JP4566624B2 - Method for producing particles for image display medium - Google Patents

Description

  The present invention relates to an image display medium used in an image display apparatus that encloses an image display medium between opposing substrates at least one of which is transparent, applies an electric field to the image display medium, and moves the image display medium to display an image. The present invention relates to a method for producing a constituent particle for an image display medium.

  2. Description of the Related Art Conventionally, image display devices using techniques such as an electrophoresis method, an electrochromic method, a thermal method, and a two-color particle rotation method have been proposed as image display devices that can replace liquid crystal (LCD).

  Compared to LCDs, these conventional technologies have advantages such as a wide viewing angle close to that of ordinary printed materials, low power consumption, and a memory function. It is considered as a technology that can be used for mobile phones, and is expected to expand to image display for mobile terminals, electronic paper, and the like. Particularly recently, an electrophoretic method in which a dispersion liquid composed of dispersed particles and a colored solution is encapsulated and disposed between opposing substrates has been proposed and is expected.

  However, the electrophoresis method has a problem that the response speed becomes slow due to the viscous resistance of the liquid because the particles migrate in the liquid. Furthermore, since particles with high specific gravity such as titanium oxide are dispersed in a solution with low specific gravity, it is easy to settle, and it is difficult to maintain the stability of the dispersed state, and there is a problem of lack of image repetition stability. . Even when microencapsulation is performed, the cell size is set to the microcapsule level, and the above-described drawbacks are hardly made to appear, and the essential problems are not solved at all.

  On the other hand, a method in which conductive particles and a charge transport layer are incorporated into a part of a substrate without using a solution is proposed instead of an electrophoresis method using behavior in a solution (see, for example, Non-Patent Document 1). ). However, the structure is complicated because the charge transport layer and further the charge generation layer are arranged, and it is difficult to inject the charges into the conductive particles.

As a method for solving the various problems described above, an image display medium is sealed between opposing substrates, at least one of which is transparent, and an electric field is applied to the image display medium to display an image obtained by moving the image display medium. An image display device is known.
趙 Kuniori and three others, “New Toner Display Device (I)”, July 21, 1999, Annual Meeting of the Imaging Society of Japan (83 times in total) “Japan Hardcopy'99” Proceedings, p.249-252

  As the image display medium used in the above-described image display device, for example, a particle group composed of particles using a thermoplastic resin such as styrene acrylic or styrene butadiene or a powder fluid using the particles is used. In these image display media, when the obtained image display media is used in an image display device as it is, there are problems in heat resistance reliability, change with time during long-time inversion, and the like.

  An object of the present invention is for an image display medium that can solve the above-mentioned problems, can give high heat resistance and strength to particles, and can obtain good heat reliability and good temporal change at the time of long-term inversion. An object is to provide a method for producing particles.

In the method for producing particles for an image display medium of the present invention, an image display medium is sealed between opposing substrates at least one of which is transparent, an electric field is applied to the image display medium, and the image display medium is moved to display an image. In the method for producing particles for an image display medium used in an image display device, the uncured particles are irradiated with an electron beam and post-crosslinked to obtain particles for an image display medium .

  Moreover, as a suitable example of the manufacturing method of the particle | grains for image display media of this invention, there exist that an image display medium is a particle group and an image display medium is a powder fluid.

  According to the present invention, the image display medium particles can be given heat resistance and strength by post-crosslinking the image display medium particles with an electron beam (EB). Further, when the composite particles having fine particles attached to the surface are subjected to electron beam crosslinking as the particles for the image display medium, the attached fine particles can be more firmly fixed to the base particles. By cross-linking the image display medium particles with an electron beam, the external additive added to the image display medium particles can be embedded in or transferred to the image display medium particles even when reversal display is performed repeatedly. Can be prevented. Furthermore, the crosslinking rate can be further increased by adding a crosslinking agent to the particles in advance.

  First, a basic configuration of an image display panel provided in an image display device that uses the particles of the present invention as particles constituting an image display medium (particle group or powder fluid) will be described. In the image display panel used in the present invention, an electric field is applied to an image display medium sealed between two opposing substrates. Along with the applied electric field direction, the image display medium charged at a low potential toward the high potential side is attracted by the force of the electric field or the Coulomb force, and is charged at a high potential toward the low potential side. The image display medium is attracted by an electric field force, a Coulomb force, or the like, and the image display medium is reciprocated by a change in the electric field direction due to the potential switching, thereby displaying an image. Therefore, it is necessary to design the image display panel so that the image display medium moves uniformly and can maintain stability during repetition or storage. Here, as the force applied to the particles constituting the image display medium, in addition to the force attracted by the Coulomb force between the particles, the electric image force with the electrode and the substrate, the intermolecular force, the liquid cross-linking force, gravity and the like can be considered. .

An example of an image display panel used in an image display device that uses particles that are targets of the production method of the present invention will be described with reference to FIGS. 1 (a), (b) to 3 (a), (b).
In the example shown in FIGS. 1A and 1B, an image display medium 3 having two or more colors and different charging characteristics (here, white particles 3W and black particles 3B are shown) from the outside of the substrates 1 and 2 is used. Depending on the applied electric field, the substrate is moved perpendicularly to the substrates 1 and 2 and the black particles 3B are visually recognized by the observer to display black, or the white particles 3W are visually recognized by the observer to display white. Is going. In the example shown in FIG. 1B, in addition to the example shown in FIG. 1A, partition walls 4 are provided, for example, in a lattice shape between the substrates 1 and 2 to define display cells.
In the example shown in FIGS. 2A and 2B, an electrode 5 in which an image display medium 3 (here, white particles 3 W and black particles 3 B are shown) having two or more colors and different charging characteristics is provided on the substrate 1. And the electrode 6 provided on the substrate 2 are moved perpendicularly to the substrates 1 and 2 in accordance with an electric field generated by applying a voltage, and the black particles 3B are visually recognized by the observer to display black. Alternatively, white display is performed by making the observer visually recognize the white particles 3W. In the example shown in FIG. 2B, in addition to the example shown in FIG. 2A, partition walls 4 are provided, for example, in a lattice form between the substrates 1 and 2 to define display cells.
In the example shown in FIGS. 3A and 3B, an image display medium 3 (in this case, white particles 3W) having one type of chargeability is placed between the electrode 5 and the electrode 6 provided on the substrate 1. In accordance with the electric field generated by applying a voltage to the substrate 1, it is moved in a direction parallel to the substrates 1 and 2, and the white particles 3W are visually recognized by the observer, or the color of the electrode 6 or the substrate 1 is displayed. The color of the electrode 6 or the substrate 1 is displayed by the observer. In the example shown in FIG. 3B, in addition to the example shown in FIG. 3A, a partition 4 is provided between the substrates 1 and 2 to form a display cell, for example.
The above description can be similarly applied to the case where the white particles 3W are replaced with the white powder fluid and the black particles 3B are replaced with the black powder fluid.

Next, the particle | grains for image display media obtained by the manufacturing method of this invention are demonstrated.
FIG. 4 is a diagram for explaining an example of a method for producing particles for an image display medium according to the present invention. In the example shown in FIG. 4, the particles for the image display medium obtained by the production method of the present invention are used as the particles constituting the image display medium. In the example shown in FIG. 4, first , uncured particles 11 are prepared. Thereafter, the prepared uncured particles 11 are irradiated with an electron beam (EB irradiation), and the particles 11 are post-crosslinked to obtain particles for an image display medium of the present invention. In this example, post-crosslinking is performed by electron beam irradiation, whereby in the resin constituting the particles 11, the chain is broken, radicals are generated, and recombination is performed, thereby imparting heat resistance and toughness to the particles themselves. And reliable particles can be obtained.

FIG. 5 is a diagram for explaining another example of the method for producing particles for an image display medium of the present invention. In the example shown in FIG. 5 , the particles for the image display medium obtained by the production method of the present invention are used as the particles constituting the image display medium. In the example shown in FIG. 5, first , composite particles 13 in which fine particles 12 are bonded to the outer periphery of uncured particles 11 are prepared. Thereafter, the prepared composite particles 13 are irradiated with an electron beam, the particles 11 are post-crosslinked, and the fine particles 12 are firmly fixed to the particles 11 to obtain the particles for an image display medium of the present invention. In this example, post-crosslinking by electron beam irradiation can impart heat resistance and toughness to the particles 11 themselves as in the example shown in FIG. Can be obtained. In addition, as shown in FIG. 6 in the case of particles for image display media that have not been subjected to conventional electron beam irradiation, when performing reversal display repeatedly, due to collision with other particles for image display media and the substrate, Deterioration due to repeated inversion such as embedding of the fine particles 12 and migration of the fine particles 12 can be prevented.

  In the method for producing particles for an image display medium of the present invention, a commercially available apparatus can be used as an apparatus for irradiating the particles for an image display medium with electrons. For example, an EB irradiation apparatus (acceleration made by Iwasaki Electric Co., Ltd.) Voltage: 150 to 250 kV, electron irradiation width: 15 cm, maximum irradiation capacity: 180 Mrad · m / min) can be used. Also, the electron beam irradiation conditions are not particularly limited, and depending on the irradiated material, a dose rate of 50 to 2000 kGy / sec is preferable, and a dose rate of 50 to 500 kGy / sec is more preferable. If the dose rate is lower than 50 kGy / sec, there is an inconvenience that the particles cannot be cured, and if the dose rate is higher than 2000 kGy / sec, there is an inconvenience that the particles are melted or molecularly collapsed.

  Moreover, as resin which comprises the particle | grains 11, although all of the resin mentioned later can be used, as resin which can acquire the effect of electron beam irradiation suitably, polystyrene, polyethylene, a polypropylene, polyacrylate, Examples include polyvinyl chloride, polyvinyl acetate, polydimethylsiloxane, natural rubber, polyamide, and polyvinyl alcohol. In addition, an allyl resin such as TAIC, an acrylate resin such as TMPTA, and a methacrylate monomer such as TMPTMA can be added to the resin that is difficult to crosslink.

  Hereinafter, each member which comprises the image display apparatus using the particle | grains for image display media calculated | required with the manufacturing method of this invention is demonstrated.

  As for the substrate, at least one of the substrates is a transparent substrate 2 on which the color of the image display medium can be confirmed from the outside of the apparatus, 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 uniform spacing between the substrates, and if it is thicker than 5000 μm, a thin image display device will be obtained. There is an inconvenience.

  Electrode forming materials for electrodes provided as necessary include metals such as aluminum, silver, nickel, copper, and gold, conductive metal oxides such as ITO, indium oxide, conductive tin oxide, and conductive zinc oxide, polyaniline , Conductive polymers such as polypyrrole and polythiophene are exemplified, and are appropriately selected and used. As a method for forming an electrode, a method of forming the above-described materials into a thin film by sputtering, vacuum deposition, CVD (chemical vapor deposition), coating, or the like, or mixing a conductive agent with a solvent or a synthetic resin binder. The method of apply | coating is used. The electrode provided on the viewing side substrate needs to be transparent, but the electrode provided on the back side substrate does not need to be transparent. In any case, the above-mentioned material that is conductive and capable of pattern formation can be suitably used. Note that the electrode thickness is not particularly limited as long as the conductivity can be secured and the light transmittance is not hindered, and is preferably 3 to 1000 nm, preferably 5 to 400 nm. The material and thickness of the electrode provided on the back side substrate are the same as those of the electrode provided on the view side substrate described above, but need not be transparent. In this case, the external voltage input may be superimposed with direct current or alternating current.

  The shape of the partition 4 provided as necessary is optimally set according to the type of image display medium involved in the display, and is not limited in general. However, the width of the partition is 2 to 100 μm, preferably 3 to 50 μm. 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. 7, the display cells formed by the partition walls made of these ribs are exemplified by a square shape, a triangular shape, a line shape, a circular shape, and a hexagonal shape as viewed from the 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 sharpness of the image display increases. Here, examples of the method for forming the partition include a screen printing method, a sand blasting method, a photolithography method, and an additive method. Of these, the photolithography method using a resist film is preferably used.

  Next, the particles 11 constituting the image display medium particles of the present invention will be described. The particles 11 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.

  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.

  The particles constituting the image display medium of the present invention preferably have an average particle diameter d (0.5) in the range of 0.1 to 50 μm and are uniform and uniform. If the average particle diameter d (0.5) is larger than this range, the display is not clear, and if it is smaller than this range, the cohesive force between the particles becomes too large, which hinders the movement of the particles.

Furthermore, in the present invention, regarding the particle size distribution of each particle, the particle size distribution Span represented by the following formula is less than 5, preferably less than 3.
Span = (d (0.9) −d (0.1)) / d (0.5)
(However, d (0.5) is a numerical value expressing the particle diameter in μm that 50% of the particles are larger than this and 50% is smaller than this, and d (0.1) is a particle in which the ratio of the smaller particles is 10%. (Numerical value expressed in μm, and d (0.9) is a numerical value expressed in μm for a particle diameter of 90% or less.)
By keeping Span within a range of 5 or less, the size of each particle is uniform, and uniform particle movement becomes possible.

  Furthermore, regarding the correlation between the particles, the ratio of d (0.5) of the particles having the minimum diameter to d (0.5) of the particles having the maximum diameter among the used particles is set to 50 or less, preferably 10 or less. It is essential.

The particle size distribution and the particle size can be obtained from a laser diffraction / scattering method or the like. When laser light is irradiated onto particles to be measured, a light intensity distribution pattern of diffracted / scattered light is spatially generated, and this light intensity pattern has a corresponding relationship with the particle diameter, so that the particle diameter and particle diameter distribution can be measured. .
Here, the particle size and particle size distribution in the present invention are obtained from a volume-based distribution. Specifically, using a Mastersizer2000 (Malvern Instruments Ltd.) measuring instrument, 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.

  Next, the powder fluid using the particles for an image display medium of the present invention will be described. In addition, about the name of the powder fluid using the particle | grains for image display media of this invention, the present applicant has acquired the right of "electronic powder fluid (trademark)."

  The “powder fluid” in the present invention is a substance in an intermediate state of both fluid and particle characteristics that exhibits fluidity by itself without borrowing the force of gas or liquid. For example, liquid crystal is defined as an intermediate phase between a liquid and a solid, and has fluidity that is a characteristic of liquid and anisotropy (optical properties) that is a characteristic of solid (Heibonsha: Encyclopedia) . On the other hand, the definition of particle is an object with a finite mass even if it is negligible, and is said to be affected by gravity (Maruzen: Physics Encyclopedia). Here, even in the case of particles, there are special states of gas-solid fluidized bed and liquid-solid fluids. When gas is flowed from the bottom plate to the particles, upward force is applied to the particles according to the velocity of the gas. Is a gas-solid fluidized bed that is in a state where it can easily flow when it balances with gravity, and it is also called a liquid-solid fluidized state that is fluidized by a fluid (ordinary) Company: Encyclopedia). As described above, the gas-solid fluidized bed body and the liquid-solid fluid are in a state of using a gas or liquid flow. In the present invention, it has been found that a substance in a state of fluidity can be produced specifically without borrowing the force of such gas and liquid, and this is defined as powder fluid.

  That is, the pulverulent fluid in the present invention is in an intermediate state having both the characteristics of particles and liquid, as in the definition of liquid crystal (liquid and solid intermediate phase), and is the characteristic of the above-mentioned particles. It is a substance that is extremely unaffected and exhibits a unique state with high fluidity. Such a substance can be obtained in an aerosol state, that is, a dispersion system in which a solid or liquid substance is stably suspended as a dispersoid in a gas, and the solid substance is used as a dispersoid in the image display device of the present invention. Is.

The image display panel which is the object of the present invention exhibits high fluidity in an aerosol state in which solid particles are stably suspended as a dispersoid as an image display medium, for example, as an image display medium between opposing substrates, at least one of which is transparent. The powder fluid is sealed, and such powder fluid can be easily and stably moved by Coulomb force or the like by applying a low voltage.
As described above, for example, the powder fluid used in the present invention is a substance in an intermediate state between fluid and particles, which exhibits fluidity by itself without borrowing the force of gas or liquid. This powder fluid can be in an aerosol state in particular, and in the image display device of the present invention, a solid substance is used in a state of relatively stably floating as a dispersoid in the gas.

The range of the aerosol state is preferably such that the apparent volume of the pulverized fluid when it is floated is twice or more that when it is not suspended, more preferably 2.5 times or more, and particularly preferably 3 times or more. Although an upper limit is not specifically limited, It is preferable that it is 12 times or less.
If the apparent volume of the pulverized fluid is less than twice that of the unfloating state, it is difficult to control the display, and if it is more than 12 times, the powder fluid will be overloaded when sealed in the device. Inconvenience in handling occurs. The apparent volume at the maximum floating time is measured as follows. That is, the powdered fluid is put into a closed container that allows the powdered fluid to permeate, and the container itself is vibrated or dropped to create a maximum floating state, and the apparent volume at that time is measured from the outside of the container. Specifically, in a container with a lid (trade name: iBoy: manufactured by ASONE Co., Ltd.) having a diameter (inner diameter) of 6 cm and a height of 10 cm, the powder fluid corresponding to 1/5 of the volume of the fluid when not floating. And set the container on a shaker, and shake at a distance of 6 cm at 3 reciprocations / sec for 3 hours. The apparent volume immediately after stopping shaking is the apparent volume at the maximum floating time.

Moreover, in this invention, what the time change of the apparent volume of a powder fluid satisfy | fills following Formula is preferable.
V ₁₀ / V ₅ > 0.8
Here, V ₅ represents an apparent volume (cm ³ ) 5 minutes after the maximum floating time, and V ₁₀ represents an apparent volume (cm ³ ) 10 minutes after the maximum floating time. In the image display device of the present invention, the apparent volumetric change V ₁₀ / V ₅ of the powder fluid is preferably larger than 0.85, and more preferably larger than 0.9. When V ₁₀ / V ₅ is 0.8 or less, it becomes the same as when ordinary so-called particles are used, and it becomes impossible to ensure the effect of high-speed response and durability as in the present invention.

  Moreover, the average particle diameter (d (0.5)) of the particulate material constituting the powder fluid is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and particularly preferably 0.9 to 8 μm. . If it is smaller than 0.1 μm, it is difficult to control the display, and if it is larger than 20 μm, the display is not clear. The average particle diameter (d (0.5)) of the particulate material constituting the powder fluid is the same as d (0.5) in the next particle diameter distribution Span.

The particle substance constituting the powder fluid preferably has a particle size distribution Span represented by the following formula of less than 5, more preferably less than 3.
Particle size distribution Span = (d (0.9) -d (0.1)) / d (0.5)
Here, d (0.5) is a numerical value expressed in μm of the particle diameter that 50% of the particulate material constituting the powder fluid is larger than this and 50% is smaller than this, and d (0.1) is less than this. A numerical value in which the ratio of the particle substance constituting the powder fluid is 10%, expressed in μm, and d (0.9) is the particle diameter in which the particulate substance constituting the powder fluid is 90% μm It is a numerical value expressed by By setting the particle size distribution Span of the particulate material constituting the powder fluid to 5 or less, the sizes are uniform and uniform powder fluid movement becomes possible.

  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 to the powder fluid to be measured, a light intensity distribution pattern of diffracted / scattered light is generated spatially, and this light intensity pattern has a corresponding relationship with the particle diameter, so the particle diameter and particle diameter distribution are measured. it can. This particle size and particle size distribution are obtained from a volume-based distribution. Specifically, using a Mastersizer2000 (Malvern Instruments Ltd.) measuring machine, the powdered fluid was introduced into a nitrogen stream, and the attached analysis software (software based on volume reference distribution using Mie theory) Measurements can be made.

  Preparation of powder fluid can be done by kneading and pulverizing the necessary resin, charge control agent, colorant, and other additives, or by polymerization from monomers, and adding existing particles to resin, charge control agent, colorant, and other It may be coated with an agent. Hereinafter, the resin, charge control agent, colorant, and other additives constituting the powder fluid will be exemplified.

  Examples of the resin include urethane resin, acrylic resin, polyester resin, urethane-modified acrylic resin, silicone resin, nylon resin, epoxy resin, styrene resin, butyral resin, vinylidene chloride resin, melamine resin, phenol resin, fluorine resin, etc. Two or more types can also be mixed. In particular, acrylic urethane resin, acrylic urethane silicone resin, acrylic urethane fluororesin, urethane resin, and fluororesin are preferable from the viewpoint of controlling the adhesive force with the substrate.

  Examples of charge control agents include quaternary ammonium salt compounds, nigrosine dyes, triphenylmethane compounds, imidazole derivatives and the like in the case of imparting positive charges, and metal-containing azo compounds in the case of imparting negative charges. Examples thereof include dyes, salicylic acid metal complexes, and nitroimidazole derivatives.

  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.

However, even if such a material is kneaded and coated without any ingenuity, a powder fluid that shows an aerosol state cannot be produced. The production method of the powder fluid showing the aerosol state is not clear, but is exemplified as follows.
First, it is appropriate to fix inorganic fine particles having an average particle diameter of 20 to 100 nm, preferably 20 to 80 nm, to the surface of the particulate material constituting the powder fluid. Furthermore, it is appropriate that the inorganic fine particles are treated with silicone oil. Here, examples of the inorganic fine particles include silicon dioxide (silica), zinc oxide, aluminum oxide, magnesium oxide, cerium oxide, iron oxide, and copper oxide. The method of fixing the inorganic fine particles is important. For example, using a hybridizer (manufactured by Nara Machinery Co., Ltd.) or mechanofusion (manufactured by Hosokawa Micron Co., Ltd.) or the like, under certain limited conditions (for example, processing time) ), A powder fluid showing an aerosol state can be produced.
Of course, the particles 11 constituting the particles for an image display medium of the present invention may be used as a powder fluid as they are.
The particles for an image display medium of the present invention can be used as a powder fluid by using the particles for the powder fluid, and the powder fluid thus adjusted can be used as an image display medium.

  The charge amount of the image display medium naturally depends on the measurement conditions, but the charge amount of the image display medium in the image display panel is almost the initial charge amount, the contact with the partition wall, the contact with the substrate, and the charge decay with the elapsed time. In particular, it was found that the saturation value of the charging behavior of the image display medium is the dominant factor.

  As a result of intensive studies, the present inventors have found that by measuring the charge amount of the image display medium using the same carrier particles in the blow-off method, it is possible to evaluate the range of the appropriate charging characteristic value of the image display medium. .

Furthermore, in the present invention, it is important to manage the gas in the gap surrounding the image display medium between the substrates, which contributes to improved display stability. Specifically, it is important that the relative humidity at 25 ° C. is 60% RH or less, preferably 50% RH or less, more preferably 35% RH or less with respect to the humidity of the gas in the gap.
1A, 1B, 3A, and 3B, the gap portion is defined by the electrodes 5 and 6 and the image display medium (particles) from the portion sandwiched between the opposing substrate 1 and substrate 2. It refers to the gas portion in contact with the so-called image display medium, excluding the group or powdered fluid 3) occupied portion, the partition 4 occupied portion (if present), and the device 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 needs to be sealed in the apparatus so that the humidity is maintained. For example, the image display medium is filled and the substrate is assembled in a predetermined humidity environment. It is important to apply a sealing material and a sealing method to prevent the above.

The distance between the substrates in the image display panel provided in the image display device of the present invention is not limited as long as the image 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 occupancy of the image display medium in the space between the opposing substrates is preferably 5 to 70%, more preferably 5 to 60%. If it exceeds 70%, the movement of the image display medium is hindered. If it is less than 5%, the contrast tends to be unclear.

  An image display device using particles obtained by the production method of the present invention includes display units of mobile devices such as notebook computers, PDAs, mobile phones, handy terminals, electronic papers such as electronic books and electronic newspapers, signboards, posters, and blackboards. Suitable for bulletin boards such as billboards, calculators, home appliances, automobile supplies, card displays such as point cards and IC cards, electronic advertisements, electronic POPs, electronic price tags, electronic musical scores, and display parts for RF-ID devices Used.

(A), (b) is a figure which shows an example of the image display apparatus using the particle | grains for image display media used as the object of the manufacturing method of this invention, respectively. (A), (b) is a figure which shows the other example of the image display apparatus using the particle | grains for image display media used as the object of the manufacturing method of this invention, respectively. (A), (b) is a figure which shows the further another example of the image display apparatus using the particle | grains for image display media used as the object of the manufacturing method of this invention, respectively. It is a figure for demonstrating an example of the manufacturing method of the particle | grains for image display media of this invention. It is a figure for demonstrating the other example of the manufacturing method of the particle | grains for image display media of this invention. It is a figure for demonstrating the problem of the conventional particle | grains for image display media for a comparison. It is a figure which shows an example of the shape of the partition in the image display panel using the particle | grains for image display media used as the object of the manufacturing method of this invention.

Explanation of symbols

1, 2 Substrate 3 Image display medium (particle group or powder fluid)
3W white particles (white powder fluid)
3B Black particles (black powder fluid)
4 Partition 5 and 6 Electrode 11 Particle 12 Fine Particle 13 Composite Particle

Claims (3)

A method for producing particles for an image display medium used in an image display device in which an image display medium is sealed between opposing substrates at least one of which is transparent, an electric field is applied to the image display medium, and the image display medium is moved to display an image The method for producing particles for an image display medium, wherein the uncured particles are irradiated with an electron beam and post-crosslinked to obtain particles for an image display medium.   The method for producing particles for an image display medium according to claim 1, wherein the image display medium is a particle group.   The method for producing particles for an image display medium according to claim 1, wherein the image display medium is a powder fluid.

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