JP2008058689A - Liquid crystal device, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal device with which a high-quality display with high transmittance and without any disclination is available by eliminating occurrence of defective alignment (reverse twist) caused by a transverse electric field in a twisted nematic mode liquid crystal, and an image display device equipped with the same. <P>SOLUTION: In relation to a twisted nematic mode liquid crystal display element having a liquid crystal layer 50 composed of a liquid crystal 21 with positive dielectric anisotropy and interposed between a pair of substrates 10, 20, the liquid crystal device 1 is constructed by arranging a plurality of pixel electrodes 9, a linear protrusion 15 extending in a direction parallel to an alignment direction of the liquid crystal 21 in the case of no voltage application between pixel electrodes 9 adjacent to each other out of pixel electrodes 9 adjacent to one another in a direction vertical to the alignment direction of the liquid crystal 21 on the substrate, an alignment layer 13 formed so as to cover the linear protrusion 15 and controlling the alignment direction of the liquid crystal 21 in the case of no voltage application on the liquid crystal layer 50 side of the TFT array substrate 10, and a counter electrode 28 arranged on the liquid crystal layer 50 side of the counter substrate 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal device and an electronic apparatus.

  There is a liquid crystal projector as a device for displaying an image on a large screen using a liquid crystal display element. In projectors, it is important to have high brightness and high contrast. In general, this type of electro-optical device employs an inversion driving method in which the polarity of the driving voltage is periodically inverted in the row and column directions so that the voltages of adjacent pixel electrodes have opposite polarities. . In such a drive system, there is a problem that a lateral electric field is generated between adjacent pixel electrodes on a TFT (Thin Film Transistor) array substrate. This lateral electric field has a problem in that it causes alignment failure of liquid crystal that is driven and controlled by a vertical electric field formed between the pixel electrode and a counter electrode opposed to the pixel electrode.

  When such alignment failure occurs, there is a risk that disclination (line defect) may be formed between the normal alignment portion and the abnormal alignment portion of the liquid crystal layer.

In order to solve such problems, the following techniques are disclosed.
As a technique for preventing this phenomenon and obtaining a stable orientation in a TN (Twist Nematic) -TFT type liquid crystal display device, Patent Documents 1 and 2 have a convex portion formed in a gap between adjacent pixel electrodes. An electro-optical device is disclosed. Thereby, it is possible to reduce the disorder of the alignment state of the liquid crystal due to the lateral electric field generated between the pixel electrodes adjacent to each other whose polarities of the applied voltages are opposite to each other.
JP 2002-40455 A JP 2005-121805 A

  In recent years, even in projectors, high aperture ratio and high definition have progressed, and the distance between pixels has become smaller and smaller. As a result, as described above, the influence of a lateral electric field generated by a potential difference between adjacent pixels has led to a serious alignment failure. Currently, TN type (twisted nematic type) liquid crystal devices are widely used as alignment methods for liquid crystal projectors. However, a twisted nematic alignment mode liquid crystal is twisted in a direction (reverse direction) different from the original twist direction (reverse twist) due to a lateral electric field generated when different voltages are applied to adjacent pixel electrodes. Is a problem. In order to solve such a problem, the above-described Patent Documents 1 and 2 form a convex portion between the pixel electrodes, and overlap the pixel electrode end portion on the convex portion, thereby substantially increasing the vertical electric field strength at the pixel electrode end. However, the horizontal electric field is not substantially weaker than the vertical electric field. Further, since the unevenness of the surface shape of the pixel electrode is generated, alignment failure due to the surface shape may occur during black display (when voltage is applied), and the contrast may be significantly reduced.

  The present invention has been made in view of the above-described problems, and its object is to eliminate the occurrence of orientation failure (reverse twist) due to a transverse electric field in a twisted nematic liquid crystal, and to achieve high transmittance and no disclination. An object of the present invention is to provide a liquid crystal device capable of displaying quality and an image display device including the same.

  In order to solve the above problems, a liquid crystal device of the present invention is a twist nematic liquid crystal display element in which a liquid crystal layer made of a liquid crystal having positive dielectric anisotropy is sandwiched between a pair of substrates. Adjacent to the liquid crystal layer side of one of the substrates in the direction perpendicular to the alignment direction of the liquid crystal when no voltage is applied to one of the adjacent pixel electrodes. A pair of protrusions extending in a direction parallel to the alignment direction of the liquid crystal between the pixel electrodes to be formed, an alignment film that covers the protrusions and restricts the alignment direction of the liquid crystal when no voltage is applied, and a pair And a counter electrode provided on the liquid crystal layer side of the other substrate.

  According to such a configuration, it is possible to prevent a liquid crystal alignment defect (reverse twist) from occurring due to the influence of a lateral electric field generated between pixel electrodes to which different voltages are applied among adjacent pixel electrodes. Can do. In other words, since a convex portion is provided along the orientation direction of the liquid crystal on the pixel electrode when no voltage is applied, when a different voltage is applied to adjacent pixel electrodes, the reverse twist is caused by the influence of the lateral electric field. The orientation of the liquid crystal to be tried can be controlled.

  That is, since the alignment film is formed so as to cover the convex portion, the behavior of the liquid crystal to be aligned parallel to the transverse electric field generated perpendicular to the initial alignment direction of the liquid crystal is It can be hindered by the orientation regulating force. The horizontal electric field acts most strongly between the pixel electrodes, and the presence of the convex portion weakens the horizontal electric field. In addition, since it is twisted nematically aligned, it is twisted 45 ° with respect to the orientation direction on the surface of the pixel electrode near the center of the liquid crystal layer in the vertical direction. The liquid crystal molecules controlled to be in the orientation orientation which is almost the same as the surrounding twisted nematic orientation state even under the influence of the transverse electric field can prevent the occurrence of reverse twist. Thus, the liquid crystal can be aligned along the rubbing direction of the alignment film without being affected by the electric field generated in the direction perpendicular to the alignment direction of the liquid crystal. As a result, alignment failure of the liquid crystal during voltage application can be prevented, high transmittance can be realized, and occurrence of disclination can be prevented and suppressed. The initial alignment direction of the liquid crystal is an alignment direction when no voltage is applied.

  Therefore, according to the present embodiment, it is possible to provide a liquid crystal device having a high-contrast, bright and uniform display quality without display defects.

  Further, in a conventional twisted nematic (TN type) liquid crystal device using a liquid crystal having positive dielectric anisotropy, when different voltages are applied to adjacent pixel electrodes, a lateral electric field is generated at each electrode end. Among these lateral electric fields, there is a problem that reverse twist of the liquid crystal occurs due to the influence of the lateral electric field generated in a direction perpendicular to the alignment direction of the liquid crystal.

  However, as described above, the present invention has a configuration in which the alignment regulating force generated along the alignment direction of the liquid crystal is stronger than the action caused by the electric field generated in the direction perpendicular to the alignment direction of the liquid crystal. Therefore, it is possible to prevent the reverse twist of the liquid crystal. Further, by preventing the occurrence of reverse twist, the area where the black mask is provided can be minimized, and the aperture ratio in the pixel area can be improved. In this way, high-quality display can be achieved by stabilizing the alignment of the liquid crystal in the pixel region.

Further, it is also preferable that the convex portion continuously extends across a plurality of pixel electrodes adjacent to the liquid crystal alignment direction so as to be along the liquid crystal alignment direction.
According to such a configuration, it is possible to reliably prevent the reverse twist of the liquid crystal that is affected by the lateral electric field perpendicular to the alignment direction of the liquid crystal. Moreover, since it can form continuously in one direction, without dividing a convex part, manufacture becomes easy.

  The above-described liquid crystal device of the present invention can be used as, for example, a display screen of an electronic device such as a liquid crystal television or a mobile phone, a monitor of a personal computer, and a light modulation device of a liquid crystal projector (projection display device). By using it for such an application, an electronic device excellent in a display device can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the film thicknesses and dimensional ratios of the respective components are appropriately changed in order to make the drawings easy to see.

[Liquid Crystal Device]
The liquid crystal device of the present embodiment described below is an active matrix liquid crystal device 1 using TFT (Thin-Film Transistor) elements as switching elements. In the present embodiment, a transmissive liquid crystal device will be described as an example of a display method for displaying an image by generating an electric field in a desired direction with respect to the liquid crystal to control the alignment of the liquid crystal.

Hereinafter, the structure of the liquid crystal device of the present embodiment will be described in more detail with reference to the drawings. 1 is a plan view of a TFT array substrate for explaining a schematic configuration of the liquid crystal device, FIG. 2 is a cross-sectional view taken along line HH ′ of FIG. 1, and FIG. 3 is a plan view schematically showing a configuration of a pixel region in the liquid crystal device. 4 is a sectional view taken along the line DD of FIG.
In the following description, an xyz orthogonal coordinate system is set, and the positional relationship of each member will be described with reference to this xyz orthogonal coordinate system. A predetermined direction in the horizontal plane is an x direction, a direction orthogonal to the x direction in the horizontal plane is a y direction, and a direction orthogonal to each of the x direction and the y direction is a z direction.

  As shown in FIGS. 1 and 2, the liquid crystal device 1 has a positive dielectric anisotropy between the TFT array substrate 10 and the counter substrate 20 bonded via the sealing material 52 via the alignment films 13 and 14. A liquid crystal layer 50 made of nematic liquid crystal (hereinafter sometimes simply referred to as “liquid crystal”) is sandwiched. Due to the alignment film 13 provided on the TFT array substrate 10 and the alignment film 14 provided on the counter substrate 20, the nematic liquid crystal has an orientation in which the molecular long axis direction is twisted about 90 °, and a TN (twisted nematic) type liquid crystal device. 1 is configured. The alignment films 13 and 14 are inclined and aligned (pretilt) by a predetermined angle with respect to the substrate surface in the major axis direction of the nematic liquid crystal.

Next, each component formed on the TFT array substrate 10 will be described in detail.
In FIG. 1, a sealing material 52 is provided on the TFT array substrate 10 along the edge of the counter substrate 20, and a second light shielding film 53 is provided in parallel to the inside thereof. An area surrounded by the second light shielding film 53 is an image display area A of the liquid crystal device 1. A data line driving circuit 101 and an external circuit connection terminal 102 are provided along one side of the TFT array substrate 10 in a region outside the sealing material 52, and the scanning line driving circuit 104 is adjacent to the one side. It is provided along two sides.

  Furthermore, a plurality of wirings 105 are provided on the remaining side of the TFT array substrate 10 for connecting the scanning line driving circuits 104 provided on both sides of the image display area A. Here, the second light shielding film A precharge circuit may be provided hidden under 53. In addition, at least one of the four corners of the counter substrate 20 is provided with a conductive material 106 for electrical conduction between the TFT array substrate 10 and the counter substrate 20. In this embodiment, it is provided in all four places.

  A plurality of pixel electrodes 9 are formed in a matrix in the TFT array substrate 10. As shown in FIG. 2, a common electrode 28 common to the plurality of pixel electrodes 9 is formed inside the common substrate 20 disposed to face the TFT array substrate 10.

(Planar structure)
Next, the planar structure in the image display area A of the TFT array substrate 10 will be described in detail with reference to FIG. FIG. 3A is a plan view seen from the TFT array substrate side, and FIG. 3B is an enlarged view of the pixel switching TFT element.
As shown in FIG. 3A, in the image display area A (see FIG. 1) on the TFT array substrate 10 of the liquid crystal device 1, vertical and horizontal boundaries of a plurality of transparent pixel electrodes 9 provided in a matrix form. A data line 6a and a scanning line 3a are provided along each line.

  On the TFT array substrate 10, a plurality of data lines 6a extending in the y direction are provided at predetermined intervals in the x direction. In addition, a plurality of scanning lines 3 a that intersect the data lines 6 a and extend in the x direction are provided at predetermined intervals in the y direction. A region surrounded by two adjacent data lines 6a and scanning lines 3a is a pixel region C (a region indicated by a one-dot difference line 9 'in the drawing). Such pixel regions C are formed in a matrix on the TFT array substrate 10.

  In each pixel region C, a pixel electrode 9 having a substantially square shape in plan view made of a transparent conductive material such as indium tin oxide (hereinafter abbreviated as “ITO”) is provided.

  As shown in FIG. 3A, the pixel switching TFT element 30 is provided in the vicinity of the intersection of the data line 6a and the scanning line 3a. More specifically, as shown in FIG. 3B, the gate electrode 26 formed by branching from the scanning line 3a in the y direction, the semiconductor layer 1a made of amorphous silicon, and the planar region of the semiconductor layer 1a and the scanning line 3a A source electrode 25 and a gate insulating film 2 are formed so as to partially overlap each other. The source electrode 25 is formed to branch from the data line 6a in the x direction.

  The pixel electrode 9 is electrically connected to the drain region 1d described later of the semiconductor layer 1a made of, for example, a polysilicon film constituting the pixel switching TFT element 30 through the contact hole 8, and the data line 6a is The semiconductor layer 1a is electrically connected to a source region 1e described later via a contact hole 5.

  As shown in FIG. 3A, the protrusion 15 is formed so as to overlap the data line 6a in a plan view, and extends along the extending direction (y direction) of the data line 6a. Yes. It is assumed that the protrusion 15 is located in a shielding area by a first light shielding film 11a described later.

(Cross-section structure)
Next, the cross-sectional structure of the liquid crystal device of this embodiment will be described in detail with reference to FIG. In FIG. 4, some components such as a pixel switching TFT element are omitted in view of the visibility of the drawing.

  In the liquid crystal device 1 of the present embodiment, as shown in FIG. 4, a liquid crystal layer 50 is sandwiched between the TFT array substrate 10 and a counter substrate 20 disposed to face the TFT array substrate 10. The liquid crystal layer 50 is composed of nematic liquid crystal 21 having a positive dielectric anisotropy aligned along an electric field, and the liquid crystal device 1 is a twisted nematic type display device. The TFT array substrate 10 and the counter substrate 20 are made of a translucent material such as glass or quartz.

  In the TFT array substrate 10, the TFT array substrate 10 is transmitted on the surface of the substrate body 10 </ b> A on the liquid crystal layer 50 side, and is reflected by the lower surface of the TFT array substrate 10 (interface between the TFT array substrate 10 and air). A first light-shielding film 11a for partially shielding the return light returning to the liquid crystal layer 50 side is provided. The first light shielding film 11 a is provided to prevent the above-described return light from entering the pixel switching TFT element 30, and is provided in a range where the light shielding effect on the pixel switching TFT element 30 can be obtained.

  Further, a pixel switching TFT element 30 that controls switching of the pixel electrode 9 is provided on the surface of the substrate body 10A via a first interlayer insulating film 12 formed on the substantially entire surface so as to cover the first light shielding film 11a. Is arranged. The first interlayer insulating film 12 is made of silicon oxide or the like, and is electrically insulated by being interposed between the first light shielding film 11 a and the pixel switching TFT element 30.

  The pixel switching TFT element 30 includes a semiconductor layer 1a formed on the first interlayer insulating film 12, a gate electrode 26, and a data line 6a. The semiconductor layer 1a is composed of a channel region 1a ′ of the semiconductor layer 1a in which a channel is formed by an electric field from the gate electrode 26, a drain region 1d and a source region 1e of the semiconductor layer 1a, and a gate insulating film 2 covering the surface. It is insulated from the gate electrode 26.

  In addition, a gate electrode 26 is disposed in the semiconductor layer 1a so as to face the channel region 1a '.

  On the substrate body 10A including the gate electrode 26 and the gate insulating film 2, a second interlayer insulating film 4 having a contact hole 8 leading to the drain region 1d and a contact hole 5 leading to the source region 1e is formed. Has been. That is, the data line 6 a is electrically connected to the source region 1 e through the contact hole 5 that penetrates the second interlayer insulating film 4.

  Further, a third interlayer insulating film 7 having a contact hole 8 leading to the drain region 1d is formed on the data line 6a and the second interlayer insulating film 4. That is, the drain region 1 d is electrically connected to the pixel electrode 9 formed on the third interlayer insulating film 7 through the contact hole 8 that penetrates the second interlayer insulating film 4 and the third interlayer insulating film 7. ing.

  The third interlayer insulating film 7 is formed with a protrusion 15 that protrudes from the surface on the liquid crystal layer 50 side into the liquid crystal layer 50. In the present embodiment, the cross-sectional shape of the protrusion 15 has a trapezoidal shape, but is not limited thereto, and may be a rectangular shape in cross-sectional view, a circular shape in cross-sectional view, or a triangular shape in cross-sectional view.

  An alignment film 13 made of polyimide or the like is formed on the substrate body 10A so as to cover the pixel electrodes 9 and the protrusions 15. The alignment film 13 is rubbed along the y direction in the figure. As the rubbing method, a method of rubbing with a rubbing machine in which a cloth made of rayon, nylon, polyester or the like is attached to a roller is often used. The alignment film 13 may be formed using SiO2.

  On the other hand, the counter substrate 20 has a translucent substrate body 20A such as glass, quartz, or plastic as a base, and the data line 6a, the scanning line 3a, and the pixels are disposed on the inner surface side (the liquid crystal layer 50 side) of the substrate body 20A. A second light shielding film 19 for preventing incident light from entering the channel region 1a ′, the drain region 1d, and the source region 1e of the semiconductor layer 1a of the switching TFT element 30 is provided.

  Furthermore, a counter electrode 28 common to all the pixel electrodes 9 provided on the TFT array substrate 10 is provided on substantially the entire surface of the second light shielding film 19 (surface on the liquid crystal layer 50 side). The counter electrode 28 functions to drive the nematic liquid crystal 21 while facing the pixel electrode 9.

  Further, an alignment film 14 is formed on the substrate main body 20 </ b> A provided with the counter electrode 28 on the liquid crystal layer 50 side so as to cover the counter electrode 28. The alignment film 14 is rubbed along the x direction in the figure.

  The alignment films 13 and 14 are used for twisting nematic alignment of the nematic liquid crystal 21 with respect to the film surface when no voltage is applied by rubbing formed on each of the alignment films 13 and 14. The rubbing directions of the alignment films 13 and 14 are shifted by 90 ° in plan view. In the present embodiment, the pretilt angle that the alignment films 13 and 14 give to the nematic liquid crystal 21 is 8 °. By giving the pretilt angle and slightly tilting the nematic liquid crystal 21 with respect to the substrate surface, the direction in which the nematic liquid crystal 21 rises (the alignment direction of the nematic liquid crystal 21) can be stabilized in one direction.

  In forming the alignment films 13 and 14, a method of forming a film of a material such as polyimide or SiO 2 by a liquid phase method such as a spin coating method can be employed. In addition, depending on the material, a film may be formed using a known vapor deposition method and may have a columnar microstructure that stands upright on the surface.

  Although the TFT array substrate 10 and the counter substrate 20 described above are not shown in FIG. 4, they are bonded to each other via a sealing material, and the dielectric anisotropy is positive from the liquid crystal injection port formed in the sealing material. A nematic liquid crystal 21 (positive type nematic liquid crystal material) is injected to obtain a liquid crystal panel 40.

  The nematic liquid crystal 21 modulates light and enables gradation display by changing the orientation and order of the molecular assembly depending on the applied voltage level. In addition to the nematic liquid crystal 21 having positive dielectric anisotropy, a chiral nematic liquid crystal material and the like can be mentioned.

  As shown in FIG. 3A, the liquid crystal panel 40 is provided with polarizing plates 22 and 23 on the outer surface side of the counter substrate 20 and the TFT array substrate 10, respectively. It arrange | positions so that it may orthogonally cross. The light transmission axes L and N are respectively set to the scanning line 3a and the data line 6a so that the light transmittance of the liquid crystal device 1 when no voltage is applied is 100% and the light transmittance of the liquid crystal device 1 when voltage is applied is 0%. It is arranged in the direction along. As described above, the polarizing plates 22 and 23 are bonded in a crossed Nicol state so that the TFT array substrate 10 and the counter substrate 20 are sandwiched between both sides of the TFT array substrate 10 and the counter substrate 20, and the liquid crystal device 1 of the present embodiment. It is said.

  Next, the structure of a plurality of adjacent pixel groups on the TFT array substrate described above will be described. FIG. 5 is a plan view showing the structure of a plurality of adjacent pixel groups on the TFT array substrate. 6 is a cross-sectional view taken along line N-N ′ of FIG. 5. In FIG. 6, the first interlayer insulating film, the second interlayer insulating film, the semiconductor layer, and various wirings are not shown.

  As shown in FIGS. 5 and 6, the protrusion 15 (projection) of the present embodiment is a liquid crystal alignment direction when no voltage is applied among the pixel electrodes 9 adjacent to each other on the TFT array substrate 10 (FIG. 3). The arrow T in the middle indicates the alignment direction of the liquid crystal) and is provided in the gap S between the pixel electrode groups U that form a column. The protruding portion 15 is formed from the third interlayer insulating film 7.

  The protrusions 15 are continuously present over the plurality of pixel electrodes 9 existing in the liquid crystal alignment direction, and extend along the y direction shown in FIGS. Further, it is formed with a predetermined height so as to protrude into the liquid crystal layer 50, and is interposed between the pixel electrodes 9 adjacent to each other in a direction perpendicular to the alignment direction of the liquid crystal.

  The dimension in the width direction of the protrusion 15 is appropriately set according to the gap S between the pixel electrodes 9. Further, the protruding amount of the protrusion 15, that is, the height thereof is appropriately set according to the cell gap between the TFT array substrate 10 and the counter substrate 20 that sandwich the liquid crystal layer 50. In this embodiment, it is formed with a height of about 0.6 to 1 μm with respect to a cell gap of 2.5 μm.

  In the drawing, a slight gap is provided between the pixel electrode 9 and the protrusion 15, but the protrusion 15 may be in contact with the pixel electrode 9 adjacent thereto. Further, FIG. 6 shows an alignment film 13 formed so as to cover the protruding portion 15 and the pixel electrode 9.

Next, a method for producing the TFT array substrate of this embodiment will be described.
FIG. 7 is an explanatory view schematically showing a method for producing a TFT array substrate.

  First, as shown in FIG. 7A, a translucent substrate body 10A made of glass or the like is prepared, and a first interlayer insulating film, a second interlayer insulating film, a semiconductor layer, and various wirings (shown above) are prepared. Abbreviation). Then, a third interlayer insulating film 7 is formed on the second interlayer insulating film including the data line. The third interlayer insulating film 7 can be formed by a film forming method such as a plasma chemical vapor deposition method (PECVD method), a low pressure chemical vapor deposition method (LPCVD method), or a sputtering method. At this time, in the third interlayer insulating film 7, a protrusion 15 extending in the y direction along the data line 6a is simultaneously formed at a location above the data line 6a.

  Next, as shown in FIG. 7B, cylindrical fine holes are formed as contact holes 8 in the third interlayer insulating film 7. The contact hole 8 is a hole that leads to a drain region (not shown). The fine holes of the contact hole 8 may be formed with a predetermined hole diameter and may have a shape other than a cylindrical shape (for example, a prismatic shape).

  Next, as shown in FIG. 7C, the pixel electrode 9 is formed on the third interlayer insulating film by a known method. The pixel electrode 9 is formed on both sides of the protrusion 15 in the width direction, and is connected to the drain region of the pixel switching TFT element via the contact hole 8.

  Next, as shown in FIG. 7D, an alignment film 13 is formed on the substrate body 10A so as to cover the pixel electrodes 9 and the protrusions 15. The alignment film 13 is formed by depositing polyimide, SiO 2 or the like using a spin coating method. The TFT array substrate 10 is formed through the above steps.

  Next, it will be described in detail how the alignment state of the liquid crystal shows the alignment method when an electric signal for display is input to the liquid crystal device of the present embodiment. FIG. 8 is an explanatory diagram showing the alignment state of the liquid crystal when a voltage is applied. FIG. 9 is an explanatory view showing the alignment direction of the liquid crystal affected by the lateral electric field. 10 is a cross-sectional view taken along the line M-M ′ of FIG. 9.

  As shown in FIG. 8, in the liquid crystal device 1 of this embodiment, the protrusions 15 are provided between the pixel electrodes 9 adjacent to each other in the direction perpendicular to the alignment direction (y direction in the figure) of the nematic liquid crystal molecules 21 as described above. Is formed. When different voltages are applied to the adjacent pixel electrodes 9a and 9b via the protrusions 15, an electric field (hereinafter referred to as a transverse electric field E) is generated in this direction between the pixel electrodes 9a and 9b. In this embodiment, it is assumed that 0V is applied to the pixel electrode 9a and 5V is applied to the pixel electrode 9b.

  Since the voltage applied to the pixel electrode 9a is equal to 0V, that is, no voltage is applied, the alignment of the nematic liquid crystal molecules 21 positioned on the pixel electrode 9a is in the initial alignment state when no voltage is applied (that is, the TFT array). The state is almost the same as that between the substrate 10 and the counter substrate 20. On the other hand, since the voltage applied to the pixel electrode 9b is 5V, the nematic liquid crystal molecules 21 are aligned perpendicular to the substrate surface by the electric field generated between the counter electrode 28 and the pixel electrode 9b.

  As shown in FIG. 9, the horizontal electric field E is generated between the pixel electrodes 9a and 9b to which different voltages are applied. The influence of the horizontal electric field E is most easily received by the nematic liquid crystal molecules 21 located on the end portions of the pixel electrodes 9a and 9b. As described above, the liquid crystal device 1 of the present embodiment uses nematic liquid crystal molecules 21 having positive dielectric anisotropy. The nematic liquid crystal molecules 21 having a positive dielectric anisotropy have a property of aligning the major axis direction along the direction of the transverse electric field E as shown in FIG.

  Therefore, in the conventional TN type liquid crystal device having no protrusion 15 between the pixel electrodes 9, different voltages are applied between adjacent pixel electrodes 9a and 9b provided on the TFT array substrate 10, as shown in FIG. In this case, the variation in liquid crystal alignment was caused by the lateral electric field E generated at each electrode end. Many alignment defects of the nematic liquid crystal molecules 21 occur in a portion surrounded by a circle in the figure, and the problem is that the alignment defect region B extends to the pixel region C.

  More specifically, the nematic liquid crystal molecules 21 located in the central portion of each pixel electrode 9a, 9b are normally oriented (alignment not affected by the lateral electric field), but are nematic located near the ends of the pixel electrodes 9a, 9b. The liquid crystal molecules 21 are reverse twisted under the influence of the transverse electric field E.

  Thus, many of the nematic liquid crystal molecules 21 that are reverse twisted tend to be generated at the end of the pixel region C. When alignment failure of the nematic liquid crystal molecules 21 occurs, disclination (line defect) due to interference between the liquid crystals occurs. Since the occurrence and disappearance of this disclination is accompanied by hysteresis, there is a concern that, for example, an afterimage or the like occurs and the display quality of the image is deteriorated.

  As shown in FIG. 3A, the alignment failure of the nematic liquid crystal molecules 21 that are not in the desired alignment state is caused by arranging two polarizing plates 22 and 23 (polarizing plates 22 and 23 in a crossed Nicols state) on the liquid crystal panel 40. Thus, the light transmission axis L of the polarizing plate 22 is parallel to the rubbing direction of the alignment film 13, and the light transmission axis N of the polarizing plate 23 is parallel to the rubbing direction of the alignment film 14. When arranged in such a manner, the change in transmittance appears to change significantly locally. Further, as shown in FIG. 11, since the alignment defect region B of the liquid crystal extends to the end portions of the pixel electrodes 9a and 9b, the shielding region by the first light shielding film 11a is extended to the inside of the pixel region C. There was a need. There has been concern about a decrease in the aperture ratio due to this.

  However, according to the present embodiment, since the alignment film 13 at the boundary portion of the pixel region C that is most susceptible to the lateral electric field E protrudes into the liquid crystal layer 50, the alignment film 13 is generated perpendicular to the alignment direction of the liquid crystal. The alignment of the nematic liquid crystal molecules 21 affected by the lateral electric field E can be regulated by rubbing the alignment film 13. Details are described below.

  As already described, the liquid crystal layer 50 is most susceptible to the influence of the lateral electric field E in a predetermined region between the end portions of the pixel electrodes 9a and 9b. Therefore, as in the present embodiment shown in FIG. 8, a protrusion 15 is formed that extends along the alignment direction of the liquid crystal and protrudes within a predetermined region of the liquid crystal layer 50 that is easily affected by the transverse electric field E, If the TFT array substrate 10 is formed by providing the alignment film 13 so as to cover the surface, the film surface of the alignment film 13 exists along the horizontal electric field E (the closed curve of the horizontal electric field E). . As a result, the nematic liquid crystal molecules 21 (liquid crystal that is most susceptible to the influence of the transverse electric field E) existing around the ridge 15 are subjected to the alignment regulating force in the direction along the ridge 15 from the alignment film 13. . That is, since the alignment regulating force of the alignment film 13 is greater than the lateral electric field E, the alignment control of the nematic liquid crystal 21 can be performed.

  Therefore, the behavior of the nematic liquid crystal molecules 21 to be reverse twisted under the influence of the lateral electric field E can be inhibited by rubbing the alignment film 13. With the alignment of the nematic liquid crystal molecules 21 regulated by the alignment film 13, the alignment direction of the other nematic liquid crystal molecules 21 positioned on the pixel electrodes 9a and 9b is defined. Therefore, even if the nematic liquid crystal molecules 21 are affected by the lateral electric field E, the nematic liquid crystal molecules 21 are in a good alignment state without being reverse twisted.

  As described above, the alignment film 13 having a rubbing capable of effectively regulating the alignment of the nematic liquid crystal molecules 21 is configured to protrude into a predetermined region of the liquid crystal layer 50 that is most susceptible to the lateral electric field E. The nematic liquid crystal 21 on the film surface is surely along the rubbing direction. Then, the other nematic liquid crystal molecules 21 are normally aligned with the alignment of the nematic liquid crystal molecules 21 on the film surface, so that the influence of the lateral electric field E can be reduced. In this way, by restricting the alignment direction of the nematic liquid crystal molecules 21 to prevent the occurrence of reverse twist, substantially all of the nematic liquid crystal molecules 21 in the pixel region C can be normally aligned.

  By controlling the alignment direction of the liquid crystal 21 in this manner, the alignment of the nematic liquid crystal molecules 21 in the pixel region C is stabilized and interference between the liquid crystals is prevented. Thereby, the occurrence of disclination can be prevented and suppressed, and high transmittance can be realized.

  Further, by preventing reverse twist of the nematic liquid crystal molecules 21, the alignment control of the nematic liquid crystal molecules 21 can be performed quickly, thereby improving the response time of the nematic liquid crystal molecules 21 and suppressing the afterimage generation of the image. it can. Thereby, the light transmittance can be maintained at a high level without generating afterimages. Therefore, the display quality of the image is improved and an image with high visibility can be provided.

  As shown in FIG. 8, when a voltage of 0V is applied to the pixel electrode 9a and a voltage of 5V is applied to the pixel electrode 9b, the upper portion of the protrusion 15 is initially aligned on the pixel electrode 9a (alignment when no voltage is applied). ) State and the liquid crystal group vertically aligned on the pixel electrode 9b, so that the alignment of the nematic liquid crystal molecules 21 is slightly disturbed. However, the alignment failure region B in the present embodiment is reduced as compared with the conventional alignment failure region B shown in FIG. That is, in the conventional liquid crystal device, the alignment defect extends to the pixel region C, whereas in this embodiment, the alignment defect of the nematic liquid crystal molecules 21 does not occur on the pixel electrodes 9a and 9b. That is, the entire pixel region C can be fully utilized for display.

  Further, the poor alignment region B in the present embodiment corresponds to a light shielding portion between pixels. In other words, by providing the first light-shielding film 11a and the second light-shielding film 19 between the pixels in a lattice shape, noise light generated above the protrusions 15 is shut out. Therefore, the light transmittance of the region B does not affect the display, and the first light shielding film 11a and the second light shielding film 19 can further improve the contrast of the image. In addition, since there are fewer liquid crystal alignment defects than in the conventional liquid crystal device, the area where the first light-shielding film 11a and the second light-shielding film 19 are provided can be reduced. The conventional first light-shielding film 11a shown in FIG. 11 is provided so as to shield not only between pixels but also the end of the pixel region C. On the other hand, the first light shielding film 11a of this embodiment shown in FIG. 8 is provided so as to shield only between pixels. Therefore, the shielding area by the first light shielding film 11a can be reduced.

  As described above, by preventing the reverse twist of the nematic liquid crystal 21 in the pixel region C, the region where the first light shielding film 11a is provided can be reduced, and the aperture ratio can be improved.

  Further, when different voltages are applied to the pixel electrodes 9 adjacent to each other along the alignment direction (rubbing direction) of the liquid crystal, the lateral electric field is generated in the same direction as the alignment direction of the liquid crystal. Therefore, this lateral electric field does not cause a liquid crystal alignment defect. Therefore, it is not necessary to provide the protrusions 15 in a lattice pattern so as to be interposed between all the pixel electrodes 9 arranged in a matrix.

  The liquid crystal device 1 as one embodiment of the present embodiment has been described above. However, the present embodiment is not limited to this, and the wording of each claim is not departed from the scope described in each claim. However, the present invention is not limited to the above, and the scope of the present invention can be easily replaced by those skilled in the art, and improvements based on the knowledge that those skilled in the art normally have can be added as appropriate.

  For example, in the present embodiment, only the active matrix type liquid crystal device using the image display switching TFT element 30 has been described. However, the present embodiment is not limited to this, and a TFD (Thin-Film Diode) element is used. The present invention can also be applied to the used active matrix liquid crystal device. In the present embodiment, only the transmissive liquid crystal device has been described. However, the present embodiment is not limited to this, and can be applied to a reflective or transflective liquid crystal device. Thus, the present embodiment can be applied to a liquid crystal device having any structure.

  In the above description, the protrusion 15 is formed integrally with the third interlayer insulating film 7, but may be provided separately from the third interlayer insulating film 7. In any case, if the alignment film 13 that has been subjected to the rubbing process can be projected into a predetermined region of the liquid crystal layer 50 that is easily affected by the transverse electric field E generated perpendicularly to the alignment direction of the liquid crystal. The protruding portion 15 may have any configuration.

[Electronics]
Examples of electronic devices including the liquid crystal device of the above embodiment will be described.
FIG. 12A is a perspective view showing an example of a mobile phone. In FIG. 12A, reference numeral 500 denotes a mobile phone body, and reference numeral 501 denotes a liquid crystal display unit using the liquid crystal device of the above embodiment.

  FIG. 12B is a perspective view showing an example of a portable information processing apparatus such as a word processor or a personal computer. In FIG. 12B, reference numeral 600 denotes an information processing apparatus, reference numeral 601 denotes an input unit such as a keyboard, reference numeral 603 denotes an information processing apparatus body, and reference numeral 602 denotes a liquid crystal display unit using the liquid crystal device of the above embodiment. .

  FIG. 12C is a perspective view illustrating an example of a wristwatch type electronic device. In FIG. 12C, reference numeral 700 denotes a watch body, and reference numeral 701 denotes a liquid crystal display unit using the liquid crystal device of the above embodiment.

  As described above, since the electronic apparatus shown in FIG. 12 uses the above-described liquid crystal device as an example of the present embodiment for the display unit, there is a problem that rubbing streaks, for example, when a rubbing process is performed is displayed. In addition, the display device can maintain a high-contrast, bright and high-quality display over a long period of time.

[Projection type display device]
Next, a configuration of a projection display device (projector) including the liquid crystal device according to the above-described embodiment as light modulation means will be described with reference to FIG. FIG. 13 is a schematic configuration diagram showing a main part of a projection display device using the liquid crystal device of the above embodiment as a light modulation device. In FIG. 13, 810 is a light source, 813 and 814 are dichroic mirrors, 815, 816 and 817 are reflection mirrors, 818 is an incident lens, 819 is a relay lens, 820 is an exit lens, 822, 823 and 824 are liquid crystal light modulators, Reference numeral 825 denotes a cross dichroic prism, and reference numeral 826 denotes a projection lens.

  The light source 810 includes a lamp 811 such as a metal halide and a reflector 812 that reflects the light of the lamp. The dichroic mirror 813 that reflects blue light and green light transmits red light out of the light flux from the light source 810 and reflects blue light and green light. The transmitted red light is reflected by the reflection mirror 817 and enters the liquid crystal light modulation device 822 for red light including the liquid crystal device as an example of the above-described embodiment.

  On the other hand, green light out of the color light reflected by the dichroic mirror 813 is reflected by the dichroic mirror 814 that reflects green light, and enters the liquid crystal light modulation device 823 for green light including the liquid crystal device according to the above-described embodiment. The Note that the blue light also passes through the second dichroic mirror 814. For blue light, light guide means 821 comprising a relay lens system including an incident lens 818, a relay lens 819, and an exit lens 820 is provided in order to compensate for the difference in optical path length from green light and red light. Through this, the blue light enters the liquid crystal light modulation device 824 for blue light including the liquid crystal device as an example of the above-described embodiment.

  The three color lights modulated by the respective light modulation devices are incident on the cross dichroic prism 825. In this prism, four right-angle prisms are bonded together, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are formed in a cross shape on the inner surface. These dielectric multilayer films combine the three color lights to form light representing a color image. The synthesized light is projected onto the screen 827 by the projection lens 826 which is a projection optical system, and the image is enlarged and displayed.

It is a top view which shows schematic structure of a liquid crystal device. It is H-H 'sectional drawing of FIG. It is a top view which shows typically the structure of the pixel area | region in a liquid crystal device. It is DD sectional drawing of FIG. It is a top view which shows the structure of the several pixel group which adjoins on a TFT array substrate. FIG. 6 is a sectional view taken along line N-N ′ of FIG. 5. It is explanatory drawing which shows one manufacturing process of the TFT array substrate in a liquid crystal device. It is explanatory drawing which shows the inclination state of the liquid crystal at the time of a voltage application. It is explanatory drawing which shows the orientation direction of the liquid crystal which received the influence of the horizontal electric field. It is M-M 'sectional drawing of FIG. It is sectional drawing which shows the liquid crystal orientation at the time of the voltage application in the conventional liquid crystal device. It is a perspective view which shows some examples about the electronic device which concerns on this embodiment. It is a figure which shows an example about the projection type display apparatus which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal device, 9 ... Pixel electrode, 10 ... TFT array substrate, 13 ... Orientation film, 14 ... Orientation film, 15 ... Projection part (convex part), 28 ... Counter electrode, 20 ... Counter substrate, 21 ... Nematic liquid crystal 50 ... Liquid crystal layer, A ... Image display area, B ... Area, C ... Pixel area, E ... Transverse electric field, L ... Transmission axis, N ... Transmission axis, S ... Gap, U ... Pixel electrode group

Claims (3)

In a liquid crystal display element of a twisted nematic type in which a liquid crystal layer made of a liquid crystal having a positive dielectric anisotropy is sandwiched between a pair of substrates,
A plurality of pixel electrodes on the liquid crystal layer side of one of the pair of substrates,
Among the pixel electrodes adjacent to each other, between the pixel electrodes adjacent to each other in a direction perpendicular to the alignment direction of the liquid crystal when no voltage is applied on the one substrate, parallel to the alignment direction of the liquid crystal. Convex portions extending in various directions,
An alignment film that is formed so as to cover the convex part and regulates the alignment direction of the liquid crystal when no voltage is applied;
And a counter electrode provided on the liquid crystal layer side of the other substrate of the pair of substrates.     2. The liquid crystal device according to claim 1, wherein the convex portion extends continuously across a plurality of pixel electrodes adjacent to the alignment direction of the liquid crystal so as to be along the alignment direction of the liquid crystal. .     An electronic apparatus comprising the liquid crystal device according to claim 1.

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