JP2000284296A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the stability of transfer connections between counter electrode substrates which utilize plastic substrates for transparent electrode substrates compatible with the prevention of chrominance non-uniformity at sealing edges. SOLUTION: This device 10 is constructed so as to comprise a liquid crystal display panel formed by confrontedly sticking a pair of plastic transparent electrode substrates 20, 30, on the one surface of each of which a transparent electrode 201 or 301 is formed, via a peripheral sealant 40 so as to produce a specified gap in between the by enclosing a liquid crystal within the gap between the transparent electrodes 201, 301, to make conductive beads 41 as a transfer material be included in the peripheral sealant 40 and to connect the transparent electrode of one of the transparent electrode substrates to external pulling leads formed on terminal parts of the other transparent electrode substrate side via the conductive beads 41. In this case, an average particle diameter of the conductive beads 41 to be put in the peripheral sealant 40 is restricted to be within the range of 1.01-1.06 times the cell gap width and besides a conductive filler 42 is added into the peripheral sealant 40 in 2-10 wt.% with respect to the peripheral sealant 40 apart from the conductive beads 41.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device using a plastic substrate as a transparent electrode substrate, and more particularly, to a liquid crystal display device via a transfer material (conductive beads) contained in a peripheral sealing material. The present invention relates to a liquid crystal display device in which a transparent electrode of a transparent electrode substrate is connected to an external lead formed at a terminal on the other transparent electrode substrate.

[0002]

2. Description of the Related Art FIG. 2 is a schematic sectional view showing a part of a terminal portion of a liquid crystal display panel 1 for black and white display, for example. Usually, this type of liquid crystal display panel 1 has a pair of transparent electrode substrates 2 and 3 each having a transparent electrode formed on one surface.
Are bonded to each other via a peripheral sealing material 4 made of, for example, an epoxy-based adhesive, and a liquid crystal is sealed in a gap between the transparent electrodes. It should be noted that the transparent electrode and the liquid crystal are not shown in FIG.

[0003] As shown in the figure, a terminal portion 31 is provided on one of the transparent electrode substrates 3 so as to protrude to the side, and the transparent electrode substrates 2 and 3 are connected to the terminal portion 31. Assuming that an external lead (not shown) for each transparent electrode is formed, a transfer material is provided in the peripheral seal material 4,
The transparent electrode (common electrode or segment electrode) on the other transparent electrode substrate 2 side is connected to an external lead lead corresponding to the transparent electrode via the transfer material.

That is, FIG. 3 (a sectional view taken along line AA in FIG. 2)
As shown in FIG. 4 and a sectional view taken along line BB of FIG.
At the same time, conductive beads 6 as a transfer material are mixed, and conduction between the transparent electrode 2a on the transparent electrode substrate 2 side and the extraction electrode 31a of the external extraction lead formed in the terminal portion 31 is established via the conductive beads 6. Like that.

[0005] Incidentally, the gap width between the transparent electrodes is 6 μm.
m, the conductive beads 6 have, for example, a diameter of 6.5.
A μm resin bead having a surface coated with Au is used, and the gap holding spacer 5 has a diameter of, for example, 6.0.
An electrically insulating cylindrical body such as a glass fiber of μm is used.

As described above, the peripheral sealing material 4 is provided with a transfer function by mixing the conductive beads 6 in the peripheral sealing material 4, but conventionally, the viscosity of the peripheral sealing material 4 is adjusted. In order to improve the strength and to improve the strength, a very small amount of filler 7 such as Al ₂ O ₃ (indicated by a dot) is mixed into the peripheral sealing material 4.

[0007]

By the way, instead of a glass substrate, a plastic substrate such as polycarbonate (having a thickness of about 0.1 to 0.4 m) is used in place of the glass substrate.
When m) is used, the following problem occurs.

That is, since the plastic substrate is softer than the glass substrate, when the transparent electrode substrates 2 and 3 are thermocompression-bonded via the peripheral sealing material 4, the conductive beads 6 cause a crater-shaped depression on the substrate surface. Along with ITO
Cracks are formed in the transparent electrode made of (indium tin oxide), which causes poor conductivity.

In order to prevent this, the conductive beads 6 may be made of a soft and easily deformable material. However,
According to this, even if the transparent electrode substrates 2 and 3 are thermocompression-bonded, since the conductive beads 6 are soft, the sealing material and the fine filler 7 between the conductive beads 6 and the transparent electrodes 2a and 31a are closest to each other. It may not be able to be completely discharged, leaving an electrical insulating film of about 0.1 μm even after the thermocompression bonding, so that conduction between the opposing electrodes 2a and 31a may not be achieved.

[0010] This problem can be solved by including a conductive filler as the filler 7. On the other hand, another problem is that color unevenness can occur around the seal when a thermal shock is applied. appear. Although the generation mechanism of the color unevenness is not necessarily clear, it is estimated as follows. That is, since the conductive filler has no affinity with the sealing material, interface delamination is likely to occur between the conductive filler and the sealing material mainly due to a thermal shock, and the microparticles are formed around the conductive filler due to this. Cracks occur.

When a large number of these micro cracks occur,
As a result, the volume of the peripheral sealing material 4 expands,
Due to this, the gap width at the time of peripheral sealing increases,
Color unevenness occurs.

In order to keep the gap width properly, a spacer 5 for holding a gap is provided in the peripheral sealing material 4. Here, assuming that the cohesive force of the peripheral sealing material 4 is F and the repulsive force of the spacer 5 is f, the design stage is set so that F ≧ f even after thermocompression bonding of both transparent electrode substrates.

However, moisture permeation at the time of sealing in a cleaning step performed after thermocompression bonding, liquid crystal injection and sealing, and heat treatment performed at a temperature higher than the nematic-isotropic transition temperature of liquid crystal for liquid crystal alignment performed thereafter ( Due to aging), the cohesive force F of the peripheral sealing material 4 is reduced, and the force relationship with the repulsive force f of the spacer 5 is reversed, so that F <f. This may increase the gap width.

[0014]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a liquid crystal display device using a plastic substrate as a transparent electrode substrate in a peripheral sealing material. It is an object of the present invention to provide a liquid crystal display element in which a transfer material is mixed to prevent color unevenness at the time of sealing.

According to the present invention, the above object is attained by opposing a pair of plastic transparent electrode substrates, each having a transparent electrode formed on one surface thereof, through a peripheral sealing material so as to form a predetermined gap therebetween. A liquid crystal display panel in which liquid crystal is sealed in a gap between the transparent electrodes is provided, and conductive beads as a transfer material are included in the peripheral sealing material, and the conductive beads are interposed through the conductive beads. In a liquid crystal display element in which a transparent electrode of the one transparent electrode substrate is connected to an external lead formed on a terminal portion on the other transparent electrode substrate side, an average particle diameter of the conductive beads is set to be equal to one of the gap width. 0.11 to 1.06 times, and no spacer for maintaining a gap other than the conductive beads is included in the peripheral sealing material, and only the conductive filler is used. Serial 2~10w to the peripheral sealing material
This is achieved by adding t%.

In this case, the amount of the conductive beads added to the peripheral sealing material is preferably 1 to 3 wt%.

According to the present invention, the gap holding spacer is removed from the peripheral sealing material. Therefore, the repulsion force f after thermocompression bonding is exclusively the repulsion force of the conductive beads, and the average particle size of the conductive beads is in the range of 1.01 to 1.06 times the gap width, and preferably By setting the addition amount to 1 to 3 wt%, the repulsion f can be suppressed to a small value without impairing the reliability of the electrical connection.

In addition, since there is no spacer for maintaining the gap, the amount of the sealing material is increased.
Becomes larger. Therefore, even if the cohesive force F decreases due to moisture penetration in the washing step or heating during aging, the relationship of F ≧ f is still maintained,
Color unevenness rarely occurs at the time of sealing.

Regarding the conductive filler, if the amount of the conductive filler is too large, the strength of the peripheral sealing material is reduced. Conversely, if the amount of the conductive filler is too small, the electrical connection becomes unstable. The amount of the conductive filler added to the material was in the range of 2 to 10 wt%.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described with reference to FIG.

In the liquid crystal display element 10 of the present invention, a plastic substrate such as polycarbonate is used as the transparent electrode substrates 20 and 30. Usually, the thickness is appropriately selected from the range of 0.1 to 0.4 mm.

On the surfaces of the transparent electrode substrates 20 and 30 facing each other, transparent electrodes 201 and 30 made of, for example, ITO are provided.
1 is formed. In the illustrated example, one of the terminal portions 3 is provided on one transparent electrode substrate 30 side so as to protrude to the side.
10 are connected in series.

The terminal portion 310 has a transparent electrode substrate 30
An extraction electrode group 302 including an extraction electrode connected to the transparent electrode 301 and an extraction electrode for the other transparent electrode substrate 20 is provided. Also, when sealing the transparent electrode substrate 20,
A transfer electrode 202 connected to the transparent electrode 201 is formed.

The transparent electrode substrates 20 and 30 are thermocompression-bonded via a peripheral sealing material 40 made of an epoxy resin so that a predetermined gap is formed therebetween. A conductive bead 41 is mixed in the peripheral sealing material 40, and the transfer electrode 202 of the transparent electrode substrate 20 is electrically connected to a predetermined lead electrode on the terminal portion 310 via the conductive bead 41. . In FIG. 1, for convenience of drawing,
Although only one conductive bead 41 is shown, many of them are actually contained in the peripheral sealing material 40.

As the conductive beads 41, a resin bead having a surface coated with a metal film of, for example, Ni or Au is used. In the present invention, in order to prevent color unevenness at the time of sealing, the particle size is reduced. Is the gap width of 1.
The range is from 01 to 1.06 times. On the other hand, if the amount of the conductive beads 41 added to the peripheral sealing material 40 is too large, the above-described repulsive force f becomes large, and color unevenness at the time of sealing tends to occur. By being easy to become, it is made into the range of 1-3 wt%.

The transparent electrode substrate 20 and the transparent electrode substrate 3
In order to eliminate the resin residue of the sealing material between the conductive bead 41 and the transfer electrode 202 and between the conductive bead 41 and the extraction electrode after the thermocompression bonding of 0, the hardness of the conductive bead is determined by the compression deformation load value. Is 0.1% for 10% strain.
It is preferably at least 26 grf.

Conventionally, in addition to the conductive beads, a gap holding spacer such as glass fiber and a conductive filler are mixed in the peripheral sealing material. However, in the present invention, a gap holding spacer other than the conductive beads is used. Is not used.

The conductive filler 42 is used for the peripheral sealing material 4.
0 is mixed in the peripheral sealing material 40 for the purpose of adjusting the viscosity, improving the strength and ensuring the reliability of the electrical connection, but particularly between the conductive beads 41 and the transfer electrode 202, and between the conductive beads 41 and the extraction electrode. From the viewpoint of improving the electrical connection between them, the average particle size is 0.2
It is preferably in the range of 0.5 to 0.5 μm.

The conductive filler 42 may be any conductive filler (particle), and preferably a conductive filler having a specific resistance of 10 Ω · cm or less. For example, TiO ₂ powder coated with SnO ₂ and further doped with antimony is used. If the amount is too large, the strength of the peripheral sealing material 40 is reduced. Connection becomes unstable. Therefore, according to the present invention, the amount of the conductive filler 42 added to the peripheral sealing material 40 is in the range of 2 to 10 wt%.

[0030]

[Example 1] <Example 1> 0.4 mm in thickness and I
Two plastic substrates made of polycarbonate resin having a film thickness of TO of 300 ° were prepared, and each of them was patterned to form a transparent electrode. Note that one of the plastic substrates had a terminal portion, and an extraction electrode was formed on the terminal portion. Except for the seal part and the extraction electrode part,
A solvent evaporation type overcoat of polyimide was transferred onto each transparent electrode, and rubbed after firing. Next, an average particle diameter of 6.0 μm was contained in the epoxy resin adhesive (main agent).
m (approximately 1.05 times the gap width), a compressive deformation load value of 10% strain, and 0.26 grf of conductive beads of 2 wt% are added. 5 wt% was added, and this was applied to one substrate as a peripheral sealing material. As the conductive beads, resin beads coated with gold were used, and as the conductive filler, TiO ₂ powder coated with SnO ₂ and doped with antimony were used. After spraying an in-plane spacer having an average particle size of 5.7 μm on the other substrate and performing heat treatment,
The two substrates were stacked and thermocompression bonded so that the cell gap between them was about 5.7 μm. Then, after injecting liquid crystal and sealing the injection port, and washing the cell, heat treatment (aging) for liquid crystal alignment was performed to produce a liquid crystal display element using a plastic substrate as a transparent electrode substrate for 400 cells. In these liquid crystal display devices, the transfer disconnection failure was 0%. The rate of occurrence of color unevenness at the time of sealing after aging was also 0%.

Comparative Example 1 A liquid crystal display device using a plastic substrate as a transparent electrode substrate for 400 cells was manufactured in the same manner as in Example 1 except that the following peripheral sealing material was used. That is, in Comparative Example 1, the average particle size was 6.2 μm (approximately 1.08 times the gap width) and the compressive deformation load value was 10% strain in the epoxy resin adhesive (main agent). 2% by weight of conductive beads of 0.26 grf, 2% by weight of cylindrical glass fiber having an average diameter of 6.0 μm as a spacer for gap maintenance, and 0.2 μm of average particle diameter
5 wt% of each of the conductive fillers was added and used as a peripheral sealing material. In Comparative Example 1, the transfer disconnection defect was 0%, but the rate of occurrence of color unevenness at the time of sealing after aging was 10%.

Comparative Example 2 A liquid crystal display device using a plastic substrate as a transparent electrode substrate was prepared for 400 cells in the same manner as in Example 1 except that the following peripheral sealing material was used. That is, in Comparative Example 2, the average particle size was 6.2 μm (about 1.08 times the gap width) and the compressive deformation load value was 10% strain in the epoxy resin adhesive (main agent). 2 wt% of conductive beads of 0.26 grf and 5 wt% of conductive filler having an average particle size of 0.2 μm were used as peripheral sealing materials. Comparative Example 2
In this case, the transfer disconnection failure was about 2%, and the rate of occurrence of color unevenness at the time of sealing after aging was about 5%.

Comparative Example 3 A liquid crystal display device using a plastic substrate as a transparent electrode substrate for 400 cells was manufactured in the same manner as in Example 1 except that the following peripheral sealing material was used. That is, in Comparative Example 3, the average particle diameter was 6.0 μm (approximately 1.05 times the gap width) and the compressive deformation load value was 10% for the epoxy resin adhesive (main agent). 5 wt% of conductive beads of 0.26 grf and 5 wt% of conductive filler having an average particle size of 0.2 μm were used as peripheral sealing materials. Comparative Example 2
In this case, the transfer disconnection failure was about 0%, and the rate of occurrence of color unevenness at the time of sealing after aging was 2.5%.

[0034]

As described above, according to the present invention,
In a liquid crystal display element using a plastic substrate as a transparent electrode substrate, the average particle size of the conductive beads to be put in the peripheral sealing material is set to be within a range of 1.01 to 1.06 times the cell gap width, and in the peripheral sealing material. Is 2 to 10 watts of conductive filler in addition to conductive beads to the surrounding sealing material.
By adding t%, it is possible to achieve both the stability of the transfer connection between the counter electrode substrates and the prevention of the occurrence of color unevenness during sealing.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a transfer portion of a liquid crystal display device according to the present invention.

FIG. 2 is a schematic cross-sectional view showing a transfer portion of a liquid crystal display element as a conventional example.

FIG. 3 is a cross-sectional view taken along line AA of FIG. 2;

FIG. 4 is a vertical sectional view taken along line BB of FIG. 2;

DESCRIPTION OF SYMBOLS 10 Liquid crystal display element 20, 30 Transparent electrode substrate 201, 301 Transparent electrode 202 Transfer electrode 302 Leading electrode group 310 Terminal section 40 Peripheral seal material 41 Conductive bead 42 Conductive filler

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Masahide Shigemura 1-2-1, Kamisakabe, Amagasaki City, Hyogo Prefecture Optrex Corporation Amagasaki Plant (72) Inventor Hikaru Nakagawa 1-2-2 Kamisakabe, Amagasaki City, Hyogo Prefecture No. 1 Optrex Corporation Amagasaki Plant (72) Inventor Yasuyuki Kurisu 1-2-1 Kamisakabe, Amagasaki City, Hyogo Prefecture Optrex Amagasaki Plant F-term (reference) 2H089 LA07 LA11 LA15 LA19 MA04X MA04Y MA06X MA06Y NA06 NA24 NA39 NA45 NA48 NA58 PA06 QA14 SA01 TA03 2H092 GA39 HA16 HA17 MA10 MA32 NA15 NA29 PA01 PA03 PA05 5C094 AA03 AA08 AA31 BA43 DA07 DB05 EA02 EA05 EC02 FB12

Claims (2)

[Claims] 1. A pair of plastic transparent electrode substrates each having a transparent electrode formed on one surface thereof are opposed to each other via a peripheral sealing material so as to form a predetermined gap therebetween. A liquid crystal display panel in which liquid crystal is sealed in a gap between the first and second transparent electrode substrates, and a conductive bead as a transfer material is included in the peripheral sealing material; In a liquid crystal display element in which an electrode is connected to an external lead formed on a terminal portion on the other transparent electrode substrate side, an average particle diameter of the conductive beads is 1.01 of the gap width.
In addition, the peripheral seal material does not include a spacer for maintaining a gap other than the conductive beads, and only the conductive filler is added in an amount of 2 to 10 wt% to the peripheral seal material. A liquid crystal display device characterized in that: 2. The liquid crystal display device according to claim 1, wherein the amount of the conductive beads added to the peripheral sealing material is 1 to 3 wt%.