JP2013007922A - Electrifiable child particle, display particle and information display panel using the display particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrifiable child particle that is a constituent of a display particle formed by fixing the electrifiable child particle on a mother particle surface and capable of keeping initial performance for a long time without causing a change in an electrification property, etc. of the display particle at the time of continuous driving in an information display device, etc. that use the display particle, and provide the display particle and an information display panel using the display particle.SOLUTION: An electrifiable child particle is a constituent of a display particle that is formed by fixing the electrifiable child particle on a mother particle surface and that is used for an information display panel for displaying image information by putting the display particle between two facing substrates at least one of which is transparent and by moving the display particle through provision of electric field between the substrates. The electrifiable child particle contains a cross-linking resin formed by polymerizing monomer components including a polymerizable monomer and cross-linkable monomer, and remaining monomer concentration by pyrolysis gas chromatography is 5000 ppm or less.

Description

  The present invention relates to a charging element constituting composite display particles used in an information display panel for displaying information such as images by moving display particles sealed between two opposing substrates at least one of which is transparent The present invention relates to particles, display particles, and an information display panel using the particles.

  A liquid crystal display (LCD) is widely used as an information display device. However, it is generally known that liquid crystal display devices have drawbacks such as large power consumption and narrow viewing angle. Therefore, as an alternative to the liquid crystal display device, a plurality of cells partitioned by a partition are formed between two substrates (for example, glass substrates) at least one of which is transparent, and display particles configured as a particle group in the cells. There is a proposal for an information display panel that displays information such as an image by moving the display particles and enclosing the particles (see, for example, Patent Document 1).

  The information display panel as described above displays information such as an intended image by electrically moving display particles between substrates according to information such as an image. Here, the particle group (display particles) repeatedly moves in the space between the substrates in accordance with the information requested to be displayed. Accordingly, there is a demand for homogeneous and durable display particles that constitute a particle group as display particles.

  Therefore, other fine particles were added to the large particles that serve as the base of the display particles, with the intention of improving the durability of the display particles when the electrical properties were stabilized and the display was repeatedly rewritten. A technique relating to so-called composite particles has been proposed (see, for example, Patent Document 2). This technique discloses a composite display particle in which a child particle is added to the surface of a mother particle, and an information display panel using the same. By adopting a form in which child particles having a predetermined condition are added to the mother particles, it is possible to improve durability when the display particles are repeatedly moved for display rewriting.

International Publication No. 2003/050606 Pamphlet JP 2006-72283 A

  However, when the composite display particles in which charged child particles (chargeable child particles) are added to the surface of the mother particles described above are used in an information display device provided with an information display panel, The surface characteristics may change, and a phenomenon such as a decrease in display contrast may occur due to a change in charging characteristics. As a result, there is a problem that the initial performance cannot be maintained for a long time.

  The present invention has been made in view of the above situation, and in an information display device or the like using display particles in which chargeable particles are fixed to the surface of the mother particles, the charging characteristics of the display particles during continuous driving, etc. It is an object of the present invention to provide a charged particle, a display particle, and an information display panel using the same, which constitute display particles that can maintain initial performance over a long period of time without change.

The above problems are solved by the present invention described below. That is, the present invention
[1] The display particles are formed by encapsulating display particles formed by fixing charged particles on the surface of the mother particles between two opposing substrates, at least one of which is transparent, and applying an electric field between the substrates. Chargeable particles constituting the display particles used in an information display panel for displaying image information by moving
Containing a crosslinked resin obtained by polymerizing a monomer component containing a polymerizable monomer and a crosslinking monomer;
Chargeable particles having a residual monomer concentration of 5000 ppm or less by pyrolysis gas chromatography,
[2] The chargeable particle according to [1], wherein the structural unit derived from the crosslinkable monomer is contained in an amount of 20 mol% or more of the entire structural unit derived from the raw material monomer component constituting the crosslinked resin.
[3] The charged particle according to [1] or [2], wherein the crosslinked resin is one or more selected from a crosslinked olefin resin, a crosslinked styrene resin, a crosslinked acrylic resin, a crosslinked urethane resin, and a crosslinked epoxy resin.
[4] Chargeable child particles according to any one of [1] to [3], wherein when a constant load is applied, the deformation rate represented by the following formula (1) is 30% or less,
Deformation rate (%) = {[closest packing height (mm) −height after loading (mm)] / closest packing height (mm)} × 100 (1)
[5] The chargeable child particles according to any one of [1] to [4] are fixed to the surface of the mother particle, and at least one of them is sealed between two transparent substrates, and an electric field is generated between the substrates. Display particles used for an information display panel in which display particles move between the substrates to display image information by being applied, and information display using the display particles according to [6] [5] Panel,
Is to provide.

  According to the present invention, in an information display device or the like using display particles in which the charge particles are fixed on the surface of the mother particles, the initial performance is maintained without changing the charging characteristics of the display particles even during continuous driving. It is possible to provide a charged particle, a display particle, and an information display panel using the same, which constitute display particles that can maintain the above for a long time.

It is a schematic diagram for demonstrating an example of the display particle comprised using the electrification child particle of this invention. (A), (b) is an expanded sectional view which shows an example of the information display panel, respectively. (A), (b) is an expanded sectional view which shows another example of the information display panel, respectively.

Hereinafter, the present invention will be described with reference to embodiments.
<Charging child particles, display particles>
In the chargeable particle of this embodiment, display particles formed by fixing the chargeable particle to the surface of the mother particle are sealed between two opposing substrates, at least one of which is transparent, and an electric field is applied between the substrates. The chargeable particles constituting the display particles used in the information display panel for moving the display particles to display image information by polymerizing a monomer component containing a polymerizable monomer and a crosslinkable monomer And a residual monomer concentration by pyrolysis gas chromatography is 5000 ppm or less.
Further, the display particles of the present embodiment are characterized in that the chargeable child particles are fixed to the surface of the mother particles.

Hereinafter, the charged particles and display particles of the present embodiment will be described in detail with reference to the drawings. In the present embodiment, the “chargeable child particles” are resin fine particles obtained by polymerizing a polymerization component containing a monomer having one or more polar groups in the molecule, except that this monomer is not included. It means that the charge amount (positive or negative) is higher or lower than resin fine particles obtained by polymerizing similar polymerization components.
The chargeable child particles of the present embodiment (hereinafter sometimes simply referred to as “child particles”) are, for example, a composite display in which at least one of the information display panels described later is sealed between two transparent substrates. The display particles are configured by fixing the chargeable child particles of the present embodiment on the surface of the mother particles. FIG. 1 is a schematic view showing an example of composite display particles (display particles of the present embodiment) configured using the chargeable particles of the present embodiment.

  In FIG. 1, the display particles 31 are formed by fixing the chargeable child particles 33 of this embodiment on the surfaces of base particles 32. That is, the chargeable child particles 33 are fixed to the surface of the mother particles 32 to form composite display particles 31.

The present embodiment is intended to improve the display performance of display particles in which the child particles are uniformly added to the surface of the mother particles by the above “adhesion”. The information display panel that employs the display particles 31 shown in FIG. 1 in which the child particles are uniformly arranged on the surface of the mother particles can improve the durability when display rewriting is repeated.
Here, the “adhesion” means that the charged particles 33 are embedded in the surface of the mother particles 32 and fixed by adhesion, adhesion, etc., and therefore, the charged particles 33 do not move when the display is rewritten repeatedly. Means things.

In the present embodiment, the chargeable child particles 33 have a residual monomer concentration of 5000 ppm or less as determined by pyrolysis gas chromatography.
As will be described later, since the chargeable particles of this embodiment are produced by an emulsion polymerization method or a non-aqueous dispersion polymerization method, unreacted monomers are present in the obtained resin fine particles. That is, when a child particle is produced by the above polymerization method using a large amount of a crosslinkable monomer with respect to the polymerizable monomer, the fluctuation of the polymer network is suppressed as the polymerization crosslinking proceeds, so the penetration rate of the monomer into the resin fine particles The monomer cannot be reacted due to the decrease in the activity or the activity at the active end, and the like, so that it will be present as unreacted monomer (residual monomer) in the finally obtained child particles.

As a result of the study by the present inventors, when the residual monomer is present in the child particles after the child particles are thus manufactured, the display particles are brought into contact with each other when the display panel is driven, Residual monomers migrate to the partner particles. This shift causes a decrease in the charge amount of the display particles, and there is a concern that driving failure may occur in the information display panel. Specifically, when driving the display panel, the positively charged display particles and the negatively charged display particles move within the panel at a high speed, so that when they come into contact with each other, they rub against each other with a strong force. Become. At this time, the remaining (unreacted) monomer in the child particles is transferred from the positively charged display particles to the negatively charged display particles or from the negatively charged display particles to the positively charged display particles. The charging characteristics of the display particles and the negatively charged display particles change (deteriorate) and the charge balance between the particles in the panel becomes unstable, causing problems in driving the display particles and in the display contrast associated therewith. .
For this reason, reducing the amount of the unreacted residual monomer by various treatments described later is effective for enhancing the durability of the display particles. In the present embodiment, necessary characteristics corresponding to the above in the chargeable particle 33 and the display particle 31 are clarified.

  That is, in this embodiment, when the component analysis is performed on the chargeable child particles by pyrolysis gas chromatography, the residual monomer concentration needs to be 5000 ppm or less. When the residual monomer concentration exceeds 5000 ppm, display characteristics deteriorate when repeated display is performed on the display panel. More specifically, when the residual monomer concentration is 5000 ppm or less, display rewriting was repeatedly performed in the information display panel using the composite display particles 31 using the chargeable particles 33 of the present embodiment. Sometimes, the chargeability of the display particles 31 can be stabilized, thereby improving the durability of the display particles 31 during repeated display rewriting and further improving the display stability of the information display panel. It becomes possible.

The residual monomer concentration needs to be 5000 ppm or less, preferably 3000 ppm or less, and more preferably 2000 ppm or less. Ideally, the lower limit is 0 ppm.
The residual monomer includes at least one of a polymerizable monomer and a crosslinkable monomer described later. Moreover, the measuring method of the pyrolysis gas chromatography for calculating | requiring a residual monomer density | concentration is mentioned later.

Further, in order to improve the durability of the display particles 31 in repeated display, it is necessary not only that the child particles are not easily peeled off from the mother particles, but also that the child particles attached and fixed to the mother particles are not easily deformed. is there. From this point of view, in the chargeable particle 33 of the present embodiment, it is preferable that the deformation rate represented by the following formula (1) is 30% or less when a constant load is applied.
Deformation rate (%) = {[closest packing height (mm) −height after loading (mm)] / closest packing height (mm)} × 100 (1)
By setting the deformation rate within this range, not only the child particles embedded in the mother particles are difficult to peel off from the mother particles, but also the child particles peeled off from the mother particles or the child particles fixed to the mother particles are not easily deformed. Thus, durability when repeatedly used as display particles can be improved. The deformation rate is more preferably 25% or less.

The chargeable particle 33 in the present embodiment preferably contains a crosslinked resin, and the crosslinked resin is one or more selected from a crosslinked olefin resin, a crosslinked styrene resin, a crosslinked acrylic resin, a crosslinked urethane resin, and a crosslinked epoxy resin. It is preferable that By containing these cross-linked resins, the above-described deformation rate of the fine particles can be set within a desired range, and chargeable particles excellent in chargeability and charge stability can be obtained.
Among the crosslinked resins, it is more preferable to use a crosslinked styrene resin or a crosslinked acrylic resin.

In order to obtain the chargeable particles 33 of the present embodiment, first, resin fine particles are formed by polymerizing and crosslinking a monomer component (polymerizable monomer, crosslinkable monomer) which is a raw material of the resin using a polymerization initiator.
Examples of the polymerizable monomer used as a raw material for the resin constituting the chargeable particle 33 include styrene monomers such as styrene, α-methylstyrene, and α-chlorostyrene; methyl acrylate, ethyl acrylate, butyl acrylate, and cyclohexyl acrylate. Acrylic monomers such as; methacrylate monomers such as methyl methacrylate, ethyl methacrylate, butyl methacrylate and cyclohexyl methacrylate; cycloolefin monomers such as vinylcyclohexane; vinyl naphthalene, 4-vinylphenyl, 1,1-diphenylethylene Etc .; and a monomer having one vinyl group. These may be used alone or in combination of two or more.

  In this embodiment, the child particles include a crosslinked resin crosslinked with a crosslinking monomer, but the crosslinking may be performed during the polymerization of the monomer or after the polymerization. As the crosslinkable monomer, a compound having at least two vinyl groups is preferably used from the viewpoint of further improving the strength of the fine particles. Examples of the crosslinkable monomer include divinylbenzene, divinylnaphthalene, divinylbiphenyl, and ethylene glycol dimethacrylate. These may be used alone or in combination of two or more.

The crosslinkable monomer is a raw material monomer (monomer) component in which the structural unit derived from the crosslinking agent constitutes the crosslinked resin in the entire monomer component containing the crosslinkable monomer (that is, in the crosslinked resin after polymerization) It is preferable that 20 mol% or more of the entire structural unit derived from (1) is contained. By making content of a crosslinkable monomer into the said range, the said deformation rate in a child particle can be made into a desired range.
As for content of the said crosslinkable monomer, it is more preferable that they are 30 mol% or more and 60 mol% or less.

The polymerization of the monomer can be performed according to an emulsion polymerization method, a non-aqueous dispersion polymerization method, a seed polymerization method, or the like. Among these, the emulsion polymerization method is preferable.
Specifically, the emulsion polymerization method can be carried out in an appropriately selected solvent in the presence of a polymerization initiator by using it as an emulsifier having a surfactant effect. The solvent used for the polymerization is not particularly limited, and a solvent used in an ordinary emulsion polymerization method can be used. Examples thereof include purified water and a mixed liquid of an arbitrary ratio of purified water and methanol.
In the non-aqueous dispersion polymerization method, a solution in which the monomer, polymerization initiator and dispersion stabilizer are dissolved in a suitable solvent is placed at a predetermined temperature to polymerize the monomer. The obtained polymerization solution is filtered, washed with an appropriately selected solvent, and then fine particles are collected by a centrifugal separator or the like and dried in an oven or the like at a predetermined temperature to obtain resin fine particles.

  The emulsion polymerization employed in the production of the child particles may be carried out in the same manner as used in the conventional production of particles, and an emulsifier may or may not be used depending on the case. When an emulsifier is used, for example, linear and branched such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium myristyl sulfate, ammonium myristyl sulfate, sodium cetyl sulfate, ammonium cetyl sulfate, sodium stearyl sulfate, ammonium stearyl sulfate, sodium oleyl sulfate, ammonium oleyl sulfate Alkyl sulfate ester salt; sodium lauryl sulfonate, ammonium lauryl sulfonate, sodium myristyl sulfonate, ammonium myristyl sulfonate, sodium cetyl sulfonate, ammonium cetyl sulfonate, sodium stearyl sulfonate, ammonium stearyl sulfonate, sodium oleyl sulfonate, Linear and branched alkanes such as ammonium oleyl sulfonate Α-olefin sulfonates such as sodium α-olefin sulfonate and ammonium α-olefin sulfonate; nonylphenol sulfate sodium salt, nonylphenol sulfate ammonium salt, dodecylphenol sulfate sodium salt (lauryl sulfate sodium salt) ), Alkylphenol sulfates such as ammonium dodecylphenol sulfate (ammonium lauryl sulfate); alkylbenzenes such as sodium dodecylbenzenesulfonate (sodium laurylbenzenesulfonate), ammonium dodecylbenzenesulfonate (ammonium laurylbenzenesulfonate) Sulfonate: Sodium butyl naphthalene sulfonate, Butyl naphthalene sulfone Alkyl naphthalene sulfonates such as ammonium; alkyl sulfosuccinates such as sodium dioctyl sulfosuccinate and sodium monooctyl sulfosuccinate; sodium dodecyl diphenyl ether disulfonate (sodium lauryl diphenyl ether disulfonate), ammonium dodecyl diphenyl ether disulfonate (ammonium lauryl diphenyl ether disulfonate) ) Alkyl diphenyl ether disulfonates such as naphthalenesulfonic acid formalin condensate salts, polyoxyethylene lauryl ether sodium sulfate, polyoxyethylene lauryl ether ammonium sulfate, polyoxyethylene myristyl ether sodium sulfate, polyoxyethylene myristyl ether ammonium sulfate, polyoxyethylene Polyoxyethylene alkyl ethers such as sodium polyethylene cetyl ether sulfate, ammonium polyoxyethylene cetyl ether sulfate, sodium polyoxyethylene stearyl ether sulfate, ammonium polyoxyethylene stearyl ether sulfate, sodium polyoxyethylene oleyl ether sulfate, ammonium polyoxyethylene oleyl ether sulfate Sulfate ester salt; polyoxyethylene nonylphenyl ether sulfate sodium salt, polyoxyethylene nonylphenyl ether sulfate ammonium salt and other polyoxyethylene alkylphenyl ether sulfate salts; polyoxyethylene-polyoxypropylene block copolymer sulfuric acid Ester sodium salt, polyoxyethylene-polyoxybuty Sulfate ester salt of polyoxyethylene-polyoxyalkylene block copolymer such as sulfuric acid ester sodium salt of polyblock copolymer; sulfate ester sodium salt of polyoxyethylene-polyoxypropylene block copolymer, polyoxyethylene-polyoxypropylene block copolymer Examples include sulfuric acid ester salts of alkyl ethers of polyoxyethylene-polyoxyalkylene block copolymers, such as sulfuric acid sodium salt of dodecyl ether of ethylene-polyoxybutylene block copolymers. A combination of the above may also be used.

Examples of the polymerization initiator used for the polymerization of the monomer of the binder resin include persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate; hydrogen peroxide solution, benzoyl peroxide, t-butylperoxy-2-ethyl Hexanoate, 3,5,5-trimethylhexanoyl peroxide, di-t-butyl peroxide, t-butylperoxy-2-ethylbutanoate, t-hexylperoxy-2-ethylhexanoate, organic peroxides such as t-butylperoxypivalate, diisopropylperoxydicarbonate, di-t-butylperoxyisophthalate, and t-butylperoxyisobutyrate; 2,2′-azobis [2- ( Trifluoromethylsulfonic acid-2-methylimidazolin-2-yl)] propane, 2, 2′-azobis [2- (2-methylimidazolin-2-yl)] propane hydrochloride, 2,2′-azobis [2- (2-methylimidazolin-2-yl)] propane sulfate, 2,2 ′ -Azobis (1-imino-1-pyrrolidino-2-methylpropane) hydrochloride, 2,2'-azobis [2- (trifluoromethylbenzenesulfonic acid-2-methylimidazolin-2-yl) propane, 2,2 Imidazoline groups such as' -azobis [2- (toluenesulfonic acid-2-methylimidazolin-2-yl) propane, 2,2'-azobis [2- (benzenesulfonic acid-2-methylimidazolin-2-yl) propane] An azo initiator having a pyridine group such as 4,4′-azobis [4-cyanovaleric acid (methylpyridine) amide]; 4,4′-azobis [4-sia Valeric acid (methylamine) amide], 4,4′-azobis [4-cyanovaleric acid (methylcyclohexylamine) amide], 2,2-azobis (2-methyl-N- (2-hydroxyethyl) propionamide, An azo initiator having an amino group such as 2,2′-azobis (2-amidinopropane) dihydrochloride; 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2,4-dimethyl) And other azo initiators such as 2,2′-azobisisobutyronitrile, and these may be used alone or in combination of two or more.
Among these, an organic peroxide is preferable because an amount of residual monomers can be reduced, and an organic peroxide ester compound (peroxyester) is more preferable. Moreover, as the usage-amount of the said polymerization initiator, it is preferable to use in 0.03-80 mass% with respect to the monomer amount. The polymerization initiator may be added all at once at the beginning of the polymerization or may be added during the polymerization.

  The polymerization temperature in the polymerization is preferably 50 ° C. or higher, more preferably 60 to 90 ° C. Moreover, the reaction time of superposition | polymerization becomes like this. Preferably it is 1 to 96 hours, More preferably, it is 12 to 48 hours.

After the polymerization of the monomer components as described above, the obtained polymerization solution is filtered, washed with an appropriately selected solvent (for example, methanol, acetone, n-hexane, etc.), and then polymerized by centrifugation. By collecting the product (fine particles) and drying it at an appropriately selected temperature and drying period, for example, 2 to 24 hours at 60 to 120 ° C., resin fine particles made of a crosslinked resin can be obtained.
When the resin fine particles in this embodiment are prepared by emulsion polymerization using an emulsifier or dispersion polymerization using a surfactant, the amount of residual emulsifier and residual surfactant in the resin fine particles is 5000 ppm or less by washing with the solvent. It is preferable to make it 2000 ppm or less.

  As the resin fine particles obtained above (that is, the chargeable particles of the present embodiment), particles having an average particle diameter of 30 to 2000 nm are preferably used, and particles of 80 to 500 nm are more preferably used. When the average particle size of the resin fine particles is less than 30 nm, the progress of embedding of the child particles into the mother particles is accelerated, and there are cases where sufficient durability for use as particles having a composite structure cannot be obtained. On the other hand, if the average particle diameter of the resin fine particles exceeds 2000 nm, embedding as a child particle becomes difficult and it may be impossible to produce particles having a composite structure.

  In the resin fine particles, a considerable amount of unreacted monomer (residual monomer) is present. The chargeable child particles of the present embodiment can be obtained by subjecting the obtained fine particles to a treatment for reducing the residual monomer amount. The treatment is not particularly limited as long as it is a treatment capable of reducing the amount of unreacted monomer (residual monomer amount) in the resin fine particles, and examples thereof include a heat drying treatment and a reduced pressure drying treatment. Further, a combination of these processes may be performed.

The heat drying treatment is a treatment in which fine particles after polymerization and drying are heated in air to distill off unreacted monomers. As treatment conditions, for example, it is preferable to leave the substrate at a heating temperature of 40 ° C. or higher and 100 ° C. or lower for 5 hours or longer. Moreover, you may carry out simultaneously with drying of the said microparticles | fine-particles.
The vacuum drying treatment is a treatment in which fine particles after polymerization and drying are dried under reduced pressure to distill off unreacted monomers. As processing conditions, for example, it is preferable to leave the drying pressure in an atmosphere of 0.001 Pa to 0.2 Pa for 2 hours or more at room temperature (20 ° C. to 30 ° C.). Moreover, you may carry out simultaneously with drying of the said microparticles | fine-particles. Furthermore, it may be performed in combination with the heat drying treatment. In addition, the case where the heat drying process or the reduced pressure drying process is performed simultaneously with the drying after the polymerization may be collectively referred to as “drying process”.

  As a method of the heat drying treatment and / or vacuum drying treatment, fine particles are laid in a container such as a glass petri dish or a metal vat, a method of heating drying treatment, or a method of putting in a vacuum drying treatment oven, spray drying, rotary kiln, etc. A method of using a heat drying process and / or a reduced pressure drying apparatus is preferable. The apparatus is not limited to these apparatuses as long as the fine particles are uniformly heated and dried and / or dried under reduced pressure.

  By applying the treatment for reducing the amount of unreacted residual monomer as described above to the resin fine particles, the above-described chargeable particles of this embodiment having a residual monomer amount of 5000 ppm or less can be obtained.

  Next, the mother particles 32 constituting the display particles 31 will be described. The base particles 32 can contain a charge control agent, a colorant, an inorganic additive, and the like, if necessary, in the resin as the main component, as in the conventional case. Examples of resins, colorants, and other additives will be given below.

  Examples of the resin include urethane resin, urea resin, acrylic resin, polyester resin, acrylic urethane resin, acrylic urethane silicone resin, acrylic urethane fluororesin, acrylic fluororesin, silicone resin, acrylic silicone resin, epoxy resin, polystyrene resin, styrene Acrylic resin, polyolefin resin, butyral resin, vinylidene chloride resin, melamine resin, phenol resin, fluororesin, polycarbonate resin, polysulfone resin, polyether resin, polyamide resin, methylpentene resin, cycloolefin resin, etc. It is also possible to mix more than one species. In particular, styrene acrylic resin, acrylic resin, polystyrene resin, polycarbonate resin, methyl pentene resin, and cycloolefin resin are preferable from the viewpoint of controlling the adhesive force with the substrate.

  The charge control agent is not particularly limited. Examples of the negative charge control agent include salicylic acid metal complexes, metal-containing azo dyes, metal-containing oil-soluble dyes (including metal ions and metal atoms), and quaternary ammonium salt systems. Examples thereof include compounds, calixarene compounds, boron-containing compounds (benzyl acid boron complexes), and nitroimidazole derivatives. Examples of the positive charge control agent include nigrosine dyes, triphenylmethane compounds, quaternary ammonium salt compounds, polyamine resins, imidazole derivatives, and the like. In addition, metal oxides such as ultrafine silica, ultrafine titanium oxide, ultrafine alumina, nitrogen-containing cyclic compounds such as pyridine and derivatives and salts thereof, various organic pigments, resins containing fluorine, chlorine, nitrogen, etc. are also charged. It can also be used as a control agent.

As the colorant, various organic or inorganic pigments and dyes as exemplified below can be used.
Examples of the black colorant include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon and the like.
Examples of blue colorants include C.I. I. Pigment blue 15: 3, C.I. I. Pigment Blue 15, Bituminous Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Metal-free Phthalocyanine Blue, Phthalocyanine Blue Partial Chlorides, Fast Sky Blue, Indanthrene Blue BC and the like.

Examples of red colorants include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, resol red, pyrazolone red, watching red, calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, Alizarin Lake, Brilliant Carmine 3B, C.I. I. Pigment Red 2 etc.
As yellow colorants, yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral first yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, C.I. I. Pigment Yellow 12 etc.
Examples of green colorants include chrome green, chromium oxide, pigment green B, C.I. I. Pigment Green 7, Malachite Green Lake, Final Yellow Green G, etc.

Examples of the orange colorant include red yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, Indanthrene Brilliant Orange RK, Benzidine Orange G, Indanthren Brilliant Orange GK, C.I. I. Pigment Orange 31 etc.
Examples of purple colorants include manganese purple, first violet B, and methyl violet lake.
Examples of white colorants include zinc white, titanium oxide, antimony white, and zinc sulfide.
Examples of extender pigments include barite powder, barium carbonate, clay, silica, white carbon, talc, and alumina white. Examples of various dyes such as basic, acidic, disperse, and direct dyes include nigrosine, methylene blue, rose bengal, quinoline yellow, and ultramarine blue.

Examples of inorganic additives include titanium oxide, zinc white, zinc sulfide, antimony oxide, calcium carbonate, lead white, talc, silica, calcium silicate, alumina white, cadmium yellow, cadmium red, cadmium orange, titanium yellow, Examples include bitumen, ultramarine blue, cobalt blue, cobalt green, cobalt violet, iron oxide, carbon black, manganese ferrite black, cobalt ferrite black, copper powder, and aluminum powder.
These pigments and inorganic additives can be used alone or in combination. Of these, carbon black is particularly preferable as the black pigment, and titanium oxide is preferable as the white pigment. Moreover, the said colorant can be mix | blended and the display particle of a desired color can be produced.

In order to obtain the mother particles 33, the resin is first pulverized with a freeze pulverizer, dried and weighed. In parallel with this, a compounding agent (for example, titanium dioxide) to be blended with the resin is prepared and weighed. The weighed base resin and compounding agent are premixed with a Henschel mixer, dried, then kneaded using a twin-screw kneader and extruded, for example, pellets having a diameter of about 2 mm and a length of about 5 mm Manufacturing.
Next, the pellets are further coarsely pulverized with a freeze pulverizer to a particle size of, for example, about 100 to 250 μm to obtain a coarsely pulverized product. After the coarsely pulverized product is dried, it is finely pulverized so as to have a particle diameter of about 8 to 10 μm, and classified to obtain mother particles of a desired size. The steps up to here are the same as those for kneading, pulverizing and classifying the resin raw material by a conventional method to obtain mother particles.

In order to uniformly add the chargeable child particles 33 to the surfaces of the mother particles 32 described later, it is effective to subject the mother particles 32 to spheroidization by heat treatment. For this reason, in this embodiment, the mother particles obtained as described above are further processed by a heat treatment apparatus. In this heat treatment apparatus, for example, particles are ejected and dispersed in hot air, the particles are melted by hot air, and spheroidized by surface tension. As the heat treatment apparatus, a melt spheronization apparatus (MR-3, manufactured by Nippon Pneumatic Industry Co., Ltd.) or the like can be used.
The treated mother particles subjected to the heat treatment (susfusion treatment) in this manner are so-called self-organized arrangements (ordered mixture) of the child particles when the child particles are added to the surface (when the child particles are combined). ) Proceeds smoothly, and the child particles can be arranged and added uniformly on the surface of the mother particles. Therefore, it is possible to produce composite particles having an ideal shape in which the child particles are uniformly arranged and added to the surface of the spherical mother particles by the child particle composite treatment.

  The display particles 31 of this embodiment are obtained by embedding (adhering) the chargeable child particles 33 in the mother particles 32 obtained as described above. Embedding can be performed by mixing and stirring the base particles 32 and the chargeable child particles 33 using a high-speed stirrer. Henschel mixer (trade name, manufactured by Mitsui Mining Co., Ltd.), super mixer (trade name, manufactured by Kawada Seisakusho Co., Ltd.), Q mixer (trade name, manufactured by Mitsui Mining Co., Ltd.), mechano-fusion system (trade name, Hosokawa Micron Co., Ltd.) Nobil Tamil (trade name, manufactured by Hosokawa Micron Corporation), Mechano Mill (trade name, manufactured by Okada Seiko Co., Ltd.), Hybridizer (trade name, manufactured by Nara Machinery Co., Ltd.), and the like.

The composite particles (display particles) obtained by embedding the chargeable child particles 33 in the base particles 32 can be subjected to surface treatment using inorganic fine particles as external additives.
Examples of the external additive include silica, titanium oxide, aluminum oxide, tin oxide, zirconium oxide, tungsten oxide, yttrium oxide, zinc oxide, calcium oxide, magnesium oxide, barium oxide, calcium carbonate, magnesium carbonate, barium carbonate, Examples thereof include titanium nitride. Of these, silica and titanium oxide are preferred. The average primary particle size of these inorganic fine particles is preferably in the range of 1 to 300 nm, more preferably in the range of 5 to 100 nm.

By charging the surface of the inorganic fine particles, the charging of the display particles can be adjusted.
Examples of the surface treatment agent that can impart positive charge to the inorganic fine particles include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, Dibutylaminopropyltrimethoxysilane, monobutylaminopropyltrimethoxysilane, dioctylaminopropyldimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, N- (2-aminoethyl)- Examples include aminosilane coupling agents such as 3-aminopropyltrimethoxysilane.
The inorganic fine particles capable of imparting positive charge are particularly preferably silica fine particles surface-treated with aminopropyltrimethoxysilane, aminopropyltriethoxysilane or dimethylaminopropyltrimethoxysilane.

Examples of the surface treatment agent that can impart negative charge to the inorganic fine particles include hexamethyldisilazane, dimethyldichlorosilane, trimethylchlorosilane, methylmethoxysilane, isobutyltrimethoxysilane, hexamethyldisilazane, tert-butyldimethylchlorosilane, Examples thereof include silazane such as vinyltrichlorosilane, vinyltrimethoxysilane, and vinyltriethoxysilane, chlorosilane, and alkoxysilane coupling agents.
The inorganic fine particles that can impart negative chargeability are particularly preferably silica fine particles that are surface-treated with hexamethyldisilazane.

  The surface treatment is performed by stirring the inorganic fine particles and the surface treatment agent. Further, a solvent may be added, and the treatment can be accelerated by heating. Further, the charge amount can be adjusted by changing the amount of the surface treatment agent, the treatment time, and the temperature, or by using a positively chargeable surface treatment agent and a negatively chargeable surface treatment agent in combination.

  The display particles of this embodiment preferably have a uniform average particle diameter d (0.5) in the range of 1 to 20 μm. If the average particle diameter d (0.5) is larger than this range, the display may not be clear. If the average particle diameter d (0.5) is smaller than this range, the cohesive force between particles becomes too large, which hinders movement as display particles. May come to you.

In the present embodiment, regarding the particle size distribution of the display particles, the particle size distribution Span represented by the following formula is preferably less than 5, and more preferably less than 3.
Span = (d (0.9) −d (0.1)) / d (0.5)
(In the above formula, d (0.5) is a numerical value representing the particle diameter in μm that 50% by volume of the particles are larger than this and 50% by volume is smaller than this, and d (0.1) is a particle smaller than this (The particle diameter in which the ratio is 10% by volume is expressed in μm, and d (0.9) is the numerical value in which the particle diameter of 90% by volume or less is expressed in μm.)
When the span represented by the above formula is less than 5, the sizes of the display particles are uniform, and movement as uniform display particles becomes possible.

  Furthermore, when an information display panel using two types of display particles having different charging polarities is used, the maximum average particle diameter d (of the display particles constituting the used information display panel is used. Preferably, the ratio of d (0.5) of the display particles exhibiting the minimum average particle diameter d (0.5) to d (0.5) of the display particles exhibiting 0.5) is 10 or less. . That is, even if the particle size distribution Span is reduced as described above, the display particles having different charging characteristics move in opposite directions, so that the display particles can be easily moved to the same size. This is preferred and this is the range.

  The particle size distribution and the particle size can be obtained from a laser diffraction / scattering method or the like. That is, when a particle to be measured is irradiated with laser light, a spatial light intensity distribution pattern of diffracted / scattered light is generated, and this light intensity pattern has a corresponding relationship with the particle diameter. It can be measured. Here, the particle size and particle size distribution in the present embodiment are obtained from a volume-based distribution. Specifically, using a Mastersizer 2000 (Malvern Instruments Ltd.) measuring machine, particles were introduced into a nitrogen stream, and the particles were analyzed using the attached analysis software (software based on volume-based distribution using Mie theory). The diameter and particle size distribution can be measured.

<Information display panel>
The information display panel according to the present embodiment uses the display particles according to the present embodiment described above, and there is no limitation on the configuration thereof. Examples thereof include a display panel that can repeatedly display and erase images. Below, the example of the information display panel using the particle | grains for display of this embodiment is demonstrated based on FIG. 2, FIG.
In the example shown in FIGS. 2 (a) and 2 (b), at least two or more kinds of display particles that are configured as a particle group having at least optical reflectance and chargeability and have different optical reflectance and charging characteristics are used. (Here, the white display particle group 3W configured to include the white display particles 3Wa and the black display particle group 3B configured to include the black display particles 3Ba are shown.) In the cell, each display particle is changed according to an electric field generated by applying a voltage between an electrode 5 (pixel electrode with TFT) provided on the substrate 1 and an electrode 6 (pixel electrode) provided on the substrate 2. Move perpendicular to the substrates 1 and 2. Then, as shown in FIG. 2A, the white display particle group 3W is visually recognized by the observer to display white dots, or as shown in FIG. 2B, the black display particle group 3B is observed. A black dot display is made to be visually recognized by a person. In addition, in FIG. 2 (a), (b), the partition in front is abbreviate | omitted. The electrodes 5 and 6 may be provided outside the substrates 1 and 2, inside the substrate, or embedded in the substrate.

  Further, in the example shown in FIGS. 3A and 3B, at least two kinds of display particles having different optical reflectance and charging characteristics, which are configured as a particle group having optical reflectance and chargeability, are used. As described above, the white display particle group 3W configured to include the white display particles 3Wa and the black display particle group 3B configured to include the black display particles 3Ba are illustrated in FIG. In each cell, display particles are applied to the substrate 1 in accordance with an electric field generated by applying a voltage between an electrode 5 (line electrode) provided on the substrate 1 and an electrode 6 (line electrode) provided on the substrate 2. 2 and move vertically. Then, as shown in FIG. 3 (a), the white display particle group 3W is visually recognized by the observer and white dot display is performed, or as shown in FIG. 3 (b), the black display particle group 3B is displayed as the observer. The black dots are displayed by visually recognizing. In addition, in FIG. 3 (a), (b), the partition in front is abbreviate | omitted. The electrodes 5 and 6 may be provided outside the substrates 1 and 2, inside the substrate, or embedded in the substrate.

  In addition, although not shown, one kind of display particles (for example, a white display particle group including white display particles) configured as a particle group having at least an optical reflectance and chargeability is used as one substrate. The display particles are moved in a direction parallel to the substrates 1 and 2 in accordance with an electric field generated by applying a voltage between the electrodes provided on each substrate and encapsulating between the substrates provided with black plates. The white display particle group may be visually recognized by the observer to perform white dot display, or the black plate color may be visually recognized by the observer to perform black dot display.

2 and 3, external electric field forming means is provided outside each of the substrates 1 and 2, and the display particles are placed on the substrate according to the electric field generated by applying a voltage between the external electric field forming means. It is also possible to perform white dot display or black dot display in the same manner by moving vertically to 1 and 2.
Further, a red color filter, a green color filter, and a blue color filter are provided on the observer side of the three cells in FIGS. 2 and 3 in order from the left side of the figure, and the display unit is configured by these three cells. Multi-color display can also be performed by performing white dot display or black dot display and changing the display method in each cell.

Hereinafter, each member constituting the information display panel using the display particles of the present embodiment will be described.
As for the substrate, at least one of the substrates is a transparent substrate 2 on which the color of display particles can be confirmed from the outside of the information display panel, and a material having high visible light transmittance and good heat resistance is preferable. The substrate 1 may be transparent or opaque. Examples of substrate materials include polymer sheets such as polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyethylene, polycarbonate, polyimide, and acrylic, flexible materials such as metal sheets, and glass and quartz. An inorganic sheet having no flexibility is mentioned. The thickness of the substrate is preferably 2 to 5000 μm, more preferably 5 to 2000 μm. If the thickness is less than 2 μm, it is difficult to maintain the strength and the uniform spacing between the substrates, and if it is thicker than 5000 μm, it is inconvenient for a thin information display panel.

As an electrode forming material when an electrode is provided on an information display panel as required, metals such as aluminum, silver, nickel, copper, and gold; indium tin oxide (ITO), indium oxide, antimony tin oxide (ATO) ), Conductive metal oxides such as zinc-doped indium oxide (IZO), aluminum-doped zinc oxide (AZO), conductive tin oxide, and conductive zinc oxide; and conductive polymers such as polyaniline, polypyrrole, and polythiophene Are appropriately selected and used. As a method for forming an electrode, a method of forming the above-described materials into a thin film by sputtering, vacuum deposition, CVD (chemical vapor deposition), coating, or the like, or a method of laminating a metal foil (for example, rolled copper foil) Alternatively, a method in which the conductive member is mixed with a solvent or a synthetic resin binder and applied. The electrode provided on the display surface side substrate 2 which is on the viewing side and needs to be transparent needs to be transparent, but the electrode provided on the back side substrate 1 does not need to be transparent. In any case, the above-mentioned material that can be patterned and is electrically conductive can be suitably used.
Note that the electrode thickness may be 0.01 to 10 [mu] m, preferably 0.05 to 5 [mu] m, as long as conductivity can be ensured and light transmittance is not hindered. The material and thickness of the electrode provided on the back side substrate 1 are the same as those of the electrode provided on the display surface side substrate described above, but need not be transparent.

The shape of the partition walls 4 provided on the substrate as required is appropriately set according to the type of display particles involved in display, the shape and arrangement of the electrodes to be arranged, and is not limited in general, but the width of the partition walls is 2 The height of the partition wall is adjusted in the range of 10 to 500 μm, preferably in the range of 10 to 200 μm.
In forming the partition wall 4, a both-rib method in which ribs are formed on each of the opposing substrates 1 and 2 and then bonded, and a single-rib method in which ribs are formed only on one substrate are conceivable. In the present embodiment, any method is preferably used.

The cells formed by the ribs 4 made of these ribs are exemplified by a square shape, a triangular shape, a line shape, a circular shape, and a hexagonal shape as viewed from the substrate plane direction, and the arrangement is exemplified by a lattice shape, a honeycomb shape, or a mesh shape. Is done. It is better to make the portion corresponding to the cross section of the partition wall visible from the display surface side (the area of the cell frame) as small as possible, and the display becomes clearer.
Examples of the method for forming the partition walls 4 include a mold transfer method, a screen printing method, a sand blast method, a photolithography method, and an additive method. Any of these methods can be suitably used for the information display panel of the present invention, and among these, a photolithography method using a resist film and a mold transfer method are suitably used.

  Furthermore, when applied to an information display panel of a system in which display particles composed of display particles are driven in a gas space, it is important to manage the gas in the void surrounding the display particles between the substrates, Contributes to improved display stability. Specifically, regarding the humidity of the gas in the void portion, the relative humidity at 25 ° C. is preferably 60% RH or less, and more preferably 50% RH or less. 2 and 3, the gap between the opposing substrate 1 and substrate 2 in FIGS. 2 and 3, electrodes 5 and 6 (when the electrode is provided inside the substrate), the occupied portion of the display particle group 3, A gas portion in contact with a so-called display particle group excluding an occupied portion of the partition wall 4 (when a partition wall is provided) and a panel seal portion for information display is assumed.

  The gas in the gap is not limited as long as it is in the humidity region described above, but dry air, dry nitrogen, dry argon, dry helium, dry carbon dioxide, dry methane, and the like are preferable. This gas needs to be enclosed in an information display panel so that the humidity is maintained. For example, filling of display particles, assembling of the information display panel, etc. are performed in a predetermined humidity environment. It is preferable to apply a sealing material and a sealing method for preventing moisture from entering from the outside.

  The distance between the substrate 1 and the substrate 2 in the information display panel is not limited as long as the display particle group can move and maintain the contrast, but the display particle group including the chargeable display particles is driven in a gas space. When it is made to adjust, it is adjusted to the range of 10-100 micrometers normally, Preferably it is the range of 10-50 micrometers. The volume occupancy of the display particle group in the space in the gas between the opposing substrates is preferably in the range of 5 to 70%, more preferably in the range of 5 to 60%. If it exceeds 70%, the movement of the display particle group may be hindered, and if it is less than 5%, the contrast tends to be unclear.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
<Measurement method and evaluation method for each characteristic>
Various characteristics such as the average particle diameter of the chargeable particles and the frictional chargeability of each particle were measured according to the following methods.
(Average particle size of the charged particles)
The average particle size of the chargeable child particles and the like was measured using a transmission electron microscope (FE-SEM7500, manufactured by JEOL Ltd.) so that the total number of particles was about 200. The diameter of the 100 particles selected for the purpose (the maximum diameter of the photographed particles) was measured with calipers, and the arithmetic average thereof was obtained as the average particle diameter.

(Residual monomer amount)
The amount of monomer remaining in the chargeable child particles was measured as follows.
0.5 mg of the obtained charged particles were measured under the following conditions using gas chromatography (GC), and the content was calculated from the peak areas of the respective polymerization components. The actual content of the monomer component was calculated from a calibration curve obtained by measuring each monomer in advance under the following conditions.
-GC: Shimadzu Corporation GCMS-QP2010
Column: DB-5 (30 mm × 0.25 mm ID)
-Thermal decomposition temperature: 590 ° C x 1 minute-Column temperature: 50-300 ° C (5 ° C / minute temperature increase)
-Detector temperature: 200 ° C

(Charging characteristics)
-Triboelectric charge-
The triboelectric charge amount was measured based on the general blow-off method using the following apparatus under the following conditions.
・ Measuring device: Blow-off type charge measuring machine (Kyocera Chemical Co., Ltd., TB-203)
・ Mesh aperture: 32 [μm]
・ Blow pressure / Suction pressure: 4.5 [kPa] /9.5 [kPa]
・ Carrier: F96-80 (Powder Tech)
・ Number of shaking: 1000 times -Charge retention rate-
The charge retention characteristics (charge retention ratio) of the display particles were measured under the following conditions.
(1) Fill a copper cell with a layer having a layer thickness of 300 (μm).
(2) Charge is applied by a scorotron charger (needle applied voltage: ± 10 (kV), grid voltage: ± 1 (kV)) so that the particle surface potential becomes ± 1 (kV).
(3) Connect to ground (GND) and start measurement at room temperature (22 ° C.) and 50 RH%. In the case of the child particles, the charge retention (%) was obtained by dividing the surface potential after 12 hours by the initial surface potential. Similarly, in the case of display particles, the charge retention (%) was obtained by dividing the surface potential after 24 hours by the initial surface potential.
The charge retention characteristics were judged to be high when the charge retention ratio was 70 (%) or more in the case of child particles and 90 (%) or more in the case of display particles.

(Deformation rate, degree of deformation of child particles after compounding)
The deformation rate of the chargeable fine particles (child particles) was measured as follows as an index of the degree of deformability of the child particles. Specifically, the bottom of the sample filling chamber of a flow tester (CFT-500D: manufactured by Shimadzu Corporation) is sealed, and 1.0 g of the sample is charged, and 300 kg / cm ² (2.94 × 10 ⁷ Pa) of the sample is put into the sample. A load was applied and the deformation rate was calculated by the following formula (1).
Deformation rate (%) = {[closest packing height (mm) −height after loading (mm)] / closest packing height (mm)} × 100 (1)
The close-packed height is the height when the sample is introduced and the close-packed with the child particles kept in a spherical shape without being deformed, and is calculated from the following formula (2).
Closest packing height (cm) = weight of charged child particles (g) / specific gravity of child particles (g / cm ³ ) / bottom area of flow tester filling chamber (cm ² ) (2)
If the deformation rate of the resin fine particles is 30% or less, there is no problem in the compositing process, and if it exceeds 30%, there is a possibility that problems such as deformation and adhesion of the resin particles occur in the compositing process. high.

(Durability evaluation on information display panel)
-Fabrication of information display panel-
The information display panel is manufactured by combining equal amounts of the white display particles and the black display particles obtained in each example, and the amount of particles filled between the panels on which the transparent electrodes (ITO) are formed. It was carried out by filling so as to be 5 g / m ² . The panel used has an electrode distance of 40 μm, and an electric field of 2 × 10 ⁶ (V / m) is applied to the display particles when a voltage of 80 V is applied.

-Evaluation of durability-
In the evaluation of the durability by the information display panel, white display and black display were performed on the evaluation panel by applying a voltage of 80 V in opposite directions between the electrodes of the evaluation panel manufactured as described above. . And in each of white display and black display, the OD value (optical density) was measured using an optical densitometer (manufactured by Sakata Inx Engineering Co., Ltd., RD19I). A contrast ratio (CR) (CR = 10 ^(BOD-WOD) ) was calculated based on the OD value (WOD) for white display and the OD value (BOD) for black display, and this was used as an index of panel performance.
In the durability test, black-and-white inversion display driving with 80 V applied was performed 500,000 times. As evaluation, the case where CR after driving was CR> 5 was determined to be acceptable (◯), and the case where CR ≦ 5 was determined to be unacceptable (x).

<Manufacture of mother particles>
(Black mother particles)
100 parts by mass of ethylene-cycloolefin copolymer (manufactured by Polyplastics Co., Ltd., TOPAS6013) and 5 parts by mass of carbon black (Evonik-Degussa Co., Ltd., SPECIAL BLACK4) were mixed and kneaded by a twin-screw kneader. To obtain a kneaded product. This was pulverized and classified with a jet mill (manufactured by Nippon Pneumatic Co., Ltd., Lab Jet Mill IDS-LJ type), and then melted and spheroidized (Meteole Inbo MR-3: manufactured by Nippon Pneumatic Industry Co., Ltd.). Melt spheroidization gave black mother particles having an average particle size of 10 μm.
(White mother particles)
100 parts by mass of ethylene-cycloolefin copolymer (manufactured by Polyplastics Co., Ltd., TOPAS 6013) and 100 parts by mass of titanium dioxide (manufactured by Ishihara Sangyo Co., Ltd., Tycop CR-50) are mixed and kneaded with a biaxial kneader. A kneaded product was obtained. This was pulverized and classified with a jet mill (manufactured by Nippon Pneumatic Co., Ltd., Lab Jet Mill IDS-LJ type), and melt-spheroidized in the same manner as described above to obtain white mother particles having an average particle diameter of 10 μm.

<Example 1>
(Production of crosslinked polystyrene resin fine particles (resin fine particles a))
To a three-necked flask, 1.5 g of potassium persulfate (manufactured by Wako Pure Chemical Industries, Ltd.), 2.0 g of Emulgen 109 (manufactured by Kao Corporation) and 920 g of purified water are added in this order to dissolve potassium persulfate and emulgen 109. I let you. Next, 200 g of a mixture in which styrene (manufactured by Tokyo Chemical Industry) and divinylbenzene (manufactured by Nippon Steel Chemical Co., Ltd.) were mixed at a mass ratio of 1: 1 (divinylbenzene in the whole was 44.7 mol%) was added to room temperature. And bubbling with nitrogen gas for 20 minutes. The flask was sealed so that no monomer would leak from the flask, and then polymerized at 80 ° C. for 24 hours to obtain a cloudy resin fine particle dispersion. The dispersion concentration of the resin fine particles in this dispersion was 15.4% by mass.
100 g of methanol was added to 100 g of the resin fine particle dispersion, and the mixture was stirred for 5 minutes, and then centrifuged at 6900 rpm for 1 hour using a centrifuge (HL-7, manufactured by Kokusan Co., Ltd.). After 1 hour, the solid content (resin fine particles) and the solution were separated into solid and liquid, and the solution was transparent. After removing the solution, 200 g of methanol was added and stirred for 2 hours, followed by centrifugation at 6900 rpm for 1 hour using a centrifuge to remove the supernatant. This operation was further repeated three times to obtain undried resin fine particles a.

(Drying treatment of crosslinked polystyrene resin fine particles)
The undried resin fine particles a prepared above were put into a glass petri dish (diameter 20 cm), and dried under reduced pressure by heating at 60 ° C. under a reduced pressure of 66.7 Pa for 24 hours using a vacuum dryer (manufactured by Advantech). . After drying, the recovered amount of the obtained child particles was 10.5 g (yield: 68.2%). The average particle diameter of the child particles (chargeable child particles A) is 280 nm, the residual monomer concentration is 2500 ppm, the triboelectric charge amount is −10.3 μC / g, the charge retention rate is 99.0%, and the deformation rate Was 4.1%. These results are summarized in Table 1.

(Evaluation as charging property evaluation particles and display particles)
The chargeable child particle A obtained above is used as a child particle, and a chargeability evaluation particle comprising this and a mother particle, and further display particles are prepared, and the performance as a chargeability evaluation particle and display particle is evaluated. did.
−Preparation and evaluation of particles for evaluation of chargeability−
The particles for evaluation of chargeability were composed of ethylene-cycloolefin copolymer spherical particles having an average particle diameter of 10 μm as mother particles and chargeable child particles A as child particles, and a composite device (manufactured by Hosokawa Micron Corporation, Nobil Tamil (NOB-130)). ) Was used to embed the child particles in the mother particles so that the input energy was 2400 kJ. The composite particles have a triboelectric charge amount of −20.5 μC / g, a charge retention rate of 91.7%, exhibit negative charge, and have a charge amount necessary for driving in a display panel and high charge retention characteristics. Had.

-Preparation and evaluation of display particles-
-Production of Display Particles As the mother particles, the white mother particles having an average particle diameter of 10 μm were used, and as the child particles, the chargeable child particles A were used. Using a compounding device (Hosokawa Micron Co., Ltd., Nobil Tamil (NOB-130)), 100 parts by weight of white mother particles and 10 parts by weight of child particles are mixed so that the input energy is 2400 kJ. The particles were embedded and combined to produce white composite particles.
Further, 100 g of the composite particles and 2.5 g of negatively charged silica (HDK H3004: manufactured by WACKER) (external coverage) as an external additive were mixed in advance, and then a carbon mixer processor (manufactured by SMT Co., Ltd.). : HFM-001C) was stirred at 4000 rpm, and the surface of the composite particles was treated so that the external additive was uniformly applied to produce white display particles.

  On the other hand, with respect to the black mother particles, fine particles of melamine formaldehyde condensation resin (manufactured by Nippon Shokubai Co., Ltd., Eposter S) are combined with a black matrix using a composite device (manufactured by Hosokawa Micron Corporation, Nobil Tamil (NOB-130)). Black composite particles were prepared by mixing 100 parts by mass of particles and 15 parts by mass of fine particles so that the input energy was 2400 kJ. Further, 100 g of black composite particles and 4.9 g of positively charged silica (HDK H3050VP: manufactured by WACKER) as an external additive were mixed in advance, and then a carbon mixer processor (manufactured by SMT Co., Ltd.). : HFM-001C) was stirred at 4000 rpm, and a treatment was performed so that the external additive was uniformly applied to the surface of the composite particles, thereby producing black display particles.

(Durability evaluation on display panel)
Using the display particles obtained above, the durability of the display panel was evaluated according to the evaluation method described above.
Each evaluation result is shown in Table 1 together with the charging characteristics of the chargeability evaluation particles.

<Example 2>
In the drying treatment of the crosslinked polystyrene resin fine particles in Example 1, the chargeable particles B, the particles for evaluating chargeability, and the display are the same as in Example 1 except that the drying conditions are 80 ° C. and atmospheric pressure for 24 hours. Particles were prepared and subjected to the same evaluation.
The results are summarized in Table 1.

<Example 3>
In the drying treatment of the crosslinked polystyrene resin fine particles in Example 1, the chargeable particles C and further for evaluation of chargeability were the same as in Example 1 except that the drying conditions were 100 ° C. and reduced pressure of 0.5 Pa for 24 hours. Particles and display particles were prepared and evaluated in the same manner.
The results are summarized in Table 1.

<Example 4>
In the drying treatment of the crosslinked polystyrene resin fine particles in Example 1, the chargeable particles D and further for evaluation of chargeability were the same as in Example 1, except that the drying conditions were 80 ° C. and reduced pressure of 0.5 Pa for 24 hours. Particles and display particles were prepared and evaluated in the same manner.
The results are summarized in Table 1.

<Example 5>
In the drying treatment of the crosslinked polystyrene resin fine particles in Example 1, the chargeable child particles E, and further charging were performed in the same manner as in Example 1 except that the drying conditions were 25 ° C. (room temperature) and reduced pressure of 0.5 Pa for 24 hours. Particles for property evaluation and display particles were produced and evaluated in the same manner.
The results are summarized in Table 1.

<Comparative Example 1>
In the drying treatment of the crosslinked polystyrene resin fine particles in Example 1, chargeable particles F and display particles were produced in the same manner as in Example 1 except that the drying conditions were 40 ° C. and atmospheric pressure for 24 hours. Similar evaluations were made.
The results are summarized in Table 1.

  As shown in Examples 1 to 5 in Table 1, it can be seen that even with the chargeable particles polymerized by the emulsion polymerization method, the amount of residual monomer is significantly reduced by performing the heat drying treatment under reduced pressure. It can also be seen that the composite type display particles using these chargeable child particles as the child particles maintain a good contrast even in the repeated display durability test on the display panel. On the other hand, the display particles of Comparative Example 1 in which the resin fine particles were not subjected to the heat drying process under reduced pressure and the resin fine particles having a large amount of residual monomer were used as the child particles, did not provide sufficient durability in display panel evaluation. .

  An information display panel that employs display particles that are compounded using the chargeable particles of the present invention includes a notebook personal computer, an electronic notebook, a PDA (Personal Digital Assistants), a portable information device, a mobile phone, a handy terminal, and the like. Display of mobile devices, electronic paper such as electronic books, electronic newspapers, electronic manuals (electronic instruction manuals), signboards, posters, bulletin boards such as blackboards and whiteboards, electronic desk calculators, home appliances, automobile supplies, etc. Card display unit such as card, point card, IC card, electronic advertisement, information board, electronic POP (Point Of Presence, Point Of Purchase advertising), electronic price tag, electronic shelf label, electronic sheet music, display unit of RF-ID device Others, POS terminal, Kana Geshon device, in addition to a display portion of various electronic devices such as watches, also suitably used as a so-called rewritable paper which rewrites the display by using an external electric field forming means or an external rewrite means only when the display rewriting.

1, 2 Substrate 3W White display particle group 3Wa White display particle 3B Black display particle group 3Ba Black display particle 4 Partition wall 5, 6 Electrode 31 Display particle 32 Base particle 33 Charged child particle

Claims (6)

The display particles formed by fixing the charged particles to the surface of the mother particles are sealed between two opposing substrates, at least one of which is transparent, and the display particles are moved by applying an electric field between the substrates. Chargeable particles constituting the display particles used in an information display panel for displaying image information,
Containing a crosslinked resin obtained by polymerizing a monomer component containing a polymerizable monomer and a crosslinking monomer;
Chargeable particles having a residual monomer concentration of 5000 ppm or less as determined by pyrolysis gas chromatography.   2. The chargeable particle according to claim 1, wherein the constituent unit derived from the crosslinkable monomer is contained in an amount of 20 mol% or more in the entire constituent unit derived from the raw material monomer component constituting the crosslinked resin.   The charged particle according to claim 1, wherein the crosslinked resin is at least one selected from a crosslinked olefin resin, a crosslinked styrene resin, a crosslinked acrylic resin, a crosslinked urethane resin, and a crosslinked epoxy resin. The chargeable child particle according to any one of claims 1 to 3, wherein a deformation rate represented by the following formula (1) is 30% or less when a constant load is applied.
Deformation rate (%) = {[closest packing height (mm) −height after loading (mm)] / closest packing height (mm)} × 100 (1)   The chargeable child particle according to any one of claims 1 to 4 is adhered or fixed to the surface of the mother particle, at least one of which is sealed between two transparent substrates, and an electric field is applied between the substrates. Display particles used for an information display panel in which display particles move between the substrates to display image information.   An information display panel using the display particles according to claim 5.