U.S. patent application number 16/401508 was filed with the patent office on 2019-08-22 for method of manufacturing electrophoretic particle, electrophoretic particle, electrophoretic dispersion liquid, electrophoretic s.
The applicant listed for this patent is E INK CORPORATION. Invention is credited to Takashi HIRAIWA, Harunobu KOMATSU, Hiroki NAKAHARA, Masahiko NAKAZAWA, Kozo SHITAGAMI.
Application Number | 20190256662 16/401508 |
Document ID | / |
Family ID | 58800216 |
Filed Date | 2019-08-22 |
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United States Patent
Application |
20190256662 |
Kind Code |
A1 |
KOMATSU; Harunobu ; et
al. |
August 22, 2019 |
METHOD OF MANUFACTURING ELECTROPHORETIC PARTICLE, ELECTROPHORETIC
PARTICLE, ELECTROPHORETIC DISPERSION LIQUID, ELECTROPHORETIC SHEET,
ELECTROPHORETIC DEVICE, AND ELECTRONIC APPARATUS
Abstract
A method of manufacturing an electrophoretic particle is a
method of manufacturing an electrophoretic particle including a
particle and a particle surface treatment agent which is bonded to
the particle, the method including preparing a mixture containing a
plurality of the particles, the particle surface treatment agent,
an unreacted product of a raw material used at the time of
generating the particle surface treatment agent, and a reaction
by-product generated at the time of generating the particle surface
treatment agent, the mixture having a content of the particle
surface treatment agent which is set to be equal to or greater than
70% by weight in the mixture except for the plurality of particles;
and bonding the particle surface treatment agent to a surface of
the particle in the mixture.
Inventors: |
KOMATSU; Harunobu;
(Matsumoto-shi, JP) ; NAKAHARA; Hiroki;
(Shiojiri-shi, JP) ; NAKAZAWA; Masahiko;
(Matsumoto-shi, JP) ; HIRAIWA; Takashi;
(Fujimi-machi, JP) ; SHITAGAMI; Kozo; (Chino-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
E INK CORPORATION |
Billerica |
MA |
US |
|
|
Family ID: |
58800216 |
Appl. No.: |
16/401508 |
Filed: |
May 2, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15365796 |
Nov 30, 2016 |
10323128 |
|
|
16401508 |
|
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|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08G 77/44 20130101;
G02F 2001/1678 20130101; C08G 77/442 20130101; C09D 183/10
20130101; G02F 1/167 20130101 |
International
Class: |
C08G 77/44 20060101
C08G077/44; C09D 183/10 20060101 C09D183/10; G02F 1/167 20060101
G02F001/167 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 2, 2015 |
JP |
2015-235350 |
Claims
1-11. (canceled)
12. An electrophoretic particle comprising a pigment particle and a
particle surface treatment agent comprising a block copolymer which
contains one or more dispersion units derived from first monomers
and a bonding portion covalently bonded to the pigment particle
derived from second monomers, and wherein the first monomer is a
silicone macromonomer expressed by the following Formula (I)
##STR00008## wherein R.sup.1 represents a hydrogen atom or a methyl
group, R.sup.2 represents a hydrogen atom or an alkyl group having
1 to 4 carbon atoms, R.sup.3 represents a structure including one
of an alkyl group having 1 to 6 carbon atoms and an ether group of
ethylene oxide or propylene oxide, and n represents an integer of 0
or greater.
13. The electrophoretic particle according to claim 12, wherein the
weight of the particle surface treatment agent is in a range of 4%
to 8% by weight of the particle.
14. The electrophoretic particle according to claim 12, wherein the
silicone macromonomer has a weight average molecular weight of
1,000 to 50,000.
15. The electrophoretic particle according to claim 12, wherein the
dispersion unit has a weight average molecular weight of 8,000 to
50,000.
16. The electrophoretic particle according to claim 12, wherein the
pigment particle comprises a material selected from the group
consisting of aniline black, carbon black, titanium black, titanium
dioxide, antimony trioxide, barium sulfate, zinc sulfide, zinc
oxide, and silicon dioxide, an azo-based pigment, isoindolinone,
chrome yellow, yellow iron oxide, cadmium yellow, titanium yellow,
antimony, quinacridone red, chrome vermilion, phthalocyanine blue,
indanthrene blue, Prussian blue, ultramarine blue, cobalt blue,
phthalocyanine green, an acrylic resin, a urethane resin, a urea
resin, an epoxy resin, polystyrene, and polyester.
17. An electrophoretic dispersion liquid comprising: the
electrophoretic particle according to claim 12; and a dispersion
medium.
18. An electrophoretic sheet comprising: a substrate; and a
structure body which is provided on the substrate and accommodates
the electrophoretic dispersion liquid according to claim 17.
19. An electrophoretic device comprising the electrophoretic sheet
according to claim 18.
Description
BACKGROUND
1. Technical Field
[0001] The present invention relates to a method of manufacturing
an electrophoretic particle, an electrophoretic particle, an
electrophoretic dispersion liquid, an electrophoretic sheet, an
electrophoretic device, and an electronic apparatus.
2. Related Art
[0002] Generally, the fact that when an electric field is applied
to a disperse system in which fine particles are dispersed in a
fluid, the fine particles move (migrate) in the fluid by Coulomb's
force has been known. This phenomenon is called electrophoresis,
and recently, an electrophoretic display device which displays
desired information (an image) by using the electrophoresis has
attracted attention as a new display device.
[0003] Such an electrophoretic display device has display memory
properties and wide viewing angle properties in a state of stopping
the application of voltage, and is capable of performing high
contrast display and low power consumption.
[0004] In addition, the electrophoretic display device is a non
light-emitting type device, and thus is easy on the eyes as
compared with a light-emitting type display device such as a
cathode-ray tube.
[0005] It has been known that such an electrophoretic display
device includes a liquid which disperses the electrophoretic
particles in a dispersion medium as the electrophoretic dispersion
liquid disposed between a pair of substrates having electrodes.
[0006] In the electrophoretic dispersion liquid of the
above-described configuration, a positively charged particle and a
negatively charged particle are used as the electrophoretic
particle, and thus it is possible to display desired information
(image) by applying a voltage across a pair of substrates
(electrodes).
[0007] As the aforementioned electrophoretic particle, typically, a
particle having a coated layer in which a polymer (coupling agent)
is bonded to a base material particle is used, and with such a
configuration of having the coated layer (polymer), it is possible
to disperse and charge the electrophoretic particles in the
electrophoretic dispersion liquid (refer to JP-A-2004-191418).
[0008] In the above-described electrophoretic particle contained in
the electrophoretic dispersion liquid, in a case where a coating
rate of a polymer with respect to the surface thereof is low,
dispersibility in the dispersion liquid is not sufficiently
obtained. For this reason, the electrophoretic particle is
precipitated, the charge of the electrophoretic particle becomes
larger, and thereby positive and negative electrophoretic particles
are aggregated with each other and are adhered to the electrode
surface. As a result, there is a problem in that degradation of the
contrast, change of the contrast with time, and the like are
caused.
SUMMARY
[0009] An advantage of some aspects of the invention is to provide
a method of manufacturing an electrophoretic particle which can
manufacture an electrophoretic particle exhibiting excellent
contrast in an electrophoretic dispersion liquid, an
electrophoretic particle exhibiting excellent contrast in an
electrophoretic dispersion liquid, an electrophoretic dispersion
liquid, an electrophoretic sheet, an electrophoretic device, and an
electronic apparatus which use the electrophoretic particle and
thus has high reliability.
[0010] Such an advantage can be achieved in the following aspects
of the invention.
[0011] According to an aspect of the invention, there is provided a
method of manufacturing an electrophoretic particle which includes
a particle, and a particle surface treatment agent which is boded
to the particle, the method including preparing a mixture
containing a plurality of the particles, the particle surface
treatment agent, an unreacted product of a raw material used at the
time of generating the particle surface treatment agent, and a
reaction by-product generated at the time of generating the
particle surface treatment agent, the mixture having a content of
the particle surface treatment agent which is set to be equal to or
greater than 70% by weight in the mixture except for the plurality
of particles; and bonding the particle surface treatment agent to
the particle in the mixture.
[0012] With this, in a case where the weight of the particle is set
to be 100% by weight, it is possible to obtain an electrophoretic
particle having the weight of the particle surface treatment agent
in a range of 4% by weight to 8% by weight. Thus, the
electrophoretic particle exhibits the excellent contrast in the
electrophoretic dispersion liquid.
[0013] In the method of manufacturing an electrophoretic particle
according to the aspect of the invention, it is preferable that in
the preparing of the mixture, a solvent for dissolving the particle
surface treatment agent be not added into the mixture.
[0014] With this, in a case where the weight of the particle is set
to be 100% by weight, it is possible to reliably obtain an
electrophoretic particle having the weight of the particle surface
treatment agent in a range of 4% by weight to 8% by weight.
[0015] In the method of manufacturing an electrophoretic particle
according to the aspect of the invention, it is preferable that
weight-average molecular weight of each of the unreacted product
and the reaction by-product be in a range of 1,000 to 50,000.
[0016] In a case where the weight-average molecular weight of the
unreacted product and the reaction by-product is within the
above-described range, the unreacted product and the reaction
by-product are mixed into the mixture.
[0017] In the method of manufacturing an electrophoretic particle
according to the aspect of the invention, it is preferable that the
particle surface treatment agent be a siloxane-based compound.
[0018] In a case where the siloxane-based compound is used as the
particle surface treatment agent, the unreacted product used at the
time of obtaining the siloxane-based compound remains in the
mixture.
[0019] In the method of manufacturing an electrophoretic particle
according to the aspect of the invention, it is preferable that the
particle surface treatment agent be a block copolymer which
contains a dispersion portion which is formed by polymerizing first
monomers and a bonding portion which is formed by polymerizing
second monomers having a functional group, and is bonded to the
particle when the functional group and a hydroxyl group are reacted
with each other in the bonding portion, and the first monomer is a
silicone macromonomer expressed by the following Formula (I).
##STR00001##
[0020] [In the formula, R.sup.1 represents a hydrogen atom or a
methyl group, R.sup.2 represents a hydrogen atom or an alkyl group
having 1 to 4 carbon atoms, R.sup.3 represents a structure
including one of an alkyl group having 1 to 6 carbon atoms and an
ether group of ethylene oxide or propylene oxide, and n represents
an integer of 0 or greater.]
[0021] In a case where the silicone macromonomer expressed by the
above-described Formula (I) is used as the first monomer, the
unreacted product used at the time of obtaining the silicone
macromonomer expressed by the above-described Formula (I) remains
in the mixture.
[0022] In the method of manufacturing an electrophoretic particle
according to the aspect of the invention, it is preferable that the
unreacted product and the reaction by-product be respectively an
unreacted product of a raw material at the time of generating the
first monomer and a reaction by-product at the time of generating
the first monomer.
[0023] According to another aspect of the invention, there is
provided an electrophoretic particle including a particle; and a
particle surface treatment agent which is bonded to the particle,
in which when a weight of the particle is set to be 100% by weight,
the weight of the particle surface treatment agent is in a range of
4% by weight to 8% by weight.
[0024] With this, the electrophoretic particle is sufficiently
dispersed in the electrophoretic dispersion liquid, and thus it is
possible to reliably suppress or prevent the positive and negative
electrophoretic particles from being aggregated with each other and
from being adhered to the electrode surface. Therefore, the problem
in that degradation of the contrast, change of the contrast with
time, and the like are caused can be solved.
[0025] According to still another aspect of the invention, there is
provided an electrophoretic dispersion liquid including the
electrophoretic particle according to the above-described aspects
of the invention; and a dispersion medium.
[0026] The electrophoretic particle is sufficiently dispersed in
the electrophoretic dispersion liquid, and thus it is possible to
reliably suppress or prevent the positive and negative
electrophoretic particles from being aggregated with each other and
from being adhered to the electrode surface. Therefore, the problem
in that degradation of the contrast, change of the contrast with
time, and the like are caused can be solved.
[0027] According to still another aspect of the invention, there is
provided an electrophoretic sheet including a substrate; and a
structure body which is provided on the substrate, and accommodates
the electrophoretic dispersion liquid of the invention.
[0028] With this, it is possible to obtain the electrophoretic
sheet with high-performance and reliability.
[0029] According to still another aspect of the invention, there is
provided an electrophoretic device including the electrophoretic
sheet of the invention.
[0030] With this, it is possible to obtain the electrophoretic
device with high-performance and reliability.
[0031] According to still another aspect of the invention, there is
provided an electronic apparatus including the electrophoretic
device of the invention.
[0032] With this, it is possible to obtain the electronic apparatus
with high-performance and reliability.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The invention will be described with reference to the
accompanying drawings, wherein like numbers reference like
elements.
[0034] FIG. 1 is a longitudinal sectional view illustrating an
electrophoretic particle contained in an electrophoretic dispersion
liquid according to a first embodiment of the invention.
[0035] FIG. 2 is a schematic diagram of a block copolymer contained
in the electrophoretic particle illustrated in FIG. 1.
[0036] FIG. 3 is a flowchart illustrating method of manufacturing
an electrophoretic dispersion liquid.
[0037] FIG. 4 is a longitudinal sectional view illustrating an
electrophoretic particle contained in an electrophoretic dispersion
liquid according to a second embodiment of the invention.
[0038] FIG. 5 is a diagram illustrating a siloxane-based coupling
agent which is bonded onto a surface of a base particle of the
electrophoretic particle illustrated in FIG. 4.
[0039] FIG. 6 is a diagram illustrating, regarding a coupling agent
and a modified silicone oil which are used to obtain the
siloxane-based coupling agent having a structure Z illustrated in
FIG. 5, specific examples of a reactive functional group X
contained in the coupling agent, and a reactive functional group Y
contained in the modified silicone oil.
[0040] FIG. 7A to FIG. 7F are diagrams illustrating a polarization
group which is bonded onto the surface of the electrophoretic
particle illustrated in FIG. 4.
[0041] FIG. 8 is a diagram for schematically illustrating a
longitudinal cross section of the electrophoretic display device of
the embodiment.
[0042] FIG. 9 is a schematic diagram illustrating an operating
principle of the electrophoretic display device illustrated in FIG.
8.
[0043] FIG. 10 is a schematic diagram illustrating an operating
principle of the electrophoretic display device illustrated in FIG.
8.
[0044] FIG. 11 is a perspective view illustrating an embodiment in
a case where an electronic apparatus of the invention is applied to
an electronic paper.
[0045] FIG. 12 is a diagram illustrating an embodiment in a case
where the electronic apparatus of the invention is applied to a
display.
[0046] FIG. 13 is a diagram illustrating an embodiment in a case
where the electronic apparatus of the invention is applied to a
display.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0047] Hereinafter, preferable embodiments of a method of
manufacturing an electrophoretic particle, an electrophoretic
particle, an electrophoretic dispersion liquid, an electrophoretic
sheet, an electrophoretic device, and an electronic apparatus of an
embodiment of the invention will be specifically described with
reference to the drawings.
[0048] First, before describing the method of manufacturing an
electrophoretic particle of the embodiment of the invention, an
electrophoretic dispersion liquid containing an electrophoretic
particle (the electrophoretic particle of the embodiment of the
invention) which is manufactured by the method of manufacturing an
electrophoretic particle of the embodiment of the invention will be
described.
Electrophoretic Dispersion Liquid
First Embodiment
[0049] The electrophoretic dispersion liquid contains at least one
type of electrophoretic particles 1, and a dispersion medium (a
liquid phase dispersion medium), and in the electrophoretic
dispersion liquid, the electrophoretic particles 1 are dispersed
(suspended) in the dispersion medium.
[0050] First, the electrophoretic particles 1 contained in the
electrophoretic dispersion liquid will be described.
Electrophoretic Particle
[0051] FIG. 1 is a longitudinal sectional view illustrating a first
embodiment of the electrophoretic particle contained in an
electrophoretic dispersion liquid of the embodiment of the
invention, and FIG. 2 is a schematic diagram of a block copolymer
contained in the electrophoretic particle illustrated in FIG.
1.
[0052] As illustrated in FIG. 1, the electrophoretic particle 1
includes a base particle (particle) 2 and a coated layer 3 provided
on a surface of the base particle 2.
[0053] As the base particle 2, for example, at least one of a
pigment particle, a resin particle, and a composite particle
thereof is preferably used. These particles are easily
manufactured.
[0054] Examples of the pigment for constituting the pigment
particle include a black pigment such as aniline black, carbon
black, and titanium black, a white pigment such as titanium
dioxide, antimony trioxide, barium sulfate, zinc sulfide, zinc
oxide, and silicon dioxide, an azo-based pigment such as monoazo,
disazo, and polyazo, a yellow pigment such as isoindolinone, chrome
yellow, yellow iron oxide, cadmium yellow, titanium yellow, and
antimony, a red pigment such as quinacridone red and chrome
vermilion, a blue pigment such as phthalocyanine blue, indanthrene
blue, Prussian blue, ultramarine blue, and cobalt blue, and a green
pigment such as phthalocyanine green. These pigments may be used
alone or in combination of two or more types thereof.
[0055] In addition, examples of a resin material for constituting
resin particles include an acrylic resin, a urethane resin, a urea
resin, an epoxy resin, polystyrene, and polyester. These resins may
be used alone or in combination of two or more types thereof.
[0056] In addition, examples of the composite particle include a
particle obtained by performing a coating treatment in which the
surface of the pigment particle is coated with the resin material,
a particle obtained by performing a coating treatment in which the
surface of the resin particle is coated with the pigment, and a
particle composed of a mixture obtained by mixing the pigment and
the resin material at an appropriate composition ratio.
[0057] Meanwhile, it is possible to set a desired color for the
electrophoretic particle 1 by appropriately selecting the type of
the pigment particle, the resin particle, and the composite
particle which are used as the base particle 2.
[0058] In addition, due to the above selection, the positive
charging properties or the negative charging properties of the base
particle 2, and the charging amount thereof can be set as a unique
matter of the base particle 2.
[0059] Note that, it is necessary that the base particle 2 includes
(exposes) a first functional group which can be bonded to (react
with) a second functional group included in a bonding portion 31 of
a block copolymer 39 described below on the surface thereof.
However, there is a case where the base particle 2 does not include
a functional group depending on the type of the pigment particle,
the resin particle, and the composite particle, and thus, in this
case, the first functional group is introduced to the surface of
the base particle 2 by performing in advance a functional group
introduction treatment such as an acid treatment, a base treatment,
a UV treatment, an ozone treatment, and a plasma treatment.
[0060] Meanwhile, the combination of the first functional group
which is provided on the surface of the base particle 2, and the
second functional group which includes the bonding portion 31 of
the block copolymer 39 is not particularly limited as long as the
materials can be bonded to each other through the reaction
therebetween. For example, examples of the combination include a
combination of an isocyanate group and a hydroxyl group or an amino
group, a combination of an epoxy group, a glycidyl group or an
oxetane group and a carboxyl group, an amino group, a thiol group,
and a hydroxyl group or an imidazole group, a combination of an
amino group and a halogen group such as Cl, Br, and I, and a
combination of an alkoxysilyl group and a hydroxyl group or an
alkoxysilyl group. Among them, a combination of the hydroxyl group
as the first functional group and the alkoxysilyl group as the
second functional group is preferably used.
[0061] Both of the base particle 2 having the above combination and
a monomer M2 can be relatively easily prepared, and are preferably
used since the monomer M2 (a block copolymer described below) can
be firmly bonded onto the surface of the base particle 2.
[0062] Hereinafter, an example of a combination of the first
functional group which is provided on the surface of the base
particle 2 as a hydroxyl group with the second functional group
provided in the monomer M2 as an alkoxysilyl group will be
described.
[0063] In the base particle 2, at least a portion (almost the
entire surface in the configuration in the drawing) of the surface
thereof is coated with the coated layer 3.
[0064] The coated layer 3 is configured to include a plurality of
the block copolymers 39 (hereinafter, simply referred to as a
"polymer 39") (refer to FIG. 2).
[0065] The block copolymer 39 includes a dispersion portion 32 and
the bonding portion 31 which is bonded to the dispersion portion
32, and the dispersion portion 32 is formed by polymerizing first
monomers M1 (hereinafter, simply referred to as a "monomer M1")
having a portion (a group) for contributing to the dispersibility
in the dispersion medium, and includes a plurality of units
(constituting units, hereinafter, referred to as a dispersion unit)
derived from the monomer M1. The bonding portion 31 is formed by
polymerizing second monomers M2 of which have an alkoxysilyl group
(the second functional group) and is reacted with a hydroxyl group
(the first functional group) on the surface of the base particle,
and includes a plurality of units (hereinafter, referred to as a
"bonding unit") derived from the monomers M2. In the bonding
portion 31, when the hydroxyl group and the functional group are
reacted with each other, the base particle 2 and the block
copolymer 39 are chemically bonded.
[0066] In the embodiment, the aforementioned block copolymer 39
forms a particle surface treatment agent (coupling agent) which is
used to form the electrophoretic particle 1.
[0067] Hereinafter, the dispersion portion 32 and the bonding
portion 31 which form the aforementioned block copolymer 39 will be
described below.
[0068] The dispersion portion 32 is provided on the surface of the
base particle 2 in the coated layer 3 so as to impart the
dispersibility to the electrophoretic particle 1 in the
electrophoretic dispersion liquid.
[0069] In the electrophoretic dispersion liquid, the aforementioned
dispersion portion 32 is formed by polymerizing the plurality of
monomers M1 which include a portion that becomes a side chain for
contributing to the dispersibility in the dispersion medium after
being polymerized, and includes the plurality of dispersion units
derived from the monomers M1, which are bonded to each other.
[0070] Each of the monomers M1 has one polymerizable group such
that the monomers M1 are polymerized by the living radical
polymerization (the radical polymerization), and is a pendant-type
monofunctional monomer which includes a portion corresponding to a
non-ionic side chain after performing polymerization.
[0071] In the embodiment, a silicone macromonomer expressed by the
following Formula (I) which has dimethyl polysiloxane as the
non-ionic side chain, and a (meth)acryloyl group as the
polymerizable group is used as the monomer M1. In a case where such
a silicone macromonomer is used as the monomer M1, the block
colpolymer 39 has a function as a siloxane-based compound.
##STR00002##
[0072] [In the formula, R.sup.1 represents a hydrogen atom or a
methyl group, R.sup.2 represents a hydrogen atom or an alkyl group
having 1 to 4 carbon atoms, R.sup.3 represents a structure
including one of an alkyl group having 1 to 6 carbon atoms and an
ether group of ethylene oxide or propylene oxide, and n represents
an integer of 0 or greater.]
[0073] When the silicone macromonomer having such a non-ionic side
chain is used as the monomer M1, the dispersion portion 32 which is
formed by the living radical polymerization exhibits excellent
affinity with respect to a silicone oil used as a dispersion medium
which is included in the electrophoretic dispersion liquid
described below. For this reason, the electrophoretic particles 1
which include the dispersion portion 32 are dispersed with
excellent dispersibility in the electrophoretic dispersion liquid
without being aggregated. In addition, when the monomer M1 having
the (meth)acryloyl group as the polymerizable group is used, the
monomers M1 can be polymerized with each other with excellent
reactivity, and thus it is possible to easily obtain the dispersion
portion 32.
[0074] The weight-average molecular weight of the silicone
macromonomer expressed by Formula (I) above as the monomer M1 is
preferably in a range of approximately 1,000 to 50,000, is further
preferably in a range of approximately 3,000 to 30,000, and is
still further preferably in a range of approximately 5,000 to
20,000. With this, it is possible to disperse the electrophoretic
particles 1 which include the dispersion portion 32 obtained by
polymerizing the monomers M1 in the dispersion medium with further
excellent dispersibility.
[0075] In addition, the weight-average molecular weight of the
dispersion portion 32 is not particularly limited, but is
preferably in a range of 8,000 to 50,000, and is further preferably
in a range of 10,000 to 35,000. With this, it is possible to make
the dispersibility of the electrophoretic particle 1 in the
electrophoretic dispersion liquid further excellent.
[0076] Further, in one polymer, the number of the dispersion units
included in the dispersion portion 32 is preferably in a range of 1
to 20, and is further preferably in a range of 1 to 5. With this,
it is possible to reliably impart the dispersibility of the
electrophoretic particle 1 in the electrophoretic dispersion
liquid.
[0077] In addition, the molecular weight distribution of the
dispersion portion 32 is preferably equal to or lower than 1.2, is
further preferably equal to or lower than 1.1, and is still further
preferably equal to or lower than 1.05.
[0078] Here, the molecular weight distribution of the dispersion
portion 32 represents the ratio (Mw/Mn) of the number average
molecular weight (Mn) of the dispersion portion 32 to the
weight-average molecular weight (Mw) of the dispersion portion 32,
and it can be said that when the molecular weight distribution of
the dispersion portion 32 is within the above-described range, the
dispersion portions 32 which are exposed in the plurality of
electrophoretic particles 1 have almost the same length. For this
reason, in the electrophoretic dispersion liquid, each of the
electrophoretic particles 1 exhibits uniform dispersion ability.
The above-described number average molecular weight (Mn) and the
weight-average molecular weight (Mw) can be measured as molecular
weight in terms of polystyrene by using, for example, a gel
permeation chromatography (GPC) method.
[0079] Further, in the dispersion portion 32, the molecular weight
of the dispersion unit of the proximal end portion side which is
bonded to the bonding portion 31 is preferably smaller than the
molecular weight of the dispersion unit of the distal end portion
side. More specifically, the molecular weight of the side chain
which is included in the monomer M1 corresponding to a precursor of
the dispersion unit positioned on the proximal end portion side is
preferably smaller than the molecular weight of the side chain
which is included in the monomer M1 corresponding to the precursor
of the dispersion unit positioned on the distal end portion side.
With this, it is possible to make further excellent dispersibility
of the electrophoretic particle 1 in the electrophoretic dispersion
liquid, and to bond the dispersion portion 32 onto the surface of
the base particle 2 with high density.
[0080] In addition, a change of molecular weight of the side chain
may become continuously larger to the proximal end side from the
distal end side, or may become gradually larger to the proximal end
side from the distal end side.
[0081] The bonding portion 31 is bonded onto the surface of the
base particle 2 in the coated layer 3 provided in the
electrophoretic particle 1. With this, the polymer 39 is bonded to
the base particle 2.
[0082] In the embodiment, the bonding portion 31 is formed by
polymerizing the plurality of second monomers M2 formed on the
surface of the base particle 2, each of which is reacted with a
hydroxyl group so as to be covalently bonded, and has the second
functional group, and includes the plurality of bonding units
(constituting units) derived from the monomers M2 which are
arranged therein.
[0083] As such, it is possible to make further excellent
dispersibility of the electrophoretic particles 1 by using the
polymer 39 including the bonding portion 31 which has the plurality
of bonding units of which has a functional group. That is, the
polymer 39 has a plurality of the functional groups, and the
plurality of functional groups are concentrically present in the
bonding portion 31. Further, the bonding portion 31 is bonded to
the plurality of bonding units, and thus has a large portion which
can be reacted with the base particle 2 as compared with a case
where only one bonding unit is present. For this reason, it is
possible to reliably bond the polymer 39 onto the surface of the
base particle 2 in the bonding portion 31 which is formed by
polymerizing the plurality of monomers M2.
[0084] In addition, in the embodiment, the hydroxyl group is
included on the surface of the base particle 2, and the functional
group included in the monomer M2 is the alkoxysilyl group, as
described above. When the hydroxyl group and the alkoxysilyl group
are combined with each other, the reaction therebetween exhibits
the excellent reactivity, and thus it is possible to reliably bond
the polymer 39 onto the surface of the base particle 2 in the
bonding portion 31. That is, the polymer 39 can reliably have a
function as a coupling agent which is bonded onto the surface of
the base particle 2.
[0085] Such a monomer M2 includes one alkoxysilyl group expressed
by the following Formula (II) as a functional group, and one
polymerizable group such that the polymerization is performed by
the living radical polymerization.
##STR00003##
[0086] [In the formula, each of R's independently represents an
alkyl group having 1 to 4 carbon atoms, and n represents an integer
of 1 to 3.]
[0087] When the above-described configuration is used as the
monomer M2, it is possible to form the bonding portion 31 in which
the monomers M2 are polymerized by the living radical
polymerization, and the bonding portion 31 which is formed by the
living radical polymerization exhibits the excellent reactivity
with respect to the hydroxyl group positioned on the surface of the
base particle 2.
[0088] In addition, examples of one polymerizable group included in
the monomers M2 include polymerizable groups having a carbon-carbon
double bond such as a vinyl group, a styryl group, and a
(meth)acryloyl group.
[0089] Examples of such monomers M2 include a vinyl monomer, a
vinyl ester monomer, a vinyl amide monomer, a (meth)acrylic
monomer, a (meth)acrylic ester monomer, a (meth)acrylamide monomer,
and a styryl monomer, each of which includes one alkoxysilyl group
expressed by Formula (II), and more specifically include a
silane-based monomer containing a silicon atom such as
3-(meth)acryloxypropyl triethoxy (methoxy)silane, vinyl triethoxy
(methoxy)silane, 4-vinyl butyl triethoxy (methoxy)silane, 8-vinyl
octyltriethoxy (methoxy)silane, 10-methacryloyloxydecyl triethoxy
(methoxy)silane, and 10-acryloyloxydecyl triethoxy (methoxy)silane.
In addition, these can be used alone or in combination of two or
more types thereof.
[0090] In addition, in one polymer, the number of bonding units
included in the bonding portion 31 may be equal to or greater than
1, and is preferably in a range of 2 to 10, and is further
preferably in a range of 3 to 6. When the number of bonding units
is larger than the upper limit, the bonding portion 31 has low
affinity with respect to the dispersion medium as compared with the
dispersion portion 32, and thus in accordance with the type of the
monomer M2, the dispersibility of the electrophoretic particles 1
may be deteriorated or the bonding portions 31 may be partially
reacted with each other. In addition, when the number of bonding
units is smaller than the lower limit, in accordance with the type
of the monomer M2, the monomer M2 cannot be sufficiently bonded to
the base particle 2, and thus the dispersibility of the
electrophoretic particles 1 may be deteriorated.
[0091] Further, the number of bonding units included in the bonding
portion 31 can be obtained by the analysis by using a
general-purpose analysis apparatus such as an NMR spectrum, an IR
spectrum, an elemental analysis, and a gel permeation
chromatography (GPC). Meanwhile, in the polymer 39, the bonding
portion 31 and the dispersion portion 32 are high-molecular weight
polymers, and thus have a certain molecular weight distribution.
Accordingly, the above-described analysis result does not
necessarily correspond to all of the polymers 39, but if the number
of bonding units which is obtained by using at least one of the
above-described methods is in a range of 2 to 8, it is possible to
achieve the reactivity between the polymer 39 and the base particle
2, and the dispersibility and electrophoretic properties (charging
properties) of the electrophoretic particle 1.
[0092] The polymer 39 can be obtained by using a manufacturing
method described below. For example, when a reversible
addition-fragmentation chain transfer polymerization (RAFT) method
described below is used, it is possible to obtain a relatively
uniform polymer. Accordingly, if 2 mole equivalents to 10 mole
equivalents of the monomer M2 is added to, and polymerized with a
chain transfer agent, it is possible to set the number of bonding
units in the bonding portion 31 to be in the above-described range.
In consideration of the aforementioned description, in a case where
the additive rate of the monomer M2 is equal to or less than 100%,
the polymerization reaction may be performed by setting the
additive amount of the monomer M2 to be 2 mole equivalents to 10
mole equivalents.
[0093] Meanwhile, in a case where the bonding portion is generated
after the dispersion portion 32 is generated, the dispersion
portion 32 serves as the chain transfer agent. In this case, for
example, the weight-average molecular weight and the number average
molecular weight of the polymer which constitute the dispersion
portion 32 are obtained by using the GPC method, and then the
additive amount of the monomer M2 may be determined based on the
obtained result values.
[0094] With this, it is possible to reliably exhibit an effect with
the configuration such that the electrophoretic particle 1 includes
the polymer 39, and thus the electrophoretic particle 1 has the
excellent dispersibility in the electrophoretic dispersion
liquid.
[0095] Such a polymer 39 which is provided with the dispersion
portion 32 and the bonding portion 31 forms the coated layer 3 by
bonding to at least a portion of the surface of the base particle
2; however, in the invention, in a case where the weight of the
base particle 2 is set to be 100% by weight, the weight of the
polymer (the particle surface treatment agent) 39 becomes in a
range of 4% by weight to 8% by weight. When the weight of the
polymer 39 which is bonded to the base particle 2 is lower than the
lower limit, the obtainable effect by bonding the polymer 39 to the
base particle 2 cannot be sufficiently obtained, and the
electrophoretic particle 1 cannot be sufficiently dispersed in the
electrophoretic dispersion liquid. In addition, in a case where the
weight of the polymer 39 which is bonded to the base particle 2 is
greater than the upper limit, the weight of the entire amount of
the electrophoretic particles 1 becomes larger, and from this
aspect, the electrophoretic particle 1 cannot be sufficiently
dispersed in the electrophoretic dispersion liquid. Therefore, the
positive and negative electrophoretic particles are aggregated with
each other and are adhered to the electrode surface, and as a
result, there is a problem in that degradation of the contrast,
change of the contrast with time, and the like are caused.
[0096] Note that, by the weight within the above range, the polymer
39 can be bonded to the base particle 2 in a case where the
electrophoretic particle 1 is manufactured by applying the method
of manufacturing an electrophoretic particle of the embodiment of
the invention, and the description thereof will be described below
in detail.
[0097] In addition, the weight of the polymer (the particle surface
treatment agent) 39 may be in a range of 4% by weight to 8% by
weight, is preferably in a range of 4.5% by weight to 7% by weight,
and is further preferably in a range of 4.8% by weight to 6% by
weight, with respect to 100% by weight of the base particle 2. With
this, the electrophoretic particle 1 can be uniformly dispersed in
the electrophoretic dispersion liquid, and thus it is possible to
reliably suppress or prevent the positive and negative
electrophoretic particles from being aggregated with each other and
from being adhered to the electrode surface, thereby realizing the
contrast improvement.
[0098] The electrophoretic particles 1 having the above described
configuration are dispersed (suspended) in the dispersion medium (a
liquid phase dispersion medium) in the electrophoretic dispersion
liquid.
Dispersion Medium
[0099] In the embodiment, a material having a silicone oil as a
main component is used as the aforementioned dispersion medium. The
silicone oil exhibits the excellent affinity with respect to the
dispersion portion 32 which is formed by the living radical
polymerization performed by using the above-described silicone
macromonomer as the monomer M1, and thus is used as a dispersion
medium.
[0100] With this, the effect of preventing the electrophoretic
particles 1 from being aggregated is enhanced, and thus it is
possible to prevent display properties of an electrophoretic
display device 920 illustrated in FIG. 8 from being deteriorated
over time. In addition, the silicone oil does not have an
unsaturated bond and thus is excellent in weather resistance, and
has high stability, which is an advantage.
[0101] Further, the kinetic viscosity of the silicone oil (the
dispersion medium) at a normal temperature (25.degree. C.) is
preferably equal to or lower than 5 cs, and is further preferably
in a range of 2 cs to 4 cs. Even though the viscosity of the
silicone oil (the dispersion medium) is in the above-described
range, if the electrophoretic particle 1 includes the dispersion
portion 32 formed by the living radical polymerization performed by
using the silicone macromonomer as the monomer M1, the
electrophoretic particles 1 can be dispersed in the dispersion
medium with the excellent dispersibility.
[0102] The weight-average molecular weight of the silicone oil is
not particularly limited; however, it is preferably in a range of
250 to 700, and is further preferably in a range of 300 to 600.
With this, it is possible to disperse the electrophoretic particle
1 in the electrophoretic dispersion liquid with more excellent
dispersibility.
[0103] In addition, the relative permittivity of the silicone oil
is preferably in a range of 1.5 to 3, and is further preferably in
a range of 1.7 to 2.8. Such silicone oil is excellent in the
dispersibility of the electrophoretic particles 1, and has
satisfactory electric insulation. For this reason, the silicone oil
contributes to the realization of the electrophoretic display
device 920 which has small power consumption and is capable of
displaying high contrast. Meanwhile, the value of dielectric
constant is a value measured at 50 Hz, and is a value obtained by
measuring the dispersion medium in which the amount of moisture is
equal to or less than 50 ppm at a temperature of 25.degree. C.
[0104] In addition, various additives such as a charge control
agent, a lubricant, a stabilizer, and various dyes which are
composed of particles such as an electrolyte, a surfactant (anionic
or cationic), metal soap, a resin material, a rubber material, oil,
varnish, and a compound are added in the dispersion medium, as
necessary.
[0105] The electrophoretic dispersion liquid in which the
above-described electrophoretic particle 1 is dispersed in the
dispersion medium, that is, the electrophoretic dispersion liquid
in which the electrophoretic particle 1, in which the weight of the
polymer 39 bonded to the surface of the base particle 2 is in a
range of 4% by weight to 8% by weight in a case where the weight of
the base particle 2 is set to be 100% by weight, is dispersed in
the dispersion medium can be manufactured as follows, for
example.
Method of Manufacturing Electrophoretic Dispersion Liquid
[0106] FIG. 3 is a flowchart illustrating a method of manufacturing
an electrophoretic dispersion liquid.
[0107] The method of manufacturing the above-described
electrophoretic dispersion liquid includes a generating step (S1)
of generating the plurality of block copolymers 39 (the particle
surface treatment agents) in which the dispersion portion 32 and
the bonding portion 31 are bonded to each other, a bonding step
(S2) of bonding the plurality of block copolymers 39 to the base
particle 2 and thus forming the coated layer 3 by the reaction
between the first functional group included in the base particle 2
and the second functional group included in the second monomer M2
so as to obtain the electrophoretic particle 1, and a dispersing
step (S3) of dispersing the obtained electrophoretic particles 1 in
the dispersion medium so as to obtain the electrophoretic
dispersion liquid.
[0108] Note that, in the generation step, through the living
radical polymerization performed by using a polymerization
initiator, the bonding portion 31 in which the second monomers M2
having the second functional group are polymerized may be formed
after forming the dispersion portion 32 in which the first monomers
M1 are polymerized, or the dispersion portion 32 may be formed
after forming the bonding portion 31. Here, the case where the
bonding portion is formed after forming the dispersion portion 32
will be described.
[0109] Hereinafter, each step will be described in detail.
[0110] 1. First, the plurality of block copolymers 39 in which the
dispersion portion 32 and the bonding portion 31 are bonded to each
other are generated (the generation step: S1).
[0111] 1-1. First, the dispersion portion 32 in which the first
monomers M1 are polymerized is formed by the living polymerization
by performed by using the polymerization initiator.
[0112] Examples of the living polymerization method include a
living radical polymerization method, a living cationic
polymerization method, and a living anionic polymerization method.
Among them, the living radical polymerization method is preferably
used. When the living radical polymerization method is used, it is
possible to simply use a reaction solution and the like generated
in the reaction system, and to polymerize the monomers M1 with
satisfactory controllability of the reaction.
[0113] In addition, examples of the living radical polymerization
method include an atom transfer radical polymerization (ATRP)
method, a radical polymerization (NMP) method via nitroxide, a
radical polymerization (TERP) method performed by using
organotellurium, and a reversible addition-fragmentation chain
transfer polymerization (RAFT) method. Among them, the reversible
addition-fragmentation chain transfer polymerization (RAFT) method
is preferably used. According to the reversible
addition-fragmentation chain transfer polymerization (RAFT) method,
it is possible to simply polymerize the monomers M1. Further, it is
possible to easily set the molecular weight distribution to be
equal to or less than 1.2 in the dispersion portion 32.
[0114] The polymerization initiator (a radical polymerization
initiator) is not particularly limited; however, examples thereof
include an azo initiator such as 2,2'-azobisisobutyronitrile
(AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile),
2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl
2,2'-azobis(2-methylpropionate),
1,1'-azobis(cyclohexane-1-carbonitrile),
2,2'-azobis[2-(2-imidazolin-2-yl) propane] dihydrochloride, and
2,2'-azobis[2-(2-imidazolin-2-yl) propane], and persulfate such as
potassium persulfate, and ammonium persulfate.
[0115] In addition, in the case where the reversible
addition-fragmentation chain transfer polymerization (RAFT) method
is used, a chain transfer agent (a RAFT agent) is used other than
the polymerization initiator. The chain transfer agent is not
particularly limited; however, examples thereof include a sulfur
compound having a functional group such as a dithioester group, a
trithiocarbamate group, a xanthate group, and a dithiocarbamate
group.
[0116] Specifically, examples of the chain transfer agent include a
compound expressed by the following Formulae (1) to (7), and these
may be used alone or in combination of two or more types thereof.
These compounds are relatively easily available, and can easily
perform control of the reaction, and thus are preferably used.
##STR00004##
[0117] Among these, the chain transfer agent is preferably
2-cyano-2-propyl benzo dithioate expressed by the above-described
Formula (6). With this, it is possible to more easily control the
reaction.
[0118] Further, in a case where the reversible
addition-fragmentation chain transfer polymerization (RAFT) method
is used, the ratio of the monomer M1, the polymerization initiator,
and the chain transfer agent is appropriately determined in
consideration of a polymerization degree of the dispersion portion
32 to be formed and the reactivity between compounds such as the
monomer M1, and the molar ratio between the monomer M1, the
polymerization initiator, and the chain transfer agent is
preferably monomer: polymerization initiator:chain transfer
agent=500 to 5:5 to 0.25:1. With this, it is possible to set the
length (polymerization degree) of the dispersion portion 32 which
is obtained by polymerizing the monomers M1 to be an appropriate
size.
[0119] In addition, examples of the solvent for preparing the
solution which polymerizes the monomers M1 by the living radical
polymerization include water, alcohol such as methanol, ethanol,
and butanol, a hydrocarbon such as hexane, octane, benzene,
toluene, and xylene, an ether such as diethyl ether and
tetrahydrofuran, an ester such as ethyl acetate and butyl acetate,
a halogenated aromatic hydrocarbon such as chlorobenzene and
o-dichlorobenzene. These may be used alone or as a mixed
solvent.
[0120] In addition, it is preferable that the solution (a reaction
solution) is subjected to a deoxygenation treatment before starting
the polymerization reaction. Examples of the deoxygenation
treatment include substitution after the vacuum degassing due to an
inert gas such as an argon gas and a nitrogen gas, and a purge
treatment.
[0121] Further, at the time of the polymerization reaction of the
monomer M1, it is possible to further rapidly and reliably perform
the polymerization reaction of the monomers by heating the solution
up to a certain temperature.
[0122] The heating temperature is slightly different depending on
the type of the monomer M1, and thus is not particularly limited;
the heating temperature is preferably in a range of approximately
30.degree. C. to 100.degree. C. In addition, the heating time
(reaction time) is preferably in a range of 3 hours to 48 hours in
a case where the heating temperature is set to be in the
above-described range.
[0123] Meanwhile, in a case where the reversible
addition-fragmentation chain transfer polymerization (RAFT) method
is used, a fragment of the chain transfer agent which is used as
one terminal (a tip end portion) of the dispersion portion 32
remains. Then, the dispersion portion 32 having the aforementioned
fragment acts as the chain transfer agent in the reaction of
polymerizing the dispersion portion 32 and the bonding portion 31
in the following step 1-2.
[0124] 1-2. Next, the bonding portion 31 in which the second
monomers M2 each of which has the second functional group having
the reactivity with the first functional group included in the base
particle 2 are polymerized is formed so as to be bonded to the
dispersion portion 32.
[0125] With this, the polymer 39 configured with a block copolymer
in which the dispersion portion 32 and the bonding portion 31 are
bonded to each other is generated.
[0126] In addition, in the step 1-2, before forming the bonding
portion 31 which uses the monomer M2, impurities such as the
solvent and the polymerization initiator which are used in the
previous step 1-1 are removed as necessary such that the dispersion
portion 32 may be subjected to a purification treatment (a removing
treatment) for isolating and purifying. With this, the obtained
polymers 39 become more uniform and are highly purified. The
aforementioned purification treatment is not particularly limited,
and for example, examples thereof include a column chromatography
method, a recrystallization method, and a re-precipitation method.
These may be used alone or in combination of two or more types
thereof.
[0127] In addition, as described above, in a case where the
reversible addition-fragmentation chain transfer polymerization
(RAFT) method is used, the fragment of the chain transfer agent
which is used as one terminal of the dispersion portion 32 remains.
For this reason, the bonding portion 31 having the above-described
configuration is formed in such a manner that a solution containing
the dispersion portion 32, the monomer M2, and the polymerization
initiator which are obtained after the previous step 1-1 is
prepared and the living polymerization is performed again in the
aforementioned solution.
[0128] Note that, as the solvent used in the current step, the same
solvent as that used in the previous step 1-1 can be used, and it
is possible to set the condition at the time of polymerizing the
monomers M2 in the solution to be the same as the condition at the
time of polymerizing the monomers M1 in the solution in the
previous step 1-1.
[0129] In addition, after the current step 1-2, impurities such as
a solvent used in the current step 1-2 are removed, and the polymer
39 is subjected to a purification treatment (a removing treatment)
for isolating and purifying. With this, the polymer 39 can be
smoothly bonded to the base particle 2 in the next step 2; however,
the description thereof will be described below in detail. The
aforementioned purification treatment is not particularly limited,
and for example, examples thereof include a column chromatography
method, a recrystallization method, and a re-precipitation method.
These may be used alone or in combination of two or more types
thereof.
[0130] 2. Next, the coated layer 3 is formed in such a manner that
the first functional group included in the base particle 2 and the
plurality of second functional groups in the bonding portion 31 are
reacted with each other and then are chemically bonded to each
other such that the plurality of block copolymers 39 (the particle
surface treatment agent) are bonded to the surface of the base
particle 2 (the bonding step; S2).
[0131] With this, it is possible to obtain the electrophoretic
particle 1 in which at least a portion of the base particle 2 is
coated with the coated layer 3.
[0132] The electrophoretic particle 1 is manufactured by applying
the method of manufacturing an electrophoretic particle of the
embodiment of the invention to the current step as described
below.
[0133] In this regard, as described above, typically, the polymer
39 is bonded onto the surface of the base particle 2 in such a
manner that a solution is prepared by mixing the polymer 39 and the
base particle 2 in the solvent, then the solution is heated while
being stirred, and thus a chemical bond is formed between the
alkoxysilyl group (the second functional group) and the hydroxyl
group (the first functional group).
[0134] In this case, it is considered that the solvent which is
used at the time of preparing the solution is the same as that in
the previous step 1-1, and the silicone oil described as the
dispersion liquid contained in the electrophoretic dispersion
liquid is used.
[0135] However, in a case where the solvent is contained in the
solution as described above, if the solvent exhibits hydrophilicity
as compared with the dispersion portion 32, the dispersion portions
32 exhibiting hydrophobicity are aggregated with each other, and as
a result, there is a problem in that the polymers 39 are aggregated
with each other in the solution, the adsorption amount of the
polymer 39 with respect to the base particle 2 is not improved.
Further, even in a case where the solvent exhibits hydrophobicity
similar to the dispersion portion 32 such as the case where the
silicone oil is used as the solvent, the solvent is adsorbed on the
surface of the base particle 2. Due to this, there is a problem in
that the adsorption amount of the polymer 39 with respect to the
base particle 2 is not improved likewise.
[0136] In contrast, the solvent for dissolving the polymer 39 is
not added into the mixture containing the base particle 2 and the
polymer 39 in the invention. With this, it is possible to increase
the number of the case where the polymer 39 comes in contact with
the base particle 2.
[0137] However, the inventors of the invention have studied and
found that even though the solvent is not added into the mixture
containing the base particle 2 and the polymer 39 as described
above, it is not possible to sufficiently increase adsorption
amount of the polymer 39 with respect to the base particle 2 in
some cases.
[0138] Here, as described in the previous step 1-2, after the
previous step 1-2, the polymer 39 is subjected to the purification
treatment (a removing treatment) for isolating and purifying so as
to remove impurities such as the solvent used in the previous step
1-2.
[0139] Further, in the dispersion portion 32 which is formed by the
living radical polymerization performed by using the silicone
macromonomer (the siloxane-based compound) expressed by the
above-described Formula (I) as the monomer M1, the silicone
macromonomer expressed by the above-described Formula (I) is
typically generated by being polymerized through the
hydrosilylation reaction as the following Reaction formula (i). For
this reason, the unreacted product expressed by the following
Formula (i-2) remains in the reaction system.
##STR00005##
[0140] [In the formula, R.sup.1 represents a hydrogen atom or a
methyl group, R.sup.2 represents a hydrogen atom or an alkyl group
having 1 to 4 carbon atoms, R.sup.3 represents a structure
including one of an alkyl group having 1 to 6 carbon atoms and an
ether group of ethylene oxide or propylene oxide, R.sup.4
represents a structure in which a methylene group is removed from
the terminal on the Si side of R.sup.3, and n represents an integer
of 0 or greater.]
[0141] As described above, even though the purification treatment
is performed by using a column chromatography method, a
recrystallization method, and a re-precipitation method in order to
isolate and purify the polymer 39, the silicone macromonomer
expressed by the above-described Formula (I), and the unreacted
product expressed by the above-described Formula (i-2) exhibit
substantially the same physical properties, and thus such an
unreacted product and the reaction by-product generated at the time
of generating the polymer 39 are mixed into the purified the
polymer 39.
[0142] Specifically, for example, the weight-average molecular
weight of the unreacted product expressed by the above-described
Formula (i-2) is preferably in a range of 1,000 to 50,000, and is
further preferably in a range of 3,000 to 30,000.
[0143] In addition, in a case where the unreacted product expressed
by the above-described Formula (i-2) is defined by a boiling point,
the boiling point is set to be preferably in a range of 180.degree.
C. to 250.degree. C., and further preferably in a range of
200.degree. C. to 240.degree. C.
[0144] The fact that the mixing of the unreacted product and the
reaction by-product is a factor that cannot sufficiently increase
the adsorption amount of the polymer 39 with respect to the base
particle 2 even in a case where the solvent is not added into the
mixture containing the base particle 2 and the polymer 39, is
apparent by the further study of the inventors, and it was found
that the above-described problem can be solved by setting the
content of the polymer (the particle surface treatment agent) 39
except for the plurality of base particles 2 in the mixture
containing the base particle 2 and the polymer 39 to be equal to or
greater than 70% by weight, and thus the invention has been
completed.
[0145] That is, in a case where the content of the polymer (the
particle surface treatment agent) 39 except for the plurality of
base particles 2 in the mixture containing the base particle 2 and
the polymer 39 is set to be equal to or greater than 70% by weight,
it is possible to sufficiently increase the adsorption amount of
the polymer 39 with respect to the base particle 2, and as a
result, it is possible to obtain the electrophoretic particle 1
which includes the coated layer 3 in which the weight of the
polymer (the particle surface treatment agent) 39 is in a range of
4% by weight to 8% by weight in a case where the weight of the base
particle 2 is set to be 100% by weight. For this reason, the
electrophoretic particle 1 is sufficiently dispersed in the
electrophoretic dispersion liquid, and thus it is possible to
reliably suppress or prevent the positive and negative
electrophoretic particles from being aggregated with each other and
from being adhered to the electrode surface. Therefore, the problem
in that degradation of the contrast, change of the contrast with
time, and the like are caused can be solved.
[0146] The current step 2 in which the content of the polymer (the
particle surface treatment agent) 39 is set to be equal to or
greater than 70% by weight as described above, and the polymer 39
is boned to the surface of the base particle 2 is more specifically
embodied as follows.
[0147] 2-1. First, the mixture containing the base particle 2 and
the polymer 39 is prepared.
[0148] At this time, as described above, the unreacted product (for
example, the unreacted product expressed by the above-described
Formula (i-2)) of the raw material used at the time of generating
the polymer 39 and the reaction by-product generated at the time of
generating the polymer 39 are mixed into the mixture; however, in
the invention, the mixture in which the content of the polymer 39
except for the base particle 2 in the mixture is set to be equal to
or greater than 70% by weight is prepared.
[0149] Note that, the content of the polymer 39 except for the base
particle 2 in the mixture may be equal to or greater than 70% by
weight, is preferably equal to or greater than 80% by weight, and
is further preferably in a range of 90% by weight to 95%. With
this, it is possible to reliably improve the adsorption amount of
the polymer 39 with respect to the base particle 2.
[0150] Further, in the mixture, in a case where the weight of the
base particle 2 is set to be 100% by weight, the weight of the
polymer 39 is preferably in a range of 50% by weight to 500%, and
is further preferably in a range of 100% by weight to 200%. When
the content of the polymer 39 is set to be within the
above-described range, it is possible to increase the number of the
case where the polymer 39 comes in contact with the surface of the
base particle 2, and thus the polymer 39 can be reliably and
uniformly adsorbed on the surface of the base particle 2.
[0151] 2-2. Subsequently, the polymer 39 is bonded onto the surface
of the base particle 2 in the mixture.
[0152] With this, it is possible to obtain the electrophoretic
particles 1 in which the coated layer 3 is formed on at least a
portion of the surface of the base particle 2.
[0153] The bonding of the polymer 39 onto the surface of the base
particle 2 is performed by heating the mixture.
[0154] The temperature at the time of heating the mixture is not
particularly limited, but is preferably in a range of 100.degree.
C. to 250.degree. C., and is further preferably in a range of
150.degree. C. to 200.degree. C.
[0155] In addition, the time for heating the mixture is preferably
in a range of 1 hour to 15 hours, and is further preferably in a
range of 3 hours to 10 hours.
[0156] When the mixture is heated under the above-described
conditions, it is possible to reliably bond the polymer 39 onto the
surface of the base particle 2, and as a result, it is possible to
reliably obtain the electrophoretic particle 1 which includes the
coated layer 3 in which the weight of the polymer (the particle
surface treatment agent) 39 is in a range of 4% by weight to 8% by
weight in a case where the weight of the base particle 2 is set to
be 100% by weight.
[0157] Note that, before heating the mixture, the mixture may be
subjected to the ultrasonic treatment. With this, it is possible to
improve the dispersibility of the base particle 2 in the
mixture.
[0158] In addition, it is preferable that the mixture be heated
while being stirred. With this, the polymer 39 can uniformly come
in contact with the surface of the base particle 2.
[0159] The mixture is stirred by using, for example, a ball mill
and a bead mill.
[0160] 2-3. Next, the remaining polymers 39 which are adsorbed onto
the surface of the base particle 2, and the unreacted product and
the reaction by-product are removed by using a centrifugal
separator without forming the aforementioned chemical bond.
[0161] In this way, it is possible to obtain the purified
electrophoretic particle 1.
[0162] 3. Next, the electrophoretic dispersion liquid is obtained
by dispersing the obtained electrophoretic particle 1 in the
dispersion medium.
[0163] In the embodiment, a material having the aforementioned
silicone oil as a main component is used as the aforementioned
dispersion medium.
[0164] In addition, the method of dispersing the electrophoretic
particle 1 in the dispersion medium is not particularly limited;
however, examples thereof include a paint shaker method, a ball
mill method, a media mill method, an ultrasonic dispersion method,
and a stirring dispersion method. These may be used alone or in
combination of two or more types thereof.
[0165] With such steps described above, it is possible to obtain
the electrophoretic dispersion liquid in which the positive and
negative electrophoretic particles are reliably suppress or prevent
from being aggregated with each other and from being adhered to the
electrode surface, and as a result, the problem in that degradation
of the contrast, change of the contrast with time, and the like are
caused is solved.
Second Embodiment
[0166] Next, the second embodiment of the electrophoretic particle
included in the electrophoretic dispersion liquid will be
described.
[0167] FIG. 4 is a longitudinal sectional view illustrating the
second embodiment the electrophoretic particle contained in the
electrophoretic dispersion liquid of the embodiment of the
invention, FIG. 5 is a diagram illustrating a siloxane-based
coupling agent which is bonded onto a surface of a base particle of
the electrophoretic particle illustrated in FIG. 4, FIG. 6 is a
diagram illustrating, regarding a coupling agent and a modified
silicone oil which are used to obtain the siloxane-based coupling
agent having a structure Z illustrated in FIG. 5, specific examples
of a reactive functional group X contained in the coupling agent,
and a reactive functional group Y contained in the modified
silicone oil, and FIG. 7A to FIG. 7F are diagrams illustrating a
polarization group which is bonded onto the surface of the
electrophoretic particle illustrated in FIG. 4.
[0168] Hereinafter, the electrophoretic particle of the second
embodiment will be described, but the description will focus on the
differences from the electrophoretic particle of the first
embodiment and the same matters will be omitted.
[0169] Regarding the electrophoretic particle of the embodiment,
the coated layer 3 which is included in the electrophoretic
particle 1 is the same as the coated layer 3 which is included in
the electrophoretic particle 1 in the first embodiment as
illustrated in FIG. 2 except for the configuration thereof as
illustrated in FIG. 4.
[0170] That is, in the electrophoretic particle 1 of the second
embodiment, instead of the block copolymer 39, a siloxane-based
coupling agent 72 and a polarization group 73 are bonded to each
other on the surface of the base particle 2 so as to form the
coated layer 3.
[0171] Accordingly, in the embodiment, the siloxane-based coupling
agent 72 and the polarization group 73 constitute the particle
surface treatment agent which is used to form the electrophoretic
particle 1.
[0172] Hereinafter, the siloxane-based coupling agent 72 and the
polarization group 73 will be described.
[0173] The siloxane-based coupling agent 72 exhibits excellent
affinity with respect to a silicone oil used as a dispersion medium
which is included in the electrophoretic dispersion liquid, and
thus is provided on the surface of the base particle 2 in the
coated layer 3 so as to impart the dispersibility to the
electrophoretic particle 1 in the electrophoretic dispersion
liquid.
[0174] The siloxane-based coupling agent 72 is a compound (particle
surface treatment agent) having a straight-chain molecular
structure which is configured to include a coupling structure in
which a plurality of siloxane bonds are coupled in series
(hereinafter, referred to as a "silicone main chain") as a main
chain, and a side chain which is bonded to the main chain while
being bonded to the surface of the base particle 2.
[0175] Specific examples of such a siloxane-based coupling agent 72
include a compound bonded onto the surface of the base particle 2
via the side chain derived from the coupling agent, as illustrated
in FIG. 5.
[0176] The siloxane-based coupling agent 72 is obtained by
performing dehydration condensation reaction between a hydrolyzable
group derived from the coupling agent and a hydroxyl group on the
surface of the base particle 2 which are the reactants obtained by
the reaction between the modified silicone oil and the coupling
agent. Such a siloxane-based coupling agent 72 is configured to
include a structure derived from the silicone oil and a structure
derived from the coupling agent, and a structure 722 derived from
the silicone oil is bonded to the base particle 2 via a structure
721 derived from the coupling agent.
[0177] The weight-average molecular weight of the siloxane-based
coupling agent 72 is preferably in a range of approximately 1,000
to 100,000, and is further preferably in a range of approximately
10,000 to 60,000. When the above weight-average molecular weight is
set to be in the above-described range, the length of the molecular
structure of the siloxane-based coupling agent 72 is optimized, and
thus the electrophoretic particle 1 to which the dispersibility
derived from the linear structure with a long chain is sufficiently
imparted while sufficiently securing an area in which the
polarization group 73 can be introduced to the surface of the base
particle 2.
[0178] Note that, the weight-average molecular weight of the
siloxane-based coupling agent 72 is the weight-average molecular
weight of the in terms of polystyrene, which is measured by using
the gel permeation chromatography (GPC) method.
[0179] Further, n in FIG. 5 is preferably in a range of
approximately 12 to 1,400, and is further preferably in a range of
approximately 130 to 800 from the same reason as that of the
above-described weight-average molecular weight.
[0180] In addition, the structure Z in FIG. 5 is a structure
obtained by reacting the reactive functional group X included in
the coupling agent and the reactive functional group Y included in
the silicone oil with each other.
[0181] Examples of the reactive functional groups X and Y include
those illustrated in FIG. 6. R in FIG. 6 represents an aliphatic
hydrocarbon group such as an alkyl group.
[0182] Meanwhile, the terminal and the side chain of the
siloxane-based coupling agent 72 are preferably configured to
include a substituent with low polarity. With this, it is possible
to further improve the dispersibility of the electrophoretic
particles 1. Examples of the specific substituent include an alkyl
group.
[0183] The polarization group 73 is provided on the surface of the
base particle 2 so as to impart the charging properties to the
electrophoretic particle 1 in the electrophoretic dispersion
liquid.
[0184] The polarization group 73 is an organic group having a main
skeleton, and a substituent bonded to the main skeleton.
[0185] In the polarization group 73, the electrons are
maldistributed (polarized) in the main skeleton by setting at least
one of conditions from the type of substituents (an electron
attracting group and/or an electron donating group), and the number
of bonding times and a bonding position with respect to the main
skeleton, and thus the charging state of the electrophoretic
particle 1 is controlled.
[0186] In other words, for example, in the polarization group 73 in
which an electron attractive group (electron attracting group) is
bonded as a substituent to the main skeleton on the end portion
side (hereinafter, referred to as a "terminal of the main
skeleton") which is the side opposite to the base particle 2, the
electrons are maldistributed in the main skeleton on the terminal
side further than the base particle 2 side. When such a
polarization group 73 is introduced, the base particle 2 (the
electrophoretic particle 1) is negatively charged.
[0187] On the other hand, in the polarization group 73 in which the
electron attracting group is bonded as a substituent to the main
skeleton on the base particle 2 side, the electrons are
maldistributed to the main skeleton on the base particle 2 side
further than the terminal side. When such a polarization group 73
is introduced, the base particle 2 (the electrophoretic particle 1)
is positively charged.
[0188] Further, in the polarization group 73 in which an electron
donative group (the electron donating group) is bonded to the main
skeleton as a substituent, the maldistribution of the electron
density which is opposite to that described above occurs, and thus
in a case where the polarization group 73 in which the electron
donating group is bonded to the main skeleton on the terminal side
is introduced, the base particle 2 (the electrophoretic particle 1)
is positively charged, and in a case where the polarization group
73 in which the electron donating group is bonded to the main
skeleton on the base particle 2 side, the base particle 2 (the
electrophoretic particle 1) is negatively charged.
[0189] In addition, as the number of substituents which are bonded
to the main skeleton is increased, the maldistribution of the
electron density tends to be increased.
[0190] It is possible to control (adjust) the base particle 2 to be
in a desired charging state by properly selecting the polarization
group 73 in which the above-described deviation of the electron
density occurs and introducing the selected polarization group 73
to the surface of the base particle 2.
[0191] The main skeleton of the polarization group 73 is preferably
in a state where the maldistribution of the electron density easily
occurs. Accordingly, the main skeleton preferably has a portion (a
structure) in which IC electrons are delocalized. With this, the
electron transfer more easily and smoothly occurs in the main
skeleton, and thus the above-described effect is more remarkably
exhibited.
[0192] The entire portion in which the IC electrons are delocalized
may be a structure in which conjugated double bonds are continuous
in a straight line; however, at least a portion thereof has
preferably a ring structure that forms a ring shape. With this, the
electron transfer more easily and smoothly occurs in the main
skeleton.
[0193] There are various types of ring structures; however, an
aromatic ring is preferable, and a benzene ring, a naphthalene
ring, a pyridine ring, a pyrrole ring, a thiophene ring, an
anthracene ring, a pyrene ring, a perylene ring, a pentacene ring,
a tetracene ring, a chrysene ring, an azulene ring, a fluorene
ring, a triphenylene ring, a phenanthrene ring, a quinoline ring,
an indole ring, a pyrazine ring, an acridine ring, a carbazole
ring, a furan ring, a pyran ring, a pyrimidine ring, or a
pyridazine ring is particularly preferable. With this, it is likely
that the maldistribution (polarization) of the electron density
occurs in the ring structure, and thereby it is possible to make
the maldistribution of the electron density more remarkable in the
main skeleton.
[0194] Further, it is preferable that the main skeleton has a ring
structure at the terminal thereof, and the substituent is bonded to
the ring structure. With this, it is likely that maldistribution
(polarization) of the electron density in the ring structure, and
thereby it is possible to make the maldistribution of the electron
density more remarkable in the main skeleton.
[0195] In the electrophoretic particle 1, the substituent is
preferably an electric attracting group or an electron donating
group. With this, it is possible to more reliably charge the base
particle in a positive or negative manner.
[0196] Here, an example of a case where the main skeleton has a
benzene ring at the terminal thereof will be described below.
[0197] In this case, I: when an electron attracting group T is
bonded as a substituent to each of at least three positions of
3-position to 5-position among 2-position to 6-position of the
benzene ring (in FIG. 7A, all of the positions in 2-position to
6-position), as illustrated in FIG. 7A, due to the existence of the
electron attracting group T, the electrons in the main skeleton is
maldistributed by being attracted to the terminal side. For this
reason, the base particle 2 is negatively charged.
[0198] II: When the electron attracting group T is bonded as a
substituent to at least one position of 3-position, 4-position, and
5-position of the benzene ring (in FIG. 7B, positions of 3-position
and 4-position), as illustrated in FIG. 7B, due to the existence of
the electron attracting group T, the electrons in the main skeleton
(particularly, on the benzene ring) are maldistributed by being
attracted to the terminal side. For this reason, the base particle
2 is negatively charged.
[0199] III: When the electron attracting group T is bonded as a
substituent to at least one position of 2-position and 6-position
of the benzene ring (in FIG. 7C, 2-position and 6-position), as
illustrated in FIG. 7C, due to the existence of the electron
attracting group T, the electrons in the main skeleton
(particularly, on the benzene ring) are maldistributed by being
attracted to the base particle 2 side. For this reason, the base
particle 2 is positively charged.
[0200] IV: When an electron donating group G is bonded as a
substituent to each of at least three positions of 3-position to
5-position among 2-position to 6-position of the benzene ring (in
FIG. 7D, four positions of 2-position to 5-position), as
illustrated in FIG. 7D, due to the existence of the electron
donating group G, the electrons in the main skeleton is
maldistributed by being attracted to the base particle 2 side. For
this reason, the base particle 2 is positively charged.
[0201] V: When the electron donating group G is bonded as a
substituent to at least one position of 3-position, 4-position, and
5-position of the benzene ring (in FIG. 7E, 4-position), as
illustrated in FIG. 7E, due to the existence of the electron
donating group G, the electrons in the main skeleton (particularly,
on the benzene ring) are maldistributed by being pushed to the base
particle 2 side. For this reason, the base particle 2 is positively
charged.
[0202] VI: When the electron donating group G is bonded as a
substituent to at least one position of 2-position and 6-position
of the benzene ring (in FIG. 7F, 2-position), as illustrated in
FIG. 7F, due to the existence of the electron donating group G, the
electrons in the main skeleton (particularly, on the benzene ring)
are maldistributed by being pushed to the terminal side. For this
reason, the base particle 2 is negatively charged.
[0203] Note that, the configuration II and the configuration VI,
and the configuration III and the configuration V may be
respectively combined with each other. With this, it is possible to
make further remarkable maldistribution of the electron density in
the main skeleton (particularly, on the benzene ring).
[0204] In addition, the main skeleton may be formed of only one
ring structure described above, or may be formed of a structure in
which a plurality of ring structures are bonded in a straight
chain. Specific examples of the main skeleton having the latter
structure include those expressed by the following Formulae (A-1)
to (A-3).
##STR00006##
[0205] Here, In Formulae (A-1) to (A-3), n represents an integer of
1 or greater.
[0206] Note that, in the main skeletons expressed by the
above-described Formulae (A-1) to (A-3), the substituent is
preferably bonded to the ring structure at the terminal, but may be
bonded to the ring structures at the position other than the
terminal.
[0207] The electron attracting group T is not particularly limited
as long as the substituent tends to strongly attract (adsorb) the
electrons as compared with the hydrogen atom; however, examples
thereof include a halogen atom such as F, Cl, Br, and I, a cyano
group, a nitro group, a carboxyl group, a trifluoromethyl group, a
formyl group, and a sulfo group. Among them, preferred examples of
the electron attracting group include at least one selected from
the group consisting of the halogen atom, the cyano group, the
nitro group, the carboxyl group, and the trifluoromethyl group.
These groups particularly have high function of attracting
electrons.
[0208] On the other hand, the electron donating group G is not
particularly limited as long as the substituent tends to strongly
push (donate) the electrons as compared with the hydrogen atom;
however, examples thereof include an amino group, an alkyl group,
an alkoxy group, and a hydroxyl group. Among them, preferred
examples of the electron donating group include at least one type
selected from the group consisting of the amino group, the alkyl
group, and the alkoxy group. These groups particularly have a high
function of pushing electrons.
[0209] An alkyl group preferably has 1 to 30 carbon atoms, and
further preferably has 1 to 18. An alkoxy group preferably has 1 to
30 carbon atoms, and further preferably has 1 to 18. In the alkyl
group and the alkoxy group, if the number of the carbons is
excessive, it is likely that the alkyl groups and the alkoxy groups
respectively aggregated, and thereby it may be difficult to adjust
the charging state of the base particle 2 to be in a desired
state.
[0210] In addition, the total number of the carbon atoms in the
main skeleton is preferably in a range of 6 to 40, and is further
preferably in a range of 6 to 35. If the total number of carbon
atoms is excessively small, it is less likely that the electrons
are delocalized, and thus the maldistribution of the electrons may
be not efficiently caused. On the other hand, if the total number
of carbon atoms in the main skeletons is excessively large, it less
likely that the polarization group 73 is introduced to the surface
of the base particle 2.
[0211] As described above, the polarization group 73 is preferably
introduced to the surface of the base particle 2 through the
covalent bond. With this, it is possible to reliably prevent the
polarization group 73 from being separated from the surface of the
base particle 2. For this reason, it is possible to maintain the
charging state of the base particle 2 for a long time of
period.
[0212] It is preferable that the polarization group 73 has a
structure derived from the coupling agent which is bonded onto the
surface of the base particle 2, and the ring structure is bonded to
the surface of the base particle 2 via the structure derived from
the coupling agent.
[0213] Here, in the electrophoretic particle 1 of the embodiment,
as described above, the siloxane-based coupling agent 72 and the
polarization group 73 constitute the particle surface treatment
agent which is used to form the electrophoretic particle 1.
[0214] That is, in the embodiment, the electrophoretic particle 1
which is provided with the coated layer 3 covering at least a
portion of the base particle 2 is formed by bonding the
siloxane-based coupling agent 72 and polarization group 73 which
form the particle surface treatment agent to the base particle
2.
[0215] The bonding of the siloxane-based coupling agent 72 and the
polarization group 73 to the base particle 2 can be embodied by
using the siloxane-based coupling agent 72 and the polarization
group 73 instead of the polymer 39 in the method of bonding the
polymer 39 to the base particle 2 as described in the first
embodiment.
[0216] Note that, the siloxane-based coupling agent (the
siloxane-based compound) 72 is typically generated through the
reaction expressed by the following Reaction formula (ii). For this
reason, the unreacted product expressed by the following Formula
(ii-2) remains in the reaction system.
##STR00007##
Electrophoretic Display Device
[0217] Next, the electrophoretic display device (the
electrophoretic device of the embodiment of the invention) to which
the electrophoretic sheet of the embodiment of the invention is
applied will be described below.
[0218] FIG. 8 is a diagram for schematically illustrating a
longitudinal cross section of the electrophoretic display device of
the embodiment, and FIGS. 9 and 10 are schematic diagrams
illustrating an operating principle of the electrophoretic display
device illustrated in FIG. 8. Note that, in the following
description, for the convenience of explanation, the upper side is
described as "up" and the lower side is described as "low" in FIGS.
8 to 10.
[0219] The electrophoretic display device 920 illustrated in FIG. 8
includes an electrophoresis display sheet (front plane) 921, a
circuit board (backplane) 922, an adhesive layer 981 which bonds
the electrophoresis display sheet 921 and the circuit board 922,
and a sealing portion 97 which air-tightly seals a gap between the
electrophoresis display sheet 921 and the circuit board 922.
[0220] The electrophoresis display sheet (the electrophoretic sheet
of the embodiment of the invention) 921 includes a substrate 912
which is provided with a flat base portion 92 and a second
electrode 94 on the lower surface of the base portion 92, and a
display layer 9400 which is provided on the lower surface (one
surface) side of the substrate 912, and is formed of a partition
wall 940 formed in a matrix shape and an electrophoretic dispersion
liquid 910.
[0221] On the other hand, a circuit board 922 includes a counter
substrate 911 which is provided with a flat base portion 91 and a
plurality of first electrodes 93 on the upper surface of the base
portion 91, a circuit (not shown) which is provided on the counter
substrate 911 (the base portion 91), and includes a switching
element such as a TFT, and a driving IC (not shown) for driving the
switching element.
[0222] Hereinafter, the configuration of each portion will be
sequentially described.
[0223] Each of the base portion 91 and the base portion 92 is
formed of a sheet-like (flat) member, and has a function of
supporting and protecting each member disposed between the base
portion 91 and the base portion 92.
[0224] Each of the base portions 91 and 92 may be formed of a
flexible material or a hard material; however, the flexible
material is preferably used. With the base portions 91 and 92
having flexibility, it is possible to obtain the electrophoretic
display device 920 having flexibility, that is, the electrophoretic
display device 920 which is useful to construct the electronic
paper.
[0225] In addition, in a case where each of the base portions (base
material layers) 91 and 92 has the flexibility, the base portions
91 and 92 are preferably formed of a resin material.
[0226] The average thickness of each of the base portions 91 and 92
is appropriately set in accordance with a constituting material and
an application. In addition, the average thickness thereof is not
particularly limited, but is preferably in a range of 20 .mu.m to
500 .mu.m, and is further preferably in a range of 25 .mu.m to 250
.mu.m.
[0227] Each of the first electrode 93 and the second electrode 94
which are formed into a layer shape (a film shape) is provided on
the surface of the base portions 91 and 92 on the partition wall
940 side, that is, on the upper surface of the base portion 91 and
the lower surface of the base portion 92.
[0228] If the voltage is applied across the first electrode 93 and
the second electrode 94, an electric field is generated
therebetween, and thus the generated electric field acts on an
electrophoretic particle 95.
[0229] In the embodiment, the second electrode 94 is set to be a
common electrode, the first electrode 93 is set to be an individual
electrode (a pixel electrode which is connected to the switching
element) which is divided in a matrix shape, and a portion in which
the second electrode 94 and one first electrode 93 are overlapped
with each other constitutes one pixel.
[0230] The constituting material of each of the electrodes 93 and
94 is not particularly limited as long as the material
substantially has conductivity.
[0231] The average thickness of such electrodes 93 and 94 is
appropriately set in accordance with a constituting material and an
application. In addition, the average thickness thereof is not
particularly limited, but is preferably in a range of 0.05 .mu.m to
10 .mu.m, and is further preferably in a range of 0.05 .mu.m to 5
.mu.m.
[0232] Further, in each of the base portions 91 and 92, and each of
the electrodes 93 and 94, each of the base portion and the
electrode (in the embodiment, the base portion 92 and the second
electrode 94) which are disposed on the display surface side has
light transmittance, that is, the base portion and the electrode
are substantially transparent (colorless and transparent, colored
transparent, or semi-transparent).
[0233] In the electrophoresis display sheet 921, the display layer
9400 is provided in a state of coming in contact with the lower
surface of the second electrode 94.
[0234] The display layer 9400 is accommodated (sealed) in a
plurality of pixel spaces 9401 in which the electrophoretic
dispersion liquid (the electrophoretic dispersion liquid of the
embodiment of the invention described above) 910 is defined by the
partition wall 940.
[0235] The partition wall 940 is formed between the counter
substrate 911 and the substrate 912 so as to divide the pixel
spaces in a matrix shape.
[0236] Examples of the constituting material of the partition wall
940 include various types of resin materials such as a
thermoplastic resin such as an acrylic resin, a urethane resin, and
an olefin resin, a thermosetting resin such as an epoxy resin, a
melamine resin, and a phenolic resin. These may be used alone or in
combination of two or more types thereof.
[0237] In the embodiment, the partition wall 940 is bonded to the
second electrode 94 via an adhesive layer 982, and thus the
partition wall 940 is fixed onto the substrate 912.
[0238] In the embodiment, the electrophoretic dispersion liquid 910
which is accommodated in the pixel space 9401 is formed by
dispersing (suspending) two types particles (at least one type of
the electrophoretic particles 1) which are coloring particles 95b
and white particles 95a in the dispersion medium 96, and the
electrophoretic dispersion liquid of the embodiment of the
invention described above is applied thereto.
[0239] In such an electrophoretic display device 920, if the
voltage is applied across the first electrode 93 and the second
electrode 94, an electric field is generated therebetween, and thus
the coloring particles 95b and the white particles 95a (the
electrophoretic particle 1) are electrophoretically moved toward
any one of the first electrode 93 and the second electrode 94.
[0240] In the embodiment, the positively charged white particles
95a and the negatively charged coloring particles (black particles)
95b are used. That is, as the white particle 95a, the
electrophoretic particle 1 in which the base particle 2 is
positively (plus) charged is used, and as the coloring particle
95b, the electrophoretic particle 1 in which the base particle 2 is
negatively (minus) charged is used.
[0241] In a case where the aforementioned electrophoretic particles
1 are used, in a case where the first electrode 93 is set to be a
negative potential, as illustrated in FIG. 10, the coloring
particles 95b are moved to the second electrode 94 side so as to be
collected in the second electrode 94. On the other hand, the white
particles 95a are moved to the first electrode 93 side so as to be
collected in the first electrode 93. For this reason, in a case
where the electrophoretic display device 920 is viewed from above
(display surface side), the color of coloring particles 95b can be
seen, that is, a black color can be seen.
[0242] In contrast, if the first electrode 93 is set to be a
positive potential, as illustrated in FIG. 9, the coloring
particles 95b are move to the first electrode 93 side so as to be
collected in the first electrode 93. On the other hand, the white
particles 95a are moved to the second electrode 94 side so as to be
collected in the second electrode 94. For this reason, in a case
where the electrophoretic display device 920 is viewed from the
above (the display surface side), the color of the white particles
95a can be seen, that is, a white color can be seen.
[0243] With such a configuration, the amount of charging the white
particles 95a and the coloring particles 95b (the electrophoretic
particle 1), the polarity of each of the electrodes 93 and 94, and
the potential difference between electrodes 93 and 94 are
appropriately set, and thus in accordance with a combination of
colors of the white particles 95a and the coloring particles 95b,
or the number of particles collecting in the electrodes 93 and 94,
desired information (images) is displayed on the display surface of
the electrophoretic display device 920.
[0244] In addition, a specific gravity of the electrophoretic
particle 1 is preferably set to be substantially the same as a
specific gravity of the dispersion medium 96. With this, the
electrophoretic particle 1 can stay at a certain position for a
long period of time in the dispersion medium 96 even after stopping
the application of a voltage across the electrodes 93 and 94. That
is, the information displayed on the electrophoretic display device
920 can be held for a long period of time.
[0245] Note that, the average particle size of the electrophoretic
particle 1 is preferably in a range of 0.1 .mu.m to 10 .mu.m, and
is further preferably in a range of 0.1 .mu.m to 7.5 .mu.m. When
the average particle size of the electrophoretic particle 1 is set
to be in the above-described range, it is possible to reliably
prevent the electrophoretic particles 1 from being aggregated each
other, and from being precipitated in the dispersion medium 96. As
a result, it is possible to preferably prevent the display quality
of the electrophoretic display device 920 from being
deteriorated.
[0246] In the embodiment, the electrophoresis display sheet 921 and
the circuit board 922 are bonded to each other via the adhesive
layer 981. With this, the electrophoresis display sheet 921 and the
circuit board 922 can be more reliably fixed to each other.
[0247] The average thickness of the adhesive layer 981 is not
particularly limited, but is preferably in a range of 1 .mu.m to 30
.mu.m, and is further preferably in a range of 5 .mu.m to 20
.mu.m.
[0248] The sealing portion 97 is provided between the base portion
91 and the base portion 92, and specifically, the sealing portion
97 is provided along the edge portion of the base portion 91 and
the base portion 92. The electrodes 93 and 94, the display layer
9400, and the adhesive layer 981 are air-tightly sealed by the
sealing portion 97. With this, it is possible to prevent water from
entering the electrophoretic display device 920, and more reliably
prevent the display performance of the electrophoretic display
device 920 from being deteriorated.
[0249] As the constituting material of the sealing portion 97, the
same materials as those which are exemplified as the constituting
material of the aforementioned partition wall 940 can be used.
Electronic Apparatus
[0250] Next, the electronic apparatus of the embodiment of the
invention will be described.
[0251] The electronic apparatus of the embodiment of the invention
is provided with the above-described electrophoretic display device
920.
Electronic Paper
[0252] First, an embodiment of a case where the electronic
apparatus of the embodiment of the invention is applied to an
electronic paper will be described.
[0253] FIG. 11 is a perspective view illustrating an embodiment in
a case where the electronic apparatus of the embodiment of the
invention is applied to the electronic paper.
[0254] The electronic paper 600 illustrated in FIG. 11 is provided
with a main body 601, which is formed of a rewritable sheet having
the same texture and flexibility as those of paper, and a display
unit 602.
[0255] In such an electronic paper 600, the display unit 602 is
formed of the above-described electrophoretic display device
920.
Display
[0256] Next, an embodiment in a case where the electronic apparatus
of the embodiment of the invention is applied to the display will
be described below.
[0257] FIGS. 12 and 13 are diagrams illustrating an embodiment in a
case where the electronic apparatus of the embodiment of the
invention is applied to a display. FIG. 12 is a sectional view and
FIG. 13 is a plan view.
[0258] A display (a display device) 800 illustrated in FIGS. 12 and
13 is provided with a main body portion 801 and the electronic
paper 600 which is detachably provided with respect to the main
body portion 801.
[0259] In the main body portion 801, an insertion port 805 which
can be inserted into the electronic paper 600 is formed in a side
portion (the right side in FIG. 12), and two pairs of transport
rollers 802a and 802b are provided thereinside. When the electronic
paper 600 is inserted into the main body portion 801 via an
insertion port 805, the electronic paper 600 is installed on the
main body portion 801 in a state being interposed between the pair
of transport rollers 802a and 802b.
[0260] In addition, a rectangular hole portion 803 is formed on the
display surface side (the front side of the paper in FIG. 13) of
the main body portion 801, and a transparent glass plate 804 is
fitted into the hole portion 803. With this, it is possible to
visually recognize the electronic paper 600 in a state of being
installed in the main body portion 801 from the outside of the main
body portion 801. That is, in the display 800, a display surface is
formed in such a way that the electronic paper 600 in the state of
being installed in the main body portion 801 is visually recognized
in the transparent glass plate 804.
[0261] In addition, a terminal portion 806 is provided at a tip end
portion (the left side in FIG. 12) of the electronic paper 600 in
an insertion direction, and a socket 807 which is connected to the
terminal portion 806 is provided in the main body portion 801 in
the state where the electronic paper 600 is installed in the main
body portion 801. A controller 808 and an operation unit 809 are
electrically connected to the socket 807.
[0262] In such a display 800, the electronic paper 600 is
detachably installed in the main body portion 801, and can be
portably used in a state of being detached from the main body
portion 801.
[0263] In addition, in such a display 800, the electronic paper 600
is formed of the above-described electrophoretic display device
920.
[0264] Note that, the application of the electronic apparatus of
the embodiment of the invention is not limited to the above
description; for example, application examples thereof include a
television, a view finder type or a monitor direct view type video
tape recorder, a car navigation device, a pager, an electronic
organizer, an electronic calculator, an electronic newspaper, a
word processor, a personal computer, a workstation, a television
telephone, a POS terminal, and a device provided with a touch
panel, and it is possible to apply the electrophoretic display
device 920 to the display portion of the aforementioned various
electronic apparatuses.
[0265] As described above, the method of manufacturing
electrophoretic particle, the electrophoretic particle, the
electrophoretic dispersion liquid, the electrophoretic sheet, the
electrophoretic device, and the electronic apparatus of the
embodiment of the invention are described with reference to
embodiments illustrated in the drawings; however, the invention is
not limited thereto, and the configuration of each portion can be
replaced with any other configuration having the same function. In
addition, other components may be added to the invention.
[0266] Further, the method of manufacturing an electrophoretic
particle of the embodiment of the invention may additionally have
one or two or more steps for a certain purpose.
EXAMPLES
[0267] Next, specific examples will be described below.
Manufacturing of Electrophoretic Particle, Preparing of
Electrophoretic Dispersion Liquid, and Evaluation of
Electrophoretic Dispersion Liquid
Example 1
1. Synthesizing of Block Copolymer by Polymerization
[0268] In a flask, 6.2 g of 2-cyano-2-propyl benzo dithioate, and
600 mg of azobisisobutyronitrile were added into 100 g of terminal
hydroxyl group silicone having the molecular weight of 16,000
("SILAPLANE FM-0426", manufactured by JNC Filter Co., Ltd.;
silicone macromonomer), the mixture was substituted with nitrogen,
100 mL of ethyl acetate was added into the mixture, thereafter, the
mixture was heated and stirred for one hour at 75.degree. C., 7.2 g
of 3-methacryloxypropyl triethoxy silane ("KBE-503", manufactured
by Shin-Etsu Silicones) was added into the mixture, and then the
mixture was heated and stirred again for three hours at 75.degree.
C. so as to carry out the polymerization. The reaction is finished
by cooling the resultant up to room temperature, and then the
solvent was removed so as to obtain a block copolymer in which the
dispersion portion and the bonding portion are bonded to each
other.
[0269] In addition, the content of the unreacted product which is
considered to remain in the obtained block copolymer at the time of
obtaining the terminal hydroxyl group silicone can be calculated by
measuring the peak of methacrylic group by using .sup.1H-NMR
("500NB", manufactured by Varian, Inc), and the value of the peak
of methacrylic group was 30% by weight, and the content of the
block copolymer was 70% by weight.
2. Adjustment of Electrophoretic Dispersion Liquid
[0270] An electrophoretic particle was obtained in such a manner
that, in the flask, 10 g of block copolymer (raw material) obtained
above and 60 g of titania particle ("CR90" manufactured by Ishihara
Sangyo Kaisha, Ltd.) were added so as to prepare a mixture, after
that, the mixture was subjected to an ultrasonic treatment for one
hour, and the mixture was heated and stirred for four hours at
180.degree. C. such that the block copolymer was bonded to the
particle. A white electrophoretic dispersion liquid was obtained by
removing unreacted block copolymer from the reacted solution, and
then adding the obtained electrophoretic particle to "KF-96-2 cs"
manufactured by Shin-Etsu Chemical Co., Ltd.
[0271] In addition, except that 60 g of titanium black particle
("SC13-MT" manufactured by Mitsubishi Materials Co., Ltd.) was used
instead of the titania particle, a black electrophoretic dispersion
liquid was obtained by using the same method as that in the above
description.
[0272] Regarding each of the white and black electrophoretic
particles contained in each of the white and black electrophoretic
dispersion liquids, the coverage of the block copolymer which
covers the base particle was measured by using a thermogravimetric
analyzer ("TGA-1", METTLER TOLEDO Co., Ltd.), and each coverage of
the block copolymer was 5.1% by weight with respect to 100% by
weight of the base particle.
Comparative Example 1
[0273] The white and black electrophoretic dispersion liquids were
obtained by using the same method as that in Example 1, except that
a material, in which the silicone oil ("KF-96L-2cs", manufactured
by Shin-Etsu Chemical Co., Ltd) is further added into the block
copolymer obtained in Example 1 such that the content of the block
copolymer becomes 60% by weight, was used as the raw material.
[0274] Regarding each of the white and black electrophoretic
particles contained in each of the white and black electrophoretic
dispersion liquids, the coverage of the block copolymer which
covers the base particle was measured by using a thermogravimetric
analyzer ("TGA-1", METTLER TOLEDO Co., Ltd.), and each coverage of
the block copolymer was 3.2% by weight with respect to 100% by
weight of the base particle.
3. Evaluation of Electrophoretic Dispersion Liquid
3-1. Evaluation of Particle Aggregation and Electrode
Adhesiveness
[0275] Regarding the electrophoretic dispersion liquids in Example
and Comparative Example, particle aggregation and electrode
adhesiveness were evaluated as follows.
Evaluation of Particle Aggregation
[0276] In other words, the black electrophoretic dispersion liquid
and the white electrophoretic dispersion liquid in Example and
Comparative Example were observed at 200-fold magnification by
using a microscope.
[0277] As a result, if the aggregation of the electrophoretic
particle was not recognized in the electrophoretic dispersion
liquid, and the electrophoretic particles were almost evenly
distributed in the electrophoretic dispersion liquid without
irregularity, the evaluation was determined as A, if the
aggregation of the electrophoretic particle was slightly
recognized, but the electrophoretic particles were almost evenly
distributed in the electrophoretic dispersion liquid and the
irregularity was almost not found, the evaluation was determined as
B, and if the aggregation of the electrophoretic particle was
apparently recognized, and the electrophoretic particles are
maldistributed in the electrophoretic dispersion liquid with
irregularity, the evaluation was determined as C.
Evaluation of Electrode Adhesiveness
[0278] Two pieces of ITO deposition glass were disposed with a gap
of 50 .mu.m therebetween, then a voltage of 15 V was applied across
electrodes in a state where the white electrophoretic dispersion
liquid and the black electrophoretic dispersion liquid of Example
and Comparative Example were added dropwise in the gap, and at that
time, the existence of electrophoretic particles adhered to the
electrode surface was observed at 200-fold magnification by using a
microscope.
[0279] As a result, if the electrophoretic particles were not
adhered onto the electrode surface in the electrophoretic
dispersion liquid, the evaluation was determined as A, if the
electrophoretic particles were slightly adhered onto the electrode
surface in the electrophoretic dispersion liquid, and the adhesion
of the particles on the electrode surface was eliminated due to the
application of voltage, the evaluation was determined as B, and if
the electrophoretic particles were apparently adhered onto the
electrode surface in the electrophoretic dispersion liquid, and the
adhesion of the particles on the electrode surface was not
eliminated due to the application of voltage, the evaluation was
determined as C.
[0280] The evaluation results are indicated in Tables 1 and 2.
TABLE-US-00001 TABLE 1 Content of Coverage of block block Particle
Block copolymer copolymer in copolymer with Evaluation (white First
Second dispersion respect to Particle Electrode particle) monomer
monomer liquid particle aggregation adhesiveness Example 1 CR90 16k
KBE-503 70% by weight 5.1% by weight B B siloxane MA Comparative
CR90 16k KBE-503 60% by weight 3.2% by weight C C Example 1
siloxane MA
TABLE-US-00002 TABLE 2 Content of block Coverage of Particle Block
copolymer copolymer in block copolymer Evaluation (black First
Second dispersion with respect to Particle Electrode particle)
monomer monomer liquid particle aggregation adhesiveness Example 1
SC13-MT 16k KBE-503 70% by weight 5.1% by weight B B siloxane MA
Comparative SC13-MT 16k KBE-503 60% by weight 3.2% by weight C C
Example 1 siloxane MA
[0281] As apparently indicated in Tables 1 and 2, in the
electrophoretic dispersion liquids of the respective Examples, the
aggregation of the electrophoretic particles in the black
electrophoretic dispersion liquid and white electrophoretic
dispersion liquid, and the adhesion of the electrophoretic
particles to the electrode were appropriately suppressed, and thus
it was found that the electrophoretic particles in the
electrophoretic dispersion liquid exhibited the excellent
dispersibility and the electrophoretic properties.
[0282] In contrast, in the electrophoretic dispersion liquid in
Comparative Example, it was recognized that since the content of
the block copolymer except for the particle in the mixture is less
than 70% by weight, a sufficient amount of the block copolymer
cannot be bonded with respect to the particle, and thus the
electrophoretic particles are aggregated with each other in the
electrophoretic dispersion liquid, and the electrophoretic
particles are adhered to the electrode. As a result, it was found
that the electrophoretic particles in the electrophoretic
dispersion liquid were not excellent in the dispersibility and the
phoretic properties (particularly, the dispersibility).
3-2. Evaluation of Display Properties
[0283] In addition, regarding the electrophoretic dispersion liquid
in Examples and Comparative Example, the evaluation of display
properties was performed as follows.
Evaluation of Display Properties
[0284] First, regarding the electrophoretic dispersion liquid
containing the white particle in Example 1 and Comparative Example
1, and the electrophoretic dispersion liquid containing the black
particle in Example 1 and Comparative Example 1, the
electrophoretic dispersion liquid containing the white particle and
the black particle was prepared by combining the white particle and
the black particle such that the volume ratio of the white
electrophoretic dispersion liquid to the black electrophoretic
dispersion liquid in the mixture is 10:1.
[0285] Then, a transparent electrode cell having the thickness of
50 .mu.m was injected into the prepared electrophoretic dispersion
liquid, and then white reflectance at the time of white display,
and black reflectance at the time of black display were measured so
as to calculate contrasts thereof.
[0286] The evaluation results are indicated in Table 3.
TABLE-US-00003 TABLE 3 White electrophoretic Black electrophoretic
White dispersion liquid dispersion liquid reflectance/ (Content of
(Content of black block copolymer) block copolymer) reflectance
Example 1 (70% by weight) Example 1 (70% by weight) 45/3.2 Example
1 (70% by weight) Comparative Example 1 38/4.1 (60% by weight)
Comparative Example 1 Example 1 (70% by weight) 37/4.5 (60% by
weight) Comparative Example 1 Comparative Example 1 34/5.1 (60% by
weight) (60% by weight)
[0287] As apparent from Table 3, in electrophoretic dispersion
liquid obtained by combining the white particle in Example and the
black particle in Example, the electrophoretic particle exhibited
the excellent contrast, that is, display properties in the
electrophoretic dispersion liquid between the white particle and
the black particle without generation of the aggregation.
[0288] In contrast, in the electrophoretic dispersion liquid
obtained by combining at least one of the white particle and the
black particle in Comparative Example, since the content of the
block copolymer except for the particle in the mixture is less than
70% by weight, a sufficient amount of the block copolymer cannot be
bonded with respect to the particle, and thus the aggregation is
generated between the white particle and the black particle. As a
result, it was found that the contrast, that is, the display
properties are deteriorated.
[0289] The entire disclosure of Japanese Patent Application No.
2015-235350, filed Dec. 2, 2015 is expressly incorporated by
reference herein.
* * * * *