JP2008026702A - Particle for display medium and panel for information display using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide particles for a display medium, wherein an adhesiveness reducing effect is stably obtained by defining a proper range of electrical resistance of fine particles to be adhered to surfaces of the particles for the display medium. <P>SOLUTION: The particles for the display medium which allow stable driving of the display medium are obtained by using the particles for the display medium for constituting the display medium, which have the fine particles adhered to the surfaces of the particles, wherein the fine particles have electrical resistance of 1.0×10<SP>10</SP>Ωcm or more specific volume resistance, and the display medium is used in a panel for information display to display information such as an image by applying an electric field to the display medium sealed in between two substrates 1, 2 of which at least one is transparent, and having optical reflectance and an electrostatic property, and transferring the display medium. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention encloses a display medium having optical reflectivity and chargeability between two substrates, at least one of which is transparent, and applies an electric field to the display medium, thereby moving the display medium to obtain information such as an image. The present invention relates to a display medium particle that constitutes a display medium used in an information display panel for displaying the information, and an information display panel using the same.

  2. Description of the Related Art Conventionally, information display devices using techniques such as an electrophoresis method, an electrochromic method, a thermal method, and a two-color particle rotation method have been proposed as information display devices that replace liquid crystal display devices (LCDs).

  Compared to LCDs, these conventional technologies have advantages such as a wide viewing angle close to that of ordinary printed materials, low power consumption, and a memory function. It is considered as a technology that can be used for mobile phones, and is expected to expand to information display for mobile terminals, electronic paper, and the like. In particular, recently, an electrophoretic method in which a dispersion liquid composed of dispersion particles and a colored solution is microencapsulated and disposed between opposing substrates has been proposed and is expected.

  However, the electrophoresis method has a problem that the response speed becomes slow due to the viscous resistance of the liquid because the particles migrate in the liquid. In addition, since particles with high specific gravity such as titanium oxide are dispersed in a solution with low specific gravity, it is easy to settle, and it is difficult to maintain the stability of the dispersed state, and there is a problem that the stability of repeated information display is lacking. ing. Even when microencapsulation is performed, the cell size is set to the microcapsule level, and the above-described drawbacks are hardly made to appear, and the essential problems are not solved at all.

  On the other hand, a method in which conductive particles and a charge transport layer are incorporated into a part of a substrate without using a solution is proposed instead of an electrophoresis method using behavior in a solution (see, for example, Non-Patent Document 1). ). However, this method has a complicated structure due to the arrangement of the charge transport layer and further the charge generation layer, and it is difficult to inject a constant charge into the conductive particles. There is also a problem of lacking.

  As a method for solving the various problems described above, by encapsulating a display medium having optical reflectivity and chargeability between two substrates, at least one of which is transparent, and applying an electric field to the display medium, An information display panel that displays information such as an image by moving a display medium is known. In an information display panel of a type that displays information such as an image by moving the display medium by such an electric field, fine particles are attached to the surface of the display medium particles in order to reduce the drive voltage of the display medium. Thus, a method of reducing the adhesion between display medium particles and the adhesion between display medium particles and a substrate is used.

趙 Kuniori and three others, “New Toner Display Device (I)”, July 21, 1999, Annual Meeting of the Imaging Society of Japan (83 times in total) “Japan Hardcopy’99”, p.249-252

  In the information display panel as described above, when the frequency of rewriting is low (for example, once a week), when the electric resistance of the microparticle is low, the charge of the display medium particle is transferred to the substrate through the microparticle. In order to escape, it is impossible to hold the charged electric charge when the display is rewritten, and the charge amount gradually decreases while the display is left. If the charge amount of the display medium particles becomes too low, a good display cannot be obtained immediately upon the next rewriting, and a certain number of inversion displays (display medium drive) are required before the charge amount is restored to the original charge amount. It is necessary to do so, and unnecessary reverse display (display medium driving) and power consumed for it are wasted.

A first object of the present invention is to provide display medium particles that can stably drive a display medium by defining an appropriate range of electrical resistance of fine particles adhered to the surface of the display medium particles. .
A second object of the present invention is to provide an information display panel that is configured using the display medium particles and has excellent display quality.

In order to achieve the first object, the display medium particles of the present invention enclose a display medium having optical reflectivity and chargeability between two substrates, at least one of which is transparent, and apply an electric field to the display medium. The display medium particles constituting the display medium used in the information display panel that displays information such as images by moving the display medium by applying the display medium particles, the fine particles on the particle surface. The fine particles are attached and have a volume resistivity of 1.0 × 10 ¹⁰ (Ωcm) or more.

  As a suitable example of the particles for display medium of the present invention, the average particle diameter of the fine particles is 1 μm or less, and the charge amount of the particles for display medium measured by a blow-off method using a carrier is 10 to 10 in absolute value. When the surface is charged by applying a voltage of 8 KV to a corona discharger in which the display medium particles are arranged at a distance of 1 mm from the surface of the display medium particles, and the particle for the display medium is charged. In other words, the maximum value of the surface potential after 0.3 seconds is larger than 300V.

  In order to achieve the second object, an information display panel of the present invention is for a display medium according to any one of claims 1 to 4 between two opposing substrates, at least one of which is transparent. At least one kind of display medium containing particles is sealed, and the display medium is moved by an electric field generated in the substrate to display information such as an image.

According to the particles for a display medium of the present invention, a display medium having optical reflectivity and chargeability is sealed between two substrates, at least one of which is transparent, and an electric field is applied to the display medium. The particles for the display medium constituting the display medium used in the information display panel for displaying information such as images by moving the particles are adhered to the particle surface, and the volumetric resistivity of the microparticles is 1.0. Since it has an electric resistance of × 10 ¹⁰ (Ωcm) or more, the leakage of electric charges is prevented, so that the display medium particles can stably drive the display medium as proved in the embodiments described later. It becomes the particle | grains for display media which can be performed.

  According to the information display panel of the present invention, at least one display medium containing the display medium particles according to any one of claims 1 to 4 is sealed between two opposing substrates, at least one of which is transparent. Since the display medium is moved by the electric field generated in the substrate to display information such as an image, the information display panel is proved in an embodiment described later. It becomes an information display panel with excellent display quality.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  First, the configuration of the information display panel of the present invention using the display medium comprising 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 sealed between two opposing substrates. Along the applied electric field direction, the charged display medium is attracted by the force of the electric field or the Coulomb force, and the display medium changes the moving direction according to the change of the electric field direction, thereby displaying information such as an image. Therefore, it is necessary to design the information display panel so that the display medium can move uniformly and maintain the stability when the display information is rewritten or when the display information is continuously displayed. 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 mounted on an information display device that is an object of the present invention will be described with reference to FIGS. 1 (a) and (b) to FIGS. 3 (a) and 3 (b).

  In the example shown in FIGS. 1A and 1B, at least two kinds of display media 3 (here, white display medium particles 3Wa) having at least one kind of particles and having different optical reflectance and charging characteristics. A white display medium 3W composed of a group of particles and a black display medium 3B composed of a group of particles 3Ba for black display medium) are perpendicular to the substrates 1 and 2 according to the electric field applied from the outside of the substrates 1 and 2. The black display medium 3B is visually recognized by the observer and black display is performed, or the white display medium 3W is visually recognized by the observer and white display is performed. In the example shown in FIG. 1B, in addition to the example shown in FIG. 1A, a partition 4 is provided between the substrates 1 and 2 to form a cell, for example. In addition, in FIG. 1B, the partition in front is omitted.

  In the example shown in FIGS. 2A and 2B, at least two kinds of display media 3 (here, white display medium particles 3Wa) having at least one kind of particles and having different optical reflectance and charging characteristics. Between the electrode 5 provided on the substrate 1 and the electrode 6 provided on the substrate 2 is a voltage between the electrode 5 provided on the substrate 1 and the electrode 6 provided on the substrate 2. In accordance with the electric field generated by applying, the substrate is moved perpendicularly to the substrates 1 and 2 so that the black display medium 3B is visually recognized by the observer and black display is performed, or the white display medium 3W is provided to the observer. A white display is made by visual recognition. In the example shown in FIG. 2 (b), in addition to the example shown in FIG. 2 (a), a partition 4 is provided between the substrates 1 and 2 to form cells, for example. Further, in FIG. 2 (b), the front partition is omitted.

In the example shown in FIGS. 3A and 3B, one type of display medium 3 (here, particles of white display medium particles 3Wa) having optical reflectivity and chargeability composed of at least one type of particles. A white display medium 3 </ b> W consisting of a group) is parallel to the substrates 1 and 2 according to an electric field generated by applying a voltage between the electrode 5 provided on the substrate 1 and the electrode 6 provided on the substrate 2. The white display medium 3 </ b> W is visually recognized by the observer to perform white display, or the color of the electrode 6 or the substrate 1 is visually recognized by the observer to display the color of the electrode 6 or the substrate 1. ing. In the example shown in FIG. 3B, in addition to the example shown in FIG. 3A, for example, a lattice-shaped partition wall 4 is provided between the substrates 1 and 2 to form a cell. Moreover, in FIG.3 (b), the partition in front is abbreviate | omitted.
In FIGS. 2A and 2B and FIGS. 3A and 3B, the electrodes may be provided outside the substrate, or may be provided so as to be embedded inside the substrate.

Hereinafter, the particles for a display medium that are the characteristics of the present invention will be described in detail. The particles for a display medium of the present invention can be applied to the information display panels shown in FIGS. 1A, 1B to 3A, 3B, and at least one of the information display panels is transparent. A display medium is configured and sealed between two substrates. As the particles for the display medium, fine particles are attached to the particle surface, and the fine particles having a volume resistivity of 1.0 × 10 ¹⁰ (Ωcm) or more can be suitably used. . Fine particles having a volume resistivity of less than 1.0 × 10 ¹⁰ (Ωcm) are inappropriate because they are insufficient in the effect of preventing charge leakage. The volume resistivity of the microparticles is calculated based on the resistance value when the microparticles are compressed into a sheet at 30 MPa using a powder resistance measurement system manufactured by Dia Instruments Co., Ltd. The average particle size of the fine particles is preferably 1 μm or less, more preferably 0.5 μm or less, and further preferably 0.2 μm or less. When the average particle diameter of the fine particles exceeds 1 μm, the fluidity of the display medium particles serving as the mother particles is deteriorated, which is inappropriate. As the material of the fine particles, inorganic materials such as silica, titanium oxide, and alumina, and organic materials such as acrylic beads and urethane beads can be used.
Further, the charge amount of the display medium particles measured by a blow-off method using a carrier is 10 to 100 μC / g in absolute value, and the display medium particles are arranged at a distance of 1 mm from the surface. When the surface is charged by applying a voltage of 8 KV to the corona discharger and the surface is charged, the maximum value of the surface potential after 0.3 seconds is preferably larger than 300V.

According to the particles for display media of the present invention, the particles for display media used in the information display panels of FIGS. 1 (a), 1 (b) to 3 (a), (b) have fine particles attached to the particle surface. The fine particles have a volume resistivity of 1.0 × 10 ¹⁰ (Ωcm) or more, so that leakage of electric charges is prevented. As proved in the embodiment, the display medium particles can be stably driven. In addition, the information display panels of FIGS. 1 (a), (b) to 3 (a), (b) using the display medium particles are displayed as demonstrated in the examples described later. An information display panel with excellent quality.

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

  Regarding the substrate, 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 substrate materials include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene (PE), polycarbonate (PC), polyimide (PI), polyethersulfone (PES), acrylic and other polymer sheets, metal Examples thereof include a flexible sheet such as a sheet and a non-flexible inorganic sheet such as glass and quartz. 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.

  Electrode forming materials for electrodes provided on the substrate as required include metals such as aluminum, silver, nickel, copper and gold, indium tin oxide (ITO), indium oxide, conductive tin oxide, antimony tin oxide (ATO). ), Conductive metal oxides such as conductive zinc oxide, and conductive polymers such as polyaniline, polypyrrole, and polythiophene are exemplified and used as appropriate. The electrode can be formed by patterning the above-described materials into a thin film by sputtering, vacuum deposition, CVD (chemical vapor deposition), coating, or the like, or by mixing a conductive agent with a solvent or synthetic resin binder. A method of applying and patterning is used. The electrode provided on the viewing side (display surface side) substrate needs to be transparent, but the electrode provided on the back side substrate does not need to be transparent. In any case, the above-mentioned material that is conductive and capable of pattern formation can be suitably used. Note that the electrode thickness is not particularly limited as long as the conductivity can be secured and the light transmittance is not hindered, and is preferably 3 to 1000 nm, preferably 5 to 400 nm. 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. In this case, the external voltage input may be superimposed with direct current or alternating current.

The shape of the partition provided on the substrate as required is appropriately set appropriately depending on the type of display medium involved in display, the shape of the electrode to be arranged, and the arrangement, and is not limited in general, but the width of the partition is 2 to 100 μm. 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. 4, the cells formed by the partition walls made up 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 plane of the substrate. 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 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 suitably used.

A method of charging the particles negatively or positively is not particularly limited, and a method of charging the particles such as a corona discharge method, an electrode injection method, and a friction method is used. It is preferable that the charge amount of particles measured by a blow-off method using a carrier is 10 to 100 μC / g in absolute value. When the absolute value of the charge amount is lower than this range, the response speed with respect to the change in the electric field is slowed, and the memory property is also lowered. If the absolute value of the charge amount is higher than this range, the mirror image force on the electrode and the substrate is too strong, and the memory property is good, but the follow-up movement of the display medium when the electric field is reversed becomes poor.
In the present invention, the charge amount was measured as follows.
<Blow-off measurement principle and measurement method>
In the blow-off method, a mixture of a display medium and a carrier is put into a cylindrical container with nets at both ends, and high-pressure gas is blown from one end to separate the display medium particles and the carrier, and the display medium is opened from the mesh of the mesh. Blow off only the particles. At this time, the charge amount equivalent to the charge amount of the display medium particles taken away from the container remains on the carrier. All of the electric flux due to this charge is collected by the Faraday cage, and the capacitor is charged by this amount. Therefore, by measuring the potential across the capacitor, the charge amount Q of the display medium particles is
Q = CV (C: capacitor capacity, V: voltage across the capacitor)
As required.
TB-200 manufactured by Toshiba Chemical Co. was used as a blow-off particle charge measuring device. In the present invention, a ferrite carrier is used to measure the charge amount of the particles to be measured. For example, the information display panel includes a display medium composed of positively charged particles and a display medium composed of negatively charged particles. When using a combination of types of display media, the same type of carrier is used when measuring the charge amount of the particles for display media constituting each display medium. Specifically, the charge amount (μC / g) of the particles was measured using a DFC100 wrinkle (Mn—Mg-containing ferrite system) manufactured by Dowa Iron Powder Industry Co., Ltd. as a carrier.

Since the particles need to retain their charged charges, insulating particles having a volume resistivity of 1 × 10 ¹⁰ Ω · cm or more are preferable, and in particular, insulating particles having a volume resistivity of 1 × 10 ¹² Ω · cm or more. Is preferred. Further, particles with slow charge decay evaluated by the method described below are more preferable.

  That is, particles to be measured are arranged on the surface of a roll-shaped measuring jig, and a corona discharge is generated by applying a voltage of 8 KV to a corona discharger arranged with a distance of 1 mm from the arranged particle surface. The surface is charged, and the change in the surface potential is measured and judged. In this case, it is important to select and prepare the particle constituent material so that the maximum value of the surface potential after 0.3 seconds is greater than 300V, preferably greater than 400V.

  In addition, the measurement of the said surface potential can be performed, for example with the apparatus (CRT2000 by QEA) shown in FIG. In the case of this apparatus, both ends of the shaft of the roll-shaped measuring jig having the particles to be measured arranged on the surface are held by the chuck 21, and the small scorotron discharger 22 and the surface electrometer 23 are set in a predetermined manner. A measurement unit that is separated from the measurement particle surface is arranged opposite to the surface of the particle to be measured with a 1 mm gap, and the measurement unit is arranged on the surface of the roll measurement jig while the roll measurement jig is stationary. A method of measuring the surface potential while applying surface charge by moving the particles from one end to the other end at a constant speed is suitably employed. The measurement environment is a temperature of 25 ± 3 ° C. and a humidity of 55 ± 5 RH%.

Next, display medium particles (hereinafter also referred to as particles) constituting the display medium in the information display panel of the present invention will be described. The display medium particles are used as they are as they are, which are composed of the display medium particles alone or in combination with other particles as a display medium.
The particles can contain a charge control agent, a colorant, an inorganic additive, and the like, if necessary, in the resin as the main component, as in the conventional case. Examples of resins, charge control agents, colorants, and other additives will be given below.

  Examples of the resin include urethane resin, urea resin, acrylic resin, polyester resin, acrylic urethane resin, acrylic urethane silicone resin, acrylic urethane fluororesin, acrylic fluororesin, silicone resin, acrylic silicone resin, epoxy resin, polystyrene resin, styrene Acrylic resin, polyolefin resin, butyral resin, vinylidene chloride resin, melamine resin, phenol resin, fluororesin, polycarbonate resin, polysulfone resin, polyether resin, polyamide resin and the like can be mentioned, and two or more kinds can be mixed. In addition, a resin polymerized in advance may be used, or the particles may be polymerized during particle formation. Furthermore, it is good also as a copolymer using several types of resin raw materials at the time of superposition | polymerization. In particular, an acrylic resin, an acrylic fluororesin, a polystyrene resin, and a styrene acrylic resin are preferable from the viewpoint of controlling the adhesive force with the substrate and ease of manufacturing.

  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), nitroimidazole derivatives, and styrene acrylic resins having negatively chargeable functional groups. Examples of the positive charge control agent include nigrosine dyes, triphenylmethane compounds, quaternary ammonium salt compounds, polyamine resins, imidazole derivatives, and styrene acrylic resins having a positively chargeable functional group. 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 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.

  The particles for display medium of the present invention (hereinafter also referred to as particles) preferably have an average particle diameter d (0.5) in the range of 1 to 20 μm and are 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 size of each particle is uniform, and movement as a uniform display medium becomes possible.

  Furthermore, regarding the correlation between the particles, the ratio of d (0.5) of the particles having the minimum diameter to d (0.5) of the particles having the maximum diameter among the used particles is set to 50 or less, preferably 10 or less. It is essential. Even if the particle size distribution Span is reduced, particles with different charging characteristics move in opposite directions, so that the particle size is close to each other and each particle can be easily moved in the opposite direction by the equivalent amount. This is within this 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 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, particles are introduced 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.

Furthermore, when a display medium composed of display medium particles is applied to a dry information display panel that is driven in an air space, it is important to manage the gas in the gap 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, 3A, and 3B, the gaps are defined as electrodes 5 and 6 (electrodes inside the substrate) from the portion sandwiched between the opposing substrate 1 and substrate 2. 2), 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 (when a partition wall is provided), and a seal portion of the information display panel.
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 substrates in the information display panel that is the subject of the present invention is not limited as long as the display medium can be moved and the contrast can be maintained, but is usually adjusted to 10 to 500 μm, preferably 10 to 200 μm.
The volume occupation ratio of the display medium in the 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.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the present invention, but the present invention is not limited to the following examples.

<Example 1>
As particles for black display medium, 60 parts by weight of methyl methacrylate (Kanto Chemical Reagent) and 40 parts by weight of ethylene glycol dimethacrylate (Wako Pure Chemical Reagent) as a polyfunctional monomer having a plurality of polymerization reactive groups in one molecule 3 parts by weight of a nigrosine compound (Bontron N07: manufactured by Orient Chemical Co., Ltd.) as a positively charged charge control agent and 5 parts by weight of carbon black (special black 5: manufactured by Degussa) as a black colorant are dispersed by a sand mill. And methacrylic) resin-hydrocarbon resin block copolymer (Modiper F600: manufactured by NOF Corporation) was dissolved, and further 2 parts by weight of lauryl peroxide (PAROIL L: manufactured by NOF Corporation) was dissolved. Liquid as a surfactant with polyoxyethylene alkyl ether sulfate. After suspending, polymerizing, filtering, and drying in purified water to which 0.5% of lithium (Latemul E-118B: manufactured by Kao) was added, it was averaged using a classifier (MDS-2: manufactured by Nippon Pneumatic Industry). Particles having a particle size of 9.3 μm were obtained. To this particle, 2% by weight of silica fine particles (H3050: made by Nippon Clariant) having an average primary particle diameter of 15 nm and a volume resistivity (at 30 MPa compacting) of 1.0 × 10 ¹³ (Ωcm) was added, and a Henschel mixer (FM5C) was added. : Mitsui Metal Mining Co., Ltd.) to obtain black display medium particles B1. Table 1 shows the characteristics of the black display medium particle B1.

As particles for white display medium, 100 parts by weight of styrene resin (Toyostyrene E640N: manufactured by Toyo Styrene), and as a white colorant, 100 parts by weight of titanium oxide (Taipaque CR-50: manufactured by Ishihara Sangyo), negatively charged As a control agent, 3 parts by weight of a salicylic acid metal complex (Bontron E88: manufactured by Orient Chemical Co., Ltd.) was stirred and mixed with a Henschel mixer (FM5C: manufactured by Mitsui Kinzoku Mine), and then mixed into a twin-screw extruder (KZW15-45MG: manufactured by Technobel). After kneading, the mixture was pulverized / classified using a pulverizer (MDS-2: manufactured by Nippon Pneumatic Industry) to obtain particles having an average particle size of 9.0 μm. To this particle, 2% by weight of silica fine particles (H3004: manufactured by Nippon Clariant) having an average primary particle diameter of 15 nm and a volume resistivity (at 30 MPa compaction) of 1.0 × 10 ¹³ (Ωcm) was added, and a Henschel mixer (FM5C) was added. : Manufactured by Mitsui Kinzoku Mine Co., Ltd.) to obtain white display medium particles W1. Table 1 shows the characteristics of the white display medium particle W1.

<Example 2>
In Example 1, as the fine particles of the black display medium particles, titanium oxide fine particles having an average primary particle diameter of 15 nm and a volume resistivity (at 30 MPa compaction) of 1.0 × 10 ¹⁰ (Ωcm) (JMT150ANO: manufactured by Teika) As a fine particle of white display medium particles, titanium oxide fine particles (JMT150IB) having an average primary particle diameter of 15 nm and a volume resistivity (at 30 MPa compaction) of 1.0 × 10 ¹⁰ (Ωcm) were added. : Manufactured by Teica) in the same manner as the black display medium particle B1 and the white display medium particle W1 of Example 1 except that 1% by weight was added, the black display medium particle B2 and the white display medium particle W2 Got. Table 1 shows the characteristics of the black display medium particle B2 and the white display medium particle W2.

<Comparative Example 1>
In Example 1, tin-antimony oxides having an average primary particle diameter of 20 nm and a volume resistivity (at 30 MPa compaction) of 1 to 5 (Ωcm) as fine particles of black display medium particles and white display medium particles ( T1: Black display medium particle B3 and white display in the same manner as black display medium particle B1 and white display medium particle W1 of Example 1 except that 0.8% by weight of T1: Mitsubishi Materials) was added. Medium particles W3 were obtained. Table 1 shows the characteristics of the black display medium particle B3 and the white display medium particle W3.

<Performance evaluation method>
[Charge amount]
It was measured by the “blow-off method” described above.
[Characteristics of information display panel]
Table 1 shows the performances of the information display panels respectively produced using the black display medium particles B1 to B3 and the white display medium particles W1 to W3 as display medium particles. For display quality, the reflection density during black display and white display when a contrast of ± 100 V is applied is measured using a reflection image densitometer (RD-191: manufactured by Gretag Macbeth), and the contrast ratio = black. The reflection density at the time of display / reflection density at the time of white display was obtained. Further, the contrast immediately after being left for 1 week at room temperature was measured.

  An information display panel using a display medium composed of particles for a display medium of the present invention is a display unit of a mobile device such as a notebook computer, an electronic notebook, a portable information device called PDA (Personal Digital Assistants), a mobile phone, or a handy terminal. , Electronic paper such as electronic books, electronic newspapers, signboards, posters, bulletin boards such as blackboards and whiteboards, electronic desk calculators, home appliances, display parts for automobiles, card display parts such as point cards and IC cards, electronic advertisements , Information board, electronic POP (Point Of Presence, Point Of Purchase advertising), electronic price tag, electronic shelf label, electronic score, display part of RF-ID equipment, various electronic devices such as POS terminal, car navigation device, clock, etc. It is suitably used for the display unit.

(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. 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. It is a figure which shows the measuring point of the surface potential of the particle | grains for display media used for 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 3B Black display medium 3Wa White display medium particle 3Ba Black display medium particle 4 Bulkhead 5, 6 Electrode 21 Chuck 22 Scorotron discharger 23 Surface potential meter

Claims (5)

Information for displaying information such as an 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 an electric field to the display medium Display medium particles constituting a display medium used for a display panel,
The display medium particles, wherein the display medium particles have fine particles attached to the particle surface, and the microparticles have an electric resistance of 1.0 × 10 ¹⁰ (Ωcm) or more. .   2. The display medium particle according to claim 1, wherein an average particle diameter of the fine particles is 1 μm or less.   3. The display medium particle according to claim 1, wherein the charge amount of the display medium particle measured by a blow-off method using a carrier is 10 to 100 μC / g in absolute value.   The surface after 0.3 seconds when the surface medium particles are charged by applying a voltage of 8 KV to the corona discharger in which the display medium particles are arranged at a distance of 1 mm from the surface. The display medium particle according to any one of claims 1 to 3, wherein the maximum potential value is a particle larger than 300V.   At least one display medium containing the display medium particles according to any one of claims 1 to 4 is encapsulated between two opposing substrates, at least one of which is transparent, and is generated in the substrate. An information display panel, wherein a display medium is moved by an electric field to display information such as an image.

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