JPH0797190B2 - Storage device and liquid crystal display device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a memory device for storing electric signals and a liquid crystal display device using the memory device. Further, the present invention relates to a storage method reading method and a storage device manufacturing method.

2. Description of the Related Art A recording device that has an XY matrix electrode and that stores electrical signals in a capacitor via a transistor provided at the intersection is Si
It is well known as a semiconductor device. Further, a liquid crystal display using an active matrix type display substrate using a TFT has been actively researched because it can obtain higher image quality than a simple matrix type liquid crystal display device. The TFT array for the active matrix display device has the same structure as the above-mentioned Si semiconductor device. An active matrix type liquid crystal display device using a TFT has a structure shown in FIG.

A source (or drain) electrode bus 121 and a gate electrode bus 122 formed on the transparent substrate 120, a TFT 123, a display substrate 125 supporting a pixel electrode 124, and a counter substrate 127 having a counter electrode 126. Consists of and these boards 1
Liquid crystal is sealed between 25 and 127.

On the other hand, an inverted stagger TFT that forms a semiconductor on an insulator
A high quality TFT can be obtained, which will be described with reference to FIG. 8 showing a method for manufacturing a matrix display substrate.
The TFT has a Cr gate 131 deposited on an insulating substrate 130 and SiNx.
An insulating layer 132 and an a-Si (amorphous silicon) layer 134,
It is formed of an Al source 135 and an Al drain 136. The pixel electrode 138 is made of ITO (Indium-Tin-Oxide). The TFT and the pixel electrode 138 are coupled to the drain 136 that follows the contact hole 142 formed in the insulating layer 132.

Problems to be Solved by the Invention An active matrix type display substrate using such a TFT has a structure in which XY electrode busbars cross each other across an insulating layer, and a short circuit between XY electrode busbars yields. It was a major cause of deterioration.

Further, the false signal due to the change of the gate pulse potential causes the potential of the picture element display electrode to deteriorate the display quality of the liquid crystal display. In addition, when used as a large-sized liquid crystal display substrate, the non-uniformity of the TFT switching time on the left and right of the screen due to the delay of the gate pulse deteriorates the display quality, specifically the non-uniformity of the brightness on the left and right of the screen.

Means for Solving the Problems A signal for designating a row is used as light, and its transmission is performed by using an optical waveguide, and an electric signal to be stored is transmitted to a first electrode forming a column. The second electrode is configured so as not to be formed, and the first electrode and the second electrode are electrically connected via the photoconductive layer formed on the optical waveguide, and the first electrode and the second electrode are sandwiched by the dielectric layer. The electric signal is stored in the capacitor formed between the second and third electrodes.

The first electrode wiring for transmitting a display signal and the first electrode wiring
An optical waveguide formed to intersect with the electrode wiring, a second electrode formed separately for each pixel and transmitting light formed without overlapping with the first electrode wiring, the first and second electrodes
Liquid crystal display device in which a first substrate having a fourth electrode including a photoconductor layer formed between the first electrode and the second electrode is formed on the optical waveguide and a second substrate having a third electrode are opposed to each other via a liquid crystal. Make up.

Action With the above configuration, the photoconductive layer formed on the optical waveguide can be made conductive by the light introduced into the optical waveguide, and the electric signal transmitted from the electrode bus line can be stored in the capacitor. The stored electric signal can be read out from the electrode bus line by making the photoconductive layer conductive again by the light introduced at another time and accumulating the electric signal.

Alternatively, since rewriting is possible, by utilizing this property, it can be used as an array for driving a liquid crystal.

Example A storage device of the present invention uses a signal designating a row as light and transmits the signal using an optical waveguide, and transmits an electric signal to be stored in a first electrode forming a column, The second electrode is electrically connected via the photoconductive layer formed on the optical waveguide, and the electric signal is stored in the capacitor formed between the second and third electrodes with the dielectric layer interposed therebetween. It is a thing.

When the present memory device is used as a matrix circuit, a plurality of second electrodes are formed separately at the locations where the plurality of optical waveguides and the plurality of first electrodes intersect. Alternatively, a plurality of optical waveguides and a plurality of first electrodes are formed without intersecting each other, a second electrode is formed separately, and a plurality of third electrodes are formed so as to intersect with the optical waveguide and the first electrode. A third electrode is installed. In this case, it is desirable to provide a light shielding layer on at least one of the lower layer and the upper layer of the photoconductor layer.

The photoconductive layer may be configured as a diode. In that case, it is preferable that a plurality of diodes are connected in series so as to have different polarities. The diode is preferably a heterojunction.

Example 1 As shown in FIG. 1, a glass substrate 10 (trade name Corning
7059), an optical waveguide 1 with a high refractive index by the ion exchange method
To form. Next, form the first ITO to a thickness of 1000A,
The third electrode 2 is formed by patterning. Next, the dielectric layer 3 made of SiO ₂ is formed to a thickness of 2000 A by the atmospheric pressure CVD method except for the first ITO electrode extraction portion in the peripheral portion of the substrate.

Next, i-aSi is formed to a thickness of 2000 A by the PCVD method and patterned to form the photoconductive layer 4. In addition, the second ITO is DC
The second electrode 5 is formed by forming 1000 A by sputtering and patterning.

The n ⁺ -aSi layer 6, the MoSi layer 7, and the Al layer 8 are 500 A and 5 respectively.
The first electrode 11 and the connection electrode 9 for connecting the second electrode 5 which is a pixel electrode and the photoconductive layer 4 are formed with a thickness of 00A and 5000A.

In this embodiment, the current from the first electrode 11 to the second electrode 5 flows in the lateral direction of the photoconductive layer 4 on the substrate.

In the above memory device, a signal designating a row is used as light and its transmission is performed using the optical waveguide 1 to form a column.
The electronic signal to be stored is transmitted to the electrode 11 of. First electrode
11 and the second electrode 5 are electrically connected via the photoconductive layer 4 formed on the optical waveguide 1, and the capacitor formed between the second and third electrodes with the dielectric layer 3 interposed therebetween is added to the above-mentioned capacitor. Accumulate electrical signals.

That is, an electric signal is transmitted from the first electrode 11 to the second electrode 5 while light is being introduced into the optical waveguide 1 to reduce the resistance of the photoconductive layer 4, and the photoconductive layer 4 is dark during storage. To store the electrical signal. At the time of reading an electric signal, light is introduced into the optical waveguide 1 to lower the resistance of the photoconductive layer 4 and the accumulated electric signal is read out through the first electrode 11.

Example 2 When the SiN layer 200A is interposed in place of the n ⁺ -aSi layer 6 of Example 1, the storage voltage becomes higher than that of Example 1, but the storage device has excellent charge retention characteristics.

Embodiment 3 As shown in FIG. 2, an optical waveguide 21 similar to that of Embodiment 1 is formed on a glass substrate 20 by ion exchange.

Next, SnO ₂ is formed by atmospheric pressure CVD method, and dry etching method
Form 2 patterns.

CdTe23 and In24 are formed to a thickness of 4000 A and 1000 A, respectively, by a vapor deposition method. After that, patterning is performed as 24a.

In this embodiment, the current flow from the electrode 1 to the electrode 2 flows in the film thickness direction of the photoconductive layer.

FIG. 3A shows an equivalent circuit of the matrix circuit in the case where the third electrode 2 of the present invention is not separated but is common. R1, C1
Is the storage capacitance or the resistance and capacitance of the liquid crystal layer, and R2 and C2 are the resistance and capacitance of the photoconductive layer. E1 (m-1), E1m, E1 (m +
1) represents a first electrode for transmitting a signal, and E3 represents a third electrode. At this time, R2 to R1> 10 ¹⁰ Ω (1) is satisfied, and both R1 and R2 have high resistance.

Light is incident on the optical waveguide of the nth row to lower the resistance of the photoconductive layer. At this time, the resistance of the photoconductive layer changes from R2 to R2 '.

R2 ′ << R1 (2) and almost all the voltage applied to C2 of the photoconductive layer can be ignored, and the nth row can be regarded as only C1 as shown in FIG. 3 (b). The other row can be regarded as the series capacitance of C1 and C2. When the signal voltage applied to the first electrode is Vm and the voltage applied to the third electrode is Vt, the voltage distributed to the capacitor C1 is Therefore, the smaller C2 is, the smaller the voltage distributed to C1 is. Most of the voltage (Vm-Vt) is applied to C2.
The above can be realized by setting C2 << C1 (4) by designing the pattern. Since R2 can be ignored in the n-th row which is trying to transmit a signal for addressing, an equivalent circuit as shown in FIG. 3 (b) is obtained.
In the nth row, a voltage of (Vm-Vt) is applied to C1.
In the other row, a voltage of (Vm-Vt) is applied to C2.

Next, the case where the signal line runs parallel to the optical waveguide and the counter electrode is separately formed to intersect the optical waveguide and the signal line will be described. The equivalent circuit is shown in FIG.

E′1n and E′1 (n + 1) represent first electrodes for transmitting signals, and E′3 (m−1), E′3m and E′3 (m + 1) represent third electrodes. Similar to FIG. 3 (a), R1 and C1 represent storage capacitance or liquid crystal resistance and capacitance, and R2 and C2 represent photoconductive layer resistance and capacitance. The same thing can be said when the conditions similar to those in FIG. 3 described above, that is, the expressions (1), (2), and (4) are satisfied. The equivalent circuit is simplified as shown in FIG. 6 (b). If the row to be addressed is the n-th row, the signal voltages are (V'm-1-Vs), (V'm-Vs),
(V'm + 1-Vs) is applied and stored in C1. In the other rows, (V'm-1-Vb), (V'm-Vb), (V'm
A voltage of + 1-Vb) is applied to C2.

Even if C1 cannot be ignored, the voltage distributed to C1 is Is. Even in this case, if Vb is set so that the absolute value of (V'm-Vs) is larger than the absolute value of (V'm-Vb), a false signal applied to C1 of an unaddressed row. Can be small.

Example 4 This example is an example in which a light shielding layer is provided, and its plan view is shown in FIG. The optical waveguide 41, the photoconductive layer 44, the ITO 42, and the first electrode 43 are sequentially formed using the same material as in the first embodiment.

A light shielding layer 45 on the opposite side of the glass substrate using Cr metal 1000
Form to thickness A.

Example 5 In this example, the memory device is applied to a liquid crystal display device. The substrate of Example 1 is used as one substrate, and a liquid crystal is inserted by setting a gap between the other substrate having ITO formed on the entire surface to 6 μm and inserting a liquid crystal.

Light having a wavelength of 680 nm is introduced into the optical waveguide from a GaAlAs LED array for 30 μsec each to reduce the resistance of the photoconductive layer on the optical waveguide and to provide a video signal in synchronization with this. The video signal may be the same as the LCD of the conventional TFT array. This allows TV images to be displayed.

Example 6 The substrate of Example 4 was used as one substrate, and ITO4 in a stripe shape was used.
A liquid crystal display device is formed by forming the substrate 5 and the other substrate with a gap of 6 μm as shown in FIG.

Light is introduced into the optical waveguide from another liquid crystal shutter.

The equivalent circuit in this case is as shown in FIG. One unit is represented by a series connection of a liquid crystal having a capacitance CL, a variable resistance RP that changes with light, and a photoconductive layer having a capacitance Cp.
This operation is as described in FIG.

If the first electrode and the photoconductive layer described above are formed with the same mask pattern, the memory device can be manufactured more easily.

Further, a liquid crystal display device having a simpler structure can be realized by a structure in which light is deflected by the liquid crystal and guided to a plurality of optical waveguides.

The configuration in which the photocurrent flows in the lateral direction of the photoconductive layer as in the example of FIGS. 1 and 4 is lighter than the configuration in which the photocurrent flows in the film thickness direction of the photoconductive layer as in FIG. The value of the capacitance C2 of the conductive layer can be reduced.

EFFECTS OF THE INVENTION According to the present invention, the address line corresponding to the gate electrode of the TFT array has an optical waveguide structure, so that the short circuit between the XY electrodes can be eliminated, and the signal transmission line can be arranged in a step-free place. Is improved. Since the row is addressed not by electrical but by light, a false signal due to the potential change of the gate pulse as in the case of TFT is not given to the capacitor.

When the storage device of the present invention having such features is applied to, for example, a liquid crystal display device, it is possible to display a flicker-free screen. Further, since the light is used as the address signal instead of the electric gate pulse signal, there is almost no delay in the address signal. Therefore, the non-uniformity on the left and right of the screen, which is a problem when the TFT array is applied to a large-sized liquid crystal display device, is eliminated.

[Brief description of drawings]

1 (a) and 1 (b) are a plan view and a sectional view, respectively, showing a memory device according to a first embodiment of the present invention, and FIGS. 2 (a) and 2 (b) are respectively a third embodiment of the present invention. FIG. 3A is a plan view and a cross-sectional view showing a memory device according to the embodiment of FIG.
And (b) are equivalent circuit diagrams for explaining the operation of the memory device of the present invention, FIG. 4 is a plan view of the fourth embodiment of the present invention,
FIG. 5 is an equivalent circuit diagram when the memory device of the present invention is applied to a liquid crystal display device, FIG. 6 is an equivalent circuit diagram illustrating the operation of the memory device of the present invention, and FIG. 7 is a conventional liquid crystal display device. A perspective view of the display device and FIGS. 8A and 8B are respectively a conventional TF.
It is sectional drawing and a top view explaining a T array. 21, 31, 41 …… Optical waveguide, 32, 33, 42 …… Transparent electrode, 3
4, 43 …… Signal electrodes, 35, 44 …… Photoconductive layer, 45 …… Light shielding layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiichi Nagata 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-1-173016 (JP, A) JP-A-1- 156724 (JP, A)

Claims (7)

[Claims] 1. An optical waveguide, a large electrode for transmitting an electric signal to be stored, and second and third electrodes which face each other with a first dielectric layer interposed therebetween. Electrode and the second
Of the first capacitor for accumulating the electric signal and the light for electrically connecting the first electrode and the second electrode with each other, the first capacitor storing the electric signal and the electrode of A memory device comprising a fourth electrode including a conductive layer. 2. The memory device according to claim 1, wherein a second capacitor having a second dielectric layer interposed between the second electrode and the fourth electrode is formed. 3. The storage device according to claim 1, wherein a second electrode is separately formed in the optical waveguide at a position where a plurality of first electrodes intersect, and the optical waveguide is installed. 4. The storage device according to claim 1, further comprising a light shielding layer provided on at least one of a lower layer and an upper layer of the photoconductor layer. 5. The memory device according to claim 4, wherein the first or second electrode also serves as a light shielding layer. 6. A second electrode between the photoconductive layer and the first and second electrodes.
2. The memory device according to claim 1, wherein the dielectric layer is included. 7. A first electrode wiring for transmitting a display signal, an optical waveguide formed so as to intersect with the first electrode wiring, and formed separately for each pixel without overlapping the first electrode wiring. A second electrode that transmits the formed light; and a fourth substrate that includes a photoconductor layer between the first and electric second electrodes and that is formed on the optical waveguide. A liquid crystal display device, which is opposed to a second substrate having three electrodes with a liquid crystal interposed therebetween.