JP2009122374A - Particle for display medium and panel for information display using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide particles for a display medium wherein defects such as reduction of fluidity and increase of adhesion force of the particles are not generated and an electrification function of the particles is not deteriorated, and to provide a panel for an information display using the same. <P>SOLUTION: In the particles for the display medium which constitute the display medium constituted of a particle group, a mixture of a monofunctional monomer and a multifunctional monomer is used as monomers as resin materials which constitute the particles for the display medium. In the panel for information display formed by encapsulating the display medium between two substrates at least one of which is transparent and displaying information such as an image by applying electric force to the display medium, the particles for the display medium are used as the particles for the display medium which constitute the display medium. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention provides an information display panel that encloses a display medium composed of particle groups between two substrates, at least one of which is transparent, and displays information such as an image by applying an electric force to the display medium. The present invention relates to a display medium particle constituting a display medium to be used and an information display panel using the same.

  As an information display device that replaces a liquid crystal display device (LCD), an information display device that drives charged particles in a liquid (electrophoresis method) or a method that drives charged particles in a gas (for example, an electronic powder fluid method) Information display devices are known.

  As an information display panel used for an information display device of a charged particle driving system, a display medium configured as a particle group including a chargeable particle is sealed between two substrates, at least one of which is transparent, and an electric field is applied to the display medium. A device using an information display panel that displays information such as an image by giving the image is known (for example, see Patent Document 1).

International Publication No. 2003/050606 Pamphlet

  The display medium particles constituting the display medium (particle group) used in the information display panel described above reduce the cohesive force between the particles, or reduce the adhesion force to members constituting the panel such as electrodes. Therefore, a design is made in which inorganic oxide fine particles such as silica, alumina, and titania having a particle diameter of about 1 to 100 nm are externally attached to the surface of particles made of resin. However, the display display is repeatedly rewritten on the information display panel, that is, by repeating the reversal movement of the particles for the display medium many times, the fine particles are buried in the particle surface, the fluidity of the particles is decreased, the adhesion force is increased, etc. And problems such as deterioration of the charging performance of the particles occur.

  An object of the present invention is to solve the above-mentioned problems, and display medium particles that do not cause problems such as a decrease in fluidity of particles and an increase in adhesion force, and further do not deteriorate the charging performance of the particles, and the same. An information display panel is to be provided.

  The display medium particles of the present invention are display medium particles constituting a display medium used in an information display panel for driving a display medium composed of a group of particles in a gas, and are resin materials constituting the display medium particles As the monomer, a mixture of a monofunctional monomer and a polyfunctional monomer is used.

  In addition, as a suitable example of the particle | grains for display media of this invention, when using the mixture of a monofunctional monomer and a trifunctional monomer, use the mixture which makes a trifunctional monomer 20-70 weight% and a monofunctional monomer the remainder. When using a mixture of a monofunctional monomer and a bifunctional monomer, a mixture of 30 to 70% by weight of the bifunctional monomer and the remainder of the monofunctional monomer may be used.

  In addition, the information display panel of the present invention encloses a display medium composed of a particle group between two substrates, at least one of which is transparent, and applies information such as an image to the display medium by applying an electric force. In the information display panel to be displayed, the display medium particles described above are used as the display medium particles constituting the display medium.

  According to the present invention, the display medium particles used in the information display panel for driving the display medium composed of the particle group in the gas, the monomer as the resin material constituting the display medium particles As described above, by using a mixture of a monofunctional monomer and a polyfunctional monomer, particles such as a decrease in fluidity of the particles and an increase in adhesion force do not occur, and further, there is no deterioration in charging performance of the particles. An information display panel using the same can be obtained.

  First, an example of the basic configuration of the information display panel of the present invention will be described. In the information display panel of the present invention, an electric field is applied to a display medium having optical reflectivity and chargeability composed of at least one kind of particles enclosed in a space 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 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 the information display panel of the present invention will be described with reference to FIGS. 1 (a) and 1 (b) to FIG.

  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. The electrode 5 (individual electrode) provided on the substrate 1 in each cell formed by the partition walls 4 is provided with a white display medium 3W composed of a group of particles and a black display medium 3B composed of a particle group of black display medium particles 3Ba. ) And an electrode 6 (individual electrode) provided on the substrate 2, the substrate 6 is moved perpendicularly to the substrates 1 and 2 in accordance with an electric field generated by applying a voltage. 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. The electrode may be provided outside the substrate or may be provided so as to be embedded inside the substrate.

  In the example shown in FIGS. 2 (a) and 2 (b), the display medium 3 (here, a particle group of particles 3Wa for white display medium) having at least an optical reflectance and chargeability composed of at least one kind of particles. In each cell formed by the partition walls 4 in accordance with an electric field generated by applying a voltage between the electrode 5 and the electrode 6 provided on the substrate 1. 2 in the direction parallel to Then, as shown in FIG. 2 (a), the white display medium 3W is visually recognized by the observer to display white dots, or as shown in FIG. 2 (b), the color of the black plate 7B is changed to the observer. The black dots are displayed by visually recognizing. In addition, in the example shown to Fig.2 (a), (b), the partition in front is abbreviate | omitted. Here, the same display can be performed when the white display medium 3W is a black display medium and the black plate 7B is a white plate. The electrode may be provided outside the substrate or may be provided so as to be embedded inside the substrate.

  In the example shown in FIGS. 3A and 3B, the basic configuration is the same as the example shown in FIG. 1, and three cells (each cell is a unit pixel. In this case, one display unit is composed of three color unit pixels. ) Shows an example of color dot display constituting a display unit. In the example shown in FIGS. 3A and 3B, 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. 3A, the white display medium 3W is moved to the observer side in all the first cells 21-1 to 21-3 in one display unit. The white dot display is performed for the observer, and as shown in FIG. 3B, the black color is displayed in the first cell 21-1 to the third cell 21-3 in one display unit on the observer side. By moving the medium 3B, black dots are displayed to the observer. Multi-color display is possible by moving the display medium of each cell. In addition, in 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, at least the optical reflectivity and charging characteristics of at least one kind of particles are different. Two or more kinds of display media 3 (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) are formed by partition walls 4. In each of the formed cells, the substrate 1 corresponds to the electric field generated by applying a voltage between the external electric field forming means 31 provided outside the substrate 1 and the external electric field forming means 32 provided outside the substrate 2. 2 and move vertically. 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. 4D, 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 33 is provided inside the substrate 1, and a conductive member 34 is provided inside the substrate 2. This conductive member may not be provided.

  In the example shown in FIG. 5, instead of the cells formed of the partition walls 4 filled with the white display medium 3W and the black display medium 3B shown in FIGS. A microcapsule 9 filled with display medium particles 3Ba together with an insulating liquid 8 is used. An inter-substrate distance securing member 40 is provided to ensure the inter-substrate distance between the opposing substrates 1 and 2.

  As a result of intensive studies on the particles for display medium constituting the display medium used in the above-described information display panel, the present inventors have found that a resin is used to suppress the phenomenon of burying fine particles functioning as external attachments. It has been found that it is necessary to harden the surface of the particles made of. As one means for that purpose, the inventors have found that it is effective to increase the crosslinking density of the particle preparation material by using a mixture of a monofunctional monomer and a polyfunctional monomer as the particle material. Thereby, it is possible to reduce the embedding of the fine particles in the particles when rewriting is repeated in the information display panel, and it is possible to prevent an increase in particle adhesion force and the like.

  In the present invention, regarding the ratio of the monofunctional monomer and the polyfunctional monomer used as materials in the mixture of the monofunctional monomer and the trifunctional monomer, first, when using a mixture of the monofunctional monomer and the trifunctional monomer, the trifunctional monomer is 20 to 70. It is preferable to use a mixture having a weight percentage of the monofunctional monomer as the balance. If the trifunctional monomer is less than 20% by weight, embedding of externally added fine particles is not suppressed because the particle hardness is low, and if the trifunctional monomer exceeds 70% by weight, the curing strain at the time of crosslinking increases and the particles become brittle. Therefore, it cannot be produced as particles. Moreover, when using the mixture of a monofunctional monomer and a bifunctional monomer, it is preferable to use the mixture which makes 30-70 weight% of bifunctional monomers and a monofunctional monomer the remainder. If the bifunctional monomer is less than 30% by weight, the particle hardness is low, so that embedding of the externally added fine particles is not suppressed, and if the bifunctional monomer exceeds 70% by weight, the strain at the time of crosslinking and curing increases. The particles become brittle and cannot be produced as particles.

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

  As for the substrate, at least one substrate (display surface side substrate) is a transparent substrate from which the color of the display medium can be confirmed from the outside of the information display panel, and a material having high visible light transmittance and good heat resistance is suitable. is there. The back substrate may be transparent or opaque. Examples of substrate materials include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyethylene (PE), polycarbonate (PC), polyimide (PI), acrylic and other plastic substrates and glass A substrate is used. The thickness of the substrate is preferably from 2 to 5000 μm, more preferably from 5 to 2000 μm. If it is too thin, it will be difficult to maintain the strength and the spacing uniformity between the substrates, and if it is thicker than 5000 μm, it will be a thin information display panel. Is inconvenient.

  As the material for forming electrodes and conductive members when providing electrodes and conductive members on information display panels, metals such as aluminum, silver, nickel, copper, and gold, indium tin oxide (ITO), and zinc-doped indium oxide (IZO) ), Aluminum-doped zinc oxide (AZO), indium oxide, conductive tin oxide, antimony tin oxide (ATO), conductive metal oxides such as conductive zinc oxide, and conductive polymers such as polyaniline, polypyrrole, and polythiophene Are illustrated and used as appropriate. As a method for forming the electrode and the conductive member, a method of forming 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) A method of laminating a conductive material and a method of applying a conductive agent mixed with a solvent or a synthetic resin binder are used. The electrodes and conductive members provided on the display surface side substrate 2 that are visible and need to be transparent need to be transparent, but the electrodes and conductive members provided on the back side substrate 1 do not need to be transparent. In any case, the above-mentioned material that can be patterned and is electrically conductive can be suitably used. The thickness of the electrode or the conductive member may be 0.01 to 10 μm, preferably 0.05 to 5 μm, as long as the electrical conductivity can be secured and the light transmittance is not hindered. The materials and thicknesses of the electrodes and conductive members provided on the back side substrate 1 are the same as those of the electrodes and conductive members 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.

In the partition for forming cells in the space between the substrates of the information display panel, the height and width of the partition are appropriately set according to the type of the display medium involved in the display and are not limited in general, but the partition width is 2 The height of the partition wall is adjusted to 10 to 500 μm, preferably 10 to 200 μm. As shown in FIG. 6, the cells in the information display panel obtained by superimposing the display side substrate and the back side substrate are polygons such as a square shape, a triangular shape, a line shape, a circular shape, and a hexagonal shape as viewed from the substrate plane direction. However, any of a circular shape, an oval shape, a race track shape, and the like may be used, or different shapes may be combined. Of these, polygons with rounded corners (especially quadrangles with rounded corners), circles, ellipses, and racetracks are preferable as the display medium that can easily move. Examples of the arrangement include a lattice shape, a honeycomb shape, and a mesh shape. Various shapes are used depending on the shape of the partition wall. Among these, a configuration in which square cells with rounded corners are arranged in a lattice shape is preferable, and a portion corresponding to a partition wall cross-sectional portion seen from the display surface side (the area of the cell frame formed by the partition wall width) is made as small as possible. It is better and the clearness of the display state increases.
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 preferably used, but among these, a photolithography method using a resist film and a mold transfer method are preferably used.

Next, the display medium particles of the present invention (hereinafter also referred to as particles) will be described. The display medium particles are used as they are as they are, which are composed of the display medium particles alone or in combination with other particles as a display medium.
The particles can contain a charge control agent, a colorant, an inorganic additive, and the like, if necessary, in the resin as the main component, as in the conventional case. Examples of resins, charge control agents, colorants, and other additives will be given below.

Examples of the resin include urethane resin, urea resin, acrylic resin, polyester resin, acrylic urethane resin, acrylic urethane silicone resin, acrylic urethane fluororesin, acrylic fluororesin, silicone resin, acrylic silicone resin, epoxy resin, polystyrene resin, styrene Acrylic resin, polyolefin resin, butyral resin, vinylidene chloride resin, melamine resin, phenol resin, fluororesin, polycarbonate resin, polysulfone resin, polyether resin, polyamide resin and the like can be mentioned, and two or more kinds can be mixed. In particular, acrylic urethane resin, acrylic silicone resin, acrylic fluororesin, acrylic urethane silicone resin, acrylic urethane fluororesin, fluororesin, and silicone resin are suitable from the viewpoint of controlling the adhesive force with the substrate.
In the present invention, a monofunctional monomer and a polyfunctional monomer are selected from the above-described resins as necessary and used in combination.

  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.

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

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

  In addition, the particles for 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.

Further, in the particles for display medium of the present invention, the particle size distribution Span represented by the following formula is set to less than 5 and preferably less than 3 with respect to the particle size distribution of each particle.
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 movement as a display medium is possible.

  Furthermore, it is important that 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 10 or less. 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 particle size of the display medium particles can be obtained from a laser diffraction / scattering method or the like. When laser light is irradiated onto particles to be measured, a light intensity distribution pattern of diffracted / scattered light is spatially generated, and this light intensity pattern has a corresponding relationship with the particle diameter, so that the particle diameter and particle diameter distribution can be measured. .
Here, the particle size and particle size distribution in the present invention are obtained from a volume-based distribution. Specifically, using a Mastersizer2000 (Malvern Instruments Ltd.) measuring instrument, particles are introduced into a nitrogen stream and the attached analysis software (software based on volume-based distribution using Mie theory) The diameter and particle size distribution can be measured.

  The charge amount of the 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 the information display panel of the present invention is a dry type information display panel that drives a display medium in a gas space, it is important to manage the gas in the void surrounding the display medium, thereby improving 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.
For example, in FIG. 1 (a), the gap portion refers to the electrodes 5 and 6 (when electrodes are provided inside the substrate), the occupied portion of the display medium 3, from the portion sandwiched between the opposing substrate 1 and substrate 2. The gas portion in contact with the so-called display medium excluding the occupied portion of the partition wall 4 and the seal portion of the information display panel is assumed.
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 information display panel so that the humidity is maintained. For example, filling of particles constituting the display medium, assembly of the information display panel, etc. are performed in a predetermined humidity environment. In addition, it is important to apply a sealing agent and a sealing method for preventing moisture from entering from the outside.

The distance between the substrates in the information display panel 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 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.

  Actually, a particle material was produced by a polymerization method in order to realize the particle characteristics required as display medium particles constituting the display medium used in the information display panel. At this time, in addition to a commonly used monofunctional monomer as a resin material as much as possible, a polyfunctional monomer was mixed and mixed to produce particles composed of a resin pair having a high crosslinking density. Hereinafter, a method for preparing a sample of display medium particles, and evaluation of the rewriting durability performance and the adhesion of display medium particles in an information display panel using the sample as a display medium will be described.

<Sample preparation method for particles for display medium>
Resin samples A to O shown in Table 1 below were prepared. Among these, the resin sample A is only a monofunctional monomer, the resin samples B to H are a mixture of a monofunctional monomer and a trifunctional monomer, and the resin samples I to O are a mixture of a monofunctional monomer and a bifunctional monomer. there were. 1 part (resin: 100) of a resin material monomer and an initiator (Wako Pure Chemical Industries: V-60) prepared in advance and carbon black as a pigment are blended and dispersed in a water bath with a stirring mixer, and the water bath temperature is 90 ° C. The resin was crosslinked for 30 minutes by heating and polymerization reaction. The resin particles crosslinked by the polymerization were sieved, and then particles for a display medium having a volume average particle diameter of about 10 μm were prepared using a classifier. Then, as a fine particle to be externally added, a surface hydrophobic treatment external additive having a primary particle diameter of 8 nm (Degussa Japan Co., Ltd .: H3004 (negatively chargeable) is added to the negatively charged particles, and positively charged. 3 parts by weight of H3050 (positively charged) was added to the particles. As described above, display medium particles of resin samples A to O were produced.

<Evaluation of repeated display rewriting durability performance>
A coloring agent and a charge control agent are added to each of the display medium particles of the prepared resin samples A to O, and positively charged and negatively charged display media are respectively processed by performing positively and negatively charged treatments, respectively. Two types of particles for display media were prepared. In the information display panels of Examples 1 to 11 and Comparative Examples 1 to 4 using the two types of produced display medium particles, a durability performance evaluation test for repetitive display rewriting was performed. The results are shown in Table 2 below. In this durability performance evaluation test, if the number of reversal movements at which the reversal movement efficiency (number of particles) of the display medium particles is 50% or less is 50,000 or more, the result is “good”.

<Evaluation of adhesion of display medium particles>
The adhesion force of the display medium particles was measured by the following procedure.
(1) Open the information display panel that has been repeatedly rewritten and take out the particles for the display medium inside.
(2) A measurement substrate is prepared by spraying particles for display medium taken out on a glass substrate treated with an ITO sputter film having the same surface as the ITO electrode of the information display panel.
(3) A particle-capturing substrate is placed opposite to a measurement substrate on which particles for display medium are dispersed, and is set in a high-speed centrifuge in that state, and the rotation speed of the centrifuge is increased stepwise. The particles for the display medium on the measurement substrate are caused to fly to the capture substrate by centrifugal force due to high-speed rotation, and the capture substrate is changed at each rotation speed. FIG. 7 shows a conceptual diagram of a high-speed centrifuge for the centrifugal adhesion measuring method.
(4) The particle capturing substrate prepared for each rotation speed is observed with a microscope, and the particle size distribution of the particles for the display medium is measured.
(5) Obtain the centrifugal force when the display medium particles flew from the rotation speed and particle size distribution and particle material density of the display medium particles, and obtain the distribution as the adhesion force of each display medium particle. The average value was defined as the adhesion of the display medium particles. The results are shown in Table 2 below.
This measurement method is a powder adhesion measurement method devised by Professor Takeuchi of Ibaraki University. CP80WX manufactured by Hitachi Koki Co., Ltd. and a dedicated swing rotor: P55ST2 were used.

As shown in FIG. 7, display medium particles are set on a measurement substrate, and the rotational speed ω of the high-speed centrifuge is increased, and the centrifugal force Fr is calculated from the rotational value and particle diameter of the display medium particles flying. Calculated as the adhesion force Fa. The centrifugal force Fr is obtained from the following equation.
Fr = mRω ²
m = (4π / 3) × (d / 2) ³ × ρ
m: particle mass d: particle diameter ρ: particle specific gravity R: distance from the center of rotation of the high-speed centrifuge to the particles for the display medium

From the results of Table 2, in the production of the display medium particles, in the case of blending 20% by weight or more of the trifunctional monomer among the monomer components to be the resin material (Examples 1 to 6), 30% by weight or more of the bifunctional monomer In the case of blending (Examples 7 to 11), in the display medium using the display medium particles produced from these resins, the adhesive strength is 4. even after display rewriting is performed 800,000 times at a frequency of 1 kHz at 70 V. 98 × 10 ⁻⁸ [N] or less, and it can be determined that the rewriting durability performance of the display medium can be improved.

  In the above-described embodiment, the distance between the panel substrates is 40 μm and the drive applied voltage is 70 V. However, for example, when designing with a voltage of 70 V or more in the display device specifications, the adhesive force for obtaining good display characteristics is more than that of the above embodiment. In this case, too, the externally added fine particles are embedded in the surface of the particles and the adhesion force increases, so that the adhesion force becomes larger than the initial value and a good image display is impossible. End up. As can be seen from the rate of change of the adhesion force in the above example, it is possible to reduce the increase in adhesion force by performing a hardening process on the particle surface.

  The information display panel of the present invention includes a notebook computer, an electronic notebook, a portable information device called PDA (Personal Digital Assistants), a display unit of a mobile device such as a mobile phone, a handy terminal, an electronic book, an electronic newspaper, an electronic manual ( Electronic paper such as instruction manuals, signboards, posters, bulletin boards such as blackboards (whiteboards), electronic desk calculators, display units such as home appliances, automobile supplies, card display units such as point cards and IC cards, electronic advertisements, In addition to information boards, electronic POPs (Point Of Presence, Point Of Purchase advertising), electronic price tags, electronic shelf labels, electronic musical scores, RF-ID device displays, various electronic devices such as POS terminals, car navigation devices, watches, etc. In addition to being suitably used for the display unit, it is also suitable as a rewritable paper for driving a display medium using external electric field forming means. Used.

  The information display panel driving method of the present invention is a simple matrix driving method or static driving method that does not use a switching element in the panel itself, a three-terminal switching device represented by a thin film transistor (TFT), or a thin film diode ( Various types of driving methods such as an active matrix driving method using a two-terminal switching element represented by TFD) and an external electric field driving method using an external electric field forming means can be applied.

(A), (b) is a figure which shows an example of the information display panel of this invention, respectively. (A), (b) is a figure which shows the other example of the information display panel of this invention, respectively. (A), (b) is a figure which shows the other example of the information display panel of this invention, respectively. (A)-(d) is a figure which shows the other example of the information display panel of this invention, respectively. It is a figure which shows the other example of 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 of this invention. It is a conceptual diagram of the high-speed centrifuge of the centrifuge adhesion force measuring method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Back side board | substrate 2 Display side transparent substrate 3 Display medium 3W White display medium (white particle group)
3B black display medium (black particle group)
3R red display medium 4 partition wall 5, 6 electrode 7B black plate 8 insulating liquid 9 microcapsule 10 display medium particle 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, 32 External electric field forming means 33, 34 Conductive member 40 Member for securing distance between substrates

Claims (4)

  A display medium particle constituting a display medium used in an information display panel for driving a display medium composed of particle groups, and a monofunctional monomer and a polyfunctional monomer as a monomer as a resin material constituting the display medium particle A particle for a display medium, characterized by using a mixture thereof.   2. The display medium particle according to claim 1, wherein when a mixture of a monofunctional monomer and a trifunctional monomer is used, a mixture containing 20 to 70% by weight of the trifunctional monomer and the remainder of the monofunctional monomer is used.   2. The display medium particle according to claim 1, wherein when a mixture of a monofunctional monomer and a bifunctional monomer is used, a mixture containing 30 to 70% by weight of the bifunctional monomer and the remainder of the monofunctional monomer is used.   In an information display panel that displays information such as an image by enclosing a display medium composed of particles between two substrates, at least one of which is transparent, and applying an electrical force to the display medium, A display medium particle according to any one of claims 1 to 3, wherein the display medium particle is used as a display medium particle.

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