JP5511457B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device having a plurality of openings (slits) in an electrode.

  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, Japanese Patent No. 4107978 (Patent Document 1) 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.

  In addition, in a liquid crystal display device of a type in which a large number of rectangular openings are provided, Japanese Unexamined Patent Application Publication No. 2007-187826 (Patent Document 2) discloses a structure that emphasizes viewing angle characteristics in the vertical and horizontal directions. Patent Document 2 shows that the viewing angle characteristics of the background can be remarkably improved by setting the transmission axis of the upper and lower polarizing plates of the liquid crystal display device in the vertical direction or the horizontal direction.

  By the way, according to the study of the present inventor, in the liquid crystal display device of the type disclosed in Patent Document 2, for example, the retardation Δnd of the liquid crystal layer (Δn is the refractive index anisotropy of the liquid crystal material and d is the thickness of the liquid crystal layer). When set to about 320 nm and operated at a driving voltage higher than the maximum voltage under a ¼ duty multiplex driving condition, the background display portion and the portion to which the off voltage is applied are obliquely When observed, it turned out that the difference of the transmittance | permeability of each part is remarkable. This is due to the oblique electric field generated in the vicinity of the rectangular opening provided on the electrode, which induces realignment of the liquid crystal molecules near the edge of the opening, and the tilt of the liquid crystal molecules compared to the region away from the opening. It is thought that the angle is different. Due to this phenomenon, particularly in the segment display type liquid crystal display device having a relatively large area of the background display portion (non-display portion) or in the liquid crystal display device in which the segment display type and the dot matrix type are mixed, the display quality is remarkably lowered. There are concerns.

Japanese Patent No. 4107978 JP 2007-187826 A

  A specific aspect of the present invention is to improve display quality in a liquid crystal display device in which a plurality of openings are provided in an electrode.

A liquid crystal display device according to one aspect of the present invention is a multiplex-driven liquid crystal display device, in which (a) a first substrate having a first electrode on one surface, and (b) a second electrode on one surface. A second substrate having, (c) a liquid crystal layer provided between the first electrode of the first substrate and the second electrode of the second substrate, and (d) a second layer disposed on the other surface side of the first substrate. And (e) a second polarizing plate disposed on the other surface side of the second substrate, and (f) the first electrode has a plurality of first openings regularly arranged in a checkered pattern. (G) the second electrode has a plurality of second openings that are regularly arranged in a checkered pattern and alternately arranged in two directions in a plan view with the plurality of first openings. , disposed at an angle of 3 0 ° ± 5 ° with respect to the left-right direction at the time of viewing by (h) a plurality of first openings and a plurality of second openings, each of the longitudinal direction the user Is, (i) the first polarizing plate, the optical axis is to the left and right direction when viewing by the user at an angle of 1 5 ° ± 5 °, and a plurality of first openings and a plurality of second openings The second polarizing plate is a liquid crystal display device that is disposed at an angle of approximately 45 ° with respect to the longitudinal direction of each of the portions, and whose optical axis is disposed in a direction substantially orthogonal to the optical axis of the first polarizing plate. is there. Here , the “ optical axis” is a transmission axis or an absorption axis.

A liquid crystal display device according to another aspect of the present invention is a multiplex-driven liquid crystal display device, wherein (a) a first substrate having a first electrode on one surface, and (b) a second electrode on one surface. (C) a liquid crystal layer provided between the first electrode of the first substrate and the second electrode of the second substrate, and (d) disposed on the other surface side of the first substrate. A first polarizing plate, and (e) a second polarizing plate disposed on the other surface side of the second substrate, and (f) the first electrode is a plurality of first electrodes regularly arranged in a matrix. (G) the second electrode has a plurality of second openings that are regularly arranged in a matrix and are alternately arranged in one direction in a plan view with the plurality of first openings. and, (h) a plurality of first openings and a plurality of second openings, the corners of the 3 0 ° ± 5 ° in each longitudinal direction with respect to the left-right direction when viewing by the user Are arranged in a time, (i) the first polarizing plate, the optical axis at an angle of 1 5 ° ± 5 ° with respect to the left-right direction when viewing by the user, and plurality of first openings and of The second polarizing plate is disposed at an angle of approximately 45 ° with respect to the longitudinal direction of each of the plurality of second openings, and the second polarizing plate is disposed in a direction in which the optical axis thereof is substantially orthogonal to the optical axis of the first polarizing plate. A liquid crystal display device. Here , the “ optical axis” is a transmission axis or an absorption axis.

  Conventionally, the optical axis of polarized light is often set to a direction of 0 °, 90 °, + 45 °, or −45 ° with respect to a reference direction (for example, the horizontal direction of the liquid crystal display device). It was rarely set (except for specific cases such as STN type liquid crystal display devices). Also, the opening was set in the direction according to the above. On the other hand, the inventor of the present application diligently studied and found that by arranging each opening and each polarizing plate under the above-described conditions, the viewing angle characteristics in the reference direction can be remarkably improved, thereby improving the display quality. The inventors have arrived at the present invention. Details thereof will be described later.

  In the liquid crystal display device described above, the plurality of first openings and the plurality of second openings may each have an outer edge in the longitudinal direction and an outer edge in the short direction intersecting each other at an angle.

  Further, in the liquid crystal display device described above, when the retardation of the liquid crystal layer is Δnd, the thickness direction retardation generated by the elements other than the liquid crystal layer existing between the polarizing layers of the first polarizing plate and the second polarizing plate. The total is also preferably expressed as (Δnd-30) ± 120 nm.

It is the external appearance schematic diagram and partial enlarged view of the liquid crystal display device of one Embodiment. It is the fragmentary sectional view in the II-II 'line | wire of the liquid crystal display device shown in FIG. It is the schematic diagram which showed a part of each 1st opening part at the time of observing from the upper side substrate side, and each 2nd opening part planarly. It is the schematic diagram which showed a part of each 1st opening part at the time of observing from the upper side substrate side, and each 2nd opening part planarly. FIG. 5 is a schematic plan view for explaining an electrode structure in a case where the lengths in the longitudinal direction of the openings are not equal in one pixel portion. FIG. 6 is a diagram showing an image obtained by actually manufacturing a liquid crystal display device having each opening having the structure shown in FIG. 5 and observing one pixel portion with a reflection microscope. It is a figure for demonstrating the aspect which changed the shape of each opening part. 1 is a schematic exploded perspective view of a liquid crystal display device of Example 1. FIG. It is a figure which shows the iso-contrast curve by the time of the on-voltage application at the time of setting to the drive voltage which can obtain substantially maximum contrast, and the time of an off-voltage application. FIG. 3 is a diagram illustrating viewing angle characteristics of the liquid crystal display device of Example 1. FIG. 6 is a schematic exploded perspective view of a liquid crystal display device of Example 2. It is a figure which shows the iso-contrast curve by the time of the on-voltage application at the time of setting to the drive voltage which can obtain substantially maximum contrast, and the time of an off-voltage application. FIG. 6 is a diagram illustrating viewing angle characteristics of the liquid crystal display device of Example 2.

  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 II-II ′ of the liquid crystal display device shown in FIG. 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.

  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. That is, the liquid crystal display device of the present embodiment is a dot matrix type liquid crystal display device in which the pixel unit 11 is arranged in two directions of the row direction and the column direction. In FIG. 1, only one pixel portion 11 is colored. In the present embodiment, the widths of the upper electrode 2 and the lower electrode 5 are equal, for example, set to 0.45 mm. Accordingly, the pixel unit 11 in the present embodiment has a square shape of 0.45 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 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 3.8 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.

  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.

  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 refractive index anisotropy Δn of 0.15 and a dielectric anisotropy Δε of negative (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. 2, the upper electrode 2 has a plurality of first openings (slits) 21 having a shape extending in one direction. Each first opening 21 is formed by partially removing the upper electrode 2. Similarly, the lower electrode 5 has a plurality of second openings (slits) 22 having a shape extending in one direction. Each second opening 22 is formed by partially removing the lower electrode 5. By adopting such an electrode structure, each first opening 21 and each second opening 22 acts as an orientation control element, so that each first opening 21 and each second opening 22 are adjacent to the boundary. Thus, a state in which the alignment directions of the liquid crystal layer 7 in the two regions are different (multi-domain alignment) is obtained. As shown in FIG. 2, 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.

  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 with an ITO transparent conductive film having a size of 300 mm × 200 mm, a thickness of 0.7 mm, and a sheet resistance of 30Ω □ can be used. A positive photoresist is applied on one surface of the substrate by a roll coater, and then the photoresist is exposed using a predetermined photomask. As the photomask, a photomask having a predetermined opening pattern formed of a chromium metal film is used. The photomask used here is provided with an opening pattern corresponding to each first opening 21 or each second opening 22.

  After the photomask as described above is brought into close contact with the photoresist surface on the substrate, the opening pattern on the photomask is baked onto the photoresist by irradiating with ultraviolet rays. Next, the photoresist is baked under predetermined conditions (for example, 120 ° C., 10 minutes). The photoresist after baking is subjected to wet development processing using an aqueous KOH solution to remove the portion of the photoresist irradiated with ultraviolet rays. Next, the strength of the resist pattern is improved by further baking the photoresist (for example, 120 ° C. for 30 minutes). The transparent electrode is etched using the resist pattern thus formed as an etching mask. Specifically, for example, wet etching using a mixed aqueous solution of hydrochloric acid and sulfuric acid at 40 ° C. is performed. Finally, the photoresist is completely removed with an aqueous NaOH solution. Thus, the transparent electrode on the substrate is patterned. That is, the upper substrate 1 having a plurality of first openings 21 and the lower substrate 4 having a plurality of second openings 22 are obtained.

  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, the material liquid of the vertical alignment film is pattern-printed on one surface of the upper substrate 1 and one surface of the lower substrate 4, and then baked (for example, 180 ° C. for 30 minutes). Next, a sealing material is formed on one substrate (for example, on one surface of the upper substrate 1). The sealing material is formed, for example, by applying a mixture of silica spacers having a particle size of several μm by a method such as screen printing. A spacer having a particle size of several μm is dispersed on the other substrate (for example, on one surface of the lower substrate 4). The plastic spacer is sprayed by, for example, a dry spraying method. Next, the upper substrate 1 and the lower substrate 4 are bonded to each other so as to face each other, and are fixed by firing in a constant pressure state. Thereafter, 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. for 60 minutes). Thereby, the liquid crystal layer 7 is formed. Thereafter, the first polarizing plate 8 is bonded to the outside of the upper substrate 1, and the second polarizing plate 9 is bonded to the outside of the lower substrate 4. Also, attach a lead frame or the like as appropriate. Thus, the liquid crystal display device is completed.

  Next, the structure of the first opening 21 and the second opening 22 will be described with reference to schematic plan views shown in FIGS. 3 and 4. 3 and 4, a part of each first opening 21 and each second opening 22 when viewed from the upper substrate 1 side is shown in a plan view. In each figure, each first opening 21 is indicated by a solid line, and each second opening 22 is indicated by a dotted line. In the following, the first opening 21 and the second opening 22 may be collectively referred to simply as “opening”. 3 and 4, S is the length of each opening in the short direction (short side length), L is the length of each opening in the longitudinal direction (long side length), and Ls is adjacent in the longitudinal direction. A distance between matching openings (opening interval), and A represents an edge interval between adjacent openings in the short direction.

  In the liquid crystal display device shown in FIG. 3, the first openings 21 are formed in a rectangular shape extending in one direction (the x direction shown in the figure), and are regularly arranged in a matrix. Similarly, each of the second openings 22 is formed in a rectangular shape extending in one direction (the x direction shown in the figure), and is regularly arranged in a matrix. The first openings 21 and the second openings 22 are arranged with their longitudinal directions aligned in substantially the same direction (the x direction shown in the figure), and more specifically, the long sides thereof are substantially parallel to each other. Are arranged as follows. Further, the first openings 21 and the second openings 22 are alternately arranged along the y direction. In other words, the first openings 21 and the second openings 22 are arranged so as to be shifted from each other by a half pitch along the y direction. The first openings 21 and the second openings 22 are arranged so as not to overlap each other in plan view. In this example, the longitudinal direction of each opening is arranged at an angle of approximately 30 ° ± 5 ° with respect to the left-right direction (reference direction) of the liquid crystal display device. The reason will be described in detail later.

  In the liquid crystal display device shown in FIG. 4, each first opening 21 is formed in a rectangular shape extending in one direction (the x direction shown in the figure), and is regularly arranged in a checkered pattern in the x direction and the y direction shown in the figure. Are arranged. Similarly, each 2nd opening part 22 is formed in the rectangular shape extended in one direction (x direction of illustration), and is regularly arranged in the checkered pattern in the x direction and y direction of illustration. That is, the first openings 21 and the second openings 22 are arranged with their longitudinal directions aligned in substantially the same direction (the x direction shown in the figure), and more specifically, the long sides of each are substantially parallel. It is arranged to become. In this example, the longitudinal direction of each opening is arranged at an angle of approximately 30 ° ± 5 ° with respect to the left-right direction (reference direction) of the liquid crystal display device. The reason will be described in detail later. In addition, each first opening 21 and each second opening 22 is between each of the two second openings 22 in which each first opening 21 is adjacent to each other in plan view of each second opening 22. It is arranged relatively so that it may be located in. In other words, the first openings 21 and the second openings 22 are both arranged at a predetermined pitch along each of the x direction and the y direction, and are shifted from each other by a half pitch. Accordingly, the distance between the two first openings 21 adjacent in the longitudinal direction and the distance between the two first openings 21 adjacent in the longitudinal direction are both L + Ls × 2, and the arrangement state shown in FIG. Compared with the case where is adopted, the distance between the adjacent openings can be increased.

  In the case of adopting a dot matrix type electrode structure, the length L in the longitudinal direction of each opening in one pixel portion 11 may be set to be not equal. That is, as shown in FIG. 5, when each end of the first opening 21 or the second opening 22 covers the edge of the pixel unit 11, the length L in the longitudinal direction may be shortened. However, it is preferable that the position of the short side where the adjacent opening exists exists substantially on a straight line in the long side direction. In this case, the boundary region of the alignment domain extends in the right upward direction (left downward direction), but the short sides of the openings arranged in this region extend in the left upward direction (right downward direction). It can be seen that they are arranged almost along the existing straight line.

  FIG. 6 is a diagram showing an image obtained by actually manufacturing a liquid crystal display device having each opening portion having the structure shown in FIG. 5 and observing one pixel portion 11 under a microscope. Specifically, FIG. 6A shows an observation image of the pixel portion 11 before the liquid crystal layer 7 is formed, and FIG. 6B shows an observation image of the pixel portion 11 after the liquid crystal layer 7 is formed. As described above, the belt-like upper electrode 2 is provided in the vertical direction of the liquid crystal display device, and the belt-like lower electrode 5 is provided in the left-right direction (see FIG. 1). Then, each opening for realizing a checkered two-domain alignment control rotated approximately 45 ° clockwise with respect to the 9 o'clock direction and approximately 45 ° clockwise with respect to the 3 o'clock direction of the liquid crystal display device is provided on the upper side. The electrode 2 and the lower electrode 5 were provided.

  One illustrated pixel portion 11 is 0.45 mm square, and the interval between adjacent pixel portions 11 is 0.03 mm. The pixel portion 11 is divided into two in the diagonal direction rising to the right in the drawing, and the openings are arranged in a checkered pattern in each of the upper electrode 2 and the lower electrode 5. Regarding the parameters of each opening, S is approximately 0.007 mm, A is approximately 0.03 mm, and Ls is approximately 0.007 mm. About each absorption axis of the upper side polarizing plate 8 and the lower side polarizing plate 9, an optical axis was arrange | positioned at about 45 degrees with respect to the longitudinal direction of each opening part. That is, the lower polarizing plate 9 is arranged in the horizontal direction of the pixel portion 11, and the upper polarizing plate 8 is arranged in the vertical direction of the pixel portion 11. A liquid crystal material having a Δn of 0.15 was used, and the thickness of the liquid crystal layer 7 was approximately 3.8 μm.

  The observation image shown in FIG. 6B is a polarization microscope observation image of the pixel unit 11 when a voltage is applied. As shown in the drawing, it can be seen that the dark region is not observed except in the vicinity of the boundary region of the alignment domain and the edge of the pixel portion 11, and a good alignment state is obtained. It was confirmed by appearance observation that uniform and good two-domain alignment control was realized.

  FIG. 7 is a diagram for explaining an aspect in which the shape of each opening is changed. As shown in FIG. 7, the first openings 21a provided in the upper electrode 2 are formed in a shape extending in one direction and are regularly arranged in a checkered pattern. Each first opening portion 21a has a longitudinal side (outer edge) and a short side (outer edge) obliquely intersecting at an angle other than 90 °, and this point is the first in each embodiment described above. It is different from the opening 21. Moreover, as shown in FIG. 7, each 2nd opening part 22a provided in the lower electrode 5 is formed in the shape extended in one direction, and is regularly arranged in the checkered pattern. Each of the second openings 22a has a longitudinal side (outer edge) and a lateral side (outer edge) obliquely intersecting at an angle other than 90 °, and this point is the second in each embodiment described above. It is different from the opening 22. By adopting such a structure, the boundary region of the alignment domain can be controlled in substantially the same direction as the short side of each opening.

  In the example shown in FIG. 7, the boundary portion of the alignment domain is arranged in the vertical direction. However, the boundary portion of the alignment domain is changed in the left-right direction by rotating the arrangement of each opening 90 ° in the left-right direction. Obviously you can. Furthermore, it is also clear that the extending direction of the boundary part of the alignment domain can be arbitrarily set by changing the angle formed between the outer edge in the short direction and the outer edge in the longitudinal direction of each opening existing in the boundary part of the alignment domain. It is. The boundary part of the alignment domain may be visually recognized, but the boundary part is controlled in the horizontal direction and the vertical direction of the liquid crystal display device, for example, by using the above structure, so that the appearance is not conspicuous. Is possible.

  Next, the relationship between the viewing angle characteristics of the background display portion and the off-voltage application portion and the arrangement of the longitudinal direction of each opening and the optical axis of each polarizing plate will be described in detail with reference to examples. In the following examples, the measurement conditions were a 1/4 duty （bias multiplex drive (frame inversion waveform), and the frame frequency was 250 Hz.

Example 1
As Example 1, a liquid crystal display device having no viewing angle compensation plate was produced. The basic structure of the liquid crystal display device of Example 1 is as described above. FIG. 8 is a schematic exploded perspective view of the liquid crystal display device according to the first embodiment. For convenience of describing the optical elements, in FIG. 8, illustration of each electrode and each alignment film is omitted, and each opening is shown in a simplified manner.

  As shown in FIG. 8, each first opening 21 is provided in the upper substrate 1, and each second opening 22 is provided in the lower substrate 4. The mode of these openings is as shown in FIG. 3 or FIG. An upper polarizing plate 8 and a lower polarizing plate 9 which are arranged in a crossed Nicol manner are bonded to the outer surfaces of the upper substrate 1 and the lower substrate 4, respectively. Further, the longitudinal directions of the first openings 21 and the second openings 22 were aligned in the 45 ° -225 ° direction in the coordinate system shown in FIG. The left-right direction of the liquid crystal display device is a 0 ° -180 ° direction. The liquid crystal material used for the liquid crystal layer 7 has a refractive index anisotropy Δn of about 0.1 and a dielectric anisotropy Δε of about −7, and a predetermined amount of chiral material (0.6 wt% in this example) is added. Has been. A spherical spacer of 2.5 μm is interposed between the upper substrate 1 and the lower substrate 4. Thereby, the layer thickness of the liquid crystal layer 7 is set to about 2.5 μm. In the coordinate system shown in FIG. 8, the absorption axis A1 of the upper polarizing plate 8 is set in the direction of 0 ° -180 °, and the absorption axis A2 of the lower polarizing plate 9 is set in the direction of 90 ° -270 °. . Further, as shown in the drawing, the upper polarizing plate 8 of the present embodiment includes a polarizing substrate (polarizing layer) 8b and base substrates (base layers) 8a and 8c sandwiching the polarizing substrate (polarizing layer) 8b. Similarly, the lower polarizing plate 9 includes a polarizing substrate (polarizing layer) 9b and base substrates (base layers) 9a and 9c sandwiching the polarizing substrate (polarizing layer) 9b. Each polarizing substrate 8b, 9b is formed using, for example, PVA (polyvinyl alcohol). Each base substrate 8a, 8c, 9a, 9c is formed using, for example, TAC (triacetyl cellulose).

  FIG. 9 is a diagram showing an isocontrast curve when an on-voltage is applied and when an off-voltage is applied when the drive voltage (5.3 V in this example) is set to obtain a substantially maximum contrast. The center in FIG. 9 corresponds to when the liquid crystal display device is observed from the normal direction, and the same contrast when the polar angle in each direction is changed radially is connected by a curve. The polar angle is 60 ° at the outermost circumference of the circle. Further, the horizontal direction in FIG. 9 corresponds to the 180 ° and 0 ° directions of the liquid crystal display device. The isocontrast curve shows 50, 100, 150, 200, 250, 300 from the outermost curve, respectively. As shown in FIG. 9, high contrast is maintained even when the polar angle increases in the directions of 0 °, 90 °, 180 °, and 270 ° corresponding to the absorption axes of the upper polarizing plate 8 and the lower polarizing plate 9. Thus, it can be seen that good left-right and up-down direction viewing angle characteristics are obtained. However, in this graph, the difference in viewing angle characteristics between the voltage non-application region, that is, the background display portion and the off-voltage application portion is unknown. Therefore, the viewing angle characteristics in five directions A-A ′, BB, C-C ′, D-D ′, and E-E ′ shown in FIG. 9 were measured. This will be described next.

  FIG. 10 is a diagram illustrating viewing angle characteristics of the liquid crystal display device according to the first embodiment. In each figure, the light-colored characteristic line shown on the upper side shows the observation (polar angle) angle dependence of the transmittance at the on-voltage, and the dark-colored characteristic line shown on the upper side shows the on-voltage and off-voltage. The transmittance ratio, that is, contrast is shown. In each figure, the light-colored characteristic line shown on the lower side shows the observation (polar angle) angle dependence of the transmittance of the background display part, and the dark-colored characteristic line shows the transmittance of the off-voltage applied part. (Polar angle) It shows angle dependency.

  FIG. 10A shows the viewing angle characteristic in the A-A ′ direction shown in FIG. 9. Since the direction is parallel to the absorption axis of the upper polarizing plate 8, the background transmittance is very low, and the dependence on the observation angle is small. However, the transmittance at the off voltage is almost equal to the background transmittance at the front, but the difference from the background transmittance tends to increase as the observation angle increases. Since the background transmittance was originally low, the difference in transmittance was visible from the external appearance at polar angles of ± 30 ° or more.

  FIG. 10B shows the viewing angle characteristics in the BB ′ direction parallel to the short direction of each opening, and FIG. 10C shows the CC ′ direction parallel to the longitudinal direction of each opening. The viewing angle characteristic is shown. Since the angle is 45 ° with respect to the respective absorption axes of the upper polarizing plate 8 and the lower polarizing plate 9, the viewing angle characteristics of the background display portion are significantly deteriorated compared to the AA ′ direction shown in FIG. . For example, it was confirmed that the transmittance reaches about 3.5% at a polar angle of ± 60 °. However, with regard to the viewing angle characteristics when the off voltage is applied, a viewing angle characteristic substantially equivalent to that of the background display portion is obtained although light leakage is large. In particular, in FIG. 10C, which is a viewing angle characteristic in the longitudinal direction of each opening, a difference in transmittance between the background display portion and the off-voltage application portion is hardly observed. When the appearance was actually observed, the difference between the background transmittance and the transmittance at the off voltage was in an unrecognizable level in both the B-B 'direction and the C-C' direction.

  Here, in the isocontrast curve shown in FIG. 9, the portion where the polar angle is the largest in the 300 curve having the highest contrast was examined, and E rotated by 15 ° counterclockwise from the AA ′ direction. -E 'direction was found. Therefore, the viewing angle characteristics in the D-D 'direction and the E-E' direction rotated by ± 15 [deg.] About the A-A 'direction were also examined. The viewing angle characteristic in the D-D ′ direction is shown in FIG. 10D, and the viewing angle characteristic in the E-E ′ direction is shown in FIG. In both cases, the viewing angle characteristics of the background transmittance are the same, but the viewing angle characteristics when an off voltage is applied are different. Specifically, the EE ′ direction is superior in viewing angle characteristics compared to the DD ′ direction, and the background viewing angle characteristics and viewing angle characteristics when an off voltage is applied are substantially equal in the EE ′ direction. I found out that Further, from the appearance observation, the difference between the background transmittance and the off-voltage transmittance in the EE ′ direction is not recognized, and the viewing angle characteristics shown in FIG. 10B and FIG. Compared with the deeper viewing angle, the transmittance was clearly lower, and the viewing angle characteristics were improved. In addition, since the two-domain orientation control is performed well in any direction, the left-right symmetry at the time of bright display is excellent, and it is almost symmetrical from FIGS. 10 (a) to 10 (e). it is obvious.

(Example 2)
As Example 2, a liquid crystal display device having a viewing angle compensation plate was produced. The basic structure of the liquid crystal display device of Example 2 is as described above. FIG. 11 is a schematic exploded perspective view of the liquid crystal display device according to the second embodiment. For convenience of describing the optical elements, in FIG. 11, illustration of each electrode and each alignment film is omitted, and each opening is simply illustrated. The liquid crystal display device of Example 2 basically has the same configuration as the liquid crystal display device of Example 1, and there is a difference in the structure of the lower polarizing plate 9. Specifically, the lower polarizing plate 9 of the present embodiment is provided with a viewing angle compensation plate 9d having negative biaxial optical anisotropy in the vicinity of the polarizing substrate 9b. In this embodiment, the viewing angle compensation plate 9 d is integrated with the lower polarizing plate 9. The liquid crystal material used for the liquid crystal layer 7 of this example has a refractive index anisotropy Δn of about 0.1 and a dielectric anisotropy Δε of about −7. A spherical spacer of 3.0 μm is interposed between the upper substrate 1 and the lower substrate 4. Thereby, the layer thickness of the liquid crystal layer 7 is set to about 3.0 μm. In the coordinate system shown in FIG. 11, the absorption axis A1 of the upper polarizing plate 8 is set in the direction of 0 ° -180 °, and the absorption axis A2 of the lower polarizing plate 9 is set in the direction of 90 ° -270 °. . The viewing angle compensation plate 9d adjacent to the polarizing substrate 9b of the lower polarizing plate 9 has an in-plane retardation Re of 55 nm and a thickness direction retardation Rth of 220 nm.

  FIG. 12 is a diagram showing isocontrast curves when an on-voltage is applied and when an off-voltage is applied when the drive voltage (5.2 V in this example) is set so as to obtain a maximum contrast. The center in FIG. 12 corresponds to when the liquid crystal display device is observed from the normal direction, and the same contrast when the polar angle in each direction is changed radially is connected by a curve. The polar angle is 60 ° at the outermost circumference of the circle. Further, the horizontal direction in FIG. 12 corresponds to the 180 ° and 0 ° directions of the liquid crystal display device. The isocontrast curve shows 50, 100, 150, 200, 250, 300 from the outermost curve, respectively. Compared with Example 1 that does not have a viewing angle compensator, the liquid crystal display device of Example 2 has significantly improved background viewing angle characteristics other than directions parallel to the absorption axes of the upper polarizing plate 8 and the lower polarizing plate 9, and polarized light. It can be seen that the viewing angle characteristics including the plate absorption axis are remarkably improved. As in the case of Example 1, the viewing angle characteristics in five directions A-A ′, B-B ′, C-C ′, D-D ′, and E-E ′ shown in FIG. 12 were measured. This will be described next.

  FIG. 13 is a diagram illustrating viewing angle characteristics of the liquid crystal display device according to the second embodiment. Also in FIG. 13, the light-colored characteristic line shown on the upper side shows the observation (polar angle) angle dependency of the transmittance at the on-voltage, and the dark-colored characteristic line shown on the upper side shows the on-voltage and off-state characteristics. The transmittance ratio at voltage, that is, contrast is shown. In each figure, the light-colored characteristic line shown on the lower side shows the observation (polar angle) angle dependence of the transmittance of the background display part, and the dark-colored characteristic line shows the transmittance of the off-voltage applied part. (Polar angle) It shows angle dependency.

  FIG. 13A shows the viewing angle characteristic in the A-A ′ direction shown in FIG. 12. Similar to the case of Example 1 (see FIG. 10A), the background transmittance shows a very low value, and the dependence on the observation angle is small. Also regarding the transmittance at the time of applying the off-voltage, the dependence on the observation angle is smaller than in the case of the first embodiment. However, there is still a difference between the background transmittance and the transmittance when the off-voltage is applied, and the difference was recognizable at the polar angle of ± 30 ° or more from the appearance observation.

  FIG. 13B shows viewing angle characteristics in the BB ′ direction parallel to the short direction of each opening, and FIG. 13C shows the CC ′ direction parallel to the longitudinal direction of each opening. The viewing angle characteristic is shown. Since the angle is 45 ° with respect to the respective absorption axes of the upper polarizing plate 8 and the lower polarizing plate 9, the viewing angle characteristics of the background display portion are significantly deteriorated compared to the AA ′ direction shown in FIG. However, compared with the liquid crystal display device of Example 1 in which the transmittance at a polar angle of ± 60 ° was about 3.5%, the increase in the transmittance at a deep observation angle is significantly suppressed by the effect of the viewing angle compensation plate 9d. ing. However, the viewing angle dependence of the background transmittance in the BB 'direction parallel to the short direction of each opening and the transmittance at the off voltage is clearly different, and the difference can be clearly recognized in appearance. there were. On the other hand, in the C-C ′ direction parallel to the longitudinal direction of each opening, it was found that the difference between the background transmittance and the transmittance at the off voltage was very small.

  FIG. 10D and FIG. 10E are diagrams showing viewing angle characteristics in the D-D ′ direction and the E-E ′ direction rotated ± 15 ° about the A-A ′ direction, respectively. In both cases, it was confirmed that the viewing angle characteristics of the background transmittance and the transmittance at the off voltage were better than those in the B-B ′ direction and the C-C ′ direction. However, regarding the D-D 'direction, the difference in viewing angle characteristics between the background transmittance and the transmittance at the off voltage is significant. On the other hand, regarding the E-E ′ direction, the difference in viewing angle characteristics between the background transmittance and the transmittance at the off voltage was very small, and it was confirmed from the appearance observation results that the transmittance difference was hardly recognized. In the above, the EE ′ direction is set to + 15 ° with respect to the AA ′ direction. However, as a result of further appearance observation, the background transmittance and the transmission at the off voltage are about 15 ° ± 5 °. It was found that the visual angle characteristic difference of the rate is difficult to recognize.

  As a result of the detailed evaluation of the viewing angle characteristics in the two embodiments as described above, the background transmittance and the transmittance at the off-voltage in the direction rotated by 15 ° ± 5 ° counterclockwise from the horizontal direction of the liquid crystal display device. There was almost no difference in viewing angle characteristics, and it was found that a highly symmetrical viewing angle characteristic can be obtained even during on-display. Therefore, if this direction is set as the reference direction, it is considered that a very good viewing angle characteristic can be realized with respect to the reference direction. That is, the openings provided in each of the upper electrode 2 of the upper substrate 1 and the lower electrode 5 of the lower substrate 4 are arranged by rotating their longitudinal directions by 30 ° ± 5 ° with respect to the reference direction. It is preferable. Further, the upper polarizing plate 8 and the lower polarizing plate 9 are arranged by rotating their transmission axes or absorption axes by 15 ° with respect to the horizontal direction of the liquid crystal display device, and with respect to the longitudinal direction of each opening. It is preferable to set to approximately 45 °. Thereby, for example, if the reference direction is set to the left-right direction in the liquid crystal display device, the viewing angle characteristics in the left-right direction can be remarkably improved. The same applies when the reference direction is set to another direction in the liquid crystal display device (for example, the vertical direction).

  If the steepness in the electro-optical characteristics is improved, it is considered that the difference in the viewing angle characteristics between the background transmittance and the transmittance at the off voltage can be eliminated also in the A-A ′ direction in FIGS. 9 and 12. An example of a method for improving the steepness in the electro-optical characteristics is to increase the retardation Δnd of the liquid crystal layer 7. In each of the above examples, Δnd in the case of Example 1 in which no viewing angle compensation plate is used is about 250 nm, and Δnd in Example 2 in which the viewing angle compensation plate is used is about 300 nm. Further, it was confirmed that it was difficult to improve the difference between the viewing angle characteristics of the background transmittance and the transmittance at the off voltage in the A-A ′ direction at about 360 nm which is a large Δnd. Basically, it was confirmed that the display quality in the AA ′ direction can be improved only during static driving, and in the case of multiplex driving, it is confirmed that the display quality is almost good at 1/2 duty 1/2 bias driving. . In addition, it was confirmed that the difference in viewing angle characteristics between the background transmittance and the transmittance at the off voltage is observed more markedly as Δnd increases or as the duty increases.

  In the liquid crystal display device having the structure shown in Example 1 (FIG. 8), elements other than the liquid crystal layer 7 existing between the polarizing substrates of the upper polarizing plate 8 and the lower polarizing plate 9, specifically, Is included in each of the upper polarizing plate 8 and the lower polarizing plate 9, and the total retardation Rth in the thickness direction by the base substrates 8a and 9a existing inside the polarizing substrates 8b and 9b and the Δnd of the liquid crystal layer 7 We also examined the relationship between As a result, it was found that Rth = (Δnd−30) ± 120 nm was good. The same applies to the liquid crystal display device having the structure shown in Example 2 (FIG. 11). The base is included in each of the upper polarizing plate 8 and the lower polarizing plate 9 and exists inside the polarizing base materials 8b and 9b. As for the relationship between the total retardation Rth in the thickness direction by the base material 8a and the viewing angle compensation plate 9d and Δnd of the liquid crystal layer 7, it was found that Rth = (Δnd−30) ± 120 nm was good.

  Further, when the driving conditions were also examined, it was found that the viewing angle characteristics in the left-right direction of the liquid crystal display device can be improved when the duty is 1/3 to 1/32 and 1/3 to 1/6. In particular, Δnd is preferably set to about 250 nm to 370 nm for 1/3 to 1/4 duty, and Δnd is set to about 450 nm to 630 nm for 1/8 to 1/16 duty. In the case of 1/16 to 1/32 duty, Δnd is preferably set to approximately 800 nm to 950 nm.

  In addition, this invention is not limited to the content of embodiment mentioned above and each Example, In the range of the summary of this invention, it can change and implement variously. For example, in the above-described embodiments, the first opening and the second opening are approximately the same size, but the sizes may be different. Further, in the above-described embodiments, the case where the present invention is applied to a dot matrix type liquid crystal display device has been exemplified. However, a segment type liquid crystal display device or a mixed type liquid crystal display of a segment type and a dot matrix type is used. The present invention can also be applied to an apparatus.

  DESCRIPTION OF SYMBOLS 1 ... Upper side substrate (1st board | substrate) 2 ... Upper side electrode (1st electrode) 3 ... Alignment film 4 ... Lower side substrate (2nd board | substrate) 5 ... Lower side electrode (2nd electrode) 6 ... Alignment film 7 ... Liquid crystal layer 8 ... Upper polarizing plate (first polarizing plate) 8a, 8c ... Base substrate (base layer), 8b ... Polarizing substrate (polarizing layer), 9 ... Lower polarizing plate (second polarizing plate) 9a, 9c ... Base Base material (base layer), 9b ... Polarizing base material (polarizing layer), 9d ... Viewing angle compensation plate 11 ... Pixel part 21, 21a ... First opening part 22, 22a ... Second opening part

Claims (4)

A multiplex-driven liquid crystal display device,
A first substrate having a first electrode on one surface;
A second substrate having a second electrode on one surface;
A liquid crystal layer provided between the first electrode of the first substrate and the second electrode of the second substrate;
A first polarizing plate disposed on the other surface side of the first substrate;
A second polarizing plate disposed on the other surface side of the second substrate;
Including
The first electrode has a plurality of first openings regularly arranged in a checkered pattern,
The second electrode has a plurality of second openings that are regularly arranged in a checkered pattern and are alternately arranged in two directions in plan view with the plurality of first openings,
Wherein the plurality of first openings and the plurality of second openings, each of the longitudinal direction are disposed at an angle of 3 0 ° ± 5 ° with respect to the left-right direction when viewing by the user,
Wherein the first polarizing plate, the optical axis at an angle of 1 5 ° ± 5 ° with respect to the left-right direction when viewing by the user, and the first opening of the plurality and the plurality of second openings The second polarizing plate is disposed in a direction substantially perpendicular to the optical axis of the first polarizing plate.
Liquid crystal display device. A multiplex-driven liquid crystal display device,
A first substrate having a first electrode on one surface;
A second substrate having a second electrode on one surface;
A liquid crystal layer provided between the first electrode of the first substrate and the second electrode of the second substrate;
A first polarizing plate disposed on the other surface side of the first substrate;
A second polarizing plate disposed on the other surface side of the second substrate;
Including
The first electrode has a plurality of first openings arranged regularly in a matrix,
The second electrode has a plurality of second openings arranged regularly in a matrix and alternately arranged in one direction with the plurality of first openings in a plan view,
Wherein the plurality of first openings and the plurality of second openings, each of the longitudinal direction are disposed at an angle of 3 0 ° ± 5 ° with respect to the left-right direction when viewing by the user,
Wherein the first polarizing plate, the optical axis at an angle of 1 5 ° ± 5 ° with respect to the left-right direction when viewing by the user, and the first opening of the plurality and the plurality of second openings The second polarizing plate is disposed in a direction substantially perpendicular to the optical axis of the first polarizing plate.
Liquid crystal display device.   3. The liquid crystal display device according to claim 1, wherein in each of the plurality of first openings and the plurality of second openings, an outer edge in a longitudinal direction and an outer edge in a short direction intersect each other at an angle. When the retardation of the liquid crystal layer is Δnd, the sum of the thickness direction retardations caused by elements other than the liquid crystal layer existing between the polarizing layers of the first polarizing plate and the second polarizing plate is (Δnd− 30) The liquid crystal display device according to any one of claims 1 to 3 , which is expressed as ± 120 nm.