JP2001222015A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active matrix liquid crystal display device capable of controlling the cell gap with high precision. SOLUTION: The liquid crystal display device is characterized by being provided with a pair of substrates respectively having an electrode formed on the one principal surface, a liquid crystal material held between the pair of the substrates arranged so that the electrodes are opposed to each other and a spacer to define the distance between the pair of the substrates, and by having a recessing part to receive a part of the spacer formed at least on a part of the one substrate out of the pair of the substrates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an active matrix type liquid crystal display device.

[0002]

2. Description of the Related Art Generally, in a liquid crystal display device, a gap between a pair of substrates facing each other has a great influence on display characteristics. If the cell gap of the liquid crystal cell of the liquid crystal display device is not uniform, color unevenness appears during display. When a twisted nematic liquid crystal is used as a liquid crystal material,
It is necessary to form a small gap of about ± 0.1 μm over the entire surface of the liquid crystal cell.

FIGS. 6 and 7 are cross-sectional views for explaining a method of controlling a cell gap in a conventional liquid crystal display device. As shown in FIG.
After performing the alignment process, the sealing material layer 113 is formed on the end of the substrate 111 by printing or the like. Next, FIG.
As shown in FIG.
Spray. The spacer 114 is, for example, a powder having a diameter of about 5 μmφ. Thereafter, the other substrate 115 is placed on the substrate 111, and both the substrates 111 and 115 are heated while being pressurized to seal both the substrates 111 and 115. Finally, after evacuating the inside from an opening provided in the seal portion in advance, a liquid crystal material is injected to obtain a liquid crystal display device.

In this conventional method, it is difficult to dispose the spacer 114 at a desired position when spraying the spacer 114. For this reason, the spacer 114 may be located on the wiring region. In particular, in an active matrix type liquid crystal display device, since the thickness of the wiring is 1 μm or more, when the spacer 114 is located on this wiring region, the cell gap is equal to the outer diameter of the spacer 114 as shown in FIG. This is the sum of the height of the wiring 116 and about 1 μm. As a result, the wiring region where the spacer 114 is located becomes thicker than other portions, and it becomes difficult to control the cell gap.

As a technique for improving the resolution of a liquid crystal display device, there is an active matrix driving method. In an active matrix type liquid crystal display device employing this method, a plurality of row selection lines (address lines) and a plurality of column selection lines (data lines) are formed on one of a pair of substrates. A transistor is provided for each pixel electrode in a region defined by the data line, a transistor at the intersection of the address line and the data line is selected, and the pixel electrode is selected and switched via this transistor. By this method, an image display with good contrast and little crosstalk can be obtained. However, this active matrix type liquid crystal display device has a drawback that when a disconnection occurs in an address line, a transistor connected to the address line does not operate and a linear display defect occurs.

As a method of compensating for a display defect due to a disconnection failure of an address line, a method of providing a plurality of transistors for one pixel electrode has been conventionally employed as disclosed in Japanese Patent Application Laid-Open No. 61-2677782. It had been. FIG. 9 is a diagram showing a configuration of a conventional active matrix liquid crystal display device having a display defect compensation function. In FIG. 9, 120A, 121A, 122A, 120B, 12
1B and 122B denote transistors;
Reference numerals 1 and 132 indicate address lines, 140 and 141 indicate data lines, and 150, 151 and 152 indicate pixel electrodes.

By configuring such a circuit, if attention is paid to, for example, the pixel electrode 151, even if the address line 131 is disconnected and the transistor 121B is not driven, if the address line 130 is normal, the transistor 121A
Is driven, the same image information as that of the pixel electrode 150 is written to the pixel electrode 151, and a linear display defect can be prevented.

FIG. 10 is a plan view showing a specific structure of a transistor of an active matrix type liquid crystal display device corresponding to the above circuit. In FIG. 10, 130, 1
31 indicates an address line, 140 indicates a data line / drain electrode, 151 indicates a pixel electrode, and 160A and 16A.
0B indicates a semiconductor layer, 170A and 170B indicate channel forming insulating films, and 180A and 180B indicate source electrodes.

When the number of address lines increases with the miniaturization of the liquid crystal display device, the time for selecting a transistor decreases, and it is necessary to increase the current between the source and drain of the transistor. However, if the gate voltage is increased for this purpose, dielectric breakdown of the transistor is likely to occur. Further, when the channel length L is shortened, there is a possibility that the rate of etching failure increases. For this reason, it is common to increase the channel width W. However, as is apparent from FIG. 10, two transistors are formed between the address lines, and the channel width W is 1/1 / the distance between the address lines. It cannot be extended beyond two. Therefore, a sufficient current cannot flow through the pixel electrode, and the display characteristics deteriorate. This disadvantage is greater than the advantage that address line defects can be compensated.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and a first invention of the present invention provides an active matrix type liquid crystal display device capable of performing cell gap control with high accuracy. The purpose is to do.

A second object of the present invention is to provide an active matrix type liquid crystal display device capable of increasing the transistor current with a simple structure and compensating for a disconnection failure of an address line.

[0012]

Means for Solving the Problems A first invention of the present invention is:
A pair of substrates each having an electrode formed on one main surface thereof, a liquid crystal material sandwiched between the pair of substrates arranged so that the electrodes face each other, and a distance between the pair of substrates are defined. An active matrix type liquid crystal display device comprising: a spacer; and a recess for accommodating a part of the spacer is formed in at least a part of one of the pair of substrates.

According to a second aspect of the present invention, a plurality of address lines, a plurality of data lines formed to intersect the plurality of address lines, and the plurality of address lines and a plurality of data lines are provided. A pair of substrates each having a pixel electrode formed in a region and transistors connected to the pixel electrode, the address line, and the data line on one main surface were opposed to each other such that the pixel electrode was inside. A liquid crystal material sandwiched between a pair of substrates, wherein an active matrix liquid crystal display device in which a pixel electrode is switched by the transistor is provided between a gate of the transistor and one address line that partitions the pixel electrode. And a second capacitor provided between the gate of the transistor and the other address line that partitions the pixel electrode. To provide an active matrix type liquid crystal display device characterized by comprising a capacitor.

In the present invention, as a substrate material, glass, a silicon wafer or the like can be used. In addition, as the electrode material, ITO, ZnO, SnO ₂ or the like can be used. As a liquid crystal material, a nematic liquid crystal or the like can be used. In addition, polystyrene, glass, or the like can be used as the spacer material.

In the first aspect of the present invention, the portion where the concave portion is formed is a region of the other substrate corresponding to a wiring region between the pixel electrodes formed on at least one substrate. Further, the depth of the recess is preferably equal to or higher than the height of the wiring.

In the second aspect of the present invention, it is preferable that the first and second capacitors are formed on an address line. With such a configuration, space can be saved even if two capacitors are provided.

In the second aspect of the present invention, it is preferable that the dielectric material of the capacitor and the insulating film material of the transistor are the same. Thereby, it can be manufactured without newly adding a process. Further, it is preferable that the material of the capacitor is the same as the material of the address line or the data line. Thereby, it can be manufactured without newly adding a process.

[0018]

According to a first aspect of the present invention, a pair of substrates having electrodes formed on one main surface, a liquid crystal material sandwiched between the substrates, and a spacer for defining a distance between the pair of substrates are provided. And a recess for accommodating a part of the spacer is formed in at least a part of the one substrate.

According to the above configuration, even if the spacer is located on the wiring portion protrudingly formed on one substrate, a part of the spacer is accommodated in the concave portion formed on the opposing substrate. Thus, the protrusion amount of the wiring portion is compensated (canceled) by the concave portion having a depth equal to or greater than the protrusion amount, and uniform gap control can be accurately performed over the entire surface of the substrate.

According to a second aspect of the present invention, a pair of substrates having a plurality of address lines, a plurality of data lines, pixel electrodes, and transistors on one main surface, and a liquid crystal material sandwiched between the substrates are provided. In an active matrix liquid crystal display device comprising a transistor for switching a pixel electrode, a first capacitor provided between a gate of the transistor and one address line for partitioning the pixel electrode, and a gate and a pixel electrode of the transistor are provided. A second capacitor provided between the second address line and the other address line.

In the above configuration, since a voltage is applied to the gate electrode via the capacitor by both address lines sandwiching the pixel electrode, disconnection of the address line can be compensated. Further, since the number of transistors is reduced, the channel width can be increased without reducing the pixel electrode,
More current can flow through the transistor.

In a most preferred aspect of the second invention of the present invention, the address line is formed of the same material as the gate electrode of the transistor, and the lower electrode of the capacitor is used as the address line.
A dielectric of the same material as that of the gate insulating film of the transistor is formed thereon by overlapping with the address line of the same material as the drain of the transistor, and the upper electrode of the capacitor is brought into contact with the gate electrode to form one pixel electrode. Against
One transistor and two capacitors are provided. Furthermore, by forming a capacitor on both address lines sandwiching the pixel electrode, the gate electrode of the transistor is sandwiched between the pixel electrodes via two different capacitors and connected to different address lines. By doing so, the manufacturing process can be simplified and space can be saved.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view showing an embodiment of an active matrix type liquid crystal display device according to the first invention of the present invention. In this embodiment, a case of a black matrix will be described. In the figure, reference numeral 10 denotes an active matrix substrate. On the active matrix substrate 10,
The wiring portion 11 having a height of 1 μm is formed. Also,
A color filter substrate 12 is arranged facing the active matrix substrate 10. A recess 13 having a depth of 1 μm (1 μm or more) is formed in a region corresponding to the wiring portion of the color filter substrate 12. Further, it is located on the wiring portion 11 and is housed in the recess 13 so as to have an outer diameter of 1 μm.
m spacers 14 are supported. In this case, when the radius of the spacer 14 is r, the width of the recess 13 is x, the depth of the recess 13 is y, and the height of the wiring portion 11 is set to be the same as the depth y of the recess 13, the dimension of the recess is It is necessary to satisfy the following conditional expression (1).

[0025]

(Equation 1)

FIG. 2 is a sectional view showing the structure of the color filter substrate 12. The color filter substrate 12 includes a substrate 12a, a color filter layer 12b formed thereon and having a stepped portion, a black matrix layer 12c formed at the bottom of the concave portion, and a color filter layer 12b and a black matrix layer 12c. The formed overcoat layer 12d and the transparent conductive layer 12 formed thereon
e.

The color filter substrate 12 is formed on the base 1
2a, a black matrix layer 12c made of Cr, epoxy resin or the like is formed.
The color filter layer 12b is printed with an epoxy resin pigment or the like at an interval equal to or greater than the width of the wiring portion 11 of FIG.
Is formed, and an overcoat layer 12d is formed thereon using a transparent resin such as an epoxy resin. At this time, by adjusting the viscosity of the transparent resin, the shape of the overcoat layer 12d covering the stepped portion is controlled. Further, a transparent conductive layer made of ITO or the like is formed thereon.

The color filter substrate 12 having the above structure is
After performing an orientation treatment by a usual method, a sealing material layer 15 was formed on an end portion of the color filter substrate 12 by printing or the like, and spacers 14 were sprayed. Further, the active matrix substrate 10 was placed on the color filter substrate 12, and both substrates were sealed by heating under pressure, and then liquid crystal material was injected to complete the active matrix type liquid crystal display device shown in FIG. .

In this active matrix type liquid crystal display device, even when the spacer 14 is located on the wiring portion 11, the recess 13 formed in the color filter substrate 12 allows the spacer 14, so that the color filter substrate 12 is not affected. The conventional cell gap control accuracy of 5μ
Cell gap control could be performed at ± 0.2 μm with respect to m ± 0.5 μm.

(Embodiment 2) FIG. 4 is a circuit diagram showing an embodiment of an active matrix type liquid crystal display device according to the second invention of the present invention. In FIG. 4, reference numerals 20, 21, and 22 denote address lines of the (k-1) th row, the kth row, and the (k + 1) th row, respectively. Numerals 30 and 31 denote data lines in the j-1st column and the jth column, respectively. 40, 41, and 42 are (j, k-1), (j, k), and (j, k +
1) The pixel electrode of the 1st pixel is shown. Reference numerals 50, 51, and 52 denote (j, k-1) th, (j, k), and (j, k + 1) th transistors, respectively. 51A, 5
1B denotes a capacitor, 51A is connected to the gate electrode of the transistor 51 and the address line 20, and 51B is connected to the gate electrode of the transistor 51 and the address line 21, respectively. Other capacitors 50A, 50B, 52A, 52
B is connected in the same manner as described above.

With this configuration, even if one of the address lines is disconnected as described below, the image signal is applied to the pixel electrode, and the address line disconnection defect can be compensated.

Next, a specific operation of the active matrix type liquid crystal display device having the above configuration will be described. The address lines are operated sequentially from top to bottom in a line sequential manner. When the address line 20 is selected, a voltage is applied to the gate electrodes of the transistors 50 and 51 via the capacitors 50B and 51A, and the transistors 50 and 51 are turned on. At this time, the image signal S (j , K-1) are sent to both the pixel electrodes 40 and 41. Focusing on the pixel electrode 41, the image signal S (j, k) sent to the data line 30 is sent via the transistor 51 when the address line 21 is selected following the address line 20. Therefore, the image signal S (j, k-1) when the address line 20 is selected is immediately rewritten. This voltage is applied until the next operation of the address line completes and the address line 20 is selected, so that the pixel itself formed by the corresponding pixel electrode is held. Therefore, this is substantially equivalent to the case where only the image signal S (j, k) is sent to the display pixel 41, and a correct display is performed.

Here, considering the case where the address line 21 is disconnected, no rewriting occurs when the address line 21 is selected, so that the pixel electrode 41 receives the image signal S (j, k).
-1) is held and displayed, so that a linear non-display state does not occur. For this reason, it can be prevented from being noticeable as a defective pixel. Furthermore, for general images, since the correlation of the image signals between adjacent pixels is high, displaying the signals to the adjacent pixels as described above makes it possible to obtain an image that is not much different from displaying the original signal. Is displayed. Therefore, practically, it can hardly be detected as a defect.
As described above, even when the address line 20 is broken, if the address line 21 is normal, a normal display is apparent. The probability that the address line 20 and the address line 21 are disconnected at the same time is very low.

The same operation is performed for the pixel electrodes 40 and 42. In this way, address line disconnection failure can be compensated for the entire pixel.

FIG. 5A is a plan view showing the structure of one embodiment of the active matrix type liquid crystal display device according to the second invention of the present invention, and FIG. −
It is sectional drawing which follows the I line.

The active matrix type liquid crystal display device shown in FIG. 5A is manufactured as follows. First, on a glass substrate 60, Mo, Ta,
A metal such as Al is formed into a film, and the gate electrode 63 and the address lines 20 and 21 are formed by photolithography. Next, a silicon oxide film (SiOx) is formed on the gate electrode 63.
Alternatively, a gate insulating film 65 made of a silicon nitride film (SiNx), a semiconductor film 68 made of amorphous silicon (a-Si), and a channel forming insulating film 69 made of a silicon nitride film are sequentially and continuously formed by a plasma CVD method. And
The channel forming insulating film 69 is patterned into a predetermined shape.

Next, n ⁺ a-Si doped with phosphorus
The film 70 is formed by a plasma CVD method, and the n ⁺ a-Si film 70, the semiconductor film 68, and the gate insulating film 65 are continuously patterned by photolithography so as to be wider than the channel forming insulating film 69.

Next, after the pixel electrode 41 is formed by using a transparent electrode material such as ITO, a part of the gate insulating film 65 above the electrode lead-out portion at the end of the address line is partially removed. 77B is removed. Furthermore, a data line / drain electrode 3 made of Mo, Al, etc.
0 is formed so as to be in contact with the n ⁺ a-Si film 70, and in this step, the source electrode 73 is formed so as to be in contact with the n ⁺ a-Si film 70 and the pixel electrode. At the same time, the capacitor upper electrode 74A is formed so as to overlap both the 77A and the address line 20, and the capacitor upper electrode 74B is formed so as to overlap both the 77B and the address 21. Finally, the n ⁺ a-Si film 70 between the drain and the source is removed by selective etching to complete the transistor.

The relationship among each address line, data line, transistor, and capacitor in this configuration has the relationship shown in FIG. 4, and a configuration capable of compensating for an address line defect is realized. As described above, the channel width of the transistor can be increased to near the width between the address lines, so that the current flowing to the pixel electrode increases, and the display characteristics are improved. Since the capacitor is formed on the address line, it is not necessary to reduce the pixel electrode by adding the capacitor. Further, since the capacitor is formed simultaneously with the formation of the transistor, the number of steps is not increased as compared with the related art.

As described above, an active matrix type liquid crystal display device having a transistor having a channel width about twice as long as the conventional one and a conventional active matrix type liquid crystal display device are manufactured. Was measured. When the voltage of each pixel was measured, the same voltage as the pixel voltage in the vicinity was applied to the pixel where the address line was disconnected. Further, in the active matrix type liquid crystal display device of the present invention, the maximum current flowing through the pixel electrode showed a value about twice that of the conventional one. Further, the active matrix type liquid crystal display device of the present invention,
It showed better display characteristics than the conventional one.

[0041]

As described above, the active matrix type liquid crystal display device according to the first aspect of the present invention comprises a pair of substrates having electrodes formed on one main surface, and a liquid crystal material sandwiched between the substrates. A spacer that defines the distance between a pair of substrates, and a recess that allows the spacer is formed in at least a part of one of the substrates, so that the cell gap can be controlled with high precision, thereby improving the display characteristics. Improve
Color unevenness in display can be prevented.

According to a second aspect of the present invention, there is provided a liquid crystal material sandwiched between a pair of substrates having a plurality of address lines, a plurality of data lines, pixel electrodes, and transistors on one main surface. A first capacitor provided between the gate of the transistor and one of the address lines for partitioning the pixel electrode, and the gate of the transistor and the pixel. Since the second capacitor is provided between the second address line and the other address line for partitioning the electrode, even if the address line is broken, it is possible to prevent a linear display defect from occurring. Further, according to the second aspect of the present invention, the channel length of the transistor can be expanded without increasing the number of conventional manufacturing steps and without reducing the area of the pixel electrode, and excellent display characteristics can be obtained. be able to.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a part of an embodiment of an active matrix liquid crystal display device according to the first invention of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of a color filter substrate in FIG.

FIG. 3 is a cross-sectional view showing an embodiment of the active matrix type liquid crystal display device according to the first invention of the present invention.

FIG. 4 is a circuit diagram showing one embodiment of an active matrix type liquid crystal display device according to the second invention of the present invention.

FIG. 5A is a plan view showing a transistor portion of an active matrix liquid crystal display device according to a second invention of the present invention;
(B) is a sectional view taken along line II in (A).

FIG. 6 is a cross-sectional view for explaining cell gap control of a conventional active matrix liquid crystal display device.

FIG. 7 is a cross-sectional view for explaining cell gap control of a conventional active matrix liquid crystal display device.

FIG. 8 is a cross-sectional view illustrating a problem of a conventional active matrix liquid crystal display device.

FIG. 9 is a circuit diagram showing an example of a conventional active matrix liquid crystal display device.

FIG. 10 is a plan view showing a transistor portion of a conventional active matrix liquid crystal display device.

[Explanation of symbols]

10 Active matrix substrate, 11 Wiring unit, 12
... color filter substrate, 12a ... substrate, 12b ... color filter layer, 12c ... black matrix layer, 12
d: overcoat layer, 12e: transparent conductive layer, 13: concave portion, 14: spacer, 15: sealing material layer, 20, 2
1, 22 ... address line, 30, 31 ... data line / drain electrode, 40, 41, 42 ... pixel electrode, 50, 51, 5
2. Transistors, 50A, 50B, 51A, 51B,
52A, 52B: condenser, 60: glass substrate, 63
... gate electrode, 65 ... gate insulating film, 68 ... semiconductor film,
69: an insulating film for forming a channel; 70: an n ⁺ a-Si film;
77A, 77B: Above the gate electrode.

Claims (6)

[Claims] 1. A first substrate having a plurality of projections regularly arranged on one principal surface, a second substrate facing the first substrate via a spacer, and sandwiched between the substrates. The second substrate has a concave portion for accommodating a part of the spacer at a position corresponding to the projecting portion of the first substrate, whereby the first substrate, the second substrate and The liquid crystal display device characterized in that the gap is kept substantially constant. 2. The liquid crystal display device according to claim 1, wherein the projecting portion is formed of a wiring electrode formed on the first substrate. 3. The liquid crystal display device according to claim 1, wherein the concave portion is controlled by a stepped portion of a color filter layer formed on the second substrate. 4. The liquid crystal display device according to claim 1, wherein the spacer has a spherical shape. 5. The liquid crystal display device according to claim 1, wherein the spacer is accommodated in the recess at a depth greater than a height of the protrusion. 6. The liquid crystal display device according to claim 5, wherein the depth at which the spacer is housed in the recess and the height of the protrusion are the same.