Patent Publication Number: US-2023165045-A1

Title: Display module and manufacturing method of display module

Description:
FIELD OF INVENTION 
     The present application relates to a display technology field, in particular to a display module and a manufacturing method of the display module. 
     BACKGROUND OF INVENTION 
     In recent years, high screen-to-body ratio display technology has become a research hotspot in the display technology field. Under the same screen size, a display module having a high screen-to-body ratio characteristic has a wider display area than a conventional display module, which is advantageous for improving a user experience. In order to achieve the high screen-to-body ratio, a preset avoidance space (or void space) is usually required to meet requirements of some functional elements. The functional element may be, for example, a camera, an earpiece, a fingerprint recognition sensor, a face recognition sensor, or the like. These functional elements may be disposed on a non-light-emitting side of the display module, and through holes are defined at positions of a display panel of the display module corresponding to these functional elements to form avoidance spaces. 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the prior art, a laser cutting process is generally used to cut a display module integrally to form a through hole. Because the integration cutting relates to a large number of film layers and a large number of regions are affected by the cutting, it is easy to generate a cutting crack. The edge crack generated by the cutting may extend to the display region and cause a problem of poor display, and may affect the aesthetics of the final product, such as a “gourd screen” phenomenon. As shown in  FIG.  1   , an approximately circular black spot region  30  is formed near a through hole  20  (e.g., a through hole for installing the camera) of a display module  10 . The through hole  20  and the black spot region  30  are connected to form a gourd-like shape, so it is called the “gourd screen” phenomenon. 
     Further, for a display module including a flexible organic light-emitting diode (OLED) display panel, a method of integrally cutting the display module to form a through hole using a laser cutting process has limitations. Since it is generally necessary to perform thin film encapsulation (TFE) on flexible OLED display panel, after cutting and defining opening (or hole) in the display module including the flexible OLED display panel, the display reliability at an edge of the opening cannot be ensured. Therefore, it is usually necessary to add an encapsulation structure to the edge of the opening, and thus, the manufacturing difficulty of the display module is increased, the production cost is increased, and the user experience is poor. 
     Technical Solution 
     In view of the disadvantages of the prior art, the present application provides a display module and a manufacturing method of the display module to improve the “gourd screen” phenomenon. 
     According to a first aspect, the present application provides a display module comprising: 
     a display panel comprising a substrate and an array substrate stacked on the substrate; 
     an optical film disposed on a light-emitting side of the display panel, wherein the optical film is provided with a first through hole, and ambient light enters the display module through the first through hole; 
     a functional layer disposed on a non-light-emitting side of the display panel, wherein the functional layer comprises a photosensitive element mounting layer, the photosensitive element mounting layer is provided with a second through hole, a position of the second through hole corresponds to the first through hole; and 
     a photosensitive member mounted to the second through hole, 
     wherein the display panel has a continuous structure, the array substrate is provided with light-transmitting non-display regions, the positions of the light-transmitting non-display regions of respective film layers correspond to each other and correspond to the first through hole and the second through hole, and a forward projection of the first through hole on the display panel falls within a range of the light-transmitting non-display region, and a forward projection of the second through hole on the display panel falls within a range of the forward projection of the first through hole on the display panel. 
     In some embodiments of the present application, the display module further comprises an optical pad disposed in the first through hole, a side of the optical pad away from the display panel is aligned with a side of the optical film away from the display panel, and a material of the optical pad is a light-transmitting material having a light transmittance greater than or equal to 90%. 
     In some embodiments of the present application, a material of the light-transmitting non-display region in each of the film layers is same as at least one material in the same film layer in display region, and a light transmittance of the at least one material is greater than or equal to 90%. 
     In some embodiments of the present application, the display module comprises an array substrate, an organic light emitting layer, an encapsulation layer, and a touch layer which are sequentially stacked, wherein the array substrate is provided with a first light-transmitting non-display region, and a material of the first light-transmitting non-display region is same as a light-transmitting material in the array substrate; the organic light emitting layer is provided with a second light-transmitting non-display region, a material of the second light-transmitting non-display region is same as a light-transmitting material in the organic light emitting layer; the encapsulation layer is provided with a third light-transmitting non-display region, a material of the third light-transmitting non-display region is same as a material in the encapsulation layer; the touch layer is provided with a fourth light-transmitting non-display region, a material of the fourth light-transmitting non-display region is same as a light-transmitting material in the touch layer. 
     In some embodiments of the present application, the first light-transmitting non-display region comprises a pixel defining layer and a planarizing layer; the second light-transmitting non-display region comprises a stacked structure other than a color filter layer; the fourth light-transmitting non-display region comprises an insulating layer other than a touch wire. 
     In some embodiments of the present application, materials of the light-transmitting non-display regions of the respective film layers are the same light-transmitting material, and a light transmittance of the light-transmitting material is greater than or equal to 90%. 
     In some embodiments of the present application, the display panel is an organic light emitting diode display panel, and the corresponding optical film is a polarizer. 
     In some embodiments of the present application, a difference between a diameter of the first through hole and a diameter of the second through hole is greater than or equal to 0.2 mm. 
     In some embodiments of the present application, the functional layer further comprises a heat dissipation buffer layer, the heat dissipation buffer layer is disposed between the non-light-emitting side of the display panel and the photosensitive element mounting layer, the heat dissipation buffer layer is provided with a third through hole, a position of the third through hole corresponds to the first through hole and the second through hole, and the forward projection of the second through hole on the display panel falls within a range of a forward projection of the third through hole on the display panel. 
     In some embodiments of the present application, a difference between a diameter of the third through hole and a diameter of the second through hole is greater than or equal to 0.6 mm. 
     In some embodiments of the present application, the functional layer further comprises a support layer, the support layer is disposed between a non-light-emitting side of the display panel and the photosensitive element mounting layer; the support layer has a continuous structure, and a material of the support layer is a light-transmitting material having a light transmittance greater than or equal to 90%. 
     In some embodiments of the present application, the functional layer further comprises a support layer, the support layer is disposed between a non-light-emitting side of the display panel and the photosensitive element mounting layer; the support layer is provided with a fourth through hole, a position of the fourth through hole corresponds to the first through hole and the second through hole, and the forward projection of the second through hole on the display panel falls within a range of a forward projection of the fourth through hole on the display panel. 
     In some embodiments of the present application, a difference between a diameter of the fourth through hole and a diameter of the second through hole is greater than or equal to 0.2 mm. 
     In some embodiments of the present application, the display module further comprises an optical clear adhesive layer, the optical clear adhesive layer is disposed on at least one side of the optical film, and the optical clear adhesive layer has a continuous structure. 
     In some embodiments of the present application, the display module further comprises an optical clear adhesive layer, the optical clear adhesive layer is disposed on at least one side of the optical film, and the optical clear adhesive layer is provided with a fifth through hole, a position of the fifth through hole corresponds to the first through hole and the second through hole, and the forward projection of the second through hole on the display panel falls within a range of a forward projection of the fifth through hole on the display panel. 
     In some embodiments of the present application, a difference between a diameter of the fifth through hole and a diameter of the second through hole is greater than or equal to 0.3 mm. 
     According to a second aspect, the present application provides a manufacturing method of a display module, the manufacturing method of the display module comprising following steps: 
     providing a display panel comprising a substrate and a plurality of film layers stacked on the substrate, wherein each of the plurality of film layers is provided with a light-transmitting non-display region, and positions of the light-transmitting non-display regions of the respective film layers correspond to each other; 
     forming an optical film on a light-emitting side of the display panel, and forming a first through hole in the optical film, wherein a position of the first through hole corresponds to the light-transmitting non-display area, and a forward projection of the first through hole on the display panel falls within a range of the light-transmitting non-display area; 
     forming a functional layer on a non-light-emitting side of the display panel, the functional layer comprising a photosensitive element mounting layer, and forming a second through hole in the photosensitive element mounting layer, wherein a position of the second through hole corresponds to the first through hole, and a forward projection of the second through hole on the display panel falls within a range of the forward projection of the first through hole on the display panel; and 
     providing a photosensitive element mounted to the second through hole. 
     In some embodiments of the present application, the step of providing the display panel comprising the substrate and the plurality of film layers stacked on the substrate, wherein each of the plurality of film layers is provided with the light-transmitting non-display region, and positions of the light-transmitting non-display regions of the respective film layers correspond to each other, comprises following steps: 
     providing a stacked structure comprising a substrate and a plurality of film layers stacked on the substrate, wherein each of the plurality of film layers is predefined with a light-transmitting non-display region, and positions of the predefined light-transmitting non-display regions of the respective film layers corresponds to each other; 
     removing film materials in the predefined light-transmitting non-display regions in the respective film layers using an etching process to obtain a stacked structure having a hollowed-out region; and 
     filling the hollowed-out region with a light-transmitting material having a light transmittance greater than or equal to 90%, and then drying to obtain the display panel. 
     In some embodiments of the present application, the step of providing the display panel comprising the substrate and the plurality of film layers stacked on the substrate, wherein each of the plurality of film layers is provided with the light-transmitting non-display region, and positions of the light-transmitting non-display regions of the respective film layers correspond to each other, comprises following steps: 
     when each of functional film layers is formed separately, a light-transmitting non-display area is defined on each of the functional film layers in advance, and non-light-transmitting functional patterns on corresponding functional film layers are disposed away from the light-transmitting non-display regions, and a light-transmitting non-display region of the display module is formed by stacking the light-transmitting non-display regions of the respective functional film layers. 
     In some embodiments of the present application, the step of providing the display panel comprising the substrate and the plurality of film layers stacked on the substrate, wherein each of the plurality of film layers is provided with the light-transmitting non-display region, and positions of the light-transmitting non-display regions of the respective film layers correspond to each other, comprises following steps: 
     when each of functional film layers is formed separately, some of the film layers are provided with the light-transmitting non-display regions by forming holes and filling the holes with a light-transmitting material, some of the film layers are provided with the light-transmitting non-display regions by arranging the non-light-transmitting functional patterns away from the light-transmitting non-display regions, and a light-transmitting non-display region of the display module is formed by stacking the light-transmitting non-display regions of the respective functional film layers. 
     Advantageous Effects 
     The present application provides a display module including a display panel, an optical film disposed on a light-emitting side of the display panel, a functional layer disposed on a non-light-emitting side of the display panel, and a photosensitive element disposed on the functional layer. The display panel has a continuous structure, and each of film layers in the display panel is provided with a light-transmitting non-display region. The optical film is provided with a first through hole, the photosensitive element mounting layer in the functional layer is provided with a second through hole serving as a mounting structure of the photosensitive element, and the positions of the first through hole, the second through hole, and the light-transmitting non-display regions of respective film layers in the display panel correspond to each other. Since the display panel is not provided with the through hole, the display panel has a strong compression resistance, so that cracks are not easily generated under compression, and the “gourd screen” phenomenon is effectively improved. 
     Preferably, an optical pad is fitted in the first through hole, and the material of the optical pad is a light-transmitting material having a light transmittance of 90% or more to balance the step between the optical film and the display panel, thereby preventing air bubbles from being generated at the step between the optical film and the display panel. 
     The present application further provides a manufacturing method of a display module. First, a light-transmitting non-display region of each of film layers in a display panel is prepared, and then the display panel, an optical film and a photosensitive element are assembled into the display module. Compared with a conventional manufacturing method of a display module, a mode in which a display module is formed by assembling and then the display module is integrally cut, so that a through hole is formed in the display panel, the optical film and a functional layer, is changed, and the through hole is not provided in the display panel. The “gourd screen” phenomenon is effectively improved under the premise of ensuring that the photosensitive element fully captures the ambient light, which is beneficial to aesthetics of the display module. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic structural diagram of a display module in which a “gourd screen” phenomenon is exhibited in the prior art. 
         FIG.  2    is a schematic structural diagram of a display module according to an embodiment of the present application. 
         FIG.  3    is a schematic structural diagram of another display module according to an embodiment of the present application. 
         FIG.  4    is a schematic structural diagram of another display module according to an embodiment of the present application. 
         FIG.  5    is a schematic structural diagram of another display module according to an embodiment of the present application. 
         FIG.  6    is a schematic structural diagram of another display module according to an embodiment of the present application. 
         FIG.  7    is a schematic structural diagram of another display module according to an embodiment of the present application. 
         FIG.  8    is a schematic structural diagram of another display module according to an embodiment of the present application. 
         FIG.  9    is a schematic structural diagram of another display module according to an embodiment of the present application. 
         FIG.  10    is a schematic structural diagram of another display module according to an embodiment of the present application. 
         FIG.  11    is a schematic structural diagram of another display module according to an embodiment of the present application. 
         FIG.  12    is a diagram of stacked functional films of a display module according to an embodiment of the present application. 
         FIG.  13    is a schematic flow chart of a manufacturing method of a display module according to an embodiment of the present application. 
         FIG.  14    is a schematic flow chart of another manufacturing method of a display module according to an embodiment of the present application. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Technical solutions in embodiments of the present application will be clearly and completely described below in conjunction with drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application. 
     In the description of the present disclosure, orientations or position relationships indicated by the terms “upper”, “side” and the like, are based on orientations or position relationships illustrated in the drawings. The terms are used to facilitate and simplify the description of the present disclosure, rather than indicate or imply that the devices or elements referred to herein are required to have specific orientations or be constructed or operate in the specific orientations. Accordingly, the terms should not be construed as limiting the present disclosure. 
     In the description of the present disclosure, the term “first”, “second” and the like, are for illustrative purposes only and are not to be construed as indicating or imposing a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature that limited by “first”, “second” may expressly or implicitly include one or more of the features. 
     In the description of the present disclosure, the meaning of “plural” is two or more, unless otherwise specifically defined. 
     In the description of the present application, “fall in (within or into)” includes a situation of completely overlapping, for example, “the forward projection of the second through hole on the display panel falls within the range of the forward projection of the first through hole on the display panel” includes following situations: (1) the forward projection of the second through hole on the display panel completely overlaps the forward projection of the first through hole on the display panel; (2) an area of the forward projection of the first through hole on the display panel is greater than an area of the front projection of the second through hole on the display panel. 
     The present application provides a display module, as shown in  FIG.  2   , a display module  1  includes a display panel  11 , an optical film (or optical film sheet)  12 , a functional layer  13 , and a photosensitive element  14 . The optical film  12  is disposed on a light-emitting side of the display panel  11 , the functional layer  13  is disposed on a non-light-emitting side of the display panel  11 , and the photosensitive element  14  is mounted on the functional layer  13 . 
     The display panel  11  may be an OLED display panel, a quantum dot display panel, a liquid crystal display panel, or the like. The display panel  11  may be rigid or flexible. The type of the display panel  11  is not specifically limited, and only a continuous structure of the display panel  11  is required, that is, the display panel  11  is not provided with a through hole through the entire display panel  11 , so that the display panel  11  has no hollowed-out area. 
     In some embodiments of the present application, the display panel  11  is a flexible OLED display panel, continuing to refer to  FIG.  2   , the display panel  11  includes a substrate  111 , and an array substrate  112 , an organic light emitting layer  113 , an encapsulation layer  114 , and a touch layer  115  disposed on the substrate  111 . 
     The material of the substrate  111  may be at least one of polyimide (PI), polyethersulfone (PES), polycarbonate (PC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyarylate (PAR), and fibreglass reinforced plastics (FRP). Preferably, the material of the substrate  111  is a light-transmitting material having a light transmittance greater than or equal to 90%, and as an example, the material of the substrate  111  is polyimide. 
     The array substrate  112  may be a thin film transistor (TFT) array substrate, and the TFT array substrate may be a top gate structure or a bottom gate structure. As an example, the array substrate  112  is a top gate type TFT array substrate. 
     The organic light emitting layer  113  may be a positive type structure including an anode, a hole transport layer, an organic light emitting layer, an electron transport layer, and a cathode, which are disposed sequentially; the organic light emitting layer  113  may also be a negative structure including a cathode, an electron transport layer, an organic light emitting layer, a hole transport layer, and an anode, which are disposed sequentially. As an example, the organic light emitting layer  113  has the positive structure. 
     The encapsulation layer  114  may be a single layer structure or a stacked structure. As an example, the encapsulation layer  114  is a stacked structure formed by alternately disposing inorganic material layers and organic material layers. 
     The touch layer  115  has a stacked structure. As an example, the touch layer  115  is a capacitive touch structure. 
     The array substrate  112 , the organic light emitting layer  113 , the encapsulation layer  114 , and the touch layer  115  are each provided with a light-transmitting non-display region, and positions of the light-transmitting non-display region of the array substrate  112 , the light-transmitting non-display region of the organic light emitting layer  113 , the light-transmitting non-display region of the encapsulation layer  114 , and the light-transmitting non-display region of the touch layer  115  correspond to each other. 
     In some embodiments of the present application, continuing to refer to  FIG.  2   , the array substrate  112  is provided with a first light-transmitting non-display region  1101 , the organic light emitting layer  113  is provided with a second light-transmitting non-display region  1102 , the encapsulation layer  114  is provided with a third light-transmitting non-display region  1103 , the touch layer  115  is provided with a fourth light-transmitting non-display region  1104 , the respective forward projections of the first light-transmitting non-display region  1101 , the second light-transmitting non-display region  1102 , the third light-transmitting non-display region  1103 , and the fourth light-transmitting non-display region  1104  on the substrate  111  are completely overlapped with each other, and the first light-transmitting non-display region  1101 , the second light-transmitting non-display region  1102 , the third light-transmitting non-display region  1103 , and the fourth light-transmitting non-display region  1104  are an integrated structure. The materials of the first light-transmitting non-display region  1101 , the second light-transmitting non-display region  1102 , the third light-transmitting non-display region  1103 , and the fourth light-transmitting non-display region  1104  are all the same light-transmitting material having a light transmittance greater than or equal to 90%, and as an example, the light-transmitting material is polyimide. 
     In another embodiments of the present application, as shown in  FIG.  3   , the array substrate  112  is provided with the first light-transmitting non-display region  1101 , the organic light emitting layer  113  is provided with the second light-transmitting non-display region  1102 , the encapsulation layer  114  is provided with the third light-transmitting non-display region  1103 , the touch layer  115  is provided with the fourth light-transmitting non-display region  1104 , the first light-transmitting non-display region  1101 , the second light-transmitting non-display region  1102 , the third light-transmitting non-display region  1103 , and the fourth light-transmitting non-display region  1104  are independent of each other, and the respective forward projections of the first light-transmitting non-display region  1101 , the second light-transmitting non-display region  1102 , the third light-transmitting non-display region  1103 , and the fourth light-transmitting non-display region  1104  on the substrate  111  are at least partially overlapped with each other, for example, completely overlapped with each other. The materials of the first light-transmitting non-display region  1101 , the second light-transmitting non-display region  1102 , the third light-transmitting non-display region  1103 , and the fourth light-transmitting non-display region  1104  may be same as each other, may be different from each other, or may be partially same, and only the light transmittance of the materials of the first light-transmitting non-display region  1101 , the second light-transmitting non-display region  1102 , the third light-transmitting non-display region  1103 , and the fourth light-transmitting non-display region  1104  needs to be greater than or equal to 90%. 
     Further, among the first light-transmitting non-display region  1101 , the second light-transmitting non-display region  1102 , the third light-transmitting non-display region  1103 , and the fourth light-transmitting non-display region  1104 , the material of each light-transmitting non-display region is same as at least one of the materials of the display area in the same film layer, the light transmittance of the at least one material is equal to or greater than 90%, and the non-light-transmitting (or opaque) function pattern on the corresponding functional film layer is disposed away from the light-transmitting non-display region, so as to constitute the display region and the light-transmitting non-display region. Continuing to refer to  FIG.  3   , the material of the first light-transmitting non-display region  1101  is same as a light-transmitting material in the array substrate  112 , the material of the second light-transmitting non-display region  1102  is same as a light-transmitting material in the organic light emitting layer  113 , the material of the third light-transmitting non-display region  1103  is same as a material of the encapsulation layer  114 , and the material of the fourth light-transmitting non-display region  1104  is same as a light-transmitting material in the touch layer  115 . Specifically, the first light-transmitting non-display region  1101  in the same film layer as the array substrate  112  includes the material of a pixel defining layer and a planarizing layer, the second light-transmitting non-display region  1102  in the same film layer as the organic light emitting layer  113  includes the basic device structure of the OLED other than the color filter layer, a hole may be formed in the cathode layer of the OLED in the second light-transmitting non-display region  1102  and filled with the light-transmitting material, or the entire cathode layer is made of a new cathode material having a transparency of more than 90%, the material of the third light-transmitting non-display region  1103  in the same film layer as the encapsulation layer  114  coincides with the organic/inorganic stacked material of the encapsulation layer  114 , and the fourth light-transmitting non-display region  1104  in the same film layer as the touch layer  115  includes the insulating layer other than the touch wires; it should be noted that the foregoing manner of forming the light-transmitting non-display region in each functional film layer is not limited to the non-transmitting functional pattern avoidance design, and the light-transmitting non-display region in each functional film layer may be realized by forming holes and filling a light-transmitting material after completion of a single functional film layer. 
     Continuing to refer to  FIGS.  2  and  3   , the optical film  12  is a polarizer having an anti-reflection effect to prevent ambient light from negatively affecting the display effect of the display panel  11 . The optical film  12  is provided with a first through hole  101  through which ambient light enters the display panel  11  and is captured by the photosensitive element  14 . The reason why the optical film  12  is not provided on an entire surface is that the optical film  12  has a low light transmittance, and if the first through hole  101  is not provided, the throughput of the ambient light is greatly reduced, thereby affecting the operation performance of the photosensitive element  14 . 
     The functional layer  13  is provided on the non-light-emitting side of the display panel  11 . The functional layer  13  includes a photosensitive element mounting layer  131  which may be, for example, a housing of the display panel  11 . The photosensitive element mounting layer  131  is provided with a second through hole  102  which may serve as a structure for mounting the photosensitive element  14 . The position of the second through hole  102  corresponds to the first through hole  101 , and the forward projection of the second through hole  102  on the display panel  11  falls within the range of the forward projection of the first through hole  101  on the display panel  11 , so that the photosensitive element  14  fully captures the ambient light transmitted from the first through hole  101 . 
     In some embodiments of the present application, the photosensitive element  14  is a camera. 
     In some embodiments of the present application, a diameter of the first through hole  101  is greater than a diameter of the second through hole  102 , and the difference between the diameter of the first through hole  101  and the diameter of the second through hole  102  is 0.2 mm or more. Under the premise of ensuring that the photosensitive element  14  fully captures the ambient light transmitted from the first through hole  101 , light leakage is avoided, and interference with the photosensitive element  14  is prevented. 
     It should be noted that in a conventional display module having a high screen-to-body ratio characteristic, the display panel has a discontinuous structure, that is, the display panel is provided with a through hole through the entire display panel, so that the display panel has a hollowed area, and therefore, a “gourd screen” phenomenon is prone to appear. In the display module of the embodiments of the present application, the display panel has a continuous and uninterrupted structure, which effectively avoids the phenomenon of “gourd screen”. 
     Since the optical film  12  is provided with the first through hole  101  and the display panel  11  is not provided with the through hole, there is a step between the optical film  12  and the display panel  11 . When the protective cover is attached on the side of the optical film  12  away from the display panel  11 , air bubbles are easily generated at the step between the optical film  12  and the display panel  11 , thereby negatively affecting the operating performance of the display module  1 . 
     In order to prevent air bubbles from being generated at the step between the optical film  12  and the display panel  11 , the display module  1  further includes an optical pad adapted to be disposed in the first through hole  101 , and a side of the optical pad away from the display panel  11  is aligned with the side of the optical film  12  away from the display panel  11 , and the material of the optical pad is a light-transmitting material having a light transmittance of 90% or more. The material of the optical pad may be, for example, a high light transmittance material such as polyethylene terephthalate (PET), cyclo olefin polymer (COP), acrylic, or the like. 
     As an example,  FIG.  4    shows a schematic cross-sectional view of another display module. On the basis of the display module shown in  FIG.  2   , the display module  1  further includes an optical pad  17  adapted to be disposed in the first through hole  101 , and a side of the optical pad  17  away from the display panel is aligned with the side of the optical film  12  away from the display panel. 
     As an example,  FIG.  5    shows a schematic cross-sectional view of another display module. On the basis of the display module shown in  FIG.  3   , the display module  1  further includes an optical pad  17  adapted to be disposed in the first through hole  101 , and a side of the optical pad  17  away from the display panel is aligned with the side of the optical film  12  away from the display panel. 
     In some embodiments of the present application, continuing to refer to  FIGS.  2  to  5   , the functional layer  13  further includes a heat dissipation buffer (super clean foam, SCF) layer  132  disposed between the non-light-emitting side of the display panel  11  and the photosensitive element mounting layer  131 , and the SCF layer  132  has the function of buffering and dissipating heat. The SCF layer  132  may be a common structure in the art. For example, the SCF layer  132  includes an adhesive layer, a foam layer, an organic material layer, and a metal layer arranged in sequence. The adhesive layer is close to the non-light-emitting side of the display panel  11 , an example of the material of the adhesive layer is network adhesive (Embo); the foam layer has the function of light shielding and buffering, and an example of the material of the foam layer is foam; the organic material layer has a reinforcing effect to improve the reliability of the SCF layer  132 , and an example of the material of the organic material layer is polyimide; the metal layer has a heat dissipation effect, and an example of the material of the metal layer is copper foil. 
     In order to allow ambient light to pass through the SCF layer to reach the photosensitive element mounting layer  131  so as to be captured by the photosensitive element  132  mounted on the photosensitive element mounting layer  131 , a third through hole  103  is provided in the SCF layer  132 , the position of the third through hole  103  corresponds to the first through hole  101  and the second through hole  102 , and the forward projection of the second through hole  102  on the display panel  11  falls into the forward projection of the third through hole  103  on the display panel  11  so as to sufficiently capture the ambient light transmitted from the first through hole  101 . 
     In some embodiments of the present application, the diameter of the third through hole  103  is greater than the diameter of the second through hole  102 , and the difference between the diameter of the third through hole  103  and the diameter of the second through hole  102  is 0.6 mm or more. Under the premise of ensuring that the photosensitive element  14  fully captures the ambient light transmitted from the first through hole  101 , light leakage is avoided, and interference with the photosensitive element  14  is prevented. 
     In order to further increase the light-capturing efficiency of the photosensitive element  14 , in other embodiments of the present application, a fourth through hole is provided on the support layer  133 , the position of the fourth through hole corresponds to the first through hole  101  and the second through hole  102 , and the forward projection of the second through hole  102  on the display panel  11  falls into the forward projection of the fourth through hole on the display panel  11 . The material of the support layer  14  includes, but is not limited to, a high light transmittance material. For example, the material of the support layer  14  may be an inorganic material such as glass, metal, or the like, and the material of the support layer  14  may be an organic material such as rigid plastic. 
     Further, the diameter of the fourth through hole  104  is greater than the diameter of the second through hole  102 , and the difference between the diameter of the fourth through hole  104  and the diameter of the second through hole  102  is 0.2 mm or more. Under the premise of ensuring that the photosensitive element  14  fully captures the ambient light transmitted from the first through hole  101 , light leakage is avoided, and interference with the photosensitive element  14  is prevented. 
     As an example,  FIG.  6    shows a schematic cross-sectional view of another display module, which differs only from the display module shown in  FIG.  4    in that: the support layer  133  is provided with a fourth through hole  104 , the position of the fourth through hole  104  corresponds to the first through hole  101 , the second through hole  102  and the third through hole  103 , and the forward projection of the second through hole  102  on the display panel  11  falls into the forward projection of the fourth through hole  104  on the display panel  11 . 
     As an example,  FIG.  7    shows a schematic cross-sectional view of another display module. The display module shown in  FIG.  7    differs only from the display module shown in  FIG.  5    in that: the support layer  133  is provided with a fourth through hole  104 , the position of the fourth through hole  104  corresponds to the first through hole  101 , the second through hole  102  and the third through hole  103 , and the forward projection of the second through hole  102  on the display panel  11  falls into the forward projection of the fourth through hole  104  on the display panel  11 . 
     In some embodiments of the present application, the display module  1  further includes an optical clear adhesive (OCA) layer disposed on at least one side of the optical film  12 , for example, the optical clear adhesive layer disposed on a side of the optical film  12  away from the display panel  11 . 
     Further, the display module  1  further includes a cover plate (cover window (CW)) disposed on a side of the optical clear adhesive layer away from the display panel  11 . The cover plate is used to prevent water, oxygen or impurities in the external environment from entering the inside of the display module, and is typically a glass or transparent organic rigid substrate. 
     It may be understood that the cover plate includes an ink layer (not shown in the drawings), the ink layer functions to shield other layer structures except for the photosensitive element (e.g., a camera), the photosensitive element is exposed by the ink layer, the size of the ink layer is not specifically limited, and only the conditions under which the photosensitive element (e.g., a camera) can be exposed from the ink layer and the other layer structures are shielded need to be satisfied. For example, when there are the first through hole  101 , the second through hole  102 , the third through hole  103 , and the fourth through hole  104  at the same time, where the aperture of the first through hole  101  is smallest, the ink layer needs to be capable of shielding the optical film  12  and the hole edge of the first through hole  101 , and the first through hole  101  cannot be covered to ensure that the photosensitive element such as a camera is exposed from the ink layer, and shields the optical film  12 , the SCF layer  132 , and the support layer  133 . In some embodiments of the present application, the optical clear adhesive layer has a continuous structure, that is, the optical clear adhesive layer is not provided with a through hole through the entire optical clear adhesive layer, so that the optical clear adhesive layer has no hollowed-out region, and the material of the optical clear adhesive layer is an optical clear adhesive material having a low modulus, good fluidity, and a light transmittance of 90% or more. Since no holes are formed in the optical clear adhesive layer, the risk of “gourd screen” phenomenon is further reduced. 
     As an example,  FIG.  8    shows a schematic cross-sectional view of another display module. On the basis of the display module shown in  FIG.  6   , the display module  1  shown in  FIG.  8    further includes an optical clear adhesive layer  15  and a cover plate  16 , the optical clear adhesive layer  15  is disposed on a side of the optical film  12  away from the display panel  11 , the cover plate  16  is disposed on a side of the optical clear adhesive layer  15  away from the optical film  12 , and a cover plate  16  completely shields an edge of the optical film  12 . The optical clear adhesive layer  15  has a continuous structure, the material of the optical clear adhesive layer  15  is a commercially available OCA material from 3M Corporation, and the modulus of the OCA material is less than 0.25 Mpa. The material of the cover plate  16  is glass. 
     As an example,  FIG.  9    shows a schematic cross-sectional view of another display module. On the basis of the display module shown in  FIG.  7   , the display module  1  shown in  FIG.  9    further includes an optical clear adhesive layer  15  and a cover plate  16 , the optical clear adhesive layer  15  is disposed on a side of the optical film  12  away from the display panel  11 , the cover plate  16  is disposed on a side of the optical clear adhesive layer  15  away from the optical film  12 , and the cover plate  16  completely shields an edge of the optical film  12 . The optical clear adhesive layer  15  has a continuous structure, the material of the optical clear adhesive layer  15  is a commercially available OCA material from 3M Corporation, and the modulus of the OCA material is less than 0.25 Mpa. The material of the cover plate  16  is glass. 
     In order to further improve the light-capturing rate of the photosensitive element  14 , in other embodiments of the present application, a fifth through hole  105  is provided in the optical clear adhesive layer  15 , the position of the fifth through hole  105  corresponds to the first through hole  101  and the second through hole  102 , and the forward projection of the second through hole  102  on the display panel  11  falls into the forward projection of the fifth through hole  105  on the display panel  11 . The material of the optical clear adhesive layer  15  is not specifically limited. 
     As an example,  FIG.  10    shows a schematic cross-sectional view of another display module. On the basis of the display module shown in  FIG.  6   , the display module  1  shown in  FIG.  10    further includes an optical clear adhesive layer  15  and a cover plate  16 , the optical clear adhesive layer  15  is disposed on a side of the optical film  12  away from the display panel  11 , the cover plate  16  is disposed on a side of the optical clear adhesive layer  15  away from the optical film  12 , and the cover plate  16  completely shields an edge of the optical film  12 . 
     The optical clear adhesive layer  15  is provided with a fifth through hole  105 , the position of the fifth through hole  105  corresponds to the first through hole  101 , the second through hole  102 , the third through hole  103  and the fourth through hole  104 , and the forward projection of the second through hole  102  on the display panel  11  falls into the forward projection of the fifth through hole  105  on the display panel  11 . 
     As an example,  FIG.  11    shows a schematic cross-sectional view of another display module. On the basis of the display module shown in  FIG.  7   , the display module  1  shown in  FIG.  11    further includes an optical clear adhesive layer  15  and a cover plate  16 , the optical clear adhesive layer  15  is disposed on a side of the optical film  12  away from the display panel  11 , the cover plate  16  is disposed on a side of the optical clear adhesive layer  15  away from the optical film  12 , and the cover plate  16  completely shields an edge of the optical film  12 . 
     The optical clear adhesive layer  15  is provided with a fifth through hole  105 , the position of the fifth through hole  105  corresponds to the first through hole  101 , the second through hole  102 , the third through hole  103  and the fourth through hole  104 , and the forward projection of the second through hole  102  on the display panel  11  falls into the forward projection of the fifth through hole  105  on the display panel  11 . 
     Referring to  FIG.  12   , stacked structural view of a specific functional films of a display module is provided according to the present invention, and includes an image pickup region and a display region outside the image pickup region, a film layer in a film thickness direction corresponding to the image pickup region is a light-transmitting non-display region. In the light-transmitting non-display region, some of the film layers which are originally made of light-transmitting material are not subjected to special light-transmitting treatment. On the contrary, a film layer which has a non-light-transmitting material or a non-light-transmitting pattern corresponding to this region is subjected to light-transmitting treatment, such as designing the non-light-transmitting pattern away from this region, or filling this region with the light-transmitting material. 
     Specifically, the aforementioned stacked structural view of a specific functional films includes a flexible substrate, the flexible substrate includes a first flexible layer  201 , a barrier layer  202  over the first flexible layer  201 , and a second flexible layer  203  over the barrier layer  202 ; an array substrate is disposed over the flexible substrate, the array substrate includes a buffer layer  204 , a base layer  205  disposed over the buffer layer  204 , and TFT devices  206  disposed over the base layer  205 , the TFT device  206  includes an active layer  207  disposed over the base layer  205 , a first gate insulating layer  208  covering the active layer  207 , a first gate electrode  209  disposed over the first gate insulating layer  208 , a second gate insulating layer  210  disposed over the first gate insulating layer  208  and covering the first gate electrode  209 , a second gate electrode  211  disposed over the second gate insulating layer  210 , a dielectric layer  212  covering the second gate electrode  211 , and source/drain electrodes  213  disposed over the dielectric layer  212 , the source/drain electrodes  213  are connected to the active layer  207 , the TFT device  206  is disposed away from the light-transmitting non-display region (image pickup region), and a portion of the TFT device  206  layer corresponding to the light-transmitting non-display region is filled with a light-transmitting material; a first planarizing layer  214  is further disposed over the layer of the TFT device  206 , a light emitting device  215  and an anode  216  connected to the light emitting device  215  are disposed over the first planarizing layer  214 , an opposite end of the anode  216  is connected to the source/drain electrode  213 , the light emitting device  215  is disposed away from the light-transmitting non-display region, a second planarizing layer  217  is disposed over the first planarizing layer  214 , a cathode layer  218  is disposed over the second planarizing layer  217 , the cathode layer  218  is electrically connected to the light emitting device  215 , and a portion of the cathode layer  218  corresponding to the light-transmitting non-display region is disposed as a transparent cathode  220 ; an encapsulation layer  220  and a touch layer  221  over the encapsulation layer  220  are also provided over the cathode layer  218 . 
     An embodiment of the present application further provides a manufacturing method of a display module, which can be used to manufacture a display module shown in  FIG.  3   , a display module shown in  FIG.  5   , a display module shown in  FIG.  7   , a display module shown in  FIG.  9   , and a display panel shown in  FIG.  11   . As shown in  FIG.  13   , the manufacturing method of the display module includes the following steps: 
     S 1 : providing a display panel including a substrate and a plurality of film layers stacked on the substrate, each of the plurality of film layers is provided with a light-transmitting non-display region, and positions of the light-transmitting non-display regions of the respective film layers correspond to each other; 
     S 2 : forming an optical film on a light-emitting side of the display panel, and forming a first through hole in the optical film, a position of the first through hole corresponds to the light-transmitting non-display region, and a forward projection of the first through hole on the display panel falls within a range of the light-transmitting non-display region; 
     S 3 : forming a functional layer including a photosensitive element mounting layer on a non-light-emitting side of a display panel, and forming a second through hole in the photosensitive element mounting layer, a position of the second through hole corresponds to the first through hole, and a forward projection of the second through hole on the display panel falls within a range of the forward projection of the first through hole on the display panel; 
     S 4 : providing a photosensitive element, and mounting the photosensitive element to the second through hole. 
     As for the manufacturing method described above, it should be noted that the manufacturing method of the light-transmitting non-display region of each film layer in the display panel may be a method of a photolithography process combined with a process of filling a light-transmitting material, that is, performing the steps of coating photoresist, exposing and developing, etching to form hollowed-out regions, filling light-transmitting materials, etc., on each film layer in the display panel one by one, if the material of the film layer itself has a high light transmittance (for example, ITO electrodes); or when each functional film layer is separately formed, a light-transmitting non-display region is defined on each functional film layer in advance, and the non-light-transmitting functional patterns on corresponding functional films are disposed away from the light-transmitting non-display region, only the light-transmitting material on the corresponding functional film layer is retained in the light-transmitting non-display region, and the light-transmitting non-display regions of respective functional film layers are stacked to form the light-transmitting non-display region of the display module; the foregoing two layer-by-layer processing methods make it unnecessary to from a light-transmitting non-display region after the display module is prepared. 
     The operation of “forming an optical film on the light-emitting side of the display panel, and forming a first through hole in the optical film” in step S 2 , and the operations of “forming a functional layer on the non-light-emitting side of the display panel, the functional layer includes a photosensitive element mounting layer and a second through hole is formed in the photosensitive element mounting layer” in step S 3  may be carried out in an interchangeable order. 
     In some embodiments of the present application, in step S 2 , the first through hole may be formed in the optical film by a laser cutting process, and in step S 3 , the second through hole may be formed in the photosensitive element mounting layer by a laser cutting process. 
     In some embodiments of the present application, in step S 3 , the first through hole may be formed in the optical film using an etching process, and in step S 3 , the second through hole may be formed in the photosensitive element mounting layer using an etching process. 
     In the manufacturing method of the conventional display module, the display panel, the optical film and the functional layer are assembled integrally, and then the display panel, the optical film and the functional layer are integrally cut to form a through hole. The integration cutting involves a large number of film layers, and a large number of regions are affected by the cutting, thus, a cutting crack is easily generated. The edge crack generated by the cutting may extend to the display region, resulting in a problem of poor display and a “gourd screen” phenomenon. In the manufacturing method of the embodiment of the present application, before the display panel is assembled into the display module, each film layer in the display panel has been prepared to form a light-transmitting non-display region, so that there is no need to perform hole processing on the display panel, and only the optical film and the photosensitive element mounting layer need to be performed the hole processing respectively, thereby greatly reducing the risk of cracking and effectively improving the “gourd screen” phenomenon. 
     An embodiment of the present application further provides a manufacturing method of a display module, which can be used to prepare the display module shown in  FIG.  2   , the display module shown in  FIG.  4   , the display module shown in  FIG.  6   , the display module shown in  FIG.  8   , and the display panel shown in  FIG.  10   . As shown in  FIG.  14   , the manufacturing method of the display module includes the following steps: 
     S 10 : providing a stacked structure including a substrate and a plurality of film layers stacked on the substrate, each of the plurality of film layers is predefined with a light-transmitting non-display region, and positions of the predefined light-transmitting non-display regions of respective film layers correspond to each other; 
     S 20 : using an etching process to remove a film material in a predefined light-transmitting non-display region in each of the film layers to obtain a stacked structure having a hollowed-out region; 
     S 30 : filling the hollowed-out region in the step S 20  with a light-transmitting material having a light transmittance of 90% or more, and then drying to obtain a display panel; 
     S 40 : forming an optical film on a light-emitting side of a display panel filled with the light-transmitting material, and forming a first through hole in the optical film, a position of the first through hole corresponds to the light-transmitting non-display region, and a forward projection of the first through hole on the display panel falls within a range of the light-transmitting non-display region; 
     S 50 : forming a functional layer including a photosensitive element mounting layer on the non-light-emitting side of a display panel filled with a light-transmitting material, and forming a second through hole in the photosensitive element mounting layer, a position of the second through hole corresponds to the first through hole, and the forward projection of the second through hole on the display panel falls within a range of the forward projection of the first through hole on the display panel; 
     S 60 : providing a photosensitive element, and mounting the photosensitive element to the second through hole. 
     It should be noted that the light-transmitting non-display regions of the respective film layers in the display panel are integrally formed, that is, the light-transmitting non-display regions predefined in the respective film layers are integrally etched to form hollowed-out regions, and then the hollowed-out regions are integrally filled with the light-transmitting material, so that the light-transmitting non-display regions of the respective film layers in the display panel are integrated structure. Compared with the manufacturing method shown in  FIG.  12   , the manufacturing process is simple. 
     The operation of “forming an optical film on a light-emitting side of a display panel, and forming a first through hole in the optical film” in step S 40  and the operation of “forming a functional layer on the non-light-emitting side of a display panel, the functional layer comprises a photosensitive element mounting layer, and forming a second through hole in the photosensitive element mounting layer” in step S 50  may be carried out in an interchangeable order. 
     In some embodiments of the present application, in step S 40 , the first through hole may be formed in the optical film using a laser cutting process, and in step S 50 , the second through hole may be formed in the photosensitive element mounting layer using a laser cutting process. 
     In some embodiments of the present application, in step S 40 , the first through hole may be formed in the optical film by an etching process, and in step S 50 , the second through hole may be formed in the photosensitive element mounting layer by an etching process. 
     In the manufacturing method of this embodiment, although a process of forming holes is performed on the display panel, the display module is not formed by assembling the display panel having the through hole with the optical film and the functional layer, that is, the through hole of the display panel needs to be filled with a light-transmitting material to form a light-transmitting non-display region before assembling. Compared with the manufacturing method of the conventional display module, the manufacturing method of this embodiment effectively improves the “gourd screen” phenomenon under the premise of ensuring that the photosensitive element fully captures the ambient light. 
     An embodiment of the present application further provides a display terminal. The display terminal includes any one of the display modules described above or a display module prepared by any one of the manufacturing methods of the display module described above. The display terminal may be an electronic product having a display function such as a smartphone, a tablet computer, a notebook computer, a digital camera, a digital video camera, a smart wearable device, a smart weighing electronic scale, a vehicle display, a television set, an electronic book reader, or the like. Among them, the smart wearable device may be, for example, a smart bracelet, a smart watch, a virtual reality (VR) helmet, etc. 
     The present invention has been described by the above-described related embodiments, however, the above-described embodiments are merely examples for implementing the present invention. It must be noted that the disclosed embodiments do not limit the scope of the invention. Conversely, modifications and equivalent arrangements included in the spirit and scope of the claims are all included in the scope of the present invention.