Patent Publication Number: US-2016238902-A1

Title: Liquid crystal display device

Description:
CLAIM OF PRIORITY 
     The present application claims priority from Japanese Patent Application JP 2015-025210 filed on Feb. 12, 2015, the content of which is hereby incorporated by reference into this application. 
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention relates to a liquid crystal display device and, in particular, relates to the liquid crystal display device making it possible to prevent generation of a domain caused by reverse rotation of liquid crystal molecules caused by a pressing pressure (pressurization) imposed on a liquid crystal display panel. 
     (2) Description of the Related Art 
     The liquid crystal display device includes the liquid crystal display panel which includes a TFT substrate on which pixels which each includes a pixel electrode, a thin film transistor (TFT) and so forth are formed in a matrix, a counter substrate which faces the TFT substrate, a liquid crystal layer which is held between the TFT substrate and the counter substrate and so forth. Then, an image is formed by controlling a transmittance of the liquid crystal molecules through which light is transmitted per pixel. 
     In the liquid crystal display device, a viewing angle plays an important role. An IPS (In Plane Switching) system liquid crystal display device is configured to control the transmittance of the liquid crystal layer by rotating the liquid crystal molecules by a horizontal electric field and has excellent viewing angle characteristics. On the other hand, a system that a touch panel through which coordinates and so forth are input by touching the panel with a finger and so forth is integrated with the liquid crystal display device is now being generally used. 
     When the liquid crystal display panel has been depressed with the finger and so forth, an orientation direction of the liquid crystal molecules may be changed and may induce generation of disclination. Non-uniformity caused by this disclination is called “depressing non-uniformity’. The pixel electrode which has taken measures against the depressing non-uniformity in the IPS system liquid crystal display device is described in Japanese Unexamined Patent Application Publication No. 2010-9004 
     SUMMARY OF THE INVENTION 
     Although the IPS system liquid crystal display device has the excellent viewing angle characteristics, when the liquid crystal molecules which are driven by an electric field generated between the pixel electrode and a common electrode all rotate in the same direction relative to an initial orientation direction defined by an orientation film, brightness and colors of the respective liquid crystal molecules are made different from one another depending on an azimuth taken. In order to avoid the above-mentioned situation, such a configuration is conceivable that the pixel electrode or the common electrode is bent in the same pixel so as to make a direction of the electric field different from the initial orientation direction of the liquid crystal molecules in the same pixel and thereby the orientation (rotation) directions of the liquid crystals are made different from one another. 
     This configuration is called a multi-domain system because the plurality of domains are present in one pixel. In the multi-domain system, for example, an upper half and a lower half of one pixel are different from each other in orientation (rotation) direction of the liquid crystal molecules when a voltage has been applied between the pixel electrode and the common electrode. 
     In the multi-domain system, a phenomenon that depression domains which are generated when the counter substrate has been depressed mutually interact in the upper half and the lower half of the pixel and the depression domains remain as they are over a long period of time occurs. 
     The present invention has been made in view of the above-mentioned circumstances and aims to take measures against screen non-uniformity caused by long-term presence of the depression domains. 
     In order to overcome the above-mentioned disadvantage, the present invention takes concrete measures as follows. 
     According to one embodiment of the present invention, there is provided a liquid crystal display device which includes a TFT substrate that scan lines are extended in a first direction and are arrayed in a second direction, video signal lines are extended in the second direction and are arrayed in the first direction, a pixel electrode is formed in a region surrounded by the scan lines and the video signal lines and a common electrode is formed via an insulation film, a counter substrate which is arranged so as to face the TFT substrate and a liquid crystal layer which is held between the TFT substrate and the counter substrate, in which the pixel electrode is extended in the second direction and includes a first side face on the side of the first direction, the pixel electrode includes a first region which includes a through-hole through which a video signal is supplied and second and third regions through which light is transmitted, the second region is inclined at an angle η relative to the second direction and the third region is inclined at an angle −η relative to the second direction, each of the second region and the third region is bent at a bending point so as to protrude in the first direction, the second region is bent in a direction opposite to the first direction in the vicinity of the first region to form a recessed part in the first side surface of the pixel electrode, the recessed part includes an upper side and a lower side, a protruded part which is extended in the first direction is included in the first region in the second direction relative to the recessed part and the lower side of the recessed part forms part of an upper side of the protruded part, an angle θ1 of the upper side of the protruded part relative to the second direction is not more than about 90° and at least about 45° and an angle θ2 of the upper side of the recessed part relative to the second direction is not more than the angle θ1. 
     In the above-mentioned liquid crystal display device, the lower side of the protruded part includes a corner cut and an angle θ3 of the corner cut relative to the second direction is not more than the angle θ1. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional diagram illustrating one example of a liquid crystal display device to which one embodiment of the present invention is applied. 
         FIG. 2  is a plan view illustrating one example of a pixel part according to one embodiment of the present invention. 
         FIG. 3  is a plan view illustrating one example of initial orientation of liquid crystal molecules according to one embodiment of the present invention. 
         FIG. 4  is a plan view illustrating one example of orientation of the liquid crystal molecules when a voltage has been applied to a pixel electrode. 
         FIG. 5  is a plan view illustrating one example of orientation disturbance of the liquid crystal molecules when one point of a counter substrate has been pressurized. 
         FIG. 6  is a plan view illustrating one example of disturbance of the liquid crystal molecules after pressurization has been released in a pixel electrode to which the present invention is not applied. 
         FIG. 7  is a plan view illustrating one example of orientation of the liquid crystal molecules after pressurization has been released in the pixel electrode according to one embodiment of the present invention. 
         FIG. 8  is a detailed plan view illustrating one example of the pixel electrode according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Although there exist various types of IPS systems, since the IPS system of the type that, for example, a common electrode is planarly formed, a comb-shaped (linear) pixel electrode is arranged on the common electrode with an insulation film being interposed between the common electrode and the pixel electrode and the liquid crystal molecules are oriented (rotated) by an electric field generated between the pixel electrode and the common electrode makes it possible to increase the transmittance comparatively, the system of the above-mentioned type is mainly used currently. 
       FIG. 1  is a sectional diagram illustrating one example of a liquid crystal display panel of the IPS system as mentioned above.  FIG. 1  is a sectional diagram taken along the A-A line in  FIG. 2  which will be described later. A TFT (Thin Film Transistor) illustrated in  FIG. 1  is a so called top-gate type TFT and as one example of a semiconductor used therein, an LTPS (Low Temperature Poly-Silicon) may be adopted. On the other hand, when an a-Si (amorphous silicon) semiconductor and some LTPSs have been used, a so-called bottom-gate type TFT is frequently used. Although, in the following, description will be made by taking a case where the top-gate system TFT has been used by way of example, it is also possible to apply the present invention to a case where the bottom-gate type TFT has been used. 
     In the example in  FIG. 1 , a first base film  101  made of silicon nitride and so forth and a second base film  102  made of silicon oxide (SiO 2 ) and so forth are formed on a TFT substrate  100  made of glass, resin and so forth by a CVD (Chemical Vapor Deposition) method. The role of the first base film  101  and the second base film  102  is to prevent a semiconductor layer  103  from being stained with impurities generated from the TFT substrate  100 . 
     The semiconductor layer  103  is formed on the second base film  102 . The semiconductor layer  103  is of the type that the a-Si film is formed on the second base film  102  by the CVD method and the a-Si film is converted into a poly-silicon (poly-Si) film by performing laser-annealing on the a-Si film. An island-like semiconductor film is formed by patterning the poly-Si film by photolithography. 
     A gate insulation film  104  is formed on the semiconductor film  103 . The gate insulation film  104  is a silicon oxide film made of, for example, TEOS (tetraethoxysilane). Also the gate insulation film  104  is formed by the CVD method. A gate electrode  105  is formed on the gate insulation film  104 . A scan line  10  also serves as the gate electrode  105 . The gate electrode  105  is formed by high-melting pint metals such as, for example, molybdenum-tungsten (MoW) and so forth, an alloy of these metals and so forth. When the resistance of the gate electrode  105  or the scan line  10  is to be reduced, a laminated film made of a low-resistance metal such as, for example, aluminum (Al), copper (Cu) and so forth and any one of the above-mentioned high-melting point metals. 
     As illustrated in  FIG. 2  which will be described later, since the semiconductor layer  103  passes under the scan line  10  two times, the semiconductor layer  1103  has a double gate structure. Then, an interlayer insulation film  106  is formed by, for example, the silicon nitride and the silicon oxide so as to cover the gate electrode  105 . The interlayer insulation film  106  is adapted to insulate between the gate electrode  105  and a contact electrode  107 . 
     A through-hole  120  adapted to connect a source part S of the semiconductor layer  103  with the contact electrode  107  and a through-hole  140  adapted to connect a drain part D of the semiconductor layer  103  with a video signal line  20  are formed in the interlayer insulation film  106  and the gate insulation film  104 . Photolithography for forming the through-holes  120  and  140  in the interlayer insulation film  106  and the gate insulation film  104  is simultaneously performed on the interlayer insulation film  106  and the gate insulation film  104 . Incidentally, the source part S and the drain part D of the TFT are mutually interchanged appropriately depending on the voltage applied to the TFT. 
     The contact electrode  107  is formed on the interlayer insulation film  106 . The contact electrode  107  is connected with a pixel electrode  112  via a through-hole  130 . The contact electrode  107  and the video signal line  20  are simultaneously formed in the same layer. In order to reduce the resistance, for example, Al and an Al alloy are used for the contact electrode  107  and the video signal line  20 . Since Al and the Al alloy generate hillocks and Al diffuses to other layers, a structure that Al and the Al alloy are sandwiched between a barrier layer and a cap layer made of the high-melting point metals such as, for example, not illustrated MoW and so forth is adopted. There are cases where part of the video signal line  20  which is connected to the drain part D is called a drain electrode and the contact electrode  107  is called a source electrode. 
     The entire of the TFT is protected by forming an organic passivation film (an insulation film)  109  so as to cover the contact electrode  107 . The organic passivation film  109  is formed with a photosensitive acrylic resin and so forth. It is also possible to form the organic passivation film  109  with resins such as a silicone resin, an epoxy resin, a polyimide resin and so forth other than the acrylic resin. Since the organic passivation film  109  has a role to serve as a flattened film, the organic passivation film  109  is formed thick. Although a film thickness of the organic passivation film  109  may be about 1 μm to about 4 μm, the organic passivation film  109  has the film thickness of about 2 μm to about 3 μm in many cases. 
     In order to electrically conduct the pixel electrode  112  with the contact electrode  107 , the through-hole  130  is formed in the organic passivation film  109 . Since the organic passivation film  109  is formed by using the photosensitive resin, when the photosensitive resin is applied and then is exposed to light, only part which has been irradiated with light dissolves in a specific developing agent. That is, it is possible to omit formation of a photoresist film by using the photosensitive resin. After the through-hole  130  has been formed in the photosensitive resin, the resin is baked at about 230° C. and thereby formation of the organic passivation film  109  is completed. 
     Then, an ITO (Indium Tin Oxide) film which will serve as a common electrode  110  is formed by sputtering and patterning is performed so as to remove the ITO film from within the through-hole  130  and from its surroundings. It is possible to form the common electrode  110  planarly in common among respective pixels. Then, a silicon nitride film which will serve as a capacitance insulation film  111  is formed on the entire surface of the common electrode  110  by the CVD method. Then, a through-hole adapted to electrically conduct the contact electrode  107  with the pixel electrode  112  in the through-hole  130  is formed in the capacitance insulation film  111 . 
     Then, the ITO film is formed by sputtering and the pixel electrode  112  is formed by patterning. An orientation film material is applied onto the pixel electrode  112  by flexography, inkjet printing and so forth and is baked to form an orientation film  113 . A photo-orientation method to be performed by using polarized ultraviolet rays is used in orientation processing of the orientation film  113  in addition to a rubbing method. 
     When a voltage is applied between the pixel electrode  112  and the common electrode  110 , such a line of electric force as illustrated in  FIG. 1  is generated. A liquid crystal molecule  301  is rotated by an electric field generated by the line of electric force, an amount of light which passes through a liquid crystal layer  300  is controlled per pixel and thereby an image is formed. 
     In the example in  FIG. 1 , a counter substrate  200  is arranged with the liquid crystal layer  300  being interposed between the TFT substrate  100  and the counter substrate  200 . A color filter  20  is formed on the liquid crystal layer side of the counter substrate  200 . As the color filters  201 , red, green and blue color filters are formed per pixel and a color image is formed by using these color filters  201 . A shading film (a black matrix)  202  is formed between the color filers  201  to as to improve the contract of the image. Incidentally, the shading film  202  also has a role of shading the TFT and prevents a photocurrent from flowing into the TFT. 
     An overcoat layer  203  is formed so as to cover the color filters  201  and the black matrix  202 . Since the surfaces of the color filters  201  and the black matrix  202  are uneven, the surfaces of the color filters  201  and the black matrix  202  are flattened by the overcoat film  203 . The orientation film  113  adapted to determine the initial orientation of the liquid crystal molecules is formed on (the liquid crystal layer  300  side) the overcoat film  203 . In the orientation processing to be performed on the orientation film  113 , the rubbing method or the photo-orientation method is used as in the case of formation of the orientation film  113  on the TFT substrate  100  side. 
     Incidentally, the above-mentioned configuration is merely one example and there are cases where an inorganic passivation film is formed between the contact electrode  107  and the organic passivation film  109  depending on the kind of device used. In addition, there are also cases where a formation process of the through-hole  130  which is different from the above-mentioned formation process is used depending on the kind of device used. In the following, the present invention will be described in detail by using a preferred embodiment. 
     Embodiment 1 
       FIG. 2  is a plan view illustrating one example of a pixel part according to the embodiment 1 of the present invention. The above-mentioned  FIG. 1  is a sectional diagram taken along the A-A line in  FIG. 2 . In the example in  FIG. 2 , the scan lines  10  are extended in a horizontal direction and are arrayed in a vertical direction. In addition, the video signal lines  20  are extended in the vertical direction and are arrayed in the horizontal direction. A region surrounded by the scan lines  10  and the video signal lines  20  is configured as the pixel part and the pixel electrode  112  is present in the region. The pixel part has a size of, for example, not more than about 30 μm in the horizontal direction and not more than about 120 μm in the vertical direction. The liquid crystal display device according to the embodiment of the present invention is particularly beneficial to such a high definition screen as mentioned above. Although in the example in  FIG. 2 , the video signal lines  20  are linearly extended in the vertical direction, there are also cases where the video signal lines  20  are extended in the vertical direction while bending modeling after bending of the later described pixel electrode  112 . 
     In the example in  FIG. 2 , the video signal line  20  and the semiconductor layer  103  are connected together through the through-hole  140 . The semiconductor layer  103  is extended under the video signal line  20 , passes under the scan line  10 , passes again under the scan line  10  by being bent and is connected with the contact electrode  107  illustrated in  FIG. 1  via the through-hole  120 . The scan line  120  serves as a gate electrode of the TFT and in the example in  FIG. 2 , the two TFTs are serially formed ranging from the video signal line  20  to the pixel electrode  112 . A set of the two TFTs which are serially formed as described above is also called a double-gate TFT. The contact electrode  107  and the pixel electrode  112  are connected together via the through-hole  130  formed in the organic passivation film  109 . 
     The pixel electrode  112  has a shape in which a slit  1121  is formed and which is long in the vertical direction (the direction that the video signal lines  20  are extended). Since in the example in  FIG. 2 , the two slits  1121  are present in the pixel electrode  112 , the pixel electrode  112  is configured by three linear (stripe-shaped) electrodes. Incidentally, the present invention is also applicable to a case where the pixel electrode  112  is configured by one to two linear electrode(s) and/or a case where the pixel electrode  112  is configured by four or more linear electrodes. 
     An orientation axis AL of the orientation film  113  is directed in the vertical direction (the direction that the video signal lines  20  are extended) in  FIG. 2 . The pixel electrode  112  includes a bent part  1122  on a vertical central part thereof. Although the upper half and the lower half of the pixel electrode  112  are inclined at an angle of η relative to the orientation axis AL, the upper side (the upper half) and the lower side (the lower half) are inclined in opposite directions. The angle η is about 5° to about 15°. The pixel electrode  112  is inclined at the angle of η relative to the orientation axis AL in order to rotate the liquid crystal molecules  301  in a fixed direction when the voltage has been applied to the pixel electrode  112 . 
     Accordingly, in the example in  FIG. 2 , when the voltage has been applied to the pixel electrode  112 , the liquid crystal molecules which are present in the upper half and the lower half of the pixel part are rotated in opposite directions. Thereby, it becomes possible to make viewing angle characteristics or azimuth characteristics more uniform. The pixel configuration illustrated in  FIG. 2  is called a dual-domain system because two domains are present in one pixel. 
       FIG. 3  is a schematic diagram illustrating one example of a general orientation state of the liquid crystal molecules  301  when no voltage is applied to the pixel electrode  112 .  FIG. 4  is a schematic diagram illustrating one example of an orientation state of the liquid crystal molecules  301  when the voltage has been applied to the pixel electrode  112 . In the example in  FIG. 4 , the liquid crystal molecules are rotated in the opposite directions above and under the bent part  1122  of the pixel electrode  112 . Thereby, the viewing angle characteristics or the azimuth characteristics are made uniform. 
     In recent years, a liquid crystal display device into which a touch panel configured to touch the counter substrate side of a liquid display panel with a finger and so forth is incorporated is widely used. When the liquid crystal display panel is touched with the finger and so forth, the liquid crystal layer corresponding to the touched part is depressed via the counter substrate and therefore the orientation of the liquid crystal molecules  301  is disturbed.  FIG. 5  is a schematic diagram illustrating one example of disturbance of the orientation directions of the respective liquid crystal molecules  301  which would occur in such a case as mentioned above. 
     In the example in  FIG. 5 , assuming that a pressurizing point at which the counter substrate  200  is pressurized is designated by PR, the disturbance occurs in orientation as illustrated by liquid crystal molecules  302  centering on the pressurizing point PR. Consequently, the transmittance of the liquid crystal is made different from others at this part and the part becomes a region where display is abnormally made. Even when such a display abnormal region as mentioned above is generated, there would be no inconvenience as long as the liquid crystals  301  return to their normal states after the finger and so forth have been detached from that part, that is, after pressurization has been released. 
     However, since the liquid crystal has a viscosity, the orientation direction of the liquid crystal molecules in the upper half of the pixel part in  FIG. 2  affects the orientation direction of the liquid crystal molecules in the lower half of the pixel part and such a phenomenon occurs that the orientation direction of the liquid crystal molecules in the lower half of the pixel part does not return to the original orientation direction and the liquid crystal molecules in the lower half of the pixel part are oriented in the orientation direction of the liquid crystal molecules in the upper half of the pixel part.  FIG. 6  is a schematic diagram illustrating one example of the above-mentioned inconvenience. 
     Although  FIG. 6  is a plan view illustrating one example of the lower half of the pixel electrode  112 , the orientation direction of the liquid crystal molecule  301  located on the right-end outer side of the pixel electrode  112  is made the same as the orientation direction of the liquid crystal molecules on the upper side of the pixel electrode  112 . Then, the orientation directions of the liquid crystal molecules are made different from one another among the part on the right-end outer side of the pixel electrode  112  and other parts on the lower side of the pixel electrode  112 . That is, liquid crystal molecules located on the right-end outer side of the pixel electrode  112  are rotated in the reverse direction as designated by  304 . A region where the liquid crystal molecules are rotated in the reverse direction is referred to as a reverse-rotation region RE. 
     Then, a part on the right-side stripe-shaped pixel electrode serves as a boundary along which the liquid crystal molecules are oriented in the opposite directions and the liquid crystal molecules in that part are in a state which is the same as that when the liquid crystal molecules are not rotated by voltage application. The liquid crystal molecules in this part are designated by  303 . This part is referred to as so-called disclination DE. Presence of the disclination DE induces a reduction in transmittance of the pixel. 
     The embodiment of the present invention is configured such that a protruded part  30  and a recessed part  40  are formed on the pixel electrode  112  on the lower part of the pixel electrode  112 , that is, in the vicinity of the through-hole  130  and a corner cut  50  is formed on the right lower side so as to apply the electric field which works so as to forcibly orient the liquid crystal molecules in the same direction as that of the liquid crystal molecules in other regions on the lower side of the pixel electrode  112  to the liquid crystal molecules  301  on the right-end outer side of the pixel electrode  112 . In the example in  FIG. 2 , a dotted-line region indicates a region of the black matrix  202  which has been formed on the counter substrate  200 . That is, the protruded part  30  and the recessed part  40  formed on the pixel electrode  112  are covered with the black matrix  202 . Accordingly, in the general state, the protruded part  30  and the recessed part  40  of the pixel electrode  112  do not affect the transmittance of the liquid crystal display device. 
     Since the liquid crystal has the viscosity, the liquid crystal molecules  301  which have been forcibly arrayed in a predetermined direction owing to the presence of the protruded part  30  and the recessed part  40  of the pixel electrode  112  also affect other regions located along a right side face of the pixel electrode  112  and thereby the orientation of the liquid crystal molecules  301  is maintained in a normal state along the entire of a lower right end of the pixel electrode  112 . 
       FIG. 7  is a schematic diagram illustrating one example of a situation which has been described above. In the example in  FIG. 7 , the protruded part  30  and the recessed part  40  are present on the lower side (the side which is close to the contact electrode  107  with the bending point of the pixel electrode  112  being set as a reference) of the pixel electrode  112  and the corner cut  50  is formed in a right lower part of the pixel electrode  112 . In the example in  FIG. 7 , a region where a force acting so as to forcibly orient the liquid crystal molecules  301  in the same direction as that of the liquid crystal molecules in other regions on the lower side of the pixel electrode  112  is generated is designated by a dotted line F. In the example in  FIG. 7 , dotted-line liquid crystal molecules  304  indicate molecules which have been oriented in the orientation direction in an existing example when pressurization has been released. In contrast, in the embodiment of the present invention, the liquid crystal molecules  301  are oriented in the same direction as that of the liquid crystal molecules in other regions on the lower side of the pixel electrode  112  owing to the presence of the region F formed by the protruded part  30 , the recessed part  40  and/or the corner cut  50  and generation of the disclination DE is suppressed. 
       FIG. 8  is an enlarged diagram illustrating one example of the shape of the pixel electrode  112  according to the embodiment of the present invention. In the example in  FIG. 8 , a width w 1  of a stripe part of the pixel electrode  112  is, for example, about 3.5 μm and a width w 2  of the slit  1121  in the pixel electrode  112  is, for example, about 3.9 μm. In the example in  FIG. 8 , after the pressing pressure (pressurization) has been released, the liquid crystal molecules  301  are maintained in the normal orientation direction owing to the presence of the protruded part  30 , the recessed part  40  and the corner cut  50 . Incidentally, the recessed part  40 , the protruded part  30  and the corner cut  50  are covered with the black matrix  202  formed on the counter substrate  200 . 
     In the example in  FIG. 8 , the stripe-shaped pixel electrode  112  is bent at a point P, the recessed part is formed starting from the bent part (the bending point) P and a distance d 1  measured from the bending point P to the innermost of the recessed part  40  is defined as a depth of the recessed part  40 . When the pixel electrode  112  gently curves and therefore the bending point P is not clearly defined, a tangential intersecting point of a side of the pixel electrode  112  and an upper side of the recessed part  40  is defined as the bending point P. 
     A length d 2  of the protruded part  30  in the horizontal direction in the drawing (the direction that the scan lines  10  are extended) is defined with a horizontal-direction position of the bending point P being set as a reference. The length d 2  is larger than zero and may be optionally selected so as to obtain the advantageous effect of the present invention. However, it is preferable not to extend the length d 2  up to the next pixel. That is, the protruded part  30  may be also formed so as to overlap the video signal line  20  in planar view. In addition, a width t of the tip of the protruded part  30  may be at least zero. A value which is at least a minimum working size, for example, at least about 2.5 μm may be ensured as a width d 3  of the corner out  50  in the horizontal direction. 
     In the example in  FIG. 8 , angles of an upper side of the protruded part  30 , the upper side of the recessed part  40  and the corner cut  50  relative to the orientation axis AL have a great effect on the orientation of the liquid crystal molecules  301 . Here, the angle between the upper side of the protruded part  30  and the orientation axis AL is defined as θ1, the angle between the upper side of the recessed part  40  and the orientation axis AL is defined as θ2 and the angle between the corner cut  50  and the orientation axis AL is defined as θ3. 
     The advantageous effect of the present invention is obtained when the angle θ1 is not more than about 90°. On the other hand, when the angle θ1 is too small, it becomes difficult to cover the protruded part  30  with the black matrix  202 . Therefore, it is desirable that the angle θ1 be at least about 45°. Accordingly, the angle θ1 is in a range from not more than about 90° to at least about 45°, more preferably, from at least about 45° to not more than about 85° and further more preferably, from at least about 45° to not more than about 80°. 
     Since it is desirable to suppress generation of the disclination on the right end of the pixel electrode  112  and ends of the pixel electrode  112  in other regions, it is desirable to determine the angle θ2 depending on the conditions for suppressing generation of the disclination. Accordingly, the angle θ2 becomes smaller than the angle θ1 by an angle ξ. 
     Although it is desirable that the angle θ3 of the corner cut  50  relative to the orientation axis AL be not more than about 90°, it is also possible to set the angle θ3 to be not more than about 45° in a range of angles that the length d 2  of the protruded part  30  in the horizontal direction is ensured. However, the most general angle θ3 is about 45° from the viewpoint of a relation between the advantageous effect of the present invention and a layout of the device used. 
     As illustrated in  FIG. 7 , it is possible to implement the liquid crystal display device which is suppressed in generation of the disclination and is high in transmittance by using the pixel electrode  112  which is configured as mentioned above. In addition, it is also possible to obtain the advantageous effect of the present invention to some extent simply by forming the recessed part  40  and the protruded part  30  with no provision of the corner cut  50 . However, it is possible to exhibit the advantageous effect of the present invention more efficiently by providing the corner out  50  in addition to the recessed part  40  and the protruded part  30 . 
     In the foregoing, although description has been made on the assumption that the bent part of the pixel electrode is oriented in the direction that the scan lines are extended as illustrated in  FIG. 2 , the present invention is also applicable to a case where the bent part of the pixel electrode is oriented in a direction opposite to that illustrated in  FIG. 2 , that is, in the direction opposite to the direction that the scan lines are extended. In this case, the recessed part, the protruded part and the corner cut are formed line-symmetrically relative to the arrangement in  FIG. 2  and so forth. 
     In addition, in the foregoing, although a case where a dielectric anisotropy of the liquid crystal is positive, that is, a case where a positive-type liquid crystal has been used has been described, the present invention is also applicable to a case where the dielectric anisotropy of the liquid crystal is negative, that is, a case where a negative-type liquid crystal is used. In this case, the direction of the initial orientation will have an angle of about 90° relative to the direction illustrated in  FIG. 2 . In addition, the color filters, the black matrix and so forth may be provided on the TFT substrate. In addition, although in the above-mentioned embodiment, the pixel electrode is installed between the common electrode and the liquid crystal layer, it is also possible to apply the present invention even to a configuration that the common electrode is installed between the pixel electrode and the liquid crystal layer and the slit is formed in the common electrode within a range not deviating from the gist of the invention of the present application.