JP2007171479A - Particle for display medium and panel for information display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide particles for a display medium which have excellent coloring property as particles, e.g., powder fluid constituting the display medium, and to provide a panel for information display using the same. <P>SOLUTION: The particles 11 constitute the display medium used for a panel for information display that have the display medium with optical reflectivity and charging characteristics 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 of an image etc., and each particle 12 has pigments 13 arranged nearby its surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention encloses a display medium having optical reflectance and charging characteristics 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 particles that constitute a display medium used for an information display panel that displays and information display panels using the same.

Conventionally, a display medium having optical reflectance and charging characteristics is sealed between two substrates, at least one of which is transparent, and an electric field is applied to the display medium to move the display medium and display information such as an image. An information display panel is known (see, for example, Patent Document 1). In this information display panel, the display state can be maintained without applying external energy because the information display panel is attached to the substrate surface by the interaction force caused by the electric charge of the particles while not being driven.
WO / 2005/098525 brochure

  The particles constituting the display medium used in such an information display panel need to satisfy various characteristics in order to reveal a predetermined display quality, one of which is tint. In particular, such an information display panel is a reflective display system that directly recognizes an aggregate of display media made up of particles for display media, as a characteristic point of an existing display system such as a liquid crystal display. Is mentioned. In this case, since each of the display medium particles constituting the display medium is recognized by reflected light, how efficiently the particles scatter light is necessary to realize clear visibility. Is important.

  The simplest way to achieve this goal is to load more pigment. However, due to restrictions on the manufacturing method, it is very difficult to fill the particles with a large excess of pigment and to make them inherent. Further, if the amount of pigment used is increased, it is disadvantageous in terms of production cost. Furthermore, charging characteristics can be cited as a basic characteristic of the display medium particles. This is an indispensable factor in the system for controlling the electric field of the particles, but the pigment itself has a considerable effect on the charging characteristics of the particles for the display medium. Result. As described above, there is a demand for a method for efficiently expressing the target color with less pigment content, and approaches such as improving efficiency by controlling the dispersibility of pigments have been attempted. There is no improvement method yet.

  An object of the present invention is to solve the above-mentioned problems and to provide display medium particles having good colorability as particles constituting a display medium such as powdered fluid and an information display panel using the same. It is.

  The particles for a display medium of the present invention move a display medium by enclosing a display medium having optical reflectance and charging characteristics between two substrates, at least one of which is transparent, and applying an electric field to the display medium. Thus, particles constituting a display medium used for an information display panel for displaying information such as images are characterized in that pigments are arranged in the vicinity of the surface of the particles.

  In addition, as a suitable example of the particles for a display medium of the present invention, a part of the pigment is exposed on the particle surface, and the exposed pigment or the pigment disposed in the vicinity of the particle surface with respect to the total surface area of the particle. The proportion of the part may be 10% or more.

  Further, the information display panel of the present invention encloses a display medium by enclosing a display medium having optical reflectance and charging characteristics between two substrates, at least one of which is transparent, and applying an electric field to the display medium. In an information display panel that moves and displays information such as an image, the above-described particles for a display medium are used as a display medium.

  According to the present invention, by disposing the pigment in the vicinity of the surface of the particles, display medium particles having good colorability as particles constituting a display medium such as a powder fluid and an information display panel using the same are obtained. be able to.

  First, the basic configuration of the information display panel of the present invention will be described. In the information display panel which is an object of the present invention, an electric field is applied to a display medium sealed between two opposing substrates. Along with the applied electric field direction, the charged display medium is attracted by the electric field force or Coulomb force, etc., and the display medium changes the moving direction by the electric field direction change due to the potential switching, thereby displaying information such as an image. Made. Therefore, it is necessary to design the information display panel so that the display medium can move uniformly and maintain stability when rewriting the display repeatedly or when displaying the display information continuously. Here, as the force applied to the particles constituting the display medium, in addition to the force attracting each other by the Coulomb force between the particles, an electric mirror image force between the electrode and the substrate, an intermolecular force, a liquid cross-linking force, gravity and the like can be considered.

  An example of an information display panel 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, for example, in the form of a lattice to form a cell. In addition, in FIG. 1B, the partition in front is omitted.

  In the example shown in FIGS. 2A and 2B, at least two or more types of display media 3 (here, white display medium particles 3Wa) having different optical reflectance and charging characteristics composed of at least one type of particles. 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. 2B, a cell is formed by providing partition walls 4 between the substrates 1 and 2, for example, in a lattice shape. Further, in FIG. 2 (b), the front partition is omitted.

  In the example shown in FIGS. 3A and 3B, the display medium 3 (here, from the particle group of the particles 3Wa for white display medium) having at least an optical reflectance and a charging property composed of at least one kind of particles. The white display medium 3W) is moved in a direction parallel to the substrates 1 and 2 in accordance with the electric field generated by applying a voltage between the electrode 5 and the electrode 6 provided on the substrate 1 to display white. The medium 3W is visually recognized by the observer and white display is performed, or the color of the electrode 6 or the substrate 1 is visually recognized by the observer and the color of the electrode 6 or the substrate 1 is displayed. In the example shown in FIG. 3B, 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.

  The above description applies in the same manner to the case where the white display medium 3W including the particle group is replaced with the white medium including the powder fluid and the black display medium 3B including the particle group is replaced with the black display medium including the powder fluid. I can do it. The powder fluid will be described later.

  As a result of various examinations on the colorability of the display medium particles used in the information display panel having the above-described configuration, even when the pigment content particles of the same degree are compared with each other, the apparent coloration may differ as a color. It turns out that there is. As a result of examining this in detail, it became clear that the particles in the vicinity of the surface of the particles, particularly preferably in a state in which a part of the pigment is exposed on the surface of the particles, have good colorability. I came to find it.

  This is presumably because if the pigment is present in the deep part from the vicinity of the particle surface, the coloring property of the pigment itself is not sufficiently developed due to the scattering of the binder layer such as resin. As a result of further detailed investigation, it has been found that the coloring efficiency is particularly reduced when the ratio of the portion depending on the exposed pigment or the pigment arranged in the vicinity of the particle surface is less than 10% with respect to the total particle surface area. It should be noted that a two-dimensional image of a reflection electron micrograph was simply used for the determination of the ratio of the portion by the pigment arranged in the vicinity of the exposed surface or the surface relative to the total particle surface area. When the pigment can be confirmed by the image evaluation, it can be determined that the pigment is present or exposed in the vicinity of the surface.

  Specific methods for realizing the above-described configuration are not limited to the following examples. For example, when desired particles are produced by pulverization classification after kneading a resin and a pigment, the dispersion method is controlled and the surface properties of the pigment. By controlling the dispersibility of the pigments and setting conditions that do not give excessive dispersion force under conditions where excessive dispersion spots do not occur, the coarse and dense period of pigment dispersion is close to the target particle size In this state, pulverization occurs selectively from the portion where the pigment becomes dense during pulverization, and as a result, the proportion of the pigment increases near the particle surface. It is also effective to directly immobilize the pigment on the particle surface using a mechanochemical method after the particles are produced.

  FIG. 4 is a diagram showing an example of the display medium particle 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 pigment 13 is arranged in the vicinity of the surface of the particle 12, here, a part of the pigment 13 is exposed on the surface of the particle 12. There is in point to do. The amount of the pigment 13 exposed on the surface of the particle 12 or the amount of the pigment arranged in the vicinity of the particle surface is not particularly limited. However, as described above, it is exposed with respect to the total surface area of the particle 12 in terms of coloring efficiency. It is preferable that the proportion of the portion depending on the pigment or the pigment arranged near the particle surface is 10% or more.

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

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

  As an electrode forming material when an electrode is provided on an information display panel as required, metals such as aluminum, silver, nickel, copper, and gold, ITO, indium oxide, conductive tin oxide, conductive zinc oxide, etc. Conductive polymers such as conductive metal oxides, polyaniline, polypyrrole, and polythiophene are exemplified and 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 display surface side substrate 2 which is on the viewing side and needs to be transparent needs to be transparent, but the electrode provided on the back side substrate 1 does not need to be transparent. In any case, the above-mentioned material that can be patterned and is electrically conductive can be suitably used. Note that the electrode thickness 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 1 are the same as those of the electrode provided on the display surface side substrate described above, but need not be transparent. In this case, the external voltage input may be superimposed with direct current or alternating current.

The shape of the partition walls 4 provided on the substrate as required is appropriately set appropriately depending on the type of display medium involved in display, the shape and arrangement of electrodes to be arranged, and is not limited in general. The height of the partition is adjusted to 100 to 100 μm, preferably 3 to 50 μm, and the height of the partition wall 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. 5, the cells formed by the partition walls made up of these ribs are illustrated in a square shape, a triangular shape, a line shape, a circular shape, and a hexagonal shape as viewed from the substrate plane direction. And a mesh shape. It is better to make the portion corresponding to the cross section of the partition wall visible from the display surface side (the area of the cell frame) as small as possible, and the display becomes clearer.
Examples of the method for forming the partition include a mold transfer method, a screen printing method, a sand blast method, a photolithography method, and an additive method. Any of these methods can be suitably used for the information display panel of the present invention, and among these, a photolithography method using a resist film and a mold transfer method are suitably used.

  Next, the powder fluid used as a display medium composed of the display medium particles of the present invention will be described. As for the name of the powder fluid used in the information display panel 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, in a dispersion system in which a solid or liquid substance is stably suspended as a dispersoid in a gas, and the solid substance is regarded as a dispersoid in the information display panel of the present invention. To do.

The information display panel of the present invention encloses a powder fluid exhibiting high fluidity in an aerosol state in which solid particles are stably suspended as a dispersoid, for example, in a gas, between opposed substrates, at least one of which is transparent. In addition, such a powder fluid can be easily and stably moved by a Coulomb force or the like with a small electric field.
As described above, for example, the powder fluid used as a display medium in the present invention is a substance in an intermediate state between 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, it is used as a display medium in a state where a solid substance floats relatively stably 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 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, as necessary, in the resin as the main component, as necessary. 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, in addition to the color pigments exemplified below, various kinds of organic or inorganic fine particles and dyes of each color 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.

  The particles for display media of the present invention (hereinafter also referred to as particles) 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. 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 the d (0.5) of the particles having the minimum diameter to the 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, put particles into a nitrogen stream and use the attached analysis software (software based on volume-based distribution using Mie theory). The diameter and particle size distribution can be measured.

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

  As a result of intensive studies, the present inventors have been able to evaluate the range of proper charging characteristics of display medium particles 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.

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

  A display medium comprising the display medium particles of the present invention was prepared as follows, an information display panel was prepared using the prepared display medium, and the color was evaluated.

<Preparation of display medium>
A display medium prepared as follows was prepared. This was case of white particles for display media using titania (TiO _2), but it is not limited to the difference in color of the pigment species and the purpose is obvious.

  A cycloolefin resin compound containing 100 parts by weight of titania for pigment as a color pigment was prepared, and this was classified using an airflow type pulverization classifier so as to have an average particle size of 9.0 μm. The specific gravity of this was 1.5. Here, particles in which the dispersion conditions during compounding were changed as shown in Table 1 below were facilitated. The obtained particles were photographed with a scanning electron microscope S-2700 manufactured by Hitachi, Ltd., and the obtained image was projected using the image analysis software Mac-View (manufactured by MOUNTECH Co., Ltd.) and the projected particle area and the inside of the projected particle area. The total exposed area of the pigment was determined, and the exposed pigment dependence ratio S (%) was calculated from the ratio. To 100 parts by weight of the particles, 2.2 parts by weight of hydrophobic fumed silica RX300 manufactured by Nippon Aerosil Co., Ltd. was mixed and stirred at 3000 rpm for 30 minutes with a carbon mixer HFM-001C (manufactured by SMT Co., Ltd.). A white display medium composed of particles for use was obtained.

<Preparation of sample for evaluation of color and evaluation of color>
A white display medium was prepared as an evaluation sample. The display medium was triboelectrically charged by carrying N ₂ air current through the stainless steel tube. Furthermore, a glass substrate (A) having a thickness of 700 μm, on which an inner surface is ITO-coated, provided with a 40 μm spacer (to be a partition wall) is prepared, and between the stainless steel tube and the ITO surface of the glass substrate. An evaluation sample was laminated by spraying the sample on the ITO surface in a dry air atmosphere of 22.5 ° C. and 5% RH where the bias voltage was superimposed and the airflow was stable. After performing the above-described steps, only the display medium attached to the spacer surface was removed.

  Furthermore, a glass substrate (B) on which one side was coated with ITO was prepared, and bonded to the glass substrate (A) on which the display medium serving as the sample was laminated so that the ITO surface faced inward. At this time, an ultraviolet (UV) curable one-part epoxy adhesive was used for adhesion. In order to standardize the laminated thickness of the display medium, it is controlled by a change in the weight of the glass substrate, and the evaluation of the color of the display medium is performed by using the reflection image densitometer (RD918, manufactured by Macbeth). It was determined by measuring using All evaluations were performed from the glass substrate (A) side, and evaluation was performed on a black plate. The results are shown in Table 1 below. As shown in Table 1 below, it can be seen that those having S of 20% or more show a higher reflectance than those having S of 20% or more.

  The information display panel of the present invention can obtain a reflected image with a wide viewing angle by using the particles for display medium of the present invention, and has high visibility like a printed paper. Display units for mobile devices such as mobile phones and handy terminals, electronic papers such as electronic books and electronic newspapers, billboards such as signboards, posters, blackboards, display units for calculators, home appliances, automotive products, point cards, IC cards, etc. Card display unit, electronic advertisement, information board, electronic POP (Point Of Presence, Point Of Purchase advertising), electronic price tag, electronic shelf label, electronic score, display unit of RF-ID device, etc.

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

Explanation of symbols

1, 2 Substrate 3 Display medium (particle group, powder fluid)
3W White display medium 3Wa White display medium particle 3B Black display medium 3Ba Black display medium particle 4 Partition wall 5, 6 Electrode 11 Display medium particle 12 Particle 13 Pigment

Claims (4)

  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 A particle for a display medium, which is a particle constituting a display medium used for a display panel, wherein a pigment is disposed in the vicinity of the surface of the particle.   2. The display medium particle according to claim 1, wherein a part of the pigment is exposed on the particle surface.   3. The display medium particle according to claim 1, wherein a ratio of the exposed pigment or a portion due to the pigment arranged in the vicinity of the particle surface is 10% or more with respect to the total surface area of the particle.   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 A display panel, wherein the display medium particle according to any one of claims 1 to 3 is used as a display medium.

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