EP0805814A1 - Oxyde de phosphine polymerisable ou polycondensable, polymeres obtenus a partir de tels oxydes et leur utilisation en optique non lineaire et en electro-optique - Google Patents

Oxyde de phosphine polymerisable ou polycondensable, polymeres obtenus a partir de tels oxydes et leur utilisation en optique non lineaire et en electro-optique

Info

Publication number
EP0805814A1
EP0805814A1 EP96901834A EP96901834A EP0805814A1 EP 0805814 A1 EP0805814 A1 EP 0805814A1 EP 96901834 A EP96901834 A EP 96901834A EP 96901834 A EP96901834 A EP 96901834A EP 0805814 A1 EP0805814 A1 EP 0805814A1
Authority
EP
European Patent Office
Prior art keywords
phosphine oxide
group
polymer
electro
optics
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.)
Ceased
Application number
EP96901834A
Other languages
German (de)
English (en)
French (fr)
Inventor
Minh Lequan
Kathleen Chane Ching
François Kajzar
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.)
Centre National de la Recherche Scientifique CNRS
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Original Assignee
Centre National de la Recherche Scientifique CNRS
Commissariat a lEnergie Atomique CEA
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 Centre National de la Recherche Scientifique CNRS, Commissariat a lEnergie Atomique CEA filed Critical Centre National de la Recherche Scientifique CNRS
Publication of EP0805814A1 publication Critical patent/EP0805814A1/fr
Ceased legal-status Critical Current

Links

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
    • G02F1/35—Non-linear optics
    • G02F1/355—Non-linear optics characterised by the materials used
    • G02F1/361—Organic materials
    • G02F1/3611—Organic materials containing Nitrogen
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
    • C07F9/02—Phosphorus compounds
    • C07F9/28—Phosphorus compounds with one or more P—C bonds
    • C07F9/50—Organo-phosphines
    • C07F9/53—Organo-phosphine oxides; Organo-phosphine thioxides
    • C07F9/5325—Aromatic phosphine oxides or thioxides (P-C aromatic linkage)
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
    • C07F9/02—Phosphorus compounds
    • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
    • C07F9/645—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having two nitrogen atoms as the only ring hetero atoms
    • C07F9/6509—Six-membered rings
    • C07F9/650952—Six-membered rings having the nitrogen atoms in the positions 1 and 4
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
    • C07F9/02—Phosphorus compounds
    • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
    • C07F9/655—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having oxygen atoms, with or without sulfur, selenium, or tellurium atoms, as the only ring hetero atoms
    • C07F9/6552—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having oxygen atoms, with or without sulfur, selenium, or tellurium atoms, as the only ring hetero atoms the oxygen atom being part of a six-membered ring
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F30/00—Homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and containing phosphorus, selenium, tellurium or a metal
    • C08F30/02—Homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and containing phosphorus, selenium, tellurium or a metal containing phosphorus

Definitions

  • the present invention relates to new polymerizable or polycondensable phosphine oxides, having good properties for applications in non-linear optics and electro-optics.
  • nonlinear optics is meant the field of optics which extends from the conversion of optical frequencies (obtaining optical radiation from two radiations of different frequencies, the frequency of the conversion radiation being equal to the sum or difference of the frequencies of the two radiations) to the electro-optical modulation (modification of one of the characteristics of a radiation by application of an electric field to a material crossed by said radiation).
  • organic material having this property amorphous and transparent polymers, functionalized with non-centrosymmetric organic molecules.
  • new polymerizable or polycondensable molecules have been developed, capable of leading to polymers having these properties.
  • These molecules are active chromophores derived from the family of phosphine oxides .
  • the subject of the invention is polymerizable or polycondensable phosphine oxides, not centrosymmetric, corresponding to the formula:
  • R 1 and R ⁇ which may be the same or different, represent an aryl group
  • R3 represents N or CH, and R 4 and R5 which may be identical or different, represent an optionally substituted alkyl group, at least one of
  • R 4 and R 5 being substituted by a hydroxyl group or a group comprising an ethylenic unsaturation, or in which R 4 and R ⁇ form, together with the nitrogen atom to which they are linked, a heterocyclic ring substituted by a group comprising a ethylenic unsaturation.
  • phosphine oxides thus consist of a donor group of the ami ⁇ o-disubstituted type (NR 4 R5), of a conjugated i ⁇ saturated chain such as stilbene or azobenzene capable of transmitting electrons from the donor system to an acceptor system. electrons consisting of a phosphorylated diaryl (OP R 1 R2).
  • the phosphine oxides corresponding to formula (I) also comprise either an ethylenically unsaturated group to allow their polymerization or their copolymerization with ethylenically unsaturated monomers, or several hydroxyl groups in order to polymerize them by polycondensation with suitable reagents.
  • the aryl groups used for R ⁇ and R ⁇ are monovalent groups obtained by removal of a hydrogen atom from an aromatic hydrocarbon.
  • aryl groups mention may be made of phenyl, ⁇ aphthyl and anthryl groups.
  • R 1 and R 2 represent the phenyl group.
  • the phosphine oxides are oxides which can be polymerized by polycondensation.
  • R 4 and R ⁇ each represent an alkyl group substituted by a hydroxyl group.
  • R 4 and R ⁇ can both represent -CH2-CH2OH.
  • Such phosphine oxides can lead to the formation of polyurethanes by polycondensation with diisocyanates.
  • the phosphine oxide can be polymerized by radical polymerization.
  • one of R 4 and R ⁇ represents an alkyl group substituted by a group comprising an ethylenic unsaturation, or R 4 and R ⁇ form together with the nitrogen atom to which they are linked, a substituted heterocyclic ring by a group comprising ethylenic unsaturation.
  • the heterocyclic rings formed by R 4 , R 5 and N may contain from four to six carbon atoms and one or more heteroatoms constituted by N, O or S.
  • heterocyclic rings mention may be made of the ring piperazine.
  • the presence of such a group makes it possible to obtaining an acrylic polymer comprising 100% phosphine oxide or an acrylic copolymer comprising between 0 and 100% phosphine oxide by polymerization of phosphine oxide with an acrylic or methacrylic monomer.
  • the phosphine oxides described above are very interesting for applications in non-linear optics because they have a high dipole moment which can vary between 6 and 7 Debye.
  • the invention also relates to amorphous and transparent polymers, functionalized with non-centrosymmetric molecules comprising an electron acceptor group of the diaryl phosphoryl type and an electron donor group of the amino-substituted type, separated by a unsaturated conjugated chain capable of transmitting electrons from the donor group to the acceptor group.
  • This polymer may in particular comprise non-centrosymmetric molecules constituted by the phosphine oxides described above.
  • the polymers functionalized by these phosphine oxides have very interesting properties, in particular a high glass transition temperature, comprised in the range from 120 to 170 ° C., chemical and thermal stability in air up to high temperatures. , for example around 220 ° C, and a significant non-linear optical response. Thanks to their high dipole moment, the chromophores constituted by the phosphine oxides described above, can be oriented at the glass transition temperature of the polymer under an external static electric field to give a system in which the chromophores are mainly directed in the direction of the field, capable of generating a second harmonic emission
  • the subject of the invention is also a process for preparing a polymer usable in non-linear optics, which consists in subjecting the functionalized polymer described above, brought to a temperature substantially equal to its glass transition temperature, to a sufficient electric field, for example the Corona technique, to orient the dipoles of the non-centrosymmetric molecules, then to cool the polymer to ambient temperature while maintaining said field to freeze the orientation of the dipoles of said molecules
  • a sufficient electric field for example the Corona technique
  • the applied electric field can have a value of 6 to 10 KV.
  • the glass transition temperature of these polymers is high compared to the temperature of use (generally room temperature), the orientation of the dipoles remains stable for a long time, which is particularly advantageous for applications in optics non-linear
  • the polymers obtained from the phosphine oxides of the invention are soluble and can be deposited in thin film on a suitable substrate from a solution of the polymer in an appropriate solvent by conventional techniques, for example using spinner.
  • the solvents used can be, for example, chloroform or dichloromethane.
  • the substrates used can be standard glass, ITO glass (indium tin oxide) or quartz.
  • the phosphine oxides corresponding to the formula (I) given above can be prepared by conventional methods.
  • R ⁇ and R? represent R 4 and R ⁇ or precursor groups of R 4 and R 5 to form the secondary alcohol of formula:
  • the phosphine oxide can be obtained by reaction of p-bromoaniline with a phenylamine, followed by a reaction with the phosphine chloride CIP R ⁇ R 2 and an oxidation of the phosphine obtained .
  • FIG. 1 represents the synthetic scheme of compound 1 of l 'example 1
  • FIG. 2 represents the synthesis scheme for compound 5 of Example 2
  • FIG. 3 shows the synthesis scheme of compound 10 of Example 11
  • FIG. 4 schematically illustrates an interferometer using a polymer according to the invention
  • Example 1 Preparation of the oxide of 4-r2- (methacryloyloxy) éthv ⁇ picherrazino) stilbén-4-yl diphénvDphosphine. (Compound 1).
  • the temperature is maintained at 5 ° C. for approximately one hour, then the mixture is allowed to return to ambient temperature, and with stirring overnight.
  • the mixture is filtered on cellite in order to separate the ammonium chloride formed. Evaporation of the solvent makes it possible to collect an orange-yellow powder.
  • the mixture is stirred) at a temperature of 80 ° C for 48 hours.
  • THP tetrahydropyran
  • the expected product is separated from the alcohol by chromatography on a silica column (eluent: dichloromethane). 8.8 g of "pyrannyl" alcohol are collected as well as 3.4 g of cleavage product.
  • reaction mixture is hydrolyzed by adding 40 cm 3 of deionized water, then extracted with ether.
  • the ethereal phase is dried over magnesium sulphate, then by evaporation of the solvent, a red oil is collected.
  • the mixture is filtered on cellite in order to separate the ammonium chloride formed. Evaporation of the solvent makes it possible to collect an orange-yellow powder.
  • acrylic polymers are prepared from the monomer obtained in Example 1 (compound 1) or in Example 2 (compound 5) by polymerizing it alone or by copolymerizing it with methyl methacrylate.
  • the polymer After removal of the supernatant by decantation, the polymer is dissolved in a minimum amount of dichloromethane, then this solution is poured dropwise into methanol with stirring. The polymer is recovered by fiitration then again dissolved in dichloromethane and isolated by precipitation in methanol.
  • Table 1 summarizes the amounts of reagents and the solvent used in each example, and gives the glass transition temperatures Tg of the polymers.
  • the product is extracted with ether.
  • the organic phase is washed with 2 times 50 cm 3 of water, then dried over magnesium sulfate. After evaporation of the solvent, the product is purified by chromatography on a silica column (eluent: pentane: 90, acetone: 10).
  • polyurethanes are prepared by polycondensation of the compound 10 obtained in example 11 with a diisocyanate, consisting of isophorone diisocyanate in example 12 and by hexamethylene diisocyanate in example 13. as follows:
  • the active compound 11 is introduced in non-linear optics.
  • the contents of the three-necked flask are dried under primary vacuum for 30 minutes.
  • the polymer is obtained by adding dropwise this solution to 50 cm 3 of methanol with stirring.
  • the isolated solid has a gummy appearance. It is again dissolved in dichloromethane. A second precipitation in ether gives an orange powder collected by fiitration and then dried under vacuum
  • Table 2 illustrates the quantities of reagents and of solvent used in each example, the yields obtained and the glass transition temperatures Tg of the polyurethanes.
  • Example 14 In this example, the optical properties of the polymers obtained in Examples 3 to 10, 12 and 13 are tested, after having put them in the form of a film of approximately 0.5 ⁇ m in thickness.
  • the polymer is dissolved in a solvent constituted by chloroform in order to have a polymer concentration of approximately 60 g / l.
  • a solvent constituted by chloroform in order to have a polymer concentration of approximately 60 g / l.
  • the thin film is formed on a glass substrate by depositing the spinning solution After evaporating the solvent by heating in an oven, the film is brought to the vicinity of the glass transition temperature of the polymer, then it is subjected while it is maintained at this temperature to an electric field by the technique Corona of approximately 6kV for 5 min, then the polymer film is cooled to the ambient temperature, while maintaining the electric field to freeze the orientation of the dipoles of the active monomer in non-linear optics.
  • the quadratic susceptibility tensor has only two independent components: ⁇ * i 3 and ⁇ 333 which correspond to the polarization induced perpendicular to the plane of the film depending on whether the excitation electromagnetic radiation is respectively in the plan of the film or according to its normal.
  • ⁇ * i 3 and ⁇ 333 which correspond to the polarization induced perpendicular to the plane of the film depending on whether the excitation electromagnetic radiation is respectively in the plan of the film or according to its normal.
  • d-j3 ⁇ 1 -
  • 3/2 and d33 ⁇ 333 / 2.
  • the measurements of the coefficients d by generation of second optical harmonic have been described by H.W. Guan and CH. Wang, J. Chem. Phys. 98 3463 (1993), and can be summarized as follows:
  • the polymers obtained in accordance with the invention can find numerous applications in non-linear optics and in electro-optics, in particular in electro-optical modulation, in frequency doubling of a light wave, for the manufacture of laser sources tunable in length. wave and for electro-optical or all-optical switching of a light wave
  • FIG. 4 the principle of the optical assembly of the Mach-Zehnder interferometer has been represented very schematically.
  • a single-mode guide 1 in which a monochromatic beam of wavelength ⁇ is coupled is divided into two arms of the same length 3 and 5 so that the phases ⁇ -
  • One of the arms can be subjected to an electric field E via a system 7 with two electrodes
  • the polymer being electro-optical, the refractive index undergoes a variation ⁇ n given by
  • the system comprises a lower electrode 11, an upper electrode 13, a lower buffer film 15, an upper buffer film 17 and a central film 19 of electro-optical polymer.
  • the buffer films 15 and 17 must have a lower refractive index than that of the central film 19 of electro-optical polymer, and their thickness must be sufficient for the electromagnetic wave (represented by the arrow) to be completely attenuated at the surface of the electrodes. These thicknesses are of the order of 3 ⁇ m.
  • This structure is obtained by depositing, by vacuum evaporation, the lower electrode 11 in aluminum on a glass substrate 21, then by successively producing on this lower electrode the lower buffer film 15 of passive polymer, the electro-optical film 19 of polymer of the invention and the upper buffer film 17 in passive polymer, by spinning from solutions of these polymers.
  • the upper electrode 13 is then deposited in aluminum by vacuum evaporation.
  • the assembly is brought to a temperature close to the glass transition point of the electro-optical polymer of layer 19 and the assembly is subjected to an intense electric field to give the polymer 19 the electro properties.
  • optical for example by applying a voltage to the upper and lower electrodes. This field is then maintained while cooling the assembly to room temperature.
  • the polymer layer 19 is subjected to an irradiation treatment to determine the guiding region 19a by bleaching the polymer by electro-optical irradiation in region 19b located around this region 19a by irradiation.
  • the upper electrode 13 can serve as a mask for this operation.
  • a very efficient optical modulator is thus obtained using a polymer according to the invention.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Molecular Biology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Nonlinear Science (AREA)
  • Optics & Photonics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
EP96901834A 1995-01-24 1996-01-23 Oxyde de phosphine polymerisable ou polycondensable, polymeres obtenus a partir de tels oxydes et leur utilisation en optique non lineaire et en electro-optique Ceased EP0805814A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9500765A FR2729667A1 (fr) 1995-01-24 1995-01-24 Oxyde de phosphine polymerisable ou polycondensable, polymeres obtenus a partir de tels oxydes et leur utilisation en optique non lineaire et en electro-optique
FR9500765 1995-01-24
PCT/FR1996/000107 WO1996022993A1 (fr) 1995-01-24 1996-01-23 Oxyde de phosphine polymerisable ou polycondensable, polymeres obtenus a partir de tels oxydes et leur utilisation en optique non lineaire et en electro-optique

Publications (1)

Publication Number Publication Date
EP0805814A1 true EP0805814A1 (fr) 1997-11-12

Family

ID=9475423

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96901834A Ceased EP0805814A1 (fr) 1995-01-24 1996-01-23 Oxyde de phosphine polymerisable ou polycondensable, polymeres obtenus a partir de tels oxydes et leur utilisation en optique non lineaire et en electro-optique

Country Status (3)

Country Link
EP (1) EP0805814A1 (enrdf_load_stackoverflow)
FR (1) FR2729667A1 (enrdf_load_stackoverflow)
WO (1) WO1996022993A1 (enrdf_load_stackoverflow)

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9019347D0 (en) * 1990-09-05 1990-10-17 Ici Plc Chromophore-containing compounds for opto-electronic applications
US5387629A (en) * 1992-07-28 1995-02-07 The Center For Innovative Technology Phosphorus containing poly(arylene ether)s useful as oxygen plasma resistant films and in nonlinear optical applications

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9622993A1 *

Also Published As

Publication number Publication date
FR2729667B1 (enrdf_load_stackoverflow) 1997-02-21
FR2729667A1 (fr) 1996-07-26
WO1996022993A1 (fr) 1996-08-01

Similar Documents

Publication Publication Date Title
CA1203541A (en) Nonlinear optical materials and processes employing diacetylenes
EP0359648B1 (fr) Polyuréthannes, actifs en optique non linéaire et matériaux les contenant dispositif optique les contenant et procédés de fabrication de ces composés et matériaux
US6514434B1 (en) Electro-optic chromophore bridge compounds and donor-bridge compounds for polymeric thin film waveguides
EP1215271B1 (fr) Dopants chiraux à induction de pas d'hélice variable et leur application à un affichage réflectif en couleur
EP0384811A1 (fr) Composés thiophéniques actifs en optique non linéaire, matériaux et dispositifs les contenant
EP0482985A1 (fr) Polymère réticulable pour applications en optique non linéaire
EP0641808B1 (fr) Matériau polymère réticulable, utilisable en optique non linéaire, et son procédé d'obtention
WO1996022993A1 (fr) Oxyde de phosphine polymerisable ou polycondensable, polymeres obtenus a partir de tels oxydes et leur utilisation en optique non lineaire et en electro-optique
EP0343019A2 (fr) Composés organosiliciés, matériaux et dispositifs électrooptiques les contenant
EP0447313B1 (fr) Polymères cristaux liquides ferroélectriques
EP0463931B1 (fr) Copolymères amorphes, transparents dans le visible, pour applications en optique non linéaire
EP0415817A1 (fr) Copolymères amorphes pour applications en optique non linéaire
CN106675574B (zh) D-A-D型弓形波拉（Bola）液晶化合物
EP1394158B1 (en) Thiophene derivatives and optical elements using the same
Cuniberti et al. Optical and Spectroscopic Properties of a Novel Polycarbazolyldiacetylene
US5445888A (en) Hydrazine compound, process for the preparation of the same, and nonlinear optical organic material
EP0415816A1 (fr) Polymères actifs en optique non linéaire
US5408009A (en) High polymer-nonlinear optical material
WO2009138643A1 (fr) Procede de reticulation par reaction de huisgen thermique, polymeres chromophores reticulables et materiaux polymeres reticules a proprietes electro-optiques stables
FR2763066A1 (fr) Nouveau compose d'ester aromatique et materiau optique non lineaire de second ordre qui en est produit
KR0152210B1 (ko) 광도파로형 광소자의 제조방법
Kim et al. Synthesis and properties of nonlinear optical chromophore containing alkoxy-substituted phenylene as conjugation bridge
EP0354077A1 (fr) Cristaux liquides non-centrosymétriques utilisables en optique non linéaire
Liu Design, synthesis and characterization of novel nonlinear optical chromophores for electro-optical applications
FR2659340A1 (en) Photocrosslinkable polymer usable in nonlinear optics

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19970707

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE GB IT

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

17Q First examination report despatched

Effective date: 19981124

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN REFUSED

18R Application refused

Effective date: 19990515