JP2940354B2 - Liquid crystal display - Google Patents

Abstract

PURPOSE:To obtain an active matrix type liquid crystal display device having such features that the contrast is high, visual angle property is good, a multi- level display can be easily performed, and that the display is bright and the cost is reduced. CONSTITUTION:The device has such a structure that an electric field 7 parallel to a substrate surface is impressed on a liquid crystal composition layer by a thin film transistor provided with a drain electrode 12 and a common electrode 2 which are extending over plural picture elements and a source electrode 1 extending in a direction same as that of the electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor type liquid crystal display device having good mass productivity, low cost and good viewing angle characteristics.

[0002]

2. Description of the Related Art In a conventional thin film transistor type liquid crystal display device, transparent electrodes formed on the interface between two substrates and opposed to each other are used as electrodes for driving a liquid crystal layer. this is,
This is because a display method typified by a twisted nematic display method, which operates by setting the direction of an electric field applied to the liquid crystal to a direction substantially perpendicular to the substrate interface, is employed. On the other hand, as a method of making the direction of the electric field applied to the liquid crystal substantially parallel to the interface of the substrate, a method using a pair of comb electrodes is proposed, for example, in Japanese Patent Publication No. 63-21907. In this case, the electrode does not need to be transparent, and an opaque metal electrode having high conductivity can be used.

[0003]

In the above-mentioned prior art, it is necessary to use a vacuum manufacturing equipment such as a sputtering apparatus to form a transparent electrode typified by ITO, and the equipment cost is enormous. Was. In addition, the use of vacuum manufacturing equipment involves work to remove contamination in the vacuum furnace,
This requires a great deal of time, which significantly increases manufacturing costs. In general, the surface of a transparent electrode has irregularities of about several tens of nm, which makes it difficult to process a fine active element such as a thin film transistor. In addition, the protruding portions of the transparent electrode are often detached and mixed into other parts such as the electrode, causing a dot-like or linear display defect,
The yield was significantly reduced. For these reasons, it has not been possible to stably provide a low-cost liquid crystal display device that meets market needs. In addition, the above-described prior art has many problems in terms of image quality. In particular, the luminance changes when the viewing angle direction is changed is remarkable, and when halftone display is performed, there is a practical problem such that the grayscale level is inverted in each strong direction. Further, the uneven structure of the thin-film transistor element causes an alignment defect domain around the thin-film transistor element, a light-shielding film having a large area is required for the countermeasure, and the light use efficiency is remarkably reduced.

On the other hand, the use of a comb-shaped electrode disclosed in Japanese Patent Publication No. 63-21907 eliminates the need to use a transparent electrode, which may solve the above-mentioned problem. However, it has been put to practical use for the following reasons. Not. That is, in this known technique, since the interdigitated comb-teeth electrode pair is used, the pattern in the pixel becomes fine and complicated, and the mass productivity is extremely low. In particular, in a display having a large amount of display information and a small pixel size, it is almost impossible to insert an electrode having a comb-teeth structure in one pixel. Even if it is inserted, the aperture ratio is extremely low, and almost all light is effectively used. Only a dark display that cannot be realized can be realized. In principle, the aperture ratio can be increased to a practical level if the electrode width of the comb electrode is reduced to about 1 to 2 μm. However, in practice, such fine lines are formed uniformly and without breakage over the entire large substrate. It is extremely difficult to do. That is, in the above-described conventional technology, since the interdigitated comb-shaped electrodes are used, the pixel aperture ratio and the manufacturing yield are in a trade-off relationship, and it is not possible to provide a liquid crystal display device having a bright image at low cost. It was difficult.

The present invention solves these problems at the same time. The object of the present invention is, firstly, to provide a high-contrast, low-cost facility that can be mass-produced with a high yield without using a transparent electrode. An object of the present invention is to provide a thin film transistor type liquid crystal display device. Second, it is an object of the present invention to provide a thin film transistor type liquid crystal display device which can be driven at a low voltage, has good viewing angle characteristics, and can easily perform multi-tone display. Third, the degree of freedom in selecting usable liquid crystal compositions and alignment film materials is increased, thereby increasing the latitude of processes such as liquid crystal panel manufacturing, and achieving both a high aperture ratio and suppression of pixel deterioration.
It is an object of the present invention to provide a brighter thin film transistor type liquid crystal display device having a higher light transmittance. Fourth, in addition to the first to third objects, it is an object of the present invention to provide a thin film transistor type liquid crystal display device having a simpler structure and a high production yield.

[0006]

The liquid crystal display device of the present invention.
Includes at least one of the pair of transparent substrates, a liquid crystal layer held the pair of substrates, one of said pair of substrates, a plurality of signal wiring electrodes, and the plurality of signal wiring electrode matrix A plurality of scanning wiring electrodes formed in a shape, and a plurality of thin film transistors formed corresponding to respective intersections, in each region surrounded by the plurality of signal wiring electrodes and the plurality of scanning wiring electrodes. at least one pixel arrangement, and one common electrode even without least in each pixel, and at least one pixel electrode connected to the corresponding thin film transistor, said at least one common electrode and the at least one the pixel electrode, and in different layers arranged layers of the plurality of scanning wiring electrodes, before
The layer on which the scanning wiring electrodes are arranged is at least an insulating film.
The electrodes are formed in the same layer, and an electric field predominantly parallel to the one substrate is formed between these electrodes.

A pixel adjacent in the direction of the signal wiring electrode is
And each corresponding common electrode is located in an adjacent pixel.
It can be configured to be interconnected with the corresponding common electrode
desirable.

Further , the plurality of common electrodes are connected to the plurality of scan electrodes.
It may be formed on the same substrate as the wiring electrodes.
No.

In addition, signals corresponding to each of a plurality of pixels are provided.
Drain electrodes for multiple thin film transistors
May be connected.

In addition, above or below the scanning wiring electrode,
An insulating layer is formed, and a pixel electrode or
A configuration in which a common electrode is overlapped to form a capacitor
Good.

With the above configuration, the transparent electrode
Is unnecessary and compared with the conventional technology using a comb-shaped electrode pair
Has a simple structure, high aperture ratio and high production yield
Liquid crystal display device can be obtained.

Similarly, the following configuration is added.
This realizes characteristics with good viewing angle characteristics and excellent multi-gradation display capability.
Can be manifested.

When the liquid crystal composition of the liquid crystal layer has a positive dielectric anisotropy,
In some cases, liquid crystal molecules on at least one substrate interface
Angle | φLC | between the orientation direction and the electric field direction must be 45 degrees or more
It is desirable that the angle be less than 90 degrees.

The dielectric anisotropy of the liquid crystal composition of the liquid crystal layer is
Is negative, the liquid on at least one substrate interface
The angle | φLC |
It is preferable to set the temperature to more than 45 degrees.

Further, the liquid on one substrate interface of the liquid crystal layer
ΦLC1 of the orientation direction of the crystal molecules and the liquid on the other substrate interface
The angle φLC2 of the orientation direction of the crystal molecules is substantially parallel to each other (φLC1
≒ φLC2), and the thickness d and the refractive index of the liquid crystal layer are different.
The product d · Δn of anisotropy Δn is from 0.21 μm to 0.36 μm
It is desirable that the thickness d and
The phase difference Rf lower than the product d · Δn of the refractive index anisotropy Δn
The optically anisotropic medium has a phase difference caused by the liquid crystal layer.
Is inserted so as to compensate, and the difference | d · Δn
| − | Rf | is set to 0.21 μm or more and 0.36 μm or less
Configuration is desirable.

The liquid crystal on one substrate interface of the liquid crystal layer
The angle φLC1 of the molecular orientation and the liquid crystal on the other substrate interface
The angle φLC2 of the molecular orientation crosses each other and the angle
Degree | φLC1-φLC2 | is 80 degrees or more and 100 degrees or less,
And the product d · of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn.
Forming Δn between 0.40 μm and 0.60 μm
Is preferred.

By adding the above structure, birefringence
Higher contrast and wider viewing angle depending on the mode
Characteristics can be obtained.

Similarly, on one substrate interface of the liquid crystal layer,
Angle LCLC of the orientation direction of the liquid crystal molecules of
And the angle φLC2 of the alignment direction of the liquid crystal molecules intersects each other,
When the angle | φLC1-φLC2 | is 80 degrees or more and 100 degrees or less
And the thickness d of the liquid crystal layer and the refractive index anisotropy Δn
The product d · Δn must be between 0.40 μm and 0.60 μm.
Is desirable.

When this configuration is added, the optical rotation mode
High contrast and wide viewing angle characteristics can be obtained.

At least one outside of the pair of substrates is
A pair of polarizing means, the polarizing means sandwiching the liquid crystal layer
Is a polarizing plate, the dielectric anisotropy of the liquid crystal composition of the liquid crystal layer is
If it is positive, the long axis direction of the liquid crystal molecules on the substrate interface
The angle φLC with the field direction is one of the pair of polarizing plates.
Larger than the angle φP of the transmission axis (or absorption axis) of the polarizing plate A
And the difference | φLC−φP | is 3 degrees or more and 15 degrees or less
And a liquid crystal composition of a liquid crystal layer.
If the dielectric anisotropy of the liquid crystal is negative,
The angle φLC between the major axis direction of the element and the electric field direction is the absorption of the polarizing plate.
Smaller than the angle φP of the storage axis or transmission axis and the difference
It is preferable that | φP−φLC | is not less than 3 degrees and not more than 15 degrees.
New

As described above, dominantly parallel to the substrate
In a liquid crystal display device in which an electric field is formed,
Liquid crystal of the liquid crystal layer near at least one of the substrates
Molecules should have a tilt angle of 4 degrees or less with respect to the substrate interface.
Is desirable.

The signal applied to a plurality of signal wiring electrodes is
A voltage synchronized with the signal voltage waveform is applied to multiple common electrodes.
Voltage can be applied efficiently at low voltage.
You.

The width of the common electrode is the width of the electrode of the signal wiring.
More than three times, the liquid crystal layer is efficiently charged.
A field can be formed.

[0024] Further , the first pair of substrates may be sandwiched.
It has a pair of polarizing means, and the polarizing means is a pair of polarizing plates.
They are in a bright state when the low voltage VL is applied, and are marked with the high voltage VH.
It is formed so as to be in a dark state upon application, and the pair of polarizing plates
In the meantime, compensate the residual phase difference at the interface of the liquid crystal layer when VH is applied.
A configuration in which a transparent medium is inserted may be adopted.

By adding these structures, the threshold
Use a drive circuit with higher voltage and higher withstand voltage
Issues that need to be available. This
According to this, as in the embodiment, a voltage of less than 10 volts is used.
Operation is possible even with a drive circuit with a lower output voltage.

As another means for increasing the aperture ratio, a small
At least one of them is a pair of transparent substrates and the pair of substrates
In a liquid crystal display device having a sandwiched liquid crystal layer, a pair of
One of the substrates has a plurality of signal wiring electrodes and the plurality of signal wiring electrodes.
A plurality of scanning lines formed in a matrix with signal wiring electrodes
Wire electrode and a plurality of thin film transformers formed at each intersection.
Transistors and a plurality of thin film transistors
Pixel electrodes, and formed in parallel with the plurality of signal wiring electrodes.
A plurality of common electrodes, and the plurality of signal wiring electrodes
And a plurality of scanning wiring electrodes.
The plurality of pixel electrodes and the plurality of common electrodes
By applying a voltage to the electrodes, the plurality of pixel
Dominantly parallel to the substrate surface between the pole and the plurality of common electrodes
A configuration in which an appropriate electric field is formed may be adopted.

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

First, the angle φ _P formed by the polarization transmission axis of the polarizing plate with respect to the direction of the electric field, the angle φ _LC formed by the long axis (optical axis) of the liquid crystal molecule near the interface, and the insertion between the pair of polarizing plates. The angle φ _R formed by the fast axis of the phase difference plate is defined (FIG. 6). Phi _P1 optionally Since the polarizer and the liquid crystal interface is a pair up and down, respectively, φ _P2, φ _LC1, referred to as phi _LC2. FIG. 6 corresponds to a front view of FIG. 1 described later.

Next, the operation of the present invention will be described with reference to FIG.

FIGS. 1A and 1B are side sectional views showing the operation of a liquid crystal in the liquid crystal panel of the present invention, and FIGS. 1C and 1D are front views thereof. In FIG. 1, the thin film transistor element is omitted. Further, in the present invention, a plurality of pixels are formed by forming a stripe-shaped electrode. Here, one pixel portion is shown. FIG. 1A shows a cross section of the cell when no voltage is applied, and FIG. 1C shows a front view at that time. Linear electrodes 1 and 2 are formed inside a pair of transparent substrates, and an alignment control film 4 is coated and aligned thereon. A liquid crystal composition is sandwiched between the two. The rod-shaped liquid crystal molecules 5 have a slight angle with respect to the longitudinal direction of the electrodes 1 and 2 when no electric field is applied, that is, 4 degrees.
It is oriented so that 5 degrees ≦ | φ _LC | <90 degrees. Here, the liquid crystal molecule alignment directions on the upper and lower interfaces are parallel,
That is, φ _LC1 = φ _LC2 will be described as an example. The dielectric anisotropy of the liquid crystal composition is assumed to be positive. Next, when an electric field 7 is applied, the liquid crystal molecules change their directions in the direction of the electric field as shown in FIGS. 1 (b) and 1 (d). By arranging the polarizing plate 6 at a predetermined angle 9, the light transmittance can be changed by applying an electric field. As described above, according to the present invention, it is possible to provide a display that provides a contrast without a transparent electrode. FIG.
In (b), the angle between the substrate surface and the direction of the electric field is large and appears to be non-parallel. However, this is the result of the enlargement in the thickness direction, which is actually 20 degrees or less. Hereinafter, in the present invention, those having an angle of 20 degrees or less are collectively referred to as a lateral electric field.
Although the electrodes 1 and 2 are formed separately on the upper and lower substrates in FIG. 1, the effect does not change even if the electrodes are provided on one substrate. Rather, when patterns such as wiring become finer, heat,
In view of various deformations and the like due to external force and the like, it is desirable to provide the one substrate with higher precision because alignment can be performed with higher accuracy. In addition, the dielectric anisotropy of the liquid crystal composition is assumed to be positive, but may be negative. In this case, the initial alignment state is changed from the direction perpendicular to the longitudinal direction of the electrodes 1 and 2 (electric field direction 7) to a slight angle | φ _LC | (that is, 0 degrees <| φ _LC | ≦ 45 degrees).
Orientation.

The operation of the present invention will be described below in accordance with the three objects.

(1) High Contrast without a Transparent Electrode As a specific configuration for imparting contrast, a mode utilizing the state in which liquid crystal molecules on upper and lower substrates are almost parallel (interference due to birefringence phase difference) is used. In this case, the color is used, which is referred to as a birefringence mode), and a mode in which the liquid crystal molecules on the upper and lower substrates intersect and the molecular arrangement in the cell is twisted (the polarization plane in the liquid crystal composition layer). Uses the optical rotation that rotates, so that it is called an optical rotation mode here). In the birefringence mode, the direction of the molecular long axis (optical axis) is changed in the plane by applying a voltage while the direction of the molecular long axis (optical axis) is substantially parallel to the substrate interface, and the angle formed with the axis of the polarizing plate set at a predetermined angle is changed. Change the transmittance. In the optical rotation mode, similarly, only the orientation in the molecular major axis direction is changed by applying a voltage, but in this case, the change in optical rotation caused by the loosening of the helical line is used.

Next, the quantitative structure and operation for increasing the contrast ratio by making the display an achromatic color will be described below in two cases, that is, the case where the birefringence mode is used and the case where the optical rotation mode is used.

I. Light transmission T / T _o when generally inserted between two polarizing plates were orthogonally arranged uniaxial birefringent medium when displaying in birefringence mode is expressed by the following equation. Here, χ _eff is the effective optical axis direction of the liquid crystal composition layer (the angle between the optical axis and the polarization transmission axis), d _eff is the effective thickness of the birefringent liquid crystal composition layer, and Δn is The refractive index anisotropy, λ, represents the wavelength of light. Here, the purpose of setting the optical axis direction of the liquid crystal composition layer as an effective value is that liquid crystal molecules are fixed on the interface in the actual cell, and all liquid crystal molecules are parallel to each other in the cell when an electric field is applied. In addition, in consideration of the fact that the orientation is not uniform and large deformation occurs particularly in the vicinity of the interface, the average value thereof is treated as an apparent value when a uniform state is assumed.

T / T _o = sin ² (2χ _eff ) · sin ² (πd _eff · Δn / λ) (1) Normally closed, which is dark when a low voltage V _{L is} applied and bright when a high voltage V _{H is} applied. In order to obtain the characteristics, the polarizing plate is arranged such that the transmission axis (or absorption axis) of one of the polarizing plates is substantially parallel to the liquid crystal molecule alignment direction (rubbing axis), that is, φ _P1 ≒ φ _LC1 =
φ _LC2, and the transmission axis of the other polarizing plate may be perpendicular to it, that is, φ _P2 = φ _P1 +90 degrees. When no electric field is applied,
Since χ _{eff in} equation (1) is 0, the light transmittance T / T _o
Is also 0. On the other hand, when an electric field is applied,
The value of _eff increases and reaches a maximum at 45 degrees. At this time, assuming that the wavelength of the light is 0.555 μm, the effective d _eff · Δn may be set to 0.28 μm, which is a half wavelength, in order to obtain an achromatic color and maximize the transmittance. Actually, since there is a margin, it is sufficient that the distance is between 0.21 and 0.36 μm, but it is desirable to set a value between 0.24 and 0.33 μm.

On the other hand, in order to obtain a normally open characteristic in which a light state is applied when the low voltage V _{L is} applied and a dark state is applied when the high voltage V _{H is} applied, when no electric field is applied or when a low electric field is applied, the following equation (1) is used.
_What is necessary is just to set the polarizing plate arrangement so that _eff becomes approximately 45 degrees. When an electric field is applied, the value of χ _eff decreases in accordance with the strength, contrary to the case of normally closed. However, even when _{eff eff} becomes minimum (ie, 0), considerable light leaks as it is because of the residual phase difference of the liquid crystal molecules fixed near the interface. d.Δn is 0.27 to 0.2.
According to experiments performed by the present inventors in which the effective voltage was set to 37 μm and an effective voltage of 3 to 10 V was applied, the value of the interface residual phase difference was about 0.02 to 0.06 μm. Therefore, 0.0
By inserting a retardation plate having a birefringence retardation of about 2 to 0.06 μm (this retardation is represented as R _f ) so as to compensate for the interface residual retardation, the dark state sinks and the high contrast ratio is reduced. Is obtained. The angle φ of the fast axis of the phase difference plate
_R is the effective optical axis of the liquid crystal composition layer when voltage is applied χ _eff
Parallel to In order to reduce the brightness of the dark state more completely, it is sufficient to exactly match the residual phase difference when a voltage for displaying the dark state is applied. As described above, in order to achieve both the sinking in the dark state and the transmittance and whiteness in the bright state, it is only necessary to satisfy the following equation.

[0041] 0.21μm <(d · Δn-R f) <0.36μm ... (2) preferably, 0.23μm <(d · Δn- R f) <0.33μm ... (3) II. Displaying in optical rotation mode Twisted Nemat (conventional method)
ic: TN) system, as generally known, d · Δn
Is set near 0.50 μm, which is the first minimum condition, high transmittance and achromatic color are obtained. In consideration of the margin, in the TN system, it is preferable to set the distance between 0.40 and 0.60 μm. The polarizing plate is arranged such that the transmission axis (or absorption axis) of one of the polarizing plates is substantially parallel to the liquid crystal molecule alignment direction (rubbing axis) on the interface, that is, φ _LC1 ≒ φ _LC2 . In order to realize a normally closed type, the transmission axis of the other polarizing plate may be made parallel to it, and to make it a normally open type, it may be made vertical.

In order to completely eliminate the optical rotatory power, it is necessary to make the liquid crystal alignment directions near the upper and lower substrate interfaces substantially parallel. You have to rotate the molecule by almost 90 degrees. When displaying in the birefringent mode, the liquid crystal molecule rotation angle may be about 45 degrees, and the threshold voltage is lower in the birefringent mode.

(2) Improvement of Viewing Angle Characteristics In the display mode of the present invention, the major axis of the liquid crystal molecules is always almost parallel to the substrate and does not rise, so that the change in brightness when the viewing angle direction is changed is small. In this display mode, a dark state is not obtained by making the birefringence phase difference substantially zero by applying a voltage as in the prior art, and the angle between the long axis of the liquid crystal molecules and the axis (absorption or transmission axis) of the polarizing plate is formed. To change,
Fundamentally different. In the case where the long axis of the liquid crystal molecule rises perpendicularly to the substrate interface as in a conventional TN type, the viewing angle direction in which the birefringence phase difference becomes 0 is only the front direction, that is, the direction perpendicular to the substrate interface. Birefringence phase difference appears,
In the normally open type, light leaks, causing a decrease in contrast and a reversal of a gradation level.

(3) Improving the degree of freedom in selecting an alignment film material and a liquid crystal material, and thereby increasing the process latitude. Further, since the liquid crystal molecules do not rise, a large inclination angle (the liquid crystal molecule length) as in the related art is used. An orientation film that gives the angle between the axis and the interface) is not required. In the conventional method, if the inclination angle is insufficient, two states having different inclination directions and a domain at a boundary between the two states are generated, which may cause a display failure. In this method, the major axis direction (rubbing direction) of the liquid crystal molecules on the substrate interface may be set to a predetermined direction shifted from 0 or 90 degrees with respect to the electric field direction, instead of providing the tilt angle. For example, when the dielectric anisotropy of the liquid crystal composition is negative, the angle φ _LC (defined as φ _LC > 0 degree) between the direction of the electric field and the direction of the long axis of the liquid crystal molecule on the substrate interface is 0 degree or more ( (Substantially 0.5 degrees or more), and preferably 2 degrees or more. If the angle is completely 0 degrees, two types of deformation in different directions occur, and two different states and domains at their boundaries occur, which may result in display failure. If it is 0.5 degrees or more, the apparent liquid crystal molecule major axis direction (defined as φ _LC (V)) uniformly increases due to the application of an electric field and an increase in the intensity, and the tilt in the opposite direction, that is, φ _LC (V) <0 degrees. As described above, in the present method, even when the angle (inclination angle) between the interface and the liquid crystal molecule is small, the operation is performed without generating a domain, and therefore, it is possible to set a lower inclination angle.
The uniformity of the liquid crystal molecule alignment is better as the lower the inclination angle, the higher the process margin such as rubbing. Therefore, if a low tilt angle is combined with the present method in which an electric field is applied in parallel to the interface, the liquid crystal molecule alignment becomes more uniform, and the display unevenness can be suppressed to be lower than in the conventional method even if there is a similar manufacturing process variation. . Generally, the types of alignment films that provide a high tilt angle are fewer than those that provide a low tilt angle,
The use of this method increases the degree of freedom in selecting the alignment film material. For example, even if an organic polymer is used for the flattening film on the color filter and the protective film on the thin film transistor, and it is directly subjected to a surface alignment treatment such as rubbing, the tilt angle is unnecessary, and the dual use of the alignment film becomes easier. Further, it is possible to simplify the process and reduce the cost associated therewith. In order to suppress display unevenness due to manufacturing process fluctuation, the tilt angle should be 4 degrees or less,
Desirably, the temperature may be set to twice or less.

Further, the degree of freedom in selecting a liquid crystal material is increased for the following reasons. That is, in the present invention, the pixel electrode and the common electrode have a structure in which an electric field is applied to the liquid crystal composition layer mainly in parallel with the substrate interface, and the distance between the electrodes is a conventional vertical electric field type active matrix type liquid crystal. The distance can be larger than the distance between the opposed transparent electrodes in the display device. Further, the equivalent electrode cross-sectional area can be suppressed smaller than that of the conventional electrode. Therefore, the electric resistance between the pair of pixel electrodes according to the present invention can be increased by an order of magnitude between the opposed transparent electrodes in the conventional active matrix type liquid crystal display device. Furthermore, the capacitance between the pixel electrode and the common electrode according to the present invention is connected in parallel with the capacitance element, and a capacitance element with sufficiently high electric resistance can be realized. Accordingly, it is easy to hold the charge accumulated in the pixel electrode, and sufficient holding characteristics can be obtained even if the area of the capacitor which has conventionally sacrificed the aperture ratio is reduced. In addition, conventionally, a liquid crystal composition having a very high specific resistance of, for example, 10 ¹² Ωcm is required, but a liquid crystal composition having a lower specific resistance does not pose a problem. This not only increases the degree of freedom in selecting the liquid crystal material, but also increases the process latitude. That is, even if the liquid crystal is contaminated during the process, the image quality is not likely to be poor. In particular, the tolerance for the variation on the interface with the alignment film described above is increased, and defects due to the interface are almost eliminated. Therefore, steps such as inspection and aging can be greatly simplified, which greatly contributes to the cost reduction of the thin film transistor type liquid crystal display device. Further, since the pixel electrode according to the present invention has a simpler shape than the comb-like electrode pair, the light use efficiency is improved. There is no need to sacrifice the opening to obtain a capacitor capable of storing a sufficient amount of charges as in the conventional method. Furthermore, if the insulating film that protects the thin film transistor is made of an organic material, the dielectric constant can be made lower than that of an inorganic material. Therefore, the electric field component generated in the vicinity of the pixel electrode in the direction perpendicular to the substrate interface is suppressed to be smaller than the horizontal electric field component. And the liquid crystal operates in a wider area. This also contributes to brightness improvement. Further, when the common electrode is shared with the common electrode of an adjacent pixel, the same operation as the common electrode in the conventional active matrix type liquid crystal display device can be performed, and the structure can be further simplified. It is possible to increase the aperture ratio.

(4) Realization of a Simple Thin Film Transistor Structure with a High Aperture Ratio and Improvement of Brightness Therewith Regarding the structure in a pixel including a thin film transistor, a comb-shaped electrode disclosed in a known example (Japanese Patent Publication No. 63-21907). In the case of using, there is a problem that the aperture ratio is remarkably reduced, whereby the brightness is reduced. In consideration of mass productivity, the width of one comb tooth electrode is required to be about 8 μm and at least 4 μm or more. For example, as shown in FIG.
The structure is such that there are a total of 17 comb teeth like diagonal 9.
It is impossible to form a 0.3 × 0.1 mm ² pixel of the 4-inch color VGA class. The present invention has been devised as means for maintaining the aperture ratio sufficiently while maintaining the advantages of the above (1) and (2). Instead of a structure in which the aperture ratio has to be reduced like a comb tooth, a practically high aperture ratio can be realized by a simpler electrode structure. Means 1 to 5 relate to the structure when the common electrode is formed on the opposite substrate or the pixel electrode is formed on the same layer.
In the above-mentioned known example (Japanese Patent Publication No. 63-21907), in order to form a comb-tooth electrode, the leading directions of the signal wiring and the common electrode are made orthogonal. That is, the signal wiring is connected in the first direction (Y
Direction), the common electrode is extended in a direction (X direction) orthogonal to the common electrode. On the other hand, the present invention avoids a complicated structure like a comb tooth by extending all of the signal wiring, the pixel electrode, and the common electrode in the first direction as in the means 1. In order to reduce the threshold voltage of the liquid crystal and shorten the response time, the distance between the pixel electrode and the common electrode may be reduced. There is no need for a simple structure.

[0047]

EXAMPLES The present invention will be specifically described with reference to examples.

Example 1 The substrate had a thickness of 1.1 mm.
Use two transparent glass substrates whose surfaces have been polished. The dielectric anisotropy Δε is positive and 4.5 between these substrates, and the refractive index anisotropy Δn is 0.072 (589 nm, 20 nm).
C)). Rubbing the polyimide alignment control film applied to the substrate surface to 3.5
Degree of pretilt angle. The rubbing directions on the upper and lower interfaces are almost parallel to each other, and the angle between the rubbing directions and the direction of the applied electric field is 8 °.
5 degrees (φ _LC1 = φ _LC2 = 85 °). The gap d was 4.5 μm in a state in which liquid crystal was sealed, with spherical polymer beads dispersed and sandwiched between substrates. Therefore, Δn · d is 0.324
μm. The panel is sandwiched between two polarizing plates (G1220DU manufactured by Nitto Denko Corporation), and the polarizing transmission axis of one of the polarizing plates is substantially parallel to the rubbing direction, that is, φ _P1 = 85 °, and the other is orthogonal to it, ie, φ _P2 = −5 °. As a result, normally closed characteristics were obtained.

As shown in FIG. 2A (front view) and FIG. 2B (side sectional view), the structure of the thin film transistor and various electrodes is such that the thin film transistor element (hatched portion in FIG. 2) is a pixel electrode (source electrode). 1, a signal electrode (drain electrode) 12,
And a scanning electrode (gate electrode) 10, the pixel electrode 1 extends in a first direction (in FIG. 2, means a vertical direction in the plane of FIG. 2), and the signal electrode 12 and the common electrode 2 The thin film transistor element extends between the common electrodes in the first direction extending between them (in FIG. 2, it means pixels arranged vertically in the plane of the paper).

A signal waveform having information is applied to the signal electrode 12, and a scanning waveform is applied to the scanning electrode 10 in synchronization with the signal waveform. Amorphous silicon (a-S
i) and a silicon nitride (Si)
The thin film transistor including the N) protective insulating film 15 is disposed between adjacent common electrodes. An information signal is transmitted from the signal electrode 12 to the pixel electrode 1 via the thin film transistor, and a voltage is applied between the common electrode 2 and the liquid crystal portion. In this embodiment, the common electrode is arranged on the counter substrate side, and FIG.
In (b), since the thickness direction is enlarged, it appears that the electric field direction 7 is inclined. However, in practice, the thickness of the liquid crystal layer 5 is about 6 μm with respect to the width of 48 μm, and the inclination is almost zero. Instead, the direction of the applied electric field is substantially parallel to the substrate surface.

The capacitive element 11, as shown in FIG. 2 (a), forming a protrusion on the pixel electrode 1 was formed as a structure sandwiching the gate insulating film 13 on the run査配line 10. The capacitance of the capacitance element 11 became about 21 fF.

The electric charge stored in the pixel electrode 1 is stored in the capacitance between the pixel electrode 1 and the common electrode 2 and about 24 fF, which is a capacitance in which the additional capacitance element 11 is connected in parallel. Even if the specific resistance of the object 50 is 5 × 10 ¹⁰ Ωcm, the voltage fluctuation of the pixel electrode 1 can be suppressed. For this reason, it was possible to prevent image quality deterioration.

The number of pixels is 40 (× 3) × 30, and the pixel pitch is 80 μm in the horizontal direction (namely, between the common electrodes) and 240 μm in the vertical direction (namely, between the scan electrodes). Scan electrode width is 1
The gap between adjacent scanning electrodes is set to 68 μm at 2 μm, and
%. Also, a stripe-shaped R,
G, B color filters were provided. A transparent resin for flattening the surface was laminated on the color filter. Epoxy resin was used as the material of the transparent resin. Further, a polyimide-based orientation control film was applied on the transparent resin. A drive circuit is connected to the panel. FIG. 8 shows the configuration of the drive circuit system according to the present embodiment. The signal electrode 23 and the common electrode 31 extend to the end of the display unit. 9 and 10 show the configuration of the optical system. FIG. 9 shows a transmission type, and FIG. 10 shows a reflection type.

In this embodiment, since no transparent electrode is required, the manufacturing process can be simplified and the yield can be improved.
The cost can be significantly reduced. In particular, extremely expensive equipment having a vacuum furnace for forming a transparent electrode is not required,
This makes it possible to significantly reduce the amount of investment in manufacturing equipment and thereby reduce costs. FIG. 3A shows the electro-optical characteristics showing the relationship between the effective value of the voltage applied to the pixel and the brightness in this embodiment.
The contrast ratio becomes 150 or more at the time of 7V drive, and the difference between the curves when the viewing angle is changed left and right and up and down is extremely small as compared with the conventional method (shown in Comparative Example 1). Even when the viewing angle is changed, the display characteristics hardly change. Did not. In addition, the liquid crystal alignment was good, and no alignment defect domain was generated. Further, the aperture ratio secured a sufficiently high value of 50% by simplification of the thin film transistor and electrode structure, and a bright display was realized. The average transmittance of the entire panel was 8.4%. Here, the brightness was defined as a luminance transmittance when two polarizing plates were arranged in parallel.

[Embodiment 2] In this embodiment, the common electrode disposed on the counter substrate side in the embodiment 1
It was placed on the same substrate side and the substrate placing the scan electrodes.
Other configurations are the same as those of the first embodiment. FIG. 4 shows a cross-sectional structure of the thin film transistor and the electrode. The pixel electrode 1, the signal electrode 12, and the scanning electrode 10 were all formed of aluminum, and were simultaneously formed and etched. No conductive substance exists on the opposing substrate. Therefore, in the configuration of the present embodiment, even if conductive foreign matter is mixed during the manufacturing process, the failure rate of the touch between the upper and lower electrodes is suppressed to zero. The material for the electrode is not particularly limited as long as it is a metallic material having a low electric resistance, and may be chromium, copper, or the like.

In general, the alignment accuracy of a photomask is significantly higher than the alignment accuracy of a combination between two glass substrates facing each other. Therefore, as in the present embodiment, 4
It is better to form all kinds of electrode groups on one substrate,
Since the alignment at the time of forming each electrode is performed only by the photomask, the misalignment between the electrodes is suppressed to be small. Therefore, the present embodiment is effective for forming a higher definition pattern as compared with the case where the scanning electrodes are formed on the counter substrate.

As in the case of Example 1, a bright display having a wide viewing angle characteristic was obtained.

[Embodiment 3] The configuration of this embodiment is the same as Embodiment 1 except for the following requirements.

As shown in FIG. 5, the structure of the thin film transistor and the various electrodes is such that the signal electrode 1 is interposed between the pixel electrodes 1 forming a pair.
2 and a pair of common electrodes 2 were arranged outside these electrodes. A signal waveform having information is applied to the signal electrode 12, and a scanning waveform is applied to the scanning electrode 10 in synchronization with the signal waveform. Amorphous silicon (a
-Si) 16 and a thin-film transistor comprising a protective insulating film 15 of silicon nitride (SiN) are arranged substantially at the center of a pair of common electrodes. The same information signal is transmitted from the signal electrode 12 to the two first electrodes 1 via the two thin film transistors, and the same voltage signal is applied to the liquid crystal portion between the common electrodes on both sides having the same potential. By doing so, the electrode spacing can be reduced to about half without complicating the structure of the thin film transistor and the electrode, and a higher electric field can be applied at the same voltage, thereby reducing the driving voltage and achieving a high-speed response. Is done.

The wide viewing angle characteristics and brightness of the first embodiment are also realized in this embodiment.

[Embodiment 4] The configuration of this embodiment is the same as Embodiment 1 except for the following requirements.

A flattening film 14 (FIG. 2B) made of a transparent polymer is laminated as an organic insulating layer on the color filter.
The surface was directly rubbed without forming another film as an orientation control film thereon. Epoxy resin was used as the material of the transparent polymer. This epoxy resin has both functions of flattening and controlling the alignment of liquid crystal molecules. The liquid crystal composition layer was in direct contact with the epoxy resin, and the tilt angle at the interface was 0.5 degrees. Thereby, the step of applying the alignment film was eliminated, and the production was easier and shorter. Generally, in the conventional TN type, the characteristics required for the orientation control film are diversified, and it is necessary to satisfy all of them. Therefore, it is limited to some materials such as polyimide. A particularly important characteristic is the tilt angle. However, as mentioned in the operation, the present invention does not require a large tilt angle, and therefore,
The choice of materials is significantly improved.

When the electro-optical characteristics in this embodiment were measured, it was found that the difference between the curves when the viewing angle was changed left and right and up and down was extremely small, and the display characteristics hardly changed, as in the first embodiment. In addition, although the tilt angle was as small as 0.5 degree, the liquid crystal alignment was good, and no alignment defect domain was generated.

[Embodiment 5] The transparent polymer for flattening in Embodiment 4 was changed from an epoxy resin to a polyimide resin.
Similarly, the surface of the polyimide resin was directly rubbed to have both functions of flattening and controlling the alignment of liquid crystal molecules. The angle of inclination at the interface was 2 degrees. As a result, the display characteristics were hardly changed as compared with the other examples. Also,
The liquid crystal alignment was good, and no alignment failure domain was generated.

Embodiment 6 The configuration of this embodiment is the same as that of Embodiment 1 except for the following requirements.

A protective insulating film 1 for protecting a thin film transistor
5 (FIG. 2B) is changed from silicon nitride to an organic insulating layer made of epoxy resin, and rubbing is performed directly on the organic insulating layer to make the organic insulating layer have both functions of a protective film and a liquid crystal molecular alignment control film. Was. The tilt angle is 0.5 degrees.

When the electro-optical characteristics in this embodiment were measured, display characteristics which were almost the same as those in Example 1 were obtained. Further, similarly to the fourth embodiment, the inclination angle is 0.5.
Despite the small degree, the liquid crystal alignment was good, and no alignment defect domain was generated.

[Example 7] The epoxy resin used for the protective film in Example 6 was similarly changed to polyimide to be an organic insulating layer.

When the electro-optical characteristics in this embodiment were measured, display characteristics which were almost the same as those in Example 1 were obtained. In addition, the tilt angle slightly increased to 2.0 degrees as compared with Example 6. The liquid crystal alignment was good, and no alignment defect domain was generated.

[Embodiments 8 to 12] The constructions of these embodiments are the same as those of the embodiment 7 except for the following requirements.

In Example 8, the major axis directions (rubbing directions) of the liquid crystal molecules on the upper and lower interfaces are substantially parallel to each other, and the angle between them and the direction of the applied electric field is 89.5 degrees (φ _LC1 = φ _LC2 = 89.5).
°), the polarization transmission axis of one of the polarizing plates is substantially parallel to the rubbing direction (φ _P1 = 89.5 °), and the other is perpendicular to it (φ _P2
= −0.5 °).

Similarly, in the ninth embodiment, φ _LC1 = φ _LC2 = φ _P1 =
88 ° and φ _P2 = −2.0 °. Similarly, in Example 10, φ _LC1 = φ _LC2 = φ _P1 = 75 ° and φ _P2 = −25 °. Similarly, in the eleventh embodiment, φ _LC1 = φ _LC2 = φ _P1 = 45
° and φ _P2 = -45 °. Similarly, in Example 12, φ
_{LC1 = φ LC2 = φ P1 =} 30 °, and a φ _P2 = -60 °. FIG. 7 shows the measurement results of the electro-optical characteristics in these examples. In this case, the brightness is represented by a normalized value in which the maximum is 100% when the applied voltage is in the range of 0 to 10 volts (effective value _Vrms ), and the minimum is 0% when the applied voltage is minimum. By increasing the angle φ _LC , the threshold characteristic curve tended to be steeper. In order to perform halftone display with a large voltage margin, φ _LC may be reduced, but when the angle is 45 degrees or less, the brightness tends to decrease. The optimum value of the angle φ _LC depends on the number of halftone levels to be displayed, the required value for brightness, the driving voltage, and whether or not a voltage is applied to the common electrode. The designer, φ
_The threshold characteristics can be controlled in a large range by selecting the _LC . In consideration of brightness, it is desirable to set φ _LC to 45 degrees or more. Still more preferably, from 60 degrees to 8
It should be between 9.5 degrees.

When the viewing angle characteristics were measured, the difference between the curves when the viewing angle was changed left and right and up and down was extremely small, and the result was that the display characteristics hardly changed in any case, as in the case of Example 1. In addition, the liquid crystal alignment was good, and no alignment defect domain was generated.

[Embodiments 13 to 16] The biggest difference between the above embodiments and this embodiment is that the value of the dielectric anisotropy of the liquid crystal composition layer was made negative and the rubbing direction was changed accordingly. It is. Δε is -4.8, Δn is 0.0437 (589n
m, 20 ° C.) nematic liquid crystal composition (manufactured by Merck, Z
LI-2806) was used. In Examples 13 to 16, all of the liquid crystal molecule major axis directions (rubbing directions φ _LC1 and φ _LC2 ) on the upper and lower interfaces are almost parallel to each other (φ _LC1
= Φ _LC2 ), and the angle φ _LC1 with the direction of the applied electric field was set to a range of more than 0 degree and less than 45 degrees. The polarization transmission axis (φ _P1 ) of one polarizing plate is almost parallel to the rubbing direction,
The other (φ _P2 ) was made orthogonal to it.

That is, in the thirteenth embodiment, φ _LC1 = φ _LC2 = φ _P1
= 1.5 ° and φ _P2 = -88.5 °.

In the fourteenth embodiment, φ _LC1 = φ _LC2 = φ _P1 = 15
° and φ _P2 = -75 °.

In the fifteenth embodiment, φ _LC1 = φ _LC2 = φ _P1 = 30
° and φ _P2 = -60 °.

In the sixteenth embodiment, φ _LC1 = φ _LC2 = φ _P1 = 45
° and φ _P2 = -45 °.

The gap d was 6.3 μm when the liquid crystal was sealed, and Δn · d was 0.275 μm. The conditions other than the structure of the thin film transistor and the electrode are the same as those of the third embodiment.

FIG. 11 shows the measurement results of the electro-optical characteristics in these examples. Contrary to the case where the dielectric anisotropy is positive, the threshold characteristic curve tends to be steeper as the angle φ _LC is made smaller. In order to perform the halftone display with a large voltage margin, it is _sufficient to increase φ _LC , but the brightness tends to decrease when the angle exceeds 45 degrees. As in the case where the dielectric anisotropy is positive, the optimal value of the angle φ _LC depends on the number of halftone levels to be displayed, the required value for brightness, the driving voltage, and whether or not to apply a voltage to the common electrode. Be replaced by The designer can control the threshold characteristics over a large range by selecting φ _LC . In consideration of brightness, it is more preferable to set φ _LC to 45 degrees or less.

When the viewing angle characteristics were measured, the difference between the curves when the viewing angle was changed to the left, right, up and down was very small, and the result was that the display characteristics hardly changed in any case as in Example 1. . In particular, no inversion of the level in the case of halftone display (8 gradations) was observed at all in the range of ± 50 degrees in the vertical and horizontal directions. In addition, the liquid crystal alignment was good, and no alignment defect domain was generated.

[Embodiments 17 to 19] In this embodiment, the embodiment 1 having the best characteristics in the embodiments 13 to 16 is shown.
4 (φ _LC1 = φ _LC2 = φ _P1 = 15 °, φ _P2 = −75 °) with the same direction of the long axis of the liquid crystal molecules and the arrangement of the polarizing plates, and the thickness d of the liquid crystal composition layer and the refractive index anisotropy Δn The product d · Δn was changed.
The thickness d of the liquid crystal composition layer in each of Examples 17, 18, and 19 was 4.0, 4.9, 7.2 μm, that is, d · Δn was 0.1748, 0.2141, 0.3146 μm, respectively. Here, while the refractive index anisotropy Δn was fixed and only the thickness d of the liquid crystal composition layer was changed, similar to other liquid crystal display methods (for example, a 90 degree twisted nematic method),
Even if the refractive index anisotropy Δn is changed, similar results can be obtained for the optimum value of the brightness. Similar results are obtained even when the value of the dielectric anisotropy of the liquid crystal composition layer is made positive. The results, including the results of Example 14, are collectively shown in FIG. FIG.
2A shows the applied voltage on the horizontal axis, and FIG.
In (a), the applied voltage is fixed at 7 volts, and the horizontal axis is d.
It is expressed as Δn. As is clear from FIG. 12B, the brightness strongly depends on d · Δn, and there is an optimum value. To make the brightness 30% or more, which is practical, d.Δn should be between 0.21 and 0.36 μm. To further increase the brightness to 50% or more, 0.2.
What is necessary is just to set it between 3 and 0.33 μm. In consideration of mass productivity such as control of the liquid crystal encapsulation time and the thickness of the liquid crystal composition layer, it is preferable that the value of d be 5.0 μm or more and Δn be 0.08 or less as in this embodiment.

[Embodiments 20 to 22] As is clear from the results of Embodiments 17 to 19, the optimum value of d · Δn is 0.21.
To 0.36 μm, preferably 0.23 to 0.33
μm. Considering that the thickness of the mass-producible liquid crystal composition layer is 5.0 μm or more, the refractive index anisotropy Δ
The value of n must be less than 0.072, preferably less than 0.066. However, there are very few types of liquid crystal compounds having such a very low Δn, and it is difficult to sufficiently achieve compatibility with other practically required characteristics. Therefore, the value of d · Δn of the liquid crystal composition layer is set to be slightly higher, and the amount exceeding the optimum value is set to an optically anisotropic medium having a phase difference R _f lower than d · Δn of the liquid crystal composition layer. Is inserted so as to compensate for the phase difference caused by the liquid crystal composition layer. As a result, the effective phase difference between the liquid crystal composition layer and the optically anisotropic medium is 0.21 to 0.2, which is the optimum value. A method was devised so as to be between .36 μm.

In Examples 20 to 22, the configuration was the same as Example 3 except for the following conditions. The thicknesses of the liquid crystal composition layers were 5.0, 5.2, and 5.5 μm, respectively. Since a nematic liquid crystal composition having a refractive index anisotropy Δn of 0.072 (589 nm, 20 ° C.) is used, the value of d · Δn is 0.360,
0.3744, 0.396 μm. If this goes on,
Since the brightness and the color tone are higher than the good range of 0.21 to 0.36 μm, the color is orange. An optically anisotropic medium of a uniaxially stretched film made of polyvinyl alcohol was laminated on the liquid crystal cell so as to compensate for the birefringence phase difference of the liquid crystal during low voltage driving (here, 0 volt). That is, φ _{R is set} to 85 degrees, which is the same as φ _LC1 (= φ _LC2 ). The phase difference R _f is 0.07, 0.08, 0.10, respectively.
μm, and the value of (d · Δn−R _f ) is 0.29, 0.30
0.21 with good brightness and color tone of 44,0.296 μm
From 0.36 μm.

As a result, a bright display with no coloration and a brightness of 50% or more was obtained.

Example 23 The liquid crystal composition layer of Example 20 had a negative dielectric anisotropy Δε and a value of −2.5,
The composition was changed to a nematic liquid crystal composition having a Δn of 0.0712 (589 nm, 20 ° C.) (manufactured by Merck, ZLI-4518). Other configurations are the same as those of the fourteenth embodiment except for the following.
The thickness of the liquid crystal composition layer is 5.5 μm, that is, d · Δn is 0.3.
916 μm. This liquid crystal cell has a phase difference R _f of 0.11.
The optically anisotropic medium of a polyvinyl alcohol uniaxially stretched film having a thickness of μm is laminated, and the value of (d · Δn−R _f ) is set to 0.1.
0.216 to 0.36 with good brightness and color tone of 2816 μm
It was set within the range of μm.

As a result, a bright display having no coloration and a brightness of 50% or more was obtained.

[Embodiment 24] The configuration of this embodiment is the same as Embodiment 8 except for the following requirements.

The Δn of the liquid crystal composition layer was 0.072 and the gap d was 7.0 μm. Therefore, Δn · d is 0.504μ
m. φ _LC1 is 89.5 degrees, and the liquid crystal molecule alignment directions on the upper and lower substrates are crossed with each other, and | φ _LC1 −φ _LC2 | = 9
0 degrees. The arrangement of the polarizing plates is orthogonal to each other (| φ _P2 −φ _P1
| = 90 °), and φ _LC1 = φ _P1 so that the relationship with the liquid crystal molecule alignment direction becomes an optical rotation mode. As a result, a normally open type was obtained.

When the electro-optical characteristics of this embodiment were measured, the brightness was the same except that the threshold voltages V ₁₀ and V ₉₀ were about twice as large as those of the other embodiments in the birefringence mode. When the viewing angle was changed to left and right and up and down, the difference between the curves was extremely small, and the display characteristics were hardly changed. In addition, the liquid crystal alignment is good,
No misalignment domain occurred.

Embodiments 25 and 26 The configuration of this embodiment is the same as Embodiment 1 except for the following requirements.

The arrangement of the polarizing plates was set so that a dark state could be obtained when the electric field was slightly applied instead of 0. That is, | φ _LC1 −φ _P1 |
Every time, and 15 degrees, | φ _P2 -φ _P1 | = was 90 degrees.

As in the other examples, good display characteristics were obtained in both brightness and viewing angle. In addition, the liquid crystal alignment was good, and no alignment defect domain was generated.

[Embodiments 27 and 28] The structure of this embodiment is the same as that of Embodiment 14 except for the following requirements.

The arrangement of the polarizing plates was set so that a dark state was obtained when the electric field was slightly applied instead of 0. That is, | φ _P1 −φ _LC1 |
And 7 degrees, and | φ _P2 −φ _P1 | = 90 degrees. Also,
The thickness d of the liquid crystal composition layer was 6.3 μm. Therefore, Δ
n · d is 0.275 μm.

FIG. 13 shows the measurement results of the electro-optical characteristics in this embodiment. In the case of the twenty-seventh embodiment, the dark state voltage V _OFF is 3.0 volts, and the brightest voltage V _ON is 9.2.
It was a bolt. If the driving is performed between V _OFF and V _ON , a sufficiently high contrast can be obtained. Similarly, Example 28
In this case, V _OFF was 5.0 volts and V _ON was 9.0 volts.

When driven between V _OFF and V _ON , good display characteristics were obtained in both brightness and viewing angle, as in the other embodiments. In addition, the liquid crystal alignment was good, and no alignment defect domain was generated.

[Embodiment 29] The structure of this embodiment is the same as Embodiment 27 except for the following requirements.

An image signal was applied to the signal electrode, and an AC waveform of 3.0 V was applied to the common electrode. As a result, the voltage supplied to the signal electrode is reduced (from 8.3V to 6.2V).
Was realized.

In this manner, driving was performed between V _OFF and V _ON , and good display characteristics were obtained in both brightness and viewing angle as in the other embodiments. In addition, the liquid crystal alignment was good, and no alignment defect domain was generated.

[Embodiment 30] The structure of this embodiment is the same as Embodiment 1 except for the following requirements.

The arrangement of the polarizing plates was set so that a dark state was obtained when an electric field was applied instead of 0. That is,
| φ _LC1 −φ _P1 | was 45 degrees, and | φ _P2 −φ _P1 | was 90 degrees. This resulted in a bright state when a low voltage was applied and a dark state when a high voltage was applied. The measurement result of the voltage dependence of the brightness at this time is shown by a solid line in FIG.

As in the other examples, good display characteristics were obtained in both the brightness and the viewing angle. The contrast ratio was 35. In addition, the liquid crystal alignment was good, and no alignment defect domain was generated.

[Example 31] In the structure of Example 30, a birefringent medium (uniaxially stretched polyvinyl alcohol film) for compensating for the residual phase difference between interfaces between two polarizing plates.
Was inserted. The stretching direction phi _R of the film was set to -45 °, it was perpendicular to the polarizer transmission axis. The phase difference R _f is 1
5 nm.

As shown by the dotted line in FIG.
The light leakage when a high voltage was applied was suppressed, and the contrast ratio was further improved to 150.

[0106]

According to the present invention, firstly, it is possible to provide a low-cost thin film transistor type liquid crystal display device which can be mass-produced with a high yield with low cost equipment without using a transparent electrode. Secondly, it is possible to provide a thin film transistor type liquid crystal display device having good viewing angle characteristics and easy multi-gradation display, and thirdly, a process and a material allowance for liquid crystal alignment are large, so that an aperture ratio is high. Fourth, it is possible to provide a brighter thin film transistor type liquid crystal display device with an increased light transmittance. It is possible to provide a brighter thin film transistor type liquid crystal display device having a higher light transmittance and a higher light transmittance.

[Brief description of the drawings]

FIG. 1 is a diagram showing an operation of a liquid crystal in a liquid crystal display device of the present invention.

FIG. 2 illustrates an example of a thin film transistor of the present invention.

FIG. 3 is a diagram showing electro-optical characteristics (viewing angle direction dependence) of the present invention (a) and comparative example (b).

FIG. 4 shows a pixel electrode (source electrode), a common electrode, a scanning electrode, and a signal electrode (drain electrode) in a thin film transistor.
FIG. 2 is a diagram showing an embodiment of the present invention in which both are arranged on one substrate.

FIG. 5 is a diagram showing an embodiment of the present invention in which a pixel electrode (source electrode) and a signal electrode (drain electrode) are arranged at the center of a pixel, and one pixel is divided into two.

FIG. 6 is a view showing an angle formed by a molecular long axis alignment direction φ _LC , a polarizing plate polarization axis φ _P , and a phase plate fast axis φ _R with respect to an electric field direction.

FIG. 7 is a diagram showing electro-optical characteristics in various examples in which the molecular long axis alignment direction φ _LC on the interface is changed. When the dielectric anisotropy is positive.

FIG. 8 is a diagram showing a liquid crystal display drive circuit system of the present invention.

FIG. 9 is a diagram showing a liquid crystal display transmission type optical system of the present invention.

FIG. 10 is a diagram showing a liquid crystal display reflective optical system of the present invention.

FIG. 11 is a diagram showing electro-optical characteristics in various examples in which the molecular long axis alignment direction φ _LC on the interface is changed. When the dielectric anisotropy is negative.

FIG. 12 is a graph showing electro-optical characteristics in various examples in which the thickness d of the liquid crystal composition layer was changed. When the dielectric anisotropy is negative.

FIG. 13 is a diagram showing electro-optical characteristics when the arrangement of a polarizing plate is set so that a dark state is obtained when an electric field is slightly applied instead of 0.

FIG. 14 is a diagram illustrating characteristics of a normally open type and characteristics when an interface residual phase difference is compensated.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pixel electrode (source electrode), 2 ... Common electrode (common electrode), 3 ... Substrate, 4 ... Alignment film, 5 ... Liquid crystal molecules in a liquid crystal composition layer, 6 ... Polarizing plate, 7 ... Electric field direction, 8 ... Molecular long axis orientation direction (rubbing direction) on the interface, 9: polarization axis direction of polarizing plate, 10: gate electrode (scanning wiring), 11: additional capacitance element, 12: signal electrode (drain electrode), 13: gate insulating film , 14: flattening film, 15: protective insulating film, 16: amorphous silicon, 17: color filter, 18: light shielding layer, 19: polarizing plate polarization transmission axis, 20: retardation plate fast axis,
21: signal electrode drive circuit, 22: scan electrode drive circuit, 2
3 ... signal electrode, 24 ... scanning electrode, 25 ... lower substrate, 26
... upper substrate, 27 ... control circuit, 28 ... phase difference plate, 29 ... backlight, 30 ... reflector, 31 ... liquid crystal composition layer.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masuyuki Ota 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (56) References JP-B-63-21907 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02F 1/1343 G02F 1/136 500

Claims (19)

(57) [Claims] At least one of the substrates includes a pair of transparent substrates and a liquid crystal layer sandwiched between the pair of substrates. One of the pair of substrates has a plurality of signal wiring electrodes and a plurality of signal wirings. An electrode and a plurality of scanning wiring electrodes formed in a matrix, and a plurality of thin film transistors formed corresponding to respective intersections, each being surrounded by the plurality of signal wiring electrodes and the plurality of scanning wiring electrodes at least one pixel composed of the region, and one common electrode even without least in each pixel, and at least one pixel electrode connected to the corresponding thin film transistor, said at least one common electrode and the At least one pixel electrode is a layer on which the plurality of scanning wiring electrodes are arranged.
Different from the layer on which the scanning wiring electrodes are arranged.
The liquid crystal display device is formed at least in the same layer via an insulating film, and an electric field predominantly parallel to the one substrate is formed between these electrodes. 2. A liquid crystal display according to claim 1, wherein, in pixels adjacent to each other in the direction of said signal wiring electrode, corresponding common electrodes are mutually connected to corresponding common electrodes in adjacent pixels. apparatus. 3. The liquid crystal display device according to claim 1, wherein said plurality of common electrodes are formed on the same substrate as said plurality of scanning wiring electrodes. 4. The method of claim 1, the signal wiring electrode corresponding to each of the plurality of pixels liquid crystal display device characterized in that it is connected to the drain electrode of the plurality of thin film transistors. 5. The method according to claim 1, wherein the liquid crystal composition of the liquid crystal layer has a positive dielectric anisotropy and an angle between an orientation direction of liquid crystal molecules and an electric field direction on at least one substrate interface. φLC | is 45 degrees or more and less than 90 degrees. However, -90 degrees ≦ φLC ≦ 90 degrees. 6. The method according to claim 1, wherein the liquid crystal composition of the liquid crystal layer has a negative dielectric anisotropy and an angle between an orientation direction of liquid crystal molecules and an electric field direction on at least one substrate interface. A liquid crystal display device wherein φLC | is more than 0 degree and less than 45 degrees. However, -90 degrees ≦ φLC ≦ 90 degrees. 7. The method of claim 5 or 6, substantially parallel to the angle of the orientation direction of the liquid crystal molecules in the orientation direction angle φLC1 the other substrate plane of liquid crystal molecules on one substrate of the liquid crystal layer φLC2 each other (ΦLC1 ≒ φLC2), and the product d · Δn of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn is 0.21 μm.
A liquid crystal display device characterized by being between m and 0.36 μm. 8. The method of claim 7, wherein the liquid crystal layer thickness d and refractive index anisotropy [Delta] n of the product d · [Delta] n low retardation Rf than
Is inserted so as to compensate for the phase difference generated by the liquid crystal layer, and the difference | d · Δ
A liquid crystal display device wherein n |-| Rf | is not less than 0.21 μm and not more than 0.36 μm. 9. The apparatus according to claim 5 or 6, the angle of the orientation direction of the liquid crystal molecules on one substrate surface of the liquid crystal layer φLC1
And the angle φLC2 of the alignment direction of the liquid crystal molecules on the substrate interface
Intersect with each other, the angle | φLC1−φLC2 | is not less than 80 degrees and not more than 100 degrees, and the product d · Δn of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn is 0.40 μm to 0.60 μm.
A liquid crystal display device characterized by being between μm. 10. The method of claim 5, a pair of polarizing plates so as to sandwich the pair of substrates, the long axis direction and angle φLC said pair of polarization of the electric field direction of the liquid crystal molecules on the interface A liquid crystal display device characterized in that the angle | P of the transmission axis (or absorption axis) of one of the polarizing plates is larger than? P and the difference |? LC-? P | is 3 degrees or more and 15 degrees or less. 11. A liquid crystal display device according to claim 6 , further comprising a pair of polarizing plates sandwiching said pair of substrates, wherein an angle φLC between a major axis direction of liquid crystal molecules on said interface and an electric field direction is set to said pair of polarizing plates. Angle φ of the absorption axis or transmission axis of one of the polarizing plates
Smaller than P and the difference | φP−φLC |
A liquid crystal display device having a temperature of 5 degrees or less. 12. In at least one of claims 5 to 11, the liquid crystal molecules of the liquid crystal layer of at least one of the substrates near the pair of substrates has an inclination angle with respect to the substrate interface 4
A liquid crystal display device characterized by being at most equal to or less than the temperature. Claim 13 In claim 1, The common electrode and the pixel electrode are the same as the signal wiring electrode.
Liquid crystal display device extending in the same direction. 14. A pair of substrates at least one of which is transparent,
Having a liquid crystal layer sandwiched between the pair of substrates, A plurality of signal wiring electrodes are provided on one of the pair of substrates.
A plurality of signal wiring electrodes and a plurality formed in a matrix
Scanning wiring electrodes, and are formed corresponding to the respective intersections
Having a plurality of thin film transistors, The plurality of signal wiring electrodes and the plurality of scanning wiring electrodes
At least one pixel in each enclosed area
And Each pixel has at least one common electrode and a corresponding
At least one pixel connected to the
And an elementary electrode, The at least one common electrode and the at least one common electrode
A pixel electrode is a layer on which the plurality of scanning wiring electrodes are arranged.
Different from the layer on which the scanning wiring electrodes are arranged.
At least in the same layer via an insulating film,
The plurality of scanning wiring electrodes are connected to the plurality of pixels via the insulating layer.
A liquid crystal display device characterized by forming a capacitor with an elementary electrode.
Place. 15. The device according to claim 14, wherein the common electrode and the pixel electrode are the same as the signal wiring electrode.
Liquid crystal display device extending in the same direction. 16. In claim 14, In a pixel adjacent in the signal wiring electrode direction,
Each common electrode has a corresponding common
A liquid crystal display device interconnected with electrodes. 17. A pair of substrates at least one of which is transparent,
Having a liquid crystal layer sandwiched between the pair of substrates;
One of the substrates has a plurality of signal wiring electrodes and the plurality of signal wiring electrodes.
No. wiring electrodes and multiple scanning wirings formed in a matrix
An electrode and a plurality of thin films formed corresponding to the respective intersections
Having a membrane transistor, The plurality of signal wiring electrodes and the plurality of scanning wiring electrodes
At least one pixel in each enclosed area
And Each pixel has at least one common electrode and a corresponding
At least one pixel connected to the
And an elementary electrode, The at least one common electrode and the at least one common electrode
A pixel electrode is a layer on which the plurality of scanning wiring electrodes are arranged.
Different from the layer on which the scanning wiring electrodes are arranged.
At least in the same layer via an insulating film,
The plurality of scanning wiring electrodes are shared by the plurality of scanning electrodes via the insulating layer.
Liquid crystal display device characterized by forming a conductive electrode and a capacitor
Place. 18. In claim 17, The common electrode and the pixel electrode are the same as the signal wiring electrode.
Liquid crystal display device extending in the same direction. (19) In claim 17, In a pixel adjacent in the signal wiring electrode direction,
Each common electrode Is the corresponding common in adjacent pixels
A liquid crystal display device interconnected with electrodes.