JP3118059B2 - Connection structure of liquid crystal display device and connection device therefor - Google Patents

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 connection terminals between a liquid crystal display element using a flexible film substrate and a drive circuit board are 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 drive circuit substrate, heat is applied by interposing an anisotropic conductive film between both terminal portions. A means for crimping is employed. As the anisotropic conductive film, one having a configuration in which conductive particles are dispersed in a thermosetting resin is used, and the difference between the polymer film substrate on which the panel terminals are formed and the drive circuit substrate on which the connection terminals are formed. An 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 reaction indicating a curing reaction. It is important to raise the temperature to the temperature.

On the other hand, as the density and capacity of liquid crystal display devices increase, there is a demand for lowering the resistance of the transparent conductive film (to increase the film thickness) and finer pitch of the transparent electrodes. For this reason, when the temperature is increased to a predetermined temperature indicating the above-described curing reaction of the thermosetting resin, the mechanical characteristics of the transparent electrode are reduced, and when the thermocompression bonding with the connection terminal of the drive circuit board is performed, There is a problem of disconnection.

A polymer film substrate having a lead electrode terminal of a transparent electrode having a thickness of about 700 ° and a drive circuit substrate having connection terminals are connected to an anisotropic conductive film made of a thermosetting resin in which conductive particles are dispersed. When the thermosetting resin is connected to the thermosetting resin at a temperature of usually 130 ° C. for 5 seconds
Assuming that a sufficient curing has been obtained by applying a pressing force of (c), the lead electrode terminal of the transparent electrode having a thickness of about 700 ° When thermocompression bonding is performed through the membrane, a highly reliable connection can be obtained.

However, the thickness of the transparent electrode has recently been
In order to reduce the resistance, it is formed as thick as 2000 °. Similarly, when thermocompression bonding is performed via an anisotropic conductive film, connection failure occurs at a rate of about 2%. It was understood from the analysis of the connection that the poor connection was caused by 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 in which a transparent electrode of a polymer film substrate and a connection terminal of a drive circuit substrate are connected by thermocompression bonding with an anisotropic conductive film interposed therebetween. Focusing on changing the temperature of the thermocompression bonding applied to the connection portion, the present invention provides 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 an object to provide a connection device.

[0007]

According to the present invention, there is provided a liquid crystal display device comprising: a lead 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 a liquid crystal display device connected by an anisotropic conductive film made of a thermosetting resin dispersed therein, the anisotropic conductive film that has been thermocompression-bonded has an electrical conduction lower than a predetermined temperature in a portion near the liquid crystal display element side. And a second region thermocompression-bonded at a predetermined temperature required for thermosetting the portion near the drive circuit board side. It is a feature.

The present invention also relates to a liquid crystal display device in which a lead 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 are made of a thermosetting resin having conductive particles dispersed therein. 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 electrically conducting are cured at a connection position between the lead electrode terminal and the connection terminal. A thermal head comprising a predetermined temperature portion is provided.

[0009]

According to the structure of the present invention, the connection portion of the anisotropic conductive film closer to the liquid crystal display element side is connected at a temperature lower than the temperature required for thermosetting, so that the liquid crystal display element has a transparent surface. The lead-out electrode terminal of the electrode does not break and can reliably achieve electrical continuity, and the connection portion of the anisotropic conductive film near the drive circuit board side is connected at a predetermined temperature. Therefore, the two substrates are connected to each other with sufficient adhesive strength at this connection portion.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The connection structure of the liquid crystal display device of the present invention will be described below with reference to the drawings. 1A and 1B show a first embodiment of the liquid crystal display device of the present invention, wherein FIG. 1A is a plan view, and FIG. 1B is a sectional view thereof. The extraction electrode terminal 2 of the transparent electrode formed on the lower substrate 1 of the liquid crystal display element composed of a polymer film substrate and the connection terminal 4 of the drive circuit substrate 3 are connected by thermocompression bonding with an anisotropic conductive film 5 interposed. Is done. As the polymer film substrate 1, PET is used, 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, the liquid crystal display element E has transparent electrodes formed on the opposing surfaces of the upper and lower substrates 1 and 1 and has an alignment film subjected to an alignment treatment. The liquid crystal 10 is sealed between the upper and lower substrates 1 and 1 arranged as described above. In the present invention, the conventional ITO film having a thickness of about 700 ° is assumed to have a thickness of 2000 ° for the purpose of lowering the resistance. Substrate 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. Usually, a predetermined pressure is applied at a temperature of 130 ° C. for 5 seconds.
By providing c, sufficient curing can be obtained. In the present invention, the disconnection of the extraction electrode terminal 2 of the transparent electrode, which is the cause of the connection failure, is a predetermined temperature during thermocompression bonding.
An anisotropic conductive film is formed by connecting an electrically conductive portion which does not require sufficient adhesive strength and a joint having sufficient adhesive strength even if there is a possibility of disconnection, because the electrical conductive portion is generated by applying a temperature of 30 ° C. Attention was paid to forming the connection portion including

According to the present invention, a lead electrode terminal 2 of a transparent electrode having a thickness of 2000 ° and a connection terminal 4 of a drive circuit board 3 are provided.
FIG. 1 shows a first embodiment relating to a connecting means for obtaining sufficient adhesive strength and preventing disconnection of a lead electrode terminal 2 of a transparent electrode when thermocompression bonding is performed through an anisotropic conductive film 5.
This will be described below.

First, the extraction electrode terminal 2 of the transparent electrode and the connection terminal 4 are aligned with each other, and an anisotropic conductive film 5 is interposed between the two terminals 2 and 4 so that the polymer film substrate 1
And each end of the drive circuit board 3 are overlapped as shown in the figure. Then, of the connection portions H superposed via the anisotropic conductive film 5, the first thermocompression bonding portion A closer to the liquid crystal display element side.
Then, a predetermined pressure is applied at a temperature of 110 ° C. at which sufficient adhesive strength is not reached, and thermocompression bonding is performed.

Next, a predetermined pressure is applied to the second thermocompression bonding portion B, which is closer to the drive circuit board 3 side, at a temperature of 130.degree. Thermocompression bonding. As described above, in the first thermocompression bonding portion A near the liquid crystal display element, which is a part of the overlapped connection portion H, electrical conduction is performed at a temperature (110 ° C.) lower than a predetermined curing temperature at which disconnection does not occur. After the connection is made, a predetermined temperature (130 ° C.) at which the adhesive strength can be obtained is applied to the second thermocompression bonding portion B near the drive circuit board 3 which is the other part, and sufficient adhesive strength is obtained. The connection is made.

In the above embodiment, the connection of the second thermocompression bonding part B is performed after the connection of the first thermocompression bonding part A.
The connection of the first thermocompression bonding section A may be performed after the connection of the second thermocompression bonding section B, or two different temperature regions may be provided at the tip of a single head and connected simultaneously. Can also. In any connection, the first thermocompression bonding portion A, which is closer to the liquid crystal display element, which is an electrically conductive portion, does not break, and the second thermocompression bonding portion B, which is closer to the drive circuit board 3, is sufficient. The adhesive strength was given, and the reliability test determined that the conventional problems could be solved.

In the embodiment, the polymer film substrate 1
In the description above, PET was used, and the curing temperature of the thermosetting resin used for the anisotropic conductive film was set to 130 ° C. in relation to the PET. Naturally, the curing temperature varies depending on the thermosetting resin selected.

Next, a second embodiment of the connection means of the liquid crystal display device of the present invention will be described with reference to FIG. In this second embodiment, a first thermocompression bonding portion A which is thermocompression-bonded to a superimposed connection portion H at a temperature of 110 ° C. which is somewhat wide.
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 Leave the portion B ₁ near the drive circuit board 3 side at 13
Thermocompression bonding was performed at a temperature of 0 ° C. to form a second thermocompression bonding portion.

In this embodiment, the first thermocompression bonding part A ₁
Part A ₁₁ of the liquid crystal display element side closer of the portion of the is connected without causing disconnection, serves as an electrical conductive portion, the drive circuit board of the first portion of the thermocompression bonded portions A ₁ 3 side portion closer to B ₁ represents, 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 longer than the connection time required for press contact with the second thermocompression bonding portion B in the first embodiment. connection time required for pressing against part B ₁ represents short, it was possible to obtain the same bonding strength.

Further, as a modification of the second embodiment of the connecting means of the present invention, as in the second embodiment, to form a first thermal bonding portions A ₁ is thermocompression bonding at a temperature of 110 ° C. after, a portion functioning as an electric conducting portion leaving the part a ₁₁ of the liquid crystal display element side closer, thereafter, with respect to the remaining first portion of the thermocompression bonded portions a ₁ and the driving circuit board 3 side portion closer , 130
It is also possible to perform thermocompression bonding at a temperature of ° C. to form a second thermocompression bonding section.

Next, a connection device used for connection according to the present invention will be described. FIG. 3 shows the structure of a thermal head 6 suitable for the first embodiment as a connecting device. That is, a first thermocompression bonding portion A (a compression bonding portion to which a temperature lower than a predetermined temperature is applied) and a second thermocompression bonding portion are applied to the anisotropic conductive film 5 disposed at the connection portion between the polymer film substrate 1 and the driving circuit substrate 2. A thermal head 6 is provided which can simultaneously form a crimping portion B (a crimping portion given a predetermined temperature).

As a heating end of the thermal head 6 made of aluminum, a portion facing the second thermocompression bonding portion B is an aluminum end portion 6a, and a portion facing the first thermocompression bonding portion A is a heat end of aluminum. It is formed from a silicon rubber rubber portion 7 to which a silicon rubber having a low conductivity is attached, and the heights of the two are equal.

As described above, the heating ends 6a,
By forming 7 from materials having different thermal conductivity,
The aluminum end 6a and the silicone rubber
A temperature difference of ３０30 ° C. can be obtained. When the temperature of the thermal head 6 is set to 130 ° C., a temperature of 130 ° C. is formed at the aluminum end 6 a and a temperature of 110 ° C. is formed at the silicon rubber rubber portion 7. In this embodiment, aluminum is used for the thermal head 6, but other metals such as stainless steel can be used, and it is natural that a material other than silicon rubber can be used for the heating end.

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 a silicone rubber is attached to the entire heating end of the thermal head 6 to provide a silicone 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
If in order to form a second thermal bonding portion B, and a position corresponding to the first thermocompression bonded portions A of the cradle 8 formed by the Bakelite 8 ₁ are arranged in the aluminum 8 ₂ material.

Therefore, when a constant temperature is applied to the thermal head 6, the first thermocompression bonding portion A, which is the connection portion of the anisotropic conductive film 5, and the second thermocompression bonding portion A due to the difference in the thermal conductivity of the pedestal 8. 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 section A is set to 110 ° C. and the temperature of the second thermocompression bonding section B is set to 130 ° C., depending on the configuration of the cradle 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 board are connected by using a heating head by an anisotropic conductive film, the disconnection of the transparent electrode is eliminated and the bonding strength is sufficient. And a highly reliable connection as a liquid crystal display device, and has an effect of increasing production efficiency. Also, the connection device for the liquid crystal display device has an effect of enabling efficient production with a small number of manufacturing steps by improving the heating head and the cradle.

[Brief description of the drawings]

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

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 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 sectional view showing another means for connecting a connecting portion of the liquid crystal display device of the present invention.

[Explanation of symbols]

DESCRIPTION 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 pedestal A, A ₁₁ Low temperature formed near the liquid crystal display element side 1
Thermocompression bonded portions B of, B ₁ second thermocompression bonded portions of the predetermined temperature to be formed on the driving circuit board side nearer

Continuation of front page (72) Inventor Yuichi Ota 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-2-173725 (JP, A) JP-A-62-27786 (JP, A) JP-A-5-173160 (JP, A) JP-A-2-29628 (JP, A) JP-A-2-228094 (JP, A) JP-A-4-43326 (JP, A) JP-A-62-226038 (JP, A) JP-A-3-142942 (JP, A) JP-A-5-226802 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1 / 1345 H01R 12/06 H01R 43/02 H05K 3/32

Claims (6)

(57) [Claims] 1. A lead 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 are connected by an anisotropic conductive film made of a thermosetting resin in which conductive particles are dispersed. In the liquid crystal display device, the anisotropic conductive film that has been thermocompression-bonded has a first region thermocompression-bonded at a temperature near the liquid crystal display element side at a temperature at which electrical conduction lower than a predetermined temperature is possible, A connection structure for a liquid crystal display device, comprising: a connection region including a second region that is thermocompression-bonded at a predetermined temperature required for thermosetting at a portion closer to the drive circuit board. 2. The connection structure for a liquid crystal display device according to claim 1, wherein the connection region includes a first region and a second region, each of which is 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 the entirety of the second region disposed on the first region. 4. An anisotropic conductive film made of a thermosetting resin in which conductive particles are dispersed is connected between a lead 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 connecting device for a liquid crystal display
For 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 including a low-temperature portion where electrical conduction is possible and a predetermined temperature portion where 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 tip facing the drive circuit board side. 5. The connection device for a liquid crystal display device according to claim 4, wherein the connection device is made of a material having a heat conductivity smaller than the heat conductivity. 6. The thermal head has a single head tip, and a material of a portion located closer to the liquid crystal display element side as a receiving base facing the head tip is closer to the drive circuit board side. 5. The connecting device for a liquid crystal display device according to claim 4, wherein the connecting device is made of a material having a thermal conductivity smaller than a thermal conductivity of a material of a portion located.