Liquid crystal display apparatus

A liquid crystal display (LCD) apparatus having a delta-type pixel structure, comprises a thin-film transistor (TFT) substrate, a color filter substrate and a liquid crystal layer. Electrodes on the TFT substrate are configured to block light leakage at boundaries between color filters. Light leakage at the color filter boundaries is blocked without having a black matrix on the color filter substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119 to Korean Patent Application No. 2006-121856, filed on Dec. 5, 2006 in the Korean Intellectual Property Office (KIPO), the contents of which are herein incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display (LCD) apparatus. More particularly, the present invention relates to an LCD apparatus having an enhanced aperture ratio.

2. Description of the Related Art

In general, a liquid crystal display (LCD) apparatus includes a thin-film transistor (TFT) substrate, a color filter substrate aligned to and attached to the TFT substrate and a liquid crystal layer interposed between the TFT substrate and the color filter substrate.

The TFT substrate includes a plurality of pixels, each pixel being located at the intersection of a gate line and a data line, with each pixel including a TFT, a storage capacitor and a pixel electrode. The TFT substrate further includes driving circuits for independently driving the plurality of pixels. The color filter substrate includes a color filter layer having red (R), green (G) and blue (B) color filters, a black matrix disposed at boundaries of the color filters and a common electrode for establishing electric fields between the common electrode and the pixel electrodes.

Recently, a delta-type pixel structure has been developed. The delta-type pixel structure has better characteristics in color uniformity than a stripe-type pixel structure. In the stripe-type pixel structure, color filters are aligned along the data line in a linear configuration, whereas in the delta-type pixel structure, color filters are aligned along the data line in a zigzag configuration.

In the delta-type pixel structure, a black matrix, located on the color filter substrate at the boundaries of color filters, is aligned to overlap with the gate and data lines in order to prevent light leakage between the color filters.

In the delta-type pixel structure, unlike the stripe-type pixel structure, light leakage occurs at corner portions where the color filters meet. The width of the black matrix disposed at the corner portions is increased to prevent the light leakage. As a result, aperture ratio is reduced. In addition, when the TFT substrate is misaligned with respect to the color filter substrate, brightness is reduced.

SUMMARY

The present invention provides a liquid crystal display (LCD) apparatus having a delta-type pixel structure, in which light leakage at boundaries between pixels is blocked by structures formed in first and second conductive layers on the TFT substrate rather than by black matrix on the color filter substrate. The LCD made in accordance with the invention has an enhanced aperture ratio.

In some embodiments, the color filters are arranged in horizontal lines on the color filter substrate. Each line of filters is offset in the horizontal direction from the adjoining lines of filters by about half the width of a color filter. With this offset, the columns of filters in the longitudinal direction have a zigzag configuration. Data lines follow the zigzag and therefore have horizontal portions as well as vertical portions. The terms horizontal and vertical, as used here, are understood as they apply to the layouts shown inFIGS. 1,2,3, and4herein.

In the first exemplary embodiment of the present invention, an LCD apparatus includes a thin-film transistor (TFT) substrate, a color filter substrate and a liquid crystal layer. The TFT substrate includes a gate line, a data line intersecting the gate line, a TFT part electrically connected to the gate line and the data line, and a storage capacitor part. At the intersection of the gate line and the data line, the gate line is electrically insulated from the data line by an insulating dielectric layer. The color filter substrate includes color filters of three different colors.

The horizontal boundaries between color filters ideally align with the center lines of gate lines. The vertical boundaries between color filters ideally align with the center lines of vertical portions of data lines on the TFT substrate. A horizontal boundary at which adjacent ones of the color filters meet is overlapped with the gate line which is made sufficiently wide to block the horizontal boundary. Along the vertical boundary, light leakage is blocked by a storage capacitor electrode located beneath a portion the vertical portion of the data line, and by the vertical portion of the data line itself where the storage capacitor electrode is absent, and by the TFT part. Thus light leakage at color filter boundaries is blocked by a gate line, by a storage capacitor electrode under a portion of a data line, by a portion of a data line without an underlying capacitor electrode, and by a TFT part.

The liquid crystal layer is disposed between the TFT substrate and the color filter substrate. The color filters are arranged along the gate line in a linear configuration, and are arranged along the data line in a zigzag configuration.

In a second exemplary embodiment of the present invention, an LCD apparatus includes a TFT substrate, a color filter substrate and a liquid crystal layer. The TFT substrate includes a gate line, a data line intersecting the gate line, a TFT part electrically connected to the gate line and the data line and a storage capacitor part. At the intersection of the gate line and the data line, the gate line is electrically insulated from the data line by a layer of insulating dielectric. The color filter substrate includes color filters of three different colors.

The liquid crystal layer is disposed between the TFT substrate and the color filter substrate. The color filters are arranged along the gate line in a linear configuration, and are arranged along the data line in a zigzag configuration.

The storage capacitor part may include a first lower storage electrode, a second lower storage electrode and an upper storage electrode. The first lower storage electrode may be formed from substantially the same conductive layer as the gate line. The second lower storage electrode may be formed from substantially the same conductive layer as the gate line, and may extend from the first lower storage electrode to the data line and extend beneath the data line. The upper storage electrode may be formed from substantially the same conductive layer as the data line, and may be electrically connected to a drain electrode of the TFT part. Also, the upper storage electrode may overlay a portion of the first lower storage electrode.

Each of the color filters may have a rectangular shape having shorter horizontal sides and longer vertical sides. The longer sides of adjacent ones of the color filters may meet at a first boundary of the color filters. The first boundary may be ideally aligned or overlapped with the data line and may be blocked by the second lower storage electrode on a major portion of the length of the first boundary, and may be blocked over the remainder of its length by a floating electrode, a gate line and a data line. The shorter sides of adjacent ones of the color filters may meet at a second boundary of the color filters, and the second boundary may be ideally aligned or overlapped with the first lower storage electrode and the upper storage. The second boundary may be blocked by the first lower storage electrode and the upper storage electrode. Three color filters may meet at a point on the second boundary, the point being called a third boundary of the color filters, The third boundary may be blocked by the upper storage electrode and the first lower storage electrode. Alternatively, the third boundary may be blocked by an area at which the first and second lower storage electrodes meet. The floating electrode is formed between the data line and the upper storage electrode in order to block an otherwise exposed portion of the first boundary.

In the LCD apparatus of the present invention, the aperture ratio of the delta-type pixel structure is increased by using structures on a TFT substrate to block stray light at color filter boundaries, thereby enhancing the brightness of the LCD apparatus.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1is a layout illustrating a portion of a liquid crystal display (LCD) apparatus in accordance with an exemplary embodiment of the present invention.FIG. 2is an enlarged view illustrating the LCD apparatus ofFIG. 1.FIG. 3is a cross-sectional view taken along a line I-I′ inFIG. 2.

ReferringFIGS. 1 to 3, an LCD apparatus100includes a thin-film transistor (TFT) substrate200, a color filter substrate300and a liquid crystal layer400.

The TFT substrate200includes a gate line210, a data line220, a TFT part230and a storage capacitor part240.

The gate line210, formed in a first conductive layer, is disposed on the insulating substrate212. The insulating substrate212may be a transparent glass substrate. The gate line210, as shown inFIG. 2, may extend along a substantially horizontal direction on the insulating substrate212.

A gate insulating layer214is disposed on the insulating substrate212having the gate line210and covers the gate line210. Examples of an insulating material that can be used for the gate insulating layer214include silicon nitride (SiNx), silicon oxide (SiOx). These insulating materials may be used alone or in combination. The thickness of the gate insulating layer214may be about 3,000 Å to about 4,500 Å.

The data line220, formed in a second conductive layer, is disposed on the gate insulating layer214. The data line220is electrically insulated from the gate line210by the gate insulating layer214. The data line220extends along a longitudinal or vertical direction crossing the gate line210in a zigzag configuration. For example, the data line220extends along a substantially longitudinal direction to the gate line210, then extends along the horizontal direction above the gate line210and then, beginning at about the middle of pixel250, extends again along the longitudinal direction.

A TFT part230is electrically connected to the gate line210and the data line220. At least one of the TFT parts230is disposed at each pixel. The TFT part230applies a data voltage from the data line220to the pixel electrode250in response to a gate voltage from the gate line210.

The TFT part230includes a gate electrode231, an active layer232, a source electrode233, and a drain electrode234.

The gate electrode231is electrically connected to the gate line210, and functions as a gate terminal of the TFT.

The active layer232is disposed on the gate insulating layer214opposite the underlying gate electrode231. The active layer232includes a channel layer232aand an ohmic contact layer232b. The channel layer232amay include amorphous silicon (a-Si), and the ohmic contact layer232bmay include N+ amorphous silicon (N+a-Si) that is formed by implanting N+ impurities into amorphous silicon.

The source electrode233is disposed on the active layer232to be electrically connected to the data line220. The source electrode233functions as a source terminal of the TFT.

The drain electrode234is formed on the active layer232, and is spaced apart from the source electrode233. The drain electrode234functions as a drain terminal of the TFT.

A portion of the channel layer232alocated between the source electrode233and the drain electrode234, the contact layer232bhaving been removed, functions as a channel of the TFT.

The storage capacitor part240is formed in each pixel, and functions as a storage capacitor Cst. The storage capacitor part240may include first and second lower storage electrodes241and242and an upper storage electrode244. The first and second lower storage electrodes241and242are formed from substantially the same first conductive layer as the gate line210. The upper storage electrode244is formed from substantially the same second conductive layer as the data line220.

The first lower storage electrode241extends in a substantially parallel direction with the gate line210. A portion of the first lower storage electrode241is located beneath the upper storage electrode244.

The second lower storage electrode242extends from the first lower storage electrode241toward the data line220, and extends under a portion of the data line220. The width of the second lower storage electrode242under the data line may be greater than the width of the data line220. A common voltage may be applied to the first and second lower storage electrodes241and242.

The upper storage electrode244is electrically connected to the drain electrode234of the TFT part230. A portion of the upper storage electrode overlays a portion of the first lower storage electrode241. The gate insulating layer214and the active layer232may be disposed between the upper storage electrode244and the first lower storage electrode241. The storage capacitor Cst is defined by the upper storage electrode244and the first lower storage electrode241. Alternatively, the active layer232may be omitted between the upper storage electrode244and the first lower storage electrode241.

A contact hole CNT is formed in a protecting layer260over the upper storage electrode244. The protecting layer260includes a layer of insulating material such as silicon nitride (SiNx) or silicon oxide (SiOx) or other insulating material and may be from about 500 to 2,000 Angstroms thick. The upper storage electrode244and the drain electrode234are electrically connected to the pixel electrode250through the contact hole CNT. Thus, the data voltage applied to the pixel electrode250through the TFT is maintained during one frame by the storage capacitor Cst.

The pixel electrodes250are disposed on the protecting layer260.

Each pixel is defined by the gate and data lines210and220and each pixel electrode occupies an area within a region bounded by two gate lines and two data lines. The pixel electrode250includes a transparent conductive material that transmits light. Examples of transparent conductive materials that may be used for the pixel electrode250include indium zinc oxide (IZO), indium tin oxide (ITO).

The pixel electrode250is electrically connected to the drain electrode234and the upper storage electrode244through the contact hole CNT formed through the protecting layer260. The data voltage applied to the pixel electrode250through the TFT is maintained during one frame by the storage capacitor Cst.

The pixel electrode250may include various features for increasing a viewing angle of the LCD apparatus100. For example, the pixel electrode250may include a main electrode and a sub-electrode. The main electrode and the sub-electrode may receive two different voltages. When the pixel electrode250includes a main electrode and a sub-electrode, two TFTs are formed in each pixel, with one of the two TFTs electrically connected to the main electrode and the second of the two TFTs connected to the sub-electrode.

The color filter substrate300is disposed close to and attached to the TFT substrate200. The liquid crystal layer400is disposed between the color filter substrate300and the TFT substrate200. The color filter substrate300includes color filters310having different colors for displaying a color image. The color filters310are disposed on an insulating substrate320. The insulating substrate320may be a transparent glass substrate. The color filters310may include a photosensitive organic material and pigments corresponding to the colors. The colors may include three colors, red, green and blue. The red, green and blue color filters R, G and B may be disposed in that order and recurring in that order along the horizontal direction of the gate line210.

The color filters310are disposed on the insulating substrate320in a uniform arrangement. Since the LCD apparatus100has a delta-type pixel structure, the color filters310are aligned along the gate line210in a horizontal direction, and are aligned along the data line220in a zigzag configuration in a longitudinal direction.

The boundaries between rectangular color filters310are designated as first boundaries BR1between the longer or vertical sides of the color filters, and second boundaries BR2between the shorter horizontal sides of the color filters310. The ideal locations of these boundaries relative to the TFT substrate200are shown by the dotted lines BR1and BR2inFIGS. 1 and 2.

The boundaries of the color filters310are blocked by various electrodes on the TFT substrate including the gate line210, the data line220, the TFT part230, and the second lower storage electrode242. Thus a black matrix may be omitted from the areas around the color filter boundaries on the color filter substrate300. Referring toFIGS. 1 to 3, an aperture ratio may be increased by about 13.4%, and brightness may be enhanced by omitting the black matrix.

This arrangement will now be described in more detail.

The first boundary BR1between adjacent longer sides of the color filters310is ideally aligned as shown by the dotted line BR1along the center of a vertical portion of the data line220. InFIGS. 1 to 3, the second lower storage electrode242having greater width than the data line220is disposed under the data line220, so that a portion of the first boundary BR1extending from the point245to the point247may be effectively blocked by the second lower storage electrode242. The portion of the first boundary BR1extending from the point245to the point247is blocked by the data line220, the data line220being made wider between the point245and247for the purpose of blocking. The portion of the first boundary BR1extending from point246to point248is blocked by a combination of the gate line and the data line.

The second boundary BR2between adjacent shorter sides of the color filters310is ideally aligned as shown by the dotted line BR2along the center of the gate line210. InFIGS. 1 to 3, the gate line210is sufficiently wide so that the second boundary BR2may be effectively blocked by the gate line210.

Since the LCD apparatus100in accordance with the first embodiment of the invention has the delta-type pixel structure, the color filters310form a third boundary at which three of the color filters310having different colors from each other meet. At least one of the third boundaries BR3is ideally located relative to the TFT substrate200, as shown inFIG. 2, next to the TFT part230. The combination of the gate electrode, the source electrode and the drain electrode of the TFT part230has a greater width than the data line220and the gate line210. Thus, the TFT part230may block the third boundary BR3at which the three of the color filters310meet.

The color filter substrate300may further include a common electrode330opposite to the pixel electrode250. The liquid crystal layer400is disposed between the pixel electrode250and the common electrode330. The common electrode330includes a conductive transparent material that transmits light. Examples of the conductive transparent material that may be used for the common electrode330include indium zinc oxide (IZO), and indium tin oxide (ITO). The common electrode330may include substantially the same material as the pixel electrode250. The common electrode330may include patterns of openings for increasing the viewing angle.

Liquid crystal molecules in the liquid crystal layer400have optical and electric characteristics such as an anisotropic index of refraction and an anisotropic dielectric constant. The liquid crystal molecules in the liquid crystal layer400may be arranged in a constant direction. An arrangement of the liquid crystal molecules in the liquid crystal layer400is changed by an electric field formed between the pixel electrode250and the common electrode330. When the arrangement of the liquid crystal molecules in the liquid crystal layer400is changed, light transmittance is controlled.

FIG. 4is a layout illustrating a portion of an LCD apparatus in accordance with another exemplary embodiment of the present invention.FIG. 5is an enlarged view illustrating the LCD apparatus ofFIG. 4.FIG. 6is a cross-sectional view taken along a line II-II′ inFIG. 5.

Referring toFIGS. 4 to 6, an LCD apparatus500includes a TFT substrate600, a color filter substrate700and a liquid crystal layer800.

The TFT substrate600includes a gate line610formed in a first conductive layer, a data line620formed in a second conductive layer, a TFT part630and a storage capacitor part640. The data line620is electrically insulated from the gate line610through an insulating layer614, and intersects the gate line610.

The gate line610, the gate insulating layer614and the data line620are substantially the same as those inFIGS. 2 and 3. Thus, any further detailed description concerning the elements will be omitted.

The TFT part630includes a gate electrode631, an active layer632, a source electrode633and a drain electrode634. The gate electrode631is electrically connected to the gate line610. The active layer632is formed on the gate insulating layer and after etch patterning a portion of the active layer remains above the gate electrode631. The source electrode633is disposed on the active layer632, and is electrically connected to the data line620. The drain electrode634is disposed on the active layer632, and is spaced apart from the source electrode633.

The TFT part630is substantially the same as that inFIGS. 2 and 3. Thus, any further detailed description of the TFT part will be omitted.

The storage capacitor part640may include first and second lower storage electrodes641and642and an upper storage electrode644. The first and second lower storage electrodes641and642are formed from substantially the same first conductive layer as the gate line610. The upper storage electrode644is formed from substantially the same second conductive layer as the data line620.

The first lower storage electrode641is located under the upper storage electrode644.

The second lower storage electrode642extends from the first lower storage electrode641towards the data line620, and extends under the data line620. The second lower storage electrode642has a greater width than the data line620. A common voltage may be applied to the first and second lower storage electrodes641and642.

The upper storage electrode644is electrically connected to the drain electrode634of the TFT part630, and overlays the first lower storage electrode641. The upper storage electrode644and the first lower storage electrode641define the storage capacitor Cst. The gate insulating layer614and the active layer632are interposed between the upper storage electrode644and the first lower storage electrode641. Alternatively, the active layer632may be omitted.

The pixel electrode650corresponds to each pixel defined by the first lower storage electrode641and the data line620, and is formed on a protecting layer660. The pixel electrode650is electrically connected to the drain electrode634and the upper storage electrode644through a contact hole CNT formed through the protecting layer660.

The pixel electrode650is substantially the same as the pixel electrode250shown inFIGS. 2 and 3except for its location Thus, any further detailed explanation concerning this element will be omitted.

The color filter substrate700is opposite to the TFT substrate600, and is combined with the TFT substrate600with the liquid crystal layer800located in the space between the filter substrate700and the TFT substrate600. The color filter substrate700includes the insulating substrate720, and the color filters710provided on the insulating substrate720and having different colors for displaying a color image. For example, the color filters710include red, green and blue color filters R, G and B alternately arranged along the extension direction of the first lower storage electrode641. The extension direction of the first lower storage electrode641may be the horizontal direction.

The LCD apparatus500in accordance with the present invention has a delta-type pixel structure. Thus, the color filters710are arranged along the first lower storage electrode641as a linear shape in the horizontal direction, and are arranged along the data line620in a zigzag configuration in the longitudinal direction.

The boundaries between the color filters710are designated as first boundaries BR1between the longer vertical sides of the color filters710, and second boundaries BR2between the shorter horizontal edges of the color filters710. The ideal locations of these boundaries relative to the TFT substrate600are shown by the dotted lines BR1and BR2inFIGS. 4 and 5.

As shown by the dotted lines BR1and BR2inFIG. 5, the boundaries of the color filters710having different colors are intended to be blocked by storage capacitor part640. The storage capacitor part640formed at the TFT substrate600blocks the boundary of the color filters710, except for a small portion of the boundary that is blocked by other electrodes as described in more detail in the next paragraph. With the boundaries of the color filters blocked by the storage capacitor and other electrodes a black matrix (not shown) is omitted from the color filter substrate700. Thus, the aperture ratio may be increased by about 16.3% compared with an LCD apparatus having a color filter substrate including a black matrix. Also, the aperture ratio of the LCD apparatus having the storage capacitor part640that blocks most of the boundary of the color filters710may be greater than an aperture ratio of an LCD apparatus of the first exemplary embodiment of the invention having a gate line, a data line and a TFT part that block the boundary of the color filters.

The first boundary BR1between adjacent longer sides of the color filters710is ideally aligned as shown by the dotted line BR1with the center of a vertical portion of the data line620. The second lower storage electrode642has a greater width than the data line620and is disposed under the data line620so that a portion of the first boundary BR1as shown inFIG. 5, may be effectively blocked by the second lower storage electrode642. A portion of the first lower storage electrode641extends along the first boundary BR1and blocks the first boundary BR1from the point647to the point648. A floating electrode670blocks the first boundary from the point648to the point646.

The second boundary BR2between adjacent shorter sides of the color filters710is ideally aligned with the first lower storage electrode641and the upper storage electrode644as shown by the dotted line BR2inFIG. 5. InFIGS. 4 to 6, the first lower storage electrode641and the upper storage electrode644have a greater width than the gate line610and the data line620, so that the second boundary BR2may be effectively blocked by the first storage electrode641and the upper storage electrode644.

Since the LCD apparatus500in accordance with the present invention has delta-type pixel structure, the color filters710form third boundaries BR3at which three of the color filters710having different colors meet. A first one of the third boundaries BR3is shown inFIG. 5as ideally placed over the lower storage electrode641and the upper storage electrode644. A second one of the third boundaries BR3is shown inFIG. 5as ideally disposed in a region in which the first lower storage electrode641is connected to the second lower storage electrode642.

The first one of the third boundaries BR3at which the three of the color filters710meet may be effectively blocked by the first lower storage electrode641and the upper storage electrode644. The first lower storage electrode641and the upper storage electrode644have greater widths than the gate line610and the data line620.

The second one of the third boundaries BR3may be effectively blocked by the region in which the first lower storage electrode641is connected to the second lower storage electrode642.

As noted above the TFT substrate600may include a floating electrode670. The floating electrode670may block a portion of the first boundary BR1which is not otherwise blocked. The floating electrode670is disposed between the first lower storage electrode641and the gate line610, and is disposed between the upper storage electrode644and the data electrode620. The floating electrode670may be formed from substantially the same second conductive layer as the upper storage electrode644and the data electrode620. No voltage is applied to the floating electrode670.

The color filter700may further include a common electrode730opposite to the pixel electrode650. The liquid crystal layer800is interposed between the common electrode730and the pixel electrode650. The common electrode730and the liquid crystal layer800are substantially the same as that ofFIG. 3. Thus, any further detailed explanation concerning these elements will be omitted.

In the first exemplary embodiment of the present invention, a gate line, a data line, a storage capacitor electrode, and a TFT part, all located on a TFT substrate block light leakage at the boundaries of color filters on a color filter substrate so that a black matrix may be omitted from the color filter substrate. Thus, an aperture ratio and brightness of the LCD apparatus having a delta-type pixel structure may be increased.

In the second embodiment of the present invention, light leakage at the boundaries of the color filters may be blocked by a storage capacitor part, a gate line, a data line and a floating electrode, all located on a TFT substrate, so that the aperture ratio may be greatly increased.

Although exemplary embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the present invention should not be limited to those precise embodiments and that various other changes and modifications may be made by one of ordinary skill in the related art without departing from the scope or spirit of the invention. All such changes and modifications are intended to be included within the scope of the invention as defined by the appended claims.