JP2006106596A - Particle for display medium used for panel for information display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide particles for a display medium which constitute the display medium such that transition and burying of additives to and in base particles can be eliminated and durability when display rewriting of a panel for information display is repeated can be improved. <P>SOLUTION: Particles for the display medium used for the panel for information display which has the display medium charged between two substrates at least one of which is transparent and moves the display medium by applying an electric field to the display medium to display information are formed by coating surfaces of particles 12 with silica particulates 13 of ≤450 nm in particle size by a sol-gel method. As a preferable embodiment, the surfaces are treated with electrostatically charged resin after being coated with silica particulates 13. Further, a surface treatment for electrification is carried out by using melamine resin at this time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is for a display medium used for an information display panel that displays information by moving the display medium by enclosing the display medium between two substrates, at least one of which is transparent, and applying an electric field to the display medium. It relates to particles.

  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 for images and the like that replace liquid crystal (LCD).

  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. Particularly recently, an electrophoretic method in which a dispersion liquid composed of dispersed particles and a colored solution is encapsulated 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, the structure is complicated because the charge transport layer and further the charge generation layer are arranged, and it is difficult to inject the charges into the conductive particles.

As one method for solving the various problems described above, a cell that is isolated from each other by a partition wall is formed after sealing a display medium between two opposing substrates, at least one of which is transparent. 2. Description of the Related Art An information display panel that displays information such as an image by applying an electric field to a display medium after the display medium is sealed therein and moving the display medium is known.
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” Proceedings, p.249-252

  Conventionally, as particles for a display medium used in an information display panel, for example, an external additive is added to one or both of white and black base particles to improve fluidity. However, in the information display panel using the display medium particles produced by this method, while the display medium particles are inverted and the information display is repeated, the external additive moves to the other base particles, There was a problem of being buried in the mother particles. The problem of migration and burying of the external additive with respect to the mother particles has caused a decrease in durability characteristics when display rewriting is repeated in the information display panel.

  The object of the present invention is to solve the above-mentioned problems, eliminate the migration and burying of external additives to the mother particles, and improve the durability performance when rewriting the display on the information display panel. The present invention intends to provide particles for a display medium used for a display panel.

  The display medium particles used in the information display panel of the present invention enclose a display medium between two substrates, at least one of which is transparent, and apply an electric field to the display medium, thereby moving the display medium to display information. The display medium particles used in the information display panel to be displayed are characterized in that the surfaces of the particles are coated with silica fine particles having a particle diameter of 450 nm or less by a sol-gel method. Here, the particle diameter of the silica fine particles is an average value obtained by image analysis by sampling a maximum of 10 particles from the SEM image.

  In addition, as a suitable example of the particle | grains for display media used for the information display panel of this invention, the surface treatment for charge amount provision was performed for the surface treatment for charge amount provision, and the surface treatment for charge amount provision was performed for the melamine resin. There are things to do.

  According to the present invention, the particles for display medium are formed by coating the surface of the particles with silica fine particles having a particle diameter of 450 nm or less by the sol-gel method, thereby eliminating migration and burying of the silica fine particles with respect to the mother particles. In addition, it is possible to obtain display medium particles capable of improving display durability by repeatedly reversing the display medium in the information display panel.

  First, a basic configuration of an information display panel using the display medium particles of the present invention will be described. In the information display panel used in the present invention, an electric field is applied to a display medium sealed between two opposing substrates. A display medium charged at a low potential toward the high potential side along the direction of the applied electric field is attracted by the electric field force or Coulomb force, and the display medium is charged at a high potential toward the low potential side. Information is displayed when the medium is attracted by a force due to an electric field, a Coulomb force, or the like, and the display medium reciprocates due to a change in the direction of the electric field due to a potential change. Therefore, it is necessary to design the information display panel so that the display medium can move uniformly and maintain stability during repetition or storage. Here, as the force applied to the particles constituting the display medium, in addition to the force attracted by the Coulomb force between the particles, an electric image force with the electrode and the substrate, an intermolecular force, a liquid cross-linking force, gravity and the like can be considered.

  An example of an information display panel using the display medium particles of the present invention will be described based on FIGS. 1 (a) and (b) to FIGS. 3 (a) and 3 (b).

  In the example shown in FIGS. 1A and 1B, at least two or more kinds of display media 3 composed of at least one kind of particles (here, the white particle group 3W and the black particle group 3B are shown). Are moved perpendicularly to the substrates 1 and 2 according to the electric field applied from the outside of the substrates 1 and 2, and the black particle group 3B is visually recognized by the observer to display black, or the white particle group 3W Is displayed in white by an observer. In the example shown in FIG. 1B, in addition to the example shown in FIG. 1A, partition walls 4 are provided, for example, in a lattice shape between the substrates 1 and 2 to define display cells.

  In the example shown in FIGS. 2A and 2B, at least two or more kinds of display media 3 composed of at least one kind of particles (here, the white particle group 3W and the black particle group 3B are shown). Is moved perpendicularly to the substrates 1 and 2 according to the 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, and the black particle group 3B is observed. A white display is performed by making the viewer visually recognize black, or the white particle group 3W is visually recognized by the viewer. In the example shown in FIG. 2B, in addition to the example shown in FIG. 2A, partition walls 4 are provided, for example, in a lattice form between the substrates 1 and 2 to define display cells.

  In the example shown in FIGS. 3A and 3B, a display medium 3 having at least one color composed of at least one kind of particles (here, the white particle group 3W is shown) is applied to the substrate 1. In accordance with the electric field generated by applying a voltage between the provided electrode 5 and electrode 6, the substrate is moved in the direction parallel to the substrates 1 and 2, and the white particle group 3W is visually recognized by the observer. Alternatively, the color of the electrode 6 or the substrate 1 is displayed by making the observer visually recognize the color of the electrode 6 or the substrate 1. 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 define a display cell.

  The above description can be similarly applied to the case where the white particle group 3W is replaced with a white powder fluid and the black particle group 3B is replaced with a black powder fluid.

  FIG. 4 is a view for explaining an example of particles for a display medium used in the information display panel of the present invention. In the example shown in FIG. 4, the feature of the display medium particle 11 of the present invention is that the surface of the particle 12 is covered with silica fine particles 13 having a particle diameter of 450 nm or less by a sol-gel method.

  By configuring in this way, first, silica fine particles 13 are formed on the surfaces of the particles 12 serving as mother particles by a sol-gel method to improve fluidity. In this case, it is not necessary to improve the fluidity by using an external additive that can be easily detached from the particles 12, so that it is difficult to adversely affect the durability when repeated display is repeated. Further, since the surface of the particle 12 is covered with the silica fine particles 13, the surface hardness of the particle 12 is improved and the mechanical durability such as the wear resistance of the particle itself is improved. From the above, it is possible to improve the durability performance when the display rewriting is repeated. Further, at this time, by controlling the particle diameter of the silica fine particles 13 covering the surfaces of the particles 12 to be 450 nm or less, the fluidity of the display medium particles 11 is further improved due to the reduction of the contact area. The particle diameter of the silica fine particles 13 can be controlled by the concentration of TEOS (tetraethoxysilane) and the degree of hydrophilicity / hydrophobicity of the medium, and can also be controlled by the amount of ammonia added.

  Further, as a preferred example, after the silica fine particles 13 are coated, the amount of charge is improved by surface treatment with a chargeable resin, and the contrast of the information display panel using the display medium particles 11 of the present invention is improved. Can be achieved. Here, examples of the positively chargeable resin include melamine and acrylic, and examples of the negatively chargeable resin include fluorine and silicone. Among these, it is more preferable to use a melamine resin as the resin used for improving the positive charge amount. The lower limit of the particle diameter of the silica fine particles 13 is not particularly limited, but a preferable value of the lower limit is about 50 nm due to manufacturing problems.

  FIG. 5 shows an example of a display medium particle used in the information display panel of the present invention, taken with a scanning electron microscope (SEM). In the example shown in FIG. 5, the particle diameter of the silica fine particles 13 is controlled to 300 nm or less, and a state in which the surfaces of the particles 12 are covered with the silica fine particles 13 is shown.

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

  As for the substrate, at least one substrate is the transparent substrate 2 from which the color of the display medium 3 can be confirmed from the outside of the information display panel, and a material having high visible light transmittance and good heat resistance is suitable. The substrate 1 may be transparent or opaque. Examples of substrate materials include polymer sheets such as polyethylene terephthalate, polyethersulfone, polyethylene, polycarbonate, polyimide, and acrylic, flexible materials such as metal sheets, and flexible materials such as glass and quartz. There are no inorganic sheets. 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 as necessary include metals such as aluminum, silver, nickel, copper, and gold, conductive metal oxides such as ITO, indium oxide, conductive tin oxide, and conductive zinc oxide, polyaniline , Conductive polymers such as polypyrrole and polythiophene are exemplified, and are appropriately selected and used. As a method for forming an electrode, a method of forming the above-described materials into a thin film by sputtering, vacuum deposition, CVD (chemical vapor deposition), coating, or the like, or mixing a conductive agent with a solvent or a synthetic resin binder. The method of apply | coating is used. The electrode provided on the viewing 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 view side substrate described above, but need not be transparent. In this case, the external voltage input may be superimposed with direct current or alternating current.

  The shape of the partition 4 provided as necessary is optimally set according to the type of display medium involved in the display, and is not limited in general. However, the partition width is 2 to 100 μm, preferably 3 to 50 μm. The height is adjusted to 10 to 500 μm, preferably 10 to 200 μm. In forming the partition walls, a both-rib method in which ribs are formed on each of the opposing substrates and then bonded, and a one-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. 6, the display cell formed by the partition walls made of these ribs is 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. The shape and the mesh shape are exemplified. It is better to make the portion corresponding to the cross section of the partition wall visible from the display side (the area of the frame portion of the display cell) as small as possible, and the display information becomes clearer. Here, 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. Among these, a photolithography method using a resist film and a mold transfer method are preferably used.

  Next, the powder fluid used as a display medium in the information display panel that is the subject of the present invention will be described. As for the name of the powder fluid as the display medium of the present invention, the present applicant has obtained the right of “Electronic Powder Fluid (registered trademark): Registration No. 4636931”.

  The “powder fluid” in the present invention is a substance in an intermediate state of both fluid and particle characteristics that exhibits fluidity by itself without borrowing the force of gas or liquid. For example, liquid crystal is defined as an intermediate phase between a liquid and a solid, and has fluidity that is a characteristic of liquid and anisotropy (optical properties) that is a characteristic of solid (Heibonsha: Encyclopedia) . On the other hand, the definition of particle is an object with a finite mass even if it is negligible, and is said to be affected by gravity (Maruzen: Physics Encyclopedia). Here, even in the case of particles, there are special states of gas-solid fluidized bed and liquid-solid fluids. When gas is flowed from the bottom plate to the particles, upward force is applied to the particles according to the velocity of the gas. Is a gas-solid fluidized bed that is in a state where it can easily flow when it balances with gravity, and it is also called a liquid-solid fluidized state that is fluidized by a fluid (ordinary) Company: Encyclopedia). As described above, the gas-solid fluidized bed body and the liquid-solid fluid are in a state of using a gas or liquid flow. In the present invention, it has been found that a substance in a state of fluidity can be produced specifically without borrowing the force of such gas and liquid, and this is defined as powder fluid.

  That is, the pulverulent fluid in the present invention is in an intermediate state having both the characteristics of particles and liquid, as in the definition of liquid crystal (liquid and solid intermediate phase), and is the characteristic of the above-mentioned particles. It is a substance that is extremely unaffected and exhibits a unique state with high fluidity. Such a substance can be obtained in an aerosol state, that is, a dispersion system in which a solid or liquid substance is stably suspended as a dispersoid in a gas, and the solid substance is used as a dispersoid in the image display device of the present invention. Is.

The information display panel subject to the present invention is a powder exhibiting high fluidity in an aerosol state in which solid particles are stably suspended as a dispersoid, for example, in a gas as a display medium between opposing substrates, at least one of which is transparent. The fluid is sealed, and such a powder fluid can be easily and stably moved by a Coulomb force or the like by applying a low voltage.
As described above, for example, the powder fluid used as the display medium in the present invention is a substance in the intermediate state between the fluid and particles that exhibits fluidity by itself without borrowing the force of gas or liquid. It is. This powder fluid can be in an aerosol state in particular, and in the information display panel of the present invention, a solid substance is used in a state of relatively stably floating as a dispersoid in the gas.

Next, display medium particles (hereinafter also referred to as particles) constituting the display medium in the information display panel that is the subject of the present invention will be described. The display medium particles are composed of the display medium particles as they are to form a display medium, or are combined with other particles to form a display medium, or adjusted and configured to become a powder fluid to form a display medium. Or used.
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 particular, acrylic urethane resin, acrylic silicone resin, acrylic fluororesin, acrylic urethane silicone resin, acrylic urethane fluororesin, fluororesin, and silicone resin are suitable from the viewpoint of controlling the adhesive force with the substrate.

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

  As the colorant, various organic or inorganic pigments and dyes as exemplified below can be used.

Examples of the black colorant include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon and the like.
Examples of blue colorants include C.I. I. Pigment blue 15: 3, C.I. I. Pigment Blue 15, Bituminous Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Metal-free Phthalocyanine Blue, Phthalocyanine Blue Partial Chlorides, Fast Sky Blue, Indanthrene Blue BC and the like.
Examples of red colorants include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, risor red, pyrazolone red, watching red, calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, Alizarin Lake, Brilliant Carmine 3B, C.I. I. Pigment Red 2 etc.

Yellow colorants include chrome yellow, zinc yellow, cadmium yellow, yellow iron oxide, mineral first yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, C.I. I. Pigment Yellow 12 etc.
Examples of green colorants include chrome green, chromium oxide, pigment green B, C.I. I. Pigment Green 7, Malachite Green Lake, Final Yellow Green G, etc.
Examples of the orange colorant include red chrome yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK, C.I. I. Pigment Orange 31 etc.
Examples of purple colorants include manganese purple, first violet B, and methyl violet lake.
Examples of white colorants include zinc white, titanium oxide, antimony white, and zinc sulfide.

  Examples of extender pigments include barite powder, barium carbonate, clay, silica, white carbon, talc, and alumina white. Examples of various dyes such as basic, acidic, disperse, and direct dyes include nigrosine, methylene blue, rose bengal, quinoline yellow, and ultramarine blue.

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

  Further, the particles of the present invention preferably have an average particle diameter d (0.5) in the range of 0.1 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, and if it is smaller than this range, the cohesive force between the particles becomes too large, which hinders the movement of the particles.

Furthermore, in the present invention, regarding the particle size distribution of each particle, the particle size distribution Span represented by the following formula is set to 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 indicating 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 size of 90% or less.)
By keeping Span within a range of 5 or less, the size of each particle is uniform and uniform particle movement is 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.

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

  As a result of intensive studies, the present inventors evaluated the range of the appropriate charging characteristic value of the particles used in the display medium by measuring the charge amount of the particles used in the display medium using the same carrier particles in the blow-off method. I found out that I can do it.

Furthermore, in the present invention, it is important to manage the gas in the void surrounding the display medium between the substrates, which contributes to improved display stability. Specifically, it is important that the relative humidity at 25 ° C. is 60% RH or less, preferably 50% RH or less, more preferably 35% RH or less with respect to the humidity of the gas in the gap.
1A, 1B, 3A, and 3B, the gap portion is defined by the electrodes 5 and 6 and the display medium (particle group) from the portion sandwiched between the opposing substrate 1 and substrate 2. Alternatively, a gas portion in contact with a so-called display medium excluding an occupied portion of powder fluid 3, an occupied portion of partition 4 (when a partition is provided), and a seal portion of an 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 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%. When it exceeds 70%, the movement of the display medium is hindered, and when it is less than 5%, the contrast tends to be unclear.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples.

<Example 1>
Silica-coated particles were produced by the following method. First, 1 g of white polystyrene particles having an average particle diameter of 9.1 μm is dispersed in 50 ml of methanol. Next, 2.5 ml of tetraethoxysilane (TEOS) and then 10 ml of aqueous ammonia (28%) are added to the dispersion and stirred for 24 hours. Finally, the produced particles are collected by centrifugal sedimentation and dried. Regarding the particles obtained by these treatments, the particle diameter of the coated silica fine particles is shown in Table 1. The particle size was measured by analyzing the SEM image, sampling 10 of the largest and taking the average value as the particle size. Next, as an evaluation of fluidity, the sieve residue after shaking for 2 minutes with a sieve having an opening diameter of 32 μm was measured (measuring device: powder tester manufactured by Hosokawa Micron Corporation, sample: 3 g). The charge amount of the silica fine particle-coated particles (display medium particles) was also measured. The charge amount was measured by mixing 10: 1 with iron carrier particles (DFC-100Mn-Mg based wrinkle, manufactured by Dowa Iron Powder Industry Co., Ltd.), shaking for 15 minutes, and then blow-off method (blow-off particle charge measuring device TB- 203: Kyocera Chemical Co., Ltd. By the silica fine particle coating treatment, a reduction in sieve residue was observed, and an improvement in fluidity could be confirmed. Although the negative charging performance of polystyrene particles not treated with silica was reduced, particles with good fluidity could be produced. The results are shown in Table 1 below.

  Next, a glass substrate with ITO and a rib were formed on the display medium composed of the white particle group and the display medium composed of the black acrylic particle group (particle diameter: 9.2 μm) prepared by the kneading / pulverization method. An information display panel was prepared by encapsulating each layer between glass substrates with ITO. Using this panel, display durability was evaluated by repeatedly reversing the display medium. A rectangular wave (200 V, 1 Hz) was used as the applied voltage. After applying the voltage and first reversing the display 300 times, the display solid image reflection density (white density and black density) at the time of + 200V application and -200V application was measured with a reflection image densitometer (Macbeth). The ratio (reflection density at white display / reflection density at black display) was used as the contrast value, and the contrast value at this time was used as the initial contrast value. Next, voltage application of a rectangular waveform was repeated on the panel again, the display medium was reversed, and the contrast value was confirmed every certain number of times (1000 times, 10,000 times, 1 million times). Table 2 below shows the results of evaluating the display durability by repeatedly reversing the display medium by the above method. Although the initial contrast value is as low as 2.0, the contrast value after the reversal movement of the display medium is repeated 1,000,000 times does not change, and the particles for the display medium used for the information display panel with good display durability are used. We were able to make it.

<Example 2>
First, silica fine particle-coated particles were prepared in the same procedure as in Example 1. The resulting silica fine particle-coated particles were further treated as follows for the purpose of imparting charging properties. After dissolving 0.4 g of melamine prepolymer in 10 ml of distilled water, 0.09 g (100%) of acetic acid was added to make it acidic (pH 5-6), and the silica fine particle-coated particles were dispersed therein. This was heated and stirred at 60 ° C. for 1 hour to condense the melamine prepolymer. After cooling the reaction solution, the particles were washed with water and cured by heating at 120 ° C. for 1 hour. The degree of aggregation and the charge amount of the particles obtained by the above treatment are shown in Table 1 below. Through a series of treatments, particles whose chargeability was controlled to be positively charged could be obtained.

  Further, similarly to Example 1, an information display panel was prepared from the display medium composed of the white particle group and the display medium composed of the black acrylic particle group produced by the kneading / pulverization method, and the initial contrast and the predetermined number of times were obtained. The contrast after the reversal movement of the display medium was evaluated (Table 2). At this time, unlike the case of Example 1, the white polystyrene particles (display medium particles) are controlled to be positively charged, and the polarity in the reversal movement of the display medium is opposite to that of Example 1. Display medium used for an information display panel having good display durability with little change in contrast value after the reversal of the display medium is repeated 1,000,000 times, although the fluidity is somewhat poor and the contrast value is as low as 2.0 Particles could be produced.

<Example 3>
First, 1 g of white polystyrene particles having a particle size of 9.1 μm is dispersed in methanol. At this time, the amount of methanol was increased from that in Examples 1 and 2, and 80 ml was used. Next, 2.5 ml of tetraethoxysilane (TEOS) and then 10 ml of aqueous ammonia (28%) are added to the dispersion and stirred for 24 hours. Finally, the produced particles are collected by centrifugal sedimentation and dried. The particle diameter of the silica fine particles covering the obtained particle surface was determined in the same manner as described above from the SEM image. The particle size was smaller than that in Examples 1 and 2 due to the change in TEOS concentration.

  Furthermore, the following treatment was further performed on the obtained silica fine particle-coated particles for the purpose of imparting chargeability. After dissolving 0.4 g of melamine prepolymer in 10 ml of distilled water, 0.09 g (100%) of acetic acid was added to make it acidic (pH 5-6), and the silica fine particle-coated particles were dispersed therein. This was heated and stirred at 60 ° C. for 1 hour to condense the melamine prepolymer. After cooling the reaction solution, the particles were washed with water and cured by heating at 120 ° C. for 1 hour. Table 1 shows the degree of aggregation and the charge amount of the particles obtained by the above treatment. Through a series of treatments, particles having good fluidity and higher positive charging performance than those of Example 2 could be obtained. The particle size of silica fine particles covering the surface of the mother particle is reduced, the contact area is reduced, the fluidity is improved, and the surface of the silica fine particles can be sufficiently covered with melamine resin. It seems to have improved.

  Further, similarly to Example 1, an information display panel was produced from the display medium constituted by the white particle group and the display medium constituted by the black acrylic particle group produced by the kneading / pulverization method, and the initial contrast and constant constant were obtained. The contrast after the reversal movement of the number display medium was evaluated (Table 2). At this time, as in the case of Example 2, the white polystyrene particles (display medium particles) are controlled to be positively charged, and the polarity in the reversal movement of the display medium is opposite to that of Example 1. Good fluidity, high contrast value of 4.2, and a contrast value of 2.4 after repeated reversal of the display medium is used for an information display panel with good display durability. The particles for display medium could be produced.

<Example 4>
First, 1 g of white polystyrene particles having a particle size of 9.1 μm is dispersed in methanol. At this time, the amount of methanol was reduced from that in Examples 1 and 2, and 45 ml was used. Next, 2.5 ml of tetraethoxysilane (TEOS) and then 10 ml of aqueous ammonia (28%) are added to the dispersion and stirred for 24 hours. Finally, the produced particles are collected by centrifugal sedimentation and dried. The particle diameter of the silica fine particles covering the obtained particle surface was determined in the same manner as described above from the SEM image. The particle size was larger than that in Examples 1 and 2 due to the change in TEOS concentration.

  Furthermore, the following treatment was further performed on the obtained silica fine particle-coated particles for the purpose of imparting chargeability. After dissolving 0.4 g of melamine prepolymer in 10 ml of distilled water, 0.09 g (100%) of acetic acid was added to make it acidic (pH 5-6), and the silica fine particle-coated particles were dispersed therein. This was heated and stirred at 60 ° C. for 1 hour to condense the melamine prepolymer. After cooling the reaction solution, the particles were washed with water and cured by heating at 120 ° C. for 1 hour. Table 1 shows the degree of aggregation and the charge amount of the particles obtained by the above treatment. Through a series of treatments, particles whose chargeability was controlled to be positively charged could be obtained.

  Further, similarly to Example 1, an information display panel was produced from the display medium constituted by the white particle group and the display medium constituted by the black acrylic particle group produced by the kneading / pulverization method, and the initial contrast and constant constant were obtained. The contrast after the reversal movement of the number display medium was evaluated (Table 2). At this time, as in the case of Example 2, the white polystyrene particles (display medium particles) are controlled to be positively charged, and the polarity in the reversal movement of the display medium is opposite to that of Example 1. Although the fluidity is slightly poor and the contrast value is as low as 2.0, the contrast value after the reversal movement of the display medium is repeated 1,000,000 times, and the contrast value does not change, and it is used for an information display panel with good display durability. The particles for display medium could be produced.

<Comparative Example 1>
A display medium composed of white polystyrene particles having a particle diameter of 9.1 μm used in Example 1 and not coated with silica fine particles, and a display composed of black acrylic particles produced by a kneading / pulverization method An information display panel was fabricated with the medium, and the initial contrast and the contrast after the reversal movement of the display medium were evaluated for a certain number of times. Table 1 shows the results of the degree of aggregation and the charge amount, and Table 2 shows the results of evaluation of display durability in which reversal movement of the display medium is repeated. Although the initial contrast was good, the contrast value after the reversal movement of the display medium was repeated 1,000,000 times greatly decreased, and the display durability was poor.

<Comparative example 2>
First, 1 g of white polystyrene particles having a particle size of 9.1 μm was dispersed in methanol. At this time, the amount of methanol was reduced from that in Example 4, and 40 ml was used. Next, 2.5 ml of tetraethoxysilane (TEOS) and then 10 ml of aqueous ammonia (28%) were added to the dispersion and stirred for 24 hours. Finally, the produced particles were collected by centrifugal sedimentation and dried. The particle diameter of the silica fine particles on the obtained particle surface was determined in the same manner as described above from the SEM image. The particle size was larger than that of Example 4 due to the change in TEOS concentration. Furthermore, the following treatment was further performed on the obtained silica fine particle-coated particles for the purpose of imparting chargeability. After dissolving 0.4 g of melamine prepolymer in 10 ml of distilled water, 0.09 g (100%) of acetic acid was added to make it acidic (pH 5-6), and the silica fine particle-coated particles were dispersed therein. This was heated and stirred at 60 ° C. for 1 hour to condense the melamine prepolymer. After cooling the reaction solution, the particles were washed with water and cured by heating at 120 ° C. for 1 hour. Table 1 shows the degree of aggregation and the charge amount of the particles obtained by the above treatment. As the particle diameter of the coated silica fine particles was increased, the fluidity and charge amount were reduced as compared with Example 4.

  Further, similarly to Example 1, an information display panel was produced from the display medium constituted by the white particle group and the display medium constituted by the black acrylic particle group produced by the kneading / pulverization method, and the initial contrast and constant constant were obtained. The contrast after the reversal movement of the number display medium was evaluated (Table 2). At this time, as in the case of Example 2, the white polystyrene particles (display medium particles) are controlled to be positively charged, and the polarity in the reversal movement of the display medium is opposite to that of Example 1. Since the amount of charge was not sufficient, the contrast value was low from the beginning, and sufficient visibility could not be ensured.

  Based on the results of Tables 1 and 2, information using the particles for display media of Examples 1 to 4 coated with silica fine particles having a particle diameter average value of 450 nm or less obtained by sampling and analyzing a maximum of 10 SEM images. The display panel was compared with Comparative Example 1 in which the silica fine particles were not coated and Comparative Example 2 in which a maximum of 10 samples were sampled from the SEM image and subjected to image analysis to cover the silica fine particles having an average particle diameter exceeding 450 nm. It can be seen that the contrast value after the reversal of the display medium is repeated 1,000,000 times is good, and the display durability can be improved.

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

(A), (b) is a figure which shows an example of the information display panel used as the object of this invention, respectively. (A), (b) is a figure which shows the other example of the information display panel used as the object of this invention, respectively. (A), (b) is a figure which shows the further another example of the information display panel used as the object of this invention, respectively. It is a figure for demonstrating an example of the particle | grains for display media used for the information display panel of this invention. The example which imaged with the scanning electron microscope (SEM) of the particle | grains for display media used for the information display panel of this invention is shown. It is a figure which shows an example of the shape of the partition in the information display panel used as the object of this invention.

Explanation of symbols

1, 2 Substrate 3 Display medium (particle group or powder fluid)
3W White particle group 3B Black particle group 4 Partition wall 5, 6 Electrode 11 Display medium particle 12 Particle 13 Silica fine particle

Claims (3)

  A display medium constituting a display medium used for an information display panel that displays information by moving the display medium by enclosing the display medium between two substrates transparent at least one and applying an electric field to the display medium Particles for display media used for information display panels, characterized in that the surface of the particles is coated with silica fine particles having a particle diameter of 450 nm or less by a sol-gel method. The average value obtained by sampling and analyzing the maximum 10 samples.   2. The display medium particle for use in an information display panel according to claim 1, wherein the surface is treated with a chargeable resin after the silica fine particles are coated. The particle for display medium used for the information display panel according to claim 2, wherein a surface treatment for imparting a charge amount is performed with a melamine resin.