JPH09127515A - Microspherical body, spacer for liquid crystal display element and liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a microspherical body with which a spherical spacer is obtainable without inducing the modulation of the orientation characteristic of liquid crystals and the degradation in display images owning to flawing of the orientation control film of a liquid crystal display element by satisfying specific conditions. SOLUTION: The value of k defined by equation K=(3/√2).F.S<-3/2> .R<-1/2> of this microspherical body is 250 to 700kgf/mm<2> at 20 deg.C and the restoration rate after compression deformation thereof is >=10 to <30% at 20 deg.C. In the equation, F denotes the load value (kgf) in the 10% compression deformation of the microspherical body, S denotes the compression deformation (mm) and R denotes the radius (mm) of the microspherical body. The gap control of the cell is difficult when the value of K is below 250kgf/mm<2> . There is the drawback that the liquid crystal orientation control surface is flawed in the production process of the liquid crystal display element if the value exceeds 700kgf/mm<2> . As a result, the spherical spacer 8 which does not flaw the orientation control film of the liquid crystal display element and does not induce the modulation of the orientation characteristic of the liquid crystals is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spherical spacer for a liquid crystal display device, a microsphere used for a conductive microsphere and the like. More specifically, the present invention relates to a spherical spacer for a liquid crystal display element, a liquid crystal display element using the spherical spacer for a liquid crystal display element, and a conductive microsphere.

[0002]

2. Description of the Related Art Microspheres are used as spherical spacers for liquid crystal display devices and as conductors for connecting fine electrodes in the electronics field.

A typical example of a conventional TN (twisted nematic) mode liquid crystal display device using a spacer is shown in FIG. This liquid crystal display device includes a pair of substrates 37, 3
9, a spacer 38 and a nematic liquid crystal 41 arranged between the pair of substrates 37 and 39 for keeping the gap between the pair of substrates 37 and 39 constant, and the pair of substrates 3
The sealing member 30 filled around the space between the substrates 7 and 39, and the polarizing sheets 42 and 43 coated on the surfaces of the substrates 37 and 39.
And The substrates 37 and 39 are formed on one surface of transparent substrates 31 and 34 made of glass by using ITO (Indium-based).
Tin-Oxide) film and other transparent electrodes 32, 35
Are patterned, and the surfaces of the transparent electrodes 32 and 35 and the transparent substrates 31 and 34 are covered with alignment control films 33 and 36 made of a polyimide film or the like. The orientation control films 33 and 36 are subjected to orientation control processing by rubbing.

The spacer 38 is formed of an inorganic material containing aluminum oxide, silicon dioxide or the like, or a synthetic resin material containing benzoguanamine, polystyrene polymer or the like. Spacers made of an inorganic material are disclosed in, for example, JP-A-63-73225 and JP-A-1-59974, and spacers made of a synthetic resin material are disclosed in JP-A-60-200228. Kaihei 1-
It is disclosed in Japanese Patent Publication No. 293316.

The liquid crystal display element having the above structure is usually manufactured as follows. Spacers 38 are scattered on the orientation control film 33 of the one substrate 37, and a sealing resin is applied to the periphery of the substrate 37 by printing. Next, the pair of substrates 37 and 39 are stacked and pressed so that the alignment control films 33 and 36 face each other. Next, the sealing resin is heated and cured to form a sealing member, and the pair of substrates 37 and 39 are fixed to each other. Next, the nematic liquid crystal 41 is filled into the gap between the pair of substrates 37 and 39 through the hole provided in the seal member, and then the hole is closed. Then, polarizing sheets 42 and 43 are laminated on the outer surfaces of the transparent substrates 31 and 34, respectively.

As a spacer used in such a liquid crystal display device, a colored spherical spacer is often used for the following reason. In a liquid crystal display device, when a voltage is applied between transparent electrodes, the liquid crystal causes an optical change to form an image. However, the spacer shows no optical change due to the applied voltage. Therefore, in the dark portion of the image when the image is displayed, the uncolored spacers may be visually recognized as bright spots, and as a result, the display contrast of the image decreases.

Colored spherical spacers made of an inorganic material are disclosed in JP-A-62-66228 and JP-A-63-89.
No. 408, JP-A No. 63-89890, and the like, colored spherical spacers made of a synthetic resin material are disclosed in JP-A Nos. 1-20227 and 1-2007.
No. 719 and Japanese Patent Laid-Open No. 214781/1990.

Further, the spacer having no adhesiveness has the following drawbacks because it is not fixed to the transparent substrate.
Therefore, adhesive spherical spacers are often used. In the process of assembling the liquid crystal display cell, air is blown onto the substrate or air is sucked from the substrate. At this time, the spacers arranged on the substrate may scatter and disappear. In the step of injecting the liquid crystal into the liquid crystal display cell, the spacer may move on the substrate, and the spacer may be arranged on the substrate unevenly. When driving the liquid crystal display cell, the spacer may move due to an electric or hydrodynamic force. When mechanical vibration from outside acts on the liquid crystal display cell,
The spacer can move. Such movement of the spacer inside the liquid crystal display cell lowers the gap accuracy between the substrates, and significantly lowers the quality of the displayed image.

A spherical spacer having adhesiveness is disclosed in, for example, Japanese Utility Model Laid-Open No. 51-22453 and Japanese Patent Laid-Open No. 63-44.
631, JP-A-63-94224, JP-A-63-200126, JP-A-1-24715, JP-A-1-247155, and JP-A-2-261.
It is disclosed in Japanese Patent No. 537. However, when the above-mentioned spacer made of an inorganic material or a spacer made of a synthetic resin material is used as a spacer for a liquid crystal display element, there are the following drawbacks.

As shown in FIG. 8, an inorganic spacer 38
When a liquid crystal display element is manufactured by using, the spacer 38 is too hard, so that the alignment control film 33 is damaged when both the substrates 37 and 39 are pressed. In the damaged portion 33a of the alignment control film 33, the molecular alignment of the liquid crystal 41 cannot be maintained in a desired state. For example, in a transmissive liquid crystal display element, the damaged portion 33a becomes a display defect. Appears.

Furthermore, since the inorganic spacer 38 is too hard to be deformed, the spacer 38 comes into contact with the inner surfaces of both substrates 37 and 39 at one point. As a result, the spacer 38 is formed in the gap where the liquid crystal 41 exists,
It becomes easy to move due to gravity and minute vibrations. This problem is very noticeable in large-sized liquid crystal display devices used for laptop type personal computers, word processors, wall-mounted televisions, etc., which are rapidly becoming popular recently, because their display surfaces are used in a vertical or oblique state. Appears in. For example, when most of the spacer 38 moves to the lower part of the liquid crystal display element, the thickness of the liquid crystal layer becomes non-uniform, so that it becomes difficult to obtain a clear image. Further, the movement of the spacer 38 damages the alignment control film 33, thereby causing the above-described image display defect.

On the other hand, if a spacer that is too soft is used in a liquid crystal display element, the following inconvenience occurs. Boards 37, 3
When spraying the spacer 38 on the surface of 9, the spacer 3
It is impossible to disperse 8 completely evenly, and considerable dispersion occurs in the dispersal density. Then, the pair of substrates 37, 3
When pressing 9 in the direction facing each other, spacer 3
In the portion 8 having a small spraying density, the pressure applied to each spacer 38 is very large, so that the spacer 38 is largely deformed. On the contrary, since the pressure applied to each of the spacers 38 is small in the portion of the spacers 38 having a high dispersion density, the spacers 38 are hardly deformed. In this way, as shown in FIG. 9, the dispersion of the distribution density of the spacers 38 is caused by the pair of substrates 37, 39.
The thickness of the liquid crystal layer provided between them becomes uneven, and as a result, a clear image cannot be obtained.

Further, when the pressure is applied to the pair of substrates 37 and 39, it is actually impossible to apply the pressure uniformly to the entire substrates 37 and 39, and the substrates 37 and 39 are different at different positions of the surfaces. You will be under pressure. Therefore, when the spacers 38 that are too soft are used, the spacers 38 may be different due to the difference in pressure received by each spacer 38.
As a result of non-uniformity in the degree of deformation, the thickness of the liquid crystal layer becomes uneven. This significantly reduces the quality of the displayed image.

By the way, in the field of electronics packaging, in order to connect a pair of fine electrodes, a conductive paste is prepared by mixing metal particles such as gold, silver and nickel and a binder resin, and this paste is used as a pair of fine electrodes. By filling between the electrodes, the fine electrodes are connected. However, it is difficult to uniformly disperse the metal particles in the binder resin because the metal particles have a non-uniform shape and have a larger specific gravity than the binder resin.

In JP-A-59-28185, a metal plating layer is provided on the surface of particles such as glass beads, silica beads, and glass fibers having a relatively uniform particle diameter to form conductive microspheres. Is disclosed. However, the conductive microspheres disclosed in the above publication are difficult to compress and deform because the base microspheres are too hard. Therefore, if an attempt is made to connect the electrodes using the conductive microspheres, the contact area between the conductive microspheres and the electrode surface does not increase, and it becomes difficult to reduce the contact resistance value.

Japanese Unexamined Patent Publication (Kokai) No. 62-185749 and Japanese Unexamined Patent Publication (Kokai) No. 1-225776 disclose conductive microspheres using polyphenylene sulfide particles, phenol resin particles, etc. as the base microspheres. However, the conductive microspheres using such synthetic resin particles as the base microspheres have poor denaturation recovery properties after compression denaturation. Therefore, when the connection between the electrodes is performed using the conductive microspheres, when a compressive load acting on both electrodes is removed, a slight gap is formed at the interface between the conductive microspheres and the electrode surface, As a result, poor contact occurs.

[0017]

SUMMARY OF THE INVENTION In view of the above, the present invention is capable of (1) damaging the alignment control film of a liquid crystal display element to induce modulation of the alignment characteristics of the liquid crystal and lowering the quality of the displayed image. No spherical spacers; (2) Spherical spacers that do not reduce the sharpness of the displayed image by causing disorder in the size of the liquid crystal layer gap of the liquid crystal display element; (3) Do not move due to gravity or minute vibration Spherical spacer and liquid crystal display device using the same; (4) Liquid crystal display device capable of obtaining a clear image without defects in the displayed image; (5) Conductive microspheres having appropriate compressive deformability and deformation recovery property;
(6) It is an object to provide a conductive microsphere having excellent connection reliability.

[0018]

[Means for Solving the Problems] The above-mentioned object is K = (3 / √2) · F · S −3 / 2 · R ^−1/2 (where F is a 10% compression deformation of a ^microsphere ). Represents the load value (kgf), S represents the compression displacement (mm), and R
Represents the radius (mm) of the microsphere. The value of K defined by) is 250 to 700 kgf / mm ² at 20 ° C, and the recovery rate after compressive deformation can be achieved by the microspheres having a recovery rate of 10% or more and less than 30% at 20 ° C. Hereinafter, the present invention will be described in detail.

First, the K value defined in the present invention will be described. According to Landau-Liftsitz theory physics course "Theory of elasticity" (published in Tokyo Book 1972), page 42, when two elastic spheres with radii R and R'contact each other, h
Is given by: h = F ^2/3 [D ² (1 / R + 1 / R ′)] ^1/3 (1) D = (3/4) [(1-σ ² ) / E + (1-σ ′ ² ) / E ′ (2) (In the formula, h represents the difference between the distances between R + R ′ and the centers of both spheres, F represents the compressive force, E and E ′ represent the elastic moduli of the two elastic spheres, σ and σ'represent the Boason's ratio of the elastic sphere.)

On the other hand, the sphere is placed on a rigid plate, and
When compressing from both sides, if R '→ ∞, E) E'
The following equation is obtained approximately. F = (2 ^1/2 / 3) (S ^3/2 ) (E · R ^1/2 ) (1-σ ² ) (3) (In the formula, S represents the amount of compressive deformation.) Then, the following equation can be easily obtained. K = E / (1−σ ² ) (4) Therefore, the equation expressing the K value: K = (3 / √2) · F · S ^−3/2
-R- ^{1 / 2} (5) is obtained. The K value universally and quantitatively represents the hardness of the sphere. By using the above K value, it is possible to quantitatively and uniquely express the suitable hardness of the microspheres or spacers (hereinafter referred to as spacers).

In the spacer and the like of the present invention, the K value at 10% compression strain is 250 to 700 kgf / mm ^2.
It is. If it is less than 250 kgf / mm ² , it becomes difficult to control the cell gap and 700 kgf / mm
^If it exceeds ² , there is a drawback that the liquid crystal orientation control film surface is scratched in the manufacturing process of the liquid crystal display element, and further, in the manufactured liquid crystal display element, the compression deformation of the spacer or the like against the shrinkage when the temperature decreases. Is less likely to occur, and bubbles are generated in the liquid crystal cell due to the reduced pressure, so the range is limited. By using a spacer or the like within the above range, for example, when manufacturing a liquid crystal display element, the alignment control film is not damaged by the spacer or the like, and a gap between both electrodes is formed by a pressure press. When
Gap control can be easily performed. More preferably, it is 350 to 550 kgf / mm ² .

By the way, it is not possible to completely express the material mechanical properties of a suitable spacer or the like simply by defining the suitable hardness of the spacer or the like used in the liquid crystal display element. Another important property is that the recovery rate after compression deformation, which is a value indicating the elasticity of the spacer or the like, is within a predetermined range. By defining the recovery rate after compressive deformation, it is possible to quantitatively and uniquely express the elasticity or plasticity of the spacers and the like.

As a recent tendency, a spacer or the like having a relatively high K value and a low recovery rate has been demanded, and particularly when it is used for a liquid crystal color filter, such demand is remarkable. As shown in FIG. 5, the structure of the color filter substrate is such that each pixel of the three primary colors is formed on the glass substrate 14.
15, 16, and 17 are provided, and a black matrix (light-shielding film) 1 is provided to improve image contrast.
8 borders each pixel 15, 16, 17. The transparent conductive layer 19 protecting the pixels 15, 16 and 17 and
An overcoat layer 20 is provided on the pixels 15, 16 and 17 to facilitate the vapor deposition. And
The transparent conductive layer 19 is present at the top. In an actual color liquid crystal display element, spacers etc. are scattered on this,
Pressure will be applied to control the cell gap.

The pixels 15, 16 and 17 are very soft as compared with the glass substrate 14. The overcoat layer 20 described above allows the pixels 15, 16,
Although the softness of 17 is covered to some extent, recently, the overcoat layer 20 is often omitted to simplify the process (called an overcoatless method). In any case,
An extremely thin transparent conductive layer 19 on a very soft pixel is brought into direct contact with a spacer or the like to apply pressure. In this case, if a spacer having a high recovery rate (high elasticity) is used, the deformation due to the pressure during the cell gap control is small, so most of the pressure is applied to the pixels 15 and 1.
As a result, the spacers are bitten into the pixels 15, 16, 17 which are very soft, and the depressions are formed on the pixels 15, 16, 17.

When such a phenomenon occurs, the ultrathin transparent conductive layer 19 on the pixels 15, 16 and 17 is naturally
It is damaged and the control of the cell gap becomes difficult. Especially,
The STN type color liquid crystal display element has a fatal impact on its performance.

The spacer or the like of the present invention can be used in a liquid crystal color filter. The recovery rate of the spacers and the like after compression deformation is 10% or more and less than 30% at 20 ° C. If a spacer or the like having a recovery rate of less than 10% is used, when the pressure is locally applied excessively when the gap between the substrates is pressed by the pressure press, the spacer or the like remains in the compressed and deformed state. For this reason, the gap does not return to the original position at that location, resulting in unevenness of the gap. If a spacer or the like of 30% or more is used, the pressure is released after the gap between the substrates is made by a pressure press in the liquid crystal cell manufacturing process. When this is done, the spacers that have been compressed and deformed are likely to elastically recover, and the gap of the liquid crystal cell taken out is disturbed. Therefore, the range is limited to the above range. The preferable recovery rate after compressive deformation is 15% or more and less than 30%.

Next, a method of measuring the K value and the recovery rate after compression deformation will be described. (A) Measurement method and conditions of K value (i) Measurement method At room temperature, a spacer or the like is sprayed on a steel plate having a smooth surface, and one spacer or the like is selected from the dispersion. Next, using a micro compression tester (PCT-200 type, manufactured by Shimadzu Corp.), the spacers and the like are compressed by the smooth end surface of a diamond cylinder having a diameter of 50 μm. At this time, the compression load is electrically detected as an electromagnetic force, and the compression displacement is electrically detected as a displacement by the operating transformer.

As a result, the compression displacement as shown in FIG.
The relationship of loads is required. From FIG. 2, 1 such as a spacer
The load value and the compressive displacement at 0% compressive deformation are obtained, respectively, and from these values and the equation (5), K as shown in FIG. 3 is obtained.
The relationship between the value and the compression strain is required. However, the compressive strain is a value obtained by dividing the compressive displacement by the particle diameter of the spacer or the like and expressed in%. (Ii) Compression speed A constant load speed compression method is used. 0.27 grams weight per second (g
The load is increased at the rate of rf). (Iii) Test load Maximum 10 grf.

(B) Method of Measuring Recovery Rate after Compressive Deformation and Conditions (i) Method of Measuring At room temperature, spacers or the like are scattered on a steel sheet having a smooth surface, and one spacer or the like is selected from them. Next, using a micro compression tester (PCT-200 type, manufactured by Shimadzu Corp.), the spacers and the like are compressed by the smooth end surface of a diamond cylinder having a diameter of 50 μm. At this time, the compression load is electrically detected as an electromagnetic force, and the compression displacement is electrically detected as a displacement by the operating transformer.

As shown in FIG. 4, after compressing the spacers and the like to the reverse load value (shown by the curve (a) in FIG. 4), the load is decreased conversely (at the curve (b) in FIG. 4). Shown).
At this time, the relationship between the load and the compression displacement is measured. However,
The end point in unloading is not a load value of zero but an origin load value of 0.1 g or more. Recovery rate is displacement L to the point of reversal
₁ and the displacement difference L ₂ from the point of inversion to the point of taking the origin load value
The ratio (L ₂ / L ₁ ) of is defined as a value expressed in%.

(Ii) Measurement conditions Reverse load value 1 grf Origin load value 0.1 grf Compression rate under load and unload 0.27 grf / sec Measuring chamber temperature 20 ° C.

As the spacer and the like of the present invention, any of inorganic particles and synthetic resin particles can be used as long as they satisfy the above K value and the above recovery rate. Among them, synthetic resin particles are preferable because the K value and the recovery rate can be easily adjusted within the above ranges.

The synthetic resin particles suitable for forming the spacers and the like are not particularly limited, and examples thereof include polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polytetrafluoroethylene, polystyrene, polymethylmethacrylate, and polyethylene. Linear or cross-linked polymer such as terephthalate, polybutylene terephthalate, polyamide, polyimide, polysulfone, polyphenylene oxide, polyacetal; epoxy resin, phenol resin, melamine resin, unsaturated polyester resin, divinylbenzene polymer, divinylbenzene-styrene copolymer It has a network structure such as polymer, divinylbenzene-acrylic acid ester copolymer, diallyl phthalate polymer, triallyl isocyanurate polymer, benzoguanamine polymer. Butter, and the like can be mentioned.

Among them, divinylbenzene polymer, divinylbenzene-styrene copolymer, divinylbenzene-
Resins having a network structure such as acrylic acid ester copolymers and diallyl phthalate polymers are preferable. The inorganic particles are not particularly limited, and conventionally known particles can be used.

The shape of the spacers and the like is preferably spherical, for example. The diameter is 0.1 to 5000 μm. If it is less than 0.1 μm, it tends to aggregate and lack practicality as a spacer, and if it exceeds 5000 μm, it is rarely used, and therefore it is limited to the above range.
It is preferably 0.1 to 1000 μm. The variation coefficient of diameter is 50% or less. When it exceeds 50%, the particle size distribution becomes too wide and the performance of the spacer becomes problematic, so the content is limited to the above range. Preferably, 35% or less,
More preferably, it is 20% or less.

The colored spherical spacer for a liquid crystal display device according to claim 7 has a K value within a predetermined range and a recovery rate after compression deformation within a predetermined range, and is colored. The coloring method is not particularly limited, and examples thereof include a method of mixing a dye and a pigment, polymerization of a dye monomer, and a method of forming a metal thin film on a spacer and oxidizing the metal thin film. The coloring method is described in, for example, JP-A-57-189117 and JP-A-63-189117.
89890, JP 1-144021, JP 1-144429, and JP 63-66228.
JP-A-63-89408, JP-A 1-2
No. 00227, Japanese Patent Laid-Open No. 1-2007719,
It is disclosed in Japanese Patent Laid-Open No. 2-214781.

The colored spherical spacer is used as a spacer for a liquid crystal display device. In a liquid crystal display device, when a voltage is applied between transparent electrodes, the liquid crystal causes an optical change to form an image. In contrast, the spacers show no optical change due to their application. Therefore, in the dark area when the image is displayed, the uncolored spacer may be recognized as a bright spot, which may lower the contrast of the image display.
The colored spherical spacers are suitable.

The adhesive spherical spacer for a liquid crystal display device according to claim 8 has a K value within a predetermined range and a recovery rate after compression deformation within a predetermined range, and has adhesiveness when heated. . The method of imparting adhesiveness to the spacer is not particularly limited, and examples thereof include a method of providing a polyethylene wax layer, a hot melt adhesive layer, an epoxy adhesive layer on the surface of the base microsphere. The method of imparting adhesiveness is described in, for example, Japanese Utility Model Publication No. 51-22435, Japanese Patent Application Laid-Open No. 63-44631, Japanese Patent Application Laid-Open No. 63-94224, Japanese Patent Application Laid-Open No. 63-200126, Japanese Patent Application Laid-Open No. 24
7154, JP-A-1-247155, and JP-A-2-261537.

The adhesive spherical spacer is used as a spacer for a liquid crystal display device. This can prevent the spacer from moving in the gap of the substrate as described above. As a result, it is possible to positively prevent the inconvenient phenomenon of damaging the alignment control film, improve the image quality of the display image, and improve the accuracy of the gap between the substrates.

The base fine particles used in the colored spherical spacer of claim 7 and the adhesive spherical spacer of claim 8 are:
It can be manufactured from the above-mentioned spacers or the like. As described above, the spacer of the present invention has a K value within a predetermined range,
By having a recovery rate after compression deformation within a predetermined range, it has physical properties suitable as a spacer of a liquid crystal display element. That is, since the hardness of the spacer is appropriate, the alignment control film is not damaged when the substrate is pressed in the process of manufacturing the liquid crystal display element.

Further, since the spacer has an appropriate deformability, the substrate and the spacer come into contact with each other over a wide area. As a result, the spacer becomes difficult to move on the surface of the substrate due to gravity or minute vibration. In addition, it is possible to prevent the alignment control film from being damaged by the movement of the spacer. Furthermore, since the spacer has an appropriate hardness,
When pressurizing the pair of substrates in the directions facing each other, the pressing force can be supported by the spacer to keep the gap between the base materials constant. Therefore, unevenness in the thickness of the liquid crystal layer can be reduced as compared with the related art.

Next, an example of the liquid crystal display device of the present invention will be described with reference to the drawings. The liquid crystal display element of the present invention can have the same configuration as that shown in FIG. 7 except that the above-mentioned spherical spacer is used. As shown in FIG.
The liquid crystal display element A includes a pair of substrates 7, 9 and a spacer 8 and a nematic liquid crystal 11 arranged between the pair of substrates 7, 9 for keeping a gap between the pair of substrates 7, 9 constant. The seal member 10 is filled around the space between the pair of substrates 7 and 9, and the polarizing sheets 12 and 13 are coated on the surfaces of the substrates 7 and 9.

The above-mentioned substrates 7 and 9 are formed of transparent substrates 1 and 4 made of glass on one surface of which ITO (Indium-Tin-Ox) is provided.
ide) transparent electrodes 2 and 5 made of a film or the like are patterned, and the surfaces of the transparent electrodes 2 and 5 and the transparent substrates 1 and 4 are covered with alignment control films 3 and 6 made of a polyimide film or the like. . The orientation control films 3 and 6 are subjected to orientation control processing by rubbing. The spacer 8 has a K value within the above-described predetermined range and a recovery rate after compression deformation within the predetermined range. This spacer 8 may be a colored spacer and / or an adhesive spacer. Therefore, according to the present invention, it is possible to obtain a liquid crystal display element capable of obtaining a clear image without a defect of a display image.

The conductive microspheres according to claim 12 are the above microspheres.
And a conductive layer provided on the surface of the microsphere. This
Conductive microspheres are used in the electronic packaging field
It can be used for conductive connection between fine electrodes. This conductive
As described above, the compressive strain of the microspheres is 10%.
K value at 250-700 kgf / mm^TwoAnd
By using conductive microspheres within this range,
For example, a liquid crystal in which a pair of electrodes are connected by conductive microspheres.
In the manufacturing process of the display element, the counter electrode surface is made of conductive microspheres.
It does not hurt your body,
When setting the gap between both electrodes,
Can be done easily. More preferably 35
0 to 550 kgf / mm ^TwoIt is.

If the K value is less than 250 kgf / mm ² , the compressive deformation is often increased when a compressive load is applied with the conductive microspheres sandwiched between the two electrodes.
The conductive layer on the surface of the conductive microsphere cannot follow this deformation, and as a result, there is a risk that the conductive layer is broken or peeled off. Further, if the amount of compressive deformation becomes excessively large and the conductive microspheres become flat, the electrodes directly contact each other, and there is a problem that a sufficient fine connection cannot be made.

When the K value exceeds 700 kgf / mm ² , the conductive microspheres are not easily deformed even if a compressive load is applied with the conductive microspheres sandwiched between two electrodes, and as a result, the conductive microspheres are electrically conductive. The contact area between the conductive microspheres and the electrode surface does not increase, and it becomes difficult to reduce the contact resistance value. Further, if a load is forcibly applied to deform the conductive microspheres, the conductive layer on the surface of the conductive microspheres may be broken or peeled off, or the electrode surface may be damaged in the manufacturing process of the liquid crystal display element. .

Furthermore, in the conductive microspheres according to claim 12, the range of the recovery rate after the compressive deformation of the conductive microspheres is 20.
It is 10% or more and less than 30% at 0 ° C. Recovery rate is 10
If it is less than%, the liquid crystal display device prepared by the method of filling the adhesive in which the conductive microspheres are dispersed between two electrodes and pressurizing and adhering the adhesive is cured, and then depressurizing is The adhesive layer repeatedly contracts and expands in a repeated environment, but since the conductive microspheres are still compressed and deformed, a gap is created between the adhesive layer and the electrode surface, causing poor contact. cause. On the other hand, when the recovery rate is 30% or more, the adhesive in which the conductive microspheres are dispersed is sandwiched between two electrodes and pressure-bonded, and when the adhesive is cured and then depressurized, the conductive material is compressed and deformed. Since the elastic microspheres are likely to recover elasticity, the adhesive layer may be peeled off from the electrode surface, so the range is limited to the above range. Preferably, 1
It is 5% or more and less than 30%.

The conductive microspheres of the present invention may be made of inorganic materials or synthetic resins as long as they satisfy the K value and recovery rate in the above ranges. As the microspheres forming the conductive microspheres, the same spacers and the like as described above can be used. Among them, preferred resins for forming microspheres are resins having a network structure such as divinylbenzene polymer, divinylbenzene-styrene copolymer, divinylbenzene-acrylic acid ester copolymer and diallyl phthalate polymer.

The diameter of the microspheres is 0.1 to 5000 μm.
m is preferred. If it is less than 0.1 μm, the microspheres tend to agglomerate and are impractical, and if it exceeds 5000 μm, it is rarely used. More preferably, 0.1-10
00 μm. The thickness of the conductive layer is 0.02 to 5
μm is preferred. If the thickness of the conductive layer is less than 0.02 μm, it is difficult to obtain the desired conductivity, and if it exceeds 5 μm, the conductive layer is separated from the surface of the microsphere due to the difference in the coefficient of thermal expansion between the microsphere and the conductive layer. Easy to peel off.

The metal used for the conductive layer is not particularly limited, and examples thereof include nickel, gold, silver, copper, cobalt tin,
Examples thereof include indium and the like or alloys containing these as the main components. Of these, indium is preferable. The method for forming the metal layer on the surface of the microspheres is not particularly limited, and for example, a method by electroless plating (also referred to as chemical plating method); a paste obtained by mixing metal fine powder alone or with a binder is microspheres. A physical vapor deposition method such as vacuum vapor deposition, ion plating, or ion sputtering.

The method of forming the metal layer by the electroless plating method will be described below by taking the case of gold displacement plating as an example. This method is divided into the following etching step, activation step, chemical nickel plating step, and gold displacement plating step. The etching step is a step in which unevenness is formed on the surface of the microsphere to attach the plating layer to the microsphere, and the etching solution includes, for example, caustic soda aqueous solution, concentrated hydrochloric acid, concentrated sulfuric acid or chromic anhydride. .

The activation step is a step for forming a catalyst layer on the surface of the etched microspheres and activating the catalyst layer. The activation of the catalyst layer promotes the deposition of metallic nickel in a chemical nickel plating step described below. Pd ²⁺ and Sn on the surface of microspheres
^The catalyst layer containing ²⁺ is treated with concentrated sulfuric acid or concentrated hydrochloric acid to dissolve and remove only Sn ²⁺ to metallize Pd ²⁺ . The metallized palladium is activated and sensitized by a palladium activator such as a concentrated solution of sodium hydroxide.

The chemical nickel plating step is a step of further forming a metallic nickel layer on the surface of the microsphere on which the catalyst layer is formed. For example, nickel chloride is reduced by sodium hypophosphite to convert nickel into microspheres. Deposit on the surface of. In the gold displacement plating step, the microspheres coated with nickel in this way are placed in an aqueous solution of potassium gold cyanide, and while elevating the temperature, nickel is eluted to deposit gold on the surface of the microspheres.

When the conductive layer is formed of an indium plated layer, the thickness of the conductive layer is preferably 0.02 to 5 μm. When the thickness of the conductive layer is less than 0.02 μm, it is difficult to obtain the desired conductivity, and when it exceeds 5 μm, the conductive fine spheres are sandwiched between a pair of electrodes and pressure is applied to both electrodes to reduce the conductive fineness. The elastic properties of the spheres are not effectively exhibited, and the conductive microspheres are likely to aggregate.

As a method for forming the indium plated layer on the surface of the microsphere, the following method can be given, for example. Method of forming indium plating layer by electroless plating method After forming a thin film of another metal (for example, copper) having a higher ionization tendency than indium on the surface of the microsphere in advance, this metal is converted into indium by the following formula. It is a plating method to replace with. By depositing indium on the surface of the microsphere by the addition to reduction reaction the reducing agent to an aqueous solution of ^{3Cu + 2In +++ → 3Cu ++ +} 2In ↓ reduction plating indium salt,
This is a plating method for forming an indium plating layer. Alternatively, after forming a thin film of another metal such as nickel on the surface of the microsphere in advance, indium may be deposited on the surface by a reduction reaction to form the thin film.

Method of forming indium plated layer by mechanical or physical method After mixing fine spheres and indium fine particles, the indium fine particles are caused to collide with the surface of the fine spheres by hybridization or mechanofusion method, or the surface of the fine spheres is mixed. An indium thin film is formed on the surface of the fine particles by rubbing indium fine particles on the surface. Alternatively, after mixing the fine spheres and the indium fine particles, the fine spheres may be heated to melt the indium and coat the surface of the fine spheres with the indium thin film.

A liquid crystal display device can be manufactured using the conductive microspheres thus obtained. This liquid crystal display element can be manufactured, for example, as follows. As shown in FIG. 6, a conductive microsphere 29 uniformly dispersed in an insulating binder 28 is applied onto one electrode 24 by screen printing or a dispenser.
Alternatively, only the conductive microspheres 29 are arranged on the electrode 24 without using the binder 28. In the latter case, the conductive microspheres 29 may be sprayed from above the electrode 24, or the conductive microspheres 29 may be charged and electrostatically attached onto the electrode 24.

Next, the other electrode 25 is connected to the above electrode 24.
On top of. In this state, both electrodes 24 and 25 are pressed. Here, no particularly large pressing force is required.
The pressure may be such that the contact between the conductive microspheres 29 and the surfaces of the electrodes 24 and 25 is maintained. Next, the pair of electrodes 24, 25
The laminated body in which the conductive microspheres 29 are sandwiched is heated.
Press heating is preferred as the heating method. In this way, the liquid crystal display element B as shown in FIG. 6 is obtained.

As the electrodes used in the above liquid crystal display element, for example, an electrode having an ITO thin film formed on a glass plate, an electrode having an aluminum thin film formed on a glass plate, a copper sheet attached on a plastic film, Electrodes formed by etching this, electrodes formed by printing silver paste, carbon black on the film, and the like are included. As described above, by using the conductive microspheres, it is possible to electrically provide a predetermined portion between the electrodes of the liquid crystal display element or the like.

Since the conductive microspheres of claim 12 can be appropriately compressed and deformed, when the conductive microspheres are used to connect the electrodes, the conductive microspheres and the electrode surface are separated from each other. The contact resistance value can be reduced by enlarging the contact area. Furthermore, since the deformation recovery property after compressive deformation is also appropriate, when the compressive load acting on both electrodes is removed in the step of connecting the electrodes by using the conductive microspheres, No gap is formed at the interface with the electrode surface, and no contact failure occurs.

As described above, the conductive fine particles of the present invention are
Since it has appropriate compressive deformability and deformation recovery property, when used by sandwiching it between two electrodes, it can exhibit excellent anisotropic conductive performance and connection reliability performance, and is suitable for the following applications. Is. Transfer material for electrical connection between upper and lower substrate electrodes in liquid crystal display devices. C between the LSI and the glass wiring board in the liquid crystal display element
Material for OG (chip on glass) connection. Electrical connection material between glass wiring board and flexible printed circuit in liquid crystal display device. COG with a plate or film substrate and LSI
(Chip on glass) or COF (Chip on film) connection material.

[0062]

Since the microsphere of the present invention has the above-mentioned constitution, it can be suitably used as a spherical spacer for a liquid crystal display device. Further, a more preferable liquid crystal display element can be obtained by coloring, imparting adhesiveness, or providing a conductive layer.

[Brief description of the drawings]

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

FIG. 2 is a graph showing the relationship between load and compressive displacement of spacers.

FIG. 3 is a graph showing the relationship between K value and compressive strain of spacers.

FIG. 4 is a diagram illustrating a method of measuring a recovery rate after compression deformation of a spacer.

FIG. 5 is a sectional view of a substrate of a general color filter.

FIG. 6 is a cross-sectional view of a main part of an element obtained by using conductive microspheres.

FIG. 7 is a cross-sectional view showing a general liquid crystal display element.

FIG. 8 is a cross-sectional view of a liquid crystal display element when a spherical spacer that is too hard is used.

FIG. 9 is a cross-sectional view of a liquid crystal display element when a spacer that is too soft is used.

[Explanation of symbols]

 1 Transparent Substrate 2 Transparent Electrode 3 Alignment Control Film 4 Transparent Substrate 5 Transparent Electrode 6 Orientation Control Film 7 Substrate 8 Spacer 9 Substrate 10 Sealing Member 11 Nematic Liquid Crystal 12 Polarizing Sheet 13 Polarizing Sheet 14 Glass Substrate 15 Red Pixel 16 Green Pixel 17 Blue Pixel 18 Black Matrix 19 Transparent Conductive Layer 20 Overcoat Layer 21a Electrode 22 Electrode 24 Electrode 25 Electrode 26 Transparent Substrate 27 Transparent Substrate 28 Binder 29 Conductive Microspheres 30 Sealing Member 31 Transparent Substrate 32 Transparent Electrode 33 Alignment Control Film 33a Alignment Control Film Damaged part 34 Transparent substrate 35 Transparent electrode 36 Alignment control film 37 Substrate 38 Spacer 39 Substrate 41 Nematic liquid crystal 42 Polarizing sheet 43 Polarizing sheet

Claims (13)

[Claims] During 1. A K = (3 / √2) · F · S -3/2 · R -1/2 ( wherein, F is, represents the load value at 10% compressive deformation of the fine spheres (kgf), S represents compression displacement (mm), R
Represents the radius (mm) of the microsphere. The value of K defined in) is 250 to 700 kgf / mm ² at 20 ° C., and the recovery rate after compression deformation is 10% or more and less than 30% at 20 ° C., a microsphere. 2. The value of K is 350 to 550 kgf / mm.
The microsphere according to claim 1, which is ² . 3. The recovery rate after compression deformation is 15% or more and 30.
The microsphere according to claim 1, which is less than%. 4. The microspheres have a diameter of 0.1 to 5000 μm.
The microsphere according to claim 1, wherein the coefficient of variation of the diameter (the value obtained by dividing the standard deviation by the diameter is represented by%) is 50% or less. 5. The diameter of the microspheres is 0.1 to 1000 μm.
And the coefficient of variation of the diameter is 50% or less. During wherein K = (3 / √2) · F · S -3/2 · R -1/2 ( wherein, F is, represents the load value at 10% compressive deformation of the fine spheres (kgf), S represents compression displacement (mm), R
Represents the radius (mm) of the microsphere. A liquid crystal display device characterized in that the K value defined in) is 250 to 700 kgf / mm ² at 20 ° C., and the recovery rate after compression deformation is 10% or more and less than 30% at 20 ° C. Spherical spacer. 7. A spacer for a liquid crystal display device containing colored ^microspheres , wherein K = (3 / √2) · F · S −3 / 2 · R ^−1/2 (where F is , Represents the load value (kgf) at 10% compression deformation of the microspheres, S represents the compression displacement (mm), R
Represents the radius (mm) of the microsphere. A liquid crystal display device characterized in that the K value defined in) is 250 to 700 kgf / mm ² at 20 ° C., and the recovery rate after compression deformation is 10% or more and less than 30% at 20 ° C. Colored spherical spacer. 8. A spacer for a liquid crystal display device containing adhesive ^microspheres , wherein K = (3 / √2) · F · S −3 / 2 · R ^−1/2 (wherein F is , Represents the load value (kgf) at 10% compression deformation of the microspheres, S represents the compression displacement (mm), R
Represents the radius (mm) of the microsphere. A liquid crystal display device characterized in that the K value defined in) is 250 to 700 kgf / mm ² at 20 ° C., and the recovery rate after compression deformation is 10% or more and less than 30% at 20 ° C. Adhesive spherical spacer. 9. A liquid crystal display device using the spherical spacer according to claim 6. 10. A liquid crystal display device comprising the colored spherical spacer according to claim 7. 11. A liquid crystal display device using the adhesive spherical spacer according to claim 8. 12. A conductive microsphere, comprising the microsphere according to claim 1 and a conductive layer provided on the surface of the microsphere. 13. A liquid crystal display device using the conductive microspheres according to claim 12.