JPH07114030A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To suppress imperfect electrical connection between the substrates of a liq. crystal display device with a sealing material mixed with electric conductive spacers. CONSTITUTION:A sealing material 4 is mixed with flexible electric conductive spacers 5 each having a slightly larger diameter than the desired gap between substrates. When the diameter of the spacers 5 is represented by X (mum) and load required to compress one of the spacers 5 by 10% is represented by Y (grf), the spacers 5 satisfy 0.2>=Y>=0.06X-0.10.

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 in which a conductive spacer having flexibility is arranged in a sealing material to form a conductive connection between different substrates.

[0002]

2. Description of the Related Art Conventionally, liquid crystal display devices have been used for watches, calculators,
It is used in many applications such as various home appliances, measuring instruments, office automation equipment, and TVs. In these liquid crystal display elements, electrodes are usually provided with a liquid crystal layer sandwiched therebetween, and a voltage is applied between the electrodes, so that electrodes connected to an external circuit are present separately on both substrates. However, in order to facilitate the connection with an external circuit, it is desired to take out the lead for external connection from only one substrate if possible.

Therefore, a conductive connection between the substrates is required for conductively connecting the electrode of one substrate to the electrode of the other substrate. As a typical example of the conductive connection between the substrates, a conductive adhesive such as a silver paste is printed in dots and cured. Since this structure is easy to manufacture and has high reliability, it is mainly used for static drive or low duty drive TN type liquid crystal display devices.
This is because the number of conductive connections between the substrates in one liquid crystal display element is small.

As the number of duty increases, the number of conductive connections between the substrates in one liquid crystal display element also increases. In this case, if a conductive adhesive is printed in dots to make a conductive connection between the substrates, the problem arises that the design is difficult. This is because when a large number of conductive adhesives are arranged side by side in a specific portion, when the liquid crystal display element is pressure-bonded, only that portion has a large resistance to pressure bonding, the substrate gap becomes large, and the substrate gap tends to be uneven. This is because.

In particular, in the case of a dot matrix liquid crystal display element, since the segment electrodes are grouped together, the common electrodes are forced to concentrate on the peripheral portions at both ends to make conductive connection between the substrates. In this case, the sealing material is hard to be crushed only in the peripheral portion, and unevenness is likely to occur in the substrate gap.

In order to avoid such a problem, a conductive spacer is used as a spacer mixed in the sealing material to keep the substrate gap, so that the sealing material itself can be anisotropically conductively connected. ing. This is because the conductive connection is made by the individual conductive spacers, and the diameter thereof is set to the space between the substrates, so that the conductive connection between the substrates can be made, but the insulating property is maintained in the lateral direction. .

[0007]

As described above, the conductive spacer is used to make an anisotropic conductive connection by the sealing material itself, so that a substrate such as that formed when a conductive adhesive is printed in a dot pattern is formed. Almost no gap unevenness occurred. However, in this structure, if the pressure at the time of pressure bonding is not uniformly and accurately applied to the entire liquid crystal display element, the connection resistance may partially increase, resulting in poor connection and poor contrast during driving. For this reason, the work allowable width during production is narrow, and the productivity tends to be reduced.

[0008]

The present invention has been made to solve the above-mentioned problems, in which liquid crystal is sealed between a pair of substrates provided with electrodes, and the electrodes of one substrate are connected to the other substrate. In the liquid crystal display element conductively connected to the electrode of the inside of the sealing material, the sealing material contains a conductive spacer having a diameter slightly larger than the desired substrate gap and having flexibility. Diameter of the flexible spacer is X (μm)
And the weight required to compress one conductive spacer by 10% is Y (grf), a conductive spacer that satisfies 0.2X ≧ Y ≧ 0.06X −0.10 is used. Provided is a display element and a liquid crystal display element characterized in that a conductive spacer thereof is a resin spacer coated with nickel.

In the present invention, a conductive spacer having a specific compression load is used as the flexible conductive spacer mixed in the sealing material. As a result, it is possible to reduce the connection failure of the conductive spacer that tends to occur during crimping, and to widen the work allowable range during crimping.
Productivity is improved.

FIG. 1 is a sectional view of a liquid crystal display device showing a conductive connection state in the sealing material of the present invention. In FIG. 1, 1A and 1B are substrates such as glass and plastic, and 2A and 2B.
Is an electrode of ITO, SnO ₂ or the like, 3 is an electrode for external connection formed on the substrate 1B, 4 is a sealing material, and 5 is a conductive spacer.

The electrode 2A on the substrate 1A is anisotropically conductively connected to the external connection electrode 3 formed on the substrate 1B by the conductive spacer 5 in the sealing material 4, and is taken out to the outside. The electrode 2B on the substrate 1B is directly connected to the external connection electrode formed on the substrate 1B. Of course, in relation to the wiring pattern, the electrode 2B on the substrate 1B is once conductively connected to the electrode on the substrate 1A, and again conductively connected from the electrode on the substrate 1A to the external connection electrode formed on the substrate 1B. You may do it.

The substrate used in the present invention may be a transparent substrate such as glass or plastic, and the inner surface thereof is I
A transparent electrode made of a transparent conductive film such as TO (In ₂ O ₃ —SnO ₂ ) or SnO ₂ is formed. In addition, a film of a low-resistance conductive material such as metal or conductive paste may be formed on the transparent electrode in a thin line shape, a grid shape, or the like. The electrodes for external connection may be made of the same material as these display electrodes,
Different materials may be used. Usually, the same material may be used and patterned at the same time.

An orientation control film is usually provided on this substrate. As the alignment control film, a liquid crystal obtained by rubbing an organic polymer material such as polyimide, polyamide, or polyvinyl alcohol, or a film made of an inorganic material such as SiO ₂ , TiO ₂ , or Al ₂ O _3, or obliquely vapor-depositing it. Any film may be used as long as it is oriented. Of course, a vertically oriented film may be used. Furthermore, if necessary, an insulating film of TiO ₂ , SiO ₂ , and Al ₂ O ₃ may be provided between the electrode and the orientation control film to prevent a short circuit between the substrates. It should be noted that these insulating films are not provided in the portion where the conductive connection between the substrates is made in the seal portion.

The adhesive for the seal material may be an organic adhesive such as a usual epoxy resin or silicone resin. In the present invention, the organic adhesive is mixed with a conductive spacer having a diameter slightly larger than a desired substrate gap and having flexibility. This conductive spacer has a diameter of X
(μm) and the weight required to compress one conductive spacer by 10% is Y (grf), 0.2X ≧ Y ≧ 0.06X
It is made to satisfy −0.10.

This is because when Y <0.06X -0.10, the conductive spacer may be easily crushed and the conductive connection may not be sufficiently obtained. Furthermore, the connection resistance is likely to increase with the passage of time. Further, when 0.2X <Y, the conductive spacer is less likely to be crushed, and the connection resistance of the conductive connection tends to increase partially.

As this conductive spacer, a conductive spacer having flexibility itself is used. Specifically, there is a spacer in which the surface of the organic resin spacer is coated with a conductive material. It is preferable to use a metal as the electrically conductive material, but if the resistance is sufficiently low, an inorganic material other than organic or metal can be used. In the case of metal, a coating layer may be formed on the surface of the spacer by a method such as plating, vapor deposition, or dipping. In particular, among the conductive materials, nickel has a low resistance value and is inexpensive, so that it is easy to use.

This conductive spacer has a diameter slightly larger than the desired substrate gap, and by being held in a slightly crushed state during seal crimping, the connection resistance becomes low and the spacer is kept for a long time. Even if it is held, the increase in connection resistance is less likely to occur. Specifically, the conductive spacer may have a diameter about 2 to 20% larger than the desired substrate gap. The mixing amount of the conductive spacer may be about 0.2 to 5 wt% with respect to the organic adhesive (solid content to be cured).

The sealant made of an organic adhesive mixed with the conductive spacer is applied to the substrate by screen printing or the like, and is superposed and pressure-bonded on the other substrate. Usually, an opening is formed in a part of it, and after it is made into cells, liquid crystal is injected from the opening to seal the opening. In the present invention, the workability is high because the allowable width of this work at the time of crimping is wide.

That is, according to the present invention, it is possible to work under the same working conditions as a normal sealing process without using an organic adhesive mixed with a conductive spacer, and yet the resistance of conductive connection between substrates is low. It is maintained and connection failure is less likely to occur.

The sealing material may be used by mixing spacers such as insulating glass fiber, plastic particles and ceramic particles in addition to the above-mentioned conductive spacers. In this case, the insulating spacer may have a diameter substantially the same as the desired substrate gap or may be slightly larger in diameter. Further, the surface of the spacer may be colored in a dark color to reduce the leakage of light from the seal portion.

As the liquid crystal used in the liquid crystal display device of the present invention, various liquid crystals can be used depending on the application. In addition to ordinary nematic liquid crystals, liquid crystals to which a chiral substance is added so as to have a twist of 160 ° to 300 ° used in a super twist (STN) type liquid crystal display element may be used. Further, a dye such as a dichroic dye may be added to the nematic liquid crystal to improve the contrast ratio or adjust the hue. Further, a ferroelectric liquid crystal or the like can also be used.

The present invention is suitable for a liquid crystal display element in which conductive connections between upper and lower substrates are provided at eight or more places, and is particularly suitable for a liquid crystal display element in which eight or more places are present in the same portion on the same side. Therefore, it is suitable for a dot matrix type liquid crystal display element having about 8 to 100 common electrodes.

Besides, in the present invention, a polarizing plate, a color filter, a reflection plate, a retardation plate, a light source, etc., which are used in a normal liquid crystal display element, may be laminated and used. Furthermore, forming a color filter layer on the inner or outer surface of the substrate,
The substrate may be a polarizing substrate, or a touch switch, an ultraviolet cut filter, or a non-reflection filter may be laminated on the outside of the substrate. In addition, spacers may be scattered in the display area, or a seal may be formed in a dot shape. Besides, various structures and manufacturing methods used for ordinary liquid crystal display devices can be applied within a range not impairing the effects of the present invention.

[0024]

In the present invention, since the conductive spacer whose hardness is adjusted to a specific range is used, precise control is not required in the seal crimping process, and it is the same as in the case of a seal that does not include a normal conductive spacer. Even if crimping is performed, conductive connection failure is unlikely to occur. This is because the conductive spacer deforms to some extent during crimping, but it prevents connection failure due to the wraparound of the adhesive of the sealing material, and the conductive force of low resistance is maintained for a long time due to the restoring force resulting from the deformation. I think that the.

[0025]

【Example】

Example 1 As a first substrate and a second substrate, ITO electrodes provided on a glass substrate were patterned, and a short circuit was prevented by SiO ₂ by a vapor deposition method except for a seal portion and a terminal portion for external connection. The insulating film was formed, a polyimide overcoat was spin-coated, and this was rubbed to prepare a substrate having an alignment control film formed thereon.

"Structbond" manufactured by Mitsui Toatsu Chemicals, Inc. as an organic adhesive, and 7.25μ in diameter as a conductive spacer
m and a conductive spacer having a hardness of 0.35 grf were mixed at 1 wt% and printing was performed on a sticker. As the in-plane spacer, a 6.7 μm resin spacer was scattered on this substrate, the other substrate was overlaid and pressure-bonded to manufacture a liquid crystal display element.
As a result, the connection resistance is several MΩ out of about 100,000 connection points.
No connection failure that resulted in almost disconnection occurred.

Comparative Example 1 A conductive spacer having a diameter of 7.25 μm and a hardness of 0.26 grf
A liquid crystal display element was manufactured in the same manner as in Example 1 except that 1.5 wt% of the electrically conductive spacer of 1 was mixed and seal printing was performed. As a result, about 0.55% of poor connection occurred.

Example 2 A conductive spacer having a diameter of 7.25 μm and a hardness of 0.38 grf
A liquid crystal display device was manufactured in the same manner as in Example 1 except that 0.5 wt% of the conductive spacers in Example 1 were mixed and the seal printing was performed. As a result, poor connection was still 0%.

Example 3 A conductive spacer having a diameter of 7.25 μm and a hardness of 0.35 grf
In the same manner as in Example 1 except that 0.2 wt% of the electrically conductive spacer of 1.0 wt% and 1.0 wt% of the insulating spacer made of glass fiber having a diameter of 7.0 μm as the insulating spacer are mixed and the seal printing is performed, A liquid crystal display device was manufactured. As a result, poor connection was still 0%.

[0030]

According to the present invention, since the sealing material mixed with the conductive spacer whose hardness is adjusted to a specific range is used, the conductive connection failure is less likely to occur and the working width in the seal crimping step is widened. That is, even when pressure bonding is performed as in the case of a seal that does not include a conductive spacer, a conductive connection failure is unlikely to occur.

In other words, by doing so, the conductive spacer is deformed to some extent at the time of pressure bonding, but it is possible to prevent a connection failure due to the adhesive of the sealing material wrapping around between the electrodes because it is too soft. . Further, due to the restoring force generated by the deformation of the conductive spacer, the conductive spacer is in strong contact with the electrode, and the phenomenon that the resistance gradually increases is unlikely to occur, and the low resistance conductive connection is maintained for a long time.

The present invention may be added with various structures used in known liquid crystal display devices within a range that does not impair the effects of the present invention, and various applications can be made in the future.

[Brief description of drawings]

FIG. 1 is a sectional view of a liquid crystal display device of the present invention.

[Explanation of symbols]

 1A, 1B: Substrate 2A, 2B: Electrode 3: External connection electrode 4: Seal material 5: Conductive spacer

Claims (2)

[Claims] 1. A liquid crystal display device, wherein a liquid crystal is sealed between a pair of substrates provided with electrodes, and an electrode of one substrate is conductively connected to an electrode of the other substrate inside a sealing material. Containing a flexible conductive spacer having a diameter slightly larger than the substrate gap, and setting the diameter of the conductive spacer as X (μm), compress one conductive spacer by 10%. A liquid crystal display device characterized by using a conductive spacer satisfying 0.2X ≧ Y ≧ 0.06X −0.10, where Y (grf) is a weight required for. 2. A liquid crystal display element according to claim 1, wherein the conductive spacer is a resin spacer coated with nickel.