JPH0980383A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid crystal display device which has a wide field angle and a high contrast and is high in the light transmissivity of its liquid crystal panel, bright, and lower in power consumption. SOLUTION: The liquid crystal display device has a couple of substrates 3, plural signal wiring electrodes 12 and scanning wiring electrodes formed on the substrates, and a liquid crystal composition layer sandwiched between the couple of substrates, and in this device, signal wiring electrodes 12 and scanning wiring electrodes cross each other in matrix to form plural pixels and an active element which turns on and off a pixel electrode 1 in a pixel is formed in the pixel. When the active element is turned on, an electric field is applied between the scanning wiring electrode 1 and a reference electrode 2 almost in parallel to the substrate surface, and a scanning wiring electrode driving circuit which supplies a scanning signal having a nonselective voltage in more than binary notation is connected to the scanning wiring electrode and a signal wiring electrode driving circuit which supplies an image signal is connected to the signal wiring electrode 12.

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 (hereinafter abbreviated as TFT-LCD).

[0002]

2. Description of the Related Art A method using a comb-teeth electrode pair has been proposed by PCT WO91 / 10936 as a method (horizontal electric field method) in which the direction of an electric field applied to a liquid crystal is substantially parallel to a substrate interface. . A liquid crystal display device combining this lateral electric field method and a thin film transistor is disclosed in Japanese Examined Patent Publication No. 63-21907.
It is proposed in JP-A-6-160878.

[0003]

In the horizontal electric field method, liquid crystal molecules do not rise from the surface of the substrate, so that the viewing angle is wide and the gradation level is not reversed, and the contrast ratio and the color tone are not changed. However, it has not been put to practical use for the following reasons.

In the horizontal electric field method, pixels are arranged, for example, by 2 to 4 via linear electrodes in order to apply an effective electric field to the liquid crystal.
It must be divided into one sub-pixel. At this time, since a plurality of linear electrodes, which are not in the method of applying an electric field in the direction perpendicular to the substrate surface (vertical electric field method), are newly interposed, the ratio of the effective area through which light is transmitted is inevitable. Will be significantly reduced compared to. Therefore, if the same backlight is used, it becomes dark, and in order to maintain the same brightness, it is necessary to increase the intensity of the backlight, and the power consumption increases significantly. In the horizontal electric field method, the liquid crystal structure (physical properties of liquid crystal material, thickness of liquid crystal layer, alignment state, arrangement of polarizing plate, etc.) and electrode structure (shape of conductive material, semiconductor material, insulating material, etc. of pixel portion, wiring portion) are simultaneously used. It has to change drastically. Further, when one of the liquid crystal structure and the electrode structure is changed, there is a close relationship such that the other optimum structure is changed, and thus it is impossible to treat one of them as a black box as in the case of a vertical electric field. In addition, due to the drastic change in the liquid crystal structure and the electrode structure, there are some parts in which the electric circuit constants are remarkably changed in each part constituting the pixel part and the peripheral part. Therefore, it is necessary to consider a driving method that takes into consideration the circuit characteristics peculiar to the lateral electric field method. That is, the liquid crystal structure, the electrode structure, and the driving circuit are related to each other, and none of them can be made into a black box, which makes the design complicated and difficult.

An object of the present invention is to obtain a bright and low power consumption TFT-LCD having a wide viewing angle, a high contrast ratio, a liquid crystal panel having a high light transmittance, and a low power consumption in an in-plane switching mode. The purpose is to clarify the optimum combination of the three driving methods.

[0006]

The present invention comprises a pair of substrates,
A liquid crystal display device having a plurality of signal wiring electrodes and scanning wiring electrodes formed on a substrate, and a liquid crystal composition layer sandwiched between a pair of substrates, wherein the plurality of signal wiring electrodes and scanning wiring electrodes are arranged in a matrix. A plurality of pixels are formed by intersecting in a circular pattern, and an active element for turning on / off the pixel electrode in the pixel is formed in the pixel, and when the active element is turned on, the substrate surface is provided between the pixel electrode and the reference electrode. An electric field is applied substantially parallel to the scanning line electrode, a scanning line electrode driving circuit for supplying a scanning signal having a non-selective voltage of two or more values is connected to the scanning line electrode, and a signal wiring electrode for supplying an image signal to the signal line electrode. A liquid crystal display device is characterized in that a drive circuit is connected.

Further, the liquid crystal composition layer and the polarizing means are set so that the contrast ratio in the direction perpendicular to the substrate is 10 or more and the luminance transmittance is 15% or more, and the pixel electrode and the reference electrode are within one pixel. It is desirable to extend in the first direction substantially parallel to the signal wiring electrode.

Since the liquid crystal composition has an electrode structure for applying an electric field substantially parallel to the substrate surface, a wide viewing angle can be obtained. By combining a liquid crystal composition layer and a polarizing means as a liquid crystal structure, the contrast ratio and the luminance transmittance can be improved. By increasing the pixel electrode and the reference electrode in a first direction substantially parallel to the signal wiring electrode within one pixel, a high aperture ratio can be obtained, and the scanning wiring electrode can be scanned with a binary non-selective voltage. By connecting the scanning wiring electrode drive circuit for applying a signal, it is possible to suppress image quality defects such as smear even with such a high aperture ratio electrode structure.

Further, the non-selection voltage of the scanning signal applied to the scanning wiring electrode changes in the same period and the same phase in all rows, and in synchronization with this, the non-selection of the pixel electrode for the entire period of the common electrode. It is desirable that a voltage waveform that changes in the same cycle and the same phase is applied during the period. It is desirable that the non-selection voltage of the scanning signal applied to the scan wiring electrode, the entire period of the common electrode, and the voltage applied during the non-selection period of the pixel electrode are substantially the same. Within one pixel of the pixels, the distance D between the pixel electrode and the reference electrode adjacent thereto is one third of any of the widths W _P and W _C of the pixel electrode and the reference electrode.
It is desirable that it be larger than. The dielectric constant anisotropy of the liquid crystal composition layer is positive, and the angle | φ _LC | formed by the orientation direction of liquid crystal molecules and the electric field direction on at least one substrate interface is 4
It is desirable that the angle is 5 degrees or more and less than 90 degrees. Where-
90 ° ≦ φ _LC ≦ 90 °. Regarding the orientation in the liquid crystal composition layer, the orientation angle φ of the liquid crystal molecule orientation on one substrate interface
_LC1 and the liquid crystal molecule orientation direction angle φ _LC2 on the other substrate interface are substantially parallel to each other (φ _LC1 ≈φ _LC2 ), and the product d · thickness d of the liquid crystal composition layer and refractive index anisotropy Δn It is desirable that Δn is between 0.21 μm and 0.36 μm.

[0010]

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 liquid crystal molecule major axis (optical axis) direction near the interface, and inserted between the pair of polarizing plates. The definition of the angle φ _R formed by the fast axis of the retardation plate is shown (Fig. 6). Since there are a pair of the polarizing plate and the liquid crystal interface above and below, respectively, they are denoted as φ _P1 , φ _P2 , φ _LC1 , and φ _LC2 as necessary.

1 (a) and 1 (b) are side sectional views showing the operation of the liquid crystal in the liquid crystal panel of the present invention, and FIGS. 1 (c) and 1 (d) are front views thereof. In the present invention, a stripe-shaped electrode is formed to form a plurality of pixels, but only one pixel is shown here. The cross section of the cell when no voltage is applied is shown in Fig. 1 (a).
A front view at that time is shown in FIG. Linear electrodes 1 and 2 are formed inside a pair of transparent substrates, and an alignment control film 4 is applied and aligned on the linear electrodes 1 and 2. A liquid crystal composition is sandwiched between them. The rod-shaped liquid crystal molecules 5 are oriented so as to have a slight angle with respect to the longitudinal direction of the electrodes 1 and 2 when the electric field is not applied, that is, 45 ° ≦ | φ _LC | <90 °. The orientation directions of liquid crystal molecules on the upper and lower interfaces are parallel here,
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). Polarizing plate 6 is polarized plate polarization direction 9
By arranging in the position, it becomes possible to change the light transmittance by applying an electric field. As described above, according to the present invention, it is possible to provide a display with contrast even without the transparent electrode. In the present invention, those of 45 degrees or less are collectively referred to as a lateral electric field. Further, in FIG. 1, the electrodes 1 and 2 are collectively formed on one substrate, but the effect does not change even if they are separately provided on the upper and lower substrates. In consideration of miniaturization of patterns such as wiring and various deformations due to heat, external force, etc., it is preferable to provide the substrate on one side because more accurate alignment is possible. Although the dielectric anisotropy of the liquid crystal composition is assumed to be positive, it may be negative. In that case, the initial alignment state is set at a slight angle │φ _LC │ (that is, 0 degree <| φ _LC │ from the direction perpendicular to the longitudinal direction of the electrodes 1 and 2 (electric field direction 7).
≦ 45 degrees). In the display mode of the present invention, the long axis of the liquid crystal molecule is always substantially parallel to the substrate and does not rise, and therefore the change in brightness when changing the viewing angle direction is small.

As a concrete structure for imparting contrast, a mode utilizing a state in which the liquid crystal molecule alignments on the upper and lower substrates are substantially parallel (which is called a birefringence mode here because the interference color due to the birefringence phase difference is utilized) And a mode using a state in which the alignment of liquid crystal molecules on the upper and lower substrates intersects and the molecular arrangement in the cell is twisted (Since the optical rotation that the polarization plane rotates in the liquid crystal composition layer is used, There is a).

Generally, the light transmittance T / T _o when a uniaxial birefringent medium is inserted between two polarizing plates arranged orthogonally is expressed by the following equation. Here, χ _eff is the effective optical axis direction of the liquid crystal composition layer (the angle formed by the optical axis and the polarization transmission axis), d _eff is the thickness of the effective liquid crystal composition layer having birefringence, and Δn is Refractive index anisotropy, λ represents the wavelength of light. Here, the purpose of making the optical axis direction of the liquid crystal composition layer an effective value is that the liquid crystal molecules are fixed on the interface in the actual cell and all the liquid crystal molecules are parallel to each other in the cell when an electric field is applied. In view of the fact that a large amount of deformation occurs, especially in the vicinity of the interface, rather than being oriented uniformly, it is treated as an average value of the apparent values when assuming a uniform state.

T / T _o = (sin (2χ _eff )) ² · (sin (πd _eff · Δn / λ)) ² (1) Dark state when low voltage V _{L is} applied and bright state when high voltage V _{H is} applied In order to obtain the normally closed characteristic, the transmission axis (or absorption axis) of one polarizing plate is almost 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 the two polarizing plates are orthogonal to each other, it is relatively easy to realize a dark level having a sufficiently low transmittance, but the arrangement is not particularly limited to this arrangement. When no electric field is applied, χ _{eff in} equation (1) is 0, so the light transmittance T / T _o is also 0. On the other hand, when an electric field is applied, the value of χ _eff increases according to its strength, and reaches a maximum at 45 degrees. At this time, the wavelength of light is 0.5
Assuming 55 μm, it is _sufficient to set d _eff · Δn to 0.28 μm which is a half wavelength in order to obtain an achromatic color and maximum transmittance. Since there is a margin in reality, d · Δn is set to 0.
It should be between 21 and 0.36 μm, but it is preferable to set it to a value between 0.24 and 0.33 μm.

On the other hand, in order to obtain a normally open characteristic in which a bright state is applied when a low voltage V _{L is} applied and a dark state is applied when a high voltage V _{H is} applied, χ in the equation (1) is applied when no electric field is applied or when a low electric field is applied.
_The polarizing plate arrangement may be set so that _{eff is} approximately 45 degrees. Contrary to the case of normally closed when the electric field is applied, the value of χ _eff decreases according to its strength. However, even if χ _eff becomes minimum (that is, 0), a considerable amount of light leaks due to the residual phase difference of the liquid crystal molecules fixed near the interface. d · Δn from 0.27 to 0.
According to an experiment conducted by the inventors of the present invention in which the voltage is set to 37 μm and an effective voltage of 3 to 10 V is applied, the value of the interface residual phase difference is about 0.02 to 0.06 μm. Further, the actual thickness d of the liquid crystal composition layer and the effective thickness d of the liquid crystal composition layer
the relationship between the _eff is a _{d eff ≒ d-R S ...} (2).

Therefore, by inserting a retardation plate having a birefringence retardation of about 0.02 to 0.06 μm (this retardation is represented by R _f ) so as to compensate for the interface residual retardation, a dark state is obtained. , And a high contrast ratio is obtained.
The angle φ _R of the fast axis of the retardation plate is made parallel to the effective optical axis χ _eff of the liquid crystal composition layer when a voltage is applied. In order to completely sink the brightness of the dark state, it is necessary to exactly match the residual phase difference when the voltage for displaying the dark state is applied. From the above, in order to achieve both the sinking in the dark state and the transmittance and the whiteness in the bright state, it is sufficient to satisfy the following equation.

[0017] 0.21μm <(d · Δn-R f) <0.36μm ... (3) preferably, 0.23μm <(d · Δn- R f) <0.33μm ... (4) This approach, In particular, it is effective in a liquid crystal having a negative dielectric anisotropy in which the alignment direction (optical axis direction of the liquid crystal) when an electric field is applied is relatively uniform in the sub-pixel.

Twisted nematic (T
In the wisted Nematic (TN) method, d.Δn is 0.50 which is a first minimum condition as is generally known.
When set to around μm, high transmittance and achromatic color are obtained. Considering the margin, the TN method is 0.40 to 0.60μ.
Set between m.

In order to completely eliminate the optical rotatory power, it is necessary to make the liquid crystal alignment directions in the vicinity of the upper and lower substrate interfaces substantially parallel, and assuming a 90 ° TN mode, the liquid crystal on one substrate side You have to rotate the molecule close to 90 degrees. When displaying in the birefringence mode, the liquid crystal molecule rotation angle may be about 45 degrees, and the threshold voltage is lower in the birefringence mode.

Further, in order to prevent the liquid crystal molecules from rising in this way, conventionally, an alignment film which gives a large tilt angle (angle formed by the long axis of the liquid crystal molecule and the interface) is used, and its size is strictly controlled under process conditions. It needed to be controlled precisely,
It does not necessarily require such an alignment film or process control. In other words, the role of the tilt angle can be expressed as follows. The angle φ _LC formed by the direction of the electric field and the initial alignment direction of the liquid crystal is 9
When the degree is 0 degree, the deformation energies when the electric field increases and when the electric field increases more than 90 degrees are equal and both are mixed, and a domain where light leaks occurs at the boundary between them, which may reduce the contrast ratio. is there. 90 degrees (substantially 89.5 degrees or less, preferably 88 degrees or less)
By shifting from 90 degrees, it is possible to forcibly select either one that increases or decreases from 90 degrees.
Instead of giving a tilt angle, the liquid crystal molecule major axis direction (rubbing direction) on the substrate interface may be set to a predetermined direction deviated from 90 degrees with respect to the electric field direction. For simplification,
The description has been made assuming liquid crystal having a positive dielectric anisotropy, but when the liquid crystal has a negative dielectric anisotropy, the liquid crystal may be designed to be shifted from 0 degree. In particular, when the liquid crystal composition has a negative dielectric anisotropy, the setting of the rubbing direction has a great advantage of preventing domains. That is, the angle φ _LC (defined as φ _LC > 0 degree) formed by the direction of the electric field and the long axis direction of the liquid crystal molecules on the substrate interface is 0 degree or more (substantially 0.5 degree or more), preferably 2 degrees. It should be more than once.

Generally, in order to control the tilt angle, a sophisticated molecular design of the alignment film and precise management of mass production processes (application of alignment film material, heating and baking, etc.) are required, and the degree of freedom of usable materials is not high. Since the function of the tilt angle of the vertical electric field method can be provided by setting the rubbing direction like this method, the degree of freedom in selecting the alignment film material is also increased. For example, even if the organic polymer is used for the flattening film on the color filter and the protective film (part or all) on the thin film transistor and it is directly subjected to surface alignment treatment such as rubbing, it can be used as an alignment film more easily. . If you use an organic polymer, you can flatten the surface irregularities,
Light leakage due to disordered orientation near the step can be suppressed, and the effect of increasing the contrast ratio can be obtained.

In the horizontal electric field system, a plurality of elongated linear electrodes are arranged and a potential difference is applied between the electrodes to drive the liquid crystal. At this time, these linear electrodes are arranged in one pixel in a substantially specific direction (first direction), and the distance L between adjacent linear electrodes is set to be 3 times the width W of the linear electrodes. By setting it to 1 or more, a practical aperture ratio of at least 20% or more can be obtained.

Generally, when performing active driving such as the TFT method, it is necessary to store charges in the liquid crystal element so that a constant voltage is continuously applied to the liquid crystal for a certain period. Therefore, a liquid crystal material having a high specific resistance is used, and an auxiliary capacitance element is formed in parallel, for example, to increase the total amount of stored charges and to extend the voltage holding period. In addition, the increase of the total capacitance of the liquid crystal element and the auxiliary capacitance element is important for improving the image quality. That is, it is also effective as a countermeasure against the formation of an unnecessary circuit element (referred to as a parasitic capacitance element) which is not preferable in designing the electrode wiring. This is because the parasitic capacitance element becomes relatively negligible as the total capacitance of the liquid crystal element and the auxiliary capacitance element increases.

In the vertical electric field system, both the pixel electrode and the common electrode form a transparent flat plate structure, and they face each other and have a large parallel plate capacitance (hereinafter, in the present invention, between the pixel electrode and the common electrode). The capacity formed is referred to as C _LC ). Therefore, if the capacitance C _{LC of the} liquid crystal element is relatively large and the capacitance C _S of the auxiliary capacitance element is designed to be large to some extent, a total capacitance that can eliminate the influence of the parasitic capacitance element was obtained. On the other hand, in the horizontal electric field method, both the pixel electrode and the common electrode have a linear structure, so that the capacitance C _LC is significantly smaller than that in the vertical electric field method. In addition, since the electrode structure is linear, even if the specific resistance of the liquid crystal is the same, the resistance value on the circuit is significantly higher than in the vertical electric field method, and the constraint condition of the specific resistance is loose from the viewpoint of maintaining the retention rate. That is, the holding time can be lengthened by combining with the high resistance without increasing the capacitance Cs of the auxiliary capacitance element so much.

In the vertical electric field method, a liquid crystal material of 10 ¹³ Ω · cm or more is required, whereas in the horizontal electric field method, 10 ¹¹ Ω · cm is sufficient. Total capacitance C _LC + Cs in lateral electric field method
If the small size can be fully used, the load on the entire panel can be reduced, which contributes to lower power consumption of the circuit. Relaxing the constraint condition of the specific resistance of the liquid crystal expands the degree of freedom in selecting the liquid crystal material.

Of the parasitic capacitance elements that are a problem in the horizontal electric field method, the capacitance (denoted as C _GS ) formed between the scanning signal electrode (gate electrode) and the pixel electrode (source electrode) is a particular problem. Do you get it. Therefore, by devising the drive waveform, a waveform is searched for in which a sufficient voltage is applied to the liquid crystal, a smaller auxiliary capacitance element functions more than in the case of the vertical electric field method, and the parasitic capacitance element disappears.
As a result, a scanning signal having, for example, an AC rectangular wave having a pulse train having a constant width and having a non-selective voltage of two or more values is applied to each of the scanning wiring electrodes, and an AC waveform having the same phase and the same polarity as the reference is applied. If the voltage is applied during the entire period of the electrodes (common electrode) and the non-selection period of the pixel electrode, the relative potential difference between the scan line electrode, the reference electrode, and the pixel electrode is low during the non-selection period, which is almost the same period (if the same amplitude, Suppressed to almost zero). As a result, the parasitic capacitance disappeared.

[0027]

【Example】

[Embodiment 1] Two glass substrates having a thickness of 0.7 mm are used as substrates. Between these substrates, the dielectric anisotropy Δε is positive and its value is 4.5, and the refractive index anisotropy Δn is 0.07.
2 (589 nm, 20 ° C.) between the nematic liquid crystal compositions. The polyimide-based orientation control film applied to the surface of the substrate on the TFT side is rubbed to obtain a pretilt angle of 3.5 degrees. The rubbing directions on the upper and lower interfaces are substantially parallel to each other, and the angle formed by the applied electric field direction is 78 degrees (φ _LC1 = φ _LC2 =
78 °). The gap d was set to 4.0 μm in a liquid crystal sealed state by dispersing spherical polymer beads between the substrates and sandwiching them. Therefore, d · Δn is 0.288 μm. The panel was sandwiched between two polarizing plates, and the polarization transmission axis of one polarizing plate was substantially parallel to the rubbing direction, that is, φ _P1 = 78 °, and the other was orthogonal thereto, that is, φ _P2 = −12 °. As a result, normally closed characteristics were obtained.

As for the structure of the thin film transistor and various electrodes, as shown in FIG. 2, the thin film transistor element 34 is connected to the pixel electrode (source electrode) 1, the signal wiring electrode 12 and the scanning wiring electrode 10, and the pixel electrode 1 and the common electrode are connected. The direction in which a certain reference electrode 2 is substantially parallel to the signal wiring electrode 12 within one pixel
(Extended in the first direction). In this embodiment, both the pixel electrode 1 and the reference electrode 2 are the signal wiring electrodes 12
However, even if it is tilted slightly (for example, about 5 degrees) in order to control the threshold characteristics of the liquid crystal, it falls within the scope of the present invention and its effect is sufficiently obtained. Further, although the reference electrode 2 is used as the reference electrode in the present embodiment, the reference electrode may be any electrode (for example, a scanning wiring electrode) that supplies a predetermined waveform regardless of the image information.

A signal waveform having image information is applied to the signal wiring electrode 12, and a scanning waveform is applied to the scanning wiring electrode 10 in synchronization with the signal waveform. An information signal is transmitted from the signal wiring electrode 12 to the pixel electrode 1 through the thin film transistor, and a voltage is applied to the liquid crystal portion between the signal electrode and the reference electrode 2. In the present embodiment, the pixel electrode 1 and the reference electrode 2 are arranged on the same substrate side and formed on the same layer as the scanning wiring electrode 10, but the present invention is not limited to this, and they may be formed on the opposite substrate, for example. Alternatively, the signal wiring electrodes 12 and the pixel electrodes 1 may be formed in the same layer on the same substrate. Of course, a conductive layer for the reference electrode may be formed separately from these electrodes and patterned.

As shown in FIG. 2, the auxiliary capacitance element 11 does not have a new area for the auxiliary capacitance element, and the auxiliary capacitance element 11 is not formed.
And a part of the wiring portion of the reference electrode 2 is used to sandwich the insulating film therebetween. The capacitance of the auxiliary capacitance element 11 was about 21 fF. A scanning wiring driving LSI and a signal wiring driving LSI were connected to the scanning wiring electrode 10 and the signal wiring electrode 12, respectively.

The charges accumulated in the pixel electrode 1 are accumulated in about 24 fF, which is a capacitance in which the electrostatic capacitance between the pixel electrode 1 and the reference electrode 2 and the auxiliary capacitance element 11 are connected in parallel. Even if the specific resistance of the object is 5 × 10 ¹⁰ Ωcm, the voltage fluctuation of the pixel electrode 1 can be suppressed. Therefore, it is possible to prevent the deterioration of image quality.

The number of pixels is 640 (× 3) × 480, and the pixel pitch is 110 μm in the horizontal direction (that is, between the common electrodes) and 330 μm in the vertical direction (that is, between the scanning wiring electrodes). The gap between the adjacent pixel electrode and reference electrode is 12 μm, and both are 1
The width was made sufficiently larger than 1/3 of the width of the pixel electrode and the reference electrode, which is 2 μm, and a practical aperture ratio of 33% was secured. In this embodiment, one pixel is divided into four rectangular sub-pixels, but the number of divisions may be two, six, or even less. Furthermore, in this embodiment, a plurality of pixel electrodes and a plurality of reference electrodes are formed, but the width may be changed between a plurality of pixel electrodes or between a plurality of reference electrodes. Furthermore, the width may be changed within one pixel electrode or one reference electrode.

Stripe-shaped R, G, and B color filters 17 are provided on the substrate opposite to the substrate having the thin film transistors (FIG. 9). A flattening film 14 made of a transparent resin for flattening the surface is laminated on the color filter. An epoxy resin was used as the material of the transparent resin. Further, a polyimide-based orientation control film was applied on this transparent resin, and the pretilt angle was adjusted to 10 degrees by rubbing treatment.
Here, the color filters are three, but may be two or four or more. Further, in this embodiment, the color filter and the black matrix are formed on the substrate opposite to the substrate having the thin film transistor, but either one or both of the color filter and the black matrix may be formed on the substrate side having the thin film transistor. .

A drive circuit is connected to the panel. The configuration of the drive circuit system of this embodiment is shown in FIG. The drive waveform at this time is shown in FIG. The non-selection voltage V _GL of the scanning signal applied to the scanning wiring electrode is binary, and changes in a certain period and a certain phase in all the rows. Further, in synchronization with this waveform, a voltage waveform that changes in the same period and in the same phase is applied to the entire period of the common electrode and the non-selection period of the pixel electrode. With such a waveform design, the parasitic capacitance C _GS shown in FIG.
Voltage can be suppressed, and its influence can be reduced. It is ideal that the voltage waveforms changing in the same period and the same phase have the same amplitude, and the voltage applied to the parasitic capacitance C _GS can be suppressed most effectively, but the effect is not required even if the amplitude width is not the same. can get.

By driving between 2 V and 6.5 V, a contrast ratio of 130 and a luminance transmittance of 22% were obtained.
The brightness transmittance referred to in the present invention is defined as a value converted when the aperture ratio is 100% and there is no color filter. The brightness transmittance in the bright state when driving the TFT-LCD including the color filter was 2.2%. A backlight consisting of a white fluorescent tube and a light guide plate is overlaid to give a surface brightness of 8
0 cd / m ² was obtained. Backlight power consumption is 6.4
It became W. The power consumption of the drive circuit is 1.2W, TF
T-LCD total power consumption is 7.6W, CR
A value sufficiently lower than T was obtained. The display characteristics hardly changed even when the viewing angle was changed.

[Embodiment 2] This embodiment is the same as Embodiment 1 except that the drive waveform is changed as shown in FIG. In the first embodiment, the binary non-selection voltage V _{GL of the} scanning signal applied to the scanning wiring electrodes is exchanged every time one line is selected, whereas it is exchanged every frame.

By driving between 2V and 6.5V, a contrast ratio of 110 and a luminance transmittance of 22% were obtained.
The brightness transmittance in the bright state when driving the TFT-LCD including the color filter was 2.2%. A backlight consisting of a white fluorescent tube and a light guide plate is overlaid, and the surface brightness is 80 cd / m ^2.
I got The power consumption of the backlight was 6.4W.
The power consumption of the drive circuit was 1.2W, and the total power consumption of the TFT-LCD was 7.6W. The display characteristics hardly changed even when the viewing angle was changed.

[Third Embodiment] The configuration of this embodiment is the same as that of the first embodiment except for the following requirements.

The gap D between the adjacent pixel electrode and reference electrode is set to 8
.mu.m, which is sufficiently larger than one-third of the widths WP and WC of the pixel electrode and the reference electrode, both of which are 13 .mu.m.
A practical aperture ratio of 6% was secured.

The display characteristics hardly changed even when the viewing angle was changed. By driving between 1.3V and 4.5V, a contrast ratio of 110 and a luminance transmittance of 21% were obtained. The brightness transmittance in the bright state when driving the TFT-LCD including the color filter was 1.8%. A backlight consisting of a white fluorescent tube and a light guide plate is overlaid, and the surface brightness is 80 cd /
It was obtained m ^2. The power consumption of the backlight was 8.1W. The power consumption of the drive circuit is 1.2W, and TFT-LCD
The total power consumption was 9.3W, which was sufficiently lower than that of a CRT.

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

FIG. 15A is a part of a plan view of the active matrix type liquid crystal display device in this embodiment. FIG. 15B is a sectional view taken along the line AA ′ in FIG.
FIG. 15C is a sectional view taken along line BB ′ of FIG. The auxiliary capacitance element 11 in Example 1 is shown in FIG.
As shown in (c), the structure is changed to sandwich the liquid crystal composition layer 50 between the pixel electrode 1 and the reference electrode 2 arranged on the counter substrate. In the present embodiment, the capacitance of the auxiliary capacitance element 11 can be connected in parallel with the capacitance between the pixel electrode 1 and the reference electrode 2 completely, so that the influence of the voltage fluctuation of the signal wiring electrode 12 is not affected. It does not reach the pixel electrode 1. Therefore, the voltage fluctuation of the pixel electrode 1 can be further suppressed, and the display unevenness does not occur.

In the liquid crystal display device of this embodiment, the image quality was not deteriorated, and the wide viewing angle and the low power consumption of 10 W or less were obtained as in the first embodiment.

[Embodiment 5] Embodiments 5 to 10 are the same as Embodiment 1 except for the points described below.

16 and 17 are a plan view and a sectional view of a unit pixel of this embodiment in which the pixel electrode 1 and the reference electrode 2 are made different layers with an insulating layer interposed therebetween. A scanning wiring electrode 10 and a reference electrode 2 made of Cr were formed on a glass substrate, and a gate insulating film 13 made of a silicon nitride (SiN) film was formed so as to cover these electrodes. A part of the scan wiring electrode 10 is covered with the amorphous silicon (a-
A Si) film 16 is formed to be an active layer of the transistor. M is formed so as to overlap a part of the pattern of the a-Si film 16.
The signal wiring electrode 12 and the pixel electrode 1 made of o were formed, and the protective insulating film 15 made of the SiN film was formed so as to cover all of them. Here, when a voltage is applied to the scanning wiring electrode 13 of the thin film transistor and the thin film transistor is turned on, a voltage is applied to the pixel electrode 1 and an electric field is induced between the pixel electrode 1 and the reference electrode 2, similar to the above-described embodiment. The liquid crystal molecules change their direction in the direction of the electric field, and the light transmittance changes.

By insulating and separating the pixel electrode 1 and the signal wiring electrode 12 from the reference electrode 2, the degree of freedom in designing the plane pattern of the pixel electrode 1 and the reference electrode 2 is increased, and the pixel aperture ratio can be improved. Also, the pixel electrode 1
Since the overlapping portion of the reference electrode 2 and the reference electrode 2 acts as an additional capacitance connected in parallel with the liquid crystal capacitance, the ability to hold the liquid crystal applied voltage can be improved. Such an effect cannot be obtained by the conventional comb-teeth-shaped electrode, and can be achieved only by insulatingly separating the pixel electrode 1, the signal wiring electrode 12, and the reference electrode 2. As is clear from FIG. 16, it is not necessary to purposely form a part of the display portion to form a capacitor as in the case where the pixel electrode and the common electrode are in the same layer, and the common electrode is laid out to the outside of the display region. It only has to overlap in a part of the wiring.

In the liquid crystal display device of this embodiment, the image quality was not deteriorated, and the wide viewing angle and the low power consumption of 10 W or less were obtained as in the first embodiment.

[Embodiment 6] FIG. 18 is a plan view of a unit pixel of this embodiment in which the pixel electrode 1 and the reference electrode 2 are made different layers with an insulating layer interposed therebetween. The present embodiment is characterized in that the reference electrode 2 has a cross shape, while the pixel electrode 1 has a ring shape.
The reference electrode 2 and the pixel electrode 1 overlap with each other to form an additional capacitance. According to this embodiment, the distance between the reference electrode 2 and the scanning wiring electrode 10 can be made large, so that a short circuit defect between the reference electrode 2 and the scanning wiring electrode 10 can be prevented. Further, by making the pixel electrode 1 of a ring type, even if disconnection occurs at an arbitrary location of the source electrode, power is supplied to the entire source electrode as long as there is no disconnection at two or more locations, and normal operation is possible.
That is, this structure has redundancy against disconnection and can improve the yield. Due to this redundancy, it is possible to narrow the wiring width of the ring-shaped electrode or bring the ring electrode and the wiring portion of the scanning wiring electrode close to each other because of the different layers, and it is possible to further increase the aperture ratio. is there.

In the liquid crystal display device of this embodiment, the image quality was not deteriorated, and the wide viewing angle and the low power consumption of 10 W or less were obtained as in the first embodiment.

[Embodiment 7] FIG. 19 is a plan view of a unit pixel according to still another embodiment of the present invention in which the pixel electrode 1 and the reference electrode 2 are different layers with an insulating layer interposed therebetween. The present embodiment is characterized in that the pixel electrode 1 is of a letter type and the reference electrode 2 is of a ring type. In this embodiment, the aperture ratio can be improved as in the sixth embodiment, and the overlap between the pixel electrode 1 and the reference electrode 2 can be increased, so that the additional capacitance can be increased.

In the liquid crystal display device of this embodiment, the image quality was not deteriorated, and the wide viewing angle and the low power consumption of 10 W or less were obtained as in the first embodiment.

[Embodiment 8] FIG. 20 is a plan view of a unit pixel of this embodiment in which the pixel electrode 1 and the reference electrode 2 are different layers with an insulating layer interposed therebetween. In this embodiment, the reference electrode 2 is composed of a new electrode provided below the scanning wiring electrode 10 with the underlying insulating film 33 interposed therebetween. Therefore, the reference electrode 2 is formed in a different layer from all of the scanning wiring electrode 10, the pixel electrode 1 and the signal wiring electrode 12. Therefore, in this embodiment, the reference electrode 2 can be drawn out not only in the direction parallel to the scanning wiring electrode 10 but also in the direction perpendicular to the scanning wiring electrode 10 to form a mesh shape.
As a result, the resistance value of the reference electrode 2 can be lowered, so that the waveform distortion of the common voltage can be reduced and the smear can be prevented.

In the liquid crystal display device of this embodiment, the image quality was not deteriorated, and the wide viewing angle and the low power consumption of 10 W or less were obtained as in the first embodiment.

[Embodiment 9] FIG. 21 is a plan view of a unit pixel of this embodiment in which the pixel electrode 1 and the reference electrode 2 are different layers with an insulating layer interposed therebetween. In this embodiment, the reference electrode 2 is composed of a new electrode provided on the protective insulating film 15. Also in this embodiment, the reference electrode 2 is formed in a different layer from all of the scanning wiring electrodes and the pixel electrodes 1 and the signal wiring electrodes 12 as in the case of the eighth embodiment. Not only can it be drawn out in the direction perpendicular to the scanning wiring electrodes to form a mesh, and the waveform distortion of the common voltage can be reduced and smear can be prevented.

In the liquid crystal display device of this embodiment, the image quality was not deteriorated, and the wide viewing angle and the low power consumption of 10 W or less as in the first embodiment were obtained.

[Embodiment 10] FIG. 22 is a plan view of a unit pixel according to still another embodiment of the present invention in which the pixel electrode 1 and the reference electrode 2 are different layers with an insulating layer interposed therebetween. The present embodiment is characterized in that the scanning wiring electrode 10 and the reference electrode 2 are made of aluminum (Al), and the surface thereof is covered with an alumina film 32 which is an Al self-oxidation film. By adopting such a two-layer insulating film structure, the insulation defect between the reference electrode 2, the signal wiring electrode 12, and the pixel electrode 1 can be reduced, so that the pixel defect can be reduced.

Even in the liquid crystal display device of this example, the image quality did not deteriorate, and a wide viewing angle and low power consumption of 10 W or less were obtained.

[Embodiment 11] The configuration of this embodiment is the same as that of the embodiment 1 except for the following requirements.

A flattening film 14 made of a transparent polymer was laminated as an organic insulating layer on the color filter, and the surface thereof was directly rubbed. An epoxy resin was used as the material of the transparent polymer. The liquid crystal composition layer was in direct contact with the epoxy resin, and the inclination angle at the interface was 0.5 degree. As a result, the step of applying the alignment film was eliminated, and the manufacturing process became easier and shorter. Generally, in the TN type which is the conventional method, the characteristics required for the orientation control film are diverse, and it is necessary to satisfy all of them, so that it is limited to some materials such as polyimide. A particularly important characteristic is the tilt angle.

When the electro-optical characteristics in this example were measured, it was found that the display characteristics hardly changed when the viewing angle was changed to the left and right and up and down. In addition, the liquid crystal alignment is good even though the tilt angle is as small as 0.5 degree,
No misaligned domains were generated. Moreover, low power consumption of 10 W or less was obtained.

Example 12 The flattening film of Example 11 was changed from epoxy resin to polyimide resin. Similarly, the surface of the polyimide resin was directly rubbed to have both the functions of flattening and controlling the alignment of liquid crystal molecules. The tilt angle at the interface was 2 degrees. As a result, the display characteristics hardly changed as compared with the other examples. In addition, the liquid crystal alignment was good, and no domain with poor alignment was generated.

Even in the liquid crystal display device of this embodiment, the image quality was not deteriorated, and a wide viewing angle and low power consumption of 10 W or less were obtained.

[Embodiment 13] The constitution of this embodiment is the same as that of the embodiment 1 except for the following requirements.

Protective insulating film 1 for protecting thin film transistors
5 was replaced with an organic insulating layer made of epoxy resin from silicon nitride, and the organic insulating layer was directly rubbed to give the organic insulating layer a function as both a protective film and a liquid crystal molecule orientation control film.
The tilt angle is 0.5 degrees.

When the electro-optical characteristics in this example were measured, display characteristics which were almost the same as those in Example 1 were obtained. Further, although the tilt angle was as small as 0.5 degree, the liquid crystal alignment was good and no misalignment domain was generated.

Even in the liquid crystal display device of this example, the image quality was not deteriorated, and a wide viewing angle and low power consumption of 10 W or less were obtained.

[Embodiment 14] The epoxy resin used for the protective film in Embodiment 13 was changed to polyimide, which is the same as the organic insulating layer.

When the electro-optical characteristics in this example were measured, display characteristics which were almost the same as those in Example 1 were obtained. Further, the tilt angle is 2.0 as compared with the thirteenth embodiment.
It went up a little. The liquid crystal alignment was good and no misaligned domains were generated.

Even in the liquid crystal display device of this example, the image quality was not deteriorated, and a wide viewing angle and low power consumption of 10 W or less were obtained.

[Examples 15 to 19] The configurations of these examples are the same as those of the example 1 except for the following requirements.

In Example 15, 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 formed by 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 almost parallel to the rubbing direction (φ _P1 = 89.5 °), and the other is orthogonal to it (φ
_P2 = -0.5 °).

Similarly, in Example 16, φ _LC1 = φ _LC2 = φ _P1
= 88 ° and φ _P2 = −2.0 °. Similarly, in Example 17, φ _LC1 = φ _LC2 = φ _P1 = 75 ° and φ _P2 = −25 °. Similarly, in Example 18, φ _LC1 = φ _LC2 = φ _P1 = 45
And φ _P2 = −45 °. Similarly, in Example 19, φ
_LC1 = φ _LC2 = φ _P1 = 30 ° and φ _P2 = −60 °. The measurement results of the electro-optical characteristics in these examples are collectively shown in FIG. In this case, the brightness is expressed as a standardized value with 100% when the applied voltage becomes the maximum again in the range of 0 to 10 V (effective value V _rms ) and 0% when the applied voltage becomes the minimum. By increasing the angle φ _LC , the curve of the threshold characteristic tended to become steeper. In order to perform halftone display with a large voltage tolerance, it is _sufficient to reduce φ _LC , but when it becomes 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 the voltage is applied to the common electrode. The designer can control the threshold characteristic in a large range by selecting φ _LC . Considering brightness, it is desirable to set φ _LC to 45 degrees or more. Further more preferably, it is set between 60 degrees and 88 degrees.

When the viewing angle characteristics were measured, it was found that the difference in the curves when the viewing angle was changed to the left, right and up and down was very small in all cases, and the display characteristics were hardly changed. In addition, the liquid crystal alignment was good, and no domain with poor alignment was generated. The power consumption was as low as 10 W or less.

Examples 20 to 23 The greatest difference between the above examples and this example is that the value of the dielectric anisotropy of the liquid crystal composition layer is made negative and the rubbing direction is changed accordingly. Is. Δε is -4.8, Δn is 0.0437 (589n)
m, 20 ° C.) nematic liquid crystal composition (Merck, Z
LI-2806) was used. In each of Examples 20 to 23, the liquid crystal molecule major axis directions (rubbing directions φ _LC1 and φ _LC2 ) on the upper and lower interfaces are substantially parallel to each other (φ).
_LC1 = φ _LC2 ), and the angle φ _LC1 formed with the direction of the applied electric field is set in a range of more than 0 degrees and less than 45 degrees. The polarization transmission axis (φ _P1 ) of one polarizing plate was made substantially parallel to the rubbing direction, and the other (φ _P2 ) was made orthogonal to it.

That is, in Example 20, φ _LC1 = φ _LC2 = φ _P1
= 1.5 ° and φ _P2 = −88.5 °.

In Example 21, φ _LC1 = φ _LC2 = φ _P1 = 15
And φ _P2 = −75 °.

In Example 22, φ _LC1 = φ _LC2 = φ _P1 = 30
And φ _P2 = -60 °.

In Example 23, φ _LC1 = φ _LC2 = φ _P1 = 45
And φ _P2 = −45 °.

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

The measurement results of the electro-optical characteristics in these examples are summarized in FIG. In addition, in FIG. 11, when the two polarizing plates are attached so that their polarization transmission axes are parallel to each other, the luminance transmittance is normalized to 100%. Contrary to the case where the dielectric anisotropy was positive, the curve of the threshold characteristic tended to become steeper as the angle φ _LC was decreased. In order to perform halftone display with a large voltage margin, it is _sufficient to increase φ _LC , but when it becomes 45 degrees or more, the brightness tends to decrease. As with the case where the dielectric anisotropy is positive, the optimum value of the angle φ _LC is 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. Replaced by. The designer can control the threshold characteristic in a large range by selecting φ _LC . Considering brightness, it is more desirable to set φ _LC to 45 degrees or less.

When the viewing angle characteristics were measured, it was found that the difference in the curves when the viewing angle was changed to the left, right, up and down was very small and the display characteristics were hardly changed in all cases. . In particular, no level reversal was observed at half-range display (8 gradations) within ± 50 degrees both vertically and horizontally. In addition, the liquid crystal alignment was good, and no domain with poor alignment was generated. The power consumption was as low as 10 W or less.

[Examples 24 to 26] In this example, Example 2 was the best in Examples 20 to 23.
1 (φ _LC1 = φ _LC2 = φ _P1 = 15 °, φ _P2 = −75 °), the liquid crystal molecule major axis direction and the polarizing plate arrangement are the same, and the thickness d of the liquid crystal composition layer and the refractive index anisotropy Δn are The product d · Δn was changed.
The thickness d of the liquid crystal composition layer of each of Examples 24, 25 and 26 was 4.0, 4.9 and 7.2 μm, that is, d · Δn was 0.1748, 0.2141 and 0.3146 μm, respectively.
Although the refractive index anisotropy Δn is constant and only the thickness d of the liquid crystal composition layer is changed here, the refractive index anisotropy is the same as in other liquid crystal display systems (for example, 90 ° twisted nematic system). Even if Δn is changed, the same result can be obtained for the optimum brightness value. Similar results can be obtained even when the value of the dielectric anisotropy of the liquid crystal composition layer is positive. The results are collectively shown in FIG. 12, including the results of Example 21. FIG.
12A shows the applied voltage on the horizontal axis, and FIG.
In (a), the applied voltage is fixed to 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 achieve a practical brightness of 30% or more, d · Δn should be set between 0.21 and 0.36 μm, and to further raise the brightness to 50% or more, it should be 0.0.
It should be between 23 and 0.33 μm. Further, considering mass productivity such as control of the liquid crystal filling time and the thickness of the liquid crystal composition layer, it is desirable that the value of d be 5.0 μm or more and Δn be 0.08 or less as in this embodiment.

In the liquid crystal display device of this embodiment, the image quality was not deteriorated, and the wide viewing angle and the low power consumption of 10 W or less were obtained as in the first embodiment.

[Embodiments 27 to 29] As is clear from the results of Embodiments 24 to 26, the optimum value of d · Δn is 0.21.
To 0.36 μm, preferably 0.23 to 0.33
between μm. Considering that the thickness of the liquid crystal composition layer having mass productivity is 5.0 μm or more, the refractive index anisotropy Δ
The value of n must be 0.072 or less, preferably 0.066 or less. However, there are very few kinds of liquid crystal compounds having such an extremely low Δn, and it is difficult to be sufficiently compatible with other practically required properties. Therefore, d · Δn of the liquid crystal composition layer is set to be slightly higher, and an optically anisotropic medium having a phase difference R _f lower than d · Δn of the liquid crystal composition layer is exceeded. Is inserted so as to compensate for the phase difference caused by the liquid crystal composition layer, and as a result, the effective phase difference of the liquid crystal composition layer and the optically anisotropic medium is 0.21 to 0, which is the optimum value. I devised a method to make it enter between 0.36 μm.

In Examples 27 to 29, the constitution was the same as that of Example 3 except for the conditions shown below. The thickness of the liquid crystal composition layer was set to 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.
It is 0.3744, 0.396 μm. If this goes on,
The value is higher than the range of 0.21 to 0.36 μm in which the brightness and the color tone are good, so that it is colored orange. An optically anisotropic medium of a uniaxially stretched film made of polyvinyl alcohol was laminated on this liquid crystal cell so as to compensate the birefringence phase difference of the liquid crystal when driven at a low voltage (here, 0 V). That is, φ _R was set to 85 °, which is the same as φ _LC1 (= φ _LC2 ). The phase difference R _f is 0.07, 0.08, and 0.10, respectively.
μm, and the value of (d · Δn−R _f ) is 0.29, 0.30.
44, 0.296 μm, with good brightness and color tone of 0.21
To 0.36 μm.

As a result, similar to the other examples, a wide viewing angle was obtained, image quality was not deteriorated, and low power consumption of 10 W or less was obtained.

Example 30 The liquid crystal composition layer of Example 27 had a negative dielectric anisotropy Δε and a value of −2.5.
The nematic liquid crystal composition (ZLI-4518, manufactured by Merck & Co., Inc.) having Δn of 0.0712 (589 nm, 20 ° C.) was used. The other structure is the same as that of the twenty-first embodiment except 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.
Good brightness and color tone of 2816μm from 0.21 to 0.2.
It was set to fall within the range of 36 μm.

As a result, as in the other examples, a wide viewing angle was obtained, no image quality deterioration was caused, and low power consumption of 10 W or less was obtained.

[Embodiment 31] The construction of the present embodiment is the same as that of Embodiment 15 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, d · Δn is 0.504μ
m. φ _{LC1 is set} to 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 plate 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 is the optical rotation mode. As a result, a normally open type was obtained.

When the electro-optical characteristics in this example were measured, other than the examples in which the birefringence mode was used, the threshold voltages V ₁₀ and V ₉₀ were about doubled, and other values were found. As in the example, a wide viewing angle was obtained, image quality was not deteriorated, and low power consumption of 10 W or less was obtained. Also, the liquid crystal alignment is good,
No misaligned domains were generated.

[Embodiments 32 and 33] The configuration of this embodiment is the same as that of the first embodiment 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 not 0 but slightly applied. That is, | φ _LC1 −φ _P1 | is 5 in each of Examples 32 and 33.
And 15 degrees, and | φ _P2 −φ _P1 | = 90 degrees.

Similar to the other examples, good display characteristics in terms of viewing angle characteristics and image quality and low power consumption of 10 W or less were obtained. In addition, the liquid crystal alignment was good, and no domain with poor alignment was generated.

[Embodiments 34 and 35] The construction of this embodiment is the same as that of Embodiment 21 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 not 0 but slightly applied. That is, | φ _P1 −φ _LC1 | is 5 in each of Examples 34 and 35.
7 degrees, and | φ _P2 −φ _P1 | = 90 degrees. The thickness d of the liquid crystal composition layer was 6.3 μm. Therefore, d · Δn is 0.275 μm.

FIG. 13 shows the measurement results of electro-optical characteristics in this example. In the case of Example 34, the dark state voltage V _OFF is 3.0 V and the brightest voltage V _ON is 9.2.
It was a bolt. If driving is performed between V _OFF and V _ON , a sufficiently high contrast can be obtained. Similarly, Example 35
In this case, V _OFF was 5.0 V and V _ON was 9.0 V.

When driven between V _OFF and V _ON , good display characteristics in terms of viewing angle characteristics and image quality and low power consumption of 10 W or less were obtained as in the other examples. In addition, the liquid crystal alignment was good, and no domain with poor alignment was generated.

[Embodiment 36] The structure of the present embodiment is the same as that of the embodiment 34 except for the following requirements.

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

In this way, driving was performed between V _OFF and V _ON , and as in the other examples, the liquid crystal alignment was good, and no alignment failure domain was generated.

[Example 37] The configuration of this example is the same as that of the example 1 except for the following requirements.

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

Similar to the other examples, good display characteristics in terms of viewing angle characteristics and image quality and low power consumption of 10 W or less were obtained. The contrast ratio was 35. In addition, the liquid crystal alignment was good, and no domain with poor alignment was generated.

Example 38 In the structure of Example 37, a birefringent medium (uniaxially stretched polyvinyl alcohol film) for compensating for an interface residual retardation between two polarizing plates.
Was inserted. The stretching direction φ _R of this film was set to −45 degrees, and was orthogonal to the polarizing plate transmission axis. The phase difference R _f is 1
It is 5 nm.

As shown by the dotted line in FIG. 14, Example 37 was used.
Compared with the above, light leakage at the time of applying a high voltage was suppressed, and the contrast ratio was further improved to 150.

[0107]

According to the present invention, a thin film transistor type liquid crystal display device having a wide viewing angle, a high contrast ratio, a high light transmittance of a liquid crystal panel and a low power consumption can be obtained.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an example of a thin film transistor and an electrode structure of the present invention.

FIG. 3 is a diagram showing an example of drive waveforms according to the present invention.

FIG. 4 is a schematic diagram showing an equivalent circuit in one pixel of the present invention.

FIG. 5 is a diagram showing another example of the drive waveform of the present invention.

FIG. 6 is a diagram showing an angle formed by a molecular long axis orientation 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 orientation 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 orientation direction φ _LC on the interface is changed. When the dielectric anisotropy is negative.

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

FIG. 13 is a diagram showing electro-optical characteristics when the arrangement of polarizing plates is set so that a dark state can be obtained when an electric field is applied rather than 0.

FIG. 14 is a diagram showing a normally open type characteristic and a characteristic when an interface residual phase difference is compensated.

FIG. 15 is a diagram showing a fourth embodiment in which a capacitive element is formed between a common electrode and a pixel electrode provided on a counter substrate.

FIG. 16 is a schematic plan view of a pixel according to a fifth embodiment in which a pixel electrode and a common electrode are different layers with an insulating layer in between when no electric field is applied.

FIG. 17 is a schematic cross-sectional view of a pixel in Example 5 in which a pixel electrode and a common electrode are formed in different layers with an insulating layer in between when no electric field is applied.

FIG. 18 is a schematic plan view of a pixel in Example 6 when no electric field is applied, in which the pixel electrode and the common electrode are different layers with an insulating layer interposed therebetween, the pixel electrode has a ring shape, and the common electrode has a cross shape.

FIG. 19 is a schematic plan view of a pixel in Example 7 in which no electric field is applied, in which the pixel electrode and the common electrode are different layers via an insulating layer, the pixel electrode has a V shape, and the common electrode has a ring shape.

20 is a schematic plan view of a pixel in Example 8 when no electric field is applied, in which the pixel electrode and the common electrode are different layers with an insulating layer interposed and an insulating layer is further inserted between the scanning wiring electrode and the common electrode.

FIG. 21 is a schematic plan view of a pixel in Example 9 in which no electric field is applied, in which the pixel electrode and the common electrode are different layers with an insulating layer in between, and the common electrode is formed on the protective insulating film.

FIG. 22 is a pixel of Example 10 in which no electric field is applied, in which the pixel electrode and the common electrode are made different layers with an insulating layer in between, and both the scanning wiring electrode and the common electrode are made of aluminum covered with a self-oxidation film. Schematic plan view.

[Explanation of symbols]

1 ... Pixel electrode (source electrode), 2 ... Reference electrode, 3 ... Substrate, 4 ... Alignment film, 5 ... Liquid crystal molecule in liquid crystal composition layer, 6 ...
Polarizing plate, 7 ... Electric field direction, 8 ... Molecular major axis alignment direction on interface (rubbing direction), 9 ... Polarizing plate polarization axis direction, 10 ... Scan wiring electrode, 11 ... Auxiliary (additional) capacitive element, 12 ... Signal wiring Electrodes, 13 ... Gate insulating film, 14 ... Flattening film, 15 ...
Protective insulating film, 16 ... Amorphous silicon, 17 ... Color filter, 18 ... Shading layer, 19 ... Polarizing plate polarization transmission axis,
20 ... Phase difference plate fast axis, 21 ... Signal wiring electrode drive circuit,
22 ... Scan wiring electrode driving circuit, 23 ... Signal wiring electrode, 2
4 ... Scan wiring electrode, 25 ... Lower substrate, 26 ... Upper substrate,
27 ... Control circuit, 28 ... Retardation plate, 29 ... Backlight, 30 ... Reflector, 31 ... Liquid crystal composition layer, 32 ...
Alumina film, 33 ... Base insulating film, 34 ... Thin film transistor element, 35 ... Image information signal source, 36 ... Common electrode drive circuit, 37 ... Display area, 38 ... Shading layer boundary.

Claims (34)

[Claims] 1. A liquid crystal display device comprising a pair of substrates, a plurality of signal wiring electrodes and scanning wiring electrodes formed on the substrates, and a liquid crystal composition layer sandwiched between the pair of substrates. The plurality of signal wiring electrodes and the scanning wiring electrodes intersect in a matrix to form a plurality of pixels, and an active element that turns on and off a pixel electrode in the pixel is formed in the pixel, and the active element is When turned on, an electric field is applied between the pixel electrode and the reference electrode substantially parallel to the substrate surface, and a scan signal having a non-selective voltage of two or more values is supplied to the scan line electrode drive. A circuit is connected, and a signal wiring electrode drive circuit for supplying an image signal is connected to the signal wiring electrode. 2. A pair of substrates, a plurality of signal wiring electrodes and scanning wiring electrodes formed on the substrates, a polarization means arranged so as to sandwich the pair of substrates, and a pair of substrates sandwiched between the pair of substrates. A liquid crystal display device having a liquid crystal composition layer, wherein the plurality of signal wiring electrodes and the scanning wiring electrodes intersect in a matrix to form a plurality of pixels, An active element for turning on and off an electrode is formed, and when the active element is turned on, an electric field is applied between the pixel electrode and the reference electrode substantially in parallel to the substrate surface, and the liquid crystal composition layer and the polarizing means are: The contrast ratio in the direction perpendicular to the substrate is set to 10 or more and the luminance transmittance is set to 15% or more, and the pixel electrode and the reference electrode are substantially parallel to the signal wiring electrode in one pixel. A scanning wiring electrode driving circuit that supplies a scanning signal having a non-selective voltage of binary or more is connected to the scanning wiring electrode, and a signal wiring electrode driving circuit that supplies an image signal to the signal wiring electrode. A liquid crystal display device characterized in that circuits are connected. 3. The liquid crystal display device according to claim 1, wherein the reference electrode is a common electrode having a common potential across a plurality of pixels. 4. The non-selection voltage of the scanning signal applied to the scanning wiring electrode changes in all rows in the same period and in the same phase, and in synchronization with this, the non-selection voltage of the pixel electrode during the entire period of the common electrode. 3. The liquid crystal display device according to claim 1, wherein voltage waveforms that change in the same cycle and in the same phase are applied during the selection period. 5. The non-selection voltage of the scanning signal applied to the scan wiring electrode, the entire period of the common electrode, and the amplitude of the voltage applied during the non-selection period of the pixel electrode are substantially the same. Item 4. The liquid crystal display device according to item 4. 6. In one pixel of the pixels, a distance D between the pixel electrode and the reference electrode adjacent thereto is a third of any one of the widths W _P and W _C of the pixel electrode and the reference electrode. It is larger than 1, The liquid crystal display device in any one of Claim 1 to 5 characterized by the above-mentioned. 7. The method according to claim 1, wherein all of the pixel electrode, the signal wiring electrode, the reference electrode and the scanning wiring electrode are arranged on one of the pair of substrates. The liquid crystal display device according to any one of claims. 8. The auxiliary electrode is arranged on the substrate opposite to the substrate having the active element, and an auxiliary capacitance element is formed between the reference electrode and the pixel electrode via an insulator. The liquid crystal display device according to any one of items 1 to 5. 9. The auxiliary electrode is formed between the pixel electrode and the reference electrode in the same layer and an insulator is formed between the pixel electrode and the scanning wiring. Item 7. The liquid crystal display device according to any one of items 1 to 6. 10. The pixel electrode and the reference electrode are formed in different layers with an insulator interposed therebetween, and the pixel electrode and the reference electrode are overlapped at least in part with the insulator interposed therebetween, and the overlap portion is provided. The liquid crystal display device according to claim 1, wherein an auxiliary capacitance element is formed. 11. A vertical scanning period in a drive signal output from the scanning wiring electrode drive circuit is set to be smaller than a time constant represented by a product of a specific resistance and a dielectric constant of an insulator forming the capacitive element. 11. The liquid crystal display device according to claim 8, wherein the liquid crystal display device is a liquid crystal display device. 12. The liquid crystal display device according to claim 8, wherein the reference electrode has a structure shared by adjacent pixels. 13. The liquid crystal display according to claim 8, wherein the reference electrode has a structure shared by adjacent pixels and is orthogonal to a part of the signal wiring of the shared wiring. apparatus. 14. The pixel electrode or the reference electrode has any one of a ring shape, a cross shape, a T shape, a Π shape, a work shape, and a ladder shape in a plan view.
A liquid crystal display device according to the item. 15. The liquid crystal display device according to claim 10, wherein the reference electrode is formed of a metal electrode whose surface is covered with an auto-oxidation film or a self-nitridation film. 16. At least two kinds of color filters having different colors are provided on one of the pair of substrates, and a boundary of the color filters overlaps with either the signal wiring electrode or the reference electrode. 16. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device. 17. An organic polymer for flattening the surface is provided on at least two kinds of color filters having different colors on one of the pair of substrates, and the organic polymer is laminated on the color filter. The polymer is a transparent polymer, and the transparent polymer is used as an alignment film for controlling the alignment of liquid crystal molecules on the interface in a predetermined direction by subjecting the transparent polymer to a surface treatment or forming a film having anisotropy. Item 1
Item 17. The liquid crystal display device according to any one of items 16 to 16. 18. The organic polymer is made of at least two kinds of materials, and the organic polymer in contact with the liquid crystal has a function of controlling alignment of liquid crystal molecules in a predetermined direction, and the organic polymer on the color filter side has a flattening function. The liquid crystal display device according to claim 17, wherein the liquid crystal display device is provided. 19. The liquid crystal display device according to claim 17, wherein the organic polymer composed of at least one layer is an organic insulating layer which is in direct contact with the active element. 20. The organic polymer is an organic insulating layer that is in direct contact with the active element and the liquid crystal composition layer, and the organic insulating layer has the functions of both a protective film for the active element and a liquid crystal molecule alignment control film. The liquid crystal display device according to claim 19, wherein the liquid crystal display device is provided. 21. The liquid crystal composition layer has a positive dielectric anisotropy, and an angle | φ _LC | formed between the liquid crystal molecule alignment direction and the electric field direction on at least one substrate interface is 45 degrees or more 9
21. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is less than 0 degree. 22. The liquid crystal display device according to claim 21, wherein the angle | φ _LC | is 60 degrees or more and 88 degrees or less. 23. The liquid crystal composition layer has a negative dielectric anisotropy, and an angle | φ _LC | formed between the liquid crystal molecule alignment direction and the electric field direction on at least one substrate interface exceeds 0 degree. Four
19. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is less than 5 degrees. 24. The liquid crystal display device according to claim 23, wherein the angle | φ _LC | is 2 degrees or more and 30 degrees or less. 25. Regarding the orientation in the liquid crystal composition layer, the liquid crystal molecule orientation direction angle φ _LC1 on one substrate interface and the liquid crystal molecule orientation direction angle φ _LC2 on the other substrate interface are substantially parallel to each other (φ _LC1 ≈ φ _LC2 ) and the product d · Δn of the thickness d of the liquid crystal composition layer and the refractive index anisotropy Δn is 0.21.
25. The liquid crystal display device according to claim 21, wherein the liquid crystal display device has a thickness of .mu.m to 0.36 .mu.m. 26. A retardation produced by the liquid crystal composition layer is an optically anisotropic medium having a retardation R _f lower than the product d · Δn of the thickness d of the liquid crystal composition layer and the refractive index anisotropy Δn. , And the difference in absolute value | d · Δn |
26. The liquid crystal display device according to claim 25, wherein − | R _f | is set between 0.21 μm and 0.36 μm. 27. Regarding the orientation in the liquid crystal composition layer, a liquid crystal molecule orientation direction angle φ _LC1 on one substrate interface and a liquid crystal molecule orientation direction angle φ _LC2 on the other substrate interface intersect with each other, and Angle | φ _LC1 −φ _LC2 | is 80 degrees or more 100
And the product d · Δn of the thickness d of the liquid crystal composition layer and the refractive index anisotropy Δn is 0.40 μm to 0.60 μm.
25. The liquid crystal display device according to claim 21, wherein the liquid crystal display device is between m. 28. The liquid crystal display device according to claim 17, wherein a tilt angle of the liquid crystal molecules is 4 degrees or less on at least one of the interfaces. 29. The liquid crystal composition layer has a positive dielectric anisotropy, the polarizing means is a pair of polarizing plates sandwiching the liquid crystal composition layer, and the length of liquid crystal molecules on at least one of the interfaces is long. The angle φ _LC formed by the axial direction and the electric field direction is substantially equal to the angle φ _P of the transmission axis (or the absorption axis) of one of the pair of polarizing plates. Liquid crystal display device. 30. The liquid crystal composition layer has a positive dielectric anisotropy, the polarizing means is a pair of polarizing plates sandwiching the liquid crystal composition layer, and the length of liquid crystal molecules on at least one of the interfaces is long. The angle φ _LC formed by the axial direction and the electric field direction has the same sign as the angle φ _P of the transmission axis (or the absorption axis) of one of the pair of polarizing plates, and the absolute value of φ _LC is φ _P. 23. The liquid crystal display device according to claim 21, wherein the liquid crystal display device is larger than the absolute value of and the difference | φ _LC −φ _P | is 3 degrees or more and 15 degrees or less. 31. The liquid crystal composition layer has a negative dielectric anisotropy, the polarizing means is a pair of polarizing plates sandwiching the liquid crystal composition layer, and the length of liquid crystal molecules on at least one of the interfaces is long. The angle φ _LC formed by the axial direction and the electric field direction and the angle φ between the transmission axis (or the absorption axis) of one of the pair of polarizing plates.
_25. The liquid crystal display device according to claim 24, wherein _P has the same sign and the absolute value of φ _LC is substantially equal to the absolute value of φ _P. 32. The liquid crystal composition layer has a negative dielectric anisotropy, and the polarizing means is a pair of polarizing plates sandwiching the liquid crystal composition layer, and the long axis direction of liquid crystal molecules on the interface. The angle φ _LC formed with the electric field direction is smaller than the angle φ _P of the absorption axis or the transmission axis of the polarizing plate, and the difference | φ _P −φ _LC | is 3 degrees or more and 15 degrees or less. The liquid crystal display device according to claim 24. 33. An image signal is applied to the pixel electrode, and a voltage signal waveform is applied to the reference electrode so that the voltage applied to the liquid crystal composition layer is further increased. 33. The liquid crystal display device according to any one of items 32 to 32. 34. The polarizing means is a pair of polarizing plates sandwiching the liquid crystal composition layer, and the polarizing means is set to a bright state when a low voltage V _{L is} applied and a dark state when a high voltage V _{H is} applied, 27. The liquid crystal display device according to claim 26, wherein a transparent medium for compensating for the residual phase difference at the interface of the liquid crystal layer when _{VH is} applied is inserted between the pair of polarizing plates.