JP2010211041A - Particle for display medium, and panel for information display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide particles for a display medium that have sufficient durability, do not require time and effort for preparation, and control the electrostatic property, and a panel for information display using the particles. <P>SOLUTION: The particles for the display medium constituting the display medium are used for the panel for information display for displaying information by moving the display medium by filling the display medium constituted as a particle group between two substrates at least one of which is transparent and applying an electric field to the display medium. In the particles 11 for the display medium where at least one kind of micro particles 13 are stuck or fixed to a surface layer of a mother particle 12, the micro particles are made of polyimide resin. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides information for displaying information such as an image by moving a display medium by enclosing a display medium configured as a particle group between two substrates, at least one of which is transparent, and applying an electric field to the display medium. Display medium particles constituting a display medium for use in a display panel, and at least one kind of micron particle adhered or fixed to the surface layer of a mother particle, and an information display panel using the same It is about.

  Conventionally, an information display for displaying information such as an image by moving a display medium by enclosing a display medium configured as a particle group between two substrates, at least one of which is transparent, and applying an electric field to the display medium Display medium particles constituting a display medium for use in a panel, which are formed by attaching or fixing at least one kind of micron particle to the surface layer of a mother particle, are known (for example, Patent Document 1). reference).

JP 2003-233092 A

  Conventionally, in the particles for display medium described above, inorganic fine particles such as silica, titania, alumina, and crosslinked resin fine particles have been used as the material for the fine particles adhered or fixed to the surface layer of the mother particles. However, the conventional micron particles are not sufficiently durable, and in some cases, pretreatment with dimethylsilazane or the like is necessary, which requires time and effort, and the chargeability cannot be controlled.

  The object of the present invention is to eliminate the above-mentioned problems, have sufficient durability, take less time for preparation, and control the chargeability of the display medium particles and information display using the same Try to provide a panel.

  The display medium particles of the present invention display information by moving a display medium by enclosing a display medium configured as a particle group between two substrates, at least one of which is transparent, and applying an electric field to the display medium. In a display medium particle constituting a display medium used for an information display panel, wherein at least one type of micron particle is attached or fixed to the surface layer of the mother particle, the micron particle is a polyimide. It is characterized by comprising a system resin.

  Moreover, as a suitable example of the particles for display media of the present invention, the microparticles have a glass transition temperature or a melting point of 200 ° C. or higher, and the microparticles have a tensile elastic modulus of 2.5 GPa or higher. In other words, the charge amount of the micronized particles may be changed by changing the structure of the polyimide resin constituting the micronized particles.

  Furthermore, the information display panel of the present invention is moved by enclosing at least one type of display medium configured as a particle group between two substrates, at least one of which is transparent, and applying an electric field to the display medium. In the information display panel for displaying information, the above-described display medium particles are used as particles constituting the display medium.

  According to the present invention, in the particles for display medium formed by attaching or fixing at least one kind of micronized particles to the surface layer of the mother particle, the micronized particles are made of the polyimide resin, so that sufficient durability is obtained. In addition, it is possible to obtain a display medium particle and an information display panel using the same, which can be prepared without much effort and whose chargeability can be controlled.

(A), (b) is a figure for demonstrating the structure of an example of the information display panel used as the object of this invention, respectively. (A), (b) is a figure for demonstrating the structure of the other example of the information display panel used as the object of this invention, respectively. (A), (b) is a figure which shows the structure of an example of the particle | grains for display media of this invention, respectively.

  First, the configuration of the information display panel that is the subject 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 configured as a particle group including a chargeable particle sealed between two opposing substrates. Along with the applied electric field direction, the display medium is attracted by an electric field force or a Coulomb force, and the display medium is moved by a 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 the stability when the display information is rewritten or when the display information is continuously displayed. Here, as the force applied to the particles constituting the display medium, in addition to the force attracting each other by the Coulomb force between the particles, an electric mirror image force between the electrode and the substrate, an intermolecular force, a liquid cross-linking force, gravity and the like can be considered.

  An example of an information display panel that is an object of the present invention will be described with reference to FIGS. 1 (a) and (b) to FIGS. 2 (a) and 2 (b). FIGS. 1A and 1B to FIGS. 2A and 2B show partial cross sections of an information display panel having a configuration in which counter electrode pairs serving as pixels are arranged in a matrix.

  In the example shown in FIGS. 1 (a) and 1 (b), at least two types of display media having different optical reflectivity and charging characteristics (here, configured as a particle group including particles having at least optical reflectivity and chargeability) The white display medium 3W configured as a particle group including the negatively charged white particles 3Wa and the black display medium 3B configured as a particle group including the positively charged black particles 3Ba are shown). In the cell, the substrates 1 and 2 correspond to the electric field generated by applying a voltage to the pixel electrode pair formed by the stripe electrode 6 provided on the substrate 2 and the stripe electrode 5 provided on the substrate 1 crossing each other at right angles. The configuration is a passive drive system that moves vertically. Then, the white display medium 3W is visually recognized by the observer as shown in FIG. 1A, or the black display medium 3B is visually recognized by the observer as shown in FIG. 1B. Are displayed in a matrix with black and white dots. In addition, in FIG. 1 (a), (b), the partition in front is abbreviate | omitted. Here, an example is shown in which a pixel and a cell are associated with each other on a one-to-one basis, but a pixel and a cell may not be associated with each other on a one-to-one basis.

  In the example shown in FIGS. 2A and 2B, at least two types of display media having different optical reflectance and charging characteristics (here, configured as a particle group including particles having at least optical reflectance and charging properties (here) The white display medium 3W configured as a particle group including the negatively charged white particles 3Wa and the black display medium 3B configured as a particle group including the positively charged black particles 3Ba are shown). In the cell, in response to an electric field generated by applying a voltage to a pixel electrode pair formed by facing an electrode 5 (pixel electrode with TFT) provided on the substrate 1 and an electrode 6 (common electrode) provided on the substrate 2. Therefore, the active drive system is configured to move perpendicularly to the substrates 1 and 2. Then, the white display medium 3W is visually recognized by the observer as shown in FIG. 2A, or the white display is displayed by the observer, or the black display medium 3B is visually recognized by the observer as shown in FIG. 2B. Are displayed in a matrix with black and white dots. In addition, in FIG. 2 (a), (b), the partition in front is abbreviate | omitted. Here, an example is shown in which a pixel and a cell are associated with each other on a one-to-one basis, but a pixel and a cell may not be associated with each other on a one-to-one basis.

  A feature of the present invention is a display medium particle in which at least one kind of micron particle is attached or fixed to a surface layer of a mother particle as a display medium particle used in the above-described information display panel. This is a point using particles for a display medium composed of a polyimide resin.

  3 (a) and 3 (b) are views showing the structure of an example of the display medium particle of the present invention, FIG. 3 (a) shows a front view thereof, and FIG. 3 (b) shows a cross-sectional view thereof. Show. In the example shown in FIGS. 3A and 3B, the display medium particle 11 of the present invention is a composite particle obtained by attaching or fixing microparticles 13 made of polyimide resin to the surface layer of the base particle 12. It is composed of In this example, the microparticle 13 is an example of a single layer, but the number of layers is not particularly limited, and the number of layers may be two or more. Here, it is important that the fine particle 13 embedded in the mother particle 12 is exposed from the surface of the mother particle 12.

  In the present invention, heat resistance having a glass transition temperature or a melting point of 200 ° C. or higher, which is a preferable characteristic of the microparticles 13, is configured by forming the microparticles 13 constituting the display medium particles 1 from a polyimide resin. And durability which has a tensile elasticity modulus of 2.5 GPa or more can be obtained. Further, by changing the structure of the polyimide resin constituting the micronized particles 13 (hereinafter, chemical formula 1), specifically, the structure of the polyimide resin is changed to an amino group type (hereinafter chemical formula 2), a carboxyl group type. The charge amount of the display medium particles 11 can be changed by using the following (Formula 3), the hydroxyl group type (Formula 4), or the like. As a result, the display medium particles 11 can be easily designed to have a predetermined charge amount, and the charge of the display medium particles 11 can be controlled.

  Hereinafter, each member which comprises the panel for information displays which uses the particle | grains for display media of this invention is demonstrated.

  As the substrate, at least one of the substrates is a transparent substrate from which the display medium can be confirmed from the outside of the panel, and a material having high visible light transmittance and good heat resistance is preferable. The back substrate as the other substrate may be transparent or opaque. Examples of the substrate material include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene (PE), polycarbonate (PC), polyimide (PI), polyethersulfine (PES), triacetyl cellulose (TAC), An organic polymer substrate such as acrylic, a glass sheet, a quartz sheet, a metal sheet coated with an insulating film, or the like is used, and a transparent one of them is used on the display surface side. The thickness of the substrate is preferably 2 to 2000 μm, more preferably 5 to 1000 μm. If it is too thin, it becomes difficult to maintain the strength and the uniform spacing between the substrates, and if it is thicker than 2000 μm, a thin information display panel is obtained. Inconvenient in case.

  As a material for forming an electrode provided on the substrate as necessary, metals such as aluminum, silver, nickel, copper, and gold, indium tin oxide (ITO), indium zinc oxide (IZO), aluminum-doped zinc oxide (AZO), Examples include conductive metal oxides such as indium oxide, conductive tin oxide, antimony tin oxide (ATO), and conductive zinc oxide, and conductive polymers such as polyaniline, polypyrrole, and polythiophene. . As a method for forming the electrode, a method of patterning the above-described materials into a thin film by a sputtering method, a vacuum deposition method, a CVD (chemical vapor deposition) method, a coating method, or the like, or a metal foil (for example, a rolled copper foil) is laminated. A method or a method of patterning by mixing and applying a conductive agent to a solvent or a synthetic resin binder is used. The electrodes provided on the display screen region of the viewing side (display surface side) substrate need to be transparent, but the electrodes provided on the outside of the display screen region and on the back side substrate do not need to be transparent. In any case, the above-mentioned material that is conductive and capable of pattern formation can be suitably used. The electrode thickness is determined in view of conductivity and light transmittance, and is 0.01 to 10 μm, preferably 0.05 to 5 μm. It is not necessary to consider the light transmittance with respect to the material and thickness of the electrode provided outside the display screen area or on the back side substrate.

If necessary, the shape of the partition provided on the substrate is appropriately set according to the type of display medium involved in display, the shape and arrangement of electrodes to be arranged, and is not limited in general. However, the width of the partition is 2 to 100 μm. The height of the partition wall is adjusted to 10 to 500 μm, preferably 10 to 200 μm. The height of the partition wall arranged for securing the inter-substrate gap is matched with the inter-substrate gap to be secured. The height of the partition wall arranged to partition the inter-substrate space into cells may be the same as or lower than the inter-substrate gap.
In forming the partition wall, a both-rib method in which ribs are formed on each of the opposing substrates 1 and 2 and then bonded, and a single-rib method in which ribs are formed only on one substrate are conceivable. Any method is used in the present invention.
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, a hexagonal shape, a stepped hexagonal shape, and a stepped octagonal shape as viewed from the substrate plane direction. Shapes, honeycomb shapes, and mesh shapes are exemplified. 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 state becomes clearer.
Here, examples of the method for forming the partition include a mold transfer method, a screen printing method, a sand blast method, a photolithography method, and an additive method. Any of these methods can be suitably used for an information display panel mounted on the information display device of the present invention, and among these, a photolithography method using a resist film and a mold transfer method are suitably used.

  Next, the chargeable particles constituting the base particles of the display medium particles in the present invention will be described. The chargeable particles can contain a charge control agent, a colorant, an inorganic additive, and the like, if necessary, in the resin as the main component. Examples of resins, charge control agents, colorants, and other additives will be given below.

  Examples of the resin include urethane resin, urea resin, acrylic resin, polyester resin, acrylic urethane resin, acrylic urethane silicone resin, acrylic urethane fluororesin, acrylic fluororesin, silicone resin, acrylic silicone resin, epoxy resin, polystyrene resin, styrene Acrylic resin, polyolefin resin, butyral resin, vinylidene chloride resin, melamine resin, phenol resin, fluororesin, polycarbonate resin, polysulfone resin, polyether resin, polyamide resin and the like can be mentioned, and two or more kinds can be mixed. In particular, acrylic urethane resin, acrylic silicone resin, acrylic fluororesin, acrylic urethane silicone resin, acrylic urethane fluororesin, fluororesin, and silicone resin are suitable from the viewpoint of controlling the adhesive force with the substrate.

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

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

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

Yellow colorants include 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, cobalt blue, cobalt green, cobalt violet, iron oxide, carbon black, manganese ferrite black, cobalt ferrite black, copper powder, and aluminum powder.
These pigments and inorganic additives can be used alone or in combination. Of these, carbon black is particularly preferable as the black pigment, and titanium oxide is preferable as the white pigment. The above colorant can be blended to produce chargeable particles of a desired color.

  Further, the chargeable particles (hereinafter also referred to as particles) 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, regarding the particle size distribution, the particle size distribution Span shown 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 indicating the particle diameter in μm that 50% of the particles are larger than this and 50% is smaller than this, and d (0.1) is a particle in which the ratio of the smaller particles is 10%. (Numerical value expressed in μm, and d (0.9) is a numerical value expressed in μm for a particle diameter of 90% or less.)
By keeping Span within a range of 5 or less, the size of the chargeable particles is uniform, and movement as a uniform display medium becomes possible.

  Furthermore, when using a plurality of display media, among the chargeable particles constituting the display medium used, the average particle relative to d (0.5) of the chargeable particles having the maximum average particle diameter d (0.5). It is important that the ratio of d (0.5) of chargeable particles having a minimum diameter d (0.5) is 10 or less. Even if the particle size distribution Span is reduced, since the charged particles having different charging polarities move in opposite directions, it is preferable because they can be easily moved by making the particle size of each other comparable, That is the 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 the particle size distribution are obtained from the volume-based distribution. Specifically, using a Mastersizer2000 (Malvern Instruments Ltd.) measuring instrument, particles are introduced into a nitrogen stream, and the attached analysis software (software based on volume-based distribution using Mie theory) The diameter and particle size distribution can be measured.

Furthermore, when a display medium that includes chargeable particles is driven in a gas space, it is important to manage the gas in the space surrounding the display medium between the panel substrates, which improves display stability. Contribute. 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, 2A and 2B, the gaps are defined as electrodes 5 and 6 (electrodes inside the substrate) from the portion sandwiched between the opposing substrate 1 and substrate 2. 2), the occupied portion of the display medium 3, the occupied portion of the partition wall 4 (when the partition wall is provided), and the gas portion in contact with the so-called display medium excluding the panel seal portion.
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 must be sealed in the panel so that the humidity is maintained. For example, the display medium is filled and the panel is assembled in a predetermined humidity environment. It is important to apply a sealing material and a sealing method to prevent it.

The distance between the substrates in the information display panel targeted by the present invention is not limited as long as the display medium can be driven and the contrast can be maintained, but is usually adjusted to 2 to 500 μm, preferably 5 to 200 μm.
When the information display panel is a space movement method in charged particle gas, the distance between the substrates is adjusted in the range of 10 to 100 μm, preferably 10 to 50 μm. Furthermore, the volume occupation ratio of the display medium in the gas space between the substrates is preferably 5 to 70%, more preferably 5 to 60%. When it exceeds 70%, the movement of particles as a display medium is hindered, and when it is less than 5%, the contrast tends to be unclear.
As a method of moving and displaying the chargeable particles, there is a method in which the chargeable particles are sealed in a microcapsule together with an insulating liquid, and the microcapsule is disposed between a pair of counter electrodes. The particles can also be applied to the display medium of such an information display panel.

  An actual example will be described below.

<Specifications of prepared micron particles>
(1) As the microparticles A, polyimide resin (BST-01: manufactured by Sumitomo Bakelite Co., Ltd.) was used.
(2) As the microparticle B, modified polyimide resin (amino group type) (BST-01 amino group type: manufactured by Sumitomo Bakelite Co., Ltd.) was used.
(3) As the microparticle C, modified polyimide resin (carboxyl group type) (BST-01 carboxyl group type: manufactured by Sumitomo Bakelite Co., Ltd.) was used.
(4) As the microparticle D, modified polyimide resin (hydroxyl type) (BST-01 hydroxyl type: manufactured by Sumitomo Bakelite Co., Ltd.) was used.

(5) The microparticles E were synthesized in the following composition according to a standard method of emulsion polymerization at 70 ° C. for 12 hours under an N ₂ gas reflux atmosphere, and then thoroughly washed with purified water, hexane, and acetone. The vacuum was opened to evaporate the cleaning solvent, and a dry powder sample was obtained. The fine particle E is blended in 100 parts by weight of styrene monomer (Wako Pure Chemical Industries, Ltd.), 1.2 parts by weight of sodium lauryl sulfate (Wako Pure Chemical Industries, Ltd.), 2,2′-azobis [2- Methyl- (2-hydroxyethyl) propionamide] (Wako Pure Chemical Industries, Ltd.) 0.4 parts by weight, and purified water 400 parts by weight.
(6) The fine particles F were synthesized in the following composition according to a standard method of emulsion polymerization at 70 ° C. for 12 hours under an N ₂ gas reflux atmosphere, and then thoroughly washed with purified water, hexane, and acetone. The vacuum was opened to evaporate the cleaning solvent, and a dry powder sample was obtained. The fine particles F are blended in 100 parts by weight of methyl methacrylate monomer (Wako Pure Chemical Industries, Ltd.), 0.9 parts by weight of sodium lauryl sulfate (Wako Pure Chemical Industries, Ltd.), 2,2′-azobis [ 2-methyl- (2-hydroxyethyl) propionamide] (Wako Pure Chemical Industries, Ltd.) 0.3 parts by weight and purified water 400 parts by weight.

  In Table 1 below, the micron particles A to F are summarized and displayed together with their average particle diameter, saturation charge amount, glass transition on, and tensile modulus. The average particle diameter was obtained from image processing by imaging 100 particles with a scanning microscope. The saturation charge amount was measured using a general blow-off charge amount measuring device TB-203 (manufactured by Kyocera Chemical Co.). As the carrier particles, ferrite-based F96-80 (manufactured by Powdertech) was used. The glass transition temperature was measured by a method according to JIS K7121 using a general DTA apparatus. The tensile elastic modulus was measured by a method according to JIS K6717-2, in which microparticles were once dissolved in a solvent and cast by heating to prepare a test piece. However, since there was no suitable good solvent for the polyimide resin, the polyamic acid, which is a precursor of the polyimide resin, was cast and molded into a test piece shape, and then heat condensed and imidized to obtain a polyimide resin test piece.

<Method for producing white mother particles and composite particles>
As white mother particles, 100 parts by weight of polystyrene resin TOYO STYROL G100C (manufactured by Toyo Styrene Co., Ltd.) and 100 parts by weight of titanium dioxide (Taipaque CR-90: manufactured by Ishihara Sangyo Co., Ltd.) are melt-kneaded with a biaxial kneader, and a jet mill (Laboret mill IDS-LJ type: manufactured by Nippon Pneumatic Co., Ltd.) was finely pulverized and classified to obtain mother particles α having an average particle size of 9.5 μm within a particle size range of 0.5 to 50 μm. The mother particles α and the microparticles A, C, D, and E are premixed at a predetermined mixing ratio and fixed and combined with Nobilta Nob-130 (manufactured by Hosokawa Micron), and white mother particles / child particles combined particles αA, αC. , ΑD, αE were obtained.

<Black mother particle and composite particle production method>
As black mother particles, 100 parts by weight of polystyrene resin TOYO STYROL G100C (manufactured by Toyo Styrene Co., Ltd.) and 7 parts by weight of carbon black (MA100: manufactured by Mitsubishi Chemical) are melt-kneaded by a twin-screw kneader, and a jet mill (Lab Jet Mill IDS- LJ type (manufactured by Nippon Pneumatic Co., Ltd.) was finely pulverized and classified to obtain base particles β having an average particle size of 9.9 μm in the range of 0.5 to 50 μm. The base particles β and the microparticles B and F were premixed at a predetermined mixing ratio and fixed and combined with Nobilta Nob-130 (manufactured by Hosokawa Micron) to obtain black base particle-child particle composite particles βB and βF.

<Initial contrast ratio evaluation method>
The particles for positively charged display medium (βB, βF) and the particles for negatively charged display medium (αA, αC, αD, αE) are mixed and agitated in equivalent amounts to perform tribocharging, and are arranged via a 100 μm spacer. Was filled with a glass substrate that was treated with ITO on the inner side and connected to a power source, and a cell that was a copper substrate on the other side with a volume occupancy of 30% to obtain a panel for evaluation. When each of the ITO glass substrate and the copper substrate is 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 positively charged display medium particles are negatively connected to the low potential electrode side. The particles for the charged display medium move to the high potential electrode side. Here, when the positively charged display medium particles are black and the negatively charged display medium particles are white, a black display state is observed through the glass substrate, and then when the potential of the applied voltage is reversed, the particles are in the opposite directions. Moving, a white display state is observed. The applied voltage is changed every 5 [V] from -200 [V] to +200 [V], the reflectance is measured in each display state, and the white display reflectance and black display when the voltage of the same absolute value is applied. The ratio with the hourly reflectance was taken as the contrast ratio at that voltage, and the contrast ratio when ± 200 [V] was applied was taken as the initial contrast ratio C200, which was used as an indicator of the clear display properties of the particles for display media.

<Initial drive voltage index value evaluation method>
In the initial contrast ratio evaluation method described above, a voltage that gives a contrast 0.5 times that of C200 was used as an initial applied voltage V50 [V], which was used as an indicator of the voltage required for driving the display medium particles.

<Durability performance evaluation method>
Furthermore, after applying the voltage ± 200 [V] to this evaluation panel alternately 1 million times at a frequency of 1 [kHz] to reversely move the particles, the contrast ratio at each applied voltage was measured in the same manner as described above. The contrast ratio C200 after repeated reversal movement 10,000 times and the applied voltage V50 after reversal movement 1,000,000 times were determined.

<Heat-resistant durability evaluation method>
Further, this evaluation panel was heated in a hot air oven at 120 ° C. for 500 hours in advance, and then tested in the same manner as in the durability performance evaluation method described above. The applied voltage V50 after movement was determined and used as an index of heat resistance.

  The evaluation results are shown in Table 2 below.

  From the results in Table 2, it can be seen that the durability performance is somewhat poor when the tensile strength of either one of the combined two-color display medium particles is 2.5 GPa or less (Examples 4 and 5). . Moreover, it turns out that durability performance is unsatisfactory when the tensile strength of both the child particle | grains of the particle | grains for display media of 2 colors combined is 2.5 GPa or less (comparative example 1). Furthermore, when the glass transition temperature or the melting point of either one of the combined two-color display medium particles is 200 ° C. or lower, the heat-resistant durability performance is somewhat poor (Examples 4 and 5). ). Furthermore, when the glass transition temperature or melting | fusing point of both the child particle | grains of the particle | grains for display media of two colors combined is 200 degrees C or less, it turns out that heat resistance performance is unsatisfactory (Comparative Example 1). In addition, it can be seen that by controlling the functional group, it is possible to select a display performance balance (high contrast or that can be driven at a low voltage), and the range of applicable products can be expanded (Examples 1 to 3).

  The information display panel using the display medium particles of the present invention is an electronic display such as a display unit of a mobile device such as a notebook computer, PDA, mobile phone, or handy terminal, an electronic book, an electronic newspaper, or an electronic manual (instruction manual). Paper, signboards, posters, bulletin boards such as blackboards, calculators, home appliances, car supplies, display units, point cards, card displays such as IC cards, electronic advertising, electronic point of purchase (POP), It is preferably used as an electronic price tag, an electronic shelf label, an electronic score, a display unit of an RF-ID device, or a display unit (so-called rewritable paper) that performs display rewriting by connecting to an external display rewriting unit.

1, 2 Substrate 3W White display medium (white particles)
3Wa White negatively charged particles 3B Black display medium (black particles)
3Ba Black positively charged particles 4 Partitions 5 and 6 Electrode 11 Display medium particles 12 Base particles 13 Micron particles

Claims (5)

  A display medium used for an information display panel for displaying information by moving a display medium by enclosing a display medium configured as a particle group between two transparent substrates at least one and applying an electric field to the display medium The display medium particles comprising the surface layer of the mother particles, wherein the microparticles are made of a polyimide-based resin. Particles for display media.   The display medium particle according to claim 1, wherein the micron particle has a glass transition temperature or a melting point of 200 ° C. or higher.   3. The display medium particle according to claim 1, wherein the micron particle has a tensile elastic modulus of 2.5 GPa or more.   4. The display medium particle according to claim 1, wherein a charge amount of the micron particle is changed by changing a structure of a polyimide resin constituting the micron particle. 5.   An information display panel that displays information by moving a display medium by enclosing at least one type of display medium configured as a particle group between two substrates, at least one of which is transparent, and applying an electric field to the display medium 5. An information display panel using the display medium particles according to claim 1 as particles constituting at least one type of display medium.

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