Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-06-08
2004-02-03
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S264000, C526S266000, C526S273000, C526S283000, C525S326900
Reexamination Certificate
active
06686425
ABSTRACT:
BACKGROUND OF THE PRESENT INVENTION
The present invention is directed to a high Tg acrylic polymer and an epoxy-blend thereof for use as a pressure sensitive adhesive.
Liquid crystal displays are used in many applications such as but not being limited to computer screens, calculator screens, telephone displays, electronic game displays and the like. Such displays are commonly manufactured utilizing liquid epoxy adhesives to form the perimeter seal for the display component containing the liquid crystal material. Epoxy resins have conventionally been used due to the structural stability and resistance to chemical attack. Such liquid epoxy adhesives, although acceptable for this purpose, require specialized mixing and dispensing equipment to apply the adhesive to the perimeter of the components to be bonded. The respective components must also be maintained in place during subsequent curing of the epoxy. It is a further disadvantage that the curing step requires undesirably high temperatures for undesirably long periods of time. The use of such high curing temperatures prohibits use of heat-sensitive plastics in the production of the displays. While glass substrates are not heat-sensitive, manufacturers desire to replace glass components of liquid crystal displays with plastic components. It would thus be desirable to provide an alternative method and adhesive composition for use in manufacturing liquid crystal displays or for adhering heat-sensitive plastic materials. It would also be desirable to provide an adhesive for use in the lamination of glass or plastic substrates, such as in the production of wave guides which are comprised of multiple layers of glass or plastic, which adhesive can be used in lieu of liquid adhesives and which may be thermocured at desirable temperatures.
OBJECTS AND SUMMARY OF THE PRESENT INVENTION
It is accordingly an object of the present invention to provide an adhesive composition that may be used as a perimeter seal in the production of liquid crystal displays.
It is accordingly a further object of the present invention to provide an adhesive composition that may be used to bond heat-sensitive plastic materials.
It is still further an object of the present invention to provide a method for the production of a liquid crystal display or other visual display devices by use of an improved adhesive composition.
In accordance with the present invention, there is thus provided a high Tg acrylic polymer comprised of the polymerization reaction product of the following monomers:
(1) an alkyl (meth)acrylate monomer whose homopolymer has a Tg>20° C.;
(2) optionally a C
1-30
(meth)acrylate monomer;
(3) a nitrogen-containing polar monomer; and
(4) an epoxy-containing monomer,
said monomers being present in an amount such that the Tg of said polymer is greater than 50° C.
In accordance with the present invention, there is further provided a pressure sensitive adhesive comprised of a thermocurable blend of an epoxy resin and a high Tg acrylic polymer comprised of the polymerization reaction product of the following monomers:
(1) an alkyl (meth)acrylate monomer whose homopolymer has a Tg>20° C.;
(2) optionally a C
1-30
(meth)acrylate monomer;
(3) a nitrogen-containing polar monomer; and
(4) an epoxy-containing monomer,
said monomers being present in an amount such that the Tg of said polymer is greater than 50° C.
The adhesive of the present invention may be used with advantage in the production of liquid crystal display (as a perimeter seal) or in the production of other optical devices such as wave guides where the adhesive is used to bond together multiple layers of glass or plastic upon being applied to substantially the entire opposing surface of the glass or plastic substrates, and subsequently being thermally cured.
In a preferred embodiment, the alkyl (meth)acrylate monomer is t-butyl methacrylate monomer, the C
1-30
(meth)acrylate monomer is a C
4-18
(meth)acrylate monomer, the nitrogen-containing polar monomer is an N-vinyl lactam monomer, and the epoxy-containing monomer is a glycidyl monomer.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
The thermocurable pressure sensitive adhesive of the present invention is comprised of a blend of an epoxy resin and a high Tg acrylic copolymer.
The novel high Tg acrylic copolymer of the present invention is comprised of the polymerization reaction product of an alkyl (meth)acrylate monomer whose homopolymer has a Tg>20° C., optionally a C
1-30
(meth)acrylate monomer, a nitrogen-containing polar monomer, and an epoxy-containing monomer, each as defined below. The monomers are present in an amount such that the Tg of the resulting polymer is greater than 50° C.
The alkyl (meth)acrylate monomer may be selected from but not limited to the group consisting of t-butyl (meth)acrylate, hexadecyl acrylate, isobornyl (meth)acrylate, cyclododecyl acrylate, methyl methacrylate, secondary butyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate and mixtures thereof.
The optional C
1-30
(meth)acrylate monomer used in the present invention may comprise a monomeric (meth)acrylic acid ester of a non-tertiary alcohol wherein the alcohol portion has from 4 to 18 carbon atoms. Exemplary (meth)acrylate monomers include but are not limited to esters of (meth)acrylic acid with non-tertiary alcohols such as 1-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 1-methyl-pentanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 2-ethyl-1-butanol, 3,5,5-trimethyl-1-hexanol, 3-heptanol, 2-octanol, 1-decanol, 1-dodecanol, etc.
Exemplary monomeric (meth)acrylate monomers having a carbon chain of at least 12 carbon atoms include but are not limited to lauryl acrylate (C
12
), tridecylacrylate (C
13
), myristyl acrylate (C
14
), palmityl acrylate (C
16
) and stearyl acrylate (C
18
). Such monomers are well-known to those skilled in the art.
The at least one nitrogen-containing polar monomer may be selected from a wide range of suitable monomers. Such monomers include, for example, vinyl monomers having at least one nitrogen atom. Such monomers include but are not limited to N-mono-substituted acrylamides, such as a (meth)acrylamide, N-methylacrylamide, N-ethylacrylamide, N-methylolacrylamide, N-hydroxyethylacrylamide and diacetone acrylamide; N,N-disubstituted acrylamides such as N,N-dimethylacrylamide, N,N-diethylacrylamide, N-ethyl-N-aminoethylacrylamide, N-ethyl-N-hydroethylacrylamide, N,N-dimethylolacrylamide, and N,N-dihydroxyethylacrylamide, etc.
Exemplary nitrogen-containing monomers may also include but are not limited to N-vinyl lactam monomers such as N-vinyl-2-pyrrolidone, 5-methyl-N-vinyl-2-pyrrolidone, 5-ethyl-N-vinyl-2-pyrrolidone, 3,3-dimethyl-N-vinyl-2-pyrrolidone, 3-methyl-N-vinyl-2-pyrrolidone, 3-ethyl-N-vinyl-2-pyrrolidone; 4-methol-N-vinyl-2-pyrrolidone; 4-ethyl-N-vinyl-2-pyrrolidone; N-vinyl-2-valerolactam; N-vinyl-2-caprolactam; N-vinyl-2-piperidone; and N,N-dimethylacrylamide and mixtures of any of the foregoing. The corresponding allyl derivatives thereof are also suitable for use in the present invention. The noted lactams may also be substituted in the lactam ring by one or more lower alkyl groups having from 1 to 4 carbon atoms, with methyl, ethyl, or propyl groups being particularly preferred. The N-vinyl lactam monomer employed preferably comprises N-vinyl-2-pyrrolidone.
The polymerizable epoxy-containing monomer may be selected from a variety of vinyl-terminated epoxy-containing monomers. Exemplary polymerizable monomers include but are not limited to glycidyl esters of an &agr;,&bgr;-ethylenically unsaturated carboxylic acid, such as (meth)acrylic or crotonoic acid.
Exemplary glycidyl monomers for use in the present invention accordingly include but are not limited to glycidyl (meth)acrylate, glycidyl ethacrylate and glycidyl itaconate, acryl glycidyl ether, (meth)allyl glycidyl ether and 3,4-epoxy-1-vinylcyclohexane.
The alkyl (meth)acrylate monomer is present in the copolymerizable reactant mixture in an amount ranging from about 20 to 80 percent by weight, the polymerizable C
1-30
McKinney Kevin J.
Wigdorski Robert M.
Zajackowski Michael J.
Adhesives Research Inc.
Birch & Stewart Kolasch & Birch, LLP
Pezzuto Helen L.
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