Abstract:
An electric controlled color change electro luminescent element is disclosed. An EL element is connected to a driving system by a first pin and a second pin. The driving system has a function of changing driving voltage. The driving system is switched through a switch for changing the way for supplying voltage or switching to different driving IC to change the output bias or current frequency. Thereby, the color and brightness of the EL element are changed.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an electric controlled color change electro luminescent element, and particularly to an electro luminescent element having a driving system to change the driving voltage and frequency so as to emit lights of different colors and chromaticity.  
         BACKGROUND OF THE INVENTION  
         [0002]    Referring to FIG. 7, a prior electric controlled color change electro luminescent element (EL element) is illustrated. The EL element has a thin film structure for applying to back light elements. In the EL element, an alternative current power system provides power to a front side electrode  91  and a backside electrode  92 . Furthermore, the electric field from an AC current is utilized to induce the light emitting particles in the light emitting layer  93  interior the EL element (not shown). Therefore, light (for example, green light) is excited. Since the driving circuit of an EL element may generate a driving AC voltage. In this AC current, the light emitting particles in the light emitting layer emits light of single color. As a result, the use of the EL element is confined. Therefore, in other way, pigments or fluorescent dye is mixed in the EL element for changing the color of the EL element. However, this way still emits light of single color.  
         SUMMARY OF THE INVENTION  
         [0003]    Accordingly, the primary object of the present invention is to provide an electric controlled color change electro luminescent element. An EL element is connected to a driving system by a first pin and a second pin. The driving system has a function of changing driving voltage. The driving system is switched through a switch for changing the way for supplying voltage or switching to different driving IC to change the output bias or current frequency. Thereby, the color and brightness of the EL element are changed.  
           [0004]    The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 is an exploded perspective view of the EL element of the present invention.  
         [0006]    [0006]FIG. 2 shows a circuit diagram of the first embodiment of the present invention, wherein the switch is switched to a first condition.  
         [0007]    [0007]FIG. 3 is a circuit diagram of the first embodiment of the present invention, wherein the switch is switched to another condition.  
         [0008]    [0008]FIG. 4 shows a CIE chromaticity diagram of the first, second and third embodiments of the present invention.  
         [0009]    [0009]FIG. 5 shows a circuit diagram of the second embodiment of the present invention, wherein the switch is switched to one condition.  
         [0010]    [0010]FIG. 6 shows a circuit diagram of the second embodiment of the present invention, wherein the switch is switched to another embodiment.  
         [0011]    [0011]FIG. 7 is a structural cross section view of a prior EL element. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]    Referring to FIGS.  1  to  3 , the electric controlled color change electro luminescent element of the present invention is illustrated. The electric controlled color change electro luminescent element is formed by overlapping a front side electrode  11 , a light emitting layer  12 , an electron-inducing layer  13 , and a backside electrode  14 . An insulating layer  15  is arranged at the exterior side. The front side electrode  11  and the backside electrode  14  have a first pin  111  and a second pin  141 , respectively, which are extended to the outer side of the EL element  1 . The first pin  111  is connected to a driving IC  2  (in this embodiment, it is an IC of D335A). The driving IC  2  is connected to a driving circuit  20  (in this embodiment, it is a standard circuit of D335A IC). Moreover, the driving IC  2  is connected to a power supply system  3  which is formed by serially connecting a first battery  31  and a second battery  32  (in this embodiment, the first battery  31  and second battery  32  are 1.5V DC batteries). A positive electrode of the first battery  31  is connected to the driving IC  2 , and the negative electrode of the second battery  32  is connected to a switch  33 . The switch  33  includes a first joint  331  and a second joint  332 . The first joint  331  is connected with the second joint  332 . The second joint  332  is connected between the first battery  31  and the second battery  32 . Furthermore, the switch  33  is connected to the second pin  141 . A point between the switch  33  and the second joint  332  is grounded. A capacitor  34  is connected to the driving IC  2  and the positive electrode connected to the first battery  31 .  
         [0013]    Referring to FIG. 4, a CIE chromaticity diagram is illustrated. When the switch  33  is switched to the first joint  331  (referring to FIG. 3), only the first battery  31  provides a 1.5V voltage to the EL element  1 , and the voltage from the first battery  31  is converted from DC to AC through the driving circuit  20 , wherein this AC current has a bias of 160V p-p  and a frequency of 220 Hz. When this AC current drives the EL element  1  to emit light. The light emitting layer  12  emits light with a brightness of 50 cd/m 2  and the chromaticity of CIE is 0.18 for x axis and 0.42 for y axis. As a result the color is green color.  
         [0014]    When the switch  33  is switched to the second joint  332  (referring to FIG. 2), the EL element  1  is provided with a voltage of 3.0V by serially connecting the first battery  31  and the second battery  32 . This voltage is converted from DC to AC through the driving IC  2  and the driving circuit  20 , wherein this AC current has a bias of 200V p-p  and a frequency of 475 Hz. When this AC current drives the EL element  1  to emit light, then the brightness of the light emitting layer  12  is increased to 170 cd/m 2  and the chromaticity of CIE is 0.17 for x axis and 0.34 for y axis. As a result the color is blue green color.  
         [0015]    Comparison in the First Embodiment.  
                                                                     Input DC   Output AC driving               driving   voltage   Brightness   CIE            voltage   Voltage   Frequency   cd/m 2     x   y               1.5 V-DC   160 V p-p     220 Hz    50   0.18   0.42       3.0 V-DC   200 V p-p     475 Hz   170   0.17   0.34                  
 
         [0016]    It is appreciated from above embodiment that in the conventional EL element  1 , the light emitting layer  12  may have different vibrating frequency by changing driving voltage and frequency. Therefore, the color of the emitting light is changeable and the brightness can be increased. As a result, single EL element  1  can present various colors.  
         [0017]    Many other examples are suitably used in the present invention. Referring to FIGS. 5 and 6, a second embodiment of the present invention is illustrated. The first pin  41  and second pin  42  of the EL element  4  have respective gated switches  4  which are interacted. The switch  4  may be connected to a front driving IC  5  (in this embodiment, it is an DCC335A IC) and a first driving circuit  50  communicable with the first driving IC  5  (in this embodiment, it is a D335 AIC standard circuit). Besides, the switch  43  may be switched to communicate with a second driving IC  6  (in this embodiment, it is a SP4422A IC). The second driving IC  6  is connected to the second driving circuit  60  (in this embodiment, it is a standard circuit of SP4422A IC). The first driving IC  5  and the first driving circuit  50  and the second driving IC  6  and the second driving circuit  60  are connected to a power supply system  7  (in this embodiment, it is a 1.5 V DC current).  
         [0018]    When the switch  43  is switched to the first driving IC  5  and the second driving circuit  50  (referring to FIG. 6), the first driving IC  5  and the first driving circuit  50  converts the 1.5 V DC into an AC current with a bias of 190 V p-p  and 220 Hz. Therefore, the EL element  1  is driven to emit light with a brightness of 70 cd/m 2  and the chromaticity of CIE is 0.18 for x axis and 0.42 for y axis. As a result the color is green color.  
         [0019]    When the switch  43  is switched to the second driving IC  6  and the second driving circuit  60  (referring to FIG. 5), the second driving IC  6  and the second driving circuit  60  (referring to FIG. 5) converts the 1.5V DC current into an AC current has a bias of 200V p-p  and a frequency of 475 Hz. When this AC current drives the EL element  1  to emit light, then the brightness of the light emitting layer  12  is increased to 170 cd/m 2  and the chromaticity of CIE is 0.17 for x axis and 0.34 for y axis. As a result the color is blue green color.  
         [0020]    Comparison in the Second Embodiment.  
                                                             Output AC driving               voltage   Brightness   CIE            Voltage   Frequency   cd/m 2     X   y               190 V p-p     220 Hz    70   0.18   0.42       200 V p-p     475 Hz   170   0.17   0.34                  
 
         [0021]    Besides, in the third embodiment of the present invention, it is similar to the first embodiment. In the third embodiment, the EL element is mixed with fluorescent pigments. Under a driven voltage of 1.5V, the driving IC performs a DC to AC conversion so as to acquire an AC current of 160V p-p  and 220 Hz. When this Ac current drives the EL element to emit light, since the vibration frequency of 220 Hz will cause the brightness to decrease to 35 cd/m 2  due to the isolation of the fluorescent pigment, and the chromaticity of CIE is 0.28 for x axis and 0.42 for y axis. The color is pink.  
                                                                     Input DC   Output AC driving               driving   voltage   Brightness   CIE            voltage   Voltage   Frequency   cd/m 2     x   Y               1.5 V-DC   160 V p-p     220 Hz    35   0.28   0.42       3.0 V-DC   200 V p-p     475 Hz   150   0.26   0.37                  
 
         [0022]    A voltage of 3.0V is provided to the EL element  1  by serially connect the first battery to the second battery. This voltage is performed with a DC to AC conversion so as to acquire an AC current with a bias of 200V p-p  and a frequency of 475 Hz. When this AC current drives the EL element to emit light, since the vibration frequency of 475 Hz will cause the brightness to increase to 50 cd/m 2 , and the chromaticity of CIE is 0.26 for x axis and 0.37 for y axis. The color is white.  
         [0023]    Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.