Abstract:
A method of filling a multilayered cell with media. In the method, a multilayered cell having at least two layers, i.e., a first and second layer, is filled with media. The method comprises forming in the first layer a first medium injection region for filling the first layer with a first medium, forming in the second layer a second medium injection region for filling the second layer with a second medium, the second medium injection region corresponding to a region different from the first medium injection region, superposing the first and second layers, forming within the first medium injection region a first through-hole extending through the multilayered cell in the layer-thickness direction, forming within the second medium injection region a second through-hole extending through the multilayered cell in the layer-thickness direction, and injecting the first and second media into the first and second through-holes, respectively, to fill the first and second layers with the first and second media. Thus, a multilayered cell can be easily produced in a shorter time while attaining a reduction in deterioration during production.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation application and is based upon PCT/JP2006/301885, filed on Feb. 3, 2006. 
    
    
     BACKGROUND 
     The embodiment relates to a multilayered cell, to an electronic terminal, and to a method of filling a multilayered cell with media. 
     In recent years, a technology has been rapidly developing in the field of electronic papers, wherein a displayed image on an electronic paper can be retained indefinitely without a power source and can be rewritten electrically. The technology of electronic papers aims to realize a display which is thin and flexible like a paper and which is of extremely low power consumption permitting an image to remain displayed as memory even when a power source is disconnected, and which provides an eye-friendly reflective display that is not wearisome to eyes. 
     The technology of electronic paper is now being actively developed in various corporations and research institutions such as universities. As promising application markets for electronic paper, various applications are proposed such as e-books (electronic books), electronic newspapers, electronic posters, as well as sub-displays of mobile terminals and displays for IC cards. 
     As a method for displaying on an electronic paper, various methods are contemplated and being actively developed, including, for example, an electrophoretic method in which charged particles are moved in air or in a liquid, a twist ball display method in which charged particles divided in two colors are rotated, a method using a bistable and selectively reflective cholesteric liquid crystal which permits interference reflection from liquid crystal layers, and the like. 
     Among these methods, the method using a cholesteric liquid crystal is overwhelmingly advantageous for color display in that, in methods other than by using a cholesteric liquid crystal, color filters need to be provided to divide each pixel into three colors so that brightness is reduced to at most ⅓ of the incident light, making these methods impractical. On the contrary, in the method using a cholesteric liquid crystal, since color is produced by interference of reflection from liquid crystal layers, color display is made possible simply by laminating the liquid crystal layers and is advantageous in that brightness of approximately 50% of the incident light can be achieved. 
     The cholesteric liquid crystal which is considered to be promising material as an electronic paper has excellent characteristics such as semi-permanent display image retaining capability (memory capability), a clear color display, high contrast and high resolution image, etc., and enables clear full color display to be realized by laminating three display layers R (red), G (green), and B (blue), reflecting red, green, and blue colors, respectively 
     Since a cholesteric liquid crystal material is a liquid crystal having the property of a memory, and can be driven in an inexpensive and simple matrix drive mode, it is relatively easy to realize, for example, a large display of A4 size or larger. Further, with the cholesteric liquid crystal, only the renewal of the content of display (rewriting an image) needs electric power, and once the image has been rewritten, the image is retained even when the electric power source is entirely turned off. 
     In this specification, an electronic paper having multilayered configuration consisting of three layers (R, G, and B layers) of cholesteric liquid crystal material is mainly described as an example which enables full-color display. However, a multilayered cell (display device) according to the embodiment is not limited to such an electronic paper, but can be applied more widely to, for example, a multilayered cell composed of a plurality of layers (that is, two or more layers) having respective media filled therein, such as an electrochemical photo-cell, and the like. 
     First, an example of driving method for cholesteric liquid crystal is described as an example of display device to which the embodiment can be applied. 
       FIG. 1A  and  FIG. 1B  are views useful for explaining orientation states of a cholesteric liquid crystal, wherein  FIG. 1A  shows a planar state and  FIG. 1B  shows a focal conic state. 
     When no electric field is applied, cholesteric liquid crystal can take one of two stable states, that is, planar state and focal conic state. 
     Thus, as shown in  FIG. 1A , in a planar state, incident light is reflected from the liquid crystal so that reflected light can be seen with human eyes. 
     As shown in  FIG. 1B , in a focal conic state, incident light passes through the liquid crystal, and therefore, by providing a light absorption layer separate from the liquid crystal layer, black color can be displayed in focal conic state. 
     Here, in planar state, light having wavelength corresponding to the spiral pitch of the liquid crystal molecules is reflected. The wavelength λ for which maximum reflection is obtained can be expressed as λ=n·p, where n is mean refractive index, and p is the spiral pitch. Reflection bandwidth Δλ increases with refractive index anisotropy Δn of the liquid crystal. 
       FIG. 2A ,  FIG. 2B , and  FIG. 2C  are views showing voltage characteristics (relation of voltage and time) for driving the cholesteric liquid crystal, showing electric field applied to the liquid crystal for respective variations of homeotropic state, focal conic state, and planar state. Here, symbols H, FC, and P represent homeotropic state, focal conic state, and planar state, respectively. 
     When a strong electric field is applied to the cholesteric liquid crystal, the spiral structure of the liquid crystal molecules is completely loosened, and the transition to homeotropic state H in which all the molecules are aligned with the electric field occurs. 
     As shown in  FIG. 2B , when the electric field is suddenly reduced to zero from the homeotropic state, the spiral axis of the liquid crystal becomes perpendicular to the electrode, and the transition to planar state P occurs in which light is selectively reflected in accordance with the spiral pitch. 
     On the other hand, when a weak electric field in which spiral axis of the liquid crystal molecules is barely loosened is formed and then reduced to zero, as shown in  FIG. 2A , or when a strong electric field is first applied and is slowly reduced to zero, as shown in  FIG. 2C , the spiral axis of the liquid crystal becomes parallel to the electrode, and the transition to the focal conic state FC occurs in which incident light is transmitted through the liquid crystal. 
     When electric field of an intermediate strength is applied to the liquid crystal and is suddenly removed, liquid crystals in planar state P and in focal conic state FC exist in a mixture, permitting a display in an intermediate tone. 
     Thus, cholesteric liquid crystal is bistable, and this phenomenon can be used to display information. 
       FIG. 3  is a view showing reflectivity characteristics (relation of reflectivity to voltage) of the cholesteric liquid crystal, which summarizes the voltage response of the cholesteric liquid crystal described above with reference to  FIGS. 2A to 2C . 
     As shown in  FIG. 3 , if the initial state is planar state P (the high reflectivity region at the left end of  FIG. 3 ), when the pulse voltage is raised to a certain range, the transition to the drive band of focal conic state FC (the low reflectivity region of  FIG. 3 ) occurs, and when the pulse voltage is raised further, the transition back to the drive band of planar state P (the high reflectivity region at the right end of  FIG. 3 ) occurs. 
     If the initial state is focal conic state FC (the low reflectivity region at the left end of  FIG. 3 ), as the pulse voltage is raised, gradual transition to the drive band of planar state P occurs. 
     In planar state P, only right hand circularly polarized light or left hand circularly polarized light is reflected and the rest of the light is transmitted, so that theoretical maximum reflectivity is 50%. 
       FIG. 4  is a block diagram schematically showing an example of an electronic terminal (display apparatus) having a display device applied thereto. In  FIG. 4 , reference numeral  1  denotes a display device (multilayered cell),  3  denotes a power supply circuit,  4  denotes a control circuit,  21  denotes a driver IC on the scanning side (scan driver), and  22  denotes a driver IC on the data side (data driver). 
     As shown in  FIG. 4 , the power supply  3  comprises a voltage step-up section  31 , a voltage generating section  32  and a regulator  33 . The voltage step-up section  31  receives an input voltage of about +3 to +5V from a battery, and raised it to a voltage suitable for driving a display device  1 , and supplies it to the voltage generating section  32 . The voltage generating section  32  generates voltages required for the scan driver  21  and for the data driver  22 , respectively. The regulator  33  regulates and stabilizes the voltages from the voltage generating section  32  and supplies them to the scan driver  21  and for the data driver  22 . 
     The control circuit  4  comprises an operational section  41 , a control signal generating section  42  and an image data generating section  43 . The operational section  41  performs operation on the externally supplied image data and control signal to transmit the image data via the image data generating section  43  as data suitable for the display device  1  to the data driver  22 , and the control signal via the control signal generating section  42  as various control signals suitable for the display device  1  to the scan driver  21  and the data driver  22 . 
     Here, the control signals transmitted from the control signal generating section  42  to the scan driver  21  and the data driver  22  includes, for example, a pulse polarity control signal CS 2  for inversion control of the polarity of pulse voltage imparted to the display device  1 , a frame start signal CS 3  for indicating the start of an image of 1 frame, a data latch scan shift signal CS 4  for controlling data for a line to be stored by the data driver  22  in synchronism with a line selected by the scan driver  21 , a driver output shutoff signal CS 5  for shutting off driver output from the data driver  22  and the scan driver  21 , and the like. Further, a data acquisition clock CS 1  for successively acquiring data for 1 line is also supplied from the control signal generating section  42  to the data driver  22 . 
       FIG. 5  is a sectional view schematically showing a part of the display device (liquid crystal display device: multilayered cell) shown in  FIG. 4 , that is, showing a layer (individual layer R, G, B). In  FIG. 5 , reference numerals  11  and  15  denote substrates (film substrates),  12  and  14  denote transparent electrodes (for example, ITO), and  13  denotes a liquid crystal composition (cholesteric liquid crystal),  16  denotes a driver circuit, and  17  denotes a sealant. 
     The display device  1  comprises the liquid crystal composition  13 , and on the inner surfaces of the transparent substrates  11  and  15  (surfaces between which the liquid crystal composition is encapsulated), a plurality of transparent electrodes  12  and  14  are formed so as to intersect each other orthogonally. That is, on the opposing substrates  11  and  15 , a plurality of scan electrodes  12  and a plurality of data electrodes  14  are formed in the shape of a matrix. It is to be understood that, in  FIG. 5 , the scan electrodes  12  and the data electrodes  14  are depicted as seemingly parallel to each other, but that, in practice, a plurality of data electrodes  14  intersect any one of the scan electrodes  12 . Thickness of each substrate  11  and  15  is, for example, about 0.2 mm, and thickness of the layer of the liquid crystal composition  13  is, for example, about 3 μm to 60 μm, although, in the Figure, proportion of the thickness is ignored for simplicity of explanation. 
     Here, coatings of an insulating thin film and an orientation stabilizing film are preferably formed on each of the electrodes  12  and  14 . Further, a light absorption layer for absorbing visible light is provided as required on the bottom (back surface) of the substrate ( 12 ) that is opposite to the light incident side of the lowermost layer (for example, R layer). The liquid crystal composition  13  is, for example, cholesteric liquid crystal that exhibits a cholesteric phase at room temperature. 
     The sealant  17  is the material for encapsulating the liquid crystal composition  13  between the substrates  11  and  15 . The driver circuit  16  is provided in order to apply a predetermined pulse voltage between the electrodes  12  and  14 . 
     The substrates  11  and  15  may be exemplified, for example, by glass substrates. Other material than the glass substrates, for example, flexible resin film substrates such as PET, PC, etc., may also be used. As the electrodes  12  and  14 , ITO (Indium Tin Oxide) is typically used. However, other material, for example, transparent conductive film such as IZO (Indium Zinc Oxide), or metal electrodes such as aluminium, or silicon, or amorphous silicon, or photoconductive film such as BSO (Bismuth Silicon Oxide) or the like, may also be used. 
     In the liquid crystal display device shown in  FIG. 5 , a plurality of mutually parallel and transparent strip electrodes  12  and  14  are formed on the inner surfaces of the transparent film substrates  11  and  15 , and these electrodes  12  and  14  are opposed to each other so as to intersect each other as seen in the direction perpendicular to the substrates. 
     Here, the display device may have an insulating thin film formed thereon which has functions of preventing short circuit between electrodes or improving reliability of the liquid crystal display device as a gas barrier layer. As an orientation stabilizing film, an organic film such as polyimide resin, polyamide-imide resin, polyether-imide resin, polyvinyl butylal resin, acryl resin, or the like, or inorganic material such as silicon oxide, aluminium oxide, or the like, may be used. The orientation stabilizing film coated on the electrode  12  and  14  may be used also as an insulating thin film. 
     The liquid crystal display device may have spacers provided between a pair of substrates for maintaining uniform gap between the substrates. As spacers, spheres of resins or inorganic oxides may be used, for example. Adhesive spacers having thermoplastic resin coated on the surface thereof may be used advantageously. 
     The multilayered cell of the embodiment is not limited to the liquid crystal display cell having liquid crystal layers such as R, G, and B layers. The embodiment may be widely applied to a multilayered cell such as an electrochemical photocell composed by filling a plurality of layers with respective media. It is to be understood that the multilayered cell can be applied in various fields such as electronic papers for e-books, electronic terminals such as mobile terminals as described above, and the like. 
       FIG. 6  is a view showing an example of multilayered cell (display device). In  FIG. 6 , reference numeral  101  denotes a blue (B) layer for reflecting blue light,  102  denotes a green (G) layer for reflecting green light,  103  denotes a red (R) layer for reflecting red light, and  104  denotes a black (K) layer for absorbing light. 
     As shown in  FIG. 6 , the display device  1  has a laminated structure having R layer  103 , G layer  102 , and B layer  101  laminated in this order on K layer  104 . B layer  101  is composed of liquid crystal  113  sandwiched by opposing substrates (film substrates) and transparent electrodes  111 ,  112 , and  115 ,  114 . G layer  102  is composed of liquid crystal  123  sandwiched by opposing substrates (film substrates) and transparent electrodes  121 ,  122 , and  125 ,  124 . R layer  103  is composed of liquid crystal  133  sandwiched by opposing substrates (film substrates) and transparent electrodes  131 ,  132 , and  135 ,  134 . Lamination in the order of B layer  101 , G layer  102 , and R layer  103  as seen from the side of incident light is intended, for example, to obtain a wide view angle as well as to obtain suitable color display by reflection from respective layers. Other order of layer arrangement may be employed. 
     The transparent electrodes  112  and  114  for B layer  101  are connected to a control circuit  110  for controlling B layer, and the transparent electrodes  122  and  124  for G layer  102  are connected to a control circuit  210  for controlling G layer, and transparent electrodes  132  and  134  for R layer  103  are connected to a control circuit  310  for controlling R layer. Here, the transparent electrodes  112 ,  114 ;  122 ,  124 ;  132 ,  134  for each layer comprise scan electrodes and data electrodes, respectively, which are opposed to and intersect each other. In each of the layers  101  to  103 , a scan driver is connected to the scan electrodes and a data driver is connected to the data electrodes. With the construction as described above, the display device  1  is capable of displaying nearly in full color. 
     In the foregoing, the display device is composed of a QVGA of A6 size, and the order of laminating B layer  101 , G layer  102 , and R layer  103 , the direction of polarization of light in the liquid crystal, and the drivers used, and the like, are the same as in the QVGA display device of A4 size described above with reference to  FIG. 5 . In  FIG. 6 , the control circuits (scan drivers)  130  to  110  for each of R, G, and B layers are provided separately. By using a common scan driver ( 130  to  110 ) for each of R, G, and B layers, cost saving is possible. 
     Conventionally, Various multilayered cells (liquid crystal optical modulation devices) have been proposed for color display using cholesteric liquid crystal, and a liquid crystal optical modulation device which is bright and exhibits good contrast and color purity, and has an excellent bistable characteristics has been proposed (see, for example, JP-2002-116461-A). 
     Also, in prior art, a liquid crystal display panel has been proposed which permits liquid crystal to be injected completely in a short time and in which at least one injection port is formed through the substrate for evacuating the inner space and for injecting the liquid crystal, and after the liquid crystal has been injected into the liquid crystal display panel which has a protruding part enclosing the injection port, the protruding part including the injection port which become unnecessary thereafter is separated and removed (see, for example, JP-2002-287157-A). 
     Further, in prior art, a manufacturing method for laminated type liquid crystal display cell formed by laminating a plurality of liquid crystal display cells each with liquid crystal material encapsulated therein has been proposed, wherein, in order to satisfactorily suppress mixing of impurities into a prescribed liquid crystal material in the individual liquid crystal display cells, and to make a cell gap of each liquid crystal display cell to reach a target value, each peripheral part of a pair of substrates opposed to each other is sealed except for at least one liquid crystal injection port communicating with an external part, and then, a laminated type hollow cell is formed by stacking a plurality of hollow cells, and liquid crystal material is filled into each hollow cell of the laminated type hollow cell through the liquid crystal injection port simultaneously or nearly simultaneously by vacuum injection (see, for example, JP-2003-161960-A). 
     Also, in prior art, in order to provide a multilayered cell such as a liquid crystal display cell or an electrochemical photo cell, etc., comprising a plurality of superposed substrates joined in pairs by a sealed frame, a multilayered cell has been proposed in which filling holes are provided so as to be at least partially disposed on the cell surface, each filling hole communicating with different space and passing through at least one space to reach a space wherein the holes are joined, filling holes being isolated from each other in the one or plural spaces where they pass through (see, for example, JP-2004-029786-A). The multilayered cell permits different liquids such as liquid crystal materials to be filled into each cell at the same time. 
     As has been described above, in recent years, an electronic paper using cholesteric liquid crystal or the like has been proposed, and an electronic paper having three layers, that is, R, G, and B layers, of cholesteric liquid crystal in a multilayered structure and permitting full color display is being developed for practical use. 
     Typically, in order to manufacture a laminated type liquid crystal color display device (multilayered cell), conventionally, R, G, and B panels are individually manufactured, and thereafter, R, G, and B panels are joined and laminated by means of adhesive or the like. 
     In the process for laminating these panels, conventionally, heat or light, for example, needs to be applied to the panels in order to harden the adhesive and to join and fix these panels to each other. This process may adversely affect individual members used in the panels, especially the liquid crystal, and may become an important factor for deteriorating the characteristics of the liquid crystal. 
     Further, when overheating of the panel is required in the lamination process, expansion of the volume of the liquid crystal in each panel (cell) or the like may cause the sealing portion to leak, or may damage the panels, resulting in lowering of the yield. 
     It is preferable, in order not to lower the efficiency for manufacturing a multilayered cell (display device), that filling of liquid crystal into each of R, G, and B layers can be carried out simultaneously. 
     SUMMARY 
     According to an aspect of an embodiment, there is provided a multilayered cell having at least a first layer and a second layer, wherein the first layer has a first medium injection region for filling the first layer with a first medium; and the second layer has a second medium injection region for filling the second layer with a second medium, the second medium injection region corresponding to a region different from the first medium injection region, and wherein the multilayered cell comprises: a first through-hole extending through the multilayered cell in a layer-thickness direction within the first medium injection region for filling the first medium only into the first layer; and a second through-hole extending through the multilayered cell in the layer-thickness direction within the second medium injection region for filling the second medium only into the second layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a view (part 1) useful for explaining an orientation state of cholesteric liquid crystal; 
         FIG. 1B  is a view (part 2) useful for explaining an orientation state of cholesteric liquid crystal; 
         FIG. 2A  is a view (part 1) showing a voltage characteristics for driving cholesteric liquid crystal; 
         FIG. 2B  is a view (part 2) showing a voltage characteristics for driving cholesteric liquid crystal; 
         FIG. 2C  is a view (part 3) showing a voltage characteristics for driving cholesteric liquid crystal; 
         FIG. 3  is a view showing reflectivity characteristics of cholesteric liquid crystal; 
         FIG. 4  is a block diagram schematically showing an example of electronic terminal having the display device applied thereto; 
         FIG. 5  is a sectional view schematically showing a portion of the display device shown in  FIG. 4 ; 
         FIG. 6  is a view showing an example of multilayered cell; 
         FIG. 7  is a view schematically showing an example of each cell comprising a multilayered cell according to the embodiment; 
         FIG. 8  is a view useful for explaining a preliminary step in a method of filling a multilayered cell with media according to the embodiment; 
         FIG. 9A  is a plan view showing a multilayered cell formed by the preliminary step of  FIG. 8 ; 
         FIG. 9B  is a sectional view taken along the line A-A of the multilayered cell shown in  FIG. 9A ; 
         FIG. 10A  is a plan view showing the multilayered cell shown in  FIG. 9A  and  FIG. 9B  having through-holes for injecting media formed therein; 
         FIG. 10B  is a sectional view taken along the line B-B of the multilayered cell shown in  FIG. 10A ; 
         FIG. 11A  is a plan view showing the multilayered cell shown in  FIG. 10A  and  FIG. 10B  having media filled into therein; 
         FIG. 11B  is a sectional view taken along the line C-C of the multilayered cell shown in  FIG. 11A ; 
         FIG. 12  is a view useful for explaining an example of injection step for injecting media in the method of filling the multilayered cell with media according to the embodiment; and 
         FIG. 13  is a view useful for explaining another example of injection step for injecting media in the method of filling the multilayered cell with media according to the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Before describing examples of the embodiment in detail, a method of filling a multilayered cell with media according to the embodiment will be outlined. In the following description, a liquid crystal display cell having liquid crystal filled into three layered cell, i.e., R, G, B layers representing three primary colors is illustrated as an example. However, the embodiment can also be applied more widely to various multilayered cells, for example, to an electrochemical photocell or the like, having a plurality of layers filled with different media. 
     First, a sealant ( 17 ,  117 ,  127 ) is applied to one of two substrates used for each cell, and an adhesive (barrier  119 ;  129   a ,  129   b ;  139 ) is thickly applied around the liquid crystal injection region ( 118 ,  128 ,  138 ). 
     Then, spacers are scattered on either the substrate having the sealant applied thereto or the other substrate, and after two substrates have been attached to each other to form a cell, three layers are laminated by using an adhesive (see  FIG. 8 ). 
     Further, after laminating three layers, through-holes ( 151 ,  152 ,  153 ) are provided in the liquid crystal injection regions ( 118 ,  128 ,  138 ) for each layer (see  FIG. 10A  and  FIG. 10B ). 
     Then, for example, the empty cell after lamination is placed into a vacuum chamber, and after evacuating the chamber, while maintaining the chamber under vacuum, desired liquid crystal to be filled into R, G, or B layer is injected into through-holes ( 151 ,  152 ,  153 ), respectively (see  FIG. 12 ). 
     Then, upon releasing the chamber from vacuum, the liquid crystal materials for R, G, B layers are filled into corresponding cell, respectively. 
     Here, the three layers of empty cell can be laminated into one unit, and a plurality of units can be stacked so that injection of liquid crystal may be performed simultaneously to a plurality of units. 
     Below, an embodiment of a multilayered cell and a method of filling the multilayered cell with media according to the embodiment will be described in detail with reference to appended drawings. 
       FIG. 7  is a view schematically showing an example of each cell composing a multilayered cell according to the embodiment, showing R, G, B layers individually. Here, the multilayered cell  1  shown in  FIG. 7  corresponds to the multilayered cell (display device) described above with reference to  FIG. 6 . 
     Thus, the multilayered cell  1  is composed of lamination of B layer  101  reflecting blue light, G layer  102  reflecting green light, and R layer  103  reflecting red light, in this order from the top (from the plane of observation). Under the lowermost R layer  103 , unshown K layer ( 104 ) absorbing light may be provided. 
     The sealant  117  for B layer  101  joins opposing substrates so as to provide a medium injection region  118  for injecting cholesteric liquid crystal for blue color (medium for blue color), and the sealant  127  for G layer  102  joins opposing substrates so as to provide a medium injection region  128  for injecting cholesteric liquid crystal for green color (medium for green color), and the sealant  137  for R layer  103  joins opposing substrates so as to provide a medium injection region  138  for injecting cholesteric liquid crystal for red color (medium for red color). 
     As shown in  FIG. 7 , the medium injection region  118  for blue color, the medium injection region  128  for green color, and the medium injection region  138  for red color are arranged such that, when the three layers, that is, B layer  101 , G layer  102  and R layer  103 , are joined and fixed to each other, these regions are disposed at different positions. 
     When three layers are joined, the barrier (filler)  119  is provided in the B layer  101  at location corresponding to the medium injection region  128  for green color and the medium injection region  138  for red color, and the barriers  129   a  and  129   b  are provided in the G layer  102  at locations corresponding to the medium injection region  138  for red-green color and to the medium injection region  118  for blue color, and the barrier (filler)  139  is provided in the R layer  103  at location corresponding to the medium injection region  118  for blue color and the medium injection region  128  for green color, wherein barriers  119 ,  129   a ,  129   b ,  139  are filled between opposing substrates ( 111 ,  115 ,  121 ,  125 ,  131 ,  135 ) in each of B, G, R layers, and heat curable resin or UV curable resin may be used. 
       FIG. 8  is a view useful for explaining a preliminary step of a method of filling a multilayered cell with media according to the embodiment. 
     First, as shown in the left of  FIG. 8 , B layer  101 , G layer  102 , and R layer  103  are respectively assembled by using sealant  117 ,  127 , and  137  and barriers  119 ,  129   a ,  129   b , and  139  of heat curable resin or the like. Positional relation between the medium injection regions  118 ;  128 ;  138  and barriers  119 ;  129   a ,  129   b ;  139  is as described above with reference to  FIG. 7 . 
     Here, if application of heat or UV irradiation is required for hardening of the sealant  117 ,  127 ,  137  and the barriers  119 ;  129   a ,  129   b ;  139 , the application of heat or UV irradiation is performed before injection of media (liquid crystal) into respective layers. 
     Next, as shown in the center figure of  FIG. 8 , B layer  101 , G layer  102 , and R layer  103 , which are empty with respective media not yet injected, are joined using adhesive  141 ,  142  to form a multilayered cell as shown in the right of  FIG. 8 . At this time, color material such as G-cut filter for attenuating specific color (for example, green) may be applied between layers. 
     Again, if application of heat or UV irradiation is required for hardening the adhesive  140  to reinforce the joint between layers  101 ,  102 , and  103 , such application of heat or UV irradiation is performed before injection of media (liquid crystal) into respective layers. 
     When, for example, a light absorption layer is provided under R layer  103  as described above, an adhesive or the like is used at this stage to join and fix the light absorption layer. In this manner, a multilayered cell is formed before media are injected (filled) into respective layers. 
       FIG. 9A  is a plan view showing a multilayered cell formed by the preliminary step of  FIG. 8 , and  FIG. 9B  is a sectional view taken along the line A-A of the multilayered cell shown in  FIG. 8 . 
     As is evident from  FIG. 9A  and  FIG. 9B , when B layer  101 , G layer  102 , and R layer  103  are joined and fixed by adhesive  141 ,  142 , the barrier  119  is present at locations in B layer  101  corresponding to the medium injection region  128  for green color and the medium injection region  138  for red color, the barriers  129   a  and  129   b  are present at locations in G layer  102  corresponding to the medium injection region  138  for red-green color and the medium injection region  118  for blue color, and the barrier  139  is present at locations in R layer  103  corresponding to the medium injection region  118  for blue color and the medium injection region  128  for green color. 
       FIG. 10A  is a plan view showing through-holes formed for injecting media into the multilayered cell shown in  FIG. 9A  and  FIG. 9B , and  FIG. 10B  is a sectional view taken along the line B-B of the multilayered cell shown in  FIG. 10A .  FIG. 11A  is a plan view showing the multilayered cell shown in  FIG. 10A  and  FIG. 10B  having media injected therein, and  FIG. 11B  is a sectional view taken along the line C-C of the multilayered cell shown in  FIG. 11A . 
     As shown in  FIG. 10A  and  FIG. 10B , a through-hole  151  for blue color extending through three layers, i.e., B, G, R layers  101 ,  102 ,  103  is formed in the medium injection region  118  for blue color in B layer  101 . As shown in  FIG. 11A  and  FIG. 11B , the through-hole  151  for blue color is formed such that, when a medium for blue color (cholesteric liquid crystal for blue color) is injected via the through-hole  151  for blue color into B layer  101 , the medium for blue color is injected only into B layer  101 , and injection of the medium for blue color into other layers, i.e., G layer  102  and R layer  103 , is inhibited by the barriers  129   b  and  139 . 
     Similarly, a through-hole  152  for green color extending through three layers is formed in the medium injection region  128  for green color in G layer  102 . The through-hole  152  for green color is formed such that, when a medium for green color (cholesteric liquid crystal for green color) is injected via the through-hole  152  for green color into G layer  102 , the medium for green color is injected only into G layer  102 , and injection of the medium for green color into other layers, i.e., B layer  101  and R layer  103 , is inhibited by the barriers  139  and  119 . 
     Further, a through-hole  153  for red color extending through three layers is formed in the medium injection region  138  for red color in R layer  103 . The through-hole  153  for red color is formed such that, when a medium for red color (cholesteric liquid crystal for red color) is injected via the through-hole  153  for red color into R layer  103 , the medium for red color is injected only into R layer  103 , and injection of the medium for red color into other layers, i.e., B layer  101  and G layer  102 , is inhibited by the barriers  119  and  129   a.    
     Injection (filling) of the media for blue color, for green color and for red color into B layer  101 , G layer  102 , and R layer  103  can be carried out simultaneously. Injection of each medium into corresponding through-hole is carried out with a shield member  160  such as silicone rubber, or the like, disposed under the lower substrate  135  of the lowermost layer, i.e., R layer  101 . 
       FIG. 12  is a view useful for explaining an example of medium injection step in the method of filling a multilayered cell with media according to the embodiment. In  FIG. 12 , reference numeral  200  denotes a vacuum chamber, and the multilayered cell in the upper right portion of the figure corresponds to that shown in  FIG. 10A  and  FIG. 10B , and the multilayered cell in the lower right portion of the figure corresponds to that shown in  FIG. 11A  and  FIG. 11B . 
     As shown in the upper portion of  FIG. 12 , the multilayered cell (empty cell)  1  after lamination is placed in the vacuum chamber  200 , and the chamber  200  is evacuated. Then, while maintaining the inside of the chamber  200  under vacuum, cholesteric liquid crystal for blue color, cholesteric liquid crystal for green color, and cholesteric liquid crystal for red color are injected (dropped) into the through-hole  151  for blue color, through-hole  152  for green color, and through-hole  153  for red color, respectively. Under the lowermost layer, i.e., R layer  101 , a shield member  160  such as silicone rubber, for example, is disposed. 
     Then, as shown in the upper portion of  FIG. 12 , upon releasing the chamber from vacuum, the cholesteric liquid crystal materials for blue color, for green color, and for red color are filled into the space between the opposing substrates of B layer  101 , G layer  102 , and R layer  103 . 
       FIG. 13  is a view useful for explaining another example of medium injection step in the method of filling a multilayered cell with media according to the embodiment. 
     As is evident from comparison of  FIG. 13  with  FIG. 12 , in the method of filling a multilayered cell with media according to this Example, the multilayered cell shown in  FIG. 12  is taken as a unit (multilayered cell unit), and two such multilayered cell units  1   a  and  1   b  are superposed one upon the other with a cohesion member  170  such as silicone rubber sandwiched therebetween, such that media can be injected simultaneously into the multilayered cell units  1   a  and  1   b.    
     Here, as is evident from  FIG. 13 , holes are provided in the cohesion member  170  at positions corresponding to the through-holes  151 ,  152 , and  153 . It is to be understood that number of superposed multilayered cell units is not limited to two. 
     Thus, in accordance with the method of filling a multilayered cell with media according to the embodiment, liquid crystal cells are laminated before being filled with media, and thereafter, respective liquid crystals are filled into individual cells. Therefore, deterioration of liquid crystal, for example, due to application of heat or UV irradiation for hardening an adhesive can be eliminated. Also, in accordance with the method of filling a multilayered cell with media according to the embodiment, respective liquid crystals can be filled into individual cells without coming into contact and to be mixed with each other, so that a multilayered cell can be easily manufactured in short time, and the amount of liquid crystal lost at the time of filling can be reduced. Further, filling of liquid crystal into a plurality of multilayered cells (a plurality of multilayered cell units) cam be carried out simultaneously, so that multilayered cells can be manufactured more easily and in shorter time.