JP2006323158A - Particles for display medium and method for manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide particles for a display medium that can keep stable display performance even when operated for a long period of time as a display medium used for an information display panel, and to provide a method for manufacturing the particles. <P>SOLUTION: The particles for a display medium are manufactured by preliminarily deciding the order of hardness in mother particles, an adhesive layer and fine particles in relation between the mother particles and fine particles and between mother particles having an adhesive layer on surfaces and fine particles, and then using a combination of mother particles, fine particles and an adhesive layer in relation concerning hardness of, from high hardness to low hardness, mother particles>fine particles>adhesive layer. Thus, the particles for a display medium comprising the mother articles, the adhesive layer disposed on the surface of the mother particles, and the fine particles buried in the adhesive layer while partially exposed to the outside but not buried in the mother particles are obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

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. The present invention relates to particles and a method for producing the same.

  2. Description of the Related Art Conventionally, information display devices using techniques such as electrophoresis, electrochromic, thermal, and two-color particle rotation have been proposed as information display devices 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 uniformly inject the charge 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 display media used in information display panels, in order to reduce the adhesion between the particles and the substrate, fine particles such as silica and titanium oxide are coated (attached) on the surface of the mother particles. Use is known. However, since the particles for display medium described above have insufficient adhesion of the fine particles to the surface of the mother particles, the desorption / migration of the fine particles in the system occurs, resulting in the charging characteristics and fluidity of the display medium particles. Has changed, and there has been a problem that optimal image display cannot be realized under the same conditions, or display becomes impossible.

  In order to prevent the detachment of the fine particles, a method of immobilizing the fine particles by using a physical interaction by an anchor effect or the like or a chemical interaction by a reactive adhesive or the like on the surface of the mother particle can be considered. However, even if this method is used, there is no problem at first, but the fine particles are gradually completely buried inside the mother particles, and the fluidity modification effect by the fine particles disappears in the long term. This also causes display characteristic fluctuations.

  As a method for solving the above problems, embedding is suppressed by a configuration in which hard fine particles are coated on the surface of hard mother particles, and at the same time, an adhesive layer made of a material softer than the mother particles and fine particles is provided on the surface of the mother particles. It is possible to consider particles designed to prevent migration over time by immobilizing the fine particles by physical / chemical interaction as described above with respect to the layer. In order to realize the particle production of this design, it is necessary that mother particles / adhesive layer material / fine particles have an appropriate hardness permutation.

  However, the hardness permutation here does not necessarily match that obtained by macroscopic comparison evaluation using a bulk material of the material constituting the base particles / adhesive layer material / fine particles. This is because the situation where the actual immobilization process proceeds is an environment of submicron order, and the shapes of the opposing materials are too different (for example, when considering the combination of mother particles / fine particles, the action on the mother particle side) The surface can be regarded as almost flat, but the fine particle side must be regarded as a large curvature surface on the submicron scale). For this reason, it is the actual situation that it is impossible to know whether it is possible to actually produce particles as designed in this test, and this point prolongs the development man-hour and constitutes the display medium of the information display panel This is a major obstacle to optimizing performance as particles for display media.

  An object of the present invention is to solve the above-mentioned problems, and as a display medium particle constituting a display medium of an information display panel, a display medium particle capable of maintaining stable display performance even when operated for a long period of time, and its production Is to provide a method.

  The display medium particle of the present invention is 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. The display medium particles used in the present invention are composed of mother particles, an adhesive layer provided on the surface of the mother particles, and fine particles that are partially exposed and buried in the adhesive layer and that are not buried in the mother particles. It is a feature.

  In addition, as a suitable example of the particles for a display medium of the present invention, when the average particle diameter of the fine particles is D2 and the final thickness of the adhesive layer is L2, there is a relationship between the average particle diameter of the fine particles and the thickness of the adhesive layer. 0.3D2 ≦ L2 ≦ D2.

  Furthermore, in the method for producing display medium particles according to the present invention, in producing the display medium particles having the above-described configuration, between the mother particles and the fine particles and between the mother particles and the fine particles having an adhesive layer on the surface. In this case, the order of hardness of the mother particles, the adhesive layer, and the fine particles is determined in advance, and the order of the hardness is mother particles> fine particles> adhesive layer. It is characterized by manufacturing.

  According to the particles for display medium and the method for producing the same of the present invention, the hardness of the mother particles, the adhesive layer, and the fine particles in advance between the mother particles and the fine particles and between the mother particles and the fine particles having the adhesive layer on the surface. The order of the hardness is determined, and the particles for the display medium are manufactured using a combination of mother particles, fine particles and an adhesive layer in which the hardness order is a relationship of mother particles> fine particles> adhesive layer. It is possible to suitably obtain a display medium particle comprising an adhesive layer provided on the surface and fine particles that are partly exposed and embedded in the adhesive layer and that are not embedded in the mother particle. As a result, it is possible to obtain display medium particles that can maintain stable display performance even when operated for a long period of time as display medium particles constituting the display medium of the information display panel.

  First, a basic configuration of an information display panel that is an object 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 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 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, in addition to the example shown in FIG. 2A, for example, a partition 4 is provided between the substrates 1 and 2 to form a cell. Further, in FIG. 2 (b), the front partition is omitted.

  In the example shown in FIGS. 3 (a) and 3 (b), 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. Group white display medium 3W) is moved in a direction parallel to substrates 1 and 2 in accordance with an electric field generated by applying a voltage between electrode 5 and electrode 6 provided on substrate 1; The white display medium 3W is visually recognized by the observer to display white, 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. In the example shown in FIG. 3B, in addition to the example shown in FIG. 3A, for example, a grid-like 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 is similarly applied to the case where the white display medium 3W including the particle group is replaced with the white display 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 feature of the present invention is a method for determining the order of hardness of particles that can be suitably used for producing particles (display medium particles) constituting the display medium 3 of the information display panel having the above-described configuration, and the structure of the display medium particles. And a production method suitable for producing the particles for a display medium. Hereinafter, these will be described.

  FIG. 4 is a diagram showing a configuration of an example of the display medium particle of the present invention. In the example shown in FIG. 4, the display medium particle 11 of the present invention includes a mother particle 12, an adhesive layer 13 provided on the surface of the mother particle 12, a part of the adhesive layer 13 exposed and buried, and a mother particle. 12 includes fine particles 14 that are not buried. In order to achieve the above configuration, it is necessary to make the hardness of the base particles 12, the adhesive layer 13, and the fine particles 14 have a predetermined relationship.

  The inventors produce particles for a display medium comprising mother particles, an adhesive layer provided on the surface of the mother particles, and fine particles that are partially exposed and buried in the adhesive layer, but are not buried in the mother particles. As a method for easily knowing the relationship between the hardness of the mother particles, fine particles, and adhesive layer necessary for this purpose, we have developed a method for determining the order of hardness of fine particle materials, the “Media Impact Method” described below.

  In the method for determining the order of hardness of the fine particle material used in the present invention (MI method), a plurality of types of fine particle materials (for example, two types of materials consisting of mother particles and fine particles) whose hardness order is to be determined are obtained from the plurality of types of fine particle materials. After mixing and shaking with a medium made of a material with high hardness and high specific gravity, the fine particle material on the high hardness side does not deform and the fine particle material on the low hardness side is deformed, and the fine particle material on the high hardness side is on the low hardness side By observing the form embedded in the fine particle material, for example, when the large fine particle is not deformed and the small fine particle is deformed, it is determined that the large fine particle is harder than the small fine particle, and the small fine particle is buried in the large fine particle. In this case, it is determined that the large particles are softer than the small particles, and if the small particles are not embedded in the large particles, it is determined that the large particles are harder than the small particles, and the hardness order of the plurality of types of particles is determined. To.

  In the MI test, a medium having high hardness and high specific gravity is used to stir the particulate material. By adding this medium and adopting a method of mixing and shaking the particulate material in a small scale container, the hardness permutation can be determined directly in a short time while minimizing the sample usage fee. As the medium, a medium made of a material having a high hardness and a high specific gravity is suitable because a certain amount of kinetic energy needs to be given to the fine particles as a sample. Specifically, iron-based compounds such as ferrite and magnetite, ceramics such as zirconia, alumina, and silicon nitride, or composite beads using these materials as core materials are suitable. It is necessary to adjust accordingly.

  Further, according to the study by the present inventors, there is a suitable relationship between the size of each particulate material and the size of the media. If it is too small, the kinetic energy given by the media will be small, and it will be too large. And the gap between the media is too wide, and the burial / deformation is accelerated for a long time, or the burial / deformation does not progress at all. Therefore, when the average particle diameter of the medium is D and the average particle diameter of the fine particle material having the largest average particle diameter among the plural kinds of fine particle materials to be compared in hardness is d, the relationship between the two is 5d ≦ D ≦ It is desirable to be 300d.

  In order to determine the hardness order of a plurality of types of microparticles by the MI test, it is desirable to observe the morphology of a plurality of types of microparticles using any one of an optical microscope, a loupe, a video microscope, and a scanning electron microscope (SEM). In the present invention, the method of directly observing the state of the fine particles is adopted to improve the simplicity of the hardness order determination. Further, in the determination of the hardness order of a plurality of types of microparticles by the MI test, the hardness order is evaluated based on the morphology observation of the plurality of types of microparticles. Desirable for order determination. Therefore, when the average particle diameter of the particulate material is d1, and the average particle diameter of the particulate material to be compared is d2, the relationship between the two is d1 ≧ 10d2 or d1 ≦ d2 / 10, Multiple types of particulate materials to be processed are a combination of an irregularly shaped particulate material having a surface with wrinkles and a spherical particulate material (for example, one is a pulverized particle) It is desirable that the fine particles have a rugged shape and the other is a true spherical particle. Further, in the MI test, when a plurality of types of fine particle materials are a combination of fine particle materials having a difference in at least one of particle diameter and particle shape, the hardness of each of the plurality of types of fine particles is compared in order of hardness. It is desirable to determine.

  As a result, the “hardness permutation” in consideration of the size and shape of the actual particle design, which is really necessary for producing the display medium particles of the present invention, is required before the display medium particles are manufactured. It became possible to judge. Using this method for determining the hardness order of particles, the order of hardness and the superiority or inferiority of the particles for display media are determined. As a result, if the adhesive layer material is not softer than the fine particles, the desired composite particle structure is produced. I knew I couldn't. That is, when the MI test is performed with the mother particles and the fine particles provided with the adhesive layer, the fine particles must be buried in the surface of the adhesive layer, and the fine particles should not be crushed on the surface of the adhesive layer.

  It was also found that when the mother particles are softer than the fine particles between the mother particles and the fine particles, defects in display performance stability occur as display medium particles. That is, when the same evaluation is performed using mother particles not provided with an adhesive layer, the embedding of fine particles should not be observed. It is necessary to adjust the thickness of the adhesive layer so that when the fine particles are completely buried until they come into contact with the mother particles, the thickness of the adhesive layer after fixing is not 0 with respect to the average particle diameter D2 of the fine particles. It is desirable that 3D2 ≦ L2 <D2.

  As a method for attaching the adhesive layer, (1) seascore-type particles are prepared by a polymerization method, (2) particles made of the material for the adhesive layer are coated on the surface of the mother particles, and agitation / heating treatment is performed. Methods such as melting and skinning the fine particles, (3) coating the adhesive layer material on the mother particles using a spray drying method, a Henschel stirring method, and the like are conceivable. In the above cases (1) and (3), it is necessary to prepare particles of a material corresponding to each adhesive layer in performing the media impact test. In the case of (2) above, the particles of the adhesive layer material described above may be used as they are. The necessity of the adhesive layer being soft is to fix the fine particles. Therefore, there is no problem even when the adhesive layer is cured by a method such as post-crosslinking after the fixing process and the final hardness permutation is out of order.

  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 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, 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 2 to 5000 μm, more preferably 5 to 2000 μm. If it is too thin, it will be difficult to maintain the strength and the uniformity of the distance between the substrates, and if it is thicker than 5000 μm, it will be a thin information display panel. Is inconvenient.

  Electrode forming materials for providing electrodes on information display panels include metals such as aluminum, silver, nickel, copper, and gold, and conductive metal oxides such as ITO, indium oxide, conductive tin oxide, and conductive zinc oxide. , Conductive polymers such as polyaniline, polypyrrole, polythiophene and the like 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 (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 partition 4 provided on the substrate as required is optimally set depending on the type of display medium involved in display, and is not limited in general. However, the width of the partition is 2 to 100 μm, preferably 3 to 50 μm. The height of the partition wall is adjusted to 10 to 500 μm, preferably 10 to 200 μm. As shown in FIG. 5, the cells formed by the partition walls made of these ribs are exemplified by a square shape, a triangular shape, a line shape, a circular shape, and a hexagonal shape as viewed from the 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.

Next, the basic part of the display medium particles (hereinafter also referred to as particles) constituting the display medium in the information display panel will be described. In the present invention, as described above, it is important that the display medium particles are composed of mother particles, an adhesive layer, and fine particles, and the following description is a description of basic mother particles.
The particles used as the base particles of the display medium particles of the present invention may contain a charge control agent, a colorant, an inorganic additive, etc., as necessary, in the resin as the main component, as necessary. it can. In addition, fine particles made of these materials can also be used as fine particles that are fixed together with the adhesive layer on the surface of the mother particles. Examples of resins, charge control agents, colorants, and other additives will be given below.

  Examples of the resin material for the mother particles include styrene resins, acrylic resins, styrene / acrylic copolymers, styrene / butadiene copolymers, styrene / maleic anhydride copolymers, polyethylene, polypropylene, epoxy resins, and polyesters. Resin, aromatic polyester resin, urethane resin, urea resin, acrylic urethane resin, acrylic urethane silicone resin, acrylic urethane fluorine resin, acrylic fluorine resin, silicone resin, acrylic silicone resin, polyolefin resin Resin, butyral resin, chlorovinylidene resin, melamine resin, phenol resin, fluorine resin, polymethylpentene resin, polycarbonate resin, polysulfone resin, polycycloolefin resin, polyether resin, Examples of the base particles of interest include at least one main skeleton of at least one of a styrene-based, acrylic-based, cycloolefin-based, methylpentene-based resin, amide-based, and aromatic ester-based structure. The cross-linking type resin contained in is particularly preferably used.

  These crosslinking methods are not particularly limited, and may be any method such as temperature, pressure, radical initiator, and radiation. Furthermore, the timing of the three-dimensional cross-linking formation is not particularly limited, and the cross-linking reaction may be started after the particle composite is formed, or after the particle surface treatment is completed. However, in general, the second and third approaches seem to be advantageous in terms of grinding efficiency.

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

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

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

As yellow colorants, yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral first yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, 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.

  In addition, the particles for display medium of the present invention have an average particle diameter d (0.5) in the range of 0.1 to 20 μm, and are preferably uniform and uniform. If the average particle diameter d (0.5) is larger than this range, the display is not clear, and if it is smaller than this range, the cohesive force between the particles becomes too large, which hinders the movement of the particles.

  Next, the fine particles used in the present invention will be described. The fine particle material is required to have hardness and strength that can withstand collision and shearing with other display medium particles and substrates. Materials satisfying these conditions include silica, titania, alumina, zirconia, yttria, calcium oxide, magnesium oxide, barium oxide, beryllium oxide, zinc oxide, tin oxide and other metal oxide inorganic particles, and crosslinked resin particles. For example, silica, titania, and crosslinked resin fine particles are particularly preferably used for this purpose.

  Next, the adhesive layer used in the present invention will be described. The adhesive layer only needs to be a material having a function of fixing the base particles and the fine particles so that they are not detached from each other, and the material is an uncrosslinked series of resins suitably used for the base particles. The type is appropriate. Of course, it goes without saying that the hardness permutation described above must be satisfied before the fine particles are fixed.

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 uniform particle movement 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 mother particles of 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 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 powdered 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, preferably 50% RH or less, more preferably 35% RH or less with respect to 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), 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%. 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.

  In the following description, first, measurement of particle specific gravity common to Examples and Comparative Examples, measurement of average particle diameter, media impact test, production of display test apparatus, durability driveability / display characteristic evaluation are described, and then actual A comparative example of the embodiment will be described.

(1) Particle specific gravity The particle specific gravity was determined from the sample volume measured with a pycnometer (multi-volume pycnometer H1305: manufactured by Shimadzu Corporation) and the weighed weight.

(2) Average particle size For the average particle size of the mother particles, put each particle into a particle size distribution analyzer (MasterSizer2000: Malvern Instruments Ltd.) and measure the particle size distribution. Was used, and a particle size of 50% was smaller than this. The average primary particle size of the fine particle and particulate adhesive layer material is converted to a sphere from the BET specific surface area (AutoSorb-1-AG: manufactured by Quantachrome) obtained from the N ₂ gas adsorption amount and the particle specific gravity obtained by the above measurement. The value calculated in (1) was used.

(3) Media Impact Test This time, we propose the “Media Impact (MI) Method” as a method for evaluating the hardness difference between particles. In this method, a “media impact (MI) test” shown below is performed to evaluate the hardness difference.
First, 20 g of sintered ferrite particles having an average particle diameter of 100 μm are put into a 100 cc polypropylene container, and two kinds of particles for determining the hardness difference are put therein. These two particles should have a certain difference in particle diameter. Specifically, the particle diameter of the fine particles is preferably 1/10 or less of the particle diameter of the mother particles. The input amount may be adjusted as appropriate depending on the type of sample to be evaluated, but the mother particles are particles having a particle size in the vicinity of a single micron to sub-millimeter scale used for display medium particles and a specific gravity of about 0.5 to 2.0. As a recommended blending condition, the equivalent of 5 wt% can be mentioned based on the particle diameter of the mother particle among the two kinds of particles. Further, the input ratio of the two kinds of particles is in accordance with the mixing ratio for obtaining desired composite particles (display medium particles). This is shaken with a hand shaker (for example, YS-8D manufactured by Yayoi Co., Ltd.) in an environment of 22.5 ° C. and 50% RH. The shaking conditions may be adjusted as appropriate depending on the type of sample to be evaluated. The recommended shaking conditions for the display medium particles include, for example, a shaking radius of 12 cm, a shaking width of 0 ° to 45 ° upward, a shaking speed of 250 shaking per minute, and shaking. Time 15 minutes. The above recommended conditions were used for all the MI tests conducted on each sample introduced in this example / comparative example.
Thereafter, the taken-out sample is observed with a SEM for burying / deformation of the mother particles with respect to the fine particles. If the mother particles are softer than the fine particles, it is observed that the fine particles are buried in the mother particles. On the other hand, if the mother particles are harder than the fine particles, the fine particles are not embedded in the mother particles, and depending on the difference, the fine particles are crushed.

(4) Production of display test apparatus Black particles and white particles were prepared as evaluation samples. Both particles were triboelectrically charged by carrying N ₂ air current through the stainless steel tube. Furthermore, a glass substrate (A) with an inner surface coated with ITO coated with a 100 μm spacer is prepared, and a bias voltage is superimposed between the stainless steel tube and the ITO surface of the glass substrate to stabilize airflow. The evaluation sample was laminated by spraying the sample on the ITO surface in a dry air atmosphere of 22.5 ° C. and 5% rh. After the process was sequentially performed on both the black particles and the white particles, only the particles adhering to the spacer surface were removed. Furthermore, the glass substrate (B) by which one side was ITO-coated was prepared, and it bonded together so that an ITO surface might face an inner side with respect to the glass substrate which laminated | stacked said sample particle. At this time, a UV curable one-component epoxy adhesive was used for adhesion. Finally, electrodes were pulled out from the ITO surfaces of both glasses to form a display test apparatus. At this time, the particles arranged in the test apparatus were appropriately adjusted so that the total volume of the black particles and the white particles was equal and the filling rate of the evaluation particles in the test apparatus was 25%. The electrode and the power source were connected with the glass substrate (A) on the ground side and the glass substrate (B) on the bias side. As a result of evaluating the series of samples prepared this time, the display medium (display medium particles) driven was displayed in black when viewed from the glass substrate (A) side when a positive potential was superimposed. When the negative potential was superimposed, the display medium (display medium particles) that was driven was displayed in white when viewed from the glass substrate (A) side.

(5) Evaluation of driving durability and display characteristics The driving durability evaluation of particles is performed by preparing a display test apparatus using the particles to be evaluated as described above, and by the following display performance evaluation method. The evaluation index Ct was compared with time.
A voltage is applied to the produced display device, and the reflection density indicated by the display test device is measured using a reflection image densitometer (RD918, manufactured by Macbeth). Next, the voltage is applied with the polarity reversed, and the reflection density is obtained again. This step is defined as one cycle, and the difference in reflection density obtained here is defined as Ct. The above cycle was repeated, and the obtained data was plotted on a graph with the horizontal axis as the number of polarity inversions and the vertical axis as the reflection density, and the driving durability of the particles to be evaluated was compared and evaluated. Further, solid display spots (uniformity) were visually observed and evaluated.

<Example 1>
As black particles, those prepared as follows were prepared. Particle A was obtained by classifying crosslinked polymethylmethacrylate (PMMA) resin particles prepared by suspension polymerization method containing 5 parts by weight of carbon black as a coloring pigment so as to have an average particle diameter of 9.5 μm. The specific gravity of the particles A was 1.2. An adhesive layer material C was obtained by classifying uncrosslinked polymethyl methacrylate (PMMA) resin fine particles produced by suspension polymerization so as to have an average particle size of 0.15 μm. The specific gravity of the adhesive layer material C was 1.2. Silica fine particles having an average primary particle diameter of 0.11 μm produced by the sol-gel method were subjected to surface treatment with a copolymer of methylhydrogenpolysiloxane and dimethylpolysiloxane, and further subjected to surface treatment with triethoxyaminosilane, to form fine particles B. The specific gravity of the fine particles B was 2.2.

  Particle A: 1.53 parts by weight of the adhesive layer material C is mixed with 100 parts by weight of the particle A, and this is stirred and mixed for 120 minutes with a Henschel mixer adjusted to 65 ° C. with warm water. Granted. To this, 6.13 parts by weight of the fine particles B were added, and the mixture was stirred and mixed for 120 minutes with a Henschel mixer similarly adjusted with 65 ° C. warm water to immobilize the fine particles B on the surface of the particles A. At this time, the final layer thickness L2 of the adhesive layer was L2 = 0.07 μm satisfying 0.3D2 ≦ L2 <D2 from cross-sectional SEM observation, where the average particle diameter of the fine particles B was D2. Further, as a result of the media impact test, as a result of using the particles A and the fine particles B, the embedding of the fine particles B into the particles A was not observed, and some of the fine particles B were deformed. On the other hand, when the particles A and the fine particles B provided with the adhesive layer were used, it was observed that the fine particles B were buried in the particles A.

  As white particles, those prepared as follows were prepared. Particle A was obtained by classifying crosslinked polystyrene / divinylbenzene copolymer resin particles prepared by suspension polymerization method containing 30 parts by weight of titania for pigment as a color pigment so as to have an average particle diameter of 9.5 μm. The specific gravity of this was 1.3. An adhesive layer material C was obtained by classifying uncrosslinked polymethyl methacrylate (PMMA) resin fine particles produced by suspension polymerization so as to have an average particle size of 0.15 μm. The specific gravity of the adhesive layer material C was 1.2. Silica fine particles having an average primary particle diameter of 0.11 μm produced by the sol-gel method were subjected to surface treatment with a copolymer of methylhydrogenpolysiloxane and dimethylpolysiloxane, and further subjected to surface treatment with triethoxyaminosilane, to form fine particles B. The specific gravity of the fine particles B was 2.2.

  1.53 parts by weight of the adhesive layer material C is mixed with 108 parts by weight of the particle A, and the mixture is stirred and mixed for 120 minutes with a Henschel mixer adjusted with warm water at 65 ° C. Granted. To this, 6.13 parts by weight of the fine particles B were added, and the mixture was stirred and mixed for 120 minutes with a Henschel mixer similarly adjusted with 65 ° C. warm water to immobilize the fine particles B on the surface of the particles A. At this time, the final layer thickness L2 of the adhesive layer was L2 = 0.07 μm satisfying 0.3D2 ≦ L2 <D2 from cross-sectional SEM observation, where the average particle diameter of the fine particles B was D2. Further, as a result of the media impact test, as a result of using the particles A and the fine particles B, the embedding of the fine particles B into the particles A was not observed, and some of the fine particles B were deformed. On the other hand, when the particles A and the fine particles B provided with the adhesive layer were used, it was observed that the fine particles B were buried in the particles A.

  When a driving durability evaluation test was performed using these black particles and white particles, the display characteristics maintained a substantially constant contrast until about 1 million cycles.

<Example 2>
The black particle and the white particle which were adjusted with the method similar to Example 1 except having changed the following points were prepared. As fine particles B for black particles, those obtained by classifying crosslinked melamine / benzoguanamine fine particles prepared by a suspension polymerization method so as to have an average particle diameter of 0.24 μm (specific gravity 1.5) were used. The amount of the adhesive layer material C added to the particles A was 4.02 parts by weight. The amount of the fine particles B added to the particles A treated with the adhesive layer was 9.13 parts by weight. As fine particles B for white particles, those obtained by classifying crosslinked polystyrene / divinylbenzene copolymer resin fine particles prepared by suspension polymerization so as to have an average particle size of 0.33 μm (specific gravity 1.1) were used. The blending amount of the adhesive layer material C in the particles A was 4.33 parts by weight. The amount of the fine particles B added to the particles A treated with the adhesive layer was 9.20 parts by weight.

  At this time, the final layer thickness L2 of the adhesive layer of black particles was L2 = 0.08 μm satisfying 0.3D2 ≦ L2 <D2 from cross-sectional SEM observation, where the average particle diameter of the fine particles B was D2. It was. At this time, the final layer thickness L2 of the adhesive layer of the white particles was L2 = 0.09 μm satisfying 0.3D2 ≦ L2 <D2 from cross-sectional SEM observation. In addition, as a result of the media impact test, as a result of using the particle A and the fine particle B for both the black particle and the white particle, the embedding of the fine particle B in the particle A was not observed, and some deformation of the fine particle B was recognized. . On the other hand, when the particles A and the fine particles B provided with the adhesive layer were used, it was observed that the fine particles B were buried in the particles A.

  When a driving durability evaluation test was performed using these black particles and white particles, the display characteristics maintained a substantially constant contrast until about 1 million cycles.

<Comparative Example 1>
The black particle and the white particle which were adjusted with the method similar to Example 1 except having changed the following points were prepared. For both black particles and white particles, an adhesive layer material was not prepared, and only the particles A and the fine particles B were used for stirring and mixing. At this time, both the black particles and the white particles were dispersed and coated with the fine particles B on the surface of the particles A, but were not buried or fixed. When these black / white particles were used to perform a durability driving evaluation test, the display characteristics showed a sharp drop in contrast from about several hundred cycles, and the display characteristics were attenuated to zero over several tens of thousands to several hundred thousand cycles.

<Comparative Example 2>
The black particle and the white particle which were adjusted with the method similar to Example 1 except having changed the following points were prepared. As black particles, those prepared as follows were prepared. Particle A was obtained by classifying uncrosslinked polymethylmethacrylate (PMMA) resin particles prepared by suspension polymerization, containing 5 parts by weight of carbon black as a coloring pigment, to an average particle size of 9.5 μm. The specific gravity of the particles A was 1.2. A material obtained by classifying crosslinked polymethyl methacrylate (PMMA) resin fine particles prepared by suspension polymerization so as to have an average particle diameter of 100 μm was used as an adhesive layer material C. The specific gravity of the adhesive layer material C was 1.2. 1.55 parts by weight of the adhesive layer material C was added to 100 parts by weight of the particles A, and the mixture was stirred and mixed for 120 minutes with a Henschel mixer whose temperature was adjusted with 65 ° C. warm water. Here, 6.13 parts by weight of the above fine particles B were additionally blended, and the mixture was stirred and mixed for 120 minutes with a Henschel mixer, which was similarly temperature-controlled with 65 ° C. warm water. At this time, the surface of the particle A was in a state where the fine particles B and the fine particles of the adhesive layer material C were dispersed and coated, and most of them were partially embedded in the surface of the particle A. Therefore, it could not be molded with the adhesive layer. As a result of the media impact test, as a result of using the particle A and the fine particle B, the embedding of the fine particle B in the particle A was recognized, and the deformation of the fine particle B was not recognized. On the other hand, since the particle A provided with the adhesive layer could not be prepared, a media impact test between the particle A and the particle B could not be performed.

  As white particles, those prepared as follows were prepared. Particle A was obtained by classifying uncrosslinked polystyrene / divinylbenzene copolymer resin particles prepared by suspension polymerization method containing 30 parts by weight of titania for pigment as a coloring pigment so as to have an average particle diameter of 9.5 μm. The specific gravity of this was 1.3. A material obtained by classifying crosslinked polymethyl methacrylate (PMMA) resin fine particles prepared by suspension polymerization so as to have an average particle diameter of 100 μm was used as an adhesive layer material C. The specific gravity of the adhesive layer material C was 1.2. 1.55 parts by weight of the adhesive layer material C was mixed with 108 parts by weight of the particles A, and the mixture was stirred and mixed for 120 minutes with a Henschel mixer adjusted with warm water at 65 ° C. Here, 6.13 parts by weight of the above fine particles B were additionally blended, and the mixture was stirred and mixed for 120 minutes with a Henschel mixer, which was similarly temperature-controlled with 65 ° C. warm water. At this time, the surface of the particle A was in a state where the fine particles B and the fine particles of the adhesive layer material C were dispersed and coated, and most of them were partially embedded in the surface of the particle A. Therefore, it could not be molded with the adhesive layer. As a result of the media impact test, as a result of using the particle A and the fine particle B, the embedding of the fine particle B in the particle A was recognized, and the deformation of the fine particle B was not recognized. On the other hand, since the particle A provided with the adhesive layer could not be produced, a media impact test between this and the fine particle B could not be performed.

  When a driving durability evaluation test was performed using these black particles and white particles, the display characteristics showed insufficient contrast from the beginning, and the contrast gradually attenuated until reaching several thousand cycles and reached zero.

<Comparative Example 3>
The black particle and the white particle which were adjusted with the method similar to Example 2 except having changed the following points were prepared. For black particles, particles obtained by classifying uncrosslinked polymethylmethacrylate (PMMA) resin particles prepared by suspension polymerization method, containing 5 parts by weight of carbon black as a color pigment, to an average particle diameter of 9.5 μm A. The specific gravity of the particles A was 1.2. Particle A was obtained by classifying uncrosslinked polystyrene resin particles prepared by suspension polymerization, containing 30 parts by weight of titania for pigment as a color pigment, so as to have an average particle diameter of 9.5 μm. The specific gravity of the particles A was 1.3. At this time, the final layer thickness L2 of the adhesive layer of black particles was L2 = 0.08 μm satisfying 0.3D2 ≦ L2 <D2 from cross-sectional SEM observation, where the average particle diameter of the fine particles B was D2. It was. At this time, the final layer thickness L2 of the adhesive layer of the white particles was L2 = 0.09 μm satisfying 0.3D2 ≦ L2 <D2 from cross-sectional SEM observation, where the average particle diameter of the fine particles B was D2. It was.

  As a result of the media impact test, as a result of using the particles A and the fine particles B for both the black particles and the white particles, the embedding of the fine particles B in the particles A was recognized, and the deformation of the fine particles B was not recognized. Similarly, when the particles A and the fine particles B provided with the adhesive layer were used, it was observed that the fine particles B were embedded in the particles A. When a driving durability evaluation test was performed using these black particles and white particles, the display characteristics showed a steady contrast from the initial stage to several thousand cycles, but after that, the display characteristics decayed rapidly, and finally several times. Reached zero after 10,000 cycles.

<Comparative example 4>
The black particle and the white particle which were adjusted with the method similar to Example 1 except having changed the following points were prepared. For both the black particles and the white particles, the blending amount of the adhesive layer material C in the particles A was 6.44 parts by weight (black particles: 100 parts by weight, white particles: 108 parts by weight). At this time, the final layer thickness L2 of the adhesive layer was L2 = 0.150 μm from the cross-sectional SEM observation for both the black particles and the white particles, and did not satisfy 0.3D2 ≦ L2 <D2. When a driving durability evaluation test was performed using these black particles and white particles, the display characteristics showed a sharp contrast decay from the initial stage to several hundred cycles, and then maintained a low level steady state, and then several thousand. Attenuation resumed until tens of thousands of cycles, reaching zero.

  The results of the above examples and comparative examples are summarized in the following Table 1, and FIG. 6 shows the relationship between Ct and the number of inversions (the number of movements of the display medium) in the above examples and comparative examples. From the results of FIG. 6, Ct of Examples 1 and 2 according to the present invention maintains a constant value regardless of the number of inversions, whereas in the examples of Comparative Examples 1 to 4, when the number of inversions increases, It can also be seen that Ct reaches zero.

  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 which shows the structure of 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 used as the object of this invention. It is a graph which shows the relationship between Ct and the inversion frequency in an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Substrate 3 Display medium 3W White display medium 3Wa White display medium particle 3B Black display medium 3Ba Black display medium particle 4 Partition 5, 6 Electrode 11 Display medium particle 12 Mother particle 13 Adhesive layer 14 Fine particle

Claims (3)

  In a display medium particle used in an information display panel for displaying information by moving a display medium by enclosing the display medium between two substrates transparent at least one and applying an electric field to the display medium, A particle for a display medium, comprising: particles; an adhesive layer provided on a surface of the mother particle; and fine particles that are partially exposed and buried in the adhesive layer but are not buried in the mother particle.   When the average particle diameter of the fine particles is D2 and the final adhesive layer thickness is L2, the relationship between the average particle diameter of the fine particles and the thickness of the adhesive layer is 0.3D2 ≦ L2 ≦ D2. The particle | grains for display media of Claim 1.   3. In producing the display medium particles according to claim 1 or 2, the mother particles, the adhesive layer, and the fine particles are previously formed between the mother particles and the fine particles, and between the mother particles and the fine particles having an adhesive layer on the surface. Display medium, wherein the order of hardness is determined, and a display medium particle is manufactured using a combination of mother particles, fine particles and an adhesive layer in which the hardness order is a relationship of mother particles> fine particles> adhesive layer Method for producing particles.

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