JP2005241779A - Particle, powder and granular material, used for picture display device, and picture display device using them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide particles, and a powder and granular material which hardly coagulate, many of which can be sealed in a cell and which are used for a picture display device with which a high contrast ratio and a high reflectance are obtained, and the picture display device using them. <P>SOLUTION: At least a kind of colored particles X is constructed with a combination of two or more kinds of particles wherein the structure of the colored particle X is expressed by a state in which a principal particle A, of which the particle diameter is represented by da, is surrounded by at least a kind of small particle B with the same color as that of the principal particle A and with the particle diameter db and satisfies inequality 10×db(0.5)>da(0.5)>2×db(0.5). Further, the colored particles X are constructed with a composite particle in which a charge polarity of the principal particle A and that of the small particle B are different from each other, and are constructed in the composite particle X in such a way that at least 40% or more of the surface area of the principal particle A is exposed at the uppermost surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention provides an image display in which at least one of two or more kinds of particles having different colors and charging characteristics is sealed between opposing substrates, at least one of which is transparent, an electric field is applied to the particles, and the particles are moved to display an image. The present invention relates to particles, powdered fluid used in the apparatus, and an image display apparatus using the same.

  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, a cell isolated from each other by a partition is formed between a front substrate and a rear substrate, and a particle group or a powder fluid is enclosed in the cell. 2. Description of the Related Art An image display device including an image display panel that displays an image by applying an electric field to a fluid and moving particles or powdered fluid by Coulomb force or the like 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

  In the above-described image display device, normally, a particle group composed of white particles and black particles or other colored particles is filled between substrates and used. Here, consider the case of two types of particle groups having different charging polarities. At this time, it is ideal that one or more layers of each particle group are stacked on each substrate. However, electrostatic repulsion force from particles of the same color (same charged polarity) in the first layer is applied to the second layer of particles. And the electrostatic attractive force from the oppositely charged particles on the other substrate works, and the second layer particles cannot exist stably on the first layer particles, and are particles of different colors (reversely charged polarity) And will aggregate. In addition, the contrast and the reflectance are reduced. Therefore, conventionally, aggregation of such particles has been prevented by making each particle group one layer or less. However, as a result, in an image display panel using these particle groups, there is a problem that the contrast ratio and the reflectance are limited and it is difficult to obtain high display performance.

  The object of the present invention is to solve the above-mentioned problems, and it is difficult for agglomeration to occur. Many particles can be enclosed in a cell, and a particle or powder fluid used in an image display device capable of obtaining a high contrast ratio and a high reflectance. And an image display device using the same.

  The particles used in the image display device of the present invention enclose at least two or more kinds of particles having different colors and charging characteristics between opposing substrates that are transparent at least one, and apply an electric field to the particles to move the particles. Particles used in an image display panel for displaying an image, wherein at least one kind of colored particle X is composed of a combination of two or more kinds of particles, and the structure is such that the particle diameter of the main particle A is da. Then, at least one kind of small particle B having the same color particle diameter db surrounds it, and 10 × db (0.5)> da (0.5)> 2 × db (0.5 ) And a composite particle in which the charge polarity of the main particle A and the charge polarity of the small particle B are different, and at least 20% or more of the surface area of the main particle A in the composite particle X Is exposed on the outermost surface Here, da (0.5) is a numerical value representing the particle diameter in which 50% of the particles A are larger than this and 50% are smaller than this, db (0.5) is a numerical value representing a particle diameter in which 50% of the particles B are larger than this and 50% are smaller than this.

  Moreover, as a suitable example of the particles used in the image display device of the present invention, the charge amount per main particle A is qa, the charge amount per small particle B is qb, and the small particles surrounding the main particle A When the total charge amount of B is Qb, when the charge polarity of X and A is the same, the condition | qa |> 1.5 × | Qb | is satisfied, and when the charge polarity of X and B is the same 1.3 × | qa | <| Qb |.

  Furthermore, as a suitable example of the particles used in the image display device of the present invention, when the amount of the particles X is arranged in the closest packing in a cell provided on the substrate, the thickness of the particle layer is 1.2. Xdx (0.5) can be configured to be greater than or equal to dx (0.5); dx (0.5) is a numerical value representing a particle diameter in which 50% of the particles X are larger than this and 50% are smaller than this.

  The powder fluid used in the image display device of the present invention is characterized in that the above-described particles are used as the particulate material constituting the powder fluid. The image display device of the present invention is characterized by using the above-described particles or the above-described powdered fluid.

  According to the present invention, both the repulsion from the same charged polar particles from the first layer and the electrostatic attractive force from the reverse charged polar particles on the opposite substrate can be alleviated. Therefore, particles can be stably present in the second and subsequent layers, and aggregation is unlikely to occur. As a result, many particles can be enclosed in the cell, and high contrast and high reflectance can be obtained.

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

  Next, an image display operation in the basic configuration of the above-described image display panel will be described. The image display panel used in the present invention is, for example, by moving particles 3 of two different colors (see FIG. 1; here, white particles 3W and black particles 3B) are moved in a direction perpendicular to the substrates 1 and 2. The present invention can be applied to both a panel used for a display method and a panel using a display method by moving particles 3W of one kind of color (see FIG. 2) in a direction parallel to the substrates 1 and 2. An example of a panel structure for display is shown in FIG. 1 to 3, reference numeral 4 denotes partition walls provided for forming cells, and reference numerals 5 and 6 denote electrodes provided as necessary to give an electric field to the particles 3. 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.

  The characteristics of the particles used in the image display device of the present invention are composed of a combination of two or more kinds of particles, and the structure is such that when the particle diameter of the main particle A is da, at least one kind of the same color around the particle diameter. In this state, small particles B having a particle diameter db are surrounded, satisfy a structure of 10 × db (0.5)> da (0.5)> 2 × db (0.5), and The composite particle X is composed of composite particles having different charge polarities and small particles B, and at least 40% or more of the surface area of the main particle A is exposed on the outermost surface in the composite particle X. Here, da (0.5) is a numerical value representing the particle diameter in which 50% of the particle A is larger than this and 50% is smaller than this, and db (0.5) is the particle B 50% is bigger than this, 50% is smaller than this It is a numerical value representing the particle diameter.

  FIG. 4 is a view for explaining an example of particles used in the image display device of the present invention. In the example shown in FIG. 4, the particles 3 are composed of composite particles having a structure in which a plurality of small particles B are provided around the main particles A. Here, the relationship between the particle diameters of the main particles A and the small particles B is 10 × db (0.5)> da (when the particle diameter of the main particles A is da and the particle diameter of the small particles B is db). 0.5)> 2 × db (0.5) must be satisfied. Further, in the particles 3, the small particles B are provided on the surface of the main particles A so that at least 40% or more of the surface area of the main particles A is exposed on the outermost surface. Further, if the charged polarity of the main particle A is different from the charged polarity of the small particle B, that is, if the main particle A is charged positively (or negatively), the particle charged negatively (or positively) as the small particle B Must be used.

  In the present invention, the relationship between the particle diameter da of the main particles A and the particle diameter db of the small particles B needs to be 10 × db (0.5)> da (0.5)> 2 × db (0.5). The reason is that if da (0.5) is smaller than this, when the main particles A are arranged in the substrate, the distance between the particles becomes too close and the (electrostatic) repulsive force is strong. This is because there is a tendency not to arrange them properly. This tendency is particularly strong in the thickness direction. On the other hand, if da (0.5) is larger than this, the sticking force between the particles A and B becomes relatively weak, and the small particles B are separated from the main particles A and go to the counter substrate side. This is because. Further, the exposure rate needs to be 40% or more because when the particle size is less than this value, there is an adverse effect due to the presence of excessively small particles B between the main particles A and A, and the effects of the present invention are reduced. It is because it cannot be demonstrated.

  With the particles used in the image display device of the present invention having the above-described configuration, the following effects can be obtained. First, as shown in FIG. 5 (a), white particles 3W and black particles 3B having different charging characteristics are placed on the substrates 1 and 2 (or electrodes 5 and 6), respectively, in the conventional particles composed of a single component. Even if one or more layers are intended to be multi-layered here, the electrostatic repulsion force from the particles 3W (or 3B) of the same color (same charged polarity) in the second layer 3W (or 3B) And electrostatic attraction from particles 3B (or 3W) of reverse charge polarity on the other substrate works, and the particles 3W (or 3B) of the second layer are on the particles 3W (or 3B) of the first layer. It cannot exist stably, and aggregates with particles 3B (or 3W) of different colors (reverse charging polarity) as shown in FIG. In addition, the contrast and the reflectance are reduced.

  On the other hand, in the particles of the present invention, the composite particles of the present invention are used as the white particles 3W and the black particles 3B having different charging characteristics. Therefore, as shown in FIG. 6, when white particles 3W are composed of composite particles of main particles A and small particles B, and black particles 3B are composed of composite particles of main particles C and small particles D, one layer Both repulsion from the same charged polar particles from the eyes and electrostatic attractive force from the reverse charged polar particles on the opposite substrate can be alleviated. Therefore, particles can be stably present in the second and subsequent layers, and aggregation is unlikely to occur. As a result, many particles can be enclosed in the cell, and high contrast and high reflectance can be obtained.

  As a preferred embodiment, when the charge amount per main particle A is qa, the charge amount per small particle B is qb, and the total charge amount of the small particles B surrounding the main particle A is Qb, When X and A have the same charging polarity, the condition | qa |> 1.5 × | Qb | is satisfied, and when X and B have the same charging polarity, 1.3 × | qa | <| Qb | May be satisfied. By comprising in this way, the effect of this invention can be acquired further favorably. Here, the charging polarity of the particles X can be obtained as follows. First, the particle diameters of the particles A and B are measured by master sizer measurement or direct observation with a microscope, as will be described later. Further, the charge amounts qa and qb per one are calculated by blow-off measurement and the previously obtained particle diameter as described later. Then, if the value qb calculated from here and the volume ratio of A and B are known, the total charge amount Qb can be calculated. In the present invention, the above-described range is preferable because various investigations have been made, and it has been empirically requested that the display tends to be beautiful within this range.

  Further, as a preferred embodiment, when the amount of the particles X is arranged in the closest packing in the cell provided on the substrate, the thickness of the particle layer is 1.2 × dx (0.5) or more. May be configured. By comprising in this way, the structure of 1 layer or more can be obtained more favorably. That is, the present invention makes sense because the thickness of the particle layer is from 1.2 × dx (0.5) to (one or more layers), and in the range below that, it is not necessary to have the above-described particle configuration. It is.

As a method for producing the composite particles of the present invention described above, a simple vibration / stirring method, a physical method using an apparatus such as Henschel, a hybridizer, a mechanofusion, or a saffusion, spray drying / cracks, etc. Although the thing by the spraying and granulation method using an apparatus is mentioned, It is not limited to this.
Hereinafter, the structure of an image display device using the particles or powdered fluid of the present invention will be described first, and then this feature will be described in detail with reference to examples.

First, each member which comprises the image display apparatus using the particle | grains or powder fluid of this invention is demonstrated in detail.
As for the substrate, at least one substrate is the transparent front substrate 2 from which the color of particles or powder fluid can be confirmed from the outside of the apparatus, and a material having high visible light transmittance and good heat resistance is suitable. The back substrate 1 may be transparent or opaque. Examples of substrate materials include polymer sheets such as polyethylene terephthalate, polyethersulfone, polyethylene, polycarbonate, polyimide, and acrylic, flexible materials such as metal sheets, and flexible materials such as glass and quartz. There are no inorganic sheets. The thickness of the substrate is preferably 2 to 400 μm, more preferably 5 to 300 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 400 μm, the stress due to bending will become strong. There is inconvenience in connection.

  For the electrodes 5 and 6, the front electrode 6 provided on the side of the front substrate 2 that needs to be visible and transparent is formed of a conductive material that is transparent and can be patterned. For example, indium oxide, aluminum, Examples thereof include metals such as gold, silver and copper, and conductive polymers such as polyaniline, polypyrrole and polythiophene, and examples thereof include vacuum deposition and coating methods. 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, thickness, and the like of the back electrode 5 provided on the back substrate 1 side are the same as those of the front electrode 6 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 wall 4 is optimally set according to the type of particle group or powder fluid involved in the display, and is not limited in general. However, the partition wall width is 2 to 100 μm, preferably 3 to 50 μm. Is adjusted to 10 to 5000 μm, preferably 10 to 500 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 is illustrated. 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 of the present invention will be described. The particles of the present invention can contain a charge control agent, a colorant, an inorganic additive, and the like, as necessary, in the resin as the main component, as necessary.
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 brie 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 yellow lead, 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 used in 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. If the average particle diameter d (0.5) 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 expressed in μm that the particle size is 50% larger than this and 50% smaller than this, and d (0.1) is a particle whose ratio is 10% or less. (Numerical value expressed in μm, and d (0.9) is a numerical value expressed in μm for a particle diameter of 90% or less.)
By keeping Span within a range of 5 or less, the size of each particle is uniform, and uniform particle movement becomes possible.

  Furthermore, regarding the correlation between the particles, the ratio of d (0.5) of the particles having the minimum diameter to d (0.5) of the particles having the maximum diameter among the used particles is set to 50 or less, preferably 10 or less. It is essential. Even if the particle size distribution Span is reduced, particles with different charging characteristics move in opposite directions, so that the particle size is close to each other and each particle can be easily moved in the opposite direction by the equivalent amount. This is within this range.

The particle size distribution and the particle size can be obtained from a laser diffraction / scattering method or the like. When laser light is irradiated onto particles to be measured, a light intensity distribution pattern of diffracted / scattered light is spatially generated, and this light intensity pattern has a corresponding relationship with the particle diameter, so that the particle diameter and particle diameter distribution can be measured. .
Here, the particle size and particle size distribution in the 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 particles naturally depends on the measurement conditions, but the charge amount of the particles in the image display device almost depends on the initial charge amount, the contact with the partition wall, the contact with the substrate, the charge decay with the elapsed time, especially It was found that the saturation value of the charging behavior of the two types of particles is the dominant factor.

  As a result of intensive studies, the present inventors have found that by using the same carrier particles in the blow-off method and measuring the charge amount of each particle, it is possible to evaluate the range of appropriate charging characteristic values of the two types of particles. It was.

  Although the measurement method will be described in detail later, the charge amount per unit weight of the particles can be measured by sufficiently bringing the particles and carrier particles into contact with each other by the blow-off method and measuring the saturated charge amount. Then, by separately obtaining the average particle diameter and specific gravity of the particles, the total number of particles and the charge amount per particle can be calculated.

Next, the powder fluid used in the image display device of the present invention will be described.
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.

  An image display device that is an object of the present invention encloses a powder fluid that exhibits high fluidity in an aerosol state in which solid particles are stably suspended as a dispersoid in a gas between opposing substrates, at least one of which is transparent Such a powder fluid can be easily and stably moved by a Coulomb force or the like by applying a low voltage.

  As described above, the pulverized fluid used 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. 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, a powder fluid equivalent to 1/5 of the volume as a powder 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 the 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 brie 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 yellow lead, 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.

Furthermore, in the present invention, it is important to manage the gas in the voids surrounding the particle group or the powder fluid between the substrates, which contributes to the improvement of 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.
1 to 3, the gaps between the opposing substrate 1 and substrate 2 in FIGS. 1 to 3, the occupied portions of the electrodes 5 and 6, the particle group (or powder fluid) 3, the occupied portion of the partition 4, and the device A gas portion that is in contact with a so-called particle group (or powder fluid) excluding the seal portion is meant.
The gas in the gap is not limited as long as it is in the humidity region described above, but dry air, dry nitrogen, dry argon, dry helium, dry carbon dioxide, dry methane, and the like are preferable. This gas needs to be sealed in the apparatus so that the humidity is maintained. For example, filling of particles or powder fluid, assembly of the substrate, etc. are performed in a predetermined humidity environment, It is important to apply a sealing material and a sealing method to prevent moisture intrusion.

The distance between the substrate in the image display panel of the present invention is not limited as long as the particle group or powder fluid can move and maintain the contrast, but is usually adjusted to 10 to 5000 μm, preferably 10 to 500 μm.
The volume occupancy of the particle group or powder fluid in the space between the opposing substrates is preferably 5 to 70%, more preferably 5 to 60%. If it exceeds 70%, the movement of particles or powder fluid is hindered, and if it is less than 5%, the contrast tends to be unclear.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples. The image display panels obtained in the examples and comparative examples were evaluated according to the following criteria.

“Production of image display panels”
First, a substrate with electrodes (7 cm × 7 cm □) was prepared, ribs having a height of 100 μm were formed on the substrate, and striped partition walls were formed.
Ribs were formed as follows. First, the paste is a glass powder obtained by melting, cooling and grinding a mixture of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , Bi ₂ O ₃ and ZnO as an inorganic powder, and a thermosetting epoxy resin as a resin. Was prepared, and a paste prepared to have a viscosity of 12000 cps with a solvent was prepared. Next, the paste was applied onto a prepared substrate, heated and cured at 150 ° C., and this application to curing was repeated to adjust the thickness (corresponding to the height of the partition wall) to 50 μm. Next, a dry photoresist was applied, and a mask was formed so that a partition wall pattern having a line of 50 μm, a space of 400 μm, and a pitch of 350 μm was formed by exposure to etching. Next, excess portions were removed by sandblasting so as to obtain a predetermined partition wall shape, thereby forming a desired striped partition wall.

  The following particles X and Y are enclosed in the cell with respect to the surface which is the inner surface of the cell in contact with the particles (or powder fluid) in the substrate with the partition wall and the other substrate thus produced, and an image is displayed. Panels were prepared. The internal atmosphere was dry air with a dew point temperature of −20 ° C. and a pressure of 760 torr. The relative humidity of this air was 35% RH or less at 25 ° C.

"Measurement of charging characteristics of particles"
<Blow-off measurement principle and method>
In the blow-off method, a mixture of powder and carrier particles is placed in a cylindrical container with nets on both ends, and high-pressure gas is blown from one end to separate the powder and carrier particles, and the powder is opened from the mesh openings. Blow off only. At this time, the charge amount equal to the charge amount taken away from the container by the powder remains in the carrier particles. All of the electric flux due to this charge is collected by the Faraday cage, and the capacitor is charged by this amount. Therefore, by measuring the potential across the capacitor, the charge quantity Q of the powder is
Q = CV (C: Capacitor capacity, V: Voltage across capacitor)
As required.
TB-200 manufactured by Toshiba Chemical Co. was used as a blow-off powder charge measuring device.
In the present invention, the same carrier particles (F963-2535 manufactured by Powder Tech Co., Ltd.) are used as carrier particles for the two types of particles to be measured, and the charge polarity and charge amount per unit weight of each particle to be measured (unit: μC / g) was first measured, and the total number of particles used in the measurement was determined from the particle diameter and particle specific gravity determined separately, and the charge amount (unit: fC / particle) per particle was calculated.

  The particle size is determined by the method described above. Specifically, using a Mastersizer2000 (Malvern Instruments Ltd.) measuring instrument, a particle group is introduced into a nitrogen stream, and the attached analysis software (volume basis using Mie theory) is used. The specific gravity was measured using a hydrometer (trade name: multi-volume density meter H1305) manufactured by Shimadzu Corporation.

"Evaluation of display function"
Black-white display was repeated by applying a voltage of 250 V to the image display device incorporating the manufactured image display panel to invert the potential. The evaluation of the display function was performed on the contrast ratio, and the measurement was repeated using a reflection image densitometer after 10,000 times. Here, the contrast ratio is: contrast ratio = reflection density during black display / reflection density during white display. At the same time, the white reflectance was also obtained.

<Example 1>
Particle X (white) was produced as follows.
First, 10 parts by weight of titanium oxide and 2 parts by weight of charge control agent Bontron N07 (manufactured by Orient Chemical Co., Ltd.) are added to PMMA (polymethyl methacrylate) resin, and the main particles A are kneaded, and then jetted. It was manufactured by pulverizing and classifying with a mill and adjusting the particle size. Further, small particles B are suspended in styrene resin using TiO ₂ (20 parts by weight), charge control agent Bontron E89 (5 parts by weight, manufactured by Orient Chemical Co., Ltd.) initiator AIBN (0.5 parts by weight). After the turbid polymerization, it was produced by aligning the particle diameter with a classifier. Next, using a hybridizer device (manufactured by Nara Machinery Co., Ltd.), these main particles A and small particles B are introduced, treated at 4800 rpm for 5 minutes, fixed on the surface of the polymerized particles, It adjusted so that it might become the particle | grain X of invention.

Particle Y (black) was produced as follows.
First, 4 parts by weight of carbon black (MA100: manufactured by Mitsubishi Chemical Corporation) and 2 parts by weight of a charge control agent Bontron E89 (manufactured by Orient Chemical Co., Ltd.) are added to styrene budadiene resin and kneaded. Next, the particle size was adjusted by pulverizing and classifying with a jet mill. Further, small particles D were added to PMMA resin by 4 parts by weight of carbon black (MA100: manufactured by Mitsubishi Chemical Corporation), 2 parts by weight of charge control agent Bontron N07 (manufactured by Orient Chemical Co., Ltd.), initiator AIBN (0. 5 parts by weight) was subjected to suspension polymerization, and then the particle size was made uniform by a classifier. Next, using a hybridizer device (manufactured by Nara Machinery Co., Ltd.), these main particles C and small particles D are introduced, treated at 4800 rpm for 5 minutes, fixed on the surface of the polymerized particles, It adjusted so that it might become the particle Y of invention.
The display function was evaluated using an image display device incorporating an image display panel produced with these particle groups. The results are shown in Table 1.

<Example 2>
In the same manner as in Example 1, particles X (white) were produced, and only the main particles C in Example 1 were used to produce particles Y (black), and an image display panel produced with these particle groups was produced. The display function was evaluated using the incorporated image display device. The results are shown in Table 1.

<Example 3>
In the same manner as in Example 1, particles X (white) and particles Y (black) were produced, and the display function was evaluated using an image display device incorporating an image display panel produced with these particle groups. It was. The results are shown in Table 1.

<Comparative Example 1>
An image display panel produced by using only the main particles A in Example 1 to produce particles X (white) and using only the main particles C to produce particles Y (black). The display function was evaluated using an image display device incorporating the. The results are shown in Table 1.

<Comparative example 2>
An image display panel produced by using only the main particles A in Example 1 to produce particles X (white) and using only the main particles C to produce particles Y (black). The display function was evaluated using an image display device incorporating the. The results are shown in Table 1.

<Comparative Example 3>
An image display panel manufactured with these particle groups is manufactured in the same manner as in Example 1, except that particles X (white) and particles Y (black) are manufactured in a state where the relationship between the particle diameter and the charge amount is changed. The display function was evaluated using the incorporated image display device. Moreover, about the small particles B and D, the commercially available surface-treated silica fine particles were used. The results are shown in Table 1.

<Comparative example 4>
Although it is the same as that of Example 1, the particle X (white) is manufactured in a state where the relationship such as the particle diameter and the charge amount is changed, and the particle Y (black) is manufactured using only the main particle C. The display function was evaluated using an image display device incorporating an image display panel made of particles. The results are shown in Table 1.

  From the results in Table 1, the composition of at least one of the particles X and the particles Y is a composite structure in which the small particles B surround the main particles A, and the particle diameters of the main particles A and the small particles B are The relationship is 10 × db (0.5)> da (0.5)> 2 × db (0.5), where da is the particle size of the main particles A and db is the particle size of the small particles B. In Examples 1 to 3 satisfying the above, the particles X and Y are constituted only from the main particles, or even in a composite structure, the white reflectance and high are high compared to Comparative Examples 1 to 4 that do not satisfy this relationship. It can be seen that it has a black and white contrast ratio.

  The image display panel using the particles of the present invention does not decrease the image contrast even when it is repeatedly used. Image display devices equipped with this image display panel are mobile devices such as notebook computers, PDAs, mobile phones, and handy terminals. Device display, electronic paper such as electronic books and electronic newspapers, signboards, posters, bulletin boards such as blackboards, calculators, display units such as home appliances, automobile supplies, card display units such as point cards and IC cards, electronic advertisements, It is suitably used for an electronic POP, an electronic price tag, an electronic score, a display unit of an RF-ID device, and the like.

It is a figure which shows an example of the drive method in the image display panel used with the image display apparatus of this invention. It is a figure which shows the other example of the drive method in the image display panel used with the image display apparatus of this invention. It is a figure which shows an example of the structure of the image display panel used with the image display apparatus of this invention. It is a figure for demonstrating an example of the particle | grains used for the image display apparatus of this invention. (A), (b) is a figure for demonstrating an example of the behavior of the particle | grains in the conventional image display apparatus, respectively. It is a figure for demonstrating an example of the behavior of the particle | grains in the image display apparatus of this invention. It is a figure which shows an example of the shape of the partition in the image display panel used with the image display apparatus of this invention.

Explanation of symbols

1, 2 Substrate 3 Particles (powder fluid)
3W white particles (white powder fluid)
3B Black particles (black powder fluid)
4 Bulkhead 5, 6 Electrode

Claims (5)

Particles used in an image display device that encloses at least two kinds of particles having different colors and charging characteristics between opposing substrates at least one of which is transparent, applies an electric field to the particles, and moves the particles to display an image Because
At least one kind of colored particle X is composed of a combination of two or more kinds of particles, and the structure is such that when the particle diameter of the main particle A is da, at least one kind of the same color particle diameter db The small particle B is surrounded,
10 × db (0.5)> da (0.5)> 2 × db (0.5)
And composed of composite particles in which the charge polarity of the main particles A and the charge polarity of the small particles B are different,
In the composite particle X, particles used for an image display panel, wherein at least 40% or more of the surface area of the main particle A is exposed on the outermost surface;
Here, da (0.5) is a numerical value representing a particle diameter in which 50% of the particles A are larger and 50% are smaller than this,
db (0.5) is a numerical value representing a particle diameter in which 50% of the particle B is larger than this and 50% is smaller than this. When the charge amount per one of the main particles A is qa, the charge amount per one of the small particles B is qb, and the total charge amount of the small particles B surrounding the main particles A is Qb,
When the charging polarity of X and A is the same,
| Qa |> 1.5 × | Qb |
Satisfy the condition
When the charging polarity of X and B is the same,
1.3 × | qa | <| Qb |
Satisfying the condition
The particles used for the image display device according to claim 1. When the amount of the particles X is arranged in a close-packed manner in a cell provided on the substrate, the particle layer has a thickness of 1.2 × dx (0.5) or more. Particles for use in the image display device according to claim 1 or 2;
Here, dx (0.5) is a numerical value representing a particle diameter in which 50% of the particle X is larger than this and 50% is smaller than this.   The powder fluid used for an image display apparatus characterized by using the particle | grains of any one of Claims 1-3.   An image display device using the particles according to claim 1 or the powder fluid according to claim 4.

Images