Classifications

• • 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
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
• • 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
  • C03C27/00—Joining pieces of glass to pieces of other inorganic material; Joining glass to glass other than by fusing
  • C03C27/06—Joining glass to glass by processes other than fusing
• • 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
  • C03C8/00—Enamels; Glazes; Fusion seal compositions being frit compositions having non-frit additions
  • C03C8/02—Frit compositions, i.e. in a powdered or comminuted form
• • 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
  • C03C8/00—Enamels; Glazes; Fusion seal compositions being frit compositions having non-frit additions
  • C03C8/14—Glass frit mixtures having non-frit additions, e.g. opacifiers, colorants, mill-additions
• • 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
  • C03C8/00—Enamels; Glazes; Fusion seal compositions being frit compositions having non-frit additions
  • C03C8/14—Glass frit mixtures having non-frit additions, e.g. opacifiers, colorants, mill-additions
  • C03C8/16—Glass frit mixtures having non-frit additions, e.g. opacifiers, colorants, mill-additions with vehicle or suspending agents, e.g. slip
• • 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
  • C03C8/00—Enamels; Glazes; Fusion seal compositions being frit compositions having non-frit additions
  • C03C8/24—Fusion seal compositions being frit compositions having non-frit additions, i.e. for use as seals between dissimilar materials, e.g. glass and metal; Glass solders
  • C03C8/245—Fusion seal compositions being frit compositions having non-frit additions, i.e. for use as seals between dissimilar materials, e.g. glass and metal; Glass solders containing more than 50% lead oxide, by weight

Definitions

• the present invention relates to a glass frit suitable for sealing glass surfaces together, said glass frit comprising lead oxide. Furthermore, the present invention relates to a sealing paste comprising such a glass paste as well as to a method for sealing two glass surfaces together. Glass frit can be used to seal glass surfaces together. To this end, a sealing glass paste is made out of the glass frit by mixing the glass frit powder with a binder solution or vehicle.
• a well-known example of the use of glass frit powders is found in the manufacture of cathode ray tubes, where the faceplate and the funnel of the CRT are sealed together using a glass frit, h order to lower the temperature necessary for CRT sealing, glass frit compositions with high PbO content are preferably used. A high PbO content leads however to a tendency towards PbO reduction and the formation of metallic lead. The presence of metallic lead is disadvantageous as it affects the glass frit adhesion and the electrical properties of the seal.
• US-A-3,973,975 deals with the above problem and discloses the incorporation of a powder of a higher oxide of a cation in the sealing glass frit in order to prevent PbO reduction.
• the higher oxide of the cation can be reduced to a lower oxide of the cation when it is exposed to reducing conditions.
• the higher oxide of said cation is selected from the group consisting of Pb 3 O 4 , BaO 2 , MnO 2 , Mn 2 O 3 , Fe 3 O 4 , CuO, Cu 2 O, Tl 2 O 3 , TeO 2 , Ta 2 O 5 , Nb 2 O 5 , V 2 O 5 , CeO 2 and Bi 2 O 3 .
• the amount of said higher oxide of said cation that has to be added in order to prevent PbO reduction is relatively high.
• the higher cation oxides only reduce to the corresponding lower cation oxides at reducing conditions.
• the present invention aims to provide a glass frit according to the preamble that prevents the reduction of the PbO that is present in said glass frit and that overcomes the above problems.
• the present invention is characterized in that the glass frit further comprises an oxidizing agent selected from the group of higher valent oxides comprising manganates (Nil), manganates (VI) and ferrates (VI).
• an oxidizing agent selected from the group of higher valent oxides comprising manganates (Nil), manganates (VI) and ferrates (VI).
• Such oxidizing agent generates oxygen at the combustion temperature of the binder that is present in the sealing glass paste, thereby preventing the reduction of PbO to metallic lead. It is emphasized that reducing conditions are not necessary for the generation of oxygen.
• a further advantage of the glass frit with the oxidizing agent according to the present invention is that organic contamination on the sealing edge is more effectively burned away due to the presence of oxygen generated by the oxidizing agent.
• the oxidizing agent is defined as X(MnO 4 ), wherein X is an element selected from the group composed of Na, K, Cs, Ba, Sr, Ca, Mg or Zn.
• X is an element selected from the group composed of Na, K, Cs, Ba, Sr, Ca, Mg or Zn.
• a particularly preferred compound is BaMnO . Said compound has proved to be especially useful as an oxidizing agent.
• a particular advantage of the above material is that no new material is introduced in the glass frit.
• the glass frit only contains 0.02 to 0.8 wt.% of oxidizing agent, based on the total amount of glass frit powder.
• the glass frit only contains 0.05 to 0.5 wt.% of oxidizing agent.
• the glass frit according to the present invention comprises an amount of PbO of at least 75 wt.%.
• the present invention furthermore relates to a sealing glass paste that comprises at least a glass frit according to the present invention and a vehicle.
• a sealing glass paste has to be made of the glass frit by mixing said glass frit with a suitable vehicle.
• Said vehicle can be an organic binder based on nitrocellulose/amyl- or butylacetate that burns away at a low temperature.
• a disadvantage of such a binder is that it causes environmental problems and that NO x is present as an end product.
• the vehicle advantageously comprises an aqueous solution of a cellulose ether.
• the oxygen that is generated by the oxidizing agent in the glass frit can be used to aid the full combustion of the vehicle.
• the present invention relates to a method for sealing two glass surfaces together, at least comprising the steps of: - providing a first and a second glass surface; applying an amount of a sealing glass paste on at least one of said surfaces; placing the glass surfaces against each other with the sealing glass paste in between; subjecting the assembly of glass surfaces and sealing paste to a temperature sufficient to fuse the sealing glass paste on both glass surfaces, thereby sealing the two surfaces together; and cooling the resulting sealed assembly.
• the sealing glass paste comprises a sealing glass paste according to the present invention.
• the first glass surface comprises a faceplate of a cathode ray tube
• the second glass surface comprises a funnel portion of a cathode ray tube.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Ceramic Engineering (AREA)
• Glass Compositions (AREA)
• Joining Of Glass To Other Materials (AREA)
• Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

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Family Applications (1)

Country Status (6)

Cited By (7)

Families Citing this family (1)

Citations (2)

• 2003
  • 2003-06-12 EP EP03735904A patent/EP1517865A1/en not_active Withdrawn
  • 2003-06-12 JP JP2004515166A patent/JP2005529836A/ja active Pending
  • 2003-06-12 CN CN 03814214 patent/CN1662461A/zh active Pending
  • 2003-06-12 AU AU2003236995A patent/AU2003236995A1/en not_active Abandoned
  • 2003-06-12 WO PCT/IB2003/002730 patent/WO2004000745A1/en not_active Application Discontinuation
  • 2003-06-17 TW TW92116419A patent/TW200404752A/zh unknown

Patent Citations (2)

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