JPS61228490A - Display unit connecting construction - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a connection structure for a display device, and particularly to a connection structure for a display device that utilizes thermocompression bonding for terminal connection.

[Background of the invention]

Display devices such as liquid crystal display devices, fluorescent display devices, electroluminescent display devices, and plasma display devices are trending towards higher definition and larger capacity, and in addition to problems with electrode formation, terminal connections have become a major problem. Various connection methods have been proposed.

One method is to use a pressure contact type connector that utilizes rubber elasticity. These connectors can be broadly classified into three types. The first type uses conductive rubber with both conductive and spring functions, and the second type does not use conductive rubber, but uses metal, carbon fiber, carbon paint, etc. as the conductor, and insulating rubber is used as a binder. It is used as a support material and at the same time functions as a spring. The third type is called anisotropic conductive rubber, in which current flows only in the thickness direction and not in the direction perpendicular to the thickness.

These are used in small liquid crystal displays such as watches and calculators. However, this kind of connection accuracy is currently 2
It cannot be applied to high-definition, large-capacity display devices because it is as low as 1/-.

Therefore, soldering using infrared rays has been proposed as an effective method for connecting high-definition, large-capacity display devices. The connection accuracy by this method is about 4/-. However, since this method uses infrared rays to melt and connect the solder, heat, solder shape,
This method has the disadvantage that it is difficult to determine connection conditions such as the elongation of the objects to be connected, and electrode formation is complicated.

Under these circumstances, as a simple connection method for high-definition and large-capacity display elements, Japanese Patent Publication No. 58-56996, Japanese Patent Publication No. 2179-1979, Japanese Patent Application Laid-Open No. 51-20941, Japanese Patent Application Laid-open No. 52-1988 have been proposed. Publication No. 41648, JP-A-51-1
No. 14439, Japanese Patent Application Laid-open No. 119732/1983,
JP-A-51-135938, JP-A-51-211
As described in Japanese Patent Application No. 92, a device using a heat seal connector has been proposed. The feature of these heat seal connectors is the conductive material dispersed in the adhesive layer.
Solder, Ni, carbon, etc. are used. A major factor that determines the connection accuracy of the connection method using this heat seal connector is this conductive material, which is determined by its shape and size.

If this connection method using a heat-seal connector is adopted, the electrodes are pressed together through a conductive substance, so the electrode material is not limited and the electrodes can be easily formed. However, with the connection method using heat-seal connectors, tens of kilograms per unit area when heated.
Due to the application of pressure, the so-called adjacent terminals are electrically connected due to misalignment and electrical connection between adjacent terminals. There have been problems in that contact failures such as so-called short circuits between adjacent terminals are likely to occur, and contact resistance varies depending on the flatness of the thermocompression bonding device, which is a connection condition.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a connection structure for a display device in which terminal connections can be easily made without causing positional displacement or poor connection.

[Summary of the invention]

The present invention uses a polymer membrane with directional conductivity containing a synthetic resin adhesive and metal particles, and connects the polymer membrane by sandwiching the polymer membrane between a pair of electrodes and applying heat and pressure to them. In order to achieve the above object, the particle diameter d1 of the metal particles, the film thickness dt of the terminal portion of the display element, and the film thickness dc of the conductor to be connected are configured to have the following relationship: .

, 0.7d, ≦dt+dc≦1.2d.

[Embodiments of the invention]

A preferred embodiment of the present invention will be described below with reference to the drawings.

1 to 5 show the construction of a preferred embodiment of the present invention.

In FIGS. 4 and 5, a polymer film 1 having directional conductivity is composed of a mixture of polyolefin rubber and synthetic resin that has an adhesive function, and a molten metal that has a conductive function. . The film thickness of this polymer film having directional conductivity (hereinafter referred to as an anisotropic conductive film) is about 30 microns, and the particle size of the molten metal 2 is about 20 microns.

Further, the curing temperature of the adhesive 1 of the anisotropic conductive film is 170°C, and the melting point of the molten metal 2 is 190°C.

Here, the reason why molten metal 2 was used as the conductive material of the anisotropic conductive film in this example is that the contact area can be increased, the contact resistance at the time of connection can be reduced, and the This is because current can flow through it.

Therefore, in carrying out the present invention, there is no problem as long as the conductive material of the anisotropic conductive film is a material with low electrical resistance and a small particle size, such as carbon, carbon fiber, nickel, or copper.

The photograph in FIG. 4 shows an anisotropic conductive film used to carry out the present invention in which solder particles 2 with a diameter of about 20 microns are dispersed in a synthetic resin adhesive with a thickness of about 30 microns. has been done.

In addition, Figure 5 shows the electrode configuration during connection in which one embodiment of the present invention is implemented. This is an electrode configuration applied to a thermal writing liquid crystal display device. As shown in FIG. 5, an anisotropic conductive film 1 shown in FIG. 4 is sandwiched between the terminal portion of the liquid crystal display element 3 and a flexible printed circuit 4 (hereinafter referred to as FPC) to prevent heat. The connection was made by applying pressure at the same time.

Figure 1 shows the structure of a liquid crystal display panel. The scanning electrode 6 is made of a resistor, and the signal electrode 7 is made of a transparent conductor. This scanning electrode 6 has an 85% A
Ω-10%5i-5%Cu alloy, film thickness 1μm, sheet resistance 0.17Ω/sq・, diffuse reflectance 68%
(λ=400 nm).

The signal electrode 7 is made of indium oxide and has a film thickness of 1000 μm.
It has a sheet resistance of 30Ω/sq· and a transmittance of 90%.

Alignment films for controlling the alignment state of liquid crystal 8 are provided on scanning electrode 6 and signal electrode 7, respectively, and liquid crystal 8 is displayed on scanning electrode substrate 10 and signal electrode substrate 11. In order to control the thickness of the liquid crystal layer, the support material 13 is dispersed in the sealant 12 and also in the portion corresponding to one display surface, thereby making the thickness of the liquid crystal layer 8 uniform.

Next, the liquid crystal 8 used to carry out the present invention is an acyloxy type liquid crystal and has the following structural formula, (1) and (2).
) and (3) in a 1:1 weight ratio.

The phase transition temperature of this liquid crystal 8 is from solid to smectic A.
Transition temperature to phase Tc5=10°C, transition temperature from smectic phase to nematic phase T1. =45°C, and the transition temperature from the nematic phase to the liquid, T,l, =47°C. Also, the dielectric constant g1 in the minor axis direction of liquid crystal molecules at 25°C is 6.
．． 59, relative permittivity in the major axis direction ε1. =16,76ε1□
and ε, the difference Δξ=10.17. Ratio t of ff1tz and C1
1*/i 1=2-54.

The alignment film 9 that controls the alignment state of the liquid crystal 8 is made by Shin-Etsu Chemical, model Lp-828Fzt (CHs)zsi (OCHs)scHs.
The mixing ratio of silanol oligomer Si film manufactured by Tokyo Ohka Co., Ltd. (model number 59000) is polyetheramide 100.
1.8 parts of the mixture of fluorine-based silane and Si film
Department.

Liquid crystal used to carry out the present invention 8. Although the alignment film 9 is as described above, it is possible to set the phase transition temperature, dielectric constant, alignment regulating force, etc. to optimum values by changing the mixing ratio of each layer depending on the usage environment, driving conditions, etc.

In addition, the liquid crystal 8 used in this example was mixed with a black dichroic dye in order to perform positive display, making it a guest-host type liquid crystal. This black dichroic dye is L manufactured by Mitsubishi Kasei.
SR-310, LSY-108, LSB-318, LS
B-278 (7) is a mixture of four types of dyes, and the mixing ratio is 5LR-310:40 parts, LSY-108:
80 copies.

LSB318: 80 parts, I, 5B-278: 100 parts. Liquid crystal 8 contains 1.7 parts of the above black dye based on 100 parts of the above smectic A-phase liquid crystal.

Note that the scanning electrode substrate 10 and the signal electrode substrate 11 have a diameter of 1.1
Soda glass with a thickness of
3 and the port material dispersed on the display surface has a diameter of 12 μm,
A glass fiber with a length of about 80 μm was used.

In such a connection method using the heat-seal connector described above for a liquid crystal display element for thermal writing, it is possible to prevent electrical short circuit between adjacent terminals and misalignment of the terminal part of the display element and the terminal part of the FPC. Moreover, the terminal configuration of the liquid crystal display element and the electrode configuration of the FPC, which can have a small contact resistance and a large current carrying capacity, are shown in FIG. 2, and the overall configuration is shown in FIG. 3.

The configuration shown in Figure 2 is suitable for connecting the FPC to the terminals of the scanning electrodes that conduct a relatively large current to heat the liquid crystal layer, and the pitch of the scanning electrodes is 250 μm.
(Definition = 4 lines/single).

The target specifications are energizing current: A and contact resistance of 1Ω or less. Note that 18 is an anisotropic conductive film, 19 is a rigid substrate, and 20 is a circuit board.

Further, as shown in FIG. 1, an anisotropic conductive film made of an adhesive 16 and metal particles 17 is sandwiched between the scanning electrode 6 provided on the scanning electrode 10 and the electrode 15 provided on the base film 14 of the FPC. Since the connection is made by applying heat and pressure, the relationship between the thickness of the FPC electrode 15 plus the scanning electrode 6 thickness and the size of the metal particles 17 of the anisotropic conductive film is important. . Furthermore, the gap between scanning electrodes is also an important factor in shorting between adjacent terminals.

That is, the size of the metal particles 17 of the anisotropic conductive film.

If the thickness is greater than the sum of the film thickness of the scanning electrode 6 and the film thickness of the FPC electrode 15, the metal particles 17 dispersed between adjacent terminals will be crushed and spread, causing a contact failure such as a short circuit between adjacent terminals. do.

A connection in which the size of the metal particles 17 of the anisotropic conductive film, which is likely to cause a short circuit between adjacent terminals, is larger than the sum of the film thickness of the conductor 15 of the FPC and the film thickness of the scanning electrode 6. The situation is shown in FIGS. 6 and 7.

Figure 6 shows the state before connection, and the base film 1
An anisotropic conductive film made of adhesive 16 and metal particles 17 is sandwiched between an FPC made of FPC 4 and electrode conductor 15, a scanning electrode substrate made of glass substrate 10, and scanning electrode 6, and the connection is made by applying heat and pressure. be done. On the other hand, FIG. 7 shows the state after connection.

Since the particle size of the metal particles 17 is larger than the sum of the film thickness of the FPC conductor 15 and the film thickness of the scanning electrode 6, the metal particles 17 dispersed between adjacent terminals are crushed and spread, and the FP
Metal particles 17 that establish conduction between the C conductor 15 and the scanning electrode 6
is further crushed and expanded, and melts with the crushed metal particles 17 between adjacent conductors, causing a short circuit between adjacent conductors.

Next, the connection state when the particle size of the metal particles is smaller than the sum of the FPC conductor thickness and the scanning electrode film thickness is described in the eighth section.
9 and 9.

FIG. 8 shows a state before connection, in which an FPC consisting of a base film 14 and an electrode conductor 15 and a glass substrate 10 are shown.
An anisotropic conductive film made of an adhesive 16 and metal particles 17 is sandwiched between a scanning electrode substrate made of the and scanning electrodes 6, and the connection is made by applying heat and pressure.

On the other hand, Fig. 9 shows the state after connection, and the FPC
Since the particle size of the metal particles 17 of the anisotropic conductive film is smaller than the sum of the film thickness of the conductor 15 and the film thickness of the scanning electrode 6,
The metal particles 17 dispersed between adjacent terminals can maintain their original particle size without being crushed. Therefore, since the particle diameter of the metal particles 17 is originally smaller than the gap between adjacent terminals, a so-called short circuit between adjacent terminals that electrically connects adjacent terminals does not occur. In the connection method, the relationship between the particle size of the conductive material of the heat seal connector and the film thickness of the electrode to be connected
The film thickness of the electrode to be connected can be made larger than the particle size of the conductive material of the heat seal connector.

However, simply increasing the thickness of the electrode to be connected to be larger than the particle size of the conductive material of the heat seal connector will only reduce the adhesive strength and will not provide a good connection.

Therefore, there is a relationship between the film thickness of the electrode to be connected and the particle size of the conductive material of the heat seal connector to obtain a good connection state.

In addition, the thermal writing liquid crystal display element has an electrode pitch of 250 μm.
, the number of scanning electrodes is 500, the number of signal electrodes is 720, and the display screen is the size of A5 size. The wire band electrode has a structure where terminals are pulled out on both sides, so the electrode pitch of the terminal part to be connected is 5.
The connection pitch is relatively loose at 00 μm (definition = 2 lines/m).

However, since scanning electrodes conduct current, the electrode pitch at the terminal part is also 250 μm (definition = 4 Aml, and the number of connection terminals is 500, which is a strict connection pitch. Also, the specifications required for connection are the current that can be passed through one current) The strict conditions are that the capacitance is IA and the contact resistance of the connection part is 1Ω or less.

Using such a thermal writing liquid crystal display element, an investigation was conducted to determine the optimum relationship between the terminal width of the scanning electrode and the terminal gap, and the relationship shown in FIG. 10 was obtained.

FIG. 10 shows the relationship between the frequency of occurrence of short circuits between adjacent terminals and the gap between terminals when the terminal pitch is constant at 250 μm. As shown in the figure, the gap between the terminals is 150 mm.
It has become clear that short circuits between adjacent terminals do not occur when the thickness is .mu.m or more. However, the film thickness of the scanning electrode used in this example is 1 μm, the film thickness of the FPC conductor electrode is 18 μm, the film thickness of the anisotropic conductive film is 30 μm, and the particle size of the solder particles of the anisotropic conductive film is 20 μm. I used the one from The heat and pressure conditions were optimal for an anisotropic conductive film.

Based on this result, the pitch of the scanning electrodes was 250 μm, the terminal width was 100 μm, and the gap between the terminals was 150 μm. Therefore, the conductor pitch, terminal width, and inter-terminal spacing of the FPC were made the same as those of the scanning electrodes.

In addition, the reason why the film thickness of the FPC conductor electrode was set to 18 μm was determined by the constraint conditions for forming 500 electrodes at a resolution of 4 lines per cabinet.
It has also become clear that a good electrode format cannot be achieved unless the thickness of the FPC conductor electrode is made thinner.

The results shown in Figure 10 show that in an electrode configuration with a terminal width of 100 μm and a gap between terminals of 150 μm, when the film thickness of the conductor electrode of the FPC is constant at 18 μm, when the film thickness of the electrode at the terminal part of the scanning electrode is changed. The relationship between contact resistance was investigated.

FIG. 11 shows the relationship between the film thickness of the terminal portion and the contact resistance. As shown in the figure, it was found that contact resistance was reduced by increasing the film thickness of the terminal portion.

Since aluminum electrodes are used for the scanning electrodes, it was found that when the film thickness of the terminal portion is thin, the aluminum electrodes are oxidized and the contact resistance increases rapidly due to the application of heat and pressure to connect them.

This result revealed that since the conductor film thickness of the FPC is 18 μm, the contact resistance becomes small when the film thickness of the terminal portion is 1.4 μm or more. That is, when the sum of the FPC conductor film thickness and the terminal part film thickness was 19.4 μm or more, the contact resistance could satisfy the target specification of 1Ω or less.

Further, when the relationship between the film thickness of the terminal portion and the adhesive strength was examined, the relationship shown in FIG. 12 was obtained.

FIG. 12 shows the relationship between the film thickness of the terminal portion and the adhesive strength. In the same figure, the adhesive force is 1.4 when the film thickness of the terminal part is 1.4.
It was found that the largest value was found in the range of μm to 2.5 μm.

In addition, the connection method must satisfy both contact resistance and adhesive strength at the same time. Therefore, the results shown in Figures 11 and 12 indicate that the connection method is suitable for thermal writing liquid crystal display devices that conduct relatively large currents. The specifications are contact resistance 1Ω or less,
Since the adhesive strength is strict at 500 g/1 or more, the range of A part shown in Fig. 13 can satisfy the specifications, and the film thickness dt of the terminal part at that time will be in the range of 1.4 μm to 2.5 μm. I understand.

Therefore, when using the heat seal connector method for a display device that has a resolution of 4/- or more, has a large screen, and carries a large current, the particle size of the metal particles used for the heat seal connector must be Since approximately 20 μm is close to the minimum particle size for manufacturing, and due to constraints on FPC conductor formation, the maximum FPC conductor thickness da is approximately 18 μm, and the FPC conductor thickness da is 18 μm. dt=1.
4-2.5pm plus dc+dt=19.4-20.
The optimum value is 5 μm, and the relationship between the particle diameter d of the metal particles and the following equation is expressed.

0.97・dII-5dc+dt≦1.025-d
.

The electrode configuration expressed by the above formula is a special case in which a relatively large current is passed through the connection, as described above, and is generally used in field-effect liquid crystal display devices, fluorescent Do not apply large currents to the connections of display devices, electroluminescent display devices, plasma display devices, etc.

Therefore, unlike thermal writing liquid crystal display devices, there is no need to apply a large current, so there is no problem as long as the contact resistance is about 100Ω or less, and the adhesive strength is 400g/cm or more because there is less heat generation at the terminals. If so, there is no practical problem.

From this, when applied to general display devices,
It can be used within the range of part B shown in FIG. 13, and the terminal film thickness dt is in the range of 5 to 2.8 μm, which is the FPC conductor thickness d.

=18pm added d o + d t=18.5-2
The optimum range is 0.8 μm.

Therefore, the particle diameter d of the metal particles in the heat seal connector
, is expressed as the following equation.

0.925-d, ≦dc+dt≦1.04
-d.

In this way, the terminal part film thickness dt and FPC when the definition is 4 lines/thickness or less and high capacity and large current are applied.
The relationship between conductor thickness da is dc+dt=19.4~20.5
μm, and in this example da=18.0 μm,
Naturally, when the value of dc is changed, d c + d t
The terminal part film thickness d is in the range of = 19.4 to 20.5.
Just change t.

Therefore, it is applicable to general display devices. Also in case.

It goes without saying that by changing the terminal part film thickness as described above, the terminal part film thickness dt can be changed so that it falls within the optimum value range.

Next, when the relationship between the terminal pitch Lp and the inter-terminal gap Lg of the terminal portion of the display element shown in FIG. 10 is rewritten as the relationship between the terminal width and the location where a short circuit occurs, the characteristics shown in FIG. 14 are obtained. FIG. 14 shows the relationship between the terminal width when the terminal film thickness is 5000 mm and the maximum current when the pulse is @ 10 ms.

From FIG. 14, the specification for the current value of a thermal writing liquid crystal display device that conducts a relatively large current is IA or more, and the terminal width Lp that does not cause short circuit between adjacent terminals is only within the shaded area. I, p is in the range of 100 to 125 μm. Therefore, the optimum range of the terminal gap is Lg=125
The optimum relationship between the terminal pitch Lp at the end and the inter-terminal gap Lg is expressed by the following equation.

0.5 L p≦L, g≦0.6 L P terminal film thickness d
t, the relationship between the FPC conductor thickness dc and the particle diameters d and l of the metal particles dispersed in the heat seal connector, and the relationship between the terminal pitch Lp and the gap between the terminals, When this embodiment is used for a display device or a connection, the film thickness dt of the terminal portion may be increased.

In addition, if the terminal gap Lg is smaller than the above range, a short circuit will occur between adjacent terminals, but by applying a pulse current to the short circuit part, the short circuit part can be fixed without damaging the terminal part. A method has also been established to eliminate the short-circuit condition by melting only the short-circuit, and if used in conjunction with this short-circuit correction method, it can be used even in locations where the relationship between the terminal gap Lg and the terminal pitch Lp is not optimal.

Further, in this example, details regarding the heat and pressure applied to the heat seal connector were not described, but the optimum value for heat was determined from the characteristics of the adhesive used for the heat seal connector, and for pressure, the optimum value was determined from the characteristics of the adhesive used for the heat seal connector. Needless to say, the optimum value is determined from the particle pitch, terminal width, and film thickness of the heat seal connector.

Furthermore, from the results of this example, in the connection method using a heat seal connector that connects by applying heat and pressure, when a relatively large current is passed through the connection part, the specific resistance of the metal particles of the anisotropic conductive pattern It has become clear that selecting a terminal electrode material with lower specific resistance or sheet resistance is an important condition.

The photograph in FIG. 15 shows the connection state as a result of connection according to this embodiment. As shown in FIG. 15, it can be seen that the solder particles 17 on the scanning electrode 6 are crushed and spread well, increasing the contact area.

Furthermore, the solder particles 17 in the gaps other than those on the scanning electrodes 6 are not crushed and maintain substantially the original particle size, and the scanning electrodes 6 are electrically connected. It can be easily seen that so-called short circuits between scanning electrodes do not occur.

In this way, by making the thickness of the solder particles, which is the sum of the film thickness of both electrodes to be connected, equal to or larger than the particle size of the solder particles, it is possible to maintain a relatively large current with low contact resistance without reducing the adhesive strength. It became clear that electricity could be applied.

Also, when the gap between the terminals is made small, a short-circuit condition occurs, but by passing a pulsed current through that part,
We were also able to establish a method to resolve the short-circuit condition.

〔Effect of the invention〕

As described above, according to the present invention, an excellent effect can be obtained in that terminal connection can be easily performed without causing positional deviation or contact failure.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the element configuration of a liquid crystal display element according to the present invention, FIG. 2 is a diagram showing the electrode configuration of terminals and connecting bodies, FIG. 3 is an exploded perspective view of FIG. 2, and FIG. A microscopic photograph of the polymer film with directional conductivity according to the invention, Fig. 5 is a diagram of the electrode configuration when connected using a heat seal connector, and Fig. 6 shows that the particle diameter of the metal particles of the heat seal connector is a scanning electrode. Figure 7 shows the electrode configuration before connection when the film thickness is greater than the sum of the film thickness of FPC and the film thickness of the conductor electrode of FPC, Figure 7 is a connection state diagram after connection of Figure 6, and Figure 8 is heat sealing. Figure 9 shows the electrode configuration before connection when the particle diameter of the metal particles of the connector is smaller than the film thickness of the scanning electrode and the film thickness of the conductor electrode of the FPC.
The figure shows the connection status after the connection shown in Figure 8. Figure 10 shows the relationship between the gap between terminals and the frequency of short circuits at a terminal pitch of 250 μm. Figure 11 shows the film thickness of the terminal electrode and the contact resistance of the terminal part. Figure 12 is a diagram showing the relationship between the film thickness of the terminal part electrode and the adhesive strength of the connection part, and Figure 13 is a diagram showing the relationship between the terminal part film thickness and the FP.
FIG. 14 is a diagram showing the relationship between the film thickness of the C conductor, FIG. 14 is a diagram showing the relationship between the terminal pitch and the gap between terminals, and FIG. 15 is a micrograph showing a connection example according to the present invention. 1... Polymer film, 2... Molten metal, 3J... Liquid crystal display element,
4... Flexible printed circuit, 5... Anisotropic conductive film,
6... Scanning electrode, 7... Signal electrode, 8... Liquid crystal, 16... Adhesive, 17.0. Metal particles, 18... Anisotropic conductive film, 19... Rigid substrate, 2o... Circuit conductor.

Claims (1)

[Claims] 1. A conductive polymer film containing a synthetic resin adhesive and metal particles is used, the polymer film is sandwiched between a pair of electrodes, and heat and pressure are applied to them. In addition, in the connecting device, the particle diameter d_M of the metal particles, the film thickness dt of the terminal portion of the display element, and the conductor film thickness dc to be connected are configured to have the following relationship. Device connection structure. 0.7d_M≦dt+dc≦1.2d_M 2. In claim 1, the display element is characterized in that the terminal pitch Lp of the terminal portion of the display element and the inter-terminal gap Lq have the following relationship. Display device connection structure. 0.2Lp≦Lg≦0.6Lp… 3. In the connection structure for a display device according to claim 1 or 2, the specific resistance of the electrode material of the terminal portion is higher than the specific resistance of the metal particles or the sheet resistance. Alternatively, there is provided a connection structure for a display device, characterized in that the sheet resistance is reduced.