JP3280139B2 - Display panel - Google Patents

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 electroluminescent 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 Application Laid-Open No. 58-182885 is known. In this method, an electro-optical substance is interposed between circuits provided on a substrate, and upper and lower circuits separated by a certain thickness by spacers are connected by using an upper and lower conductive material made of conductive particles and an adhesive. . The publication discloses conductive particles obtained by plating (metallizing) the surface of a hard spacer material such as glass fiber or alumina, or plating the surface of an elastic material having a larger particle diameter than a spacer such as a plastic ball or plastic fiber (metaizing). Rising)
An example is shown in which the upper and lower circuits are connected using a connection member in which the conductive particles thus dispersed are dispersed in an adhesive.

[0003] In the case of using a plated hard spacer material as the conductive particles, the conductive particles are in point contact with the circuit surface, and may change with temperature or in an environment of high humidity, etc. with the adhesive. Since the thermal expansion coefficient and the 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 on an elastic material are used, it is extremely difficult to control the connection with the same thickness as the gap thickness, and in addition to the fact that many of the upper and lower conductive portions of the display panel are provided at the panel end. As a result, residual stress is generated in the panel substrate, and sufficient connection reliability cannot be obtained.

[0005] In addition, if the temperature and pressure at the time of connection are set high to increase the contact area between the conductive particles and the electrode in order to obtain good connection reliability, the thin metal layer may peel off from the elastic material. It scatters around the connection circuit due to partial destruction or the like, and the insulation between adjacent circuits becomes insufficient when a fine circuit is connected.

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

In general, a display panel has a circuit thickness of 2
It is often formed of a thin film having a thickness of μm or less, and the step between the circuit portion and the space portion is small. It is a means for improving the connection reliability of deformable conductive particles, which are conductive particles plated on a conventionally known elastic material. Means for obtaining insulation from an adjacent circuit is not suitable for a connection structure of a display panel because there is little difference between a circuit portion and a space portion.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and the space between the upper and lower circuits is substantially separated by the size of the hard particles, and the conductive particles are made of thin metal. An object of the present invention is 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, a spacer particle 9 is sandwiched together with an electro-optical substance 8 between circuits (6, 7) of two opposing substrates on which circuits are formed, and an upper and lower circuit is formed. The upper and lower circuits (6, 7) are separated by a certain thickness between (6, 7).
7) connecting the conductive particles to the hard particles 1 having substantially the same diameter as the spacer particles 9 in the display panel connecting the conductive particles with the adhesive 5. The conductive particles formed by coating and further covering the conductive metal thin layer 3, wherein the distance between the upper and lower circuits (6, 7) is substantially separated by the distance of the particle diameter of the hard particles 9, and the conductive particles The display panel is characterized in that the metal thin layers 3 are in surface contact with each other.

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

Reference numeral 1 denotes hard particles serving as nuclei of the conductive particles. Metal particles such as nickel, inorganic particles such as glass fiber, alumina and silica, and resin cured particles such as cured benzoguanamine are preferably used. Also, polymer particles such as epoxy resin and polystyrene may be used. Here, the meaning of “hard” means that the conductive particles are relatively harder than the soft polymer layer 2 under the connection condition considered to be the highest temperature in the usage environment of the conductive particles. That is, a general index of hardness such as elastic modulus or hardness at a certain temperature or a difference between thermal transformation points such as a melting point, a glass transition temperature, and a softening point can be determined as a guide.

The average particle size of the hard particles 1 is 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 electrodes after connection can be reduced to improve connection reliability. The particle size of the hard particles 1 is preferably uniform, and it is preferable to use the spacer particles between circuits in which the electro-optical material is sandwiched as the hard particles as they are. In this case, the hard particles have the same diameter as the spacer particles. The thickness of the soft polymer layer 2 or the conductive metal thin layer 3 may be subtracted to make the thickness after connection more consistent with the diameter of the spacer particles. It is assumed that the diameter is substantially the same as the particle diameter.

The soft polymer layer 2 is made of a polymer such as polystyrene, nylon, or various rubbers as it is or as a crosslinked body. Since this crosslinked product has excellent solvent resistance, it is preferably used because when a solvent is contained in the adhesive, it does not elute into the adhesive and has little effect on the properties of the adhesive. Specifically, those obtained by crosslinking polystyrene with divinylbenzene are preferably used.
The thickness of the soft polymer layer 2 is 0.1 to 10
About μm is preferable. If the thickness is less than 0.1 μm, sufficient deformation cannot be obtained and reliability is insufficient. If the thickness exceeds 10 μm, the deformation is excessive and the coating of the thin metal layer is easily peeled off. For these reasons, 0.3 to 5 μm is preferable, and 0.5 to 3 μm is preferable.
μm is more preferred. 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 is easily controlled.

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

The metal thin layer 3 can be made of various conductive metals, alloys, oxides and the like. Materials preferably used in view of conductivity and corrosion resistance include Ni, Cu,
There are Al, Sn, Zn, Au, Pd, Ag, Co, Pb, and the like, and these can have a single-layer structure or a multilayer structure.

The means for forming the thin metal layer 3 includes a vapor deposition method,
Sputtering, ion plating, thermal spraying,
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 is 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 that can be melted under connection conditions. In this case, the resin layer is melted on the contact surface with the electrode under heating and pressurization, and connection becomes possible.
In the adjacent electrode direction, the amount of heat is insufficient, so that the resin layer hardly melts, so that the insulating property is hardly reduced, so that a finer electrode with higher density can be mounted. The resin layer 4 can be made of an adhesive resin.

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

The upper and lower circuits are connected using the conductive particles and the adhesive. It is preferable that the conductive particles are uniformly dispersed in the adhesive. It is necessary to make the particle size of the conductive particles smaller than the minimum width of the distance between adjacent wiring patterns in order to prevent short circuit with adjacent wiring patterns and to cope with thinning of wiring. The conductive particles dispersed in the adhesive can serve both to connect the upper and lower circuits and to serve as a sealant for sandwiching the electro-optical substance between the circuits of the two opposing substrates. . The dispersion form may be any of a liquid form, a paste form, and a film form. In this case, when the film is in the form of a film, a constant thickness can be easily obtained, and a coating operation is not required, which is particularly useful for improving workability. An epoxy resin or the like is preferably used as the adhesive. Although a thermoplastic material may be used, a curable material using energy such as heat, light, or an electron beam is preferably used because of its excellent heat resistance and moisture resistance. As the sealing material, it is necessary to lower the impurity level of the adhesive, and it is preferable to use an adhesive having Na ⁺ and Cl ⁻ of 20 ppm or less, respectively, in the extraction water after extraction with pure water at 100 ° C. for 10 hours.

The proportion of the conductive particles mixed in the adhesive is as follows:
It is 0.1 to 20% by volume, preferably 0.2 to 10% by volume, more preferably 0.5 to 6% by volume, based on the total amount of the adhesive and the conductive particles. If the addition amount is small, the number of conductive particles on the electrode (circuit) to be connected is reduced, so that the reliability is reduced. If the addition amount is too large, the insulating property in the direction of the adjacent electrode is reduced, and it becomes difficult to connect the fine electrode.

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

In connecting the upper and lower circuits 6 and 7 at the end, the distance between the upper and lower circuits is controlled to the particle size of the hard particles 1 in the conductive particles by the heating and pressurizing at the time of connection, and the adhesive 5 is used. Fixed. At this time, since the soft high-molecular polymer layer 2 on the hard particles 1 has a deformability, it becomes extremely thin at a contact portion with a circuit by heating and pressing, and accompanying this, the thin metal layer 3 is broken small. Makes surface contact with circuit. At this time, since the thin metal layer 3 follows the soft polymer layer 2, there is no peeling. Insulating properties can be maintained in the lateral direction of the electrode 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 and heated using 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, FIG.
As shown in FIG. 4, the electro-optical material 8 may be sealed by separately providing a sealing means using an 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 metal thin layer 3 is formed on the soft polymer layer 2, it has a deformation follow-up property, and the maximum deformation amount is controlled by the hard particles 1 serving as nuclei. Also, it is hard to peel off due to excessive deformation at the time of connection. Further, the soft polymer layer 2 on the hard particles 1 can easily obtain deformability as compared with metal, and can easily obtain adhesion to metal and hard particles. Therefore, a connection with low resistance and excellent reliability can be obtained. Also,
Combinations can be set as appropriate depending on the heat resistance and hardness of the connection electrodes and the substrate.

The hard particles 1 serving as nuclei are hardly deformed or hardly deformed when heated and pressurized at the time of electrode connection because they are harder than the soft polymer layer 2. be able to. Therefore, since the thickness after connection by heating and pressing can be controlled to the size of the particle size of the hard particles 1, a stable connection can be obtained even if the connection conditions are not taken into account.

The display panel of the present invention is excellent in reliability because the conductive particles can surely make surface contact even in the case of 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 it should not be construed that the invention is limited thereto.

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

After dispersing the particles in water and activating a palladium chloride system, the particles are dispersed in Ni using an electroless Ni plating solution.
After plating was performed 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 above-mentioned conductive particles were added at 2% by volume to an adhesive mainly composed of a high molecular weight epoxy resin, and the thickness was 20 μm.
Adhesive (Na of extraction water after extraction with pure water at 100 ° C for 10h)
^{+ And} Cl ^- are each 10 ppm or less) to obtain a connection member having a layer formed on a polytetrafluoroethylene film of 50 μm.

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 members were placed at 1.5 mm width on the ends of two panels having thin film circuits, and after positioning of the upper and lower circuits, the connection conditions were changed for evaluation and the upper and lower circuits were connected. . Each circuit has a circuit pitch of 100 μm and an electrode width of 50 μm
The electrodes are composed of m parallel circuits. The connection conditions were as follows: connection temperature: 150, 170, 190 ° C .;
It was widely varied to 0 and 100 kgf / mm ² . Thereafter, a liquid crystal was sealed using the cured benzoguanamine particles having an average particle size of 3.5 μm as spacers to produce a display panel.

As a result of the evaluation, the connection thickness was controlled to 3.5 μm, which was substantially equal to the sum of the average grain size of the spacer and the thickness of the thin metal layer, under the above-described wide range of connection conditions. It showed long-term connection reliability. In addition, when the conductive particles at the connection part under different connection conditions were observed with a scanning electron microscope, the contact part with the electrode was buckled and small cracks were observed, and the shape of the metal layer was Peeling was not seen and surface contact was made.

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

Example 2 As in Example 1, but cured benzoguanamine particles having an average particle size of 3 μm were replaced with silica particles (100
(Stable at 0 ° C.) to obtain particles having the configuration shown in FIG. 1, and the same evaluation was performed. As in 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 size of the hard particles. In this example, since the hard particles were harder inorganic particles, the gap control could be performed more accurately.

Example 3 Polystyrene / divinylbenzene (weight ratio) = 100 /
On a 6 μm particle having a particle size of 20 (glass transition point 170 ° C.),
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. Next, a thin metal layer was formed on the surface of the composite particles in the same manner as in Example 1 to produce conductive particles, and a connection member was obtained using the conductive particles. Using this connecting member, one upper and lower circuit
The connection was performed at 50 ° C., 20 kgf / mm ² for 20 seconds. Also in this case, the connection thickness was controlled to 6 μm, which is the average particle size of the hard particles. In this example, since the materials of the hard particles and the coating layer were changed only by changing the crosslink density, particles having excellent adhesion between the layers could be easily obtained.

Example 4 The conductive particles of Example 1 were converted to nylon (glass transition point 110
C.), dried at 60.degree. C. to obtain particles having a nylon layer having a thickness of 1 to 2 .mu.m on the surface and having the structure shown in FIG. The particles were placed in the same adhesive as in 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 size of the hard particles.

In this example, the insulation in the adjacent direction was good even though the addition amount of the conductive particles was increased to 6% by volume.

[0039]

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

[Brief description of the drawings]

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

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

FIG. 3 is a schematic sectional view showing conductive particles suitable for carrying out the present invention.

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hard particle 2 Soft polymer layer 3 Metal thin layer 4 Resin layer 5 Adhesive 6 Upper circuit 7 Lower circuit 8 Electro-optical material 9 Spacer particle

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yasushi Goto 1500 Ogawa Ogawa, Shimodate City, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd. (56) References JP-A-4-153625 (JP, A) JP-A-4-3333025 (JP, A) JP-A-5-249483 (JP, A) Jpn. (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/1345 G09F 9/30 331 G02F 1/1339

Claims (1)

(57) [Claims] A spacer particle (9) together with an electro-optical substance (8) between circuits (6, 7) of two opposing substrates on which circuits are formed.
In a display panel in which the upper and lower circuits (6, 7) are connected to each other by a conductive material and an adhesive 5 with a predetermined thickness between the upper and lower circuits (6, 7), the conductive particles are The conductive particles are formed by coating the surface of hard particles 1 having substantially the same diameter as the polymer polymer layer 2 which is softer than this, and further covering the conductive metal thin layer 3. 6. A display panel wherein the intervals of 6 and 7) are separated by the interval of the particle size of the hard particles 9 and the thin metal layer 3 of conductive particles is in surface contact with the circuit surface.