MXPA06008619A - Polarizing beam splitter comprising a presure-sensitive adhesive - Google Patents

Abstract

A polarizing beam splitter (PBS) includes a multilayer reflective polarizing film, a pressure sensitive adhesive is disposed on the multilayer reflective polarizing film, a first rigid cover is disposed on the pressure sensitive adhesive. The PBS can be used in a variety of applications.

Description

POLARIZING BEAM DIVIDER COMPRISING A PRESSURE-SENSITIVE ADHESIVE FIELD OF THE INVENTION The present invention is directed in general to polarizing beam splitters and to the use of such devices in, for example, systems for displaying information, and more particularly to reflective projection systems. BACKGROUND OF THE INVENTION Imaging systems commonly include a transmitter or a reflective image former, also referred to as a light valve or a light valve arrangement, which superimposes an image on a light beam. The light transmitting valves are typically translucent and allow the passage of light through them. The reflective light valves, on the other hand, reflect only selected portions of the inserted light beam to form an image. Reflective light valves provide important advantages, as control circuits can be placed behind the reflective surface and more advanced integrated circuit technology can be achieved when the substrate materials are not limited by their opacity. New configurations of compact and potentially less expensive liquid crystal display (LCD) configurations can reach Ref.:i74575 made possible by the use of reflective micro-screens of liquid crystal as the image former. Many of the reflective LCD imagers rotate the polarization of light incidence. In other words, the polarized light is reflected either by the imager with its polarization state substantially unchanged for the dark state or with a degree of polarization rotation imparted to provide a desired scale of grays. A rotation of 90 ° provides the state of brilliance in these systems. Accordingly, generally a polarized beam of light is used as the input beam for the reflective LCD imagers. A desirable compact array includes a cross light path between a polarizing beam splitter (PBS) and the image former, wherein the illumination beam and the projected image reflected from the imager share the same physical space between the PBS and the imager. The PBS separates the incoming light from the polarized-rotated image light. A conventional PBS used in a projector system, sometimes referred to as a MacNeille polarizer, uses a stack of inorganic dielectric films placed at Brewster angle. The light that counts polarization-s is reflected, while the light in the polarization-p state is transmitted through the polarizer.

A simple imager can be used to form a monochromatic image or a color image. Multiple image producers are typically used to form a color image, where the lighting light is divided into multiple beams of different colors. An image is superimposed on each of the beams individually, and these beams are then recombined to form a complete color image. SUMMARY OF THE INVENTION In general, the present invention relates to an apparatus for improving the performance of a projection system. In particular, the invention is based around a core of images that includes improvements in the image quality, stability and lifespan of a polarizing beam splitter (PBS). The present invention provides a PBS that includes a pressure sensitive adhesive disposed between a multilayer reflective polarizing film and a rigid cover. The combination of the pressure sensitive adhesive between the multi-layer reflective polarizing film and the rigid cover can reduce the stress-induced birefringence within the PBS assembly. Additionally, the combination of the pressure sensitive adhesive disposed between the reflective polarizing film and the rigid cover can provide a PBS assembly that exhibits improved image quality., improved assembly stability, and improved service life over other adhesives. The use of two (or more) films in the PBS construction of the present invention can decrease the diffusion that reaches the projection screen and can be formed effectively by lamination. The two film constructions can be used with any material as a cover (for example, prisms). Such materials include glass. The glass can have any refractive index although the index is typically in the range of 1.4 to 1.8 and can be found in the range of 1.4 1.6. This low-index crystal can reduce astigmatism. One embodiment of the present invention provides a polarizing beam splitter (PBS) that includes a multi-layer reflective polarizing film, and a first rigid cover is disposed over the pressure sensitive adhesive. A second rigid cover may be disposed adjacent the multilayer reflective polarizing film. An optional structural adhesive may be disposed between the multi-layer reflective polarizing film and the second rigid cover. Another embodiment of the present invention is directed to a polarizing beam splitter (PBS) that includes a first multilayer reflective polarizing film and a second multilayer reflective polarizing film proximate the first multilayer reflective polarizing film. A larger surface of the second multi-layer reflective polarizing film is directed towards a larger surface of the first multi-layer reflective polarizing film. An adhesive is disposed between the first multi-layer reflective polarizing film and the second multi-layer reflective polarizing film. A first pressure sensitive adhesive is disposed on the first multi-layer reflective polarizing film. A first rigid cover is disposed on the pressure sensitive adhesive and a second rigid cover is disposed adjacent to the second multi-layer reflective polarizing film. Another embodiment of the present invention is directed to a projection system that includes a light source for generating light and an image forming core for superimposing an image on the light generated by the light source to form image light. The image core includes at least one polarizing beam splitter and at least one image producer. The polarizing beam splitter includes: a multilayer reflective polarizing film; a pressure sensitive adhesive disposed on the multilayer reflective polarizing film and between the light source and the multi-layer reflective polarizing film; and a first rigid cover disposed over the pressure sensitive adhesive. The system also includes a projection lens system for projecting image light from the image core. Another embodiment of the present invention is directed to a method for manufacturing a polarizing beam splitter which includes supplying a pressure sensitive adhesive between a multilayer reflective polarizing film and a first rigid cover to form a polarizing beam splitter. The method may also include the placement of a second rigid cover adjacent to the multi-layer reflective polarizing film. An optional structural adhesive can be supplied between the polarizing film, multi-layer reflective and the second rigid cover. Another embodiment of the present invention is directed to a method for manufacturing a polarizing beam splitter which includes: supplying a first pressure sensitive adhesive between a first multi-layer reflective polarizing film and a first rigid cover; supplying a second pressure-sensitive adhesive between a second multi-layer reflective polarizing film and a second rigid cover; and placing the first multi-layer reflective polarizing film adjacent to the second multi-layer reflective polarizing film to form a polarizing beam splitter. An optional structural adhesive can be supplied between the multi-layer reflective polarizing film and the second multi-layer reflective polarizing film. Other features and advantages of the invention will be apparent from the following description and from the figures, and from the claims. X - BRIEF DESCRIPTION OF THE FIGURES The invention can be better understood completely by considering the following detailed description of various embodiments of the invention in connection with the appended figures, in which: Figure 1 schematically illustrates a mode of a PBS that counts with a multilayer reflective polarizing film, - Figure 2 schematically illustrates one embodiment of a PBS having two multilayer reflective polarizing films; Figure 3 illustrates schematically one embodiment of a projection unit based on a single reflective imager; and Figure 4 schematically illustrates another embodiment of a projection unit based on multiple reflective image generators. DETAILED DESCRIPTION OF THE INVENTION The present invention can be applied to optical generators and is particularly applicable to optical systems of large numerical aperture optical images that can produce projected, high quality and low aberration images.

An exemplary type of optical imaging system includes a Cartesian wide angle polarizing beam splitter (PBS), as discussed in US Patent No. 6,486,997 Bl, with the title REFLECTIVE LCD REFLECTION SYSTEM USING WIDE-ANGLE CARTESIAN POLARIZING BEAM SPLITTER. A Cartesian PBS is a PBS in which the polarizations of the transmitted and reflected beams are referenced to principal axes, usually orthogonal and invariant of a PBS. In contrast, with a non-Cartesian PBS, the polarization of the separated beams is substantially dependent on the angle of incidence of the beams in the PBS. An example of a Cartesian PBS is a multilayer reflective polarizing film, which can be exemplified by a film that is formed of alternating layers of isotropic and birefringent material. If the plane of the film is considered to be the xy plane, and the thickness of the film is measured in the z-direction, then the refractive index-z is the refractive index in the birefringent material for the light that has an electric vector parallel to the z-direction. Similarly, the refractive index-x is the refractive index in the birefringent material for light that counts its electric vector parallel to the x-direction, and the refractive index-y is the refractive index in the birefringent material for light that has its electric vector parallel to the y-direction. For the multilayer reflective polarizing film, the refractive index-y of the birefringent material is substantially the same as the refractive index of the isotropic material, while the refractive index-x of the birefringent material is different from that of the isotropic material. If the thicknesses of the layers are properly selected, the film reflects visible light polarized in the x-direction and transmits polarized light in the y-direction. An example of a useful multi-layer reflective polarizing film is a z-index polarized film, in which the refractive index-z of the birefringent material is substantially the same as the refractive index-y of the birefringent material. Polarization films having an adjusted z-index have been described in U.S. Patent Nos. 5,882,774 and 5,962,114, and in the following co-assigned U.S. Patent Applications: 60 / 294,940, filed May 31, 2001; 2002-0190406, filed May 28, 2002; 2002-0180107, filed on May 28, 2002; 10 / 306,591, filed on November 27, 2002; and 10 / 306,593, filed November 27, 2002. Polarizing films having an adjusted z-index are also described in U.S. Patent 6,609,795. In some cases, polarizing beam splitters using polymer based on multilayer optical film (MOF) such as, for example, polarizing films of adjusted z-index or multilayer reflecting polarization, may have birefringence induced by tension in the PBS assembly and / or adhesive layers that are unstable over time. For consumer applications, durability / reliability and shelf life are some of the important criteria for useful PBS assemblies. The polymer assembly based on a multilayer optical film (MOF) for rigid substrates is challenged to meet the life and environmental requirements for the useful PBS assemblies. The adhesive must have a good adhesion for the MOF as well as the rigid substrate, and additionally, it does not induce tension in the MOF and / or the rigid substrate. PBS performance is sensitive to any voltage, and even very small voltages can result in degradation of PBS performance. The properties of the adhesive should be balanced with those of the MOF and the rigid substrate with the purpose of achieving the maximum stability and useful life of the PBS assembly. Structural adhesives can be reduced during curing and / or curing in a different way, which causes tension in the MOF and / or the rigid substrate. It is also possible that a fully cured structured adhesive undergoes a gradual cure by light and heat under normal use conditions, which may decrease the stability of the PBS. For the particular embodiment of two multilayer reflective polarizing films, a type of lead-free and fairly common type crystal, such as SK5, manufactured by Schott, can be used for the cover, as described in the US Patent Application Series No. 10. / 439,444 filed on May 16, 2003, entitled POLARIZING BEAM SPLITTER AND PROJECTION USING THE "" POLARIZING BEAM SPLITTER. The low index glass cover provides several important advantages over the high index glass cover, such as PBH56, including the reduction of astigmatism, lead free, and the removal of the antireflective coating on various optical surfaces. However, lead-free crystal is much less stable to light, heat, and mechanical induced stress. The low mechanical stress induced in the PBS assembly process could degrade optical performance, such as uniformity of contrast and darkness. The structured cured adhesive can induce mechanical stress in the lead-free crystal, such as SK5, and generate birefringence which causes an unacceptable dark non-uniform state. The pressure sensitive adhesive, with its low modulus and does not need to be cured during assembly, can induce much less stress on the glass; therefore, it can provide a much improved dark state uniformity. Additionally, the structural adhesives have a tendency to yellow and the effect of the optical properties of the PBS, after being exposed to high density light used with PBS assemblies.

The contrast of a PBS can be defined with reference to Figure 3, with the image producer 226 replaced with a quarter wave film laminated to the front surface of a mirror. When the quarter-wave film on a mirror is oriented with its optical axis at 45 ° towards the direction of polarization of the central beam of the illumination beam, it will function as a quarter-wave film oriented at 45 ° towards a transmitted polarized beam: in this case, the polarization direction of the beam will rotate by 90 °. Due to the previously described function of the PBS, this will result in substantially all of the light that is reflected from the sling-room film / mirror that is projected through the lens 228 on the screen. If the quarter-sling film is otherwise oriented at 0o toward the polarization state of the center ray, it will behave like a half-wave film oriented with the polarization state of a transmitted beam of light and leaves the polarization direction of the beam without change. This will result substantially in the total light that is directed back to the light source by the PBS, without being projected onto the screen by the lens 228. To measure the contrast ratio of the PBS, the state of brightness flows through the the projection lenses 228 are first characterized by orienting the optical axis of the quarter-wave film / mirror at 45 degrees towards the polarization direction of the central beam of the light illumination beam.This flow can be characterized by measuring the illuminance of the beam at a fixed distance from the lens 228, by collecting the total projected light into an integrating sphere with a calibrated photodiode, or by other available means known to persons skilled in the art.The dark state is then produced by the orientation of the quarter-wave film so that its optical axis is aligned with the polarization state of the central beam of the illumination beam. The lens 228 resulting from this state is then measured with the use of the same technique used to characterize the flow in the state of brightness providing a measurement of the contrast ratio, or the quarter wave film contrast ratio. For some types of image producers, for example producers of Ferro-electric Liquid Crystal images, the dark state is very similar to that produced in the test described above. However, for most other types of image producers the dark state is more similar to that produced by a mirror without a quarter wave film on it. In this case, only as regards the quarter-wave film mirror at 0o, there is no rotation of the polarization direction of the illumination beam, and in this way a dark image will be obtained. In order to test the performance of the PBS for these types of image producers, it is desirable to use a pure mirror to provide the dark state, but otherwise to follow the same prescription as previously provided to characterize the contrast ratio of the PBS. . The result is referred to as the mirror contrast ratio of the PBS. The difference between the proportion of mirror contrast and - the quarter wave film contrast ratio has to do with the behavior of several oblique rays. Help for understanding this difference can be obtained from US Patent 5,327,270, although the prior art only applies to the MacNeille PBS systems and not to the Cartesian PBSs. For our purposes, it is sufficient to understand that the combination of quarter-wave film mirror compensates for the polarization of a number of causes, and that it may be important to test both types of contrast to ensure good results with all types of producers of images . The contrast of PBS made with multilayer reflective polarizing films depends on several parameters, including, for example, index differences together with the address not adapted (for example, x-direction), the degree of index adjusted in the direction of coupling of the interior plane (for example, y-direction), the degree of index of coupling in the thickness direction (eg, z-direction), and the total number of film layers. The index difference between the layers along the decoupled direction and the index of coupling along the coupled direction (s) are limited by the pair of polymer resins. Moreover, the polymer resins are preferably substantially transparent in the range of visible spectrum (or any range spectrum will be of interest in the application of PBS) from blue to green for red light. A pair is described later in the Examples and includes polyethylene terephthalate (PET) and a PET copolymer (coPET). These polymers are substantially transparent with respect to the total visible wavelength range, including blue light. However, the index difference of these polymers along the decoupled direction is only about 0.15. To achieve the desired level of contrast in an optical system as described below, an adjusted z-index polarizing film utilizing this combination of polymers typically uses a pair of high index crystal cousins. 'When using high-index glass with the PBS film two effects can occur: generation of astigmatism in the PBS, and an increase in the decompensation of the brightness of the dark mirror state. An approach to the elimination of astigmatism is described in co-assigned US Patent 6,672,721 and US Patent Application No. 2003-0048423. These describe the use of a 'very high index glass plate near the film to compensate for astigmatism. However, this plate can add significant cost to the PBS. -In addition, the use of such a plate can cause "a longer back focal length and a more difficult lateral color situation for the projection lens." Additionally, a PBS that has a compensation plate may require a larger color combination cube. Additionally, the high index PBS crystal causes light to propagate at very high angles within the PBS film.If a crystal with a refractive index of less than 1.6 is used for the PBS, then the contrast for the dark mirror state does not compensated is typically about the same as the contrast obtained with a quarter-wave oriented film arranged on the mirror.According to how it is used here, the term "dark state of uncompensated mirror" is defined the dark state obtained when a mirror Naked is used in its place of the imager in an image system, such as those described below, and the transmission of light is observed. sultant through the image system. When the index of the crystal is reduced to 1.85, the value of the dark uncompensated state is reduced to less than half the contrast with the quarter-wave film arranged on the mirror, particularly when an index adaptation layer is used. for coupling the high birefringence glass prisms with the multi-layer reflective polarizing film and thereby reduce reflections. This loss in contrast can be claimed by the placement of a quarter wave film on the mirror or image former that is aligned with its fast axis along the polarization direction of the incoming light. However, these special compensation plates (for example, the quarter-wave film) can increase the cost and make it difficult to align it. Therefore, a technique for using a PBS film in a low index crystal (for example, n <; 1.60) would decrease the cost by eliminating the need for dark mirror state compensation plates such as a quarter wave film. An approach for eliminating light diffusion in a PBS assembly is described in US Patent Application Serial No. 10 / 439,444, filed May 16, 2003, entitled POLARIZING BEAM SPLITTER AND PROJECTION SYSTEM USING THE POLARIZING BEAM SPLITTER. This reference describes the use of two multilayer reflective polarizing films in a PBS assembly to reduce light diffusion.

Figure 1 illustrates one embodiment of a polarizing beam splitter 10 utilizing a multilayer reflective polarizing film in accordance with the present invention. In this embodiment, the polarizing beam splitter 10 includes a multilayer reflective polarizing film 12. The film 12 can be any suitable multi-layer reflective polarizing film known in the art, preferably a polarizing film of index-s adjusted. A pressure sensitive adhesive (PSA) 60 is provided on the multi-layer reflective polarizing film 12. A first rigid cover 30 is disposed on the pressure sensitive adhesive 60. A second rigid cover 40 is adjacent to the multilayer reflective polarizing film 12. An adhesive layer 50 may be provided between the second rigid cover 40 and the multi-layer reflective polarizing film 12. The adhesive layer may be a structural adhesive. Although depicted as including two prisms 30 and 40, the PBS 10 may include any appropriate cover (s) disposed on one or either side of the multilayer reflective polarizing film 12. Prisms 30 and 40 may be constructed of any material light transmitter having an appropriate refractive index to achieve the desired purposes of the PBS. The prism should have lower refractive indices than those that would create an internal reflection condition, in this case, a condition where the angle of propagation approaches or exceeds 90 ° under conditions of normal use (for example, where the incidence light is normal to one side of the prism). Such a condition can be calculated with the use of Snell's law. Preferably, the prisms are made of isotropic materials although other materials may be used. A "light transmitting" material is one that allows at least a portion of incident light to be transmitted from the light source through the material. In some applications, the incident light can be pre-filtered to eliminate undesirable wavelengths. Suitable materials to be used as raw materials include, but are not limited to, ceramics, glass, and polymers. A particularly useful category of crystal includes crystals that contain a metal oxide such as lead oxide. A commercially available crystal is PBH 55, available from Ohara Corporation (Rancho Santa Margarita, CA, USA), which has a refractive index of 1.85 and has approximately 75% lead oxide by weight. The PBS assembly 10 may have a rigid high intensity light cover 30 and a rigid low intensity light cover 40. The high intensity light rigid cover 30 is the rigid cover that is closest to the light source (see Figures 3 and 4). The rigid high intensity light cover 30 undergoes light at a higher intensity than the rigid low intensity light cover 40. It is desirable to place the pressure sensitive adhesive 60 between this high intensity rigid cover of light 30 and the film Multilayer Reflective Polarizing 12. The optical and physical properties of a pressure-sensitive adhesive, as described below, the pressure-sensitive adhesive remains stable under a high intensity of light.The adhesive layer 50 can be any adhesive or a pressure sensitive adhesive Figure 2 illustrates one embodiment of a polarizing beam splitter 110 utilizing two or more multilayer reflective polarizing films (multilayer reflective polarization) in accordance with the present invention In this embodiment, the beam splitter polarizing sensing 110 includes a first multi-layer reflective polarizing film 112, a second reflective polarizing film multilayer suede 120, and an adhesive layer 150 between the first film 112 and the second film 120. One or both of the first and second films 112 and 120 may be any suitable multilayer reflective polarizing film known in the art., preferably adjusted z-index polarizing films. The adhesive layer 150 can be a structural adhesive. Although the PBS 110 includes the first and second films 112 and 120 respectively, three or more movies can also be used. A first pressure sensitive adhesive 160 is disposed on the first multi-layer reflective polarizing film 112. A second pressure sensitive adhesive or adhesive layer 161 is disposed on the second multi-layer reflective polarizing film 120. A first rigid cover 130 is disposed on the first pressure sensitive adhesive 160. A second rigid cover 140 is disposed on the second pressure sensitive adhesive or adhesive layer 161. Although depicted as including two prisms 130 and 140, the PBS 110 can. suitable cover (s) disposed on one or either side of the first and second multilayer reflecting polarizing films 112 and 120. Prisms 130 and 140 can be constructed with any light transmitting material having an appropriate refractive index to achieve the desired purpose of the PBS. Premiums should have refractive indices lower than those that would be created in a total internal reflection condition, in this case, a condition where the angle of propagation approaches or exceeds 90 ° under conditions of normal use (for example, in where the incident light is normal with respect to one face of the prism). Such a condition can be calculated with the use of Snell's law. Preferably, the prisms are manufactured from isotropic materials, although other materials may be used. A "light transmitting" material is one that allows to transmit through the material at least a portion of incident light from the light source. In some applications, incident light can be prefiltered to eliminate undesirable wavelengths. Materials suitable for use as raw materials include, but are not limited to, ceramics, crystals, and polymers. A low index material can be used for prisms 30 and 40, for example, crystal SK5 manufactured by Schott Corporation (Mainz, Germany) particularly when two or more films are used. The PBS assembly 110 may have a rigid high intensity light cover 130 and a low light intensity rigid cover 140. The rigid high intensity light cover 130 is the rigid cover that is closest to the light source (see Figures 3 and 4). The rigid high intensity light cover 130 undergoes light at a higher intensity than the rigid low intensity light cover 140. It is desirable to place the pressure sensitive adhesive 160 between this rigid high intensity light cover 130 and the polarizing film. reflective multilayer 112. The optical and physical properties of a pressure sensitive adhesive, according to what is described below, allow the pressure sensitive adhesive to remain stable during a high intensity of light. The adhesive layer 150 can be either a structural adhesive or a pressure sensitive adhesive. Adhesive layer 161 can be either a structural adhesive or a pressure sensitive adhesive. Pressure sensitive adhesives (PSA) are known to those skilled in the art. Useful pressure sensitive adhesives can be, for example, substantially free of substantially unreacted, substantially unreacted monomers and oligomers and / or photoinitiators. PSA materials are preferably substantially free of UV-absorbing chromophores such as extended aromatic structures or conjugated double bonds. The Council of Sensitive-Pressure Tapes (Test Methods for Pressure Sensitive Adhesive Tapes (1994), Pressure Sensitive Tape Board, Chicago, IL) has defined pressure sensitive adhesives as materials with the following properties.- (1) aggressive and permanent adhesiveness, (2) adhesion with a pressure not greater than that imposed with the fingers, (3) sufficient capacity to support on a carrier substrate, (4) sufficient cohesive strength, and (5) does not require activation by any energy source. PSAs are usually adhesives at the assembly temperature, which typically is the ambient temperature or higher (in this case, approximately 20 ° C or up to approximately 30 ° C or higher). The materials that have been discovered to function as PSAs are the polymers designed and formulated to show the required viscoelastic properties that result in a desired balance of adhesiveness, adhesion detachment, and shear-holding power at assembly temperature. The polymers most commonly used to prepare PSAs are polymers based on natural rubber, synthetic rubber (for example, styrene / butadiene copolymers (SBR) and styrene / isoprene / styrene copolymer blocks (SIS)), silicone elastomers , -poly-alpha olefins, and several (meth) acrylates (e.g., acrylate and methacrylate) (Handbook of Pressure Sensitive Adhesive Technology, 2nd Edition, edited by D. Satas, 1989). Of these, the PSAs of polymer based on (meth) acrylates have evolved as a preferred class of PSA for the present invention due to their optical clarity, permanence of properties over time (stability in aging), and versatility of the levels of membership, to name a few of its benefits. It is known as prepares PSAs that comprise mixtures of certain polymers based on - (meth) crilate with other certain types of polymers (Handbook of Pressure Sensitive Adhesive Technology, 2nd Edition, edited by D. Satas, page 396, 1989). Suitable pressure sensitive adhesives include, but are not limited to, PSAs Soken 1885, 2092, 2137 (commercially available from Soken Chemical &; Engineering Co., Ltd, Japan) and the PSAs described in US Patent Applications Series No. 10 / 411,933, filed April 11, 2003, entitled ADHESIVE BLENDS, ARTICLES, AND METHODS. A structural adhesive is a material used to bond high strength materials, such as wood, composites, plastics, glass, or metal, whereby the practical strength of the adhesive bond exceeds 6.9 MPa (1000 psi) at room temperature. Due to performance demands, structural adhesives generally take part during curing and / or crosslinking reaction by an external energy source such as UV or heat during assembly leading to the development of the final adhesive properties (Structural Adhesives - Chemistry and Technology, Edited by SR Hartshorn, 1986). Structural adhesives can be classified in various ways, such as by their physical form, chemical compositions, and curing conditions of the adhesives. Examples of structural adhesives commonly include phenolics, epoxies, acrylics, urethanes, polyamides and bismaleimides, as described in the Adhesion and Adhesives Technology book - An Introduction, page 184, AV Pocius, 1997. Polarizing films multilayer reflective elements include, for example, that described in US Patent No. 5,882,774. One embodiment of a suitable multilayer reflective polarizing film includes the alternation of layers of two materials, at least one of which is birefringent and oriented. Films which work well in glass prisms may have additional characteristics to provide the appropriate values of the refractive indices for each layer, especially in the direction normal to the surface of the film. In particular, the refractive indices in the direction of the film thickness of alternating layers are ideally adjusted. This is in addition to the indices in the y-direction (step direction) of the polarizer that is adjusted. --For a polarizer have a high transmission along its pitch axis for all angles of incidence, both indexes y and z (normal to the film) of the alternating layers can be coupled. Reach a link for both indexes y and z can be used a different material for the film layers than the one used when only the index is coupled and. The oldest multi-layer 3M films, such as the 3M brand film "DBEF", where they were manufactured with an adaptation of the indexes and. Surprisingly, the use of a PSA layer between the multilayer reflecting polarizing film and the high intensity light side of the PBS assembly improves the optical properties and the life span of the PBS assembly even with a structural adhesive disposed between the multilayer reflective polarizing film. and the side of low intensity of light and / or between multilayer reflective polarizing films. Suitable structural adhesives include, for example: N0A61, a UV curable thiol-ene based adhesive available from Norland Company (Cranbury, NJ); UV-cured acrylic adhesives Loctite series (e.g., 3492, 3175) available from Henkel Loctite Corp., 1001 Trout Brook Crossing, Rocky Hill, CT 06067 (www.loctite.com). UV-cured acrylic adhesives OP series (eg, 21, 4-20632, 54, 44) available from Dy ax Corporation, 51 Greenwoods Road, Torrington, CT, 06790 (http: // dymax. Com /). One technique for coupling both indices y and z of the total layers is to impart a true uniaxial elasticity where the film is allowed to relax (in this case, contract) in both directions y and z while it is stretching in the x direction. When the film is stretched in such a way, the refractive indices y and z are the same in a given layer. Then it turns out that if a second material is selected to fit the index and the first material, the z index must also be coupled because the second layers of material are also subjected to the same stretching conditions. In general, the decoupling in the index between the "and" indices of the two materials should be small for high transmission in the pass state while maintaining a high reflectance in the blocking state. The allowed magnitude of the index decoupling can be described in relation to the decoupling of the index x because the last value suggests the number of layers used in the stack of polarizing thin films to obtain a desired degree of polarization. The total reflectivity of a stack of thin films is correlated with the? N of the decoupling of the index and the number of layers in stack N, in this case, the product of (? N) 2xN is correlated. with the reflectivity of a pile. For example, to provide a film of the same reflectivity but with half the number of layers requires (2) 1/2 times the index differential between layers, and so on. The absolute value of the ratio? N? /? Nx is the relevant parameter that is desirable to control, where? N? = N? L ~ nY2 and? Nx = nX? -nX2 for the first material and the second material in a optical repeat unit as described in this description. It is preferred that the absolute value of the ratio of? N? /? Nx is not greater than 0.1, more preferably not greater than 0.05, and even more preferably not greater than 0.02, and in some case, this ratio may be 0.01 or less . Preferably, the ratio? N? /? Nx is kept below the desired limit over the entire range of wavelength of interest (in this case, over the visible spectrum). Typically,? N? has a value of at least 0.1 and can be 0.14 or greater. In many practical applications, a small decoupling of the z-index between these layers is acceptable, depending on the angle of incidence that the light makes with the film layers. However, when the film is laminated between glass prisms, in this case, immersed in a high index medium, the light rays are not deflected towards the normal with the film plane. In this case, a ray of light will detect the decoupling of the z-index with a much greater degree compared to the incidence of air, and a ray of polarized-x light will be partially or even strongly reflected. A coupling of the closest index x may be preferred by light rays having a greater angle towards the normal of the film within the film. However, when the film is laminated between glass prisms that have a lower refractive index (eg, n = 1.60), the light rays are deviated more towards the normal with the plane of the film; therefore, the light rays will sense the decoupling of the z-index to a lesser degree. With the same decoupling of the z-index, the reflection of polarized-p light will be generally lower when using low-prism prisms than when using high index prisms. The light-polarized-p transmission, therefore, may be higher when using low-index prisms than when using high-index prizes with the same films. The allowed magnitude of the decoupling of the z-index, as well as the decoupling of the index y, can be described in relation to the decoupling of the index x. The absolute value of ratio? Nz /? Nx is the relevant parameter that is desirable to control, where? Nz = nZ? ~ Nz2 and? Nx = nX? -nX2 for the first material and the second material in a repeating unit optics according to what is described here. For a beam divider film intended for use in air, the absolute value of the ratio? Nz /? Nx is preferably less than 0.2. For a film immersed in a higher index medium such as glass, the absolute value of the ratio? Nz /? Nx is preferably less than 0.1 and more preferably less than 0.05, and may be 0.03 or less for incident light having a length wave at 632.8 nm. Preferably, the ratio? Nz /? Nx is kept below the desired limit over the total wavelength range of interest (eg, over the visible spectrum). Typically,? Nx has a value of at least 0.1 and can be 0.14 or greater at 632.8 nm. The decoupling of the z-index is relevant for the transmission of polarized light-s normally. By definition, polarized light does not nominally feel the refractive index of a film. However, as described in co-assigned US Patent No. 6,486,997 Bl, entitled REFLECTIVE LCD PROJECTION SYSTEM USING WIDE-ANGLE CARTESIAN POLARIZING BEAM SPLITTER, the reflective properties of multi-layer birefringent polarizers at various azimuthal angles are such that performance of the projection system is superior when the PBS is configured to reflect polarized-x light (approximately polarized-s) and transmits polarized-y light (approximately polarized-p). The optical power or integrated reflectance of a multilayer optical film is derived from the decoupling of the index within an optical unit or pair of layers, although more than two layers can be used to form the optical unit. The use of multilayer reflective films include alternating layers of two or more polymers to reflect light is known and is described, for example, in U.S. Patent No. 3,711,176; U.S. Patent No. 5,103,337; World Patent 96/19347; and World Patent 95/17303. The placement of this optical power in the optical spectrum is a function of the thickness of the layer. The reflection and transmission spectrum of a particular multilayer film depends mainly on the optical thickness of the individual layers, which is defined as the product of the actual thickness of a layer and its refractive index. Accordingly, the films can be projected to reflect infrared, visible, or ultraviolet light wavelengths by selecting the appropriate optical thickness of the layers according to the following formula:? M = (2 / M) * Dr where M is an integer representing the particular order of the reflected light and Dr is the optical thickness of an optical repeat unit, which is typically a pair of layers that includes a layer of an isotropic material and a layer of an anisotropic material . Therefore, Dr is the sum of the optical thicknesses of the individual polymer layers that make up the optical repeat unit. Dr, therefore, is a lambda medium in thickness, where lambda is the wavelength of the first-order reflection peak. In general, the reflective peak has a finite bandwidth, which increases with the increase in the index difference. Due to the variation of the optical thickness of the optical repeating units together with the thickness of the multilayer film, a multilayer film can be projected to reflect light over a wide band of wavelengths. This band is commonly referred to as the band reflection or band elimination. The resulting collection of bands in this band is commonly known as a multilayer stack. Thus, the optical thickness distribution of the optical repeat units within the multilayer film manifests itself in the reflection and transmission spectrum of the film. When the index coupling is very high in the direction of passage, the transmission spectrum of the passage state can be almost flat and above 95% in the desired spectrum range. Various thickness distributions of optical thicknesses can be used in the films of the present invention. For example, the thickness distributions of one or both films may vary monotonically. In other words, the thickness of the optical repeat unit shows a consistent tendency either to decrease or increase along the thickness of the multilayer reflective polarizing film (for example, the thickness of the optical repeat unit does not show a trend of increase along part of the thickness of the multilayer film and a tendency of decrease along part of the thickness of the multilayer film). Back to Figure 2, the first film 112 includes a plurality of layers having a first distribution of optical thicknesses. In addition, the second film 120 includes a plurality of layers having a second distribution of optical thicknesses. The first distribution and second distribution of optical thicknesses can be any suitable distribution known in the art. For example, the first and second distributions may include such distributions with those described in U.S. Patent No. 6,157,490 entitled OPTICAL FILM WITH SHARPENED BANDEDGE.

In addition, for example, the first distribution can exhibit the same distribution of the optical thicknesses as well as that of the second distribution. Alternatively, the first and second distributions may exhibit different distributions of optical thicknesses.

The multilayer reflective polarizing films useful in the present invention can include thickness distributions that include one or more bundles of strips. A band pack is a multilayer stack having a range of layer thickness such that a wide band of wavelengths is reflected by the multilayer stack. For example, a blue band package can have an optical thickness distribution such that it reflects blue light, in this case, approximately 400 nm to 500 nm. The multilayer reflective polarizing films of the present invention may include one or more band packets each reflecting a different wavelength band, for example, a multilayer reflective polarizer having a red, green and blue packet. The multilayer reflective polarizing films useful in the present invention can also include UV and / or IR band packages. In general, blue packages include optical repeating unit thicknesses so the package tends to reflect blue light and, therefore, will have optical repeating unit thicknesses that are less than the optical repeating unit thicknesses of the packages green or red The bundles of strips can be separated within a multilayer reflective polarizing film by one or more internal delimiting layers. Increasing the angle of incidence of light in a multilayer stack can cause the stack to reflect light of a shorter wavelength than when the light is "normal incident to the stack." An IR packet can be provided to help reflect red light the rays that are incidents in the stack at the higher angles According to what has been described, US Pat Nos. 5,882,774 and 5,962,114, the multilayer reflective polarizing films have a unique transmission or reflection spectrum. that the different multilayer reflective polarizing films can exhibit different contrast ratios for different wavelengths and incident polarizations, where the contrast ratio is defined as the ratio of transmitted intensities of light to that of desired transmission (e.g. polarized light-p) on the light with the desired polarization of reflection (for example, polarized light-s). For example, the first film 112 may have a first contrast ratio spectrum, a first transmission spectrum, or first reflection spectrum, and the second film 120 may have a second contrast spectrum, a second transmission spectrum, or a second reflection spectrum. The first spectrum of contrast ratio, the first transmission spectrum, or first reflection spectrum may coincide with the second spectrum of contrast ratio, second transmission spectrum, or second reflection spectrum, respectively, for a wavelength band default Alternatively, the first contrast ratio spectrum, the first transmission spectrum, or the first reflection spectrum may be different from (and in some cases, spectrally switched from) the second contrast ratio spectrum, the second transmission ratio spectrum , or second reflection ratio spectrum, respectively, according to what is further described herein. As illustrated further in Figure 2, the second film 120 is placed proximate the first film 112 whereby a larger surface 122 of the second film 120 faces a larger surface 114 of the first film 112. The larger surfaces 114 and 122 of the first and second films 112 and 120 facing each other may come into contact, or the larger surfaces may be separated with an adhesive layer 150 disposed between the first film 112 and the second film 120. The larger surfaces 114 and 122 may be parallel as illustrated in Figure 2. Adhesive layers 50 and 150 may include an optical adhesive. Any suitable optical adhesive can be used, for example, thermally cured structural adhesive, photo curing structural adhesive, pressure sensitive adhesive, etc. For some multilayer reflective polarizing films, optical absorption can cause undesirable effects. To reduce optical absorption, the preferred multilayer stack is constructed so that the wavelengths that should be strongly absorbed by the stack are the wavelengths reflected by the stack. For most clear optical materials, including the poor majority of polymers, the absorption increases towards the blue end of the visible spectrum. Thus, it may be preferred to tune the multi-layer reflective polarizing film stack so that the "blue" layers, or packages, are on the incident side of the multilayer reflective polarizing film. Although the present invention provides polarizing beam splitters that include one or more multi-layer reflective polarizing films with a pressure sensitive adhesive disposed between a multilayer reflective polarizing film and the rigid cover, and systems using such polarizing beam splitters, they can use one or more multi-layer reflective polarizing films arranged on a pressure sensitive adhesive in other configurations or optical devices, eg, film constructions with improved brightness, polarizers, deployment applications, projection applications, and other optoelectronic applications. This combination of one or more multi-layer reflective polarizing films disposed on a pressure sensitive adhesive disposed on a pressure sensitive adhesive can generally be used to increase the optical stability of the PBS assemblies. One embodiment of the present invention may include a PBS that has substantially straight triangular prisms used to form a cube. In this case, the multilayer reflective polarizing film (s) is sandwiched between the hypotenuses of the two prisms, according to what is described herein. A cubic-shaped PBS can be preferred in several projection systems because it provides for a compact design, by. For example, the light source and other components, such as "-: filters, can be positioned to provide a small, portable, lightweight projector." Even though a cube is a modality, other forms of PBS can be used. For example, a combination of several prisms can be assembled to provide a rectangular PBS.For some systems, the cubic-form PBS can be modified so that one or more faces are not square.If non-square faces are used, a coupling, parallel to the face can be provided by the next adjacent component, such as the color prism or projection lens The dimensions of the prism, and the dimensions of the resulting PBS, depend on the intended application. liquid crystal in silicone (LCoS) described here with reference to Figure 4, the PBS can be 17 mm in length and width, with a height of 24 mm when using a small arc-type lamp of Hg pressure, such as the UHP type commercially available for sale by Philips Corp. (Aachen, Germany), with its beam prepared as a light F / 2.3 cone and presented for PBS cubes to be used with diagonal imagers 0.7 inches with an aspect ratio of 16: 9, such as imagers available from JVC (Wayne, NJ, USA), Hitachi (Fremont, CA, USA), or Three-Five Systems (Tempe, AZ, USA) . The F # of the beam and the size of the imager are some of the factors that determine the size of the PBS. A single layer multilayer reflective polarizing PBS assembly can be formed by the following method. A pressure sensitive adhesive can be provided (coated or laminated, for example) between a multi-layer reflective polarizing film and a rigid cover. The pressure sensitive adhesive can be arranged (coated or laminated), for example) either on multilayer reflective polarizing film or rigid cover. The pressure sensitive adhesive may be flexible enough so that the PSA can be flexed while being applied to the multilayer reflective polarizing film and / or rigid cover. By laminating or coating the PSA on the multilayer reflective polarizing film and / or rigid cover, it is possible, in some embodiments, to prevent noticeable air gaps from forming between the PSA and the multi-layer reflective polarizing film and / or the rigid cover. In an illustrative embodiment, the PSA may be disposed on the multilayer reflective polarizer to form a lamination of adhesive polarizing film. A second rigid cover can be placed adjacent to the lamination of adhesive polarizing film to form a polarizing beam splitter. An optional structural adhesive may be disposed between the lamination of adhesive polarizing film and the second rigid cover. The above PBS assembly can be formed without curing (thermal curing or cured photo, for example) of the pressure sensitive adhesive. However, if an additional structural adhesive is used to adhere the multi-layer reflective polarizing film to the second rigid cover, such structural adhesive may be cured by heat or light as desired. A multilayer two-layer reflective polarizing PBS assembly can be formed by the following method. A first pressure-sensitive adhesive may be disposed (coated or laminated, for example) between a first multi-layer reflective polarizing film and a first rigid cover, as described above. A second pressure sensitive adhesive may be disposed (coated or laminated, for example) between a second multi-layer reflective polarizing film and a second rigid cover, as described above. The first multilayer reflective polarizing film is then placed adjacent to the second multi-layer reflective polarizing film to form a polarizing beam splitter. An additional structural adhesive may be disposed between the first multi-layer reflective polarizing film and the second multi-layer reflective polarizing film. The PBS assembly can be formed without curing (photo cured or thermal cured, for example). Pressure sensitive adhesive. However, if an additional structural adhesive is used to adhere the second multilayer reflective polarizing film with the second rigid cover or the first multi-layer reflective polarizing film with the second multi-layer reflective polarizing film, such adhesive may be cured with heat or light as desired . The pressure sensitive adhesive described herein can be flexible, flexed or curved with a radius that can be used with the lamination and which can be effective to avoid the formation of noticeable air gaps between the lamination layers in this case, from 0.5 to 5 mm. The multi-film PBS of the present invention can be used in various optical imaging systems. The term "optical imaging system" as used herein means that it includes a wide variety of optical systems that reproduce an image for a viewer to, observe. The optical imaging systems of the present invention can be used, for example, in front or rear projection systems, projection screens, stereoscopic vision screens, virtual viewers, head-up displays, computer optical systems , and other optical display systems and viewers.A modality of optical imaging systems is illustrated in Figure 3, wherein the system 210 includes a light source 212, for example an arc lamp 214 with a reflector 216 for directing light 218 in one direction Light source 212 can also be a solid state light source, such as light emitting diodes or a laser light source. The system 210 also includes a PBS 220, for example, the single or multi-film PBS described herein. The polarized-x light, in this case, polarized in a direction parallel to the x-axis, is indicated by the circulated x. Light with polarization-and, in this case, polarized in a direction parallel to the y-axis, is indicated by a solid arrow. The solid lines indicate the incident light, while the dotted lines indicate the light that has been returned from a reflective imager 226 with a changed polarization state. The light. provided by the source 212 may be conditioned by the optical conditioning 222 before illuminating the PBS 220. The optical conditioning 222 changes the characteristics of the light emitted by the source 212 to characteristics that are desirable by the projection systems. For example, the optical conditioning 222 can alter one or more of the light divergences, the polarization state of the light, the spectrum of the light. Optical conditioning 222 may include, for example, one or more lenses, a polarization converter, a pre-polarizer, and / or a filter to eliminate undesirable infrared or ultraviolet light. The x-polarized components of the light are reflected by the PBS 220 towards the reflective image former 226. The liquid crystal mode of the reflective image former 226 can be smectic, nematic, or some other appropriate type of reflective image former. If the reflective imager 226 is smectic, the reflective imager 226 may be a ferroelectric liquid crystal display (FLCD) screen. The imager 226 reflects and modulates an image beam having y-polarization. The polarized-and reflected light is transmitted through the PBS 220 and is projected by a projection lens system 228, the design of which is typically optimized for each particular optical system, taking into account all the components between the lens system 228 and the imager (s). A controller 252 is coupled to the reflective imager 226 to control the operation of the reflective imager 226. Typically, the controller 252 activates the different pixels of the imager 226 to create an image in the reflected light. One embodiment of a multi-image projection system 300 is illustrated schematically in Figure 4. Light 302 is emitted from a source 304. Source 304 may be an arc or filament lamp, or any other appropriate light source to generate appropriate light to project images. The source 304 may be surrounded by a reflector 306, such as an elliptical reflector (as shown), a parabolic reflector, or the like, to increase the amount of light directed towards the projection engine. Light 302 is typically treated before being divided into different color bands. For example, light 302 can be passed through an optional pre-polarizer 308, whereby light of a desired polarization is directed towards the projection engine. The pre-polarizer may be in the form of a reflective polarizer, whereby the light reflected in the unwanted polarization state is redirected to the light source 304 for recycling. The light 302 can also be homogenized so that the imagers in the projection engine are illuminated uniformly. An approach to homogenize the light 302 through a reflective tunnel 310, although it should be appreciated that other approaches can be used to homogenize the light. In the illustrated embodiment, the homogenized light 312 passes through a first lens 314 to reduce the divergence angle. The light 312 is then incident on a first color separator 316, which may be, for example, a thin dielectric film filter. The first color separator 316 separates the light 318 in a first color band from the remaining light 320. The light 318 in the first color band can be passed through a second lens 322, and optionally a third lens 323, for controlling the size of the light beam 318 in the first incident color band on the first PBS 324. The light 318 passes from the first PBS 324 to a first image former 326. The former images reflect light of image 328 in a state of polarization that is transmitted through PBS 324 to a color combiner of cube-x 330. Imager 326 may include one or more compensation elements, such as a retarding element, to provide additional polarization rotation and thereby increase contrast in the image light. The remaining light 320 can be passed through a third lens 332. The remaining light 320 is then incident on a second color separator 334, for example a thin film filter or the like, to produce a light beam 336 in a second one. color band and a light beam 338 in a third color band. The light 336 in the second color band is directed towards a second imager 340 by means of a second PBS 342. The second imager 340 directs image light 344 in the second color band towards the color cube combiner. x 330. The light 338 in the third color band is directed towards a third imager 346 by means of a third PBS 348. The third imager 346 directs image light 350 in the third color band towards the combiner of color cube-x 330. The image light 328, 344 and 350 in the first, second and third color band is combined in the cube-x 330 color combiner and directed as a full-color image beam towards the optical projection 352. The optical polarization rotation 354, for example half-wave retardant plates or the like, can be conditioned between the PBSs 324, 342 and 348 and the cube-x color combiner 330 to control the polarization of the combined light in the color combiner 330 cube-x. In the illustrated embodiment, the polarization rotation optics 354 are arranged between the cube-x color combiner 330 and the first PBS 324 and the third PBS 348. Some, two or all three PBSs 324, 342, and 348 may include one or more multi-layer reflective polarizing films as described herein. It should be appreciated that the variations of the illustrated modality can be used. For example, rather than reflect light to the imagers and then transmit the image light, the PBSs can transmit light to the imagers and then reflect the image light. The projection systems described above are only examples; a variety of systems using the multi-film PBSs of the present invention can be designed. EXAMPLES The multilayer reflective polarizing films of the following examples are similar in construction and processing, they vary essentially only through their thicknesses and through secondary variations that result from the use of different pouring speeds that are needed to achieve these thickness variations. at constant melt pumping speeds. The films were extruded and stretched in accordance with the general methods described in US Patent 6,609,795 and in accordance with the general methods described in US Patent Application Serial No. 10 / 439,444, filed May 16, 2003, entitled POLARIZING BEAM SPLITTER AND PROJECTION SYSTEM USING THE POLARIZING BEAM SPLITTER. The acrylic PSAs used in the following examples are PSA Soken 1885 (commercially available from Soken Chemical &Engineering Co., Ltd, Japan) and the NEA PSA described in Example 1 of US Patent Application Serial No. 10 / 411,933. , presented on April 11, 2003, entitled ADHESIVE BLENDS, ARTICLES, AND METHODS. The PSA Soken 1885 is received as a solution with 20% solids in a solvent mixture of Ethyl Acetate / Toluene / MEK. After being compounded with the L-45 and E-5XM crosslinkers (also from Soken Co.) at a ratio recommended by Soken of Soken 1885 / L-45 / E-5XM = lKg / 1.78g / 0.64g. , the PSA Soken solution is ready to be coated in the production of the Soken 1885 PSA film for lamination. The NEA PSA was prepared in accordance with Example 1 of the US Patent Application Serial No. 10 / 411,933, for coating in the making of the PSA NEA film for lamination. The structural adhesives used in the following examples are all commercially available as indicated below. Lens Adheater (Type C59) is a thermally cured styrene-based adhesive available from Summers Optical, 1560 Industry Road, Post Office Box 380, Hatfield, PA 19440 (A Division of EMS Acquisition Corp., http: / www.emsdiasum.com / Summers / optical / cements / cements / cement s.hatml). NOA61 is a UV-curing thiol-ene based adhesive, which is available from Norland Company (Cranbury, NJ). The thermal N0A61 is a blend of UV cured N0A61 adhesive with 0.5% 2, 2'-azobis (2,4-dimethyl valeronitrile), commercially available from DuPont, Wilmington, DE, under the trade designation "Vazo 52". A number of adhesive / film PBS constructions were made in accordance with the following procedure. Procedures for manufacturing PBS optical cores using PSA Films and structural adhesives: 1. The Soken 1885 PSA solution above and the NEA PDA solution were coated by a knife coater over a removable cover (A31 cover -LINTEC OF AMERICA, INC., 64 Industrial Parkway, Woburn, Massachusetts 01888 U.S.A.) and thermally dried in an oven at 70 degrees C for 10 minutes at a dry thickness of 25 um for the respective PSA layers. The crosslinking reactions in the PSAs were completed during drying. No additional reaction is required for the PSA films during assembly, for example in Steps 2 and 3. 2. Samples of the PSA coated films were laminated with PBS films using a laminator and then cut to a specific size for the lamination with rigid glass prism. 3. The PSA films of die-cast reflective polarizing support were joined to the rigid glass prism by a manual roller. 4. For an optical core of PBS layers of individual multi-layer reflective polarizer, the Prisma / PSA / multilayer reflective polarizer construction was then joined to another prism by a structural adhesive. The adhesive was thermally cured at 60 degrees C for 24 hours. 5. For an optical core of two-layer reflective polarizing PBS, the Prisma / PSA / multilayer reflective polarizing construction was then joined with another Prisma / PSA / multilayer reflective polarizing construction by a structural adhesive. The structural adhesive was cured by a low intensity rear luminaire (UVA: 7.5 mW / cm2) for 10 minutes. The total exposure dose is 4.5 j / cm2. The above procedure was designed to form single layer or two layer multilayer reflecting polarizing PBS optical cores. PBS cores having a pressure-sensitive adhesive disposed between the prism and the multi-layer reflective polarizing film were found with results such as an improved lifetime by at least a factor of 2x compared to similar constructions having structural adhesive disposed between the prism and the multilayer reflective polarizing film. Additionally, these invented PBS cores exhibit a more uniform dark mirror state compared to similar constructions where a structural adhesive is disposed between the prism and the multilayer reflective polarizing film.

Illustrative embodiments of this invention are discussed and references have been made to make possible variations within the scope of this invention. These and other variations and modifications to the invention will be apparent to those skilled in the art without departing from the spirit of this invention, and it should be understood that this invention is not limited to the illustrative embodiments set forth herein, therefore, the invention is limited. only by the claims provided below It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (8)

2. Having described the invention as above, the content is claimed as property in the following claims. A polarizing beam splitter, characterized in that it comprises: a first multi-layer reflective polarizing film; a pressure sensitive adhesive disposed on the first multi-layer reflective polarizing film; a first rigid prism disposed on the pressure sensitive adhesive, a second rigid prism disposed adjacent to the first multi-layer reflective polarizing film. The polarizing beam splitter according to claim 1, characterized in that it further comprises structural adhesive disposed between the second rigid prism and the first multi-layer reflective polarizing film.
3. 3. The polarizing beam splitter according to claim 1, characterized in that the first prism is a crystal prism and the second prism is a crystal prism.
4. 4. The polarizing beam splitter according to claim 1, characterized in that the pressure sensitive adhesive is substantially free of photo initiators.
5. 5. The polarizing beam splitter according to claim 1, characterized in that the pressure sensitive adhesive is substantially unreacted or substantially free of unreacted oligomers.
6. 6. The polarizing beam splitter according to claim 1, further comprising: a second multilayer reflective polarizing film proximate the first multilayer reflective polarizing film, wherein a larger surface of the second multi-layer reflective polarizing film faces a larger surface of the first multilayer reflective.-polarizing film; and an adhesive disposed between the first multi-layer reflective polarizing film and the second multi-layer reflective polarizing film
7. 7. The polarizing beam splitter according to claim 6, characterized in that it further comprises a structural adhesive disposed between the second rigid prism and the second film Multilayer reflective polarizer.
8. 8. The polarizing beam splitter according to claim 6, further comprising a second pressure sensitive adhesive disposed between the second rigid prism and the second multi-layer reflective polarizing film. . The polarizing beam splitter according to claim 6, characterized in that it further comprises a structural adhesive disposed between the first multi-layer reflective polarizing film and the second multi-layer reflective polarizing film. 10. A projection system, characterized in that it comprises: a light source for generating light; an image core for superimposing an image on the light generated from the light source to form image light, wherein the image core comprises at least one polarizing beam splitter and at least one image former, wherein the polarizing beam splitter comprises: a multilayer reflective polarizing film; a pressure sensitive adhesive disposed on the multilayer reflective polarizing film and between the light source and the multi-layer reflective polarizing film; a first rigid prism on the pressure sensitive adhesive, and a projection lens system for projecting the image light from the image core, a second rigid prism disposed adjacent the multilayer reflective polarizing film. A method for manufacturing a polarizing beam splitter, characterized in that it comprises: arranging a first pressure sensitive adhesive between a first multi-layer reflective polarizing film and a first prism; and placing a second rigid prism to the first multi-layer reflective polarizing film to form a polarizing beam splitter. The method according to claim 11, characterized in that the laying step comprises arranging a first pressure sensitive adhesive on a first multi-layer reflective polarizing film to form a lamination of adhesive polarizing film and applying the adhesive polarizing film laminate on a first rigid prism. 13. The method according to claim 11, characterized in that it further comprises applying a structural adhesive between the first multi-layer reflective polarizing film and the second rigid prism. The method according to claim 12, characterized in that the step of applying comprises laminating the laminate of adhesive polarizing film onto a first rigid prism. 15. The method according to claim 11, characterized in that the step of disposing and placing are executed without curing the pressure sensitive adhesive. The method according to claim 11, characterized in that it further comprises: arranging a second pressure-sensitive adhesive between a second multi-layer reflective polarizing film and a second prism; and placing the first multi-layer reflective polarizing film adjacent to the second multi-layer reflective polarizing film to form a polarizing beam splitter. 17. The method according to claim 16, characterized in that it further comprises applying a structural adhesive between the first multi-layer reflective polarizing film and the second multi-layer reflective polarizing film. 18. The method according to claim 16, characterized in that the provision of a second: "pressure-sensitive adhesive comprises laminating a second pressure-sensitive adhesive on a second rigid prism.