING PRIMARY ELEMENTS IN THE DRAWINGS

DETAILED DESCRIPTION OF THE EMBODIMENTS

Now, a liquid crystal display according to an exemplary embodiment will be described with reference toFIG. 1andFIG. 2.

FIG. 1is a block diagram of a liquid crystal display according to an exemplary embodiment, andFIG. 2is an equivalent circuit diagram of two subpixels and a structure of a liquid crystal display according to an exemplary embodiment.

Referring toFIG. 1, a liquid crystal display according to an exemplary embodiment includes a liquid crystal panel assembly300, a gate driver400, and a data driver500.

In an equivalent circuit of the liquid crystal panel assembly300, the liquid crystal panel assembly300includes a plurality of signal lines G1-Gn and D1-Dm, and a plurality of pixels PX arranged in an approximate matrix. In the structure shown inFIG. 2, the liquid crystal panel assembly300includes a lower panel100and an upper panel200that are facing each other, and a liquid crystal layer3interposed there between.

The signal lines G1-Gn and D1-Dm that are provided in the lower panel100include a plurality of gate lines G1to Gn for transmitting gate signals (referred to as “scanning signals”) and a plurality of data lines D1to Dm for transmitting a data voltage.

Each pixel PX, for example the pixel PX connected to the i-th (i=1, 2, . . . , n) gate line Gi and the j-th (j=1, 2, . . . , m) data line Dj, includes a first subpixel and a second subpixel. The first and second subpixels respectively include first and second liquid crystal capacitors Clch and Clcl. The first and second subpixels further include a switching element (not shown) connected to the gate lines G1-Gn, the data lines D1-Dm, and the first and second liquid crystal capacitors Clch and Clcl.

The first and second liquid crystal capacitor Clch and Clcl include a first and second subpixel electrode191hand191l, respectively, on the lower panel100and a common electrode270on the upper panel200as two terminals. The liquid crystal layer3between the two terminals serves as a dielectric material. The first and second subpixel electrodes191hand191lare separated from each other and form one pixel electrode191. The common electrode270is formed on the whole surface of the upper panel200and is applied with the common voltage Vcom. The liquid crystal layer3has negative dielectric anisotropy, and liquid crystal molecules of the liquid crystal layer3may be aligned such that their major axes are perpendicular to the surfaces of the two display panels when an electric field is not applied. In an alternative to the structure illustrated inFIG. 2, the common electrode270may be formed on the lower panel100.

For the color display, each pixel PX uniquely displays one of three primary colors (spatial division) or each pixel PX alternately displays the three primary colors (temporal division) as time passes, and a desired color is recognized by a spatial or temporal sum of the primary colors. For example, the primary colors may be three primary colors of red, green, and blue.FIG. 2shows a color filter230displaying one of the primary colors on a region of the upper panel200for each of the pixels as an example of spatial division. In an alternative to the case illustrated inFIG. 2, the color filter230may be provided on or under the subpixel electrodes191hand191lof the lower panel100.

Polarizers (not shown) may be provided on the outer surface of the display panels100and200, and the polarization axes of the two polarizers may be crossed.

Referring again toFIG. 1, the data driver500is connected to the data lines D1-Dm of the liquid crystal panel assembly300, and applies the data voltage to the data lines D1-Dm.

The gate driver400is connected to the gate lines G1to Gn of the liquid crystal panel assembly300, and applies gate signals obtained by combining a gate-on voltage

Von for turning on a switching element and a gate-off voltage Voff for turning off the switching element to the gate lines G1to Gn.

Next, one example of the liquid crystal display will be described with reference toFIG. 3as well asFIG. 1andFIG. 2.

FIG. 3is an equivalent circuit diagram of one pixel of a liquid crystal display according to an exemplary embodiment.

Referring toFIG. 3, a liquid crystal display according to an exemplary embodiment has signal lines that include a first gate line121, a second gate line123, a common voltage line125, and a data line171, and a plurality of pixels PX connected thereto.

The pixel PX includes a first switching element Qh, a second switching element Ql, a third switching element Qc, a first liquid crystal capacitor Clch, a second liquid crystal capacitor Clcl, and a voltage-changing capacitor Cstd.

The first and second thin film transistors Qh and Ql are three terminal elements provided in the lower panel100and have a control terminal connected to the gate line121, an input terminal connected to the data line171, and an output terminal connected to the first and second liquid crystal capacitors Clch and Clcl, respectively.

The third thin film transistor Qc is a three terminal element provided in the lower panel100and has a control terminal connected to the second gate line123, an input terminal connected to the second liquid crystal capacitor Clcl, and an output terminal connected to the voltage-changing capacitor Cstd.

The voltage-changing capacitor Cstd is connected to the output terminal of the third switching element Qc and the common voltage line125. The common voltage line125provided in the lower panel100and the output terminal of the third switching element Qc overlap via an insulator.

The first liquid crystal capacitor Clch and the second liquid crystal capacitor Clcl are described above such that redundant description is omitted.

An operation of a liquid crystal display according to an exemplary embodiment will be described with reference toFIG. 4as well asFIG. 1toFIG. 3.

FIG. 4is a view showing a gate signal Vgn of the first gate line121and a gate signal Vgc of the second gate line123in the liquid crystal display shown inFIG. 3.

If the first gate line121is applied with a gate-on voltage Von, the first switching element Qh and the second switching element Ql connected thereto are turned on.

Accordingly, the data voltage of the data line171is simultaneously applied to both the first and second subpixel electrodes191hand191lthrough the turned-on first and second switching elements Qh and Ql. The first and second liquid crystal capacitors Clch and Clcl are charged by a difference between the common voltage Vcom of the common electrode270and the voltage of the first and second subpixel electrodes191hand191l, such that the charging voltage of the first liquid crystal capacitor Clch is the same as the charging voltage of the second liquid crystal capacitor Clcl. In this case, the second gate line123is applied with the gate-off voltage Voff.

Next, if the first gate line121is applied with the gate-off voltage Voff, and simultaneously the second gate line123is applied with the gate-on voltage Von, the first and second switching elements Qh and Ql connected to the gate line121are turned off, and the third switching element Qc is turned on. Accordingly, the charges of the second subpixel electrode191lconnected to the output terminal of the second switching element Ql flow into the voltage-changing capacitor Cstd such that the voltage of the second liquid crystal capacitor Clcl is decreased.

In an example of the case in which the liquid crystal display according to the present exemplary embodiment is driven by frame inversion, when the data line171has the positive data voltage with respect to the common voltage Vcom in the present frame, negative charges are gathered in the voltage-changing capacitor Cstd after the previous frame is finished. Accordingly, in the present frame, if the third switching element Qc is turned on, the positive charges of the second subpixel electrode191lflow into the voltage-changing capacitor Cstd through the third switching element Qc, and the negative charges of the voltage-changing capacitor Cstd flow into the second subpixel electrode191lsuch that the voltage of the second subpixel electrode191is decreased. Next, in the immediately following frame, if the third switching element Qc is turned on in the state in which the negative charges are charged in the second subpixel electrode191l, the negative charges of the second subpixel electrode191lflow into the voltage-changing capacitor Cstd such that the negative charges are gathered in the voltage-changing capacitor Cstd, and the voltage of the second liquid crystal capacitor Clcl is decreased.

Accordingly, the charging voltages of the first and second liquid crystal capacitors Clch and Clcl are different such that the lateral visibility of the liquid crystal display may be improved.

A liquid crystal display according to an exemplary embodiment of the present invention and a manufacturing method thereof will be described with reference toFIG. 5toFIG. 7.

FIG. 5is a layout view of a liquid crystal display according to an exemplary embodiment,FIG. 6is an enlarged view of a portion of the liquid crystal display shown inFIG. 5, andFIG. 7is a cross-sectional view of the liquid crystal display shown inFIG. 5andFIG. 6taken along the line VII-VII.

The liquid crystal display according to the present exemplary embodiment includes the lower panel100and the upper panel200which are facing each other, and a liquid crystal layer3interposed between two display panels100and200. Polarizers (not shown) may be provided at the outer surface of the display panels100and200.

The lower panel100will now be described.

A plurality of gate conductors including a plurality of first gate lines121, a plurality of second gate lines123, and a common voltage line125are formed on an insulation substrate110.

The first gate line121and the second gate line123extend in a substantially transverse direction and each transmits a gate signal. The first gate line121includes a first gate electrode124hand a second gate electrode124lthat protrude upward, and the second gate line123includes a third gate electrode124cthat protrudes upward. The first gate electrode124hand the second gate electrode124lare connected to each other, thereby forming one protrusion.

The common voltage line125is mainly extended in the transverse direction, and transfers a predetermined voltage such as a common voltage Vcom. The common voltage line125includes left and right common voltage electrodes128bthat protrude downward, and an expansion126bconnected to the ends of the right common voltage electrode128b.

A gate insulating layer140is formed on the gate conductors121,123, and125.

A plurality of semiconductor stripes151made of amorphous silicon (a-Si), polysilicon, or the like are formed on the gate insulating layer140. The semiconductor stripes151are mainly extended in the longitudinal direction.

Each semiconductor stripe151includes first and second semiconductors154hand154lthat extend toward the first and second gate electrodes124hand124land which are connected to each other, and a third semiconductor154cconnected to the second semiconductor154l.

A plurality of ohmic contact stripes161are formed on the semiconductor stripes151, a pair of ohmic contacts163hand165hare formed on the first semiconductor154h, and a pair of ohmic contacts163land165lare formed on the second semiconductor154l. A pair of ohmic contacts (not shown) are also formed on the third semiconductor154c. The ohmic contacts163land163hare connected to the ohmic contact stripes161.

A data conductor including a plurality of data lines171, a plurality of first drain electrodes175h, a plurality of second drain electrodes175l, a plurality of third source electrodes173c, and a plurality of third drain electrodes175cis formed on the ohmic contacts161,165h, and165l.

The data lines171transmit data signals and extend in the longitudinal direction thereby intersecting the first gate lines121and the second gate lines123. Each data line171includes a first source electrode173hand a second source electrode173lextending, respectively, toward the first gate electrode124hand the second gate electrode124l. The first source electrode173hand the second source electrode173lare connected to each other.

The first drain electrode175h, the second drain electrode175l, and the third drain electrode175ceach have one end portion that has a wide area and the other end portion that has a linear, or bar shape. The bar-shaped end portions of the first drain electrode175hand the second drain electrode175lare partially enclosed by the first source electrode173hand the second source electrode173l, respectively. The bar-shaped end portion of the third source electrode173cis partially enclosed by the third source electrode173c. The wide end of the second drain electrode175lis connected to the third source electrode173c. The wide end177cof the third drain electrode175coverlaps the expansion126bof the common voltage line125, thereby forming the voltage-changing capacitor Cstd.

The first, second, and third gate electrodes124h,124l, and124c, the first, second, and third source electrodes173h,173l, and173c, and the first, second, and third drain electrodes175h,175l, and175cform, respectively, the first, second, and third thin film transistors (TFT) Qh, Ql, and Qc along with the first, second, and third semiconductor islands154h,154l, and154c. A channel of the thin film transistors is respectively formed in the semiconductor154h,154l, and154cbetween the source electrodes173h,173l, and173cand the drain electrodes175h,175l, and175c.

Also, the semiconductor stripes151including the semiconductors154h,154l, and154c, with the exception of the channel region between the source electrodes173h,173l, and173c, and the drain electrodes175h,175l, and175c, have substantially the same shape as the data conductors171,175h,175l, and175c, and the underlying ohmic contacts161and165h. That is, the semiconductor stripes151including the semiconductors154h,154l, and154chave a portion that is exposed without being covered by the data conductors171,175h,175l, and175c, and a portion between the source electrodes173h,173l, and173cand the drain electrodes175h,175l, and175c.

A passivation layer180is formed on the data conductors171,175h,175land175cand the exposed semiconductors154h,154l, and154c.

The passivation layer180has a plurality of contact holes185hand185lrespectively exposing the wide end of the first drain electrode175hand the wide end of the second drain electrode175l.

A pixel electrode191is formed on the passivation layer180.

The overall shape of pixel electrode191is substantially rectangular. Pixel electrode191includes the first and second subpixel electrodes191hand191lthat are engaged with each other and have a gap91there between. The first subpixel electrode191his formed in the central portion of the second subpixel electrode191l, and the gap91includes one longitudinal portion and a pair of oblique portions respectively disposed upward and downward with respect to an imaginary transverse central line (or the common voltage line125).

The second subpixel electrode191lincludes a central electrode191la, upper and lower electrodes191lb, and a protrusion192lthat protrudes downward from the lower electrode191lb. The central electrode191laincludes a cutout93that has a substantially triangular shape, and is formed in the central portion of the left edge of the central electrode. The upper and the lower electrodes191beach include a cutout92.

The edges of the oblique portion of the gap91, and the cutouts92and93, are inclined with respect to the first and second gate lines121and123and the common voltage line125by an angle of about 45°.

The number of cutouts may vary depending on design factors, such as the length ratio of the horizontal side and the vertical side of the pixel electrode191, the type of liquid crystal layer3, or other characteristics.

The area of the second subpixel electrode191lmay be in the range of 1.0 to 2.2 times the area of the first subpixel electrode191h.

The first subpixel electrode191hreceives the data voltage from the first drain electrode175hthrough the contact hole185h, and the second subpixel electrode191lreceives the data voltage from the second drain electrode175lthrough the protrusion192land the contact hole185l.

An alignment layer11is formed on the first and second subpixel electrodes191hand191land the passivation layer180. The alignment layer11may be a vertical alignment layer.

Next, the upper panel200will be described.

A light blocking member220referred to as a black matrix and a plurality of color filters230are formed on an insulation substrate210, and an overcoat250is formed on the light blocking member220and the color filters230.

A common electrode270made of a transverse conductor or metal such as ITO or IZO is formed on the overcoat250. The common electrode270has a plurality of cutouts71formed substantially parallel to the oblique portions of the cutouts92of the pixel electrode191.

An alignment layer21may be formed on the common electrode270. The alignment layer21may be a vertical alignment layer.

The liquid crystal layer3between the lower panel100and the upper panel200includes liquid crystal molecules having dielectric anisotropy, and may be oriented such that the major axes of the liquid crystal molecules of the liquid crystal layer3are almost perpendicular to the surfaces of the two display panels100and200when no electric field is applied.

The first and second subpixel electrodes191hand191lapplied with the data voltage form the electric field along with the common electrode270of the upper panel200such that the electric field determines the direction of the liquid crystal molecules in the liquid crystal layer3between two electrodes191and270. The degree of change of the polarization of the light that is incident to the liquid crystal layer3depends upon the inclination degree of the liquid crystal molecules, and this change of the polarization appears as a change of transmittance by the polarizer, thereby displaying images of the liquid crystal display.

The first subpixel electrode191hand the common electrode270form the first liquid crystal capacitor Clch along with the liquid crystal layer3interposed there between, and the second subpixel electrode191land the common electrode270form the second liquid crystal capacitor Clcl along with the liquid crystal layer3interposed there between, thereby maintaining the voltage of the subpixel electrodes after the first and second thin film transistors Qh and Ql are turned off.

After the first and the second thin film transistors Qh and Ql are turned off, the third thin film transistor Qc is turned on such that the second liquid crystal capacitor Clcl is connected to the voltage-changing capacitor Cstd, and thereby the voltage of the second liquid crystal capacitor Clcl is decreased. If the voltages of the first and second liquid crystal capacitors Clch and Clcl are different, the luminances of the display at the first subpixel191hand the second subpixel electrode191lare also different, and accordingly, the voltages of the first and second liquid crystal capacitors Clca and Clcb are appropriately controlled, thereby improving the lateral visibility. Various characteristics and operations of the liquid crystal display according to the exemplary embodiments shown inFIG. 1toFIG. 4may also be applied to the present exemplary embodiment.

Next, a manufacturing method of a lower panel100of the liquid crystal display shown inFIG. 5toFIG. 7will be described.

First, a gate conductive layer (not shown) is deposited on an insulation substrate110made of transparent glass, and a photosensitive film is coated thereon. The photosensitive film is irradiated by light through a mask (not shown) and is developed to form a photosensitive film pattern (not shown), and the gate conductive layer is etched by using the photosensitive film pattern as an etching mask to form a plurality of gate conductors including a plurality of first gate lines121, a plurality of second gate lines123, and a common voltage line125.

Next, a gate insulating layer140made of an inorganic insulator or an organic insulator is deposited on the gate conductor.

Next, a semiconductor layer (not shown) and a semiconductor layer (not shown) that is doped with an impurity are sequentially deposited by chemical vapor deposition on the gate insulating layer140, a data conductive layer (not shown) is formed by sputtering, and a photosensitive film is coated thereon. Next, the photosensitive film is irradiated by light using a light exposer through a mask (not shown), and is developed to form a photosensitive film pattern (not shown) which has different thicknesses in different positions. Next, the data conductive layer, the semiconductor layer doped with an impurity, and the semiconductor layer are etched by using the photosensitive film pattern as the etching mask to form a data conductor layer (not shown), an ohmic contact layer (not shown), and a plurality of semiconductor stripes151having the same plane shape.

Next, a portion of the photosensitive film pattern is removed, and the exposed data conductor layer and ohmic contact layer are etched to form (i) the channel regions of the first, second, and third thin film transistors Qh, Ql, and Qc, and (ii) a data conductor that includes a plurality of data lines171, a plurality of first drain electrodes175h, a plurality of second drain electrodes175l, a plurality of third source electrodes173c, and a plurality of third drain electrodes175c, and a plurality of ohmic contacts161,165h, and165l.

Next, a passivation layer180is formed on the data conductor and patterned to form a plurality of contact holes185hand185l, and a transparent conductive layer of IZO or ITO is formed on the passivation layer180by sputtering, and then patterned to form a plurality of pixel electrodes191including a gap91and cutouts92and93.

In the manufacturing process of the liquid crystal display, forming the first, second, and third gate electrodes124h,124l, and124c, the first, second, and third semiconductors154h,154l, and154c, the first, second, and third source electrodes173h,173l, and173c, and the first, second, and third drain electrodes175h,175l, and175c, which form the first, second, and third thin film transistors Qh, Ql, and Qc requires exposing the liquid crystal display to light. As the result of various causes in the manufacturing of the liquid crystal display, for instance if the light used is not appropriately focused or is misaligned, or if external foreign particles are introduced into the display device, defects can occur in the channel regions of the first, second, and third thin film transistors Qh, Ql, and Qc. As a result of such defects, the first, second, and third thin film transistors Qh, Ql, and Qc may always be turned on, regardless of the state of the gate signal. Particularly, if the first and second thin film transistors Qh and Ql that are connected to the first and second subpixel electrodes191hand191land applied with the data voltage are defective, the first and second subpixel electrodes191hand191lmay be applied with the data voltage for the different pixels PX such that the image of the corresponding pixel PX may not be displayed. Accordingly, the deteriorated pixel PX is repaired to always display black. Particularly, referring toFIG. 5toFIG. 7, the first thin film transistor Qh and the second thin film transistor Ql are close to each other such that they may be simultaneously defective.

Next, a method for repairing a defective pixel that may occur in the liquid crystal display shown inFIG. 5toFIG. 7, and the resulting repaired liquid crystal display will be described with reference toFIG. 8toFIG. 11. InFIG. 8toFIG. 11, the same constituent elements as described in the previous exemplary embodiment are indicated by the same reference numerals. Certain redundant description is therefore omitted.

FIG. 8is a layout view of a repaired pixel of a liquid crystal display according to an exemplary embodiment,FIG. 9is a cross-sectional view of the liquid crystal display shown inFIG. 8taken along the line IX-IX,FIG. 10is an equivalent circuit diagram of a repaired pixel of the liquid crystal display according to an exemplary embodiment, andFIG. 11is a view showing two subpixel electrodes and a display area of a liquid crystal display according to an exemplary embodiment.

Referring toFIG. 8toFIG. 10, when the first thin film transistor Qh of the pixel of the liquid crystal display according to an exemplary embodiment is defective, or the first and second thin film transistors Qh and Ql are defective, the portion A between the first source electrode173hof the first thin film transistor Qh and the data line171is disconnected by, for example, using a laser, and the wide end177cof the third drain electrode175cand the expansion126bof the common voltage line125forming two terminals of the voltage-changing capacitor Cstd are shorted (portion B) by using, for example, a laser.

Thus, the first and second thin film transistors Qh and Ql are separated from the data line171such that they do not receive the data voltage, and the function of the voltage-changing capacitor Cstd is lost. The third drain electrode175cof the third thin film transistor Qc is directly connected to the common voltage Vcom. Accordingly, if the gate-on voltage Von is applied to the second gate line123, thereby turning on the third thin film transistor Qc, the common voltage Vcom is applied to the second subpixel electrode191lthrough the contact hole185lsuch that the voltage applied to the second liquid crystal capacitor Clcl is substantially 0. As a result, therefore, the first display area A1corresponding to the second subpixel electrode191lofFIG. 11displays black. InFIG. 11, the first display area Al is an image display area corresponding to the second subpixel electrode191l, and the second display area A2is the image display area corresponding to the first subpixel electrode191h.

On the other hand, when the channel region of the third thin film transistor Qc is defective, the second subpixel electrode191lis applied with the common voltage Vcom regardless of the gate signal Vgc of the second gate line123such that the first display area A1ofFIG. 11may display black.

Next, if the gate-on voltage Von is applied to the first gate line121, the first and the second thin film transistors Qh and Ql are turned on such that the first subpixel electrode191his connected to the second subpixel electrode191lthrough the turned-on first and second thin film transistors Qh and Ql and the contact hole185l.Accordingly, the voltage of the first subpixel electrode191his moved to the side of the common voltage Vcom, and the voltage of the first subpixel electrode191hconverges to the common voltage Vcom as the frame is repeated. Accordingly, the voltage applied to the first liquid crystal capacitor Clch is substantially 0 such that the second display area A2corresponding to the first subpixel electrode191hofFIG. 11displays black.

When the channel regions of the first and second thin film transistors Qh and Ql are defective, the first and second thin film transistors Qh and Ql may always be turned on, regardless of the gate signal Vgn of the first gate line121, such that the common voltage Vcom is simultaneously applied the first subpixel electrode191hwhen the common voltage Vcom is applied to the second subpixel electrode191lin this case.

When the third thin film transistor Qc is defective as well as the first and second thin film transistors Qh and Ql, the common voltage Vcom may be applied to both the first subpixel electrode191hand the second subpixel electrode191lregardless of the gate signal Vgn of the first gate line121and the gate signal Vgc of the second gate line123.

As described above, when the pixel of the liquid crystal display is defective, for instance when defects in the first thin film transistor Qh or the first and second thin film transistors Qh and Ql exist, the pixel defect that causes an abnormally bright light is turned off so that the pixel displays black. This change is accomplished by easily repairing the corresponding pixel through the above-described method, and thereby display deterioration may be prevented.

In the above-described exemplary embodiment, the pixel defects due to a defect of the channel region of the first thin film transistor Qh and the second thin film transistor Ql is described. However the embodiment is not limited thereto, and the method of repairing the liquid crystal display according to the exemplary embodiments may be applied to various cases in which the second display area A2corresponding to the first subpixel electrode191h, or the first display area A1corresponding to the second subpixel electrode191l, does not execute the normal display operation.

Next, a method of repairing a liquid crystal display and a repaired pixel of a liquid crystal display according to another exemplary embodiment will be described with reference toFIG. 12andFIG. 13. The same constituent elements described in the previous exemplary embodiment are indicated by the same reference numerals. Certain redundant description is therefore omitted.

FIG. 12is a layout view of a liquid crystal display according to an exemplary embodiment, andFIG. 13is a cross-sectional view of the liquid crystal display shown inFIG. 12taken along the line XIII-XIII.

A liquid crystal display according to the present exemplary embodiment includes a lower panel100and an upper panel200that are facing each other, and a liquid crystal layer3interposed between the two display panels100and200.

First, referring to the upper panel200, a common electrode270is formed on an insulation substrate210, and an alignment layer (not shown) is formed on the common electrode270.

The liquid crystal layer3between the lower panel100and the upper panel200has negative dielectric anisotropy, and may be oriented such that the major axes of the liquid crystal molecules of the liquid crystal layer3are almost perpendicular to the surfaces of the two display panels100and200when no electric field is applied.

Next, referring to the lower panel100, a plurality of gate conductors including a plurality of first gate lines121, a plurality of second gate lines123, and a common voltage line125are formed on an insulation substrate110. The common voltage line125includes an electrode129that protrudes upward and downward, a pair of longitudinal portions128that extend vertically to the first gate line121, and a transverse portion127connecting the ends of a pair of longitudinal portions128to each other. The transverse portion127includes an expansion126expanding downward and a protrusion122that protrudes downward.

A gate insulating layer140is formed on the gate conductor121,123, and125.

A plurality of semiconductor stripes151are formed on the gate insulating layer140. The semiconductor stripe151includes first and second semiconductors154hand154lthat are connected to each other, and a third semiconductor154cconnected to the second semiconductor154l.

A plurality of ohmic contact stripes161are formed on the semiconductor stripe151, a pair of ohmic contacts163hand165hare formed on the first semiconductor154h, and a pair of ohmic contacts (not shown) are respectively formed on the second semiconductor154land the third semiconductor154c.

A data conductor that includes a plurality of data lines171, a plurality of first drain electrodes175h, a plurality of second drain electrodes175l, and a plurality of third drain electrodes175cis formed on the ohmic contacts161and165h. Data line171includes a first source electrode173hand a second source electrode173l. The first drain electrode175h, the second drain electrode175l, and the third drain electrode175ceach have one end portion that has a wide area and the other end portion that has a linear, bar shape. The bar-shaped end portions of the first drain electrode175hand the second drain electrode175lare partially enclosed by the first source electrode173hand the second source electrode173l, respectively. The wide end of the second drain electrode175lis again extended, thereby forming the third source electrode173cthat is curved and has a “U” shape. The wide end177cof the third drain electrode175coverlaps with the expansion126of the common voltage line125thereby forming the voltage-changing capacitor Cstd, and the bar-shaped end thereof is partially enclosed by the third source electrode173c.

The first, second, and third gate electrode124h,124l, and124c, the first, second, and third source electrode173h,173l, and173c, and the first, second, and third drain electrode175h,175l, and175cform the first, second, and third thin film transistor Qh, Ql, and Qc along with the first, second, and third semiconductor island154h,154l, and154c.

A lower passivation layer180ptypically made of an inorganic insulator such as silicon nitride or silicon oxide is formed on the data conductors171,175h,175l, and175cand the exposed semiconductors154h,154l, and154c, and a color filter230is formed on the lower passivation layer180p.

A light blocking member220is formed on the region that the color filter230does not occupy and on a portion of the color filter230. The light blocking member220includes a portion that covers the region where the first thin film transistor Qh, the second thin film transistor Ql, and the third thin film transistor Qc, and also a portion that extends along the data line171. The light blocking member220includes an opening225exposing a substantial part of the first subpixel electrode191hand the second subpixel electrode191l. The light blocking member220may include an opening227disposed on the first thin film transistor Qh and the second thin film transistor Ql, an opening226hdisposed on the wide end of the first drain electrode175h, an opening226ldisposed on the wide end of the second drain electrode175l, and an opening228disposed on the third thin film transistor Qc. The openings226h,226l,227, and228where the light blocking member220is removed are capable of being used to test for defects in the thin film transistor etc. in the manufacturing process of the liquid crystal display.

An upper passivation layer180qis formed on the color filter230and the light blocking member220.

The lower passivation layer180pand the upper passivation layer180qhave a plurality of contact holes185hand185lrespectively exposing the wide ends of the first drain electrode175hand the second drain electrode175l. The contact holes185hand185lare disposed in the openings226hand226lof the light blocking member220.

A pixel electrode including the first subpixel electrode191hand the second subpixel electrode191lis formed on the upper passivation layer180q.

The overall shape of the first subpixel electrode191his a quadrangle, and includes a cross stem195hthat has a transverse stem and a longitudinal stem, an outer stem196hthat encloses the periphery, and a protrusion192hthat protrudes downward from the longitudinal stem of the cross stem195h.

The overall shape of the second subpixel electrode191lis also a quadrangle, and includes a cross stem195lthat has a transverse stem and a longitudinal stem, an upper transverse portion196la, a lower transverse portion196lb, and a protrusion192lthat protrudes upward from the upper portion of the longitudinal stem of the cross stem195land right and left longitudinal portions193laand193lbdisposed on the right and left sides of the first subpixel electrode191h. The right and left longitudinal portions193laand193lbmay prevent capacitive coupling between the data line171and the first subpixel electrode191h.

The first subpixel electrode191hand the second subpixel electrode191lare respectively divided into four subregions by the cross stems195hand195l. Each sub region includes a plurality of tiny branch electrodes199hand199lobliquely extending outside from the cross stems195hand195l, and tiny slits91hand91lare disposed between the neighboring tiny branches199hand199l.

The protrusion192hof the first subpixel electrode191hreceives the data voltage from the first drain electrode175hthrough the first contact hole185h, and the protrusion192lof the second subpixel electrode191lreceives the data voltage from the second drain electrode175lthrough the second contact hole185l. Here, the data voltage applied to the second subpixel electrode191lmay be less than the data voltage applied to the first subpixel electrode191h.

An alignment layer (not shown) may be formed on the first and second subpixel electrodes191hand191l, and the upper passivation layer180q.

In an exemplary embodiment, the first and second subpixel electrodes191hand191linclude four subregions where the length directions of the tiny branches199hand199lor the tiny slits91hand91lare different such that the inclined directions of the liquid crystal molecules of the liquid crystal layer3are all four directions. Therefore, the viewing angle of the liquid crystal display is widened by varying the inclined directions of the liquid crystal molecules.

Also, the several characteristics and the operations of the liquid crystal display according to the exemplary embodiment shown inFIG. 1toFIG. 4may be applied to the present exemplary embodiment.

When the pixel is defective in an exemplary embodiment as shown inFIG. 12andFIG. 13, the portion A is disconnected between the data line171and the first source electrode173hof the first thin film transistor Qh by using, for example, a laser, and the wide end177cof the third drain electrode175cand the expansion126of the common voltage line125forming two terminals of the voltage-changing capacitor Cstd are shorted (the portion B) by, for example, using a laser.

Thus, as in the above-described exemplary embodiment, the first and second thin film transistors Qh and Q1are separated from the data line171such that they are not applied with the data voltage, and the drain electrode175cof the third thin film transistor Qc is directly connected to the common voltage Vcom. The repairing method and the several characteristics of the liquid crystal display according to the exemplary embodiment shown inFIG. 8toFIG. 10may be applied to the present exemplary embodiment.

According to an exemplary embodiment, the source electrodes of the first and second thin film transistors in the pixel that is defective in a liquid crystal display are disconnected from the data line and the two terminals of the voltage-changing capacitor are shorted such that the first subpixel electrode or the first and second subpixel electrodes are applied with the common voltage, thereby repairing the defective pixel.