Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J3/00—Typewriters or selective printing or marking mechanisms characterised by the purpose for which they are constructed
  • B41J3/407—Typewriters or selective printing or marking mechanisms characterised by the purpose for which they are constructed for marking on special material
  • B41J3/4076—Typewriters or selective printing or marking mechanisms characterised by the purpose for which they are constructed for marking on special material printing on rewritable, bistable "electronic paper" by a focused electric or magnetic field
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/02—Printing inks
  • C09D11/03—Printing inks characterised by features other than the chemical nature of the binder
  • C09D11/033—Printing inks characterised by features other than the chemical nature of the binder characterised by the solvent
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/02—Printing inks
  • C09D11/03—Printing inks characterised by features other than the chemical nature of the binder
  • C09D11/037—Printing inks characterised by features other than the chemical nature of the binder characterised by the pigment
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/165—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field
  • G02F1/166—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field characterised by the electro-optical or magneto-optical effect
  • G02F1/167—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field characterised by the electro-optical or magneto-optical effect by electrophoresis
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/165—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field
  • G02F1/1675—Constructional details
  • G02F2001/1678—Constructional details characterised by the composition or particle type

Definitions

• the present invention relates to the field of inks for electrophoretic display devices, and more particularly to polychromatic inks.
• the invention relates to a polychromatic electrophoretic ink, to a process for manufacturing said ink, to a polychromatic electrophoretic display device comprising said ink and to a use of said polychromatic electrophoretic ink for producing a device. polychromic electrophoretic display.
• LCD liquid crystal display
• plasma plasma type
• paper printing the electronic displays
• the electronic displays are a great advantage because they are able to quickly update information displayed and therefore to change content, it is also said that they are rewritable.
• This type of display is however complex to achieve since its manufacture requires clean room work and advanced electronics. It is therefore relatively expensive. Displays made by print on paper, meanwhile, can be mass produced because very inexpensive, but do not re-register information over the old. This type of display is part of non-rewritable displays.
• This type of display is based on the EPIDS (ElectroPhoretic Image DisplayS) technology.
• EPIDS ElectroPhoretic Image DisplayS
• This technology consists of dispersing charged particles in a nonconductive medium between two parallel electrodes. More specifically, the display comprises a conductive surface electrode, a cavity comprising pixels filled with electrophoretic ink, and a bottom electrode connected to transistors for controlling each pixel.
• the pixels can be made in different ways. They can for example be made by means of a grid which compartmentalizes the cavity in as many pixels as necessary for the display, or they can be in the form of microcapsules, each microcapsule defining a pixel and being filled with said ink .
• the electrophoretic ink has generally negatively charged white nanoparticles dipped in a black dye.
• the white nanoparticles of each pixel When applying an electric field, the white nanoparticles of each pixel will migrate towards one or the other of the electrodes. Thus, when a negative electric field is applied, the white nanoparticles are placed on one end of the pixel revealing their white color or the color of the black dye according to their position relative to the surface of the display. Therefore, by placing millions of pixels in the display cavity and controlling them by electric fields, by means of an electronic circuit for managing the display of information, a two-color image can be generated.
• One of the advantages of this type of display is that the contrast obtained depends directly on the migration of the nanoparticles and the color thereof. In addition, the display obtained is bistable since the image remains in place even after the electric field is cut.
• Such displays based on the EPIDS technology are particularly envisioned for equipping mobile phones, electronic tablets, electronic books or on-board displays on smart cards for example.
• screens based on EPIDS technology currently only display two-color information.
• display and propose a full-color display in order to be competitive in the screens market.
• the subject of the invention is a polychromic electrophoretic ink, comprising at least four types of particles dispersed in an apolar organic medium, each type of particles containing a pigment of a color associated with it, having a positive electrostatic charge. or negative, characterized in that at least one of the above types of particles has a magnetic property (magnetic core) so that each type of particles can migrate in a predetermined manner under the combined action of an electrostatic force and a magnetic return force.
• a polychromic electrophoretic ink comprising at least four types of particles dispersed in an apolar organic medium, each type of particles containing a pigment of a color associated with it, having a positive electrostatic charge. or negative, characterized in that at least one of the above types of particles has a magnetic property (magnetic core) so that each type of particles can migrate in a predetermined manner under the combined action of an electrostatic force and a magnetic return force.
• the ink comprises at least two types of magnetic core particles and two types of non-magnetic particles. Both types of magnetic core particles are further electrostatically charged respectively positively and negatively. Likewise, the two types of non-magnetic particles are also electrostatically charged respectively positively and negatively.
• Both types of magnetic core particles are each associated with a color. Each magnetic core is covered by the pigment associated with it, and then encapsulated in a functional polymer electrostatically chargeable respectively positively and negatively. Likewise, each type of non-magnetic particle is associated with a color. The pigment chosen for a non-magnetic particle type is encapsulated in a functional polymer electrostatically chargeable respectively positively and negatively.
• three of the types of particles each contain a pigment such that, according to their migration, said three types of particles are capable of displaying the colors of the RGB system (acronym for the additive synthesis system "Red Green Blue” which is based on the three primary colors) or the colors of the CMY system (acronym for the "Cyan Magenta Yellow” subtractive synthesis system).
• the fourth type of particles preferably contains a pigment of white or black color.
• the process for producing this polychromic electrophoretic ink consists in synthesizing each type of particles separately in an organic medium apolar such as an oil or an organic solvent apolar or slightly polar, such as toluene or an alkane for example, and then to mix them.
• apolar organic medium in which the syntheses of the various particles have taken place, advantageously constitutes the dispersing medium of the ink or, at least, it is compatible with the latter.
• magnetic core particles their syntheses consist in covering a magnetic core with an inorganic pigment and then encapsulating it in a chargeable functional polymer.
• the synthesis of the magnetic core consists in synthesizing stable magnetic particles in apolar organic medium, then in synthesizing a latex containing the magnetic core, by polymerization techniques in a heterogeneous medium in aqueous or organic media.
• polar or apolar from a monomer of styrene or methyl methacrylate.
• latex means a dispersion in a solvent of particles formed partially or entirely of polymer.
• the magnetic particles synthesized or used are metal oxides.
• a magnetic latex is first synthesized and then covered with a pigment and finally encapsulated in an electrostatically chargeable polymer shell.
• the polymers forming the outer shell have acid units (for the negative particles), or basic (for the positive particles). Therefore, a simple acid-base reaction allows these patterns to tear or capture a proton and thus to acquire the respective negative or positive charge desired.
• acid particles instead of capturing a proton, they can also capture any chemical group that can bind to a nitrogen atom of the basic units.
• Magnetic latex still called magnetic core in the following description, is manufactured in several steps.
• a first step is to prepare an organic ferrofluid, according to a process known as “process Massart ".
• This process consists of co-precipitating ferric chloride (FeCl 3 ) and ferrous chloride (FeCl 2 ) in an aqueous medium to form magnetite (Fe 3 O 4 ).
• This co-precipitation takes place in a basic medium, in the presence of concentrated ammonia.
• Oleic acid then makes it possible to pass from an aqueous ferrofluid to a ferrofluid in the organic phase, by grafting, on the surface of the magnetite nanoparticles, carbon chains.
• a second step then consists in synthesizing a magnetic latex intended to encapsulate the magnetite obtained and thus to form the core of the magnetic particle.
• the magnetite synthesized in the first step is dispersed in hexadecane, which is a very hydrophobic agent, with styrene which is the monomer used to encapsulate magnetite.
• Sodium dodecasulphate (SDS) for example is used as a surfactant, and potassium persulfate is used as the initiator of the polymerization.
• nonionic surfactants such as Tween 80 (Polysorbate 80) or Span 80 (sorbitan monooleate) may also be used.
• a pigment is then precipitated on the surface of this magnetic core, by hydrolysis of a precursor.
• This step of encapsulation of a colored magnetic particle consists in dispersing said colored magnetic particle in said apolar organic medium, then in synthesizing at least one stable polymer latex in said organic medium, said latex precipitating around said particle to form a shell protective, said synthesis of the latex being carried out by polymerization, in said organic medium, of an electrostatically chargeable functional monomer, from a combined use of a macro-initiator and a co-initiator.
• an associated pigment is encapsulated directly in a polymer that can be loaded according to the encapsulation process that has just been described.
• the ink thus manufactured is then used in particular for producing a polychromic electrophoretic display device.
• the invention furthermore relates to a polychromatic electrophoretic display device comprising the ink which has just been described.
• This device comprises a conductive surface electrode, a cavity comprising cells filled with polychrome ink, each cell being in fluid communication with its neighbor and defining a pixel, a bottom electrode comprising a contact pad under each pixel, each pad being connected to a transistor of an integrated circuit for controlling the application of an electrostatic force on each pixel, and finally a magnetic means adapted to apply a magnetic restoring force on the magnetic core particles.
• the magnetic means may advantageously be chosen from the following elements: a magnetic tape, or an electromagnet, for example.
• FIG. 1 represents a very simplified diagram of 4 pixels juxtaposed with a display in FIG. which are diagrammatically the four different types of particles composing the polychromatic electrophoretic ink.
• Each pixel is controlled on the one hand by a magnetic force and on the other hand by a different electrostatic force, so that one or more different types of particles migrate to the surface electrode in each of the pixels, so that get a full color display.
• Electrophoretic ink is made by mixing all types of particles separately.
• the synthesis of a magnetic or amagnetic particle is based on the same process with more or fewer steps. In this example is described the synthesis of a white particle with a magnetic core. Of course, this synthesis can be performed with any pigment to obtain the desired color particle.
• the first steps of the synthesis consisting of preparing a magnetic core (steps 1 and 2), then covering it with a pigment (step 3) will not be reproduced.
• 1st stage preparation of an organic ferrofluid:
• the synthesis of the ferrofluid is carried out according to a process known as the "Massart process”. This process consists in co-precipitating ferric chloride (FeCl 3 ) and ferrous chloride (FeCl 2 ) in an aqueous medium to obtain magnetite (Fe 3 O 4 ).
• FeCl 3 ferric chloride
• FeCl 2 ferrous chloride
• magnetite Fe 3 O 4
• 180 g of FeCl 2 100 ml of HCl and 500 ml of water are mixed in a beaker.
• Chloridic acid (HCI) is added at the beginning of the synthesis essentially to facilitate the dissolution of FeCl 2 .
• oleic acid makes it possible to pass from a ferrofluid in aqueous phase to a ferrofluid in organic phase by grafting carbon chains on the surface of the nanoparticles of magnetite.
• the ferrofluid is then decanted, washed and then re-dispersed in the organic phase in an alkane, such as octane or cyclohexane, for example.
• the magnetite obtained in the first step is then encapsulated in a polymer in order to produce the magnetic core of the magnetic core-type particles within the meaning of the invention.
• 2 g of this magnetite obtained in 6 g of styrene and 0.25 g of hexadecane are dispersed.
• the whole is subjected to ultrasound to disperse the magnetite and create a mini-emulsion.
• Styrene is the monomer used to encapsulate magnetite.
• Hexadecane is a very hydrophobic agent allowing the realization of the mini-emulsion.
• SDS sodium dodecyl sulphate
• SDS sodium dodecyl sulphate
• KPS potassium persulfate
• the whole is then heated for 12 hours at 70 ° C. All the while, a polymer precipitates and covers each particle of magnetite. Magnetic latex particles, also called magnetic cores, are then obtained.
• the magnetic latex obtained in the preceding step is first dispersed in an alcoholic solvent, such as ethanol for example.
• an alcoholic solvent such as ethanol for example.
• a solution of water / ammonia is then added to this mixture, and tetrabutyl titanate is then added dropwise for about 1 hour and the mixture is then left stirring for a further 2 hours.
• the water / ammonia solution in this case allows the precursor (tetrabutyl titanate) to condense into titanium oxide (TiO 2 ) around the magnetic latex.
• the resulting assembly is then washed by centrifugation / redispersion cycles. At the end of these cycles, a magnetic latex coated with a white layer of titanium oxide is obtained.
• this example is only illustrative and we can color the magnetic latex in any color through the use of suitable pigments.
• a magnetic latex with a yellow-colored layer, for example with cadmium sulphide
• this chromium oxide is precipitated on the magnetic core by hydrolysis of its precursor, for example.
• the CdS precursor is a solution of Cd 2+ ion obtained from cadmium acetate in water to which thioacetamide is added to.
• the precipitation of the yellow pigment is then done over time. In this case, there is no need to have a water / ammonia solution, the two reactants spontaneously react together.
• the coloration of a magnetic latex by any one of the pigments may be carried out according to methods already known to those skilled in the art by mixing the compounds making it possible to precipitate the pigment on the surface of the magnetic latex.
• a final step in the method of manufacturing the magnetic-type particle is to encapsulate it in an electrostatically chargeable polymer.
• an intermediate step (the fourth step described below) consists in synthesizing a macro-initiator.
• This macro-initiator used in combination with a co-initiator, will allow not only the polymerization of the polymer shell around the pigment, or the magnetic core colored according to the type of particle, but also the stabilization of the particles thus synthesized in the organic medium. apolar and control of their sizes so that they are all homogeneous.
• co-initiator or "initiator” denotes an additive for starting a polymerization reaction. After the initiation of the polymerization reaction, the initiator forms a homopolymer which, by its precipitation will be at the origin of the particles and responsible for their magnification.
• the co-initiator used is an initiator manufactured and marketed by Arkema under the trademark "Blockbuilder”.
• a macro-initiator is an additive composed of a hydrophobic polymer chain for stabilizing the particles, and an initiator portion which serves to initiate the polymerization reaction and ultimately results in the formation of a copolymer.
• the macro-initiator is advantageously synthesized from the co-initiator. Therefore, the initiator portion of the macro-initiator is identical to the co-initiator.
• the macro-initiator and co-initiator both initiate in parallel the polymerization reaction of a functional monomer.
• a copolymer comprising a newly formed polymer chain at the end of the steric repulsion hair is formed and which is anchored in the particle.
• the steric repulsion hair remains attached to the particle and can thus stabilize it in the apolar organic medium.
• the co-initiator serves just to initiate the reaction and only makes a homopolymer.
• the combination of these two initiators in adequate proportions allows to precisely control the size of the latex particles that will be obtained in the end. Indeed, the proportion between the two types of initiators is influence the ratio of homopolymer to copolymer and thus the size of the particles obtained.
• a 250 ml beaker 3 g of the previously synthesized particles are mixed, that is to say, according to the types of final particles to be synthesized either the colored magnetic cores, or the inorganic pigments, and 4 g of SPAN 80 (Sorbitan monooleate).
• SPAN80 is the surfactant that allows a better dispersion of colored magnetic particles or inorganic pigments in the apolar organic solvent used (here toluene). Stirring is carried out for 5 minutes until the SPAN 80 is completely dissolved, and the mixture is then sonicated to disperse the particles to be encapsulated.
• 4vinylpyridine is one of the monomers that makes it possible to form the polymer shell around inorganic pigments or colored magnetic cores. This hull can then be positively charged (in the case of the 4 vinylpyridine) or negatively (if one takes an acidic monomer type acrylic acid, methacrylic or their derivatives, copolymerized or not).
• the dispersion of particles is immediately poured into a 250 ml reactor with mechanical stirring at 300 rpm.
• the mixture of macro-initiator and co-initiator dissolved in toluene and then 4-vinylpyridine are then added to the reactor and the mixture is heated at 120 ° C. for 12 hours under a nitrogen sweep.
• the white magnetic particles thus synthesized are then recovered and then purified by centrifugation / redispersion at 3000 rpm in toluene. This centrifugation step allows to keep only particles of uniform size. Another way to recover particles of uniform size is to perform dialysis.
• the functional monomers for forming the electrostatically chargeable polymer shell are selected based on the final charge that the particle will have to carry.
• the functional polymer covering the pigments is formed from 4-vinylpyridine monomers, or dimethylaminomethacrylate-co-styrene for example.
• the functional polymer covering the pigments is formed from an acrylic acid, or methacrylic acid and its derivatives, copolymerized or otherwise, with another neutral monomer such as styrene or MMA (methyl methacrylate).
• the method makes it possible to obtain latex particles with a size of between 50 nm and 50 ⁇ m. Below 50 nm there is a risk of polymer chains being too short which will not precipitate and therefore do not form particles.
• the particle size for the intended application, is preferably between 0.5 and 2 ⁇ .
• the choice of size is obtained by varying the percentage of co-initiator relative to the percentage of fixed-monomer macro-initiator.
• the macro-initiator / co-initiator molar ratio for the intended application is preferably between 2.5 and 30.
• by increasing the molar concentration of co-initiator relative to the molar concentration of macro-initiator increases the particle size and vice versa.
• the polymer shell itself charges in the presence of a suitable compound.
• the polymers forming the outer shell have patterns that are either acidic (for the negative particles) or basic (for the positives). So a simple acid-base reaction allows these patterns to tear or capture a proton and thus acquire the charge.
• the particles instead of capturing a proton, they can also capture any chemical group that can bind to a nitrogen atom of the basic units. This is for example what happens when one puts the white particles thus synthesized in the presence of iodomethane: the particles are charged positively.
• steps 4 and 5 are carried out, that is to say the synthesis of the macro-initiator necessary for the step 5 of encapsulation of an inorganic pigment.
• the inorganic pigment is previously dispersed in the apolar organic medium by means of a surface treatment or a surfactant.
• the surface treatment may for example consist of a grafting of carbon chains on the hydroxyl groups of the pigment in order to increase its hydrophobicity. Once the surface modification is done, the ultrasound is used for 5 to 10 minutes to disperse the pigment.
• a surfactant such as sorbitan monooleate (SPAN 80) is used, so as to modify the surface tension of the pigment.
• the inorganic pigment is then dispersed in the apolar organic medium by means of ultrasound for 5 to 10 minutes.
• the products used for this synthesis are the following: a black pigment of magnetite Fe 3 O 4 , Span 80 (sobitan monooleate) as a surfactant to allow a good dispersion of the pigment particles in the apolar solvent, the co-polymer initiator marketed by Arkema under the trademark "Blockbuilder”, 2-ethylhexyl acrylate intended to be used for the synthesis of the macro-initiator, 4-vinylpyridine which is the monomer intended to form the positively charged polymer shell and encapsulating the black pigment, toluene as apolar solvent.
• the monomers of 2-ethylhexyl acrylate and 4-vinylpyridine are pre-purified on a desiccant, such as calcium hydride CaH 2 , and distilled under reduced pressure in order to eliminate any residual inhibitor.
• Step 2 Encapsulation of pigment FeSO 4 by dispersion polymerisation
• the black particles thus synthesized are then recovered and then purified by centrifugation / redispersion at 3000 rpm in toluene. This centrifugation step allows to keep only particles of uniform size. Another way to recover particles of uniform size is to perform dialysis.
• the black particles synthesized as described in the exemplary embodiment are then positively charged in the presence of iodomethane for example or in contact with other particles having acidic groups. Black, magnetic, positively charged particles are thus obtained.
• Example 3 Display Device Comprising Polychromic Electrophoretic Ink
• FIG. 1 are diagrammatically 4 pixels respectively referenced P1, P2, P3 and P4 of a display device.
• the display device comprises a transparent surface electrode referenced 10, covering all the pixels. It further comprises a bottom electrode referenced 20. Between the two electrodes, a cavity January 1 is formed and filled with polychrome electrophoretic ink. In fact, the cavity comprises cells that communicate with each other. These cells are delimited on the one hand by vertical walls 21 perpendicular to the bottom electrode 20 and on the other hand by the bottom electrode 20. These cells in fact define the pixels P1 to P4 of the display . They communicate with each other to let the ink flow freely and fill all the cells.
• the bottom electrode 20 comprises contact pads 22.
• each pad 22 is connected to a transistor 32 of an integrated circuit 30 intended to control the application of a different electrostatic force on each pixel.
• a magnetic means referenced 40 is disposed under the bottom electrode 20.
• This magnetic means 40 may for example be in the form of a magnetic strip or an electromagnet, for example.
• the ink filling each of the pixels P1 to P4 is represented by four types of particles composing it, these particles being respectively referenced A, B, C, D.
• the particle A is for example blue in color. non-magnetic and positively charged, the particle B is for example yellow, with a magnetic core and positively charged, the particle C is red, amagnetic and negatively charged, and finally the particle D is black, with a magnetic core and negatively charged.
• Each of the magnetic core particles i.e. the particles B and D in this example, undergo a magnetic resetting force induced by the magnetic tape or the electromagnet 40 disposed at the bottom of the display device. Therefore, to migrate the magnetic particles to the surface electrode 10, it is necessary to increase the voltage applied between the electrodes with respect to the voltage applied to move non-magnetic type particles, in order to surpass this magnetic restoring force. In the remainder of the description, therefore, V + (V-), the voltage threshold necessary to move the nonmagnetic particles and V ++ (V-) the voltage threshold necessary to move the magnetic particles.
• a voltage V + is applied between the electrodes so that the amagnetic and negatively charged particle C moves to the positive surface electrode. Consequently, the pixel P1 displays the red color of the particle C.
• a voltage V ++ is applied between the electrodes, so that the amagnetic and negatively charged particle C, as well as the negatively charged magnetic particle D, migrate towards the pixel P2. the positive surface electrode.
• the red and black colors of the two particles C and D are superimposed on the surface of the pixel P2, so that the latter displays a black color.
• a voltage V- is applied between the electrodes so that the positively charged amagnetic particle A migrates to the negatively charged surface electrode.
• the pixel P3 therefore appears blue, of the color of the particle A.
• a voltage V- is applied so that the particle A, non-magnetic and positively charged, as well as the particle B, magnetic and positively charged. migrate to the negatively charged surface electrode.
• the blue and yellow colors of Part A and Part B are superimpose on the surface of the pixel P4 so that the latter displays a green color.
• the case just described is only an illustrative example to explain the operation of a polychrome display containing such an ink.
• the colors displayed will depend on the choice of colored particles that will be magnetic or not and negatively or positively charged.
• the particles composing the ink are preferably chosen so that, according to their migration in the pixels, they can display the colors of the RGB system or of the CMY system and the black color. Of course, one could choose another system of color representation without departing from the scope of the invention.
• the human eye Since the pixels are very small and very close together, the human eye does not have enough resolution to be able to distinguish them from each other, which is why the colors displayed by 3 or 4 juxtaposed pixels also appear to be superimposed on each other. the human eye. Thus, the eye reconstructs a whole palette of colors with many nuances. Thus, for example when looking at a set of pixels, each displaying the three primary colors of the RGB system, the human eye superimposing them, it will see a point of white color displayed on the screen.
• the polychrome ink thus synthesized has many advantages. These include a unique ink, capable of displaying at least the 3 colors of the RGB system (red-green-blue) necessary for the production of full-color display devices. With this ink, there is no loss of contrast compared to displays by filters or by juxtaposition of two-color pixels, which can in some cases lose between 50 and 75% of the maximum contrast. This is made possible by the fact that each pixel can display all the colors. Another advantage lies in the method of producing the color display device itself. Indeed no control at the filling of the pixels by the ink is necessary because it is a single ink.

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• 2012
  • 2012-10-09 KR KR1020147012414A patent/KR20150067083A/ko not_active Application Discontinuation
  • 2012-10-09 WO PCT/FR2012/052284 patent/WO2013167814A1/fr active Application Filing
  • 2012-10-09 EP EP12787037.6A patent/EP2678166A1/de not_active Withdrawn
  • 2012-10-09 CN CN201280060124.8A patent/CN104144791A/zh active Pending
  • 2012-10-09 JP JP2015535078A patent/JP2015530625A/ja not_active Withdrawn

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