Liquid crystal display device and fabricating method thereof

A liquid crystal display device includes a pixel electrode at a pixel area between a gate line and a data line, a switching device at an intersection between the gate line and the data line, the switching device comprising a light-shielding member overlapping the switching device and extending from an end at the pixel electrode side of a metal thin film provided within the switching device into the pixel area, for blocking light incident on the metal thin film.

This application claims the benefit of Korean Patent Application No. P00-26876 filed May 19, 2000, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a liquid crystal display, and more particularly to a liquid crystal display device and method of fabricating the same that reduces a reflectivity of an LCD display screen.

2. Description of the Related Art

Generally, a liquid crystal display (LCD) of an active matrix driving system uses thin film transistors (TFT's) as switching devices to display images. Since such LCD's can be made smaller than cathode ray tubes, they have been widely used as monitors for personal computers or notebook computers, as well as in office automation equipment, such as copy machines, etc. . . and in portable equipment, such as a cellular phones and pagers, etc.

Referring toFIGS. 1 and 2, in the conventional LCD device, a gate line14and a data line13is formed on a rear substrate1crossing each other, and a pixel electrode10is formed at the interior thereof. A TFT12is formed at an intersection between the gate line14and the data line13.

The TFT12includes a gate electrode3, a source electrode6and a drain electrode7to apply a data signal at the data line13to the pixel electrode10during an application of a scanning pulse to the gate electrode3. The gate electrode3is connected to the gate line14, while the source electrode6is connected to the data line13. The drain electrode7is connected, via a contact hole9, to the pixel electrode10, which is deposited with a transparent conductive material such as indium-tin-oxide (ITO). A gate insulating film4, deposited using an inorganic insulating material, is formed on the gate electrode3and the gate line14, and an active layer20and an ohmic contact layer5are deposited thereon. A passivation layer8made from either an inorganic insulating material or an organic insulating material is formed on the TFT12.

In the conventional LCD device, a storage capacitor19is provided on the gate line14. The storage capacitor19accumulates a driving voltage (charge) of the next scanning line during the previous scanning period, to thereby lower the driving voltage. An upper electrode15of the storage capacitor19is made from a metal alloy upon formation of the source electrode6and the drain electrode7, as shown inFIG. 3. The gate line14that overlaps the upper electrode15serves as a lower electrode of the storage capacitor19. The upper electrode15of the storage capacitor19is connected, via a contact hole16passing through a passivation layer8, to the pixel electrode10.

A black matrix11is provided on a front substrate2, which is opposed to the rear substrate1, with a liquid crystal therebetween. The black matrix11is positioned at a portion other than an effective display area of a pixel to absorb all wavelengths of light incident thereon. Further, on the front substrate2there are provided a common electrode, a color filter and an alignment film (not shown) in addition to the black matrix11.

Such an LCD device has a problem in that a large amount of reflective light is generated at the display screen due to a structure of the black matrix11. More specifically, the black matrix11does not overlap with a pixel electrode side portion17of the drain electrode7and a pixel electrode side portion18of the upper electrode15of the storage capacitor, as shown inFIG. 1, due to its pattern structure. As a result, as shown inFIGS. 2 and 3, when external light is incident on areas O1and O2of the black matrix11, the upper electrode15of the storage capacitor and on the drain electrode7, it is reflected from the upper electrode15and the drain electrode7, which are made of metal. Such a reflected light is incident on a user's eye, and reduces the contrast, thereby reducing quality of a displayed image. For instance, since an aircraft cockpit is exposed to direct sunlight, various LCD panels installed in the cockpit of the aircraft generate a large amount of reflected light. Therefore, the LCD panel in an aircraft may have a deterioration of picture clarity due to the reflected light, sometimes causing pilot error.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a liquid crystal display and a fabricating method thereof that reduce a reflectivity of the display screen.

In order to achieve these and other objects of the invention, a liquid crystal display device according to one aspect of the invention includes a pixel electrode at a pixel area between a gate line and a data line, a switching device at an intersection between the gate line and the data line, the switching device comprising a light-shielding member overlapping the switching device and extending from an end at the pixel electrode side of a metal thin film provided within the switching device into the pixel area, for blocking light incident on the metal thin film.

A liquid crystal display device according to another aspect of the present invention includes a pixel electrode at a pixel area between a gate line and a data line, a charging device on the gate line, the charging device including a metal thin film, a light-shielding member overlapping the charging device and extending from an end at the pixel electrode side of a metal thin film into the pixel area, for blocking light incident on the metal thin film.

A liquid crystal display device according to still another aspect of the present invention includes a pixel electrode at a pixel area between a gate line and a data line, a thin film transistor at an intersection between the gate line and the data line and including a first metal thin film a storage capacitor on the gate line and including a second metal thin film, a black matrix at a boundary portion between pixel areas, first dummy black matrix connected to the black matrix and extending from an end at the pixel electrode side of the metal thin film into the pixel area, and a second dummy black matrix connected to the black matrix and extending from an end at the pixel electrode side of the second metal thin film into the pixel area.

A method of fabricating a liquid crystal display device according to still another aspect of the present invention includes the steps of forming a pixel electrode at a pixel area between a gate line and a data line, forming a switching device including a metal thin film at an intersection between the gate line and the data line, and forming a light-shielding member for blocking light incident on the metal thin film to overlap with the switching device, the light-shielding member extending from an end at the pixel electrode side of a metal thin film of the switching device into the pixel area.

A method of fabricating a liquid crystal display device according to still another aspect of the present invention includes the steps of forming a pixel electrode at a pixel area between a gate line and a data line, forming a charging device including a first metal thin film on the gate line, and forming a light-shielding member for blocking light incident on the metal thin film to overlap the metal thin film, the light-shielding member extending from an end at the pixel electrode side of the first metal thin film into the pixel area.

A method of fabricating a liquid crystal display device according to still another aspect of the present invention includes the the steps of forming a pixel electrode at a pixel area between a gate line and a data line on a rear substrate, forming a thin film transistor including a first metal thin film at an intersection between the gate line and the data line on the rear substrate, forming a storage capacitor including a second metal thin film on the rear substrate and overlapping the gate line, forming a black matrix on a front substrate opposed to the rear substrate at a boundary portion between pixel areas, forming a first dummy black matrix extending from an end at the pixel electrode side of the first metal thin film into the pixel area on the front substrate, and forming a second dummy black matrix extending from an end at the pixel electrode side of the second metal thin film into the pixel area on the front substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown inFIGS. 4 and 5, an LCD device according to an embodiment of the present invention includes a gate line34and a data line33formed on a rear substrate21crossing each other. A pixel electrode30is formed at the interior thereof. A TFT32is formed at an intersection between the gate line34and the data line33.

The TFT32includes a gate electrode23, a source electrode26and a drain electrode27to apply a data signal at the data line33to the pixel electrode30during an “on” period of a scanning pulse to the gate electrode23. The gate electrode23is connected to the gate line34while the source electrode26is connected to the data line33. The drain electrode27is connected to the pixel electrode30.

A process of fabricating such a TFT will be described below. First, a metal thin film is formed by depositing aluminum (Al) or copper (Cu) on the rear substrate1using, for example, a sputtering technique. The metal thin film is selectively patterned, to remain only at a desired portion of the rear substrate21using photolithography. A wet etching method may be used for the photolithography. The patterned metal thin film is formed into the gate electrode23and the gate line34.

Subsequently, an insulating material, such as silicon oxide or silicon nitride, is deposited onto the entire substrate by chemical vapor deposition (CVD) to form a gate insulating film24. The gate insulating film24covers the gate electrode23and the gate line14. An active layer40and an ohmic contact layer25are sequentially deposited onto the gate insulating film4by, for example, CVD. The active layer40is made of an amorphous silicon or polycrystalline silicon, and is not doped with impurities. The ohmic contact layer25is made of amorphous silicon or polycrystalline silicon, and is doped with n-type or p-type impurities at a high concentration. The active layer40and the ohmic contact layer25are patterned by photolithography, including isotropic etching, to remain only at a portion corresponding to the gate electrode23. The source electrode26and the drain electrode27are formed on the ohmic contact layer25. The source electrode26and the drain electrode27are formed by depositing a metal such as molybdenum (Mo), titanium (Ti) or tantalum (Ta), etc., or a molybdenum alloy, such as MoW, MoTa or MoNb, etc. on the ohmic contact layer25using CVD or sputtering, and then patterning it. Upon patterning of the source electrode26and the drain electrode27, the ohmic contact layer25on the gate electrode23is patterned due to an over-etching, to expose the active layer40.

On the TFT32that has the structure as described above, an inorganic insulating material such as silicon oxide or silicon nitride, or an organic insulating material such as an acrylic compound, BCB (β-stagged-divinyl-siloxane-benzocyclobutene) or PFCB (perfluorocyclobutane), is deposited. The insulating material deposited on the TFT32in this manner becomes a passivation layer28. A portion of the passivation layer28covering the drain electrode27is patterned. A contact hole29exposing the drain electrode27is defined in the patterned passivation layer28. Subsequently, a transparent conductive material, such as ITO or IZO (indium-zinc-oxide), is deposited on the passivation layer28and the contact hole29. The transparent conductive film contacts the drain electrode27through the contact hole29. The transparent conductive film is patterned to remain only at a pixel area between the gate line34and the data line33, thereby forming the pixel electrode30.

The LCD device further includes a storage capacitor39formed on the gate line14. The storage capacitor39accumulates a driving voltage (charge) for the next scanning line during the previous scanning period, to thereby lower the required driving voltage. An upper electrode35of the storage capacitor39is formed by patterning a metal or a metal alloy to overlap the gate line34upon formation of the source electrode26and the drain electrode27, as shown inFIG. 6. The gate line34overlaps the upper electrode35and serves as a lower electrode of the storage capacitor39. The upper electrode35of the storage capacitor39is connected, via a contact hole36formed by patterning of the passivation layer30, to the pixel electrode30.

A black matrix31is provided on a front substrate22, which is opposed to the rear substrate21, with a liquid crystal therebetween. The black matrix31is positioned at a portion other than an effective display area of a pixel, that is, at a boundary portion between pixels where the TFT32, the data line33, the gate line34and the storage capacitor39are positioned, so as to prevent a color signal interference between pixels and to shut off a reflected light inputted from the display screen. To this end, the black matrix31includes a first shield31aoverlapping the TFT32, and a second shield31boverlapping the storage capacitor39. The first shield31aextends, by a desired distance C1, from an end at the pixel electrode side of the drain electrode27as shown inFIG. 5, to thereby absorb light incident to the metal thin film of the TFT32, including the drain electrode27. The second shield31bextends, by a desired distance C2, from an end at the pixel electrode side of the upper electrode35, as shown inFIG. 6to absorb light incident to the metal thin film of the storage capacitor39, including the upper electrode35. The black matrix31is formed on the front substrate22by coating an organic material, such as polyimide, to which a black pigment is added. Furthermore, on the front substrate22there is a common electrode, a color filter and an alignment film (not shown), in addition to the black matrix31.

As described above, the black matrix formed at a boundary portion between pixels extends into the drain electrode of the TFT and the upper electrode of the storage capacitor. Accordingly, a deterioration of contrast caused by a reflected light incident on the metal thin film can be minimized. Such an LCD device is suitable, for example, for a display panel for aircraft cockpits exposed to direct sunlight.