JP2008020521A - Liquid crystal device and image display device with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal device wherein an alignment state of a vertical alignment type liquid crystal is arranged in one direction and high quality display having high transmittance and no disclination is made possible, and to provide an image display device with the same. <P>SOLUTION: The liquid crystal device has a liquid crystal layer comprising the liquid crystal having positive dielectric anisotropy, held between a TFT array substrate 10 and a counter substrate and controls alignment of the liquid crystal by an electric field so that an initial alignment state is made to be in a vertical alignment direction, wherein a pixel electrode 9 and a common electrode 17 are provided on the liquid crystal layer side of the TFT array substrate 10, alignment control electrode 18 having the same potential with the pixel electrode 9 is included and the alignment control electrode 18 is disposed in a lower layer on the side of the common electrode 17 having a different potential. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal device and an image display device including the same.

  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. The vertical alignment enables high-contrast display and has recently been adopted as a liquid crystal alignment method for liquid crystal display elements for projectors.

  However, in the vertical alignment method, the liquid crystal stands perpendicular to the substrate surface when no voltage is applied, and it is difficult to define the direction in which the liquid crystal tilts when a voltage is applied. In other words, since the interaction in the azimuth direction that tilts when a voltage is applied is weak, the liquid crystal tilts in various directions due to a lateral electric field generated from the electrode end when a voltage is applied. Then, depending on the orientation, it does not contribute to the display (because liquid crystal parallel to the transmission axis of any polarizing plate does not cause a phase difference under crossed Nicols), the light transmittance is lower than in the case of parallel alignment. There was a problem. Further, when the alignment of the liquid crystal is disturbed, light deflection occurs, which may cause disclination (line defect).

In order to solve such problems, the following techniques are disclosed.
Japanese Patent Application Laid-Open No. 2004-228561 describes a method of giving a pretilt angle to an alignment film in order to align the alignment direction in one direction.
JP 2004-163921 A

  However, in the method of the above-mentioned Patent Document 1, when the pretilt angle is increased, a phase difference is generated in the liquid crystal when no voltage is applied, and there is a problem that light leakage occurs even in black display and the contrast is lowered. . By giving a pretilt angle to the liquid crystal, it is possible to align the alignment direction of the liquid crystal in one direction, but at the same time, light leakage has occurred. Therefore, controlling the molecular orientation and preventing light leakage have become future issues.

  The present invention has been made in view of the above problems, and its purpose is to make it possible to align the alignment state of the vertically aligned liquid crystal in one direction and to display high-quality display without disclination with high transmittance. An object of the present invention is to provide a liquid crystal device and an image display device including the same.

  In order to solve the above problems, a liquid crystal device of the present invention has a liquid crystal layer sandwiched between a pair of substrates, and a pixel electrode, a common electrode, and a common electrode on one liquid crystal layer side of the pair of substrates, An alignment control electrode having the same potential as either the pixel electrode or the common electrode is provided, and the alignment control electrode is disposed in a lower layer on the electrode side of the pixel electrode and the common electrode that has a different potential from the alignment control electrode. It is characterized by that. The present invention is a technique effective when the liquid crystal layer is made of a liquid crystal having a positive dielectric anisotropy whose initial alignment state is vertical alignment. However, the liquid crystal is not necessarily limited to a liquid crystal having a positive dielectric anisotropy, and may be a liquid crystal having a negative dielectric anisotropy.

  According to such a configuration, the alignment control electrode can generate an electric field obliquely with respect to the substrate surface between the pixel electrode and the alignment control electrode or between the common electrode and the alignment control electrode. Here, for example, the alignment control electrode is described as having the same potential as the pixel electrode. When an alignment control electrode having the same potential as the pixel electrode is arranged in the lower layer on the common electrode side and a voltage is applied to the liquid crystal layer, an electric field along the arrangement direction can be generated between the common electrode and the alignment control electrode. In the liquid crystal of the present invention, when the dielectric anisotropy is positive, the liquid crystal tilts along the electric field. When the dielectric anisotropy is negative, the liquid crystal is directed toward the direction perpendicular to the electric field. Will be inclined.

  In the case of such a configuration, the alignment control electrode is insulated from the common electrode and the pixel electrode by an insulating film. The insulating film is generally formed with a very thin film thickness of, for example, 1 μm or less. On the other hand, the common electrode and the pixel electrode are formed with an interval of about several μm from each other. For this reason, the orientation control electrode is positioned in the vicinity of the common electrode having a different potential rather than the pixel electrode having the same potential. Therefore, when a voltage is applied to the liquid crystal layer, the electric field density generated between the alignment control electrode and the common electrode that are arranged at a short distance is much higher than the electric field density on the other part of the pixel, that is, the pixel electrode side. It will be expensive. For this reason, the liquid crystal above the alignment control electrode and the common electrode is much more susceptible to the electric field than other liquid crystals in the pixel.

  As a result, in the liquid crystal layer on the alignment control electrode and the common electrode, tilt due to application of the electric field of the liquid crystal occurs preferentially, and in the pixel, the liquid crystal follows the tilt of the liquid crystal on the common electrode and alignment control electrode. Will tilt in the same direction. As a result, it is possible to align the tilt direction of the liquid crystal when applying an electric field in one direction, to realize high transmittance due to the liquid crystal tilting in the same direction, and to prevent and suppress the occurrence of disclination. it can.

  Similarly, when the alignment control electrode having the same potential as that of the common electrode is disposed in the vicinity of the pixel electrode, the alignment control electrode and the pixel electrode are also controlled by the intensity of the electric field density generated in the liquid crystal layer on the alignment control electrode and the pixel electrode. The tilt accompanying the electric field application of the upper liquid crystal is preferentially generated.

  In addition, according to such a configuration, the tilt direction of the liquid crystal can be controlled without increasing the pretilt angle by the alignment film, so that the occurrence of light leakage due to the pretilt angle can be prevented and suppressed. it can.

  Therefore, according to the present invention, the tilt of the liquid crystal can be aligned in one direction by the oblique electric field generated between the common electrode and the alignment control electrode, so that a liquid crystal device having high contrast, bright and uniform display quality can be obtained. It becomes possible to provide.

It is also preferable that the liquid crystal has a vertical direction in the initial alignment and the pretilt angle is 0 °.
According to such a configuration, since the pretilt angle in the initial alignment is 0 °, the polarization state of the light is not changed by the liquid crystal, and thus a clearer black display is possible. Thereby, improvement in contrast can be realized.

It is also preferable that the vertical alignment film is formed so as to cover the pixel electrode and the common electrode arranged on the same layer.
According to such a configuration, a flat surface can be formed without forming a step on the substrate by the vertical alignment film formed on the pixel electrode and the common electrode arranged on the same layer. As a result, the sandwiching surface of the liquid crystal layer becomes flat, so that the occurrence of light leakage or the like is prevented and suppressed, and it is possible to contribute to the improvement of contrast. For planarization, a method of forming an organic material or an inorganic material forming the alignment film by a liquid phase method such as a spin coating method can be employed.

The vertical alignment film is preferably not subjected to rubbing treatment.
According to such a configuration, it is possible to suitably realize vertical alignment with a pretilt angle of 0 ° in a state in which no voltage is applied (initial alignment state) by not performing the rubbing treatment on the vertical alignment film, thereby improving contrast. Can be achieved. Further, by not performing the rubbing treatment, the number of treatment steps is reduced, and there is no fear that fibers such as cloth used in the rubbing treatment remain in the liquid crystal layer to cause deterioration in display quality.

  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 having excellent display performance 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 shown below is an active matrix type liquid crystal device using a TFT (Thin-Film Transistor) element as a switching element. 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. FIG. 1 is a plan view showing the structure of a plurality of pixel groups adjacent to each other on a TFT array substrate in the liquid crystal device of this embodiment. FIG. 2 is a plan view showing the structure of one pixel of the TFT array substrate. FIG. 3 is a cross-sectional view taken along the line AA 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 to 3, the liquid crystal device 1 includes a liquid crystal layer 50 made of a liquid crystal 21 having a positive dielectric anisotropy via vertical alignment films 13 and 14 between the TFT array substrate 10 and the counter substrate 20. It is configured to be sandwiched. The TFT array substrate 10 includes a pixel electrode 9 and a common electrode 17 that are formed on the surface on the liquid crystal layer 50 side at predetermined intervals, and is formed below the pixel electrode 9 and the common electrode 17. And an alignment control electrode 18 having the same potential.

  In the present embodiment, as will be described in detail later, the orientation control electrode 18 is provided in the lower layer in the vicinity of the common electrode 17 (lower right in FIG. 3), and its potential is equal to the potential of the pixel electrode 9. It is controlled to become. The liquid crystal device 1 tilts the liquid crystal 21 in one direction by applying a voltage between the common electrode 17 and the alignment control electrode 18 arranged in this way and generating an electric field in an oblique direction with respect to the substrate surface. The optical characteristics can be controlled.

First, the pixel structure of the TFT array substrate 10 will be described in detail with reference to FIGS.
As shown in FIG. 1, 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. An area surrounded by two adjacent data lines 6a and scanning lines 3a is a pixel area 9 ′ indicated by a two-dot chain line in FIG. 2, and such a pixel area 9 ′ is on the TFT array substrate 10. Are formed in a matrix.

  As shown in FIG. 2, in each pixel region 9 ′, a pixel electrode 9 having a substantially rectangular shape in plan view made of a transparent conductive material such as indium tin oxide (hereinafter abbreviated as “ITO”) and the like. The common electrode 17 is provided in parallel with the data line 6a in a state where the longitudinal direction thereof is along the y direction, and is arranged at a constant interval. The arrangement pitch between the pixel electrode 9 and the common electrode 17 in this embodiment is about 8 μm. Further, as shown in the figure, the pixel electrode 9 is provided on one data line 6a side (right side in the figure) of the two data lines 6a constituting the pixel region 9 ′, and the common electrode 17 is It is provided on the other data line 6a (left side in the figure) side.

  As shown in FIGS. 1 and 2, the common electrode 17 provided in the pixel region 9 adjacent in the x direction is along one scanning line 3 a (lower side in the drawing) constituting the pixel region 9 ′. They are connected to each other by a common electrode wiring 16 extending in the x direction.

  As shown in FIG. 2, the pixel switching TFT element 30 is provided in the vicinity of the intersection of the data line 6a and the scanning line 3a, and the pixel electrode 9 and a gate formed by branching from the scanning line 3a in the y direction. The electrode 26 includes a semiconductor layer 1a made of amorphous silicon, and a source electrode 25 formed so as to partially overlap in a plane region of the semiconductor layer 1a and the scanning line 3a. The source electrode 25 is branched from the data line 6a in the x direction, and is formed on the same layer as the orientation control electrode 18 described later.

  As shown in FIG. 3, the pixel electrode 9 is electrically connected to a drain region 1d (described later) through a contact hole 8 in the semiconductor layer 1a made of, for example, a polysilicon film constituting the pixel switching TFT element 30. The data line 6a is electrically connected to a source region 1e described later in the semiconductor layer 1a through a contact hole 5.

  As shown in FIGS. 1 and 2, a plurality of alignment control electrodes 18 having the same potential as either the common electrode 17 or the pixel electrode 9 are provided as third electrodes on the TFT array substrate 10 side. In this embodiment, the alignment control electrode 18 has the same potential as the pixel electrode 9. The orientation control electrode 18 has a substantially rectangular shape in plan view, and is formed to have a length equal to or longer than the width of the common electrode 17. For example, the length of the common electrode 17 in the width direction is formed. Is about 1 μm, the width direction length of the alignment control electrode 18 may be set to about 2 μm.

  The orientation control electrode 18 is arranged along the y direction on the lower layer in the vicinity of the common electrode 17 (obliquely in FIG. 3), that is, on the right side of the common electrode 17 in plan view, and has one end in the longitudinal direction. The side is electrically connected to the pixel electrode 9 via the contact hole 24 and the pattern wiring 9 a on the TFT array substrate 10. The pattern wiring 9 a extends from the end of the pixel electrode 9 in the x direction and is connected to a contact hole 24 formed on the alignment control electrode 18. As a result, the alignment control electrode 18 has the same potential as the pixel electrode 9, and the potential is arbitrary.

  When the orientation control electrode 18 is provided on the TFT array substrate 10, as described above, it is provided in the lower layer in the vicinity of the common electrode 17 in each pixel region 9 '. At that time, as shown in FIG. The center line O in the width direction 17 and the center line P in the width direction of the orientation control electrode 18 are not matched in plan view (thickness direction of the substrate).

For example, when the width direction lengths of the alignment control electrode 18 and the common electrode 17 are equal, the center line P of the alignment control electrode 18 is at least the center line O of the common electrode 17 with respect to the pixel electrode 9 side. Shift to position. Alternatively, when the width direction length of the alignment control electrode 18 is longer than the width direction length of the common electrode 17, the end portion 18 a of the alignment control electrode 18 is closer to the data line 6 a side than the end portion 17 a of the common electrode 17. Arrange them so that they do not protrude.
In this way, the orientation control electrode 18 is arranged in the vicinity of the common electrode 17 having a different potential from the pixel electrode 9 having the same potential, so that the direction between the common electrode 17 and the orientation control electrode 18 is set in this direction. That is, an electric field oblique to the substrate surface is efficiently generated.

  As shown in FIG. 2, the pixel electrode 9, the common electrode 17, and the orientation control electrode 18 are disposed in the pixel region 9 ′ partitioned by the data line 6 a and the scanning line 3 a, which is referred to as one pixel in this embodiment. These are composed of three electrodes of the pixel electrode 9, the common electrode 17, and the orientation control electrode 18. As described above, the liquid crystal device 1 can perform display for each pixel region 9 ′ arranged in a matrix on the TFT array substrate 10.

  Next, a cross-sectional structure of the liquid crystal device of the present embodiment will be described based on FIG. In FIG. 3, some components such as a pixel switching TFT element are omitted in view of the visibility of the drawing.

  As shown in FIG. 3, in the liquid crystal device 1 of the present embodiment, a liquid crystal layer 50 is sandwiched between the TFT array substrate 10 and the counter substrate 20 disposed to face the TFT array substrate 10. The liquid crystal layer 50 is composed of the liquid crystal 21 having an initial alignment state of vertical alignment and positive dielectric anisotropy, and the liquid crystal device 1 is a vertical alignment mode display device.

  The TFT array substrate 10 covers the substrate body 10A made of a light-transmitting material such as quartz and the pixel electrode 9, the common electrode 17, and the pixel electrode 9 and the common electrode 17 formed on the surface of the liquid crystal layer 50 side. The counter substrate 20 is mainly composed of a substrate body 20A made of a light-transmitting material such as glass or quartz, and the liquid crystal layer 50 side. It is mainly composed of a vertical alignment film 14 formed on the surface.

  As shown in FIG. 3, in the TFT array substrate 10, the TFT array substrate 10 is transmitted through the surface of the substrate body 10 </ b> A on the liquid crystal layer 50 side, and the lower surface of the TFT array substrate 10 (the TFT array substrate 10 and air) The first light-shielding film 11a is provided to partially shield the return light that is reflected at the interface) and returns to the liquid crystal layer 50 side. 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 1 a, a scanning line 3 a, a data line 6 a, and a pixel electrode 9 formed on the first interlayer insulating film 12. 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 scanning line 3a, 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 scanning line 3a.

  In the semiconductor layer 1a, the scanning line 3a is disposed so as to face the channel region 1a ', and the scanning line 3a functions as a gate electrode in a portion facing the channel region 1a'.

  A second interlayer insulating film 4 in which a contact hole 8 leading to the drain region 1d and a contact hole 5 leading to the source region 1e are formed on the substrate body 10A including the scanning line 3a and the gate insulating film 2 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.

  On the second interlayer insulating film 4, an alignment control electrode 18 is formed so as to be in the same layer as the data line 6a. The alignment control electrode 18 is arranged at a predetermined interval in the x direction from the pixel electrode 9, and the contact hole 24 opened in the third interlayer insulating film 7 and the pattern wiring 9 a formed on the third interlayer insulating film 7. (See FIGS. 1 and 2), the pixel electrode 9 is electrically connected. Thereby, it functions as an electrode having the same potential as the pixel electrode 9.

A common electrode 17 is formed on the third interlayer insulating film 7 so as to be in the same layer as the pixel electrode 9. The common electrode 17 is an electrode common to all the pixels. Here, the common electrode 17 is disposed so that the end 17a of the common electrode 17 substantially coincides with the end 18a of the orientation control electrode 18 in the x direction. A vertical alignment film 13 made of polyimide or SiO ₂ is formed on the substrate body 10A so as to cover the common electrode 17 and the pixel electrode 9.

  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 is provided 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.

Furthermore, the vertical alignment film 14 is formed on the liquid crystal layer 50 side of the substrate body 20 </ b> A provided with the second light shielding film 19 so as to cover the second light shielding film 19. These vertical alignment films 13 and 14 may be any film that aligns the liquid crystal 21 in the liquid crystal layer 50 in the vertical direction with respect to the TFT array substrate 10 when no voltage is applied, and is made of polyimide, SiO ₂ or the like. . In addition to polyimide and SiO ₂ , any material may be used as long as it is a material that exhibits vertical alignment with respect to the liquid crystal 21.

The vertical alignment films 13 and 14 align the liquid crystal 21 vertically with respect to the film surface when no voltage is applied. The vertical alignment films 13 and 14 are subjected to an alignment process such as a rubbing process. It has not been. Further, by forming the vertical alignment films 13 and 14, a flat surface can be formed without forming a step on the inner surfaces (opposing surfaces) of the substrate bodies 10A and 20A. Thereby, since the clamping surface of the liquid crystal layer 50 becomes flat, the occurrence of light leakage or the like is prevented and suppressed, and it is possible to contribute to the improvement of contrast. In forming the vertical 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 is formed using a known vapor deposition method and has a columnar microstructure that is perpendicular to the surface.

  The TFT array substrate 10 and the counter substrate 20 are bonded to each other via a sealing material (not shown), and liquid crystal 21 (positive liquid crystal material) having positive dielectric anisotropy from a liquid crystal injection port formed in the sealing material. ) Is injected to obtain the liquid crystal panel 40.

  The 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. Examples of the liquid crystal 21 having positive dielectric anisotropy include a nematic liquid crystal material or a chiral nematic liquid crystal material.

  In the liquid crystal panel 40, polarizing plates 22 and 23 are provided on the outer surface sides of the counter substrate 20 and the TFT array substrate 10, respectively, and are arranged so that their light transmission axes are orthogonal to each other. As shown in FIG. 3, these transmission axes are common so that the light transmittance of the liquid crystal device 1 when no voltage is applied is 0% and the light transmittance of the liquid crystal device 1 when a voltage is applied is 100%. The electrode 17 and the alignment control electrode 18 are arranged in a direction that forms 45 ° with respect to the arrangement direction (that is, the direction in which the liquid crystal 21 is aligned). In this way, 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, the polarizing plates 22 and 23 are bonded in a crossed Nicol state, and predetermined wiring is connected. In this embodiment, the liquid crystal device 1 is used.

Next, a method for producing the TFT array substrate of this embodiment will be described.
FIG. 4 is an explanatory view schematically showing, in particular, a method for forming alignment control electrodes (a method for producing a TFT array substrate).

  First, as shown in FIG. 4A, a translucent substrate body 10A made of glass or the like is prepared, and a first interlayer insulating film 12, a semiconductor layer 1a, various wirings 3a and 6a, an insulating film 4, 7 (not shown) is formed.

  Next, as shown in FIG. 4B, on the second interlayer insulating film (not shown) formed on the surface of the substrate body 10A, a plurality of alignment control electrodes 18 are formed in an array at a predetermined interval. Subsequently, as shown in FIG. 4C, a third interlayer insulating film 7 is formed on the second interlayer insulating film 4 including the orientation control electrode 18. 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. Then, as shown in FIG. 4D, a cylindrical fine hole is formed on the alignment control electrode 18 as the contact hole 24 in the third interlayer insulating film 7. The fine holes of the contact hole 24 may be formed with a predetermined hole diameter and may have a shape other than a cylindrical shape (for example, a prism shape).

Next, as shown in FIG. 4E, the common electrode 17 and the pixel electrode 9 are formed on the third interlayer insulating film by a known method. In the present embodiment, first, ITO is formed on the third interlayer insulating film 7. At this time, the contact hole 24 is filled with ITO. Thereafter, by patterning ITO into a predetermined shape, the pixel electrode 9 and the pattern wiring 9a are integrally formed, and at the same time, the common electrode 17 and the common electrode wiring 16 are integrally formed. In this manner, a pattern wiring 9a (not shown) that connects the contact hole 24 and the pixel electrode 9 is formed on the third interlayer insulating film 7, and the common electrode 17 and the common electrode common to each pixel are formed. A wiring 16 is formed.
Then, the alignment control electrode 18 is configured to be electrically connected to the pixel electrode 9 on the third interlayer insulating film 7 by the contact hole 24 and the pattern wiring 9a.

Next, as illustrated in FIG. 4F, the vertical alignment film 13 is formed on the substrate body 10 </ b> A including the pixel electrode 9 and the common electrode 17. The vertical 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. 5 is an explanatory diagram showing the alignment state, equipotential lines, and light transmittance of the liquid crystal when a voltage is applied. FIG. 6 is an explanatory diagram showing the tilt direction of the liquid crystal.

  In the liquid crystal device 1 of the present embodiment, as described above, the potential of the alignment control electrode 18 is equal to that of the pixel electrode 9. Then, by arranging the alignment control electrode 18 having a potential different from that of the common electrode 17 in the vicinity of the common electrode 17, an electric field relatively stronger than the electric field strength generated between the common electrode 17 and the pixel electrode 9 is shared. It can be generated between the electrode 17 and the orientation control electrode 18.

  The third interlayer insulating film 7 interposed between the orientation control electrode 18 and the common electrode 17 and the pixel electrode 9 is generally formed with a very thin film thickness of, for example, 1 μm or less. On the other hand, the common electrode 17 and the pixel electrode 9 are formed with an interval of about several tens of μm. Therefore, it is clear from the drawings referred to so far that the orientation control electrode 18 is positioned in the vicinity of the common electrode 17 having a different potential than the pixel electrode 9 having the same potential. Therefore, if a predetermined voltage is applied between the common electrode 17 and the orientation control electrode 18 and at the same time, the pixel electrode 9 and the orientation control electrode 18 are controlled to be kept at an equal potential, the common electrode 17 and the orientation control are controlled. An electric field is generated between the electrodes 18 along the direction in which the electrodes 18 are arranged, and is oblique to the substrate surface (the direction in which the common electrode 17 and the alignment control electrode 18 are arranged).

  At this time, the electric field density generated between the alignment control electrode 18 and the common electrode 17 which are disposed at a short distance is much higher than the electric field density on the other part in the pixel, that is, on the pixel electrode 9 side. . Therefore, the liquid crystal 21 above the alignment control electrode 18 and the common electrode 17 is much more easily affected by the electric field than the other liquid crystals 21 in the pixel.

  Here, in the liquid crystal device 1 of the present embodiment, the liquid crystal 21 having a positive dielectric anisotropy is used as described above. The liquid crystal 21 having a positive dielectric anisotropy has the property that the major axis direction of the liquid crystal molecules is aligned with the direction of the electric field, and tends to be perpendicular to the equipotential lines. In order to explain the tilting direction of the liquid crystal 21 more easily, the explanation will be made based on FIG. 5 showing the equipotential lines T perpendicular to the electric field. According to this figure, the equipotential lines T are the most dense between the common electrode 17 and the alignment control electrode 18, and the influence on the liquid crystal 21 on the common electrode 17 and the alignment control electrode 18 is the strongest. .

  That is, as the liquid crystal 21 is tilted on the common electrode 17 and the alignment control electrode 18, the tilted state of the liquid crystal 21 between the common electrode 17 and the alignment control electrode 18 shown in the drawing changes. At this time, the liquid crystal 21 shows a liquid crystal alignment method that can change its state with a smaller tilt. Specifically, as shown in FIG. 6, the direction of the liquid crystal 21 that is vertically aligned when no voltage is applied is indicated by the direction indicated by the broken-line arrow (perpendicular to the arrangement direction of the common electrode 17 and the alignment control electrode 18 Tilting in the direction indicated by the solid line arrow is allowed. That is, the molecular long axis is tilted by a certain angle θ with respect to the equipotential line, and is held in a vertical posture with respect to the equipotential line.

  Therefore, as shown in FIG. 5, in the liquid crystal layer 50 on the common electrode 17 and the alignment control electrode 18, the liquid crystal 21 is preferentially tilted due to voltage application, and the pixel electrode 9 and the alignment control electrode 18 in the pixel In the meantime, the other liquid crystal 21 tilts in the same direction following the tilt of the liquid crystal 21 on the common electrode 17 and the alignment control electrode 18.

  As a result, it is possible to align the tilt direction of the liquid crystal 21 when an electric field is applied in one direction, to realize high transmittance due to the liquid crystal 21 tilting in the same direction, and to prevent and suppress the occurrence of disclination. be able to.

  FIG. 5 also shows a graph of the light transmittance within the pixel. According to this graph, it can be seen that the light transmittance G is high in the pixel, more specifically, between the orientation control electrode 18 and the pixel electrode 9. Based on the fact that the alignment change is regulated in one direction by the alignment force caused by the oblique electric field between the common electrode 17 and the alignment control electrode 18, it can be seen that light is efficiently transmitted, and the description so far has been verified. It can be said that. A region between the alignment control electrode 18 and the pixel electrode 9 having a good light transmittance G is a display region A that contributes to display.

  On the other hand, it can be seen that between the pixels (region indicated by B in the figure), there are a portion where the light transmittance G is rapidly decreased and a portion where the light transmittance G is locally increased. This is partly due to the difference in potential distribution between the pixels, which is also apparent from the equipotential line T shown in FIG. According to FIG. 5, the liquid crystal 21 showing the alignment state substantially perpendicularly can be seen in part by the equipotential lines T that can be substantially parallel to the surfaces of the common electrode 17 and the pixel electrode 9, but most of the liquid crystal 21 between the pixels can be seen. The liquid crystal 21 has various orientation directions and pretilt angles due to the equipotential lines T that are bent and densely arranged at the opposite ends of the common electrode 17 and the pixel electrode 9 of adjacent pixels.

  As described above, the alignment failure of the liquid crystal 21 that occurs when the alignment state is not the desired alignment state, as shown in FIG. 2, the two polarizing plates 22 and 23 (the polarizing plates 22 and 23 are arranged in crossed Nicols) on the liquid crystal panel 40. And the transmission axis L of the polarizing plate 22 and the transmission axis N of the polarizing plate 23 are arranged at an angle of 45 ° with respect to the electric field E generated between the alignment control electrode 18 and the pixel electrode 9). When arranged, it appears that the transmittance change changes significantly locally (region B in FIG. 5).

  However, the region B corresponds to the light shielding portion in the pixel. That is, noise light is shut out by providing the first light-shielding film 11a and the second light-shielding film 19 in a lattice shape between the pixels. Therefore, the light transmittance G 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 a conventional VA (Vertical Alignment) type liquid crystal device in which the alignment control electrode 18 is not provided, when a voltage is applied between the pixel electrode provided on the TFT array substrate and the common electrode provided on the counter substrate, each electrode end As a result of the horizontal electric field generated in the liquid crystal, variation in liquid crystal alignment as occurs between the pixels of the present embodiment (region B in the present embodiment) also occurs in the display region (display region A in the present embodiment). Disclination (line defect) due to mutual interference occurred. 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.

  However, according to the configuration of the present embodiment, an electric field oblique to the substrate surface can be formed in the liquid crystal layer 50 on the common electrode 17 and the alignment control electrode 18. In the present embodiment, since the liquid crystal 21 having positive dielectric anisotropy is used, the orientation in which the major axis direction of the liquid crystal 21 is parallel to the electric field, that is, perpendicular to the equipotential line T when voltage is applied. It becomes a state.

  In the liquid crystal layer 50 on the common electrode 17 and the alignment control electrode 18, the liquid crystal 21 is preferentially tilted due to voltage application, so that the switch function is activated, and the other liquid crystal 21 tilts in the same direction. Therefore, almost all the liquid crystals 21 in the display area A can be tilted all at once in the same direction without giving a pretilt angle to the liquid crystals 21. Thereby, by controlling the alignment direction of each liquid crystal 21, interference between the liquid crystals 21 is prevented, and the occurrence of disclination can be eliminated.

  In addition, since the alignment direction of the liquid crystal 21 is restricted to one direction, the tilt control of the liquid crystal 21 is performed quickly, and thereby the response time of the liquid crystal 21 is improved, so that the afterimage of the image can be suppressed. Thereby, the light transmittance can be maintained at a high level without generating afterimages. Therefore, it is possible to obtain the liquid crystal device 1 that can improve the display quality of the image and provide an image with high visibility.

  In the liquid crystal device 1 of the present embodiment, as described above, the liquid crystal 21 is in the vertical direction in the initial alignment, and the pretilt angle is substantially 0 °. That is, by not performing the rubbing process on the vertical alignment films 13 and 14, a vertical alignment with a pretilt angle of 0 ° is suitably realized in a state where no voltage is applied (initial alignment state). That is, since the pretilt angle of the liquid crystal 21 is 0 °, the polarization state of the incident light is not changed by the liquid crystal 21, so that a clearer black display is possible and the contrast can be improved. In addition, since the pretilt by the vertical alignment films 13 and 14 becomes unnecessary, generation | occurrence | production of the light leakage resulting from a pretilt angle can also be prevented and suppressed.

  Therefore, according to the present embodiment, the tilt of the liquid crystal 21 can be aligned in one direction by an oblique electric field generated between the common electrode 17 and the alignment control electrode 18, so that a high-contrast, bright and uniform display quality can be obtained. It is possible to provide the liquid crystal device 1 having the same.

  Note that the rubbing process is not performed on the vertical alignment films 13 and 14, so that the number of processing steps is reduced, and fibers such as cloth used in the rubbing process may remain in the liquid crystal layer 50 to cause deterioration in display quality. Disappear.

  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. In addition, the present invention is a technique effective when the liquid crystal layer is made of a liquid crystal having an initial alignment state of vertical alignment and a positive dielectric anisotropy, and the above embodiment has been described with an example. However, the liquid crystal is not necessarily limited to a liquid crystal having a positive dielectric anisotropy, and may be a liquid crystal having a negative dielectric anisotropy. Thus, the present invention can be applied to a liquid crystal device having any structure.

[Electronics]
Examples of electronic devices including the liquid crystal device of the above embodiment will be described.
FIG. 7A is a perspective view showing an example of a mobile phone. In FIG. 7A, 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. 7B is a perspective view illustrating an example of a portable information processing apparatus such as a word processor or a personal computer. In FIG. 7B, 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. 7C is a perspective view showing an example of a wristwatch type electronic device. In FIG. 7C, 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. 7 uses the liquid crystal device as an example of the above-described embodiment for the display unit, there is a problem in 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 of the above embodiment as a light modulation unit will be described with reference to FIG. FIG. 8 is a schematic configuration diagram showing a main part of a projection display device using the liquid crystal device of the embodiment as a light modulation device. In FIG. 8, 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.

  Since the projection display device having the above-described structure includes the liquid crystal device as an example of the above-described embodiment, there is no problem of displaying the rubbing streaks as in the case of performing the rubbing process, and the high contrast. Thus, the display device can maintain a bright and high-quality display for a long time.

It is a top view which shows the structure of the several pixel group which the TFT array substrate in a liquid crystal device adjoins. It is a top view which shows typically the structure of the pixel area | region in a liquid crystal device. It is AA sectional drawing of FIG. 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 orientation state of a liquid crystal at the time of a voltage application, an equipotential line, and a light transmittance. It is explanatory drawing which shows the inclination state of the liquid crystal at the time of a voltage application. 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, 3 ... Electrode, 9 ... Pixel electrode, 10 ... Substrate, 13 ... Vertical alignment film, 14 ... Vertical alignment film, 17 ... Common electrode, 18 ... Orientation control electrode, 20 ... Counter substrate, 21 ... Liquid crystal, 50 ... Liquid crystal layer

Claims (6)

A liquid crystal layer is sandwiched between a pair of substrates,
A pixel electrode on the liquid crystal layer side of one of the pair of substrates,
A common electrode;
An alignment control electrode having the same potential as either the pixel electrode or the common electrode, and
The liquid crystal device, wherein the alignment control electrode is disposed in a lower layer on the electrode side of the pixel electrode and the common electrode that has a different potential from the alignment control electrode.     The liquid crystal device according to claim 1, wherein the liquid crystal layer is a liquid crystal having an initial alignment state of vertical alignment and positive dielectric anisotropy.     The liquid crystal device according to claim 1, wherein the liquid crystal is aligned in a vertical direction in an initial alignment state, and a pretilt angle is 0 °.     The liquid crystal device according to claim 1, wherein a vertical alignment film is formed so as to cover the pixel electrode and the common electrode arranged on the same layer.     The liquid crystal device according to claim 4, wherein the vertical alignment film is not rubbed. An electronic apparatus comprising the liquid crystal device according to claim 1.

Images