U.S. patent application number 10/249998 was filed with the patent office on 2004-12-09 for curable (meth)acrylate compositions.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Chisholm, Bret Ja, Herrmann, Anne.
Application Number | 20040249100 10/249998 |
Document ID | / |
Family ID | 33449411 |
Filed Date | 2004-12-09 |
United States Patent
Application |
20040249100 |
Kind Code |
A1 |
Chisholm, Bret Ja ; et
al. |
December 9, 2004 |
CURABLE (METH)ACRYLATE COMPOSITIONS
Abstract
A curable composition includes a multifunctional (meth)acrylate;
a substituted or unsubstituted arylether (meth)acrylate monomer; a
brominated aromatic (meth)acrylate monomer; and a polymerization
initiator. The compositions exhibit high refractive indices and,
upon polymerization, the compositions provide films having
excellent thermomechanical properties.
Inventors: |
Chisholm, Bret Ja; (Clifton
Park, NY) ; Herrmann, Anne; (Clifton Park,
NY) |
Correspondence
Address: |
CANTOR COLBURN, LLP
55 GRIFFIN ROAD SOUTH
BLOOMFIELD
CT
06002
|
Assignee: |
GENERAL ELECTRIC COMPANY
1 River Road
Schenectady
NY
|
Family ID: |
33449411 |
Appl. No.: |
10/249998 |
Filed: |
May 27, 2003 |
Current U.S.
Class: |
526/328 ;
428/64.1; 522/182; 522/26; 522/28; 522/64; 526/329.7 |
Current CPC
Class: |
G02B 1/04 20130101; C08F
222/1025 20200201; Y10T 428/21 20150115 |
Class at
Publication: |
526/328 ;
522/028; 522/026; 522/064; 522/182; 526/329.7; 428/064.1 |
International
Class: |
C08F 002/46 |
Claims
1. A curable composition, comprising: a multifimctional
(meth)acrylate according to the formula 7wherein R.sup.1 is
hydrogen or methyl; X.sup.1 is O or S; R.sup.2 is C.sub.1-C.sub.6
alkylene disubstituted bisnbenol-A or bisphenol-F, C.sub.1-C.sub.6
hydroxyalkylene disubstituted bisphenol-A or bisphenol-F, or their
brominated forms; and n is 2, 3, or 4; a substituted or
unsubstituted arylether (meth)acrylate monomer; a brominated
aromatic (meth)acrylate monomer according to the formula 8wherein
R.sup.5 is hydrogen or methyl; X.sup.4 is O or S; X.sup.5 is O or
S; m is 1, 2, or 3; p is 0 or 1; and q is 4 or 5; and a
polymerization initiator.
2. (Canceled)
3. The composition of claim 1, wherein the multifunctional
(meth)acrylate is the reaction product of (meth)acrylic acid with a
di-epoxide comprising bisphenol-A diglycidyl ether; bisphenol-F
diglycidyl ether; tetrabromo bisphenol-A diglycidyl ether;
tetrabromo bisphenol-F diglycidyl ether;
1,3-bis-{4-[1-methyl-(4-oxiranylmethoxy-phenyl)-ethyl]--
phenoxy}-propan-2-ol;
1,3-bis-{2,6-dibromo-4-[1-(3,5-dibromno-4-oxiranylme-
thoxy-phenyl)-1-methyl-ethyl]-phenoxy}-propan-2-ol; or a
combination comprising at least one of the foregoing
di-epoxides.
4. The composition of claim 1, wherein the multifunctional
(meth)acrylate comprises about 25 to about 75 weight percent based
on the total weight of the composition.
5. The composition of claim 1, wherein the substituted or
unsubstituted arylether (meth)acrylate monomer comprises 9wherein
R.sup.3 is hydrogen or methyl; X.sup.2 is O or S; X.sup.3 is O or
S; R.sup.4 is substituted or unsubstituted C.sub.1-C.sub.6 alkyl or
alkenyl; Ar is substituted or unsubstituted C.sub.6-C.sub.12 aryl,
including phenyl; wherein the substitution on the R.sup.4 and Ar
independently include fluorine, chlorine, bromine, iodine,
C.sub.1-C.sub.6 alkyl C.sub.1-C.sub.3 perhalogenated alkyl,
hydroxy, C.sub.1-C.sub.6 ketone, C.sub.1-C.sub.6 ester,
N,N--(C.sub.1-C.sub.3) alkyl substituted amide, or a combination
comprising at least one of the forgoing substituents.
6. The composition of claim 5, wherein the substituted or
unsubstituted arylether (meth)acrylate monomer is phenoxyethyl
(meth)acrylate, phenylthioethyl (meth)acrylate, or a combination
comprising at least one of the foregoing substituted or
unsubstituted arylether (meth)acrylate monomers.
7. The composition of claim 5, wherein the substituted or
unsubstituted arylether (meth)acrylate monomer comprises about 15
to about 70 weight percent based on the total weight of the
composition.
8. The composition of claim 5, further comprising all additional
substituted or unsubstituted arylether (meth)acrylate monomer.
9. (Canceled)
10. The composition of claim 1, wherein the brominated aromatic
(meth)acrylate monomer is pentabromobenzyl (meth)acrylate,
pentabromophenyl (meth)acrylate or a combination comprising at
least one of the foregoing brominated aromatic (meth)acrylate
monomers.
11. The composition of claim 1, wherein the brominated aromatic
(meth)acrylate monomer comprises about 1 to about 20 weight percent
based on the total weight of the composition.
12. The composition of claim 1, wherein the polymerization
initiator is a phosphine oxide photoinitiator.
13. The composition of claim 1, wherein the multifunctional
(meth)acrylate is the reaction product of (meth)acrylic acid with a
di-epoxide comprising bisphenol-A diglycidyl ether, bisphemol-F
diglycidyl ether, tetrabromo bisphenol-A diglycidyl ether,
tetrabromo bisphenol-F diglycidyl ether,
1,3-bis-{4-[1-methyl-1-(4-oxiranylmethoxy-phenyl)-ethyl-
]-phenoxy}-propan-2-ol,
1,3-bis-{2,6-dibromo-4-[1-(3,5-dibromo-4-oxiranylm-
ethoxy-phenyl)-1-methyl-ethyl]-phenoxy}-propan-2-ol, or a
combination comprising at least one of the foregoing di-epoxides;
wherein the substituted or unsubstituted arylether (meth)acrylate
monomer is phenylthioethyl (meth)acrylate, phenoxyethyl
(meth)acrylate, or a combination comprising at least one of the
foregoing substituted or unsubstituted arylether (meth)acrylate
monomers; wherein the brominated aromatic (meth)acrylte monomer is
pentabromobenzyl (meth)acrylate; and wherein the polymerization
initiator is a phosphine oxide photoinitiator.
14. The composition of claim 1, comprising about 45 to about 65
weight percent of the multifunctional (meth)acrylate; about 30 to
about 45 weight percent of the substituted or unsubstitated
arylether (meth)acrylate monomer; about 1 to about 10 weight
percent of the brominated aromatic (meth)acrylate monomer; and
about 0.1 to about 5 weight percent of the phosphine oxide
photoinitiator based on the total weight of the composition.
15. The composition of claim 14, cured by ultraviolet
radiation.
16. An article formed from the cured composition of claim 15.
17. An optical film for backlit displays formed from the cured
composition of claim 15.
18. A composition comprising, a multifuictional (meth)acrylate
comprising the reaction product of (meth)acrylic acid with a
di-epoxide comprising bisphenol-A diglycidyl ether, bisphenol-F
diglycidyl ether, tetrabromo bisphenol-A diglycidyl ether,
tetrabromo bisphenol-F diglycidyl ether,
1,3-bis-{4-[1-methyl-1-(4-oxiranylmethoxy-phenyl)-ethyl]-phenoxy}-propan--
2-ol,
1,3-bis-{2,6-dibromo-4-[1-(3,5-dibromo-4-oxiranylmethoxy-phenyl)-1-m-
ethyl-ethyl]-phenoxy}-propan-2-ol, or a combination comprising at
least one of the foregoing di-epoxides; phenylthioethyl
(meth)acrylate; pentabromobenzyl (meth)acrylate; and a phosphine
oxide photoinitiator.
19. A method of making a curable composition, comprising: blending
a multifunctional (meth)acrylate according to the formula 10wherein
R.sup.1 is hydrogen or methyl: X.sup.1 is O or S; R.sup.2 is
C.sub.1-C.sub.6 alkylene disubstituted bisphenol-A or bisnhenol-F,
C.sub.1-C.sub.6 hydroxyalkylene disubstituted bisphenol-A or
bisphenol-F, or their brominated forms; and n is 2, 3, or 4, a
substituted or unsubstituted arylether (meth)acrylate monomer, a
brominated aromatic (meth)acrylate monomer according to the formula
11wherein R.sup.5 is hydrogen or methyl: X.sup.4 is O or S; X.sup.5
is O or S; m is 1, 2, or 3; p is 0 or 1; and q is 4 or 5, and a
polymerization initiator.
20. A curable composition, consisting of: a multifunctional
(meth)acrylate according to the formula 12wherein R.sup.1 is H or
methyl; X.sup.1 is O or S; R.sup.2 is C.sub.1-C.sub.6 alklene
disubstituted bisphenol-A or bisphenol-F, C.sub.1-C.sub.6
hydroxyalkylene disubstituted bisphenol-A or bisphenol-F, or their
brominated forms; and n is 2, 3, or 4; a substituted or
unsubstituted arylether (meth)acrylate monomer according to the
formula 13wherein R.sup.3 is hydrogen or methyl; X.sup.2 is O or S;
X.sup.3 is S; R.sup.4 is substituted or unsubstituted
C.sub.1-C.sub.6 alkyl or alkenyl; Ar is substituted or
unsubstituted C.sub.6-C.sub.12 aryl including phenyl; wherein the
substitution on the R.sup.4 and Ar is, independently, fluorine,
chlorine, bromine, iodine, C.sub.1-C.sub.6 alkyl, C.sub.1-C.sub.3
perhalogenated alkyl, hydroxy, C.sub.1-C.sub.6 ketone,
C.sub.1-C.sub.6 ester, N,N-(C.sub.1-C.sub.3) alkyl substituted
amide, or a combination comprising at least one of the forgoing
substituents; and a polymerization initiator.
Description
BACKGROUND OF INVENTION
[0001] Disclosed herein are curable (meth)acrylate compositions
and, more specifically ultraviolet (UV) radiation curable
(meth)acrylate compositions. The compositions are suitable for
optical articles and particularly for light management films.
[0002] In backlight computer displays or other display systems,
optical films are commonly used to direct light. For example, in
backlight displays, light management films use prismatic structures
(often referred to as microstructure) to direct light along a
viewing axis (i.e., an axis substantially normal to the display).
Directing the light enhances the brightness of the display viewed
by a user and allows the system to consume less power in creating a
desired level of on-axis illumination. Films for turning or
directing light can also be used in a wide range of other optical
designs, such as for projection displays, traffic signals, and
illuminated signs.
[0003] Compositions used to form light management films to direct
light desirably have the ability to replicate the microstructure
needed to provide the light directing capability upon cure. It is
furthermore desirable for the glass transition temperature (Tg) of
the cured composition to be high enough for shape retention during
storage and use. It is also desirable for light management films
made from the cured composition to exhibit high brightness.
Finally, the composition used to make light management film
advantageously provides a cured composition having a high
refractive index (RI). While a variety of materials are presently
available for use in light management films, there remains a
continuing need for still further improvement in the materials used
to make them, particularly materials that upon curing possess the
combined attributes desired to satisfy the increasingly exacting
requirements for light management film applications.
SUMMARY OF INVENTION
[0004] The above-described needs are alleviated by a curable
composition comprising a multifunctional (meth)acrylate; a
substituted or unsubstituted arylether (meth)acrylate monomer; a
brominated aromatic (meth)acrylate monomer; and a polymerization
initiator.
[0005] Other embodiments, including a method of preparing a curable
composition, a cured composition comprising the reaction product of
the curable composition, and articles comprising the cured
composition, are described below.
DETAILED DESCRIPTION
[0006] It has been unexpectedly discovered that the addition of a
brominated aromatic (meth)acrylate monomer to a multifunctional
(meth)acrylate and a substituted or unsubstituted arylether (meth)
acrylate monomer in the presence of a polymerization initiator
provides a composition having improved RI. Furthermore, upon curing
the cured composition exhibits improved Tg. Finally, a cured,
microstructured film made from the curable composition exhibits
improved brightness compared to cured, microstructured film made
from curable compositions lacking the brominated aromatic (meth)
acrylate monomer. As used herein, "(meth)acrylate" is inclusive of
both acrylate and methacrylate functionality, in addition to
thioester (meth)acrylate functionality.
[0007] In one aspect, the curable composition is a solventless,
high refractive index, radiation curable composition that provides
a cured material having an excellent balance of properties. The
compositions are ideally suited for light management film
applications. In one aspect, light management films prepared from
the curable compositions exhibit good brightness.
[0008] The curable compositions comprise a multifunctional (meth)
acrylate, i.e., a molecule containing at least two (meth)acrylate
functional groups. In a preferred embodiment, the multifunctional
(meth)acrylate is represented by the formula (I) 1
[0009] wherein R.sup.1 is hydrogen or methyl; X.sup.1 is O or S;
R.sup.2 is substituted or unsubstituted C--C alkyl, aryl, alkaryl,
arylalkyl, or heteroaryl; and n is 2, 3, or 4. The substitution on
R.sup.2 includes, but is not limited to, fluorine, chlorine,
bromine, iodine, C.sub.1-C.sub.6 alkyl, C.sub.1-C.sub.3
perhalogenated alkyl, hydroxy, C.sub.1-C.sub.6 ketone,
C.sub.1-C.sub.6 ester, N,N-(C.sub.1-C.sub.3) alkyl substituted
amide, or a combination comprising at least one of the forgoing
substituents. Preferred R.sup.2 groups include such groups as
alkylene and hydroxy alkylene disubstituted bisphenol-A or
bisphenol-F ethers, especially the brominated forms of bisphenol-A
and -F. Suitable R.sup.2 groups include those according to the
formula (II) 2
[0010] wherein Q is --C(CH.sub.3).sub.2, --CH.sub.2-, --C(O)--,
--S(O)--, or --S(O).sub.2--; Y is C.sub.1-C.sub.6 alkyl or hydroxy
substituted C.sub.1-C.sub.6 alkyl; b is 1 to 10; t is 0, 1, 2, 3,
or 4; and d is about 1 to about 3.
[0011] The multifunctional (meth)acrylates may include compounds
produced by the reaction of an acrylic or methacrylic acid with a
di-epoxide, such as bisphenol-A diglycidyl ether; bisphenol-F
diglycidyl ether; tetrabromo bisphenol-A diglycidyl ether;
tetrabromo bisphenol-F diglycidyl ether;
1,3-bis-{4-[1-methyl-1-(4-oxiranylmethoxy-phenyl)-ethyl]phenoxy}-propan-2-
-ol;
1,3-bis-{2,6-dibromo-4-[1-(3,5-dibromo-4-oxiranylmethoxy-phenyl)-1-me-
thyl-ethyl]phenoxy}-propan-2-ol; and the like; and a combination
comprising at least one of the foregoing di-epoxides. Examples of
such compounds include 2,2-bis(4-(2-(meth)acryloxyethoxy)phenyl)
propane; 2,2-bis((4-(meth)acryloxy)phenyl)propane; acrylic acid
3-(4-{1-[4-(3-acryloyloxy-2-hydroxy-propoxy)-3,5,
-dibromo-phenyl]-1-meth-
yl-ethyl}2,6-dibromo-phenoxy)-2-hydroxy-propyl ester; acrylic acid
3-[4-(1-{4-[3-(4-{1-[4-(3-acryloyloxy-2-hydroxy-propoxy)-3,5-dibromo-phen-
yl]-1-methyl-ethyl}-2,6-dibromo-phenoxy)-2-hydroxy-propoxy]3,5-dibromo-phe-
nyl}-1-methyl-ethyl)-2,6-dibromo-phenoxy]2-hydroxy-propyl ester;
and the like, and a combination comprising at least one of the
foregoing multifunctional (meth) acrylates. A suitable
multifunctional (meth)acrylate based on the reaction product of
tetrabrominated bisphenol-A di-epoxide is RDX 51027 available from
UCB Chemicals.
[0012] The multifunctional (meth)acrylate is present in the curable
composition in an amount of about 25 to about 75 weight percent
based on the total composition. Within this range, an amount of
greater than or equal to about 35 weight percent may be used, with
greater than or equal to about 45 weight percent preferred, and
greater than or equal to about 50 weight percent more preferred.
Also within this range, an amount of less than or equal to about 70
weight percent may be used, with less than or equal to about 65
weight percent preferred, and less than or equal to about 60 weight
percent more preferred.
[0013] The curable composition further comprises a substituted or
unsubstituted arylether (meth)acrylate monomer. A preferred
substituted or unsubstituted arylether (meth)acrylate monomer is
represented by the formula (III) 3
[0014] wherein R.sup.3 is hydrogen or methyl; X.sup.2 is O or S;
X.sup.3 is O or S; R.sup.4 is substituted or unsubstituted
C.sub.1-C.sub.6 alkyl or alkenyl; Ar is substituted or
unsubstituted C.sub.1-C.sub.12 aryl, including phenyl; wherein the
substitution on the R.sup.4 and Ar independently include fluorine,
chlorine, bromine, iodine, C.sub.1-C.sub.6 alkyl, C.sub.1-C.sub.3
perhalogenated alkyl, hydroxy, C.sub.1-C.sub.6 ketone,
C.sub.1-C.sub.6 ester, N,N-(C.sub.1-C.sub.3) alkyl substituted
amide, or a combination comprising at least one of the forgoing
substituents. The Ar group, when substituted, may be mono-, di-,
tri-, tetra- or penta-substituted. As used herein, "arylether" is
inclusive of both ethers and thioethers. Particularly preferred
substituted or unsubstituted arylether (meth)acrylate monomers
include 2-phenoxyethyl (meth)acrylate and 2-phenylthioethyl (meth)
acrylate.
[0015] The substituted or unsubstituted arylether (meth)acrylate
monomer is present in the curable composition in an amount of about
15 to about 70 weight percent based on the total composition.
Within this range, it may be preferred to use an amount of greater
than or equal to about 20 weight percent, more preferably greater
than or equal to about 30 weight percent. Also within this range,
it may be preferred to use an amount of less than-or equal to about
60 weight percent, more preferably less than or equal to about 50
weight percent, yet more preferably less than or equal to about 40
weight percent.
[0016] In one aspect, the composition may comprise two or more
substituted or unsubstituted arylether (meth)acrylate monomers of
different chemical compounds. In one embodiment, a first
substituted or unsubstituted arylether (meth)acrylate monomer
comprises the formula (III) above wherein X.sup.3 is S and a second
substituted or unsubstituted arylether(meth)acrylate monomer
comprising the formula (II) wherein X.sup.3 is O.
[0017] The brominated aromatic (meth)acrylate monomer may be
present in the curable composition to impart increased refractive
index of the curable composition or increased thermomechanical
properties (i.e., increased Tg) of the composition upon curing.
Useful brominated aromatic (meth)acrylate monomers may be
represented by the formula (IV) 4
[0018] wherein R.sup.5 is hydrogen or methyl; X.sup.4 is O or S;
X.sup.5 is O or S; m is 0, 1, 2, or 3; p is 0 or 1; and q is 1, 2,
3, 4, or 5. Highly preferred brominated aromatic (meth)acrylate
monomers include 2,4,6-tribromobenzyl (meth)acrylate,
tetrabromobenzyl (meth)acrylate, tribromophenyl (meth)acrylate, and
pentabromobenzyl (meth)acrylate.
[0019] The brominated aromatic (meth)acrylate monomer is present in
the curable composition in an amount of about 1 to about 20 weight
percent based on the total composition. Within this range, an
amount of greater than or equal to about 3 weight percent may be
used, with an amount of greater than or equal to about 4 preferred,
and an amount of greater than or equal to about 5 weight percent
more preferred. Also within this range, it may be preferred to use
an amount of less than or equal to about 15 weight percent, more
preferably less than or equal to about 10 weight percent, yet more
preferably less than or equal to about 8 weight percent.
[0020] The composition further comprises a polymerization initiator
to promote polymerization of the (meth)acrylate components.
Suitable polymerization initiators include photoinitiators that
promote polymerization of the components upon exposure to
ultraviolet radiation. Particularly suitable photoinitiators
include phosphine oxide photoinitiators. Examples of such
photoinitiators include the IRGACURE.RTM.and DAROCUR.TM. series of
phosphine oxide photoinitiators available from Ciba Specialty
Chemicals; the LUCIRIN.RTM.series from BASF Corp.; and the
ESACURE.RTM.series of photoinitiators. Other useful photoinitiators
include ketone-based photoinitiators, such as hydroxy- and
alkoxyalkyl phenyl ketones, and thioalkylphenyl morpholinoalkyl
ketones. Also suitable are benzoin ether photoinitiators.
[0021] The polymerization initiator may include peroxy-based
initiators that may promote polymerization under thermal
activation. Examples of useful peroxy initiators include, for
example, benzoyl peroxide, dicumyl peroxide, methyl ethyl ketone
peroxide, lauryl peroxide, cyclohexanone peroxide, t-butyl
hydroperoxide, t-butyl benzene hydroperoxide, t-butyl peroctoate,
2,5-dimethylhexane-2,5-dihydroperoxide,
2,5-dimethyl-2,5-di(t-butylperoxy)-hex-3-yne, di-t-butylperoxide,
t-butylcumyl peroxide,
alpha,alpha'-bis(t-butylperoxy-m-isopropyl)benzene- ,
2,5-dimethyl-2,5-di(t-butylperoxy)hexane, dicumylperoxide,
di(t-butylperoxy isophthalate, t-butylperoxybenzoate,
2,2-bis(t-butylperoxy)butane, 2,2-bis(t-butylperoxy)octane,
2,5-dimethyl-2,5-di(benzoylperoxy)hexane, di
(trimethylsilyl)peroxide, trimethylsilylphenyltriphenylsilyl
peroxide, and the like, and combinations comprising at least one of
the foregoing polymerization initiators.
[0022] In a preferred embodiment, the polymerization initiator
comprises a phosphine oxide photoinitiator.
[0023] The polymerization initiator may be used in an amount of
about 0.01 to about 10 weight percent based on the total weight of
the composition. Within this range, it may be preferred to use a
polymerization initiator amount of greater than or equal to about
0.1 weight percent, more preferably greater than or equal to about
0.5 weight percent. Also within this range, it may be preferred to
use a polymerization initiator amount of less than or equal to
about 5 weight percent, more preferably less than or equal to about
3 weight percent.
[0024] The composition may, optionally, further comprise an
additive selected from flame retardants, antioxidants, thermal
stabilizers, ultraviolet stabilizers, dyes, colorants, anti-static
agents, and the like, and a combination comprising at least one of
the foregoing additives, so long as they do not deleteriously
affect the polymerization of the composition. Selection of
particular additives and their amounts may be performed by those
skilled in the art.
[0025] In another embodiment, a curable composition consists of a
multifunctional (meth)acrylate according to the formula 5
[0026] wherein R.sup.1 is H or methyl; X.sup.1 is O or S; R.sup.2
is substituted or unsubstituted C.sub.1-C.sub.300 alkyl, aryl,
alkaryl, arylalkyl; or heteroaryl; and n is 2, 3, or 4; a
substituted or unsubstituted arylether (meth)acrylate monomer
according to the formula 6
[0027] wherein R.sup.3 is hydrogen or methyl; X.sup.2 is O or S;
X.sup.3 is S; R.sup.4 is substituted or unsubstituted
C.sub.1-C.sub.6 alkyl or alkenyl; Ar is substituted or
unsubstituted C.sub.1-C.sub.12 aryl including phenyl; wherein the
substitution on the R.sup.4 and Ar is, independently, fluorine,
chlorine, bromine, iodine, C.sub.1-C.sub.6 alkyl C.sub.1-C.sub.3
perhalogenated alkyl, hydroxy, C.sub.1-C.sub.6 ketone,
C.sub.1-C.sub.6 ester, N,N-(C.sub.1-C.sub.3) alkyl substituted
amide, or a combination comprising at least one of the forgoing
substituents; and a polymerization initiator.
[0028] In one aspect, the curable composition has a RI greater than
or equal to about 1.54, with greater than or equal to about 1.56
preferred, greater than or equal to about 1.58 more preferred, and
greater than or equal to about 1.59 most preferred.
[0029] In an additional aspect, the cured composition may have a RI
greater than or equal to about 1.54, with greater than or equal to
about 1.56 preferred, greater than or equal to about 1.58 more
preferred, and greater than or equal to about 1.59 most
preferred.
[0030] In yet another aspect, the cured composition has a Tg of
greater than or equal to about 40.degree. C., with greater than or
equal to about 60.degree. C. preferred, greater than or equal to
about 80.degree. C. more preferred, and greater than or equal to
about 90.degree. C. most preferred.
[0031] In another aspect, light management films made from the
cured composition exhibits a brightness of greater than or equal to
about 1400 candela per meter squared (cd/m.sup.2), with greater
than or equal to about 1450 cd/m.sup.2 preferred, and greater than
or equal to about 1490 cd/m.sup.2 more preferred.
[0032] The curable composition may be prepared by simply blending
the components thereof, with efficient mixing to produce a
homogeneous mixture. When forming articles from the curable
composition, it is often preferred to remove air bubbles by
application of vacuum or the like, with gentle heating if the
mixture is viscous, and casting or otherwise creating a film of the
composition on a desired surface. The composition can then be
charged to a mold that may bear a microstructure to be replicated
and polymerized by exposure to ultraviolet radiation or heat to
produce a cured article.
[0033] An alternative method includes applying the radiation
curable, uncured, composition to a surface of a base film
substrate, passing the base film substrate having the uncured
composition coating through a compression nip defined by a nip roll
and a casting drum having a negative pattern master of the
microstructures. The compression nip applies a sufficient pressure
to the uncured composition and the base film substrate to control
the thickness of the composition coating and to press the
composition into full dual contact with both the base film
substrate and the casting drum to exclude any air between the
composition and the drum. The radiation curable composition is
cured by directing radiation energy through the base film substrate
from the surface opposite the surface having the composition
coating while the composition is in full contact with the drum to
cause the microstructured pattern to be replicated in the cured
composition layer.
[0034] The curable compositions are preferably cured by UV
radiation. The wavelength of the UV radiation may be from about
1800 angstroms to about 4000 angstroms. The lamp systems used to
generate such radiation include ultraviolet lamps and discharge
lamps, as for example, xenon, metallic halide, metallic arc, low or
high pressure mercury vapor discharge lamp, etc. Curing is meant
both polymerization and cross-linking to form a non-tacky
material.
[0035] When heat curing is used, the temperature selected may be
about 80.degree. C. to about 130.degree. C. Within this range, a
temperature of greater than or equal to about 90.degree. C. may be
preferred. Also within this range, a temperature of greater than or
equal to about 100.degree. C. may be preferred. The heating period
may be of about 30 seconds to about 24 hours. Within this range, it
may be preferred to use a heating time of greater than or equal to
about 1 minute, more preferably greater than or equal to about 2
minutes. Also within this range, it may be preferred to use a
heating time of less than or equal to about 10 hours, more
preferably less than or equal to about 5 hours, yet more preferably
less than or equal to about 3 hours. Such curing may be staged to
produce a partially cured and often tack-free composition, which
then is fully cured by heating for longer periods or temperatures
within the aforementioned ranges.
[0036] In one embodiment, the composition may be both heat cured
and UV cured.
[0037] In one embodiment, a curable composition comprises about 35
to about 65 weight percent of a multifunctional (meth)acrylate;
about 30 to about 45 weight percent of a substituted or
unsubstituted arylether (meth)acrylate monomer; about 1 to about 10
weight percent of a brominated aromatic (meth)acrylate monomer; and
about 0.1 to about 5 weight percent of a phosphine oxide
photoinitiator.
[0038] In another embodiment, the curable composition comprises the
reaction product of (meth)acrylic acid with a di-epoxide that is
bisphenol-A diglycidyl ether, bisphenol-F diglycidyl ether,
tetrabromo bisphenol-A diglycidyl ether, tetrabromo bisphenol-F
diglycidyl ether,
1,3-bis-{4-[1-methyl-1-(4-oxiranylmethoxy-phenyl)-ethyl]-phenoxy}-propan--
2-ol,
1,3-bis-{2,6-dibromo-4-[1-(3,5-dibromo-4-oxiranylmethoxy-phenyl)-1-m-
ethyl-ethyl]-phenoxy}-propan-2-ol, or a combination comprising at
least one of the forgoing di-epoxides; phenylthioethyl
(meth)acrylate, phenoxyethyl (meth)acrylate, or a combination
comprising at least one of the foregoing substituted or
unsubstituted arylether (meth)acrylate monomer; pentabromobenzyl
(meth)acrylate; and a phosphine oxide photoinitiator.
[0039] In yet another embodiment, a method of making the
composition comprises blending a multifunctional (meth)acrylate, a
substituted or unsubstituted arylether (meth)acrylate monomer, a
brominated aromatic (meth)acrylate monomer, and a polymerization
initiator.
[0040] Other embodiments include the reaction product obtained by
curing any of the above curable compositions.
[0041] Still other embodiments include articles made from any of
the cured compositions. Articles that may be fabricated from the
compositions include, for example, optical articles, such as light
management films for use in back-light displays; projection
displays; traffic signals; illuminated signs; optical lenses;
Fresnel lenses; optical disks; diffuser films; holographic
substrates; or as substrates in combination with conventional
lenses, prisms or mirrors.
[0042] All cited patents, patent applications, and other references
are incorporated herein by reference in their entirety. The
invention is further illustrated by the following non-limiting
examples.
EXAMPLES
[0043] The formulations for the following Examples were prepared
from the components listed in Table 1.
1TABLE 1 Component Trade Name Description Source RDX51027 RDX51027
Diacrylate of tetrabromo UCB Chemicals bisphenol-A di-epoxide PTEA
BX-PTEA Phenylthioethyl acrylate Bimax Company PEA SR339
2-Phenoxyethyl acrylate Sartomer PBrBA FR1025M Pentabromobenzyl
Ameribrom acrylate Irgacure Irgacure 819 Bis(2,4,6- Ciba-Geigy
trimethylbenzoyl)- phenylphosphine oxide
[0044] Examples of cured flat films and cured microstructured films
coated on a substrate were prepared according to the following
procedures. As used in the Examples, coated films means a
two-layered film of the composition and film-substrate. Coated
cured flat films having a 7 to 10 micrometer thick cured
composition layer atop a 0.005-inch (0.127 centimeter) thick
polycarbonate film substrate were prepared using a custom-made
laminating unit and Fusion EPIC 6000UV curing system. The
laminating unit consists of two rubber rolls: a bottom variable
speed drive roll and a pneumatically driven top nip roll. This
system is used to press together laminate stacks that are passed
between the rolls. The laminate stacks contain a tool with or
without a desired geometry to replicate lying face up, a curable
composition coated on the tool, and a film substrate on the top of
the curable composition. The coated flat films were prepared by
transferring approximately 0.5 mL of curable composition to a
highly polished, flat, chrome-plated 5 by 7-inch (12.7 by 17.8
centimeter) steel plate tool in a continuous line at the front, or
leading edge of the plate. A piece of film substrate was then
placed over the curable composition and the resulting stack sent
through the laminating unit to press and distribute the curable
composition uniformly between the tool and film substrate. With
higher viscosity formulations, higher pressure and lower speeds
were used and the tool was heated to obtain the desired thickness.
Photopolymerization of the curable composition within the stack was
accomplished by passing the stack twice under a 600-watt V-bulb at
a speed of 16 feet/minute (0.081 meters/second), using high power
and a focal length of 2.1 inches (5.3 centimeter), curing through
the film substrate top layer. The coated cured flat film was then
peeled off of the flat tool and used for abrasion, % haze, %
transmission, color, yellowness index, and adhesion
measurements.
[0045] Coated cured microstructured films for measuring luminance
were made in the same manner as coated cured flat films by
substituting the highly polished flat steel plate for an
electroformed tool with a prismatic geometry. The geometry of the
prisms can be found in FIG. 6 of the copending U.S. application
Ser. No. 10/065,981 entitled "Brightness Enhancement Film With
Improved View Angle" filed Dec. 6, 2002, which is incorporated
herein in its entirety.
[0046] Glass transition temperatures (Tg) of the cured compositions
were measured by dynamic mechanical analysis (DMA) using a
Rheometrics Solids Analyzer RSA II operating in tension with a
frequency of 1.0 rad/s, strain of 0.01%, and temperature ramp of
2.degree. C./minute. Cured free films (no film substrate) for DMA
were prepared by placing approximately one gram of a curable
composition into an aluminum pan having a 2 inch (5.08 centimeter)
diameter, spreading the curable composition across the bottom of
the pan by tilting it, and photopolymerizing the composition under
a nitrogen atmosphere. If the curable composition was viscose, the
pan and curable composition were mildly heated to reduce the
viscosity and enhance the flowability. Photopolymerization was
accomplished using a Fusion EPIC 6000UV processor equipped with a
600 watt V-bulb. The distance of the lamp from the conveyor belt
was 2.1 inches (5.3 centimeter). The belt speed used was 16
feet/minute (0.081 meters/second) and the sample was passed under
the lamp three times.
[0047] The refractive index (RI) of the liquid curable compositions
was measured using a Bausch and Lomb Abbe-3L refractometer; the
wavelength associated with the measurement was 589.3
nanometers.
[0048] The percent (%) haze and % transmission of light through the
coated cured flat films were determined according to ASTM D1003
using a BYK-Gardner Haze-guard Plus Hazemeter.
[0049] Oscillating Sand Abrasion Test (OST % haze) was performed on
the coated cured flat films using a modification to the procedure
described in ASTM F735. The major modification consisted of a
change in the mode of sand oscillation from linear oscillation to
circular oscillation. The apparatus used for the abrasion process
was a vortex shaker manufactured by Glas-Col Company equipped with
a metal tray to hold the sample and sand. The sand was silica sand
from Fairmount Minerals of Wedron, Ill. (C.A.S. 14808-60-7). One
thousand milliliters of sand and an oscillation time of 10 minutes
were used for the test.
[0050] The brightness of the coated cured microstructured films was
determined using the Display Analysis system Microvision SS220.
Microvision SS220, a computer based measurement system, uses a
goniometric assembly and a mechanical positioner for the collection
of in-axis and off-axis data at various locations of the films. The
brightness measurements are achieved by utilizing a diffraction
grating spectrometer with a collimation optical probe. The
microstructured or light management film is mounted onLG-Phillips
backlight module, which is composed of a bottom diffuser D177 and
crossed light management films. A 13 point test and hemi test are
conducted to provide the uniformity of the brightness over 13
specific locations on the film and the range of viewing angle at
the center location of the film. The brightness is provided in
units of candela per meter squared (cd/m.sup.2).
[0051] The adhesion was measured for the coated cured flat film
according to ASTM D3359.
[0052] The viscosity for each curable composition included in the
following examples was measured using a Brookfield LVDV-II
Cone/Plate Viscometer at 25.degree. C., with a CPE40 or CPE51
spindle attachment, 0.5 mL liquid curable composition sample volume
while maintaining a torque range within 15% to 90% of the equipment
maximum for the specific cone attachment. The viscosity
measurements are provided in centipoise (cP).
[0053] The color of the coated cured flat films was determined by
measuring L*, a*, and b* using a Gretag Macbeth Color-Eye 7000A
colorimeter using L*, a*, b* color space, the D65 illuminant, and a
10 degree observer inclusive of a specular reflection.
[0054] The yellowness index (YI) of the coated cured flat films was
measured using a Gretag Macbeth Color-Eye 7000A calorimeter.
[0055] Table 2 provides glass transition temperature data for free
films made from PTEA and RDX51027 (Examples 1-4) and free films
made from PTEA, RDX51027, and PBrBA (Examples 5-8). The results
illustrate the dramatic increase in Tg of the resulting cured
compositions made from formulations containing PBrBA. In the
following tables, all of the amounts are shown in weight percent
based on the total weight of the composition, with the actual
amount of each component of the formulation enclosed in parenthesis
(in grams).
2 TABLE 2 Components in Weight percent (grams) Example RDX51027
PTEA PBrBA Irgacure Tg (.degree. C.) 1 69.5 (7) 30 (3) -- 0.5
(0.05) 90 2 59.5 (6) 40 (4) -- 0.5 (0.05) 63 3 49.5 (5) 50 (5) --
0.5 (0.05) 47 4 39.5 (4) 60 (6) -- 0.5 (0.05) 28 5 69.5 (7) 21
(2.1) 9 (0.9) 0.5 (0.05) 99 6 59.5 (6) 28 (2.8) 12 (1.2) 0.5 (0.05)
86 7 49.5 (5) 35 (3.5) 15 (1.5) 0.5 (0.05) 71 8 39.5 (4) 42 (4.2)
18 (1.8) 0.5 (0.05) 54
[0056] Table 3 provides glass transition data for free films made
from PEA and RDX51027 (Examples 9, 13, 17, and 21) and free films
made from PEA, RDX51027, and PBrBA (Examples 10-12, 14-16, 18-20,
and 22-24). The results illustrate the dramatic increase in Tg of
the resulting cured compositions containing PBrBA. Again, the
amounts are shown in weight percent with the actual amount of each
component of the formulation encl in parenthesis (in grams).
3 TABLE 3 Components in Weight percent (grams) Tg Example RDX51027
PEA PBrBA Irgacure (.degree. C.) 9 69.5 (7) 30 (3) -- 0.5 (0.05) 93
10 69.5 (7) 27 (2.7) 3 (0.3) 0.5 (0.05) 101 11 69.5 (7) 24 (2.4) 6
(0.6) 0.5 (0.05) 106 12 69.5 (7) 21 (2.1) 9 (0.9) 0.5 (0.05) 112 13
59.5 (6) 40 (4) -- 0.5 (0.05) 74 14 59.5 (6) 36 (3.6) 4 (0.4) 0.5
(0.05) 79 15 59.5 (6) 32 (3.2) 8 (0.8) 0.5 (0.05) 91 16 59.5 (6) 28
(2.8) 12 (1.2) 0.5 (0.05) 96 17 49.5 (5) 50 (5) -- 0.5 (0.05) 57 18
49.5 (5) 45 (4.5) 5 (0.5) 0.5 (0.05) 65 19 49.5 (5) 40 (4.0) 10
(1.0) 0.5 (0.05) 70 20 49.5 (5) 35 (3.5) 15 (1.5) 0.5 (0.05) 78 21
39.5 (4) 60 (6) -- 0.5 (0.05) 45 22 39.5 (4) 54 (5.4) 6 (0.6) 0.5
(0.05) 48 23 39.5 (4) 48 (4.8) 12 (1.2) 0.5 (0.05) 56 24 39.5 (4)
42 (4.2) 18 (1.8) 0.5 (0.05) 66
[0057] Table 4 displays formulations for compositions of RDX51027,
PTEA, and PBrBA.
4 TABLE 4 Components in Weight percent (grams) Exam- PTEA: ple
RDX51027 PTEA PBrBA PBrBA Irgacure 25 69.5 (10.46) 27 3 90:10
(4.48) 0.5 (0.08) 26 59.5 (10.15) 36 4 90:10 (6.77) 0.5 (0.085) 27
49.5 (9.54) 45 5 90:10 (9.54) 0.5 (0.095) 28 39.5 (11.33) 54 6
90:10 (17.00) 0.5 (0.14) 29 69.5 (10.96) 24 6 80:20 (4.70) 0.5
(0.078) 30 59.5 (9.58) 32 8 80:20 (6.39) 0.5 (0.080) 31 49.5
(10.43) 40 10 80:20 (10.43) 0.5 (0.104) 32 39.5 (9.13) 48 12 80:20
(13.70) 0.5 (0.114)
[0058] Table 5 displays data on free films and coated cured flat
films produced from curing films of the compositions in Table 4.
The results illustrate that increasing PBrBA concentration in the
compositions increases refractive index (RI) and Tg of the curable
composition and cured free films, respectively.
5 TABLE 5 Examples Properties 25 26 27 28 RI Measured (liquid)
1.594 1.589 1.582 1.581 % Haze 0.17 0.44 1.27 1.23 OST % Haze 81.1
77.0 68.0 65.7 Adhesion 0B 5B 5B 5B Viscosity (cP) NA 2,130 580 135
Tg (.degree. C.) 98 74 48 38 L* 95.7 95.9 95.8 95.8 a* -0.1 0.0 0.0
0.0 b* 0.5 0.3 0.3 0.3 YI 0.8 0.5 0.4 0.4 Examples Properties 29 30
31 32 RI Measured (liquid) 1.596 1.593 1.588 1.585 % Haze 1.23 1.27
1.25 1.28 OST % Haze 77.8 76.7 77.9 38.4 Adhesion 0B 0B 1B 5B
Viscosity (cP) NA 3,570 873 250 Tg (.degree. C.) 101 80 30 52 L*
95.7 95.8 95.8 95.8 a* -0.2 0.0 0.0 0.0 b* 0.8 0.4 0.3 0.3 YI 1.2
0.6 0.5 0.4
[0059] Table 6 displays formulations based on compositions derived
from RDX51 PTEA, and PBrBA.
6 TABLE 6 Components in Weight percent (grams) Example RDX51027
PTEA PBrBA Irgacure 33 29.5 (5.9) 56 (11.2) 14 (2.8) 0.5 (0.1) 34
29.5 (5.9) 70 (14) -- 0.5 (0.1) 35 49.5 (9.9) 50 (10.0) -- 0.5
(0.1) 36 49.5 (9.9) 45 (9.0) 5 (1.0) 0.5 (0.1) 37 49.5 (9.9) 40
(8.0) 10 (2.0) 0.5 (0.1) 38 69.5 (13.9) 30 (6.0) -- 0.5 (0.1) 39
69.5 (13.9) 27 (5.4) 3 (0.6) 0.5 (0.1) 40 69.5 (13.9) 24 (4.8) 6
(1.2) 0.5 (0.1)
[0060] Table 7 displays data on free films, coated cured flat films
as well as coate cured microstructured films produced from the
compositions in Table 6. T results of Examples 33 and 34 illustrate
that the presence of PBrBA in the compositions provides an
unexpected increase in brightness in the resulti microstructured
films. Furthermore, the addition of only small amounts of PBrBA to
formulations containing about 70 percent of the RDX compound
resulted in free films having substantially increased Tg (Examples
38-40).
7 TABLE 7 Examples Properties 33 34 35 36 RI Measured 1.579 1.569
1.5777 1.5818 (liquid) % Haze 0.59 0.55 0.61 0.65 Adhesion 5B 5B 5B
5B Viscosity (cP) 56 29 216 334 Tg (.degree. C.) 33 28 49 54 L*
95.8 95.9 95.9 95.9 a* 0.0 0.0 0.0 0.0 b* 0.4 0.3 0.4 0.4 YI 0.6
0.6 0.6 0.6 Transmission 92.7 92.7 92.7 92.8 (%) Brightness 1491
1431 -- -- (cd/m.sup.2) Examples Properties 37 38 39 40 RI Measured
1.5861 1.5878 1.5910 1.5942 (liquid) % Haze 0.67 0.64 0.60 0.64
Adhesion 5B 5B 5B 5B Viscosity (cP) 533 5,743 10,629 20,481 Tg
(.degree. C.) 66 88 95 106 L* 95.8 95.9 95.9 95.9 a* 0.0 0.0 0.0
0.0 b* 0.4 0.3 0.3 0.4 YI 0.6 0.5 0.6 0.6 Transmission 92.8 92.9
92.7 92.7 (%) Brightness (%) -- -- -- --
[0061] Table 8 provides the formulations for compositions
comprising RDX1027, PEA, and PBrBA.
8 TABLE 8 Components in Weight percent (grams) Example RDX51027 PEA
PBrBA Irgacure 41 29.5 (5.9) 56 (11.2) 14 (2.8) 0.5 (0.1) 42 29.5
(5.9) 70 (14) -- 0.5 (0.1) 43 49.5 (9.9) 50 (10.0) -- 0.5 (0.1) 44
49.5 (9.9) 47.5 (9.5) 2.5 (0.5) 0.5 (0.1) 45 49.5 (9.9) 42.5 (8.5)
7.5 (1.5) 0.5 (0.1) 46 49.5 (9.9) 40 (8.0) 10 (2.0) 0.5 (0.1) 47
69.5 (13.9) 30 (6.0) -- 0.5 (0.1) 48 69.5 (13.9) 27 (5.4) 3 (0.6)
0.5 (0.1) 49 69.5 (13.9) 24 (4.8) 6 (1.2) 0.5 (0.1)
[0062] Table 9 displays data on free films, coated cured flat
films, and coated cured microstructured films produced from curing
the compositions in Table 8. As with the PTEA formulations of Table
6 and 7, the results in Examples 41 and 42 illustrate that the
presence of PBrBA in the PEA containing compositions provides an
unexpected increase in brightness in the resulting microstructured
films. Also, the addition of minor amounts of PBrBA to the
formulations containing about 70% of the RDX compound resulted in
cured free films having significantly increased Tg (Examples
47-49).
9 TABLE 9 Examples Properties 41 42 43 44 RI Measured (liquid)
1.552 1.538 1.5530 1.5563 % Haze 0.59 0.47 0.63 0.66 Adhesion 5B 5B
5B 5B Viscosity (cP) 96 49 362 451 Tg (.degree. C.) 48 31 58 60 L*
96.0 96.1 96.0 96.0 a* 0.0 0.0 0.0 0.0 b* 0.3 0.3 0.3 0.3 YI 0.5
0.5 0.5 0.5 Transmission (%) 92.9 93.2 93.1 93.1 Brightness
(cd/m.sup.2) 1470 1387 -- -- Examples Properties 45 46 47 48 49 RI
Measured (liquid) 1.5617 1.5650 1.5719 1.5764 1.5803 % Haze 0.65
0.62 .60 .60 .68 Adhesion 5B 5B 5B 5B 5B Viscosity (cP) 743 1015
11,179 19,316 34,459 Tg (.degree. C.) 67 69 97 104 113.5 L* 96 96.0
96.0 95.9 95.9 a* 0.0 0.0 0.0 0.0 0.0 b* 0.3 0.3 0.3 0.3 0.3 YI 0.5
0.5 0.5 0.5 0.5 Transmission (%) 93.0 93.0 92.9 92.9 92.6
Brightness (%) -- -- -- -- --
[0063] Comparing similar samples of PTEA, RDX51027 and PBrBA
(Example 33) with PEA, RDX51027 and PBrBA (Example 41) it is
discovered that the formulation containing the PTEA has better RI
that its PEA counterpart. Example 33 also provides a curable
composition having a lower viscosity than Example 41, thereby
providing better processability than a more viscous composition.
Finally, Example 33 provides a cured microstructured film having
improved brightness when compared to its PEA counterpart.
[0064] Table 10 provides the formulations of compositions
comprising a combination of phenylthioethyl acrylate and
phenoxyethyl acrylate in addition to the RDX51027 and the
pentabromobenzyl acrylate.
10 TABLE 10 Components in Weight percent (grams) Example RDX51027
PEA PTEA PBrBA Irgacure 50 29.5 (5.9) 35 (7.0) 35 (7.0) -- 0.50
(0.1) 51 29.5 (5.9) 31.5 (6.3) 31.5 (6.3) 7 (1.4) 0.50 (0.1) 52
29.5 (5.9) 28 (5.6) 28 (5.6) 14 (2.8) 0.50 (0.1)
[0065] Table 11 provides the data of the cured free films and
coated cured flat films based on the formulations found in Table
10. As shown in Table 11, the addition of PBrBA increases Tg of
cured free films and RI of the curable composition.
11 TABLE 11 Examples Properties 50 51 52 RI Measured (liquid)
1.5525 1.5590 1.5662 % Haze 0.56 0.53 0.63 Adhesion 5B 5B 5B
Viscosity (cP) 37 51 76 Tg (.degree. C.) 25 31 37 L 96.0 95.9 95.9
a 0.0 0.0 0.0 b 0.3 0.3 0.3 YI 0.5 0.5 0.5 Transmission (%) 93.0
92.8 92.7
[0066] Since PBrBA is a powder and RDX51027 is a solid, the maximum
amoun PBrBA that can be added to a blend of RDX51027 and
substituted or unsubstituted arylether (meth)acrylate monomer is
dependent on the solu of PBrBA in the substituted or unsubstituted
arylether (meth)acrylate monomer. The maximum solubility of PBrBA
in PEA or PTEA was determ as follows. Solutions of PBrBA in PTEA,
PEA, or 50/50 wt./wt. PTEA/PEA were prepared at different
concentrations by heating the materials to prom solubility. The
homogenous solutions were then allowed to sit overnight a room
temperature and the appearance of crystallization was observed vis
The data obtained is shown in Table 12. The results show that PTEA
offe higher solubility of PBrBA than PEA.
12TABLE 12 Wt. % PBrBA Reactive Diluent Crystallization overnight
10 PEA No 20 PEA No 30 PEA Yes 10 PTEA No 20 PTEA No 30 PTEA No 10
50/50 PTEA/PEA No 20 50/50 PTEA/PEA No 30 50/50 PTEA/PEA Yes
[0067] While the invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
* * * * *