JPH06230414A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To realize the liquid crystal display element having a high display grade by improving the excellent controllability in gradation display and improving a visual angle characteristic. CONSTITUTION:The electric resistance formed out of a first TFT element 15 and a second TFT element 17 is connected in series to a liquid crystal cell 21 of a second display region, there by, the difference between the electric field intensity by the voltage impressed to the liquid crystal cell 19 of a first display region by the partial voltage of the electric resistance thereof and the electric field intensity by the voltage impressed to the liquid crystal cell 21 of the second display region, is largely taken and the controllability of the gradation display is improved, and the visual angle characteristic is improved as well. Moreover, the drop of the holding voltage with the lapse of time and the fluctuation therein occurring in the redistribution, etc., of the accumulated charges between the liquid crystal cell 19 and the liquid crystal cell 21, are averted.

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 device.

[0002]

2. Description of the Related Art In recent years, an active matrix type liquid crystal display device has been attracting attention as a display device capable of high resolution display. Among them, an active matrix type liquid crystal display element equipped with a field effect transistor (TFT) as a switching element is particularly suitable for gradation display and is being applied to televisions and the like.

The operation mode of the liquid crystal display element is TN.
Type, DS type, GH type, DAP type, thermal writing type, etc., but the TN type is generally used for the active matrix type liquid crystal display element.

FIG. 9 shows an equivalent circuit of one pixel of the active matrix type liquid crystal display element. A field-effect thin film transistor (hereinafter abbreviated as TFT) 805 is arranged near the intersection of the address line 801 and the signal line 803, and
The gate 807 of T805 is connected to the address line 801, the drain 809 is connected to the signal line 803, and the source 811 is connected to the pixel electrode 813. A liquid crystal layer 817 is sandwiched between the pixel electrode 813 and the counter electrode 815.
Further, an alignment layer or the like (not shown) for aligning liquid crystal molecules is formed on the surfaces of the pixel electrode 813 and the counter electrode 815 which are in contact with the liquid crystal layer 817.

By the way, the relationship (VT characteristic) between the liquid crystal applied voltage and the transmittance in the normally white mode (mode in which black display is performed on a white background) of the TN type liquid crystal display element is the voltage at which the transmittance starts to change. (Called threshold voltage Vth)
And the voltage at which the change in transmittance is almost completed (saturation voltage Vsat
There is a difference of, for example, about 1 to 2V. In the active matrix type liquid crystal display element using the TFT as a switching element, gradation display is performed by providing some voltage levels between Vth and Vsat.

[0006]

However, since the above-mentioned difference between Vth and Vsat is not so large as about 1 to 2 V, the difference between the applied voltage levels becomes smaller as the number of gray scales increases, and the applied voltage can be controlled. There is a problem that it becomes difficult. That is, in the active matrix type liquid crystal display device, for example, when 64-gradation display is performed, a band-shaped unevenness of light and shade may occur on the entire screen due to a slight variation in the output of the driving IC. This is because the variation in the output voltage of the driving IC is much larger than the difference in the voltage between the gray levels, and this variation is visually recognized as a more distinct gray level difference than the gray level difference due to the voltage difference between the gray levels. Therefore, there is a problem that the display quality is significantly impaired.

Further, when gradation display is performed by such a method, due to the operating principle of the TN type liquid crystal display element, there is a large change in transmittance when the viewing angle is changed, and as a result, the viewing angle is narrowed. There are also problems.

In addition, an operation mode other than the TN type, for example, G
Even in a liquid crystal display device based on an operating principle such as an H type or a DAP type, it is more difficult to control the applied voltage as the total number of gray levels to be expressed increases.

As a technique intended to solve such a problem, a technique of providing display regions in which the electric field strengths applied to the liquid crystal layer are different from each other in one pixel is disclosed in, for example, Japanese Patent Laid-Open Nos. 2-12 and 2- It is known from Japanese Patent No. 310534, Japanese Patent Laid-Open No. 3-122621, and the like.

To summarize these techniques, when the same voltage is applied between the pixel electrode and the counter electrode in one pixel, the electric field strengths applied to the liquid crystal layer are different from each other.
It is to provide two or more areas. And if each pixel is sufficiently small compared to the entire liquid crystal display element,
The transmittance characteristic (VT characteristic) with respect to the voltage applied between the electrodes of each individual pixel appears to the observer as the sum of the transmittance characteristics of the two or more regions. as a result,
This means that the difference between Vth and Vsat is substantially enlarged, and multi-gradation display can be realized more easily. Further, it is intended to reduce the narrow viewing angle when gradation display is performed.

In such a technique as disclosed in Japanese Patent Laid-Open No. 12-12, the display areas are connected in parallel, and the electric field applied to each liquid crystal layer is changed by making the capacitance of the capacitive element different in each display area. The strength is different.

However, since the capacitive element and the liquid crystal layer are connected in series, it is not easy to change the voltage applied to the liquid crystal layer by setting the voltage applied to the capacitive element to different values. For example, in order to increase the voltage and reduce the voltage applied to the liquid crystal layer, the capacitance of the capacitive element must be reduced. For that purpose, the relative permittivity ε of the capacitive element must be large, the area S must be small, and the thickness t must be large, but the specifications of the dielectric used are limited due to process factors, and the area of the capacitive element is limited. If is smaller, there is a possibility of short circuit, and since the thickness is limited to the thickness between the substrates of the liquid crystal element, it cannot be so large. As described above, even in the known technique as described above, it is actually difficult to control the electric field strength of each display area and the difference in the electric field strength of each display area cannot be increased so much. There is a problem that it is not easy to improve the viewing angle characteristics.

The present invention has been made in order to solve the above problems, and has excellent controllability of gradation display and improved viewing angle characteristics to provide a liquid crystal display device having high display quality. It is intended to be realized.

[0014]

In order to solve the above problems, a liquid crystal display device according to the present invention comprises a matrix wiring formed of a plurality of address lines and a plurality of signal lines, and an input terminal for the signal lines. A switching element that is connected to and disconnects conduction to an output end of a signal input from the signal line based on a signal input from the address line, and a pixel electrode connected to an output end of the switching element, In a liquid crystal display element having a counter electrode facing the pixel electrode, and a liquid crystal layer sandwiched between the counter electrode and the pixel electrode, the pixel electrode is at least the pixel electrode in the first display region and the second electrode. The pixel electrode in the display area is divided into two, and the pixel electrode in the second display area is inserted through an electric resistance formed by combining two thin film transistors to output the output terminal of the switching element. And is connected in parallel with the pixel electrode of the first display region.

Alternatively, in the liquid crystal display device of the present invention, a matrix wiring formed of a plurality of address lines and a plurality of signal lines, and an input end connected to the signal line, and a signal input from the signal line is connected. A switching element that interrupts conduction to an output end based on a signal input from the address line, a pixel electrode of a first display region connected to the output end of the switching element, and the first display The pixel electrode of the second display region formed avoiding the connection with the pixel electrode of the region and the gate are connected to the output end of the switching element, and one of the source and drain is connected to the output end of the switching element. A first transistor element that is connected and the other is connected to the pixel electrode of the second display region, and produces a potential difference when a current flows between the source and the drain; Connected to the pixel electrode in the second display area, one of the source and drain connected to the output terminal of the switching element, and the other connected to the pixel electrode in the second display area. Second transistor which is inserted in parallel between the output terminal and the pixel electrode of the second display region in parallel with the transistor element and produces a potential difference when a current flows between the source and the drain. An element, a counter electrode facing the pixel electrode in the first display area and the pixel electrode in the second display area, a pixel electrode in the first display area and a pixel electrode in the second display area, and And a liquid crystal layer sandwiched between the counter electrode and the counter electrode.

The source of the transistor element
In order to generate a potential difference between the drains, the transistor element must have electric resistance (internal resistance, etc.). Regarding the magnitude of the electric resistance, the physical properties of the liquid crystal layer to be used, particularly the dielectric constant and the liquid crystal layer It is necessary to design considering the thickness of the. That is, since the electrical resistance of the transistor element and the liquid crystal layer form a series circuit, the liquid crystal applied voltage applied between the electrodes of the first and second pixel regions and the counter electrode is different from that of the transistor element. The voltage is divided into the liquid crystal layer. At this time, the ratio of the voltage division is determined by the resistance value (or impedance) of each. Need to be kept. At this time,
Since the liquid crystal itself has a dielectric anisotropy, the impedance of the liquid crystal layer is preferably set in consideration of the fact that it changes depending on the applied voltage.

The first transistor element and the second transistor element
The electric resistance formed by combining the transistor elements may be inserted in only one set, or a plurality of sets may be inserted in series. At this time, the plurality of sets of transistor elements may have the same electric resistance or different electric resistance, and may be formed so as to have a necessary resistance value. Further, the pixel electrode is not necessarily limited to one that is divided into only two regions, the first display region and the second display region. For example, in addition to the third display area adjacent to the second display area,
It is also possible to arrange the display region of No. 1 and to connect the third display region with more one or more sets of the first and second transistor elements in series as compared with the second display region.

[0018]

In the liquid crystal display element of the present invention, since the electric resistance formed by the first transistor element and the second transistor element is connected to the pixel electrode in the second display area, Thus, the signal applied from the signal line through the switching element, that is, the video signal voltage is divided. Since the applied voltage thus divided and reduced in voltage is applied to the pixel electrode in the second display region,
Due to the difference with the video signal voltage applied to the pixel electrode of the first display area, the difference in the electric field strength between the liquid crystal cells corresponding to the two different areas of the first display area and the second display area is Can be large.

Moreover, since the electric resistance is formed by combining the first transistor element and the second transistor element, the conduction threshold Vth of these elements is formed.
It has a non-linear I-V characteristic that no current flows (high resistance state) at the following voltages. Therefore, it is possible to avoid the fluctuation of the voltage due to the potential difference between the pixel electrode of the first display region and the second electrode when the switching element is turned off after the scanning selection period has passed,
During the scan selection period, the voltage once written in each pixel electrode can be held while avoiding a temporal drop or fluctuation.

[0020]

Embodiments of the liquid crystal display device of the present invention will be described below in detail with reference to the drawings.

Example 1 The liquid crystal display element of the present invention is shown in FIG.
It can be represented by an equivalent circuit as shown in. That is, the matrix wiring formed of the plurality of address lines 1 and the plurality of signal lines 3 is arranged in the vicinity of the intersection of the matrix wirings, and the drain 309 serving as the input end of the signal line 3 is provided.
Is connected to the source electrode 311 which is the output terminal of the video signal voltage input from the signal line 3, and the address line 1
Field-effect TFT 5 as a switching element that is connected and disconnected based on the scanning pulse input to the gate 307 from the
And a first pixel electrode 7 forming a first display area in one pixel and a first pixel electrode 7 which is arranged so as to avoid connection with the first pixel electrode 7 and is separated from the first display area in one pixel. A second pixel electrode 9 forming a second display region of the
And a counter electrode 11 facing the second pixel electrode 9, a liquid crystal layer 13 sandwiched between the pixel electrodes 7 and 9 and the counter electrode 11, a source electrode 311 as an output end of the TFT 5, and a second display. The TFT 5 is inserted between the pixel electrode 9 in the area and
Having an internal resistance that causes a potential difference when a current flows between the source electrode 311 and the drain 309 of the first
The TFT element 15 and the second TFT element 17 are provided, and a first display area and a second display area having different applied electric field strengths are formed for each pixel.

The liquid crystal cell 19 in the first display area has a main part composed of the first pixel electrode 7, the liquid crystal layer 13 and the counter electrode 11, and the liquid crystal cell 21 in the second display area is Second pixel electrode 9, liquid crystal layer 13, and counter electrode 11
Its main part is composed of and. As shown in FIG. 1, the first TFT element 15 and the second TFT element 17 are not connected to the liquid crystal cell 19 in the first display area, and these are connected to the liquid crystal cell 21 in the second display area. It is connected in series.

In the first TFT element 15, the gate is connected to the source electrode 311 of the TFT 5, one of the source / drain is connected to the source electrode 311 of the TFT 5, and the other is connected to the second pixel electrode 9. . Also the second T
The gate of the FT element 17 is connected to the second pixel electrode 9,
One of the source and drain is the source electrode 311 of the TFT5
And the other is connected to the second pixel electrode 9.

Thus, the liquid crystal display element of the present invention is
By connecting the electric resistance formed by the TFT element 15 and the second TFT element 17 in series to the liquid crystal cell 21 in the second display area, the voltage division of the electric resistance causes the liquid crystal cell in the first display area to be divided. The difference between the electric field strength due to the voltage applied to 19 and the electric field strength due to the voltage applied to the liquid crystal cell 21 in the second display region can be made large, and as a result, the controllability of gradation display is excellent. In addition, the viewing angle characteristics can be improved.

Moreover, since the electric resistance is formed by combining the first TFT element 15 and the second TFT element 17, no current flows at a voltage lower than the conduction threshold voltage Vth of the transistor element. Non-linear I-
It has V characteristics. Therefore, even when the scanning selection period has passed and the TFT 5 as a switching element is turned off and the external power supply to the first pixel electrode 7, the second pixel electrode 9 and the liquid crystal layer 13 is stopped, inside the liquid crystal display element. It is possible to avoid temporal reduction or fluctuation of the holding voltage due to redistribution of accumulated charges between the liquid crystal cell 19 and the liquid crystal cell 21, or the like. As a result, the first pixel electrode 7 and the second pixel electrode 7
The voltage written in each pixel electrode 9 of the liquid crystal cell 19
And the liquid crystal cell 21.

Next, the operation will be described. The voltage of the first pixel electrode 7 is V1, the voltage of the second pixel electrode 9 is V2, the voltage drop due to the electric resistance of the first TFT element 15 and the second TFT element 17 combined in parallel is Vdn, The threshold voltage of the first TFT element 15 and the second TFT element 17 is Vth. When writing applied voltage | V1
When a voltage V1 of −V2 |> | Vth | is applied through the TFT 5, the source and drain of the first TFT element 15 become conductive, and the voltage is written in the second pixel electrode 9. To go. This writing is continued until the voltage V2 of the second pixel electrode 9 becomes equal to the voltage | V1 |-| Vdn | at the output end of the second TFT element 17. That is, it is continued while | V2 | <(| V1 |-| Vdn |).

When the TFT 5 is turned off, the voltage V2 of the second pixel electrode 9 at that time is │V2 │ <(│V1
|-| Vdn |). The voltage V of the second pixel electrode 9
2 and the voltage V1 of the first pixel electrode 7 have a potential difference of Vdn at the maximum, but this | Vdn | is previously set to | Vdn | <|
If it is set to Vth |, the first TFT element 15 does not conduct, so that fluctuations or reductions in the voltages of the first pixel electrode 7 and the second pixel electrode 9 can be suppressed, and the liquid crystal cell The voltages written in 19 and the liquid crystal cell 21 can be held respectively. When the polarity of the applied voltage is reversed, the second TFT element 17 performs the above operation.

In order to set Vdn as described above, the electric resistance formed by the first TFT element 15 and the second TFT element 17 must be preset to a value suitable for it. . It is important to design the magnitudes of the electric resistances of the first TFT element 15 and the second TFT element 17 in consideration of the physical properties of the liquid crystal layer 13 to be used, particularly the dielectric constant and the thickness.
That is, the first TFT element 15 and the second T element
Since the electric resistance by the FT element 17 and the liquid crystal cell 21 form a series circuit, the voltage caused by the electric resistance is divided, but the ratio of the divided voltage at this time is the resistance value (or Since it is determined by the impedance, it is necessary to calculate the electric resistance of the liquid crystal layer 13 in advance and
It is necessary to determine the electric resistances of the TFT element 15 and the second TFT element 17 in advance.

If the above-mentioned first TFT element 15 and second TFT element 17 are combined in parallel and are interposed between the TFT 5 and the second pixel electrode 9, The number of sets may be plural. That is, the first TFT
The element 15 and the second TFT element 17 may be inserted in only one set, or a plurality of sets may be inserted in series.
At this time, the plurality of sets of the first TFT element 15 and the second TFT element 17 may have the same electric resistance or different electric resistances, and have appropriate resistance values satisfying the above-described conditions. It may be formed.

Next, the structure of such a liquid crystal display device of the present invention will be described. 2 is a plan view showing the structure of the liquid crystal display element of the first embodiment, and FIG. 3 is a sectional view of the TFT 5 taken along the line AA '.

The liquid crystal display element of the first embodiment is mainly composed of an array substrate 301, a counter substrate 303, and a liquid crystal layer 13 sandwiched between these substrates.

In the array substrate 301, as shown in FIGS.
As shown in, the address lines 1 made of metal are formed on the glass substrate 305 at predetermined intervals, and the surface thereof is covered with an insulating film. Further, signal lines 3 made of metal are formed at predetermined intervals so as to intersect with the address lines 1,
A first pixel electrode 7 and a second pixel electrode 9 made of ITO and ITO are formed at each intersection.
The TFT 5 includes a gate electrode 307 made of metal, a drain electrode 309, a source electrode 311, a semiconductor film 313 made of, for example, amorphous silicon, and a low resistance semiconductor 3.
15, 317. Gate electrode 307
Is the address line 1, the drain electrode 309 is the signal line 3,
The source electrodes 311 are connected to the first pixel electrodes 7, respectively. The etching stopper layer 319 and the passivation film 321 are both made of SiN _x . A SiO _x film 323 and a SiN _x film 325 are stacked on the gate electrode 307 as a gate insulating film. In addition, the pixel electrode 7,
9 and the storage capacitance line 201 are used as a pair of electrodes, and the SiO _x film 323 sandwiched between the electrodes is used as a dielectric to form a storage capacitance Cs (this storage capacitance Cs is omitted in FIG. 1 for simplification of description). is doing). And the first pixel electrode 7
Are connected to the source electrode 311 of the TFT 5 and are arranged so as to avoid direct connection with the second pixel electrode 9, and a pair of the first TFT element 15 and the second TFT
It is connected to the second pixel electrode 9 via an electric resistance formed by the element 17. The entire surface of the array substrate 305 is covered with an alignment film 327 made of polyimide.

On the other hand, in the counter substrate 303, on the glass substrate 329, a lattice-shaped light-shielding film 33 made of a metal such as Cr is formed so as to cover a portion not related to display as a pixel.
1 is formed, and the color filter 333 and the ITO are formed on it.
Is formed on the counter electrode 11, and an alignment film 335 made of polyimide is formed thereon.

Further, the array substrate 301 and the counter substrate 30
A liquid crystal layer 13 made of TN type liquid crystal is sandwiched between them and the thickness thereof is about 5 μm. The liquid crystal molecules are pre-tilted by the action of the alignment films 327 and 335 and are aligned substantially parallel to the substrate, and the orientation of the liquid crystal molecules is twisted by 90 degrees between the alignment films 327 and 335 to form a TN liquid crystal display element. ing. In addition, the array substrate 301 and the counter substrate 30
Polarizing plates 337 and 339 are formed on each of the three.

Next, the structures of the TFT element 15 and the second TFT element 17 of the liquid crystal display element of the first embodiment according to the present invention will be described. FIG. 4A is a partially enlarged plan view showing the first TFT element 15 and the second TFT element 17, and FIG. 4B is a sectional view taken along the line BB ′.

The first TFT element 15 has a gate electrode 15
01, a gate insulating film composed of a SiO _x film 323 and a SiN _x film 325, an active layer 1503, an etching stopper layer 1505, an ohmic contact layer 1507, a drain electrode 1509, an ohmic contact layer 1511, and a source electrode 1513. ing. And the upper part is protected by a passivation film (not shown).

In the second TFT element 17, the gate electrode 1701, the gate insulating film composed of the SiO _x film 323 and the SiN _x film 325, the active layer 1703, the etching stopper layer 1705, the ohmic contact layer 1707, the source electrode 1709, Ohmic contact layer 1711,
The main part is formed from the drain electrode 1713. And the upper part is protected by a passivation film.

The gate electrode 150 is formed on the glass substrate 301.
1, a gate electrode 1701 is formed. The gate electrodes 1501 and 1701 are the gate electrodes 30 of the TFT 5.
It is formed from the same film as 7. In this way, the first TFT element 15 and the second TFT element 17 are
If the same film as the film for forming the FT5 is used, the normal TFT5 forming process can be used if only the pattern is changed at the time of manufacturing, so that the inconvenience of the process can be avoided.

Then, the SiO _x film 323 and SiN also used for the TFT 5 are covered so as to cover almost the entire surface including the above.
_{The x} film 325 is stacked as a gate insulating film. Then, active layers 1503 and 1703 are formed thereon. The active layers 1503 and 1703 are formed of the same film as the semiconductor film 313 of the TFT 5. However, various material-related conditions such as the amount of impurities to be doped are set to values at which the optimum effect as the electric resistance according to the present invention can be exhibited. Then, the active layers 1503 and 1703
Etching stopper layers 1505 and 1705 as channel protection films are provided so as to cover the channel region of the.

A drain electrode 1509 is connected to the drain of the active layer 1503 through an ohmic contact layer 1507, and the ohmic contact layer 1 is connected to the source.
The source electrode 1513 is connected via 511.
A source electrode 1709 is connected to the drain of the active layer 1703 via an ohmic contact layer 1707, and a drain electrode 1713 is connected to the source via an ohmic contact layer 1711. The above electrodes and ohmic contact layers are formed of the same film as that used for the TFT 5.

Drain electrode 15 of the first TFT element 15
09 is connected to the first pixel electrode 7 and is also connected to the gate electrode 1501 through the through hole 1515. The drain electrode 1509 of the first TFT element 15 is the source electrode 1 of the second TFT element 17.
709 is formed integrally. In this way the first T
The drain electrode 1509 and the gate electrode 15 of the FT element 15
01 and the source electrode 1709 of the second TFT element 17 are connected to the first pixel electrode 7.

The source electrode 1513 of the first TFT element 15 and the drain electrode 171 of the second TFT element 17 are also provided.
3 is integrally formed and connected, and the drain electrode 1713 and the gate electrode 1701 of the second TFT element 17 are connected through the through hole 1715, and the gate electrode 1701 is electrically connected to the second pixel electrode 9. It is connected. With such a structure, a circuit as shown by an equivalent circuit in FIG. 1 is formed.

Next, a method of manufacturing the liquid crystal display element of the first embodiment as described above will be described.

A Mo-Ta film having a thickness of 3000 angstrom was sputter-deposited on a non-alkali glass substrate having a thickness of 1.1 mm, and the gate electrode 307, the storage capacitor line 201, and the storage capacitor line 201 were formed by photolithography into a shape as shown in FIG. Address line 1
And the gate electrode 1501 of the first TFT element 15 and the gate electrode 1 of the second TFT element 17
701 is formed.

Next, Si having a film thickness of 3600 angstroms
O _x , 400 Å thick SiN _x , 700 thick
An a-Si film having a thickness of 2000 angstroms and a SiN _x film having a thickness of 2000 angstroms are formed by a CVD method and formed into a predetermined pattern by photolithography.
325, the semiconductor film 313, and the active layers 1503 and 170.
3, etching stopper layers 319, 1505, 170
Got 5. At this time, through holes 1515 and 1715 as shown in FIG. 4 are formed in the insulating films 323 and 325.

Subsequently, n ⁺ a having a film thickness of 300 angstrom is formed.
-Si is formed by CVD, and patterned by photolithography to form low resistance semiconductor films (ohmic contact layers) 315, 317, 1507, 1511, 170.
7, 1711 was formed.

Next, an ITO film having a film thickness of 1000 Å is formed by sputtering, and then patterned by photolithography to form the first pixel electrode 7 and the second pixel electrode 9.
Was formed. At this time, the patterning is performed so that the first pixel electrode 7 and the second pixel electrode 9 are prevented from being directly electrically connected.

Next, Mo and Al are deposited by sputtering and patterned by photolithography to obtain a film thickness.
4000 angstrom source electrodes 311, 1513,
1713 and drain electrodes 309, 1509, 170
Got 9.

Then, Si having a film thickness of 2000 angstroms
N _x was deposited by the CVD method to form a passivation film. After forming a 1000 angstrom polyimide thin film so as to cover it, a rubbing alignment treatment was performed on the surface thereof to form an alignment film 327. (The passivation film and the alignment film 327 are not shown in FIG. 4 for the sake of simplicity.) In this way, the signal lines 3 and the address lines 1 are formed in a matrix shape, and their respective crossings are formed. Pixels are formed in the
An array substrate 301 having a total of 10,000 pixels (pixels × 100 pixels horizontally) was produced.

On the other hand, the counter substrate 303 is the glass substrate 32.
A light-shielding film 331 was formed by depositing Cr with a film thickness of 3000 angstroms on the substrate 9 by sputtering and photolithography, and a color filter 333 on which predetermined R, G, and B was formed for each pixel was formed thereon. Then, an ITO film having a film thickness of 1000 angstrom was formed by sputtering to obtain the counter electrode 11. Polyimide thin film 10 to cover almost all over it
After forming a film of 00 angstrom, the surface was subjected to a rubbing alignment treatment to form an alignment film 335.

Along the periphery of the alignment film 335 of the counter substrate 303, an epoxy adhesive (not shown) is printed on a portion other than the injection port (not shown), and on the display screen portion of the counter substrate 303. Micropearls (manufactured by Sekisui Fine Chemical Co., Ltd.) having a particle size of 5 μm were dispersed as a gap material (not shown).

Then, the substrates 301 and 303 are combined so that the orientation films 327 and 335 face each other and the angle formed by the respective rubbing directions is 90 degrees, and the substrates 301 and 303 are heated to cure the adhesives. Pasted together

Next, S811 was applied to ZLI-1565 (manufactured by E. Merck) as a liquid crystal composition from the injection port by a usual method.
After the injection of 0.1 wt% added, the injection port was sealed with an ultraviolet curable resin.

After that, polarizing plates 337 and 339 were attached to the array substrate 301 and the counter substrate 303, and a short ring (not shown) on the surface of the array substrate 301 was cut off to complete a liquid crystal display element.

As described above, in the liquid crystal display element of the present embodiment, the first TFT element 15 and the second TFT element 17 can be formed by the same process as the manufacturing of the TFT 5.

When an active matrix type liquid crystal display device manufactured in this manner was made to display 64 gradations, the transmittance was almost equal to the set value at each gradation, and the displayed image was displayed. When visually inspected,
It was confirmed that the display quality was good. It was also confirmed that the change in transmittance when the viewing angle direction was changed was small and the viewing angle characteristics were high. FIG. 5 shows the result of measuring the change in the VT characteristic of the liquid crystal display device according to the present invention depending on the viewing angle direction.

As is clear from FIG. 5, the VT characteristic of the liquid crystal display element according to the present invention is compared with the viewing angle characteristic of the conventional liquid crystal display element shown in the curve of FIG. Figure 5
It was confirmed that the viewing angle characteristics were dramatically improved and a wide viewing angle could be realized, as shown by the curve (b).

(Embodiment 2) Next, the liquid crystal display element of the second embodiment will be described with reference to FIG. FIG. 6 is a plan view showing the structure of the liquid crystal display element of the second embodiment. In the active matrix type liquid crystal display element of the second embodiment, one pixel is vertically (upper and lower in the figure) divided into a pixel electrode in a first area and a pixel electrode in a second area. Is different from the first embodiment. For simplification of description, the same parts as those in the first embodiment are designated by the same reference numerals as those in the first embodiment.

A metal layer 701 made of a metal such as Mo-Ta.
Are disposed directly on the glass substrate 305. A SiO _x layer 323 and a SiN _x layer 325 are formed on this metal layer 701. Further, the first pixel electrode 7 made of ITO
07 and the second pixel electrode 709 are formed at a predetermined distance so as to partially overlap with each other on the metal layer 701. Storage capacitors are formed by using the metal layer 701 as a lower electrode and the first pixel electrode 707 and the second pixel electrode 709 as an upper electrode.

By inserting the first TFT element 15 and the second TFT element 17 between the first pixel electrode 707 and the second pixel electrode 709, the first TFT element 15 and the second TFT element 17 are inserted as in the first embodiment. An electric resistance formed by the first TFT element 15 and the second TFT element 17 is connected to the second pixel electrode 709, and the second pixel electrode 709 and the first pixel electrode 7 are connected.
07 are connected in parallel.

The liquid crystal display element of the second embodiment having such a configuration also has a small change in transmittance when the viewing angle direction is changed and has a high viewing angle characteristic, and the quality of the display image is similar to that of the first embodiment. It was confirmed to be good.

(Embodiment 3) FIG. 7 is a plan view showing the structure of a liquid crystal display element of the third embodiment, which is a modification of the liquid crystal display element of the second embodiment described above, and FIG. ′ It is a cross-sectional view. The feature is that a TFT element 919 having a double gate structure is used as an electric resistance. The other configurations are similar to those of the above-described second embodiment and the like. A gate / black matrix metal 903 is formed on the passivation film 901. Then, the gate electrode 905, the active layer 907 made of a-Si, the etching stopper layer 909, the source electrode 911, the drain electrode 913, and the ohmic contact layers 915 and 917.
Therefore, the main part of the double-gate structure TFT element 919 as the electric resistance element of this embodiment is formed.
An equivalent circuit of such a TFT element 919 is shown in FIG.

It has been confirmed that the liquid crystal display device of the third embodiment having such a structure has good display image quality as in the first and second embodiments. It was also confirmed that the change in transmittance when changing the viewing angle direction was small and the viewing angle characteristics were high. Further, in the liquid crystal display element of the present embodiment, the occupied area can be formed small due to the structure of the TFT element 919, so that there is an advantage that the aperture ratio of the pixel can be increased. The pixel electrodes divided and formed like the above-mentioned first pixel electrode 7 and second pixel electrode 9 are necessarily divided into only two regions, the first display region and the second display region. Is not limited. For example, in addition to this, a third display area is arranged adjacent to the second display area, and one or more sets of the first and second display areas are provided in the third display area more than the second display area. TF
You may connect a T element.

Since the liquid crystal itself has a dielectric anisotropy, the impedance of the liquid crystal layer 13 is preferably set in consideration of the fact that it changes depending on the applied voltage. .

Further, in the above-described first to fourth embodiments, two TFT elements forming an electric resistance connected to the second pixel electrode 9 are used as one set, but only this is used. Is not limited. For example, the TF connected to the first area
The number of T-elements is set to 2 and the T-element is connected to the second region.
The number of FT elements may be four and two. At this time, it is clear that the greater the difference in the number of sets of TFT elements connected in series, the greater the difference in applied voltage. Therefore, the difference in applied voltage is adjusted depending on the case where the technique of the present invention is used. Therefore, the difference between the sets of TFT elements may be determined.

Further, the first TFT element 15 and the second TFT element 17 used as the electric resistance element of the present invention.
In addition to the above-mentioned applications, such a TFT element as described above is also used when the TFT 5 as a switching element is deteriorated or malfunctions (defectives), by rewiring the wires by a laser repair method or the like. Alternatively, it can be used as a so-called redundant circuit that is used as a switching element. In this case, the first pixel electrode 7
Is electrically connected directly to the signal line 3 and the second pixel electrode 9 is connected to the signal line 3 and the address line 1 via the first TFT element 15 and the second TFT element 17 as switching elements. It is possible to do so.

Needless to say, various changes can be made to the material for forming the liquid crystal display device of the present invention without departing from the scope of the present invention.

[0068]

As is clear from the detailed description above, according to the present invention, a liquid crystal display device having a high display quality can be provided with excellent controllability of gradation display and improved viewing angle characteristics. Can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing an equivalent circuit of a liquid crystal display device of a first embodiment according to the present invention.

FIG. 2 is a plan view showing the structure of the liquid crystal display element according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing a structure of a TFT 5 which is a switching element of the liquid crystal display element of the first embodiment according to the present invention.

FIG. 4 is a plan view (a) showing a structure of a first TFT element 15 and a structure of a second TFT element 17 which form an electric resistance of the liquid crystal display element of the first embodiment according to the present invention and a cross section thereof. Figure (b).

5A and 5B are diagrams showing a result of a measurement experiment of applied voltage-light transmittance characteristics of the liquid crystal display element of the first embodiment according to the present invention, and FIG. 5A showing that of a conventional liquid crystal display element.

FIG. 6 is a plan view showing the structure of a liquid crystal display element according to a second embodiment of the present invention.

FIG. 7 is a plan view showing the structure of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 8 is a sectional view showing a structure of a liquid crystal display element of a third embodiment according to the present invention.

FIG. 9 is a diagram showing an equivalent circuit of a liquid crystal display element according to a third embodiment of the present invention.

FIG. 10 is a diagram showing an equivalent circuit of a conventional liquid crystal display element.

[Explanation of symbols]

1 ... Address line, 3 ... Signal line, 5 ... TFT, 7 ... First pixel electrode, 9 ... Second pixel electrode, 11 ... Counter electrode, 13
... liquid crystal layer, 15 ... first TFT element, 17 ... second TF
T element, 19, 21 ... Liquid crystal cell

Claims (2)

[Claims] 1. A matrix wiring formed of a plurality of address lines and a plurality of signal lines, and an input line connected to the signal line to connect a signal input from the signal line to an output end of the address line. A switching element that is interrupted based on a signal input from the pixel element, a pixel electrode that is connected to the output terminal of the switching element, a counter electrode that faces the pixel electrode, and a pinch between the counter electrode and the pixel electrode. In the liquid crystal display element having a liquid crystal layer, the pixel electrode is divided into at least a pixel electrode in the first display region and a pixel electrode in the second display region, and the pixel electrode in the second display region is a thin film transistor. The 2
A liquid crystal display element, characterized in that it is connected to the output terminal of the switching element through an electric resistance formed by combining the two and is connected in parallel to the pixel electrode of the first display area. 2. A matrix wiring formed of a plurality of address lines and a plurality of signal lines, an input end of which is connected to the signal line, and a conduction of a signal input from the signal line to an output end of the address line. A switching element that connects and disconnects based on a signal input from a line, a pixel electrode of the first display region connected to the output terminal of the switching device, and a pixel electrode of the first display region are connected. The pixel electrode of the second display region formed avoiding the above, the gate is connected to the output end of the switching element, one of the source / drain is connected to the output end of the switching element, and the other is connected to the second end. A first transistor element that is connected to a pixel electrode in the display region and that generates a potential difference when a current flows between the source and the drain; and a gate whose image is in the second display region. One of a source and a drain is connected to the output terminal of the switching element and the other is connected to a pixel electrode of the second display region, and the source terminal and the drain are connected to the output terminal in parallel with the first transistor element. A second transistor element that is interposed between the pixel electrode of the second display region and generates a potential difference when a current flows between the source and the drain; and a pixel of the first display region. An electrode and a counter electrode facing the pixel electrode in the second display area, and a liquid crystal layer sandwiched between the pixel electrode in the first display area and the pixel electrode in the second display area and the counter electrode And a liquid crystal display element.