Patent Publication Number: US-2022236469-A1

Title: Laminated structure, display panel, and electronic device

Description:
This application claims priority to Chinese Patent Application No. 201910415213.3, filed with the China National Intellectual Property Administration on May 17, 2019 and entitled “LAMINATED STRUCTURE, DISPLAY PANEL, AND ELECTRONIC DEVICE”, which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to the field of display technologies, and in particular, to a laminated structure, a display panel, and an electronic device. 
     BACKGROUND 
     Recently, more electronic devices are provided with an optical fingerprint recognition module under a display panel, to facilitate unlocking of the electronic devices by users. Light needs to pass through laminated layers, such as a protective layer, a linear polarizing layer, and a quarter-wave plate, of the display panel before entering the optical fingerprint recognition module. However, because of differences in materials of the laminated layers of the display panel, the stability of light transmission in the display panel are affected, resulting in low stability of the light intensity of light entering the optical fingerprint recognition module, and reducing the recognition precision of the optical fingerprint recognition module. 
     SUMMARY 
     A technical problem to be resolved by embodiments of this application is about a laminated structure, a display panel, and an electronic device that can improve the stability of light transmission. 
     To achieve the foregoing objective, implementations of this application adopt the following technical solutions: 
     According to a first aspect, an implementation of this application provides a laminated structure, including a protective layer, a linear polarizing layer, and a quarter-wave plate that are laminated in sequence. The protective layer is used to polarize light to form linearly polarized light. An angle between an absorption axis of the protective layer and an absorption axis of the linear polarizing layer is zero degrees. An angle between the absorption axis of the linear polarizing layer and an absorption axis of the quarter-wave plate is 45 degrees. 
     In this implementation, the angle between the absorption axis of the linear polarizing layer and the absorption axis of the protective layer is zero degrees, and there is no difference between a direction of the absorption axis of the protective layer and a direction of the absorption axis of the linear polarizing layer. Therefore, a luminous flux of light passing through the protective layer is roughly the same as that of light passing through the linear polarizing layer. In other words, the light intensity of the light passing through the protective layer is consistent with that of the light passing through the linear polarizing layer. In this way, the light loss during light transmission in the laminated structure can be reduced, and the stability of light transmission in the laminated structure can be improved, to stabilize the light intensity of light passing through the laminated structure, and improve the stability of light entering an optical fingerprint recognition module, thereby improving recognition precision of the optical fingerprint recognition module. 
     In a possible implementation, the laminated structure further includes a reinforcing layer, and the reinforcing layer is arranged between the protective layer and the linear polarizing layer, and used to protect the laminated structure and enhance the strength of the laminated structure. 
     In a possible implementation, the material strength of the reinforcing layer is greater than that of the protective layer. 
     In a possible implementation, the reinforcing layer is made of an isotropic material, to reduce the light loss during light transmission in the laminated structure, and enhance the stability of light transmission. 
     In a possible implementation, the linear polarizing layer is fixed to the reinforcing layer through an optical adhesive layer, to improve the bonding strength between the linear polarizing layer and the reinforcing layer. 
     In a possible implementation, the optical adhesive layer is made of an isotropic material, to further reduce the light loss during light transmission in the laminated structure, and enhance the stability of light transmission. 
     In a possible implementation, the reinforcing layer is a glass cover plate, to enhance the strength and protection performance of the laminated structure; and the protective layer is a film layer attached to one side of the reinforcing layer away from the linear polarizing layer, to prevent the reinforcing layer from being scratched and worn. 
     In a possible implementation, the reinforcing layer is used to polarize light to form linearly polarized light. An angle between an absorption axis of the reinforcing layer and the absorption axis of the linear polarizing layer is zero degrees. The reinforcing layer is set as a laminated layer in a direction consistent with the direction of the absorption axis of the linear polarizing layer, so that the optical performance of the reinforcing layer, the protective layer, and the linear polarizing layer can be matched, and the light intensity of light passing through the protective layer is consistent with that of light passing through the reinforcing layer and the linear polarizing layer, thereby enhancing the stability of light transmission. 
     In a possible implementation, the protective layer is a cover plate, and the protective layer is made of a material including one of ceramic and plastic, helping reduce a thickness of the laminated structure while increasing the strength of the protective layer. 
     In a possible implementation, the protective layer is made of materials including polyethylene terephthalate plastic and thermoplastic polyurethane elastomer rubber. 
     According to a second aspect, this application further provides a display panel, applied to an electronic device with an optical fingerprint recognition module. The display panel includes a functional substrate and the foregoing laminated structure that are laminated. The functional substrate is located on one side of a quarter-wave plate away from a protective layer, and the functional substrate has a light-transmitting area, to allow light emitted from the quarter-wave plate to enter the optical fingerprint recognition module through the light-transmitting area. 
     In this implementation, an angle between an absorption axis of the protective layer located on an outermost side of the display panel and an absorption axis of a linear polarizing layer is zero degrees, and there is no difference between a direction of the absorption axis of the protective layer and a direction of the absorption axis of the linear polarizing layer. Therefore, a luminous flux of light passing through the protective layer is roughly the same as that of light passing through the linear polarizing layer. In other words, the light intensity of light passing through the protective layer is consistent with that of light passing through the linear polarizing layer. In this way, the light loss during light transmission in the display panel can be reduced, and the stability of light transmission in the display panel can be improved, to stabilize the light intensity of light entering the optical fingerprint recognition module through the light-transmitting area of the functional substrate, and improve the stability of light entering the optical fingerprint recognition module, thereby improving the recognition precision of the optical fingerprint recognition module. 
     Further, the linearly polarized light passing through the protective layer becomes circularly polarized light passing through the linear polarizing layer and the quarter-wave plate. Part of the circularly polarized light is reflected into reversely polarized light due to a reflection structure in the display panel (such as a metal part in the functional substrate or an interface between adjacent laminated layers). The reversely polarized light is further rotated by 45 degrees after being incident to the quarter-wave plate to become linearly polarized light perpendicular to the direction of the absorption axis of the linear polarizing layer. Therefore, reflected light reflected by the reflection structure in the display panel can be effectively eliminated, thereby improving display and visual effects of the display panel. 
     In a possible implementation, the functional substrate includes a first light-transmitting layer, a plurality of reflection units, and a second light-transmitting layer. The plurality of reflection units are spaced on the first light-transmitting layer, the second light-transmitting layer covers the reflection units and the first light-transmitting layer, and the second light-transmitting layer is located between the quarter-wave plate and the first light-transmitting layer. Because the first light-transmitting layer and the second light-transmitting layer are arranged around the reflection units, an impact force when the laminated structure is collided can be buffered, which is beneficial to prolong life of the laminated structure. 
     In a possible implementation, both the first light-transmitting layer and the second light-transmitting layer are made of isotropic materials, to further reduce the light loss during light transmission in the laminated structure, and enhance the stability of the light intensity of light transmitting through the laminated structure, thereby improving the recognition precision of the optical fingerprint recognition module. 
     In a possible implementation, the first light-transmitting layer and the second light-transmitting layer are made of resin. 
     In a possible implementation, the reflection units are configured to emit light. When a finger touches one side of the protective layer away from the linear polarizing layer, or when a finger is at a specific distance from one side of the protective layer away from the linear polarizing layer, the light emitted by the reflection units can be reflected by the finger and enter the optical fingerprint recognition module through the light-transmitting area, thereby completing an optical fingerprint recognition function. 
     In a possible implementation, the display panel further includes a touch layer, arranged between the functional substrate and the quarter-wave plate. 
     According to a third aspect, an implementation of this application further provides an electronic device, including the foregoing laminated structure and an optical fingerprint recognition module. The optical fingerprint recognition module is located on one side of a functional substrate away from a protective layer, and configured to receive light passing through a light-transmitting area of the functional substrate. 
     In this implementation, an angle between an absorption axis of the protective layer located on an outermost side of the display panel and an absorption axis of a linear polarizing layer is zero degrees, and there is no difference between a direction of the absorption axis of the protective layer and a direction of the absorption axis of the linear polarizing layer. Therefore, a luminous flux of light passing through the protective layer is roughly the same as that of light passing through the linear polarizing layer. In other words, the light intensity of the light passing through the protective layer is consistent with that of the light passing through the linear polarizing layer. In this way, the light loss during light transmission in the display panel can be reduced, and the stability of light transmission in the display panel can be improved, to stabilize the light intensity of light entering the optical fingerprint recognition module through the light-transmitting area of the functional substrate, and improve the stability of light entering the optical fingerprint recognition module, thereby improving the recognition precision of the optical fingerprint recognition module. 
     According to a fourth aspect, an implementation of this application further provides a method for preparing a laminated structure, including the following steps: providing a quarter-wave plate, a linear polarizing layer, and a protective layer; attaching the linear polarizing layer to the quarter-wave plate, and arranging the protective layer on one side of the linear polarizing layer away from the quarter-wave plate, so that the protective layer, the linear polarizing layer, and the quarter-wave plate are laminated. The protective layer is used to polarize light to form linearly polarized light. An angle between an absorption axis of the protective layer and an absorption axis of the linear polarizing layer is zero degrees. An angle between the absorption axis of the linear polarizing layer and an absorption axis of the quarter-wave plate is 45 degrees. 
     In a possible implementation, the arranging the protective layer on one side of the linear polarizing layer away from the quarter-wave plate includes: arranging a reinforcing layer on one side of the linear polarizing layer away from the quarter-wave plate, and arranging the protective layer on one side of the reinforcing layer away from the linear polarizing layer. 
     In a possible implementation, the arranging a reinforcing layer on one side of the linear polarizing layer away from the quarter-wave plate includes: fixing the reinforcing layer on the linear polarizing layer through an optical adhesive layer. 
     It should be understood that, the descriptions of technical features, technical solutions, beneficial effects, or similar expressions in this application are not intended to imply that all the features and advantages can be achieved in any single embodiment. On the contrary, it may be understood that the description of features or beneficial effects means that a specific technical feature, technical solution, or beneficial effect is included in at least one embodiment. Therefore, the descriptions of technical features, technical solutions, or beneficial effects in this specification do not necessarily refer to the same embodiment. In addition, the technical features, technical solutions, and beneficial effects described in this embodiment can also be combined in any appropriate manner. A person skilled in the art can understand that the embodiments can be implemented without one or more specific technical features, technical solutions, or beneficial effects of a specific embodiment. In other embodiments, additional technical features and beneficial effects can also be identified in a specific embodiment that does not embody all embodiments. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram of a partial structure of an electronic device according to a first implementation of this application. 
         FIG. 2  is a schematic diagram of a light path of light incident to a display panel in the first implementation of this application. 
         FIG. 3  is a schematic diagram of absorption axes of laminated layers of the display panel in the first implementation of this application. 
         FIG. 4 a    is a schematic diagram of an application scenario when fingerprint recognition is performed by an electronic device according to an implementation of this application. 
         FIG. 4 b    is a schematic diagram when fingerprint recognition is performed by a partial structure of an electronic device according to an implementation of this application. 
         FIG. 5  is a flowchart of a method for preparing a laminated structure according to an implementation of this application. 
         FIG. 6  is a schematic diagram of absorption axes of laminated layers of a display panel according to a second implementation of this application. 
         FIG. 7  is a schematic diagram of absorption axes of laminated layers of a display panel according to a third implementation of this application. 
         FIG. 8  is a schematic diagram of absorption axes of laminated layers of a display panel according to a fourth implementation of this application. 
         FIG. 9  is a schematic diagram of an absorption axis of a laminated structure according to a fifth implementation of this application. 
         FIG. 10  is a schematic diagram of an absorption axis of a laminated structure according to a sixth implementation of this application. 
         FIG. 11  is a schematic diagram of an absorption axis of a laminated structure according to a seventh implementation of this application. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 1  is a schematic diagram of a partial structure of an electronic device according to a first implementation. The electronic device  100  includes a display panel  101  and an optical fingerprint recognition module  103  that are laminated. The display panel  101  is located on a light entrance side of the optical fingerprint recognition module  103 , and is configured to display an image. The optical fingerprint recognition module  103  is configured to receive light transmitting through the display panel  101  to implement a fingerprint recognition function. The electronic device  100  may be any electronic device such as a smartphone, a smart watch, a tablet computer, a personal digital assistant (personal digital assistant, PDA for short), a point of sales (point of sales, POS for short), an on-board computer, a desktop computer, a laptop computer, or a smart TV. This is not limited in the embodiments of the present invention. 
     The display panel  101  includes a laminated structure  10  and a functional substrate  30  that are laminated. The functional substrate  30  is located between the laminated structure  10  and the optical fingerprint recognition module  103 . The functional substrate  30  has a light-transmitting area  31 , to allow light to enter the optical fingerprint recognition module  103  through the light-transmitting area  31 . 
     Specifically, the laminated structure  10  includes a quarter-wave plate (quarter-wave plate, QWP for short)  12 , a linear polarizing layer  13 , and a protective layer  15 . The functional substrate  30  is located between the optical fingerprint recognition module  103  and the quarter-wave plate  12 . The quarter-wave plate  12  can make ordinary light (o light) and extraordinary light (e light) equal to n/2 or an odd multiple thereof. The quarter-wave plate  12  is sandwiched between the functional substrate  30  and the linear polarizing layer  13 . The protective layer  15  is arranged on one side of the linear polarizing layer  13  away from the quarter-wave plate  12 . Both the protective layer  15  and the linear polarizing layer  13  can polarize light to form linearly polarized light. An angle between an absorption axis of the linear polarizing layer  13  and an absorption axis of the protective layer  15  is zero degrees. An angle between an absorption axis of the quarter-wave plate  12  and the absorption axis of the linear polarizing layer  13  is 45 degrees. An angle between the absorption axis of the protective layer  15  and the absorption axis of the quarter-wave plate  12  is 45 degrees. 
     In this implementation, in the linear polarizing layer  13 , light parallel to the absorption axis of the linear polarizing layer  13  may be absorbed by the linear polarizing layer  13 , and light perpendicular to the absorption axis of the linear polarizing layer  13  may be emitted through the linear polarizing layer  13 ; and in the protective layer  15 , light parallel to the absorption axis of the protective layer  15  may be absorbed by the protective layer  15 , and light perpendicular to the absorption axis of the protective layer  15  may be emitted through the protective layer  15 . 
     Light is incident from the protective layer  15  in a direction opposite to the linear polarizing layer  13 , becomes linearly polarized light passing through the protective layer  15 , enters the linear polarizing layer  13 , and then is converted into circularly polarized light by the quarter-wave plate  12 . Part of the circularly polarized light enters the optical fingerprint recognition module  103  through the functional substrate  30 . 
     The protective layer  15  can polarize the light incident therein to form linearly polarized light, an angle between the absorption axis of the linear polarizing layer  13  and the absorption axis of the protective layer  15  is zero degrees, and there is no difference between a direction of the absorption axis of the protective layer  15  and a direction of the absorption axis of the linear polarizing layer  13 . Therefore, a luminous flux of light passing through the protective layer  15  is roughly the same as that of light passing through the linear polarizing layer  13 . In other words, the light intensity of the light passing through the protective layer  15  is consistent with that of the light passing through the linear polarizing layer  13 . In this way, the light loss during light transmission from the display panel  10  to the optical fingerprint recognition module  30  can be reduced, and the stability of light passing through the display panel  101  can be improved, to stabilize the light intensity of the light passing through the display panel  101 , and improve the stability of the light entering the optical fingerprint recognition module  103 , thereby improving the recognition precision of the optical fingerprint recognition module  103 . 
     The protective layer  15  is arranged on one side of the laminated structure  10  away from the optical fingerprint recognition module  103 , namely, an outermost side of the electronic device  100 . The laminated structure  10  further includes a reinforcing layer  17  arranged between the protective layer  15  and the linear polarizing layer  13 , and used to protect other laminated structures of the laminated structure  10  and enhance the strength of the laminated structure  10 . The reinforcing layer  17  is a glass cover plate and can enhance the strength of the laminated structure  10 . In this implementation, the material strength of the reinforcing layer  17  is greater than that of the protective layer  15 . The protective layer  15  is a film layer attached to one side of the reinforcing layer  17  away from the linear polarizing layer  13 , for example, a protective film on the outermost side of the display panel  101  of a smartphone, to prevent the reinforcing layer  17  from being scratched and worn. 
     The protective layer  15  is made of materials including polyethylene terephthalate (polyethylene terephthalate, PET for short) plastic and thermoplastic polyurethane (thermoplastic polyurethane, TUP for short) elastomer rubber. The reinforcing layer  17  is fixed to the linear polarizing layer  13  through an optical adhesive layer  19 . The reinforcing layer  17  is made of an isotropic material, to reduce the light loss during light transmission in the laminated structure  10 , and enhance the stability of light transmission. The isotropic refers to a property that physical and chemical properties of an object do not change due to different directions, namely, performance values of an object measured in different directions are completely the same, and is also known as homogeneity. The optical adhesive layer  19  is made of an isotropic material, to further reduce the light loss during light transmission in the laminated structure  10 , and enhance the stability of light transmission. It may be understood that, implementations of this application do not limit the material of the protective layer  15  and the material of the reinforcing layer  17 . For example, the reinforcing layer  17  may be made of plastic or ceramic. 
     In a possible implementation, the reinforcing layer  17  is used to polarize light to form linearly polarized light. An angle between an absorption axis of the reinforcing layer  17  and the absorption axis of the linear polarizing layer  13  is zero degrees. The reinforcing layer  17  is set as a laminated layer in a direction consistent with the direction of the absorption axis of the linear polarizing layer, so that the light intensity of light passing through the protective layer  15  is consistent with that of light passing through the reinforcing layer  17  and the linear polarizing layer  13 , and the optical performance of the reinforcing layer  17 , the protective layer  15  and the linear polarizing layer  13  can be matched, thereby enhancing the stability of light transmission in the laminated structure  10 . 
     In this implementation, the display panel  101  is a flexible display panel. The functional substrate  30  is an organic light-emitting diode (organic light-emitting diode, OLED for short) substrate. More specifically, the functional substrate  30  includes a first light-transmitting layer  32 , a plurality of reflection units  33 , and a second light-transmitting layer  35 . The reflection units  33  are configured to reflect light irradiated thereon. The reflection units  33  are also light-emitting units, configured to emit light. Light emitted by the reflection units  33  can be reflected by a finger and enter the optical fingerprint recognition module  103  through the light-transmitting area  31 , thereby implementing an optical fingerprint recognition function. The plurality of reflection units  33  are spaced on one side of the first light-transmitting layer  32 . The second light-transmitting layer  35  covers the reflection units  33  and the first light-transmitting layer  32 . The light-transmitting area  31  is formed between the adjacent reflection units  33 . The second light-transmitting layer  35  is located between the quarter-wave plate  12  and the first light-transmitting layer  32 . It may be understood that, the functional substrate  30  may also be a touch layer. 
     Because the reflection units  33  are surrounded by the first light-transmitting layer  32  and the second light-transmitting layer  35 , namely, the first light-transmitting layer  32  and the second light-transmitting layer  35  are arranged around the reflection units  33 , an impact force on the reflection units  33  when the laminated structure  10  is collided can be buffered, which is beneficial to prolong life of the display panel  101 . In this implementation, both the first light-transmitting layer  32  and the second light-transmitting layer  35  are made of isotropic materials, to reduce the light loss during light transmission in the display panel  101 , and enhance the stability of the light intensity when light passes through the display panel  101 . The reflection units  33  may be a circuit part such as a cathode and an anode. 
     In some implementations, the display panel  101  may be a touch display panel, and the display panel  101  further includes a touch layer, arranged between the functional substrate  30  and the quarter-wave plate  12 . 
     In some implementations, the protective layer  15  only needs to meet a condition that the angle between the absorption axis of the linear polarizing layer  13  and the absorption axis of the protective layer  15  is zero degrees. 
     It may be understood that, the laminated structure  10  includes the protective layer  15 , the linear polarizing layer  13 , and the quarter-wave plate  12  that are laminated in sequence. The protective layer  15  is used to polarize light to form the linearly polarized light, the angle between the absorption axis of the protective layer  15  and the absorption axis of the linear polarizing layer  13  is zero degrees, and the angle between the absorption axis of the linear polarizing layer  13  and the absorption axis of the quarter-wave plate  12  is 45 degrees. 
       FIG. 2  is a light path of light incident to a laminated structure in the first implementation of this application. 
     The light is natural light. After light  1  is incident from one side of the protective layer  15  away from the reinforcing layer  17 , the protective layer  15  first polarizes the incident light to form linearly polarized light  2 . 
     The linearly polarized light  2  enters the linear polarizing layer  13  after passing through the reinforcing layer  17  and the optical adhesive layer  19 . Because the angle between the absorption axis of the linear polarizing layer  13  and the absorption axis of the protective layer  15  is zero degrees, the linearly polarized light  2  is still linearly polarized light passing through the linear polarizing layer  13 . 
     The linearly polarized light passing through the reinforcing layer  17 , the linearly polarized light passing through the optical adhesive layer  19 , and the linearly polarized light passing through the linear polarizing layer  13  are marked as linearly polarized light  3 , linearly polarized light  4 , and linearly polarized light  5  respectively. The linearly polarized light  5  is converted into circularly polarized light  6 , for example, right circularly polarized light shown in  FIG. 2 , after passing through the quarter-wave plate  12 . 
     The circularly polarized light  6  enters the functional substrate  30 . Part of the circularly polarized light  6  is reflected by the reflection units  33  of the functional substrate  30  and becomes reversely polarized light  7 , for example, left circularly polarized light shown in  FIG. 2 . The reversely polarized light  7  is emitted from the functional substrate  30  and enters the quarter-wave plate  12 . The reversely polarized light  7  is converted into linearly polarized light  8  after passing through the quarter-wave plate  12 . Obviously, a polarization angle of the linearly polarized light  8  is rotated by 90 degrees with respect to the linearly polarized light  5 . Because the linearly polarized light  8  is perpendicular to the absorption axis of the linear polarizing layer  13 , part of the linearly polarized light  8  cannot pass through the linear polarizing layer  13 , thereby reducing reflected light caused by the reflection units  33  in the laminated structure  10 . Part of the circularly polarized light  6  enters the optical fingerprint recognition module  103  through the light-transmitting area  31 . 
       FIG. 3  is a schematic diagram of absorption axes of laminated layers of the laminated structure in the first implementation of this application. The absorption axis of the protective layer  15  is a bidirectional absorption axis, the absorption axis of the linear polarizing layer  13  is a bidirectional absorption axis, and the absorption axis of the quarter-wave plate  12  is a unidirectional absorption axis. An inclination angle of the absorption axis of the protective layer  15  with respect to a first direction (for example, a Y direction shown in  FIG. 3 ) is defined as N degrees. The bidirectional absorption axis means that a laminated layer (for example, the protective layer  15  or the linear polarizing layer  13 ) has the same effects on light in a positive direction and a negative direction of the absorption axis. The unidirectional absorption axis means that a laminated layer (for example, the quarter-wave plate  12 ) has different effects on light in a direction positive and a negative direction of the absorption axis. For example, because the absorption axis of the protective layer  15  is the bidirectional absorption axis, the light intensity of light passing through the protective layer  15  is the same when the absorption axis of the protective layer  15  is inclined by 45 degrees and 135 degrees with respect to the first direction. Because the absorption axis of the quarter-wave plate  12  is the unidirectional absorption axis, the light intensity of light passing through the quarter-wave plate  12  is different when the absorption axis of the quarter-wave plate  12  is inclined by 45 degrees and 135 degrees with respect to the first direction. It may be understood that, the N degrees can be any angle. An angle between the absorption axis of the protective layer  15  and the first direction and an angle between the absorption axis of the linear polarizing layer  13  and the first direction (for example, the Y direction shown in  FIG. 3 ) are N degrees. An angle between the absorption axis of the quarter-wave plate  12  and a positive direction of the first direction is N−45 degrees. In this implementation, N is 45 degrees, that is, the absorption axis of the quarter-wave plate  12  is consistent with the positive direction of the first direction. The angle between the absorption axis of the quarter-wave plate  12  and the absorption axis of the protective layer  15  is 45 degrees. In other words, the angle between the absorption axis of the quarter-wave plate  12  and the positive direction of the first direction is zero degrees. 
     An example in which the electronic device  100  is a mobile phone is used below for description. 
       FIG. 4 a    is a schematic diagram of an application scenario when fingerprint recognition is performed by an electronic device according to an implementation of this application.  FIG. 4 b    is a schematic diagram when fingerprint recognition is performed by a partial structure of an electronic device according to an implementation of this application. A finger  200  touches a display panel  101  to enable the electronic device  100  to perform fingerprint recognition. The finger  200  is located on one side of a protective layer  15  away from a linear polarizing layer  13 , to facilitate an optical fingerprint recognition module  103  to perform fingerprint recognition. It may be understood that, there may also be a specific gap between the finger  200  and the protective layer  15 , and a surface of the finger  200  can reflect light to the display panel  101 . 
     External light  201  is incident from the protective layer  15  and transmitted to a functional substrate  30  through a reinforcing layer  17 , an optical adhesive layer  19 , the linear polarizing layer  13 , and a quarter-wave plate  12 . Part of the external light  201  is reflected by reflection units  33  into first reflected light  202 , and part of the external light  201  enters the optical fingerprint recognition module  103  through a light-transmitting area  31 . In actual application, only part of the first reflected light  202  cannot pass through the linear polarizing layer  13  after passing through the quarter-wave plate  12 , namely, is eliminated, while part of the first reflected light  202  can still be emitted from the protective layer  15  to reach the surface of the finger  200 . The first reflected light  202  emitted from the protective layer  15  is reflected by the surface of the finger  200  into second reflected light  203 . The second reflected light  203  enters the functional substrate  30  through the protective layer  15 , the reinforcing layer  17 , the optical adhesive layer  19 , the linear polarizing layer  13 , and the quarter-wave plate  12 , and is incident to the optical fingerprint recognition module  103  through the light-transmitting area  31  of the functional substrate  30 . 
     The reflection units  33  emit light  204 . The light  204  is emitted to the surface of the finger  200  through the quarter-wave plate  12 , the linear polarizing layer  13 , the optical adhesive layer  19 , the reinforcing layer  17 , and the protective layer  15 . The light  204  is reflected by the surface of the finger  200  into third reflected light  205 . The third reflected light  205  then enters the optical fingerprint recognition module  103  through the protective layer  15 , the reinforcing layer  17 , the optical adhesive layer  19 , the linear polarizing layer  13 , the quarter-wave plate  12 , and the light-transmitting area  31  of the functional substrate  30 . The optical fingerprint recognition module  103  performs fingerprint recognition. 
     An angle between an absorption axis of the protective layer  15  and an absorption axis of the linear polarizing layer  13  is zero degrees, and a luminous flux of the reflected light (for example, the second reflected light  203  or the third reflected light  205 ) reflected from the surface of the finger  200  after passing through the protective layer  15  is roughly the same as that after passing through the linear polarizing layer  13 . In other words, the light intensity of light passing through the protective layer  15  is consistent with that of light passing through the linear polarizing layer  13 , to stabilize the light intensity of light passing through the display panel  101 , and improve the stability of the light passing through the display panel  101 , thereby improving the recognition precision of the optical fingerprint recognition module  103 . 
       FIG. 5  a flowchart of a method for preparing a laminated structure according to an implementation of this application. The method for preparing a laminated structure includes the following steps: 
     Step  501 : Provide a quarter-wave plate, a linear polarizing layer and a protective layer. 
     Step  502 : Attach the linear polarizing layer to the quarter-wave plate, and arrange the protective layer on one side of the linear polarizing layer away from the quarter-wave plate, so that the protective layer, the linear polarizing layer and the quarter-wave plate are laminated, where the protective layer is used to polarize light to form linearly polarized light, an angle between an absorption axis of the protective layer and an absorption axis of the linear polarizing layer is zero degrees, and an angle between the absorption axis of the linear polarizing layer and an absorption axis of the quarter-wave plate is 45 degrees. 
     In an implementation, the arranging the protective layer on one side of the linear polarizing layer away from the quarter-wave plate includes: arranging a reinforcing layer on one side of the linear polarizing layer away from the quarter-wave plate, and arranging the protective layer on one side of the reinforcing layer away from the linear polarizing layer. 
     In another implementation, the arranging a reinforcing layer on one side of the linear polarizing layer away from the quarter-wave plate includes: fixing the reinforcing layer on the linear polarizing layer through an optical adhesive layer. 
     Embodiment 2 
       FIG. 6  is a schematic diagram of absorption axes of laminated layers of a display panel according to a second implementation of this application. The display panel provided in the second implementation is roughly the same as the display panel provided in the first implementation, except that an angle between an absorption axis of a quarter-wave plate  12  and a positive direction of a first direction is N+45 degrees, where N is 45 degrees. In this case, the angle between the absorption axis of the quarter-wave plate  12  and the positive direction of the first direction is 90 degrees, and an angle between an absorption axis of a protective layer  15  and the absorption axis of the quarter-wave plate  12  is 45 degrees. 
     The protective layer  15  can polarize light incident therein to form linearly polarized light, an angle between an absorption axis of a linear polarizing layer  13  and the absorption axis of the protective layer  15  is zero degrees, and there is no difference between a direction of the absorption axis of the protective layer  15  and a direction of the absorption axis of the linear polarizing layer  13 . Therefore, a luminous flux of light passing through the protective layer  15  is roughly the same as that of light passing through the linear polarizing layer  13 . In other words, the light intensity of the light passing through the protective layer  15  is consistent with that of the light passing through the linear polarizing layer  13 , and the stability of light passing through the display panel is improved, to stabilize the light intensity of the light passing through the display panel, and improve the stability of light entering an optical fingerprint recognition module, thereby improving the recognition precision of the optical fingerprint recognition module. 
     Embodiment 3 
       FIG. 7  is a schematic diagram of absorption axes of laminated layers of a display panel according to a third implementation of this application. The display panel provided in the third implementation is roughly the same as the display panel provided in the first implementation, except that an angle between an absorption axis of a quarter-wave plate  12  and a positive direction of a first direction is N+3×45 degrees, where N is 45 degrees. In this case, the angle between the absorption axis of the quarter-wave plate  12  and the positive direction of the first direction is 180 degrees, and an angle between an absorption axis of a protective layer  15  and the absorption axis of the quarter-wave plate  12  is 45 degrees. 
     Embodiment 4 
       FIG. 8  is a schematic diagram of absorption axes of laminated layers of a display panel according to the fourth implementation of this application. The display panel provided in the fourth implementation is roughly the same as the display panel provided in the first implementation, except that an angle between an absorption axis of a quarter-wave plate  12  and a positive direction of a first direction is N+5×45 degrees, where N is 45 degrees. In this case, the angle between the absorption axis of the quarter-wave plate  12  and the positive direction of the first direction is 270 degrees, and an angle between an absorption axis of a protective layer  15  and the absorption axis of the quarter-wave plate  12  is 45 degrees. 
     Embodiment 5 
       FIG. 9  is a schematic diagram of an absorption axis of a laminated structure according to a fifth implementation of this application. A laminated structure of a display panel provided in the fifth implementation is roughly the same as that of the display panel provided in the first implementation, except that an inclination angle of an absorption axis of a protective layer  15  with respect to a first direction (for example, a Y direction shown in  FIG. 9 ) is 90 degrees, namely, N is 90 degrees, an inclination angle of an absorption axis of a linear polarizing layer  13  with respect to the first direction (for example, the Y direction shown in  FIG. 9 ) is 90 degrees, and an angle between an absorption axis of a quarter-wave plate  12  and a positive direction of the first direction is N−45 degrees. In this case, the angle between the absorption axis of the quarter-wave plate  12  and the positive direction of the first direction is 45 degrees, and an angle between the absorption axis of the protective layer  15  and the absorption axis of the quarter-wave plate  12  is 45 degrees. 
     Embodiment 6 
       FIG. 10  is a schematic diagram of an absorption axis of a laminated structure according to a sixth implementation of this application. A laminated structure of a display panel provided in the sixth implementation is roughly the same as that of the display panel provided in the first implementation, except that an inclination angle of an absorption axis of a protective layer  15  with respect to a first direction (for example, a Y direction shown in  FIG. 10 ) is 90 degrees, namely, N is 90 degrees, an inclination angle of an absorption axis of a linear polarizing layer  13  with respect to the first direction (for example, the Y direction shown in  FIG. 10 ) is 90 degrees, and an angle between an absorption axis of a quarter-wave plate  12  and a positive direction of the first direction is N+45 degrees. In this case, the angle between the absorption axis of the quarter-wave plate  12  and the positive direction of the first direction is 135 degrees, and an angle between the absorption axis of the protective layer  15  and the absorption axis of the quarter-wave plate  12  is 45 degrees. 
     Embodiment 7 
       FIG. 11  is a schematic diagram of an absorption axis of a laminated structure according to a seventh implementation of this application. A laminated structure of a display panel provided in the seventh implementation is roughly the same as that of the display panel provided in the first implementation, except that an inclination angle of an absorption axis of a protective layer  15  with respect to a first direction (for example, a Y direction shown in  FIG. 11 ) is 90 degrees, namely, N is 90 degrees, an inclination angle of an absorption axis of a linear polarizing layer  13  with respect to the first direction (for example, the Y direction shown in  FIG. 11 ) is 90 degrees, and an angle between an absorption axis of a quarter-wave plate  12  and a positive direction of the first direction is N+3×45 degrees. In this case, the angle between the absorption axis of the quarter-wave plate  12  and the positive direction of the first direction is 225 degrees (also 135 degrees), and an angle between the absorption axis of the protective layer  15  and the absorption axis of the quarter-wave plate  12  is 45 degrees. 
     The foregoing descriptions are merely specific implementations of the present invention, but are not intended to limit the protection scope of the present invention. Any variation or replacement readily figured out by a person skilled in the art within the technical scope disclosed in the present invention shall fall within the protection scope of the present invention Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.