U.S. patent application number 09/942780 was filed with the patent office on 2002-04-18 for novel organometallic luminescent materials and organic electroluminescent device containing same.
This patent application is currently assigned to NESSDISPLAY CO., Ltd.. Invention is credited to Kim, Youngkyoo, Lee, Jae-Gyoung.
Application Number | 20020045065 09/942780 |
Document ID | / |
Family ID | 19540443 |
Filed Date | 2002-04-18 |
United States Patent
Application |
20020045065 |
Kind Code |
A1 |
Kim, Youngkyoo ; et
al. |
April 18, 2002 |
Novel organometallic luminescent materials and organic
electroluminescent device containing same
Abstract
An organometallic luminescent material selected from the group
consisting of the compounds of formulae (I) to (V) of the present
invention can emit blue, green and red lights.
Inventors: |
Kim, Youngkyoo; (Pusan,
KR) ; Lee, Jae-Gyoung; (Seongnam-shi, KR) |
Correspondence
Address: |
JACOBSON HOLMAN PLLC
400 SEVENTH STREET N.W.
SUITE 600
WASHINGTON
DC
20004
US
|
Assignee: |
NESSDISPLAY CO., Ltd.
|
Family ID: |
19540443 |
Appl. No.: |
09/942780 |
Filed: |
August 31, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09942780 |
Aug 31, 2001 |
|
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|
09336713 |
Jun 21, 1999 |
|
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Current U.S.
Class: |
428/690 ;
252/301.16; 313/504; 428/917; 546/10; 546/101 |
Current CPC
Class: |
H01L 51/0089 20130101;
C07D 215/36 20130101; H01L 51/0059 20130101; H01L 51/5012 20130101;
H01L 51/0034 20130101; H01L 51/0035 20130101; Y10S 428/917
20130101; H01L 51/0077 20130101 |
Class at
Publication: |
428/690 ;
428/917; 313/504; 546/10; 546/101; 252/301.16 |
International
Class: |
H05B 033/14; C07D
221/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 23, 1998 |
KR |
98-23645 |
Claims
What is claimed is:
1. An organometallic luminescent material selected from the group
consisting of the compounds of formulae (I) 5 to (V): 5wherein,
M.sup.1 and M.sup.4 are each independently a monovalent or
tetravalent metal selected from the group consisting of Li, Na, K,
Zr, Si, Ti, Sn, Cs, Fr, Rb, Hf, Pr, Pa, Ge, Pb, Tm and Md; M.sup.2
is a mono-, di-, tri- or tetravalent metal selected from the group
consisting of Li, Na, K, Ca, Be, Ga, Zn, Cd, Al, Cs, Fr, Rb, Mg,
Mn, Ti, Cu, Zr, Si, Hf, Pr, Pa, Ge, Sn, Pb, Tm and Md; M.sup.3 is
selected from the group consisting of Li.sup.+, Na.sup.+, K.sup.+,
Cs.sup.+, Fr.sup.+, Rb.sup.+, Ca.sup.2+, Be.sup.2+, Ga.sup.3+,
Zn.sup.2+, Al.sup.3+, Mg.sup.2+, Mn.sup.2+, Ti.sup.2+and Cu.sup.2+;
R is a hydrogen or C.sub.1-.sub. alkyl; X and Y, which can be the
same or different, are independently a hydrogen, Cl, F, I, Br or
SO.sub.3H; A is a hydrogen, F, Cl, Br or I; B is O, S, Se or Te; D
is O or S; and n is an integer ranging from 1 to 4.
2. A process for preparing a complex of formula(II) by vapor
depositing 8-hydroxylquinolin-5-sulfonic acid metal complex of
formula(VI) and subjecting the deposited complex to an in-situ
reaction with a compound of formula(VII): 6M.sup.3Z (VII) wherein,
M.sup.2, M.sup.3, R and n have the same meanings as defined in
claim 1, and Z is a halogen atom or hydroxy group.
3. An electroluminescent device which comprises an organic
luminescent layer containing the organometallic luminescent
material defined in claim 1.
4. The device of claim 3 wherein the organometallic luminescent
material is present alone, or in combination with a polymer or an
inorganic material, or in the form of a dopant in a polymer.
5. The device of claim 3 wherein the organic luminescent layer is
formed by a spin coating, vapor deposition, vacuum thermal
deposition, sputtering or electron beam deposition method.
Description
FIELD OF THE INVENTION
[0001] The present invention is directed to novel organometallic
luminescent materials, and, more particularly, to a novel
organometallic luminescent material having the capability of
emitting a wide range of colors including blue and green light, and
high thermal stability, and an organic luminescent device
containing same.
BACKGROUND OF THE INVENTION
[0002] Conventional organometallic luminescent compounds used in
organic electroluminescent devices are mostly complexes of di- or
trivalent metals such as zinc and aluminium.
[0003] For example, U.S. Pat. No. 5,456,988 describes
8-hydroxyquinoline complexes of zinc, aluminium and magnesium as
organic luminescent materials; U.S. Pat. No. 5,837,390 discloses
magnesium, zinc and cadmium complexes of
2-(o-hydroxyphenylbenzoxazole); Japanese Patent Laid-Open
Publication No. 07-133483 reports luminescent complexes of
2-(o-hydroxyphenylbenzoxazole) with divalent metals such as
magnesium and copper; and U.S. Pat. No. 5,529,853, and Japanese
Patent Laid-Open Publication Nos. 06-322362, 08-143548 and
10-072580 disclose divalent or trivalent metal complexes of
10-hydroxybenzo[10]quinoline.
[0004] The above organometallic luminescent compounds containing a
divalent or trivalent metal have relatively loosely bound ligands
and an extended system of conjugation. As a result, they are
relatively unstable and emit green or red light but not a blue
light.
[0005] Therefore, there has existed a need to develop an
organometallic luminescent material having improved stability and
light emission characteristics such as the capability of emitting a
blue light.
SUMMARY OF THE INVENTION
[0006] Accordingly, it is a primary object of the present invention
to provide a novel organometallic luminescent material having the
stability and desired emission characteristics, and an organic
luminescent device containing same.
[0007] In accordance with the present invention, there is provided
an organometallic luminescent material selected from the group
consisting of the compounds of, formulae (I) to (V). 1
[0008] wherein,
[0009] M.sup.1 and M.sup.4 are each independently a monovalent or
tetravalent. metal selected from the group consisting of Li, Na, K,
Zr, Si, Ti, Sn, Cs, Fr, Rb, Hf, Pr, Pa, Ge, Pb, Tm and Md;
[0010] M.sup.2 is a mono-, di-, tri- or tetravalent metal selected
from the group consisting of Li, Na, K, Ca, Be, Ga, Zn, Cd, Al, Cs,
Fr, Rb, Mg, Mn, Ti, Cu, Zr, Si, Hf, Pr, Pa, Ge, Sn, Pb, Tm and
Md;
[0011] M.sup.3 is selected from the group consisting of Li.sup.+,
Na.sup.+, K.sup.+, Cs.sup.+, Fr.sup.+, Rb.sup.+, Ca.sup.2+,
Be.sup.2+, Ga.sup.3+, Zn.sup.2+, Al.sup.3+, Mg.sup.2+, Mn.sup.2+,
Ti.sup.2+and Cu.sup.2+;
[0012] R is a hydrogen or C.sub.1-.sub.10 alkyl;
[0013] X and Y, which can be the same or different, are 25
independently a hydrogen, Cl, F, I, Br or SO.sub.3H;
[0014] A is a hydrogen, F, Cl, Br or I;
[0015] B is O, S, Se or Te;
[0016] D is O or S; and
[0017] n is an integer ranging from 1 to 4.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The above and other objects and features of the present
invention will become apparent from the following description
thereof, when taken in conjunction with the accompanying drawings
wherein:
[0019] FIGS. 1a, 1b and 1c illustrate schematic diagrams of organic
electroluminescent devices having an organic layer in the form of a
single layer, a double layer or a multilayer, respectively;
[0020] FIG. 2 shows the light emission spectrum of the
organometallic luminescent material of Example 1 of the present
invention;
[0021] FIG. 3 demonstrates variations of the current
density(A/m.sup.2)(3-1) and brightness(cd/m.sup.2)(3-2) of the
electroluminescent device of Example 2 of the present invention as
a function of applied voltage(V);
[0022] FIGS. 4a and 4b depict changes in the luminous
efficiency(lm/w) of the electroluminescent device of Example 2 with
current density(A/m.sup.2) and brightness(cd/m.sup.2),
respectively; and
[0023] FIG. 5 exhibits the electroluminous spectra of the
electroluminescent device of Example 2 of the present invention at
various applied voltages(V).
DETAILED DESCRIPTION OF THE INVENTION
[0024] The organometallic luminescent materials of the present
invention include 8-hydroxyquinoline-metal complexes of formula
(I)-8-hydroxyquinoline-5-sulfonate-metal complexes of formula (II),
benzoxazole- or benzthiazole-metal complexes of formula(III),
benzotriazole-metal complexes of formula (IV), and
benzoquinoline-metal complexes of formula (V)
[0025] Among the organometallic luminescent materials of the
present invention, preferred are those listed in Table I.
1 TABLE I Compound .gamma. max Formula No. M* M.sub.3 X Y A B D n R
(nm) color (I) 1 Li -- H H -- -- -- 1 H 495 bluish green 2 Li -- H
H -- -- -- 1 CH.sub.3 490 bluish green 3 Zr -- H H -- -- -- 4 H 535
light green 4 Zr -- H H -- -- -- 4 CH.sub.3 532 light green (II) 5
Li Li -- -- H -- -- 1 H 460 blue 6 Li Na -- -- H -- -- 1 H 462 blue
7 Na Li -- -- H -- -- 1 H 460 blue 8 Na Na -- -- H -- -- 1 H 463
blue 9 Zn Li -- -- H -- -- 2 H 461 blue 10 Zn Na -- -- H -- -- 2 H
464 blue 11 Al Li -- -- H -- -- 3 H 462 blue 12 Al Na -- -- H -- --
3 H 465 blue (III) 13 Li -- -- -- -- O O 1 H 450 blue 14 Na -- --
-- -- -- O 1 H 455 blue (IV) 15 Li -- -- -- -- -- O 1 H 508 green
16 Na -- -- -- -- -- O 1 H 512 green (V) 17 Li -- -- -- -- -- O 1 H
515 green 18 Na -- -- -- -- -- O 1 H 650 red Note: M* is M.sup.1,
M.sup.2 or M.sup.4.
[0026] The organometallic luminescent compound of the present
invention may be prepared by reacting an organic compound that can
serve as a ligand with an appropriate metal compound in a suitable
solvent.
[0027] Exemplary solvents which can be used in the present
invention include water, ethanol, methanol, propanol and the
like.
[0028] Representative metal compounds that can be used to prepare
the organometallic luminescent compounds of the present invention
are LiOH, NaOH, KOH, NaCl, KCl, LiCl, ZrCl.sub.4, SnCl.sub.4,
TiCl.sub.4, SiCl.sub.4, BeC.sub.2, MgCl.sub.2, AlC.sub.3,
CaCl.sub.2, ZnCl.sub.2 and the like.
[0029] Representative organic compounds which can be used as
ligands in the present invention include 2-(2-hydroxy-phenyl
)benzoxazole, 8-hydroxyquinoline, 8-hydroxy-quinoline -5-sulfonic
acid, 2-(2-benzo-triazolyl)-p-cresol, 10-hydroxybenzoquinoline and
the like.
[0030] The reaction of the organic and metal compounds to prepare
the organometallic luminescent compound of the present invention
may be carried out in a stoichiometric molar ratio which depends on
n at a temperature ranging from 25 to 100.degree. C. for 1 to 24
hours.
[0031] In the preparation of 8-hydroxyquinoline-5-sulfonate metal
derivative of formula(II), 8-hydroxyquinoline -5-sulfonic acid and
a suitable M.sup.2 compound are reacted to give
8-hydroxyquinoline-5-sulfon- ate derivatives of formula (VI).
Subsequently, the compound of formula(VI) is reacted with a
compound of M.sup.3 to obtain the 8-hydroxyquinoline -5-sulfonate
derivative of formula (II).
[0032] Alternatively, the 8-hydroxyquinoline-5-sulfonate metal
derivative of formula(II) may be prepared by a dry process. That
is, a compound of formula (VI) and a compound of formula(VII) may
be deposited separately on a substrate and an in-situ reaction
thereof may be incurred, e.g., at 150 to 450.degree. C. under a
reduced pressure(about 10.sup.-6 torr). The metallation of the
sulfonic acid group in accordance with the in-situ reaction of
scheme 1 accompanies a blue shift in the emitted light. For
example, the maximum wavelength of the emitting light of the
compound of formula(VI) is 510 nm while that of the compound of
formula(II) is 460 nm. 2
[0033] wherein, M.sup.2, M.sup.3 and n have the same meanings as
defined above, and Z is a halogen atom or hydroxy group.
[0034] The organometallic complex of the present invention can be
used as a luminescent doping material as well. For example, when it
is doped in an amount of about 2% in a blue light emitting
luminescent layer, the emitting light changes from blue to light
blue or green. Accordingly, an efficient electroluminescent device
capable of emitting a tuned color can be prepared.
[0035] The organic luminescent device of the present invention has
a structure comprising an organic thin layer in the form of a
single layer, or in the form of a double layer and multilayer
containing a hole transporting layer and/or an electron
transporting layer. In this case, the organometallic luminescent
material of the present invention can be used alone, or in
combination with a polymer or an inorganic material. Further, it
may be doped in a polymer to give a fluorescent thin layer.
[0036] An example of the electroluminescent device of the present
invention contains a single organic layer as shown in FIG. 1a. The
device consists of (i) a glass substrate, (ii) a transparent
ITO(indium tin oxides) anode electrode layer, (iii) an organic
luminescent layer containing an organometallic luminescent material
of the present invention, and (iv) a metal cathode electrode layer.
Another example of the inventive device has an additional hole
transporting layer(iii-1) as shown in FIG. 1b, or a multilayered
structure shown in FIG. 1C wherein (iii-2) denotes an additional
electron transporting layer. The electroluminescent device of the
present invention may be operated with direct or alternative
current, while the direct current is preferred.
[0037] The organic luminescent layer of the present invention may
be formed by a conventional method including a wet process such as
spin coating, and a dry process such as a vapor deposition, vacuum
thermal deposition, sputtering and electron beam deposition
method.
[0038] The novel organometallic luminescent compound of the present
invention is capable of emitting blue, green or red light. The
inventive complexes containing monovalent metals in particular are
excellent blue light emitting luminescent materials which are
stable even at a high temperature.
[0039] The present invention is further described and illustrated
in Examples, which are, however, not intended to limit the scope of
the present invention.
EXAMPLE 1
Preparation Compound 13
[0040] 2-(2-hydroxyphenyl)benzoxazole and lithium oxide were added
to 250 ml of ethanol in a molar ratio of 1:1 and the mixture was
refluxed at 78.degree. C. for 4 hours. The reaction mixture was
filtered and the solvent and moisture were removed under a reduced
pressure to give 2-(2-hydroxyphenyl)benzoxazole-lithium complex of
formula(VIII) (compound 13). 3
[0041] FIG. 2 shows light emission spectrum of the complex thus
obtained.
EXAMPLE 2
[0042] Indium-tin-oxide(ITO) was coated on a glass substrate to
form a transparent anode layer. The coated substrate was subjected
to photolithography and the patterned ITO glass was cleaned with a
solution containing a non-phosphorous detergent, acetone and
ethanol.
[0043] A mixture of polyetherimide of formula(IX) and
triphenyldiamine of formula(X) in a weight ratio of 50:50 were
dissolved in chloroform to a concentration of 0.5 wt %, and the
resulting mixture was spin-coated on the ITO glass to form a hole
transporting layer. 4
[0044] wherein m is an integer of two or higher.
[0045] 2-(2-hydroxyphenyl)benzoxazole-lithium complex obtained in
Example 1 was vapor deposited as a luminescent material on the hole
transporting layer to a thickness of 20 nm to form an organic
luminescent layer, and then, aluminium was vapor deposited to a
thickness of 500 nm to form a cathode layer. Subsequently, the
device was packaged to obtain an electroluminescent device.
[0046] The luminescence characteristics of the electroluminescent
device are shown in FIGS. 3, 4 and 5.
[0047] FIG. 3 illustrates the variation of the current
density(A/m.sup.2)(3-1) and brightness(cd/m.sup.2) of the
electroluminescent device thus obtained as a function of the
applied voltage(V). The current injection starts at about 6V, turn
on voltage is about 7 to 8V, and the brightness is 500cd/m.sup.2 at
11V.
[0048] FIGS. 4a and 4b depict the changes in the luminous
efficiency(lm/w) of the above electroluminescent device with
current density(A/m.sup.2) and brightness(cd/m.sup.2),
respectively. The luminous efficiency is steady at 1.2 lm/W at a
current density of 200A/m.sup.2 and beyond.
[0049] FIG. 5 exhibits electroluminous spectra of the above
electroluminescent device at various applied voltages of 8, 9, 10,
11, 12 and 13V. The main peak appears at 456 nm and shoulder peaks
are observed at 430 and 487 nm. The emitted light is blue.
EXAMPLE 3
Preparation of Compounds 5 and 6
[0050] 8-hydroxyquinoline-5-sulfonic acid and lithium hydroxide
were added to 250 ml of ethanol in a molar ratio of 1:1 and the
mixture was refluxed at 78.degree. C. for 4 hours. The reaction
mixture was filtered and dissolved in an excess amount of water.
Subsequently, water was removed under a reduced pressure to obtain
lithium complex of 8-hydroxyquinoline-(5-sulfonic
acid)-(LiQSA).
[0051] LiQSA thus obtained and LiOH(or NaOH) were added to 100 ml
of ethanol in a molar ratio of 1:1 and the mixture was reacted at a
room temperature for 1 hour. Precipitates were separated from the
reaction mixture and dried for 24 hours under a reduced pressure to
obtain a lithium complex of lithium
8-hydroxyquinolinato-5-sulfonate (LiQSLi, Compound 5), or a lithium
complex of sodium 8-hydroxyquinolinato-5-sulfon- ate (LiQSNa,
Compound 6), respectively.
[0052] The maximum wavelength and emitted colors of the complexes
thus obtained were measured and shown in Table I.
EXAMPLE 4
Preparation of Compounds 7 and 8
[0053] 8-hydroxyquinoline-5-sulfonic acid and sodium hydroxide were
added to 250 ml of ethanol in a molar ratio of 1:1 and the mixture
was refluxed at 78.degree. C. for 4 hours. The reaction mixture was
filtered and dissolved in an excess amount of water. Subsequently,
water was removed under a reduced pressure to obtain
8-hydroxyquinolin-(5-sulfonic acid) sodium complex (NaQSA).
[0054] NaOSA thus obtained and LiOH(or NaOH) were added to 100 ml
of ethanol in a molar ratio of 1:1 and the mixture was reacted at a
room temperature for 1 hour. Precipitates were separated from the
reaction mixture and dried for 24 hours under a reduced pressure to
obtain a sodium complex of lithium 8-hydroxyquinolinato-5-sulfonate
(NaQSLi, Compound 7) or a sodium complex of sodium
8-hydroxyquinolinato-5-sulfonat- e (NaQSNa, Compound 8).
[0055] The maximum wavelengths and emitted colors of the complexes
thus obtained were measured and shown in Table I.
EXAMPLE 5
Preparation of Compounds 9 and 10
[0056] 8-hydroxyquinoline-5-sulfonic acid and zinc chloride
(ZnCl.sub.2) were added to 250 ml of ethanol in a molar ratio of
2:1 and the mixture was refluxed at 78.degree. C. for 4 hours. The
reaction mixture was filtered and dissolved in an excess amount of
water. Subsequently, water and HCl were removed under a reduced
pressure to give a zinc complex of
bis(8-hydroxyquinolinato-5-sulfonic acid) (Zn(QSA).sub.2).
[0057] Zn(QSA).sub.2 thus obtained and LiOH(or NaOH) were added to
100 ml of ethanol in a molar ratio of 1:2 and the mixture was
reacted at a room temperature for 1 hour. Precipitates were
separated from the reaction mixture and dried for 24 hours under a
reduced pressure to obtain a zinc complex of lithium
bis(8-hydroxyquinolinato-(5-sulfonate) (Zn(QSLi).sub.2, Compound
9), or a zinc complex of sodium bis(8-hydroxyquinolin-5-sulfonate)
(Zn(QSNa).sub.2, Compound 10).
[0058] The maximum wavelengths and emitted colors of the complexes
thus obtained were measured and shown in Table I.
EXAMPLE 6
Preparation of Compounds 11 and 12
[0059] 8-hydroxyquinoline-5-sulfonic acid and AlCl.sub.3 were added
to 250 ml of ethanol in a molar ratio of 3:1 and the mixture was
refluxed at 78.degree. C. for 4 hours. The reaction mixture was
filtered and dissolved in an excess amount of water. Subsequently,
water and HCl were removed under a reduced pressure to obtain
aluminium tris(8-hydroxyquinolinato-5-sulfonic acid)
(Al(QSA).sub.3).
[0060] Al(QSA).sub.3 thus obtained and LiOH (or NaOH) were added to
100 ml of ethanol in a molar ratio of 1:3 and the mixture was
reacted at a room temperature for 1 hour. Precipitates were
separated from the reaction mixture and dried for 24 hours under a
reduced pressure to obtain an aluminium complex of lithium
tris(8-hydroxyquinolin-(5-sulfonate) (Al(QSLi).sub.31 Compound 11),
or an aluminium complex of sodium
tris(8-hydroxyquinolin-5-sulfonate) complex (Zn(QSNa).sub.3).
[0061] The maximum wavelengths and emitted colors of the complexes
thus obtained were measured and shown in Table I.
EXAMPLE 7
Preparation of Compound 14
[0062] 2-(2-hydroxyphenyl)benzoxazole and NaOH were added to 250 ml
of ethanol in a molar ratio of 1:1 and the mixture was refluxed at
78.degree. C. for 4 hours. The reaction mixture was filtered and
the solvent and moisture were removed under a reduced pressure to
obtain 2-(2-hydroxyphenyl)-benzoxazole -sodium complex.
[0063] The maximum wavelength and emitted color of the complex thus
obtained were measured and shown in Table I.
EXAMPLE 8
Preparation of Compounds 15 and 16
[0064] 2-(2-hydroxybenzotriazole)-p-cresol and LiOH(or NaOH) were
added to 250 ml of ethanol in a molar ratio of 1:1 and the mixture
was refluxed at 78.degree. C. for 4 hours. The reaction mixture was
filtered and the solvent and moisture were removed under a reduced
pressure to give 2-(2-hydroxybenzotriazole)-p-cresol-lithium
complex (LiBTZC, Compound 15), or
2-(2-hydroxybenzotriazole)-p-cresol -sodium complex(NaBTZC,
Compound 16).
[0065] The maximum wavelengths and emitted colors of the complexes
thus obtained were measured and shown in Table I.
EXAMPLE 9
Preparation of Compounds 17 and 18
[0066] 10-hydroxyquinoline and LiOH (or NaOH) were added to 250 ml
of ethanol in a molar ratio of 1:1 and the mixture was refluxed at
78.degree. C. for 4 hours. The reaction mixture was filtered and
the solvent and moisture were removed under a reduced pressure to
obtain 10-hydroxyquinoline-lithium complex(LiBQ, Compound 17), or
10-hydroxyquinoline-sodium complex(NaBQ, Compound 18).
[0067] The maximum wavelengths and emitted colors of the complexes
thus obtained were measured and shown in Table I.
EXAMPLE 10
Preparation of Compound 3
[0068] 8-hydroxyquinoline and ZrCl.sub.4 were added to 250 ml of
ethanol in a molar ratio of 4:1 and the mixture was refluxed at
78.degree. C. for 4 hours. The reaction mixture was filtered and
the solvent, HCl and moisture were removed under a reduced pressure
to obtain tetra(8-hydroxyquiloninato)-zirconium complex (ZrQ.sub.4,
Compound 3).
[0069] The maximum wavelength and emitted color of the complex thus
obtained were measured and shown in Table I.
[0070] As can be seen from the above result, the organometallic
luminescent material of the present invention exhibits blue, green
or red light emission. Therefore, an electroluminescent device
containing the same is capable of exhibiting a full range of colors
in the visible region with a high efficiency.
[0071] While the embodiments of the subject invention have been
described and illustrated, it is obvious that various changes and
modifications can be made therein without departing from the spirit
of the present invention which should be limited only by the scope
of the appended claims.
* * * * *