JP2009139751A - Particle for display medium and information display panel using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide particles for a display medium having ruggedness of high hardness introduced on the surfaces of the particles to enhance heat resistance and secure a satisfactory charge amount and used for an information display panel and to provide the information display panel using the same. <P>SOLUTION: The particles 31 for the display medium constitutes the display medium used for the information display panel which displays information such as an image by enclosing the display medium having optical reflectance and charge properties between two substrates at least one of which is transparent and which are opposed to each other and applying an electric field to the display medium to move the display medium. The particles 31 have surface ruggedness manufactured by adsorbing fine particles 33 composed of a cross-linkable resin on the surface of a mother particle 32 and then cross-linking the cross-linkable resin. The information display panel uses the particles 31 as the display medium. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  Conventionally, by encapsulating at least one type of display medium having at least one type of particles having optical reflectivity and chargeability between two substrates, at least one of which is transparent, and applying an electric field to the display medium, As a display medium particle that constitutes a display medium in an information display panel that displays information such as an image by moving the display medium, there is a technology that reduces the voltage required for driving by embedding fine particles on the particle surface to create irregularities. It is known (see, for example, Patent Document 1). In order to make the surface of the particles for display medium uneven, a method of embedding high-hardness fine particles in a thermoplastic resin-based mother particle by mechanical shearing force (for example, see Patent Document 1) or a dispersed mother material A method of depositing and adsorbing inorganic particles on the particle surface by a sol-gel method (see, for example, Patent Document 2), and depositing a soluble resin on the surface of the mother particle with a poor solvent, thereby adsorbing fine particles on the surface of the mother particle. The method is known.

JP 2006-313340 A JP 2006-106596 A

  Among the above-described techniques, in the method of embedding fine particles by mechanical shearing force, the base resin of the mother particle is thermoplastic, and as a result, the embedding of particles by heating is promoted, so that excellent heat resistance is ensured. Have difficulty. On the other hand, there is a method using a resin having a high glass transition temperature (Tg), but a large energy is required for embedding the fine particles, which is not practical.

  Moreover, in the method of depositing inorganic particles by the sol-gel method, it is possible to use a crosslinked resin having higher heat resistance as the material of the mother particles. It is difficult to ensure a large charge amount because functional groups remain and a hydrophobic material cannot be introduced.

  In the method of forming fine particles by precipitating a resin soluble in an organic solvent on the surface of the mother particle with a poor solvent, in addition to using a crosslinked resin as the material of the mother particle, Although it is possible to use an insulating resin material as the material, since the soluble resin constituting the fine particles is generally thermoplastic, the heat resistance improving effect obtained by using a cross-linked resin as the material of the mother particle There is a risk of canceling.

  Accordingly, an object of the present invention is to solve the above-mentioned problems, and to provide particles for display media used in information display panels in which high hardness irregularities are introduced on the particle surface, heat resistance is improved, and sufficient charge amount is secured. An object is to provide an information display panel using the same.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have adsorbed fine particles made of resin on the surface of the mother particles, and then crosslinked them to obtain a crosslinked resin having higher heat resistance as the material of the mother particles. It can be used, and a surface roughness structure with a high hardness can be introduced into the display medium particles, and as a result, heat resistance is improved and display medium particles having a sufficient charge amount can be obtained. The headline and the present invention were completed.

That is, the particles for display medium of the present invention can be obtained by encapsulating a display medium having optical reflectivity and chargeability between two opposing substrates, at least one of which is transparent, and applying an electric field to the display medium. Display medium particles constituting a display medium used in an information display panel that displays information such as images by moving the medium,
It is characterized by having surface irregularities produced by adsorbing fine particles of a crosslinkable resin on the surface of the mother particles and then crosslinking the crosslinkable resin.

  In a preferred example of the display medium particle of the present invention, the crosslinkable resin constituting the fine particle is polyvinyl butyral having an azo group.

  In another preferred embodiment of the display medium particle of the present invention, the mother particle is made of a crosslinked resin.

  The information display panel of the present invention is characterized in that the display medium particles are used as a display medium.

  According to the present invention, it is possible to provide particles for a display medium in which irregularities having high hardness are introduced on the particle surface, heat resistance is improved, and sufficient charge amount is ensured. By using it as a display medium for a display panel, there is an advantageous effect that an information display panel having good heat resistance and durability can be provided.

  The present invention is described in detail below. First, a basic configuration of an information display panel used as a display medium made of the display medium particles of the present invention will be described. In the information display panel according to the present invention, an electric field is applied to a display medium configured to include display medium particles sealed between two opposing substrates. In accordance with the applied electric field direction, the display medium is attracted by the force of the electric field, the Coulomb force, or the like, and the display medium changes the moving direction according to the change in the electric field direction, whereby information such as an image is displayed. 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 using the display medium particles of the present invention as a display medium will be described with reference to FIGS. 1 (a), 1 (b) to 5 (a), (b). In the example shown in FIGS. 1A and 1B, the optical reflectivity and charging characteristics of each other, which are configured as a particle group composed of at least one kind of particles including particles having optical reflectivity and chargeability. At least two or more types of display media different from each other (here, a white display medium 3W composed of particles of white display medium particles 3Wa and a black display medium 3B composed of particles of black display medium particles 3Ba are shown) between substrates. In each cell formed by the partition walls 4, the electric field generated by applying a voltage between the electrode 5 (individual electrode) provided on the substrate 1 and the electrode 6 (individual electrode) provided on the substrate 2 is determined according to the electric field generated. The substrate 1 and 2 are moved vertically. Then, as shown in FIG. 1A, the white display medium 3W is visually recognized by the observer and white dot display is performed, or as shown in FIG. 1B, the black display medium 3B is visually recognized by the observer. Black dots are displayed. In addition, in FIG. 1 (a), (b), the partition in front is abbreviate | omitted.

  In the example shown in FIGS. 2A and 2B, the optical reflectivity and the charging characteristics of each other are configured as a particle group composed of at least one kind of particles including particles having optical reflectivity and chargeability. At least two or more types of display media different from each other (here, a white display medium 3W composed of particles of white display medium particles 3Wa and a black display medium 3B composed of particles of black display medium particles 3Ba are shown) between substrates. In each cell formed by the partition walls 4, a voltage is applied between an electrode 5 (line electrode) provided on the substrate 1 and an electrode 6 (line electrode) provided on the substrate 2 in accordance with an electric field generated. The substrate 1 and 2 are moved vertically. Then, as shown in FIG. 2 (a), the white display medium 3W is visually recognized by the observer and white dot display is performed, or as shown in FIG. 2 (b), the black display medium 3B is visually recognized by the observer. Black dots are displayed. In addition, in FIG. 2 (a), (b), the partition in front is abbreviate | omitted.

  In the example shown in FIGS. 3A and 3B, one type of display medium configured as a particle group including at least one type of particles including particles having optical reflectance and chargeability (here, white) (Showing white display medium 3W composed of particles of display medium particles 3Wa) between each substrate formed between the substrates and formed by the partition walls 4, the electrode 5 provided on the substrate 1 and the electrode 6 provided on the substrate 2 The substrate is moved in a direction parallel to the substrates 1 and 2 in accordance with an electric field generated by applying a voltage therebetween. Then, as shown in FIG. 3 (a), the white display medium 3W is visually recognized by the observer and white dot display is performed, or the color of the black plate 7 is shown to the observer as shown in FIG. 3 (b). A black dot is displayed by visual recognition. In addition, in the example shown to Fig.3 (a), (b), the partition in front is abbreviate | omitted.

  In the example shown in FIGS. 4A to 4D, first, as shown in FIGS. 4A and 4C, from at least one kind of particles including particles having optical reflectivity and chargeability. At least two kinds of display media having different optical reflectivity and charging characteristics from each other (here, white display medium 3W composed of particles of white display medium particles 3Wa and black display medium particles 3Ba). (Showing a black display medium 3B made of a group of particles) between the substrates and in each cell formed by the partition walls 4, the external electric field forming means 11 provided outside the substrate 1 and the external electric field provided outside the substrate 2 The substrate is moved perpendicularly to the substrates 1 and 2 in accordance with an electric field generated by applying a voltage between the forming unit 12 and the forming unit 12. Then, as shown in FIG. 4B, the white display medium 3W is visually recognized by the observer and white dot display is performed, or as shown in FIG. 2D, the black display medium 3B is visually recognized by the observer. Black dots are displayed. In addition, in FIG. 4 (a)-(d), the partition in front is abbreviate | omitted. In addition, a conductive member 13 is provided inside the substrate 1, and a conductive member 14 is provided inside the substrate 2. This conductive member may not be provided.

  In the example shown in FIGS. 5A and 5B, an example of color display in which a display unit (1 dot) is configured by three cells is shown. In the example shown in FIGS. 5A and 5B, as the display medium, all the cells 21-1 to 21-3 are filled with the white display medium 3W and the black display medium 3B, and the first cell 21-1 is filled. A red color filter 22R is provided on the viewer side, a green color filter 22G is provided on the viewer side of the second cell 21-2, a blue color filter 22BL is provided on the viewer side of the third cell 21-3, A display unit is composed of three cells, the first cell 21-1, the second cell 21-2, and the third cell 21-3. In this example, as shown in FIG. 5A, the white display medium 3 </ b> W is moved in the first cell 21-1 to the third cell 21-3 on the viewer side, so that By performing white dot display or moving the black display medium 3B in all the first cells 21-1 to 21-3 to the viewer side as shown in FIG. 5B. Black dots are displayed to the observer. In addition, in FIG. 5 (a), (b), the partition in front is abbreviate | omitted. Multicolor display can be performed by moving the display medium in each cell.

  Next, the particles for a display medium that are the characteristics of the present invention will be described in detail with reference to the drawings. The particles for display medium of the present invention can be applied to the information display panels shown in FIGS. 1A, 1B to 5A, 5B, and at least one of the information display panels is transparent. A display medium is configured and sealed between two substrates. FIG. 6 is a diagram showing an example of the display medium particle of the present invention. In the example shown in FIG. 6, the feature of the display medium particle 31 of the present invention is that the surface produced by adsorbing fine particles 33 made of a crosslinkable resin on the surface of the mother particle 32 and then crosslinking the crosslinkable resin. It has unevenness. By configuring the display medium particles 31 in this manner, the heat resistance can be improved, and a sufficient charge amount can be secured.

  In the display medium particles of the present invention, the resin constituting the fine particles 33 needs to be a crosslinkable resin. Here, the crosslinkable resin refers to a resin having a functional group that can be crosslinked by heat, a crosslinking agent, or the like. The heat resistance can be improved by forming the fine particles 33 with a crosslinkable resin and subsequently performing crosslinking of the crosslinkable resin. Examples of the crosslinkable resin include polyvinyl butyral resin, polyvinyl alcohol resin, melamine resin, benzoguanamine resin, phenol resin, acrylic resin, epoxy resin, and urea resin. Of these, polyvinyl butyral having an azo group that can be thermally cross-linked is preferred from the viewpoint of avoiding the problem of pot life, since it is usually unnecessary to use a separately added cross-linking agent.

  The adsorption of the fine particles 33 onto the surface of the mother particles 32 can be performed by a poor solvent precipitation method in which the fine particles 33 are precipitated on the surfaces of the mother particles 32 using a poor solvent of a crosslinkable resin constituting the fine particles 33. In this method, a crosslinked resin that has high heat resistance but cannot physically embed fine particles can be used as the material of the base particles 12.

  After the fine particles are adsorbed on the surface of the mother particles, the crosslinkable resin constituting the fine particles is crosslinked. Here, the crosslinking method of the crosslinkable resin is determined by the crosslinkable functional group in the crosslinkable resin, and can be performed, for example, by heating, a crosslinking agent, electron beam irradiation, ultraviolet (UV) irradiation, or the like.

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

  Electrode forming materials for electrodes provided on the substrate side include metals such as aluminum, silver, nickel, copper and gold, ITO, indium oxide, zinc-doped indium oxide (IZO), aluminum-doped zinc oxide (AZO), and antimony tin oxide. Examples include conductive metal oxides such as products (ATO), conductive tin oxide, and conductive zinc oxide, and conductive polymers such as polyaniline, polypyrrole, and polythiophene, which 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 a method of laminating a metal foil (for example, rolled copper foil) Alternatively, a method in which a conductive agent is mixed and applied to a solvent or a synthetic resin binder is used. The electrode provided on the viewing substrate side needs to be transparent, but the electrode provided on the back substrate side 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 may be 0.01 to 10 [mu] m, preferably 0.05 to 5 [mu] m, as long as conductivity can be ensured and light transmittance is not hindered. Is preferred. The material and thickness of the electrode provided on the back substrate side are the same as those of the electrode provided on the viewing substrate side described above, but need not be transparent. In this case, the external voltage input may be superimposed with direct current or alternating current.

  The shape of the partition 4 provided as necessary is optimally set according to the type of display medium involved in the display, and is not limited in general. However, the partition width is 2 to 100 μm, preferably 3 to 50 μm. The height is adjusted to 10 to 500 μm, preferably 10 to 200 μm. In forming the partition walls, a both-rib method in which ribs are formed on each of the opposing substrates and then bonded, and a one-rib method in which ribs are formed only on one substrate are conceivable. In the present invention, any method is preferably used.

  As shown in FIG. 5, the display cells formed by the partition walls made up of these ribs are exemplified by a square shape, a triangular shape, a line shape, a circular shape, and a hexagonal shape as viewed from the substrate plane direction. The shape and the mesh shape are exemplified. It is better to make the portion corresponding to the cross section of the partition wall visible from the display side (the area of the frame portion of the display cell) as small as possible, and the clear display of information such as images will increase. Here, examples of the method for forming the partition include a mold transfer method, a screen printing method, a sand blast method, a photolithography method, and an additive method. Among these, a photolithography method using a resist film and a mold transfer method are preferably used. In any method, the present invention can be suitably used.

  Next, the display medium particle 31 of the present invention will be described. The display medium particles 31 are used as the display medium by being composed of the display medium particles 31 as they are, or by being combined with other particles as the display medium. The base particles 32 mainly constituting the display medium particles 31 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. Examples of resins, charge control agents, colorants, and other additives are 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, from the viewpoint of further improving the heat resistance, it is preferable that the base particles are made of a crosslinked type resin of these resins. Examples of the crosslinked resin include an acrylic resin, a polystyrene resin, and a styrene acrylic resin containing a crosslinking agent.

  Examples of the positively chargeable charge control agent include charge control resins such as polyamine resins, tertiary amino group-containing copolymers, and quaternary ammonium base-containing copolymers, imidazole compounds, nigrosine dyes, quaternary ammonium salts, and triglycerides. An aminotriphenylmethane compound or the like can be used.

  Examples of negatively chargeable charge control agents include sulfonic acid group-containing copolymers, sulfonate group-containing copolymers, carboxylic acid group-containing copolymers, and charge control resins such as carboxylic acid group-containing copolymers, and Cr. Azo dyes containing metals represented by element symbols such as Co, Al, and Fe, salicylic acid metal compounds, and alkyl salicylic acid metal oxides.

  Among the above charge control agents, it is preferable to use a charge control resin, and the charge control resin preferably has a content of a functional group imparting chargeability of 0.5 to 15% by mass, and preferably 1 to 10%. More preferably, it is mass%.

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

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

  Examples of the black colorant include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon and the like.

  Examples of blue colorants include C.I. I. Pigment blue 15: 3, C.I. I. Pigment Blue 15, Bituminous Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Metal-free Phthalocyanine Blue, Phthalocyanine Blue Partial Chlorides, Fast Sky Blue, Indanthrene Blue BC, and the like.

  Examples of red colorants include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, risor red, pyrazolone red, watching red, calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, Alizarin Lake, Brilliant Carmine 3B, C.I. I. Pigment Red 2 etc.

  Yellow colorants include chrome yellow, zinc yellow, cadmium yellow, yellow iron oxide, mineral first yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, C.I. I. Pigment Yellow 12 etc.

  Examples of green colorants include chrome green, chromium oxide, pigment green B, C.I. I. Pigment Green 7, Malachite Green Lake, Final Yellow Green G, etc.

  Examples of the orange colorant include red chrome yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK, C.I. I. Pigment Orange 31 etc.

  Examples of purple colorants include manganese purple, first violet B, and methyl violet lake.

  Examples of white colorants include zinc white, titanium oxide, antimony white, and zinc sulfide.

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

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

  Further, the particles as the display medium of the present invention have an average particle diameter d (0.5) in the range of 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. 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 sizes of the particles for each display medium are uniform, and movement as a uniform display medium becomes possible.

  Furthermore, in the case of using a plurality of display media, among the display medium particles constituting the used display medium, the minimum value for d (0.5) of the display medium particles showing the maximum average particle diameter d (0.5). It is important that the ratio of d (0.5) of the display medium particles having the average particle diameter d (0.5) is 10 or less. Even if the particle size distribution Span is reduced, the display medium particles having different charging characteristics move in opposite directions, so that the display medium particles are close in size, and the display medium particles are equivalent in opposite directions. It is preferable that it can be easily moved, and this is the range.

  The above particle size distribution and 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, the particles are put 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 inventors of the present invention have been able to evaluate the range of proper charging characteristics of display medium particles by measuring the charge amount of display medium particles using the same carrier particles in the blow-off method. I found it.

  Furthermore, when applied to an information display panel in which a display medium composed of particles for display medium is driven in a gas space, it is important to manage the gas in the void surrounding the display medium between the substrates. Contributes to improved stability. Specifically, it is important that the relative humidity at 25 ° C. is 60% RH or less, and preferably 50% RH or less for the humidity of the gas in the gap. 1A, 1B, 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 information display panel seal portion are excluded, and the gas portion in contact with the so-called display medium is meant.

  The gas in the gap is not limited as long as it is in the humidity region described above, but dry air, dry nitrogen, dry argon, dry helium, dry carbon dioxide, dry methane, and the like are preferable. This gas needs to be sealed in an information display panel so that the humidity is maintained, for example, filling a display medium, assembling an information display panel, etc. in a predetermined humidity environment, It is important to apply a sealing material and a sealing method that prevent moisture from entering from the outside.

  The distance between the substrates in the information display panel is not limited as long as the display medium can be moved and the contrast can be maintained, but when the display medium configured as a particle group including the chargeable particles is driven in a gas space. Usually, it is adjusted to 10 to 100 μm, preferably 10 to 50 μm. The volume occupation ratio of the display medium in the gas space between the opposing substrates is preferably 5 to 70%, more preferably 5 to 60%. 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.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

  The information display panels of the examples and comparative examples were evaluated by the following methods according to the following criteria.

<Example 1>
As negatively charged mother particles, 75 parts by mass of styrene monomer (manufactured by Kanto Chemical Co., Ltd.) and divinylbenzene (manufactured by Wako Pure Chemical Industries, Ltd.) as a multifunctional monomer having a plurality of polymerization reactive groups in one molecule ) 5 parts by mass of a phenol-based condensate (Bontron E89: Orient Chemical) as a charge control agent imparting negative chargeability to 25 parts by mass and titanium oxide (Typek CR-50: Ishihara Sangyo Co., Ltd.) as a white colorant After the dispersion of 80 parts by mass with a sand mill, a solution in which 2 parts by mass of azobisisobutyronitrile (V-60: manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved as a polymerization initiator, Suspended, polymerized, filtered, dried in purified water to which 0.5% polyoxyethylene alkyl ether sodium sulfate (Latemul E-118B: manufactured by Kao Corporation) was added as a surfactant, and then classified by a classifier (MDS -2: Japanese Numa Classification was performed using Chick Kogyo Co., Ltd. to obtain negatively chargeable mother particles A having an average particle size of 9.2 μm. Next, 4,4′-azobis (4-cyanopentanoic acid) (V-501: sum) in a liquid in which 4.0 g of the negatively chargeable mother particle A was dispersed in 48 ml of ethanol (manufactured by Kanto Chemical Co., Inc.). Polyvinyl butyral (Esreck BL-1H: Sekisui Chemical Co., Ltd.) (PVB1) 0.04 g grafted with 10% by mass of Kojunkaku Kogyo Co., Ltd. is dissolved, and n-hexane is a poor solvent for PVB1 (Made by Kanto Chemical Co., Inc.) Slowly drop 320 ml to deposit and adsorb PVB1 particles on the surface of the base particles, then crosslink PVB1 with azo groups at a temperature of 80 ° C Particle Aa was obtained. When this particle Aa was observed with a scanning electron microscope (SEM), the entire surface of the mother particle was covered with PVB1 particles, and surface irregularities were confirmed. Further, the charge amount of the particles Aa was measured. In the charge amount measurement, the charge amount was measured based on a general blow-off method. That is, using a blow-off type charge amount measuring device (TB-203, manufactured by Kyocera Chemical Co., Ltd.) as a measuring device, mesh aperture: 32 (μm), flow pressure / suction pressure: 4.5 (kPa) /9.5 ( kPa), carrier: F96-80 (manufactured by Powdertech), sample / carrier blending mass ratio: 1/100, number of shaking: 120 times. As a result of the measurement, the charge amount of the particles Aa was −10.8 μC / g, which was an appropriate value as particles for display media.

  Next, 2% by mass of silica fine particles (H3004: manufactured by Clariant Japan Co., Ltd.) is added to the particles Aa and stirred with a Henschel mixer (KM5C: manufactured by Mitsui Mining Co., Ltd.). Particle Aa1 was obtained.

  As the positively charged mother particles, 60 parts by mass of methyl methacrylate (manufactured by Kanto Chemical Co., Ltd.) and ethylene glycol dimethacrylate (Wako Pure) as a polyfunctional monomer having a plurality of polymerization reactive groups in one molecule. 40 parts by mass of Yakuhin Kogyo Co., Ltd., 3 parts by mass of nigrosine compound (Bontron N07: manufactured by Orient Chemical Co., Ltd.) as a charge control agent for imparting positive chargeability, and carbon black (special black) as a black colorant 5: 5 parts by mass of Degussa Co., Ltd.) was dispersed with a sand mill, and 2 parts by mass of azobisisobutyronitrile (V-60: manufactured by Wako Pure Chemical Industries, Ltd.) was further dissolved as a polymerization initiator. The resulting liquid was suspended in purified water to which 0.5% of polyoxyethylene alkyl ether sulfate sodium (Latemul E-118B: manufactured by Kao Corporation) was added as a surfactant, polymerized, filtered and dried. , Grade Machine: - followed by classification using (MDS-2 Nippon New matic Kogyo Co.) to obtain a positively chargeable mother particles B having an average particle size of 9.0 .mu.m. When the charge amount of the particle B was measured by the same method as described above, it was +25.0 μC / g, which was an appropriate value as a particle for a display medium. Next, 2% by mass of silica fine particles (H3050: manufactured by Clariant Japan Co., Ltd.) is added to the particles B, and the mixture is stirred with a Henschel mixer (KM5C: manufactured by Mitsui Kinzoku Mine Co., Ltd.), and positively charged black particles B2 was obtained.

  A glass substrate in which the white particles Aa1 and the black particles B2 are mixed and stirred by an equal volume and triboelectrically charged and arranged through a 100 μm spacer, one of which is treated with an inner ITO and connected to a power source, A cell having a copper substrate as the other side was filled at a volume occupation rate of 30% to obtain a test display panel. When each ITO glass substrate and copper substrate are connected to a power source and a direct current voltage is applied so that the ITO glass substrate is at a low potential and the copper substrate is at a high potential, the black particles are on the low potential side and the white particles are on the high potential. Move to the pole side respectively. Here, since black particles are positively charged and white particles are negatively charged, a black display state is observed through the glass substrate.Next, when the potential of the applied voltage is reversed, the particles move in the opposite direction and become white. The display state of is observed. When the applied voltage is +200 [V] or -200 [V], the contrast ratio is the ratio of reflectivity during white display and reflectivity during black display. The initial contrast ratio of this test display panel is 8.6. there were. Furthermore, the contrast ratio after changing the display from -200 V (low potential) to +200 V (high potential) 5 million times at 1 kHz was 8.2 and there was almost no change. When this panel was disassembled and the white particles inside were observed with a scanning electron microscope (SEM), no change was observed in the PVB1 fine particle layer on the surface. Next, switching from -200 V (low potential) to +200 V (high potential) was repeated 5 million times at 1 kHz and the display was rewritten in an oven at 60 ° C., and the display was rewritten 5 million times. Later contrast ratio was almost unchanged at 8.0. When this panel was disassembled and the white particles inside were observed by SEM, no change was observed in the PVB1 fine particle layer on the particle surface.

<Example 2>
Polyvinyl butyral grafted with 20% by mass of 4,4′-azobis (4-cyanopentanoic acid) (V-501: manufactured by Wako Pure Chemical Industries, Ltd.) instead of PVB1 (ESREC BL-1H: Sekisui Chemical Co., Ltd.) Negatively chargeable mother particles Ab were obtained in the same manner as in Example 1 except that (PVB2) was used. When this particle Ab was observed with an SEM, the entire surface of the mother particle was covered with PVB2 particles, and surface irregularities were confirmed. Further, when the charge amount of the particle Ab was measured by the same method as described above, it was an appropriate value as a particle for a display medium at −9.9 μC / g.

  Next, 2% by mass of silica microparticles (H3004: manufactured by Clariant Japan Co., Ltd.) is added to the particles Ab, and the mixture is stirred with a Henschel mixer (KM5C: manufactured by Mitsui Kinzoku Mine Co., Ltd.). Particles Ab1 were obtained.

  B2 was used as the particles for black display medium. Using the white particles Ab1 and the black particles B2, a test display panel was prepared and evaluated in the same manner as in Example 1. As a result, the initial contrast ratio was 8.7. In addition, the contrast ratio after repeated display rewriting under the same conditions as described above was 8.4, showing almost no change. When this panel was disassembled and the white particles inside were observed by SEM, no change was observed in the PVB2 fine particle layer on the particle surface. Further, the contrast ratio after rewriting the display repeatedly in the same condition as described above in an oven at 60 ° C. was almost unchanged at 8.2. When this panel was disassembled and the white particles inside were observed by SEM, no change was observed in the PVB2 fine particle layer on the particle surface.

<Example 3>
Using a biaxial kneader, 100 parts by mass of cycloolefin resin (ZEONEX 330R: manufactured by Nippon Zeon Co., Ltd.) and 80 parts by mass of titanium dioxide (Taipaque CR-90: manufactured by Ishihara Sangyo Co., Ltd.) as negatively charged mother particles Melt-kneaded, finely pulverized with a jet mill (lab jet mill IDS-LJ type: manufactured by Nippon Pneumatic Industry Co., Ltd.), and classified using a classifier (MDS-2: manufactured by Nippon Pneumatic Industry Co., Ltd.) Then, using a melt spheronizer (MR-10: manufactured by Nippon Numatic Kogyo Co., Ltd.), the mixture was spheroidized to obtain negatively chargeable mother particles C having an average particle diameter R0 of 8.2 μm. Next, 95 parts by mass of the negatively chargeable mother particles C and 5 parts by mass of the negatively charged silica particles c (Seahoster KE-S30: manufactured by Nippon Shokubai Co., Ltd.) are used with a mechanofusion apparatus (manufactured by Hosokawa Micron Corporation). The composite particles Cc were obtained by compounding at a rotational speed of 4000 rpm and an operation time of 90 minutes. When this particle Cc was observed by SEM, fine particles were embedded in the entire surface of the mother particle, and surface irregularities were confirmed. Further, when the charge amount of the particles Cc was measured by the same method as described above, it was -15.6 μC / g, which was an appropriate value for display medium particles.

  Next, 2% by mass of silica fine particles (H3004: manufactured by Clariant Japan Co., Ltd.) is added to the particles Cc, and the mixture is stirred with a Henschel mixer (KM5C: manufactured by Mitsui Kinzoku Mine Co., Ltd.). Particle Cc1 was obtained.

  As positively chargeable black particles, 5 g of the above positively chargeable mother particles B are dispersed in 50 mL of a 1.5% aqueous solution of a melamine prepolymer (Sumitex Resin M3: Sumitomo Chemical Co., Ltd.) to which 0.30 g of acetic acid has been added. And then adsorbed and precrosslinked, diluted with 50 g of purified water, separated by centrifugal sedimentation, and the precipitated particles were dried and cured at 120 ° C. for 2 hours to obtain positively charged black particles Bd. When this particle Bd was observed by SEM, the entire surface of the mother particle was covered with melamine microparticles, and surface irregularities were confirmed.The charge amount of this particle Bd was measured by the same method as described above. However, it was an appropriate value as a particle for a display medium at 18.7 μC / g.

  Next, 2% by mass of silica fine particles (H3050: manufactured by Clariant Japan Co., Ltd.) is added to the particles Bd, and the mixture is stirred with a Henschel mixer (KM5C: manufactured by Mitsui Kinzoku Mine Co., Ltd.). Particles Bd2 were obtained.

  Using the white particles Cc1 and the black particles Bd2, a test display panel was prepared and evaluated in the same manner as in Example 1. As a result, the initial contrast ratio was 9.0. Further, the contrast ratio after repeated display rewriting under the same conditions as described above was 8.7, showing almost no change. When this panel was disassembled and the black particles inside were observed by SEM, no change was observed in the melamine microparticle layer on the particle surface. In addition, the contrast ratio after repeated display rewriting in the 60 ° C. oven under the same conditions as described above was almost 8.6, which was almost unchanged. When this panel was disassembled and the black particles inside were observed by SEM, no change was observed in the melamine microparticle layer on the particle surface.

<Comparative Example 1>
The Cc1 was used as the white display medium particles, and the B2 was used as the black display medium particles. A test display panel was prepared using the white particles Cc1 and the black particles B2 and evaluated in the same manner as in Example 1. As a result, the initial contrast ratio was 8.7. Further, the contrast ratio after repeated display rewriting under the same conditions as described above was 8.5, which was almost unchanged. When this panel was disassembled and the white particles inside were observed with an SEM, it was confirmed that the fine particles on the surface were not embedded and the coating on the surface of the mother particles was retained. The contrast ratio after repeated display rewriting in the 60 ° C. oven under the same conditions as described above deteriorated to 3.5. When this panel was disassembled and the white particles inside were observed with an SEM, the mother particles were a thermoplastic resin, so the surface fine particles were not embedded and the surface irregularities were not retained. It is presumed that the drive voltage increased and the contrast was lowered.

<Comparative example 2>
After 5 g of the negatively chargeable mother particles A are dispersed in 50 g of methanol, 7.5 ml of ammonia water (manufactured by Kanto Chemical Co., Ltd.) and 1.25 ml of tetraethoxysilane (manufactured by Kanto Chemical Co., Ltd.) are added, and 2 hours are added. The silicon oxide particles were precipitated and adsorbed, diluted with 50 g of purified water, separated by centrifugal sedimentation, and the precipitated particles were dried to obtain negatively chargeable mother particles Ae. When this particle Ae was observed with an SEM, silica fine particles were fixed to the entire surface of the mother particle, and surface irregularities were confirmed. When the charge amount was measured in the same manner as described above, the charge amount was -0.6 μC / The value of g was too low for particles for display media. This is presumed to be due to charge decay due to the hydrophilicity of the silica microparticles produced by the sol-gel method.

  Next, 2% by mass of silica fine particles (H3004: manufactured by Clariant Japan Co., Ltd.) is added to the particles Ae, and the mixture is stirred with a Henschel mixer (KM5C: manufactured by Mitsui Kinzoku Mine Co., Ltd.). Particle Ae1 was obtained.

  As the positively charged black particles, B2 was used. Using the white particles Ae1 and the black particles B2, a test display panel was prepared and evaluated in the same manner as in Example 1. As the charge amount of Ae1 was too low, good display quality could not be obtained. It was.

<Comparative Example 3>
Polyvinyl butyral (ESLEC BL-1H: Sekisui Chemical Co., Ltd.) not grafted with 4,4'-azobis (4-cyanopentanoic acid) (V-501: Wako Pure Chemical Industries, Ltd.) instead of PVB1 Manufactured) Negatively charged mother particles Af were obtained in the same manner as in Example 1 except that PVB0 was used and the crosslinking step at 80 ° C. was omitted. When this particle Af was observed by SEM, the entire surface of the mother particle was covered with PVB0 fine particles, and surface irregularities were confirmed. Further, when the charge amount of the particles Af was measured by the same method as described above, it was an appropriate value as display medium particles of −12.2 μC / g.

  Next, 2% by mass of silica fine particles (H3004: manufactured by Clariant Japan Co., Ltd.) is added to the particles Af and stirred with a Henschel mixer (KM5C: manufactured by Mitsui Kinzoku Mine Co., Ltd.). Particle Af1 was obtained.

  B2 was used as the particles for black display medium. Using the white particles Af1 and the black particles B2, a test display panel was prepared and evaluated in the same manner as in Example 1. As a result, the initial contrast ratio was 8.8. Further, the contrast ratio after repeated display rewriting under the same conditions as described above was 8.0, showing almost no change. When this panel was disassembled and the white particles inside were observed by SEM, it was confirmed that the PVB0 fine particle layer on the particle surface was slightly smoothed. In addition, when an attempt was made to rewrite the display repeatedly in the above-described oven at 60 ° C. under the same conditions as described above, the particles were fused in the middle, and the display could not be rewritten 5 million times.

  The above results are summarized in Table 1. As for the evaluation results of display characteristics, (○) indicates that good display characteristics were obtained, (×) indicates that good display characteristics were not obtained, and (−) indicates that display characteristics were not evaluated. As shown.

  An information display panel which is an object of the present invention includes a display unit of a mobile device such as a notebook computer, a PDA, a mobile phone, and a handy terminal, an electronic paper such as an electronic book and an electronic newspaper, a signboard, a poster, a bulletin board such as a blackboard, and a calculator. Display units for home appliances, automobile products, card display units such as point cards and IC cards, electronic advertisements, electronic POPs, electronic price tags, electronic shelf labels, electronic musical scores, display units for RF-ID devices, external electric fields It is suitably used for a display portion (so-called rewritable paper) that performs display rewriting using a forming means.

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

Explanation of symbols

1, 2 Substrate 3 Display medium (particle group)
3W White display medium 3Wa White display medium particle 3B Black display medium 3Ba Black display medium particle 4 Bulkhead 5, 6 Electrode 7 Black plate 11, 12 External electric field forming means 13, 14 Conductive member 21-1 First cell 21- 2 Second cell 21-3 Third cell 22R Red color filter 22G Green color filter 22BL Blue color filter 31 Display medium particles 32 Mother particles 33 Child particles

Claims (4)

A display medium having optical reflectivity and chargeability is sealed between two opposing substrates, at least one of which is transparent, and an electric field is applied to the display medium, thereby moving the display medium to display information such as an image. Particles for a display medium constituting a display medium used for an information display panel,
A display medium particle having surface irregularities produced by adsorbing fine particles of a crosslinkable resin on the surface of a base particle and then crosslinking the crosslinkable resin.   The display medium particle according to claim 1, wherein the crosslinkable resin is polyvinyl butyral having an azo group.   The display medium particle according to claim 1, wherein the base particle is made of a crosslinked resin.   An information display panel using the display medium particle according to claim 1 as a display medium.

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