JPH02216129A - Liquid crystal image display device and production thereof - Google Patents

Abstract

PURPOSE:To block or drastically decrease the DC component to deteriorate a liquid crystal by flowing into a liquid crystal cell and to prevent the degradation of display image quality by coating the surfaces of signal lines and drain wirings consisting of Al with an insulating alumina film. CONSTITUTION:The thin conductive films 22 and signal lines 12 for connecting picture element electrodes 14 and the drains of insulated gate type transistors (TRs) on an active substrate 2 of an active type liquid crystal panel disposed with the insulated gate TRs as switching elements to each of the picture elements are formed of the same material Al. An anodic oxidation stage for selectively insulating only the signal lines 12 and the drain wirings 22 is introduced to this active substrate 2 to selectively form Al2O3 (alumina) films on the signal lines 12 and the drain wirings 22. Connecting lines 23 are cut if the active substrate 2 is cut along cutting lines 33 after the end of the anodic oxidation. The active substrate 2 is thus completed. The DC component flowing into the liquid crystal cell is blocked or drastically decreased by this active substrate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal panel having an image display function, particularly an active type liquid crystal image display device in which each picture element has a built-in switching element, and a method for manufacturing the same.

Conventional Technology Recent advances in microfabrication technology, liquid crystal materials, mounting technology, etc. have made it possible to obtain television images on a commercial basis with liquid crystal panels that are small in size, about 2 to 6 inches, but have no problem in practical use. Ta. Configuring the LCD panel 2
By forming a colored layer of ROB on one side of a glass plate, color display can be easily realized, and so-called active type liquid crystal panels, in which each picture element has a built-in switching element, have little crosstalk. An image with a high contrast ratio is guaranteed. Such a liquid crystal panel typically has a matrix configuration of 120 to 240 scanning lines and 240 to 720 It lines, for example, as shown in Figure 6, a liquid crystal panel L is configured. A C0G (Chip-
For example, a connection film 4 based on a polyimide resin thin film and having a terminal group of gold-plated copper foil (not shown) is pressed onto an electrode terminal group 5 of a signal line using an adhesive. Electric signals are supplied to the image display section by mounting means such as a fixing method.

Although two mounting methods are illustrated here for convenience, it goes without saying that one of the mounting methods is actually selected. Note that 7.8 is a wiring path that connects the image display section at the center of the liquid crystal panel l and the electrode terminal group 5.6 for signal lines and scanning lines, and it does not necessarily need to be made of the same conductive material as the electrode terminal group. There isn't.

9 is a glass plate which is another transparent insulating substrate having a transparent conductive counter electrode common to all picture elements, and the two glass plates 2.9 are spacers such as quartz fibers or plastic beads. The gap is a closed space sealed with a sealing material and a sealing material, and the closed space is filled with liquid crystal. In many cases, the glass substrate 9 is called a color filter because a colored layer, an organic thin film containing one or both of dyes and pigments, is deposited on the closed space side of the glass plate to provide a color display function. Depending on the properties of the liquid crystal material, a polarizing plate is pasted on either or both of the glass plate 9-L surface or the lower surface of the glass plate 2, and the liquid crystal panel 1 functions as an electro-optical element.

FIG. 7 is an equivalent circuit diagram of an active liquid crystal panel in which an insulated gate transistor 10 is arranged as a switching element for each picture element, and FIG. 8 is a sectional view of a main part of the panel. The elements drawn with solid lines are on one glass substrate 2,
The elements drawn with broken lines are formed on the other glass substrate 97. Scanning line 11 (8) and signal line 12 (
7) is a thin film transistor 1 in which, for example, amorphous silicon is used as a mid-conductor layer and a silicon nitride film (SNN4) is used as a gate insulating film.
0 is produced on the glass substrate 2 at the same time. The liquid crystal cell 13 is composed of two glass plates: a transparent conductive pixel electrode 14 formed on a glass substrate 2, and a transparent conductive counter electrode 5 formed on a color filter 9. It is composed of a liquid crystal 16 that fills a closed space, and is treated electrically in the same way as a capacitor.

Coloring made of colored photosensitive gelatin or colored photosensitive resin [17, as mentioned above, is arranged in the three primary colors of ROB according to a predetermined arrangement on the closed space side of the color filter 9 corresponding to the picture element electrode 14. There is. All picture element electrodes 14
The common counter electrode 15 is colored P! In order to avoid voltage distribution loss due to the presence of the layer 17, the layer 17 is formed on the colored layer 17 as shown. A thin polyimide resin film N18 having a thickness of, for example, about 0.1 μrn, which is deposited on the two glass plates in contact with the liquid crystal 16, is an alignment film for aligning liquid crystal molecules in a predetermined direction. In addition, if a twisted nematic (TN) type liquid crystal is used as the liquid crystal 16, two polarizing plates 19 are required, one above and the other.

When a low-reflectivity opaque film 20 is arranged at the boundary of the RGB colored layer 17, reflected light from wiring layers such as signal lines on the glass substrate 2 can be prevented, the contrast ratio is improved, and the external part of the switching element 10 can be prevented. This prevents an increase in leakage current due to light irradiation, making it possible to operate even under strong external light, and has been put into practical use as a black matrix. There are many possible configurations of the black matrix material, but considering the occurrence of steps at the boundaries of colored layers and the light transmittance,
A Cr filtration film with a thickness of about 0.1 μm is convenient, although the cost is high.

Note that in FIG. 7, the Tt volume ff121 is not necessarily an essential component for an active liquid crystal panel, but it is useful for improving the utilization efficiency of the driving signal source, suppressing disturbances caused by stray parasitic loads, and during high temperature operation. It is effective in preventing flickering in images and is appropriately employed. Also, to simplify understanding, thin film transistor 10, scanning line 1
In addition to the storage capacitor 21 and the storage capacitor 21, main factors such as a light source and a spacer are omitted in FIG. 22 is the picture element electrode 14
This is a conductive thin film for connecting the signal line 12 and the input line of the insulated gate transistor 10, and is formed of the same material as the signal line 12 at the same time.

Problems to be Solved by the Invention However, in active type liquid crystal panels, because the device structure is complex, all liquid crystal cells 13 are driven under the same conditions, resulting in a phenomenon in which the displayed image appears to flicker. Easy to do. Flickering in an image is also called flicker, and it is a well-known fact that it occurs even in a simple matrix liquid crystal panel when it is observed from an oblique angle or when the drive signal contains a large amount of DC component. In order to reduce flicker, the liquid crystal cells 13, which are constituent elements, should be set so that all liquid crystal cells are in the same driving state. There are two methods: one is to manufacture the insulated gate transistor 10 and the storage capacitor 21 with high precision, and the other is to drive adjacent liquid crystal cells 13 in opposite phases so that the liquid crystal panel as a whole is not observed visually.

In the former case, not only are the manufacturing conditions for the active substrate and panel dark blue finish stricter, but also a large storage capacity is required, which lowers the yield and closure rate. However, since the counter electrode 15 is held at a constant voltage and AC driven, the signal voltage becomes higher, and therefore the DC voltage component due to minute variations between liquid crystal cells, which causes flicker, also increases. When using a long leap, the liquid crystal deteriorated and turned brown, impairing image quality.

Originally, as shown in FIG. 8, if the alignment film 18, which is an organic thin film, could exhibit an insulating function and insulate the surfaces of conductive electrodes such as the signal line 12, drain wiring 22, and pixel electrode 14, the picture would be as follows. No direct current will flow into the liquid crystal cell 13 consisting of the elementary electrode 14, the counter electrode 15, and the liquid crystal [16], and no deterioration of the liquid crystal layer 16 should occur. However, the alignment film 18
As mentioned earlier, it is thin at about 0.171 tn, - The alignment film coating method is offset printing, which tends to cause holes and holes, and the temperature is below 300°C to prevent active elements from being destroyed by heat. Due to the fact that the alignment film is cured (thermally cured) at a relatively low temperature, the surfaces of the signal line 12, drain wiring 22, pixel electrode 14, etc. can only be incompletely insulated using the alignment film 18 alone. Although there are differences in degree, it is difficult to prevent the deterioration of the liquid crystal F'16. In particular, since a signal voltage is continuously supplied to the signal line 12 from the outside, a DC component tends to flow between the signal line 12 and the counter electrode 15. Therefore, instead of using a thin alignment film, as shown in FIG. 9, the entire surface of the active substrate 2 is coated with Si3N4 as a transparent insulating film 23 with a thickness of about 0.5 μm, thereby preventing the deterioration of the liquid crystal N16. It is easy to understand that it can be avoided.

However, forming thick passivation N23 on the entire surface requires a long manufacturing process! Two-element electrode 14
This is not a preferable situation since the voltage applied to the liquid crystal layer 16 is reduced due to the presence of an insulating layer thereon. Regarding the latter, it is possible to selectively remove the passivation N23 on the picture element electrode 14, but if there is a high level difference in the passivation layer on the picture element electrode 14 or in the very vicinity of the picture element electrode 14, the alignment film 18 may be removed. The rubbing process with a dry cloth was not performed regularly, causing side effects such as disordering the orientation of the liquid crystal, creating reverse domains, and deteriorating the display image quality.

The present invention aims to solve the problems of the prior art.

Means for Solving the Problems The present invention introduces an anodic oxidation process to selectively insulate only the signal line and drain wiring made of Al.
A 203 (alumina) film is selectively formed on the signal line and the drain 5 wiring.

Since the alumina thin film, which is an insulator, is selectively formed only on the working signal lines and drain wiring, there is no drop in the voltage applied to the liquid crystal layer, and there is no need for a process to apply a passivation layer, making manufacturing easier. Process shortening is promoted.

Example Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5. FIG. 1 shows a pattern on an active substrate 2 constituting a liquid crystal image display device according to a first embodiment of the present invention. In anodic oxidation, it is necessary to electrically connect all the wiring on which you want to grow an oxide film, and the signal line 12
is connected to the common connection line 23 via the terminal electrode 5,
The connection line 23 is connected to a connection portion 24 which is a solid pattern at the periphery of the glass substrate Fi2. The connection line 23 and the connection part 24 are made of the same A1 material as the signal line 12. 1st
The active substrate 2 shown in the figure is installed in a container 26 filled with a chemical liquid 25 as shown in FIG. 23 using a jig such as a clip, and the - (minus) terminal 29 is connected to an electrode plate 30 made of gold, platinum, or the like. When anodizing A1, a chemical solution containing oxalic acid or sulfuric acid as the main component grows porous alumina oxide (alumina, Al201), whereas an ethylene glycol chemical solution containing oxalic acid grows a non-porous, dense layer. Although it is known that alumina grows, details of the anodic oxidation of A1 are disclosed in Japanese Patent Publication No. 34798/1983, which is an example of an earlier application. In any case, in anodic oxidation, when the concentration and temperature of the chemical solution are constant, the thickness of the oxide film that grows is determined by the chemical formation voltage, so if appropriate conditions are selected, the thickness of the oxide film that grows will be as shown in Figure 3. For example, it is extremely easy to form an alumina film 31 with a thickness of approximately o, io, a μm on the A1 signal line 12 having a film thickness of IBm. Drain arrangement! Some current flows through I22 through the channel resistance of the insulated gate transistor, so when the active substrate 2 is irradiated with strong external light during anodic oxidation, the channel resistance decreases and an oxide film 32 grows on the surface of the drain wiring 22. However, since the channel resistance is an order of magnitude higher than that of A1, it is inefficient to continue anodizing for a long time until an alumina film with the same thickness as the signal line 12 grows on the drain wiring 22. Will. After the anodization is completed, the active substrate 2 is cut along the cutting line 33 as shown in FIG.
By cutting along the lines, the electrode terminals 5 become independent as the connecting wires 23 are cut, and the active substrate 2 is completed.

If the electrode terminal is compatible with COG and is small, it is difficult to separate the electrode terminal by cutting the active substrate 2. In such a case, for example, a photosensitive resin pattern is selectively formed on the connection line 23, and after the anodization is completed, the photosensitive resin pattern is first removed, and then A1 is etched using the alumina film as an etching mask. If selectively removed, it becomes possible to make the electrode terminals independent.

In the first embodiment, the surface of the active substrate 2 is exposed, and if the purity of the chemical solution is insufficiently controlled, ionic impurities in the chemical solution will mix into the insulated gate transistor, causing the transistor characteristics to deteriorate. If there is a risk of stability and there is enough room in the pattern layout to connect both ends of the signal line to the connection line, countermeasures can be easily taken, but if there is a disconnection in the signal line, use a positive FS oxide film. The drawback is that there are areas where the growth does not occur.

In the second embodiment, as shown in FIG. 4, after the AIFj 34 which becomes the signal line (source wiring wA) and the drain wiring is deposited, a photosensitive resin layer 35 is formed in a reverse pattern to the above pattern.
are formed by a well-known photolithography process, and the surface of the A1 layer 34 is selectively anodized using the reverse pattern 35 as a mask for anodic oxidation to form 36 and 37. After the anodization, the photosensitive resin pattern 35 is removed and the anodic oxide film 3 is removed.
Using 6.37 as a mask, the A1 layer 34 is selectively etched to complete the active substrate 2 shown in FIG. Impurities in the chemical solution are incorporated into the anodic oxide film, thereby avoiding the possibility that the electrical characteristics of the insulated gate transistor will become unstable.

In FIG. 3, the entire surface of the signal line 12 and the drain wiring 22 is coated with an alumina film 31,32, but in FIG. .37, and the difference is that A1 is exposed on the sides of the signal line 12 and drain wiring 22.

Since the pattern width of the signal line 12 and the drain wiring 22 is generally about 10 μrn, impurities in the liquid crystal material and alignment film should be avoided in order to maintain the purity of the 16 liquid crystal layers sufficiently high.
In particular, if ionic impurities can be excluded, it is understood that in the second embodiment as well, the direct current component due to ionic impurities is reduced to about 115 compared to the conventional example, so the deterioration of the liquid crystal can be greatly improved. It will be.

Regarding the configuration of the active substrate, where the picture element electrodes are formed in the thickness direction largely depends on the structure and manufacturing method of the insulated gate transistor, so the explanation is omitted in the above description. The pixel electrode is only connected to the signal line in a switch-like manner by the insulated gate transistor, so the drain wiring that connects the pixel electrode and the insulated gate transistor does not necessarily need to have an insulated surface; If there is a defect where the transistor is always on, there is a high possibility that the liquid crystal will deteriorate in the vicinity, so it is preferable to insulate the drain wiring as well, as in the present invention. For the same reason, the picture element electrodes are also made of transparent insulating SiO rather than being located on the top layer on the active substrate.
When 2 or 5i3Nn is deposited on the picture element electrode, a more reliable liquid crystal image display device can be obtained. Furthermore, if the signal line does not also serve as the source wiring of an insulated gate transistor and is not covered with an insulating film, there is no need to explain that the same treatment as for the signal line is required for the source wiring. Probably.

Effects of the Invention As described above, the present invention provides the surfaces of the signal line and drain wiring made of A1 with an insulating material in order to prevent or significantly reduce the direct current component that flows into the liquid crystal cell and deteriorates the liquid crystal. Coated with alumina film. For this reason, flickerless drive was adopted to solve the quality problem in which the liquid crystal layer deteriorates and the displayed image appears brown even when a high signal voltage is applied. In addition, by insulating the surfaces of signal lines and drain wiring without increasing the film thickness, it is possible to effectively prevent a drop in the voltage supplied to the liquid crystal cell compared to full-surface passivation using a conventional transparent insulating thin film. There is no risk that the display image will become dark due to the M1 function.
Excellent effects such as being able to maintain the alignment state of the alignment film were obtained.

[Brief Description of the Drawings] Fig. 1 is a pattern diagram on an active substrate constituting a liquid crystal image display device according to a first embodiment of the present invention, and Fig. 2 is a conceptual cross section showing an anodizing method in the same device. Figure, 3rd
The figure is a cross-sectional view of a main part of the substrate of the same device, and FIGS. 4 and 5 are cross-sectional views of main parts in the manufacturing process of an active substrate constituting a liquid crystal image display device according to a second embodiment of the present invention. Figure 6 is a perspective view showing the mounting means on the liquid crystal panel, Figure 7 is an equivalent circuit diagram of an active type liquid crystal panel, Figure 8 is a cross-sectional view of the main part of the same panel, and Figure 9 is a method for preventing liquid crystal deterioration. FIG. 2 is a cross-sectional view showing passivation on an active substrate in a conventional example. l...Liquid crystal panel, 2...Glass plate, 9...Color filter, 10...Insulated gate transistor, l
l...Scanning line, 12...Signal line, 13...Liquid crystal cell, 14...Picture element electrode, 15...Counter electrode, 16...
...Liquid crystal, 18.Alignment film, 22.Drain wiring, 23.Connection line, 24.Heta pattern, 25.
... Chemical liquid, 26 ... Container, 27 ... DC power supply, 2
8...+ (plus) terminal, 29...- (minus)
Terminal, 30... Electrode plate, 31. 36... Alumina film on signal line, 32. 37... Alumina film on drain wiring, 33... Cutting line, 34... A1 layer, 35...・
・Photosensitive resin butter. 2-°- 5-・- 24-・- no-. Actizu 1 & Flea Den Flea Duck 1tTa Teki embroidery solid pattern rn+tr* Fig. 2-Awatitsu back board j2-・-19 22-m-do-in E 髪Iy-Aluminum bottle 2-7 Kutei 25- fjii ++! Plug board error - Positive terminal - - Finus fan 30 - t ii [ ■ Yu crystal spring 4 - Connection film 9 - Katana foo fielder ++ - m - I2 -... +3 - - - 15 - - JP binding Kate type transistor running 1m l5 No. 9 jl f@t! Le pair pick Is No. 8 Figure 9 4-16-m- +9--- n-・- Picture element 1i Flea rT Gai Electricity Qing Akira Wz Phrases Yen leak Light transmission drain distribution Q? -・-Cufflink number I2-・-fW No. Keyaki

Claims (3)

[Claims] (1) A first light-transmitting insulating substrate having a plurality of scanning lines and signal lines and having an insulated gate transistor and a pixel electrode for each unit pixel, and a transparent conductive counter electrode. In the liquid crystal image display device, the signal line is made of aluminum whose surface is anodized, and is electrically insulated from the liquid crystal. A liquid crystal image display device characterized by: (2) A first light-transmitting insulating substrate having a plurality of scanning lines and signal lines and having an insulated gate transistor and a pixel electrode for each unit pixel, and a transparent conductive counter electrode. In the liquid crystal image display device, the signal line and the drain wiring of the insulated gate transistor are made of aluminum, and the signal line and the insulating substrate are made of aluminum. A liquid crystal image display device characterized in that a drain wiring of a gate type transistor is insulated by anodization. (3) A first light-transmitting insulating substrate having a plurality of scanning lines and signal lines and having an insulated gate transistor and a pixel electrode for each unit pixel, and a transparent conductive counter electrode. In the method for manufacturing a liquid crystal image display device in which a liquid crystal is filled between a second transparent insulating substrate and a second transparent insulating substrate, in forming the signal line and the drain wiring of the insulated gate transistor, after depositing aluminum, A photosensitive resin pattern having a reverse pattern of the signal line and the drain wiring of the insulated gate transistor is selectively formed on the aluminum, and after the aluminum is anodized, the photosensitive resin pattern and the aluminum are removed. A method for manufacturing a liquid crystal image display device.