JP2009122242A - Particle for display medium and information display panel using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide particles for a display medium, in which a formation situation of child particle layers to mother particles is made uniform, and to provide an information display panel using the same. <P>SOLUTION: The particles for a display medium constitutes a display medium used for the information display panel which has the display medium charged in a space between two opposite substrates, at least one of the substrates being transparent, and displays information such as an image by moving the display medium, and the particles for the display medium is made of composite particles obtained by sticking or fixing child particles to mother particles, wherein the particles have no recessed parts in mother particle surface layers, alternatively the particles have recessed parts in the mother particle surface layers, the recessed part satisfying b<0.8d1 or 0<a≤0.3d<SB>1</SB>and 3d<SB>1</SB><b or 0.3d<SB>1</SB>≤a and 5a≤b wherein a denotes the depth of the recessed part of the mother particle, b denotes the diameter of the recessed part of the mother particle and d<SB>1</SB>denotes the particle diameter of the child particle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an information display panel for displaying information such as an image by moving a display medium by enclosing the display medium in a space between two substrates, at least one of which is transparent, and applying an electric field to the display medium. The present invention relates to a display medium particle as a particle constituting the display medium used in the invention and an information display panel using the same.

  2. Description of the Related Art Conventionally, information 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 information display devices that replace liquid crystal display devices (LCDs). 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 information 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.

  In addition, after sealing the display medium between two opposing substrates, at least one of which is transparent, or after forming a cell isolated from each other by a partition and encapsulating the display medium in the cell, An information display panel that displays an information such as an image by applying an electric field and moving a display medium is known (for example, Patent Document 1).

A display medium used for this information display panel is formed on a mother particle surface layer having a particle diameter d ₀ in the range of 1.0 μm <d ₀ <50 μm and a particle diameter d in the range of 0.03 μm <d ₁ <1.00 μm. _The composite particles obtained by adhering or fixing the child particles having ₁ to the particles satisfying the condition of d ₁ / d ₀ <0.33 without causing the child particles to dissociate even in the inversion durability test. It is known that the initial performance can be maintained even during the inversion durability test (for example, Patent Document 2).
International Publication No. 2003/050606 Pamphlet JP 2006-72283 A

  When the display medium having the above-described configuration is used, there is a problem that the formation state of the child particle layer on the mother particle becomes non-uniform when the mother particle and the child particle are combined.

  An object of the present invention is to solve the above-mentioned problems, and when forming a mother particle and a child particle, the particles for a display medium in which the formation state of the child particle layer on the mother particle is uniform and information using the same It is intended to provide a display panel.

  The display medium particles of the present invention are used for an information display panel in which a display medium is sealed in a space between two opposing substrates, at least one of which is transparent, and the display medium is moved to display information such as an image. A particle for a display medium, which is a particle constituting a medium and made of composite particles obtained by adhering or fixing a child particle to a mother particle, is characterized in that the mother particle surface layer has no recess.

In addition, as a suitable example of the case where the surface of the mother particle has a recess, the display medium particle according to the present invention has a depth of the recess of the mother particle and a diameter of the recess of the mother particle as b. particle size _{d 1,} it may satisfy b <0.8d _1. This is because if the concave portion (crack) is sufficiently smaller than the child particle diameter, the concave portion does not work as a retention portion of the child particles.
As another preferred example, 0 <a ≦ 0.3d ₁ and 3d ₁ <b may be satisfied. This is because if the concave portion is sufficiently shallow and the width is wide to some extent, the force of the composite processing is efficiently transmitted to the child particles on the surface of the mother particle, and the embedding of the child particles proceeds. In addition, since the processing force is transmitted well, it is possible to prevent the child particles from staying in the recesses, so that uniform processing proceeds.
As another preferred example, 0.3d ₁ ≦ a and 5a ≦ b may be satisfied. This is because even if the concave portion is deep, if the width of the concave portion is wide, the composite processing force is efficiently transmitted to the child particles on the surface of the mother particle, and the embedding of the child particles proceeds. In addition, since the processing force is transmitted well, it is possible to prevent the child particles from staying in the recesses, so that uniform processing proceeds.
Further, it is preferable that the particle diameter d ₀ of the mother particles is in the range of 1.0 μm <d ₀ <50 μm, and the particle diameter d ₁ of the child particles is in the range of 0.03 μm <d ₁ <1.00 μm. .

  The information display panel of the present invention is characterized in that the display medium particles having the above-described conditions are used as a display medium.

According to the present invention, a display medium is sealed in a space between two opposing substrates, at least one of which is transparent, and the display medium is used for an information display panel that displays information such as images by moving the display medium. In the case of a display medium particle comprising composite particles obtained by adhering or fixing child particles to a mother particle, the mother particle surface layer has no recess or the mother particle surface layer has a recess. When the depth of the concave portion is a and the diameter of the concave portion of the mother particle is b, the particle diameter d ₁ of the child particles satisfies b <0.8d ₁ and 0 <a ≦ 0.3d ₁ and 3d ₁ <b, or display medium particles satisfying the condition of 0.3d ₁ ≦ a and 5a ≦ b, whereby the formation of the child particle layer on the mother particles is uniform. The used information display panel can be provided.

  First, a basic configuration of an information display panel that is an object of the present invention will be described. In the information display panel which is the subject of the present invention, an electric field is applied to the display medium sealed in the space between two opposing substrates. In accordance with the applied electric field direction, the charged display medium is attracted by the electric field force or the Coulomb force, and the display medium is moved by the change in the electric field direction, whereby information such as an image is displayed. Therefore, it is necessary to design the information display panel so that the display medium can move uniformly and maintain stability when rewriting the display repeatedly or when displaying the display information continuously. Here, as the force applied to the particles constituting the display medium, in addition to the force attracting each other by the Coulomb force between the particles, an electric mirror image force between the electrode and the substrate, an intermolecular force, a liquid cross-linking force, gravity and the like can be considered.

  A basic configuration of an information display panel that is an object of the present invention will be described with reference to FIGS. 1 (a) and 1 (b) to FIGS. 5 (a) and 5 (b).

  In the example shown in FIGS. 1A and 1B, at least two types of display media 3 (here, the display white particles 3Wa) having different optical reflectance and charging characteristics composed of at least one type of particles are used. A white display medium 3W made of a particle group and a black display medium 3B made of a particle group of black particles for display 3Ba), each of the cells formed by the partition walls 4, and electrodes 5 (individual electrodes) provided on the substrate 1; The substrate is moved perpendicularly to the substrates 1 and 2 in accordance with an electric field generated by applying a voltage between the electrodes 6 (individual electrodes) provided on the substrate 2. Then, the white display medium 3W is visually recognized by the observer as shown in FIG. 1A, or white display is performed, or the black display medium 3B is visually recognized by the observer as shown in FIG. 1B. The display is black. In addition, in FIG. 1 (a), (b), the partition in front is abbreviate | omitted. The electrode may be provided outside the substrate or may be provided so as to be embedded inside the substrate.

  In the example shown in FIGS. 2A and 2B, at least two or more types of display media 3 (here, display white particles 3Wa) having different optical reflectance and charging characteristics composed of at least one type of particles are used. A white display medium 3W made of a particle group and a black display medium 3B made of a particle group of display black particles 3Ba), each of the cells formed by the partition walls 4, and the electrode 5 (line electrode) provided on the substrate 1; The substrate 6 is moved perpendicular to the substrates 1 and 2 in accordance with an electric field generated by applying a voltage between the electrodes 6 (line electrodes) provided on the substrate 2. Then, the white display medium 3W is visually recognized by the observer as shown in FIG. 2A, or white display is performed, or the black display medium 3B is visually recognized by the observer as shown in FIG. 2B. The display is black. In addition, in FIG. 2 (a), (b), the partition in front is abbreviate | omitted. The electrode may be provided outside the substrate or may be provided so as to be embedded inside the substrate.

  In the example shown in FIGS. 3A and 3B, the display medium 3 (here, a group of particles of white particles for display 3Wa) having at least an optical reflectance and a charging property composed of at least one kind of particles. A white display medium 3W) in each cell formed by the partition walls 4, in accordance with the electric field generated by applying a voltage between the electrode 5 and the electrode 6 provided on the substrate 1, the substrates 1, 2 And move it in a parallel direction. Then, as shown in FIG. 3 (a), the white display medium 3W is visually recognized by the observer to display white, or as shown in FIG. 3 (b), the color of the black plate 27B is changed to the observer. Is displayed in black. In addition, in the example shown to Fig.3 (a), (b), the partition in front is abbreviate | omitted. The electrode may be provided outside the substrate or may be provided so as to be embedded inside the substrate. The same display can be performed even when the white display medium is replaced with a black display medium and the black plate is replaced with a white plate.

  In the example shown in FIGS. 4A to 4D, first, as shown in FIGS. 4A and 4C, at least the optical reflectivity and charging characteristics of at least one kind of particles are different. Two or more kinds of display media 3 (here, a white display medium 3W composed of a group of particles of display white particles 3Wa and a black display medium 3B composed of a group of particles of display black particles 3Ba are shown) are formed of partition walls 4. In each cell, the substrates 1 and 2 correspond to the electric field generated by applying a voltage between the external electric field forming means 31 provided outside the substrate 1 and the external electric field forming means 32 provided outside the substrate 2. And move vertically. Then, the white display medium 3W is visually recognized by the observer as shown in FIG. 4B, or white display is performed, or the black display medium 3B is visually recognized by the observer as shown in FIG. 4D. The display is black. In addition, in FIG. 4 (a)-(d), the partition in front is abbreviate | omitted. In addition, a conductive member 33 is provided inside the substrate 1, and a conductive member 34 is provided inside the substrate 2. This conductive member may not be provided.

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

  The above description is similarly applied to the case where the white display medium 3W including the particle group is replaced with the white display medium including the powder fluid and the black display medium 3B including the particle group is replaced with the black display medium including the powder fluid. I can do it.

FIGS. 6A and 6B are diagrams showing examples of the display medium particles of the present invention. In the example shown in FIGS. 6 (a) and 6 (b), the characteristic of the display medium particle 11 of the present invention is that the surface layer of the mother particle 12 having a particle diameter d ₀ in the range of 1.0 μm <d ₀ <50 μm Composite particles obtained by adhering or fixing child particles 13 having a particle diameter d ₁ in the range of 0.03 μm <d ₁ <1.00 μm in a state satisfying the condition of d ₁ / d ₀ <0.33 This is the point that the particles 11 for display medium are constituted. FIG. 6A shows an example in which a child particle 13 is fixed to the surface layer of the mother particle 12 to form a composite particle, and FIG. 6B shows a child particle 13 attached to the surface layer of the mother particle 12. The example which comprised is shown. Here, “adhesion” means that the child particles 13 are fixed to the surface layer of the mother particles 12 by electrostatic force, Coulomb force, van der Waals force, and the like, and therefore the child particles 13 move during reversal durability. “Fixed” means that the child particles 13 do not move during reversal durability because the child particles 13 are embedded in the surface layer of the mother particles 12 and fixed by adhesion, adhesion, or the like.

As shown in FIGS. 6A and 6B, even if the child particles 13 are attached or fixed to the surface layer of the mother particles 12 to form the display medium particles 11, the child particles 13 are still present on the surface layer of the mother particles 12. It was found that the non-uniform formation of the child particle layer was caused by the aggregation of the child particles 13 in the recesses on the surface of the mother particles 12. As a countermeasure, the concave shape on the surface of the mother particle 12 was defined as follows.
FIG. 7 is a view for explaining the definition of the concave shape on the surface of the mother particle. Most preferably, there are no recesses on the surface of the base particles 12, but even if there are recesses, the depth of the recesses of the base particles is a and the diameter of the recesses of the base particles is b as shown in FIG. The display medium particles (particle size d _{1 of the} child particles) satisfy b <0.8d ₁ , or satisfy 0 <a ≦ 0.3d ₁ and 3d ₁ <b, or 0 .3d ₁ ≦ a and 5a ≦ b are preferably satisfied.

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

  Regarding the substrate, one substrate on the viewing side is a transparent substrate 2 on which the color of the display medium 3 can be confirmed from the outside of the panel, and a material having high visible light transmittance and good heat resistance is suitable. The substrate 1 may be transparent or opaque. Examples of substrate materials include polymer sheets such as polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyethylene, polycarbonate, polyimide, and acrylic, flexible materials such as metal sheets, and glass and quartz. An inorganic sheet having no flexibility is mentioned. The thickness of the substrate is preferably from 2 to 5000 μm, more preferably from 5 to 2000 μm. If it is too thin, it will be difficult to maintain the strength and the spacing uniformity between the substrates, and if it is thicker than 5000 μm, it will be a thin information display panel. Is inconvenient.

  The electrodes and conductive member forming materials provided as necessary include metals such as aluminum, silver, nickel, copper, and gold, indium tin oxide (ITO), antimony tin oxide (ATO), indium oxide, and conductive oxide. Examples include conductive metal oxides such as tin and conductive zinc oxide, and conductive polymers such as polyaniline, polypyrrole, and polythiophene, which are appropriately selected and used. The electrode can be formed by patterning the above-described materials into a thin film by sputtering, vacuum deposition, CVD (chemical vapor deposition), coating, or the like, or by mixing a conductive agent with a solvent or synthetic resin binder. A method of applying and patterning is used. The electrodes and conductive members provided on the viewing side (display surface side) substrate need to be transparent, but the electrodes and conductive members provided on the back side substrate do not need to be transparent. In any case, the above-mentioned material that is conductive and capable of pattern formation can be suitably used. The thickness of the electrode and the conductive member 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 materials and thicknesses of the electrodes and conductive members provided on the back side substrate are the same as those of the electrodes and conductive members provided on the display surface side substrate described above, but need not be transparent. In this case, the external voltage input may be superimposed with direct current or alternating current.

The shape of the partition walls 4 provided on the substrate is optimally set as appropriate depending on the type of display medium involved in display, the shape and arrangement of electrodes to be arranged, and is not limited in general, but the width of the partition walls is 2 to 100 μm, preferably The height of the partition wall is adjusted to 10 to 100 μm, preferably 10 to 50 μm, to 3 to 50 μm.
In forming the partition wall, a both-rib method in which ribs are formed on each of the opposing substrates 1 and 2 and then bonded, and a single-rib method in which ribs are formed only on one substrate are conceivable. In the present invention, any method is preferably used.
As shown in FIG. 8, the cells formed by the partition walls made of these ribs are exemplified by a square shape, a triangular shape, a line shape, a circular shape, and a hexagonal shape as viewed from the substrate plane direction. And a mesh shape. It is better to make the portion corresponding to the cross section of the partition wall visible from the display surface side (the area of the cell frame) as small as possible, and the display becomes clearer.
Examples of the method for forming the partition include a mold transfer method, a screen printing method, a sand blast method, a photolithography method, and an additive method. Any of these methods can be suitably used for the information display panel of the present invention, and among these, a photolithography method using a resist film and a mold transfer method are suitably used.

Next, examples of display medium particles (hereinafter also referred to as particles) constituting the display medium in the information display panel that is the subject of the present invention will be described. The display medium particles may be composed of the display medium particles as they are to form a display medium, or may be combined with other particles to form a display medium, or the particles may be adjusted and configured to form a display medium. Used.
The particles can contain a charge control agent, a colorant, an inorganic additive, and the like, if necessary, in the resin as the main component, as in the conventional case. Examples of resins, charge control agents, colorants, and other additives will be given below.

  Examples of the resin for the mother particles 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, etc. it can. 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 for the mother particles is not particularly limited, but 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), quaternary Ammonium salt compounds, calixarene compounds, boron-containing compounds (benzyl acid boron complexes), nitroimidazole derivatives and the like can be mentioned. 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 for the mother particles, various organic or inorganic pigments and dyes as exemplified below can be used.

Examples of the black colorant for the mother particles include carbon black, copper oxide, manganese dioxide, aniline black, and activated carbon.
Examples of blue colorants for base particles 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 for mother particles include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, resol 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 for mother particles include yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral first yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, C.I. I. Pigment Yellow 12 etc.
Examples of green colorants for base particles include chrome green, chromium oxide, pigment green B, C.I. I. Pigment Green 7, Malachite Green Lake, Final Yellow Green G, etc.
Examples of orange colorants for mother particles 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 for mother particles include manganese purple, first violet B, and methyl violet lake.
Examples of white colorants for base particles include zinc white, titanium oxide, antimony white, and zinc sulfide.

  Examples of base pigments for base particles 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 for mother particles 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, Examples thereof include titanium yellow, bitumen, ultramarine, cobalt blue, cobalt green, cobalt violet, iron oxide, carbon black, manganese ferrite black, cobalt ferrite black, copper powder, and aluminum powder.
These pigments and inorganic additives can be used alone or in combination. Of these, carbon black is particularly preferable as the black pigment, and titanium oxide is preferable as the white pigment. By blending the colorant, particles for a display medium having a desired color can be produced.
Although the mother particles have been described, the same resin, charge control agent, colorant, and other additives as the mother particles can be used for the child particles.

The particles for display medium of the present invention have a particle diameter d ₁ in the range of 0.03 μm <d ₁ <1.00 μm on the surface of the base particle having a particle diameter d ₀ in the range of 1.0 μm <d ₀ <50 μm. This is a composite particle obtained by adhering or adhering child particles in a state satisfying the condition of d ₁ / d ₀ <0.33.

The mother particles used for the display medium particles of the present invention preferably have an average particle diameter d ₀ (0.5) in the range of 1 to 50 μm and are uniform and uniform. If the average particle diameter d ₀ (0.5) is larger than this range, the display is not clear. If the average particle diameter d ₀ (0.5) is smaller than this range, the cohesive force between the mother particles becomes too large, which hinders movement as a display medium. Become.

Furthermore, in the present invention, regarding the particle size distribution of each mother particle, the particle size distribution Span represented by the following formula is less than 5, preferably less than 3.
Span = (d ₀ (0.9) −d ₀ (0.1)) / d ₀ (0.5)
(However, d ₀ (0.5) is a numerical value indicating the particle diameter in μm that 50% of the mother particles are larger than this and 50% is smaller than this, and d ₀ (0.1) is the ratio of the mother particles less than 10%. (The particle diameter is% expressed in μm, and d ₀ (0.9) is the numerical value expressed in μm, which is 90% of the parent particles below this value.)
By keeping Span within a range of 5 or less, the sizes of the respective mother particles are uniform, and the display medium can be moved uniformly.

Furthermore, regarding the correlation between the mother particles, the ratio of the d ₀ (0.5) of the mother particle having the smallest diameter to the d ₀ (0.5) of the mother particle having the largest diameter among the used mother particles is 50 or less, preferably It is important to set it to 10 or less. Even if the particle size distribution Span is reduced, the mother particles having different charging characteristics move in opposite directions, so that the particle sizes are close to each other and each mother particle can easily move in the opposite direction by the equivalent amount. This is preferred, and this is the range.

The particle size distribution and the particle size can be obtained from a laser diffraction / scattering method or the like. When laser light is irradiated to the mother particle 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.
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 machine, the mother particles were put into a nitrogen stream, and with the attached analysis software (software based on volume reference distribution using Mie theory) The particle size and particle size distribution can be measured.

  The charge amount of the display medium particles naturally depends on the measurement conditions, but the charge amount of the display medium particles in the information display panel is almost the same as the initial charge amount, the contact with the partition walls, the contact with the substrate, and the elapsed time. It was found that depending on the charge decay, the saturation value of the charging behavior of the particles for the display medium is a dominant factor.

  As a result of intensive studies, the present inventors have been able to evaluate the range of proper charging characteristics of display medium particles by measuring the charge amount of the particles used in the display medium using the same carrier particles in the blow-off method. I found.

Furthermore, when the display medium is applied to a dry information display panel that is driven in an air space, it is important to manage the gas in the gap surrounding the 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, and preferably 50% RH or less for the humidity of the gas in the gap.
1A, 1B, 5A, and 5B, the gaps are defined as electrodes 5 and 6 (electrodes on the inner side of the substrate). ), An occupied portion of the display medium 3, an occupied portion of the partition wall 4 (when the partition wall is provided), a color filter 27 portion (when the color filter is provided inside the substrate), and an information display panel seal. A gas portion in contact with a so-called display medium excluding the 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 an information display panel so that the humidity is maintained, for example, filling a display medium, assembling an information display panel, etc. in a predetermined humidity environment, It is important to apply a sealing material and a sealing method that prevent moisture from entering from the outside.

The distance between the substrates in the information display panel that is the subject of the present invention is not limited as long as the display medium can be moved and the contrast can be maintained, but is usually adjusted to 10 to 500 μm, preferably 10 to 200 μm.
The volume occupation ratio of the display medium in the air space between the opposing substrates is preferably 5 to 70%, more preferably 5 to 60%. When it exceeds 70%, the movement of the display medium is hindered, and when 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.

As shown in Table 1 below, recesses having a depth and a diameter are formed in a mother particle having a material of polystyrene (PS) and a particle diameter d ₀ of 10 μm. The material and particles shown in Table 1 are formed for each of the mother particles. The child particles having a diameter d ₁ were combined to obtain Examples 1 to 4 and Comparative Examples 1 and 2. A method for producing child particles and mother particles and a method for combining child particles and mother particles will be described below.

First, the child particles were polymerized according to a standard technique of emulsion polymerization in an N ₂ gas reflux atmosphere at 70 ° C. for 12 hours to obtain predetermined child particles. An example of the formulation is 100 parts by weight of trimethylolpropane trimethacrylate (Wako Pure Chemical Industries, Ltd. reagent grade), 33 parts by weight of isoamyl acetate (Wako Pure Chemical Industries, Ltd. reagent grade), sodium lauryl sulfate (Wako Pure Chemical Industries, Ltd.) Reagent grade) 3 parts by weight and lauryl peroxide (Nippon Yushi Co., Ltd.) 0.4 parts by weight.
The mother particles are prepared by kneading a raw material composed of a base resin and a pigment (for example, a white pigment such as titanium oxide or a black pigment such as carbon black) with a biaxial kneader, and then finely pulverizing with a jet mill. Thus, predetermined mother particles were obtained.
Furthermore, the composite (adhesion or adhesion) treatment method of the mother particles and the child particles is performed by mixing a mixed powder (bulk volume = apparent volume 100 cm ³ ) obtained by mixing the mother particles and the child particles at a predetermined ratio into a sample mill SK. -M10 (manufactured by Kyoritsu Riko Co., Ltd.) was collectively charged and subjected to a composite treatment under conditions of 45 ° C. and 16500 rpm × 10 minutes, and then passed through a SUS sieve having an opening of 150 μm to obtain composite particles. The obtained composite particles were obtained as display medium particles.

  Table 1 also shows the results of the covering properties of the child particles on the mother particles, where “◯” indicates that the surface of the composite particles is uniform, and “×” indicates that the surface of the composite particles is not uniform. 9A to 9F show SEM photographs of the composite particles of Examples 1 to 4 and Comparative Examples 1 and 2, respectively.

Example 1 is an example in which mother particles without recesses are coated with silica child particles (particle size d ₁ = 0.11). As shown in FIG. 9A, the composite particles are round and uniform. It can be seen that the particles are coated.
Example 2 is an example in which the base particles having a depth of 0.6 μm and a diameter of 0.2 μm and having a recess narrower than the particle size d ₁ 0.3 of the child particles are coated with child particles of crosslinked PMMA, As shown in FIG. 9B, it can be seen that the composite particles are round, and the child particles are uniformly coated.
Example 3 is an example in which parent particles having a shallow depth of 0.1 μm and a diameter of 2 μm are coated with child particles of crosslinked PS (particle size d ₁ = 0.15). FIG. As shown, it can be seen that the child particles are uniformly coated.
In Example 4, a parent particle having a depth of 1 μm and a diameter of 5 μm but having a sufficiently wide recess (diameter is 5 times or more of the depth) is coated with child particles of crosslinked PS (particle size d ₁ = 0.3). As shown in FIG. 9D, it can be seen that the child particles are uniformly coated.
In Comparative Example 1, cross-linked PMMA child particles (particle size d ₁ = 0.24) are formed on mother particles having a shallow narrow recess (diameter is less than 5 times the depth) having a depth of 0.5 μm and a diameter of 0.7 μm. In this example, as shown in FIG. 9E, it can be seen that the child particles are coated non-uniformly.
Comparative Example 2 is an example in which the parent particles having a deep and narrow concave portion (diameter is less than 5 times the depth) having a depth of 1 μm and a diameter of 4 μm are coated with crosslinked PS child particles (particle size d ₁ = 0.1). In addition, as shown in FIG. 9 (f), it can be seen that the child particles are unevenly coated.

  Information display panels subject to the present invention include display devices for mobile devices such as notebook computers, PDAs, mobile phones, handy terminals, electronic papers such as electronic books, electronic newspapers, and electronic manuals (instruction manuals), signboards, Billboards such as posters, blackboards, calculators, home appliances, automotive supplies, card displays such as point cards, IC cards, electronic advertisements, electronic POPs, electronic price tags, electronic shelf labels, electronic musical scores, RF-ID devices It is also suitably used as an information display panel (so-called rewritable paper) for rewriting the display using an external electric field forming means.

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

(A), (b) is a figure which shows an example of the information display panel used as the object of this invention, respectively. (A), (b) is a figure which shows the other example of the information display panel used as the object of this invention, respectively. (A), (b) is a figure which shows the further another example of the information display panel used as the object of this invention, respectively. (A)-(d) is a figure which shows the further another example of the information display panel used as the object of this invention, respectively. (A), (b) is a figure which shows the further another example of the information display panel used as the object of this invention, respectively. (A), (b) is a figure which shows an example of the particle | grains used for the display medium of this invention, respectively. It is a figure for demonstrating prescription | regulation of the recessed part shape of a mother particle surface. It is a figure which shows an example of the shape of the partition in the information display panel used as the object of this invention. (a)-(f) is the SEM photograph of the composite particle of the Example and comparative example of this invention, respectively.

Explanation of symbols

1, 2 Substrate 3 Display medium (particle group)
3W White display medium 3Wa White particles for display 3B Black display medium 3Ba Black particles for display 4 Partition 7B Black plate 11 Display medium particles (composite particles)
12 mother particles 13 child particles 21-1 first cell 21-2 second cell 21-3 third cell 22R red color filter 22G green color filter 22BL blue color filter 31, 32 external electric field forming means 33, 34 conductive Element

Claims (6)

Particles constituting a display medium used for an information display panel for enclosing a display medium in a space between two opposing substrates at least one of which is transparent and moving the display medium to display information such as an image, In particles for display media composed of composite particles obtained by attaching or fixing child particles to mother particles,
A particle for a display medium, wherein the mother particle surface layer has no recess. Particles constituting a display medium used for an information display panel for enclosing a display medium in a space between two opposing substrates at least one of which is transparent and moving the display medium to display information such as an image, In particles for display media composed of composite particles obtained by attaching or fixing child particles to mother particles,
Wherein if there is a recess in the base particle surface, the diameter of the recess of the base particles when expressed by a and b, respectively, the particle diameter d ₁ of the child particles, b <particles for display media and satisfies the 0.8d _1. Particles constituting a display medium used for an information display panel for enclosing a display medium in a space between two opposing substrates at least one of which is transparent and moving the display medium to display information such as an image, In particles for display media composed of composite particles obtained by attaching or fixing child particles to mother particles,
When the surface of the mother particle has a recess, when the depth of the recess of the mother particle is a and the diameter of the recess of the mother particle is b, the particle diameter d ₁ of the child particle is 0 <a ≦ 0.3d ₁ and 3d 1 _<particles for display media and satisfies the _b. Particles constituting a display medium used for an information display panel for enclosing a display medium in a space between two opposing substrates at least one of which is transparent and moving the display medium to display information such as an image, In particles for display media composed of composite particles obtained by attaching or fixing child particles to mother particles,
When the surface of the mother particle has a recess, when the depth of the recess of the mother particle is a and the diameter of the recess of the mother particle is b, the particle diameter d ₁ of the child particle is 0.3d ₁ ≦ a and 5a Particles for display medium, characterized by satisfying ≦ b. The particle diameter d ₀ of the mother particles is in the range of 1.0 μm <d ₀ <50 μm, and the particle diameter d ₁ of the child particles is in the range of 0.03 μm <d ₁ <1.00 μm. The particle | grains for display media of any one of 1-4.   An information display panel, wherein the display medium particle according to claim 1 is used as a display medium.