Abstract:
A self-illumination display is provided, including a first substrate, a light-absorbing structure, a filter layer, a driving circuit unit, and a self-illumination unit. The light-absorbing structure and the filter layer are juxtaposedly disposed over the first substrate. The driving circuit unit is disposed over and shielded by the light-absorbing structure. The self-illumination unit is disposed over the filter layer, including a light-transmissible electrode, a light emitting layer, and a black electrode. The self-illumination unit is disposed over the filter layer, including a light-transmissible electrode, a light emitting layer, and a black electrode. The light-transmissible electrode is disposed over the filter layer while the light emitting layer and the black electrode are sequentially tiered on the light-transmissible electrode. The light-absorbing structure, the filter layer and the black electrode together reduce the reflection of the ambient light and enhance the image contrast.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a divisional of application Ser. No. 11/668,056, filed on Jan. 29, 2007, now U.S. Pat. No. 7,675,064, which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a pixel unit structure of a self-illumination display, and more particularly to a pixel unit structure of a self-illumination display with low-reflection. 
     2. Description of the Prior Art 
     As the purchasing demand of the slim displays increases day after day, the development of the self-illumination display technique is become more and more important. The technique of the self-illumination display, such as organic light emitting diode (OLED), is now well developed. For example, for the organic light emitting diode, the illumination of the display panel is the main consideration to determine whether the display device is good or not. In the display field, how to efficiently increase the utilizing rate of the self-illumination display is the main target for the engineers. 
     In regards to the contrast of the display panel, when the contrast is higher, the color and the image performance of the display panel is desirable. However, in the way of enhancing the contrast, the method is to increase the illumination of the self-illumination unit and isolate the reflection of the light from the external environment. Since the light from the external environment can enter the display panel through the display surface and then reflect by the electrode or the transistor within the display panel back to the display surface, the reflective light will affect the performance of the light generated from the display panel and the contrast of the display panel will be reduced. Therefore, how to reduce the reflection of the external environment light is the main issue in the development of the display panel. 
     As shown in  FIG. 1 , in order to reduce the reflective rate of the display panel, a polarizing film  30  is installed in the external surface  11  of the substrate  10  of the display panel. When the polarizing film  30  with the low transmitting rate is used, the reflective rate is reduced and the contrast is enhanced. However, the lost of the illumination is needed to recover; therefore the illuminative rate of the self-illumination element  50  must be increased. Yet, in this case, the lifetime of the self-illumination element  50  is reduced. As the polarizing film  30  with the high transmitting rate is used, the utilizing rate of the light is better but the efficiency of the contrast is decreased. 
     SUMMARY OF THE INVENTION 
     One purpose of the present invention is to provide a pixel unit structure of a self-illumination display which has a low external environment light reflective rate. 
     Another purpose of the present invention is to provide a pixel unit structure of a self-illumination display which has better contrast performance. 
     The other purpose of the present invention is to provide a pixel unit structure of a self-illumination display which has a better utilizing rate for the illumination. 
     The pixel unit structure of the self-illumination display includes a first substrate, a light-absorbing structure, a filter layer, a driving circuit and a self-illumination unit. The first substrate is used to be the base board of the display panel and includes an illuminative region and a non-illuminative region. The light-absorbing structure is formed over the first substrate and disposed within the non-illuminative region. By the installation of the light-absorbing structure, the amount of the external environment light to the non-illuminative region of the first substrate is reduced. Therefore, the reflective light caused by the external environment light reflected from the circuit or the electronic components is reduced. 
     The filter layer is disposed over the first substrate and close to the light-absorbing structure. Because of the isolation of the filter layer, the amount of the external environment light emitted into the first substrate is reduced and the contrast of the image shown on the self-illumination display is enhanced. The driving circuit is disposed over the light-absorbing structure and sheltered by the light-absorbing structure. In other words, the external environment light emitted into the first substrate is hard to contact with the driving circuit components. Therefore, the probability that the external environment light reflected from the driving circuit or the metal material thereof is reduced. 
     The self-illumination unit is disposed over the filter layer and substantially corresponding to the illuminative region of the first substrate. The self-illumination unit includes a light-transmissible electrode layer, a light emitting layer and a black electrode layer. The light-transmissible electrode layer is formed over the filter layer and is made of the light-transmissible and conductive material. The light emitting layer and the black electrode layer are sequentially formed over the light-transmissible electrode layer. Because the reflection of the black electrode layer is lower than the common metal electrode, the reflective light generated by the black electrode layer is lower than the reflective light generated by the common metal electrode when the external environment light emits into the black electrode layer through the first substrate and the filter layer. When the reflective light is reduced, the light generated by the self-illumination unit is able to enhance the contrast of the image. Besides, by the installation of the light-absorbing structure, the filter layer and the black electrode layer, it is more efficient to reduce the amount of the reflective light generated by the external environment light and the contrast of the display device is enhanced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a cross-sectional view of a light emitting diode display panel in the prior art. 
         FIG. 2  illustrates an exploded view of the self-illumination display according to one embodiment of the present invention. 
         FIG. 3  shows a cross-sectional view of the pixel unit structure of the self-illumination display according to one embodiment of the present invention. 
         FIG. 4  illustrates a view of the projection position of the exemplary self-illumination display according to the present invention. 
         FIG. 5  illustrates another embodiment of the black electrode layer. 
         FIG. 6  illustrates a cross-sectional view of the self-illumination display according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A pixel unit structure of a self-illumination display is disclosed in the present invention. In the preferred embodiment, the self-illumination display of the present invention is a color organic light emitting diode (OLED) display. In a different embodiment, the self-illumination display of the present invention is a monochromatic OLED display. Besides, in other embodiment, the self-illumination display of the present invention is a polymer light emitting diode (PLED) display. The self-illumination display of the present invention can be used in any display panels, home used flat panel TV, flat panel monitor for desktop or laptop, or display screen for mobile phone or digital camera. 
     As the preferred embodiment shown in  FIG. 2 , the pixel unit structure of the self-illumination display includes a first substrate  100 , a light-absorbing structure  300 , a filter layer  500 , a driving circuit  700 , a self-illumination unit  900  and a backside substrate  250 . In the present embodiment, the first substrate  100  is the base board for the display panel. The light is emitted out through the first substrate  100  to display the images. The material of the first substrate  100  is made by the transparent materials, such as glass or organic material with polymers. Besides, in the present embodiment, the first substrate  100  is divided into an illuminative region  111  and a non-illuminative region  113 . 
     The light-absorbing structure  300  is formed over the first substrate  100  and disposed within the non-illuminative region  113 . In the preferred embodiment, the light-absorbing structure  300  fully covers the non-illuminative region  113 . In a different embodiment, the light-absorbing structure  300  covers a portion of the non-illuminative region  113 . By disposing the light-absorbing structure  300 , the light from the external environment enters into the non-illuminative region  113  of the first substrate  100  is reduced. Therefore, the reflective light caused by the circuit or the electronic device reflecting the external environment light is reduced. In the preferred embodiment, the light-absorbing structure  300  is a dark light-absorbing structure and includes black matrix. The structure of the black matrix can be a single-layered organic film, a single-layered non-organic film, a compound organic film, a compound non-organic film and etc. In the preferred embodiment, the black matrix is a chromium (Cr) black matrix. In a different embodiment, the black matrix is a resin black matrix, a graphite black matrix or any other materials with similar structure. 
     As the embodiment shown in  FIG. 3 , the filter layer  500  is disposed over the first substrate  100  and is close to the light-absorbing structure  300 . In this preferred embodiment, the filter layer  500  is disposed over the illuminative region  111  and one side of the filter layer  500  is connected to the light-absorbing structure  300 . The filter layer  500  fully covers the illumination region  111 . In a different embodiment, the filter layer  500  covers a portion of the illumination region  111 . In this embodiment, the filter layer  500  is a color filter. However, the filter layer  500  can also be the filter photoresist, directly formed over the first substrate  100 , such as Color Filter on Array. Because of the isolation of the filter layer  500 , the light from the external environment enters into the first substrate  100  is reduced to enhance the contrast of the self-illumination display. Besides, due to install the filter layer  500  and the light-absorbing structure  300 , it is more efficient to reduce the reflective light caused by the external environment light to enhance the contrast of the display panel. 
     As shown in  FIG. 3 , the driving circuit  700  is disposed over the light-absorbing structure  300 . The light-absorbing structure  300  shelters the driving circuit  700  from the light emitted through the first substrate  100 . Therefore, the driving circuit  700  is isolated from the external environment light which avoids the external environment light reflected from the driving circuit  700  or other metal materials to the first substrate  100 . As the preferred embodiment shown in  FIG. 4 , the light-absorbing structure  300  shelters the vertical projection of the driving circuit  700  on the first substrate  100  and the better sheltering result is achieved. The driving circuit  700  includes thin-film-transistor (TFT). In a different embodiment, the driving circuit  700  includes a different circuit with same functions, such as a metal isolator metal thin film diode (MIM-TFD) circuit. The method of forming TFT includes amorphous silicon (a-Si) process, low temperature poly-silicon (LTPS) process or other processes with same functions. Besides, the gate  710  of the driving circuit  700  in each pixel unit is electrically connected to the adjacent driving circuit  700 . 
     As the embodiment shown in  FIG. 3 , the self-illumination unit  900  is disposed over the filter layer  500  and substantially corresponding to the illuminative region  111  of the first substrate  100 . On the other hand, the light generated by the self-illumination unit  900  is emitted from the illuminative region  111  to the outside of the first substrate  100 . In the preferred embodiment, as shown in  FIG. 4 , the vertical projection of the self-illumination unit  900  of the first substrate  100  falls on the internal surface  110  of the illuminative region  111 . The self-illumination unit  900  includes a light-transmissible electrode  910 , a light emitting layer  930  and a black electrode layer  950 . The light-transmissible electrode  910  is on the top of the filter layer  500  and is the anode of the self-illumination unit  900 . As the embodiment shown in  FIG. 3 , the light-transmissible electrode  910  is formed directly over the filter layer  500  and is electrically connected to the driving  700 . The light-transmissible electrode  910  includes the conductive layer formed by the indium tin oxide (ITO). In a different embodiment, the light-transmissible electrode  910  includes other light-transmissible conductive materials. 
     As shown in  FIG. 3 , the light emitting layer  930  is formed over the light-transmissible electrode  910 . The light emitting layer  930  is formed by coating, physically or chemically depositing, yellow light, etching and so on. The light emitting layer  930  can include any self-illuminative materials. Besides, In the present embodiment, the light emitting layer  930  includes white light illuminative material and used with the filter layer  500  to generate different color light. In a different embodiment, the light emitting layer  930  includes any other different color light instead of white light. 
     The black electrode layer  950  is formed over the light emitting layer  930  and is used to be the cathode of the self-illumination unit  900 . The black electrode layer  950  is formed by coating, physically or chemically depositing, yellow light, etching and so on. In the preferred embodiment, the black electrode layer  950  includes titanium (Ti) electrode. In a different embodiment, the black electrode layer  950  includes titanium alloy electrode, chromium electrode, chromium alloy electrode, graphite electrode or any other less reflective metal. Because the reflection of the black electrode layer  950  is less than the common metal electrode, as the reflected light is reduced, the image contrast generated from the self-illumination unit  900  is enhanced. Besides, due to the installation of the filter layer  500  and the light-absorbing structure  300 , it is efficient to reduce the reflective light generated by the external environment light and enhance the effect of the contrast of the display. 
     Another embodiment of the black electrode layer  950  is showing in  FIG. 5 . In the present embodiment, the black electrode layer  950  further includes a bottom metal electrode layer  951 , a middle metal electrode layer  953  and a top metal electrode layer  955 . The bottom metal electrode layer  951  is disposed over the light emitting layer  930 . The thickness of the bottom electrode layer  951  is thinner and is about 1˜25 nm thick. Therefore, the light is able to penetrate through the bottom electrode layer  951 . The bottom metal electrode layer  951  is made by aluminum or aluminum alloy. In a different embodiment, the bottom metal electrode layer  951  is made by copper, any other conductive metal or metal alloy. The middle metal electrode layer  953  is light-transmissible and formed over the bottom metal electrode layer  951 . In the preferred embodiment, the material of the middle metal electrode layer  953  is ITO. In a different embodiment, the material of the middle metal electrode layer  953  is any other conductive materials and is light-transmissible. The top metal electrode layer  955  is directly formed over the middle metal electrode layer  953 . The material of the top metal electrode layer  955  is made by aluminum or aluminum alloy. Besides, the material of the top metal electrode layer  955  is the same as the material of the bottom electrode layer  951 . In a different embodiment, the material of the top metal electrode layer  955  is copper or any other conductive metal alloy and is not the same as the material of the bottom metal electrode layer  953 . 
     In the present embodiment, the bottom metal electrode layer  951 , the middle metal electrode layer  953  and the top metal electrode layer  955  are together formed an optical chamber. Because the bottom metal electrode layer  951  is light-transmissible, the light emitted into the first substrate  100  is transmitted to the bottom metal electrode layer  951  and entered to the optical chamber. Because the optical effect is in the internal of the optical chamber, the light emitted into the optical chamber is hard to exit out of the bottom metal electrode layer  951  and it is able to reduce the reflective effect. 
     As the embodiment shown in  FIG. 3  and  FIG. 5 , the light generated by the self-illumination unit  900  passes through the anode of the light-transmissible electrode layer  910  and transmits out. As another embodiment shown in  FIG. 6 , the light generated by the self-illumination unit  900  transmits out through the cathode of the light-transmissible electrode layer  910 . As shown in  FIG. 6 , the pixel unit structure of the self-illumination unit display further includes a second substrate  200  opposite to the first substrate  100 . Alternatively, in accordance with the first substrate  100  of the display panel, the second substrate  200  is used to be a back board. The material of the second substrate  200  is metal, high polymer material or any other non-light-transmissible materials. 
     As shown in  FIG. 6 , the driving circuit  700  and the self-illumination  900  are sequentially formed over the second substrate  200 . The light-absorbing structure  300  and the filter layer  500  are directly formed over the first substrate  100 . When assembling the first substrate  100  and the second substrate  200 , the light-absorbing structure  300  shelters the corresponding driving circuit  700 . The self-illumination unit  900  is opposite to the filter layer  500 . The black electrode layer  950  is used to be the anode and is electrically connected to the driving circuit  700 . By installing the light-absorbing structure  300 , the filter layer  500  and the black electrode layer  950 , it is efficient to reduce the amount of the reflective light caused by the external environment lights and the contrast of the display is enhanced. 
     Although the preferred embodiments of the present invention have been described herein, the above description is merely illustrative. Further modification of the invention herein disclosed will occur to those skilled in the respective arts and all such modifications are deemed to be within the scope of the invention as defined by the appended claims.