Pixel structure of electroluminescent display panel

A pixel structure of an electroluminescent display panel includes display pixel units. Each display pixel unit is composed of one first sub-pixel, one second sub-pixel, and one third sub-pixel. Each first sub-pixel is disposed adjacent to another first sub-pixel along a column direction to form a first pixel unit with a first frame. Each second sub-pixel is disposed adjacent to another second sub-pixel along the column direction to form a second pixel unit with a second frame. Each third sub-pixel is disposed adjacent to another third sub-pixel along the column direction to form a third pixel unit with a third frame. Each first, second, and third pixel units respectively have an identical first length along the column direction. Each first pixel unit and one adjacent first pixel unit disposed in a different row are shifted relatively along the row direction by the first length.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pixel structure of an electroluminescent display panel, and more particularly, to the pixel structure with the higher aperture ratio and the higher alignment tolerance by adjusting the arrangement of the sub-pixels.

2. Description of the Prior Art

Without a color filter but with the advantage of self-luminous characteristic (i.e., without a backlight module) and low power consumption, an organic electroluminescent display has been regarded as a promising candidate to replace LCD display technology for the next generation display technology for long.

Please refer toFIGS. 1 and 2.FIG. 1is a schematic diagram illustrating a conventional pixel structure of an organic electroluminescent display panel.FIG. 2is a schematic diagram illustrating a conventional shadow mask. As shown inFIGS. 1 and 2, the shadow mask100M with a plurality of stripe openings100H extending along a column direction Y is employed to perform a vapor deposition process of organic luminescent materials in the manufacturing process of the pixel structure100of the conventional organic electroluminescent display panel so as to form a plurality of blue sub-pixels120B, a plurality of green sub-pixels120G and a plurality of red sub-pixels120R on a substrate110. Each of the blue sub-pixels120B, each of the green sub-pixels120G and each of the red sub-pixels120R are alternately disposed in a row direction X. Each of the display pixel units120is composed of one of the blue sub-pixels120B, one of the green sub-pixels120G and one of the red sub-pixels120R disposed adjacent to one another along the row direction X. The blue sub-pixels120B in each column, the green sub-pixels120G in each column and the red sub-pixels120R in each column, which are adjacent to each other along the column direction Y, are respectively formed through one single stripe opening100H on the shadow mask100M by vapor deposition processes of different organic luminescent materials. This kind of arrangement of the sub-pixels is generally referred to as a stripe pixel arrangement structure. In this structure, according to alignment precision and fabrication variation of the vapor deposition process, there must be enough space among the sub-pixels to prevent the materials from being mixed in the vapor deposition process and affecting the manufacturing yield. Relatively, there must be enough space among the openings100H on the shadow mask100M to ensure enough structure strength. Accordingly, the distribution density of the sub-pixels, in this condition, is limited, thereby restricting the resolution. Moreover, the aperture ratio of each of sub-pixels and the fabrication of the shadow mask100M are affected negatively.

SUMMARY OF THE INVENTION

It is one of the objectives of the invention to provide a pixel structure of an electroluminescent display panel, thereby increasing the aperture ratio and the alignment tolerance in a vapor deposition process by adjusting the arrangement of the sub-pixels.

To achieve the purposes described above, an embodiment of the invention provides a pixel structure of an electroluminescent display panel. The pixel structure of the electroluminescent display panel includes a substrate and a plurality of display pixel units. The display pixel units are disposed on the substrate. Each of the display pixel units is composed of a first sub-pixel, a second sub-pixel and a third sub-pixel. The first sub-pixel, the second sub-pixel and the third sub-pixel are arranged in a delta arrangement. The first sub-pixel of each of the display pixel units is disposed adjacent to one first sub-pixel of an adjacent display pixel unit in a column direction. Two of the first sub-pixels adjacent to each other compose a first pixel unit. The second sub-pixel of each of the display pixel units is disposed adjacent to the second sub-pixel of the adjacent display pixel unit in the column direction. Two of the second sub-pixels adjacent to each other compose a second pixel unit. The third sub-pixel of each of the display pixel units is disposed adjacent to one third sub-pixel of an adjacent display pixel unit in the column direction. Two of the third sub-pixels adjacent to each other compose a third pixel unit. Each of the first pixel units, each of the second pixel units and each of the third pixel units respectively have a first length identical to one another along the column direction. The first pixel units disposed in any two different rows are shifted relatively along a row direction by the first length.

DETAILED DESCRIPTION

To provide a better understanding of the present invention, features of the embodiments will be made in detail. The embodiments of the present invention are illustrated in the accompanying drawings with numbered elements.

Please refer toFIGS. 3-7.FIG. 3is a schematic diagram illustrating a pixel structure of an electroluminescent display panel according to a first embodiment of the present invention.FIG. 4is a schematic diagram illustrating a locally enlarged view of the pixel structure of the electroluminescent display panel according to the first embodiment.FIG. 5is a schematic diagram illustrating a shadow mask according to the first embodiment.FIG. 6is a comparison diagram illustrating the relation curve between the resolution and the aperture ratio of the pixel structure in the electroluminescent display panel according to the first embodiment and the relation curve between the resolution and the aperture ratio of the pixel structure according to a control group.FIG. 7is a comparison diagram illustrating the relation curve between the resolution and the alignment tolerance of the pixel structure in the electroluminescent display panel according to the first embodiment and the relation curve between the resolution and the alignment tolerance of the pixel structure according to a control group. For brevity purposes, please note that the figures are only for illustration and the figures may not be to scale. The scale may be further modified according to different design considerations. As shown inFIGS. 3-5, the pixel structure201of the electroluminescent display panel provided in this embodiment includes a substrate210and a plurality of display pixel units220. The display pixel units220are disposed on the substrate210. Each of the display pixel units220is composed of a first sub-pixel221B, a second sub-pixel221G and a third sub-pixel221R. The first sub-pixel221B, the second sub-pixel221G and the third sub-pixel221R of each of the display pixel units220are arranged in a delta arrangement. The display pixel units220are arranged by alternate regular delta arrangement and inverted delta arrangement in a row direction X, but not limited thereto. The first sub-pixel221B of each of the display pixel units220is disposed adjacent to the first sub-pixel221B of an adjacent display pixel unit220in a column direction Y (i.e., the first sub-pixel221B of the adjacent display pixel unit220along a column direction Y). Two of the first sub-pixels221B adjacent to each other (i.e., the two mutually adjacent first sub-pixels221B) compose a first pixel unit230B. The second sub-pixel221G of each of the display pixel units220is disposed adjacent to the second sub-pixel221G of an adjacent display pixel unit220in the column direction Y. Two of the second sub-pixels221G adjacent to each other compose a second pixel unit230G. The third sub-pixel221R of each of the display pixel units220is disposed adjacent to the third sub-pixel221R of an adjacent display pixel unit220in the column direction Y. Two of the third sub-pixels221R adjacent to each other compose a third pixel unit230R. The column direction Y is preferably perpendicular to the row direction X. The first frame222B surrounds the two first sub-pixels221B adjacent to each other. The second frame222G surrounds the second sub-pixel221G adjacent to each other. The third frame222R surrounds the third sub-pixel221R adjacent to each other. Moreover, each of the first sub-pixels221B, each of the second sub-pixels221G and each of the third sub-pixels221R preferably comprise a rectangle sub-pixel respectively. Each of the first pixel units230B, each of the second pixel units230G and each of the third pixel units230R are preferably a rectangle pixel unit respectively. It is worth noting that the four edges are eased by rounding or chamfering to form a round or chamfer respectively because of the limitation or variation of fabrication or other consideration, but not limited thereto. In other embodiments, the shape of each of the first pixel units230B, each of the second pixel units230G, each of the third pixel units230R, the first frame222B, the second frame222G and the third frame222R may be a circle, a polygon (for example, a triangle, a diamond/rhombus, a quadrangle, a trapezoid, a pentagon, a hexagon or other suitable shapes), an arc/curve or other suitable shapes. At least one edge of the polygon may be eased by rounding or chamfering to form a round or chamfer, but not limited thereto. It is worth noting that the frames, such as the first frame222B, the second frame222G and the third frame222R, are substantially regarded as non-luminous regions. The sub-pixels, such as each of the first sub-pixels221B, each of the second sub-pixels221G and each of the third sub-pixels221R are substantially regarded as luminous regions. The non-luminous regions surround the luminous regions.

Each of the first pixel units230B, each of the second pixel units230G and each of the third pixel units230R respectively have a first length P1 identical to one another along the column direction Y. Each of the first pixel units230B and the first pixel unit230B disposed adjacently in an adjacent row are shifted relatively along the row direction X by the first length P1. Each of the second pixel units230G and the second pixel unit230G disposed adjacently in an adjacent row are shifted relatively along the row direction X by the first length P1. Each of the third pixel units230R and the third pixel unit230R disposed adjacently in an adjacent row are shifted relatively along the row direction X by the first length P1. Furthermore, each of the first pixel units230B, the adjacent second pixel unit230G along the row direction X and the third pixel unit230R adjacent to the second pixel unit230G along the row direction X constitute a second length P2 in row direction X, and the second length P2 is twice as long as the first length P1, but not limited thereto. It is worth noting that each of the first pixel units230B preferably partially neighbors with the second pixel unit230G adjacent to the first pixel unit230B and partially neighbors with the third pixel unit230R adjacent to the first pixel unit230B along the column direction Y. Each of the second pixel units230G preferably partially neighbors with the first pixel unit230B adjacent to the second pixel unit230G and partially neighbors with the third pixel unit230R adjacent to the second pixel unit230G along the column direction Y. Each of the third pixel units230R preferably partially neighbors with the first pixel unit230B adjacent to the third pixel unit230R and partially neighbors with the second pixel unit230G adjacent to the third pixel unit230R along the column direction Y. In other words, the first sub-pixels221B, which are disposed in the adjacent rows and belong to different first pixel units230B, are preferably shifted relatively along the row direction X. The second sub-pixel221G, which are disposed in the adjacent rows and belong to different second pixel unit230G, is preferably shifted relatively along the row direction X. The second sub-pixel221G, which are disposed in the adjacent rows and belong to different third pixel unit230R, is preferably shifted relatively along the row direction X. As a result, the first sub-pixel221B, the second sub-pixel221G and the third sub-pixel221R of each of the display pixel units220are closely disposed and arranged in the delta arrangement.

In the pixel structure201of the electroluminescent display panel in this embodiment, each of the first pixel units230B, each of the second pixel units230G and each of the third pixel units230R can be formed by performing evaporation processes of different luminous materials, such as organic luminescent materials, through the opening200H on the shadow mask200M. In other words, each of the openings200H can be employed to form one of the first pixel units230B, one of the second pixel units230G or one of the third pixel units230R. With the arrangement of each of the first pixel units230B, each of the second pixel units230G and each of the third pixel units230R in this embodiment, both the aperture ratio of the sub-pixel and the alignment tolerance of the shadow mask200M increase compared with the prior art shown inFIG. 1andFIG. 2. The width of each of the openings200H on the shadow mask200M are broadened, and the difficulty of fabricating the shadow mask200M is reduced. For example, as shown inFIG. 6, Table 1,FIG. 7and Table 2, the curve L1 represents the pixel structure of the electroluminescent display panel in this embodiment. The curve L2 represents a conventional stripe pixel structure serving as a control group. Compared with the conventional stripe pixel structure, the aperture ratio in the pixel structure of the electroluminescent display panel of this embodiment increases and the alignment tolerance is enhanced under the same solution requirements.

TABLE 1the aperture ratio inthe aperture ratio inPPIL1L21200.670.551500.590.462000.480.312570.370.163000.290.053260.250.003500.210.004000.150.004500.100.005000.050.00

Furthermore, as shown inFIGS. 3 and 4, the center of each of the first pixel units230B is aligned with the center of the second pixel unit230G adjacent to the first pixel unit230B and the center of the third pixel unit230R adjacent to the first pixel unit230B in the row direction X. Each of the first pixel units230B, each of the second pixel units230G and each of the third pixel units230R have a first width W1, a second width W2 and a third width W3 along the row direction X respectively. In this embodiment, preferably, the first width W1, the second width W2 and the third width W3 are substantially equal. In other words, preferably, each of the first pixel units230B, each of the second pixel units230G and each of the third pixel units230R have an identical width substantially along the row direction X. Preferably, each of the first pixel units230B, each of the second pixel units230G and each of the third pixel units230R have an identical area substantially, but not limited thereto. Moreover, the first sub-pixel221B, the second sub-pixel221G and the third sub-pixel221R are preferably sub-pixels of different colors respectively. For example, each of the first sub-pixels221B is preferably a blue sub-pixel, each of the second sub-pixels221G is preferably a green sub-pixel, and each of the third sub-pixels221R is preferably a red sub-pixel. However, the present invention is not limited to this and sub-pixels of other different colors may also be employed to achieve the desire effects according to other considerations. In addition, there is a first spacing S1 between two of the first sub-pixels221B (i.e., the two first sub-pixels221B) of each of the first pixel units230B. There is a second spacing S2 between two of the second sub-pixels221G of each of the second pixel units230G. There is a third spacing S3 between two of the third sub-pixels221R of each of the third pixel units230R. If the first sub-pixel221B, the second sub-pixel221G and the third sub-pixel221R are respectively a blue sub-pixel, a green sub-pixel and a red sub-pixel, the second spacing S2 is preferably wider than or substantially equal to the third spacing S3, and the third spacing S3 is preferably wider than or substantially equal to the first spacing S1 so as to adjust the display effect relating to the color mixing of the white light and the pixel color center of the white light in each of the display pixel units220, but not limited thereto. Moreover, there is a fourth spacing S4 between each of the first sub-pixels221B and the second sub-pixel221G adjacent to the first sub-pixel221B along the row direction X (i.e., the adjacent second sub-pixel221G along the row direction X) or between each of the first sub-pixels221B and the third sub-pixel221R adjacent to the first sub-pixel221B along the row direction X (i.e., the adjacent third sub-pixel221R along the row direction X). There is a fifth spacing S5 between each of the first sub-pixels221B and the second sub-pixel221G adjacent to the first sub-pixel221B along the column direction Y (i.e., the adjacent second sub-pixel221G along the column direction Y) or between each of the first sub-pixels221B and the third sub-pixel221R adjacent to the first sub-pixel221B along the column direction Y (i.e., the adjacent third sub-pixel221R along the column direction Y). The first spacing S1 is preferably smaller than the fourth spacing S4, and the first spacing S1 is preferably smaller than the fifth spacing S5.

In this embodiment, the first spacing S1, the second spacing S2 and the third spacing S3 are substantially equal, but not limited thereto. In addition, each of the first sub-pixels221B in this embodiment has a first color center WP1. Each of the second sub-pixels221G in this embodiment has a second color center WP2. Each of the third sub-pixels221R in this embodiment has a third color center WP3. Each of the display pixels units220in this embodiment has a pixel color center WP4. If the size of the first sub-pixel221B, the second sub-pixel221G and the third sub-pixel221R are substantially equal, and if the first sub-pixel221B, the second sub-pixel221G and the third sub-pixel221R are respectively a blue sub-pixel, a green sub-pixel and a red sub-pixel, the pixel color center WP4 of each of the display pixel units220comes closer to the second sub-pixel221G. Because the first sub-pixel221B, the second sub-pixel221G and the third sub-pixel221R of each of the display pixel units220are arranged in a delta arrangement, and because the display pixel units220are arranged by alternate regular delta arrangement and inverted delta arrangement along the row direction X, the pixel color centers WP4 of two of the display pixel units220adjacent to each other along the row direction X (i.e., the two adjacent display pixel units220along the row direction X) are shifted relatively along the column direction Y. In other words, there is a first distance D1 along the column direction Y between two of the first color centers WP1 in two of the display pixel units220adjacent to each other along the row direction X (i.e., the two first color centers WP1 in the two adjacent display pixel units220along the row direction X). There is a second distance D2 along the column direction Y between two of the second color centers WP2 in two of the display pixel units220adjacent to each other along the row direction X (i.e., the two second color centers WP2 in the two adjacent display pixel units220along the row direction X). There is a third distance D3 along the column direction Y between two of the third color centers WP3 in two of the display pixel units220adjacent to each other along the row direction X (i.e., the two third color centers WP3 in the two adjacent display pixel units220along the row direction X). The second distance D2 is preferably shorter than or substantially equal to the third distance D3. The third distance D3 is preferably shorter than or substantially equal to the first distance D1. If the first distance D1, the second distance D2 and the third distance D3 are substantially equal, the two pixel color centers WP4 of the two adjacent display pixel units220along the row direction X are shifted relatively along the column direction Y by a fourth distance D4. In the pixel structure201of the electroluminescent display panel in this embodiment, the relation among the first spacing S1, the second spacing S2 and the third spacing S3 can be modified according to other considerations. Alternatively, the relation among the first distance D1, the second distance D2 and the third distance D3 may be modified so that the pixel color center WP4, which may also be regarded as a white color center, of each of the display pixel units220can be adjusted to achieve the desired display effects.

Other embodiments or modifications will be detailed in the following description. In order to simplify and show the differences or modifications between the following embodiments and the above-mentioned embodiment, the same numerals denote the same components in the following description, and the similar parts are not detailed redundantly.

Please refer toFIGS. 8 and 9.FIG. 8is a schematic diagram illustrating a pixel structure of an electroluminescent display panel according to a second embodiment of the present invention.FIG. 9is a diagram illustrating the relation between the second spacing and the pixel color center of the pixel structure of the electroluminescent display panel according to the second embodiment. As shown inFIG. 8, the difference between the pixel structure202of the electroluminescent display panel in this embodiment and that in the first embodiment is that the second spacing S2 is preferably wider than the third spacing S3 and the first spacing S1 so that the second distance D2, which exists along the column direction Y between two of the second color centers WP2 in two of the display pixel units220adjacent to each other (the two second color centers WP2 in the two adjacent display pixel units220) along the row direction X, is shorter than the first distance D1 and the third distance D3. By this means, the fourth distance D4, by which the two pixel color centers WP4 of the two adjacent display pixel units220along the row direction X are shifted relatively along the column direction Y, is shortened and the relative shift condition of the pixel color centers WP4 of each of the display pixel units220is improved. As shown inFIGS. 8 and 9, in the case that the resolution is 257 ppi (pixel per inch) and that the first spacing S1 and the third spacing S3 are respectively about 13 micrometers, the line L3 represents the relation between the second spacing S2 and the second distance D2, and the line L4 represents the relation between the second spacing S2 and the fourth distance D4. As shown inFIG. 9and Table 3, as the second spacing S2 is broadened, the second distance D2 is shortened. At the same time, the fourth distance D4, by which the two pixel color centers WP4 of the two adjacent display pixel units220along the row direction X are shifted relatively along the column direction Y, is shortened and even approaches zero—that is to say, the two pixel color centers WP4 of the two adjacent display pixel units220along the row direction X are substantially aligned along a straight line parallel to the row direction X. In terms of the display quality, the smaller the second distance D2 and the fourth distance D4 are, the better the display quality to display a line and the less obvious the jagged edge is. Theoretically, the wider the second spacing S2, the shorter the second distance D2 and the fourth distance D4, thereby achieving better display quality. In practical, as the second spacing S2 becomes wider, the life duration of the second sub-pixel221G is shorten because the aperture ratio decreases. Therefore, preferably, the second spacing S2 is wider than or substantially equal to the first spacing S1 while the second spacing S2 is less than three times the first spacing S1. More preferably, the second spacing S2 is wider than or substantially equal to the first spacing S1 while the second spacing S2 is less than two times the first spacing S1. It is worth noting that the aforementioned adjustment approaches focus on the adjustment of the second sub-pixel221G, but the present invention is not limited to this and the size and the color centers of the sub-pixels of other colors may be modified as well to achieve the required effects.

Please refer toFIGS. 10 and 11.FIG. 10is a schematic diagram illustrating a pixel structure of an electroluminescent display panel according to a third embodiment of the present invention.FIG. 11is a schematic diagram illustrating a locally enlarged view of the pixel structure of the electroluminescent display panel according to the third embodiment. As shown inFIGS. 10 and 11, the pixel structure300of the electroluminescent display panel provided in this embodiment includes a substrate210and a plurality of display pixel units320. The display pixel units320are disposed on the substrate210. Each of the display pixel units320is composed of a first sub-pixel321B, a second sub-pixel321G and a third sub-pixel321R. The first sub-pixel321B, the second sub-pixel321G and the third sub-pixel321R of each of the display pixel units320are arranged in a delta arrangement. The display pixel units320are arranged by alternate regular delta arrangement and inverted delta arrangement in the row direction X, but not limited thereto. The first sub-pixel321B of each of the display pixel units320is disposed adjacent to the first sub-pixel321B of an adjacent display pixel unit320in a column direction Y (i.e., the first sub-pixel321B of the adjacent display pixel unit320along a column direction Y). Two of the first sub-pixels321B adjacent to each other (i.e., the two mutually adjacent first sub-pixels321B) compose a first pixel unit330B. The second sub-pixel321G of each of the display pixel units320is disposed adjacent to the second sub-pixel321G of an adjacent display pixel unit320in a column direction Y. Two of the second sub-pixels321G adjacent to each other compose a second pixel unit330G. The third sub-pixel321R of each of the display pixel units320is disposed adjacent to the third sub-pixel321R of an adjacent display pixel unit320in a column direction Y. Two of the third sub-pixels321R adjacent to each other compose a third pixel unit330R. The difference between this embodiment and the aforementioned first embodiment is that each of the first pixel units330B, each of the second pixel units330G and each of the third pixel units330R have different widths along the row direction X respectively. In other words, preferably, each of the first pixel units330B, each of the second pixel units330G and each of the third pixel units330R have different areas respectively so as to compensate for the brightness ratio and the difference in the emission efficiency among the sub-pixels of different colors. More specifically, each of the first pixel units330B, each of the second pixel units330G and each of the third pixel units330R have the first width W1, the second width W2 and the third width W3 along the row direction X respectively. If the first sub-pixel321B, the second sub-pixel321G and the third sub-pixel321R are respectively a blue sub-pixel, a green sub-pixel and a red sub-pixel, the first width W1 is preferably wider than the second width W2, and the second width W2 is preferably wider than the third width W3. In other words, the width of each of the first pixel units330B along the row direction X is preferably wider than the width of each of the second pixel units330G along the row direction X. Moreover, the width of each of the second pixel units330G along the row direction X is preferably wider than the width of each of the third pixel units330R along the row direction X. The area of each of the first pixel units330B is preferably larger than the area of each of the second pixel units330G. Moreover, the area of each of the second pixel units330G is preferably larger than the area of each of the third pixel units330R. It is worth noting that methods to adjust the area in the present invention is not limited to the aforementioned approaches and the area allocation of the sub-pixels of other colors may be modified as well to achieve and balance the required white points and the device duration.

Please refer toFIG. 12.FIG. 12is a schematic diagram illustrating a pixel structure of an electroluminescent display panel according to a fourth embodiment of the present invention. As shown inFIG. 12, the pixel structure400of the electroluminescent display panel is provided in this embodiment. The difference between the fourth embodiment and the above-mentioned embodiments is that each of the first sub-pixels321B does not align the second sub-pixel321G adjacent to the first sub-pixel321B nor the third sub-pixel321R adjacent to the first sub-pixel321B along the column direction Y. Each of the second sub-pixels321G does not align the first sub-pixel321B adjacent to the second sub-pixel321G nor the third sub-pixel321R adjacent to the second sub-pixel321G along the column direction Y. Each of the third sub-pixels321R does not align the first sub-pixel321B adjacent to the third sub-pixel321R nor the second sub-pixel321G adjacent to the third sub-pixel321R along the column direction Y. It is worth noting that, considering the alignment tolerance, as the solution of the pixel structure of the electroluminescent display panel in the present invention is increased, each of sub-pixels, preferably, does not align the other adjacent sub-pixels of other colors along the column direction Y. Accordingly, in the evaporation process, the deposited materials are prevented from being mixed, which results from the alignment precision and fabrication variation, and the yield loss may be improved. However, the present invention is not limited to this.

To sum up, because the sub-pixels arranged in a delta arrangement in each of the display pixel units and the adjacent sub-pixels of the same color compose a display pixel unit respectively, the alignment tolerance of the shadow mask increases in the evaporation process, the openings on the shadow mask are broadened, and the difficulty of fabricating the shadow mask is reduced. Moreover, by adjusting the distance between two sub-pixels in each of the display pixel units, or by adjusting the distribution of the color center of each sub-pixel in the display pixel unit, the shift issues among the pixel color centers (i.e., the color centers of white color) of the display pixel units are improved, and the display quality can be further enhanced.