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  Adhesives inhibiting formation of artifacts in polymer based optical elementsThe Patent Description & Claims data below is from USPTO Patent Application 20080079903. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001]This application claims the benefit of U.S. Provisional Application No. 60/827,659 (Attorney Docket No. 62467US002) filed on Sep. 29, 2006, which is incorporated herein by reference in its entirety. BACKGROUND [0002]Polarizing beam splitter (PBS) assemblies are found in a variety of optical imaging assemblies, such as front and rear projection systems, projection displays, head-mounted displays, virtual viewers, head up displays, optical computing, optical correlation, and other similar optical viewing and display systems. A PBS assembly may include at least one multilayer reflective optical polarizing film (MOF). In general, a MOF is a multi-layer polymer based film that functions as a polarizer and contains at least two different materials, at least one of which exhibits birefringence after uniaxial orientation. The MOF film is sandwiched between two prisms and functions to reflect a particular polarization of light while transmitting orthogonal polarizations. An adhesive is disposed between the MOF and a surface of at least one of the prisms to provide for structural integrity of the PBS assembly as well as provide optical coupling. [0003]One example of a PBS assembly use is in a liquid crystal on silicon (i.e., LCOS) rear projection television system. LCOS rear projection television systems generate relatively high amounts of light energy and heat. Impingement onto the PBS assembly of such light energy levels and heat, especially over time, can have significant adverse effects on the average lifetimes of PBS assemblies. More particularly, relatively high amounts of light energy and heat can reduce transmissivity of the MOF over time. SUMMARY [0004]There is a need for continuing improvements, whereby the stability and/or useful life of optical imaging assemblies, particularly those utilizing polarizing elements, can be extended in a manner that does not otherwise compromise their optical benefits. [0005]The present description includes a polarizing beam splitter, comprising a polymer based polarizing film. An adhesive layer is disposed on the polarizing film and a first optical element is disposed on the adhesive layer. The adhesive layer includes at least a crystallization inhibiting plasticizer component in an amount effective for inhibiting formation of (i) crystallized domains; (ii) particles; or (iii) a combination thereof that cause optical artifacts in the polarizing film. [0006]In another aspect, the present description provides an optical apparatus comprising a polymer based optical element and an adhesive disposed on the optical element. The adhesive comprises a crystallization inhibiting plasticizer component in an amount effective for inhibiting formation of (i) crystallized domains; (ii) particles; or (iii) a combination thereof in the optical element that cause optical artifacts in the optical element. [0007]Yet another aspect of the present description provides a polarizing beam splitter comprising a birefringent film having a plurality of first material layers and a plurality of second material layers. The first material layers include a polymer selected from the group consisting of polyethylene terephthalate and copolymers of polyethylene terephthalate and polyethylene naphthalate. The second material layers include a copolyester. The polarizing beam splitter further includes at least one prism comprising a base adjacent a first major surface of the birefringent film and an adhesive disposed between the first major surface and the birefringent film. The adhesive comprises at least a crystallization inhibiting plasticizer in an amount effective for inhibiting crystallization and/or particle formation in the polarizing film. [0008]Another aspect of the description provides a method of stabilizing a polymer based optical element comprising disposing an adhesive on a polymer based optical element. The adhesive comprises a crystallization inhibiting plasticizer component in an amount effective for inhibiting formation of (i) crystallized domains; (ii) particles; or (iii) combinations thereof, that cause optical artifacts in an adjacent polymer based optical element. The method further includes passing radiation through the adhesive and the optical element wherein crystallized domains and/or particles are inhibited from forming in the optical element. BRIEF DESCRIPTION OF THE DRAWING [0009]This description may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying drawings, in which: [0010]FIG. 1 schematically illustrates an embodiment of a PBS having a multilayer reflective polarizing film; [0011]FIG. 2 schematically illustrates an enlarged cross-section of a multilayer reflective polarizing film and adhesive; [0012]FIG. 3 schematically illustrates an enlarged perspective of a portion the multilayer reflective polarizing film; [0013]FIG. 4 schematically illustrates a projection system; [0014]FIG. 5 schematically illustrates another projection system; and, [0015]FIG. 6 illustrates a graph comparing a PBS having an adhesive(s) to a PBS that does not have such adhesive(s). DETAILED DESCRIPTION [0016]One aspect of this description relates to adhesives utilized in combination with a polymer based polarizing film for avoiding optical artifacts induced in such film when used, for example, in an optical imaging system that includes a Cartesian polarizing beam splitter ("PBS") of a kind used in projection systems. Particularly useful embodiments of the invention address the use of PBS's that are subject to continued exposures under relatively high light energy and heat conditions which tend to reduce stability and/or useful life of standard PBS assemblies. For example, after extended periods of use some MOF films can yellow and char in a relatively short time period following initiation of the formation of haze in the MOF films. This rapid and pronounced failure is a special concern when utilized in extremely expensive projection systems, such as rear projection television systems. [0017]It has been determined that the haze formed in polarizing films of PBS assemblies may be influenced by humidity and that average lifetimes are generally lower in dryer environments than in wetter environments. Accordingly, the average lifetimes of such PBS assemblies while operated under such relatively high light irradiance and associated heat especially in dry conditions are diminished significantly. [0018]While the following illustrated embodiments are described in the context of such a projection system, the principles and scope of the present invention are not limited thereby. Rather, the present invention is more broadly directed to adhesives particularly adapted for use in combination with polymer based optical elements, whereby optical artifacts, such as haze, can be minimized or eliminated. Hence, optical imaging systems described herein are exemplary of many different kinds in which the present invention is useful. [0019]FIG. 1 illustrates one embodiment of a polarizing beam splitter (PBS) assembly 10. A PBS assembly is an optical component that splits incident light rays into a first (transmitted) polarization component and a second (reflected) polarization component. PBS assembly 10 includes a thin film, polymer based, multilayer reflective polarizing film 12, at least one adhesive layer 14 adhered between mutually opposing surfaces of multilayer reflective polarizing film 12 and an optical substrate, such as prism 16; at least one adhesive layer 18 adhered between mutually opposing surfaces of multilayer reflective polarizing film 12 and an optical substrate, such as prism 20. PBS assembly 10 is similar to one described in commonly assigned U.S. Pat. No. 6,486,997 and to copending and commonly assigned US Patent Publication No. 2005/0168697A1. Continue reading... Full patent description for Adhesives inhibiting formation of artifacts in polymer based optical elements Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Adhesives inhibiting formation of artifacts in polymer based optical elements patent application. Patent Applications in related categories: 20080284984 - Projection device with a folded optical path and wire-grid polarizer - A folded projection display system includes a wire-grid polarizer placed immediately behind the system's imaging screen. The display system includes an image projector that projects an image beam containing light of a predetermined linear polarization toward the imaging screen. The wire-grid polarizer reflects the light in the image beam away ... ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Adhesives inhibiting formation of artifacts in polymer based optical elements or other areas of interest. ### Previous Patent Application: Apparatus and method for monitoring the position of a subject's hand Next Patent Application: Display systems with spatial light modulators Industry Class: Optics: image projectors ### FreshPatents.com Support Thank you for viewing the Adhesives inhibiting formation of artifacts in polymer based optical elements patent info. IP-related news and info Results in 0.18928 seconds Other interesting Feshpatents.com categories: Medical: Surgery , Surgery(2) , Surgery(3) , Drug , Drug(2) , Prosthesis , Dentistry |
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