JP2009288604A - Liquid crystal display device and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device and an electronic apparatus which are adaptable to polarizing sunglasses in consideration of cost performance. <P>SOLUTION: The liquid crystal display device includes a pair of substrates, a liquid crystal layer interposed between the pair of substrates, pixel electrodes 9 and a common electrode 19 provided on one of the pair of substrates, a plurality of pixels each of which includes a pixel electrode 9 and the common electrode 19, and polarizing elements provided on the pair of substrates. An initial alignment direction of liquid crystal molecules in the liquid crystal layer is set to a direction inclined upward to the right at 15° from a row direction (X-axis direction) of pixels, and transmission axes of the polarizing elements coincide with the initial alignment direction, and each pixel electrode 9 has a plurality of slits 29 crossing the initial alignment direction at a prescribed angle (5°). The liquid crystal layer is driven by an electric field generated between the pixel electrodes 9 and the common electrode 19. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a horizontal electric field mode liquid crystal display device and an electronic apparatus including the same.

  FIG. 17 is a schematic plan view showing a unit pixel of a conventional liquid crystal display device. As shown in FIG. 17, the lateral electric field mode liquid crystal display device includes first and second transparent substrates arranged to face each other through a liquid crystal layer, and a thin film transistor provided in each unit pixel on the first transparent substrate. A fringe field switching mode (FFS) liquid crystal display device 300 having 301, a counter electrode connected to a common signal line 304, and a pixel electrode 305 disposed so as to be insulated from the counter electrode is known. (Patent Document 1).

  The pixel electrode 305 includes a reference slit 306 disposed parallel to the gate bus line 302 at the center of the long side of the pixel, a plurality of upper slits 307 disposed at a predetermined inclination above and below the reference slit 306, and a lower portion. And a slit 308. In the case of positive liquid crystal (liquid crystal having positive dielectric anisotropy), the liquid crystal is aligned in parallel with the gate bus line 302. In the case of a negative liquid crystal (a liquid crystal having negative dielectric anisotropy), the liquid crystal is aligned in parallel with the data bus line 303. The first and second polarizing plates arranged on the outer surface have transmission axes orthogonal to each other, and any one transmission axis is assumed to be the same as the alignment treatment direction.

  According to the liquid crystal display device, when the liquid crystal display device is viewed through the polarized sunglasses, the transmission axis of the polarized sunglasses and the transmission axis of the polarizing plate provided on the front side are orthogonal to each other, and there is a risk that the display cannot be properly viewed. There is.

  As a method for improving such a problem, a method of disposing a retardation plate on the front surface of a front polarizing plate is disclosed (Patent Document 2).

JP 2002-182230 A JP-A-6-258633

  Combining the liquid crystal display device 300 of Patent Document 1 with the retardation plate of Patent Document 2 is not a technical problem for polarizing sunglasses, but causes an increase in cost. In addition, there is a problem of going against the recent market demand for thinner display devices.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A liquid crystal display device according to this application example includes a pair of substrates, a liquid crystal layer sandwiched between the pair of substrates, a first electrode and a second electrode provided on one of the pair of substrates. An electrode; a plurality of pixels each provided with the first electrode and the second electrode; and a polarizing element provided on the pair of substrates, wherein the liquid crystal layer includes the first electrode and the second electrode. Driven by an electric field generated between the electrodes, the initial alignment direction of the liquid crystal molecules in the liquid crystal layer is set at an angle other than parallel or orthogonal to the arrangement direction of the pixels, and the transmission axis of the polarizing element is the initial The first electrode or the second electrode has a plurality of slits that intersect at a predetermined angle with respect to the initial alignment direction.

  According to this configuration, even when the liquid crystal display device is viewed through polarized sunglasses generally having either a horizontal or vertical transmission axis, the transmission axis of the polarizing element provided on the pair of substrates and the transmission of the polarized sunglasses. Since it is not orthogonal to the axis, the display can be confirmed in an appropriate state. In other words, it is not necessary to provide a retardation plate for dealing with polarized sunglasses, and it is possible to provide a thin-type lateral electric field type liquid crystal display device with excellent cost performance. Even in a liquid crystal device having a function of rotating the liquid crystal device by 90 degrees and displaying an image, the transmission axis of the polarizing element provided on the pair of substrates and the transmission axis of the polarized sunglasses are not orthogonal, so that the display is confirmed in an appropriate state. can do.

Application Example 2 In the liquid crystal display device according to the application example described above, it is preferable that the plurality of slits have an inclination angle other than parallel or orthogonal to the arrangement direction of the pixels.
According to this configuration, in addition to the initial alignment direction, the inclination angles of the plurality of slits are set to angles other than parallel or orthogonal to the pixel arrangement direction. Therefore, when the plurality of slits are used as a reference, the angle between the initial alignment direction, that is, the transmission axis of the polarizing element and the pixel arrangement direction becomes larger. Therefore, the angle formed by the transmission axis of the polarized sunglasses and the transmission axis of the polarizing element is increased. Therefore, more effective polarization sunglasses correspondence is realized.

Application Example 3 In the liquid crystal display device according to the application example, it is preferable that the predetermined angle with respect to the initial alignment direction of the slit is 5 degrees to 10 degrees.
The liquid crystal molecules are twisted in the direction in which the angle formed by the initial alignment direction and the electric field direction is smaller. The direction of the electric field generated between the first electrode and the second electrode (electric field direction) is basically generated in a direction perpendicular to the longitudinal direction of the slit.
Therefore, when the predetermined angle of the slit intersecting with the initial alignment direction of the liquid crystal molecules is reduced, one of the angles formed by the initial alignment direction and the electric field direction approaches 90 degrees, that is, the stability in the twist direction is easily lost. . On the other hand, when the predetermined angle increases, one of the angles formed by the initial alignment direction and the electric field direction decreases. Therefore, although the twist direction stability is increased, the twist angle of the liquid crystal molecules is reduced, so that the transmittance of the transmitted light converted into linearly polarized light by the polarizing element is likely to decrease.
According to this configuration, by providing a predetermined angle in the range of 5 degrees to 10 degrees, a liquid crystal display device capable of realizing a polarized display while realizing compatibility with polarized sunglasses and ensuring stability in the twist direction is provided. can do.

Application Example 4 In the liquid crystal display device according to the application example, the first electrode or the second electrode intersects the initial alignment direction at a predetermined angle, and the inclination with respect to the pixel arrangement direction. It is preferable that the liquid crystal layer corresponding to the at least two types of slits is driven so that the liquid crystal molecules are twisted in directions opposite to each other.
According to this configuration, the twist angle of the liquid crystal molecules has a substantially wide twist angle as compared with the case where the twist direction is one direction. Therefore, it is possible to provide a liquid crystal display device which is applied with polarized sunglasses and has a wide viewing angle characteristic.

Application Example 5 In the liquid crystal display device according to the application example described above, it is preferable that the at least two types of the slits have the predetermined angle symmetrical with respect to the initial alignment direction.
According to this configuration, since the twist angles of the liquid crystal molecules twisted in the opposite directions are the same, it is possible to prevent bias in the viewing angle characteristics.

Application Example 6 In the liquid crystal display device according to the application example, the at least two types of the slits include a first slit whose tilt angle is a first angle and a second slit whose tilt angle is a second angle. It is preferable that the slit includes a third slit having a first angle portion and a second angle portion.
When at least two types of slits having different inclination angles are provided, the liquid crystal molecules in the pixel portion sandwiched between the slits having different inclination angles are difficult to twist in any of the electric field directions generated by the slits having different inclination angles. In other words, it becomes difficult to drive the liquid crystal molecules in the pixel portion, and the substantial aperture ratio of the pixel tends to decrease. According to this configuration, by providing the third slit having the first angle portion and the second angle portion, the number of pixel portions where it is difficult to drive the liquid crystal molecules can be reduced. . That is, the aperture ratio of the pixel at the time of driving is substantially improved, and the luminance when illuminated using the illumination device can be improved.

Application Example 7 In the liquid crystal display device according to the application example described above, a boundary portion between the first angle and the second angle in the third slit is set so as to obliquely intersect with the arrangement direction of the pixels. It is preferable that
The boundary portion between the first angle and the second angle in the third slit is a portion where it is difficult to control the twist direction. According to this configuration, since the boundary portion is set so as to obliquely intersect the pixel arrangement direction, the portion in which the twist direction is difficult to control can be continuously recognized in a streak shape between the pixels and easily visible. prevent. That is, display unevenness can be reduced.

Application Example 8 In the liquid crystal display device according to the application example described above, of the at least two types of the slits, the slit having a small inclination angle and / or at least a part of the slit having a small inclination angle are It is preferable that the first electrode or the second electrode is disposed on both ends of the pixel in the column direction.
According to this configuration, by disposing at least a part of the slit having a small inclination angle and / or the portion having the small inclination angle of the slit at both ends in the column direction of the pixels, the change is caused by the change in the electric field direction at the both ends. Generation | occurrence | production of the reverse twist of a liquid crystal molecule can be suppressed. Therefore, it is possible to provide a liquid crystal display device that can suppress a substantial decrease in the aperture ratio of the pixel due to the reverse twist and obtain higher contrast and brightness.

Application Example 9 An electronic apparatus according to this application example includes the liquid crystal display device according to the application example described above.
According to this configuration, it is possible to provide an electronic device that is compatible with polarized sunglasses and that can display properly.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings. In each drawing used for the following description, the scale of each member is appropriately changed to make each member a recognizable size.

<Embodiment 1>
First, the liquid crystal display device of this embodiment will be described with reference to FIGS. FIG. 1 is a schematic view showing a liquid crystal display device. FIG. 4A is a schematic front view, and FIG. 4B is a schematic cross-sectional view taken along the line HH ′ in FIG.

  As shown in FIGS. 1A and 1B, the liquid crystal display device 100 of this embodiment includes an element substrate 10 and a counter substrate 20 as a pair of substrates. The counter substrate 20 is bonded to the element substrate 10 having a size slightly larger at a predetermined position via a sealing material 40.

  A liquid crystal layer 50 is configured by filling a liquid crystal having positive dielectric anisotropy into a gap (gap) between the element substrate 10 and the counter substrate 20 bonded by the sealing material 40. That is, the liquid crystal layer 50 is sandwiched between the element substrate 10 and the counter substrate 20.

  The outside of the sealing material 40 is a peripheral circuit region, and a plurality of mounting terminals 80 for connecting to the data line driving circuit 70 and an external circuit are provided along one side of the element substrate 10. A scanning line driving circuit 90 is provided along each of the other two sides facing each other in the X-axis direction of the element substrate 10. A plurality of wirings 13 for connecting the two scanning line driving circuits 90 are provided along the remaining side of the element substrate 10.

  Inside the sealing material 40, a plurality of pixels are arranged in a matrix in the X-axis direction and the Y-axis direction. One pixel is composed of three sub-pixels corresponding to the three color filters 22R (red), 22G (green), and 22B (blue). The three color filters 22R, 22G, and 22B are formed on the counter substrate 20 side so that the color filters of the same color are continuous in the Y-axis direction. On the element substrate 10 side, a plurality of TFTs (Thin Film Transistors) 30 serving as switching elements for driving and controlling the sub-pixels are provided. That is, the liquid crystal display device 100 is an active display device that includes a stripe-type color filter and enables color display.

  In the present embodiment, a region of a plurality of pixels that actually contributes to display is defined as a display region AR, and a light shielding film 61 that partitions each sub pixel and shields the display region AR in a frame shape is provided. The light shielding area 60 provided with the light shielding film 61 is a guideline for defining the position of the display area AR when the liquid crystal display device 100 is attached to an electronic device.

  Further, polarizing plates 14 and 24 as polarizing elements are attached to the outer surfaces (surfaces opposite to the liquid crystal layer 50) of the element substrate 10 and the counter substrate 20, respectively. Such a liquid crystal display device 100 is illuminated by an illumination device (not shown) using an LED or the like as a light source. A more detailed structure of the liquid crystal display device 100 will be described later.

  FIG. 2 is an equivalent circuit diagram of the liquid crystal display device. As shown in FIG. 2, each sub-pixel SG constituting the display area AR of the liquid crystal display device 100 performs switching control of the pixel electrode 9 as the first electrode, the common electrode 19 as the second electrode, and the pixel electrode 9. And a TFT 30 for the purpose. A liquid crystal layer 50 is interposed between the pixel electrode 9 and the common electrode 19. The common electrode 19 is electrically connected to the common line 3b extending from the scanning line driving circuit 90, and is held at a common potential in each subpixel SG.

  A data line 6 a extending from the data line driving circuit 70 is electrically connected to the source of the TFT 30. The data line driving circuit 70 supplies the image signals S1, S2,..., Sn to each subpixel SG via the data line 6a. The image signals S1 to Sn may be supplied line-sequentially in this order, or may be supplied for each group to a plurality of adjacent data lines 6a.

  Further, the scanning line 3 a extending from the scanning line driving circuit 90 is electrically connected to the gate of the TFT 30. Scan signals G1, G2,..., Gm, which are supplied from the scanning line driving circuit 90 to the scanning line 3a at a predetermined timing, are applied to the gates of the TFTs 30 in this order. The pixel electrode 9 is electrically connected to the drain of the TFT 30.

  The TFT 30 serving as a switching element is turned on for a certain period by the input of the scanning signals G1, G2,..., Gm, so that the image signals S1, S2,. Writing is performed on the pixel electrode 9. Image signals S1, S2,..., Sn of a predetermined level written in the liquid crystal layer 50 via the pixel electrode 9 are held for a certain period between the pixel electrode 9 and the common electrode 19 via the liquid crystal layer 50.

  The liquid crystal display device 100 of the present embodiment employs an FFS (Fringe Field Switching mode) method in which the liquid crystal layer 50 is driven by a lateral electric field generated between the pixel electrode 9 and the common electrode 19. In addition, the pixel structure and the optical design are devised so that the display is not visually recognized or difficult to visually recognize when the liquid crystal display device 100 is viewed through polarized sunglasses. Hereinafter, an example is given and demonstrated.

Example 1
3 is a schematic plan view showing the structure of the pixel of Example 1, and FIG. 4 is a schematic cross-sectional view showing the structure of the pixel taken along the line AA ′ of FIG.

As shown in FIG. 3, one pixel of the liquid crystal display device 100 includes three sub-pixels SG corresponding to three color (R, G, B) color filters 22R, 22G, 22B. Each sub-pixel SG is provided with a rectangular pixel electrode 9 in which a plurality of slits (gap) 29 are formed in a substantially ladder shape. That is, the shape of the subpixel SG is rectangular.
The plurality of pixels are arranged (arranged) in a matrix so that the longitudinal direction of the sub-pixels SG is the pixel column direction.
A scanning line 3a, a common line 3b, and a plurality of data lines 6a are arranged so as to surround the outer periphery of the pixel electrode 9.
A TFT 30 is formed in the vicinity of the intersection of the scanning line 3a and the data line 6a, and the TFT 30 is electrically connected to the data line 6a and the pixel electrode 9.
Further, a rectangular common electrode 19 is formed at a position substantially overlapping the pixel electrode 9 in plan view. The common electrode 19 may be provided in a solid shape over the adjacent subpixels SG.

The pixel electrode 9 is a conductive film made of a transparent conductive material after film formation of ITO (Indium Tin Oxide) or the like. A plurality (24 in the drawing) of slits 29 are formed in the pixel electrode 9 of one subpixel SG. Each slit 29 extends in a direction intersecting with both the scanning line 3a and the data line 6a (an oblique direction in the figure), and is formed so as to be arranged at equal intervals in the Y-axis direction along the data line 6a. The slits 29 are formed to have substantially the same width and are parallel to each other. Thereby, the pixel electrode 9 has a plurality (23 in the drawing) of strip-shaped electrode portions 9a. Since the slits 29 have a constant width and are arranged at equal intervals, the strip-shaped electrode portions 9a are also arranged with a constant width and at equal intervals. In Example 1, the width of the slit 29 and the width of the strip electrode portion 9a are both 4 μm.
In this case, the inclination angle formed by the slit 29 with the X axis along the scanning line 3a is 20 degrees. Hereinafter, such a slit 29 is referred to as a slit 29 that rises to the right (20 degrees).
The reference of the inclination angle of the slit 29 is the X axis along the scanning line 3a, but it may be replaced with the row direction in the pixel array. Alternatively, the Y axis may be replaced with the column direction in the pixel array, and this may be used as a reference.

  The common electrode 19 is a conductive film made of a transparent conductive material such as ITO, and is formed integrally with the common line 3b extending in parallel with the scanning line 3a. Therefore, the common electrode 19 is electrically connected to the common line 3b.

The common line 3b and the common electrode 19 may be formed using different conductive films. As a method for electrically connecting them, there is a method in which the common electrode 19 and the common line 3b are formed in different wiring layers through an interlayer insulating film, and both are connected through a contact hole opened in the interlayer insulating film. Can be mentioned.
The scanning line 3a, the data line 6a, and the common line 3b are each preferably formed using a low-resistance conductive material from the viewpoint of transmitting an electrical signal, and examples thereof include aluminum and an aluminum alloy.

The TFT 30 includes a semiconductor layer 35 made of an island-shaped amorphous silicon film partially formed on the scanning line 3a, a source electrode 31 branched from the data line 6a and extended onto the semiconductor layer 35, and a semiconductor layer. 35 and a rectangular drain electrode 32 extending from above to the formation region of the pixel electrode 9.
The scanning line 3 a functions as a gate electrode of the TFT 30 at a position facing the semiconductor layer 35. The drain electrode 32 and the pixel electrode 9 are electrically connected via a pixel contact hole 47 formed at a position where they overlap in a plane.
In the illustrated subpixel SG, a region where the pixel electrode 9 and the common electrode 19 overlap in plan view functions as a capacitor of the subpixel SG. Therefore, a separate storage capacitor is provided to hold the image signal. Therefore, it is not necessary to provide in the formation region, and a high aperture ratio can be obtained.
In this case, a region where the pixel electrode 9 and the common electrode 19 overlap in a plan view is a transmissive display region T.

As shown in FIG. 4, in the liquid crystal display device 100, the liquid crystal layer 50 is sandwiched between the element substrate 10 having the pixel electrode 9 and the common electrode 19 and the counter substrate 20.
On the counter substrate 20 made of transparent glass or the like, the color filter 22 (22B, 22G, 22R) and the light shielding film 61 that partitions the color filter 22 for each sub-pixel SG (for each color) toward the liquid crystal layer 50 side. And an alignment film 23 covering the color filter 22 and the light shielding film 61 is formed.

  The light shielding film 61 is called a black matrix (BM). For example, a thin film of a metal or a metal compound is formed on the surface of the counter substrate 20 (on the liquid crystal layer 50 side) as a light-shielding material, and an opening corresponding to the sub-pixel SG is formed by photolithography. And a patterning method. Typical metals or metal compounds include chromium (Cr) or chromium oxide. Another example is a method of patterning a resin containing a black pigment or the like as a light shielding material by a printing method such as offset.

  For example, the color filter 22 is formed by applying a photosensitive resin material containing a coloring material of each color to the counter substrate 20 on which the light shielding film 61 is formed, and exposing and developing the same by a photolithography method. The opening 61 can be filled. As a coating method, methods such as spin coating and slit coating can be used. Alternatively, a droplet discharge method may be used in which a partition wall is provided on the light shielding film 61 and a liquid material containing a coloring material of each color is applied as a droplet to a region partitioned by the partition wall.

Similarly, the scanning line 3a, the common electrode 19, and the common line 3b are formed on the element substrate 10 made of transparent glass or the like. An insulating thin film 11 made of a silicon oxide film or the like is formed so as to cover the scanning line 3a, the common electrode 19 and the common line 3b.
On the insulating thin film 11, an island-shaped semiconductor layer 35 and a source electrode 31 and a drain electrode 32 are formed so as to partially overlap the semiconductor layer 35. An interlayer insulating film 12 made of a silicon oxide film or a resin film is formed so as to cover the semiconductor layer 35, the source electrode 31, and the drain electrode 32.
A pixel electrode 9 is formed on the interlayer insulating film 12, and the pixel electrode 9 and the drain electrode 32 are electrically connected through a pixel contact hole 47 that penetrates the interlayer insulating film 12 and reaches the drain electrode 32. ing.
An alignment film 18 made of polyimide or the like is formed so as to cover the pixel electrode 9 of the element substrate 10. The alignment film 18 on the element substrate 10 side facing the liquid crystal layer 50 and the alignment film 23 on the counter substrate 20 side are subjected to an alignment process such as a rubbing process to align the liquid crystal in a predetermined direction. Details of the alignment process will be described in the optical design conditions described later.

  The polarizing plate 24 is attached to the surface of the counter substrate 20 (surface opposite to the liquid crystal layer 50 side), and the polarizing plate 14 is applied to the surface of the element substrate 10 (surface opposite to the liquid crystal layer 50 side). It is pasted. The optical arrangement of the pair of polarizing plates 14 and 24 is crossed Nicol (a state where the transmission axes are orthogonal to each other).

  5A is a schematic diagram showing the optical design conditions of Example 1, and FIG. 5B is a schematic diagram showing the behavior of the liquid crystal molecules of Example 1. FIG.

As shown in FIG. 5A, the optical design condition of Example 1 is that the rubbing direction (direction of the alignment process) is 15 degrees to the right with respect to the slit 29 that is 20 degrees to the right. More specifically, the alignment film 18 on the element substrate 10 side is rubbed so as to go from the upper right to the lower left at an inclination angle of 15 degrees with respect to the X axis along the scanning line 3a in plan view. . In contrast, the alignment film 23 on the counter substrate 20 side is subjected to a rubbing process from the lower left to the upper right at an inclination angle of 15 degrees with respect to the X axis in a plan view in a state of being opposed to the element substrate 10. Has been. Therefore, the rubbing directions of each other are opposite to each other by 180 degrees.
The optical arrangement of the pair of polarizing plates 14 and 24 is crossed Nicol as described above. The transmission axis of the polarizing plate 14 coincides with the rubbing direction, that is, the initial alignment direction of the liquid crystal molecules. The transmission axis of the other polarizing plate 24 is orthogonal to the transmission axis of the polarizing plate 14 and is indicated by a broken line in FIG.
Accordingly, the liquid crystal display device 100 is normally black, which is a black display in which light incident from the illumination device cannot be transmitted in the non-driven state.

  As shown in FIG. 5B, a lateral electric field is generated between the pixel electrode 9 and the common electrode 19 in the driving state. The electric field direction is a direction orthogonal to the longitudinal direction of the slit 29. The liquid crystal molecules arranged in the initial alignment direction are twisted in the electric field direction. In Example 1, the slits 29 intersect with the initial alignment direction at a predetermined angle (5 degrees), and the liquid crystal molecules have a direction in which the energy required for twisting is small (the initial alignment direction and the electric field direction). Twisted clockwise), that is, in this case, clockwise.

  According to Example 1, the pair of polarizing plates 14 and 24 are both arranged at an angle other than parallel or perpendicular to the X axis and the Y axis. Therefore, even when the liquid crystal display device 100 is viewed through the polarized sunglasses, the light emitted from the liquid crystal display device 100 is not absorbed by the polarized sunglasses. Therefore, it becomes possible to visually recognize the display appropriately.

(Example 2)
6 is a schematic plan view showing the structure of the pixel of Example 2, FIG. 7A is a schematic diagram showing the optical design conditions of Example 2, and FIG. 6B shows the behavior of the liquid crystal molecules of Example 2. FIG. FIG. Hereinafter, in the description of the pixel structure, one sub-pixel SG will be taken up and described. Needless to say, the same applies to the other sub-pixels SG. Further, the same components as those in the first embodiment will be described with the same reference numerals.

  As shown in FIG. 6, the second embodiment is characterized in that the pixel electrode 9 has two types of slits 29 and 29 a having different inclination angles as compared with the first embodiment.

  Specifically, in the longitudinal direction of the pixel electrode 9, there are a plurality of slits 29 as first slits having a tilt angle of 20 degrees rising to the right as in the first embodiment, and the tilt angle rising to the right by 10 degrees. A plurality of slits 29a as second slits are provided. A portion where the inclination angle rises to the right and is 20 degrees is defined as a first region 9b. A portion where the inclination angle rises to the right and is 10 degrees is defined as a second region 9c. A plurality of slits 29, 29a are provided so that the first region 9b and the second region 9c have substantially the same area.

  As shown in FIG. 7A, the optical design conditions of Example 2 are basically the same as those of Example 1. That is, the rubbing direction is 15 degrees to the right, and the transmission axis of the polarizing plate 14 coincides with the rubbing direction. The transmission axes of the pair of polarizing plates 14 and 24 are orthogonal to each other. Therefore, the description will be made by paying attention to the slit 29a whose inclination angle increases to the right by 10 degrees.

As shown in FIG. 7B, the slit 29a intersects the rubbing direction at a predetermined angle (5 degrees) because the rubbing direction is 15 degrees rising to the right. As described in the first embodiment, the electric field direction is generated in a direction orthogonal to the longitudinal direction of the slit 29a.
Accordingly, the liquid crystal molecules of the liquid crystal layer 50 corresponding to the slits 29a are twisted counterclockwise during driving.

  Therefore, the liquid crystal molecules are twisted clockwise in the first region 9b shown in FIG. 6, and the liquid crystal molecules are twisted counterclockwise in the second region 9c. In this way, a method in which two types of twist directions exist in the sub-pixel SG is referred to as a two-domain method. In addition to realizing polarization sunglasses, the substantial twist angle is widened, and a wider viewing angle characteristic than that of the first embodiment can be obtained.

  As in Example 2, the predetermined angle at which the slits 29 and 29a intersect with the rubbing direction, that is, the initial alignment direction, is hereinafter referred to as 5 degrees clockwise with reference to the twist direction of the liquid crystal molecules, and -5 counterclockwise. Define as degrees. That is, the slits 29 and 29a of Example 2 intersect with the initial alignment direction at ± 5 degrees (same angle in absolute value), although the inclination angles are different. Since the predetermined angles of the slits 29 and 29a are axisymmetric with respect to the initial alignment direction, the twist angles twisted in the opposite directions are the same, and bias in the viewing angle characteristics is suppressed.

(Example 3)
FIG. 8 is a schematic plan view illustrating the structure of the pixel according to the third embodiment. In addition, the part of the same structure as Example 1 and Example 2 attaches | subjects and demonstrates the same code | symbol.

  As shown in FIG. 8, in addition to the slits 29 and 29a of the second embodiment, the pixel structure of the third embodiment has a third slit having a portion with an inclination angle of 10 degrees rising to the right and a portion of 20 degrees rising to the right. It is one of the features that it has the slit 29b as. The optical design conditions are the same as in Example 2.

Specifically, in the longitudinal direction of the pixel electrode 9, the lower side has a plurality of slits 29 with an inclination angle of 20 degrees rising to the right, and the upper side has a plurality of slits 29a with an inclination angle of 10 degrees to the right. A slit group including a plurality of slits 29b is disposed between a slit group including a plurality of slits 29 and a slit group including a plurality of slits 29a.
The slit 29b has an inclination angle rising from 20 degrees to 10 degrees. The portion where the inclination angle is changed is located on a broken line 9 d that substantially obliquely crosses the pixel electrode 9.
In the third embodiment, similarly to the second embodiment, the plurality of slits 29, 29a, 29b are formed so that the first region 9b and the second region 9c in which the twist direction of the liquid crystal molecules is reversed have substantially the same area. Is provided. The portion where the inclination angle is changed is a boundary portion between regions having different twist directions.

By arranging the slits 29b having two kinds of inclination angles in this way, it is difficult to control the twist direction of the liquid crystal molecules generated between the first region 9b and the second region 9c as compared with the second embodiment. The area can be reduced. Further, by positioning the portion where the inclination angle changes on the broken line 9d inclined with respect to the longitudinal direction of the pixel electrode 9, the liquid crystal molecules between the sub-pixels SG are compared with the case where the broken line 9d is orthogonal to the longitudinal direction. It is possible to suppress the area in which the twist direction is difficult to control (area that does not contribute to display) from being emphasized in a streak shape. Therefore, the occurrence of streaky display unevenness can be reduced.
Furthermore, the degree of freedom in design for arranging the slits according to the size and shape of the pixel electrode 9 can be increased. Specifically, it is possible to suppress an increase in dead space that does not contribute to display in the pixel electrode 9 when the inclination angle is large or there are a plurality of types.

Example 4
9 is a schematic plan view showing the structure of the pixel of Example 4, FIG. 10A is a schematic diagram showing the optical design conditions of Example 4, and FIGS. 9B and 9C are liquid crystal molecules of Example 4. FIG. It is the schematic which shows the behavior of. In addition, the part of the same structure as Example 1 attaches | subjects and demonstrates the same code | symbol.

  As shown in FIG. 9, in the pixel structure of the fourth embodiment, the slopes of the slits 29c, 29d, 29e, and 29f are lower than those of the first to third embodiments. Also, the inclination angle is different. Further, the slit 29d having a small inclination angle and the portions of the slits 29e and 29f having a small inclination angle are arranged at both ends in the longitudinal direction of the pixel electrode 9.

  Specifically, the pixel electrode 9 includes a slit 29c having an inclination angle of 50 degrees downward to the right, a slit 29d having an inclination of 40 degrees to the right, a slit 29e having a portion of 40 degrees to the lower right and a part of 50 degrees to the lower right. 29f.

  The center side of the pixel electrode 9 is constituted by a portion of the slits 29e and 29f having a downward right angle of 50 degrees centered on a slit 29c having an inclination angle of downward 50 degrees. Both end sides in the longitudinal direction of the pixel electrode 9 are composed of a slit 29d that is 40 degrees to the right and 40 degrees to the right of the slits 29e and 29f.

  As shown in FIG. 10A, the optical design condition of Example 4 is that the rubbing direction is 45 degrees to the right with respect to the slit 29c that is 50 degrees to the right. The rubbing direction and the transmission axis of the polarizing plate 14 coincide. The transmission axes of the pair of polarizing plates 14 and 24 are orthogonal. The transmission axis of the polarizing plate 24 is indicated by a broken line.

  As shown in FIG. 10B, paying attention to the slit 29c having a downward right angle of 50 degrees, the slit 29c intersects the initial alignment direction of the liquid crystal molecules at -5 degrees. Since the direction of the electric field generated during driving is perpendicular to the longitudinal direction of the slit 29c, the liquid crystal molecules are twisted counterclockwise. On the other hand, when attention is paid to the slit 29d having a downward right angle of 40 degrees, the slit 29c intersects the initial alignment direction of the liquid crystal molecules at 5 degrees as shown in FIG. Since the direction of the electric field generated during driving is perpendicular to the longitudinal direction of the slit 29d, the liquid crystal molecules are twisted clockwise. That is, it has a configuration of two domains.

  Therefore, in FIG. 9, the third region 9e and the fourth region 9f have different twist directions of the liquid crystal molecules. The boundary between the third region 9e and the fourth region 9f is located on the broken lines 9h and 9g. The portions where the inclination angles of the slits 29e and 29f change are located at the straight portions of the broken lines 9h and 9g. This prevents a substantial decrease in the aperture ratio of the pixel as in the third embodiment.

  According to the fourth embodiment, compared with the first to third embodiments, the tilt angle of the transmission axes of the polarizing plates 14 and 24 is further inclined 45 degrees to the right or 45 degrees to the right. The angle of intersection with the axis is maximized. That is, it is possible to suppress a change in color tone or the like when the liquid crystal display device 100 is viewed through the polarized sunglasses, and to confirm the display in a more appropriate state.

  FIG. 13 is a schematic plan view for explaining the reverse twist generation mechanism. As shown in FIG. 13, for example, when the slit 29c extends to both ends in the longitudinal direction of the pixel electrode 9, the angle formed by one short side and the long side of the slit 29c on both ends is 50 degrees. And 130 degrees. On the other hand, the angle formed between the other short side and the long side of the slit 29c is 40 degrees and 140 degrees. The electric field direction E on the one short side is more likely to be the angle at which the twist direction of the liquid crystal molecules is reversed compared to the other short side. Therefore, reverse twist in which the twist direction of the liquid crystal molecules is reversed is likely to occur.

  In the fourth embodiment, in consideration of the ease of occurrence of reverse twist at both ends in the longitudinal direction of the pixel electrode 9, the slit 29d and the slit having a small inclination angle of 40 degrees and 50 degrees, and the slit 29d and the slit having a small inclination angle are used. Portions 29e and 29f having an inclination angle of 40 degrees are arranged on both ends in the longitudinal direction of the pixel electrode 9. As a result, the occurrence of reverse twist at both ends of the pixel electrode 9 was suppressed, and a substantial decrease in the aperture ratio due to the reverse twist was prevented.

(Example 5)
FIG. 11 is a schematic plan view showing the structure of the pixel of Example 5, FIG. 12 (a) is a schematic diagram showing the optical design conditions of Example 5, and FIGS. 11 (b) and (c) are liquid crystal molecules of Example 5. FIG. It is the schematic which shows the behavior of. In addition, the part of the same structure as Example 1 attaches | subjects and demonstrates the same code | symbol.

  As shown in FIG. 11, the pixel structure of the fifth example has a sharper inclination angle than that of the fourth example.

  Specifically, the pixel electrode 9 includes a slit 29g having a right-down 70 degree, slits 29h and 29i having a right-down 70 degree part and a right-down 80 degree part, and both ends are 70 degrees right downward and the gap therebetween. And a slit 29j of 80 degrees to the right.

  A portion (80 degrees) where the inclination angle of the slits 29h, 29i, 29j is large is arranged on the center side in the longitudinal direction of the pixel electrode 9, and the inclination angle of the slit 29g and the slits 29h, 29i, 29j where the inclination angle is small on both ends. A small part (70 degrees) is arranged.

  As shown in FIG. 12A, in the optical design conditions of Example 5, when focusing on the slit 29j, the rubbing direction is 75 degrees downward to the right with respect to the main part where the inclination angle is 80 degrees downward to the right. . The transmission axis of the polarizing plate 14 coincides with the rubbing direction. The transmission axis of the polarizing plate 24 whose transmission axis is orthogonal to the polarizing plate 14 is indicated by a broken line.

As shown in FIG. 12 (b), the 80 ° downward slit portion intersects the initial alignment direction of the liquid crystal molecules at an angle of −5 °. The electric field direction at the time of driving is a direction orthogonal to the longitudinal direction of the slit. Therefore, the liquid crystal molecules are twisted counterclockwise.
On the other hand, as shown in FIG. 12 (c), the slit 29g having a downward right angle of 70 degrees intersects the initial alignment direction of the liquid crystal molecules at an angle of 5 degrees. The electric field direction at the time of driving is a direction orthogonal to the longitudinal direction of the slit 29g. Accordingly, the liquid crystal molecules are twisted clockwise. That is, it has a configuration of two domains.

  Accordingly, the liquid crystal molecules are twisted clockwise in the fifth region 9i shown in FIG. 11, and are twisted counterclockwise in the sixth region 9j. The boundary between the fifth area 9i and the sixth area 9j is indicated by broken lines 9m and 9k. The portions of the slits 29h, 29i, and 29j where the inclination angle changes are located on the straight line portions of the broken lines 9m and 9k.

  According to the fifth embodiment, the angle of the transmission axis of the polarizing plate 14 is 75 degrees downward to the right, and the transmission axis of the polarizing plate 24 is 15 degrees upward to the right, so that the arrangement of the polarizing plates is substantially the same as that of the first embodiment. . That is, polarization sunglasses correspondence is realized.

According to the liquid crystal display device 100 to which the pixel structure of any one of the first to fifth embodiments is applied, the transmission axes of the pair of polarizing plates 14 and 24 are in the pixel arrangement direction (row direction and column direction). It is configured with an angle other than parallel or orthogonal. Therefore, even when the liquid crystal display device 100 is viewed through the polarized sunglasses, the display can be confirmed without being difficult to visually recognize. Moreover, since it is not necessary to provide a retardation plate for polarizing sunglasses on the front surface, it is possible to provide a liquid crystal display device 100 that has high cost performance and is thinner. In addition, even in the case of normally white in which a pair of polarizing plates 14 and 24 are arranged so that the transmission axes are in the same direction and white display is performed when not driven, such slit arrangement and initial alignment state of liquid crystal molecules That is, it goes without saying that optical design conditions can be applied.
Further, as a technical idea corresponding to polarized sunglasses, the transmission axis of the polarizing element, the initial alignment direction of the liquid crystal molecules, and the inclination angle of the slit 29 with respect to the display horizontal direction or display vertical direction of the image displayed on the liquid crystal display device 100 It prescribes.

  FIG. 14 is a graph showing the contrast characteristics depending on the viewing angle. Specifically, this is a case of a two-domain method in which slits intersect at 5 degrees / -5 degrees with respect to the initial alignment direction of liquid crystal molecules, and shows a contrast ratio depending on a viewing angle. Such a concentric graph is called a contrast cone.

  When the contrast cone shown in FIG. 14 is applied to the first to fifth embodiments, the following is obtained. In Example 2 and Example 3, the contrast cone of FIG. 14 is rotated 15 degrees counterclockwise. In Example 4, the contrast cone in FIG. 14 is rotated 45 degrees clockwise. In Example 5, the contrast cone of FIG. 14 is rotated by 75 degrees clockwise. The comparison table shown in FIG. 15 compares the display characteristics of each embodiment with the display characteristics of the conventional liquid crystal display device 300 shown in FIG. 17 based on the contrast characteristics depending on the viewing angle.

As shown in the comparison table of FIG. 15, the liquid crystal display device 100 of Examples 1 to 5 is superior to the liquid crystal display device 300 of the conventional example from the viewpoint of being compatible with polarized sunglasses. That is, the evaluations of Examples 1 to 3 and Example 5 were evaluated as ○, the evaluation of Example 4 was evaluated as ◎, and the evaluation of the conventional example was evaluated as ×.
Further, from the viewpoint of viewing angle characteristics, the second to fifth embodiments and the conventional example adopting the two-domain method are superior to the single-domain method example 1. Comparing Example 2 and Example 3 with Example 4 even in the same two-domain system, Example 4 was viewed from the vertical and horizontal directions because the contrast cone in FIG. 14 was rotated 45 degrees clockwise. The contrast is lowered. Therefore, depending on the method of using the liquid crystal display device 100, the original wide viewing angle may not contribute, so the evaluation is Δ to ○.
In terms of luminance characteristics, Example 3 and Example 4 in which the substantial aperture ratio is improved by devising the shape and arrangement of the slits are superior to others. Therefore, evaluation of Example 3 and Example 4 was set as (double-circle). Regarding the conventional liquid crystal display device 300 (see FIG. 17), since the reference slit 306 is provided between the upper slit 307 and the lower slit 308, this is also evaluated as excellent. Since the slits 29g, 29h, 29i, and 29j of Example 5 have steep inclination angles, when they are arranged at different inclination angles with respect to the so-called vertically long pixel electrodes 9, there are boundary regions in which the twist direction is difficult to control. Since it is easy to widen (that is, the substantial aperture ratio is likely to be lowered), the evaluation was evaluated as Δ to ○.

<Embodiment 2>
FIG. 16 is a schematic perspective view showing a mobile phone as an electronic apparatus. As shown in FIG. 16, a mobile phone 200 as an electronic apparatus according to the present embodiment includes a main body 201 including input buttons, a display unit 202, and the like.

  The display unit 202 incorporates the liquid crystal display device 100 according to the first embodiment and a lighting device using LEDs or the like as light sources.

  Accordingly, even when the mobile phone 200 is viewed through polarized sunglasses, the display can be properly confirmed.

  Various modifications other than the above embodiment are conceivable. Hereinafter, a modification will be described.

(Modification 1) In Examples 1 to 5 of the first embodiment, the inclination angle of the slit is limited to 10 degrees / 20 degrees rising right, 40 degrees / 50 degrees falling right, and 70 degrees / 80 degrees falling right. Not. When the liquid crystal display device 100 is viewed from the front through the polarized sunglasses, the arrangement of the slits and the transmission axis of the polarizing plate 14 or 24 provided in the liquid crystal display device 100 and the transmission axis of the polarized sunglasses are not orthogonal to each other. It is most important to set optical design conditions.
Further, the predetermined angle of the slit that intersects the initial alignment direction of the liquid crystal molecules is not limited to 5 degrees (actually ± 5 degrees). For example, Δn (birefringence) of the liquid crystal material having positive dielectric anisotropy, setting of the thickness d of the liquid crystal layer 50 shown in FIG. 4, and the tilt angle of the liquid crystal molecules in the alignment films 18 and 23 after the rubbing treatment, etc. Selection can be made in the range of 5 degrees to 15 degrees in consideration of the optical characteristics based on them.
When the predetermined angle of the slit intersecting with the initial alignment direction of the liquid crystal molecules becomes small, one of the angles formed by the initial alignment direction and the electric field direction approaches 90 degrees, that is, the stability in the twist direction is easily lost. On the other hand, when the predetermined angle increases, one of the angles formed by the initial alignment direction and the electric field direction decreases. Therefore, although the twist direction stability is increased, the twist angle of the liquid crystal molecules is reduced, so that the transmittance of the transmitted light converted into linearly polarized light by the polarizing element is likely to decrease.
Therefore, it is preferable to provide a liquid crystal display device 100 that can achieve a bright display while realizing compatibility with polarized sunglasses and ensuring stability in the twist direction by setting the predetermined angle in the range of 5 degrees to 10 degrees. can do.

  (Modification 2) In the liquid crystal display device 100 of the first embodiment, the shape of the slit in the pixel electrode 9 is not limited to this. For example, each slit of the first to fifth embodiments is closed at both ends in the longitudinal direction, but may be in a state where one of both ends is opened. According to this, the direction of the electric field of the opened portion can easily be directed in the direction orthogonal to the longitudinal direction of the slit, and the aperture ratio of the pixel can be substantially improved.

  (Modification 3) In the liquid crystal display device 100 of the first embodiment, the configuration of the pixel electrode 9 and the common electrode 19 is not limited to this. For example, in the element substrate 10, the pixel electrode 9 having no slit is arranged in the lower layer, the common electrode 19 is superimposed on the pixel electrode 9 through an interlayer insulating film, and a plurality of slits are formed in the common electrode 19. It may be electrically connected to the common line 3b. That is, the plurality of slits may be formed in either the first electrode or the second electrode in the claims, and the first electrode is not limited to the pixel electrode 9 (the second electrode is the common electrode 19).

  (Modification 4) In the liquid crystal display device 100 of the first embodiment, the areas of the sub-pixels SG corresponding to the three color filters 22R, 22G, and 22B are not necessarily the same for each color. For example, the area of the subpixel SG may be changed according to the visibility. In other words, the area of the pixel electrode 9 may be changed corresponding to each color. Specifically, the area may be increased in the order of G (green) <R (red) <B (blue).

  (Modification 5) The liquid crystal display device 100 of the first embodiment is not limited to the transmissive type having the transmissive display region T. For example, in the transflective liquid crystal display device including the transmissive display region T and the reflective display region having a reflector in the sub-pixel SG, the slit arrangement and optical design conditions of the first to fifth embodiments are the same. Can be applied.

(Modification 6) In the liquid crystal display device 100 of the first embodiment, the polarizing element is not limited to being provided outside the element substrate 10 and the counter substrate 20 as a pair of substrates. For example, a polarizing element may be provided inside a pair of substrates facing the liquid crystal layer 50. Examples of such an inner surface polarizing element include a wire grit polarizing element and a coating polarizing element.
In the case where the liquid crystal display device 100 is a reflective type having a reflecting plate, a polarizing element may be provided on a substrate on which external light is incident. That is, the polarizing elements are not limited to the upper and lower pairs.

  (Modification 7) In the first embodiment, the liquid crystal display device 100 is not limited to the FFS method. For example, the present invention can also be applied to an IPS (In Place Switching) type liquid crystal display device which is a horizontal electric field type.

  (Modification 8) In the second embodiment, the electronic device on which the liquid crystal display device 100 of the first embodiment can be mounted is not limited to the mobile phone 200. For example, it is suitable if it is installed in an electronic device such as a notebook personal computer, an electronic notebook, a viewer for displaying video information, a DVD player, or a portable information terminal.

(A) is a schematic front view which shows the structure of a liquid crystal display device, (b) is a schematic sectional drawing which shows the structure of the liquid crystal display device cut | disconnected by the HH 'line | wire of (a). The equivalent circuit diagram of a liquid crystal display device. FIG. 2 is a schematic plan view illustrating a structure of a pixel according to the first embodiment. FIG. 4 is a cross-sectional view of the liquid crystal display device taken along line AA ′ in FIG. 3. (A) is schematic which shows the optical design conditions of Example 1, (b) is schematic which shows the behavior of the liquid crystal molecule of Example 1. FIG. FIG. 6 is a schematic plan view showing the structure of a pixel of Example 2. (A) is the schematic which shows the optical design conditions of Example 2, (b) is the schematic which shows the behavior of the liquid crystal molecule of Example 2. FIG. 10 is a schematic plan view illustrating a pixel structure of Example 3. FIG. 6 is a schematic plan view showing the structure of a pixel of Example 4. (A) is the schematic which shows the optical design conditions of Example 4, (b) and (c) is the schematic which shows the behavior of the liquid crystal molecule of Example 4. FIG. 10 is a schematic plan view showing the structure of a pixel of Example 5. (A) is schematic which shows the optical design conditions of Example 5, (b) and (c) are schematic which shows the behavior of the liquid crystal molecule of Example 5. The schematic plan view explaining the generation | occurrence | production mechanism of a reverse twist. The graph which shows the contrast characteristic by a viewing angle. The comparison table which evaluated the liquid crystal display device of the prior art example and the Example. The schematic perspective view which shows the portable telephone as an electronic device. FIG. 6 is a schematic plan view showing unit pixels of a conventional liquid crystal display device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 9 ... Pixel electrode as 1st electrode, 10 ... Element board | substrate as one board | substrate, 14, 24 ... Polarizing plate as a polarizing element, 19 ... Common electrode as 2nd electrode, 29, 29a, 29b, 29c, 29d 29e, 29f, 29g, 29h, 29i, 29j ... slits, 50 ... liquid crystal layer, 100 ... liquid crystal display device, 200 ... portable telephone as an electronic device, 300 ... conventional liquid crystal display device, SG ... subpixel.

Claims (9)

A pair of substrates;
A liquid crystal layer sandwiched between the pair of substrates;
A first electrode and a second electrode provided on one of the pair of substrates;
A plurality of pixels each provided with the first electrode and the second electrode;
A polarizing element provided on the pair of substrates,
The liquid crystal layer is driven by an electric field generated between the first electrode and the second electrode,
The initial alignment direction of the liquid crystal molecules in the liquid crystal layer is set at an angle other than parallel or orthogonal to the alignment direction of the pixels,
The transmission axis of the polarizing element is the same direction as the initial alignment direction;
The liquid crystal display device, wherein the first electrode or the second electrode has a plurality of slits that intersect with the initial alignment direction at a predetermined angle.   The liquid crystal display device according to claim 1, wherein the plurality of slits have an inclination angle other than parallel or orthogonal to the arrangement direction of the pixels.   The liquid crystal display device according to claim 2, wherein the predetermined angle of the slit with respect to the initial alignment direction is 5 degrees to 10 degrees. The first electrode or the second electrode has at least two kinds of the slits that intersect with the initial alignment direction at a predetermined angle and have different inclination angles with respect to the arrangement direction of the pixels,
4. The liquid crystal display device according to claim 2, wherein the liquid crystal layer corresponding to the at least two types of slits is driven such that the liquid crystal molecules are twisted in opposite directions.   5. The liquid crystal display device according to claim 4, wherein the at least two types of the slits have the predetermined angle symmetrical with respect to the initial alignment direction.   The at least two types of the slits include a first slit having the first inclination angle, a second slit having the second inclination angle, and a portion having the first inclination angle. 6. The liquid crystal display device according to claim 4, wherein the liquid crystal display device comprises a third slit having a second angle portion and a second angle portion.   The boundary portion between the first angle and the second angle in the third slit is set so as to obliquely intersect the arrangement direction of the pixels. Liquid crystal display device.   Of the at least two types of the slits, the slit having a small inclination angle and / or at least a part of the slit having a small inclination angle are positioned on both ends in the column direction of the pixels. The liquid crystal display device according to claim 4, wherein the liquid crystal display device is disposed on one electrode or the second electrode.   An electronic apparatus comprising the liquid crystal display device according to any one of claims 1 to 8.

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