JPH0553122A - Spacer particle and liquid crystal display device containing this particle - Google Patents

Abstract

PURPOSE:To prevent generation of uneven density and color shading of a display image even if a large load or shock is applied to a part, of a liquid crystal display cell by providing the liquid crystal display cell in which a specific spacer particle is interposed between transparent electrodes. CONSTITUTION:In a liquid crystal display cell, a pair of substrates 2, 2 are placed by opposing transparent, electrodes 2a through a spacer particle 1. On this transparent electrode 2a, an oriented film 2b is provided, a peripheral edge part of the substrates 2, 2 is sealed by hardening a sealing resin 2c, and a liquid crystal 2d is closed up by a pair of substrates 2, 2 and the hardened sealing resin 2c. Also, the spacer particle 1 consists of a spherical particle group whose CV value is <=10%, and contains at least 20% flock. Moreover, the spacer particle in which >=90%, of this flock is coagulated like a plane is used, and even if external force is applied, the flock is dispersed, a cell gap is held uniformly, and unevenness of a display image is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to spacer particles and a liquid crystal display device including the spacer particles, and more particularly, to a spacer particle without breaking even when a large load or impact is locally applied to the liquid crystal display cell. Therefore, the present invention relates to spacer particles capable of maintaining a uniform cell gap and a liquid crystal display device including such spacer particles.

[0002]

BACKGROUND OF THE INVENTION In a liquid crystal display device, a liquid crystal display cell having a structure in which liquid crystal is sealed between a pair of transparent electrodes formed on a transparent substrate is used. , Ie distance between electrodes (cell gap)
Are required to be as uniform as possible.

Therefore, a spacer made of an insulating material is interposed between the electrodes to maintain the uniformity of the cell gap. As such spacers, spherical, columnar, and fibrous spacers made of synthetic resin or an inorganic compound such as silica or alumina are known.

Among these, when spherical particles are used as spacers, uniformity of particle size is required. For example, Japanese Patent Laid-Open No. 62-269933 discloses a coefficient of variation (CV value) indicating uniformity of particle size. ) Is used as a spacer.

The present applicant has previously filed an application for a liquid crystal display device using a spherical particle group having a CV value of 2% or less and a ratio of agglomerated particles in all particles of 5% or less (Japanese Patent Application No. 2- 26
5532). Even if spherical particles having uniform individual particles are used as spacers, if the particles have randomly aggregated particles, the cell gap becomes non-uniform. This is done by the technical idea of making uniform the cell gap by using monodisperse particles having a small amount as a spacer.

However, in the case where most of such spherical particle groups are composed of monodisperse particles, when a large external load or impact is locally applied to the liquid crystal display cell, the load per particle is large, such as silica particles. Inorganic compound particles may be broken. Further, when such particle destruction occurs, there is a problem that the cell gap becomes non-uniform in the area where the particles are destroyed, resulting in uneven density and uneven color in the displayed image.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to overcome the above-mentioned problems of the prior art. Spacer particles existing inside the liquid crystal display cell can be formed even if a large load or impact is locally applied to the liquid crystal display cell. Therefore, it is an object of the present invention to provide spacer particles which can maintain a uniform cell gap without breaking.

Another object of the present invention is to provide a liquid crystal display device in which uneven density and color unevenness of a displayed image do not occur even after a large load or impact is locally applied to the liquid crystal display cell. ..

[0009]

SUMMARY OF THE INVENTION Spacer particles according to the present invention are composed of spherical particles having a CV value of 10% or less, contain at least 20% of agglomerated particles, and 90% of the agglomerated particles.
The above is characterized in that they are aggregated in a plane.

In the liquid crystal display device according to the present invention, liquid crystal is enclosed between a pair of transparent electrodes formed on a transparent substrate,
A liquid crystal display device comprising a liquid crystal display cell in which a spacer is interposed between the transparent electrodes, the spacer particles being included as the spacer.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The spacer particles and the liquid crystal display device according to the present invention will be specifically described below.

The spacer particles according to the present invention are composed of spherical particles having a CV value of 10% or less, preferably 5% or less. The CV value as referred to in the present invention is a value calculated by the following formula by measuring the individual particle diameters of the spherical particle group and determining the average particle diameter (D) and standard deviation (σ) of the spherical particle group. Means

CV (%) = (σ / D) × 100 When the particles are aggregated, the particle size of each individual particle constituting the aggregated particles is measured.

The spacer particles according to the present invention have the above-mentioned C content.
At the same time as satisfying the V value, it consists of spherical particle groups containing 20% or more, preferably 30% or more, more preferably 50% or more of agglomerated particles, and 90% or more, preferably 95% or more of the agglomerated particles are planar. Aggregated particles that are aggregated into.

In the present invention, the agglomerated particles that are agglomerated in a plane means that when the agglomerated particles are placed on a flat surface such as glass as shown in FIG. It means agglomerated particles that come into contact with a flat surface. Note that FIG. 2 shows aggregated particles that are not aggregated in a plane.

In the agglomerated particles that are agglomerated in a plane as described above, two or more particles are agglomerated on the same plane. In the present invention, the number of spherical particles constituting the aggregated particles is not particularly limited, but the number of particles constituting the aggregated particles is 5
If the number exceeds the number, the number becomes visible, and low-temperature bubbles are easily generated, so 2 to 5 are preferable.

The aggregated particles contained in the spacer particles according to the present invention do not necessarily have to have the same number of aggregated particles. That is, most of the spacer particles according to the present invention are composed of monodisperse particles having a uniform particle size and agglomerated particles in which particles having a uniform particle size are planarly aggregated. When a spherical particle group containing such agglomerated particles is used as a spacer of a liquid crystal display cell, the local load or impact applied to the liquid crystal display cell is shared by the individual particles constituting the agglomerated particles. Therefore, the load per particle is reduced, and the destruction of particles is prevented.

Therefore, the breakage of the spacer particles makes the cell gap non-uniform, and uneven density and color unevenness of the display image generated in the liquid crystal display device due to the non-uniform cell gap are prevented.

Furthermore, since the agglomerated particles contained in the spacer particles according to the present invention are agglomerated in a plane, unlike the agglomerated particles randomly aggregated, the individual particles constituting the agglomerated particles are different from each other. As long as the particle size is uniform, the uniformity of the cell gap will not be impaired.

The spherical particle group containing the specific CV value and the specific amount of the specific agglomerated particles as described above can be obtained by classifying the spherical particle group produced by the following method. ． A metal alkoxide is added to a water-alcohol-based dispersion liquid in which a metal oxide or a metal hydroxide is dispersed as a seed, while keeping such a dispersion liquid to be hydrolyzed, and contained in the dispersion liquid. A method of adhering a decomposition product of a metal alkoxide on a seed to grow particles (Japanese Patent Laid-Open No. 62-275005).

[0021]. After the particles are grown by the method described in (1), the particles are separated from the dispersion, and the particles are heat-treated at a temperature of 250 ° C. or higher to blacken the particles (JP-A-63-89408).
Publication).

.. Seed particles dispersed water - by adding tetraethoxysilane to an organic solvent dispersion liquid, the tetraethoxysilane, the following formula [I] _{(CH 3 O) n · (} C 2 H 5 O) 4-n Si ... [I] (wherein n is 1 to 4) is hydrolyzed in the presence of an alkoxysilane represented by the formula, and silica is allowed to adhere to the seed particles in the dispersion to grow the particles. Method of performing (Japanese Patent Application No. 1-310023).

When spherical particles are produced by this method, the above formula [I] is added to 1 mol of tetraethoxysilane.
It is preferable that the alkoxysilane represented by is used in an amount of 0.05 × 10 ^-2 mol to 6.0 × 10 ^-2 mol (each molar ratio converted to SiO ₂ ).

[0024]. To a water-alcohol-based dispersion in which a metal oxide or metal hydroxide is dispersed as a seed, tetraalkoxysilane and silicic acid solution are added while keeping such a dispersion, and hydrolysis of tetraalkoxylane is performed. A method of adhering a product and a silicic acid polymer onto a seed contained in a dispersion to grow particles (Japanese Patent Application No. 122403/1990).

As described in JP-A-63-94224, the spherical particles obtained by the above-mentioned method and method are synthesized with the diameter of each particle being D on the surface of each particle. If the diameter of the resin powder is d, a synthetic resin powder having d of D / 5 or less may be attached, and the particles to which the synthetic resin powder is attached in this manner are subjected to an impact force. While joining particles by fusing at least a part of the synthetic resin powder to the particles,
The synthetic resin powder may be fixed to the particles.

It is also possible to blacken the spherical particles obtained by the methods (1) and (2) in the same manner as described above. The spherical particle group produced as described above is classified by a method such as a water sieving method to obtain a spherical particle group used as spacer particles in the present invention.

Next, the liquid crystal display device according to the present invention will be specifically described. FIG. 3 is a sectional view showing an example of a liquid crystal display cell used in the liquid crystal display device of the present invention.

In this liquid crystal display cell, a pair of substrates 2 and 2 are arranged with spacer particles 1 in between, with transparent electrodes 2a provided on one surface of each substrate 2 facing each other. An alignment film 2b is provided on the transparent electrode 2a. Further, the peripheral edges of the substrates 2 and 2 are sealed by curing the sealing resin 2c, and the liquid crystal 2d is sealed by the pair of substrates 2 and 2 and the cured sealing resin 2c.

In the present invention, the spacer particles 1 consist of the above-mentioned spacer particles, that is, spherical particles having a CV value of 10% or less, contain at least 20% of agglomerated particles, and 90% or more of the agglomerated particles. Spacer particles in which the particles are aggregated in a plane are used.

This spacer particle 1 is usually a liquid crystal 2d.
Although it is used by being dispersed therein, it may be used by being dispersed in the sealing resin 2c. An example of the liquid crystal display cell used in the liquid crystal display device of the present invention has been described above.
Need not be formed on the transparent electrode 2a, and a polarizing plate is attached to the surface of the substrate 2 located on the opposite side of the transparent electrode 2a and is further reflected by the polarizing plate located inside the liquid crystal display device. The plates can be glued together. As described above, the liquid crystal display device according to the present invention has various embodiments.

In the present invention, glass or plastic can be used as the transparent substrate. As the transparent plastic, for example, polycarbonate, polyether sulfone, polysulfone, polyolefin, etc. are used, and the plastic transparent substrate may be in the form of a sheet or a film.

A known transparent electrode can be used as the transparent electrode according to the present invention. For example, an ITO film or Sn.
An O ₂ film, an Sb-doped SnO ₂ film, or the like is used. Furthermore, as an alignment film, sealing resin and liquid crystal,
As with the transparent electrode, known materials can be used.

[0033]

The spacer particles according to the present invention are composed of spherical particle groups containing aggregated particles, and most of the aggregated particles are planarly aggregated. A uniform cell gap is maintained as in the case of using it as a spacer of a display cell, and at the same time, even if a large load or impact is locally applied to the liquid crystal display cell from the outside, This load or impact is dispersed. Therefore, even if a large load or shock is locally applied to the liquid crystal display cell from the outside, the spacer particles existing inside the liquid crystal display cell are prevented from being destroyed, and the cell gap is prevented from being broken due to the destruction of the spacer particles. Uniformity is prevented.

Therefore, the liquid crystal display device according to the present invention comprises a liquid crystal display cell in which such spacer particles are interposed between transparent electrodes, and a large load or impact is locally applied to the liquid crystal display cell from the outside. Even though the cell gap is prevented from becoming non-uniform due to the breakage of the spacer particles, uneven density and color unevenness of the displayed image may occur even after a large load or impact is locally applied to the liquid crystal display cell. Absent.

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0036]

Example 1 1) Production of spherical particles for spacers In a mixed solution of 3686 g of ethanol, 1365 g of pure water and 922 g of ammonia water, 249 g of spherical silica having an average particle size of 5.0 μm (Mazuka SW manufactured by Catalyst Kasei Kogyo Co., Ltd.) was used. After dispersion, 161 g of 1 wt% NaOH aqueous solution was added to prepare a seed particle dispersion.

This dispersion was placed in an autoclave at 120 ° C.
The temperature is maintained at this temperature and the silicic acid solution (S
4 g of a solution obtained by dealkalizing a water glass aqueous solution by cation exchange treatment with an io ₂ concentration of 5 wt%) was added. Next, 132 g of an ethanol / water / ammonia mixed solution (weight ratio 1.0 / 0.3 / 0.1) and 21 g of ethyl silicate (SiO ₂ concentration 28 wt%) were simultaneously added.

This operation was repeated until 120 g of the silicic acid solution, 3938 g of the above ethanol / water / ammonia mixed solution, and 625 g of ethyl silicate were added.

Thereafter, a 1 wt% NaOH aqueous solution 117
After adding g and holding at 150 ° C. for 1 hour, a silica particle dispersion was obtained. In order to obtain desired spacer particles from the silica particles thus obtained, the silica particles were dispersed in water and classified by a hydraulic classification method to obtain spacer spherical particles shown in Table 1.

The average particle diameter, CV value, and ratio of agglomerated particles are measured as follows. (1) Average particle size (D) The average particle size (D) was determined by an image analysis method of electron micrographs of the particles.

(2) CV value The average particle diameter (D) obtained in (1) above and the standard deviation (σ) obtained by the same image analysis as in (1) were obtained by the following equation.

CV = (σ / D) × 100 (3) Ratio of Aggregated Particles Calculated from the above-mentioned electron micrograph by the following formula from the total number of particles (N) and the total number of aggregated particles (n ₁ ).

N₁/ N × 100 (4) Ratio of specific agglomerated particles according to the present invention Total number of agglomerated particles in the above (3) (n₁), On the same plane
Number of particles aggregated in (n ₂) Was calculated by the following formula.

(N ₂ / n ₁ × 100 2) Destruction test of particles The particles for spacers described above were dispersed almost uniformly on a glass substrate (dispersion density of about 2,500 particles / cm ² ), and the same size was applied on this. Glass substrates were stacked.

A ratio of particles cracked after applying a load of 10 g per particle on the glass substrate was measured by an optical microscope. The results are shown in Table 1.

3) Evaluation of Liquid Crystal Display Cell An ink composition was prepared by dispersing 1 g of the silica fine particles obtained as described above in 100 g of an epoxy-based sealing resin. The obtained ink composition was printed with a screen printer on the periphery of the alignment film of the laminate in which the transparent electrode and the alignment film were formed on the polished glass substrate for a liquid crystal display device to obtain a substrate for a liquid crystal display device. ..

Then, 0.01 g of the silica fine particles obtained as described above is dispersed in 1 liter of ethyl alcohol,
This dispersion was sprayed onto the portion of the substrate for a liquid crystal display device where the sealing resin was not provided so that the dispersion density of the silica fine particles was about 2,500 particles / cm ² . Then, this liquid crystal display device substrate and another liquid crystal display device substrate having a transparent electrode and an alignment film provided on a glass substrate were dispersed so that their transparent electrodes face each other and as described above. Ten cells were prepared by laminating at a temperature of about 150 ° C. while applying a load of about 0.2 g per silica fine particle.

STN liquid crystal (manufactured by Merck) was injected into the cell thus obtained to obtain a liquid crystal display panel. The liquid crystal display panel thus obtained was evaluated for cell gap, color unevenness and low temperature vacuum bubbles by the following methods. The results are shown in Table 2.

(A) Cell Gap An interferometric film thickness meter (TM-005 manufactured by Canon Inc.) was used to measure the cell gaps at a plurality of points to determine the average cell gap and the variation (3σ).

(B) Color unevenness The presence or absence of color unevenness was determined by visual observation. (C) Low-temperature vacuum bubbles 10 liquid crystal display panels were cooled to -30 ° C and then returned to room temperature, and visually observed to count the number of liquid crystal display panels in which bubble-like low-temperature vacuum bubbles were generated. It was

[0051]

Comparative Example 1 Ethyl alcohol 3685.5 g, water 13
In a mixed solution of 65 g and 921.5 g of 28% ammonia water, spherical silica with an average particle size of 5.0 μm (catalytic chemical industry Co., Ltd., Masaki sphere SW-1.4 aggregated particles were separated by a centrifugation method. And CV: 1.9%, aggregation ratio 1.5%
After dispersing 249 g of spherical silica), 1 wt%
161 g of NaOH aqueous solution was added, and ultrasonic treatment was performed to prepare a seed particle dispersion liquid.

This seed particle dispersion was placed in an autoclave, heated to 120 ° C., and while maintaining this temperature, a sodium silicate aqueous solution was dealkalized to obtain a silicic acid solution (SiO ₂ concentration). : 5.0wt
%) 4 g, and then a mixed solution of ethyl alcohol / water / ammonia (weight ratio: 1.0 / 0.3 / 0.1)
131.5 g and 21 g of ethyl silicate (28 wt% as SiO ₂ ) were added simultaneously. This operation was repeated so that the outermost layer of the obtained silica particles became a layer of a polymer of the silicic acid solution, and the silicic acid solution of 120.5 was added in 5 hours.
g, 3937.5 g of a mixed solution of ethyl alcohol / water / ammonia having the same compounding ratio as described above, and 625 g of ethyl silicate were added. After adding the whole amount, 1 wt% NaO
After adding 117 g of the H aqueous solution, the mixture was kept at 150 ° C. for 1 hour to obtain a dispersion liquid in which silica particles were monodispersed.

Then, the particles were separated from this dispersion and dried at 200 ° C. to obtain powdery silica fine particles.
The obtained fine particles were used and evaluated according to the same test method as in Example 1.

The results are shown in Tables 1 and 2.

[0055]

[Table 1]

[0056]

[Table 2]

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating aggregated particles that are aggregated in a plane.

FIG. 2 is a cross-sectional view illustrating aggregated particles that are not aggregated in a plane.

FIG. 3 is a cross-sectional view showing an example of a liquid crystal display cell used in the liquid crystal display device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Spacer particle, 2 ... Substrate, 2a ... Transparent electrode, 2b ... Alignment film, 2c ... Resin cured material for sealing, 2d ... Liquid crystal.

Claims (2)

[Claims] 1. A spherical particle group having a CV value of 10% or less, at least 20% or more of aggregated particles, and 90% or more of the aggregated particles are planarly aggregated. Spacer particles. 2. A liquid crystal display device comprising a liquid crystal display cell in which a liquid crystal is sealed between a pair of transparent electrodes formed on a transparent substrate, and a spacer is interposed between the transparent electrodes, wherein the spacer is used. A liquid crystal display device comprising the described spacer particles.