JP3625283B2 - Active matrix liquid crystal display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an active matrix liquid crystal display device.
[0002]
[Prior art]
A conventional active matrix type liquid crystal display device uses a transparent electrode formed to face each other on the interface between two substrates as an electrode for driving a liquid crystal layer. This is because a twisted nematic display system that operates by setting the direction of the electric field applied to the liquid crystal to a direction substantially perpendicular to the substrate interface is employed.
[0003]
On the other hand, an active matrix type liquid crystal display device using a method in which the direction of the electric field applied to the liquid crystal is substantially parallel to the substrate interface has been proposed by, for example, Japanese Patent Laid-Open No. 56-91277.
[0004]
[Problems to be solved by the invention]
In the prior art using the twisted nematic display method, a transparent electrode typified by Indium Tin Oxide (ITO) must be formed. However, the transparent electrode has irregularities of about several tens of nanometers on its surface, making it difficult to process fine active elements such as thin film transistors (hereinafter referred to as TFTs). Further, the convex portion of the transparent electrode is often separated and mixed into other portions such as the electrode, causing a dot-like or line-like display defect, so that the yield of the product is significantly reduced.
[0005]
The prior art has many problems in terms of image quality. In particular, the change in luminance when the viewing angle direction is changed is significant, making halftone display difficult. Furthermore, in an active matrix display element using a switching transistor element, in addition to a pixel electrode that applies a voltage or an electric field to liquid crystal to modulate transmitted light or reflected light, a scanning electrode for driving the switching transistor element and A signal electrode is required. The scanning electrode and the signal electrode change the potential of the pixel electrode by the parasitic capacitance Cgs between the scanning electrode and the pixel electrode and the parasitic capacitance Cds between the signal electrode and the pixel electrode. In particular, since the potential of the signal electrode constantly fluctuates depending on the video information, the potential of the pixel electrode varies due to the parasitic capacitance Cds between the signal electrode and the pixel electrode, causing image quality defects called contrast reduction or crosstalk. Yes.
[0006]
In the method in which the direction of the electric field applied to the liquid crystal is in a direction substantially parallel to the substrate interface, the parasitic capacitance Cds between the signal electrode and the pixel electrode is increased and the crosstalk is intense as compared with the twisted nematic display method. There is a problem that the contrast is lowered depending on the image pattern. This is because, in the method in which the direction of the electric field applied to the liquid crystal is substantially parallel to the substrate interface, unlike the twisted nematic display method, a common electrode is not formed on the entire surface of the substrate facing the substrate having the switching transistor element. This is because the lines of electric force from are not shielded and terminate in the pixel electrode. For this reason, active matrix driving has a problem in image quality when the electric field direction is substantially parallel to the substrate interface.
[0007]
A first object of the present invention is to provide an active matrix liquid crystal display device that does not require a transparent electrode.
[0008]
A second object of the present invention is to provide an active matrix liquid crystal display device that has good viewing angle characteristics and facilitates multi-gradation display.
[0009]
A third object of the present invention is to provide an active matrix liquid crystal display device with high contrast and high image quality that does not cause crosstalk.
[0010]
[Means for Solving the Problems]
The gist of the present invention for achieving the above object is as follows.
[0011]
(1)A liquid crystal composition is held between the first and second substrates, and a plurality of pixels are configured on the first substrate by a plurality of scanning electrodes and signal electrodes arranged in a matrix. In an active matrix liquid crystal display device provided with a switching element,
The switching element is connected to a pixel electrode, and is configured such that the direction of the electric field applied to the liquid crystal is substantially parallel to the substrate interface by the pixel electrode and a common electrode facing the pixel electrode.
The pixel has a signal electrode, a pixel electrode, and a shield electrode between the signal electrode and the pixel electrode,
The shield electrode is formed on a second substrate;
Pigment in the light transmission part between the signal electrode of the pixel and the pixel electrode, the light transmission part between the signal electrode and the common electrode, the light transmission part on the semiconductor layer of the switching element and the lines of electric force from the scanning electrode Or an active matrix type liquid crystal display device comprising a black or low light transmittance light-shielding film containing a dyePlace.
[0012]
(2)The active matrix liquid crystal display device, wherein the shield electrode is formed on a light transmitting portion between the signal electrode and the pixel electrode, a light transmitting portion between the signal electrode and the common electrode, and a semiconductor layer of the switching element..
[0013]
(3)The active matrix type liquid crystal display device formed so that a part of the shield electrode overlaps with the signal electrode.
[0014]
(4)The active matrix liquid crystal display device, wherein the shield electrode reduces a parasitic capacitance generated between at least one portion of the signal electrode and the pixel electrode as compared with a case where the electrode is not disposed..
[0015]
Next, the operation of the present invention will be described with reference to FIG.(Reference Example 1)Will be described. 1 (a) and 1 (b)Reference Example 1FIGS. 1C and 1D are plan views showing a side cross section of one pixel in the liquid crystal cell. In FIG. 1, active elements are omitted. In the present invention, a plurality of pixels are formed by forming scanning electrodes and signal electrodes in a matrix, but here, only one pixel portion is shown.
[0016]
FIG. 1A shows a cross-sectional side view of the cell when no voltage is applied, and FIG. 1C shows a plan view at that time. Striped pixel electrodes 3, common electrodes 4, signal electrodes 2 and shield electrodes 5 are formed inside a pair of transparent substrates 8 and 9, and alignment control films 14 and 15 (alignment direction 28) are formed thereon. The liquid crystal composition is sandwiched between them.
[0017]
The rod-like liquid crystal molecules 25 have a slight angle with respect to the longitudinal direction of the striped electrode when no electric field is applied, that is, the angle formed by the major axis (optical axis) of the liquid crystal molecule in the vicinity of the interface with respect to the electric field direction. Oriented so that | <90 degrees. Here, a case where the alignment directions at the upper and lower interfaces of the liquid crystal molecules are parallel will be described as an example. The dielectric anisotropy of the liquid crystal composition is positive.
[0018]
Next, when an electric field E is applied to the pixel electrode 3 and the common electrode 4, the liquid crystal molecules change in the direction of the electric field E, as shown in FIGS. By arranging the polarization transmission axes 29 of the polarizing plates 26 and 27 to be at a predetermined angle, the light transmittance can be changed by applying an electric field.
[0019]
Thus, according to the present invention, a display with contrast can be achieved without a transparent electrode. Specific configurations for providing contrast include a mode using a state in which liquid crystal molecular alignments on the upper and lower substrates are substantially parallel (referred to as a birefringence mode because an interference color due to a birefringence phase difference is used), and upper and lower A mode that utilizes a state in which the alignment directions of liquid crystal molecules on the substrate intersect and the molecular arrangement in the cell is twisted (this is referred to as an optical rotation mode because it uses the optical rotation that rotates the polarization plane in the liquid crystal composition layer) )
[0020]
In the birefringence mode, by applying a voltage, the direction of the molecular long axis (optical axis) remains substantially parallel to the substrate interface while changing its orientation in the plane, and the axes of the polarizing plates 26 and 27 (absorption axes or The angle formed with the transmission axis changes to change the light transmittance. Similarly, in the optical rotation mode, the orientation in the molecular long axis direction is changed by applying a voltage. In this case, the change in optical rotation due to the dissolution of the spiral is utilized.
[0021]
In this display mode in which the direction of the electric field applied to the liquid crystal is substantially parallel to the substrate interface, the major axis of the liquid crystal molecules is always substantially parallel to the substrate and does not rise. Therefore, even if the viewing angle direction is changed, the change in brightness is small (no viewing angle dependency), and so-called viewing angle characteristics are excellent.
[0022]
This display mode does not obtain a dark state by making the birefringence phase difference almost zero by applying voltage as in the conventional case, but the angle formed by the liquid crystal molecule long axis and the axis of the polarizing plate (absorption axis or transmission axis). The dark state is obtained by changing, and its action is basically different. In the case where the long axis of the liquid crystal molecule rises perpendicularly to the substrate interface as in the conventional TN type, the viewing angle direction where the birefringence phase difference is zero is the front, that is, the direction perpendicular to the substrate interface, and the viewing angle is slight. When tilted, a birefringence phase difference appears. Therefore, in the normally open type, light leaks, causing a decrease in contrast and inversion of gradation levels.
[0023]
Next, another important operation of the liquid crystal display device of the present invention will be described. When the pixel electrode 3 is configured adjacent to the signal electrode 2, the electric lines of force from the signal electrode 2 terminate at the pixel electrode 3 and between the signal electrode 2 and the pixel electrode 3 as represented by the following equation: Parasitic capacitance Cds is generated.
[Expression 1]
[0024]
W is the width of the pixel electrode 3 (the length in the short direction), d is the distance between the signal electrode 2 and the pixel electrode 3, ε is the dielectric constant of the medium between the electrodes, π is the circular ratio, and the parasitic capacitance Cds Indicates the capacity per unit length. In the above description, it is assumed that the dielectric constant of the medium between the electrodes is constant and the width of the signal electrode 2 is equal to or greater than the width of the pixel electrode 3.
[0025]
In the liquid crystal display device of the present invention, since the shield electrode 5 is provided between the signal electrode 2 and the pixel electrode 3, most of the lines of electric force from the signal electrode 2 terminate at the shield electrode 5. If the potential is always applied from the outside so that the potential of the shield electrode 5 becomes constant, the parasitic capacitance Cds between the signal electrode 2 and the pixel electrode 3 is drastically reduced. Thereby, even if the potential of the signal electrode 2 changes, the potential of the pixel electrode 3 does not change, so that crosstalk is eliminated. As a result, this display mode can be applied to an active matrix, and a liquid crystal display device with good viewing angle characteristics, high contrast, and high image quality can be obtained.
[0026]
Further, since the shield electrode 5 can also be used as a light shielding layer (black matrix), it is not necessary to form a light shielding layer, and the manufacturing yield can be improved in combination with the point that a transparent electrode is not required. Furthermore, the shield electrode can also be used as a common electrode. Since the shield electrode can use the area occupied by the common electrode, the aperture ratio can be improved, and high luminance or low power consumption can be achieved.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be specifically described with reference to examples. In the following embodiments, on the display panel surface of the liquid crystal display device, the direction parallel to the longitudinal direction of the signal electrode (perpendicular to the longitudinal direction of the scanning electrode) is the vertical direction, and the longitudinal direction of the signal electrode (vertical direction of the scanning electrode) The direction parallel to the longitudinal direction is the horizontal direction, the column direction of the matrix electrodes is parallel to the vertical direction, and the row direction is parallel to the horizontal direction. The number of pixels was 640 (× 3) × 480, and the pitch of each pixel was 110 μm in the horizontal direction and 330 μm in the vertical direction.
[0028]
[Example 1]
FIG. 2A shows a schematic plan view of a pixel portion of the liquid crystal display panel of this embodiment, and FIG. 2B shows a schematic cross-sectional view taken along line AA ′ of FIG. FIG. 3 shows a configuration diagram of a driving system of the liquid crystal display device of this embodiment. The substrates 8 and 9 were 1.1 mm thick glass substrates whose surfaces were polished.
[0029]
On the substrate 8, the scanning electrodes 1 and 17 of Cr were formed in the horizontal direction. Further, Cr / Al signal electrodes 2 and 18 were formed perpendicular to the scanning electrodes 1 and 17. Further, the pixel includes amorphous silicon 6 and a part of the scanning electrode 1 (acting as a gate electrode), a part of the signal electrode 2 (acting as a drain electrode or a source electrode), and a pixel electrode 3 (as a source electrode or a drain electrode). A thin film transistor (TFT) element using the above was formed. A silicon nitride film was used as the gate insulating film 10 of the TFT element.
[0030]
The pixel electrode 3 is formed of the same material as the signal electrodes 2 and 18 in the same layer and in the same process so that the longitudinal direction is the vertical direction. Further, an n + type amorphous silicon 7 for forming an ohmic contact was formed between the signal electrode 2 and the pixel electrode 3 and the amorphous silicon 6.
[0031]
The common electrode 4 was formed in the same material and in the same layer as the pixel electrode 3 and the signal electrodes 2 and 18 in a stripe shape, drawn in the vertical direction, and commonly connected to the common electrodes in other columns.
[0032]
The orientation of the liquid crystal molecules in the liquid crystal layer is controlled mainly by the electric field E applied in the horizontal direction between the pixel electrode 3 and the common electrode 4. The light passes between the pixel electrode 3 and the common electrode 4, enters the liquid crystal layer 16, and is modulated. Therefore, the pixel electrode 3 does not need to be particularly light-transmitting (for example, a transparent electrode such as ITO).
[0033]
A protective film 11 made of silicon nitride for protecting the TFT element was formed on the TFT element. A shield electrode 5 was formed on a substrate 9 (hereinafter referred to as a counter substrate) opposite to a substrate 8 provided with a TFT element group (hereinafter referred to as a TFT substrate). At this time, the shield electrode 5 was formed so as to be arranged in a stripe shape between the signal electrode 2 and the pixel electrode 3, and was drawn out in the vertical direction to be connected in common with the shield electrodes in other columns.
[0034]
Further, on the counter substrate 9, three color filters 12 composed of R, G, and B in a stripe shape in the vertical direction were formed. On the color filter 12, a flattening film 13 made of a transparent resin for flattening the surface was laminated. An epoxy resin was used as the material for the planarizing film 13. Further, polyimide-based orientation control films 14 and 15 were applied and formed on the planarizing film 13 and the protective film 11.
[0035]
A nematic liquid crystal composition 16 having a positive dielectric anisotropy Δε, a value of 7.3, and a birefringence Δn of 0.073 (589 nm, 20 ° C.) was sandwiched between the substrates 8 and 9. In this embodiment, a liquid crystal having a positive dielectric anisotropy Δε is used, but a negative liquid crystal may be used.
[0036]
The alignment control films 14 and 15 were rubbed so that the pretilt angle was 1.0 degree. The rubbing directions of the upper and lower interfaces were substantially parallel to each other, and the angle formed with the applied electric field E was 85 degrees. In addition, the gap (d) between the upper and lower substrates was 4.5 μm in a liquid crystal sealed state in which spherical polymer beads were dispersed and held between the substrates. Accordingly, Δn · d is 0.329 μm.
[0037]
The above panel is sandwiched between two polarizing plates [G1220DU manufactured by Nitto Denko Corporation] (the polarizing plate is not shown), the polarizing transmission axis of one polarizing plate is substantially parallel (85 degrees) to the rubbing direction, and the other is orthogonal to it. (−5 degrees). As a result, a normally closed liquid crystal display device was obtained.
[0038]
Next, a vertical scanning circuit 19 and a video signal driving circuit 20 are connected on the TFT substrate 8 of the liquid crystal display panel 22 as shown in FIG. 3, and a scanning signal voltage, a video signal voltage, a timing signal, A common electrode voltage and a shield electrode voltage were supplied, and active matrix driving was performed.
[0039]
In this example, the shield electrode voltage and the common electrode voltage were made independent, and the shield electrode voltage was electrically connected to the shield electrode on the counter electrode from the TFT substrate 8 using silver paste and supplied. In this embodiment, an amorphous silicon TFT element is used, but a polysilicon TFT element may be used. In the case of a reflective display device, a MOS transistor formed on a silicon wafer may be used. The wiring material is not limited.
[0040]
In this embodiment, the alignment control film is provided. However, the surface of the planarization film 13 may be directly rubbed to serve as the alignment control film. Similarly, an epoxy resin can be used for the protective film 11 of the TFT and a rubbing process can be performed.
[0041]
Next, FIG. 4 shows the relationship between the voltage applied to the liquid crystal of this embodiment and the brightness. The contrast ratio is 150 or more when driven at 7V, and the curve difference when the viewing angle is changed to the left, right, up and down is extremely small compared to the conventional method (Comparative Example 1), and the display characteristics hardly change even when the viewing angle is changed. It was. In addition, the orientation of the liquid crystal was good, and no domain or the like based on poor alignment was generated.
[0042]
FIG. 5 shows a change in the signal voltage Vsig-brightness curve due to the difference in the waveform of the signal electrode voltage Vd in this embodiment. 5A shows a voltage waveform, and FIG. 5B shows a change in the signal voltage Vsig-brightness curve. After the scanning electrode voltage Vg was turned on and the signal voltage Vsig was written, the signal electrode voltage Vd was changed, but no noticeable change occurred in the signal voltage Vsig-brightness curve.
[0043]
As described above, in this example, the intensity of transmitted light can be modulated without using a transparent electrode, and the viewing angle dependency can be remarkably improved. Furthermore, vertical crosstalk, which is a weak point of the method of applying an electric field in parallel with the substrate interface, can be suppressed, and a high-throughput, high yield, wide viewing angle, high contrast, high-quality liquid crystal display device is obtained. I was able to.
[0044]
[Comparative Example 1]
A conventional twisted nematic (TN) type display device having a transparent electrode was prepared and compared with the first embodiment. As the liquid crystal composition, the nematic liquid crystal composition having a positive dielectric anisotropy Δε used in Example 1 was used, the gap (d) was 7.3 μm, and the twist angle was 90 degrees. Therefore, Δn · d is 0.526 μm.
[0045]
The electro-optical characteristics are shown in FIG. The curve changed remarkably depending on the viewing angle direction, and a domain based on poor alignment of the liquid crystal occurred in the vicinity of the gap between the adjacent portions of the TFT.
[Comparative Example 2]
[0046]
FIG. 7 shows changes in the signal voltage-brightness characteristics accompanying changes in the signal electrode voltage when the shield electrode 5 of FIG. 2 is not formed. It was found that the signal voltage Vsig-brightness curve has a large difference due to the difference in the waveform of the signal electrode voltage Vd. In terms of image quality, vertical crosstalk occurred, and the contrast was significantly lowered as shown by the Vd 'curve in the figure.
[0047]
[Example 2]
The configuration of the present embodiment is the same as that of the first embodiment except for the following requirements. FIG. 8A is a schematic plan view of a pixel of the liquid crystal display panel of this embodiment, and FIG. 8B is a schematic cross-sectional view taken along the line BB ′ of FIG. The structural feature of the present embodiment is that a shield electrode 5 a is formed that covers all of the light transmission portions between the pixel electrode 3 and the signal electrode 2 and between the common electrode 4 and the signal electrode 18. As a result, light leakage did not occur without providing a light shielding layer, and high contrast could be obtained.
[0048]
Furthermore, since the amorphous silicon 6 was also covered, there was no increase in leakage current due to the light of the amorphous silicon, and good display characteristics could be obtained. In addition, a slit-like opening is provided in the portion of the shield electrode 5a on the signal electrodes 2 and 18 so that the capacitance between the signal electrode and the shield electrode does not increase as much as possible, and only an overlap for a margin of alignment accuracy is provided. Thus, the overlap with the signal electrodes 2 and 18 was minimized.
[0049]
As described above, in this example, an effect equivalent to that of Example 1 was obtained, and an active matrix liquid crystal display device with higher contrast and higher image quality could be obtained.
[0050]
Example 3
The configuration of the present embodiment is the same as that of the first embodiment except for the following requirements. FIG. 9A shows a schematic plan view of a pixel of the liquid crystal display panel of this embodiment, and FIG. 9B shows a schematic cross-sectional view taken along CC ′ of FIG. 9A. A structural feature of the present embodiment is that a matrix-like light-shielding film 23 (black matrix) is formed in the same layer as the color filter 12a on the counter substrate 9 with an insulator containing a black pigment.
[0051]
The light shielding film 23 made of an insulator has no influence on the electric field E applied between the pixel electrode 3 and the common electrode 4, and between the pixel electrode 3 and the scan electrodes 1, 17 and between the common electrode 4 and the scan. The poor alignment region (domain) due to the electric field between the electrodes 1 and 17 could be covered and the contrast could be further improved.
[0052]
Further, since it was formed so as to cover the amorphous silicon 6 as in Example 2, there was no increase in leakage current due to light, and good display characteristics could be obtained. In this embodiment, a black pigment is used, but a dye may be used. Note that the visible light transmittance is not limited to black and may be sufficiently low.
[0053]
Further, since no electrode is present on the signal electrodes 2 and 18, the capacitance between the signal electrode and the shield electrode is reduced as compared with the second embodiment, the load on the video signal drive circuit 20 is reduced, and the chip size of the drive LSI is reduced. In addition, the power consumption can be reduced by reducing the load on the signal electrode.
[0054]
As described above, in this example, the same effects as those in Examples 1 and 2 were obtained, and an active matrix type liquid crystal display device with high contrast and low power consumption could be obtained.
[0055]
Example 4
The configuration of the present embodiment is the same as that of the first embodiment except for the following requirements. FIG. 10A is a schematic plan view of a pixel of the liquid crystal display panel of this embodiment, and FIG. 10B is a schematic cross-sectional view taken along DD ′ of FIG. In this embodiment, in the configuration of one pixel, two shield electrodes 5a and 5b are formed on the counter substrate 9 so as to be adjacent to the signal electrodes 2a and 18a, and the pixel electrode 3a is formed between the shield electrode 4a and the shield electrode 40a. Arranged.
[0056]
As a result, the electric field E from the signal electrodes 2a and 18a terminates at the shield electrodes 5a and 5b, and the parasitic capacitance Cds between the signal electrode and the pixel electrode is greatly reduced. In addition, since the pixel electrode 3a is disposed at a position where the distance from the signal electrodes 2a and 18a is farthest (a central portion between the signal electrode 2a and the signal electrode 18a), the pixel electrode 3a is disposed between the signal electrodes 2a and 18a and the pixel electrode 3a. The capacity could be further reduced. The feature of this embodiment is that even if the common electrode is not configured, the electric field between the shield electrodes 5a and 5b and the pixel electrode 3a is operated while the major axis direction of the liquid crystal molecules is kept substantially parallel to the substrate surface. The amount of transmission can be controlled.
[0057]
FIG. 11 shows the configuration of the drive system of the liquid crystal display device of this embodiment. In the present embodiment, since the shield electrodes 5a and 5b also serve as a common electrode, no common electrode voltage is required. In this embodiment, the pixel electrode 3a is arranged at the center of the signal electrode 2a and the signal electrode 18a to divide the pixel into two, but a plurality of pixel electrodes may be provided to divide into four or more. Note that in the method in which the common electrode is also used as the shield electrode as in this embodiment, the number of divided pixels is 2n (n is a natural number).
[0058]
Further, in this embodiment, the area on the pixel plane occupied by the common electrode can be used for the shield electrode, and further, by using the opening between the shield electrode and the pixel electrode, a high aperture ratio is obtained. A liquid crystal display device with high luminance or low power consumption and low power consumption can be obtained.
[0059]
As described above, in this example, the shield electrode is also used as the common electrode, so that the same effect as that of Example 1 was obtained, and an active matrix liquid crystal display device with higher luminance or lower power consumption could be obtained.
[0060]
Example 5
The configuration of this example is the same as that of Example 4 except for the following requirements. FIG. 12A shows a schematic plan view of a pixel of the liquid crystal display panel of this embodiment, and FIG. 12B shows a schematic cross-sectional view taken along line FF ′ of FIG. The structural feature of this example is that the shield electrode 5a and the signal electrode 2a, and the shield electrode 5b and the signal electrode 18a are overlapped in the horizontal direction.
[0061]
As a result, there was no excessive light leakage between the shield electrode and the signal electrode without providing a light shielding layer, and high contrast could be obtained. Further, the distance between the pixel electrode 3a and the shield electrodes 5a and 5b is increased, and the area (aperture ratio) of the light transmission portion between the pixel electrode 3a and the shield electrodes 5a and 5b is increased, thereby improving the transmittance.
[0062]
As described above, in this example, an effect equivalent to that of Example 4 was obtained, and an active matrix type liquid crystal display device with high contrast, high luminance, and low power consumption could be obtained.
[0063]
Example 6
The configuration of this example is the same as that of Example 4 except for the following requirements. FIG. 13A is a schematic plan view of a pixel of the liquid crystal display panel of this embodiment, and FIG. 13B is a schematic cross-sectional view taken along line GG ′ in FIG. A structural feature of the present embodiment is that a matrix-like light-shielding film 23 (black matrix) is formed in the same layer as the color filter 12a on the counter substrate 9 with an insulator containing a black pigment.
[0064]
The light shielding film 23 made of an insulator has no influence on the electric field E applied between the pixel electrode 3 and the shield electrodes 5a and 5b, and between the pixel electrode 3 and the scanning electrodes 1 and 17, and between the shield electrodes 5a and 5b. In addition, it was possible to cover up a misalignment region (domain) due to the electric field between the scanning electrode 1 and the scanning electrode 1 and 17, and to further improve the contrast.
[0065]
Further, since the amorphous silicon 6 was also formed so as to cover it, a good display characteristic could be obtained without an increase in leakage current due to light. Further, misalignment of the substrates 8 and 9 has no problem in the horizontal direction, and the aperture ratio does not decrease even if the light shielding film 23 is displaced between the shield electrodes 5a and 5b. In this embodiment, a black pigment is used, but a dye may be used. Note that the visible light transmittance is not limited to black and may be sufficiently low.
[0066]
As described above, in this example, an effect equivalent to that of Example 4 was obtained, and an active matrix liquid crystal display device with higher contrast and higher image quality could be obtained.
[0067]
[referenceExample2]
BookreferenceThe configuration of the example is the same as that of the first embodiment except for the following requirements. In FIG.referenceA schematic plan view of a pixel of the liquid crystal display panel of Example 2 is shown, and FIG. 14B is a schematic cross-sectional view taken along line HH ′ of FIG. The structural feature of this reference example is that the shield electrode 5 is formed on the protective film 11 of the TFT substrate 8.
[0068]
Therefore, no conductive substance is present on the counter substrate 9. Therefore, even if conductive foreign matter is mixed during the manufacturing process, there is no possibility of contact between the electrodes through the counter substrate 9, thereby the defect rate is suppressed to zero, formation of an alignment film, rubbing, The degree of cleanliness, such as the liquid crystal sealing process, is widened, and the manufacturing process management can be simplified. Electrical connection between the TFT substrate 8 and the counter substrate 9 for supplying a potential to the shield electrode 5 is also unnecessary.
[0069]
This is the bookreferenceIn the example, the same effect as in Example 1 was obtained, and the manufacturing yield could be improved. Also bookreferenceAlthough the example has been described based on Example 1, it is possible in Examples 2, 3, 4, 5, and 6 that the shield electrode is formed on the TFT substrate 8 as in this reference example.referenceThe same effect as the example can be obtained.
[0070]
[Reference example 3]
BookreferenceThe configuration of the example is the same as that of the fourth embodiment except for the following requirements. Figure 15 (a) shows the bookreferenceA schematic plan view of a pixel of an example liquid crystal display panel is shown, and FIG. 15B is a schematic cross-sectional view taken along line II ′ of FIG. BookreferenceThe structural feature of the example is that the shield electrodes 5a and 5b are formed of the same material and in the same layer as the signal electrodes 2a and 18a in the same process. For the electrical connection between the common electrode 4b and the shield electrode 5b, a through hole 42 was formed in the gate insulating film 11, and a wiring 41 formed of the same material and in the same layer as the scanning electrodes 1 and 17 in the same process was used.
[0071]
This eliminates the need to provide a shield electrode in a separate process.referenceExample2Similarly to the above, since no conductive substance is present on the counter substrate 9, there is no possibility of contact between the electrodes through the counter substrate 9. Therefore, the defect rate due to this is suppressed to zero, and the degree of cleanliness such as alignment film formation, rubbing, and liquid crystal encapsulation process is widened, and manufacturing process management can be simplified.
[0072]
The intensity of the electric field E varies depending on the distance between the pixel electrode 3 and the shield electrode 5a. Therefore, the variation in the distance between the pixel electrode and the shield electrode causes a variation in brightness, which becomes a problem. Accordingly, high alignment accuracy between the pixel electrode and the common electrode is required. In the method of bonding two substrates each having an electrode, the alignment accuracy is two to three times worse than the alignment accuracy of the photomask. In this reference example, since the pixel electrode 3 and the shield electrodes 5a and 5b are formed of the same material and in the same layer in the same process, there is no problem of the alignment accuracy.
[0073]
This is the bookreferenceIn the example, the same effect as in Example 4 was obtained, and an active matrix type liquid crystal display device with higher throughput and higher yield could be obtained. Also bookreferenceThe example was described based on Example 4, but thisreferenceIn the first, third and sixth embodiments, it is possible to form the shield electrode in the same layer and in the same layer as the signal electrode as in the example.referenceThe same effect as the example can be obtained.
[0074]
[Reference example 4]
BookreferenceThe configuration of the example is the same as that of the fourth embodiment except for the following requirements. Figure 16 (a) shows the bookreferenceA schematic plan view of a pixel of an example liquid crystal display panel is shown, and FIG. 16B is a schematic cross-sectional view taken along line JJ ′ of FIG. BookreferenceThe structural feature of the example is that the shield electrode 5 is formed of the same material and in the same layer as the scanning electrodes 1 and 17 in the same process, is drawn out in the horizontal direction, and is commonly connected to the common electrode in other rows. .
[0075]
The liquid crystal molecules are controlled by an electric field E between the pixel electrode 3 whose longitudinal direction is in the vertical direction and the protrusion protruding in the vertical direction of the shield electrode 5. ThisReference example 3Similarly to the above, it is not necessary to provide the shield electrode 5 in a separate process.
[0076]
Further, since there is no conductive substance on the counter substrate 9 as in the second embodiment, there is no possibility of electrode-to-electrode contact through the counter substrate 9, and the defect rate based thereon is suppressed to zero. . Therefore, the tolerance of cleanliness such as alignment film formation, rubbing, and liquid crystal sealing process has been expanded, and manufacturing process management has been simplified.
[0077]
Furthermore,Reference example 3Thus, there is no need to provide a through hole, and there is no connection failure between the common electrodes. Also bookreferenceIn the example, since the pixel electrode 3 and the shield electrode 5 are formed on the same substrate, the alignment accuracy of the pixel electrode 3 and the shield electrode 5 is also high. Further, the protrusion protruding in the vertical direction of the shield electrode 5 may be formed so as to overlap the signal electrodes 2a and 18a in the horizontal direction. As a result, as in the fifth embodiment, there is no extra light leakage between the signal electrode and the shield electrode without providing a light shielding layer, and a high contrast can be obtained.
[0078]
Further, the distance between the projections of the pixel electrode 3 and the common electrode 4 is increased, the area (aperture ratio) of the light transmission portion between the projections of the pixel electrode 3 and the shield electrode 5 is increased, and the transmittance is improved. Also bookreferenceIn the example, the shield electrode is connected as shown in FIG. 16, but the connection position is not particularly limited.
[0079]
This is the bookreferenceIn the example, the same effect as in Example 4 was obtained, and an active matrix type liquid crystal display device with higher throughput and higher yield could be obtained. Also bookreferenceThe example was described based on Example 4, but thisreferenceIt is possible in Examples 1, 2, 3, 5, and 6 that the shield electrode is formed of the same material and in the same layer as the scan electrode as in the example.referenceThe same effect as the example can be obtained.
[0080]
【The invention's effect】
According to the present invention, since the pixel electrode does not need to be transparent and a normal metal electrode can be used, an active matrix liquid crystal display device that can be mass-produced with a high yield can be obtained.
Further, an active matrix liquid crystal display device with favorable viewing angle characteristics and easy multi-gradation display can be obtained.
[0081]
In particular, by forming the shield electrode, the parasitic capacitance between the signal electrode and the pixel electrode can be reduced, and an active matrix liquid crystal display device with high contrast and no crosstalk can be obtained. Both effects can be achieved. Furthermore, since the shield electrode also serves as the common electrode, the number of manufacturing steps is reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of the operation of Reference Example 1. FIG.
FIG. 2 is a schematic diagram illustrating a configuration of a pixel unit according to the first exemplary embodiment.
FIG. 3 is a schematic diagram showing a drive system configuration of Examples 1-3, 7;
FIG. 4 is a view showing the viewing angle dependency of the liquid crystal display device of the present invention.
[Figure 5]In an embodiment of the present inventionIt is a figure which shows the viewing angle dependence of a liquid crystal display device.
FIG. 6 is a diagram showing a change in signal voltage-brightness characteristics accompanying a change in signal electrode voltage of the liquid crystal display device of the present invention.
FIG. 7 is a diagram illustrating a change in signal voltage-brightness characteristics accompanying a change in signal electrode voltage of a conventional liquid crystal display device.
FIG. 8 is a schematic diagram illustrating a configuration of a pixel unit according to the second exemplary embodiment.
FIG. 9 is a schematic diagram illustrating a configuration of a pixel unit according to a third embodiment.
10 is a schematic diagram illustrating a configuration of a pixel portion according to Embodiment 4. FIG.
FIG. 11 is a schematic diagram showing a drive system configuration of Examples 4 to 6 and 8 to 9.
12 is a schematic diagram illustrating a configuration of a pixel portion according to Embodiment 5. FIG.
13 is a schematic diagram illustrating a configuration of a pixel portion according to Embodiment 6. FIG.
FIG. 14reference6 is a schematic diagram illustrating a configuration of a pixel unit in Example 2. FIG.
FIG. 15reference10 is a schematic diagram illustrating a configuration of a pixel unit in Example 3. FIG.
FIG. 16reference10 is a schematic diagram illustrating a configuration of a pixel unit in Example 4. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,17 ... Scan electrode, 2,18 ... Signal electrode, 3 ... Pixel electrode, 4 ... Common electrode, 5 ... Shield electrode, 6 ... Amorphous silicon, 7 ... N + type amorphous silicon, 8, 9 ... Substrate, 10 ... Gate Insulating film, 11 ... protective film, 12 ... color filter, 13 ... flattening film, 14, 15 ... orientation control film, 16 ... liquid crystal layer, 19 ... vertical scanning circuit, 20 ... video signal drive circuit, 21 ... power supply and control Circuit, 22 ... Liquid crystal display panel, 23 ... Light shielding film, 25 ... Liquid crystal molecule, 26, 27 ... Deflection plate, 28 ... Orientation direction, 29 ... Deflection transmission axis, 41 ... Wiring, 42 ... Through hole.

Claims (4)

A liquid crystal composition is held between the first and second substrates, and a plurality of pixels are configured on the first substrate by a plurality of scanning electrodes and signal electrodes arranged in a matrix. In an active matrix liquid crystal display device provided with a switching element,
The switching device is connected pixel electrodes, by the pixel electrode and the common electrode facing thereto, the direction of the electric field applied to the liquid crystal is to so that configuration and a direction substantially parallel to the substrate surface,
The pixel has a signal electrode, a pixel electrode, and a shield electrode between the signal electrode and the pixel electrode,
The shield electrode is formed on the second substrate,
Pigment in the light transmission part between the signal electrode of the pixel and the pixel electrode, the light transmission part between the signal electrode and the common electrode, the light transmission part on the semiconductor layer of the switching element and the lines of electric force from the scanning electrode Alternatively, an active matrix liquid crystal display device comprising a black or low light transmittance light-shielding film containing a dye. 2. The active matrix liquid crystal according to claim 1, wherein the shield electrode is formed on a light transmission portion between the signal electrode and the pixel electrode, a light transmission portion between the signal electrode and the common electrode, and a semiconductor layer of the switching element. Display device. The active matrix type liquid crystal display device according to claim 1, wherein a part of the shield electrode overlaps with the signal electrode. 5. The active device according to claim 1, wherein the shield electrode reduces a parasitic capacitance generated between at least one portion of the signal electrode and the pixel electrode as compared with a case where the electrode is not disposed. Matrix type liquid crystal display device.

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