JPS6227722A - Electrochromic display element - Google Patents

Abstract

PURPOSE:To maintain the insulating characteristic of an interlayer insulating film and to obtain an ECD having less short-circuit defects at a good yield by forming wirings on the top and bottom of the interlayer insulating film, irradiating a laser to the parts necessary for conductive connection to take conduction in the vertical direction and making conductive connection. CONSTITUTION:A source line 23, source electrodes 25, 26 of the 1st and 2nd TFTs, a drain electrode 27 and a power bus line 28 are formed on an insulating substrate such as glass by one patterning. The interlayer insulating film and thin transparent conductive film consisting of ITO, SnO2, etc. are continuously formed by vapor deposition thereon and thereafter the remaining electrodes are formed by one patterning. The layer is then irradiated to a juncture 33 between the power bus line 28 and power line 32, a juncture 34 between the power line and the 2nd TFT, a juncture 35 between the drain electrode 25 of the 1st TFT and a gate electrode 31 of the 2nd TFT and the drain electrode 27 and display picture element electrode 37 of the 2nd TFT by a laser device to take the conduction in the vertical direction and to make connections.

Description

[Detailed description of the invention] [Not for industrial use! ? ] The present invention relates to an electrochromic display element (ECD) that exhibits γi decolorization by electrochemical oxidation far-viewing reaction,
More specifically, the present invention relates to an active matrix drive type ECD in which a thin film transistor is added to each display pixel.

[Prior Art] An ECD has the configuration shown in FIG. 3, a display electrode substrate 4 having four parts, an electrode 5 formed on the substrate 4, and a counter electrode 6 made of glass, plastic,
An opposing It electrode substrate made of ceramic, metal, etc. is placed facing each other.

Both of these can be obtained by enclosing the I[solite 7 and, if necessary, the 17 view board 8 between the boards.

Such a display element has a display '+t' with respect to a counter electrode.
When the J pole is set negative (or tE) and the '-2 pressure is applied,
The EC material is reduced (or oxidized) into 11 color states. On the contrary, one display electrode is connected to iE for opposite polarization.
(or negative) and apply voltage, the display will be erased,
Return to state.

In a display element using an amorphous tungsten oxide lTL film, which is an EC material, for example, the coloring density of Eim C/crn' can be changed by applying a negative voltage of -1.OV to -2.2v. The speed at which a crystalline tungsten oxide thin film changes from a transparent state to six colors is usually 500m5e.
The range is from c to 50m5ec. Also.

The speed when erasing this by applying a voltage from -0.2V to +1.0V is usually 300m5ec to 50m5ec.
Takes values in the range of .

Here, the voltage at which the response time during coloring becomes infinite is
This corresponds to the state in which the electromotive force of the amorphous tungsten oxide fishing film in the colored state is balanced with the externally applied voltage (■■) and the back electromotive force indicated by the ECD.

This emf, which EC materials generally exhibit, increases with the degree of coloration. When time-division driving is performed using an ECD, this electromotive force becomes a large IlQ power. In other words, when a display pixel in a colored state and a display pixel in a decolored state are connected to each other in an XY matrix type electrode arrangement, the display pixel in a colored state goes from a display pixel in a decolored state to a display pixel in a decolored state. A charge movement occurs, and both change to an intermediate colored state.

As a method of compensating for these basic drawbacks of ECD and obtaining a dot matrix type display device using time-division driving, it is known to add a privately moving element such as a thin film transistor to each display pixel. FIG. 3 shows an example of a one-pixel thin film transistor structure used in a liquid crystal display element, etc., in which 11 is a row electrode, 12 is a column electrode, 13 is a display pixel, and 1
4 indicates an 8-gap transistor. To drive such a display pixel, one row electrode is driven one line to the other, and at this time, the corresponding column electrode of the display pixel on the selected line is simultaneously connected to the display pixel. A signal corresponding to coloring or decoloring is applied.

Adding one fJj film transistor to each pixel,
In the method of writing and erasing by line sequential scanning, as the number of scanning lines increases, the response of the EC material becomes slow, so it takes time to display all pixels. To overcome this, two thin film transistors are added to each pixel as shown in FIG. 4, and the drain electrode of the first thin film transistor 15 is connected to the drain electrode of the second thin film transistor 15. jiII! 2 to the gate electrode of the transistor 16, and addresses the first thin film transistor at a high speed to control the gate potential of the second thin film transistor, thereby increasing the O of the second thin film transistor.
A so-called screen sequential drive has been devised in which after determining N and OFF, a voltage is applied to the power line 18 connected to the power path line 17 to display the entire screen at the same time. With this method, as can be seen from the method of operation, coloring and decoloring cannot be done at the same time.

In any case, the dot matrix display with many display contents is
When using CU, each display pixel has at least one
thin film transistors are required. This thin film transistor is formed on a single crystal or glass substrate, but it is often formed on a glass substrate, which has no size restrictions and is advantageous in terms of cost. Silicon or polycrystalline silicon produced by low pressure CVD is used, but other semiconductor materials that can form thin film transistors may also be used.

Aluminum, which has low resistance and is easily etched, is mainly used for the source electrode, gate electrode, and train electrode of thin film transistors. The display pixel electrode is usually formed of tin-doped indium oxide (ITO), and is made of Si3
It is connected to the drain electrode through a contact hole made in an insulating film such as N4, 5i07.5iON. An EC material such as tungsten oxide or molybdenum oxide is formed on the display pixel electrode 1-.

After the display electrode substrate incorporating such a thin 112 transistor in each pixel and the counter electrode substrate incorporating the counter electrode are placed facing each other and sealed, a lithium salt such as lithium perchlorate is mixed with a non-containing material such as propylene carbonate. EC that can display dot matrix by injecting electrolyte dissolved in water solvent
D is produced.

[Problems to be Solved by the Invention] There are two methods for displaying dot matrix type electro comics: a static method in which each display pixel is operated individually, and an active method in which switching elements such as thin film transistors are used. be. Of these, the former has a limit in terms of display capacity because the number of leads taken out is large. The latter method has no problem with display capacity.
However, with ECD, which is a charge control type element, it takes time to color or decolor one pixel, so if there is one thin film transistor per pixel, it will take a long time to display the entire screen when there are many operation lines. U-There's a problem. For this reason, a method has been devised in which two thin film transistors are added to each pixel and the pixels are sequentially driven. In the double thin film transistor method in which two thin film transistors are added to each pixel, as shown in FIG. 4, it is necessary to electrically connect the drain electrode of the first thin film transistor and the gate electrode of the second thin film transistor. This requires making contact holes in the interlayer insulating film, but the pinholes generated in the interlayer insulating film during this process can cause problems between the interconnects that will be deposited later and the interconnects that have already been formed under the insulating film. The problem was that short circuits occurred frequently.

The probability of short-circuit defects per unit area is 1 to 3 times higher than the probability of defects caused by pinholes originally in the interlayer insulating film.
It has been confirmed that it is several orders of magnitude larger. Therefore, it is believed that the large number of short-circuit defects is caused by defects in the photoresist. In any case, there is a strong demand for a structure and manufacturing method that can reliably connect the drain electrode of the first thin film transistor and the gate electrode of the second thin film transistor, and that can provide sufficient insulation without causing short circuits in the living room.

In addition, since two transistors are required for each pixel in order to perform field sequential driving, the process is more complicated than display elements such as liquid crystals and electroluminescent devices that can be driven with a single transistor. This caused an increase in manufacturing costs.

[Means for solving problems].

The present invention has been made to solve the above-mentioned problems, and is an electronic device having a plurality of EC display pixels formed on an insulating substrate-H and a plurality of thin film transistors added to each display pixel. An electrochromic display element characterized in that an interlayer insulating film is sandwiched between the conductive thin films patterned below as electrodes of each transistor, and a mutual conductive connection is made after all electrodes are formed. It provides:

The structure of the 9J film transistor used in the present invention is as shown in FIGS. There are several types of structures: (a) coplanar type;
(b) staggered type and their inverted structures; (c) inverted covelar type; and (d) inverted staggered type. In the present invention,
Any combination of the above four types can be implemented. However, within that combination, other process conditions,
In view of the required wiring resistance value, transistor characteristics, etc., and in the present invention, it is desirable that these two TPTs have the same structure.

Note that since the ECD is a current display type display element, a large current is required for coloring and decoloring, so it is preferable to use polycrystalline silicon for at least the second TPT connected to the display pixel electrode. Therefore, when polycrystalline silicon recrystallized by a lamp annealing method, a laser annealing method, or the like is used for the semiconductor layer, it is preferable to select a coplanar structure from the viewpoint of the process.

Based on the above, in the following description, a case will be described in which two transistors have a coplanar structure.

This will be explained below with reference to the drawings.

FIGS. 1(a) and 1(b) are an enlarged plan view of one pixel of a typical example of the electrochromic display element of the present invention (a) and its A
, A' plane sectional view (b) is shown.

In this figure, 21 is the semiconductor layer of the first TFT, 2
2 is the semiconductor layer of the second TPT, 23 is the source line, 2
4 is the source electrode of the first TPT, 25 is the drain electrode of the first TPT, 2B is the source electrode of the second TPT,
27 is a drain electrode of the second TPT, 28 is a power pass line, 29 is a gate line, 30 is a gate electrode of the first TPT, 31 is a gate electrode of the second TPT, and 32 is a power line. Reference numerals 33, 34, 35, and 36 are connection portions in which the electrodes on the upper and lower sides of the interlayer insulating film 40 are vertically connected by a laser repair device according to the present invention. 37 is 1 made of a transparent conductive thin film such as ITO.
The surface shows a boron electrode, and 43 shows an EC material such as a-WO2.

In the present invention, a semiconductor layer is first formed and patterned on an insulating substrate such as glass to form two TPT semiconductor layers 2.
After obtaining 1 and 22, metals such as AI and Cr are deposited,
Source line 23, first TFT source' electrode 25.
The drain electrode 24, the source electrode 26 of the second TPT, the drain electrode 27, and the power pass line are formed by one patterning of the zero-order interlayer insulating film and ITO, 5.
After successive deposition of transparent conductive thin films such as n02, the remaining electrodes, gate lines 29. The gate electrodes 30 and 31 of the first and second TPTs, the power line 32, and the display pixel electrode 37 are formed by one patterning. After that, the part where you want to make conduction with the laser device,
That is, a connection portion 33 between the power path line 28 and the power line 32, a connection portion 34 between the power line and the second TPT.
The connection part 35 between the drain electrode 25 of the first TPT and the gate electrode 31 of the second TPT, and the drain electrode 27 of the second TPT and the display pixel electrode 3 are irradiated with a laser to establish conduction in the northward direction. Connecting. In this way, two TPTs per display pixel can be formed by patterning three times.

Here I will add a brief explanation of the subjunctive method using the wooden sword style. A cross-sectional view of the three-layer structure is shown in FIG. 6(a). 81 is a glass substrate, 82, 64 is a conductive IS, and 63 is an interlayer insulating film. A laser beam is applied to this structure from the L direction. When irradiated, the shape becomes as shown in (b). At this time, the upper or lower conductive material covers the exposed surface of the insulating film, allowing electrical continuity between the upper and lower electrodes. A cleaning process, a current test, etc. were performed on the substrate in such a state, but no change occurred.

The TPT semiconductor layer is not particularly limited, but amorphous silicon, pre-polycrystalline silicon, CdSe, etc. are mainly used.

Examples of the EC material of the present invention include, but are not limited to, amorphous tungsten oxide, molybdenum oxide, Iv
oxides such as vanadium oxide, titanium oxide, niobium oxide, and ihyridium oxide, or complexes thereof, organic viologen compounds, rare earth siphthalodianine, mixed valence complexes of transition metals such as Prussian blue, polythiophene, etc. A conductive polymer material such as polypyrrole is used.

The electrolyte can be used as either a solid electrolyte or an electrolytic solution, and can be used depending on the purpose. Examples of solid electrolytes include:
Sin, 5i02. CaF, +, MgF2゜Zr
O2, a20s* porous body of inorganic insulating material.

A thin film consisting of moisture occluded in this, β-A12Qa
, RbAga 15. No representative Sarel a for Li3N etc.
Examples include m4-on conductor materials and ionically conductive polymers, and electrolytes include various inorganic acids, organic acids, and LiC.
lO4, LiBFa, LiAlC1a, LiPF6
．． Salts such as LiAsF6 are converted to propylene carbonate, γ
- A nonaqueous electrolyte obtained by dissolving in butyrolactone, acetonitrile, etc. may be used.

For the counter electrode, background plate, counter electrode substrate, etc., known materials and shapes can be used.

As the counter electrode, carbon or carbon is used.
A porous ceramic plate is used as the background plate, and glass, ceramics, plastic, etc. are used as the counter electrode.

[Operation] The present invention uses a double TFT having two TPTs in one pixel.
In this type of ECD, after forming the gate electrode, source electrode, drain electrode, and all wiring of the TPT, vertical conduction is established using a laser, thereby providing a method for manufacturing the TPT.

In this structure, the curly portion between the upper and lower wires, where short-circuit defects occur, is formed in advance. Therefore, drilling holes in the living room insulation film is not affected by the increase in pinholes during the process, which not only improves reliability, but also significantly shortens the process compared to conventional processes, reducing costs. There are also great benefits.

[Example] A Si07 film and then an amorphous silicon film were sequentially deposited on a glass substrate L using a plasma CVD method to form a film of 1000 ml each.
After depositing 2,000 people, the amorphous silicon was deposited in Figure 1 and 2.
As shown in 1.22, the semiconductor layer of the first TPT and the second TPT was formed by depositing 3000 layers of AI using EBA and patterning to form the source line 2.
3. Source electrode 24 of the first TPT, drain electrode 25 of the first TPT. The source electrode 2B of the second TPT, the second
A TPT drain electrode 27 and a power pass line were formed for two days.

Next, 3,000 SiON films were deposited as interlayer insulating films by plasma CVD.

After that, 1000 ITO layers were deposited by EB evaporation method, and then patterned to connect the gate line 29, power line 32, and the gate of the first TPT to the electrode 30 and the second TPT.
A TPT gate electrode 31 and display pixel electrode 37 were formed. After that, a laser was irradiated to the portions 33, 34 and 35, 38 to establish continuity in the vertical direction.

Use photosensitive polyimide to cover areas other than the display pixel electrode and the surrounding glue extraction area for passivation! l! 41
And so. Finally, an EC material 42 made of tungsten oxide is formed in the display pixel portion, and an EC material 42 with a thin film transistor is formed.
A D board was created.

The occurrence rate of short circuit defects in the substrate thus produced was the same as the defect occurrence rate of the insulating film itself, and was very small. This defect level is considered to be within the range that can be eliminated by increasing the thickness of the interlayer insulating film and improving the process.

In the example, a passivation film of photosensitive polyimide was used, but 5i02. There is no problem with Sin or 5iON, and although the TPT structure has been given as an example of coplanar, it is clear that it is not limited to this.

[Effects of the Invention] Conventionally, an ECD that performs so-called field sequential driving by adding two thin film transistors to each pixel has a contact hole formed in an interlayer insulating film to connect a first TPT and a second TPT. However, this hole formation is caused by pinholes caused in the interlayer insulating film other than the contact hole area during the process, and short-circuit defects between the wiring that will be formed later and the wiring that has already been formed under the insulating film are extremely likely to occur. It was increasing. For this reason, even if a display element is actually manufactured and driven, there is a problem in that short circuits occur frequently.

In the present invention, after forming wiring above and below the interlayer insulating film,
Conductive connections are made by irradiating laser beams onto the areas necessary for conductive connections to establish vertical continuity. Therefore, defects due to the hole-drilling process do not occur, and the inherent insulation properties of the interlayer insulating film can be maintained, and ECDs with few short circuit defects can be obtained with a high yield.

Furthermore, as an application of the present invention, a structure may be considered in which the positional relationships of the source electrode and the drain electrode with respect to the gate electrode of the two TPTs are different from each other with respect to the substrate, thereby eliminating the need for laser irradiation between the TPTs. The present invention is advantageous in that it requires fewer film deposition steps and photoetching steps than this.

When attempting to make an ECD with a large display capacity using TPT, it is required to reduce defects in TPT and reduce the number of steps to increase yield.The present invention was developed in view of these points. It is very good.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are a top view and a sectional view of a display pixel to which the TPT of the present invention (7) is added. FIG. 2 is a cross-sectional view of a typical ECD. FIG. 3 is a circuit diagram of an active matrix type ECD in which one TPT is added to each pixel. FIG. 4 is a circuit diagram of an active matrix type ECU in which two TPTs are added to each pixel. FIG. 5(a) is a cross-sectional view of a coplanar TPT, and FIG. 5(b)
) is a cross-sectional view of a staggered TPT, (C) is a cross-sectional view of an inverted coplanar TPT, and (d) is a cross-sectional view of an inverted staggered TPT.
A cross-sectional view of T. FIGS. 6(a) and 6(b) are cross-sectional views before and after connection of an example of vertical conduction according to the present invention. 24: Source terminal of first TFT; 125: First TFT
Drain electrode 26 of PT: Source electrode 27 of second TFT: Drain electrode 30 of second TFT: Gate electrode 31 of first TPT: Gate electrode 33, 34, 35, 3Ei of second TPT: Connection part 61 Glass substrate 82. 84: Conductive thin film 83: Interlayer insulating film 1 Figure tb No. 2 Concave 1α,
(b) 2nd Kasumi Figure 5 + C1 + d Figure 3

Claims (4)

[Claims] (1) In an electrochromic display element that has a plurality of electrochromic display pixels formed on an insulating substrate and a plurality of thin film transistors added to each display pixel, an interlayer insulating film is sandwiched, and each An electrochromic display element characterized in that conductive connections between conductive thin films patterned as transistor electrodes are made after all electrodes are formed. (2) A laser beam is irradiated to a part of a three-layer structure consisting of an interlayer insulating film and a conductive thin film on the top and bottom to establish vertical conduction and conductive connection between the electrodes.
The electrochromic display element described in . (3) The electrochromic display element according to claim 1, wherein the conductive thin film formed above the interlayer insulating film is a transparent conductive thin film. (4) The electrochromic display element according to claim 1, wherein the electrochromic substance is amorphous tungsten.