Display apparatus including pixels having improved brightness and contrast ratio

A display apparatus having pixel areas defined on a substrate. First color pixels having a white color and second color pixels having a color different from that of the first color pixels are aligned in each pixel area in the form of a matrix. The second color pixels are adjacent to the first color pixels in the row and column directions.

CROSS-REFERENCE TO RELATED APPLICATION

This application relies for priority upon Korean Patent Application No. 10-2007-42721 filed on May 2, 2007, the contents of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display apparatus. More particularly, the present invention relates to a display apparatus capable of providing improved display quality.

2. Description of the Related Art

In general, display apparatuses display images corresponding to data processed in an information processor. The display apparatuses are classified into various types according to the method of displaying images and components used to display the images. For instance, an electrophoretic display apparatus includes an electrophoretic layer between two transparent substrates to display images.

The electrophoretic display apparatus includes top and bottom electrodes formed on two opposite substrates, respectively. The electrophoretic layer including first and second particles is provided between the top and bottom electrodes. The first particles are charged with a polarity opposite to that of the second particles and have a color different from that of the second particles.

If an electric field is applied between the top and bottom electrodes due to the electric potential between the top and bottom electrodes, the alignment state of the first and second particles is changed between the top and bottom electrodes. As a result, when an external light is reflected from the first particles, a viewer may recognize the color of the first particles. When the external light is reflected from the second particles, the viewer may recognize the color of the second particles.

However, because the electrophoretic display apparatus is a reflective display apparatus, the brightness of the image is lower as compared to that of other display apparatuses having additional light sources.

SUMMARY OF THE INVENTION

Therefore, the present invention provides a display apparatus capable of improving a display quality thereof.

In one aspect, a display apparatus includes a first base substrate on which pixel areas are defined, a second base substrate facing the first base substrate, pixel electrodes formed on the first base substrate, a common electrode formed on the second base substrate, and color pixels formed on the first base substrate or the second base substrate corresponding to the pixel areas, respectively.

The color pixels include first color pixels and second color pixels. The first color pixels represent a white color and the second color pixels represent a color different from that of the first color pixels. The second color pixels have an area equal to or less than an area of the first color pixels. The brightness of the display apparatus is improved by the first color pixel, so that the display quality of the display apparatus is improved.

In another aspect, a display apparatus includes color pixels consisting of first white color pixels and second color pixels representing a color different from the color of the first color pixels. The second color pixels are aligned in a form of a matrix in cooperation with the first color pixels and positioned adjacent to the first color pixels in row and column directions.

That is, the first color pixels are adjacent to the second color pixels in the column and row directions in the display apparatus and the second color pixels are adjacent to the first color pixels in the column and row directions in the display apparatus. Thus, the brightness of the display apparatus is improved by the first color pixels. In addition, light leakage phenomenon that occurs when the first color pixels are consecutively aligned may be prevented.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention are described in detail with reference to accompanying drawings. However, the present invention is not limited to the following embodiments but includes various applications and modifications. The following embodiments are provided to clarify the technical spirit disclosed in the present invention and to sufficiently transmit the technical spirit of the present invention to the one having mean knowledge and skill in this field. Therefore, the scope of the present invention is not limited to the following embodiments. In addition, the size of the layers and regions of the attached drawings along with the following embodiments are simplified or exaggerated for precise explanation or emphasis and the same reference numeral represents the same component.

FIG. 1is a plan view showing an electrophoretic display apparatus500aaccording to a first embodiment of the present invention, andFIG. 2is a plan view showing a thin film transistor substrate of the electrophoretic display apparatus500ashown inFIG. 1.

Referring toFIGS. 1 and 2, the electrophoretic display apparatus500aincludes an opposite substrate200a, a thin film transistor (TFT) substrate100facing the opposite substrate200a, and an electrophoretic layer350(see,FIG. 3) interposed between the opposite substrate200aand the TFT substrate100.

The opposite substrate200ais a transparent glass substrate. A red pixel R having a red color, a green pixel G having a green color, and a blue pixel B having a blue color are formed on the opposite substrate200a.

The red pixel R includes a red filter410(see,FIG. 3) formed on the opposite substrate200a. The red pixel R is defined as an area showing the red color. That is, a white light passing through the red filter is filtered to have red color components, so that the red color is displayed to the exterior.

In the same manner, the green pixel G and the blue pixel B are defined as areas showing the green color and the blue color, and include the green filter430(see,FIG. 3) and the blue color420(see,FIG. 3), respectively.

The red pixel R, the green pixel G and the blue pixel B are aligned on the opposite substrate200ain the form of a matrix. The red pixel R, the green pixel G, and the blue pixel B correspond to pixel electrodes PE formed on the TFT substrate100in a one-to-one correspondence.

In addition, a white pixel W having a white color is aligned on the opposite substrate200a. The white pixel W is defined on a predetermined area of the opposite substrate200awhere two of the red pixel R, the green pixel G and the blue pixel B are spaced apart from each other. As a result, the opposite substrate200ahas no color filter corresponding to the white pixel W. Therefore, according to the present exemplary embodiment, when a light irradiated onto the white pixel W is reflected from the white particles, an external white light is reflected from the white particles, so that the white color is displayed. The white pixel W is described later in more detail with reference toFIG. 3.

The red pixel R, the green pixel G, the blue pixel B, and the white pixel W are aligned in the form of the matrix according to first and second rules.

According to the first rule, the white pixel W is adjacent to the red pixel R, the green pixel G, and the blue pixel B in the first and second directions D1and D2. In other words, one white pixel W is not adjacent to the other white pixel W in the first and second directions D1and D2, but adjacent to one pixel of the red pixel R, the green pixel G, and the blue pixel B.

According to the second rule, the red pixel R, the blue pixel B, and the green pixel G are repeatedly aligned in each row of the matrix, and only one pixel of the red pixel R, the blue pixel B and the green pixel G is aligned in each column of the matrix.

When the matrix is divided into sub-matrices A, each sub-matrix A includes three white pixels W, one red pixel R, one green pixel G and one blue pixel B. Thus, in the sub-matrix A having six pixels, the white pixel W has a proportion of 50%. In addition, since the matrix consists of a plurality of sub-matrices A, the white pixel W has a proportion of 50% in the matrix.

Accordingly, the number of the white pixels W provided in the electrophoretic display apparatus500ais identical to the sum of the red pixels R, the green pixels R and the blue pixels B. As a result, the brightness of the electrophoretic display apparatus500amay be improved by means of the white pixels W.

In addition, since the electrophoretic display apparatus500amay display the white color and black color using the electrophoretic layer350(see,FIG. 3), the contrast ratio of the electrophoretic display apparatus500amay be improved. For instance, when the electrophoretic display apparatus500adisplays the white color, the white pixel W exhibits the white color. When the electrophoretic display apparatus500adisplays the black color, the white pixel W exhibits the black color. That is, the brightness of the electrophoretic display apparatus500ais not improved in all display modes, but is improved only when the electrophoretic display apparatus500adisplays the white color using the white pixel W. As a result, the contrast ratio of the electrophoretic display apparatus500amay be improved.

In addition, since the white pixels W are not consecutively aligned, light leakage phenomenon may be prevented in the electrophoretic display apparatus500a. That is, since the white pixels W are aligned in the row and column directions alternately with other pixels representing the color different from that of the white pixel W, the brightness may be uniformly improved over the whole pixel area of the electrophoretic display apparatus500a.

The TFT substrate100is a transparent glass substrate on which pixel electrodes PE are aligned in the form of the matrix. Each pixel electrode PE is electrically connected to the thin film transistor T. The thin film transistor T receives the gate signal from the gate lines GL and switches the data signal, which is transferred to the pixel electrodes PE from the data lines, by using the gate signal.

Pixel electrodes PE formed on the TFT substrate100correspond to the red pixel R, the green pixel G, the blue pixel B, and the white pixel W, respectively. Accordingly, the pixel electrodes PE are aligned in the form of the matrix on the TFT substrate100.

FIG. 3is a sectional view taken along line I-I′ shown inFIG. 1according to an embodiment of the present invention.

Referring toFIG. 3, a first insulating layer110is formed on the TFT substrate100and data lines DL are formed on the first insulating layer110. In addition, a second insulating layer120is formed on the data lines DL in order to insulate the thin film transistor T (see,FIG. 2) from the pixel electrodes PE. The pixel electrodes PE are formed on the second insulating layer120. The pixel electrodes PE are provided in the TFT substrate100to form the electric field in cooperation with a common electrode220of the opposite substrate200afacing the TFT substrate100. The pixel electrode PE is a transparent conductive layer including ITO (indium tin oxide) or IZO (indium zinc oxide).

The opposite substrate200afurther includes a red filter410, a blue filter420, and a green filter430. The red filter410is positioned in a red pixel area of the opposite substrate200a, the blue filter420is positioned in a blue pixel area of the opposite substrate200a, and the green filter430is positioned in a green pixel area of the opposite substrate200a.

A planar layer210is formed on the red filter410, the blue filter420and the green filter430. The planar layer210covers the red filter410, the blue filter420and the green filter430, and the common electrode220is planarly formed on the planar layer210.

The common electrode220is provided on the opposite substrate200ato form the electric field in cooperation with the pixel electrode PE. Similar to the pixel electrode PE, the common electrode220includes ITO (indium tin oxide) or IZO (indium zinc oxide).

The electrophoretic layer350is interposed between the TFT substrate100and the opposite substrate200a. According to the first embodiment of the present invention, the electrophoretic layer350includes capsules310.

Each capsule310includes particles305charged with a positive polarity, opposite particles308charged with a negative polarity, and an insulating material303. In addition, each particle305includes TiO2representing the white color, and each opposite particle308includes carbon black representing the black color.

If the electric field is not formed between the pixel electrode PE and the common electrode220, the particles305and opposite particles308are randomly aligned in the capsule310. In contrast, if the electric field is formed between the pixel electrode PE and the common electrode220, the alignment state of the particles305and opposite particles308is changed according to the direction of the electric field.

For instance, if the electric field is directed from the pixel electrode PE to the common electrode220, the particles305move toward the common electrode220in the capsule310, and the opposite particles308move toward the pixel electrode PE in the capsule310. Thus, the external white light irradiated onto the opposite substrate220bis reflected from the particles305, so the user may recognize the white color represented by the particles305.

That is, the color (white color or black color) represented by the capsule310is determined according to the alignment state of the particles305and the opposite particles308in the capsule310.

FIG. 4is a sectional view taken along line I-I′ shown inFIG. 1according to another embodiment of the present invention.

Referring toFIG. 4, first to fourth electrophoretic layers360,390,370and380are interposed between the TFT substrate100and the opposite substrate200b.

The first electrophoretic layer360is interposed between the TFT substrate100and the opposite substrate200bin correspondence with the red pixel area. The first electrophoretic layer360includes first capsules355and each first capsule355has first particles357, which are charged with the positive polarity and represent the red color, first opposite particles358, which are charged with the negative polarity and represent the black color, and an insulating material353. Thus, the alignment state of the first particles357and the first opposite particles358are changed in the first capsule355according to the electric field formed between the common electrode220and the pixel electrode PE.

For instance, if the electric field is directed from the pixel electrode PE to the common electrode220, the first particles357move toward the common electrode220in the first capsule355, and the first opposite particles358move toward the pixel electrode PE in the capsule355. Thus, the external white light irradiated onto the opposite substrate220bis reflected from the first particles357, so the user may recognize the green pixel area as the red color represented by the first capsule355.

The second electrophoretic layer370is interposed between the TFT substrate100and the opposite substrate200bin correspondence with the white pixel area. The second electrophoretic layer370includes second capsules365and each second capsule365includes second particles367, which are charged with the positive polarity and represent the white color, second opposite particles368, which are charged with the negative polarity and represent the black color, and an insulating material363. Thus, the white color or the black color is represented according to the alignment state of the second particles367and the second opposite particles368in the second capsule365.

The third electrophoretic layer380is interposed between the TFT substrate100and the opposite substrate200bin correspondence with the green pixel area. The third electrophoretic layer380includes third capsules375and each third capsule375includes third particles377, which are charged with the positive polarity and represent the green color, third opposite particles378, which are charged with the negative polarity and represent the black color, and an insulating material373. Thus, the green color or the black color is represented according to the alignment state of the third particles377and the third opposite particles378in the third capsule375.

The fourth electrophoretic layer390is interposed between the TFT substrate100and the opposite substrate200bin correspondence with the blue pixel area. The fourth electrophoretic layer390includes fourth capsules385and each fourth capsule385includes fourth particles387, which are charged with the positive polarity and represent the blue color, fourth opposite particles388, which are charged with the negative polarity and represent the black color, and an insulating material383. Thus, the blue color or the black color is represented according to the alignment state of the fourth particles387and the fourth opposite particles388in the fourth capsule385.

FIG. 5is a plan view showing an electrophoretic display apparatus500baccording to a second embodiment of the present invention. In the following description ofFIG. 5, the same reference numerals are assigned to the same elements and the detailed description thereof will be omitted in order to avoid redundancy.

Referring toFIG. 5, the red pixel R, the green pixel G, the blue pixel B, and the white pixel W are aligned on the opposite substrate200bin the form of the matrix according to first and second rules.

According to the first rule, the white pixel W is adjacent to the red pixel R, the green pixel G, and the blue pixel B in the first and second directions D1and D2. In other words, one white pixel W is not adjacent to another white pixel W in the first and second directions D1and D2, but is adjacent to one pixel of the red pixel R, the green pixel G, and the blue pixel B.

According to the second rule, only one pixel of the red pixel R, the blue pixel B and the green pixel G is aligned in each row of the matrix, and the red pixel R, the blue pixel B and the green pixel G are repeatedly aligned in each column of the matrix.

When the matrix is divided into sub-matrices S, each sub-matrix S includes three white pixels W, one red pixel R, one green pixel G and one blue pixel B. Thus, in the sub-matrix S having six pixels, the white pixel W has a proportion of 50%. In addition, since the matrix consists of a plurality of sub-matrices S, the white pixel W has a proportion of 50% in the matrix.

Accordingly, the number of white pixels W provided in the electrophoretic display apparatus500bis identical to the sum of the red pixels R, the green pixels R and the blue pixels B. As a result, the brightness of the electrophoretic display apparatus500amay be improved by means of the white pixels W.

Therefore, similar to the electrophoretic display apparatus500aaccording to the first embodiment of the present invention, the electrophoretic display apparatus500baccording to the second embodiment of the present invention may improve the brightness and contrast ratio thereof. Since the white pixels W are not consecutively aligned, light leakage phenomenon may be prevented in the electrophoretic display apparatus500b. Although electrophoretic layers of the electrophoretic display apparatus500bare not described in the second embodiment, the electrophoretic display apparatus500baccording to the second embodiment of the present invention may include the electrophoretic layers in the form of capsules310(see,FIG. 3) or first to fourth electrophoretic layers360to390(see,FIG. 5).

FIG. 6is a plan view showing an electrophoretic display apparatus500caccording to a third embodiment of the present invention. In the following description ofFIG. 6, the same reference numerals are assigned to the same elements and the detailed description thereof will be omitted in order to avoid redundancy.

Referring toFIG. 6, the red pixel R, the green pixel G, the blue pixel B and the white pixel W are aligned on the opposite substrate200bin the form of the matrix. The matrix includes odd rows, in which the red pixel R, the green pixel G, and the blue pixel B are sequentially and repeatedly aligned, and even rows, in which only the white pixels W are aligned. The odd and even rows are alternately aligned in the first direction D1.

In other words, in the matrix, the red pixel R, the green pixel G or the blue pixel B is interposed between the white pixels W in the first direction D1.

When the matrix is divided into sub-matrices C, each sub-matrix C includes three white pixels W, one red pixel R, one green pixel G and one blue pixel B. Thus, in the sub-matrix C having six pixels, the white pixel W has a proportion of 50%. In addition, since the matrix consists of a plurality of sub-matrices C, the white pixel W has a proportion of 50% in the matrix.

Therefore, similar to the electrophoretic display apparatuses500aand500baccording to the first and second embodiments of the present invention, the electrophoretic display apparatus500caccording to the third embodiment of the present invention may improve the brightness and contrast ratio thereof.

Although electrophoretic layers of the electrophoretic display apparatus500care not described in the third embodiment, the electrophoretic display apparatus500caccording to the third embodiment of the present invention may include the electrophoretic layers in the form of capsules310(see,FIG. 3) or first to fourth electrophoretic layers360to390(see,FIG. 5) according to the first and second embodiments.

FIG. 7Ais a plan view of a first photo mask used to manufacture the electrophoretic display apparatus according to the first embodiment of the present invention,FIG. 7Bis a plan view of a second photo mask used to manufacture the electrophoretic display apparatus according to the second embodiment of the present invention, andFIGS. 8A to 8Gare views showing the manufacturing procedure for the electrophoretic display apparatus according to the first embodiment of the present invention.

In detail,FIG. 7AandFIGS. 8A to 8Gshow the case in which one photo mask is used for three photolithograph processes to form the pixels on the opposite substrate200ain the alignment state as shown inFIG. 1. The detailed process of forming the pixels in the alignment state as shown inFIG. 5by using the second photo mask is similar to the process shown inFIGS. 8A to 8G, and accordingly a description thereof is not required.

For the purpose of convenience, a pixel area formed on the opposite substrate200awill be denoted as a pixel area PAab if the pixel area is aligned in an athrow and a bthcolumn in the matrix.

The opposite substrate200ais disposed under the first photo mask800ainFIG. 7Ain order to facilitate explanation of the first photo mask800a. Light transmission units803to810are defined on the first photo mask800a. According to an embodiment of the present invention, the light transmission units803to810are obtained by cutting predetermined portions of the first photo mask800a. Therefore, the light proceeding toward the opposite substrate200afrom the top of the first photo mask800ais partially irradiated onto the opposite substrate200athrough the light transmission units803to810.

Pixel areas PA11to PA40are defined on the opposite substrate200a. As described above, the pixels are formed in the pixel areas PA11to PA40on the opposite substrate200a.

If the alignment state of the light transmission units803to810is identical to the alignment state of the red pixel R, the green pixel G or the blue pixel B, the red pixel R, the green pixel G or the blue pixel B having the alignment state identical to that of the pixels shown inFIG. 1may be formed on the opposite substrate200aby using the first photo mask800a. That is, the red pixel R, the green pixel G, the blue pixel B, and white pixel W may be formed on the opposite substrate200aby using one photo mask.

For instance, after covering the opposite substrate200awith the first photo mask800asuch that the light transmission units803to810are placed on first pixel areas PA11, PA17, PA24, PA30, PA37, PA44, and PA40, the first exposure process is performed relative to the opposite substrate200a, thereby forming the red pixel R on the first pixel areas.

In order to form the blue pixel B, the first photo mask800ais moved in the second direction D2such that the light transmission units803to810are placed on second pixel areas PA13, PA19, PA26, PA33, PA39, and PA46, and then the second exposure process is performed relative to the opposite substrate200a, thereby forming the blue pixel B on the second pixel areas.

Similarly, in order to form the green pixel G, the first photo mask800ais moved in the second direction D2such that the light transmission units803to810are placed on third pixel areas PA15, PA22, PA28, PA35, PA42, and PA48, and then the third exposure process is performed relative to the opposite substrate200a, thereby forming the green pixel G on third second pixel areas.

Therefore, the red pixel R, the green pixel G, and the blue pixel B having the alignment state identical to that of the pixels shown inFIG. 1may be formed on the opposite substrate200aby using one photo mask800a. The white pixels W are defined on pixel areas (for instance, PA12, PA14, PA16, PA18, etc) where two of the red pixel R, the green pixel G, and the blue pixel B are spaced apart from each other.

Referring toFIG. 7B, light transmission units813,815,818and828are defined on the second photo mask800b. The red pixel R, the blue pixel B, the green pixel G, and the white pixel W having the alignment state as shown inFIG. 5may be formed on the opposite substrate200aby performing the exposure process three times using one second photo mask800b.

For instance, the red pixel R is formed on the opposite substrate200ain correspondence with the light transmission units813,815,818and828through the first exposure process. Then, the photo mask is moved in the first direction D1by a predetermined distance corresponding to one pixel area, and then is moved in the second direction D2by a predetermined distance corresponding to one pixel area. In this state, the second exposure process is performed to form the green pixel G. In addition, after the green pixel G has been formed, the photo mask is moved in the first direction D1by a predetermined distance corresponding to one pixel area, and then is moved in the second direction D2by a predetermined distance corresponding to one pixel area. In this state, the third exposure process is performed to form the blue pixel B.

In this manner all of the red pixel R, the green pixel G, and the blue pixel B having the alignment state identical to the alignment state of the pixels shown inFIG. 5may be formed on the opposite substrate200aby using one second photo mask800b.

FIGS. 8A to 8Gare views showing the manufacturing procedure for the electrophoretic display apparatus500aaccording to the first embodiment of the present invention. In detail,FIGS. 8A to 8Gshow the process of forming the red pixel R, the green pixel G, and the blue pixel B on the opposite substrate200aby using the first photo mask800a. The following description ofFIGS. 8A to 8Gincludes the above-mentioned first to third exposure process using the first photo mask800a.

Referring toFIG. 8A, in order to form the red pixel R on the opposite substrate200ain correspondence with the pixel areas PA11and PA17, a red photoresist film410ais primarily formed on the opposite substrate200a. When the red photoresist film410ahas been formed on the opposite substrate200a, the opposite substrate200ais covered with the first photo mask800ain such a manner that the first and second light transmission units803and805are aligned corresponding to the pixel areas PA11and PA17, respectively. Then, the first exposure process is performed by irradiating the light that reacts with the red photoresist film410aonto the opposite substrate200a.

The light is selectively irradiated onto the red photoresist film410aby means of the first photo mask800a, so that predetermined portions of the red photoresist film410acorresponding to the pixel areas PA11and PA17may have special property. That is, the predetermined portions of the red photoresist film410aare not etched even if the developing solution is applied thereto.

Referring toFIG. 8B, after the first exposure process has been completed, the red photoresist film410ais developed, so that red filters410and415are formed on the opposite substrate200ain correspondence with the pixel areas PA11and PA17.

Referring toFIG. 8C, in order to form the green pixel G on the opposite substrate200ain correspondence with the pixel areas PA13and PA19, a green photoresist film410bis primarily formed on the opposite substrate200a.

When the green photoresist film410bhas been formed on the opposite substrate200a, the opposite substrate200ais covered with the first photo mask800ain such a manner that the first and second light transmission units803and805are aligned corresponding to the pixel areas PA13and PA19, respectively. Then, the second exposure process is performed by irradiating the light that reacts with the green photoresist film410bonto the opposite substrate200a.

As a result, the light is selectively irradiated onto the green photoresist film410bby means of the first photo mask800a, so that predetermined portions of the green photoresist film410bcorresponding to the pixel areas PA13and PA19may have special property. That is, the predetermined portions of the green photoresist film410bare not etched even if the developing solution is applied thereto.

Referring toFIG. 8D, after the second exposure process has been completed, the green photoresist film410bis developed, so that green filters420and425are formed on the opposite substrate200ain correspondence with the pixel areas PA13and PA19.

Referring toFIGS. 8E and 8F, a blue photoresist film430ais formed on the opposite substrate200a, and then the opposite substrate200ais covered with the first photo mask800ain such a manner that the first and second light transmission units803and805are aligned corresponding to the pixel areas PA15and PA21.

After that, the third exposure process and the developing process are performed relative to the opposite substrate200a, so that blue filters430and435are formed on the opposite substrate200acorresponding to the pixel areas PA15and PA21, respectively.

Referring toFIG. 8G, a planarization layer215and the common electrode220are sequentially formed on the opposite substrate200a. Then, the TFT substrate100is combined with the opposite substrate200afrom the top of the opposite substrate200a. In addition, the electrophoretic layer350is interposed between the opposite substrate200aand the TFT substrate100.

According to an embodiment of the present invention, the electrophoretic layer350includes capsules310. Each capsule310includes particles and opposite particles therein, in which the particles represent the color different from that of the opposite particles and are charged with polarity different from that of the opposite particles. Accordingly, when the electric field is formed between the pixel electrode PE and the common electrode, the alignment state of particles and opposite particles is changed in the capsule310, so that the color corresponding to the alignment state is displayed to the exterior.

As described above, the brightness of the display apparatus is improved by means of the white pixels provided in the pixel areas of the display apparatus. In addition, when the display apparatus exhibits the black color, the white pixel W displays the black color. Further, when the display apparatus exhibits the white color, the white pixel W displays the white color, so the contrast ratio of the display apparatus may be improved.