JP4858896B2 - Display device using electrophoresis or rotation of particles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a display device that displays an image using electrophoresis or rotation of particles.
[0002]
[Prior art]
A sheet-like display medium and a display device, which are called electronic paper, paper-like display, digital paper, and the like, and display an image by changing an optical absorptance or optical reflectance by an electric field have been proposed. Japanese Patent Application Laid-Open No. 1-86116 discloses a display device having a microcapsule in which a solvent in which electrophoretic particles are dispersed is colored and the solvent is encapsulated. Japanese Patent Laid-Open No. 8-234686 discloses a display device having a microcapsule including a rotating body in which hemispheres having different colors and electrical characteristics are combined. In addition, a display device including a liquid crystal / polymer composite film including a dichroic dye and a smectic liquid crystal is known.
[0003]
These display devices have a memory property that can hold image information without a power source. Further, since a display layer can be formed on a PET film on which electrodes are formed, it is expected as a sheet-type display device that can be thin, light, and bent.
[0004]
The display media described in US Pat. Nos. 4,126,854 and 4,143,103, that is, two hemispheres having different colors and charging characteristics on the surface of charged particles A display medium including charged particles in which a ridge-like region is formed exhibits excellent contrast as compared with other methods.
[0005]
With reference to FIG. 5, the operation principle of the display medium described in the specification of US Pat. No. 4,126,854 will be described.
[0006]
A plurality of voids 101 are formed inside the transparent substrate 100. The charged particles 103 are loaded in the voids 101 and the translucent liquid 102 is filled. On the surface of the charged particle 103, two hemispherical areas, for example, a white area and a black area, which are different from each other in both color and charging characteristics are defined. Surface charges generated at the solid-liquid interface are accumulated on the surfaces of the charged particles 103. Since the charging characteristics of the white area and the black area are different, the surface charge densities of the two areas are different.
[0007]
For this reason, when an electric field is generated in the gap 101, the charged particles 103 are electrophoresed and rotated in accordance with the direction of the electric field. For example, FIG. 5A shows a state where the charged particles 103 are sinking under the void 101 with the white region facing down. When an electric field is generated, the charged particles 103 float while rotating as shown in FIG. Eventually, as shown in FIG. 5C, the charged particles 103 move upward in the gap 101 while directing the white region upward.
[0008]
In the state of FIG. 5A, when the display device is viewed from above, black is visually recognized. In the state of FIG. 5C, white is visually recognized. In this way, the white display and the black display can be switched by rotating the charged particles 103.
[0009]
Japanese Patent Application Laid-Open No. 11-212501 describes a method of driving a sheet type display device with a circuit having a simple matrix configuration. According to this method, it is possible to prevent a reduction in image formation time and a decrease in image quality due to crosstalk. A method of using charged particles as a dipole electret is disclosed in Japanese Patent Laid-Open No. 11-327470. Dipole electrets are formed by dissolving a wax or polymer medium wrapped in a shell and solidifying it with an electric field applied. JP-A-9-18687 discloses a method using a ferroelectric material such as barium titanate or lead titanate as a material for charged particles. In either method, polarization is induced in charged particles by an electric field applied from the outside, and polarization is maintained by resin orientation or spontaneous polarization. By maintaining the polarization, the voltage (threshold voltage) at which the charged particles begin to migrate in the dielectric liquid can be reduced.
[0010]
Japanese Patent Application Laid-Open No. 11-119704 discloses a display device using charged particles containing a quaternary ammonium compound by adding a surfactant to a dielectric liquid. Thereby, display unevenness due to aggregation of charged particles can be prevented.
[0011]
[Problems to be solved by the invention]
In the conventional method of reducing the driving voltage, it is difficult to produce charged particles because there are many restrictions on the manufacturing method and materials of charged particles.
[0012]
In the method of forming the dipole electret, the pigment added therein is precipitated during the period in which the wax or polymer medium is dissolved, and the regions having different colors are mixed. For this reason, the contrast is lowered. Further, in the method using a ferroelectric material as the material of the charged particles, it is difficult to contain the pigment inside the particles. Therefore, the pigment must be deposited on the hemispherical region of the charged particle surface. In addition, the ferroelectric material is inferior in workability as compared with wax and resin.
[0013]
In the method of adding a surfactant to the dielectric liquid, if the addition amount is small, aggregation of the charged particles can be suppressed and the dispersion effect can be enhanced, but the charge amount of the charged particles cannot be increased.
[0014]
An object of the present invention is to provide a technique capable of reducing a driving voltage of a display device that displays an image by performing electrophoresis or rotational movement of charged particles.
[0015]
[Means for Solving the Problems]
According to one aspect of the invention,
A substrate defining a plurality of cavities;
A dielectric liquid containing a first liquid and a second liquid filled in the interior of each of the cavities of the substrate,
Particles immersed in the dielectric liquid to generate a surface charge at the solid-liquid interface ;
An electrode for generating an electric field in the cavity ;
The second liquid is charged with the same polarity as the charge that appears on the surface of the particles when the particles are immersed in the first liquid ;
There are a plurality of the particles filled in each of the cavities, and when an electric field is generated in the cavities, the particles are electrophoresed in the dielectric liquid and are unevenly distributed in the cavities. A display device is provided.
[0016]
According to another aspect of the invention,
A substrate defining a plurality of cavities;
A dielectric liquid filled in each of the cavities of the substrate, comprising a silicone oil and a modified silicone oil;
Particles immersed in the dielectric liquid to generate a surface charge at the solid-liquid interface;
Possess an electrode for generating an electric field in the cavity,
A display device in which the modified silicone oil is charged to the same polarity as the surface charge of the particles is provided.
[0017]
By using the above-described dielectric liquid, it is possible to reduce the driving voltage.
In addition, sticking and aggregation of particles can be suppressed.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a sectional view of a display device according to a first embodiment of the present invention. A plurality of voids 11 are formed inside a sheet substrate 10 having a thickness of 1 μm. As the sheet substrate 10, a two-component silicone rubber (KE106 manufactured by Toray Dow Corning) was used. Each void 11 is filled with charged particles 12 and filled with a dielectric liquid 13. The charged particles 12 are composed of a white hemisphere portion and a black hemisphere portion. The black hemisphere portion is formed of a polyester resin colored with carbon black, and the white hemisphere portion is formed of a polyester resin colored with titanium oxide. The particle size of the charged particles 12 is about 300 μm. The surface of the hemispherical part containing carbon black and the surface of the hemispherical part containing titanium oxide have different charging characteristics.
[0019]
The dielectric liquid 13 is a mixed liquid obtained by adding 1% by weight of fluorine-modified silicone oil (FS 1265, 300 cs, manufactured by Toray Dow Corning) to dimethyl silicone oil (SH 200, 10 cs, manufactured by Toray Dow Corning).
[0020]
A transparent film 17A on which a transparent electrode 15A made of indium tin oxide (ITO) is formed is in close contact with one surface of the sheet substrate 10. Similarly, a transparent film 17B on which a transparent electrode 15B made of ITO is formed is in close contact with the other surface. The planar shape of the transparent electrodes 15A and 15B is a square having a side length of 1 cm. The power source 21 applies a driving voltage to the electrodes 15A and 15B.
[0021]
Next, a method for manufacturing charged particles used in the display device according to the first embodiment will be described.
[0022]
270 parts by weight of a polyester resin (softening point 100 ° C.) and 30 parts by weight of titanium oxide (KA-30S manufactured by Titanium Industry Co., Ltd.) are kneaded with a roll mill to obtain a white block resin. Next, 294 parts by weight of a polyester resin and 6 parts by weight of carbon black (Regal 660 manufactured by Cabot) are kneaded by a roll mill to obtain a black block resin.
[0023]
Each of these bulk resins is heated to 120 ° C. and extruded from a nozzle having a diameter of 150 μm to obtain a fibrous resin. A white fibrous resin and a black fibrous resin are heated and bonded to produce a fibrous resin having a cross section divided into regions of two colors. The fibrous resin is cut at a pitch of 300 μm to obtain particles divided into two colors. It is made spherical by immersing it in silicone oil at a temperature of 100 ° C. (SRX310 manufactured by Toray Dow Corning). In this way, charged particles composed of a white hemisphere portion and a black hemisphere portion are obtained. The charged polarity of the charged particles was negative.
[0024]
Next, a method for manufacturing the display device shown in FIG. 1 using the charged particles will be described.
[0025]
By depositing an ITO film on a PET film having a thickness of 150 μm, a laminated film composed of the transparent film 17A and the transparent electrode 15A and a laminated film composed of the transparent film 17B and the transparent electrode 15B are produced. A synthetic paper having a thickness of 80 μm (manufactured by Oji Oil Chemical Co., Ltd.) is attached to the surface of one laminated film on the transparent film 17B side.
[0026]
The produced charged particles are dispersed in a two-part silicone rubber (KE 106 manufactured by Toray Dow Corning) and uniformly applied on a Teflon sheet so as to have a thickness of 500 μm. The silicone rubber is cured in an environment of 80 ° C. for 8 hours.
[0027]
The cured silicone rubber is immersed for 12 hours in a mixed solution obtained by adding 1% by weight of fluorine-modified silicone oil to dimethyl silicone oil. The silicone rubber swells, and voids 13 filled with a mixed liquid of silicone oil and fluorine-modified silicone oil are formed at the interface between the charged particles and the silicone rubber.
[0028]
The swollen silicone rubber is sandwiched between laminated films on which transparent electrodes are formed, and the laminated films are bonded together with a one-component silicone rubber. Through the steps so far, the display device shown in FIG. 1 is obtained.
[0029]
When an AC voltage of 100 V is applied between the transparent electrodes 15A and 15B of the display device according to the first embodiment, the white display state and the black display state can be reversed every half cycle up to a frequency of 2 Hz. Met. Even after being allowed to stand for 1 week at room temperature, the charged particles did not stick to the silicone rubber and could be operated stably.
[0030]
For comparison, a display device was produced in which fluorine-modified silicone oil was not added to the dielectric liquid filled in the gap. Although a voltage of 2000 V was applied between the transparent electrodes of this display device, the movement of charged particles hardly occurred.
[0031]
Furthermore, instead of fluorine-modified silicone oil, a display device in which an amino-modified silicone oil exhibiting positive polarity (BY16-853, 30 cs manufactured by Toray Dow Corning) was added was produced. Although a voltage of 2000 V was applied between the transparent electrodes of this display device, the movement of charged particles hardly occurred.
[0032]
From the evaluation results of this comparative example, it is considered preferable to use a modified silicone oil that is charged to the same polarity as the charged particles of the charged particles as the modified silicone oil added to the silicone oil. This is presumably because when the modified silicone oil is added, the chargeability of the charged particles is strengthened and the surface charge density increases, and the migration and rotation of the charged particles occur even in a small electric field.
[0033]
Examples of modified silicone oils exhibiting negative polarity include chloroalkyl-modified silicone oils, carboxyl-modified silicone oils (BY16-750, 125 cs manufactured by Toray Dow Corning), phenol-modified silicone oils (BY16-752, 80 cs manufactured by Toray Dow Corning), etc. Is mentioned.
[0034]
In addition, when the electric charge which appears on the surface of a charged particle is positive polarity, it is possible to use amino modified silicone oil as modified oil added to silicone oil.
[0035]
Hereinafter, an example of a method for determining the charging polarity will be described. In a glass cell, charged particles are dispersed in silicone oil, and a DC electric field is applied to the cell. The charge polarity can be determined from the moving direction of the charged particles at this time. For example, the charged particles if close to the positive electrode side, the charged particles can be said to be negatively charged property.
[0036]
The charged polarity of the added modified silicone oil can be determined by adding the modified silicone oil to the silicone oil and measuring the change in the moving speed of the charged particles. For example, when the speed at which the charged particles approach the positive electrode side is increased by the addition of the modified silicone oil, it is considered that an electrical repulsion has occurred between the added oil and the charged particles, and the charged polarity of the added oil depends on the charged particles. It is considered to be the same as the charging polarity. On the other hand, when the moving speed of the charged particles decreases, the charged polarity of the added oil is considered to be opposite to the charged polarity of the charged particles.
[0037]
In the above embodiment, silicone oil was used as the dielectric liquid. In addition, aliphatic hydrocarbons, aromatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, various esters, various vegetable oils and mineral oils were used. Can be used. In particular, silicone oil is suitable for use as a dielectric liquid because it is chemically stable and has no odor, and can be easily obtained with various molecular weights and viscosities.
[0038]
As an additive to be added to the dielectric liquid, it is desirable that the additive is highly compatible with the dielectric liquid, has a viscosity equivalent to that of the dielectric liquid, and is chemically stable. In particular, a modified product based on a dielectric liquid and having a highly polar functional group is desirable. Examples of modified silicone oils include modified silicone oils such as fluorine modified, chloroalkyl modified, methyl hydrogen modified, alcohol modified, carboxyl modified, mercapto modified, polyether modified, amino modified and epoxy modified. Modified silicone oils are broadly classified into side chain type, both end types, one end type, and both side chain end types depending on the position where the organic group is introduced. Any type of modified silicone oil may be used. The addition amount of the modified silicone oil is preferably set to such an extent that the insulation degree of the dielectric liquid is not extremely lowered.
[0039]
In the first embodiment, polyester is used as the material of the charged particles, but other resins such as polyethylene, polystyrene, polyvinyl chloride, polypropylene, polyacetal, polycarbonate, acrylic, and nylon may be used alone. You may mix and use these resin. Furthermore, a monomer copolymer constituting these resins may be used. As colorants, soluble azo, monoazo, disazo and other azo pigments, phthalocyanine, quinacridone, periline, perinone, isoindoline and other polycyclic pigments, carbon black pigments, titanium oxide, silica White pigments such as alumina and calcium carbonate can be used. The resin to which the pigment has been added can be made into particles by a known method such as injection molding, blow molding, extrusion molding, calendar molding or the like.
[0040]
In the first embodiment, the silicone rubber is swollen with the silicone oil to form a void filled with the dielectric liquid at the interface between the charged particles and the sheet base material. It is also possible to manufacture a display device having a structure. For example, a method in which charged particles are coated with a toluene-soluble resin, dispersed in polyvinyl alcohol and cured, and then immersed in toluene is “A Newly Developed Electrical Twisting Ball Display” (M. Saitoh et al .: Proc. of SID, Vol. 23/4, 1982). Japanese Patent Application No. 7-343133 discloses a method of forming microcapsules by covering a dielectric liquid and charged particles with a resin film using interfacial polymerization and dispersing the microcapsules in a sheet substrate. Has been.
[0041]
In the first embodiment, the pair of transparent electrodes are made of ITO. However, one electrode (display surface side electrode) may be transparent and the other electrode opaque. As the electrode material, a metal, a conductive polymer, a resin in which conductive powder is dispersed, or the like can be used. Examples of metals include gold, silver, copper, and iron.
[0042]
Examples of the conductive polymer include polyacetylene polymers, polyphenylene polymers, heterocyclic polymers, ionic polymers, ladder polymers, and the like. Specific examples of the polyacetylene polymer include polyacetylene and poly (1,6-heptadiyne). Specific examples of the polyphenylene-based polymer include polyparaphenylene, polymetaphenylene, polyphenylene vinylene, polyphenylene oxide, polyphenylene sulfide, polypyrene, polyazulene, and polyolefin. Examples of the heterocyclic polymer include polypyrrole, polythiophene, polyselenophene, polytellurophene, polythienylene vinylene, and the like. Specific examples of the ionic polymer include polyanilene. Examples of the ladder-like polymer include polyacene, polyphenanthrene, polyperinautane and the like.
[0043]
Examples of the conductive powder dispersed in the resin include metals such as gold, silver, copper, and iron, and graphite. In addition, ITO powder having high transparency and conductivity can be used. As the binder resin for dispersing the ITO powder, polyester, epoxy, silicone, polyvinyl acetal, polycarbonate, acrylic, urethane, or the like can be used alone or as a mixture of these resins.
[0044]
The thickness of the conductive resin film is preferably set to 0.1 to 20 μm in order to make the display device thin and reduce the change in color.
[0045]
In addition, it is preferable to provide a resin protective film on the electrode on the display surface side. This protective film can be formed, for example, by applying a solution obtained by diluting a known dielectric resin with a solvent onto the electrode and drying it. Examples of the dielectric resin used for the protective film include polyester, epoxy, silicone, polyvinyl acetal, polycarbonate, acrylic, and urethane. The thickness of the protective film is preferably 0.1 to 20 μm in order to reduce the influence on the total thickness of the display device.
[0046]
Next, a display device according to a second embodiment of the present invention will be described with reference to FIGS.
[0047]
FIG. 2 is a sectional view of a display device according to the second embodiment. One transparent electrode 15B shown in FIG. 1 is divided into a plurality of pixel electrodes. The diameter of the charged particles 12 is less than the size of one pixel. The DC power source 25 applies a positive voltage to the transparent electrode 15A. The drive circuit 20 selectively applies a signal voltage to a specific electrode among the plurality of pixel electrodes 15 </ b> B based on a control signal from the control circuit 22.
[0048]
3A and 3B are plan views of the pixel electrode 15B and the transparent electrode 15A, respectively. A plurality of pixel electrodes 15B are arranged in a matrix. A wiring 18 is connected to each pixel electrode 15B. The wiring 18 extends between the pixel columns and extends to an external connection terminal provided in the vicinity of the edge of the display device. Image display can be performed by selectively applying a signal voltage to the plurality of pixel electrodes 15 </ b> B through the wiring 18.
[0049]
FIG. 3C shows another configuration example of the transparent electrode. One transparent electrode 15C may be a plurality of linear electrodes extending in the column direction, and the other transparent electrode 15D may be a plurality of linear electrodes extending in the row direction. By applying a voltage between the specific electrodes 15C and 15D, an electric field can be generated at the intersection.
[0050]
In the first and second embodiments, a voltage is applied to the pair of electrodes 15A and 15B to generate an electric field in the space where the charged particles 12 are disposed. However, the writing is separated from the display layer. It is also possible to perform writing using this driving device. For example, writing is performed by scanning the display layer while applying a signal voltage to each electrode of the electrode array using a writing device including a small battery, wireless communication means, a one-dimensional electrode array, and a driver for driving the same. It can be performed. Writing can also be performed by using a pen-like writing device provided with a single electrode at the tip and tracing the surface of the display layer.
[0051]
Next, a display device according to a third embodiment of the present invention will be described with reference to FIG. In the first and second embodiments, one charged particle is loaded in one gap, but in the third embodiment, as disclosed in JP-A-11-119704, 1 A large number of charged particles are loaded in one microcapsule.
[0052]
FIG. 4 is a sectional view of a display device according to the third embodiment. A pair of transparent substrates 30 and 31 made of a glass plate or a plastic sheet are opposed to each other with a predetermined gap therebetween. A large number of microcapsules 32 are arranged in the gap. Each of the microcapsules 32 includes a colored dielectric liquid 33 and a large number of charged particles 34. Such a microcapsule can be produced by a method that is already known in the art. For example, a phase separation method from an aqueous solution as shown in the specifications of U.S. Pat. Nos. 2,800,047 and 2,800,498, JP-B-38-19574, JP-B-42-446, and JP-B-42-771 It can be produced using an interfacial polymerization method as shown in the publication.
[0053]
A striped transparent electrode 35 is formed on the inner surface of the transparent substrate 30, and a striped transparent electrode 36 is also formed on the inner surface of the other transparent substrate 31. The transparent electrodes 35 and 36 are orthogonal to each other and are driven in a simple matrix. 4 shows a state in which only the transparent substrate 31 is rotated by 90 degrees for convenience of explanation. Ideally, the microcapsules 32 are spread in one layer so as to be in a close-packed state, and are fixed between the substrates by a fixing agent 38 made of an ultraviolet curable adhesive or the like.
[0054]
The colored dielectric liquid 33 is obtained by adding a modified silicone oil to a silicone oil. The added modified silicone oil is charged to the same polarity as the charged polarity of the charged particles 34. By applying a voltage between the electrodes 35 and 36, the charged particles can be electrophoresed and unevenly distributed on the electrode 35 side or the electrode 36 side. When the microcapsules 32 in which the charged particles 34 are unevenly distributed on the electrode 36 side are viewed from the surface on the electrode 36 side, the color of the charged particles 34 is visually recognized. Conversely, when the charged particles 34 are unevenly distributed on the electrode 35 side, the color of the dielectric liquid 33 is visually recognized. By adding the modified silicone oil, the charged particles 34 can be prevented from sticking or agglomerating.
[0055]
Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.
[0056]
【Effect of the invention】
As described above, according to the present invention, it is possible to reduce the drive voltage of a display device that performs image display by causing electrophoresis or rotation of charged particles.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a display device according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view of a display device according to a second embodiment of the present invention.
FIG. 3 is a plan view showing an electrode arrangement of a display device according to a second embodiment of the present invention.
FIG. 4 is a cross-sectional view of a display device according to a third embodiment of the present invention.
FIG. 5 is a cross-sectional view of charged particles and voids for explaining a rotating operation of charged particles.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Sheet | seat base material 11 Space | gap 12 Charged particle 13 Dielectric liquid 15A, 15B Transparent electrode 17A, 17B Transparent film 21 Power supply 22 Control apparatus 25 DC power supply 30, 31 Transparent substrate 32 Microcapsule 33 Dielectric liquid 34 Charged particle 35, 36 Transparent electrode

Claims (3)

A substrate defining a plurality of cavities;
A dielectric liquid containing a first liquid and a second liquid filled in the interior of each of the cavities of the substrate,
Particles immersed in the dielectric liquid to generate a surface charge at the solid-liquid interface ;
An electrode for generating an electric field in the cavity ;
The second liquid is charged with the same polarity as the charge that appears on the surface of the particles when the particles are immersed in the first liquid ;
There are a plurality of the particles filled in each of the cavities, and when an electric field is generated in the cavities, the particles are electrophoresed in the dielectric liquid and are unevenly distributed in the cavities. Display device that performs . A substrate defining a plurality of cavities;
A dielectric liquid comprising a first liquid and a second liquid filled in each of the cavities of the substrate;
Particles immersed in the dielectric liquid to generate a surface charge at the solid-liquid interface;
An electrode for generating an electric field in the cavity;
Have
The second liquid is charged with the same polarity as the charge that appears on the surface of the particles when the particles are immersed in the first liquid;
The particles, both color and charge characteristics contains at least two different parts to each other, when an electric field is generated spatial sinusoids rotated particles, intends rows displayed by changing the particle orientation Viewing equipment. A substrate defining a plurality of cavities;
A dielectric liquid filled in each of the cavities of the substrate, comprising a silicone oil and a modified silicone oil;
Particles immersed in the dielectric liquid to generate a surface charge at the solid-liquid interface;
An electrode for generating an electric field in the cavity,
The display device in which the modified silicone oil is charged with the same polarity as the surface charge of the particles.

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