JPH0629920B2 - Method for manufacturing liquid crystal electro-optical device - Google Patents

Description

The present invention relates to a method of manufacturing a liquid crystal electro-optical device in which driving performance is improved by a non-linear element having a non-linear voltage-current characteristic (VI characteristic).

By combining a non-linear element (varistor, diode, metal-insulator-metal element (hereinafter abbreviated as MIM element), discharge tube, etc.) and a liquid crystal electro-optical device, multi-digit driving can be realized as compared with the conventional one. Are known. As a result, a liquid crystal display device that can display a large amount of information, an optical switch that enables a finer pattern, and the like are realized. Although the electro-optical device has great advantages as described above, the installation of the non-linear element causes various problems not found in the conventional liquid crystal electro-optical device. These are listed below.

(1) Technology to fabricate non-linear elements uniformly and to suppress defects to a very low level in a large area (2) Electric circuit matching between liquid crystal layer and non-linear element performance during driving (3) Non-linear Both element stability and reliability are important issues, but when a liquid crystal panel is completed, it is pixel defects that significantly impair the display quality. When the cause of the pixel defect was investigated, it was classified as follows.

(1) Disconnection and short circuit in non-linear element manufacturing process (2) Mechanical breakdown of non-linear element in liquid crystal panel assembly process,
Destruction due to static electricity (3) Destruction due to static electricity in non-linear elements after liquid crystal encapsulation Also, from the viewpoint of the number of defects, the breakdown due to static electricity accounted for a large proportion. This was mainly due to the manufacturing process.
In the conventional manufacturing method, as shown in FIG. 1, a substrate 1 on which a non-linear element is installed is manufactured and then assembled with a counter substrate 2 and a spacer 3 interposed therebetween. Then, the liquid crystal is sealed through the sealing hole 5, and the external connection terminals 4 and 19 are connected to the drive circuit.

However, according to this method, when the external connection terminal of one substrate is grounded through the jig, if the static electricity is received from the human body or the like, the non-linear element will be destroyed.
This is understood as follows.

The equivalent circuit for one pixel of the liquid crystal panel is as shown in FIG.
It is composed of a non-linear element 6, an equivalent capacitance C _LC of the liquid crystal layer and an equivalent resistance R _LC of the liquid crystal layer. Now, when the voltage V is applied to both ends, as shown in FIG. 3, at the moment when V is applied,
All V is applied to the non-linear element. This voltage causes the non-linear element to have a low resistance, that is, the switch is turned on, and the liquid crystal layer starts to be charged. Thus, the voltage of the liquid crystal layer rises. Next, when the voltage across both ends drops, the applied voltage V _NL of the non-linear element drops, and the high resistance, that is, the switch becomes OF
The liquid crystal layer voltage V _LC is lowered to F state only by discharging inside the liquid crystal layer. As understood from this operation, in order to improve the driving performance by the non-linear element, it is necessary for the non-linear element to switch across the equivalent resistance R _LC of the liquid crystal layer. As a result, quick writing and holding of a sufficiently long voltage are performed. The above is a brief explanation that the driving performance is improved by the non-linear element. However, the breakdown of the non-linear element occurs when the voltage V exceeds the breakdown voltage of the non-linear element. It is inevitable in operation that the voltage V is initially applied to the non-linear element as shown in FIG. By the way, the static electricity of the human body is 1000
It is about 5000V. Since this is applied to the non-linear element, it can be said that the element is destroyed.

FIG. 4 shows a three-dimensional circuit of the pixels 7, the electrodes 8 and the electrodes 9 viewed topologically in a multiplex drive liquid crystal panel. The same applies to the case where a non-linear element is added, and the pixel impedance Z7 of FIG. 4 is replaced with the equivalent circuit of FIG. FIG. 5 is a drawing in which X _i is selected from the X electrodes 8 and Y _j is selected from the Y electrodes 9 and an equivalent circuit viewed from both ends is drawn. The capacitance 10C _Lij is an interelectrode capacitance between the X _i electrode and the Y _j electrode. Where C
_Lij is C when the interelectrode capacitance for one pixel is C _0.
Lij can be expressed by equation (1).

C _Lij = (N ² / (2N-1)) · C ₀ (1) (N is the number of X electrodes and Y electrodes) In this case, the pixel size is set to 0.5 mm ² and the aperture ratio is set to 95%. In the panel, C _Lij = 20 pF when C ₀ = 0.4 pF and N = 100.

Z / (N-1) is another pixel on the X _i electrode and the Y _j electrode, Z
/ (N-1) ² represents the equivalent impedance of another pixel that is not related to any of the X _i and Y _j electrodes.

Therefore, in the circuit of FIG. 5, the equivalent capacitance C _M 11 (several hundred p
When a static electricity equivalent to being charged by several kV is applied to F), C _Lij = 20 pF, so Z, Z / (N−
1), Z / (N-1) ² and Z / (N-1) series impedance, a few kV is instantaneously applied. The highest voltage per unit pixel is of course applied to the pixel (i, l), the non-linear element of the pixel (i, j) is destroyed, and the static electricity is neutralized. When a large amount of charges are accumulated, other pixels, especially the non-linear elements of the pixels on the X _i electrode and the Y _j electrode, are destroyed.

According to the conventional manufacturing method, static electricity is easily picked up from the external connection terminal in this way, and many non-linear elements are broken.

The present invention eliminates such drawbacks, and an object of the invention is to prevent external high voltage of static electricity from being applied to a non-linear element by connecting external connection terminals, and a liquid crystal electro-optical device having few defects. It is to provide an easy manufacturing method for realizing the above.

Hereinafter, the present invention will be described in detail with reference to examples.

FIG. 6 shows an example in which the external connection terminals are connected by a vapor deposition film 16 of gold and the panel assembling process and subsequent steps are performed. The signal electrode external connection terminals 19 are plated with Ni and electroplated with solder in advance, and a vapor deposition film 16 for gold connection is provided thereon. In this state, the panel is assembled and the liquid crystal is sealed. Next, the drive circuit and the panel are connected, but the connecting tape 15 (copper hut is placed on the polyimide tape) is brought into close contact with the terminal and heated from above. At this time, the solder melts and the terminals are connected to the melted tape, and at the same time, the gold vapor deposition film 16 for connection is absorbed by the solder, and the connected terminals are separated.

In the embodiment shown in FIG. 6, the external connection terminal for the signal electrode is X
Connect between the terminals, but connect the external connection terminal for the scan electrode to Y
You may connect between terminals.

FIG. 7 illustrates this equivalent circuit. If the total number of pixels is N ² (N electrodes for both X and Y electrodes), the impedance Z of the equivalent circuit for one pixel shown in FIG. 2 is (Z /
The impedance 18 becomes N ² ), and the inter-electrode capacitance C _{0 for} one pixel is multiplied by N ² to become the inter-electrode capacitance C _L 17. Consider a case where the X electrode and the Y electrode are connected as shown by a broken line. Now, it is assumed that static electricity equivalent to the equivalent capacitance 11 of the human body charged to several kV is applied between the X electrode and the Y electrode. As shown by the broken line, if the X and Y electrodes are connected together, all the charge will flow through the circuit shown by the broken line.
Naturally, no voltage is applied to the non-linear element. Therefore, no destruction occurs.

Next, consider the case of the embodiment of FIG. 6 in which the X electrode and the Y electrode are not connected. The equivalent capacitance 11 of the human body is several hundred pF, and the inter-electrode capacitance C _L 17 is N = 100, C ₀ = 0.4.
If it is pF, it will be about 4000 pF, which is one digit larger than the equivalent capacitance C _{M of the} human body. Therefore, even if several kV is applied between the XY electrodes, the voltage is lowered to the moment C _M / (C _M + C _L ), and in this case, tens to hundreds of V of 1/20 is applied to the non-linear element. It will be only. In this way destruction can be avoided. For the same reason, the voltage applied to the non-linear element can be lowered even when only the non-linear element side external connection terminal is connected or when only the counter substrate side external connection terminal is connected. However, in these cases, the interelectrode capacitance cannot greatly exceed the equivalent capacitance of the human body as compared with the case where the terminals of both substrates are connected, so the effect is reduced. However, it also has the advantage of being simple to implement.

In this way, by adopting the process of connecting the external connection terminals so that the static electricity can be absorbed by the short circuit or the capacitance between the electrodes, there is no destruction of the non-linear element due to static electricity, or the number is extremely small. Became possible. Since the gist of the present invention is the absorption of static electricity due to the short circuit or the inter-electrode capacitance as described above, the method of connecting the external connection terminals is not limited to this embodiment.

As described above, according to the present invention, it is possible to prevent a defect, which is peculiar to a liquid crystal electro-optical device using a non-linear element, due to destruction of the non-linear element due to static electricity, and to realize a liquid crystal electro-optical device with high display quality. Further, by reducing the number of defects, it is attempted to dramatically improve the yield in manufacturing.

The present invention provides an epoch-making manufacturing method in the field of a liquid crystal electro-optical device using a non-linear element capable of handling a large amount of information.

[Brief description of drawings]

FIG. 1 shows a conventional manufacturing process. 1 ... Non-linear element side substrate 2 ... Counter substrate 3 ... Spacer 4 ... Counter electrode external connection terminal 5 ... Liquid crystal sealing hole 19 ... Signal electrode external connection terminal Fig. 2 is equivalent to one pixel Circuit. 6 ... Non-linear element FIG. 3 shows the applied voltage, the voltage V _NL applied to the non-linear element, and the voltage V applied to the liquid crystal in order from the top when the voltage V is applied.
It is a waveform which shows the time change of _LC . FIG. 4 shows an equivalent stereoscopic circuit of a multiplex drive liquid crystal panel. 7 ... Equivalent impedance of one pixel Z 8 ... X electrode 9 ... Y electrode FIG. 5 shows an equivalent circuit as seen from between the X electrode X _i and the Y electrode Y _j . 10 ... Capacitance between electrodes 11 ... Equivalent capacitance of human body FIG. 6 shows a case where the external connection terminals according to the present invention are connected one by one. 15 ... External connection tape 16 ... Gold vapor deposition film for short-circuiting terminals FIG. 7 shows an equivalent circuit seen from the X electrode and the Y electrode in FIG. 17 ... Inter-electrode capacitance C _L 18 ... Equivalent impedance Z / N ^{2 of} all pixels

Claims (1)

[Claims] 1. A) A plurality of pixel electrodes, a plurality of non-linear elements arranged corresponding to the plurality of pixel electrodes for controlling signals supplied to the plurality of pixel electrodes, and a signal to the plurality of non-linear elements. A first step of forming a plurality of signal electrodes for supplying and a plurality of external connection terminals for supplying a signal to the plurality of signal electrodes on a first substrate; and b) a plurality of counter electrodes. And a second step of forming a plurality of external connection terminals for supplying signals to the plurality of counter electrodes on a second substrate, and c) between the first substrate and the second substrate. A third step of encapsulating liquid crystal in, d) a fourth step of connecting the first external drive circuit to a plurality of external connection terminals for supplying signals to the plurality of signal electrodes, and e) the above Second external connection terminals for supplying signals to the plurality of counter electrodes 5. A method for manufacturing a liquid crystal electro-optical device, comprising: a fifth step of connecting an external drive circuit to the step of: (4) before the fourth step, a plurality of electrodes for supplying a signal to the plurality of signal electrodes are provided. A step of forming a solder thin film layer on the top of the external connection terminals, and then electrically connecting a plurality of external connection terminals for supplying a signal to the plurality of signal electrodes with a gold thin film layer; G) During the fourth step, when connecting a plurality of external connection terminals for supplying a signal to the plurality of signal electrodes and a first external drive circuit, heat is applied to the connection portion to apply the heat. Manufacturing of a liquid crystal electro-optical device, characterized in that gold in a gold thin film layer is absorbed by the solder thin film layer, and a plurality of external connection terminals for supplying signals to the plurality of signal electrodes are electrically separated from each other. Method.