JPH04212935A - Display cell - Google Patents

Abstract

PURPOSE:To manufacture a display device of large picture plane in a good yield rate inexpensively by forming an active element by a specific method, in the case of a display cell for which the active element is used. CONSTITUTION:A transistor use base layer 2 is laminated respectively independently further closely on a polyimide film 1 by using a mask in a size necessary for each picture element. Next, a semiconductor layer 3 is formed while masking on this base layer 2 to dope P, S or the like, and an active switching element 4 is formed. Electric connection parts 5a to 5c are laminated on the respective active elements 14. Next, the polyimide film 1, in which many of these active elements 4 are closely formed, is immersed in etching liquid to separate the active element 4 by removing a polyimide part. This element 4 is rearranged as matched with a pattern on a display drive substrate, overlapped previously with a picture element electrode and the display driving substrate, formed with a lead wire, and transferred onto the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to the realization of a flat display device using liquid crystal, EC, etc., and is a display cell for a display device that realizes a larger screen.

``Summary of the Invention'' The present invention is a display cell using an active element, in which the formation of the active element is realized by a new method, and a large screen display device can be provided at a high yield and at low cost.

"Prior Art and Problems" Conventionally, there are active methods and passive methods for driving display devices such as liquid crystals, and the active method is overwhelmingly superior in display characteristics such as good image quality and responsiveness. However, until now, it has been difficult to manufacture large-screen display devices, so it has not been possible to actually supply large-screen display devices to the market. The creation of cells with a display system that uses active elements to drive is done by Sharp,
It has been actively developed by Hitachi and many other manufacturers since the 1970s based on semiconductor manufacturing technology.

These display cells are arranged on a glass substrate 1 as shown in FIG.
2, a semiconductor such as a-Si is laminated on one side, and then an active switching element 7 such as a transistor or diode that drives each pixel 15 is connected to a scanning line 14 for controlling each pixel.
This is a method in which the semiconductor layer is formed only at positions where it can intersect with the signal line 13, and the semiconductor layer at other positions is removed by etching or the like to create a display drive substrate for display driving each pixel and use it as a cell.

This process includes photolithography, etching, and plasma CV.
This is done using techniques used in the manufacture of semiconductors such as D. In this conventional method, the formation of all patterns on the glass substrate is the creation of the display drive substrate that will ultimately be used, so transparent pixel electrodes, wiring, and active elements are formed at that pitch, so it is possible to create large-area display devices. To manufacture this, active elements would have to be formed very sparsely on a large area of glass. Therefore, active elements with uniform characteristics must be formed over a large area without defects, and this is a major impediment to improving manufacturing yields, which is why large flat display panels have not been able to be provided at a commercial level to this day. It is.

As mentioned above, the problem with the conventional method is that the active elements are manufactured in a very sparse density within a large area, resulting in poor yields.Moreover, a semiconductor process that can handle large areas is required, and manufacturing equipment is required. It became very expensive, and the display substrate also became very expensive, making it impractical.

"Means and operations for solving the problems" In order to solve the above problems, the present invention provides active elements on a substrate different from the display driving substrate that will ultimately be used in the display cell. They are formed very densely like normal semiconductor elements, separated into individual parts by etching, etc., rearranged to match the pattern on the display drive substrate, and finally placed on the display drive substrate. Then, the necessary electrical connections are made to create a large-area display driving substrate.

The present invention realizes a display cell by forming a large number of active elements densely, separating them, arranging them in a positional relationship corresponding to the final substrate, and electrically connecting them to the final substrate.

Conventionally, in order to form an a-Si transistor, a-Si is formed from silane or the like on a flat glass substrate by plasma CVD at a fairly high temperature using the same semiconductor process used for IC manufacturing, and then It was doped with P, S, etc. However, today it has become possible to form a-Si using a low-temperature process of 400° C. or lower, and polymers such as polyimide, which are highly heat resistant and have uniform surfaces, have become possible. Therefore, by effectively utilizing these, it has become possible to separate the transistors formed at high density and transfer them to a large-area substrate, thereby creating a large-area display substrate.

FIG. 1 is an explanatory diagram of the formation of a substrate used in the present invention. The process proceeds from A to E in order.

First, a highly heat-resistant polyimide is formed into a film 1, and a base layer 2 such as SiO2 necessary for forming the Tr is formed on it.
are individually but densely patterned using a mask to the size required for the Tr of each pixel, and then laminated using a low-temperature process.

Next, a-Si3 or the like is formed by low-temperature plasma CVD or the like while being masked on the individual base layers, doped with P, S, etc., and formed into active switching elements such as FET transistors or diodes using photolithography technology. Form. If each active element 4 has three terminals, connection portions 5a, 5b, and 5c for electrical connection of three terminals are laminated with Al, Au, or the like. If there are two terminals, provide a connection for two terminals.

FIG. 2 is a partial plan view of a polyimide film in which a large number of active elements are densely formed.

Next, the polyimide film in which a large number of active elements (hereinafter, active elements and electrical connection parts are referred to as switching elements) are densely formed is immersed in a polyimide etching solution to remove the polyimide parts. At this time, the individual switching elements are separated and independent. FIG. 3 is a cross-sectional view of a switching element group separated from a polyimide film by etching. The switching element is separated into one unit on the base layer 2, including an active element part and a junction part.

These switching elements must finally be rearranged to match the pitch of the switching elements on the display driving substrate.

FIG. 4 is a sectional view when a rearrangement board is used to rearrange individual switching elements.

A rearrangement board 9 corresponding to the pattern pitch 1-1 of the switching elements on the final display drive board is prepared, and a diffusion support 8 such as glycol or mercury having a higher specific gravity than the switching elements is soaked thereon. Next, a large number of switching elements 7 are placed on top of it all at once, dispersed by constant vibration, etc.
This diffusion support liquid is slowly removed from the hole 10 under the rearrangement board, and the switching elements are aligned at the array positions on the rearrangement board. For this purpose, the shapes of the switching elements are made so that they can be partially matched. Thereafter, the rearrangement board 9 is raised relative to the rearrangement board guide 11.

FIG. 5 is a plan view of the switching element group rearranged on the rearrangement board.

The switching elements whose patterns and pitches have been adjusted in this way are superimposed on the display driving substrate 31 on which the pixel electrodes 15 and lead wires have been formed in advance, and the switching elements are transferred onto the substrate. At this time, the connection between the switching element and the pre-formed lead wires is ensured by laser irradiation or heating.

FIG. 6 is a partial plan view of the display driving substrate, and when a switching element group is transferred onto this and electrically connected, it becomes a display driving substrate.

In this manner, the display substrate and its drive system are completed by carrying out the transfer operation of the switching elements in units of a certain area.

By repeating this process, the manufacturing cost of large-area (4 or more) display panels can be dramatically reduced, and display panels with as large an area as desired can be created.

"Example" FIG. 1 is a process explanatory diagram showing the steps of forming a display substrate, which is a basic element forming a display cell of the present invention.

On the polyimide film 1, a large number of individual SiO2 base layers for transistors with a thickness of 3000 ohms are formed on a 70 um square with a spacing of about 20 um by photolithography. In this case, SiO2 was directly laminated on the film by low-temperature plasma CVD, but a coating layer may be further provided below this to improve the adhesion between the film and the base layer. The formed base layer 2 is regarded as a glass substrate used in normal panel formation, and the following process is carried out. The semiconductor formed on the base layer may be not only a-Si but also Poli-Si or other compound semiconductors.

However, since the substrate is made of polyimide, it must be able to be formed by a low-temperature process. In order to create an active switching element in the semiconductor part formed above,
FETs and diodes 4 are formed by sequentially doping with P, S, etc.

Bonding portions 5a, 5b, 5c, etc. are formed of Au or Al for electrical connection between the active element and the signal line, scanning line, and pixel electrode. Next, the switching element sections formed up to this point are individually separated and made independent. To do this, the polymer film is soaked in an etching solution and removed, and only the individual switching elements are taken out. In this case, a polyimide etchant must be used to transfer and add separate and independent switching elements onto the display driving substrate 31 that will ultimately perform the display to form the display driving substrate 32.

For this purpose, mercury, which is a liquid with a higher specific gravity than the switching element and has good fluidity, is used as a diffusion support, onto which the individually separated Tr is placed all at once, and constant vibration is applied to separate and diffuse the mercury. At the same time, the diffusion supports are slowly pulled out from the prepared holes 10 of the rearrangement plate 9 for forming a 120 um pitch Tr pattern, and are placed on the rearrangement plate 9 at regular intervals. The Tr's thus rearranged at the same pitch as the switching elements on the final display drive substrate 32 are transferred to the substrate 31 on which wiring and pixel electrodes have been formed in advance.

FIG. 6 is a partial plan view of the display driving substrate.

13 is a signal line, 14 is a scanning line, and 15 is a pixel electrode.

At this time, electrical connection between each Tr and the wiring was performed by heating with a YAG laser. Furthermore, this Tr was added to the fixative 1
By fixing with 6, the display driving board is completed.

When the area of the panel is large, by repeating this transfer operation, a sufficiently large panel can be manufactured.

A display cell is completed by sealing liquid crystal between the display drive substrate 32 formed in this manner and the counter substrate 18 on which the counter electrode 19 and color filter are formed.

FIG. 8 is a sectional view of the display cell of the present invention.

FIG. 9 is a plan view of a display device using the present invention. External connections are made electrically using flexible cables, TAB, etc., and connected to the driver IC 21, control IC 24, signal lines, etc. to form a display device.

In the above description, the film substrate is made of polyimide, but other highly heat-resistant polymer films may be used.

Further, the diffusion support may be any other material as long as it has good fluidity, high specific gravity or surface tension, and does not have any adverse electrical effects.

"Effects of the Invention" By manufacturing the display cell as described above, it becomes possible to easily and inexpensively create a large-area flat display device with a diagonal of 20" or more, which was previously impossible.
The economic significance is huge.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the main process of forming a display cell according to the present invention, FIG. 2 is a partial plan view of a substrate on which active elements are densely formed, and FIG. 3 is a cross-sectional view of a group of separated switching elements. Fig. 4 is a cross-sectional view of the re-arranging board in use, Fig. 5 is a plan view of the switching elements on the re-arranging board when they are being rearranged, and Fig. 6 is a partial plan view of the display driving board. 7 is a plan view of the display driving substrate, FIG. 8 is a sectional view of the display cell of the present invention, and FIG. 9 is a plan view of the display device. 1 Polymer film 2 Base layer 3 Semiconductor layer 4 Active element section 7 Switching element section 8 Diffusion support 12 Glass substrate 13 Signal line 14 Scanning line 15 Pixel electrode or higher

Claims (2)

[Claims] Claim 1: A substance such as liquid crystal or EC that can electrically control properties such as light transmission, refraction, and absorption is sealed between opposing electrodes, and one side of the substrate is equipped with active elements such as transistors and diodes for each pixel. In a display cell that performs display using a display drive board that electrically drives each pixel, the active elements are formed in advance with wiring for display signals and control signals, and transparent electrodes for each pixel. The active elements are formed densely on a substrate different from the display driving substrate, the active elements are individually separated from the substrate, and the active elements are transferred to the positions of the active elements for each pixel on the display driving substrate. A display cell with the active element electrically connected and used as a display driving substrate. 2. The active element is formed by densely forming a base layer such as SiO2 on a high heat resistant polymer substrate such as polyimide using a low temperature process such as plasma CVD in an area unit required for each active element. A semiconductor layer such as a-Si is laminated on the base layer, P, S, etc. are injected into the semiconductor layer, active elements such as FETs and diodes are formed, and furthermore, the elements and signal lines are formed. , a switching element is formed by forming a connection part using Al, Au, etc. for electrical connection with a scanning line, a transparent pixel electrode, etc., and etching, etc. is performed from the substrate on which the densely formed switching element is formed. The switching elements are separated and made independent by the display driving substrate, and the switching elements are rearranged on the array board through the diffusion support so that the switching elements are transferred to the required position. The display cell according to claim 1, characterized in that the switching element is transferred onto a display driving substrate and electrically connected to a signal line, a scanning line, a transparent pixel electrode, etc., and used as a display driving substrate. .