JP6902312B2 - Liquid crystal display element - Google Patents

Description

The present invention relates to a liquid crystal display element.

The vertically oriented liquid crystal display element has extremely low light transmittance in the background display portion (no voltage applied portion) when observed from the normal direction of the substrate (when observed in front), and two polarizing plates arranged substantially in cross Nicols. It is possible to realize a dark state equivalent to that of a board. Further, by using a viewing angle compensating plate or the like having a negative biaxial optical anisotropy, the viewing angle characteristics in a dark state can be ideally realized. It has such excellent display performance.

FIG. 9 is a schematic cross-sectional view showing the vertically oriented liquid crystal display element 10.

The vertically oriented liquid crystal display elements 10 are arranged between the upper substrate (common substrate) 11, the lower substrate (segment substrate) 12, and both substrates 11, 12 which are arranged so as to face each other substantially in parallel at specific intervals. The vertically oriented liquid crystal layer 13 is included.

The upper substrate 11 and the lower substrate 12 are adhered to each other by the main seal portion 14 arranged in a frame shape in a plan view (when viewed from the positive direction of the Z axis). The vertically oriented liquid crystal layer 13 is arranged inside the main seal portion 14.

The upper substrate 11 is formed on (i) the upper transparent substrate 11a, (ii) the upper transparent electrode (common electrode) 11b formed on the upper transparent substrate 11a, (iii) on the upper transparent substrate 11a and the upper transparent electrode 11b. The upper insulating film 11c formed therein and (iv) the upper vertical alignment film 11d formed on the upper insulating film 11c are included. Similarly, the lower substrate 12 is formed on (i) the lower transparent substrate 12a, (ii) the lower transparent electrode (segment electrode) 12b formed on the lower transparent substrate 12a, and (iii) on the lower transparent substrate 12a. And the lower insulating film 12c formed on the lower transparent electrode 12b, and (iv) the lower vertical alignment film 12d formed on the lower insulating film 12c.

The upper transparent substrate 11a and the lower transparent substrate 12a are, for example, glass substrates. The upper transparent electrode 11b and the lower transparent electrode 12b are formed of a transparent conductive material such as ITO (indium tin oxide).

Both electrodes 11b and 12b overlap each other in a plan view with the vertically oriented liquid crystal layer 13 interposed therebetween, and define a display unit (pixel) in the overlapping region. The upper and lower transparent electrodes 11b and 12b are patterned so as to realize, for example, a segment display unit (pixel) for displaying a specific pattern, a number, or a plurality of rectangular display units (pixels) in a dot matrix shape. There is.

The vertically oriented liquid crystal layer 13 is composed of a liquid crystal material having a negative dielectric anisotropy. Spacers 13s are dispersedly arranged in the vertically oriented liquid crystal layer 13.

The end portion of the lower substrate 12 projects outward from the upper substrate 11, and the external take-out terminal portion 15 is defined in the overhanging region. An external take-out electrode 15b is arranged on the external take-out terminal portion 15. The external take-out electrode 15b is electrically connected to the lower transparent electrode 12b.

The upper polarizing plate 17 is arranged on the surface of the upper substrate 11 opposite to the vertically oriented liquid crystal layer 13. The viewing angle compensation plate 16 and the lower polarizing plate 18 are arranged in this order on the surface of the lower substrate 12 opposite to the vertically oriented liquid crystal layer 13. The viewing angle compensation plate 16 and the polarizing plates 17 and 18 are fixed to the substrates 11 and 12 by an adhesive. The upper and lower polarizing plates 17 and 18 are arranged, for example, on a cross Nicol. The viewing angle compensating plate 16 has a function of improving the viewing angle characteristics by optically compensating for the deviation of the phase difference of the vertically oriented liquid crystal layer 13 during oblique observation, for example.

FIG. 10 is a schematic cross-sectional view showing a vertically oriented liquid crystal display device 20.

The vertically oriented liquid crystal display device 20 includes a vertically oriented liquid crystal display element 10, a drive circuit 21, a backlight unit 22, and a housing (housing, cover, etc.) 23.

The drive circuit 21 is electrically connected to, for example, the external extraction electrode 15b of the vertically oriented liquid crystal display element 10 and applies a voltage between the electrodes 11b and 12b of the vertically oriented liquid crystal display element 10 to drive the liquid crystal display element 10. To do.

The backlight unit 22 includes, for example, an LED light source (backlight) that emits white light, a light guide plate, a diffuser plate, a brightness improving film, and the like, and includes a lower side (Z) of the lower polarizing plate 18 of the vertically oriented liquid crystal display element 10. It is arranged on the negative axis side).

The vertically oriented liquid crystal display element 10, the drive circuit 21, and the backlight unit 22 are fixed and integrated at predetermined positions in the housing 23.

The drive circuit 21 may be arranged outside the housing 23.

The vertically oriented liquid crystal display element 10 shown in FIG. 9 is, for example, a monodomain vertically oriented liquid crystal display element. In the monodomain vertically oriented liquid crystal display element 10, for example, the alignment films 11d and 12d are oriented (rubbed) in one direction, for example, in antiparallel, and a voltage is applied between the electrodes 11b and 12b. When not present, the liquid crystal molecules of the liquid crystal layer 13 are oriented in one direction.

In the monodomain vertically oriented liquid crystal display element 10, a dark region may be generated in a part of the display unit (pixel) in the bright display state, and display unevenness may be observed.

FIG. 11A is an external photograph showing a bright display unit when the monodomain vertically oriented liquid crystal display element 10 configured as a segment display type is operated by multiplex drive of 1/8 duty and 1/4 vias. A dark area is generated in the portion surrounded by the ellipse of the two substantially isosceles triangle-shaped (strictly isosceles trapezoidal) display portions in the bright display state, and display unevenness is observed.

FIG. 11B is an external photograph showing a bright display state in one pixel when the monodomain vertically oriented liquid crystal display element 10 is configured as a dot matrix display type. Dark areas are generated in the peripheral areas and the central area (the part surrounded by the ellipse) on the upper side and the left and right sides of the pixel, and display unevenness is observed.

It is considered that the generation of the dark region is caused by an oblique electric field (an oblique electric field generated when a voltage is applied between the electrodes 11b and 12b) in the contour portion of the display portion. Specifically, it is considered that a dark region is generated because the liquid crystal molecules of the vertically oriented liquid crystal layer 13 are oriented in an orientation different from the orientation orientation defined by the alignment films 11d and 12d due to the oblique electric field.

12A and 12B are schematic plan views showing a part of an upper transparent electrode (common electrode) 11b and a lower transparent electrode (segment electrode) 12b that realize the display portion shown in FIG. 11A, respectively. The 12 o'clock direction corresponds to the X-axis positive direction in FIG. 9, and the 9 o'clock direction corresponds to the Y-axis positive direction.

In FIG. 12C, the overlapping portion of both electrodes 11b and 12b (display portion of two substantially isosceles triangles (strictly, isosceles trapezoidal shape)) is shown by a solid line. In the monodomain vertical alignment type liquid crystal display element 10 that realizes the display unit shown in FIG. 11A, for example, the upper substrate 11 (upper vertical alignment film 11d) is subjected to a rubbing process at 6 o'clock, and the lower substrate 12 (lower) is subjected to a rubbing process. The side vertical alignment film 12d) is subjected to a rubbing treatment at 12 o'clock. At this time, the orientation of the liquid crystal molecule (center molecule of the liquid crystal layer 13) located at the center in the thickness direction (Z-axis direction) of the vertically oriented liquid crystal layer 13 (orientation defined by the alignment films 11d and 12d when no voltage is applied). Direction) is 12 o'clock.

In this figure, the direction of the oblique electric field (the oblique electric field generated from the upper transparent electrode 11b toward the lower transparent electrode 12b in the contour portion of the display portion) when the vertically oriented liquid crystal display element 10 is viewed in a plan view is indicated by an arrow. Indicated.

Comparing and referring to this figure and FIG. 11A, in the dark region, the direction of the diagonal electric field in the plan view is opposite to that of the liquid crystal layer 13 central molecular orientation (12 o'clock orientation), that is, the direction of the oblique electric field is 6 o'clock. It can be seen that it occurs in the contour part.

13A and 13B are schematic plan views showing a part of an upper transparent electrode (common electrode) 11b and a lower transparent electrode (segment electrode) 12b that realize the display portion shown in FIG. 11B, respectively. The 12 o'clock direction corresponds to the X-axis positive direction in FIG. 9, and the 9 o'clock direction corresponds to the Y-axis positive direction.

The upper transparent electrode 11b is a plurality of strip-shaped electrodes extending in the 3 o'clock-9 o'clock direction, and the lower transparent electrode 12b is a plurality of strip-shaped electrodes extending in the 12 o'clock-6 o'clock direction. Both electrodes 11b and 12b are arranged at right angles to each other in a plan view, and rectangular pixels are defined at overlapping (intersecting) portions.

FIG. 13C is a schematic plan view showing one rectangular pixel. In the monodomain vertical alignment type liquid crystal display element 10 that realizes the pixels shown in FIG. 11B, for example, the upper substrate 11 (upper vertical alignment film 11d) is subjected to a rubbing process at 12 o'clock, and the lower substrate 12 (lower side) is subjected to a rubbing process. The vertical alignment film 12d) is subjected to a rubbing treatment at 6 o'clock. At this time, the central molecular orientation of the vertically oriented liquid crystal layer 13 is 6 o'clock.

In this figure, the direction of the oblique electric field (the oblique electric field generated from the upper transparent electrode 11b toward the lower transparent electrode 12b in the contour portion of the pixel in the contour portion of the pixel) when the vertically oriented liquid crystal display element 10 is viewed in a plan view is indicated by an arrow. It was.

Comparing and referring to this figure and FIG. 11B, a dark region is observed in the peripheral region of the upper side of the pixel (the side where the direction of the central molecular orientation of the liquid crystal layer 13 and the direction of the oblique electric field in the plan view are opposite), and the lower side of the pixel (the lower side of the pixel No dark region is observed in the peripheral region of the liquid crystal layer 13 (the side where the direction of the central molecular orientation of the liquid crystal layer 13 is equal to the direction of the oblique electric field in a plan view). The dark region is also observed in the peripheral region of the left side and the right side of the pixel (the side in which the direction of the central molecular orientation of the liquid crystal layer 13 and the direction of the oblique electric field in the plan view are orthogonal to each other). It is presumed that the dark area in the center of the pixel is caused by the influence of the dark area generated around the pixel.

With respect to the display unevenness that occurs when the monodomain vertically oriented liquid crystal display element 10 is driven, the display is displayed by making the relationship between the drive waveform, frame frequency, and design parameters of the liquid crystal display element particularly appropriate during multiplex drive. Inventions that realize homogenization are known (see, for example, Patent Document 1). The invention described in Patent Document 1 was made by the inventor of the present application.

FIG. 14 is the same diagram as FIG. 5 of Patent Document 1, and each drive waveform (A waveform = line inversion drive waveform , B waveform = frame inversion drive waveform, C waveform = N line inversion drive waveform (N = 7), In addition, a graph summarizing the conditions under which stable display can be performed with the MLS waveform (N = 2)) is shown. For example, with respect to the pretilt angle setting of the liquid crystal display element, the minimum frame frequency at which display uniformity is realized is plotted in the A waveform, the B waveform, and the C waveform when the 1/16 duty and 1/5 bias are driven. The graph (boundary line) shown for each drive waveform and the upper side thereof are regions where the occurrence of dark regions can be suppressed and good display can be performed.

From the graph, it can be seen that it is necessary to set the frame frequency high when the pre-tilt angle of the liquid crystal display element is brought close to 90 ° in order to perform a good display in common with each drive waveform.

In the monodomain vertically oriented liquid crystal display element 10, it is effective to bring the pretilt angle of the liquid crystal layer 13 close to 90 ° in order to maintain good display quality even if the display capacity is increased. However, as described above, when the pre-tilt angle is brought close to 90 °, the frame frequency needs to be set high in order to perform a good display, so that the load on the drive circuit becomes large. Therefore, there is a concern that the choice of drive circuit will be narrowed.

There is a need for a technique capable of reducing the frame frequency while maintaining the steepness of the electro-optical characteristics in the pixel in a good state.

Japanese Patent No. 5324754

An object of the present invention is to provide a liquid crystal display element that enables good display quality.

According to one aspect of the present invention, a first substrate having electrodes, a second substrate having electrodes and arranged facing the first substrate, and arranged between the first substrate and the second substrate. The pixels are defined in a region where the electrodes of the first substrate and the electrodes of the second substrate overlap in a plan view, and at least one of the first and second substrates is said to have the vertically oriented liquid crystal layer. A vertical alignment liquid crystal layer side is provided with an alignment film, and a region having a relatively high pretilt angle is arranged in the central portion of the pixel, and a region having a relatively low pretilt angle is located in a peripheral portion of the pixel. Orientation processing is performed so that the layers are arranged, and the pre-tilt angle changes depending on the position at the boundary between the region having a relatively high pre-tilt angle and the region having a relatively low pre-tilt angle, and the relative the pretilt angle of the high pretilt angle region is 89.5 ° ~89.95 °, the pretilt angle of the relatively low pretilt angle region is 89 ° ~89.7 °, vertical alignment liquid crystal of Display elements are provided.

According to the present invention, it is possible to provide a liquid crystal display element that enables good display quality.

1A and 1B are schematic plan views showing a part of the electrode structures of the upper transparent electrode 11b and the lower transparent electrode 12b used in the analysis, respectively, and FIG. 1C is a region of 3 pixels × 3 pixels. It is a schematic plan view which shows. FIG. 2A is a result of orientation structure calculation when the pretilt angle is 89.95 °, and FIG. 2B is a schematic plan view showing the direction of an oblique electric field when the vertically oriented liquid crystal display element 10 is viewed in a plan view. Is. 3A and 3B are graphs showing the distribution of light transmittance, and FIG. 3C is a graph showing the pretilt angle dependence of the distance E and the distance G from the pixel edge. FIG. 4 is a schematic plan view showing a pixel structure devised by the inventor of the present application. FIG. 5A is a graph showing the overlap distance d dependence of the distance E when the pretilt angle of the low pretilt angle region 32 is set to 89 °, 89.5 °, and 89.7 °, and FIG. 5B is a graph showing the overlap distance d dependence. 5C and 5D are graphs showing the calculation results of the coefficients a and b, respectively. FIG. 6A is a graph showing the overlap distance d dependence of the distance G when the pretilt angle of the low pretilt angle region 32 is set to 89 °, 89.5 °, and 89.7 °, and FIG. 6B is a graph. 6C and 6D are graphs showing the calculation results of the coefficients a and b, respectively. FIG. 7A is a schematic cross-sectional view showing a vertically oriented liquid crystal display element 10 according to an embodiment, and FIGS. 7B and 7C show a part of the electrode structure of the upper transparent electrode 11b and the lower transparent electrode 12b, respectively. It is a schematic plan view which shows. FIG. 7D is a schematic plan view showing a region of 3 pixels × 3 pixels, and FIG. 7E shows the direction of the oblique electric field in one pixel when the vertically oriented liquid crystal display element 10 according to the embodiment is viewed in a plan view. FIG. 7F is a schematic plan view showing a schematic cross-sectional view showing a vertically oriented liquid crystal display device 20 using the vertically oriented liquid crystal display element 10 according to the embodiment. 8A and 8B are schematic plan views showing a pixel structure of a vertically oriented liquid crystal display element according to a modified example. FIG. 9 is a schematic cross-sectional view showing the vertically oriented liquid crystal display element 10. FIG. 10 is a schematic cross-sectional view showing a vertically oriented liquid crystal display device 20. FIG. 11A is an external photograph showing a bright display unit when the monodomain vertically oriented liquid crystal display element 10 configured as a segment display type is operated by multiplex drive of 1/8 duty and 1/4 pixel. Reference numeral 11B is an external photograph showing a bright display state in one pixel when the monodomain vertically oriented liquid crystal display element 10 is configured as a dot matrix display type. 12A and 12B are schematic plan views showing a part of the upper transparent electrode 11b and the lower transparent electrode 12b that realize the display portion shown in FIG. 11A, respectively, and FIG. 12C shows both electrodes 11b, respectively. It is a schematic plan view which shows the overlap part of 12b. 13A and 13B are schematic plan views showing a part of the upper transparent electrode 11b and the lower transparent electrode 12b that realize the display portion shown in FIG. 11B, respectively, and FIG. 13C is a rectangular 1 It is a schematic plan view which shows a pixel. FIG. 14 is the same diagram as FIG. 5 of Patent Document 1, and is a graph summarizing the conditions under which stable display can be performed for each drive waveform.

The inventor of the present application has performed a three-dimensional analysis (simulation) on the pretilt angle dependence of the oriented structure of the dot matrix display type monodomain vertically oriented liquid crystal display element 10 (see FIG. 9) at the time of multiplex driving. For the analysis, 3D analysis software LCD MASTER 8.7 manufactured by Shintec Co., Ltd. was used.

1A and 1B are schematic plan views showing a part of the electrode structures of the upper transparent electrode (common electrode) 11b and the lower transparent electrode (segment electrode) 12b used in the analysis, respectively. The 12 o'clock direction corresponds to the X-axis positive direction in FIG. 9, and the 9 o'clock direction corresponds to the Y-axis positive direction.

The upper transparent electrode 11b is a plurality of strip-shaped electrodes having a width of 136 μm extending in the 3 o'clock-9 o'clock direction, and the lower transparent electrode 12b is a plurality of strips having a width extending in the 12 o'clock-6 o'clock direction. It is a strip-shaped electrode. In both the upper transparent electrode 11b and the lower transparent electrode 12b, the distance between adjacent strip-shaped electrodes is 24 μm. The electrodes 11b and 12b are arranged orthogonal to each other in a plan view, and define a rectangular pixel (a square shape having a side of 136 μm) at an overlapping (intersecting) portion.

FIG. 1C is a schematic plan view showing a region of 3 pixels × 3 pixels. Each pixel is arranged in a matrix along the 3 o'clock-9 o'clock direction and the 12 o'clock-6 o'clock direction at intervals of 24 μm.

The range of analysis is shown by the alternate long and short dash line. The analysis was performed in a range of 160 μm × 160 μm in which one pixel of 136 μm × 136 μm was surrounded by the same width (12 μm) in the vertical and horizontal directions. For example, the orientation state of the vertically oriented liquid crystal layer 13 inside the alternate long and short dash line was calculated, and the orientation structure in a plan view was reproduced.

In the analysis, the rubbing direction of the upper substrate 11 (upper vertical alignment film 11d) was set to 12 o'clock, and the rubbing direction of the lower substrate 12 (lower vertical alignment film 12d) was set to 6 o'clock. The central molecular orientation of the vertically oriented liquid crystal layer 13 is 6 o'clock. The pretilt angle is assumed to be equal over the entire area of the liquid crystal display element 10 including the inside of the pixel.

The thickness of the vertically oriented liquid crystal layer 13 was set to 4 μm, and a negative liquid crystal material having a refractive index anisotropy (birefringence) Δn of 0.0914 and a dielectric anisotropy Δε of −5.1 was used.

The absorption axis orientation of the upper polarizing plate 17 was 45 ° -225 °, and the absorption axis orientation of the lower polarizing plate 18 was 135 ° -315 °.

The analysis was performed by a model in which a 160 μm × 160 μm region was divided into 40 × 40 meshes and the liquid crystal layer 13 was divided into 20 in the thickness direction. A potential difference of 4 V was applied between the upper and lower transparent electrodes 11b and 12b.

The analysis was performed in the range of the pretilt angle of 89 ° to 89.95 °, and the stable state of the oriented structure was calculated.

FIG. 2A shows the orientation structure calculation result when the pretilt angle is 89.95 °. Further, in FIG. 2B, the direction of the oblique electric field (the oblique electric field generated from the upper transparent electrode 11b toward the lower transparent electrode 12b in the contour portion of the pixel in the contour portion of the pixel) when the vertically oriented liquid crystal display element 10 is viewed in a plan view is indicated by an arrow. Shown. In FIGS. 2A and 2B, the distances (unit "μm") to the 3 o'clock direction and the 12 o'clock direction are entered with the lower left corner of the 160 μm × 160 μm square analysis range (see FIG. 1C) as 0.

As shown in FIG. 2A, a dark region (dark line) is generated around three sides (upper side and left and right sides) of the square pixel edge.

The dark region is generated because the orientation direction of the liquid crystal layer 13 rotates in a plan view due to the influence of the oblique electric field generated near the pixel edge when the voltage is applied. Especially in the dark dark region, the position where the liquid crystal molecules are rotated by 45 ° or 135 ° with respect to the orientation of the central molecule of the liquid crystal layer 13 when no voltage is applied (the orientation direction of the liquid crystal layer 13 is the absorption axis orientation of the polarizing plates 17 and 18). That is, it is observed at a position substantially parallel to the approximately 45 ° -225 ° and approximately 135 ° -315 ° directions), and a dark state tends to be observed even in the intermediate region.

Around the upper side of the pixel, the orientation of the central molecule of the liquid crystal layer 13 is rotated by approximately 180 ° from the center of the pixel toward the pixel edge (upper side of the pixel) due to the oblique electric field when a voltage is applied, so that the dark region (dark line) is X-shaped. Two are recognized in the shape. Further, in the periphery of the upper side of the pixel, the rotation directions of the liquid crystal molecules are opposite in the left side region and the right side region of the pixel, and a point dispersion is formed at a position at the intersection of the X-shapes. In point dispersion, the liquid crystal molecules do not tilt when a voltage is applied.

In the periphery of the right side and the left side of the pixel, the orientation of the central molecule of the liquid crystal layer 13 is rotated by approximately 90 ° from the center of the pixel toward the pixel edge (right side or left side of the pixel) due to the oblique electric field when a voltage is applied. An area (dark line) is generated.

At the lower side of the pixel, the central molecular orientation of the liquid crystal layer 13 when no voltage is applied and the molecular orientation of the liquid crystal when the voltage is applied are substantially the same, so that no dark region is generated.

3A and 3B are graphs showing the distribution of light transmittance. FIG. 3A is a light transmittance distribution along the line AB of the analysis range shown in FIG. 2A (a position 40 μm away from the left end of the analysis range, that is, a position 28 μm closer to the center of the pixel from the left side of the pixel), and FIG. 3B is a diagram. It is a light transmittance distribution along the CD line of the analysis range shown in 2A (a position 40 μm away from the lower end of the analysis range, that is, a position 28 μm closer to the center of the pixel from the lower side of the pixel). The horizontal axis of FIG. 3A indicates the distance from the lower end of the analysis range to the 12 o'clock direction in the unit "μm", and the horizontal axis of FIG. 3B indicates the distance from the left end of the analysis range to the 3 o'clock direction in the unit "μm". The vertical axis of both figures shows the light transmittance in arbitrary units when the light transmittance when two polarizing plates (upper polarizing plate 17 and lower polarizing plate 18) are superposed on the parallel Nicol is 100%. Represent.

See FIG. 3A. The distance from the upper side of the pixel to the position where the light transmittance becomes 50% for the first time after passing through two dark areas (dark areas generated around the upper side) (distance along the 12 o'clock to 6 o'clock direction) is defined as E. Define. Further, the distance from the upper end of the analysis range to the position (distance along the 12 o'clock-6 o'clock direction) is defined as F. There is a relationship of E [μm] = F [μm] -12 [μm].

See FIG. 3B. The distance from the right side of the pixel to the position where the light transmittance becomes 50% for the first time after passing through the dark area (the dark area generated around the right side) (distance along the 3 o'clock-9 o'clock direction) is defined as G. Further, the distance from the right end of the analysis range to the position (distance along the 3 o'clock-9 o'clock direction) is defined as H. There is a relationship of G [μm] = H [μm] -12 [μm].

FIG. 3C is a graph showing the pretilt angle dependence of the distance E and the distance G from the pixel edge. The horizontal axis of the graph indicates the pretilt angle in the unit "°", and the vertical axis indicates the distance E and the distance G from the pixel edge in the unit "μm". The diamond plot represents the distance E and the square plot represents the distance G.

It can be seen that both the distance E and the distance G tend to increase as the pretilt angle increases. That is, the dark region around the upper side and the left and right sides (upper side, right side, and left side edge) of the pixel differs in the generation position and area depending on the pretilt angle, and when the pretilt angle becomes smaller, the dark area becomes relatively close to the pixel edge. , Tends to occur in small areas.

With reference to this figure and FIG. 14 (a graph showing the pretilt angle dependence of the lowest frame frequency that can achieve display uniformity), the lower the values of the distances E and G, the lower the lowest frame frequency in each drive waveform. It turns out that there is a relationship of becoming. That is, even if the pre-tilt angle in the pixel is close to 90 °, for example, if the orientation structure can be made equivalent to the state where the pre-tilt angle is low, it is possible to suppress display unevenness (realize display uniformity) at a low frame frequency. Be done.

Therefore, the inventor of the present application has devised the pixel structure shown in FIG. 4 as a structure capable of achieving display uniformity even at a low frame frequency, for example.

The pixel structure shown in FIG. 4 is obtained by adopting the electrode structures shown in FIGS. 1A and 1B for the vertically oriented liquid crystal display element 10 shown in FIG. 9, for example. However, until now, the vertically oriented liquid crystal display element 10 shown in FIG. 9 has been described and analyzed as "for example, a monodomain vertically oriented liquid crystal display element", but the vertically oriented liquid crystal display element having the pixel structure shown in FIG. 4 has been described and analyzed. The liquid crystal display element 10 is a multi-domain vertically oriented liquid crystal display element. Specifically, for example, the pixels analyzed so far (see FIG. 1C) are set to have a pretilt angle equal to the entire area within the pixels, but the pixels shown in FIG. 4 are pixels. A region having a relatively high pretilt angle (close to 90 °) (high pretilt angle region 31) and a region having a relatively low pretilt angle (far from 90 °) (low pretilt angle region 32) coexist. .. Specifically, the pixel shown in FIG. 4 includes a high pretilt angle region 31 arranged in the central portion of the pixel and a low pretilt angle region 32 arranged in the peripheral portion of the pixel.

In FIG. 4, the edges of the pixels are indicated by solid lines. The area inside the dotted line shown in the pixel is the high pretilt angle area 31, and the other area (the shaded area) is the low pretilt angle area 32. Within one pixel, the low pretilt angle region 32 is arranged from the pixel edge toward the inside of the pixel. In the example shown in this figure, the low pretilt angle region 32 is arranged in a region having an equal distance d (overlap distance d) from the four sides of the square pixel toward the inside of the pixel. The high pretilt angle region 31 is surrounded by the low pretilt angle region 32. The outermost alternate long and short dash line corresponds to the alternate long and short dash line (outline of the analysis range) in FIG. 1C.

The inventor of the present application also performed a three-dimensional analysis using LCD MASTER 8.7 for the pixels having the structure shown in FIG. The condition setting for performing the analysis includes a mode for imparting a pretilt angle (a liquid crystal display element having the same pretilt angle in all regions inside and outside the pixel, but a high pretilt angle region 31 and a low pretilt angle region 32 in the pixel. Except for the point of using a liquid crystal display element), the analysis was the same as that obtained the results of FIGS. 2A and 3A to 3C. The pretilt angle in the high pretilt angle region 31 was fixed at 89.9 °.

FIG. 5A is a graph showing the overlap distance d dependence of the distance E when the pretilt angle of the low pretilt angle region 32 is set to 89 °, 89.5 °, and 89.7 °. As explained with reference to FIG. 3A, the distance E is from the upper side of the pixel (the side in which the direction of the central molecular orientation of the liquid crystal layer 13 when no voltage is applied and the direction of the oblique electric field in the plan view when the voltage is applied are opposite). It is the distance to the position where the light transmittance becomes 50% for the first time after passing through the two dark regions. The horizontal axis of the graph indicates the overlap distance d in the unit "μm", and the vertical axis indicates the distance E in the unit "μm". The diamond plot shows the relationship between the two when the pretilt angle of the low pretilt angle region 32 is 89 °. The square plot and the triangular plot represent the relationship between the two when the pretilt angles of the low pretilt angle region 32 are 89.5 ° and 89.7 °, respectively. The analysis was also performed on a mode in which the low pretilt angle region 32 is arranged only outside the pixel edge (not arranged inside the pixel), assuming that the overlap distance d is negative. Further, in this figure, the analysis value (see FIG. 3C) of the distance E in the monodomain vertically oriented liquid crystal display element whose pretilt angles are 89 ° and 89.9 ° is indicated by a dotted line.

When the overlap distance d is 0 μm or less, there is no difference from the condition of the pre-tilt angle of 89.9 ° for monodomain orientation. However, in each low pretilt angle setting value of 89 ° to 89.7 °, in the range of d> 0 μm, the distance E becomes smaller than the analysis value under the pretilt angle 89.9 ° condition of monodomain orientation. Further, as the overlap distance d increases, the distance E tends to decrease.

That is, in the pixel structure shown in FIG. 4, the entire pixel is formed by the high pretilt angle region 31 by arranging the low pretilt angle region 32 from the edge of the pixel, in this case, from the upper side of the pixel toward the inside of the pixel. The dark area can be generated closer to the pixel edge (upper side) than the configuration, and the generated area can be reduced.

In addition, referring to the 89 ° plot (diamond plot), it can be seen that the distance E is saturated at the position where the overlap distance d exceeds 10 μm. This is because, in the pixel structure shown in FIG. 4, even when the overlap distance d is increased, the distance E cannot be made smaller than the configuration in which the entire pixel is formed in the low pretilt angle region 32. ..

FIG. 5B is a graph showing the pretilt angle dependence of the distance E. In this figure, the data shown in FIG. 5A is taken with the pretilt angle (unit "°") of the low pretilt angle region 32 on the horizontal axis and the distance E (unit "μm") on the vertical axis, and the overlap distance d (unit "unit"). It is plotted again with μm ”) as a parameter. In this figure, the cases where the overlap distance d is 0 μm, 5 μm, 10 μm, and 15 μm are displayed in the order of circular, triangular, square, and rhombic plots.

As described above, at the pretilt angle 89 °, saturation occurs at a position where the overlap distance d exceeds 10 μm. Therefore, excluding this, when the overlap distance d is 0 μm, 5 μm, and 10 μm, respectively, A linear relationship is observed between the pretilt angle of the low pretilt angle region 32 and the distance E.

Therefore, in each overlap distance d condition (d = 0 μm, 5 μm, 10 μm), the plot is _{fitted by the least squares method of the linear model E = aθ p} + b, and the values of the coefficients a and b in each overlap distance d condition. Was calculated. Here, θ _p represents the pretilt angle of the low pretilt angle region 32.

The calculation results are shown in FIGS. 5C and 5D. In FIG. 5C, the calculation result (value of coefficient a when d = 0 μm, 5 μm, 10 μm) is plotted with the horizontal axis as the overlap distance d (unit “μm”) and the vertical axis as the coefficient a. Further, in FIG. 5D, the calculation result (value of the coefficient b when d = 0 μm, 5 μm, 10 μm) is plotted with the horizontal axis as the overlap distance d (unit “μm”) and the vertical axis as the coefficient b.

で表される。 The inventor of the present application further curves the plots by a quadratic function model (a = αd ² + βd + γ in ^{the case of FIG. 5C, b = αd 2} + βd + γ in the case of FIG. 5D) in each of FIGS. 5C and 5D. Found that it can be fitted. As a result of calculation using the least squares method, in FIG. 5C, α = 0.1, β = 1.3464, γ = 1.1538, and in FIG. 5D, α = -9.0004, β = -120. The result of 84, γ = -66.821 was obtained. That is, the distance E is the following equation (1) using _{the pretilt angle θ p of the low pretilt angle region 32 and the overlap distance d.}

It is represented by.

Equation (1) is based on a side in which the orientation of the central molecule of the liquid crystal layer 13 when no voltage is applied and the orientation of the liquid crystal molecule due to the oblique electric field when a voltage is applied differ by 180 °. As a result, it was found that it can be applied to the side where the angle between the central molecular orientation of the liquid crystal layer 13 when no voltage is applied and the liquid crystal molecular orientation by the oblique electric field when the voltage is applied is 165 ° or more and 180 ° or less. .. That is, after the dark region is exceeded from the pixel edge where the angle between the central molecular orientation of the liquid crystal layer 13 when no voltage is applied and the molecular orientation of the liquid crystal due to the oblique electric field when the voltage is applied is 165 ° or more and 180 ° or less. The distance to the position where the light transmittance becomes 50% for the first time is E, the distance (overlap distance) from the pixel edge to the end of the low pretilt angle region 32 arranged toward the inside of the pixel is d, and the low pretilt. Equation (1) also holds when the pretilt angle of the angular region 32 is θ _p.

The same analysis was performed for the distance G.

FIG. 6A is a graph showing the overlap distance d dependence of the distance G when the pretilt angle of the low pretilt angle region 32 is set to 89 °, 89.5 °, and 89.7 °. As explained with reference to FIG. 3B, the distance G is from the right side of the pixel (the side where the orientation of the central molecule of the liquid crystal layer 13 when no voltage is applied and the direction of the oblique electric field in the plan view when the voltage is applied are orthogonal to each other). , The distance to the position where the light transmittance becomes 50% for the first time after passing through the dark region. The horizontal axis of the graph indicates the overlap distance d in the unit "μm", and the vertical axis indicates the distance G in the unit "μm". The diamond plot shows the relationship between the two when the pretilt angle of the low pretilt angle region 32 is 89 °. The square plot and the triangular plot represent the relationship between the two when the pretilt angles of the low pretilt angle region 32 are 89.5 ° and 89.7 °, respectively. The analysis was also performed on a mode in which the low pretilt angle region 32 is arranged only outside the pixel edge (not arranged inside the pixel), assuming that the overlap distance d is negative. Further, in this figure, the analysis value (see FIG. 3C) of the distance G in the monodomain vertically oriented liquid crystal display element whose pretilt angles are 89 ° and 89.9 ° is indicated by a dotted line.

When the overlap distance d is 0 μm or less, there is no difference from the condition of the pre-tilt angle of 89.9 ° for monodomain orientation. However, in each low pretilt angle setting value of 89 ° to 89.7 °, in the range of d> 0 μm, the distance G becomes smaller than the analysis value under the pretilt angle 89.9 ° condition of monodomain orientation. Further, as the overlap distance d increases, the distance G tends to decrease.

That is, in the pixel structure shown in FIG. 4, the entire pixel is formed by the high pretilt angle region 31 by arranging the low pretilt angle region 32 from the edge of the pixel, in this case, from the right side of the pixel toward the inside of the pixel. The dark region can be generated closer to the pixel edge (right side) than the configuration, and the generated area can be reduced.

In addition, referring to the 89 ° plot (diamond plot), it can be seen that the distance G is saturated at the position where the overlap distance d exceeds 10 μm. This is because, in the pixel structure shown in FIG. 4, even when the overlap distance d is increased, the distance G cannot be reduced as compared with the configuration in which the entire pixel is formed in the low pretilt angle region 32. ..

FIG. 6B is a graph showing the pretilt angle dependence of the distance G. In this figure, the data shown in FIG. 6A is taken with the pretilt angle (unit "°") of the low pretilt angle region 32 on the horizontal axis and the distance G (unit "μm") on the vertical axis, and the overlap distance d (unit "unit"). It is plotted again with μm ”) as a parameter. In this figure, the cases where the overlap distance d is 0 μm, 5 μm, 10 μm, and 15 μm are displayed in the order of circular, triangular, square, and rhombic plots.

As described above, at the pretilt angle 89 °, saturation occurs at a position where the overlap distance d exceeds 10 μm. Therefore, excluding this, when the overlap distance d is 0 μm, 5 μm, and 10 μm, respectively, A linear relationship is observed between the pretilt angle of the low pretilt angle region 32 and the distance G.

Therefore, in each overlap distance d condition (d = 0 μm, 5 μm, 10 μm), the plot is _{fitted by the least squares method of the linear model G = aθ p} + b, and the values of the coefficients a and b in each overlap distance d condition. Was calculated.

The calculation results are shown in FIGS. 6C and 6D. In FIG. 6C, the calculation result (value of coefficient a when d = 0 μm, 5 μm, 10 μm) is plotted with the horizontal axis as the overlap distance d (unit “μm”) and the vertical axis as the coefficient a. Further, in FIG. 6D, the calculation result (value of the coefficient b when d = 0 μm, 5 μm, 10 μm) is plotted with the horizontal axis as the overlap distance d (unit “μm”) and the vertical axis as the coefficient b.

で表される。 The inventor of the present application further curves in each of FIGS. 6C and 6D by a quadratic function model (a = αd ^{2 + βd + γ in the case of FIG. 6C, b = αd 2} + βd + γ in the case of FIG. 6D). Found that it can be fitted. Result of calculation using the least squares method, in Figure 6C, α = 0.0538, β = 0.5769 , γ = -7 × 10 -15, in FIG. 6D, α = -4.834, β = The results were -51.942 and γ = 21. That is, the distance G is the following equation (2) using _{the pretilt angle θ p of the low pretilt angle region 32 and the overlap distance d.}

It is represented by.

Equation (2) is based on the side where the orientation of the central molecule of the liquid crystal layer 13 when no voltage is applied and the orientation of the liquid crystal molecule due to the oblique electric field when the voltage is applied are different by 90 °. As a result, it was found that it can be applied to the side where the angle between the central molecular orientation of the liquid crystal layer 13 when no voltage is applied and the liquid crystal molecular orientation by the oblique electric field when the voltage is applied is 75 ° or more and 105 ° or less. .. That is, after the dark region is exceeded from the pixel edge where the angle between the central molecular orientation of the liquid crystal layer 13 when no voltage is applied and the molecular orientation of the liquid crystal due to the oblique electric field when the voltage is applied is 75 ° or more and 105 ° or less. The distance to the position where the light transmittance becomes 50% for the first time is G, the distance (overlap distance) from the pixel edge to the end of the low pretilt angle region 32 arranged toward the inside of the pixel is d, and the low pretilt. Equation (2) also holds when the pretilt angle of the angular region 32 is θ _p.

The distance G is the distance from the right side of the pixel to the position where the light transmittance becomes 50% for the first time after passing through the dark region. For example, in the pixel structure shown in FIG. 4, the orientation structure is bilaterally symmetrical. Therefore, the same argument holds for the distance G from the left side of the pixel to the position where the light transmittance becomes 50% for the first time after passing through the dark region. Like the right side of the pixel, the left side of the pixel is also the side where the orientation of the central molecule of the liquid crystal layer 13 when no voltage is applied and the direction of the oblique electric field in the plan view when the voltage is applied are orthogonal to each other.

Based on the above analysis results, for example, the following liquid crystal display element can be used as an example.

FIG. 7A is a schematic cross-sectional view showing the vertically oriented liquid crystal display element 10 according to the embodiment. The vertically oriented liquid crystal display element 10 according to the embodiment is a multi-domain vertically oriented liquid crystal display element.

The vertically oriented liquid crystal display elements 10 are arranged between the upper substrate (common substrate) 11, the lower substrate (segment substrate) 12, and both substrates 11, 12 which are arranged so as to face each other substantially in parallel at specific intervals. The vertically oriented liquid crystal layer 13 is included.

The upper substrate 11 and the lower substrate 12 are adhered to each other by the main seal portion 14 arranged in a frame shape in a plan view. The vertically oriented liquid crystal layer 13 is arranged inside the main seal portion 14.

The upper substrate 11 is formed on (i) the upper transparent substrate 11a, (ii) the upper transparent electrode (common electrode) 11b formed on the upper transparent substrate 11a, (iii) on the upper transparent substrate 11a and the upper transparent electrode 11b. The upper insulating film 11c formed therein and (iv) the upper vertical alignment film 11d formed on the upper insulating film 11c are included. Similarly, the lower substrate 12 is formed on (i) the lower transparent substrate 12a, (ii) the lower transparent electrode (segment electrode) 12b formed on the lower transparent substrate 12a, and (iii) on the lower transparent substrate 12a. And the lower insulating film 12c formed on the lower transparent electrode 12b, and (iv) the lower vertical alignment film 12d formed on the lower insulating film 12c.

The upper transparent substrate 11a and the lower transparent substrate 12a are, for example, glass substrates. The upper transparent electrode 11b and the lower transparent electrode 12b are formed of a transparent conductive material such as ITO. The upper insulating film 11c and the lower insulating film 12c are, for example, a SiO ₂ film. The upper vertical alignment film 11d and the lower vertical alignment film 12d are formed by using the vertical alignment film material.

Both electrodes 11b and 12b overlap each other in a plan view with the vertically oriented liquid crystal layer 13 interposed therebetween, and define a display unit (pixel) in the overlapping region. The upper and lower transparent electrodes 11b and 12b realize, for example, a segment display unit (pixels) for displaying a specific pattern, a number, or the like, or a plurality of rectangular display units (pixels) arranged in a matrix (dot matrix). It is patterned like this. In the embodiment, the pattern is formed so that a plurality of rectangular pixels are arranged in a dot matrix along the X-axis direction and the Y-axis direction.

The vertically oriented liquid crystal layer 13 is composed of a liquid crystal material having a negative dielectric anisotropy Δε, for example, Δε = −5.1, and has a thickness of 4 μm as an example. The refractive index anisotropy (birefringence) Δn of the liquid crystal material is, for example, 0.0914. Spacers 13s are dispersedly arranged in the vertically oriented liquid crystal layer 13.

The end portion of the lower substrate 12 projects outward from the upper substrate 11, and the external take-out terminal portion 15 is defined in the overhanging region. An external take-out electrode 15b is arranged on the external take-out terminal portion 15. The external take-out electrode 15b is electrically connected to the lower transparent electrode 12b. The external extraction electrode 15b conducts with the electrode corresponding to each display unit (pixel).

The upper polarizing plate 17 is arranged on the surface of the upper substrate 11 opposite to the vertically oriented liquid crystal layer 13. The viewing angle compensation plate 16 and the lower polarizing plate 18 are arranged in this order on the surface of the lower substrate 12 opposite to the vertically oriented liquid crystal layer 13. The viewing angle compensation plate 16 and the polarizing plates 17 and 18 are fixed to the substrates 11 and 12 by an adhesive. The upper and lower polarizing plates 17 and 18 are arranged, for example, on a cross Nicol. The viewing angle compensating plate 16 has a function of improving the viewing angle characteristics by optically compensating for the deviation of the phase difference of the vertically oriented liquid crystal layer 13 during oblique observation, for example.

7B and 7C are schematic plan views showing a part of the electrode structures of the upper transparent electrode 11b and the lower transparent electrode 12b, respectively. The 12 o'clock direction corresponds to the X-axis positive direction, and the 9 o'clock direction corresponds to the Y-axis positive direction.

The upper transparent electrode 11b is a plurality of strip-shaped electrodes having a width of 136 μm extending in the 3 o'clock-9 o'clock direction (Y-axis direction), and the lower transparent electrode 12b is a 12 o'clock-6 o'clock direction (X-axis direction). ), A plurality of strip-shaped electrodes having a width of 136 μm. In both the upper transparent electrode 11b and the lower transparent electrode 12b, the distance between adjacent strip-shaped electrodes is 24 μm. The electrodes 11b and 12b are arranged orthogonal to each other in a plan view, and define a rectangular pixel (a square shape having a side of 136 μm) at an overlapping (intersecting) portion.

FIG. 7D is a schematic plan view showing a region of 3 pixels × 3 pixels. Each pixel is arranged in a matrix along the 3 o'clock-9 o'clock direction and the 12 o'clock-6 o'clock direction at intervals of 24 μm. In this figure, the edges of the pixels are shown by solid lines.

In the pixel arrangement region, the upper vertical alignment film 11d and the lower vertical alignment film 12d are oriented. For example, the upper vertical alignment film 11d is subjected to a rubbing treatment in which the 12 o'clock direction is the rubbing direction, and the lower vertical alignment film 12d is subjected to a rubbing treatment in which the 6 o'clock direction is the rubbing direction. When no voltage is applied between the electrodes 11b and 12b, the liquid crystal molecules in the liquid crystal layer 13 are oriented in one direction.

Further, in the alignment film 11d and the alignment film 12d, a region having a relatively high pretilt angle (close to 90 °) (high pretilt angle region 31) and a region having a relatively low pretilt angle (far from 90 °) are included in the pixel. ) Region (low pretilt angle region 32) is mixed, specifically, the high pretilt angle region 31 is arranged in the center of the pixel and the low pretilt angle region 32 is arranged in the peripheral portion of the pixel. Orientation treatment is applied. In one pixel, the low pretilt angle region 32 is arranged, for example, from the pixel edge toward the inside of the pixel.

In the example shown in FIG. 7D, in detail, in one pixel, the same distance d from the four sides of the square pixel toward the inside of the pixel so that the low pretilt angle region 32 surrounds the high pretilt angle region 31. The orientation treatment is performed so that the low pretilt angle region 32 is arranged in the region (overlap distance d) and the high pretilt angle region 31 is arranged inside the low pretilt angle region 32. The overlap distance d is, for example, 5 μm. The orientation treatment is performed so that, for example, an inter-pixel region having a width of 24 μm is also a low pretilt angle region 32. In FIG. 7D, the low pretilt angle region 32 is shown with diagonal lines. The high pretilt angle region 31 is an region inside the dotted line shown in the pixel.

The pretilt angle in the high pretilt angle region 31 is, for example, 89.9 °, and the pretilt angle in the low pretilt angle region 32 is, for example, 89.5 °. The pretilt angle in the high pretilt angle region 31 can be, for example, in the range of 89.5 ° to 89.95 °, and the pretilt angle in the low pretilt angle region 32 can be, for example, in the range of 89 ° to 89.7 °.

In the vertically oriented liquid crystal display element 10 according to the embodiment, the central molecular orientation of the liquid crystal layer 13 when no voltage is applied is 6 o'clock. The absorption axis orientation of the upper polarizing plate 17 is 45 ° -225 °, and the absorption axis orientation of the lower polarizing plate 18 is 135 ° -315 °.

FIG. 7E shows an oblique electric field in one pixel when the vertically oriented liquid crystal display element 10 according to the embodiment is viewed in a plan view (an oblique electric field generated from the upper transparent electrode 11b toward the lower transparent electrode 12b at the edge portion of the pixel). The direction of is indicated by an arrow.

The upper side of the pixel is a pixel edge in which the orientation of the central molecule of the liquid crystal layer 13 when no voltage is applied and the direction of the oblique electric field in a plan view when a voltage is applied are opposite (180 ° different). When a voltage is applied, for example, two dark regions (dark lines) are generated around the upper side of the pixel due to the influence of the oblique electric field.

The lower side of the pixel is a pixel edge in which the orientation of the central molecule of the liquid crystal layer 13 when no voltage is applied and the direction of the oblique electric field in a plan view when a voltage is applied are the same. No dark area is generated when a voltage is applied.

The right side of the pixel and the left side of the pixel are pixel edges in which the orientation of the central molecule of the liquid crystal layer 13 when no voltage is applied and the direction of the oblique electric field in a plan view when a voltage is applied are orthogonal (different by 90 °). When a voltage is applied, for example, one dark region (dark line) is generated around the right side of the pixel and the left side of the pixel due to the influence of the oblique electric field.

Although the liquid crystal display element 10 according to the embodiment is a multi-domain type, the dark region generated in the pixel is, for example, a dark region similar to the dark region shown in FIG. 2A (dark region in the mono-domain type).

In the vertically oriented liquid crystal display element 10 according to the embodiment, a high pretilt angle region 31 (a region where the pretilt angle is relatively close to 90 °) is arranged in the center of the pixel, and is located in the peripheral portion of the pixel from the pixel edge to the inside of the pixel. A low pre-tilt angle region 32 (a region where the pre-tilt angle is relatively far from 90 °) is arranged. Therefore, the steepness in the electro-optical characteristics in the pixel is maintained, and the dark region is the pixel edge (in the case of the embodiment, the upper side and the left and right sides) rather than the configuration in which the entire pixel is formed by the high pretilt angle region 31. ) Can be generated at a position close to) to reduce the generated area.

The liquid crystal display element 10 according to the embodiment can maintain steepness in the electro-optical characteristics in the pixel, for example, and even when driven at a low frame frequency, display unevenness is suppressed and uniform display is suppressed. It is a liquid crystal display element that can realize the above. For example, it is a liquid crystal display element capable of lowering the minimum frame frequency capable of achieving display uniformity while maintaining steepness in the electro-optical characteristics in the pixel, that is, enabling good display quality.

で表される。これを実施例による垂直配向型液晶表示素子１０に適用すると、画素の上辺から２本の暗領域（暗線）を超えた後、光透過率がはじめて５０％となる位置までの距離Ｅは、Ｅ＝３３．５０μｍとなる。 It should be noted that, for example, the dark region is exceeded from the pixel edge where the angle formed by the central molecular orientation of the liquid crystal layer 13 when no voltage is applied and the direction of the oblique electric field in the plan view when the voltage is applied is 165 ° or more and 180 ° or less. After that, the distance to the position where the light transmittance becomes 50% for the first time is E, and the distance (overlap distance) from the pixel edge to the end of the low pretilt angle region 32 arranged toward the inside of the pixel is d. When the pretilt angle of the low pretilt angle region 32 is θ _p , the distance E is

It is represented by. When this is applied to the vertically oriented liquid crystal display element 10 according to the embodiment, the distance E from the upper side of the pixel to the position where the light transmittance becomes 50% for the first time after exceeding two dark regions (dark lines) is E. = 33.50 μm.

で表される。これを実施例による垂直配向型液晶表示素子１０に適用すると、画素の左辺または右辺から暗領域を超えた後、光透過率がはじめて５０％となる位置までの距離Ｇは、Ｇ＝１８．９８μｍとなる。 Further, after the dark region is exceeded from the pixel edge where the angle formed by the central molecular orientation of the liquid crystal layer 13 when no voltage is applied and the direction of the oblique electric field in the plan view when the voltage is applied is 75 ° or more and 105 ° or less. The distance to the position where the light transmittance becomes 50% for the first time is G, the distance (overlap distance) from the pixel edge to the end of the low pretilt angle region 32 arranged toward the inside of the pixel is d, and the low pretilt. When the pretilt angle of the angular region 32 is θ _p , the distance G is

It is represented by. When this is applied to the vertically oriented liquid crystal display element 10 according to the embodiment, the distance G from the left side or the right side of the pixel to the position where the light transmittance becomes 50% for the first time after exceeding the dark region is G = 18.98 μm. It becomes.

FIG. 7F is a schematic cross-sectional view showing a vertically oriented liquid crystal display device 20 using the vertically oriented liquid crystal display element 10 according to the embodiment.

The vertically oriented liquid crystal display device 20 shown in this figure includes a multi-domain vertically oriented liquid crystal display element 10 according to an embodiment, a drive circuit 21, a backlight unit 22, and a housing (housing, cover, etc.) 23. Will be done.

The drive circuit 21 is electrically connected to, for example, the external extraction electrode 15b of the vertically oriented liquid crystal display element 10 according to the embodiment, and a voltage is applied between the electrodes 11b and 12b of the vertically oriented liquid crystal display element 10 to display the liquid crystal. The element 10 is driven in multiplex.

The backlight unit 22 includes, for example, an LED light source (backlight) that emits white light, a light guide plate, a diffuser plate, a brightness improving film, and the like, and is under the lower polarizing plate 18 of the vertically oriented liquid crystal display element 10 according to the embodiment. It is arranged on the side (Z-axis negative direction side).

The vertically oriented liquid crystal display element 10, the drive circuit 21, and the backlight unit 22 according to the embodiment are fixed and integrated at predetermined positions in the housing 23. The drive circuit 21 may be arranged outside the housing 23.

The vertically oriented liquid crystal display device 20 shown in this figure can maintain steepness in electro-optical characteristics in pixels, for example, and display unevenness even when multiplex drive is performed at a low frame frequency. It is a liquid crystal display device that can realize a uniform display with suppressed frequency, that is, a good display quality.

8A and 8B are schematic plan views showing a pixel structure of a vertically oriented liquid crystal display element according to a modified example.

In the embodiment (see FIG. 7D), the low pretilt angle region 32 is arranged in the region of the same distance d (overlap distance d) from the four sides of the square pixel toward the inside of the pixel, but the pixel structure is the same. Not limited.

For example, as shown in FIG. 8A, it is low on the lower side of the pixel where the dark region does not occur (the pixel edge in which the orientation of the central molecule of the liquid crystal layer 13 when no voltage is applied and the direction of the oblique electric field in the plan view when the voltage is applied are equal). The pre-tilt angle region 32 may not be provided. In this case, for example, in the 6 o'clock direction of the pixels, the high pretilt angle region 31 is arranged up to approximately half (12 μm) of the inter-pixel region (width 24 μm). That is, in the 12 o'clock direction of the pixels, the low pretilt angle region 32 is arranged up to approximately half (12 μm) of the inter-pixel region (width 24 μm).

The orientation of the central molecule of the liquid crystal layer 13 when no voltage is applied is not limited to the pixel edge where the direction of the oblique electric field in the plan view when the voltage is applied is the same. For example, the orientation of the central molecule of the liquid crystal layer 13 when no voltage is applied and the voltage application. The low pre-tilt angle region 32 is not provided on the pixel edge where the angle formed by the direction of the oblique electric field in the plan view of time is 15 ° or less, and the high pre-tilt angle region 31 can be arranged.

Further, as shown in FIG. 8B, the overlap distance d from each pixel edge (in this figure, the four sides of the square pixel) may be different depending on the edge. In the example shown in FIG. 8B, for example, the overlap distance from the upper side of the pixel is the largest, and the overlap distance from the lower side of the pixel is the smallest. The overlap distance from the right side of the pixel and the overlap distance from the left side of the pixel are equal to each other, and take an intermediate value between the overlap distance from the upper side of the pixel and the overlap distance from the lower side of the pixel.

Further, at the boundary portion between the high pretilt angle region 31 and the low pretilt angle region 32, the pretilt angle may be configured to be inclined and changed in a stepped manner or the like. In this case, for example, the region other than the high pretilt angle region 31 is considered as the low pretilt angle region 32, and the distance from the pixel edge to the position where the inclination of the pretilt angle of the high pretilt angle region 31 begins toward the inside of the pixel is exceeded. As the lap distance d, it is possible to calculate the distance E and the distance G by the equations (1) and (2).

The vertically oriented liquid crystal display element 10 according to the embodiment can be manufactured, for example, as follows.

Two 0.7 mm-thick blue glass substrates (upper transparent substrate 11a, lower transparent) with ITO films (upper transparent electrode 11b, lower transparent electrode 12b) patterned on one side by photolithography and etching. The substrate 12a) is prepared.

_{For example, the SiO 2} film is formed as the upper insulating film 11c and the lower insulating film 12c so as to cover at least the region corresponding to the effective display portion of the electrode 11b, 12b forming surface of the substrates 11a, 12a.

For example, the vertical alignment film material SE4811 manufactured by Nissan Chemical Industries, Ltd. is coated on the insulating films 11c and 12c so as to cover at least the region corresponding to the effective display portion of the electrode 11b and 12b forming surfaces of the substrates 11a and 11b. , 180 ° C to 220 ° C.

The vertical alignment film material surface is rubbed to one side with a cotton rubbing cloth having a cloth thickness of about 2.8 mm to 3.2 mm. Depending on the rubbing conditions, the pretilt angle of the high pretilt angle region 31 of the completed liquid crystal display element 10 is controlled in the range of, for example, 89.5 ° to 89.95 °.

For example, the pretilt angle of the irradiation range can be lowered by irradiating the light emitted from the high-pressure mercury lamp or the alkali halide lamp with the range of the high pretilt angle region 31 metal masked. Depending on the irradiation conditions, the pretilt angle of the low pretilt angle region 32 of the completed liquid crystal display element 10 is controlled in the range of, for example, 89 ° to 89.7 °. In this way, for example, the upper vertical alignment film 11d and the lower vertical alignment film 12d are formed on the insulating films 11c and 12c.

By the above steps, the upper substrate 11 and the lower substrate 12 are manufactured.

The sealing material 14 is printed in a frame shape on the alignment film 11d, 12d forming surface of one of the substrates 11 and 12 so as to surround at least a region larger than the effective display portion. The sealing material 14 includes a glass fiber spacer manufactured by Nippon Electric Glass Co., Ltd. with a diameter of 4 μm , and a gold-coated plastic ball manufactured by Sekisui Chemical Industry Co., Ltd. that ensures continuity between the substrates 11 and 12, respectively. .0 wt% is added.

Plastic ball spacers 13s manufactured by Sekisui Chemical Co., Ltd. having a diameter of 4 μm are sprayed on the alignment films 11d and 12d forming surfaces of the other substrates 11 and 12 ^{to 200 pieces / mm 2} by a dry spraying method.

Both substrates 11 and 12 are aligned and overlapped so that the alignment films 11d and 12d forming surfaces face each other, and the substrates 11 and 12 are fired (150 ° C.) in a pressed state to cure the sealing material 14. Complete an empty cell.

A liquid crystal material having a negative dielectric anisotropy Δε (for example, Δε = -5.1) manufactured by DIC Corporation is injected into an empty cell by a vacuum injection method, and then the injection port is sealed with an ultraviolet curable resin. , 120 ° C. for 1 hour to form the liquid crystal layer 13. The refractive index anisotropy (birefringence) Δn of the liquid crystal material is, for example, 0.0914.

After cleaning the 11th and 12th surfaces of the substrate with a neutral detergent, the upper polarizing plate 17 is attached to the 11th surface of the upper substrate, and the polarizing plate 18 with the viewing angle compensating plate 16 is attached to the 12th surface of the lower substrate. As the polarizing plates 17 and 18, for example, the polarizing plate SHC13U manufactured by Polatechno Co., Ltd. can be used. The polarizing plates 17 and 18 are arranged on the cross Nicol so that their respective absorption axis orientations form an angle of 45 ° with respect to the central molecular orientation orientation of the liquid crystal layer 13 defined by the rubbing treatment.

A lead frame, a flexible film via an anisotropic conductive film, and a driver IC are bonded to the external take-out electrode 15b portion.

Through the above steps, the multi-domain vertically oriented liquid crystal display element 10 is manufactured.

The drive circuit 21 is electrically connected to the vertically oriented liquid crystal display element 10. Further, a backlight unit 22 including, for example, a white light source is arranged below the lower polarizing plate 18 of the vertically oriented liquid crystal display element 10. The vertically oriented liquid crystal display element 10, the drive circuit 21, and the backlight unit 22 are fixedly arranged in the housing 23.

In this way, a multi-domain vertically oriented liquid crystal display device is manufactured.

In the method for manufacturing the liquid crystal display element 10 described above, the high-pressure mercury lamp light or the alkali halide lamp light is irradiated after the rubbing treatment, but the rubbing treatment may be performed after the light irradiation.

In addition, multi-domainization can be performed by other methods.

For example, alignment film materials that realize different pretilt angles may be applied and arranged at positions corresponding to the high pretilt angle region 31 and the low pretilt angle region 32, respectively. For example, after the rubbing process, it is possible to realize regions in which the pretilt angles are different from each other.

There is also a method of irradiating a visible laser beam at a position corresponding to the low pretilt angle region 32. For example, the pretilt angle of the irradiation region can be lowered by irradiating a bluish-purple or blue laser beam having a wavelength of about 405 nm or 450 nm before the liquid crystal is injected, after the liquid crystal is injected, and before the polarizing plates 17 and 18 are attached.

Although the present invention has been described above with reference to analysis, examples, and modifications, the present invention is not limited thereto.

For example, in the embodiment, both the substrates 11 and 12 (alignment films 11d and 12d) are subjected to the alignment treatment, but at least one of the substrates 11 and 12 is provided with the alignment films 11d and 12d on the liquid crystal layer 13 side and the alignment treatment is performed. May be applied to at least one side of the substrates 11 and 12 (alignment films 11d and 12d).

Further, in the embodiment, the vertically oriented liquid crystal display element 10 having a dot matrix electrode structure is used, but a vertically oriented liquid crystal display element having a segment electrode structure in which the outer shape of the pixel is arbitrary can also be used.

In addition, it will be obvious to those skilled in the art that various changes, improvements, combinations, etc. are possible.

It can be used for various vertically oriented liquid crystal display elements.

In conventional liquid crystal display elements and liquid crystal display devices, for example, it is necessary to increase the frame frequency in order to achieve both suppression of display unevenness in a bright display unit and high steepness in electro-optical characteristics. For this reason, for example, the burden on the drive circuit for operating the liquid crystal display element becomes heavy, and it becomes necessary to use a high-cost driver.

For example, by using the vertically oriented liquid crystal display element 10 according to the embodiment, low frame frequency drive can be easily realized, and a low-cost driver can be used. In addition, since a frame inversion waveform or the like can be adopted, power saving can be realized.

10 Vertically oriented liquid crystal display element 11 Upper substrate (common substrate)
11a Upper transparent substrate 11b Upper transparent electrode (common electrode)
11c Upper insulating film 11d Upper vertical alignment film 12 Lower substrate (segment substrate)
12a Lower transparent substrate 12b Lower transparent electrode (segment electrode)
12c Lower insulating film 12d Lower vertical alignment film 13 Vertical alignment liquid crystal layer 13s Spacer 14 Main seal part 15 External take-out terminal part 15b External take-out electrode 16 Viewing angle compensation plate 17 Upper polarizing plate 18 Lower polarizing plate 20 Vertical alignment type liquid crystal display Device 21 Drive circuit 22 Backlight unit 23 Housing 31 High pre-tilt angle region 32 Low pre-tilt angle region

Claims (5)

A first substrate with electrodes and
A second substrate provided with electrodes and arranged to face the first substrate, and
It has a vertically oriented liquid crystal layer arranged between the first substrate and the second substrate, and has.
In a plan view, pixels are defined in a region where the electrodes of the first substrate and the electrodes of the second substrate overlap.
At least one of the first and second substrates is provided with an alignment film on the vertically aligned liquid crystal layer side.
The alignment film is subjected to alignment processing so that a region having a relatively high pretilt angle is arranged in the central portion of the pixel and a region having a relatively low pretilt angle is arranged in a peripheral portion of the pixel. ,
At the boundary between the region having a relatively high pretilt angle and the region having a relatively low pretilt angle, the pretilt angle changes depending on the position.
The pretilt angle of the region having a relatively high pretilt angle is 89.5 ° to 89.95 °, and the pretilt angle of the region having a relatively low pretilt angle is 89 ° to 89.7 °.
Vertical alignment type liquid crystal display element of. A first substrate with electrodes and
A second substrate provided with electrodes and arranged to face the first substrate, and
With a vertically oriented liquid crystal layer arranged between the first substrate and the second substrate
Have,
In a plan view, pixels are defined in a region where the electrodes of the first substrate and the electrodes of the second substrate overlap.
At least one of the first and second substrates is provided with an alignment film on the vertically aligned liquid crystal layer side.
The alignment film is subjected to alignment processing so that a region having a relatively high pretilt angle is arranged in the central portion of the pixel and a region having a relatively low pretilt angle is arranged in a peripheral portion of the pixel. ,
At the boundary between the region having a relatively high pretilt angle and the region having a relatively low pretilt angle, the pretilt angle changes stepwise.
Vertically oriented liquid crystal display element. The region having a relatively low pretilt angle is arranged from the edge of the pixel toward the inside of the pixel.
The pixel has a rectangular shape including a first edge and a second edge facing each other, and a third edge and a fourth edge orthogonal to the first edge and the second edge and facing each other.
In the first edge of the pixel, the central molecular orientation of the vertically oriented liquid crystal layer when no voltage is applied and the plan view when a voltage is applied between the electrodes of the first substrate and the electrodes of the second substrate. The angle formed by the direction of the oblique electric field is 165 ° or more and 180 ° or less.
At a position 28 μm closer to the inside of the pixel from the third edge of the pixel, the distance from the first edge of the pixel to the position where the light transmittance becomes 50% for the first time after exceeding the dark region is E. The distance from the first edge of the pixel to the end of the region having a relatively low pretilt angle, which is arranged toward the inside of the pixel, is d ₁ , and the pretilt angle of the region having a relatively low pretilt angle is d 1. when was the theta _p, the distance E, the distance d _1, and, between the angle theta _p is

The liquid crystal display element according to claim 1 or 2, which is related to the above. In the third edge of the pixel, the central molecular orientation of the vertically oriented liquid crystal layer when no voltage is applied and the plan view when a voltage is applied between the electrodes of the first substrate and the electrodes of the second substrate. The angle formed by the direction of the oblique electric field is 75 ° or more and 105 ° or less.
At a position 28 μm closer to the inside of the pixel from the second edge of the pixel, the distance from the third edge of the pixel to the position where the light transmittance becomes 50% for the first time after exceeding the dark region is G. The distance from the third edge of the pixel to the end of the region having a relatively low pretilt angle, which is arranged toward the inside of the pixel, is d ₂ , and the pretilt angle of the region having a relatively low pretilt angle is d 2. when was the theta _p, the distance G, the distance d _2, and, between the angle theta _p is

The liquid crystal display element according to claim 3, which is related to the above. The liquid crystal display element according to any one of claims 1 to 4, wherein the region having a relatively low pretilt angle surrounds the region having a relatively high pretilt angle in the pixel.

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