JP4114773B2 - Liquid crystal display element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display element in which a bus substrate is connected to a terminal portion of a liquid crystal panel via a flexible substrate, and more particularly to a means for supporting the bus substrate with respect to the terminal portion.
[0002]
[Prior art]
As shown in FIG. 5, the liquid crystal panel 1 is provided with a terminal portion 2. In this example, terminal portions 2 are provided on two opposite sides of the panel, and although not shown, each terminal portion 2 has a lead lead connected to the transparent display electrode.
[0003]
When the liquid crystal panel 1 is assembled into an exterior case and commercialized, various driving components are attached to the liquid crystal panel 1. As one of them, a bus (BUS) board 3 is arranged along each terminal portion 2 and is connected to the terminal portion 2. In many cases, a TCP (tape carrier package) 4 in which a bare chip such as an IC or LSI is mounted on a flexible substrate is used for this connection.
[0004]
When the terminal portion 2 and the bus substrate 3 are connected by the TCP 4, normally, the output terminal side of the TCP 4 is connected to the lead lead of the terminal portion 2 through an anisotropic conductive film (ACF), and the input terminal of the TCP 4 The side is soldered to a predetermined electrode terminal of the bus substrate 3.
[0005]
By the way, when the liquid crystal panel 1 becomes a medium-sized or large-sized panel having a size of about 7 inches or more, for example, a long substrate is used for the bus substrate 3 and a terminal portion on one side is connected to the bus substrate 3. A plurality of TCP4s per 2 are used.
[0006]
However, due to the difference in thermal expansion coefficient between the glass substrate constituting the liquid crystal panel 1 and the bus substrate 3, the internal wiring of the TCP 4 and the bus substrate 3 at the time of the heat shock test, for example, are obtained. Disconnection frequently occurs at the connecting part.
[0007]
Incidentally, the thermal expansion coefficient of the glass substrate of the liquid crystal panel 1 is about 8 × 10 ⁻⁶ / ° C., whereas the thermal expansion coefficient of the bus substrate 3 is about 13 × 10 ⁻⁶ / ° C. 3 is elongated. Therefore, when the ambient temperature is greatly swung alternately, for example, at −45 ° C. and + 85 ° C. during the heat shock test, the bus substrate 3 greatly expands and contracts in the length direction (left and right direction in FIG. 5).
[0008]
As a result, stress is generated in the TCP 4, particularly peeling occurs at the connection portion between the bus substrate 3 and the TCP 4, and internal wiring from the connection portion to the bare chip of the TCP 4 may be disconnected.
[0009]
This phenomenon occurs more frequently in the TCP 4 connected to the end side than the central part of the bus board 3, and the TCP 4 used per side is small, and the total connection length of these connection parts is the bus board 3. In the case where the length is shorter than the length, the same occurs.
[0010]
[Problems to be solved by the invention]
In order to prevent such disconnection, conventionally, measures such as adopting a low thermal expansion coefficient substrate for the bus substrate 3 or reducing the thermal expansion coefficient by meshing the solid copper foil pattern portion of the bus substrate 3 are taken. However, none of them may be effective for the heat shock test described above.
[0011]
In addition to this, there is also known a method of dispersing a stress applied to each TCP 4 by adding a reinforcing dummy TCP (or dummy flexible substrate). However, for example, depending on the wiring pattern formed on the terminal portion 2 or the bus substrate 3, the dummy TCP may not be attached, so it cannot be said to be the best countermeasure.
[0012]
The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a liquid crystal display element in which a bus substrate is connected to a terminal portion of a liquid crystal panel via a flexible substrate, particularly in a heat shock test. It is to reliably prevent peeling of the flexible substrate and disconnection of internal wiring due to thermal expansion of the substrate with a simple configuration.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the present invention includes a liquid crystal panel having a terminal portion having a lead electrode for a transparent electrode formed on a predetermined side, and a bus substrate disposed along the terminal portion, and the terminal portion And a board support means for supporting the bus board with respect to the terminal part on both sides of the flexible board group. The lead-out leads of the bus board and the output electrode part of the bus board are connected via a plurality of flexible boards. In the liquid crystal display element, the substrate support means is made of a metal or synthetic resin plate material, and has a clip portion formed in a bifurcated shape that elastically sandwiches the terminal portion on one end side thereof, and the other end side substrate attachment portion attached to the bus substrate is formed in, together with the bus board are fixed via a predetermined fixing means to the substrate attachment portion of the substrate supporting means, the end Parts and and the clip portion of the substrate supporting means is characterized in that the shear modulus is connected via the fixing resin is 5MPa or more at 25 ° C..
[0014]
According to this arrangement, especially the thermal expansion of the bus board is pressed during heat shock test, thereby preventing an excessive stress is applied to the flexible substrate. TCP is included in the flexible substrate as a kind of flexible substrate.
[0015]
The present invention also includes an aspect in which the board mounting portion on the other end side of the board support means is provided with a bifurcated clip part that elastically holds the bus board.
[0016]
The present invention, in the bus substrate opposite to the upper SL terminal portion side to the length, when the total connection length of the connecting portions of the upper Symbol plurality of flexible substrate and the bus substrate is 50% or less It is particularly effective.
[0017]
Further, the fixing resin prevents the substrate supporting means from falling off from the terminal portion. The condition that the shear modulus at 25 ° C. imposed on the fixing resin is 5 MPa or more is to absorb and relax the stress generated by the difference in thermal expansion coefficient between the terminal portion and the bus board with the fixing resin. It is a condition.
[0018]
According to a preferred aspect of the present invention, the fixing resin is further applied between a connection portion between the terminal portion and the flexible substrate, and a connection portion between the bus substrate and the flexible substrate.
[0019]
The substrate support means and the bus substrate may be connected via the fixing resin. In the case where the fixing resin is a thermosetting resin, it is preferably a resin that can be thermoset at 90 ° C. or lower in order not to adversely affect the polarizing film.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Next, two embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a plan view schematically showing the first embodiment, and FIG. 2 is an enlarged sectional view taken along line AA. FIG. 3 is a plan view schematically showing the second embodiment, and FIG. 4 is an enlarged sectional view taken along line BB.
[0021]
In both the first and second embodiments, the liquid crystal panel 1 is, for example, a medium-sized or large-sized panel of 7 inches or more, as described above with reference to FIG. It has been. In this example, the terminal portion 2 of the liquid crystal panel 1 and the bus substrate 3 are connected by four TCPs 4.
[0022]
Here, referring to the cross-sectional view of FIG. 4, the signal output portion 4 a of the TCP 4 is connected to the terminal portion 2 of the liquid crystal panel 1 through the anisotropic conductive film (ACF) 11. The signal input unit 4 b is connected to the bus substrate 3 by solder 12.
[0023]
4 is a bare chip such as an IC or LSI mounted on the TCP 4, but is not a TCP 4 as a connection board between the terminal portion 2 and the bus board 3, but a simple flexible board on which no bare chip is mounted. May be used.
[0024]
The present invention includes substrate support means 20 that supports the bus substrate 3 with respect to the terminal portion 2. The substrate support means 20 is basically disposed on both sides of the TCP 4, but when it includes four TCPs 4 as in this example, it may be disposed on both sides of those TCP groups.
[0025]
In this example, the substrate support means 20 is provided at a total of four locations on both sides of the one terminal portion 2 and on both sides of the other terminal portion 2, but the configuration may be the same, so one of them is shown in FIG. Will be described.
[0026]
The substrate support means 20 includes a clip portion 21 having a spring elasticity formed in a bifurcated shape that sandwiches the terminal portion 2, and a plate-like substrate attachment portion 22 attached to the bus substrate 3. In this example, in order to solder the substrate support means 20 to the bus substrate 3, the entire substrate support means 20 is formed of a solder-plated metal plate.
[0027]
As a modification, the substrate support means 20 may be made of synthetic resin, and the substrate mounting portion 22 may be a clip portion similar to the clip portion 21 regardless of the material of the substrate support means 20 .
[0028]
The clip part 21 is fixed to the terminal part 2 of the liquid crystal panel 1 by a fixing resin 30. In the present invention, the fixing resin 30 has a shear elastic modulus at 25 ° C. of 5 MPa or more. As a result, when an external force in a direction away from the terminal portion 2 is applied to the substrate support means 20, the force is supported not only by the TCP 4 but also by the fixing resin 30, so that the reliability of the connection state is improved. To do.
[0029]
The fixing resin 30 may be a photocurable resin, a room temperature curable resin, or a thermosetting resin. However, when the thermosetting resin is employed, for example, a thermal detrimental effect is exerted on the polarizing film. In order to avoid this, it is preferable that the resin be thermosetting at 90 ° C. or lower. The board attaching portion 22 is fixed to the bus board 3 by the solder 12, but the fixing resin 30 may be used in the same manner as the clip portion 21 instead of being fixed by the solder.
[0030]
According to the first embodiment, since both ends of the substrate 3 are supported by the terminal portion 2 via the substrate support means 20, the expansion and contraction of the substrate 3 during a particularly severe heat shock test is effectively suppressed, The peeling of the signal input unit 4b of the TCP 4 and the disconnection of the internal wiring from the signal input unit 4b to the bare chip 4c of the TCP 4 can be prevented.
[0031]
According to the second embodiment, in order to further improve the operation and effect of the first embodiment, as shown in FIGS. 3 and 4, the connection between the terminal portion 2 and the bus substrate 3 by the TCP 4 is performed. Also, the fixing resin 30 is applied. That is, the fixing resin 30 is applied between the connection portion between the signal output portion 4 a of the TCP 4 and the terminal portion 2, and the connection portion between the signal input portion 4 b of the TCP 4 and the connection portion of the bus substrate 3.
[0032]
In this case, as shown in FIG. 4, it is preferable that a part of the fixing resin 30 enters both the terminal portion 2 side and the bus substrate 3 side. In this example, the fixing resin 30 is provided in all of the connection parts by the TCP 4. However, the fixing resin 30 is provided only in the connection part on the end side where the expansion and contraction of the bus substrate 3 is the largest. May be.
[0033]
【Example】
Along with one side of the terminal part of the liquid crystal panel (thermal expansion coefficient 8 × 10 ⁻⁶ / ° C.) of 258.3 mm × 109.0 mm, a long and narrow bus substrate (thermal expansion coefficient 13 × 10 ^{− 6} / ° C.) and these were connected by three TCPs. The TCPs were arranged at equal intervals, the signal output part and the terminal part were connected by ACF, and the signal input part and the bus substrate were connected by soldering. The total connection length of TCP to the bus substrate was 54 mm / side (22.6% / side).
[0034]
Also, a metal clip as shown in FIG. 2 is arranged at both ends of the terminal part as shown in FIG. 2, the clip part is engaged with the terminal part and fixed with fixing resin, and the bus board side is soldered. Connected. As the fixing resin, an epoxy thermosetting resin having a shear elastic modulus at 25 ° C. of 16 MPa was used and cured at 80 ° C. for 2 hours.
[0035]
10 liquid crystal display elements configured as described above were prepared, and a heat shock test was performed for 100 cycles at −40 ° C. (30 minutes) and 85 ° C. (30 minutes). The breakage was 2 out of 10 (2/10 defective rate). As a comparative example, a similar heat shock test was performed on 10 units not provided with a metal clip. As a result, the TCP signal input portion was broken in 5 units out of 10 units (defective rate 5/10 units).
[0036]
Next, as described in the second embodiment, in addition to the metal clip, a fixing resin is further applied and cured between the connection portion between the terminal portion and the bus substrate by TCP. When the same heat shock test was performed, no breakage of the signal input part was observed for all 10 units (defective rate 0/10 units).
[0037]
【The invention's effect】
As described above, according to the present invention, the bus substrate is connected to the terminal portion of the liquid crystal panel via the plurality of flexible substrates, and the substrate support that supports the bus substrate with respect to the terminal portion on both sides of the flexible substrate group. In the liquid crystal display element in which the means is arranged, the substrate support means is made of a metal or synthetic resin plate material, and has a bifurcated clip portion elastically sandwiching the terminal portion on one end side thereof, A board mounting portion to be attached to the bus board is formed on the other end side, and the bus board is fixed to the board mounting portion of the board support means via a predetermined fixing means, and the terminal portion and the above by the above-described clip portion of the substrate supporting means is connected through the fixing resin shear modulus is 5MPa or more at 25 ° C., in particular severe heat shock test It is possible to reliably prevent the breakage of the separation and the internal wiring of the flexible substrate due to thermal expansion of the bus board in.
[Brief description of the drawings]
FIG. 1 is a schematic plan view showing a first embodiment of the present invention.
FIG. 2 is an enlarged sectional view taken along line AA in FIG.
FIG. 3 is a schematic plan view showing a second embodiment of the present invention.
4 is an enlarged sectional view taken along line BB in FIG.
FIG. 5 is a schematic plan view showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 2 Terminal part 3 Bus board 4 TCP
4a Signal output part 4b Signal input part 4c Bare chip 11 Anisotropic conductive film 12 Solder 20 Substrate support means 21 Clip part 22 Substrate attachment part 30 Fixing resin

Claims (6)

A liquid crystal panel having a terminal portion having a lead electrode for a transparent electrode formed on a predetermined side; and a bus substrate disposed along the terminal portion, wherein the lead lead of the terminal portion and the output electrode portion of the bus substrate Are connected via a plurality of flexible substrates, and on both sides of the flexible substrate group, a liquid crystal display element in which substrate support means for supporting the bus substrate with respect to the terminal portion is disposed ,
The substrate support means is made of a metal or synthetic resin plate material, and has a bifurcated clip portion that elastically clamps the terminal portion on one end side, and is attached to the bus substrate on the other end side. A board mounting part is formed,
The bus substrate is fixed to the substrate mounting portion of the substrate support means via predetermined fixing means, and the shear modulus at 25 ° C. of the terminal portion and the clip portion of the substrate support means is 5 MPa or more. A liquid crystal display element, wherein the liquid crystal display elements are connected via a fixing resin. 2. The liquid crystal display element according to claim 1, wherein a clip portion formed in a bifurcated shape for elastically holding the bus substrate is also provided in the substrate mounting portion on the other end side of the substrate support means . Claim with respect to the upper Symbol terminal portion opposite to the length of one side of the bus board, total connection length of the connecting portions of the upper Symbol plurality of flexible substrate and the bus substrate is 50% or less 1 or 2 A liquid crystal display element according to 1. A connecting portion of the terminal portion and the flexible substrate, even between the connection points of the bus board and the flexible board, according to any one of 3 claims 1 said fixing resin is further coated Liquid crystal display element. 5. The liquid crystal display element according to claim 1, wherein the substrate mounting portion of the substrate support means and the bus substrate are also connected via the fixing resin. 6. The liquid crystal display element according to claim 1, wherein the fixing resin is a thermosetting resin that can be thermoset at 90 ° C. or less.

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