U.S. patent application number 11/098116 was filed with the patent office on 2006-10-05 for radiation- or thermally-curable oxetane barrier sealants.
Invention is credited to Shengqian Kong.
Application Number | 20060223978 11/098116 |
Document ID | / |
Family ID | 36950282 |
Filed Date | 2006-10-05 |
United States Patent
Application |
20060223978 |
Kind Code |
A1 |
Kong; Shengqian |
October 5, 2006 |
Radiation- or thermally-curable oxetane barrier sealants
Abstract
This invention relates to cationically curable sealants that
provide low moisture permeability and good adhesive strength after
cure. The composition consists essentially of an oxetane compound
and a cationic initiator.
Inventors: |
Kong; Shengqian; (Edison,
NJ) |
Correspondence
Address: |
Jane E. Gennaro;National Starch and Chemical
10 Finderne Avenue
Bridgewater
NJ
08807
US
|
Family ID: |
36950282 |
Appl. No.: |
11/098116 |
Filed: |
April 4, 2005 |
Current U.S.
Class: |
528/417 ;
525/523; 528/421 |
Current CPC
Class: |
G03F 7/038 20130101;
C08G 65/18 20130101 |
Class at
Publication: |
528/417 ;
528/421; 525/523 |
International
Class: |
C08G 59/06 20060101
C08G059/06; C08G 59/08 20060101 C08G059/08; C08L 63/00 20060101
C08L063/00 |
Goverment Interests
[0001] This Invention was made with support from the Government of
the United States of America under Agreement No. MDA972-93-2-0014
awarded by the Army Research Laboratories. The Government has
certain rights in the Invention.
Claims
1. A cationically curable barrier composition consisting
essentially of (a) an oxetane compound, (b) a cationic initiator,
(c) optionally, one or more fillers, (d) optionally one or more
adhesion promoters, or one or more epoxy resins.
2. The cationically curable barrier composition in accordance with
claim 1, in which the oxetane compound has the structure: ##STR20##
in which R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6 are
selected from the group consisting hydrogen, and alkyl, haloalkyl,
alkoxy, aryloxy, aryl, ester, thio-ester, and sulfide groups.
3. The cationically curable barrier composition in accordance with
claim 1, in which the oxetane compound is selected from the group
of oxetane compounds having the structures: ##STR21##
4. The cationically curable barrier composition in accordance with
claim 1, in which the oxetane compound has an aromatic core, onto
which aromatic core are substituted in a meta-position with each
other, the oxetane functionality and an additional polymerizable
functionality.
5. The cationically curable barrier composition in accordance with
claim 1, in which the oxetane compound has the structure: ##STR22##
in which R.sup.7, R.sup.8, R.sup.9, R.sup.10 and R.sup.11 are
independently selected from the group consisting of hydrogen,
alkyl, haloalkyl, alkoxy, aryloxy, aryl, alkyloyl and aryloyl
groups; n is 0, 1, 2, 3, or 4; Z is a cationically reactive
functionality selected from the group consisting of ##STR23## in
which R.sup.11 and R.sup.12 are independently selected from the
group consisting of hydrogen, alkyl, haloalkyl, alkoxy, aryloxy,
aryl, alkyloyl and aryloyl groups; and R.sup.13 is a linking group
selected from the group consisting of alkyl, haloalkyl, aryl,
ether, thio-ether, ester, thio-ester, silane, carbonate, or
ketone.
6. The cationically curable barrier composition in accordance with
claim 5, in which the oxetane compound is selected from the group
having the structures: ##STR24##
7. The cationically curable barrier composition in accordance with
claim 1, in which the oxetane compound is a hybrid compound having
both an oxetane and a second reactive functionality extending from
a cycloaliphatic backbone.
8. The cationically curable barrier composition in accordance with
claim 1, in which the oxetane compound has the structure ##STR25##
in which L, L', L'' and L''' are linking groups independently
selected from the group consisting of ##STR26## R and R'
independently are selected from the group consisting of linear
alkyl, branched alkyl, cycloalkyl, aryl, heteroaryl, silane or
siloxane groups; R'' is independently selected from the group
consisting of hydrogen, alkyl, haloalkyl, alkoxy, aryloxy, aryl,
alkyloyl and aryloyl groups; X is a reactive group independently
selected from the group consisting of glycidyl epoxy, aliphatic
epoxy, and cycloaliphatic epoxy; oxetane; vinyl, propenyl, crotyl,
allyl, and propargyl ether and thio-ethers of those groups;
acrylate and methacrylate; itaconate; maleimide; maleate, fumarate,
and cinnamate esters; styrenic; acrylamide and methacrylamide;
chalcone; thiol; allyl, alkenyl, and cycloalkenyl groups; n, k, l,
n', k', and l' are 0 or 1; and y is 1 to 10.
9. The cationically curable barrier composition in accordance with
claim 8, in which the oxetane compound has the structure selected
from the group consisting of: ##STR27##
10. The cationically curable barrier composition in accordance with
any of claims 1 through 9 in which the cationic initiator is a
Br.phi.nsted acid, a Lewis acid, or a photo or thermal acid
generator.
11. The cationically curable barrier composition in accordance with
any of claims 1 through 9 in which one or more fillers are
present.
12. The cationically curable barrier composition in accordance with
any of claims 1 through 9 in which one or more fillers are present
and are selected from the group consisting of ground quartz, fused
silica, amorphous silica, talc, glass beads, graphite, carbon
black, alumina, clays, mica, vermiculite, aluminum nitride, boron
nitride; silver, copper, gold, tin, tin/lead alloys,
poly(tetrachloroethylene), poly(chlorotriflouroethylene),
poly(vinylidene chloride), CaO, BaO, Na.sub.2SO.sub.4, CaSO.sub.4,
MgSO.sub.4, zeolites, silica gel, P.sub.2O.sub.5, CaCl.sub.2, and
Al.sub.2O.sub.3
13. The cationically curable barrier composition in accordance with
any of claims 1 through 9 in which one or more epoxy resins are
present.
14. The cationically curable barrier composition in accordance with
any of claims 1 through 9 in which one or more epoxy resins are
present and are selected from the group consisting of bisphenol F
diglycidyl ether, resorcinol diglycidyl ether, novolac glycidyl
ethers, and halogenated glycidyl ethers.
15. The cationically curable barrier composition in accordance with
any of claims 1 through 9 in which one or more adhesion promoters
are present.
16. The cationically curable barrier composition in accordance with
any of claims 1 through 9 in which an adhesion promoter is present
and is a silane.
17. A hybrid compound containing both oxetane and epoxy
functionality selected from the group consisting of: ##STR28##
18. An electronic or optoelectronic device sealed with the
cationically-curable barrier sealant according to any one of claims
1 to 9.
19. The electronic or optoelectronic device according to claim 18
in which the device is an OLED.
Description
FIELD OF THE INVENTION
[0002] This invention relates to barrier sealants, adhesives,
encapsulants, and coatings for use in electronic and optoelectronic
devices. (As used in this specification and claims, adhesives,
sealants, encapsulants, and coatings are similar materials, all
having adhesive, sealant, and coating properties and functions.
When any one is recited, the others are deemed to be included.)
BACKGROUND
[0003] Radiation curable materials have found increased use as
coatings, adhesives, and sealants over the past three decades for
reasons including low energy consumption during cure, rapid cure
speed through either radical or cationic mechanisms, low curing
temperature, wide availability of curable materials, and the
availability of solvent-free products. These benefits have made
such products especially suited for rapidly adhering and sealing
electronic and optoelectronic devices that are temperature
sensitive or cannot conveniently withstand prolonged curing times.
Optoelectronic devices particularly are often thermally sensitive
and may need to be optically aligned and spatially immobilized
through curing in a very short time period.
[0004] Numerous optoelectronic devices are also moisture or oxygen
sensitive and need to be protected from exposure during their
functional lifetime. A common approach is to seal the device
between an impermeable substrate on which it is positioned and an
impermeable glass or metal lid, and seal or adhere the perimeter of
the lid to the bottom substrate using a radiation curable adhesive
or sealant.
[0005] A common manifestation of this package geometry is
exemplified in FIG. 1, which discloses the use of a radiation
curable perimeter sealant (1) to bond a metal or glass lid (2) over
an organic light emitting diode (OLED) stack (3) fabricated on a
glass substrate (4). Although various configurations exist, a
typical device also contains an anode (5), a cathode (6), and some
form of electrical interconnect between the OLED pixel/device and
external circuitry (7). For the purposes of this invention, no
particular device geometry is specified or required aside from one
which incorporates an adhesive/sealant material such as a perimeter
sealant (1).
[0006] In many configurations, as for the example in FIG. 1, both
the glass substrate and the metal/glass lid are essentially
impermeable to oxygen and moisture, and the sealant is the only
material that surrounds the device with any appreciable
permeability. For electronic and optoelectronic devices, moisture
permeability is very often more critical than oxygen permeability;
consequently, the oxygen barrier requirements are much less
stringent, and it is the moisture barrier properties of the
perimeter sealant that are critical to successful performance of
the device.
[0007] Good barrier sealants will exhibit low bulk moisture
permeability, good adhesion, and strong interfacial
adhesive/substrate interactions. If the quality of the substrate to
sealant interface is poor, the interface may function as a weak
boundary, which allows rapid moisture ingress into the device
regardless of the bulk moisture permeability of the sealant. If the
interface is at least as continuous as the bulk sealant, then the
permeation of moisture typically will be dominated by the bulk
moisture permeability of the sealant itself.
[0008] It is important to note that one must examine moisture
permeability (P) as the measure of effective barrier properties and
not merely water vapor transmission rate (WVTR), as the latter is
not normalized to a defined path thickness or path length for
permeation. Generally, permeability can be defined as WVTR
multiplied by unit permeation path length, and is, thus, the
preferred way to evaluate whether a sealant is inherently a good
barrier material.
[0009] The most common ways to express permeability are the
permeability coefficient (e.g. g-mil/(100 in.sup.2dayatm)), which
applies to any set of experimental conditions, or the permeation
coefficient (e.g. gmil/(100 in.sup.2day) at a given temperature and
relative humidity), which must be quoted with the experimental
conditions in order to define the partial pressure/concentration of
permeant present in the barrier material. In general, the
penetration of a permeant through some barrier material
(permeability, P) can be described as the product of a diffusion
term (D) and a solubility term (S): P=DS
[0010] The solubility term reflects the affinity of the barrier for
the permeant, and, in relation to water vapor, a low S term is
obtained from hydrophobic materials. The diffusion term is a
measure of the mobility of a permeant in the barrier matrix and is
directly related to material properties of the barrier, such as
free volume and molecular mobility. Often, a low D term is obtained
from highly crosslinked or crystalline materials (in contrast to
less crosslinked or amorphous analogs). Permeability will increase
drastically as molecular motion increases (for example as
temperature is increased, and particularly when the T.sub.g of a
polymer is exceeded).
[0011] Logical chemical approaches to producing improved barriers
must consider these two fundamental factors (D and S) affecting the
permeability of water vapor and oxygen. Superimposed on such
chemical factors are physical variables: long permeation pathways
and flawless adhesive bondlines (good wetting of the adhesive onto
the substrate), which improve barrier performance and should be
applied whenever possible. The ideal barrier sealant will exhibit
low D and S terms while providing excellent adhesion to all device
substrates.
[0012] It is not sufficient to have only a low solubility (S) term
or only a low diffusivity (D) term in order to obtain high
performance barrier materials. A classic example can be found in
common siloxane elastomers. Such materials are extremely
hydrophobic (low solubility term, S), yet they are quite poor
barriers due to their high molecular mobility due to unhindered
rotation about the Si--O bonds (which produces a high diffusivity
term (D). Thus, many systems that are merely hydrophobic are not
good barrier materials despite the fact that they exhibit low
moisture solubility. Low moisture solubility must be combined with
low molecular mobility and, thus, low permeant mobility or
diffusivity.
[0013] For liquid materials that are cured to solid sealants, such
as the inventive compositions, the attainment of lower molecular
mobility within the cured matrix is approached through high
crosslink density, microcrystallinity, or close packing of
molecular backbones between the crosslinked portions of the
matrix.
BRIEF DESCRIPTION OF THE DRAWING
[0014] FIG. 1 is a perimeter sealed optoelectronic device.
SUMMARY OF THE INVENTION
[0015] The inventors have discovered that certain resin and
resin/filler systems provide superior barrier performance,
particularly to moisture, through the incorporation of an oxetane
resin and a cationic initiator into the barrier composition. The
oxetane resin in general will have the structure which the oxetane
compound has the structure: ##STR1## in which R.sup.1, R.sup.2,
R.sup.3, R.sup.4, R.sup.5, R.sup.6 are selected from the group
consisting hydrogen, and alkyl, haloalkyl, alkoxy, aryloxy, aryl,
ester, thio-ester, and sulfide groups. Such barrier materials may
be used alone or in combination with other curable resins and
various fillers. The resulting compositions exhibit a commercially
acceptable cure rate, a balance of high crosslink density and
molecular packing (low permeant mobility/diffusivity term, D),
hydrophobicity (low water solubility term, S), and adhesion (strong
adhesive/substrate interfaces) to make them effective for use in
sealing and encapsulating electronic, optoelectronic, and MEMS
devices.
DETAILED DESCRIPTION OF THE INVENTION
[0016] This invention is a cationically curable barrier sealant
consisting essentially of (a) an oxetane compound and (b) a
cationic initiator. The barrier adhesive or sealant optionally
contains (c) one or more fillers and optionally, (d) one or more
adhesion promoters or one or more epoxy resins. When one or more
epoxy resins are present, preferably they are selected from the
group consisting of bisphenol F diglycidyl ether, resorcinol
diglycidyl ether, novolac glycidyl ethers, and halogenated glycidyl
ethers, although other epoxies may be used. The use of a cationic
photoinitiator results in a radiation-curable formulation; however,
the use of a cationic catalyst that can trigger polymerization at
room or elevated temperatures may be used for thermal cure. The
resulting compositions are suitable for use in sealing and
encapsulating electronic and optoelectronic devices.
[0017] Within this specification, the term radiation is used to
describe actinic electromagnetic radiation. Actinic radiation is
defined as electromagnetic radiation that induces a chemical change
in a material, and for purposes within this specification will also
include electron-beam curing. In most cases electromagnetic
radiation with wavelengths in the ultraviolet (UV) and/or visible
regions of the spectrum are most useful.
[0018] Within this specification, the term oxetane compound refers
to any small molecule, oligomer, or polymer carrying an oxetane
functionality. The oxetane compound in general will have the
structure ##STR2## in which R.sup.1, R.sup.2, R.sup.3, R.sup.4,
R.sup.5, and R.sup.6 are selected from the group consisting of
hydrogen, and alkyl, haloalkyl, alkoxy, aryloxy, aryl, ester,
thio-ester, and sulfide groups. In one embodiment, the oxetane
compounds are selected from the group of oxetane compounds having
the structures: ##STR3##
[0019] In another embodiment, the oxetane compound will have an
aromatic core, onto which aromatic core are substituted in a
meta-position with each other, the oxetane functionality and an
additional polymerizable functionality. In this embodiment, the
oxetane compound will have the structure: ##STR4## in which
R.sup.7, R.sup.8, R.sup.9, R.sup.10, and R.sup.11 are independently
selected from the group consisting of hydrogen, alkyl, haloalkyl,
alkoxy, aryloxy, aryl, alkyloyl and aryloyl groups; n is 0, 1, 2,
3, or 4; Z is a cationically reactive functionality selected from
the group consisting of, but not limited to: ##STR5## in which
R.sup.11 and R.sup.12 are independently selected from the group
consisting of hydrogen, alkyl, haloalkyl, alkoxy, aryloxy, aryl,
alkyloyl and aryloyl groups; and R.sup.13 is a linking group
selected from the group consisting of alkyl, haloalkyl, aryl,
ether, thio-ether, ester, thio-ester, silane, carbonate, or
ketone.
[0020] Exemplary oxetane compounds meeting the above description
include, but are not limited to, ##STR6##
[0021] In another embodiment the oxetane compound is a hybrid
compound having both oxetane and a second reactive functionality
extending from a cycloaliphatic backbone. In general, such
compounds will have the structure ##STR7## in which L, L', L'' and
L''' are linking groups independently selected from the group
consisting of ##STR8## R and R' independently are selected from the
group consisting of linear alkyl, branched alkyl, cycloalkyl, aryl,
heteroaryl, silane or siloxane groups; R'' is independently
selected from the group consisting of hydrogen, alkyl, haloalkyl,
alkoxy, aryloxy, aryl, alkyloyl and aryloyl groups; X is a reactive
group independently selected from the group consisting of glycidyl
epoxy, aliphatic epoxy, and cycloaliphatic epoxy; oxetane; vinyl,
propenyl, crotyl, allyl, and propargyl ether and thio-ethers of
those groups; acrylate and methacrylate; itaconate; maleimide;
maleate, fumarate, and cinnamate esters; styrenic; acrylamide and
methacrylamide; chalcone; thiol; allyl, alkenyl, and cycloalkenyl
groups; n, k, l, n', k', and l' are 0 or 1; and y is 1 to 10.
[0022] When n, k, and l in the above structures are 0, and X is a
form of epoxy, X can be attached to the cycloaliphatic backbone by
a direct bond or can be a part of the cycloaliphatic backbone.
Exemplary embodiments of the cycloaliphatic hybrid compounds
include, but are not limited to, ##STR9##
[0023] Within this specification, the terms cycloaliphatic or
alicyclic refer generally to a class of organic compounds
containing carbon and hydrogen atoms joined to form one or more
rings, which may contain other atoms, such as, halogens (e.g. Cl,
Br, I), substituent atoms (e.g. O, S, N), or substituent groups
(e.g. OR, SR, NR.sub.2 in which R is a linear or branched alkyl or
cycloalkyl or aryl group). In general, cycloaliphatic resins are
defined as resins that contain a cyclic carbon-based ring structure
in their backbone, which cyclic carbon backbone may have
heteroatoms within the backbone or attached to it. It is preferable
that the cycloaliphatic resin backbone be composed primarily of
carbon, hydrogen and halogen atoms.
[0024] The selection of an initiator for the inventive radiation
curable barrier materials is familiar to those skilled in the art
of radiation curing. For photocuring, the curing initiator be a
photoinitiator. The selection of an appropriate photoinitiator is
highly dependent on the specific application in which the barrier
sealant is to be used. A suitable photoinitiator is one that
exhibits a light absorption spectrum that is distinct from that of
the resins, fillers, and other additives in the radiation curable
system. If the sealant must be cured through a cover or substrate,
the photoinitiator will be one capable of absorbing radiation at
wavelengths for which the cover or substrate is transparent. For
example, if a barrier sealant is to be cured through a sodalime
glass coverplate, the photoinitiator must have significant UV
absorbance above ca. 320 nm. UV radiation below 320 nm will be
absorbed by the sodalime glass coverplate and not reach the
photoinitiator. In this example, it would be beneficial to include
a photosensitizer with the photoinitiator into the photoinitiating
system, to augment the transfer of energy to the
photoinitiator.
[0025] Exemplary cationic photoinitiators are disclosed in Ionic
Polymerizations and Related processes, 45-60, 1999, Kluwer Academic
Publishers; Netherlands; J. E. Puskas et al. (eds.). Preferred
cationic photoinitiators include diaryliodonium salts and
triarylsulfonium salts. Well known commercially available examples
include UV9380C (GE Silicones), PC2506 (Polyset), SR1012
(Sartomer), Rhodorsil 2074 (Rhodia), and UVI-6974 (Dow). Preferred
sensitizers for diaryliodonium salts are isopropylthioxanthone
(referred to herein as ITX, often sold as a mixture of 2- and
4-isomers) and 2-chloro-4-propoxythioxanthone. The selection of an
efficient cationic photoinitiating system for a particular curing
geometry and resin system is known to those skilled in the art of
cationic UV curing, and is not limited within the scope of this
invention.
[0026] Less common initiating systems, such as thermally generated
acids are also anticipated in cases where such catalysts,
initiators, and curing agents are appropriate. Exemplary catalysts
include Br.phi.nsted acids, Lewis acids, and latent thermal acid
generators. Representative examples of Br.phi.nsted and Lewis acids
may be found in literature sources such as Smith, M. B. and March,
J. in March's Advanced Organic Chemistry, Reactions, Mechanisms,
and Structures, 5.sup.th Edition, 2001, John Wiley & Sons,
Inc., New York, N.Y. pp. 327-362. Examples of latent thermal acid
generators include, but not limited to, diaryliodonium salts,
benzylsulfonium salts, phenacylsulfonium salts, N-benzylpyridinium
salts, N-benzylpyrazinium salts, N-benzylammonium salts,
phosphonium salts, hydrazinium salts, ammonium borate salts,
etc.
[0027] Common fillers include, but are not limited to ground
quartz, fused silica, amorphous silica, talc, glass beads,
graphite, carbon black, alumina, clays, mica, vermiculite, aluminum
nitride, and boron nitride. Metal powders and flakes consisting of
silver, copper, gold, tin, tin/lead alloys, and other alloys are
contemplated. Organic filler powders such as
poly(tetrachloroethylene), poly(chlorotriflouroethylene), and
poly(vinylidene chloride) may also be used. Fillers that act as
desiccants or oxygen scavengers, including but not limited to, CaO,
BaO, Na.sub.2SO.sub.4, CaSO.sub.4, MgSO.sub.4, zeolites, silica
gel, P.sub.2O.sub.5, CaCl.sub.2, and Al.sub.2O.sub.3 may also be
utilized.
EXAMPLES
Example 1
Synthesis of Oxetane, 3,3'-[1,3-Phenylenebis
(Methyleneoxymethylene)]bis[3-Methyl-
[0028] ##STR10##
[0029] Into a 250 mL three-neck round bottom flask equipped with a
reflux condenser, a mechanic stirrer were added 12.0 g NaOH (0.3
mol), 0.6 g n-Bu.sub.4N.sup.+Br.sup.- (0.0019 mol), 30.0 g
3-methyl-3-hydroxymethyl-oxetane (0.29 mol), 25.0 g .alpha.,
.alpha.'-dibromo-m-xylene (0.095 mol), and 100 mL of toluene. The
reaction was brought to 110.degree. C. for 3.5 hours. The organic
phase was collected by filtration and the solvents were removed.
The light yellow crude product was redissolved in 200 mL of toluene
and washed with deionized water three times. After drying over
magnesium sulfate, the toluene solution was passed through a short
column of neutral alumina to remove trace amount of the ammonium
salt phase transfer catalyst. Finally, the solvents were removed
with rotary evaporator and Kugelrohr and the sample was purified by
distillation. .sup.1H NMR (CDCl.sub.3): .delta. ppm 1.36 (6H), 3.56
(4H), 4.38-4.55 (8H), 4.60 (4H), 7.18-7.38 (4H).
Example 2
Synthesis of Oxetane,
3,3'-[1,4-Phenylenebis(Methyleneoxymethylene)]bis[3-Methyl-
[0030] ##STR11##
[0031] The reaction conditions of Example 1 were adopted except
25.0 g .alpha., .alpha.'-dibromo-p-xylene (0.095 mol) was used
instead of 25.0 g a,a'-dibromo-m-xylene (0.095 mol). .sup.1H NMR
(CDCl.sub.3): .delta. ppm 1.36 (6H), 3.55 (4H), 4.37-4.55 (8H),
4.59 (4H), 7.36 (4H)
Example 3
Synthesis of Oxetane,
3,3'-[1,3-Phenylenebis(Methyleneoxymethylene)]bis[3-Ethyl-
[0032] ##STR12##
[0033] The reaction conditions of Example 1 were adopted except
34.1 g 3-ethyl-3-hydroxymethyl-oxetane (0.29 mol) was used instead
of 30.0 g 3-methyl-3-hydroxymethyl-oxetane (0.29 mol). .sup.1H NMR
(CDCl.sub.3): .delta. ppm 0.87-0.91 (6H), 1.77-1.83 (4H), 3.61
(4H), 4.40-4.49 (8H), 4.59 (4H), 7.28-7.38 (4H).
Example 4
Synthesis of Oxetane, 3,3'-[1,4-Phenylenebis
(Methyleneoxymethylene)]bis[3-Ethyl-
[0034] ##STR13##
[0035] The reaction conditions of Example 3 were adopted except
25.0 g .alpha., .alpha.'-dibromo-p-xylene (0.095 mol) was used
instead of 25.0 g .alpha., .alpha.'-dibromo-m-xylene (0.095 mol).
.sup.1H NMR (CDCl.sub.3): .delta. ppm 0.89-0.92 (6H), 1.77-1.83
(4H) 3.61 (4H), 4.40-4.49 (8H), 4.58 (4H), 7.34 (4H).
Example 5
Oxetane-Based Barrier Sealant 1
[0036] The oxetane from example 3, a photoinitiating system
(cationic photoinitiator and ITX) were placed in a plastic jar and
mixed with a vortex mixer for one hour until clear. Micron sized
silica and a nanosilica rheology modifier were then added to the
jar and the whole sample was mixed for another hour with the vortex
mixer. The resulting paste was further mixed with a ceramic
three-roll mill and degassed in a vacuum chamber. The components
and parts by weight are disclosed in Table 1. TABLE-US-00001 TABLE
1 BARRIER SEALANT # 1 COMPONENT PARTS BY WEIGHT Oxetane in Example
3 35.3 Photoinitiator 0.7 ITX 0.1 Micron sized silica 63.1
Nanosilica rheology modifier 0.9 Total: 100.0
[0037] After the formulation was thoroughly mixed, 1-2 grams of
formulation material were placed on a TEFLON coated aluminum plate.
An eight-path variable scraper was used to cast an even thickness
of film. The sample was then placed inside a Dymax stationary
curing unit and cured for 70 seconds (3.3 J/cm.sup.2 UVA) with a
medium pressure mercury lamp. Irradiance on the sample surface was
measured with a UV Power Puck high energy UV radiometer (EIT Inc.,
Sterling, Va.) and was found to be 47 (UVA), 32 (UVB), 3 (UVC), 35
(UW) mW/cm.sup.2 respectively. Moisture permeation coefficient
(50.degree. C., 100% relative humidity) of the above film was
measured with Mocon Permeatran 3/33 and was found to be 3.1
gmil/100 in.sup.2day.
[0038] Adhesion performance was tested by applying two pieces of
tape (.about.5 mils) approximately a quarter of an inch apart on
TEFLON coated aluminum plates. Using a blade, the formulation was
drawn into a film between the tapes. The glass slides and the dies
were wiped clean with isopropanol and sonicated for ten minutes in
isopropanol. The slides and dies were removed from the isopropanol
and air-dried followed by 5 min UV ozone cleaning. The dies were
then placed in the film of formulation and slightly tapped to wet
out the entire die. The dies were picked from the formulation
coating and placed onto the slides. The dies were slightly tapped
to allow the formulation to wet out between the die and the slide.
The sealant formulations were cured in a Dymax UV curing unit with
3.3 J/cm.sup.2 UVA. The shear adhesion of the cured samples was
tested using a Royce Instrument 552 100K equipped with a 100 kg
head and a 300 mil die tool. The adhesion was found to be
44.7.+-.1.6 kg.
[0039] In another embodiment, the cationically curable barrier
composition will further consist essentially of an adhesion
promoter, preferably a silane adhesion promoter. The effect of the
addition of a silane adhesion promoter was investigated by adding
3.5 wt % Silquest A-186 silane (based on the total formulation) to
the formulation in Table 1. Moisture permeation of the cured sample
(3.3 J/cm.sup.2 UVA) was found to be 3.1 gmil/100 in.sup.2day and
the die shear was 17.0.+-.4.0 kg, sufficient for some commercial
applications.
Example 6
Oxetane-Based Barrier Sealant 2
[0040] Oxetane resins may be combined with platelet fillers such as
talc in order to reduce moisture permeability. A formulation was
prepared similarly to Example 5. The components and parts by weight
are disclosed in Table 2. After curing with 6.0 J/cm.sup.2 UVA, the
permeation coefficient was 4.2 g-mil/100 in.sup.2day at 50.degree.
C., 100% relative humidity. TABLE-US-00002 TABLE 2 BARRIER SEALANT
#2 COMPONENT PARTS BY WEIGHT Oxetane in Example 3 58.8
Photoinitiator 1.2 ITX 0.2 Filler: Vertal 410 talc 39.8 Total:
100.0
Example 7
Synthesis and Performance of an Aromatic Epoxy-Oxetane Hybrid
[0041] ##STR14##
[0042] 3-Hydroxybenzyl alcohol (24.8 g, 0.2 mol),
3-methyl-3-bromomethyl oxetane (36.3 g, 0.22 mol), potassium
carbonate fine powder (30.4 g, 0.22 mol), and 200 mL methyl ethyl
ketone were combined in a four neck, 1000 mL round bottom flask
equipped with a condenser and mechanical stirrer. The reaction was
heated to 65.degree. C. in an oil bath with stirring, and heating
and stirring were continued for a total of five days. The solid was
filtered off and the liquid portion was washed with 3% aqueous NaOH
solution followed by water. Solvent removal by rotary evaporator
gave a low viscosity liquid.
[0043] This liquid (40.0 g, 0.19 mol) was combined with allyl
bromide (36.3 g, 0.3 mol), NaOH (12.0 g, 0.3 mol),
tetrabutylammonium bromide (0.82 g, 0.0025 mol), and 100 mL toluene
in a four-neck, 1000 mL round bottom flask equipped with a
mechanical stirrer and condenser. The reaction was heated to
65.degree. C. with stirring, and the color changed from brown to
orange within ten minutes. Heating and stirring were continued
overnight. Finally, the solid was filtered off and toluene was
removed to give the allylated oxetane product, which was purified
by vacuum distillation.
[0044] Epoxidation of the allylated oxetane was conducted by
combining 17.5 g (0.1 mol) of 3-chloroperoxybenzoic acid in 225 mL
of dichloromethane in a four-neck, 500 mL round bottom flask
equipped with a mechanical stirrer and thermometer. The flask was
chilled to 0.degree. C. in an ice/water bath, and 20.5 g of the
above allylated oxetane product dissolved in 50 mL of
CH.sub.2Cl.sub.2 was added dropwise over 2.5 hours. The flask was
warmed to room temperature one hour later, and stirring continued
for three days. The solid was filtered off to obtain a clear,
orange liquid. The CH.sub.2Cl.sub.2 solution was washed with
saturated NaHCO.sub.3 solution in water and then three times with
water.
[0045] The organic layer was collected and dried over sodium
sulfate. The CH.sub.2Cl.sub.2 was removed by rotary evaporation.
Purification by vacuum distillation gave 1.5 g of pure hybrid
epoxy-oxetane product at 155.degree. C./147 micron. This product
was a clear, colorless liquid. .sup.1H NMR (CDCl.sub.3): .delta.
ppm 1.45 (3H), 2.61-2.82 (2H), 3.19 (1H), 3.43-3.80 (2H), 4.04
(2H), 4.45 (2H), 4.46-4.58 (2H), 4.62-4.64 (2H), 6.86-6.95 (3H),
7.25-7.29 (1H). This product was mixed with a photoinitiating
system (2.0 wt % cationic photoinitiator SR1012 and 0.12% ITX) and
cured with 3.3 J/cm.sup.2 UVA. Permeation of the cured film was 6.3
gmil/100 in.sup.2day at 50.degree. C., 100% relative humidity.
Example 8
Synthesis and Performance of a Cycloaliphatic Epoxy-Oxetane
Hybrid
[0046] ##STR15##
[0047] A four-neck, 500 mL round bottom flask equipped with
mechanical stirrer and condenser was charged with 150.0 g (0.2 mol)
hydroxycyclopentadiene (TCI America), 165.0 g (0.24 mol)
3-methyl-3-bromomethyl oxetane (Chemada), 9.6 g (0.24 mol) sodium
hydroxide, 0.64 g (1.0 mol %) tetrabutylammonium bromide (TBAB),
and 100 mL toluene. The reaction mixture was heated at 80.degree.
C. in an oil bath for two hours, and the temperature was then
increased to 110.degree. C. for 24 hours. An additional 26.4 g
(0.16 mol) 3-methyl-3-bromomethyl oxetane, 6.4 g (0.16 mol) sodium
hydroxide, and 0.64 g TBAB were added and stirring continued for 24
hours. The mixture was filtered and toluene was removed by rotary
evaporation, and the oxetane product was separated by vacuum
distillation.
[0048] Next, 13.8 g (0.061 mol) of 77% m-chloroperoxybenzoic acid
(mCPBA) and 200 mL dichloromethane were combined to form a 0.4 M
solution in a 500 mL round bottom flask equipped with mechanical
stirrer and thermometer, and chilled to 0.degree. C. in an
ice/water bath. Using an additional funnel, 12.3 g (0.0525 mol)
above oxetane product dissolved in 65 mL dichloromethane was added
dropwise to the mCPBA solution over 1.5 hours. The mixture was
warmed to room temperature and allowed to stir for another 24
hours.
[0049] After the reaction, the mixture was filtered, and the
dichloromethane solution was washed with 70 mL saturated
NaHCO.sub.3 solution, and then with 70 mL water three times. The
organic layer was collected and dried over sodium sulfate, and the
dichloromethane was removed by rotary evaporation. Vacuum
distillation gave the desired product as a colorless liquid in
10.5% yield. .sup.1H NMR (CDCl.sub.3): .delta. ppm 1.29 (3H),
1.27-2.32 (11H), 3.24-3.41 (2H), 3.43-3.50 (2H), 4.32-4.34 (2H),
4.46-4.50 (2H). The resin was combined with a photoinitiating
system (2.0 wt % cationic photoinitiator SR1012 and 0.24 wt % ITX).
The formulation cured well and the moisture permeation coefficient
was 6.6 milg/100 in.sup.2 day at 50.degree. C., 100% relative
humidity.
Example 9
Effect of Aromatic Substitution on Permeation Coefficient
[0050] The oxetanes in Examples 1 to 4 were each blended with a
photoinitiating system (2 wt % photoinitiator GE 9380C) and cured
with 6.0 J/cm.sup.2 UVA followed by annealing at 175.degree. C. for
one hour. The permeation coefficient of the cured films were
measured and are reported in Table 3. As the data indicate, the
meta-substituted oxetanes in examples 1 and 3 are better moisture
barrier materials than their para-substituted counterparts,
examples 2 and 4.
[0051] The permeation coefficient of a 50/50 (wt/wt) solution of
the oxetane in example 3 and an aromatic epoxy (EPON 862) using a
photoinitiating system of 2 wt % cationic photoinitiator (UV 9380C)
was compared with the permeation coefficient of the oxetane in
example 4. Again, the meta-substituted oxetane formulation resulted
in lower permeation coefficient. As shown in table 3, one may also
tailor the moisture barrier performance of the cured samples by
choosing different epoxies.
[0052] In the following formulations brominated BPADGE is
brominated bisphenol A diglycidyl ether and has the structure:
##STR16## EPON 862 has the structure: ##STR17##
[0053] EPON 828 has the structure ##STR18## TABLE-US-00003 TABLE 3
PERMEATION COEFFICIENT (g mil/100 in.sup.2 day at 50.degree. C.,
100% relative humidity) OF VARIOUS FORMULATIONS 50/50 50/50 50/50
(WT) (WT) WITH (WT) WITH WITH BY EPON EPON BROMINATED OXETANE
ITSELF 862 828 BPADGE Oxetane in 7.0 -- -- -- example 1 Oxetane in
9.4 -- -- -- example 2 Oxetane in 5.9 6.2 -- -- example 3 Oxetane
in 9.5 10.5 11.0 9.1 example 4
Example 10
Oxetane/Epoxy Blends with Various Fillers
[0054] In this example, epoxy/oxetane formulations with different
fillers were tested and compared. The results are reported in Table
4 and indicate that, in general, platy fillers such as talc work
better at reducing moisture permeation (formulations A, B, C in
table 4) than nanosilica fillers (formulation D), on an equal
weight basis. The results further indicate that aromatic epoxy EPON
862 in formulation D is a better barrier material than aromatic
epoxy EPON 828 in formulation E, when used in cationic UV curable
systems. It is also possible to use both talc and silica as fillers
for better barrier performance as shown in formulations F and G. No
difference in permeation was observed when nanosilica filler was
replaced with micron sized silica. TABLE-US-00004 TABLE 4
PERMEATION COEFFICIENTS OF OXETANE/EPOXY BLENDS WITH VARIOUS
FILLERS FORMULATION COMPONENTS A B C D E F G Oxetane in example 3
24.7 24.7 Oxetane in example 4 32.9 32.9 32.9 32.9 32.9 Aromatic
epoxy 32.9 32.9 32.9 32.9 24.7 24.7 Epon 862 Aromatic epoxy 32.9
EPON 828 Cationic photoinitiator 1.0 1.0 SR1012 Cationic
photoinitiator 1.3 1.3 1.3 1.3 1.3 UV 9380C Photosensitizer 0.1 0.1
ITX Filler 32.9 Vertal 7 talc Filler 32.9 FDC talc Filler 32.9 33.0
33.0 Mistrofil P403 talc Filler 32.9 32.9 16.5 Nanosilica Filler
16.5 Micron sized silica Total 100.0 100.0 100.0 100.0 100.0 100.0
100.0 Permeation Coefficient 5.7 9.3 5.4 7.7 8.8 3.5 3.5 g mil/100
in.sup.2 day at 50.degree. C., 100% RH
Example 11
Oxetane/Vinyl Ether Formulation
[0055] Oxetanes may be blended with diluents, such as vinyl ethers,
in UV curable cationic formulations. In this example, a
cycloaliphatic vinyl ether (CAVE) having the below structure was
used as a reactive diluent and the resulting formulation exhibited
a very low moisture permeation coefficient. The formulation and
results are reported in Table 5. ##STR19## TABLE-US-00005 TABLE 5
PERMEATION COEFFICIENT OF OXETANE/VINYL ETHER FORMULATION
COMPONENTS PARTS BY WEIGHT Oxetane in example 3 17.5 CAVE 11.7
Photoinitiator (GE9380C) 0.87 Photosensitizer (ITX) 0.045 Micron
sized silica 69.9 Total 100.0 Viscosity (cP) 10 rpm 6,676 1 rpm
9,420 Permeation Coefficient 2.8 g mil/100 in.sup.2 day at (3
J/cm.sup.2 UVA) 50.degree. C., 100% RH
Example 12
Oxetane/Epoxy Blends with Different Additives
[0056] Oxetane/epoxy resin mixtures may also be blended with
diluents, such as vinyl ethers or alcohols in UV curable cationic
formulations. The formulation and results are reported in Table 6.
Cure speed was measured with a Perkin Elmer Differential Scanning
Calorimetry 7 equipped with a UV light source. TABLE-US-00006 TABLE
6 OXETANE/EPOXY BLENDS WITH DIFFERENT ADDITIVES COMPONENTS PARTS BY
WEIGHT Oxetane in example 3 4.0 4.0 4.0 Aromatic epoxy 4.0 4.0 4.0
EPON 862 Cationic Photoinitiator SR1012 0.16 0.16 0.16 CAVE 0.82
Tricyclodecane dimethanol (Aldrich) 0.82 Curing Speed Excellent
Excellent Fair Time to Peak Exotherm(min) 0.13 0.12 0.78 Time to
90% Total Exotherm (min) 0.69 0.69 1.78 .DELTA.H (J/g) 294 271 328
Permeation Coefficient 6.3 6.4 7.2 g mil/100 in.sup.2 day at
50.degree. C., 100% RH (cured with 3 J/cm.sup.2 UVA)
Example 13
Properties and Performances of Oxetane/Epoxy/Talc Formulations with
Various Oxetane/Epoxy Ratios
[0057] UV cure speed and the reactivity of a perimeter sealant is
critical to production throughput, and the minimization of thermal
processing is generally required for many display applications. UV
curing kinetics and thermodynamics can be measured using
differential photocalorimetry ("photo DSC"). The cure speed for a
series of oxetane/epoxy/talc formulations with various
oxetane/epoxy ratios are reported in Table 7. Differential
photocalorimetry was performed on the samples using a Perkin-Elmer
Differential Scanning Calorimeter 7 equipped with a Hg-arc lamp UV
light source. All samples were cured through an indium/tin oxide
(ITO)-coated sodalime glass.
[0058] Each of the resin combinations contains oxetane (OXT-121,
Toagosei), EPON 862 aromatic epoxy, 35 wt % talc (Mistrofil P403
talc), and a photoinitiating system of 2.0 wt % cationic
photoinitiator (SR1012), and 0.21 wt % ITX (all based on total
weight). For each barrier sealant, the time from UV initiation to
maximum curing exotherm was recorded, as well as the time taken to
reach 90% of the observed UV curing exotherm. Shorter time to peak
and time to 90% conversion are indications of good curing
performance.
[0059] As the table indicates, good curing performance and good die
shear adhesion were observed for formulations K, L, M where the
oxetane/epoxy ratio ranged from 75:25 to 25:75. Most significantly,
the fastest UV cure speed came from a 50:50 mole ratio of the
oxetane and epoxy, which has the sharpest and narrowest exothermic
peak. In addition, die shear adhesion of the oxetane rich (H, I)
formulations were found to be better than epoxy rich (M, N)
formulations. TABLE-US-00007 TABLE 7 PROPERTIES AND PERFORMANCES OF
OXETANE/EPOXY/TALC FORMULATIONS WITH VARIOUS OXETANE/EPOXY RATIOS
OXT 121: Cure EPON Viscosity Speed (min) Die shear 862 (cPs) Time
to Time to Adhesion Formula (mole) 1.0 rpm 10.0 rpm Peak 90% (kg) H
100:0 2,867 1,597 0.43 3.92 40.9 I 95:5 4,096 2,252 0.27 4.44 40.9
J 75:25 8,601 4,198 0.17 0.93 45.2 K 50:50 7,987 4,301 0.12 0.70
44.4 L 25:75 11,870 6,553 0.13 1.73 44.2 M 5:95 15,560 9,093 0.15
2.04 33.1 N 0:100 18,020 10,420 0.20 2.34 35.5
Example 14
Permeability of Oxetane/Epoxy Blends with Various
Photoinitiators
[0060] Several cationic photoinitiators were used to cure 50/50 (by
weight) blends of OXT-121 oxetane and EPON 862 epoxy. The results
are reported in Table 8 and indicate there is little difference in
the permeabilities obtained using these different photoinitiators.
The loading of the photoinitiators were normalized so that equal
molar amounts of the active catalyst were used. The sulfonium salt
catalyst is proprietary to National Starch and Chemical Company.
TABLE-US-00008 TABLE 8 PERMEABILITY OF OXETANE/EPOXY BLENDS WITH
VARIOUS PHOTOINITIATORS PERMEATION FOR- LOADING (g mil/ MULA
PHOTOINITIATOR (WT %) 100 in.sup.2 day) O solid iodonium SR1012 1.0
10.1 salt P solid iodonium SR1012 1.0 10.3 salt with a perylene 0.1
sensitizer Q sulfonium salt proprietary 1.1 9.9 R liquid UV 9380C
2.0 9.1 iodonium salt I
[0061] Different levels of photoinitiator SR 1012 were also
explored using 50/50 (by weight) blends of OXT-121 oxetane and EPON
862 epoxy and the results are reported in Table 9. Within
experimental error, the change in the photoinitiator level did not
show significant impact on the moisture permeation performance of
the sealant. This clearly demonstrates that the barrier performance
of the sealants is mostly dominated by the choice of resins and
less affected by ways of curing. TABLE-US-00009 TABLE 9 VARIATIONS
IN PHOTOINITIATOR LEVEL PHOTOINITIATOR PERMEATION LOADING (WT %) (g
mil/100 in.sup.2 day) 0.25 9.6 0.50 9.3 1.00 10.1 2.00 9.7 3.00
10.1
Example 15
Curing of Oxetane/Epoxy Blends by Heat
[0062] A series of oxetane (OXT-121) and epoxy (EPON 862) resin
blends were prepared and cured by heat. The oxetane and epoxy
blends at different weight ratios were polymerized using DSC ramp
from room temperature to 300.degree. C. at 10.degree. C./min. Each
sample contained 2.0% cationic photoinitiator (SR1012). The onset,
peak temperatures and total heat of polymerization are reported in
Table 10. TABLE-US-00010 TABLE 10 CURING OF OXETANE/EPOXY BLENDS BY
HEAT RATIO OXETANE:EPOXY 100:0 67:33 50:50 33:67 0:100 ONSET
(.degree. C.) 138 135 133 138 171 PEAK (.degree. C.) 158 153 158
203 214 .DELTA.H (J/G) 627 724 681 637 646
* * * * *