JP2011197112A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve multi-domain orientation in pixels to achieve orientation uniformity and a high aperture ratio.SOLUTION: A liquid crystal display device includes a first electrode 2 and a second electrode 5 disposed oppositely and intersected mutually and a liquid crystal layer of vertical orientation, which is provided between the first electrode and the second electrode. An intersection region 11 where the first electrode and the second electrode are mutually overlapped is composed in a substantially rectangular shape. The first electrode has a plurality of substantially V-shaped first openings 21 linearly and symmetrically arranged by sandwiching a virtual reference line m along a first direction in the intersection region. The second electrode has a plurality of substantially V-shaped second openings 22 linearly and symmetrically arranged by sandwiching the reference line in the intersection region. Each first opening and each second opening have a part arranged to be inclined at about 45 degrees to the reference line and a part arranged to be inclined at about -45 degrees to the reference line, and are alternately arranged without being overlapped along a first direction in a planar view.

Description

  The present invention relates to a liquid crystal display device operated by simple matrix driving.

  As an information display device, a display device having a very low display brightness of a background display portion or a dark display portion is required, and a vertical alignment type liquid crystal display device is known as one that can realize this. The vertical alignment type liquid crystal display device has almost the same optical characteristics when viewed from the front in the initial alignment state as that of the polarizing plate in the crossed Nicols arrangement, so the transmittance in the initial alignment state can be very low. It becomes.

  In the vertical alignment type liquid crystal display device as described above, in order to obtain good viewing angle characteristics even when a voltage is applied, the alignment direction of liquid crystal molecules is divided into a plurality of directions within one pixel (multi-domain alignment). Is effective, and various techniques have been proposed to realize this. For example, in Japanese Patent No. 2507122 (Patent Document 1), a strip electrode is provided on each of the upper and lower substrates, and the strip electrode on the upper substrate and the strip electrode on the lower substrate are arranged so as to intersect each other. In a dot matrix type liquid crystal display device in which the intersection of each pixel is one pixel, an electrode structure for realizing the multi-domain alignment is disclosed. Japanese Patent No. 4107978 (Patent Document 2) discloses an electrode structure that realizes the above multi-domain alignment in a segment display type liquid crystal display device. In this liquid crystal display device, each of the vertically arranged upper and lower electrodes is provided with an elongated rectangular opening, and the upper and lower electrodes are arranged so that the openings of the upper electrode and the openings of the lower electrode are arranged alternately in a plan view. Is arranged. Thereby, since an oblique electric field can be generated around each opening, the alignment direction of the liquid crystal molecules can be rotated 180 ° with the opening as a boundary.

  There is also a known example in which rectangular openings are provided obliquely with respect to the upper and lower electrodes of the liquid crystal display device with reference to the horizontal or vertical direction of the visual field in the display area. For example, an example of realizing two-domain alignment is disclosed in Japanese Patent Application Laid-Open No. 2007-187826 (Patent Document 3), and an example of realizing four-domain alignment is disclosed in Japanese Patent Application Laid-Open No. 2007-256300 (Patent Document 4) and This is disclosed in Japanese Unexamined Patent Application Publication No. 2008-129050 (Patent Document 5). The methods shown in these documents are particularly effective for a segment display type liquid crystal display device having an arbitrary electrode shape.

  In addition, in an active matrix liquid crystal display device in which each pixel is provided with a TFT (thin film transistor) element, an electrode structure for realizing the above multi-domain alignment is disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-188242 (Patent Document 6). ing. However, a specific example for realizing multi-domain alignment is not shown for a dot matrix type liquid crystal display device using a simple matrix driving method. Therefore, there is a demand for a technology that can realize multi-domain alignment and can achieve alignment uniformity and a high aperture ratio in the liquid crystal display device.

Japanese Patent No. 2507122 Japanese Patent No. 4107978 JP 2007-187826 A JP 2007-256300 A JP 2008-129050 A JP 2001-188242 A

  A specific embodiment according to the present invention is a technology that can realize multi-domain alignment in a pixel and also achieve alignment uniformity and a high aperture ratio in a dot matrix type liquid crystal display device using a simple matrix driving method. One of the purposes is to provide it.

  A liquid crystal display device according to an aspect of the present invention is a liquid crystal display device that is driven in a simple matrix, and includes: (a) a first substrate and a second substrate that are disposed so as to face each other; and (b). A strip-shaped first electrode provided on one side of the first substrate and extending in the first direction; and (c) a second electrode provided on the one side of the second substrate and substantially orthogonal to the first direction. A band-shaped second electrode extending in the direction, and (d) liquid crystal molecules provided between the one surface side of the first substrate and the one surface side of the second substrate, and having negative dielectric anisotropy And (e) a crossing region in which the first electrode and the second electrode overlap each other is substantially rectangular, and (f) the first electrode is in the crossing region. A plurality of substantially V-shaped first openings arranged symmetrically with respect to a virtual reference line along the first direction, and (g) second The pole has a plurality of substantially V-shaped second openings arranged symmetrically with respect to the reference line in the intersection region, and (h) the plurality of first openings and the plurality of second openings. Each of the two openings is a portion disposed in the first region with an inclination of approximately 45 ° with respect to the reference line, and a portion disposed with an inclination of approximately −45 ° with respect to the reference line in the second region. (I) A liquid crystal display device in which a plurality of first openings and a plurality of second openings are alternately arranged along the first direction without overlapping in plan view.

  A liquid crystal display device according to another aspect of the present invention is a liquid crystal display device that is driven in a simple matrix, and includes (a) a first substrate and a second substrate that are disposed so as to face each other, and (b) ) Provided on one surface side of the first substrate and extending in the first direction; and (c) provided on the one surface side of the second substrate and substantially perpendicular to the first direction. A zigzag-shaped second electrode extending in two directions and intermittently arranged along the second direction and having an inner angle of approximately 90 °, and (d) one surface side of the first substrate; A liquid crystal layer that is provided between one surface side of the second substrate and includes liquid crystal molecules having negative dielectric anisotropy and is vertically aligned, and (e) a first electrode and a first electrode The intersecting region where the two electrodes overlap each other is substantially V-shaped, and (f) the first electrode is a temporary region along the first direction in the intersecting region. A plurality of substantially V-shaped first openings arranged symmetrically with respect to a common reference line, and (g) the second electrode is a line across the reference line in the intersection region. A plurality of substantially V-shaped second openings arranged symmetrically; and (h) the plurality of first openings and the plurality of second openings are each about 45 ° with respect to the reference line. A portion disposed in the first region by tilting and a portion disposed in the second region by tilting by approximately −45 ° with respect to the reference line, and (i) a plurality of first openings and a plurality of second openings. This is a liquid crystal display device in which the portions are alternately arranged along the first direction without overlapping in plan view.

  According to any one of the above liquid crystal display devices, in a dot matrix type liquid crystal display device using a simple matrix driving method, 4-domain alignment control indicating four alignment directions is realized with each opening as a boundary in a pixel. In addition, alignment uniformity and a high aperture ratio can be realized.

It is the external appearance schematic diagram and partial enlarged view of the liquid crystal display device of one Embodiment. It is a fragmentary sectional view of the liquid crystal display device shown in FIG. It is a top view which shows the upper side electrode and lower side electrode of 1st Example, and the some opening part provided in them. It is a figure which shows the microscope observation image of the pixel part of the liquid crystal display device of 1st Example. It is the figure which showed typically the orientation direction of the liquid crystal molecule near each dark area with the arrow. It is a top view which shows the upper side electrode and lower side electrode of 2nd Example, and the some opening part provided in them. It is a figure which shows the microscope observation image of the pixel part of the liquid crystal display device of 2nd Example. It is the top view which expanded the upper electrode and lower electrode of the liquid crystal display device of 3rd Example partially. It is a top view which shows the upper side electrode of 3rd Example, a lower side electrode, and the some opening part provided in them. It is a figure which shows the microscope observation image of the pixel part of the liquid crystal display device of 3rd Example. It is the top view which expanded the upper electrode and lower electrode of 4th Example partially. It is a top view which shows one of the pixel parts which are the cross | intersection parts of the upper electrode and lower electrode of 4th Example.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic external view and a partially enlarged view of a liquid crystal display device according to an embodiment. FIG. 2 is a partial cross-sectional view taken along the line a-a ′ of the liquid crystal display device shown in FIG. 1. The liquid crystal display device of this embodiment shown in each figure includes an upper substrate (first substrate) 1, a plurality of upper electrodes (first electrodes) 2, an alignment film 3, a lower substrate (second substrate) 4, and a plurality of lower substrates. It includes a side electrode (second electrode) 5, an alignment film 6, a liquid crystal layer 7, an upper polarizing plate (first polarizing plate) 8, and a lower polarizing plate (second polarizing plate) 9.

  The upper substrate 1 and the lower substrate 4 are transparent substrates such as a glass substrate and a plastic substrate, respectively. Between the upper substrate 1 and the lower substrate 4, spacers (granular bodies) are dispersed and arranged. By these spacers, the gap between the upper substrate 1 and the lower substrate 4 is kept at a predetermined distance (for example, about 4.0 μm).

  The plurality of upper electrodes 2 are provided on one surface of the upper substrate 1. Each upper electrode 2 is formed in a strip shape (stripe shape), and extends in one direction on one surface of the upper substrate 1. In the present embodiment, each upper electrode 2 extends in the vertical direction (first direction) in FIG. Each upper electrode 2 is configured by appropriately patterning a transparent conductive film such as indium tin oxide (ITO), for example. Although not shown in FIGS. 1 and 2 for convenience, each upper electrode 2 has a rectangular opening at its edge portion. This will be described in detail later.

  The plurality of lower electrodes 5 are provided on one surface of the lower substrate 4. Each lower electrode 5 is formed in a belt shape and extends in one direction on one surface of the lower substrate 4. In the present embodiment, each lower electrode 5 extends in the left-right direction (second direction) in FIG. Each lower electrode 5 is configured by appropriately patterning a transparent conductive film such as indium tin oxide (ITO), for example.

  As shown in the partially enlarged view of FIG. 1, in the liquid crystal display device of the present embodiment, each of the portions (intersection regions) where the upper electrode 2 and the lower electrode 5 overlap in plan view is the pixel unit 11. In FIG. 1, only one pixel portion 11 is shown colored. In the present embodiment, the widths of the upper electrode 2 and the lower electrode 5 are equal to each other, for example, set to 0.42 mm. Accordingly, the pixel unit 11 in the present embodiment has a square shape of 0.42 mm square. Further, the distance between two adjacent upper electrodes 2 is set to 0.03 mm, for example. Similarly, the distance between two adjacent lower electrodes 5 is set to 0.03 mm, for example.

  The alignment film 3 is provided on one surface side of the upper substrate 1 so as to cover each upper electrode 2. Similarly, the alignment film 6 is provided on one surface side of the lower substrate 4 so as to cover each lower electrode 5. In the present embodiment, as the alignment film 3 and the alignment film 6, a film (vertical alignment film) that restricts the alignment state of the liquid crystal layer 3 in the initial state (when no voltage is applied) to the vertical alignment state is used.

  The liquid crystal layer 7 is provided between each upper electrode 2 of the upper substrate 1 and each lower electrode 5 of the lower substrate 4. In the present embodiment, the liquid crystal layer 7 is configured using a liquid crystal material (nematic liquid crystal material) having a negative dielectric anisotropy Δε (Δε <0). A thick line 10 illustrated in the liquid crystal layer 7 schematically shows an alignment direction (director) of liquid crystal molecules when a voltage is applied. In the liquid crystal display device of the present embodiment, the alignment state of the liquid crystal molecules in the liquid crystal layer 7 is vertical alignment in the initial state (no voltage applied state), and the alignment state of the liquid crystal molecules so as to intersect the electric field direction by voltage application. Changes.

  The upper polarizing plate 8 is disposed outside the upper substrate 1. The lower polarizing plate 9 is disposed outside the lower substrate 4. The upper polarizing plate 8 and the lower polarizing plate 9 are, for example, in a crossed Nicols arrangement. As shown in FIG. 1, in this embodiment, the absorption axis of the upper polarizing plate 8 is set in the 3 o'clock to 9 o'clock direction (extending direction of the lower electrode 5), and the absorption axis of the lower polarizing plate 9 is the upper polarization. It is set in a direction substantially orthogonal to the absorption axis of the plate 8.

  Next, an example of a manufacturing method of the liquid crystal display device will be described in detail.

First, a substrate having a transparent electrode on one surface is prepared. As the substrate, for example, a glass substrate in which one surface is polished, SiO ₂ is coated on the surface, and a transparent conductive film made of ITO (indium tin oxide) is formed thereon can be used. The plate thickness of the glass substrate is, for example, 0.7 mm, and the sheet resistance is, for example, 30Ω □.

  A known photolithography process and etching process are performed on the substrate. For example, a positive photoresist is applied to the substrate with a roll coater or the like. Thereafter, using a photomask having a desired pattern formed of a chromium metal film or the like, the photoresist surface and the metal film surface of the photomask are brought into close contact with each other, and then the photoresist pattern is baked by irradiating ultraviolet rays. Thereafter, the photoresist is baked under a predetermined condition (for example, 120 ° C. for 10 minutes), and wet development is performed with a predetermined solution (for example, KOH aqueous solution), thereby removing the resist irradiated with the ultraviolet rays. Thereafter, the resist pattern strength is improved by baking under predetermined conditions (for example, 120 ° C. for 30 minutes), and the ITO film is etched using a predetermined solution (for example, a mixed aqueous solution of hydrochloric acid and sulfuric acid at 40 ° C.). . Finally, the resist is removed using a predetermined solution (for example, NaOH aqueous solution). Thereby, an upper substrate 1 having each upper electrode 2 and a lower substrate 4 having each lower electrode 5 are formed.

  Next, the alignment film 3 is formed on one surface of the upper substrate 1, and the alignment film 6 is formed on one surface of the lower substrate 4. Specifically, after each substrate is washed with an alkali solution or the like, the material liquid of the vertical alignment film is applied onto one surface of each substrate by a method such as flexographic printing, and these are baked in a clean oven (for example, , 180 ° C., 30 minutes).

  Next, spacers having a particle diameter of, for example, about 4 μm are dispersed on one substrate (for example, one surface of the upper substrate 1). The spacer is sprayed by, for example, a dry spraying method. Further, a sealing material is formed on the other substrate (for example, on one surface of the lower substrate 4). The sealing material is formed by applying a mixture of silica spacers having a particle size of about 4.2 μm by a method such as screen printing.

  Next, the upper substrate 1 and the lower substrate 4 are bonded together so that their one surfaces face each other and the alignment treatment directions for the alignment films 3 and 6 are antiparallel, and fired in a constant pressure state. To do. Thereby, the sealing material is cured, and the upper substrate 1 and the lower substrate 4 are fixed (an empty cell is completed). The upper substrate 1 and the lower substrate 4 are arranged so that the upper electrode 2 and the lower electrode 5 intersect (see FIG. 1).

  Next, a liquid crystal material (with a dielectric anisotropy Δε <0) is injected into the gap between the upper substrate 1 and the lower substrate 4 by a method such as vacuum injection, and the injection port used for the injection is sealed. Later, firing is performed (for example, 120 ° C., 1 hour). Thereby, the liquid crystal layer 7 is formed.

  Thereafter, the empty cell is appropriately washed and dried, and the upper polarizing plate 8 is bonded to the outside of the upper substrate 1, and the lower polarizing plate 9 is bonded to the outer side of the lower substrate 4. As described above, each of the upper polarizing plate 8 and the lower polarizing plate 9 has an angle of approximately 45 ° with respect to the alignment direction of the liquid crystal molecules at the center of the liquid crystal layer 7 and is mutually crossed Nicol. Placed in. Thus, the liquid crystal display device shown in FIGS. 1 and 2 is completed.

  The basic structure of the liquid crystal display device of the present embodiment is as described above. Next, several examples in which the structures of a plurality of openings provided in each of the upper electrode 2 and the lower electrode 5 are different will be described.

(First embodiment)
As a first embodiment, a liquid crystal display element that generates an oblique electric field using a plurality of openings and thereby controls the alignment direction of liquid crystal molecules will be described. First, the operation principle will be described based on the cross-sectional view of the liquid crystal display device shown in FIG. As shown in FIG. 2, each of the upper electrode 2 and the lower electrode 5 has a plurality of openings arranged at regular intervals. In these openings, the openings of the upper electrode 2 and the openings of the lower electrode 5 are alternately arranged. In this case, when a voltage equal to or higher than the threshold voltage of the liquid crystal layer 7 is applied between the upper electrode 2 and the lower electrode 5, an oblique electric field is generated in the vicinity of each opening as shown by the dotted line in the figure. Since the liquid crystal molecules of the liquid crystal layer 7 are re-orientated in the vicinity of each opening so as to be orthogonal to the oblique electric field, multi-domain alignment control with a different orientation direction by 180 ° is possible with each opening as a boundary.

  FIG. 3 is a plan view showing the upper electrode 2 and the lower electrode 5 and a plurality of openings provided in them. Specifically, FIG. 3A is a plan view showing one of the pixel portions 11 which is an intersection region (intersection) of the upper electrode 2 and the lower electrode 5, and FIG. FIG. 3C is a partial plan view of the lower electrode 5.

  First, the pixel unit 11 will be described with reference to FIG. The pixel unit 11 is provided in an intersecting region between the upper electrode 2 and the lower electrode 5 and has two regions adjacent to each other with a virtual reference line m interposed therebetween as illustrated. For convenience, the area on the right side of the drawing with the reference line m interposed therebetween is called “first area”, and the area on the left side of the figure is called “second area”. In the illustrated example, the reference line m is set so as to pass through the center of the pixel unit 11.

  As shown in FIG. 3B, the upper electrode 2 has a plurality of first openings 21 arranged along the first direction. Each of the first openings 21 has a first inclined portion 21a arranged with the longitudinal direction inclined 45 ° clockwise relative to the reference line m, and a longitudinal direction 45 ° counterclockwise with respect to the reference line m ( In other words, the second inclined portion 21b is disposed so as to be inclined. As shown in the figure, the first inclined portion 21a and the second inclined portion 21b are arranged symmetrically with respect to the reference line m as an axis of symmetry and are connected to each other, and have a substantially V shape with an apex angle of about 90 ° as a whole. A first opening 21 having a shape is formed.

  Further, in order to electrically connect the portions of the upper electrode 2 that are spaced across the first openings 21, the first openings 21 are intermittently arranged in the longitudinal direction of the first inclined portion 21a. A plurality of joint portions 25 and a plurality of joint portions 26 arranged intermittently in the longitudinal direction of the second inclined portion 21b (only one joint portion 25, 26 is given a reference in the figure). . These joint portions 25 and 26 are preferably arranged at a constant period (interval). By arranging many joint portions 25 and 26, it is possible to suppress an increase in resistance of the upper electrode 2. However, it is not preferable to arrange too many of these joint portions 25 and 26 because there is a concern of inducing an orientation failure described later. In the first embodiment, the joint portions 25 and 26 are arranged at intervals of approximately 0.1 mm.

  As shown in FIG. 3B, the lower electrode 5 has a plurality of second openings 22 arranged along the first direction. Each of the second openings 22 includes a first inclined portion 22a disposed with a longitudinal direction inclined 45 ° clockwise with respect to the reference line m, and a longitudinal direction 45 ° counterclockwise with respect to the reference line m ( That is, the second inclined portion 22b is disposed to be inclined. As shown in the drawing, the first inclined portion 22a and the second inclined portion 22b are arranged symmetrically with respect to the reference line m as the symmetry axis, and are connected to each other, and have a substantially V-shaped apex angle of about 90 ° as a whole. The shape 2nd opening part 22 is comprised.

  In addition, in order to electrically connect the portions of the lower electrode 5 that are spaced across the second openings 22, the second openings 22 are intermittently formed in the longitudinal direction of the first inclined portion 22a. A plurality of joint portions 27 arranged and a plurality of joint portions 28 arranged intermittently in the longitudinal direction of the second inclined portion 22b (in the figure, only one joint portion 27, 28 is given a reference numeral). ). These joint portions 27 and 28 are preferably arranged at a constant period (interval). By disposing a large number of joint portions 27 and 28, it is possible to suppress an increase in resistance of the lower electrode 5. However, since there is a concern of inducing an orientation failure described later, it is not preferable to arrange too many of these joint portions 27 and 28. In the first embodiment, the joint portions 27 and 28 are arranged at intervals of approximately 0.1 mm.

  As shown in FIG. 3A, the first openings 21 and the second openings 22 in the pixel unit 11 do not overlap each other and are alternately arranged in the first direction. . Specifically, in the first region (right region in the drawing) of the pixel unit 11, the first inclined part 21 a of each first opening 21 and the first inclined part 22 a of each second opening 22 overlap each other. They are alternately arranged. Further, in the second region (left region in the drawing) of the pixel portion 11, the second inclined portions 21 b of the first openings 21 and the second inclined portions 22 b of the second openings 22 are alternately not overlapped with each other. Are arranged. According to such an electrode structure, the alignment direction of the liquid crystal molecules is controlled so that the alignment directions are different by 90 ° with the apex angle of each of the first opening 21 and the second opening 22 each having a V shape. Therefore, it is possible to realize 4-domain alignment control indicating four alignment directions with each first opening 21 and each second opening 22 as a boundary.

  FIG. 4 is a view showing a microscope observation image of the pixel portion 11 of the actually manufactured liquid crystal display device. Specifically, FIG. 4A is an observation image of the pixel unit 11 observed in an empty cell state before the liquid crystal layer 7 is formed. It can be confirmed that the first opening 21, the second opening 22, and the joint portions 25 to 28 equivalent to those described in FIG. 3 are formed. FIG. 4B is an observation image of the pixel portion 11 observed after the liquid crystal layer 7 is formed. Here, the liquid crystal layer 7 was formed using a liquid crystal material having a refractive index anisotropy Δn = 0.15 and a dielectric anisotropy Δε <0. The setting of the absorption axes of the upper polarizing plate 8 and the lower polarizing plate 9 is as described above. Further, a voltage equal to or higher than the threshold voltage of the liquid crystal layer 7 was applied to the pixel portion 11. The dimensions of each part of the pixel unit 11 are as shown in the figure, and the unit is “mm”. The length (width) S in the short direction of each opening is 0.007 mm, and the distance between the first opening 21 and the second opening 22 adjacent to each other (planar edge distance) A in plan view is It was set to 0.03 mm.

  As shown in FIG. 4B, a uniform alignment domain is formed in most of the first opening 21 and the second opening 22 that are adjacent in a plan view. It has occurred. More specifically, dark regions are observed in the vicinity of the top, bottom, left, and right edges of the pixel unit 11 every other domain between the openings. A dark region is also observed at the alignment domain boundary portion in the vicinity of the substantially V-shaped apex angle (that is, in the vicinity of the reference line m) at the center of the pixel portion 11 of each first opening portion 21 and each second opening portion 22. In these dark regions, due to the influence of the edge of the pixel portion 11 and the domain boundary, the alignment direction of the central liquid crystal molecules in the layer thickness direction of the liquid crystal layer 7 is in the vicinity of the substantially V-shaped apex angle of each first opening 21 and the like. This is considered to be caused by deviation from the original orientation direction due to the generated oblique electric field (because rotation of the orientation direction occurred). FIG. 5 is a diagram schematically showing the alignment direction of the liquid crystal molecules in the vicinity of each dark region with arrows. When the direction of the arrow in the figure is in the direction of 45 ° with each absorption axis of the upper polarizing plate 8 and the lower polarizing plate 9, the dark region is the upper polarizing plate 8 and the lower polarized light. It is considered that the rotation occurred in the alignment direction of the liquid crystal molecules in the center of the liquid crystal layer 7 in the direction close to each absorption axis or transmission axis of the plate 9.

  In addition, dark regions are observed around the joint portions 25 to 28, and regions where the transmittance is slightly reduced are also observed between the adjacent joint portions. In addition, there is also a tendency that each of the joint portions 25 to 28 promotes the alignment failure even with respect to the alignment failure occurring at the boundary portion of the alignment domain near the apex angle of the substantially V shape at the center of the pixel portion 11 described above. In order to suppress the alignment failure caused by the joint portions 25 to 28, the distance between adjacent joint portions is set to the length (width) of each first opening portion 21 and each second opening portion 22 in the short direction. ) Is effective.

(Second embodiment)
As a second embodiment, a liquid crystal display device in which a new opening is added to each of the upper electrode 2 and the lower electrode 5 in order to suppress the above-described poor alignment with respect to the liquid crystal display device of the first embodiment described above. Will be explained. In the following, differences from the liquid crystal display device of the first embodiment will be mainly described, and description of common points will be omitted.

  FIG. 6 is a plan view showing the upper electrode 2 and the lower electrode 5 and a plurality of openings provided in them. Specifically, FIG. 6A is a plan view showing one of the pixel portions 11 that is an intersection of the upper electrode 2 and the lower electrode 5, and FIG. 6B is a partial plan view of the upper electrode 2. FIG. 6C is a partial plan view of the lower electrode 5.

  As shown in FIG. 6A, the pixel unit 11 according to the second embodiment is provided in an intersecting region of the upper electrode 2 and the lower electrode 5, and is adjacent to each other with the reference line m interposed therebetween as illustrated. It has two areas. As in the first embodiment, the area on the right side of the drawing with respect to the reference line m is referred to as “first area”, and the area on the left side in the figure is referred to as “second area”. In the illustrated example, the reference line m is set so as to pass through the center of the pixel unit 11. The first openings 21 and the second openings 22 are provided in the same manner as in the first embodiment.

  As shown in FIGS. 6A and 6B, the upper electrode 2 includes a plurality of third openings 33 provided in the vicinity of the upper and lower edges in the plan view of the pixel unit 11 and the reference line m. A plurality of fourth openings 34 provided in an overlapping manner. Each third opening 33 is formed in a rectangular shape that is long in one direction, and is arranged near the upper edge or the lower edge of the pixel unit 11. In the present embodiment, as shown in the figure, each third opening 33 is connected (coupled) to one adjacent first opening 21. Each of the fourth openings 34 is formed in a rectangular shape that is long in one direction, and is disposed along the first direction (the extending direction of the upper electrode 2). In the present embodiment, as shown in the drawing, each of the fourth openings 34 is connected to (coupled to) the outer corner of the substantially V-shaped apex portion of any of the first openings 21.

  6A and 6C, the lower electrode 5 includes a plurality of fifth openings 35 provided in the vicinity of the left and right edges in the plan view of the pixel unit 11, and a reference. A plurality of sixth openings 36 provided to overlap the line m. Each fifth opening 35 is formed in a rectangular shape that is long in one direction, and is arranged in the vicinity of the left edge or right edge of the pixel unit 11. Each of the sixth openings 36 is formed in a rectangular shape that is long in one direction, and is disposed along the first direction (the extending direction of the upper electrode 2). In the present embodiment, as shown in the drawing, each of the sixth openings 36 is interconnected with (connected to) the outer corner of the apex corner of the substantially V-shaped opening of any second opening 22. )

  As shown in FIG. 6A described above, the first openings 21 and the second openings 22 do not overlap each other in the pixel unit 11 and are alternately arranged along the first direction. . The fourth openings 34 and the sixth openings 36 are arranged alternately along the first direction. Even with such an electrode structure, the alignment direction of the liquid crystal molecules can be controlled so that the alignment direction differs by 90 ° with respect to the reference line m. Domain orientation control can be realized. Further, by providing the third openings 33 and the fourth openings 34, the vicinity of the upper and lower edges and the left and right edges of the pixel portion 11 and the vicinity of the reference line m (near the boundary between the first area and the second area) ) Can be suppressed and display uniformity can be improved.

  FIG. 7 is a diagram showing a microscope observation image of the pixel portion 11 of the actually manufactured liquid crystal display device. Specifically, FIG. 7A is an observation image of the pixel unit 11 observed in an empty cell state before the liquid crystal layer 7 is formed. It can be confirmed that an opening and a joint portion equivalent to those described in FIG. 6 described above are formed. FIG. 7B is an observation image of the pixel portion 11 observed after the liquid crystal layer 7 is formed. The conditions of the liquid crystal display device are the same as in the first embodiment. Compared with the first embodiment, in the liquid crystal display device of the second embodiment, the vicinity of the left and right edges of the pixel portion 11 provided with each opening and the top of the V-shaped opening are provided in order to suppress alignment defects. It can be seen that the dark region in the alignment domain boundary region near the corner is remarkably improved. It is clear that these improvements have improved relative transmission. On the other hand, there are regions where alignment uniformity is still insufficient near the upper and lower edges of the pixel portion 11.

(Third embodiment)
As a third embodiment, a liquid crystal display device in which the structure of the lower electrode in the liquid crystal display device of the first embodiment or the second embodiment described above is changed will be described. In the following, differences from the liquid crystal display device of the first embodiment or the second embodiment will be mainly described, and description of common points will be omitted.

  FIG. 8 is a partially enlarged plan view of the upper electrode and the lower electrode. As shown in the partially enlarged view of FIG. 8, in the liquid crystal display device of the third embodiment, each of the portions (intersection regions) where the upper electrode 2 and the lower electrode 5a overlap in plan view is the pixel portion 11a. In FIG. 8, only one pixel portion 11a is colored.

  The upper electrode 2 is formed in a strip shape (strip shape) extending in one direction as described above. On the other hand, the lower electrode 5a is formed in a zigzag belt shape having periodic flexibility. Specifically, in the lower electrode 5a, the internal angle of the apex angle that exists periodically is approximately 90 °, and these apex angles are approximately 45 with respect to the extending direction (second direction) of the lower electrode 5a. It is defined by a side in the ° direction and a side of approximately −45 °. Each upper electrode 2 is arranged such that it overlaps with one apex angle of each lower electrode 5 a and another apex angle adjacent to this apex angle overlaps with the gap between each upper electrode 2. Thereby, as shown in the figure, the pixel portion 11a of the present embodiment is substantially V-shaped.

  FIG. 9 is a plan view showing the upper electrode 2 and the lower electrode 5a and a plurality of openings provided in them. Specifically, FIG. 9A is a plan view showing one of the pixel portions 11a that is an intersection region of the upper electrode 2 and the lower electrode 5a, and FIG. 9B is a partial plan view of the upper electrode 2. FIG. 9C is a partial plan view of the lower electrode 5a.

  As shown in FIG. 9A, the pixel portion 11a according to the third embodiment is provided in an intersecting region of the upper electrode 2 and the lower electrode 5a, and is adjacent to each other with the reference line m interposed therebetween as shown. It has two areas. Similar to the first embodiment and the like, the area on the right side of the drawing with the reference line m interposed therebetween is called “first area”, and the area on the left side of the drawing is called “second area”. In the illustrated example, the reference line m is set so as to pass through the center of the pixel unit 11.

  As shown in FIGS. 9A and 9B, the upper electrode 2 has a plurality of first openings 21 and a plurality of fourth openings 34. The details of these openings are the same as in the second embodiment. 9A and 9C, the lower electrode 5a has a plurality of second openings 42, a plurality of fifth openings 35, and a plurality of sixth openings 36. The details of these openings are basically the same as those of the second embodiment. As illustrated, each second opening 42 includes a first inclined portion 42a and a second inclined portion 42b that do not have a joint portion.

  In the present embodiment, since the pixel portion 11a is substantially V-shaped, each first opening portion 21 and each second opening portion 42 disposed therein is substantially omitted with respect to the upper and lower edges of the pixel portion 11a. They can be arranged in parallel. Thereby, the plurality of third openings 33 provided at the upper and lower edges of the pixel portion 11 in order to suppress alignment defects in the second embodiment can be omitted. Further, since there is no fear of disconnection or high resistance for each second opening 42, the joint portions 27 and 28 provided in the first and second embodiments can be omitted.

  FIG. 10 is a diagram showing a microscope observation image of the pixel portion 11a of the actually manufactured liquid crystal display device. Specifically, FIG. 10A is an observation image of the pixel portion 11a observed in an empty cell state before the liquid crystal layer 7 is formed. It can be confirmed that an opening and a joint portion equivalent to those described in FIG. 9 described above are formed. FIG. 10B is an observation image of the pixel portion 11a observed after the liquid crystal layer 7 is formed. Various conditions of the liquid crystal display device are the same as those in the first embodiment. No alignment failure is observed in the vicinity of the top, bottom, left, and right edges of the pixel portion 11a, and since the lower electrode 5a does not have a joint portion as described above, the orientation failure due to the joint portion is improved. I understand. In addition, since the joint portion in the upper electrode 2 cannot be omitted, there is an alignment defect in the periphery of the upper electrode 2, but the joint portion can be omitted in the lower electrode 5a. Therefore, the entire pixel portion 11a has a gap between the joint portions. The distance increases. As a result, it was confirmed that the dark region between the adjacent joint portions, which was observed in the first embodiment and the second embodiment, did not occur. As described above, according to the third embodiment, alignment defects caused by the vertical and horizontal edges of the pixel portion 11a, the alignment domain boundary region and the joint portions in the vicinity of the apex angle of the substantially V-shaped opening are suppressed, It was found that the alignment uniformity was improved and the aperture ratio was increased.

(Fourth embodiment)
As a fourth embodiment, a liquid crystal display device in which the structure of the upper electrode in the liquid crystal display device of the third embodiment described above is changed will be described. In the following, differences from the liquid crystal display device of the third embodiment will be mainly described, and description of common points will be omitted.

  FIG. 11 is a partially enlarged plan view of the upper electrode and the lower electrode. As shown in the partial enlarged view of FIG. 11, in the liquid crystal display device of the fourth embodiment, each of the portions (intersection regions) where the upper electrode 2b and the lower electrode 5b overlap in plan view is the pixel portion 11b. In FIG. 11, only one pixel portion 11b is colored. As shown in the drawing, the pixel portion 11b has a rectangular shape whose long side is inclined at approximately 45 ° as shown in the drawing.

  Both the upper electrode 2b and the lower electrode 5b are formed in a zigzag belt shape having periodic flexibility. More specifically, the upper electrode 2b has an apex angle that is periodically present at approximately 90 °, and these apex angles are approximately −45 ° with respect to the extending direction of the upper electrode 2b. It is defined by a 45 ° side. The same applies to the lower electrode 5b.

  FIG. 12 is a plan view showing one of the pixel portions 11b that is an intersection of the upper electrode 2b and the lower electrode 5b. In the illustrated example, each of the reference lines m and n passes through one of two opposing vertices of the pixel portion 11b and is in a direction of 45 ° with the long and short sides of the pixel portion 11b (in the vertical direction in the figure). ) Is set.

  As illustrated, the upper electrode 2 b includes a plurality of first openings 21 and a plurality of fourth openings 34. Among these, the first openings 21 on the right side in the figure are arranged in line symmetry with the reference line m as the axis of symmetry, as in the third embodiment. The first openings 21 on the left side in the figure are arranged symmetrically with respect to the reference line n as the axis of symmetry, and the first openings on the right side in the figure are arranged upside down. Yes. Each first opening 21 is provided with joint portions 25 and 26. The upper electrode 2b has a plurality of seventh openings 47 provided in the vicinity of the upper right edge and lower left edge of the pixel portion 11b. Each seventh opening 47 is disposed so as to straddle the edge of the pixel portion 11b.

  Further, as illustrated, the lower electrode 5 b has a plurality of second openings 42 and a plurality of sixth openings 36. The details of these openings are the same as in the third embodiment. Among these, the second openings 42 on the right side in the figure are arranged in line symmetry with the reference line m as the axis of symmetry, as in the third embodiment. Further, the second openings 42 on the left side in the drawing are arranged symmetrically with respect to the reference line n as the axis of symmetry, and the second openings on the right side in the drawing are arranged upside down. Yes. Each second opening 42 is not provided with a joint portion.

  In the present embodiment, the pixel portion 11b has an obliquely arranged rectangular shape, whereby each first opening portion 21 and each second opening portion 42 disposed therein are connected to each edge (long side and short side) of the pixel portion 11b. Can be arranged substantially parallel to the side. Thereby, the plurality of third openings 33 provided at the upper and lower edges of the pixel portion 11 in order to suppress alignment defects in the second embodiment can be omitted. Further, since there is no concern about disconnection or high resistance for each second opening 42, the joint portion can be omitted as in the third embodiment. Further, by providing the seventh openings 47 in the portion of the edge of the pixel portion 11b where the edge of the lower electrode 5b is disposed, alignment failure near the edge of the pixel portion 11b can be suppressed. On the other hand, an opening for suppressing alignment failure is not necessary in the portion where the edge of the upper electrode 2b is disposed. Therefore, it can be considered that higher resistance of the lower electrode 5b can be further suppressed as compared with the third embodiment.

  In addition, this invention is not limited to the content of embodiment mentioned above, In the range of the summary of this invention, it can change and implement variously. For example, in the above description, the apex angle of each substantially V-shaped opening is arranged downward or upward in one pixel portion, but this is not restrictive. It is obvious that the same operation is possible even when the apex angle is right or left by rotating these arrangement patterns by 90 °.

  DESCRIPTION OF SYMBOLS 1 ... Upper substrate (1st substrate) 2, 2b ... Several upper electrode (1st electrode) 3 ... Alignment film 4 ... Lower substrate (2nd substrate) 5, 5a, 5b ... Lower electrode (2nd electrode) DESCRIPTION OF SYMBOLS 6 ... Alignment film 7 ... Liquid crystal layer 8 ... Upper polarizing plate (1st polarizing plate) 9 ... Lower polarizing plate (2nd polarizing plate) 11, 11a, 11b ... Pixel part 21 ... 1st opening part 22, 42 ... 1st 2 opening 25, 26, 27, 28 ... joint part 33 ... 3rd opening 34 ... 4th opening 35 ... 5th opening 36 ... 6th opening 47 ... 7th opening

Claims (4)

A liquid crystal display device driven by a simple matrix,
A first substrate and a second substrate disposed so as to face each other on one side;
A band-shaped first electrode provided on one surface side of the first substrate and extending in a first direction;
A belt-like second electrode provided on one surface side of the second substrate and extending in a second direction substantially orthogonal to the first direction;
A liquid crystal layer that is provided between the one surface side of the first substrate and the one surface side of the second substrate, contains liquid crystal molecules having negative dielectric anisotropy, and is vertically aligned;
Including
The intersecting region where the first electrode and the second electrode overlap each other is substantially rectangular,
The first electrode has a plurality of substantially V-shaped first openings arranged symmetrically with respect to a virtual reference line along the first direction in the intersection region,
The second electrode has a plurality of substantially V-shaped second openings arranged symmetrically with respect to the reference line in the intersection region,
The plurality of first openings and the plurality of second openings are each inclined by approximately 45 ° with respect to the reference line and disposed in the first region, and approximately −45 with respect to the reference line. Having a portion disposed in the second region at an angle;
The plurality of first openings and the plurality of second openings are alternately arranged along the first direction without overlapping in plan view.
Liquid crystal display device. The first electrode has a plurality of joint portions that connect adjacent portions across either of the plurality of first openings.
2. The liquid crystal display device according to claim 1, wherein the second electrode has a plurality of joint portions that connect adjacent portions across one of the plurality of second openings. A liquid crystal display device driven by a simple matrix,
A first substrate and a second substrate disposed so as to face each other on one side;
A band-shaped first electrode provided on one surface side of the first substrate and extending in a first direction;
The inner angle of the apex angle provided on one surface side of the second substrate, extending in a second direction substantially orthogonal to the first direction, and intermittently disposed along the second direction is approximately 90. A zigzag strip-like second electrode of °,
A liquid crystal layer that is provided between the one surface side of the first substrate and the one surface side of the second substrate, contains liquid crystal molecules having negative dielectric anisotropy, and is vertically aligned;
Including
The intersection region where the first electrode and the second electrode overlap each other is substantially V-shaped,
The first electrode has a plurality of substantially V-shaped first openings arranged symmetrically with respect to a virtual reference line along the first direction in the intersection region,
The second electrode has a plurality of substantially V-shaped second openings arranged symmetrically with respect to the reference line in the intersection region,
The plurality of first openings and the plurality of second openings are each inclined by approximately 45 ° with respect to the reference line and disposed in the first region, and approximately −45 with respect to the reference line. Having a portion disposed in the second region at an angle;
The plurality of first openings and the plurality of second openings are alternately arranged along the first direction without overlapping in plan view.
Liquid crystal display device.   4. The liquid crystal display device according to claim 3, wherein the first electrode has a plurality of joint portions that connect adjacent portions across any one of the plurality of first openings.