JP5322726B2 - Liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve display uniformity in vertical alignment liquid crystal display device. <P>SOLUTION: In a liquid crystal display device comprising: a mono-domain vertical alignment layers subjected to a mono-domain vertical alignment process in parallel to a longitudinal direction of a first transparent electrodes at least to one; a vertical alignment mode liquid crystal layer with a pretilt angle placed between a pair of substrates; and a pair of polarizers held between the pair of the substrates, each intersection of the first and second transparent electrodes forms one pixel, an alignment direction of liquid crystal molecules in a mid-plane of the liquid crystal layer is in parallel to the longitudinal direction of the first transparent electrodes, and a rectangle aperture is formed in an area inside the pixel from the edge of the pixel from a center part between the electrodes of the second transparent electrode in a portion of each first transparent electrode forming one side of the pixel where the alignment direction and a direction to which liquid crystal molecules are tilted by an oblique electric field at the edge of each second transparent electrode are opposite to each other. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a liquid crystal display element.

  The vertical alignment type liquid crystal display element in which the liquid crystal molecules in the liquid crystal layer are aligned perpendicular to the substrate has a very good black level when no voltage is applied, and between the upper and lower polarizing plates on one or both sides of the liquid crystal cell. In addition, by introducing an optical compensator having a negative optical anisotropy having an appropriate parameter, it has a very good viewing angle characteristic (see, for example, Patent Document 1).

  In recent years, in a vertical alignment type liquid crystal display device, in order to obtain not only a viewing angle characteristic at the time of dark display but also a good viewing angle characteristic at a bright display, the alignment direction of the liquid crystal is directed to a plurality of directions within one pixel. "Domain orientation" is often used. For example, multi-domain alignment (for example, refer to Patent Document 2) in which an opening is provided in the pixel electrode to generate an oblique electric field to control the alignment, or a protrusion structure is provided in the pixel electrode to control the alignment by an inclined surface. Multi-domain orientation (see, for example, Patent Document 3) has been proposed. However, when the electrode structure for generating the oblique electric field described above or the protrusion structure is provided on the substrate surface, for example, the aperture ratio is reduced in one pixel of the dot matrix display portion, and the transmittance of the liquid crystal display element is reduced.

  On the other hand, when importance is attached only to the viewing angle characteristics in the left-right direction of the liquid crystal display device, not the multi-domain alignment as described above, but a mono-domain alignment in which a uniform alignment process is performed on the entire surface of the liquid crystal display element. The uniform alignment treatment can be performed by a photo-alignment treatment for a so-called vertical alignment film (for example, see Patent Document 4) or a rubbing treatment method for a vertical alignment film having a specific surface free energy (for example, see Patent Document 1). .

  The alignment of the monodomain vertical alignment type liquid crystal display element is controlled so that the alignment state in the liquid crystal layer is uniform regardless of the presence or absence of voltage application. The steepness in the electro-optical characteristics greatly depends on the pretilt angle in the liquid crystal layer, and it tends to be better as it approaches 90 degrees. At this time, in order to prevent alignment defects when a voltage is applied, it is necessary to give a pretilt angle so that the liquid crystal molecules are slightly tilted from the perpendicular to the substrate even when no voltage is applied.

  Also, in the vertical alignment type liquid crystal display element, the steepness in the electro-optical characteristics is good in order to achieve high contrast while realizing good on-display transmittance under high duty driving conditions of 1/32 or more. Therefore, it is effective to adjust the retardation Δnd (Δn: birefringence of the liquid crystal material, d: liquid crystal layer thickness) in the liquid crystal layer to be set larger than the low duty driving condition of ¼ or less. is there.

  The driving method is divided into an active matrix using an active element such as a TFT and a simple matrix. The simple matrix includes a character display that displays 7 segments and arbitrary marks, and a dot matrix display that displays dots using vertical and horizontal electrodes. In the dot matrix display, on / off display is performed by applying a voltage waveform to the scanning electrode in the horizontal direction and the signal electrode in the vertical direction. The voltage waveform at this time, also called multiplex drive or duty drive, is determined by an arbitrary duty ratio and bias ratio, and an optimum bias method, an active addressing method for selecting all scan electrodes, and a multi-line selection method for selecting multiple scan electrodes Alternatively, a multi-line addressing method is used. In general, scan electrodes are sequentially selected in one direction. The contents of the display are read from the display data RAM in the drive circuit, and sequentially driven one screen at a time via the segment driver connected to the signal electrode and the common driver connected to the scan electrode.

  FIG. 11 is a schematic cross-sectional view showing an example of a conventional vertical alignment type liquid crystal display element. 8 is a cross-sectional view taken along the line XY in FIG.

  A first substrate (upper substrate) 1 and a second substrate (lower substrate) 2 face each other, and a liquid crystal layer 3 is sandwiched therebetween. The first substrate 1 is formed by forming a transparent electrode (segment electrode) 14 on an opposing surface of a transparent substrate 13, applying a vertical alignment film 15 thereon, and rubbing the surface in a direction indicated by 18. On the outer surface, a viewing angle compensation plate 12 and a polarizing plate 11 are arranged. Similar to the first substrate 1, the second substrate 2 forms a transparent electrode (common electrode) 24 on the opposite surface of the transparent substrate 23, covers the surface with a vertical alignment film 25, and is rubbed in the direction of the arrow 28. It is a thing. A viewing angle compensation plate 22 and a polarizing plate 21 are disposed on the outer surface. The liquid crystal layer 3 includes liquid crystal molecules having a property of being aligned perpendicular to the planes of the substrates 1 and 2, and is rubbed 18 and 28 to form a fixed angle (in this example, approximately 89.9 ° from the normal direction of the substrate). ) Pretilt. A backlight 4 and a light source 5 are disposed below the lower substrate 2.

  FIG. 12 is a schematic plan view showing electrode patterns of the transparent electrode (segment electrode) 14 and the transparent electrode (common electrode) 24 of FIG. This plan view is the liquid crystal display element of FIG. 11 viewed from the normal direction. In addition, since the same reference number as FIG. 11 represents the same member, the description is abbreviate | omitted.

  In FIG. 12, the upper electrode is a segment electrode 14 having a strip-like electrode shape from 6:00 to 12:00, and the lower electrode is a common electrode 24 having a strip-like electrode shape in the orthogonal direction. A square area where the segment electrode 14 and the common electrode 24 intersect constitute one pixel.

  The best viewing direction is the 6 o'clock orientation because of the orientation relationship in which the liquid crystal layer center molecule collapses when a voltage is applied. On the other hand, the opposite orientation (anti-viewing direction) has an angle at which the bright display becomes dark and difficult to see when the observation polar angle is changed with respect to the element normal direction.

JP 2006-243102 A JP 2004-212582 A JP 2006-243102 A JP 2004-212582 A

  The conventional vertical alignment type liquid crystal display device shown in FIG. 11 is manufactured using a liquid crystal material having a retardation value Δnd of about 900 nm, and a driving voltage that can obtain the maximum contrast under 1/64 Duty and 1/9 bias driving conditions. When the external appearance of the liquid crystal display element is observed, the entire dot matrix display unit realizes a uniform display state even if the observation polar angle is changed in the best viewing direction and the horizontal direction of the element, whereas the anti-viewing direction In the case of a clockwise and counterclockwise direction of about 70 °, the display uniformity is insufficient. In particular, when observed from the counter-viewing direction, the display feels rough, and the display quality may be significantly reduced.

  An object of the present invention is to provide a vertical alignment type liquid crystal display element that realizes display uniformity.

According to one aspect of the present invention, a pair of transparent substrates disposed to face each other at a predetermined interval, and a plurality of first transparent electrodes formed in a strip shape on one facing surface side of the transparent substrate, A plurality of second transparent electrodes formed in a strip shape so as to intersect perpendicularly to the first transparent electrode on the other opposing surface side of the transparent substrate, and the opposing surfaces of the transparent substrate A monodomain vertical alignment film formed on the side and subjected to a monodomain vertical alignment treatment so that at least one of the liquid crystal layer center molecules is aligned parallel to the longitudinal direction of the first transparent electrode, and the pair of substrates A liquid crystal display element having a vertical alignment mode liquid crystal layer sandwiched between the first and second transparent electrodes and having a pretilt angle and a pair of polarizing plates disposed across the pair of substrates. forming each one pixel in the portion, the liquid crystal layer In some of the first transparent electrode and the direction of liquid crystal molecules by oblique electric fields of the edge portion of the alignment direction and the second transparent electrode of the molecule is inclined to form one side of the pixel to be inverted, the second A rectangular opening is formed from the center of the line between the transparent electrodes to the area inside the pixel from the pixel edge.

According to another aspect of the present invention, a pair of transparent substrates arranged to face each other at a predetermined interval, and a plurality of first transparent electrodes formed in a strip shape on one facing surface side of the transparent substrate. And a plurality of second transparent electrodes formed in a strip shape so as to intersect perpendicularly to the first transparent electrode on the other opposing surface side of the transparent substrate, and the respective opposing surfaces of the transparent substrate A monodomain vertical alignment film formed on the surface side and subjected to a monodomain vertical alignment treatment so that at least one of the liquid crystal layer center molecules is aligned parallel to the longitudinal direction of the first transparent electrode; A liquid crystal display element having a vertical alignment mode liquid crystal layer sandwiched between substrates and having a pretilt angle, and a pair of polarizing plates disposed with the pair of substrates sandwiched between the first and second transparent electrodes. One pixel is formed at the intersection, and the second In the region of the first transparent electrode facing the between the lines of the transparent electrode, a rectangular opening is formed, the opening that is provided across the edges of the two pixels adjacent to the opening It is characterized by.

  According to the present invention, display uniformity can be realized in a vertical alignment type liquid crystal display element.

1 is a schematic cross-sectional view illustrating a configuration of a liquid crystal display element 100 according to a first embodiment of the present invention. FIG. 2 is a schematic plan view illustrating electrode patterns of a segment electrode and a common electrode 24 in FIG. It is a schematic plan view showing the electrode pattern which has the opening part 34a by the 1st Example of this invention. It is a schematic plan view showing electrode pattern A1-A4 by the 1st Example of this invention. It is a front observation photograph of the liquid crystal display element 100 by the 1st Example of this invention. It is a front observation photograph of the liquid crystal display element 100 by the 1st Example of this invention. It is a schematic plan view showing the electrode pattern which has the opening part 34b by the 2nd Example of this invention. It is a schematic plan view showing electrode pattern B1-B4 by the 2nd Example of this invention. It is a front observation photograph of the liquid crystal display element 100 by the 2nd Example of this invention. It is a front observation photograph of the liquid crystal display element 100 by the 2nd Example of this invention. It is a schematic sectional drawing showing an example of the conventional vertical alignment type liquid crystal display element. It is a schematic plan view showing the dot matrix electrode pattern of the conventional vertical alignment type liquid crystal display element. It is a front observation photograph which shows the orientation state at the time of ON voltage application in the electrode pattern and electrode structure shown in FIG. 12, and an orientation direction. It is a conceptual diagram showing the liquid crystal director distribution in 1 pixel at the time of ON voltage application in the electrode pattern and electrode structure shown in FIG. 12, and an orientation direction.

  The present inventor analyzed the cause of the display non-uniformity when the liquid crystal display element was observed from the anti-viewing direction in the prior art, and found that the oblique electric field generated between the electrodes was the cause.

  As shown in FIG. 11, it is generally known that an oblique electric field is generated at the edge of the electrode pattern between the two substrates. However, particularly in the case of a vertical alignment type liquid crystal display element, it is easily affected. I know that.

The negative type liquid crystal used in the vertical alignment type liquid crystal display element falls in a direction perpendicular to the electric lines of force of the electric field. The tilt also occurs in the oblique electric field generated at the edge of the electrode pattern. Since an upward electric field is generated on the side of the segment electrode 14, the liquid crystal molecules (director) fall down inward . Similarly, a downward spreading electric field is generated on the side of the common electrode 24, and the liquid crystal molecules (directors) fall down toward the outside . Therefore, when the liquid crystal director by the oblique electric field generated at the edge of the electrode pattern is in a different direction from the liquid crystal director by the alignment treatment, a black linear domain boundary is recognized at the boundary portion.

  FIG. 13 is a front view photograph when an ON voltage is applied in the electrode pattern, electrode structure, and orientation direction shown in FIG. The white region is considered to indicate a region in which the liquid crystal molecules that have been vertically aligned fall in the alignment direction and pass through the polarizing plate in the crossed Nicols arrangement so that light is transmitted. The black area around the white area is considered to indicate an area where light is not yet transmitted, and the alignment of liquid crystal molecules is considered to be disturbed.

  As shown in FIG. 13, a black line was observed along the square pixel shape as when the “U” was rotated 90 degrees to the left inside the pixel. With reference to FIG. 14, the cause of the black line will be described.

  FIG. 14 is a conceptual diagram showing a liquid crystal director distribution in one pixel when an ON voltage is applied in the electrode pattern and electrode structure and alignment direction shown in FIG.

  In the central portion of the pixel, it is considered that the liquid crystal molecules are tilted upward in the figure in accordance with the vertical alignment process, depolarization occurs, and light is transmitted. On the left-hand side, the liquid crystal molecules fall in an oblique direction due to the synergistic effect of the horizontal fringe electric field and the vertical alignment treatment, resulting in a component that matches the polarization axis direction of the polarizing plate, preventing depolarization, It is considered that the light shielding state is maintained.

  The liquid crystal director at the center of the pixel indicated by the hatched arrow is determined in the 12 o'clock direction depending on the rubbing directions of both the upper substrate 1 and the lower substrate 2 because there is no oblique electric field. The liquid crystal director at the pixel edge indicated by the white arrow is determined by the influence of the oblique electric field. Since the liquid crystal layer 3 exhibits the nature of a continuum, the liquid crystal director continuously rotates 90 degrees from the center to the left and right edges. In the figure, this is simplified and the middle part is shown as a liquid crystal director inclined by 45 degrees with a black arrow. Further, in the side 7 of the upper part of the pixel (upper part in the figure), the liquid crystal director at the center of the pixel and the liquid crystal director at the pixel edge are in an inverted relationship, so that both liquid crystal directors rotate 180 degrees. (Boundary area) and discontinuous areas exist.

  In such a state, when the lower and upper polarizing plate absorption axes are inclined by ± 45 degrees with respect to the rubbing direction of both substrates as shown in the figure, the liquid crystal director region indicated by the black arrows The boundary region where the liquid crystal directors at the center and the edge of the upper part of the pixel are inverted is parallel or substantially parallel to the polarizing plate absorption axis, so that a bright state is not obtained and a black line is observed.

  In the discontinuous region, it is presumed that the liquid crystal is kept vertical even when a voltage is applied. The discontinuous region is an intersection of the black lines, and here, since the liquid crystal molecules do not tilt despite voltage application, it is considered that a dotted dark region is formed. In the present specification, this black line region is referred to as “black cross”.

  The cause of the black cross is that the orientation direction of the liquid crystal molecules is parallel and parallel to the absorption axis of the polarizing plate, or the liquid crystal molecules are substantially perpendicular to the substrate even when voltage is applied. It is thought to be because.

  In FIG. 13, when the black cross near the upper edge is observed, an intersection is observed, but a phenomenon in which the number and position of the intersection is different for each pixel is observed. Due to the difference in the position and number of intersections of black crosses for each pixel, it is considered that the area ratio of the regions with different orientation orientations near the edges changes, and this is the cause of display non-uniformity when observed from the anti-viewing direction of the liquid crystal display It is thought that it can be specified.

  It can be seen that in the counter-viewing direction, the transmittance at the center of the pixel is low and only the pixel edge portion is transmitted. The transmissive portion of the edge portion is a black cross region when viewed from the front (for example, FIG. 13), and when the viewing direction is changed from the counter-viewing direction clockwise and counterclockwise, the liquid crystal director distribution in the black cross region Affects. As described above, since the intersection position and the number of black crosses are different for each pixel, it is considered that the liquid crystal director distribution in the black cross region is different for each pixel. Here, assuming that the liquid crystal director distribution in the black cross region is approximately 45 degrees to the right and 45 degrees to the left, the intersections are different for each pixel, so the size (area) of the right 45 degrees region and the left 45 degrees region is different. Are also expected to be different. In this case, the transmittance when the viewing angle is changed clockwise from the anti-viewing direction and the transmittance when the viewing angle is changed counterclockwise are different, and when observing a plurality of pixels or the entire screen, it becomes rough. As a result, the liquid crystal display element has poor display uniformity and low display quality.

  FIG. 1 is a schematic cross-sectional view showing a configuration of a liquid crystal display device 100 according to a first embodiment of the present invention. The liquid crystal display element 100 is a monodomain vertical alignment type liquid crystal display element having a matrix-like dot matrix electrode pattern.

  A segment electrode substrate (upper substrate) 1 and a common electrode substrate (lower substrate) 2 face each other, and a liquid crystal layer 3 is sandwiched therebetween. The segment electrode substrate 1 is obtained by forming a transparent electrode (segment electrode) 34 on the opposite surface of the transparent substrate 13, applying a vertical alignment film 15 thereon, and rubbing the surface in a direction indicated by 18. The viewing angle compensation plate 12 and the polarizing plate 11 are disposed on the outer surface.

  Similar to the segment electrode substrate 1, the common electrode substrate 2 is formed by forming a transparent electrode (common electrode) 24 on the opposite surface of the transparent substrate 23, covering the surface with a vertical alignment film 25, and rubbing in the direction of an arrow 28. It is. A viewing angle compensation plate 22 and a polarizing plate 21 are disposed on the outer surface.

  The liquid crystal layer 3 includes liquid crystal molecules having a property of being aligned perpendicular to the surfaces of the substrates 1 and 2 and has a pretilt of a certain angle from the normal direction of the substrate by the alignment treatment. A backlight 4 and a light source 5 are disposed below the lower substrate 2. An insulating film or the like for preventing a short circuit between the substrates may be formed between the transparent electrode 34 and the vertical alignment film 15 on the substrate 1 and between the transparent electrode 24 and the vertical alignment film 25 on the substrate 2.

  The segment electrode 34 is formed of ITO, which is a transparent electrode, and has a line width of 460 μm, a space between the lines of 15 μm, and 128 linear electrodes.

  The common electrode 24 was formed of ITO, which is a transparent electrode, and had a line width of 460 μm, a line spacing of 15 μm, and 64 linear electrodes.

  For example, an indium tin oxide (ITO) film, which is a transparent film, is formed on each substrate to a thickness of 500 mm by CVD, vapor deposition, sputtering, etc., and shaped by photolithography. The segment electrode 34 was provided with an opening 34a as shown in FIG. As a first example, liquid crystal display elements were actually manufactured by providing openings 34a1 to a4 using electrode patterns A1 to A4 shown in FIGS. Each electrode pattern A1 to A4 will be described in detail later with reference to FIG.

  A vertical alignment film was formed by flexographic printing on the substrates 1 and 2 on which the transparent electrodes 24 and 34 were formed, and then fired. The film was given a pretilt angle by a process such as rubbing. In the first embodiment, for the electrode patterns A1 to A4 shown in FIGS. 4A to 4D, the pretilt angles are set to 89.95 ° and 89.9 °, respectively. A liquid crystal display element 100 was produced.

  The azimuth angle of the pre-tilt of the segment electrode substrate (upper substrate) 1 is 6 o'clock (when the right is 0 degree, the counterclockwise position is 90 degrees, leftward in FIG. 1), the common electrode substrate (lower side) The azimuth angle of the pre-tilt of the substrate 1 was set to an anti-parallel orientation in the direction of 12 o'clock (90 ° clockwise when the right is 0 °, rightward in FIG. 1). Note that the rubbing treatment method is not particularly limited as long as uniform alignment treatment is realized in the pixel. For example, ultraviolet irradiation with respect to the vertical alignment film, oblique deposition of metal oxide, an alignment method using a sputtered film, or the like can be used. The rubbing process may be performed only on one of the substrates 1 and 2.

  The cell thickness d was set to 4.0 μm by dispersing spacers. As the liquid crystal material, a negative liquid crystal having Δε <0 and Δn <0.23 was used. As long as the liquid crystal material is a negative material having a negative Δε, there is no limitation on a physical property value such as Δn.

  The absorption axis angles of the polarizing plates 11 and 21 were 45 ° for the upper polarizing plate 11 and 135 ° for the lower polarizing plate 21. The polarizing plate angle is preferably 90 ° when the crossing angle is 90 ° because a good black state can be obtained. However, it can be shifted by several degrees. As the polarizing plate material, either an iodine polarizing plate or a dye polarizing plate can be used.

  For the optical compensation plates 12 and 22, two C plates (Re = 0 nm, Rth = 220 nm) were laminated between the polarizing plate on one side and the substrate. It is also possible to insert an optical compensation plate (A plate, C plate, B plate: biaxial retardation plate) between the polarizing plates on both sides and the substrate.

  FIG. 2 is a schematic plan view showing electrode patterns of the segment electrode 34 and the common electrode 24 of FIG. This plan view is a view of the liquid crystal display element of FIG. 1 as viewed from the normal direction. In this example, the common electrode 34 employs a third electrode pattern shown in FIG.

  In FIG. 2, the upper electrode is a segment electrode 34 having a strip-like electrode shape from 6 o'clock to 12 o'clock, and the lower electrode indicated by a broken line is a common electrode 24 having a strip-like electrode shape in the orthogonal direction. A square area where the segment electrode 34 and the common electrode 24 intersect constitute one pixel.

  The best viewing direction is the 6 o'clock orientation because of the orientation relationship in which the liquid crystal layer center molecule collapses when a voltage is applied. On the other hand, the opposite direction has an angle at which the bright display becomes dark and difficult to view when the observation polar angle is changed with respect to the element normal direction.

  FIG. 3 is a schematic plan view showing an electrode pattern having openings 34a according to the first embodiment of the present invention.

  As described above, the cause of the display non-uniformity is considered to be that the occurrence position of the black cross is not fixed. Therefore, as a method for solving this, the black cross itself does not occur in the vicinity of the pixel upper edge 7. It is conceivable that the black cross is uniform in each pixel.

  Therefore, in the first embodiment, as shown in FIG. 3, the upper edge of the pixel (liquid crystal director at the center of the pixel by the alignment process (inclination direction of the liquid crystal molecules) and the liquid crystal director at the edge of the pixel by the oblique electric field (inclination of the liquid crystal molecules). A pixel-shaped opening 34a is arranged in the segment electrode 34 in the vicinity of the pixel side 7) that is in a relationship (in the reverse direction) with the direction (in the reverse direction).

  In FIG. 3, a rectangular opening 34 a is provided in the segment electrode 34 facing the line portion of the common electrode 24 arranged in the left-right direction. The upper edge position of the opening 34 a is a position closer to the pixel upper edge 7 than the center in the vertical direction of the line portion of the common electrode 24. The lower edge position of the opening 34 a is the position of the pixel inner surface from the pixel upper edge 7. The distance W between the upper and lower edges of the opening 34a is set to be at least half the distance d between the common electrodes 24 (W ≧ 1 / 2d). The opening 34a is arranged so that at least a part of the opening 34a and a part of the line portion of the common electrode 24 overlap in plan view.

  A plurality of openings 34a are periodically arranged with a height W and a width s and spaced from adjacent openings 34a. Note that a plurality of openings 34a are preferably provided per pixel as shown in FIG. 3, but only one may be provided. Further, in the drawing, the opening portions 34a are provided at the left and right edge portions of the segment electrode 34, but the opening portions 34a may be provided at a certain interval from the edge portion.

  FIG. 4 is a schematic plan view showing electrode patterns A1 to A4 according to the first embodiment. This plan view is a view of the liquid crystal display element of FIG. 1 as viewed from the normal direction. 4A to 4D correspond to patterns A1 to A4 each having an opening 34a having four types of dimensions shown in Table 1 below. Table 1 shows the dimensions of each part shown in FIG. In Table 1, “n” represents the number of openings 34a per pixel. The electrode width P of the segment electrode 34 has a relationship of P = n × s + e × (n−1) with respect to each parameter. In this embodiment, P is 0.46 mm and the electrode interval is 0.015 mm.

FIG. 4A is a schematic plan view showing an electrode pattern A1 according to the first embodiment. Pattern A1 is an example in which five openings 34a1 are arranged per pixel. As shown in Table 1, the dimensions of the opening 34a1 are set such that the height W is 25 μm and the width s is 0.0511 mm, and the interval e between the openings 34a1 is 0.0511 mm, which is the same as the width s of the opening 34a1. It is.

  FIG. 4B is a schematic plan view showing an electrode pattern A2 according to the first embodiment. Pattern A2 is an example in which three openings 34a2 are arranged per pixel. As shown in Table 1, the dimensions of the opening 34a2 are set such that the height W is 25 μm and the width s is 0.092 mm, and the interval e between the openings 34a2 is 0.092 mm, which is the same as the width s of the opening 34a2. It is.

  FIG. 4C is a schematic plan view showing an electrode pattern A3 according to the first embodiment. Pattern A3 is an example in which five openings 34a3 are arranged per pixel. As shown in Table 1, the dimensions of the opening 34a3 are set to a height W = 25 μm and a width s = 0.0354 mm, and the interval e between the openings 34a3 is twice the width s of the opening 34a3. It is set to 0.0708 mm.

  FIG. 4D is a schematic plan view showing an electrode pattern A4 according to the first embodiment. Pattern A4 is an example in which three openings 34a4 are arranged per pixel. As shown in Table 1, the dimensions of the opening 34a4 are set such that the height W = 25 μm and the width s = 0.0657 mm, and the interval e between the openings 34a4 is twice the width s of the opening 34a4. It is set to 0.1314 mm.

  FIG. 5 is a front view photograph of the liquid crystal display element 100 according to the first embodiment of the present invention. FIGS. 5A to 5D are images obtained by manufacturing the liquid crystal display element 100 using the electrode patterns A1 to A4 shown in FIGS. 4A to 4D, respectively. In this example, only the common substrate 2 was rubbed in the 12 o'clock direction, and the pretilt angle was set to about 89.95 °.

  As shown in FIGS. 5A to 5D, when the upper part (near the upper edge 7) of one pixel is observed, the black cross pattern is observed in each pixel regardless of which of the electrode patterns A1 to A4 is used. It can be seen that the black cloth was fixed evenly.

  It can also be seen that no black cross has occurred near the edge of the opening 34a. The reason why the black cross does not occur is considered to be that by providing the opening 34a, the oblique electric field generation direction of the opening 34a is reversed, and the vicinity of the lower edge of the pixel and the direction of the liquid crystal director are the same. That is, it is considered that the inversion of the liquid crystal director does not occur near the edge of the opening 34a.

  As described above, by providing the opening 34a, the electrode opening ratio is lowered, but no black cross is generated near the edge of the opening 34a. Therefore, the effective opening ratio in one pixel tends to increase.

  In terms of appearance, even when observed from the opposite viewing direction, the alignment nonuniformity was remarkably improved in any pattern, and there was no problem at all.

  FIG. 6 is a front view photograph of the liquid crystal display element 100 according to the first embodiment of the present invention. FIGS. 6A to 6D are images obtained by manufacturing the liquid crystal display element 100 using the electrode patterns A1 to A4 shown in FIGS. 4A to 4D, respectively. In this example, the pre-tilt angle was set to about 89.9 ° in the anti-parallel orientation in which the common substrate 2 was rubbed in the 12 o'clock direction and the segment substrate 1 was rubbed in the 6 o'clock direction.

  As shown in FIGS. 6A to 6D, since the pretilt angle is set lower than in the example shown in FIG. 5, the black cross is generated from the center of the pixel to the edge, and the effective open efficiency is increased. Can be observed.

  In addition, as in the example shown in FIG. 5, it can be seen that no black cross is generated near the edge of the opening 34a.

Further, as shown in FIGS. 6A to 6C, when the electrode patterns A1 to A3 were used, the black cross pattern was uniformly generated in each pixel, and the black cross could be fixed. I understand. However, as shown in FIG. 6D, when the electrode pattern A4 having a small width s and a small number of openings 34a is used, a part of the black cross pattern is disturbed between the openings 34a. Is observed. From this, it can be seen that the distance e = 0.1314 mm between the openings 34a employed in the electrode pattern A4 is too wide to fix the black cloth. Therefore, in order to fix the black cloth, it is considered preferable to set the interval e between the openings 34a to 0.092 mm or less as in the pattern A2. Further, it is considered that the width s of the opening 34a is preferably set to be less than the electrode width P.

  In this example as well, in terms of appearance, display nonuniformity was not observed in any pattern even when observed from the opposite viewing direction.

  As described above, according to the first embodiment of the present invention, in the liquid crystal display element using the dot matrix electrode pattern, when the portion where the common electrode 24 and the segment electrode 34 intersect is one pixel, A liquid crystal director at the center of the pixel (direction in which the liquid crystal molecules tilt) by the alignment treatment and a liquid crystal director at the pixel edge (in the direction in which the liquid crystal molecules tilt) due to the oblique electric field are reversed (in the reverse direction). By providing the segment electrode 34 with a rectangular opening 34a in the region inside the pixel from the pixel edge from the center between the electrodes of the common electrode 24, the occurrence of black crossing in the vicinity of the edge of the opening 34a is suppressed and the opening is opened. The black cloth can be fixed in the region between the portions 34a. Therefore, it is possible to eliminate the display non-uniformity that occurs in the counter-viewing direction and the clockwise and counterclockwise directions around 70 ° azimuth, and to obtain display uniformity equivalent to the best viewing azimuth.

  FIG. 7 is a schematic plan view showing an electrode pattern having openings 34b according to the second embodiment of the present invention. The difference between the second embodiment and the first embodiment is only the electrode pattern, and the other configurations are the same.

  In the second embodiment, as shown in FIG. 7, the pixel upper edge (the liquid crystal director at the center of the pixel by the alignment process (the direction in which the liquid crystal molecules tilt) and the liquid crystal director at the pixel edge by the oblique electric field (the direction in which the liquid crystal molecules tilt) A pixel-shaped opening 34b is arranged in the segment electrode 34 in the vicinity of the pixel side 7 that is in a relationship (in the reverse direction).

  In FIG. 7, a rectangular opening 34 b is provided in the segment electrode 34 that is opposed to the line portion of the common electrode 24 arranged in the left-right direction. The difference from the first embodiment is that the distance W between the upper and lower edges of the opening 34b according to the second embodiment is larger than the distance d between the lines of the common electrode 24 (W> d), and two adjacent pixels in the vertical direction. The opening 34b is formed so as to straddle. The upper edge position of the opening 34b is the inner surface of the pixel adjacent to the upper direction from the lower edge 8 of the pixel adjacent in the upper direction, and the lower edge position of the opening 34b is the inner surface of the pixel from the upper edge 7 of the pixel. It becomes the position.

  The plurality of openings 34b have a height W and a width s, and are periodically arranged with an interval s from the adjacent openings 34b. Note that a plurality of openings 34b are preferably provided per pixel as shown in FIG. 7, but only one may be provided. Further, in the drawing, the openings 34b are provided at the left and right edge portions of the segment electrode 34, but the openings 34b may be provided at a certain interval from the edge portion.

  FIG. 8 is a schematic plan view showing electrode patterns B1 to B4 according to the second embodiment of the present invention. This plan view is a view of the liquid crystal display element of FIG. 1 as viewed from the normal direction. 8A to 8D respectively correspond to patterns B1 to B4 having openings 34b having four types of dimensions shown in Table 2 below. Table 2 shows the dimensions of each part shown in FIG. In Table 2, n indicates the number of the opening 34b per pixel. The electrode width P of the segment electrode 34 has a relationship of P = n × s + e × (n−1) with respect to each parameter. In this embodiment, P is 0.46 mm and the electrode interval is 0.015 mm.

FIG. 8A is a schematic plan view showing an electrode pattern B1 according to the second embodiment. Pattern B1 is an example in which five openings 34b1 are arranged per pixel. As shown in Table 2, the dimensions of the opening 34b1 are set such that the height W = 45 μm and the width s = 0.0511 mm, and the interval e between the openings 34b1 is 0.0511 mm, which is the same as the width s of the opening 34b1. It is.

  FIG. 8B is a schematic plan view showing an electrode pattern B2 according to the second embodiment. Pattern B2 is an example in which three openings 34b2 are arranged per pixel. As shown in Table 2, the dimensions of the opening 34b2 are set such that the height W is 45 μm and the width s is 0.092 mm, and the interval e between the openings 34b2 is 0.092 mm, which is the same as the width s of the opening 34b2. It is.

  FIG. 8C is a schematic plan view showing an electrode pattern B3 according to the second embodiment. Pattern B3 is an example in which five openings 34b3 are arranged per pixel. As shown in Table 1, the dimensions of the opening 34b3 are set to a height W = 45 μm and a width s = 0.0354 mm, and the interval e between the openings 34b3 is twice the width s of the opening 34b3. It is set to 0.0708 mm.

  FIG. 8D is a schematic plan view showing an electrode pattern B4 according to the second embodiment. Pattern AB is an example in which three openings 34b4 are arranged per pixel. As shown in Table 2, the dimensions of the opening 34b4 are set to a height W = 45 μm and a width s = 0.0657 mm, and the interval e between the openings 34b4 is twice the width s of the opening 34b4. It is set to 0.1314 mm.

  FIG. 9 is a front view photograph of the liquid crystal display element 100 according to the second embodiment of the present invention. FIGS. 9A to 9D are images of the liquid crystal display element 100 produced using the electrode patterns B1 to B4 shown in FIGS. 8A to 8D, respectively. In this example, only the common substrate 2 was rubbed in the 12 o'clock direction, and the pretilt angle was set to about 89.95 °.

  As shown in FIGS. 9A to 9D, when the upper part (near the upper edge 7) of one pixel is observed, the black cross pattern is observed in each pixel regardless of which of the electrode patterns B1 to B4 is used. It can be seen that the black cloth was fixed evenly. In the vicinity of the pixel edge between the opening portion 34b and the opening portion 34b, a characteristic pattern in which the black cross generation sites are alternately staggered was observed. This is because the oblique electric field generation azimuth and the easy orientation axis on the substrate are reversed in the opening 34b and the region in between. Compared with the conventional example and the first embodiment, although the black open occurs on the lower side of the pixel and the effective open efficiency is slightly lowered, the height of the opening 34b is set to be large. There is an advantage that a large margin for allowing a positional shift between the substrates 2 can be obtained.

In terms of appearance, even when observed from the opposite viewing direction, the alignment nonuniformity was remarkably improved in any pattern, and there was no problem at all. In addition, the alignment accuracy was about ± 20 μm, and it was confirmed that no alignment non-uniformity occurred when observed from the anti-viewing direction even when a deviation occurred.

FIG. 11 is a front view photograph of the liquid crystal display element 100 according to the second embodiment of the present invention. FIGS. 11A to 11D are images of the liquid crystal display element 100 produced using the electrode patterns B1 to B4 shown in FIGS. 8A to 8D, respectively. In this example, the pre-tilt angle was set to about 89.9 ° in the anti-parallel orientation in which the common substrate 2 was rubbed in the 12 o'clock direction and the segment substrate 1 was rubbed in the 6 o'clock direction.

  As shown in FIGS. 6A to 6D, since the pretilt angle is set lower than in the example shown in FIG. 9, the occurrence position of the black cross is from the center of the pixel to the edge, and the effective open efficiency is increased. Can be observed.

  In addition, as in the example shown in FIG. 9, it can be seen that no black cross has occurred near the edge of the opening 34b above the pixel. In some patterns, the black cross pattern is slightly different for each pixel. However, in terms of appearance, display nonuniformity was not observed in any pattern even when observed from the opposite viewing direction.

  As described above, according to the second embodiment of the present invention, as in the first embodiment, the display non-uniformity that occurs in the anti-viewing direction and in the clockwise and counterclockwise directions around 70 degrees azimuth. The display uniformity equivalent to the best viewing direction can be obtained. In addition, since the height of the opening 34b is set large, the allowable range of positional deviation between the upper and lower substrates can be increased.

  Note that the occurrence state of black cross greatly depends on the pretilt angle. In the study by the present inventor, when the pretilt angle is less than 89.5 degrees, display nonuniformity from the anti-viewing direction was not observed. Therefore, the first and second embodiments of the present invention are suitable for a liquid crystal display element having a pretilt angle of 89.5 degrees or more.

  In the first and second embodiments described above, only the case where the rubbing process is performed in the orthogonal direction with respect to the lower edge of the pixel has been described. However, the present invention is not limited to this. For example, it was confirmed by appearance observation that the center molecule of the liquid crystal layer is oriented in that direction and is effective even under twisted alignment conditions.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

DESCRIPTION OF SYMBOLS 1, 2 ... Board | substrate, 3 ... Liquid crystal layer, 4 ... Back light, 5 ... Light source, 11, 12 ... Polarizing plate, 13, 23 ... Viewing angle compensator, 14, 24, 34 ... Transparent electrode, 15, 25 ... Vertical alignment Film, 18, 28 ... rubbing direction

Claims (10)

A pair of transparent substrates arranged to face each other at a predetermined interval;
A plurality of first transparent electrodes formed in a strip shape on one opposing surface side of the transparent substrate;
A plurality of second transparent electrodes formed in a strip shape so as to intersect perpendicularly to the first transparent electrode on the other facing surface side of the transparent substrate;
Monodomain vertical formed on each opposing surface side of the transparent substrate and subjected to monodomain vertical alignment treatment so that at least one of the central molecules of the liquid crystal layer is aligned parallel to the longitudinal direction of the first transparent electrode An alignment film;
A vertical alignment mode liquid crystal layer sandwiched between the pair of substrates and having a pretilt angle;
A liquid crystal display element having a pair of polarizing plates arranged with the pair of substrates interposed therebetween,
Forming one pixel at each intersection of the first and second transparent electrodes;
In a part of the first transparent electrode constituting one side of the pixel in which the alignment direction of the center molecule of the liquid crystal layer and the direction in which the liquid crystal molecules are inclined by the oblique electric field at the edge portion of the second transparent electrode are reversed. The liquid crystal display element is characterized in that a rectangular opening is formed from the center of the line between the second transparent electrodes to the area inside the pixel from the pixel edge. 2. The liquid crystal display element according to claim 1, wherein a dimension of the rectangular opening in a longitudinal direction of the first transparent electrode is not less than ½ of a distance between lines of the second transparent electrode. The liquid crystal display element according to claim 1, wherein at least three of the rectangular openings are arranged in parallel to the width direction of the first transparent electrode.   The liquid crystal display element according to claim 3, wherein an interval between the rectangular openings adjacent in the width direction of the first transparent electrode is 92 μm or less. A pair of transparent substrates arranged to face each other at a predetermined interval;
A plurality of first transparent electrodes formed in a strip shape on one opposing surface side of the transparent substrate;
A plurality of second transparent electrodes formed in a strip shape so as to intersect perpendicularly to the first transparent electrode on the other facing surface side of the transparent substrate;
Monodomain vertical formed on each opposing surface side of the transparent substrate and subjected to monodomain vertical alignment treatment so that at least one of the central molecules of the liquid crystal layer is aligned parallel to the longitudinal direction of the first transparent electrode An alignment film;
A vertical alignment mode liquid crystal layer sandwiched between the pair of substrates and having a pretilt angle;
A liquid crystal display element having a pair of polarizing plates arranged with the pair of substrates interposed therebetween,
Forming one pixel at each intersection of the first and second transparent electrodes;
A rectangular opening is formed in a region of the first transparent electrode facing between the lines of the second transparent electrode ,
The liquid crystal display element , wherein the opening is provided across the edges of two pixels adjacent to the opening . The liquid crystal display element according to claim 5 , wherein at least three of the rectangular openings are arranged in parallel to the width direction of the first transparent electrode. The liquid crystal display element according to claim 6, wherein an interval between the rectangular openings adjacent in the width direction of the first transparent electrode is 92 μm or less.   The liquid crystal display element according to claim 1, wherein the alignment film with respect to the alignment film is subjected to a rubbing process.   The liquid crystal display element according to claim 1, wherein the vertical alignment film is disposed so that an easy axis of alignment is antiparallel alignment.   The liquid crystal display element according to claim 1, wherein a pretilt angle of the liquid crystal layer is 89.5 ° or more.