Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J11/00—Gas-filled discharge tubes with alternating current induction of the discharge, e.g. alternating current plasma display panels [AC-PDP]; Gas-filled discharge tubes without any main electrode inside the vessel; Gas-filled discharge tubes with at least one main electrode outside the vessel
  • H01J11/20—Constructional details
  • H01J11/34—Vessels, containers or parts thereof, e.g. substrates
• • 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
  • H01J9/24—Manufacture or joining of vessels, leading-in conductors or bases
  • H01J9/241—Manufacture or joining of vessels, leading-in conductors or bases the vessel being for a flat panel display
  • H01J9/242—Spacers between faceplate and backplate
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B23/00—Re-forming shaped glass
  • C03B23/04—Re-forming tubes or rods
  • C03B23/047—Re-forming tubes or rods by drawing
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B33/00—Severing cooled glass
  • C03B33/06—Cutting or splitting glass tubes, rods, or hollow products
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
  • C03C17/02—Surface treatment of glass, not in the form of fibres or filaments, by coating with glass
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C4/00—Compositions for glass with special properties
  • C03C4/14—Compositions for glass with special properties for electro-conductive glass
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
  • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
  • H01J29/028—Mounting or supporting arrangements for flat panel cathode ray tubes, e.g. spacers particularly relating to electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
  • H01J29/86—Vessels; Containers; Vacuum locks
  • H01J29/864—Spacers between faceplate and backplate of flat panel cathode ray tubes
• • 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
  • H01J9/02—Manufacture of electrodes or electrode systems
  • H01J9/18—Assembling together the component parts of electrode systems
  • H01J9/185—Assembling together the component parts of electrode systems of flat panel display devices, e.g. by using spacers
• • E—FIXED CONSTRUCTIONS
  • E06—DOORS, WINDOWS, SHUTTERS, OR ROLLER BLINDS IN GENERAL; LADDERS
  • E06B—FIXED OR MOVABLE CLOSURES FOR OPENINGS IN BUILDINGS, VEHICLES, FENCES OR LIKE ENCLOSURES IN GENERAL, e.g. DOORS, WINDOWS, BLINDS, GATES
  • E06B3/00—Window sashes, door leaves, or like elements for closing wall or like openings; Layout of fixed or moving closures, e.g. windows in wall or like openings; Features of rigidly-mounted outer frames relating to the mounting of wing frames
  • E06B3/66—Units comprising two or more parallel glass or like panes permanently secured together
  • E06B3/663—Elements for spacing panes
  • E06B3/66309—Section members positioned at the edges of the glazing unit
  • E06B2003/6638—Section members positioned at the edges of the glazing unit with coatings
• • E—FIXED CONSTRUCTIONS
  • E06—DOORS, WINDOWS, SHUTTERS, OR ROLLER BLINDS IN GENERAL; LADDERS
  • E06B—FIXED OR MOVABLE CLOSURES FOR OPENINGS IN BUILDINGS, VEHICLES, FENCES OR LIKE ENCLOSURES IN GENERAL, e.g. DOORS, WINDOWS, BLINDS, GATES
  • E06B3/00—Window sashes, door leaves, or like elements for closing wall or like openings; Layout of fixed or moving closures, e.g. windows in wall or like openings; Features of rigidly-mounted outer frames relating to the mounting of wing frames
  • E06B3/66—Units comprising two or more parallel glass or like panes permanently secured together
  • E06B3/663—Elements for spacing panes
  • E06B3/66304—Discrete spacing elements, e.g. for evacuated glazing units
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2211/00—Plasma display panels with alternate current induction of the discharge, e.g. AC-PDPs
  • H01J2211/20—Constructional details
  • H01J2211/34—Vessels, containers or parts thereof, e.g. substrates
  • H01J2211/36—Spacers, barriers, ribs, partitions or the like
  • H01J2211/366—Spacers, barriers, ribs, partitions or the like characterized by the material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2329/00—Electron emission display panels, e.g. field emission display panels
  • H01J2329/86—Vessels
  • H01J2329/8625—Spacing members
  • H01J2329/864—Spacing members characterised by the material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2329/00—Electron emission display panels, e.g. field emission display panels
  • H01J2329/86—Vessels
  • H01J2329/8625—Spacing members
  • H01J2329/8645—Spacing members with coatings on the lateral surfaces thereof
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P40/00—Technologies relating to the processing of minerals
  • Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
  • Y02P40/57—Improving the yield, e-g- reduction of reject rates

Definitions

• the present invention relates to spacers (or spacers) intended to keep spaced apart two substrates constituted by sheets of a material such as glass.
• spacers used to maintain a space between two sheets of glass more particularly a space of limited thickness, generally less than a millimeter or a few millimeters, over the entire surface of the glass sheets.
• Such a configuration is widely sought for the production of screens for viewing, whatever the technology; these are for example plasma screens, field emission screens (FED), such as microtip screens, electroluminescence screens, etc.
• Such a configuration can also be sought for the production of insulating glazing under vacuum or of flat lamps, such devices comprising at least two sheets of glass, at least one spacing having to be maintained between two neighboring sheets.
• flat lamps should be understood to include lamps which may have a curvature on at least part of their surface, whatever the technology of these lamps.
• this phenomenon is due to the implantation of charges at the level of the spacer because of the secondary emission coefficient of the material, defined by the ratio of the number of secondary electrons re-emitted on the number of primary electrons received; a coefficient different from 1 leads to a local charge effect which, depending on whether it is positive or negative, leads to a shine or darkening effect, linked to the deviation of the electron trajectory.
• a first type of known spacer is a glass spacer, in particular in the form of balls or cylinders polished so as to be as less visible as possible. It is also known to produce fiber type glass spacers having a rectangular type section.
• a particular embodiment consists of composite ceramic spacers, an electrically insulating core and an electrically conductive coating layer, formed of ceramic comprising oxides of transition metals, such as Cr, Ti, Fe and V.
• a conductive coating which can be produced from amorphous silicon, doped or not with boron, phosphorus, arsenic or antimony deposited by gas phase pyrolysis (CVD), or from conductive elements (silver, gold, copper), but which are migrated to the surface by applying a heat treatment or an ion exchange.
• the glass matrix comprises at least minus 1% of oxides of transition elements existing under several degrees of oxidation.
• the Applicant Company sought to remedy this drawback and to manufacture spacers capable of meeting the requirements of thermo-mechanical properties while having an electronic conductivity allowing them to remain invisible as a result of the evacuation of positive or negative charges liable to s 'accumulate locally ("local charge effect", see page 3, lines 1 to 7 of WO 01/66478). She discovered that it was not necessary to use a special glass as described in WO 01/66478 to constitute the entire spacer, and that it was enough to use this glass or a glass of the same type of coating of all or part of the spacer, the latter being made of the material that best meets the desired thermo-mechanical properties.
• the spacer according to the invention therefore remains invisible because the electronically conductive layer which coats it allows the abovementioned charges to be removed to a depth less than or equal to 10 ⁇ m, equivalent to the depth of penetration of the electrons.
• the spacers of the invention therefore have a core which can advantageously be made of the same glass as the substrates, the thermomechanical properties of the spacers then being similar to those of the substrates. They also make it possible to have a good compromise between cost and mechanical strength.
• the present invention therefore firstly relates to a spacer intended to maintain a space between two substrates formed from glass sheets, more particularly a space of limited thickness, generally less than a few millimeters, over the entire surface of the sheet substrates, in a device such as a display screen, insulating glass or a flat lamp, the surface of said spacer being at least partly electronically conductive, characterized in that said spacer- is formed of a heart not exhibiting electronic conductivity, the shape and the constituent material of which are chosen to ensure the thermo-mechanical behavior of the substrates in the final device, said core being coated at least in part with at least one layer of a glass having an electronic conductivity and capable of giving the spacer an electronic conductivity at 50 ° C.
• Electronic conductivity is distinct from ionic conductivity as observed for traditional soda-lime glasses which contain alkalis.
• the electronic conductivity of the core is zero or substantially zero since there can always be a residue of electronic conductivity due for example to iron impurities always present in the raw materials.
• the coating there may for example be a few alkalines capable of migrating and thus contributing to an ionic conductivity, even if its value is much lower than the electronic conductivity.
• the power lost by the electronic conduction of the spacers must remain below a fixed value; it is for example between 1 and 50 W / m 2 for microtip screens.
• the glass constituting a coating layer comprises at least 1 mol%, preferably at least 5 mol%, of at least one oxide of a transition element from groups IB, IIIB, VB, VIB, VIIB and VIII of the Periodic Table of the Elements being able to exist under several degrees of oxidation.
• a transition element from groups IB, IIIB, VB, VIB, VIIB and VIII of the Periodic Table of the Elements being able to exist under several degrees of oxidation.
• transition elements mention may be made of V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Ru, Rh, Ta, W, Re, Os, Ir, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Tm and Yb.
• corresponding oxides mention may be made of Fe 2 0 3 and V0 5 .
• transition elements can have another advantage than that of imparting electronic conductivity to the spacer.
• these transition elements have a strong coloring power, for example in the case of Fe and Cr, it is possible to obtain a black or dark appearance of the resulting spacer, at least as regards the cross-section of the spacers seen through the substrate on which they are deposited.
• This black aspect can make it possible, in the case of certain screens, to consider the spacer as a constituent element of the “black matrix”, that is to say of the black network which defines the pixels and which corresponds to the area where the spacers are fixed. Indeed, it is then possible to fix the spacers directly on the substrates without intermediate "bonding" material.
• a first possibility is then to insert the spacers in the "black matrix” in which an area is hollowed out beforehand, for example by photolithography, in order to release an imprint of dimensions barely greater than those of the spacer. This operation may be sufficient to secure the spacer with the substrate.
• a second possibility possibly implemented simultaneously with the previous one, consists in fixing the spacer to the substrate by "anodic bonding", that is to say in applying a given electric field and temperature to establish a chemical link between the two materials, insofar as alkaline ions are present in the glass matrix of the spacer core.
• the glass constituting a layer of the coating is in particular a glass having the following composition, in mol%, for a total of 100 mol%: (A) Si0 2 25 - 75
• (A) Si0 2 is a network forming oxide; its content will advantageously be less than 73% to reduce the melting temperatures and prevent too rapid degradation of the refractories constituting the oven. Below 25%, the stability of the glasses becomes insufficient and the risks of devitrification increase.
• (C) Al 2 0 3 provides the glass matrix with a stabilizing role and makes it possible in particular to limit the risks of devitrification, particularly for low silica contents. Its content is advantageously less than 35% and preferably less than 20%, so that the viscosity of the glass matrix at high temperature is not too great.
• (D) Zr0 2 unlike Al 2 0 3 , does not increase the viscosity of the glass matrix at high temperature. Its content does not exceed 10% and preferably 8% for simplify the merger and limit the risk of devitrification.
• alkaline earth oxides (F) Concerning the alkaline earth oxides (F), they are introduced for reasons similar to those of the alkaline oxides and, in addition, they make it possible to improve the stability of the glass with respect to the risks of devitrification. Heavy oxides, such as SrO or BaO, are particularly favored to limit the mobility of alkaline ions and, consequently, reduce ionic conductivity and prevent the risks of contamination, for example of screens, by alkaline ions. It is in fact indicated that the diffusion of the alkalis disturbs the electronic conductivity and leads to a phenomenon of aging of the layer when it is stressed under a strong electric field (difference in anode / cathode potential) for example in the EDFs.
• a strong electric field difference in anode / cathode potential
• the invention also provides for being able to introduce the oxide B 2 0 3 in contents not exceeding 30% and advantageously less than 10%, in order to maintain satisfactory mechanical properties.
• B 2 0 3 makes it possible in particular to improve the homogeneity of the composition during melting and reduces the melting temperatures of said composition, when it replaces Si0 2 . It also makes it possible to reduce the viscosity at high temperature.
• the glass matrix is of the borosilicate type and the B 2 0 3 content is then greater than 8% and preferably greater than 10%.
• the oxide P 2 0 5 can also be used in contents not exceeding 5%, in particular for reducing the viscosity at high temperature.
• the oxides Ti0 2 and ZnO can also be used for reasons similar to those mentioned for B 2 0 3 and P 2 0 5 , in particular in terms of regulating the melting parameters of the glass compositions.
• the choice of all the oxides is made so as to control the conductivity ⁇ (electronic + ionic conductivity), the coefficient secondaire of secondary emission and the dielectric characteristics ⁇ of the spacer. Indeed, the three quantities ⁇ , ⁇ and ⁇ have an impact on the value of the charge and the surface potential and therefore for example in the EDFs, on the amplitude of the phenomenon of darkening / brightness around the spacers.
• the choice of oxides is also made so as to limit, on the one hand, the aging phenomena, and, on the other hand, the energy losses.
• Additional elements may be present in the glass matrix, with contents of less than 1%. They are introduced, for example, to facilitate melting and refining (As, Sb, F, Cl, S0 3 , ...), or else they are introduced in the form of impurities in the raw materials used or d '' impurities from wear of refractories.
• the coating glass can be produced in a crucible at high temperature.
• the control of the redox conditions of the glass is carried out by controlling the more or less reducing nature of the melting atmosphere, by the temperature of the molten bath, possibly by the insertion of reducing elements such as coke or the like, for example a gas, in the molten bath.
• This control of the redox will in particular make it possible to control the electronic conduction so that it allows an evacuation of the charges while limiting the energy losses.
• the coating can consist of several layers, but a coating with a single layer is preferred for cost reasons.
• the thickness of a layer of the coating glass can vary to a large extent: it can be from 1 to 10,000 nm, preferably from 1 to 2000 nm.
• between the core and the coating may have been arranged at least one layer of at least one agent improving the adhesion and / or the attachment of the coating to the core .
• these agents mention may be made of NiCr and A1 2 0 3 .
• the core of the spacer according to the invention can be made of a material chosen from glasses; ceramics; and polymers.
• glasses because unlike polymers, glass does not tend to deform or sag under the effect of heat (heat treatment is necessary to seal the edges of a screen).
• Ceramics have good mechanical strength, but compared to glass, it is more difficult to make varying their form and also their implementation is more costly.
• any type of glass can be used, but preferably the glass will be chosen from soda-lime glasses, alumino-silicate type glasses and borosilicate type glasses.
• the glass chosen may be photosensitive, but this choice is not particularly preferred.
• the core glass is chosen to have thermo-mechanical properties similar to those of the substrates.
• the core of a spacer according to the invention can even very advantageously consist of the same glass as that forming the substrates with which the spacer is intended to be used.
• a heart glass having a coefficient of expansion between 20 and 300 ° C of between 60 x 10 "7 and 105 x 10 " 7 K “1 , preferably between 60 x 10 " 7 and 95 x 10 "7 K “ 1 , in particular between 75 x 10 ⁇ 7 and 95 x 10 "7 K “ 1
• the coefficient of expansion for a borosilicate type glass can however be between 30 x 10 "7 and 50 x 10 "7 K “ 1 .
• the core glass having a temperature corresponding to the Strain Point, high enough so that it does not collapse during the peripheral sealing step of the substrates in order to form FED screens in particular.
• this temperature (T stra i n ) is greater than 500 ° C, preferably greater than 540 ° C.
• the core glass advantageously has a high elastic modulus E, for example greater than 90 GPa, preferably greater than 100 GPa, in particular greater than 130 GPa.
• the elastic modulus E is increased by introducing oxides (G ') into the composition of the glass - which also has the effect of increasing the density of the glass - or even by introducing nitrogen - which allows an E module greater than 130 GPa.
• the Applicant Company has demonstrated that in particular in the case of spacers produced according to the method described in EP-A-0 627 389, the mechanical properties of the spacer depend directly on its elastic instability and therefore on its modulus. elasticity; it interprets this phenomenon by a particularly remarkable surface condition of the spacers after manufacture according to this process, without any other intervention; that is to say that the spacers produced according to this process are free from defects which can lead to rupture when they are subjected to the stresses linked to their applications.
• the advantage of having a high module E is important because then the mechanical strength of the core glass being improved, the number of spacers can be reduced. Consequently, the electronic conductivity and / or the thickness of the coating layer can be increased while preserving an overall energy loss via the spacer function to an acceptable value. Another advantage is that the cost of placing the spacer is reduced. Mention may be made of a heart glass having the following composition, in mol%, for a total of 100 mol%:
• the Si0 2 content will preferably be less than 55% when it is desired to favor the mechanical properties, in particular the modulus of elasticity. Below 25%, the stability of the glasses becomes insufficient and the risks of devitrification increase.
• Al 2 0 3 advantageously contributes to improving the mechanical properties, in particular the modulus of elasticity.
• the presence of the oxide Li 2 0 is favored, when mechanical properties, in particular the modulus of elasticity, are sought, the oxides Na 2 0 and K 2 0 possibly being totally absent from the matrix .
• the oxide Li 2 0 can be absent from the matrix, this oxide being more expensive than the others.
• An alkaline oxide content of at least 1% is advantageously required to obtain an adhesion of the “anodic bonding” type.
• the alkaline earth oxides increase the temperature of Strain Point. MgO and CaO oxides are particularly favored when looking for a high elastic modulus.
• the introduction of at least one oxide (G') into the glass matrix makes it possible to reach elasticity modulus values of up to 140 GPa.
• the sum of the oxide contents (G ') is greater than 1% and advantageously does not exceed 25%.
• the oxides (G ') are preferably chosen from the following: Y 2 0 3 , La 2 0 3 , Ce 2 0 3 , Pr 2 0 3 , Nd 2 0 3 , Sm 2 0 3 , Eu 2 0 3 , Gd 2 0 3 , Tb 2 0 3 , Dy 2 0 3 , Ho 2 0 3 , Er 2 0 3 , Tm 2 0 3 , Yb 2 0 3 , Lu 2 0 3 .
• (I ′) P 2 0 5 can also be used in contents not exceeding 5%, in particular for reducing the viscosity at high temperature without degrading the mechanical properties too much, in particular the modulus of elasticity.
• the invention also advantageously provides for introducing nitrogen into the glass matrix.
• This introduction allows according to the invention to obtain elastic moduli greater than 140 GPa and up to 180 GPa.
• the introduction of nitrogen can be obtained during the fusion by carrying out the latter under a neutral or reducing atmosphere, for example of argon, nitrogen or a mixture of nitrogen and hydrogen.
• Nitrogen is then introduced into the raw materials in the form, for example, of Si 3 N 4 , AIN, BN. Nitrogen also has the advantage of being able to obtain a black coloration of the spacers.
• the core of the spacer according to the invention can have any shape, such as a prism, in particular a straight prism with a square, rectangular, trapezoidal, cruciform ... base, a cylinder, in particular a straight cylinder of circular section, or a sphere.
• the hearts of. spherical shape is not preferred because it tends to roll and to stress strongly the substrates because of the small surface of contact spacer / substrate.
• glass polyhedra as described in EP-A-0 627 389 and / or manufactured by the process as described in this same document, as well as all the shapes described for the spacers in WO 99/56302.
• the latter are described as having a substantially polygonal support section having at least one rectilinear support surface which fits into a rectangle having the dimensions a, b and the spacer rising to a height 1, and their dimensions verifying the following relationships: a ⁇ 300 ⁇ m; 0.2 mm ⁇ 1 ⁇ 20 mm; and b / a ⁇ 1000, and preferably b / a ⁇ 200: -
• the bearing surface that is to say the surface in contact, for example, of a glass sheet, is rectangular and has the dimensions a, b, the height 1 of the spacer making it possible to maintain an identical space 1 between two sheets
• pillar or "pillar" type hearts the drawing section of which is in the shape of a cross, the support section which this time corresponds to the drawing section has a straight surface rectangular of dimensions a, b, the spacer further having a height 1.
• Figures 3 and 4 of WO 99/56302 respectively illustrate a form of beam and a form of pillar of cruciform section. These two forms are given as examples for reasons of mechanical strength, and also because the parts are easier to place on the substrate because of their geometry.
• cylindrical cores with a diameter of the same order of magnitude as the value a above.
• the spacer according to the present invention advantageously has an electrical resistance to the passage of current between 10 "5 and 10 7 G ⁇ , and preferably greater than 0.1 G ⁇ .
• the spacer has a density greater than 3, which facilitates its handling and its positioning.
• the spacer according to the present invention is advantageously of the type of those having the form of pillars or elongated beams, metal electrodes having been deposited on the sections of the pillars or the edges of the elongated beams to facilitate the evacuation of surface loads from the spacer to the electrodes disposed on the substrates.
• the present invention also relates to a method of manufacturing a spacer as defined above, characterized in that at least one layer of coating glass is deposited on at least part of at least one element chosen from a heart already manufactured or an element obtained at a stage of the manufacture of the latter, the glass used for the deposition having a composition chosen so that, if this composition is modified during deposition, it has in the finished product the composition such that defined above.
• the heart can be made by the following successive operations:
• the operations of depositing the coating layer (s) being carried out on the pitch bar before it is stretched and / or the rod before it is cut to the desired length and / or on the ends of the assembled spacers and / or on the individual spacers.
• the coating can thus be deposited:
• a primitive rod passes through a heating ring which makes it possible to stretch the glass into rods which are assembled parallel to each other and secured in an appropriate binder , for example a low melting point wax or an adhesive.
• an appropriate binder for example a low melting point wax or an adhesive.
• the set of rods is cut, possibly mechanically polished at the glass sections, to form spacers which are recovered by melting or dissolving the binder. This way of proceeding makes it possible to obtain precise dimensions at a reduced cost.
• the coating layer (s) is formed by evaporation, said method comprising the steps consisting in: - in a vacuum enclosure, depositing at least one element to be coated placed on a support and place a refractory container containing the glass to be deposited; and
• the coating layer (s) is formed by spraying, said method comprising the steps consisting in:
• redox plays an important role in the properties of the coating which influence the value of the surface charge, in particular on the electronic conductivity.
• the redox and / or the composition of the glass constituting the coating may be different from that of the initial glass placed in the crucible (case of evaporation) or constituting the target (case of spraying ).
• the elements to be coated at least one layer of an agent improving the adhesion or the bonding of the coating before depositing a layer of coating glass; it is also possible to apply to the coated element constituted by the rod before cutting to the desired length or by the final core a heat treatment under an oxidizing or reducing atmosphere in order to adjust the electronic conductivity and / or the secondary emission coefficient and / or the dielectric properties and / or the adhesion of the coating.
• a metallic deposit serving as an electrode can be formed on the final spacer.
• a metallic deposit serving as an electrode can be formed on the pitch rod before it is stretched and / or on the individual rods and / or on the assembled spacers. and / or on the individual spacers.
• the present invention also relates to a spacer obtained by the method as defined above; on the use of the spacer as defined above or manufactured by the process as defined above as a spacer for display screens, vacuum glazing and flat lamps comprising at least two glass sheets; as well as on display screens, in particular of the plasma or field emission type, in particular of the field emission (FED) type, vacuum glazing and flat lamps comprising at least two sheets of glass spaced apart by spacers as defined above or manufactured by a process as defined above.
• a spacer obtained by the method as defined above on the use of the spacer as defined above or manufactured by the process as defined above as a spacer for display screens, vacuum glazing and flat lamps comprising at least two glass sheets; as well as on display screens, in particular of the plasma or field emission type, in particular of the field emission (FED) type, vacuum glazing and flat lamps comprising at least two sheets of glass spaced apart by spacers as defined above or manufactured by a process as defined above.
• FED field emission
• the conductivity of the layer is measured as follows.
• the layer is deposited on a substrate comprising fine electrodes.
• the conductivity is deduced from the current measurement when a known potential difference is applied between two electrodes, and having moreover measured the thickness of the layer, the length of the electrodes and the distance separating these electrodes. In addition, the measurements were verified for temperatures ranging from 50 to 100 ° C.
• the electronic conductivity is then distinguished from the ionic conductivity either by measurements at different frequencies and at different temperatures, or by observing the evolution of the conductivity when the samples are subjected to a direct voltage of 100 volts and at a temperature of 100 °. vs.
• a rapid decrease in the conductivity as a function of time is observed. This decrease in conductivity is due to the mobility of ions which easily migrate under the electric field, for example Na ions.
• the conductivity is substantially stable as a function of time.
• E expresses the modulus of elasticity or Young's modulus.
• E was measured by four-point bending on test pieces of dimensions 100 x 10 x 4 mm 3 , made from the glasses studied.
• the bars, in which the test pieces were then cut, were first annealed for one hour at a temperature corresponding to a viscosity of 10 13 Poise, then were brought back to room temperature at a rate of 2 ° C./ min.
• T s train (Strain Point) is the temperature corresponding to a viscosity of 10 14 ' 5 Poise.
• ⁇ is the coefficient of expansion measured between 20 and 300 ° C.
• a first batch of spacer cores (CEI) having the shape described in FIG. 4 of WO 99/56302 was manufactured from a primitive rod, in a known drawing installation as described in EP-A- 0 627 389, WO 99/56302 or WO 01/66478.
• the glass composition of the CEI cores, expressed as a molar percentage, and the corresponding values of ⁇ , E, T stra i- ⁇ . ⁇ and d are shown in Table 1 below.
• VR glass has the following properties ⁇ at 50 ° C (ohm -1 , cm “1 ): 8 x 10 " 11 E (GPa) 81
• An absolute pressure of approximately 10 "6 mbar is established in the enclosure and a layer of VR glass 200 nm thick is deposited at a speed of 1 nm / s.
• the sample holder is rotated on which the CEI cores are maintained, so as to obtain a layer of uniform thickness on all the faces of the cores.
• Example 1 was reproduced by replacing the heart glass CEI by the heart glasses respectively CE2 and CE3, whose compositions and values ⁇ , E, T stra i n . and and d are reported in Table 1.
• the glass VRc forming the surface layer of the spacers according to Examples 1 to 3 was analyzed by SIMS. Its composition is as follows, in mol%:
• VRc glass is enriched with oxides of transition elements Fe and V which help improve electronic conductivity.
• VRc glass has an electrical conductivity ⁇ equal to 3 x 10 "7 ohm " 1 , cm “1 measured at 20 ° C. This value is much greater than the value of ⁇ equal to 8 x 10 ⁇ 12 ohm " 1 .cm "1 obtained for VR glass measured under the same conditions.
• a fusion test has shown that VRc glass is not fusible: it is believed that this is due to the low content of alkaline earth oxides Na, Sr and Ba which play the role of fondants.
• the deposition of the coating glass on the cores by evaporation is particularly advantageous because it makes it possible to reach a higher level of electronic conductivity than that of the starting glass, and also to form a layer of non-fusible glass in bulk.
• FED type screens formed with the spacers of Examples 1 to 3 and IEC glass substrates do not show darkening / gloss phenomena or aging near the spacers.
• the mechanical strength of the screen is satisfactory, in particular during the step of sealing the edges.

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