JP2008026469A - Particle for display medium and panel for information display using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide particles for a display medium with an excellent property of concealing other colors by manufacturing at least one kind of the particles for the display medium for constituting the display medium from a material for the particles containing a coloring agent and titanium oxide. <P>SOLUTION: The particles for the display medium with the excellent property of concealing other colors are obtained by using colored particles containing the coloring agent and titanium oxide, as at least one kind of the particles for the display medium for constituting the display medium, which are used in a panel for information display to display information such as an image by applying an electric field to the display medium sealed in between two substrates 1, 2 of which at least one is transparent, and transferring the display medium. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is used for an information display panel that displays information such as an image by moving a display medium by enclosing a display medium between two substrates, at least one of which is transparent, and applying an electric field to the display medium. The present invention relates to particles for a display medium constituting a display medium, 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. In particular, recently, an electrophoretic method in which a dispersion liquid composed of dispersion particles and a colored solution is microencapsulated 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. In addition, 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 that the stability of repeated information display is lacking. ing. 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, this method has a problem that the structure is complicated because the charge transport layer and further the charge generation layer are arranged, and that it is difficult to inject the charges into the conductive particles, so that the stability is lacking. .

  As a method for solving the various problems described above, a display medium is sealed between two substrates, at least one of which is transparent, and an electric field is applied to the display medium, thereby moving the display medium to An information display panel for displaying information is known. In an information display panel of a type that displays information such as images by moving the display medium by such an electric field, as a method for forming colored display medium particles, a transparent resin such as toner is colored with a pigment or the like. A method of dispersing the agent and a method of coloring the particle surface with a dye are generally used.

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”, p.249-252

  Display medium particles produced by dispersing a colorant such as a pigment in a transparent resin such as a toner have a certain degree of transparency. Therefore, such display medium particles are used as an information display panel. When it is used, the colors of the display medium particles on the back surface of the display medium particles can be seen through, resulting in a blurred color with low contrast. In addition, display medium particles prepared by a method of coloring the particle surface using a dye have a problem that the dye can be removed by friction between the display medium particles over a long period of use.

The present invention provides particles for a display medium having good concealability of other colors by producing at least one of the particles for display medium constituting the display medium from a particle raw material containing a colorant and titanium oxide. The first purpose.
A second object of the present invention is to provide an information display panel that is configured using the display medium particles and has excellent display quality.

  In order to achieve the first object, the display medium particles of the present invention move the display medium by enclosing the display medium between two substrates, at least one of which is transparent, and applying an electric field to the display medium. Display medium particles constituting a display medium used for an information display panel for displaying information such as images, wherein at least one of the display medium particles is a colored particle containing a colorant and titanium oxide. It is characterized by.

  As a suitable example of the particles for a display medium of the present invention, the content of the titanium oxide is 20 to 100 parts by weight with respect to the resin, the particle diameter of the titanium oxide is 100 to 500 nm, and the display medium The glass transition temperature Tg of the resin constituting the particles for display is 60 ° C. or higher, the average particle diameter of the particles for display medium is 1 to 20 μm, and the particles for display medium measured by a blow-off method using a carrier The corona discharge is performed by applying a voltage of 8 KV to the corona discharger in which the display medium particles are 10 to 100 μC / g in absolute value and the display medium particles are arranged at a distance of 1 mm from the surface thereof. When the surface is charged by being generated, the maximum value of the surface potential after 0.3 seconds may be particles larger than 300V.

  In order to achieve the second object, an information display panel of the present invention is for a display medium according to any one of claims 1 to 7 between two opposing substrates at least one of which is transparent. At least one kind of display medium containing particles is sealed, and the display medium is moved by an electric field generated in the substrate to display information such as an image.

  According to the display medium particles of the present invention, the display medium is sealed between two substrates, at least one of which is transparent, and an electric field is applied to the display medium. Since at least one of the display medium particles constituting the display medium used for the information display panel to be displayed is a colored particle containing a colorant and titanium oxide, this display medium particle is proved in an embodiment described later. As shown in the figure, the particles for display medium have good concealability of other colors.

  According to the information display panel of the present invention, at least one display medium containing the display medium particles according to any one of claims 1 to 7 is enclosed between two opposing substrates, at least one of which is transparent. Since the display medium is moved by the electric field generated in the substrate to display information such as an image, the information display panel is proved in an embodiment described later. It becomes an information display panel with excellent display quality.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  First, the configuration of the information display panel of the present invention using the display medium comprising the display medium particles of the present invention will be described. In the information display panel of the present invention, an electric field is applied to a display medium sealed between two opposing substrates. Along the applied electric field direction, the charged display medium is attracted by the force of the electric field or the Coulomb force, and the display medium changes the moving direction according to the change of the electric field direction, thereby displaying information such as an image. Therefore, it is necessary to design the information display panel so that the display medium can move uniformly and maintain the stability when the display information is rewritten or when the display information is continuously displayed. Here, as the force applied to the particles constituting the display medium, in addition to the force attracting each other by the Coulomb force between the particles, an electric mirror image force between the electrode and the substrate, an intermolecular force, a liquid cross-linking force, gravity and the like can be considered.

  An example of an information display panel mounted on an information display device that is an object of the present invention will be described with reference to FIGS. 1 (a) and (b) to FIGS. 3 (a) and 3 (b).

  In the example shown in FIGS. 1A and 1B, at least two kinds of display media 3 (here, white display medium particles 3Wa) having at least one kind of particles and having different optical reflectance and charging characteristics. A white display medium 3W composed of a group of particles and a black display medium 3B composed of a group of particles 3Ba for black display medium) are perpendicular to the substrates 1 and 2 according to the electric field applied from the outside of the substrates 1 and 2. The black display medium 3B is visually recognized by the observer and black display is performed, or the white display medium 3W is visually recognized by the observer and white display is performed. In the example shown in FIG. 1B, in addition to the example shown in FIG. 1A, a partition 4 is provided between the substrates 1 and 2 to form a cell, for example. In addition, in FIG. 1B, the partition in front is omitted.

  In the example shown in FIGS. 2A and 2B, at least two kinds of display media 3 (here, white display medium particles 3Wa) having at least one kind of particles and having different optical reflectance and charging characteristics. Between the electrode 5 provided on the substrate 1 and the electrode 6 provided on the substrate 2 is a voltage between the electrode 5 provided on the substrate 1 and the electrode 6 provided on the substrate 2. In accordance with the electric field generated by applying, the substrate is moved perpendicularly to the substrates 1 and 2 so that the black display medium 3B is visually recognized by the observer and black display is performed, or the white display medium 3W is provided to the observer. A white display is made by visual recognition. In the example shown in FIG. 2 (b), in addition to the example shown in FIG. 2 (a), a partition 4 is provided between the substrates 1 and 2 to form cells, for example. Further, in FIG. 2 (b), the front partition is omitted.

In the example shown in FIGS. 3A and 3B, one type of display medium 3 (here, particles of white display medium particles 3Wa) having optical reflectivity and chargeability composed of at least one type of particles. A white display medium 3 </ b> W consisting of a group) is parallel to the substrates 1 and 2 according to an electric field generated by applying a voltage between the electrode 5 provided on the substrate 1 and the electrode 6 provided on the substrate 2. The white display medium 3 </ b> W is visually recognized by the observer to perform white display, or the color of the electrode 6 or the substrate 1 is visually recognized by the observer to display the color of the electrode 6 or the substrate 1. ing. In the example shown in FIG. 3B, in addition to the example shown in FIG. 3A, for example, a lattice-shaped partition wall 4 is provided between the substrates 1 and 2 to form a cell. Moreover, in FIG.3 (b), the partition in front is abbreviate | omitted.
In FIGS. 2A and 2B and FIGS. 3A and 3B, the electrodes may be provided outside the substrate, or may be provided so as to be embedded inside the substrate.

Hereinafter, the particles for a display medium that are the characteristics of the present invention will be described in detail. The particles for a display medium of the present invention can be applied to the information display panels shown in FIGS. 1A, 1B to 3A, 3B, and at least one of the information display panels is transparent. A display medium is configured and sealed between two substrates. The content of one titanium oxide in the display medium particles is preferably 20 to 100 parts by weight with respect to the resin. When the content of titanium oxide is less than 20 parts by weight with respect to the resin, the desired other color hiding effect cannot be obtained, and when the content of titanium oxide is more than 100 parts by weight with respect to the resin, white Is excessively strong and requires a large amount of a colorant (for example, a pigment) to color other colors, and the chargeability of the pigment affects the overall chargeability of the particles for other color display media. Moreover, it is preferable that the particle diameter of a titanium oxide is 100-500 nm. When the particle diameter of titanium oxide is smaller than 100 nm, uniform dispersion in the particles becomes difficult, the effect of hiding other colors decreases, and when the particle diameter of titanium oxide is larger than 500 nm, The volume occupied by titanium oxide in the particles increases, and the performance of the particles for other color display media deteriorates. In addition, in order to improve the weather resistance of titanium oxide and to suppress photocatalytic properties, titanium oxide whose surface is coated with alumina, silica, or the like may be used.
The glass transition temperature Tg of the resin constituting the display medium particles is 60 ° C. or higher, the average particle diameter of the display medium particles is 1 to 20 μm, and measured by a blow-off method using a carrier. A voltage of 8 KV is applied to the corona discharger in which the charge amount of the particles for display medium is 10 to 100 μC / g in absolute value and the particles for display medium are arranged at a distance of 1 mm from the surface. When the surface is charged by generating corona discharge, it is preferable that the maximum value of the surface potential after 0.3 seconds is a particle larger than 300V.

  According to the display medium particles of the present invention, one of the display medium particles used in the information display panels of FIGS. 1A and 1B to FIGS. 3A and 3B is for a white display medium. FIG. 1A and FIG. 1B using the particles for the colored display medium because the particles have an optical density (OD value) close to the particles, and the particles are particles composed of colored particles containing a colorant and titanium oxide. 3), the information display panel shown in FIGS. 3A and 3B is difficult to see through the color of the display medium particles of other colors (for example, black) on the back of the colored display medium particles. Since the color concealing effect is obtained, the information display panel is excellent in display quality, as proved in the embodiments described later.

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

  Regarding the substrate, at least one of the substrates is a transparent substrate on which the color of the display medium can be confirmed from the outside of the panel, and a material having high visible light transmittance and good heat resistance is preferable. The back substrate as the other substrate may be transparent or opaque. Examples of substrate materials include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene (PE), polycarbonate (PC), polyimide (PI), polyethersulfone (PES), acrylic and other polymer sheets, metal Examples thereof include a flexible sheet such as a sheet and a non-flexible inorganic sheet such as glass and quartz. 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.

  Electrode forming materials for electrodes provided on the substrate as required include metals such as aluminum, silver, nickel, copper and gold, indium tin oxide (ITO), indium oxide, conductive tin oxide, antimony tin oxide (ATO). ), Conductive metal oxides such as conductive zinc oxide, and conductive polymers such as polyaniline, polypyrrole, and polythiophene are exemplified and used as appropriate. 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 electrode provided on the viewing side (display surface side) substrate needs to be transparent, but the electrode provided on the back side substrate does not need to be transparent. In any case, the above-mentioned material that is conductive and capable of pattern formation can be suitably used. Note that the electrode thickness is not particularly limited as long as the conductivity can be secured and the light transmittance is not hindered, and is preferably 3 to 1000 nm, preferably 5 to 400 nm. The material and thickness of the electrode provided on the back side substrate are the same as those of the electrode provided on the 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 provided on the substrate as required is appropriately set appropriately depending on the type of display medium involved in display, the shape of the electrode to be arranged, and the arrangement, and is not limited in general, but the width of the partition is 2 to 100 μm. The height of the partition wall is adjusted to 10 to 100 μm, preferably 10 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. 4, the cells formed by the partition walls made up 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 plane of the substrate. 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 an information display panel mounted on the information display device of the present invention, and among these, a photolithography method using a resist film and a mold transfer method are suitably used.

A method of charging the particles negatively or positively is not particularly limited, and a method of charging the particles such as a corona discharge method, an electrode injection method, and a friction method is used. It is preferable that the charge amount of particles measured by a blow-off method using a carrier is 10 to 100 μC / g in absolute value. When the absolute value of the charge amount is lower than this range, the response speed with respect to the change in the electric field is slowed, and the memory property is also lowered. If the absolute value of the charge amount is higher than this range, the mirror image force on the electrode and the substrate is too strong, and the memory property is good, but the followability of the display medium movement when the electric field is reversed becomes poor.
In the present invention, the charge amount was measured as follows.
<Blow-off measurement principle and measurement method>
In the blow-off method, a mixture of a display medium and a carrier is put into a cylindrical container with nets at both ends, and high-pressure gas is blown from one end to separate the display medium particles and the carrier, and the display medium is opened from the mesh of the mesh. Blow off only the particles. At this time, the charge amount equivalent to the charge amount of the display medium particles taken away from the container remains on the carrier. 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 amount Q of the display medium particles is
Q = CV (C: capacitor capacity, V: voltage across the capacitor)
As required.
TB-200 manufactured by Toshiba Chemical Co. was used as a blow-off particle charge measuring device. In the present invention, a ferrite carrier is used to measure the charge amount of the particles to be measured. For example, the information display panel includes a display medium composed of positively charged particles and a display medium composed of negatively charged particles. When using a combination of types of display media, the same type of carrier is used when measuring the charge amount of the particles for display media constituting each display medium. Specifically, the charge amount (μC / g) of particles (display medium particles) was measured using DFC100 wrinkle (Mn—Mg containing ferrite system) manufactured by Dowa Iron Powder Industry Co., Ltd. as a carrier.

Since the particles need to retain their charged charges, insulating particles having a volume resistivity of 1 × 10 ¹⁰ Ω · cm or more are preferable, and in particular, insulating particles having a volume resistivity of 1 × 10 ¹² Ω · cm or more. Is preferred. Further, particles with slow charge decay evaluated by the method described below are more preferable.

  That is, particles to be measured are arranged on the surface of a roll-shaped measuring jig, and a corona discharge is generated by applying a voltage of 8 KV to a corona discharger arranged with a distance of 1 mm from the arranged particle surface. The surface is charged, and the change in the surface potential is measured and judged. In this case, it is important to select and prepare the particle constituent material so that the maximum value of the surface potential after 0.3 seconds is greater than 300V, preferably greater than 400V.

  In addition, the measurement of the said surface potential can be performed, for example with the apparatus (CRT2000 by QEA) shown in FIG. In the case of this apparatus, both ends of the shaft of the roll-shaped measuring jig having the particles to be measured arranged on the surface are held by the chuck 21, and the small scorotron discharger 22 and the surface electrometer 23 are set in a predetermined manner. A measurement unit that is separated from the measurement particle surface is arranged opposite to the surface of the particle to be measured with a 1 mm gap, and the measurement unit is arranged on the surface of the roll measurement jig while the roll measurement jig is stationary. A method of measuring the surface potential while applying surface charge by moving the particles from one end to the other end at a constant speed is suitably employed. The measurement environment is a temperature of 25 ± 3 ° C. and a humidity of 55 ± 5 RH%.

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

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

  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. You may use the pigment which mixed the 2 or more types of pigment and adjusted the color. In addition, when using a pigment as a coloring agent, 2-20 weight part is suitable for content of the pigment with respect to resin of particle | grain raw material. When the pigment content is less than 2 parts by weight with respect to the resin of the particle raw material, the coloring power is insufficient, and when the pigment content is more than 20 parts by weight with respect to the resin of the particle raw material. Is not preferable because the chargeability of the pigment affects the chargeability of the entire particles for the display medium.

Examples of the black colorant include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon and the like.
Examples of blue colorants include C.I. I. Pigment blue 15: 3, C.I. I. Pigment Blue 15, Bituminous Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Metal-free Phthalocyanine Blue, Phthalocyanine Blue Partial Chlorides, Fast Sky Blue, Indanthrene Blue BC, and the like.
Examples of red colorants include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, 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 include chrome yellow, zinc yellow, cadmium yellow, yellow iron oxide, mineral first yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, C.I. I. Pigment Yellow 12 etc.
Examples of green colorants include chrome green, chromium oxide, pigment green B, C.I. I. Pigment Green 7, Malachite Green Lake, Final Yellow Green G, etc.
Examples of the orange colorant include red chrome yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK, C.I. I. Pigment Orange 31 etc.
Examples of purple colorants include manganese purple, first violet B, and methyl violet lake.
Examples of white colorants include zinc white, titanium oxide, antimony white, and zinc sulfide.

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

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

  The particles for display medium of the present invention (hereinafter also referred to as particles) preferably have an average particle diameter d (0.5) in the range of 1 to 20 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 movement as a display medium.

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

Furthermore, when a display medium composed of particles for a display medium is applied to a dry information display panel, it is important to manage the gas in the void 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, 3A, and 3B, the gaps are defined as electrodes 5 and 6 (electrodes inside the substrate) from the portion sandwiched between the opposing substrate 1 and substrate 2. 2), a gas portion in contact with a so-called display medium excluding an occupied portion of the display medium 3, an occupied portion of the partition wall 4 (when a partition wall is provided), and a seal portion of the information display panel.
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 space between the opposing substrates is preferably 5 to 70%, more preferably 5 to 60%. If it exceeds 70%, the movement of the display medium is hindered, and if it is less than 5%, the contrast tends to be unclear.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the present invention, but the present invention is not limited to the following examples.

<Example 1>
[Preparation of particles for black display medium]
100 parts by weight of acrylic resin (Delpet 80NH: manufactured by Asahi Kasei Kogyo) as particles for black display medium, 5 parts by weight of carbon black (Special Black 5: manufactured by Degussa) as a black pigment, and nigrosine derivative as a positive charge control agent 3 parts by weight (Bontron N07: manufactured by Orient Chemical Co., Ltd.) was mixed by stirring with a Henschel mixer (FM5C: Mitsui Mining Co., Ltd.), then kneaded with a twin screw extruder (KZW15-45MG: manufactured by Technobel), and then pulverized. Using a machine (MDS-2: Nippon Pneumatic Industry), pulverization / classification was performed to obtain black particles having an average particle size of 9.0 μm. 2% by weight of silica fine particles (H3050: Nippon Clariant) were added to the particles and stirred with a Henschel mixer (FM5C: Mitsui Metal Mine) to obtain black display medium particles K1. Table 1 shows the characteristics of the black display medium particles K1. Moreover, when the black display medium particle | grains K1 were observed with the transmitted light using the electron microscope (VHX-100: product made by Keyence), light did not permeate | transmit through the black display medium particle | grains K1, and concealment property was confirmed.
[Preparation of particles for yellow display medium]
100 parts by weight of styrene resin (Toyostyrene E640N: manufactured by Toyo Styrene) as particles for yellow display medium, and 100 parts by weight of titanium oxide (Taipaque CR-60-2: manufactured by Ishihara Sangyo) having a particle diameter of 240 nm as white pigment. Henschel mixer, 3 parts by weight of salicylic acid metal complex (Bontron E88: manufactured by Orient Chemical Co., Ltd.) as negative charge control agent, and 10 parts by weight of Pigment Yellow 93 (Chromofine Yellow 5930: manufactured by Dainichi Seika Kogyo) as yellow pigment (FM5C: Mitsui Mining Co., Ltd.) After stirring and mixing, the mixture was kneaded with a twin-screw extruder (KZW15-45MG: manufactured by Technobel) and then used with a pulverizer (MDS-2: Nippon Pneumatic Industry). Grinding / classification yielded yellow particles having an average particle size of 9.0 μm. To this particle, 2% by weight of silica fine particles (H3004: Nippon Clariant) was added and stirred with a Henschel mixer (FM5C: Mitsui Metal Mine) to obtain yellow display medium particles Y1. Table 1 shows the characteristics of the yellow display medium particle Y1. Further, when the yellow display medium particles Y1 were observed with transmitted light using an electron microscope (VHX-100: manufactured by Keyence), light was not transmitted through the yellow display medium particles Y1, and the concealability was confirmed.

<Comparative Example 1>
In Example 1, yellow particles having an average particle diameter of 9.1 μm were obtained in the same manner as the yellow particles described in Example 1 except that titanium oxide was removed when preparing the yellow display medium particles. To this particle, 2% by weight of silica fine particles (H3004: Nippon Clariant) was added and stirred with a Henschel mixer (FM5C: Mitsui Mining Co., Ltd.) to obtain yellow display medium particles Y2. Table 1 shows the characteristics of the yellow display medium particle Y2. Further, when the yellow display medium particles Y2 were observed with transmitted light using an electron microscope (VHX-100: manufactured by Keyence), light was transmitted through the yellow display medium particles Y2, and it was confirmed that there was a lack of concealability.

<Comparative example 2>
In Example 1, except that the amount of titanium oxide was increased to 150 parts by weight and Pigment Yellow 93 (Chromofine Yellow 5930: manufactured by Dainichi Seika Kogyo Co., Ltd.) was increased to 15 weights when producing yellow display medium particles. In the same manner as the yellow particles described in Example 1, yellow particles having an average particle diameter of 8.9 μm were obtained. To the particles, 2% by weight of silica fine particles (H3004: Nippon Clariant) was added and stirred with a Henschel mixer (FM5C: Mitsui Metal Mine) to obtain yellow display medium particles Y3. Table 1 shows the characteristics of the yellow display medium particle Y3. Further, when the yellow display medium particles Y3 were observed with transmitted light using an electron microscope (VHX-100: manufactured by Keyence), light was not transmitted through the yellow display medium particles Y3, and concealability was confirmed.

<Performance evaluation method>
[Charge amount]
It was measured by the conventional “blow-off method” described above.
[Titanium oxide content]
About 0.3 g of particles were placed in a crucible and weighed, and then heated in an electric furnace at 650 ° C. for 2 hours, and the weight after heating was measured. From the difference in weight before and after heating, the number of titanium oxide parts actually present in the particles was calculated.
[Characteristics of information display panel]
Table 1 shows the performance of the information display panel produced using the black display medium particles K1 and the yellow display medium particles Y1, Y2, or Y3 as display media. Contrast was measured using a reflection image densitometer (RD-191: manufactured by Gretag Macbeth Co., Ltd.) at the time of black display and yellow display when ± 100 V was applied, and contrast ratio = reflection at black display. It was determined as density / reflection density at yellow display. Further, the change in contrast ratio was small even after 10,000 display rewrites, and the display medium was driven well.

<Example 2>
[Preparation of particles for red display medium]
In Example 1, instead of carbon black, 50 parts by weight of titanium oxide (Taipaque CR-60-2: manufactured by Ishihara Sangyo) having a particle diameter of 240 nm as a white pigment, Brilliant Carmine 6B (Seika First Carmine 1476T-) as a red pigment 7: manufactured by Dainichi Seika Kogyo Co., Ltd.) Red particles having an average particle size of 9.1 μm were obtained in the same manner as the black particles described in Example 1 except that 10 parts by weight were used. To this particle, 2% by weight of silica fine particles (H3050: Nippon Clariant) was added and stirred with a Henschel mixer (FM5C: Mitsui Metal Mine) to obtain red display medium particles R1. Table 1 shows the characteristics of the red display medium particle R1. Moreover, when the particle | grains R1 for red display media were observed with the transmitted light using the electron microscope (VHX-100: product made by Keyence), light was not permeate | transmitted through the particle | grains R1 for red display media, and concealment property was confirmed.
[Preparation of particles for white display medium]
As white display medium particles, 100 parts by weight of styrene resin (Toyostyrene E640N: manufactured by Toyo Styrene) and 100 parts by weight of titanium oxide (Taipaque CR-60-2: manufactured by Ishihara Sangyo) having a particle diameter of 240 nm as white pigments Then, 3 parts by weight of a salicylic acid metal complex (Bontron E88: manufactured by Orient Chemical Co., Ltd.) as a negatively chargeable charge control agent was stirred and mixed in a Henschel mixer (FM5C: Mitsui Mining Co., Ltd.), and then a twin screw extruder (KZW15-45MG). : Manufactured by Technobel) and then pulverized / classified using a pulverizer (MDS-2: Nippon Pneumatic Industry) to obtain white particles having an average particle size of 9.0 μm. To this particle, 2% by weight of silica fine particles (H3004: Nippon Clariant) was added and stirred with a Henschel mixer (FM5C: Mitsui Metal Mine) to obtain white display medium particles W1. Table 1 shows the characteristics of the white display medium particle W1. Moreover, when the white display medium particle | grains W1 were observed with the transmitted light using the electron microscope (VHX-100: product made by Keyence), light did not permeate | transmit through the white display medium particle | grains W1, and concealment property was confirmed.

<Comparative Example 3>
In Example 2, red particles having an average particle diameter of 9.0 μm were obtained in the same manner as the red particles described in Example 2 except that titanium oxide was removed when the red display medium particles were produced. To this particle, 2% by weight of silica fine particles (H3050: Nippon Clariant) was added and stirred with a Henschel mixer (FM5C: Mitsui Mining Co., Ltd.) to obtain red display medium particles R2. Table 1 shows the characteristics of the red display medium particle R2. Further, when the red display medium particle R2 was observed with transmitted light using an electron microscope (VHX-100: manufactured by Keyence), light was transmitted through the red display medium particle R2, and it was confirmed that there was no concealability.

[Characteristics of information display panel]
Table 1 shows the performance of an information display panel produced using the white display medium particles W1 and the red display medium particles R1 or R2 as display media. Contrast is measured by using a reflection image densitometer (RD-191: manufactured by Gretag Macbeth Co., Ltd.) for reflection density during red display and white display when ± 100 V is applied, and contrast ratio = reflection during red display. It was determined as density / reflection density during white display. Further, the change in contrast ratio was small even after 10,000 display rewrites, and the display medium was driven well.

<Example 3>
[Preparation of particles for blue display media]
Instead of carbon black in Example 1, 50 parts by weight of titanium oxide having a particle diameter of 240 nm as a white pigment (Taipaque CR-60-2: manufactured by Ishihara Sangyo), Pigment Blue 15: 3 (cyanine blue 4920) as a blue pigment : Dainichi Seika Kogyo Co., Ltd.) Blue particles having an average particle size of 9.1 μm were obtained in the same manner as the black particles described in Example 1 except that 10 parts by weight were used. To this particle, 2% by weight of silica fine particles (H3050: Nippon Clariant) was added and stirred with a Henschel mixer (FM5C: Mitsui Mining Co., Ltd.) to obtain blue display medium particle B1. Table 1 shows the characteristics of the blue display medium particle B1. Further, when the blue display medium particles B1 were observed with transmitted light using an electron microscope (VHX-100: manufactured by Keyence), light was not transmitted through the blue display medium particles B1, and the concealability was confirmed.
[Preparation of particles for white display medium]
The same white display medium particles W1 as in Example 2 were used.

<Comparative Example 4>
In Example 3, blue particles having an average particle diameter of 9.1 μm were obtained in the same manner as the blue particles described in Example 3 except that titanium oxide was removed when producing the particles for a blue display medium. To the particles, 2% by weight of silica fine particles (H3050: Nippon Clariant) was added and stirred with a Henschel mixer (FM5C: Mitsui Metal Mine) to obtain blue display medium particles B2. Table 1 shows the characteristics of the blue display medium particle B2. Further, when the blue display medium particles B2 were observed with transmitted light using an electron microscope (VHX-100: manufactured by Keyence), light was transmitted through the blue display medium particles B2, and it was confirmed that there was a lack of concealability.

[Characteristics of information display panel]
Table 1 shows the performance of an information display panel manufactured using the white display medium particles W1 and the blue display medium particles B1 or B2 as display media. Contrast is measured by using a reflection image densitometer (RD-191: manufactured by Gretag Macbeth Co., Ltd.) at the time of blue display and white display when ± 100 V is applied, and contrast ratio = reflection at blue display. It was determined as density / reflection density during white display. Further, the change in contrast ratio was small even after 10,000 display rewrites, and the display medium was driven well.

<Example 4>
[Preparation of particles for green display medium]
In Example 1, instead of carbon black, 50 parts by weight of titanium oxide having a particle diameter of 240 nm as a white pigment (Typek CR-60-2: manufactured by Ishihara Sangyo), Pigment Green 7 (cyanine green 2GN: large) as a green pigment Green particles having an average particle diameter of 9.2 μm were obtained in the same manner as the black particles described in Example 1 except that 10 parts by weight of Nissei Kagaku Kogyo Co., Ltd. were used. To this particle, 2% by weight of silica fine particles (H3050: Nippon Clariant) was added and stirred with a Henschel mixer (FM5C: Mitsui Metal Mine) to obtain green display medium particles G1. Table 1 shows the characteristics of the green display medium particle G1. Moreover, when the green display medium particle | grains G1 were observed with the transmitted light using the electron microscope (VHX-100: product made by Keyence), light did not permeate | transmit through the green display medium particle | grains G1, and concealment property was confirmed.
[Preparation of particles for white display medium]
The same white display medium particles W1 as in Example 2 were used.

<Comparative Example 5>
In Example 4, green particles having an average particle diameter of 8.8 μm were obtained in the same manner as the green particles described in Example 4 except that titanium oxide was removed when producing the green display medium particles. To this particle, 2% by weight of silica fine particles (H3050: Nippon Clariant) was added and stirred with a Henschel mixer (FM5C: Mitsui Metal Mine) to obtain green display medium particles G2. Table 1 shows the characteristics of the green display medium particle G2. Further, when the green display medium particles G2 were observed with transmitted light using an electron microscope (VHX-100: manufactured by Keyence), light was transmitted through the green display medium particles G2, and it was confirmed that there was a lack of concealment.

[Characteristics of information display panel]
Table 1 shows the performance of an information display panel produced using the white display medium particles W1 and the green display medium particles G1 or G2 as display media. Contrast was measured using a reflection image densitometer (RD-191: manufactured by Gretag Macbeth Co., Ltd.) at the time of green display and white display when ± 100 V was applied, and contrast ratio = reflection at green display. It was determined as density / reflection density during white display. Further, the change in contrast ratio was small even after 10,000 display rewrites, and the display medium was driven well.

  An information display panel using a display medium composed of particles for a display medium of the present invention is a display unit of a mobile device such as a notebook computer, an electronic notebook, a portable information device called PDA (Personal Digital Assistants), a mobile phone, or a handy terminal. , Electronic paper such as electronic books, electronic newspapers, signboards, posters, bulletin boards such as blackboards and whiteboards, electronic desk calculators, home appliances, display parts for automobiles, card display parts such as point cards and IC cards, electronic advertisements , Information board, electronic POP (Point Of Presence, Point Of Purchase advertising), electronic price tag, electronic shelf label, electronic score, display part of RF-ID equipment, various electronic devices such as POS terminal, car navigation device, clock, etc. It is suitably used for the display unit.

(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. 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. It is a figure which shows the measuring point of the surface potential of the particle | grains for display media used for the information display panel used as the object of this invention.

Explanation of symbols

1, 2 Substrate 3 Display medium (particle group)
3W White display medium 3B Black display medium 3Wa White display medium particle 3Ba Black display medium particle 4 Bulkhead 5, 6 Electrode 21 Chuck 22 Scorotron discharger 23 Surface potential meter

Claims (8)

A display medium used for an information display panel that displays information such as an image by moving the display medium by enclosing the display medium between two substrates transparent at least one and applying an electric field to the display medium Display medium particles,
At least one of the display medium particles is a colored particle containing a colorant and titanium oxide.   The display medium particle according to claim 1, wherein the content of the titanium oxide is 20 to 100 parts by weight with respect to the resin.   The particle for a display medium according to claim 1 or 2, wherein a particle diameter of the titanium oxide is 100 to 500 nm.   4. The display medium particle according to claim 1, wherein a glass transition temperature Tg of a resin constituting the display medium particle is 60 ° C. or higher.   5. The display medium particle according to claim 1, wherein an average particle diameter of the display medium particle is 1 to 20 μm.   The display medium particle according to any one of claims 1 to 5, wherein the charge amount of the display medium particle measured by a blow-off method using a carrier is 10 to 100 µC / g in absolute value. .   The surface after 0.3 seconds when the surface medium particles are charged by applying a voltage of 8 KV to the corona discharger in which the display medium particles are arranged at a distance of 1 mm from the surface. The particles for display medium according to any one of claims 1 to 6, wherein the maximum potential value is particles larger than 300V.   At least one display medium containing the display medium particles according to any one of claims 1 to 7 is sealed between two opposing substrates, at least one of which is transparent, and is generated in the substrate. An information display panel, wherein a display medium is moved by an electric field to display information such as an image.

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