WO2000036625A1 - Barrier rib formation for plasma display panels - Google Patents

Barrier rib formation for plasma display panels Download PDF

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Publication number
WO2000036625A1
WO2000036625A1 PCT/US1999/028241 US9928241W WO0036625A1 WO 2000036625 A1 WO2000036625 A1 WO 2000036625A1 US 9928241 W US9928241 W US 9928241W WO 0036625 A1 WO0036625 A1 WO 0036625A1
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WIPO (PCT)
Prior art keywords
polystyrene
barrier rib
photopolymerizable composition
photopolymer film
elastomeric
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Application number
PCT/US1999/028241
Other languages
French (fr)
Inventor
Lap-Tak Andrew Cheng
Original Assignee
E.I. Du Pont De Nemours And Company
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Application filed by E.I. Du Pont De Nemours And Company filed Critical E.I. Du Pont De Nemours And Company
Publication of WO2000036625A1 publication Critical patent/WO2000036625A1/en

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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00Apparatus 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
    • H01J9/24Manufacture or joining of vessels, leading-in conductors or bases
    • H01J9/241Manufacture or joining of vessels, leading-in conductors or bases the vessel being for a flat panel display
    • H01J9/242Spacers between faceplate and backplate
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00Apparatus 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
    • H01J9/02Manufacture of electrodes or electrode systems
    • H01J9/18Assembling together the component parts of electrode systems
    • H01J9/185Assembling together the component parts of electrode systems of flat panel display devices, e.g. by using spacers
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2211/00Plasma display panels with alternate current induction of the discharge, e.g. AC-PDPs
    • H01J2211/20Constructional details
    • H01J2211/34Vessels, containers or parts thereof, e.g. substrates
    • H01J2211/36Spacers, barriers, ribs, partitions or the like

Definitions

  • This invention relates to the formation of barrier ribs used in plasma display panels (PDP).
  • PDP plasma display panels
  • Plasma display panels also known as flat-panel displays, are generally used in applications such as displays for lap-top computers, televisions, and other end-uses historically serviced by cathode ray tubes. They generally consist of an array of closely spaced, separately contacted picture elements or pixels which are cells coated with a phosphor material chosen from blue, green and red.
  • the basic structure of a flat panel display comprises two glass plates with a conductor pattern of electrodes on the inner surfaces of each plate and separated by a gas filled gap. The electrodes can be covered with a thin dielectric film. The glass plates are put together to form a sandwich with the distance between the two plates fixed by spacers.
  • barrier ribs disposed between the substrates prevent cross-color and cross- pixel interference between the electrodes and increased resolution to provide a sharply defined picture.
  • the barrier ribs provide a uniform discharge space between the glass plates by utilizing the barrier ribs height, width and pattern gap to achieve a desired pixel pitch.
  • barrier rib designs must minimize wall thickness and maximize depth for high gas volume.
  • precise control of these dimensions and generally high aspect ratios (barrier rib height:barrier rib width) of 2 to 3 are preferred. See generally Kakizaki et al., Journal of the SLD, 5/1, 1997, pp. 57-60, and Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley & Sons, Inc., Vol. 21, 1997, p. 745.
  • Barrier ribs for plasma display panels have been formed in a variety of ways including screen printing and sandblasting.
  • Screen printing involves printing a paste in layers to a specific thickness usually using a screen printing mesh mask. Usually at least three or four layers, and up to about fifteen layers are built up through repeated printing. This multiple printing requires an accuracy check of position at each stage of the printing and care must be taken to avoid oozing of the paste at each stage.
  • the paste thickness must be precisely controlled so that the final height of the layers is uniform, all of which makes this an extremely complicated method with a low yield. An experienced printing technician must spend a great deal of time and effort to get around the drawbacks to this method, which incurs tremendous costs.
  • Sandblasting involves solid unpatterned printing and therefore positioning is easier than in the screen printing method.
  • Japanese Publication No. 9-283016 discloses barriers formed from glass paste which is printed into a recessed part of a photosensitive resist layer.
  • Other methods for preparing barrier ribs include etching the ribs in a glass substrate or by etching them in a separate glass layer placed on a glass substrate (see U.S. Patent 5,723,945).
  • U.S. Patent 4,975,104 barrier ribs of a glass are formed in a photoresist after the photoresist has been masked, exposed to radiation and portions of the photoresist removed by etching. The panel is then heated to about 580°C to solidify the ribs.
  • Japanese Publication No. 8-171863 discloses the addition of a hydroxyl-functional polymer component to the barrier rib material as a curing site for crosslinking with other components of the barrier rib material, such as an isocyanate, for the purpose of strengthening the ribs.
  • Japanese Publication No. 6-139922 discloses the use of paraffin and acrylic resin material as a peeling protectant for the barrier ribs once they are formed.
  • This invention concerns a method of forming a barrier rib for a plasma display panel, comprising: applying an elastomeric photopolymerizable composition onto a substrate, said substrate carrying thereon a plurality of electrodes; exposing to actinic radiation through an image corresponding at least in part to a barrier rib structure the elastomeric photopolymerizable composition to form a photopolymer film; removing the image; removing the unexposed areas of the photopolymerizable composition to form channels; filling said channels with a barrier rib material, said photopolymer film, barrier rib material, and substrate forming an assembly; contacting said photopolymer film with a swelling agent; heating said assembly to effect swelling of the photopolymer film; and sintering said assembly for a time sufficient to burn off the photopolymer film and solidify the barrier rib material to form a barrier rib.
  • FIG. 1 is a stepwise depict
  • FIG. 2 is a photograph of a photomask used in the Example of the present invention below.
  • FIG. 3 is a photograph of a substrate which has been exposed to UV radiation after masking, showing the unfilled channels.
  • FIG. 4 is a photograph of the channels shown in FIG. 3 that have been filled with barrier rib material after exposure to heat to activate a swelling agent placed in contact with the photopolymer film.
  • a photopolymerizable composition is placed onto a substrate.
  • the substrate can be any material generally used in plasma display panels which includes but is not limited to glass.
  • the substrate carries on its surface a plurality of electrodes.
  • the electrodes are of a type well known in the art.
  • the electrodes can be thin film electrodes positioned generally parallel to one another and prepared by selectively metalizing a thin layer of metals such as Au, Cr and Au, Cu and Au, Ta and Au, Cu and Cr, ITO and Au, Ag or Cr and the like.
  • the electrodes can be applied to the substrate by screen printing or thin film deposition. Other methods are well-known to those of ordinary skill in the art.
  • a uniform electron emissive film such as a dielectric film or electron emitting material of a type well known in the art can cover the electrodes by a variety of planar techniques well known in the art of display manufacture, such as screen printing and firing.
  • the dielectric film may be of most any, suitable material such as a lead glass material and the like, and the electron emitting material may be most any suitable material such as a diamond overcoating, MgO, or the like and may be applied as a surface film.
  • the electron emissive film may be overcoated with a second thin film of MgO.
  • the elastomeric photopolymerizable composition comprises an elastomeric binder, at least one monomer, and an initiator, where the initator is sensitive to actinic radiation.
  • photopolymerizable is intended to encompass systems which are photopolymerizable, photocrosslinkable, or both.
  • the elastomeric photopolymerizable composition can contain a single monomer or a mixture of monomers which must be compatible with the binder to the extent that a clear, non-cloudy photopolymerizable composition is produced.
  • Monomers that can be used in the photopolymerizable composition are well known in the art and include but are not limited to addition-polymerization ethylenically unsaturated compounds having relatively low molecular weights (generally less than about 30,000), and preferably having molecular weight less than about 5000. Examples of such monomers can be found in Chen U.S. Patent No.
  • Preferred monomers that can be used alone or used as combinations with other monomers include t- butyl acrylate and methacrylate, 1,5-pentanediol diacrylate and dimethyacrylate, N,N-dimethylaminoethyl acrylate and methacrylate, ethylene glycol diacrylate and dimethacrylate, 1,4-butanediol diacrylate and dimethacrylate, diethylene glycol diacrylate and dimethacrylate, hexamethylene glycol diacylate and dimethacrylate, 1,3-propanediol diacrylate and dimethacrylate, decamethylene glycol diacrylate and dimethacrylate, 1,4-cyclohexanediol diacrylate and dimethacrylate, 2,2-dimethylolpropane diacrylate and dimethacrylate, glycerol diacrylate and dimethacrylate, tripropylene glycol diacrylate and dimethacrylate, gly
  • Patent No. 3,380, 381 2,2-di(p-hydroxy- phenyl)-propane diacrylate and dimethacrylate, ethylated pentaerythritol triacrylate, pentaerythritol tetraacrylate and tetramethacrylate, triethylene glycol diacrylate, polyoxyethyl-1 ,2-di-(p-hydroxyethyl)propane dimethacrylate, bisphenol-A di-(3-methacryloxy-2-hydroxypropyl)ester, bisphenol-A di(3- acryloxy-2-hydroxypropyl)ether, bisphenol-A di(2-methacryloxyethyl) ether, bisphenol-A di(2-acryloxyethyl) ether, 1,4-butanediol di-(3-methacryloxy-2- hydroxypropyl)ether, triethylene glycol dimethacrylate, polyoxypropyl trimethylolpropane triacrylate, but
  • ethylenically unsaturated compounds having molecular weights of at least 300, for example, alkylene or polyalkylene glycol diacrylates producted from alkylene glycols or polyalkylene glycols with 1-10 ether bonds of 2-15-carbon alkylene glycols and those present in U.S. Patent No. 2,927,022, for example, those having several addition-polymerizable ethylene bonds, particularly when they exist as terminal bonds.
  • Other useful monomers are disclosed in U.S. Patent No. 5,032,490.
  • Other favorable monomers are monohydroxypolycarpolactone monoacrylate, polyethylene glycol diacrylate (molecular weight of about 200), and polyethylene glycol 400 dimethacrylate (molecular weight of about 400).
  • Unsaturated monomer components can be present in amounts of 1 20 wt %, based on the total weight of the dry photopolymerizable composition.
  • the initiator can be any single compound or combination of compounds which is sensitive to actinic radiation, generating free radicals which initiate the polymerization of the monomer or monomers without excessive termination.
  • the initiatior is generally sensitive to actinic light, and preferably sensitive to ultraviolet radiation.
  • suitable initiators include the substituted and unsubstituted polynuclear quinones which are compounds having two intracyclic carbon atoms in a conjugated carbocyclic ring system. Examples of suitable systems have been disclosed in Gruetzmacher, U.S. Patent No.
  • Initiators are generally present in amounts from 0.0001% to 10.0% based on the weight of the photopolymerizable composition.
  • a preferred initiator is Irgacure 651, 2,2-dimethoxy-p-phenylacetophenone.
  • compositions comprising at least one monomer and an initiator have been disclosed, for example, in Chen et al., U.S. Patent No. 4,323,637, Gruetzmacher et al., U.S. Patent No. 4,427,749; and Feinberg et al., U.S. Patent No. 4,894,315.
  • An advantage of the present invention is the inclusion of a swellable elastomeric binder in the photopolymerizable composition.
  • the elastomeric binder acts as a crosslinker with the at least one monomer changing the solubility of the film after exposure to actinic radiation
  • the elastomeric binder assists in enabling the swelling of the photopolymer film upon contact with a swelling agent.
  • binder can encompass a single polymer, a mixture of polymers, block copolymers, gels, core shell microgels, blends of microgels, and preformed macromolecular polymers, such as those disclosed in Feinberg et al., U.S. Patent No.
  • Binders can include natural or synthetic polymers of conjugated diolefin hydrocarbons, including polyisoprene, 1 ,2-polybutadiene, 1 ,4-polybutadiene, butadiene/acrylonitrile, styrene-butadiene di-block copolymers, ethylene methacrylate copolymers, crosslinked styrene- meth( acrylate) copolymers, butadiene/styrene thermoplastic-elastomeric block copolymers and other copolymers.
  • Patent No. 4,323,636 Heinz et al., U.S. Patent No. 4,430,417; and Toda et al., U.S. Patent No. 4,045,231 can be used.
  • the Kraton® family of triblock copolymers manufactured by the Shell
  • the Kraton® triblock copolymers include polystyrene- polybutadiene-polystyrene, polystyrene-polyisoprene-polystyrene, and polystyrene-poly(ethylenebutylene)-polystyrene polymers.
  • the preferred tri-block copolymer is polystyrene-polybutadiene-polystyrene triblock.
  • Preferred polystyrene-polybutadiene-polystyrene and polystyrene-polyisoprene-polystyrene copolymers are those with about 14 to about 30 wt % polystyrene.
  • the concentration of the elastomeric binder is preferably greater than 30 weight percent of the total weight of the elastomeric photopolymerizable composition.
  • the elastomeric photopolymerizable composition can further include other additives depending on the final properties desired.
  • additives include sensitizers, plasticizers, rheology modifiers, thermal polymerization inhibitors, tackifiers, colorants, antioxidants, antiozonants, or fillers and are well known to those in the art.
  • the elastomeric photopolymerizable composition can be prepared in many ways by admixing the elastomeric binder, the at least one monomer, the initiator, and other desired additives in any order. Conventional milling, mixing, and solution techniques can be used in making the elastomeric photopolymerizable composition.
  • the elastomeric photopolymerizable composition can be formed into a layer in any desired manner. For example, solvent casting, hot pressing, calendering, or melt extrusion are suitable methods for preparing a layer. This layer can then be applied to the substrate by methods well known in the art including lamination, solution coating, or if necessary, affixing of the layer by means of a suitable adhesive.
  • the elastomeric photopolymerizable composition is in the form of a laminated film.
  • the image can be an image-bearing transparency or photomask having areas essentially transparent to actinic radiation and areas opaque to actinic radiation.
  • the image includes at least in part artwork corresponding to a barrier rib structure which can be of any pattern including cell-form or stripe form depending on whether the barrier ribs are for a plasma display panel that will be used with alternate or direct current.
  • the transparent areas of the image allow addition polymerization or crosslinking to take place in the exposed areas of the photopolymerizable composition, while the opaque areas remain uncrosslinked. Exposure is of sufficient duration to crosslink the exposed areas down to the substate which become insoluble to solvents used during image development. For good results, crosslinking should occur only in the exposed areas of the photopolymerizable composition with no significant crosslinking occurring in the non-image, unexposed areas. The unexposed photopolymerizable layer areas under the photomask remain soluble and are washed away with a suitable solvent.
  • Actinic radiation may be provided from any light source at 200-600 nm, preferably about 300 nm to about 460 nm, and a wattage of 10 to 1000 watts, such as sunlight, phosphorescent discharge lamps (fluorescent lamps), carbon arc lamps, metal arc lamps such as low, medium or high pressure mercury lamps, xenon lamps, argon lamps, tungsten lamps and metal halide lamps.
  • Preferred sources are high pressure mercury lamps, such as the very high output so-called black-light fluorescent types due to their high ratio of ultraviolet to infrared output.
  • Exposure times may vary from fractions of a second to minutes, depending on the composition of the photopolymerizable composition, the intensity and spectral energy distribution of the radiation, the distance of the composition from the radiation source and the thickness of the photopolymerizable composition.
  • a mercury vapor arc or a sunlamp can be used at a distance of about 1.5 to about 60 inches (3.8-163 cm) from the photopolymerizable composition.
  • Exposure temperatures are preferably at about ambient temperature or slightly higher, i.e., about 20 to about 35°C.
  • the uncrosslinked portions of the photopolymerizable composition are dissolved away with any suitable aqueous or organic solvent known in the art. Channels will remain where the uncrosslinked portions of the photopolymerizable composition have been dissolved away.
  • the solvent liquid used for removing the uncrosslinked photopolymerizable composition should have good solvent action on the solvent-soluble photopolymerizable composition and little action on the insolubilized areas in the period required to remove the nonpolymerized or uncrosslinked areas. Alkaline solutions, solutions with suitable surfactants, alcohols, and acetates can be used.
  • Methyl ethyl ketone, benzene, toluene, xylene, carbon tetrachloride, trichloroethane, trichloroethylene, methylchloroform, and tetrachloroethylene can be useful solvents. Removal time can be varied, but it is preferably in the range of about 5 to 25 minutes.
  • the solvent can be applied in any convenient manner, including immersion, spraying, brush, or roller application. Brushing can aid in removing the unpolymerized or non-crosslinked portions of the compositions. Washout can be carried out in an automatic processing unit which uses solvent and mechanical brushing action to remove the unexposed portions of the photopolymerizable composition.
  • the channels formed after removal of the unpolymerized areas of the elastomeric photopolymerizable composition are subsequently filled with a barrier rib material, which material has desirable sintering and barrier properties, to form an assembly comprising the substrate, the photopolymer film and the barrier rib material.
  • the barrier rib material comprises a ceramic paste or a cementious paste, preferably is a good barrier to plasma gas, and most preferably comprises glass.
  • Representative examples of such barrier rib material include, but are not limited to, pastes comprising ceramic, glass frits, Portland cement, other metal oxide ceramic powders, and the like, and any combination of the foregoing.
  • Suitable glass frits include borosilicate frits, such as lead borosilicate frit, bismuth, cadmium, barium, calcium or other alkaline earth borosilicate frits.
  • the preparation of such glass frits is well known in the art and consists, for example, of melting together the constituents of the glass in the form of the oxides of the constituents and pouring such molten composition into water to form the frit.
  • an organic resin binder, a solvent, and optionally a surfactant may be added to the ceramic oxides or cement.
  • Filling can be conveniently performed using a doctor blade or similar device. Screen printing may also be used.
  • the channel washout and filling is simplified by the low initial aspect ratio of the channels, low viscosity of the barrier rib material, and good surface wetting between the barrier rib material and the photopolymer film.
  • a swelling agent is advantageously used in the present process. Before or after the channels are filled with the barrier rib material, a swelling agent is placed in contact with the photopolymer film to effect swelling of the photopolymer film.
  • the swelling agent can be placed in contact with the photopolymer film before or after filling the channels.
  • the swelling agent can be placed in contact with the photopolymer film by various methods including spray or spin coating.
  • the swelling agent is mixed with the barrier rib material.
  • Such mixtures of the swelling agent and barrier rib material are preferably a relatively low viscosity paste of about 20-50 weight percent solids, most preferably about 40 weight percent solids. Since swelling can occur slowly at room temperature, a precise dose of any swelling agent/barrier rib material mixture can be spread into the channels using a doctor blade or similar device.
  • Heating the assembly causes the swelling agent to migrate into the photopolymer film and thereby activates swelling of the photopolymer film which in turn acts to increase the aspect ratio of the channel (and ultimately the aspect ratio of the barrier rib formed within that channel). Heating can also increase the solid density of the barrier rib material within the channels.
  • the temperature for this heating step should be below the volatizing temperature of the swelling agent and is preferably about 90°C when paraffin is used as the swelling agent.
  • Swelling agents for use in the present invention include agents known to those of skill in the art for elastomer swelling including, but are not limited to, non-volatile paraffin oils, such as Shellflex® 371 (Shell Oil Co, Houston, TX).
  • paraffin oil is meant a rubber oil containing a high proportion of paraffinic, i.e. linear, saturated hydrocarbon structures.
  • Such oils typically comprise aromatic, naphthalene and paraffinic components and a variety of such oils are commercially available.
  • a solvent for the pre-crosslinked elastomeric binder can be used as a swelling agent.
  • swelling agents will depend on the particular elastomeric binder used in the photopolymerizable composition.
  • Representative examples of such swelling agents include alkyl adipates and alkyl acetates, such as dimethyl adipate or heptyl acetate. These types of solvents are commercially available.
  • the assembly can be sintered at a temperature below the softening point of the substrate, preferably about 400°C to 600°C for glass, for a time sufficient to burn off the photopolymer film and solidify the barrier rib material so as to form a barrier rib with good strength.
  • the temperature used during sintering is also dependent upon the sintering temperature of the material to be used to form the barrier ribs and on the burn-off temperature of any organic components within the paste.
  • the aspect ratio of a barrier rib can be enhanced by a factor of 1.5 or greater when the swelling agent is used in formation of the barrier ribs.
  • the assembly can be combined with the remaining components needed to prepare a plasma display panel. These components are well known in the art. DETAILED DESCRIPTION OF THE DRAWINGS
  • FIG. 1 is a stepwise depiction of one embodiment of the method of the present invention herein described.
  • FIG. la shows unit 1 comprised of substrate 10 onto which is coated an elastomeric photopolymerizable composition 12. Photomask 14 is applied to the surface of the coated substrate as shown in FIG. lb and exposed to actinic radiation 16. The unexposed photopolymerizable composition is removed by washing solvent as depicted in FIG. lc to leave channels 18. Channels 18 are subsequently filled with barrier rib material 20, which includes a swelling agent, as shown in FIG. Id. The unit is then heated to activate swelling of the photopolymer film and the subsequent narrowing of barrier rib material 20, as shown in FIG. le. FIG.
  • FIG. 2 is a photograph of the photomask used in the Example below. It is a window screen with dark lines 30 of 15 mils thickness and open squares of 50 x 50 mils.
  • FIG. 3 is a photograph of a substrate and photopolymer film which has been exposed to UV radiation after photomasking with the screen shown in FIG. 2. Unfilled channels 32 are 15 mils wide and 10 mils deep, yielding an aspect ratio of 0.67. The photopolymer is shown as gray area 34.
  • FIG. 4 is a photograph of channels 32 of FIG. 3 after the unit has been subjected to heat to activate swelling of photopolymer film 34. Channels 32 are noticeably narrower after filling and heating.
  • a 10 mil thick film of Cyrel® photopolymer (E. I. du Pont de Nemours and Company, Wilmington, DE) which contained 60 weight percent of a styrene- butadiene-styrene block copolymer was prepared by melt processing with appropriate multifunctional acrylate cross-linking monomers and photoinitiator, namely hexamethylene glycol diacrylate and hexamethylene glycol dimethacrylate and Irgacure 651, 2,2-dimethoxy-p-phenylacetophenone. The film was laminated onto a glass substrate. A window screen with dark lines of 15 mils thickness and open squares of 50 x 50 mils was used as a contact mask (see FIG. 2).
  • the task of channel washout and filling was made simple by the low viscosity (estimated to be less than 10,000 cps at 25°C) of the paste and good surface wetting between the paste and the photopolymer film.
  • the assembly was heated at 90°C for 5 minutes to activate swelling wherein the paraffin oil migrated from the paste in the channels into the photopolymer film. Swelling increased the channel aspect ratio and the solid density of the paste within the channel. Channels of 5x12 mils with an aspect ratio of 2.4 were measured (see FIG. 4). An aspect ratio enhancement of 3.4 was noted.
  • the assembly was subsequently heated from room temperature to 600°C with a linear lamp over the period of 1 hour to burn out the remaining photopolymer film and then cooled to room temperature in a period of one hour.

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Abstract

Barrier ribs with improved aspect ratios are formed in plasma display panels by swelling of an elastomeric photopolymer component.

Description

TITLE BARRIER RLB FORMATION FOR PLASMA DISPLAY PANELS
FIELD OF THE INVENTION This invention relates to the formation of barrier ribs used in plasma display panels (PDP). The method provides barrier ribs with an improved aspect ratio.
BACKGROUND OF THE INVENTION Plasma display panels, also known as flat-panel displays, are generally used in applications such as displays for lap-top computers, televisions, and other end-uses historically serviced by cathode ray tubes. They generally consist of an array of closely spaced, separately contacted picture elements or pixels which are cells coated with a phosphor material chosen from blue, green and red. The basic structure of a flat panel display comprises two glass plates with a conductor pattern of electrodes on the inner surfaces of each plate and separated by a gas filled gap. The electrodes can be covered with a thin dielectric film. The glass plates are put together to form a sandwich with the distance between the two plates fixed by spacers. The edges of the plates are sealed and the cavity between the plates is evacuated and filled with an inert gas. As voltage is applied across the electrodes, the pixels form a visual image. Barrier ribs disposed between the substrates prevent cross-color and cross- pixel interference between the electrodes and increased resolution to provide a sharply defined picture. The barrier ribs provide a uniform discharge space between the glass plates by utilizing the barrier ribs height, width and pattern gap to achieve a desired pixel pitch. In order to achieve high display resolution and brightness, barrier rib designs must minimize wall thickness and maximize depth for high gas volume. Thus, precise control of these dimensions and generally high aspect ratios (barrier rib height:barrier rib width) of 2 to 3 are preferred. See generally Kakizaki et al., Journal of the SLD, 5/1, 1997, pp. 57-60, and Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley & Sons, Inc., Vol. 21, 1997, p. 745.
Barrier ribs for plasma display panels have been formed in a variety of ways including screen printing and sandblasting. Screen printing involves printing a paste in layers to a specific thickness usually using a screen printing mesh mask. Usually at least three or four layers, and up to about fifteen layers are built up through repeated printing. This multiple printing requires an accuracy check of position at each stage of the printing and care must be taken to avoid oozing of the paste at each stage. The paste thickness must be precisely controlled so that the final height of the layers is uniform, all of which makes this an extremely complicated method with a low yield. An experienced printing technician must spend a great deal of time and effort to get around the drawbacks to this method, which incurs tremendous costs. Sandblasting involves solid unpatterned printing and therefore positioning is easier than in the screen printing method. However, printing still has to be repeated a number of times, and achieving a uniform film thickness is difficult. Thus sandblasting does not lend itself to commercial production due to its high cost and low yield. U.S. Patents 5,674,634 and 5,714,840 describe aspects of these methods.
Japanese Publication No. 9-283016 discloses barriers formed from glass paste which is printed into a recessed part of a photosensitive resist layer. Other methods for preparing barrier ribs include etching the ribs in a glass substrate or by etching them in a separate glass layer placed on a glass substrate (see U.S. Patent 5,723,945). In U.S. Patent 4,975,104, barrier ribs of a glass are formed in a photoresist after the photoresist has been masked, exposed to radiation and portions of the photoresist removed by etching. The panel is then heated to about 580°C to solidify the ribs.
Others have made use of certain components in order to improve particular characteristics of the barrier ribs. Japanese Publication No. 8-171863 discloses the addition of a hydroxyl-functional polymer component to the barrier rib material as a curing site for crosslinking with other components of the barrier rib material, such as an isocyanate, for the purpose of strengthening the ribs. Japanese Publication No. 6-139922 discloses the use of paraffin and acrylic resin material as a peeling protectant for the barrier ribs once they are formed.
There is a need for easy to perform, low cost, and high yield processes of producing barrier ribs with high aspect ratios for flat panel displays.
SUMMARY OF THE INVENTION This invention concerns a method of forming a barrier rib for a plasma display panel, comprising: applying an elastomeric photopolymerizable composition onto a substrate, said substrate carrying thereon a plurality of electrodes; exposing to actinic radiation through an image corresponding at least in part to a barrier rib structure the elastomeric photopolymerizable composition to form a photopolymer film; removing the image; removing the unexposed areas of the photopolymerizable composition to form channels; filling said channels with a barrier rib material, said photopolymer film, barrier rib material, and substrate forming an assembly; contacting said photopolymer film with a swelling agent; heating said assembly to effect swelling of the photopolymer film; and sintering said assembly for a time sufficient to burn off the photopolymer film and solidify the barrier rib material to form a barrier rib. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a stepwise depiction of the formation of a barrier rib of the present invention as described in the details below.
FIG. 2 is a photograph of a photomask used in the Example of the present invention below.
FIG. 3 is a photograph of a substrate which has been exposed to UV radiation after masking, showing the unfilled channels.
FIG. 4 is a photograph of the channels shown in FIG. 3 that have been filled with barrier rib material after exposure to heat to activate a swelling agent placed in contact with the photopolymer film.
DETAILS OF THE INVENTION In the process of the present invention, a photopolymerizable composition is placed onto a substrate. The substrate can be any material generally used in plasma display panels which includes but is not limited to glass. The substrate carries on its surface a plurality of electrodes. The electrodes are of a type well known in the art. The electrodes can be thin film electrodes positioned generally parallel to one another and prepared by selectively metalizing a thin layer of metals such as Au, Cr and Au, Cu and Au, Ta and Au, Cu and Cr, ITO and Au, Ag or Cr and the like. The electrodes can be applied to the substrate by screen printing or thin film deposition. Other methods are well-known to those of ordinary skill in the art.
A uniform electron emissive film such as a dielectric film or electron emitting material of a type well known in the art can cover the electrodes by a variety of planar techniques well known in the art of display manufacture, such as screen printing and firing. The dielectric film may be of most any, suitable material such as a lead glass material and the like, and the electron emitting material may be most any suitable material such as a diamond overcoating, MgO, or the like and may be applied as a surface film. The electron emissive film may be overcoated with a second thin film of MgO. The elastomeric photopolymerizable composition comprises an elastomeric binder, at least one monomer, and an initiator, where the initator is sensitive to actinic radiation. As used herein, the term "photopolymerizable" is intended to encompass systems which are photopolymerizable, photocrosslinkable, or both. The elastomeric photopolymerizable composition can contain a single monomer or a mixture of monomers which must be compatible with the binder to the extent that a clear, non-cloudy photopolymerizable composition is produced. Monomers that can be used in the photopolymerizable composition are well known in the art and include but are not limited to addition-polymerization ethylenically unsaturated compounds having relatively low molecular weights (generally less than about 30,000), and preferably having molecular weight less than about 5000. Examples of such monomers can be found in Chen U.S. Patent No. 4,323,636; Gruetzmacher et al., U.S. Patent No. 4,460,675; Fryd et al., U.S. Patent No. 4,753,865; Fryd et al., U.S. Patent No. 4,726,877; and Feinberg et al., U.S. Patent No. 4,894,315, incorporated by reference herein. Preferred monomers that can be used alone or used as combinations with other monomers include t- butyl acrylate and methacrylate, 1,5-pentanediol diacrylate and dimethyacrylate, N,N-dimethylaminoethyl acrylate and methacrylate, ethylene glycol diacrylate and dimethacrylate, 1,4-butanediol diacrylate and dimethacrylate, diethylene glycol diacrylate and dimethacrylate, hexamethylene glycol diacylate and dimethacrylate, 1,3-propanediol diacrylate and dimethacrylate, decamethylene glycol diacrylate and dimethacrylate, 1,4-cyclohexanediol diacrylate and dimethacrylate, 2,2-dimethylolpropane diacrylate and dimethacrylate, glycerol diacrylate and dimethacrylate, tripropylene glycol diacrylate and dimethacrylate, glycerol triacrylate and trimethacrylate, trimethylolpropane triacrylate and trimethacrylate, polyoxyethylated trimethylolpropane triacrylate and trimethacrylate, and compounds like those present in U.S. Patent No. 3,380, 381, 2,2-di(p-hydroxy- phenyl)-propane diacrylate and dimethacrylate, ethylated pentaerythritol triacrylate, pentaerythritol tetraacrylate and tetramethacrylate, triethylene glycol diacrylate, polyoxyethyl-1 ,2-di-(p-hydroxyethyl)propane dimethacrylate, bisphenol-A di-(3-methacryloxy-2-hydroxypropyl)ester, bisphenol-A di(3- acryloxy-2-hydroxypropyl)ether, bisphenol-A di(2-methacryloxyethyl) ether, bisphenol-A di(2-acryloxyethyl) ether, 1,4-butanediol di-(3-methacryloxy-2- hydroxypropyl)ether, triethylene glycol dimethacrylate, polyoxypropyl trimethylolpropane triacrylate, butylene glycol diacrylate and dimethacrylate, 1 ,2,4-butanediol triacrylate and trimethacrylate, 2,2,4-trimethyl-l,3-pentanediol diacrylate and dimethacrylate, l-phenylethylene-l,2-dimethacrylate, diallyl fumarate, styrene, 1,4-benzenediol dimethacrylate, 1 ,4-diisopropenyl benzene, 1,3-5-triisopropenylbenzene, dipentaerythritol monohydroxyphentaacrylate, and 1,10-decanediol dimethacrylate.
Also useful are ethylenically unsaturated compounds having molecular weights of at least 300, for example, alkylene or polyalkylene glycol diacrylates producted from alkylene glycols or polyalkylene glycols with 1-10 ether bonds of 2-15-carbon alkylene glycols and those present in U.S. Patent No. 2,927,022, for example, those having several addition-polymerizable ethylene bonds, particularly when they exist as terminal bonds. Other useful monomers are disclosed in U.S. Patent No. 5,032,490. Other favorable monomers are monohydroxypolycarpolactone monoacrylate, polyethylene glycol diacrylate (molecular weight of about 200), and polyethylene glycol 400 dimethacrylate (molecular weight of about 400). Unsaturated monomer components can be present in amounts of 1 20 wt %, based on the total weight of the dry photopolymerizable composition.
Most preferred are the monomers used to prepare CYREL® photopolymer which include hexamethylene glycol diacrylate, hexamethylene glycol dimethacrylate or both. The initiator can be any single compound or combination of compounds which is sensitive to actinic radiation, generating free radicals which initiate the polymerization of the monomer or monomers without excessive termination. The initiatior is generally sensitive to actinic light, and preferably sensitive to ultraviolet radiation. Examples of suitable initiators include the substituted and unsubstituted polynuclear quinones which are compounds having two intracyclic carbon atoms in a conjugated carbocyclic ring system. Examples of suitable systems have been disclosed in Gruetzmacher, U.S. Patent No. 4,460,675; Feinberg et al., U.S. Patent No. 4,894,315; and Fryd et al., U.S. Patent No. 4,956,252. Initiators are generally present in amounts from 0.0001% to 10.0% based on the weight of the photopolymerizable composition. A preferred initiator is Irgacure 651, 2,2-dimethoxy-p-phenylacetophenone.
Examples of compositions comprising at least one monomer and an initiator have been disclosed, for example, in Chen et al., U.S. Patent No. 4,323,637, Gruetzmacher et al., U.S. Patent No. 4,427,749; and Feinberg et al., U.S. Patent No. 4,894,315.
An advantage of the present invention is the inclusion of a swellable elastomeric binder in the photopolymerizable composition. In addition to the elastomeric binder acting as a crosslinker with the at least one monomer changing the solubility of the film after exposure to actinic radiation, the elastomeric binder assists in enabling the swelling of the photopolymer film upon contact with a swelling agent. The term binder, as used herein, can encompass a single polymer, a mixture of polymers, block copolymers, gels, core shell microgels, blends of microgels, and preformed macromolecular polymers, such as those disclosed in Feinberg et al., U.S. Patent No. 4,894,315 and Fryd et al., U.S. Patent No. 4,956,252, incorporated by reference herein. Binders can include natural or synthetic polymers of conjugated diolefin hydrocarbons, including polyisoprene, 1 ,2-polybutadiene, 1 ,4-polybutadiene, butadiene/acrylonitrile, styrene-butadiene di-block copolymers, ethylene methacrylate copolymers, crosslinked styrene- meth( acrylate) copolymers, butadiene/styrene thermoplastic-elastomeric block copolymers and other copolymers. The block copolymers discussed in Chen U.S. Patent No. 4,323,636; Heinz et al., U.S. Patent No. 4,430,417; and Toda et al., U.S. Patent No. 4,045,231 can be used. The Kraton® family of triblock copolymers (manufactured by the Shell
Chemical Company, Houston, TX) are also suitable binders for practicing the present invention. The Kraton® triblock copolymers include polystyrene- polybutadiene-polystyrene, polystyrene-polyisoprene-polystyrene, and polystyrene-poly(ethylenebutylene)-polystyrene polymers. The preferred tri-block copolymer is polystyrene-polybutadiene-polystyrene triblock. Preferred polystyrene-polybutadiene-polystyrene and polystyrene-polyisoprene-polystyrene copolymers are those with about 14 to about 30 wt % polystyrene.
The concentration of the elastomeric binder is preferably greater than 30 weight percent of the total weight of the elastomeric photopolymerizable composition.
The elastomeric photopolymerizable composition can further include other additives depending on the final properties desired. Such additives include sensitizers, plasticizers, rheology modifiers, thermal polymerization inhibitors, tackifiers, colorants, antioxidants, antiozonants, or fillers and are well known to those in the art.
The elastomeric photopolymerizable composition can be prepared in many ways by admixing the elastomeric binder, the at least one monomer, the initiator, and other desired additives in any order. Conventional milling, mixing, and solution techniques can be used in making the elastomeric photopolymerizable composition. The elastomeric photopolymerizable composition can be formed into a layer in any desired manner. For example, solvent casting, hot pressing, calendering, or melt extrusion are suitable methods for preparing a layer. This layer can then be applied to the substrate by methods well known in the art including lamination, solution coating, or if necessary, affixing of the layer by means of a suitable adhesive. Preferably, the elastomeric photopolymerizable composition is in the form of a laminated film.
Following application of the photopolymerizable composition onto the substrate, selected areas of the elastomeric photopolymerizable composition are exposed to actinic radiation through an image to form a photopolymer film. The image can be an image-bearing transparency or photomask having areas essentially transparent to actinic radiation and areas opaque to actinic radiation. The image includes at least in part artwork corresponding to a barrier rib structure which can be of any pattern including cell-form or stripe form depending on whether the barrier ribs are for a plasma display panel that will be used with alternate or direct current.
On exposure to actinic radiation, such as UV radiation, the transparent areas of the image allow addition polymerization or crosslinking to take place in the exposed areas of the photopolymerizable composition, while the opaque areas remain uncrosslinked. Exposure is of sufficient duration to crosslink the exposed areas down to the substate which become insoluble to solvents used during image development. For good results, crosslinking should occur only in the exposed areas of the photopolymerizable composition with no significant crosslinking occurring in the non-image, unexposed areas. The unexposed photopolymerizable layer areas under the photomask remain soluble and are washed away with a suitable solvent.
Actinic radiation may be provided from any light source at 200-600 nm, preferably about 300 nm to about 460 nm, and a wattage of 10 to 1000 watts, such as sunlight, phosphorescent discharge lamps (fluorescent lamps), carbon arc lamps, metal arc lamps such as low, medium or high pressure mercury lamps, xenon lamps, argon lamps, tungsten lamps and metal halide lamps. Preferred sources are high pressure mercury lamps, such as the very high output so-called black-light fluorescent types due to their high ratio of ultraviolet to infrared output. Exposure times may vary from fractions of a second to minutes, depending on the composition of the photopolymerizable composition, the intensity and spectral energy distribution of the radiation, the distance of the composition from the radiation source and the thickness of the photopolymerizable composition. A mercury vapor arc or a sunlamp can be used at a distance of about 1.5 to about 60 inches (3.8-163 cm) from the photopolymerizable composition. Exposure temperatures are preferably at about ambient temperature or slightly higher, i.e., about 20 to about 35°C.
After exposure, the uncrosslinked portions of the photopolymerizable composition are dissolved away with any suitable aqueous or organic solvent known in the art. Channels will remain where the uncrosslinked portions of the photopolymerizable composition have been dissolved away. The solvent liquid used for removing the uncrosslinked photopolymerizable composition should have good solvent action on the solvent-soluble photopolymerizable composition and little action on the insolubilized areas in the period required to remove the nonpolymerized or uncrosslinked areas. Alkaline solutions, solutions with suitable surfactants, alcohols, and acetates can be used. Methyl ethyl ketone, benzene, toluene, xylene, carbon tetrachloride, trichloroethane, trichloroethylene, methylchloroform, and tetrachloroethylene can be useful solvents. Removal time can be varied, but it is preferably in the range of about 5 to 25 minutes. The solvent can be applied in any convenient manner, including immersion, spraying, brush, or roller application. Brushing can aid in removing the unpolymerized or non-crosslinked portions of the compositions. Washout can be carried out in an automatic processing unit which uses solvent and mechanical brushing action to remove the unexposed portions of the photopolymerizable composition.
The channels formed after removal of the unpolymerized areas of the elastomeric photopolymerizable composition are subsequently filled with a barrier rib material, which material has desirable sintering and barrier properties, to form an assembly comprising the substrate, the photopolymer film and the barrier rib material. The barrier rib material comprises a ceramic paste or a cementious paste, preferably is a good barrier to plasma gas, and most preferably comprises glass. Representative examples of such barrier rib material include, but are not limited to, pastes comprising ceramic, glass frits, Portland cement, other metal oxide ceramic powders, and the like, and any combination of the foregoing.
Suitable glass frits include borosilicate frits, such as lead borosilicate frit, bismuth, cadmium, barium, calcium or other alkaline earth borosilicate frits. The preparation of such glass frits is well known in the art and consists, for example, of melting together the constituents of the glass in the form of the oxides of the constituents and pouring such molten composition into water to form the frit. In order to prepare such pastes an organic resin binder, a solvent, and optionally a surfactant may be added to the ceramic oxides or cement.
Filling can be conveniently performed using a doctor blade or similar device. Screen printing may also be used. The channel washout and filling is simplified by the low initial aspect ratio of the channels, low viscosity of the barrier rib material, and good surface wetting between the barrier rib material and the photopolymer film.
A swelling agent is advantageously used in the present process. Before or after the channels are filled with the barrier rib material, a swelling agent is placed in contact with the photopolymer film to effect swelling of the photopolymer film. The swelling agent can be placed in contact with the photopolymer film before or after filling the channels. The swelling agent can be placed in contact with the photopolymer film by various methods including spray or spin coating. Preferably, the swelling agent is mixed with the barrier rib material. Such mixtures of the swelling agent and barrier rib material are preferably a relatively low viscosity paste of about 20-50 weight percent solids, most preferably about 40 weight percent solids. Since swelling can occur slowly at room temperature, a precise dose of any swelling agent/barrier rib material mixture can be spread into the channels using a doctor blade or similar device.
Heating the assembly causes the swelling agent to migrate into the photopolymer film and thereby activates swelling of the photopolymer film which in turn acts to increase the aspect ratio of the channel (and ultimately the aspect ratio of the barrier rib formed within that channel). Heating can also increase the solid density of the barrier rib material within the channels. The temperature for this heating step should be below the volatizing temperature of the swelling agent and is preferably about 90°C when paraffin is used as the swelling agent. Swelling agents for use in the present invention include agents known to those of skill in the art for elastomer swelling including, but are not limited to, non-volatile paraffin oils, such as Shellflex® 371 (Shell Oil Co, Houston, TX). By "paraffin oil" is meant a rubber oil containing a high proportion of paraffinic, i.e. linear, saturated hydrocarbon structures. Such oils typically comprise aromatic, naphthalene and paraffinic components and a variety of such oils are commercially available.
Alternatively, a solvent for the pre-crosslinked elastomeric binder can be used as a swelling agent. The selection of such swelling agents will depend on the particular elastomeric binder used in the photopolymerizable composition. Representative examples of such swelling agents include alkyl adipates and alkyl acetates, such as dimethyl adipate or heptyl acetate. These types of solvents are commercially available.
The assembly can be sintered at a temperature below the softening point of the substrate, preferably about 400°C to 600°C for glass, for a time sufficient to burn off the photopolymer film and solidify the barrier rib material so as to form a barrier rib with good strength. The temperature used during sintering is also dependent upon the sintering temperature of the material to be used to form the barrier ribs and on the burn-off temperature of any organic components within the paste. The aspect ratio of a barrier rib can be enhanced by a factor of 1.5 or greater when the swelling agent is used in formation of the barrier ribs.
Following formation of the barrier ribs, the assembly can be combined with the remaining components needed to prepare a plasma display panel. These components are well known in the art. DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 1 is a stepwise depiction of one embodiment of the method of the present invention herein described. FIG. la shows unit 1 comprised of substrate 10 onto which is coated an elastomeric photopolymerizable composition 12. Photomask 14 is applied to the surface of the coated substrate as shown in FIG. lb and exposed to actinic radiation 16. The unexposed photopolymerizable composition is removed by washing solvent as depicted in FIG. lc to leave channels 18. Channels 18 are subsequently filled with barrier rib material 20, which includes a swelling agent, as shown in FIG. Id. The unit is then heated to activate swelling of the photopolymer film and the subsequent narrowing of barrier rib material 20, as shown in FIG. le. FIG. If depicts unit 1 after it has been sintered to burn out the photopolymer film and to form barrier ribs of the present invention. FIG. 2 is a photograph of the photomask used in the Example below. It is a window screen with dark lines 30 of 15 mils thickness and open squares of 50 x 50 mils.
FIG. 3 is a photograph of a substrate and photopolymer film which has been exposed to UV radiation after photomasking with the screen shown in FIG. 2. Unfilled channels 32 are 15 mils wide and 10 mils deep, yielding an aspect ratio of 0.67. The photopolymer is shown as gray area 34.
FIG. 4 is a photograph of channels 32 of FIG. 3 after the unit has been subjected to heat to activate swelling of photopolymer film 34. Channels 32 are noticeably narrower after filling and heating. EXAMPLE
A 10 mil thick film of Cyrel® photopolymer (E. I. du Pont de Nemours and Company, Wilmington, DE) which contained 60 weight percent of a styrene- butadiene-styrene block copolymer was prepared by melt processing with appropriate multifunctional acrylate cross-linking monomers and photoinitiator, namely hexamethylene glycol diacrylate and hexamethylene glycol dimethacrylate and Irgacure 651, 2,2-dimethoxy-p-phenylacetophenone. The film was laminated onto a glass substrate. A window screen with dark lines of 15 mils thickness and open squares of 50 x 50 mils was used as a contact mask (see FIG. 2).
After exposure of the photopolymer film to the UV radiation of a mercury lamp for 10 sec at 100 mJ/cm2 channels with aspect ratio of 0.67 were washed out with a low swelling solvent, dipropylene glycol methylether acetate (see FIG. 3). A 40% weight solids paste of household tile grout, Portland cement, (TEC Inc., H. B. Fuller Co., Palatine, IL) was made using a non-volatile paraffin oil, Shellflex 371®, as a carrier and swelling agent. Since swelling was generally very slow at room temperature, a precise dose of swelling agent and paste was spread into the channels with a doctor blade. The task of channel washout and filling was made simple by the low viscosity (estimated to be less than 10,000 cps at 25°C) of the paste and good surface wetting between the paste and the photopolymer film. The assembly was heated at 90°C for 5 minutes to activate swelling wherein the paraffin oil migrated from the paste in the channels into the photopolymer film. Swelling increased the channel aspect ratio and the solid density of the paste within the channel. Channels of 5x12 mils with an aspect ratio of 2.4 were measured (see FIG. 4). An aspect ratio enhancement of 3.4 was noted. The assembly was subsequently heated from room temperature to 600°C with a linear lamp over the period of 1 hour to burn out the remaining photopolymer film and then cooled to room temperature in a period of one hour.

Claims

CLAIMS What is claimed is:
1. A method of forming a barrier rib for a plasma display panel, comprising: applying an elastomeric photopolymerizable composition onto a substrate, said substrate carrying thereon a plurality of electrodes; exposing to actinic radiation through an image corresponding at least in part to a barrier rib structure the elastomeric photopolymerizable composition to form a photopolymer film; removing the image; removing the unexposed areas of the photopolymerizable composition to form channels; filling said channels with a barrier rib material, said photopolymer film, barrier rib material, and substrate forming an assembly; contacting said photopolymer film with a swelling agent; heating said assembly to effect swelling of the photopolymer film; and sintering said assembly to burn off the photopolymer film and solidify the barrier rib material to form a barrier rib.
2. The method of Claim 1 wherein the swelling agent is a paraffin oil.
3. The method of Claim 1 wherein the swelling agent is an alkyl adipate or an alkyl acetate.
4. The method of Claim 1 wherein the photopolymerizable composition comprises an elastomeric binder, at least one monomer, and an initiator, wherein the at least one monomer is hexamethylene glycol diacrylate, hexamethylene glycol dimethacrylate, or both.
5. The method of Claim 4 wherein the elastomeric binder comprises a triblock copolymer selected from the group consisting of polystyrene- polybutadiene-polystyrene, polystyrene-polyisoprene-polystyrene, and polystyrene-poly(ethylenebutylene)-polystyrene.
6. The method of Claim 5 wherein the triblock copolymer is polystyrene- polybutadiene-polystyrene or polystyrene-polyisoprene-polystyrene and the weight percent of styrene in the copolymer ranges from about 14 to about 30.
7. The method of Claim 1 wherein said barrier rib material comprises glass.
8. The method of Claim 4, wherein the initiator is 2,2-dimethoxy-p- phenylacetophenone.
PCT/US1999/028241 1998-12-17 1999-11-30 Barrier rib formation for plasma display panels WO2000036625A1 (en)

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Publication number Priority date Publication date Assignee Title
FR2855644A1 (en) * 2003-05-27 2004-12-03 Thomson Plasma PLASMA PANEL WHOSE CEMENT BARRIERS ARE CEMENT
WO2004107381A2 (en) * 2003-05-27 2004-12-09 Thomson Plasma Plasma panel comprising cement partition barriers
WO2004107381A3 (en) * 2003-05-27 2005-02-10 Thomson Plasma Plasma panel comprising cement partition barriers
JP2007523442A (en) * 2003-05-27 2007-08-16 トムソン プラズマ エス アー エス Plasma panel with cement partition walls
US7710033B2 (en) 2003-05-27 2010-05-04 Thomson Licensing Plasma panel comprising cement partition barriers

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