JP5584091B2 - 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 the approximate center in the 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.

  Further, in the VA mode liquid crystal display device, when a bright display state in front view is obtained during multiplex driving, a dark region may be generated in each pixel, and display quality may be deteriorated. Since this phenomenon appears conspicuously by reducing the frame frequency, it is necessary to set the drive frequency higher in order to eliminate this phenomenon. However, when the drive frequency is raised, the impedance between the electrodes increases, so that the current consumption increases, the load on the drive device increases, and the potential difference on the electrodes becomes obvious, resulting in a reduction in display quality. Specifically, so-called crosstalk is likely to occur.

JP 2005-234254 A

  In a specific aspect of the present invention, in a vertical alignment type liquid crystal display device that operates by multiplex driving, the light omission near the edge of each pixel when observed from the opposite viewing direction is homogenized to improve display quality. One of the purposes is to realize display uniformity at the time of front observation with a frame frequency as low as possible.

  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. Further, in such a pixel structure, it was further found that an effect of lowering the frame frequency can be obtained by providing a rectangular opening on one of the intersecting electrodes. 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. And having at least one rectangular opening that is long in the first direction, and (h) the second electrode is an electrode on both sides Tsu di is the polygonal line shape containing oblique line with respect to the second direction, (i) the pixel is, the swash pixel edge of the second electrode and the electrode edge of the first electrode Pixel edges are defined by intersecting line segments, (j) the oblique line segments obliquely form an angle greater than 0 ° and less than or equal to 15 ° with respect to the first direction, and (k) the The opening is a liquid crystal display device disposed so as to overlap with the pixel. Here, “obliquely intersect” means that they intersect obliquely at an angle other than orthogonal.

  In the liquid crystal display device described above, it is preferable that the opening is arranged with a longitudinal direction parallel to the first direction. In the above liquid crystal display device, it is also preferable that the opening is disposed with its longitudinal direction inclined with respect to the first direction. In this case, it is also preferable that the opening is arranged so that the longitudinal direction is substantially orthogonal to 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 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. And having at least one rectangular opening that is long in the first direction, and (h) the second electrode is an electrode on both sides And (i) the pixel includes the pixel edge of the first electrode and the pixel edge of the second electrode. A pixel edge is defined by intersecting line segments, and (j) the opening is disposed so as to overlap the pixel, and the longitudinal direction is disposed to be inclined with respect to the first direction. is there. Here, “obliquely intersect” means that they intersect obliquely at an angle other than orthogonal.

  In the above liquid crystal display device, the opening is preferably arranged so that the longitudinal direction is substantially orthogonal to the oblique line segment.

  According to each of the above configurations, since the pixel edge is defined including a line segment that obliquely intersects with the direction of the alignment process, the light omission near the edge of each pixel when viewed from the opposite viewing direction is homogenized. Display quality can be improved. In addition, by providing the rectangular portion that overlaps the pixel, an effect of reducing the frame frequency at which display uniformity during frontal observation can be obtained can be obtained.

It is typical sectional drawing which shows the structure of the liquid crystal display device of one Embodiment. It is a typical top view showing an example of the electrode structure of the 2nd electrode. It is a typical top view showing other examples of the electrode structure of the 2nd electrode. It is a typical top view showing other examples of the electrode structure of the 2nd electrode. It is a typical top view showing other examples of the electrode structure of the 2nd electrode. It is a typical top view which shows an example of the electrode structure of the 1st electrode which has an opening part. It is a typical top view which shows another example of the electrode structure of the 1st electrode which has an opening part. It is a typical top view showing an example of pixel structure. It is a typical top view showing other examples of pixel structure. It is a typical top view showing other examples of pixel structure. It is a figure which shows an orientation structure | tissue observation image. It is a figure which shows an orientation structure | tissue observation image. It is a figure which shows an orientation structure | tissue observation image. 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. 14 is a plan view schematically showing the alignment direction (alignment distribution) of liquid crystal molecules at the approximate center of the liquid crystal layer when a voltage is applied in one rectangular pixel obtained by crossing strip-shaped electrodes. is there. 14 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. 14 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. 15 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 distance 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 of FIG. 15 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. Further, by providing each first electrode 11 with a rectangular opening, the frame frequency is reduced. Below, some specific structures are illustrated.

  FIG. 2 is a schematic plan view showing an example of the electrode structure of the second electrode. 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 a 1/2 pitch of the sawtooth is an electrode of each first electrode 11. It is set almost equal to the width. As shown in FIG. 2B, each second electrode 12 is arranged such that one apex angle portion (bending point) of the saw blade overlaps with 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 parallelogram defined by Hereinafter, the electrode structure shown in FIG. 2 may be referred to as a “type A electrode structure”.

  In FIG. 2, 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, 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. In each pixel in the type A 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. 3 is a schematic plan view showing another example of the electrode structure of the second electrode. 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, 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 A electrode structure shown in FIG. 2 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. As shown in FIG. 3B, each second electrode 12 is arranged 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. It becomes the substantially trapezoid shape defined by. Hereinafter, the electrode structure shown in FIG. 3 may be referred to as a “type B electrode structure”.

  In FIG. 3, 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 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. Each pixel in the type B electrode structure is different in adjacent pixels in the vertical direction and adjacent pixels in the horizontal direction, and every other first electrode 11 and every other second electrode 12. The difference in shape is repeated.

  FIG. 4 is a schematic plan view showing another example of the electrode structure of the second electrode. 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, and one pitch of the sawtooth corresponds to the electrode width of each first electrode 11. It is set almost equal. Then, as shown in FIG. 4B, 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. 4 may be referred to as a “type C electrode structure”.

  In FIG. 4, 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, 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. In each pixel in the type C 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. 5 is a schematic plan view showing another example of the electrode structure of the second electrode. 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 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 C electrode structure shown in FIG. 4 is that the direction of bending at one electrode edge and the other electrode edge of each second electrode 12 is staggered, and the bending points of both electrode edges approach each other. It is that we are going away. As shown in FIG. 5 (b), each second electrode 12 has one bending point (vertex) of the sawtooth overlapping 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. 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 different shapes, and adjacent pixels in the horizontal direction have the same shape.

  FIG. 6 is a diagram illustrating an example of an electrode structure of a first electrode having an opening. As shown in FIG. 6, each first electrode 11 is provided with a rectangular opening portion 15 that is long along the first direction that is the extending direction thereof. In the illustrated example, the longitudinal direction of each opening 15 is substantially parallel to the first direction and is arranged along the longitudinal direction. In addition, as shown in FIG. 7, the longitudinal direction of each opening 15 may be arranged at a predetermined angle with respect to the first direction. For example, the longitudinal direction of each opening 15 may be a direction substantially orthogonal to the electrode edge of the second electrode 12. In the illustrated example, the inclination directions of the openings 15 are staggered between the adjacent first electrodes 11, but the inclination directions may be aligned.

  Next, the structure of a pixel configured by combining the first electrode 11 and the second electrode 12 will be described.

  FIG. 8 is a diagram illustrating an example of a pixel structure. This example is a one-pixel electrode structure in which the second electrode 12 having the type C electrode structure described above and the first electrode 11 having the opening 15 shown in FIG. 6 are combined. The electrode pitch of the first electrode 11 is Ws, the electrode pitch of the second electrode 12 is Wc, and the long side length (length in the longitudinal direction) of the opening 15 provided in the first electrode 11 is Ls. In this example, the opening 15 is arranged such that one end (short side) overlaps between the electrodes of the adjacent second electrodes 12 and overlaps with the bending point of the second electrode 12.

  FIG. 9 is a diagram illustrating another example of the electrode structure. This example is an electrode structure of two pixels when the second electrode 12 having the type A electrode structure described above and the first electrode 11 having the opening 15 shown in FIG. 6 are combined. The electrode pitch of the first electrode 11 is Ws, the electrode pitch of the second electrode 12 is Wc, and the long side (length in the longitudinal direction) of the opening 15 provided in the first electrode 11 is Ls. In this example, the opening 15 is disposed in the center of the pixel with respect to the width direction of the first electrode 11, and one end (short side) overlaps between adjacent electrodes of the second electrode 12. Is arranged.

  FIG. 10 is a diagram illustrating another example of the electrode structure. This example is a two-pixel electrode structure in which the second electrode 12 having the type A electrode structure described above and the first electrode 11 having the obliquely arranged openings 15 shown in FIG. 7 are combined. The electrode pitch of the first electrode 11 is Ws (see FIG. 9), and the electrode pitch of the second electrode 12 is Wh. Further, the long side length (length in the longitudinal direction) of the opening 15 in the inclined arrangement provided in the first electrode 11 is Lt. In this example, the opening 15 is arranged so as to include the center of gravity of the pixel (indicated by crossing alternate long and short dashed lines in the drawing).

  In addition to the combinations exemplified, it is possible to appropriately combine each electrode structure of the second electrode 12 of types A to D and each electrode structure of the first electrode 11 shown in FIGS. It is.

Next, the results of actually producing a liquid crystal display device having the above-described pixel structures and observing the orientation structure and the appearance thereof will be described. In the actually manufactured liquid crystal display device, specific numerical conditions in each electrode structure type are as follows.
(1) For Type A, the distance between adjacent refraction points was 0.43 mm, and θ was set to 5 °, 10 °, and 15 °.
(2) For Type B, the same settings as for Type A were used.
(3) For Type C, the distance between adjacent refraction points was 0.215 mm, and θ was set to 5 °, 10 °, and 15 °.
(4) For Type D, the same settings as for Type C were used.
The electrode pitch Ws of the first electrode 11 is 0.43 mm, the electrode pitch Wc of the second electrode 12 is 0.43 mm, and the long side length Ls of the opening 15 is 0.43 mm, 0.32 mm, and 0.215 mm. Set to either. For the opening 15 in the inclined arrangement, the long side length Lt of the opening 15 is 1 time (Lt = Wh), 0.75 times (Lt = 0.75 Wh) with respect to the electrode width Wh of the second electrode 12. One of 0.5 times (Lt = 0.5 Wh) was set.
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.

  First, the results of the alignment structure observation and appearance observation of the liquid crystal display device when the opening 15 is not provided in the first electrode 11 will be described.

  FIG. 11A is a diagram showing an alignment texture observation image when voltage is applied when θ is set to 10 ° in the type A electrode structure. As shown in the figure, a dark region is observed near the pixel edge, but it can be seen that the distribution pattern of the dark region is regular and highly uniform as compared with the above-described conventional liquid crystal display device. However, since the pixel shape is different with respect to the direction in which the second electrode 12 extends, the pattern of the dark region does not completely match. However, in appearance observation, it was confirmed that the uniformity of light leakage from the vicinity of the pixel edge when observed from the opposite viewing direction was improved, thereby improving the display uniformity.

  FIG. 11B is a diagram showing an alignment texture observation image when voltage is applied when θ is set to 10 ° in the type B electrode structure. As in the case of type A, uniformity is observed in the distribution pattern of the dark region near the pixel edge as compared with the liquid crystal display device of the conventional example. Although the pixel shapes in the extending directions of the adjacent first electrode 11 and second electrode 12 are different, pixels having the same shape are arranged in a checkered pattern. In appearance observation from the opposite viewing direction, it was confirmed that the uniformity of light leakage near the pixel edge was improved, and the display uniformity was thereby improved. The display uniformity was superior to that of the above-described type A electrode structure (see FIG. 11A).

  FIG. 11C is a diagram showing an alignment structure observation image at the time of voltage application when θ is set to 10 ° in the type D electrode structure. Although inferior to the case of the type A and B electrode structures described above, uniformity is observed in the distribution pattern of the dark region near the pixel edge as compared with the liquid crystal display device of the conventional example. In the appearance observation from the opposite viewing direction, it was found that the uniformity of light leakage near the pixel edge was slightly improved, thereby improving the display uniformity. Although not shown, the same observation result was obtained for the type C electrode structure.

  For each of the liquid crystal display devices having the electrode structures of types A to D and the conventional liquid crystal display device, the drive frequency dependence of display uniformity during bright display during frontal observation was evaluated. The drive condition is 1/64 duty, 1/9 bias, bright display drive voltage that obtains almost maximum contrast by multiplex drive with frame inversion waveform, and the lower limit of the frame frequency at which display non-uniformity is observed The appearance was evaluated by observation.

  As a result, the conventional liquid crystal display device is 105 Hz, 115 Hz for the type A electrode structure, 95 Hz for the type B electrode structure, 135 Hz for the type C electrode structure, and the type D electrode structure. In this case, it was found that display uniformity cannot be obtained unless the lower limit value of the frame frequency is higher than that of the conventional example except 130 Hz. Furthermore, when θ changed to 5 °, 10 °, and 15 ° in Type B, the lower limit value of the frame frequency was observed to change to 120 Hz, 135 Hz, and 150 Hz. On the other hand, since the display uniformity when observed from the opposite viewing direction is improved as θ increases, it has been found that the two have a trade-off relationship. This trend was similar for the other types.

  Next, the results of the alignment structure observation and appearance observation of the liquid crystal display device when the opening 15 is provided in the first electrode 11 will be described.

  FIG. 12 is a diagram showing an alignment structure observation image at the time of voltage application when the above-described type C electrode structure and the electrode structure shown in FIG. 6 are combined and θ is set to 10 °. The long side length Ls of the opening 15 is set to 0.43 mm, 0.32 mm, or 0.215 mm, and the observed images are shown in FIGS. 12 (a), 12 (b), and 12 (c). ). In the observation image shown in FIG. 12A, the uniformity of the shape of the dark region expressed on the long side portion of the opening 15 is good, but the dark region generated near the electrode edge of the second electrode 12 is compared. It turned out that it was regularly distributed. In FIG. 12B and FIG. 12C, since the side area of the opening 15 is reduced by reducing the long side length of the opening 15, the aperture ratio of the pixel is increased and the dark area is increased. It is observed that the uniformity of the distribution pattern is improved.

  Moreover, as a result of observing the appearance of the liquid crystal display device of each condition from the anti-viewing direction, it was found that the non-uniformity for each pixel becomes difficult to observe and the display uniformity is remarkably improved by arranging the opening 15. . This is probably because the multi-domain alignment structure in the pixel is stabilized by the opening 15 being arranged at the bending point of the second electrode 12. In particular, when the opening 15 is not provided, it is considered that the orientation is improved in the vicinity of the upper edge of the pixel where the dark region is generated, and the appearance uniformity is improved.

  Using the liquid crystal display device under the above conditions, the frame frequency dependence of display uniformity during bright display during front observation was observed, and the lower limit of the frame frequency at which display uniformity was obtained was evaluated by appearance observation. Similar to the above, the driving conditions are 1/64 duty, 1/9 bias, a multiplex drive with a frame inversion waveform, a bright display drive voltage that can obtain almost the maximum contrast, and a frame in which display non-uniformity is observed. The lower limit of the frequency was evaluated by appearance observation. As a result, in each liquid crystal display device in which the long side length Ls of the opening 15 is 0.43 mm, 0.32 mm, and 0.215 mm, the lower limit values of the frame frequency are 80 Hz, 90 Hz, and 95 Hz, respectively. It was found that the liquid crystal display device in the case where the opening 15 is not provided and the liquid crystal display device of the conventional example are significantly reduced. In addition, when Ls became short, the tendency for the lower limit of a frame frequency to become high was seen. However, it was confirmed that the effect was obtained if Ls was at least 1/2 of the electrode width or electrode pitch of the second electrode 12. In this study, the opening 15 and the bending point of the electrode edge of the second electrode 12 overlap each other, but it was confirmed that the effect of lowering the lower limit value of the frame frequency can be obtained even if the both do not overlap.

  FIG. 13A is a diagram showing an alignment structure observation image when voltage is applied when the above-described type A electrode structure is combined with the electrode structure shown in FIG. 6 and θ is set to 10 °. Note that θ is set to 10 °, and the long side length Ls of the opening 15 is 0.43 mm. The distribution pattern of the dark region is clearly improved in uniformity compared to that shown in FIG. 12, and the dark region near the electrode edge of the second electrode 12 is also distributed relatively uniformly. It was confirmed that the uniformity of light leakage near the pixel edge observed from the anti-viewing direction was remarkably improved as compared with the case where the opening 15 was not provided, and the display uniformity was greatly improved. As a result of observing the frame frequency dependency of the display uniformity during bright display during frontal observation and evaluating the lower limit of the frame frequency to obtain display uniformity by appearance observation, the lower limit of the frame frequency is 80 Hz. It has been found that this can be improved significantly compared to the case where the portion 15 is not provided.

  FIG. 13B is a diagram showing an alignment texture observation image when voltage is applied when the above-described type A electrode structure is combined with the electrode structure shown in FIG. 6 and θ is set to 10 °. Note that θ is set to 10 °, and the long side length Lt of the opening 15 is made equal to the electrode width of the second electrode 12. The distribution pattern of the dark region is considered to be good with high uniformity as in FIG. It was confirmed that the uniformity of light leakage near the pixel edge observed from the anti-viewing direction was remarkably improved as compared with the case where the opening 15 was not provided, and the display uniformity was greatly improved. As a result of observing the frame frequency dependence of the display uniformity during bright display during frontal observation and evaluating the lower limit of the frame frequency at which display uniformity can be obtained by external appearance observation, the lower limit of the frame frequency is 75 Hz, and the aperture Compared with the case where the portion 15 is not provided, the improvement can be made significantly, and the lowest value can be obtained as compared with other electrode structures.

  As described above, the lower limit value of the frame frequency at which the display uniformity in the anti-viewing direction and the display uniformity at the time of front observation of the liquid crystal display device having the electrode structure 15 has been evaluated. Even when combined with 12 electrode structures, the same improvement effect is expected.

  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, one opening is disposed in each pixel, but two or more openings may be disposed in each pixel. It is considered that the lower limit of the frame frequency can be further lowered by providing a plurality of openings.

  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 (5)

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 at least one rectangular opening that has a linear shape with electrode edges on both sides extending in the first direction and is long in the first direction;
The second electrode has a folded line shape including a line segment in which electrode edges on both sides are oblique to the first direction,
The pixel has a pixel edge defined by the oblique line segment of the electrode edge of the first electrode and the pixel edge of the second electrode,
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 opening is disposed so as to overlap the pixel.
Liquid crystal display device.   The liquid crystal display device according to claim 1, wherein the opening is arranged with a longitudinal direction parallel to the first direction.   The liquid crystal display device according to claim 1, wherein the opening is disposed with a longitudinal direction inclined with respect to the first direction. 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 at least one rectangular opening that has a linear shape with electrode edges on both sides extending in the first direction and is long in the first direction;
The second electrode has a folded line shape including a line segment in which electrode edges on both sides are oblique to the first direction,
The pixel has a pixel edge defined by the oblique line segment of the electrode edge of the first electrode and the pixel edge of the second electrode,
The opening is disposed so as to overlap the pixel, and the longitudinal direction is disposed to be inclined with respect to the first direction.
Liquid crystal display device.   The liquid crystal display device according to claim 4, wherein the opening is disposed so that the longitudinal direction is substantially orthogonal to the oblique line segment.

Images