JPH0618914A - Connecting structure of electrode terminal of liquid crystal display panel for external connection - Google Patents

Abstract

PURPOSE:To prevent the deformation of a flexible liq. crystal display panel having a large screen and the exfoliation of flexible printed boards when the electrode terminals of the panel for external connection are connected to the flexible printed boards. CONSTITUTION:When a flexible liq. crystal display panel 1 is connected to a driving circuit board with flexible printed boards 8, 9, the circuit patterns 8A, 9A of the printed boards 8, 9 are connected to the electrode terminals 2A, 3A of the panel 1 for external connection and the printed boards 8, 9 are notched 12 at prescribed intervals so as to relieve thermal strain in the connected parts due to the difference between the coefft. of thermal expansion of the panel 1 and that of the printed boards 8, 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection structure for connecting a flexible printed board to an external connection electrode terminal portion of the liquid crystal display panel when connecting the liquid crystal display panel and the drive circuit board using the flexible printed board. In particular, the present invention relates to a connection structure capable of preventing peeling of a connection portion due to heat stress.

[0002]

2. Description of the Related Art Generally, a flexible printed circuit board is used to connect an external connection electrode terminal portion of a liquid crystal display panel and a drive circuit board. Also, in connection between a liquid crystal display panel using a flexible plastic substrate and a drive circuit board, a flexible printed board called a heat seal connector or a plated electrode flexible printed board is used. By the way, as a method for connecting a flexible printed board to an external connection electrode terminal portion of a liquid crystal display panel, for example, Japanese Patent Laid-Open No. 60-205
A method described in Japanese Patent No. 427 and Japanese Patent Laid-Open No. 63-313127, that is, a method of connecting a strip-shaped flexible printed board to an external connection electrode terminal portion of a liquid crystal display panel using a plastic substrate is known. ing.

[0003]

However, when the liquid crystal display panel and the flexible printed circuit board are connected using the above-mentioned connection method, the coefficient of thermal expansion (the coefficient of linear expansion) of the plastic substrate and the flexible printed circuit board of the liquid crystal display panel. From the difference of, even a slight temperature difference causes distortion in the connection part, the flexible printed circuit board peels off,
The panel may be deformed or the electrode terminals may be broken. Further, even when the plastic substrate or the flexible printed circuit board of the liquid crystal display panel absorbs moisture and expands, problems such as peeling of the flexible printed circuit board and deformation of the panel occur. In particular, in a liquid crystal display panel having a large area with one side of 300 mm or more, such a phenomenon remarkably appears.

The present invention has been proposed in order to solve the problems of the prior art, and in particular, an external connection electrode terminal portion and a flexible print of a liquid crystal display panel having a large screen and flexibility. An object of the present invention is to provide a connection structure capable of preventing deformation of a panel and peeling of a flexible printed circuit board when connecting boards.

[0005]

In order to achieve this object, the present invention provides an external connection of a liquid crystal display panel in a structure for connecting a flexible liquid crystal display panel and a drive circuit board using a flexible printed board. In order to connect each wiring pattern of the flexible printed circuit board to the electrode terminal for use and to remove the thermal strain of the connection part due to the difference in the coefficient of thermal expansion of the liquid crystal display panel and the flexible printed circuit board, the flexible printed circuit board is connected in the connecting direction. It has a structure in which it is cut at predetermined intervals or cuts are made.

The plastic substrate used for the liquid crystal display panel is not particularly limited as long as it has flexibility. For example, a crystalline polymer such as uniaxially or biaxially oriented polyethylene terephthalate, polysulfone,
A substrate made of an amorphous polymer such as polyethersulfone, a polyolefin such as polyethylene or polypropylene, a polycarbonate, or a polyamide such as nylon can be used.

The transparent electrode for driving the liquid crystal formed on the plastic substrate is not limited as long as it has conductivity, but it may be a conventionally known vapor deposition method, ion beam vapor deposition method, sputtering method or the like. An indium oxide film formed by deposition, an ITO film formed of a mixture of indium oxide and tin oxide, a metal vapor deposition film of aluminum, nickel, copper, or a laminated film can be used.

Further, as the flexible printed board, a heat seal connector or a plated electrode flexible printed board can be used. In the former heat seal connector, a conductive coating is screen-printed on a polyester film to form a wiring pattern, and then an insulating hot metal adhesive is screen-printed on a portion other than the pattern to have a film thickness of 20 to 30 μm. It was adjusted so that Here, as the conductive coating material, graphite, carbon black, silver powder or the like dispersed in a hot melt adhesive is used. The latter plated electrode flexible printed circuit board has a wiring pattern formed on a polyimide film by a plating method.

In the liquid crystal display panel 1, as shown in FIGS. 7 and 8, the electrode forming surfaces of the plastic substrates 4 and 5 having the stripe electrode patterns 2 and 3 formed on one surface thereof are orthogonal to each other. Thus, the liquid crystal composition 6 is sandwiched between the upper and lower substrates 4 and 5 so as to face each other, and is sealed by the sealing material 7. The external connection electrode terminal portions 2A and 3A are provided on the respective substrates 4, which extend from the display portion 1A.
It is pulled out from the end of No. 5. Here, 2A indicates a common-side electrode terminal portion, and 3A indicates a segment-side electrode terminal portion.

To connect the external connection electrode terminal portion of the liquid crystal display panel and the plated electrode flexible printed circuit board,
Connection can be made by sandwiching an anisotropic conductive film or an anisotropic conductive adhesive between the substrates, aligning the connection portions, and then thermocompression bonding. When a heat seal connector is used, the connection can be made by matching the electrode pitch between the substrates and thermocompression bonding as it is.

Here, when polyether sulfone is used for the plastic substrate of the liquid crystal display panel and a polyimide film is used for the flexible printed substrate, the difference in thermal expansion coefficient between the two is 2.5 × 10 ^-5 m / m. Since the temperature is around ℃, if one side of the liquid crystal display panel is 400 mm, 1
A strain of 0 μm occurs. In order to eliminate such distortion (deviation), it suffices to make cuts in the flexible printed circuit board at regular intervals to absorb the difference in the coefficient of thermal expansion, whereby stable connection can be achieved.

As the flexible printed circuit board, a strip-shaped one (see FIG. 1) or a sheet-like one (see FIG. 6) is generally used. The strip-shaped flexible printed boards 8 and 9 are separately connected to the external connection electrode terminal portions 2A and 3A drawn from the upper and lower boards 4 and 5, respectively. When a single sheet-shaped flexible printed board 10 is used, the wiring patterns 10A and 10B formed on both sides of the flexible printed board 10 have upper and lower boards 4, 5 respectively.
Of the external connection electrode terminal portions 2A and 3A, respectively.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the connection structure of the external connection electrode terminal portion of the liquid crystal display panel according to the present invention will be described in detail below with reference to the drawings. FIG. 1 shows an example in which the strip-shaped flexible printed boards 8 and 9 are connected to the liquid crystal display panel 1. In this example, plated electrode flexible printed boards are used as the flexible printed boards 8 and 9.

The external connection electrode terminal portion 2A drawn out to the end portion of the upper substrate 4 on the common electrode side aligns the wiring patterns 8A of the strip-shaped flexible printed board 8 with the anisotropic conductive film 11 sandwiched therebetween. After that, it is in a state of being thermocompression bonded. Further, the external connection electrode terminal portion 3A drawn out to the end portion of the lower substrate 5 on the segment electrode side aligns each wiring pattern 9A of the flexible printed board 9 with the anisotropic conductive film 11 interposed therebetween, and then It is in a state of being thermocompression bonded to. 2 which is a cross-sectional view taken along the line AA of FIG. 1 shows a cross-sectional structure of a connection portion between the lower substrate 5 and the flexible substrate 9, and FIG. 3 which is a cross-sectional view taken along the line BB of FIG. 4 shows a cross-sectional structure of a connecting portion between the flexible substrate 8 and the flexible substrate 8.
Here, thermocompression bonding is performed at a temperature of 190 ° C. and 30 kg / cm ²
The pressure is applied for 3 seconds.

External connection electrode terminal portion 3A on the segment side
The lateral length of the liquid crystal display panel 1 on the side where the light is drawn out is about 400 mm.
The flexible substrate 9 connected to A has an electrode terminal portion 3
Two cuts 12 are made in the formation direction of the wiring pattern 9A at a predetermined interval of, for example, 130 mm without cutting A and the wiring pattern 9A. FIG. 4 shows an enlarged view of the cut portion. By inserting the notch 12, it is possible to absorb thermal strain due to expansion and contraction of the substrate 9. From the viewpoint of absorbing strain (deviation), it is preferable that the interval between the two cuts 12 is 300 mm or less.

Next, the results of a heat cycle test for examining the stability of the connection with and without the notches 12 will be described. When the test condition of leaving for 2 hours in the environment of 0 ° C. for 2 hours and then for 2 hours in the environment of 55 ° C. was set as one cycle, 25 cycles and 200 hours of continuous tests were conducted. It was confirmed that both ends of the liquid crystal display panel 1 to which the substrate 9 was connected were warped, and the display unit 1
The alignment of the liquid crystal of A was partly broken. On the other hand, no abnormality was confirmed in the case where the cut 12 was provided. From the above verification, it was confirmed that the effect of the present invention was sufficient.

Also, in the case where a heat seal connector is used as the flexible printed boards 8 and 9,
As a result of conducting an experiment under the same conditions as in the case of using the above-mentioned metal-plated flexible printed circuit board, the display panel 1 was deformed without the cut 12, but the cut 12
There was no abnormality in the one provided with, confirming the effectiveness of the present invention.

Next, another embodiment shown in FIG. 5 will be described.
In this embodiment, the flexible printed circuit board 9 connected to the external connection terminal portion 3A is placed at a predetermined interval, for example, 130 m.
It is cut into m intervals so that thermal strain can be removed. 13 shows a cutting line.

Still another embodiment shown in FIG. 6 will be described. In this embodiment, one sheet-shaped flexible printed board 10 is used for connection to the external connection electrode terminal portions 2A and 3A drawn from the liquid crystal display panel 1. Wiring patterns 10A and 10B are formed on both surfaces of the flexible printed circuit board 10 and can be collectively connected to the external connection electrode terminal portions 2A and 3A. In this flexible printed circuit board 10, the expansion of the substrate 10
In order to absorb the strain due to contraction, the printed board portion connected to the segment-side electrode terminal portion 3A is provided with notches 14 at equal intervals, and the printed board portion connected to the common-side electrode terminal portion 2A. A cut 15 is made in the center of the. Furthermore, a cut 16 is formed in the vicinity of the corner of the flexible printed circuit board 10, and a cut 17 is also formed diagonally at a corner of a connection point to both electrode terminal portions.

When the examples shown in FIGS. 5 and 6 were tested under the same conditions as above, no abnormality was found in any case.

The present invention is not limited to the above-mentioned embodiments, but various modifications can be made within the scope of the invention.

[0022]

As described above, according to the present invention, when the flexible printed circuit board is used to connect the liquid crystal display panel and the drive circuit board, the flexible printed circuit board is connected to the external connection electrode terminals of the liquid crystal display panel. Since a notch is made in an appropriate portion of the printed circuit board so that the strain due to heat stress or moisture absorption can be absorbed, it is possible to prevent the warp of the liquid crystal display panel and the peeling of the flexible printed circuit board. Thereby, the durability of a large-screen liquid crystal display panel having a long side of 300 mm or more can be improved, and a highly reliable liquid crystal display can be provided.

[Brief description of drawings]

FIG. 1 is a plan view of a liquid crystal display panel to which a flexible printed board according to the present invention is connected.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

FIG. 4 is an enlarged plan view showing a cut portion.

FIG. 5 is a plan view of a liquid crystal display panel showing a connection structure of another embodiment.

FIG. 6 is a plan view of a liquid crystal display panel showing a connection structure of still another embodiment.

FIG. 7 is a partial enlarged plan view for explaining the configuration of the liquid crystal display panel.

8 is a sectional view taken along line CC of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal display panel 2, 3 Electrode pattern 2A, 3A External connection electrode terminal part 4 Upper board 5 Lower board 6 Liquid crystal composition 7 Sealing material 8, 9, 10 Flexible printed board 8A, 9A, 10A, 10B Wiring pattern 11 Anisotropically conductive film 12, 14, 15, 16, 17 Notch 13 Cutting line

Claims (4)

[Claims] 1. In a structure for connecting a flexible liquid crystal display panel and a drive circuit board using a flexible printed board, each wiring pattern of the flexible printed board is connected to an external connection electrode terminal portion of the liquid crystal display panel. Along with the liquid crystal display panel and the flexible printed board, in order to remove the thermal strain of the connection portion due to the difference in thermal expansion coefficient, the flexible printed board is cut at a predetermined interval in the connecting direction, or a structure having a notch A connection structure of an electrode terminal portion for external connection of a liquid crystal display panel, characterized in that. 2. A flexible printed circuit board connected to external connection electrode terminal portions of upper and lower substrates of a liquid crystal display panel,
The connection structure of an electrode terminal portion for external connection of a liquid crystal display panel according to claim 1, wherein the connection structure is one sheet-shaped flexible printed board. 3. The connection structure of an electrode terminal portion for external connection of a liquid crystal display panel according to claim 1, wherein the flexible printed circuit board can be connected to the electrode terminal for external connection on both sides. 4. The connection structure of an electrode terminal portion for external connection of a liquid crystal display panel according to claim 1, wherein the predetermined interval of cutting or cutting in the flexible printed board is 300 mm or less.