Patent Publication Number: US-2010122480-A1

Title: Apparatus for producing an optical effect or for simulating fires and simulated fireplaces including such apparatus

Description:
The present invention relates to apparatus for producing an optical effect, and more particularly to apparatus for simulating fires, especially flames of fires, and to simulated fireplaces including such apparatus. 
     Simulated fireplaces are well known and established in the marketplace. The realism achieved by such fireplaces in simulating glowing embers and, more especially, flames has reached a high level. However, as always, there is room for improvement. Most simulated fireplaces currently on the market use electro-mechanical means for the simulation of flames. Such known apparatus are typified by that described in GB 2 230 335 which includes a light source, a viewing screen and reflective “flags” mounted behind the viewing screen. The flags are illuminated by the light source and viewed through the viewing screen. The flags are caused to billow in an air flow. The screen is partially diffusing of light, which enhances the appearance of flames caused by the billowing of the illuminated flags. Electro-mechanical devices have at least the potential to be less reliable than might be desired and are also relatively expensive to manufacture. Accordingly, the present invention seeks to provide an alternative means of simulating flames and glowing embers and the like in a fire. 
     The present invention seeks to fulfil this desideratum by using electroluminescent materials and/or materials of changeable opacity for the simulation of flames. 
     According to a first aspect of the present invention there is provided an apparatus for producing an optical effect comprising:
         a housing;   an electroluminescent screen comprising a supporting substrate, a first electrode layer, a layer comprising at least one electroluminescent material, and a second electrode layer, wherein the first electrode layer is divided into separately excitable segments, each segment causing an adjacent portion of the electroluminescent layer to emit light when said segment is excited; and   a control unit for exciting said segments of the first electrode layer in a predetermined, random or pseudo-random sequence.       

     According to a second aspect of the invention there is provided a simulated flame fire comprising an apparatus according to the first aspect wherein said control means is operative to sequentially to excite segments or groups of segments of said first electrode layer having a shape resembling that of flames. 
     In one preferred embodiment of this aspect of the invention the simulated flame fire further comprises distinct areas of the electroluminescent material layer which are shaped to be representative of flames, each said area including one or more electroluminescent materials emitting light of flame like colours. 
     Preferably said simulated flame fire further comprises a simulated fuel bed mounted in said housing directly below said electroluminescent screen. 
     In one embodiment of the first and second aspects of the invention, preferably a plurality of said electroluminescent screens is provided. 
     Optionally, one or more light sources are provided, effective to illuminate local areas of the electroluminescent screen. 
     Preferably said light source or light sources illuminate said electroluminescent screen from the rear. 
     Preferably said light sources comprise individual LEDs or groups or arrays of LEDs.
         According to a third aspect of the invention there is provided an apparatus for producing an o a housing;   a screen including means for providing a variable opacity comprising a supporting substrate, a first electrode layer, a layer of material for providing a variable opacity when subjected to an electric field, and a second electrode layer, wherein the first electrode layer is divided into separately excitable segments, each segment causing an adjacent portion of the layer of material for providing a variable opacity to change its opacity when said segment is excited;   one or more light sources effective to illuminate local areas of the said screen; and   a control unit for exciting said segments of the first electrode layer in a predetermined, random or pseudo-random sequence.       

     According to a fourth aspect of the invention there is provided a simulated flame fire comprising an apparatus according to the third aspect of the invention wherein said control means is operative to sequentially to excite segments or groups of segments of said first electrode layer having a shape resembling that of flames. 
     In one preferred embodiment of this aspect of the invention the layer of material for providing a variable opacity is divided into distinct areas of predetermined shape. 
     Preferably said distinct areas of the layer of material for providing a variable opacity are shaped to be representative of flames and wherein said light source or light sources are adapted to provide light of flame-like colours. 
     Preferably said simulated flame effect fire further comprises a simulated fuel bed mounted in said housing directly below said screen. 
     Preferably said light source or light sources illuminate said screen from the rear. 
     Preferably said light sources comprise individual LEDs or groups or arrays of LEDs. 
     Preferably the means for providing a variable opacity is a liquid crystal polymer (LCP) device or a suspended particle device (SPD). 
     According to a fifth aspect of the invention there is provided an apparatus for producing an optical effect comprising:
         a housing;   a screen comprising
           a supporting substrate; a first electrode layer; a layer of electroluminescent material; and a second electrode layer; wherein the first electrode layer is divided into separately excitable segments, each segment causing an adjacent portion of the electroluminescent layer to emit light when said segment is excited; a third electrode layer; a layer of material for providing a variable opacity when subjected to an electric field; and a fourth electrode layer, wherein the third electrode layer is divided into separately excitable segments, each segment causing an adjacent portion of the layer of material for providing a variable opacity to change its opacity when said segment is excited; and   a control unit for exciting said segments of the first and third electrode layers in a predetermined, random or pseudo-random sequence   
               

     According to a sixth aspect of the invention there is provided a simulated flame fire comprising an apparatus according to the fifth aspect of the invention wherein said control means is operative to sequentially to excite segments or groups of segments of said first electrode layer having a shape resembling that of flames. 
     In one preferred embodiment, the simulated flame fire of this aspect of the invention comprises distinct areas of the electroluminescent material layer which are shaped to be representative of flames each said area including one or more electroluminescent materials emitting light of flame like colours. 
     Preferably said control means is operative to sequentially to excite segments or groups of segments of said third electrode layer having a shape resembling that of flames. 
     Preferably the layer of material for providing a variable opacity is divided into distinct areas of predetermined shape. 
     Preferably said distinct areas of the layer of material for providing a variable opacity are shaped to be representative of flames. 
     Preferably the simulated flame effect fire of this aspect further comprises one or more light sources effective to illuminate local areas of said screen. 
     Preferably said light source or light sources are adapted to provide light of flame-like colours. 
     Preferably the simulated flame effect fire of this aspect further comprises a simulated fuel bed mounted in said housing directly below said screen. 
    
    
     
       For a better understanding of the invention and to show how the same may be carried into effect, reference will be made, by way of example only, the following drawings in which: 
         FIG. 1  is a schematic cross-section showing the general arrangement of a fire according to one embodiment of the invention; 
         FIG. 2  is a typical arrangement on a flame-simulating screen according to the invention; 
         FIG. 3  shows a typical construction of an electroluminescent screen according to the invention; 
         FIG. 4  shows a variation of the embodiment of  FIG. 1 ; 
         FIG. 5  shows an alternative construction of a simulated fire or stove according to the invention; 
         FIG. 6  is a cross section along line VI-VI of  FIG. 5 ; 
         FIG. 7  shows a further alternative construction of a simulated stove or fire according to the invention; 
         FIG. 8  shows a further alternative construction of a simulated stove or fire according to the invention including a plurality of screens; 
         FIG. 9  is a schematic cross-section showing the general arrangement of a fire according to another embodiment of the invention; 
         FIG. 10  is a typical arrangement on a flame-simulating screen according to the embodiment of  FIG. 9 ; 
         FIG. 11  shows a typical construction of a LCP or SPD screen according to the invention; 
         FIG. 12  shows a typical construction of an electroluminescent and LCP/SPD screen according to the invention; 
         FIG. 13  is a schematic cross-section showing the general arrangement of a fire according to another embodiment of the invention; 
         FIG. 14  shows a schematic cross-section showing the general arrangement of a fire similar to that of  FIG. 4  including a non-planar electroluminescent screen; and 
         FIG. 15  shows a typical arrangement of an OLED. 
     
    
    
     Electroluminescent materials as such are well known. Electroluminescence is the emission of light by a material when subjected to an electric field. Phosphor electroluminescence was discovered in the early 20 th  century and was initially used in electroluminescent powder lamps, with limited success. The technology was further developed in the 1980s resulting in flexible electroluminescent phosphors which are incorporated as backlights in LCD displays. Such flexible phosphor materials are produced by embedding or encapsulating the phosphor in a matrix, such as of a glass or polymer material, and sandwiching a layer of the resulting powder between two electrodes. Devices incorporating such powder-type phosphors are known as “thick film” or “powder” electroluminescent devices. 
     So-called “thin film” devices are also known which employ a thin film of an electroluminescent phosphor deposited on a substrate. Thin film technology has been used to make electroluminescent displays, as described, for example, in U.S. Pat. No. 5,463,279. 
     In addition to inorganic electroluminescent materials noted above, organic electroluminescent materials are also known. A selection of such materials is described in GB 2 394 109, the contents of which are incorporated herein by reference. 
     The use of light emitting conjugated polymers (LEPs) is also known in electroluminescent devices. Examples of LEPs such as poly(p-phenylenevinyline) are described in WO 90/13148 the contents of which are incorporated herein by reference. 
     Organic electroluminescent materials, and especially polymeric electroluminescent materials are often referred to as OLEDs (either Organic Light Emitting Diodes or Organic Light Emitting Devices). The semi-conducting polymers used in OLEDs are known as PLEDs (Polymer LEDs). The development of OLEDs is progressing rapidly, in particular as a substitute of LCD displays as used, for example, in portable (laptop) computers. Numerous PLEDs which emit light in various different colours are known. OLEDs are advantageous as compared to LCDs in that the OLED polymers are inherently light emitting, allowing a significantly lower power consumption than LCDs, which must be back-lit. More information on OLEDs can be found in numerous patent sources, such as the numerous patents of Cambridge Display Technology Ltd. Polymers for OLEDs are available from, for example, H W Sands Corp, Jupiter, Fla., USA. A typical arrangement of an OLED is shown in  FIG. 15 . The device of  FIG. 15  comprises a substrate  50  which is typically a glass substrate, an electrode layer  52  of a material having a relatively large work function, such as indium tin oxide (ITO), a polymer layer (PLED layer)  54  and a further electrode layer  56  of a material of relatively low work function such as calcium. Contacts  58 ,  60  provide connection to control circuitry  62 . Barrier and cover layers for protection of the OLED may, of course also be provided. 
     The apparatus and simulated flame fire of the present invention can, in principle, employ any of the above technologies. 
     Referring now to the drawings, in which  FIG. 1  shows in a general, non-limiting, arrangement a simulated fire  10  comprising a housing  12 . The housing  12  may be constructed in any desired form to simulate the construction of a real solid fuel fire or stove and may optionally include a transparent front screen or window  12 A. In front of the housing  12  is a simulated fuel bed  14 . The fuel bed  14  may comprise a moulding formed from a plastic material which is shaped and coloured to resemble pieces of fuel resting on an ember bed. For example, the moulding may represent logs (coloured primarily dark brown) resting on a bed of glowing embers (coloured primarily red and orange). In alternative constructions, the fuel bed may comprise an ember bed formed from a shaped and coloured plastic moulding, with discrete pieces of simulated fuel, such as logs or coals, resting on the ember bed. Fuel bed  14  may be illuminated from below by a light source  16 . Light from the light source  16  may be reflected by a device  18  for providing a flicker effect which in the illustrated example is a shaft having generally radial pieces of reflective material. The shaft is rotated about its axis, as indicated by arrow  18 A. A baffle  20  may be provided so that light from the light source  16  cannot fall on the fuel bed  14  other than via the flicker device  18 . If desired, a light source  22  may be provided for illuminating the fuel bed from above. 
     For providing the flame effect to simulate the flames of a real fire, the simulated fire  10  is provided with an electroluminescent screen  30 . The screen  30  comprises a supporting substrate  32  which is preferably substantially rigid and is fixedly mounted in the housing  12 . A suitable supporting substrate can be a glass sheet or a plastic web or sheet. A supporting layer  34  (which may be the same as supporting substrate  32 ) carries a first electrode layer  36 . A layer of electroluminescent material  38  is sandwiched between the first electrode layer  36  and a second electrode layer  40 . Typical electrode layers are formed from materials such as indium tin oxide (ITO). A barrier substrate layer  42  is provided to enclose and protect the various layers below. Other layers may be included in the screen, as will be known to those skilled in the art of electroluminescent materials. The barrier substrate and the second electrode layer are necessarily formed from transparent (or at least translucent) materials so that the luminescence of the layer  38  is freely viewable. 
     In the embodiment shown in  FIG. 1 , the first electrode layer  36 , supporting substrate  32  and supporting layer  34  need not be transparent since there is no requirement for a user to see through the screen  30 . Indeed, it may be desirable for the screen to be opaque so that any components located behind the screen  30  are not visible to a user. To the contrary, as seen in  FIG. 4 , in an alternative embodiment of a fire or stove  110 , a screen  130  (which is otherwise equivalent to screen  30  of  FIG. 1 ) is mounted in the middle of the fuel bed  14 . In screen  130 , all the component layers are made to be transparent (or at least substantially transparent) so that the portion  14 A of the fuel bed  14  lying behind the screen  130  is visible to the user. In this way, the illusion of flames created by the screen  130  appears to come from the middle of the fuel bed  14 , providing a more realistic effect. A similar effect can be achieved in the embodiment of  FIG. 1  by providing the screen  30  with a partially reflective front surface  42 ′. In this way, the user sees a reflection of the fuel bed  14  in the front of the screen  30 , so that the illusion of flames appears to be located between the fuel bed  14  and its reflection, so giving the appearance of a fuel bed with greater front-to-back depth. 
     As may be seen in particular from  FIG. 3 , the first electrode layer  36  may be divided into discrete segments  36 A,  36 B,  36 C,  36 D,  36 E, each of which is independently excitable by a control unit or driver  24  mounted in the housing  12  in a location not visible to a user in normal use. The term “excite” is used herein to mean the application of a voltage to a given segment, say  36 N, of the first electrode layer  36  sufficient to cause local luminescence of the electroluminescent layer and the terms “excited”, “excitation” and the like are construed accordingly. The apparatus of the invention is not, of course limited to five segments of the first electrode layer  36 . In principle any number of segments may be provided as necessary properly to simulate flames. For example, the first and second electrodes may be constructed as active or passive matrix electrodes (on suitable substrates) so that the segments  36 A-E,N may be of pixel scale. Depending on the nature of the image (especially the flame image) which is desired, much larger segments  36 A-E,N are possible and may be desirable. The control unit  24  includes necessary electronic hardware and software to control the excitation of segments  36 A-E of the first electrode layer. Control unit  24  may be constructed to excite given segments of electrode layer  36  individually or in groups. For example, if excitation of a large area of electrode layer  36  is required, this may be achieved by simultaneous excitation of a number of adjacent segments which together comprise the desired large area. 
     As can be seen from  FIG. 2 , in one embodiment, the electroluminescent screen  30  comprises a plurality of generally flame-shaped regions X, Y, Z. These regions X, Y, Z correspond to one or more of the first electrode layer segments  36 A-E. Each region X, Y Z may equate to a single segment  36 A-E of the first electrode layer, or to a number of such segments. The control unit  24  may be set up to excite the segments  36 A-E underlying regions X, Y, Z in a predetermined sequence which may, for example, be random or pseudo-random. A pseudo-random sequence will appear to an observer to be random but is actually repeating over a period of time. 
     Layer  38  of electroluminescent material may also preferably be divided into segments or zones  38 A,  38 B,  38 C,  38 D and  38 E. These zones may or may not correspond directly to segments  36 A-E of the first electrode layer. For example, a given zone of the electroluminescent layer  38  may be excited by more than one segment of the first electrode layer. The zones  38 A-E may comprise the same, or, where required, different, electroluminescent materials. For example, different materials may be used in adjacent zones to provide different flame colours. Flame colours will typically be largely yellows, reds and oranges, but other colours such as are know to occur in real flames may be included, in particular blues and greens. A given region X, Y, Z as shown in  FIG. 2  may comprise more than one zone  38 A-E, so that a given flame shape may comprise more than one colour, for example. 
     Thus, in this embodiment, to provide a flame effect, the control unit  24  excites in its predetermined sequence selected segments  36 A-E of the first electrode layer. Excitation of these segments causes luminescence of the adjacent parts of the electroluminescent layer  38 . For example, the sequence of excitation under the control of control unit  24  may be (a) excitation of all segments of the first electrode layer corresponding to regions X, (b) excitation of all segments of the first electrode layer corresponding to regions Y, (c) excitation of all segments of the first electrode layer corresponding to regions Z, (d) excitation of all segments of the first electrode layer corresponding to regions X and so on. 
     In an alternative embodiment, where the segments of the first electrode is or at or near conventional pixel size, the specific areas X, Y, Z are not necessary and the requisite flame shapes are produced by excitation of appropriate combinations of segments under the control of control unit  24 . In this case, electroluminescent materials emitting in different colours may also preferably be arranged in the electroluminescent layer in areas which correspond with the segments  36 A-E,N. 
       FIGS. 5 and 6  show another embodiment of a stove or fire  210  according to the invention. Whereas in the embodiments of  FIGS. 1 and 3 , the electroluminescent screens  30 ,  130  are essentially planar, in  FIGS. 5 and 6  an electroluminescent screen  230  is provided which is generally cylindrical. Screen  230  is an electroluminescent flame-simulating arrangement which is equivalent in function and construction to the screens  30 ,  130 , except that it is formed into a substantially cylindrical shape. By constructing the screen  230  in this way, it is possible to simulate the sort of real solid fuel fire or stove which is typically disposed in the middle of a room (or at least spaced from the walls), with its own chimney stack or flue  240  which rises to the roof. A user is able if desired to walk all around the stove  210  and view it from all angles. The stove  210  comprises a housing  212  in which the screen  230  is supported by any suitable means. The housing  212  also supports a fuel bed  214  which may comprise portions  214 A and  214 B respectively in front of and behind the screen  230 . If screen  230  is made opaque, and optionally reflective, then fuel bed portion  214 B is not necessary. The housing  212  may include an inner column  213  if necessary. Inner column  213  may be structural and provide support for upper housing portion  212 A, if necessary. Alternatively the screen  230  may have sufficient strength to support housing portion  212 A. The outer surface of column  213  may be coloured matt black or similar, so that its presence is not obvious to a user. Alternatively, the surface of the column  213  may be provided with a reflective or partially reflective finish to provide a reflection of the fuel bed  214  and so to increase a user&#39;s perception of the front-to-back depth of the fuel bed  214 . Column  213  may also provide a location for mounting components of the stove  210 , such as a control unit  24 . The fuel bed  214  may be illuminated from below in a similar manner to fuel bed  14  of  FIGS. 1 and 3 , using one or more light sources  16  and one or more flicker devices  18 . 
       FIG. 7  shows another embodiment of a stove or fire  310  according to the invention which is intended for mounting against a wall, such as in a fireplace or hearth. The fire  310  includes a curved electroluminescent screen  330  mounted in a housing  312 . The housing  312  also supports a fuel bed  314  having portions  314 A and  314 B respectively in front of and behind the screen  330 . Where, in a similar manner to  FIG. 1 , the front surface of screen  330  is made partially reflective fuel bed portion  314 B may be absent. In this case also, the screen  330  need not be transparent. 
     In a further embodiment of the invention shown in  FIG. 8 , the fire  410  includes a housing  412  supporting a fuel bed  414 . The housing  412  also supports a plurality of discrete electroluminescent screens  430 A,  430 B,  430 C,  430 D etc. The screens  430 A-D may be straight and/or curved but are otherwise of generally the same construction as the screens  30 ,  130 ,  230 ,  330  of the above-described embodiments. The screens  430 A-D are disposed at various locations with respect to the fuel bed  414 , giving the illusion of flames appearing from different parts of the fuel bed. A control unit  424 , indicated in ghost lines, mounted below the fuel bed  414  controls the sequence of illumination of each screen  430 A-D and also the sequence of excitation of each segment  36 A-E,N of the first electrode of the respective screens  430 A-D. In alternative arrangement, one or more of screens  430 A-D may be sized to represent a single flame and so may consist of a single zone  38 A-E,N. Alternatively, each screen may have different segments  38 A-E, preferably of different flame-like colours, to represent the true colours of a real flame. 
       FIG. 14  shows a flame simulating fire generally similar to that of  FIG. 4 . Similar components are given corresponding reference numbers, with the addition of the prefix “ 9 ”. The fire of  FIG. 14  includes an electroluminescent screen  930  which is non-planar. For example, the screen may comprises a supporting substrate  932  which is a shaped plastic moulding. In other respects the screen is generally of the same layer construction as screens  30 ,  130 ,  230 ,  330 ,  430 . The non-planar construction of screen  930  enhances the three-dimensional appearance of the simulated flames. A screen  930 A may be mounted in front of the screen  930 . Screen  930 A is transmissive of light from screen  930  and includes a reflective front surface  930 A′ by means of which a user sees a reflected image of fuel bed  914 , so enhancing the perceived depth of fuel bed  914 . In alternative arrangements, the screen  930 A may be absent and fuel bed  914  may extend both in front of, and behind, screen  930 . Screen  930  is merely illustrative of a non-planar screen and other non-planar shapes are possible, in accordance with a designer&#39;s wishes. In this respect, the electroluminescent laminate may be supplied in a flexible form which is attached to a shaped support such as a shaped plastic moulding. For example, layers  34  and  42  in  FIG. 3  may be flexible plastic films, supporting the electrode and electroluminescent material layers. 
       FIGS. 9 ,  10  and  11  illustrate an alternative embodiment of the invention.  FIG. 9  shows in a general, non-limiting, arrangement a simulated fire  510  comprising a housing  512 . The housing  512  may be constructed in any desired form to simulate the construction of a real solid fuel fire or stove and may optionally include a transparent front screen or window  512 A. The housing  512  supports a simulated fuel bed  514 . The fuel bed  514  may comprise a moulding formed from a plastic material, which is shaped and coloured to resemble pieces of fuel resting on an ember bed. For example, the moulding may represent logs (coloured primarily dark brown) resting on a bed of glowing embers (coloured primarily red and orange). In alternative constructions, the fuel bed may comprise an ember bed formed from a shaped and coloured plastic moulding, with discrete pieces of simulated fuel, such as logs or coals, resting on the ember bed. Fuel bed  514  may be illuminated from below by a light source  516 . Light from the light source  516  may be reflected by a device  518  for providing a flicker effect which in the illustrated example is a shaft having generally radial pieces of reflective material. The shaft is rotated about its axis, as indicated by arrow  518 A. A baffle  520  may be provided so that light from the light source  516  cannot fall on the fuel bed  514  other than via the flicker device  518 . If desired, a light source  522  may be provided for illuminating the fuel bed from above. 
     For providing the flame effect to simulate the flames of a real fire, the simulated fire  510  of this embodiment is provided with a “suspended particle device” (SPD) or liquid crystal polymer (LCP) screen  530 . SPDs are described, for example in U.S. Pat. No. 6,156,239 and in numerous other patents of Research Frontiers Inc, New York, USA. Preferred SPDs comprise a laminate in which the SPD material and associated electrodes are mounted on one or more polymeric films. The screen  530  comprises a supporting substrate  532  which is preferably substantially rigid and is fixedly mounted in the housing  512 . A suitable supporting substrate  532  can be a glass sheet or a plastic sheet. A supporting layer  534  (which may be the same as supporting substrate  532  or may be a polymeric film) carries a first electrode layer  536 . A layer of SPD or LCP material  538  is sandwiched between the first electrode layer  536  and a second electrode layer  540 . Typical electrode layers  536 ,  540  are formed from materials such as indium tin oxide (ITO). A barrier substrate layer  542  is provided to enclose and protect the various layers below. Other layers may be included in the screen, as will be known to those skilled in the art of SPD and LCP materials. The barrier substrate and the second electrode layer are necessarily formed from transparent (or at least translucent) materials. The supporting substrate  532  and the supporting layer  534  are formed from transparent (or at least largely translucent) materials, at least in specific areas, as discussed below. 
     SPDs, which are sometimes known as “light valves”, are currently used, for example, to provide windows of buildings with enhanced properties. SPDs have the property of being substantially opaque when no electric field is applied but become substantially transparent on application of an electric field. More specifically an SPD comprises a pair of electrodes (as noted above) between which is a plastic film in which molecular-scale rod-like particles are encapsulated in very many uniformly distributed cells. Each such cell contains many of the rod-like particles. With no applied voltage, the particles are randomly oriented and block light. When a voltage is applied (via the electrodes) the particles are caused to align with the electric field and so let light through. The degree of light transmission can be varied by varying the applied voltage. Thus the degree of opacity of the SPD can be varied. LCP screens behave similarly in that in the absence of an applied electric field the polymer molecules are randomly oriented and so block transmission of light. On application of an electric field, the LCP polymer molecules are aligned, allowing light to be transmitted. In contrast to SPDs, LCP devices have only transparent or opaque conditions, with no ability to vary the opacity. A typical LCP screen may be (but is not necessarily) white or a similar pale colour in the opaque condition. In either case (SPD or LCP), the “opaque” non-aligned state does not necessarily block the transmission of all light, but the transmission is reduced to an extent sufficient to render it difficult or substantially impossible to see through the screen  530 . 
     In the present embodiment, the first electrode layer  536  is divided into discrete segments  536 A,  536 B,  536 C,  536 D,  536 E, . . .  538 N etc. which may be individually excited under the control of a control unit  524 . Similarly the SPD or LCP layer  538  may be divided into segments or zones  538 A-E etc., which may or may not correspond directly to segments  536 A-E of first electrode layer  536 . For example, a given zone  538 N of the SPD or LCP layer  538  may be of larger area than segments of electrode layer  536  and so may be excited by more than one segment of the first electrode layer  536 . Where, for example, the segment size of the first electrode layer  536  is sufficiently small, zones  538 A-E, N are not required. 
     As can be seen from  FIG. 10 , the screen  530  comprises a plurality of generally flame-shaped regions R, S, T. These regions R, S, T correspond to one or more of the first electrode layer segments  536 A-E. Each region R, S T may equate to a single segment  536 A-E of the first electrode layer, or to a number of such segments. The control unit  524  may be set up to excite the segment(s)  536 A-E underlying regions R, S, T in a predetermined sequence which may, for example, be random or pseudo-random. A pseudo-random sequence will appear to an observer to be random but is actually repeating over a period of In the alternative there are no fixed flame shaped regions X, Y, Z and the flame shapes are generated only by appropriate excitation of segments, or groups of segment  536 A-E, N of the first electrode. 
     Thus, when a given segment  536 N of first electrode  536  is excited, the area of the SPD layer adjacent that segment  536 N becomes substantially transparent. In order to provide the appearance of flames, illumination is provided behind the screen  530 , as shown schematically in  FIG. 9  by light sources  550 A and  550 B. Light from the light sources  550 A,B is transmitted at a maximum perceived intensity through a given area of the screen  530  only when a given area of the SPD or LCP layer  538  is made transparent by excitation of a particular segment or group of segments  536 N of the first electrode  536 . Given that even at its maximum opacity (no electric field), the SPD or LCD material may not be wholly opaque, some light from the light sources  550 A,B may pass through the screen  530  whenever the light sources  550 A,B are illuminated. 
     The light sources  550 A,  550 B may be selected from a range of possibilities. For example the light source  550 A,B may comprise one or more conventional incandescent or halogen bulbs in a suitable location. In this case filters or coloured reflectors may be used to provide desired colours of light and reflectors and baffles may be provided to ensure that light falls in desired local regions of the screen  530 . In alternative arrangements, specific individual light sources may be provided in register with a given specific local areas of the screen  530 , such as a particular segment or group of segments  536 N of the first electrode layer  536 . These individual light sources can be of individually selected colours and intensities to provide an optimum simulated flame effect. In one preferred arrangement, the light sources comprise appropriately coloured LEDs or arrays of LEDs (more than one LED may be required to illuminate a given local area, segment or group of segments  536 N). The use of LEDs allows the location, colour and intensity of the light sources to be tailored for optimum effect. If required, means  552  may be provided for diffusing the light from the light source(s)  550 A,B. Such means may be an additional screen or screen layer which is inherently diffusing, such as a transparent plastic material doped with an opaque powder such as titanium dioxide, or a layer which has been made diffusing for example by abrasion of its surface. Alternatively, discrete areas of the screen  530  corresponding to regions R, S, T, or parts thereof, may be made diffusing. Regions P of the screen  530  outside the regions R, S, T may be permanently opaque. The front surface of screen  530  may be at least partially reflective to provide a reflected image of the fuel bed  514  and so to achieve the perception of flames appearing from the middle of the fuel bed. 
     Thus, in one embodiment of the invention, to provide a flame effect, the control unit  524  excites in its predetermined sequence selected segments  536 A-E of the first electrode layer. Excitation of these segments causes the corresponding areas of layer  538 , such as zones  538 A-E, to become transparent. The control unit  24  may also preferably control selective illumination of the light sources  550 A,B in accordance with the particular segments  536 A-E which are excited at any given time. 
     For example, the sequence of excitation under the control of control unit  24  may be (a) excitation of all segments of the first electrode layer corresponding to regions R, (b) excitation of all segments of the first electrode layer corresponding to regions S, (c) excitation of all segments of the first electrode layer corresponding to regions T, (d) excitation of all segments of the first electrode layer corresponding to regions R and so on. As noted above, a given region R, S, T may comprise one or more segments of the first electrode layer  536 . Thus, different areas of a given region R, S, T may be made transparent at different times, or the whole region R, S, T may be made transparent, and said different areas may exhibit different colours in accordance with the choice and particular arrangement of the light source or source  550 A,B. Thus a very realistic flame effect may be achieved. 
     The above embodiment has been described in terms of an LCP/SPD screen  530  which is opaque when not subjected to an electric field and which is transparent when subjected to an electric field. Of course, the same result can be achieved by a screen, which incorporates a layer which is transparent in the presence of an electric field and which becomes opaque in the absence of an electric field. In this context, the term “excite” in relation to the electrode layer  536  is interpreted to mean that the electric field is switch from an “on” state to an “off” state to result in a transparent zone  538 N of the screen  536 . The application and claims should be construed accordingly. 
     The control unit  24 ,  524  is arranged so that the various segments  36 A-E,N or  536 A-E,N are excited in a sequence and timing so that the user&#39;s eye always perceives flames to be present, in one location or another. Also, the control unit  24 ,  524  may optionally be programmed so that a user may select from a range of parameters for the simulated fire, such as the speed of change of the flames, or the intensity of the light emitted. 
     The present invention also relates to a simulated flame effect fire which includes a screen  630  which includes both an electroluminescent layer  738  and an LCD or SPD layer  638 , as illustrated in  FIG. 12 . The screen  630  includes first and second electrodes  636 ,  640  associated with the LCD or SPD layer  638  and first and second electrodes  736 ,  740  associated with the electroluminescent layer  738 . Screen  630  also includes a supporting substrate  632 , a supporting layer  634  (which may be the same as supporting substrate  632 ), a barrier substrate layer  642  and a separating layer  644 . In the same manner as described in relation to the embodiments above, the respective first electrodes  736 ,  636  may be divided into discrete segments  736 A-E,N and  636 A-E,N which are individually excitable by a control unit (not illustrated) and likewise electroluminescent layer  738  and SPD/LCP layer  638  may optionally be divided into zones  738 A-E and  638 A-E,N respectively. In this way, even though a given zone, say  738 N, of electroluminescent layer  738  is caused to be luminescent by excitation of corresponding segment, say  736 N of first electrode  736 , a part (or even, for a given time, all) of the zone  738 N may be obscured as a corresponding zone  638 N of SPD/LCD layer  638  is caused to be opaque. Thus an enhanced degree of variation in the flame simulating effect is achieved. 
       FIG. 13  shows a simulated flame effect similar in construction to the fire of  FIG. 4  and like components have like numbers with the addition of the prefix “ 8 ”. Screen  830  corresponds to screen  130  and need not be transparent but should be translucent. Thus, for example, first electrode layer  36 , or any other layer lying behind electroluminescent layer  38  (with respect to a user) is preferably translucent. To supplement or enhance the light emitted by electroluminescent layer  38 , additional light sources  850 A,  850 B are provided. Thus, when a given segment  36 N of first electrode  36  is excited, the area of the zone electroluminescent layer  38  adjacent that segment  36 N becomes emits light. Light from the light sources  850 A,B is transmitted through the screen  830  in addition to light emitted by electroluminescent layer  38 . SPD or LCD layers and corresponding first and second electrodes may be provided so that light from the light sources  850 A,B is transmitted through the screen  830  only where a given zone of the SPD or LCP layer, corresponding to luminescing zone  36 N, is made transparent. 
     The light sources  850 A,  850 B may be selected from a range of possibilities. For example the light source  850 A,B may comprise one or more conventional incandescent or halogen bulbs in a suitable location. In this case filters or coloured reflectors may be used to provide desired colours of light and reflectors and baffles may be provided to ensure that light falls in desired local regions of the screen  830 . In alternative arrangements, specific individual light sources may be provided in register with a given specific segment or group of segments  36 N of the first electrode layer  36 . These individual light sources can be of individually selected colours and intensities to provide an optimum simulated flame effect. For example, a light source of a particular colour can be chosen to modify and enhance, in the user&#39;s perception, the colour of light emitted by a given zone  36 N of luminescent layer  36 . In one preferred arrangement, the light sources comprise appropriately coloured LEDs or arrays of LEDs (more than one LED may be required to illuminate a given segment or group of segments  36 N). The use of LEDs allows the location, colour and intensity of the light sources to be tailored for optimum effect. If required, means  852  may be provided for diffusing the light from the light source(s)  850 A,B. Such means may be an additional screen or screen layer which is inherently diffusing, such as a transparent plastic material doped with an opaque powder such as titanium dioxide, or a layer which has been made diffusing for example by abrasion of its surface. Alternatively, discrete areas of the screen  830  corresponding to regions X, Y, Z, or parts thereof, as in  FIG. 2  may be made diffusing. Regions of the screen  830  outside the regions X, Y, Z may be permanently opaque. The front surface of screen  830  may be at least partially reflective to provide a reflected image of the fuel bed  814  and so to achieve the perception of flames appearing from the middle of the fuel bed. 
     Thus, to provide a flame effect, the control unit  24  excites in its predetermined sequence selected segments  36 A-E of the first electrode layer. Excitation of these segments causes the corresponding areas, such as zones  38 A-E, of the electroluminescent layer to emit light. If present, corresponding zones of an SPD/LCD become transparent by excitation of their corresponding first electrode segment. The control unit  24  may preferably also control selective illumination of the light sources  850 A,B in accordance with the particular segments  36 A-E which are excited at any given time. 
     For example, the sequence of excitation under the control of control unit  24  may be (a) excitation of all segments of the first electrode layer corresponding to regions X, (b) excitation of all segments of the first electrode layer corresponding to regions Y, (c) excitation of all segments of the first electrode layer corresponding to regions Z, (d) excitation of all segments of the first electrode layer corresponding to regions X and so on. As noted above, a given region X, Y, Z may comprise one or more segments of the first electrode layer  36 . Thus, different areas of a given region X, Y, may be caused to emit light at different times, or the whole region X, Y, Z may be caused to emit light, and said different areas may exhibit different colours in accordance with the choice and particular arrangement of the light source or source  850 A,B and the particular electroluminescent materials. Thus a very realistic flame effect may be achieved. Where a diffusing element as indicated at  852  is present, the screen  830  may not require an LCP/SPD device, as selective control of the illumination of the light sources, which are then preferably small light sources such as LEDs in register with specific local regions of the screen, is sufficient to achieve a satisfactory flame effect in conjunction with selective excitation of the zones of the electroluminescent layer. 
     The control unit  24 ,  524  is arranged so that the various segments  36 A-E or  536 A-E are excited in a sequence and timing so that the user&#39;s eye always perceives flames to be present, in one location or another. Also, the control unit  24 ,  524  may optionally be programmed so that a user may select from a range of parameters for the simulated fire, such as the speed of change of the flames, or the intensity of the light emitted 
     When the simulated flame effect fire of the invention is not in use, the screen,  530 ,  630  is opaque and, preferably, of a dark colour. Screens  30 ,  130 ,  230 ,  330 ,  430  can be made opaque by addition of an LCP or SPD device. A pleasing unobtrusive effect is thereby obtained. Where the simulated flame effect fire includes a front screen such as  12 A in  FIG. 1 , that too can be constructed as an LCP or SPD screen which is transparent when the fire is in use and opaque when the fire is not in use. 
     An advantage of screens  30 ,  130 ,  230 ,  330   430 ,  530  is that they are very thin, typically  10 mm or less. Thus the simulated fires constructed in accordance with the invention may be made to have a very small front to back dimension and as such may are suitable for direct mounting on a plane wall. In other words a hearth or chimney is not needed. This is advantageous when the simulated fire is to be installed in a house of modern construction, an apartment or the like. 
     In an advantageous embodiment, the apparatus and simulated flame effect fires of the invention may be provided with an additional electroluminescent screen, or with an additional electroluminescent material and associated electrodes on the screen  30 ,  130 ,  230 ,  330 ,  430 ,  530 ,  830 ,  930  which is arranged to provide an aesthetically pleasing image or pattern, different from the simulated flame effect, when the flame effect is turned off. In an alternative variation, where the screen is transparent, an image or picture may be located behind the screen so that when the electroluminescent flame effect is not required, the picture is visible. 
     Whereas the devices described in relation to the present invention have been described in relation to flame effect fires, other effects are possible and are within the scope of the invention. For example the constructions described herein may be used simply to provide an aesthetically pleasing effect of changing light patterns which may or may not resemble flames. The fuel bed  14 ,  114 ,  214 ,  314 ,  414 ,  514  may be replaced with another aesthetically pleasing construction, such as a bed of coloured or colourless glass or plastic beads, a bed of real or simulated pebbles and the like. 
     The simulated flame effect fires according to the invention may or may not be provided with a heat source. A typical heat source is a fan heater mounted within housing  12 ,  212 ,  312 ,  412 ,  512  which expels a current of heated air. Radiant heaters may also be employed. However, many residences, offices, hotels and so on are now centrally heated so that additional heating is no longer required. Thus the flame effect fire of the invention may be used, for example to provide an attractive focal point in a room, with any heat source being necessary. 
     The use of an SPD or LCP screen may also be adapted to the types of simulated fire construction illustrated in  FIGS. 5 ,  6  and  7  which employ curved screens.