Patent Publication Number: US-2022231257-A1

Title: Display substrate and display apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This disclosure is based on and claims priority under 35 U.S.C 119 to Chinese Patent Application No. 202110074512.2, filed on Jan. 20, 2021, in the China National Intellectual Property Administration. The entire disclosure of the above application is incorporated herein by reference. 
     FIELD 
     The present disclosure relates to the field of display technology, in particular to a display substrate and a display apparatus. 
     BACKGROUND 
     An organic light-emitting diode (OLED) display apparatus includes a display screen based on an organic light-emitting diode and has excellent characteristics such as self-illumination, high contrast, low thickness, wide viewing angle, high response speed, capability of being used for a flexible panel, wide operating temperature range, simple structure and manufacturing process, etc., thereby attracting more and more attention and having broad application prospects. 
     Components such as water vapor and oxygen in the air have a great influence on the life of an OLED device in the OLED display apparatus. This is because electrons need to be injected from a cathode during operation of the OLED device, which requires a cathode work function to be as low as possible. However, the cathode is usually made of metal materials such as aluminum, magnesium, calcium, etc., the chemical properties of which are relatively active. As such, the cathode is likely to react with the infiltrating water vapor and oxygen. In addition, water vapor and oxygen are also likely to chemically react with a hole transport layer and an electron transport layer of the OLED device, which will cause the failure of the OLED device. Therefore, effective encapsulation of the OLED device is required to sufficiently separate functional layers of the OLED device from the water vapor, oxygen and other components in the atmosphere, to allow prolong the life of the OLED device, thereby prolonging the service life of the OLED display apparatus. 
     SUMMARY 
     Embodiments of the present disclosure provide a display substrate and a display apparatus. 
     In one aspect, some embodiments of the disclosure provide a display substrate. The display substrate includes: a base substrate, including a display region and a non-display region; an encapsulation dam, disposed on the base substrate and located in the non-display region, and annularly surrounding the display region; and an overflow detection structure, disposed on the base substrate and located in the non-display region, and annularly surrounding the display region, where the overflow detection structure is located between a region where the encapsulation dam is located and the display region. The overflow detection structure includes: at least one convex part; and a reflection part on a side, facing away from the base substrate, of the convex part and at least partially covering the at least one convex part. 
     In another aspect, some embodiments of the present disclosure provide a display apparatus including a display substrate. The display substrate includes: a base substrate, including a display region and a non-display region; an encapsulation dam, disposed on the base substrate and located in the non-display region, and annularly surrounding the display region; and an overflow detection structure, disposed on the base substrate and located in the non-display region, and annularly surrounding the display region, where the overflow detection structure is located between a region where the encapsulation dam is located and the display region. The overflow detection structure includes: at least one convex part; and a reflection part on a side, facing away from the base substrate, of the convex part and at least partially covering the at least one convex part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic structural diagram of a display substrate according to some embodiments of the present disclosure. 
         FIG. 2  illustrates a cross-sectional view of the display substrate along a line III-IV in  FIG. 1 . 
         FIG. 3  illustrates a light path diagram when an organic encapsulation layer does not overflow according to some embodiments of the present disclosure. 
         FIG. 4  illustrates another light path diagram when an organic encapsulation layer does not overflow according to some embodiments of the present disclosure. 
         FIG. 5  illustrates a light path diagram when an organic encapsulation layer overflows according to some embodiments of the present disclosure. 
         FIG. 6  is another cross-sectional view of the display substrate along a line III-IV in  FIG. 1 . 
         FIG. 7  is yet another cross-sectional view of the display substrate along a line III-IV in  FIG. 1 . 
         FIG. 8  is yet another cross-sectional view of the display substrate along a line III-IV in  FIG. 1 . 
         FIG. 9  is yet another cross-sectional view of the display substrate along a line III-IV in  FIG. 1 . 
         FIG. 10  is yet another cross-sectional view of the display substrate along a line III-IV in  FIG. 1 . 
         FIG. 11  is a cross-sectional view of the display substrate along a line I-II in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     In order to make objectives, technical solutions, and advantages of embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be described clearly and completely with reference to accompanying drawings of the embodiments of the present disclosure. It should be noted that the dimensions and shapes of various figures in the drawings do not reflect a true scale and are only intended to illustrate contents of the present disclosure. Meanwhile, same or similar reference numerals refer to same or similar elements or elements having same or similar functions throughout. Apparently, the described embodiments are merely some, but not all embodiments of the present disclosure. Based on the described embodiments of the present disclosure, all other embodiments obtained by those ordinarily skilled in the art without any inventive effort are within the protection scope of the present disclosure. 
     Unless defined otherwise, technical or scientific terms used in the present disclosure shall have common meaning as understood by those ordinary skilled in the art to which the present disclosure belongs. “First”, “second”, and similar words used in the specification and claims of the present disclosure do not denote any order, quantity, or importance, but are solely used to distinguish one from another. “Include” or “comprise”, and the like mean that elements or items that precede the word cover the elements or items listed after the word and equivalents thereof, but do not exclude other elements or items. The terms “Inner”, “Outer”, “Upper”, “Lower”, and the like are used merely to denote a relative positional relationship that may change accordingly when the absolute position of an object being described changes. 
     In order to keep the following descriptions of the embodiments of the present disclosure clear and concise, the present disclosure omits detailed descriptions of known functions and known components. 
     In related technologies, a thin film encapsulation (TFE) technology is generally adopted to encapsulate the OLED device. Specifically, a thin film encapsulation structure includes two inorganic layers and an organic layer between the two inorganic layers. At present, the organic layer is generally prepared by screen printing or inkjet printing. However, neither of the above two methods can block the overflow of the organic materials in the process of coating to curing due to characteristics of organic materials. In the thin film encapsulation structure, the coverage region of the organic layer is smaller than that of the inorganic layers, that is, the organic layer is wrapped by the inorganic layers. As such, if overflow occurs, the actual encapsulation reliability of the thin film encapsulation structure will be affected. 
     A display substrate provided by embodiments of the present disclosure, as shown in  FIG. 1  and  FIG. 2 , include: 
     a base substrate  101 , including a display region AA and a non-display region BB. In some embodiments, the base substrate  101  may be a flexible base substrate or a rigid base substrate; 
     an encapsulation dam  102 , in the non-display region BB of the base substrate  101  and annularly surrounding the display region AA; and 
     an overflow detection structure  103 , in the non-display region BB of the base substrate  101 , annularly surrounding the display region AA, and located between a region where the encapsulation dam  102  is located and the display region AA; wherein the overflow detection structure  103  includes at least one convex part  31  and a reflection part  32  on one side, facing away from the base substrate  101 , of the convex part  31  and at least partially covering the at least one convex part  31 . 
     In the above-mentioned display substrate provided by the present disclosure, as shown in  FIG. 3  and  FIG. 4 , when no overflow occurs in an organic encapsulation layer  104  formed subsequently, a detection light ray L 1  is reflected by the by the reflection part  32 , and a first reflected light ray L 2  has a first deflection angle relative to the detection light ray L 1 . As shown in  FIG. 5 , when the organic encapsulation layer  104  overflows to the overflow detection structure, based on a refractive index difference between the organic encapsulation layer  104  and the reflection part  32 , the detection light ray L 1  is refracted by the organic encapsulation layer  104  and then reflected by the reflection part  32 , a second reflected light ray L 3  has a second deflection angle relative to the detection light ray L 1 . As such, the present disclosure can detect whether the organic encapsulation layer  104  overflows. In addition, since the reflection part  32  at least partially covers the at least one the convex part  31 , the reflection part  32  has an uneven surface. Accordingly, a reflection area of the detection light ray L 1  is effectively increased, and the detection light ray L 1  is reflected on the reflection part  32  multiple times, so that the second reflected light ray L 3  greatly deflects relative to the first reflected light ray L 2 , which helps the overflow detection of the organic encapsulation layer  104 . In addition, the overflow detection structure  103  may limit outflow of the organic encapsulation layer  104  to a certain extent. 
     In some embodiments, a material of the organic encapsulation layer  104  may be a high-molecular material containing a desiccant or a high-molecular material that can block water vapor, or the like. 
     In some embodiments, in the above-mentioned display substrate provided by the embodiments of the present disclosure, as shown in  FIG. 2 , in order to improve the overflow detection efficiency of the organic encapsulation layer  104 , the overflow detection structure  103  may include at least two convex parts  31  annularly arranged, and the reflection part  32  further at least fills a gap between the convex parts  31 . In some embodiments, the reflection part  32  is conformally disposed on the convex parts  31 , that is, fully covering the gap between the convex parts  31 . 
     In some embodiments, in the above-mentioned display substrate provided by the embodiments of the present disclosure, as shown in  FIG. 6 , in order to increase adhesive force between the convex parts  31  and the reflection part  32 , a protection part  33  is also arranged between each convex part  31  and the reflection part  32 . An orthographic projection of each protection part  33  on the base substrate  101  fully covers an orthographic projection of the corresponding convex part  31  on the base substrate  101 . 
     In some embodiments, a material of the convex parts  31  may be an organic insulating material such as polyimide, polyphthalimide, polyamide, acrylic resin, benzocyclobutene, or phenolic resin. A material of the protection parts  33  may be a dielectric material such as silicon oxide, silicon nitride, or silicon oxynitride. By covering the convex parts  31  with the protection parts  33 , etching selection ratios of the organic material used for the convex parts  31  and an inorganic material used for the protection parts  33  are different, so that the convex parts  31  and the protection parts  33  form an undercut structure. In some embodiments, a convex part  31  and the protection part  33  may also form a “T”-shaped structure, which is not limited herein. 
     In some embodiments, in the above-mentioned display substrate provided by the embodiments of the present disclosure, as shown in  FIG. 2 , the overflow detection structure  103  may further include: a refraction part  34  on the reflection part  32 . An orthographic projection of the refraction part  34  on the base substrate  101  fully covers the orthographic projection of the at least one convex part  31  on the base substrate  101 . 
     In some embodiments, the refraction part  34  fully covers the at least two convex parts  31 . In some embodiments, the refraction part  34  fully covers all the convex parts  31 . The coating of the refraction part  34  increases a refraction path of the detection light ray L 1 , deepens the deflection of a light path, and even changes a direction, and further improves the overflow detection efficiency of the organic encapsulation layer  104 . 
     In some embodiments, in the above-mentioned display substrate provided by the embodiments of the present disclosure, as shown in  FIG. 7 , the overflow detection structure  103  may further include: a blocking dam  35  on the refraction part  34 . An orthographic projection of the blocking dam  35  on the base substrate  101  is located within the orthographic projection of the refraction part  34  on the base substrate  101 . 
     A height of the overflow detection structure  103  increases due to the arrangement of the blocking dam  35 , thereby effectively restricting the outflow of the organic encapsulation layer  104  to a certain extent. 
     In some embodiments, in the above-mentioned display substrate provided by the embodiments of the present disclosure, as shown in  FIG. 1  and  FIG. 2 , the encapsulation dam  102  may include a first encapsulation dam  1021  and a second encapsulation dam  1022 . The first encapsulation dam  1021  surrounds the second encapsulation dam  1022 , the first encapsulation dam  1021  has a first side S 1  facing to the second encapsulation dam  1022 , and the second encapsulation dam  1022  has a second side S 2  facing away from the first encapsulation dam  1021 . 
     In some embodiments, the first encapsulation dam  1021  and/or the second encapsulation dam  1022  may be a closed ring or a non-closed ring. For example, a plurality of segments may be included, and at least some segments partially overlap along the surrounding direction. In some embodiments, the closed or non-closed ring may have partial branches. 
     The overflow detection structure  103  may be located between the first side S 1  and the second side S 2 . In some embodiments, as shown in  FIG. 7  and  FIG. 8 , when the overflow detection structure  103  includes the blocking dam  35 , the overflow detection structure  103  may be reused as the second encapsulation dam  1022 . In other embodiments, as shown in  FIG. 2 ,  FIG. 6  and  FIG. 9 , the overflow detection structure  103  may be located between the first encapsulation dam  1021  and the second encapsulation dam  1022 . 
     In some embodiments, the overflow detection structure  103  may be located between the first side of the first encapsulation dam  1021  and a side of the second encapsulation dam  1022  facing to the first encapsulation dam  1021 . 
     In some embodiments, in the above-mentioned display substrate provided by the embodiments of the present disclosure, as shown in  FIG. 10  and  FIG. 11 , the display substrate may further include: a source-drain metal layer  105  disposed between a layer where the first encapsulation dam  1021  is located and the base substrate  101 , a planarization layer  106 , an anode layer  107 , a pixel defining layer  108  and a spacer layer  109  which are disposed on one side, facing away from the base substrate  101 , of the source-drain metal layer  105 , and a cathode line  111  on the same layer as a cathode layer  111 ′. 
     In some embodiments, the first encapsulation dam  1021  may include: a first encapsulation part a in the planarization layer  106 , a second encapsulation part b in the pixel defining layer  108 , and a third encapsulation part c in the spacer layer  109 . The second encapsulation dam  1022  may include a fourth encapsulation part d in the pixel defining layer  108  and a fifth encapsulation part o in the spacer layer  109 . The convex part  31  is disposed in the planarization layer  106 , the reflection part  32  is disposed in the anode layer  107 . One end of the reflection part  32  extends to that between the first encapsulation part a and the second encapsulation part b, and the other end of the reflection part  32  extends along a direction of ascending distance from the first encapsulation dam  1021 . The blocking dam  35  is disposed in the spacer layer  109 , and the refraction part  34  is disposed in the pixel defining layer  108 . The source-drain metal layer  105  may include a low-level signal line  110 , one end of the low-level signal line  110  is covered with the first encapsulation part a, and the other end of the low-level signal line  105  is electrically connected with the reflection part  32 . The cathode line  111  is electrically connected with the reflection part  32 . 
     The low-level signal line  110 , the reflection part  32  and the cathode line  111  are used as trace structures to be configured to transmit electrical signals provided by a control chip disposed in a peripheral region to an OLED light-emitting device disposed in the display region AA. By adopting the above-mentioned embodiment solutions of the present disclosure, the low-level signal line (VSS)  110 , the reflection part  32  and the cathode line  111  do not need to be fabricated by a patterning process, thereby simplifying the manufacturing process and saving the manufacturing cost. 
     In addition, the first encapsulation part a covers one end of the low-level signal line  110 , and the second encapsulation part b covers one end of the reflection part  32 , which can also protect the low-level signal line  110  and the reflection part  32 , thus water vapor, oxygen and the like are prevented from corroding the low-level signal line  110  and the reflection part  32 . Moreover, since the overflow detection structure  103  is located at one end of the low-level signal line  110 , influence of the overflow detection structure  103  on signals transmitted by the low-level signal line  110  is small. 
     In some embodiments, as shown in  FIG. 2 , the display substrate may include a gate driving circuit GOA (which may include a transistor TFT and a capacitor C) at an inner side (that is, a side away from the first encapsulation dam  1021 ) of the second encapsulation dam  1022 , and the other end of the low-level signal line  110 , that is the end other than that with the overflow detection structure  103 , may extend to an edge, close to the second encapsulation dam  1022 , of the gate driving circuit GOA. That is, the low-level signal line  110  may be disposed in a region between the first encapsulation dam  1021  and the gate driving circuit GOA. 
     In the embodiment of the present disclosure, both the first encapsulation dam  1021  and the second encapsulation dam  1022  may limit the overflow of the organic encapsulation layer  104  manufactured subsequently. Moreover, since the second encapsulation dam  1022  does not have the planarization layer  106  than the first encapsulation dam  1021 , a height of the second encapsulation dam  1022  relative to the base substrate  101  is lower than a height of the first encapsulation dam  1021  relative to the base substrate  101 . In this way, a path for external water vapor and oxygen to enter the display region AA becomes longer, and the difficulty of entering the display region AA is increased. 
     In some embodiments, a material of the source-drain metal layer  105  may be molybdenum, aluminum, silver, copper, titanium, platinum, tungsten, tantalum, tantalum nitride, alloys and combinations thereof, or other suitable materials; and the source-drain metal layer  105  may be a single layer or multiple layers made of metal, for example a molybdenum metal layer/aluminum metal layer/molybdenum metal layer or a titanium metal layer/aluminum metal layer/titanium metal layer. A material of the planarization layer  106  may be organic insulating materials such as polyacrylic resin, polyepoxy acrylic resin, photosensitive polyimide resin, polyester acrylate, urethane acrylate resin, and novolac epoxy acrylic resin, which is not limited herein. A material of the pixel defining layer  108  and a material of the spacer layer  109  may be organic materials, for example, may include organic insulating materials such as polyimide, polyphthalimide, polyamide, acrylic resin, benzocyclobutene, and phenolic resin. A material of the anode layer  107  may include metals and metal oxides (such as indium tin oxide, and indium zinc oxide). For example, a structure of the anode layer  107  is a stacked structure formed by indium tin oxide/silver/indium tin oxide, or aluminum/indium tin oxide. A material of the cathode line  111  may be magnesium, silver, calcium, aluminum, manganese oxide, and indium tin oxide. 
     In some embodiments, in the above-mentioned display substrate provided by the embodiments of the present disclosure, as shown in  FIG. 2 ,  FIG. 6  to  FIG. 9 , in order to prevent cracks caused by cutting etc. from extending to the first encapsulation dam  1021  which may affect the encapsulation effect, the display substrate may further include: a buffer layer  112 , a gate insulating layer  113 , and an interlayer dielectric layer  114  which are sequentially disposed on the side, facing the source-drain metal layer  105 , of the base substrate  101 . 
     In some embodiments, the planarization layer  106  further includes: a crack barrier dam  115  surrounding the first encapsulation dam  1021 , and part of the crack barrier dam  115  is at least embedded in at least one of the buffer layer  112 , the gate insulating layer  113  or the interlayer dielectric layer  114 . 
     In some embodiments, as shown in  FIG. 2  and  FIGS. 6-9 , the crack barrier dam  115  may be located at a peripheral region (Bezel) of an outer side (that is, a side away from the second encapsulation dam  1022 ) of the first encapsulation dam  1021 , and part of the crack barrier dam  115  is embedded in the buffer layer  112 , the gate insulating layer  113  and the interlayer dielectric layer  114 , so that the adhesive force of the crack barrier dam  115  is significantly increased and the crack barrier dam  115  is effectively prevented from falling off 
     In some embodiments, the buffer layer  112  may prevent or reduce the diffusion of metal atoms and/or impurities from the base substrate  101  into an active layer. In some embodiments, the buffer layer  112  may include an inorganic material such as silicon oxide, silicon nitride, and/or silicon oxynitride, and may be formed as multiple layers or a single layer. The gate insulating layer  113  may include, for example, a silicon compound, and metal oxides, for example, silicon oxynitride, silicon oxide, silicon nitride, silicon oxycarbide, silicon carbide nitride, aluminum oxide, aluminum nitride, tantalum oxide, hafnium oxide, zirconium oxide, and titanium oxide. The gate insulating layer  113  may be formed as a single layer or multiple layers. A material of the interlayer dielectric layer  114  may be lead oxide, tantalum pentoxide, zirconium dioxide, aluminum oxide, silicon nitride, silicon oxide, and silicon oxynitride. In addition, as shown in  FIG. 2 , the interlayer dielectric layer  114  may include a first interlayer dielectric layer  1141  and a second interlayer dielectric layer  1142 . 
     Generally, in the above-mentioned display substrate provided by the embodiments of the present disclosure, as shown in  FIG. 11 , the display substrate may further include an OLED light-emitting device, a pixel driving circuit (including a transistor TFT and a storage capacitor Cst), and an encapsulation layer TFE. The OLED light-emitting device may include a light-emitting function layer  116  located between the anode layer  107  and the cathode layer  111 ′. In some embodiments, the light-emitting function layer  116  may include, but is not limited to, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting material layer, a hole blocking layer, an electron transport layer and an electron injection layer. A material of the light-emitting material layer may include small molecular organic materials or polymer molecular organic materials, which may be fluorescent light-emitting materials or phosphorescent light-emitting materials, and may emit red light, green light, blue light, or white light. The transistor TFT may include an active layer Poly, a gate G, a source S, and a drain D; and the storage capacitor Cst may include a first electrode C 1  and a second electrode C 2 . The encapsulation layer TFE may further include a first inorganic encapsulation layer  117  and a second inorganic encapsulation layer  118 . In some embodiments, materials of the first inorganic encapsulation layer  117  and the second inorganic encapsulation layer  118  may include insulating materials such as silicon oxynitride, silicon oxide, silicon nitride, and high-molecular resin; and inorganic materials such as silicon oxynitride, silicon oxide, and silicon nitride are highly dense and can effectively prevent the intrusion of water vapor and oxygen. 
     Based on the same inventive concept, an embodiment of the present disclosure further provides a display apparatus, including the above-mentioned display substrate provided by the embodiments of the present disclosure. The display apparatus may be any product or component with a display function, such as a mobile phone, a tablet computer, a television, a display, a notebook computer, a digital photo frame, a navigator, a smart watch, a fitness wristband, and a personal digital assistant. Other essential components of the display apparatus will be apparent to those ordinarily skilled in the art and will not be described in detail herein, nor supposed to limit the present disclosure. In addition, since a principle of solving the problem of the display apparatus is similar to a principle of solving the problem of the above-mentioned display substrate, the implementation of the display apparatus may refer to the above-mentioned embodiments of the display substrate, and repetitive parts will not be repeated. 
     It is apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the spirit or scope of the present disclosure. In this case, if these modifications and variations of the present disclosure fall within the scope of claims and their equivalents, the present disclosure also intends to include these modifications and variations.