JP2005189476A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MVA mode liquid crystal display device which is accompanied with few disclination defects on the periphery of a pixel and with little display unevenness, and which exhibits excellent display quality even when no auxiliary protrusion is arranged. <P>SOLUTION: In the MVA mode liquid crystal display device 10 which has a first substrate 71 with pixel electrodes 74, placed on positions partitioned by mutually almost perpendicularly intersecting signal lines 73 and scanning lines 72, disposed in a matrix, a second substrate 78 with a transparent electrode 81 formed thereon, belt-shaped protrusions 82 formed on the second substrate 78 and intersecting edge parts of the pixel electrodes 74 in inclined directions, and slits 76 formed on the pixel electrodes 74 and disposed in parallel to the adjacent protrusions 82, grooves 99 are arranged on parts located between positions where the edge parts of the pixel electrodes 74 overlap with the protrusions 82 and the slits 76 and further having an angle between the slits 76 and the edge parts being 90° or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device, and more particularly to an MVA (Multi-domain Vertically Aligned) type liquid crystal display device in which disclination is suppressed and display quality is good.

  In general, liquid crystal display devices are characterized by thinness, light weight and low power consumption. In particular, TFT (Thin Film Transistor) type liquid crystal display devices are widely used from portable terminals to large-sized televisions. As this liquid crystal display device, a twisted nematic (TN) type liquid crystal display device has been often used for a long time, and maintains high performance and quality as a display device.

  The configuration of the TN mode liquid crystal display device will be described with reference to FIG. 3. As shown in FIG. 3A, the TN mode liquid crystal display device 50 includes a substrate 52 on which a pixel electrode 51 is formed and a common electrode 53. The formed substrate 54 is disposed so as to face each other, and liquid crystal is sealed between the pair of substrates to form a liquid crystal layer. The alignment films 56 and 57 on both the substrates 52 and 54 are subjected to alignment treatment by rubbing or the like, and the alignment direction is set to be 90 degrees different from the alignment direction of the opposing substrate (crossed Nicol arrangement). The liquid crystal molecules 55 are regulated in this orientation direction and are horizontally aligned in that direction, and are twisted by 90 degrees in the horizontal direction between the substrates 52 and 54.

  Polarizers 58 and 59 are arranged on the outer sides of the substrates 52 and 54 so as to face the substrates. In the normally black mode, the polarizers 58 and 59 are arranged so that the transmission axes thereof are in the same direction. In the normally white mode, the polarizing axes of the polarizing plates 58 and 59 are arranged so as to form 90 degrees. The transmitted light that has passed through one polarizing plate passes through the liquid crystal layer as linearly polarized light. At this time, since the liquid crystal molecules 55 are twisted and arranged 90 degrees, the transmitted light rotates and the polarization direction is twisted 90 degrees. . At this time, in the normally black mode, the transmitted light that has passed through one liquid crystal layer cannot pass through the other polarizing plate, so that dark display is performed. However, in the normally white mode, the transmitted light that has passed through the liquid crystal layer does not pass through the other polarizing plate. Since it can pass, it becomes bright display. The latter normally white mode TN type liquid crystal display is usually used.

  Next, when an electric field is applied between the electrodes 51 and 53, as shown in FIG. 3B, the liquid crystal molecules 55 rise in the vertical direction and are twisted. However, since the alignment regulation force is stronger on the surfaces of the alignment films 56 and 57, the alignment direction of the liquid crystal molecules 55 remains along the alignment films 56 and 57. In such a state, since the liquid crystal molecules 55 are isotropic with respect to the light passing therethrough, the polarization direction of the linearly polarized light incident on the liquid crystal layer does not rotate. Therefore, in the normally white mode TN liquid crystal display device, the linearly polarized light that has passed through the upper polarizing plate 59 cannot pass through the lower polarizing plate 58 and is in a dark state. Thereafter, when the electric field is not applied again, the state shown in FIG. 3A is obtained due to the alignment regulating force, and the display returns to the bright state.

  The manufacturing technology of this TN liquid crystal display device has made remarkable progress in recent years, and the contrast and color reproducibility in the front have surpassed those of CRT. However, the TN liquid crystal display device has a great disadvantage that the viewing angle dependency is large and the viewing angle is narrow.

  Therefore, a VA (vertically aligned) liquid crystal display device has been developed as a method that has a fast response while maintaining a wide viewing angle. In this type of liquid crystal display device 60, as shown in FIG. 4, a liquid crystal having a negative dielectric anisotropy is sealed between a pair of substrates 62 and 64. A common electrode 63 is disposed on the substrate 64. When the alignment films 66 and 67 on both the substrates 62 and 64 are both subjected to the vertical alignment process and no electric field is applied to the electrodes 61 and 63, the liquid crystal molecules 65 are vertically aligned as shown in FIG. Are arranged. Polarizing plates 68 and 69 are arranged in crossed Nicols on the outer sides of both substrates 62 and 64. When no electric field is applied between the electrodes 61 and 63, the liquid crystal molecules 65 between the substrates are arranged vertically, so that the linearly polarized transmitted light that has passed through one polarizing plate passes through the liquid crystal layer as it is. The other polarizing plate blocks the dark state, that is, black display. When an electric field is applied between the electrodes 61 and 63, as shown in FIG. 4B, the liquid crystal molecules 65 between the substrates are arranged horizontally, so that transmission of linearly polarized light that has passed through one polarizing plate is transmitted. When the light passes through the liquid crystal layer, it becomes elliptically polarized light due to the birefringence of the liquid crystal molecules, passes through the other polarizing plate, and becomes a bright state, ie, white display.

  In this VA mode liquid crystal display device, when no electric field is applied between the electrodes 61 and 63, all the liquid crystal molecules 65 are aligned in a state of standing vertically on the alignment films 66 and 67. Since the direction in which the liquid crystal molecules 65 are tilted in the horizontal direction cannot be controlled, the liquid crystal molecules 65 are tilted in a random direction and are horizontally aligned as they are, and display unevenness is conspicuous. There is a problem that the orientation of the film is disturbed and disclination occurs.

  To regulate the direction in which the liquid crystal molecules standing vertically when an electric field is applied between the electrodes is tilted to achieve a uniform display state, the liquid crystal molecules are completely vertical when no electric field is applied between the electrodes. Instead, it is necessary to stand at a slight angle with respect to the vertical axis, and the distribution state in the tilt direction must be substantially equal for each pixel.

In order to further improve the viewing angle of this VA liquid crystal display device, an MVA (Multi-domain vertically aligned) method is proposed in which a plurality of domains are formed in one pixel by providing protrusions and grooves in the pixel. (See Patent Documents 1 and 2)
The pixel configuration of this conventional MVA liquid crystal display device will be described with reference to FIGS. 5 is a plan view of a pixel of a conventional MVA liquid crystal display device 70, and FIG. 6 is a cross-sectional view taken along the line AA 'in FIG.

  On a transparent first substrate 71 such as a glass substrate, scanning lines 72 and signal lines 73 are arranged in a matrix via a gate insulating film 71 '. A region surrounded by the scanning line 72 and the signal line 73 corresponds to one pixel, a pixel electrode 74 is disposed in this region, and a switching element connected to the pixel electrode 74 is disposed at the intersection of the scanning line 72 and the signal line 73. A certain TFT 75 is formed. A part of the pixel electrode 74 overlaps the adjacent scanning line 72 with an insulating film 71 ″ interposed therebetween, and this part functions as a storage capacitor. A plurality of slits 76 to be described later are formed in the pixel electrode 74. The alignment film 77 covering the electrode 74 is subjected to a vertical alignment process.

  A black matrix 79 is formed on a transparent second substrate 78 such as a glass substrate so as to divide each pixel, and a color filter 80 is laminated corresponding to each pixel. The color filter 80 is provided with one color filter 80 of red (R), green (G), and blue (B) corresponding to each pixel. A transparent electrode 81 such as ITO is laminated on the color filter 80, a projection 82 having a predetermined pattern is formed on the transparent electrode 81, and the transparent electrode 81 and the projection 82 are formed by an alignment film 83 subjected to a vertical alignment process. Covering.

  A liquid crystal layer 84 having a negative dielectric anisotropy is interposed between the substrates 71 and 78. When no electric field is generated between the pixel electrode 74 and the transparent electrode 81, the liquid crystal molecules 84 ′ are vertically aligned by being regulated by the alignment films 77 and 83, and an electric field is generated between the pixel electrode 74 and the transparent electrode 81. The liquid crystal molecules 84 'are inclined in the horizontal direction. At this time, the liquid crystal molecules 84 ′ are regulated by the slits 76 and the protrusions 82 and tilted in a predetermined direction, so that a plurality of domains can be formed in one pixel. FIG. 6 schematically shows a state where an electric field is generated between the pixel electrode 74 and the transparent electrode 81 and the liquid crystal molecules 84 ′ are tilted.

  A first polarizing plate 85 is disposed outside the first substrate 71, and a second polarizing plate 86 is disposed outside the second substrate 78, and the first polarizing plate 85 and the second polarizing plate 86 have their respective transmission axes. It is set to be orthogonal. The direction of both polarizing plates 85 and 86 is set by the relationship between the transmission axis and the direction of the liquid crystal molecules 84 ′ when tilted, but the transmission axis of the polarizing plates 85 and 86 and the direction of inclination of the liquid crystal molecules 84 ′ Since the relationship will be described later, here, for the sake of convenience, the transmission axis of the first polarizing plate 85 coincides with the extending direction of the scanning line 72, and the transmission axis of the second polarizing plate 86 coincides with the extending direction of the signal line 73. Set as follows.

  When no electric field is generated between the pixel electrode 74 and the transparent electrode 81, the liquid crystal molecules 84 'are aligned vertically, so that the linearly polarized transmitted light that has passed through the first polarizing plate 85 passes through the liquid crystal layer 84 as linearly polarized light. Then, it is blocked by the second polarizing plate 86 and a black display is obtained. In addition, when a predetermined voltage is applied to the pixel electrode 74 and an electric field is generated between the pixel electrode 74 and the transparent electrode 81, the liquid crystal molecules 84 ′ are inclined in the horizontal direction, so that the linearly polarized light that has passed through the first polarizing plate 85. The transmitted light becomes elliptically polarized light in the liquid crystal layer 84, passes through the second polarizing plate 86, and becomes white display.

  Next, the shapes of the slits 76 and the protrusions 82 will be described. The slit 76 is formed by removing a part of the pixel electrode 74 by a photolithography method or the like, and the protrusion 82 is formed in a predetermined pattern by using a resist made of, for example, an acrylic resin or the like by a photolithography method.

  The protrusions 82 are formed in a zigzag shape across a plurality of pixels, and the straight portions extend in a direction of 45 ° with respect to the signal lines 73 when viewed from the vertical direction of the second substrate 78. In a substantially central portion of one pixel, a protrusion 82a extending from one adjacent pixel bends 90 ° and extends to an adjacent pixel again, and a protrusion 82b extending from the other adjacent pixel is a straight portion of the protrusion 82a bent at a right angle. And is located near the corner of the pixel.

  The slits 76 are formed so as to be respectively located in the middle of the plurality of protrusions 82 when viewed in plan, and in this example, as shown in FIG. 5, three slits 76 are formed in each pixel electrode 74. . A slit 76 a is formed between the protrusion 82 a and the protrusion 82 b, and a slit 76 b is formed between the protrusion 82 a and the edge portion of the pixel electrode 74. The slit 76 a has a center line parallel to the adjacent protrusion 82 and is at a 45 ° direction with respect to the signal line 73. The center line of the slit 76a corresponds to the extending direction of the slit 76a. Similarly, the extending direction of the slit 76b is parallel to the adjacent protrusion 82a. Since the extending direction of the protrusion 82a adjacent to the slit 76b is bent at a right angle within the pixel, the extending direction of the slit 76b is also bent.

  The liquid crystal molecules 84 ′ are inclined in the 90 ° direction with respect to the protrusions 82 and the slits 76, and are inclined in the opposite direction with respect to the protrusions 82 and the slits 76. A pair of crossed Nicols polarizers are arranged outside the pair of glass substrates, the angle between the transmission axis of the polarizer and the direction of the projection 82 is set to 45 °, and the normal direction of the polarizer The angle between the tilted liquid crystal molecules and the transmission axis of the polarizing plate is 45 °. When the angle between the tilted liquid crystal molecules and the transmission axis of the polarizing plate is 45 °, the transmitted light can be most efficiently obtained from the polarizing plate.

  This MVA liquid crystal display device has an advantage that alignment film is not required to be rubbed and alignment division can be achieved by arrangement of linear structures. Therefore, this MVA liquid crystal display device can obtain a wide viewing angle and high contrast. Further, since it is not necessary to perform rubbing, the manufacture of the liquid crystal display device is simple, and there is no contamination due to shaving of the alignment film during rubbing, and the reliability of the liquid crystal display device is improved.

  However, in the conventional MVA-type liquid crystal display device, the actual display state of the liquid crystal molecules is not ideal, and thus an optimal display state cannot be obtained. In particular, in the peripheral portion of the pixel electrode 74, when the liquid crystal molecules 84 'are tilted, not only the protrusion 82 and the slit 76 but also the edge portion of the pixel electrode 74 is affected, so that display unevenness is likely to occur.

  FIG. 7 schematically shows the tilted state of the liquid crystal molecules. The arrow in the pixel electrode 74 indicates the tilt direction of the liquid crystal molecules, and the direction of the arrow is from the end close to the glass substrate having the protrusions 82 to the glass substrate having the pixel electrode 74 when the liquid crystal molecules are tilted. The direction toward the near end is shown.

  The liquid crystal molecules 84 ′ are regulated so as to incline in the direction of about 90 ° with respect to the protrusions 82 and the slits 76. The contour portions of the protrusion 82 and the slit 76 facing each other are in the same direction. The edge portion of the pixel electrode 74 affects the liquid crystal molecules to be inclined in the 90 ° direction, and the edge portion is not parallel to the slits 76 and the protrusions 82, so that the inclined state of the liquid crystal molecules 84 'is adversely affected. The influence of the edge portion is greatly different depending on the arrangement positional relationship between the slit 76 and the protrusion 82 near the edge portion. For example, in the area A1 in FIG. 7, the direction of the arrow near the slit 76 and the protrusion 82 is deviated by about 45 ° from the direction of the arrow near the edge, but in the area A2, the direction of the arrow near the slit 76 and the protrusion 82 is changed. The direction of the arrow in the vicinity of the edge portion is shifted by about 135 °, and the tilted state of the liquid crystal molecules is greatly disturbed in the region A2. Therefore, display unevenness is more likely to occur in the area A2 than in the area A1.

  As described above, in the conventional MVA type liquid crystal display device, the alignment of the liquid crystal molecules 84 ′ is disturbed due to the presence of the edge portion of the pixel electrode 74 at the peripheral portion of one end of each pixel in the pretilt direction. However, there was a problem that disclination occurred.

  In order to solve the problem peculiar to this MVA type liquid crystal display device (occurrence of misalignment region), a new structure is proposed in Patent Document 2 below. Hereinafter, an MVA liquid crystal display device 90 disclosed in the following Patent Document 2 will be described with reference to FIGS. 8 and 9. The same configuration as that of the MVA liquid crystal display device 70 shown in FIGS. The same reference numerals are assigned to the portions, and detailed description of the portions is omitted. 8 is a plan view of a pixel of an MVA liquid crystal display device disclosed in Patent Document 2 below, and FIG. 9 is a cross-sectional view taken along the line AA ′ of FIG. FIG. 9A shows a state before an electric field is applied, and FIG. 9B shows a state after the electric field is applied.

The MVA liquid crystal display device 90 as shown in FIGS. 8 and 9 is different from the MVA liquid crystal display device 70 shown in FIGS. 5 and 6 in order to control the alignment of liquid crystal molecules. This is that an auxiliary projection 89 is provided outside the effective pixel range on the projection 82, and the other configuration is substantially the same as the configuration of the MVA liquid crystal display device 70 shown in FIGS. 6 and 7. According to the MVA liquid crystal display device 90, the influence of the electric field from the edge portion of the pixel electrode 74 and the adjacent pixel on the liquid crystal molecules 84 'is reduced, and the generation of disclination can be effectively suppressed. It can be done.
JP-A-11-024225 (Claims, FIGS. 10 to 12) JP 2001-083517 A (paragraphs [0007] to [0037], FIGS. 32 to 34)

  However, in the MVA type liquid crystal display device 90 having such a configuration, there is a slight difference in the degree of exposure between the central portion and the peripheral portion of the exposure lens in the exposure process. Accordingly, some variation occurs in the components formed on the glass substrate, resulting in variations in protrusion positions, protrusion shapes, and the like. Further, a bonding deviation between the substrates also occurs in manufacturing. As a result, the positional relationship between the pixel electrode 74 and the auxiliary protrusion 89 is inevitably shifted in manufacturing, and the effect of the auxiliary protrusion 89 also varies depending on the location, resulting in the occurrence of luminance unevenness.

  Further, in the liquid crystal display device, spherical spacers are scattered to form a cell gap. However, when the spherical spacers are placed on the auxiliary protrusions 89, there is a problem that the cell gap becomes particularly large in this portion. Was.

  Therefore, as a result of various studies to solve the problems of the above-described MVA liquid crystal display device 90, the present inventors have caused this problem due to the presence of the auxiliary protrusion 89. When a configuration capable of performing the same operation as that provided with the auxiliary projection 89 is sought, the above-mentioned problem can be solved by providing a groove in the edge portion of the pixel electrode 74. As a result, the present invention has been completed.

  That is, it is an object of the present invention to provide an MVA liquid crystal display device with good display quality with little generation of disclination and less display unevenness without providing auxiliary projections.

  The above object of the present invention can be achieved by the following configurations. That is, the invention of the liquid crystal display device according to claim 1 of the present application includes a first substrate in which pixel electrodes provided on an insulating film are arranged in a matrix at positions partitioned by substantially orthogonal signal lines and scanning lines. A second substrate disposed opposite to the first substrate to form a transparent electrode; and an edge portion of the pixel electrode formed on the second substrate and observed from a vertical direction of the second substrate. Strip-shaped protrusions that intersect in an oblique direction, slits that are formed in the pixel electrode and are arranged parallel to the adjacent protrusions when viewed from the vertical direction of the first substrate, and on both the substrates And a liquid crystal layer having a negative dielectric anisotropy sandwiched between the two substrates, and when no electric field is applied to the liquid crystal layer, the liquid crystal molecules are vertical. Arranged on the liquid crystal layer In a liquid crystal display device in which liquid crystal molecules are inclined and arranged in a direction regulated by the slit and the protrusion when a field is applied, the pixel is observed when observed from the vertical direction of the first substrate and the second substrate. The electrode is located between the position where the edge of the electrode and the protrusion intersect with the slit, and the angle between the extending direction of the slit and the edge of the pixel electrode is 90 ° or less. A groove is provided in the insulating film at a position along the edge portion of the pixel electrode.

  The invention according to claim 2 of the present application is characterized in that, in the liquid crystal display device according to claim 1, the extending direction of the slit and the edge portion of the pixel electrode intersect at about 45 °. To do.

  Further, according to a third aspect of the present invention, in the liquid crystal display device according to the first or second aspect, the inclination angle of the side wall of the groove is equal to the inclination angle on the edge portion side of the pixel electrode. It is characterized by being smaller than the inclination angle.

  Furthermore, the invention according to claim 4 of the present application is the liquid crystal display device according to any one of claims 1 to 3, wherein the pixel electrode extends to a side wall side of a groove provided in the insulating film. It is characterized by being provided.

By providing the above-described configuration, the present invention has the following excellent effects. That is, according to the liquid crystal display device according to claim 1 of the present application, since the tilt, that is, the tilt angle of the liquid crystal molecules in the vicinity of the edge portion of the pixel electrode is stabilized, the alignment direction of these liquid crystal molecules is less likely to occur. Therefore, according to the liquid crystal display device of the first aspect, the disclination in the peripheral portion of the pixel is reduced, and in addition, it is not necessary to provide the auxiliary projection, so that the step variation and the projection are formed as in the conventional example. Luminance unevenness caused by misalignment such as position variation and protrusion shape variation is eliminated, and there is no problem based on auxiliary protrusions and spacers as in the conventional example, so high quality display is possible. In addition, according to the liquid crystal display device according to claim 2 of the present application, the tilt direction of the actual liquid crystal molecules in the pixel and the polarizing plate when observed from the normal direction of the substrate. Since the difference from the ideal inclination angle that is 45 ° with respect to the transmission axis is reduced, display unevenness is reduced.

  Further, according to the liquid crystal display device according to claim 3 of the present application, it becomes possible to give a desired tilt angle close to vertical to the alignment direction of the liquid crystal molecules in the vicinity of the edge portion of the pixel electrode. Generation of associations is suppressed.

  Furthermore, according to the liquid crystal display device according to claim 1 of the present application, since an electric field can be applied to the liquid crystal molecules in the groove when the electric field is applied, the liquid crystal molecules in the groove or in the vicinity of the groove are accurately aligned. As a result, the disclination at the periphery of the pixel is reduced, the luminance unevenness is small, and a liquid crystal display device with good display quality can be obtained.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to FIGS. 1 and 2, and the same components as those of the MVA liquid crystal display device 70 shown in FIGS. The detailed description of the portion is omitted. FIG. 1 is a plan view of a pixel of the MVA liquid crystal display device 10 of the present invention, and FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG. 1, and FIG. Fig. 2 (b) shows the state after applying the electric field, before applying the electric field.

  In the MVA liquid crystal display device 10, a scanning line 72 and a signal line 73 are arranged in a matrix on a transparent first substrate 71 such as a glass substrate via a gate insulating film 71 ′. A black matrix 79 is formed on a transparent second substrate 78 such as a substrate so as to divide each pixel, and a color filter 80 is laminated corresponding to each pixel. The color filter 80 is provided with one color filter 80 of red (R), green (G), and blue (B) corresponding to each pixel. A transparent electrode 81 is laminated on the color filter 80, a projection 82 having a predetermined pattern is formed on the transparent electrode 81, and the transparent electrode 81 and the projection 82 are covered with an alignment film 83 subjected to a vertical alignment process. ing. In addition, a slit 76 is formed in the pixel electrode 74.

  The protrusions 82 are formed in a zigzag shape across a plurality of pixels, and the straight portions extend in a direction of 45 ° with respect to the signal lines 73 when viewed from the vertical direction of the second substrate 78. In a substantially central portion of one pixel, a protrusion 82a extending from one adjacent pixel is bent by 90 ° and extends again toward the adjacent pixel. The protrusion 82b extending from the other adjacent pixel is arranged in parallel to the straight portion of the protrusion 82a bent at a right angle, is located near the corner of the pixel, and extends by bending 90 ° on the scanning line 72. . That is, the protrusion 82 changes the signal line 73 while changing the extending direction by 90 ° at two locations, approximately on the scanning line 72 and approximately in the middle of the pixel, in the area of two pixel columns formed along the signal line 73. It is formed along the direction.

  The slits 76 are formed so as to be positioned in the middle of the plurality of protrusions 82. In this embodiment, three slits 76 are formed in each pixel electrode 74. A slit 76 a is formed between the protrusion 82 a and the protrusion 82 b, and a slit 76 b is formed between the protrusion 82 a and the edge portion of the pixel electrode 74. The slit 76 a has a center line parallel to the adjacent protrusion 82 and is positioned in the 45 ° direction with respect to the signal line 73. The center line of the slit 76a corresponds to the extending direction of the slit 76a. Similarly, the extending direction of the slit 76b is parallel to the adjacent protrusion 82a. Since the extending direction of the protrusion 82a adjacent to the slit 76b is bent at a right angle within the pixel, the extending direction of the slit 76b is also bent. Further, the slit 76 does not completely divide the pixel electrode 74, and is formed in the region of the pixel electrode 74 to the last, so that a part of the pixel electrode 74 is not electrically floated.

  The projections 82 and the slits 76 restrict the orientation directions of the liquid crystal molecules 84 ′ in each pixel to four opposite directions, so that the viewing angle is improved in almost all directions. The shape of the protrusion 82 and the slit 76 is intended to improve the viewing angle in all directions, and is limited to this shape as long as it is formed in a direction that intersects the edge of the pixel electrode 74 from an oblique direction. It is not something. For example, the protrusions 82 may be formed in a zigzag shape along the direction of the signal line 73 in an area corresponding to three pixel columns formed along the signal line 73. Further, the protrusions 82 may not be extended to adjacent pixels, but may have a shape independent for each pixel.

  The MVA type liquid crystal display device 10 of the present invention is different in configuration from the MVA type liquid crystal display device 70 shown in FIGS. 5 and 6 that does not have auxiliary projections. The groove 99 is provided along the edge of the pixel electrode in the direction toward the slit 76 until reaching the first substrate 71 at the portion of the pixel electrode 74 corresponding to the portion that intersects with. The groove 99 is provided at a position corresponding to the auxiliary protrusion 89 in the MVA liquid crystal display device 90 having the auxiliary protrusion 89 shown in FIGS.

  With such a configuration, when no voltage is applied between the pixel electrode 74 and the transparent electrode 81, the liquid crystal molecules on the alignment film 83 in the first substrate 71 subjected to the vertical alignment process as in the prior art. 84 ′ is aligned in a substantially vertical direction, and the liquid crystal molecules 84 ′ in the vicinity of the groove 99 are slightly inclined with respect to the surface of the first substrate 71 due to the influence of the inclined surface of the groove (FIG. 2A).

  On the other hand, when a voltage is applied between the pixel electrode 74 and the transparent electrode 81, the liquid crystal molecules 84 ′ other than the vicinity of the groove 99 are aligned in a certain direction by the alignment regulating force by the protrusions 89 and the slits 76 as in the conventional case. At this time, if the liquid crystal molecules 84 ′ near the groove 99 are conventional, the regulating force due to the electric field near the edge of the pixel electrode 74 works and tilts toward the inside of the pixel electrode 74, and the liquid crystal molecules 84 ′ due to the regulating force by the slit 76 However, when the groove 99 is provided, the inclination of the groove 99 causes a physical inclination to the outside of the pixel electrode 74, that is, to the adjacent signal line 73 side. The regulating force works, and the inward inclination of the pixel electrode 74 is suppressed. That is, the regulatory force due to the electric field is offset by the physical regulatory force. Therefore, the inclination of the liquid crystal molecules 84 ′ in the vicinity of the groove 99 to the inside of the pixel electrode 74 is suppressed, and the contrast with the inclination of the liquid crystal molecules 84 ′ due to the regulating force by the slits 76 is eliminated. It becomes difficult to occur. For this reason, it is not necessary to separately provide auxiliary protrusions that have been conventionally required.

  In the embodiment, the trench 99 is formed by etching the gate insulating film 71 ′ and the insulating film 71 ″ formed below the pixel electrode 74. However, the groove 99 may be formed only in the insulating film 71 ″. . The inclination angle of the sidewall of the groove 99 may be determined in consideration of the properties of the liquid crystal molecules and the material of the pixel electrode 74 so that the inclination of the liquid crystal molecules 84 ′ toward the pixel electrode 74 is suppressed. By making the inclination angle on the edge side smaller than the inclination angle on the signal line 73 side, the distance between the signal line 73 and the bottom surface of the groove 99 is stabilized while stabilizing the orientation of the liquid crystal molecules 84 ′ when no voltage is applied. Can be brought closer. Further, by extending the pixel electrode 74 on the side wall side of the groove 99 as shown in FIG. 2B, the orientation of the liquid crystal molecules 84 'can be further stabilized.

  According to the MVA-type liquid crystal display device 10 of the present invention, the disclination in the peripheral portion of the pixel is reduced, and in addition, there is no need to provide auxiliary projections. Brightness unevenness due to misalignment, unevenness of protrusion shape, etc., and no problems due to auxiliary protrusions and spacers as in the conventional example, and high quality display is possible. An MVA liquid crystal display device can be obtained.

1 is a plan view of a pixel of an MVA liquid crystal display device of the present invention. 2A and 2B are cross-sectional views taken along line AA ′ in FIG. 1, FIG. 2A shows a state before an electric field is applied, and FIG. 2B shows a state after the electric field is applied. FIG. 3A is a diagram illustrating a configuration of a TN mode liquid crystal display device, FIG. 3A is a diagram illustrating a state before an electric field is applied, and FIG. 3B is an alignment state of liquid crystal molecules after the electric field is applied. FIG. 4A and 4B are diagrams illustrating a configuration of a VA mode liquid crystal display device, in which FIG. 4A is a diagram illustrating a state before an electric field is applied, and FIG. 4B is an alignment state of liquid crystal molecules after the electric field is applied. FIG. It is a top view of the pixel of the conventional MVA-type liquid crystal display device. FIG. 6 is a cross-sectional view taken along line A-A ′ of FIG. 5. It is a figure which shows typically the inclination state of the liquid crystal molecule in the MVA type liquid crystal display device of FIG. It is a top view of the pixel of the liquid crystal display device of another MVA system of a prior art example. FIG. 9A is a cross-sectional view taken along the line AA ′ in FIG. 8, FIG. 9A shows a state before an electric field is applied, and FIG. 9B shows a state after the electric field is applied.

Explanation of symbols

71 First substrate 72 Scan line 73 Signal line 74 Pixel electrode 76 Slit 77, 83 Alignment film 78 Second substrate 81 Transparent electrode 82 Projection 84 Liquid crystal layer 84 ′ Liquid crystal molecule 85, 86 Polarizing plate 89 Auxiliary projection 99 Groove

Claims (4)

A first substrate in which pixel electrodes provided on an insulating film are arranged in a matrix at positions partitioned by substantially orthogonal signal lines and scanning lines, and a first substrate in which a transparent electrode is formed opposite to the first substrate. Formed on the pixel electrode, two substrate, and a band-shaped protrusion formed on the second substrate and obliquely intersecting the edge portion of the pixel electrode when observed from the vertical direction of the second substrate. And slits arranged in parallel to the adjacent projections when observed from the vertical direction of the first substrate, alignment films subjected to a vertical alignment process laminated on both the substrates, and both the substrates A liquid crystal layer having a negative dielectric anisotropy sandwiched therebetween, and when no electric field is applied to the liquid crystal layer, liquid crystal molecules are vertically aligned, and when an electric field is applied to the liquid crystal layer, the slit and the The rule by the protrusion In the liquid crystal display device in which liquid crystal molecules are aligned to be inclined in a direction that is,
When observed from the vertical direction of the first substrate and the second substrate, the edge portion of the pixel electrode and the protrusion are positioned between the slit and the slit, and the extending direction of the slit And a groove formed in the insulating film at a position along the edge of the pixel electrode at an angle of 90 ° or less between the edge of the pixel electrode and the edge of the pixel electrode. The liquid crystal display device according to claim 1, wherein an extending direction of the slit and an edge portion of the pixel electrode intersect at about 45 °. 3. The liquid crystal display device according to claim 1, wherein the inclination angle of the side wall of the groove is such that the inclination angle on the edge portion side of the pixel electrode is smaller than the inclination angle on the signal line side. The liquid crystal display device according to claim 1, wherein the pixel electrode is provided so as to extend to a side wall side of a groove provided in the insulating film.

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