JPH1090701A - Ferroelectric liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high luminance, low heat generation and high contrast. SOLUTION: This device has ferroelectric liquid crystal 13 held between a couple of substrates 11 and 12 and has a switching element 14 equipped with a pixel electrode 14a on the side of the substrate 12 and is provided with a transparent electrode 111 on the opposite substrate 11. Orientation films 15a and 15b are formed all over the part of the substrate surrounded with a seal material 16a. On the pixel electrode 14a, a dielectric mirror 18, a transparent electrode 19 for optical compensation, and the orientation film 15b are laminated in order. A voltage which makes a black display on the ferroelectric liquid crystal between pixels is applied between a lead-out electrode 11a of the transparent electrode 111 and a lead-out electrode 19a of the transparent electrode 19 for optical compensation to obtain the high-contrast and low-heat-generation display device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display (G02) using a ferroelectric liquid crystal having a switching element.
F1 / 133). In particular, the present invention relates to a high-brightness reflective ferroelectric liquid crystal display device using a dielectric mirror.

[0002]

2. Description of the Related Art Hitherto, a liquid crystal display device using a ferroelectric liquid crystal has been expected to be applied to a display having a large display capacity since it has a high response speed and can display a memory.

FIG. 4 shows a conventional reflection type ferroelectric liquid crystal display device having a switching element.

FIG. 1A is a plan view of a main part, and FIG.
It is -A 'sectional drawing. As shown in FIG.
A switching element 44 composed of, for example, a MOSFET, having a ferroelectric liquid crystal 43 sandwiched between 1 and 42, and having a reflective electrode 44a composed of an Al film for each pixel on the substrate 41 side, A transparent electrode 45 is provided. Further, alignment films 46a and 46b for aligning the ferroelectric liquid crystal molecules in parallel with and in the same direction as the substrate are formed on the entire portion of the substrate surrounded by the sealing material 47a. 47b is a sealing material. Switching element 44
Are driven by a scanning signal bus line 48 composed of, for example, a gate bus line, and a video signal bus line 49 composed of, for example, a source bus line for supplying a video signal. In the figure, 44b is a semiconductor layer, and 44c is a gate insulating film layer. Reference numeral 43c denotes an insulating layer that insulates the reflective electrode 44a from the video signal bus line 49 and the semiconductor layer 44b.

However, in the above-described configuration, since the reflective electrode made of an Al film is used, the reflectance of the Al film is about 85%, and the light absorption when the liquid crystal cell is irradiated with high-luminance illumination light. The exothermic heat is very large. Accordingly, there is a problem that the phase transition temperature of the ferroelectric liquid crystal becomes close to that of the ferroelectric liquid crystal, and deterioration of image quality such as deterioration of contrast and reflection efficiency cannot be avoided.

In order to solve this, the following configuration has been considered. That is, the adoption of the dielectric mirror improves the reflectivity to 95% or more, and reduces heat generation due to high-luminance illumination light. In this case, deterioration in image quality due to heat generation can be reduced.

A sectional structure of a main part of the ferroelectric liquid crystal display device is shown in FIG. In FIG. 5, 41, 42, 43,
44, 44a, 44b, 44c, 45, 46a, 46
b, 47a, 47b, 48, and 49 are the same as those in FIG.
That is, the dielectric mirror 51 and the alignment film 46b are sequentially laminated on the reflective electrode 44a.

[0008]

However, in the above configuration, on the other hand, no voltage is applied to the ferroelectric liquid crystal in the region between the pixels, so that the ferroelectric liquid crystal is not optically off. Therefore, when black display is performed, the area between pixels becomes gray, and there is a problem that the contrast is reduced.

[0009]

In order to solve the above-mentioned problems, a ferroelectric liquid crystal display device according to the present invention comprises a pair of substrates having switching elements and driving electrodes fixed on the inner surfaces of opposing substrates with a sealing material. A ferroelectric liquid crystal cell in which a dielectric mirror and a ferroelectric liquid crystal having bistability with respect to an electric field are sandwiched between the pair of substrates; A transparent electrode is laminated, and the ferroelectric liquid crystal at the pixel boundary is optically turned off.

As a result, even when the liquid crystal cell is irradiated with high-luminance illumination light, a ferroelectric liquid crystal display device that generates a small amount of heat and does not lower the contrast can be obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a ferroelectric material in which a pixel electrode provided in a pixel, a dielectric mirror and a ferroelectric liquid crystal having bistability against an electric field are sandwiched between a pair of substrates. In a ferroelectric liquid crystal display device having a liquid crystal cell, a transparent electrode for optical compensation is laminated on a pixel boundary on the dielectric mirror, and the ferroelectric liquid crystal on the pixel boundary is optically turned off. In the case of displaying black, the area between pixels is in a black state, and there is an effect that the contrast is not reduced.

According to the present invention, in the above invention, a predetermined voltage is applied to the transparent electrode for optical compensation, and the ferroelectric liquid crystal at the pixel boundary is optically turned off. Since a predetermined voltage can be applied to the ferroelectric liquid crystal in the region between the pixels, the ferroelectric liquid crystal can be optically turned off. The region is in a black state, and has an effect that there is no decrease in contrast.

According to the present invention, in the above-mentioned invention, the pixel is constituted by a scanning signal bus line, a switching element, and a signal bus line, and the ferroelectric liquid crystal in an area between the pixels is optically compensated. Since a predetermined voltage can be applied between the transparent electrode for use and the transparent electrode on the opposite substrate side,
Since the ferroelectric liquid crystal can be turned off optically, the region between pixels is in a black state even when a black display is performed, and has an effect that the contrast does not decrease.

According to the present invention, in the above invention, a transparent electrode,
A photoconductive layer, a dielectric mirror, and a transparent electrode for optical compensation are sequentially laminated, and the transparent electrode for optical compensation and the transparent substrate side are formed on the ferroelectric liquid crystal in a region between pixels. Because a predetermined voltage can be applied between the electrodes,
Since the ferroelectric liquid crystal can be turned off optically, the region between pixels is in a black state even when a black display is performed, and has an effect that the contrast does not decrease.

An embodiment of the present invention will be described below with reference to FIGS. (Embodiment 1) FIG. 1A is a plan view of Embodiment 1, FIG. 1B is a sectional view of a principal part, and FIG. 1C is a sectional view of a principal part of a pixel portion.

In FIG. 1, a ferroelectric liquid crystal 13 having a liquid crystal cell thickness of 1 μm is sandwiched between a pair of substrates 11 and 12, for example.
On the substrate 12 side, a pixel electrode 14a made of an Al film for each pixel
And a transparent electrode 111 made of, for example, an ITO film is provided on the substrate 11 on the opposite side.

Alignment films 15a and 15 for aligning the ferroelectric liquid crystal molecules in parallel with the substrate in the same direction.
b is formed on the entire portion of the substrate surrounded by the sealing material 16a. 16b is a sealing material. The switching element 14 is driven by a scanning signal bus line 17a composed of, for example, a gate bus line, and a video signal bus line 17b composed of, for example, a source bus line for supplying a video signal.

In the figure, 14b is a semiconductor layer, 14c
Is a gate insulating film layer. 14d is the pixel electrode 1
4a, video signal bus line 17b and semiconductor layer 14
b is an insulating layer for insulating b.

On the pixel electrode 14a, a dielectric mirror 18 is provided.
Then, a transparent electrode, for example, an ITO film is vapor-deposited and patterned by photolithography so as to overlap between pixels to form an optical compensation transparent electrode 19. Thereafter, an alignment film 15b is laminated. As shown in FIG. 3C, for example, in the case of a rectangular pixel, the optical compensation transparent electrode 19 is formed in a lattice shape.

A voltage is applied between the extraction electrode 111a of the transparent electrode 111 and the extraction electrode 19a of the optical compensation transparent electrode 19, and a voltage is applied to the ferroelectric liquid crystal between pixels.

FIG. 2 shows the operation of the ferroelectric liquid crystal. FIG. 11A shows a gate voltage waveform VGi of the i-th gate bus line 17a, and FIG.
The gate voltage waveform VGi + 1 of 7a, (c) is the voltage waveform Vce of the opposite ITO electrode 111, (d) is the signal waveform VSj of the jth source bus line 17b, and (e) is the intensity of the i-th row and j-th column. The voltage waveform VLC of the dielectric liquid crystal 13 and (f) show the voltage waveform VOE of the transparent electrode 19 for optical compensation. The figure shows the operation when the display changes to black display one field (1 V period) after white display. Since the voltage of the opposing ITO electrode 111 is constant at Vce, when the signal waveform (change from white display voltage VSH to black display voltage VSL) shown in FIG. The voltage is as shown in FIG.

That is, when the white display voltage VSH is applied to the opposing ITO electrode 111, a positive voltage is applied and when the black display voltage VSL is applied, a negative voltage is applied, and white and black are displayed, respectively. You. The unevenness of the voltage waveform VLC when the gate voltage is applied in FIG. 9E is due to the parasitic capacitance of the MOSFET.

On the other hand, by applying a voltage VOE at which the ferroelectric liquid crystal causes black display to the optical compensation transparent electrode 19, a black display state is always maintained between the pixel electrodes, and a good contrast can be obtained. Have.

(Embodiment 2) FIG. 3A is a plan view of Embodiment 2, FIG. 3B is a cross-sectional view of a main part, and FIG. 3C is a cross-sectional view of a main part of a pixel portion. ing.

A ferroelectric liquid crystal 33 having, for example, a liquid crystal cell thickness of 1 μm is sandwiched between a pair of substrates 31 and 32, a transparent electrode 32 a made of, for example, an ITO film, and a photoconductive layer p-a-Si The film 32b and the ia-Si film 32c are sequentially stacked. The na-Si film 32d is provided separately for each pixel. A dielectric mirror 34 is laminated on this to form a reflection surface. The transparent electrode 35 for optical compensation made of, for example, an ITO film for applying a voltage to the ferroelectric liquid crystal between the pixels to perform a black display operation is formed in a lattice shape as shown in FIG. The substrate 31 on the opposite side is provided with a transparent electrode 31a made of, for example, an ITO film.

Alignment films 36a and 36 for aligning the ferroelectric liquid crystal molecules in parallel with the substrate in the same direction.
b is formed over the entire portion of the substrate surrounded by the sealing material 37a. 37b is a sealing material. That is, by applying a voltage for displaying black between the extraction electrode 35a of the optical compensation transparent electrode 35 and the transparent electrode 31a on the opposite substrate side, the pixel electrodes are always in a black display state, and good contrast is obtained. It has the action of:

In the pixel driving method, an image is displayed by injecting charges into the ferroelectric liquid crystal using the PIN photodiode having the above-described configuration.

In the above description, the optical compensation transparent electrode is formed on the dielectric mirror. However, even if the optical compensation transparent electrode is formed below the dielectric mirror, the optical compensation transparent electrode may be formed on the opposing substrate. The same effect as in the present embodiment can be obtained by applying a voltage for black display between the transparent electrodes.

[0029]

As described above, according to the present invention, by providing a transparent electrode for optical compensation between pixels on a dielectric mirror, it is possible to prevent a decrease in contrast between pixels.
An advantageous effect that good contrast is obtained and heat generation by illumination light is low is obtained.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram of a voltage waveform of each part according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a ferroelectric liquid crystal display device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a conventional ferroelectric liquid crystal display device.

FIG. 5 is a plan view showing a conventional ferroelectric liquid crystal display device.

[Explanation of symbols]

 11, 12, 31, 32 Substrate 111, 311 Transparent electrode 13, 33 Ferroelectric liquid crystal 14 Switching element 14a Pixel electrode 14b Semiconductor layer 14c Gate insulating film layer 14d Insulating layer 15a, 15b, 36a, 36b Orientation film 16a, 37a Seal Material 16b, 37b Sealing material 17a Scan signal bus line 17b Video signal bus line 18, 34 Dielectric mirror 19, 35 Optical compensation transparent electrode 32 Substrate 32a Transparent electrode 32b Pa-Si film 32Cia-Si film 32d na-Si film

Claims (4)

[Claims] 1. A ferroelectric liquid crystal cell comprising: a pair of substrates; a pixel electrode provided in a pixel; and a ferroelectric liquid crystal cell in which a dielectric mirror and a ferroelectric liquid crystal having bistability against an electric field are sandwiched. In a dielectric liquid crystal display device, a transparent electrode for optical compensation is laminated on a pixel boundary on the dielectric mirror, and the ferroelectric liquid crystal at the pixel boundary is optically turned off. Liquid crystal display device. 2. The ferroelectric liquid crystal display according to claim 1, wherein a predetermined voltage is applied to the transparent electrode for optical compensation, and the ferroelectric liquid crystal at the pixel boundary is turned off optically. Dielectric liquid crystal display. 3. The ferroelectric liquid crystal display device according to claim 2, wherein the pixels include a scanning signal bus line, a switching element, and a signal bus line. 4. The ferroelectric liquid crystal display device according to claim 2, wherein a transparent electrode, a photoconductive layer, a dielectric mirror, and an optical compensation transparent electrode are sequentially laminated.