JP2011248012A - Particle for display medium, information display panel using the particle for display medium, and method for producing particle for display medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide compound particles for a display medium with addition of an external additive, which can be stably driven for a long period of time.SOLUTION: The particles for a display medium are to be used for an information display panel, which has a display medium, having optical reflectance and charging property, sealed between two substrates at least one of which is transparent, and displays an information image by applying charges to the display medium to move the medium. The particle comprises a mother particle 32 as a particle main body, a plurality of child particles 33 fixed to the surface of the mother particle, first external additive particles CA-1 with a large particle diameter that fill spaces among the child particles, and second external additive particles CA-2 adhering to the surfaces of the mother particle, child particles and first external additive particles, and having a smaller particle diameter than that of the first external additive particles.

Description

  The present invention relates to a technology related to an information display panel in which a display medium is sealed between two substrates, at least one of which is transparent, and the display medium is moved to display information such as an image. The particles for display medium (hereinafter referred to as particles for display medium), and the particles for display medium in a form in which an external additive is attached to the surface thereof.

  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. Accordingly, as an alternative to a 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 a display medium configured as a particle group in the cells is provided. There is a proposal for an information display panel that encloses and moves the display medium to display information such as images.

  The information display panel as described above displays a desired image or the like by electrically moving a display medium between substrates according to information such as an image, for example. Here, the display medium particles (particle groups) repeatedly move in the space between the substrates in accordance with the information requested to be displayed. Then, while an electric field for rewriting is not applied again after the movement, the state can be maintained and images and the like can be stably displayed, so that power consumption can be suppressed.

  As for the particles for display media used in the information display panel as described above, particles having an external additive attached to the surface for the purpose of stabilizing electrical characteristics and improving fluidity and charging characteristics are conventionally used. Various studies have been conducted. For example, Patent Document 1 discloses display medium particles in which an external additive is attached to the particles. As a result, the charging characteristics and fluidity of the display medium particles are improved, and the durability for use when repeated display and rewriting are performed is improved.

  In recent years, composite-type particles comprising display medium particles composed of mother particles and child particles have also been studied (see Patent Document 2, etc.). Such composite particles have a form in which a large number of child particles are fixed on the surface of the mother particle, and the chargeability as display medium particles and surface durability when rewriting is repeated as compared with the form of the mother particle alone. It can be improved.

JP 2006-64815 A JP 2006-72283 A

Established technology to further improve particle characteristics such as charging characteristics, fluidity, and durability by further attaching the above-mentioned external additives to the outside of composite type display media particles consisting of mother particles and child particles. Is expected to do.
In the present specification, the child particles arranged on the surface of the base particle are sufficiently large particles as compared with the external additive. The average particle diameter of the mother particles in the composite particles is, for example, about 1 to 20 μm, and the average particle diameter of the child particles is, for example, about 100 to 1000 nm. Conventionally, external additives having an average particle diameter of about 5 to 10 nm have been generally used.
In order to measure the primary particle size of a very fine external additive having a nano (nm) size, direct observation with a transmission electron microscope (TEM) is a commonly used method. A large number of primary additive primary particle diameters can be measured from an observation image by TEM, and the average particle diameter can be defined as a representative value of the primary particle diameter from the average value.

  In the situation as described above, a display medium particle having an external additive attached to the outside of the composite type particle was produced and adopted in an information display panel. When the movement was repeated, it was confirmed that the external additive was insufficient from the surface and the functions such as fluidity were lowered. As a cause, it was confirmed that the external additive was buried in the gap between the child particles arranged on the surface by repeated driving. As described above, it has been recognized that it is difficult to stably obtain the improvement obtained by the addition of the external additive for a long period of time simply by adding the conventional external additive to the composite particles.

  Therefore, an object of the present invention is to propose composite type display medium particles to which an external additive is attached, which can be driven stably over a long period of time.

The purpose is to display an information image by moving a display medium by enclosing a display medium having optical reflectivity and chargeability between two substrates, at least one of which is transparent, and applying a charge to the display medium. In particles for display media used in information display panels,
A mother particle serving as a particle body; a plurality of child particles fixed to the surface of the mother particle; a first external additive particle having a large particle size that fills a gap between the child particles; the mother particle; and the child And a second external additive particle having a particle size smaller than that of the first external additive particle, which adheres to the surface of the first external additive particle. Can be achieved with particles.

The first external additive particles preferably have an average particle size of 20 nm to 50 nm, and the second external additive particles preferably have an average particle size of less than 20 nm.
The average particle diameter of the first external additive particles may be 3 to 10 times the average particle diameter of the second external additive particles.

  The first external additive particles and the second external additive particles are preferably both silica fine particles.

  If it is an information display panel using the particle | grains for display media in any one of said, it will become an information display apparatus which is excellent in display performance, has few functions fall, and has high reliability.

In addition, the object is to enclose a display medium having optical reflectivity and chargeability between two substrates, at least one of which is transparent, and by applying charge to the display medium, the display medium is moved to obtain an information image. A method for producing particles for a display medium used in an information display panel for displaying
A particle compositing step in which a plurality of child particles are arranged and fixed on the surface of the mother particle serving as the particle body,
A gap filling step of filling gaps between the child particles with the first external additive particles having a large particle size;
An external additive attaching step of attaching second external additive particles having a smaller particle diameter than the first external additive particles to the surfaces of the mother particles, the child particles, and the first external additive particles; It can also be achieved by a method for producing particles for a display medium characterized by comprising.

The first external additive particles preferably have an average particle size of 20 nm to 50 nm, and the second external additive particles preferably have an average particle size of less than 20 nm.
The average particle diameter of the first external additive particles may be 3 to 10 times the average particle diameter of the second external additive particles.

  In the composite type display medium particles according to the present invention, the first external additive particles having a large particle diameter are positioned so as to fill the gaps between the child particles, and the second external additive having a small particle diameter is formed thereon. The agent particles are formed in a novel form uniformly attached to the whole. Since the first external additive particles fill the gaps between the child particles, the second external additive particles having a small particle size are prevented from being buried in the child particles. Therefore, when the display medium particles are repeatedly driven by using the information display panel, it is possible to suppress a decrease in the function such as fluidity generated by burying the external additive between the child particles. An information display panel that employs such particles for a display medium can be provided as a display device that is excellent in display performance, has little function deterioration, and has high reliability.

(A), (b) is the figure shown in order to demonstrate the principle structure of the information display panel of the charged particle movement system used as an example using the particle | grains for display media produced with the manufacturing method of this invention. (A), (b) is the figure shown in order to demonstrate the other fundamental structure of the information display panel of the charged particle movement system used as an example using the particle | grains for display media produced with the manufacturing method of this invention. is there. It is the figure shown about the particle | grains for composite type display media which concern on this invention, (a) is the figure which showed typically the external appearance of the particle | grains for composite type display media which consist of a mother particle and a child particle, (b ) Is a diagram showing a part of the surface in more detail. It is the figure shown in order to demonstrate the mode between the child particle tops of the mother particle surface.

  Hereinafter, the configuration of particles suitable for display medium particles according to an embodiment of the present invention will be described in detail with reference to the drawings. Here, in order to facilitate understanding of the present invention, as an example, a moving type information display panel that employs charged particles as display medium particles and moves the display medium particles to display an image or the like. First, the schematic configuration will be described.

  The charged particle movement type information display panel includes a group of particles composed of composite mother particles having chargeability sealed in a space between two opposing substrates, and composite display medium particles having child particles on the surface thereof. An electric field is applied. The display medium particles are attracted by the electric field force or the Coulomb force along the applied electric field direction, and the display medium particles are moved by the change in the electric field direction, thereby displaying information such as an image. Therefore, it is necessary to design the information display panel so that the particles for the display medium move uniformly and can maintain the stability when the display information is rewritten or when the display information is continuously displayed. is there. Here, the force applied to the particles for the display medium constituting the display medium is the force due to the electric field, the force attracted by the Coulomb force between the particles, the electric mirror image force between the electrode and the substrate, the intermolecular force, the liquid crosslinking force, gravity, etc. Can be considered.

An example of the 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) and 1 (b) and FIGS. 2 (a) and 2 (b).
The examples shown in FIGS. 1A and 1B include at least two types having different optical reflectivity and charging characteristics that are configured as a particle group including particles for display medium having at least optical reflectivity and chargeability. The display medium (here, the white display medium 3W configured as a particle group including the negatively charged white particles 3Wa and the black display medium 3B configured as the particle group including the positively charged black particles 3Ba) is shown. Is generated by applying a voltage between an electrode pair formed by the electrode 5 (pixel electrode with TFT) provided on the substrate 1 and the electrode 6 (common electrode) provided on the substrate 2 in each cell formed in (1). The substrate is moved perpendicular to the substrates 1 and 2 according to the electric field. Then, the white display medium 3W is visually recognized by the observer as shown in FIG. 1A, or the black display medium 3B is visually recognized by the observer as shown in FIG. 1B. For example, black and white dot matrix display can be performed.
In addition, in FIG. 1 (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. Although an example in which a pixel (dot) and a cell are associated with each other on a one-to-one basis is shown, the pixel and the cell may not be associated with each other.

Further, in the example shown in FIGS. 2A and 2B, at least two types having different optical reflectivity and charging characteristics are configured as a particle group including particles having at least optical reflectivity and chargeability. The display medium (here, the white display medium 3W configured as a particle group including the negatively charged white particles 3Wa and the black display medium 3B configured as a particle group including the positively charged black particles 3Ba) is shown by the partition walls 4. In each formed cell, a voltage is applied between a pair of pixel electrodes formed by an electrode 5 (line electrode) provided on the substrate 1 and an electrode 6 (line electrode) provided on the substrate 2 at an opposing orthogonal intersection. The substrate is moved perpendicular to the substrates 1 and 2 in accordance with the generated electric field. Then, the white display medium 3W is visually recognized by the observer as shown in FIG. 2A, or the black display medium 3B is visually recognized by the observer as shown in FIG. 2B. A black and white dot matrix display is possible.
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. Although an example in which a pixel (dot) and a cell are associated with each other on a one-to-one basis is shown, the pixel and the cell may not be associated with each other.

  In addition, as said board | substrates 1 and 2, substrates, such as a glass substrate, a resin sheet board | substrate, and a resin film board | substrate, can be used. The substrate 2 on the display surface side (observation side) is a transparent substrate. When an electrode for applying a voltage having a predetermined voltage and polarity (positive / negative) (common electrode or line electrode 5 described in FIG. 1 or the like) is disposed in the information display screen area of the substrate 2 Is a transparent electrode. On the surface of the substrate 1 constituting the information display panel shown in FIGS. 1 and 2, pixel electrodes or line electrodes with thin film transistors (TFTs) are formed so as to form matrix electrode pairs. When a voltage is applied to the counter electrode pair, the above-described structure in which a desired display is performed by moving by applying an electric field to the display medium (particle group) can be realized.

  As the substrate described above, at least one of the substrates is a transparent substrate on which the color of the display medium can be confirmed from the outside of the panel, and a material having high visible light transmittance and good heat resistance is preferable. The back substrate as the other substrate may be transparent or opaque. Examples of the substrate material include organic polymer substrates such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene (PE), polycarbonate (PC), polyimide (PI), polyethersulfine (PES), and acrylic. Alternatively, a glass sheet, a quartz sheet, a metal sheet, or the like is used, and a transparent one is used on the display surface side. The thickness of the substrate is preferably 2 to 2000 μm, more preferably 5 to 1000 μm. If it is too thin, it will be difficult to maintain the strength and the uniformity of the distance between the substrates, and if it is thicker than 2000 μm, it will be a thin information display panel. It becomes inconvenient.

If necessary, the electrode forming material provided on the substrate may be made of metals such as aluminum, silver, nickel, copper, and gold, indium tin oxide (ITO), indium zinc oxide (IZO), zinc aluminum oxide (AZO). And conductive metal oxides such as indium oxide, conductive tin oxide, antimony tin oxide (ATO), and conductive zinc oxide, and conductive polymers such as polyaniline, polypyrrole, and polythiophene. Can be used. As a method for forming the electrode, a method of patterning the above-exemplified materials into a thin film by sputtering, vacuum deposition, CVD (chemical vapor deposition), coating, or the like, or a method of laminating metal foil (for example, rolled copper foil) Method) and a method of forming a pattern by mixing a conductive agent with a solvent or a synthetic resin binder and applying it.
The electrodes provided on the information display screen region of the viewing side (display surface side) substrate need to be transparent, but the electrodes provided outside the information display screen region and on the back side substrate do not need to be transparent. In any case, the above-mentioned material that is conductive and capable of pattern formation can be suitably used. In addition, the electrode thickness should just be sufficient if electroconductivity is ensured and there is no trouble in light transmittance, and 0.01-10 micrometers, Preferably 0.05-5 micrometers is suitable. The material and thickness of the electrode provided on the back side substrate 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 provided on the substrate is appropriately set according to the type of display medium involved in display, the shape and arrangement of the electrodes to be arranged, and is not generally limited. However, the width of the partition is 2 to 100 μm, preferably 3 ~ 50 μm. The height of the partition wall can be within the inter-substrate gap, the substrate gap securing portion being the same as the inter-substrate gap, and the other cell forming portions being the same or lower than the inter-substrate gap. 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. The height of the partition wall is adjusted to the distance between the substrates, but may be partially lower than the distance between the substrates.
The cells formed by the partition walls made of these ribs are exemplified by, for example, a square shape, a triangular shape, a line shape, a circular shape, and a hexagonal shape as viewed from the plane of the substrate. The shape is illustrated. 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 portion) as small as possible, and the clearness of the display state can be increased.
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 an information display panel mounted on the information display device of the present invention, and among these, a photolithography method using a resist film and a mold transfer method are preferably used.

Furthermore, the display medium particle | grains used as the object of this invention are demonstrated in detail. The particles for display medium of the present invention can be applied to the information display panels shown in FIGS. 1A and 1B and FIGS. 2A and 2B, and constitute a display medium between two substrates. Is to be enclosed. In particular, the particles for display media of the present invention are composite particles in which a plurality of child particles are fixed to the surface of the mother particle that is the particle body, and the surface has large and small particle sizes different from each other. It is formed in a novel form with an external additive attached.
As described above, an external additive has been conventionally used to improve the fluidity and chargeability of the display medium particles, and generally has one size (particle size), for example, a particle size of 7 to 7 The thing of about 8 nm was employ | adopted. Since the conventional external additive particles are extremely small as compared with the child particles of the composite type particles, they are easily buried in the gaps formed between the child particles. Therefore, since the external additive particles covering the surface of the display medium particles in the initial stage of production are buried in the gaps of the child particles by continuous use of the information display panel, they should be present on the surface of the display medium particles. External additives were in short supply, causing the inconveniences pointed out earlier.

  In contrast to the above, FIG. 3 is a diagram showing the composite type display medium particles according to the present invention, and FIG. 3A schematically shows the appearance of the composite type display medium particles composed of mother particles and child particles. FIG. 3B is a diagram showing the state of a part of the surface in more detail. As shown in FIG. 3A, the composite-type display medium particles 31 have a basic form in which the child particles 33 are uniformly fixed to the surfaces of the base particles 32. Here, a case where the child particle 33 is buried in a depression (concave portion) on the surface of the mother particle 32 is illustrated as an example, but the present invention is not limited to this, and the child particle 33 may be securely fixed to the surface of the mother particle 32. The method is not particularly limited.

  As shown in FIG. 3B, the composite type display medium particles according to the present invention include a first external additive particle CA-1 having a large particle size and a second external additive having a small particle size. Particles CA-2 are added to the surface. The larger first external additive particles CA-1 are particles that are assumed to mainly fill gaps between the child particles. The smaller second external additive particles CA-2 are particles that are supposed to improve the fluidity and chargeability of the display medium particles as in the conventional external additive. The composite display medium particles of the present invention can stably maintain the function of improving the fluidity and chargeability of the external additive for a long period of time by adopting such a novel form. Hereinafter, each structure of the particles for a display medium according to the present invention will be described in order.

  First, the mother particles of the composite type display medium particles will be described. The base resin that is the main component of the mother particles is preferably a thermoplastic resin, and can contain a charge control agent, a colorant, an inorganic additive, and the like, if necessary. Examples of resins, charge control agents, colorants, and other additives will be given below.

  The base particles of the display medium particles include a pigment as a colorant in the base resin as a main component thereof, and may further include a charge control agent, an inorganic additive, and the like as necessary. Examples of resins, charge control agents, colorants, and other additives will be given below.

  Examples of base resin for base particles 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. Two or more of these may be mixed. Moreover, what grind | pulverized the resin superposed | polymerized previously may be used, and what was formed by suspension polymerization may be used. In the case of suspension polymerization, acrylic resin, acrylic fluororesin, polystyrene resin, and styrene acrylic resin are suitable because of their ease.

  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.

  Yellow colorants include 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, and 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. The above colorant can be blended to produce mother particles that are display medium particle precursors of a desired color.

  And as the child particle 33 fixed to the surface of the mother particle 32 in FIG. 3, fine particles made of an inorganic material such as silica may be adopted, or fine particles made of an organic material may be adopted.

  In addition, it is preferable that the particle | grains for display media manufactured by this invention are the range whose average particle diameter d (0.5) is 1-20 micrometers, and is 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. Incidentally, the average particle diameter of the mother particles at this time is about 1 to 20 μm, and the child particles are about 100 to 1000 nm.

Furthermore, in the present invention, regarding the particle size distribution of each display medium particle, it is desirable that 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 size of each particle is uniform, and movement as a uniform display medium becomes possible.

  Furthermore, in an information display panel using two types of display media composed of two types of display media particles having different charging polarities, the average grain of the display media having the larger average particle diameter d (0.5) It is important that the ratio between the diameter and the average particle diameter of the display medium having the smaller average particle diameter d (0.5) is 10 or less. Even if the particle size distribution Span is reduced, the display medium particles with different charging polarities move in the opposite directions, so the particle sizes of each other are the same, and the display medium particles move easily in the opposite directions. It is preferable to be able to do this, 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. When laser light is irradiated onto particles to be measured, a light intensity distribution pattern of diffracted / scattered light is spatially generated, and since this light intensity pattern has a corresponding relationship with the particle diameter, 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. For example, using a Mastersizer 2000 (Sysmex Corp.) measuring instrument, particles can be introduced into a nitrogen stream and the particle size and particle size distribution can be measured with the attached analysis software.

Furthermore, in a dry information display panel in which a display medium composed of display medium particles is driven in a gas space, it is important to manage the gas in the gap surrounding the display medium between the substrates, which contributes to improved display stability. To do. Specifically, it is important that the relative humidity at 25 ° C. is 60% RH or less, preferably 50% RH or less with respect to the humidity of the gas in the void portion.
1A, 1B, 2A, and 2B, the gaps are defined as electrodes 5 and 6 (electrodes on the substrate). In the case of being provided on the inner side), a gas portion in contact with a so-called display medium excluding an occupied portion of the display medium 3, an occupied portion of the partition wall 4, and a seal portion of the information display panel 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 in which the particles for a display medium according to the present invention are employed is only required to be able to move the display medium and maintain the contrast, but is usually 10 to 500 μm, preferably 10 to 200 μm In the information display panel of the charged particle movement type, the thickness is adjusted to 10 to 100 μm, preferably 10 to 50 μm.
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%. Note that 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.

Furthermore, two types of external additives having a large particle size and a small particle size added to the surface of the composite particle from the mother particle and the child particle will be described. The first external additive particles having a large particle size are designed to stay in the gaps between the child particles, and preferably have an average particle size of 20 nm to 50 nm, and more preferably an average particle size of 30 nm. More preferably, it is set to ˜50 nm. An external additive having a small particle size easily aggregates, but if the particle size is 20 nm or more, it can be embedded between the child particles relatively efficiently.
The average particle diameter of the first external additive particles is preferably 3 to 10 times the average particle diameter of the second external additive particles, which will be described later. The first external additive particles are designed to fill the gaps between the child particles. If the first external additive particles are too small to be close to the particle size of the second external additive particles, It is easy to come out, and if the particle size is too large, it is difficult to enter the gap between the child particles.

  The second external additive particles having a small particle diameter are added to improve the fluidity and chargeability of the display medium particles of the present invention, as in the case of conventional external additives. The average particle diameter is less than 20 nm, more preferably the average particle diameter (primary particle diameter) is 7 to 8 nm, and the one having 80% or more of the total weight within ± 2 nm from the median value is adopted. desirable.

As each external additive, silica can be suitably employed. For example, silica having a small particle size can be synthesized by a flame method using SiCl _4, and silica having a large particle size can be prepared by a precipitation method or a wet method using silica gel. These silica external additives are preferably subjected to a hydrophobic treatment. And it is preferable that the total compounding rate of an external additive shall be 2 to 10% of the weight of a composite type particle. If it is 2% or less, sufficient fluidity cannot be obtained, and if it exceeds 10%, it is preferable to be within this range because defects such as desorption from the particles are remarkable.

  The above-mentioned composite type particles having two types of large and small external additives added to the surface include a particle compounding step in which a plurality of child particles are arranged and fixed on the surface of the mother particle as the particle body, and a large particle size A gap filling step of filling a gap between the child particles with the first external additive particles; a second external additive particle having a smaller particle diameter than the first external additive particles; It can be manufactured through a particle and a step of attaching an external additive to the surface of the first external additive particle.

  Hereinafter, although the particle | grains for display media which concern on an Example are further demonstrated, this invention is not limited to the following Example at all.

(Manufacture of composite negatively charged particles)
1) Polyplastic Co., Ltd. TOPAS: 5013 (COC: cycloolefin copolymer polymer) as a spherical base particle is kneaded, melted and pulverized with a pigment, etc. The child particles were prepared by copolymerizing styrene and divinylbenzene. These were subjected to a composite treatment using a powder mixing treatment apparatus (Nobilta) manufactured by Hosokawa Micron Corporation to obtain composite basic type negatively charged white particles A0. The negatively charged white particles A0 had an average particle size of 10 μm, the mother particles used had an average particle size of 9.0 μm, and the child particles had an average particle size of 240 nm.
At this time, when morphological observation of the surface of the composite particle was performed using a scanning electron microscope (SEM): a scanning electron microscope apparatus, the distance (interval) between the child particles was approximately 20 nm in the vicinity of the surface of the mother particle (embedded surface). The distance was about 260 nm between the tops of the child particles at the highest position in the portion protruding from the surface of the mother particle. Accordingly, it can be expected that a concave volume as shown in FIG. 4 exists on the particle surface.
2) With respect to the negatively charged white particles A0, external additive particles (first external additive particles) CA-1 made of silica (SiO ₂ ) having a large particle diameter compared with conventional external additives are added. The mixture was stirred together with the composite particles using a carbon mixer device manufactured by SMT, and subjected to a process of filling in the gaps between the child particles of the negatively charged white particles A0 (gap filling step) to obtain negatively charged white particles A1. When the surface of the negatively charged white particles A1 is confirmed by a scanning electron microscope (SEM): a scanning electron microscope apparatus, the first external additive particles CA-1 are positioned so as to fill the gaps between the child particles. It was confirmed.
3) Furthermore, the surface of the negatively charged white particles A1 (the surfaces of the mother particles, the child particles and the first external additive particles) is made of silica (SiO ₂ ) having a smaller particle diameter than the first external additive particles. Second external additive particles (particles having the same particle size as conventional external additives) CA-2 was applied (external additive attaching step) to finally obtain negatively charged white particles A2. .

As an external additive (silica (SiO ₂ )) used for the negatively charged white particles A2, as shown in the following “Table 1”, large particles (20 nm, 30 nm, 40 nm, 50 nm) are used for the negatively charged white particles. Got ready. In addition, particles having a particle size similar to that of conventional particles (8 nm) were prepared as small particles, and these were used to produce a plurality of types of negatively charged white particles A2.

(Manufacture of composite positively charged particles)
In accordance with the negatively charged particles, cross-linked melamine resin particles (Epester 240 nm, manufactured by Nippon Shokubai Co., Ltd.) are used as the child particles, and carbon black (CB) (Mitsubishi Chemical Corporation: Special Black 4) is used as the black pigment. Charged black particles B0 were produced.
In the case of the positively charged black particles B0, as shown in Table 1 below, 30 nm was prepared as the external additive particle having a large particle size for the positively charged black particles as shown in Table 1 below. Also, as external additive particles having a small particle size, particles having a conventional particle size (8 nm) were similarly prepared, and positively charged black particles B2 were produced through positively charged black particles B1 in the same manner as described above.

In Table 1 above, when only the external additive having a conventional small diameter (8 nm) is used for white (1), white (2) has a large particle diameter (20 nm) and white (3) has a large diameter. The particle size (30 nm) and white (4) are the cases where a large particle size (40 nm) is added thereto. Moreover, white (5) is a case where a large particle size (50 nm) is added thereto. Each particle is subjected to surface hydrophobic treatment with HMDS (hexamethyl gin lazan).
Similarly, in Table 1, black (1) is a case where only a conventional external additive having a small diameter (8 nm) is used, and black (2) is a case where a large particle diameter (30 nm) is added thereto. The black (1) particles having only the small diameter (8 nm) external additive are subjected to a surface treatment with PDMS (polydimethylsiloxane) + aminosilane, and the black (2) is subjected to a surface treatment with HMDS.

Prepare negatively charged white particles A2 manufactured using each of white (1) to white (5) shown in Table 1 and positively charged black particles B2 manufactured using each of black (1) and (2). did.
The negatively charged white particles A2 manufactured using white (1) and the positively charged black particles B2 manufactured using black (1) are used as comparative examples, and then the combinations are sequentially shifted as shown in Table 2 below. About Examples 1-7, contrast evaluation was performed as display performance after durability.

  In the above, the negatively charged white particles A2 and the positively charged black particles B2 are mixed and stirred in an equivalent amount to perform tribocharging, and are arranged through a 100 μm spacer, one of which is treated with the inner ITO and connected to the power source. A substrate and a cell, which is a copper substrate on the other side, were filled at a volume occupation ratio of 30% to obtain a display panel. When each ITO glass substrate and copper substrate are connected to a power source and a direct current voltage is applied so that the ITO glass substrate is at a low potential and the copper substrate is at a high potential, the black particles are on the low potential side and the white particles are on the high potential. Move to the pole side respectively.

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.
Here, the distance between the electrodes arranged on the information display panel was 40 μm, and the particle filling amount was 5 g / m ² , and ± 70 V was used for voltage drive evaluation. The display performance was measured by optical density measurement as the higher the difference between black and white display in the panel display, the better the performance. As the optical densitometer, RD19 manufactured by Gretag Macbth (Germany) was used. As a quantitative value of the difference in black and white display performance, here, the contrast is defined as follows.
Contrast = 10 ^∧ (Black density-White density)
That is, the contrast value is obtained using the difference between the black density and the white density as an index value. The case where the contrast value was 5 or more was determined to be a pass (◯). And the case where the contrast value was less than 5 was set to be rejected (x).

  From the results shown in Table 2, in the design of the external additive for the display medium particles used in the information display panel, the external additive having a large particle size of 20 nm to 50 nm is added to the external additive having the same particle size as the conventional one. The display performance after durability is improved by adding the agent. Desirably, an external additive having a large particle size should be applied to both the black and white particles as in the above-described example, but sufficient durability has been confirmed in either one of them.

In the above embodiment, the case where the first external additive particles having a small particle diameter are those having a primary particle diameter of 8 nm is exemplified. In the case where the agent particles are 7 nm, the same follow-up test is performed and the same result as above is obtained.
Furthermore, in the above, the total blending ratio of the external additives is 5% with respect to the total weight of the composite type particles, and in the case of the present invention in which two types are mixed, 2.5% respectively, and 5% in total.

  As described above, the particles for display medium according to the present invention include the external additive of the first particles having a large particle size and the second particles having a small particle size, and the first particle having a large particle size. The external additive particles are designed to have a size suitable for filling the gaps between the child particles. On the other hand, the second external additive particles having a small particle size have the same size as that of conventionally used external additives. That is, the first external additive particles having a large particle size serve a protective wall function so that the second external additive particles that perform the original function of the external additive do not enter the gaps between the child particles. The particle size is designed. Similarly, the external additive particles having large and small particle diameters are similarly formed of a material such as silica, so that new inconveniences are not generated, and the fluidity and chargeability of the particles are improved. It can be maintained stably.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

The information display panel employing the composite display medium particles according to the present invention is a display for mobile devices such as notebook computers, electronic notebooks, portable information devices called PDA (Personal Digital Assistants), mobile phones, and handy terminals. Departments, electronic books, electronic newspapers, electronic manuals such as electronic manuals (electronic instruction manuals), signboards, posters, bulletin boards such as blackboards and whiteboards, electronic desk calculators, display units for home appliances, automobile supplies, point cards, IC card and other card display units, electronic advertisements, information boards, electronic POPs (Point Of Presence, Point Of Purchase advertising), electronic price tags, electronic shelf labels, electronic musical scores, display units for RF-ID devices, POS terminals, It is suitably used for display units of various electronic devices such as car navigation devices and watches. In addition, the display panel can be suitably used as a display panel that performs display rewriting by an external electric field forming unit or a display panel that performs display rewriting by connecting to an external display rewriting unit (both are so-called rewritable papers).
As for the driving method of the information display panel, a simple matrix driving method and a static driving method that do not use a switching element in the panel itself, a three-terminal switching element represented by a thin film transistor (TFT), or a thin film diode (TFD). Various types of driving methods such as an active matrix driving method using a representative two-terminal switching element and an external electric field driving method using an external electric field forming means can be applied.

1, 2 Substrate 3Wa, 3Ba Display medium particle 3W, 3B Display medium (particle group)
31 Composite type display medium particle 32 Base particle 33 Child particle CA-1 First external additive particle having a large particle size CA-2 Second external additive particle having a small particle size

Claims (8)

An information display for displaying an information image by moving a display medium by enclosing a display medium having optical reflectivity and chargeability between two substrates, at least one of which is transparent, and applying charge to the display medium In particles for display media used in panels,
A mother particle serving as a particle body; a plurality of child particles fixed to the surface of the mother particle; a first external additive particle having a large particle size that fills a gap between the child particles; the mother particle; and the child And a second external additive particle having a particle size smaller than that of the first external additive particle, which adheres to the surface of the first external additive particle. particle.   2. The display medium according to claim 1, wherein the first external additive particles have an average particle diameter of 20 nm to 50 nm, and the second external additive particles have an average particle diameter of less than 20 nm. Particles.   3. The display medium according to claim 1, wherein an average particle diameter of the first external additive particles is 3 to 10 times an average particle diameter of the second external additive particles. 4. particle.   4. The display medium particle according to claim 1, wherein the first external additive particle and the second external additive particle are both silica fine particles. 5.   An information display panel using the display medium particle according to claim 1. An information display for displaying an information image by moving a display medium by enclosing a display medium having optical reflectivity and chargeability between two substrates, at least one of which is transparent, and applying charge to the display medium A method for producing particles for a display medium used in a panel,
A particle compositing step in which a plurality of child particles are arranged and fixed on the surface of the mother particle serving as the particle body,
A gap filling step of filling gaps between the child particles with the first external additive particles having a large particle size;
An external additive attaching step of attaching second external additive particles having a smaller particle diameter than the first external additive particles to the surfaces of the mother particles, the child particles, and the first external additive particles; A method for producing particles for a display medium.   The display medium according to claim 6, wherein the first external additive particles have an average particle diameter of 20 nm to 50 nm, and the second external additive particles have an average particle diameter of less than 20 nm. Method for producing particles.   8. The display medium according to claim 6, wherein an average particle diameter of the first external additive particles is 3 to 10 times an average particle diameter of the second external additive particles. 9. Particle production method.

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