JP2010276917A - Particle for display medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide particles for information display having satisfactory static charge holding characteristics, by making the remaining amount of surface hydroxyl groups of child particles reduce. <P>SOLUTION: In the particles for a display medium which constitute the display medium used for an information display panel wherein the display medium is encapsulated between two substrates, at least one of which is transparent and the display medium is moved by applying an electric field to the display medium to display information and have a construction, wherein the child particles are embedded in the surfaces of mother particles, the child particles are formed, by subjecting metal oxide fine particles to primary surface treatment with an alkyl group-containing silane, and then to secondary surface treatment with a disilazane compound. <P>COPYRIGHT: (C)2011,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 a display medium particle constituting a display medium, wherein the display medium particle is formed by fixing at least one kind of child particle on a surface layer of a mother particle.

  Conventionally, as for the display medium particles constituting the display medium used in the information display panel, as disclosed in Patent Document 1, at least one kind of child particle is fixed to the surface layer of the mother particle. It has been known.

JP 2006-72283 A

In the particles for display medium described above, the voltage for driving can be lowered by embedding the child particles in the surface layer of the mother particles to form irregularities. As a method for forming irregularities on the surface layer, a method is known in which high-hardness child particles produced by a sol-gel method are embedded mechanically by shearing force into thermoplastic resin-based mother particles. .
On the other hand, surface treatment with a silane coupling agent having an alkyl group effective for securing the charge amount has been conventionally performed on the child particles in order to control the chargeability. However, in recent years, with the development of information display panels, there has been a growing demand for further improving the charge retention characteristics of the entire particles for display media. The problem of not being satisfied has arisen.

  An object of the present invention is to solve the above-described problems and to provide particles for a display medium with little charge attenuation.

  And this time, in the surface treatment with the conventional alkyl group-containing silane coupling agent, the applicant cannot sufficiently arrange the silane coupling agent on the surface of the child particle because the alkyl group becomes sterically hindered. It was found that hydroxyl groups remain on the surface of the film. As a result, it was found that the charge retention characteristics of the entire display medium particles were not sufficiently satisfied.

  Accordingly, in order to solve the above problems, the display medium particles of the present invention enclose the display medium between two substrates, at least one of which is transparent, and apply an electric field to the display medium. A display medium particle constituting a display medium used in an information display panel for displaying information such as an image by moving a medium, wherein the display medium particle has a child particle embedded in a surface of a mother particle The child particles are obtained by subjecting metal oxide fine particles to a primary surface treatment with an alkyl group-containing silane and a secondary surface treatment with a disilazane compound.

  In the particles for display media of the present invention, the disilazane compound is hexamethyldisilazane, and further, the treatment amount of the disilazane compound is 2% by mass or more and 50% by mass or less compared to the child particles. The metal oxide fine particles are preferably silica fine particles.

  According to the present invention, after the child particles are surface-treated with the alkyl group-containing silane and then further treated with a disilazane compound, the residual amount of hydroxyl groups on the child particle surfaces can be reduced, so that the charge attenuation is small. Thus, it is possible to obtain display medium particles capable of maintaining a sufficient charge amount.

(A), (b) is a figure for demonstrating the structure of an example of the information display panel used as the object of this invention, respectively. (A), (b) is a figure for demonstrating the structure of the other example of the information display panel used as the object of this invention, respectively. (A), (b) is a figure which shows the structure of an example of the particle | grains for display media of this invention, respectively. It is a figure explaining the steric hindrance in the child particle of the present invention.

  First, the configuration of the information display panel that is the subject of the present invention will be described. In the information display panel which is an object of the present invention, an electric field is applied to a display medium configured as a particle group including a chargeable particle sealed between two opposing substrates. Along with the applied electric field direction, the display medium is attracted by an electric field force or a Coulomb force, and the display medium is moved by a change in the electric field direction, whereby information such as an image is displayed. Therefore, it is necessary to design the information display panel so that the display medium can move uniformly and maintain 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 that is an object of the present invention will be described with reference to FIGS. 1 (a) and (b) to FIGS. 2 (a) and 2 (b).

  In the example shown in FIGS. 1 (a) and 1 (b), at least two types of display media having different optical reflectivity and charging characteristics (here, configured as a particle group including particles having at least optical reflectivity and chargeability) The white display medium 3W configured as a particle group including the negatively charged white particles 3Wa and the black display medium 3B configured as a particle group including the positively charged black particles 3Ba are shown). In the cell, the substrates 1 and 2 correspond to the electric field generated by applying a voltage to the pixel electrode pair formed by the stripe electrode 6 provided on the substrate 2 and the stripe electrode 5 provided on the substrate 1 crossing each other at right angles. The configuration is a passive drive system that moves vertically. Then, the white display medium 3W is visually recognized by the observer as shown in FIG. 1A, or the black display medium 3B is visually recognized by the observer as shown in FIG. 1B. Are displayed in a matrix with black and white dots. In addition, in FIG. 1 (a), (b), the partition in front is abbreviate | omitted.

  In the example shown in FIGS. 2A and 2B, at least two types of display media having different optical reflectance and charging characteristics (here, configured as a particle group including particles having at least optical reflectance and charging properties (here) The white display medium 3W configured as a particle group including the negatively charged white particles 3Wa and the black display medium 3B configured as a particle group including the positively charged black particles 3Ba are shown). In the cell, in response to an electric field generated by applying a voltage to a pixel electrode pair formed by facing an electrode 5 (pixel electrode with TFT) provided on the substrate 1 and an electrode 6 (common electrode) provided on the substrate 2. Therefore, the active drive system is configured to move perpendicularly to the substrates 1 and 2. Then, the white display medium 3W is visually recognized by the observer as shown in FIG. 2A, or the white display is displayed by the observer, or the black display medium 3B is visually recognized by the observer as shown in FIG. 2B. Are displayed in a matrix with black and white dots. In addition, in FIG. 2 (a), (b), the partition in front is abbreviate | omitted.

  A feature of the present invention is a display medium particle used in the information display panel described above, wherein the display medium particle is composed of a mother particle and a child particle having a smaller diameter than the mother particle, and the child particle is the mother particle. In general, a plurality of at least one child particle is surface-treated with an alkyl group-containing silane on the metal oxide fine particles and then post-treated with a disilazane compound.

3 (a) and 3 (b) are views showing the structure of an example of the display medium particle of the present invention, FIG. 3 (a) shows a front view thereof, and FIG. 3 (b) shows a cross-sectional view thereof. Show. In the present example, an example in which the child particle 13 is a single layer is shown, but the number of layers is not particularly limited, and the number of layers may be two or more. Here, it is important to configure so that the child particles 13 attached to the mother particles 12 are exposed from the surface of the mother particles 12.
In the present invention, the mother particles 12 have a particle size in the range of 1.0 to 50 μm, and the child particles 13 have a particle size in the range of 0.03 to 1.00 μm.

In the present invention, for the display medium, the child particles 13 that have been surface-treated with an alkyl group-containing silane (for example, the following chemical formula (1)) and then post-treated with a disilazane (SiH ₃ —NH—SiH ₃ ) compound are used. Construct particles 11. Specifically, the child particles 13 are post-treated with hexamethyldisilazane (the following chemical formula (2)), which has less steric hindrance than the alkyl group-containing silane. If hydroxyl groups remain on the surface of the child particles 13, charge leakage (attenuation) due to moisture adsorbed on the surface hydroxyl groups occurs. However, by performing post-treatment as described above, hydroxyl groups on the surface of the child particles 13 can be obtained. The remaining amount of can be reduced.
Therefore, according to the present invention, it is possible to obtain a child particle having a sufficient amount of charge retention characteristics with less charge attenuation as compared with the case of only the conventional silane treatment. As a result, even after the information display device is left for a long period of time, the child particles maintain a sufficient amount of charge, so that good image quality can be maintained.

なお、Ｘは無機材料と反応する官能基、Ｙは有機材料と反応する官能基、Ｒはアルキル基を表している。

X represents a functional group that reacts with an inorganic material, Y represents a functional group that reacts with an organic material, and R represents an alkyl group.

Here, steric hindrance means that atoms or atomic groups that are close to each other within and between molecules collide with each other, distorting the normal direction of atomization, and limiting rotation around the bond. To tell. In the conventional treatment process in which the surface treatment is performed only with the alkyl group-containing silane coupling agent, as shown in FIG. 4, when the coupling agent approaches the surface of the child particle surface, the alkyl group contained in the silane becomes this three-dimensional structure. It becomes an obstacle and is obstructed by this, so that the coupling agent cannot be made sufficiently close to the surface of the child particle surface. For this reason, H of a silane coupling agent and OH on the child particle surface layer cannot be sufficiently reacted, and as a result, there is a problem that hydrophilic child particles (surface hydroxyl groups) remain. . If this surface hydroxyl group remains, charge leakage due to moisture adsorbed on the surface hydroxyl group occurs as described above, so that the charge retention characteristics cannot be sufficiently satisfied.
In the present invention, in order to solve the problem due to the steric hindrance as described above, first, after performing the surface treatment with the alkyl group-containing silane as described above, the treatment efficiency is further high (the amount of the treatment agent attached is large). ) Has a small effect on chargeability, and preferably has a surface treatment (secondary treatment) using hexamethyldisilazane to reduce the residual amount of surface hydroxyl groups on the surface layer of the child particles 13.

  Regarding the post-treatment (secondary treatment), tetramethyldisilazane and diphenyltetramethyldisilazane can be used as the disilazane compound in addition to hexamethyldisilazane. Furthermore, in addition to the disilazane compound, trimethylchlorosilane and trichloromethylsilane can also be used.

Moreover, in this invention, it is suitable that a disilazane compound is 2 mass% or more and 50 mass% or less with respect to 13 child particles. This is because, when the disilazane compound is less than 2% by mass relative to the child particles 13, the composite of the display medium particles 11 composed of the child particles 13 and the mother particles 12 after the surface treatment as shown below. This is because the charge decay rate becomes relatively large.
On the other hand, when the disilazane compound is more than 50% by mass with respect to the child particles 13, the ultrafine particles produced by curing with an excess of the treating agent inhibits the embedding of the child particles into the mother particles, and thus good particles. Cannot be combined.

  As the particle surface treatment method, a dry method in which a liquid surface treatment agent is dropped into particles stirred in a mixer, or a particle and a surface treatment agent are added to a medium and mechanically dispersed. A wet method in which the surface treatment is performed while performing the treatment is mentioned, but it is not particularly limited thereto.

  In the present invention, it is preferable that fine particles such as silica are further added to the surface of the display medium particle 11 as an external additive.

  Hereinafter, each member which comprises the panel for information displays which uses the particle | grains for display media of this invention is demonstrated.

  As the substrate, at least one of the substrates is a transparent substrate from which 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), polyethersulfine (PES), acrylic, and other organic polymer substrates. Alternatively, a glass sheet, a quartz sheet, a metal sheet coated with an insulating film, or the like is used, and a transparent one of them is used on the display surface side. The thickness of the substrate is preferably 2 to 2000 μm, more preferably 5 to 1000 μm. If it is too thin, it becomes difficult to maintain the strength and the uniform spacing between the substrates, and if it is thicker than 2000 μm, a thin information display panel is obtained. Inconvenient in case.

  Electrode forming materials include metals such as aluminum, silver, nickel, copper, and gold, indium tin oxide (ITO), indium zinc oxide (IZO), aluminum-doped zinc oxide (AZO), indium oxide, and conductive tin oxide. Examples thereof include conductive metal oxides such as antimony tin oxide (ATO) and conductive zinc oxide, and conductive polymers such as polyaniline, polypyrrole and polythiophene, which are appropriately selected and used. As a method for forming the electrode, a method of patterning the above-described materials into a thin film by a sputtering method, a vacuum deposition method, a CVD (chemical vapor deposition) method, a coating method, or the like, or a metal foil (for example, a rolled copper foil) is laminated. A method or a method of patterning by mixing and applying a conductive agent to a solvent or a synthetic resin binder 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. The electrode thickness is determined in view of conductivity and light transmittance, and is 0.01 to 10 μm, preferably 0.05 to 5 μm. The material and thickness of the electrode provided on the back substrate need not be considered in light transmittance.

If necessary, the shape of the partition provided on the substrate is appropriately set according to the type of display medium involved in display, the shape and arrangement of electrodes to be arranged, and is not limited in general. However, the width of the partition is 2 to 100 μm. The height of the partition wall is adjusted to 10 to 500 μm, preferably 10 to 200 μm. The height of the partition wall arranged for securing the inter-substrate gap is matched with the inter-substrate gap to be secured. The height of the partition wall arranged to partition the inter-substrate space into cells may be the same as or lower than the inter-substrate gap.
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. Any method is used in the present invention.
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 the arrangement is exemplified by a lattice shape, a honeycomb shape or a mesh shape. The 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 state becomes clearer.
Here, 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.

  Next, the chargeable particles constituting the base particles of the display medium particles in the present invention will be described. The chargeable particles can contain a charge control agent, a colorant, an inorganic additive, and the like, if necessary, in the resin as the main component. Examples of resins, charge control agents, colorants, and other additives will be given below.

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

  The charge control agent is not particularly limited. Examples of the negative charge control agent include salicylic acid metal complexes, metal-containing azo dyes, metal-containing oil-soluble dyes (including metal ions and metal atoms), and quaternary ammonium salt systems. Examples thereof include compounds, calixarene compounds, boron-containing compounds (benzyl acid boron complexes), and nitroimidazole derivatives. Examples of the positive charge control agent include nigrosine dyes, triphenylmethane compounds, quaternary ammonium salt compounds, polyamine resins, imidazole derivatives, and the like. In addition, metal oxides such as ultrafine silica, ultrafine titanium oxide, ultrafine alumina, nitrogen-containing cyclic compounds such as pyridine and derivatives and salts thereof, various organic pigments, resins containing fluorine, chlorine, nitrogen, etc. are also charged. It can also be used as a control agent.

  As the colorant, various organic or inorganic pigments and dyes as exemplified below can be used.

Examples of the black colorant include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon and the like.
Examples of blue colorants include C.I. I. Pigment blue 15: 3, C.I. I. Pigment Blue 15, Bituminous Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Metal-free Phthalocyanine Blue, Phthalocyanine Blue Partial Chlorides, Fast Sky Blue, Indanthrene Blue BC, and the like.
Examples of red colorants include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, risor red, pyrazolone red, watching red, calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, Alizarin Lake, Brilliant Carmine 3B, C.I. I. Pigment Red 2 etc.

Yellow colorants include 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 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, cobalt blue, cobalt green, cobalt violet, iron oxide, carbon black, manganese ferrite black, cobalt ferrite black, copper powder, and aluminum powder.
These pigments and inorganic additives can be used alone or in combination. Of these, carbon black is particularly preferable as the black pigment, and titanium oxide is preferable as the white pigment. The above colorant can be blended to produce chargeable particles of a desired color.

  Further, the chargeable particles (hereinafter also referred to as particles) have an average particle diameter d (0.5) in the range of 1 to 20 μm, and are preferably uniform and uniform. If the average particle diameter d (0.5) is larger than this range, the display is not clear. If the average particle diameter d (0.5) is smaller than this range, the cohesive force between the particles becomes too large, which hinders movement as a display medium.

Furthermore, regarding the particle size distribution, the particle size distribution Span shown 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 indicating 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 the chargeable particles is uniform, and movement as a uniform display medium becomes possible.

  Furthermore, when using a plurality of display media, among the chargeable particles constituting the display medium used, the average particle relative to d (0.5) of the chargeable particles having the maximum average particle diameter d (0.5). It is important that the ratio of d (0.5) of chargeable particles having a minimum diameter d (0.5) is 10 or less. Even if the particle size distribution Span is reduced, since the charged particles having different charging polarities move in opposite directions, it is preferable because they can be easily moved by making the particle size of each other comparable, That 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 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 the particle size distribution are obtained from the 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 that includes chargeable particles is driven in a gas space, it is important to manage the gas in the space surrounding the display medium between the panel substrates, which improves display stability. Contribute. Specifically, it is important that the relative humidity at 25 ° C. is 60% RH or less, and preferably 50% RH or less for the humidity of the gas in the gap.
1A, 1B, 2A and 2B, 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), the occupied portion of the display medium 3, the occupied portion of the partition wall 4 (when the partition wall is provided), and the gas portion in contact with the so-called display medium excluding the panel seal portion.
The gas in the gap is not limited as long as it is in the humidity region described above, but dry air, dry nitrogen, dry argon, dry helium, dry carbon dioxide, dry methane, and the like are preferable. This gas must be sealed in the panel so that the humidity is maintained. For example, the display medium is filled and the panel is assembled in a predetermined humidity environment. It is important to apply a sealing material and a sealing method to prevent it.

The distance between the substrates in the information display panel targeted by the present invention is not limited as long as the display medium can be driven and the contrast can be maintained, but is usually adjusted to 2 to 500 μm, preferably 5 to 200 μm.
When the information display panel is a space movement method in charged particle gas, the distance between the substrates is adjusted in the range of 10 to 100 μm, preferably 10 to 50 μm. Furthermore, the volume occupation ratio of the display medium in the gas space between the substrates is preferably 5 to 70%, more preferably 5 to 60%. When it exceeds 70%, the movement of particles as a display medium is hindered, and when it is less than 5%, the contrast tends to be unclear.
As a method for displaying the charged particles by moving them, there is a method in which the charged particles are sealed in a microcapsule together with an insulating liquid, and the microcapsule is arranged between a pair of counter electrodes. The present invention can also be applied to driving various information display panels.

  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.

  First, as the negatively charged mother particles, a cycloolefin resin (ZEONEX 330R: manufactured by Nippon Zeon Co., Ltd.) 100% by mass and titanium dioxide (Typaque CR-90: manufactured by Ishihara Sangyo Co., Ltd.) 100% by mass is a biaxial kneader. Kneaded with a solvent, finely pulverized with a jet mill (Lab Jet Mill IDS-LJ type: manufactured by Nippon Pneumatic Co., Ltd.), classified using a classifier (MDS-2: Nippon Pneumatic Industry), and spheroidized into a solvent Using an apparatus (MR-10: Nippon Pneumatic Kogyo Co., Ltd.), the mixture was spheroidized to obtain negatively charged mother particles A having an average particle size R0 = 8.1 μm.

  Further, as the child particles for surface treatment, commercially available spherical sol-gel silica (manufactured by Nippon Shokubai Co., Ltd .: Seahoster KE-P30) was used.

  Next, surface treatment was performed with an alkyl group-containing silane which has been conventionally performed. Specifically, decylsilane having a treatment amount of 0.5% by mass was used as the surface treatment agent (primary treatment). Specifically, with respect to 100% by mass of sol-gel silica particles, 0.5% by mass of decylsilane (manufactured by Shin-Etsu Silicone: Decyltrimethoxysilane KBM-3103C) and 900% by mass of toluene (Kanto Chemical Reagent) ) With a three-one motor equipped with a stirring blade at room temperature for 4 hours, cast into a tray, remove toluene in a vacuum oven, and further heat in a vacuum oven at 120 ° C for 2 hours to complete the reaction. To produce primary surface-treated particles.

  Next, surface treatment was performed using hexamethyldisilazane as a surface treatment agent (secondary treatment). Specifically, for the child particles in the Henschel mixer (KM5C: Mitsui Mining Co., Ltd.), the amount of the surface treatment agent is adjusted and dropped as shown in Examples 1 to 4 below. The mixture was stirred for 5 minutes at 3000 rpm to clean the particles adhering to the inside of the tank, and further stirred for 10 minutes, then developed on a metal pad and reacted in a hot air oven at 120 ° C. for 2 hours.

After finishing the primary treatment and the secondary treatment, 95% by mass of the negatively charged mother particles A and the child particles a are combined with a mechanofusion device (manufactured by Hosokawa Micron) at a rotational speed of 4000 rpm and an operation time of 90 minutes. Composite particles Aa were obtained.
Furthermore, 2% by weight of silica fine particles (H3004: Nippon Clariant Co., Ltd.) prepared by a vapor phase method was added to the composite particles Aa, and stirred with a Henschel mixer to obtain negatively charged white particles Aa1. Thereafter, when the negatively charged particles Aa1 were filled with a layer thickness of 300 μm and a surface voltage of 1000 V was applied by corona discharge, the charge decay rate after 12 hours was measured. The results are shown in Table 1 below.

From the results in Table 1, in Examples 1 to 5 in which the child particles used as the display medium particles were surface-treated with decylsilane and then further treated with hexamethyldisilazane (secondary treatment), surface treatment with decylsilane was performed. It can be seen that both the charge decay rate of the child particles themselves and the charge decay rate after compositing are lower than those of Comparative Example 1 in which only the process is performed.
Moreover, among Examples 1-5, the processing amount of the surface treatment agent in the secondary treatment is 2.0% by mass in Examples 1-4, which is 2.0% by mass or more based on the weight of the child particles. Compared with Example 5 which was carried out at 1.5% by weight, which is less than 1%, particles having a lower charge decay rate and good characteristics could be obtained.
In addition, even when the child particles used as the display medium particles are surface-treated with decylsilane and further post-treated with hexamethyldisilazane (secondary treatment), the treatment amount of the surface treatment agent in the secondary treatment is In the case of Example 6 performed at 60% by mass greater than 50% by mass with respect to the weight of the child particles, the ultrafine particles produced by curing with the surplus treatment agents inhibit the embedding of the child particles in the mother particles. As a result, it was found that a composite failure occurred.
In this example, it is determined that particles having the most preferable characteristics have been obtained when the charge decay rate after compounding is 12% or less.

  The information display panel using the display medium particles of the present invention is an electronic display such as a display unit of a mobile device such as a notebook computer, PDA, mobile phone, or handy terminal, an electronic book, an electronic newspaper, or an electronic manual (instruction manual). Paper, signboards, posters, bulletin boards such as blackboards, calculators, home appliances, car supplies, display units, point cards, card displays such as IC cards, electronic advertising, electronic point of purchase (POP), It is preferably used as an electronic price tag, an electronic shelf label, an electronic score, a display unit of an RF-ID device, or a display unit (so-called rewritable paper) that performs display rewriting by connecting to an external display rewriting unit.

DESCRIPTION OF SYMBOLS 1, 2 Substrate 3W White display medium 3Wa White negatively charged particle 3B Black display medium 3Ba Black positively charged particle 4 Partition 5, 6 Electrode 11 Display medium particle 12 Base particle 13 Child particle

Claims (4)

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 forming a display medium used for an information display panel that moves the display medium to display information. Particles for a display medium,
The display medium particles have a configuration in which child particles are embedded in the surface of the mother particles,
The particles for display media, wherein the child particles are obtained by subjecting metal oxide fine particles to a primary surface treatment with an alkyl group-containing silane and then a secondary surface treatment with a disilazane compound.   The display medium particle according to claim 1, wherein the disilazane compound is hexamethyldisilazane.   The display medium particle according to claim 1, wherein the disilazane compound is 2% by mass or more and 50% by mass or less with respect to the child particle.   The display metal particles according to claim 1, wherein the metal oxide fine particles are silica fine particles.

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