JPH07140481A - Display panel - Google Patents

Abstract

PURPOSE:To provide a display panel which is parted in spacing between upper and lower circuit to substantially the spacing of the grain size of hard particles, is formed with the metallic thin layers of conductive particles being face-to-face contact with the planes of the connected circuits and has excellent reliability. CONSTITUTION:This display panel is formed by clamping spacer particles 9 together with an electro-optical material 8 between the circuits (6, 7) of two sheets of counter substrates formed with the circuits, parting the upper and lower substrates to a specified thickness and connecting the upper and lower circuits 6, 7 by the conductive particles and adhesives 5. The conductive particles are formed by coating the surfaces of the hard particles 1 of substantially the same diameter as the diameter of the spacer particles 9 with high polymer layers 2 softer than these particles and further, coating these particles with conductive metallic thin layers 3. The spacing between the upper and lower circuits 6 and 7 is parted to substantially the spacing of the grain size of the hard particles 9, by which the metallic thin layers 3 of the conductive particles are brought into surface-to-surface contact with the circuit planes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display panel using an electro-optical material such as a liquid crystal panel, an electroluminescence panel and an electrochromic panel.

[0002]

2. Description of the Related Art As a vertical connection structure of a display panel, for example, a structure described in Japanese Patent Laid-Open No. 182685/1983 is known. This is a method in which an electro-optical substance is sandwiched between circuits provided on a substrate and upper and lower circuits separated by a spacer to have a constant thickness are connected using a vertical conductive material composed of conductive particles and an adhesive. . In this publication, conductive particles obtained by plating (metalizing) the surface of a hard spacer material such as glass fiber or alumina, or the surface of an elastic substance having a larger particle size than the spacer such as a plastic ball or plastic fiber is plated (metametal). Rising)
An example is shown in which the upper and lower circuits are connected using a connecting member in which the conductive particles are dispersed in an adhesive.

When the hard spacer material plated as the conductive particles is used, the conductive particles are in point contact with the circuit surface, so that when the temperature changes or in an environment of high humidity, the conductive particles are used as an adhesive. Since the thermal expansion coefficient and elastic modulus of the conductive particles are different, sufficient contact points cannot be secured, and sufficient connection reliability cannot be obtained.

When conductive particles plated with an elastic material are used, it is extremely difficult to control connection with the same thickness as the gap thickness, and most of the vertical conduction parts of the display panel are provided at the panel end. As a result, residual stress occurs in the panel substrate, and sufficient connection reliability cannot be obtained.

In addition, in order to obtain good connection reliability, if the temperature and pressure at the time of connection are set high in order to increase the contact area between the conductive particles and the electrode, the thin metal layer may peel off from the elastic substance. Partially destroyed, and scattered around the connection circuit, resulting in insufficient insulation from adjacent circuits when connecting fine circuits.

Further, it is possible to mix the above-mentioned two kinds of conductive particles and disperse them in an adhesive. In this case, it is necessary to uniformly disperse these mixed particles, but the uniform dispersibility in the minute portion is insufficient due to the difference in specific gravity and the difference in surface charge.

Generally, a display panel has a circuit thickness of 2
It is often formed of a thin film having a thickness of less than μm, and there is little step difference between the circuit portion and the space portion. It is a means for improving the connection reliability of deformable conductive particles that are conductive particles plated on a conventionally known elastic substance, and greatly deforms the particles of the circuit part to make surface contact to reduce the deformation of the conductive particles of the space part. The means for obtaining insulation from the adjacent circuit is not suitable for the connection structure of the display panel because the difference between the circuit portion and the space portion is small.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and the upper and lower circuits are substantially separated from each other by the particle size of the hard particles, and the conductive particles are thin. It is intended to provide a highly reliable display panel in which a layer is in surface contact with a connection circuit surface.

[0009]

That is, according to the present invention, spacer particles 9 are sandwiched together with electro-optical substance 8 between circuits (6, 7) of two opposed substrates on which circuits are formed, and upper and lower circuits are provided. The upper and lower circuits (6, 7) are separated by a constant thickness.
In the display panel in which 7) is connected to the conductive particles by the adhesive 5, the conductive particles have a softer polymer layer 2 on the surface of the hard particles 1 having substantially the same diameter as the spacer particles 9. Conductive particles formed by coating and further coating the conductive metal thin layer 3, wherein the upper and lower circuits (6, 7) are substantially separated from each other by the particle size of the hard particles 9. The present invention provides a display panel characterized in that the metal thin layer 3 of 1 is in surface contact.

FIG. 1 is a schematic cross-sectional view of an example of conductive particles used in the present invention.

Reference numeral 1 is a hard particle serving as a core of the conductive particle, and metal particles such as nickel, inorganic particles such as glass fiber, alumina and silica, and resin cured product particles such as cured benzoguanamine are preferably used. Further, polymer particles such as epoxy resin and polystyrene may be used. Here, the meaning of “hard” means that the conductive particles are relatively hard as compared with the soft polymer layer 2 under the connection conditions considered to be the maximum temperature under the use environment. That is, it is possible to make a judgment using a general index of hardness such as elastic modulus and hardness at a constant temperature or a difference of thermal transformation points such as a melting point, a glass transition temperature and a softening point.

The hard particles 1 have an average particle size of 0.1 to 20 μm.
m, preferably 0.5 to 12 μm, more preferably 1 to
The thickness of 8 μm is preferable because the distance between the electrodes after connection can be narrowed and the connection reliability can be improved. It is preferable that the hard particles 1 have a uniform particle diameter, and it is preferable to use the spacer particles between the circuits sandwiching the electro-optical material as they are as the hard particles. In this case, the hard particles have the same diameter as the spacer particles. Further, the thickness of the soft polymer layer 2 and the thin conductive metal layer 3 may be subtracted so that the thickness after connection may be made more equal to the diameter of the spacer particles. In this case also, the diameter of the hard particles is a spacer. It is assumed to be substantially the same as the particle diameter.

For the soft polymer layer 2, a polymer such as polystyrene, nylon and various rubbers is used as it is or as a crosslinked body. Since this crosslinked product has excellent solvent resistance, it does not elute into the adhesive when the solvent is contained in the adhesive and has little effect on the properties of the adhesive, and is therefore preferably used. Specifically, one obtained by cross-linking polystyrene with divinylbenzene is preferably used.
The thickness of the soft polymer layer 2 is 0.1 to 10
About μm is preferable. If it is less than 0.1 μm, a sufficient amount of deformation cannot be obtained and reliability is insufficient, and if it exceeds 10 μm, the amount of deformation becomes excessive and the coating of the metal thin layer easily peels off. For this reason, 0.3-5 μm is preferable, and 0.5-3
μm is more preferable. At this time, the soft polymer layer 2
Is less than or equal to the particle size of the hard particles 1, more preferably 1 /
When it is 2 or less, the amount of deformation of the conductive particles can be easily controlled.

The soft high molecular weight polymer layer 2 may be present in the form of particles as shown in FIG. 2, or may be composed of a single layer or multiple layers. Those having a structure of two or more layers are preferably used because the functions such as strength retention, solvent resistance, adhesiveness, flexibility, heat resistance, and plating solution resistance can be shared by each layer. The means for forming the soft polymer layer 2 is not limited, and examples thereof include a spray method, a high-speed stirring method, a spray dryer method, and a hot melt fixing method.

For the thin metal layer 3, various conductive metals, alloys and oxides can be used. Materials preferably used in consideration of conductivity and corrosion resistance include Ni, Cu, and
There are Al, Sn, Zn, Au, Pd, Ag, Co, Pb, and the like, and these can be configured as a single layer or multiple layers.

The metal thin layer 3 can be formed by vapor deposition,
Sputtering method, ion plating method, thermal spraying method,
Although a general method such as a plating method may be used, an electroless plating method is preferable because a coating layer having a uniform thickness can be obtained, and the thickness is preferably 1 μm or less in order to obtain deformation followability.

As shown in FIG. 3, if necessary, the surface of the thin metal layer 3 may be further covered with a resin layer 4 which is meltable under the connecting condition. In this case, the resin layer melts and becomes connectable on the contact surface with the electrode under heat and pressure,
Since the amount of heat is insufficient in the direction of the adjacent electrodes, the resin layer is less likely to melt, so that the insulation is less deteriorated and it is possible to mount higher density fine electrodes. The resin layer 4 can also be an adhesive resin.

If necessary, an auxiliary layer such as a coupling agent or a primer for improving the adhesion can be formed between the above-mentioned coating layers.

The upper and lower circuits are connected using the above-mentioned conductive particles and an adhesive. It is preferable that the conductive particles be uniformly dispersed in the adhesive. It is necessary to make the particle diameter of the conductive particles smaller than the minimum width of the distance between the adjacent wiring patterns in order to prevent a short circuit with the adjacent wiring patterns and to cope with the thinning of the wiring. The conductive particles dispersed in the adhesive can have a role of connecting the upper and lower circuits and a role of a sealing material for sandwiching the electro-optical substance between the circuits of the two opposing substrates. . The dispersion form may be liquid, paste, film or the like. In this case, the film-like shape is particularly useful for improving workability since a uniform thickness is easily obtained and a coating operation is unnecessary. An epoxy resin or the like is preferably used as the adhesive. A thermoplastic material may be used, but a curable material by energy of heat, light, electron beam or the like is preferably used because it has excellent heat resistance and moisture resistance. As the sealing material, it is necessary to reduce the impurity level of the adhesive, and it is preferable to use an adhesive in which the extracted water after extraction with pure water at 100 ° C. for 10 hours has Na ⁺ and Cl ⁻ levels of 20 ppm or less, respectively.

The ratio of the conductive particles mixed in the adhesive is
The amount is 0.1 to 20% by volume, preferably 0.2 to 10% by volume, and more preferably 0.5 to 6% by volume, based on the total amount of the adhesive and the conductive particles. If the amount added is small, the number of conductive particles on the electrodes (circuits) to be connected is reduced, resulting in a decrease in reliability.

A connection structure of a display panel using the conductive particles of the present invention will be described with reference to FIGS. 4 and 5. In FIG. 4, an electro-optical material 8 such as liquid crystal is sandwiched between the upper and lower circuits 6 and 7 by the hard particles 1 which also serve as spacers and have a constant thickness. Although not shown, these circuits are formed on a substrate such as glass or plastic.

When connecting the upper and lower circuits 6 and 7 at the terminal end, the space between the upper and lower circuits is controlled by the particle size of the hard particles 1 in the conductive particles by heating and pressurizing at the time of connection. Fixed. At this time, since the soft polymer layer 2 on the hard particles 1 is deformable, it becomes extremely thin at the contact portion with the circuit by heating and pressurization, and the metal thin layer 3 is broken to a small extent. Makes surface contact with the circuit. At this time, the thin metal layer 3 does not peel off because it follows the soft polymer layer 2. In the lateral direction of the electrode, insulation can be maintained by controlling the amount of conductive particles added and the particle size.

In the case of the conductive particles having the resin layer 4 on the surface shown in FIG. 3, as shown in FIG. 5, the conductive particles are heated with the resin layer 4 as an adhesive without being dispersed in the adhesive. It can also be fixed to the circuit surface by pressure or the like. In this case,
As described above, the electro-optical substance 8 may be sealed by separately providing a sealing means by using the adhesive 5 which is a normal sealing material, or may be mixed with the adhesive 5 and used together as in FIG. Good.

[0024]

In the present invention, since the conductive thin metal layer 3 is formed on the soft polymer layer 2, it has deformation followability, and the maximum amount of deformation is controlled by the hard particles 1 serving as the core. , It is difficult to peel off even if it is excessively deformed at the time of connection. In addition, the soft polymer layer 2 on the hard particles 1 is more likely to be deformable than a metal, and more easily adhesive to a metal or hard particles. Therefore, a connection with low resistance and excellent reliability can be obtained. Also,
It is possible to set an appropriate combination depending on the heat resistance and hardness of the connection electrode and the substrate.

Hard particles 1 serving as nuclei are harder than soft polymer layer 2 when heated and pressed at the time of electrode connection, so that there is almost no deformation, or there is little deformation. be able to. Therefore, the thickness after connection by heating and pressurization can be controlled to the size of the particle diameter of the hard particles 1, so that a stable connection can be obtained even if the connection conditions are not taken into consideration.

The display panel of the present invention is excellent in reliability because the conductive particles can surely make surface contact with a thin film having a low circuit height.

[0027]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1 Polystyrene / divinylbenzene (weight ratio) = 100/2 (glass transition point 120) on the surface of cured benzoguanamine particles having an average particle size of 3 μm (glass transition point 180 ° C. or higher).
Particles having an average particle diameter of 1 μm, which are formed by using a spray dryer with alcohol as a dispersant, and then heated at 130 ° C. by this apparatus to fix the coating layer.

The particles are dispersed in water, and after a palladium chloride-based activation treatment, an electroless Ni plating solution is used to obtain Ni.
After plating at 90 ° C., displacement plating was performed at 70 ° C. using an Au plating solution to obtain conductive particles. At this time Ni
The thickness of / Au was 0.2 / 0.02 μm. The particles had the structure shown in FIG.

The conductive particles are added in an amount of 2% by volume to an adhesive containing a high molecular weight epoxy resin as a main component, and a thickness of 20 μm
Adhesive (Na in the extracted water after extraction with pure water at 100 ° C for 10 hours)
^+, Cl ^- to obtain a connection member formed with 10ppm or less) layer polytetrafluoroethylene film 50μm on each.

On a glass substrate having a thickness of 1.1 mm, indium oxide having a thickness of 0.2 μm (ITO, surface resistance 20 Ω /
The connection member was placed at a width of 1.5 mm on the ends of the two panels having the thin film circuit of □), the upper and lower circuits were aligned, and the upper and lower circuits were connected by changing the connection conditions for evaluation. . Each circuit has a circuit pitch of 100 μm and an electrode width of 50 μm.
m is an electrode composed of a parallel circuit. The connection condition is that the temperature of the connection part is 150, 170, 190 ° C and the pressure is 5, 2.
The value was widely varied from 0 to 100 kgf / mm ² . After that, a liquid crystal was sealed by using hardened benzoguanamine particles having an average particle diameter of 3.5 μm as a spacer, and a display panel was produced.

As a result of the evaluation, under the above-mentioned wide range of connection conditions, the connection thickness was controlled to 3.5 μm, which is approximately equal to the sum of the average particle size of the spacer and the thickness of the thin metal layer, and all of them were excellent. It showed long-term connection reliability. In addition, when observing the conductive particles of the connection part under different connection conditions with a scanning electron microscope, the contact part with the electrode buckled and micro cracks were seen in both cases, and it was a chrysanthemum flower shape, but No peeling was observed and they were in surface contact.

Further, the impurity level of the adhesive was low, and it could be used also as a sealing material for liquid crystal.

Example 2 Similar to Example 1, except that cured benzoguanamine particles having an average particle size of 3 μm were replaced with silica particles (100 μm) having an average particle size of 5 μm.
The composition was changed to stable at 0 ° C.) to obtain particles having the constitution of FIG. 1 and the same evaluation was performed. Similar to Example 1, good connection reliability was exhibited under a wide range of connection conditions, and the connection thickness was controlled to 5 μm, which is the average particle diameter of the hard particles. In this example, the hard particles were harder inorganic particles, so that the gap control could be performed more accurately.

Example 3 Polystyrene / divinylbenzene (weight ratio) = 100 /
20 (glass transition point 170 ° C.) particle size of 6 μm,
A layer of polystyrene / divinylbenzene (weight ratio) = 100/1 (glass transition point 115 ° C.) was provided as a coating layer, and then polymerized at 80 ° C. to obtain composite particles having a particle size of 8 μm. Then, in the same manner as in Example 1, a thin metal layer was formed on the surfaces of the composite particles to prepare conductive particles, which were used to obtain a connecting member. Use this connecting member to connect the upper and lower circuits to 1
Connection was made at 50 ° C., 20 kgf / mm ² , 20 seconds. Also in this case, the connection thickness was controlled to 6 μm, which is the average particle diameter of the hard particles. In this example, since the hard particles and the material of the coating layer were changed only by changing the crosslink density, it was possible to easily obtain particles having excellent adhesion between layers.

Example 4 The conductive particles of Example 1 were prepared using nylon (glass transition point 110
C.) alcohol solution, and then dried at 60.degree. C. to obtain particles having the constitution of FIG. 3 having a nylon layer with a thickness of 1-2 .mu.m on the surface. The particles were placed in an adhesive similar to that of Example 1,
The same evaluation was performed by increasing the addition amount to 6% by volume.

Also in this case, good connection reliability was obtained under a wide range of connection conditions, and the distance between the electrodes was controlled to 3 μm, which is the average particle diameter of the hard particles.

In this example, although the amount of conductive particles added was increased to 6% by volume, the insulating property in the adjacent direction was good.

[0039]

As described in detail above, according to the present invention, the conductive particles are obtained by coating the surface of hard particles with a polymer layer softer than the hard particles and further coating with a thin conductive metal layer. By doing so, it is possible to easily obtain a display panel having a stable connection thickness under a wide connection condition and good connection reliability due to surface contact of the conductive particles.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing conductive particles suitable for carrying out the present invention.

FIG. 2 is a schematic sectional view showing conductive particles suitable for carrying out the present invention.

FIG. 3 is a schematic cross-sectional view showing conductive particles suitable for implementing the present invention.

FIG. 4 is a schematic sectional view showing a display panel showing one embodiment of the present invention.

FIG. 5 is a schematic sectional view showing a display panel showing one embodiment of the present invention.

[Explanation of symbols]

 1 Hard Particles 2 Soft High Polymer Layer 3 Metal Thin Layer 4 Resin Layer 5 Adhesive 6 Upper Circuit 7 Lower Circuit 8 Electro-Optical Material 9 Spacer Particles

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Goto 1500 Ogawa, Shimodate, Ibaraki Prefecture Shimodate Laboratory, Hitachi Chemical Co., Ltd. (72) Kyohisa Ota 1500 Ogawa, Shimodate, Ibaraki Hitachi Chemical Co. Company Shimodate Institute

Claims (1)

[Claims] 1. Spacer particles 9 together with an electro-optical substance 8 between circuits (6, 7) of two opposed substrates on which circuits are formed.
In the display panel in which the upper and lower circuits (6, 7) are sandwiched by a constant thickness and the upper and lower circuits (6, 7) are connected by the conductive particles and the adhesive 5, the conductive particles are the spacer particles 9 Is a conductive particle formed by coating a surface of a hard particle 1 having substantially the same diameter as that of a high molecular polymer layer 2 softer than the hard particle 1 and further coating a conductive metal thin layer 3 thereon. The display panel is characterized in that the thin metal layer 3 of the conductive particles is in surface contact with the circuit surface with the intervals of 6 and 7) being separated by the interval of the particle diameter of the hard particles 9.