Abstract:
A display device is disclosed, which comprises: a first substrate; a first metal layer disposed on a surface of the first substrate; a first insulating layer disposed on the first metal layer; a second insulating layer disposed on the first insulating layer; and a second metal layer covering a part of the second insulating layer and comprising a connecting region, wherein the first metal layer and the second metal layer are electrically connected to each other in the connecting region, wherein the second metal layer corresponding to the connecting region comprises a sidewall region and a non-sidewall region, a first thickness of the sidewall region corresponding to the second insulating layer along a direction parallel to the surface of the first substrate is smaller than a second thickness of the non-sidewall region along a direction perpendicular to the surface of the first substrate.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 14/572,460, filed Dec. 16, 2014, which claims the priority of Taiwan Patent Application Serial Number 103116212, filed on May 7, 2014, the subject matter of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a display device and, more particularly, to a display device capable of decreasing resistance, reducing current leakage, improving capacity value and increasing storage capacity in pixels. 
         [0004]    2. Description of Related Art 
         [0005]    In recent years, all the display devices are developed toward having small volume, thin thickness and light weight as the display techniques progresses. Hence, a conventional cathode ray tube (CRT) display is gradually replaced by flat panel display devices such as a liquid crystal display (LCD) device and an organic light emitting diode (OLED) display device. The flat panel display devices can be applied to various fields. For example, the daily used devices such as cell phones, notebooks, video cameras, cameras, music players, navigation devices, and televisions are equipped with the flat panel display devices. 
         [0006]    Although the LCD device and the OLED display device are commercially available and especially the techniques for the LCD device are much mature, every manufacturer is desired to develop display devices with improved display quality to meet customers&#39; requirement as the display devices developed. In particular, the OLED display device is one important target for manufacturers. 
         [0007]    Even though the LCD device and the OLED display device are well developed and commercialized, it is still necessary to develop a display device with improved display quality to meet the customers&#39; requirement. 
       SUMMARY OF THE INVENTION 
       [0008]    An object of the present invention is to provide a display panel to decrease resistance, reduce current leakage, improve capacity value and increase storage capacity in pixels. 
         [0009]    To achieve the object, the present invention provides a display device, comprising: a first substrate; a first insulating layer disposed on the first substrate; a second insulating layer disposed on the first insulating layer; and a metal layer disposed on the second insulating layer and comprising plural conductive lines, wherein an opening region is located between two adjacent conductive lines to expose the second insulating layer, wherein a thickness of the second insulating layer under the metal layer is larger than that exposed from the opening region. More specifically, the metal layer of the present invention is a patterned metal layer, and the thickness of the second insulating layer under the conductive lines of the patterned metal layer is larger than that exposed from the opening region. 
         [0010]    In other words, the present invention provides a display device, comprising: a first substrate; a first insulating layer disposed on the first substrate; a second insulating layer disposed on the first insulating layer; and a metal layer covering a part of the second insulating layer, wherein a thickness of the second insulating layer under the metal layer (i.e. covered with the metal layer) is larger than that uncovered with the metal layer. 
         [0011]    In the display device of the present invention, the thickness of the second insulating layer covered with the metal layer is increased to achieve the purpose of decreasing resistance and reducing current leakage. Meanwhile, the thickness thereof uncovered with the metal layer and exposed from the opening region is decreased to achieve the purpose of improving capacity value and increasing storage capacity in pixels. 
         [0012]    In the display panel of the present invention, the thickness of the second insulating layer exposed from the opening region (i.e. uncovered with the metal layer) is smaller than that under the metal layer (especially, the conductive lines of the metal layer). The thickness of the second insulating layer exposed from the opening region is preferably 10˜95%, more preferably 20˜80%, and most preferably 25%˜35% of that under the conductive lines. 
         [0013]    In addition, in the display panel of the present invention, the first insulating layer and the second insulating layer can be made of any dielectric material generally used in the art, such as silicon oxide and silicon nitride. Preferably, the first insulating layer is a silicon oxide layer; and/or the second insulating layer is a silicon nitride layer. 
         [0014]    Furthermore, in the display panel of the present invention, an undercut is present in the first insulating layer under the second insulating layer. More specifically, the first insulating layer comprises a first side wall, the second insulating layer comprises a second side wall, and the second side wall is protruded beyond the first side wall. 
         [0015]    In the display panel of the present invention, a sealant may be further disposed on the first substrate, and the thickness of the second insulating layer under the conductive lines of the patterned metal layer is larger than that under the sealant. Herein, the material for the sealant can be selected based on the types of the display panel. In one case that the display device of the present invention is a liquid crystal display (LCD) device, a frame sealant known in the art can be used as the sealant. In another case that the display device is an organic light emitting diode (OLED) display device, a frit sealant known in the art can be used as the sealant, which has excellent moisture barrier property and air impermeability. 
         [0016]    The display device of the present invention can be applied as an OLED display device or a LCD device. In the case that the display device of the present invention is an OLED display device, the device may further comprise a planer layer disposed on the metal layer (especially, the conductive lines of the patterned metal layer) and in the opening region uncovered with the metal layer; additionally, the device may further comprise an organic light emitting diode unit, which comprises a first electrode, a second electrode and an organic light emitting layer disposed therebetween, wherein the metal layer (i.e. the conductive lines of the patterned metal layer) is electrically connected to the first electrode. 
         [0017]    Furthermore, in the case that the display device of the present invention is a LCD device, the device may further comprise a liquid crystal display unit, which comprises a first electrode, a second electrode and a liquid crystal layer disposed therebetween, wherein the metal layer (i.e. the conductive lines of the patterned metal layer) is electrically connected to the first electrode. 
         [0018]    Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a cross-sectional view of an OLED display device according to Embodiment 1 of the present invention; 
           [0020]      FIG. 2  is a perspective view showing a layout of an OLED display device according to Embodiment 1 of the present invention; 
           [0021]      FIG. 3  is a cross-sectional view showing a part of a display region of an OLED display device according to Embodiment 1 of the present invention; 
           [0022]      FIGS. 4A and 4B  are respectively cross-sectional views showing parts of an OLED display device according to Embodiment 1 of the present invention; 
           [0023]      FIG. 5  is a perspective view showing a part of a non-display region of an OLED display device according to Embodiment 1 of the present invention; 
           [0024]      FIG. 6  is a cross-sectional view of an OLED display device along a P-P′ line in  FIG. 5  according to Embodiment 1 of the present invention; 
           [0025]      FIG. 7  is an enlarged view showing a region E of an OLED display device in  FIG. 3  according to Embodiment 1 of the present invention; 
           [0026]      FIG. 8  is a cross-sectional view showing a sealant region of an OLED display device in  FIG. 1  according to Embodiment 1 of the present invention; 
           [0027]      FIG. 9  is a cross-sectional view of a LCD device according to Embodiment 2 of the present invention; and 
           [0028]      FIG. 10  is a cross-sectional view showing a part of a display region of a LCD device according to Embodiment 2 of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0029]    The present invention has been described in an illustrative manner, and it is to be understood that the terminology used is intended to be in the nature of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it is to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. 
       Embodiment 1 
       [0030]      FIG. 1  is a cross-sectional view of an OLED display device of the present embodiment. During the process for manufacturing the OLED display device, a first substrate  11  and a second substrate  12  are firstly provided. Organic light emitting diode (OLED) units  15  and pixel defining layers  16  are disposed on the first substrate  11 , wherein each pixel defining layer  16  is disposed between two adjacent OLED units  15 . In addition, plural spacers  14  are disposed on the second substrate  12 , and a sealant  13  (a frit sealant in the present embodiment) is formed on a periphery of the second substrate  12  in advance, which is formed through a dispensing process and a sintering process to fix on the second substrate  12 . Then, the first substrate  11  is assembled with the second substrate  12 , wherein the spacers  14  on the second substrate  12  correspond to regions outside the pixel opening  161  of the pixel defining layer  16 . After the sealant  13  is adhered onto the first substrate  11  through a laser process, an OLED display device of the present embodiment is obtained. 
         [0031]    In the present embodiment, both the first substrate  11  and the second substrate  12  are glass substrates. In addition, the OLED display device of the present embodiment comprises a display region A and a non-display region B, which is a region with circuits formed thereon. Furthermore, in the present embodiment, the OLED units  15  can respectively emit red, green and blue light; but the present invention is not limited thereto. For example, the OLED units  15  can be white OLED units, and a color filter unit (not shown in the figure) may be further disposed on the second substrate  12 . 
         [0032]      FIG. 2  is a perspective view showing a layout of an OLED display device of the present embodiment. As shown in  FIG. 2 , in the OLED display device of the present embodiment, each pixel unit respectively comprises: a scan line, a data line, a capacitor line, a supply line, a switching thin film transistor unit (shown as switching TFT in  FIG. 2 ), a driving thin film transistor unit (shown as driving TFT in  FIG. 2 ), a storage capacitor, and an OLED unit (shown as OLED in  FIG. 2 ) connecting to a first electrode and a second electrode. 
         [0033]      FIG. 3  is a cross-sectional view showing a part of a display region of an OLED display device of the present embodiment. As shown in  FIGS. 1  and  3 , the OLED display device of the present embodiment comprises: a first substrate  11  and a second substrate  12  opposite thereto. In the present embodiment, the thin film transistor (TFT) units used in the OLED display device are low temperature poly-silicon (LTPS) TFT units. As shown in  FIG. 3 , in the display region A, a first substrate  11  is firstly provided, and a silicon nitride buffer layer  101  and a silicon oxide buffer layer  102  are sequentially formed thereon. In the TFT unit region T, a poly-silicon layer  103  formed by annealing amorphous silicon with laser is further disposed on the silicon oxide buffer layer  102 . Next, a silicon oxide insulating layer  104 , a first metal layer  111 , a gate insulating layer  112  and a Mo layer  111 ′ are sequentially formed on the first substrate  11 . Herein, the first metal layer  111  in the TFT unit region T is used as a gate electrode. The material for the gate insulating layer  112  can be any insulating material generally used in the art, such as silicon oxide. Next, a first insulating layer  114 , a second insulating layer  115  and a second metal layer  116  are sequentially laminated on the gate insulating layer  112  and the Mo metal layer  111 ′. Herein, the second metal layer  116  in the TFT unit region T is further penetrated through the gate insulating layer  112 , the first insulating layer  114  and the second insulating layer  115  to connect to the poly-silicon layer  103 . Finally, a planer layer  117 , a first electrode  151  and a pixel defining layer  16  are sequentially formed thereon, wherein the first electrode  151  locates not only on the planer layer  117  but also in a planer layer opening  117   a  thereof to electrically connect to the second metal layer  116 , and the pixel defining layer  16  further has a pixel opening  161 . 
         [0034]    Herein, the first metal layer  111  and the second metal layer  116  are used as conductive lines. For example, as shown in  FIG. 3 , the first metal layer  111  is used as a gate electrode of the TFT unit, and the second metal layer  116  is used as a source and drain electrode of the TFT unit. The second metal layer  116  is a patterned metal layer with an opening region  116   a  to expose the second insulating layer  115  under the second metal layer  116 . In addition, the gate electrode and the scan line formed by the first metal layer  111  electrically connect to each other, and the source and drain electrode and the data line formed by the second metal layer  116  also electrically connect to each other. In the present embodiment, the material for the first metal layer  111  and the second metal layer  116  can be any conductive material generally used in the art, such as metal, alloy, metal oxide, metal oxynitride, or other electrode materials generally used in the art; and preferably is metal. In the present embodiment, the first metal layer  111  is made of Mo, and the second metal layer  116  is a composite metal layer with a Ti layer, an Al layer and another Ti layer sequentially laminated from a side facing to the first substrate  11 . 
         [0035]    Not only the LTPS TFT units shown in  FIG. 3  but also IGZO TFT units can be used in the OLED display device of the present embodiment.  FIGS. 4A and 4B  are respectively cross-sectional views showing TFT unit regions of the OLED display device of the present embodiment. As shown in  FIG. 4A , a first metal layer  111 , a gate insulating layer  112 , a semiconductor layer  113 , a first insulating layer  114 , a second insulating layer  115  and a second metal layer  116  are sequentially laminated on the first substrate  11  to form a TFT unit, wherein the second metal layer  116  connects to the semiconductor layer  113 . In addition, the semiconductor layer  113  is made of IGZO, and the materials for the first metal layer  111  and the second metal layer  116  are the same as those illustrated above. Next, a protection layer  118  with a protection layer opening  118   a  is laminated on the second metal layer  116  and in an opening region  116   a  thereof, and then a planer layer  117  with a planer layer opening  117   a  is further laminated on the protection layer  118 . Herein, the second metal layer  116  is exposed from the protection layer opening  118   a  and the planer layer opening  117   a.    
         [0036]    Next, as shown in  FIG. 4A , a first electrode  151  is formed on the planer layer  117  and in the planer layer opening  117   a  thereof, and a pixel defining layer  16  with a pixel opening  161  is sequentially formed on the first electrode  151 . Then, as shown in  FIG. 4B , an organic light emitting layer  152  and a second electrode  153  are sequentially laminated on the first electrode  151  and the pixel defining layer  16  and in the pixel opening  161  thereof, to obtain the OLED unit  15  (as shown in  FIG. 1 ) of the present embodiment. Hence, as shown in  FIGS. 1 and 4B , the OLED unit  15  of the present embodiment comprises: the first electrode  151 , a second electrode  153  and an organic light emitting layer  152  disposed therebetween, wherein the second metal layer  116  is electrically connected to the first electrode  151 . In addition, as shown in  FIGS. 4A and 4B , the pixel defining layer  16  locates between the first electrode  151  and the organic light emitting layer  152 , and a light emitting region is defined by the pixel opening  161  of the pixel defining layer  16 . 
         [0037]    For either the LTPS TFT unit shown in  FIG. 3  or the IGZO TFT unit shown in  FIGS. 4A and 4B , the first insulating layer  114  and the second insulating layer  115  can be made of any dielectric material generally used in the art, such as silicon oxide and silicon nitride. In the present embodiment the first insulating layer  114  is a silicon oxide layer, and the second insulating layer  115  is a silicon nitride layer. 
         [0038]    For either the LTPS TFT unit shown in  FIG. 3  or the IGZO TFT unit shown in  FIGS. 4A and 4B , the first electrode  151  and the second electrode  153  can be a transparent electrode or a semi-transparent electrode known in the art. Herein, the transparent electrode can be a transparent conductive oxide (TCO) electrode, such as an ITO electrode and an IZO electrode; and the semi-transparent electrode can be a metal thin film electrode, such as an Mg/Ag alloy thin film electrode, an Au thin film electrode, a Pt thin film electrode and an Al thin film electrode. In addition, at least one of the first electrode  151  and the second electrode  153  can be a composite electrode of a transparent electrode and a semi-transparent electrode such as a composite electrode of a TCO electrode and a Pt thin film electrode, if it is necessary. Herein, only the OLED unit comprising the first electrode  151 , the organic light emitting layer  152  and the second electrode  153  are exemplified, but the present invention is not limited thereto. Other OLED unit generally used in the art can also be applied to the OLED display device of the present invention, for example, the OLED unit comprising an electron transporting layer, an electron injection layer, a hole transporting layer, a hole injection layer, and/or other layers capable of facilitating the combination of holes and electrons. 
         [0039]      FIG. 5  is a perspective view showing a part of a non-display region of the OLED display device of the present embodiment. As shown in  FIGS. 1 and 5 , in the non-display region, a first metal layer  111 , a first insulating layer (not shown in the figure), a second insulating layer (not shown in the figure) and a second metal layer  116  are sequentially laminated on the first substrate  11 , wherein the first metal layer  111  and the second metal layer  116  are used as conductive lines, and electrically connected to each other in a connecting region R 1 . 
         [0040]      FIG. 6  is a cross-sectional view of the OLED display device of the present embodiment along a P-P′ line in  FIG. 5 . As shown in  FIG. 6 , the first metal layer  111  is disposed on the first substrate  11 , the first insulating layer  114  is disposed on the first metal layer  111 , the second insulating layer  115  is disposed on the first insulating layer  114 , and the second metal layer  116  is disposed on the second insulating layer  115 . Herein, the second metal layer  116  is a patterned metal layer and comprises conductive lines, and an opening region  116   a  is located between two adjacent conductive lines to expose the second insulating layer  115 , as shown in  FIGS. 5 and 6 . 
         [0041]      FIG. 7  is an enlarged view of the OLED display device of the present embodiment showing the region E indicated in  FIG. 3 . As shown in  FIG. 7 , a thickness T 1  of the second insulating layer  115  covered with the second metal layer  116  (i.e. the second insulating layer  115  under the conductive lines of the second metal layer  116 ) is larger than a thickness T 2  thereof exposed from the opening region  116   a  (i.e. the second insulating layer  115  uncovered with of the second metal layer  116 ). Preferably, the thickness T 2  of the second insulating layer  115  exposed from the opening region  116   a  is 10˜95% of the thickness T 1  thereof under the conductive lines of the second metal layer  116 . More preferably, the thickness T 2  is 20˜80% of the thickness T 1 . Most preferably, the thickness T 2  is 25˜35% of the thickness T 1 . In the present embodiment, the thickness T 2  is 70% less than the thickness T 1 , i.e. the thickness T 2  is 30% of the thickness T 1 . 
         [0042]    Herein, only a part of the OLED display device of the present embodiment is used to illustrate the thickness of the second insulating layer; and a person skilled in the art can understand that the same design for the thickness thereof is also applied onto other parts of the OLED display device. 
         [0043]    Furthermore, as shown in  FIG. 6 , an undercut is present in the first insulating layer  114  under the second insulating layer  115 . More specifically, the first insulating layer  114  comprises a first side wall  114   a , the second insulating layer  115  comprises a second side wall  115   a,  and the second side wall  115   a  is protruded beyond the first side wall  114   a.    
         [0044]      FIG. 8  is a cross-sectional view showing a sealant region of the OLED display device in  FIG. 1 . In addition, as shown in  FIGS. 1 and 8 , a sealant  13  is further disposed on the first substrate  11 . As shown in  FIGS. 3, 4A, 4B and 8 , the thickness of the second insulating layer  115  covered with the second metal layer  116  is larger than that under the sealant  13 . 
       Embodiment 2 
       [0045]      FIG. 9  is a cross-sectional view of a LCD device of the present embodiment. During the process for manufacturing the LCD device, a first substrate  11  and a second substrate  12  are firstly provided, and different units are respectively disposed thereon (not shown in the figure). For example, in some embodiments, as shown in  FIG. 10 , TFT units are disposed on the first substrate  11 , and color filter units are disposed on the second substrate  12  (wherein the color filter units are not shown in  FIG. 10 ). In other embodiments, both the TFT units and the color filter units are disposed on the first substrate  11 . In addition, one of the first substrate  11  and the second substrate  12  are disposed with plural spacers  17 , and a sealant  13  (a frame sealant in the present embodiment) is formed on a periphery of the second substrate  12  in advance. After the second substrate  12  is assembled with the first substrate  11 , a liquid crystal material is injected into the space between the first substrate  11  and the second substrate  12  through any known manner used in the art, such as a drop-type injection process or an injection method using a capillary effect, to form a liquid crystal layer  181  to obtain the LCD device of the present embodiment. 
         [0046]      FIG. 10  is a cross-sectional view showing a part of a display region of the LCD device of the present embodiment. As shown in  FIG. 10 , in the present embodiment, a first metal layer  111 , a gate insulating layer  112 , a first insulating layer  114 , a second insulating layer  115 , a semiconductor layer  113  and a second metal layer  116  are sequentially laminated on the first substrate  11  to form a TFT unit. In addition, a protection layer  118  is laminated on the second metal layer  116  and in an opening region  116   a  thereof. A first electrode  151  is formed on the protection layer  118 , which is electrically connected to the second metal layer  116 . Herein, the material for the protection layer  118  can be any known material for the passivation layer such as silicon oxide. Furthermore, in the present embodiment, the thickness of the second insulating layer  115  related to the second metal layer  116  is the same as that illustrated in Embodiment 1, and not described herein. 
         [0047]    In addition, as shown in  FIG. 10 , the LCD device of the present embodiment comprises: a liquid crystal display unit  18 , which comprises the first electrode  151 , a second electrode  153  and the liquid crystal layer  181  disposed therebetween, wherein the second metal layer  116  is electrically connected to the first electrode  151 . Furthermore, in the present embodiment, the second electrode  153  is disposed on the second substrate  12 , and a color filter unit (not shown in the figure) is further disposed on the second substrate  12 . 
         [0048]    Moreover, the LCD device of the present embodiment may further comprise a backlight module disposed under the first substrate  11  to provide an incident light to the liquid crystal layer  181 . 
         [0049]    In conclusion, in the display devices provided by the present invention, the thickness of the second insulating layer covered with the metal layer (which is the second metal layer illustrated in the aforementioned embodiments) to achieve the purpose of decreasing resistance and reducing current leakage. Meanwhile, the thickness thereof exposed from the opening region (which is the opening region without covering with the second metal layer illustrated in the aforementioned embodiments) is decreased to achieve the purpose of improving capacity value and increasing storage capacity in pixels. Therefore, the display quality of the display device can be improved to meet the customer&#39;s requirement for electronic products. 
         [0050]    Furthermore, the display device provided by the present invention can be applied to any electronic device for displaying images, such as a mobile phone, a notebook, a camera, a video camera, a music player, a navigation system, or a television. 
         [0051]    Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.