JPH11166023A - Spacer for liquid crystal display device, and liquid crystal display device by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a core-shell type spacer for a liquid crystal display device having functions such as properties for preventing an abnormal aligning imparted into a shell layer while keeping a physical strength required for a spacer, and further to provide a liquid crystal display element by using the same. SOLUTION: This liquid crystal display device is obtained by forming a graft polymerized layer formed on the surface of a fine particle by reacting the fine particle having a reducing group on the surface with a persulfate as an oxidant. The liquid crystal display device is obtained by arranging two glass substrates having aligned membranes and transparent electrodes arranged thereon to face each other via the spacer for the liquid crystal display device described in the claims 1 or 2, and sealing a liquid crystal between the opposed glass substrates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a spacer for a liquid crystal display device and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art As shown in FIG. 1, a conventional twisted nematic (TN) mode liquid crystal display device using spacers comprises a pair of substrates 8, 10,
0, a nematic liquid crystal 11 sealed between
A sealing member 1 filled around the substrate 10;
In order to keep the gap between the pair of substrates 8 and 10 constant, a spacer 9 is disposed between the substrates 8 and 10 using the polarizing sheets 12 and 13 coated on the surfaces of the substrates as constituent materials. .

The substrates 8 and 10 are made of glass transparent substrates 2 and
5, a pattern of transparent electrodes 3 and 6 made of an ITO film or the like is formed on one side, and the surfaces of the transparent electrodes 3 and 6 and the transparent substrates 2 and 5 are coated with alignment control films 4 and 7 made of a polyimide film or the like. Is obtained by The alignment control films 4 and 7 are subjected to an alignment control process by rubbing.

As a material for the spacer 9, generally,
Organic or inorganic materials are used. Examples of the spacer made of an inorganic material include those containing aluminum oxide, silicon dioxide, and the like (see, for example, JP-A-63-73225, JP-A-1-599974). But,
Conventional inorganic spacers have a high hardness, which damages the alignment film, and makes it difficult for the thickness change due to thermal expansion and shrinkage to follow the substrate, thereby causing poor gap unevenness.

Further, the spacer made of an organic material has an appropriate hardness that does not damage the alignment film, easily follows a change in thickness due to thermal expansion or thermal shrinkage, and further has a feature that spacer movement in a cell is small. There are mainly used polystyrene-based or benzoguanamine-based polymers (for example, JP-A-60-200288, JP-A-1-29331).
No. 6).

However, the liquid crystal display device manufactured using the above-described spacer has a problem that abnormal alignment of liquid crystal occurs around the liquid crystal spacer immediately after the cell is manufactured (hereinafter referred to as an “initial state”) and after a high voltage is applied. there were. In particular, a display device using a super twisted nematic (STN) liquid crystal has a problem that the tendency is remarkable and a uniform image cannot be maintained. The cause of the abnormal alignment is that the liquid crystal molecules are aligned around the spacer, and the magnitude of the abnormal alignment is estimated to depend on the degree of alignment of the liquid crystal molecules.

In order to solve such an abnormal orientation, the dielectric constant of the spacer (see Japanese Patent Application Laid-Open No. 6-67182)
Further, studies have been made to change the spacer surface composition (see JP-A-6-118421). However, if the composition of the polymer is largely changed in order to prevent abnormal alignment, there is a problem that the particles become fragile particles which do not have the necessary strength for the spacer and are broken when the liquid crystal display element is assembled.

[0008] Therefore, what is called a core-shell type spacer in which the inside of the particle has a sufficient strength and only the surface of the particle has a composition suitable for preventing abnormal orientation has been studied. However, there have been problems such as the inability to uniformly modify the entire surface and the necessity of a complicated multi-step operation for forming a shell layer.

[0009]

SUMMARY OF THE INVENTION In view of the above, the present invention has been developed, while maintaining the mechanical strength required for a spacer.
It is an object of the present invention to provide a core-shell type liquid crystal display element spacer in which a shell layer is provided with a function such as abnormal alignment prevention performance, and a liquid crystal display element using the same.

[0010]

According to the present invention, there is provided a liquid crystal display device comprising a fine particle having a reducing group on its surface, a persulfate being reacted with an oxidizing agent to form a graft polymerization layer on the surface of the fine particles. It is a spacer for. Hereinafter, the present invention will be described in detail.

The spacer for a liquid crystal display element of the present invention is a so-called core-shell type spacer in which a shell layer composed of a graft polymer layer is formed on the surface of fine particles as a core.

Since the fine particles used in the present invention function as core particles of a spacer for a liquid crystal display element, various performances are required in a particle size, a particle size distribution, a mechanical strength, and the like.

The particle size of the fine particles is preferably 1 to 10 μm. The particle size distribution of the fine particles is preferably 10% or less as a CV value obtained by dividing the standard deviation by the particle size. The mechanical strength of the fine particles preferably has a 10% K value of 250 to 1,000. If it is less than 250, the strength of the fine particles is not sufficient, so that the spacer is broken when assembling the liquid crystal display element and an appropriate gap does not appear. The alignment film is damaged, and display abnormalities occur.

[0014] The above 10% K value is defined as Table 6-5.
No. 03180, a micro compression tester (PCT
-200, manufactured by Shimadzu Corporation), the fine particles are compressed at a compression endurance of 0.27 g / sec and a maximum test load of 10 g on a smooth end surface of a diamond-made cylinder having a diameter of 50 μm. .

K = (3 / √2) ・^FS -3 / 2 ・ R- ^{1 / 2} F: Overload value (kg) at 10% compressive deformation of fine particles S: Compressive displacement at 10% compressive deformation of fine particles (Mm) R: radius of fine particles (mm)

In the present invention, the fine particles have a reducing group on the surface. The reducing group is not particularly limited, and includes, for example, a hydroxyl group, a thiol group, an aldehyde group, a mercapto group, an amino group and the like.

The method for obtaining the fine particles having a reducing group on the surface is not particularly limited. For example, a method by a polymerization method such as emulsion polymerization, suspension polymerization, seed polymerization, dispersion polymerization, and dispersion seed polymerization; A method using an agent; a method using a surfactant, and the like.

As the method by the above polymerization method, for example,
A reducing group-containing monomer, and another monomer copolymerizable with the reducing group-containing monomer and / or a crosslinkable monomer copolymerizable with the reducing group-containing monomer. And a method of obtaining fine particles by copolymerization.

The reducing group of the reducing group-containing monomer is not particularly limited, and includes, for example, a hydroxyl group, a thiol group, an aldehyde group, a mercapto group, an amino group and the like. The reducing group-containing monomer is not particularly limited, and examples thereof include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, 2-methacryloyloxyethyl succinic acid, and 2-methacryloyloxy. (Meth) acrylic acid ester derivatives such as phthalic acid, mono [2 (meth) acryloyloxyethyl] acid phosphate, glycerol mono (meth) acrylate, glycerin di (meth) acrylate; styrene derivatives; vinyl esters; conjugated dienes, etc. Is mentioned.

Other monomers copolymerizable with the reducing group-containing monomer are not particularly restricted but include, for example, styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene, chloromethylstyrene. Vinyl esters such as vinyl chloride, vinyl acetate and vinyl propionate; unsaturated nitriles such as acrylonitrile; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, ethylene glycol (meth) acrylate, trifluoroethyl (meth) acrylate, pentafluoropropyl (meth) acrylate, cyclohexyl (meth)
(Meth) acrylate derivatives such as acrylates;
Conjugated dienes such as butadiene and isoprene are exemplified.

The crosslinkable monomer copolymerizable with the reducing group-containing monomer is not particularly limited. For example, divinylbenzene, polyethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) ) Acrylate, neopentyl glycol di (meth) acrylate,
Examples include trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolpropanetetra (meth) acrylate, diallyl phthalate and its isomers, triallyl isocyanurate and its derivatives, and the like.

Further, the fine particles are prepared from a radical polymerizable monomer such as γ-methacryloxypropyltrimethoxysilane having a reactive point on a side chain thereof, and sufficient mechanical strength is obtained by a crosslinking reaction of the side chain portion. It may be provided.

The reducing group-containing monomer, the other monomer, and the crosslinkable monomer may be used alone.
Two or more kinds may be used in combination. However, from the viewpoint of the strength of the obtained spacer for a liquid crystal display element, it is desirable that the above-mentioned crosslinkable monomer accounts for 30% or more of all monomers.

As a method using the above-mentioned polymer protective agent,
For example, a method of introducing a reducing group into the surface of the obtained fine particles by using a polymer protecting agent having a reducing group at the time of polymerizing the fine particles can be mentioned. The polymer protective agent is not particularly limited as long as it contains a reducing group, and examples thereof include polyvinyl alcohol and derivatives thereof, cellulose, cellulose acetate, starch, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and polymethacrylic acid. And the like.

As a method of using the above-mentioned surfactant, for example, a reactive surfactant having a reducing group or the like is used at the time of polymerizing the fine particles to introduce a reducing group onto the surface of the obtained fine particles. Method and the like.

As the fine particles having a reducing group on the surface, fine particles made of an inorganic compound having a reducing group on the surface can be used.

The fine particles may be colored fine particles for improving the contrast of the liquid crystal display device. The colored fine particles are not particularly limited, and include, for example,
Those obtained by treating the fine particles with carbon black, disperse dye, acid dye, basic dye, metal oxide, etc .; those formed by forming an organic film on the surface of the fine particles and dissolving or carbonizing at a high temperature, etc. Is mentioned.
When the material forming the fine particles has a color, it can be used as the colored fine particles without coloring.

The method for producing the above-mentioned colored fine particles is not particularly limited. For example, a composition obtained by dispersing a pigment in the above-mentioned reducing group-containing monomer or the like is mixed with an aqueous medium in the presence of a polymerization initiator. And a method of performing suspension polymerization.

The pigment used in producing the colored fine particles is not particularly limited, and examples thereof include inorganic color pigments such as carbon black, graphite, iron black, chrome green, cobalt green, and chromium oxide; brilliant carmine BS, lake Azo or condensed azo organic coloring pigments such as Carmine FB, Brilliant Fast Scarlet, Lake Red 4R, Permanent Red R, Fast Red FGR, Toluidine Malon, Bisazo Yellow, First Yellow G, Bisazo Orange, Vulcan Orange, Pyrazolone Red, etc. Phthalocyanine-based organic coloring pigments such as phthalocyanine blue, fast ska blue, and phthalocyanine green; dye lake organic coloring pigments such as yellow lake, rose lake, violet lake, blue lake, and green lake; Futaron organic coloring pigments. These may be used alone or in combination of two or more.

In the present invention, a graft polymerization layer is formed on the surface of the fine particles by reacting the fine particles having a reducing group on the surface with a persulfate as an oxidizing agent. .

The method for reacting the persulfate with the fine particles is not particularly limited. For example, the fine particles are dispersed in a polymerization system, and the persulfate and the graft polymerization layer are formed in the polymerization system. A method of adding a polymerizable monomer and the like can be mentioned.

The persulfate is not particularly restricted but includes, for example, ammonium persulfate, sodium persulfate, potassium persulfate and lithium persulfate. The concentration of the above persulfate is 0.05 to 50 × 10 ^{−3 with} respect to the polymerization system.
mol / L is preferred. If it is less than 0.05 × 10 ⁻³ mol / L, the grafting rate is reduced because the overall polymerization conversion does not increase, and if it exceeds 50 × 10 ⁻³ mol / L,
Since the molecular weight of the generated graft chain is low, the effect of modifying the surface of the fine particles is low.

The polymerizable monomer is not particularly limited as long as it is a radical polymerizable monomer, and a polymer having a property desired to be imparted to the obtained liquid crystal display element spacer may be used. For example, when it is desired to impart hydrophilicity, hydroxyethyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate and the like can be mentioned. When it is desired to impart hydrophobicity, alkyl (meth) acrylates such as butyl (meth) acrylate and stearyl (meth) acrylate; fluorine-containing (meth) acrylates such as trifluoroethyl (meth) acrylate; styrene; and styrenes such as p-chlorostyrene. When a reaction site is to be introduced, glycidyl (meth) acrylate, (meth) acrylamide and the like can be mentioned. These may be used alone,
More than one species may be used in combination.

The reaction temperature during the graft reaction in the above polymerization system is not particularly limited, but is preferably 30 to 100 ° C. in consideration of the reaction time and the viscosity of the system. The solvent for the polymerization system is not particularly limited, but water alone or a mixed solvent of water and a polar organic solvent is preferable in view of the solubility of the oxidizing agent. The polar organic solvent is not particularly limited and includes, for example, alcohols such as methanol, ethanol, propanol, i-propanol, butanol, t-butyl alcohol; ketones such as acetone and methyl ethyl ketone; ethers such as methyl ether; dimethyl Sulfoxide, dimethylformamide and the like.

Further, the graft polymerization layer obtained as described above can be further subjected to various reactions. For example, when a hydroxyl group, a glycidyl group, or the like is introduced on the surface of the fine particles, a compound having an isocyanate group, a carboxylic acid group, a carboxylic acid chloride, an amino group, or the like is reacted with the fine particles having the graft polymerization layer formed on the surface. It is also possible to form a new surface.

The present invention 2 relates to a liquid crystal display device comprising a fine particle having a reducing group on its surface, a persulfate and an acidic sulfite being reacted as an oxidizing agent to form a graft polymerization layer on the surface of the fine particles. It is a spacer.

The spacer for a liquid crystal display element of the present invention 2 is the same as the spacer for a liquid crystal display element of the present invention 1 except that an acidic sulfite is used in addition to a persulfate as an oxidizing agent.

The acidic sulfite is not particularly restricted but includes, for example, sodium bisulfite, potassium bisulfite, lithium bisulfite, ammonium bisulfite and the like. The concentration of the acidic sulfite is preferably 0.01 to 1 × 10 ⁻³ mol / L with respect to the polymerization system. 0.
When it is less than 01 × 10 ⁻³ mol / L, the grafting efficiency and the polymerization rate decrease, and when it exceeds 1 × 10 ⁻³ mol / L,
Although the conversion increases, the grafting efficiency decreases.

According to a third aspect of the present invention, two glass substrates on which an alignment film and a transparent electrode are disposed are opposed to each other via the liquid crystal display element spacer of the first aspect or the liquid crystal display element spacer of the second aspect. This is a liquid crystal display element in which liquid crystal is sealed between glass substrates. Examples of the liquid crystal display element include those shown in FIG.

[0040]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

The evaluation of the mechanical strength and the analysis of the surface composition in Examples and Comparative Examples were performed by the following methods.

(Evaluation of Mechanical Strength) Micro Compression Tester (PC
Using a T-200 (manufactured by Shimadzu Corporation), the obtained fine particles were subjected to a compression test at a compression rate of 0.27 g / sec and a maximum test load of 10 g using a diamond-made cylindrical smooth end face having a diameter of 50 μm. The K value was determined from this. K = (3 / √2) ・^FS -3 / 2 ・ R- ^{1 / 2} F: Overload value at 10% compressive deformation of fine particles (kg) S: Compressive displacement at 10% compressive deformation of fine particles (mm) R: radius of fine particles (mm)

(Surface Composition Analysis) Analysis was performed by a delinquency time type secondary ion mass spectrometer (TOF-SIMS). According to this apparatus, the area of 0.2 μm square is set to 0.01 in the thickness direction.
Only the polar surface of about μm can be analyzed, and a mass spectrum of the sample surface can be obtained. By comparing this spectrum with a standard sample, the polymer constituting the surface of each sample was identified.

Example 1 (Preparation of core particles) A mixture of 100 parts by weight of divinylbenzene and 2 parts by weight of benzoyl peroxide was added to 800 parts by weight of a 3% aqueous solution of polyvinyl alcohol, and the mixture was stirred with a homogenizer to adjust the particle size. went. Thereafter, the temperature was raised to 80 ° C. under a nitrogen stream with stirring, and the reaction was carried out for 15 hours. After the obtained fine particles were washed with hot ion-exchanged water and methanol, a classification operation was performed. The obtained fine particles had an average particle size of 6.0 μm and a CV value of 5, and the following operation was performed using the fine particles as core particles. In addition, TOF-SIM
When surface analysis was performed by S, OH groups derived from polyvinyl alcohol were confirmed.

(Preparation of Core-Shell Particles) A separable flask was charged with 100 parts by weight of dimethyl sulfoxide, 10 parts by weight of ion-exchanged water, 45 parts by weight of methyl methacrylate, and 5 parts by weight of the core particles obtained by the above operation.
After sufficiently dispersing with a sonicator, the mixture was uniformly stirred. Further, 0.8 parts by weight of ammonium persulfate (20 × 1
0 ^-3 mol / L), dissolved sufficiently, and stirred. The system was once depressurized with a pump, and then nitrogen gas was introduced and stirring was continued for 30 minutes. This was heated to 50 ° C. in a water bath, and the reaction was continued for 5 hours. After 5 hours, cool the system,
The reaction was stopped by adding 100 parts by weight of tetrahydrofuran and a small amount of hydroquinone. After the completion of the reaction, the reaction solution was taken out, and the particles and the reaction solution were separated by filtration with a 3 μm membrane filter. The particles were sufficiently washed with tetrahydrofuran, and dried under reduced pressure with a vacuum drier.

For the obtained particles, the mechanical strength (10%
K value) and surface analysis by TOF-SIMS. As a result, the mechanical strength is 450 kgf / mm ² ,
Methyl methacrylate was present on the particle surface.

Example 2 (Preparation of core particles) The same operation as in Example 1 was performed.

(Preparation of Core-Shell Particles) 150 parts by weight of ion-exchanged water, 45 parts by weight of methyl methacrylate and 5 parts by weight of the core particles obtained by the above operation were added to a separable flask, and sufficiently dispersed by a sonicator. Stirring was performed uniformly. In addition, ammonium persulfate 0.1.
15 parts by weight (3.4 × 10 ⁻³ mol / L) and 0.003 parts by weight of sodium bisulfite (0.15 × 10 ⁻³ mol)
/ L), dissolved sufficiently, and stirred. The system was once depressurized with a pump, and then nitrogen gas was introduced and stirring was continued for 30 minutes. This was heated to 50 ° C. in a water bath,
The reaction was continued for hours. Two hours later, the system was cooled, and the reaction was stopped by adding 100 parts by weight of tetrahydrofuran and a small amount of hydroquinone. After the reaction, take out the reaction solution,
The particles and the reaction solution were separated by filtration with a 3 μm membrane filter. The particles are sufficiently washed with tetrahydrofuran,
Vacuum drying was performed with a vacuum dryer.

For the obtained particles, the mechanical strength (10%
K value) and surface analysis by TOF-SIMS. As a result, the mechanical strength is 420 kgf / mm ² ,
Methyl methacrylate was present on the particle surface.

Example 3 (Preparation of core particles) The same operation as in Example 1 was performed.

(Preparation of Core-Shell Particles) Example 1 was repeated except that butyl methacrylate was used instead of methyl methacrylate, and 100 parts by weight of ion-exchanged water and 30 parts by weight of i-propyl alcohol were used as a reaction solvent.
The same operation as described above was performed. About the obtained particle, evaluation of mechanical strength (10% K value) and surface analysis by TOF-SIMS were performed. As a result, the mechanical strength was 450 kgf / mm
² , and butyl methacrylate was present on the particle surface.

Example 4 (Preparation of core particles) The same operation as in Example 1 was performed.

(Preparation of core-shell particles) In a separable flask, 110 parts by weight of ion-exchanged water, 20 parts by weight of t-butyl alcohol, and 45 parts of hydroxyethyl methacrylate
After the addition of 5 parts by weight of the core particles and 5 parts by weight of the core particles obtained by the above operation, the mixture was sufficiently dispersed by a sonicator, and then uniformly stirred. Further, 0.15 parts by weight of ammonium persulfate (3.4 × 10 ⁻³ mol / L) and 0.003 (0.15 × 10 ⁻³ mol / L) of sodium hydrogen sulfite are added, sufficiently dissolved and stirred. Was. The system was once depressurized with a pump, and then nitrogen gas was introduced and stirring was continued for 30 minutes. This was heated to 50 ° C. in a water bath, and the reaction was continued for 2 hours. After 2 hours, the system was cooled and the reaction was stopped by adding 100 parts by weight of methanol and a small amount of hydroquinone. After the completion of the reaction, the reaction solution was taken out, and the particles and the reaction solution were separated by filtration with a 3 μm membrane filter. The particles were sufficiently washed with tetrahydrofuran, and dried under reduced pressure with a vacuum drier.

For the obtained particles, the mechanical strength (10%
K value) and surface analysis by TOF-SIMS. As a result, the mechanical strength is 450 kgf / mm ² ,
Hydroxyethyl methacrylate was present on the particle surface.

Example 5 (Preparation of core particles) The same operation as in Example 1 was performed.

(Preparation of Core-Shell Particles) Same as Example 1 except that glycidyl methacrylate was used instead of methyl methacrylate, and 100 parts by weight of ion-exchanged water and 30 parts by weight of i-propyl alcohol were used as a reaction solvent. Was performed. About the obtained particle, evaluation of mechanical strength (10% K value) and surface analysis by TOF-SIMS were performed. As a result, the mechanical strength was 450 kgf /
a mm ^2, the surface of the particles were present glycidyl methacrylate.

Example 6 (Preparation of core particles) 50 parts by weight of trimethylolpropane triacrylate, 40 parts by weight of divinylbenzene, and 10 parts by weight of acrylonitrile were uniformly mixed, and 12 parts by weight of carbon black was added thereto. 4 using
Stirring was performed for 8 hours. 2 parts by weight of benzoyl peroxide were uniformly mixed with this stirred mixture, and further added to 850 parts by weight of a 3% aqueous solution of polyvinyl alcohol. After sufficiently stirring and adjusting the viscosity, the mixture was heated to 80 ° C. under a nitrogen stream.
And the reaction was carried out for 15 hours. After the obtained fine particles were washed with hot water and methanol, a classification operation was performed. The obtained fine particles had an average particle size of 6.0 μm and a CV value of 5.
0 and black. The following operation was performed using these fine particles as core particles. In addition, when surface analysis was performed by TOF-SIMS, OH derived from polyvinyl alcohol was analyzed.
The group was identified.

(Preparation of Core-Shell Particles) The same operation as in Example 1 was performed except that the core particles obtained by the above operation were used. The mechanical strength (10%
K value) and surface analysis by TOF-SIMS. As a result, the mechanical strength is 400 kgf / mm ² ,
Methyl methacrylate was present on the particle surface.

Example 7 (Preparation of core particles) Surfactant Hytenol N-08
A mixture of 80 parts by weight of divinylbenzene, 20 parts by weight of hydroxyethyl methacrylate, and 2 parts by weight of benzoyl peroxide was added to 800 parts by weight of a 3% aqueous solution (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and the mixture was stirred with a homogenizer to obtain a viscosity. Adjustments were made. Thereafter, the temperature was raised to 80 ° C. under a nitrogen stream with stirring, and the reaction was carried out for 15 hours. After the obtained fine particles were washed with hot water and methanol, a classification operation was performed. The obtained fine particles had an average particle size of 6.0 μm and a CV value of 5.0. The following operation was performed using these fine particles as core particles.
In addition, when surface analysis was performed by TOF-SIMS, OH groups derived from hydroxyethyl methacrylate were confirmed.

(Preparation of core-shell particles) The same operation as in Example 1 was performed except that the core particles obtained by the above operation were used. The mechanical strength (10%
K value) and surface analysis by TOF-SIMS. As a result, the mechanical strength is 420 kgf / mm ² ,
Methyl methacrylate was present on the particle surface.

Example 8 (Preparation of core particles) The same operation as in Example 1 was performed except that hydroxypropyl cellulose was used instead of polyvinyl alcohol. The following operation was performed using the obtained fine particles as core particles. In addition, when surface analysis was performed by TOF-SIMS, OH groups derived from hydroxypropyl cellulose were confirmed.

(Preparation of core-shell particles) The same operation as in Example 1 was performed except that the core particles obtained by the above operation were used. The mechanical strength (10%
K value) and surface analysis by TOF-SIMS. As a result, the mechanical strength is 450 kgf / mm ² ,
Methyl methacrylate was present on the particle surface.

Example 9 (Preparation of core particles) The same operation as in Example 1 was performed.

(Preparation of core-shell particles) The amount of sodium bisulfite was adjusted to 0.012 (0.7 × 10 ⁻³ mol / L).
Other than that described above, the same operation as in Example 2 was performed. About the obtained particle, evaluation of mechanical strength (10% K value) and surface analysis by TOF-SIMS were performed. As a result, the mechanical strength was 450 kgf / mm ² , and methyl methacrylate was present on the particle surface.

Example 10 (Preparation of core particles) The same operation as in Example 1 was performed.

(Preparation of Core-Shell Particles) The same operation as in Example 2 was performed, except that potassium bisulfite was used instead of sodium bisulfite. About the obtained particles, evaluation of mechanical strength (10% K value) and TOF-SI
Surface analysis by MS was performed. As a result, the mechanical strength is 450
kgf / mm ² , and methyl methacrylate was present on the particle surface.

Comparative Example 1 (Preparation of core particles) The same operation as in Example 1 was performed.

(Preparation of Core-Shell Particles) A separable flask was charged with 100 parts by weight of ion-exchanged water, 40 parts by weight of t-butyl alcohol, 45 parts by weight of methyl methacrylate, and 5 parts by weight of the core particles obtained by the above operation.
After sufficiently dispersing with a sonicator, the mixture was uniformly stirred. Further, 0.15 parts by weight of azobisisobutyronitrile was added, dissolved sufficiently, and stirred. The system was once depressurized with a pump, and then nitrogen gas was introduced and stirring was continued for 30 minutes. This was heated to 50 ° C. in a water bath, and the reaction was continued for 2 hours. Two hours later, the system was cooled, and the reaction was stopped by adding 100 parts by weight of tetrahydrofuran and a small amount of hydroquinone. After completion of the reaction, take out the reaction solution, 3 μm
The particles and the reaction solution were separated by filtration using a membrane filter.
The particles were sufficiently washed with tetrahydrofuran, and dried under reduced pressure with a vacuum drier.

For the obtained particles, the mechanical strength (10%
K value) and surface analysis by TOF-SIMS. As a result, the mechanical strength is 450 kgf / mm ² ,
No methyl methacrylate was present on the particle surface, and only core particles were observed.

Comparative Example 2 Divinylbenzene 20 parts by weight, methyl methacrylate 4
Using 0 parts by weight and 40 parts by weight of glycidyl methacrylate, the same operation as in the synthesis of the core particles of Example 1 was performed.
About the obtained particle, evaluation of mechanical strength (10% K value) and surface analysis by TOF-SIMS were performed. result,
The obtained particles were very fragile and the mechanical strength could not be measured. Divinylbenzene and glycidyl methacrylate were present on the particle surface.

[0071]

Since the spacer for a liquid crystal display element of the present invention has the above-described structure, it has a function such as an abnormal alignment preventing property while maintaining the mechanical strength required for the spacer. Therefore, by using the spacer for a liquid crystal display element of the present invention, it is possible to easily improve the abnormal alignment phenomenon of the liquid crystal, the adhesion of the spacer, the dispersibility, etc., and to obtain a liquid crystal display element capable of obtaining a uniform and good image. Can be provided.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Seal member 2 Transparent substrate 3 Transparent electrode 4 Alignment control film 5 Transparent substrate 6 Transparent electrode 7 Alignment control film 8 Substrate 9 Spacer 10 Substrate 11 Nematic liquid crystal 12 Polarizing sheet 13 Polarizing sheet

Claims (3)

[Claims] 1. A spacer for a liquid crystal display element, wherein a graft polymerization layer is formed on the surface of fine particles by reacting fine particles having a reducing group on the surface with a persulfate as an oxidizing agent. 2. A liquid crystal display comprising a graft polymer layer formed on the surface of fine particles by reacting fine particles having a reducing group on the surface with a persulfate and an acidic sulfite as an oxidizing agent. Element spacer. 3. Two glass substrates on which an alignment film and a transparent electrode are disposed are opposed to each other via the liquid crystal display element spacer according to claim 1 or 2, and a liquid crystal is sealed between the glass substrates. A liquid crystal display device characterized by the above-mentioned.