JP3324798B2 - Electro-optical device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electro-optical device, such as a liquid crystal display device, having a characteristic of conductive connection with a circuit board, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Various methods are known for electrically connecting a circuit board, such as a flexible printed circuit board, to an external circuit by connecting a terminal portion formed on a glass substrate, such as a liquid crystal display device, with a circuit board. ing.

Specifically, In ₂ O ₃ —SnO at a terminal portion is used.
A method of applying electroless nickel plating or the like to a transparent electrode such as ₂ (ITO) or SnO ₂ and soldering, a method of using an anisotropic conductive film, a method of using a conductive rubber connector, and the like have been used.

[0004] The soldering method has the highest adhesion and the highest reliability, but requires a plating step, and has a problem that terminals are short-circuited by a solder bridge or exposed to a high temperature during soldering. . In addition, the reliability of the conductive rubber connector is reduced when the pitch of the terminals is narrow, and the connection is maintained by the elastic force of the rubber, so that there is a problem in reliability for a long period of time. In addition, for connection using an anisotropic conductive film, a relatively high temperature and pressure such as heating to about 170 to 180 ° C. and pressurizing to about 30 to 40 kg / cm ² during curing of the film are required. The adhesion is weak, and there is a problem that it is about 0.5 to 1 kg / cm.

Therefore, taking advantage of the characteristics of the anisotropic conductive film,
To compensate for the shortage of adhesive force, which is a drawback, after conducting conductive connection with an anisotropic conductive film, supply another insulating uncured resin from above and cure it, or hold it with clips. It has been reinforced.

[0006]

However, when another insulating uncured resin is supplied and cured later as described above,
The process is troublesome, and the gap between the end face of the board facing the board on which the terminal portion is formed, the circuit board, and the tip is extremely narrow, so that it is difficult to fill the gap with a resin without any gap. The part where the electrode of the terminal is exposed outside the seal of the electro-optical element is susceptible to corrosion due to the influence of moisture in the air, etc., and particularly, when only a specific narrow area is exposed, the part becomes remarkable. There was a problem of being easily corroded.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and comprises a pair of substrates with electrodes arranged such that the electrode surfaces face each other, and sealing the periphery to form an inner portion. In addition to sandwiching the electro-optic medium, one substrate protrudes from the other substrate to form a portion that does not face the other substrate, and the electrode of the portion that does not face the other substrate is used as a terminal portion to be flexible. in the electro-optical device formed by connecting a printed circuit board and the conductive, terminal partial electrodes and off
The electrodes on the flexible printed circuit board face each other
Are arranged so that the end face and the other end face of the substrate of the flexible printed circuit board is opposed, terminal portions electrodes and flexible
The electrodes of the shivable printed circuit board are connected by a connecting material including an insulating photocurable material and conductive particles mixed in the photocurable material, and the connecting material is at least the other end of the electrode of the terminal portion. An electro-optical device characterized by being filled to a height reaching the end face of the substrate.

Further, a pair of substrates with electrodes are arranged so that the electrode surfaces face each other, the periphery is sealed, an electro-optical medium is sandwiched inside, and one substrate is projected from the other substrate. Form a part that does not face the other substrate,
In the production process of the electro-optical device for connecting a flexible printed circuit board and the conductive electrode substrate and the opposite is not part of the other as a terminal portion, the terminal portion electrodes and Furekishibu
At least one of the electrodes of the printed circuit board is supplied with an uncured connection material containing an insulating photocurable material and conductive particles mixed in the photocurable material, and is electrically connected to the electrode of the terminal part by a flexible material. crimp by opposite the printed circuit board electrodes, electrodes and flexible connection member is the terminal portion of the uncured
A method of manufacturing an electro-optical device, comprising: flowing out of a portion of a shiver printed circuit board facing an electrode to a seal side so as to reach at least an end surface of the other circuit board; and thereafter irradiating light to cure a connecting material. I do.

In the electro-optical element used in the electro-optical device of the present invention, a pair of substrates with electrodes are arranged so that the electrode surfaces face each other, the periphery is sealed to hold the electro-optical medium inside, A substrate is formed so as to protrude with respect to the other substrate to form a portion not opposed to the other substrate, and an electrode of a portion not opposed to the other substrate is electrically connected to the flexible printed board. It is a terminal part.
As a specific example, there is a liquid crystal optical element in which a liquid crystal is sandwiched between substrates with electrodes in which a transparent electrode such as ITO or SnO ₂ is formed on a substrate such as glass or plastic. Other optical elements can be used.

On this substrate, a color filter, a light shielding film, a retardation plate, a polarizing plate, a TFT,
An IM, a metal wiring, a reflective layer, various insulating layers, and the like may be formed. Further, the substrate itself may be a color filter, a retardation plate, a polarizing plate, a reflecting plate, a semiconductor substrate, or the like, if necessary.

The electro-optical device according to the present invention has a terminal portion outside a region where two electrode substrates are sealed opposite to each other, that is, one electrode substrate is opposed to another electrode substrate. It has an electrode part which is not provided, and that part becomes a terminal part. The structure is such that a conductive connection is made to the flexible printed board through the electrodes at the terminal portions.

A flexible pre- electro-optical device according to the present invention.
The cross-sectional view of a state of connecting cement substrate and a conductive shown in FIG.
In FIG. 1, 1A and 1B are substrates made of glass, plastic or the like, 2A and 2B are electrodes made of ITO or SnO ₂ , 3 is a seal for bonding both substrates, and 4 is a connector for connecting to an external circuit.
A circuit board which is a flexible printed board , 5 is an electrode on the circuit board, 6 is a conductive particle, 7 is an insulating photocurable material, and a board on which the end surface of the circuit board 4 and the terminal portion are formed. The substrate 1B is disposed so that an end face of the substrate 1B facing the substrate 1A faces the end face of the substrate 1B.

As is apparent from this figure, the lower substrate 1A extends and protrudes to the right with respect to the opposite substrate 1B on the right side of the figure, and the electrodes formed thereon constitute the terminal portions. ing. The electrode of this terminal part is the electrode 5 of the circuit board 4.
Are arranged such that the electrodes face each other, are adhered by an insulating photo-curable material 7, and a conductive connection is established by conductive particles 6 therein.

This diagram is exaggerated for the sake of simplicity. Therefore, only three conductive particles are shown between the electrodes. However, while in the actual device the conductive particles are diameter of about several [mu] m, the substrate and the frame
The opposing portions of the electrodes of the xivable printed circuit board have a length on the order of mm and the width of the electrodes is several hundred μm, so that an extremely large number of conductive particles contribute to the conductive connection.

According to the present invention, a connecting material obtained by mixing conductive particles into the insulating photo-curable material is used to form a flexible connection with an electrode of a substrate.
The filling is performed not only at the portion where the electrode of the shivable printed board is opposed, but also at a height from the electrode of the terminal portion to at least the end face of the substrate facing the substrate on which the terminal portion is formed. This allows flexible printing
The adhesion of the substrate to the substrate is increased, and
It has the advantage of requiring only one light irradiation. In addition, since the photocuring is performed, no heating is required or a much lower temperature may be used, so that deterioration due to heating can be prevented.

Furthermore, since it is possible to use the same material as the material for the electrically conductive connection as the material for reinforcement, a flexible flop
It is easy to fill the space between the tip of the lint substrate and the end surface of the substrate facing the substrate on which the terminal portion is formed, and it is also useful for suppressing corrosion due to exposure of the electrodes.

Although various methods are conceivable for manufacturing the electro-optical device of the present invention, the electro-optical device can be easily manufactured by the following method. At least one of an electrode of a terminal portion of an electro-optical element and an electrode of a flexible printed board using a connecting material in which conductive particles are mixed with an insulating photo-curable material having a relatively low viscosity in an uncured state. Then, an uncured connecting material is attached by a method such as printing or a dispenser.

Next, the electrode of the terminal portion and the flexible
The electrodes of the lint substrate are opposed to each other and pressure-bonded. As a result, the connection material flows toward the seal side from the opposing portion of the electrode of the terminal portion and the electrode of the flexible printed board, and spreads.
At this time, excess material that has flowed out to the opposite side may be wiped off as necessary. This pressure bonding is performed by appropriately adjusting the viscosity of the photocurable material in the uncured state, so that the pressure is considerably lower than that of the anisotropic conductive film (6 to 10 kg / kg).
cm ² ).

[0019] The connection material flowing out to the seal side, frame
The space between the tip of the xivable printed board (the left end of the circuit board 4 in FIG. 1) and the end face of the board 1B (the right end of the board 1B in FIG. 1) facing the board 1A on which the terminal portion is formed is filled. You. In this case, by increasing the amount flowing out, frame
You may make it reach | attain to the upper surface (surface opposite to the electrode 5) of a xivable printed circuit board. However, it is preferable not to reach the upper surface (the surface opposite to the electrode 2B) of the substrate 1B. This is because a polarizing plate is provided on the upper surface of the substrate 1B,
This is because a color filter, a phase difference plate, and the like are often mounted. Further, it is preferable that the gas is also flown out to the right end side of the substrate 1A so as to partially cover the right end surface of the substrate 1A.

As the insulating photocurable material used in the present invention, a material known as an insulating photocurable resin is usually employed. The insulating property may be any as long as it does not cause a short circuit between adjacent terminals, and may be selected within a range in which leakage current does not cause a problem for each electro-optical device. Specifically, a cured product having a specific resistance of about 10 ⁸ Ω · cm or more is recommended. In the case where the terminal interval is wide, the device can be used even if the specific resistance is lower than this, so that the selection may be made within the range where the leak current does not cause a problem in each element as described above.

In the present invention, the uncured photocurable material is
It is cured by light irradiation. As the light, visible light, ultraviolet light, or the like can be used, but it is advantageous that the curing hardly progresses during storage and application steps. Therefore, it is preferable that the light be cured by ultraviolet light. Specifically, a material that is cured using a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, or the like is preferable.

The photocurable material is, specifically, a resin such as an acrylic resin, a polyimide resin, a polyamide resin, or a silicone resin, such as a photocurable resin. This photocurable material can be appropriately selected and used as long as it has sufficient insulating properties and adhesive force and does not adversely affect the electrodes.

As the conductive particles to be mixed into the insulating photocurable material, there can be used solid conductor particles, conductor hollow particles, particles having a conductor layer formed on the surface of an insulator, and the like. Specific examples include metal particles such as nickel and gold, and particles obtained by coating a resin such as polystyrene or glass or ceramic particles with a conductor such as nickel or gold. In particular, since it is preferable that the particles have elasticity, it is preferable to use conductive particles in which a conductor is coated on resin particles.

Since the conductive particles are required to have anisotropy in conductivity, those having a small variation in diameter are required. Specifically, it is preferable to make the particle diameter of the particles used as a spacer of the liquid crystal uneven.

The diameter of the conductive particles is preferably 50 μm or less. In order to reduce poor connection, 20
It is preferable that the thickness be not more than μm. Usually, it is preferable that the thickness is about 5 to 10 μm, which is equal to the gap between the substrates of the liquid crystal display element. By adjusting the diameter, a sufficient number of particles are brought into contact with the electrodes at the terminal portions, so that poor connection hardly occurs.

The amount of the conductive particles mixed into the photocurable material is as follows:
It depends on the distance between the terminals, the facing area of the electrodes in the terminal portion, the required resistance, the diameter of the conductive particles, and the like.
What is necessary is just to select in the range of about 20 wt%. Specifically, a resistance lower than a predetermined connection resistance can be obtained in this range, a short circuit between the terminals does not occur, and the leak current between the terminals may be set to a predetermined value or less. .

This connection material is supplied in an uncured state on the electrode of the terminal portion of the electro-optical element or on the electrode of the flexible printed circuit board. This supply method may be performed by a known method such as printing and a dispenser. In this case, the electrodes and the flexible printed terminal portion of the electro-optical element during crimping
Flows out between the bets substrate electrodes, it is preferred to supply the amount that reaches the end face of the substrate facing the substrate formed of at least a terminal portion. Thereby, it is possible to obtain an improvement in adhesion and an effect of suppressing corrosion of an electrode outside the seal without an extra step.

As the uncured photocurable material,
A material curable by light irradiation is used. A monomer, oligomer or polymer such as a photopolymerizable material and a photocrosslinkable material may be used by adding a photopolymerization initiator, a pigment, a viscosity modifier and the like as necessary.

When a semiconductor chip or a circuit component is mounted on a part of the terminal portion, and the distance between the terminal portions is long, or when the electrode of the terminal portion of the electro-optical element is connected to the flexible electrode.
If the area of the portion of the printed circuit board facing the electrodes is considerably larger than the area of the terminal portion, the uncured connecting material supplied first may be insufficient. In such a case, only the supply step of the uncured connection material may be performed again, and the curing step by light irradiation may be performed once.

In this way, after the uncured connecting material reaches the end face of the substrate facing the substrate on which the terminal portions are formed, it is cured by light irradiation. This light irradiation is performed on a substrate or flexible
It is cured by irradiating light from the printed circuit board side. When both substrates of the liquid crystal display element are transparent substrates, the substrate is usually irradiated with light from the lower surface side of the substrate 1A and cured. When there are many uncured connecting members protruding from the opposing portions of the electrodes of the terminal portions of the electro-optical element and the electrodes of the flexible printed circuit board, the curing may be performed by irradiating light from both upper and lower sides.

The circuit board connected in the electro-optical device of the present invention is a full lexical Bull PCB.

[0032]

EXAMPLES Examples 1 and 2 and Comparative Examples 1, 2, 3, and 4 A transparent electrode made of ITO was 1 mm on a soda glass substrate.
A nematic liquid crystal was sealed inside using a pattern patterned in a stripe pattern at a pitch to produce a liquid crystal display device. An uncured material in which about 1 wt% of gold and nickel-coated resin particles having an average particle diameter of 6 μm as conductive particles were mixed into a photocurable acrylic material (manufactured by Loctite) as a connecting material was prepared.

This connecting material is supplied to a terminal portion of a liquid crystal display element by a dispenser, and a flexible printed circuit board (circuit board 4) of a polyimide type (Example 1) and a polyester type (Example 2) as shown in FIG. It was press-bonded at a pressure of 7 kg / cm ² and protruded from the press-bonded portion. Thereby, the uncured material reaches the end surface of the substrate 1B facing the substrate 1A on which the terminal portions are formed, and the substrate 1A
Of the substrate 1A so as to protrude from a right end of the substrate 1A.

As Comparative Examples 1 and 2, the supply amount of the photocurable acrylic material (connecting material) mixed with the conductive particles onto the electrodes was reduced, and as shown in FIG. Electrode 12A on substrate 11A and electrode 15 on circuit board 14
And the extent to which it just spreads to the part where it faces. In addition, as Comparative Examples 3 and 4, those obtained by pressing a conventional anisotropic conductive film at 170 ° C. and 35 kg / cm ² were also manufactured.

Next, the samples of Examples 1 and 2 and Comparative Examples 1 and ² were irradiated with ultraviolet rays of 1000 mJ / cm ² from below the substrate 1A or 11A to cure the uncured photocurable acrylic material. Was done. As a result, the adhesive strength is
The samples of Examples 1 and 2 averaged about 4 kg / cm, the samples of Comparative Examples 1 and 2 averaged about 2.5 kg / cm, and the samples of Comparative Examples 3 and 4 averaged about 1 kg / cm or less. All of the samples of the examples have improved adhesion strength than the samples of the comparative examples, and have improved reliability,
Electrolytic corrosion under high temperature and high humidity could be prevented.

Examples 3 and 4 The amount of the photocurable acrylic material (connecting material) mixed with the conductive particles on the electrodes was increased as compared with Examples 1 and 2.
As shown in FIG. 3 , the circuit board 24 reached the upper surface (the surface opposite to the electrode 25) of the flexible printed circuit board. In FIG. 3, 21A and 21B are substrates,
22A and 22B are electrodes, 23 is a seal, 24 is a circuit board, 25 is an electrode, 26 is conductive particles, and 27 is a photocurable material.

Next, curing was performed in the same manner as in Examples 1 and 2. As a result, in the samples of Examples 3 and 4, the adhesive strength was about 5 kg / cm on average, and the adhesive strength was further improved as compared with Examples 1 and 2, and the reliability was improved.

[0038]

According to the electro-optical device of the present invention, the electrode of the terminal portion and the electrode of the flexible printed circuit board are conductively connected by a connecting material in which conductive particles are mixed into an insulating photo-curable material, and the connection is performed. The material is filled between the front end of the flexible printed board and the end face of the board facing the board on which the terminal portion is formed. Therefore, the bonding strength is high and the reliability is high. In particular, since the electrode outside the seal of the electro-optical element is covered with an insulating photocurable material, corrosion is unlikely to occur even in a high humidity atmosphere.

Further, since the conductive connection and the reinforcement for the connection are made of the same photocurable material, the supply step and the curing step of the uncured material can be performed in one step, and the productivity is good. In particular, the electrodes of the terminals and the flexible print
At least one of the bets substrate electrodes, it is preferable to larger amount of adhered connection material in an uncured state. After that, the electrode of the terminal portion and the electrode of the flexible printed circuit board are pressed against each other so as to face each other, and the uncured connecting material is squeezed with the electrode of the terminal portion.
The flexible printed circuit board is caused to flow toward the seal side from the portion facing the electrode, so as to reach at least the end face of the substrate facing the substrate on which the terminal portion is formed.

Thus, it is easy to fill the narrow portion between the end face of the substrate facing the substrate on which the terminal portion is formed and the front end of the flexible printed board without any gap. In addition, there is an advantage that the supply step and the curing step need only be performed once.

Further, since a photocurable material is used,
Can be cured at room temperature. Of course, heating may be performed to some extent, but since the temperature may be much lower than the curing temperature of the anisotropic conductive film, it is hardly affected by thermal expansion and the electro-optical element is hardly deteriorated.

Further, the plurality of flexible printed boards can be easily aligned and conductively connected. That is, since the operation of heating and cooling is not repeated, even if the conductive connection is performed one by one as described above (even if the curing step is repeatedly performed), problems such as deterioration hardly occur.

Further, as compared with the conductive connection by soldering, a heating step is not required, and cleaning of a flux is not required, so that the productivity is good and the effect of suppressing corrosion is high. The present invention can be applied to various applications within a range that does not impair the effects of the present invention.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a basic structure of an electro-optical device according to the present invention.

FIG. 2 is a cross-sectional view illustrating an electro-optical device according to a comparative example.

FIG. 3 is a cross-sectional view illustrating the structure of another example of the electro-optical device according to the invention.

[Explanation of symbols]

Substrate: 1A, 1B, 11A, 11B, 21A, 21B Electrode: 2A, 2B, 5, 12A, 12B, 15, 22
A, 22B, 25 Seals: 3, 13, 23 Circuit boards: 4, 14, 24 Conductive particles: 6, 16, 26 Photocurable materials: 7, 17, 27

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/1345

Claims (3)

(57) [Claims] 1. A pair of substrates with electrodes are arranged so that electrode surfaces are opposed to each other, the periphery is sealed, an electro-optical medium is sandwiched inside, and one substrate is protruded from the other substrate. form the other substrate and the opposed portion not, off the electrode substrate and the opposite is not part of the other as a terminal portion
In an electro-optical device that is conductively connected to a flexible printed board, an electrode of a terminal portion and an electrode of a flexible printed board are opposed to each other, and an end face of the flexible printed board and an end face of the other board. Are arranged so as to face each other, and the electrode of the terminal portion and the electrode of the flexible printed circuit board are connected by a connecting material including an insulating photocurable material and conductive particles mixed in the photocurable material. An electro-optical device, wherein the connecting material is filled to a height reaching at least an end face of the other substrate from the electrode of the terminal portion. 2. The electro-optical device according to claim 1, wherein the conductive particles are elastic particles having at least a surface having conductivity. 3. A pair of electrodes-equipped substrates are arranged so that electrode surfaces face each other, an electro-optical medium is sandwiched inside by sealing the periphery, and one substrate is projected from the other substrate. form the other substrate and the opposed portion not, off the electrode substrate and the opposite is not part of the other as a terminal portion
In a method of manufacturing an electro-optical device that is conductively connected to a flexible printed board, an electrode at a terminal portion and a flexible
At least one of the cement board of the electrodes, the connection member including an insulating light-curable material and conductive particles mixed into the light-curable material supplied in an uncured state, the terminal portion electrode and off
Crimp by electrodes and opposed to the lexical Bull PCB, connection material of the uncured terminal portion electrode and Furekishibu
Flow from the part of the printed circuit board facing the electrode to the seal side and reach at least the end face of the other substrate,
A method of manufacturing an electro-optical device, comprising irradiating light to cure the connection material.