JPH10333180A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To widen the field angle by preventing the orientation of liquid crystal from being disordered with the electric fields of a TFT(thin film transistor) and its electrode line and excellently dividing pixels. SOLUTION: A TFT is formed by providing a drain electrode 11, a source electrode 12, a drain line, a semiconductor layer 14, a gate insulating film 15, a gate electrode 16, and a gate line on a substrate 10 and on an insulating film 28 between flattening layers covering TFTs and their electrode lines, reflection electrodes 29 are formed and connected to source electrodes 12. A common electrode 31 is provided with an orientation control window 32 formed having no electrode, the orientation of liquid crystal molecules 41 is controlled with the oblique electric field 42 of the edges of the reflection electrodes 29 and the weak electric field of the orientation control window 32, and the pixels are divided without disordering the orientation with electric fields from the TFTs and their electrode lines.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display (LCD) for performing display utilizing the electro-optical anisotropy of liquid crystal.
In particular, the present invention relates to a liquid crystal display device having a high aperture ratio and a wide viewing angle.

[0002]

2. Description of the Related Art LCDs have advantages such as small size, thin shape, and low power consumption, and are being put to practical use in fields such as OA equipment and AV equipment. In particular, an active matrix type using a thin film transistor (hereinafter abbreviated as TFT) as a switching element can perform static driving with a duty ratio of 100% in principle in a multiplex manner, and has a large screen and a high-definition moving image display. Used in

The TFT is a field-effect transistor, is arranged in a matrix on a substrate, and is connected to a display electrode forming one of pixel capacitances using a liquid crystal as a dielectric layer. The TFTs are simultaneously turned on / off for the same row by a gate line, and a pixel signal voltage is supplied from a drain line, and a display voltage specified in a matrix is charged to a pixel capacitance with the TFT turned on. Is done. Display electrode and TFT
Are formed on the same substrate, and the common electrode that constitutes the other of the pixel capacitors is formed entirely on another substrate that is opposed to the liquid crystal layer. That is, the liquid crystal and the common electrode are partitioned by the display electrode to form a display pixel. The voltage charged in the pixel capacitance is insulated by the off resistance of the TFT for one field period until the next turn on of the TFT. The liquid crystal has electro-optical anisotropy, and the transmittance is controlled according to the voltage applied to the pixel capacitance. By controlling the transmittance for each display pixel, these light and dark areas are visually recognized as a display image.

[0004] The initial alignment state of the liquid crystal is elastically fixed by an alignment film provided at the interface between the two substrates. For example, there is a twisted nematic (TN) system in which a nematic phase having a positive dielectric anisotropy is used as a liquid crystal and an orientation vector is twisted at 90 ° between both substrates. Normal,
Polarizing plates are provided outside the two substrates, and in the TN method, the polarization axes of the respective polarizing plates coincide with the orientation directions of the respective substrates. Therefore, when no voltage is applied, the linearly polarized light that has passed through one of the polarizing plates rotates in the liquid crystal layer along the twisted orientation of the liquid crystal and is emitted from the other polarizing plate, and the display is recognized as white. Then, by applying a voltage to the pixel capacitor to form an electric field in the liquid crystal layer, the liquid crystal changes its orientation so as to be parallel to the electric field due to its dielectric anisotropy, and the twist arrangement is broken. As a result, the incident linearly polarized light is no longer rotated in the liquid crystal layer, the amount of light emitted from the other polarizing plate is narrowed down, and the display gradually becomes black. As described above, a system in which white is displayed when no voltage is applied and becomes black in response to voltage application is called a normally white mode, and is a mainstream of TN cells.

FIGS. 20 and 21 show the structure of a unit pixel portion of a conventional liquid crystal display device. FIG. 20 is a plan view, and FIG. 21 is a cross-sectional view along the line GG. A gate electrode (101) made of Cr or the like on a substrate (100) such as glass.
And a gate line (102) for integrally connecting the same to the same row is formed.
A gate insulating film (103) such as 3N4 is formed.
The gate electrode (101) on a gate insulating film (103);
Is formed in an amorphous silicon (a-Si) (104) as an operation layer of the TFT so as to be an operation layer of the TFT, and amorphous silicon doped with an impurity as an contact layer is formed on both ends of the a-Si (104). Silicon (N +
a-Si) (106). Further, an etching stopper (105) made of Si3 N4 is formed between the a-Si (104) and the N + a-Si (106) due to manufacturing requirements. Further, N + a-Si
On the (106), a source electrode (107) and a drain electrode (108) each made of a high melting point metal such as Al / Si.
Are formed. In another region on the gate insulating film (103), a display electrode (110) made of transparent conductive ITO (indium tin oxide) is formed, and a source electrode (10) is formed.
7) and a drain electrode (108)
Are connected together in the same column.
09) is formed. On the entire surface covering all of these,
An alignment film (111) made of a polymer film such as polyimide is formed, and the initial alignment of the liquid crystal is controlled by a predetermined rubbing treatment. On the other hand, on another glass substrate (120) placed at a position facing the substrate (100) with the liquid crystal layer (130) interposed, a common electrode (121) formed entirely of ITO is provided. An alignment film (122) of polyimide or the like is formed on the common electrode (121), and is subjected to a rubbing process.

Here, a nematic phase having negative dielectric anisotropy is used for the liquid crystal (130), and the alignment film (111, 1) is used.
22) DAP (deformation) using a vertical alignment film
of vertially aligned phase) type. The DAP type is a voltage controlled birefringence (ECB).
This is one of the d birefringence systems in which the transmittance is controlled by utilizing the difference in the refractive index between the major axis and the minor axis of the liquid crystal molecules, that is, birefringence. In the DAP type, when a voltage is applied, incident linearly polarized light transmitted through one of the orthogonally arranged polarizing plates is converted into elliptically polarized light by birefringence in the liquid crystal layer. By controlling the difference between the phase velocities of the light components, the light is emitted from the other polarizing plate at a desired transmittance. In this case, the display changes from black to white by increasing the applied voltage from the voltage non-applied state, and the normally black mode is set.

[0007] As described above, the liquid crystal display device is prepared in a pre-displayable state by voltage control, so that the power consumption is extremely small. However, in order to actually visually recognize a display screen created by this liquid crystal display device, generally, in order to visualize display information created on a transparent substrate, a back side behind the display device viewed from an observer is required. A method of providing a light and recognizing it as transmitted light passing through a display pixel has been adopted. Therefore, there has been a problem that the power consumption of the backlight is large and the advantage of low power consumption of the liquid crystal display device cannot be fully utilized.

Therefore, a reflective plate is provided behind the liquid crystal display device, or one of the electrodes of the pixel capacitor is formed of a material having a high reflectivity, so that the reflective electrode can be visualized using external light. As a result, a reflective liquid crystal display device that allows a display screen to be viewed has been developed. This reflective liquid crystal display device does not require a backlight, so that power consumption can be significantly reduced.

[0009]

As described above, in a liquid crystal display device, by applying a desired voltage to a liquid crystal loaded between a pair of substrates on which predetermined electrodes are formed, the light in the liquid crystal layer is reduced. The desired transmittance or hue is displayed by controlling the rotation or birefringence of the object. That is, by controlling the amount of retardation by changing the orientation of the liquid crystal, the amount of transmitted light can be adjusted in the TN mode, and the hue can be separated by controlling the wavelength-dependent transmittance in the ECB mode.

However, the amount of retardation depends on the angle between the major axis of the liquid crystal molecules and the direction of the electric field. Therefore, even if the angle between the electric field and the long axis of the liquid crystal molecules is primarily controlled by adjusting the electric field strength, the retardation is relatively dependent on the angle that the observer visually recognizes, that is, depending on the viewing angle. When the amount changes and the viewing angle changes, the amount of transmitted light or the hue also changes, which is a so-called viewing angle dependency problem.

[0011] Further, in the reflection type, improvement of display quality such as increase in luminance and contrast ratio has been a problem.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to solve these problems, and comprises a display electrode for driving liquid crystal and a source electrode provided in a matrix on a first substrate. A thin film transistor connected to the, a gate line connected to the gate electrode of the thin film transistor,
A liquid crystal display device comprising: a drain line connected to a drain electrode of the thin film transistor; and a common electrode for driving liquid crystal provided on a second substrate opposed to the first substrate with a liquid crystal layer interposed therebetween. Wherein the display electrode is provided on an interlayer insulating film formed so as to cover the thin film transistor, the gate line and the drain line, and a thickness of the interlayer insulating film is half a distance between the display electrodes. The configuration is as described above.

This prevents the electric field from the thin film transistor and its electrode line from affecting the liquid crystal from the gap between the display electrodes, and a good alignment control is performed by the edge of the display electrode and the alignment control window. A display electrode for driving liquid crystal provided in a matrix on the first substrate; a thin film transistor having a source electrode connected to the display electrode; a gate line connected to a gate electrode of the thin film transistor; A liquid crystal display device comprising: a drain line connected to a drain electrode; and a common electrode for driving liquid crystal provided on a second substrate opposed to the first substrate with a liquid crystal layer interposed therebetween. The thin film transistor, the gate line, and the drain line are arranged below the display electrode with the interlayer insulating film interposed therebetween.

This prevents the electric field from the thin film transistor and its electric wiring from affecting the liquid crystal above the display electrode, and good alignment control is performed by the edge of the display electrode and the alignment control window. In particular, the width of the thin film transistor, the gate line, and the drain line protruding from the lower part of the display electrode is half or less of the thickness of the interlayer insulating film.

Even if the thin film transistor and its electrode wiring protrude from the lower part of the display electrode to this extent, the electric field can be prevented from greatly affecting the liquid crystal above the display electrode. In particular, the width of the thin film transistor, the gate line, and the drain line protruding from the lower part of the display electrode is less than half the distance between the display electrodes.

Even if the thin film transistor and its electrode wiring protrude from the lower part of the display electrode to this extent, the electric field is prevented from greatly affecting the liquid crystal above the display electrode from the gap between the display electrodes. Particularly, the display electrode is configured to be a reflection electrode made of a conductive light reflection material. This prevents the display from being adversely affected even if the thin film transistor and its electrode wiring are arranged below the display electrode.

[0017]

FIG. 1, FIG. 2, FIG. 3, and FIG. 4 show a unit pixel structure of a liquid crystal display device according to a first embodiment of the present invention. 1 is a plan view, and FIGS. 2, 3 and 4 are cross-sectional views taken along lines AA, BB, and CC of FIG. 1, respectively. On a substrate (10), a drain electrode (11), a source electrode (12), and a drain line (13) integral with the drain electrode (11) are formed of a low-resistance metal such as Cr, Al, Ta, or ITO. I have. Above this, a
A gate line (17) made of Al or the like in which a semiconductor layer (14) such as Si and a gate insulating film (15) are arranged in the same shape;
Is formed, and a part of the gate line (17) is arranged as a gate electrode (16) on a region extending between the drain electrode (11) and the source electrode (12) to constitute a TFT. On the entire surface covering these TFTs and their electrode lines,
SiNx, SiO2, or a well-known SOG (spin on glass) or BPSG (boro-phospho) having a planarizing action
An interlayer insulating film (18) such as silicate glass is formed. On the interlayer insulating film (18), a display electrode (19) made of a transparent conductive material such as ITO or a conductive light reflecting material such as Al is formed, and a contact hole opened in the interlayer insulating film (18). It is connected to the source electrode (12) via (CT). An alignment film (20) of polyimide or the like is formed on the entire surface covering the display electrode (19).

At positions opposed to each other with the liquid crystal layer (40) interposed therebetween, a common electrode (3) of ITO is formed on a transparent substrate (30).
1) is formed, and in the common electrode (31), an alignment control window (32) formed in an X shape due to the absence of the ITO electrode is provided. An alignment film (33) such as polyimide is formed on the entire surface covering these common electrodes (31). In addition, a gate electrode (16) is formed as a TFT on a semiconductor layer (1
Although the normal stagger type arranged in a layer higher than 4) is adopted, the present invention is not limited to this, and an inverted stagger type in which the gate electrode is arranged below the semiconductor layer may be used.

Here, as an example of the cell structure, DAP
A vertical alignment film is used as a mold, that is, an alignment film (20, 33),
The liquid crystal has a negative dielectric anisotropy, but is not limited thereto. However, in TN, it is preferable that the alignment control window (33) is formed in a single band along the diagonal line of the pixel. The present invention is characterized in that a display electrode (19) is arranged in a layer above a TFT, and an orientation control window (32) comprising an electrode-free region of a predetermined shape is provided in a common electrode (31) opposed thereto. There is. As a result, as shown in FIGS.
At the edge portion of (9), the liquid crystal molecules (41) are inclined obliquely from the normal direction depending on the intensity of the electric field due to the obliquely generated electric field (42) having a shape spreading toward the common electrode (31). Is controlled, and the inclination direction is controlled to be stable.

The orientation control at the edge of the display electrode (19) is performed in a direction perpendicular to the four sides. That is, the tilt directions of the liquid crystal molecules (41) are different in four directions. The orientations controlled differently on each side of the display electrode (19) extend to the inner region of the pixel due to the continuity of the liquid crystal, but the boundaries of the orientations different in these directions are defined by the common electrode (31). ) Provided in the orientation control window (3)
2) elastically fixed. That is, the orientation control window (3
In the region near 2), the liquid crystal molecules (41) have an intensity equal to or lower than the threshold value at which the liquid crystal molecules (41) start to tilt even when an electric field is formed in the liquid crystal layer (40). Is maintained. For this reason, the alignment controlled in different directions at the edge of the display electrode (19) is controlled by the alignment control window (3).
1) It has an upper boundary and is totally stable.

In particular, in this embodiment, each area divided by the X-shaped alignment control window (31) has a preferential viewing angle direction in a different direction. The brightness and the contrast ratio of each of the vertically and horizontally divided areas are recognized on average, and the same viewing angle characteristics are realized at any of the up, down, left and right viewing angles, and the reduction of the viewing angle dependency is achieved. Further, in the present invention, as described below, by specifying the mutual positional relationship between the display electrode (19) and the TFT and its electrode line, the electric field of the TFT and its electrode line is changed to the display electrode (19) and the orientation control window. (32) The liquid crystal alignment controlled by (32) is not disturbed. 5 to 7
Next, on the gate line (17) side, an interlayer insulating film (1) is formed.
The results obtained by examining the state of alignment of liquid crystal molecules during driving when the film thickness is changed in 8) by electric field simulation are shown.
In each figure, the equipotential lines are shown by dotted lines when the interlayer separation distance between the gate line (GATE) and the display electrodes (PX1, PX2) sandwiching the gate line is 1 μm, 3 μm, and 5 μm, respectively. 2 shows the orientation (DIR) of liquid crystal molecules depending on the shape of equipotential lines.
In each figure, the display electrode (PX1) is a pixel on which a side in a normal alignment state is shown, and the display electrode (PX2) is a pixel on which a side where a reverse tilt domain is generated is shown.

In each case, the display electrode (PX)
Are set to be twice the interlayer separation distance.
That is, 2 μm in FIG. 5, 6 μm in FIG. 6, and 10 μm in FIG.
μm. According to FIG. 5, when the interlayer distance between the display electrode (PX) and the gate line (GATE) is relatively close to 1 μm, a reverse tilt domain (RT) is generated on the PX2 side and the orientation (DIR) is also generated on the PX1 side. )
Is disturbed. This is because the gate voltage is large negatively and GA
This is probably due to the influence of the electric field from the TE.

On the other hand, in FIG. 6, on the PX2 side,
A reverse tilt domain (RT) has occurred, but P
On the X1 side, the disturbance of the orientation (DIR) is small. This is because the display electrode (PX) and the gate line (GA)
Since the interlayer distance with TE) has increased to 3 μm,
It is considered that the influence of the electric field from the TE was reduced.

Also in FIG. 7, since the interlayer distance between the display electrode (PX) and the gate line (GATE) is further increased to 5 μm, a reverse tilt drain (RT) is generated on the PX2 side. On the PX1 side, the disturbance of the orientation (DIR) is further reduced. FIG.
The display electrodes (PX) correspond to FIG. 5 to FIG.
1, PX2) and the gate line (GATE) in the case where the interlayer separation distance was 1 μm, 3 μm, and 5 μm, the relationship between the transmittance and the position of the pixel end was shown. On the vertical axis, the maximum of the transmittance is 0.5 in the cell having the polarizing plate in the crossed Nicols arrangement. In the horizontal axis, the line width of the gate line (GATE) is 10 μm, and the display electrodes (PX1, PX2) are overlapped with a width of 3 μm at both ends. Is taking the position. As shown in the figure, in the case of 1 μm, PX
1 and PX2, there is a peak of the transmittance, and there is a boundary between the no-multi tilt region and the reverse tilt region in this portion, and it can be seen that light passes through. In the case of 3 μm, the transmittance peak is not in the area of PX1, but is located slightly outside the pixel in the area of PX2 than the peak at 1 μm. In the case of 5 μm, there is a peak at the edge of PX1,
Since it is superimposed on GATE, the display is not affected. In the area of PX2, there is a peak further outside the pixel than in the case of 1 μm and 3 μm.

In each of these results, the mutual separation distance between the display electrodes is twice as large as the interlayer separation distance. However, if the mutual separation distance between the display electrodes is larger than this, the gate line (GATE) The electric field from the display electrode (P
X) has a greater effect on the liquid crystal layer than the gap of X).
Simulation results are worse than either of these. Further, due to miniaturization or restrictions on layout, the mutual separation distance between the display electrodes (19) is 4-5.
6 or 7, the thickness of the interlayer insulating film (18) is actually 3 μm or more, and the mutual separation distance between the display electrodes (19) at that time is 6 μm, which is twice as large. It is desirable to make the above.

FIGS. 9 to 11 show drain lines (1).
Regarding 3), similarly to FIGS. 5 to 7, the drain line (DRAIN) and the display electrodes (PX1, PX) sandwiching the drain line (DRAIN) are provided.
2), the interlayer separation distance is 1 μm, 3 μm,
When the potential is changed to 5 μm, the equipotential lines are indicated by dotted lines, and the orientation of the liquid crystal molecules (DI
R). In each figure, the display electrode (PX1)
Is a pixel on which a side in a normal alignment state is shown, and the display electrode (PX2) is a pixel on which a side where a reverse tilt domain is generated is shown. In each case, the distance between the display electrodes (PX) is twice as large as the distance between the layers. That is, it is 2 μm in FIG. 9, 6 μm in FIG. 10, and 10 μm in FIG.

FIG. 9 shows that the reverse tilt domain (R) in PX2 is affected by the electric field from DRAIN.
It can be seen that T) has occurred. Since the drain voltage has less effective value than the gate voltage and has little effect on the liquid crystal layer, the PX1 does not show a large disturbance of the orientation (DIR) as close to the gate side. Further, in FIG. 10, the reverse tilt domain (RT) in the PX2 region is reduced, and the disorder in the orientation (DIR) is completely eliminated in the PX1 region. In FIG. 11, PX1, P
No reverse tilt domain or alignment disorder is observed in any of the regions X2.

FIG. 12 shows that the display electrodes (PX1, PX2) and the drain line (D
RAIN) is 1 μm, 3 μm, 5 μm
In each case, the vertical axis shows the transmittance, and the horizontal axis shows the position in the direction perpendicular to the drain line (DRAIN).
These relationship curves are shown. In the case of 1 μm, there is a transmittance peak in the area of PX2, but most of the peak is DR.
It is superimposed on AIN. In the case of 3 μm and 5 μm, the peaks are completely superimposed by DRAIN and have no effect on the display. On the PX1 side, 1 μm, 3 μm
m and 5 μm, the peak was completely DRAI
N superimposed, there is no adverse effect on the display.

From the above considerations, in particular, on the gate side, the thickness of the interlayer insulating film (18) is increased to 1 μm or more, and the gate electrode and the lines (16, 17) and the display electrode (19) are formed.
By increasing the distance between the layers, the alignment of the liquid crystal due to the influence of the gate voltage could be suppressed. TN
In comparison with the DAP type, the alignment control effect is better. Therefore, as shown in FIGS. 1, 2, 3, and 4, the edge portion of the display electrode (19) and the alignment control window (32) are congruent. By the operation, good pixel division is performed.

At the same time, in this structure, the display electrode (19) extends over the gate electrode and its line (16, 17) and over the drain electrode and its line (11, 13) to provide an effective display. An area can be secured in the largest area defined by the edges of each electrode and line (11, 13, 16, 17), and the aperture ratio can be greatly improved. That is, by increasing the interlayer separation distance between the display electrode (19) and the gate line (11) and the drain line (13), the electric field in the liquid crystal layer is reduced from the electric field of the gate line (17) and the drain line (13). The display electrode (19) can extend over the gate line (13) and the drain line (13) without being affected by the above. According to the actual measurement by the applicant, it is confirmed that the aperture ratio is improved by 10% or more as compared with the related art.

FIGS. 13 to 16 show a unit pixel structure of a liquid crystal display device according to a second embodiment of the present invention. FIG.
3 is a plan view, and FIGS. 14, 15 and 16 are cross-sectional views taken along lines AA, BB, and CC of FIG. 13, respectively.
This embodiment is different from the first embodiment shown in FIG. 1 in that a liquid crystal having a negative dielectric anisotropy is used,
This is a DAP type in which the initial alignment of the liquid crystal molecules (41) is set in the direction of the normal to the substrate. In particular, the display electrode is a reflective electrode (29) made of Al or the like. Therefore,
In order to make the reflective electrode (29) flat, the underlying interlayer insulating film (28) is a flattening insulating film such as SOG or BOSG. In order to minimize the step, the TFT preferably employs a positive stagger type in which the gate electrode (16) is disposed above the semiconductor layer (14).

Further, since the display electrode is a reflection electrode (29), the TFT and its electrode wiring (11, 12, 13,
16 and 17) have a structure arranged below the reflective electrode (29), and the reflective electrode (29) is made as large as possible to greatly increase the aperture ratio. Also in the present embodiment, similarly to the first embodiment, the orientation is controlled by the oblique electric field at the edge of the reflective electrode (29) and the weak electric field of the orientation control window (32), and pixel division is performed. A wide viewing angle is realized.

In the present embodiment, in particular, FIGS.
As shown in FIGS. 15 and 16, the TFT and its electrode lines (11) (12) (13) (16) (1)
7) has a structure arranged below the reflective electrode (29). Therefore, the liquid crystal layer (4
An uncontrolled electric field is applied to 0) to prevent the alignment of the liquid crystal from being disturbed. This eliminates the necessity of increasing the distance between the reflective electrode (29) and the electrode line in the vertical direction. Therefore, by increasing the thickness of the interlayer insulating film (28), the throughput is deteriorated.
An increase in contact resistance between the source electrode (9) and the source electrode (12) is also prevented.

FIG. 17 shows that among the electrode lines of the TFT,
In particular, the gate line (GATE) is arranged below the reflective electrode (RF1) on the gate line side where the signal amplitude is large and an electric field is applied to the liquid crystal, and the edge of the reflective electrode (RF1) and the gate line (GATE) Equipotential line (dotted line) in the cell regarding the state where the edge coincides with the plane
And simulation results of the orientation state of liquid crystal molecules (DIR) at that time. At this time, the thickness of the interlayer insulating film (28), that is, the reflection electrode (RF1) and the gate line (GAT)
Although the interlayer separation distance from E) is 1 μm or less, distortion of the equipotential line due to the gate line (GATE) is slightly observed, but does not reach the pixel area and does not affect the alignment. Alignment control is performed.

Also, empirically, the gate line (GAT)
Even when E) protrudes from the lower part of the reflective electrode (RF1), half of the width is less than half the interlayer separation distance, or the protruded width is smaller than the mutual distance between the reflective electrodes (RF1) and (RF2). When the distance is smaller than half of the distance, a potential distribution similar to that in FIG. 17 is obtained, and the disturbance of the orientation caused by the electric field of the gate line (GATE) is suppressed.

FIG. 18 is a plan view of a unit pixel portion of a liquid crystal display according to a third embodiment of the present invention.
In the present embodiment, the display electrode (19) is formed to be vertically longer than in the first embodiment shown in FIG. 13, and accordingly, the shape of the alignment control window (32) is changed to the display electrode (19). The difference is that a straight portion extending in the long-side direction is provided at the center of ().

In the above-described embodiment, the display electrode (19) and the alignment control window (32) are not in a parallel relationship, and the alignment controlled in the vertical direction at the edge of the display electrode (19) and the alignment control window (32). The orientation controlled in the vertical direction by the control window (32) was only continuous smoothly due to the continuity of the liquid crystal itself. Therefore, a boundary of the orientation may be generated between the edge of the display electrode (19) and the orientation control window (32). For this reason, in the present embodiment, in the vertically long display electrode (19), the area where the edge of the display electrode (19) and the alignment control window (32) are in a parallel relationship is enlarged, thereby increasing the edge of the display electrode (19). And orientation control window (32)
The region where orientation control is performed in the same direction as the display electrode (19)
The edge and the orientation control window (32) are made sufficiently large as compared with the region where the orientation is controlled in different directions, and the display electrode (1
9) The influence of the boundary of the orientation formed between the edge and the orientation control window (32) is relatively reduced, so that better orientation control is performed.

FIG. 19 is a plan view of a unit pixel section of a liquid crystal display according to a fourth embodiment of the present invention. In this embodiment, a reflective electrode such as Al is used as a display electrode as compared with the third embodiment shown in FIG. This point
This is the same as the second embodiment. Therefore, in the present embodiment, the vertically long reflective electrode (29) and the corresponding alignment control window (32) perform extremely good pixel division by the joint action of the reflective electrode (19) edge and the TFT.
And their electrode lines (11) (12) (13) (16)
(17) is a structure arranged below the reflective electrode (29),
These TFTs and their electrode lines (11) (12) (1)
3) It is configured to prevent the electric field of (16) and (17) from affecting the liquid crystal layer (40).

[0039]

As is clear from the above description, by separating the display electrode for driving the liquid crystal from the thin film transistor for driving the display electrode and its electrode wiring, the alignment of the liquid crystal is prevented from being affected by these electrode wirings. In addition, the disturbance of the orientation is suppressed. For this reason, in the structure in which the pixel is divided by the secondary control of the liquid crystal alignment using the oblique electric field by the edge of the display electrode and the alignment control window on the common electrode side, the oblique electric field is prevented from being disturbed. The control action of the edge and orientation control window becomes effective, good pixel division is performed, and the viewing angle is widened.

Further, by disposing the thin film transistor and its electrode wiring below the reflective electrode for driving the liquid crystal, the electric field from these thin film transistor and its electrode wiring does not affect the liquid crystal layer. Disturbing the orientation controlled by the orientation control window is prevented, good pixel division is performed, and the viewing angle is widened.

[Brief description of the drawings]

FIG. 1 is a plan view of a unit pixel section of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 1;

FIG. 4 is a sectional view taken along the line CC of FIG. 1;

FIG. 5 is a cross-sectional view showing equipotential lines and liquid crystal orientation in a liquid crystal cell.

FIG. 6 is a cross-sectional view showing equipotential lines and liquid crystal alignment in a liquid crystal cell.

FIG. 7 is a cross-sectional view showing equipotential lines and liquid crystal orientation in a liquid crystal cell.

FIG. 8 is a diagram illustrating the relationship between the transmittance and the position of a pixel unit.

FIG. 9 is a cross-sectional view showing equipotential lines and liquid crystal orientation in a liquid crystal cell.

FIG. 10 is a cross-sectional view showing equipotential lines and liquid crystal orientation in a liquid crystal cell.

FIG. 11 is a cross-sectional view showing equipotential lines and liquid crystal orientation in a liquid crystal cell.

FIG. 12 is a diagram illustrating a relationship between transmittance and a position of a pixel unit.

FIG. 13 is a plan view of a unit pixel section of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 14 is a sectional view taken along line DD of FIG.

FIG. 15 is a sectional view taken along the line EE in FIG. 13;

FIG. 16 is a sectional view taken along the line FF of FIG. 13;

FIG. 17 is a cross-sectional view showing equipotential lines and liquid crystal orientation in a liquid crystal cell.

FIG. 18 is a plan view of a unit pixel section of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 19 is a plan view of a unit pixel section of a liquid crystal display device according to a fourth embodiment of the present invention.

FIG. 20 is a plan view of a unit pixel portion of a conventional liquid crystal display device.

FIG. 21 is a sectional view taken along line GG of FIG. 20;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10, 30 Substrate 11 Drain electrode 12 Source electrode 13 Drain line 14 Semiconductor layer 15 Gate insulating film 16 Gate electrode 17 Gate line 18 Interlayer insulating film 19 Display electrode 20, 33 Orientation film 28 Flattening insulating film 29 Reflecting electrode 31 Common electrode 32 Alignment control window 40 liquid crystal layer 41 liquid crystal molecules 42 electric field

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI H01L 29/78 619A

Claims (5)

[Claims] A liquid crystal driving display electrode provided in a matrix on a first substrate; a thin film transistor having a source electrode connected to the display electrode; a gate line connected to a gate electrode of the thin film transistor; A liquid crystal display device comprising: a drain line connected to a drain electrode of the thin film transistor; and a common electrode for driving liquid crystal provided on a second substrate opposed to the first substrate with a liquid crystal layer interposed therebetween. In the above, the display electrode is provided on an interlayer insulating film formed so as to cover the thin film transistor, the gate line, and the drain line, and a thickness of the interlayer insulating film is half a distance between the display electrodes. A liquid crystal display device characterized by the above. 2. A display electrode for driving a liquid crystal provided in a matrix on a first substrate, a thin film transistor having a source electrode connected to the display electrode, a gate line connected to a gate electrode of the thin film transistor, A liquid crystal display device comprising: a drain line connected to a drain electrode of the thin film transistor; and a common electrode for driving liquid crystal provided on a second substrate opposed to the first substrate with a liquid crystal layer interposed therebetween. In the above, the display electrode is provided on an interlayer insulating film formed to cover the thin film transistor, the gate line and the drain line, and the thin film transistor, the gate line and the drain line sandwich the interlayer insulating film. And a liquid crystal display device disposed below the display electrode. 3. The width of the thin film transistor, the gate line and the drain line protruding from a lower portion of the display electrode, and a half of the width is less than or equal to the thickness of the interlayer insulating film. Liquid crystal display device. 4. The display device according to claim 3, wherein the width of the thin film transistor, the gate line, and the drain line protruding from a lower portion of the display electrode is less than a half of a distance between the display electrodes. Liquid crystal display device. 5. The display device according to claim 2, wherein the display electrode is a reflective electrode made of a conductive light reflecting material.
Or the liquid crystal display device according to claim 4.