1. Field of the Disclosure
The present disclosure relates to vertical alignment liquid crystal displays (LCDs).
2. Description of Related Art
Since liquid crystal displays are thin and light, consume relatively little electrical power, and generally do not exhibit flickering, they have helped spawn product markets such as laptop personal computers. The first type of LCD developed was the TN (twisted nematic) mode LCD. Even though TN mode LCDs have been put into use in many applications, they have an inherent drawback that cannot be eliminated; namely, a very narrow viewing angle. By adding compensation films in the TN mode LCDs, this problem can be ameliorated to some extent. However, the cost of such a TN mode LCD is increased. Therefore, a multi-domain vertical alignment (MVA) mode LCD was developed. In an MVA mode LCD, each pixel is divided into multiple domains. Liquid crystal molecules of the pixel are vertically aligned when no voltage is applied, and are inclined in different directions according the domains where they are located when a voltage is applied. In other words, in each pixel, the effective direction of the electric field in one domain is different from the effective direction of the electric field in a neighboring domain. A typical MVA mode LCD uses protrusions and/or slits to form the domains.
However, when fabricating the MVA LCD, an additional process is need for forming the protrusions and/or slits. Thus the method for fabricating the MVA LCD is correspondingly complicated and costly. Furthermore, light leakage may occur due to the presence of the protrusions and/or slits structure, and when this happens the MVA LCD has a lower contrast ratio.
What is needed, therefore, is a vertical alignment LCD which can overcome the described limitations.
A vertical alignment LCD includes a first substrate, a second substrate opposite to the first substrate, a liquid crystal layer disposed between the first and second substrates, a plurality of first electrodes formed at an inner side of the second substrate adjacent to the liquid crystal layer, and at least one second electrode formed at the inner side of the second substrate. The liquid crystal layer comprises a plurality of liquid crystal molecules having the positive dielectrics constants and being vertically aligned. The first electrodes and the at least one second electrode are configured for generating electric fields to drive the liquid crystal molecules to orient in a plurality of different directions all parallel to the first substrate and the second substrate.
Other novel features and advantages will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. All the views are schematic.
Reference will now be made to the drawings to describe preferred and exemplary embodiments in detail.
Referring to
The vertical alignment LCD 100 further includes a plurality of scanning lines 140 parallel to each other, a plurality of data lines 142 parallel to each other and extending orthogonal to the scanning lines 140, a plurality of thin film transistors (TFTs) 144 at intersections of the data lines 142 and the scanning lines 140, a plurality of first electrodes 150, a plurality of the second electrodes 160, and a plurality of common lines 146 parallel to the scanning lines 140. The scanning lines 140 and the common lines 146 are arranged alternately. The scanning lines 140, the data lines 142, the TFTs 144, the first electrodes 150, the second electrodes 160, and the common lines 146 are disposed on an inner side of the second substrate 120 adjacent to the liquid crystal layer 130.
The scanning lines 140 and data lines 142 cross each other, thereby defining an array of pixel regions 170. Each pixel region 170 includes a TFT 144, a plurality of the first electrodes 150, and a plurality of the second electrodes 160. The TFT 144 includes a gate electrode connected to a corresponding scanning line 140, a source electrode connected to a corresponding data line 142, and a drain electrode connected to one of the first electrodes 150 adjacent thereto.
Each pixel region 170 may be divided into two sub-pixel regions, e.g. a first sub-pixel region 172, and a second sub-pixel region 174, by an axis O-O which is parallel to the scanning line 140. Preferably, the axis O-O is in the middle of the pixel region 170.
Each first electrode 150 is rectilinear and has two extending directions. Each first electrode 150 includes a first sub-electrode 150a in the first sub-pixel region 172 and a second sub-electrode 150b in the second sub-pixel region 174. The first sub-electrode 150a extends from a middle of the first electrode 150 toward a periphery of the first sub-pixel region 172 along a first extending direction which is inclined to the axis O-O. The second sub-electrode 150b extends from the middle of the first electrode 150 toward a periphery of the second sub-pixel region 174 along a second extending direction which is also inclined to the axis O-O. Preferably, the first and second sub-electrodes 150a, 150b form a right angle, the first sub-electrode 150a and the scanning line 140 define an angle of about 45 degrees therebetween, and the second sub-electrode 150b and the scanning line 140 define an angle of about 45 degrees therebetween. In
The first sub-electrodes 150a in each first sub-pixel region 172 are parallel to each other with a uniform distance between any two adjacent first sub-electrodes 150a. The first sub-electrodes 150a may have a uniform width. The second sub-electrodes 150b in each second sub-pixel region 174 are parallel to each other with a uniform distance between any two adjacent second sub-electrodes 150b. The second sub-electrodes 150b may have a uniform width. The first and second sub-electrodes 150a, 150b are both straight.
Each second electrode 160 includes a third sub-electrode 160a in the first sub-pixel region 172 and a fourth sub-electrode 160b in the second sub-pixel region 174. The third sub-electrode 160a extends from a middle of the second electrode 160 toward the periphery of the first sub-pixel region 172 along the first extending direction which is inclined to the axis O-O. The fourth sub-electrode 160b extends from the middle of the second electrode 160 toward the periphery of the second sub-pixel region 174 along the second extending direction which is also inclined to the axis O-O.
The third sub-electrodes 160a in each first sub-pixel region 172 are parallel to each other with a uniform distance between any two adjacent third sub-electrodes 160a. The third sub-electrodes 160a may have a uniform width. The third sub-electrodes 160a and the first sub-electrodes 150a are parallel to each other, and arranged alternately. That is, each third sub-electrode 160a has two neighboring first sub-electrodes 150a. Preferably, each third sub-electrode 160a is located halfway between the two neighboring first sub-electrodes 150a, with the third sub-electrode 160a being spaced a same distance apart from the two neighboring first sub-electrodes 150a.
The fourth sub-electrodes 160b in each second sub-pixel region 174 are parallel to each other with a uniform distance between any two adjacent fourth sub-electrodes 160b. The fourth sub-electrodes 160b may have a uniform width. The fourth sub-electrodes 160b and the second sub-electrodes 150b are parallel to each other, and arranged alternately. That is, each fourth sub-electrode 160b has two neighboring second sub-electrodes 150b. Preferably, each fourth sub-electrode 160b is located halfway between the two neighboring second sub-electrodes 150b, with the fourth sub-electrode 160b being spaced a same distance apart from the two neighboring second sub-electrodes 150b. The third and fourth sub-electrodes 160a, 160b are both straight.
When the vertical alignment LCD 100 is in an on state, in each pixel region, a same pixel voltage is applied to the first electrodes 150, and a same common voltage is applied to the second electrodes 160 via the common line 146. The first electrodes 150 are electrically connected to each other by a connection structure so as to have a same voltage, and the second electrodes 160 are electrically connected to each other by a connection structure so as to have a same voltage. The connection structures may have any of various configurations. For example, referring to
Referring also to
When the vertical alignment LCD 100 is in the on state, corresponding pixel and common voltages are applied to the first and second electrodes 150, 160, respectively. Accordingly, an electric field E is generated between each first electrode 150 and the two corresponding adjacent second electrodes 160. Because the liquid crystal molecules 131 have positive dielectrics constants and anisotropic properties, they are oriented in directions parallel to the electric field E. As a result, the vertical alignment LCD 100 is in a white state, in which an image can be displayed. The electric field E includes a horizontal component parallel to the first and second substrates 110, 120, and a vertical component perpendicular to the first and second substrates 110, 120. In the region adjacent to the first and second electrodes 150, 160, the perpendicular component is stronger, and the liquid crystal molecules 131 are aligned perpendicular to the first and second substrates 110, 120. In the region between the first and second electrodes 150, 160, the horizontal component is stronger, and the liquid crystal molecules 131 are aligned parallel to the first and second substrates 110, 120.
The electric field E varies gradually, and so in different regions of the electric field E, the horizontal component and the perpendicular component affect the orientations of the liquid crystal molecules 131 differently. That is, inhomogeneous rotation angles of the liquid crystal molecules 131 result from the inhomogeneous distribution of the electric field E. Because the first and second electrodes 150, 160 are parallel to each other, and provided on the one same second substrate 120, the horizontal component is generally stronger than the perpendicular component in most of the regions of the electric field E. Thereby, most of the liquid crystal molecules 131 are aligned parallel to the first and second substrates 110, 120 in regions having the stronger horizontal component, while some of the liquid crystal molecules 131 are aligned perpendicular to the first and second substrates 110, 120 in regions having the stronger perpendicular component.
Furthermore, the electric field E adjacent to the second substrate 120 is stronger than that adjacent to the first substrate 110 far away from the second substrate 120. Thus, the liquid crystal molecules 131 adjacent to the first substrate 110 maintain their original orientations, perpendicular to the first and second substrates 110, 120.
As detailed above, each of the first and second electrodes 150, 160 have two extending directions. That is, the first and third sub-electrodes 150a, 160a extend along the first extending direction, and the second and fourth sub-electrodes 150b, 160b extend along the second extending direction. Therefore, the direction of the electric field E generated between the first and third sub-electrodes 150a, 160a is different from the direction of the electric field E generated between the second and fourth sub-electrodes 150b, 160b. Because the first and second electrodes 150, 160 are provided on the one same second substrate 120, the horizontal component is generally stronger than the perpendicular component at most regions of the electric field E. Thereby, most of the liquid crystal molecules 131 are aligned parallel to the first and second substrates 110, 120. Additionally, in the first sub-pixel region 172, the horizontal component of the electric field E is perpendicular to the first extending direction, and in the second sub-pixel region 174, the horizontal component of the electric field E is perpendicular to the second extending direction. Therefore the directions of the electric field E in the first and second sub-pixel regions 172, 174 are perpendicular to each other, and the liquid crystal molecules 131 in the pixel region 170 have additional different alignment directions. Thus overall, the vertical alignment LCD 100 provides a better display performance at various viewing angles.
In summary, because the first and second electrodes 150, 160 are disposed on the one same second substrate 120, when the electric field E is supplied, most of the liquid crystal molecules 131 are aligned parallel to the first and second substrates 110, 120. In addition, in each pixel region 170, each of the first and second electrodes 150, 160 has two extending directions, thereby providing alignment directions of the liquid crystal molecules 131. Thus the vertical alignment LCD 100 provides a better display performance at various viewing angles. Furthermore, these advantages are achieved without the need for an additional process of forming protrusions and/or slits. Thus, fabricating the vertical alignment LCD 100 is correspondingly simple and inexpensive.
Moreover, when the vertical alignment LCD 100 is in an off state, all the liquid crystal molecules 131 are aligned perpendicular to the first and second substrates 110, 120. Because the light transmission ratio of the liquid crystal molecules 131 along their long axes is the lowest, there is little or no light leakage in the off state. That is, the vertical alignment LCD 100 is sufficiently black in the off state. When the vertical alignment LCD 100 is in the on state, most of the liquid crystal molecules 131 are aligned parallel to the first and second substrates 110, 120. Because the light transmission ratio of the liquid crystal molecules 131 along their short axes is the highest, the vertical alignment LCD 100 is sufficiently white in the on state, and has high contrast.
Referring to
Because the distance L1 and distance L2 are different, the strength of the electric field E generated by the first and second electrodes 250, 260 spaced the distance L1 is different from that of the electric field E generated by the first and second electrodes 250, 260 spaced the distance L2. Therefore the liquid crystal molecules 231 have additional different alignment directions, and the vertical alignment LCD 200 provides a better display performance at various viewing angles.
Referring to
The shape of the second electrodes 360 is not limited to the above-described embodiments. For example, each of the second electrodes 360 can be wavy, comprising multiple gently curved “S” shapes. Each of the second electrodes 360 can be gently “S” shaped. Each of the second electrodes 360 can be arcuate.
Referring to
Referring to
Referring to
The vertical alignment LCD 600 is not limited to the above-described embodiments. For example, the insulating layer 666 may still be disposed between the electrode layer 664 and the first electrodes 650, but with there being no second electrodes 660 and no third electrodes 652 provided on the second and first substrates 620, 610, respectively. In such case, the common voltage is applied to the electrode layer 664, the pixel voltage is applied to the first electrodes 650, and liquid crystal molecules 631 are directed to incline only by the peripheral electric fields E4 generated by the first electrodes 650 and the electrode layer 664.
Referring to
The vertical alignment LCD of this disclosure is not limited to the above-described embodiments. For example, in the third embodiment of the present disclosure, the first electrodes 350 can be curved in the same way as the second electrodes 360.
It will be further apparent to those skilled in the art that various modifications can be made to the present embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of the embodiments provided that such modifications or variations fall within the scope of the following claims or their equivalents. Any one of the embodiments or any one of the claims of the disclosure does not necessarily have to achieve all of the advantages or features disclosed herein. Moreover, the abstract and the headings are merely used to aid in searches of patent files and are not intended to limit the scope of the claims.
Number | Date | Country | Kind |
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98137693 | Nov 2009 | TW | national |