JPH0660979B2 - Electrical connection method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrical connection method for conducting electrical extraction from a transparent electrode such as a display element without reducing an effective display area.

2. Description of the Related Art FIG. 4 shows a conventional electrical connection method for a display element made of glass having two transparent electrodes. In the figure, one of the glass plates 1 and 2 having two transparent electrodes is made to project from the other end face, and the flexible substrate 4 as shown in FIG. Are bonded with a conductive adhesive 5 or are brought into pressure contact with a connecting circuit board 7 via an elastomer connector 6 as shown in FIG. 6 to obtain an electrical connection.

As another example, FIG. 7 shows a display element which is electrically drawn from the end surface on the element side. In the figure, the display element side end surface is formed in the same plane, and the conductive paste 8 is formed in conformity with the transparent electrode shape so as to wrap around the side end surface or the bottom surface of the element for printing to form an extraction electrode. The electrical connection is obtained by a method of adhering a flexible substrate or a method of pressing an elastomer connector on the electrodes that are wound under the element.

Problems to be Solved by the Invention The connecting electrode portion projecting from the end face of the display element shown in FIG. 4 has no display function and has a drawback of reducing the effective display area. Further, in the method of forming the connection electrode on the display element side end surface, which is an electrical connection method for reducing the area of the connection electrode portion shown in FIG. 7, since the conductive paste 8 is directly printed on the side end surface, Printing technology is required.

That is, since the printing is performed on a surface that has poor smoothness and is extremely limited, there is a problem that the risk of short circuit or disconnection is very high when the distance between adjacent electrodes is narrow.

Means for Solving the Problems In order to solve the above problems, the electrical connection method of the present invention prints a conductive paste on a sheet-shaped anisotropic conductive adhesive in an electrode shape to be formed on the end surface of the display element side. Forming, transferring the printed pattern to the element side end surface together with the sheet-like anisotropic conductive adhesive, and thermocompression bonding the connecting circuit board such as a flexible board onto the transferred anisotropic conductive adhesive. Is.

Operation The operation of the above means is as follows.

That is, first, the electrodes to be formed on the end surface of the display element side are printed on the sheet-shaped anisotropic conductive adhesive, so that it can be easily printed by a normal screen printing machine. Pattern formation is also easy. Then, by transferring the conductive paste after forming a predetermined pattern onto the end face of the display element side together with the anisotropic conductive adhesive sheet, the adhesive for the electrode formation by the conductive paste on the transparent electrode and the connection circuit board adhesion The formation can be done simultaneously.

Further, by thermocompression-bonding the flexible substrate through the transferred anisotropically conductive adhesive, it is possible to provide an external connection structure on the end face of the display element, which requires a thickness equal to that of the flexible substrate.

As a result, highly reliable electrical drawing can be performed from the display element without reducing the effective display area.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a liquid crystal display element that has been subjected to an electrical drawing process according to an embodiment of the present invention. 1 in the figure
Reference numerals 1 and 12 denote glass plates forming a display element. The transparent electrodes 13 are opposed to each other (only one electrode on the glass on one side is shown in the figure), and they are bonded together by a sealant 14 with a slight gap therebetween. Is filled with liquid crystal material.
Further, the side end surfaces of the two glass plates 11 and 12 are cut into the same plane slightly outside the sealing agent 14.

FIG. 2 is a cross-sectional view of a sheet-shaped anisotropic conductive adhesive. First, an anisotropic conductive adhesive 16 having a structure in which a conductive powder such as carbon is dispersed in a hot-melt type resin is applied to a film 17 such as PET which has been subjected to a surface release treatment so as to have a thickness of about 20 to 40 microns. A wiring pattern 15 made of a conductive paste is formed on the surface of the coated sheet by screen printing so as to have the same shape as the transparent electrode at the end portion on the display element side.

Next, as shown in FIG. 3, the sheet-shaped anisotropic conductive adhesive is aligned on the display element side end face between the transparent electrode 13 and the wiring pattern 15 and then thermocompression bonded, and the release film 17 is further formed. To remove.

Since this thermocompression bonding step is for the purpose of thermal transfer of the anisotropic conductive adhesive 16, the thermocompression bonding temperature and pressure may be a relatively low temperature and a low pressure due to the main compression bonding in the subsequent step.

Further, since the wiring pattern conductive paste is forcibly transferred to the display element side end surface by the anisotropic conductive adhesive 16, the adhesive force to the glass plates 11 and 12 is not important, and the conductive paste has other characteristics such as low. The degree of freedom in selecting the conductive paste material is extremely large, such as the use of materials having excellent resistance and bending resistance. At this time, as shown in the figure, the wiring pattern 15 is the glass plate 11 of the display element,
A stable connection can be obtained by slightly penetrating the gap of 12 and increasing the connection area.

Therefore, as described above, the glass plates 11 and 12 of the display element are
It is necessary to slightly cut the outside of the sealing agent 14 when cutting the sealing material 14. However, when the cutting position is on or near the sealing material 14, the glass plate 1 of the wiring pattern 15 is cut.
If 1, 2 is prevented from entering the gap, the connection becomes unstable, and if it is too far from the sealant 14, the effective display area is reduced. Therefore, a suitable cutting position is about 0.1 to 1 mm outside the sealant 14. Further, by using a thermoplastic paste as the conductive paste for forming the wiring pattern 15, penetration of the conductive paste into the gap between the glass plates 11 and 12 at the time of thermocompression bonding is promoted to obtain a more stable connection. You can

Next, the flexible substrate 18, which is a circuit board for connection, in which a pattern having the same shape as the wiring pattern 15 of the conductive paste is formed, is thermocompression-bonded to the end face of the display element side through the anisotropically conductive adhesive 16 that is thermally transferred and the wiring pattern 15. By this main pressure bonding step, the electrical connection between the flexible substrate 18 and the transparent electrode 13 at the end portion on the display element side is obtained. At this time, since the flexible substrate 18 is connected by the anisotropic conductive adhesive 16 formed on the side end face in advance, no pretreatment such as adhesive application is required.

Although a liquid crystal display element is used as a display element in the present embodiment, this is not limited to liquid crystal, and for example, EL,
The present invention can be applied to ECD and the like as in the case of liquid crystal.

EFFECTS OF THE INVENTION The electrical connection method of the present invention has a configuration in which an anisotropic conductive adhesive having a printed wiring pattern formed thereon is transferred to an end surface of a display element side, and a connection circuit board is connected via the transfer surface. It is not necessary to provide a connecting terminal portion, which has been conventionally required, at the element end portion, and it is possible to expand the effective area in which characters, images, etc. can be displayed.

Further, the connection electrode is not directly printed on the display element side end surface, but is printed on the sheet-shaped anisotropic conductive adhesive surface and is transferred to the display element side end surface, so that a fine pattern can be easily formed. Furthermore, it is of extremely high industrial value because it is possible to obtain excellent effects such as an increase in connection area and an increase in connection reliability when it is formed using a thermoplastic conductive paste.

[Brief description of drawings]

FIG. 1 is a sectional view in an embodiment of the electrical connection method of the present invention, FIG. 2 is a sectional view of an anisotropic conductive adhesive sheet in the same embodiment, and FIG. 3 is a sectional view of a main part in the same embodiment. FIG. 4 is a perspective view of a conventional example, FIGS. 5 and 6 are sectional views of the conventional example, and FIG. 7 is a perspective view of another conventional example. 11, 12 ...... Glass plate, 13 ...... Transparent electrode, 14 ......
Sealant, 15 ... Wiring pattern, 16 ... Anisotropic conductive adhesive, 18 ... Flexible substrate.

Claims (2)

[Claims] 1. A step of printing a wiring pattern on the surface of a sheet-shaped anisotropic conductive adhesive, and a step of transferring the anisotropic conductive adhesive to an end surface of a display element side composed of two or more glass plates. An electrical connection method comprising a step of connecting a connection circuit board to a display element side end face via the anisotropic conductive adhesive. 2. The electrical connection method according to claim 1, wherein the wiring pattern on the surface of the anisotropic conductive adhesive is formed by using a thermoplastic conductive paste.