JP2012108335A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize satisfactory display quality.SOLUTION: The liquid crystal display element comprises: a first substrate on which a first electrode is formed; a second substrate on which a second electrode is formed; a vertical alignment liquid crystal layer arranged between the first and second substrates; a first polarizer arranged on the first substrate and opposite to the liquid crystal layer; and a second polarizer arranged on the second substrate and opposite to the liquid crystal layer so as to be substantially in a cross-nicol manner with respect to the first polarizer. The first and second polarizers are arranged such that an absorption axis azimuth has an angle of approximately 45° to the oriented azimuth of liquid crystal molecule located in the center of the liquid crystal layer in the direction of its thickness when a voltage is not applied between the first and second electrodes. A first portion of the border line of the display portion in which the first and second electrodes are formed one on the other in the normal directions of the first and second substrates is formed from an edge of the first electrode and an edge of an opening formed in the second electrode. In the first portion, in a case where there is no opening, the angle between the azimuth in which the liquid crystal molecule located in the center of the liquid crystal layer in its thickness direction is oriented when a voltage is applied between the first and second electrodes and the azimuth in which it is oriented when the voltage is not applied is 135° or greater.

Description

  The present invention relates to a liquid crystal display element.

  The vertical alignment type liquid crystal display element is a vertical alignment (VA) mode liquid crystal cell in which the liquid crystal molecular alignment in the liquid crystal layer disposed between the two front and back glass substrates is aligned substantially perpendicular to the substrate. It is comprised by arrange | positioning between the polarizing plates arrange | positioned at cross nicol. When observed from the normal direction of the glass substrate, the light transmittance of the background display part (voltage non-applied part) of the vertical alignment type liquid crystal display element is almost the same as that of the polarizing plate arranged substantially in crossed Nicols, and is very low. For this reason, the vertical alignment type liquid crystal display element can realize display with a high contrast ratio relatively easily.

In the VA mode liquid crystal cell, the following technique is known as a method for performing uniform alignment treatment inclined from the vertical direction between the inner surfaces of the front and back substrates. For example, (i) a metal oxide film such as SiO _x as an orientation film is obliquely deposited on the surface to be the inner surface of the substrate from a direction inclined with respect to the substrate normal, thereby forming the deposited surface in a saw shape. A method for realizing uniform alignment by a shape effect; (ii) so-called light in which an organic alignment film material such as polyimide is formed on a surface to be an inner surface of a substrate and then ultraviolet light is irradiated to the alignment film surface from an oblique direction from the substrate normal line Alignment processing method (for example, see Patent Document 1), (iii) Method of performing a rubbing process after forming a vertical alignment film having a specific surface free energy on the surface to be the inner surface of the substrate (for example, see Patent Document 2) It is. These methods are monodomain alignment treatment methods capable of aligning liquid crystal molecules in a certain position in the liquid crystal layer of the VA mode liquid crystal cell when no voltage is applied.

  FIG. 12A is a cross-sectional view showing an outline of a conventional vertical alignment type liquid crystal display element, and FIGS. 12B to 12D are schematic plan views showing a part of the electrode structure.

  Reference is made to FIG. The conventional vertical alignment type liquid crystal display element includes a front side substrate 11, a back side substrate 12, and a vertical alignment liquid crystal layer 13 disposed between the substrates 11 and 12. The front substrate 11 includes a front glass substrate 11a, a segment transparent electrode 11b formed on the front glass substrate 11a, and a front vertical alignment film 11c formed on the front glass substrate 11a and the segment transparent electrode 11b. The Similarly, the back side substrate 12 includes a back side glass substrate 12a, a common transparent electrode 12b formed on the back side glass substrate 12a, and a back side vertical alignment film 12c formed on the back side glass substrate 12a and the common transparent electrode 12b. Consists of. The segment transparent electrode 11b and the common transparent electrode 12b are made of, for example, indium tin oxide (ITO).

  The front side and back side vertical alignment films 11c and 12c are subjected to an alignment process at one position by, for example, the alignment process method (ii) or (iii) described above. In a plane parallel to the front and back substrates 11 and 12, the vertical orientation on the paper surface is 12:00 (90 ° azimuth), the right orientation on the paper is 3 o'clock (0 ° azimuth), and the front vertical orientation on the paper is 6 o'clock ( 270 ° azimuth), and when defining an azimuth coordinate system in which the left side of the paper is 9 o'clock (180 ° azimuth), for example, the front vertical alignment film 11c has a 12 o'clock orientation and the back vertical alignment film 12c has a 6 o'clock orientation. In addition, the alignment treatment is performed so that the liquid crystal molecules are uniformly aligned.

  The vertical alignment liquid crystal layer 13 is a substantially vertically aligned liquid crystal layer disposed between the front side vertical alignment film 11 c of the front side substrate 11 and the back side vertical alignment film 12 c of the back side substrate 12. For example, it is formed using a liquid crystal material having negative dielectric anisotropy and has a monodomain structure. For example, in a state where no voltage is applied between the segment transparent electrode 11 b and the common transparent electrode 12 b, the liquid crystal molecules of the liquid crystal layer 13 are arranged substantially perpendicular to the front side and back side substrates 11 and 12. When a voltage larger than the threshold voltage is applied between the electrodes 11b and 12b (hereinafter, when a voltage is applied or in a voltage applied state), most of the liquid crystal molecules in the liquid crystal layer 13 are in the in-plane direction of the substrates 11 and 12. It falls to the orientation processing direction.

  The spacer 14 keeps a space between the front substrate 11 and the back substrate 12, for example. Both substrates 11 and 12 are bonded together by a seal portion 15.

  The front-side viewing angle compensation plate 16 and the front-side polarizing plate 18 are arranged in this order on the front-side glass substrate 11a on the side opposite to the liquid crystal layer 13. Similarly, the back-side viewing angle compensation plate 17 and the back-side polarizing plate 19 are disposed on the back-side glass substrate 12a on the side opposite to the liquid crystal layer 13 in this order. The front-side and back-side polarizing plates 18 and 19 are, for example, substantially in crossed Nicols, and in the plane parallel to the substrate surface, the absorption axis orientation is at the center of the liquid crystal layer 13 in the thickness direction when no voltage is applied. It is arranged so as to form an angle of 45 ° with the orientation direction (6 o'clock direction). As an example, the front-side polarizing plate 18 is disposed so that the absorption axis orientation is 45 ° -225 °, and the back-side polarizing plate 19 is disposed so that the absorption axis orientation is 135 ° -315 °.

  The front-side and back-side viewing angle compensation plates 16 and 17 are viewing angle compensation plates having negative uniaxial or negative biaxial optical anisotropy. When the front side and back side viewing angle compensation plates 16 and 17 have in-plane slow axes, the slow side axis of the front and back side viewing angle compensation plates 16 and 17 are substantially parallel to the transmission axes of the adjacent polarizing plates 18 and 19. It arrange | positions so that it may become.

  Although not shown, a backlight is disposed outside the back side polarizing plate 19. Light emitted from the backlight passes through the back side polarizing plate 19 and the back side viewing angle compensation plate 17 and enters the liquid crystal cell. Even when a voltage larger than the threshold voltage is not applied between the segment transparent electrode 11b and the common transparent electrode 12b, and even when a voltage is applied, both electrodes in the normal direction of the substrates 11 and 12 are displayed. In a region other than the region in which display is performed by overlapping the layers 11 b and 12 b, the light incident on and transmitted through the liquid crystal cell is shielded by the front polarizing plate 18. For this reason, dark display (black display) is performed for an observer who observes the liquid crystal display element from the outside of the front-side polarizing plate 18. On the other hand, in the display unit in a state where a voltage larger than the threshold voltage is applied between the electrodes 11b and 12b, the light incident on the liquid crystal cell is transmitted through the liquid crystal cell and the front side polarizing plate 18. For this reason, bright display (white display) is performed for an observer who observes the liquid crystal display element from the outside of the front-side polarizing plate 18.

  12B and 12C are schematic plan views showing a part of the segment transparent electrode 11b and the common transparent electrode 12b, respectively. FIG. 12D is a schematic plan view showing a part of both the electrodes 11b and 12b observed from vertically above the front substrate 11 (in the normal direction of the substrate).

  The liquid crystal display elements shown in FIGS. 12A to 12D are so-called segment display liquid crystal display elements in which the shape of the display portion is realized mainly by the shape of the segment electrode 11b. In the segment display liquid crystal display element, a display portion having an arbitrary shape can be manufactured depending on the shape of the electrode. FIGS. 12B to 12D show the regions of the electrodes 11b and 12b in which the display unit is a character string “AUTO”. The segment display liquid crystal display element is operated by, for example, simple matrix driving, for example, multiplex driving.

  In order to realize the display of “AUTO”, the segment transparent electrode 11b is formed on the front glass substrate 11a, for example, in the shape shown in FIG. The common transparent electrode 12b is formed on the back glass substrate 12a in the shape shown in FIG. The front-side substrate 11 and the back-side substrate 12 are arranged substantially in parallel so that the electrodes 11b and 12b formation surfaces face each other, and when viewed from the normal direction of both the substrates 11 and 12, the overlapping portions of the electrodes 11b and 12b formation regions Is aligned and pasted as shown in FIG. 12D, for example, so that only “AUTO” is obtained. By combining the electrode structure shown in FIGS. 12B to 12D and the monodomain vertical alignment liquid crystal layer, it is possible to realize good dark display other than the display portion.

  The liquid crystal display element shown in FIGS. 12A to 12D has a polar azimuth observation angle in which a bright display state is observed well from the 12:00 direction, and conversely, a bright display is not observed from the 6 o'clock direction. It is known to exist. The 12 o'clock direction is called the best viewing direction, and the 6 o'clock direction is called the anti-viewing direction.

Japanese Patent No. 2872628 JP 2005-234254 A

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

  According to one aspect of the present invention, a first substrate on which a first electrode is formed, and a second substrate on which a second electrode is formed, the second electrode being the first electrode A second substrate disposed substantially parallel to the first substrate so as to oppose, a vertically aligned liquid crystal layer disposed between the first substrate and the second substrate, and the first substrate A first polarizing plate disposed on the opposite side of the first substrate to the liquid crystal layer, and substantially crossed Nicols on the opposite side of the second substrate from the liquid crystal layer. The first and second polarizing plates have an absorption axis direction when no voltage is applied between the first electrode and the second electrode. The liquid crystal layer is arranged so as to form an angle of about 45 ° with the orientation direction of the liquid crystal molecules located in the center in the thickness direction of the liquid crystal layer, and is normal to the first and second substrates. The first portion of the outline of the display portion formed by overlapping the first electrode and the second electrode with respect to the direction is formed on the edge of the first electrode and the second electrode. In the first portion, when there is no opening, the liquid crystal molecule located in the center of the liquid crystal layer in the thickness direction has the first electrode and the first portion. There is provided a liquid crystal display element in which an angle between an orientation when a voltage is applied between the two electrodes and an orientation when a voltage is not applied is 135 ° or more.

  ADVANTAGE OF THE INVENTION According to this invention, the liquid crystal display element which has favorable display quality can be provided.

FIG. 13 is a schematic view showing a liquid crystal cell portion having a cross section different from that of FIG. 12A in the conventional vertical alignment type liquid crystal display element shown in FIGS. (A) and (B) are the vicinity of the horizontal bar of the letter “A” in the display section “AUTO” of the conventional vertical alignment type liquid crystal display element shown in FIGS. It is a polarizing microscope photograph which shows the orientation structure | tissue at the time of the voltage application of the lower curve part of the character of "U". It is a schematic plan view showing the relationship between the dark region and the orientation direction of the liquid crystal layer center molecule 13m in the vicinity of the upper edge of the horizontal bar portion of “A”. It is a schematic top view which shows the orientation azimuth | direction at the time of the voltage application of the liquid crystal layer center molecule 13m in the inner and outer edges of the diagonal line part on the left side of "A". (A)-(C) are schematic plan views which show an example of the electrode structure which suppresses light omission. It is sectional drawing which shows the outline of the monodomain vertical alignment type liquid crystal display element by an Example. (A)-(C) are schematic top views which show the segment transparent electrode 11B and the common transparent electrode 12B of the mono domain vertical alignment type liquid crystal display element by an Example. (A)-(C) are schematic plan views which show the example of the shape and arrangement | positioning of an opening part. (A) and (B) are voltages in the vicinity of the horizontal bar of the letter “A” in the display section “AUTO” of the vertical alignment type liquid crystal display element according to the embodiment, and the lower curve portion of the letter “U”, respectively. It is a polarizing microscope photograph which shows the orientation structure | tissue at the time of application. FIG. 10A is a schematic plan view showing the orientation direction when a voltage is applied to the liquid crystal layer central molecule 13m in the I part of FIG. 9A. FIG. 10A is a schematic plan view showing the orientation direction at the time of voltage application of the liquid crystal layer central molecule 13m in a J portion in FIG. (A) is sectional drawing which shows the outline of the conventional vertical alignment type liquid crystal display element, (B)-(D) is a schematic plan view which shows a part of the electrode structure.

  A dark state is observed when the conventional vertical alignment type liquid crystal display element is viewed from the opposite viewing direction when a voltage is applied. However, if the display unit has a side that is substantially orthogonal to the best viewing direction or the anti-viewing direction (for example, the horizontal bar “A” in the examples shown in FIGS. 12A to 12D), Light leakage occurs near the edge (contour line of the display portion). In addition, nonuniformity is observed in the degree of light leakage, which may reduce the display quality. Furthermore, despite the same display pattern, a difference may be observed in the light leakage state near the edge of the display portion when viewed from the opposite viewing direction, and the display quality is degraded depending on the arrangement of the display pattern. The deterioration of the display quality is recognized when the image is observed from a range of about 70 ° or less in each of the clockwise direction and the counterclockwise direction around the anti-viewing direction.

  The light omission is recognized near the edge of the display unit that is affected by the oblique electric field in the voltage application state, other than near the edge of the side substantially orthogonal to the best viewing direction or the anti-viewing direction. Also in this case, the display quality is degraded within a range of about 70 ° in each of the clockwise direction and the counterclockwise direction around the counter-viewing direction.

  The inventors of the present application have considered the reason why light leakage and unevenness of the degree occur as follows.

  FIG. 1 is a schematic view showing a liquid crystal cell portion having a cross section different from that of FIG. 12A, for the conventional vertical alignment type liquid crystal display element shown in FIGS. As described above, the front vertical alignment film 11c is rubbed at 12 o'clock and the back vertical alignment film 12c is rubbed at 6 o'clock. For this reason, in the voltage application state, the liquid crystal molecule (liquid crystal layer central molecule 13m) located at the center in the thickness direction of the liquid crystal layer 13 is inclined so as to fall in the 6 o'clock direction. For this reason, the best viewing direction of the liquid crystal display element is the 12 o'clock direction, and the anti-viewing direction is the 6 o'clock direction.

  An oblique electric field is generated in the liquid crystal layer 13 at the edge portions of the segment transparent electrode 11b and the common transparent electrode 12b. In this figure, the oblique electric field in the liquid crystal layer 13 is indicated by a broken line. In a region in the liquid crystal layer 13 that is strongly influenced by the oblique electric field, the liquid crystal layer central molecules 13m are aligned so as to be orthogonal to the oblique electric field. Therefore, in a partial region near the edges of the electrodes 11b and 12b, the orientation direction of the liquid crystal layer central molecule 13m is not affected by the oblique electric field (the orientation treatment direction of the liquid crystal molecules on the orientation films 11c and 12c). In the liquid crystal layer central molecule 13m in the region in which the liquid crystal layer is determined) is opposite to the orientation (180 ° different orientation). As described above, even in a liquid crystal display element having a monodomain structure, a multidomain structure having a different orientation orientation in the vicinity of the edge is realized in the display portion in a voltage application state. As a result, it is considered that light leakage is observed near the edge of the display unit, despite being from the anti-viewing direction.

  2 (A) and 2 (B) show the vicinity of the horizontal bar of the letter “A” in the display section “AUTO” of the conventional vertical alignment type liquid crystal display element shown in FIGS. 12 (A) to 12 (D), respectively. , “U” is a polarized light micrograph showing an oriented structure at the time of voltage application of the lower curve portion.

  Reference is made to FIG. It can be seen that two curved dark regions (dark lines) are formed near the upper edge of the horizontal bar portion of “A”. The inventors of the present application considered the dark region as follows.

  FIG. 3 is a schematic plan view showing the relationship between the dark region and the orientation direction of the liquid crystal layer center molecule 13m near the upper edge of the horizontal bar portion “A”. In this figure, the orientation direction of the center molecule 13m of the liquid crystal layer when a voltage is applied at that position is shown in the direction of the arrow.

  As shown in the drawing, the orientation direction of the liquid crystal layer central molecule 13m in the region not affected by the oblique electric field (the orientation direction when no voltage is applied) is the 6 o'clock direction. The orientation direction of the center molecule 13m of the liquid crystal layer at the upper edge of the horizontal bar “A” is the 12:00 orientation. Two dark regions (for example, a first dark region (dark line) and a second dark region (dark line)) are formed between the two.

  In the intermediate region between the liquid crystal layer center molecules 13m whose orientation directions are opposite to each other, the orientation directions of the liquid crystal layer center molecules 13m continuously change from one side to the other side. For this reason, the first dark region is formed, for example, at a position where the orientation direction of the center molecule 13m of the liquid crystal layer is a 45 ° azimuth that is parallel to the front-side polarizing plate absorption axis azimuth (45 ° -225 ° azimuth). The The second dark region is formed, for example, at a position where the orientation direction of the center molecule 13m of the liquid crystal layer is a 315 ° orientation, which is an orientation parallel to the back side polarizing plate absorption axis orientation (135 ° -315 ° orientation). .

  In a region where the first and second dark regions are formed and a region adjacent in the 3 o'clock direction or the 9 o'clock direction, the direction in which the orientation direction of the liquid crystal layer central molecule 13m continuously changes (rotation direction) ) Is the opposite. For example, in the region where the first and second dark regions are formed, when the orientation direction of the liquid crystal layer central molecule 13m continuously changes so as to rotate in the right direction, The orientation direction of the molecule 13m rotates to the left. For this reason, for example, the liquid crystal layer center molecule 13m has an orientation direction of 135 ° azimuth, a dark region near the upper edge of the horizontal bar of “A” is formed, and a position of 225 ° azimuth is connected, A dark region far from the upper edge of the “A” horizontal bar is formed. A disclination in which the orientation of the liquid crystal molecules becomes discontinuous appears at a position where the orientation in which the orientation direction of the center molecule 13m of the liquid crystal layer continuously changes is reversed.

  As described above, the inventors of the present application have described that the dark region generated in the middle region between the orientation directions of the liquid crystal layer central molecules 13m opposite to each other is, for example, the orientation orientation when no voltage is applied to the liquid crystal layer central molecules 13m. The orientation direction of the liquid crystal layer center molecule 13m is formed at a position substantially parallel to the absorption axis direction of the polarizing plate due to the oblique electric field oriented in the opposite direction to the disclination. It was considered that the 13m orientation orientation was formed at a position where the direction of continuous change was reversed.

  Reference is again made to FIG. The inventors consider that two curved dark areas are formed near the upper edge of the horizontal bar “A”, while the areas affected by the oblique electric field and the areas not affected are This is consistent with the fact that no dark region is observed at the lower edge where the orientation directions of the liquid crystal molecules are the same.

  In addition, as a result of studying the same electrode pattern by the present inventors, the position of the disclination generated near the upper edge of the horizontal bar portion of “A” and the curve shape of the dark region are completely different and irregular. I understood it. Based on this, the inventors of the present application considered that the irregularity of the dark region pattern caused nonuniformity in light leakage when observed from the anti-viewing direction.

  The above is the consideration on the position where the orientation direction of the center molecule 13m of the liquid crystal layer is opposite to each other when the voltage is applied and when no voltage is applied (for example, the upper edge of the horizontal bar of the display unit “A”). Next, let us consider the expanded range.

  Referring to FIG. 2A, in the left and right diagonal lines (slopes) of “A”, it is recognized that one dark region is generated in the vicinity of both the inner edge and the outer edge.

  FIG. 4 is a schematic plan view showing the orientation direction during voltage application of the liquid crystal layer central molecule 13m at the inner and outer edges of the diagonal line portion on the left side of “A”. In this figure, the orientation direction of the center molecule 13m of the liquid crystal layer when a voltage is applied at that position is shown in the direction of the arrow.

  As shown in the figure, at the inner edge when the voltage is applied, the liquid crystal layer center molecule 13m is in an orientation rotated by an angle of 45 ° or more and less than 135 ° counterclockwise with reference to the orientation orientation when no voltage is applied. Orient. Therefore, in the dark region near the inner edge of the diagonal line portion “A”, the orientation direction of the center molecule 13m of the liquid crystal layer is an orientation parallel to the back side polarizing plate absorption axis orientation (135 ° -315 ° orientation). It is thought that it is formed at a position that becomes an azimuth.

  At the outer edge when a voltage is applied, the liquid crystal layer central molecules 13m are aligned in an orientation rotated by an angle of 45 ° or more and less than 135 ° in the clockwise direction with reference to the orientation direction when no voltage is applied. Therefore, in the dark region near the outer edge of the diagonal line portion “A”, the orientation direction of the center molecule 13m of the liquid crystal layer is 225 °, which is parallel to the front-side polarizing plate absorption axis orientation (45 ° -225 ° orientation). It is thought that it is formed at a position that becomes an azimuth.

  Although FIG. 4 shows the diagonal line portion on the left side of “A”, the diagonal line portion on the right side can be considered in the same manner. That is, at the inner edge of the right oblique line portion, when a voltage is applied, the liquid crystal layer central molecule 13m is rotated by an angle of 45 ° or more and less than 135 ° clockwise relative to the orientation direction when no voltage is applied. Oriented to Therefore, the dark region is formed at a position where the orientation direction of the center molecule 13m of the liquid crystal layer is a 225 ° azimuth that is parallel to the front-side polarizing plate absorption axis azimuth (45 ° -225 ° azimuth).

  At the outer edge of the right diagonal line portion, when a voltage is applied, the center molecule 13m of the liquid crystal layer rotates counterclockwise by an angle of 45 ° or more and less than 135 ° with reference to the orientation direction when no voltage is applied. Oriented in the specified direction. Therefore, the dark region is formed at a position where the orientation direction of the center molecule 13m of the liquid crystal layer is 315 ° azimuth that is parallel to the back side polarizing plate absorption axis azimuth (135 ° -315 ° azimuth).

  Considering in this way, the dark region is formed by connecting the alignment direction when the voltage of the liquid crystal layer central molecule 13m is applied with the position where the orientation direction of the absorption axis of the front-side or back-side polarizing plates 18 and 19 is substantially parallel. It does not occur in the vicinity of the position where the orientation azimuth of the liquid crystal layer central molecule 13m when the voltage is applied and the orientation azimuth when no voltage is applied is less than 45 °, and the position is 45 ° or more and less than 135 °. It can be said that only one occurs in the vicinity, and two occur in the vicinity of the position of 135 ° or more.

  At the display portion edge where the dark region occurs, light omission is observed when observed from within a range of about 70 ° in each of the clockwise direction and the counterclockwise direction centering on the anti-viewing direction. Since the best viewing direction changes, it is considered that light leakage occurs depending on the viewing direction.

  Reference is made to FIG. In the lower curve portion of the letter “U” at the time of voltage application, generation of a dark region is recognized in the entire upper edge and a part of the lower edge. Also for this, the same description as that described with reference to FIGS. 3 and 4 can be added. Note that the dark region is formed in the entire upper edge because all the electrode edges constituting the upper edge (contour line) of the lower curved portion of the letter “U” are shown in FIGS. This is because it is an electrode edge of the segment transparent electrode 11b as shown in FIG. As shown in FIGS. 12B to 12D, the lower edge (contour line) of the lower curved portion of the letter “U” is partly composed of the electrode edge of the common transparent electrode 12 b, The remainder is composed of the electrode edges of the segment transparent electrode 11b. The occurrence of the dark region is recognized in a portion where the lower edge (contour line) is constituted by the electrode edge of the common transparent electrode 12b.

  As a method for preventing light from being observed when the display unit edge is viewed from a range within about 70 ° in each of the clockwise direction and the counterclockwise direction around the anti-viewing direction, for example, light The structure of the segment transparent electrode and the common transparent electrode may be devised so as not to cause an oblique electric field that is a cause of disconnection.

  5A to 5C show an example of an electrode structure that suppresses light leakage. 5A and 5B are schematic plan views showing a part of the segment transparent electrode 11b ′ and the common transparent electrode 12b ′, respectively, and FIG. 5C is seen from the substrate normal direction. It is a schematic plan view which shows a part of both electrodes 11b 'and 12b'.

  For example, as shown in FIGS. 5A and 5B, the electrode shapes of the segment transparent electrode 11b ′ and the common transparent electrode 12b ′ in the display unit are made as equal as possible, and the lead line connecting portion is made as thin as possible. As shown in FIG. 5C, the edges of both electrodes 11b ′ and 12b ′ can be overlapped at the surface position. However, in reality, when such an electrode structure is employed, positional displacement may occur when the substrates are superimposed, and the wiring resistance becomes high due to the thin wiring line, which makes long wiring difficult. Therefore, the size of the liquid crystal display element is restricted. Furthermore, depending on the display pattern, there may be a case where it is extremely difficult to design a pattern to be superimposed at the surface position.

  The inventors of the present application, for example, arrange an opening in a region corresponding to a display portion edge (outline) with respect to the electrode structure of the conventional vertical alignment type liquid crystal display element shown in FIGS. By setting the direction of a part of the oblique electric field in the vicinity of the opening to be opposite to the conventional direction, the range is within about 70 ° in each of the clockwise direction and the counterclockwise direction around the anti-viewing direction. Thus, a liquid crystal display element capable of suppressing light leakage when viewing the edge of the display portion was produced. This liquid crystal display element is also a liquid crystal display element capable of controlling the generation position and curve shape of the dark region, eliminating irregularities in the dark region pattern, and suppressing nonuniformity of light leakage.

  FIG. 6 is a cross-sectional view schematically showing a monodomain vertical alignment type liquid crystal display device according to an example. The vertical alignment type liquid crystal display device according to the example differs from the conventional example shown in FIGS. 12A to 12D in the segment transparent electrode 11B and the common transparent electrode 12B. Other structural requirements are the same as in the conventional example.

  Hereinafter, a method for manufacturing a monodomain vertical alignment type liquid crystal display device according to the embodiment will be described with reference to FIG.

After polishing one side and applying SiO ₂ undercoat to the surface, prepare two blue plate glass substrates on which ITO film is formed, and pattern the ITO film on each substrate by photolithography process and etching process Then, the front glass substrate 11a on which the segment transparent electrode 11B is formed and the back glass substrate 12a on which the common transparent electrode 12B is formed are manufactured. If necessary, an insulating layer made of SiO ₂ or the like may be formed on part of the surfaces of the electrodes 11B and 12B.

  After glass substrates 11a and 12a with electrodes 11B and 12B are washed with an alkaline solution or the like, a vertical alignment film made by Chisso Petrochemical Co., Ltd. is applied to the electrodes 11B and 12B and the glass substrates 11a and 12a by flexographic printing. And baked at 180 ° C. for 30 minutes in a clean oven. Each of the front side and back side vertical alignment films 11c and 12c thus obtained is rubbed in a predetermined direction within the substrate surface using a cotton rubbing cloth. Thus, the front side glass substrate 11a, the segment transparent electrode 11B formed on the front side glass substrate 11a, and the front side glass substrate 11a, the front side substrate configured to include the front side vertical alignment film 11c formed on the segment transparent electrode 11B. (Segment substrate) 11 is obtained. Further, a back side substrate including a back side glass substrate 12a, a common transparent electrode 12B formed on the back side glass substrate 12a, and a back side vertical alignment film 12c formed on the back side glass substrate 12a and the common transparent electrode 12B. (Common substrate) 12 is obtained.

  A black plastic spacer made of Hayakawa Rubber Co., Ltd. having a particle size of about 5 μm is sprayed on the entire surface of the front substrate 11 by a dry spraying method. The back side substrate 12 is coated with a thermosetting sealing material 15 made by Mitsui Chemicals Co., Ltd. mixed with a rod-shaped glass spacer 14 made by Nippon Electric Glass Co., Ltd. in a predetermined pattern with a dispenser. Thereafter, the substrates 11 and 12 are aligned so that the surfaces on which the electrodes 11B and 12B are formed face each other and the orientation direction (rubbing direction) is anti-parallel, and are bonded substantially in parallel, and the sealing material is cured by thermocompression bonding. To complete the empty cell. The orientation directions of the front substrate 11 and the back substrate 12 are a 12 o'clock orientation and a 6 o'clock orientation, respectively.

  A liquid crystal material manufactured by Merck Co., Ltd. having a negative dielectric anisotropy Δε is injected into an empty cell using a vacuum injection method, then sealed while being pressed, and baked at 120 ° C. for 1 hour.

  On the front and back glass substrates 11a, 12a surface, Polaratechno polarizing plate SHC13U, front and back polarizing plates 18, 19 are substantially crossed Nicol, and the absorption axis of each polarizing plate 18, 19 is rubbed The liquid crystal layer 13 is bonded so as to form an angle of approximately 45 ° with the orientation direction of liquid crystal molecules located in the center of the liquid crystal layer 13 in the thickness direction (the orientation direction when no voltage is applied, the 6 o'clock direction). If necessary, front and back side viewing angle compensation plates 16 and 17 can be disposed between the front and back glass substrates 11a and 12a and the polarizing plates 18 and 19, respectively. Finally, a lead frame is attached to the electrode extraction terminal of the liquid crystal cell.

  As a result of the measurement, the thickness of the liquid crystal layer 13 of the vertical alignment type liquid crystal display element according to the example was about 4.3 μm, and the pretilt angle in the liquid crystal layer 13 was about 89.9 °. The retardation of the liquid crystal layer 13 is about 1100 nm.

  7A to 7C are schematic plan views showing the segment transparent electrode 11B and the common transparent electrode 12B of the monodomain vertical alignment type liquid crystal display element according to the embodiment.

  FIG. 7A shows the structure of the segment transparent electrode 11B. The segment transparent electrode 11B is different from the segment transparent electrode 11b of the conventional example shown in FIG.

  FIG. 7B shows the structure of the common transparent electrode 12B. The common transparent electrode 12B is different from the conventional common transparent electrode 12b shown in FIG. The external shapes of the electrode patterns of the segment transparent electrode 11B and the common transparent electrode 12B are equal to those of the segment transparent electrode 11b and the common transparent electrode 12b in the conventional example, respectively.

  FIG. 7C is a schematic plan view showing the arrangement of the electrodes 11B and 12B viewed from the normal direction of the substrates 11 and 12. Similarly to the electrodes 11b and 12b of the conventional example shown in FIG. 12D, the electrodes 11B and 12B have overlapping portions of the regions where the electrodes 11B and 12B are formed when viewed from the normal direction of both the substrates 11 and 12. , “AUTO” is aligned.

  When the liquid crystal display element according to the embodiment is viewed from the normal direction of the substrates 11 and 12, the openings 20 and 21 are arranged at the edges (contour lines) of the display portion “AUTO”. Is formed. Further, the openings 20 and 21 are the center of the liquid crystal layer in the region where the alignment direction of the liquid crystal molecules is determined by the alignment treatment direction on the alignment films 11c and 12c in the voltage application state of the conventional example without the openings 20 and 21. Due to a mismatch between the orientation direction of the molecules 13m and the orientation direction of the liquid crystal layer central molecule 13m in the region affected by the oblique electric field generated in the liquid crystal layer 13 at the electrode edge portion, a dark region is formed in a remarkable region. Further, the openings 20 and 21 are formed in the electrodes 11B and 12B that do not have an edge in the edge portion of the display portion (electrodes that are opposed to the electrodes that constitute the edge portion of the display portion by their own electrode edges). Yes.

  8A to 8C are schematic plan views showing examples of the shape and arrangement of the openings.

  FIG. 8A shows the opening 21 formed in the common transparent electrode 12B at the upper edge portion of the horizontal bar “A” of “AUTO”.

  The opening 21 has, for example, a rectangular shape having a long side length L of 0.0656 mm and a short side length W of 0.0328 mm. The plurality of openings 21 are arranged along the edge part of the display part (the upper edge part of the horizontal bar of the electrode part indicating “A” of the segment transparent electrode 11B), for example, the alignment direction of the openings 21 and the edge part of the display part As an example, the common transparent electrode 12B is formed so that the long side of the opening 21 is parallel to the edge portion of the display unit. In this case, for example, as shown in FIG. 8A, the plurality of openings 21 are formed so that the adjacent openings 21 are regularly arranged with a constant interval S, for example, 0.0328 mm.

  Since it is preferable to make the size of the rectangular opening 21 invisible from the appearance, it is desirable that the short side length W is 0.05 mm or less. Further, the ratio of the long side length L to the short side length W is not limited to 2: 1. Although it is possible to set the distance S between the adjacent openings 21 to 0, it is necessary to consider so that the electrodes are not disconnected. When S is 0, the length L of the long side depends on the design shape of the display unit. S is preferably 0.1 mm or less. This is because when the thickness exceeds 0.1 mm, the shape of a dark region generated between adjacent openings 21 described later may not be completely controlled.

  FIG. 8B shows the positional relationship between the upper edge of the horizontal bar of the segment transparent electrode 11B showing “A” and the opening 21 formed in the common transparent electrode 12B. As shown in this figure, when the opening 21 is viewed from the normal direction of the substrate 11 and 12, for example, the edge of the segment transparent electrode 11B exists inside each opening 21 (each opening 21 is a segment). The common transparent electrode 12B is formed so as to overlap the edge of the transparent electrode 11B. As described above, the liquid crystal display element according to the embodiment has the other electrode on at least a part of the electrode edge of the one electrode constituting the edge (contour line) of the display unit when viewed from the normal direction of the substrates 11 and 12. The electrode structure has an opening.

  In the liquid crystal display element according to the embodiment, for example, the openings 21 and 20 along the upper and lower edges of the lower curved portion of the letter “U” have a long side length L of 0.0656 mm and a short side. Is formed in a rectangular shape having a length W of 0.0328 mm.

  As shown in FIG. 8C, the openings 20, 21 are curved so that, for example, the long sides thereof are parallel to the edges of the opposing electrodes 12B, 11B when viewed from the normal direction of the substrates 11, 12. It may be formed in a shape. The openings 20 and 21 may be openings having a shape corresponding to the line shape of the edges of the electrodes 12B and 11B, including a rectangular shape.

  9 (A) and 9 (B) are respectively the vicinity of the horizontal bar of the character “A” in the display portion “AUTO” of the vertical alignment type liquid crystal display device according to the embodiment and the lower curved portion of the character “U”. It is a polarizing microscope photograph which shows the orientation structure | tissue at the time of voltage application of.

  Reference is made to part I in FIG. 9A (the upper edge of the horizontal bar displaying “A”). In the portion I, the concave range of the upper edge (from 3 o'clock to 9 o'clock of the upper edge of the horizontal bar of “A” (the orientation in which the display portion edge extends as a whole, the extension orientation of the edge of the segment transparent electrode 11B) In the arrangement direction of the openings 21) (the range in which the edges are formed by the long edges of the openings 21), no dark region is observed. On the other hand, regular darkening in the convex range of the upper edge (the range where the 3 o'clock to 9 o'clock azimuth edge of the upper edge of the horizontal bar of “A” is composed of the segment transparent electrode 11B edge, the range between the openings 21). The occurrence of a region can be seen. The same applies to the M portion in FIG. 9B (the edge of the lower curve portion in which the angle formed between the tangential direction of the edge portion of the display portion and the 3 o'clock to 9 o'clock orientation) is less than 45 °.

  As a result of the inventors' research, when the distance S between the adjacent openings 21 is 0.1 mm or less, the shape of the dark region appearing in the convex range of the upper edge of the horizontal bar of “A” is substantially equal, It was found that the irregularity of the dark area pattern was eliminated, and the degree of light leakage at the edge of the display portion was made uniform.

  FIG. 10 is a schematic plan view showing the orientation direction when voltage is applied to the liquid crystal layer center molecule 13m in the I part of FIG. 9A. In this figure, the orientation direction of the center molecule 13m of the liquid crystal layer when a voltage is applied at that position is shown in the direction of the arrow.

  As shown in the figure, on the edge extending in the 3 o'clock to 9 o'clock direction of the convex range of the upper edge, the orientation direction of the liquid crystal layer central molecule 13m by the oblique electric field is equal to that shown in FIG. . In addition, the liquid crystal layer central molecule 13m on the short side of the opening that forms the display edge that displays the upper edge of the horizontal bar of “A” is oriented in the direction parallel to the long side of the opening (three o'clock direction). Or oriented at 9 o'clock). Furthermore, the liquid crystal layer central molecule 13m orientation direction (the orientation direction of the liquid crystal layer central molecule 13m when no voltage is applied) in the central portion (the portion away from the edge) of the display portion displaying the horizontal bar “A” is 6 o'clock. It is an azimuth.

  In the convex range of the upper edge where the occurrence of a regular dark region is observed, one side between the edge where the orientation direction of the liquid crystal layer central molecule 13m is 12 o'clock and the center where it is 6 o'clock From one side to the other side, the orientation direction of the liquid crystal layer center molecule 13m continuously changes. While continuously changing, the center molecule 13m of the liquid crystal layer has a 225 ° azimuth that is parallel to the front-side polarizing plate absorption axis azimuth (45 ° -225 ° azimuth), or the back-side polarizing plate absorption axis azimuth (135 ° It is considered that a dark region appears at a position oriented in the 315 ° azimuth that is parallel to the −315 ° azimuth).

  On the other hand, in the concave range of the upper edge, the orientation orientation of the liquid crystal layer central molecule 13m by the oblique electric field on the edge extending in the 3 to 9 o'clock orientation is 6 o'clock orientation, which is the same as the orientation orientation when no voltage is applied. For this reason, no dark region appears in the concave range of the upper edge.

  Referring to part M in FIG. 9B, in order to obtain the same effect as part I in FIG. 9A, the long side edge of the opening along the display part edge and the liquid crystal layer when no voltage is applied. It can be seen that the orientation direction of the central molecule 13m does not necessarily have to be substantially orthogonal. (In part I of FIG. 9A, both are substantially orthogonal.) According to the study by the inventors of the present application, the electrode structure shown in FIGS. 12A to 12D without an opening. In the liquid crystal display element, an opening is similarly arranged at the display portion edge where the orientation direction of the liquid crystal layer center molecule 13m when no voltage is applied and the orientation direction of the liquid crystal layer center molecule 13m by an oblique electric field differ by 45 ° or more. In this case, if the relationship between the long side edge of the opening and the orientation direction of the liquid crystal layer center molecule 13m when no voltage is applied satisfies the relationship of more than 45 ° and less than 135 °, the opening edge region (concave region) is formed. It was found that no dark area occurred. In the J portion and the K portion shown in FIG. 9A and the N portion and the O portion shown in FIG. 9B, dark regions in both the opening edge region (concave range) and the inter-opening region (convex range). Has occurred. This is because the above relationship is not satisfied in the J part, the K part, the N part, and the O part.

  FIG. 11 is a schematic plan view showing the orientation direction at the time of voltage application of the liquid crystal layer central molecule 13m in the J portion of FIG. 9A. In this figure, the orientation direction of the center molecule 13m of the liquid crystal layer when a voltage is applied at that position is shown in the direction of the arrow.

  In the J portion, the angle formed by the extending direction of the display unit edge (the extending direction of the edge of the segment transparent electrode 11B, the arrangement direction of the opening 21) and the alignment direction of the liquid crystal layer center molecule 13m when no voltage is applied. Is about 25 °. For this reason, the above-described condition that the dark region does not occur in the opening edge region (concave region) (the angle between the long edge of the opening and the orientation direction of the liquid crystal layer center molecule 13m when no voltage is applied is greater than 45 °. (Relationship of less than 135 °) is not satisfied.

  As shown in FIG. 11, in the J portion, the orientation direction of the liquid crystal layer center molecule 13m at the convex range edge of the display portion (the edge constituted by the edge of the segment transparent electrode 11B) and the center of the liquid crystal layer when no voltage is applied. The angle formed by the orientation direction of the molecule 13m is about 115 °. Further, the angle formed by the orientation direction of the liquid crystal layer center molecule 13m at the concave edge of the display portion (the edge formed by the long edge of the opening 21) and the orientation direction of the liquid crystal layer center molecule 13m when no voltage is applied. Is about 65 °. Further, the liquid crystal layer central molecules 13m on the short side of the opening constituting the edge of the display portion are oriented in the direction parallel to the long side of the opening toward the inside of the opening. Therefore, in both the convex range and the concave range, the orientation direction of the liquid crystal layer central molecule 13m is between the outer edge and the central part (part away from the edge) of the display unit displaying the diagonal line of “A”. A position parallel to the absorption axis direction of the front or back polarizing plate appears. It is considered that a dark region as shown in this figure is formed at this position and its periphery.

  Even in the J portion where the dark region is generated in both the convex range and the concave range, the generation pattern is regular and stable as shown in FIG. 9A. As a result of the present inventors' study, when the distance S between the adjacent openings 21 is 0.1 mm or less, the shape of the dark region appearing in each range of the convex range and the concave range becomes substantially equal, and the dark region The irregularity of the pattern is eliminated, and the degree of light leakage at the edge of the display portion is made uniform. As a result, it was found that a uniform display state can be obtained in appearance.

  As shown in FIGS. 2A and 2B, a liquid crystal display element having an electrode structure without an opening (conventional liquid crystal display elements shown in FIGS. 12A to 12D) also has J The dark areas of the part, the K part, the N part, and the O part are generated relatively uniformly as compared with that of the I part. However, like the L portion in FIG. 9A, the dark region shape may be partially disturbed due to the influence of the peripheral spherical gap material or dust. Arranging openings in the J, K, N, and O portions is also very effective as a countermeasure.

  A part of a position where two dark regions are formed in the vicinity (position where the angle between the orientation direction when the voltage is applied to the liquid crystal layer center molecule 13m and the orientation direction when no voltage is applied is 135 ° or more) or Display quality can be remarkably improved by providing openings in all of them. Further, a position where one dark region is formed in the vicinity (position where the angle between the orientation direction when the voltage of the liquid crystal layer central molecule 13m is applied and the orientation direction when no voltage is applied is 45 ° or more and less than 135 °. The display quality can be improved by providing an opening in part or all of ().

  Further, P part shown in FIG. 9 (A) is a display in which the orientation direction of the liquid crystal layer center molecule 13m by the oblique electric field at the time of voltage application and the orientation direction of the liquid crystal layer center molecule 13m at the time of no electric field application are substantially coincident. Part edge. When the angle formed by the two orientation directions is less than 45 °, no dark region is observed at the edge of the display unit. Therefore, it is considered that it is not necessary to provide an opening in the display portion edge under this condition. However, even if an opening is provided at a part or all of the position where the angle between the orientation direction when the voltage is applied to the center molecule 13m of the liquid crystal layer and the orientation direction when no voltage is applied is less than 45 °, the opening is provided. An alignment state in which a dark region is generated in the vicinity of the edge where the portion exists is obtained, and if the distance S between the adjacent openings 21 is 0.1 mm or less, the display uniformity in appearance is particularly deteriorated. In some cases, for example, the display quality can be improved from the viewpoint of the balance of the entire display unit. For this reason, when viewed from the normal direction of the substrates 11 and 12, it is also possible to employ a configuration in which openings are arranged at all display portion edges.

  In these cases, the openings 20 and 21 are such that the edge (contour line) of the display unit is the edge of the segment transparent electrode 11B and the edge of the opening 21 formed in the common transparent electrode 12B, and the common transparent electrode. What is necessary is just to be provided so that it may be comprised using the edge of 12B and the edge of the opening part 20 formed in the segment transparent electrode 11B.

    Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto.

  For example, in the embodiment, the alignment treatment is performed on both the vertical alignment films 11c and 12c. However, for example, the alignment treatment may be performed on only one of them. Further, alignment treatment or addition of a chiral material may be performed so that the liquid crystal molecules of the liquid crystal layer 13 are twisted.

  It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like are possible.

  For example, it can be suitably used for a vertical alignment type liquid crystal display element having a segment display portion, for example, an in-vehicle information display device or a consumer information display device.

11 Front side substrate 11a Front side glass substrate 11b, 11b ', 11B Segment transparent electrode 11c Front side vertical alignment film 12 Back side substrate 12a Back side glass substrate 12b, 12b', 12B Common transparent electrode 12c Back side vertical alignment film 13 Vertical alignment liquid crystal layer 13m Liquid crystal layer Central molecule 14 Spacer 15 Sealing portion 16 Front side viewing angle compensation plate 17 Back side viewing angle compensation plate 18 Front side polarizing plate 19 Back side polarizing plate 20, 21 Opening

Claims (9)

A first substrate on which a first electrode is formed;
A second substrate on which a second electrode is formed, wherein the second substrate is disposed substantially parallel to the first substrate so that the second electrode faces the first electrode; ,
A vertically aligned liquid crystal layer disposed between the first substrate and the second substrate;
A first polarizing plate disposed on the opposite side of the first substrate from the liquid crystal layer;
On the opposite side of the second substrate from the liquid crystal layer, the first polarizing plate and a second polarizing plate disposed substantially in crossed Nicols,
The first and second polarizing plates are positioned at the center in the thickness direction of the liquid crystal layer when the voltage is not applied between the first electrode and the second electrode. It is arranged to form an angle of about 45 ° with the orientation direction of the liquid crystal molecules,
The first portion of the outline of the display portion formed by overlapping the first electrode and the second electrode with respect to the normal direction of the first and second substrates is an edge of the first electrode And an edge of an opening formed in the second electrode,
In the first portion, when there is no opening, the liquid crystal molecule located in the center in the thickness direction of the liquid crystal layer applies a voltage between the first electrode and the second electrode. A liquid crystal display element in which an angle formed by an orientation when applied and an orientation when not applied with a voltage is 135 ° or more.   In the contour line of the display portion, when there is no opening, the liquid crystal molecule located at the center in the thickness direction of the liquid crystal layer generates a voltage between the first electrode and the second electrode. All of the portions where the angle formed between the azimuth oriented when applied and the azimuth oriented when no voltage is applied are 135 ° or more were formed on the edge of the first electrode and the second electrode. The liquid crystal display element according to claim 1, wherein the liquid crystal display element is configured using an edge of the opening and at least one of an edge of the second electrode and an edge of the opening formed in the first electrode. And a second portion of the contour line of the display unit, which includes an edge of one of the first and second electrodes and an edge of an opening formed in the other electrode,
In the second portion, when there is no opening, the liquid crystal molecule located at the center in the thickness direction of the liquid crystal layer applies a voltage between the first electrode and the second electrode. 3. The liquid crystal display element according to claim 1, wherein an angle formed between an orientation when applied and an orientation when no voltage is applied is 45 ° or more and less than 135 °.   In the contour line of the display portion, when there is no opening, the liquid crystal molecule located at the center in the thickness direction of the liquid crystal layer generates a voltage between the first electrode and the second electrode. All of the portions where the angle formed between the azimuth oriented when applied and the azimuth oriented when no voltage is applied are not less than 45 ° and less than 135 ° are formed on the edge of the first electrode and the second electrode. 4. The liquid crystal display element according to claim 3, wherein the liquid crystal display element is configured by using an edge of the formed opening and at least one of an edge of the second electrode and an edge of the opening formed in the first electrode. . And a third portion of the contour line of the display unit, which is constituted by an edge of one of the first and second electrodes and an edge of an opening formed in the other electrode,
In the third portion, when there is no opening, the liquid crystal molecule located at the center in the thickness direction of the liquid crystal layer applies a voltage between the first electrode and the second electrode. The liquid crystal display element according to any one of claims 1 to 4, wherein an angle formed by an orientation that is aligned when applied and an orientation that is aligned when no voltage is applied is less than 45 °.   In the contour line of the display portion, when there is no opening, the liquid crystal molecule located at the center in the thickness direction of the liquid crystal layer generates a voltage between the first electrode and the second electrode. All of the portions where the angle formed by the orientation oriented when applied and the orientation oriented when no voltage is applied are less than 45 ° were formed on the edge of the first electrode and the second electrode. The liquid crystal display element according to claim 5, wherein the liquid crystal display element is configured using an edge of the opening and at least one of an edge of the second electrode and an edge of the opening formed in the first electrode.   When viewed from the normal direction of the first and second substrates, the openings are arranged along the edges of the opposing electrodes at intervals of 0.1 mm or less. 2. A liquid crystal display element according to item 1.   The liquid crystal display element according to claim 1, wherein the opening has a shape corresponding to a line shape of an edge of an opposing electrode.   The liquid crystal display element according to claim 8, wherein the opening has a rectangular shape.