Abstract:
Disclosed are a double-sided luminescent organic light emitting device and the manufacturing method thereof. The double-sided luminescent organic light emitting device comprises a transparent substrate ( 21 ), an anode ( 22 ), a transparent cathode ( 25 ), and at least two organic light emitting structures ( 23   a,    23   b ) and at least a charge-generation layer ( 24 ) set between the anode ( 22 ) and the transparent cathode ( 25 ), and the charge-generation layer ( 24 ) is set between the two neighboring organic light emitting structures ( 23   a,    23   b ), the charge-generation layer ( 24 ) and the organic light emitting structures ( 23   a,    23   b ) are alternately arranged. The charge-generation layer ( 24 ) includes an n-type semiconductor layer ( 241 ) and a p-type semiconductor ( 242 ) layer combined with the n-type semiconductor layer. Said double-sided light emitting organic light emitting device requires low driving current, and has high luminescence efficiency, high brightness, and high light extraction efficiency. In addition, said device enables nearly 360 degrees omnidirectional illumination, enlarges the illumination area and the application range, and has long lifetime, simple preparation procedures and low production cost.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to the field of electric light source, and more specifically, to a double-sided light emitting organic electroluminescent device and the manufacturing method thereof. 
       BACKGROUND 
       [0002]    The electric light industry has always been a research hotspot attracts many researchers to study on competing all over the world, and it has a very important position in the world economy. Nowadays the gas discharge light source is widely employed, and the principle of such light source is that the inner space of the lamp is evacuated prior to being fulfilled with mixed gas containing mercury, and the light is generated by means of gas discharge or emitted from the phosphor powder under the stimulation of the ultraviolet generated by the gas discharge. However, the pulsed light of gas discharge light source can easily lead to visual fatigue, and the mercury can pollute the environment. With the development of the society and the advancement of technology, it is important to research and development of energy-saving and environmental friendly, green light sources to replace traditional light sources, and it has been an important issue for the researchers to study on competing in all countries. 
         [0003]    The organic electroluminescent device is one of the electric light sources. The organic light emission diode (OLED for short) has the properties of high brightness, wide range of material selection, low drive voltage, solid state active light-emission and the like, and also has the advantages of high definition, wide viewing angle, fast response and the like, meanwhile the OLED has excellent flexibility, thus it can be folded or bent, so it is a light source with much potential for the flexible display technology, and the development thereof is in line with the trends of the mobile communication and information display in the information age, and meets the requirement of the green lighting technology, accordingly it is currently a research focus for the researchers to study at home and abroad. 
         [0004]    The organic electroluminescent device has a sandwich-like structure, which substantially includes an anode, an organic electroluminescent structure and a cathode, wherein the organic electroluminescent structure comprises at least one selected from the group consisting of a hole injection layer and a hole transport layer, and a light emitting layer, as well as at least one selected from the group consisting of an electron transport layer and an electron injection layer.  FIG. 1  shows the structural schematic diagram of an organic electroluminescent device including all of these structures in prior art, this device comprises a transparent substrate  11  and an anode  12 , an organic electroluminescent structure  13  and a cathode  14  sequentially arranged on the transparent substrate  11  and conjugated together. Wherein the organic electroluminescent structure  13  includes a hole injection layer  131 , a hole transport layer  132 , a light emitting layer  133 , an electron transport layer  134 , and an electron injection layer  135 . 
         [0005]    Up to now, researchers all over the world have improved the indicators of the device performance by selecting suitable organic materials and reasonable device structure designs, but due to the heavy driving current, low luminous efficiency, short lifetime of the light emitting device, it is desired to develop a light emitting device with small driving current, and high luminous efficiency, in order to achieve the practical use of the organic electroluminescent device. 
         [0006]    Furthermore, the OLED in prior art can only emit light from one side of the anode or the cathode, as a result the OLED can only be the style of bottom emission or top emission. Some researchers have invented a double-sided light emitting or display OLED device with double-layer structure design, i.e. two sets of OLED light emitting or display units are combined together by means of “back to back” to achieve the double-sided light emitting or display. This kind of structure makes the configuration of the OLED device more complicated, and increases the thickness and weight thereof, and the cost is significantly increased. 
       SUMMARY 
       [0007]    The technical problem to be dissolved by the present invention is to overcome the above-discussed deficiencies in prior art, and to provide a double-sided light emitting organic electroluminescent device with small driving current, high brightness, high current efficiency, furthermore, a manufacture method of the organic electroluminescent device is also provided. 
         [0008]    The technical problems of the present invention can be solved through the following technical solutions: 
         [0009]    a double-sided light emitting organic electroluminescent device, which includes a light-transmissive substrate, an anode, a light-transmissive cathode, and there are at least two organic electroluminescent structures and at least one charge generation layer arranged between the anode and the light-transmissive cathode; 
         [0010]    wherein the charge generation layer is sandwiched between the two neighboring organic electroluminescent structures and conjugated thereto, and the charge generation layer and the organic electroluminescent structure are alternatively arranged and combined together; 
         [0011]    the charge generation layer includes an N-type semiconductor layer and a P-type semiconductor layer combined with the N-type semiconductor. 
         [0012]    And, a method for manufacturing the double-sided light emitting organic electroluminescent device, which comprises: 
         [0013]    providing a light-transmissive substrate; 
         [0014]    plating an anode on one surface of the light-transmissive substrate; 
         [0015]    plating at least two organic electroluminescent structures and at least one charge generation layer on the surface of the anode opposite to the light-transmissive substrate, wherein the charge generation layer is disposed between the two neighboring organic electroluminescent structures and conjugated thereto, the charge generation layer and the organic electroluminescent structures are alternately arranged, the charge generation layer includes an N-type semiconductor layer and a P-type semiconductor layer combined with the N-type semiconductor, 
         [0016]    plating a light-transmissive cathode at last to obtain the organic electroluminescent device. 
         [0017]    The double-sided light emitting organic electroluminescent device according to the present invention has a charge generation layer connected with two or more organic electroluminescent structures, so as to allow the double-sided light emitting organic electroluminescent device to illuminate nearly 360° omnidirectionally, which enlarges the illumination area and the application range. The double-sided light emitting organic electroluminescent device with this configuration has small driving current, high luminous efficiency, high brightness, and high light output efficiency. Meanwhile, due to the small driving current, the lifetime of the double-sided light emitting organic electroluminescent device is significantly increased. The method of producing the double-sided light emitting organic electroluminescent device may be carried out by simply plating each layer sequentially, which has simple process, increased production efficiency, reduces the production cost and it is suitable for industrial production. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  shows the schematic structure of the single-sided light emitting organic electroluminescent device in prior art. 
           [0019]      FIG. 2  shows the first schematic structure of the double-sided light emitting organic electroluminescent device according to the embodiment of the present invention. 
           [0020]      FIG. 3  shows the second schematic structure of the double-sided light emitting organic electroluminescent device according to the embodiment of the present invention. 
           [0021]      FIG. 4  shows the third schematic structure of the double-sided light emitting organic electroluminescent device according to the embodiment of the present invention. 
           [0022]      FIG. 5  shows the fourth schematic structure of the double-sided light emitting organic electroluminescent device according to the embodiment of the present invention. 
           [0023]      FIG. 6  shows the schematic structure of the double-sided light emitting organic electroluminescent device according to the embodiment of the present invention after packaging. 
           [0024]      FIG. 7  shows the flow chart of the method for manufacturing the double-sided light emitting organic electroluminescent device according to the embodiment of the present invention. 
           [0025]      FIG. 8  shows the relational graphs of the brightness and the current density of the double-sided light emitting organic electroluminescent device prepared in Example 1 of the present invention and the organic electroluminescent device without a charge generation layer prepared in the Comparative Example 5. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    Objects, embodiments and advantages of the present invention will be explained below in detail with reference to the accompanying drawings and embodiments. However, it should be appreciated that the following description of the embodiment is merely exemplary in nature and is not intended to limit this invention. 
         [0027]    The emission principle of OLED is that under applied electric field, the electrons are injected from the cathode to the lowest unoccupied molecular orbital (LUMO) of the organic compound, meanwhile the holes are injected from the anode to the highest occupied molecular orbital (HOMO) of the organic compound. An electron and a hole meet with each other in the light emitting layer, then recombine to form an exciton, and the exciton migrates under the applied electric field, transferring energy to the light emitting material, then excite the electron to jump from the ground state to the excited state. The excited state electron loses energy and becomes enactive by radiation and emits a photon, releasing light energy. When the light is emitted to the substrate, the refraction and reflection of the light will occur at the interface between the substrate and/or the anode conjugated thereto, and the refracted light may cause loss of the light emitted by the organic electroluminescent device, and the reflected light may emit outside the organic electroluminescent device through the top side thereof, which may enhance the luminous efficiency of the organic electroluminescent device. Accordingly, the originally refracted light may be perfectly reflected after emitted to the interface by changing the characteristics of the refraction interface, thus the luminous efficiency of the organic electroluminescent device may be further improved. 
         [0028]    According to the above mentioned principle, the embodiment of the present invention provides a double-sided light emitting organic electroluminescent device with small driving current, high brightness, high current efficiency, as shown in  FIGS. 2 to 6 . The double-sided light emitting organic electroluminescent device comprises a light-transmissive substrate  21 , an anode  22 , a light-transmissive cathode  25 , at least two organic electroluminescent structures  23  and at least one charge generation layer  24 . The arrangement relationship of the above components is: the charge generation layers  24  are separately disposed between two neighboring organic electroluminescent structures  23  and conjugated thereto, and the charge generation layers  24  and the organic electroluminescent structure  23  are alternatively arranged and integrated into a whole body; the surface of an organic electroluminescent structure  23   a  opposite to the charge generation layer  24  is combined with the anode  22  and the light-transmissive substrate  21  sequentially, the surface of another organic electroluminescent structures  23   b  opposite to the charge generation layer  24  is conjugated with the light-transmissive cathode  25 . The charge generation layer  24  includes an N-type semiconductor layer  241  and a P-type semiconductor layer  242  combined with the N-type semiconductor layer  241 . 
         [0029]    Accordingly, the double-sided light emitting organic electroluminescent device has the configuration of a charge generation layer combined with two or more organic electroluminescent structures, this configuration allows the double-sided light emitting organic electroluminescent device to illuminate nearly 360 degrees omnidirectionally, enlarge the luminous area and extends the application field. The double-sided light emitting organic electroluminescent device of this configuration has small driving current, high luminous efficiency, high brightness, and high light output efficiency. Meanwhile, because of the small driving current, the lifetime of the double-sided light emitting organic electroluminescent device is significantly increased. The charge generation layer  24  according to the embodiments of the present invention has an N-type semiconductor layer  241  conjugated with a P-type semiconductor layer  242 . Under an applied voltage, the electrons and the holes may be generated in the charge generation layer  24 , and move to the external anode and light-transmissive cathode  25  respectively and they are injected into the organic electroluminescent structure  23 , finally recombine with the holes and electrons generated in the external electrodes respectively to form excitons, and the light will be emitted by radiation attenuation in the light emitting layer. Accordingly, the charge generation layer  24  reduces the desired operating current of the double-sided light emitting organic electroluminescent device according to the embodiment of the present invention, endows the double-sided light emitting organic electroluminescent device with more emitting brightness, high current efficiency. 
         [0030]    In particular, in the above-said charge generation layer  24 , the N-type doped organic layer  241  preferably has a thickness of 10 to 30 nm, the P-type doped organic or metal oxide layer  242  preferably has a thickness of 3 to 30 nm. 
         [0031]    The N-type semiconductor layer  241  is an N-type doped organic layer, the P-type semiconductor layer  241  is a P-type doped organic compound or metal oxide layer. 
         [0032]    When the charge generation layer  24  is formed by combining an N-type doped organic layer  241  and a P-type doped organic layer  242 , the material of the N-type doped organic layer  241  is preferably at least one selected from the group consisting of Li:Alq 3 , Li:TPBi, Cs:Bphen, Mg:Alq 3 , F 16 CuPc, Cs 2 CO 3 :Alq 3 , Li:Bphen, Cs:BCP and Li:BCP; the material of the P-type doped organic layer  242  is preferably at least one selected from the group consisting of FeCl 3 :NPB, F4-TCNQ:NPB, F4-TCNQ:m-MTDATA, and CuPc. 
         [0033]    When the charge generation layer  24  is formed by combining an N-type doped organic layer  241  and a metal oxide layer  242 , the material of the N-type doped organic layer  241  is preferably at least one selected from the group consisting of Li:Alq 3 , Li:TPBi, Cs:Bphen, Mg:Alq 3 , F 16 CuPc, Cs 2 CO 3 :Alq 3 , Li:Bphen, Cs:BCP, and Li:BCP; and the material of the metal oxide layer  242  is preferably at least one selected from the group consisting of MoO 3 , V 2 O 5 , WO 3 , and nano indium tin oxide. 
         [0034]    Accordingly, the structure of the charge generation layer  24  may be selected from the group consisting of Li:Alq 3 /FeCl 3 :NPB, Li:TPBi/FeCl 3 :NPB, Cs:Bphen/F4-TCNQ:NPB, Mg:Alq 3 /F4-TCNQ:m-MTDATA, F 16 CuPc/CuPc, Cs 2 CO 3 :Alq 3 /MoO 3 , Li:Bphen/MoO 3 , Cs:BCP/ITO, Li:BCP/V 2 O 5 , Mg:Alq 3 /WO 3  and the like. 
         [0035]    The above-mentioned material and the thickness of the charge generation layer  24  facilitates the generation of electrons and holes, and at the same time, it is also favorable to the transmission of light. 
         [0036]    In particular, the material of the above-mentioned light-transmissive substrate  21  is preferably selected from the group consisting of a light-transmissive glass and a transparent polymer film material, and of course the material may be replaced with other materials commonly used in the art. The thickness of the light-transmissive substrate  21  can be that often used in this technical field, but it endows the substrate  21  with excellent light-transmissive property. According to measurement, the above preferred material may have a light transmittance up to 95%. 
         [0037]    In particular, the anode  22  is preferably made of one selected from the group consisting of indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), and indium-doped zinc oxide (IZO). Of course, the material thereof may alternatively be replaced by other materials commonly used in the field, such as fluorine-doped tin oxide (FTO). The thickness of the light-transmissive anode  22  may be that commonly used in this field, if only the thickness may endow the anode with good conductivity, so as to reduce the heat produced in the electrifying process of the anode  22 , meanwhile the anode  22  should also have good light-transmissive property. 
         [0038]    In particular, the material of the light-transmissive cathode  25  is preferably selected from the group consisting of gold (Au), silver (Ag), calcium (Ca), magnesium (Mg), aluminum (Al), magnesium-aluminum alloy and magnesium-silver alloy, the thickness of the light-transmissive cathode  25  may be that commonly used in this field, if only it may endow the cathode with good conductivity, so as to reduce its heat during the electrifying process, meanwhile the cathode should have good light-transmissive property. The light-transmissive cathode  25  preferably has a structure of Al/Ag double-layer, wherein the preferred thickness of the Al layer is 0.5 nm, the preferred thickness of the Ag layer is 20 nm. 
         [0039]    In particular, the organic electroluminescent structure  23  includes a light emitting layer  233 , and/or at least one selected from the group consisting of a hole injection layer  231 , a hole transport layer  232 , an electron transport layer  234 , and an electron injection layer  235 . Wherein the light emitting layer  233  may be made of red, yellow, blue, green color materials. When there are a plurality of light emitting layers in the electroluminescent device, the light emitting materials may be the same or different, and when different light emitting materials are employed, the type of the light emitting materials may be adjusted to achieve white light emitting. When there are two organic electroluminescent structures  23 , and one charge generation layer  24 , as shown in  FIG. 2 , one side of the organic electroluminescent structure  23   a  is conjugated with the anode  22 , the opposite side thereof is conjugated with the charge generation layer  24 , wherein the organic electroluminescent structure  23   a  also has at least one selected from the group consisting of a hole injection layer  231   a  and a hole transport layer  232   a  arranged between the light emitting layer  233   a  and the anode  22 , and there is also at least one selected from the group consisting of an electron transport layer  234   a  and an electron injection layer disposed between the light emitting layer  233   a  and N-type semiconductor layer  241  of the charge generation layer  24 . The organic electroluminescent structure  23   b  is conjugated with the light-transmissive cathode  25  at one side, and conjugated with the charge production layer  24  at the opposite side. The organic electroluminescent structure  23   b  also has at least one selected from the group consisting of an electron transport layer  234   b  and an electron injection layer  235   b  disposed between the light emitting layer  233   b  and the light-transmissive cathode  25 , and at least one selected from the group consisting of a hole injection layer  231   b  and a hole transport layer  232   b  arranged between the light emitting layer  233   b  and the P-type semiconductor layer  242  of the charge generation layer  24 . 
         [0040]    When there are three organic electroluminescent structures  23 , and two charge generation layers  24 , as shown in  FIG. 3 , the organic electroluminescent structures  23  and the charge generation layers  24  are arranged alternatively and combined into a whole body, one organic electroluminescent structure  23   a  is conjugated with the anode at one side, and combined with the charge generation layer  24   a  at the opposite side, and another organic electroluminescent structure  23   b  at the other end is conjugated with the light-transmissive cathode  25  at one side, and combined with the charge generation layer  24   b  at the opposite side. The organic electroluminescent structures  23   a  and  23   b  include a light emitting layer  233 , and/or at least one selected from the group consisting of a hole injection layer  231 , a hole transport layer  232 , an electron transport layer  234 , an electron injection layer  235  respectively, and the combination manner of the hole injection layer  231 , the hole transport layer  232 , the electron transport layer  234 , the electron injection layer  235  is similar to that of the above-mentioned configuration including two organic electroluminescent structures  23  and one charge generation layer  24 . The third organic electroluminescent structure  23   c  is arranged between the charge generation layer  24   a  and the charge generation layer  24   b  and combined thereto, wherein at least one selected from the group consisting of a hole injection layer  231   c  and a hole transport layer  232  are sandwiched between the P-type semiconductor layer  242   a  of the charge generation layer  24   a  and the light emitting layer  233   c  of the organic electroluminescent structure  23   c , and at least one selected from the group consisting of an electron transport layer  234   c  and an electron injection layer  235   c  are sandwiched between the N-type semiconductor layer  241   b  of the charge generation layer  24   b  and the light emitting layer  233   c  of the organic electroluminescent structure  23   c . Wherein, compared with the P-type semiconductor layer, the N-type semiconductor layer of the charge generation layer is much closer to the anode, and the P-type semiconductor layer is adjacent to the light-transmissive cathode  25 , that is, the orientations of the charge generation layer  24   a  and the charge generation layer  24   b  are identical in orientation when combined in the double-sided light emitting organic electroluminescent device of this embodiment. 
         [0041]    Likewise, when there are three or more organic electroluminescent structures  23 , and two or more charge generation layers  24 , the organic electroluminescent structure  23  and the charge generation layer  24  are alternatively arranged and combined into a whole body. The configuration of the double-sided light emitting organic electroluminescent device is similar to that shown in  FIG. 3 , differing only in that the numbers of the alternatively arranged and combined organic electroluminescent structures  23  and charge generation layers  24  being increased or reduced. Accordingly, all changes which come within the meaning and range of equivalency of the present invention are intended to be embraced therein. 
         [0042]    As described above, the configuration of the double-sided light emitting organic electroluminescent device according to the embodiments of the present invention may be, but not limited to, followings examples: 
         [0043]    The first configuration: as shown in  FIG. 2 , the double-sided light emitting organic electroluminescent device according to this embodiment includes sequentially a light-transmissive substrate  21 , an anode  22 , a hole injection layer  231   a , a hole transport layer  232   a , a light emitting layer  233   a , an electron transport layer  234   a , an N-type semiconductor layer  241 , a P-type semiconductor layer  242 , a hole injection layer  231   b , a hole transport layer  232   b , a light emitting layer  233   b , an electron transport layer  234   b , an electron injection layer  235   b , and a light-transmissive cathode  25 , and they are combined into a whole body. 
         [0044]    The second configuration: as shown in  FIG. 3 , the double-sided light emitting organic electroluminescent device according to this embodiment includes sequentially a light-transmissive substrate  21 , an anode  22 , a hole injection layer  231   a , a hole transport layer  232   a , a light emitting layer  233   a , an electron transport layer  234   a , an N-type semiconductor layer  241   a , a P-type semiconductor layer  242   a , a hole injection layer  231   c , a hole transport layer  232   c , a light emitting layer  233   c , an electron transport layer  234   c , an electron injection layer  235   c , an N-type semiconductor layer  241   b , a P-type semiconductor layer  242   b , a hole injection layer  231   b , a hole transport layer  232   b , a light emitting layer  233   b , an electron transport layer  234   b , an electron injection layer  235   b , a light-transmissive cathode  25 , and they are combined into a whole body. 
         [0045]    The third configuration: as shown in  FIG. 4 , the double-sided light emitting organic electroluminescent device according to this embodiment includes sequentially a light-transmissive substrate  21 , an anode  22 , a hole transport layer  232   a , a light emitting layer  233   a , an N-type semiconductor layer  241 , a P-type semiconductor layer  242 , the light emitting layer  233   b , the electron transport layer  234   b , and a light-transmissive cathode  25 , and they are combined into a whole body. 
         [0046]    The above hole injection layer  231  preferably has a thickness of 20 to 80 nm, the material thereof is preferably a transition metal oxide, more preferably m-MTDATA, and other materials in this art may be used. The hole transport layer  232  preferably has a thickness of 20 to 80 nm, the material thereof is preferably at one selected from the group consisting of NPB, m-MTDATA, TPD, β-NPB, Spiro-NPB, DMF-NPB, α,β-NPB, spiro-TAD, DMF-TPD. The electron transport layer  234  preferably has a thickness of 20 to 80 nm, the material thereof is preferably one or more selected from the group consisting of Bphen, Alq 3 , BCP, Galq, BeBq 2 , Balq, TPBi, OXD-7, and TAZ. The electron injection layer  235  preferably has the thickness of 20 to 80 nm, the material thereof is preferably LiF, and of course, other materials in this art can also be used, such as, alkaline earth metal fluoride (NaF, CsF, CaF 2 , MgF 2 ) or chloride (NaCl, KCl, RbCl). 
         [0047]    The light emitting layer  233  preferably has a thickness of 20 to 80 nm, and the light emitting layer  233  may be made of red, yellow, blue, green luminescent materials and the like. When the number of the organic electroluminescent structures is two or more, the materials employed may be same or different, when there are different materials employed, the types of luminescent materials may be adjusted, so as to achieve white or other color light emitting. The light emitting layer  233  is preferably made of one or more selected from the group consisting of C545T:Alq 3 , (F-BT) 2 Ir(acac):CBP, DPVBi, FIrPic:CBP, Ir(ppy) 3 :CBP, and Ir(piq) 3 :CBP. Other materials in the art of course can be used, such as dimethyl quinacridone (DMQA) and the like. 
         [0048]    In the light emitting process of the organic electroluminescent device, the transmission rate of the holes and electrons are inconsistent, as a result the probability of the electron-hole recombination is low, and the brightness and efficiency of the organic electroluminescent device cannot be improved. Therefore, the employment of the hole injection layer  231 , the hole transport layer  232 , the light emitting layer  233 , the electron transport layer  234 , the electron injection layer  235  may effectively regulate the injection and transport rates of the electrons and holes, balance the carriers, control the recombination area, so as to obtain a desired luminous brightness and luminous efficiency, meanwhile, the organic electroluminescent device of this embodiment can not only ensure that the organic electroluminescent structure have a good adhesion with the charge generation layer  24 , the anode  22  and the light-transmissive cathode  25  respectively, but also make sure that the carriers from the anode  22  and the light-transmissive cathode  25  can be injected into the organic electroluminescent structure more easily. For example, the hole injection layer  231  is preferably made of a transition metal oxide, which may match with the energy level of the organic hole transport layer  232 , thus the hole injection to the anode  22  may be significantly strengthened, and the injection and the transmission rate of the electrons and holes may be effectively regulated, so as to balance the carriers and control the recombination area, such that the double-sided light emitting organic electroluminescent device according to the embodiment of the present invention may obtain a desired luminous brightness and luminous efficiency. 
         [0049]    Furthermore, in the double-sided light emitting organic electroluminescent device according to the embodiment of the present invention, a vapor barrier layer  26  may be provided between the anode  22  and the light-transmissive substrate  21 , as shown in  FIG. 5 . The function of the vapor barrier layer  26  is to prevent atmospheric moisture from penetrating into the double-sided light emitting organic electroluminescent device in use, the penetration of moisture may affect the efficiency of the double-sided light emitting organic electroluminescent device. The vapor barrier layer  26  preferably has a thickness of 50 to 200 nm, the material thereof is preferably at least one selected from the group consisting of SiN x , SiO 2 , Si 3 N 4 , Al 2 O 3 , and Ta 2 O 5 . The vapor barrier layer  26  with this kind of material and this thickness may prevent the penetration of vapor more effectively, meanwhile the layer  26  has a good light-transmissive performance. For example, the vapor barrier layer  26  of SiN x  is dense, has good light-transmissive property, and may effectively isolate the vapor. How to arrange the vapor barrier layer  26  may depend on the material type of the light-transmissive substrate  21 , for example, when the light-transmissive substrate  21  is made of transparent polymer film material, it is preferred to arrange a vapor barrier layer  26  on one surface of the light-transmissive substrate  21  of transparent polymer film material. Of course, when the light-transmissive substrate  21  is made of transparent polymer film material, a vapor barrier layer  26  may be also further disposed. 
         [0050]    Furthermore, in the double-sided light emitting organic electroluminescent device according to the embodiment of the present invention, an antireflection film layer  27  is adhered to the surface of the light-transmissive cathode  25  opposite to the organic electroluminescent structure  23 , as shown in  FIG. 5 . Since the light transmittance of the metal light-transmissive cathode  25  is lower than that of the light-transmissive substrate, the arrangement of the antireflection film layer  27  may further enhance the light transmittance of the light-transmissive cathode  25 , and improve the light output efficiency of light-transmissive cathode  25 . The antireflection film  26  preferably has a thickness of 40 to 100 nm, the material thereof is preferably at least one selected from the group consisting of Alq 3 , ZnSe, TeO 2 , MoO x , BCP, m-MTDATA, and ZnS. According to measurement, the light transmittance of the light-transmissive cathode  25  of the double-sided light emitting organic electroluminescent device according to the embodiment of the present invention has been increased by 8 to 10% by means of additionally providing an antireflection film layer  27 . 
         [0051]    A transparent cover layer  28  may also be arranged on the outer surface of the antireflection film layer  27  or directly on the outer surface of the light-transmissive cathode  25 , the function of the transparent cover layer  28  is to further prevent the oxidation of the light-transmissive cathode  25 . In order to prevent vapor permeating from the side of the light-transmissive cathode  25  to the double-sided light emitting organic electroluminescent device according to the embodiment of the present invention, the vapor barrier layer  26  above-mentioned may be arranged between the antireflection film layer  27  (or the light-transmissive cathode  25 ) and the transparent cover layer  28 , as shown in  FIG. 6 . 
         [0052]    Furthermore, in order to protect the structure of each layer in the double-sided light emitting organic electroluminescent device of layers according to the embodiment of the present invention, as well as to ensure the luminous intensity and luminous efficiency of the organic electroluminescent device, a layer of transparent adhesive  29  may be packaged between the light-transmissive substrate  21  and the transparent cover layer  28  as well as around  22 ,  23 ,  24 ,  25 , or around  22 ,  23 ,  24 ,  25 ,  26 ,  27 , the transparent packaging adhesive  29  can be made of ultraviolet-curable adhesive (UV adhesive), of course, it also may be replaced with other adhesive commonly used in this art. The configuration of the double-sided light emitting organic electroluminescent device packaged with a transparent packaging adhesive  29  of the present invention is shown in  FIG. 6 . 
         [0053]    According to the above-mentioned principle, the embodiments of the present invention provide a method for manufacturing the above-mentioned double-sided light emitting organic electroluminescent device, the flow chat of the process thereof is shown in  FIG. 7 , referring to  FIGS. 2 to 6  at the same time, the process comprises: 
         [0054]    S 1 : providing a light-transmissive substrate  21 ; 
         [0055]    S 2 : plating an anode  22  on one surface of the light-transmissive substrate  21 ; 
         [0056]    S 3 : plating at least two organic electroluminescent structures  23  and at least one charge generation layer  24  on the surface of the anode  22  opposite to the light-transmissive substrate  21 , wherein the charge generation layer  24  is arranged between the two adjacent organic electroluminescent structures  23  and conjugated thereto, and disposed alternately with the organic electroluminescent structure  23 ; the charge generation layer  24  includes an N-type semiconductor layer  241  and a P-type semiconductor layer  242  combined with the N-type semiconductor layer  241 ; 
         [0057]    S 4 : plating a light-transmissive cathode  25  at last, to obtain a double-sided light emitting organic electroluminescent device. 
         [0058]    In the above-mentioned process of manufacturing the double-sided light emitting organic electroluminescent device, the operating process is only to plate each layer, and the preparation process is simple, and may improve production efficiency, reduce production cost, suitable for industrial production. 
         [0059]    In particular, in step S 1  of the manufacture method of the double-sided light emitting organic electroluminescent device, the configuration, material and specification of the light-transmissive substrate  21  are as described above, which will not be detailed again. 
         [0060]    In step S 2  of the manufacture method of the double-sided light emitting organic electroluminescent device, the manner of plating anode  2  is preferably selected from the group consisting of evaporation, sputtering and spray plating. Wherein the sputtering may be magnetron sputtering. The material and plating thickness of the anode  2  has been described, which will not be detailed again. Before the following step of evaporation, a pre-treatment is necessary for the anode  22 , which includes cleaning, oxygen plasma treatment and the like. Wherein the preferred manner of cleaning is to wash in detergent, deionized water, acetone, ethanol, isopropanol sequentially under ultrasonic, each for 15 min, to completely remove the impurity on the surface of the anode  22  so that the surface of the anode  22  has the maximum degree of cleaning; after cleaning the anode  22  is treated with oxygen plasma, the duration thereof is preferably 5-15 min, the power thereof is preferably 10-150 W, and the main function of this treatment is to reduce the roughness and the contact angle on the surface of the conductive glass, so as to improve the wettability and adsorption of the surface, meanwhile the organic pollutants on the surface may be further removed by surface treatment. 
         [0061]    In the step S 3  of the manufacture method of the double-sided light emitting organic electroluminescent device, the manner of plating the organic electroluminescent structure  23  and the charge generation layer  24  is preferably selected from the group consisting of evaporation, sputtering, spray plating and chemical deposition. When the organic electroluminescent structure  23  sequentially contains a hole injection layer  231 , a hole transport layer  232 , a light emitting layer  233 , an electron transport layer  234  and an electron injection layer  235 , the hole injection layer  231 , hole transport layer  232 , light emitting layer  233 , electron transport layer  234  and electron injection layer  235  are sequentially plated on the anode  2  by means of evaporation, sputtering, spray plating or chemical deposition. The figurations of organic electroluminescent structure  23  and the charge generation layer  24  have been described above, which will not be detailed here. 
         [0062]    In the step S 4  of the manufacture method of the double-sided light emitting organic electroluminescent device, the manner of plating light-transmissive cathode  25  is the same as that of plating the organic light emitting structure  23 , alternatively, the manner of plating the anode  22  may be employed. The thickness and material of the light-transmissive cathode  25  are as described above. 
         [0063]    The method for manufacturing the double-sided light emitting organic electroluminescent device may be carried out by simply plating each layer sequentially on the light-transmissive substrate  21 , thus obtain the final product, and this method has simple process, increased production efficiency, reduced production cost and it is suitable for industrial production. 
         [0064]    Furthermore, following the step S 1  and prior to the step S 2  of the manufacture method of the double-sided light emitting organic electroluminescent device, a vapor barrier layer  26  may be plated on one surface of the light-transmissive substrate  21 . 
         [0065]    Furthermore, after the step S 4  of the manufacture method of the double-sided light emitting organic electroluminescent device, an antireflection film layer  27  may be plated on the outer surface of the light-transmissive cathode  25 . 
         [0066]    The thickness, material and function of the vapor barrier layer  26 , the antireflection film layer  27  have been described above, and will not be repeated again. Wherein the plating of vapor barrier layer  26  is preferably carried out under an N 2  atmosphere. For example, when plating the vapor barrier layer  26  of SiN x , under an N 2  environment, by employing a high-purity Si target, the vapor barrier layer  26  of SiN x  is plated on one surface of the light-transmissive substrate  21  in a magnetron sputtering system. Of course, the vapor barrier layer  26 , the antireflection film layer  27  may be plated by means of other manners commonly used in this art such as evaporation, sputter plating, and the like. 
         [0067]    The present invention will be explained in detail referring to following Examples. 
       Example 1 
       [0068]    The configuration of the double-sided light emitting organic electroluminescent device of this Example is shown in  FIGS. 2 and 6 , the double-sided light emitting organic electroluminescent device sequentially comprised a light-transmissive substrate  21 , an anode  22 , a hole injection layer  231   a , a hole transport layer  232   a , a light emitting layer  233   a , an electron transport layer  234   a , an N-type doped organic layer  241 , a P-type doped organic layer  242 , a hole injection layer  231   b , a hole transport layer  232   b , a light emitting layer  233   b , an electron transport layer  234   b , an electron injection layer  235   b , a light-transmissive cathode  25 , an antireflection film layer  27 , a vapor barrier layer  26  and a transparent cover layer  28 , and they were combined together, electroluminescent device included a transparent packaging adhesive layer  29  packaged between the transparent substrate  21  and the transparent cover layer  28  and around the components of the anode  22  to the vapor barrier layer  2 . 
         [0069]    Wherein, the light-transmissive substrate  21  was a 200 nm thick transparent glass, the anode  22  was a 100 nm thick indium tin oxide (ITO) layer, the hole injection layer  231   a  was a 30 nm thick m-MTDATA layer, the hole transport layer  232   a  was a 50 nm thick NPB layer, the light emitting layer  233   a  was a 20 nm thick C545T:Alq 3  layer, the electron transport layer  234   a  was a 40 nm thick Alq 3  layer, the N-type doped organic layer  241  was a 20 nm thick Li:Alq 3  layer, the P-type doped organic layer  242  was a 5 nm thick MoO 3 , the hole injection layer  231   b  was a 30 nm thick m-MTDATA layer, the hole transport layer  232   a  was a 50 nm thick NPB layer, the light emitting layer  233   a  was a 20 nm thick C545T:Alq 3  layer, the electron transport layer  234   a  is a 40 nm thick Alq 3  layer, the electron injection layer  235   b  was a 1 nm thick LiF layer, the light-transmissive cathode  25  was an Al/Ag layer, the Al layer had a thickness of 0.5 nm, the Ag layer had the thickness of 20 nm, the vapor barrier layer  26  was a 50 nm thick SiN x , the antireflection film layer  27  is an 80 nm thick Alq 3 , the transparent cover layer  28  was a transparent glass, and the packaging adhesive layer  29  was made of UV glue. 
         [0070]    The preparation method thereof was as follows: 
         [0071]    (1) a transparent glass was provided as a light-transmissive substrate  21 , and a layer of ITO was sputter plated on one surface of the light-transmissive substrate  21  to obtain an anode  22 ; the anode  22  was washed sequentially with a detergent, deionized water, acetone, ethanol, isopropanol under ultrasonic, each for 15 min; 
         [0072]    (2) in the coating system with a vacuum degree of 5×10 −4  Pa, the hole injection layer  231   a , the hole transport layer  232   a , the light emitting layer  233   a , the electron transport layer  234   a , the N-type doped organic layer  241 , the P-type doped organic layer  242 , the hole injection layer  231   b , the hole transport layer  232   b , the light emitting layer  233   b , the electron transport layer  234   b , the electron injection layer  235   b , the light-transmissive cathode  25  were plated sequentially by evaporation; 
         [0073]    (3) the light-transmissive cathode  25  and the antireflection film  27  were sputter plated sequentially on the outer surface of the electron injection layer  235   b;    
         [0074]    (4) under the atmosphere of N 2 , by employing a magnetron sputtering system, an SiN x  layer of 50 nm was sputter plated on one surface of the antireflection film layer  27  to give a vapor barrier layer  26 ; 
         [0075]    (5) a transparent glass layer  28  was additionally arranged on the outer surface of the vapor barrier layer  26 ; 
         [0076]    (6) a transparent packaging adhesive layer  29  was packaged between the light-transmissive substrate  21  and the transparent cover layer  28 , and around the components of the anode  22  to the vapor barrier layer  26 , to obtain the double-sided light emitting organic electroluminescent device as shown in  FIG. 6 . 
         [0077]    In the double-sided light emitting organic electroluminescent device prepared in this Example, the C545T:Alq 3  doped structure was used as the green light emitting layer, the laminated Li:Alq 3 /MoO 3  structure was used as a charge generation layer  24 , and the Alq 3  film was used as the antireflection film. The relationship of the brightness and the current density of the double-sided light emitting organic electroluminescent device may be seen in  FIG. 8 . As shown in  FIG. 8 , compared with the organic electroluminescent device without the charge generation layer  24  of Comparative Example 5, with the same current density, the brightness of the double-sided light emitting organic electroluminescent device prepared in this Example has been significantly improved, which increases by about 1.9 times. Also, it can be seen that the double-sided light emitting organic electroluminescent device prepared in this Example has a small drive current, and high luminous efficiency, high brightness, and high light output efficiency; and because of the small drive current the lifetime of the double-sided light emitting organic electroluminescent device is improved correspondingly. 
       Example 2 
       [0078]    The configuration of the double-sided light emitting organic electroluminescent device of this Example is similar to that of Example 1, which is shown in  FIG. 6 . 
         [0079]    The preparation method of the organic electroluminescent device was as follows: 
         [0080]    (1) a PET film was provided, then it was treated by washing; 
         [0081]    (2) under the atmosphere of N 2 , with a magnetron sputtering system, an SiN x  layer of 50 nm thickness was sputter coated on one surface of the transparent substrate  21  to give a vapor barrier layer  26 ; 
         [0082]    (3) an AZO layer of 150 nm thickness was sputter coated on the outer surface of the vapor barrier layer  26  to give an anode  22 , then the anode  22  was treated by washing, the manner of cleaning was the same as that of step (1) of the manufacturing method of Example 1; 
         [0083]    (4) in a coating system of 4×10 −4  Pa vacuum degree, an m-MTDATA layer  231   a  of 30 nm thickness, an NPB layer  232   a  of 50 nm thickness, a DPVBi layer  233   a  of 30 nm thickness, a Bphen layer  234   a  of 20 nm thickness, an Alq 3  layer  235   a  of 20 nm, a Mg:Alq 3  layer  241  of 30 nm thickness, an MoO 3  layer  242  of 3 nm thickness, an m-MTDATA layer  231   b  of 30 nm thickness, an NPB layer  232   b  of 50 nm thickness, an (F-BT) 2 Ir(acac):CBP layer  233   b  of 30 nm thickness, a Bphen layer  234   b  of 20 nm thickness, and an LiF layer  235   b  of 1 nm thickness were sequentially arranged by evaporation; 
         [0084]    (5) an Al layer of 0.5 nm and an Ag layer of 20 nm thickness were sequentially evaporated on the outer surface of the electron injection layer  235   b  to give a light-transmissive cathode  25 , and BCP antireflection film layer  27  of 100 nm thickness; 
         [0085]    (6) under the atmosphere of N 2 , with a magnetron sputtering system, an SiN x  layer of 50 nm thickness was sputter coated on the antireflection film layer  27  to give another vapor barrier layer  26 ; 
         [0086]    (7) a PET film layer  28  was additionally disposed on the outer surface of the vapor barrier layer  26 ; 
         [0087]    (8) a transparent packaging adhesive layer  29  was packaged between the light-transmissive substrate  21  and the transparent cover layer  28 , and around the components of the anode  22  to another vapor barrier layer  26 , to obtain a double-sided light emitting organic electroluminescent device. 
         [0088]    In the double-sided light emitting organic electroluminescent device prepared in this Example, the (F-BT) 2 Ir(acac):CBP doped structure was used as the yellow light emitting layer, the DPVBi was used as the blue light emitting layer, the Mg:Alq 3 /MoO 3  laminated structure was used as the charge generation layer. According to the measurement, the relationship of the brightness and the current density of the double-sided light emitting organic electroluminescent device had a similar trend with that show in  FIG. 7 . 
       Example 3 
       [0089]    The configuration of the double-sided light emitting organic electroluminescent device of this Example is shown in  FIG. 2 . The double-sided light emitting organic electroluminescent device sequentially comprised a light-transmissive substrate  21 , an anode  22 , a hole injection layer  231   a , a hole transport layer  232   a , a light emitting layer  233   a , an electron transport layer  234   a , an N-type doped organic layer  241 , a P-type doped organic layer  242 , a hole injection layer  231   b , a hole transport layer  232   b , a light emitting layer  233   b , an electron transport layer  234   b , an electron injection layer  235   b , and a light-transmissive cathode  25 , and they were combined together. 
         [0090]    Wherein, the light-transmissive substrate  21  was a transparent glass of 200 nm thickness, the anode  22  was an IZO layer of 150 nm thickness, the hole injection layer  231   a  was an m-MTDATA layer of 30 nm thickness, the hole transport layer  232   a  was an NPB layer of 50 nm thickness, the light emitting layer  233   a  was a DPVBi layer of 20 nm thickness, the electron transport layer  234   a  was an Alq 3  layer of 40 nm thickness, the N-type doped organic layer  241  was a Cs:Bphen layer of 25 nm thickness, the P-type doped organic layer  242  was a WO 3  layer of 10 nm thickness, the hole injection layer  231   b  was an m-MTDATA layer of 30 nm thickness, the hole transport layer  232   b  was an NPB layer of 50 nm thickness, the light emitting layer  233   b  was a Rubrene:Alq 3  layer of 20 nm thickness, the electron transport layer  234   b  was an Alq 3  layer of 40 nm thickness, the electron injection layer  235   b  was an LiF layer of 1 nm thickness, the light-transmissive cathode  25  was a Ca layer of 20 nm thickness. 
         [0091]    The preparation method of the organic electroluminescent device was as follows: 
         [0092]    (1) a transparent glass was provided, and it was treated by washing; 
         [0093]    (2) an IZO layer of 150 nm thickness was sputter coated on the outer surface of the vapor barrier layer  26  to give an anode  22 , then it was treated by washing, the manner of washing was the same as the step (1) in the manufacturing method of Example 1; 
         [0094]    (3) in the coating system with a vacuum degree of 4×10 −4  Pa, the m-MTDATA layer  231   a  of 30 nm thickness, the NPB layer  232   a  of 50 nm thickness, the DPVBi layer  233   a  of 20 nm thickness, the Alq 3  layer  234   a  of 40 nm thickness, the Cs:Bphen layer  241  of 25 nm thickness, the WO 3  layer  242  of 10 nm thickness, the m-MTDATA layer  231   b  of 30 nm thickness, the NPB layer  232   b  of 50 nm thickness, the Rubrene:Alq 3  layer  233   b  of 30 nm thickness, the Alq 3  layer  234   b  of 40 nm thickness, the LIF layer  235   b  of 1 nm thickness; 
         [0095]    (4) an Al layer of 0.5 nm thickness and an Ag layer of 20 nm thickness were evaporated sequentially on the outer surface of the electron injection layer  235   b  to give a light-transmissive cathode  25  and the antireflection film layer  27  respectively; 
         [0096]    (5) an SiO2 layer of 50 nm thickness was additionally evaporated on the outer surface of the antireflection film layer  27  to give another vapor barrier layer  26 ; 
         [0097]    (6) a transparent glass cover plate  28  was additionally arranged on the outer surface of the vapor barrier layer  26 ; 
         [0098]    (7) a transparent packaging adhesive layer  29  was packaged between the light-transmissive substrate  21  and the transparent cover layer  28 , and around the components of the anode  22  to the vapor barrier layer  26 , to obtain the double-sided light emitting organic electroluminescent device. 
         [0099]    In the double-sided light emitting organic electroluminescent device prepared in this Example, the Rubrene:Alq 3  doped structure was used as the yellow light emitting layer, the DPVBi was used as a blue light emitting layer, and the Cs:Bphen/WO 3  laminated structure was used as the electron generation layer. According to the measurement, the relationship of the brightness and the current density of the double-sided light emitting organic electroluminescent device is similar with that shown in  FIG. 8 . 
       Example 4 
       [0100]    The configuration of the double-sided light emitting organic electroluminescent device of this Example is shown in  FIGS. 3 and 6 . The double-sided light emitting organic electroluminescent device included sequentially a transparent substrate  21 , an anode  22 , a hole injection layer  231   a , a hole transport layer  232   a , a light emitting layer  233   a , the electron transport layer  234   a , an N-type doped organic layer  241   a , a P-type doped organic layer  242   a , a hole injection layer  231   c , a hole transport layer  232   c , a light emitting layer  233   c , an electron transport layer  234   c , an electron injection layer  235   c , an N-type doped organic layer  241   b , a metal oxides  242   b , a hole injection layer  231   b , a hole transport layer  232   b , a light emitting layer  233   b , an electron transport layer  234   b , an electron injection layer  235   b , a light-transmissive cathode  25 , an antireflection coating layer  27 , a vapor barrier layer  26  and a transparent cover layer  28 , they were combined together, the electroluminescent device further included a transparent packaging adhesive layer  29  packaged between the light-transmissive substrate  21  and the transparent cover layer  28 , around the components of the anode  22  to the vapor barrier layer  26 . 
         [0101]    The preparation methods of the organic electroluminescent device was as follows: 
         [0102]    (1) a transparent glass was provided, and it was treated by washing, the process thereof was the same as step (1) in the manufacture method of Example 1; 
         [0103]    (2) in the atmosphere of N 2 , with a magnetron sputtering system, an SiN x  layer of 50 nm thickness was sputter coated on one surface of the transparent substrate  21  to give a vapor barrier layer  26 ; 
         [0104]    (3) an ITO layer of 150 nm thickness was sputter coated on the outer surface of the vapor barrier layer  26  to give an anode  22 ; 
         [0105]    (4) in a coating system with a vacuum degree of 3×10 −4  Pa, an m-MTDATA layer  231   a  of 30 nm thickness, an NPB layer  232   a  of 50 nm thickness, an FIrPic:CBP  233   a  of 20 nm thickness, a TPBi layer  234   a  of 20 nm thickness, an Li:Alq 3  layer  241  of 20 nm thickness, an FeCl 3 :NPB layer  242  of 30 nm thickness, an m-MTDATA layer  231   c  of 40 nm thickness, an NPB layer  232   c  of 40 nm thickness, an Ir(ppy) 3 :CBP layer  233   c  of 20 nm thickness, a TPBi layer  234   c  of 20 nm, an NaF235c of 1 nm, an Li:TPBi layer  241   b  of 10 nm thickness, a V 2 O 5  layer  242   b  of 5 nm thickness, an m-MTDATA layer  231   b  of 40 nm thickness, an NPB layer  232   b  of 40 nm thickness, an Ir(piq) 3 :CBP layer  233   b  of 20 nm thickness, a TPBi layer  234   b  of 20 nm thickness, and an LiF layer  235   b  of 1 nm thickness were plated by evaporation; 
         [0106]    (5) an Al layer of 0.5 nm thickness and an Ag layer of 20 nm thickness were sputter coated sequentially on the outer surface of the electron injection layer  235   b  to obtain a light-transmissive cathode  25 , and an m-MTDATA layer  27  of 40 nm thickness was also coated; 
         [0107]    (6) under an atmosphere of N 2 , with a magnetron sputtering system, an SiN x  layer of 50 nm thickness was sputter coated on the surface of the antireflective film layer  27  to give another vapor barrier layer  26 ; 
         [0108]    (7) a transparent glass layer  28  was additionally plated on the outer surface of the vapor barrier layer  26 ; 
         [0109]    (8) a UV transparent packaging adhesive layer  29  was packaged between the light-transmissive substrate  21  and the transparent glass layer  28 , and around the components of the anode  22  to another vapor barrier layer  26 , to obtain the double-sided light emitting organic electroluminescent device. 
         [0110]    The performance of this organic electroluminescent light emitting device of this Example is similar to that described in Example 1. 
       Comparative Example 5 
       [0111]    The organic electroluminescent device of this comparative Example comprised sequentially a transparent glass  21 , an ITO anode  22 , an m-MTDATA hole injection layer of 30 nm thickness, an NPB hole transport layer of 50 nm thickness, a C545T:Alq 3  light emitting layer of 20 nm thickness, an Alq 3  electron transport layer of 40 nm thickness, an LiF electron injection layer of 1 nm thickness, a cathode of Al (0.5 nm)/Ag (20 nm), an Alq 3  antireflective film layer of 80 nm thickness, an SiN x  vapor barrier layer of 50 nm thickness and a transparent cover layer of transparent glass, they were combined together, the electroluminescent device also comprised a UV transparent packaging adhesive layer  29  packaged between the transparent substrate and the transparent cover layer, around the components of the anode to the vapor barrier layer. 
         [0112]    According to the measurement, the relationships of the luminous intensity and the current density of the double-sided light emitting organic electroluminescent devices of this comparative Example and that of Example 1 are shown in  FIG. 8 . 
         [0113]    The description above is merely the preferable embodiments of the present invention and not intended to limit the present invention. And all changes, equivalent substitution and improvements which come within the meaning and range of equivalency of the present invention are intended to be embraced therein.