JPH0229628A - liquid crystal display device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a liquid crystal display device.

Conventional technology In recent years, as the demand for lighter and thinner liquid crystal display panels has increased, research and development has become active in using polymer film substrates such as PES and PET instead of glass substrates as substrates for liquid crystal display elements. ing. Here, for electrical connection and fixation between a liquid crystal display element constructed using a polymer film substrate and a drive circuit board, anisotropic conductive rubber (zebra connector), which is often used in the case of liquid crystal display elements with glass substrates, is used. Instead, there is a tendency to use heat sealing methods. According to the heat sealing method, it is possible to make the product much thinner than anisotropic conductive rubber, the positioning work during bonding is easy, and there is no need for a support frame to fix the connection part. This is because it has advantages such as being inexpensive.

FIGS. 3 and 4 show a conventional example in which a liquid crystal display element 1 using a polymer film substrate and a drive circuit board 2 are connected and fixed by a heat sealing method.

First, as is well known, the liquid crystal display element 1 has two transparent substrates each having a transparent conductive film electrode formed thereon, arranged so that the electrodes face each other in a matrix shape, and liquid crystal sealed between the substrates. Here, in FIGS. 3 and 4, for example,
Only the connection portion of one of the polymer film substrates 3 and the transparent conductive film electrode 4 formed on the substrate 3 made of ITo or the like is shown outside the display area. The drive circuit board 2 side is made of a glass epoxy substrate or the like, and has connection lead electrodes formed by arranging lead electrodes 5 individually connected to the transparent conductive film electrodes 4 in an array as shown in FIG. It has part 6. The other ends of these connection lead electrodes 5 are connected to a driving IC 7 and the like. 8 is a cover lay.

Then, an anisotropic conductive film 11 made of a film-like thermoplastic resin 9 and conductive particles 10 is used to connect and fix the drawn-out portion of the transparent conductive film electrode 4 and the connecting lead electrode 5, and a heat sealer head 12 This is done by applying heat and pressure.

Problems to be Solved by the Invention The important points in connection using such a heat seal method are:
The thickness of the connector after connection is equal to the particle size of the conductive particles 10, and the gap between the electrodes is filled with thermoplastic resin 9. This is because the former affects conduction resistance, and the latter affects adhesive strength. Here, the thermoplastic resin 9 on the electrode 5 plastically flows due to heating and pressurization by the heat sealer head 12, and moves between the gaps until the thickness reaches the particle size of the conductive particles 10. Here, the gap is filled with the thermoplastic resin 9 that has moved from above the electrodes 5 on both sides and the thermoplastic resin 9 that has been present between the gaps from the beginning. If the volume of the gap is larger than the amount of resin, charging of the resin 9 into the gap will be incomplete and the adhesive strength will decrease. Conversely, when the amount of resin is larger, the thickness of the resin on the electrode 5 becomes larger than the particle size of the conductive particles 10,
The conduction resistance between the electrodes 4 and 5 becomes large. heating·
If the pressurization is insufficient, none of the above conditions will be met,
This results in unreliable fixed connections.

Therefore, it is important to select a connector thickness that matches the electrode thickness and gap width, and to select the optimum heating/pressing force and pressurizing time in order to ensure the reliability of the connection and fixation.

Particularly, problems that arise when a polymer film substrate is connected and fixed by a heat sealing method are that the polymer film substrate lacks rigidity and is inferior in heat resistance and moisture resistance. For this reason, after the connection as shown in FIG. 3 is made, connection failure is likely to occur due to external stress (Beering stress) or being left under high temperature/high temperature conditions. Such connection failures may occur at discontinuous locations in the extraction electrode array, such as locations where the volume of the inter-electrode gap is different, or locations where heat conduction from the heat sealer head 12 is more difficult than other locations.
Specifically, the area is near the lead electrode 5a located at the end of the lead electrode part 6, and the block is near the time division part.

Means to solve the problem: Liquid crystal is sealed between two transparent substrates each having a transparent conductive film electrode formed thereon, and the electrodes of the transparent substrate are connected to connection lead electrodes on the drive circuit board using thermoplastic resin and conductive particles. In a liquid crystal display device connected and fixed by an anisotropic conductive film including Provide electrodes.

Due to the presence of the working dummy electrode, for example, even the connection lead electrode located at the extreme end is in the same situation as the normal connection lead electrode located inside. Therefore, even if a connection failure occurs after heat sealing, it remains near the dummy electrode.

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 and 2. The same parts as those shown in FIGS. 3 and 4 are indicated using the same reference numerals. In this embodiment, for the lead electrode portion 6 of the drive circuit board 2, the original connection lead electrode 5 is connected to the electrode 4 on the liquid crystal display element 1 side and contributes to electrical signal transmission.
In addition, dummy electrodes 1 are placed outside both ends of the array group.
3. However, if the liquid crystal display element 1 has a high display capacity and the connecting lead electrodes 5 are divided into two or more groups, dummy electrodes are also provided at the divided locations. That is, the gap volume between the connecting lead electrodes 5 arranged in an array is discontinuous due to discontinuation, division, etc. at the end. Furthermore, the pitch and electrode width of the dummy electrodes 13 are set so that the thickness of the resin 9 after connection and the degree of filling of the resin 9 in the gap between the electrodes 5 and 13 do not become discontinuous. It is preferable that the arrangement pitch be the same as the original arrangement pitch of the electrodes 5.

In this way, the dummy electrode 13 is added to the lead electrode 5 within the bonded and fixed area by the anisotropic conductive film 11, so that after heat sealing, the vicinity of the lead electrode 5 at the end is exposed to vibration stress and high temperature/high temperature environment. Even if a connection failure occurs due to being left in the dummy electrode 1
It stays within the third group, and even if the original connection lead electrode 5 itself is at the end, it is equivalent to the one inside the play, and no defects occur. In this case, a dummy electrode 1 is connected to the polymer film substrate 3 side of the liquid crystal display element 1.
Although the dummy electrode corresponding to (3) is not provided, there is no particular problem. That is, the thickness of the transparent electrode 4 on this substrate 3 side is approximately 30 mm.
It is about 0 to 1000 people, and is negligibly thin compared to the thickness of the connection lead electrode 5 on the drive circuit board 2 side, which is 18 μm to 36 μm, so the presence or absence of the dummy electrode on the board 3 side determines the reliability of the connection. This is because it does not have a large effect on

Effects of the Invention As described above, the present invention provides for discontinuous portions of the extraction electrode array such as ends and divided portions in the connection lead electrode portion of the driving circuit board, which are located within the connection region by the anisotropic conductive film. Since a dummy electrode is provided at the dummy electrode, even if a connection failure occurs after heat sealing, the location where it is likely to occur is essentially replaced by the dummy electrode, and the original connection failure between the electrodes can be prevented. , it is possible to improve the yield of liquid crystal display devices using the heat-sealing method, and also to improve the reliability after connection.

Transparent substrate, 4... Transparent conductive film electrode, 5... Lead electrode for connection, 6... Lead electrode part for connection, 9... Thermoplastic resin, 10... Conductive particles, 11... Anisotropic conductive film, 13... dummy electrode

Claims (1)

[Claims] A liquid crystal is sealed between two transparent substrates each having a transparent conductive film electrode formed thereon, and the electrodes of the transparent substrate are connected to connection lead electrodes on a driving circuit board using an anisotropic conductive material containing thermoplastic resin and conductive particles. In a liquid crystal display device connected and fixed by a film, a dummy electrode is provided at a discontinuous portion of the electrode array in a connection lead electrode portion of the drive circuit board, and is located within a connection region by the anisotropic conductive film. Characteristic liquid crystal display device.