Classifications

• • 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
  • H01J29/867—Means associated with the outside of the vessel for shielding, e.g. magnetic shields
  • H01J29/868—Screens covering the input or output face of the vessel, e.g. transparent anti-static coatings, X-ray absorbing layers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2209/00—Apparatus and processes for manufacture of discharge tubes
  • H01J2209/01—Generalised techniques
  • H01J2209/012—Coating
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2229/00—Details of cathode ray tubes or electron beam tubes
  • H01J2229/89—Optical components associated with the vessel
  • H01J2229/8913—Anti-reflection, anti-glare, viewing angle and contrast improving treatments or devices

Definitions

• the invention relates to a method of manufacturing a cathode ray tube provided with a multilayer antistatic filter on a display window.
• the invention also relates to a cathode ray tube provided with a multilayer antistatic filter on a display window.
• Cathode ray tubes are used, inter alia, in television receivers and computer monitors.
• a method of the type mentioned in the opening paragraph and a cathode ray tube of the type mentioned in the second paragraph are known from European Patent Application EP 649160.
• the display window is statically charged and incident light is reflected by the display window.
• the conductive layer provides for the removal of the static charge, and the conductive layer and the second layer together form or are part of an anti- reflective filter to reduce reflection of incident light.
• the known method provides a filter having the desired antistatic effect, the conductance of the antistatic layer (approximately 1 M ⁇ /square) is insufficient to shield the viewer from electromagnetic fields emitted by the cathode ray tube. This would require resistance values ⁇ approximately 1 k ⁇ /square. It is an object of the invention to provide a method of manufacturing a multilayer filter which demonstrates antistatic, shielding and reflection-suppressing properties, and which can be manufactured in a simple manner.
• the method in accordance with the invention is characterized in that a first, conductive layer, preferably on the basis of indium-tin oxide, having a surface resistance 1 k ⁇ /square is sputtered onto the display window, and a further layer, which is predominantly composed of SiO 2 , and which serves to influence the reflection properties of the filter is provided by means of a wet-chemical process.
• the surface resistance of the conductive layer provided by sputtering is so low that, unlike the known method, a surface resistance below 1 k ⁇ /square is achieved at layer thicknesses of the order of 10-20 run or less.
• the layer may be, for example, a metallic layer or, preferably, a layer on the basis of indium-tin oxide (for example a layer containing ITO or ATO).
• Metallic layers absorb more visible light than indium-tin-oxide layers. If the contrast is to be improved, a metallic layer can be provided, for example a very thin layer of aluminium. If the light intensity of the image displayed is important, then, preferably, a transparent conductive layer on the basis of metal oxides, for example on the basis of indium-tin oxide, is applied. In the known method, such resistance values would require much larger layer thicknesses. A resistive layer of such thickness actually does not exhibit useful interference phenomena. On layers of such a large thickness, at least two further layers of materials having different refractive indices must be applied to bring about a reflection-influencing effect.
• the further layer which is predominantly composed of silicon dioxide, is in the method in accordance with the invention, not applied by sputtering but provided by means of a wet-chemical process, for example by means of spinning a TEOS solution as described in European Patent Application EP 649160 (PHN 14.663).
• the thickness of said further layer is preferably of the order of 80-150 run, and forming one layer of such thickness by means of sputtering is very difficult. If sputtering were to be employed, the desired reflection-influencing effect could only be achieved by applying various layers to the first layer or by very long sputtering times.
• the combination of sputtering the conductive layer and providing a further layer containing silicon dioxide by means of a wet-chemical process, such as spinning, enables a multilayer antistatic filter to be manufactured which has a reflection- suppressing effect as well as a shielding effect, and which, nevertheless, can be applied in a relatively simple manner.
• "reflection-influencing" layers are to be understood to include layers which influence the glare (diffuse reflection) as well as layers which influence the specular reflection (the reflection coefficient R), either independently or in combination with the conductive layer.
• the first, conductive, sputtered layer is provided, with an anti-glare layer containing silicon dioxide.
• This embodiment of the method provides a double layer AGES filter (Anti-Glare, Electromagnetic Shielding).
• the anti-glare layer is provided by means of a wet-chemical process, for example, by spraying.
• the first, conductive, sputtered layer is provided, with an anti-reflective layer containing silicon dioxide
• an anti-reflective layer containing silicon dioxide By means of this embodiment of the method a double layer ARES filter (Anti-Reflective Electromagnetic Shielding) filter is obtained.
• ARES filter Anti-Reflective Electromagnetic Shielding
• the anti- reflective layer is provided by means of a wet-chemical process, for example, by spinning,
• the first, conductive, sputtered layer is provided with an anti-reflective layer containing silicon-dioxide which anti-reflective layer is coated with an anti-glare layer containing silicon dioxide.
• an anti-reflective layer containing silicon-dioxide which anti-reflective layer is coated with an anti-glare layer containing silicon dioxide.
• the first, sputtered layer is provided with a second layer of a material other than silicon dioxide by means of sputtering, which second layer is provided with an anti-glare layer containing silicon dioxide
• the second layer may comprise, for example, titanium oxide
• the first layer is provided with a second layer of a material other than silicon dioxide by means of sputtering, which second layer is provided with an anti-reflective layer containing silicon dioxide
• a three-layer ARES Anti-Reflective Electromagnetic Shielding
• the anti- reflective layer is provided by means of a wet-chemical process
• the surface resistance of the first layer is below 500 ⁇ /square
• the further layer comprises an absorbing substance
• the color of the filter can be influenced
• the anti-glare layer may be provided, for example, by spraying or atomizing an alcoholic solution of an alkoxysilane compound, followed by a treatment at an elevated temperature, thereby forming a layer of silicon dioxide
• the resultant layer is scratch-resistant and has anti-glare properties owing to the surface texture formed by spraying Said anti-glare effect is substantially independent of the wavelength of light.
• Additional advantages of the additional layers of silicon dioxide include the reduced sensitivity to fingerprints and the greater hardness and scratch-resistance.
• the method according to the invention comprises an intermediate method step, between the sputtering process and the application of the further layer, in which intermediate method step the surface on which the further layer is to be provided is activated to increase the adhesion of the further layer.
• etching solution ed. caustic solution.
• the above-mentioned layer serves as a primer layer deposited on top of the sputtered conductive layer.
• Activation of said primer layer can alternatively be done by e.g. rubbing or etching in an Ar-gas.
• Fig. 1 shows a display device
• Fig. 2 is a schematic, sectional view of a display window of a display device
• Figs. 3a through 3c illustrate an embodiment of the method in accordance with the invention
• Fig. 4 illustrates a number of possible embodiments of the method in accordance with the invention.
• Fig. 1 is a schematic cut-away view of a cathode ray tube 1 having a glass envelope 2 comprising a display screen 3, a cone 4 and a neck 5.
• An electron gun 6 for generating an electron beam is accommodated in said neck.
• This electron beam is focused on a phosphor layer on the inner surface 7 of the display screen 3.
• the electron beam is deflected across the display screen 3 in two mutually perpendicular directions by means of a deflection-coil system (not shown).
• the display screen 3 is provided on the outside with an antistatic coating 8 in accordance with the invention.
• Fig. 2 is a schematic, sectional view of a display screen in accordance with the invention.
• Display screen 3 is provided with an antistatic coating 8.
• Said antistatic coating 8 comprises a first layer 9 (AS), a second layer 10 and a third layer 11
• the first layer 9 comprises tin oxide and is provided by sputtering
• the second layer is made of silicon dioxide
• the first layer and the second layer together form an antireflection filter (AR)
• the second layer may be provided with absorbing constituents, for example, polypyrrole-latex particles, by means of which the transmission properties of the second layer can be changed
• the third layer 11 (AG) provides for an anti-glare effect and is made, for example, of silicon dioxide which is provided by spraying
• Figs 3a through 3c illustrate a method in accordance with the invention
• a conductive layer 31, which is predominantly composed of mdium-tin oxide (ITO) is sputtered onto the display screen 3
• a second layer 32 of silicon dioxide is applied to said layer 31 by means of a wet-chemical process
• a TEOS-solution is spin coated onto layer 31
• a thermal treatment is carried out This treatment results in the formation of a silicon-dioxide layer
• a third layer for example a silicon-dioxide anti-glare layer, is provided by spraying so as to achieve an anti-glare effect
• Fig 4 illustrates a number of possible embodiments of the method in accordance with the invention
• the method in accordance with the invention has still other advantages which render the method very suitable for application on a large scale. Both sputtering and wet-chemical processes can be applied to cathode ray tubes which already are in the assembled state, and heating of the surface to be coated is hardly necessary, or perhaps not necessary at all.
• the filter is provided on a display window of an evacuated cathode ray tube.
• the method in accordance with the invention has a number of distinct advantages over methods requiring the display windows to be in the unassembled state, such as Chemical Vapor Deposition (CVD).
• CVD Chemical Vapor Deposition
• a filter is provided on an unassembled display window, said display window must subsequently be attached to the cone and evacuated. This process involves high temperatures (up to 450 °C). There is a risk that the filter provided is damaged by said high temperatures. Damage to the filter leads to reject and costs.
• the sputtered layer is mainly composed of indium-tin oxide, the refractive index of a sputtered indium-tin oxide layer is relatively high (above 1.9), which has a positive effect in embodiments in which the conductive layer, in combination with a layer containing silicon dioxide (refractive index 1.46), should provide for an anti-reflective effect.
• the above-mentioned advantages are independent of the exact value of the surface resistance of the conductive layer as well as of the composition of the conductive layer. Therefore, as regards these advantages, the surface resistance may be higher (for example 10M0 5 ⁇ /square) and/or the conductive layer may be composed predominantly of another material (for example tin oxide).
• a display screen 3 is disposed in a sputter arrangement.
• a layer of a conductive material in this example indium-tin oxide (ITO) or antimony-doped indium-tin oxide (ATO) having a thickness of the order of 10-15 run, is sputtered onto the display window.
• ITO indium-tin oxide
• ATO antimony-doped indium-tin oxide
• the refractive index is approximately 2.1
• the optical thickness of such a layer is approximately 20-30 run.
• the first layer (ES, see Fig. 4), which is obtained as described hereinabove, (a dried layer comprising conductive particles (for example ATO)), is provided, by means of spinning, with a layer of the TEOS-solution manufactured in accordance with Table 1.
• the temperature of the layer is maintained at 160 °C for approximately 90 minutes, thereby forming a properly adhering, smooth layer of silicon dioxide (AR' , see Fig. 4).
• This additional layer of silicon dioxide has a thickness, for example, of 135 run and a refractive index of 1.44.
• this layer In combination with the antistatic layer (ES), this layer has an anti-reflective effect. The reflection of visible light is reduced to approximately 0.8% by this two-layer coating (ES-AR').
• the high refractive index of the sputtered, conductive layer (preferably above 1.9) has the advantage that the reflection has been reduced relative to the known method.
• the surface resistance of a sputtered ITO layer having a thickness of 10-15 nm is approximately 500 ⁇ /square, which is much lower than the surface resistance of the known filter.
• a second, additional layer (AG) of silicon dioxide is provided by spraying a TEOS solution and subjecting said solution to a similar temperature treatment
• This layer has a matt surface texture with anti-glare effect
• the resultant coating is less sensitive to fingerprints
• the reflection becomes less dependent on the wavelength because the incident light is scattered in a diffuse manner
• the method described hereinabove can be applied to provide a (two-layer or multilayer) coating on an unassembled display screen, that is, a display screen which does not form part of a cathode ray mbe (yet)
• the method is used to provide a coating on a display screen which forms part of an already evacuated cathode ray tube In this case, the risk of damage to the coating is reduced
• the method according to the invention comprises an intermediate method step, between the sputtering process and the application of the further layer, in which intermediate method step the surface on which the further layer is to be provided is activated to increase the adhesion of the further layer
• This can e g be done by sputtering a preferably thin (l-15nm) layer of
• the above-mentioned layer serves as a primer layer deposited on top of the sputtered conductive layer Activation of said primer layer can alternatively be done by e g rubbing or etching m an Ar-gas
• the invention relates to a method of manufacturing a cathode ray tube comprising an antistatic filter, in which method a conductive layer (for example a material on the basis of tin oxide or tin-oxide compounds, such as indium-tin oxide) is applied by sputtering, and said conductive layer is provided with a further layer containing S ⁇ O 2 by means of a wet-chemical process, for example spinning and, subsequently, drying of a TEOS-compound
• a conductive layer for example a material on the basis of tin oxide or tin-oxide compounds, such as indium-tin oxide
• a conductive layer for example a material on the basis of tin oxide or tin-oxide compounds, such as indium-tin oxide
• cathode ray tube is to be understood to mean, apart from conventional cathode ray tubes as shown in Fig. 1, devices in which electroluminescent phosphor is excited- by means of controlled, charged particles (electrons and/or ions). Examples of such devices are so-called PDPs (Plasma Displays) in which phosphors are excited by means of plasma discharges, and flat display devices, as known from United States Patent US 5,313, 136. The above-mentioned problems also occur in such devices.

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• 1997
  • 1997-06-02 TW TW86107537A patent/TW392189B/zh not_active IP Right Cessation
• 1998
  • 1998-01-12 DE DE69817711T patent/DE69817711T2/de not_active Expired - Fee Related
  • 1998-01-12 JP JP10529169A patent/JP2000507041A/ja not_active Abandoned
  • 1998-01-12 EP EP98900024A patent/EP0894331B1/de not_active Expired - Lifetime
  • 1998-01-12 CN CN 98800033 patent/CN1199228C/zh not_active Expired - Fee Related
  • 1998-01-12 WO PCT/IB1998/000027 patent/WO1998032152A1/en active IP Right Grant

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