JP2002338642A - Image display medium using silicone oil-miscible polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display medium which uses an environmentally excellent silicone oil, allows reversible display, has memory performance and has good long-term stability; and an image display medium which further acts at a high response velocity. SOLUTION: The polymer for use in the medium comprises polymerizing a monomer being miscible in a silicone oil solvent and having at least an acidic group and a monomer represented by formula (1) (wherein R1 is hydrogen or a methyl group, R1 ' is hydrogen or a 1-4C alkyl group, n is a natural number, and x is an integer of 1-3).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display medium capable of reversibly changing the visual state by moving white or colored particles charged by the action of an electric field.

[0002]

2. Description of the Related Art Conventionally, CRTs and liquid crystal displays have been used as terminals for displaying so-called images such as characters, still images, and moving images. These can display and rewrite digital data instantly, but it is difficult to carry around the device at all times, and there are many disadvantages such as tired eyes during long hours of work and inability to display with the power off. is there.
On the other hand, when characters and still images are distributed or stored as documents, they are recorded on a paper medium by a printer. It is widely used as so-called hard copy. Hard copies are easier to read than on the display, less fatigued, and can be read in any position. Furthermore, it has the feature that it is lightweight and can be carried freely. However, after the hard copy is used, it is discarded and recycled, but this requires much labor and cost, so that there is a problem in terms of resource saving.

There is a great need for a rewritable paper-like display medium that has the advantages of both display and hard copy.
Bistable cholesteric liquid crystals, electrochromic devices, devices using electrophoretic devices, and the like have attracted attention as reflective display media capable of bright display and having memory properties. Among them, those using electrophoretic elements have display quality,
An electrophoretic display device as shown in FIG. 3 is known as a typical example because of its excellent power consumption during the display operation (for example, Japanese Patent Application Laid-Open Nos. 5-173194 and 261472). Described). In the figure, reference numerals (6) and (7) denote a transparent substrate made of glass or the like and a transparent electrode formed on one surface thereof in a required pattern, and a pair of these transparent electrodes (7), A dispersion liquid (8) in which a plurality of electrophoretic particles having a color different from the color of the dispersion medium is dispersed in a white or colored dispersion medium is enclosed between (7). The migrating particles are charged on the surface in the dispersion medium, and when a voltage opposite to the charge of the migrating particles is applied to one of the transparent electrodes (7) and (7), the migrating particles accumulate there. When the voltage of the same direction as the charge of the migrating particles is applied, the migrating particles move to the opposite side and the color of the dispersion medium is observed. Thereby, display can be performed. Here, in the structure in which the dispersion liquid (8) is simply sealed between the electrodes (7) and (7), display unevenness may occur due to the aggregation or adhesion phenomenon of the migrating particles. By disposing a mesh or porous perforated spacer (9) between (7), the dispersion liquid (8) is discontinuously divided to stabilize the display operation. However, in the case of such a structure, there is a problem that it is difficult to uniformly enclose the dispersion liquid, or it is difficult to obtain reproducibility due to a change in characteristics of the dispersion liquid during the encapsulation.

[0004] It is known that the stability of dispersed particles is generally obtained by the action of an electrostatic effect or a steric effect (also called an adsorption layer effect). The DLVO theory has been established for the electrostatic effect, and in this theory, the spread of the electric double layer and the interface potential (so-called ζ potential) are important factors. Therefore, the presence of ions that form them is necessary, and some studies have been made on aqueous solvent systems in which the presence of such ions is clear. on the other hand,
As for the steric effect, a thing equivalent to the DLVO theory has not yet been established, but the following research is known in non-aqueous solvent systems (mainly petroleum solvents). That is, FAWa
The work described in ite, J. Oil Col. Chem. Assoc., 54, 342 (1971) relates to a basic method for preparing a stable non-aqueous solvent-based dispersion, which method comprises the steps of: This is to produce a block or graft copolymer containing a component compatible with particles to be dispersed (insoluble in a solvent) and a component soluble in the solvent. As a method utilizing this method, Japanese Patent Publication No. 40-7047 discloses methyl methacrylate (M) in a hydrocarbon solvent in the presence of a degraded rubber.
A method of obtaining a stable polymethyl methacrylate (PMMA) dispersion by radical polymerization of MA) is described. It is not considered that the degraded rubber is adsorbed to the PMMA particles by this method, and it is considered that MMA is graft-polymerized to the degraded rubber from the fact that the PMMA particles are dispersion-stabilized. In addition, it is considered that the insoluble portion of the graft polymer associates with the particle surface, and the dissolved portion has a steric effect, and as a result, maintains the dispersion stability of the particle. However, conventionally, it is not known to disperse solid particles sufficiently in a non-aqueous solvent-based dispersion such as a petroleum solvent, that is, a non-polar aprotic solvent, by clearly charging them with ions. Therefore, the service life of an electrodeposition coating material, an electrophotographic liquid developer, or a dispersion for a display is particularly limited.

As a means for solving this problem, Japanese Patent Publication No. 23005/1996 discloses a method of charging solid particles based on acid-base ion dissociation in a solvent such as an aliphatic hydrocarbon or an aromatic hydrocarbon. ing. on the other hand,
Solvents such as aliphatic hydrocarbons and aromatic hydrocarbons are currently desired not to be used as much as possible from environmental considerations, and silicone oils have been used as an alternative. However, it has not been known to disperse the solid particles sufficiently stably by clearly charging solid particles with ions in the conventional silicone oil. In addition, the substance described in JP-B-8-23005 is directly used as the silicone oil. Even if used, the effect is not obtained. That is, there was no substance having an acidic group or a basic group suitable for charging the particles with silicone oil.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image display medium which is capable of reversible display, has memory properties, and has good long-term stability, using an environmentally-friendly silicone oil. Another object of the present invention is to provide an image display medium having a high response speed.

[0007]

Means for Solving the Problems The object of the present invention is to provide (1) a monomer which is soluble in a silicone oil solvent and has at least an acidic group and a monomer represented by the following general formula (I): A polymer characterized by being polymerized as a constituent requirement;

[0008]

Embedded image [In the formula, R ₁ represents a hydrogen atom or a methyl group, R ₁ ′ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, n represents a natural number, and x represents an integer of 1 to 3. ], (2) "a monomer soluble in a silicone oil solvent and having at least an acidic group, a monomer represented by the general formula (I), and a monomer having a nonionic polar group. (3) a polymer which is soluble in a silicone oil solvent and has at least an acidic group, a monomer represented by the general formula (I), and A polymer obtained by polymerizing a monomer represented by the following general formula (II) as a constituent;

[0009]

Embedded image [Wherein, R ₂ is a hydrogen atom or a methyl group, R ₃ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, x is an integer of 1 to 3,
y represents a natural number of 25 or less. ], (4) "A monomer soluble in a silicone oil solvent and having at least an acidic group, a monomer represented by the general formula (I), and a monomer represented by the general formula (II)" , And a polymer having a monomer having a nonionic polar group other than a (poly) oxyalkylene group as a constituent component,
(5) “Polymer characterized in that it is soluble in a silicone oil solvent and is polymerized by using a monomer having at least a basic group and a monomer represented by the general formula (I) as constituent elements”; (6) "It is soluble in a silicone oil solvent,
A monomer having at least a basic group, the general formula (I)
And a polymer characterized by being polymerized with a monomer having a nonionic polar group as a constituent requirement ”, (7)“ soluble in a silicone oil solvent and at least a basic group And (8) a polymer obtained by polymerizing a monomer represented by the general formula (I) and a monomer represented by the general formula (II) as constituent elements. "A monomer which is soluble in a silicone oil solvent and has at least a basic group, a monomer represented by the general formula (I), a monomer represented by the general formula (II),
And a polymer having a monomer having a nonionic polar group other than a (poly) oxyalkylene group as a constituent element. "

[0010] The object of the present invention is to provide at least (9) at least white or colored particles and a silicone oil solvent between two conductive layers which are arranged at a desired interval and at least one or both of which are light-transmitting. An image display medium characterized by containing a dispersion comprising a resin soluble in the silicone oil solvent ";(10)" a resin soluble in the silicone oil solvent has an acidic group but a basic group; (9) The image display medium according to the above (9), wherein the resin soluble in the silicone oil solvent has a basic group but has no acidic group. The image display medium according to the above (9) ", (12)
“The image display medium according to any one of the above items (9) to (11), wherein the resin soluble in the silicone oil solvent has a nonionic polar group”, (1
3) White or colored particles having an acidic group but not a basic group at least on the surface between two conductive layers at least one or both of which are light-transmissive and arranged at a desired interval, and silicone oil An image display medium comprising a dispersion comprising a solvent ", (1
4) White or colored particles having at least a basic group but no acidic group at least on the surface between two conductive layers, at least one or both of which are light-transmissive, arranged at a desired interval, and silicone oil An image display medium comprising a dispersion comprising a solvent ", (1
5) “the image display medium according to the above item (13) or (14), wherein the white or colored particles have a nonionic polar group on the surface”; The image display medium according to any one of the above items (13) to (15), comprising a resin soluble in a silicone oil solvent ”, (17)“ white or colored particles ” Wherein the resin having an acidic group on the surface but not having a basic group and the resin soluble in a silicone oil solvent has a basic group but does not have an acidic group; (11), (12), (13)
Item, Item (15), Image display medium according to any one of Items (16) ”, (18),“ White or colored particles have a basic group on the surface but no acidic group, and are silicone. (9) and (10), wherein the resin soluble in the oil solvent has an acidic group but no basic group.
Item, Item (12), Image display medium according to any one of Items (14) to (16) ”, (19)“ The resin soluble in the silicone oil solvent, the (1) ) To (8), wherein the polymer described in (9) is used.

The polymer soluble in the silicone oil solvent described in the above items (1) to (8) has a charge even in the silicone oil which is a non-polar solvent due to ion generation based on acid-base dissociation in the silicone oil. Can be given.

The operation principle of the image display by the image display medium according to the above mode (9) is as follows. FIG.
It is sectional drawing which shows an example of the display medium of said (9) of this invention. Symbols (1) and (2) indicate two conductive layers,
One or both are light-transmissive and contain therein a dispersion comprising white or colored particles (3) which are electrophoretic particles, a silicone oil solvent (4), and a resin (5) soluble in the silicone oil solvent. Have. Further, a dye that is soluble in the silicone oil solvent and has a color different from that of the white or colored particles (3) is added to the solvent. Here, when the conductive layer (2) is translucent, when this medium is viewed from above (2), the color of white or colored particles (3) can be seen. At this time, the resin (5) soluble in the silicone oil solvent is adsorbed on the white or colored particles (3), and the steric effect increases the dispersion stability of the white or colored particles (3), thereby realizing long-term stability. Make it possible.

On the other hand, FIG. 2 is a sectional view showing an example of an operating mechanism when an image is displayed by actually driving the medium of FIG.
In FIG. 2A, when a charge is externally applied to the conductive layers (1) and (2) separated from the right and left halves of the display medium by an appropriate means, white or colored particles (3) having the charge are applied. Move upward along the external electric field as shown in FIG. FIG. 2C shows a state in which the white or colored particles (3) have reached the conductive layer (2). Here, the conductive layer (2) and the white or colored particles (3) adhere by electrostatic force to complete the movement. When the state of FIG. 2C is viewed from above the medium (outside the conductive layer (2)), the left half is white or the color of the colored particles (3), and the right half is the dye added to the silicone oil solvent (4). You can expect the color of The above is the basic operation principle of image display by the image display medium described in the above item (1). This display mode is reversible and can be used repeatedly.

[0014] In the image display medium according to the above item (10), the resin soluble in the silicone oil solvent has an acidic group but does not have a basic group. The adsorbed white or colored particles can positively control the charging polarity and control the response.

[0015] In the image display medium described in the above item (11), the resin soluble in the silicone oil solvent has a basic group but does not have an acidic group, so that the resin soluble in the silicone oil solvent is reduced. The adsorbed white or colored particles can negatively control the charge polarity and control the response.

In the image display medium described in the above item (12), since the resin soluble in the silicone oil solvent further has a nonionic polar component, the amount of charge generated by solvation of an acid or a base is reduced. It is possible to increase the display and display with a quick response.

[0017] In the image display medium described in the above item (13), the white or colored particles have an acidic group on the surface but do not have a basic group. And response control becomes possible.

In the image display medium described in the above item (14), since the white or colored particles have a basic group on the surface but do not have an acidic group, the charged polarity of the white or colored particles is positively controlled. And response control becomes possible.

In the image display medium described in the above item (15), since the white or colored particles further have a nonionic polar component on the surface, the amount of charge generation is increased by solvation of an acid or a base. Thus, a display with a quick response becomes possible.

In the image display medium described in the above item (16), since the dispersion contains a resin soluble in a silicone oil solvent, the dispersion is caused by the steric effect of the resin adsorbed on white or colored particles. Stability,
An image display medium having good long-term stability can be provided.

In the image display medium described in the above items (17) and (18), charge is generated by acid-base dissociation between the surface of the white or colored particles and the resin adsorbed on the particles, and A synergistic effect of dispersion stability is obtained by the steric effect of the adsorbed resin, and an image display medium having both long-term stability and fast response speed can be provided.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. Silicone oils have various features unlike aqueous solvents and conventional non-aqueous solvents. For example,
Excellent in heat resistance, cold resistance, chemically inert,
Odorless solvents, small changes in viscosity with temperature, high viscosity are non-volatile, low surface tension, water and oil repellency, excellent releasability, etc. It is widely used as an industrial material in the fields of electrical machinery, machinery, chemical industry, etc.

As described above, in a conventional non-aqueous solvent, particularly in a nonpolar aprotic solvent-based dispersion, the existence of ions or charges was unclear. This is because in this type of solvent
It is considered that interaction (solvation) hardly occurs between the ion and the solvent molecule. This is the same for silicone oil. Thus, the present inventors have determined that a) an organic substance having an acidic group but not having a basic group, b) an organic substance having a basic group but having no acidic group, and c) compatibility with the solvent. And any of the components (a) and (b) containing three components of an organic substance having a nonionic polar component may be present as a copolymer with the component (c).] Silicone oil dispersion As a result of various experiments, it was found that components a) and b) caused acid-base ion dissociation in the solvent. It was also suggested that ion-dipole interaction, ie, solvation, was present. Thus, the present inventors have found that when the three components a), b) and c) are present in the solvent, the silicone oil is dissociated by acid-base ion dissociation via the solvation of the polar group in the component c). It has been found that ions can stably exist even in the inside. This fact was similarly observed whether both components a) and b) were soluble or insoluble in the solvent. Further, as described above, the present inventors, when a fixed particle such as a pigment or a metal oxide coexists in a system containing the three components a), b) and c), The acid group or the basic group of the component) is fixed by chemical bonding, adsorption, or the like, and ion dissociation occurs at the interface between the solid particle surface and the solvent via the solvation of the component c), so that the solid particles are uniform. It has been found that the solid particles are more stably dispersed than before because of the electrostatic effect and the steric effect as well as being charged to a positive or negative polarity. Further, the present inventors have found that the ion amount and the charge amount can be controlled by the types and amounts of the components a), b) and c). The present invention is based on the above findings.

The polymer in the present invention includes an acrylic monomer having a dimethylpolysiloxane chain, a monomer having an acidic group or a basic group, and an acrylic monomer having a (poly) oxyalkylene chain, if necessary. And, if necessary, copolymerized with a monomer having a polar group. Examples of the polar group include a hydroxyl group, an ester group, an ether group, a ketone group, an aldehyde group, a halogen group, and an amide group. Hereinafter, the polymerizable monomer in the present invention will be described. First, a monomer represented by the general formula (I)

[0025]

Embedded image [In the formula, R ₁ represents a hydrogen atom or a methyl group, R ₁ '
Represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms,
Preferably it is a methyl group. A preferred combination of substituents is when R ₁ and R ₁ ′ are methyl groups. n represents a natural number, preferably 2 to 200, more preferably 5 to 1
And x represents an integer of 1 to 3, preferably 3
It is. ] Has a strong affinity for silicone oil, and has the characteristic that it is difficult for ordinary polymers to dissolve in silicone oil. However, when a polymer composed of such a monomer is a homopolymer, it is compatible with silicone oil. Giving a soluble polymer,
Even in the case of a copolymer with another monomer, even if it is soluble or insoluble, it has a high affinity for silicone oil and can provide a stable dispersion. Monomer represented by general formula (II)

[0026]

Embedded image [In the formula, R ₂ represents a hydrogen atom or a methyl group, and R ₃ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and is preferably a methyl group. A preferred combination of substituents is where R ₂ and R ₃ are methyl groups. x represents an integer of 1 to 3, preferably 2, and y represents a natural number of 25 or less, preferably 1 to 20, more preferably 2 to
It is 10. Has a (poly) alkylene glycol chain having a repeating unit of an oxyalkylene group of 25 or less,
The copolymer having the monomer as a component is adsorbed on particles insoluble in a solvent, and the dispersion of the particles is stabilized by the steric effect exhibited by the (poly) alkylene glycol chain.

Examples of the resin soluble in the silicone oil solvent used in the first embodiment of the present invention include:
(Meth) acrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, cinnamic acid, crotonic acid, vinylbenzoic acid, 2-methacryloxyethyl succinic acid, 2-methacryloxyethyl maleic acid, 2 -Methacryloxyethyl hexahydrophthalic acid, 2-methacryloxyethyl trimellitic acid, vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, 2-sulfoethyl methacrylate, 2-acrylamide-2-methylpropane sulfonic acid, 3-chloro Obtained from at least one kind of monomer having an acidic group such as amidophosphoxypropyl methacrylate, 2-methacryloxyethyl acid phosphate and hydroxystyrene, and a monomer having a high affinity for the silicone oil solvent represented by the general formula (I). Is the copolymer It is below. A preferred combination of monomers is (meth) acrylic acid and (meth) acryloxypropyl-modified polydimethylsiloxane, and a more preferred combination of monomers is methacrylic acid and methacryloxypropyl-modified polydimethylsiloxane (n = 5 to 10).
0).

As a specific example of the resin used in the second embodiment of the present invention, at least one of the specific examples of the monomer having an acidic group in the first embodiment of the present invention is used. A monomer having a high affinity for a silicone oil solvent represented by the general formula (I), 2-hydroxyethyl (meth) acrylate, 2,3-dihydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxy-3-propyl methacrylate, 2-chloroethyl (meth) acrylate, 2,3-dibromopropyl (meth) acrylate, (meth) acrylonitrile, isobutyl-2-cyanoacrylate, 2-cyanoethyl acrylate, ethyl-2-cyano Acrylate, methacrylacetone,
Tetrahydrofurfuryl methacrylate, trifluoroethyl methacrylate, p-nitrostyrene, vinylpyrrolidone, acrylamide, methacrylamide, N, N-
Copolymers with polar monomers such as dimethyl methacrylamide and N, N-dibutyl methacrylamide are exemplified.
Preferred monomer combinations are (meth) acrylic acid, (meth) acryloxypropyl-modified polydimethylsiloxane, 2-hydroxyethyl methacrylate, vinylpyrrolidone, N-acryloylmorpholine, N, N-dimethylmethacrylamide, and more preferred monomer combinations. Are methacrylic acid and methacryloxypropyl-modified polydimethylsiloxane (n = 5 to 10
0) and 2-hydroxyethyl methacrylate or vinylpyrrolidone or N-acryloylmorpholine.

As specific examples of the resin used in the third embodiment of the present invention, at least one of the specific examples of the monomer having an acidic group in the first embodiment of the present invention is used. And a copolymer of a monomer having a high affinity for a silicone oil solvent represented by the general formula (I) and a monomer having a specific steric effect represented by the general formula (II). A preferred combination of monomers is (meth) acrylic acid, (meth) acryloxypropyl-modified polydimethylsiloxane and (poly) alkylene glycol (meth) acrylate, and a more preferred combination of monomers is methacrylic acid and methacryloxypropyl-modified polydimethylsiloxane (N = 5 to 100) and (poly) ethylene glycol methacrylate (y = 2 to
4).

As a specific example of the resin used in the fourth embodiment of the present invention, at least one of the specific examples of the monomer having an acidic group in the first embodiment of the present invention is used. A monomer having a high affinity for a silicone oil solvent represented by the general formula (I), a monomer having a specific steric effect represented by the general formula (II), and a polar monomer according to the second embodiment of the present invention. And copolymers with at least one of the above specific examples. Preferred combinations of monomers include (meth) acrylic acid, (meth) acryloxypropyl-modified polydimethylsiloxane, (poly) alkylene glycol (meth) acrylate, 2-hydroxyethyl methacrylate, vinylpyrrolidone, N-acryloylmorpholine, N, N -Dimethyl methacrylamide, a more preferred monomer combination is methacrylic acid and methacryloxypropyl-modified polydimethylsiloxane (n = 5 to 100)
And (poly) ethylene glycol methacrylate (y = 2
4) and 2-hydroxyethyl methacrylate or vinylpyrrolidone or N-acryloylmorpholine.

Examples of the resin soluble in the silicone oil solvent used in the fifth embodiment of the present invention include:
N-methylaminoethyl (meth) acrylate, N-ethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl Acrylate, N-phenylaminoethyl methacrylate, N, N-diphenylaminoethyl methacrylate, aminostyrene, dimethylaminostyrene, N-methylaminoethylstyrene, dimethylaminoethoxystyrene, diphenylaminoethylstyrene, N-phenylamino At least one monomer having a basic group such as ethylstyrene, 2-N-piperidylethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine, or 2-vinyl-6-methylpyridine; ) And a monomer having a high affinity for the silicone oil solvent. Preferred monomer combinations are N, N-dialkylaminoethyl (meth) acrylate and (meth) acryloxypropyl-modified polydimethylsiloxane, and more preferred monomer combinations are N, N-dimethylaminoethyl methacrylate or N, N-diethylamino. Examples include ethyl methacrylate and methacryloxypropyl-modified polydimethylsiloxane (n = 5 to 100).

As a specific example of the resin used in the sixth embodiment of the present invention, at least one of the specific examples of the monomer having a basic group in the fifth embodiment of the present invention is used. And a copolymer of a monomer having a high affinity for the silicone oil solvent represented by the general formula (I) and at least one of the specific examples of the polar monomer in the second embodiment of the present invention. .

As a specific example of the resin used in the seventh embodiment of the present invention, at least one of the specific examples of the monomer having a basic group in the fifth embodiment of the present invention is used. And a monomer having a high affinity for the silicone oil solvent represented by the general formula (I) and a monomer having a specific steric effect represented by the general formula (II).

As specific examples of the resin used in the eighth embodiment of the present invention, at least one of the specific examples of the monomer having a basic group in the fifth embodiment of the present invention is used. A monomer having a high affinity for the silicone oil solvent represented by the general formula (I), a monomer having a specific steric effect represented by the general formula (II),
A copolymer with at least one of the specific examples of the polar monomer according to the second embodiment of the present invention is given.

Other monomers copolymerizable with the monomers used in the first to eighth embodiments of the present invention include 2-ethylhexyl (meth) acrylate and octyl (meth) acrylate. , Nonyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, vinyl laurate, lauryl methacrylamide, stearyl methacrylamide, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate , Butoxyethyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth ) Acrylates, styrene, vinyl toluene, vinyl acetate, and the like.

A ninth embodiment of the present invention will be described with reference to FIG. In FIG. 1, (1) and (2) are conductive layers, at least one of which is light transmissive. A for the conductive layer
metals such as l, Ag, Ni, Cu, ITO, SnO ₂ , Z
A transparent conductor such as nO: Al is formed into a thin film by a sputtering method, a vacuum evaporation method, a CVD method, a coating method, or the like, or a transparent conductor mixed with a solvent or a synthetic resin binder and applied. Examples of the conductive agent include cationic polymer electrolytes such as polymethylbenzyltrimethyl chloride and polyallylpolymethylammonium chloride, anionic polymer electrolytes such as polystyrene sulfonate and polyacrylate, and electron conductive zinc oxide and tin oxide. And indium oxide fine powder. The conductive layer may be thick enough to have a self-holding function,
In some cases, a conductive layer is provided on a substrate having a self-holding function (not shown), and in either case, the conductive layer can be suitably used. Further, the conductive layers (1) and (2) may be layers exhibiting anisotropic conductivity, or layers having pattern-like or multi-dot-like segments in which conductive portions penetrate in the thickness direction. You may. In each case, the conductive layer (1),
If a power supply electrode is brought into contact with a part of (2), an electric field can be generated between the conductive layers (1) and (2), so that the white or colored particles (3) can move without fail. Display can be performed simply by providing a voltage applying means between the conductive layers (1) and (2).

In FIG. 1, reference numeral (3) denotes white or colored particles. The simplest example is a solid particle such as a metal oxide. In addition, a resin in which a white or colored component is dispersed or mixed in a binder resin that is insoluble in at least a silicone oil solvent may be used. As the binder resin, known thermoplastic resins, all of the thermosetting resins that are insoluble in the silicone oil solvent can be used,
In particular, non-adhesive materials can be preferably used. As a simple example of such a resin, a styrene such as polyester resin, polystyrene, poly p-chlorostyrene, and polyvinyltoluene and a homopolymer of a substituted product thereof can be exemplified. Further, as the coloring component, all known components can be used. As a black colorant, for example,
Carbon black, aniline black, furnace black, lamp black and the like can be used. As the cyan coloring agent, for example, phthalocyanine blue, methylene blue, Victoria blue, methyl violet, aniline blue, ultramarine blue and the like can be used. As the magenta colorant, for example, rhodamine 6G lake, dimethylquinacridone, watching red, rose bengal, rhodamine B, alizarin lake, and the like can be used. As the yellow colorant, for example, chrome yellow, benzidine yellow, Hanza yellow, naphthol yellow, molybdenum orange, quinoline yellow, tartrazine and the like can be used. The amount of the colorant that can be used is preferably from 0.1 part by weight to 300 parts by weight of the colorant with respect to 10 parts by weight of the binder resin, more preferably
1 part by weight of coloring agent to 1 part by weight of binder resin
00 parts by weight.

In FIG. 1, reference numeral (4) denotes a silicone oil solvent. Examples of the silicone oil used as the solvent in the present invention include a dialkyl silicone oil represented by the following general formula (III); a cyclic polydialkylsiloxane or a cyclic polyalkylphenylsiloxane; and a polyalkylphenylsiloxane. In addition, higher fatty acid-modified silicone oil, methyl-chlorinated phenyl silicone oil, alkyl-modified silicone oil, methyl-hydrogen silicone oil, amino-modified silicone oil, epoxy-modified silicone oil and the like can be used.

[0039]

Embedded image _{[However, R 11, R 12, R} 13, R 14, R 15, R 16, R 17,
R ₁₈ represents —CnH ₂ n + 1 (n = 1 to 20), which may be the same or different. z is 0 or an integer of 1 or more. In the case where the dialkyl silicone oil represented by the general formula (III) is used, it is particularly advantageous to use it as a solvent when polymerizing a resin and to freely change the temperature. Among them, the use of dimethylpolysiloxane is advantageous. The silicone oil represented by the general formula (III) has a viscosity at 25 ° C. of 0.0
Those having 1 to 1,000,000 cs (centistokes) are preferable, and more preferably 0.5 to 1,000 cs.
s. Furthermore, in the general formula (III), z is 1 to 20,
It is desirable to use what is 000.

When an alkylphenylsiloxane (particularly, methylphenylsilicone oil is preferably used) is used, the solubility is improved by the introduction of a phenyl group (5 to 50 mol%). This is advantageous for increasing the dispersion stability. Specific examples of these various silicone oils are as follows. (III) Examples of dialkyl silicone oils:

[0041]

[Table 1]

(IV) Examples of cyclic polydialkylsiloxane and cyclic polyalkylphenylsiloxane (the content of phenyl groups is 5, 10, 20, and 50 mol%, respectively): cyclic polydimethylsiloxane, cyclic polymethylphenylsiloxane, cyclic polydimethylsiloxane Diethylsiloxane, cyclic polyethylphenylsiloxane, cyclic polydibutylsiloxane, cyclic polybutylphenylsiloxane, cyclic polydihexylsiloxane, cyclic polyhexylphenylsiloxane, cyclic polydilaurylsiloxane, cyclic polymethylchlorophenylsiloxane, cyclic polydistearylsiloxane, cyclic polymethyl Bromophenylsiloxane and the like.

(V) Examples of alkyl phenyl silicone oil:

[Table 2]

Examples of commercially available silicone oils include KF-96L [0.65, manufactured by Shin-Etsu Chemical Co., Ltd.]
1.0, 1.5, 2.0 centistokes (cs)],
KF-96 [10, 20, 30, 50, 500, 100
0,3000 (cs)], KF-56, KF-58, K
F-54, etc., and Toshiba Silicone Co., Ltd.
TSF451 series, TSF456 series, T
SF410,411,440,4420,484,48
3,431,433 series, THF450 series,
TSF404, 405, 406, 451-5A, 451
-10A, 437 series, TSF440, 400, 4
01,4300,4445,4700,4450,47
02, 4730 series, TSF434, 4600 series, and SH200 manufactured by Dow Corning Toray Silicone Co., Ltd., and the like.

The silicone oil described above can be mixed with other solvents to such an extent that the properties of the silicone oil are not impaired. Examples of such a solvent include aromatic hydrocarbon solvents such as toluene, xylene, and benzene; ethers; esters; alcohol solvents; n-hexane, n-octane, iso-octane, iso-dodecane, and mixtures thereof. Aliphatic hydrocarbons (commercially available products such as Isopar HGLV manufactured by Exxon Chemical Co., Ltd.)
And the like. The mixing ratio of such another solvent is preferably 0.1 to 5 parts per 100 parts by weight of silicone oil.
00 parts by weight, more preferably 0.5 to 10 parts by weight based on 100 parts by weight of the silicone oil. Also,
It is preferable to add a dye soluble in the silicone oil solvent and having a color different from white or colored particles to the dispersion.

In FIG. 1, reference numeral (5) denotes a resin soluble in a silicone oil solvent. As the resin soluble in the silicone oil solvent, any of known thermoplastic resins and thermosetting resins which are soluble in the silicone oil solvent can be used. Those having strong interaction are preferable. When the resin is adsorbed on the white or colored particles, the dispersion stability of the white or colored particles is increased by the steric effect. Examples of such a resin include a copolymer containing as a component at least one monomer having a high affinity for a silicone oil solvent, such as a methacryloxyalkyl-modified silicone at both ends and a methacryloxyalkyl-modified silicone at one end.

To prepare the dispersion of the present invention, the above components may be mixed and dispersed in a silicone oil solvent. In this case, a ball mill, a sand mill, an attritor, or the like may be used as the dispersing means. The mixing order is not particularly limited.

In the tenth embodiment of the present invention,
The dispersion contains a resin having an acidic group but not having a basic group used in the first to third embodiments of the present invention as a resin soluble in the silicone oil solvent. When the resin adsorbs to the white or colored particles in the silicone oil solvent, the surface of the white or colored particles is uniformly charged to a positive polarity due to the acidic group of the solvent-soluble resin.

In the eleventh embodiment of the present invention,
The dispersion has a resin having a basic group but not having an acidic group used in the fifth to seventh embodiments of the present invention as a resin soluble in the silicone oil solvent. When the resin is adsorbed to the white or colored particles in the silicone oil solvent, the surface of the white or colored particles is uniformly charged to a negative polarity due to the basic group of the solvent-soluble resin.

In the twelfth embodiment of the present invention,
In the dispersion, as a resin soluble in the silicone oil solvent, (a) a resin having an acidic group used in the second to fourth embodiments of the present invention but having no basic group, and a nonionic resin (B) a resin having a basic group but having no acidic group and having a nonionic polar group used in the sixth to eighth embodiments of the present invention. Having. When these resins are adsorbed to the white or colored particles in the silicone oil solvent, the surface of the white or colored particles is uniformly formed due to the interaction between the acidic or basic groups of the solvent-soluble resin and the polar groups. It is charged to positive or negative polarity.

In the thirteenth and fourteenth embodiments of the present invention, the white or colored particles have an acidic group on the surface but no basic group, or have a basic group but no acidic group. Such white or colored particles are uniformly charged to positive or negative polarity in a silicone oil solvent due to their acidic or basic groups. The white or colored particles used in the present invention include the ninth of the present invention.
Silicone having as a component a monomer having an acidic group or a monomer having a basic group according to the first and fifth embodiments of the present invention as a binder for solid particles such as metal oxides and a colorant according to the embodiment of the present invention. An example using a resin insoluble in an oil solvent is given. Further, when a substance that can be chemically bonded by grafting or the like, such as carbon black or metal oxide, is used as the solid particles, the acid is reacted by reacting a monomer having the acidic group or the basic group with these substances. Groups or basic groups may be chemically bonded.

In a fifteenth embodiment of the present invention, the white or colored particles have a nonionic polar group on the surface,
In addition, the surface has (a) an acidic group but no basic group, or (b) a basic group but no acidic group. Such white or colored particles are uniformly charged to a positive or negative polarity in a silicone oil solvent due to the interaction between the acidic group or basic group and the nonionic polar group.

The white or colored particles used in the present invention include solid particles such as metal oxides in the ninth embodiment of the present invention and a binder for a colorant, and a white or colored particle in the first embodiment of the present invention. Insoluble resin in a silicone oil solvent having a monomer having an acidic group and a polar monomer according to the second embodiment of the present invention as a component, or a monomer having a basic group according to the fifth embodiment of the present invention and the polarizer Examples include those using a resin insoluble in a silicone oil solvent having a monomer as a component. In addition, when substances that can be chemically bonded by grafting or the like, such as carbon black or metal oxide, are used as the solid particles, the monomer having the acidic group or the basic group and the polar monomer are allowed to react with these substances. Thus, an acidic group or a basic group may be chemically bonded to a polar group.

In the sixteenth embodiment of the present invention,
The dispersion contains a resin soluble in the silicone oil solvent. By adsorbing the resin to white or colored particles,
The steric effect increases the dispersion stability of the white or colored particles. Examples of the resin soluble in the silicone oil solvent include the resin soluble in the silicone oil in the ninth embodiment of the present invention.

In the seventeenth embodiment of the present invention, the white or colored particles have an acidic group on the surface but do not have a basic group, and the resin soluble in the silicone oil solvent has a basic group. No group. At this time, acid-base dissociation occurs between the acidic groups on the surface of the white or colored particles and the basic groups of the resin soluble in the silicone oil solvent.
When the resin soluble in the white or colored particle surface and / or the silicone oil solvent has a nonionic polar group, ion generation via solvation occurs at the interface between the white or colored particle surface and the solvent. As a result, the white or colored particles are uniformly charged to a negative polarity, and the solid particles are dispersed more stably than before by the additive effect of this electrostatic effect and the steric effect. As the white or colored particles in this embodiment, the white or colored particles in the thirteenth and fifteenth embodiments of the present invention can be used. Further, as the resin soluble in the silicone oil solvent in the present embodiment, the resin soluble in the silicone oil solvent in the fifth to eighth embodiments of the present invention can be used.

In the eighteenth embodiment of the present invention, the white or colored particles have a basic group on the surface but no acidic group, and the resin soluble in the silicone oil solvent has an acidic group but has a basic group. No group. At this time, acid-base dissociation occurs between the basic groups on the surface of the white or colored particles and the acidic groups of the resin soluble in the silicone oil solvent.
When the resin soluble in the white or colored particle surface and / or the silicone oil solvent has a nonionic polar group, ion generation via solvation occurs at the interface between the white or colored particle surface and the solvent. As a result, the white or colored particles are uniformly charged to a positive polarity, and the solid particles are dispersed more stably than before by the sum of the electrostatic effect and the steric effect. As the white or colored particles in the present embodiment, the white or colored particles in the fourteenth and fifteenth embodiments of the present invention can be used. Further, as the resin soluble in the silicone oil solvent in the present embodiment, the resin soluble in the silicone oil solvent in the first to fourth embodiments of the present invention can be used.

In the present invention, the particle size of the white or colored particles is preferably from 0.1 μm to 10 μm, more preferably from 0.2 μm to 5 μm. The smaller the particle size, the higher the resolution of the image display medium, but the larger the cohesion of the particles, and the more difficult it is to obtain dispersion stability. Conversely, when the particle size is large, the dispersion stability is improved, but it is difficult to realize high resolution.

The white or colored particles of the present invention comprise at least solid particles or colored pigments such as metal oxides and a resin, and specific examples thereof include titanium oxide, aluminum oxide, zinc oxide and silicon oxide. Titanium is preferred. The weight ratio of the solid particles such as the metal oxide and the coloring pigment to the resin is 0.1 parts by weight of the solid particles such as the metal oxide and the colorant to 10 parts by weight of the resin.
It is preferably 0 parts by weight, more preferably 1 part by weight to 100 parts by weight of solid particles such as a metal oxide and a colorant per 10 parts by weight of the resin. When the proportion of the pigment, which is a white or colored component, is large, the image density when displayed as an image is high, and an image display medium with good contrast can be obtained. On the other hand, when the amount of the resin component responsible for ion generation due to acid-base dissociation on the surface of the white or colored particles decreases, the amount of generated charges decreases, and it becomes difficult to increase the response speed. Conversely, if the proportion of the pigment which is white or a coloring component is small, the response speed becomes faster, but it becomes difficult to display an image with good contrast.

The water content of the dispersion in the present invention is 100
It is preferably in the range of ppm to 2000 ppm. The silicone oil solvent originally absorbs moisture in the atmosphere and contains a small amount of water, but the water content of the dispersion can be controlled by further adding water thereto. If the water content is small, the amount of generated ions will be small, and it will be difficult to increase the response speed. Conversely, if the water content is high, it becomes impossible to uniformly mix with the silicone oil solvent.

[0060]

EXAMPLES The present invention will be described in more detail with reference to Examples. However, the present invention is not limited to the following examples. All parts used in the following examples are parts by weight. (Examples 1 to 8) (Synthesis example of polymer) A silicone oil (SH200; 1c) was placed in a reaction vessel equipped with a stirrer, a thermometer, and a reflux condenser.
s) 300 parts were taken and heated to 80 ° C. Table 3 in this
Was added dropwise over 1 hour. Next, stirring was continued at the same temperature for 5 hours to complete the reaction. The silicone oil as a solvent was evaporated from the obtained resin solution to obtain a copolymer having a conversion and an average molecular weight shown in Table 3.

[0061]

[Table 3-1]

[0062]

[Table 3-2]

[0063]

[Table 3-3]

(Examples 9 to 16) (Preparation of Dispersion and Preparation of Display Cell)
0 parts, 8 parts of a binder resin described below, titanium oxide 2
The mixture was dispersed in a ball mill for 24 hours. Next, 0.1 part of a dye (Bayer Macrolex Blue RR) and 10 parts of a solvent-soluble resin were added to the dispersion, and subjected to ultrasonic dispersion treatment for 1 hour. Next, a space is created by sandwiching a 100 μm-thick polyester film having an opening of 1 cm square between two substrates with ITO electrodes. The dispersion was sealed in the space.

(Display operation) -100 V applied to the upper ITO electrode
Was applied to observe the movement of the dispersed particles. Next, +
A voltage of 100 V was applied to observe the movement of the dispersed particles. This polarity switching was performed about 100 times. Further, the state after the voltage was released was observed.

(Synthesis of Binder Resin A) Into the reaction vessel used in Example 1, 500 parts of silicone oil (Toray Dow Corning Silicone SH200, 1cs) was placed, and
Heated to 5 ° C. A solution consisting of 5 parts of methacryloxypropyl-modified dimethylpolysiloxane, 5 parts of diethylaminoethyl methacrylate, 40 parts of methyl methacrylate, and 3 parts of azobisisobutyronitrile was added dropwise over 1.5 hours. Next, the temperature was raised to 90 ° C., and the mixture was stirred at this temperature for 4 hours to complete the reaction. By evaporating the silicone oil, the target resin was obtained at a polymerization rate of 98.2%.

(Synthesis of Binder Resin B) Silicone oil (SH200, 1c) was added to the reaction vessel used in Example 1.
s) 500 parts were taken and heated to 80 ° C. In this, methacryloxypropyl-modified dimethylpolysiloxane 20
, A solution consisting of 20 parts of ethylene glycol dimethacrylate, 5 parts of vinylpyrrolidone, 5 parts of dimethylaminoethyl methacrylate and 5 parts of azobisisobutyronitrile was added dropwise over 3 hours. Then the temperature was raised to 85 ° C,
The mixture was stirred at this temperature for 4 hours to complete the reaction. By evaporating the silicone oil, the target resin was obtained with a conversion of 94.5%.

(Synthesis of Binder Resin C) 500 parts of silicone oil (Toray Dow Corning Silicone SH200, 1cs) was placed in the reaction vessel used in Example 1,
Heated to 5 ° C. A solution composed of 5 parts of methacryloxypropyl-modified dimethylpolysiloxane, 5 parts of methacrylic acid, 40 parts of methyl methacrylate and 3 parts of azobisisobutyronitrile was added dropwise thereto over 1.5 hours. Then, the temperature was raised to 90 ° C., and the mixture was stirred at this temperature for 4 hours to complete the reaction. By evaporating the silicone oil, the target resin was obtained at a polymerization rate of 96.4%.

(Synthesis of Binder Resin D) Silicone oil (SH200, 1c) was placed in the reaction vessel used in Example 1.
s) 500 parts were taken and heated to 80 ° C. In this, methacryloxypropyl-modified dimethylpolysiloxane 20
, 20 parts of ethylene glycol dimethacrylate, 5 parts of lauryl methacrylamide, 5 parts of styrene sulfonic acid and 5 parts of azobisisobutyronitrile were added dropwise over 3 hours. Then, the temperature was raised to 85 ° C., and the mixture was stirred at this temperature for 4 hours to complete the reaction. By evaporating the silicone oil, the target resin was obtained at a conversion of 90.1%.

(Solvent A) Dimethyl silicone oil (1cs): n-butanol = 9: 1 (Solvent B) Methyl phenyl silicone oil: ethanol = 9: 1

[0071]

[Table 4] ：: The dispersed particles moved quickly. The switching of the polarity was performed about 100 times, and the switching was performed stably. Further, the electrodeposited state was maintained even when the voltage was removed. Δ: Response speed is slightly slow, but switching of voltage polarity is 100
The operation was repeated about once, and the operation could be repeated stably. Further, the electrodeposited state was maintained even when the voltage was removed. X: The response speed was slow and the repetition was only about 10 times.

[0072]

As is apparent from the detailed and specific description above, according to the polymer of the present invention of claims 1 to 8, ions can be stably generated in silicone oil by acid-base dissociation. Therefore, it is possible to provide a stable electrophoretic dispersion liquid. According to the image display medium of the ninth aspect, since the dispersion stability of the white or colored particles is increased, it is possible to provide an image display medium having reversible display, having memory properties, and having good long-term stability. Claim 1
According to the image display media of Nos. 0 and 11, the surface of the white or colored particles is uniformly charged to a positive or negative polarity due to the acidic group or the basic group of the resin soluble in the silicone oil solvent. An image display medium with a high speed can be provided. According to the image display medium of claim 12, the surface of the white or colored particles is uniformly positive or negative due to the interaction between the acidic group or the basic group of the resin soluble in the silicone oil solvent and the polar group. Since it is charged to a polarity, an image display medium having a higher response speed can be provided. According to the image display medium of claim 13 or 14, the white or colored particles are uniformly charged to a positive or negative polarity due to the acidic group or the basic group on the surface, so that the image display medium has a high response speed. Can be provided. According to the image display medium of the present invention, the white or colored particles are uniformly charged to a positive or negative polarity due to the interaction between the acidic group or the basic group on the surface and the polar group. An image display medium with a high speed can be provided.
According to the image display medium of the sixteenth aspect, since the dispersion stability of white or colored particles is increased, it is possible to provide an image display medium having reversible display, having a memory property, and having good long-term stability. According to the image display medium of claim 17 or 18, the acid-base dissociation between the acidic group or the basic group on the surface of the white or colored particles and the basic group or the acidic group of the resin soluble in the silicone oil solvent. Therefore, the present invention has an extremely excellent effect that an image display medium having a high response speed and good long-term stability can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of an image display medium according to the present invention.

FIG. 2 is a schematic diagram showing a principle of a display operation mechanism according to the present invention.

FIG. 3 is a cross-sectional view schematically showing a conventional display device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive layer 2 conductive layer 3 white or colored particles 4 silicone oil solvent 5 resin soluble in silicone oil solvent 6 transparent substrate 7 transparent electrode 8 dispersion 9 perforated spacer

Claims (18)

[Claims] 1. A polymer which is soluble in a silicone oil solvent, and is polymerized with a monomer having at least an acidic group and a monomer represented by the following general formula (I) as constituent components. Embedded image [In the formula, R ₁ represents a hydrogen atom or a methyl group, R ₁ ′ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, n represents a natural number, and x represents an integer of 1 to 3. ] 2. A monomer which is soluble in a silicone oil solvent and has at least an acidic group, a monomer represented by the general formula (I), and a monomer having a nonionic polar group. A polymer characterized by being polymerized as: 3. A monomer which is soluble in a silicone oil solvent and has at least an acidic group, a monomer represented by the general formula (I), and a monomer represented by the following general formula (II) A polymer characterized by being polymerized as a constituent requirement. Embedded image [Wherein, R ₂ is a hydrogen atom or a methyl group, R ₃ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, x is an integer of 1 to 3,
y represents a natural number of 25 or less. ] 4. A monomer soluble in a silicone oil solvent and having at least an acidic group, a monomer represented by the general formula (I), a monomer represented by the general formula (II), and A polymer obtained by polymerizing a monomer having a nonionic polar group other than a (poly) oxyalkylene group as a constituent requirement. 5. A polymer which is soluble in a silicone oil solvent, and is obtained by polymerizing a monomer having at least a basic group and a monomer represented by the general formula (I) as constituent components. 6. A monomer which is soluble in a silicone oil solvent and has at least a basic group, a monomer represented by the general formula (I), and a monomer having a nonionic polar group. A polymer characterized by being polymerized as a requirement. 7. A monomer that is soluble in a silicone oil solvent and has at least a basic group, a monomer represented by the general formula (I), and a monomer represented by the general formula (II) A polymer characterized by being polymerized as a constituent requirement. 8. A monomer which is soluble in a silicone oil solvent and has at least a basic group, a monomer represented by the general formula (I), a monomer represented by the general formula (II),
And a polymer having a monomer having a nonionic polar group other than a (poly) oxyalkylene group as a constituent element. 9. At least one or both light-transmitting conductive layers disposed at a desired distance between two conductive layers,
An image display medium comprising at least white or colored particles, a silicone oil solvent, and a dispersion comprising a resin soluble in the silicone oil solvent. 10. The image display medium according to claim 9, wherein the resin soluble in the silicone oil solvent has an acidic group but has no basic group. 11. The image display medium according to claim 9, wherein the resin soluble in the silicone oil solvent has a basic group but does not have an acidic group. 12. The resin according to claim 9, wherein the resin soluble in the silicone oil solvent has a nonionic polar group.
12. The image display medium according to any one of claims 1 to 11. 13. A white or colored particle having at least a surface having an acidic group but not having a basic group between two conductive layers at least one or both of which are light-transmissive and arranged at a desired interval, and An image display medium comprising a dispersion comprising a silicone oil solvent. 14. White or colored particles having at least a basic group but no acidic group at least on the surface between two conductive layers, at least one or both of which are light-transmissive, provided at a desired interval; and An image display medium comprising a dispersion comprising a silicone oil solvent. 15. The image display medium according to claim 13, wherein the white or colored particles have a nonionic polar group on the surface. 16. The image display medium according to claim 13, wherein the dispersion contains a resin soluble in a silicone oil solvent. 17. The white or colored particles have an acidic group on the surface but do not have a basic group, and the resin soluble in a silicone oil solvent has a basic group but does not have an acidic group. Claims 9, 11, 12, 13, 1
17. The image display medium according to any one of items 5 and 16. 18. The white or colored particles have a basic group on the surface but no acidic group, and the resin soluble in the silicone oil solvent has an acidic group but no basic group. Claims 9, 10, 12, 14 to 16
The image display medium according to any one of the above.