JP2008241851A - Method of manufacturing charged particle, charged particle, and electrophotoresis display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing charged particles, which comprise two kinds of particles differing in particle size and are hardly peeled off mutually, to provide the charged particle, and to provide an electrophotoresis display panel. <P>SOLUTION: The method of manufacturing the charged particles which are used for the electrophotoresis display panel and each have a mother particle and a plurality of child particles disposed on the surface of the mother particle comprises: a polymerization stage of polymerizing a particle material containing a resin material having a bridging functional group to form a mother particle intermediate body first (S10); a child particle burying stage of burying child particles in the surface of the mother particle intermediate body is carried out (S20); and a bridging stage (S30) of bridging the particle material contained in the mother particle intermediate body to form the mother particle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing charged particles used in an electrophoretic display panel that displays an image using an electrophoretic phenomenon, charged particles, and the electrophoretic display panel.

  Conventionally, an electrophoretic display panel that displays an image using an electrophoretic phenomenon is known. In this electrophoretic display panel, a sealed space having a predetermined interval is formed by surrounding a gap spacer between a transparent display substrate on one side and a back substrate disposed opposite thereto. A display medium is formed by filling the sealed space with a dispersion medium made of a colored liquid in which charged particles, which are colored spherical particles, are dispersed.

  Under such a configuration, by generating an electric field in the display portion, the charged particles in the dispersion medium are moved to obtain a desired image. Various types of electrophoretic display panels have been proposed. For example, there are proposed ones that switch colors by moving charged particles in a direction perpendicular to the display surface and those that switch colors by moving them in a direction parallel to the display surface. Also proposed are two types of charged particles of different colors that switch colors depending on the color of the charged particles, and those that switch colors depending on the color of the dispersion medium and charged particles. Yes.

In such a conventional electrophoretic display panel, even when the voltage is switched to reverse the direction of the electric field, charged particles remain attached to any substrate due to intermolecular force, mirror image force, etc. There is a problem in that the contrast is reduced due to the aggregation of each other. Therefore, in order to obtain a high contrast, it has been proposed that the charged particles are composed of a combination of two types of particles having different particle diameters and chargeability (for example, Patent Document 1).
JP 2002-72256 A

  However, the conventional electrophoretic display panel has a problem that the child particles are peeled off from the mother particles when repeatedly used. The problem that the child particles are peeled off from the mother particles has led to a decrease in contrast of the electrophoretic display panel.

  The present invention has been made to solve the above problems, and a method for producing charged particles in which a plurality of child particles arranged on the surface of the mother particles are difficult to peel off from the mother particles, charged particles, and electricity using the charged particles. An object is to provide an electrophoretic display panel.

  In order to solve the above-mentioned problem, the charged particle manufacturing method of the invention according to claim 1 is a method for manufacturing charged particles comprising a mother particle and a plurality of child particles arranged on the surface of the mother particle. A polymerization step of polymerizing a particle material containing a mother particle intermediate to form a mother particle intermediate; a child particle embedding step of embedding the child particle on a surface of the mother particle intermediate; and after the child particle embedding step, the mother particle A crosslinking step of crosslinking the particulate material contained in the intermediate to form the mother particles.

  In addition to the structure of the invention according to claim 1, the method for producing charged particles of the invention according to claim 2 forms a mother particle intermediate by emulsion polymerization of a particle material containing a resin material in the polymerization step. It is characterized by doing.

  According to a third aspect of the present invention, there is provided a method for producing charged particles, in addition to the constitution of the first or second aspect of the invention, in the polymerization step, polymerizing a particle material including a resin material having a crosslinkable functional group. Forming a base particle intermediate, and in the cross-linking step, the cross-linkable functional group is reacted to cross-link the particle material contained in the base particle intermediate to form the base particle. To do.

  In addition to the constitution of the invention according to any one of claims 1 to 3, the method for producing charged particles of the invention according to claim 4 adds a crosslinking agent having a crosslinkable functional group in the crosslinking step. The base material is formed by crosslinking the particulate material contained in the base particle intermediate.

  In addition to the constitution of the invention according to claim 3 or 4, the method for producing charged particles of the invention according to claim 5 includes that the crosslinkable functional group includes at least one of a diazo group and an azide group. Features.

  A charged particle according to a sixth aspect of the present invention is manufactured by the method for manufacturing a charged particle according to any one of the first to fifth aspects.

  An electrophoretic display panel according to a seventh aspect of the invention includes the charged particle according to the sixth aspect.

  According to the method for producing charged particles of the invention of claim 1, in the polymerization step, after the particle material containing the resin material is polymerized to form the mother particle intermediate, the mother particle intermediate step is performed in the child particle embedding step. Embed child particles on the surface of the body. In the polymerization step, the polymerization reaction proceeds, but the crosslinking reaction has not progressed, or even if the crosslinking reaction has progressed, it is only a part. After the child particle embedding step, the particle material contained in the particles is crosslinked. By this cross-linking reaction, the particle material of the base particle intermediate formed in the polymerization step is cross-linked in a network shape to form base particles. The mother particles are harder than the mother particle intermediate before the crosslinking step, and the child particles are tightly surrounded by the particle material crosslinked in a network. Therefore, according to the method for producing charged particles of the present invention, it is possible to produce charged particles in which the child particles are not easily separated from the mother particles.

  Further, according to the method for producing charged particles of the invention of claim 2, in addition to the effect of the invention of claim 1, the polymerization reaction is advanced by emulsion polymerization in the polymerization step, so that the temperature of the polymerization reaction system can be easily adjusted. It is.

  According to the method for producing charged particles of the invention of claim 3, in addition to the effect of the invention of claim 1 or 2, in the polymerization step, a particle material containing a resin material having a crosslinkable functional group is used. Polymerize to form a base particle intermediate. In the polymerization step, the polymerization reaction proceeds, but the crosslinking reaction has not progressed, or even if the crosslinking reaction has progressed, it is only a part. In the cross-linking step, cross-linkable functional groups are reacted to cross-link the particle material contained in the base particle intermediate to form base particles. Since the crosslinkable functional group is provided in the mother particle intermediate, the particle material contained in the mother particle intermediate can be reliably crosslinked without newly adding a crosslinking agent in the crosslinking step.

  According to the method for producing charged particles of the invention according to claim 4, in addition to the effect of the invention according to any one of claims 1 to 3, a crosslinking agent having a crosslinkable functional group is added in the crosslinking step. Thus, the particle material contained in the mother particle intermediate is crosslinked. For this reason, the particle material contained in the mother particle intermediate can be crosslinked in the crosslinking step without causing the crosslinking reaction to proceed in the polymerization step.

  Further, according to the method for producing charged particles of the invention according to claim 5, in addition to the effect of the invention of claim 3 or 4, as a crosslinkable functional group, a diazo group that undergoes a crosslinking reaction upon light irradiation, and It contains at least one of azide groups. For this reason, the reaction conditions for allowing only the polymerization reaction to proceed without proceeding the crosslinking reaction in the polymerization step can be easily set depending on the presence or absence of light irradiation.

  Further, according to the charged particle of the invention of claim 6, the charged particle includes a mother particle and a plurality of child particles arranged on the surface of the mother particle, and the child particle is made of a particle material crosslinked in a mesh shape included in the mother particle. , Firmly surrounded. For this reason, in the charged particles of the present invention, the child particles are hardly peeled off from the mother particles.

  According to the electrophoretic display panel of the invention according to claim 7, the charged particles included in the electrophoretic display panel include a mother particle and a plurality of child particles arranged on the surface of the mother particle. It is tightly surrounded by a network of particulate materials that make up the particles. For this reason, it is possible to prevent the contrast of the electrophoretic display panel from being lowered due to the child particles that are hardly peeled off from the mother particles and the child particles constituting the charged particles are peeled off from the mother particles.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described in order with reference to the drawings. First, the configuration of the electrophoretic display panel 2 and the charged particles 50 and 60 included in the electrophoretic display panel 2 of the present embodiment will be described with reference to the drawings. FIG. 1 is a partial cross-sectional view showing a schematic configuration of the electrophoretic display panel 2. In the electrophoretic display panel 2 shown in FIG. 1, the upper surface on the paper is the upper surface of the electrophoretic display panel 2, and the lower surface is the lower surface of the electrophoretic display panel 2.

  The electrophoretic display panel 2 of this embodiment is mounted on, for example, a portable electronic device, and can display various images by being driven and controlled by a control device (not shown). The electrophoretic display panel 2 shown in FIG. 1 corresponds to the “electrophoretic display panel” of the present invention.

  First, the configuration of the electrophoretic display panel 2 will be described. As shown in FIG. 1, the electrophoretic display panel 2 includes a display substrate 10 provided on the upper side, and a back substrate 20 disposed on the lower side of the display substrate 10 with a spacer 31 therebetween. In the gap between the display substrate 10 and the back substrate 20, a display unit 30, which is a plurality of regions divided by the partition walls 32, is formed like a grid in a plan view.

  Next, the structure of the display substrate 10 will be described. As shown in FIG. 1, the display substrate 10 is formed of a transparent member, is provided with a transparent layer 11 having a display surface, and a lower surface (back surface) side of the transparent layer 11, and generates an electric field in the display unit 30. The transparent transparent electrode layer 12 is comprised. The transparent layer 11 is formed of a material having high transparency and high insulation, for example, polyethylene naphthalate (PEN), polyethersulfone (PES), polyethylene terephthalate (PET), polyimide (PI), glass Etc. are used. On the other hand, the transparent electrode layer 12 is made of a material having high transparency and can be used as an electrode. For example, indium tin oxide which is a metal oxide, tin oxide doped with fluorine, indium or aluminum oxide is doped. Zinc oxide or the like is used. In the present embodiment, the transparent layer 11 is a transparent glass substrate, and the transparent electrode layer 12 is a transparent electrode formed of indium tin oxide (ITO). By providing such a structure, the user can visually recognize the display unit 30 through the transparent display substrate 10.

  Next, the structure of the back substrate 20 will be described. As shown in FIG. 1, the back substrate 20 is provided for each display unit 30 on the upper surface of the housing support layer 21 that supports the electrophoretic display panel 2 and on the upper surface of the housing support layer 21. The back electrode layer 22 generates an electric field. The casing support layer 21 is made of a highly insulating material such as an inorganic material such as glass or an insulated metal film, or an organic material such as polyethylene terephthalate (PET). Each layer forming the back substrate 20 may be transparent or colored, unlike the display substrate 10. In the present embodiment, the housing support layer 21 is a glass substrate, and the back electrode layer 22 is an electrode formed of indium tin oxide (ITO).

  Each back electrode layer 22 is connected to a channel CH1 and the transparent electrode layer 12 is connected to a channel CH2. When these channels CH1 and CH2 are controlled by a control device (not shown) and a voltage is applied to the back electrode layer 22 and the transparent electrode layer 12, an electric field is generated in the display unit 30. . Insulating fluororesin or the like may be applied to the surface of the transparent electrode layer 12 and the surface of the back electrode layer 22. In this case, the affinity between each charged particle and the surface of each electrode layer can be further reduced. Moreover, you may provide a protective layer in the surface (lower surface) of the transparent electrode layer 12 of this embodiment, and the surface (upper surface) of the back electrode layer 22. FIG.

  Next, the structure of the display unit 30 will be described. As shown in FIG. 1, a spacer 31 is provided between the display substrate 10 and the back substrate 20, and the spacer 31 is disposed along the outer periphery of the electrophoretic display panel 2. Further, a sealed space is formed between the display substrate 10, the back substrate 20, and the spacer 31. The sealed space has a predetermined thickness and a predetermined height, and is equally divided into a plurality of display portions 30 by a partition wall 32 having a lattice shape in plan view. Therefore, the electrophoretic display panel 2 is configured as a panel in which a plurality of display units 30 are formed side by side like a grid. The spacer 31 and the partition wall 32 are made of a resin film such as polyethylene terephthalate (PET). A display liquid 40 is sealed in the sealed space of each display unit 30.

  Next, the display liquid 40 will be described. The display liquid 40 is a dispersion medium in which a plurality of black charged particles 50 and a plurality of white charged particles 60 are dispersed. Here, the dispersion medium refers to a liquid substance in which particles (dispersoid) are dispersed, and a liquid having high electrical resistance and high transparency is used. For example, aromatic hydrocarbon solvents such as benzene, toluene and xylene, aliphatic hydrocarbon solvents such as hexane and cyclohexane, insulating organic solvents such as polysiloxane and high-purity petroleum are used. In the electrophoretic display panel 2, each of the above-described dispersion media may be used alone or as a mixture of two or more. Furthermore, the display liquid 40 can contain other components as necessary. Examples of the other components include a dispersant such as a surfactant used to assist the dispersion of the charged particles 50 and 60, an alcohol used to adjust the electrophoretic properties of the charged particles in the dispersion medium, and the like. Examples thereof include a charge control agent and a viscosity adjusting agent such as a polymer resin used for preventing sedimentation of charged particles in the dispersion medium. In this embodiment, the case where the dispersion medium is a liquid will be described. However, the present invention can be applied to an electrophoretic display panel in which the dispersion medium is a gas.

  Next, the black charged particles 50 and the white charged particles 60 that are the characteristics of the present invention will be described. As shown in FIG. 1, the charged particles of the display liquid 40 include black charged particles 50 that are positively charged and white charged particles 60 that are negatively charged. Therefore, when the electric field is generated in the display unit 30 with the back substrate 20 side being positive than the display substrate 10 side, the black charged particles 50 move to the display substrate 10 side, and the white charged particles 60 are on the back substrate 20 side. Move to. At this time, black is displayed on the display unit 30 of the display substrate 10. Further, when an electric field in the reverse direction is generated in the display unit 30 with the back substrate 20 side minus than the display substrate 10 side, the black charged particles 50 move to the back substrate 20 side, and the white charged particles 60 are displayed. Move to the substrate 10 side. At this time, the black color displayed on the display unit 30 is switched to white.

  Next, the particle structure of the black charged particles 50 and the white charged particles 60 will be described with reference to FIG. Since the black charged particles 50 and the white charged particles 60 have the same configuration except for the color (colorant) and polarity of the charged particles, the black charged particles 50 will be described here as an example. FIG. 2 is a schematic diagram schematically showing the structure of the black charged particles 50. As shown in FIG. 2, the black charged particle 50 includes a spherical mother particle 51 that forms the central portion of the black charged particle 50, and a plurality of spherical child particles 52 that are arranged on the surface of the mother particle 51. .

  First, the mother particles 51 included in the black charged particles 50 will be described with reference to FIG. The mother particle 51 is a particle constituting the central part of the charged particle, and includes at least a resin obtained by polymerizing and crosslinking a resin material, and if necessary, a colorant, a charge control agent, and other additives. Examples of the mother particle 51 include crosslinked polymethyl methacrylate (crosslinked PMMA), crosslinked polyvinyl alcohol unit (crosslinked PVA unit), crosslinked polyvinyl cinnamate, and crosslinked polyazide vinyl benzoate as a resin. A method for producing the polymerized and cross-linked resin will be described later with reference to FIGS.

  The mother particle 51 contains carbon black as a colorant, and the mother particle 51 is black. The colorant included in the mother particles can be appropriately selected in consideration of the color of the charged particles and the chargeability and fluidity imparted to the charged particles. In addition to the black colorant such as carbon black, for example, titanium oxide or the like. White colorants, various organic or inorganic pigments and dyes are used. The above colorants may be used alone or in combination of two or more.

  The charge control agent includes a negative charge control agent and a positive charge control agent. As the positive charge control agent, for example, a quaternary ammonium salt compound is used. Further, as the negative charge control agent, for example, a metal-containing azo dye or the like is used. The charge control agents as described above may be used alone or in combination of two or more. As the shape of the mother particle 51, various shapes such as an ellipse, a cylindrical shape, and a triangular pyramid shape can be adopted in addition to a spherical shape as shown in FIG.

  Next, the child particles 52 included in the black charged particles 50 will be described with reference to FIG. The child particles 52 of the present embodiment indicate that the black charged particles 50 adhere to the display substrate 10 and the back substrate 20, or the black charged particles 50, the white charged particles 60, and the black charged particles 50 aggregate. It is a member that plays a role to prevent. When the child particles 52 are provided, the contact area between the display substrate 10 and the back substrate 20 is reduced, and therefore, the charged particles 50 and 60 can be prevented from adhering to the substrates 10 and 20. Similarly, since the contact area with the other charged particles 50 and 60 is reduced, the charged particles 50 and 60 can be prevented from aggregating. The child particles 52 are in contact with the mother particle 51 in a state where a part of the child particle 52 is buried in the surface of the mother particle 51. The diameter of the child particle 52 is, for example, 50 nm, which is about 1/100 of the diameter of the mother particle 51. Therefore, since the shape, weight, etc. of the black charged particles 50 are not greatly changed, the influence on the mobility of the black charged particles 50 can be suppressed low. The size of the child particle 52 is only required to be smaller than the average particle diameter of the mother particle 51 and is appropriately determined in consideration of the fluidity, chargeability, and surface characteristics of the charged particles. The above-mentioned average particle diameter refers to a volume average particle diameter, and is measured by, for example, Microtrack 3100 (manufactured by Microtrack) using a laser diffraction / scattering method.

As the material of the child particles 52, for example, resin particles are used in addition to inorganic particles such as hydrophobized silica fine particles (silicon dioxide: SiO ₂ ). In addition to the spherical shape, the child particles 52 may have various shapes such as an ellipse, a cylinder, and a triangular pyramid. When the child particles 52 are spherical, it is preferable that half or more of the volume is buried in the mother particles 51. This is because in this case, the child particles 52 are firmly fixed by the mother particles 51 and are difficult to peel off from the mother particles 51. In addition, the larger the contact area between the child particle 52 and the mother particle 51, the better the adhesion between the mother particle 51 and the child particle 52 compared to the case where the contact area is small. In addition, it is desirable that the mother particles 51 surrounded by the child particles 52 are densely polymerized or crosslinked because the child particles 52 are firmly fixed. In addition, the process for closely polymerizing or cross-linking the mother particles 51 surrounding the child particles 52 will be described later as a method for producing charged particles of the present embodiment.

Although not shown, the configuration of the white charged particles 60 is composed of a mother particle and a plurality of child particles bonded to the surface of the mother particle, similar to the configuration of the black charged particle 50. The same material as the base particle 51 of the black charged particle 50 (for example, cross-linked PMMA) is used. Further, since the mother particles contain titanium dioxide (TiO ₂ ) as a colorant, the entire mother particles are white.

  Next, the effect of preventing the black charged particles 50 and the white charged particles 60 from adhering to the display substrate 10 and the back substrate 20 will be described. As described above, in the present embodiment, the black charged particles 50 are positively charged and the white charged particles 60 are negatively charged. Therefore, for example, when an electric field is generated in the display unit 30 with the display substrate 10 side being positive and the back substrate 20 side being negative, the white charged particles 60 move to the display substrate 10 side, and the black charged particles 50 are the back substrate. Move to the 20 side. At this time, the white charged particles 60 are in contact with the transparent electrode layer 12 of the display substrate 10. Among the particles of the white charged particles 60 with respect to the hydrophilic (polar) surface of the transparent electrode layer 12, Child particles having a surface that is more hydrophobic than the surface of the particles act and repel. Thereby, it is possible to prevent the white charged particles 60 from adhering to the surface of the transparent electrode layer 12.

  On the other hand, the black charged particles 50 are also in contact with the back electrode layer 22 of the back substrate 20. At this time, the child particles 52 having a surface that is more hydrophobic than the surface of the mother particles 51 among the particles of the black charged particles 50 act on the hydrophilic (polar) surface of the back electrode layer 22. resist. Thereby, it is possible to prevent the black charged particles 50 from adhering to the surface of the back electrode layer 22. Next, when the direction of the electric field is switched and the display substrate 10 side becomes negative and the back substrate 20 side becomes positive, the white charged particles 60 move to the back substrate 20 side, and the black charged particles 50 move to the display substrate 10 side. (See FIG. 1). Also in this case, the same effect as the adhesion preventing effect described above can be obtained. As described above, even when the electric field of the display unit 30 is repeatedly switched, the black charged particles 50 and the white charged particles 60 do not adhere to the display substrate 10 and the back substrate 20, so that the contrast of the image displayed on the display substrate 10 decreases. Can be prevented.

  Next, the manufacturing method of the charged particles 50 and 60 of the present embodiment will be described with reference to FIGS. As an example, the case of the black charged particles 50 will be described, but the white charged particles 60 are also manufactured by the same manufacturing method. FIG. 3 is a manufacturing flow of the black charged particles 50, and FIG. 4 is an explanatory diagram for explaining a reaction system in which the surfactant 103 is added in the polymerization step. FIG. 5 is an explanatory diagram for explaining a reaction system in which a monomer 105, a resin material 107 having a crosslinkable functional group, and a colorant 106 are added in the polymerization step. FIG. 6 is an explanatory diagram for explaining a state in which a polymerization initiator is added to the reaction system in the polymerization step, and FIG. 7 is a diagram in which a polymerization reaction between monomers proceeds and a polymer is formed in the polymerization step. It is explanatory drawing for demonstrating a state. FIG. 8 is an explanatory diagram for explaining a process of filtering the solution 205 in order to stop the polymerization reaction in the polymerization step, and FIG. 9 explains the mother particle intermediate 53 formed in the polymerization step. It is explanatory drawing for. FIG. 10 is an explanatory diagram for explaining a state in which the mother particle intermediate 53 and the child particle 52 are provided to the hybridization system (NHS) in the child particle embedding step, and FIG. 3 is a schematic diagram schematically showing a state in which child particles 52 are embedded in the surface of an intermediate 53. FIG. FIG. 12 is an explanatory diagram for explaining a state in which light is irradiated to the mother particle intermediate 53 in which the child particles 52 are embedded in the crosslinking step. 4 to 12 are diagrams schematically illustrating a method for producing charged particles, and therefore the number, size, shape, and the like of each illustrated component are different from the actual reaction system.

  As shown in the production flow of FIG. 3, the method for producing the black charged particles 50 is a polymerization step in which a particle material containing a resin material having a crosslinkable functional group is emulsion-polymerized to form a mother particle intermediate 53 (S10). And a child particle embedding step (S20) for embedding the child particles 52 on the surface of the mother particle intermediate 53. Furthermore, the manufacturing method of the black charged particles 50 includes a crosslinking step (S30) in which the particle material contained in the mother particle intermediate 53 is crosslinked to form the mother particles 51 after the child particle embedding step. Hereafter, the detail of each manufacturing process is demonstrated in order.

  As shown in the manufacturing flow of FIG. 3, a polymerization process is first performed (S10). In the polymerization step, at least one of monomers or oligomers contained in the particulate material is polymerized. As an example, the case where the polymerization reaction is advanced by emulsion polymerization will be described, but other polymerization reactions such as suspension polymerization and solution polymerization may be employed. When the polymerization reaction is allowed to proceed by emulsion polymerization, it is preferable because the temperature of the polymerization reaction system can be easily adjusted. In the polymerization process of this embodiment in which the polymerization reaction proceeds by emulsion polymerization, first, as shown in FIG. 4, the surfactant 103 is added to the solvent 104 in the container 102, and the stirring rod 101 is rotated in the direction indicated by the arrow 110. The solution 201 is stirred. This surfactant is appropriately selected from surfactants used for emulsion polymerization.

Subsequently, in the polymerization step (S10), as schematically shown in FIG. 5, a resin material 107 having a crosslinkable functional group, a monomer 105, and a colorant 106 are added to the solution 201 shown in FIG. And stir. The particle material of the present embodiment may include at least a resin material having a crosslinkable functional group as a constituent element, and may include a colorant, a charge control agent, and other additives as constituent elements as necessary. Examples of the crosslinkable functional group provided in the resin material include a diazo group (N ₂ =), an azide group (N ₃ —), a cinnamoyl group (C ₆ H ₅ CH═CHCO—), and an acryloyl group (CH ₂ CHCOO—). Etc. are used. The crosslinkable functional groups may be used alone or in combination of two or more. The resin material preferably has at least one of a diazo group and an azide group among the crosslinkable functional groups as described above as a crosslinkable functional group. The diazo group and the azide group undergo a crosslinking reaction at the time of light irradiation. Therefore, in the polymerization step provided in the method for producing charged particles described later, the reaction conditions for allowing only the polymerization reaction to proceed without proceeding the crosslinking reaction are as follows. It can be easily set by the presence or absence of light irradiation. In addition, the acryloyl group, like the diazo group and the azide group, undergoes a crosslinking reaction only at the time of light irradiation, so that it is easy to set reaction conditions during the crosslinking step. Furthermore, since the acryloyl group is similar to the methyl methacrylate (MMA) skeleton, it has a small influence on the color of the charged particles, and is preferable in that only the hardness can be expected at the time of crosslinking. The crosslinkable functional group may be used alone or in combination of two or more.

  Examples of the resin material having the crosslinkable functional group as described above include monomers, oligomers, and polymers having the crosslinkable functional group as described above in the side chain. Examples of the crosslinkable functional group include monomers, oligomers, and polymers having side chains represented by the following general formulas (1) to (7) having a diazo group. A resin material having a crosslinkable functional group may be used alone or in combination of two or more. In addition, the addition amount of the resin material containing a crosslinkable functional group is appropriately determined in consideration of the hardness of the mother particle intermediate 53 and the mother particle 51 and the like.

  Moreover, as the monomer 105 contained in the particle material, for example, methacrylic acid, acrylic acid, or the like is used. The above monomers may be used alone or in combination of two or more. In the present embodiment, a monomer is used as a material for generating a polymer in the polymerization step. However, the present invention is not limited to this, and it is sufficient that at least one of a monomer and an oligomer is included. Further, when the resin material 107 having a crosslinkable functional group is a monomer or oligomer having a crosslinkable functional group, a polymerization reaction can proceed between the resin materials 107 having a crosslinkable functional group. The particle material may not contain a monomer or oligomer that does not have a crosslinkable functional group.

  As the colorant 106, as described above, for example, a white colorant such as titanium oxide, various organic or inorganic pigments, and dyes are used in addition to a black colorant such as carbon black. The above colorants may be used alone or in combination of two or more. The resin material 107 having a crosslinkable functional group, the monomer 105, and the colorant 106 added to the solution 201 in FIG. 4 are taken into the micelle 130 formed by the surfactant 103 as shown in FIG.

In the polymerization step, as schematically shown in FIG. 6, the polymerization initiator 108 is added to the solution 202 (see FIG. 5) in which the particulate material is suspended, and the stirring bar 101 is moved in the direction indicated by the arrow 110. Rotate and stir. As the polymerization initiator 108, a polymerization initiator that does not act on the crosslinkable functional group of the resin material is appropriately selected and used. For example, when the resin material has a crosslinkable functional group and a functional group that undergoes a crosslinking reaction by light irradiation, examples of the polymerization initiator 108 include potassium persulfate (K ₂ S ₂ O ₈ ), persulfate. Sodium (Na ₂ S ₂ O ₈ ), ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ ), hydrogen peroxide (H ₂ O ₂ ), or the like is used. As schematically shown in FIG. 6, when the polymerization initiator 108 enters the micelle 130 containing the monomer 105, the polymerization reaction starts and proceeds in the micelle 130 suspended in the solution 203. By such a polymerization reaction, a spherical polymer 120 is generated in the micelle 130 suspended in the solution 204 as schematically shown in FIG. This spherical polymer 120 surrounds and captures the colorants that make up the particulate material. Subsequently, in the polymerization step, as schematically shown in FIG. 8, as a treatment for stopping the polymerization reaction, the solution 205 is subjected to the funnel 150 and filtered, and then the polymerization initiator 108, Cleaning is performed to remove the surfactant 103 and the like. Through the above-described treatment, a spherical mother particle intermediate 53 is obtained as schematically shown in FIG. The mother particle intermediate 53 becomes a mother particle 51 by crosslinking the particle material contained in the mother particle intermediate 53 in a crosslinking step described later.

  Subsequent to the polymerization step, a child particle embedding step is performed (S20). In the child particle embedding step of this embodiment, the child particles 52 are made to collide with the surface of the mother particle 51 by a hybridization method using a hybridization system (NHS) manufactured by Nara Machinery Co., Ltd.

  The treatment method by the hybridization method is as follows. Hybridization system (NHS) manufactured by Nara Machinery Co., Ltd. used as a processing device controls a mixer that forms a mixture of powders, a hybridizer that joins fine powders together in a dry process, a collector, and each device. And a control panel for operating the apparatus. In the child particle embedding step, the NHS is used to disperse the mother particle intermediate 53 and the child particles 52 in the gas phase (FIG. 10), and to give mechanical thermal energy mainly composed of impact force to the particles. Thus, the child particles 52 are embedded in the surface of the mother particle intermediate 53. As schematically shown in FIG. 11, the child particles 52 are bonded to the surface of the mother particle intermediate 53 in a partially embedded state by this child particle embedding step.

  Subsequently, a crosslinking step is performed (S30). In the cross-linking step, the cross-linkable functional group included in the resin material is reacted to cross-link the particle material. When the resin material has a crosslinkable functional group that undergoes a crosslinking reaction by light irradiation as a crosslinkable functional group, in this crosslinking step, as schematically shown in FIG. 12, light having a predetermined wavelength (in FIG. (Illustrated by an arrow 140) is irradiated to the mother particle intermediate 53 that has undergone the child particle embedding step. The predetermined wavelength is appropriately determined according to the crosslinkable functional group. In this cross-linking step, the cross-linkable functional group reacts to cross-link the particle material, and the resin material has a finer stitch-like cross-linking structure than before the cross-linking step, and is harder than the base particle intermediate 53. Is formed. For example, when polyvinyl cinnamate having a cinnamoyl group as a crosslinkable functional group is included in the particle material of the mother particle intermediate 53 that has undergone the child particle embedding step, a crosslinking reaction occurs between the cinnamoyl groups by light irradiation. As it proceeds, the polyvinyl cinnamate is crosslinked. Also, for example, when the particle material of the mother particle intermediate 53 that has undergone the child particle embedding step includes polyazide vinyl benzoate having an azide group as a crosslinkable functional group, nitrene is generated by light irradiation, and The polyazide vinyl benzoate is crosslinked by the ring reaction. Further, for example, the particle material of the mother particle intermediate 53 that has undergone the child particle embedding step includes a polymer having a diazo group as represented by the above general formulas (1) to (7) as a crosslinkable functional group. In some cases, radicals generated by photolysis of diazo groups by light irradiation are contained in the main polymer. For example, a reaction with a hydroxyl group causes a crosslinking reaction to crosslink two or more polymers. The child particles 52 that have undergone such a crosslinking step are firmly surrounded by the particle material of the mother particles 51 that are crosslinked in a network, and the child particles 52 are less likely to be separated from the mother particles 51.

  In this crosslinking step, when the child particle 52 is a resin, or when the surface of the child particle 52 has a crosslinkable functional group or a functional group that reacts with the crosslinkable functional group, the mother particle intermediate The particle material contained in 53 and the child particles 52 are cross-linked. In this case, since the mother particle 51 and the child particle 52 can be chemically bonded, the effect that the child particle 52 becomes more difficult to peel from the mother particle 51 is obtained.

  As described above, the black charged particles 50 are manufactured by the charged particle manufacturing method of the present embodiment. The white charged particles 60 can also be manufactured by a similar manufacturing method.

  According to the charged particle manufacturing method of the present embodiment described in detail above, the mother particle intermediate 53 is formed by polymerizing the particle material including the resin material having a crosslinkable functional group in the polymerization step (S10). Thereafter, in the child particle embedding step (S20), the child particles are embedded in the surface of the mother particle intermediate 53. In the polymerization step (S10), the polymerization reaction proceeds, but the crosslinking reaction has not progressed, or even if the crosslinking reaction has progressed, it is only a part. When the polymerization reaction is advanced by emulsion polymerization in the polymerization step, the temperature of the polymerization reaction system can be easily adjusted.

  After the child particle embedding step (S20), the particle material contained in the particles is cross-linked (S30). When the crosslinkable functional group contains at least one of a diazo group and an azide group, the reaction conditions for proceeding only the polymerization reaction without proceeding the crosslinking reaction in the polymerization step (S10) are as follows. It can be easily set by the presence or absence of light irradiation. By this cross-linking step (S30), the particle material formed in the polymerization step is cross-linked in the form of a network to form mother particles 51. The mother particles 51 are harder than the mother particle intermediate 53 before the crosslinking step, and the child particles 52 are firmly surrounded by the particle material crosslinked in a network. Therefore, in the charged particles 50 and 60 manufactured by the manufacturing method of the present invention, the child particles are not easily separated from the mother particles. For this reason, in the electrophoretic display panel 2 using the charged particles 50 and 60, the contrast of the electrophoretic display panel 2 is lowered due to the child particles constituting the charged particles being peeled off from the mother particles. It can be avoided.

  The present invention is not limited to the first and second embodiments described in detail above, and various modifications may be made without departing from the scope of the present invention. For example, an electrophoretic display panel of the present invention includes a pair of substrates that are transparent at least one of them, a display unit that is formed between the substrates and generates an electric field, and is included in the display unit. It is only necessary to include charged particles that are manufactured by a manufacturing method and move by the action of an electric field. For this reason, for example, in the electrophoretic display panel 2 of the first and second embodiments, one back electrode layer 22 is provided for one of the display units 30 divided by the partition wall 32. A plurality of back electrode layers 22 may be provided in the display unit 30.

  In the electrophoretic display panel of this embodiment, the transparent electrode layer 12 is used as a common electrode for all the display units 30 and the back electrode layer 22 is provided separately for each display unit 30. The transparent electrode layer 12 may be provided separately for each display unit 30 as a common electrode for all the display units 30.

  In the above embodiment, the active matrix electrophoretic display panel has been described. However, it goes without saying that the present invention may be applied to a simple matrix electrophoretic display panel.

  Furthermore, although the electrophoretic display panel 2 of the above embodiment includes two types of charged particles, the present invention is not limited to this, and may include one type or three or more types of charged particles. The color of the charged particles is not limited to black and white, and two different charged particles may be used, or two or more kinds of charged particles may be used. In addition, the charged particles 50 and 60 of the above embodiment have an externally added structure in which a large number of child particles are bonded to the surface of the mother particle in each of the black charged particle 50 and the white charged particle 60. It may be a structure. When there are a plurality of types of charged particles having an externally added structure, only a part of the charged particles may be manufactured by the above-described manufacturing method. The charged particles are preferably produced by the production method as described above.

  In addition, the child particles 52 of the above embodiment play a role of preventing the black charged particles 50 from adhering to the display substrate 10 and the back substrate 20 or aggregating the black charged particles 50 and the white charged particles 60. Although it was a member, it is not limited to this. For example, the child particle 52 may be a member arranged on the surface of the base particle 51 in order to adjust the charge amount of the charged particle or adjust the fluidity of the charged particle.

  In the charged particle manufacturing method of the above embodiment, the child particles 52 are embedded in the surface of the mother particle intermediate 53 by the hybridization method in the child particle embedding step (S20). However, the method is not limited to this method. .

  In the method for producing charged particles of the above embodiment, only the crosslinking reaction is allowed to proceed in the crosslinking step (S30). However, the charged particles are polymerized in the particle material contained in the mother particle intermediate subjected to the polymerization step. When a monomer or oligomer that is not present is contained, in the crosslinking step, the polymerization reaction may be advanced in addition to the crosslinking reaction. In this case, since the child particles can be surrounded more firmly, the effect that the child particles are less likely to be separated from the mother particles can be further enhanced.

  In the charged particle manufacturing method of the above embodiment, the particle material used in the polymerization step is exemplified by monomers, oligomers and polymers having a crosslinkable functional group as a resin material having a crosslinkable functional group. However, a crosslinking agent having a crosslinkable functional group such as a tetradinium salt having a diazo group may be provided as a resin material having a crosslinkable functional group. Furthermore, as in Modification 1 described later, the particulate material used in the polymerization step may not include a resin material having a crosslinkable functional group. Next, as a first modification, a case where a crosslinking agent having a crosslinkable functional group and a particle material contained in the mother particle intermediate are reacted in the crosslinking step to crosslink the particle material contained in the mother particle intermediate will be described. To do.

  The charged particle manufacturing method of Modification 1 includes a polymerization step, a child particle embedding step, and a crosslinking step in this order, as in the above embodiment. Among these, the polymerization step and the crosslinking step differ from the above embodiment. The description of the child particle embedding step similar to that in the above embodiment will be omitted, and the polymerization step and the crosslinking step will be described.

  First, in the polymerization step, at least one of monomers or oligomers contained in the particulate material is polymerized. In Modification 1, the particle material used in the polymerization step includes a resin material as a constituent element, and if necessary, a resin material including a crosslinkable functional group, a colorant, a charge control agent, and other additives as constituent elements. Prepare. Therefore, unlike the above embodiment, the particle material may or may not include a resin material having a crosslinkable functional group as described above. However, the particulate material used in the polymerization step includes a resin material that reacts with a crosslinking agent added in the crosslinking step described later. For example, in the cross-linking step, when a tetrazonium salt having two diazo groups is added as a cross-linking agent, a monomer or oligomer having a functional group (for example, a hydroxyl group) that proceeds from the diazo group as a starting point is used as a resin material. Use. When a resin material having a crosslinkable functional group is included, it is preferable to perform the polymerization step under conditions where the crosslinking reaction does not start or proceed. On the other hand, when a resin material having a crosslinkable functional group is not included, there is no possibility that the crosslinking reaction proceeds, and therefore, the reaction conditions for the polymerization step can be set without considering that the crosslinking reaction proceeds.

  In the crosslinking step, the mother particle intermediate and a crosslinking agent having a crosslinkable functional group are added to the reaction system to crosslink the particle material of the mother particle intermediate. As a crosslinkable functional group with which a crosslinking agent is provided, it is the same as the crosslinkable functional group with which the resin material of the said embodiment is provided. Moreover, as a crosslinking agent provided with a crosslinkable functional group, the crosslinker provided with two or more crosslinkable functional groups, for example, the tetrazonium salt provided with two diazo groups is used. In this cross-linking step, it is preferable to advance the cross-linking reaction while stirring in order to prevent the cross-linking reaction from proceeding between the plurality of mother particle intermediates. The reaction conditions in the crosslinking step are appropriately determined according to the crosslinking agent. For example, when the crosslinking agent has a crosslinkable functional group that undergoes a crosslinking reaction by light irradiation, in this crosslinking step, light having a predetermined wavelength is used. The mother particle intermediate that has undergone the child particle embedding process is irradiated. The predetermined wavelength is appropriately determined according to the crosslinkable functional group. The child particles that have undergone the cross-linking step of Modification 1 are firmly surrounded by the particle material of the base particles that are cross-linked in the same manner as in the above-described embodiment, and the child particles are unlikely to peel off from the base particles.

  According to Modification 1 described above, in the crosslinking step, a crosslinking agent having a crosslinkable functional group is added to crosslink the particle material contained in the mother particle intermediate. For this reason, the particle material contained in the mother particle intermediate can be crosslinked in the crosslinking step without causing the crosslinking reaction to proceed in the polymerization step.

2 is a partial cross-sectional view showing a schematic configuration of an electrophoretic display panel 2. FIG. 3 is a schematic view schematically showing the structure of black charged particles 50. FIG. 4 is a manufacturing flow of black charged particles 50. It is explanatory drawing for demonstrating the reaction system which added surfactant 103 in the superposition | polymerization process. It is explanatory drawing for demonstrating the reaction system which added the monomer 105, the resin material 107 provided with a crosslinkable functional group, and the coloring agent 106 in the superposition | polymerization process. It is explanatory drawing for demonstrating the state which added the polymerization initiator 108 to the reaction system in the superposition | polymerization process. It is explanatory drawing for demonstrating the state in which the polymerization reaction between the monomers 105 advanced and the polymer was formed in the superposition | polymerization process. It is explanatory drawing for demonstrating the process which filters the solution 205 in order to stop a polymerization reaction in a superposition | polymerization process. It is explanatory drawing for demonstrating the mother particle intermediate body 53 formed in the superposition | polymerization process. It is explanatory drawing for demonstrating the state by which the mother particle intermediate body 53 and the child particle 52 were provided to the hybridization system (NHS) in the child particle embedding process. 4 is a schematic diagram schematically showing a state in which child particles 52 are embedded in the surface of a mother particle intermediate 53. FIG. It is explanatory drawing for demonstrating the state in which light is irradiated to the mother particle intermediate body 53 in which the child particle 52 was embedded in a bridge | crosslinking process.

Explanation of symbols

2 Electrophoretic display panel 10 Display substrate 20 Rear substrate 30 Display unit 50 Black charged particles 51 Mother particles 52 Child particles 53 Mother particle intermediate 60 White charged particles

Claims (7)

In a method for producing charged particles comprising a mother particle and a plurality of child particles arranged on the surface of the mother particle,
A polymerization step of polymerizing a particle material including a resin material to form a mother particle intermediate;
A child particle embedding step of embedding the child particles in the surface of the mother particle intermediate;
A charged particle manufacturing method comprising: a cross-linking step of forming the base particles by cross-linking the particle material contained in the base particle intermediate after the child particle embedding step.   The method for producing charged particles according to claim 1, wherein in the polymerization step, a particle material including a resin material is emulsion-polymerized to form a mother particle intermediate. In the polymerization step, a particle material containing a resin material having a crosslinkable functional group is polymerized to form a mother particle intermediate,
3. The method for producing charged particles according to claim 1, wherein in the crosslinking step, the crosslinkable functional group is reacted to crosslink the particle material to form the mother particles. 4.   4. The cross-linking step includes adding a cross-linking agent having a cross-linkable functional group to cross-link the particle material contained in the base particle intermediate to form the base particle. The manufacturing method of the charged particle in any one.   The method for producing charged particles according to claim 3 or 4, wherein the crosslinkable functional group includes at least one of a diazo group and an azide group.   Charged particles produced by the method for producing charged particles according to claim 1.   An electrophoretic display panel comprising the charged particles according to claim 6.

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