Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2000-06-28
2002-04-23
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C560S081000
Reexamination Certificate
active
06376704
ABSTRACT:
TECHNICAL FIELD
This invention relates to naphthyloxyalkyl(meth)acrylate compounds with a high refractive index and whose respective homopolymer has a low glass transition temperature.
BACKGROUND
Adhesives or coatings used in optical applications preferably have a refractive index closely matched to the refractive index of a substrate to which they are applied. The matched refractive indices reduce glare and reflectance at the interface between the substrate and coating materials and enhance the optical performance of the construction.
Polymeric substrate materials typically used in optical applications have refractive indices of about 1.48 to about 1.65, such as, for example, polymethyl(meth)acrylate (1.489), polycarbonate (1.585), and polyethylene terephthalate (1.64). However, many polymeric coatings and adhesives intended for application to these substrates have refractive indices that differ substantially from the refractive indices of the substrates. The mismatched refractive indices may cause glare and reflectance at the interface between the materials.
Reactive chemical monomers can be used, alone or in combination with other materials, to produce adhesives and coatings with high indices of refraction. However, these adhesive and coating compositions may have other less desirable physical and chemical properties. For example, certain naphthalene derivatives of Formula 1 below have an index of refraction of about 1.57-1.58:
wherein R
1
is H or CH
3
, R
2
is CH
2
CH
2
O or CH(CH
3
)CH
2
O, X is H, and m is 1. While the refractive index of the monomers in Formula 1 may match well with polymeric substrates commonly used in optical applications, homopolymers made from known compounds of this type typically have a glass transition temperature (Tg) of about 25 to about 40° C. For this reason, polymers including these monomeric units would be expected to be essentially non-tacky at or near room temperature (about 20 to about 30° C.), which limits their usefulness in optical adhesives and flexible coatings.
SUMMARY
In one aspect, the invention is a naphthyloxyalkyl(meth)acrylate monomer with an index of refraction of greater than about 1.55 and a glass transition temperature of its respective homopolymer of less than about 10° C. The naphthyloxyalkyl(meth)acrylate monomers include a (meth)acrylate functional group and a naphthyloxy functional group linked by an alkyl functional group.
The preferred naphthyloxyalkyl(meth)acrylate monomers of the invention have the general Formula 2:
wherein L is a straight chain or branched alkyl group containing greater than 5 carbon atoms, preferably from about 6 to about 8 carbon atoms, and R is H or CH
3
.
In a second aspect, the invention is a polymerizable composition containing the monomer of Formula 2. The polymerizable composition can contain one or more other compatible comonomers.
In a third aspect, the invention is a polymer or polymeric material including a chemical segment of Formula 3:
wherein L is a straight chain or branched alkyl group containing greater than 5 carbon atoms, preferably from about 6 to about 8 carbon atoms, and R
1
is H or CH
3
. The polymers with the monomeric segment of Formula 3 have a low glass transition temperature of less than about 10° C., and are well suited for use in optical adhesives and flexible coating compositions. The adhesives and coating compositions made from the monomers of the invention would be expected to reduce glare and reflectance when applied to a polymeric substrate with a similarly high refractive index.
In a fourth aspect, the invention is an optical element including a composition with the polymer or polymeric material with the segment of Formula 3.
In a fifth aspect, the invention is an optical device including a composition with the polymer or polymeric material with the segment of Formula 3.
In a sixth aspect, the invention is a method for reducing glare and/or reflectance on a substrate that includes coating the substrate with a composition with the polymer or polymeric material with the segment of Formula 3.
The details of one or more embodiments of the invention are set forth in the description below. Other features, objects, and advantages of the invention will be apparent from the description and from the claims.
DETAILED DESCRIPTION
The invention is a naphthyloxyalkyl(meth)acrylate monomer with a high refractive index and whose respective homopolymer has a low glass transition temperature. The monomers have specific index of refraction, melting point, and viscosity properties that are particularly suited for use in polymeric materials intended for application to a substrate in an optical element or an optical device.
As used within the present description, “monomer” refers to a monomer on an individual (i.e., molecular) scale, and also to a composition of such monomers on a macroscopic scale such that the composition can be described as having a physical state of matter (e.g., liquid, solid, etc.) and physical properties (e.g., melting point, viscosity, glass transition temperature (of a polymeric form), and index of refraction).
The naphthyloxyalkyl(meth)acrylate monomers of the invention have an index of refraction of at least about 1.54, preferably between about 1.54 and 1.56. “Index of refraction,” or “refractive index,” refers to the absolute refractive index of a material (e.g., a monomer), which is understood to be the ratio of the speed of electromagnetic radiation in free space to the speed of the radiation in that material, with the radiation being of sodium yellow light at a wavelength of about 583.9 nanometers (nm). Index of refraction can be measured by known methods, and is generally measured using an Abbe Refractometer.
Homopolymers of the naphthyloxyalkyl(meth)acrylate monomers of the invention have a Tg below about 10° C., preferably less than about 7° C., and most preferably less than about 5° C. “Glass transition temperature,” (Tg), is the temperature range over which a thermoplastic polymer changes from a brittle, glass state to a plastic state. Glass transition temperature of a composition can be measured by methods known in the art, such as Differential Scanning Calorimetry (DSC), modulated DSC (MDSC), or Dynamic Mechanical Analysis (DMA).
The naphthyloxyalkyl(meth)acrylate monomers include a (meth)acrylate functional group and a naphthyloxy functional group linked by an alkyl functional group.
The alkyl group is a divalent organic hydrocarbon group. The alkyl group, which is preferably unsubstituted, can be straight or branched and includes greater than 5 carbon atoms, more preferably from 6 to 8 carbon atoms. The size of the alkyl group can affect the physical properties of the monomer and a polymer prepared from the monomer including, for example, the refractive index of the monomer and the refractive index and glass transition temperature of a polymer prepared from the monomer. While not wishing to be bound by any theory, a relatively larger alkyl group may result in a monomer or a polymer with a relatively lower index of refraction compared to an otherwise similar monomer or polymer having a relatively smaller alkyl group. Again, while not wishing to be bound by any theory, relatively larger or more branched alkyl groups may provide a monomer which, when polymerized, has a relatively lower Tg compared to a polymer prepared from otherwise similar monomers having relatively smaller or less branched alkyl groups.
The naphthyloxy group in the monomer of the invention is also preferably unsubstituted.
The (meth)acrylate group in the monomer of the invention can be prepared by methods well known to those skilled in the art. The naphthyloxy alkanol intermediates can be esterified with (meth)acyloyl chloride using a suitable base. They can also be prepared by condensation with (meth)acrylic acid, or by transesterification using, for instance, methyl (meth)acylate. Suitable inhibitors can be added to the reactions during the synthesis of the monomers to prevent premature polymerization of the monomers.
Examples of useful naphthyloxy alkyl acrylate
3M Innovative Properties Company
Fagan Lisa M.
Killos Paul J.
Oh Taylor
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