JPS61167925A - Liquid-crystal display device - Google Patents

Abstract

PURPOSE:To improve a deficiency in adhesive strength by pressing a flexible wiring board against the surface of a bent part whose tip is bent by 90 deg. and spreading an anisotropic conductive adhesive not only to the exposed glass surface of a transparent electrode, but also to the flank of another glass plate. CONSTITUTION:The anisotropic conductive adhesive 3 is provided to an end part of the flexible wiring board 4 to width (l) and the tip of the flexible wiring board 4 at the side where the anisotropic conductive adhesive 3 is provided is bent by 90 deg. by using a proper jig so that the length from the bent to the tip is nearly equal to the length (a) of a cover part. This flexible wiring board 4 is pressed by using a heat plate after an electrode 2 and a wiring pattern 5 are position-matched, and then the part of length (c) is fused with the heat of the heat plate and adhered to the end surface of lower glass 1b. When tensile stress operates on the flexible wiring board 4 along the main surface, shearing stress is generated in the adhesive layer on the lower glass plate 1b, so resistance to a large load is obtained. Consequently, the stress applied to the connection part between the transparent electrode and wiring pattern is dispersed to other parts and absolute strength is increased, so that the reliability of the connection part is improved greatly.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a liquid crystal display device with highly reliable connection leads.

(Prior Art) Anisotropic conductive adhesives are increasingly being used to connect liquid crystal display elements and circuit boards. Conventionally, the most commonly used connecting material is an elastic connector called zebra rubber, but when configured as a liquid crystal display device, it requires a mechanical pressure-welding mechanism and is susceptible to vibration. Since fine pitch electrodes have drawbacks such as difficulty in positional alignment, the use of the anisotropic conductive adhesive is increasing. Anisotropic conductive adhesive is composed of conductive powder of appropriate particle size dispersed in an insulating and hot-melt synthetic resin, and can be used between connected substrates, between liquid crystal display elements and flexible wiring boards, etc. Electrical connection can be obtained by inserting it and pressing the peripheral board.

A liquid crystal display device using this anisotropic conductive adhesive is shown in FIG. 3. 1 is a glass plate constituting the liquid crystal display element;
A transparent electrode 2 for external connection is formed on the surface in an eave-like portion as shown in the figure, and a flexible wiring board 4 is adhered via an anisotropic conductive adhesive 3. The flexible wiring board 4 is connected to the drive circuit board, and signals are transmitted to the liquid crystal display element.

Note that 5 is a wiring pattern and 6 is a sealant.

FIG. 4 shows another example, in which the flexible wiring board 4 in FIG. 3 is bonded in the opposite direction. Either one of them is used depending on the positional relationship with the drive circuit board, which is suitable in terms of configuration.

(Problems to be Solved by the Invention) Connection using an anisotropic conductive adhesive does not require a pressure welding mechanism after connection, and since the conductive powder that contributes to the connection is minute, it can be used for fine patterns. The layer is very thin, measuring approximately 20 to 50 microns, so it is easy to align the positions, but the most serious drawback is that the adhesive strength is weak, and if there is not enough connection area, external force may cause connection failure. This is what happens. Particularly recently, there has been a strong desire to reduce the connecting eaves part in order to downsize devices, and the lack of adhesive strength of anisotropically conductive adhesives has become a major problem.

(Objective of the Invention) The object of the present invention is to solve the above-mentioned problems, and to improve the insufficient adhesive strength when a liquid crystal display device is constructed using an anisotropic conductive adhesive, and to provide a highly reliable liquid crystal display. The purpose is to provide equipment.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the liquid crystal display device of the present invention has an eave-like terminal provided with an external connection electrode in the liquid crystal display element, the tip of which is bent at 90 degrees. A flexible wiring board with an anisotropically conductive adhesive provided on the surface of the bent part was crimped, and the anisotropically conductive adhesive wrapped around not only the exposed glass surface of the transparent electrode but also the side surface of the other glass plate. It is structured as follows.

(Function) It is generally known that when bonding a thin film to a substrate using an adhesive, the shear strength is greater than the 90 degree peeling strength. When a flexible wiring board is bonded to a liquid crystal display element, the peeling stress that acts on the glass surface where the transparent electrode of the liquid crystal display element is exposed is absorbed by the shear stress that acts on the end face of the other glass. This greatly increases the strength of the joint against external forces.

(Example) An example of the present invention will be described based on FIGS. 1 and 2. FIG. 1 is a cross-sectional view of a liquid crystal display device according to an embodiment of the present invention, in which 1a is an upper glass plate constituting a liquid crystal display element, and a transparent electrode 2 is formed on the surface of the upper glass plate, which is exposed in an eaves-like part. . 3 is an anisotropic conductive adhesive in which conductive powder is dispersed in a hot melt type adhesive, and flexible wiring board 4
is adhered to the transparent electrode 2 on the surface of the upper glass plate 18, but also goes around and adheres to the side end face of the lower glass plate 1b. When a tensile stress is applied to the flexible wiring board 4 along its main surface, shearing stress is generated in the adhesive layer between the flexible wiring board 4 and the lower glass plate 1b, so that it can withstand a large load. 1st
The steps for realizing the configuration shown in the figure will be explained with reference to FIG. In FIG. 2(A), the length of the eaves part is a, and the glass thickness including the seal part is b. Next, as shown in FIG. 2(B), an anisotropic conductive adhesive 3 is applied to the end of the flexible wiring board 4.
is provided over a width Ω. However, Ω is larger than the sum of the eave length a and the glass thickness (M)a+b), and as shown in FIG. Using an appropriate jig, cut the tip of the side into 9
Bend to 0 degrees. At this time, the length from the bent part to the tip is approximately equal to the length a of the eave part, so the remaining length C is slightly longer than the thickness of the glass. As shown in FIG. 1, the flexible wiring board 4 thus formed is aligned with the electrode 2 and the wiring pattern 5, and then pressed together using a hot plate. The portion of length C in Fig. 2 (C) is melted by the heat of the hot plate and the lower glass 1b
Glue to the end surface.

(Effects) According to the present invention, when stress due to external force, thermal strain, etc. is applied to the flexible wiring board that electrically connects the liquid crystal display element and the circuit board, the stress applied to the connection portion between the transparent electrode and the wiring pattern is reduced. This not only disperses stress but also increases the absolute strength and significantly improves the reliability of the connection.

As a result, it is of great industrial value as it solves the biggest problem in the use of anisotropically conductive adhesives, which have excellent electrical properties but have reliability problems due to insufficient mechanical strength.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a liquid crystal display device according to an embodiment of the present invention, and FIG. 2 is a sectional view showing an example of a method for processing a flexible wiring board in the same liquid crystal display device. Figure 3 is a cross-sectional view showing an example of a conventional liquid crystal display device;
The figure is a sectional view showing another example. la, lb...Glass plate, 2...Transparent electrode, 3
...Anisotropic conductive adhesive, 4...Flexible wiring board, 5...Wiring pattern on flexible wiring board, 6...Sealant, 7...Liquid crystal. Patent applicant Matsushita Electric Industrial Co., Ltd. Figure 1 Figure 2 n

Claims (1)

[Claims] In a liquid crystal display element, the tip of the glass plate on the side where the transparent electrode of the eave-shaped terminal part with the electrode for external connection is exposed is bent at 90 degrees, and an anisotropic conductive adhesive is applied to the surface of the bent part. 1. A liquid crystal display device, wherein a wiring board is crimped and the anisotropically conductive adhesive extends to an end surface of another glass plate constituting a liquid crystal display element.