JP2007256300A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To equalize viewing angle characteristics in all upward and downward, and right and left directions, in a liquid crystal display device which has slits formed in a pair of transparent electrodes for alignment division. <P>SOLUTION: The slits 61 and 71 in the transparent electrodes comprise: first slit portions 61a and 71a which are longitudinal in a direction inclined to an X axis, and second slit portions 61b and 71b which are longitudinal in a direction inclined to the X axis in the opposite direction from the first slit portions. The first slit portion 61a of one transparent electrode and the first slit portion 71a of the other transparent electrode are arranged alternately along the Y axis, and the second slit portion 61b of the one transparent electrode and the second slit portion 71b of the other transparent electrode are arranged alternately along the Y axis. Cross slits may be arranged on the one transparent electrode and the other transparent electrode while shifted by a half pitch along the X axis and Y axis. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display element with improved viewing angle characteristics.

  Conventionally, as this type of liquid crystal display element, the one described in Patent Document 1 is known. As shown in FIG. 10, this liquid crystal display element is provided on a pair of substrates 1 and 2 on the back side and the front side that are arranged opposite to each other, and on both substrates 1 and 2 and overlaps with the liquid crystal layer 3 interposed therebetween. And a pair of transparent electrodes 4 and 5 on the front side. A plurality of slits 6 and 7 (described later) for dividing the alignment are formed at portions corresponding to the display areas of the transparent electrodes 4 and 5, respectively.

  In the production of this liquid crystal display element, a vertical alignment film is applied and fired on each of the substrates 1 and 2 so as to cover the transparent electrodes 4 and 5, and then a main sealant is applied to each of the substrates 1 and 2, Further, after spraying a gap control material having a predetermined diameter, the substrates 1 and 2 are overlapped to cure the main seal material. Next, a liquid crystal layer 3 is formed by injecting liquid crystal into an empty cell between the substrates 1 and 2. The liquid crystal molecules 8 of the liquid crystal layer 3 are vertically aligned by the action of the vertical alignment film. Thereafter, the back-side polarizing plate 9 is bonded to the outside of the back-side substrate 1, and the viewing angle compensation plate 10 and the front-side polarizing plate 11 are stacked and bonded to the outside of the front-side substrate 2. Here, as shown in FIG. 11, the transmission axis 9a of the back-side polarizing plate 9 and the transmission axis 11a of the front-side polarizing plate 11 are orthogonal to each other, so that a normal black liquid crystal display element is obtained.

  The slits 6 and 7 formed in both the transparent electrodes 4 and 5 are rectangular as shown in FIG. 12 and are arranged at intervals in the slit longitudinal direction, and the slits 6 and the front side of the back side transparent electrode 4 are arranged. The slits 7 of the transparent electrode 5 are alternately arranged in the slit short direction. The longitudinal direction of the slit coincides with the horizontal direction of the visual field when the liquid crystal display element is viewed in a normal state (X-axis direction in FIGS. 11 and 12). The eleven transmission axes 9a and 11a cross at an angle of ± 45 ° with respect to the slit longitudinal direction.

  In this case, when a voltage is applied, an oblique electric field whose tilt direction is reversed between the transparent electrodes 4 and 5 on the back surface side and the front surface side with respect to the slits 6 and 7 as shown by dotted lines in FIG. appear. Then, as shown in FIG. 14, the liquid crystal molecules 8 are tilted in the opposite direction with respect to the slits 6 and 7, so that a so-called two-domain alignment structure is realized and the viewing angle characteristics are improved.

In the above conventional example, the vertical alignment film is SE-1211 manufactured by Nissan Chemical Industries, the thickness of the liquid crystal layer 3 is 4 μm, the liquid crystal is a liquid crystal having a birefringence of 0.1 manufactured by Merck, and the viewing angle compensation plate 10 is manufactured by Sumitomo Chemical. It is a VAC-180 film, and the longitudinal length (slit length) L of the slits 6 and 7 is 100 μm, and the width (slit width) W perpendicular to the longitudinal direction of the slits 6 and 7 is 20 μm, the slit longitudinal direction. A liquid crystal display element is manufactured in which the distance A between the slits 6 and 6 adjacent to each other and the distance A between the slits 7 and 7 are both 20 μm, and the distance B between the slits 6 and 7 adjacent in the lateral direction of the slit is 40 μm. The viewing angle characteristic (isocontrast curve) when the element was displayed by 1/4 duty driving was measured, and the result shown in FIG. 15 was obtained. As is apparent from FIG. 15, in the above-described conventional example, the vertical direction of the visual field (the direction connecting the azimuth angles 90 ° and 270 °) and the left-right direction (the direction connecting the azimuth angles 0 ° and 180 °). , Symmetric viewing angle characteristics can be obtained. However, the viewing angle characteristics are different between the up-down direction and the left-right direction, and the viewing angle characteristics in the up-down direction are narrower than the viewing angle characteristics in the left-right direction.
JP 2004-252298 A

  In view of the above points, an object of the present invention is to provide an excellent liquid crystal display element in which viewing angle characteristics are equal in all directions, up, down, left, and right.

  The present invention includes a pair of substrates disposed opposite to each other, and a pair of transparent electrodes provided on both substrates and overlapping each other with a liquid crystal layer interposed therebetween to form a display region, and matches the display region of both transparent electrodes. In a liquid crystal display element in which a plurality of slits for alignment division are formed in each portion, the following matters are employed in order to solve the above problems.

  That is, according to the first aspect of the present invention, the slit of each transparent electrode is long in the direction inclined with respect to the X axis, with one coordinate axis of predetermined orthogonal coordinates set in the display area as the X axis and the other coordinate axis as the Y axis. 1 slit part and a 2nd slit part long in the direction inclined in the opposite direction to the 1st slit part to the X-axis, the 1st slit part of one transparent electrode, and the 1st of the other transparent electrode The slit portions are alternately arranged in the Y-axis direction, and the second slit portions of one transparent electrode and the second slit portions of the other transparent electrode are alternately arranged in the Y-axis direction. .

  In the second invention, one of the predetermined orthogonal coordinates set in the display area is set to the X axis, and the other coordinate axis is set to the Y axis. It is formed in a cross shape in which the second slit portion that is long in the Y-axis direction intersects, and a plurality of cross-shaped slits are disposed in each transparent electrode with an interval in the X-axis direction and the Y-axis direction. The distance between the centers of the cross-shaped slits adjacent in the direction is the X-axis direction slit pitch, and the distance between the centers of the cross-shaped slits adjacent in the Y-axis direction is the Y-axis direction slit pitch. The cross-shaped slit of the transparent electrode is arranged so as to be shifted by half of the X-axis direction slit pitch and the Y-axis direction slit pitch in the X-axis direction and the Y-axis direction, respectively.

  According to the first invention, a two-domain alignment structure is realized by alternately arranging the first slit portion of one transparent electrode and the first slit portion of the other transparent electrode in the Y-axis direction, and one transparent electrode By arranging the second slit portion of the second transparent electrode and the second slit portion of the other transparent electrode in the Y-axis direction, a two-domain alignment structure having a direction different from the two-domain alignment by the first slit portion is realized. The structure is realized, and the viewing angle characteristics are equal in all directions of the field of view.

  Further, in the first invention, the X axis is a coordinate axis that matches the horizontal direction or the vertical direction of the visual field when the liquid crystal display element is viewed in a normal state, and the longitudinal direction of the first slit portion of each transparent electrode and the second slit If the inclination angle with respect to the X axis in the longitudinal direction of the portion is + 45 ° and −45 °, respectively, one transmission axis and the other transmission axis of the pair of polarizing plates provided along the pair of substrates are respectively The Y axis, that is, the horizontal direction of the visual field when the liquid crystal display element is viewed in a normal state and the vertical direction can be made parallel. Thereby, the viewing angle characteristics in the vertical and horizontal directions, which are important viewing angle directions when the liquid crystal display element is viewed in a normal state, can be further widened.

  Although the reason will be described later, in the first invention, the slit width in the direction perpendicular to the longitudinal direction of each of the first and second slit portions of each transparent electrode is preferably 10 μm or more and 30 μm or less. The first and second slit portions of one transparent electrode, and the slit portions between the first and second slit portions of the other transparent electrode adjacent to the slit portion in the Y-axis direction. The interval in the direction perpendicular to the longitudinal direction is preferably not less than 10 μm or not less than the slit width and not more than 60 μm.

  According to the second aspect of the invention, the four-domain alignment structure is substantially formed by the staggered arrangement in which the cross-shaped slit of one transparent electrode and the cross-shaped slit of the other transparent electrode are shifted by a half pitch in the X-axis direction and the Y-axis direction. As in the first invention, the viewing angle characteristics are equal in all directions, up, down, left, and right. In the second invention, one of the pair of polarizing plates provided along the pair of substrates, if the X axis is a coordinate axis that matches the horizontal direction or the vertical direction of the visual field when the liquid crystal display element is viewed in a normal state. And the other transmission axis can be made parallel to the X-axis and Y-axis, that is, the horizontal and vertical directions of the visual field when the liquid crystal display element is viewed in a normal state. Thereby, the viewing angle characteristics in the vertical and horizontal directions, which are important viewing angle directions when the liquid crystal display element is viewed in a normal state, can be further widened.

  Although the reason will be described later, in the second invention, the slit width in the direction perpendicular to the longitudinal direction of each of the first and second slit portions is preferably 10 μm or more and 30 μm or less, and one transparent electrode The value obtained by subtracting the slit width from the amount of deviation in the X-axis direction and the amount of deviation in the Y-axis direction between the cruciform slit of the other transparent electrode and the cruciform slit of the other transparent electrode is 10 μm or more, or 60 μm or less. Is desirable.

  The liquid crystal display elements of the first and second inventions are preferably vertical alignment elements in which the liquid crystal elements of the liquid crystal layer are vertically aligned. When the liquid crystal display element is a horizontal alignment type element in which the liquid crystal molecules of the liquid crystal layer are horizontally aligned, the alignment direction of the liquid crystal molecules close to the substrate is determined by rubbing or the like, and the azimuthal anisotropy of the response to the oblique electric field occurs. The four-domain orientation cannot be obtained successfully. On the other hand, in the case of a vertical alignment type element, azimuthal anisotropy in response to an oblique electric field does not occur, so that four-domain alignment can be reliably obtained.

  First, a first embodiment in which the present invention is applied to a vertical alignment type liquid crystal display element will be described. As shown in FIG. 1, the liquid crystal display element includes a glass back side substrate 1 and a glass front side substrate 2 facing the back side substrate 1, and a liquid crystal layer between the substrates 1 and 2. 3 is provided. A rear transparent electrode 4 serving as a segment electrode is provided on the rear substrate 1, and a front transparent electrode 5 serving as a common electrode is provided on the front substrate 2. Then, both transparent electrodes 4 and 5 overlap with the liquid crystal layer 3 interposed therebetween, and a display region is formed at the overlapping portion. In addition, a plurality of slits 61 and 71 for dividing the orientation are formed in portions corresponding to the display areas of the transparent electrodes 4 and 5, respectively, as will be described later.

  In manufacturing the liquid crystal display element, a vertical alignment film is applied and baked on each of the substrates 1 and 2 so as to cover the transparent electrodes 4 and 5, and then a main sealant is applied to each of the substrates 1 and 2. After spraying a gap control material having a predetermined diameter, the substrates 1 and 2 are overlapped to cure the main seal material. Next, a liquid crystal layer 3 is formed by injecting liquid crystal into an empty cell between the substrates 1 and 2. The liquid crystal molecules 8 of the liquid crystal layer 3 are vertically aligned by the action of the vertical alignment film. Thereafter, the back-side polarizing plate 9 is bonded to the outside of the back-side substrate 1, and the viewing angle compensation plate 10 and the front-side polarizing plate 11 are stacked and bonded to the outside of the front-side substrate 2. Here, as shown in FIG. 2, the transmission axis 9a of the back-side polarizing plate 9 and the transmission axis 11a of the front-side polarizing plate 11 are orthogonal to each other, so that a normal black liquid crystal display element is obtained.

  Next, with reference to FIG. 3, the slits 61 and 71 will be described with the directionality defined by the orthogonal coordinates composed of the X axis and the Y axis set in the display area. In the first embodiment, the X axis is a coordinate axis that matches the horizontal direction of the visual field when the liquid crystal display element is viewed in a normal state, and the Y axis is the coordinate axis that matches the vertical direction of the visual field. A slit 61 shown by a solid line formed on the transparent electrode 4 on the back side and a slit 71 shown by a dotted line formed on the transparent electrode 5 on the front side are first slit portions 61a and 71a long in the direction inclined with respect to the X axis, The second slit portions 61b and 71b are long in the direction inclined in the opposite direction to the first slit portions 61a and 71a with respect to the X axis. And the 1st slit part 61a of the back side transparent electrode 4 and the 1st slit part 71a of the front side transparent electrode 5 are alternately arrange | positioned in the Y-axis direction, and the 2nd slit part 61b of the back side transparent electrode 4 and The second slit portions 71b of the front transparent electrode 5 are alternately arranged in the Y-axis direction.

  Here, in the first embodiment, the inclination angle of the first slit portions 61a and 71a with respect to the X axis in the longitudinal direction is + 45 °, and the inclination angle of the second slit portions 61b and 71b with respect to the X axis in the longitudinal direction is −45 °. It is set. Although these inclination angles can be set to angles other than ± 45 °, in order to further improve the symmetry of the viewing angle characteristics in all directions, up, down, left, and right, the inclination angle can be set to ± 45 °. desirable. In the first embodiment, the first slits 61a and 71a and the second slits 61b and 71b of the transparent electrodes 4 and 5 are alternately arranged with an interval in the X-axis direction. The first slit portions 61a and 71a of the same number are arranged alternately in the X-axis direction, and the portions where a certain number of second slit portions 61b and 71b are arranged in the X-axis direction are alternately provided in the X-axis direction. May be.

  According to the first embodiment, when a voltage is applied, as shown in FIG. 4, the oblique electric fields Ea1 and Ea2 whose inclination directions are reversed with respect to the first slit portions 61a and 71a are generated, and the second slits are generated. Diagonal electric fields Eb1 and Eb2 in which the inclination directions are reversed with respect to the portions 61b and 71b are generated. Here, as shown in FIG. 5, the horizontal components of the vectors of the oblique electric fields Ea1 and Ea2 generated by the first slit portions 61a and 71a (components in the direction parallel to the substrates 4 and 5) are the first slit portions 61a and 71a. The horizontal components of the vectors of the oblique electric fields Eb1 and Eb2 generated by the second slit portions 61b and 71b are orthogonal to the longitudinal direction of the second slit portions 61b and 71b. Therefore, in the X-axis direction region where the first slit portions 61a and 71a are arranged, the tilt direction of the liquid crystal molecules is orthogonal to the longitudinal direction of the first slit portions 61a and 71a with the first slit portions 61a and 71a as boundaries. Similarly, in the X-axis direction region where the second slit portions 61b and 71b are arranged, the direction in which the liquid crystal molecules fall is second from the respective second slit portions 61b and 71b. The slit portions 61b and 71b are reversed to one side and the opposite side in the longitudinal direction. Since the longitudinal direction of the first slit portions 61a and 71a and the longitudinal direction of the second slit portions 61b and 71b are different from each other, a four-domain alignment structure is realized.

  Note that the transmittance does not change even if the liquid crystal molecules 8 are tilted in the direction parallel to or orthogonal to the transmission axes 9a and 11a of the polarizing plates 9 and 11 on the back side and the front side. The direction is oblique to the longitudinal direction of the first slits 61a and 71a and the longitudinal direction of the second slits 61b and 71b, that is, the direction parallel to the X axis and the Y axis.

  In the first embodiment, the vertical alignment film is SE-1211 manufactured by Nissan Chemical Industries, the thickness of the liquid crystal layer 3 is 4 μm, the liquid crystal is a liquid crystal having a birefringence of 0.1 manufactured by Merck, and the viewing angle compensation plate 10 is Sumitomo Chemical. An industrial VAC-180 film is used, and the first slit portions 61a and 71a and the second slit portions 61b and 71b have a longitudinal length (slit length) L of 100 μm, and the first slit portions 61a and 71a and the second slit portion. The slit width W in the direction perpendicular to the longitudinal direction of 61b, 71b is 20 μm, the interval A in the X-axis direction between the first slit portions 61a, 71a and the second slit portions 61b, 71b is 20 μm, and the back-side transparent electrode 4 Of the first and second slit portions 61a and 61b and the first and second slit portions 71a and 71b of the front-side transparent electrode 5 adjacent to the slit portions 61a and 61b in the Y-axis direction. A liquid crystal display element having an interval B in the direction perpendicular to the longitudinal direction of each of the slit portions (hereinafter referred to as a slit interval between the back side and the front side) B of 40 μm is manufactured, and this liquid crystal display element is driven by a 1/4 duty drive. The viewing angle characteristic (isocontrast curve) when displayed was measured, and the result shown in FIG. 6 was obtained. Note that FIG. 6 is drawn so that the horizontal and vertical directions of the visual field when the liquid crystal display element is viewed in a normal state are the 0 ° -180 ° azimuth and the 90 ° -270 ° azimuth, respectively.

  As is apparent from FIG. 6, a display with very good symmetry is obtained in which the viewing angle characteristics are substantially the same in all directions. This is because a 4-domain alignment structure is realized as described above. Further, in order to incline the longitudinal direction of the first slit portions 61a and 71a and the longitudinal direction of the second slit portions 61b and 71b by + 45 ° and −45 °, respectively, with respect to the X axis that matches the left-right direction, the polarizing plates 9 and 11 The transmission axes 9a and 11a can be set to the horizontal and vertical directions. As a result, the viewing angle characteristics in the vertical and horizontal directions, which are important viewing angles when viewing the liquid crystal display element in a normal state, are shown in FIG. Compared to the conventional example shown in FIG.

  Next, the dimensions of the first and second slit portions 61a, 71a, 61b, 71b will be described. When the slit width W of each of the slit portions 61a, 71a, 61b, 71b is increased to a certain extent, the electric field at the central portion of the slit portions 61a, 71a, 61b, 71b becomes extremely weak, and the liquid crystal molecules react to voltage application. An area that disappears occurs, and a display defect occurs in that area. Furthermore, the area other than the slit portions 61a, 71a, 61b, 71b, that is, the area of the liquid crystal molecules responding to the electric field is reduced, and so-called aperture ratio is reduced. It will decline. In order to avoid such a problem, it is desirable that the slit width W be 30 μm or less. On the other hand, if the slit width W is too narrow, a sufficient oblique electric field is not generated, and a four-domain alignment cannot be obtained sufficiently. According to experiments conducted with various slit widths W, it was found that when the slit width W is 5 μm, a clean 4-domain alignment cannot be obtained. In this case, when the liquid crystal display element is visually observed, a rough feeling of display due to domain instability is felt when the viewing angle is tilted. It was found that when the slit width W is 10 μm, the liquid crystal molecules are somewhat unstable in the direction in which the liquid crystal molecules are tilted, but the rough feeling when the viewing angle is tilted is within an acceptable range. Therefore, the slit width W is desirably 10 μm or more. When the slit width W is 20 μm, a clean and stable four-domain orientation is obtained, and no rough feeling is felt even when the viewing angle is tilted.

  The slit interval B between the back side and the front side is preferably large in order to secure a sufficient display area. However, in order to ensure the stability of the 4-domain orientation, the 4-domain pattern is visually identified. In order to prevent, it is better to be as narrow as possible. Experiments were conducted with various slit intervals B between the back side and the front side. When this interval B was 70 μm, the stability of the 4-domain alignment was not obtained. It turned out to be preferable in terms of stability. Moreover, if it was 60 micrometers or less, the pattern of 4 domains was not identified. Further, in order to avoid an extreme decrease in the aperture ratio due to the reduction of the slit interval B between the back side and the front side, it is desirable that the interval B be 10 μm or more or the slit width W or more.

  In addition, if the slit length L of the first slit portions 61a and 71a and the second slit portions 61b and 71b is too long, a 4-domain pattern is identified. As a result of conducting experiments with various slit lengths L, it was found that the slit length L is preferably about 20 μm to 200 μm. Furthermore, it has also been found that the X-axis direction interval A between the first slit portions 61a and 71a and the second slit portions 61b and 71b is preferably about 10 μm to 50 μm.

  Next, the liquid crystal display element of 2nd Embodiment is demonstrated. This liquid crystal display element is a vertical alignment type liquid crystal display element as in the first embodiment, and its cross-sectional structure and the directions of the transmission axes 9a and 11a of the polarizing plates 9 and 11 are the same as those in FIGS. . Further, as shown in FIG. 7, the slit 61 formed in the back side transparent electrode 4 and the slit 71 formed in the front side transparent electrode 5 are each inclined by + 45 ° with respect to the X axis, as in the first embodiment. The first slit portions 61a and 71a that are long in the direction and the second slit portions 61b and 71b that are long in the direction inclined by −45 ° with respect to the X axis, and the first slit portion 61a of the back-side transparent electrode 4 and The first slits 71a of the front transparent electrode 5 are alternately arranged in the Y-axis direction, and the second slits 61b of the rear transparent electrode 4 and the second slits 71b of the front transparent electrode 5 are Y Alternatingly arranged in the axial direction.

  The difference of the second embodiment from the first embodiment is that the first slit portions 61a and 71a and the second slit portions 61b and 71b of the transparent electrodes 4 and 5 on the back side and the front side are not spaced from each other. This is a point formed alternately and continuously in the X-axis direction. Even in this case, a 4-domain alignment structure is realized as in the first embodiment.

  In the second embodiment, the vertical alignment film is SE-1211 manufactured by Nissan Chemical Industries, the thickness of the liquid crystal layer 3 is 4 μm, the liquid crystal is a liquid crystal having a birefringence of 0.1 manufactured by Merck, and the viewing angle compensation plate 10 is Sumitomo Chemical. The VAC-180 film is manufactured, the slit length L of the first slit portions 61a and 71a and the second slit portions 61b and 71b is 100 μm, and the slit width W of the first slit portions 61a and 71a and the second slit portions 61b and 71b. A liquid crystal display element having a slit distance B of 40 μm between the back side and the front side was manufactured, and the viewing angle characteristics when this liquid crystal display element was displayed by ¼ duty drive were measured. The result is almost the same as in FIG. 6, and a display with very good symmetry is obtained with the same viewing angle characteristics in all directions. Further, similarly to the first embodiment, the directions of the transmission axes 9a and 11a of the polarizing plates 9 and 11 can be set to the horizontal direction and the vertical direction. The viewing angle characteristics in the vertical and horizontal directions that are the viewing angle azimuth are wider than those of the conventional example shown in FIG.

  Also in the second embodiment, preferable ranges of the slit width W, the slit length L, and the slit interval B on the back side and the front side of the first slit portions 61a and 71a and the second slit portions 61b and 71b are the same as those in the first embodiment. In other words, the slit width W is desirably 10 μm or more and 30 μm or less, the slit length L is desirably 20 μm or more and 200 μm or less, and the slit interval B between the back side and the front side is desirably 10 μm or more or the slit width B is not less than 60 μm. .

  Next, the liquid crystal display element of 3rd Embodiment is demonstrated. This liquid crystal display element is a vertical alignment type liquid crystal display element as in the first embodiment, and its cross-sectional structure and the directions of the transmission axes 9a and 11a of the polarizing plates 9 and 11 are the same as those in FIGS. However, the shape of the slit formed in each of the transparent electrodes 4 and 5 on the back side and the front side is completely different from that of the first embodiment. Hereinafter, this point will be described in detail.

  In the third embodiment, as shown in FIG. 8, a cross-shaped slit 62 in which the first slit portion 62a long in the X-axis direction and the second slit portion 62b long in the Y-axis direction intersect the back side transparent electrode 4. Are arranged at intervals in the X-axis direction and the Y-axis direction, and the front-side transparent electrode 5 also has a first slit portion 72a that is long in the X-axis direction and a second slit portion 72b that is long in the Y-axis direction. A plurality of cross-shaped slits 72 intersecting with each other are arranged at intervals in the X-axis direction and the Y-axis direction. Then, the distance between the centers of the cross-shaped slits adjacent in the X-axis direction is the X-axis direction slit pitch, and the distance between the centers of the cross-shaped slits adjacent in the Y-axis direction is the Y-axis direction slit pitch. The slit 62 and the cruciform slit 72 of the front transparent electrode 5 are arranged so as to be shifted in the X-axis direction and the Y-axis direction by half of the X-axis direction slit pitch and the Y-axis direction slit pitch, respectively.

  Note that the slit length of the first slit portions 62a and 72a is Lx, the slit length of the second slit portions 62b and 72b is Ly, and the distance between the first slit portions 62a and 62a of the back-side transparent electrode 4 adjacent in the X-axis direction. And the distance between the first slit portions 72a, 72a of the front transparent electrode 5 is Ax, the distance between the second slit portions 62b, 62b of the rear transparent electrode 4 adjacent in the Y-axis direction, and the first transparent portion 5 of the front transparent electrode 5. The distance between the two slit portions 72b, 72b is Ay, the X-axis direction slit pitch is Lx + Ax, and the Y-axis direction slit pitch is Ly + Ay. Therefore, the cross-shaped slit 62 of the back side transparent electrode 4 and the front side transparent electrode 5 The X-axis direction deviation amount ΔX with respect to the cross-shaped slit 72 is (Lx + Ax) / 2, and Y between the cross-shaped slit 62 of the back surface side transparent electrode 4 and the cross shape slit 72 of the front surface side transparent electrode 5 Direction shift amount ΔY becomes (Ly + Ay) / 2. In FIG. 8, Lx = Ly and Ax = Ay are set. However, Lx ≠ Ly and Ax ≠ Ay may be set.

  According to the third embodiment, when a voltage is applied, as shown in FIG. 9, one half (right half) in the X-axis direction and the second half of the first slit 62a of the cross-shaped slit 62 of the back side transparent electrode 4 and the second One half part (lower half part) of the slit part 62b in the Y-axis direction and the other half part in the X-axis direction of the first slit part 72a of the cross-shaped slit 72 of the front transparent electrode 5 located obliquely below and to the right of the slit part 62b ( An oblique electric field E1 tilted by 45 ° on the upper left side on average is generated in a region surrounded by the other half (upper half) in the Y-axis direction of the second slit portion 72b. Similarly, the other half (left half) in the X-axis direction of the first slit 62a of the cross-shaped slit 62 of the back side transparent electrode 4 and one half (lower half) of the second slit 62b in the Y-axis direction. ) And one half (right half) of the first slit 72a of the cross-shaped slit 72 of the cross-shaped slit 72 of the front transparent electrode 5 located obliquely below the left side and the other of the second slit 72b in the Y-axis An oblique electric field E2 tilted by 45 ° on the upper right side on average is generated in a region surrounded by the half portion (upper half portion). Further, the other half (left half) in the X-axis direction of the first slit 62a of the cross-shaped slit 62 of the back side transparent electrode 4 and the other half (upper half) in the Y-axis direction of the second slit 62b. And one half (right half) of the first slit 72a of the cross-shaped slit 72 of the cross-shaped slit 72 of the front transparent electrode 5 located diagonally above and to the left of the first slit 72b and one of the second slit 72b in the Y-axis direction. On the average, an oblique electric field E3 tilted by 45 ° to the lower right is generated in a region surrounded by the half (lower half). Furthermore, one half (right half) in the X-axis direction of the first slit portion 62a of the cross-shaped slit 62 of the back side transparent electrode 4 and the other half (upper half) in the Y-axis direction of the second slit portion 62b. The other half (left half) of the first slit 72a of the cross-shaped slit 72 of the cross-shaped slit 72 of the front transparent electrode 5 located diagonally above and to the right of the second slit 72b and one of the second slits 72b in the Y-axis direction. An oblique electric field E4 tilted by 45 ° to the lower left on average is generated in a region surrounded by the half (lower half). Thus, a four-domain alignment structure is realized. In the vicinity of the slit portions 62a, 62b, 72a and 72b, the electric fields E1 to E4 are directed in a direction orthogonal to the longitudinal direction of the slit portions. Accordingly, in more detail, a multi-domain alignment structure having four or more domains is realized.

  In the third embodiment, the vertical alignment film is SE-1211 manufactured by Nissan Chemical Industries, the thickness of the liquid crystal layer 3 is 4 μm, the liquid crystal is a liquid crystal with a birefringence of 0.1 manufactured by Merck, and the viewing angle compensation plate 10 is Sumitomo Chemical. The VAC-180 film is manufactured, the slit width W of the first slit portions 62a, 72a and the second slit portions 62b, 72b is 20 μm, the slit length Lx of the first slit portions 62a, 72a and the second slit portions 62b, 72b. The slit length Ly of both is 100 μm, the distance between the first slit parts 62a, 62a of the rear transparent electrode 4 adjacent in the X-axis direction, and the distance between the first slit parts 72a, 72a of the front transparent electrode 5 Ax and Y The distance between the second slit portions 62b, 62b of the back side transparent electrode 4 adjacent in the axial direction and the distance Ay between the second slit portions 72b, 72b of the front side transparent electrode 5 are both 20 μm. A liquid crystal display element in which the X-axis direction deviation amount ΔX and the Y-axis direction deviation amount ΔY between the cruciform slit 62 of the rear surface side transparent electrode 4 and the cruciform slit 72 of the front surface side transparent electrode 5 are both 60 μm is manufactured. The viewing angle characteristics when the liquid crystal display element was displayed with 1/4 duty driving were measured. The result is almost the same as in FIG. 6, and a display with very good symmetry is obtained with the same viewing angle characteristics in all directions. Further, similarly to the first embodiment, the directions of the transmission axes 9a and 11a of the polarizing plates 9 and 11 can be set to the horizontal direction and the vertical direction. The viewing angle characteristics in the vertical and horizontal directions that are the viewing angle azimuth are wider than those of the conventional example shown in FIG.

  Next, the dimensions of the cross-shaped slits 62 and 72 in the third embodiment will be described. When the slit width W of each of the first and second slit portions 62a, 72a, 62b, 72b of the cross-shaped slits 62, 72 is increased to a certain extent, the electric field at the center of the slit portions 62a, 72a, 62b, 72b becomes extremely large. A region where the liquid crystal molecules are weakened and the liquid crystal molecules do not react to voltage application is generated, and a display defect occurs in that region. Further, the area other than the slits 62a, 72a, 62b, 72b, that is, the area where the liquid crystal molecules respond to the electric field is reduced, and so-called aperture ratio is reduced. It will decline. In order to avoid such a problem, it is desirable that the slit width W be 30 μm or less. On the other hand, if the slit width W is too narrow, a sufficient oblique electric field is not generated, and a four-domain alignment cannot be obtained sufficiently. According to experiments conducted with various slit widths W, it was found that when the slit width W is 5 μm, a clean 4-domain alignment cannot be obtained. In this case, when the liquid crystal display element is visually observed, a rough feeling of display due to domain instability is felt when the viewing angle is tilted. It was found that when the slit width W is 10 μm, the liquid crystal molecules are somewhat unstable in the direction in which the liquid crystal molecules are tilted, but the rough feeling when the viewing angle is tilted is within an acceptable range. Therefore, the slit width W is desirably 10 μm or more. When the slit width W is 20 μm, a clean and stable four-domain orientation is obtained, and no rough feeling is felt even when the viewing angle is tilted.

  Further, the X-axis direction interval Bx between the second slit portion 62b of the cruciform slit 62 of the rear surface side transparent electrode 4 and the second slit portion 72b of the cruciform slit 72 of the front surface side transparent electrode 5 (this is the rear surface side transparent electrode). Equal to a value obtained by subtracting the slit width W from the X-axis direction deviation amount ΔX between the cruciform slit 62 of the electrode 4 and the cruciform slit 72 of the front transparent electrode 5), and the cross slit 62 of the rear transparent electrode 4. Y-axis direction interval By between the first slit portion 62a and the first slit portion 72a of the cross-shaped slit 72 of the front transparent electrode 5 (this is the cross-shaped slit 62 of the rear transparent electrode 4 and the front transparent electrode 5). Is equal to the value obtained by subtracting the slit width W from the amount of deviation ΔY in the Y-axis direction with respect to the cross-shaped slit 72). To do In order to prevent the four-domain pattern from being visually identified, it is preferable that the pattern is as narrow as possible. Experiments were conducted with various changes in the spacings Bx and By. When the spacings Bx and By were 70 μm, the stability of the 4-domain alignment could not be obtained. It turned out that it was preferable from the surface. Moreover, if it was 60 micrometers or less, the pattern of 4 domains was not identified. Further, in order to avoid an extreme decrease in the aperture ratio caused by reducing the distances Bx and By, the distances Bx and By are preferably set to 10 μm or more or the slit width W or more. The slit length Lx of the first slit portions 62a and 72a and the slit length Ly of the second slit portions 62b and 72b are semi-automatically determined by setting the intervals Bx and By.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to this. For example, in the first to third embodiments, the X-axis is the coordinate axis that matches the horizontal direction of the visual field when the liquid crystal display element is viewed in a normal state, but when the liquid crystal display element is viewed in a normal state. The coordinate axis that matches the vertical direction of the field of view may be the X axis. In this case, in the first and second embodiments, the first slit portion 61a and the second slit portion 61b of the back surface side transparent electrode 4 and the first slit portion 71a and the second slit portion 71b of the front surface side transparent electrode 5 are Y They are alternately arranged in the left-right direction which is the axial direction. Note that the X axis can also be set in a direction inclined with respect to the horizontal direction or the vertical direction of the visual field when the liquid crystal display element is viewed in a normal state.

  The liquid crystal display elements of the first to third embodiments are all vertical alignment type liquid crystal display elements in which the liquid crystal molecules 8 of the liquid crystal layer 3 are vertically aligned, but the horizontal alignment type in which the liquid crystal molecules are horizontally aligned. It is also conceivable to apply the present invention to such a liquid crystal display element. However, in the horizontal alignment type element, the alignment direction of the liquid crystal molecules close to the substrate is determined by rubbing or the like, and the azimuthal anisotropy of the response to the oblique electric field is generated, so that the above-described four-domain alignment may not be obtained well. On the other hand, in the case of a vertical alignment type element, azimuthal anisotropy in response to an oblique electric field does not occur, so that four-domain alignment can be reliably obtained. For vertical alignment type liquid crystal display elements, segment display type, simple matrix drive dot matrix type, type having both segment display type area and simple matrix drive dot matrix type area, active matrix type The present invention can be applied to various types of liquid crystal display elements.

FIG. 6 is a schematic cross-sectional view of a liquid crystal display element common to the first to third embodiments of the present invention. Explanatory drawing which shows the direction of the transmission axis of the polarizing plate of the liquid crystal display element common to 1st thru | or 3rd embodiment. Explanatory drawing which shows the arrangement | sequence of the slit of the liquid crystal display element of 1st Embodiment. Sectional drawing which shows the generation | occurrence | production state of the diagonal electric field in the liquid crystal display element of 1st Embodiment. Explanatory drawing which shows the horizontal direction component of the diagonal electric field in the liquid crystal display element of 1st Embodiment. The figure which shows the viewing angle characteristic of the liquid crystal display element of 1st Embodiment. Explanatory drawing which shows the arrangement | sequence of the slit of the liquid crystal display element of 2nd Embodiment. Explanatory drawing which shows the arrangement | sequence of the slit of the liquid crystal display element of 3rd Embodiment. Explanatory drawing which shows the horizontal direction component of the diagonal electric field in the liquid crystal display element of 3rd Embodiment. FIG. 10 is a schematic cross-sectional view of a conventional liquid crystal display element. Explanatory drawing which shows the direction of the transmission axis of the polarizing plate of the liquid crystal display element of a prior art example. Explanatory drawing which shows the arrangement | sequence of the slit of the liquid crystal display element of a prior art example. Sectional drawing which shows the generation | occurrence | production state of the diagonal electric field in the liquid crystal display element of a prior art example. Explanatory drawing which shows the behavior of the liquid crystal molecule by an oblique electric field. The figure which shows the viewing angle characteristic of the liquid crystal display element of a prior art example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 2 ... Substrate, 3 ... Liquid crystal layer, 4, 5 ... Transparent electrode, 61, 71 ... Slit, 61a, 71a ... 1st slit part, 61b, 71b ... 2nd slit part, 62, 72 ... Cross-shaped slit, 62a, 72a ... 1st slit part, 62b, 72b ... 2nd slit part, 8 ... Liquid crystal molecule, 9, 11 ... Polarizing plate, 9a, 11a ... Transmission axis.

Claims (11)

A pair of substrates disposed opposite to each other and a pair of transparent electrodes that are provided on both substrates and overlap each other with a liquid crystal layer interposed therebetween to form a display region. In a liquid crystal display element in which a plurality of slits for alignment division are formed,
With one coordinate axis of a predetermined orthogonal coordinate set in the display area as the X axis and the other coordinate axis as the Y axis, the slit of each transparent electrode has a first slit portion that is long in a direction inclined with respect to the X axis, and the X axis. On the other hand, it is composed of a second slit portion that is long in a direction inclined in the opposite direction to the first slit portion,
The first slit portion of one transparent electrode and the first slit portion of the other transparent electrode are alternately arranged in the Y-axis direction, and the second slit portion of one transparent electrode and the second slit of the other transparent electrode The liquid crystal display element is characterized in that the portions are alternately arranged in the Y-axis direction.   The X axis is a coordinate axis that matches the horizontal direction or the vertical direction of the visual field when the liquid crystal display element is viewed in a normal state, and the longitudinal direction of the first slit portion and the longitudinal direction of the second slit portion of each transparent electrode The inclination angles of the direction with respect to the X axis are + 45 ° and −45 °, respectively, and one transmission axis and the other transmission axis of the pair of polarizing plates provided along the two substrates are parallel to the X axis and the Y axis, respectively. The liquid crystal display element according to claim 1, wherein the liquid crystal display element is provided.   3. The liquid crystal display element according to claim 1, wherein a slit width of each of the transparent electrodes in a direction perpendicular to the longitudinal direction of each of the first and second slit portions is 10 μm or more and 30 μm or less.   Between the first and second slit portions of the one transparent electrode, and between the first and second slit portions of the other transparent electrode adjacent to the respective slit portions in the Y-axis direction. The liquid crystal display element according to any one of claims 1 to 3, wherein an interval in a direction perpendicular to a longitudinal direction of each of the slit portions is 10 µm or more and 60 µm or less.   Between the first and second slit portions of the one transparent electrode, and between the first and second slit portions of the other transparent electrode adjacent to the respective slit portions in the Y-axis direction. The liquid crystal according to any one of claims 1 to 3, wherein an interval in a direction orthogonal to the longitudinal direction of each slit portion is not less than a slit width in a direction orthogonal to the longitudinal direction of each slit portion and not more than 60 µm. Display element. A pair of substrates disposed opposite to each other and a pair of transparent electrodes that are provided on both substrates and overlap each other with a liquid crystal layer interposed therebetween to form a display region. In a liquid crystal display element in which a plurality of slits for alignment division are formed,
With one coordinate axis of predetermined orthogonal coordinates set in the display area as the X axis and the other coordinate axis as the Y axis, each slit of each transparent electrode has a first slit portion that is long in the X-axis direction and a first slit portion that is long in the Y-axis direction. It is formed in a cross shape intersecting with two slit parts,
A plurality of cross-shaped slits are arranged in each transparent electrode with an interval in the X-axis direction and the Y-axis direction,
The distance between the centers of the cross-shaped slits adjacent in the X-axis direction is defined as the X-axis direction slit pitch, and the distance between the centers of the cross-shaped slits adjacent in the Y-axis direction is defined as the Y-axis direction slit pitch. A liquid crystal display element, wherein the cross-shaped slit of the other transparent electrode is arranged so as to be shifted by half of the X-axis direction slit pitch and the Y-axis direction slit pitch in the X-axis direction and the Y-axis direction, respectively.   The X axis is a coordinate axis that matches the horizontal or vertical direction of the field of view when the liquid crystal display element is viewed in a normal state, and one transmission axis and the other transmission of a pair of polarizing plates provided along the two substrates. 7. The liquid crystal display element according to claim 6, wherein the axes are parallel to the X axis and the Y axis, respectively.   The liquid crystal display element according to claim 6 or 7, wherein a slit width in a direction orthogonal to the longitudinal direction of each of the first and second slit portions is 10 µm or more and 30 µm or less.   From the amount of deviation in the X-axis direction and the amount of deviation in the Y-axis direction between the cruciform slit of the one transparent electrode and the cruciform slit of the other transparent electrode, the first and second slit portions 9. The liquid crystal display element according to claim 6, wherein the values obtained by subtracting the slit width in the direction orthogonal to the longitudinal direction are 10 μm or more and 60 μm or less, respectively.   From the amount of deviation in the X-axis direction and the amount of deviation in the Y-axis direction between the cruciform slit of the one transparent electrode and the cruciform slit of the other transparent electrode, the first and second slit portions 9. The liquid crystal display element according to claim 6, wherein a value obtained by subtracting a slit width in a direction perpendicular to the longitudinal direction is not less than the slit width and not more than 60 [mu] m.   The liquid crystal display element according to claim 1, wherein the liquid crystal display element is a vertical alignment element in which liquid crystal molecules of the liquid crystal layer are vertically aligned.

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