Abstract:
This invention relates to a transflective LCD device using different common voltages in the transmissive and reflective regions to present the same gray scale performance on the transmissive and reflective regions. The liquid crystal display device includes a first substrate including a plurality of transmissive regions and a plurality of reflective regions; a transmissive electrode formed on said transmission electrode region; a reflective electrode formed on said reflective regions and connected electrically with said transmissive electrode; a second substrate including a plurality of first common electrodes and a plurality of second common electrodes, wherein said first common electrodes are formed over said transmissive regions, said second common electrodes are formed over said reflective regions, and said first common electrodes are not connected electrically with said second common electrodes; and a liquid crystal layer interposed between said first substrate and said second substrate.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to a transflective LCD device, more particularly to a transflective LCD device using different common voltages in the transmissive and reflective regions to present the same gray scale performance on the transmissive and reflective regions.  
         [0003]     2. Description of the Prior Art  
         [0004]     A color liquid crystal display (LCD) panel comprises two transparent substrates and a liquid crystal layer interposed therebetween. Normally, the commonly used liquid crystal of the TFT LCD device is TN (Twisted nematic) liquid crystal, which is nematic. The liquid crystal molecules are arranged with regularity in one-dimension. All the long axes of the clubbed liquid crystal molecules are correlatively arranged in parallel according to a specific direction. The nematic liquid crystal easily flows due to its low viscosity because this molecule easily flows along the direction of its long axis.  
         [0005]     As the structure of liquid crystal molecule is anisotropic, the induced photo-electronic effect will differ according to its arranging direction. In other words, the photo-electronic properties of liquid crystal molecule such as the dielectric permittivity or the refractive constant are anisotropic, too. Thus, the different gray scales displayed on the LCD can be formed by using the above matters to change the intensity of the incident light. For example, the dielectric permittivity can be divided into two vectors: ε∥ (in parallel with the long axis of liquid crystal molecule)and ε⊥ (vertical to the long axis of liquid crystal molecule). If ε∥&gt;ε⊥, the dielectric anisotropy of the liquid crystal is called as positive and If ε∥&lt;ε⊥, the dielectric anisotropy of the liquid crystal is called as negative. When a voltage is applied on the liquid crystal molecule, which will rotate parallel to or vertical to the electric field due to the positive or negative value of the dielectric anisotropy for permitting the light rays to pass through the liquid crystal or not. Now, the dielectric anisotropy of the TN type liquid crystal used in the TFT-LCD is almost positive.  
         [0006]      FIG. 1A  shows the arrangement of the positive type liquid crystal that is not applied the voltage. Presently, the pixel electrode  12  and the common electrode  13  are not applied voltage or the voltage difference on the liquid crystal layer  11  is zero so that the liquid crystal molecules  14  are arranged parallel to each other. Thus, the light can passes through not only the transmissive region but also the reflective region so as to be displayed on the screen of LCD. On the contrary, when a voltage is applied to the liquid crystal layer  11 , the liquid crystal molecules  14  begin to rotate and are not arranged parallel to each other. Then the liquid crystal molecules  14  will arrange vertically to the pixel electrode  12  and the common electrode  13  until the voltage achieves a specific value V 1  as shown in  FIG. 1B . Thus, the light cannot pass through not only the transmissive region but also the reflective region, so it cannot be displayed on the screen of LCD.  
         [0007]      FIG. 2A  shows a transmissive rate to applied voltage curve (T-V Curve )and a refractive rate to applied voltage curve (R-V Curve). As shown in  FIG. 2A , we can understand that the transmissive rate or the refractive rate is decreased while the applied voltage is increased. Therefore, the intensity of incident light rays can be varied by means of the above properties in order to display different gray scales on the screen of LCD. The conventional transflective liquid crystal display device is described with reference to  FIG. 2B . The pixel electrode comprises a transmissive electrode  21  and a reflective electrode  22  that are connected electrically each other. The common electrode  23  is a transparent conductive layer formed in the transmissive and reflective regions. When a voltage is applied to the pixel electrode and the common electrode, the external voltage applied in the transmissive region is the same as that in the reflective region. As the T-V curve does not overlap the R-V curve as shown in  FIG. 2A , the measured transmissive rate and the reflective rate are different when a fixed applied voltage is provided. It causes the gray scale displayed in the transmissive region is different from the gray scale displayed in the reflective region. In other words, the gray scale displayed on the screen of LCD by interior light source through the transmissive region (transmissive mode) is different from the gray scale displayed on the screen of LCD by exterior light source through reflective region (reflective mode). For example, the, LCD presents blue under transmissive mode, while the LCD presents pale blue under reflective mode. The users will query the quality of the product.  
       SUMMARY OF THE INVENTION  
       [0008]     In the light of the state of the art described above, it is an object of the present invention to provide a transflective LCD device which is immune to the problems of the conventional transflective LCD device described above.  
         [0009]     It is another object of this invention to provide a transflective LCD device using different common voltages in the transmissive and reflective regions to present the same gray scale performance on the transmissive and reflective regions.  
         [0010]     In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention A liquid crystal display device which comprises a first substrate including a plurality of transmissive regions and a plurality of reflective regions; a transmissive electrode formed on at lest one of the said transmission regions; a reflective electrode formed on at least one of the said reflective regions and connected electrically with said transmissive electrode; a second substrate including a plurality of first common electrodes and a plurality of second common electrodes, wherein said first common electrodes are formed over said transmissive regions, said second common electrodes are formed over said reflective regions, and said first common electrodes are not connected electrically with said second common electrodes; and a liquid crystal layer interposed between said first substrate and said second substrate.  
         [0011]     Base on the idea described above, wherein said first and second substrates are transparent.  
         [0012]     Base on the aforementioned idea, wherein said transmissive electrode is a transparent conductive layer.  
         [0013]     Base on the idea described above, wherein said transparent conductive layer is selected from the group consisting of ITO and IZO.  
         [0014]     Base on the aforementioned idea, wherein said reflective electrode is a metal layer.  
         [0015]     Base on the idea described above, wherein said metal layer is selected from the group consisting of Al, Ag, and AlNd.  
         [0016]     Base on the idea described above, wherein said first and second common electrodes are transparent conductive layers.  
         [0017]     Base on the aforementioned idea, wherein said transparent conductive layer is selected from the group consisting of ITO and IZO.  
         [0018]     Base on the idea described above, wherein the distance between said first common electrode and said second substrate is equal to the distance between said second common electrode and said second substrate.  
         [0019]     Base on the aforementioned idea, wherein the distance between said first common electrode and said second substrate is shorter than the distance between said second common electrode and said second substrate.  
         [0020]     Base on the idea described above, wherein the distance between said first common electrode and said second substrate is longer than the distance between said second common electrode and said second substrate.  
         [0021]     In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention A liquid crystal display device which comprises a first substrate including a plurality of transmissive regions and a plurality of reflective regions; a transmissive electrode formed on at least one of the said transmission regions; a reflective electrode formed on at least one of the said reflective regions and connected electrically with said transmissive electrode; a second substrate including a plurality of first common electrode regions and a plurality of second common electrode regions, wherein said first common electrode regions are formed over said transmissive regions, and said second common electrode regions are formed over said reflective regions; a first common electrode formed over said first and second common electrode regions; a second common electrode formed over said second common electrode regions and isolated from said first common electrode by a dielectric layer; and a liquid crystal layer interposed between said first substrate and said second substrate.  
         [0022]     Base on the idea described above, wherein said first and second substrates are transparent.  
         [0023]     Base on the aforementioned idea, wherein said transmissive electrode is a transparent conductive layer.  
         [0024]     Base on the idea described above, wherein said transparent conductive layer is selected from the group consisting of ITO and IZO.  
         [0025]     Base on the aforementioned idea, wherein said reflective electrode is a metal layer.  
         [0026]     Base on the idea described above, wherein said metal layer is selected from the group consisting of Al, Ag, and AlNd.  
         [0027]     Based on the idea described above, wherein said first and second common electrodes are transparent conductive layers.  
         [0028]     Based on the aforementioned idea, wherein said transparent conductive layer is selected from the group consisting of ITO and IZO.  
         [0029]     In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention A liquid crystal display device which comprises a first substrate including a plurality of transmissive regions and a plurality of reflective regions; a transmissive electrode formed on at least one of the said transmission regions; a reflective electrode formed on at least one of the said reflective regions and connected electrically with said transmissive electrode; a second substrate including a plurality of first common electrode regions and a plurality of second common electrode regions, wherein said first common electrode regions are formed over said transmissive regions, and said second common electrode regions are formed over said reflective regions; a first common electrode formed over said first and second common electrode regions; a second common electrode formed over said first common electrode regions and isolated from said first common electrode by a dielectric layer; and a liquid crystal layer interposed between said first substrate and said second substrate.  
         [0030]     Based on the idea described above, wherein said first and second substrates are transparent.  
         [0031]     Based on the aforementioned idea, wherein said transmissive electrode is a transparent conductive layer.  
         [0032]     Based on the idea described above, wherein said transparent conductive layer is selected from the group consisting of ITO and IZO.  
         [0033]     Based on the aforementioned idea, wherein said reflective electrode is a metal layer.  
         [0034]     Based on the idea described above, wherein said metal layer is selected from the group consisting of Al, Ag, and AlNd.  
         [0035]     Based on the idea described above, wherein said first and second common electrodes are transparent conductive layers.  
         [0036]     Based on the aforementioned idea, wherein said transparent conductive layer is selected from the group consisting of ITO and IZO. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0037]     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:  
         [0038]      FIG. 1A  shows the arrangement of positive type liquid crystal that is not applied the voltage;  
         [0039]      FIG. 1B  shows the arrangement of positive type liquid crystal that is applied the voltage V 1 ;  
         [0040]      FIG. 2A  shows the figure of transmissive and reflective rates of liquid crystal that is applied the voltage;  
         [0041]      FIG. 2B  schematically illustrates a cross-sectional view of conventional transflective liquid crystal display device;  
         [0042]      FIG. 3  schematically illustrates a cross-sectional view of transflective liquid crystal display device according to the first embodiment of the present invention;  
         [0043]      FIG. 4  schematically illustrates a cross-sectional view of transflective liquid crystal display device according to the second embodiment of the present invention;  
         [0044]      FIG. 5  schematically illustrates a cross-sectional view of transflective liquid crystal display device according to the third embodiment of the present invention;  
         [0045]      FIG. 6  schematically illustrates a cross-sectional view of transflective liquid crystal display device according to the fourth embodiment of the present invention; and  
         [0046]      FIG. 7  schematically illustrates a cross-sectional view of transflective liquid crystal display device according to the fifth embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0047]     Some sample embodiments of the present invention will now be described in greater detail. Nevertheless, it should be recognized that the present invention can be practiced in a wide range of other embodiments besides those explicitly described, and the scope of the present invention is expressly not limited except as specified in the accompanying claims.  
         [0048]     Please refer to  FIG. 3 , a cross-sectional view of transflective liquid crystal display (LCD) device according to the first embodiment of the present invention is shown. Each pixel of the transflective LCD device can be divided into the transmissive region II and the reflective region I. The process of manufacturing the device will be described. First, a thin film transistor (TFT)  31  and a transparent dielectric layer  321  are sequentially formed on the transparent substrate  301 . The transparent dielectric layer  321  can be a silicon oxide (SiO x ) layer, a silicon nitride (SiN x ) layer, or their stacked layers. Subsequently, a pad dielectric layer  322  with bumps is formed on the surface of reflective region I. The pad dielectric layer  322  can be photosensitive resin or other dielectric materials. When the material of pad dielectric layer  322  is photosensitive resin, it can be directly coated on the transparent substrate  301 , then the transmissive region II and the reflective region I are patterned with the photolithography process. Then, the transmissive electrode  34  in the transmission electrode region II can be formed with ITO or IZO by the sputtering process. Similarly, the reflective electrode  33  in the reflection electrode region I can be formed with Al, Ag, or AlNd by the sputtering process. As mentioned above, the transmissive electrode  34  and the reflective electrode  33  are electrically connected each other for forming a pixel electrode. Besides, the pixel electrode is electrically connected with the TFT  31 .  
         [0049]     After the color filter  35  formed on the transparent substrate  302 , a reflective common electrode  36  in the reflective region I and a transmissive common electrode  37  in the transmissive region II are formed. First, an ITO or IZO layer is coated on the color filter  35  with the sputtering process, and then the ITO or IZO layer are patterned and isolated by the photolithography and etching processes to form the reflective and transmissive common electrodes  36 , 37  that are not connected electrically each other. Finally, the transparent substrate  301  and the transparent substrate  302  are sealed with electrodes  33 , 34 , 36 , 37  face to face and vacuumed, and liquid crystal is injected into the space between the transparent substrate  301 , 302  to form a liquid crystal layer  39 . Hence, we can apply the different voltages to the reflective common electrode  36  in the reflective region I and the transmissive common electrode  37  in the transmissive region II in order to achieve a perfect gray scale presented on the screen of transflective LCD device.  
         [0050]     Please refer to  FIG. 4 , a cross-sectional view of transflective liquid crystal display (LCD) device according to the second embodiment of the present invention is shown. Each pixel of the transflective LCD device can be divided into the transmissive region II and the reflective region I. The process of manufacturing the device will be described. First, a thin film transistor (TFT)  41  and a transparent dielectric layer  421  are sequentially formed on the transparent substrate  401 . The transparent dielectric layer  421  can be a silicon oxide (SiO x ) layer, a silicon nitride (SiN x ) layer, or their stacked layers. Subsequently, a pad dielectric layer  422  with bumps is formed on the surface of reflective region I. The pad dielectric layer  422  can be photosensitive resin or other dielectric materials. When the material of pad dielectric layer  422  is photosensitive resin, it can be directly coated on the transparent substrate  401 , then the transmissive region II and the reflective region I are patterned with the photolithography process. Then, the transmissive electrode  44  in the transmission electrode region II can be formed with ITO or IZO by the sputtering process. Similarly, the reflective electrode  43  in the reflection electrode region I can be formed with Al, Ag, or AlNd by the sputtering process. As mentioned above, the transmissive electrode  44  and the reflective electrode  43  are electrically connected each other for forming a pixel electrode. Besides, the pixel electrode is electrically connected with the TFT  41 .  
         [0051]     After the color filter  45  formed on the transparent substrate  402 , a reflective common electrode  46  in the reflective region I and a transmissive common electrode  47  in the transmissive region II are formed. First, a transparent dielectric layer  48  is coated on the color filter  45  with the deposition process, and the transparent dielectric layer in the transmissive region II is removed by the photolithography and etching processes. Next, an ITO or IZO layer is coated with the sputtering process, and the ITO or IZO layer are patterned and isolated by the photolithography and etching processes to form the reflective and transmissive common electrodes  46 , 47  that are not connected electrically each other. Finally, the transparent substrate  401  and the transparent substrate  402  are sealed with electrodes  43 , 44 , 46 , 47  face to face and vacuumed, and liquid crystal is injected into the space between the transparent substrate  401 , 402  to form a liquid crystal layer  49 . Hence, we can apply the different voltages to the reflective common electrode  46  on the reflective region I and the transmissive common electrode  47  on the transmissive region II in order to achieve a perfect gray scale presented on the screen of transflective LCD device.  
         [0052]     Please refer to  FIG. 5 , a cross-sectional view of transflective liquid crystal display (LCD) device according to the third embodiment of the present invention is shown. Each pixel of the transflective LCD device can be divided into the transmissive region II and the reflective region I. The process of manufacturing the device will be described. First, a thin film transistor (TFT)  51  and a transparent dielectric layer  521  are sequentially formed on the transparent substrate  501 . The transparent dielectric layer  521  can be a silicon oxide (SiO x ) layer, a silicon nitride (SiN x ) layer, or their stacked layers. Subsequently, a pad dielectric layer  522  with bumps is formed on the surface of reflective region I. The pad dielectric layer  522  can be photosensitive resin or other dielectric materials. When the material of pad dielectric layer  522  is photosensitive resin, it can be directly coated on the transparent substrate  501 , then the transmissive region II and the reflective region I are patterned with the photolithography process. Then, the transmissive electrode  54  in the transmission electrode region II can be formed with ITO or IZO by the sputtering process. Similarly, the reflective electrode  53  in the reflection electrode region I can be formed with Al, Ag, or AlNd by the sputtering process. As mentioned above, the transmissive electrode  54  and the reflective electrode  53  are electrically connected each other for forming a pixel electrode. Besides, the pixel electrode is electrically connected with the TFT  51 .  
         [0053]     After the color filter  55  formed on the transparent substrate  502 , a reflective common electrode  56  in the reflective region I and a transmissive common electrode  57  in the transmissive region II are formed. First, an ITO or IZO layer is coated on the color filter  55  with the sputtering process, a transparent dielectric layer  58  is coated on the ITO or IZO layer with the deposition process, and the transparent dielectric layer in the transmissive region II is removed by the photolithography and etching processes. Next, another ITO or IZO layer is coated with the sputtering process, and the ITO or IZO layer are patterned and isolated by the photolithography and etching processes to form the reflective and transmissive common electrodes  56 , 57  that are not connected electrically each other. Finally, the transparent substrate  501  and the transparent substrate  502  are sealed with electrodes  53 , 54 , 56 , 57  face to face and vacuumed, and liquid crystal is injected into the space between the transparent substrate  501 , 502  to form a liquid crystal layer  59 . Hence, we can apply the different voltages to the reflective common electrode  56  on the reflective region I and the transmissive common electrode  57  on the transmissive region II in order to achieve a perfect gray scale presented on the screen of transflective LCD device.  
         [0054]     Please refer to  FIG. 6 , a cross-sectional view of transflective liquid crystal display (LCD) device according to the fourth embodiment of the present invention is shown. Each pixel of the transflective LCD device can be divided into the transmissive region II and the reflective region I. The process of manufacturing the device will be described. First, a thin film transistor (TFT)  61  and a transparent dielectric layer  621  are sequentially formed on the transparent substrate  601 . The transparent dielectric layer  621  can be a silicon oxide (SiO x ) layer, a silicon nitride (SiN x ) layer, or their stacked layers. Subsequently, a pad dielectric layer  622  with bumps is formed on the surface of reflective region I. The pad dielectric layer  622  can be photosensitive resin or other dielectric materials. When the material of pad dielectric layer  622  is photosensitive resin, it can be directly coated on the transparent substrate  601 , then the transmissive region HI and the reflective region I are patterned with the photolithography process. Then, the transmissive electrode  64  in the transmission electrode region II can be formed with ITO or IZO by the sputtering process. Similarly, the reflective electrode  63  in the reflection electrode region I can be formed with Al, Ag, or AlNd by the sputtering process. As mentioned above, the transmissive electrode  64  and the reflective electrode  63  are electrically connected each other for forming a pixel electrode. Besides, the pixel electrode is electrically connected with the TFT  61 .  
         [0055]     After the color filter  65  formed on the transparent substrate  602 , a reflective common electrode  66  in the reflective region I and a transmissive common electrode  67  in the transmissive region II are formed. First, a transparent dielectric layer  68  is coated on the color filter  65  with the deposition process, and the transparent dielectric layer in the reflective region I is removed by the photolithography and etching processes. Next, an ITO or IZO layer is coated with the sputtering process, and the ITO or IZO layer are patterned and isolated by the photolithography and etching processes to form the reflective and transmissive common electrodes  66 , 67  that are not connected electrically each other. Finally, the transparent substrate  601  and the transparent substrate  602  are sealed with electrodes  63 , 64 , 66 , 67  face to face and vacuumed, and liquid crystal is injected into the space between the transparent substrate  601 , 602  to form a liquid crystal layer  69 . Hence, we can apply the different voltages to the reflective common electrode  66  on the reflective region I and the transmissive common electrode  67  on the transmissive region II in order to achieve a perfect gray scale presented on the screen of transflective LCD device.  
         [0056]     Please refer to  FIG. 7 , a cross-sectional view of transflective liquid crystal display (LCD) device according to the fifth embodiment of the present invention is shown. Each pixel of the transflective LCD device can be divided into the transmissive region II and the reflective region I. The process of manufacturing the device will be described. First, a thin film transistor (TFT)  71  and a transparent dielectric layer  721  are sequentially formed on the transparent substrate  701 . The transparent dielectric layer  721  can be a silicon oxide (SiO x ) layer, a silicon nitride (SiN x ) layer, or their stacked layers. Subsequently, a pad dielectric layer  722  with bumps is formed on the surface of reflective region I. The pad dielectric layer  722  can be photosensitive resin or other dielectric materials. When the material of pad dielectric layer  722  is photosensitive resin, it can be directly coated on the transparent substrate  701 , then the transmissive region II and the reflective region I are patterned with the photolithography process. Then, the transmissive electrode  74  in the transmission electrode region II can be formed with ITO or IZO by the sputtering process. Similarly, the reflective electrode  73  in the reflection electrode region I can be formed with Al, Ag, or AlNd by the sputtering process. As mentioned above, the transmissive electrode  74  and the reflective electrode  73  are electrically connected each other for forming a pixel electrode. Besides, the pixel electrode is electrically connected with the TFT  71 .  
         [0057]     After the color filter  75  formed on the transparent substrate  702 , a reflective common electrode  76  in the reflective region I and a transmissive common electrode  77  in the transmissive region II are formed. First, an ITO or IZO layer is coated on the color filter  75  with the sputtering process, a transparent dielectric layer  78  is coated on the ITO or IZO layer with the deposition process, and the transparent dielectric layer in the reflective region I is removed by the photolithography and etching processes. Next, another ITO or IZO layer is coated with the sputtering process, and the ITO or IZO layer are patterned and isolated by the photolithography and etching processes to form the reflective and transmissive common electrodes  76 , 77  that are not connected electrically each other. Finally, the transparent substrate  701  and the transparent substrate  702  are sealed with electrodes  73 , 74 , 76 , 77  face to face and vacuumed, and liquid crystal is injected into the space between the transparent substrate  701 , 702  to form a liquid crystal layer  79 . Hence, we can apply the different voltages to the reflective common electrode  76  on the reflective region I and the transmissive common electrode  77  on the transmissive region II in order to achieve a perfect gray scale presented on the screen of transflective LCD device.  
         [0058]     Although the specific embodiment has been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from what is intended to be limited solely by the appended claims.