Display device displaying single or dual images and method of driving the same

A display device includes a display cell having a plurality of sub-pixels to make a single image or dual images, and a control cell for passing through the single image, and guiding a first image of the dual images toward a first direction and a second image of the dual images toward a second direction different from the first direction.

The present invention claims the benefit of Korean Patent Application No. 10-2005-0127740, filed in Korea on Dec. 22, 2005, which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a display device, and more particularly, to a display device and a method of driving the same.

DISCUSSION OF THE RELATED ART

Until recently, cathode-ray tubes (CRTs have been typical display devices). Presently, much effort is being expanded to study and develop various types of flat panel displays, such as liquid crystal display (LCD) devices, plasma display panels (PDPs), field emission displays (FED), and electro-luminescence displays (ELDs), as a substitute for CRTs. These types of flat panel displays have been driven in an active matrix type display in which a plurality of pixels arranged in a matrix form are driven using a plurality of thin film transistors therein. Among the active matrix types of flat panel displays, liquid crystal display (LCD) devices and electroluminescent display (ELD) devices are widely used for notebook computers and desktop computers because of their high resolution, ability to display colors and superiority in displaying moving images.

In general, an LCD device includes two substrates that are spaced apart and face each other with a layer of liquid crystal molecules interposed between the two substrates. The two substrates include electrodes that face each other such that a voltage applied between the electrodes induces an electric field across the layer of liquid crystal molecules. Alignment of the liquid crystal molecules changes in accordance with the intensity of the induced electric field in the direction of the induced electric field, thereby changing the light transmissivity of the LCD device. Thus, the LCD device displays images by varying the intensity of the induced electric field across the layer of liquid crystal molecules.

FIG. 1is a schematic exploded perspective view of a twisted nematic mode LCD device according the related art. As shown inFIG. 1, the LCD device of the related art includes a first substrate110, a second substrate120and a layer of twisted nematic liquid crystal molecules130between the first and second substrates110and120. The first substrate110is often referred to as an array substrate and the second substrate120is often referred to as a color filter substrate.

A gate line GL and a data line DL are disposed on an inner surface of the first substrate110and cross each other to define a sub-pixel region PA. A thin film transistor T is disposed at the crossing of the gate and data lines GL and DL. A pixel electrode112is disposed in the sub-pixel region PA and connected to the thin film transistor T.

A black matrix124is disposed on the second substrate120for shielding light except in pixel regions. A color filter layer126, including red (R), green (G) and blue (B) color filters126a,126band126c, are disposed on an inner surface of the second substrate120in the black matrix124corresponding to the pixel regions. A common electrode122is disposed on the black matrix124and the color filter layer126.

The twisted nematic liquid crystal molecules are initially twisted by 90 angle degrees along a vertical direction. Then, when voltages are applied across the pixel and common electrodes112and122, alignment of the twisted nematic liquid crystal molecules changes in accordance with the vertical electric field induced between the two electrodes112and122. Therefore, contrast ratio and brightness are abruptly changed as a viewing angle changes, and thus it is difficult to achieve a wide viewing angle. To resolve this problem, an in-plane switching (IPS) mode LCD device, a fringe field switching (FFS) mode LCD device, a vertical alignment (VA) mode LCD device and the like are suggested.

FIGS. 2A to 2Care cross-sectional views illustrating an IPS mode LCD device, a FFS mode LCD device and a VA mode LCD device, respectively, according to the related art. As shown inFIG. 2A, the IPS mode LCD device includes first and second substrates210and220, and a layer of liquid crystal molecules230between the two substrates210and220. A pixel electrode212and a common electrode222are disposed on the first substrate210to induce an in-plane electric field200. The in-plane electric field200controls alignment of the liquid crystal molecules. In the IPS mode LCD device, the change in the refraction of liquid crystal molecules is low as the viewing angle changes, and thus the viewing angle becomes wide. However, aperture ratio is reduced, and the transmissivity is not good. To improve these problems, an FFS mode LCD device is suggested.

As shown inFIG. 2B, the FFS mode LCD device includes first and second substrates210and220and a layer of liquid crystal molecules230between the two substrates210and220. A common electrode222is disposed uniformly in a pixel region on the first substrate210. A plurality of pixel electrodes212are spaced apart from one another. An insulating layer214is interposed between the common electrode222and the pixel electrode212. In this structure, a strong, in-plane electric field200is induced at an interval of several angstroms, and makes liquid crystal molecules over the pixel electrodes212re-arrange. Therefore, the aperture ratio and transmissivity are improved. The common electrode222may have a different shape, for example, a rod shape, where the common electrode222may be closely disposed to the pixel electrode212.

As shown inFIG. 2C, the VA mode LCD device includes first and second substrates210and220and a layer of liquid crystal molecules230between the two substrates210and220. A sub-pixel region is divided into multiple domains. Liquid crystal molecules are arranged vertically in an initial state. The multiple domains have different main viewing angles. By using the multiple domains, a viewing angle can be improved. To make the multiple domains, a groove or protrusion is formed in the common electrode222. Therefore, in the multiple domains, different vertical electric fields200are induced, and liquid crystal molecules are arranged in accordance with the electric fields200.

The above explained IPS mode, FF mode and VA mode LCD devices have a wide viewing angle, and users can see the same image over a wide range of different angles. This is useful when many users want to view the same image. However, when users want to view differently displayed images, for example, kids want to view a movie while adults want to view the news at the same time, a separate display device is needed for each image or a portion of the display is used for one image and another portion of the display is used for the other image. Therefore, to display different images in the related are, either display panel space is sacrificed or cost increase due to the purchase of another display panel.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a display device and a method of driving the same that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a display device for displaying a single image or dual images

Another object of the present invention is to provide a display device for displaying a first image within a first viewing angle range and a second image in a second viewing angle range.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a display device includes a display cell having a plurality of sub-pixels to make a single image or dual images, and a control cell for passing through the single image, and guiding a first image of the dual images toward a first direction and a second image of the dual images toward a second direction different from the first direction.

In another aspect, a method of driving a display device includes making a single image or dual images in a display cell having a plurality of sub-pixels, and passing the single image through a control cell to display the single image, and guiding a first image of the dual images toward a first direction and a second image of the dual images toward a second direction different from the first direction through the control cell to display the dual images.

In another aspect, a method of driving a display device includes a method of driving a display device includes making a single image or dual images in a display cell, and making a control cell entirely transparent for the single image to pass through when displaying the single image, alternatingly transparent and opaque to pass first and second images of the dual images toward first and second directions, respectively, and blocking the first and second images toward the second and first directions, respectively, when the display cell displays the dual images

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

FIG. 3Ais a cross-sectional view of a liquid crystal display device according to an exemplary embodiment of the present invention,FIG. 3Bis a plan view of an array portion ofFIG. 3A, andFIG. 3Cis a cross-sectional view illustrating a method of displaying dual images in the liquid crystal display device ofFIG. 3A. As shown inFIGS. 3A to 3C, the liquid crystal display device includes a display cell310and a control cell350. The display cell310displays one image or dual images, as users need, and the control cell350controls light path of the images emitted from the main cell310.

The display cell310includes first and second substrates312and314, and a layer of liquid crystal molecules320between the two substrates312and314. The display cell310has a plurality of pixels P, and each pixel P has first, second and third sub-pixels SP1, SP2and SP3. The first, second and third sub-pixels SP1, SP2and SP3may emit red (R), green (G) and blue (B) colors, respectively. The first and second substrates312and314are transparent.

An array portion316is disposed on an inner surface of the first substrate312. In the array portion316, a gate line GL and a data line DL are disposed on the first substrate312and cross each other to define a sub-pixel region PA. A common line380is spaced apart from the gate line GL. A thin film transistor T is disposed adjacent to a crossing of the gate and data lines GL and DL. In each sub-pixel region PA, a pixel electrode372and a common electrode382are alternately arranged. The pixel electrode372is connected to the thin film transistor T through a connection line370. The common electrode382branches off from the common line380. The pixel and common electrodes372and382induce an in-plane electric field, and a region390between the pixel and common electrodes372and382is an aperture region where the liquid crystal molecules in the layer of liquid crystal molecules320are driven by the in-plane electric field.

On an inner surface of the second substrate314, a color filter layer is disposed. A color filter layer includes first, second and third color filters318a,318band318cin the corresponding sub-pixels SP1, SP2and SP3. The first, second and third color filters318a,318band318cmay be red (R), green (G) and blue (B) color filters, respectively. Although not shown in the drawings, a black matrix is disposed on the inner surface of the second substrate314. The black matrix may correspond to the gate and data lines GL and DL and the thin film transistor T.

First and second polarizing films332and334are disposed on outer surfaces of the first and second substrates312and314, respectively.

The display cell310driven in an IPS mode is explained in reference toFIGS. 3A to 3C. The display cell310may be driven in other modes, for example, an FFS mode or a VA mode. Although not shown in theFIGS. 3A to 3C, a backlight unit is disposed below the display cell310to supply light to the display cell310. The control cell350is disposed on the display cell310. The control cell350includes third and fourth substrates352and354and an electro-chromic material layer360between the two substrates352and354. The third and fourth substrates352and354are transparent.

A plurality of first electrodes356are disposed on an inner surface of the third substrate352and spaced apart from one another. A plurality of second electrodes358are disposed on an inner surface of the fourth substrate354and spaced apart from one another. The first and second electrodes356and358directly face each other. The first and second electrodes356and358may be made of a transparent conductive material, such as indium-tin-oxide (ITO), indium-zinc-oxide (IZO) and indium-tin-zinc-oxide (ITZO). The first and second electrodes356and358may have various sizes.

The electro-chromic material has a reversible color change property in accordance with an applied voltage. In other words, the electro-chromic material has a reversible color change corresponding to an electric field. Color of the electro-chromic material is changed reversibly by an electrochemical oxidation-reduction reaction. The electro-chromic material is colorless (transparent) for one of an oxidation and a reduction and has a color for the other of an oxidation and a reduction. The electro-chromic material may include at least one of tungsten oxide (WO3), molybdenum oxide (MoO3), titanium oxide (TiO3), vanadium oxide (V2O5), iridium oxide (IrO2), niobium oxide (Nb2O5) and nickel oxide (NiO).

Although not shown inFIGS. 3A to 3C, lines applying voltages to the first and second electrodes356and358are disposed on the inner surface of the third and fourth substrates352and354, respectively. Some of the plurality of first electrodes356may have a voltage applied and some of the plurality of second electrodes358may have a voltage applied when displaying dual images. The liquid crystal display device can display a single image or dual images. Hereinafter, methods of displaying a single image and dual images with the liquid crystal display device are explained.

To display a single image in the liquid crystal display device, the display cell310makes a single image. To do this, the gate lines GL are sequentially applied with an ON gate signal, and the thin film transistors T connected to the gate line GL applied with the ON gate signal are turned on. When the thin film transistors T are turned on, data signals for making the single image are applied to the corresponding sub-pixels SP1, SP2and SP3through the corresponding data lines DL. Accordingly, the single image desired is made in the display cell310.

The control cell350is entirely transparent when the single image is displayed in the liquid crystal display device, thereby allowing the single image to pass straight through. The electro-chromic material is colorless when the first and second electrodes356and358are not supplied with voltages and have color when the first and second electrodes356and358are supplied with voltages. All of the entire first and second electrodes356and358are not supplied with voltages, and thus the electro-chromic material layer360is transparent. Since the control cell350is transparent, light of the single image made in the display cell310passes straight through the control cell350. Therefore, users can see the single image desired. In particular, when the display cell310has a wide viewing angle property, the liquid crystal display device also has a wide viewing angle property, and thus users can see the single image over a wide range of various directions.

To display dual images in the liquid crystal display device, the display cell310makes dual images, referring toFIG. 3C. To do this, the gate lines GL are sequentially applied with an ON gate signal, and the thin film transistors T connected to the gate line GL applied with the ON gate signal are turned on. When the thin film transistors T are turned on, data signals for making the dual images are applied to the corresponding sub-pixels SP1, SP2and SP3through the corresponding data lines DL. In more detail, the data signals are divided into first and second data signals. The first data signals are for making a first image of the dual images, and the second data signals are for making a second image of the dual images. If the first data signals are supplied to the sub-pixels SP1, SP2and SP3of odd pixels P, the second data signals are supplied to the sub-pixels SP1, SP2and SP3of even pixels P. In other words, the first data signals and the second data signals are alternately applied to the sub-pixels SP1, SP2and SP3by the pixel P. Accordingly, the dual images desired are simultaneously made in the display cell310.

The control cell350is transparent and opaque alternately when the dual images are displayed in the liquid crystal display device, thereby guiding the dual images toward different directions desired. In other words, the control cell350has a transmissive region430and a blocking region440arranged alternately. The electro-chromic material is colorless when the first and second electrodes356and358are not supplied with voltages and has color when the first and second electrodes356and358are supplied with voltages. The first and second electrodes356and358of a number of M are not supplied with voltages to form the transmissive region430, and the first and second electrodes356and358of a number of N are supplied with voltages to form the blocking region440(where m and n may be equal or different). Accordingly, the transmissive region430and the blocking region440are alternately formed in the control cell350. The electro-chromatic material may be discolored on surfaces of the first and second electrodes356and358when voltages are applied. As shown inFIGS. 3A to 3C, the first and second electrodes356and358may have a size corresponding to the pixel P.

The arrangement of the alternated pixels P (or sub-pixels) for first and second images and the arrangement of the alternated transmissive and blocking regions430and440make light of the first image from the display cell310going toward a first direction410and not going toward a second direction420, and makes light of the second image from the display cell310going toward the second direction420and not going toward the first direction410. Accordingly, the first and second images are mainly displayed at the first and second directions, respectively, so that a main viewing angle of the first image is generally in the first direction410and a main viewing angle range of the second image is generally in the second direction420. Therefore, users generally viewing in the first direction can see the first image, and users generally viewing in the second direction can see the second image.

The transmissive region430may be disposed such that the transmissive region430overlaps both the pixel P for the first image and the pixel P for the second image. Further, the blocking region440may be disposed such that the blocking region440overlaps both the pixel P for the first image and the pixel P for the second image. The alternating number of the pixels may correspond to the alternating number of the transmission and blocking regions430and440.

FIGS. 4A to 4Eare cross-sectional views of liquid crystal display devices according to another exemplary embodiment of the present invention. The liquid crystal display devices ofFIGS. 4A to 4Eare similar to the liquid crystal display device ofFIGS. 3A to 3C, except for a structure of the control cell. Thus, explanations of parts similar to parts ofFIGS. 3A to 3Care omitted for simplicity.

As shown inFIG. 4A, first and second electrodes356and358have a size corresponding to the sub-pixel, different from those ofFIG. 3C. When dual images are displayed, three first and second electrodes356and358are not supplied with voltages to form a transmissive region430, and next three first and second electrodes356and358are supplied with voltages to form a blocking region440. A position relation between the transmissive and blocking regions430and440and the pixel is similar to a position relation ofFIG. 3C, and thus, the viewing angles for the dual images are similar to the main viewing angle ranges ofFIG. 3C.

As shown inFIG. 4B, first and second electrodes356and358have a size corresponding to the sub-pixel, like those ofFIG. 4A. When dual images are displayed, three first and second electrodes356and358are not applied with voltages to form a transmissive region430, and next three first and second electrodes356and358are applied with voltages to form a blocking region440. A position relation between the transmissive and blocking regions430and440and the pixel is different from a position relation ofFIG. 4A, and thus, the main viewing angles for the dual images are different from the main viewing angles ofFIG. 4A.

As shown inFIG. 4C, first and second electrodes356and358have a size less than the sub-pixel, different from those ofFIGS. 4A and 4B. When dual images are displayed, four first and second electrodes356and358are not applied with voltages to form a transmissive region430, and next four first and second electrodes356and358are applied with voltages to form a blocking region440. A position relation between the transmissive and blocking regions430and440and the pixel is similar to a position relation ofFIG. 4A, and thus, the main viewing angles for the dual images are similar to the main viewing angles ofFIG. 4A.

As shown inFIG. 4D, first and second electrodes356and358have a size less than the sub-pixel, like those ofFIG. 4C. When dual images are displayed, four first and second electrodes356and358are not applied with voltages to form a transmissive region430, and next four first and second electrodes356and358are applied with voltages to form a blocking region440. A position relation between the transmissive and blocking regions430and440and the pixel is different from a position relation ofFIG. 4C, and thus, the main viewing angles for the dual images are different from the main viewing angles ofFIG. 4C.

As shown inFIG. 4E, a control cell is similar to that ofFIG. 4A, except for a cell gap. A position relation between the transmissive and blocking regions430and440and the pixel is similar to a position relation ofFIG. 4A, and the cell gap i.e., a distance between the first and second electrodes356and358is more than that ofFIG. 4A. Therefore, the main viewing angles for the dual images are different from the main viewing angles ofFIG. 4A. As explained above, the main viewing angles for the dual images can be adjusted as the positions of the transmissive and blocking regions and the cell gap are adjusted.

FIG. 5is a cross-sectional view of a liquid crystal display device according to another exemplary embodiment of the present invention. The liquid crystal display device ofFIG. 5is similar to the liquid crystal display devices ofFIGS. 3A to 4E, except for arrangement of the sub-color filters. Thus, explanations of parts similar to parts ofFIGS. 3A to 4Eare omitted for simplicity.

As shown inFIG. 5, arrangement of color filters is different from arrangement of color filters ofFIGS. 3A to 4E. As shown inFIGS. 3A to 4E, when dual images are displayed, since color filters are arranged such that one pixel makes a first image and adjacent pixel makes a second image, the color filters having the same color are spaced apart by three sub-pixels.FIGS. 3A to 4Eshow a structure that a pixel for the first image and a pixel for the second image are adjoined and alternately arranged. InFIG. 5, two color filters having the same color are adjoined. One of the adjacent two color filters of the same color is for a first image, and the other of the adjacent two color filters of the same color is for a second image.

The arrangement of the alternated sub-pixels for first and second images and the arrangement of the alternated transmissive and blocking regions make light of the first image from the display cell310going toward a first direction410and not going toward a second direction420, and makes light of the second image from the display cell310going toward the second direction420and not going toward the first direction410. Accordingly, the first and second images are mainly displayed at the first and second directions, respectively, so that a main viewing angle of the first image is the first direction410and a main angle of the second image is the second direction420. Therefore, users in the first direction can see the first image, and users in the second direction can see the second image. The alternating number of the sub-pixels may correspond to the alternating number of the transmission and blocking regions430and440. The transmissive region430may be disposed such that the transmissive region430overlaps the adjacent two same color filters for the first and second images, and the blocking region440may be also disposed such that the blocking region440overlaps the adjacent two different color filters for the first and second images.

FIG. 6is a cross-sectional view of a liquid crystal display device according to another exemplary embodiment of the present invention. The liquid crystal display device ofFIG. 6is similar to the liquid crystal display device ofFIGS. 3A to 3C, except for a structure of the control cell. Thus, explanations of parts similar to parts ofFIG. 3A to 3Care omitted for simplicity. As shown inFIG. 6, first and second electrodes556and558are formed only in a blocking region540and not in a transmissive region530. Accordingly, when dual images are displayed, the transmissive region530and the blocking region540are fixed, and thus main viewing angles for each of the dual images are also fixed.

FIG. 7is a cross-sectional view of a liquid crystal display device according to another exemplary embodiment of the present invention. The liquid crystal display device ofFIG. 7is similar to the liquid crystal display device ofFIG. 5, except for a structure of the control cell. Thus, explanations of parts similar to parts ofFIG. 5are omitted for simplicity. As shown inFIG. 7, first and second electrodes556and558are formed only in a blocking region540and not in a transmissive region530. Accordingly, when dual images are displayed, the transmissive region530and the blocking region540are fixed, and thus main viewing angles for each of the dual images are also fixed.

As explained in the above exemplary embodiments, the display cell makes a single image or dual images, and the control cell selectively adjusts light path depending on the number of images made by the display cell. Therefore, not only the single image but also the dual images having the different main viewing angles can be displayed effectively. The main viewing angles can be adjusted as positions of the transmissive and blocking regions and the cell gap are adjusted.

In the above exemplary embodiments, a liquid crystal cell is mainly explained as the display cell. However, other type cells can be used as the display cell, such as a plasma display panel and an organic electroluminescent display, as long as the cells of these displays can make a single image and dual images like the above-described liquid crystal cell. An electro-chromatic cell is mainly explained as the control cell. However, other types of light guide cells can be used as the control cell if those cells can adjust a light path like the electro-chromatic cell. In the above exemplary embodiments, the display of the dual images is mainly explained. However, display of more than dual images can be achieved by adjusting the arrangement of the pixels (or sub-pixels) and the transmissive and blocking regions.

It will be apparent to those skilled in the art that various modifications and variations can be made in the method of fabricating the display device and the method of fabricating the display device the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.