EP1059655A2 - Vorrichtung zur Aufrechthalung des Heliumdrucks in den Kanälen einer Palc-Anzeigetafel - Google Patents

Vorrichtung zur Aufrechthalung des Heliumdrucks in den Kanälen einer Palc-Anzeigetafel Download PDF

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Publication number
EP1059655A2
EP1059655A2 EP00303363A EP00303363A EP1059655A2 EP 1059655 A2 EP1059655 A2 EP 1059655A2 EP 00303363 A EP00303363 A EP 00303363A EP 00303363 A EP00303363 A EP 00303363A EP 1059655 A2 EP1059655 A2 EP 1059655A2
Authority
EP
European Patent Office
Prior art keywords
substrate
channel
helium
channels
glass
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00303363A
Other languages
English (en)
French (fr)
Other versions
EP1059655A3 (de
Inventor
Kevin J. Ilcisin
Thomas S. Buzak
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Technical Visions Inc
Original Assignee
Technical Visions Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Technical Visions Inc filed Critical Technical Visions Inc
Publication of EP1059655A2 publication Critical patent/EP1059655A2/de
Publication of EP1059655A3 publication Critical patent/EP1059655A3/de
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J17/00—Gas-filled discharge tubes with solid cathode
    • H01J17/38—Cold-cathode tubes
    • H01J17/48—Cold-cathode tubes with more than one cathode or anode, e.g. sequence-discharge tube, counting tube, dekatron
    • H01J17/485—Plasma addressed liquid crystal displays [PALC]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J17/00—Gas-filled discharge tubes with solid cathode
    • H01J17/02—Details
    • H01J17/22—Means for obtaining or maintaining the desired pressure within the tube
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J17/00—Gas-filled discharge tubes with solid cathode
    • H01J17/02—Details
    • H01J17/22—Means for obtaining or maintaining the desired pressure within the tube
    • H01J17/26—Means for producing, introducing, or replenishing gas or vapour during operation of the tube
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2217/00—Gas-filled discharge tubes
    • H01J2217/38—Cold-cathode tubes
    • H01J2217/40—Gas discharge switches
    • H01J2217/402—Multiple switches
    • H01J2217/4025—Multiple switches for addressing electro-optical devices, i.e. LCD's

Definitions

  • This invention relates to a mechanism for maintaining pressure of helium in channels of a PALC display panel.
  • U.S. Patent 5,077,553 discloses apparatus for addressing data storage elements. A practical implementation of the apparatus shown in U.S. Patent 5,077,553 is illustrated schematically in FIG. 1 of the accompanying drawings.
  • the display panel shown in FIG. 1 comprises, in sequence from below, a polarizer 2, a channel member 4, a cover sheet 6 (commonly known as a microsheet), a layer 10 of electro-optic material, an array of parallel transparent data drive electrodes (only one of which, designated 12, can be seen in the view shown in FIG. 1), an upper substrate 14 carrying the data drive electrodes, and an upper polarizer 16.
  • the panel includes color filters (not shown) between the layer 10 and the upper substrate 14.
  • the panel may also include layers for improving viewing angle and for other purposes.
  • the channel member 4 is typically made of glass and is formed with multiple parallel channels 20 in its upper main face.
  • the channels 20, which are separated by ribs 22, are filled with an ionizable gas, such as helium.
  • An anode 24 and a cathode 26 are provided in each of the channels 20.
  • the channels 20 are orthogonal to the data drive electrodes and the region where a data drive electrode crosses a channel (when viewed perpendicularly to the panel) forms a discrete panel element 28.
  • Each panel element can be considered to include elements of the layer 10 and the lower and upper polarizers 2 and 16.
  • the region of the upper surface of the display panel that bounds the panel element constitutes a single pixel 30 of the display panel.
  • the gas in the channel forms a plasma which provides a conductive path to the reference potential at the lower surface of the cover sheet 6. If a data drive electrode is at the reference potential, there is no significant electric field in the volume element of electro-optic material in the panel element at the crossing of the channel and the data drive electrode and the panel element is considered to be off, whereas if the data drive electrode is at a substantially different potential from the reference potential, there is a substantial electric field in that volume element of electro-optic material and the panel element is considered to be on.
  • the lower polarizer 2 is a linear polarizer and that its plane of polarization can be arbitrarily designated as being at 0° relative to a reference plane
  • the upper polarizer 16 is a linear polarizer having its plane of polarization at 90°
  • the electro-optic material rotates the plane of polarization of linearly polarized light passing therethrough by an angle which is a function of the electric field in the electro-optic material.
  • the angle of rotation is 90°; and when the panel element is on, the angle of rotation is zero.
  • the panel is illuminated from the underside by an extended light source 34 which emits unpolarized white light.
  • a rear glass diffuser 18 having a scattering surface may be positioned between the light source and the panel in order to provide uniform illumination of the panel.
  • the light that enters a given panel element from the source is linearly polarized at 0° by the lower polarizer 2 and passes sequentially through the channel member 4, the channel 20, the cover sheet 6, and the volume element of the electro-optic material toward the upper polarizer 16 and a viewer 32. If the panel element is off, the plane of polarization of linearly polarized light passing through the volume element of electro-optic material is rotated through 90°, and therefore the plane of polarization of light incident on the upper polarizer element is at 90°.
  • the light is passed by the upper polarizer element and the pixel is illuminated. If, on the other hand, the panel element is on, the plane of polarization of the linearly polarized light is not changed on passing through the volume element of electro-optic material. The plane of polarization of light incident on the upper polarizer element is at 0° and therefore the light is blocked by the upper polarizer element and the pixel is dark. If the electric field in the volume element of electro-optic material is intermediate the values associated with the panel element being off and on, light is passed by the upper polarizer element with an intensity which depends on the electric field, allowing a gray scale to be displayed.
  • the channel member 4 is etched back around the area in which the channels are formed in order to provide a plateau 36 in which the channels 20 are formed, and the cover sheet 6 is secured to the channel member by an endless frit bead 38 in a rabbet 40 extending around the periphery of the plateau.
  • An upper substrate assembly including the upper substrate 14 and the data drive electrodes 12 carried thereby, is attached to the channel member 4 by means of a glue bead 42.
  • the permeation rate of helium into glass depends strongly on the temperature of the glass.
  • the permeation rate of helium into glass of the kind that is conventionally used in fabrication of the channel substrate of a PALC panel is approximately 100 times greater at 150° C than at about 18° C.
  • the channel surface of the channel substrate cools and some of the helium that previously permeated into the channel substrate tends to permeate back toward the channel. Because the channel surface of the channel substrate cools rapidly, the permeation rate of helium from the bulk of the channel substrate back into the channel when the plasma is off is much lower than the permeation rate toward the bulk when the plasma is operating. Helium is therefore trapped in the channel surface. If sufficient helium is trapped in the channel surface to reduce the pressure of the helium remaining in the channel by a factor of about two, the voltage required to form the plasma will increase. If the voltage increases to such an extent that it exceeds the capability of the drive circuits, the panel becomes inoperable.
  • a channel substrate for a PALC panel comprising a glass substrate having channels formed therein, and wherein a channel surface of the substrate is loaded with helium to a sufficient partial pressure that when the channel substrate is used in a PALC panel with helium as ionizable gas, helium is depleted from the channel at a substantially lower rate than if the channel surface had not been loaded with helium.
  • a channel substrate assembly for a PALC panel comprising a glass substrate having channels formed therein and a glass cover sheet attached to the glass substrate, and wherein a channel surface of the channel substrate assembly is loaded with helium to a sufficient partial pressure that when the channel substrate assembly is used in a PALC panel with helium as ionizable gas, helium is depleted from the channel at a substantially lower rate than if the channel surface had not been loaded with helium.
  • a channel substrate for a PALC panel comprising a glass substrate having channels formed therein, and wherein a surface of the substrate is provided with a coating of a material having a lower permeation rate with respect to helium than the glass of the substrate and having a higher melting point than the glass of the substrate, so that when the coated channel substrate is used in a PALC panel with helium as ionizable gas, helium is depleted from the channel at a substantially lower rate than if the surface had no coating.
  • a method of manufacturing a channel substrate for a PALC panel comprising providing a glass substrate having channels formed therein, loading a channel surface of the substrate with helium, subsequently filling the channels with helium and sealing the channels.
  • a method of processing a channel substrate assembly for a PALC panel which channel substrate assembly includes a glass substrate formed with channels and a cover sheet attached to the substrate over the channels, said method comprising heating the channel substrate assembly to an elevated temperature, establishing a partial pressure P of helium in the channels of the substrate, and sealing the channels.
  • a method of manufacturing a channel substrate for a PALC panel comprising providing a glass substrate formed with channels, and forming a coating on a surface of the substrate, the coating being of a material having a lower permeation rate with respect to helium than the glass of the substrate and having a higher melting point than the glass of the substrate.
  • the permeation rate of helium into glass from a space bounded by a surface of the glass depends not only on the temperature of the glass but also on the partial pressure of helium in the glass and the partial pressure of helium in the space bounded by the glass.
  • the channel surfaces of a PALC display panel are preloaded with helium. Accordingly, the partial pressure of helium in the bulk is increased, reducing the difference between the partial pressure of helium in the channel and the bulk and reducing the permeation rate of helium from the channel into the bulk.
  • the channel surfaces can be preloaded with helium by filling and sealing the panel at elevated temperatures and pressure.
  • the panel is filled and sealed at a pressure in the range from about 100 to 500 mb and a temperature in the range from about 20 to 50° C.
  • elevated temperatures and pressures 200-900 mb and 250-400° C
  • helium permeates into the glass.
  • the helium that remains in the channels is at a sufficient partial pressure for operation of the panel.
  • the channel surfaces of the substrate can be preloaded by heating the substrate in a helium atmosphere before filling and sealing but after high temperature processes required for fabrication of the channel substrate assembly have been completed.
  • the channel substrate can be heated to near 550° C, where the glass is near its softening point.
  • a third possibility is to subject the channel substrate assembly (the channel substrate and the cover sheet) to an RF helium plasma.
  • the channel substrate assembly Before the filling and sealing operation, the channel substrate assembly is placed in a cavity which contains helium and in which an RF field suitable to ionize the helium can be generated.
  • an RF field suitable to ionize the helium can be generated.
  • helium permeates into the surface layer and is trapped when the plasma is removed.
  • the temperature is sufficiently low, and the pressure is sufficiently high, that the helium remains trapped in the glass.
  • Glasses that are conventionally used in fabrication of PALC display panels are typically borosilicate glasses, such as the glass sold by Schott Glass under the designation D263.
  • Other glasses, such as the alkali-free borosilicate glass sold by Schott Glass under the designation AF45, which has a high concentration of barium oxide and aluminum oxide, are also suitable for fabrication of a PALC display panel and have a significantly lower permeation rate with respect to helium in the temperature ranges involved.
  • a suitable surface barrier can be provided by vapor deposition of a material that has a lower permeation rate with respect to helium and a higher melting point than the borosilicate glasses that are conventionally used in fabrication of PALC display panels.
  • a barrier layer 46 of such a material is provided on the surfaces bounding the channels of the channel substrate 4 before the channel electrodes are deposited.
  • the relative temperature of the channel surface of the substrate is lower than it would be if the channel were bounded by borosilicate glass.
  • One material having both a lower permeation rate with respect to helium than borosilicate glasses and a higher melting point than borosilicate glasses is sapphire. Techniques for depositing a layer of sapphire on a glass surface are well known.

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  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Plasma & Fusion (AREA)
  • Liquid Crystal (AREA)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)
EP00303363A 1999-05-03 2000-04-20 Vorrichtung zur Aufrechthaltung des Heliumdrucks in den Kanälen einer Palc-Anzeigetafel Withdrawn EP1059655A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US13215799P 1999-05-03 1999-05-03
US132157P 1999-05-03

Publications (2)

Publication Number Publication Date
EP1059655A2 true EP1059655A2 (de) 2000-12-13
EP1059655A3 EP1059655A3 (de) 2002-08-21

Family

ID=22452753

Family Applications (1)

Application Number Title Priority Date Filing Date
EP00303363A Withdrawn EP1059655A3 (de) 1999-05-03 2000-04-20 Vorrichtung zur Aufrechthaltung des Heliumdrucks in den Kanälen einer Palc-Anzeigetafel

Country Status (2)

Country Link
EP (1) EP1059655A3 (de)
JP (1) JP2000347164A (de)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3419625A1 (de) * 1983-08-11 1985-11-28 Siemens AG, 1000 Berlin und 8000 München Gasentladungsanzeigevorrichtung mit einem nachbeschleunigungsraum
US4663564A (en) * 1984-08-31 1987-05-05 Siemens Aktiengesellschaft Device for maintaining constant pressure in gas discharge vessels, particularly flat plasma picture screens with electron post-acceleration
EP0833362A2 (de) * 1996-09-30 1998-04-01 Tektronix, Inc. Struktur einer plasmagesteuerten Flüssigkristallanzeigetafel (PALC) mit einer Füllung von wasserstoffdopiertem Helium
WO2000070397A1 (en) * 1999-05-14 2000-11-23 Koninklijke Philips Electronics N.V. Plasma addressed liquid crystal display

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3419625A1 (de) * 1983-08-11 1985-11-28 Siemens AG, 1000 Berlin und 8000 München Gasentladungsanzeigevorrichtung mit einem nachbeschleunigungsraum
US4663564A (en) * 1984-08-31 1987-05-05 Siemens Aktiengesellschaft Device for maintaining constant pressure in gas discharge vessels, particularly flat plasma picture screens with electron post-acceleration
EP0833362A2 (de) * 1996-09-30 1998-04-01 Tektronix, Inc. Struktur einer plasmagesteuerten Flüssigkristallanzeigetafel (PALC) mit einer Füllung von wasserstoffdopiertem Helium
WO2000070397A1 (en) * 1999-05-14 2000-11-23 Koninklijke Philips Electronics N.V. Plasma addressed liquid crystal display

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Publication number Publication date
JP2000347164A (ja) 2000-12-15
EP1059655A3 (de) 2002-08-21

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