Temperature activated optical films

Abstract

The present invention discloses a multilayer dielectric optical structure wherein one of the optical materials in the multilayer structure shows an optically isotropic state above and a birefringent state below a characteristic temperature Tc near the room temperature. The optical structure reflects a predetermined wavelength range of electromagnetic radiation above the Tc but allow the same to transmit through below the Tc. The predetermined wavelength can be the near infrared radiation from 700 nm to 2500 nm, and the optical structure rejects solar heat in warm summer days but admits the same to interior on a colder winter day.

1 . A multilayer dielectric optical structure, for selectively reflecting a predetermined wavelength, comprising:
 a transparent substrate;   a plurality of alternating first layers and second layers on the substrate, wherein the first layers comprise a first optical material having a first optical axis and a first refractive index along the first optical axis, and the second layers comprise a second optical material having a second optical axis and a second refractive index along the second optical axis below a characteristic transition temperature Tc and a third refractive index above the Tc, the first and second optical axis are substantially parallel and the first and second refractive indices are substantially equal, the third refractive index differ from the second refractive index and from the first refractive index; and   wherein the optical thickness of each of the first layer is equal to ¼ times the predetermined wavelength and the optical thickness of each of the second layer when the temperature is above the Tc is equal to ¼ times the predetermined wavelength. A human stem cell that is pluripotent, somatic, non-embryonic, and having the property of long-term self renewal.   
   
   
       2 - 23 . (canceled) 
   
   
       24 . A reflective polarizer film for regulating reflection of incident radiant energy comprising
 a first optical layer;   a second optical layer; and   a temperature sensitive optical material positioned between the first optical layer and the second optical layer.   
   
   
       25 . The film of  claim 24 , wherein
 at a first temperature a first percentage of the incident radiant energy is reflected from the film and a second percentage of the incident radiant energy is transmitted through the film; and   at a second temperature a third percentage of the incident radiant energy is reflected from the film and a fourth percentage of the incident radiant energy is transmitted through the film.   
   
   
       26 . The film of  claim 24 , wherein
 the temperature sensitive optical material adjusts polarization of incident light when below a threshold temperature;   above the threshold temperature up to 100% of incident light is reflected by the film, and below the threshold temperature up to 50% of incident light is reflected by the film.   
   
   
       27 . The film of  claim 24 , wherein
 the first optical layer reflects up to 50% of the incident radiant energy and transmits a majority of non-reflected radiant energy; and   the second optical layer reflects up to 100% of radiant energy transmitted by the first optical layer when the temperature sensitive optical material is above the threshold temperature and transmits up to 100% of radiant energy transmitted by the first optical layer when the temperature sensitive optical material is below the threshold temperature.   
   
   
       28 . The film of  claim 24 , wherein the second optical layer is frequency selective with respect to polarization of the radiant energy. 
   
   
       29 . The film of  claim 24 , wherein the film is in the form of a thin and flexible film. 
   
   
       30 . The film of  claim 24  further comprising a transparent substrate that supports the first optical layer, the second optical layer, and the temperature sensitive optical material. 
   
   
       31 . The film of  claim 30 , wherein the transparent substrate is a solid substrate. 
   
   
       32 . The film of  claim 24 , wherein the film is incorporated into a construction material for regulating the flow of incident light into, and thus regulating the internal temperature of, a building, a vehicle, or other structure. 
   
   
       33 . The film of  claim 32 , wherein the construction material is an insulating glass unit. 
   
   
       34 . The film of  claim 24  further comprising a transparent substrate. 
   
   
       35 . The film of  claim 24 , wherein a range of wavelengths of radiant energy regulated by the film comprises one or more of visual, infrared, or near-infrared wavelengths. 
   
   
       36 . The film of  claim 24 , wherein either or both of the first optical layer and the second optical layer is spectrally selective. 
   
   
       37 . The film of  claim 24 , wherein the first optical layer and the second optical layer each have different polarizing efficiencies, polarizing responses, or both at different frequencies. 
   
   
       38 . The film of  claim 24 , wherein each of the first optical layer and the second optical layer has a different polarizing nature at different frequencies. 
   
   
       39 . The film of  claim 24 , wherein either or both of the first optical layer and the second optical layer comprises a combination of multiple optical layers. 
   
   
       40 . The film of  claim 24 , wherein the temperature sensitive optical material comprises a liquid crystal. 
   
   
       41 . The film of  claim 40 , wherein the liquid crystal further comprises an additive in a mixture with the liquid crystal to affect optical properties of the liquid crystal, a speed of transition between physical states of the liquid crystal, or both. 
   
   
       42 . The film of  claim 41 , wherein the additive comprises a second type of liquid crystal mixed with the liquid crystal. 
   
   
       43 . The film of  claim 40 , where the additive is selected to improve the stability of a functional response of the film to environmental conditions. 
   
   
       44 . The film of  claim 24 , where the temperature sensitive optical material is designed or selected based upon frequency dependent properties of the temperature sensitive optical material with respect to a rotation of polarized light to affect one or more of aesthetic, color, light or energy transmission, absorption, and reflection properties of the film. 
   
   
       45 . A reflective polarizer film for regulating the reflection of light comprising a first optical layer that reflects up to 50% of incident light and passes up to 50% of the incident light;
 a second optical layer, and   a temperature sensitive optical material positioned between the first optical layer and the second optical layer that adjusts polarization of incident light below a threshold temperature, wherein   above the threshold temperature up to 100% of incident light is reflected by the film, and below the threshold temperature up to 50% of incident light is reflected by the film.   
   
   
       46 . The film of  claim 45  further comprising a transparent substrate that supports the first optical layer, the second optical layer, and the temperature sensitive optical material. 
   
   
       47 . The film of  claim 46 , wherein the transparent substrate is a solid substrate. 
   
   
       48 . The film of  claim 45 , wherein the film is in the form of a thin and flexible film. 
   
   
       49 . A reflective polarizer film for regulating the reflection of incident radiant energy comprising
 a first layer of birefringent optical material; and   a second layer of temperature sensitive optical material, wherein   above a threshold temperature down to 0% of incident radiant energy is transmitted by the film, and   below the threshold temperature up to 100% of the incident radiant energy is transmitted by the film;   at a first temperature a first percentage of the incident radiant energy is reflected from the film and a second percentage of the incident radiant energy is transmitted through the film; and   at a second temperature a third percentage of the incident radiant energy is reflected from the film and a fourth percentage of the incident radiant energy is transmitted through the film.   
   
   
       50 . A method for regulating reflection and transmission of radiant energy comprising orienting a first optical layer of birefringent optical material perpendicular to a second layer of temperature sensitive optical material;
 reflecting up to 100% of incident radiant energy with the first and second layers when above a threshold temperature; and   wherein when below a threshold temperature the first and second layers cease to polarize below the threshold temperature,   transmitting up to 100% of the incident radiant energy.   
   
   
       51 . A method for regulating an internal temperature of a building, a vehicle, or other structure comprising
 placing a temperature activated optical film on an exterior of a structure; and   inverting a temperature response of the film whereby the film is primarily reflective of incident radiant energy at high temperatures and comparatively more transparent to, absorbent of, or both, incident radiant energy at low temperatures.   
   
   
       52 . The method of  claim 51  further comprising positioning the film on the structure to receive maximum incident radiant energy at cold temperatures or in the winter season and to receive minimum incident radiant energy at high temperatures or in the summer season. 
   
   
       53 . A switchable shutter device for regulating reflection of incident radiant energy comprising
 a first reflective polarizer;   a second polarizer; and   a thermotropic depolarizer positioned between the first reflective polarizer and the second polarizer.   
   
   
       54 . The device of  claim 53 , wherein
 at a first temperature a first percentage of the incident radiant energy is reflected from the device and a second percentage of the incident radiant energy is transmitted through the device; and   at a second temperature a third percentage of the incident radiant energy is reflected from the device and a fourth percentage of the incident radiant energy is transmitted through the device.   
   
   
       55 . The device of  claim 53 , wherein the device is incorporated into a construction material for regulating the flow of incident light into, and thus regulating the internal temperature of, a building, a vehicle, or other structure. 
   
   
       56 . The device of  claim 54 , wherein the construction material is an insulating glass unit. 
   
   
       57 . The device of  claim 53  further comprising one or more of the following components: an external reflector, a color filter, a UV or harmful radiation filter, a transparent substrate, a filled or hollow space to provide thermal insulation, an antireflective coating, conductive or insulating adhesives or layers to improve the temperature sensing ability of the device, phase change materials, and low emissivity coatings or devices. 
   
   
       58 . The device of  claim 53 , wherein a range of wavelengths of radiant energy regulated by the device comprises one or more of visual, infrared, ultraviolet, radio, radar, or microwave wavelengths. 
   
   
       59 . The device of  claim 53 , wherein the thermotropic depolarizer comprises a liquid crystal. 
   
   
       60 . The device of  claim 59 , wherein the liquid crystal further comprises an additive in a mixture with the liquid crystal to affect optical properties of the liquid crystal, a speed of transition between physical states of the liquid crystal, or both. 
   
   
       61 . A switchable optical shutter device for regulating the reflection of light comprising a first reflective polarizer that reflects up to 50% of incident light and passes up to 50% of the incident light;
 a second reflective polarizer, and   a thermotropic depolarizer positioned between the first reflective polarizer and the second polarizer that adjusts polarization of incident light below a threshold temperature, wherein   above the threshold temperature up to 100% of incident light is reflected by the device, and   below the threshold temperature up to 50% of incident light is reflected by the device.   
   
   
       62 . An insulating glass unit comprising
 a first plate of glass;   a second plate of glass;   a first reflective polarizer positioned between the first plate of glass and the second plate of glass that reflects up to 50% of incident radiant energy and transmits a majority of non-reflected radiant energy;   a second reflective polarizer positioned between the first plate of glass and the second plate of glass; and   a thermotropic depolarizer positioned between the first reflective polarizer and the second polarizer that adjusts polarization of incident light below a threshold temperature, wherein   above the threshold temperature up to 100% of incident light is reflected by the device;   below the threshold temperature up to 50% of incident light is reflected by the device; and   the second polarizer reflects up to 100% of radiant energy transmitted by the first reflective polarizer when the thermotropic depolarizer is above the threshold temperature and transmits up to 100% of radiant energy transmitted by the first reflective polarizer when the thermotropic polarizer is below the threshold temperature.   
   
   
       63 . A switchable shutter device for regulating the reflection of incident radiant energy comprising
 a first thermotropic polarizer; and   a second thermotropic polarizer, wherein   above a threshold temperature down to 0% of incident radiant energy is transmitted by the device, and   below the threshold temperature up to 100% of the incident radiant energy is transmitted by the device;   at a first temperature a first percentage of the incident radiant energy is reflected from the device and a second percentage of the incident radiant energy is transmitted through the device; and   at a second temperature a third percentage of the incident radiant energy is reflected from the device and a fourth percentage of the incident radiant energy is transmitted through the device.   
   
   
       64 . A method for regulating reflection and transmission of radiant energy comprising
 orienting a first reflective polarizer crosswise with a second polarizer;   reflecting up to 50% and absorbing up to 50% of incident radiant energy with the first reflective polarizer and the second polarizer when above a threshold temperature; and   when below the threshold temperature,   depolarizing a portion of the incident radiant energy transmitted between the first reflective polarizer and the second polarizer;   transmitting up to 50% of the radiant energy through the first reflective polarizer and the second polarizer; and   reflecting up to 50% of the incident radiant energy.   
   
   
       65 . A method for regulating reflection and transmission of radiant energy comprising
 orienting a first thermotropic polarizer crosswise with a second thermotropic polarizer;   reflecting up to 100% of incident radiant energy with the first and second thermotropic polarizers when above a threshold temperature; and   wherein when below a threshold temperature the first and second thermotropic polarizers cease to polarize below the threshold temperature,   transmitting up to 100% of the incident radiant energy.   
   
   
       66 . A method for regulating reflection and transmission of radiant energy comprising
 orienting a reflective polarizer crosswise with a polarity-rotating polarizer;   interposing a thermotropic depolarizer between the reflective polarizer and the polarity-rotating polarizer   reflecting up to 100% of incident radiant energy with the reflective polarizer and the polarity-rotating polarizer when the thermotropic depolarizer is above a threshold temperature; and   when below a threshold temperature,   transmitting up to 100% of the incident radiant energy through the reflective polarizer, thermotropic depolarizer, and the polarity-rotating polarizer.   
   
   
       67 . A method for displaying a reflective image comprising
 arranging a thermoreflective material or device on a surface in a shape of a desired image or removing the thermoreflective material in an area to form an image area; and   reflecting incident light from the thermoreflective material above or below a particular threshold temperature or range of temperatures, wherein the reflective image becomes visible.   
   
   
       68 . A method for regulating an internal temperature of a buildings, a vehicle, or other structure comprising
 placing a thermoreflective material on an exterior of a structure; and   inverting a temperature response of the thermoreflective material whereby the thermoreflective material is primarily reflective of incident radiant energy at high temperatures and comparatively more transparent to, absorbent of, or both, incident radiant energy at low temperatures.