JPH05241180A - Connected structure of liquid crystal display device and connecting device therefor - Google Patents

Abstract

PURPOSE:To obtain a connected part having satisfactory bonding strength without breaking a transparent electrode when hot press bonding is carried out through the electric conductive anisotropic film of a liq. crystal display device to form a connected structure. CONSTITUTION:When the leading-out electrode terminal 2 of a transparent electrode on a flexible film 1 is connected to the connecting terminal 4 of a driving circuit board 3, the first region A of an electric conductive anisotropic film 5 which cures by hot press bonding on the liq. crystal display element side is bonded by hot press bonding at a temp. below the curing temp. and the second region B on the driving circuit board side is bonded by hot press bonding at the curing temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device in which a connection terminal between a liquid crystal display element using a flexible film substrate and a drive circuit board is connected by an anisotropic conductive film, and a connection device therefor. is there.

[0002]

2. Description of the Related Art Conventionally, in order to electrically connect a panel terminal in a liquid crystal display device using a polymer film substrate and a connection terminal of a driving circuit board, an anisotropic conductive film is interposed between both terminals to prevent heat. A means for crimping is used. As the anisotropic conductive film, one having a structure in which conductive particles are dispersed in a thermosetting resin is used, and the anisotropic conductive film is different between the polymer film substrate on which the panel terminals are formed and the drive circuit substrate on which the connection terminals are formed. The anisotropic conductive film is arranged and thermocompression-bonded at a predetermined temperature. In this case, in order to obtain a highly reliable adhesive strength, the thermosetting resin of the anisotropic conductive film exhibits a predetermined curing reaction. It is important to raise the temperature to temperature.

On the other hand, with the increase in density and capacity of liquid crystal display devices, there is a demand for lower resistance (increasing film thickness) of transparent conductive films and fine pitch of transparent electrodes. From this, when the temperature is raised to a predetermined temperature that indicates the curing reaction of the thermosetting resin described above, the mechanical characteristics of the transparent electrode deteriorate, and when the thermocompression bonding with the connection terminal of the drive circuit board is performed. It causes the problem of disconnection.

By the way, an anisotropic conductive film made of a thermosetting resin in which conductive particles are dispersed is used for a polymer film substrate having a lead-out electrode terminal of a transparent electrode having a film thickness of about 700 Å and a drive circuit board having a connection terminal. This thermosetting resin is usually used at a temperature of 130 ° C for 5 sec.
Assuming that sufficient hardening has been obtained by applying a pressing force of c, the lead-out electrode terminal of the transparent electrode having a film thickness of about 700 Å is Thermocompression bonding through the membrane will provide a highly reliable connection.

However, in recent years, the film thickness of the transparent electrode has been
It was formed to a thickness of 2000 Å to reduce the resistance, and when thermocompression bonding was performed via an anisotropic conductive film as well, connection failure occurred at a rate of about 2%. It was understood from the analysis of the connecting portion that this defective connection was due to the disconnection of the lead electrode terminal of the transparent electrode.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a liquid crystal display device for connecting a transparent electrode of a polymer film substrate and a connection terminal of a drive circuit substrate by thermocompression bonding through an anisotropic conductive film. Focusing on changing the temperature of thermocompression bonding applied to the connection portion, it is possible to provide a liquid crystal display device having a connection structure that does not cause disconnection of the transparent electrode as described above, and is suitable for obtaining the connection structure. It is intended to provide a connection device.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention has a structure in which a lead electrode terminal of a transparent electrode formed on a flexible film of a liquid crystal display device and a connection terminal of a drive circuit board are made of conductive particles. In the liquid crystal display device in which the anisotropic conductive film made of a thermosetting resin having dispersed therein is connected, the anisotropically conductive film thermocompression-bonded is electrically conductive at a portion closer to the liquid crystal display element side than a predetermined temperature. And a second region thermocompression bonded at a temperature close to the driving circuit board and a second region thermocompression bonded at a predetermined temperature necessary for thermosetting. It is a feature.

Further, according to the present invention, an anisotropy made of a thermosetting resin in which conductive particles are dispersed is used as a lead-out electrode terminal of a transparent electrode formed on a flexible film of a liquid crystal display element and a connection terminal of a drive circuit board. As a connection device of a liquid crystal display device connected by a conductive film, a thermosetting resin of an anisotropic conductive film and a low temperature portion capable of electrical conduction are cured at a connection position between the extraction electrode terminal and the connection terminal. It is characterized in that it is provided with a thermal head composed of a predetermined temperature portion.

[0009]

With the structure of the present invention, the transparent conductive film on the substrate of the liquid crystal display device is formed by connecting the connecting portion of the anisotropic conductive film, which is closer to the liquid crystal display device side, at a temperature lower than the temperature required for thermosetting. The lead-out electrode terminal of the electrode does not break, and electrical conduction can be surely achieved. Moreover, in the anisotropic conductive film, the connection portion on the drive circuit board side is connected at a predetermined temperature. Therefore, the two substrates are connected at this connecting portion with sufficient adhesive strength.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A connection structure of a liquid crystal display device of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the liquid crystal display device of the present invention, (a) is a plan view and (b) is a sectional view thereof. The lead-out electrode terminal 2 of the transparent electrode formed on the lower substrate 1 of the liquid crystal display element made of the polymer film substrate and the connection terminal 4 of the drive circuit substrate 3 are thermocompression-bonded with the anisotropic conductive film 5 interposed therebetween to be connected. To be done. PET is used as the polymer film substrate 1, and an indium tin oxide film (ITO film) is formed on the substrate 1 by a sputtering method or an EB vapor deposition method.

In FIG. 1, a liquid crystal display element E has a transparent electrode formed on each of the opposing surfaces of the upper and lower substrates 1 and 1 and an alignment film subjected to an alignment treatment. A liquid crystal 10 is enclosed between the upper and lower substrates 1 and 1 arranged in this manner. Regarding the conventional ITO film having a film thickness of about 700 Å, in the present invention, the film thickness is increased to 2000 Å in order to reduce the resistance. Board 3
The connection with the connection terminal 4 will be described.

The anisotropic conductive film 5 used in the present invention is made of a thermosetting resin in which conductive particles are dispersed, and usually, at a temperature of 130 ° C. and a predetermined pressure of 5 se.
By giving c, sufficient curing can be obtained. In the present invention, the disconnection of the lead-out electrode terminal 2 of the transparent electrode, which is the cause of the connection failure, is the predetermined temperature during thermocompression bonding.
An anisotropic conductive film has an electrically conductive portion that does not require sufficient adhesive strength and a joint portion that has sufficient adhesive strength even if there is a possibility of disconnection, since they are generated by applying a temperature of 30 ° C. Attention was paid to the formation of the connecting portion including.

According to the present invention, the lead-out electrode terminal 2 of the transparent electrode having a film thickness of 2000 Å and the connection terminal 4 of the drive circuit board 3 are provided.
A first embodiment relating to a connecting means which, when thermocompression-bonded to each other via an anisotropic conductive film 5, obtains sufficient adhesive strength and does not cause disconnection of the lead electrode terminal 2 of the transparent electrode.
Will be explained.

First, the lead-out electrode terminal 2 of the transparent electrode and the connection terminal 4 are aligned with each other, and the anisotropic conductive film 5 is interposed between the two terminals 2 and 4, so that the polymer film substrate 1 is formed.
And the respective end portions of the drive circuit board 3 are overlapped as shown. Then, the first thermocompression bonding part A closer to the liquid crystal display element side of the connection parts H overlapped with each other with the anisotropic conductive film 5 interposed therebetween.
On the other hand, thermocompression bonding is performed by applying a predetermined pressing force at a temperature of 110 ° C. at which sufficient adhesive strength is not reached.

Next, a predetermined pressure is applied for 5 seconds to the second thermocompression bonding portion B of the superposed connection portions H, which is closer to the drive circuit board 3 side, at a temperature of 130 ° C. at which sufficient bonding strength is reached. Perform thermocompression bonding. As described above, in the first thermocompression bonding portion A closer to the liquid crystal display element, which is a part of the overlapped connecting portions H, the electrical continuity is maintained at a temperature (110 ° C.) lower than a predetermined curing temperature and not broken. After the connection, the second thermocompression bonding portion B, which is the other part, closer to the drive circuit board 3 side is given a predetermined temperature (130 ° C.) at which adhesive strength can be obtained, and sufficient adhesive strength is obtained. The connection is made.

In the above embodiment, the second thermocompression bonding portion B is connected after the first thermocompression bonding portion A is connected.
The first thermocompression bonding portion A may be connected after the second thermocompression bonding portion B is connected, or two different temperature regions may be provided at the tip of a single head to be connected simultaneously. You can also In any connection, the first thermocompression bonding portion A closer to the liquid crystal display element side, which is an electrically conductive portion, does not cause disconnection, and the second thermocompression bonding portion B closer to the driving circuit board 3 side is sufficient. Adhesive strength was given, and as a result of a reliability test, it was determined that the conventional problems could be solved.

In the embodiment, the polymer film substrate 1
In the above description, PET was used, and the curing temperature of the thermosetting resin used for the anisotropic conductive film was explained as 130 ° C. in relation to the PET. It goes without saying that the curing temperature changes depending on the thermosetting resin selected.

Next, a second embodiment of the connecting means of the liquid crystal display device of the present invention will be described with reference to FIG. In the second embodiment, the first thermocompression bonding part A is thermocompression bonded to the superposed connection part H at a temperature of 110 ° C. which is wide to some extent.
To form a _1. That is, for thermocompression bonding part A ₁ of the first, by thermal compression bonding at a temperature of 110 ° C., thereafter, of the first thermocompression bonded portions A _1, part A ₁₁ of the liquid crystal display element side closer The portion B ₁ near the side of the drive circuit board 3 is left to be 13
Thermocompression bonding was performed at a temperature of 0 ° C. to obtain a second thermocompression bonding part.

In this embodiment, the first thermocompression bonding portion A ₁
The portion A ₁₁ of the portion of FIG. 3 that is closer to the liquid crystal display element side is connected without causing a disconnection, functions as an electrical conducting portion, and is the drive circuit board of the portion of the _first thermocompression-bonding portion A _1. The portion B ₁ closer to the 3 side has sufficient adhesive strength to firmly connect the two substrates 1 and 3. In the connection means of the second embodiment of the present invention, the second thermocompression bonding in the second embodiment is more than the connection time required for the pressure contact with the second thermocompression bonding portion B in the first embodiment. The connection time required for pressure contact with the portion B ₁ was short, and similar adhesive strength could be obtained.

As a modification of the second embodiment of the connecting means of the present invention, the first thermocompression bonding portion A ₁ which is thermocompression bonded at a temperature of 110 ° C. is formed as in the second embodiment. After that, the portion functioning as an electrical conduction portion is left as a portion A ₁₁ closer to the liquid crystal display element side, and thereafter, with respect to the remaining portion of the first thermocompression bonding portion A _{1 and} the portion closer to the driving circuit board 3 side. , 130
It is also possible to perform thermocompression bonding at a temperature of ° C to form the second thermocompression bonding part.

Next, the connection device used for connection of the present invention will be described. FIG. 3 shows the configuration of the thermal head 6 suitable for the first embodiment as a connecting device. That is, the first thermocompression bonding portion A (compression bonding portion applied with a temperature lower than a predetermined temperature) and the second heat bonding are provided on the anisotropic conductive film 5 arranged at the connecting portion between the polymer film substrate 1 and the driving circuit substrate 2. The thermal head 6 has a structure capable of simultaneously forming the pressure-bonded portion B (pressure-bonded portion to which a predetermined temperature is applied).

As a heating end portion of the thermal head 6 made of aluminum, a portion facing the second thermocompression bonding portion B has an aluminum end portion 6a, and a portion facing the first thermocompression bonding portion A has a temperature higher than that of aluminum. It is formed from a silicone rubber rubber portion 7 to which a silicone rubber having a low conductivity is attached, and the heights of both are made equal.

In this way, the heating end 6a of the thermal head 6 is
Since 7 is made of materials having different thermal conductivity,
20 on the aluminum end 6a and the silicone rubber rubber part 7
A temperature difference of up to -30 ° C can be obtained. When the temperature of the thermal head 6 is set to 130 ° C., a temperature of 130 ° C. is formed on the aluminum end portion 6a and a temperature of 110 ° C. is formed on the silicon rubber rubber portion 7. In this embodiment, the thermal head 6 is made of aluminum, but it is also possible to use other metal such as stainless steel, and it goes without saying that a material other than silicon rubber can also be used for the heating end portion.

FIG. 4 shows another embodiment of the connection device of the present invention. In this embodiment, the thermal head 6 is made of aluminum, and silicon rubber is attached to the entire heating end of the thermal head 6 to provide a silicon rubber portion 7.
The cradle 8 for supporting a connecting portion which is thermocompression-bonded by the thermal head 6 constituted by Bakelite 8 _1, the temperature of the thermal head 6, a first thermocompression bonded portions A to the connecting portion of the anisotropic conductive film 5
In order to form the second thermocompression bonding part B, a material of aluminum 8 ₂ is arranged at a position corresponding to the first thermocompression bonding part A of the pedestal 8 formed of the bakelite 8 ₁ .

Therefore, when a constant temperature is applied to the thermal head 6, due to the difference in thermal conductivity of the pedestal 8, the first thermocompression bonding portion A and the second thermocompression bonding portion A, which are the connection portions of the anisotropic conductive film 5, are formed. Thermocompression bonding part B
, A temperature difference of 20 to 30 ° C. is obtained. When the temperature of the thermal head 6 is set to 150 ° C., the temperature of the first thermocompression bonding portion A is 110 ° C. and the temperature of the second thermocompression bonding portion B is 130 ° C. due to the configuration of the pedestal 8. Is set.

[0026]

According to the structure of the present invention, when the substrate of the liquid crystal display element and the driving circuit substrate are connected by using the heating head with the anisotropic conductive film, the disconnection of the transparent electrode is eliminated, and the adhesive strength is sufficient. It is possible to provide a connection part having a high reliability, a highly reliable connection as a liquid crystal display device, and an effect of good production efficiency. Also, as a connecting device for a liquid crystal display device, the heating head and the pedestal are improved, which has the effect of enabling efficient production with a small number of manufacturing steps.

[Brief description of drawings]

FIG. 1 shows an example of a connecting portion of a liquid crystal display device of the present invention,
(A) is a top view and (b) is a schematic sectional drawing.

FIG. 2 is a plan view showing another connection portion of the liquid crystal display device of the present invention.

FIG. 3 is a schematic cross-sectional view showing a means for connecting a connecting portion of the liquid crystal display device of the present invention.

FIG. 4 is a schematic cross-sectional view showing another means for connecting the connecting portion of the liquid crystal display device of the present invention.

[Explanation of symbols]

1 Polymer Film Substrate 2 Transparent Electrode Lead-out Electrode Terminal 3 Drive Circuit Board 4 Connection Terminal 5 Anisotropic Conductive Film 6 Thermal Head 7 Silicon Rubber Rubber Part 8 Receiving Stand A, A ₁₁ Low Temperature No. 1 Formed on the Liquid Crystal Display Side 1
Thermocompression bonding part B, B ₁ Second thermocompression bonding part formed at a predetermined temperature near the drive circuit board side

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuichi Ota 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (6)

[Claims] 1. An anisotropic conductive film made of a thermosetting resin in which conductive particles are dispersed is connected to a lead-out electrode terminal of a transparent electrode formed on a flexible film of a liquid crystal display element and a connection terminal of a drive circuit board. In the liquid crystal display device according to claim 1, the thermocompression bonded anisotropic conductive film has a first region thermocompression bonded at a temperature near a liquid crystal display element side at a temperature below a predetermined temperature at which electrical conduction is possible. A connection structure for a liquid crystal display device, comprising: a connection region including a second region thermocompression bonded at a predetermined temperature necessary for thermosetting at a portion near the drive circuit board side. 2. The connection structure for a liquid crystal display device according to claim 1, wherein the connection region has a first region and a second region arranged in parallel. 3. The connection structure for a liquid crystal display device according to claim 1, wherein the connection region has a part or all of the second region arranged on the first region. 4. An anisotropic conductive film made of a thermosetting resin in which conductive particles are dispersed is connected to a lead-out electrode terminal of a transparent electrode formed on a flexible film of a liquid crystal display element and a connection terminal of a drive circuit board. As a connection device of the liquid crystal display device
With respect to the connection position between the extraction electrode terminal and the connection terminal,
A connection device for a liquid crystal display device, comprising a thermal head comprising a low temperature portion capable of electrical conduction and a predetermined temperature portion at which a thermosetting resin of an anisotropic conductive film is cured. 5. The thermal head has two head tips, and a first head tip facing the liquid crystal display element side is a second head tip facing the driving circuit board side. The connection device for a liquid crystal display device according to claim 4, wherein the connection device is made of a material having a thermal conductivity smaller than that of the thermal conductivity. 6. The thermal head has a single head tip portion, and as a pedestal facing the head tip portion, a material of a portion located closer to the liquid crystal display element side is closer to the drive circuit board side. The connection device for a liquid crystal display device according to claim 4, wherein the connection device is made of a material having a thermal conductivity smaller than that of the material of the portion located.