JP2009133906A - Particle for display medium and information display panel using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide particles for a display medium to be used for an information display panel with improved durability, and to provide the information display panel using the same. <P>SOLUTION: The particles 31 for the display medium constitute the display medium used in the information display panel which includes the display medium composed of the particles having an optical reflectance and charging property filled between two opposite substrates at least one of which is transparent, and displays information such as an image by moving the display medium applied with an electric field. The particles are composite particles each of which is fabricated by burying child particles 33 into the surface of a mother particle 32 made of a resin with the glass transition temperature (Tg) of 60°C or higher, and the particle size distribution (cv) of the child particles 33 is 18% or less in burying the child particles 33. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display medium used for an information display panel that encloses a display medium configured as a particle group between two opposing substrates, at least one of which is transparent, and displays information such as an image by moving the display medium. The present invention relates to particles for a display medium as constituting particles and an information display panel using the particles.

  Conventionally, at least one type of display medium having optical reflectivity and chargeability configured as a particle group composed of at least one type of particles is sealed between two substrates at least one of which is transparent, and an electric field is applied to the display medium. As a display medium particle constituting a display medium in an information display panel that displays information such as an image by moving the display medium by embedding, the surface of the thermoplastic mother particle is embedded with high-hardness child particles. Particles having a high hardness and improved physical durability are known (for example, Patent Document 1).

JP 2006-072283 A

  In the information display panel using the above-described display medium particles as a display medium, if display rewriting is repeatedly performed, the child particles may be buried in the mother particles, and as a result, the durability may deteriorate. . In addition, when the display medium particles are manufactured, a phenomenon that the child particles are not sufficiently coated on the entire surface of the base particles may occur, which may deteriorate the durability or display with such display medium particles. When the medium is configured, there are cases where the charging characteristics are adversely affected due to the presence of free child particles in the display medium that are not covered during production.

  Accordingly, an object of the present invention is to provide a display medium particle for use in an information display panel that has solved the above-described problems and has improved durability compared to the conventional one, and an information display panel using the same.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have shown that composite particles prepared by embedding child particles on the surface of mother particles made of a resin having a glass transition temperature (Tg) of 60 ° C. or higher. By making the particle size distribution (cv) of the child particles 18% or less when the child particles are embedded, it is possible to suppress the child particles from being embedded inside the mother particles even when display rewriting is repeated. Occasionally, it has been found that durability can be improved by sufficiently covering the entire surface of the mother particles with the child particles, and the present invention has been completed.

That is, the display medium particles of the present invention enclose a display medium configured as a particle group including particles having optical reflectivity and chargeability between two opposing substrates, at least one of which is transparent, and the display medium Display medium particles constituting a display medium used for an information display panel that displays information such as an image by moving the display medium by applying an electric field to the display medium,
It is a composite particle produced by embedding child particles on the surface of a mother particle made of a resin having a glass transition temperature (Tg) of 60 ° C. or higher. When the child particles are embedded, the particle size distribution (cv) of the child particles is 18 % Or less. Here, the cv value of the child particle is obtained by observing the particle using a scanning electron microscope (SEM) and measuring the particle diameter of the particle with a scaler by 100 samples or more.

  In a preferred example of the display medium particle of the present invention, the volume ratio of the child particles of 50 nm or less is 5% by volume or less in the embedding of the child particles. Here, the volume ratio of the particles of 50 nm or less of the child particles was obtained by calculation from the ratio of the number of particles having a particle diameter of 50 nm or less and the respective particle diameters among the data of 100 samples or more obtained using the SEM. Is.

  The information display panel of the present invention is characterized in that a group of particles including the display medium particles is used as a display medium.

  According to the present invention, it is possible to suppress the embedding of the child particles in the mother particles in the display medium particles when display rewriting is repeated, and to sufficiently cover the mother particles on the surface of the mother particles during the production. By using the particle group including the particles for the medium as a display medium, there is an advantageous effect that durability can be improved.

  The present invention is described in detail below. First, a basic configuration of an information display panel used as a display medium composed of a particle group including the display medium particles of the present invention will be described. In the information display panel of the present invention, an electric field is applied to a display medium configured as a particle group including particles for display medium sealed between two opposing substrates. In accordance with the applied electric field direction, the display medium is attracted by the force of the electric field, the Coulomb force, or the like, and the display medium changes the moving direction according to the change in the electric field direction, whereby information such as an image is displayed. Therefore, it is necessary to design the information display panel so that the display medium can move uniformly and maintain stability when rewriting the display repeatedly or when displaying the display information continuously. Here, as the force applied to the particles constituting the display medium, in addition to the force attracting each other by the Coulomb force between the particles, an electric mirror image force between the electrode and the substrate, an intermolecular force, a liquid cross-linking force, gravity and the like can be considered.

  An example of an information display panel using the display medium particles of the present invention as a display medium will be described with reference to FIGS. 1 (a), 1 (b) to 5 (a), (b). In the example shown in FIGS. 1A and 1B, the optical reflectivity and charging characteristics of each other, which are configured as a particle group composed of at least one kind of particles including particles having optical reflectivity and chargeability. At least two or more types of display media different from each other (here, a white display medium 3W composed of particles of white display medium particles 3Wa and a black display medium 3B composed of particles of black display medium particles 3Ba are shown) between substrates. In each cell formed by the partition walls 4, the electric field generated by applying a voltage between the electrode 5 (individual electrode) provided on the substrate 1 and the electrode 6 (individual electrode) provided on the substrate 2 is determined according to the electric field generated. The substrate 1 and 2 are moved vertically. Then, as shown in FIG. 1A, the white display medium 3W is visually recognized by the observer and white dot display is performed, or as shown in FIG. 1B, the black display medium 3B is visually recognized by the observer. Black dots are displayed. In addition, in FIG. 1 (a), (b), the partition in front is abbreviate | omitted.

  In the example shown in FIGS. 2A and 2B, the optical reflectivity and the charging characteristics of each other are configured as a particle group composed of at least one kind of particles including particles having optical reflectivity and chargeability. At least two or more types of display media different from each other (here, a white display medium 3W composed of particles of white display medium particles 3Wa and a black display medium 3B composed of particles of black display medium particles 3Ba are shown) between substrates. In each cell formed by the partition walls 4, a voltage is applied between an electrode 5 (line electrode) provided on the substrate 1 and an electrode 6 (line electrode) provided on the substrate 2 in accordance with an electric field generated. The substrate 1 and 2 are moved vertically. Then, as shown in FIG. 2 (a), the white display medium 3W is visually recognized by the observer and white dot display is performed, or as shown in FIG. 2 (b), the black display medium 3B is visually recognized by the observer. Black dots are displayed. In addition, in FIG. 2 (a), (b), the partition in front is abbreviate | omitted.

  In the example shown in FIGS. 3A and 3B, one type of display medium configured as a particle group including at least one type of particles including particles having optical reflectance and chargeability (here, white) (Showing white display medium 3W composed of particles of display medium particles 3Wa) between each substrate formed between the substrates and formed by the partition walls 4, the electrode 5 provided on the substrate 1 and the electrode 6 provided on the substrate 2 The substrate is moved in a direction parallel to the substrates 1 and 2 in accordance with an electric field generated by applying a voltage therebetween. Then, as shown in FIG. 3 (a), the white display medium 3W is visually recognized by the observer and white dot display is performed, or the color of the black plate 7 is shown to the observer as shown in FIG. 3 (b). A black dot is displayed by visual recognition. In addition, in the example shown to Fig.3 (a), (b), the partition in front is abbreviate | omitted.

  In the example shown in FIGS. 4A to 4D, first, as shown in FIGS. 4A and 4C, from at least one kind of particles including particles having optical reflectivity and chargeability. At least two kinds of display media having different optical reflectivity and charging characteristics from each other (here, white display medium 3W composed of particles of white display medium particles 3Wa and black display medium particles 3Ba). (Showing a black display medium 3B made of a group of particles) between the substrates and in each cell formed by the partition walls 4, the external electric field forming means 11 provided outside the substrate 1 and the external electric field provided outside the substrate 2 The substrate is moved perpendicularly to the substrates 1 and 2 in accordance with an electric field generated by applying a voltage between the forming unit 12 and the forming unit 12. Then, as shown in FIG. 4B, the white display medium 3W is visually recognized by the observer and white dot display is performed, or as shown in FIG. 2D, the black display medium 3B is visually recognized by the observer. Black dots are displayed. In addition, in FIG. 4 (a)-(d), the partition in front is abbreviate | omitted. In addition, a conductive member 13 is provided inside the substrate 1, and a conductive member 14 is provided inside the substrate 2. This conductive member may not be provided.

  In the example shown in FIGS. 5A and 5B, an example of color display in which a display unit (1 dot) is configured by three cells is shown. In the example shown in FIGS. 5A and 5B, as the display medium, all the cells 21-1 to 21-3 are filled with the white display medium 3W and the black display medium 3B, and the first cell 21-1 is filled. A red color filter 22R is provided on the viewer side, a green color filter 22G is provided on the viewer side of the second cell 21-2, a blue color filter 22BL is provided on the viewer side of the third cell 21-3, A display unit is composed of three cells, the first cell 21-1, the second cell 21-2, and the third cell 21-3. In this example, as shown in FIG. 5A, the white display medium 3 </ b> W is moved in the first cell 21-1 to the third cell 21-3 on the viewer side, so that By performing white dot display or moving the black display medium 3B in all the first cells 21-1 to 21-3 to the viewer side as shown in FIG. 5B. Black dots are displayed to the observer. In addition, in FIG. 5 (a), (b), the partition in front is abbreviate | omitted. Multicolor display can be performed by moving the display medium in each cell.

  Next, the particles for a display medium that are the characteristics of the present invention will be described in detail with reference to the drawings. The particles for display medium of the present invention can be applied to the information display panels shown in FIGS. 1A, 1B to 5A, 5B, and at least one of the information display panels is transparent. A display medium is configured and sealed between two substrates. FIG. 6 is a diagram showing an example of the display medium particle of the present invention. In the example shown in FIG. 6, the display medium particle 31 according to the present invention is characterized in that a child particle 33 is embedded in the surface of a mother particle 32 made of a resin having a glass transition temperature (Tg) of 60 ° C. or more. The display medium particles 31 are composed of composite particles having a particle size distribution (cv) of 33 of 18% or less. In the display medium particles 31, the child particles 33 are embedded in the surface layer of the mother particles 32 made of a resin having a glass transition temperature of 60 ° C. or higher, and the particle size distribution (cv) of the child particles 33 is embedded in the child particles 33. ) Of 18% or less, it is possible to prevent the child particles 33 from being buried in the mother particles 32 even when the display is rewritten repeatedly. It can be fully coated. Furthermore, by forming the mother particles 32 from a resin having a glass transition temperature of 60 ° C. or higher, problems occur due to fusion of particles even when stored or used for a long time at 60 ° C., which is the maximum temperature during storage and use. Further, in the production process, it is possible to prevent the particles from fusing at the temperature when the mother particles and the child particles are combined.

  In the display medium particle 31 of the present invention, from the viewpoint of further improving the durability, in the embedding of the child particles 33, the volume ratio of the child particles 33 having a particle diameter of 50 nm or less is preferably 5% by volume or less.

  Hereinafter, each member which comprises the information display panel used as the object of this invention is demonstrated.

  As for the substrate, at least one substrate is the transparent substrate 2 from which the color of the display medium 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 from 2 to 5000 μm, more preferably from 5 to 2000 μm. If it is too thin, it will be difficult to maintain the strength and the spacing uniformity between the substrates, and if it is thicker than 5000 μm, it will be a thin information display panel. Is inconvenient.

  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. It is 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 is used. 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. In this case, the external voltage input may be superimposed with direct current or alternating current.

The shape of the partition 4 provided on the substrate as necessary is appropriately set according to the type of display medium involved in display, the shape and arrangement of electrodes to be arranged, and is not limited in general. The height of the partition wall is adjusted to 100 μm, preferably 3 to 50 μm, and the height of the partition wall is 10 to 500 μm, preferably 10 to 200 μm.
In order to obtain flexibility of the information display panel, it is preferable that the partition wall height is low, and in order to obtain a high electric field by applying a low voltage, it is preferable that the partition wall height is low. The height of the partition wall is adjusted to 10 to 100 μm, preferably 10 to 50 μm.
In forming the partition wall, 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 invention, any method is preferably used.
As shown in FIG. 7, the cells formed by the partition walls 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 a mesh shape. 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 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.

  Next, the display medium particle 31 of the present invention will be described. The display medium particles 31 are used as the display medium by being composed of the display medium particles 31 as they are, or by being combined with other particles as the display medium. The mother particles 32 and the child particles 33 constituting the display medium particles 31 contain a charge control agent, a colorant, an inorganic additive, and the like, if necessary, in the resin as the main component, as necessary. I can do it. Further, the child particles 33 made of these materials can also be used as child particles embedded in the surface of the mother particle 32. Examples of resins, charge control agents, colorants, and other additives are 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 and the like can be mentioned, and two or more kinds can be mixed. In particular, a styrene acrylic resin, an acrylic resin, an acrylic fluororesin, and a polystyrene resin are preferable from the viewpoint of controlling the adhesive force with the substrate.

  Examples of the positively chargeable charge control agent include charge control resins such as polyamine resins, tertiary amino group-containing copolymers, and quaternary ammonium base-containing copolymers, imidazole compounds, nigrosine dyes, quaternary ammonium salts, and triglycerides. An aminotriphenylmethane compound or the like can be used.

  Examples of negatively chargeable charge control agents include sulfonic acid group-containing copolymers, sulfonate group-containing copolymers, carboxylic acid group-containing copolymers, and charge control resins such as carboxylic acid group-containing copolymers, and Cr. Azo dyes containing metals represented by element symbols such as Co, Al, and Fe, salicylic acid metal compounds, and alkyl salicylic acid metal oxides.

  Among the above charge control agents, it is preferable to use a charge control resin, and the charge control resin preferably has a content of a functional group imparting chargeability of 0.5 to 15% by mass, and preferably 1 to 10%. More preferably, it is mass%.

  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, risor 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.

  Yellow colorants include chrome yellow, 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 chrome yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene 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.

  Further, the particles as the display medium of the present invention have an average particle diameter d (0.5) in the range of 1 to 20 μm, and are preferably uniform and uniform. If the average particle diameter d (0.5) is larger than this range, the display is not clear. If the average particle diameter d (0.5) is smaller than this range, the cohesive force between the particles becomes too large, which hinders movement as a display medium.

Furthermore, in the present invention, regarding the particle size distribution of each particle, the particle size distribution Span represented by the following formula is less than 5, preferably less than 3.
Span = (d (0.9) −d (0.1)) / d (0.5)
(However, d (0.5) is a numerical value expressing the particle diameter in μm that 50% of the particles are larger than this and 50% is smaller than this, and d (0.1) is a particle in which the ratio of the smaller particles is 10%. (Numerical value expressed in μm, and d (0.9) is a numerical value expressed in μm for a particle diameter of 90% or less.)
By keeping Span within a range of 5 or less, the sizes of the particles for each display medium are uniform, and movement as a uniform display medium becomes possible.

  Furthermore, in the case of using a plurality of display media, among the display medium particles constituting the used display medium, the minimum value for d (0.5) of the display medium particles showing the maximum average particle diameter d (0.5). It is important that the ratio of d (0.5) of the display medium particles having the average particle diameter d (0.5) is 10 or less. Even if the particle size distribution Span is reduced, the display medium particles having different charging characteristics move in opposite directions, so that the display medium particles are close in size, and the display medium particles are equivalent in opposite directions. It is preferable that it can be easily moved, and this is the range.

  The above particle size distribution and particle size can be obtained from a laser diffraction / scattering method or the like. When laser light is irradiated onto particles to be measured, a light intensity distribution pattern of diffracted / scattered light is spatially generated, and this light intensity pattern has a corresponding relationship with the particle diameter, so that the particle diameter and particle diameter distribution can be measured. . Here, the particle size and particle size distribution in the present invention are obtained from a volume-based distribution. Specifically, using a Mastersizer2000 (Malvern Instruments Ltd.) measuring instrument, the particles are put into a nitrogen stream and the attached analysis software (software based on volume-based distribution using Mie theory) The diameter and particle size distribution can be measured.

  The charge amount of the display medium particles naturally depends on the measurement conditions, but the charge amount of the display medium particles in the information display panel is almost the same as the initial charge amount, the contact with the partition walls, the contact with the substrate, and the elapsed time. It was found that depending on the charge decay, the saturation value of the charging behavior of the particles for the display medium is a dominant factor.

  As a result of intensive studies, the inventors of the present invention have been able to evaluate the range of proper charging characteristics of display medium particles by measuring the charge amount of display medium particles using the same carrier particles in the blow-off method. I found it.

  Furthermore, when applied to an information display panel in which a display medium composed of particles for display medium is driven in a gas space, it is important to manage the gas in the void surrounding the display medium between the substrates. Contributes to improved stability. Specifically, it is important that the relative humidity at 25 ° C. is 60% RH or less, and preferably 50% RH or less for the humidity of the gas in the gap. 1A, 1B, 3B, 3B, and 3B, the gaps are defined as electrodes 5 and 6 (electrodes on the inner side of the substrate). 2), the occupied portion of the display medium 3, the occupied portion of the partition wall 4 (when the partition wall is provided), and the information display panel seal portion are excluded, and the gas portion in contact with the so-called display medium is meant.

  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 sealed in an information display panel so that the humidity is maintained, for example, filling a display medium, assembling an information display panel, etc. in a predetermined humidity environment, It is important to apply a sealing material and a sealing method that prevent moisture from entering from the outside.

  The distance between the substrate and the substrate in the information display panel is not limited as long as the display medium can move and maintain the contrast, but when the display medium configured as a particle group including charged particles is driven in a gas space, Usually, it adjusts to 10-100 micrometers, Preferably it is 10-50 micrometers. The volume occupation ratio of the display medium in the gas space between the opposing substrates is preferably 5 to 70%, more preferably 5 to 60%. If it exceeds 70%, the movement of the display medium is hindered, and if it is less than 5%, the contrast tends to be unclear.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

  The information display panels of the examples and comparative examples were evaluated by the following methods according to the following criteria.

<Example 1>
100 parts by mass of cycloolefin resin (ZEONEX 330R: manufactured by Nippon Zeon Co., Ltd., Tg = 123 ° C.) and 100 parts by mass of titanium dioxide (Taipaque CR-90: manufactured by Ishihara Sangyo Co., Ltd.) as negatively charged mother particles Melt-kneaded with a twin-screw kneader, finely pulverized with a jet mill (lab jet mill IDS-LJ type: manufactured by Nippon Pneumatic Industry Co., Ltd.), and classifier (MDS-2: manufactured by Nippon Newmatic Industry Co., Ltd.) ) And then melt spheronized using a melt spheronizer (MR-10: manufactured by Nippon Numatic Kogyo Co., Ltd.) to obtain negatively chargeable mother particles A having an average particle diameter R0 of 8.0 μm. . In addition, the glass transition temperature (Tg) of the resin component of the particles A was 123 ° C.

  Next, negatively chargeable silica particles having 95 parts by mass of the negatively chargeable mother particles A and child particles, an average particle diameter of 240 nm, a CV value of 5.0%, and a volume ratio of particles having a particle diameter of 50 nm or less is 0.5 volume%. 5 parts by mass (Seahoster KE-S30: manufactured by Nippon Shokubai Co., Ltd.) was compounded with a mechanofusion apparatus (manufactured by Hosokawa Micron Corporation) at a rotational speed of 4000 rpm and an operating time of 90 minutes to obtain composite particles Aa. The particle size and CV value of the child particles are determined by observing the particles using a scanning electron microscope (SEM) (JSM-7500F: manufactured by JEOL) and measuring the particle size of the particles with a scaler over 100 samples. It was. Further, the volume ratio of particles having a particle diameter of 50 nm or less contained in the child particles was determined in the same manner as described above. When this particle Aa was observed with an SEM, it was confirmed that the child particles were embedded in the entire surface of the mother particle, and the composite progressed well.

  Next, 2% by mass of silica fine particles (H3004: manufactured by Nippon Clariant Co., Ltd.) is added to the particles Aa and stirred with a Henschel mixer (KM5C: manufactured by Mitsui Mining Co., Ltd.), and negatively charged white particles Aa1 was obtained.

  As positively charged mother particles, 65 parts by mass of methyl methacrylate (manufactured by Kanto Chemical Co., Ltd.) and ethylene glycol dimethacrylate (Japanese) as a polyfunctional monomer having a plurality of polymerization reactive groups in one molecule. 35 parts by mass of Kojun Pharmaceutical Co., Ltd.), 3 parts by mass of nigrosine compound (Bontron N07: manufactured by Orient Chemical Co., Ltd.) as a positively chargeable charge control agent, and carbon black (special as a black colorant) After 5 parts by weight of Black 5 (Degussa) was dispersed by a sand mill, 2 parts by weight of azobisisobutyronitrile (V-60: Wako Pure Chemical Industries, Ltd.) was used as a polymerization initiator. The resulting solution is suspended in purified water supplemented with 0.5% polyoxyethylene alkyl ether sodium sulfate (Latemul E-118B: manufactured by Kao Corporation) as a surfactant, polymerized, filtered and dried. Let , Classifier: - followed by classification using (MDS-2 Nippon New matic Kogyo Co.), average particle diameter to obtain a positively chargeable mother particles B of 8.5 .mu.m. The Tg of the resin component of the particle B was not observed due to the high crosslink density.

  Next, 2% by mass of silica fine particles (H3050: manufactured by Nippon Clariant Co., Ltd.) are added to the particles B, and the mixture is stirred with a Henschel mixer (KM5C: manufactured by Mitsui Kinzoku Mine Co., Ltd.), and positively charged black particles B2 was obtained.

  The white particles Aa1 and the black particles B2 are mixed and stirred at an equivalent amount to perform triboelectric charging, and are arranged via a 100 μm spacer, one of which is an inner ITO processed and connected to a power source, and A cell, one of which is a copper substrate, was filled at a volume occupation rate of 30% to obtain a display panel. When the ITO glass substrate and the copper substrate are connected to a power source and the ITO glass substrate is set to a low potential and the copper substrate is set to a high potential, the black particles are on the low potential electrode side and the white particles are on the high potential electrode side. Move to each side. Here, since black particles are positively charged and white particles are negatively charged, a black display state is observed through the glass substrate.Next, when the potential of the applied voltage is reversed, the particles move in the opposite direction and become white. The display state of is observed. The ratio of the reflectance during white display and the reflectance during black display when the applied voltage was ± 200 [V] was taken as the contrast ratio, and the initial contrast ratio of this display panel was 8.8.

  Furthermore, the contrast ratio after the endurance test in which switching between the low potential of ± 200 V and the high potential was repeated 5 million times at 1 kHz was 8.5, showing almost no change. When this panel was disassembled and the white particles inside were observed by SEM, it was confirmed that the child particles on the surface were not detached and the coating on the surface of the mother particles was retained.

<Example 2>
To a three-necked flask, 2.4 g of V-501 (4,4′-azobis (4-cyanovaleric acid)) manufactured by Wako Pure Chemical Industries, Ltd. was added, 1 mol / L sodium hydroxide 14.4 g, and purified water 780 g. In this order, V-501 was dissolved. After adding 15 g of a 1: 1 mixed solution of styrene and divinylbenzene by Tokyo Chemical Industry Co., Ltd., bubbling was performed with nitrogen gas at room temperature for 20 minutes. The flask was sealed so that the monomer did not leak from the flask, and then polymerized at 75 ° C. for 24 hours to obtain a cloudy polymerization solution. The polymerization solution was filtered and then washed with methanol, acetone, and n-hexane in this order. The polymer was recovered by centrifugation and dried at 60 ° C. for 24 hours to obtain negatively charged crosslinked polystyrene particles b having a carboxyl group on the particle surface layer. The volume ratio of particles having a particle diameter of 190 nm, a CV value of 9.8%, and a particle diameter of 50 nm or less was 1.2% by volume. Next, in the manufacture of the composite particles of Example 1, composite particles Ab were obtained in the same manner except that the crosslinked polystyrene particles b were used instead of the silica particles a. When this particle Ab was observed with an SEM, it was confirmed that the child particles were embedded in the entire surface of the mother particle, and the composite formation proceeded well. Next, 2% by mass of silica fine particles (H3004: manufactured by Nippon Clariant Co., Ltd.) are added to the particles Ab, and the mixture is stirred with a Henschel mixer (KM5C: manufactured by Mitsui Kinzoku Mine Co., Ltd.), and negatively charged white particles Obtained Ab1.

  B2 was used as the particles for black display medium. Using the white particles Ab1 and the black particles B2, an information display panel was prepared and evaluated in the same manner as in Example 1. As a result, the initial contrast ratio was 9.0. The contrast ratio after the durability test was 8.7, showing almost no change. When this panel was disassembled and the white particles inside were observed by SEM, it was confirmed that the child particles on the surface were not detached and the coating on the surface of the mother particles was retained.

<Example 3>
In the production of the negatively charged crosslinked polystyrene particles of Example 2, 780 g of purified water was changed to 700 g of purified water and 80 g of methanol (manufactured by Wako Pure Chemical Industries, Ltd.) in the same manner as in the negatively charged crosslinked polystyrene particles. c was obtained. The particle diameter was 180 nm, the CV value was 18.0%, and the volume ratio of particles having a particle diameter of 50 nm or less was 5.0% by volume. Next, in the production of the composite particles of Example 1, composite particles Ac were obtained in the same manner except that the crosslinked polystyrene particles c were used instead of the silica particles a. When this particle Ac was observed by SEM, it was confirmed that the child particles were embedded in the entire surface of the mother particle, and the composite progressed well. Next, 2% by mass of silica fine particles (H3004: manufactured by Nippon Clariant Co., Ltd.) is added to the particles Ac, and the mixture is stirred with a Henschel mixer (KM5C: manufactured by Mitsui Kinzoku Mine Co., Ltd.), and negatively charged white particles Ac1 was obtained.

  B2 was used as the particles for black display medium. Using the white particles Ac1 and the black particles B2, an information display panel was prepared and evaluated in the same manner as in Example 1. As a result, the initial contrast ratio was 8.6. Further, the contrast ratio after the endurance test was 8.5 with little change. When this panel was disassembled and the white particles inside were observed by SEM, it was confirmed that the child particles on the surface were not detached and the coating on the surface of the mother particles was retained.

<Example 4>
As positively charged mother particles, 100 parts by mass of cycloolefin resin (ZEONEX 330R: manufactured by Nippon Zeon Co., Ltd.) and 5 parts by mass of carbon black (Special Black 5: manufactured by Degussa Co., Ltd.) are melted by a biaxial kneader. Kneaded, finely pulverized with a jet mill (lab jet mill IDS-LJ type: manufactured by Nippon Pneumatic Industry Co., Ltd.), and classified using a classifier (MDS-2: manufactured by Nippon Pneumatic Industry Co., Ltd.). Then, melt spheronization was performed using a melt spheronization apparatus (MR-10: manufactured by Nippon Numatic Kogyo Co., Ltd.) to obtain positively chargeable mother particles C having an average particle diameter R0 of 8.7 μm. The Tg of the resin component of the particle C was 123 ° C.

  Next, 95 parts by mass of this positively chargeable mother particle C, crosslinked melamine particles g having an average particle diameter of 195 nm, a CV value of 18.0%, and a volume ratio of particles having a particle diameter of 50 nm or less is 5.0% (Eposter S: (stock) 5 parts by mass) (made by Nippon Shokubai Co., Ltd.) were compounded with a mechanofusion apparatus (manufactured by Hosokawa Micron Corporation) at a rotation speed of 4000 rpm and an operation time of 90 minutes to obtain composite particles Cg. When the particles were observed with an SEM, it was confirmed that the child particles were embedded in the entire surface of the mother particles, and the compositing proceeded well. Next, 2% by mass of silica fine particles (H3050: manufactured by Nippon Clariant Co., Ltd.) are added to the particles Cg, and the mixture is stirred with a Henschel mixer (KM5C: manufactured by Mitsui Kinzoku Mine Co., Ltd.) to produce particles for black display media. Cg2 was obtained.

  As the white display medium particles, Aa1 was used. Using the white particles Aa1 and the black particles Cg2, an information display panel was prepared and evaluated in the same manner as in Example 1. As a result, the initial contrast ratio was 9.5. The contrast ratio after the endurance test was 9.4, showing almost no change. When this panel was disassembled and the internal white particles and black particles were observed with an SEM, it was confirmed that both particles were not detached from the surface and the coating on the surface of the mother particles was retained.

<Comparative Example 1>
In the production of the negatively chargeable crosslinked polystyrene particles of Example 2, 780 g of purified water was changed to 600 g of purified water and 180 g of methanol (manufactured by Wako Pure Chemical Industries, Ltd.). d got. The particle diameter was 175 nm, the CV value was 20.5%, and the volume ratio of particles having a particle diameter of 50 nm or less was 6.0% by volume. Next, in the production of the composite particles of Example 1, composite particles Ad were obtained in the same manner except that the crosslinked polystyrene particles d were used instead of the silica particles a. When this particle Ad is observed by SEM, a part of the surface of the mother particle is embedded with fine particles having a particle diameter of 50 nm or less, so that larger particles are not embedded and the mother particle surface is not covered. It was observed that there was a part. Next, 2% by mass of silica fine particles (H3004: manufactured by Nippon Clariant Co., Ltd.) is added to the particles Ad, and the mixture is stirred with a Henschel mixer (KM5C: manufactured by Mitsui Kinzoku Mine Co., Ltd.), and negatively charged white particles I got Ad1.

  B2 was used as the particles for black display medium. Using the white particles Ad1 and the black particles B2, an information display panel was prepared and evaluated in the same manner as in Example 1. As a result, the initial contrast ratio was 9.0. However, the contrast ratio after the durability test was greatly deteriorated to 3.7. When this panel was disassembled and the white particles inside were observed with an SEM, the part where the particles with a particle diameter of 50 nm or less were embedded in the previous observation was exposed through the endurance test, and the surface of the mother particle was exposed. It has been confirmed that. It is thought that the loss of the outer surface with high hardness caused the surface deterioration by the endurance test, resulting in the deterioration of the particle characteristics.

<Comparative example 2>
As particles, silica particles a (4 parts by weight), silica particles e (AEROSIL R202: Nippon Aerosil Co., Ltd.) having an average particle size of 12 nm, a CV value of 12.0%, and a volume ratio of particles having a particle size of 50 nm or less are 85.0% by volume. 1) Part by mass was mixed to prepare silica particles f having an average particle diameter of 210 nm, a CV value of 19.5%, and a volume ratio of particles having a particle diameter of 50 nm or less of 15.0% by volume. In the production of the composite particles of Example 1, composite particles Af were obtained in the same manner except that the silica particles f were used instead of the silica particles a. When this particle Af was observed with SEM, a part of the surface of the mother particle was embedded with fine particles having a particle diameter of 50 nm or less, so that larger particles were not embedded and the mother particle surface was not covered. It was observed that there was a part. Next, 2% by mass of silica fine particles (H3004: manufactured by Nippon Clariant Co., Ltd.) is added to the particles Af, and the mixture is stirred with a Henschel mixer (KM5C: manufactured by Mitsui Mining Co., Ltd.). Af1 was obtained.

  B2 was used as the particles for black display medium. Using the white particles Af1 and the black particles B2, an information display panel was prepared and evaluated in the same manner as in Example 1. As a result, the initial contrast ratio was 9.2. However, the contrast ratio after the durability test was greatly deteriorated to 3.2. When this panel was disassembled and the white particles inside were observed with an SEM, the part where the particles with a particle diameter of 50 nm or less were embedded in the previous observation was exposed through the endurance test, and the surface of the mother particle was exposed. It has been confirmed that. It is thought that the loss of the outer surface with high hardness caused the surface deterioration by the endurance test, resulting in the deterioration of the particle characteristics.

<Comparative Example 3>
As negatively chargeable mother particles, 60 parts by mass of styrene (manufactured by Kanto Chemical Co., Ltd.) and 40 parts by mass of n-butyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.), titanium dioxide (Taipaque CR-90: Ishihara Sangyo ( After dispersion of 100 parts by mass with a sand mill, a solution in which 2 parts by mass of azoisobutyronitrile (V-60: manufactured by Wako Pure Chemical Industries, Ltd.) was further dissolved as an initiator for polymerization was Suspended and polymerized in 0.5% purified water to which sodium polyoxyethylene alkyl ether sulfate (Latemul E-118B: manufactured by Kao Corporation) was added as a surfactant, filtered, dried, and then classified by a classifier (MDS -2: Nippon Pneumatic Kogyo Co., Ltd.) was used to obtain negatively chargeable mother particles D having an average particle size of 9.8 μm. The Tg of the resin component of the particle D was 58 ° C.

  Using 95 parts by mass of the negatively chargeable mother particles D and child particles, the negatively chargeable silica particles a (with an average particle diameter of 240 nm, a CV value of 5.0%, and a volume ratio of particles having a particle diameter of 50 nm or less of 0.5 volume%) Sea Hoster KE-S30: (manufactured by Nippon Shokubai Co., Ltd.) 5 parts by mass was complexed with a mechanofusion device (manufactured by Hosokawa Micron Co., Ltd.) at a rotational speed of 4000 rpm and an operation time of 90 minutes to obtain composite particles The particles were fused together, and good composite particles could not be obtained.

  The above results are summarized in Table 1.

  An information display panel which is an object of the present invention includes a display unit of a mobile device such as a notebook computer, a PDA, a mobile phone, and a handy terminal, an electronic paper such as an electronic book and an electronic newspaper, a signboard, a poster, a bulletin board such as a blackboard, and a calculator. Appropriately used for display units for home appliances, automobiles, etc., card display units for point cards, IC cards, etc., electronic advertisements, electronic POPs, electronic price tags, electronic shelf labels, electronic musical scores, display units for RF-ID devices, etc. It is done.

(A), (b) is a figure which shows an example of the information display panel used as the object of this invention, respectively. (A), (b) is a figure which shows the other example of the information display panel used as the object of this invention, respectively. (A), (b) is a figure which shows the further another example of the information display panel used as the object of this invention, respectively. (A)-(d) is a figure which shows the further another example of the information display panel used as the object of this invention, respectively. (A), (b) is a figure which shows the further another example of the information display panel used as the object of this invention, respectively. It is a figure for demonstrating an example of the particle | grains for display media used for the information display panel of this invention. It is a figure which shows an example of the shape of the partition in the information display panel used as the object of this invention.

Explanation of symbols

1, 2 Substrate 3 Display medium (particle group)
3W White display medium 3Wa White display medium particle 3B Black display medium 3Ba Black display medium particle 4 Bulkhead 5, 6 Electrode 7 Black plate 11, 12 External electric field forming means 13, 14 Conductive member 21-1 First cell 21- 2 Second cell 21-3 Third cell 22R Red color filter 22G Green color filter 22BL Blue color filter 31 Display medium particles 32 Mother particles 33 Child particles

Claims (3)

By encapsulating a display medium configured as a particle group including particles having optical reflectivity and chargeability between two opposing substrates, at least one of which is transparent, and applying an electric field to the display medium, Display medium particles constituting a display medium used for an information display panel that displays information such as images by moving the display medium,
It is composed of composite particles produced by embedding child particles on the surface of mother particles made of a resin having a glass transition temperature (Tg) of 60 ° C. or more. In the embedding of the child particles, the particle size distribution (cv) of the child particles Is a particle for a display medium, characterized by being 18% or less.   2. The display medium particle according to claim 1, wherein, in the embedding of the child particles, a volume ratio of the child particles having a particle diameter of 50 nm or less is 5% by volume or less.   An information display panel, wherein a particle group containing the display medium particles according to claim 1 or 2 is used as a display medium.

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