JP3074101B2 - Liquid crystal display - Google Patents

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 used as an image display terminal of a TV or a computer.

[0002]

With reference to the Prior Art The following figures, the liquid crystal display device (to hereinafter PDLCD commonly referred to using the conventional polymer dispersed liquid crystal, P olymer D ispersed L iqu
id C rystal D abbreviation isplay), describing an example of. FIG. 6 is a schematic view of a general reflection type PDLCD. The left half of the figure is a schematic view in a state where no electric field is applied, and the right half of the figure is a schematic view in a state where an electric field is applied. The upper substrate 1, the lower substrate 2, the color reflector 4, the polymer dispersed liquid crystal 5, the transparent conductive film 6, and the lower electrode 7 are main components. When no electric field is applied, the directions of the liquid crystal molecules in the polymer droplet are random, and the incident light is scattered. When a voltage is applied between the transparent electrode 6 and the lower electrode 7, the liquid crystal molecules having a positive dielectric anisotropy (Δε> 0) are used, and the liquid crystal molecules are oriented perpendicular to the substrate. Then, the light is reflected by the color reflection plate 4 on the lower substrate 2, and the pixel appears colored. By providing a color reflector of three primary colors of R, G, and B, a full-color display is possible. Further, when a black film is arranged instead of the color reflector, a black-and-white display type LCD is obtained. For example, “Japanese Patent Laid-Open No. 03-256
024 ”, a reflective PDL driven by a nonlinear element
A CD is shown, and the concept of a color PDLCD using a translucent color filter is disclosed in Japanese Patent Application Laid-Open No. 03-186816.

[0003]

In the conventional PDLCD as shown in the above example, each of them has a structure in which the PDLC is sandwiched between a transparent conductive film 6 and a metal film arranged in parallel with the substrates 1 and 2, Regardless of the transmission type or the reflection type, since the light transmitted through the transparent conductive film 6 is observed, a light amount loss due to this is inevitable. For example, when a general ITO film is used as the transparent conductive film 6, the light transmittance is about 90% at a wavelength of 550 nm, and a light amount loss of 19% occurs when transmitted twice. Also, in JP-A-03-186816, PDLC
Although the scattering state of D is used for white display, in this method,
Since the scattering efficiency of the PDLCD is low, there is a disadvantage that a bright and high-contrast display cannot be expected.

Further, as the transparent conductive film 6, a general ITO is used.
Since the film contains a rare metal called In, the sputtering target is expensive, and the etching solution such as HI commonly used for etching is also expensive, which is one of the factors that increase the LCD manufacturing cost. I have. It has also been widely pointed out that galvanic corrosion due to contact between the ITO film and other metals causes a reduction in LCD production yield.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a liquid crystal display device which does not require a transparent conductive film for lowering the light transmittance and can realize bright display characteristics.

[0006]

According to a first aspect of the present invention, there is provided a liquid crystal display device comprising: a pair of driving electrodes; wherein arranged on at least one of the inner surfaces of the substrates, enclosing the polymer dispersed liquid crystal having a negative permittivity anisotropy between a pair of said substrates, said electric field by applying a voltage between the pair of the drive electrodes And the liquid crystal can be driven.

According to a second aspect of the present invention, in the liquid crystal display of the first aspect, a color reflector is disposed on an inner surface of one of the substrates between the pair of drive electrodes, and a black dye is dispersed in the liquid crystal. In the state where no electric field is applied, the incident light is absorbed by the dye to make black display, and in the state where the electric field is applied, the liquid crystal is made transparent, and the incident light is reflected by the color reflector to make color display.

According to a third aspect of the present invention, there is provided the liquid crystal display of the first aspect, wherein a black film is disposed on the inner surface of one of the substrates between the pair of drive electrodes, and the incident light is scattered when no electric field is applied. The liquid crystal is made transparent in a state where an electric field is applied, and the black film absorbs incident light to make a black display.

[0009]

According to the structure of the present invention, since the liquid crystal having a negative dielectric anisotropy (Δε <0) is used, the liquid crystal molecules are oriented perpendicular to the substrate in the presence of an electric field, become transparent, and have no electric field. In this case, the liquid crystal molecules are randomly oriented and are in a scattering state. However, if the guest-host mode (GH-mode) is obtained by adding a black dye to the liquid crystal, the dye is arranged in the same direction as the liquid crystal molecules. And the pixel appears colored.
Without an electric field, the incident light is absorbed by the black dye, and a black display is obtained. In addition, when a black film is disposed on the substrate, incident light is scattered in the absence of an electric field to produce white display, and the presence of an electric field makes the liquid crystal transparent and the black film absorbs light to produce black display, thereby enabling black and white image display.

As described above, the voltage is applied between the electrodes arranged on the substrate.
Pressure to generate an electric field in a substantially horizontal direction on the substrate surface,
Structure for driving polymer dispersed liquid crystal showing negative dielectric anisotropy
Therefore, it is possible to omit the transparent conductive film that reduces the light transmittance or the light reflectance, and a PDLCD having brighter display characteristics is realized. In addition, since a transparent conductive film is not required, the manufacturing steps of film formation and patterning are simplified, and the cost can be reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal display according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram of a PDLCD of a liquid crystal display device according to an embodiment of the present invention. The left half of the diagram is a schematic diagram in a state where no electric field is applied, and the right half of the diagram is a schematic diagram in a state where an electric field is applied. It is. This liquid crystal display device includes an upper substrate 1 and a lower substrate 2 opposed to each other, a pair of drive electrodes 3 and 3 arranged at predetermined intervals on the inner surface of the lower substrate 2, and a lower substrate 2 between these drive electrodes 3 and 3. A color reflector 4 disposed on the inner surface, and a polymer dispersed liquid crystal 5 sealed between the upper substrate 1 and the lower substrate 2 are provided.

In the guest-host mode by adding a black dye to the liquid crystal 5, the direction of the liquid crystal molecules in the polymer droplet is random when no electric field is applied, and the incident light is absorbed because the black dye is also arranged randomly. And a black display is obtained. The drive electrode 3 is made of Ti (0.1 μm) / Al (2 μm)
The electrode was a two-layer film, the electrode width was 3 μm, and the electrode interval was 12.5 μm. The color reflection plate 4 has a configuration in which a color filter is applied on an Al reflection film. When a voltage is applied to the drive electrode 3, an electric field is generated in a direction parallel to the substrates 1 and 2, and a liquid crystal having a negative dielectric anisotropy (Δε <0) is used. It is oriented vertically, so that light is transmitted and reflected by the color reflector 4 on the lower substrate 2, and the pixels appear colored. By providing a color reflector of three primary colors of R, G, and B, a full-color display is possible. In the above embodiments, the black dye was added. However, if black display is unnecessary, it is not necessary to add the black dye.

When a black film is arranged in place of the color reflector 4, a black-and-white display type LCD is obtained. However, in this case, the black dye is unnecessary, and in the absence of an electric field, the direction of the liquid crystal molecules is random, so that the incident light is scattered and white display is performed. With the presence of the electric field, the liquid crystal molecules are oriented perpendicular to the substrates 1 and 2. The liquid crystal 5 is made transparent so that light is absorbed by the black film, and a black display is obtained. As a result, it is possible to display a bright and clear black-and-white image close to the current printed matter.

In the above embodiment, the driving electrode 3 is provided with a thin film transistor.
Configuration that does not use nonlinear elements such as transistors and MIMs.
However, each pixel has a thin film transistor, MIM, etc.
Active matrix LCD with non-linear elements
You may. FIG. 2 is applicable to the liquid crystal display device of the present invention.
Plane showing structure of one pixel portion of thin film transistor integrated device
FIG. 3 is a schematic cross-sectional view taken along line AB in FIG.
is there. Substrate 17, gate line (gate electrode) 10, signal
No. line 12, drain line 13, counter electrode line 1
4, storage capacitor section 15, gate insulating film 16, contact hole
The rule 11 is a main component. For the counter electrode line 14
About the source / drain level counter electrode line
Connect the gate-level counter electrode line to the gate-level counter electrode.
Contact opened in gate insulating film 16 above electrode line
In this configuration, electrical connection is made directly through the
ing. That is, an Al film is formed on the substrate 17 by 3500%.
The gate line 10 and the gate level counter electrode line
The pattern 14 is patterned. Next, by anodic oxidation, Al
An Al oxide film is formed on the film surface. However, contact
The vicinity of the rule 11 is not anodized. Next, the PCVD method
SiN_x/ A-Si: H / SiN_xMany
After forming the layer film, patterning is performed to produce a TFT portion. Io
Highly doped layers (n⁺Layer) formation
Then, the insulating film 16 on the gate level counter electrode line 14 is formed.
Then, a contact hole 11 is opened. Next, Ti, Z
Conductive single layer composed of r, Cr, Mo, W, Al, etc.
After forming the film or the multilayer film, the drain line 13 and the signal line
The in 12 and the counter electrode line 14 are patterned.
Gate line 10, signal line 12, counter electrode line 1
4 is continuous as a line from end to end of each pixel in the substrate
Connected outside, and take out the electrode terminal outside the pixel.
It is becoming In this embodiment, Ti (thickness 1000)
Ii) / Al (2 μm thick) two-layer film was used. In FIG.
As shown in FIG.₁ , A_Two , A_Three ,
a_Four Are all 12.5 μm, and are paired with the drain line 13.
The width of the counter electrode was 3 μm. The storage capacitor 15 is a counter electrode
It was provided at the intersection of the line 14 and the drain line 13.
SiN as protective film _x2000mm coating of membrane and protection
A polyimide alignment film is applied on the film. In this case, the polymer
Droplets of dispersed liquid crystal are random without electric field
In the presence of an electric field, the drain line 13
The liquid flows in a direction perpendicular to the direction of the electric field between the counter electrode lines 14.
The crystal molecules are arranged so that the major axis directions are aligned.

FIG. 2 is a plan view of the completed thin film transistor integrated device, and FIGS. 4 and 5 are explanatory views in the order of the manufacturing steps. FIG. 4 shows a state in which the patterns of the gate electrode 10 and the counter electrode line 14 are formed, and FIG. 5 shows a state in which the patterns of the contact hole 11 and the TFT portion 17 are formed. Thereafter, the signal line 12, the drain line 13, and the counter electrode line 14 are formed to reach the completed view in FIG. The counter electrode line 14 has a gate level bus line portion and a source / drain level portion which forms one side of a comb-shaped electrode in a pixel.
The components are electrically connected to each other via a common electrode line, and the components are collectively referred to as a counter electrode line 14.

As described in the above embodiments, in the liquid crystal display device of the present invention, a voltage is applied between the electrodes arranged on the substrate, an electric field is generated in a substantially horizontal direction on the substrate surface, and a negative dielectric constant is applied. The method is characterized in that a polymer-dispersed liquid crystal exhibiting anisotropy is driven, and this method eliminates the need for a transparent conductive film that lowers light transmittance and realizes a bright LCD.

[0017]

[0018]

According to the liquid crystal display device of the present invention, since the liquid crystal having a negative dielectric anisotropy (Δε <0) is used, the liquid crystal molecules are oriented perpendicular to the substrate in the presence of an electric field, and the liquid crystal display device is in a transparent state. In the absence of an electric field, the liquid crystal molecules are randomly oriented and are in a scattering state. However, adding a black dye to the liquid crystal
In the host mode (GH-mode), the dye is arranged in the same direction as the liquid crystal molecules. Therefore, in the presence of an electric field, the incident light is transmitted, reflected by the color reflector on the substrate, and the pixel appears colored. Without an electric field, the incident light is absorbed by the black dye, and a black display is obtained. In addition, when a black film is disposed on the substrate, incident light is scattered in the absence of an electric field to produce white display, and the presence of an electric field makes the liquid crystal transparent and the black film absorbs light to produce black display, thereby enabling black and white image display.

As described above, the voltage is applied between the electrodes arranged on the substrate.
Pressure to generate an electric field in a substantially horizontal direction on the substrate surface,
Structure for driving polymer dispersed liquid crystal showing negative dielectric anisotropy
Therefore, it is possible to omit the transparent conductive film that reduces light transmittance or light reflectance.
Thus, a PDLCD having brighter display characteristics is realized. Further, since a transparent conductive film is not required, the manufacturing steps of film formation and patterning are simplified, and a reduction in manufacturing cost and a high manufacturing yield can be obtained.

[Brief description of the drawings]

FIG. 1 shows a power supply of a liquid crystal display device according to an embodiment of the present invention.
FIG. 3 is a schematic diagram separately showing a case of f (left half) and a case of power-on (right half).

FIG. 2 is a schematic plan view showing the structure of one pixel portion of a thin film transistor integrated device used in the liquid crystal display device according to one embodiment of the present invention.

FIG. 3 is a schematic sectional view taken along line AB in FIG. 2;

FIG. 4 is an explanatory diagram of a manufacturing process of the thin film transistor integrated device.

FIG. 5 is an explanatory diagram of a manufacturing step subsequent to FIG. 4;

FIG. 6 shows a power supply off (left half) in a conventional liquid crystal display device.
FIG. 3 is a schematic diagram separately showing a case where power is turned on (right half).

[Explanation of symbols]

 Reference Signs List 1 upper substrate 2 lower substrate 3 drive electrode 4 color reflector 5 polymer dispersed liquid crystal

Continuation of the front page (56) References JP-A-5-11235 (JP, A) JP-A-5-11281 (JP, A) JP-A-4-366925 (JP, A) JP-A-4-156427 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/1334

Claims (3)

(57) [Claims] A pair of driving electrodes disposed on at least one inner surface of the pair of substrates so that an electric field substantially parallel to the pair of substrates facing each other is generated between the pair of driving electrodes; characterized in that encapsulating the polymer dispersed liquid crystal having a negative permittivity anisotropy, to generate the electric field by applying a voltage between the pair of the drive electrodes, and enables driving the liquid crystal between the substrate Liquid crystal display device. 2. A color reflector is disposed on the inner surface of one of the substrates between a pair of drive electrodes, a black dye is dispersed in the liquid crystal, and when no electric field is applied, incident light is absorbed by the dye to produce a black display. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal is made transparent when an electric field is applied, and the color reflector is used to reflect incident light to perform color display. 3. A black film is disposed on the inner surface of one of the substrates between the pair of drive electrodes, and when no electric field is applied, the incident light is scattered to display white, and when the electric field is applied, the liquid crystal is made transparent. 2. The liquid crystal display device according to claim 1, wherein the black film absorbs incident light to perform black display.