JPH0822880A - Method for connecting electric circuit - Google Patents

Abstract

PURPOSE:To stabilize liquid crystal drive by enabling the external-connection electrode terminal portion of a liquid-crystal display device to be connected to the conductive line of a heat seal connector smoothly and firmly. CONSTITUTION:The external-connection electrode terminal portion 2 of a liquid- crystal display device 10 is positioned with respect to the conductive line 23 of a heat seal connector 20. Next, this stack is pressed from the conductive line 23 of the heat seal connector 20 by a thermocompression bonding jig 30 which has a plurality of projecting and recessed parts 34 on its pressing surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for connecting an electric circuit. More specifically, the present invention relates to a method for connecting an electric circuit which is preferably used in the field of mounting and manufacturing a liquid crystal display.

[0002]

2. Description of the Related Art In general, a liquid crystal display element can be displayed by electrically connecting an external connection electrode portion provided on the peripheral portions of a pair of substrates and an external circuit for driving liquid crystal. . Various heat seal connectors are used as parts for connecting the drive circuit and the liquid crystal display element. For example, conductive lines (for example, screen-printed with silver or graphite paste) are formed on a PET or polyimide film so as to match the pitch interval of the liquid crystal display element, and conductive particles are dispersed in an adhesive resin on the conductive lines. An anisotropic conductive layer (anisotropic conductive connector) may be used.

When connecting the external connection terminal portion of the liquid crystal display element and the external drive circuit through such a heat seal connector, first, the external connection electrode terminal portion of the liquid crystal display element and the conductivity of the heat seal connector. It is necessary to connect with the line. In the case of such connection, a thermocompression bonding jig has usually been used.

On the other hand, a thin film such as a liquid crystal alignment film (alignment film) or a conduction prevention film (insulating film) between opposing electrodes is formed on the external connection electrode terminal portion which is the connection portion of the liquid crystal display element. Since it is necessary and it is difficult for the conductive particles to break through this film, it has been difficult to obtain reliable conduction between the external connection electrode terminal portion and the heat seal connector. Therefore, there are problems that it is difficult to drive the liquid crystal and stable driving cannot be performed.

Further, the improvement of materials for liquid crystal display elements has progressed,
Since the substrate used is also lightweight, thin, and does not break, a plastic film substrate has been used in place of the glass substrate. As such a plastic substrate, a long one is used in order to improve the productivity of the manufacturing process, but in such a case, it is difficult to perform strict dimensional control, so that the tendency of difficulty in conduction is not remarkable. I had no choice.

[0006]

In order to solve such a problem, the following various proposals have been made. A method in which a film is not formed at the connection points on the external connection electrode terminals. For example, in the case of vapor deposition, it is blocked by a mask, and in the case of a coating film, the part to be connected is not partially coated. However, with this method, it was difficult or complicated to set the extraction electrode at an arbitrary position. A method of forming a protrusion on the surface of an electrode connection terminal portion of a flexible connection board without using a heat seal connector, and applying an insulating adhesive to any one of the electrode terminal portions to be connected to make a connection (Patent Document 1 No. 5-14255). This method is also not practical because it requires special processing on the surface of the electrode connection terminal portion. A method of forming a plurality of recesses in the anisotropic conductive film in advance (Japanese Patent Laid-Open No. 4-256926). This method also has to be specially formed with a through hole in the anisotropic conductive film, which is not advantageous in terms of cost. A method using an anisotropic conductive adhesive film having a lead surface of a TAB semiconductor device, a flexible tape or the like roughened and having an extremely low particle dispersion density (JP-A-6-5656). This method is also not practical because it requires a special step of roughening the lead surface. A thermocompression bonding device in which a heater is divided and installed according to the shape and number of objects to be adhered (Japanese Patent Laid-Open No. 5-323351). This device is also a tool with a concave shape in order to avoid thermocompression bonding to an obstacle such as a protrusion or a tape-like object when a plurality of TAB-ICs are arranged. It could not be applied to thermocompression bonding, which requires precise processing such as connection between the transparent electrode and the transparent electrode.

The present invention has been made in view of the above problems, and enables smooth and reliable connection between the external connection electrode terminal portion of the liquid crystal display element and the conductive line of the heat seal connector to stabilize the liquid crystal drive. It is an object of the present invention to provide a method of connecting an electric circuit that can perform the above.

[0008]

In order to achieve the above object, according to the present invention, an external connection electrode terminal portion provided on the peripheral portions of a pair of substrates of a liquid crystal display element and a heat-fusible adhesive are provided. With a conductive line of a heat-seal connector in which conductive particles are dispersed in the agent, a method for connecting an electric circuit in which the conductive particles are connected by a thermocompression bonding jig through the conductive particles,
(A) A step of aligning and laminating the external connection electrode terminal portion of the liquid crystal display element and the conductive line of the heat seal connector, and (B) the aligned laminate.
And a step of pressing from a conductive line side of the heat seal connector with a thermocompression bonding jig having a plurality of irregularities formed on its pressing surface.

As a preferred embodiment thereof, the plurality of irregularities formed on the pressing surface of the thermocompression bonding jig have a repeating shape, and the repeating pitch P is on the peripheral portions of the pair of substrates. Provided is a method for connecting an electric circuit, which satisfies the following formula (I), where m is the narrower electrode width of each external connection electrode terminal portion. m / 10 ≤ P ≤ m (I)

Further, the pair of substrates of the liquid crystal display element are flexible substrates, and external connection electrode terminal portions provided on the peripheral portions thereof are covered with a thin film. A method of connecting an electric circuit is provided.

The present invention will be specifically described below. The present invention comprises a step (A) of aligning and laminating an external connection electrode terminal portion of a liquid crystal display element and a conductive line of a heat seal connector, and pressing the laminated body by a constant thermocompression bonding jig. It is roughly divided into a step (B) of performing. 1. Positioning and Laminating Step (A) (1) Liquid Crystal Display Element The liquid crystal display element used in the present invention is not particularly limited, but for example, a flexible plastic film substrate is used as a pair of substrates with electrodes, and a liquid crystal is used. A liquid crystal display element using a ferroelectric liquid crystal material can be preferably used. This liquid crystal display element has a thin and flexible substrate and has the characteristics of a ferroelectric liquid crystal, so that it is thin, light, does not break, can be bent, and can be configured on a large screen. It has excellent features such as the display does not disappear and the memory is good.

In order to manufacture a liquid crystal display element using such a film substrate, for example, first, liquid crystal is continuously applied to a long substrate with an electrode fed from a roll, and a liquid crystal coated surface becomes a counter substrate. Laminate substrates with electrodes. Then, after performing alignment treatment and inspecting display defects,
A liquid crystal display device can be obtained by cutting into a predetermined size. This liquid crystal display device is used by being mounted on a drive circuit board.

In such a liquid crystal display device, the electrode forming surfaces of a plastic substrate having a stripe electrode pattern formed on one surface are opposed to each other so that the electrode patterns are orthogonal to each other, and the liquid crystal composition is sandwiched between the upper and lower substrates. It is configured. The external connection electrode terminal portion (common side electrode terminal portion and segment side electrode terminal portion) is drawn out from the peripheral edge portion of each substrate protruding from the display portion.

(2) Heat-seal connector Generally, as a method of connecting the external connection electrode terminal portion drawn out from the liquid crystal display element and the electrode on the drive circuit board side, other than the method using the heat-seal connector, the present invention is used. , A conductive rubber connector, an anisotropic conductive film, wire bonding, or chip bonding, but in the case of a liquid crystal display device using a plastic film substrate, it is excellent in adhesiveness and stretchability due to the same material.
A heat-seal connector that is light, thin, short and compact is suitable.

The heat-seal connector used in the present invention may be screen-printed by using silver or graphite paste on a polyethylene terephthalate (PET) or polyimide film or the like so as to match the pitch interval of the liquid crystal display element. A line) is formed and conductive particles are dispersed in an adhesive resin (anisotropic). Specifically, examples of the insulating film include films that have insulating properties and are flexible (flexible), such as polyethylene terephthalate (PET), polyimide, and polyamide. Its thickness is 25-3
5 μm is preferable.

As the conductive line provided on the inner surface of the insulating film, for example, one or more kinds of conductive powder such as silver, copper, nickel, palladium, tin, solder, graphite, carbon black or the like can be used. A conductive coating material dispersed in a flexible polymer resin binder and a hot melt adhesive is adjusted to a film thickness of about 5 to 10 μm by screen printing according to the electrode pitch of a liquid crystal display element, and dried by heating. Can be mentioned.

Examples of the heat-fusible adhesive layer containing conductive particles include graphite having a particle size of 0.5 to 60 μm, silver, copper, nickel, palladium, tin, solder, gold-plated resin, gold-plated nickel, gold-plated copper, gold-plated. 0.5 to 20% by weight of conductive fine powder composed of one or two or more of powders of tin and carbon black having a particle size of 0.1 μ or less is added to chloroprene synthetic rubber, ethylene vinyl acetate copolymer resin, acrylic resin, poly Thermocompression-bonding polymer binder 5 to 55% by weight consisting of one or more of methyl methacrylate resin, epoxy resin, polyester resin, polyamide resin, polyurethane resin, and isophorone, methyl isobutyl ketone, xylene, toluene, diethyl carbitol And 30 to 90% by weight of an organic solvent consisting of one or more of cellosolve acetate, Further, an apparent specific gravity of 0.7 to 0.5 is obtained by mixing and dissolving calcium carbonate powder and titanium oxide powder of 0.5 to 5% by weight so-called extender pigment, and uniformly dispersing them.
It can be formed by applying a resin having a viscosity of 50 to 1500 poises of 2.0 and screen drying on the entire desired thermocompression-bonded portion on the conductive line formed by the screen printing and drying. In this case, the thickness of the adhesive layer is usually about the same as the diameter of the conductive particles.
-30 μm is preferable. If it is less than 20 μm, there is a problem in long-term stability due to instability of conductive particles (migration, surface oxidation, peeling, etc.) and a decrease in adhesiveness. In addition,
On the exposed conductive line, to protect the conductive line, rubber such as ethylene vinyl acetate copolymer resin, acrylic resin, polymethylmethacrylate resin, polyester resin, polyamide resin, polyurethane resin, natural rubber, synthetic rubber, etc. It is preferable to form a protective layer made of a resin.

(3) Positioning and Laminating Operation The procedure of an example of the positioning and laminating operation of the external connection terminal portion of the liquid crystal display element and the conductive line of the heat seal connector will be described below. First, in a series of flow work, the liquid crystal display element is transported onto the drive circuit board to be mounted. As this conveying means, the movable conveyor method, which is commonly used for moving the conveyed object, is used in which the electrodes on the liquid crystal display element side and the electrodes on the drive circuit board side are aligned by the punching method (concave and convex method). You can In this concavo-convex method, as shown in FIG.
A plurality of alignment protrusions 50 (projections) are provided at appropriate positions, and holes (recesses) into which the protrusions 50 fit are formed in the liquid crystal display element 10 and the heat seal connector 20. The positioning protrusion 50 on the drive circuit board 40 is positioned and inserted through the holes of the liquid crystal display element 10 and the heat seal connector 20, and the position between the electrodes of the liquid crystal display element 10, the heat seal connector 20 and the drive circuit board 40 is set. Make a match. Although the hole method is used in this example, a microscopic method can also be used.

That is, when the alignment between the electrodes is performed by the microscopic method, the vacuum chuck method is adopted, and the liquid crystal display element is conveyed while suctioning some places of the non-display portion of the liquid crystal display element by the vacuum suction cup. In the microscopic method, a common alignment mark is marked on the liquid crystal display element and the drive circuit board instead of the convex portion and the concave portion in the concavo-convex method, and the both are aligned while confirming the alignment mark with a microscope. Then, the heat seal connector is positioned on the electrodes of the liquid crystal display element and the electrodes of the drive circuit board.

2. Thermocompression bonding process (B) (1) Connection by thermocompression bonding Hereinafter, referring to FIG.
Will be described with reference to. FIG. 1 is an explanatory view schematically showing the connection situation in the connection method of the present invention, in which (a) aligns the external connection electrode terminal portion of the liquid crystal display element with the conductive line of the heat seal connector before connection. FIG. 4B is a sectional view showing the situation, FIG. 9B is a sectional view showing a connection state when thermocompression bonding is performed by a thermocompression bonding jig, and FIG. In the connection shown in FIG. 1, as shown in FIG. 1A, as a liquid crystal display element 10, an external connection electrode terminal portion 2 is provided on a peripheral portion of a substrate 1, and a thin film 3 is coated thereon. Further, as the heat-seal connector 20, a conductive line 23 provided on the insulating film 21 so as to face the electrode terminal portion 2 for external connection, and a heat-fusible adhesive in which conductive particles 22 are dispersed. 24 and 24 are used. FIG. 1A shows a state before the connection, just before the alignment, the lamination and the thermocompression bonding.

In FIG. 1 (b), after the layers are aligned and laminated, the laminated bodies 10 and 20 are heat-sealed to each other.
From the conductive line 23 side (outside of the insulating film 21) by a thermocompression bonding jig 30 having a thermocompression bonding head 33 having a plurality of irregularities 34 formed on its surface (thermocompression bonding).
It shows the connection status at the time of doing. As shown in FIG. 1B, the heat seal connector 2 of the portion pressed by the convex portion of the unevenness 34 formed on the pressing surface of the thermocompression bonding jig 30.
The 0 conductive line 23 comes into contact with the conductive particles and is pressed downward, and the insulating film 21
As the heat enters, the heat-sealable adhesive 24 flows in. Therefore, the thickness of the adhesive 24 at the portion corresponding to the convex portion of the unevenness 34 is made relatively thin, and the conductive particles are relatively largely extruded from the adhesive layer. As a result, the thin film is effectively pierced, and reliable conduction between the external connection electrode terminal portion 2 and the conductive line 23 of the heat seal connector 20 can be achieved.

FIG. 1C shows the connection points. FIG. 1C shows a connection state of one of the substrates of the liquid crystal display element 10.

(2) Thermocompression bonding jig As the thermocompression bonding jig used in the present invention, for example, the "thermocompression bonding device" of Japanese Patent Application Laid-Open No. 4-206751 or Japanese Patent Application No.
The one described in "Connecting method for liquid crystal display element" in Japanese Patent No. 166087, that is, the thermocompression bonding jig 30 as shown in FIG. 2 of the present application can be preferably used. The thermocompression bonding jig 30 includes a processing stage 31, a lift 32, and a thermocompression bonding head 33. The processing stage 31 can rotate 360 ° and can move in parallel in the front-rear direction. Further, a thermocompression bonding head 33 is attached to an elevator 32 driven by an air cylinder.

(3) Formation of irregularities In the present invention, as the thermocompression bonding jig 30, one having a plurality of irregularities formed on its pressing surface is used. This unevenness is
As described above, at the time of thermocompression bonding, a space for excluding the inflow of the heat-fusible adhesive is formed, and the thickness of the adhesive is relatively thin at the portion corresponding to the convex portion, and the heat-sealing connector is electrically conductive by the conductive particles. Conduction between the line and the external connection electrode terminal portion of the liquid crystal display element can be smoothly and reliably achieved.

The method of forming the unevenness is not particularly limited, but it is preferable to attach rubber to the tip of the thermocompression bonding head 33 and form the unevenness on the pressing surface. This rubber acts as a buffer and can ensure the flatness of the entire pressure-bonded surface. The mounting method may be, for example, a mechanical insertion method in which a convex portion provided on rubber is press-fitted into a concave portion provided on the metal fitting.

Further, by using this rubber, it is easy to form and replace the unevenness, and the shape of the unevenness can be various shapes depending on the shape of the connecting portion between the liquid crystal display element and the heat seal connector to be connected. Can be prepared. Therefore, the manufacturing cost of the jig is reduced,
The replacement work can be simplified.

As the rubber material to be used, various kinds of rubber such as silicone rubber can be used.

Further, for example, a thermocompression bonding head 33 made of copper or the like is used.
The unevenness may be formed directly on the main body metal fitting.

Further, for example, irregularities may be formed on the processing stage 31 made of stainless steel or the like.

The shape of the concavities and convexities can be appropriately selected according to the combination of the liquid crystal display element used and the heat seal connector. For example, the circular convex shape shown in FIG. 5A, the circular concave shape shown in FIG. 5B, the linear vertical shape shown in FIG. 5C and the linear horizontal shape shown in FIG.

The shape of the unevenness is, for example, as shown in FIG.
It is preferable to make the shape repetitive as shown in (d) in terms of reliability of connection and easiness in manufacturing. In this case, the repeating pitch P preferably satisfies the following formula (I), where m is the narrower electrode width of the external connection terminal portion. m / 10 ≦ P ≦ m (I) When the pitch is less than m / 10, jig processing is practically impossible, and when it exceeds m, it becomes larger than the pitch interval of the electrodes, which is not effective.

(4) Thermocompression bonding conditions As standard thermocompression bonding conditions in this step, head surface temperature: 130 to 190 ° C. pressing force: 30 to 50 kg / cm ² pressing time: 30 seconds or less can be mentioned.

[0033]

EXAMPLES The present invention will be described in more detail with reference to examples. [Example] Fabrication of thin film on substrate Polyethersulfone (PES) substrate (thickness 100 μm) on which indium-tin oxide (hereinafter referred to as ITO, abbreviated as ITO, surface resistance 300Ω / □) was formed (1 mm pitch patterning) as a transparent electrode. Polyimide (Nissan Chemical Co., Ltd., Sun Ever SP-910) is coated on the above with a roll coater, and 1
It was dried and cured at 30 ° C. for 30 minutes to obtain a thin film (film thickness 0.2 μm) as an insulating film. Thermocompression bonding of heat seal connector As shown in FIG. 4, as a thermocompression bonding jig 30 having irregularities, thermocompression bonding with a silicon rubber attached to the tip processed into a round convex surface shape (pitch 0.5 mm) A head 33 (thermocompression bonding width 3 mm) was used. P formed with the insulating film 3
Electrode terminal of ES board 1 and heat seal connector 20
(JS type manufactured by Shin-Etsu Polymer Co., Ltd.) is aligned with the conductive line and thermocompression bonded (head surface temperature 150 ° C, pressure 4
0 kg / cm ² , time 10 seconds). Evaluation Conduction was measured on 100 lines between the ITO electrode and the conductive line side of the heat seal connector. The ratio of those having a resistance of 1 kΩ or less was defined as the good conductivity (%). As a result, the good conductivity was 98%.

Example 2 Epoxy resin (main agent: Epicoat 828 manufactured by Yuka Shell Co., Ltd.) was replaced with methyl ethyl ketone (M
EK) and coat with a roll coater to 100
Dry and cure at 60 ° C for 60 minutes to form a thin film (film thickness 0.4μ
m) was obtained, and the head metal fitting (made of copper) in which the pressing surface shape was linearly processed (pitch 0.5 mm) was used as a thermocompression bonding jig having irregularities. I did the same. As a result, the good conductivity was 100%.

[Example 3] A thin film (200 Å) was formed by vapor deposition of silicon oxide, and a head metal fitting whose pressing surface shape was linearly processed (pitch 0.5 mm) was thermocompression-bonded with irregularities. Same as Example 1 except that it was used as a jig. As a result, the good conductivity was 100%.

[Embodiment 4] The same operation as in Embodiment 3 was carried out except that a head metal fitting having a pressing surface shape laterally processed (pitch 1.0 mm) was used as a thermocompression bonding jig having irregularities. . As a result, the good conductivity was 98%.

[Embodiment 5] Implementation was carried out except that a mounting plate whose pressing surface was laterally processed (pitch 0.5 mm) was used as a thermocompression bonding jig (made of stainless steel) having irregularities. Same as Example 3. As a result, the good conductivity is 90.
%Met.

[Comparative Example 1] The same procedure as in Example 1 was carried out except that a thermocompression bonding rubber head (silicon rubber) having a flat pressing surface was used as the thermocompression bonding jig. As a result, good conductivity is 65%
Met.

[Comparative Example 2] The same procedure as in Example 3 was carried out except that a thermocompression bonding rubber head (silicon rubber) having a flat pressing surface was used as the thermocompression bonding jig. As a result, good conductivity is 23%
Met. The above results are shown in Table 1 below.

[Table 1] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Insulation film type thermocompression bonding jig Concavo-convex pitch Continuity evaluation (mm) (Good conductivity%) ──────────────────────────────────── Example 1 Poly-imid coating film Head gum Round convex 0.5 98 2 Epoxy coating film Head metal fittings Horizontal width 0.5 100 3 Silicon oxide vapor deposition film Head metal fittings Horizontal width 0.5 100 4 Silicon oxide vapor deposition film Head metal fittings Linear width 1.0 98 5 Silicon oxide vapor-deposition film Linear plate on mounting plate 0.5 90 ────────────────────────────── ─────── Comparative Example 1 Polyimide coating film Surface flat Silicon comb head 65 2 Silicon oxide vapor deposition film Surface flat Rikongo Muhetto Bu 23 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Example 6 Production of Liquid Crystal Display Device ITO (1 mm pitch, electrode width 0.5 m) as a transparent electrode
m) (300 segment electrodes, 150 common electrodes)
A structure (size: 300 (L) × 150 (W) × (100) in which the liquid crystal shown in the following chemical formula 1 is sandwiched between the polyether sulfone (PES) films (thickness 100 μm) formed with
μm × 2) (T)) was used. A silicon oxide vapor deposition film was formed on the electrodes. The segment electrodes were stacked on top of the display element, and the common electrodes were stacked with the film offset so that the electrode edge appears on the left side of the display element. A hole for electrode alignment was provided so as to avoid the display portion of the display element.

[0042]

Embedded image

Alignment-thermocompression bonding step The obtained liquid crystal display device was moved onto the working stage of the thermocompression bonding jig. The liquid crystal display element was mounted on the drive board on the stage. A heat seal connector (JS type manufactured by Shin-Etsu Polymer Co., Ltd.), which is a connecting part, is interposed between each of the segment electrode and the common electrode of the liquid crystal display element and the drive board, and the positioning is performed using the positioning protrusions.
Thermocompression bonding (150 ° C., 30 kg / cm ² , time 10 seconds) was performed with a thermocompression bonding jig to which a head metal fitting (made of copper) having a linear lateral pressing surface was attached.

As a result, when the liquid crystal display device was operated by connecting it to a driving power supply, both the segment side and the common side were driven without problems, and good display was obtained.

[Comparative Example 3] The same procedure as in Example 6 was carried out except that a flat head rubber was used in place of the head metal fitting having a linear pressing surface used in Example 6. When it was connected to the drive power source and driven, 70 lines could not be driven.
%, And no indication was obtained.

[0046]

As described above, according to the present invention,
The external connection electrode terminal portion of the liquid crystal display element and the conductive line of the heat seal connector can be smoothly and reliably conducted by the conductive particles, and the liquid crystal display element can be driven stably.
Further, it is possible to improve the production yield. Further, the present invention is difficult to conduct, when using a long plastic substrate on which a thin film such as an insulating film is formed,
It can be used particularly effectively.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing a connection situation in a connection method of the present invention, in which (a) shows an external connection electrode terminal portion of a liquid crystal display element and a conductive line of a heat seal connector before connection. A sectional view showing a combined state, (b) is a sectional view showing a connection state when thermocompression bonding is performed by a thermocompression bonding jig,
And (c) are explanatory views showing connection points.

FIG. 2 is an explanatory view schematically showing an example of a thermocompression bonding jig used in the present invention.

FIG. 3 is a plan view schematically showing a method of performing alignment using alignment protrusions in the step (A) of the present invention.

FIG. 4 is a cross-sectional view schematically showing an arrangement immediately before thermocompression bonding in the step (B) of the present invention.

FIG. 5 is an explanatory view schematically showing the shape of irregularities provided on the thermocompression bonding head used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Electrode terminal part for external connection 3 ... Thin film 10 ... Liquid crystal display element 20 ... Heat seal connector 21 ... Insulating resin film 22 ... Conductive particles 23 ... Conductive line 24 ... Thermal adhesive adhesive 30 ... Heat Crimping tool 31 ... Processing stage 32 ... Elevator 33 ... Thermocompression bonding head 34 ... Roughness 40 ... Drive circuit board 50 ... Positioning protrusion

Claims (3)

[Claims] 1. A conductive line of a heat-seal connector, wherein external connection electrode terminal portions are respectively provided on the peripheral portions of a pair of substrates of a liquid crystal display element, and conductive particles are dispersed in a heat-fusible adhesive. In the connection method of the electric circuit, which is connected by a thermocompression bonding jig through the conductive particles,
(A) A step of aligning and laminating the external connection electrode terminal portion of the liquid crystal display element and the conductive line of the heat seal connector, and (B) the aligned laminate.
And a step of pressing from a conductive line side of the heat seal connector with a thermocompression bonding jig having a plurality of irregularities formed on its pressing surface. 2. A plurality of irregularities formed on the pressing surface of the thermocompression bonding jig have a repeating shape, and the repeating pitch P is provided on the peripheral portions of the pair of substrates, respectively. The method for connecting an electric circuit according to claim 1, wherein the following formula (I) is satisfied, where m is the narrower electrode width of the connecting electrode terminal portion. m / 10 ≤ P ≤ m (I) 3. A pair of substrates of the liquid crystal display element are flexible substrates, and external connection electrode terminal portions provided on a peripheral portion of the flexible substrate are covered with a thin film. The method of connecting an electric circuit according to claim 1 or 2.