JP5511626B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a multiplex-driven vertical alignment type liquid crystal display device.

  Liquid crystal display devices are widely used as information display units in, for example, various consumer and in-vehicle electronic devices. A general liquid crystal display device is configured by disposing a liquid crystal layer made of a liquid crystal material between two substrates arranged to face each other with a gap of about several μm. As one of such liquid crystal display devices, a vertical alignment type liquid crystal display device is known (for example, JP-A-2005-234254). A vertical alignment type liquid crystal display device is a vertical alignment mode (hereinafter referred to as “VA mode”) in which liquid crystal molecules in a liquid crystal layer disposed between two substrates are aligned substantially perpendicular to the surface of each substrate. And a polarizing plate provided outside the liquid crystal cell as main components. Each polarizing plate is often in a crossed Nicol arrangement. In this way, since the transmittance of the liquid crystal display device when no voltage is applied becomes very low, a high contrast can be realized relatively easily.

  When realizing image display of a liquid crystal display device by multiplex driving, substrates each having strip-shaped (stripe) electrodes are arranged facing each other so that the extending directions of the respective electrodes are substantially orthogonal to each other. Each of the regions where the electrode on one substrate and the electrode on the other substrate intersect is defined as a pixel. At this time, the shape of each pixel is substantially rectangular. Further, the surface of each substrate is subjected to an alignment process such as a rubbing process. The direction of the alignment treatment with respect to the surface of each substrate is set to, for example, opposite directions (anti-parallel alignment). As a result, the alignment direction of the liquid crystal molecules is determined in one direction when no voltage is applied at substantially the center in the layer thickness direction of the liquid crystal layer provided between the substrates. For example, when the direction of alignment treatment on each substrate is 6 o'clock and 12 o'clock as viewed from the front of the liquid crystal display device, the alignment direction of the liquid crystal molecules at the approximate center of the liquid crystal layer is determined to be 6 o'clock. At this time, the extending direction of the electrode on one substrate is substantially parallel to the alignment direction of the liquid crystal layer at the approximate center of the liquid crystal layer, and the extending direction of the electrode on the other substrate is substantially orthogonal.

  In the above VA mode liquid crystal display device, a case is considered in which a pair of polarizing plates arranged substantially in crossed Nicols are arranged outside each substrate. One polarizing plate has its absorption axis disposed at an angle of approximately 45 ° with respect to the direction of the alignment treatment applied to the one substrate. When a liquid crystal layer is formed using a liquid crystal material having a negative dielectric anisotropy and a voltage higher than the threshold voltage is applied between the electrodes of each substrate, the majority of the liquid crystal molecules in the liquid crystal layer are oriented in the alignment process. In the horizontal alignment direction. When this liquid crystal display device is observed, the bright display state is observed well from the 6 o'clock direction, and conversely, the bright display is not observed from the 12 o'clock direction. The 6 o'clock direction at this time is called the best viewing direction (best viewing direction), and the 12 o'clock direction is called the anti-viewing direction (anti-viewing direction).

  In the VA mode liquid crystal display device, when viewed from the opposite viewing direction in a bright display state when viewed from the front, the inside of the pixel is observed in a dark state, but the four sides of the rectangular pixel are observed. Light leakage occurs in the vicinity of one side of the pixel edge. This light omission is not regular in the state of occurrence and is different for each pixel, and the display quality in appearance is remarkably deteriorated.

JP 2005-234254 A

  According to a specific aspect of the present invention, in a vertical alignment type liquid crystal display device operating by multiplex driving, light leakage near the edge of each pixel when observed from the opposite viewing direction is homogenized to improve display quality. Is one of the purposes.

  As a result of diligent examination by the inventors of the present invention in solving the above-described problems, the shape of the dark region generated in each pixel is made more uniform by preventing the pixel edge of each pixel and the direction of orientation processing from being orthogonal as much as possible. The knowledge that display quality can be improved was acquired. And based on the said knowledge, this inventor came to create the following invention.

A liquid crystal display device according to an aspect of the present invention includes (a) a first substrate and a second substrate which are disposed to face each other, and (b) provided on one surface of the first substrate, and extending in a first direction. A first electrode; (c) a second electrode provided on one surface of the second substrate and extending in a second direction intersecting the first direction; and (d) a surface of the first substrate and the first electrode. And (e) a pixel is formed in a region where the first electrode and the second electrode intersect, and (f) the first substrate. And at least one of the second substrates is subjected to an alignment process in a direction substantially parallel to the first direction, and (g) the first electrode has a linear shape with electrode edges on both sides extending in the first direction. (H) The second electrode has a line segment in which at least one electrode edge is obliquely crossed with respect to the first direction. I I is a polygonal line shape, (i) the oblique line segment, the second direction forms a 0 15 ° angle of less than greater than ° with respect to the obliquely intersects, (j) the pixel A liquid crystal display device in which pixel edges are defined including the oblique line segments.

  A liquid crystal display device according to an aspect of the present invention includes (a) a first substrate and a second substrate which are disposed to face each other, and (b) provided on one surface of the first substrate, and extending in a first direction. A first electrode; (c) a second electrode provided on one surface of the second substrate and extending in a second direction intersecting the first direction; and (d) a surface of the first substrate and the first electrode. And (e) a pixel is formed in a region where the first electrode and the second electrode intersect, and (f) the first substrate. And at least one of the second substrates is subjected to an alignment process in a direction substantially parallel to the first direction, and (g) the first electrode has a linear shape with electrode edges on both sides extending in the first direction. (H) The second electrode has a line segment in which at least one electrode edge is obliquely crossed with respect to the first direction. (I) The oblique line segment is configured by connecting a first straight line and a second straight line extending in different directions, and (j) the first straight line and The length of the second straight line when projected in the first direction is Xa and Xb, respectively, and Xa is more than three times the length of Xb. (K) The first straight line is in the second direction. And (1) the pixel is a liquid crystal display device in which a pixel edge is defined including the oblique line segment.

  A liquid crystal display device according to an aspect of the present invention includes (a) a first substrate and a second substrate which are disposed to face each other, and (b) provided on one surface of the first substrate, and extending in a first direction. A first electrode; (c) a second electrode provided on one surface of the second substrate and extending in a second direction substantially perpendicular to the first direction; (d) one surface of the first substrate; A liquid crystal layer having a substantially vertical alignment provided between one surface of the second substrate; (e) a pixel is formed in a region where the first electrode and the second electrode intersect; and (f) the first substrate. At least one of the substrate and the second substrate is subjected to an alignment process in a direction substantially parallel to the first direction. (G) The first electrode has a linear shape with electrode edges on both sides extending in the first direction. (H) the second electrode has a line segment in which at least one electrode edge is oblique to the first direction. (I) The oblique line segments are configured by connecting the first straight line and the second straight line that are substantially equal to each other and extend in different directions. (J) The first straight line and the second straight line are obliquely formed at an angle greater than 0 ° and not greater than 15 ° with respect to the second direction, and (k) the pixel is obliquely intersected. This is a liquid crystal display device in which a pixel edge is defined including a line segment.

  Here, “obliquely intersect” means that they intersect obliquely at an angle other than orthogonal.

  According to such a configuration, since the pixel edge is defined including the line segment oblique to the direction of the alignment process, the light omission near the edge of each pixel when viewed from the opposite viewing direction is homogenized and displayed. It becomes possible to improve the quality.

  The oblique line segments described above are preferably arranged on the side opposite to the visual recognition direction of the pixel edge.

It is typical sectional drawing which shows the structure of the liquid crystal display device of one Embodiment. It is a typical top view which shows an example of an electrode structure. It is a typical top view which shows another example of an electrode structure. It is a typical top view which shows another example of an electrode structure. It is a typical top view which shows another example of an electrode structure. It is a typical top view which shows another example of an electrode structure. It is a typical top view which shows another example of an electrode structure. It is a typical top view which shows another example of an electrode structure. It is a figure which shows the orientation structure observation image at the time of the voltage application of the liquid crystal display device which has a type A electrode structure. It is a figure which shows the orientation structure observation image at the time of the voltage application of the liquid crystal display device which has a type B electrode structure. It is a figure which shows the orientation structure | tissue observation image at the time of the voltage application of the liquid crystal display device which has a type C electrode structure. It is a figure which shows the orientation structure | tissue observation image at the time of the voltage application of the liquid crystal display device which has a type D electrode structure. It is a figure which shows the orientation structure | tissue observation image at the time of the voltage application of the liquid crystal display device (in the case of (theta) = 10 degrees) which has a type E electrode structure. It is a figure which shows the orientation structure observation image at the time of the voltage application of the liquid crystal display device (in the case of (theta) = 10 degrees) which has a type G electrode structure. It is the top view which showed typically the orientation direction (alignment distribution) of the liquid crystal layer in the approximate center of the liquid crystal layer at the time of the voltage application in one pixel obtained by making strip-shaped electrodes cross | intersect. It is a figure which shows the polarization microscope observation image of the pixel at the time of the voltage application of the liquid crystal display device of the prior art example actually produced.

  The inventor of the present application has studied the cause of light leakage near the pixel edge of each pixel when the vertically aligned liquid crystal display device is multiplex driven. FIG. 15 is a plan view schematically showing the alignment direction (alignment distribution) of the liquid crystal molecules at the approximate center of the liquid crystal layer when a voltage is applied in one rectangular pixel obtained by crossing the strip electrodes. is there. 15 corresponds to the 12 o'clock direction, the horizontal direction corresponds to the 9 o'clock direction, the 3 o'clock direction, and the lower direction corresponds to the 6 o'clock direction, respectively, and the lower direction is the best viewing direction. . The pixel shown in FIG. 15 is formed by crossing strip-shaped electrodes 111 and strip-shaped electrodes 112. The strip electrode 111 is provided on a first substrate (not shown), and the strip electrode 112 is provided on a second substrate (not shown). The direction 114 of the alignment treatment applied to the first substrate is 6 o'clock, and the direction 113 of the alignment treatment applied to the second substrate is 12 o'clock. In the vicinity of the pixel edge in the 12 o'clock direction, which is the anti-viewing direction, the alignment direction when no voltage is applied and the alignment direction defined by the generation of the oblique electric field differ by 180 °. Will occur. On the other hand, even in the vicinity of each pixel edge in the left-right direction, rotation of the alignment direction 121 occurs because the oblique electric field differs by 90 ° from the alignment direction when no voltage is applied. If each absorption axis of the polarizing plate in the crossed Nicol arrangement is arranged at approximately 45 ° with respect to the alignment direction when no voltage is applied, the region parallel to this is not brightly displayed even when a voltage is applied. It is expected not to be. Further, in the vicinity of the pixel edges on the left, right, and upper three sides, regions having different alignment directions 121 are generated when a voltage is applied. Therefore, this liquid crystal display device exhibits multi-domain alignment when a voltage is applied. Therefore, the best viewing direction is different in the vicinity of each pixel edge, and it is visually recognized as a region where light is lost particularly when observed from the 12:00 direction which is the anti-viewing direction.

  FIG. 16 is a diagram showing a polarization microscope observation image of a pixel when a voltage is applied to a liquid crystal display device of a conventional example actually manufactured. In the liquid crystal display device, one pixel is 0.43 mm square, and the electrode interval between the strip electrodes is 30 μm. Observing the inside of one pixel shows that a cross-shaped dark region is observed. As described above, the rotation of the alignment direction of the liquid crystal molecules occurred due to the influence of the oblique electric field in the vicinity of the pixel edge during voltage application.Therefore, the alignment direction near the direction parallel to or perpendicular to the absorption axis of the polarizing plate is near this dark region. It is thought that it has become. In particular, in the vicinity of the pixel edge in the 12 o'clock direction where the rotation angle of the alignment direction of the liquid crystal molecules is large at the approximate center of the liquid crystal layer, it can be seen that the dark region has entered the pixel from the pixel edge. Further, a cross point in the dark region is observed near the pixel edge. This cross point is considered to be a disclination in which the liquid crystal molecules are held in a substantially vertical orientation despite the application of voltage. When each pixel is observed, there are cases where there are one or three cross points, and the occurrence of the cross points is irregular. Further, the shape of the cross-shaped dark region is completely different depending on the pixel. If the shape of the dark region is not uniform, a difference occurs in the area ratio of each domain in the multi-domain alignment, which is considered to cause a difference in viewing angle characteristics. That is, this is considered to be a factor that causes display non-uniformity in the anti-viewing direction.

  Therefore, when the observation image in FIG. 16 was examined in more detail, it was found that the dark region shape in each pixel was irregular in the vicinity of the pixel edge in the 12 o'clock direction. In this region, the electrode edge of the strip-shaped electrode 112 and the orientation processing directions 113 and 114 are substantially orthogonal. On the other hand, dark areas regularly occur in each pixel in the vicinity of each pixel edge in the 9 o'clock direction and the 3 o'clock direction where dark areas similarly occur. In this region, the electrode edge of the strip-shaped electrode 111 and the orientation processing directions 113 and 114 are substantially parallel to each other. From these facts, it can be considered that by reducing the number of locations where the pixel edge and the direction of the alignment treatment are orthogonal, the shape of the dark region generated in each pixel can be made uniform and the display quality can be improved.

  An embodiment of the present invention based on the above knowledge will be described below.

  FIG. 1 is a schematic cross-sectional view showing the structure of a liquid crystal display device according to an embodiment. The liquid crystal display device according to the present embodiment shown in FIG. 1 mainly includes a first substrate 1 and a second substrate 2 that are disposed to face each other, and a liquid crystal layer 3 that is disposed between the two substrates. A first polarizing plate 4 is disposed outside the first substrate 1, and a second polarizing plate 5 is disposed outside the second substrate 2. A first viewing angle compensation plate 6 is disposed between the first substrate 1 and the first polarizing plate 4, and a second viewing angle compensation plate 7 is disposed between the second substrate 2 and the second polarizing plate 5. The periphery of the liquid crystal layer 3 is sealed with a sealing material. Hereinafter, the structure of the liquid crystal display device will be described in more detail.

  The first substrate 1 and the second substrate 2 are transparent substrates such as a glass substrate and a plastic substrate, respectively. Between the first substrate 1 and the second substrate 2, spacers (granular bodies) are arranged in a dispersed manner. By these spacers, the gap between the first substrate 1 and the second substrate 2 is maintained at a predetermined distance (about 4.3 μm in this embodiment).

  The liquid crystal layer 3 is provided between the first electrode 11 of the first substrate 1 and the second electrode 12 of the second substrate 2. In the present embodiment, the liquid crystal layer 3 is configured using a liquid crystal material (nematic liquid crystal material) having a negative dielectric anisotropy Δε (Δε <0). The bold line shown in the liquid crystal layer 3 schematically shows the alignment direction of the liquid crystal molecules when no voltage is applied. As shown in the figure, in the liquid crystal display device of the present embodiment, the alignment state of the liquid crystal molecules in the liquid crystal layer 3 is restricted to monodomain alignment. The pretilt angle of the liquid crystal layer 3 in this embodiment is set to approximately 89.9 °. The retardation of the liquid crystal layer 3 is approximately 1100 nm.

  The polarizing plate 4 and the polarizing plate 5 are arranged so that their absorption axes are substantially orthogonal to each other (crossed Nicol arrangement). In addition, the polarizing plate 4 and the polarizing plate 5 each have an angle of about 45 ° in each of the alignment processing direction 14 applied to the first substrate 1 and the alignment processing direction 13 applied to the second substrate. It is arranged to make. Thereby, the absorption axis of each polarizing plate 4 and 5 makes an angle of about 45 ° with respect to the alignment direction of the liquid crystal layer at the approximate center of the liquid crystal layer 3 defined by the directions 13 and 14 of the alignment treatments. Become.

  The alignment film 8 is provided on one surface side of the first substrate 1 so as to cover the first electrode 11. Similarly, the alignment film 9 is provided on one surface side of the second substrate 2 so as to cover the second electrode 12. Each alignment film 8, 9 is subjected to an alignment process such as a rubbing process. A direction 14 of the alignment treatment applied to the alignment film 8 is as shown in the figure, and substantially coincides with the extending direction (first direction) of the first electrode 11. Further, the direction 13 of the alignment treatment applied to the alignment film 9 is as shown in the figure, and substantially coincides with the extending direction (second direction) of the second electrode 12. In the present embodiment, as the alignment film 8 and the alignment film 9, one that regulates the alignment state in the initial state (when no voltage is applied) of the liquid crystal layer 3 to the vertical alignment state (vertical alignment film) is used. More specifically, as the alignment films 8 and 9, those that can give a pretilt angle of an angle very close to 90 ° to the liquid crystal molecules of the liquid crystal layer 3 are used.

  The first electrode 11 is provided on one surface of the first substrate 1. The second electrode 12 is provided on one surface of the second substrate 2. In the present embodiment, a plurality of first electrodes 11 and a plurality of second electrodes 12 each extending in a specific direction are opposed to each other with their extending directions substantially orthogonal to each other. Each first electrode 11 and each second electrode 12 are configured by appropriately patterning a transparent conductive film such as indium tin oxide (ITO), for example. In the liquid crystal display device of this embodiment, each of the portions where the first electrode 11 and the second electrode 12 overlap in a plan view is a pixel.

  In the present embodiment, the electrode edge of each second electrode 12 is formed into a polygonal line shape including a line segment that obliquely intersects with the extending direction (first direction) of the first electrode. Among these, a structure is realized in which the pixel edge of the portion defined by the electrode edge of each second electrode 12 and the orientation processing directions 13 and 14 are not orthogonal to each other. Below, some specific structures are illustrated.

  FIG. 2 is a schematic plan view showing an example of an electrode structure. As shown in FIG. 2A, the electrode edge of each second electrode 12 extending in the left-right direction in the drawing is formed in a sawtooth shape, and one pitch of the sawtooth corresponds to the electrode width of each first electrode 11. Almost complete. An enlarged view of the electrode portion corresponding to one pixel is shown in FIG. In FIG. 2B, each first electrode 11 extending in the vertical direction in the figure is indicated by a dotted line (the same applies to FIG. 3 and subsequent figures). Since the region where each first electrode 11 and each second electrode 12 intersect becomes one pixel, the shape of one pixel is two sides by the electrode edge of the first electrode 11 and two sides by the electrode edge of the second electrode 12. The substantially parallelogram shape demarcated by, and all the pixels have the same shape. Hereinafter, the electrode structure shown in FIG. 2 may be referred to as a “type A electrode structure”. In addition, when each electrode interval of the 1st electrode 11 and the 2nd electrode 12 is wide, the shape of 1 pixel becomes a substantially hexagonal shape.

  If an angle formed by the electrode edge of the sawtooth second electrode 12 and the horizontal direction (left-right direction in the figure) is defined as θ, this angle θ is set to be greater than 0 ° and not more than 15 °. By doing so, it is possible to realize a structure in which the upper and lower sides of each pixel and the directions 13 and 14 of each alignment treatment are not orthogonal to each other. Note that the electrode edge of the second electrode 12 shown in FIG. 2 has a sawtooth shape that rises to the right, but conversely, it is considered that the same effect can be obtained if the electrode edge has a sawtooth shape that falls to the right.

  FIG. 3 is a schematic plan view showing another example of the electrode structure. As shown in FIG. 3A, the electrode edge of each second electrode 12 extending in the left-right direction in the drawing is formed in a sawtooth shape, but unlike the structure shown in FIG. One pitch is not aligned with the electrode width of each first electrode 11. As shown in FIG. 3B, each second electrode 12 is in a state where the downward apex portion of the sawtooth and the interelectrode portion of the first electrode 11 do not overlap. The upper and lower electrode edges in one pixel have a shape in which two sides (first straight line and second straight line) having different inclination directions are connected. Assuming that length components parallel to the horizontal direction (projected lengths) for each electrode edge are Xa and Xb, the total length of Xa and Xb and the electrode width of each first electrode 11 are set to be approximately equal. . Each first electrode 11 and each second electrode 12 are arranged so that both ends of the electrode edge formed by connecting two sides having different inclination directions overlap each other between the electrodes of the first electrode 11. Hereinafter, the electrode structure shown in FIG. 3 may be referred to as a “type B electrode structure”. It can be said that the type A electrode structure is a special case where Xa = 0 in the type B electrode structure.

  In the type B electrode structure, Xa> Xb, and Xa is preferably set within 4 times (more preferably within 3 times) Xb. If the angle formed between the side having the length component Xa and the horizontal direction is defined as θ, the angle θ is set to be greater than 0 ° and equal to or less than 15 °. By doing so, it is possible to realize a structure in which the upper and lower sides of each pixel and the directions 13 and 14 of each alignment treatment are not orthogonal to each other. The shape of each pixel in the type B electrode structure is a deformed "<" shaped hexagon, and all the pixels have the same shape. Note that the electrode edge of the second electrode 12 shown in FIG. 3 is set such that the left side (rising side) is relatively long and the right side (right side) is relatively short. However, it is considered that the same effect can be obtained even if this is reversed left and right.

  FIG. 4 is a schematic plan view showing another example of the electrode structure. As shown in FIG. 4A, the electrode edge of each second electrode 12 extending in the left-right direction in the drawing is formed in a sawtooth shape, but unlike the structure shown in FIG. One pitch is not aligned with the electrode width of each first electrode 11. Then, as shown in FIG. 4B, each second electrode 12 is in a state where one apex angle portion of the sawtooth and the interelectrode portion of the first electrode 11 do not overlap. The upper and lower electrode edges in one pixel have a shape in which two sides having different inclination directions are connected. Similarly to the type B electrode structure described above, assuming that the length components parallel to the left and right direction for each electrode edge are Xa and Xb, the total length of Xa and Xb and the electrode width of each first electrode 11 are set to be approximately equal. Has been. Each first electrode 11 and each second electrode 12 are arranged so that both ends of the electrode edge formed by connecting two sides having different inclination directions overlap each other between the electrodes of the first electrode 11. Hereinafter, the electrode structure shown in FIG. 4 may be referred to as a “type C electrode structure”.

  The difference between the type C electrode structure and the type B electrode structure is that the vertices of the sawtooth are not uniform at both electrode edges of each second electrode 12. In the example shown in the drawing, one vertex of the sawtooth is arranged so as to be shifted by about Xb in the left-right direction with respect to the other vertex. The amount to be shifted is not limited to Xb. Also in the type C electrode structure, it is preferable that Xa> Xb and that Xa is set within 4 times (more preferably within 3 times) of Xb. If the angle formed between the side having the length component Xa and the horizontal direction is defined as θ, the angle θ is set to be greater than 0 ° and equal to or less than 15 °. By doing so, it is possible to realize a structure in which the upper and lower sides of each pixel and the directions 13 and 14 of each alignment treatment are not orthogonal to each other. The shape of each pixel in the type C electrode structure is a deformed hexagon, but the shape of adjacent pixels is different in the vertical direction, and the difference in shape is repeated every other second electrode 12. As in the case of the type B electrode structure, it is considered that the same effect can be obtained even if the pixel shape is reversed left and right.

  FIG. 5 is a schematic plan view showing another example of the electrode structure. As shown in FIG. 5A, the electrode edge of each second electrode 12 extending in the left-right direction in the drawing is formed in a sawtooth shape, and a 1/2 pitch of the sawtooth is an electrode of each first electrode 11. It is set almost equal to the width. Then, as shown in FIG. 5B, each second electrode 12 is disposed in a state where one apex angle portion (bending point) of the sawtooth overlaps with the interelectrode portion of the first electrode 11. Since the region where each first electrode 11 and each second electrode 12 intersect becomes one pixel, the shape of one pixel is two sides by the electrode edge of the first electrode 11 and two sides by the electrode edge of the second electrode 12. Is a substantially parallelogram defined by Hereinafter, the electrode structure shown in FIG. 5 may be referred to as a “type D electrode structure”.

  In FIG. 5, if the angle formed by the electrode edge of the second electrode 12 and the horizontal direction (left-right direction in the figure) is defined as θ, this angle θ is set to be greater than 0 ° and not more than 15 °. By doing so, it is possible to realize a structure in which the upper and lower sides of each pixel and the directions 13 and 14 of each alignment treatment are not orthogonal to each other. In each pixel in the type D electrode structure, adjacent pixels in the vertical direction have the same shape, but adjacent pixels in the left-right direction are different, and the difference in shape is every other first electrode 11. Repeated.

  FIG. 6 is a schematic plan view showing another example of the electrode structure. As shown in FIG. 6A, the electrode edge of each second electrode 12 extending in the left-right direction in the drawing is formed in a sawtooth shape, and a 1/2 pitch of the sawtooth is an electrode of each first electrode 11. It is set almost equal to the width. The difference from the type D electrode structure shown in FIG. 5 is that the direction of bending at one electrode edge and the other electrode edge of each second electrode 12 is staggered, and the bent vertices of both electrode edges approach each other. It is that it repeats moving away. Then, as shown in FIG. 6B, each second electrode 12 is arranged in a state where one apex angle portion (bending point) of the sawtooth overlaps the interelectrode portion of the first electrode 11. Since the region where each first electrode 11 and each second electrode 12 intersect becomes one pixel, the shape of one pixel is two sides by the electrode edge of the first electrode 11 and two sides by the electrode edge of the second electrode 12. It becomes the substantially trapezoid shape defined by. Hereinafter, the electrode structure shown in FIG. 6 may be referred to as “type E electrode structure”.

  In FIG. 6, when the angle formed between the electrode edge of the second electrode 12 and the horizontal direction (left-right direction in the figure) is defined as θ, this angle θ is set to be greater than 0 ° and not more than 15 °. By doing so, it is possible to realize a structure in which the upper and lower sides of each pixel and the directions 13 and 14 of each alignment treatment are not orthogonal to each other. Each pixel in the electrode structure of type E is different from each other in the vertical direction and adjacent in the horizontal direction, and every other first electrode 11 and every other second electrode 12. The difference in shape is repeated.

  FIG. 7 is a schematic plan view showing another example of the electrode structure. As shown in FIG. 7A, the electrode edge of each second electrode 12 extending in the left-right direction in the drawing is formed in a sawtooth shape, and one pitch of the sawtooth is equal to the electrode width of each first electrode 11. It is set almost equal. Then, as shown in FIG. 7B, each second electrode 12 has one apex angle portion (bending point) of the sawtooth overlapped with the substantially central portion of the first electrode 11, and the other one apex angle portion ( (Bending point) is arranged so as to overlap the inter-electrode portion of the first electrode 11. Since the region where each first electrode 11 and each second electrode 12 intersect becomes one pixel, the shape of one pixel is two sides by the electrode edge of the first electrode 11 and two sides by the electrode edge of the second electrode 12. Is a substantially inverted V-shaped hexagon defined by Hereinafter, the electrode structure shown in FIG. 5 may be referred to as “type F electrode structure”.

  In FIG. 7, when the angle formed by the electrode edge of the second electrode 12 and the horizontal direction (left-right direction in the figure) is defined as θ, this angle θ is set to be greater than 0 ° and not more than 15 °. By doing so, it is possible to realize a structure in which the upper and lower sides of each pixel and the directions 13 and 14 of each alignment treatment are not orthogonal to each other. In each pixel in the type F electrode structure, adjacent pixels have the same shape in both the vertical and horizontal directions. The shape of each pixel may be a substantially V-shaped hexagon.

  FIG. 8 is a schematic plan view showing another example of the electrode structure. As shown in FIG. 8A, the electrode edge of each second electrode 12 extending in the left-right direction in the drawing is formed in a sawtooth shape, and one pitch of the sawtooth is equal to the electrode width of each first electrode 11. It is set almost equal. The difference from the type F electrode structure shown in FIG. 7 is that the bending directions of one electrode edge and the other electrode edge of each second electrode 12 are staggered, and the bending points of both electrode edges approach each other. It is that we are going away. As shown in FIG. 8B, each second electrode 12 has one bending point (vertex) of the sawtooth overlapped with the substantially central portion of the first electrode 11, and the other one bending point (vertex). It arrange | positions in the state which overlaps with the part between 1st electrodes 11 electrodes. Since the region where each first electrode 11 and each second electrode 12 intersect becomes one pixel, the shape of one pixel is two sides by the electrode edge of the first electrode 11 and two sides by the electrode edge of the second electrode 12. It becomes the substantially hexagon defined by. Hereinafter, the electrode structure shown in FIG. 8 may be referred to as “type G electrode structure”.

  In FIG. 8, if the angle formed by the electrode edge of the second electrode 12 and the horizontal direction (left-right direction in the figure) is defined as θ, this angle θ is set to be greater than 0 ° and not more than 15 °. By doing so, it is possible to realize a structure in which the upper and lower sides of each pixel and the directions 13 and 14 of each alignment treatment are not orthogonal to each other. In each pixel in the type G electrode structure, adjacent pixels in the vertical direction have different shapes, and adjacent pixels in the horizontal direction have the same shape.

Next, the results of actually producing a liquid crystal display device having each of the above-described pixel structures of types A to G and performing the orientation structure observation and appearance observation will be described. In the actually manufactured liquid crystal display device, specific numerical conditions in each electrode structure type are as follows. In any type, the distance between adjacent electrodes of each second electrode 12 is set to 0.03 mm so that the opening area does not decrease. Moreover, about the 1st electrode 11, the electrode arrangement period was 0.43 mm and the distance between adjacent electrodes was 0.03 mm. The direction of the alignment treatment, the alignment direction of the liquid crystal molecules at the approximate center of the liquid crystal layer 3, and the arrangement state of each polarizing plate are as described above.
(1) For Type A, the sawtooth vertex period was set to 0.43 mm, and θ was set to 5 °, 10 °, and 15 °.
(2) For Type B, Xa = 0.225 mm, Xb = 0.015 mm, Xa + Xb = 0.43 mm, and θ was set to 5 °, 10 °, and 15 °.
(3) For Type C, Xa = 0.3225 mm, Xb = 0.015 mm, Xa + Xb = 0.43 mm, the deviation distance of the apex portion between both electrode edges is 0.1075 mm, and θ is 5 °, 10 ° , 15 °.
(4) For Type D, the distance between adjacent bending points was 0.43 mm, and θ was set to 5 °, 10 °, and 15 °.
(5) For Type E, the same setting as Type D was used.
(6) For Type F, the distance between adjacent bending points was 0.215 mm, and θ was set to 5 °, 10 °, and 15 °.
(7) For Type G, the same setting as Type F was used.

  FIG. 9 is a diagram showing an alignment structure observation image when a voltage is applied to a liquid crystal display device having a type A electrode structure. Specifically, FIG. 9A is an observation image of θ = 5 °, FIG. 9B is an observation image of θ = 10 °, and FIG. 9C is an observation image of θ = 15 °. As shown in the figure, the shape of each pixel is a substantially parallelogram or a deformed hexagon. Similar to the liquid crystal display device according to the above-described conventional example (see FIG. 16), in this example, a dark region is observed near the pixel edge of each pixel. . However, when comparing the dark regions of the respective pixels, the shapes are almost the same, and it can be seen that the uniformity of the dark regions is greatly improved as compared with the conventional example. Further, when the dependency on the angle θ was observed in more detail, it was found that the uniformity of the dark region was improved more when θ = 10 ° and θ = 15 ° than when θ = 5 °. As a result of external observation of the liquid crystal display device of this embodiment from the 70 ° azimuth direction in the counterclockwise direction and in the clockwise and counterclockwise directions, the display uniformity, that is, the uniformity of light leakage at the pixel edge compared to the conventional example. It was confirmed that the display quality was significantly improved and the display quality was remarkably improved. The display uniformity was better when the angle θ was larger.

  FIG. 10 is a diagram showing an alignment structure observation image when a voltage is applied to a liquid crystal display device having a type B electrode structure. FIG. 11 is a diagram showing an alignment structure observation image when a voltage is applied to a liquid crystal display device having a type C electrode structure. In both cases, θ = 10 ° was set. It was found that the uniformity of the shape of the dark region was improved for both types B and C as in the case of type A. As a result of external observation of the liquid crystal display device of each of the types B and C from the 70 ° azimuth direction in the counter-viewing direction and in the clockwise and counterclockwise directions, the display uniformity compared to the conventional example, that is, the light at the pixel edge It was confirmed that the uniformity of omission was remarkably improved and the display quality was remarkably improved. However, it was also found that the display uniformity was slightly inferior to that of Type A. This is presumably because some pixels have different dark area shapes and disclination positions. However, in comparison with the conventional example, it was confirmed that the display uniformity was sufficiently improved.

  From the above observation results, it was found that the display quality of the liquid crystal display device can be remarkably improved by adopting an electrode structure in which both electrode edges of the second electrode 12 are bent in a sawtooth shape. The angle θ at the time of bending is more preferably 5 ° or more and 15 ° or less. In addition, although it is effective even if there is a bending point of each side formed by the electrode edge of the second electrode 12 in one pixel, the position of the bending point may be set to Xa at least three times Xb. More preferred.

  FIG. 12 is a diagram showing an alignment structure observation image when a voltage is applied to a liquid crystal display device having a type D electrode structure. Specifically, FIG. 12A is an observation image of θ = 5 °, FIG. 12B is an observation image of θ = 10 °, and FIG. 12C is an observation image of θ = 15 °. Observing each of the three oriented structures, the uniformity of the dark region is improved as compared with the conventional liquid crystal display device. However, when observed in more detail, the uniformity is slightly insufficient at θ = 5 °, and θ It can be seen that the uniformity of the dark region is higher when = 10 ° and θ = 15 °. As a result of external appearance observation similar to the case of types A to C described above, it was found that the display uniformity was slightly inferior to these. However, in comparison with the conventional example, it was confirmed that the display uniformity was sufficiently improved. It was also found that θ = 10 ° or more is more preferable.

  FIG. 13 is a diagram showing an alignment structure observation image when a voltage is applied to a liquid crystal display device having a type E electrode structure (when θ = 10 °). Observing the orientation structure, it can be seen that although the dark region differs for each pixel, the position of the disclination is almost fixed at a specific position, and the orientation uniformity is relatively good. As a result of appearance observation similar to that of Type D described above, it was found that the display uniformity was slightly inferior to Types A to C but better than Type D. However, in comparison with the conventional example, it was confirmed that the display uniformity was sufficiently improved.

  The difference in display uniformity between Type D and Type E can be attributed to the difference in pixel structure. In type D, the distribution of multi-domain orientations differs when the voltage is applied to pixels adjacent in the left-right direction, and the viewing angle characteristics tend to be different. On the other hand, in Type E, the shape of adjacent pixels differs in the vertical direction and the horizontal direction, but since the same shape of pixels is actually arranged in a checkered pattern, the distribution of multi-domain alignment at the time of voltage application is equal. By arranging the pixels in a checkered pattern, it is considered that the display uniformity by appearance observation is better than that of Type D.

  FIG. 14 is a diagram showing an alignment structure observation image when a voltage is applied to a liquid crystal display device having a type G electrode structure (when θ = 10 °). Observing the oriented structure, it was found that the dark region has disclinations corresponding to the bending points formed by the electrode edges of the first electrode 11, but the uniformity of the shape is not sufficient. Probably, the disclination is fixed by making the angle of the apex more acute, and the dark region is likely to be fixed. Although not shown, this tendency is the same for a liquid crystal display device having a type F electrode structure. A liquid crystal display device having type G and type F electrode structures was visually observed, but display uniformity was not obtained as compared with types A to E. Even when compared with the liquid crystal display device of the conventional example, a significant difference could not be observed. Therefore, as shown for types B and C, it was found that it is not effective when the bending points are arranged so that Xa and Xb are equal in the horizontal direction of the pixel. However, in the above description, the case where the pretilt angle is 89.9 ° is shown, and when the pretilt angle is set lower, for example, when it is set to 89.8 °, compared to the conventional liquid crystal display device. Significant differences can be observed, and it has been confirmed that uniformity from the anti-viewing direction can be realized in appearance observation as in other types.

  In addition, this invention is not limited to the content of embodiment mentioned above, In the range of the summary of this invention, it can change and implement variously. For example, in the above-described embodiment, the electrode edges on both sides of the second electrode are formed in a polygonal line, but only one electrode edge may be formed in a polygonal line. In that case, it is desirable that the line segments that intersect diagonally be arranged on the non-viewing side of the pixel edge.

  DESCRIPTION OF SYMBOLS 1 ... 1st board | substrate 2 ... 2nd board | substrate 3 ... Liquid crystal layer 4 ... 1st polarizing plate 5 ... 2nd polarizing plate 6 ... 1st viewing angle compensation plate 7 ... 2nd viewing angle compensation plate 8, 9 ... Orientation film 11 ... 1st Electrode 12 ... Second electrode 13, 14 ... Direction of orientation treatment

Claims (4)

A first substrate and a second substrate disposed opposite to each other;
A first electrode provided on one surface of the first substrate and extending in a first direction;
A second electrode provided on one surface of the second substrate and extending in a second direction intersecting the first direction;
A substantially vertically aligned liquid crystal layer provided between one surface of the first substrate and one surface of the second substrate;
A pixel is formed in a region where the first electrode and the second electrode intersect,
At least one of the first substrate and the second substrate is subjected to an alignment process in a direction substantially parallel to the first direction,
The first electrode has a linear shape with electrode edges on both sides extending in the first direction;
The second electrode has a folded line shape including a line segment in which at least one electrode edge is obliquely crossed with respect to the first direction,
The oblique line segments obliquely form an angle greater than 0 ° and less than or equal to 15 ° with respect to the second direction,
The pixel includes a diagonal line segment to define a pixel edge;
Liquid crystal display device.   A first substrate and a second substrate disposed opposite to each other;
  A first electrode provided on one surface of the first substrate and extending in a first direction;
  A second electrode provided on one surface of the second substrate and extending in a second direction intersecting the first direction;
  A substantially vertically aligned liquid crystal layer provided between one surface of the first substrate and one surface of the second substrate;
  A pixel is formed in a region where the first electrode and the second electrode intersect,
  At least one of the first substrate and the second substrate is subjected to an alignment process in a direction substantially parallel to the first direction,
  The first electrode has a linear shape with electrode edges on both sides extending in the first direction;
  The second electrode has a folded line shape including a line segment in which at least one electrode edge is obliquely crossed with respect to the first direction,
  The oblique line segment is configured by connecting a first straight line and a second straight line extending in different directions,
  The first straight line and the second straight line are in a relationship where Xa is three times greater than Xb, where Xa and Xb are the lengths when projected in the first direction, respectively.
  The first straight line is skewed at an angle greater than 0 ° and less than or equal to 15 ° with respect to the second direction;
  The pixel includes a diagonal line segment to define a pixel edge;
  Liquid crystal display device.   A first substrate and a second substrate disposed opposite to each other;
  A first electrode provided on one surface of the first substrate and extending in a first direction;
  A second electrode provided on one surface of the second substrate and extending in a second direction intersecting the first direction;
  A substantially vertically aligned liquid crystal layer provided between one surface of the first substrate and one surface of the second substrate;
  A pixel is formed in a region where the first electrode and the second electrode intersect,
  At least one of the first substrate and the second substrate is subjected to an alignment process in a direction substantially parallel to the first direction,
  The first electrode has a linear shape with electrode edges on both sides extending in the first direction;
  The second electrode has a folded line shape including a line segment in which at least one electrode edge is obliquely crossed with respect to the first direction,
  The oblique line segments are configured by connecting a first straight line and a second straight line that are substantially equal to each other and extend in different directions.
  The first straight line and the second straight line cross each other at an angle of greater than 0 ° and less than or equal to 15 ° with respect to the second direction,
  The pixel includes a diagonal line segment to define a pixel edge;
  Liquid crystal display device.   4. The liquid crystal display device according to claim 1, wherein the oblique line segments are arranged on a side opposite to the visual recognition direction of the pixel edges. 5.

Images