1. Field of the Invention
The present invention relates to a device for electrically connecting a connecting terminal portion of a transparent electrode to an electrode connecting portion formed on a substrate of a driving circuit, etc. in a liquid crystal display element in which each of upper and lower substrates is constructed by a flexible film.
2. Description of the Related Art
In a conventional liquid crystal display element having a flexible film as a substrate, an anisotropic conductive film is used when a driving circuit is electrically connected to a transparent electrode formed on one substrate. The anisotropic conductive film is formed by dispersing conductive particles having several microns in diameter into an adhesive. The transparent electrode and the driving circuit are electrically connected to each other through the anisotropic conductive film by pressure welding or thermal press-fixing.
In a conventional electrode connecting means of the liquid crystal display element, adhesive force of the transparent electrode supported by the flexible film substrate is weak in comparison with that in the electrode connection of a liquid crystal display element constructed by forming the transparent electrode on a glass substrate. Accordingly, when an opposite electrode of the driving circuit is connected to the flexible film having such a transparent electrode, the transparent electrode on the flexible film tends to be disconnected and deteriorated by pressure and thermal stresses.
A peripheral substrate portion in a connecting portion may be coated with a backup agent such as a processing agent to prevent the connecting portion from being peeled. For example, the processing agent as a backup agent is constructed by a rubber adhesive or an adhesive of a UV effect type. There are no effects obtained by using the backup agent at an initial stage of time passage. This is probably because the transparent electrode is already damaged at a thermal press-fixing time so that the above effects cannot be obtained even when the backup agent is used after a thermal press-fixing operation. In a thermal press-fixing portion having no backup agent, the resistance value of a connecting terminal is continuously increased in accordance with the passage of an operating time. In this state, it is assumed that no signal waveforms are sharpened and the connecting terminal is not conductive and is in a disconnecting state.