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
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/078—Glass compositions containing silica with 40% to 90% silica, by weight containing an oxide of a divalent metal, e.g. an oxide of zinc
• • 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
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
  • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
• • 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
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/11—Glass compositions containing silica with 40% to 90% silica, by weight containing halogen or nitrogen
  • C03C3/112—Glass compositions containing silica with 40% to 90% silica, by weight containing halogen or nitrogen containing fluorine
• • 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
  • C03C4/08—Compositions for glass with special properties for glass selectively absorbing radiation of specified wave lengths
  • C03C4/087—Compositions for glass with special properties for glass selectively absorbing radiation of specified wave lengths for X-rays absorbing glass

Definitions

• the invention relates to PbO-free glasses for cathode-ray tubes with a high x-ray protection effect and at the same time good acid resistance and radiation stability.
• compositions of radiation-stable glasses for the production of cathode ray tubes are known.
• the X-ray absorption coefficient ⁇ for 0.6 A is at values of
• the stability against UV, electron and X-rays is achieved by the lack of easily reducible components, such as PbO and As 2 O 3 , and by the introduction of known stabilizing additives, such as 0.3 -
• CeO 2 especially for preventing tanning by X-rays
• TiO 2 especially for preventing solarization, ie preventing discoloration by UV rays
• the glasses mentioned in DE-OS 31 03 345 are preferably used for the production of television tubes or television sets with large-area image displays (large-volume picture tube) or also smaller television projection tubes with high operating voltages up to approx. 40 KV with image projected onto a wall.
• large-area image displays large-volume picture tube
• smaller television projection tubes with high operating voltages up to approx. 40 KV with image projected onto a wall.
• Glass parts are subjected to an acidic washing process with dilute HF or with differently concentrated NH 4 HF 2 solutions. No visible attack may occur, for example due to the formation of etching structures. The same applies to the process of recovering glass parts from defective picture tubes.
• the glasses In addition to the mandatory high level of X-ray protection and high resistance to discoloration due to UV, e and ⁇ rays, the glasses must therefore also have sufficient acid resistance.
• the ⁇ values for 0.6 ⁇ are generally between 20 and 28 x cm -1 . This is achieved with glasses that are round
• the known glasses according to DE-OS 31 03 345 do not meet the requirement for sufficient acid resistance, such as shows up in comparison tests;
• Examples 3, 5, 11, 13 and 14 were remelted in a 1 liter platinum crucible between 1450/1400 ° C for 2.5 h, homogenized by subsequent stirring with a Pt stirrer up to approx. 1200 ° C, finally after 45 min standing at 1380 ° C poured into an NCT 3 steel mold and cooled in a cooling oven from 520 ° C at 20 ° C / h to room temperature.
• the acid resistance of the cooled castings was determined in accordance with DIN 12116 and the water resistance in accordance with DIN 12111.
• Table 1 The test results are summarized in Table 1:
• the aim of the present invention is glasses for cathode ray tubes with a high x-ray protective effect and good radiation stability, which at the same time have sufficient acid resistance.
• the components which are decisive for the radiation stability are present in the following areas:
• the glasses achieve values of 18.3 - 82 mg / dm 2 weight loss and are thus far superior to all similar glasses that have become known. As a result of the overall moderate acid resistance of the
• the superiority of the glasses becomes even clearer when the very high x-ray absorption values ⁇ resulting from the composition are also taken into account.
• the ⁇ value for 0.6 ⁇ for these glasses is between 53.5 - 63 x cm -1 . Since the product of glass thickness and absorption coefficient ⁇ is responsible for the total absorption of X-rays, this means that, for example, the screen of a heavy-duty projection tube can be pressed with thinner walls compared to a less absorbent glass, which advantageously means a higher thermal resistance of the Tube is reached in operation and thus at the same time a certain countermeasure to the negative influence of the relatively high E-moduli on the mechanical strength of these glasses.
• the UV stability of the glasses corresponds to that of the prior art.
• 5 mm thick, polished glass samples at a distance of 7 cm are exposed to 24-hour radiation with a high-pressure mercury lamp, the maximum of which is 365 nm with another band at 254 cm.
• the decrease in transmission from irradiated to unirradiated sample is a measure of. the UV or. the resistance to solarization.
• the critical wavelength range is between 360 and 420 nm for glasses, and the decrease lies in this wavelength range, which is not perceptible to the eye
• the UV stability can be increased by adding TiO 2 (up to approx. 1% by weight).
• CeO 2 Content of CeO 2 (up to approx. 2% by weight) as the most effective means of reducing discoloration by X-rays
• a CeO 2 additive is absolutely necessary for these glasses, which are suitable for high operating voltages, because, as already stated, this can significantly reduce the discoloration of the secondary X-rays triggered by the electrons.
• a compromise will therefore be sought for the addition of TiO 2 and CeO 2 , for example with 0.3-0.5% by weight TiO 2 and 0.65-0.80% by weight CeO 2 .
• the glasses according to the invention were exposed to radiation with the electron gun at 0.14 A sec / cm 2 at an acceleration voltage of 50 KV (corresponds to a radiation dose of 20.6 r), and then the transmission measured by
• the decrease in permeability compared to the unirradiated sample is a measure of the discoloration due to e- and ⁇ -browsing. If the irradiated sample is then heated to 400 ° C at 20 ° C / h and kept at this temperature for 4 h, the ⁇ -browning disappears while the e-browning is retained.
• the degree of discoloration due to e- and ⁇ -browsing is influenced by the operating conditions of the cathode ray tube, by the sum of the alkalis, by the ratio Na 2 O / K 2 O and by the CeO 2 concentration. Pure Na 2 O-rich glasses have the greatest tendency to discolour, even against UV rays.
• Table 3 lists examples of glasses of the composition range according to the invention in% by weight.
• Table 4 contains the main property values of the glasses of Table 3.
• Example 1 in Table 3 is a glass that is outside the claimed range; it is intended to show how critical the selected areas of composition are.

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Glass Compositions (AREA)

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• 1982
  • 1982-12-04 DE DE3244970A patent/DE3244970C1/de not_active Expired
• 1983
  • 1983-11-24 EP EP83903526A patent/EP0127633B1/de not_active Expired
  • 1983-11-24 WO PCT/EP1983/000314 patent/WO1984002127A1/de not_active Ceased
  • 1983-11-24 JP JP83503712A patent/JPS60500371A/ja active Granted
• 1984
  • 1984-07-06 US US06/629,729 patent/US4599319A/en not_active Expired - Fee Related

Patent Citations (3)

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