JP2546445B2 - Method of forming TFT of optical shutter array - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a display device such as a display or an optical shutter utilizing the birefringence of PLZT, and an optical shutter array formed in the PLZT is driven by an active element (TFT; thin film transistor) in an active matrix. The present invention relates to a possible method of forming a TFT of an optical shutter array.

[0002]

_2. Description of the Related Art In recent years, PLZT (PbO, LaO, ZrO.sub.2, Ti) which is a transparent ceramic in which La is added to PZT is used.
O) is about to be used for optical shutters and displays.

When an optical shutter array is manufactured by using the PLZT, the method of driving the optical shutter forming the optical shutter array cannot be performed by a simple matrix due to the property of PLZT, so that each optical shutter is activated. A matrix driving method will be adopted.

By the way, as shown in FIG. 6, for example, in a liquid crystal display device, a TFT is already used as an active element 1.
The active matrix method used as is adopted. In this case, each active element 1 is formed between each pixel (a portion corresponding to a liquid crystal) 2, and the drive line of each active element 1, that is, the data line 3 and the address line 4 is formed.
Are formed between each pixel 2. Therefore, in the case of liquid crystal, for example, since the driving voltage is several V, the active element 1 can be made small, and the aperture ratio of each pixel 2 is not affected.

[0005]

However, the above PLZT
When trying to drive the optical shutter of
The drive electrode is as large as several tens of volts to hundreds of tens of volts, and the electric capacitance of each pixel is 100 to 1000 times as large as that of each pixel 2 of the liquid crystal reflecting the high dielectric constant of PLZT. The active element of the driven TFT has a large area, and the aperture ratio of each pixel is reduced.

That is, when the PLZT optical shutter array is used as a display device, there are two conditions tw = C × the time (tw) for writing a signal to each optical shutter (pixel) and the time (th) for holding the signal. Vd / Ia <
This is because it is necessary to satisfy 1 / (N × f) and th = C × Vd / Ib> 1 / f. Note that C is the electric capacity of each pixel, Vd is the driving voltage, Ia is the current of the active state of the TFT active element, Ib is the current of the active state of the active element of the TFT, N is the number of rows of the frame, and f is the frame frequency. Is.

Here, taking a current television as an example, the writing time is tw <50 μsec and the holding time is th> 30 msec.
Regarding Vd, PLZT becomes about 10,000 times as large as that of the liquid crystal, and it is necessary to increase the current Ia and decrease Ib accordingly.

By the way, as shown in FIG. 7, the current in the ON state of the TFT is in inverse proportion to the channel length L of the TFT and in proportion to the channel width W. Therefore, if W / L is increased, the ON state of the TFT is changed. The current Ia can be increased. As is clear from FIG. 7, the current flows from the drain to the source, the channel length L corresponds to the distance (distance) between the drain electrode and the source electrode of the TFT, and the channel width W corresponds to the drain electrode of the TFT. It corresponds to the width of the source electrode.

However, since the channel length L cannot be reduced, the channel width W must be increased, and the channel width W must be increased considerably, for example, 10 times to 100 times. Therefore, it is difficult to form it between each pixel, that is, the interval between each pixel is widened, or the TFT is spread over each pixel.
Therefore, there is a problem that the aperture ratio of each pixel is greatly reduced.

The present invention has been made in view of the above problems, and an object thereof is that the current of an active element for driving each pixel formed in a PLZT in an active matrix satisfies the driving condition of the pixel and the aperture ratio of each pixel. It is an object of the present invention to provide a method of forming a TFT of an optical shutter array that does not reduce the above.

[0011]

In order to achieve the above object, the present invention is designed to drive an optical shutter array formed on a PLZT substrate in an active matrix system.
PLZT substrate with active elements (thin film transistor; TFT)
Transparent substrate facing the PLZT substrate without forming
Was placed, the active element in the transparent substrate, when that form the data lines and address lines, a plurality per pixel them active element in a comb-shaped electrode and the opposite position of the optical shutter constituting the optical shutter array The gist is that the active elements are individually formed and connected in parallel. What
If the active element and the comb-shaped electrode do not face each other, the incident light will
It is not preferable because it is blocked by the moving element.

[0012]

[Action] Since the above method, the optical shutter (pixels) driving active element is formed on the electrode that faces the position of the pixel and its electrodes are comb electrodes constituting the optical shutter array to the transparent substrate Therefore , as many active elements as the maximum number of combs are formed and the active elements are connected in parallel, so that one pixel is driven by a plurality of active elements. Therefore, it is not necessary to enlarge the electrode of the active element, and since each active element is located on the electrode of the pixel, it is possible to prevent the reduction of the aperture ratio of the pixel.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. In FIGS. 1 and 2, an optical shutter (pixel) 13 having a comb-shaped pixel electrode 11 and a common electrode 12 is formed on a PLZT substrate 10, while the transparent substrate 14 has the pixel electrode 11 and the common electrode 12 formed thereon. A plurality of TFTs (thin film transistors) active elements 15 are formed at positions opposite to, and these active elements 15 are connected in parallel. The active element 1 is provided between each pixel 13.
Data lines 16 and address lines 17 for driving 5 are formed.

Further, as shown in FIG. 3, in order to connect the pixel electrode 11 of the pixel 13 and the source electrode of the active element 15, an electrode pattern 18 is formed adjacent to each pixel 13 of the PLZT substrate 10. An electrode pattern 19 is formed on the transparent substrate 14 at a position facing the electrode pattern 18, and the bump 20 is provided between the electrode patterns 18 and 19.
Connected by.

The data line 16, the address line 17, and the electrode patterns 18 and 19 correspond to the black matrix portion of the color filter of the PLZT optical shutter array device.

Here, the case where the active element 15 is formed so that the pixel 13 can be driven by the active matrix will be described. As shown in FIG. 4, the pixel electrodes 11 and the common electrodes 12 of the pixels 13 formed in a matrix are comb-shaped.

In this case, an electrode pattern 18 adjacent to the pixel 13 and connected to the pixel electrode 11 is formed on the PLZT substrate 10. On the other hand, as shown in FIG. 5, the pixel electrode 11 and the common electrode 12 are provided on the transparent substrate 10.
A plurality of active elements 15 are formed at the positions corresponding to the above, in accordance with the driving conditions of the pixel, data lines 16 for drawing out the drain electrodes 15a of these active elements 15 to the outside are formed, and the gate electrodes 15b of these active elements 15 are formed. Is formed to the outside. further,
Electrode patterns 19 are formed on the transparent substrate 14 so as to be connected to the source electrodes 15c of the active elements 15 and correspond to the electrode patterns 18.

The transparent substrate 14 on which the active element 15 is formed is superposed on the PLZT substrate 10, but the electrode patterns 18 and 19 are connected by the bumps 20, so that the pixel electrode 11 of each pixel is connected. It is connected to the source electrodes 15c of the plurality of active elements 15 via the bumps 20.

Therefore, when a pixel 13 is driven by signals on the data line 16 and the address line 17, a plurality of active elements 15 corresponding to the pixel 13 are all turned on or off. The current Ia or the current Tb in the off state is the drain electrode 1
5a to the source electrode 15c.

That is, since a plurality of active elements 15 for driving one pixel 13 are formed and connected in parallel, the current flowing through the pixel 13 can be increased and the channel width W of the active element 15 can be increased. It is possible to drive the optical shutter array of the PLZT substrate by the active matrix method without having to increase the size. Further, since each active element 15 is formed corresponding to the pixel electrode 11 and the common electrode 12 of each pixel 13, that is, the active element 15
Since the channel portion of the pixel overlaps the pixel electrode 11 and the common electrode 12 and does not cover other opening portions, it does not affect the reduction of the aperture ratio of each pixel 13.

In the above embodiment, the comb-shaped electrode of each pixel 13 is a groove-shaped electrode, but a TFT can be formed in the same manner even if it is a surface electrode.

[0022]

As described above, according to the method of forming a TFT of an optical shutter array of the present invention, when an active element for driving each pixel formed on a PLZT substrate is formed on a transparent substrate, the pixel of each pixel is formed. Since the active elements of the plurality of TFTs are formed at the position facing the comb-shaped electrode according to the driving condition of the pixel and the active elements are connected in parallel, the active element for driving each pixel is A plurality of pixels can be used to pass a large current, and each pixel can be driven by the active matrix method. Moreover, since each active element is located above the electrode of each pixel, the aperture ratio of that pixel is reduced. There is an effect that it will not be done.

[Brief description of drawings]

FIG. 1 is a schematic partial front view of an optical shutter array device to which a method of forming a TFT of an optical shutter array is applied according to an embodiment of the present invention.

FIG. 2 is a schematic partial cross-sectional view of the optical shutter array device shown in FIG.

FIG. 3 is a schematic partial circuit diagram of the optical shutter array device shown in FIG.

FIG. 4 is a schematic partial front view of a PLZT substrate used in the optical shutter array device shown in FIG.

5 is a schematic partial front view of a TFF forming substrate used in the optical shutter array device shown in FIG.

FIG. 6 is a schematic partial front view of a conventional liquid crystal display device.

FIG. 7 is a schematic configuration diagram showing electrodes of active elements for driving pixels.

[Explanation of symbols]

 10 PLZT substrate 11 Pixel electrode (comb type) 12 Common electrode (comb type) 13 Pixel 14 Transparent substrate 15 Active element (TFT) 15a Drain electrode 15b Gate electrode 15c Source electrode 16 Data line 17 Address line 18 Electrode pattern 19 Electrode pattern 20 bump

Claims (1)

(57) [Claims] 1. A plurality of pixels formed on a PLZT substrate are formed.
In order to drive the formed optical shutter array by the active matrix method, an active element (thin film transistor; TF
T), when the data line and the address line are formed on the transparent substrate, the active elements are formed at positions facing the comb-shaped electrodes of the optical shutters forming the optical shutter array, and the active elements are formed per pixel. A method of forming a TFT of an optical shutter array, characterized in that a plurality of active elements are connected in parallel.