EP0715004B1 - Suspension for electrophoretic depositing luminescent materials, particularly for the manufacture of flat screens - Google Patents

Suspension for electrophoretic depositing luminescent materials, particularly for the manufacture of flat screens Download PDF

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EP0715004B1
EP0715004B1 EP95402449A EP95402449A EP0715004B1 EP 0715004 B1 EP0715004 B1 EP 0715004B1 EP 95402449 A EP95402449 A EP 95402449A EP 95402449 A EP95402449 A EP 95402449A EP 0715004 B1 EP0715004 B1 EP 0715004B1
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Prior art keywords
suspension
luminescent material
colour
tracks
suspension according
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German (de)
French (fr)
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EP0715004A1 (en
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Danh Van Tran
Joel Danroc
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D13/00—Electrophoretic coating characterised by the process
    • C25D13/02—Electrophoretic coating characterised by the process with inorganic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/20—Manufacture of screens on or from which an image or pattern is formed, picked up, converted or stored; Applying coatings to the vessel
    • H01J9/22—Applying luminescent coatings
    • H01J9/221—Applying luminescent coatings in continuous layers
    • H01J9/225—Applying luminescent coatings in continuous layers by electrostatic or electrophoretic processes

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  • the subject of the present invention is non-aqueous suspensions for depositing materials luminescent by electrophoresis, intended for particular to the realization of flat screens.
  • FIG. 1 there is shown a display device of this type which includes a electron source 1 with microtips whose we see insulating substrate 1a, the resistive layer 1b, the microtips 1c, the insulating layer 1d and a grid the.
  • a space 3 in which we made the vacuum separates this microtip source 1 of a substrate electrically insulating and transparent 5 which is provided an electrically conductive and transparent layer 7 forming an anode.
  • On this anode is arranged in look at the microtip source a layer 9 of a cathodo-luminescent material, also called phosphor.
  • this layer 9 emits light 11 that a user 13 of the screen observes through the transparent substrate 5. With this screen, the phosphor is therefore observed from the side opposed to his excitement.
  • the deposit of the phosphor layer must be carried out on a transparent and insulating substrate comprising a transparent and conductive coating, for example in indium tin oxide (ITO).
  • ITO indium tin oxide
  • the screen must have three families of conductive tracks with a width of a few tens of micrometers on which will be respectively deposited the corresponding phosphors in red, blue and green colors.
  • the different layers deposited must present the following properties: good adhesion to the substrate, homogeneity of thickness, high degree of purity for avoid mixing colors and suitable composition deposit mode.
  • the deposition technique must be reproducible, easy to use and suitable for high serial production rates.
  • the coating transparent and conductive, forming the tracks conductive for example indium tin oxide, must withstand the conditions for depositing phosphors, that is to say keep its transparency and electrical conductivity.
  • a widely used technique for making deposits of this type is the technique electrophoresis according to which the phosphor particles from a suspension of these particles, under the action of an electric field, the part to be coated playing the role of anode (anaphoresis) or cathode (cataphoresis).
  • the document FR-A-2 532 957 describes non-aqueous suspensions allowing the deposition of powders phosphors by anaphoresis.
  • the liquid phase of the suspension used consists of a solvent based ketone containing a dispersing agent consisting of nitro-cellulose, and a strong acid and a strong base to give the suspension conductivity sufficient. With such suspensions, the time to deposit is of the order of 0.3 sec.
  • the suspension used is a non-aqueous suspension to avoid problems due to the presence of H + ions on the electrode.
  • a suspension can consist of an organic solvent containing a water-miscible cathode depolarizing agent, such as acetone, a little water and a metal salt such as hydrated magnesium nitrate, which makes it possible to electrically charge.
  • the organic solvent can be isopropanol.
  • This cataphoresis deposition technique is not satisfactory in the case where the substrate includes transparent film and electrically indium tin oxide conductor because it does not not withstand the deposit conditions, it is reduced and thus loses its transparency.
  • the present invention has precisely for subject a non-aqueous suspension for deposition by cataphoresis of luminescent materials, in particular of phosphors, which avoids this drawback.
  • nitromethane in alcohol-based organic solvent, we can avoid when depositing the luminescent material the reduction and loss of transparency of the substrate deposit when this is an indium oxide and tin (ITO). Furthermore, thanks to this addition nitromethane, we can use the same bath and avoid this destruction of the ITO whatever the luminescent material, for example the phosphor, used
  • Aliphatic alcohols susceptible to be used, in combination with nitromethane in the organic solvent can be of different types. It can be ethyl alcohol or isopropyl. Generally, alcohol is preferred isopropyl.
  • the nitromethane content of the solvent organic must be sufficient for it to prevent deterioration of the transparent film. Generally, it is from 1 to 90% by volume. Good results are obtained with an organic solvent comprising 40% by volume of nitromethane and 60% by volume of isopropyl alcohol.
  • the organic solvent phase of the deposition suspension also comprises at least one mineral salt which acts as an inorganic binder and improves the adhesion of the layer of luminescent material deposited.
  • the mineral salts used for this purpose can be of different types. By way of examples, they can belong to the family of rare earth salts and alkaline earth metal salts. It is also possible to use thorium, aluminum and / or cobalt salts.
  • the salt is in the form of a hydrated nitrate, for example Mg (NO 3 ) 2 , 6H 2 O; La (NO 3 ) 3 , 6H 2 O; Al (NO 3 ) 3 , 9H 2 O; Th (NO 3 ) 4 , xHO and Co (NO 3 ) 2 , 6H 2 O.
  • the metal salt in particular in its nitrate form, makes it possible to increase the conductivity of the suspension and to lower the voltage necessary for the deposit, for example, at 40 V / cm. This is particularly interesting for making deposits on indium tin oxide (ITO) because too high a voltage causes the reduction of ITO to indium black in color.
  • the presence of metallic salt also allows improve the adhesion of the material layer luminescent deposited, which allows it to resist washes required between the deposit of the different layers, for example when making a screen trichrome dish.
  • the amount of metal salt (s) present in the suspension is generally from 10 -4 to 10 -6 mol / l.
  • the layer of luminescent material deposited by electrophoresis from the suspension of the invention further comprises a protein of plant origin which improves adhesion grains of luminescent material between them and with the substrate.
  • the protein (s) of plant origin added to the suspension may be holoproteins belonging to the prolamin family.
  • prolamine contained in cereal seeds, especially corn, which is rich in (l) -leucine and methionine As example of a protein of suitable plant origin, we may cite zein from corn; the amount total added vegetable protein can be 0.1 to 3 g / l.
  • Powders of luminescent materials introduced into the suspension can be different types but they have a finest possible particle size, to ensure stable dispersion of the powder in the suspension for limit harmful sedimentation phenomena to obtaining a uniform thickness deposit on malls.
  • the average particle sizes are less than or equal to 20 ⁇ m, for example of the order from 1 to 10 ⁇ m.
  • the luminescent materials used can be any material available on the market which has this property, especially phosphors such as oxides, oxysulfides and sulfides.
  • the powder concentration of material luminescent of the pendant light can vary within a wide range. Generally, it is from 1 g / l to 100 g / l.
  • the suspensions described above can be used in particular to deposit luminescent materials on an insulating substrate transparent coated with a transparent film and electrically conductive such as an oxide film indium and tin.
  • the subject of the invention is also a method of depositing a luminescent material on a coated electrically insulating and transparent substrate a transparent and electrically conductive film, which consists in depositing said material by cataphoresis from a powder suspension of said material with the given characteristics above, using the coated substrate as cathode and a metal anode, and applying between the anode and the cathode a voltage of 1 to 40 V / cm.
  • the metal anode can be platinum or Stainless steel.
  • the control of electrical parameters during the deposition phase is essential to preserve the properties of transparency and conductivity of the transparent film and electrically conductive.
  • the tension does not exceed step 40 V / cm, because if this value is exceeded results in deterioration of conductive films transparencies such as indium oxide films and of tin.
  • This deposition process can be used to successively deposit the three colors: red, blue and green, on the corresponding tracks of a screen flat trichrome, in particular a screen with microtips.
  • the tracks corresponding to the colors to drop which are usually very narrow in width, for example 80 ⁇ m, can be made as it is described in FR-A-2 633 763 by methods of engraving.
  • Figure 1 already described shows in vertical section, a visualization device by cathodoluminescence.
  • Figure 2 schematically shows a trichrome microdot cathodoluminescent screen.
  • the anode is slightly different because the film electrically conductive and transparent which supports luminophores, consists of separate tracks 15, 16 and 17 corresponding respectively to the phosphors of the first color 18, of the second color 19 and of the third color 20.
  • the first suspension contains 20 g / l of phosphor ZnS, CuAl which has a particle size average of 5 ⁇ m.
  • the second suspension includes as phosphor a powder of ZnS, Ag with a particle size average 8 ⁇ m, and the third suspension includes a ZnCdS, Ag powder with an average particle size of 8 ⁇ m.
  • suspensions the invention is very interesting because it allows the production of large screens (up to several tens of inches diagonally). By elsewhere, we can use the same bath to make a large number of screens and the lifetime of suspensions is several months.
  • the amounts of binder and additives in the suspension are weak and do not therefore affect the light output of low voltage excited phosphors.

Description

La présente invention a pour objet des suspensions non aqueuses pour le dépôt de matériaux luminescents par électrophorèse, destinées en particulier à la réalisation d'écrans plats.The subject of the present invention is non-aqueous suspensions for depositing materials luminescent by electrophoresis, intended for particular to the realization of flat screens.

Elle s'applique notamment à la réalisation d'afficheurs simples, permettant la visualisation d'images fixes, et à la réalisation d'écrans complexes multiplexés, permettant la visualisation d'images animées, par exemple du type des images de télévision.It applies in particular to the realization simple displays, allowing viewing still images, and the production of complex screens multiplexed, allowing the visualization of images animated, for example of the type of television images.

Elle présente un intérêt particulier pour les dispositifs de visualisation par cathodoluminescence excitée par émission de champ, comprenant une source d'électrons à cathode émissive à micropointes. Des dispositifs de visualisation de ce type sont décrits par exemple dans les documents FR-A-2 687 839, FR-A-2 633 763 et US-A-5 231 387.It is of particular interest for visualization devices by cathodoluminescence excited by field emission, comprising an electron source with an emissive cathode at microtips. Display devices for this type are described for example in the documents FR-A-2 687 839, FR-A-2 633 763 and US-A-5 231 387.

Sur la figure 1 annexée, on a représenté un dispositif d'affichage de ce type qui comprend une source d'électrons 1 à micropointes dont on voit le substrat isolant 1a, la couche résistive 1b, les micropointes 1c, la couche isolante 1d et une grille le. Un espace 3 dans lequel on a fait le vide, sépare cette source à micropointes 1 d'un substrat électriquement isolant et transparent 5 qui est pourvu d'une couche électriquement conductrice et transparente 7 formant une anode. Sur cette anode, est disposée en regard de la source à micropointes une couche 9 d'un matériau cathodo-luminescent, encore appelé luminophore.In Figure 1 attached, there is shown a display device of this type which includes a electron source 1 with microtips whose we see insulating substrate 1a, the resistive layer 1b, the microtips 1c, the insulating layer 1d and a grid the. A space 3 in which we made the vacuum, separates this microtip source 1 of a substrate electrically insulating and transparent 5 which is provided an electrically conductive and transparent layer 7 forming an anode. On this anode, is arranged in look at the microtip source a layer 9 of a cathodo-luminescent material, also called phosphor.

Sous l'impact des électrons émis par les micropointes 1c lorsque la source fonctionne, cette couche 9 émet une lumière 11 qu'un utilisateur 13 de l'écran observe à travers le substrat transparent 5. Avec cet écran, le luminophore est donc observé du côté opposé à son excitation.Under the impact of electrons emitted by 1c microtips when the source is working, this layer 9 emits light 11 that a user 13 of the screen observes through the transparent substrate 5. With this screen, the phosphor is therefore observed from the side opposed to his excitement.

Dans le cas de ces écrans plats à micropointes, les électrons sont accélérés à des tensions très faibles (quelques centaines de volts) comparativement aux tensions utilisées dans les écrans cathodiques (20 à 25 kV). De ce fait, dans de tels écrans, les luminophores sont essentiellement excités en surface et doivent comporter le minimum de pollution. Une contamination ou la présence d'une couche mince à la surface des grains de luminophores se traduira par une baisse du rendement lumineux. La qualité de la couche de luminophore déposée constitue donc un paramètre important.In the case of these flat screens microtips, electrons are accelerated to very low voltages (a few hundred volts) compared to the voltages used in the screens cathodic (20 to 25 kV). Therefore, in such screens, the phosphors are basically excited on the surface and must include the minimum of pollution. Contamination or the presence of thin layer on the surface of the phosphor grains is will result in a decrease in light output. The quality of the phosphor layer deposited constitutes therefore an important parameter.

Dans ces écrans plats à micropointes, le dépôt de la couche de luminophore doit être effectué sur un substrat transparent et isolant comportant un revêtement transparent et conducteur, par exemple en oxyde d'indium et d'étain (ITO). Par ailleurs, pour l'affichage en couleur, l'écran doit comporter trois familles de pistes conductrices d'une largeur de quelques dizaines de micromètres sur lesquelles seront déposés respectivement les luminophores correspondant aux couleurs rouge, bleu et vert.In these microtip flat screens, the deposit of the phosphor layer must be carried out on a transparent and insulating substrate comprising a transparent and conductive coating, for example in indium tin oxide (ITO). Furthermore, for color display, the screen must have three families of conductive tracks with a width of a few tens of micrometers on which will be respectively deposited the corresponding phosphors in red, blue and green colors.

Pour obtenir une qualité satisfaisante, les différentes couches déposées doivent présenter les propriétés suivantes : bonne adhérence sur le substrat, homogénéité d'épaisseur, haut degré de pureté pour éviter les mélanges de couleurs et composition adaptée au mode de dépôt.To obtain satisfactory quality, the different layers deposited must present the following properties: good adhesion to the substrate, homogeneity of thickness, high degree of purity for avoid mixing colors and suitable composition deposit mode.

De plus, la technique de dépôt doit être reproductible, facile à mettre en oeuvre et adaptée aux cadences élevées de production en série. In addition, the deposition technique must be reproducible, easy to use and suitable for high serial production rates.

Une autre condition importante qui doit être remplie, réside dans le fait que le revêtement transparent et conducteur, formant les pistes conductrices, par exemple l'oxyde d'indium et d'étain, doit résister aux conditions de dépôt des luminophores, c'est-à-dire garder sa transparence et sa conductibilité électrique.Another important condition which must to be fulfilled, is that the coating transparent and conductive, forming the tracks conductive, for example indium tin oxide, must withstand the conditions for depositing phosphors, that is to say keep its transparency and electrical conductivity.

Une technique largement utilisée pour réaliser des dépôts de ce type est la technique d'électrophorèse selon laquelle on dépose les particules de luminophores à partir d'une suspension de ces particules, sous l'action d'un champ électrique, la pièce à revêtir jouant le rôle d'anode (anaphorèse) ou de cathode (cataphorèse).A widely used technique for making deposits of this type is the technique electrophoresis according to which the phosphor particles from a suspension of these particles, under the action of an electric field, the part to be coated playing the role of anode (anaphoresis) or cathode (cataphoresis).

Le document FR-A-2 532 957 décrit des suspensions non aqueuses permettant le dépôt de poudres de luminophores par anaphorèse. La phase liquide de la suspension utilisée se compose d'un solvant à base de cétone contenant un agent dispersant constitué par la nitro-cellulose, et un acide fort et une base forte pour conférer à la suspension une conductivité suffisante. Avec de telles suspensions, le temps de dépôt est de l'ordre de 0,3 sec.The document FR-A-2 532 957 describes non-aqueous suspensions allowing the deposition of powders phosphors by anaphoresis. The liquid phase of the suspension used consists of a solvent based ketone containing a dispersing agent consisting of nitro-cellulose, and a strong acid and a strong base to give the suspension conductivity sufficient. With such suspensions, the time to deposit is of the order of 0.3 sec.

L'emploi de cette technique permet d'éviter une détérioration de la couche conductrice et transparentes de l'électrode de dépôt, car celui-ci est effectué par anaphorèse en utilisant le substrat en position anodique, ce qui évite l'apparition d'ions H+ sur l'électrode. Néanmoins, la durée de dépôt étant très faible, on ne peut garantir l'obtention d'une épaisseur reproductible et homogène des couches déposées. Les rendements lumineux des écrans ne sont donc pas reproductibles et l'aspect n'est pas homogène.The use of this technique makes it possible to avoid deterioration of the conductive and transparent layer of the deposition electrode, since this is carried out by anaphoresis using the substrate in the anodic position, which avoids the appearance of ions. H + on the electrode. However, the deposition time being very short, it cannot be guaranteed that a reproducible and uniform thickness of the deposited layers will be obtained. The light yields of the screens are therefore not reproducible and the appearance is not uniform.

Le document US-A-3 714 011 décrit une technique de dépôt de luminophores par cataphorèse. La suspension utilisée est une suspension non -aqueuse pour éviter les problèmes dus à la présence d'ions H+ sur l'électrode. Une telle suspension peut être constituée d'un solvant organique contenant un agent dépolarisant cathodique miscible à l'eau, tel que l'acétone, un peu d'eau et un sel métallique tel que le nitrate de magnésium hydraté, qui permet de charger électriquement les particules de luminophore et joue le rôle de liant qui permet l'obtention d'un revêtement fortement adhérent. Le solvant organique peut être l'isopropanol.Document US-A-3,714,011 describes a technique for depositing phosphors by cataphoresis. The suspension used is a non-aqueous suspension to avoid problems due to the presence of H + ions on the electrode. Such a suspension can consist of an organic solvent containing a water-miscible cathode depolarizing agent, such as acetone, a little water and a metal salt such as hydrated magnesium nitrate, which makes it possible to electrically charge. the phosphor particles and plays the role of binder which makes it possible to obtain a highly adherent coating. The organic solvent can be isopropanol.

Cette technique de dépôt par cataphorèse n'est pas satisfaisante dans le cas où le substrat comprend un film transparent et électriquement conducteur d'oxyde d'indium et d'étain, car celui-ci ne résiste pas aux conditions de dépôt, il est réduit et perd ainsi sa transparence.This cataphoresis deposition technique is not satisfactory in the case where the substrate includes transparent film and electrically indium tin oxide conductor because it does not not withstand the deposit conditions, it is reduced and thus loses its transparency.

La présente invention a précisément pour objet une suspension non aqueuse pour le dépôt par cataphorèse de matériaux luminescents, notamment de luminophores, qui permet d'éviter cet inconvénient.The present invention has precisely for subject a non-aqueous suspension for deposition by cataphoresis of luminescent materials, in particular of phosphors, which avoids this drawback.

Selon l'invention, la suspension pour le dépôt d'un matériau luminescent par électrophorèse, comprend :

  • un solvant organique polaire constitué par un mélange de nitrométhane et d'un alcool aliphatique sauf l'alcool méthylique, contenant en solution au moins un sel métallique et au moins une protéine végétale, et
  • une poudre de matériau luminescent à déposer, en suspension dans ledit solvant.
According to the invention, the suspension for depositing a luminescent material by electrophoresis, comprises:
  • a polar organic solvent consisting of a mixture of nitromethane and an aliphatic alcohol except methyl alcohol, containing in solution at least one metal salt and at least one vegetable protein, and
  • a luminescent material powder to be deposited, suspended in said solvent.

Selon l'invention, grâce à l'adjonction de nitrométhane au solvant organique à base d'alcool, on peut éviter lors du dépôt du matériau luminescent la réduction et la perte de transparence du substrat de dépôt lorsque que celui-ci est un oxyde d'indium et d'étain (ITO). Par ailleurs, grâce à cette adjonction de nitrométhane, on peut utiliser le même bain et éviter cette destruction de l'ITO quelque soit le matériau luminescent, par exemple le luminophore, utiliséAccording to the invention, thanks to the addition of nitromethane in alcohol-based organic solvent, we can avoid when depositing the luminescent material the reduction and loss of transparency of the substrate deposit when this is an indium oxide and tin (ITO). Furthermore, thanks to this addition nitromethane, we can use the same bath and avoid this destruction of the ITO whatever the luminescent material, for example the phosphor, used

Les alcools aliphatiques susceptibles d'être utilisés, en association avec le nitrométhane dans le solvant organique peuvent être de différents types. Il peut s'agir d'alcool éthylique ou isopropylique. Généralement, on préfère l'alcool isopropylique.Aliphatic alcohols susceptible to be used, in combination with nitromethane in the organic solvent can be of different types. It can be ethyl alcohol or isopropyl. Generally, alcohol is preferred isopropyl.

La teneur en nitrométhane du solvant organique doit être suffisante pour qu'il puisse empêcher la détérioration du film transparent. Généralement, elle est de 1 à 90 % en volume. De bons résultats sont obtenus avec un solvant organique comprenant 40 % en volume de nitrométhane et 60 % en volume d'alcool isopropylique.The nitromethane content of the solvent organic must be sufficient for it to prevent deterioration of the transparent film. Generally, it is from 1 to 90% by volume. Good results are obtained with an organic solvent comprising 40% by volume of nitromethane and 60% by volume of isopropyl alcohol.

La phase solvant organique de la suspension de dépôt comprend également au moins un sel minéral qui joue le rôle de liant inorganique et améliore l'adhérence de la couche de matériau luminescent déposée. Les sels minéraux utilisés dans ce but peuvent être de différents types. A titre d'exemples, ils peuvent appartenir à la famille des sels de terres rares et des sels de métaux alcalino-terreux. On peut aussi utiliser des sels de thorium, d'aluminium et/ou de cobalt. De préférence, le sel se présente sous la forme d'un nitrate hydraté, par exemple Mg(NO3)2, 6H2O ; La(NO3)3, 6H2O ; Al(NO3)3, 9H2O ; Th(NO3)4, xHO et Co(NO3)2, 6H2O. En effet, le sel métallique, notamment sous sa forme nitrate permet d'augmenter la conductivité de la suspension et d'abaisser la tension nécessaire pour le dépôt, par exemple, à 40 V/cm. Ceci est intéressant notamment pour réaliser des dépôts sur l'oxyde d'indium et d'étain (ITO) car une tension trop importante entraíne la réduction de l'ITO en indium de couleur noire.The organic solvent phase of the deposition suspension also comprises at least one mineral salt which acts as an inorganic binder and improves the adhesion of the layer of luminescent material deposited. The mineral salts used for this purpose can be of different types. By way of examples, they can belong to the family of rare earth salts and alkaline earth metal salts. It is also possible to use thorium, aluminum and / or cobalt salts. Preferably, the salt is in the form of a hydrated nitrate, for example Mg (NO 3 ) 2 , 6H 2 O; La (NO 3 ) 3 , 6H 2 O; Al (NO 3 ) 3 , 9H 2 O; Th (NO 3 ) 4 , xHO and Co (NO 3 ) 2 , 6H 2 O. In fact, the metal salt, in particular in its nitrate form, makes it possible to increase the conductivity of the suspension and to lower the voltage necessary for the deposit, for example, at 40 V / cm. This is particularly interesting for making deposits on indium tin oxide (ITO) because too high a voltage causes the reduction of ITO to indium black in color.

La présence de sel métallique permet aussi d'améliorer l'adhérence de la couche de matériau luminescent déposée, ce qui lui permet de résister aux lavages nécessaires entre le dépôt des différentes couches, par exemple lors de la réalisation d'un écran plat trichrome.The presence of metallic salt also allows improve the adhesion of the material layer luminescent deposited, which allows it to resist washes required between the deposit of the different layers, for example when making a screen trichrome dish.

Pour introduire le ou les sels métalliques dans la phase organique, on les dissout tout d'abord dans une très faible quantité d'eau. La quantité de sel(s) métallique(s) présente dans la suspension est généralement de 10 -4 à 10-6 mol/l.To introduce the metal salt (s) into the organic phase, they are first dissolved in a very small amount of water. The amount of metal salt (s) present in the suspension is generally from 10 -4 to 10 -6 mol / l.

Pour améliorer encore les propriétés de la couche de matériau luminescent déposée par électrophorèse à partir de la suspension de l'invention, celle-ci comprend de plus une protéine d'origine végétale qui permet d'améliorer l'adhérence des grains de matériau luminescent entre eux et avec le substrat.To further improve the properties of the layer of luminescent material deposited by electrophoresis from the suspension of the invention, it further comprises a protein of plant origin which improves adhesion grains of luminescent material between them and with the substrate.

La ou les protéines d'origine végétale ajoutées à la suspension peuvent être des holoprotéides appartenant à la famille des prolamines. En particulier, on peut utiliser la prolamine contenue dans les graines de céréales, notamment de maïs, qui est riche en (l)-leucine et en méthionine. A titre d'exemple de protéine d'origine végétale appropriée, on peut citer la zéine provenant du maïs ; la quantité totale de protéine végétale ajoutée peut être de 0,1 à 3 g/l.The protein (s) of plant origin added to the suspension may be holoproteins belonging to the prolamin family. In particular, we can use the prolamine contained in cereal seeds, especially corn, which is rich in (l) -leucine and methionine. As example of a protein of suitable plant origin, we may cite zein from corn; the amount total added vegetable protein can be 0.1 to 3 g / l.

Les poudres de matériaux luminescents introduites dans la suspension peuvent être de différents types mais elles présentent une granulométrie la plus fine possible, afin d'assurer une dispersion stable de la poudre dans la suspension pour limiter les phénomènes de sédimentation nuisibles à l'obtention d'un dépôt homogène en épaisseur sur de grandes surfaces.Powders of luminescent materials introduced into the suspension can be different types but they have a finest possible particle size, to ensure stable dispersion of the powder in the suspension for limit harmful sedimentation phenomena to obtaining a uniform thickness deposit on malls.

Les granulométries moyennes sont inférieures ou égales à 20 µm, par exemple de l'ordre de 1 à 10 µm.The average particle sizes are less than or equal to 20 µm, for example of the order from 1 to 10 µm.

Les matériaux luminescents utilisés peuvent être n'importe quel matériau disponible sur le marché qui présente cette propriété, en particulier des luminophores tels que des oxydes, des oxysulfures et des sulfures.The luminescent materials used can be any material available on the market which has this property, especially phosphors such as oxides, oxysulfides and sulfides.

La concentration en poudre de matériau luminescent de la suspension peut varier dans une large gamme. Généralement, elle est de 1 g/l à 100 g/l.The powder concentration of material luminescent of the pendant light can vary within a wide range. Generally, it is from 1 g / l to 100 g / l.

Les suspensions décrites ci-dessus peuvent être utilisées en particulier pour déposer des matériaux luminescents sur un substrat isolant transparent revêtu d'un film transparent et électriquement conducteur tel qu'un film d'oxyde d'indium et d'étain.The suspensions described above can be used in particular to deposit luminescent materials on an insulating substrate transparent coated with a transparent film and electrically conductive such as an oxide film indium and tin.

Aussi, l'invention a également pour objet un procédé de dépôt d'un matériau luminescent sur un substrat électriquement isolant et transparent revêtu d'un film transparent et électriquement conducteur, qui consiste à réaliser le dépôt dudit matériau par cataphorèse à partir d'une suspension de poudre dudit matériau présentant les caractéristiques données ci-dessus, en utilisant le substrat revêtu comme cathode et une anode métallique, et en appliquant entre l'anode et la cathode une tension de 1 à 40 V/cm.The subject of the invention is also a method of depositing a luminescent material on a coated electrically insulating and transparent substrate a transparent and electrically conductive film, which consists in depositing said material by cataphoresis from a powder suspension of said material with the given characteristics above, using the coated substrate as cathode and a metal anode, and applying between the anode and the cathode a voltage of 1 to 40 V / cm.

L'anode métallique peut être en platine ou en acier inoxydable.The metal anode can be platinum or Stainless steel.

Dans ce procédé de dépôt, le contrôle des paramètres électriques durant la phase de dépôt est primordial pour conserver les propriétés de transparence et de conductivité du film transparent et électriquement conducteur. Dans ce but, on peut aussi régler la distance entre l'anode et la cathode à un intervalle approprié qui peut se situer dans la gamme allant de 1 cm à 5 cm. De même, la tension ne dépasse pas 40 V/cm, car un dépassement de cette valeur se traduit par une détérioration des films conducteurs transparents tels que les films d'oxyde d'indium et d'étain.In this deposition process, the control of electrical parameters during the deposition phase is essential to preserve the properties of transparency and conductivity of the transparent film and electrically conductive. For this purpose, we can also set the distance between the anode and the cathode to a suitable interval which can be in the range ranging from 1 cm to 5 cm. Similarly, the tension does not exceed step 40 V / cm, because if this value is exceeded results in deterioration of conductive films transparencies such as indium oxide films and of tin.

Dans une variante, on travaille à courant constant en veillant à ce que la tension reste inférieure ou égale à 40 V/cm pour ne pas détériorer l'ITO. On pourra aussi utiliser la méthode des courants pulsés avec toujours la tension inférieure ou égale à 40V/cm.In a variant, we work with current constant ensuring that tension remains less than or equal to 40 V / cm so as not to deteriorate ITO. We can also use the current method pulsed with always the voltage less than or equal to 40V / cm.

Ce procédé de dépôt peut être utilisé pour déposer successivement les trois couleurs : rouge, bleu et vert, sur les pistes correspondantes d'un écran plat trichrome, en particulier d'un écran à micropointes. Dans ce cas, on réalise tout d'abord sur un substrat électriquement isolant et transparent des pistes individuelles électriquement conductrices et transparentes, aux emplacements qui correspondent aux trois couleurs à déposer ; on prépare trois suspensions présentant les caractéristiques données ci-dessus, mais contenant pour la première suspension un premier matériau luminescent correspondant à la première couleur à déposer, pour la deuxième suspension un second matériau luminescent correspondant à la deuxième couleur à déposer et pour la troisième suspension un troisième matériau luminescent correspondant à la troisième couleur. Pour réaliser le dépôt de la première couleur, on connecte les pistes correspondant à la première couleur à un générateur de courant électrique et on dépose sur ces pistes la première couleur par mise en oeuvre du procédé décrit ci-dessus au moyen de la première suspension. On répète ensuite cette opération de dépôt sur les pistes correspondant à la deuxième couleur en utilisant la deuxième suspension, puis sur les pistes correspondant à la troisième couleur en utilisant la troisième suspension.This deposition process can be used to successively deposit the three colors: red, blue and green, on the corresponding tracks of a screen flat trichrome, in particular a screen with microtips. In this case, we first realize on an electrically insulating and transparent substrate individual electrically conductive tracks and transparent, in the locations corresponding to the three colors to deposit; we are preparing three suspensions having the characteristics given above, but containing for the first suspension a first luminescent material corresponding to the first color to deposit, for the second suspension one second luminescent material corresponding to the second color to deposit and for the third suspension one third luminescent material corresponding to the third color. To file the first color, we connect the corresponding tracks at the first color to a current generator electric and we put the first on these tracks color by implementing the method described above by means of the first suspension. We then repeat this deposit operation on the tracks corresponding to the second color using the second suspension, then on the tracks corresponding to the third color using the third suspension.

Les pistes correspondant aux couleurs à déposer qui sont généralement de largeur très faible, par exemple de 80 µm, peuvent être réalisées comme il est décrit dans FR-A-2 633 763 par des procédés de gravure.The tracks corresponding to the colors to drop which are usually very narrow in width, for example 80 µm, can be made as it is described in FR-A-2 633 763 by methods of engraving.

D'autres caractéristiques et avantages de l'invention apparaítront mieux à la lecture de la description qui suit, donnée bien entendu à titre illustratif et non limitatif, en référence aux dessins annexés sur lesquels :Other features and benefits of the invention will appear better on reading the description which follows, of course given as illustrative and not limiting, with reference to the drawings annexed on which:

La figure 1 déjà décrite représente en coupe verticale, un dispositif de visualisation par cathodoluminescence.Figure 1 already described shows in vertical section, a visualization device by cathodoluminescence.

La figure 2 représente schématiquement un écran cathodoluminescent trichrome à micropointes.Figure 2 schematically shows a trichrome microdot cathodoluminescent screen.

Sur la figure 2, on a utilisé les mêmes références que celles de la figure 1 pour désigner les composants communs. Dans cette réalisation, l'anode est légèrement différente car le film électriquement conducteur et transparent qui supporte les luminophores, est constitué par des pistes séparées 15, 16 et 17 correspondant respectivement aux luminophores de la première couleur 18, de la seconde couleur 19 et de la troisième couleur 20.In Figure 2, we used the same references than those in FIG. 1 to designate the common components. In this embodiment, the anode is slightly different because the film electrically conductive and transparent which supports luminophores, consists of separate tracks 15, 16 and 17 corresponding respectively to the phosphors of the first color 18, of the second color 19 and of the third color 20.

On décrit ci-après la réalisation des dépôts de luminophores 18, 19 et 20 sur ces pistes individuelles pour réaliser un écran à micropoints de 25,4 cm de diagonale. The implementation of the phosphor deposits 18, 19 and 20 on these tracks individual to make a microtip screen of 25.4 cm diagonal.

Les pistes ont été préparées de façon classique. Elles sont réalisées en oxyde d'indium et d'étain et ont une largeur de 80 µm. Pour réaliser les dépôts, on prépare trois suspensions dans lesquelles la phase solvant organique a la composition suivante :

  • nitrométhane : 40 % en volume.
  • alcool isopropylique : 60 % en volume.
  • Mg(NO3)2, 6H2O : 5.10-4 mol/l.
  • zéine : 0,8 g/l.
The tracks have been prepared in a classic way. They are made of indium tin oxide and have a width of 80 µm. To carry out the deposits, three suspensions are prepared in which the organic solvent phase has the following composition:
  • nitromethane: 40% by volume.
  • isopropyl alcohol: 60% by volume.
  • Mg (NO 3) 2 .6H 2 O: 5.10 -4 mol / l.
  • zein: 0.8 g / l.

La première suspension contient 20 g/l du luminophore ZnS,CuAl qui présente une granulométrie moyenne de 5 µm.The first suspension contains 20 g / l of phosphor ZnS, CuAl which has a particle size average of 5 µm.

La deuxième suspension comprend comme luminophore une poudre de ZnS, Ag d'une granulométrie moyenne de 8 µm, et la troisième suspension comprend une poudre de ZnCdS, Ag d'une granulométrie moyenne de 8 µm.The second suspension includes as phosphor a powder of ZnS, Ag with a particle size average 8 µm, and the third suspension includes a ZnCdS, Ag powder with an average particle size of 8 µm.

Pour réaliser le dépôt de la première couleur, on connecte les pistes 15 correspondant à la première couleur, à un générateur de courant électrique, on immerge le substrat 5 revêtu des pistes 15 convenablement connectées dans la première suspension de dépôt, puis on effectue le dépôt en disposant en face une anode de platine à une distance de 3 cm et en appliquant entre cette anode et les pistes conductrices 15 une tension de 8 V avec une intensité de 16 mA pendant 30 sec. On soumet ensuite l'ensemble à un rinçage avec le même alcool que celui utilisé dans le mélange de départ. On obtient ainsi les dépôts 18 de la première couleur.To deposit the first color, we connect tracks 15 corresponding to the first color, to a current generator electric, immerse the substrate 5 coated with tracks 15 suitably connected in the first suspension of deposit, then the deposit is carried out having opposite a platinum anode at a distance 3 cm and applying between this anode and the conductive tracks 15 a voltage of 8 V with a intensity of 16 mA for 30 sec. We then submit the whole in a rinse with the same alcohol as that used in the starting mixture. We thus obtain the deposits 18 of the first color.

On réalise ensuite les dépôts de la deuxième couleur en connectant les pistes 16 au générateur de courant électrique, en utilisant la deuxième suspension et en réalisant le dépôt dans les mêmes conditions que précédemment (8 V , 16 mA et 30 sec) . Après dépôt, on effectue un rinçage. On réalise ensuite le dépôt de la troisième couleur de la même façon, mais en utilisant la troisième suspension.Then the deposits of the second color by connecting tracks 16 to electric current generator, using the second suspension and by filing in same conditions as above (8 V, 16 mA and 30 sec). After deposition, a rinsing is carried out. We then make the deposit of the third color of the same way, but using the third suspension.

On obtient ainsi un écran trichrome comportant des dépôts adhérents, sans mélange de couleurs, avec une bonne homogénéité d'épaisseur.This gives a three-color screen with adherent deposits, without mixing colors, with good homogeneity of thickness.

L'utilisation des suspensions de l'invention est très intéressante, car elle permet la réalisation d'écrans de grandes dimensions (jusqu'à plusieurs dizaines de pouces de diagonale). Par ailleurs, on peut utiliser le même bain pour réaliser un grand nombre d'écrans et la durée de vie des suspensions est de plusieurs mois.The use of suspensions the invention is very interesting because it allows the production of large screens (up to several tens of inches diagonally). By elsewhere, we can use the same bath to make a large number of screens and the lifetime of suspensions is several months.

Par ailleurs, les quantités de liant et d'additifs contenues dans la suspension sont faibles et n'affectent pas de ce fait le rendement lumineux des luminophores excités à basse tension.Furthermore, the amounts of binder and additives in the suspension are weak and do not therefore affect the light output of low voltage excited phosphors.

Claims (16)

  1. Suspension for the deposition of a luminescent material by electrophoresis, characterized in that it comprises:
    a polar organic solvent constituted by a mixture of nitromethane and an aliphatic alcohol, excepting methyl alcohol, containing in solution at least one metal salt and at least one vegetable protein and
    a powder of the luminescent material to be deposited in suspension in said solvent.
  2. Suspension according to claim 1, characterized in that the aliphatic alcohol is isopropyl alcohol.
  3. Suspension according to claim 2, characterized in that the organic solvent comprises 40 vol.% nitromethane and 60 vol.% isopropyl alcohol.
  4. Suspension according to claim 1, characterized in that the metal salt is constituted by at least one metal salt chosen from among alkaline earth metal salts, rare earth salts, thorium salts, aluminium salts and cobalt salts.
  5. Suspension according to claim 1, characterized in that the metal salt is hydrogenated magnesium nitrate of formula Mg(NO3)2, 6H2O.
  6. Suspension according to any one of the claims 1, 4 and 5, characterized in that the metal salt concentration of the suspension is 10-4 to 10-6 mole/l.
  7. Suspension according to claim 1, characterized in that the vegetable protein is a zein.
  8. Suspension according to either of the claims 1 and 7, characterized in that the protein concentration of the suspension is 0.1 to 3 g/l.
  9. Suspension according to claim 1, characterized in that the luminescent material powder has an average grain size equal to or below 20 µm.
  10. Suspension according to either of the claims 1 and 9, characterized in that the luminescent material powder concentration of the suspension is 1 to 100 g/l.
  11. Suspension according to any one of the claims 1 to 10, characterized in that the luminescent material is a phosphor.
  12. Suspension according to claim 1, characterized in that it comprises:
    40 vol.% nitromethane,
    60 vol.% isopropyl alcohol,
    0.8 g/l zein,
    5.10-4 mol/l Mg(NO3)2, H2O, and
    20 g/l of luminescent material powder with an average grain size 5 to 8 um.
  13. Process for the deposition of a luminescent material on an electrically insulating, transparent substrate coated with an electrically conductive, transparent film, characterized in that it consists of carrying out the deposition of said luminescent material by cataphoresis from a powder suspension of said luminescent material in accordance with any one of the claims 1 to 12, using the coated substrate as the cathode and a metal anode, and by applying a voltage of 1 to 40 V/cm between the anode and the cathode.
  14. Process according to claim 13, characterized in that the electrically conductive, transparent film is an indium and tin oxide.
  15. Process for producing a tricolour, flat screen, characterized in that it comprises the following stages:
    1) producing on an electrically insulating, transparent substrate individual, conductive, transparent tracks at locations corresponding to the three colours to be deposited,
    2) preparing three suspensions according to claim 1 containing for the first suspension a first luminescent material of the first colour, for the second suspension a second luminescent material of the second colour and for the third suspension a third luminescent material of the third colour,
    3) depositing the first colour by connecting the tracks corresponding to said first colour to an electric current generator and by depositing on said tracks the first colour by performing the process according to any one of the claims 1 to 12 using the first suspension and
    4) repeating said deposition operation on the tracks corresponding to the second colour using the second suspension and on the tracks corresponding to the third colour using the third suspension.
  16. Process according to claim 15, characterized in that the conductive tracks are of indium and tin oxide.
EP95402449A 1994-11-08 1995-11-03 Suspension for electrophoretic depositing luminescent materials, particularly for the manufacture of flat screens Expired - Lifetime EP0715004B1 (en)

Applications Claiming Priority (2)

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FR9413370 1994-11-08
FR9413370A FR2726581B1 (en) 1994-11-08 1994-11-08 SUSPENSION FOR THE DEPOSITION OF LUMINESCENT MATERIALS BY ELECTROPHORESIS, IN PARTICULAR FOR THE PRODUCTION OF FLAT SCREENS

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EP0715004B1 true EP0715004B1 (en) 1998-04-08

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US6071633A (en) * 1996-09-03 2000-06-06 Advanced Vision Technologies, Inc Oxide based phosphors and processes therefor
US6015326A (en) * 1996-09-03 2000-01-18 Advanced Vision Technologies,Inc. Fabrication process for electron field-emission display
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US6169357B1 (en) 1997-07-28 2001-01-02 Advanced Vision Technologies, Inc. Electron field-emission display cell device having opening depth defined by etch stop
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KR100265859B1 (en) * 1996-12-21 2000-09-15 정선종 Luminous particle for field emission display
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JP3595718B2 (en) 1999-03-15 2004-12-02 株式会社東芝 Display element and method of manufacturing the same
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FR2726581A1 (en) 1996-05-10
DE69502005D1 (en) 1998-05-14
FR2726581B1 (en) 1996-12-06

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