Patent Grant
8194021
This application claims the benefit of priority based on Taiwan Patent Application No. 097120491 filed on Jun. 2, 2008, the disclosures of which are incorporated herein by reference in their entirety.
Not applicable.
1. Field of the Invention
The present invention relates to a display apparatus, a pixel structure and a drive method thereof. More particularly, the present invention relates to a display apparatus, a pixel structure and a drive method thereof for lower color washout.
2. Descriptions of the Related Art
With the advancement of science and technology, various electronic products have become indispensable. Displays play an important role in multimedia electronic products. Among various displays, liquid crystal displays (LCDs), which have low power consumption, a small volume, small space occupation, flat square panel, high definition, stable picture quality and are radiation-free, have gradually replaced conventional cathode ray tube (CRT) displays and found a wide application in many electronic products such as mobile phones, screens, digital televisions and notebook computers.
When a user views a conventional LCD at different viewing angles, different directions of brightness will be perceived by the user's naked eyes due to different phase differences at different viewing angles. Furthermore, the gray scale inversion may be observed by the user.
To overcome these problems, a variety of technologies aimed to increase the range of viewing angles have been developed in the art to prevent the gray scale inversion in conventional LCDs. One of these technologies is known as the multi-domain vertical alignment (MVA) technology, in which the liquid crystal material in the LCD is divided into multiple alignment domains and are aligned complementary to each other. Thus, the user will observe a same phase difference at different viewing angles, thus increasing the range of the viewing angles to prevent gray scale inversion.
However, despite the high contrast ratio and wide viewing angles, the MVA technology also has some shortcomings, one of which is that the color may be washed out when viewing the LCD adopting the MVA technology at large viewing angles. Color washout is caused by the difference in the transmittance of the liquid crystal molecules at different feed voltages when the user views the display panel at different viewing angles. Consequently, the particular color originally perceived by the naked eyes will wash out as the viewing angle increases.
In summary, although the MVA technology delivers a high contrast ratio and a wide range of viewing angles which remarkably improve the users' experience of using such LCDs, washout at large viewing angles has been a great challenge. Lower color washout is necessary for LCDs to be competitive in the large-sized display panel market. As a result, it is important to prevent washout at large viewing angles.
One objective of this invention is to provide a pixel structure for a display apparatus having a gate drive chip. The pixel structure comprises a first gate line, a second gate line and a pixel unit. The first gate line is configured to receive a first gate drive signal generated by the gate drive chip. The second gate line is configured to receive a second gate drive signal generated by the gate drive chip. The pixel unit has a first pixel area and a second pixel area. The first pixel area is operatively coupled to the first gate line via a first capacitance and a first thin film transistor (TFT), and is configured to generate a first feed through (FT) voltage. The second pixel area is operatively coupled to the first and the second gate lines via a second TFT and a second capacitance respectively, and is configured to generate a second FT voltage. The first and the second FT voltages are adjusted to be different values according to the first and the second gate drive signals.
Another objective of this invention is to provide a drive method for the pixel structure described above. The drive method of this invention comprises the following steps: enabling the first gate line according to the first gate drive signal when the display apparatus displays a first frame of an image, so that the first FT voltage is larger than the second FT voltage; and enabling the first and the second gate lines at the same time according to the first and the second gate drive signals when the display apparatus displays a second frame of the image, so that the second FT voltage is larger than the first FT voltage.
Yet a further objective of this invention is to provide a display apparatus, comprising a gate drive chip, a first gate line, a second gate line, a first pixel unit and a second pixel unit. The first pixel unit has a first pixel area and a second pixel area, the second pixel unit has a third pixel area and a fourth pixel area. The first pixel area of the first pixel unit is operatively coupled to the first gate line via a first capacitance and a first TFT, and is configured to generate a first FT voltage; the second pixel area of the first pixel unit is operatively coupled to the first and the second gate lines via a second TFT and a second capacitance respectively, and is configured to generate a second FT voltage. The first third pixel area of the second pixel unit is operatively coupled to the first and the second gate lines via a third TFT and a third capacitance respectively, and is configured to generate a third FT voltage; the fourth pixel area of the second pixel unit is operatively coupled to the first gate line via a fourth capacitance and a fourth TFT, and is configured to generate a fourth voltage. The first and the second FT voltages are adjusted to be different values according to the first and the second gate drive signals, and the third and the fourth FT voltages are adjusted to be different values according to the same.
Yet another objective of this invention is to provide a drive method for the display apparatus described above. The drive method of this invention comprises the following steps: enabling the first gate line according to the first gate drive signal when the display apparatus displays a first frame of an image, so that the first FT voltage is larger than the second FT voltage, and the fourth FT voltage is larger than the third FT voltage; enabling the first and the second gate lines at the same time according to the first and the second gate drive signals when the display apparatus displays a second frame of the image, so that the second FT voltage is larger than the first FT voltage, and the third FT voltage is larger than the fourth FT voltage.
This invention provides two FT voltages of different values in a single pixel unit without adding gate lines and data lines in the display apparatus. In other words, this invention can provide two FT voltages of different values in a single pixel by simply using the original number of gate lines and data lines in the display apparatus. In this way, washout at large viewing angles is addressed successfully, and since no additional gate lines and data lines are needed, the aperture ratio of the display apparatus remains unchanged instead of being decreased.
The detailed technology and preferred embodiments implemented for the subject invention are described in the following paragraphs accompanying the appended drawings for people skilled in this field to well appreciate the features of the claimed invention.
In the following description, this invention will be explained with reference to the embodiments thereof. However, these embodiments are not intended to limit this invention to any specific environment, applications or particular implementations described in these embodiments. Therefore, description of these embodiments is only intended to illustrate rather than to limit this invention. It should be appreciated that in the following embodiments and the attached drawings, elements not related directly to this invention are omitted from depiction.
The first pixel unit 151 comprises a first pixel area 151a, a second pixel area 151b, a first capacitance 1511, a second capacitance 1513, a first thin film transistor (TFT) 1515 and a second TFT 1517. The first capacitance 1511 is composed of the first gate line 111 and an electrode (not shown) of the first pixel unit 151. The second capacitance 1513 is composed of the second gate line 112 and the electrode of the first pixel unit 151. The first pixel area 151a of the first pixel unit 151 is coupled to the first gate line 111 via the first capacitance 1511, and also coupled to the first gate line 111 and the first data line 131 via the first TFT 1515. The second pixel area 151b of the first pixel unit 151 is coupled to the second gate line 112 via the second capacitance 1513, and also coupled to the first gate line 111 and the first data line 131 via the second TFT 1517.
Likewise, the second pixel unit 153 comprises a third pixel area 153a, a fourth pixel area 153b, a third capacitance 1531, a fourth capacitance 1533, a third TFT 1535 and a fourth TFT 1537. The third capacitance 1531 is composed of the second gate line 112 and an electrode (not shown) of the second pixel unit 153. The fourth capacitance 1533 is composed of the first gate line 111 and the electrode of the second pixel unit 153. The third pixel area 153a of the second pixel unit 153 is coupled to the second gate line 112 via the third capacitance 1531, and also coupled to the first gate line 111 and the second data line 132 via the third TFT 1535. The fourth pixel area 153b of the second pixel unit 153 is coupled to the first gate line 111 via the fourth capacitance 1533, and also coupled to the first gate line 111 and the second data line 132 via the fourth TFT 1537.
Each of the first capacitance 1511, the second capacitance 1513, the third capacitance 1531 and the fourth capacitance 1533 has a capacitance value, in which the capacitance value of the first capacitance 1511 is less than that of the second capacitance 1513, and the capacitance value of the fourth capacitance 1533 is less than that of the third capacitance 1531.
The source drive chip 13 comprises a gamma value storage unit 1301, a first switch unit 1303 and a second switch unit 1305. The gamma value storage unit 1301 is configured to store a first positive polarity gamma value 1300, a first negative polarity gamma value 1302, a second positive polarity gamma value 1304 and a second negative gamma value 1306. It should be noted that, although two buses shown in
In the same way, the second positive polarity gamma value 1304 and the second negative gamma value 1306 can be indicated via another single bus. Based on the above description, those of ordinary skill in the art will realize how to transmit the second positive polarity gamma value 1304 and the second negative gamma value 1306 via a single bus, and thus this will not be further described herein.
Since the display apparatus 1 of this embodiment is an LCD adopting a dot inversion drive method, the first polarity data signal 141 and the second polarity data signal 142 are outputted to the first data line 131 and the second data line 132 alternately. Also, since the display panel 10 has two kinds of pixel units with different pixel structures (i.e., the first pixel unit 151 and the second pixel unit 153) which receive the first polarity data signal 141 and the second polarity data signal 142 alternately through the first data line 131 and the second data line 132, the gamma value storage unit 1301 outputs the first positive polarity gamma value 1300, the first negative polarity gamma value 1302, the second positive polarity gamma value 1304 and the second negative gamma value 1306 to endow the first pixel unit 151 and the second pixel unit 153 with identical and optimized display performance.
When the display apparatus 1 displays a first frame of an image, the first data line 131 receives the first polarity data signal 141 with the first positive polarity gamma value 1300 via the first switch unit 1303. Simultaneously, the second data line 132 receives the second polarity data signal 142 with the second negative gamma value 1306 via the second switch unit 1305. On the other hand, when the display apparatus 1 displays a second frame of the image, the first data line 131 receives the second polarity data signal 142 with the first negative polarity gamma value 1302 via the first switch unit 1303. Simultaneously, the second data line 132 receives the first polarity data signal 141 with the second positive gamma value 1304 via the second switch unit 1304.
In a preferred embodiment, the first polarity data signal 141 and the second polarity data signal 142 have mutually opposite phases; i.e., if the first polarity data signal 141 is of a positive polarity, the second polarity data signal 142 is of a negative polarity, or if the first polarity data signal 141 is of a negative polarity, the second polarity data signal 142 is of a positive polarity. Based on the above description, those of ordinary skill in the art will realize how to switch the first positive polarity gamma value 1300, the first negative polarity gamma value 1302, the second positive polarity gamma value 1304 and the second negative gamma value 1306, and thus this will not be further described herein.
As described above, when the display apparatus 1 displays the first frame of the image, the gate drive chip 11 outputs the first gate drive signal 121 and the second gate drive signal 122 as depicted in
Accordingly, the first pixel area 151a of the first pixel unit 151 generates a first FT voltage 411. The second pixel area 151b of the first pixel unit 151 is charged by the first data line 131 via the second TFT 1517 to generate a second FT voltage 412 in the second pixel area 151b.
Similarly, when the display apparatus 1 displays the first frame of the image, the third pixel area 153a of the second pixel unit 153 is charged by the second data line 132 via the third TFT 1535 to generate a third FT voltage 421 in the third pixel area 153a. The fourth pixel area 153b of the second pixel unit 153 is charged by the second data line 132 via the fourth TFT 1537. Simultaneously, because of the variation of the first gate drive signal 121, the fourth capacitance 1533 coupled to the fourth pixel area 153b of the second pixel unit 153 and the first gate line 111 will cause a corresponding variation of the internal voltage of the fourth pixel area 153b. Accordingly, the fourth pixel area 153b of the second pixel unit 153 generates a fourth FT voltage 422.
When the display apparatus 1 displays the first frame of the image, the first pixel area 151a of the first pixel unit 151 is charged via the first TFT 1515. Simultaneously, because of the variation of the first gate drive signal 121, the first capacitance 1511 coupled to the first pixel area 151a of the first pixel unit 151 and the first gate line 111 will cause a corresponding variation of the internal voltage of the first pixel area 151a. On the other hand, the second pixel area 151b is charged only via the second TFT 1517. Hence, the first FT voltage 411 of the first pixel unit 151 is higher than the second FT voltage 412. Likewise, the fourth pixel area 153b of the second pixel unit 153 is charged via the fourth TFT 1537. At the same time, the fourth capacitance 1533 coupled to the fourth pixel area 153b of the second pixel unit 153 and the first gate line 111 will cause a corresponding variation of the internal voltage of the fourth pixel area 153b and simultaneously, because of the variation of the first gate drive signal 121. On the other hand, the third pixel area 153a is charged only via the third TFT 1535. Hence, the fourth FT voltage 422 of the second pixel unit 153 is higher than the third FT voltage 421.
When the display apparatus 1 displays the second frame of the image, the gate drive chip 11 outputs the first gate drive signal 121 and the second gate drive signal 122 as depicted in
Accordingly, the first pixel area 151a of the first pixel unit 151 generates another first FT voltage 413. The second pixel area 151b of the first pixel unit 151 is charged by the first data line 131 via the second TFT 1517. At the same time, the second capacitance 1513 coupled to the second pixel area 151b of the first pixel unit 151 and the second gate line 112 will cause a corresponding variation of the internal voltage of the second pixel area 151b because of the variation of the second gate drive signal 122. Accordingly, the second pixel area 151b of the first pixel unit 151 generates another second FT voltage 414.
Similarly, when the display apparatus 1 displays the second frame of the image, the third pixel area 153a of the second pixel unit 153 is charged by the second data line 132 via the third TFT 1535. At the same time, because of the variation of the second gate drive signal 122, the third capacitance 1531 coupled to the third pixel area 153a of the second pixel unit 153 and the second gate line 112 will cause a corresponding variation of the internal voltage of the first third pixel area 153a. Accordingly, the third pixel area 153a of the second pixel unit 153 generates another third FT voltage 423. On the other hand, the fourth pixel area 153b of the second pixel unit 153 is charged by the second data line 132 via the fourth TFT 1537. At the same time, because of the variation of the first gate drive signal 121, the fourth capacitance 1533 coupled to the fourth pixel area 153b of the second pixel unit 153 and the first gate line 111 will cause a corresponding variation of the internal voltage of the fourth pixel area 153b. Accordingly, the fourth pixel area 153b of the second pixel unit 153 generates another fourth FT voltage 424.
When the display apparatus 1 displays the second frame of the image, the first pixel area 151a of the first pixel unit 151 is charged via the first TFT 1515. At the same time, the first capacitance 1511 coupled to the first pixel area 151a of the first pixel unit 151 and the first gate line 111 will cause a corresponding variation of the internal voltage of the first pixel area 151a because of the variation of the first gate drive signal 121. On the other hand, the second pixel area 151b is also charged via the second TFT 1517. Likewise, the second capacitance 1513 coupled to the second pixel area 151b of the first pixel unit 151 and the second gate line 112 will cause a corresponding variation of the internal voltage of the second pixel area 151b because of the variation of the second gate drive signal 122. Since the first capacitance 1511 has a capacitance value less than that of the second capacitance 1513, the second FT voltage 422 of the first pixel unit 151 is higher than the first FT voltage 421.
Furthermore, the fourth pixel area 153b of the second pixel unit 153 is charged via the fourth TFT 1537. Simultaneously, the fourth capacitance 1533 coupled to the fourth pixel area 153b of the second pixel unit 153 and the first gate line 111 will cause a corresponding variation of the internal voltage of the fourth pixel area 153b because of the variation of the first gate drive signal 121. On the other hand, the third pixel area 153a is also charged via the third TFT 1535. Likewise, the third capacitance 1531 coupled to the third pixel area 153a of the second pixel unit 153 and the second gate line 112 will cause a corresponding variation of the internal voltage of the third pixel area 153a because of the variation of the second gate drive signal 122. Since the fourth capacitance 1533 has a capacitance less than that of the third capacitance 1531, the third FT voltage 423 of the second pixel unit 153 is higher than the fourth FT voltage 424.
Although this embodiment only describes the operations and functions of the first pixel unit 151 and the second pixel unit 153 in the context of the dot inversion drive method, this invention is not limited to use for an LCD adopting the dot inversion drive method. Instead, based on the above descriptions, those of ordinary skill in the art will realize operations and functions of the first pixel unit 151 and the second pixel unit 153 when a column inversion drive method or other drive methods are adopted. Thus, this will not be further described herein.
A process flow of driving the display apparatus 1 described above is depicted in
Since the display apparatus 1 is an LCD adopting the dot inversion drive method, the first and the second polarity data signals provided in step 501 are outputted alternately, so that the first and the second frames of the image will be displayed according to the first and the second polarity data signals.
In addition to the steps described above, the process flow of driving the display apparatus is also capable of performing all the operations or functions recited in the display apparatus 1 previously described. Those of ordinary skill in the art can straightforwardly realize how the process flow depicted in
In summary, the display apparatus disclosed in this invention can provide two FT voltages of different values in a single pixel unit without adding gate lines and data lines. In other words, the display apparatus disclosed in this invention can provide two FT voltages of different values in a single pixel by simply using the original number of gate lines and data lines. In this way, color washout at large viewing angles in conventional LCDs is eliminated. In addition, because no additional gate lines and additional data lines are needed, the aperture ratio of the display apparatus remains unchanged instead of being decreased.
The above disclosure is related to the detailed technical contents and inventive features thereof. People skilled in this field may proceed with a variety of modifications and replacements based on the disclosures and suggestions of the invention as described without departing from the characteristics thereof. Nevertheless, although such modifications and replacements are not fully disclosed in the above descriptions, they have substantially been covered in the following claims as appended.
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