JP2007102073A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device, in which the center position of alignment can be fixed to the center of a solid part without increasing a manufacturing cost. <P>SOLUTION: In the liquid crystal display device, a pixel electrode is arranged on a first substrate. The pixel electrode is provided with a plurality of solid parts 1 disposed in an array shape and branch parts 3 extended from outer circumferential parts of the solid parts 1 between the solid parts 1. Therein, virtual lines AL extended in the extension directions of the branch parts 3 do not pass through the center of the solid part 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and particularly to a liquid crystal display device having a pixel electrode composed of a plurality of solid portions.

  There is a so-called liquid crystal display device in which a liquid crystal layer is formed between a first substrate and a second substrate facing the first substrate. Further, a technique related to a liquid crystal display device using a vertical alignment type liquid crystal layer already exists. The reason why the vertical alignment type liquid crystal layer is used is to realize a wide viewing angle.

  Here, the vertical alignment type liquid crystal layer refers to a liquid crystal layer composed of liquid crystal molecules having negative dielectric anisotropy. When no voltage is applied between the first substrate and the second substrate, the molecules constituting the liquid crystal layer are aligned perpendicular to both substrates. However, when a voltage is applied between the first substrate and the second substrate, each molecule constituting the liquid crystal layer falls in a predetermined direction.

  That is, no front phase difference occurs when no voltage is applied. However, when the voltage is applied, the front phase difference occurs due to the liquid crystal molecules falling in a predetermined direction.

  In a liquid crystal display device using a vertical alignment type liquid crystal layer, if a radial tilt alignment in which liquid crystal molecules are tilted almost uniformly in all directions is obtained, good viewing angle characteristics with excellent symmetry can be obtained. As a liquid crystal display device that realizes the radial tilt alignment, for example, devices related to Patent Documents 1 and 2 exist.

  In the liquid crystal display devices according to Patent Documents 1 and 2, an oblique electric field can be generated in the periphery of the solid part made of a conductive material. The direction in which the liquid crystal molecules fall is controlled by the oblique electric field.

JP 2003-43525 A JP 2003-315803 A

  However, in the technique related to Patent Document 1, the center position of the radial tilt alignment sometimes deviates from the center of the solid part. The misalignment of the alignment center is likely to occur when a relatively high voltage (4.5 V or more) is applied with a voltage that is equal to or lower than a threshold (about 2.0 to 2.5 V) at which liquid crystal molecules start to fall.

  When such a deviation occurs, the ratio of the orientation in which the liquid crystal molecules fall within the solid part is not uniform. That is, the viewing angle becomes asymmetric and narrows.

  As a technique for fixing the center position of the radial inclined orientation to the center of the solid part, there is a technique related to Patent Document 2. In the technique related to Patent Document 2, a protrusion structure is provided on the counter substrate facing the solid portion.

  However, providing a new protrusion structure on the counter substrate leads to an increase in manufacturing cost of the liquid crystal display device.

  Therefore, an object of the present invention is to provide a liquid crystal display device that can fix the center position of the alignment to the center of the solid portion without increasing the manufacturing cost.

  In order to achieve the above object, a liquid crystal display device according to claim 1 of the present invention is opposed to a first substrate on which a pixel electrode is disposed, and the first substrate. A second substrate on which an electrode is disposed; and a vertical alignment type liquid crystal layer formed between the first substrate and the second substrate. A plurality of solid portions provided in an array, and a branch portion extending from an outer peripheral portion of the solid portion between the solid portions, and extending in the extending direction of the branch portions The extending virtual line does not pass through the center of the solid part.

  According to a first aspect of the present invention, there is provided a liquid crystal display device comprising: a first substrate on which a pixel electrode is disposed; and a second substrate on which the counter electrode is disposed, facing the first substrate. And a vertical alignment type liquid crystal layer formed between the first substrate and the second substrate, and the pixel electrodes are arranged in a plurality of arrangements. A solid portion and a branch portion extending from an outer peripheral portion of the solid portion between the solid portion, and a virtual line extending in the extending direction of the branch portion is Since it does not pass through the center, a spiral alignment of liquid crystal molecules can be formed stably. Therefore, it can suppress that the center of orientation shifts from the center of the solid part. Further, the production cost does not increase when the branch part or the like is created.

  Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.

<Embodiment 1>
In this embodiment mode, a structure of a pixel electrode which is a constituent member of a liquid crystal display device will be described. FIG. 1 is a plan view showing the structure of the pixel electrode according to the present embodiment.

  As shown in FIG. 1, the pixel electrode is composed of a plurality of solid portions 1 and openings 2. In addition, four branch portions 3 are formed on the outer peripheral portion of each solid portion 1. Here, the branch part 3 is substantially rectangular. That is, the pixel electrode includes a plurality of solid portions 1 provided in a predetermined arrangement, and a branch portion 3 extending from the outer peripheral portion of the solid portion 1 between the solid portions 1. .

  Here, the portion constituting the main area of the pixel electrode is referred to as the solid portion 1 (hereinafter simply referred to as the solid portion). Further, a portion extending from the outer peripheral portion of the solid portion 1 between the solid portions 1 is referred to as the branch portion 3 (hereinafter simply referred to as the branch portion 3). In FIG. 1, the substantially rectangular portion is the solid portion 1, and the portion extending from the outer peripheral portion of the substantially rectangular solid portion 1 is the branch portion 3 ( The solid part 1 has four branches).

  Further, the branch part 3 includes not only the branch part 3 existing between the solid parts 1 but also the following parts. That is, as shown in FIG. 1, the solid portions 1 are provided in a predetermined arrangement. The solid part 1 existing on the outermost side of the solid part 1 in the array is also formed with a branch part 3 extending toward the outer side of the solid part 1. That is, in the solid part 1 existing on the outermost side of the solid part 1 provided in an array, the branch part 3 extends toward the outer side of the solid part 1.

  The pixel electrode constitutes a plurality of pixel regions. In the present embodiment, one pixel region is formed by the three solid portions 1. That is, one unit of the pixel region is formed by the solid portion 1 shown in FIG. In FIG. 1, the pixel area is partitioned by dotted lines.

  Here, in a predetermined number of solid portions 1 existing in one pixel region, adjacent solid portions 1 are electrically connected via a branch portion 3. Further, as will be described later, one switching element (for example, a TFT or the like) is formed in one pixel region, although not shown.

  The solid part 1 is substantially rectangular. A single branch portion 3 is formed on each side of the solid portion 1. Also, pay attention to one solid part 1. Then, as shown in FIG. 1, the virtual line AL extending in the extending direction of each branch part 3 does not pass through the center of the solid part 1. That is, the virtual line AL is formed with a predetermined distance from the center of the solid part 1.

  Also, pay attention to one solid part 1. Then, as can be seen from FIG. 1, in each virtual line AL extending in the extending direction of the branch part 3, the center position of the solid part 3 with respect to each virtual line AL is set so that each virtual line AL is within the solid part 1. Seen in the direction, located on the same side. That is, the branch part 3 formed in one solid part 1 is 2 or more, and the center position of the solid part 1 with respect to each virtual line AL of the two or more branch parts 3 is determined based on each virtual line AL. Seeing inward of the solid part 1, it is on the same side.

  For example, in FIG. 1, attention is paid to one solid part 1 located in the second row from the top and the second column from the right. Then, in each virtual line AL, the center of the solid part 1 is on the left side of the virtual line when viewed inward of the solid part 1.

  On the other hand, in FIG. 1, attention is paid to one solid part 1 located in the third row from the top and the second column from the right. Then, in each virtual line AL, the center of the solid part 1 exists on the right side of the virtual line when viewed inward of the solid part 1.

  In the present embodiment, each branch part 3 formed in one solid part 1 is formed such that the distance from the virtual line AL to the center of the solid part 1 is substantially the same. ing. For example, as shown in FIG. 1, there are four branch parts 3 formed in one solid part 1, and the branch part 3 has a distance from the virtual line AL to the center of the solid part 1. , So as to be substantially the same. In other words, the branch part 3 is formed so as to have approximately four-fold symmetry with respect to the center of the solid part 1.

  Further, attention is paid to each of the adjacent solid parts 1 connected through the branch part 3. Then, the formation position of the branch part 3 is mirror-symmetric. For example, the formation position of the branch part 3 is mirror-symmetric with respect to the connection part (branch part 3) of the solid part 1.

  Next, the mechanism of alignment of liquid crystal molecules by an oblique electric field will be described with reference to FIG. The mechanism is the same as that described in Patent Documents 1 and 2. Here, the oblique electric field is generated due to the edge portion (outer peripheral portion) of the solid portion 1.

  As shown in FIG. 2, a pixel electrode (a part of the solid portion 1 constituting the pixel electrode is shown in FIG. 2) is disposed on the first substrate 10. . Further, a second substrate 20 is disposed so as to face the first substrate 10. A counter electrode 15 is formed on the second substrate 20.

  As shown in FIG. 2, the solid part 1 and the counter electrode 15 face each other. A liquid crystal layer 30 is formed between the first substrate 10 and the second substrate 20. A vertical alignment film (not shown) is formed between the first substrate 10 and the liquid crystal layer 30 and between the second substrate 20 and the liquid crystal layer 30.

  Here, the liquid crystal layer 30 is a vertical alignment type.

  The vertical alignment type liquid crystal layer is a liquid crystal layer composed of liquid crystal molecules having negative dielectric anisotropy. When no voltage is applied between the pixel electrode (solid portion 1) and the counter electrode 15, the molecules constituting the liquid crystal layer 30 are aligned perpendicular to both substrates (conceptual diagram). (See FIG. 3). However, when a voltage is applied between the pixel electrode (solid portion 1) and the counter electrode 15, each molecule constituting the liquid crystal layer 30 falls in a predetermined direction (see FIG. 4 which is a conceptual diagram).

  That is, no front phase difference occurs when no voltage is applied. However, when the voltage is applied, the front phase difference occurs due to the liquid crystal molecules falling in a predetermined direction.

  In the present embodiment, an oblique electric field (oblique electric field) is generated between the pixel electrode (solid part 1) and the counter electrode 15 due to the edge portion of the solid part 1 during voltage application. To do. Therefore, in the present embodiment, due to the oblique electric field, the liquid crystal molecules are tilted in the direction from the outside to the inside of the solid portion 1 (reference numeral 30a in FIG. 2).

  When the applied voltage is as low as about 2.5 to 3.5 V, or when a voltage higher than the voltage (about 2.0 to 2.5 V) at which the liquid crystal molecules in the outer periphery of the solid part 1 starts to fall is applied. In, liquid crystal molecules start to fall from the outer peripheral portion of the solid portion 1, and the orientation change propagates to the inside of the solid portion 1. When attention is paid to one solid part 1, a radially inclined alignment of liquid crystal molecules is obtained transiently in a plan view.

  FIG. 5 shows a state of radial tilt alignment of liquid crystal molecules that is transiently formed in one solid portion 1 when a voltage is applied. Specifically, the orientation is confirmed by a quenching pattern (thick line shown in FIG. 5) seen when observed in a crossed Nicols arrangement using a deflection microscope or the like.

  Here, in FIG. 5, each branch part 3 is formed in the outer peripheral part of the solid part 1 as follows. That is, each virtual line (not shown) extending in the extending direction of each branch part 3 is formed so as to pass through the center of the solid part 1.

  In FIG. 5, the liquid crystal molecules 31 are illustrated in a nail pattern. The head of the nail pattern is positioned in front of the paper (the same applies to the drawings corresponding to FIG. 5 below). Therefore, the side opposite to the head of the nail pattern is located in the depth direction of the paper surface (the same applies to the drawings corresponding to FIG. 5 below).

  As can be seen from FIG. 5, each liquid crystal molecule 31 falls radially so that the nail-shaped head faces the center of the solid part 1. This is because, in a region other than the center of the solid portion 1, the state is a state in which the alignment distortion of the liquid crystal molecules 31 is the smallest.

  However, this state is transitional. This is because, as can be seen from FIG. 6 showing the A-B cross section of FIG. 5, in the vicinity of the center of the solid portion 1, the splay alignment (that is, the liquid crystal molecules 31 on both sides are mirror-symmetrical with one liquid crystal molecule 31 as an axis). This is because an orientation that tilts in the direction of is formed. In this way, when the liquid crystal molecules 31 are splayed, the elastic energy of the liquid crystal molecules 31 in the portion becomes high.

  Now, consider the case where the liquid crystal molecules 31 are twisted as shown in FIG. Then, the elastic energy of the twist-aligned liquid crystal molecules 31 becomes about half as low as the elastic energy of the splay alignment.

  Here, FIG. 7 is a view showing a cross section perpendicular to the cross section AB of FIG. As shown in FIG. 7, in the twist alignment, the direction in which the liquid crystal molecules are tilted is twisted along the AB cross-sectional line with reference to the AB cross-sectional line.

  From the comparison of the elastic energies, the solid portion 1 of the structure shown in FIG. 5 (that is, each imaginary line extending in the extending direction of the branch portion 3 passes through the center of the solid portion 1, so that In the case of the structure in which 3 is formed (hereinafter simply referred to as the structure shown in FIG. 5), the twist orientation shown in FIG.

  Therefore, when the solid part 1 of the structure shown in FIG. 5 is adopted, finally, as shown in FIGS. 8 and 9, the liquid crystal molecules 31 are generally clockwise (or counterclockwise). A spiral orientation is formed. Specifically, the orientation is confirmed by a quenching pattern (thick line shown in FIGS. 8 and 9) seen when observed in a crossed Nicols arrangement using a deflection microscope or the like.

  Here, the clockwise spiral orientation and the counterclockwise spiral orientation occur with substantially the same probability. However, when a liquid crystal material having chirality is used, spiral orientation in either direction occurs with a higher probability.

  By the way, in the case of the solid part 1 of the structure shown in FIG. 5, as described above, in the region other than the center of the solid part 1, the radial inclination orientation (orientation shown in FIG. 5) is originally more than the spiral orientation. Is more stable (less distortion).

  Therefore, in the case of the spiral orientation shown in FIGS. 8 and 9, orientation distortion occurs in a region other than the center of the solid portion 1. Therefore, there is a high possibility that the liquid crystal molecules do not settle in the spiral orientation of FIGS. That is, there is a high possibility that the liquid crystal molecules 31 take an alignment in which the center of the alignment deviates from the center of the solid portion 1.

  Also, when the applied voltage is as low as about 2.5 to 3.5 V, or when a voltage higher than the voltage (about 2.0 to 2.5 V) at which the liquid crystal molecules in the outer periphery of the solid part 1 starts to fall is applied. , The orientation center of the orientation is easily formed at the center of the solid portion 1.

  However, when a relatively high voltage (4.5 V or more) is applied with a voltage below a threshold (approximately 2.0 to 2.5 V) or less at which the liquid crystal molecules start to fall, It becomes easy to shift from the center of the real part 1. This is because when the voltage is applied, the liquid crystal molecules in the vicinity of the center of the solid part 1 and the liquid crystal molecules in the outer periphery of the solid part 1 collapse simultaneously. As described above, the liquid crystal molecules near the center of the solid part 1 are not controlled in the direction in which the liquid crystal molecules are tilted. Therefore, immediately after voltage application, the liquid crystal molecules are tilted in a random direction, and a deviation occurs between the alignment center and the center of the solid part 1. (It may also occur when a plurality of alignment centers are formed).

  With the passage of time, the extinction pattern, which will be described later, changes to a shape with a large curvature, and an approximately radial inclined orientation is obtained. However, the alignment center does not necessarily move to the center of the solid part 1, and a deviation between the alignment center and the center of the solid part 1 remains.

  Thus, when the center position of the alignment deviates from the center of the solid portion 1, the ratio of the orientation in which the liquid crystal molecules fall within the solid portion 1 is not uniform. That is, the viewing angle becomes asymmetric and narrows.

  On the other hand, when the pixel electrode according to the present embodiment is employed, a voltage not higher than a threshold value (about 2.0 to 2.5 V) at which liquid crystal molecules start to fall is set to a relatively high voltage (4. Even when 5 V or higher) is applied, it is possible to suppress the deviation of the center position of the alignment from the center of the solid portion 1.

  That is, in the present embodiment, the branch portion 3 is formed on the outer peripheral portion of the solid portion 1, and the virtual line AL extending in the extending direction of each branch portion 3 passes through the center of the solid portion 1. Absent.

  Therefore, as shown in FIG. 10, due to the formation position of the branch part 3, twist orientation can be taken near the center of the solid part 1. Further, in a region other than the vicinity of the center of the solid portion 1, the liquid crystal molecules 3 can be spirally aligned with less distortion due to the formation position of the branch portion 3. That is, the position of the “side” of the spiral orientation is controlled by the branch part 3.

  As described above, when the pixel electrode according to the present embodiment is employed, the spiral orientation can be formed with less distortion than the case shown in FIGS. A spiral orientation).

  Therefore, it is possible to prevent the orientation center from being formed at a position other than the center of the solid portion 1 without performing an extra manufacturing process (that is, without increasing the manufacturing cost).

  As described above, when a liquid crystal display device is manufactured using the pixel electrode according to this embodiment, the liquid crystal device has a wide viewing angle with respect to all directions, and further, a displayed image is good.

  Note that the spiral alignment of the liquid crystal molecules 31 shown in FIG. 10 in the solid part 1 of the present embodiment was confirmed using a deflection microscope or the like. Specifically, the orientation was confirmed by a quenching pattern (thick line shown in FIG. 10) seen when observed in a crossed Nicols arrangement using a deflection microscope or the like.

  Further, a predetermined number (three in FIG. 1) of solid portions 1 existing in one pixel region are electrically connected to each other through branch portions 3. Accordingly, one pixel region can be formed by the predetermined number of solid portions 1.

  Further, attention is paid to each of the adjacent solid parts 1 connected via the branch part 3. Then, as shown in FIG. 1, the formation position of the branch part 3 is mirror-symmetric with respect to the connection part (branch part 3) of the solid part 1, for example.

  Therefore, for example, the area occupied by the solid portion 1 in the pixel region is larger than in the case shown in FIG. FIG. 11 shows a case where the formation positions of the branch portions 3 are the same in each solid portion 1. In the case shown in FIG. 11, there is a dead space due to the shape of the branch 3L.

  As described above, since the area occupied by the solid portion in the pixel region increases, the area that effectively contributes to the display increases, and as a result, a liquid crystal display with high luminance becomes possible.

  In addition, in the solid parts 1 connected via the branch part 3, when the formation position of the branch part 3 is mirror-symmetric, the solid part 1 has a clockwise spiral orientation. In the other solid part 1, a counterclockwise spiral orientation is formed.

  In this configuration, it is assumed that a liquid crystal material having chirality is employed for the liquid crystal layer. Then, a spiral orientation in one direction (that is, an orientation that matches the chirality direction) is stably formed. However, the spiral orientation in the other direction (that is, the orientation that does not coincide with the chirality direction) becomes unstable. In such a case, the orientation center may deviate from the center of the solid part 1.

  Therefore, in the solid parts 1 connected via the branch part 3, when the formation position of the branch part 3 is mirror-symmetric, the liquid crystal material 30 is preferably composed of a liquid crystal material without chirality. desirable. Thereby, in the solid part 1 of the said structure, the stable spiral orientation can be formed in both.

  Moreover, the branch part 3 formed in one solid part 1 may be one. In this case, the branch part 3 may be formed at a position where the virtual line AL extending in the extending direction of the branch part 3 does not pass through the center of the solid part 1. By doing in this way, compared with the structure shown in FIG. 5, the spiral alignment of a liquid crystal molecule can be formed stably.

  Moreover, the branch part 3 formed in one solid part 1 may be two or more. In this case, in each virtual line AL extending in the extending direction of the branch part 3, the center position of the solid part 1 with respect to the virtual line AL is viewed from the virtual line AL in the inward direction of the solid part 1. It is desirable to form the branch part 3 so as to be located on the same side.

  By adopting this configuration, it is possible to form a spiral orientation more stably than when only one branch portion 3 is formed in one solid portion 1.

  When the number of branch portions 3 formed in one solid portion 1 is 2 or more, there is a possibility that there is a branch portion 3 that does not contribute to the connection between the solid portions 1. It can be understood that the branch part 3 is formed exclusively for controlling the spiral orientation.

  Further, as described above, four branch portions 3 are formed in one solid portion 1, and the distance between the branch portion 3 and the center of the solid portion 1 from the virtual line AL is substantially the same. Thus, it is more desirable to be formed. By adopting this configuration, the spiral orientation can be formed most stably.

  Further, the shape of the solid part 1 excluding the branch part 3 may include a rectangular solid part 1 as shown in FIG. 12 in addition to the square shown in FIG. However, as shown in FIG. 12, when the solid part 1 of the rectangle is introduced, the ratio of the vertical side to the horizontal side of the solid part 1 is 1: 0.5 to 1: 2. It is desirable to be within the range.

  If the ratio of the vertical side to the horizontal side of the solid part 1 is outside the above range, the center of the spiral orientation may be formed near the branch part 3 on the long side. (This matter has been confirmed by experiments). In this case, the liquid crystal display is roughly observed (for example, bright pixels and dark pixels are mixed when viewed from the right direction).

  Further, as shown in FIG. 13, the solid portion 1 may have a rectangular shape (square or rectangular shape) (A in FIG. 13), or a rectangular shape with corners being curved. It may be good (B in FIG. 13), or may be circular (or elliptical) or the like (C in FIG. 13).

  Regardless of the shape of the solid part 1, the center of the solid part 1 and the center of gravity of the solid part 1 substantially coincide.

  Moreover, when the solid part 1 is elliptical, the ratio of the major axis to the minor axis of the ellipse is preferably within the range of 1: 0.5 to 1: 2.

  If the ratio of the major axis to the minor axis of the solid part 1 is outside the above range, the center of the spiral orientation may be formed with a deviation from the center of the solid part 1. (This matter has been confirmed by experiments). In this case, the liquid crystal display is roughly observed (for example, bright pixels and dark pixels are mixed when viewed from the right direction).

  The size of one solid part 1 is preferably within the following range.

  That is, in the case of a square, it is desirable that the size of each side is not less than 30 microns and not more than 100 microns according to empirical rules. In the case of the rectangular solid portion 1, the size of the short side is preferably 30 microns or more. Further, the size of the long side is desirably 100 microns or less.

  Further, according to an empirical rule, in the case of the circular solid part 1, it is desirable that the diameter is not less than 30 microns and not more than 100 microns. Further, according to the same rule of thumb, in the case of the elliptical solid part 1, the size of the minor axis is preferably 30 microns or more. The major axis is desirably 100 microns or less.

  In addition, the size of each side of the substantially rectangular branch part 3 is preferably within the range shown below.

  That is, the width of the branch part 3 defined in FIG. 14 is preferably within a range of 5 to 15 microns. Further, the length of the branch part 3 defined in FIG. 14 is preferably within the range of 3 to 10 microns.

  When the size of the branch part 3 is small, the effect of controlling the orientation by the oblique electric field around the branch part, that is, the effect of controlling the position of the “skirt” of the spiral orientation becomes small.

  In the above description, the case where one pixel region is configured by three solid portions 1 has been described. However, the present invention is not limited to this. That is, one pixel region may be formed by one or more solid portions 1. Further, the solid portion 1 forming one pixel region is referred to when arranged in a line. However, they may be arranged in an arbitrary matrix.

  For example, as shown in FIG. 15, one pixel region may be configured by arranging 12 solid portions 1 in 6 rows and 2 columns. As can be seen from FIG. 15, the twelve solid portions 1 constituting one pixel region are electrically connected to each other through the branch portions 3.

<Embodiment 2>
In this embodiment, a liquid crystal display device (particularly, a liquid crystal panel portion) including the pixel electrode according to Embodiment 1 will be described.

  First, the configuration of each member on the first substrate will be described. FIG. 16 is a perspective plan view showing the configuration of each member formed on the first substrate.

  In FIG. 16, the member formed in the lowermost layer is illustrated by hatching. In addition, members existing in the upper layer than the hatched members are indicated by thick lines. Further, the members existing above the thick line members are shown by dotted lines. Note that the hatched members, the thick members, and the dotted members are formed in the same layer.

  In FIG. 16, only one pixel region is shown. Therefore, although not shown, the structures are actually arranged in a matrix with the structure shown in FIG. 16 as a unit. Note that one pixel region is composed of three solid portions (dotted line outlines).

  The first substrate (not shown) is a transparent substrate such as glass. On the first substrate, as shown in FIG. 16, gate wiring 51 is arranged in one direction (lateral direction in FIG. 16). Here, the gate wiring 51 also serves as a gate electrode.

  On the first substrate, as shown in FIG. 16, auxiliary capacity wiring 52 is arranged in the same direction as the gate wiring 51. Further, as shown in FIG. 16, an auxiliary capacitance electrode 53 is disposed on the first substrate. Here, the auxiliary capacitance line 52 is electrically connected to the auxiliary capacitance electrode 53.

  A first insulating film (not shown), a semiconductor layer (not shown), an ohmic contact is formed on the first substrate so as to cover the gate wiring 51, the auxiliary capacitance wiring 52, the auxiliary capacitance electrode 53, and the like. A contact film (not shown) is formed in this order.

  A source wiring (signal wiring) 54 is disposed on the first insulating film. Here, as shown in FIG. 16, the source wiring 54 is arranged in a direction (vertical direction in FIG. 16) substantially perpendicular to the arrangement direction of the gate wiring 51. Here, one pixel region is configured in a region partitioned by the gate wiring 51 and the source wiring 54.

  As shown in FIG. 16, a source electrode 55 is connected to the source wiring 54. As is clear from the above, the gate wiring 51, the auxiliary capacitance wiring 52, and the source wiring 54 are arranged in different layers via the first insulating film. Therefore, the former two wirings 51, 52 and the like and the source wiring 54 and the like are not electrically connected.

  A drain electrode 56 is disposed in a region partitioned by the gate wiring 51 and the source wiring 54. Here, the source electrode 55 and the drain electrode 56 are connected via a semiconductor layer (not shown).

  In FIG. 16, a switching element is formed from a gate wiring (particularly a portion functioning as a gate electrode) 51, a source electrode 55, a drain electrode 56, a first insulating film (not shown), a semiconductor layer (not shown), and the like. The TFT (Thin Film Transistor) is configured. In FIG. 16, a portion surrounded by a circle is a portion where a TFT is configured.

  A second insulating film (not shown) is formed on the first substrate so as to cover the source wiring 54, the source electrode 55, the drain electrode 56, and the like. Here, the second insulating film is formed, for example, by laminating an inorganic insulating film and an organic insulating film in this order. A contact hole 57 is provided in the second insulating film. Here, as shown in FIG. 16, the contact hole 57 is formed at a predetermined location on the drain electrode 56.

  A pixel electrode 58 shown in FIG. 16 is formed on the second insulating film. Here, the pixel electrode 58 is a pixel electrode according to the first embodiment. Further, as described above, one pixel region is composed of three solid portions. Further, the three solid parts are connected to each other through branch parts.

  A part of the pixel electrode 58 is also formed in the contact hole 57. Therefore, the pixel electrode 58 and the drain electrode 56 are electrically connected. Further, the pixel electrode 58 is made of a transparent conductive material such as ITO (Indium Tin Oxide).

  In addition, a vertical alignment film (not shown) is formed on the first substrate on which the above members are formed. Here, for example, polyimide, polyamide or the like can be employed as the vertical alignment film.

  In the configuration of the first substrate, the branch portions that do not contribute to the connection between the solid portions are formed in the following arrangement. That is, as shown in FIG. 16, the branch portion is arranged so as to overlap with either the source wiring 54 or the gate wiring 51 in plan view.

  Next, the structure of the second substrate facing the first substrate having the above structure will be described without using the drawings. Here, the second substrate is a substrate having transparency such as glass.

  On the second substrate, a black matrix for light shielding, red, green, and blue color material layers are formed. Further, a counter electrode made of a transparent conductive material is disposed on them. On the second substrate, a vertical alignment film is formed in a layer corresponding to an interface with a liquid crystal layer described later.

  When the first substrate and the second substrate having the above-described configuration are prepared, the first substrate and the second substrate are then disposed so as to face each other. Here, both substrates are disposed so that the counter electrode and the pixel electrode 58 face each other.

  A liquid crystal layer is formed between the first substrate and the second substrate. Here, as described in Embodiment 1, the liquid crystal layer is made of a vertically aligned liquid crystal material.

  Next, a method for manufacturing a liquid crystal display device (particularly, a liquid crystal panel unit) according to the present embodiment will be described with reference to FIG.

  First, a method for forming a predetermined member on the first substrate will be described.

  First, a metal chromium film is formed on a first substrate such as glass. The film thickness of the metal chromium film is about 300 nm.

  Next, a photolithography process is performed on the metal chromium film. Thereby, the gate wiring 51, the auxiliary capacitance wiring 52, and the auxiliary capacitance electrode 53 having the above-described configuration can be formed on the first substrate.

  Next, a silicon nitride film (which can be grasped as a first insulating film) is formed so as to cover the gate wiring 51, the auxiliary capacitance wiring 52, the auxiliary capacitance electrode 53, and the like. Here, the thickness of the silicon nitride film is about 400 nm.

  In order to prevent conduction between the upper and lower layers of the silicon nitride film due to pinholes in the film, it is better to form the silicon nitride film in a plurality of times. For example, it is better to adopt a method in which a silicon nitride film is formed to a thickness of about 300 nm, and then a silicon nitride film is further formed to a thickness of about 100 nm.

  Next, an amorphous silicon film (semiconductor layer) and a doped amorphous silicon film (ohmic contact film) are formed in this order on the silicon nitride film. Here, the film thickness of the amorphous silicon film is about 100 nm. The film thickness of the doped amorphous silicon film is about 50 nm.

  Next, a photolithography process is performed on the amorphous silicon film and the doped amorphous silicon film. As a result, the respective films are patterned into a predetermined shape (the TFT portion is formed).

  Next, a metal chromium film is formed again so as to cover the above portions. The film thickness of the metal chromium film is about 300 nm.

  Next, a photolithography process is performed on the metal chromium film. Thereby, the source wiring 54, the source electrode 55, and the drain electrode 56 having the above-described configuration can be formed on the first substrate.

  Next, a silicon nitride film (a second insulating film, particularly an inorganic insulating film can be grasped) is formed so as to cover the source wiring 54 and the like. The silicon nitride film has a thickness of about 400 nm. Further, an acrylic resin film (a second insulating film, particularly an organic insulating film can be grasped) is formed on the silicon nitride film. The acrylic resin film has a thickness of about 3 microns.

  Next, a photolithography process is performed on the second insulating film. Thereby, a contact hole 57 is formed in the second insulating film. Here, the contact hole 57 is formed so that the drain electrode 56 is exposed from the bottom of the contact hole 57.

  Next, an ITO film is formed on the second insulating film. The thickness of the ITO film is about 100 nm. Here, the contact hole 57 is also filled with an ITO film.

  Next, a photolithography process is performed on the ITO film. Thereby, a pixel electrode 58 made of an ITO film is formed. The pixel electrode 58 is the pixel electrode according to Embodiment 1 as described above. Here, an ITO film is formed in the contact hole 57. Therefore, the pixel electrode 58 and the drain electrode 56 are electrically connected.

  Further, in the solid portion constituting the pixel electrode, the branch portions that do not contribute to the connection between the solid portions are formed in the following arrangement. That is, the branch is arranged so as to overlap with either the source wiring 54 or the gate wiring 51 in plan view (see FIG. 16).

  Next, a method for forming a predetermined member on the second substrate will be described without using the drawings.

  First, a metal chromium film is formed on a second substrate such as glass. The film thickness of the metal chromium film is about 300 nm.

  Next, a photolithography process is performed on the metal chromium film. Thereby, a black matrix having a predetermined pattern can be formed on the first substrate.

  Next, a red color material layer is formed so as to cover the black matrix. A photolithography process is performed on the red color material layer. As a result, the red color material layer remains in a predetermined area partitioned by the black matrix.

  Next, a green color material layer is formed so as to cover the black matrix. Photoengraving is performed on the green color material layer. As a result, the green color material layer remains in a predetermined area partitioned by the black matrix.

  Next, a blue color material layer is formed so as to cover the black matrix. Photoengraving is performed on the blue color material layer. As a result, the blue color material layer remains in a predetermined area partitioned by the black matrix.

  Next, a protective film is formed so as to cover the red, green, and blue color material layers.

  Next, an ITO film is formed on the protective film. The thickness of the ITO film is about 100 nm. Thereby, a counter electrode made of an ITO film is formed.

  Now, when the first substrate and the second substrate having the above-described configuration are prepared, the process proceeds to the assembly operation of the liquid crystal panel unit.

  Specifically, a vertical alignment film is formed on each side of the first substrate where the respective members are formed and on the side of the second substrate where the respective members are formed. As the vertical alignment film, for example, Optomer AL1H659 (registered trademark) manufactured by JSR Corporation can be adopted. The thickness of the vertical alignment film is about 80 nm.

  Next, a sealing agent is applied to the periphery of the first substrate on the side where the above-described members are formed. On the other hand, resin spacers are scattered on the side of the second substrate where the above-described members are formed. As the spacer, Micropearl (registered trademark) manufactured by Shimizu Chemical Industry Co., Ltd. can be used.

  Next, the side on which the sealing agent of the first substrate is applied and the side on which the spacers of the second substrate are scattered are faced. Then, the two substrates are thermocompression bonded (that is, bonded together). Here, the panel gap between the two substrates is about 4 μm.

  Next, a liquid crystal material is injected into the panel gap from an opening provided in advance in the sealant. Thereby, a liquid crystal layer can be formed between both substrates. Here, as described above, the liquid crystal layer is made of a vertically aligned liquid crystal material. In this embodiment, a liquid crystal material having the characteristics shown in FIG. 17 is used.

  As can be seen from FIG. 17, the liquid crystal material has no chirality. Therefore, there is almost no difference between the clockwise spiral orientation and the counterclockwise spiral orientation from the viewpoint of orientation stability.

  Now, after the injection of the liquid crystal material, the opening of the sealing agent is sealed. Here, the sealing treatment can be performed using an ultraviolet curable resin. The liquid crystal panel portion is completed through the above steps.

  After the liquid crystal panel is completed, a driving circuit is connected to the gate wiring 51, the auxiliary capacitance wiring 52, the source wiring 54, the counter electrode, and the like, and a circuit configuration is formed so that a predetermined voltage can be applied thereto.

  Further, as shown in FIG. 18, both main surfaces of the liquid crystal panel 60 having the above-described configuration (specifically, the surface where the members of the first substrate are not formed and the members of the second substrate are formed. The optical films 61 are respectively provided on the surfaces that are not. The optical film 61 is usually attached to the liquid crystal panel 60 using an adhesive sheet or the like.

  In the present embodiment, the optical film 61 shown in FIG. 19 is employed. The two optical films 61 shown in FIG. 19 both have a laminated structure including one linear polarizing plate and two retardation films. Here, the retardation film has in-plane retardation as shown in FIG. One optical film as a whole is a circularly polarizing plate.

  In FIG. 19, directions such as the transmission axis and the slow axis are directions seen from the normal direction of the display surface of the liquid crystal panel. Further, the right horizontal direction of the display surface is set to 0 degree, and the angle increases counterclockwise. The phase difference is a value when light having a wavelength of 550 nm is used.

  As shown in FIG. 18, a liquid crystal panel 60 provided with the optical film 61 and a light source 62 are combined. Specifically, the liquid crystal panel 60 is disposed on the light source 62. In the case of a reflective liquid crystal display device that uses external light, the light source 62 is not necessary.

  Thus, the liquid crystal display device is completed.

  Note that after the liquid crystal display device was completed as described above, a predetermined voltage was applied to each wiring or the like. And the orientation state in a pixel electrode was observed using the polarization microscope. Here, a voltage of about 4 V was applied between the counter electrode and the pixel electrode 58.

  As a result of the observation, spiral orientation as shown in FIG. 10 was observed in each solid part. Further, it was also observed that the orientation center of the spiral orientation and the center of the solid part almost coincide.

  In addition, FIG. 20 shows observation results of viewing angle characteristics (isocontrast curves) of the liquid crystal display device according to this embodiment.

  FIG. 20 is a diagram illustrating an angle on the circumference (azimuth 0 to 360 °) when the liquid crystal display device is viewed from the front. The angle in the radial direction from the center toward the outside corresponds to the inclination angle. That is, the center is in front of the liquid crystal display device. For example, the right side of the outermost circle corresponds to the case where the liquid crystal display device is viewed from the right side at an angle of 80 °. The line inside the circle is an isocontrast curve, and the curve of the contrast value of the legend is drawn from 5 to 500. For example, the contrast is 50 or more when viewed from 80 ° diagonally to the right.

  As can be seen from FIG. 20, the liquid crystal display device achieves a very wide viewing angle with excellent symmetry.

  In the liquid crystal display device according to this embodiment, attention is paid to the first substrate. Then, the source wiring 54 and the gate wiring 51 are disposed on the first substrate. Further, in plan view, branch portions (particularly, branch portions that do not contribute to the connection between the solid portions) are arranged so as to overlap with either the source wiring 54 or the gate wiring 51.

  Therefore, the area occupied by the solid part in one pixel region can be maximized. Therefore, a liquid crystal display device with high luminance can be provided.

  As can be seen from the above, an organic insulating film is formed above the gate wiring 51 and the source wiring 54. A pixel electrode 58 (solid portion) is formed above the organic insulating film. Here, as described above, it is assumed that the branch portion is arranged so as to overlap with either the source wiring 54 or the gate wiring 51.

  If the organic insulating film is thin, the oblique electric field around the solid portion outer periphery and the branch portion may be disturbed by the potential applied to the gate wiring 51, the source wiring 54, and the like. Therefore, when the configuration is adopted, it is desirable that the organic insulating film has a thickness of 2 microns or more from the viewpoint of preventing the disturbance of the oblique electric field.

<Embodiment 3>
In this embodiment, a liquid crystal display device (particularly, a liquid crystal panel portion) including the pixel electrode according to Embodiment 1 will be described. Here, in the second embodiment, the case where the pixel electrode according to the first embodiment is applied to the transmissive liquid crystal display device is described. In this embodiment, a case where the pixel electrode according to Embodiment 1 is applied to a transflective liquid crystal display device (a liquid crystal display device having both a transmissive type and a reflective type) will be described.

  FIG. 21 is a perspective plan view showing a configuration on the first substrate included in the transflective liquid crystal display device according to the present embodiment.

  FIG. 21 is compared with FIG. Then, although both structures are substantially the same, they differ in the following points.

  That is, in the first substrate according to the present embodiment, the reflective film is formed on a part of the solid part. Furthermore, the organic insulating film existing in the lower layer of the solid part where the reflective film is formed has an uneven shape. Therefore, the reflective film formed on the organic insulating film also has an uneven shape.

  Also in the present embodiment, one pixel region is constituted by a predetermined number (three in FIG. 21) of solid portions existing in one pixel region. These solid parts are electrically connected to each other through branch parts.

  As shown in FIG. 21, the reflective film 70 is formed on a part of the predetermined number of solid parts (in this embodiment, one of the three solid parts) (see FIG. 21). It can be grasped that the solid part where the reflective film 70 is formed is a reflective electrode). Here, for example, aluminum or silver can be employed as the reflective film 70.

  Also, pay attention to the organic insulating film that exists in the lower layer of the solid part where the reflective film 70 is formed. The front (upper) surface of the organic insulating film has an uneven shape. Therefore, as shown in FIG. 21, the front (upper) surface of the solid part formed on the organic insulating film and the front (upper) surface of the reflective film 70 formed on the solid part are also It has an uneven shape according to the uneven shape.

  In addition, the method of forming uneven | corrugated shape on the surface of an organic insulating film (for example, acrylic resin) is as follows.

  First, the first acrylic resin is formed to a thickness of about 1 micron. Then, a photoengraving process is performed on the first acrylic resin. Thereby, an uneven shape can be formed on the first acrylic resin. Next, a second acrylic resin is formed to a thickness of about 1 micron. Then, a photoengraving process is performed on the second acrylic resin. Thereby, the contact hole 57 can be formed on the second acrylic resin.

  Thus, an organic insulating film in which the contact hole 58 and the uneven shape are formed can be formed.

  Since the reflective film 70 has the uneven shape, the light scattering property of the reflective film 70 can be increased.

  In FIG. 21, attention is paid to a solid part constituting one pixel region. The solid part (reflective part) where the reflective film 70 is formed is of the reflective type, and the solid part part (transmissive part) where the reflective film 70 is not formed is of the transmissive type. That is, the entire one pixel region constitutes a transflective type.

  Attention is paid to the reflective portion of the transflective liquid crystal display device having the above-described configuration. Then, in the reflection part, incident light from the second substrate side passes through the liquid crystal layer twice at the time of incidence and at the time of reflection. That is, the incident light has a phase difference twice in the liquid crystal layer.

  On the other hand, attention is paid to the transmission part of the transflective liquid crystal display device having the above configuration. Then, in the transmissive part, the transmitted light passes through the liquid crystal layer once. That is, the incident light has a phase difference once in the liquid crystal layer.

  As is clear from the above, the display characteristics in the reflective portion and the display characteristics in the transmissive portion are different.

  In order to suppress the occurrence of the difference in display characteristics, it is necessary to make the thickness of the liquid crystal layer on the reflective portion thinner than the thickness of the liquid crystal layer on the transmissive portion.

  As described above, as a method of providing a difference in the thickness of the liquid crystal layer, for example, there is a method of providing a difference in the thickness of the organic insulating film existing below the pixel electrode. There is also a method of providing a step on the second substrate.

  In the present embodiment, a step of 2 microns is provided on the second substrate. Therefore, the thickness of the liquid crystal layer on the transmission portion is 4 microns, and the thickness of the liquid crystal layer on the reflection portion is 2 microns.

  In FIG. 21, configurations other than those described above (other than those described in detail in this embodiment) are the same as the configurations described with reference to FIG. In the configuration of the liquid crystal layer and the second substrate, configurations other than those described above are the same as those described in the second embodiment.

  Therefore, description of these similar configurations is omitted here. As described above, the configuration of the pixel electrode 58 is the configuration described in the first embodiment. Further, in FIG. 21, illustration of the auxiliary capacitance electrode 53, the contact hole 57, and the like is omitted.

  Also in the transflective liquid crystal display device according to the present embodiment, as shown in FIG. 18, two optical films 61 are attached to the liquid crystal panel 60. The liquid crystal panel 60 and the light source 62 are combined.

  In the present embodiment, the optical film 61 shown in FIG. 22 is used.

  The optical film 61 attached to the first substrate side has a laminated structure composed of one linearly polarizing plate and two retardation films. Here, the retardation film has an in-plane retardation as shown in FIG. One optical film as a whole is a circularly polarizing plate.

  The optical film 61 attached to the second substrate side has a laminated structure composed of one linearly polarizing plate and three retardation films. Here, the two retardation films have in-plane retardation as shown in FIG. And one retardation film has the retardation of the thickness direction, as shown in FIG.

  In FIG. 22, directions such as the transmission axis and the slow axis are directions seen from the normal direction of the display surface of the liquid crystal panel. Further, the right horizontal direction of the display surface is set to 0 degree, and the angle increases counterclockwise. The phase difference is a value when light having a wavelength of 550 nm is used.

  In the present embodiment, a reflective film is formed on some solid portions. Therefore, even in the transflective liquid crystal display device, the effects described in Embodiments 1 and 2 can be achieved regardless of the environment of external light.

  In the transflective liquid crystal display device according to this embodiment, a predetermined voltage is applied to each of the wirings 51 and 54 and the like. And the orientation state in a pixel electrode was observed using the polarization microscope. As a result of the observation, spiral orientation as shown in FIG. 10 was observed in each solid part. Further, it was also observed that the orientation center of the spiral orientation and the center of the solid part almost coincide.

  Here, the solid part of the transmission part was observed using a transmission light source. The solid part of the reflection type was observed using an incident light source. The above observation results were obtained in any solid part.

  In addition, viewing angle characteristics (isocontrast curves) of the transflective liquid crystal display device according to this embodiment were observed. The observation was performed when the light source was turned on and when the light source was turned off and under external light. In both cases, it was observed that the transflective liquid crystal display device realized a very wide viewing angle with excellent symmetry.

3 is a plan view illustrating a configuration of a pixel electrode according to Embodiment 1. FIG. It is a figure which shows a mode that a liquid crystal molecule falls in a predetermined direction by the diagonal electric field which originates in the outer peripheral part of a solid part. It is a figure which shows notionally the mode of the orientation of the liquid crystal molecule at the time of voltage non-application. It is a figure which shows notionally the mode of the orientation of the liquid crystal molecule at the time of voltage application. It is a conceptual diagram which shows the mode of radial inclination orientation. It is a conceptual diagram which shows a spray orientation. It is a conceptual diagram which shows twist orientation. It is a conceptual diagram which shows the mode of spiral orientation. It is a conceptual diagram which shows the mode of spiral orientation. FIG. 3 is a conceptual diagram showing a spiral orientation in a solid part according to the first embodiment. It is a figure which shows the case where the occupied area of a solid part deteriorates in a pixel area. 6 is a plan view showing another configuration of the pixel electrode according to Embodiment 1. FIG. FIG. 6 is a diagram for explaining a variation of a solid part according to the first embodiment. It is a figure for demonstrating the definition of the predetermined dimension of a solid part. It is a figure which shows the variation which comprises one pixel area | region by the some solid part. 6 is a perspective plan view showing a configuration on a first substrate included in a liquid crystal display device according to Embodiment 2. FIG. It is a figure which shows the characteristic of liquid crystal material. It is a perspective view which shows the mode of arrangement | positioning of a liquid crystal panel, an optical film, and a light source. It is a figure which shows the structure of an optical film. FIG. 10 is a diagram illustrating a state of an isocontrast curve of the liquid crystal display device according to the second embodiment. 6 is a perspective plan view showing a configuration on a first substrate included in a liquid crystal display device according to Embodiment 3. FIG. It is a figure which shows the structure of an optical film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solid part, 2 opening part, 3 branch part, 10 1st board | substrate, 15 Counter electrode, 20 2nd board | substrate, 30 Liquid crystal layer, 31 Liquid crystal molecule, 51 Gate wiring, 52 Auxiliary capacity wiring, 53 Auxiliary capacity electrode , 54 source wiring, 55 source electrode, 56 drain electrode, 57 contact hole, 58 pixel electrode, 60 liquid crystal panel, 61 optical film, 62 light source, 70 reflective film, AL virtual line.

Claims (9)

A first substrate on which a pixel electrode is disposed;
A second substrate facing the first substrate and provided with a counter electrode;
A vertically aligned liquid crystal layer formed between the first substrate and the second substrate,
The pixel electrode is
A plurality of solid parts arranged in an array;
The solid portion includes a branch portion extending from the outer peripheral portion of the solid portion,
The imaginary line extending in the extending direction of the branch part does not pass through the center of the solid part,
A liquid crystal display device characterized by the above. In the solid part existing on the outermost side of the solid part provided in the array,
The branch is
It extends toward the outer side of the solid part,
The liquid crystal display device according to claim 1. In the predetermined number of the solid portions existing in one pixel region, the adjacent solid portions are connected to each other via the branch portions.
The liquid crystal display device according to claim 1. The formation position of the branch part in each of the adjacent solid parts connected via the branch part is a mirror-symmetrical position.
The liquid crystal display device according to claim 3. The branch part formed in one of the solid parts is 2 or more,
The center position of the solid part with respect to each virtual line of the two or more branches is on the same side when the virtual line is viewed inward of the solid part,
The liquid crystal display device according to claim 1. The branch portions formed in one solid portion are four,
The branch is
The distance from the virtual line to the center of the solid part is formed to be substantially the same,
The liquid crystal display device according to claim 5. The liquid crystal layer is
Consists of liquid crystal material without chirality,
The liquid crystal display device according to claim 4. The first substrate includes
A source wiring and a gate wiring are further provided,
In plan view, the branch portion is arranged so as to overlap with either the source wiring or the gate wiring.
The liquid crystal display device according to claim 1. Among the plurality of solid parts,
In some solid parts, a reflective film is formed,
The liquid crystal display device according to claim 1.

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