WO2000003177A1 - Light-polarizing particles of improved particle size distribution - Google Patents
Light-polarizing particles of improved particle size distribution Download PDFInfo
- Publication number
- WO2000003177A1 WO2000003177A1 PCT/US1999/015508 US9915508W WO0003177A1 WO 2000003177 A1 WO2000003177 A1 WO 2000003177A1 US 9915508 W US9915508 W US 9915508W WO 0003177 A1 WO0003177 A1 WO 0003177A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- particles
- light
- precursor
- suspension
- polarizing
- Prior art date
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Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/03—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect
- G02F1/055—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect the active material being a ceramic
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/17—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on variable-absorption elements not provided for in groups G02F1/015 - G02F1/169
- G02F1/172—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on variable-absorption elements not provided for in groups G02F1/015 - G02F1/169 based on a suspension of orientable dipolar particles, e.g. suspended particles displays
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
- G02B5/3008—Polarising elements comprising dielectric particles, e.g. birefringent crystals embedded in a matrix
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/0009—Materials therefor
Definitions
- the present invention relates to a method of making light-polarizing particles of improved particle size distribution for use in liquid suspensions and light valves, films, and set suspensions.
- a light valve may be described as a cell formed of two walls that are spaced apart by a small distance, at least one wall being transparent, the walls having electrodes thereon usually in the form of transparent conductive coatings.
- the cell contains a light-modulating element, which may be either a liquid suspension of particles or a plastic film in which droplets of a liquid suspension of particles are distributed and encapsulated.
- the liquid suspension (sometimes herein called a liquid light valve suspension) comprises small particles suspended in a liquid suspending medium.
- the particles in the liquid suspension exhibit random Brownian movement, and hence a beam of light passing into the cell is reflected, transmitted or absorbed, depending upon the cell structure, the nature and concentration of the particles and the energy content of the light.
- the light valve is thus relatively dark in the OFF state.
- an electric field is applied through the light valve suspension in the light valve, the particles become aligned and for many suspensions most of the light can pass through the cell.
- the light valve is thus relatively transparent in the ON state.
- Light valves have been proposed for many purposes including e.g., alpha-numeric displays, television displays, windows, sun roofs, sun visors, mirrors, eyeglasses and the like to control the amount of light passing therethrough.
- Light valves of the type described herein are also known as “suspended particle devices” or SPDs".
- the activatable material is a plastic film rather than a liquid suspension.
- a plastic film in which droplets of liquid suspension are distributed is preferable to a liquid suspension alone because hydrostatic pressure effects e.g., bulging associated with a high column of liquid suspension can be avoided through use of a film, and the risk of possible leakage can also be avoided.
- Another advantage of using a plastic film is that in a plastic film the particles are generally present only within very small droplets, and hence do not noticeably agglomerate when the film is repeatedly activated with a voltage.
- a "light valve film” as used herein is thus a film having droplets of a liquid suspension of particles distributed in the film.
- a type of light valve film made by phase separation from a homogeneous solution is disclosed in U.S. Patent No. 5,409,734.
- Light valve films made by cross-linking emulsions are disclosed in U.S. Patent Nos. 5,463,491 and 5,463,492 assigned to the assignee of the present invention. All of those patents and other patents and other sources cited herein are incorporated herein by reference thereto.
- set suspensions such as light-polarizing sheets, sometimes called "sheet polarizers", which can be cut up and formed into polarized sunglass lenses or used as filters
- light-polarizing particles can be dispersed or distributed throughout a sheet of suitable film-forming material, such as cellulose acetate or polyvinyl alcohol or the like.
- suitable film-forming material such as cellulose acetate or polyvinyl alcohol or the like.
- the liquid light valve suspension may be any liquid light valve suspension known in the art and may be formulated according to known techniques.
- the term “liquid light valve suspension” as used herein means a “liquid suspending medium” in which a plurality of small particles are dispersed.
- the “liquid suspending medium” comprises one or more non-aqueous, electrically resistive liquids in which there is preferably dissolved at least one type of polymeric stabilizer which acts to reduce the tendency of the particles to agglomerate and to keep them dispersed and in suspension.
- the liquid light valve suspension of the present invention may include any of the liquid suspending media previously proposed for use in light valves for suspending the particles.
- Liquid suspending media known in the art are useful herein, such as but not limited to the liquid suspending media disclosed in U.S. Pat. Nos. 4,247,175 and 4,407,565.
- one or both of the liquid suspending medium or the polymeric stabilizer dissolved therein is chosen so as to maintain the suspended particles in gravitational equilibrium.
- the polymeric stabilizer when employed can be a single type of solid polymer that bonds to the surface of the particles but also dissolves in the non-aqueous liquid or liquids of the liquid suspending medium.
- the particles can be coated with a first type of solid polymeric stabilizer such as nitrocellulose, which in effect, provides a plain surface coating for the particles and one or more additional types of solid polymeric stabilizer that bond to or associate with the first type of solid polymeric stabilizer and also dissolve in the liquid suspending medium to provide dispersion and steric protection for the particles.
- liquid polymeric stabilizers may be used to advantage, especially in SPD light valve films, as described in U.S. Patent No. 5,463,492. 2.
- inorganic and organic particles may be used in a light valve suspension.
- the present invention relates to an improved method of preparing particles that are polyhalides (sometimes referred to in the prior art as perhalides) of organic compounds, such as alkaloid acid salts and the like.
- the polyhalide particles of the present invention may be light-polarizing, such as halogen-containing light-polarizing materials, e.g., polyhalides of alkaloid acid salts.
- alkaloid is used herein to mean an organic nitrogenous base, as defined inhackh's Chemical Dictionary, Fourth Edition, McGraw-Hill Book Company, New York, 1969).
- the alkaloid moiety may be a quinine alkaloid, as defined inhackh's Chemical Dictionary, supra.
- U.S. Pat. Nos. 2,178,996 and 2,289,712 refer in detail to the use of polyhalides of quinine alkaloid acid salts.
- the particles may be light- absorbing or light-reflecting.
- the particles may be particles of a hydrogenated polyhalide of a quinine alkaloid acid salt, such as dihydrocinchonidine sulfate polyiodide, as described in U.S. Patent No. 4,131,334.
- polyhalide particles having advantageous features for use in light valves have been proposed in U.S. Pat. No. 4,877,313, 5,002,701, 5,093,041 and 5,516,463.
- These "polyhalide particles” are formed by reacting organic compounds, usually containing nitrogen, with elemental iodine and a hydrohalide acid or an ammonium alkali metal halide or alkaline earth metal halide. Such organic compounds are referred to herein as a "Precursor".
- Prior art polyhalide particles are also discussed in detail in "The Optical Properties and Structure of Polyiodides” by D.A. Godina and G.P. Faerman published in The Journal of General Chemistry, U.S.S.R. Vol. 20, pp.
- Herapathite for example, is quinine bisulfate polyiodide, and its formula is given under the heading "quinine iodosulfate” as 4C2 0 H 2 4N 2 O2.3H 2 SO 4 .2HI.I4.6H2O in The Merck Index, 10 th Ed. (Merck & Co., Inc., Rahway, N.J.).
- the iodide anion is thought to form chains and the compounds are strong light polarizers. See U.S. Patent No. 4,877,313 and Teitelbaum et al. JACS 100 (1978), pp. 3215-3217.
- polyhalide is used herein to mean a compound such as a polyiodide, but wherein at least some of the iodide anion may be replaced by another halide anion.
- polyhalide particles that are useful for light valves are preferably of colloidal size, that is the particles will have a largest dimension averaging about 1 micron or less. It is preferred that most polyhalide particles have their largest dimension less than one-half of the wavelength of blue light i.e., 2000 Angstroms or less to keep light scatter extremely low.
- the present invention provides a method of preparing polyhalide particles that are especially well suited for use as the particles of a liquid light valve suspension, which comprises reacting a "Precursor" of a specified particle size with elemental iodine and a hydrohalide acid or an ammonium, alkali metal or alkaline earth metal halide.
- the Precursor may be any of the compounds previously used to form organic polyhalide particles by reaction with elemental iodine and a hydrohalide acid or an ammonium, alkali metal or alkaline earth metal halide.
- the Precursor may be a quinine alkaloid acid salt (U.S.
- Patents 2,178,996 and 2,289,712) a hydrogenated alkaloid acid salt (U.S. Patent 4,131,334) or an organic compound containing one or more groups that chelate hydrogen, ammonium or metal ions (U.S. Patents 4,877,313, 5,002,701, 5,093,041 and 5,516,463), all of such U.S. patents being incorporated herein by reference thereto.
- the Precursor can be any color but generally is comprised of small white or off- white colored crystals (sometimes referred to herein as "particles").
- the average size and/or median size of the Precursor is less than 1 micron, preferably less than 0.75 micron, the quality of the polyhalide particles made therefrom is substantially improved.
- Comminution (size reduction) of the Precursor particles to provide the desired particle size may be accomplished by any means that reduces their size, provided that the process does not cause the comminuted particles to cluster or clump up, which could offset the advantages of comminution and might actually cause the effective size of the particles to increase.
- the Precursor particles can be pulverized or ground with a mortar and pestle or with a ball mill or any other convenient means, either dry or wet with a liquid, or with another solid inert substance present to aid pulverization.
- the Precursor particles can be caused to collide with one another by being subjected to rapidly moving gas streams, for example, by being blasted with a supersonic stream or streams of air.
- Precursor particles or crystals are said to have been comminuted or reduced in size, what is meant is that their average size and/or their median size has been reduced.
- size of a particle as used herein means and refers to the particle's largest dimension.
- a typical modern prior art type of polyhalide particle is pyrazine-2 ,5- dicarboxylic acid dihydrate calcium iodide polyiodide.
- a procedure for making such crystals and a liquid suspension thereof for use in a light valve is disclosed in Example 1.
- EXAMPLE 1 (PRIOR ART) Formulation For Making Polyiodide Crystals And A Liquid Light Valve Suspension Thereof
- the decay time is determined by the following procedure.
- a suspension of the formed particles in a light valve suspending medium is filled into a light valve cell comprising glass sheets carrying suitable electrodes, spaced 5 mils apart.
- the light valve suspension is illuminated with continuous illumination such as from a tungsten lamp.
- the suspension of particles in the light valve is energized by applying to the electrodes about 55 volts at 10 kHz to a baseline measurement. About 2-3 milliseconds are required to reach an open state of the light valve, and approximately 20 milliseconds thereafter the electrical field is discontinued. Decay to the fully closed (off) state of the light valve is measured thereafter. (See col. 2, lines 37-48 of U.S. Patent No.
- the decay time should be 8 to 12 milliseconds; if higher, recentrifuge supernatant.
- TNPTM Tri-n-pentyl-trimellitate
- TNPTM Tri-n-pentyl-trimellitate
- the amount of TNPTM to be added can be determined empirically depending on how concentrated with particles one desires the resulting final concentrate (i.e., the dried initial concentrate) to be.
- the final concentrate can then be diluted with any other desired solvent or solvents in which the concentrate polymer is soluble.
- Other plasticizer liquids can be used.
- Example 2 sets forth a prior art method of making the Precursor material used in Example 1, namely pyrazine-2,5-dicarboxylic acid dihydrate.
- 2,5-dimethylpyrazine 25g
- pyridine 500 ml
- selenium dioxide 125g
- water 50 ml
- the mixture was refluxed for 11-12 hours; the boiling solution assumes an orange-red color after about 20 minutes while selenium is gradually precipitated.
- the suspension is allowed to cool to room temperature, and the precipitate, a mixture of pyrazine 2,5-dicarboxylic acid and selenium, is filtered off. Flask and stirrer are rinsed out with the filtered reaction solvent. The reaction solvent is returned to the flask and reused. The precipitate is washed with 2N NH 4 OH until all of the pyrazine 2,5- dicarboxylic acid is dissolved. The 2N NH 4 OH with pyrazine 2,5-dicarboxylic acid is run through a chromatography column of slurried Darco activated carbon (12-20 mesh, 250g) at a rate of 30ml/min.
- the optical density of a light valve window test cell in the unactivated condition is its off-state optical density or "OD 0ff ".
- OD on This decreased optical density when the cell is activated or turned on.
- a voltage of 55 volts RMS is applied at a frequency of 10 Kilohertz using a test cell which has an internal gap of 5 mils between its electrodes. Hence the field strength applied in a test cell would be 11 volts RMS per mil.
- ODR optical density ratio
- EXAMPLE 3A In an Erlenmeyer flask the following materials in the quantities shown were dissolved into 132.5 g. of a hexyl acetate solution (including 0.11 g. of water) comprising 6.98% of dissolved 1/4 ss-type nitrocellulose:
- pyrazine-2,5-dicarboxylic acid dihydrate made by the prior art method described in Example 2 above, was added to the aforesaid solution, and the flask was placed for 3 hours at 45°C in a Waterbath Shaker Model-WB-20 manufactured by Elmeco Engineering, Rockville, Maryland. Then the suspension was ultrasonically agitated for two hours.
- the particle size of the Precursor is reported in Table 1, below.
- Example 3B Example 3 A was repeated except that the Precursor had been previously comminuted by a supplier (Aveka, Inc., Woodbury, Minnesota) in a machine referred to herein as a "pancake mill" which utilizes supersonic air streams to cause Precursor particles to collide violently with one another.
- the particle size of the Precursor is reported in Table 1 , below.
- Example 3 A and 3B were removed from the Erlenmeyer flasks and centrifuged following the procedure of Example 1 to obtain the initial concentrate.
- Table 1 summarizes the data for each of the suspensions described in Examples 3A and 3B with respect to ODR, decay time, efficiency, and the average and median sizes of the Precursor particles used.
- Example 3A 6.33 microns 1.12 microns 3.13 23 ms 136
- Example 3B 0.74 micron 0.68 micron 3.00 10.5 ms 285
- any solid Precursor used in the prior art or invented hereinafter, which can be used to make polyhalide particles, can be comminuted advantageously as disclosed in the present invention.
Abstract
Description
Claims
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA002336371A CA2336371C (en) | 1998-07-09 | 1999-07-09 | Light-polarizing particles of improved particle size distribution |
EP99937224A EP1105776A4 (en) | 1998-07-09 | 1999-07-09 | Light-polarizing particles of improved particle size distribution |
JP2000559376A JP3947359B2 (en) | 1998-07-09 | 1999-07-09 | Polarizing particles with improved particle size distribution |
AU52099/99A AU737670B2 (en) | 1998-07-09 | 1999-07-09 | Light-polarizing particles of improved particle size distribution |
US09/720,561 US6334967B1 (en) | 1998-07-09 | 1999-07-09 | Light-polarizing particles of improved particle size distribution |
BR9911937-4A BR9911937A (en) | 1998-07-09 | 1999-07-09 | Process for producing particles of light polarizing material, particle, light valve, light polarizing body, and liquid suspension |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US9219898P | 1998-07-09 | 1998-07-09 | |
US60/092,198 | 1998-07-09 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2000003177A1 true WO2000003177A1 (en) | 2000-01-20 |
Family
ID=22232124
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1999/015508 WO2000003177A1 (en) | 1998-07-09 | 1999-07-09 | Light-polarizing particles of improved particle size distribution |
PCT/US1999/015564 WO2000003178A1 (en) | 1998-07-09 | 1999-07-09 | Polyhalide particles and light valves comprising same |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1999/015564 WO2000003178A1 (en) | 1998-07-09 | 1999-07-09 | Polyhalide particles and light valves comprising same |
Country Status (8)
Country | Link |
---|---|
EP (1) | EP1105776A4 (en) |
JP (1) | JP3947359B2 (en) |
KR (1) | KR100391748B1 (en) |
CN (1) | CN1107199C (en) |
AU (1) | AU737670B2 (en) |
BR (1) | BR9911937A (en) |
CA (1) | CA2336371C (en) |
WO (2) | WO2000003177A1 (en) |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
TWI275835B (en) * | 2002-10-08 | 2007-03-11 | Nitto Denko Corp | Polarizer, optical film, and image display |
KR101275728B1 (en) * | 2005-08-23 | 2013-06-14 | 엘지디스플레이 주식회사 | Flat panel display |
KR101232136B1 (en) * | 2005-09-14 | 2013-02-12 | 엘지디스플레이 주식회사 | Method of repair an Liquid Crystal Cell, method of manufacturing Liquid Crystal Display Device using the same, and Liquid Crystal Display repaired using the same |
SI3147317T1 (en) | 2015-09-28 | 2018-01-31 | Evonik Degussa Gmbh | Tripentylester of trimellitic acid |
CN111471448B (en) * | 2020-05-11 | 2023-07-11 | 江苏铁锚玻璃股份有限公司 | Liquid bipolar color-changing particles, preparation method of electrochromic layer and electrochromic device |
WO2022163492A1 (en) * | 2021-01-28 | 2022-08-04 | コニカミノルタ株式会社 | Polarizing plate and display device |
CN115093407A (en) * | 2022-06-20 | 2022-09-23 | 深圳市华科创智技术有限公司 | Method for preparing quinine iodosulfate nanorods in controllable manner under assistance of ball milling |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4422963A (en) * | 1977-05-11 | 1983-12-27 | Research Frontiers Incorporated | Light valve polarizing materials and suspensions thereof |
US5409734A (en) * | 1992-01-10 | 1995-04-25 | Hankuk Glass Industries, Inc. | Making liquid suspension type light valve film |
US5516463A (en) * | 1993-07-21 | 1996-05-14 | Research Frontiers Incorporated | Method of making light-polarizing particles |
US5650872A (en) * | 1994-12-08 | 1997-07-22 | Research Frontiers Incorporated | Light valve containing ultrafine particles |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5002701A (en) * | 1989-02-10 | 1991-03-26 | Research Frontiers Incorporated | Light polarizing materials and suspensions thereof |
US5093041A (en) * | 1990-07-30 | 1992-03-03 | Research Frontiers Incorporated | Light-polarizing material based on ethylenediamine polyacetic acid derivatives |
-
1999
- 1999-07-09 EP EP99937224A patent/EP1105776A4/en not_active Ceased
- 1999-07-09 WO PCT/US1999/015508 patent/WO2000003177A1/en active IP Right Grant
- 1999-07-09 CN CN99808446A patent/CN1107199C/en not_active Expired - Fee Related
- 1999-07-09 WO PCT/US1999/015564 patent/WO2000003178A1/en active IP Right Grant
- 1999-07-09 JP JP2000559376A patent/JP3947359B2/en not_active Expired - Lifetime
- 1999-07-09 CA CA002336371A patent/CA2336371C/en not_active Expired - Fee Related
- 1999-07-09 BR BR9911937-4A patent/BR9911937A/en not_active IP Right Cessation
- 1999-07-09 AU AU52099/99A patent/AU737670B2/en not_active Ceased
- 1999-07-09 KR KR10-2001-7000148A patent/KR100391748B1/en not_active IP Right Cessation
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4422963A (en) * | 1977-05-11 | 1983-12-27 | Research Frontiers Incorporated | Light valve polarizing materials and suspensions thereof |
US5409734A (en) * | 1992-01-10 | 1995-04-25 | Hankuk Glass Industries, Inc. | Making liquid suspension type light valve film |
US5516463A (en) * | 1993-07-21 | 1996-05-14 | Research Frontiers Incorporated | Method of making light-polarizing particles |
US5650872A (en) * | 1994-12-08 | 1997-07-22 | Research Frontiers Incorporated | Light valve containing ultrafine particles |
Non-Patent Citations (1)
Title |
---|
See also references of EP1105776A4 * |
Also Published As
Publication number | Publication date |
---|---|
EP1105776A1 (en) | 2001-06-13 |
KR20010071747A (en) | 2001-07-31 |
CA2336371A1 (en) | 2000-01-20 |
CN1107199C (en) | 2003-04-30 |
JP2002520645A (en) | 2002-07-09 |
KR100391748B1 (en) | 2003-07-16 |
CN1308716A (en) | 2001-08-15 |
CA2336371C (en) | 2005-01-04 |
JP3947359B2 (en) | 2007-07-18 |
BR9911937A (en) | 2001-03-27 |
EP1105776A4 (en) | 2005-04-13 |
AU737670B2 (en) | 2001-08-30 |
WO2000003178A1 (en) | 2000-01-20 |
AU5209999A (en) | 2000-02-01 |
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