JPH0454931B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structure for bonding a display device such as an electrochromic display panel or a liquid crystal display panel to a substrate using an adhesive that can provide anisotropy in conductivity. . Specifically, at least a first electrode substrate provided with electrode lead terminals on one surface and a second electrode substrate disposed opposite to the first electrode substrate so that the electrode lead terminals are exposed. a display device comprising: a circuit board having a conductive contact portion formed near an end of the surface thereof, the substrate thickness of the end portion of the circuit board having the conductive contact portion being the same as that of the second electrode substrate; Thinner than the thickness, and the electrode lead terminal and the conductive contact portion have conductive particles mixed and dispersed in an insulating adhesive, and have conductivity in the thickness direction and insulation in the surface direction. The present invention relates to a connection structure for a display device, characterized in that the electrical connection is made within the thickness of the second electrode substrate via a conductive anisotropic adhesive.

More specifically, fine metal particles such as copper, nickel, silver, and gold, and conductive fine particles such as carbon fiber are dispersed in an adhesive, and the content, shape, size, distribution state, etc. of the metal particles, etc. By controlling the thickness of the adhesive layer and applying pressure as necessary to the parts where electrical connections are to be made, the adhesive layer maintains conductivity in the thickness direction and insulation in the surface direction. This invention relates to a method of making electrical connections using an adhesive whose conductivity is anisotropic.

A feature of the present invention is that the adhesive conductive layer can be made thinner or thicker by arbitrarily selecting one conductive particle or adhesive to be dispersed, and as a result, the conductive anisotropy can be improved by making it particularly thin. The effect becomes significantly more pronounced. That is, it is possible to very effectively separate electrical conduction and insulation in a fine semiconductor pattern such as an IC. Further, in the present invention, since the effect of conductive anisotropy is produced by adhesion, no other press or support is required after the conduction is established. Therefore, the conductive anisotropic adhesive layer once fixed by adhesive is extremely robust against changes over time. In other words, the two steps of fixing and electrical connection are simplified into one step. A further feature is the ease of forming the adhesive on the substrate. That is, to make an electrical connection with another point, it is possible to simply print or apply the conductive anisotropic adhesive according to the present invention and adhere it, or simply to place a sheet of adhesive.

The conductive anisotropic adhesive according to the present invention is characterized in that the adhesive layer formed by the adhesive method is anisotropic in terms of conductivity, and as described above, the cross-sectional shape is uneven, and It is also convenient when electrically coupling items with complicated shapes. In addition, since it is an adhesive, it is effective to use it in places where it not only electrically connects but also combines to form an organic bond and increase its function. Another advantage is that the adhesive can be used directly as a protective agent for the surrounding area. In addition, if the object of the present invention is a liquid adhesive, since it is liquid in its initial state without being dried, this object can be applied to the required area with something like a brush, or it can be applied to an arbitrarily shaped and complex adhesive. By using a pattern mask to transfer the pattern, it is possible to impart conductive properties to the pattern.

To specifically explain the principle of the conductive anisotropic adhesive of the present invention using drawings, as shown in FIG. The adhesive layer 3 is formed by a pressure bonding method using the adhesive capable of having conductive anisotropy according to the invention, and the parts A, B, C, where the substrates 1 and 2 are located,
Assuming D, it is possible to provide a property in which conduction occurs in the A→B, C→D directions, but insulation occurs in the A→C, B→D, A→D, and C→B directions. Adhesives that can have conductive anisotropy include various adhesives such as epoxy and silicone adhesives that have insulating properties.
By dispersing conductive noble metal particles, heavy metal particles, light metal particles alone or alloys, plating particles, carbon fibers, etc., and appropriately controlling the content, shape, size, dispersion state, thickness bonding method, etc. can get. The conduction mechanism of conductive anisotropic adhesives is basically interpreted to be due to the contact between conductive particles, and the conductive particles in the dispersion medium are affected by the non-uniformity of their dispersion and the crowding effect of particles forming clusters. Furthermore, it is estimated that countless islands of conductive regions are formed due to the agglomeration effect near the adhesive interface.

FIGS. 2(1) and 2(2) are simple model diagrams illustrating the principle of conduction of the electrically conductive anisotropic adhesive according to the present invention. 4 and 5 are substrates to be electrically connected, 6 is an adhesive layer formed by an adhesive method,
7 and 7' represent conductive particles. In FIG. 2(2), the size of the particles 7' is approximately equal to the thickness of the adhesive layer 6, and the way to make conductive contact is simple.
Point contact generally has a large contact resistance, so Figure 2 (1)
It is better to make conductive contact using a plurality of conductive particles 7 as shown in FIG. When the conductive properties of a composition in which conductive particles are dispersed in an insulating adhesive are investigated, the results are generally as shown in FIG. That is, if the horizontal axis is the ratio Vm of the conductive particles and the insulating adhesive, and the vertical axis is the conductivity σ, then when the ratio of the conductive particles is below a certain value K point, the conductivity becomes significantly lower. Above point K, good conductivity begins to occur. here,
By controlling the thickness of an adhesive with a composition that has a low conductivity near or below the K point, and by appropriately selecting the particle size and bonding method, it is possible to achieve electrical conductivity in the thickness direction while insulating in the lateral direction. You can obtain characteristics that have sex.

A prior example of the present invention relating to a connection structure for a display device using such a conductive anisotropic adhesive will be described below.

FIG. 4 is a model diagram showing an embodiment of a connection structure of a display device showing a prior example of the present invention. 22 and 23 are upper and lower electrode substrates of the liquid crystal display panel, and 18 is a lead terminal made of a transparent conductive film of the liquid crystal electrode. 1
Reference numeral 9 is a board to establish electrical continuity, and 20 is a conductive contact on the circuit board. For example, a sheet-shaped adhesive layer 21 that can have conductive anisotropy according to the present invention is arranged between such a liquid crystal panel and the substrate. Although the conductive anisotropic adhesive layer 21 is located in the middle for illustration purposes in the drawings, in actual work it is located on the substrate 19 or the electrode terminals of the liquid crystal panel.

In addition, as a prior art related to the connection structure of a display device, an adhesive corresponding to the conductive anisotropic adhesive 21 of the prior example of the present invention shown in FIG. 4 has conductivity in both the thickness direction and the surface direction. They simply used conductive adhesive or conductive rubber.

However, in the connection structure of the display device shown in the preceding example of the present invention, since the lower electrode glass substrate 23 protrudes downward, when the lower electrode glass substrate 23 is brought into contact with the circuit board 19, the distance between the lead terminal 18 and the conductive contact 20 is large. Since at least the thickness of the lower electrode glass substrate is required, there is a problem that the total thickness becomes thick after the upper and lower electrode glass substrates 22, 23 of the liquid crystal display panel and the circuit board are bonded and fixed. Also,
Due to the large distance between the two, electrical continuity cannot be established unless a plurality of conductive particles mixed and dispersed in the conductive anisotropic adhesive layer 21 are connected in the thickness direction. There are also issues of uncertainty.

In addition, in the above-mentioned conventional technology, the total thickness of the connection structure of the display device is similarly increased, and the conductive adhesive or conductive rubber does not have insulating properties in the plane direction, so the connection between the liquid crystal display panel and the circuit board increases. Since each electrode terminal must be arranged so as to ensure insulation in both directions, there is a problem in that the number of assembly steps is large and the cost is high.

Therefore, the present invention aims to solve these problems, and its purpose is to provide a connection structure for a display device that can be made thinner, as well as electrically connected simply, reliably, and at extremely low cost. It is in a place where we provide.

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 5 is a diagram showing an embodiment of the connection structure of the display device of the present invention.

In FIG. 5, numerals 29 and 30 constitute the liquid crystal display device, and are upper and lower electrode substrate glass for liquid crystal display, and 24 is a metalized transparent electrode lead terminal. 25 is a rigid or flexible circuit board, 26 is a hollow part, and 27 is a conductive contact part arranged near the end surface of the circuit board in correspondence with the transparent electrode lead terminal 24 so as to be electrically conductive. , 28 is an adhesive layer capable of having conductive anisotropy according to the present invention.

In this case, the lower electrode substrate glass 30 is attached with its outer end shifted inward with respect to the upper electrode substrate glass 29, so that it is exposed from the outer end of the transparent electrode lead terminal 24 on the lower surface of the upper electrode substrate 29. The exposed portion is pressed against the adhesive layer 28 (heated if necessary) to be electrically connected and fixed to the conductive contact portion 27 of the circuit board 25. In this way, the liquid crystal display device can be attached to the circuit board 25 by passing each electrode lead terminal therethrough. In the case of FIGS. 5 and 6, the upper electrode substrate glasses 29 and 33 and the lower electrode substrate glasses 30 and 34
When the adhesives 28 and 35 are provided at the bonding boundaries A and B, the adhesives 28 and 35 seal the bonding boundaries A and B, so that air, moisture, etc. can be prevented from entering the inside of the liquid crystal display device. can be prevented from entering.
Furthermore, if the adhesive is intentionally made thicker than necessary for conductive bonding and a raised portion 32 is formed around the liquid crystal display panel as shown in FIG. 6, the bonding strength between the liquid crystal display panel and the circuit board 31 is increased. Improve more. That is, in addition to bonding by the adhesive 35 disposed between the lower surface of the upper electrode substrate 33 and the upper surface of the circuit board 31, the upper electrode substrate 33 is also bonded by the raised portion 32 of the adhesive around the upper electrode substrate 33. This is because that.

Further, by making the circuit board 31 thinner than the electrode substrate 34 as shown in FIG. 6, the thickness at the connection portion can be kept within the thickness of the electrode substrate 34.

In this way, when the electrical connection method according to the present invention is applied to a liquid crystal display panel, the connection method that previously required the lead terminals to be taken out individually one by one can be extremely simply replaced with a conductive anisotropic adhesive. The required electrical conductivity can be obtained individually by simply applying screen printing or placing a sheet adhesive and bonding by pressure.

This makes it extremely easy to apply the above electrical elements, whether analog or digital, to electronic watches and electronic desktop calculators, and to areas that were previously considered difficult due to complex micro-electrical wiring. It is also possible to apply

In the actual application of the method according to the present invention, applying pressure to the curing process of the adhesive or using ultrasonic waves in combination will lead to important special improvements.

As described above, according to the present invention, in particular, the substrate thickness of the end portion of the circuit board having the conductive contact portion is thinner than the substrate thickness of the second electrode substrate, and the direct connection is made through the conductive anisotropic adhesive. Since it is fixed, the display device can be made thinner. In other words, since a conductive anisotropic adhesive is used, it is possible to make the thickness of the electrical connection part extremely thin, and in addition, the board thickness at the end of the circuit board having the conductive contact part can be reduced to a second level.
Since the thickness of the first electrode substrate is thinner than that of the second electrode substrate, the thickness of the connecting portion between the first electrode substrate and the circuit board is within the thickness of the second electrode substrate.

Therefore, it is possible to realize a much thinner connector than the conventional technology using a conductive connector in which conductive rubber and insulating rubber are alternately laminated.

Furthermore, since the second electrode substrate side is a flat plane, it is possible to attach parts such as a backlight to this surface, and in this case, the thickness of the display device including the backlight can be made extremely thin. It has an effect.

Further, since the display device is attached to the circuit board using a conductive anisotropic adhesive, no other holding member or supporting means is required. Therefore, manufacturing is easy and inexpensive.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a phenomenon related to the present invention.
1, 2... Electrical members that need to be electrically connected, 3
...A conductive anisotropic adhesive according to the present invention. FIGS. 2(1) and 2(2) are diagrams showing the principle of conductive anisotropic bonding according to the present invention. 4, 5... Substrate to be electrically conductive, 6... Adhesive layer, 7, 7'... Conductive particle group and particles. FIG. 3 is a graph showing the relationship between the ratio of conductive particles and base adhesive to the conductivity. FIG. 4 is an explanatory diagram in which the adhesive method according to the present invention is applied to a liquid crystal display panel. 22, 23... Upper and lower electrode glass substrate for liquid crystal display, 18... Transparent conductive lead terminal, 19... Circuit board, 20... Lead wire on circuit board, 21... Conductive anisotropic adhesive according to the present invention layer. FIG. 5 is an improved sectional view of FIG. 4. 29,3
0... Upper and lower electrode glass substrate for liquid crystal display, 24...
Metallized transparent conductive lead terminal, 25... circuit board, 26... hollow, 27... lead wire on circuit board, 28... electrically conductive anisotropic adhesive according to the present invention, A... bonding boundary. FIG. 6 is an explanatory diagram of a side effect of an application example of the present invention. 33, 34... Upper and lower electrode substrate glass for liquid crystal display, 31... Hollowed out circuit board, 32...
Adhesive raised part, 35... Conductive anisotropic adhesive according to the present invention, B... Bonding boundary part.

Claims (1)

[Claims] 1. A first electrode with an electrode lead terminal provided on one side.
a second electrode substrate disposed opposite to the first electrode substrate such that the electrode substrate and the electrode lead terminal are exposed;
a display device comprising at least an electrode substrate of The electrode lead terminal and the conductive contact portion are thinner than the substrate thickness of the electrode substrate of No. 2, and the electrode lead terminal and the conductive contact portion have conductive particles mixed and dispersed in an insulating adhesive, so that the surface has conductivity in the thickness direction. 1. A connection structure for a display device, characterized in that the electrical connection is made within the thickness of the second electrode substrate via a conductive anisotropic adhesive having insulating properties in the direction.