Display substrate and display device

Abstract

A display substrate and a display device, the display substrate comprising a light emitting element disposed on a substrate, and a packaging layer, a connecting layer, a light extraction layer, a polarization conversion layer and a polarizing layer sequentially stacked on a light emitting side of the light emitting element; the light extraction layer is configured to convert at least part of the light emitted by the light emitting element and incident on the light extraction layer into circularly polarized light of a set handedness and transmit; the polarization conversion layer is configured to convert the circularly polarized light transmitted by the light extraction layer into linearly polarized light, the polarization direction of the linearly polarized light is parallel to the direction of the light transmission axis of the polarizing layer; the connecting layer is configured to bond the light extraction layer and the packaging layer, the thickness of the connecting layer is greater than 3 times the thickness of the light extraction layer, and the difference between the refractive index of the connecting layer and the refractive index of the film layer of the packaging layer close to the connecting layer is greater than 0.25.

Description

TECHNICAL FIELD

[0001] The embodiment of the present disclosure relates to, but is not limited to, the technical field of display, in particular to a display substrate and a display device. BACKGROUND

[0002] Active matrix organic light emitting diode (AMOLED for short) is widely used in terminal display products with high-resolution color screen due to its self-emission, high contrast, wide viewing angle, high color gamut, fast response speed, low power consumption and other advantages. Some organic electroluminescent diode (OLED) display panels use electrodes with strong reflection characteristics, which will greatly reduce the contrast of the panel under bright field of view due to strong reflection of external light. Therefore, an anti-reflection optical structure is usually used to improve the visibility of the panel. However, the general anti-reflection film structure contains a linear polarizer, which will cause a great loss (not less than 50%) of the luminous intensity of the panel itself, and further cause many problems such as power consumption increase and service life loss. SUMMARY

[0003] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0004] The embodiment of the present disclosure provides a display substrate, comprising a light emitting element disposed on a substrate, and a packaging layer, a connecting layer, a light extraction layer, a polarization conversion layer and a polarizing layer which are sequentially disposed on the light emitting side of the light emitting element; the light extraction layer is configured to convert at least part of the light emitted by the light emitting element and incident on the light extraction layer into circularly polarized light of a set handedness and transmit the circularly polarized light; the polarization conversion layer is configured to convert the circularly polarized light transmitted by the light extraction layer into linearly polarized light, the polarization direction of the linearly polarized light being parallel to the transmission axis direction of the polarizing layer; the connecting layer is configured to bond the light extraction layer and the packaging layer, the thickness of the connecting layer being greater than 3 times the thickness of the light extraction layer, and the difference between the refractive index of the connecting layer and the refractive index of the film layer of the packaging layer close to the connecting layer being greater than 0.25.

[0005] The embodiment of the present disclosure also provides a display device comprising the display substrate.

[0006] Other aspects can become apparent after reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0007] The accompanying drawings are included to provide a further understanding of the technical solutions of the present disclosure, and constitute a part of the specification, and are used together with the embodiments of the present disclosure to explain the technical solutions of the present disclosure, and do not constitute a limitation on the technical solutions of the present disclosure. The shapes and sizes of the components in the drawings do not reflect the true proportions, and the purpose is only to schematically illustrate the present disclosure.

[0008] Figure 1A schematic diagram of a film layer structure of a display substrate of some example embodiments;

[0009] Figure 2 A schematic diagram of a cross-sectional structure of a display substrate in some example embodiments Figure 1

[0010] Figure 3 A schematic diagram of light emitted by light emitting elements of a red sub-pixel, a green sub-pixel and a blue sub-pixel of a display substrate of some example embodiments sequentially passing through a light extraction layer, a polarization conversion layer, a one-half phase retardation film and a polarizing layer;

[0011] Figure 4 A graph of wavelength dispersion of three different polarization conversion film materials;

[0012] Figure 5a A light emission effect diagram of ambient light from a polarizing layer being incident into a display substrate and being emitted from a one-quarter phase retardation film having positive wavelength dispersion;

[0013] Figure 5b A light emission effect diagram of ambient light from a polarizing layer being incident into a display substrate and being emitted from a one-quarter phase retardation film having negative wavelength dispersion;

[0014] Figure 6 A transmittance graph of a display substrate of some example embodiments using a connection layer of different thicknesses;

[0015] Figure 7 A transmittance graph of a display substrate of some example embodiments using a connection layer of different thicknesses.

[0016] Reference signs:

[0017] 101, substrate, 102, drive circuit layer, 103, light emitting structure layer, 210, drive transistor, 211, storage capacitor;

[0018] 301, anode, 302, hole injection layer, 303, hole transport layer, 3041, electron blocking layer of a red sub-pixel, 3042, electron blocking layer of a green sub-pixel, 3043, electron blocking layer of a blue sub-pixel, 3051, light emitting layer of a red sub-pixel, 3052, light emitting layer of a green sub-pixel, 3053, light emitting layer of a blue sub-pixel, 306, hole blocking layer, 307, electron transport layer, 308, electron injection layer, 309, cathode;

[0019] 310, light emitting element, 510, pixel definition layer;

[0020] ​601, encapsulation layer, 602, connection layer, 603, light extraction layer, 604, polarization conversion layer, 605, half phase retardation film, 606, polarizing layer. DETAILED DESCRIPTION

[0021] Those skilled in the art should understand that the technical solutions of the embodiments of the present disclosure can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the embodiments of the present disclosure, and all modifications and equivalent replacements should be included in the scope of the claims of the present disclosure.

[0022] The embodiments of the present disclosure provide a display substrate, as shown in Figure 1 , Figure 2 and Figure 3 , Figure 1 is a schematic diagram of a film layer structure of a display substrate of some exemplary embodiments, Figure 2 is a schematic diagram of a cross-sectional structure of a display substrate of some exemplary embodiments, Figure 1 , and Figure 3 is a schematic diagram of light emitted by light emitting elements of red sub-pixels, green sub-pixels and blue sub-pixels of a display substrate of some exemplary embodiments in turn passing through a light extraction layer, a polarization conversion layer, a half phase retardation film and a polarizing layer. The display substrate includes light emitting elements 310 (shown in Figure 2 ) disposed on a substrate 101, and an encapsulation layer 601, a connection layer 602, a light extraction layer 603, a polarization conversion layer 604 and a polarizing layer 606 sequentially stacked on the light emitting side of the light emitting elements 310; the light extraction layer 603 is configured to convert at least a portion of the light emitted by the light emitting elements 310 incident on the light extraction layer 603 into circularly polarized light of a set handedness and transmit the circularly polarized light; the polarization conversion layer 604 is configured to convert the circularly polarized light transmitted through the light extraction layer 603 into linearly polarized light, the polarization direction of the linearly polarized light being parallel to the direction of the light transmission axis of the polarizing layer 606; the connection layer 602 is configured to bond the light extraction layer 603 and the encapsulation layer 601, the thickness of the connection layer 602 being greater than 3 times the thickness of the light extraction layer 603, and the difference between the refractive index of the connection layer 602 and the refractive index of the film layer of the encapsulation layer 601 close to the connection layer 602 being greater than 0.25.

[0023] In this embodiment of the display substrate, the light extraction layer 603 is configured to convert at least a portion of the light emitted by the light-emitting element 310 incident on the light extraction layer 603 into circularly polarized light with a predetermined rotation direction and allow it to pass through. The circularly polarized light passing through the light extraction layer 603 can be converted into linearly polarized light after passing through the polarization conversion layer 604. The polarization direction of the linearly polarized light is parallel to the light transmission axis direction of the polarization layer 606. Thus, the linearly polarized light can pass through the polarization layer 606 with almost no loss. In this way, compared with some technologies where the light emitted by the light-emitting element 310 is emitted from the polarization layer 606 without polarization modulation, light loss can be reduced, the light extraction efficiency of the display substrate can be improved, thereby increasing the brightness of the display substrate and reducing power consumption. Furthermore, by setting the thickness of the connecting layer 602 to be greater than three times the thickness of the light extraction layer 603, the difference between the refractive index of the connecting layer 602 and the refractive index of the film layer of the encapsulation layer 601 near the connecting layer 602 is greater than 0.25. This helps to reduce light loss when passing through the connecting layer 602, improve the light extraction efficiency of the display substrate, and also reduce the interference fringes generated by ambient light after it is incident on the display substrate, thereby improving the anti-reflection effect of the display substrate.

[0024] In some exemplary embodiments, such as Figure 1 As shown, the refractive index of the connecting layer 602 can be from 1.35 to 1.65. The thickness of the connecting layer 602 can be from 5 μm to 40 μm, and the thickness of the light extraction layer 603 can be from 1 μm to 30 μm. The connecting layer 602 can assist in light extraction and also serve to bond the encapsulation layer 601 and the light extraction layer 603.

[0025] In some exemplary embodiments, such as Figure 1 and Figure 2 As shown, the display substrate may include a variety of sub-pixels configured to display different colors, and each sub-pixel includes a light-emitting element. Figure 1 The diagram illustrates three color sub-pixels: red sub-pixel R, green sub-pixel G, and blue sub-pixel B. Taking blue sub-pixel B as an example, the light-emitting element 310 may include an anode 301, a light-emitting layer 3053, and a cathode 309 sequentially stacked along a direction away from the substrate 101. Figure 3As shown, the light extraction layer 603 is further configured to convert another portion of the light emitted by the light emitting element 310 incident on the light extraction layer 603 into circularly polarized light of the opposite handedness to the set handedness and reflect the same. The circularly polarized light of the opposite handedness reflected by the light extraction layer 603 is converted into circularly polarized light of the same handedness after being reflected by the cathode 309 and can be transmitted through the light extraction layer 603. In this way, the circularly polarized light reflected by the light extraction layer 603 can be recycled by the reflection of the cathode 309, reducing light loss and improving light extraction efficiency. In other embodiments, a reflective layer can be provided on the side of the cathode 309 facing away from the substrate 101 to reflect the circularly polarized light reflected by the light extraction layer 603.

[0026] In one example of the present embodiment, as shown in Figure 1 and Figure 2 The light emitting element 310 can be a top-emitting OLED device. The anode 301 of the top-emitting OLED device can have a composite film layer structure of a high-reflectivity high-work-function metal layer and a transparent metal oxide layer, such as Ag / ITO (silver / indium tin oxide), Ag / IZO (silver / indium zinc oxide), or ITO / Ag / ITO, etc. The thickness of the metal layer can be 80-100 nm, and the thickness of the metal oxide layer can be 5-10 nm. The average reflectivity of the anode 301 in the visible light region can be 85-95%. The anode 301 can be formed by magnetron sputtering, etching, or other processes. The cathode 309 can be made of a metal material, such as magnesium, silver, or aluminum, or an alloy material (such as a magnesium-silver alloy, with a magnesium-to-silver ratio of 3:7 to 1:9); the cathode 309 can have a transmittance of 50-60% for light of 530 nm, forming a semi-transparent cathode; or the cathode 309 can be made of a transparent oxide ITO, IZO, IGZO (indium gallium zinc oxide), or other material to form a transparent cathode. The cathode 309 can be formed by vacuum deposition, and the thickness of the cathode 309 can be 10-20 nm. The material of the light emitting layer can include a host material and a fluorescent guest material. To improve the transportability of electrons and holes in the OLED device, taking the red sub-pixel R as an example, a hole injection layer 302, a hole transport layer 303, and an electron blocking layer 3041 can be sequentially stacked between the anode 301 and the light emitting layer 3051, and a hole blocking layer 306, an electron transport layer 307, and an electron injection layer 308 can be sequentially stacked between the light emitting layer 3051 and the cathode 309. All the film layers between the anode 301 and the cathode 309 can be referred to as organic functional layers.

[0027] In one example of the present embodiment, as shown in Figure 1 and Figure 2As shown, the light extraction layer 603 may include a cholesteric liquid crystal material (or a chiral nematic liquid crystal) having a cured chiral direction (e.g., left-handed). Exemplarily, the light extraction layer 603 includes a cholesteric liquid crystal layer, which may be a polymer-stabilized cholesteric liquid crystal film with a fixed chiral direction, formed by photocuring a mixture of a nematic liquid crystal monomer containing photopolymerization properties and a chiral agent (the doping ratio of the chiral agent may be less than 20%, for example, less than 10%). The prepared cholesteric liquid crystal film is adhered to the surface of the encapsulation layer 601 facing away from the substrate 101 via a connecting layer 602. The light extraction layer 603 may not contain substrates such as PET (polyethylene terephthalate) or PMMA (polymethyl methacrylate).

[0028] like Figure 3 As shown, the cholesteric liquid crystal layer (light extraction layer 603) can be configured to convert a portion (50%) of the natural light incident on the cholesteric liquid crystal layer within a set wavelength range (e.g., blue light) into circularly polarized light with the opposite chiral direction (e.g., right-handed) and transmit it, and to convert another portion (50%) of the natural light within the set wavelength range into circularly polarized light with the same chiral direction (e.g., left-handed) and reflect it; the circularly polarized light reflected by the cholesteric liquid crystal layer with the same chiral direction (e.g., left-handed) is reflected by the cathode 309 and its rotation direction is reversed (e.g., left-handed is reversed to right-handed), becoming circularly polarized light (e.g., right-handed) that can pass through the cholesteric liquid crystal layer. If the reflectivity of the cathode 309 is calculated to be 50%, approximately 75% or more of the light emitted by the light-emitting element 310 can pass through the cholesteric liquid crystal layer and has a fixed rotation direction (e.g., right-handed) circular polarization characteristic. Circularly polarized light extracted by the light extraction layer 603 is converted into linearly polarized light after passing through the polarization conversion layer 604. The polarization direction of this linearly polarized light is parallel to the transmission axis of the polarizing layer 606. Therefore, natural light within the set wavelength range (e.g., blue light) can pass through the polarizing layer 606 almost without loss. The cholesteric liquid crystal layer can also be configured to not produce a polarization state change for natural light incident on the cholesteric liquid crystal layer outside the set wavelength range (e.g., red and green light). That is, natural light outside the set wavelength range remains natural light after being incident on and passed through the cholesteric liquid crystal layer.

[0029] In some display substrate technologies, phosphorescent materials are used for the light-emitting materials of red and green OLED devices, while fluorescent materials are used for blue OLED devices due to lifespan limitations. Because of the difference in the light-emitting mechanisms of phosphorescent and fluorescent materials, the fluorescence efficiency is much lower than the phosphorescence efficiency. Therefore, the blue light emission efficiency of the display substrate is much lower than that of red and green light. Some technologies have attempted to improve the blue light emission efficiency of the display substrate by optimizing the light-emitting system of the blue light-emitting material, but it is difficult to balance the efficiency and lifespan of blue OLED devices, thus failing to meet mass production requirements.

[0030] In this embodiment, the light extraction layer 603 can be configured to convert light with a wavelength range of 400nm to 500nm into circularly polarized light with the predetermined rotation direction and allow it to pass through; the light extraction layer 603 has a transmittance of 35% to 65% (e.g., 40% to 55%) for light with a wavelength range of 400nm to 500nm, and a transmittance of greater than 90% (e.g., greater than 95%) for light with a wavelength greater than 500nm. Thus, since 400nm to 500nm is the wavelength range of blue light, therefore, as... Figure 3 As shown, the light extraction layer 603 can convert a portion of the blue light emitted by the blue OLED device in the wavelength range of 400nm to 500nm into circularly polarized light with the set rotation direction and transmit it, while converting the other portion into circularly polarized light with the opposite rotation direction and reflecting it. This improves the blue light extraction efficiency of the display substrate. The light extraction layer 603 does not cause a polarization state change for red light emitted by red OLED devices or green light emitted by green OLED devices; the red and green light remain natural light after passing through the light extraction layer 603, and the transmittance of the light extraction layer 603 for red and green light can be greater than 90%.

[0031] In some exemplary embodiments, such as Figure 1 and Figure 2 As shown, the polarization conversion layer 604 can be a quarter-phase retardation film. This quarter-phase retardation film can exhibit inverse wavelength dispersion, meaning that as the wavelength of the incident light increases, the optical path difference between the o-ray (ordinary ray) and e-ray (extraordinary ray) generated by the quarter-phase retardation film after birefringence of the incident light increases. Correspondingly, the optical path difference ratio R / R0 increases, where R is the optical path difference between the o-ray and e-ray generated by the quarter-phase retardation film after birefringence of the incident light, and R0 is the optical path difference between the o-ray and e-ray generated by the quarter-phase retardation film after birefringence of the incident light with a center wavelength (e.g., 580nm green light). Figure 4 As shown, Figure 4The wavelength dispersion curves of three different polarization conversion film materials, wherein the optical path difference ratio R / R0 of the polarization conversion film material a and the polarization conversion film material b increases with the increase of the wavelength of the incident light, and has inverse wavelength dispersion; the optical path difference ratio R / R0 of the polarization conversion film material c decreases with the increase of the wavelength of the incident light, and has positive wavelength dispersion.

[0032] If the quarter phase retardation film has positive wavelength dispersion, when the ambient light is incident from the polarizing layer into the display substrate and is emitted from the polarization conversion layer, the central wavelength (such as 580 nm) of the quarter phase retardation film is green light, so the emitted green light is close to circularly polarized light, and the emitted red light and blue light are both elliptically polarized light, as shown in Figure 5a Figure 5a The emitted red light and blue light from the polarization conversion layer are elliptically polarized light, which is reflected by the cathode, and then is still elliptically polarized light after passing through the polarization conversion layer. When the elliptically polarized light passes through the polarizing layer, part of the light is emitted from the polarizing layer, and cannot achieve good anti-reflection effect. In the embodiment, the quarter phase retardation film has inverse wavelength dispersion, so that when the ambient light is incident from the polarizing layer into the display substrate and is emitted from the polarization conversion layer, the emitted red light, blue light and green light are all close to circularly polarized light, as shown in Figure 5b Figure 5b The emitted red light and blue light from the polarization conversion layer are elliptically polarized light, which is reflected by the cathode, and then is still elliptically polarized light after passing through the polarization conversion layer. When the elliptically polarized light passes through the polarizing layer, part of the light is emitted from the polarizing layer, and cannot achieve good anti-reflection effect. In the embodiment, the quarter phase retardation film has inverse wavelength dispersion, so that when the ambient light is incident from the polarizing layer into the display substrate and is emitted from the polarization conversion layer, the emitted red light, blue light and green light are all close to circularly polarized light, as shown in Figure 5b

[0033] In one example of the embodiment, the quarter phase retardation film can satisfy: 0.78 B / R0<1.1, 0.9 G / R0<1.1, 1 R / R0<1.1;

[0034] R0 is the optical path difference between the o light and the e light generated by the birefringence of the quarter phase retardation film to the incident light of the central wavelength (such as green light of 580 nm); R B is the optical path difference between the o light and the e light generated by the birefringence of the quarter phase retardation film to the incident blue light; R G is the optical path difference between the o light and the e light generated by the birefringence of the quarter phase retardation film to the incident green light; and R​R The optical path difference between the o light and the e light generated by the birefringence of the quarter phase retardation film to the incident red light.

[0035] In some example embodiments, as shown in Figure 1 and Figure 2 The display substrate can further include a half phase retardation film 605 between the polarization conversion layer 604 and the polarizing layer 606, so that when the ambient light is incident from the polarizing layer 606 into the display substrate, the light emitted by the red light, the blue light and the green light will be closer to circularly polarized light after sequentially passing through the half phase retardation film 605 and the quarter phase retardation film with reverse wavelength dispersion, and then the circularly polarized light is reflected by the cathode 309 and finally absorbed by the polarizing layer 606, which can increase the anti-reflection effect.

[0036] For example, the polarizing layer 606, the half phase retardation film 605 and the polarization conversion layer (quarter phase retardation film) 604 satisfy: β-2α=45°; wherein α is the angle between the optical axis of the half phase retardation film 605 and the transmission axis of the polarizing layer 606, and β is the angle between the optical axis of the polarization conversion layer 604 and the transmission axis of the polarizing layer 606; or α is the angle between the optical axis of the half phase retardation film 605 and the absorption axis of the polarizing layer 606, and β is the angle between the optical axis of the polarization conversion layer 604 and the absorption axis of the polarizing layer 606. In this way, it can be ensured that the ambient light can form circularly polarized light after sequentially passing through the polarizing layer 606, the half phase retardation film 605 and the polarization conversion layer 604.

[0037] In some example embodiments, the quarter phase retardation film and the half phase retardation film can be a liquid crystal material layer or a polymer film layer. The liquid crystal material can adopt discotic liquid crystal or cholesteric liquid crystal material, which can be prepared into a film by coating.

[0038] In some example embodiments, as shown in Figure 1 and Figure 2 The packaging layer 601 includes a plurality of film layers stacked together, and the refractive index of the packaging layer 601 can alternately increase and decrease along the direction away from the substrate 101. In this way, it is beneficial to the coupling output of the light emitted by the light emitting element 310, improves the light extraction efficiency of the display substrate, and also improves the normal viewing angle brightness of the display substrate; in addition, it can also improve the reflection characteristics of the cathode 309, which is helpful to recycle the circularly polarized light reflected by the light extraction layer 603, thereby improving the light extraction efficiency of the display substrate.

[0039] In one example of the embodiment, the refractive index of one of the two adjacent film layers in the encapsulation layer is 1.3 to 1.7, and the refractive index of the other film layer is 1.7 to 2.3.

[0040] In some example embodiments, the light-emitting element comprises, in sequence from the direction away from the substrate, an anode, a light-emitting layer, and a cathode; the display substrate further comprises a cover layer (CPL) disposed between the cathode and the encapsulation layer (TFE); the encapsulation layer can comprise, in sequence from the direction away from the substrate, a first inorganic encapsulation layer, an organic encapsulation layer, and a second inorganic encapsulation layer; the first inorganic encapsulation layer can comprise one or more film layers, when the first inorganic encapsulation layer comprises one film layer, the refractive index of the first inorganic encapsulation layer is higher than the refractive index of the organic encapsulation layer; when the first inorganic encapsulation layer comprises multiple film layers, the refractive index of the film layer in the first inorganic encapsulation layer close to the organic encapsulation layer is higher than the refractive index of the organic encapsulation layer.

[0041] In one example of the embodiment, the difference between the refractive index of the cover layer and the refractive index of the film layer in the encapsulation layer close to the cover layer can be greater than 0.1.

[0042] In one example of the embodiment, the first inorganic encapsulation layer comprises one film layer, and the refractive index of the first inorganic encapsulation layer can be higher than the refractive index of the cover layer (which can be one film layer); or, the cover layer can comprise, in sequence from the direction away from the substrate, a first sub-cover layer and a second sub-cover layer, the refractive index of the first sub-cover layer is higher than the refractive index of the second sub-cover layer, and the refractive index of the second sub-cover layer is lower than the refractive index of the first inorganic encapsulation layer. Illustratively, the material of the cover layer is an aromatic amine or a xanthene organic material (illustratively, the refractive index of the first sub-cover layer and the second sub-cover layer can be adjusted by adjusting the difference in molecular structure of the organic material forming the first sub-cover layer and the second sub-cover layer), the material of the first inorganic encapsulation layer is silicon nitride or silicon oxynitride, the material of the organic encapsulation layer is a resin material, and the material of the second inorganic encapsulation layer is silicon nitride or silicon oxynitride. Illustratively, when the cover layer is one film layer, the refractive index of the cover layer can be 1.3 to 1.7, or the cover layer comprises the first sub-cover layer and the second sub-cover layer, the refractive index of the first sub-cover layer can be 1.7 to 2.3, and the refractive index of the second sub-cover layer can be 1.3 to 1.7; the refractive index of the first inorganic encapsulation layer can be 1.7 to 2.3, the refractive index of the organic encapsulation layer can be 1.3 to 1.7, and the refractive index of the second inorganic encapsulation layer can be 1.7 to 2.3. In this example, the refractive index of the composite structure layer formed by the combination of the cover layer and the encapsulation layer alternates in height along the direction away from the substrate.

[0043] In one example of this embodiment, the first inorganic encapsulation layer may include a first sub-inorganic encapsulation layer and a second sub-inorganic encapsulation layer sequentially stacked along a direction away from the substrate. The refractive index of the first sub-inorganic encapsulation layer may be lower than that of the second sub-inorganic encapsulation layer; the refractive index of the capping layer is higher than that of the first sub-inorganic encapsulation layer. Exemplarily, the material of the first sub-inorganic encapsulation layer may be lithium fluoride or silicon dioxide, the material of the second sub-inorganic encapsulation layer may be silicon nitride or silicon oxynitride, the material of the organic encapsulation layer is a resin material, and the material of the second inorganic encapsulation layer is silicon nitride or silicon oxynitride; the material of the capping layer may be an aromatic amine or a azine organic material. Wherein, the thickness of the capping layer is 50 nm to 150 nm, the thickness of the first sub-inorganic encapsulation layer is 40 nm to 100 nm, the thickness of the second sub-inorganic encapsulation layer is 500 nm to 2000 nm, the thickness of the organic encapsulation layer is 5000 nm to 20000 nm, and the thickness of the second inorganic encapsulation layer is 400 nm to 1000 nm. For example, the thickness of the capping layer is 80nm to 100nm, the thickness of the first sub-inorganic encapsulation layer is 50nm to 70nm, the thickness of the second sub-inorganic encapsulation layer is 800nm ​​to 1200nm, the thickness of the organic encapsulation layer is 8000nm to 12000nm, and the thickness of the second inorganic encapsulation layer is 500nm to 700nm. The total transmittance of the composite structure layer formed by the combination of the capping layer and the encapsulation layer to visible light can be no less than 90%. Alternatively, the materials of the first and second sub-inorganic encapsulation layers can both be silicon oxynitride, and the refractive index of the first and second sub-inorganic encapsulation layers can be adjusted by regulating the ratio of nitrogen to oxygen in the silicon oxynitride forming the first and second sub-inorganic encapsulation layers. For example, the refractive index of the capping layer can be from 1.7 to 2.3, the refractive index of the first sub-inorganic encapsulation layer can be from 1.3 to 1.7, the refractive index of the second sub-inorganic encapsulation layer can be from 1.7 to 2.3, the refractive index of the organic encapsulation layer can be from 1.3 to 1.7, and the refractive index of the second inorganic encapsulation layer can be from 1.7 to 2.3. In this example, the refractive index of the composite structure layer formed by the combination of the capping layer and the encapsulation layer alternates between high and low along the direction away from the substrate.

[0044] In some exemplary embodiments, such as Figure 1 and Figure 2 As shown, the encapsulation layer 601 may include three or more stacked film layers, wherein the difference between the refractive index of at least one film layer in the encapsulation layer 601 and the refractive index of the connecting layer 602 is less than or equal to 0.2, and the refractive index of at least two film layers in the encapsulation layer 601 is greater than 1.65.

[0045] The following compares the effects of different thicknesses of the bonding layer on the light transmittance and anti-reflection effect of the display substrate.

[0046] Example 1: OLED light-emitting element / encapsulation layer / connection layer 1 (10μm) / light extraction layer (5μm) / polarization conversion layer / polarizing layer

[0047] Example 2: OLED light-emitting element / encapsulation layer / connection layer 2 (25μm) / light extraction layer (5μm) / polarization conversion layer / polarizing layer

[0048] Film structure 1: Polarizing layer / polarization conversion layer / light extraction layer / connector layer 1 (thickness is twice that of the light extraction layer)

[0049] Film structure 2: Polarizing layer / polarization conversion layer / light extraction layer / connector layer 2 (thickness is 5 times that of the light extraction layer)

[0050] like Figure 6 As shown, Figure 6 The figures show the transmittance curves of the display substrates in Examples 1 and 2. Curve A1 represents the transmittance curve of the display substrate in Example 1, and curve A2 represents the transmittance curve of the display substrate in Example 2. It can be seen that the transmittance of the display substrate in Example 2 is significantly higher than that of the display substrate in Example 1. Furthermore, in the blue light wavelength range of 420nm to 500nm, the increase in transmittance of the display substrate in Example 2 is even greater than that of the display substrate in Example 1, which is more conducive to improving the blue light extraction efficiency.

[0051] like Figure 7 As shown, Figure 7 The above-mentioned transmittance curves of film structure 1 and film structure 2 to ambient light are shown. Curve A1 is the transmittance curve of film structure 1 to ambient light, and curve A2 is the transmittance curve of film structure 2 to ambient light. It can be seen that when ambient light is incident, film structure 1 shows obvious interference fringes, while film structure 2 does not show obvious interference fringes. Therefore, film structure 2 has a better anti-reflection effect than film structure 1.

[0052] In some exemplary embodiments, such as Figure 1 and Figure 2 As shown, the display substrate includes a display area, which includes multiple pixel units arranged in an array. Each pixel unit includes a red sub-pixel R, a green sub-pixel G, and a blue sub-pixel B. Each sub-pixel includes a light-emitting element 310. Any one of the following film layers of all sub-pixels in the display area is connected into an integral structure and covers the display area: the encapsulation layer 601, the connection layer 602, the light extraction layer 603, the polarization conversion layer 604, and the polarizing layer 606.

[0053] In some example embodiments, as shown in Figure 1 and Figure 2 The display substrate includes, in sequence, a driving circuit layer 102, a light emitting structure layer 103, an encapsulation layer 601, a connecting layer 602, a light extraction layer 603, a polarization conversion layer 604, a half phase retardation film 605, and a polarizing layer 606 on the substrate 101. The driving circuit layer 102 includes a plurality of pixel driving circuits, and the light emitting structure layer 103 includes a plurality of light emitting elements 310, each of which is connected to a corresponding pixel driving circuit. The display substrate can include a plurality of pixel units arranged in an array, each of which can include sub-pixels of multiple colors, and a plurality of sub-pixels of the same color can be referred to as the same kind of sub-pixel, and each sub-pixel includes a light emitting element 310. For example, the light emitting element 310 is a top-emitting OLED device, and each pixel unit includes sub-pixels of three colors, such as a red sub-pixel R, a green sub-pixel G, and a blue sub-pixel B, and the light emitting element 310 of each color sub-pixel emits light of the display color of the sub-pixel, such as the light emitting element (which can be referred to as a red light emitting element) 310 of the red sub-pixel R emitting red light.

[0054] In some example embodiments, the substrate 101 can be glass, transparent polyimide, or other hard or flexible substrates, and the refractive index can be 1.3 to 1.5.

[0055] In some example embodiments, as shown in Figure 2 The driving circuit layer 102 can include a plurality of transistors and a storage capacitor constituting a pixel driving circuit, Figure 2 For example, in some embodiments, the driving circuit layer 102 can include a first insulating layer disposed on the substrate 101, an active layer disposed on the first insulating layer, a second insulating layer covering the active layer, a gate electrode and a first capacitor electrode disposed on the second insulating layer, a third insulating layer covering the gate electrode and the first capacitor electrode, a second capacitor electrode disposed on the third insulating layer, a fourth insulating layer covering the second capacitor electrode, a via hole formed in the second, third, and fourth insulating layers to expose the active layer, a source electrode and a drain electrode disposed on the fourth insulating layer and connected to the active layer through corresponding via holes, and a planarization layer covering the foregoing structure and having a via hole to expose the drain electrode. The active layer, the gate electrode, the source electrode, and the drain electrode constitute a driving transistor 210, and the first capacitor electrode and the second capacitor electrode constitute a storage capacitor 211.

[0056] In some example embodiments, as shown in Figure 1 and Figure 2As shown, the light-emitting structure layer 103 may include an anode 301, a pixel definition layer 510, a cathode 309, and an organic functional layer located between the anode 301 and the cathode 309. The organic functional layer includes at least a light-emitting layer. Figure 1 and Figure 2 In the example, the emitting layer of the red sub-pixel R is 3051, the emitting layer of the green sub-pixel G is 3052, and the emitting layer of the blue sub-pixel B is 3053. The organic functional layer may also include the hole injection layer 302, the hole transport layer 303, and the electron blocking layer. Figure 1 and Figure 2 In the example, the red sub-pixel R has an electron blocking layer of 3041, the green sub-pixel G has an electron blocking layer of 3042, the blue sub-pixel B has an electron blocking layer of 3043, a hole blocking layer of 306, an electron transport layer of 307, and an electron injection layer of 308. The anode 301 is disposed on the planarization layer of the driving circuit layer 102 and is connected to the drain electrode of the driving transistor 210 through vias formed in the planarization layer. A pixel definition layer 510 is disposed on the side of the anode 301 facing away from the substrate 101. The pixel definition layer 510 has a pixel opening, covering the portion of the anode 301 surface near its circumferential edge. The pixel opening exposes the remaining portion of the anode 301 surface. Multiple layers of organic functional layers and a cathode 309 are sequentially stacked on the portion of the anode 301 surface exposed by the pixel opening. The anode 301, organic functional layer, and cathode 303 of each sub-pixel form an OLED device (light-emitting element), configured to emit light of the corresponding color under the drive of the corresponding pixel driving circuit. The light-emitting structure layer 103 may also include other film layers, such as spacers disposed on the pixel definition layer 510.

[0057] In some exemplary implementations, such as Figure 1 and Figure 2As shown, the display substrate including the OLED device can be prepared by the following method. First, a driving circuit layer 102 is formed on a substrate by a patterning process, which can include driving transistors 210 and storage capacitors 211 constituting a pixel driving circuit. Subsequently, a planarization layer is formed on the substrate with the foregoing structure, and a via exposing the drain electrode of the driving transistor 210 is formed on the planarization layer. Subsequently, a plurality of anodes 301 are formed on the substrate with the foregoing structure by a patterning process, and the anode 301 of each sub-pixel is connected to the drain electrode of the driving transistor 210 of the corresponding pixel driving circuit through the via on the planarization layer. Subsequently, a pixel definition layer 510 is formed on the substrate with the foregoing structure by a patterning process, and the pixel definition layer 510 of each sub-pixel is formed with a pixel opening exposing the anode 301, and each pixel opening serves as a light-emitting area of each sub-pixel. Subsequently, a hole injection layer 302 and a hole transport layer 303 are sequentially evaporated on the substrate with the foregoing structure using an open mask, and the hole injection layer 302 and the hole transport layer 303 are common layers, i.e., the hole injection layer 302 of all sub-pixels is integrally connected, and the hole transport layer 303 of all sub-pixels is integrally connected. The area of the hole injection layer 302 and the hole transport layer 303 is approximately the same, and the thickness is different. Subsequently, the electron blocking layer 3041 and the light-emitting layer 3051 of the red sub-pixel R, the electron blocking layer 3042 and the light-emitting layer 3052 of the green sub-pixel G, and the electron blocking layer 3043 and the light-emitting layer 3053 of the blue sub-pixel B are respectively evaporated in the red sub-pixel R, the green sub-pixel G, and the blue sub-pixel B using a fine metal mask, and the electron blocking layers and the light-emitting layers of adjacent sub-pixels can have a small amount of overlap or can be isolated. Subsequently, a hole blocking layer 306, an electron transport layer 307, an electron injection layer 308, and a cathode 309 are sequentially evaporated using an open mask, and the hole blocking layer 306, the electron transport layer 307, the electron injection layer 308, and the cathode 309 are common layers, i.e., the hole blocking layer 306 of all sub-pixels is integrally connected, the electron transport layer 307 of all sub-pixels is integrally connected, the electron injection layer 308 of all sub-pixels is integrally connected, and the cathode 309 of all sub-pixels is integrally connected. Subsequently, an encapsulation layer 601, a connection layer 602, a light extraction layer 603, a polarization conversion layer 604, a one-half phase retardation film 605, and a polarizing layer 606 are sequentially formed on the side of the cathode 309 away from the substrate 101.

[0058] In some example embodiments, the light-emitting layer can be evaporated by a multi-source co-evaporation method to form a light-emitting layer containing a host material and a dopant material, and the dopant material can be a fluorescent light-emitting material. The doping concentration of the dopant material can be adjusted by controlling the evaporation rate of the dopant material during evaporation, or by controlling the evaporation rate ratio of the host material and the dopant material.

[0059] In some example embodiments, the hole injection layer can be prepared using at least one of HATCN (2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene) or CuPc (copper phthalocyanine). The hole injection layer can also be prepared using a mixture of a hole transport material (host material) and a p-type dopant material, where the doping concentration of the p-type dopant material is 0.5% to 10%. For example, the hole injection layer can be a material formed by doping F4TCNQ (2,3,5,6-tetrafluoro-7,7',8,8'-tetra cyanodimethyl-p-benzoquinone) in NPB (N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4-4'-diamine), i.e., NPB:F4TCNQ, or a material formed by doping MoO3 (molybdenum trioxide) in TAPC (4,4'-cyclohexyl di[N,N-di(4-methylphenyl) aniline]), i.e., TAPC:MoO3. The thickness of the hole injection layer can be 5 nm to 20 nm. The hole injection layer can reduce the injection barrier of holes from the anode and improve the hole injection efficiency.

[0060] In some example embodiments, the hole transport layer can be prepared using a material with a high hole mobility, such as a carbazole-based material. The highest occupied molecular orbital (HOMO) energy level of the hole transport layer can be between -5.2 eV and -5.6 eV. The thickness of the hole transport layer can be 100 nm to 200 nm. The hole transport layer can improve the hole transport rate and reduce the hole injection barrier to improve the hole injection efficiency.

[0061] In some example embodiments, the electron blocking layer can be prepared using a material such as a carbazole-based material. The electron blocking layer of each color sub-pixel can be prepared separately using an evaporation process. The thickness of the electron blocking layer of the blue sub-pixel can be 1 nm to 10 nm. The thickness of the electron blocking layer of the red sub-pixel can be 40 nm to 60 nm. The thickness of the electron blocking layer of the green sub-pixel can be 15 nm to 30 nm.

[0062] In some example embodiments, the light-emitting layer can include a host material responsible for charge transport and a guest material responsible for light emission. The light-emitting color and spectral characteristics of the light-emitting layer are mainly determined by the guest material. Alternatively, the light-emitting layer material can be a delayed fluorescence material system, and the light-emitting layer material can further include a sensitizer having a delayed fluorescence characteristic. The light-emitting layer of each color sub-pixel can be prepared separately using an evaporation process. The thickness of the light-emitting layer of the blue sub-pixel can be 15 nm to 25 nm. The thickness of the light-emitting layer of the red sub-pixel can be 25 nm to 40 nm. The thickness of the light-emitting layer of the green sub-pixel can be 25 nm to 40 nm.

[0063] Exemplarily, the material of the hole blocking layer can be derivatives of azine, imidazole, etc. The main role of the hole blocking layer is to transfer electrons and block holes and excitons generated in the light-emitting layer from migrating to the side where the cathode is located. The thickness of the hole blocking layer can be 2 nm to 10 nm.

[0064] Exemplarily, the electron transport layer can be prepared by blending derivatives of thiophene, imidazole or azine, etc. with lithium quinolate, and the proportion of lithium quinolate can be 30% to 70%. The thickness of the electron transport layer can be 20 nm to 40 nm.

[0065] Exemplarily, the material of the electron injection layer can be 8-hydroxyquinolinol lithium (Liq), lithium fluoride (LiF), lithium (Li), ytterbium (Yb), magnesium (Mg) or calcium (Ca), etc. The thickness of the electron injection layer can be 0.5 nm to 2 nm. The electron injection layer can reduce the electron injection barrier and improve the electron injection efficiency.

[0066] The display device can be any product or component with a display function, such as a mobile phone, a tablet computer, a television, a display, a notebook computer, a digital photo frame, a navigator, etc.

[0067] In the drawings, the size of the constituent elements, the thickness of the layers or the regions are exaggerated for the sake of clearness in some cases. Therefore, the embodiments of the present disclosure are not necessarily limited to such a scale. In addition, the drawings schematically show some examples, and the embodiments of the present disclosure are not limited to the shapes or the numerical values shown in the drawings.

[0068] In the description herein, "parallel" refers to a state in which the angle formed by two straight lines is -10° or more and 10° or less, and thus includes a state in which the angle is -5° or more and 5° or less. In addition, "perpendicular" refers to a state in which the angle formed by two straight lines is 80° or more and 100° or less, and thus includes a state in which the angle is 85° or more and 95° or less.

[0069] In the description herein, the terms "upper", "lower", "left", "right", "top", "inner", "outer", "axial", "quadrangle", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are merely for the convenience of the simplified description of the embodiments of the present disclosure, and do not indicate or imply that the structure referred to has a particular orientation, is constructed and operated in a particular orientation, and thus cannot be understood as a limitation on the present disclosure.

[0070] In the description herein, unless specifically stated and limited otherwise, the terms "connected", "fixedly connected", "mounted", "assembled" shall be understood broadly, for example, can be fixedly connected, or detachably connected, or integrally connected; the terms "mounted", "connected", "fixedly connected" can be directly connected, or indirectly connected through an intermediate medium, or internal communication of two elements. The meanings of the above terms in the embodiments of the present disclosure can be understood according to the circumstances by those skilled in the art.

Claims

1. A display substrate, comprising a light-emitting element disposed on a substrate, and an encapsulation layer, a connection layer, a light extraction layer, a polarization conversion layer and a polarizing layer sequentially stacked on the light-emitting side of the light-emitting element; The light extraction layer is configured to convert at least a portion of the light emitted by the light-emitting element incident on the light extraction layer into circularly polarized light with a predetermined rotation direction and allow it to pass through; The polarization conversion layer is configured to convert circularly polarized light transmitted through the light extraction layer into linearly polarized light, wherein the polarization direction of the linearly polarized light is parallel to the transmission axis of the polarization layer. The connecting layer is configured to bond the light extraction layer to the encapsulation layer. The thickness of the connecting layer is greater than 3 times the thickness of the light extraction layer, and the difference between the refractive index of the connecting layer and the refractive index of the encapsulation layer near the connecting layer is greater than 0.

25. The encapsulation layer comprises three or more stacked film layers, wherein the difference between the refractive index of at least one film layer and the refractive index of the connecting layer is less than or equal to 0.2, and the refractive index of at least two film layers in the encapsulation layer is greater than 1.

65.

2. The display substrate as claimed in claim 1, wherein, The refractive index of the connecting layer is 1.35 to 1.65, and the thickness of the connecting layer is 5 μm to 40 μm.

3. The display substrate as described in claim 1, wherein, The light-emitting element includes an anode, a light-emitting layer, and a cathode stacked sequentially in a direction away from the substrate; The light extraction layer is further configured to convert another portion of the light emitted by the light-emitting element incident on the light extraction layer into circularly polarized light opposite to the set rotation direction and reflect it. The circularly polarized light reflected by the light extraction layer, which is opposite to the set rotation direction, is converted into circularly polarized light with the same rotation direction as the set rotation direction after being reflected by the cathode, and can pass through the light extraction layer.

4. The display substrate according to any one of claims 1 to 3, wherein, The light extraction layer comprises a cholesteric liquid crystal material.

5. The display substrate as claimed in claim 1, wherein, The light extraction layer is configured to convert light with a wavelength range of 400nm to 500nm into circularly polarized light with the set rotation direction and allow it to pass through; The light extraction layer has a transmittance of 35% to 65% for light with a wavelength range of 400nm to 500nm, and a transmittance of more than 90% for light with a wavelength greater than 500nm.

6. The display substrate as claimed in claim 1, wherein, The polarization conversion layer is a quarter-phase retardation film, which has inverse wavelength dispersion.

7. The display substrate as claimed in claim 6, wherein, The quarter-phase retardation film satisfies: 0.78 < R B / R0 < 1.1, 0.9 < R G / R0<1.1,1<R R / R0<1.1; Wherein, R0 is the optical path difference between the o-ray and e-ray produced by the quarter-phase retardation film after birefringence of the incident center wavelength light; R B R is the optical path difference between the o-ray and e-ray produced by the quarter-phase retardation film after birefringence of incident blue light; G R is the optical path difference between the o-ray and e-ray produced by the quarter-phase retardation film after birefringence of incident green light; R The optical path difference between the o-ray and e-ray produced by the quarter-phase retardation film after birefringence of incident red light.

8. The display substrate of claim 6 further includes a half-phase retardation film disposed between the polarization conversion layer and the polarizing layer.

9. The display substrate as claimed in claim 8, wherein, The polarizing layer, the half-phase retardation film, and the polarization conversion layer satisfy: β-2α=45°; Wherein, α is the angle between the optical axis of the half-phase retardation film and the transmission axis of the polarizing layer, and β is the angle between the optical axis of the polarization conversion layer and the transmission axis of the polarizing layer; or, α is the angle between the optical axis of the half-phase retardation film and the absorption axis of the polarizing layer, and β is the angle between the optical axis of the polarization conversion layer and the absorption axis of the polarizing layer.

10. The display substrate as claimed in claim 1, wherein, The light-emitting element includes an anode, a light-emitting layer, and a cathode stacked sequentially in a direction away from the substrate; The display substrate further includes a cover layer disposed between the cathode and the encapsulation layer, wherein the difference between the refractive index of the cover layer and the refractive index of the film layer of the encapsulation layer near the cover layer is greater than 0.

1.

11. The display substrate as claimed in claim 1, comprising a display area, the display area comprising a plurality of pixel units arranged in an array, the pixel units comprising red sub-pixels, green sub-pixels and blue sub-pixels, each sub-pixel comprising a light-emitting element; The following film layers of all sub-pixels within the display area are connected into a single structure and cover the display area: the encapsulation layer, the connection layer, the light extraction layer, the polarization conversion layer, and the polarizing layer.

12. The display substrate as claimed in claim 1, wherein, The encapsulation layer comprises multiple stacked film layers, and the refractive index of the encapsulation layer alternates between high and low along the direction away from the substrate.

13. The display substrate as claimed in claim 12, wherein, The light-emitting element includes an anode, a light-emitting layer, and a cathode stacked sequentially in a direction away from the substrate; The display substrate further includes a cover layer disposed between the cathode and the encapsulation layer; The encapsulation layer includes a first inorganic encapsulation layer, an organic encapsulation layer, and a second inorganic encapsulation layer, which are sequentially stacked along a direction away from the substrate. The first inorganic encapsulation layer includes one or more film layers. When the first inorganic encapsulation layer includes one film layer, the refractive index of the first inorganic encapsulation layer is higher than the refractive index of the organic encapsulation layer. When the first inorganic encapsulation layer includes multiple film layers, the refractive index of the film layer in the first inorganic encapsulation layer that is closer to the organic encapsulation layer is higher than the refractive index of the organic encapsulation layer.

14. The display substrate as claimed in claim 13, wherein, The first inorganic encapsulation layer includes a film layer; The refractive index of the first inorganic encapsulation layer is higher than that of the cover layer; or, the cover layer includes a first sub-cover layer and a second sub-cover layer stacked sequentially in a direction away from the substrate, wherein the refractive index of the first sub-cover layer is higher than that of the second sub-cover layer, and the refractive index of the second sub-cover layer is lower than that of the first inorganic encapsulation layer.

15. The display substrate as claimed in claim 14, wherein, The material of the cover layer is an aromatic amine or azinoid organic material, the material of the first inorganic encapsulation layer is silicon nitride or silicon oxynitride, the material of the organic encapsulation layer is a resin material, and the material of the second inorganic encapsulation layer is silicon nitride or silicon oxynitride.

16. The display substrate as claimed in claim 15, wherein, The first inorganic encapsulation layer includes a first sub-inorganic encapsulation layer and a second sub-inorganic encapsulation layer stacked sequentially along a direction away from the substrate, wherein the refractive index of the first sub-inorganic encapsulation layer is lower than the refractive index of the second sub-inorganic encapsulation layer; The refractive index of the capping layer is higher than that of the first inorganic encapsulation layer.

17. The display substrate as claimed in claim 16, wherein, The first inorganic encapsulation layer is made of lithium fluoride or silicon dioxide, the second inorganic encapsulation layer is made of silicon nitride or silicon oxynitride, the organic encapsulation layer is made of resin, and the second inorganic encapsulation layer is made of silicon nitride or silicon oxynitride; the cover layer is made of aromatic amine or azine organic materials.

18. The display substrate according to any one of claims 12 to 17, wherein, In any two adjacent film layers of the encapsulation layer, one film layer has a refractive index of 1.3 to 1.7, and the other film layer has a refractive index of 1.7 to 2.

3.

19. A display device comprising the display substrate according to any one of claims 1 to 18.

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