JPH11142819A - Liquid crystal display - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a liquid crystal display device which can achieve both high luminance and a wide viewing angle and which can reduce power consumption. A liquid crystal panel having a liquid crystal layer sandwiched between a pair of substrates on which various electrodes for pixel selection are formed, a pair of polarizing plates laminated with the liquid crystal panel interposed therebetween, and Control means for applying a voltage corresponding to the display image signal to the electrodes, and a light source device 7 for illuminating the liquid crystal panel from the back,
The backlight comprises a linear lamp 5 and a reflector 6 for reflecting the light emitted from the lamp toward the liquid crystal panel, and condensing the light emitted from the backlight between the backlight 7 and the liquid crystal panel 3. An element 12 and a light scattering element 10 that scatters the condensed emitted light are provided, and the degree of scattering of the light scattering element can be adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having a high-luminance, wide viewing angle, and low power consumption lighting device.

[0002]

2. Description of the Related Art A high-definition and color display liquid crystal display device for a notebook computer or a computer monitor is provided with a light source (so-called backlight) for illuminating a liquid crystal panel from behind. As the backlight, there are known a side edge type in which a linear lamp is arranged on a side surface of a transparent plate formed of an acrylic resin or the like called a light guide plate, and a direct type in which a lamp is arranged just below the back surface of a liquid crystal panel. .

[0003] A side-edge type is used in a notebook computer which requires a thinner type, and a side-edge type is also used in a monitor liquid crystal display device in order to reduce the depth.

However, large-sized liquid crystal display devices such as computer monitors often employ a direct-type backlight to obtain higher-luminance illumination light.

[0005] This type of liquid crystal display device basically comprises a so-called liquid crystal panel in which a liquid crystal layer is sandwiched between two substrates at least one of which is made of transparent glass or the like. A method of selectively applying a voltage to the various electrodes for forming a pixel to turn on and off a predetermined pixel, forming the various electrodes and an active element for pixel selection, and selecting the active element to form a predetermined pixel. Are turned on and off.

The latter type of liquid crystal display device is called an active matrix type, and has become the mainstream of the liquid crystal display device because of its contrast performance, high-speed display performance and the like. A conventional active matrix type liquid crystal display device employs a so-called vertical electric field method in which an electric field for changing the orientation direction of a liquid crystal layer is applied between an electrode formed on one substrate and an electrode formed on the other substrate. I was

In recent years, a so-called lateral electric field method (I
A liquid crystal display device of the PS type is also realized. As this in-plane switching mode liquid crystal display device, a device in which a very wide viewing angle is obtained by using a comb electrode on one of two substrates is known (Japanese Patent Publication No. 63-21907,
U.S. Pat. No. 4,345,249).

FIG. 24 is a developed perspective view for explaining a schematic structure of a general liquid crystal display device. This liquid crystal display device employs a direct type backlight as a backlight. An upper polarizing plate 2a and a lower polarizing plate 2b are laminated on and under a liquid crystal panel 3 having printed circuit boards 3a and 3b on which driving circuits and the like are mounted. Upper diffusion film 4a, lower diffusion film 4 on back
b, the upper prism sheet 5a and the lower prism sheet 5b are arranged, and the backlight 6 composed of the linear lamp 7, the reflector 8, and the reflection film 9 is arranged, and fixed integrally with the upper frame 1 and the lower frame 10. I have.

The screen size of a liquid crystal display device for a computer monitor of various information processing devices is increasing year by year.
Demands for higher luminance and lower power consumption are increasing. In order to increase the luminance, it is necessary to increase the number of linear lamps used in both side-edge type and direct-type backlights, and / or to increase the lamp current. Further, it is necessary to change the brightness of the display screen according to the usage environment.

[0010]

Conventionally, a lamp current of an illumination light source is made variable as a display brightness variable means for that purpose. However, when the lamp current is increased, the brightness is increased. However, the temperature of the linear lamp is increased, the luminous efficiency is reduced, the required brightness cannot be obtained, and the power consumption further increases.

In a notebook computer that can be driven by a battery, the front luminance is improved by a light-collecting film called a prism sheet in order to reduce power consumption. This light-condensing film increases the front luminance, but has a characteristic that the luminance sharply decreases when the luminance shifts from the front to the left or right or up and down. When the luminance is reduced by the luminance adjustment, the display becomes invisible from an oblique direction. There's a problem.

Further, with the enlargement of the liquid crystal display device, the liquid crystal display device has been used as a computer monitor. In the case of a monitor, there is basically no strict restriction on power consumption because it is not driven by a battery, but since a wide viewing angle is important, the prism sheet as described above is often not used. For this reason, there is a problem that the luminance of the front is insufficient and the luminance and the viewing angle characteristics are not compatible.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to realize a liquid crystal display capable of achieving both high brightness and a wide viewing angle and low power consumption even when the screen is enlarged. It is to provide a device.

[0014]

In order to achieve the above object, a liquid crystal display according to the present invention comprises a liquid crystal composition (hereinafter, referred to as a liquid crystal composition) between a pair of substrates having various electrodes for selecting pixels formed on at least one inner surface. (Also referred to simply as liquid crystal layer or liquid crystal)
, A pair of polarizing plates laminated with the liquid crystal panel interposed therebetween, control means for applying a voltage corresponding to a display image signal to the electrodes, and a light source device (backlight) for illuminating the liquid crystal panel from the back. ), Wherein the backlight comprises a linear lamp and a reflector for reflecting the light emitted from the lamp toward the liquid crystal panel, and a light collector for condensing the light emitted from the backlight between the backlight and the liquid crystal panel. It is characterized by comprising an element and a light scattering element that scatters the condensed emitted light, wherein the degree of scattering of the light scattering element can be adjusted.

In the above arrangement, the light-collecting element that collects the light emitted from the backlight uses an optical sheet such as a prism sheet, a lens sheet, and a mirror sheet. This light collection improves the front luminance of the liquid crystal display device, but lowers the viewing angle characteristics.

FIG. 25 shows the vertical viewing angle and the luminance when two prism sheets are installed between the backlight and the liquid crystal panel, when one prism sheet is installed, and when only the light diffusion sheet is used without using the prism sheet. FIG.

FIG. 2A shows a case where two prism sheets are provided as a light-collecting element between a backlight and a liquid crystal panel, FIG. 2B shows a case where only one prism sheet is used, and FIG. Indicates a case where only the light scattering element is arranged without using the light collecting element.

As shown in the figure, when the two prism sheets shown in (a) are arranged, the luminance in the front direction of the screen (front luminance) becomes high, but the vertical viewing angle becomes narrow.

When only one prism sheet is used as shown in (b), the front luminance decreases but the viewing angle remains narrow.

On the other hand, when only the light-scattering sheet (c) is used, the front luminance decreases but the viewing angle increases.

From this, it is possible to adjust the brightness and the viewing angle characteristics of the screen by disposing a light scattering element such as a light diffusion sheet on a light condensing element such as a prism sheet and changing the degree of scattering of the light diffusion element. Is understood.

Examples of the light-scattering element include a film in which an organic low-molecular nematic liquid crystal is dispersed in a polymer and the orientation of the film is changed by a voltage applied to the dispersed liquid crystal, a so-called polymer-dispersed liquid crystal film (polymer-dispersed liquid crystal) An organic low-molecular nematic liquid crystal having at least one transparent electrode, an organic low-molecular nematic liquid crystal layer sandwiched between a pair of transparent substrates disposed opposite to each other, and an alignment state changing by applying a voltage to the liquid crystal layer. Cells and the like can be used.

Further, by using a light-scattering plate (mirror sheet) comprising a large number of light-scattering plates planted on a transparent substrate and changing the inclination angle of the large number of light-scattering plates, scattering of transmitted light is performed. The one in which the degree is changed can also be adopted.

Each of the above-mentioned means adjusts the viewing angle characteristic and the front luminance by controlling the light scattering degree, but can also adjust the viewing angle characteristic and the front luminance by changing the light condensing degree. .

That is, the liquid crystal display device according to the present invention comprises:
A liquid crystal panel having a liquid crystal composition (hereinafter, also simply referred to as a liquid crystal layer or liquid crystal) sandwiched between a pair of substrates having various electrodes for pixel selection formed on at least one inner surface; And a control means for applying a voltage corresponding to a display image signal to the electrode, and a light source device (backlight) for illuminating the liquid crystal panel from the back, wherein the backlight is a linear lamp and light emitted from the lamp. A light-scattering element that scatters the emitted light of the backlight between the backlight and the liquid crystal panel, and a light-collecting element that collects the scattered emitted light. The feature is that the degree of light collection of the light collection element can be adjusted.

In the above configuration, the condensing element for condensing the light emitted from the backlight is the same prism sheet as described above,
An optical sheet such as a lens sheet and a mirror sheet is used.
Although the front luminance of the liquid crystal display device is improved by this light collection,
The viewing angle characteristics are degraded.

That is, in order to achieve the above object, the present invention is characterized in having the following constitutions (1) to (6).

(1) A liquid crystal panel having a liquid crystal layer sandwiched between a pair of transparent substrates having a pixel selection electrode on at least one of the opposed polarizers, and an upper polarizing plate arranged with the liquid crystal panel interposed therebetween And a lower polarizing plate, a driving unit for applying a voltage according to a display signal to the electrode, and a backlight installed on the back surface of the liquid crystal panel, fixed by an upper frame and a lower frame connected to the upper frame. Between the backlight and the liquid crystal panel,
A light-collecting element that collects light emitted from the backlight;
A light-scattering element is provided on the liquid crystal panel side of the light-collecting element, the light-scattering element having a variable degree of scattering of light transmitted from the light-collecting element.

(2) A liquid crystal panel having a liquid crystal layer sandwiched between a pair of transparent substrates having a pixel selection electrode on at least one of them facing each other, and an upper polarizing plate arranged with the liquid crystal panel interposed therebetween And a lower polarizing plate, a driving unit for applying a voltage according to a display signal to the electrode, and a backlight installed on the back surface of the liquid crystal panel, fixed by an upper frame and a lower frame connected to the upper frame. Between the backlight and the liquid crystal panel,
A light scattering element having a variable degree of scattering transmitted light of the light emitted from the backlight, and a light-collecting element which is stacked on the liquid crystal panel side of the light-scattering element and collects light from the light-scattering element And characterized in that:

(3) The light scattering element according to (1),
It is a polymer-dispersed liquid crystal sheet in which an organic low-molecular nematic liquid crystal is dispersed in a polymer between a pair of transparent electrodes.

(4) The polymer dispersed liquid crystal sheet according to (1) is characterized in that an organic low molecular nematic liquid crystal is sandwiched between a pair of transparent electrodes.

(5) The light scattering element according to (1),
The light-scattering plate includes a plurality of light-scattering plates having a tilt angle variably set on a transparent substrate, and the degree of scattering of transmitted light is changed according to the tilt angle.

(6) The light-collecting device according to (2) is a transparent piezoelectric film in which the degree of condensing transmitted light changes according to an applied voltage value.

According to the above-described configurations, both the front luminance and the viewing angle characteristics of the liquid crystal panel can be adjusted, and the usability of a large-screen liquid crystal display device is particularly improved.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to examples.

FIG. 1 is a schematic sectional view for explaining a first embodiment of the liquid crystal display device according to the present invention.
b denotes a lower substrate, 3 denotes a liquid crystal panel having a liquid crystal layer 2 sandwiched between an upper polarizing plate 4a and a lower polarizing plate 4b, and 7 denotes a linear light source (lamp).
A direct-type backlight composed of 5 and a reflector 6 is a light-scattering element which is a light-scattering element in which a low-molecular nematic liquid crystal 9b is dispersed in a polymer layer 9a between an upper transparent electrode layer 8a and a lower transparent electrode layer 8b. Reference numeral 12 denotes a light condensing sheet, which is a light condensing element composed of an upper prism sheet 11a and a lower prism sheet 11b; 13, a light control power supply; and 14, a light control switch.

As the liquid crystal panel shown in the figure, various known types are used. When the liquid crystal display device is of the TN type and the vertical electric field type, the product Δnd · d of the refractive index anisotropy Δn of the liquid crystal layer 2 and the cell gap (gap between the upper and lower substrates) is 0.
The range of 2 to 0.6 μm is preferable for achieving both the contrast ratio and the brightness, and the range of 0.5 to 1.2 μm for the STN type, and the range of 0.2 to 0.
A range of 5 μm is preferred.

Here, as a pair of transparent substrates constituting a liquid crystal panel, the surfaces are polished to a thickness of 0.7 mm,
Two glass substrates on which a transparent electrode of O (indium tin oxide) is formed by a sputtering method are used. Between these substrates, the dielectric anisotropy Δnε is positive, the value is 4.5, and the birefringence Δn is 0.13 (589 nm, 20 ° C.).
And a cell gap of 6 μm
Therefore, Δn · d was set to 0.78 μm.

Then, the polyimide-based orientation control film applied to the substrate surface was applied using a spinner, baked at 250 ° C. for 30 minutes, and rubbed to form a pretilt angle of 3.5 degrees. In addition, this pretilt angle was measured by a rotating product method. The rubbing directions of both substrates were set such that the twist angle (twist angle) of the liquid crystal molecules was 240 degrees in order to perform time-division driving. Here, the twist angle is defined by the rubbing direction and the type and amount of the optical rotatory substance added to the nematic liquid crystal.

The maximum value of the torsion angle is limited because the lighting state near the threshold value is an orientation that scatters light, the upper limit is 260 degrees, the lower limit is limited by contrast, and the limit is 200 degrees.

The purpose of this embodiment is to provide a liquid crystal display device capable of displaying black and white with sufficient contrast even when the number of scanning lines is 200 or more, and the twist angle is set to 240 degrees. In addition, a single retardation film of Δn · d = 0.4 μm made of polycarbonate is arranged between the lower substrate 1b, the upper substrate 1a, and the polarizing plates 4b and 4a (not shown).

In FIG. 1, the illuminating light emitted from the backlight 7 is converged in the direction of the liquid crystal panel by a condensing sheet 12 composed of two prism sheets 11a and 11b.
The groove directions (or crest directions) forming the prisms of the two prism sheets 11a and 11b are formed so as to intersect with each other, and a function of condensing light from the backlight 7 from two directions toward the liquid crystal panel. have.

The light condensed by the condensing sheet 12 passes through the light scattering sheet 10. At this time, when the light control switch 14 is turned off, for example, the molecules of the low-molecular nematic liquid crystal are in a random alignment state, and the transmitted light is scattered. That is, in this case, the display has a low front luminance and a wide viewing angle.

On the other hand, the dimming power source 1 is
By applying a voltage between 3 and the upper transparent electrode layer 8a and the lower transparent electrode layer 8b, the alignment state of the low molecular nematic liquid crystal 9b dispersed in the polymer layer 9a is aligned in the vertical direction, The incident light passes through as it is. This increases the front luminance and narrows the viewing angle.

Therefore, the degree of the scattering state can be changed by adjusting the voltage applied from the dimming power supply 13 between the upper transparent electrode layer 8a and the lower transparent electrode layer 8b,
The front luminance and the viewing angle can be arbitrarily adjusted.

FIG. 2 is a schematic diagram for explaining the dimming function of the light scattering element in FIG. FIG. 2A shows the light scattering sheet 1.
The low-molecular nematic liquid crystal molecules 9b constituting 0 show a random state, and in this state, light incident from the light-collecting sheet is scattered.

On the other hand, FIG. 6B shows a state in which the low molecular nematic liquid crystal molecules 9b constituting the light scattering sheet 10 are aligned in the vertical direction. In this state, the light incident from the light collecting sheet keeps the light collecting state. Pass as it is.

The states (a) and (b) can be arbitrarily adjusted by the magnitude of the voltage applied from the dimming power supply shown in FIG. That is, both the front luminance and the viewing angle of the screen can be set to required states.

FIG. 3 is an explanatory diagram of the relationship between the viewing angle and the luminance corresponding to FIG. 2 for explaining the effect of the first embodiment of the present invention.

FIG. 2A shows the state shown in FIG. 2B, that is, the state in which the front luminance is increased. In this case, the front luminance is 20
0 cd / m ² or more, but visible luminance 80 cd / m ²
The luminance at a viewing angle of about 50 degrees near m ² is reduced to about 1/3 of the front luminance.

On the other hand, FIG. 2B shows the state shown in FIG. 2A, that is, the state where the viewing angle is widened. In this case, the front luminance is about 130 cd / m ² , but the luminance change due to the change in the viewing angle is small, and the visible luminance is 80 cd / m ^2.
The viewing angle near m ² is about 70 degrees.

As described above, according to this embodiment, it is possible to arbitrarily adjust both the luminance and the viewing angle, and it is possible to set the liquid crystal display device to an optimal screen state according to the use environment. .

FIG. 4 is a schematic sectional view for explaining a second embodiment of the liquid crystal display device according to the present invention, wherein 18a and 18b are a pair of transparent substrates on which transparent electrodes are formed, and 19 is an organic low molecular nematic liquid crystal. The layer 20 is a light scattering sheet, and the same reference numerals as those in FIG. 1 correspond to the same functional parts. The details of the liquid crystal panel 3 and other components are the same as in the first embodiment.

In this embodiment, the light scattering sheet 20 provided between the light-condensing sheet 12 and the liquid crystal panel 3 comprises an organic low-molecular nematic liquid crystal layer 19 between a pair of transparent substrates 18a and 18b on which transparent electrodes are formed. Is used.

The light condensed by the light condensing sheet 12 passes through the light scattering sheet 20. At this time, when the light control switch 14 is turned off, for example, the molecules of the low-molecular nematic liquid crystal are in a random alignment state, and the transmitted light is scattered. That is, in this case, the display has a low front luminance and a wide viewing angle.

On the other hand, the light control power supply 1 is controlled by the light control switch 14.
3 through application of a voltage between the upper transparent substrate 18a and the lower transparent substrate 18b,
Are aligned in the vertical direction, and the incident light passes through as it is. This increases the front luminance and narrows the viewing angle.

Therefore, by adjusting the voltage applied between the dimming power supply 13 and the upper transparent substrate 18a and the lower transparent substrate 18b, the degree of the scattering state can be changed.
The front luminance and the viewing angle can be arbitrarily adjusted.

FIG. 5 is a schematic diagram for explaining the dimming function of the light scattering element in FIG. FIG. 2A shows the light scattering sheet 2.
The low-molecular nematic liquid crystal molecules 19 constituting 0 show a random state, and in this state, light incident from the light-collecting sheet is scattered.

On the other hand, FIG. 7B shows a state in which the low molecular nematic liquid crystal molecules 19 constituting the light scattering sheet 20 are aligned in the vertical direction. In this state, the light incident from the light collecting sheet keeps the light collecting state. Pass as it is.

The states (a) and (b) can be arbitrarily adjusted by the magnitude of the voltage applied from the dimming power supply shown in FIG. That is, both the front luminance and the viewing angle of the screen can be set to required states.

FIG. 6 is a schematic cross-sectional view for explaining a third embodiment of the liquid crystal display device according to the present invention, wherein 30 is a piezoelectric lens sheet as a condensing element, 31 is a light scattering sheet as a light diffusing element, 1 and 4 correspond to the same functional parts.

In this embodiment, a light scattering sheet 31 is provided between the backlight 7 and the liquid crystal panel 3, and a piezoelectric lens sheet 30 is provided on the light scattering sheet 31 as a condensing element. This piezoelectric lens sheet 30 is made of a transparent sheet of piezoelectric material,
A dimmer switch 14 is provided from a dimmer power supply 13 in two directions on its surface.
The piezoelectric lens sheet is deformed in a protruding manner by applying a voltage via the above, and a large number of microlenses 30a are formed.

FIG. 7 is a schematic diagram for explaining the dimming function of the piezoelectric lens sheet shown in FIG. FIG. 2A is a plan view,
(B) is a cross-sectional view showing a flat surface state when no voltage is applied, and (c) is a cross-sectional view showing a state in which many microlenses are formed without applying a voltage. The microlens 30a has a semicircular cross section as shown in FIG. 4C, and improves the front luminance by condensing light from the light scattering sheet in the direction of the liquid crystal panel. In the state, it has a function to scatter light to the liquid crystal panel and enlarge the viewing angle.

Therefore, by changing the voltage applied to the piezoelectric lens sheet 30, both the front luminance and the viewing angle of the screen can be arbitrarily adjusted.

FIG. 8 is a schematic diagram for explaining an example of a dimming device which can be applied to the first or second embodiment of the present invention and which can adjust the front luminance and the viewing angle. 3A is a plan view, FIG. 3B is a cross-sectional view showing a scattering state, and FIG. 3C is a cross-sectional view showing a condensing state.

The light control element 40 is a light scattering plate in which a large number of light scattering plates 42 are erected on a transparent substrate 41, and is disposed on the upper layer of the prism sheet 12 shown in FIG. 1 or FIG. Is done.

The light-scattering plate 42 changes the planting angle by using a mechanical mechanism or a piezoelectric mechanism to scatter the collected light emitted from the backlight as shown in FIG. The illumination light is converged as shown in FIG.

As a result, in the case of (b), the front luminance decreases and the viewing angle increases, and in the case of (c), the front luminance increases and the viewing angle decreases.

Therefore, both the front luminance and the viewing angle of the screen can be arbitrarily adjusted by arbitrarily changing the planting angle of the light scattering plate 42 of the light control element 40.

According to each of the above embodiments, both the front luminance and the viewing angle characteristic of the liquid crystal panel can be adjusted, and particularly, the screen state according to the use environment of the large-screen liquid crystal display device can be easily set.

Next, the details of the liquid crystal display device of the present invention are shown in FIG.
This will be described with reference to FIG.

FIG. 9 is a plan view showing one pixel of an active matrix type color liquid crystal display device which is an example of the liquid crystal display device of the present invention, a light shielding region of the black matrix BM, and its periphery.

As shown in FIG. 9, each pixel has a scanning signal line (gate signal line or horizontal signal line) GL, a counter voltage signal line (counter electrode line) CL, and two adjacent video signal lines (drain). The signal line or the vertical signal line) is arranged in an intersecting region with the DL (in a region surrounded by four signal lines).

Each pixel includes a thin film transistor TFT, a storage capacitor Cstg, a pixel electrode PX, and a counter electrode CT. The scanning signal lines GL and the counter voltage signal lines CL extend in the left-right direction in FIG. The video signal lines DL extend in the up-down direction, and a plurality of video signal lines DL are arranged in the left-right direction. The pixel electrode PX is connected to the thin film transistor TFT, and the counter electrode CT is integrated with the counter voltage signal line CL.

The pixel electrode PX and the counter electrode CT are opposed to each other, and the alignment state of the liquid crystal LC is controlled by the electric field between each pixel electrode PX and the counter electrode CT, and the display is controlled by modulating the transmitted light. The pixel electrode PX and the counter electrode CT are formed in a comb-like shape, and each is an electrode that is elongated in the vertical direction in FIG.

The number O (number of comb teeth) of the counter electrode CT in one pixel is equal to the number P (number of comb teeth) of the pixel electrode PX and O =
It is configured to always have the relationship of P + 1 (O = 2, P = 1 in this embodiment). This is because the counter electrode CT and the pixel electrode PX are alternately arranged, and the counter electrode CT is always adjacent to the video signal line DL.

As a result, the counter electrode CT and the pixel electrode PX
The electric field lines from the video signal line DL can be shielded by the counter electrode CT so that the electric field between them is not affected by the electric field generated from the video signal line DL.

Since the potential of the counter electrode CT is always supplied from the outside by the counter voltage signal line CL, the potential is stable. Therefore, there is almost no change in potential even adjacent to the video signal line DL. In addition, since the geometric position of the pixel electrode PX from the video signal line DL becomes farther,
The parasitic capacitance between the pixel electrode PX and the video signal line DL is greatly reduced, and the fluctuation of the pixel electrode potential Vs due to the video signal voltage can be controlled.

Thus, crosstalk (defective image quality called vertical smear) occurring in the vertical direction can be suppressed.

The electrode width W between the pixel electrode PX and the counter electrode CT
Each of p and Wc is set to 6 μm, which is set sufficiently larger than 4.5 μm which exceeds the maximum set thickness of the liquid crystal layer described later.
It is preferable to have a margin of 20% or more in consideration of processing variations in manufacturing. Therefore, it is preferable that the margin be sufficiently larger than 5.4 μm.

As a result, the electric field component applied to the liquid crystal layer parallel to the substrate surface becomes larger than the electric field component in the direction perpendicular to the substrate surface, so that an increase in the voltage for driving the liquid crystal can be suppressed. The maximum value of the electrode width Wp, Wc of each electrode is
It is preferable that the distance be smaller than the distance L between the pixel electrode PX and the counter electrode CT.

This is because if the distance between the electrodes is too small, the curvature of the electric field lines becomes severe, and the area where the electric field component perpendicular to the substrate surface is larger than the electric field component parallel to the substrate surface increases. This is because an electric field component parallel to the above cannot be efficiently applied to the liquid crystal layer. Therefore, the pixel electrode PX and the counter electrode C
The interval L between T needs to be larger than 7.2 μm if the margin is 20%. In this embodiment, the diagonal is about 1
Since the pixel pitch is about 60 μm because the resolution is 4.5 cm (5.7 inches) and the resolution is 640 × 480 dots, the distance L> 7.2 μm by dividing the pixel into two.
Was realized.

The electrode width of the video signal line DL is set to 8 μm which is slightly wider than the pixel electrode PX and the counter electrode CT in order to prevent disconnection, and the interval between the video signal line DL and the counter electrode CT is short-circuited. In order to prevent this, an interval of about 1 μm is provided, a video signal line DL is formed on the upper side of the gate insulating film, and a counter electrode CT is formed on the lower side.

On the other hand, the electrode interval between the pixel electrode PX and the counter electrode CT changes depending on the liquid crystal material used. this is,
Since the electric field strength that achieves the maximum transmittance varies depending on the liquid crystal material, the electrode spacing is set according to the liquid crystal material, and within the range of the maximum amplitude of the signal voltage set by the withstand voltage of the video signal driving circuit (signal side driver) used. , So that the maximum transmittance can be obtained. When a liquid crystal material described later is used, the electrode interval is about 15 μm.

In the present configuration example, a black matrix BM is formed on the gate line GL, the counter voltage signal line CL, the thin film transistor TFT, the drain line DL, and between the drain line DL and the counter electrode CT in plan view.

<< Cross-Sectional Structure of Matrix (Pixel) >> FIG. 10 shows a thin film transistor T taken along the line FF in FIG.
FIG. 11 is a cross-sectional view of the storage capacitor Cstg taken along the line GG in FIG. 9; It is sectional drawing of a part.

As shown in FIG. 12, a thin film transistor TFT, a storage capacitor Cstg (not shown), and an electrode group C are provided on the lower transparent glass substrate SUB1 side with respect to the liquid crystal layer LC.
T, PX are formed, and a color filter FIL and a black matrix B for shading are formed on the upper transparent glass substrate SUB2 side.
An M pattern is formed. Although not publicly known,
As proposed in Japanese Patent Application No. 7-198349 by the same applicant, it is also possible to form the pattern of the light-shielding black matrix BM on the lower transparent glass substrate SUB1 side.

On the inner surface (on the liquid crystal LC side) of each of the transparent glass substrates SUB1 and SUB2, alignment films ORI11 and ORI12 for controlling the initial alignment of the liquid crystal are provided. Polarizing plates POL1 and POL2 whose polarization axes are orthogonally arranged (crossed Nicol arrangement) are provided on the outer surfaces of each.

Next, the lower transparent glass substrate SUB1 side (T
The configuration of the FT substrate will be described in detail.

TFT Substrate << Thin Film Transistor >> The thin film transistor TFT operates so that the channel resistance between the source and the drain decreases when a positive bias is applied to the gate electrode GT, and the channel resistance increases when the bias is set to zero.

As shown in FIG. 10, the thin film transistor TFT has a gate electrode GT, a gate insulating film GI, and an i-type (intrinsic, not doped with a conductivity type determining impurity) amorphous silicon (Si) made of i. Type semiconductor layer AS, a pair of source electrode SD1, drain electrode SD
2

It should be understood that the source and the drain are originally determined by the bias polarity between them, and in the circuit of this liquid crystal display device, the polarity is inverted during the operation, and therefore, it should be understood that the source and the drain are switched during the operation. However, in the following description, one is fixed and the other is fixed as a drain for convenience.

<< Gate Electrode GT >> The gate electrode GT is formed continuously with the scanning signal line GL, and a part of the scanning signal line GL is configured as the gate electrode GT. The gate electrode GT is a portion exceeding the active region of the thin film transistor TFT, and is formed larger than that so as to completely cover the i-type semiconductor layer AS (as viewed from below).

Thus, in addition to the role of the gate electrode GT, the gate electrode GT is designed so that external light and backlight do not hit the i-type semiconductor layer AS. In this example, the gate electrode GT is formed of a single-layer conductive film g1. As the conductive film g1, for example, an aluminum (Al) film formed by sputtering is used, and an anodic oxide film AOF of Al is provided thereon.

<< Scanning Signal Line GL >> The scanning signal line GL is formed of the conductive film g1. The conductive film g1 of the scanning signal line GL is formed in the same manufacturing process as the conductive film g1 of the gate electrode GT, and is integrally formed. Through this scanning signal line GL, a gate voltage Vg is supplied from an external circuit to the gate electrode GT.

Also, an anodic oxide film AOF of Al is provided on the scanning signal line GL. The portion that intersects with the video signal line DL is made thin to reduce the probability of short-circuit with the video signal line DL, and is made bifurcated so that even if it is short-circuited, it can be separated by laser trimming.

<< Counter Electrode CT >> The counter electrode CT is formed of a conductive film g1 in the same layer as the gate electrode GT and the scanning signal line GL. Also, an anodic oxide film A of Al is formed on the counter electrode CT.
An OF is provided. The counter electrode CT has an anodic oxide film A
Since they are completely covered with the OF, even if they are brought as close as possible to the video signal lines, they will not be short-circuited.

Further, they may be configured to cross each other. The counter electrode CT is configured to apply a counter voltage Vcom. In this embodiment, the counter voltage Vc
om is a potential lower than an intermediate DC potential between the minimum level drive voltage Vdmin and the maximum level drive voltage Vdmax applied to the video signal line DL by a feedthrough voltage ΔVs generated when the thin film transistor element TFT is turned off. However, if you want to reduce the power supply voltage of the integrated circuit used in the video signal drive circuit to about half,
An AC voltage may be applied.

<< Counter Voltage Signal Line CL >> Counter Voltage Signal Line C
L is composed of the conductive film g1. The conductive film g1 of the counter voltage signal line CL is formed in the same manufacturing process as the conductive film g1 of the gate electrode GT, the scanning signal line GL, and the counter electrode CT, and is formed integrally with the counter electrode CT.

The counter voltage Vcom is supplied from the external circuit to the counter electrode CT through the counter voltage signal line CL. or,
An anodic oxide film AOF of Al is also provided on the counter voltage signal line CL. Note that the portion that intersects with the video signal line DL is
Like the scanning signal line GL, it may be made thinner to reduce the probability of short-circuiting with the video signal line DL, or it may be split into two parts so that even if it is short-circuited, it can be separated by laser trimming.

<< Insulating Film GI >> The insulating film GI is used as a gate insulating film for applying an electric field to the semiconductor layer AS together with the gate electrode GT in the thin film transistor TFT. The insulating film GI is formed above the gate electrode GT and the scanning signal line GL.

As the insulating film GI, for example, plasma CVD
The silicon nitride film formed by
It is formed to a thickness of nm (240 nm in this embodiment).

The gate insulating film GI is formed in the matrix portion A
R is formed so as to surround the entirety of R, and the peripheral portion is removed so as to expose the external connection terminals DTM and GTM. Also,
The insulating film GI also contributes to electrical insulation between the scanning signal lines GL and the counter voltage signal lines CL and the video signal lines DL.

<< i-type semiconductor layer AS >> i-type semiconductor layer AS
Is amorphous silicon and is formed with a thickness of 20 to 220 nm (about 200 nm in this embodiment). Layer d
Numeral 0 denotes an N (+)-type amorphous silicon semiconductor layer doped with phosphorus (P) for ohmic contact. An i-type semiconductor layer AS is present on the lower side, and a conductive film d1 (d2) is present on the upper side. It is left only in places.

The i-type semiconductor layer AS is also provided between the scanning signal line GL and the intersection of the opposing signal line CL and the video signal line DL. The i-type semiconductor layer AS at the intersection reduces a short circuit between the scanning signal line GL and the opposing signal line CL and the video signal line DL at the intersection.

<< Source electrode SDI, drain electrode SD
2 >> Each of the source electrode SDI and the drain electrode SD2 is composed of a conductive film d1 in contact with the N (+) type semiconductor layer d0 and a conductive film d2 formed thereon.

The conductive film d1 is formed of a chromium (Cr) film formed by sputtering to a thickness of 50 to 100 nm (about 60 nm in this embodiment). Since the stress increases when the Cr film is formed to have a large thickness, the Cr film has a thickness of 200 nm.
It is formed in a range that does not exceed a certain thickness. Cr film is N
To improve the adhesion to the (+) type semiconductor layer d0,
2 is used for the purpose of a so-called barrier layer that prevents Al from diffusing into the N (+) type semiconductor layer d0.

As the conductive film d1, a refractory metal (Mo, Ti, Ta, W) film or a refractory metal silicide (MoSi ₂ , TiSi ₂ , TaSi ₂ , WSi ₂ ) film may be used in addition to the Cr film. .

The conductive film d2 has a thickness of 30
It is formed to a thickness of 0 to 500 nm (about 400 nm in this embodiment). The Al film has a smaller stress than the Cr film and can be formed to have a large thickness.
It has functions of reducing the resistance values of D1, the drain electrode SD2, and the video signal line DL, and ensuring the step over caused by the gate electrode GT and the i-type semiconductor layer AS (to improve the step coverage).

After patterning the conductive films d1 and d2 with the same mask pattern, the N (+) type semiconductor layer d0 is removed using the same mask or using the conductive films d1 and d2 as masks. That is, the i-type semiconductor layer AS
The remaining N (+) type semiconductor layer d0 is a conductive film d1,
Portions other than the conductive film d2 are removed by self-alignment.
At this time, since the N (+)-type semiconductor layer d0 is etched so as to completely remove its thickness, the i-type semiconductor layer A is removed.
Although the surface portion of S is also slightly etched, its degree may be controlled by the etching time.

<< Video Signal Line DL >> The video signal line DL is composed of the second conductive film d2 and the third conductive film d3 in the same layer as the source electrode SD1 and the drain electrode SD2. The video signal line DL is formed integrally with the drain electrode SD2.

<< Pixel Electrode PX >> The pixel electrode PX is the second conductive film d of the same layer as the source electrode SD1 and the drain electrode SD2.
2, the third conductive film d3. Also, the pixel electrode P
X is formed integrally with the source electrode SD1.

<< Storage Capacitor Cstg >> The pixel electrode PX is formed so as to overlap the counter voltage signal line CL at the end opposite to the end connected to the thin film transistor TFT. As shown in FIG. 11, this superimposition constitutes a storage capacitor (capacitance element) Cstg in which the pixel electrode PX serves as one electrode PL2 and the counter voltage signal line CL serves as the other electrode PL1. The dielectric film of the storage capacitor Cstg includes an insulating film GI used as a gate insulating film of the thin film transistor TFT and an anodic oxide film AOF.

As shown in FIG. 9, the storage capacitor Cstg is formed in the conductive film g1 of the counter voltage signal line CL in plan view.

In this case, the storage capacitor Cstg is made of aluminum because the material of the electrode positioned below the insulating film GI is made of Al and the surface thereof is anodized. It is possible to obtain a storage capacitor which is less likely to cause adverse effects due to a point defect (short-circuit with an electrode positioned on the upper side) caused by a so-called hillock or the like.

<< Protective Film PSV1 >> Thin Film Transistor TF
On T, a protective film PSV1 is provided. Protective film PS
V1 is formed mainly to protect the thin film transistor TFT from moisture and the like, and uses a material having high transparency and good moisture resistance. The protective film PSV1 is formed of, for example, a silicon oxide film or a silicon nitride film formed by a plasma CVD apparatus, and has a thickness of about 500 nm.

The protective film PSV1 is formed so as to surround the whole of the matrix part AR, and the peripheral part is connected to the external connection terminal DT.
M and GTM have been removed to expose. Regarding the thickness relationship between the protective film PSV1 and the gate insulating film GI, the former is made thicker in consideration of the protective effect, and the latter is made thinner in consideration of the transconductance gm of the transistor.

Color Filter Substrate Next, referring to FIGS. 12 and 15, the upper transparent glass substrate SUB
The configuration of the two sides (color filter substrate) will be described in detail.

<< Light shielding film BM >> Upper transparent glass substrate SUB
On the second side, an unnecessary gap (pixel electrode PX and counter electrode CT)
Transmitted light from the gap other than the gap between
A light-shielding film BM (a so-called black matrix) is formed so as not to lower the contrast ratio and the like. Light shielding film BM
Also serves to prevent external light or backlight light from entering the i-type semiconductor layer AS. That is, the i-type semiconductor layer AS of the thin film transistor TFT is sandwiched between the upper and lower light-shielding films BM and the large gate electrode GT, so that external natural light or backlight does not shine.

The closed rectangular outline of the light-shielding film BM shown in FIG. 7 indicates an opening in which the light-shielding film BM is not formed. This contour pattern is an example.

In a horizontal electric field type liquid crystal display device, a black matrix having the highest possible resistance is suitable.
Generally, a resin composition is used. For this resistance standard,
Although it is not publicly known, Japanese Patent Application No. 7-1919 filed by the same applicant
No. 94. That is, if the specific resistance of the liquid crystal composition LC is described as 10 ^N as 10 ^N , then the specific resistance of the black matrix BM is 10 ^N Ω · cm or more, and the specific resistance of the black matrix BM is 10 M
When written as 10 ^M and 10 ^M Ω · cm or more and, N ≧
9, a relationship that satisfies M ≧ 6. Alternatively, N ≧ 13,
It is desirable that the relationship satisfy M ≧ 7.

Further, from the viewpoint of reducing the surface reflection of the liquid crystal display device, it is desirable to use a resin composition as a material for forming the black matrix.

Further, as compared with the case where a metal film of Cr or the like is used for the black matrix, the step of etching the metal film is not required, so that the manufacturing process of the color filter substrate can be simplified. When a metal film is used, the manufacturing steps are: 1) metal film formation, 2) resist coating, 3) exposure, 4) development, 5)
Metal film etching, 6) resist stripping.

On the other hand, when a resin is used, the manufacturing process is as follows.
1) resin application, 2) exposure, and 3) development, and the process can be significantly shortened.

However, the resin composition has a lower light-shielding property than the metal film. Increasing the thickness of the resin improves the light-shielding properties, but increases the variation in the thickness of the black matrix. This means that, for example, when there is a thickness variation of ± 10%, when the thickness of the black matrix is 1.0 μm, ± 0.1 μm,
This is because when it is 2 μm, it becomes ± 0.2 μm.

When the thickness of the black matrix is increased, the thickness variation of the color filter substrate increases, and it becomes difficult to improve the gap accuracy of the liquid crystal display substrate.
For the above reasons, it is desirable that the thickness of the resin is 2 μm or less.

In order to increase the OD value to about 4.0 or more at a film thickness of 1 μm, for example, when blackening is performed by increasing the carbon content, the specific resistance value of the black matrix BM is about 10 ⁶
Ω · cm or less and cannot be used at present. OD
The value can be defined as the value obtained by multiplying the extinction coefficient by the film thickness.

For this reason, in this embodiment, the light shielding film BM
Is formed of a resin composition obtained by mixing a black inorganic pigment into a resist material, and is formed to a thickness of about 1.3 ± 0.1 μm. Examples of the inorganic pigment include palladium and electroless plated Ni. Further, the specific resistance of the black matrix BM was set to about 10 ⁹ Ω · cm, and the OD value was set to about 2.0.

The calculation result of the light transmission amount when this resin composition black matrix BM is used is shown below.

OD value = log (100 / Y) Y = ∫A (λ) · B (λ) · C (λ) dλ / ∫A (λ)
C (λ) dλ Here, A is the visibility, B is the transmittance, C is the light source spectrum, and λ is the wavelength of the incident light.

When light is shielded by a film having an OD value of 2.0, Y = 1% is obtained from the above equation (1), and the incident light intensity is 4000 cd /
Assuming m ² , about 40 cd / m ² of light will be transmitted. This light intensity is sufficiently bright to be visually recognized by humans.

The light-shielding film BM is also formed in a frame shape in the peripheral portion, and its pattern is a pattern in which a plurality of openings are provided in a dot shape in FIG.
Are formed continuously with the pattern of the matrix section shown in FIG.

<< Color Filter FIL >> The color filter FIL is formed in a stripe shape by repeating red, green, and blue at a position facing the pixel. The color filter FIL is formed so as to overlap the edge portion of the light shielding film BM.

In the present invention, the plane layout of the overlapping portion is defined. Details will be described later.

The color filter FIL can be formed, for example, as follows. First, the upper transparent glass substrate SU
A dye base such as an acrylic resin is formed on the surface of B2, and the dye base other than the red filter formation region is removed by photolithography. Thereafter, the dyed base material is dyed with a red dye and subjected to a fixing treatment to form a red filter R. Next, the green filter G,
Blue filters B are sequentially formed.

<< Overcoat Film OC >> The overcoat film OC is provided to prevent the dye of the color filter FIL from leaking to the liquid crystal LC and to flatten the steps formed by the color filter FIL and the light shielding film BM. The overcoat film OC is formed of, for example, a transparent resin material such as an acrylic resin or an epoxy resin.

[0137] The liquid crystal layer and the polarizing plate Subsequently, the liquid crystal layer, orientation film, described polarizing plate or the like.

<< Liquid Crystal Layer >> As the liquid crystal material LC, the dielectric anisotropy Δ △ is positive and its value is 13.2, and the refractive index anisotropy Δn
Is 0.081 (589 nm, 20 ° C.), a dielectric anisotropy Δ △ is negative and the value is −7.3, and a refractive index anisotropy Δn is 0.053 (589 nm, 20 ° C.). The nematic liquid crystal of C) was used.

The thickness (gap) of the liquid crystal layer is set to be more than 2.8 μm and less than 4.5 μm when the dielectric anisotropy Δε is positive.
This is because the retardation Δn · d exceeds 0.25 μm.
When it is less than 32 μm, a dielectric constant characteristic having almost no wavelength dependence within the visible light range is obtained, and most of the liquid crystal having a positive dielectric anisotropy Δ △ has a birefringence anisotropy Δn of 0. 0.07 or more
This is because it is less than 09.

On the other hand, when the dielectric anisotropy Δ △ was negative, the thickness (gap) of the liquid crystal layer was more than 4.2 μm and less than 8.0 μm. This is because, like the liquid crystal having a positive dielectric anisotropy Δε, the retardation Δn · d exceeds 0.25 μm by 0.32 μm.
Most of the liquid crystal having a negative dielectric anisotropy Δ △ has a birefringence anisotropy Δn of more than 0.04 to suppress the dielectric anisotropy Δ △ is negative.
This is because it is less than 6.

Further, the maximum transmittance can be obtained when the liquid crystal molecules are rotated by 45 ° from the rubbing direction to the electric field direction by a combination of an alignment film and a polarizing plate described later. The thickness (gap) of the liquid crystal layer is controlled by polymer beads.

The liquid crystal material LC is not particularly limited as long as it is a nematic liquid crystal. Dielectric anisotropy △ ε
The larger the value, the lower the driving voltage, and the smaller the refractive index anisotropy Δn, the smaller the thickness (gap) of the liquid crystal layer.
Can be made thicker, the liquid crystal filling time can be shortened, and the gap variation can be reduced.

<< Orientation Film >> Polyimide is used as the orientation film ORI. The rubbing direction RDR is parallel to each other between the upper and lower substrates, and the angle φLC between the applied electric field direction EDR and the angle φLC.
Is 75 °. FIG. 13 shows the relationship.

The rubbing direction RDR and the applied electric field direction E
The angle with DR is 45 ° or more and less than 90 ° when the dielectric anisotropy △ ε of the liquid crystal material is positive, and is more than 0 ° and 45 ° or less when the dielectric anisotropy △ ε is negative. Is fine.

<< Polarizing Plate >> As the polarizing plate POL, G1220DU (trade name) manufactured by Nitto Denko Corporation was used. As shown in FIG. 11, the polarization transmission axis MAX1 of the lower polarizing plate POL1 was used.
With the rubbing direction RDR, and the upper polarizer POL
The polarization transmission axis MAX2 is orthogonal to it.

Thus, it is possible to obtain a normally-closed characteristic in which the transmittance increases as the voltage applied to the pixel of the present invention (the voltage between the pixel electrode PX and the counter electrode CT) increases.

Further, in the liquid crystal display device referred to as the in-plane switching method disclosed in the present invention, display abnormalities occur when a high potential such as static electricity is applied from the outside of the upper substrate SUB2 side surface. . Therefore, a layer of a transparent conductive film having a sheet resistance of 1 × 10 ⁸ Ω / □ or less is formed further above or on the surface of the upper polarizing plate POL2, or a sheet resistance of 1 × is provided between the polarizing plate and the transparent substrate. I of 10 ⁸ Ω / □ or less
Forming a layer of a transparent conductive film such as TO, or mixing conductive particles such as ITO, SnO ₂ , and In ₂ O _{3 with} the adhesive layer of the polarizing plate to reduce the sheet resistance to 1 × 10 ⁸ Ω / □ or less. It becomes necessary. Regarding this measure, it is not publicly known, but in Japanese Patent Application No. 7-264443 filed by the same applicant,
There is a detailed description of the improvement of the shield function.

<< Configuration around Matrix >> FIG. 14 shows a display panel PNL including upper and lower glass substrates SUB1 and SUB2.
2 is a plan view of a main part around a matrix (AR) of FIG. FIG. 15 shows an external connection terminal GTM to which a scanning circuit is connected on the left side.
It is sectional drawing of a vicinity.

In the manufacture of this panel, if the size is small, a plurality of devices are processed simultaneously on one glass substrate to improve the throughput in order to improve the throughput. If the size is large, the manufacturing equipment is shared. For each type, a glass substrate of a standardized size is processed and then reduced to a size suitable for each type. In each case, the glass is cut after passing through a single process.

FIGS. 14 and 15 show examples of the latter.
14 and 15, the upper and lower substrates SUB1 and SUB2 are used.
LN indicates the edge of both substrates before cutting. In any case, in the completed state, the external connection terminal group T
The size of the upper substrate SUB2 is limited to the inside of the lower substrate SUB1 so that g, Td, and the terminal CTM are present (the upper side and the left side in the figure) so as to expose them.

The terminal groups Tg and Td are respectively a scanning circuit connection terminal GTM and a video signal circuit connection terminal DT described later.
M and a plurality of lead wiring portions are collectively named for a unit of a tape carrier package TCP (see FIGS. 15 and 16) on which the integrated circuit chip CHI is mounted.

The lead wiring from the matrix section of each group to the external connection terminal section is inclined as approaching both ends. This is because the display panel P is set in the arrangement pitch of the package TCP and the connection terminal pitch in each package TCP.
This is for adjusting to the terminals DTM and GTM of the NL.

The counter electrode terminal CTM is connected to the counter electrode CT.
Is a terminal for applying a counter voltage from the outside. The counter electrode signal line CL in the matrix portion is connected to a scanning circuit terminal GTM.
, And the common voltage signal lines are grouped together by a common bus line CB to form a common electrode terminal CT
M.

Between the transparent glass substrates SUB1 and SUB2, along the edges thereof, except for the liquid crystal filling opening INJ, the liquid crystal L
A seal pattern SL is formed so as to seal C.
The sealing material is made of, for example, an epoxy resin.

The alignment films ORI1 and ORI2 are formed inside the seal pattern SL. Polarizing plates POL1, P
OL2 is formed on the outer surfaces of the lower transparent glass substrate SUB1 and the upper transparent glass substrate SUB2, respectively.

The etching LC is sealed in a region partitioned by the seal pattern SL between the lower alignment film ORI1 and the upper alignment film ORI2 for setting the direction of the liquid crystal molecules.
The lower alignment film ORI1 is formed above the protective film PSV1 on the lower transparent glass substrate SUB1 side.

In this liquid crystal display device, various layers are separately stacked on the lower transparent glass substrate SUB1 side and the upper transparent glass substrate SUB2 side, and the seal pattern SL is formed on the substrate SUB2.
Side, the lower transparent glass substrate SUB1 and the upper transparent glass substrate SUB2 are overlapped with each other to form a seal pattern SL
The liquid crystal LC is injected from the opening INJ, the inlet INJ is sealed with an epoxy resin or the like, and the upper and lower substrates are cut to be assembled.

<< Equivalent Circuit of Entire Display Device >> FIG. 17 is a schematic explanatory diagram of peripheral circuits of a liquid crystal display device according to the present invention.
As shown in the figure, the liquid crystal display substrate is constituted by a set of a plurality of pixels in which an image display unit is arranged in a matrix,
Each pixel is configured to independently control the modulation of transmitted light from a backlight disposed behind the liquid crystal display substrate.

An active pixel area is provided on an active matrix substrate SUB1, which is one of the components of the liquid crystal display substrate.
The gate signal line GL and the counter voltage signal line CL, which extend in the x direction (row direction) and are arranged in parallel in the y direction (column direction), extend in the y direction while being insulated from the AR, and extend in the x direction. The provided drain signal line DL is formed.

Here, a unit pixel is formed in a rectangular area surrounded by each of the gate signal line GL, the counter voltage signal line CL, and the drain signal line DL.

The liquid crystal display substrate is provided with a vertical scanning circuit V and a video signal driving circuit H as external circuits, and the vertical scanning circuit V sequentially supplies a scanning signal (voltage) to each of the gate signal lines GL. From the video signal drive circuit H to the drain signal line DL in accordance with the timing.
Is supplied with a video signal (voltage).

The vertical scanning circuit V and the video signal driving circuit H are supplied with power from the liquid crystal driving power supply circuit 3 and input image information from the CPU 1 after being divided into display data and control signals by the controller 2. It is supposed to be.

<< Driving Method >> FIG. 18 is a driving waveform diagram of the liquid crystal display device of the present invention. The opposite voltage is VCH and VCL.
Value AC rectangular wave and the scanning signal VG
(I-1) The non-selection voltage of VG (i) is changed by two values of VCH and VCL every scanning period. The amplitude width of the counter voltage and the amplitude value of the non-selection voltage are the same.

The video signal voltage is a voltage obtained by subtracting half of the amplitude of the counter voltage from the voltage to be applied to the liquid crystal layer.

The counter voltage may be DC, but by converting it to AC, the maximum amplitude of the video signal voltage can be reduced, and a video signal drive circuit (signal-side driver) having a low withstand voltage can be used.

<< Function of Storage Capacitance Cstg >> Storage Capacitance Cs
tg is written to the pixel (thin film transistor TFT
Is provided for long storage of video information (after the power is turned off).

In the method of applying an electric field parallel to the substrate surface used in the present invention, unlike the method of applying the electric field perpendicular to the substrate surface, the capacitance (the so-called liquid crystal capacitance) composed of the pixel electrode and the counter electrode is different. Since there is almost no storage, the storage Cstg is an essential component.

The storage capacitor Cstg also functions to reduce the influence of the gate potential change ΔVg on the pixel electrode potential Vs when the thin film transistor TFT switches. This situation is represented by the following equation.

ΔVs = [Cgs / (Cgs + Cstg +
Cpix)] × ΔVg where Cgs is a parasitic capacitance formed between the gate electrode GT and the source electrode SDI of the thin film transistor TFT,
Cpix represents a capacitance formed between the pixel electrode PX and the counter electrode CT, and ΔVs represents a change in pixel electrode potential due to ΔVg, a so-called feedthrough voltage.

The change ΔVs causes a DC component applied to the liquid crystal LC, but the value can be reduced as the storage capacitance Cstg is increased.

The reduction of the DC component applied to the liquid crystal LC is as follows.
It is possible to improve the life of the liquid crystal LC and reduce so-called burn-in in which a previous image remains when the liquid crystal display screen is switched.

As described above, since the gate electrode GT is made large so as to completely cover the i-type semiconductor layer AS, the area of overlap with the source electrode SDI and the drain electrode SD2 increases, and therefore the parasitic capacitance Cgs increases. The pixel electrode potential Vs has an adverse effect of being easily affected by the gate (scanning) signal Vg. However, the storage capacity Cs
By providing tg, this disadvantage is also eliminated.

<< Manufacturing Method >> Next, a method of manufacturing the above-described liquid crystal display device on the substrate SUB1 side will be described.

FIGS. 19, 20 and 21 are explanatory views of the manufacturing process of the liquid crystal display device according to the present invention. In FIG. 19, the characters in the center are the abbreviations of the process names, and the left side in FIG. The right side of the thin film transistor TFT portion shown in the drawing shows the flow of processing viewed from the cross-sectional shape near the gate terminal. Except for Step B and Step D, Step A to Step I are classified according to each photographic process (photolithography).
Each cross-sectional view of each step shows a stage where the processing after the photoprocessing is completed and the photoresist is removed.

In the present invention, photographic processing refers to a series of operations from application of a photoresist, through selective exposure using a mask to development of the photoresist, and a repetitive description will be omitted. Description will be given below according to the divided steps.

Step A (FIG. 19) A 300 nm thick Al-Pd or Al-Pd is formed on a lower transparent glass substrate SUB1 made of AN635 glass (trade name).
Conductive film g made of W, Al-Ta, Al-Ti-Ta, etc.
1 is provided by sputtering. After the photographic processing, the conductive film g1 is selectively etched with a mixed acid solution of phosphoric acid, acid and glacial acetic acid. Thereby, the gate electrode GT, the scanning signal line GL, the counter electrode CT, the counter voltage signal line CL, and the electrode PL
1, gate terminal GTM, first conductive layer of common bus line CB, first conductive layer of counter electrode terminal CTM, gate terminal GT
An anodizing bus line SHg (not shown) connecting M and an anodizing pad (not shown) connected to the anodizing bus line SHg are formed.

Step B (FIG. 19) After the formation of the anodic oxidation mask AO by direct writing, a solution in which 3% tartaric acid was adjusted to PH 6.25 ± 0.05 with ammonia and diluted 1: 9 with ethylene glycol solution was used. The substrate SUB1 is immersed in an anodic oxidizing solution to adjust the formation current density to 0.5 mA / cm ² (constant current formation).

Next, anodic oxidation is performed until the formation voltage of 125 V necessary for obtaining a predetermined alumina (Al ₂ O ₃ ) film thickness is reached. Thereafter, it is desirable to maintain this state for several tens of minutes (constant voltage formation). This is a uniform Al ₂ O
_This is important for obtaining _three films. Thereby, the conductive film g1 is anodized, and the gate electrode GT and the scanning signal line G
L, counter electrode CT, counter voltage signal line CL and electrode PL1
An anodic oxide film AOF having a thickness of 180 bnm is formed thereon.

Step C (FIG. 19) A transparent conductive film g2 made of an ITO film having a thickness of 140 nm is provided by sputtering. After the photographic processing, the transparent conductive film g2 is selectively etched with a mixed acid solution of hydrochloric acid and nitric acid as an etchant, thereby forming the uppermost layer of the gate terminal GTM, the drain terminal DTM, and the second conductive film of the counter electrode terminal CTM. I do.

Step D (FIG. 20) An ammonia gas, a silane gas, and a nitrogen gas are introduced into a plasma CVD apparatus to provide a 220-nm-thick Si nitride film, and a silane gas and a hydrogen gas are introduced into the plasma CVD apparatus to form a film. After an i-type amorphous Si film having a thickness of 200 nm is provided, a silane gas, a hydrogen gas, and a phosphine gas are introduced into a plasma CVD apparatus to form an N (+)-type amorphous Si film having a thickness of 30 nm.

Step E (FIG. 20) After the photographic processing, the N (+)-type amorphous Si film and the i-type amorphous Si film are selectively etched using SF6 as a dry etching gas, whereby i An island of the type semiconductor layer AS is formed.

Step F (FIG. 20) After the photographic processing, the Si nitride film is selectively etched using SF6 as a dry etching gas.

Step G (FIG. 21) A conductive film d1 made of Cr having a thickness of 60 nm is provided by sputtering, and an Al-P film having a thickness of 400 nm is further formed.
A conductive film d2 made of d, Al-Si, Al-Ta, Al-Ti-Ta, or the like is provided by sputtering. After the photographic processing, the conductive film d2 is etched with the same liquid as in Step A,
The conductive film d1 is etched with a ceric ammonium nitrate solution, and the video signal line DL, the source electrode SD1, the drain electrode SD2, the pixel electrode PX, the electrode PL2, the second conductive layer, the third conductive layer and the drain of the common bus line CB are formed. Terminal D
A bus line SHd (not shown) for short-circuiting TM is formed. Next, SF6 is introduced into the dry etching apparatus,
By etching the N (+) type amorphous Si film,
The N (+) type semiconductor layer d0 between the source and the drain is selectively removed.

Step H (FIG. 21) An ammonia gas, a silane gas, and a nitrogen gas are introduced into a plasma CVD apparatus to form a 500-nm-thick Si nitride film. After photographic processing, SF is used as the drain etching gas.
The protective film PSV1 is formed by selectively etching the Si nitride film by a photolithography technique using No. 6.

<< Display Panel PNL and Drive Circuit Board PCB
1 >> FIG. 22 is a top view showing a state where the display panel PNL, the video signal driving circuit H, and the vertical scanning circuit V shown in FIG. 17 are connected.

CH1 is a drive IC chip for driving the display panel PNL (the lower five are drive ICs on the vertical scanning circuit side)
Chip, drive ICs on the left side of the 10 video signal drive circuits
Chip). TCP is a tape carrier package in which the driving IC chip CH1 is mounted by a tape automated bonding (TAB) method as shown in FIGS. 15 and 16, and PCB1 is a driving circuit in which the above-described TCP, capacitors and the like are mounted. The substrate is divided into two, one for a video signal drive circuit and one for a scan signal drive circuit.

FGP is a frame ground pad.
A spring-shaped fragment provided by cutting into the shield case SHD is soldered. FC is the lower drive circuit board PC
This is a flat cable for electrically connecting B1 to the left drive circuit board PCB1.

As shown in the figure, the flat cable FC is formed by sandwiching and supporting a plurality of lead wires (phosphor bronze material plated with Sn) with a striped polyethylene layer and a polyvinyl alcohol layer. use.

<< Connection Structure of TCP >> FIG.
FIG. 14 is a diagram showing a cross-sectional structure of a tape carrier package in which an integrated circuit chip CHI constituting a scanning signal driving circuit V and a video signal driving circuit H is mounted on a flexible wiring board, and FIG. FIG. 3 is a cross-sectional view of a main part showing a pair connected to a scanning signal circuit terminal GTM.

In the figure, TTB is an input terminal / wiring portion of the integrated circuit CHI, and TTM is an output terminal / wiring portion of the integrated circuit CHI, which is made of, for example, Cu, and has an inner tip (commonly referred to as an inner portion). The bonding pads PAD of the integrated circuit CHI are connected to the leads by a so-called face-down bonding method.

The outer ends (commonly called outer leads) of the terminals TTB and TTM are respectively connected to the semiconductor integrated circuit chips CH
Corresponds to input and output of I, CRT /
Anisotropic conductive film AC for TFT conversion circuit / power supply circuit SUP
F connects to the liquid crystal display panel PNL.

[0192] The package TCP is connected to the panel PNL so that the tip thereof covers the protective film PSV1 exposing the connection terminal GTM on the panel PNL side. Therefore,
Since the outer connection terminal GTM (DTM) is covered with at least one of the protective film PSV1 and the package TCP, the outer connection terminal GTM (DTM) is resistant to electric contact.

BF1 is a base film made of polyimide or the like, and SRS is a solder resist film for masking so that solder does not adhere to unnecessary portions during soldering. The gap between the upper and lower glass substrates outside the seal pattern SL is protected by an epoxy resin EPX or the like after cleaning, and the space between the package TCP and the upper substrate SUB2 is further filled with a silicon resin SIL to multiplex protection.

<< Drive Circuit Board PCB2 >> Drive Circuit Board P
The CB2 has electronic components such as an IC, a capacitor, and a resistor mounted thereon. The drive circuit board PCB2 includes a power supply circuit for obtaining a plurality of divided and stabilized voltage sources from one voltage source, and a CR (Crystal Control Unit) from a host (upper processing unit).
A circuit SUP including a circuit for converting information for T (cathode ray tube) into information for a TFT liquid crystal display device is mounted. C
J is a connector connection portion to which a connector (not shown) connected to the outside is connected.

Driving Circuit Board PCB1 and Driving Circuit Board PC
B2 is electrically connected by a joiner JN such as a flat cable FC.

FIG. 23 is an external view of a computer monitor mounted with a liquid crystal display device according to the present invention.
LCD panel 3 with a large screen
It is a thin, lightweight monitor with zero.

It is needless to say that the liquid crystal display device according to the present invention can be used not only for the above-mentioned desktop monitor but also for a display device of a portable personal computer such as a notebook type.

It should be noted that, again, the present invention is not limited to the above-mentioned horizontal electric field type active matrix type liquid crystal display device, but is applicable to a vertical electric field type or simple matrix type liquid crystal display device. The present invention can be similarly applied to a method and an apparatus which do not require the liquid crystal alignment control ability.

[0199]

As described above, according to the present invention,
The combination of an optical element that diffuses the illumination light of the backlight and an optical element that collects the illumination light can arbitrarily adjust the luminance and the viewing angle of the liquid crystal panel by the illumination light. A liquid crystal display device capable of reducing power consumption can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating a first embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is a schematic diagram illustrating a dimming function of the light scattering element in FIG.

FIG. 3 is an explanatory diagram of a relationship between a viewing angle and luminance corresponding to FIG. 2 for explaining the effect of the first embodiment of the present invention.

FIG. 4 is a schematic sectional view illustrating a second embodiment of the liquid crystal display device according to the present invention.

FIG. 5 is a schematic diagram illustrating a dimming function of the light scattering element in FIG.

FIG. 6 is a schematic sectional view illustrating a liquid crystal display device according to a third embodiment of the present invention.

FIG. 7 is a schematic diagram illustrating a dimming function of the piezoelectric lens sheet illustrated in FIG.

FIG. 8 is a schematic diagram illustrating an example of a dimming element that can be applied to the first or second embodiment of the present invention and that can adjust the front luminance and the viewing angle.

FIG. 9 is a plan view showing one pixel of an active matrix type color liquid crystal display device of the present invention, a light-shielding region of a black matrix BM, and its periphery.

FIG. 10 is a sectional view of the thin film transistor TFT taken along section line 4-4 in FIG. 9;

FIG. 11 shows a storage capacitance Cst along a section line 5-5 in FIG. 9;
It is sectional drawing of g.

12A and 12B are a cross-sectional view of the vicinity of an electrode of one pixel and a cross-sectional view of a peripheral portion of the substrate in an image display area of a liquid crystal display substrate of a horizontal electric field type.

FIG. 13 shows a rubbing direction of an alignment film and an applied electric field direction EDR.
FIG. 4 is an explanatory diagram of an angle formed by

FIG. 14 is a plan view of a main part around a matrix of a display panel including upper and lower substrates.

FIG. 15 is a cross-sectional view near an external terminal to which a scanning circuit is connected on the left side.

FIG. 16 is an explanatory diagram of a cross-sectional structure of an output side and an input side of a gate TCP.

FIG. 17 is a schematic explanatory diagram of a peripheral circuit of a liquid crystal display device according to the present invention.

FIG. 18 is a driving waveform diagram of the liquid crystal display device of the present invention.

FIG. 19 is an explanatory diagram of a manufacturing process of the liquid crystal display device according to the present invention.

FIG. 20 is a view showing a manufacturing process of the liquid crystal display device according to the present invention;
It is explanatory drawing following 9.

FIG. 21 is a view showing a manufacturing process of the liquid crystal display device according to the present invention;
It is explanatory drawing following 0.

22 is a top view showing a state where the display panel PNL, the video signal driving circuit H, and the vertical scanning circuit V shown in FIG. 17 are connected.

FIG. 23 is an external view of a computer monitor mounted with a liquid crystal display device according to the present invention.

FIG. 24 is a developed perspective view for explaining a schematic structure of a general liquid crystal display device.

FIG. 25 shows the relationship between the vertical viewing angle and the luminance when two prism sheets are installed between the backlight and the liquid crystal panel, when one prism sheet is installed, and when only the light diffusion sheet is used without using the prism sheet. FIG.

[Explanation of symbols]

 1a Upper substrate 1b Lower substrate 3 Liquid crystal panel 4a Upper polarizer 4b Lower polarizer 5 Linear light source (lamp) 6 Reflector 7 Backlight 8a Upper transparent electrode layer 8b Lower transparent electrode layer 9a Polymer layer 9b Low molecular nematic liquid crystal 10 Light scattering sheet 11a Upper prism sheet 11b Lower prism sheet 12 Condenser sheet 13 Light control power supply 14 Light control switch.

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[Procedure amendment]

[Submission date] October 21, 1998

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

FIG. 3

Claims (6)

[Claims] 1. A liquid crystal panel having a liquid crystal layer sandwiched between a pair of transparent substrates having a pixel selection electrode on at least one of them opposed to each other, an upper polarizer disposed on both sides of the liquid crystal panel, and A lower polarizing plate, a driving unit for applying a voltage corresponding to a display signal to the electrodes, and a backlight installed on the back of the liquid crystal panel are fixed by an upper frame and a lower frame connected to the upper frame. A light-collecting element that collects light emitted from the backlight between the backlight and the liquid crystal panel; and a light-collecting element that is stacked on the liquid crystal panel side of the light-collecting element. A liquid crystal display device comprising a light scattering element that makes the degree of scattering of transmitted light variable. 2. A liquid crystal panel having a liquid crystal layer sandwiched between a pair of transparent substrates having an electrode for selecting a pixel on at least one of them opposed to each other, and an upper polarizing plate arranged with the liquid crystal panel interposed therebetween. A lower polarizing plate, a driving unit for applying a voltage corresponding to a display signal to the electrodes, and a backlight installed on the back of the liquid crystal panel are fixed by an upper frame and a lower frame connected to the upper frame. Between the backlight and the liquid crystal panel, a light scattering element having a variable degree of scattering transmitted light of light emitted from the backlight, and a light scattering element laminated on the liquid crystal panel side of the light scattering element. A light-collecting element for condensing light from the light-scattering element. 3. A liquid crystal display according to claim 1, wherein said light scattering element is a polymer dispersed liquid crystal sheet in which an organic low molecular nematic liquid crystal is dispersed in a polymer between a pair of transparent electrodes. apparatus. 4. The liquid crystal display device according to claim 1, wherein the polymer dispersed liquid crystal sheet has an organic low molecular nematic liquid crystal sandwiched between a pair of transparent electrodes. 5. The light-scattering element comprises a light-scattering plate comprising a large number of light-scattering plates planted on a transparent substrate with a variable inclination angle, and the degree of scattering of transmitted light varies according to the inclination angle. The liquid crystal display device according to claim 1, wherein: 6. The liquid crystal display device according to claim 2, wherein the light condensing element is a transparent piezoelectric film whose light condensing degree changes according to an applied voltage value.