U.S. patent application number 09/745801 was filed with the patent office on 2002-01-31 for liquid crystal display cell spacer and liquid crystal display cell.
This patent application is currently assigned to Sekisui Chemical Co., Ltd. Invention is credited to Tanaka, Susumu, Yamada, Kunikazu.
Application Number | 20020012757 09/745801 |
Document ID | / |
Family ID | 26364429 |
Filed Date | 2002-01-31 |
United States Patent
Application |
20020012757 |
Kind Code |
A1 |
Tanaka, Susumu ; et
al. |
January 31, 2002 |
Liquid crystal display cell spacer and liquid crystal display
cell
Abstract
The present invention relates to a liquid crystal display cell
spacer with improved in coloring effect and light shielding effect
and optimal electrical, physical, chemical, and optical properties
and a liquid crystal display cell with use thereof. A liquid
crystal display cell spacer comprising surface-coated carbon black;
a liquid crystal display cell spacer comprising a pigment component
comprising carbon black and at least one set of organic pigments of
dissimilar colors other than carbon black; and a liquid crystal
display cell spacer comprising a pigment component comprising
surface-coated carbon black and at least one set of organic
pigments of dissimilar colors other than carbon black. A liquid
crystal display cell with use any of above liquid crystal display
cell spacers.
Inventors: |
Tanaka, Susumu; (Shiga,
JP) ; Yamada, Kunikazu; (Shiga, JP) |
Correspondence
Address: |
Pollock, Vande Sande & Amernick, R.L.L.P.
Suite 800
1990 M Street, N.W.
Washington
DC
20036-3425
US
|
Assignee: |
Sekisui Chemical Co., Ltd
4-4 Nishitenma 2-chome, Kita-ku
Osaka
JP
530-8565
|
Family ID: |
26364429 |
Appl. No.: |
09/745801 |
Filed: |
December 26, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
09745801 |
Dec 26, 2000 |
|
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|
09125315 |
Aug 14, 1998 |
|
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6190774 |
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09125315 |
Aug 14, 1998 |
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PCT/JP97/00386 |
Feb 14, 1997 |
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Current U.S.
Class: |
428/1.1 ;
349/155 |
Current CPC
Class: |
C09K 2323/00 20200801;
G02F 1/133512 20130101; Y10T 428/2826 20150115; G02F 1/13392
20130101; Y10T 428/2991 20150115; G02F 1/1339 20130101; Y10T
428/2998 20150115; Y10T 428/24488 20150115; C09K 2323/05
20200801 |
Class at
Publication: |
428/1.1 ;
349/155 |
International
Class: |
G02F 001/1339 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 14, 1996 |
JP |
HEI-8-26621 |
Feb 14, 1996 |
JP |
HEI-8-26622 |
Claims
1. A liquid crystal display cell spacer comprising surface-coated
carbon black.
2. A liquid crystal display cell spacer comprising a pigment
component comprising carbon black and at least one set of organic
pigments of dissimilar colors other than carbon black.
3. A liquid crystal display cell spacer comprising a pigment
component comprising surface-coated carbon black and at least one
set of organic pigments of dissimilar colors other than carbon
black.
4. A liquid crystal display cell comprising a liquid crystal
display cell spacer according to claim 1, 2, or 3.
Description
TECHNICAL FIELD
[0001] The present invention relates to a liquid crystal display
cell spacer with improved in coloring effect and light shielding
effect and to a liquid crystal display cell with use thereof.
BACKGROUND ART
[0002] While the liquid crystal display cell has been used widely
in a variety of electronic equipment such as personal computers and
portable electronic devices, there has been much need for improving
its performance by increasing its display contrast of images.
Japanese Kokai Publication Sho-57-189117 discloses such a
technology which comprises disposing two transparent
electrode-carrying substrates with the respective electrodes facing
each other and a liquid crystal hermetically sandwiched between
said substrates, with particles of a colored spacer being dispersed
on the entire surfaces of the substrates which are adjoining to the
liquid crystal so as to prevent deterioration of the display
contrast of images.
[0003] The liquid crystal display cell spacer for such a
high-contrast liquid crystal display cell must have been colored to
a deep shade. While many production methods have heretofore been
proposed for the fabrication of such a liquid crystal display cell
spacer, they can be roughly divided into the technology which
comprises dyeing polymer particles previously manufactured and the
technology which comprises dyeing polymer particles in the course
of their manufacture.
[0004] The technology which comprises dyeing polymer particles
previously manufactured includes the following processes. Japanese
Kokai Publication Hei-1-144429 describes a process which comprises
treating polymer particles with an acid and then dyeing them.
Japanese Kokai Publication Hei-1-207719 discloses a process which
comprises subjecting polymer particles to heat treatment at 200 to
700.degree. C. to provide flame-resistant sintered particles.
Japanese Kokai Publication Hei-5-165033 discloses a process which
comprises coating polymer particles with a conjugated polymer such
as polyacetylene. Japanese Kokai Publication Hei-1-200227 describes
a process which comprises disposing a metallic layer on the surface
of crosslinked polymer particles and oxidizing the metal to the
metal oxide.
[0005] Japanese Kokai Publication Hei-4-15623 discloses a process
which comprises striking ultrafine black metal oxide particles into
the surface layers of organic polymer particles, while Japanese
Kokai Publication Hei-3-101713 discloses a process which comprises
dispersing particles of a polymer containing anionic functional
groups in a solution containing an oxidizing agent to let the
oxidizing agent adsorbed or impregnated, adding at least one member
selected from the group consisting of 5-membered heterocyclic
compounds and aromatic hydrocarbons, and causing the mixture to
undergo chemical oxidative polymerization. Disclosed in Japanese
Kokoku Publication Hei-4-27242 is a process in which particles of a
water-soluble polymer available upon polymerization of an
ethylenically unsaturated sulfonic acid compound or a salt thereof
are dyed with a basic dye.
[0006] Furthermore, Japanese Kokai Publication Hei-3-351639
discloses a process which comprises dyeing polymer particles
comprising amino resin with an acidic dye in the presence of a
solvent at high temperature, while Japanese Kokai Publication
Hei-4-363331 discloses a process which comprises dispersing an oily
solution of an oily dye uniformly in an aqueous medium, mixing the
resulting dye emulsion with an emulsion of polymer particles so as
to dye the particles.
[0007] However, this technology of coloring polymer particles
prepared beforehand not only entails high production costs but also
has the drawback that the performance and quality charcteristics of
the final product cannot be easily controlled.
[0008] The technology which comprises dyeing polymer particles in
the course of their manufacture includes the following and other
processes. Japanese Kokoku Publication Sho-50-33821, Japanese
Kokoku Publication Sho-56-50883, and Japanese Kokoku Publication
Hei-4-89805 disclose technologies for producing liquid crystal
display cell spacers in which a polymerizable monomer is
suspension-polymerized in the presence of a pigment. However, these
methods have limitations in the kind of polymerizable monomer that
can be used and in production scale and, moreover, the incorporated
pigment tends to be exposed on the spacer surface with the result
that the pigment itself dissolves out upon exposure to an organic
solvent or the like or that impurities in the pigment are liable to
dissolve out.
[0009] Japanese Kokoku Publication Hei-4-59321 discloses a process
for producing a liquid crystal display cell spacer which comprises
mixing a lipophilicity-imparted pigment with a monomeric component
comprising a polyfunctional vinyl compound and an lipophilic vinyl
compound and subjecting the mixture to suspension-polymerization in
an aqueous medium. This process is conducive to improvements in the
dispersibility of the pigment and solvent resistance but in order
to insure a substantial absence of the pigment on the spacer
surface, the vinyl compound must be subjected to a suspension
polymerization or emulsion polymerization as a post-treatment.
Since this process involves two stages of polymerization, the
production cost is high of necessity.
[0010] Japanese Kokai Publication Hei-7-2913 describes a process
for producing a liquid crystal display cell spacer which comprises
mixing a pigment uniformly with a (meth) acrylonitrile-containing
polyfunctional ethylenically unsaturated component and subjecting
the mixture to suspension polymerization in an aqueous medium.
However, this technology cannot provide a liquid crystal display
cell spacer colored to a deep shade, for although it is conducive
to improvements in the dispersibility of the pigment and the
mechanical strength and solvent resistance of the spacer, the
impurities in the pigment tend to dissolve and diffuse into the
spacer to reduce its electrical resistance of the spacer, so that
there is a limit to the proportion of the pigment that can be
added.
[0011] Thus, by the technology of coloring polymer particles in the
course of manufacture thereof, too, it is difficult to obtain a
liquid crystal display cell spacer with good coloring effect and
light shielding effect and physical properties necessary for a
spacer in an expedient and efficient manner.
SUMMARY OF THE INVENTION
[0012] The present invention has for its object to solve the above
problems and accordingly provide a liquid crystal display cell
spacer with improved coloring effect and light shielding effect and
satisfactory electrical, physical, chemical, and optical properties
and a liquid crystal display cell with use thereof.
[0013] The present invention relates, in a first aspect, to a
liquid crystal display cell spacer comprising surface-coated carbon
black. This liquid crystal display cell spacer can be
advantageously applied to liquid crystal display cells.
[0014] The present invention relates, in a second aspect, to a
liquid crystal display cell spacer comprising a pigment component
comprising carbon black and at least one set of organic pigments of
dissimilar colors other than carbon black. This liquid crystal
display cell spacer can be advantageously applied to liquid crystal
display cells.
[0015] The present invention relates, in a third aspect, to a
liquid crystal display cell spacer comprising a pigment component
comprising surface-coated carbon black and at least one set of
organic pigments of dissimilar colors other than carbon black. This
liquid crystal display cell spacer can be advantageously applied to
liquid crystal display cell.
[0016] The present invention relates, in a fourth aspect, to a
liquid crystal display cell comprising the liquid crystal display
cell spacer according to said first, second, or third aspect of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a sectional view showing one embodiment of the
liquid crystal display cell according to the present invention; in
which the reference numeral 1 represents a transparent substrate, 2
a transparent electrode, 3 an alignment layer, 4 a transparent
substrate, 5 a transparent electrode, 6 an orientation control
film, 7 a substrate, 8 a spacer, 9 a substrate, 10 a sealing
member, 11 nematic liquid crystals, 12 a polarizing sheet, and 13 a
polarizing sheet.
DISCLOSURE OF THE INVENTION
[0018] The first aspect of the present invention relates to a
liquid crystal display cell spacer comprising surface-coated carbon
black.
[0019] The carbon black for use in this first aspect of the
invention has a coated surface which precludes dissolution and
diffusion of its impurities. By using this surface-coated carbon
black, the electrical resistance of the liquid crystal display cell
spacer can be prevented from reducing even if its proportion is
increased and, moreover, the dispersibility of carbon black is
improved so that sufficiently deep black shading of the spacer can
be achieved with a smaller amount of carbon black. The coating can
be applied by, for example, using a thermoplastic resin.
[0020] As used throughout this specification, the term "impurities"
means the contaminants which are unavoidably contained in ordinary
carbon black and, if dissolved out and diffused into the liquid
crystal display cell spacer, reduce the electrical resistance of
the spacer, such as sodium ion, potassium ion, chloride ion, and
sulfate ion, among others.
[0021] The carbon black for said surface-coated carbon black is not
particularly restricted in kind, thus including but not limited to
channel black, roll black, furnace black, and thermal black.
[0022] The thermoplastic resin is not particularly restricted in
kind but includes alkyd resin, modified alkyd resin, phenolic
resin, natural resin-modified phenolic resin, maleic acid resin,
natural resin-modified maleic acid resin, fumaric acid resin, ester
gum, rosin, petroleum resin, coumarone resin, indene resin,
polyester resin, polyamide resin, polycarbonate resin, polyethylene
resin, epoxy resin, styrene resin, vinyl resin, acrylic resin,
chlorinated rubber, benzoguanamine resin, urea resin, etc. These
resins may be used independently or in combination.
[0023] The technique for coating the surface of carbon black with
the above-mentioned thermoplastic resin is not restricted. A
typical method comprises pulverizing carbon black in the presence
of a hydrophobic medium containing said thermoplastic resin by
means of a crusher such as a ball mill or the like. An alternative
method comprises mixing an aqueous dispersion of carbon black with
a hydrophobic medium containing said thermoplastic resin to prepare
an emulsion and removing water by heating. In a further alternative
process, a hydrophobic medium containing said thermoplastic resin
is heated beforehand, an aqueous dispersion of carbon black is
added with stirring, and the water is simultaneously distilled off.
The surface-coated carbon black thus obtained can be precipitated
by mixing the system with a lower alcohol, e.g. ethanol or
isopropyl alcohol, which is miscible with the hydrophobic medium,
and recovered by filtration or decantation.
[0024] The liquid crystal display cell spacer according to the
first aspect of the invention can be produced by dispersing said
surface-coated carbon black uniformly in a polymerizable monomer
and subjecting the dispersion to polymerization reaction. The
method for this polymerization is not particularly restricted.
Thus, for example, suspension polymerization and emulsion
polymerization can be mentioned. Particularly in order to provide a
uniformly colored liquid crystal display cell spacer, a suspension
polymerization process is preferred.
[0025] The suspension polymerization is carried out by dispersing
said surface-coated carbon black uniformly in said polymerizable
monomer and subjecting the dispersion to polymerization in the
presence of a polymerization initiator in an aqueous medium.
[0026] There is no particular limitation on the polymerizable
monomer that can be used, thus including unsaturated carboxylic
acids such as acrylic acid, methacrylic acid, maleic acid, maleic
anhydride, fumaric acid, crotonic acid, itaconic acid, etc.;
acrylic esters such as methyl acrylate, ethyl acrylate, n-propyl
acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate,
2-ethylhexyl acrylate, stearyl acrylate, etc.; methacrylic esters
such as methyl methacrylate, ethyl methacrylate, propyl
methacrylate, n-butyl methacrylate, t-butyl methacrylate,
2-ethylhexyl methacrylate, lauryl methacrylate, stearyl
methacrylate, dodecyl methacrylate, glycidyl methacrylate,
.beta.-hydroxyethyl methacrylate, hydroxymethyl methacrylate, etc.;
styrenic monomers such as styrene, vinyltoluene,
.alpha.-methylstyrene, p-methoxystyrene, t-butylstyrene,
chlorostyrene, etc.; diene type monomers such as butadiene,
isoprene, etc.; ethylene, vinyl chloride, vinyl acetate, vinyl
propionate, acrylamide, methacrylamide, acrylonitrile,
methylolacrylamide, vinyl stearate, acryl acetate, diallyl adipate,
dimethyl itaconate, diethyl maleate, allyl alcohol, vinylidene
chloride, vinylpyridine, N-vinylpyrrolidone, N-hydroxyacrylamide,
2-vinyl-2-oxazoline, 2-isopropenyl-2-oxazoline, dimethylaminoethyl
acrylate, glycidyl methacrylate, allyl glycidyl ether, monomethyl
fumarate, etc. These monomers can be used independently or in
combination and there is no particular limitation on the kinds of
monomers to be used in combination.
[0027] In addition to the polymerizable monomer mentioned above,
one or more other crosslinking compounds can be optionally
employed. Among such optional monomers can be mentioned aromatic
divinyl compounds such as divinylbenzene, divinylnaphthalene and
their derivatives; diethylenically or triethylenically unsaturated
carboxylic esters such as ethylene glycol di(meth)acrylate,
diethylene glycol di(meth) acrylate, triethylene glycol
di(meth)acrylate, trimethylolpropane tri(meth)acrylate,
1,3-butanediol di(meth) acrylate, etc.; divinyl compounds such as
N,N-divinylaniline, divinyl ether, divinyl sulfide, divinyl
sulfone, etc.; and compounds each containing 3 or more vinyl
groups. The preferred proportion of such crosslinking compounds is
0.005 to 100 weight percent based on the combined amount of the
crosslinking compound and the polymerizable monomer.
[0028] The proportion of said polymerizable monomer per 100 parts
by weight of the aqueous medium is preferably 1 to 200 parts by
weight. If the proportion is less than 1 part by weight, the
production cannot be profitably carried out. On the other hand, if
the upper limit of 200 parts by weight is exceeded, it will be
difficult to remove the heat of polymerization.
[0029] The proportion of surface-coated carbon black is preferably
0.1 to 200 parts by weight relative to 100 parts by weight of the
polymerizable monomer. If the proportion is smaller than 0.1 part
by weight, the spacer can hardly be colored to a deep shade. On the
other hand, if the upper limit of 200 parts by weight is exceeded,
the mechanical strength of the product liquid crystal display cell
spacer tends to be sacrificed.
[0030] In order that the surface-coated carbon black may be
uniformly dispersed in said polymerizable monomer, a mechanical
device such as a ball mill, bead mill, sand mill, attriter, sand
grinder, nanomizer, or the like can be used with advantage. In this
operation, a dispersing agent can be used to improve dispersibility
of the surface-coated carbon black.
[0031] The dispersing agent that can be used is not particularly
restricted in kind. Thus, it may be any of water-soluble polymers
such as polyvinyl alcohol, starch, methylcellulose,
carboxymethylcellulose, hydroxyethylcellulose, poly(sodium
methacrylate), etc.; barium sulfate, calcium sulfate, aluminum
sulfate, calcium carbonate, calcium phosphate, talc, clay,
diatomaceous earth, metal oxide powder, etc.
[0032] The proportion of said dispersing agent is 0.01 to 20 weight
% based on the polymerizable monomer component.
[0033] The aqueous medium that can be used is not particularly
restricted in kind and may for example be an aqueous solution of a
water-soluble organic compound such as polyvinyl alcohol,
polyacrylic acid, polymethacrylic acid, gelatin, methylcellulose,
polymethacrylamide, polyethylene glycol, polyethylene oxide
monostearate, sorbitan tetraoleate, glycerin monooleate,
dodecylbenzenesulfonic acid, etc., as well as water.
[0034] In the above aqueous medium is in a microfine fashion
suspended a uniform dispersion of surface-coated carbon black in
said polymerizable monomer. This suspending operation can be
carried out using a homogenizer or the like.
[0035] The reaction temperature preferred for said suspension
polymerization is 20 to 100.degree. C. If the temperature is below
20.degree. C. the polymerization reaction rate will not be
acceptably high. On the other hand, if the reaction temperature
exceeds 100.degree. C., the polymerization reaction can hardly be
controlled.
[0036] The suspension polymerization time is preferably 1 to 50
hours. If the reaction time is less than 1 hour, the rate of
polymerization will be too low. On the other hand, a prolonged
reaction over 50 hours is unnecessary.
[0037] The liquid crystal display cell spacer obtained by the above
suspension polymerization reaction can be separated by filtration,
centrifugation or other known procedure. The separated liquid
crystal display cell spacer is rinsed with water or the like and
dried by heating or in vacuo.
[0038] The polymerization initiator that can be used in said
suspension polymerization is not particularly restricted, thus
including but not limited to azo compounds such as
2,2'-azobisisobutyronitrile,
2,2'-azobis-2,4'-dimethylvaleronitrile,
2,2'-azobis-methylbutyronitrile, 2,2'-azobis-methylheptonitrile,
2,2'-azobis-2,3-dimethylbutyronitrile,
2,2'-azobis-2,3,3-trimethylbutyronitrile,
2,2'-azobis-2-isopropylbutyroni- trile, 4,4-azobis-4-cyanovaleric
acid, dimethyl-2,2'-azobis-isobutyrate, etc. and organic peroxides
such as acetyl peroxide, decanoyl peroxide, lauroyl peroxide,
benzoyl peroxide, octanoyl peroxide, orthomethoxybenzoyl peroxide,
p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, diisopropyl
peroxycarbonate, 2-ethylhexyl peroxydicarbonate, acetyl
cyclohexanesulfonyl peroxide, t-butyl peroxyisobutyrate, t-butyl
peroxypivarate, t-butyl peroxy-2-ethylhexanoate, di-t-butyl
peroxide, t-butyl cumyl peroxide, dicumyl peroxide, methyl ethyl
ketone peroxide, cumene hydroperoxide, t-butyl hydroperoxide,
etc.
[0039] The amount of said polymerization initiator is 0.01 to 30
parts by weight based on 100 parts by weight of the polymerizable
monomer. If the proportion is smaller than 0.01 part by weight, the
rate of polymerization reaction will be too low. On the other hand,
addition of the initiator in excess of 30 parts by weight is
unnecessary. The preferred range is 0.1 to 10 parts by weight.
[0040] The preferred liquid crystal display cell spacer according
to the first aspect of the present invention has a mean particle
diameter of 0.5 to 500 .mu.m. If the mean particle diameter is less
than 0.5 .mu.m, the particles tend to coagulate and will not be
practically useful. The spacer with a mean particle diameter
exceeding 500 .mu.m will find little application. The preferred
range is 1 to 300 .mu.m.
[0041] The coefficient of variation of the particle size of the
liquid crystal display cell spacer according to the first aspect of
the present invention is preferably not greater than 20%. If the
coefficient of variation exceeds 20%, the particle size
distribution will be too broad so that the performance of the
spacer tends to be sacrificed. More preferably, the coefficient of
variation is not greater than 10%. For still better results, the
coefficient is not greater than 5%.
[0042] In order to preclude dissolution and diffusion of impurities
etc. (inclusive of the pigment itself) and impart an interfacial
chemical modification to the surface of the liquid crystal display
cell spacer, the spacer surface may be coated with a coating
material such as a silane coupling agent as necessary. The coating
agent is preferably applied in a monomolecular layer or as a thin
polymer film.
[0043] The silane coupling agent that can be used as above is not
particularly restricted, thus including but not limited to amino
silane coupling agents such as .gamma.-aminopropyltrimethoxy
silane, N-.beta.-(aminoethyl)-.gamma.-aminopropyltrimethoxysilane,
3-[N-allyl-N-(2-aminoethyl)]aminopropyltrimethoxysilane,
3-(N-allyl-N-glycidyl)aminopropyltriethoxysilane,
3-(N-allyl-N-methacryl)- aminopropyltrimethoxysilane,
3-(N,N-diglycidyl) aminopropyltrimethoxysilan- e, etc.; amide
silane coupling agents such as N,N-bis[3-(methyldimethoxysi-
lyl)propyl]amine, N,N-bis[3-(trimethoxysilyl)propyl]amine,
N,N-bis[3-(methyldimethoxysilyl)propyl]ethylenediamine,
N,N-bis[3-(trimethoxysilyl)propyl]ethylenediamine,
N-glycidyl-N,N-bis[3-(methyldimethoxysilyl)propyl]amine,
N-glycidyl-N,N-bis[3-(trimethoxysilyl)propyl]amine, etc.; vinyl
silane coupling agents such as vinyltriethoxysilane,
vinyl-tris(2-methoxyethoxy)- silane, etc.; methacrylic silane
coupling agents such as .gamma.-methacryloxypropyltrimethoxysilane
etc.; glycidyl silane coupling agents such as
.gamma.-glycidoxypropyltrimethoxysilane etc.; and mercaptosilane
coupling agents such as .gamma.-mercaptopropyltrimethoxysi- lane
etc.
[0044] There is no particular limitation on the method for covering
the surface of the liquid crystal display cell spacer with said
coating agent. A typical method comprises mixing the coating agent
with the liquid crystal display cell spacer in an inorganic solvent
such as water or an organic solvent such as alcohol, heating the
mixture with stirring, thereafter separating the liquid crystal
display cell spacer by, for example, decantation, and finally
removing the solvent by drying in vacuo. An alternative method
comprises mixing said coating agent with the liquid crystal display
cell spacer directly and heating the mixture.
[0045] The liquid crystal display cell spacer according to the
first aspect of the present invention comprises a surface-coated
carbon black and, therefore, is free from the dissolution and
diffusion of any impurities in the carbon black, with the result
that not only a uniform deep black shade but also a high solvent
resistance can be obtained. Furthermore, the surface-coated carbon
black is suppressed in the loss of electrical resistance and
improved in dispersibility compared with the uncoated carbon black,
with the result that it is uniformly dispersed and imparts a higher
degree of darkness to the liquid crystal display cell spacer.
[0046] The second aspect of the present invention relates to a
liquid crystal display cell spacer which comprises a pigment
component comprising carbon black and at least one set of organic
color pigments of dissimilar colors other than carbon black.
[0047] There is no particular limitation on the kind of carbon
black that can be used, thus including but not limited to acetylene
black, channel black, and furnace black. In this second aspect of
the invention, a surface-treated carbon black such as Microlith
(Ciba-Geigy) can be used for improved in carbon black
dispersibility.
[0048] Referring to said one set of organic color pigments of
dissimilar colors other than carbon black, those organic color
pigments which are comparatively high in transparency and high in
heat resistance, weather resistance, and solvent resistance are
preferably used. Particularly preferred is a set of organic color
pigments which, upon admixture, give a substantially black shade.
In this second aspect of the invention, at least one such set of
organic color pigments is used.
[0049] The color pigments constituting said set of organic color
pigments of dissimilar colors other than carbon black are not
restricted in kind but can for example be selected from among azo
and condensed azo organic color pigments such as Brilliant Carmine
BS, Lake Carmine FB, Brilliant Fast Scarlet, Lake Red 4R, Permanent
Red R, Fast Red FGR, Toluidine Maroon, Bisazo Yellow, Fast Yellow
G, Bisazo Orange, Vulcan Orange, Pyrazolone Red, etc.; organic
color pigments in the phthalocyanine series, such as phthalocyanine
Blue, Fast Sky Blue, phthalocyanine Green, etc.; lake series
organic color pigments such as Lake Yellow, Rose Lake, Violet Lake,
Blue Lake, Green Lake, etc.; oxazine series organic color pigments;
and quinophthalone series organic color pigments, among others.
[0050] Referring to said one set of organic color pigments of
dissimilar colors other than carbon black, two or more of the
above-mentioned color pigments can be selectively employed.
[0051] The combination of said organic color pigments constituting
said one set of organic color pigments of dissimilar colors other
than carbon black is preferably such that when said at least one
set of organic color pigments of dissimilar colors other than
carbon black is used in conjunction with said carbon black, the
maximum spectral transmittance of the liquid crystal display cell
spacer according to the second aspect of the present invention over
the entire visible wavelength region from about 400 to about 700 nm
is less than 3% and the total light transmittance over the entire
visible wavelength region is 0.1 to 2.5%. The more preferred
combination is such that the maximum spectral transmittance value
is less than 2.7% and the total light transmittance value is 0.2 to
2.0%.
[0052] There is no particular limitation on such combination. For
example, such combinations as blue and violet pigments, red and
blue pigments, yellow, blue, and violet pigments, green, blue, and
violet pigments, and red, blue, and violet pigments can be
mentioned.
[0053] From the standpoints of optical transmittance and uniformity
of film surface, the organic pigments are preferably not greater
than 1 .mu.m in particle diameter.
[0054] In the pigment component, the preferred proportion of said
carbon black is 5 to 60 weight % and the preferred proportion of
said at least one set of organic color pigments of dissimilar
colors other than said carbon black is 95 to 40 weight %. If the
proportion of said carbon black is less than 5 weight % and the
proportion of said at least one set of organic color pigments of
dissimilar colors other than said carbon black is greater than 95
weight %, the excessive amount of said at least one set of organic
color pigments other than said carbon black tends to detract from
the mechanical strength of the liquid crystal display cell spacer
according to the second aspect of the present invention.
[0055] If the proportion of said carbon black exceeds 60 weight %
and that of said at least one set of organic color pigments of
dissimilar colors other than said carbon black is less than 40
weight %, the excessive amount of carbon black leads to an
amplified influence of impurities dissolving and diffusing out of
the carbon black so that the electrical resistance of the liquid
crystal display cell spacer of the second aspect of the invention
tends to be decreased. More preferably, the proportion of said
carbon black is 10 to 40 weight % and that of said at least one set
of organic color pigments of dissimilar colors other than carbon
black is 90 to 60 weight %.
[0056] If the pigment component consists solely of said at least
one set of organic color pigments of dissimilar colors other than
said carbon black, even if the color pigments constitute the
optimum combination for rendition of sufficient darkness, the
increased amount of said set of organic color pigments may detract
from the mechanical strength of the liquid crystal display cell
spacer.
[0057] Since the color component of the liquid crystal display cell
spacer of the second aspect of the invention comprises carbon black
and at least one set of organic color pigments of dissimilar colors
other than carbon black, the necessary amount of carbon black can
be smaller so that the dissolution and diffusion of impurities are
decreased. Moreover, the decrease in electrical resistance can be
prevented and, at the same time, sufficient darkness and
satisfactory physical properties can be secured.
[0058] The liquid crystal display cell spacer according to the
second aspect of the invention can be obtained by dispersing said
pigment component comprising said carbon black and said at least
one set of organic color pigments of dissimilar colors other than
said carbon black uniformly in a polymerizable monomer and causing
the mixture to polymerize. There is no particular limitation on the
method of polymerization. Thus, suspension polymerization and
emulsion polymerization can be mentioned by way of example but in
order to obtain a uniformly colored liquid crystal display cell
spacer, a suspension polymerization process is preferred.
[0059] The suspension polymerization process comprises dispersing
said pigment component uniformly in said polymerizable monomer and
causing the mixture to polymerize in the presence of a
polymerization initiator in aqueous medium.
[0060] The polymerizable monomer that can be used includes the same
monomers as mentioned for the first aspect of the invention.
[0061] One or more suitable crosslinking compounds can be used in
combination with said polymerizable monomer. The kind of
crosslinking compound and its proportion may be similar to those
mentioned for the first aspect of the invention.
[0062] The proportion of said pigment component is preferably 1 to
180 parts by weight based on 100 parts by weight of said
polymerizable monomer. If the proportion is less than 1 part by
weight, the cell spacer may hardly be colored to a deep shade,
while the mechanical strength of the spacer tends to be sacrificed
if the pigment component accounts for more than 180 parts by
weight. The particularly preferred range is 3 to 160 parts by
weight.
[0063] For dispersing said pigment component uniformly in said
polymerizable monomer, the same machine as mentioned for the first
aspect of the invention, for instance, can be employed.
[0064] A dispersing agent may be added for improved dispersibility
of said pigment component. The kind of dispersing agent and its
amount may be similar to those mentioned for the first aspect of
the invention.
[0065] The aqueous medium may also be the same medium as mentioned
for the first aspect of the invention.
[0066] A uniform dispersion of the pigment component in the
polymerizable monomer is suspended in a microfine fashion in said
aqueous medium. This suspending operation can be performed using a
homogenizer or the like.
[0067] The temperature of suspension polymerization may be similar
to that mentioned for the first aspect of the invention.
[0068] The polymerization time of suspension polymerization may be
similar to that mentioned for the first aspect of the
invention.
[0069] The liquid crystal display cell spacer obtained by the above
suspension polymerization can be isolated by, for example,
filtration or centrifugation. The isolated spacer is rinsed with
water or the like and dried by heating or in vacuo.
[0070] The polymerization initiator and its amount may for example
be similar to those mentioned for the first aspect of the
invention.
[0071] The mean particle diameter and coefficient of variation of
particle size of the liquid crystal display cell spacer according
to the second aspect of the invention may be similar to those
mentioned for the first aspect of the invention.
[0072] Where necessary, the liquid crystal display cell spacer
according to the second aspect of the present invention may have
been surface-coated with a coating material such as a silane
coupling agent. The silane coupling agent can be selected from
among the compounds mentioned for the first aspect of the
invention.
[0073] Since the liquid crystal display cell spacer according to
the second aspect of the invention contains a pigment component
comprising carbon black and at least one set of organic color
pigments of dissimilar colors other than carbon black, it not only
assumes a deep black color despite the small proportion of the
pigment component but also has satisfactory electrical resistance.
Moreover, chances for contamination of the liquid crystals due to
the pigment component are minimized.
[0074] The third aspect of the present invention is a liquid
crystal display cell spacer comprising a pigment component
comprising surface-coated carbon black and at least one set of
organic color pigments of dissimilar colors other than carbon
black.
[0075] The carbon black for use in this third aspect of the
invention has been surface-coated for preventing the dissolution
and diffusion of impurities. The surface-coated carbon black may be
selected from among those species of carbon black mentioned for the
first aspect of the invention.
[0076] The above-mentioned set of organic color pigments of
dissimilar colors other than carbon black and its proportion can be
similar to those mentioned for the second aspect of the
invention.
[0077] The liquid crystal display cell spacer according to the
third aspect of the invention can be produced by using said
surface-coated carbon black in otherwise the same manner as
described for the liquid crystal display cell spacer according to
the second aspect of the invention.
[0078] The mean particle diameter and coefficient of variation of
particle size of the liquid crystal display cell spacer according
to the third aspect of the invention are similar to those mentioned
for the first aspect of the invention.
[0079] Where necessary, the liquid crystal display cell spacer
according to the third aspect of the invention may have been
covered with a coating material such as a silane coupling agent.
The silane coupling agent may be selected from among the compounds
mentioned for the first aspect of the invention.
[0080] Since the liquid crystal display cell spacer according to
the third aspect of the invention contains a surface-coated carbon
black, there is little dissolution and diffusion of impurities into
the spacer. This effect coupled with the effect of concomitant use
of at least one set of organic color pigments of dissimilar colors
other than carbon black results in a black shade even if the
smaller amount of carbon black is used as compared with the first
and the second aspect of the invention and insures high solvent
resistance, electrical resistance and mechanical strength.
[0081] The fourth aspect of the present invention is a liquid
crystal display cell incorporating said liquid crystal display cell
spacer according to the first, second, or third aspect of the
present invention.
[0082] The liquid crystal display cell according to the fourth
aspect of the invention gives an excellent display image contrast
without the spacer being visually recognized as luminescent spots
in the dark or black area of the image.
[0083] An embodiment of the liquid crystal display cell according
to the fourth aspect of the invention is now described with
reference to the accompanying drawings.
[0084] As shown in FIG. 1, a liquid crystal display cell A
comprises a pair of substrates 7, 9, a spacer 8, a sealing member
10, a nematic liquid crystalline component 11, and polarizing
sheets 12, 13.
[0085] The spacer 8 is disposed between the substrates 7 and 9
constituting said pair for the purpose of maintaining a
predetermined gap between the substrates 7 and 9. The sealing
member 10 is disposed around said pair of substrates 7, 9. The
nematic liquid crystal line component 11 is sealed in the space
between said substrates 7 and 9. The polarizing sheets 12 and 13
are bonded to the surfaces of the substrates 7 and 9,
respectively.
[0086] Each of the substrates 7 and 9 comprises a transparent glass
substrate 1 or 4 with a transparent electrode 2 or 5 formed upon a
pattern on one side thereof and an alignment layer 3 or 6 (e.g. a
polyimide film) coated on the surface of the transparent electrode
(2 or 5)-transparent substrate (1 or 4) assembly. The alignment
layer 3 or 6 has been treated to control alignment by rubbing.
[0087] The spacer 8 is a liquid crystal display cell spacer
according to the first, second, or third aspect of the
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0088] The following examples are intended to illustrate the
present invention in further detail and should by no means be
construed as defining the scope of the invention.
Example 1
Preparation of a Liquid Crystal Cell Spacer
[0089] To a uniform mixture of 60 parts by weight of
tetramethylolmethane triacrylate, 20 parts by weight of
divinylbenzene, and 20 parts by weight of acrylonitrile was added
12 parts by weight of polyethylene-coated carbon black and the
carbon black was uniformly dispersed by means of a bead mill for 48
hours.
[0090] This colored polymerizable monomer mixture in which said
surface-coated carbon black had been dispersed was evenly mixed
with 2 parts by weight of benzoyl peroxide and the mixture was
poured in 850 parts by weight of a 3 weight % aqueous solution of
polyvinyl alcohol. After thorough stirring, the mixture was
suspended with a homogenizer so that the diameter of droplets of
the colored polymerizable monomer would be about 3 to 10 .mu.m to
provide a suspension.
[0091] This suspension was transferred to a 2-L separable flask
equipped with a thermometer, stirrer, and reflux condenser and
heated at 85.degree. C. in a nitrogen gas atmosphere with constant
stirring. This polymerization reaction was carried out for 7 hours,
at the end of which time the temperature was increased to
90.degree. C. and the reaction mixture was maintained at that
temperature for 3 hours to carry the polymerization reaction to
completion. This polymerization reaction mixture was cooled and the
resulting colored particles were recovered by filtration, rinsed
well with water, and dried to provide 120 parts by weight of
colored particles containing dispersing pigment within the size
range of 3 to 10 .mu.m. These colored particles were subjected to
classification to provide a liquid crystal display cell spacer with
a mean particle diameter of 5.55 .mu.m and a coefficient of
variation in particle size of 2.48%.
[0092] The degree of darkness (light transmittance) of the liquid
crystal display cell spacer thus obtained, the concentration of
impurities in the spacer, and the electrical resistance of the
spacer were evaluated by the following methods. The results are
presented in Table 1.
Evaluation Methods
[0093] (1) Degree of Darkness
[0094] A mixture of the polymerizable monomer of the same
composition as that of the above liquid crystal display cell spacer
and the color component was polymerized to prepare a 1 mm-thick
wafer. The spectral transmittance of this wafer was measured over
the entire visible wavelength range of 400 to 700 nm with a
spectrophotometer and the maximum value was regarded as the degree
of darkness of the liquid crystal display cell spacer.
[0095] (2) The Concentrations of Impurities in the Liquid Crystal
Display Cell Spacer
[0096] Ten (10) grams of the liquid crystal display cell spacer
obtained was put in 330 ml of a solvent mixture (water/isopropyl
alcohol=7/3, v/v) with stirring and the mixture was allowed to
stand at room temperature for one week (with stirring once a day).
The mixture was allowed to stand without agitation in the final
2-day period to let the liquid crystal display cell spacer settle.
The supernatant was recovered with a filter paper (0.2 .mu.m
thick), concentrated to 30 ml, and analyzed. The analyses for
sodium and potassium ions were carried out with Jarrell-Ash SPQ8000
atomic absorption spectrophotometer. The analyses for chloride and
sulfate ions were carried out with Dionex 2010I ion chromatographic
analyzer.
[0097] (3) Electrical Resistance of the Liquid Crystal Display Cell
Spacer
[0098] Using Toa Dempa Ultra Megohmmeter SM-8210, the liquid
crystal display cell spacer was filled into the accessory liquid
sample electrode and the electrical resistance of the liquid
crystal display cell spacer was measured according to the
instruction manual for liquid samples.
Fabrication of a TN Liquid Crystal Display Cell
[0099] In order to evaluate the performance of a liquid crystal
display device incorporating the liquid crystal display cell spacer
obtained, a TN liquid crystal display cell of the normally black
display mode, which faciliates assessment of the light shielding
effect of spacers, was fabricated. The light shielding effect of
the spacer or the effect on cell gap formation as evaluated using
this test liquid crystal display cell is translatable to the effect
obtainable with an STN or other liquid crystal display cell, so
that the results of evaluation are not exclusively valid for TN
liquid crystal display cells but valid for all kinds of liquid
crystal display cells.
[0100] A transparent electrically conductive indium oxide-tin oxide
film was formed in a thickness of about 500 Angstrom units on a 0.7
mm-thick glass sheet by the low-temperature sputtering technique
and a predetermined electrode pattern was formed by
photolithography. Then, the surface was coated with an alignment
material and heated to obtain an alignment layer. This glass sheet
was cut to 5 cm.times.12.5 cm to provide glass substrates for a
liquid crystal display cell.
[0101] The peripheral edge of the glass substrate obtained was then
printed with a glass fiber spacer-mixed epoxy adhesive in a breadth
of 1 mm by the screen printing technique.
[0102] After this glass substrate was set in a horizontal position,
the liquid crystal display cell spacer was scattered over with the
aid of pressurized nitrogen gas and allowed to fall uniformly on
the glass substrate. The scattering time was adjusted so that the
density of the liquid crystal display cell spacer particles on the
glass substrate would be about 150 particles/mm.sup.2.
[0103] After another glass substrate was superimposed on the liquid
crystal display cell spacer-scattered glass substrate, a load of 1
kg/cm.sup.2 was applied uniformly on the whole glass substrate by
means of a press. At the same time, the assembly was heated at a
temperature of 160.degree. C. for 20 minutes to cure the peripheral
epoxy adhesive.
[0104] After a vacuum was established in the fabricated cell by
aspiration, the liquid crystal was injected from a bore formed in a
part of the peripheral seal and the injection bore was closed up
under a subatmospheric intracellular pressure of 0.6 atmosphere.
The cell was then heated to a predetermined temperature for liquid
crystal realignment to provide a finished liquid crystal display
cell.
[0105] The measured gap between the top and bottom substrates of
this liquid crystal display cell was 5.38.mu.m.
Evaluation Methods
[0106] (1) Unevenness of Color of the TN Liquid Crystal Display
Cell
[0107] Polarizing sheets were set on either surface of the liquid
crystal display cell so that the color of the reflecting light of
the light projected against the TN liquid crystal display cell
would be olive. The olive color was uniform all over without
unevenness.
[0108] The following evaluation criteria were used.
[0109] .circleincircle.: no color unevenness
[0110] .largecircle.: a practically acceptable degree of color
unevenness
[0111] X: a practically unacceptable degree of color unevenness
[0112] (2) The Light Shielding Effect of the Cell Spacer in the TN
Liquid Crystal Display Cell
[0113] The polarizing sheets bonded to the liquid crystal display
cell were set to the TN normally black mode and the assembly was
observed under a transmission microscope at .times.200
magnification.
[0114] With the drive voltage OFF, the darkness in the center of
the spacer and the darkness of the spacer-free liquid crystal area
were compared visually by using a panel of 10 assessors.
[0115] The evaluation was .circleincircle. when the number of
assessors who judged that the darkness in the center of the spacer
was deeper or equivalent accounted for 80% or more of the panel,
.largecircle. when it accounted for 70 to 80%, .DELTA. when it
accounted for 50 to 70%, and X when it accounted for less than
50%.
[0116] The mean cell gap values and the results of evaluation of
color unevenness and light shielding effect are shown in Table
1.
Examples 2 to 4
[0117] Except that the compositions shown in Table 1 were used,
liquid crystal display cell spacers and cells were fabricated and
evaluated in the same manner as in Example 1. The results are shown
in Table 1.
Comparative Example 1
[0118] Except that uncoated carbon black was used and the
composition shown in Table 1 was used, a liquid crystal display
cell spacer and a liquid crystal display cell were fabricated and
evaluated in the same manner as in Example 1. The results are shown
in Table 1.
Comparative Example 2
[0119] Except that the composition shown in Table 1 was used with
omission of carbon black, a liquid crystal display cell spacer and
a liquid crystal display cell were fabricated and evaluated as in
Example 1. The results are shown in Table 1.
1 TABLE 1 Comparative Examples Examples 1 2 3 4 1 2 Composition
Polymerizable Tetramethylomethane triacrylate 60 60 60 -- 60 60
(weight part) monomer Divinylbenzene 20 20 20 50 20 20
Acrylonitrile 20 20 20 -- 20 20 Ethylene glycol dimethacrylate --
-- -- 50 -- -- Carbon Surface-coated carbon black 12 6 18 12 -- --
Carbon black -- -- -- -- 30 -- Quality and Spacer quality Mean
particle size (.mu.m) 5.55 3.59 7.42 4.55 6.05 5.78 performance
Coefficient of variation 2.48 2.66 2.85 2.89 3.71 4.11 parameters
of particle size (%) Degree of darkness (spectral 2.6 3.0 2.2 2.5
1.5 75.7 transmittance) (%) Electrical resistance (.OMEGA.
.multidot. cm) 10.sup.14 10.sup.14 10.sup.19 10.sup.11 <10.sup.9
10.sup.14 Levels of Sodium ion (ppm) 0.02 0.01 0.03 0.02 0.1 0.03
impurities Potassium ion (ppm) 0.04 0.03 0.05 0.03 0.1 0.05
Chloride ion (ppm) 0.1 0.1 0.2 0.1 0.9 0.3 Sulfate ion (ppm) 0.5
0.4 0.7 0.6 1.5 0.5 Cell quality Mean cell gap (.mu.m) 5.38 3.38
7.03 4.00 5.63 5.65 Eveness of color .circleincircle.
.circleincircle. .circleincircle. .circleincircle. X
.circleincircle. Light shielding effect .circleincircle.
.largecircle. .circleincircle. .circleincircle. X X
Example 5
Preparation of a Liquid Crystal Display Cell Spacer
[0120] To a uniform mixture of 60 parts by weight of
tetramethylolmethane triacrylate, 20 parts by weight of
divinylbenzene, and 20 parts by weight of acrylonitrile was added
12 parts by weight of carbon black, 6 parts by weight of
Phthalocyanine Blue (blue pigment), and 6 parts by weight of
Dioxane Violet (violet pigment) as the black pigment component and
the black pigment component was evenly dispersed by means of a bead
mill for 48 hours.
[0121] This colored polymerizable monomer mixture in which said
black pigment component had been dispersed was evenly mixed with 2
parts by weight of benzoyl peroxide and the mixture was poured in
850 parts by weight of a 3 weight % aqueous solution of polyvinyl
alcohol. After thorough stirring, the mixture was suspended with a
homogenizer so that the diameter of droplets of the colored monomer
would be about 3 to 10 .mu.m to provide a suspension.
[0122] This suspension was transferred to a 2-L separable flask
equipped with a thermometer, stirrer, and reflux condenser and
heated to 85.degree. C. in a nitrogen gas atmosphere with constant
stirring. This polymerization reaction was carried out for 7 hours,
at the end of which time the temperature was raised to 90.degree.
C. and the reaction mixture was maintained at that temperature for
3 hours to carry the polymerization reaction to completion. This
polymerization reaction mixture was cooled and the resulting
colored particles were recovered by filtration, rinsed well with
water, and dried to provide 120 parts by weight of colored
particles cotaining dispersing pigment within the size range of 3
to 10 .mu.m. Colored particles obtained were subjected to
classification to provide a liquid crystal display cell spacer with
a mean particle diameter of 6.45 .mu.m and a coefficient of
variation in particle size of 2.88%.
[0123] The liquid crystal display cell spacer thus obtained was
evaluated in the same manner as in Example 1, and a liquid crystal
display cell was fabriated and evaluated in the same manner as in
Example 1. The results are presented in Table 2.
Examples 6 to 8 and Comparative Examples 3 and 4
[0124] Except that the compositions shown in Table 2 were used,
liquid crystal display cell spacers and cells were fabricated and
evaluated in the same manner as in Example 5. The results are shown
in Table 2.
2 TABLE 2 Comparative Examples Examples 5 6 7 8 3 4 Composition
Polymerizable Tetramethylomethane triacrylate 60 60 60 -- 60 60
(weight part) monomer Divinylbenzene 20 20 20 50 20 20
Acrylonitrile 20 20 20 -- 20 20 Ethylene glycol dimethacrylate --
-- -- 50 -- -- Carbon Surface-coated carbon black -- -- -- -- -- --
Carbon black 12 10 20 25 30 -- Pigment Phthalocyanine blue 6 10 5
10 -- 15 Dioxazine violet 6 10 5 10 -- 5 Isoindoline yellow -- 10
-- -- -- -- Quinacridone red -- -- 15 -- -- 20 Quality and Spacer
quality Mean particle size (.mu.m) 6.45 4.17 8.63 5.29 7.03 6.72
performance Coefficient of variation 2.88 3.10 2.75 2.58 3.54 4.05
parameters of particle size (%) Degree of darkness (spectral 2.5
2.8 2.0 1.7 1.6 76.4 transmittance) (%) Electrical resistance
(.OMEGA. .multidot. cm) 10.sup.14 10.sup.14 10.sup.14 10.sup.13
<10.sup.11 10.sup.13 Levels of Sodium ion (ppm) 0.02 0.02 0.03
0.02 0.1 0.03 impurities Potassium ion (ppm) 0.05 0.02 0.03 0.02
0.1 0.03 Chloride ion (ppm) 0.1 0.2 0.2 0.2 0.8 0.3 Sulfate ion
(ppm) 0.5 0.3 0.3 0.4 1.2 0.4 Cell quality Mean cell gap (.mu.m)
6.04 3.61 8.22 4.87 6.81 6.32 Eveness of color .circleincircle.
.circleincircle. .largecircle. .largecircle. X X Light shielding
effect .circleincircle. .circleincircle. .circleincircle.
.largecircle. .DELTA. X
Examples 9 and 10
[0125] Except that the surface-coated carbon black of Example 1 and
the compositions shown in Table 3 were used, liquid crystal display
cell spacers and cells were fabricated and evaluated in the same
manner as in Example 5. The results are shown in Table 3.
3 TABLE 3 Examples 9 10 Composition (weight part) Polymerizable
monomer Tetramethylolmethane triacrylate 50 50 Divinylbenzene 30 30
Acrylonitrile 10 10 Carbon Surface-coated carbon black 6 10 Carbon
black -- -- Pigment Phthalocyanine blue 7 15 Dioxazine violet 7 5
Isoindoline yellow 7 5 Quinacridone red 7 20 Quality and
performance parameters Spacer quality Mean particle size (.mu.m)
6.8 4.9 Coefficent of variation of 2.94 3.6 particle size (%)
Degree of darkness (spectral 2.9 2.7 transmittance) (%) Electrical
resistance (.OMEGA..cm) 10.sup.14 10.sup.14 Levels of impurities
Sodium ion (ppm) 0.02 0.03 Potassium ion (ppm) 0.02 0.01 Chloride
ion (ppm) 0.2 0.2 Sulfate ion (ppm) 0.4 0.5 Cell quality Mean cell
gap (.mu.m) 6.49 4.66 Evenness of color .circleincircle.
.smallcircle. Light shielding effect .smallcircle.
.circleincircle.
INDUSTRIAL APPLICABILITY
[0126] Its construction having been described hereinabove, the
liquid crystal display cell spacer of the present invention is very
satisfactory in coloring effect and light shielding effect and has
optimal electrical, physical, chemical, and optical properties. The
liquid crystal display cell in corporating this cell spacer shows a
good display contrast of the image with the spacer not visualized
as luminessent points in the dark area of the image.
* * * * *