JP4629135B2 - Liquid crystal display device - Google Patents

Description

  The present invention relates to a liquid crystal display device. In particular, the present invention relates to a liquid crystal display device that turns on and off liquid crystal molecules by forming an electric field in a direction substantially parallel to a substrate surface in order to realize a liquid crystal display device having excellent viewing angle characteristics.

  A liquid crystal display device that turns on and off liquid crystal molecules by forming an electric field in a direction substantially parallel to the substrate surface is also called a lateral electric field drive type liquid crystal display device. In a horizontal electric field drive type liquid crystal display device, one of a pair of substrates sandwiching liquid crystal has a first electrode and a second electrode, and the first electrode is directed to the second electrode. An electric field is formed. Such a liquid crystal display device is described in Patent Document 1, for example.

  In a horizontal electric field drive type liquid crystal display device, a horizontal alignment type liquid crystal is used. The liquid crystal is initially aligned in parallel to the substrate surface and in the first direction. When a voltage is applied, the liquid crystal is aligned in parallel to the substrate surface and in the second direction rotated from the first direction. Become. That is, when a voltage is applied, the liquid crystal molecules try to line up parallel to the electric field formed between the first and second electrodes. Since the movement of the liquid crystal molecules occurs in a plane parallel to the substrate surface, the viewing angle characteristic is not deteriorated unlike the TN liquid crystal, and a liquid crystal display device having a wide viewing angle characteristic is realized.

  Patent Document 2 discloses a modification of a horizontal electric field drive type liquid crystal display device. In this liquid crystal display device, one of the pair of substrates sandwiching the liquid crystal has the first electrode, the other substrate has the second electrode, and the first electrode, the second electrode, Are arranged in a positional relationship shifted in a direction parallel to the substrate surface. In this case, the first and second substrates extend in a strip shape having a small width in parallel with each other. A plane including the first electrode and the second electrode is inclined with respect to the substrate surface, and an oblique electric field is formed. However, since the distance between the first electrode and the second electrode is considerably larger than the thickness of the liquid crystal layer, the plane including the first electrode and the second electrode is substantially parallel to the substrate surface. Can do. Therefore, also in this case, a horizontal alignment type liquid crystal is used, and the behavior of the liquid crystal is the same as described above.

Patent Document 3 discloses a liquid crystal display device driven by an oblique electric field. Both the pixel electrode and the common electrode are formed in a comb-teeth shape, and each of the pixel electrode and the common electrode includes a plurality of parallel linear electrode elements.
Japanese Patent Laid-Open No. 7-36058 (published February 7, 1995) JP 7-159807 A (published on June 23, 1995) Japanese Patent Laid-Open No. 10-48671 (published on February 20, 1998)

  In a horizontal electric field driving type liquid crystal display device in which the first and second electrodes are formed on one substrate, the electric field is formed from the first electrode to the second electrode, but the electric field strength is the same as that of the electrode. Strong on the substrate side and weak on the substrate side without electrodes. Therefore, when a voltage is applied, the alignment of the liquid crystal is not uniform between the first and second substrates, and disclination may occur in the pixel. Further, if the electrode is on only one substrate and the other substrate has no electrode, static electricity may accumulate in the alignment film of the substrate without the electrode.

  In the case of a lateral electric field drive type liquid crystal display device in which the first substrate has the first electrode and the second substrate has the second electrode, the problem of static electricity is solved. However, the electric field is actually formed obliquely on the substrate surface from the first electrode to the second electrode. Therefore, when a voltage is applied, the horizontally aligned liquid crystal rises obliquely while rotating in order to be parallel to the electric field. However, it is difficult for the horizontal alignment type liquid crystal to stand up obliquely while rotating, and the behavior of the liquid crystal may be disturbed.

Further, in the horizontal electric field drive type liquid crystal display device, at least one of the first electrode and the second electrode is provided in the pixel, and the aperture ratio is often small. Therefore, there is a demand for an electrode arrangement that can perform bright display with a large aperture ratio.
In the oblique electric field method in which different voltages are applied to the respective electrodes on the two substrates constituting the liquid crystal panel to drive the liquid crystal, if the displacement between the two substrates occurs, the electrode on one substrate and the other There is a problem that the gap between the electrodes of the substrate changes and the voltage-transmittance characteristics change. Therefore, the bonding accuracy of the two substrates is very strict and the manufacturing margin is very small.

An object of the present invention is to provide a lateral electric field drive type liquid crystal display device capable of accurately controlling the behavior of liquid crystal.
Another object of the present invention is to provide a horizontal electric field drive type liquid crystal display device which can perform bright display with a large aperture ratio.
Another object of the present invention is to provide a liquid crystal display device in which a change in voltage-transmittance characteristics is small even when a positional deviation between two substrates occurs.

A liquid crystal display device according to the present invention includes first and second opposing substrates, a liquid crystal layer sealed between the first and second substrates, and a first electrode provided on the first substrate. And a second electrode provided on the second substrate, and when no voltage is applied, the liquid crystal molecules in the liquid crystal layer are aligned perpendicular to the substrate surfaces of the first and second substrates. And the first electrode and the second electrode are composed of a plurality of parallel electrode elements in one pixel, and at least one of the electrode width and the electrode gap of the electrode elements of the electrode is non-uniform. It is a feature.

A liquid crystal display device according to a reference of the present invention includes first and second opposing substrates, a liquid crystal layer sealed between the first and second substrates, and a first liquid crystal provided on the first substrate. 1 and a second electrode, and when no voltage is applied, the liquid crystal molecules in the liquid crystal layer are aligned perpendicular to the substrate surfaces of the first and second substrates, and the first The electrode and the second electrode are composed of a plurality of parallel electrode elements in one pixel, and at least one of the electrode width and the electrode gap of the electrode element of the electrode is non-uniform.

Preferably, at least one of the electrode width and the electrode gap of at least one electrode element of the first and second electrodes is non-uniform. At least one of the first and second electrodes is formed in a comb shape. At least one electrode element of the first and second electrodes is parallel or perpendicular to the data bus line.
Preferably, the electrode width of at least one of the first and second electrodes is constant, and the electrode gap is non-uniform. Alternatively, the electrode gap of at least one of the first and second electrodes is constant, and the electrode width is non-uniform.

  Moreover, a part or all of at least one electrode element of the first and second electrodes is not parallel to the data bus line. Alternatively, one electrode element of the first and second electrodes is parallel to the bus line, and the electrode element of the other substrate has an angle with the bus line. Alternatively, part or all of the width of the electrode element of at least one of the first and second electrodes changes discontinuously.

  In addition, at least one electrode element of the first and second electrodes has a step shape. In this case, both the electrode elements of the first and second electrodes may be stepped, and the direction in which the electrode width decreases may be the same. Alternatively, one electrode element of the first electrode and the second electrode is shifted from each other with respect to the other electrode element.

  When no voltage is applied, the liquid crystal molecules are aligned parallel to the substrate. Alternatively, the liquid crystal molecules are aligned perpendicular to the substrate when no voltage is applied.

  According to the present invention, it is possible to realize a liquid crystal display device that has a high aperture ratio, is bright, and has favorable viewing angle characteristics. In addition, a liquid crystal display device with a small change in voltage-transmittance characteristics can be obtained.

  In the liquid crystal display device according to the present invention, the first electrode and the second electrode are not uniform in at least one of the electrode width and the electrode gap of the electrode element of the first electrode in one pixel. Even if the first and second substrates are misaligned, the change in voltage-transmittance characteristics can be reduced.

[Reference form]
First, a reference form on which the present invention is based will be described.

  FIG. 1 shows the principle configuration of this embodiment. 1A shows a liquid crystal display device when no voltage is applied, FIG. 1B shows a liquid crystal display device when a voltage is applied, and FIG. 1C shows a voltage applied. The display of one pixel is shown. In FIG. 1, the liquid crystal display device 10 includes first and second opposing transparent glass substrates 12 and 14, and a liquid crystal layer 16 sealed between the first and second substrates 12 and 14.

  The first electrode 18 is provided on the first substrate 12, and the second electrode 20 is provided on the second substrate 14. The first electrode 18 and the second electrode 20 extend long and straight in a direction perpendicular to the paper surface of FIG. The second electrode 20 is provided at a position shifted in a direction parallel to the substrate surface without overlapping (or facing) the first electrode 18. In the reference example, the first electrode 18 is a common electrode, and the second electrode 20 is a pixel electrode.

  The liquid crystal of the liquid crystal layer 16 is vertically aligned. The dielectric anisotropy of the liquid crystal is positive. Further, alignment films 22 and 24 are provided on the first and second substrates 12 and 14, respectively. The alignment films 22 and 24 are vertical alignment type alignment films. As the vertical alignment films 22 and 24, a polyimide vertical alignment film manufactured by Nippon Synthetic Rubber Co., Ltd. can be used. As the liquid crystal, a liquid crystal having a positive dielectric anisotropy manufactured by Merck can be used. The liquid crystal is a blend liquid crystal containing at least one of a fluorine-based liquid crystal and a cyano-based liquid crystal.

  Therefore, as shown in FIG. 1A, when no voltage is applied, the liquid crystal molecules are aligned substantially perpendicular to the substrate surface. As shown in FIG. 1B, when a voltage is applied between the first electrode 18 and the second electrode 20, the second electrode 20 to the first electrode 18 are indicated by arrows. An electric field toward is formed. Although the electric field is formed obliquely with respect to the substrate surface, the distance between the first electrode 18 and the second electrode 20 is considerably larger than the thickness of the liquid crystal layer 16. Accordingly, the inclination of the plane including the first electrode 18 and the second electrode 20 is relatively small and can be regarded as being substantially parallel to the substrate surface. Therefore, the liquid crystal display device 10 can be considered as a kind of lateral electric field drive type liquid crystal display device. Here, the electric field formed obliquely with respect to the substrate surface is referred to as an oblique electric field.

  When a voltage is applied, the liquid crystal molecules that are vertically aligned and have a positive dielectric anisotropy are aligned so as to be parallel to the oblique electric field. Many liquid crystal molecules in one pixel shift from the state of FIG. 1R> 1 (A) to FIG. 1 (B) very smoothly and stably align so as to be parallel to the oblique electric field. Therefore, as shown in FIG. 1C, the one pixel region 10a of the liquid crystal display device 10 can realize a bright display without disclination.

  FIG. 2 is a diagram showing a comparative example of the liquid crystal display device of FIG. In FIG. 2, the first electrode 18 a and the second electrode 20 a are provided only on the second substrate 14. The liquid crystal layer 16 includes a liquid crystal having a vertical alignment type and a positive dielectric anisotropy. Therefore, when a voltage is applied, the liquid crystal molecules are aligned so as to be parallel to the transverse electric field as indicated by arrows. However, it is unclear whether the liquid crystal molecules located in the middle part between the two electrodes 18a and 20a follow the alignment direction of the liquid crystal molecules on the right end side or the alignment direction of the liquid crystal molecules on the left end side. It becomes unstable. Therefore, as shown in FIG. 2C, a disclination D is generated at the center of one pixel region 10b of the liquid crystal display device.

  In the configuration of FIG. 1, when the liquid crystal molecules have negative dielectric anisotropy, the liquid crystal molecules are aligned perpendicular to the electric field. This is similar to, for example, the alignment of liquid crystal molecules located in the middle part of FIG. In this case, the liquid crystal molecules are almost vertically aligned, and a bright display cannot be realized. In the reference example of FIG. 1, an orientation without disclination is realized in a voltage application state. Since there is no disclination, there is no portion where the elastic energy stays, and the threshold voltage can be reduced.

  FIG. 3 is a diagram showing an example of a change in the configuration of FIG. 3A shows a liquid crystal display device when no voltage is applied, FIG. 3B shows a liquid crystal display device when a voltage is applied, and FIG. 3C shows a voltage application. The display of one pixel is shown. In FIG. 3, the liquid crystal display device 10 includes first and second opposing transparent glass substrates 12 and 14 and a liquid crystal layer 16 sealed between the first and second substrates 12 and 14.

  The first electrode 18 is provided on the first substrate 12, and the second electrode 20 and the third electrode 26 are provided on the second substrate 14. The first electrode 18, the second electrode 20, and the third electrode 26 extend long and straight in a direction perpendicular to the paper surface of FIG. 3. The second electrode 20 is provided at a position shifted from the first electrode 18 in a direction parallel to the substrate surface without overlapping with each other. The third electrode 26 is provided at a position overlapping (or facing) the first electrode 18. In FIG. 3, the first electrode 18 and the third electrode 26 are common electrodes, and the second electrode 20 is a pixel electrode. The liquid crystal of the liquid crystal layer 16 is vertically aligned, and the dielectric anisotropy of the liquid crystal is positive. Further, vertical alignment films 22 and 24 are provided on the first and second substrates 12 and 14, respectively.

  Therefore, as shown in FIG. 3A, when no voltage is applied, the liquid crystal molecules are aligned substantially perpendicular to the substrate surface. When a voltage is applied between the first electrode 18 and the second electrode 20 and between the third electrode 26 and the second electrode 20 as shown in FIG. As shown, an electric field from the second electrode 20 toward the first electrode 18 and the third electrode 26 is formed.

In this way, by using the oblique electric field and the horizontal electric field in combination, the alignment of the liquid crystal molecules located particularly in the middle portion is stabilized, and as shown in FIG. The pixel area 10a can realize a bright display without disclination. In addition, the drive voltage can be lowered.
4 is a cross-sectional view showing a reference example in which the configuration of FIG. 1 is detailed. The first substrate 12 is a color filter substrate having a color filter 28 and a black matrix 30. The color filter 28 includes a red pixel 28R, a green pixel 28G, and a blue pixel 28B. The first electrode 18 is constituted by a portion extending in a straight line extending in a direction perpendicular to the paper surface of the black matrix 30.

  The black matrix 30 is formed in contact with the first substrate 12 with a metal such as chromium. The color filter 28 is formed on the black matrix 30, but the color filter 28 is slit in the portion of the black matrix 30 corresponding to the first electrode 18 in order to make it easy to apply a voltage to the liquid crystal. There is no color filter layer on the first electrode 18. The portion where the alignment film 22 appears to protrude upward is the slit portion of the color filter 28.

  The second substrate 14 is a TFT substrate on which a TFT (not shown) is formed. The TFT substrate is formed by forming TFTs at intersections between gate lines (scanning lines) extending in a grid pattern and data lines. The TFT includes a gate electrode connected to the gate line, a drain electrode connected to the data line, and a source electrode. The second electrode 20 is formed by extending the source electrode together with the source electrode. The data line 32 is also visible in FIG. The data line 32 is below the first electrode 18, and the second electrode 20 is between the two first electrodes 18. In this way, the first electrode 18 is a common electrode, and the second electrode 20 is a pixel electrode.

  FIG. 5 is a diagram showing a modification of the reference example of FIG. In this example, a solid electrode 34 made of ITO is formed on the first substrate 12 which is a color filter substrate. The color filter 28 is formed on the solid electrode 34 made of ITO. Similar to the example of FIG. 4, the color filter 28 is formed with a slit, and the ITO portion forming the first electrode 18 is exposed from the slit. Since the color filter 28 is relatively thick at 1 to 2 μm, the portion of the ITO solid electrode 34 covered with the color filter 28 does not contribute to driving the liquid crystal. Further, the configurations of FIGS. 4 and 5 sufficiently work as a countermeasure against static electricity.

  6 and 7 show an application example of the reference example of FIG. A TFT 38 is formed at the intersection of the gate line 36 and the data line 32. The TFT 38 includes a gate electrode 40, a drain electrode 42, and a source electrode 44, and the second electrode 20 passes through the first portion 20 b extending from the source electrode 44 to the middle portion of the pixel in parallel with the gate line 36 and the data line 32. Extending parallel to Thus, the second electrode 20 is disposed at the center of the pixel.

  The first electrode 18 is formed by the black matrix 30, covers the TFT 38, and extends wider than the data line 32 above the data line 32. The first electrode 18 overlaps the data line 32 with a margin m, thereby preventing the influence of the electric field generated from the data line 32. That is, a region where the alignment of the liquid crystal is disturbed is formed by the electric field formed between the first electrode 18 and the data line 32, but the display is not affected because it is shielded by the first electrode 18. The color filter 28 is omitted.

  8 and 9 show a modification of the reference example of FIGS. In this example, the second electrode 20 extends in parallel with the data line 32 from the source electrode 44 through the first portion 20 b extending in parallel to the gate line 36 to the middle portion of the pixel, and further extends in overlap with the gate line 36. It has two portions 20c. In this way, the second electrode 20 forms the Cs-on-Gate structure that acts in the same manner as the previous reference example and provides an auxiliary capacitance for the liquid crystal.

  10 and 11 are diagrams showing an example in which the number of pixel divisions is increased as a modification of the reference example of FIGS. 8 and 9. In this example, two second electrodes 20 extend in parallel with the data line 32 from the first portion 20 b extending from the source electrode 44 to the middle portion of the pixel in parallel with the gate line 36. Further, the first electrode 18 is located on both outer sides of the two second electrodes 20, and the first electrode 18 is added between the two second electrodes 20. In this way, a plurality of electric fields from the second electrode 20 toward the first electrode 18 are formed at a shorter pitch. It is also possible to divide a pixel into four or more.

  FIG. 12 and FIG. 13 show a modification of the reference example of FIG. 10 and FIG. 11 and show an example in which a gate line is extended and a TFT is formed at the tip thereof. The gate line 36 has an extended portion 36 a extending downward in the drawing along the data line 32, and the data line 32 is formed on the extended portion 36 a of the gate line 36 through the insulating layer 46. The TFT 38 is formed at the tip of the downward extension 36 a of the gate line 36.

  Further, the second electrode 20 is connected to the TFT 38 positioned above in the drawing. That is, the second electrode 20 has a third portion 20d that extends slightly downward from the source electrode of the TFT 38 positioned above, and then turns to the first portion 20b that turns to the right and extends along the gate line 36. Like the example, it becomes two strips and extends downward. The first portion 20 b extending along the gate line 36 of the second electrode 20 is formed so as to overlap the gate line 36. Accordingly, in the previous example, since the first portion 20b extends to the inside of the pixel from the gate line 36, the aperture ratio is reduced, but in this reference example, the aperture ratio is increased. The first portion 20b and the second portion 20c overlap with the gate line 36 to form an auxiliary capacitor.

  FIG. 14 and FIG. 15 are diagrams showing an example in which an oblique electric field and a lateral electric field are used in combination as a modification of the reference example of FIG. 6 and FIG. The first electrode 18 and the second electrode 20 are formed in substantially the same manner as in the reference example of FIGS. A third electrode 26 similar to that shown in FIG. 3 is formed in a square frame shape. The third electrode 26 is formed in the same layer as the gate line 36. The third electrode 26 is set to the same potential as the first electrode 18. As described above, when the second electrode 20 and the third electrode 26 are provided on the TFT substrate side, there is a problem that the structure is complicated and the aperture ratio is lowered, but the function of shielding the electric field from the data line is reduced. large. In addition, the first portion 20 b and the second portion 20 c of the second electrode 20 and the portion where the third electrode 26 overlaps form an auxiliary capacitance. Needless to say, an insulating layer is interposed between the overlapping portions of these electrodes.

  FIGS. 16 and 17 show a modification of the reference example of FIGS. 14 and 15 and show an example in which a third electrode 26 is added at the center of the pixel. In this case, the second electrode 20 has two lines, and the first electrode 18 and the third electrode 26 have three lines. Thus, the pixels are divided and driven. The third electrode 26 has a frame shape. It is desirable that the first electrode 18 and / or the third electrode 26, which are common electrodes, be formed so as to surround the pixel in order to minimize the influence of a lateral electric field from the data line 32 or the gate line 36. For example, the reference examples in FIGS. 6 to 17 are designed with this in mind.

  In the above reference example, the gate is the lowermost layer because an inverted stagger type TFT is assumed, but if a top gate type is used (Cs is formed between the source electrode and the gate electrode) Cs-on It is possible to form a gate with a -Gate structure on the data line, which is more preferable. In this case, since the data line 32 can be covered with the lower extension 36a of the gate line 36, it is possible to prevent the adverse effect of the lateral electric field caused by the data electrode.

  This situation is shown in FIG. 22 and FIG. This reference example is substantially the same as the reference example of FIGS. 12 and 13 if the gate line 36 (having the downward extension 36a) and the drain line 32 are turned upside down. Here, the distance between the first electrode 18 and the second electrode 20 was in the range of 6 μm to 20 μm. Thereby, the liquid crystal could be driven only by applying a voltage of 15 V or less between the electrodes. It has been confirmed that the drive voltage decreases as the cell thickness increases. The cell thickness was set in the range of 3 μm to 6 μm. When the panel Δnd was 0.5 μm ± 0.2 μm, good white display luminance could be obtained. Further, since the liquid crystal display device includes vertically aligned liquid crystal, a configuration in which a uniaxial optical film having a negative refractive index anisotropy is superposed is effective in improving the viewing angle. For example, in the liquid crystal panel portion, the cell thickness is d, and the anisotropy of the refractive index of the liquid crystal is Δn. The film thickness was d2, and the refractive index anisotropy was Δn2, so that Δn × d and Δn2 × d2 were almost the same.

  18 and 19 are diagrams showing a reference example in which the gate electrode of the TFT substrate is used as a display common electrode. In this case, a liquid crystal display device having a high aperture ratio driven by a lateral electric field can be realized. The first electrode 18 of the first substrate 12 of the reference example described above is not provided, and a lateral electric field is formed by the second electrode 20 and the third electrode 26 of the second substrate 14. The second electrode 20 is connected to the source electrode 44 of the TFT 38, and the third electrode 26 is connected to the gate line 36. Similar to the reference example of FIGS. 12 and 13, the gate line 36 includes a downward extension 36 a extending along the data line 32. The gate line 36 further includes a second downward extension 36b located in the central portion of the pixel. These downward extending portions 36 a and 36 b serve as the third electrode 26.

  As shown in FIGS. 18 and 19, the overlap between the gate line 36 and the first portions 20b and 20c of the second electrode 20 is used as an auxiliary capacitor in order to improve the aperture ratio in driving using a lateral electric field. It is also possible. Here, the third electrode 26 connected to the gate line 36 is set to a common potential during the non-selection period, and an electric field is formed between this electrode and the second electrode 20 to drive the liquid crystal. As a result, it is possible to configure a horizontal electric field type LCD having a further improved aperture ratio. In addition to the constriction for forming the TFT 38 (the portion indicated by A in the figure), the shape of the tip of the downward extension portion 36a extended on the data line is a separate downward extension portion for applying a uniform electric field to the liquid crystal. The tip of 36a was extended (part shown by B in the figure).

  20 and 21 are diagrams showing a modification of the reference example of FIGS. 18 and 19. In this example, the gate line 36 includes a lower extension 36 a (gate electrode 40) and an upper extension 36 c that extend along the data line 32. The TFT 38 is provided in the lower extension portion 36 a, and the upper extension portion 36 c serves as the third electrode 26. Further, the gate line 36 has a central extension portion 36 d extending in the center of the pixel, and the central extension portion 36 d also becomes the third electrode 26. In this case, the upper extension 36 c extends in parallel with the data line 32 at the time of the data line 32. The upper and lower portions of the central extension portion 36d are overlapped with the first portion 20b and the second portion 20c of the second electrode 20 to form an auxiliary capacitance.

  In the reference examples of FIGS. 18 to 21, the first electrode 18 of the first substrate 12 is not provided, but the first electrode 18 may be provided at the position of the first substrate 12 corresponding to the third electrode 20. Needless to say, you can. FIG. 24 shows an example of a drive waveform when the extended portions 36c and 36d of the gate line 36 are used as a common. Due to the driving relationship of the TFT 38, it is necessary to apply about minus 5V as the gate OFF voltage. Since this is used as a common, it is necessary to swing the data voltage around this minus 5V. This configuration was realized with -10V as the reference for the driver drive voltage. Since the data itself comes in as logic up to 3V, for example, adjustment is necessary.

  25 and 26 show another reference example in which an oblique electric field is applied. In this example, an oblique electric field is formed between the first electrode 58 and the second electrode 20. The first electrode 58 performs the same operation as that of the first electrode 18 of FIG. However, both the first electrode 58 and the second electrode 20 are located on the second substrate 14.

  The first electrode 58 is disposed in contact with the substrate surface of the second substrate 14. The second electrode 20 is disposed away from the substrate surface of the second substrate 14. Specifically, the second electrode 20 is formed on the silicon nitride layer 50 and the amorphous silicon layer 52. That is, when the TFT 38 is formed, a source electrode layer is provided on the silicon nitride layer 50 and the amorphous silicon layer 52, and the second electrode 20 is formed together with the source electrode layer and the silicon nitride layer 50 and the amorphous silicon layer. It is provided on the layer 52.

  Accordingly, the first electrode 58 and the second electrode 20 have different heights, and thus an oblique electric field can be formed. By utilizing this oblique electric field, orientation without disclination can be realized. Here, when the displacement between the first and second electrode layers forming the oblique electric field is 0.3 μm or more, preferably 0.6 μm or more, a display with particularly little disclination can be realized. That is, when the thickness of the silicon nitride layer 50 and the amorphous silicon layer 52 is set to 0.3 μm or more, a good display can be realized.

  In order to provide a difference in height between the first electrode 58 and the second electrode 20, it is possible to provide a special layer in addition to the silicon nitride layer 50 and the amorphous silicon layer 52. For example, it is possible to apply an ultraviolet curable resin, form an electrode thereon, connect it to the source electrode, and further move the position of the source electrode away from the glass substrate. In this case, the electric field between the second electrode 20 and the first electrode 58 in the gate line layer becomes more oblique.

  In the above example, the reverse stagger is described, but a similar configuration can be realized even with a staggered type. In this case, the gate serving as the common layer is located farthest from the substrate, the second electrode in FIGS. 25 and 26 is the first electrode that is the common electrode, and the second electrode is the pixel electrode. . In addition, the positional relationship between SiN and a-Si is reversed, or there is a structure in which there is further SiN on the overlap of SiN and a-Si. In this case, since there are two SiN layers, the difference in height between the electrodes may further increase.

  FIG. 27 is a diagram showing an example in which each electrode is composed of a plurality of parallel electrode elements in one pixel in order to describe a liquid crystal display device according to still another reference example. FIG. 27 is a view of the electrode configuration in one pixel as viewed from above one substrate of the liquid crystal display device. The first electrode 70 is formed in a comb shape and has a plurality of parallel electrode elements 72. The second electrode 74 is formed in a comb shape and has a plurality of parallel electrode elements 76. The electrode elements 72 of the first electrode 70 and the electrode elements 76 of the second electrode 74 are alternately formed in parallel with each other.

  FIG. 28 is a diagram illustrating a state when no voltage is applied to the oblique electric field type liquid crystal display device, and FIG. 29 is a diagram illustrating a state when voltage is applied to the liquid crystal display device of FIG. 28 and 2929, the liquid crystal display device 10 includes first and second substrates 12 and 14 and a liquid crystal layer 16. Further, the first substrate 12 has a first electrode element 72 and the second substrate 14 has a second electrode element 76. As shown in FIG. 27, the first electrode element 72 and the second electrode element 76 are arranged so as to be shifted from each other in a direction parallel to the substrate surface.

  The first electrode 70 having the first electrode element 72 can be formed on the first substrate (color filter substrate) 12 in the same manner as the common electrode 18 shown in FIGS. The second electrode 74 having the second electrode element 76 can be connected to the TFT 38 of the active matrix in the same manner as the pixel electrode 20 shown in FIGS.

  The liquid crystal layer 16 includes a liquid crystal having positive dielectric anisotropy, and a vertical alignment film (not shown) is provided on the first and second substrates 12 and 14. Therefore, when no voltage is applied, the liquid crystal molecules are aligned perpendicular to the substrate surface (FIG. 28), and when no voltage is applied, the liquid crystal molecules are aligned along an oblique electric field (FIG. 29). This action is similar to the previous reference example.

  FIG. 30 is a diagram showing a state in which no voltage is applied to another liquid crystal display device with an oblique electric field method. Again, the first substrate 12 has a first electrode element 72 and the second substrate 14 has a second electrode element 76. As shown in FIG. 27, the first electrode element 72 and the second electrode element 76 are shifted from each other in the direction parallel to the substrate surface and arranged in parallel to each other. In FIG. 30, the liquid crystal layer 16 includes a liquid crystal having positive dielectric anisotropy, and the first and second substrates 12 and 14 are provided with a horizontal alignment film (not shown). Accordingly, when no voltage is applied, the liquid crystal molecules are aligned substantially parallel to the substrate surface. When no voltage is applied, the liquid crystal molecules are aligned along an oblique electric field. The reference example described below applies to both the vertical alignment type liquid crystal display device of FIG. 28 and the horizontal alignment type liquid crystal display device of FIG.

  In the electrode configuration as shown in FIG. 27, if a displacement occurs when the first substrate 12 and the second substrate 14 are bonded together, the first electrode element 72 and the second electrode 12 on the first substrate 12 The gap (electrode gap) between the substrate 14 and the second electrode element 76 changes, and the voltage-transmittance characteristics change when the liquid crystal display device is used. FIG. 31 is a diagram showing an example of voltage-transmittance characteristics in the case where the liquid crystal is aligned perpendicular to the substrate when no voltage is applied in the oblique electric field type liquid crystal display device. Curve P shows the voltage-transmittance characteristics when the electrode gap is 15 μm, curve Q shows the electrode gap is 10 μm, and curve R shows the voltage-transmittance characteristics when the electrode gap is 6 μm. As can be seen from FIG. 31, the voltage-transmittance characteristic is greatly affected by the electrode gap. Therefore, in assembling the liquid crystal display device, it is necessary to pay close attention so that positional displacement does not occur when the first substrate 12 and the second substrate 14 are bonded together, and the manufacturing margin is very small.

  Curve S is a diagram showing the voltage-transmittance characteristics when the above three curves are averaged. A curve S shows a case where a plurality of electrode gaps are mixed in one pixel. In this case, as shown by the curve S, the voltage-transmittance characteristic becomes gentle, and the change in transmittance due to voltage fluctuation is reduced. In addition, when the bonding deviation between the first and second substrates 12 and 14 occurs, a region where the voltage-transmittance characteristics shift to the low voltage side and a region where the voltage-transmission characteristic shifts to the high voltage side are generated. Is smaller than when the electrode gap is uniform. For the above reasons, it is possible to suppress a change in voltage-transmittance characteristics due to a bonding deviation or a change in electrode width during manufacturing.

  FIG. 32 is a diagram showing voltage-transmittance characteristics in the case where there is a bonding deviation between the first and second substrates in the oblique electric field type liquid crystal display device. Curve H has a bonding deviation of 3.9 μm, Curve I has a bonding deviation of 1.8 μm, Curve J has a bonding deviation of 5.8 μm, and Curve J has a bonding deviation of 0.4 μm. The voltage-transmittance characteristic in the case is shown. Two different electrode gaps are generated due to the bonding deviation, the voltage-transmittance characteristic becomes a two-stepped shape, and the degree of misalignment differs depending on the liquid crystal panel, so that the voltage-transmittance characteristic varies depending on the liquid crystal panel.

Accordingly, the first electrode 70 and the second electrode 74 are composed of a plurality of electrode elements 72 and 76 that are parallel in one pixel, and the electrode widths and electrode gaps of the electrode elements 72 and 76 of the first and second electrodes. By making at least one non-uniform, it is possible to reduce the change in the voltage-transmittance characteristics even if a positional deviation occurs.
Embodiment
33 to 42 are views showing an embodiment of the present invention in which at least one of the electrode width and the electrode gap is non-uniform. In any case, the cell thickness was 4 μm, and the Δε of the liquid crystal material was 14.8.

FIG. 33 is a diagram showing an example of the electrode elements 72 and 76 in which the electrode gap is changed while keeping the electrode width constant. The electrode width of the parallel and linear electrode elements 72 and 76 is constant at 4 μm. In the example, the electrode gaps (portions through which light passes) between the two electrode elements 72 and 76 forming the oblique electric field were 12 μm, 10 μm, 8 μm, 12 μm, 10 μm, and 8 μm. FIG. 34 shows the voltage-transmittance characteristics at this time. A plurality of different electrode gaps coexist, and voltage-transmittance characteristics corresponding to the respective electrode gaps appear in one pixel, and they are the sum of them as a whole.

  In FIG. 35, the electrode width is changed to 8 μm, 6 μm, and 4 μm while keeping the electrode gap constant (10 μm). The electrode elements 72 and 76 are linearly arranged in parallel, and a plurality of electrode widths are changed. Therefore, voltage-transmittance characteristics corresponding to the respective electrode widths appear in one pixel, and the sum is obtained as a whole. FIG. 36 shows the voltage-transmittance characteristics at this time.

  In FIG. 37, the electrode elements 76 on the TFT substrate side are arranged at a constant width and pitch, and the electrode elements 72 on the color filter substrate side are trapezoidal to change the electrode gap. The electrode width of the trapezoidal electrode element 72 was 12 μm at a wide site and 4 μm at a narrow site. The electrode gap was 8 μm at the wide electrode portion of the electrode element 72 and 12 μm at the narrow portion. The electrode gap changes continuously in the longitudinal direction of the electrode element 72. FIG. 38 shows the voltage-transmittance characteristics at this time.

  In FIG. 39, the electrode elements 72 on the color filter substrate side are arranged at a constant width and pitch, and the electrode elements 76 on the TFT substrate side are trapezoidal to change the electrode gap. The dimensional relationship is the same as that obtained by reversing the example of FIG. FIG. 40 shows the voltage-transmittance characteristics at this time. In FIG. 37R> 7 and FIG. 39, since the electrode element has a trapezoidal shape, there are an infinite number of different electrode gaps, and an infinite number of different voltage-transmittance characteristics corresponding to them appear. Become.

  In FIG. 41, the electrode elements 72 and 76 are stepped to change the electrode gap. At this time, in order to finely change the electrode gap, the steps of the steps are shifted between the electrode element 76 on the TFT substrate side and the electrode element 72 on the color filter substrate side. The electrode gap in FIGS. 37 and 39 changes continuously, whereas the electrode gap in FIG. 41 changes discretely at the same rate of change as the rate of change in the electrode gap in FIGS. In order to change the electrode gap as finely as possible, the steps of the respective electrode elements of the first and second substrates are shifted. FIG. 42 shows the voltage-transmittance characteristics at this time.

  FIG. 43 shows a reference example, in which the electrode gap is changed by intersecting the electrode element 76 on the TFT substrate side and the electrode element 72 on the color filter substrate side. The electrode element 72 on the color filter substrate side is parallel to the bus line (for example, the bus line 32 in FIG. 6), whereas the electrode element 76 on the TFT substrate side is formed at an angle of 30 degrees with respect to the same bus line. ing. The electrode elements 76 on the TFT substrate side are arranged at a pitch of 16 μm. In this way, countless different electrode gaps are created. FIG. 44 shows the voltage-transmittance characteristics at this time. Alternatively, the electrode element 76 on the TFT substrate side may be parallel to the bus line, and the electrode element 72 on the color filter substrate side may be arranged at an angle (for example, 30 degrees) with respect to the bus line.

  In any of the cases shown in FIGS. 33 to 43, the change in the electrode gap is offset to some extent within one pixel against the bonding deviation between the first and second substrates 12 and 14. Also, as shown in FIG. 33 to FIG. 43, when the electrode gap is changed in one pixel, a plurality of voltage-transmittance characteristics are obtained in one pixel. It becomes the sum of a plurality of voltage-transmittance characteristics. As a result, the behavior of the transmittance with respect to the voltage becomes gradual, and the change in the voltage-transmittance characteristic becomes smaller with respect to the change in the electrode gap.

  In the conventional liquid crystal display device of the oblique electric field method, as described with reference to FIG. 32, two different electrode gaps are generated due to the misalignment of the first and second substrates, and the voltage-transmittance characteristics are The voltage-transmittance characteristics differed depending on the liquid crystal panel because the two-step staircase shape and the degree of misalignment differ depending on the liquid crystal panel. In the oblique electric field type 15-type XGA liquid crystal display device having stepped electrode elements 72 and 76 as shown in FIG. 41, there is no change in the voltage-transmittance characteristics due to the misalignment of the first and second substrates. There was no difference in voltage-transmittance characteristics due to the liquid crystal panel.

  The present invention relates to a liquid crystal display device, and in particular, to realize a liquid crystal display device having excellent viewing angle characteristics.

It is a figure which shows the principle structure of the reference form of this invention. It is a figure which shows the comparative example of the liquid crystal display device of FIG. It is a figure which shows the example of a change of the structure of FIG. It is sectional drawing which shows the reference example which detailed the structure of FIG. It is sectional drawing which shows the example of a change of the reference example of FIG. It is a top view which shows the application example of the reference example of FIG. FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 6. FIG. 7 is a diagram showing an example in which an auxiliary capacitor is formed as a modification of the reference example of FIG. 6. It is sectional drawing along line IX-IX of FIG. FIG. 9 is a diagram illustrating an example in which the number of pixel divisions is increased in a modification of the reference example in FIG. 8. It is sectional drawing along line XI-XI of FIG. FIG. 11 is a diagram showing an example in which a gate line is extended and a TFT is formed at the tip of the modification of the reference example of FIG. 10. FIG. 13 is a cross-sectional view taken along line XIII-XIII in FIG. 12. It is a figure which shows the example which uses an oblique electric field and a horizontal electric field together in the modification of the reference example of FIG. It is sectional drawing along line XV-XV of FIG. FIG. 15 is a diagram illustrating an example in which a common electrode of a counter substrate is added to the center of a pixel as a modification of the reference example of FIG. It is sectional drawing along line XVII-XVII of FIG. It is a figure which shows the reference example which uses the gate electrode of a TFT substrate as an electrode for a display. It is sectional drawing along line XIX-XIX of FIG. It is a figure which shows the modification of the reference example of FIG. It is sectional drawing along line XXI-XXI of FIG. It is a figure which shows the reference example containing TFT comprised by the top gate system. It is sectional drawing along line XXIII-XXIII of FIG. It is a figure which shows the example of the drive waveform in the case of using a gate electrode as a common. It is a figure which shows the other reference example which applies an oblique electric field. It is sectional drawing along line XXVI-XXVI of FIG. It is a figure which shows the example which each electrode consists of a several electrode element parallel in one pixel in order to demonstrate another reference example. It is a figure which shows the state at the time of no voltage application of the liquid crystal display device of an oblique electric field system. It is a figure which shows the state at the time of the voltage application of the liquid crystal display device of FIG. It is a figure which shows the state at the time of no voltage application of the other liquid crystal display device of an oblique electric field system. It is a figure which shows the example of the voltage-transmittance characteristic in case a liquid crystal is orientated perpendicularly | vertically with respect to a board | substrate at the time of no voltage application in a slant electric field type liquid crystal display device. It is a figure which shows the voltage-transmittance characteristic in the case where there is a bonding deviation between the first and second substrates in the oblique electric field type liquid crystal display device. It is a figure which shows the example of the electrode element which is one Example of this invention, and changed the electrode gap, making the electrode width constant. It is a figure which shows the voltage-transmittance characteristic at the time of using the electrode element of FIG. It is a figure which shows the example of the electrode element which is the other Example of this invention, and changed the electrode width, making the electrode gap constant. It is a figure which shows the voltage-transmittance characteristic at the time of using the electrode element of FIG. It is a figure which shows the example of the electrode element which is the other Example of this invention, the electrode element by the side of a color filter is constant, the electrode element by the side of TFT is made trapezoid shape, and the electrode gap was changed. It is a figure which shows the voltage-transmittance characteristic at the time of using the electrode element of FIG. It is a figure which shows the example of the electrode element which made the electrode element by the side of a color filter which is another Example of this invention into the trapezoid shape, changed the electrode gap | interval, making the electrode element by the side of TFT constant. It is a figure which shows the voltage-transmittance characteristic at the time of using the electrode element of FIG. It is a figure which shows the example of the electrode element which is another Example of this invention and made the electrode element the step shape, and changed the electrode gap | interval. It is a figure which shows the voltage-transmittance characteristic at the time of using the electrode element of FIG. It is a figure which shows the example of the electrode element which changed the electrode gap by making the electrode element by the side of a TFT and the electrode element by the side of a color filter which is a reference example of this invention cross | intersect. It is a figure which shows the voltage-transmittance characteristic at the time of using the electrode element of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display device 12 ... 1st board | substrate 14 ... 2nd board | substrate 16 ... Liquid crystal layer 18 ... 1st electrode 20 ... 2nd electrode 22, 24 ... Alignment film | membrane 26 ... 3rd electrode 28 ... Color filter 30 ... Black matrix 32 ... Data line 34 ... Solid electrode 36 ... Gate line 38 ... TFT
58 ... 1st electrode 72 ... 1st electrode element 76 ... 2nd electrode element

Claims (3)

First and second opposing substrates, a liquid crystal layer sealed between the first and second substrates, a first electrode provided on the first substrate, and a second substrate The liquid crystal molecules in the liquid crystal layer are aligned perpendicular to the substrate surfaces of the first and second substrates when no voltage is applied, and the first electrode And the second electrode comprises a plurality of parallel electrode elements in one pixel,
A liquid crystal display device , wherein a part or all of the width of at least one of the first and second electrodes changes discontinuously , and the electrode width of the electrode elements is non-uniform . First and second opposing substrates, a liquid crystal layer sealed between the first and second substrates, a first electrode provided on the first substrate, and a second substrate The liquid crystal molecules in the liquid crystal layer are aligned perpendicular to the substrate surfaces of the first and second substrates when no voltage is applied, and the first electrode And the second electrode comprises a plurality of parallel electrode elements in one pixel,
At least one of the electrode elements of the first and second electrodes Ri stepped der, a liquid crystal display device, wherein the electrode width of the electrode elements is non-uniform. First and second opposing substrates, a liquid crystal layer sealed between the first and second substrates, a first electrode provided on the first substrate, and a second substrate The liquid crystal molecules in the liquid crystal layer are aligned perpendicular to the substrate surfaces of the first and second substrates when no voltage is applied, and the first electrode And the second electrode comprises a plurality of parallel electrode elements in one pixel,
A liquid crystal display device characterized in that the electrode elements of the first and second electrodes are both stepped, the direction in which the electrode width decreases is the same, and the electrode widths of the electrode elements are non-uniform .

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