Holographically-formed polymer dispersed liquid crystals with multiple gratings

Abstract

A multicolored reflection liquid crystal display device includes a pair of substrates having a reflective holographic polymer dispersed liquid crystal (H-PDLC) film disposed therebetween. The H-PDLC film contains at least two different reflection gratings capable of reflecting two different wavelengths of light. A multicolored reflection H-PDLC is obtained by simultaneously illuminating a plurality of regions of a film comprised of a mixture of a liquid crystal and a photo-polymerizable monomer with a plurality of holographic light patterns capable of providing liquid crystal layers of different spacings so as to obtain different reflection gratings in each of the regions. A mask is placed between each of the laser light beams and the film to form a pattern of light and dark regions on the film. Each mask is positioned such that at least one light region of a first beam pair coincides with at least one dark region of a second beam pair within the film. A multiple grating liquid crystal display device including an H-PDLC film having a first region comprising liquid crystal and matrix polymer layers forming a transmission grating and a second region comprising liquid crystal and matrix polymer layers forming a reflection grating capable of reflecting a preselected wavelength of light also is described.

What is claimed is:  
     
         1 . A single layered multispectral reflection liquid crystal display device, comprising: 
 a pair of substrates having a reflective holographic polymer dispersed liquid crystal (H-PDLC) film disposed therebetween,    the H-PDLC film comprised of liquid crystal and matrix polymer layers forming a plurality of different reflection gratings capable of reflecting and/or diffracting a plurality of different wavelengths of energy.    
     
     
         2 . The display of  claim 1 , wherein the substrate comprises ITO-coated glass or plastic.  
     
     
         3 . The display of  claim 1 , wherein the H-PDLC comprises three different reflection gratings capable of reflecting three different wavelengths of energy.  
     
     
         4 . The display of  claim 1  or  3 , wherein the different reflection gratings spatially overlap a region of the film.  
     
     
         5 . The display of  claim 1  or  3 , wherein the different reflection gratings are spatially non-overlapping.  
     
     
         6 . The display of  claim 1 , wherein the different reflection gratings are arranged in a preselected pattern.  
     
     
         7 . The display of  claim 1  or  3 , wherein the film comprises spectrally non-overlapping reflection gratings.  
     
     
         8 . The display of  claim 7 , wherein the spectrally non-overlapping reflection gratings are selected to reflect wavelengths of light from the group consisting of red-green-blue and cyan-magenta-yellow.  
     
     
         9 . The display of  claim 7 , wherein the reflection gratings further are spatially non-overlapping.  
     
     
         10 . The display of  claim 1 , wherein the reflection gratings are selected to provide a broadband reflection.  
     
     
         11 . The display of  claim 10 , wherein the reflection gratings are spectrally overlapping.  
     
     
         12 . The display of  claim 1 , wherein different wavelengths of energy are any desired wavelength of the visible spectra.  
     
     
         13 . The display of  claim 1 , wherein different wavelengths of energy are any desired wavelength of the IR spectrum.  
     
     
         14 . A method of making a multicolored reflective liquid crystal display, comprising: 
 simultaneously illuminating a film comprised of a mixture of a liquid crystal and a photo-polymerizable monomer with a plurality of holographic light patterns capable of providing liquid crystal layers of different spacings so as to obtain different reflection gratings in said film.    
     
     
         15 . The method of  claim 14 , wherein said holographic light pattern is obtained by providing at least two pairs of laser light beams, each said beam pair incident on said film at a different angle to form an optical interference pattern associated with reflection of a different wavelength of energy.  
     
     
         16 . The method of  claim 14 , wherein said holographic light pattern is obtained by providing laser light of a different wavelength, each said laser light forming an optical interference pattern associated with reflection of a different wavelength of energy.  
     
     
         17 . The method of  claim 15 , wherein the step of illuminating the film comprises illuminating a plurality of regions of the film, each said region illuminated with laser beam pairs with different angles of incidence.  
     
     
         18 . The method of  claim 17 , further comprising: 
 placing a mask between each of said laser light beams and said film, each said mask forming a pattern of light and dark regions on said film and each said mask positioned such that at least one light region of said first beam pair coincides with at least one dark region of said second beam pair within the film; and    illuminating the film whereby photo-polymerization of the monomer takes place and formation of polymer and liquid crystal layers occurs.    
     
     
         19 . The method of  claim 14 , wherein at least two different gratings are introduced into the film in a single illumination step.  
     
     
         20 . The method of  claim 14 , wherein power of said light beams is substantially equal.  
     
     
         21 . The method of  claim 17 , wherein said mask is of a grid pattern having transparent and opaque grid squares.  
     
     
         22 . The method of  claim 17 , wherein two beam pairs are used and a film comprising reflection gratings of two different wavelengths is obtained.  
     
     
         23 . The display of  claim 17 , wherein three beam pairs are used and a film comprising reflection gratings of three different wavelengths is obtained.  
     
     
         24 . The method of  claim 14  or  17 , wherein the method provides spectrally non-overlapping holographic elements.  
     
     
         25 . The method of  claim 14  or  17 , wherein the method provides spectrally overlapping holographic elements.  
     
     
         26 . The method of  claim 14  or  17 , wherein the method provides spatially non-overlapping holographic elements.  
     
     
         27 . The method of  claim 14 , wherein the method provides spatially overlapping holographic elements.  
     
     
         28 . The method of  claim 14 , wherein illumination of the film by a selected beam pair is blocked for a portion of the illumination time.  
     
     
         29 . An apparatus for preparation of a multicolored reflective liquid crystal display, comprising: 
 means for supporting a film comprised of a mixture of liquid crystal and a photo-polymerizable monomer;    a laser source;    means for producing at least two pairs of laser light beams from said laser source, each said beam pair capable of directing light onto a film housed in the supporting means at a different angle to form an optical interference pattern within a film associated with reflection of a different wavelength of energy; and    a mask disposed between each of said laser light beams and said supporting means, each said mask forming a pattern of light and dark regions on a film housed in the supporting means and each said mask positioned such that at least one light region of said first beam pair coincides with at least one dark region of said second beam pair within a film.    
     
     
         30 . The apparatus of  claim 29 , further comprising: 
 switchable shutters disposed between a laser beam pair and the film to block light of a beam pair from illuminating said film.    
     
     
         31 . A method of making a holographic polymer dispersed liquid crystal having multiple gratings, comprising: 
 providing a film comprised of a mixture of liquid crystal and a photo-polymerizable monomer and having a first and second opposing surfaces; and    illuminating the film with at least three beams of laser light, wherein at least one beam is incident on the first opposing surface of the film and at least one beam is incident of the second opposing surface of the film, and having at least one region in which three laser beams overlap to form a transmission grating the three-beam overlapping region upon photopolymerization of the monomer.    
     
     
         32 . The method of  claim 31 , wherein multiple reflection gratings further are formed in the three-beam overlapping region.  
     
     
         33 . The method of  claim 31 , wherein the intensity of light incident on the first opposing surface of the film is approximately equal to the intensity of light incident on the second opposing surface.  
     
     
         34 . The method of  claim 31 , wherein each laser beam is incident on the film at a different angle.  
     
     
         35 . A multiple grating polymer dispersed liquid crystal display device, comprising: 
 a pair of substrates having a holographic polymer dispersed liquid crystal (H-PDLC) film disposed therebetween,    the H-PDLC film comprised of a first region comprising liquid crystal and matrix polymer layers forming a transmission grating capable of transmitting a fixed wavelength of light and a second region comprising liquid crystal and matrix polymer layers forming multiple reflection gratings capable of reflecting a fixed wavelength of energy.    
     
     
         36 . The display of  claim 35 , wherein the device further includes a plurality of spatially overlapping reflection gratings in said first region.  
     
     
         37 . A method of making a holographic polymer dispersed liquid crystal having reflection in the infrared band, comprising: 
 providing a film comprised of a mixture of liquid crystal and a photo-polymerizable monomer and having a first and second opposing surfaces;    optically coupling the first and second opposing surfaces of the film with a pair of prisms which bend light at an angle to shift its wavelength into the infrared; and    illuminating the coupled film/prism arrangement with a holographic light pattern capable of providing liquid crystal layers of spacings on the order of infrared band so as to obtain an infrared reflecting reflection grating in said film.    
     
     
         38 . A method of making a holographic polymer dispersed liquid crystal having reflection in the infrared band, comprising: 
 providing a film comprised of a mixture of liquid crystal and a photo-polymerizable monomer and having first and second opposing surfaces;    optically coupling the first opposing surface of the film with a prism which bends light at an angle to shift its wavelength into the infrared;    optically coupling the second opposing surface of the film with a mirror, said mirror positioned at an angle with respect to the second opposing surface of the film; and    illuminating the coupled film/prism arrangement with a laser beam, wherein the transmitted light reflects back out at a preselected angle from its original incident path to create an interference pattern on the sample and thereby obtain an infrared reflecting reflection grating.    
     
     
         39 . The method of  claim 37  or  38 , wherein said film is simultaneously illuminated with a plurality of holographic light patterns, each said pattern capable of producing a reflection grating associated with a different wavelength.  
     
     
         40 . The method of  claim 37  or  38 , wherein the prism is selected from the group consisting of a 45°-right angle prism and a 30°-60°-90° prism.  
     
     
         41 . An apparatus for preparation of an infrared reflecting holographic polymer dispersed liquid crystal display, comprising: 
 means for supporting a film comprised of a mixture of liquid crystal and a photo-polymerizable monomer;    a laser source;    means for producing a pair of laser light beams from said laser source, said beam pair capable of directing light onto a film housed in the supporting means at an angle to form an optical interference pattern within a film associated with reflection of a wavelength of light; and    a prism optically coupled to said film supporting means for bending light from said laser source into the angles necessary to shift the laser wavelength into the near infrared.    
     
     
         42 . The apparatus of  claim 41 , further comprising: 
 a mask disposed between each of said laser light beams and said supporting means, each said mask forming a pattern of light and dark regions on a film housed in the supporting means and each said mask positioned such that at least one light region of said first beam pair coincides    
     
     
         43 . The apparatus of  claim 41 , further comprising a second prism optically coupled to the opposing surface of the supporting means.  
     
     
         44 . The apparatus of  claim 41 , further comprising a mirror positioned at the opposing surface of the supporting means to reflect recreate the holographic pattern.