JP4847134B2 - Liquid crystal display element - Google Patents

Description

  The present invention relates to a liquid crystal display element, and more particularly to a liquid crystal display element including a transparent electrode having a slit.

  In order to improve the viewing angle characteristics, the liquid crystal display device proposed by the present inventors has been patented (for example, see Patent Document 1) and has been published (for example, see Patent Document 2).

  The liquid crystal display element described in Patent Document 1 is a twisted nematic (TN) type, and the liquid crystal display element described in Patent Document 2 is a vertical alignment type, and both include a substrate with a transparent electrode in which a slit is formed. .

  Patent Document 1 describes, as an example, a liquid crystal display element having a transparent electrode provided with an elongated (striped) slit connected from end to end of a display area. Patent Document 2 describes a liquid crystal display element having a rectangular slit in a transparent electrode as an example. In both liquid crystal display elements described in both documents, when the upper and lower substrates are overlapped, the slit formed in the upper substrate and the slit formed in the lower substrate are parallel to each other in the longitudinal direction, and It arrange | positions so that it may become alternate in the direction orthogonal to a longitudinal direction.

  With this configuration, a viewing angle characteristic is improved as a result of realizing a two-domain alignment structure.

Japanese Patent No. 3108768 JP 2004-252298 A

  An object of the present invention is to provide a liquid crystal display element having excellent visibility.

According to one aspect of the present invention, a pair of opposed substrates, a liquid crystal layer sandwiched between the pair of substrates, and a pair of transparent electrodes that overlap each other and form a display region with the liquid crystal layer interposed therebetween In the display region, both transparent electrodes are provided with slits that are long in one direction, and the slit of one transparent electrode and the slit of the other transparent electrode are viewed from the normal direction of the pair of substrates. In the liquid crystal display element having a two-domain alignment structure realized by a pair of transparent electrodes alternately arranged in a direction intersecting the longitudinal direction of the slit in the display region, each of the pair of substrates A pair of polarizing plates disposed on the side opposite to the side on which the liquid crystal layer is sandwiched, wherein an angle formed by a transmission axis direction of at least one polarizing plate and a horizontal direction or a vertical direction in which display is performed Normally black liquid crystal display device having a pair of polarizing plates is 0 ° or less is provided.

  A liquid crystal display element having excellent visibility can be provided.

  FIG. 1A is a schematic cross-sectional view showing a structure common to liquid crystal display elements according to the following examples and a liquid crystal display element according to a comparative example. FIGS. 1B and 1C are schematic cross-sectional views showing structures common to TN type and vertical alignment type liquid crystal display elements among the liquid crystal display elements according to Examples and Comparative Examples. In addition, all the liquid crystal display elements by an Example and a comparative example are liquid crystal display elements provided with 2 domain structure.

  Reference is made to FIG. The liquid crystal display elements according to the example and the comparative example include an upper substrate 31, a lower substrate 32 disposed substantially parallel to the upper substrate 31, and a liquid crystal layer 33 sandwiched between the substrates 31 and 32. .

  The upper substrate 31 is, for example, an upper transparent substrate 31a, which is a transparent glass substrate, and an upper transparent electrode 31b and an upper transparent electrode 31b formed of, for example, ITO (indium tin oxide) on the upper transparent substrate 31a. An upper alignment film 31d formed on the transparent substrate 31a is included. The upper transparent electrode 31b includes a slit 31c that is long in one direction (in the drawing, from the front to the back of the drawing). The slit 31c is formed in, for example, a rectangular shape or a stripe shape when the liquid crystal display element is viewed from the normal direction of the substrate. This will be described later with reference to a plan view.

  The same applies to the lower substrate 32. The lower substrate 32 is formed on the lower transparent substrate 32a so as to cover the lower transparent substrate 32a, the lower transparent electrode 32b formed on the lower transparent substrate 32a, and the lower transparent electrode 32b. An alignment film 32d is included. The corresponding components of the upper substrate 31 and the lower substrate 32 are formed of the same material. The lower transparent electrode 32b also includes a slit 32c that is long in one direction. The slit 32c is formed corresponding to the slit 31c, and the length directions of both are substantially parallel. That is, in this figure, the length direction of the slit 32c is also the front-back direction of the drawing. Further, when viewed from the normal direction of the substrate, the slits 31c and 32c are arranged so as to be alternately arranged in a direction orthogonal to the length direction. The slit 32c is also formed, for example, in a rectangular shape or a stripe shape when the liquid crystal display element is viewed from the normal direction of the substrate.

  The upper transparent electrode 31b and the lower transparent electrode 32b overlap each other with the liquid crystal layer 33 interposed therebetween, thereby defining a display area.

  By providing the slits 31c and 32c in the upper and lower transparent electrodes 31b and 32b, respectively, as described above, an oblique electric field (an electric field in which the direction of the electric field is tilted from the normal direction of the substrate) is applied to the slit portion during voltage application. As it occurs, the direction of the oblique electric field is reversed on both sides of the slit. In the display area defined by the pair of electrodes, when the voltage is applied, the small areas having the opposite directions of the rising directions of the liquid crystal molecules are formed at the same time. The viewing angle dependency is reduced, the visibility is improved, and the display quality is improved.

  In this figure, the electric field directions in the small region P and the small region R are the same. The electric field directions in the small region Q and the small region S are the same. Furthermore, the directions of the oblique electric fields in the small area P and the small area Q are opposite. For this reason, the best viewing direction in the small area P and the small area R is, for example, the right direction in the figure, and that in the small area Q and the small area S is the left direction in the figure.

  Reference is made to FIG. In the TN type liquid crystal display element, an upper polarizing plate 34 is disposed outside the upper substrate 31 and a lower polarizing plate 35 is disposed outside the lower substrate 32 of the structure (liquid crystal cell) shown in FIG. Is done. Each of the upper and lower polarizing plates 34 and 35 has a transmission axis in the in-plane direction of the polarizing plate, and transmits only light polarized in the transmission axis direction.

  Reference is made to FIG. In the vertical alignment type liquid crystal display element, a viewing angle compensation plate 36 is disposed between the upper substrate 31 and the upper polarizing plate 34 having the structure shown in FIG. The viewing angle compensation plate 36 has a function of compensating for changes in visibility due to viewing angles.

  The liquid crystal display element according to the first embodiment will be described with reference to FIGS. The liquid crystal display element according to the first embodiment is a vertical alignment type liquid crystal display element. In the upper and lower transparent electrodes, rectangular slits were formed as long slits in one direction, and the upper and lower transparent electrodes defined display areas for displaying the arithmetic numeral “1”. In addition, when the X direction is defined in the horizontal direction of the character “1” and the Y direction (the direction orthogonal to the X direction) is defined in the vertical (height) direction, the slit is 45 ° in both the X direction and the Y direction. It was formed to make. The transmission axis direction of the upper polarizing plate is the horizontal direction of the character “1” (direction parallel to the X direction), and the transmission axis direction of the lower polarizing plate is the vertical direction of the character “1” (parallel to the Y direction). Direction). In this specification, the horizontal direction of the display unit of the liquid crystal display element is a direction parallel to the X direction.

  Reference is made to FIG. FIG. 2A is a schematic plan view showing a display area of the liquid crystal display element according to the first embodiment. In this figure, the right direction of the drawing is the X direction and the upward direction is the Y direction.

  The transparent electrode in the display area is formed with a slit from which a part of the transparent electrode is removed. In the figure, the slit formed in the upper transparent electrode is indicated by a solid line, and the slit formed in the lower transparent electrode is indicated by a broken line. All the slits have a rectangular shape with a length of 100 μm and a width of 20 μm, and are arranged in a matrix at regular intervals along the length direction and the width direction of the slit in each of the upper and lower transparent electrodes. In both the upper and lower transparent electrodes, the slits are spaced by 20 μm in the length direction (that is, at a pitch of 120 μm), and spaced by 100 μm in the width direction (that is, at a pitch of 120 μm). It is formed.

  The slit of the upper substrate and the slit of the lower substrate are arranged in parallel to the length direction and the width direction when viewed from the substrate normal direction. They are alternately arranged at equal positions in the width direction with the end portions in the length direction (short sides of the rectangle) aligned in the width direction. That is, the distance between the slits of the upper substrate and the lower substrate adjacent in the width direction in plan view is 40 μm. As described above, the length direction of the slit is a direction that forms 45 ° in both the X direction and the Y direction.

  The liquid crystal cell of the liquid crystal display element according to the first example was manufactured as follows. A vertical alignment film (SE-1211 manufactured by Nissan Chemical Industries, Ltd.) is applied and baked on the upper and lower transparent substrates having the transparent electrodes with slits as described above to prepare upper and lower substrates. . After applying the main seal material to the upper and lower substrates and further spraying a gap control material having a diameter of 4 μm, they are overlapped to cure the main seal material. A liquid crystal cell having a birefringence of 0.15 manufactured by Merck Co., Ltd. was injected into the empty cell thus produced, thereby completing a liquid crystal cell.

  With reference to FIG. 2B, the arrangement of the upper and lower polarizing plates will be described. Since the liquid crystal display element according to the first embodiment is a vertical alignment type liquid crystal display element, the viewing angle compensation plate and the polarizing plate are bonded to the liquid crystal cell with the configuration shown in FIG.

  In FIG. 2B, the solid arrow indicates the transmission axis direction of the upper polarizing plate, which is parallel to the X direction. Also, the dashed arrow indicates the transmission axis direction of the lower polarizing plate, which is parallel to the Y direction. In the figure, the longitudinal direction of the slit is written as a 45 ° direction for reference.

  A VAC-180 film manufactured by Sumitomo Chemical Co., Ltd. was used as the viewing angle compensation plate.

  A liquid crystal display device according to the second embodiment will be described with reference to FIGS. The liquid crystal display element according to the second embodiment is a vertical alignment type liquid crystal display element. Similar to the first embodiment, a rectangular slit was formed, and the upper and lower transparent electrodes defined a display area for displaying the arithmetic numeral “1”. In addition, when the X direction is defined in the horizontal direction of the character “1” and the Y direction (the direction orthogonal to the X direction) is defined in the vertical (height) direction, the slit is arranged such that its longitudinal direction is parallel to the X direction. Formed. The transmission axis direction of the upper polarizing plate is the horizontal direction of the character “1” (direction parallel to the X direction), and the transmission axis direction of the lower polarizing plate is the vertical direction of the character “1” (parallel to the Y direction). Direction).

  Reference is made to FIG. FIG. 3A is a schematic plan view showing a display area of the liquid crystal display element according to the second embodiment. In this figure, the right direction of the drawing is the X direction and the upward direction is the Y direction.

  The transparent electrode in the display area is formed with a slit from which a part of the transparent electrode is removed. In the figure, the slit formed in the upper transparent electrode is indicated by a solid line, and the slit formed in the lower transparent electrode is indicated by a broken line. Except for the fact that the longitudinal direction of the slit is a direction parallel to the X direction, the shape, size, interval and arrangement of the slit are the same as in the first embodiment.

  The manufacturing method of the empty cell of the liquid crystal display element according to the second embodiment is the same as that of the liquid crystal display element according to the first embodiment. In the first embodiment, a liquid crystal having a birefringence of 0.15 manufactured by Merck Co., Ltd. was injected into the empty cell. In the second embodiment, the birefringence manufactured by Merck Co., Ltd. was used. A liquid crystal cell was completed by injecting a chiral material manufactured by Merck Co., Ltd. together with 0.15 liquid crystal to give twist to the liquid crystal. The chiral material was added so that the ratio of cell thickness d to natural pitch p, d / p, was 0.6.

  With reference to FIG. 3B, the arrangement of the upper and lower polarizing plates will be described. The liquid crystal display element according to the second embodiment is also a vertical alignment type liquid crystal display element, similar to the liquid crystal display element according to the first embodiment. Therefore, the viewing angle compensation plate and the polarizing plate are liquid crystal with the configuration shown in FIG. Paste it into a cell.

  In FIG. 3B, the solid line arrow indicates the transmission axis direction of the upper polarizing plate, which is parallel to the X direction. Also, the dashed arrow indicates the transmission axis direction of the lower polarizing plate, which is parallel to the Y direction. A VAC-180 film manufactured by Sumitomo Chemical Co., Ltd. was used as the viewing angle compensation plate.

  A liquid crystal display device according to a first comparative example will be described with reference to FIGS. The liquid crystal display element according to the first comparative example is a vertical alignment type liquid crystal display element. Also in the liquid crystal display element according to the first comparative example, the upper and lower transparent electrodes define a display area for displaying the arithmetic numeral “1”, and the horizontal direction of the character “1” is the X direction, A Y direction (a direction perpendicular to the X direction) was defined in the longitudinal (height) direction.

  Reference is made to FIG. FIG. 4A is a schematic plan view showing a display area of the liquid crystal display element according to the first comparative example, which is the same as FIG.

  The transparent electrode in the display area is formed with a slit from which a part of the transparent electrode is removed. In the figure, the slit formed in the upper transparent electrode is indicated by a solid line, and the slit formed in the lower transparent electrode is indicated by a broken line. The shape, size, longitudinal direction (direction parallel to the X direction), spacing, and arrangement of the slits are the same as in the second embodiment shown in FIG.

  The manufacturing method of the liquid crystal cell of the liquid crystal display element according to the first comparative example is the same as that of the liquid crystal cell of the liquid crystal display element according to the first embodiment.

  With reference to FIG. 4B, the arrangement of the upper and lower polarizing plates will be described. Since the liquid crystal display element according to the first comparative example is a vertical alignment type liquid crystal display element, the viewing angle compensation plate and the polarizing plate are bonded to the liquid crystal cell with the configuration shown in FIG.

  In FIG. 4B, the solid arrow indicates the transmission axis direction of the upper polarizing plate, which is a direction that forms 45 ° with the X negative direction and the Y positive direction. Also, the broken arrow indicates the transmission axis direction of the lower polarizing plate, which is a direction that forms 45 ° with the X positive direction and the Y positive direction. In the figure, the longitudinal direction of the slit is written as the 0 ° direction for reference.

  A VAC-180 film manufactured by Sumitomo Chemical Co., Ltd. was used as the viewing angle compensation plate.

  FIGS. 5A, 5B, and 5C show the cases in which the liquid crystal display elements according to the first comparative example, the first example, and the second example are displayed with 1/8 duty drive, respectively. It is a viewing angle characteristic view.

  In all the visual angle characteristic diagrams of FIGS. 5A to 5C, polar angles are indicated by concentric circles. The center of the concentric circle is the position where the polar angle is 0 °. 5A and 5B, the polar angle is represented by six concentric circles up to 60 ° in increments of 10 °. In FIG. 5C, the polar angle is represented by four concentric circles up to 80 ° in increments of 20 °.

  The right direction of the center of the concentric circle is defined as the 0 ° direction, and angle coordinates are defined counterclockwise to represent the viewing angle direction. In FIGS. 5A to 5C, angles are shown in increments of 30 °. In the figure, the 0 ° -180 ° direction is a direction parallel to the X direction (a horizontal direction of “1”), and the 90 ° -270 ° direction is a direction parallel to the Y direction (a vertical direction of “1”).

  FIGS. 5A and 5B show viewing angle characteristics for each of the displays performed at four contrast ratios (CR) of 5, 10, 50, and 300. FIG. FIG. 5C shows the viewing angle characteristics for each of the displays performed at six contrast ratios (CR) of 2, 3, 5, 10, 20, and 50.

  Reference is made to FIG. All the measured contrast ratios (CR) have substantially symmetrical viewing angle characteristics with respect to the left-right direction (0 ° -180 ° direction) and the vertical direction (90 ° -270 ° direction). Further, for example, when the contrast ratio (CR) is 10, it can be seen that good visibility is obtained in the left-right direction and the up-down direction when the polar angle is up to about 40 °.

  Reference is made to FIG. All the contrast ratios (CR) measured show viewing angle characteristics that are substantially symmetrical with respect to the horizontal direction and the vertical direction. For example, when the contrast ratio (CR) is 10, good visibility is obtained in the left and right direction and the up and down direction up to a polar angle of about 60 °. Thus, it can be seen that the liquid crystal display element according to the first example has a good visibility (a wide viewing angle) up to a deep angular position as compared with that according to the first comparative example. The inventors of the present invention actually displayed both of them side by side, and as a result of evaluation, the liquid crystal display element according to the first example has a deeper angle when the viewing angle is swung in the vertical direction and the horizontal direction. It was confirmed that the clear display was maintained and the display characteristics were excellent in actual use.

  In this visual angle characteristic diagram, although the symmetry of the visual angle characteristic is slightly disrupted in the vertical direction and the horizontal direction, as a result of observation by the inventors of the present application, it is confirmed that the level is not problematic in practical use. It was done.

  The slit of the liquid crystal display element according to the first embodiment is formed so that the right direction of the center of the concentric circle is defined as 0 ° direction and the longitudinal direction is 45 ° when angle coordinates are defined counterclockwise. . As a result of the study by the inventors of the present application, if the longitudinal direction of the slit is 20 ° to 70 °, the vertical direction and the left / right direction exhibit better display characteristics than the liquid crystal display element according to the first comparative example. Was confirmed. The most excellent display characteristic was in the 45 ° direction.

  In the liquid crystal display element according to the first embodiment, the transmission axis direction of the upper polarizing plate is 0 ° -180 ° direction in terms of the angle coordinates, and the transmission axis direction of the lower polarizing plate is 90 ° -270 ° direction. did. The transmission axis directions of the upper and lower polarizing plates are arranged within ± 20 ° from these arrangements (that is, for the upper polarizing plate, −20 ° -160 ° direction to 20 ° -200 ° direction, lower polarization) With respect to the plate, it was confirmed that the display characteristics superior to those of the liquid crystal display element according to the first comparative example were exhibited in the direction of 70 ° -250 ° to 110 ° -290 °.

  Further, the liquid crystal display element according to the first embodiment employs a liquid crystal layer that does not give the liquid crystal molecules a twist force. For example, a liquid crystal with a twist force as employed in the liquid crystal display element according to the second embodiment. It was confirmed that a layer may be used.

  Reference is made to FIG. All the contrast ratios (CR) measured show viewing angle characteristics that are substantially symmetrical with respect to the horizontal direction and the vertical direction. For example, when the contrast ratio (CR) is 10, good visibility is obtained up to a range in which the polar angle exceeds 80 ° with respect to the horizontal direction and the vertical direction. Thus, it can be seen that the liquid crystal display element according to the second example has a good visibility (wide viewing angle) up to a deep angular position as compared with the first comparative example. The inventors of the present application actually displayed both of them side by side, and as a result of evaluation, the liquid crystal display element according to the second embodiment has a deeper angle when the viewing angle is swung in the vertical direction and the horizontal direction. It was confirmed that the clear display was maintained and the display characteristics were excellent in actual use.

  However, it was confirmed that the liquid crystal display element according to the second example had lower display brightness than that according to the first comparative example. This is considered to be due to the fact that the effective retardation change is reduced because the liquid crystal molecules are twisted.

  In the liquid crystal display element according to the second embodiment, the longitudinal direction of the slit is the direction parallel to the X direction, but may be the direction parallel to the Y direction.

  The liquid crystal display element according to the second embodiment employs a liquid crystal layer in which liquid crystal molecules are twisted. When the inventors of the present application used a liquid crystal layer that does not have twisting force and was used in the liquid crystal display element according to the first comparative example instead of the liquid crystal layer of the liquid crystal display element according to the second embodiment, the contrast was almost the same. It was difficult to see and it was difficult to see.

  A viewing angle compensation plate is used in the liquid crystal display elements according to the first and second embodiments. However, even when a viewing angle compensation plate is not used or when a viewing angle compensation plate having a small compensation value is used, the viewing angles in the vertical and horizontal directions can be kept wide.

  Next, the liquid crystal display element according to the third embodiment and the liquid crystal display element according to the second comparative example will be described. The above-described examples (the liquid crystal display elements according to the first and second examples) and the comparative example (the liquid crystal display element according to the first comparative example) were vertical alignment type liquid crystal display elements. Two are TN alignment type liquid crystal display elements having a twist angle of 90 °.

  A liquid crystal display device according to the third embodiment will be described with reference to FIGS. In the upper and lower transparent electrodes, rectangular slits were formed as long slits in one direction, and the upper and lower transparent electrodes defined display areas for displaying the arithmetic numeral “1”. In addition, when the X direction is defined in the horizontal direction of the character “1” and the Y direction (the direction orthogonal to the X direction) is defined in the vertical (height) direction, the slit is 45 ° in both the X direction and the Y direction. It was formed to make. The rubbing was performed in the direction parallel to the X direction for one substrate and in the direction parallel to the Y direction for the other substrate. The transmission axis directions of the upper and lower polarizing plates were both parallel to the X direction.

  Reference is made to FIG. FIG. 6A is a schematic plan view showing the display area of the liquid crystal display element according to the third embodiment, which is the same as FIG.

  The transparent electrode in the display area is formed with a slit from which a part of the transparent electrode is removed. In the figure, the slit formed in the upper transparent electrode is indicated by a solid line, and the slit formed in the lower transparent electrode is indicated by a broken line. The shape, size, longitudinal direction (direction that forms 45 ° in both X and Y directions), spacing, and arrangement of the slits are the same as those in the first embodiment shown in FIG.

  The liquid crystal cell of the liquid crystal display element according to the third example was manufactured as follows. A low pretilt angle alignment film (SE-510, manufactured by Nissan Chemical Industries, Ltd.) is applied onto the upper and lower transparent substrates having the transparent electrodes with slits as described above, and rubbed. The rubbing was performed using a rayon rubbing cloth, and an equal pretilt angle was given to the upper and lower substrates.

  FIG. 6B illustrates the rubbing direction. In FIG. 6B, the solid line arrow indicates the rubbing direction of the upper substrate, which is the Y positive direction. Also, the dashed arrow indicates the rubbing direction of the lower substrate and the X negative direction.

  The twist direction of the liquid crystal is left-handed. By rubbing as shown in FIG. 6B, the liquid crystal molecules are splay aligned, and the tilt angle of the liquid crystal molecules at the center of the cell is 0 °.

  A main sealing material is applied to the upper and lower substrates produced as described above. Further, after spraying a gap control material having a diameter of 9 μm, they are overlapped to cure the main seal material. A liquid crystal cell having a birefringence of 0.25 manufactured by Dainippon Ink Co., Ltd. was injected into the empty cell thus produced, thereby completing a liquid crystal cell.

  With reference to FIG. 6C, the arrangement of the upper and lower polarizing plates will be described. Since the liquid crystal display element according to the third embodiment is a TN alignment type liquid crystal display element, the polarizing plate is bonded to the liquid crystal cell in the configuration shown in FIG.

  In FIG. 6C, the solid line arrow indicates the transmission axis direction of the upper polarizing plate, and the broken line arrow indicates the transmission axis direction of the lower polarizing plate. Both are parallel to the X direction.

  In this way, a normally black display 2-domain TN type liquid crystal display element was produced.

  A liquid crystal display element according to a second comparative example will be described with reference to FIGS. Also in the liquid crystal display element according to the second comparative example, the upper and lower transparent electrodes define a display area for displaying the arithmetic numeral “1”, and the horizontal direction of the character “1” is the X direction, A Y direction (a direction perpendicular to the X direction) was defined in the longitudinal (height) direction.

  Reference is made to FIG. FIG. 7A is a schematic plan view showing a display region of the liquid crystal display element according to the second comparative example, which is the same as FIG.

  The transparent electrode in the display area is formed with a slit from which a part of the transparent electrode is removed. In the figure, the slit formed in the upper transparent electrode is indicated by a solid line, and the slit formed in the lower transparent electrode is indicated by a broken line. The shape, size, longitudinal direction (direction parallel to the X direction), spacing, and arrangement of the slits are the same as in the second embodiment shown in FIG.

  The manufacturing method of the liquid crystal cell of the liquid crystal display element according to the second comparative example is the same as that of the liquid crystal cell of the liquid crystal display element according to the third embodiment except for the rubbing direction.

  FIG. 7B is a plan view showing a rubbing direction in the liquid crystal display element according to the second comparative example. In FIG. 7B, the solid line arrow indicates the rubbing direction of the upper substrate, which is a direction of 45 ° in both the X positive direction and the Y positive direction. Also, the broken arrow indicates the rubbing direction of the lower substrate, which is a direction that forms 45 ° with the X negative direction and the Y positive direction.

  The twist direction of the liquid crystal is left-handed. By rubbing as shown in FIG. 7B, the liquid crystal molecules are splay aligned, and the tilt angle of the liquid crystal molecules at the center of the cell is 0 °.

  With reference to FIG. 7C, the arrangement of the upper and lower polarizing plates will be described. Since the liquid crystal display element according to the second comparative example is a TN alignment type liquid crystal display element, the polarizing plate is bonded to the liquid crystal cell with the configuration shown in FIG.

  In FIG. 7C, the solid arrow indicates the transmission axis direction of the upper polarizing plate, and the broken arrow indicates the transmission axis direction of the lower polarizing plate. Both directions are 45 ° with the X negative direction and the Y positive direction.

  In this way, a normally black display 2-domain TN type liquid crystal display element was produced.

  FIGS. 8A and 8B are visual angle characteristic diagrams when the liquid crystal display elements according to the second comparative example and the third example are displayed by ¼ duty driving, respectively. The representation of polar angles and angular coordinates in both figures is the same as those in FIGS. 5 (A) and 5 (B).

  FIGS. 8A and 8B show the viewing angle characteristics for each of the displays performed at four contrast ratios (CR) of 5, 10, 20, and 50. FIG.

  Reference is made to FIG. All the measured contrast ratios (CR) have substantially symmetrical viewing angle characteristics with respect to the left-right direction (0 ° -180 ° direction) and the vertical direction (90 ° -270 ° direction). However, there is a significant difference in the viewing angle between the horizontal direction and the vertical direction. For example, when the contrast ratio (CR) is 20, good visibility can be obtained up to about 40 ° in the horizontal direction, but good visibility can be obtained up to about 25 ° in the vertical direction. Absent.

  Reference is made to FIG. All the contrast ratios (CR) measured show viewing angle characteristics that are substantially symmetrical with respect to the horizontal direction and the vertical direction. In addition, there is no large gap between the viewing angle in the left-right direction and the viewing angle in the up-down direction. For example, when the contrast ratio (CR) is 20, good visibility can be obtained up to about 45 ° with respect to the left and right direction and over 50 ° with respect to the up and down direction.

  When compared with the liquid crystal display element according to the second comparative example shown in FIG. 8A, the liquid crystal display element according to the third embodiment has a wide viewing angle in the vertical direction, and the wide viewing angle is in the horizontal direction and vertical direction. Excellent in that the direction is balanced.

  The inventors of the present application actually displayed both of them side by side, and as a result of evaluation, the liquid crystal display element according to the third embodiment has a deeper angle when the viewing angle is swung in the vertical direction and the horizontal direction. It was confirmed that the clear display was maintained and the display characteristics were excellent in actual use.

  Note that in the viewing angle characteristic diagram of the liquid crystal display element according to the third embodiment shown in FIG. 8B, the symmetry of the viewing angle characteristic is slightly disturbed in the vertical direction and the horizontal direction. As a result of observation, it was confirmed that the level was not problematic in actual use.

  The slit of the liquid crystal display element according to the third embodiment is formed so that the right direction of the center of the concentric circle is defined as 0 ° direction and the longitudinal direction is 45 ° when angle coordinates are defined counterclockwise. . As a result of the study by the inventors of the present application, it was found that when the longitudinal direction of the slit is 20 ° to 70 °, substantially the same viewing angle characteristic can be obtained as when the longitudinal direction is 45 °. The fact that the longitudinal direction of the slit is 20 ° to 70 ° means that the alignment direction of the liquid crystal molecules at the center of the cell when no voltage is applied is in the range of 90 ° ± 25 ° with respect to the longitudinal direction of the slit. It shows that. In the TN type liquid crystal display element, even when the longitudinal direction of the slit and the alignment direction of the liquid crystal molecules at the center of the cell are not orthogonal to each other, an effect almost equal to that when they are orthogonal can be exhibited.

  In the liquid crystal display element according to the third embodiment, the transmission axis directions of the upper and lower polarizing plates are both parallel to the X direction. Both of these may be parallel to the Y direction. Further, the upper and lower polarizing plates can be arranged by defining the transmission axis direction within a range of ± 20 ° from the direction parallel to the X direction or within a range of ± 20 ° from the direction parallel to the Y direction. The arrangement in this case does not necessarily need to be a parallel Nicol arrangement. Even when the transmission axis directions of the upper and lower polarizing plates are not set to the X direction or the direction parallel to the Y direction, the same effects as those obtained when the directions are set in parallel can be obtained. As a result of research, the inventors of the present application have positively adopted a range of ± 20 ° or less, or arranged the upper and lower polarizing plates in parallel Nicols in the case of a TN type liquid crystal display device having a twist angle other than 90 °. I found out that it might be better to deviate from.

  In the third embodiment, which is a TN type liquid crystal display element having a twist angle of 90 °, the upper and lower substrates were rubbed in the vertical and horizontal directions, respectively. In a TN liquid crystal display device having a twist angle other than 90 °, the rubbing direction may be determined so that the alignment direction of the liquid crystal molecules at the center of the cell is orthogonal to the longitudinal direction of the slit.

  As mentioned above, although this invention was demonstrated along the Example, this invention is not limited to these.

  FIG. 9 is a schematic plan view showing a display area of the liquid crystal display element. In the first to third embodiments, rectangular slits were formed as long slits in one direction, but striped slits were formed on the upper and lower transparent electrodes as shown in this figure. May be. It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like are possible.

  The liquid crystal display elements according to the first to third embodiments are liquid crystal display elements excellent in visibility from a direction parallel to the X direction or a direction parallel to the Y direction perpendicular to the X direction. The X direction and the Y direction are directions defined in the horizontal direction and the vertical (height) direction of the character “1” in the display area, respectively. The X direction is a direction parallel to the left-right direction of the display unit of the liquid crystal display element.

  The X direction and the Y direction are, for example, a horizontal direction and a vertical direction, which are directions with high human visibility, respectively. They are the horizontal direction and the vertical direction in a liquid crystal display element placed on the ground surface or on the basis of the ground surface. Further, in a liquid crystal display element for in-vehicle use, for example, a horizontal direction and a vertical direction of a car are provided.

  The present invention can be used for a liquid crystal display element for segment display, a liquid crystal display element for dot matrix display, and a liquid crystal display element for performing display combining both displays. Further, the present invention can also be used for an active matrix type liquid crystal display element using a switching element such as a TFT.

(A) is schematic sectional drawing which shows the structure common to the liquid crystal display element by an Example, and the liquid crystal display element by a comparative example, (B) and (C) are the liquid crystal displays by an Example and a comparative example. It is a schematic sectional drawing which shows the structure which is common to a TN type | mold and a vertical alignment type liquid crystal display element respectively among elements. (A) And (B) is a figure for demonstrating the liquid crystal display element by a 1st Example. (A) And (B) is a figure for demonstrating the liquid crystal display element by a 2nd Example. (A) And (B) is a figure for demonstrating the liquid crystal display element by a 1st comparative example. (A), (B), and (C) are viewing angle characteristics when the liquid crystal display elements according to the first comparative example, the first example, and the second example are displayed with a 1/8 duty drive, respectively. FIG. (A)-(C) are the figures for demonstrating the liquid crystal display element by a 3rd Example. (A)-(C) are the figures for demonstrating the liquid crystal display element by a 2nd comparative example. (A) And (B) is a viewing angle characteristic figure at the time of displaying the liquid crystal display element by a 2nd comparative example and a 3rd Example by 1/4 duty drive, respectively. It is a schematic plan view which shows the display area of a liquid crystal display element.

Explanation of symbols

31 Upper substrate 31a Upper transparent substrate 31b Upper transparent electrode 31c Slit 31d Upper alignment film 32 Lower substrate 32a Lower transparent substrate 32b Lower transparent electrode 32c Slit 32d Lower alignment film 33 Liquid crystal layer 34 Upper polarizing plate 35 Lower polarizing plate 36 viewing angle compensator PS

Claims (10)

A pair of opposed substrates;
A liquid crystal layer sandwiched between the pair of substrates;
A pair of transparent electrodes that form a display region overlapping each other with the liquid crystal layer interposed therebetween, and both transparent electrodes have slits that are long in one direction in the display region, and the slits of one transparent electrode and the other The slit of the transparent electrode is realized by a pair of transparent electrodes alternately arranged in a direction intersecting with the longitudinal direction of the slit in the display region when viewed from the normal direction of the pair of substrates. In a liquid crystal display device having a two-domain alignment structure ,
Each of the pair of substrates is a pair of polarizing plates disposed on the side opposite to the side on which the liquid crystal layer is sandwiched, and the transmission axis direction of at least one polarizing plate and the horizontal or vertical direction for performing display A normally black liquid crystal display element having a pair of polarizing plates having an angle of 20 ° or less with the direction. 2. The liquid crystal display element according to claim 1, wherein a transmission axis direction of at least one of the pair of polarizing plates is parallel to a horizontal direction or a vertical direction in which display is performed. 3. The liquid crystal display element according to claim 1, wherein an angle formed by a horizontal direction or a vertical direction in which display is performed and a longitudinal direction of the slit is 20 ° or more and 70 ° or less. The liquid crystal display element according to claim 1, wherein an angle formed by a horizontal direction or a vertical direction for performing display and a longitudinal direction of the slit is 45 °. The horizontal direction or vertical direction for performing display and a longitudinal direction of the slit are parallel or orthogonal to each other, and the liquid crystal layer includes liquid crystal molecules that are vertically aligned and have a twisting force. 3. The liquid crystal display element according to 1 or 2. The liquid crystal layer includes liquid crystal molecules that are twisted nematically aligned , and each of the pair of substrates and the liquid crystal layer has a liquid crystal molecule that has an orientation orientation in one direction, and the thickness of the liquid crystal layer The angle formed by the alignment direction when no voltage is applied to the liquid crystal molecules located in the center of the vertical direction and the longitudinal direction of the slit is 65 ° or more and 115 ° or less. Liquid crystal display element. The liquid crystal layer includes a liquid crystal molecule that is twisted nematically aligned, and the alignment direction when no voltage is applied to the liquid crystal molecule located in the center of the liquid crystal layer in the thickness direction is orthogonal to the longitudinal direction of the slit. It is a direction, The liquid crystal display element of any one of Claims 1-4. The liquid crystal display element according to claim 1, wherein the slits are alternately arranged in a direction orthogonal to the longitudinal direction of the slits. The liquid crystal display element according to claim 1, wherein the slit is formed in a rectangular shape. The liquid crystal display element according to claim 1, wherein the slit is formed in a stripe shape.

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