Patent Publication Number: US-2004041517-A1

Title: Electroluminescence light emitting display system and electroluminescence light emitting sheet

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to an electroluminescence light emitting display system and an electroluminescence light emitting sheet.  
       [0003] 2. Description of Related Art  
       [0004] An electroluminescence, hereinafter, which may be referred to EL simply, material is known as one of light emitting materials. Various types of EL light emitting sheets have been developed and put to practical use. The EL light emitting sheet is generally formed by laminating a first electrode, a light-emitting layer, an insulating layer, i.e., a light reflecting layer, a second electrode and a protective layer, i.e., a top coating layer, in order. Generally, by applying an alternating voltage (AC voltage) between the fist electrode and the second electrode, a fluorescent material, i.e., EL light emitting elements, in the light-emitting layer emits light.  
       [0005] As another type of EL light emitting sheet, one having peculiar operation and effects is known (see, for example, Patent Document 1: Japanese Patent Laid-Open Publication No. Hei-8-153582). The EL light emitting sheet is formed by laminating an electrode section, an insulating layer and a light-emitting layer in order. The electrode section includes a plurality of electrode pairs each of which have a first electrode and a second electrode, which are formed like a comb. Then, an electrically conductive material in arbitrary shape is formed on the light-emitting layer as a film and the film is dried to be formed as a display electrode. Thereby, the parts in the light-emitting layer on which the display electrode is formed as a film emit light. In the EL light emitting sheet, a display electrode having a shape corresponding to the taste of a user can be formed, and then a desired light emission shape can be obtained.  
       [0006] However, in the EL light emitting sheet according to such an earlier development, when a chart for light emission, of a thin line or a dot-shaped chart for light emission is placed thereon, the EL light-emitting layer often emits insufficient light or often creates flecks of light emission. The light emitting sheet according to the earlier development has a further problem that it is not possible to make the display electrode easily because deposition and drying of the electrically conductive material are required for making the display electrode.  
       SUMMARY OF THE INVENTION  
       [0007] The present invention has been developed in view of the above-described circumstances.  
       [0008] An object of the invention is mainly to provide an EL light emitting display system and an EL light emitting sheet, having a high probability of forming an AC electric field.  
       [0009] In accordance with a first aspect of the present invention, the electroluminescence light emitting display system comprises: an electroluminescence light emitting sheet which comprises a light-emitting layer containing electroluminescence light-emitting elements therein, and an electrode section comprising a plurality of electrode pairs which are disposed with a predetermined arrangement, wherein each of the electrode pairs includes first and second electrodes which are electrically separated from each other with a spacing region and disposed in one surface side of the light-emitting layer with a predetermined arrangement; and a voltage application unit for applying a predetermined voltage between the first and second electrodes, wherein when an electrically conductive material is placed on the other surface side of the light-emitting layer and a voltage application between the first and second electrodes is performed by the voltage application unit, a portion of the light-emitting layer corresponding to the placed electrically conductive material emits light; and each width of the first and second electrodes is 0.2-0.5 mm and a width of the spacing region between the first and second electrodes is 0.2-0.3 mm.  
       [0010] The reason for the above-described definition of gap or width is as follows.  
       [0011] When the gap between the first electrode and the second electrode is less than 0.2 mm, there is a large possibility that a light emission (spontaneous emission) which is not negligible is created in also a region onto which no conductive material is placed. When the gap is more than 0.3 mm, particularly, in a case of placing a chart of a thin line, flecks of light emission stand up. Under conditions, that is, EL sheet with a light emitting region of 140 mm×92 mm, starting voltage of 250V to 270V and current of 100 mA to 130 mA, luminance of emitted lights from two EL light emitting sheets which have gaps of 0.2 mm and 0.15 mm, respectively, were compared. As a result, the luminance of emitted lights from the EL light emitting sheet having the gap of 0.2 mm was 3±0.5 candela and that of 0.15 mm was 6±0.5 candela which was approximately twice that of 0.2 mm gap case. Therefore, it is considered that when assuming a regular use condition in an ordinary room as an industrial product, the luminance of emitted light, of 3±0.5 candela which is obtained by the gap of 0.2 mm is a lower limit. On the other hand, when the width sizes of the first electrode and the second electrode themselves are less than 0.2 mm, there are problems that the luminance of emitted lights may be lowered and the productivity may deteriorate by bridge or disconnection, occurred in mass production. When the width sizes are more than 0.5 mm, there is a problem that in a case of placing a dot-shaped chart for light emission by using a pen for drawing a thin line, probability of AC electric field formation with another electrode is lowered because the thin chart may be within the width of one electrode. When the width sizes are not more than 0.5 mm, the probability of AC electric field formation with another electrode is increased because the probability of the placed dot-shaped chart being out of the one electrode is much larger than that of the chart being placed at the center of the one electrode.  
       [0012] Thus, according to the EL light emitting display system, it is possible to emit light surely with maintaining a predetermined luminance, and to restrain occurrence of flecks of light emission, in comparison with the case of the earlier development, even when the electrically conductive material is a chart of a thin line or a dot-shaped chart.  
       [0013] Preferably, the electrically conductive material is attachable onto and detachable from the other surface side of the light-emitting layer.  
       [0014] According to the EL light emitting display system, it is possible to attach also a chart of a thin line or a dot-shaped chart thereon freely, to enable various change of light emission.  
       [0015] The electrode section may comprise a plurality of electrode pairs.  
       [0016] According to the EL light emitting display system, it is possible to perform various types of light emission with different light emission systems and/or different light emission ranges by controlling the voltage application to each of electrode pairs because of having a plurality of electrode pairs.  
       [0017] In accordance with a second aspect of the present invention, the electroluminescence light emitting sheet comprises: a light-emitting layer containing electroluminescence light-emitting elements therein; and an electrode section comprising a plurality of electrode pairs which are disposed with a predetermined arrangement, wherein each of the electrode pairs includes first and second electrodes which are electrically separated from each other with a spacing region and disposed in one surface side of the light-emitting layer with a predetermined arrangement, each width of the first and second electrodes is 0.2-0.5 mm and a width of the spacing region between the first and second electrodes is 0.2-0.3 mm.  
       [0018] According to the EL light emitting sheet, it is possible to emit light surely with maintaining a predetermined luminance, and to restrain occurrence of flecks of light emission, in comparison with the case of the earlier development, even when the electrically conductive material is a chart of a thin line or a dot-shaped chart. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0019]FIG. 1 is a partially enlarged sectional view of a principal part of an EL light emitting sheet according to an embodiment of the invention;  
     [0020]FIG. 2 is a schematic plan view showing a part of an electrode layer;  
     [0021]FIG. 3 is a perspective view of the external appearance of a drawing board;  
     [0022]FIG. 4 is a plan view showing an example of the external shape of the electrode pattern of the EL light emitting sheet built in the drawing board;  
     [0023]FIG. 5 is a functional block diagram of the drawing board;  
     [0024]FIG. 6 is a partially enlarged sectional view of a principal part according to variation  1  of the EL light emitting sheet;  
     [0025]FIG. 7 is a plan view showing the external shape of the electrode pattern according to variation  7  of the EL light emitting sheet;  
     [0026]FIGS. 8A and 8B are plan views of a signboard according to variation  1  of the EL light emitting display system;  
     [0027]FIG. 9 is a control block diagram for the signboard according to variation  1  of the EL light emitting display system; and  
     [0028]FIG. 10 is a perspective view of a drawing board according to variation  2  of the EL light emitting display system. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0029] Hereinafter, the preferred embodiments of the present invention will be described in detail by reference to the attached drawings.  
     [0030] A. EL Light Emitting Sheet  
     [0031] 1. Whole Configuration  
     [0032]FIG. 1 is an enlarged sectional view of a principal part of an EL light emitting sheet  10  to which the present invention is applied. In FIG. 1, the EL light emitting sheet  10  is formed by laminating a base layer  11 , an electrode layer (electrode section)  12 , a waterproof layer  13 , an EL light-emitting layer  14  and a top coat layer  15  in this order.  
     [0033] 2. Detailed Configuration  
     [0034] (1) Base Layer  11   
     [0035] The base layer  11  is made of an insulating material such as polyethylene terephthalate (PET) or the like. The base layer  11  may be configured as a base film (substrate sheet). In this case, the base film is made of a transparent or opaque resin. As the resin in this case, for example, PET is used. The base layer  11  may be made of glass.  
     [0036] (2) Electrode Layer  12   
     [0037] The electrode layer  12  having a predetermined electrode pattern is formed by depositing a metal such as copper, aluminum or the like on the base layer  11 , and thereafter by performing etching or the like to the deposited metal layer. Alternatively, the electrode layer  12  is formed by depositing, for example, a pasty silver paste including silver powder, a pasty copper paste including copper powder, another electrically conductive paste such as carbon, or the like on the base layer  11  in a predetermined pattern by the screen printing process, and thereafter by performing a heat drying process of the paste.  
     [0038]FIG. 2 is a schematic plan view showing a part of the electrode layer  12 . The electrode layer  12  of FIG. 1 shows the cross section of the electrode layer  12 , taken along the A-A′ line of FIG. 2. As shown in FIG. 2, first electrodes  12   a ,  12   a , . . . and second electrodes  12   b ,  12   b , . . . are formed to have a comb-like pattern shape severally, and they are formed to be engaged with each other with a predetermined gap between their teeth with putting a spacing region between each tooth so that each tooth does not touch each other. Since each of first electrodes  12   a ,  12   a , . . . is electrically connected with one another, each of them has the same electric potential. Since each of second electrodes  12   b ,  12   b , . . . is also electrically connected with one another similarly, each of them has the same electric potential.  
     [0039] Preferably, a plurality of electrode pairs each of which has the first electrodes  12   a ,  12   a , . . . and the second electrodes  12   b ,  12   b , . . . , as described above, are disposed with a predetermined arrangement.  
     [0040] Incidentally, it is preferable to form the first electrodes  12   a  and the second electrodes  12   b  so that the spacing regions therebetween may substantially be the same per a unit area in a light emitting region.  
     [0041] The gap S 1  between the first electrode  12   a  and the second electrode  12   b  which are next to each other in the light emission region may be, for example, about 0.1-2.0 mm, and the width S 2  of the first electrode  12   a  and the second electrode  12   b  themselves may be, for example, about 0.1-5.0 mm, which are enough for light emission only.  
     [0042] However, when taking into account the case of placing a chart for light emission, of a thin line which is approximately parallel to the extending direction of comb-shaped pattern electrode, or a dot-shaped chart for light emission, the gap S 1  between the first electrode  12   a  and the second electrode  12   b  which are next to each other is preferably about 0.2-0.3 mm, and the widths S 2  of the first electrode  12   a  and the second electrode  12   b  themselves are preferably about 0.2-0.5 mm, by the above-described reason.  
     [0043] (3) Waterproof Layer  13   
     [0044] The waterproof layer  13  is a layer for protecting the electrode layer  12  and is made of a resin. As the resin, the following resins can be used. That is, they are, for example, a fluorocarbon resin such as a 4-fluorinated ethylene resin, fluororubber and the like; a silicon resin such as silicon rubber and the like. Another resin having a high sealing property such as an epoxy resin, an acrylic resin, a urethane resin, a polyester resin, an ethylene-vinyl acetate copolymer or the like, can also be used. These resins are cured by a method such as ultraviolet (UV) curing, infrared (IR) curing, two-liquid curing, heat curing and the like.  
     [0045] (4) EL Light-Emitting Layer  14   
     [0046] The EL light-emitting layer  14  is made of organic or inorganic EL light-emitting material elements (fluorescent material) sealed with a sealing resin. The EL light-emitting material elements are fixed with being dispersed in a transparent resin binder.  
     [0047] As the resin binder, a resin having a high dielectric constant such as a polyester resin or the like may suitably be selected. The EL light-emitting layer  14  has a thickness of about 30-40 μm, a withstanding voltage of about 50-150 V, and a dielectric constant of about 10-30. The thickness of the EL light-emitting layer  14  is preferably one and a half times as large as the diameter of an EL light emitting material element or more. With such a thickness, the surfaces of the EL light-emitting layer  14  is regarded as being smooth, and for example, their surface roughness is regarded as being 30 μm or less.  
     [0048] The EL light-emitting layer  14  configured as above emits the light of a predetermined luminescent color such as a bluish green color when an AC power supply voltage is applied between the first electrodes  12   a  and the second electrodes  12   b.    
     [0049] (5) Top Coat Layer  15   
     [0050] The top coat layer  15  is stuck or fixed, closely to the EL light-emitting layer  14  to protect the EL light-emitting layer  14 . The top coat layer  15  is laminated on the EL light-emitting layer  14  also for improving the smoothness of the EL light-emitting layer  14  and the removability of an electrically conductive material  30 . When the EL light-emitting layer  14  itself can secure necessary smoothness and removability, it is unnecessary to provide the top coat layer  15  in particular.  
     [0051] As the top coat layer  15 , the following resins can be used. That is, they are, for example, a fluorocarbon resin such as a 4-fluorinated ethylene resin, fluororubber and the like; a silicon resin such as silicon rubber and the like; a polyester resin; an urethane resin and the like. Since the main object of providing the top coat layer  15  is, as described above, to smooth the surface of the EL light-emitting layer  14  and to improve the removability of conductive material out of the surface thereof, the thickness of the top coat layer  15  is enough to be a degree which makes it possible to attain the object. On the other hand, it is suitable that the top coat layer  15  is as thin as possible. The reason for this is that the more the thickness is, the more the luminous intensity of the EL light-emitting sheet  10  decreases. The thickness is practically preferable to be about 1-2 μm as the effective value. Hereupon, the “effective value” means the size of the thickness of the top coat layer  15  placed on the uppermost part of the EL light-emitting layer  14 . It is sufficient for obtaining the thickness of about 1-2 μm as the effective value to make the coating value of the thickness about 5-8 μm. Hereupon, the “coating value” means the thickness of the protection layer  15  when the coating is performed on a surface having no irregularities.  
     [0052] The top coat layer  15  may be formed by gluing a film-like or sheet-like member fixedly onto the EL light-emitting layer  14 , or by placing a flexible material member thereto closely.  
     [0053] (6) Electrically Conductive Material  30   
     [0054] As the electrically conductive material  30 , the following known materials can be used. That is, the conductive material includes: a stick type painting material such as a well-known ink, a pencil, a crayon, a pastel and the like; a sheet material having electrical conductivity (hereinafter referred to as a conductor sheet) and the like. As the stick type painting material such as the ink, the pencil, the crayon, the pastel and the like, ones including an organic or an inorganic coloring pigment may be used.  
     [0055] As the ink, one having the following properties is preferable. The properties are, for example, to have a surface resistance value equal to or less than 10 6  Ω/□ in the state of being coated, to have optical transparency, and to include at least one kind of powder of the electrically conductive materials such as indium oxide, tin oxide, antimony, zinc oxide and the like, in a solvent. Further, as the ink, an electrically conductive polymer such as polyethylene dioxi thiophene and the like or a mixture of the electrically conductive polymer with the powder of the electrically conductive material may be used. In this case, it is possible to make the ink emit light for a long period until removal of the ink by wiping or the like. Moreover, the electrically conductive material  30  may be composed of water or a solvent, which have a high dielectric constant. In this case, the electrically conductive material  30  can easily be removed by drying it with a dryer, or by wiping it with a tissue, a piece of gauze, a sponge and the like.  
     [0056] 3. Operation and Function  
     [0057] The electrically conductive material  30  is attached on the top coat layer  15  with a desired pattern. The attachment of the electrically conductive material  30  is performed by drawing with a brush, a pencil, a pastel, a crayon or the like, by performing printing with an ink jet printer or screen printing, by sticking an electrically conductive sheet, or the like. In the state, an AC power supply voltage is applied between the first electrode  12   a  and the second electrode  12   b . Incidentally, the electrically conductive material  30  may be attached on the top coat layer after the AC power supply voltage has previously been applied.  
     [0058] Then, by the attachment of the electrically conductive material  30  on the top coat layer, an AC electric field is formed in the EL light-emitting layer  14 , and only the portion thereof just under the attached electrically conductive material  30  emits light locally. That is, since the EL light-emitting layer  14  has a high dielectric constant, a circuit composed of the first electrode  12   a , the EL light-emitting layer  14 , the electrically conductive material  30 , the EL light-emitting layer  14 , the second electrode  12   b  and the like is formed to create an AC electric field in the EL light-emitting layer  14 . Then, the portion of the EL light-emitting layer just under the attachment part of the electrically conductive material  30  emits light. On the other hand, the intensity of the AC electric field at the rest portion of the EL light-emitting layer  14  just under the part where the electrically conductive material  30  is not attached is insufficient for the EL light-emitting layer  14  to emit light, and consequently the rest portion does not emit light. The thickness and the dielectric constant of the EL light-emitting layer  14  or the like are set in order that the portion of the EL light-emitting layer just under the attached electrically conductive material  30  may emit light selectively.  
     [0059] When the electrically conductive material  30  is liquid, there is a case where the electrically conductive material  30  permeates the EL light-emitting layer  14  to reach the waterproof layer  13  through a scratch, a pinhole or the like. However, the waterproof layer  13  prevents the further permeation of the electrically conductive material  30 . Moreover, the waterproof layer  13  also prevents the permeation of moisture or humidity in the air.  
     [0060] 4. Advantageous Effects  
     [0061] According to the present embodiment, an AC electric field is formed at the portion of the EL light-emitting layer  14  just under the attached electrically conductive material  30 , and only the portion locally emits light. This thing indicates that, when the electrically conductive material  30  is attached to the top coat layer  15  in the same pattern as a desired pattern, a light emitting with the desired pattern can be obtained. Consequently, an EL light emitting sheet  10  with which a user can easily produce a desired light emitting pattern can be provided.  
     [0062] The electrode layer  12  of the EL light emitting sheet  10  is, as described above, formed by deposition of a metal. When it is intended to form the electrode layer  12  by, for example, deposition of aluminum, the thickness of the electrode layer  12  is preferably about 300-1,000 Å (10 −10  m), more preferably about 400-800 Å. Since the electrode layer  12  is very thin and is formed by deposition of aluminum, if a user, for example, scratches the EL light emitting sheet with a cutter or strikes a nail, only a part of the electrode layer  12  contacting with the cutter or the nail, is melted almost simultaneously with the shortage. Consequently, the worst case where the whole of the electrode layer  12  is shorted is not generated, and the user does not receive electric shock.  
     [0063] The luminescent color of the EL light emitting sheet  10  can be changed by forming the EL light-emitting layer  14  by sealing the EL light-emitting elements with a coloring pigment mixed therein, by disposing a color filter between the EL light-emitting layer  14  and the top coat layer  15 , by coloring the top coat layer  15 , or by mixing a coloring pigment with the electrically conductive material  30 .  
     [0064] B. EL Light Emitting Display System  
     [0065]FIG. 3 is a perspective view showing the external appearance of a drawing board  50  as an example of an EL light emitting display system incorporating the above-mentioned EL light emitting sheet therein.  
     [0066] 1. Whole Configuration  
     [0067] In the drawing board  50 , a main body  59  with a shape like a board having a predetermined thickness holds the EL light emitting sheet  51  which is provided in the inside of the main body  59 . The EL light emitting sheet  51  having the top coat layer  15  on the top surface thereof is exposed from an opening  59   a . The drawing board  50  is configured to be provided with a highlight pen  53  having a pen point  53   a  made of an impregnating material impregnating the electrically conductive material  30  using electrically conductive ink which includes a fluorescent material, holders  52  for holding the highlight pens  53  in the state of standing up, a tray  54  having a shape of a recess capable of holding the highlight pens  53  in the state of lying on their sides in the inside of the tray  54 , a removal member  58  carrying a sponge  58   a  which is superior in water absorbing property, for removing the electrically conductive member  30  from the top surface of the EL light emitting sheet  51 , a tray  57  for holding the removal member  58  to allow the removal member to be taken out thereof, a change-over switch  55  for switching the light-emitting modes, and a power supply switch  56 .  
     [0068] 2. How to Use  
     [0069] A user may take a pen  53  out of the tray  54 , and may draw an arbitrary light emitting chart by applying the electrically conductive material  30  on a drawing screen  61 , namely the top surface part of the top coat layer  15  exposed from the opening  59   a . In FIG. 3, a word “ABC” is drawn. When the power supply switch  56  is turned on, a closed circuit is formed with the electrically conductive material  30 , the electrodes  12   a ,  12   b , and the like. As a result, the EL light-emitting layer  14  emits light, and the emitted light is transmitted through the electrically conductive material  30  to be radiated. That is, since the lower parts where the pen  53  has drawn emit light, the drawing acts as if the characters “A”, “B” and “C” themselves were emitting light.  
     [0070] 3. Detailed Configuration  
     [0071] (1) Electrode Pattern  
     [0072] Next, an electrode pattern of the EL light emitting sheet  51  built in the drawing board  50  will be described. FIG. 4 is a plan view showing the outline of the electrode pattern  70  of the EL light emitting sheet  51  built in the drawing board  50 . The electrode pattern  70  means the shape of the electrode layer  12  formed on the base layer  11 . In the figure, an electrode (first electrode)  71   a  and an electrode (second electrode)  71   b  constitute an electrode pair  71 , and the electrode  71   a  and  71   b  have substantially the same figures as the comb-like pattern shapes of the electrodes  12   a  and  12   b . The electrode pattern  70  includes six electrode pairs  71 - 76  having substantially the same configuration as the electrode pair  71  severally. The electrode pairs  71 - 76  are aligned. The upper end parts of the electrodes  71   b - 76   b  of respective electrode pairs  71 - 76  in the figure are connected with one another to form an electrode line (earth line)  70   b  which is connected to the ground. On the other hand, the electrodes  71   a - 76   a  are not connected with one another.  
     [0073] When a predetermined voltage (AC voltage) is applied to each of the electrodes  71   a - 76   a , each of the electrode pairs  71 - 76  takes the state capable of forming a closed circuit. To put it more concretely, when the electrically conductive material  30  is coated on the drawing screen  61  while the voltage is applied to all of the electrodes  71   a - 76   a , a closed circuit is formed between the electrically conductive material  30  and an electrode pair at any place on the drawing screen  61  through the EL light-emitting layer  14  and the like. However, when the voltage is applied to only a part of the electrodes  71   a - 76   a , only the part of the electrode pair corresponding to the electrode to which the voltage is applied can form a closed circuit (the sate may be referred to as a “closed circuit formation possible state”, and a state other than the above-mentioned state may be referred to as a “closed circuit formation impossible state” in the present specification).  
     [0074] When taking into account the case of placing a chart for light emission, of a thin line which is approximately parallel to the extending direction of comb-shaped pattern electrode, or a dot-shaped chart for light emission, the gap S 1  between the first electrode  12   a  and the second electrode  12   b  which are next to each other is preferably about 0.2-0.3 mm, and the widths S 2  of the first electrode  12   a  and the second electrode  12   b  themselves are preferably about 0.2-0.5 mm, according to the same reason as the above-described one.  
     [0075] (2) Internal Circuits  
     [0076]FIG. 5 is a functional block diagram of the drawing board  50 . In the figure, the drawing board  50  is provided with a control unit  110  composed of a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM) and the like, a battery  130  composed of dry cells, and a voltage application unit  120 . The voltage application unit  120  includes an inverter circuit  121  for converting a direct-current (DC) voltage supplied from the battery  130  to an AC voltage, and a booster circuit (not shown). The voltage application unit  120  applies an effective AC voltage of about 100-300 V between the earth line  70   b  of the electrode pattern  70  and each of the electrode pair  71 - 76  according to a control signal input from the control unit  110 .  
     [0077] The control unit  110  stores programs instructing the procedures of applying the voltage to the electrode pattern  70  into the ROM at every light emitting mode. The control unit  110  reads a corresponding program according to a mode selection signal which is input from the change-over switch  55 , and outputs a control signal to the voltage application unit  120 .  
     [0078] Then, various light emitting modes can be realized by controlling the voltage application to the electrode pairs  71 - 76 . In the drawing board  50 , an entirely light-emitting mode (mode I), an entirely blinking mode (mode II), a sequentially light-emitting mode (mode III) and a wavy light-emitting mode (mode IV) are executed by the switching of the change-over switch  55 .  
     [0079] (3) Light-Emitting Modes  
     [0080] (a) Entirely Light-Emitting Mode  
     [0081] The entirely light-emitting mode is a mode in which an voltage is applied to all of the electrode pair  71 - 76  simultaneously and continuously. In other words, the mode is one in which all of the electrode pairs  71 - 76  are in the closed circuit formation possible state. If the electrically conductive material  30  is coated on all over the drawing screen  61 , the whole surface of the drawing screen  61  continuously emits light.  
     [0082] (b) Entirely Blinking Mode  
     [0083] The entirely blinking mode is a mode in which a voltage is applied to all of the electrode pairs  71 - 76  simultaneously and intermittently. In other words, the mode is one in which all of the electrode pairs  71 - 76  simultaneously take the closed circuit formation possible state or the closed circuit formation impossible state alternately at predetermined time gaps. If the electrically conductive material  30  is coated on all over the drawing screen  61 , the whole surface of the drawing screen  61  intermittently emits light.  
     [0084] (c) Sequentially Light-Emitting Mode  
     [0085] The sequentially light-emitting mode is a mode in which a voltage is accumulatively applied to the electrode pairs  71 - 76  in the order of their arrangement. In other words, the mode is one in which the electrode pairs  71 - 76  which have been in the closed circuit formation impossible state sequentially become the closed circuit formation possible state at predetermined time gaps. If the electrically conductive material  30  is coated on all over the drawing screen  61 , an area part of one sixth of the whole area of the drawing screen  61  sequentially emits light (since there are six electrode pairs), and the area emitting light gradually increases. Incidentally, after all of the electrode pairs have become the closed circuit formation possible state, the application of the voltage to all of the electrode pairs  71 - 76  is stopped after a predetermined time to make all of the electrode pairs  71 - 76  be in the closed circuit formation impossible state. Thereby, the electrode pairs  71 - 76  return to the initial state, and the execution of the sequential light-emitting is repeated.  
     [0086] (d) Wavy Light-Emitting Mode  
     [0087] The wavy light-emitting mode is a mode in which a voltage is intermittently applied to the electrode pairs  71 - 76  in the order of their arrangement. In other words, the mode is one in which each of the electrode pairs  71 - 76  repeatedly transits the closed circuit formation possible state and the closed circuit formation impossible state with a predetermined time lag. If the electrically conductive material  30  is coated on all over the drawing screen  61 , each area part of one sixth of the whole area of the drawing screen  61  sequentially emits light and does not emit light, and consequently the parts emitting light operates to appear as if they were moving while waving.  
     [0088] 4. Advantageous Effects  
     [0089] As described above, in the drawing board  50 , it is possible to draw a light emitting chart by applying the electrically conductive material  30  easily with the highlight pen  53 . Moreover, it is also possible to remove the coated electrically conductive material  30  easily. Consequently, the repeating drawing of charts for light emitting can easily be realized.  
     [0090] Furthermore, a plurality of electrode pairs are formed in the EL light emitting sheet, and the control unit  110  controls the execution of the voltage application to each electrode pair. Thereby, light-emitting modes for light emitting charts can variously be changed, which makes it possible to realize interesting light emission together with the aid of the variation of the places where the electrically conductive material  30  is coated.  
     [0091] Incidentally, it is needless to say that the EL light emitting display system may be applied to other toys. In that case, the toys are not limited to the ones aiming to draw the light emitting charts like the EL light emitting display toys (for example, the drawing board  50 ), but the toys may be ones incorporating the EL light emitting display system as a part of them.  
     [0092] C. Variations of EL Light Emitting Sheet  
     [0093] 1. Variation  1  of EL Light Emitting Sheet  
     [0094] (1) Whole Configuration  
     [0095] As shown in FIG. 6, the EL light emitting sheet  10   a  according to the variation  1  has a configuration in which a base layer  11 , an electrode layer  12 , a waterproof layer  13 , a light reflecting layer  16 , an EL light emitting layer  14  and a top coat layer  15  are laminated in this order. Since each structure of the base layer  11 , the electrode layer  12 , the waterproof layer  13 , the EL light-emitting layer  14  and the top coat layer  15  is substantially the same as that of the EL light emitting sheet  10  in the embodiment of the present invention, the same reference numeral as that of the sheet  10  is attached to each element and the description for them are omitted. Mainly, the light-reflecting layer  16  will be described in the following.  
     [0096] (2) Detailed Configuration  
     [0097] The light-reflecting layer  16  is arranged between the waterproof layer  13  and the EL light-emitting layer  14 . The light-reflecting layer  16  adheres to the EL light-emitting layer  14 . The light-reflecting layer  16  has a thickness of about 10-30 μm, a withstanding voltage of about 200-300 V, and a dielectric constant of about 30-100, preferably about 60-100.  
     [0098] The light-reflecting layer  16  is made by dispersing inorganic powder which is ferroelectric powder such as barium titanate or Rochelle salt, into a resin functioning as a bonding agent such as an acrylic resin or the like. Since the inorganic powder such as the ferroelectric powder is a pigment showing white, the light-reflecting layer  16  becomes white, and therefore the light-reflecting layer  16  exhibits the light-reflecting function effectively.  
     [0099] 2. Variation  2  of EL Light Emitting Sheet  
     [0100] Although in the variation  1 , the waterproof layer  13  is arranged between the electrode layer  12  and the light-reflecting layer  16 , in the variation  2 , the waterproof layer  13  is arranged between the light-reflecting layer  16  and the EL light-emitting layer  14 . In this case, the top coat layer  15  are not necessarily required.  
     [0101] 3. Variation  3  of EL Light Emitting Sheet  
     [0102] Variation  3  is one that a further change is given to variation  1 . The EL light emitting sheet according to the variation  3  has a structure in which a base layer  11 , one of first and second electrodes  12   a  and  12   b , a waterproof layer  13 , the other of first and second electrodes  12   a  and  12   b , a light reflecting layer  16 , and an EL light-emitting layer  14  are laminated in this order. In this case, the top coat layer  15  are not necessarily required, and the light reflecting layer  16  may be omitted.  
     [0103] 4. Variation  4  of EL Light Emitting Sheet  
     [0104] Variation  4  is one that a further change is given to variation  1 . The EL light emitting sheet according to the variation  4  has a structure in which a base layer  11 , one of first and second electrodes  12   a  and  12   b , a light reflecting layer  16 , a waterproof layer  13 , the other of first and second electrodes  12   a  and  12   b , and an EL light-emitting layer  14  are laminated in this order. In this case, the top coat layer  15  are not necessarily required.  
     [0105] 5. Variation  5  of EL Light Emitting Sheet  
     [0106] Variation  5  is one that a further change is given to the EL light emitting sheet  10 ,  10   a  or  51  according to the embodiment, or one of variations  1 - 4 . The EL light emitting sheet according to the variation  5  has a structure in which the EL light-emitting layer  14  and/or the light reflecting layer  16  has a permeation prevention function to water or the like, instead of or in addition to the waterproof layer  13 . In this case, the top coat layer  15  are not necessarily required.  
     [0107] The EL light-emitting layer  14  with the permeation prevention function is composed of, for example, an organic or inorganic EL light-emitting elements being phosphor particles or phosphorescent particles, and a transparent resin binder for fixing the EL light-emitting elements in the state of being dispersed. The variation  5  uses a resin having a waterproof property or a moisture-proof property as the resin binder. The following resins are used. That is, the resins are, for example, for example, a fluorocarbon resin such as a 4-fluorinated ethylene resin, fluororubber and the like; a silicon resin such as silicon rubber and the like; the other epoxy resins; an acrylic resin; a urethane resin; a polyester resin; and a resin having a high sealing property such as an ethylene-vinyl acetate copolymer and the like. These resins are cured by a method such as the UV curing, the IR curing, the two-liquid curing, the heat curing and the like.  
     [0108] Further, as the resins constituting the light-reflecting layer  16  having the permeation prevention function, the following resins having the waterproof property or the moisture-proof property are used. The resins are, for example, a fluorocarbon resin such as a 4-fluorinated ethylene resin, fluororubber and the like; a silicon resin such as silicon rubber and the like; the other epoxy resins; an acrylic resin; a urethane resin; a polyester resin; and a resin having a high sealing property such as an ethylene-vinyl acetate copolymer and the like. These resins are cured by a method such as the UV curing, the IR curing, the two-liquid curing, the heat curing and the like.  
     [0109] According to the variation  4 , since the light-reflecting layer  16  prevents the permeation of water and the like, the generation of electrolysis between the first electrode  12   a  and the second electrode  12   b  can be prevented. Moreover, the snapping (damage) of a wire caused by the oxidation of the first electrode  12   a  and the second electrode  12   b  can be prevented.  
     [0110] 6. Variation  6  of EL Light Emitting Sheet  
     [0111] In the variation  6 , the first electrode  12   a  and the second electrode  12   b  are formed on the back surface of a base film or a sheet of glass (base layer  11 ) which have a permeation prevention function. As the base film in this case, one made of, for example, polyethylene terephthalate (PET) is used.  
     [0112] According to the variation  6 , since the base film or the sheet of glass prevents the permeation of water and the like from the front side, the generation of electrolysis between the first electrode  12   a  and the second electrode  12   b  can be prevented. Moreover, the snapping (damage) of a wire caused by the oxidation of the first electrode  12   a  and the second electrode  12   b  can be prevented.  
     [0113] Incidentally, the configuration is used in the case where the EL light emitting sheet is incorporated in a case body or the like. In the case where the EL light emitting sheet is incorporated in the case body as described above, the back surface side is generally sealed not to be exposed. Consequently, it is needless to consider the attachment of water and the like from the back surface side. If necessary, it is enough to coat the exposing electrodes with a resin having the permeation prevention function, or to perform the alumite processing of the exposing electrodes.  
     [0114] Incidentally, although the first electrode  12   a  and the second electrode  12   b  are provided on the back surface of the substrate sheet in the variation  6 , the first electrode  12   a  and the second electrode  12   b  may be provided with putting the substrate sheet between them.  
     [0115] 7. Variation  7  of EL Light Emitting Sheet  
     [0116]FIG. 7 shows the outline of the electrode pattern of the variation  7 . In the figure, the electrode pattern  700  is a two dimensional arrangement composed of six comb-shaped electrode pairs  710  in all, three of which are arranged at the upper row in the right and left direction in the figure, and the other three of which are arranged at the lower row in the right and left direction in the figure. Moreover, the electrode pairs  710  are arranged so that the electrodes of each electrode pair are engaged in the upper and lower direction in the figure. Then, the electrode end of the earth side electrode of each electrode pair is integrally formed as an earth line  700   b  between the upper row electrode pairs and the lower electrode pairs of the two rows. In a case of adhering a chart for light emission, of a thin line, or in a case of adhering a dot-shaped chart for light emission, the gap of about 0.2-0.3 mm, between the first electrode  12   a  and the second electrode  12   b  which are next to each other is preferable, and the width sizes of the first electrode  12   a  and the second electrode  12   b  themselves, of about 0.2-0.5 mm, are preferable.  
     [0117] By means of the electrode pattern  700 , a wide variety of light emitting patterns can be formed with the six electrode pairs in all.  
     [0118] Furthermore, owing to the arrangement of the earth line  700   b  between the upper row electrode pairs and the lower row electrode pairs of the two rows, the gap of the upper row electrode pairs and the lower row electrode pairs can be narrowed. That is, if a displacement side electrode  710   a  is arranged between the upper row electrode pairs and the lower row electrode pairs of the two rows, it is impossible to connect the upper row electrode  710   a  and the lower row electrode  710   a  cannot connected with each other, and then it is necessary to arrange them with a predetermined space between them. Consequently, the gap between the upper row and the lower row of the two rows becomes wide, and the gap becomes clear in some light emission patterns. On the other hand, if the earth line  700   b  is arranged at the center, it becomes possible to remove, or at least to reduce, the defect as above.  
     [0119] D. Variations of EL Light Emitting Display System  
     [0120] 1. Variation  1  of EL Light Emitting Display System  
     [0121] A signboard  900  according to a variation of the EL light emitting system is shown in FIGS. 8A and 8B. The signboard  900  is provided with an EL light emitting sheet  910  therein. The EL light emitting sheet  910  includes rectilinearly arranged four electrode pairs formed by depositing aluminum on a base layer  11 . Buttons  931 ,  932 ,  933  and  934  (hereinafter referred to as buttons  930  comprehensively) corresponding to each of the electrode pairs  921 ,  922 ,  923  and  924  (hereinafter referred to as electrode pairs  920  comprehensively) are arranged on one side of a drawing screen, i.e., the top surface of the top coat layer of the EL light emitting sheet. The EL light emitting sheet  910  and the signboard  900  have the same configuration as those of the EL light emitting sheet  10  and the drawing board  50  except the arrangement configuration of the electrode pairs. The buttons  930  are made to be toggle switches. The buttons  930  are configured to output pushed signals when the buttons  930  are pushed down.  
     [0122]FIG. 9 is a control block diagram of the signboard  900 . The configuration of the signboard is substantially the same as that of the drawing board  50  shown in FIG. 3. The configuration of the signboard is provided with the buttons  930 . In FIG. 10, the control unit  110  selects and decides a region where light is to be emitted, that is, an electrode pair to which a predetermined voltage is applied on the basis of the pushed signal inputted from the buttons  930 . For example, when the buttons  931  and  932  are pushed down, the control unit  110  selects and decides the electrode pairs  921  and  922 . Then, the control unit  110  performs voltage application to the selected and decided electrode pairs  921  and  922  on the basis of the light emitting mode selected with the change-over switch  55 .  
     [0123]FIG. 8B is a view showing an embodiment of the signboard  900  in the state in which the button  931  is pushed down. Since the electrode pair  921  is in the state of closed circuit formation possible state, the portion of the characters indicating “TODAY&#39;S BARGAIN!”, which have been drawn with the electrically conductive material  30 , emit light in the region of the drawing screen where the electrode pair  921  is arranged.  
     [0124] Incidentally, the buttons  930  may be composed of change-over switches to make it possible to select light emitting modes in addition to the turning on and off, of the electrode pairs. In this case, for example, a light emitting form in which light emission is blinked in the region drawn as “TODAY&#39;S BARGAIN!” in FIG. 8B, while a continuous light emission is given in the other regions, can be realized.  
     [0125] 2. Variation  2  of EL Light Emitting Display System  
     [0126] (1) Schematic Configuration  
     [0127]FIG. 10 is a perspective view showing an external appearance of a drawing board  1000  as an embodiment of the EL light emitting display system incorporating the above-mentioned EL light emitting sheets.  
     [0128] As shown in FIG. 11, the drawing board  1000  is provided with a transparent cover  1110  on an EL light emitting sheet  1100 . The cover  1110  is configured to be capable of being opened and closed. On the back side of the cover  1110 , a projection  1111  is annexed. The projection  1110  is provided to turn on a power supply control switch (not shown in the figure) which is arranged on the inside of the drawing board  1000  when the cover  1110  is closed. Other configurations and the like of the EL light emitting sheet  1100  are substantially the same as those of the drawing board  50 .  
     [0129] (2) Function and Advantageous Effect  
     [0130] The EL light emitting display system does not work only by turning the power supply switch  1256  on. Only when both the power supply switch  1256  and the power supply control switch are turned on, the system does work to become in a closed circuit formation possible state. Therefore, even if the liquid electrically conductive material  30  penetrates into the EL light emitting sheet  1100  to short-circuit the electrode pair, no AC current are applied to the electrode pair unless the cover  1110  is closed. Accordingly, it is possible to enhance the safety.  
     [0131] E. Another Variation of the Invention  
     [0132] (1) It is preferable to contain organic or inorganic colored pigment in the waterproof layer  13  of the EL light emitting sheet, to make the electrode pattern invisible from the front side by coloring. Such coloring enables not only making the electrode pattern invisible from the front side but also widening the range of choice for design from the front side. In a case of providing a light reflecting layer  16 , it is required to arrange the light reflecting layer  16  near the EL light emitting layer in comparison with the waterproof layer  13 .  
     [0133] (2) In the variation  2  of EL light emitting display system, a projection  1111  is annexed on the back side of the cover  1110 , and when the cover  1110  is closed, the system works to become in a closed circuit formation possible state. However, opening and closing of the cover  1110  may be detected by any one of appropriate mechanical, electrical and optical manners, to become in a closed circuit formation possible state only when the cover  1110  is closed. Alternatively, a structure in which the power supply switch  1256  is locked during the cover  1110  is opened, may also be used.  
     [0134] According to the invention, it is possible to obtain an EL light emitting display system and an EL light emitting sheet, having an improved probability of light emission and to restrain occurrence of flecks of light emission when placing an electrically conductive material thereon.  
     [0135] The entire disclosure of Japanese Patent Application No. Tokugan 2002-254617 which was filed on Aug. 30, 2002, and Japanese Patent Application No. Tokugan 2003-122787 which was filed on Apr. 25, 2003, including specification, claims, drawings and summary are incorporated herein by reference in its entirety.