WO2022083304A1 - 显示面板及其制备方法、显示装置 - Google Patents

显示面板及其制备方法、显示装置 Download PDF

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Publication number
WO2022083304A1
WO2022083304A1 PCT/CN2021/115974 CN2021115974W WO2022083304A1 WO 2022083304 A1 WO2022083304 A1 WO 2022083304A1 CN 2021115974 W CN2021115974 W CN 2021115974W WO 2022083304 A1 WO2022083304 A1 WO 2022083304A1
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Prior art keywords
layer
wavelength conversion
light
pixel
emitting
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PCT/CN2021/115974
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English (en)
French (fr)
Inventor
黄维
舒适
李伟
孙中元
靳倩
袁广才
王路
张宜驰
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京东方科技集团股份有限公司
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Priority to EP21881723.7A priority Critical patent/EP4145530A4/en
Priority to US17/790,333 priority patent/US20230037592A1/en
Publication of WO2022083304A1 publication Critical patent/WO2022083304A1/zh

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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/30—Devices specially adapted for multicolour light emission
    • H10K59/38—Devices specially adapted for multicolour light emission comprising colour filters or colour changing media [CCM]
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H10K50/125—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers specially adapted for multicolour light emission, e.g. for emitting white light
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/80—Constructional details
    • H10K50/86—Arrangements for improving contrast, e.g. preventing reflection of ambient light
    • H10K50/865—Arrangements for improving contrast, e.g. preventing reflection of ambient light comprising light absorbing layers, e.g. light-blocking layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/10—OLED displays
    • H10K59/12—Active-matrix OLED [AMOLED] displays
    • H10K59/122—Pixel-defining structures or layers, e.g. banks
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2102/00—Constructional details relating to the organic devices covered by this subclass
    • H10K2102/301—Details of OLEDs
    • H10K2102/351—Thickness
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/80—Constructional details
    • H10K59/87—Passivation; Containers; Encapsulations
    • H10K59/873—Encapsulations
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/80—Constructional details
    • H10K59/87—Passivation; Containers; Encapsulations
    • H10K59/873—Encapsulations
    • H10K59/8731—Encapsulations multilayered coatings having a repetitive structure, e.g. having multiple organic-inorganic bilayers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/80—Constructional details
    • H10K59/875—Arrangements for extracting light from the devices

Definitions

  • the present disclosure relates to the field of color display, and in particular, to a display panel and a manufacturing method thereof, and a display device.
  • OLED organic light-emitting display
  • RGB type organic light-emitting materials that emit light of different colors (such as red light-emitting materials, green light-emitting materials and blue light-emitting materials) to form sub-pixels of different colors.
  • RGB type has a high color gamut and has occupied the small and medium-sized application market.
  • FMM fine metal mask
  • the color gamut value is not high enough due to the limitation of research and development of solution-based OLED materials.
  • the other is to use OLED as a backlight with a color film to achieve color display, which can be called a backlight-color film type. Since the entire surface of the open mask can be used for evaporation, the white backlight with color filter has become one of the mainstream technologies for large-size OLEDs.
  • the color filter functions to filter out light waves of wavelengths other than the desired color in the white light.
  • the color gamut of the color film directly limits the color gamut range of large-size OLED products.
  • the present disclosure provides a display panel, comprising:
  • the wavelength conversion layer on the side of the light-emitting layer away from the base substrate,
  • the light-emitting layer includes a plurality of light-emitting units and a first pixel defining layer defining the plurality of light-emitting units
  • the wavelength conversion layer includes a plurality of wavelength conversion units and a second pixel defining the plurality of wavelength conversion units a defining layer
  • each of the plurality of wavelength conversion units is configured to convert the wavelength of light emitted by at least one of the plurality of light emitting units
  • the thickness of the second pixel-defining layer is more than twice the thickness of the first pixel-defining layer.
  • the area of the light incident surface of each of the wavelength conversion units is larger than the area of the light emitting surface of the light emitting unit that emits the light it converts.
  • the orthographic projection of the second pixel-defining layer on the base substrate falls within the orthographic projection of the first pixel-defining layer on the base substrate.
  • a first encapsulation layer on the side of the light-emitting layer close to the wavelength conversion layer includes a first inorganic layer and a side of the first inorganic layer away from the light-emitting layer the second inorganic layer
  • the second inorganic layer includes a stack of a plurality of inorganic sub-layers, and the reflectivity of the stack to the light whose wavelength is converted by the wavelength conversion unit is stronger than that of the light emitting unit.
  • the reflectance of light, and the transmittance of the light emitted by the light-emitting unit is greater than the transmittance of the light whose wavelength is converted by the wavelength conversion unit.
  • the thickness of the first encapsulation layer is 1 to 6 ⁇ m.
  • the display panel further includes:
  • the color filter layer on the side of the wavelength conversion unit away from the light-emitting layer is the color filter layer on the side of the wavelength conversion unit away from the light-emitting layer
  • the color filter layer includes multiple color filter units and a black matrix defining the multiple color filter units.
  • the orthographic projection of the black matrix on the base substrate falls within the orthographic projection of the second pixel defining layer on the base substrate.
  • the thickness of the first pixel-defining layer is 1-2 ⁇ m, and the thickness of the second pixel-defining layer is 6-20 ⁇ m.
  • the plurality of light-emitting units sequentially include an anode, a light-emitting layer, and a cathode, and a surface of the cathode away from the base substrate and the wavelength conversion unit close to the base substrate.
  • the distance between one side surfaces is smaller than the thickness of the second pixel-defining layer and larger than the thickness of the first pixel-defining layer.
  • the wavelength conversion layer further includes a transparent unit disposed in the same layer as the plurality of wavelength conversion units, and a second pixel defining layer is disposed between the transparent unit and the wavelength conversion unit.
  • the cross-sectional shape of the first pixel-defining layer in a direction perpendicular to the base substrate to be parallel to the substrate through a point of the cross-sectional shape that is farthest from the base substrate
  • the straight line of the base substrate is the first side
  • the line segment passing through the two ends of the boundary between the cross-sectional shape and the adjacent layers on the side of the base substrate layer is the second side, so as to pass through the two sides respectively.
  • the straight lines of the end extending to the first side and circumscribing the cross-sectional shape are the third side and the fourth side, and in the quadrilateral enclosed by the first, second, third and fourth sides, the second side and the Each of the included angle of the third side and the included angle of the second side and the fourth side is in the range of 20° to 40°.
  • the material of the first pixel-defining layer and the second pixel-defining layer are different.
  • the display panel further includes:
  • the bank layer encapsulates the filler layer with the light emitting layer and the wavelength conversion layer.
  • the cross-sectional shape of the second pixel-defining layer in a direction perpendicular to the base substrate to be parallel to the substrate through the point of the cross-sectional shape closest to the base substrate.
  • the straight line of the base substrate is the first side
  • the line segment passing through the two ends of the boundary between the cross-sectional shape and the adjacent layers on the side away from the base substrate layer is the second side, so as to pass through the two sides respectively.
  • the straight lines of the end extending to the first side and circumscribing the cross-sectional shape are the third side and the fourth side, and in the quadrilateral enclosed by the first, second, third and fourth sides, the first side and the Each of the included angle of the third side and the included angle of the first side and the fourth side is in the range of 60° to 90°.
  • the surface of the second pixel-defining layer has a contact angle to deionized water ⁇ 90°, and a contact angle to propylene glycol methyl ether acetate ⁇ 35°, and
  • each of the included angle of the first side and the third side and the included angle of the first side and the fourth side is in the range of 60° to 85°.
  • the thickness of the dike layer is 15 to 50 ⁇ m, and the thickness of the filler layer is 5 to 30 ⁇ m.
  • the plurality of wavelength conversion units are overlapped on a side surface of the second pixel defining layer close to the base substrate.
  • the overlapped width of the wavelength conversion unit on the second pixel defining layer is within 10% of the width of the overlapped surface of the second pixel defining layer.
  • the plurality of wavelength conversion units include adjacently arranged first color wavelength conversion units and second color wavelength conversion units, and the first color wavelength conversion units overlap with the first color wavelength conversion units.
  • the widths on the second pixel defining layer separating the two are different.
  • the display panel further includes:
  • the color filter layer on the side of the wavelength conversion unit away from the light-emitting layer is the color filter layer on the side of the wavelength conversion unit away from the light-emitting layer
  • the color filter layer includes a plurality of color filter units and a black matrix defining the plurality of color filter units
  • the plurality of color filter units are overlapped on the side surface of the black matrix close to the base substrate, and
  • the width of the overlap of the wavelength conversion unit on the second pixel defining layer is different from the width of the overlap of the color filter unit that belongs to the same sub-pixel on the black matrix.
  • the wavelength conversion layer is in contact with a first encapsulation layer, and the first encapsulation layer is in contact with the light-emitting layer.
  • the cross-sectional shape of the second pixel-defining layer in a direction perpendicular to the base substrate to be parallel to the substrate through the point of the cross-sectional shape farthest from the base substrate.
  • the straight line of the base substrate is the first side
  • the line segment passing through the two ends of the boundary between the cross-sectional shape and the adjacent layers on the side of the base substrate layer is the second side, so as to pass through the two sides respectively.
  • the straight lines of the end extending to the first side and circumscribing the cross-sectional shape are the third side and the fourth side, and in the quadrilateral enclosed by the first, second, third and fourth sides, the second side and the Each of the included angle of the third side and the included angle of the second side and the fourth side is in the range of 70° to 90°.
  • the surface of the second pixel-defining layer has a contact angle to deionized water ⁇ 90°, and a contact angle to propylene glycol methyl ether acetate ⁇ 35°, and
  • the cross-sectional shape of the second pixel-defining layer in a direction perpendicular to the base substrate as a line parallel to the base substrate passing through the point of the cross-sectional shape farthest from the base substrate It is the first side, and the line segments passing through the two ends of the boundary between the cross-sectional shape and its adjacent layers on the side close to the base substrate layer are the second sides, so as to pass through the two ends to the two sides respectively.
  • the straight lines extending from the first side and circumscribing the cross-sectional shape are the third side and the fourth side.
  • the second side and the third side are Each of the included angle and the included angle of the second side and the fourth side is in the range of 95° to 120°.
  • the plurality of wavelength conversion units are overlapped on a side surface of the second pixel defining layer away from the base substrate.
  • the overlapped width of the wavelength conversion unit on the second pixel defining layer is within 10% of the width of the overlapped surface of the second pixel defining layer.
  • the plurality of wavelength conversion units include adjacently arranged first color wavelength conversion units and second color wavelength conversion units, and the first color wavelength conversion units overlap with the first color wavelength conversion units.
  • the widths on the second pixel defining layer separating the two are different.
  • the color filter layer includes a plurality of color filter units and a black matrix defining the plurality of color filter units
  • the plurality of color filter units are overlapped on the side surface of the black matrix away from the base substrate, and
  • the width of the overlap of the wavelength conversion unit on the second pixel defining layer is different from the width of the overlap of the color filter unit that belongs to the same sub-pixel on the black matrix.
  • the quadrilateral is a trapezoid with the third and fourth sides as sides.
  • the second pixel-defining layer is a light-reflective pixel-defining layer or a light-absorbing pixel-defining layer.
  • the second pixel-defining layer includes scattering particles or metal is provided on the surface of the second pixel-defining layer close to the wavelength conversion unit.
  • the wavelength conversion unit is a quantum dot down conversion unit.
  • the display panel includes green sub-pixels, red sub-pixels and blue sub-pixels, and each sub-pixel includes one of the light-emitting units,
  • the light-emitting area of the light-emitting unit in the green sub-pixel ⁇ the light-emitting area of the light-emitting unit in the red sub-pixel ⁇ the light-emitting area of the light-emitting unit in the blue sub-pixel.
  • the light incident surface of each of the wavelength conversion units is at the edge of the orthographic projection of the base substrate and the light exit surface of the light-emitting unit that emits the light converted by the light-emitting unit is at the edge of the base substrate.
  • the distance a between the edge of the orthographic projection and the distance b between the light-emitting surface of the OLED light-emitting unit and the light-incident surface of the backlight down-conversion unit satisfies a ⁇ 1.8b.
  • the wavelength conversion layer includes a second encapsulation layer, and the thickness of the second encapsulation layer is less than 1 ⁇ m.
  • the present disclosure provides a method of fabricating the above-mentioned display panel, comprising:
  • the light-emitting layer includes a plurality of light-emitting units and a first pixel defining layer defining the plurality of light-emitting units
  • the wavelength conversion layer includes a plurality of wavelength conversion units and a second pixel defining layer defining the plurality of wavelength conversion units
  • each of the wavelength conversion units is configured to convert the wavelength of light emitted by at least one of the plurality of light emitting units
  • the thickness of the second pixel-defining layer is more than twice the thickness of the first pixel-defining layer.
  • the wavelength conversion layer formed on the side of the light-emitting layer away from the base substrate includes:
  • the wavelength conversion unit is formed by inkjet printing and curing the ink containing the wavelength conversion material
  • the wavelength conversion layer and the light-emitting layer are assembled into a cell to form the display panel, wherein a filler layer and a bank layer are arranged between the wavelength conversion layer and the light-emitting layer.
  • the wavelength conversion layer formed on the side of the light-emitting layer away from the base substrate includes:
  • the wavelength conversion unit is formed by coating and photolithographic photoresist containing a wavelength conversion material
  • the wavelength conversion layer and the light-emitting layer are assembled into a cell to form the display panel, wherein a filler layer and a bank layer are arranged between the wavelength conversion layer and the light-emitting layer.
  • the base plate is a color filter layer.
  • the method further includes:
  • a second encapsulation layer covering the second pixel defining layer and the wavelength conversion unit is formed at a temperature of ⁇ 180°C.
  • the wavelength conversion layer formed on the side of the light-emitting layer away from the base substrate includes:
  • the wavelength conversion unit is formed by inkjet printing and curing an ink containing a wavelength conversion material.
  • the wavelength conversion layer formed on the side of the light-emitting layer away from the base substrate includes:
  • the wavelength conversion unit is formed by applying and photolithographic photoresist containing a wavelength conversion material.
  • the method further includes:
  • the method further includes:
  • a second encapsulation layer covering the second pixel defining layer and the wavelength conversion unit is formed at a temperature of ⁇ 100°C.
  • the present disclosure provides a display device including the above-mentioned display panel.
  • FIG. 1 schematically shows a schematic structural diagram of the display device of the present disclosure.
  • Figure 2 shows one embodiment of an OLED light-emitting layer.
  • FIG. 3 shows a schematic film layer structure of the first encapsulation layer.
  • FIG. 4 shows a schematic diagram of a color filter layer serving as a backplane in a cell-to-box mode.
  • FIG. 5 shows the cooperation between the filter property of the color filter unit and the luminescence property of the wavelength conversion unit.
  • FIG. 6(a)-(b) show a photomicrograph and a schematic diagram of a mushroom-shaped cross-section of the structure of a cell-mode inkjet-printed down-conversion color filter substrate in one example of the present disclosure.
  • FIG. 7(a) to 7(e) schematically illustrate some embodiments of wavelength-converting color filter substrates in cell-to-cell mode of the present disclosure.
  • Figures 8(a)-(f) show photomicrographs of some of the second pixel-defining layers.
  • Figure 9 shows a 45° top view SEM image after the wavelength conversion unit fills a single sub-pixel in one embodiment.
  • FIG. 10 schematically illustrates preferred angular ranges for modes I-IV of the present disclosure.
  • FIG. 11 schematically shows one embodiment of a display panel after being boxed.
  • FIG. 12 shows the relationship between the light-emitting surface of the light-emitting unit, the light-incident surface of the wavelength conversion unit, and the cell thickness.
  • FIG. 13(a)-(b) schematically illustrate embodiments of wavelength conversion units and transparent units formed by photolithography on a color filter layer.
  • 15(a)-(b) show photomicrographs of structures formed by on-EL and inkjet printing in examples of the present disclosure.
  • FIG. 16 schematically shows a display device formed by on-EL and photolithography.
  • Figure 17 shows a photomicrograph of a QD photoresist layer containing a downconversion material in the sub-pixel space defined by PDL-2.
  • Figures 20(a) and (b) exemplarily show the characteristic quadrilateral of the pixel-defining layer.
  • the inventor has conducted in-depth research and unexpectedly found that by designing a more compact light extraction structure, the light extraction efficiency of the display panel can be improved, thereby improving the Luminous efficacy and color gamut to enhance critical optical performance.
  • the light extraction structure can be applied to QD-OLEDs and other wavelength conversion materials other than QDs.
  • a display panel comprising:
  • the wavelength conversion layer on the side of the light-emitting layer away from the base substrate,
  • the light-emitting layer includes a plurality of light-emitting units and a first pixel defining layer defining the plurality of light-emitting units
  • the wavelength conversion layer includes a plurality of wavelength conversion units and a second pixel defining layer defining the plurality of wavelength conversion units
  • each of the wavelength conversion units is configured to convert the wavelength of light emitted by at least one of the plurality of light emitting units
  • the thickness of the second pixel-defining layer is more than twice the thickness of the first pixel-defining layer.
  • the display panel of the present disclosure can achieve higher light extraction efficiency through specific light extraction structure settings.
  • the display panel of the present disclosure may be an OLED display panel.
  • OLED display panels use OLEDs as light-emitting units.
  • the display panel of the present disclosure may also use other types of light emitting devices as light emitting units.
  • the display panel of the present disclosure is a display panel including a wavelength conversion element.
  • the wavelength conversion element is used to convert the wavelength of the light emitted by the light-emitting unit into light of other colors. It should be noted that in this disclosure, wavelength conversion is not the same as wavelength selective transmission. Wavelength conversion refers to converting the wavelength of incident light to another wavelength without additional use of energy, while wavelength selective transmission refers to allowing only some wavelengths of incident light to pass through and blocking other wavelengths from passing through. Pass. Wavelength conversion can be down-conversion or up-conversion. Down-conversion is the opposite of up-conversion and refers to the conversion of shorter wavelength light into longer wavelength light. By using different wavelength conversion units to change the color of light, color display can be achieved using only one color light emitting unit.
  • the display panel of the present disclosure may be a down-conversion OLED display panel.
  • the down-conversion OLED display panel uses one-color short-wavelength OLEDs as light-emitting units, typically blue-light OLEDs.
  • different down-conversion materials such as QDs
  • QDs different down-conversion materials
  • a short wavelength blue OLED is used to emit light for all color sub-pixels.
  • the down-conversion material converts the blue light emitted by the blue OLED into red light.
  • the down-conversion material converts the blue light emitted by the blue OLED to green light.
  • blue since blue itself is one of the sub-pixel colors displayed by RGB, in the blue sub-pixel, the blue light can be directly used for blue sub-pixel display without down-conversion. Thereby, red-green-blue (RGB) color display is realized.
  • RGB red-green-blue
  • the blue backlight as the short-wavelength backlight and the down-conversion to green and red light are sometimes described as examples. However, it should be understood that other colors of luminescence or other colors of converted light may also be selected as required.
  • the light-emitting side of the display panel is referred to as the "top side”, and the opposite side thereof is referred to as the "bottom side", for the convenience of describing the relative directions. Accordingly, the direction perpendicular to the direction from the bottom side to the top side is “lateral”. It should be understood that these directions are relative and not absolute.
  • the display panel of the present disclosure has a base substrate on the bottom side and a light exit side of the display panel on the top side, and includes, in order from the bottom side to the top side: a light emitting layer; a wavelength conversion layer; and an optional color filter layer.
  • the light-emitting layer functions to emit light.
  • the emitted light passes through the wavelength converting layer above it and can be converted to other colors, or optionally not, to achieve a color display.
  • a color filter layer may be further provided to allow only the light of the desired color in the light from the wavelength conversion layer to pass through, thereby improving the color purity.
  • the color filter layer refers to a layer that selectively transmits light of a specific wavelength.
  • the light emission of the display panel of the present disclosure is realized by the light emitting unit.
  • the light-emitting units are arranged in an array, and each light-emitting unit in the array may be an OLED, comprising a cathode, an anode and an organic light-emitting layer between them, or a portion of organic light-emitting material, with carriers supplied from the cathode and the anode Recombination emission in the organic light-emitting layer.
  • a plurality of such light-emitting units are arrayed parallel to the display surface of the display panel to form a light-emitting dot matrix.
  • Each sub-pixel of the display panel of the present disclosure may have an independent OLED, which may cooperate with the array substrate to realize the individual lighting and extinguishing of the backlight of each sub-pixel.
  • a first pixel defining layer defining the light emitting unit array is included in the light emitting layer. It should be understood that the “pixel-defining layer” referred to in the present disclosure, including the first pixel-defining layer described here and the second pixel-defining layer described in detail below, actually defines the range of each sub-pixel, such as The range of red, green, and blue subpixels, rather than the total range of a color RGB pixel.
  • the patterned first pixel-defining layer is disposed in the light-emitting layer, and encloses a plurality of spaces arranged in an array for disposing light-emitting units.
  • the first pixel defining layer at least separates the organic light emitting material portion of the adjacent light emitting unit, and may also separate other parts of the light emitting unit, such as the anode and the like.
  • the display panel of the present disclosure further includes a wavelength conversion layer on the light-emitting side of the light emitting layer, the wavelength conversion layer including an array of wavelength conversion units configured to convert wavelengths emitted by the light emitting units.
  • the wavelength conversion unit is used to convert the wavelength emitted by the light emitting unit into a desired color in one sub-pixel.
  • the red wavelength conversion unit may convert the blue backlight into red light
  • the green wavelength conversion unit may convert the blue backlight into green light.
  • the wavelength conversion unit may be a QD material part, an inorganic phosphor material part or an organic fluorescent material part, which includes a transparent host material and quantum dots, inorganic phosphor powder or organic fluorescent material dispersed in the host material.
  • the wavelength converting unit can also be made of other wavelength converting materials.
  • the matrix material may be a transparent organic material such as a resin, eg a cured photoresist resin, or a cured ink.
  • the down-conversion material can be any suitable down-conversion material, which is not particularly limited in the present disclosure. Among them, QD down-conversion materials are particularly preferred because the down-conversion properties can be controlled by particle size. In the present application, unless otherwise specified, QDs are used as examples of wavelength conversion materials for description.
  • the wavelength conversion unit includes a wavelength conversion unit of a first color, which can convert incident light into light of the first color.
  • the first color may be red, that is, a red wavelength conversion unit exists in the wavelength conversion unit.
  • the wavelength conversion unit may further include wavelength conversion units of a second color, or wavelength conversion units of more other colors.
  • red can be chosen as the first color and green as the second color.
  • red may be used as the first color
  • green may be used as the second color
  • blue may be used as the third color.
  • the wavelength conversion layer may further include a transparent unit.
  • the transparent unit is transparent to incident light and does not undergo wavelength conversion.
  • blue OLED light emission in a blue subpixel can pass through the wavelength conversion layer without undergoing wavelength conversion, directly for blue display.
  • the transparent unit may be a light diffusing unit, for example, containing scattering particles, so that the incident light is scattered without changing the wavelength, which is favorable for uniform display.
  • the light diffusing unit may be made of a light diffusing resin having light diffusing ability, so that the blue light is more uniform after passing through it.
  • transparent refers to allowing light to be transmitted without wavelength conversion at varying angles.
  • a second pixel defining layer defining a wavelength conversion unit is included in the wavelength conversion layer.
  • the second pixel defining layer also defines transparent cells.
  • the patterned second pixel defining layer at least encloses a plurality of spaces arranged in an array for filling the wavelength conversion material portion or the transparent material.
  • the second pixel defining layer at least separates the wavelength conversion unit from the adjacent wavelength conversion unit or transparent unit.
  • the light-emitting units are respectively matched with the wavelength conversion units of the first color, the wavelength conversion units of the second color, the transparent units and the like defined by the second pixel defining layer.
  • the plurality of light-emitting units may sequentially include an anode, a light-emitting layer, and a cathode, and the distance between the side surface of the cathode far away from the base substrate and the side surface of the wavelength conversion unit close to the base substrate is smaller than the first
  • the thickness of the second pixel defining layer is greater than the thickness of the first pixel defining layer.
  • the side surface of the wavelength conversion unit close to the base substrate refers to the side surface of the quantum dots close to the base substrate. The benefit of this setting is to reduce the thickness of the box and avoid cross-coloring.
  • the display panel of the present disclosure may further include a color filter layer.
  • the color filter layer is on the top side of the wavelength conversion layer and includes a color filter unit.
  • the color filter unit is used to filter light, that is, to allow light in a part of the wavelength range of the incident light from the wavelength conversion layer to pass through, thereby further improving color purity.
  • the color filter unit includes a color filter unit of a first color, and may further include a color filter unit of a second color, or more color filter units of other colors.
  • a red color filter unit may be provided on the light-emitting side of the red wavelength conversion layer
  • a green color filter unit may be provided on the light-emitting side of the green wavelength conversion layer
  • a blue color film unit may be provided on the light-emitting side of the transparent unit membrane unit.
  • the color filter can be prepared from color filter materials commonly used in the display field.
  • the color filter layer includes a black matrix defining the color filter unit.
  • the projection of the black matrix into the wavelength converting layer is within the top surface of the second pixel defining layer.
  • the black matrix is not located above the light emitting surface of the wavelength conversion unit or the backlight diffusion unit defined by the second pixel defining layer, and will not block the light emitted by the black matrix.
  • the projected area of the color filter unit in the wavelength conversion layer is larger than the area of the top surface of the wavelength conversion unit or the backlight diffusion unit. This can make full use of the non-vertical light emitted from the top surface of the wavelength conversion unit or the backlight diffusion unit, thereby improving the luminous efficacy.
  • the black matrix can also be formed of conventional black matrix materials in the art.
  • the thickness of the second pixel-defining layer is more than twice the thickness of the first pixel-defining layer.
  • the inventors found that when the thickness of the second pixel-defining layer is much larger than the thickness of the first pixel-defining layer, such as more than 2 times, the wavelength conversion unit can fully realize wavelength conversion of light emitted by the light-emitting unit. This facilitates the further design of a more compact light extraction structure and improves the light extraction efficiency of the device, thereby improving the luminous efficacy and color gamut, and enhancing key optical performance.
  • the thickness of the second pixel-defining layer may be 2 times, 2.5 times, 3 times, 4 times, 5 times, etc., of the thickness of the first pixel-defining layer.
  • the layer thickness direction is the direction perpendicular to the base substrate, that is, the height direction of the pixel-defining layer walls.
  • the first pixel-defining layer thickness may be 1-2 ⁇ m, while the second pixel-defining layer thickness may be in the range of 6-20 ⁇ m in different designs.
  • the preferred thickness range of the cooperating first pixel-defining layer and the second pixel-defining layer can take into account the guarantee of the wavelength conversion optical effect and the actual process capability, which not only achieves the wavelength conversion optical effect well, but does not significantly increase the difficulty of preparation. The above preferred range can realize a display panel with a compact structure and high light extraction efficiency.
  • the first pixel layer and the second pixel defining layer of the present disclosure not only play the role of defining the areas of the light-emitting unit, the wavelength conversion unit and the transparent unit, but also participate in the reflection and absorption of light.
  • the panel plays the role of improving light transmission and conversion performance and improving light extraction efficiency.
  • the shapes of the first and second pixel-defining layers also have a favorable effect on the fabrication process in the formation process of the light emitting unit, the wavelength conversion unit and the backlight diffusion unit.
  • the present disclosure proposes various specific structures of the second pixel defining layer.
  • the thickness of the second pixel-defining layer is less than 6 ⁇ m, the conversion efficiency of the wavelength conversion layer may be insufficient, and the reflectivity of blue light may be improved while the reflectivity of yellow light may be reduced, which is not conducive to improving the luminous performance of the display panel.
  • the conversion efficiency can be increased, but the light transmittance also decreases accordingly.
  • the thickness of the second pixel-defining layer is greater than 20 ⁇ m, an excessively thick wavelength conversion unit is formed, and the overall conversion efficiency will decrease. Therefore, a thickness of 6 to 20 ⁇ m can guarantee acceptable low values of wavelength conversion efficiency.
  • the light incident surface area of the wavelength conversion unit may be larger than the light exit surface area of the light emitting unit.
  • the light incident surface area of the wavelength conversion unit refers to the surface area of the wavelength conversion unit facing the base substrate, which can receive light into its interior.
  • the area of the light-emitting surface of the light-emitting unit refers to the area of the opening defined by the first pixel-defining layer, and the area of the plane that can emit light to the outside thereof.
  • the light-emitting surface of the light-emitting unit is located inside the orthographic projection of the light-incident surface of the wavelength conversion unit in the light-emitting layer.
  • the non-vertical light emitted from the top surface of the light emitting unit can be fully utilized, and the luminous efficacy can be improved.
  • the ratio of the above two areas may vary according to differences in optical paths brought about by the structure and deviations in the fabrication process.
  • the wavelength conversion unit area of the cell-to-cell device structure is relatively larger to avoid light leakage between pixels.
  • the projection of the second pixel-defining layer in the light-emitting layer is within the top surface of the first pixel-defining layer.
  • the second pixel-defining layer is not located above the light-emitting surface of the light-emitting unit defined by the first pixel-defining layer, and will not block its light emission.
  • the projected area of the second pixel-defining layer in the light-emitting layer is smaller than the top surface area of the first sub-pixel-defining layer.
  • the materials of the first pixel-defining layer and the second pixel-defining layer may be different.
  • the transmittance of the first pixel-defining layer to visible light may be higher than the transmittance of the second pixel-defining layer to visible light.
  • FIG. 1 schematically shows a structural principle diagram of a display panel of the present disclosure.
  • the display panel of the present disclosure includes a light emitting layer 1 , a wavelength conversion layer 2 and an optional color filter layer 3 . They are drawn separately in Figure 1 to illustrate their relationship. However, in an actual display panel, they may be combined with each other.
  • the wavelength conversion layer 2 and the light emitting layer 1 may be in direct contact
  • the wavelength conversion layer 2 and the color filter layer 3 may also be in direct contact.
  • the light emitting layer 1 includes a first pixel defining layer PDL- 1 , which defines an array of light emitting cells 10 .
  • the light-emitting units 10 may be short-wavelength light-emitting units, such as blue OLED light-emitting units. These light-emitting units can be driven by, for example, the array substrate S. In the present disclosure, each light-emitting unit emits light for one sub-pixel.
  • the wavelength conversion layer 2 includes a second pixel defining layer PDL-2 and a first color wavelength conversion unit 21, a second color wavelength conversion unit 22 and a transparent unit 23 defined by them.
  • the first color wavelength conversion unit 21 may be a green wavelength conversion unit
  • the second color 22 wavelength conversion unit may be a red wavelength conversion unit
  • the transparent unit 23 transmits light without conversion and may be a light diffusion unit.
  • the wavelength conversion materials used in the first and second color wavelength conversion units can be QDs, or other materials with down-conversion functions such as inorganic phosphors or organic fluorescent materials, or other materials with up-conversion functions. It should be noted that in the present disclosure, the QD down-conversion layer is sometimes used for schematic illustration, but the scope of the present disclosure is not limited to the QD down-conversion layer.
  • the light leaving the wavelength conversion layer 2 enters the corresponding sub-pixel color filters in the color filter layer, such as the first color filter 31 , the second color filter 32 and the third color filter 33 , and the color purity is further improved.
  • the final color display A black matrix BM can be set between the color filter units to avoid cross color.
  • the top of the color filter layer may also have a substrate, which may also be an external packaging layer or a cover plate.
  • the light incident surface of the wavelength conversion unit is larger than the light emitting surface of the light emitting unit.
  • the thickness of PDL-2 is more than twice that of PDL-1. Such a thickness enables the light emitted by the OLED unit to have enough space for wavelength conversion, scattering, reflection and other processes in the wavelength conversion unit, which is beneficial to finally obtain high-quality uniform light emission.
  • FIG. 1 only shows the basic principle and structure of the display panel of the present disclosure.
  • the display panel of the present disclosure may optionally include a filler layer and a support column structure between the light-emitting layer and the wavelength conversion layer, and a sealing filler surrounding the periphery of the display panel. layer of the embankment layer and other structures.
  • an encapsulation layer may also be provided for the light emitting unit and the wavelength conversion unit/transparent unit.
  • a polarizer, an optical compensation sheet, and the like may also be provided in the display panel.
  • FIG. 1 is only intended to illustrate the mutual positional relationship of each element, and does not limit the specific shape and details of each component.
  • a drive control unit is provided for each light-emitting unit.
  • the driving control unit may be a thin film transistor (TFT), and thus, the light emitting layer may be composed of a TFT array substrate and an array of light emitting cells connected to the array substrate.
  • the light emitting layer may further include a TFT array substrate on the bottom side of the first pixel defining layer.
  • the TFT array substrate may be a conventional array substrate in the art. More specifically, the TFT array substrate may be an oxide TFT (Oxide TFT) or a low temperature polysilicon (LTPS) substrate.
  • the TFT array substrate may include a first base substrate and TFTs arranged in an array on the first base substrate, and the source/drain electrodes of the TFTs are electrically connected to pixel electrodes such as anodes in the light emitting unit.
  • the pixel electrode connected to the TFT at the bottom of the light-emitting unit may be a reflective anode.
  • the light-emitting unit adopts a reflective anode device structure to form a top emission OLED. The reflective anode is used to reflect the light emitted to the non-light-emitting side toward the light-emitting side, thereby improving the luminous efficacy.
  • FIG. 2 shows one embodiment of the light-emitting layer 1 .
  • the figure shows a partial schematic diagram containing 3 complete OLED light-emitting units and 4 PDL-1s.
  • the base substrate BS has a buffer layer BUF on it.
  • a TFT unit is configured for each sub-pixel.
  • the TFT unit includes a source S, a drain D, a gate G, and an active layer ACT.
  • Below the gate and between the active layer is a first gate insulating layer GI1 , and a second gate insulating layer GI2 is covered around and above the gate.
  • An interlayer dielectric layer ILD and a planarization layer PLN are sequentially arranged above the second gate insulating layer.
  • the enable signal lines Ce1 and Ce2 are further arranged between the second insulating layer and the interlayer dielectric layer.
  • the light emitting unit LE is formed between the first pixel defining layers PDL-1.
  • the light emitting unit LE includes an anode AD, an organic light emitting part EL, and a cathode CD from the bottom side to the top side.
  • the anode is connected to the drain of the TFT, and the cathode is the common electrode.
  • the first encapsulation layer Encap-1 Above the cathode, there is also the first encapsulation layer Encap-1.
  • the first encapsulation layer is located on the side of the light-emitting layer close to the wavelength conversion layer. As exemplarily shown in FIG.
  • PDL-1 is a wall with a trapezoidal longitudinal section. It should be understood that it forms a grid on the array substrate and defines many spaces for arranging the light emitting units.
  • the structure of the OLED light-emitting unit as described above is known in the art, and includes an anode, an organic light-emitting layer, a cathode, and the like.
  • the anode AD of the light-emitting unit may be a reflective anode, which reflects the light emitted by the OLED toward the light-emitting surface, so as to increase the light-emitting efficiency.
  • the light-emitting layer of the present disclosure has only one color of light-emitting material layer, so it can be formed on the entire surface using Open Mask, without the need to use, for example, fine metal masks to form sub-pixels one by one,
  • the projection of the TFT on the base substrate can overlap with both the PDL-1 and the light-emitting unit. That is, the TFT may also be partially under the PDL-1 and partially under the reflective anode.
  • a first encapsulation layer Encap-1 may also be included on the top side of the light-emitting layer.
  • the first encapsulation layer is substantially transparent to the light emitted by the light emitting unit, plays the role of encapsulating the OLED unit, and can planarize the upper surface of the light emitting layer.
  • a short pass (short wave pass) structure may be provided in the first encapsulation layer.
  • the short-pass structure can reflect red light and green light stronger than blue light, and play the role of increasing the red and green light obtained by the transmission and reflection conversion of the light emitted by the blue light-emitting unit.
  • the thickness of Encap-1 is typically less than 10 ⁇ m.
  • the thickness of Encap-1 is related to pixel design and resolution. The higher the resolution and the smaller the pixel design, the thinner the encapsulation film thickness needs to be. The main reason is that in the light-emitting direction, the light emitted from the light-emitting unit will pass through the Encap-1 to reach the surface of the wavelength conversion unit. When a material with a lower index of refraction exists in Encap-1, the light will gradually diverge to the surroundings due to the low index of refraction of the material.
  • An example of a lower refractive index material may be the organic flat layer in the Encap-1 layer, which may have a thickness of about 4-8 ⁇ m and may account for a major portion of the thickness of Encap-1.
  • the thickness of the encapsulation layer increases, the light emitted by the light emitting unit is refracted farther to the surroundings through the encapsulation layer, which may eventually affect adjacent sub-pixels and cause unnecessary light leakage.
  • the preferred thickness is ⁇ 6 ⁇ m. Considering the packaging performance requirements, the minimum thickness of the packaging layer should not be less than 1 ⁇ m.
  • Encap-1 can be a single-layer inorganic layer, or can be a laminated structure of multiple sub-layers, such as a first inorganic layer/organic layer/second inorganic layer stack, or a first inorganic layer/second inorganic layer stack, etc. .
  • Encap-1 adopts a bottom-up first inorganic layer/organic layer/second inorganic layer stack or a first inorganic layer/second inorganic layer stack, and a short-pass structure is also provided therein.
  • An example of a short-pass structure is when at least one of the first inorganic layer or the second inorganic layer consists of a multilayer inorganic film, and at least a portion of the inorganic film in the multilayer inorganic film tends to optically more easily reflect yellow light.
  • the short-pass structure can play the role of optical adjustment.
  • the transmittance of the blue light emitted by the lower light emitting unit is higher, and the red/green light generated by the upper wavelength conversion unit is more reflected, thereby improving the overall optical utilization rate of the display panel.
  • the first encapsulation layer may be a first inorganic layer containing a short-pass structure and a second inorganic layer thereon, a first inorganic layer and a second inorganic layer containing a short-pass structure thereon, a short-pass structure containing The first inorganic layer of the structure and the organic planar layer thereon and the second inorganic layer, the first inorganic layer and the organic planar layer thereon and the second inorganic layer containing the short-pass structure, and so on.
  • the first encapsulation layer containing the organic flat layer is more preferable.
  • the first encapsulation layer may include a first inorganic layer and a second inorganic layer on a side of the first inorganic layer away from the light-emitting layer, the second inorganic layer including a laminate of a plurality of inorganic sublayers, the laminate is The reflectivity of the light whose wavelength is converted by the wavelength conversion unit is stronger than that of the light emitted by the light emitting unit, and the transmittance of the light emitted by the light emitting unit is greater than that of the light whose wavelength is converted by the wavelength conversion unit.
  • the short-pass structure can be prepared by semiconductor technology, for example, a three-layer inorganic film structure of SiOx/TiO2/SiOx with a total thickness of 100 to 700 nm, preferably 170 to 350 nm, is used as the short-pass structure in one inorganic layer. It is also possible to use an inorganic film structure comprising more alternating layers of SiOx/TiO2 as the short-pass structure, such as SiOx/TiO2/SiOx/TiO2, SiOx/TiO2/SiOx/TiO2/SiOx, and the like.
  • the first inorganic layer and the second inorganic layer containing the short-pass structure thereon or the first inorganic layer and the organic flat layer thereon and the second inorganic layer containing the short-pass structure thereon are used, that is, the first inorganic layer on the top side is used.
  • a short-pass structure is formed in the two inorganic layers. In this way, the first inorganic layer and the optional organic layer under the short-pass structure can be used to keep the distance from the OLED device, thereby alleviating the possible degradation effect of the local high temperature when the short-pass structure is formed by the semiconductor thin film deposition process on the OLED device. .
  • FIG. 3 shows a schematic layer stack structure of Encap-1 of FIG. 2 . It includes a first inorganic layer Encap-1.1, an organic layer Encap-1.2, and a second inorganic layer Encap-1.3, and the second inorganic layer further includes a short-pass structure formed by a three-layer inorganic film of SiOx/TiO2/SiOx.
  • the second inorganic layer is relatively far away from the bottom side, so that the local high temperature during its preparation has little effect on the light emitting units on the bottom side.
  • the first pixel defining layer PDL-1 is a wall with a certain thickness and width on both sides of the organic light-emitting material portion of the light-emitting unit.
  • the wall is in the shape of a regular trapezoid, ie having a top side, a bottom side and symmetrical sides, wherein the bottom side is longer than the top side.
  • a normal trapezoidal wall is beneficial to form an inverted trapezoid in the organic light-emitting material portion between the two walls, so that the emitted light can be fully emitted, thereby improving the luminous efficacy.
  • such a normal trapezoidal wall is also advantageous for the deposition process in which each film layer of the OLED unit is performed.
  • trapezoid includes a regular trapezoid, an inverted trapezoid, and also a rectangle, wherein the inverted trapezoid is a bottom side shorter than the top side, and a rectangle is a bottom side equal to the top side.
  • the shape of a trapezoid can be characterized by the angle between the base and the side. In this article, the angle between the base and the side refers to the interior angle of the trapezoid.
  • the trapezoidal shape is ideal in terms of characterization simplicity, but it is not easy to achieve in terms of technology.
  • the inventors of the present disclosure have found that the actually formed PDL often does not have a standard trapezoid shape, and sometimes even has a large difference from the standard trapezoid.
  • the inventors have found that a particular quadrilateral can be used to characterize the cross-sectional shape of the pixel-defining layer. In the present disclosure, such a quadrilateral is called a characteristic quadrilateral.
  • the inventors further found that when the characteristic quadrilateral of the cross-sectional shape of the pixel defining layer satisfies certain requirements, it is helpful to further optimize the light extraction structure of the present disclosure.
  • the pixel defining layer here includes both the first pixel defining layer PDL-1 and the second pixel defining layer PDL-2.
  • the characteristic quadrilateral is done as follows.
  • the free edges of the cross-sectional shape of the pixel-defining layer are first distinguished.
  • the pixel-defining layer must be formed on a base plate, and the side that does not contact the base plate is its free edge. Find the point farthest away from the bottom plate among the free edges of the pixel-defining layer, and make a line segment parallel to the substrate substrate of the display panel, which is called the first edge.
  • the two ends of the non-free edge of the pixel-defining layer ie, the boundary between it and the bottom plate
  • Line segments circumscribed from the two ends to the cross-sectional shape and extending toward the first side serve as the third side and the fourth side, and the quadrilateral enclosed by the four sides is the characteristic quadrilateral.
  • characteristic quadrilaterals surrounded by the first to fourth sides 1 to 4 are made for different pixel-defining layer cross-sectional shapes.
  • the characteristic quadrilateral may be non-trapezoid, but trapezoid is preferred.
  • the present disclosure basically takes a trapezoid as an example to illustrate the cross-sectional shape of the pixel defining layer, but it should be understood that the description and definition of the trapezoid can be extended to feature quadrilaterals.
  • each of the angle between the second side and the third side and the angle between the second side and the fourth side is in the range of 20° to 60°, more preferably 20° to 40°.
  • a regular trapezoid is preferably used, and the included angle between the side and the base is preferably between 20° and 60°, more preferably between 20° and 40°.
  • the height of PDL-1 is preferably between 1 and 2 ⁇ m.
  • the openings formed by such trapezoidal cross-sections and thicknesses are particularly convenient for forming various film layers of the light-emitting unit, especially the OLED light-emitting unit, through a deposition process, and advantageously making full use of the light emission of the light-emitting unit.
  • the inventor unexpectedly found that the shape of the PDL-1 will affect the electrical connection or overlap performance of the cathode in the light-emitting unit, and the high-efficiency blue OLED device has higher requirements for the cathode overlap.
  • Overlap refers to the laying of the cathode along the side walls and top of the PDL-1.
  • the cathode eg, a thin metal layer about 15 nm thick
  • the cathode can be formed by an evaporation process using an open mask, which is deposited on the side and top surfaces of PDL-1.
  • the cross section of the PDL-1 is a regular trapezoid and the angle between the side and the bottom is within the above-mentioned preferred range, it is beneficial to achieve good overlap of the cathode of the light-emitting unit of the present disclosure. If the above-mentioned angle is too large, the side wall of PDL-1 is relatively steep, which makes it easy to have poor overlap when laying the cathode, which affects the effect of the device.
  • the above-mentioned preferred angles are also advantageous for preparing small-sized OLED display panels. Therefore, the above-mentioned shape of the PDL-1 is beneficial to improve the efficiency of the light-emitting unit, thereby improving the light-emitting and display effects.
  • PDL-1 can be colored or transparent.
  • PDL-1 is colored, more preferably black.
  • the colored, especially black, PDL-1 helps shield crosstalk caused by the lateral propagation of light between adjacent subpixels.
  • the light-emitting area of the light-emitting unit defined by PDL-1 is G ⁇ R ⁇ B in each sub-pixel. That is, the light-emitting area of the light-emitting unit of the green sub-pixel ⁇ the light-emitting area of the light-emitting unit of the red sub-pixel ⁇ the light-emitting area of the light-emitting unit of the blue sub-pixel. This is because the human eye is most sensitive to green light, followed by red light and blue light.
  • the green sub-pixel can effectively improve the brightness that the human eye can perceive.
  • the green sub-pixel has a larger light-emitting unit area because the available green light-emitting energy is lower than the available red light-emitting energy. For simplicity, however, equal light-emitting areas are shown in Figure 2.
  • the width of the PDL-1 wall can be designed according to the design resolution and aperture ratio of the display panel.
  • Substrate substrates can use rigid glass or plastic base materials.
  • the PDL-1 can be formed on the TFT substrate with the pixel-defining layer materials and fabrication processes commonly used in OLED devices.
  • a reflective anode electrically connected to the TFT is formed at the bottom of the space defined by the PDL-1.
  • the subsequent film layers of the OLED light-emitting unit can be deposited in an Open Mask manner, including But not limited to organic light-emitting material layer, semi-transparent cathode layer, light extraction layer, etc. It is more economical because fine metal masks do not have to be used.
  • the light-emitting unit preferably emits blue light, more preferably a wavelength center range of 420 to 470 nm, and a half width of 10 to 30 nm.
  • the display panel forming process may include a cell-to-cell method and an on-EL method.
  • the cell-to-cell method refers to separately forming the light-emitting layer and the wavelength conversion layer, and then assembling the two to the cell.
  • the on-EL method is to continue to prepare the wavelength conversion layer layer by layer in the light emitting layer.
  • the preparation process of the wavelength conversion unit/backlight diffusion unit may include ink jet printing and photolithography.
  • the light-emitting layer needs to be formed first.
  • the light-emitting layer In the cell-matching mode, the light-emitting layer is cell-matched with the overall wavelength conversion layer; while in the on-EL mode, the wavelength conversion layer is formed layer by layer on the light-emitting layer.
  • the wavelength conversion layer of the present disclosure is described below in conjunction with specific modes.
  • Mode I Inkjet printing method to form wavelength conversion layer and assemble the cell
  • mode I is to form the wavelength conversion layer separately from the light-emitting layer by inkjet printing first, and then assemble the wavelength conversion layer and the light-emitting layer into a cell.
  • the wavelength conversion layer is formed on a substrate separate from the light emitting layer. With the wavelength conversion unit or optional transparent unit of each sub-pixel in the wavelength conversion layer aligned with the light emitting unit, the light emitting layer and the wavelength conversion layer are assembled together to form a display panel. In order to form a display panel with a cell, between the light-emitting layer and the wavelength conversion layer, a filler layer and a support pillar structure are usually arranged in the center of the display panel, and a bank layer at the periphery is required.
  • the wavelength conversion layer is preferably formed directly on the color filter layer. That is, the color filter layer is used as the bottom plate of the wavelength conversion layer, so it is unnecessary to provide an additional bottom plate for forming the wavelength conversion layer, so that the wavelength conversion unit is in direct contact with the color filter, which not only simplifies the process and materials, but also improves the luminous efficiency.
  • This combination can also be referred to as a wavelength-converting color filter substrate.
  • quantum dots are used as down-conversion materials, it can be called a quantum dot color filter substrate
  • FIG. 4 shows a schematic diagram of a color filter layer as a base plate.
  • the color filter layer 3 has a transparent substrate 31 and has a black matrix BM thereon for light shielding. Between the black matrices, the required color filter units, such as blue, green, and red color filter units B-CF, G-CF, R-CF, are formed.
  • BM/B-CF/R-CF/G-CF can be prepared sequentially on the transparent substrate 31 according to the conventional process flow, and the preferred thickness is BM ⁇ 2 ⁇ m, R/G/B CF ⁇ 3 ⁇ m. Since the color filter unit is slightly thicker than the BM, in general, the CF will partially overlap the BM. This ensures that there is no light leakage gap between the BM and the color filter unit. Specifically, the edge of the color filter can overlap the top of the BM in an inclined curved surface.
  • the transmittance spectrum needs to be well matched with the spectrum of the wavelength conversion material such as QD after being excited by the B-OLED.
  • R-CF/G-CF needs to filter out the blue light that is not absorbed by the wavelength conversion material well, and also needs to cover the down-converted excitation peak range.
  • a wavelength conversion layer can be formed, and the wavelength conversion color filter substrate thus obtained is then assembled with the light-emitting layer to form a display panel.
  • FIG. 5 shows an example of the cooperation between the filter property of the color filter unit and the luminescence property of the wavelength conversion unit.
  • the ordinate in the figure is the light transmittance for the color filter unit, the spectral energy after excitation for the wavelength conversion unit, and the abscissa is the wavelength.
  • the dark solid line G-QD represents the spectral energy of the green wavelength conversion layer
  • the light solid line R-QD represents the spectral energy of the red wavelength conversion layer
  • the dense dashed line G-CF represents the light transmittance of the green color filter unit
  • the thin dashed line R-CF represents the light transmittance of the red color film unit.
  • the light below 480nm is filtered out by the color filter.
  • the green color filter allows the passage of green converted light at around 540nm
  • the red color filter allows the passage of red converted light at around 640nm. Therefore, under the irradiation of blue light, the wavelength conversion color filter substrate can display red light and green light well.
  • the light-emitting energy of the green wavelength conversion unit in the green color filter transmission wavelength range is low.
  • the green sub-pixel area can be the largest, while the blue sub-pixel can have the smallest area because there is no down-conversion loss.
  • a second pixel defining layer PDL-2 is formed on the color filter layer, which defines the space of the wavelength conversion unit or the transparent unit. Subsequently, a wavelength conversion unit or a transparent unit is formed in the space enclosed by the walls of the PDL-2.
  • the second pixel defining layer PDL-2 may be formed directly on the BM, and in this mode, a bank layer (Bank) of the wavelength conversion unit is formed as inkjet printing.
  • a bank layer (Bank) of the wavelength conversion unit is formed as inkjet printing.
  • the process of forming the wavelength conversion unit by inkjet printing is to use ink (Ink) containing a wavelength conversion material, printing the ink into the space between the dam layers, and then curing (eg photocuring) the ink layer to form the wavelength conversion unit. Processes for inkjet printing such as QDs are known.
  • the color filter layer may also have a protective layer covering the black matrix and/or the color filter unit, and the PDL-2 and the wavelength conversion unit are formed on the protective layer.
  • the dam layer needs to have a lyophobic surface, including side and top surfaces, to reduce ink climbing along the side of the wall.
  • the top surface has a higher requirement for lyophobicity than the side surface.
  • the entirety of PDL-2 is prepared from a material having lyophobicity.
  • raw materials for the lyophobic material may include mixtures of acrylate polymers and multifunctional monomers, mixtures of silicone polymers and acrylic monomers, and the like.
  • the lyophobicity can be characterized by the contact angle.
  • each of the angle between the second side and the third side and the angle between the second side and the fourth side is between 80° and 140°, more preferably between 95° and 120°.
  • each of the included angle between the first side and the third side and the included angle between the first side and the fourth side is between 40° and 100°, preferably between 60° and 85°.
  • the cross section may be a trapezoid (including a rectangle), and when the side of the color filter layer is the bottom side of the trapezoid, the angle between the side and the bottom is between 80° and 140°, preferably between 95° and 120°.
  • the angle between the side edge and the bottom edge of the cross-section of the bank layer is between 40° and 100°, preferably between 60° and 85°.
  • the wavelength conversion unit formed by inkjet printing defined by the bank layer has a high utilization rate of optical energy. Outside this angle, light energy loss increases. It should be noted that this preferred range not only takes into account the optical performance, but also the difficulty of process realization of the bank layer at such an angle.
  • the bank layer on the color filter layer is actually an "inverted trapezoid".
  • FIG. 6( a ) shows a photomicrograph of the structure of a wavelength-converting color filter substrate printed in a cell mode inkjet in one example of the present disclosure.
  • the photo shows the dam layer, the wavelength conversion unit on both sides of the dam layer, and the encapsulation layer, packing layer, etc.
  • 61 is part of the Encap-1 layer.
  • the OLED unit and the first pixel-defining layer thereon have been peeled off for preparing SEM samples, and the shallow depression at the arrow is where the first pixel-defining layer is located in the case of cell alignment.
  • 62 is the filler layer
  • 63 is the second encapsulation layer Encap-2
  • 64 is the wavelength conversion unit
  • 65 is the PDL-2 layer (ie the bank layer Bank)
  • 66 is the color filter unit
  • 67 is the black matrix
  • 68 is the substrate.
  • the reason for the delamination of the wavelength conversion unit on the right side of the figure is the difference in curing efficiency caused by the process.
  • the schematic diagram of the mushroom-shaped section can be shown in Fig. 6(b), the two upper top corners are rounded, and the undercut depth at the root may be reduced.
  • an inverted trapezoid that circumscribes the mushroom shape is used to represent it.
  • the top edge of the circumscribed inverted trapezoid is flush with the highest point of the mushroom shape, and the bottom edge is the root of the mushroom shape.
  • the trapezoid representing this mushroom-shaped cross-section is shown in grey line in Figure 6(b).
  • the scope of the inverted trapezoid design of the present disclosure also includes the mushroom-shaped dam layer represented by such a trapezoid. It should be noted that if the process allows, the deviation of the product by the trapezoid should be avoided as much as possible, that is, the standard trapezoid is more ideal.
  • the thickness of the bank layer is preferably 6-20 ⁇ m, more preferably 10-16 ⁇ m, that is, the thickness may be 3 to 20 times, more preferably 5 to 16 times, the thickness (1-2 ⁇ m) of PDL-1.
  • a trapezoidal cross-sectional shape of this size is beneficial for reducing critical dimension bias (CD bias) while reducing ink climb.
  • the thickness setting range is an optimal range after balancing optical conversion efficiency and brightness for the existing ink materials containing wavelength conversion materials. When the thickness is too low, the absorption rate of wavelength conversion materials such as QDs to luminescence is insufficient; while when the thickness is too high, the quantum efficiency of wavelength conversion will appear quantum annihilation and decrease after reaching the saturation value. If the ink formulation is further improved in the future, the thickness can be further reduced, but it should still be kept above 6 ⁇ m.
  • the wavelength conversion color filter substrate includes a color filter layer and a wavelength conversion layer.
  • Figure 7(a) shows that PDL-2 is first formed on the black matrix, defining spaces for the wavelength conversion unit and the transparent unit.
  • Figure 7(b) shows the formation of green, red wavelength conversion units G-QD and R-QD and transparent unit T, respectively, on the green, red and blue color film units by inkjet printing into the above space.
  • Figure 7(c) shows that the second encapsulation layer Encap-2 can then be formed.
  • Figure 7(d) shows that the support post structure (PS) required for the cell pairing can also be formed on PDL-2.
  • Figure 7(e) shows that the top surface of the wavelength converting layer may also be slightly lower than the top surface of PDL-2 in some embodiments, eg, due to uniformity control resulting in differences in ink holding capacity.
  • the dam layer needs to use a liquid-repellent material, and its adhesion to the substrate is comprehensively considered, so its shape is affected by the preparation process.
  • the PDL-2 layer can typically be patterned by exposure and development, that is, by UV curing with light under a mask, followed by removal of uncured portions to form PDL-2.
  • colored PDL-2 such as black PDL-2, is preferred.
  • PDL-2 is colored and thick, the UV light received by the PDL material close to the color filter layer is not enough to cure it, and it is easily removed during development, forming an undercut, resulting in a trapezoidal cross-section
  • the included angle between the side edge and the bottom edge is greater than 95° within the aforementioned preferred range.
  • the reflection type PDL-2 is also preferable.
  • the reflective PDL-2 can be a gray dam layer, which appears gray due to the presence of scattering particles, or a yellow dam layer with a stronger reflection effect for the yellow wavelength band.
  • the gray dam layer can provide proper reflection and can be easily made into an inverted trapezoid or a regular trapezoid by controlling the exposure level.
  • the advantage of the yellow dam layer is that it is particularly beneficial to improve the light extraction efficiency.
  • the reflective effect can be improved by adding side metal, such as metal Al and alloys, on the dam layer by a photolithography process.
  • the thickness of the metal layer can be 200-400 nm, which can provide sufficient reflectivity without affecting the configuration of the dam layer.
  • the use of reflective PDL-2 and the corresponding increase in reflectivity can help to improve the light extraction effect.
  • the patterned reflective metal layer prepared on the side of the second pixel defining layer can increase the optical wavelength conversion distance of blue light emission in the wavelength conversion unit.
  • reflective PDL-2 which adds metal layers by photolithography, sometimes reduces the process window for patterned photolithography.
  • the reflectivity of the reflective PDL-2 is 50 to 70% in the yellow wavelength band, and 20 to 40% in the blue wavelength band.
  • the reflectivity of the reflective PDL-2 is 50 to 70% in the yellow wavelength band, and 20 to 40% in the blue wavelength band.
  • the reflective performance of PDL-2 to color light is also related to its thickness.
  • the reflectivity of the dam layer for various colors of light may be different.
  • Both the gray dam layer and the yellow dam layer have high reflectivity in the longer wavelength yellow region and low reflectivity in the shorter wavelength blue region.
  • the thickness has little effect on the reflectivity in the blue light region, and in the yellow light region, the higher the thickness, the higher the reflectivity.
  • the yellow PDL-2 dam layer in the yellow light region, the higher the thickness, the higher the reflectivity, while in the blue light region, when the thickness is smaller, especially less than 6 ⁇ m, the reflectivity in the blue light region is higher. . Therefore, a large PDL-2 thickness is advantageous, which ensures high reflection in the yellow light region and avoids high reflection in the blue light region. Therefore, from the perspective of reflection effect, the thickness of PDL-2 should not be less than 6 ⁇ m.
  • the line width of the second pixel defining layer is usually 10-50 ⁇ m, preferably 15-30 ⁇ m.
  • the line width of the widest part of the second pixel defining layer is taken as its line width.
  • the width of the critical geometric dimension generally adopts the widest width, so as to facilitate the determination of the critical dimension in the photolithography process, for example.
  • the resin can be main cured by conventional 230°C process. More preferably, PDL-2 is prepared using a lyophobic and colored resin that can be cured at low temperature (eg curing conditions of 85 to 105°C).
  • Figures 8(a)-(f) show photomicrographs of some of the second pixel-defining layers.
  • Figure 8(a) shows a regular trapezoidal gray embankment layer.
  • Figure 8(c) shows an inverted trapezoidal grey dam layer. The gray embankment layer with scattering particles can easily obtain a normal trapezoid or inverted trapezoid section by adjusting the photocuring parameters.
  • Figure 8(c) shows an approximately rectangular yellow dam layer, which is beneficial for increasing red and green light reflection and reducing blue light reflection.
  • Figure 8(d) shows a mushroom-shaped black dam layer whose undercut is easily formed by a photocuring process.
  • Figure 8(e) shows an inverted trapezoidal dam layer with metal sides for reflection.
  • Figure 8(e) shows one side of an inverted trapezoidal dam layer with metal sides for reflection, ie bright edges in it.
  • Figure 8(f) shows an oblique view of an inverted trapezoidal dam layer with metal sides for reflection.
  • Mode I after the PDL-2, ie, the dam layer, is formed on the color filter layer, the inkjet printing method is used to prepare the wavelength conversion unit with the ink containing the wavelength conversion material.
  • the ink containing the wavelength conversion material is printed and cured by an ink jet printing method.
  • the wavelength-converting material-containing ink may be composed of a wavelength-converting material (such as QD particles) and a matrix, and the matrix in the wavelength-converting material-containing ink is photocurable.
  • the ink layer containing the wavelength conversion material is transformed into a wavelength conversion resin film.
  • the thickness of the wavelength conversion resin film can be extended to 6 to 30 microns based on the thickness of the lyophobic dam layer (eg, 6 to 20 microns), which depends on the lyophobicity of the dam layer and the volume of printing ink.
  • the thickness of the wavelength converting resin is preferably 10 to 20 ⁇ m.
  • the lyophobicity of the bank layer is as described above, and may preferably be a contact angle of ⁇ 90° with respect to deionized water, and a contact angle with respect to propylene glycol methyl ether acetate (PGMEA) ⁇ 35°.
  • Figure 9 shows a 45[deg.] top view SEM photograph of a wavelength converting unit defined by an inverted trapezoidal second pixel-defining layer in one embodiment.
  • area A is the upper surface of the cured wavelength conversion unit
  • area B is its cross section.
  • the wavelength conversion unit is flanked by an inverted trapezoidal bank layer (ie, the second pixel defining layer), more specifically, it is in a "mushroom" shape.
  • Its side wall is C
  • the cross section is D
  • the top surface is E
  • the downwardly inclined edge of the top surface is F.
  • a wavelength conversion unit is arranged in the space enclosed by the middle of the dam layer.
  • the space G defined by the dam layer that has not yet been filled with ink can be seen in the lower right corner of the image.
  • the figure shows that inkjet printing can be performed well with the help of the inverted trapezoidal hydrophobic dam layer, and the space defined by the dam layer is well filled with the ink containing the conversion material and cured to form a wavelength conversion unit.
  • the angle between the side wall C and the bottom edge may be 80 to 140°, preferably 95 to 120° in the shape of an inverted trapezoid.
  • the angle between the side edge and the bottom edge may be 40 to 100 degrees, preferably 60 to 85 degrees.
  • Figure 10(a) shows the preferred angular range for Mode I. It should be understood that the trapezoidal shapes in Figures 10(a)-(d) are only schematic and represent the characteristic quadrilaterals of the respective modes.
  • a second encapsulation layer Encap-2 can be covered, as shown in Figure 5(c).
  • the second encapsulation layer covers the surfaces of the second pixel defining layer and the wavelength conversion unit to protect the fabricated wavelength conversion unit.
  • the second encapsulation layer is an encapsulation layer that protects the wavelength conversion unit after the wavelength conversion unit is formed
  • the first encapsulation layer is an encapsulation layer that protects the light emitting unit after the light emitting unit is formed.
  • the second encapsulation layer is optional. When a sufficiently high-stability wavelength conversion material or a sufficiently good stack integration process is used, the wavelength conversion unit may not need to be packaged.
  • Encap-2 can be a low-stress, dense inorganic thin film prepared by a low temperature process ( ⁇ 180°C), such as SiOx/SiNx/Al2O3, etc. Specifically, CVD, ALD and other processes can be used.
  • the thickness of the film layer is less than 1 ⁇ m, preferably less than 0.5 ⁇ m, and the refractive index is in the range of 1.7 to 2.0, preferably 1.75 to 1.85, for protecting the wavelength conversion resin film layer and maintaining the wavelength conversion optical efficiency.
  • Such a thickness range of the second encapsulation layer can reduce the thickness of the optical box described below and reduce crosstalk.
  • the film with such a refractive index has better compactness, which is more favorable for protecting the wavelength conversion resin film layer.
  • Such a second encapsulation layer can also be used in Mode II.
  • the wavelength conversion color filter substrate comprising the color filter layer and the wavelength conversion layer is assembled into a cell with the prepared light-emitting layer.
  • the filler is filled, the supporting column structure is optionally provided, and the embankment layer enclosing the filler layer is surrounded at the periphery of the display panel.
  • the bank layer and filler can be applied and filled in a vacuum or nitrogen environment. Specifically, in a vacuum or nitrogen environment, on the light-emitting surface of the light-emitting layer or the light-incident surface of the wavelength conversion layer, the material of the embankment layer is coated on the periphery and the filler is coated in the effective display area (AA) of the panel, and then After the two layers are close to each other, high-precision alignment and box alignment are realized.
  • AA effective display area
  • the bank layer is cured using ultraviolet (UV) light.
  • UV ultraviolet
  • the filler can be thermally cured at low temperature ( ⁇ 100°C).
  • the thickness of the bank layer is 15 to 50 ⁇ m, preferably 20 to 40 ⁇ m, more preferably 20 to 30 ⁇ m.
  • the bank layer may be resin, which may contain fiber or microsphere fillers of controlled particle size or thickness.
  • the filler is preferably a low-temperature curing resin (main curing temperature ⁇ 100°C, preferably ⁇ 90°C), and the outgas value is less than or equal to 100ppm after curing at 100°C for 2 hours.
  • the thickness of the filler after curing is in the range of 5 to 30 um, preferably 10 to 15 um. Too thin fillers and embankments will affect the cell-to-box performance of the components on both sides, and too thick will affect the display performance of the display panel.
  • the area of the wavelength conversion unit can increase accordingly, and the difference between the area of the wavelength conversion unit and the light emitting area of the light emitting unit and the thickness of the optical box (between the light incident surface of the wavelength conversion unit and the light emitting surface of the light emitting unit)
  • the distance which can be the sum of the thicknesses of the filler layer and the encapsulation layer) is positively correlated.
  • the greater the thickness of the optical box the greater the difference between the area of the wavelength conversion unit and the light-emitting area of the light-emitting unit, so as to avoid the influence of cross-color caused by excitation light between pixels.
  • the optical box thickness is also related to the pixel design and resolution. The higher the resolution and the smaller the pixel design, the smaller the required optical box thickness. Similarly, an excessively thick optical box thickness may result in crosstalk of light refraction to adjacent sub-pixels.
  • FIG. 11 schematically shows an embodiment of a QD-OLED display panel after cell alignment. Assemble the blue B-OLED light-emitting layer and the QD wavelength conversion color filter substrate with the support column structure PS of FIG. 5(d) into a box, and fill the filling with Filler and have a surrounding bank layer DAM to assemble one of the disclosed display panels. implementation plan.
  • T represents the transparent unit
  • G-QD and R-QD represent the green and red QD wavelength conversion units
  • B-CF, G-CF and R-CF represent the color filter units of blue, green and red.
  • Figure 11 highlights the filler and bank layers, and the OLEDs are depicted as being completely separated by PDL-1 for clarity of illustration of the individual sub-pixels. However, it should be understood that, as described above, the luminescent material layers, cathodes, etc. in adjacent OLEDs can also be connected to each other across the PDL-1.
  • the thickness of the bank layer in the present disclosure can be about 30 ⁇ m similar to the conventional bank layer, and the thickness of the filler layer (in terms of the distance between the light emitting unit and the wavelength conversion unit or the transparent unit) can be thinned to 5 to 10 ⁇ m, which is much smaller than that of the conventional bank layer.
  • the support pillar structure may be formed on both the second pixel defining layer and the first pixel defining layer, and in some cases, there may be no support pillar structure, only relying on the bank layer and filler The distance between the OLED light-emitting unit and the wavelength conversion unit or the transparent unit is maintained.
  • the support post may or may not be in direct contact with the pixel defining layer.
  • the support pillar structure may be selectively provided only on a part of the pixel defining layer.
  • the support pillar structure may be prepared in a general method in the related art, and its distribution density in the display panel is appropriately designed.
  • the support pillar structure is preferentially fabricated on the pixel-defining layer between the red sub-pixel and the green sub-pixel with a larger opening area, because the optically high brightness sensitivity and process window capability of green can be taken into account.
  • the human eye is not sensitive to green, so the brightness of the green sub-pixel is high; on the other hand, the physical size of the green and red sub-pixels is large, which can provide better processing capability for forming the support column structure.
  • the light-emitting surface of the light-emitting unit is in the orthographic projection of the light-incident surface of the wavelength conversion unit in the light-emitting layer.
  • the light-emitting surface of the light-emitting unit is smaller than the light-incident surface of the wavelength conversion unit.
  • FIG. 12 shows the relationship between the light-emitting surface of the light-emitting unit, the light-incident surface of the wavelength conversion unit, and the cell thickness.
  • the thickness between the light-emitting surface of the lower light-emitting unit and the lower surface of the upper wavelength conversion unit is the cell thickness, and the thickness may include a filler layer (Filler) and an optional encapsulation layer (Encap, such as the first 1.
  • a/b is not greater than tan 60° (ie ⁇ 60° in the figure). If the value of a/b is too large, the angle deviation of the light-emitting unit from the vertical direction when entering the wavelength conversion unit is too large, and total reflection is likely to occur on the light-emitting path in the thin-film laminate structure with the difference in refractive index, which affects the luminous efficiency. .
  • a plurality of wavelength conversion units may be overlapped on a side surface of the second pixel defining layer close to the base substrate.
  • the plurality of wavelength conversion units may include adjacently arranged first color wavelength conversion units and second color wavelength conversion units, and the first color wavelength conversion units overlap with the first color wavelength conversion units to separate the two.
  • the widths of the second pixel-defining layers are different.
  • the display panel may further include: a color filter layer on a side of the wavelength conversion unit away from the light-emitting layer, wherein the color filter layer includes a plurality of color filter units and a black matrix defining the plurality of color filter units, The plurality of color filter units are overlapped on a side surface of the black matrix close to the base substrate, and the overlapped width of the wavelength conversion unit on the second pixel defining layer and the same sub-pixel belong to the same sub-pixel.
  • the overlapping widths of the color filter units on the black matrix are different.
  • the width of the finally formed wavelength conversion unit overlapped on the second pixel defining layer is preferably 10 times the width of the overlapped surface of the second pixel defining layer. % or less.
  • overlapping refers to the color filter units, wavelength conversion units, or light-emitting layers filled in the black matrix, the first pixel-defining layer, and the second pixel-defining layer (which may be collectively referred to as unit-defining layers), respectively, on top of them Instead, these cell-defining layers are covered. If the top surface of the cell-defining layer is flat, the overlapping portion is the portion that is on the plane of the top surface. The horizontal distance between the edge of the overlapping portion and the edge of the top surface is the overlapping width.
  • FIG. 11 shows that the color filter unit is overlapped on the side of the black matrix close to the base substrate, and the wavelength conversion unit is overlapped on the side of the second pixel defining layer close to the base substrate.
  • the overlap width of the two is different.
  • FIG. 11 shows that the overlapping widths of adjacent wavelength conversion units on the second pixel-defining layer are substantially the same, but they may also be different, and each overlapping width is the overlapped surface of the second pixel-defining layer. within 10% of the width.
  • the surface to be overlapped is the lower surface of PDL-2.
  • Mode II is the same as Mode I at least in the light-emitting layer and the cell assembling process, and the main difference from Mode I is that the wavelength conversion unit is formed by photolithography instead of inkjet printing.
  • the wavelength conversion unit is formed by directly coating a photoresist resin or photoresist containing a wavelength conversion material such as QDs and patterning it using a photolithography method.
  • a second pixel defining layer PDL-2 is prepared on the black matrix BM of the color filter layer.
  • PDL-2 is no longer a dam layer for inkjet printing. Therefore, it does not need to have lyophobicity for the printing ink, and it no longer acts as a bank layer.
  • the embankment layer is formed on the bottom plate opposite to the base substrate in the characteristic quadrilateral of its cross-section, so the side close to the base substrate is the first side of the characteristic quadrilateral.
  • each of the angle between the second side and the third side and the angle between the second side and the fourth side is between 60° and 120°, more preferably between 90° and 120°.
  • each of the included angle between the first side and the third side and the included angle between the first side and the fourth side is between 60° and 120°, preferably between 60° and 90°.
  • the cross section can be a trapezoid (including a rectangle), and when the side of the color filter layer is the bottom side of the trapezoid, the angle between the side and the bottom is between 60° and 120°, preferably between 90° and 120°.
  • the angle between the side edge and the bottom edge of the cross-section of the bank layer is between 60° and 120°, preferably between 60° and 90°.
  • the optical energy utilization rate of the wavelength conversion unit formed by photolithography is high. Outside this angle, light energy loss increases.
  • Figure 10(b) shows the preferred angular range for Mode II.
  • the thickness of PDL-2 is 6 to 12 ⁇ m.
  • the resin density is higher and the volume occupied is smaller, so the thickness of PDL-2 can be slightly lower than that of Mode I, but the lower limit should still be more than 2 times that of PDL-1 , preferably 6 ⁇ m or more.
  • a photoresist resin containing a wavelength conversion material also called a wavelength conversion photoresist
  • a photoresist resin containing a wavelength conversion material also called a wavelength conversion photoresist
  • photolithography steps such as irradiation, development, and etching under a mask
  • the unwanted part of the wavelength conversion photoresist is removed, and the wavelength conversion photoresist is retained in a part of the space defined by the PDL-2, that is, to achieve patterned to form wavelength conversion units.
  • different photoresists are applied and each photolithography process is performed once.
  • the baking and curing temperature after photoresist development is preferably ⁇ 180° C. to reduce the influence of heat treatment on the material.
  • the transparent unit can be formed of light-diffusing resin doped with scattering particles, so as to ensure the consistency of display viewing angle of each sub-pixel.
  • the thickness of the wavelength conversion unit is similar to that of the PDL-2, in the range of 6-12 ⁇ m.
  • the similar thicknesses of the two are beneficial to the window control of the subsequent integration process and the planarization of the subsequent process, thereby maintaining the uniformity of the optical performance and maintaining the viewing angle.
  • FIG. 13(a)-(b) schematically illustrate embodiments of wavelength conversion units and transparent units formed by photolithography on a color filter layer.
  • PDL-2 in order to facilitate sufficient filling of the wavelength conversion photoresist, PDL-2 has a positive trapezoid shape (with the color filter layer side as the bottom side). In this figure, it is shown that the area of the green cell ⁇ the area of the red cell ⁇ the area of the blue cell.
  • the support pillar structure PS can be re-formed on top of the PDL-2, and the figure shows that the PS is placed only between the green and red sub-pixels. As mentioned above, this is due to both the process window capability and the optically high brightness sensitivity of G.
  • the thickness of the wavelength conversion unit and the transparent unit formed by applying photoresist and subsequent photolithography process is similar to that of PDL-2. Compared with the inkjet printing method, in the photolithography method, it is simpler to adjust the thickness of the wavelength conversion unit by the thickness of the PDL-2.
  • Figure 13(b) shows that a second encapsulation layer Encap-2 may also be formed thereon.
  • steps such as cell assembling can be performed in a process similar to that described in Mode I to further fabricate the display panel.
  • the same process parameters can be used in most common parts for Modes I, II.
  • the same color filter layer, filler layer and bank layer can be used.
  • Modes I and II are methods of making the display panels of the present disclosure, including:
  • a second pixel defining layer is formed on the color filter layer as the bottom plate
  • the wavelength conversion layer is formed by inkjet printing ink containing the wavelength conversion material or by coating and photolithography containing the photoresist containing the wavelength conversion material to prepare a wavelength conversion color filter substrate, and
  • the wavelength conversion color filter substrate and the light-emitting layer are assembled into a display panel, wherein a filler layer and a bank layer are arranged between the wavelength conversion color filter substrate and the light-emitting layer.
  • the wavelength conversion layer is formed in a low temperature process at a temperature of ⁇ 180°C, including but not limited to forming PDL-2, wavelength conversion unit, and Encap-2.
  • a plurality of wavelength conversion units may be overlapped on a surface of the second pixel defining layer on one side of the second pixel defining layer close to the base substrate.
  • the plurality of wavelength conversion units may include adjacently arranged first color wavelength conversion units and second color wavelength conversion units, and the first color wavelength conversion units overlap with the first color wavelength conversion units to separate the two.
  • the widths of the second pixel-defining layers are different.
  • the display panel may further include: a color filter layer on a side of the wavelength conversion unit away from the light-emitting layer, wherein the color filter layer includes a plurality of color filter units and a black matrix defining the plurality of color filter units, The plurality of color filter units are overlapped on a side surface of the black matrix close to the base substrate, and the overlapped width of the wavelength conversion unit on the second pixel defining layer and the same sub-pixel belong to the same sub-pixel.
  • the overlapping widths of the color filter units on the black matrix are different.
  • FIG. 13 shows that the color filter unit is overlapped on the side of the black matrix close to the base substrate, but the wavelength conversion unit is not shown overlapped on the second pixel defining layer.
  • Mode III on-EL inkjet printing of wavelength converting layers
  • the on-EL as described in the present disclosure refers to a method in which a wavelength conversion layer and a color filter layer are continuously formed on the light emitting layer to form a display panel, which does not require cell assembly.
  • Mode III similar to Mode I, the wavelength conversion unit is formed by inkjet printing.
  • the PDL-2 is formed with the light emitting layer instead of the color filter layer as the backplane and then the wavelength conversion unit is formed.
  • FIG. 14(a)-(e) schematically illustrate the process of forming a display panel by on-EL and inkjet printing.
  • FIG. 14( a ) shows that PDL-2 is first formed at the position of PDL-1 of the light-emitting layer.
  • Figure 14(b) shows the subsequent formation of the QD wavelength conversion unit and the transparent unit T by inkjet printing in the space defined by the PDL-2.
  • Figure 14(c) shows that a second encapsulation layer can then be formed.
  • Figure 14(d) shows the subsequent formation of a color filter layer comprising a black matrix.
  • FIG. 14(e) shows that the reflective polarizer P and the cover film Cover are finally formed.
  • the respective legends in the light-emitting layer are the same as those of the light-emitting layer shown in FIG. 2 . It can be seen that no filler layer is required in the on-EL mode.
  • each of the angle between the second side and the third side and the angle between the second side and the fourth side is between 80° and 140°, preferably between 95° and 120°.
  • the section can be trapezoidal. Ideally, regardless of whether the display panel is formed in an on-EL manner or a cell-to-cell manner, from an optical point of view, the most preferred angles for the shape of the PDL-2 are similar, being slightly wider at the top and slightly narrower at the bottom.
  • the PDL-2 here is still a dam layer and the lyophobicity and climbing issues of the ink should be considered.
  • the included angle between the side edge and the bottom angle of the PDL-2 is between 80° and 140°, preferably between 95° and 120°, that is, Some concessions were made to the angle. It should be noted that this preferred range not only takes into account the optical performance, but also the difficulty of process realization of PDL-2 at this angle. Although this angle range does not achieve a wavelength conversion unit with a slightly wider top and a slightly narrower bottom, better display performance is still obtained in this preparation mode.
  • Figure 10(c) shows the preferred angular range for Mode III.
  • the thickness of PDL-2 is preferably 6-20 ⁇ m, more preferably 10-16 ⁇ m, that is, the thickness may be 3 to 20 times, more preferably 5 to 16 times, the thickness of PDL-1 (1-2 ⁇ m).
  • CD bias critical dimension bias
  • the thickness setting range is an optimal range after balancing optical conversion efficiency and brightness for the existing ink materials containing wavelength conversion materials. If the ink formulation is further improved in the future, the thickness can be further reduced, but it should still be kept above 6 ⁇ m.
  • FIG. 15(a)-(b) show photomicrographs of structures formed by on-EL and inkjet printing in one example of the present disclosure.
  • FIG. 15( a ) shows PDL-1 in a right trapezoid below, a first encapsulation layer above PDL-1, and PDL-2 in an inverted trapezoid above the first encapsulation layer.
  • the light-emitting units on both sides of PDL-2PDL-1 are so thin that they are not visible at this microscopic scale.
  • Fig. 15(b) shows the inverted trapezoid PDL-2 and the wavelength conversion unit formed by inkjet printing filling on the left side, and the right side is not filled by inkjet printing.
  • Inkjet printing is also used in Mode III, therefore, similar to Mode I, colored PDL-2, such as black PDL-2, is preferred in order to form the preferred undercut.
  • the reflective PDL-2 is also preferred.
  • the reflective PDL-2 can be a gray dam layer containing scattering particles, or a yellow dam layer with stronger reflection for the yellow wavelength band.
  • the reflective effect can be improved by adding side metal, such as metal Al and alloys, on the dam layer by a photolithography process.
  • the thickness of the metal layer can be 200-400 nm, which can provide sufficient reflectivity without affecting the configuration of the dam layer.
  • the use of reflective PDL-2 and the corresponding increase in reflectivity can help to improve the light extraction effect.
  • the patterned reflective metal layer prepared on the side of the second pixel defining layer can increase the optical wavelength conversion distance of blue light emission in the wavelength conversion unit.
  • the angle between the side edge and the bottom edge of the reflective PDL-2 is also between 80° and 140°, preferably between 95° and 120°.
  • the lyophobicity can be characterized by the contact angle.
  • its contact angle to deionized water should be ⁇ 90°
  • its contact angle to propylene glycol methyl ether acetate (PGMEA) should be ⁇ 35°.
  • the line width of the second pixel defining layer is usually 10-50 ⁇ m, preferably 15-30 ⁇ m.
  • the lyophobic resin should be selected to form PDL-2 with a primary cure temperature of not more than 100°C, rather than the conventional primary cure temperature of up to 230°C as in Mode I. This is attributable to the fact that the heat resistance of the light emitting layer as the base plate is inferior to that of the color filter layer.
  • the ink containing the wavelength conversion material is printed and cured by an ink jet printing method.
  • the wavelength-converting material-containing ink consists of a wavelength-converting material (eg, QD particles) and a matrix, and the matrix in the wavelength-converting material-containing ink is photocurable.
  • the ink layer containing the wavelength conversion material is transformed into a wavelength conversion resin film.
  • the thickness of the wavelength conversion resin film can be extended to 6 to 30 microns based on the thickness of the lyophobic dam layer (eg, 6 to 20 microns), which depends on the lyophobicity of the dam layer and the volume of printing ink.
  • the thickness of the wavelength conversion resin is preferably 10 to 20 ⁇ m.
  • a second encapsulation layer may be covered.
  • a low-stress, dense inorganic thin film that is, an Encap-2 film layer, such as SiOx/SiNx/Al2O3, etc.
  • an ultra-low temperature process ⁇ 100°C.
  • CVD, ALD and other processes The thickness of the film layer is less than 1 um, preferably less than 0.5 um, and the refractive index ranges from 1.7 to 2.0, preferably from 1.75 to 1.85.
  • a reflective polarizer can be prepared or attached to the color filter layer, preferably in the blue light band.
  • Reflective polarizer with slightly higher reflectivity such as DBEF film from 3M company or light-cured broad-spectrum liquid crystal reflective polarizer. It can be attached with a high transmittance, scratch-resistant cover film material or other optical compensation film.
  • the thickness of the optical cell can be further reduced without the packing layer, the bank layer and the support column structure.
  • the on-EL device structure with smaller optical box thickness has greater productization space.
  • the heat resistance of the light-emitting layer is not as good as that of the color filter layer, the requirements for ultra-low temperature processes in the on-EL route are higher.
  • a plurality of wavelength conversion units may be overlapped on a side surface of the second pixel defining layer away from the base substrate.
  • the plurality of wavelength conversion units may include adjacently arranged first color wavelength conversion units and second color wavelength conversion units, and the first color wavelength conversion units overlap with the first color wavelength conversion units to separate the two.
  • the widths of the second pixel-defining layers are different.
  • the display panel may further include: a color filter layer on a side of the wavelength conversion unit away from the light-emitting layer, wherein the color filter layer includes a plurality of color filter units and a black matrix defining the plurality of color filter units, The plurality of color filter units are overlapped on a side surface of the black matrix close to the base substrate, and the overlapped width of the wavelength conversion unit on the second pixel defining layer and the same sub-pixel belong to the same sub-pixel.
  • the overlapping widths of the color filter units on the black matrix are different.
  • the width of the finally formed wavelength conversion unit overlapped on the second pixel defining layer is preferably 10 times the width of the overlapped surface of the second pixel defining layer. % or less.
  • FIG. 14 shows that the wavelength conversion unit is overlapped on the side of the second pixel defining layer close to the base substrate, but the color filter unit is not shown overlapped on the black matrix.
  • Mode IV on-EL lithography wavelength conversion layer
  • Mode IV similar to Mode II, the wavelength conversion unit is formed by means of photolithography.
  • the PDL-2 is formed with the light emitting layer instead of the color filter layer as the backplane and then the wavelength conversion unit is formed.
  • FIG. 16 schematically shows a display panel formed by on-EL and photolithography. Among them, the layer structure of its product is similar to that shown in Figure 14(e).
  • each of the angle between the second side and the third side and the angle between the second side and the fourth side is between 60-100°.
  • the included angle is between 70° and 90°.
  • the cross section can be trapezoidal or nearly rectangular. As mentioned above, the most preferred angles for the shape of the PDL-2 are slightly wider at the top and slightly narrower at the bottom. The angle between the side edge and the bottom edge of the PDL-2 is between 60-100°.
  • the included angle is between 70° and 90°, so as to form a space with a large opening and a small bottom to facilitate the coating of the resin containing the wavelength conversion material. It should be noted that this preferred range not only takes into account the optical performance, but also the difficulty of process realization of PDL-2 at this angle.
  • Figure 10(d) shows the preferred angular range for Mode II.
  • Figure 17 shows a photomicrograph of a cured QD wavelength converting material-containing photoresist layer in the sub-pixel space defined by PDL-2. It can be seen from the figure that the QD-containing photoresist resin is fully filled in the space defined by PDL-2.
  • the PDL-2 and QD cells are formed on Encap-1 and overlaid with Encap-2.
  • the thickness of PDL-2 is 6 to 12 ⁇ m.
  • the resin density is higher and the volume occupied is smaller, so the thickness of PDL-2 can be slightly lower than that of Mode II, but the lower limit should still be more than 2 times that of PDL-1 , preferably 6 ⁇ m or more.
  • a wavelength conversion unit or a transparent unit is formed in the space defined by the PDL-2 using photolithography.
  • the baking curing temperature after photoresist development is preferably ⁇ 100°C, rather than ⁇ 180°C in the cell-to-cell route.
  • the thickness of the wavelength conversion unit is similar to that of the PDL-2.
  • the second encapsulation layer Encap-2 may also be formed in Mode IV.
  • the difference between the second encapsulation layer Encap-2 and mode II is that the ultra-low temperature process ( ⁇ 100°C) is used instead of the low temperature process ( ⁇ 180°C) to prepare low-stress, dense inorganic thin films, such as SiOx/SiNx/Al2O3, etc. Processes such as CVD and ALD can be used.
  • the thickness of the film layer is less than 1 ⁇ m, preferably less than 0.5 ⁇ m, and the refractive index is in the range of 1.7 to 2.0, preferably 1.75 to 1.85, for protecting the wavelength conversion resin film layer and maintaining the wavelength conversion optical efficiency.
  • the Encap-2 film produced by the ultra-low temperature process is not resistant to scratches and needs to be stored carefully.
  • the impurity gas that is not fully released from the wavelength conversion unit or the transparent unit during the low-temperature curing of the lithography process can be further released, which is beneficial to further improve the quality of the wavelength conversion unit or the transparent unit.
  • the patterned black matrix BM and each color film R-CF/G-CF/B-CF, as well as optional reflective polarizers, cover film materials, or other optics can continue to be fabricated on the Encap-2 Compensation diaphragm.
  • the patterned black matrix BM and each color film R-CF/G-CF/B-CF were subsequently prepared on the Encap-2, and an ultra-low temperature process ( ⁇ 100° C.) should also be used.
  • the thickness and optical requirements of the color filter layer are the same as those in the cell-to-box route.
  • a reflective polarizer can be prepared or attached to the color filter layer, preferably a reflective polarizer with slightly higher reflectivity in the blue light band (such as DBEF from 3M Company). film or photocured broad-spectrum liquid crystal reflective polarizing film). It can be attached with a high transmittance, scratch-resistant cover film material or other optical compensation film.
  • Modes III and IV are both methods of making the display panels of the present disclosure, including:
  • the wavelength conversion layer is formed by ink jet printing of an ink containing a wavelength conversion material or by coating and photolithography of a photoresist containing a wavelength conversion material, and
  • a color filter layer is formed on the wavelength conversion layer to form a display panel.
  • the wavelength conversion layer is formed in an ultra-low temperature process at a temperature of ⁇ 100° C., including but not limited to forming PDL-2, wavelength conversion unit, Encap-2, and color filter layer.
  • a plurality of wavelength conversion units may be overlapped on a side surface of the second pixel defining layer away from the base substrate.
  • the plurality of wavelength conversion units may include adjacently arranged first color wavelength conversion units and second color wavelength conversion units, and the first color wavelength conversion units overlap with the first color wavelength conversion units to separate the two.
  • the widths of the second pixel-defining layers are different.
  • the display panel may further include: a color filter layer on a side of the wavelength conversion unit away from the light-emitting layer, wherein the color filter layer includes a plurality of color filter units and a black matrix defining the plurality of color filter units, The plurality of color filter units are overlapped on a side surface of the black matrix close to the base substrate, and the overlapped width of the wavelength conversion unit on the second pixel defining layer and the same sub-pixel belong to the same sub-pixel.
  • the overlapping widths of the color filter units on the black matrix are different.
  • the wavelength conversion unit and the color filter unit are not overlapped.
  • Six sub-pixels of the first color in the display panel of Mode I were prepared by the inkjet printing method and the cell-to-cell assembly method.
  • the angle between the second side of the characteristic quadrilateral and the third and fourth sides is different, which are 60°, 70°, 80°, 100°, 110° and 120°, respectively.
  • the bottom edge is the edge of one side of the light-emitting layer, and the included angle is the inner angle of the trapezoid. Then, the effective light-emitting energy ratio of these display panels was tested. The test results are shown in FIG. 18 .
  • the ratio of the effective light output energy refers to the observed energy of the wavelength-converted light transmitted through the wavelength conversion unit and the energy traced back to the light emission of the light-emitting unit (in this embodiment, the blue light emitted by the blue OLED), and the difference between the energy emitted by the wavelength conversion unit and the incident light emitted by the pixel. Ratio of internal luminous energy.
  • the ratio of the effective light output energy is less than 100%, mainly due to the design of the light extraction structure, so that part of the light emission may enter other pixels, or be derived from the same layer of medium.
  • Six Mode II display panels are prepared by photolithography and cell-to-cell assembly.
  • the difference between these display panels is only the angle between the side and bottom of the trapezoid of the second pixel-defining layer (that is, the second side of the characteristic quadrilateral and the first side of the characteristic quadrilateral).
  • the included angles of the fourth side are different, which are 60°, 70°, 80°, 100°, 110° and 120° respectively.
  • the bottom edge is the edge of one side of the light-emitting layer, and the included angle is the inner angle of the trapezoid.
  • the device blue light absorption ratio of these display panels was then tested. The test results are shown in FIG. 19 .
  • the blue light absorptivity of the device refers to the ratio of the energy emitted by the light emitting unit in the local area of multiple sub-pixels after removing the leaked light emission ratio (the blue light emitted by the blue OLED in this embodiment).
  • the blue light absorption rate of the device is less than 100%, mainly due to the design of the light extraction structure.
  • the present disclosure provides a more compact light extraction structure, It can improve the light extraction efficiency of the display panel, thereby improving the luminous efficacy and color gamut, and improving the key optical performance.

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Abstract

本公开提供了一种显示面板，具有衬底基板，在衬底基板一侧的发光层，和在发光层远离衬底基板一侧的波长转换层，其中，发光层具有多个发光单元以及限定多个发光单元的第一像素限定层，波长转换层具有多个波长转换单元以及限定多个波长转换单元的第二像素限定层，并且多个波长转换单元中的每个被配置为转换多个发光单元中的至少一者发出的光的波长，其中，在垂直于衬底基板的方向上，第二像素限定层的厚度为第一像素限定层的厚度的2倍以上。本公开还提供显示面板的制备方法和显示装置。

Description

显示面板及其制备方法、显示装置
对相关申请的交叉引用
本公开要求2020年10月22日提交的中国专利申请号202011143647.1的优先权，其通过引用以其全部结合在此。
技术领域
本公开涉及彩色显示领域，具体涉及一种显示面板及其制备方法，和一种显示装置。
背景技术
有机发光显示(OLED)作为主流显示技术已占领移动显示市场，在TV等显示应用上也引起了厂商们极大的兴趣。从显示色彩的方式看，OLED技术路线主要分为两种。一种是用发不同颜色光的有机发光材料(如红色发光材料、绿色发光材料和蓝色发光材料)形成不同颜色的子像素，可称为RGB型。RGB型色域高，已占领中小尺寸应用市场。但是，其因为受到精细金属掩模(FMM)工艺的限制而无法大面积化。喷墨打印RGB OLED的RGB型虽是大尺寸OLED的潜在技术，但因为溶液法OLED材料的研发限制，色域值不够高。另一种是采用OLED作为背光配合彩膜实现彩色显示，可称为背光-彩膜型。由于可采用开口掩模(open mask)整面蒸镀，白色背光配合彩膜的方式已是大尺寸OLED的主流技术之一。在白色背光-彩膜技术中，彩膜起到滤除白光中所需颜色以外波长的光波的作用。彩膜的色域直接限制了大尺寸OLED产品的色域范围。
已经出现了采用波长转换元件将单色的OLED发出的光变色来实现彩色显示的技术。例如，相关技术中已经提出了用蓝光OLED与QD结合的技术，以蓝光OLED作为光源，配合QD将蓝光下转换为红光、绿光，实现彩色显示，称为QD-OLED。
对于包含波长转换元件的显示装置，仍存在着改进的需要。
概述
在一个方面，本公开提供一种显示面板，包括：
衬底基板，
在所述衬底基板一侧的发光层，和
在所述发光层远离所述衬底基板一侧的波长转换层，
其中，所述发光层包括多个发光单元以及限定所述多个发光单元的第一像素限定层，所述波长转换层包括多个波长转换单元以及限定所述多个波长转换单元的第二像素限定层，并且所述多个波长转换单元中的每个被配置为转换所述多个发光单元中的至少一者发出的光的波长，
其中，在垂直于所述衬底基板的方向上，所述第二像素限定层的厚度为所述第一像素限定层的厚度的2倍以上。
可选地，所述波长转换单元中的每个的入光面的面积大于发出其所转换的光的所述发光单元的出光面的面积。
可选地，所述第二像素限定层在所述衬底基板的正投影落入所述第一像素限定层在所述衬底基板的正投影内。
可选地，在所述发光层靠近所述波长转换层一侧的第一封装层，所述第一封装层包括第一无机层和在所述第一无机层远离所述发光层的一侧的第二无机层，所述第二无机层包括多个无机子层的层叠体，所述层叠体对其波长经所述波长转换单元转换的光的反射率强于对所述发光单元发出的光的反射率，并且对所述发光单元发出的光的透射率大于对其波长经所述波长转换单元转换的光的透射率。
可选地，在垂直于所述衬底基板的方向上，所述第一封装层的厚度为1至6μm。
可选地，显示面板还包括：
在所述波长转换单元远离所述发光层一侧的彩膜层，
其中，所述彩膜层包括多个彩膜单元以及限定所述多个彩膜单元的黑矩阵。
可选地，所述黑矩阵在所述衬底基板的正投影落入所述第二像素限定层在所述衬底基板的正投影内。
可选地，在垂直于所述衬底基板的方向上，所述第一像素限定层的厚度为1-2μm，且所述第二像素限定层的厚度为6至20μm。
可选地，沿远离衬底基板的方向上，所述多个发光单元依次包括阳极、发光层、阴极，所述阴极远离衬底基板的一侧表面与所述波长转换单元靠近衬底基板的一侧表面之间的距离小于所述第二像素限定层的所述厚度，且大于所述第一像素限定层的所述厚度。
可选地，所述波长转换层还包括与多个波长转换单元同层设置的透明单元，所述透明单元与所述波长转换单元之间设置有第二像素限定层。
可选地，对于所述第一像素限定层的在垂直于所述衬底基板方向上的横截面形状，以通过所述横截面形状最远离所述衬底基板的点的平行于所述衬底基板的直线为第一边，以经过所述横截面形状与其在靠近所述衬底基板层一侧的相邻层之间的边界的两端的线段为第二边，以分别经过所述两端的向所述第一边延伸并与所述横截面形状外切的直线为第三边和第四边，在由所述第一、二、三、四边围成的四边形中，第二边与第三边的夹角和第二边与第四边的夹角中的每一个在20°至40°的范围内。
可选地，所述第一像素限定层与所述第二像素限定层材料不同。
可选地，显示面板还包括：
在所述发光层和所述波长转换层之间的填料层，和
围堤层，所述围堤层与所述发光层和所述波长转换层包封所述填料层。
可选地，对于所述第二像素限定层的在垂直于所述衬底基板方向上的横截面形状，以通过所述横截面形状最靠近所述衬底基板的点的平行于所述衬底基板的直线为第一边，以经过所述横截面形状与其在远离所述衬底基板层一侧的相邻层之间的边界的两端的线段为第二边，以分别经过所述两端的向所述第一边延伸并与所述横截面形状外切的直线为第三边和第四边，在由所述第一、二、三、四边围成的四边形中，第一边与第三边的夹角和第一边与第四边的夹角中的每一个在60°至90°的范围内。
可选地，所述第二像素限定层的表面对去离子水的接触角≥90°，并且对丙二醇甲醚醋酸酯的接触角≥35°，并且
在所述四边形中，第一边与第三边的夹角和第一边与第四边的夹角中的每一个在60°至85°的范围内。
可选地，所述围堤层厚度为15至50μm，填料层厚度为5至30微米。
可选地，所述多个波长转换单元搭接在所述第二像素限定层靠近所述 衬底基板的一侧表面。
可选地，所述波长转换单元搭接在所述第二像素限定层上的宽度为所述第二像素限定层的被搭接表面的宽度的10％以内。
可选地，所述多个波长转换单元包括相邻设置的第一颜色波长转换单元和第二颜色波长转换单元，所述第一颜色波长转换单元与所述第一颜色波长转换单元搭接在将两者隔开的所述第二像素限定层上的宽度不同。
可选地，显示面板还包括：
在所述波长转换单元远离所述发光层一侧的彩膜层，
其中，所述彩膜层包括多个彩膜单元以及限定所述多个彩膜单元的黑矩阵，
所述多个彩膜单元搭接在所述黑矩阵靠近所述衬底基板的一侧表面，并且
波长转换单元在第二像素限定层上的所述搭接的宽度和与其同属于同一子像素的彩膜单元在黑矩阵上的所述搭接的宽度不同。
可选地，所述波长转换层与第一封装层接触，所述第一封装层与所述发光层接触。
可选地，对于所述第二像素限定层的在垂直于所述衬底基板方向上的横截面形状，以通过所述横截面形状最远离所述衬底基板的点的平行于所述衬底基板的直线为第一边，以经过所述横截面形状与其在靠近所述衬底基板层一侧的相邻层之间的边界的两端的线段为第二边，以分别经过所述两端的向所述第一边延伸并与所述横截面形状外切的直线为第三边和第四边，在由所述第一、二、三、四边围成的四边形中，第二边与第三边的夹角和第二边与第四边的夹角中的每一个在70°至90°的范围内。
可选地，所述第二像素限定层的表面对去离子水的接触角≥90°，并且对丙二醇甲醚醋酸酯的接触角≥35°，并且
对于所述第二像素限定层的在垂直于所述衬底基板方向上的横截面形状，以通过所述横截面形状最远离所述衬底基板的点的平行于所述衬底基板的直线为第一边，以经过所述横截面形状与其在靠近所述衬底基板层一侧的相邻层之间的边界的两端的线段为第二边，以分别经过所述两端的向所述第一边延伸并与所述横截面形状外切的直线为第三边和第四边，在 由所述第一、二、三、四边围成的四边形中，第二边与第三边的夹角和第二边与第四边的夹角中的每一个在95°至120°的范围内。
可选地，所述多个波长转换单元搭接在所述第二像素限定层远离所述衬底基板的一侧表面。
可选地，所述波长转换单元搭接在所述第二像素限定层上的宽度为所述第二像素限定层的被搭接表面的宽度的10％以内。
可选地，所述多个波长转换单元包括相邻设置的第一颜色波长转换单元和第二颜色波长转换单元，所述第一颜色波长转换单元与所述第一颜色波长转换单元搭接在将两者隔开的所述第二像素限定层上的宽度不同。
可选地，在所述波长转换单元远离所述发光层一侧的彩膜层，
其中，所述彩膜层包括多个彩膜单元以及限定所述多个彩膜单元的黑矩阵，
所述多个彩膜单元搭接在所述黑矩阵远离所述衬底基板的一侧表面，并且
波长转换单元在第二像素限定层上的所述搭接的宽度和与其同属于同一子像素的彩膜单元在黑矩阵上的所述搭接的宽度不同。
可选地，所述四边形为以所述第三边和第四边为侧边的梯形。
可选地，所述第二像素限定层为光反射型像素限定层或光吸收型像素限定层。
可选地，所述第二像素限定层包括散射粒子或所述第二像素限定层靠近所述波长转换单元的表面设置有金属。
可选地，所述波长转换单元是量子点下转换单元。
可选地，所述显示面板包括绿色子像素、红色子像素和蓝色子像素，每个子像素包含一个所述发光单元，
其中，所述绿色子像素中所述发光单元的出光面积≥所述红色子像素中所述发光单元的出光面积≥所述蓝色子像素中所述发光单元的出光面积。
可选地，所述波长转换单元中的每个的入光面在所述衬底基板的正投影的边缘与发出其所转换的光的所述发光单元的出光面在所述衬底基板的正投影的边缘的距离a与所述OLED发光单元的出光面与所述背光下转 换单元的入光面的距离b满足a≤1.8b。
可选地，所述波长转换层包含第二封装层，所述第二封装层厚度小于1μm。
在另一个方面，本公开提供一种制备上述显示面板的方法，包括：
提供衬底基板，
形成在所述衬底基板一侧的发光层，以及
形成在所述发光层远离所述衬底基板一侧的波长转换层，
其中，所述发光层包括多个发光单元以及限定所述多个发光单元的第一像素限定层，所述波长转换层包括多个波长转换单元以及限定多个波长转换单元的第二像素限定层，并且所述波长转换单元中的每个被配置为转换所述多个发光单元中的至少一者发出的光的波长，
其中，在垂直于所述衬底基板的方向上，所述第二像素限定层的厚度为所述第一像素限定层的厚度的2倍以上。
可选地，形成在所述发光层远离所述衬底基板一侧的波长转换层包括：
在底板上形成所述第二像素限定层，
在所述第二像素限定层限定的空间中，通过喷墨打印并固化含有波长转换材料的墨水，形成所述波长转换单元，
并且将所述波长转换层与所述发光层对盒组装成所述显示面板，其中在所述波长转换层与所述发光层对盒之间设置填料层和围堰层。
可选地，形成在所述发光层远离所述衬底基板一侧的波长转换层包括：
在底板上形成所述第二像素限定层，
在所述第二像素限定层限定的空间中，通过涂敷并光刻含有波长转换材料的光刻胶，形成所述波长转换单元，
并且将所述波长转换层与所述发光层对盒组装成所述显示面板，其中在所述波长转换层与所述发光层对盒之间设置填料层和围堰层。
可选地，所述底板是彩膜层。
可选地，方法还包括：
在形成所述波长转换单元之后，在≤180℃的温度下形成覆盖所述第二像素限定层和所述波长转换单元的第二封装层。
可选地，形成在所述发光层远离所述衬底基板一侧的波长转换层包括：
在所述发光层上形成所述第二像素限定层，
在所述第二像素限定层限定的空间中，通过喷墨打印并固化含有波长转换材料的墨水，形成所述波长转换单元。
可选地，形成在所述发光层远离所述衬底基板一侧的波长转换层包括：
在所述发光层上形成所述第二像素限定层，
在所述第二像素限定层限定的空间中，通过涂敷并光刻含有波长转换材料的光刻胶，形成所述波长转换单元。
可选地，方法还包括：
形成在所述波长转换层上的彩膜层。
可选地，方法还包括：
在形成所述波长转换单元之后，在≤100℃的温度下形成覆盖所述第二像素限定层和所述波长转换单元的第二封装层。
在又一个方面，本公开提供了一种显示装置，所述显示装置包含上述显示面板。
附图说明
图1示意性地示出了本公开的显示器件的结构原理图。
图2示出了OLED发光层的一个实施方案。
图3示出了第一封装层的一种示意性膜层结构。
图4示出了在对盒模式中作为底板的彩膜层的示意图。
图5示出了彩膜单元的滤光性与波长转换单元的发光性的配合。
图6(a)-(b)示出了本公开的一个实例中对盒模式喷墨打印的下转换彩膜基板的结构的显微照片和蘑菇形截面的示意图。
图7(a)至7(e)示意性示出了本公开的对盒模式中的波长转换彩膜基板的一些实施方案。
图8(a)-(f)示出了一些第二像素限定层的显微照片。
图9示出了在一个实施方案中波长转换单元填充单个子像素后的45°角俯视SEM图。
图10示意性示出了本公开的模式I-IV的优选角度范围。
图11示意性显示了对盒后的显示面板的一个实施方案。
图12显示了发光单元的出光面、波长转换单元的入光面和盒厚的关系。
图13(a)-(b)示意性示出了在彩膜层上通过光刻法形成的波长转换单元和透明单元的实施方案。
图14(a)-(e)示意性示出了通过on-EL及喷墨打印形成显示器件的过程。
图15(a)-(b)示出了本公开的实例中通过on-EL及喷墨打印形成的结构的显微照片。
图16示意性示出了通过on-EL及光刻形成的显示器件。
图17示出了一个位于PDL-2所限定的子像素空间中的含下转换材料的QD光刻胶层的显微照片。
图18示出了本公开的一个实施例中，依照本公开模式I制成的显示面板中第二像素限定层的梯形侧边与第一边夹角与有效出光能量比例的关系。
图19示出了本公开的一个实施例中，依照本公开模式II制成的显示面板中第二像素限定层的梯形侧边与第二边夹角与器件蓝光吸收比例的关系。
图20(a)和(b)示例性显示了像素限定层的特征四边形。
具体实施方式
包含波长转换元件的显示装置的发展仍面临许多实际技术挑战。发明人发现，存在许多造成发光效能和色域下降的问题，例如较低的波长转换效率、波长转换元件对背光吸收不足等。
从目前基于蓝光OLED的QD-OLED发光效能和色域下降的问题出发，发明人进行了深入研究，并且出人意料地发现，通过设计更加紧凑的取光结构，可以提高显示面板取光效率，从而改善发光效能和色域，提升关键的光学性能。该取光结构可适用于QD-OLED，也可适用于除QD之外的其他波长转换材料。
在本公开的一个实施方案中，提供了一种显示面板，包括：
衬底基板，
在所述衬底基板一侧的发光层，和
在所述发光层远离所述衬底基板一侧的波长转换层，
其中，所述发光层包括多个发光单元以及限定所述多个发光单元的第一像素限定层，所述波长转换层包括多个波长转换单元以及限定多个波长转换单元的第二像素限定层，并且所述波长转换单元中的每个被配置为转换所述多个发光单元中的至少一者发出的光的波长，
其中，在垂直于所述衬底基板的方向上，所述第二像素限定层的厚度为所述第一像素限定层的厚度的2倍以上。
本公开的显示面板可以通过特定的取光结构设置实现更高的取光效率。
本公开的显示面板可以是OLED显示面板。OLED显示面板使用OLED作为发光单元。本公开的显示面板也可以使用其他类型的发光器件作为发光单元。
本公开的显示面板是包含波长转换元件的显示面板。波长转换元件用于将发光单元发出的光进行波长转换，变为其他颜色的光。应注意，在本公开中，波长转换与波长选择性透过不同。波长转换是指在无需额外使用能量的情况下将入射光的波长转换为另一种波长，而波长选择性透过是指仅允许入射光中一部分波长的光透过并阻止其他波长的光透过。波长转换可以是下转换，也可以是上转换。下转换与上转换相反，是指将波长较短的光转换为波长较长的光。通过使用不同的波长转换单元改变光的颜色，可以仅使用一种颜色的发光单元来实现彩色显示。
在一个实施方案中，本公开的显示面板可以为下转换型OLED显示面板。下转换型OLED显示面板使用一种颜色的短波长的OLED作为发光单元，典型地使用蓝光OLED。在不同颜色的子像素中，利用不同的下转换材料(如QD)对上述短波长的光进行下转换，变为波长相对较长的光，从而基于同一颜色的发光单元实现彩色显示。作为一个实例，对于所有颜色的子像素，都使用短波长的蓝色OLED发光。在红色子像素中，下转换材料将蓝色OLED发出的蓝光转换为红光。在绿色子像素中，下转换材料将蓝色OLED发出的蓝光转换为绿光。此外，由于蓝色本身为RGB显示的子像素颜色之一，因此在蓝色子像素中，可以不对蓝光进行下转换，直接 用于蓝色子像素显示。由此，实现红绿蓝(RGB)彩色显示。在本公开以下的讨论中，有时以蓝色背光作为短波长背光以及向绿色、红色光的下转换为例进行说明。但是，应当理解，根据需要，也可以选择其他颜色的发光或其他颜色的转换光。
在本公开中，如无特别说明，以显示面板的出光侧为“顶侧”，其相反侧为“底侧”，以便于描述相对方向。相应地，与底侧到顶侧的方向垂直的方向为“横向”。应当理解，这些方向都是相对而非绝对方向。
本公开的显示面板具有在底侧的衬底基板和在顶侧的显示面板出光侧，并且从底侧向顶侧依次包括：发光层；波长转换层；和任选的彩膜层。
如上所述，发光层起到发光的作用。发出的光经过其上方的波长转换层，可以转换为其他颜色，或任选地不转换颜色，从而实现彩色显示。可以进一步设置彩膜层，仅允许来自波长转换层的光中所需的颜色的光透过，提高颜色纯度。在本公开的显示面板中，彩膜层是指选择性透过特定波长的光的层。
本公开的显示面板的光发射由发光单元实现。典型地，发光单元布置为阵列，阵列中每个发光单元可以为OLED，包括阴极、阳极和在它们之间的有机发光层，或称为有机发光材料部，从阴极和阳极提供的载流子在有机发光层中复合发光。在发光层中，平行于显示面板的显示面阵列排布多个这样的发光单元，从而组成发光点阵。本公开的显示面板的每个子像素可以具有独立的OLED，可以配合阵列基板以实现每个子像素背光的单独点亮和熄灭。
在所述发光层中包括限定所述发光单元阵列的第一像素限定层。应当理解，在本公开中所称的“像素限定层”，包括此处所述的第一像素限定层和下文详述的第二像素限定层，实际上限定的是各个子像素的范围，例如红、绿、蓝子像素的范围，而不是一个彩色RGB像素的总范围。
图案化的第一像素限定层设置在发光层中，围成了阵列排布的多个用于设置发光单元的空间。当发光单元是OLED时，第一像素限定层至少将相邻发光单元的有机发光材料部隔开，并且也可以将发光单元的其他部分，例如阳极等隔开。
本公开的显示面板还包括在所述发光层出光侧的波长转换层，所述波 长转换层包括波长转换单元的阵列，所述波长转换单元被配置为将所述发光单元发出的波长转换。
波长转换单元用于在一个子像素中将发光单元发出的波长转换为所需颜色。例如，红色波长转换单元可以将蓝色背光转换为红色光，绿色波长转换单元可以将蓝色背光转换为绿色光。波长转换单元可以是一个QD材料部、无机荧光粉材料部或有机荧光材料部，其包括透明基质材料和分散在基质材料中的量子点、无机荧光粉或有机荧光材料。波长转换单元也可以由其他波长转换材料制成。基质材料可以是透明有机材料如树脂，例如固化的光刻胶树脂，或者固化的墨水。下转换材料可以采用任何合适的下转换材料，本公开对此没有特别的限定。其中，QD下转换材料由于可以通过粒径控制下转换性能而是特别优选的。在本申请中，以下若无特别说明，均以QD作为波长转换材料的示例进行说明。
波长转换单元包括第一颜色的波长转换单元，其可以将入射的光转换为第一颜色光。例如，第一颜色可以为红色，即波长转换单元中存在红色波长转换单元。应当理解，第一颜色、第二颜色等用语仅是为了区分颜色，而非对颜色进行任何排序。为了实现彩色显示，波长转换单元还可以包括第二颜色的波长转换单元、或更多其他颜色的波长转换单元。例如，可以选择红色为第一颜色，绿色为第二颜色。又例如，可以以红色为第一颜色，绿色为第二颜色，蓝色为第三颜色。
可选地，除了波长转换单元之外，波长转换层还可以包括透明单元。透明单元对入射光是透明的，不发生波长转换。这样，例如，蓝色子像素中的蓝色OLED发光可以穿过波长转换层但不经历波长转换，直接用于蓝色显示。优选地，透明单元可以是光扩散单元，例如包含散射粒子，使得入射光在波长不发生改变的情况下发生散射，利于均匀显示。光扩散单元可以由具有光扩散能力的光扩散树脂制备，从而使蓝光穿过它之后更加均匀。本公开中，透明是指允许光在改变角度但不发生波长转换的情况下透射。
在波长转换层中，包括限定波长转换单元的第二像素限定层。当存在透明单元时，第二像素限定层也限定透明单元。图案化的第二像素限定层至少围成了阵列排布的多个用于填充波长转换材料部或透明材料的空间。 第二像素限定层至少将波长转换单元与相邻的波长转换单元或透明单元隔开。在不同的子像素中，发光单元分别与第二像素限定层限定的第一颜色的波长转换单元、第二颜色的波长转换单元、透明单元等配合。
沿远离衬底基板的方向上，多个发光单元可以依次包括阳极、发光层、阴极，阴极远离衬底基板的一侧表面与波长转换单元靠近衬底基板的一侧表面之间的距离小于第二像素限定层的厚度，且大于第一像素限定层的厚度。在波长转换单元包括量子点的情况下，波长转换单元靠近衬底基板的一侧表面是指量子点靠近衬底基板的一侧表面。如此设置的好处可降低盒厚，避免串色。
本公开的显示面板还可以包括彩膜层。彩膜层在波长转换层的顶侧，包括彩膜单元。彩膜单元用于滤光，即允许来自波长转换层的入射光中一部分波长范围的光透过，从而进一步提高颜色纯度。彩膜单元包括第一颜色的彩膜单元，并且还可以包括第二颜色的彩膜单元，或更多其他颜色的彩膜单元。例如，在蓝色OLED发光的情况下，可以在红色波长转换层的出光侧设置红色彩膜单元，在绿色波长转换层的出光侧设置绿色彩膜单元，并且在透明单元的出光侧设置蓝色彩膜单元。彩膜可以用显示领域常用的彩膜材料制备。
优选地，彩膜层包括限定所述彩膜单元的黑矩阵。优选地，黑矩阵在所述波长转换层中的投影在第二像素限定层的顶面内。换言之，黑矩阵不位于由第二像素限定层所限定的波长转换单元或背光扩散单元的出光面上方，不会遮挡其发出的光。或者说，彩膜单元在波长转换层中的投影面积大于波长转换单元或背光扩散单元的顶面的面积。这可以充分利用从波长转换单元或背光扩散单元的顶面非垂直射出的光，提高发光效能。黑矩阵也可以由本领域常规的黑矩阵材料形成。
在本公开中，在垂直于所述衬底基板的方向上，所述第二像素限定层的厚度为所述第一像素限定层的厚度的2倍以上。发明人发现，当第二像素限定层的厚度远大于第一像素限定层的厚度，如2倍以上时，波长转换单元可以充分实现对发光单元发光的波长转换。这便于进一步设计更加紧凑的取光结构，提高器件取光效率，从而改善发光效能和色域，提升关键的光学性能。第二像素限定层的厚度可以为第一像素限定层的厚度的2倍、 2.5倍，3倍，4倍，5倍等。当第二像素限定层与第一像素限定层的厚度比例过低时，难以充分实现对发光单元发光的彼此转换。这不便于进一步设计提高取光效率的结构。应当注意，在本公开中，层厚度方向即为垂直于所述衬底基板的方向，即像素限定层壁的高度方向。
优选地，第一像素限定层厚度可以为1-2μm，而第二像素限定层厚度可以在不同设计中在6-20μm的范围内。相互配合的第一像素限定层和第二像素限定层的优选厚度范围可以兼顾对波长转换光学效果的保障和实际工艺能力，既良好地达到了波长转换光学效果，又不明显增加制备难度。上述优选范围可以实现结构紧凑且取光效率高的显示面板。本公开的第一像素层和第二像素限定层不仅仅起到限定发光单元、波长转换单元和透明单元的面积的作用，而且可以参与光的反射和吸收，两者正确配合时，可以在显示面板中起到改善光传播和转换性能、提高取光效率的作用。此外，第一和第二像素限定层的形状在发光单元、波长转换单元和背光扩散单元的形成工艺中还对制备工艺产生有利影响。例如，如后文所述，针对不同的波长转换单元和背光扩散单元形成工艺，本公开提出了多种具体的第二像素限定层的结构。当第二像素限定层的厚度小于6μm时，波长转换层的转化效率可能不足，另外还可能对蓝光反射性提高而对黄光反射性下降，不利于提高显示面板的发光性能。波长转换单元厚度增加时，可增加转化效率，但随之光透过性也有所下降。第二像素限定层的厚度大于20μm时，形成过厚的波长转换单元，总的转换效率将下降。因此，6至20μm的厚度可以保证可接受的波长转换效率低值。
在本公开中，波长转换单元的入光面面积可以大于发光单元的出光面面积。波长转换单元的入光面面积是指其朝向衬底基板的表面面积，可以将光线接收至其内部。发光单元的出光面面积是指第一像素限定层限定的开口面积，可以将光发出至其外部的平面的面积。换言之，在所述显示面板中的每个子像素中，所述发光单元的出光面处于所述波长转换单元的入光面在所述发光层中的正投影内部。由此，可以充分利用从发光单元的顶面非垂直射出的光，提高发光效能。根据结构带来的光学路径以及制备工艺偏差的差异，上述两个面积的比例可以有所变化。一般来说，对盒式的器件结构相比于on-EL器件结构，其波长转换单元面积会相对更大，以避 免像素间的漏光。
此外，在本公开中，所述第二像素限定层在所述发光层中的投影在所述第一像素限定层的顶面内。换言之，第二像素限定层不位于由第一像素限定层所限定的发光单元的发光面的上方，不会遮挡其发光。更优选地，第二像素限定层在所述发光层中的投影面积小于所述第一子像素限定层的顶面面积。
本公开中，第一像素限定层与第二像素限定层的材料可以不同。第一像素限定层对可见光的透过率可以高于第二像素限定层对可见光的透过率。
图1示意性地示出了本公开的显示面板的结构原理图。本公开的显示面板包含发光层1、波长转换层2和任选的彩膜层3。图1中将它们分开绘制，以示意它们之间的关系。不过，在实际显示面板中，它们可以是彼此结合在一起的。例如，波长转换层2和发光层1可以是直接接触的，波长转换层2和彩膜层3也可以是直接接触的。
发光层1中包含第一像素限定层PDL-1，其限定发光单元10的阵列。发光单元10可以是均为短波长发光单元，如蓝光OLED发光单元。可以通过例如阵列基板S驱动这些发光单元。在本公开中，每个发光单元为一个子像素发光。
发光层1的发光单元10向上发出的光照射到波长转换层2的下表面。波长转换层2包含第二像素限定层PDL-2和由它们限定的第一颜色波长转换单元21、第二颜色波长转换单元22和透明单元23。例如，第一颜色波长转换单元21可以是绿色波长转换单元，第二颜色22波长转换单元可以是红色波长转换单元，并且透明单元23用于无转换地透过光且可以是光扩散单元。这样，照射到波长转换层2的下表面的光经过波长转换层2后，在至少部分子像素处颜色改变，实现例如RGB显示。
第一、第二颜色波长转换单元中使用的波长转换材料可以为QD，也可以是其他具有下转换功能的材料如无机荧光粉或有机荧光材料，或者其他具有上转换功能的材料。应注意，在本公开中，有时以QD下转换层进行示意性说明，但本公开的范围不限于QD下转换层。
从波长转换层2离开的光又进入彩膜层中相应的子像素彩膜中，如第 一颜色彩膜31、第二颜色彩膜32和第三颜色彩膜33，颜色纯度进一步提升，实现最终的彩色显示。彩膜单元之间可以设置黑矩阵BM，以避免串色。彩膜层的顶部还可以有基板，其也可以是外部封装层或盖板。
波长转换单元的入光面大于发光单元的出光面。此外，PDL-2的厚度为PDL-1的2倍以上。这样的厚度使得OLED单元发出的光在波长转换单元中有足够的空间发生波长转换以及散射、反射等过程，有利于最终得到高质量的均匀发光。
图1仅示出了本公开的显示面板的基本原理和结构。除了发光层、波长转换层和彩膜层之外，本公开的显示面板还可以任选地包含在发光层与波长转换层之间的填料层和支撑柱结构、以及在显示面板周边包围封闭填料层的围堤层等结构。此外，对于发光单元和波长转换单元/透明单元，还可以设置封装层。而且，在显示面板中还可以设置偏光片、光学补偿片等。图1仅意在说明各个元件的相互位置关系，对各个部件的具体形状和细节不构成限制。
应注意，如无特别说明，本公开中的附图均是示意图并且其中的具体角度和长度等不构成对本公开的限制。
典型地，在发光层中，为每个发光单元设置驱动控制单元。驱动控制单元可以是薄膜晶体管(TFT)，并且因此，发光层可以由TFT阵列基板和连接到阵列基板上的发光单元阵列组成。换言之，发光层还可以包括在所述第一像素限定层的底侧的TFT阵列基板。
TFT阵列基板可以是本领域常规的阵列基板。更具体地，TFT阵列基板可以采用氧化物TFT(Oxide TFT)或低温多晶硅(LTPS)基板。TFT阵列基板可以包括第一衬底基板和在第一衬底基板上阵列排布的TFT，并且TFT的源/漏极与发光单元中的像素电极如阳极电连接。优选地，在发光单元的底部与TFT连接的像素电极可以是反射阳极。发光单元采用反射阳极器件结构，形成顶发射OLED。反射阳极用于将向非出光侧发射的光反射向出光侧，从而提高发光效能。
图2示出了发光层1的一个实施方案。图中示出了包含3个完整OLED发光单元和4个PDL-1的局部示意图。衬底基板BS上具有缓冲层BUF。缓冲层上，为每个子像素配置一个TFT单元。TFT单元包括源极S，漏极 D，栅极G，有源层ACT。栅极下方与有源层之间为第一栅极绝缘层GI1，栅极周围和上方覆盖第二栅极绝缘层GI2。在第二栅极绝缘层上方依次设有层间介质层ILD和平坦化层PLN。在第二绝缘层和层间介质层之间还设置有使能信号线Ce1和Ce2。在平坦化层上，第一像素限定层PDL-1之间形成发光单元LE。发光单元LE从底侧到顶侧包括包括阳极AD、有机发光部EL和阴极CD。阳极与TFT的漏极相连，阴极为公用电极。在阴极上方，还有第一封装层Encap-1。第一封装层位于发光层靠近波长转换层一侧。图2中示例性示出了，PDL-1是纵截面为梯形的壁。应当理解，其在阵列基板上形成网格，并且限定出许多用于安置发光单元的空间。如上所述的OLED发光单元的结构是本领域已知的，其包括阳极、有机发光层、阴极等。在图2中，发光单元的阳极AD可以是反射阳极，将OLED发出的光向出光面反射，以增加出光效率。此外，与多颜色的OLED阵列不同，本公开的发光层中仅有一种颜色的发光材料层，因此其可以使用Open Mask整面形成，无需使用例如精细金属掩模逐个子像素形成、
TFT在衬底基板上的投影可以与PDL-1及发光单元均有重叠。即，TFT也可以部分位于PDL-1之下，另一部分位于反射阳极之下。
如图2所示，在发光层的顶侧，还可以包含第一封装层Encap-1。第一封装层对于发光单元的发出的光基本上是透明的，起到封装OLED单元的作用，并且可以将发光层的上表面平坦化。在第一封装层中可以设置短通(短波通过)结构。短通结构可以对红光和绿光的反射强于对蓝光的反射，起到增加蓝色发光单元发出的光透过和反射转换所得的红、绿光的作用。
Encap-1的厚度通常小于10μm。Encap-1的厚度与像素设计及分辨率有相关性。分辨率越高、像素设计越小，则封装膜层厚度需要越薄。主要原因在于，在出光方向上，从发光单元发出的光将经过Encap-1到达波长转换单元表面。当Encap-1中存在折射率较低的材料时，光将由于材料的低折射率逐步向周围发散。折射率较低的材料的实例可以是Encap-1层中的有机平坦层，其可以具有约4-8μm的厚度并可以占Encap-1的厚度的主要部分。封装层厚度增加时，由发光单元发出的光经封装层向周围折射得更远，最终有可能影响到相邻的子像素，造成不必要的漏光。随着分辨率的提升，单位面积内的像素数目会增多，从而对光线发散漏光的限制要 求更高。因此，当分辨率越高、像素越小时，需要较低的封装膜层厚度。优选的厚度≤6μm。考虑到封装性能要求，封装层厚度最小不低于1μm。
Encap-1可以是单层无机层，也可以是多个亚层的层叠结构，如第一无机层/有机层/第二无机层层叠体，或者第一无机层/第二无机层层叠体等。优选地，Encap-1采用由下至上的第一无机层/有机层/第二无机层层叠体或第一无机层/第二无机层层叠体，并且在其中还设置短通结构。短通结构的一个实例是，第一无机层或第二无机层中的至少一个由多层无机膜组成，且多层无机膜中至少有一部分无机膜在光学上倾向于更容易反射黄光。短通结构可起到光学调整的作用。其对下方的发光单元发出的蓝光透过率较高，而对上方波长转换单元产生的红/绿光反射得更多，由此提高了显示面板整体的光学利用率。在本公开中，第一封装层可以为含短通结构的第一无机层和其上的第二无机层，第一无机层和其上的含短通结构的第二无机层，含短通结构的第一无机层和其上的有机平坦层及第二无机层，第一无机层和其上的有机平坦层及含短通结构的第二无机层，等等。对于后述的on-EL工艺而言，含有有机平坦层的第一封装层是更优选的。
简言之，第一封装层可以包括第一无机层和在第一无机层远离发光层的一侧的第二无机层，第二无机层包括多个无机子层的层叠体，层叠体对其波长经波长转换单元转换的光的反射率强于对发光单元发出的光的反射率，并且对发光单元发出的光的透射率大于对其波长经波长转换单元转换的光的透射率。
短通结构可以利用半导体工艺制备，例如以总厚度为100至700nm、优选170至350nm的SiOx/TiO2/SiOx三层无机膜结构作为一个无机层中的短通结构。也可以使用包含更多的交替层叠的SiOx/TiO2无机膜结构作为短通结构，例如SiOx/TiO2/SiOx/TiO2、SiOx/TiO2/SiOx/TiO2/SiOx等。优选地，采用第一无机层和其上的含短通结构的第二无机层或第一无机层和其上的有机平坦层及含短通结构的第二无机层，即在顶侧的第二无机层中形成短通结构。这样，可以利用短通结构下方的第一无机层和任选的有机层，保持其与OLED器件的距离，从而缓解采用半导体薄膜沉积工艺形成短通结构时的局部高温对OLED器件的可能劣化影响。
图3示出了图2的Encap-1的一个示意性膜层层叠结构。其包括第一 无机层Encap-1.1、有机层Encap-1.2、第二无机层Encap-1.3，并且第二无机层又包括SiOx/TiO2/SiOx三层无机膜形成的短通结构。优选地，第二无机层相对远离底侧，从而其制备过程的局部高温对底侧的发光单元影响较小。
回到图2，在垂直于显示面的剖面中，第一像素限定层PDL-1为发光单元的有机发光材料部两侧的具有一定厚度和宽度的壁。典型地，该壁的形状为正梯形，即具有顶边、底边和对称的侧边，其中底边长于顶边。这样的正梯形的壁有利于在两个壁之间的有机发光材料部形成倒梯形，从而使发出的光充分射出，进而改善发光效能。此外，这样的正梯形的壁也有利于采用在其中进行OLED单元各膜层的沉积工艺。
在本公开中，“梯形”包括正梯形、倒梯形，也包括矩形，其中倒梯形是底边短于顶边，矩形是底边等于顶边。梯形的形状可以由底边与侧边所夹的夹角来表征。在本文中，底边与侧边的夹角是指梯形的内角。
梯形形状从表征简单性来说是较为理想的，但在工艺上并不容易达到。本公开的发明人发现，实际形成的像素限定层常常不具有标准的梯形形状，甚至有时与标准梯形相差较大。发明人发现，可以使用特别的四边形来表征像素限定层的横截面形状。在本公开中，称这样的四边形为特征四边形。发明人进而发现，当像素限定层的横截面形状的特征四边形满足一定要求时，有助于进一步优化本公开的取光结构。此处的像素限定层既包括第一像素限定层PDL-1，也包括第二像素限定层PDL-2。
特征四边形的作法如下。首先区分像素限定层的横截面形状的自由边。像素限定层必然是在一个底板上形成的，而其不接触该底板的边即是其自由边。找到像素限定层的自由边中最远离该底板的一点，并且作平行于显示面板衬底基板的线段，称其为第一边。随后，将像素限定层的非自由边(即其与底板的边界)的两端连成线段，称其为第二边。从该两端作外切于横截面形状并且向第一边延伸的线段作为第三边和第四边，此四边围成的四边形即为特征四边形。
如图20(a)和(b)所示，对不同的像素限定层横截面形状作出了由第一至第四边1-4围成的特征四边形。特征四边形可以是非梯形的，但梯形是优选的。
为了简明，本公开以下基本上以梯形为实例说明像素限定层横截面形状，但应当理解，关于梯形的描述和限定都可以扩展至特征四边形。
PDL-1的截面的特征四边形中，由于其形成在衬底基板一侧的底板上，因此其远离衬底基板的一侧为其特征四边形的第一边。优选其第二边与第三边的夹角和第二边与第四边的夹角中的每一个在20°至60°，更优选在20°至40°的范围内。优选采用正梯形，侧边与底边夹角优选在20°至60°之间，更优选在20°至40°之间。此外，如上所述，PDL-1的高度优选在1-2μm之间。这样的梯形截面和厚度形成的开口特别便于通过沉积工艺形成发光单元特别是OLED发光单元的各个膜层，以及有利地充分利用发光单元的发光。发明人更出人意料地发现，当PDL-1的形状将会影响发光单元中阴极的电连接或者说搭接性能，而高效蓝光OLED器件对阴极搭接的要求较高。搭接是指阴极沿PDL-1的侧壁和顶部的铺设。典型地，阴极例如约15nm厚的薄金属层可采用开口掩模通过蒸镀工艺形成，其沉积在PDL-1的侧面和顶面上。当PDL-1的截面为正梯形且侧边与底边夹角在上述优选范围时，有利于实现本公开的发光单元的阴极的良好搭接。若上述角度过大，PDL-1侧壁较陡峭，使得阴极铺设时容易出现搭接不良，影响器件效果。此外，上述优选角度对于制备小尺寸OLED显示面板也是有利的。因此，PDL-1的上述形状有利于提高发光单元的效率，进而改善发光和显示效果。
PDL-1可以是带有颜色的或透明的。优选地，PDL-1是带有颜色的，更优选为黑色的。有颜色的、特别是黑色的PDL-1有助于屏蔽相邻子像素之间光线横向传播造成的串扰。从亮度考虑，由PDL-1定义的发光单元的发光面积在各子像素中为G≥R≥B。即，绿色子像素的发光单元的发光面积≥红色子像素的发光单元的发光面积≥蓝色子像素的发光单元的发光面积。这是因为人眼对绿光最敏感，红光次之，蓝光又次之。因此，将绿色子像素设计得具有较大面积可有效提高人眼可感知的亮度。另外，从下文所述的波长变换能力与彩膜层的配合效果来看，绿色子像素中发光单元面积较大也是较优的，因为可用的绿色的发光能量低于可用的红色发光能量。不过为简便起见，图2中显示的是相等的发光面积。
PDL-1壁的宽度可根据显示面板的设计分辨率和开口率进行设计。衬 底基板可以使用刚性玻璃或者塑料基底材质。可以以OLED器件中常用的像素限定层材料和制备工艺在TFT基板上形成PDL-1。
在TFT基板上形成PDL-1之后，在PDL-1限定的空间底部形成与TFT电连接的反射阳极，随后，可以以Open Mask(开口掩模)的方式沉积OLED发光单元的后续膜层，包括但不限于有机发光材料层、半透明阴极层、取光层等。由于不必使用精细金属掩模，因此更加经济。
发光单元优选发射蓝光，更优选波长中心范围420至470nm，半峰宽10至30nm。
针对不同的显示面板形成工艺，本公开提出了多种具体的第二像素限定层及波长转换单元的结构。显示面板形成工艺可以包括对盒方式和on-EL方式。对盒方式是指分别形成发光层和波长转换层，随后将两者对盒组装。on-EL方式是在发光层继续逐层制备波长转换层。此外，从波长转换单元/背光扩散单元的制备工艺上分可以包括喷墨打印方式和光刻方式。上述技术分别组合，可以得到喷墨打印波长转换层对盒组装、光刻波长转换层对盒组装、on-EL喷墨打印波长转换层、和on-EL光刻波长转换层四种模式。在本公开中，针对以上四种模式提供更加优选的器件结构。
在所有模式中，都需先形成发光层。在对盒型模式中，将发光层与整体的波长转换层对盒；而在on-EL型模式中，在发光层上逐层形成波长转换层。
以下结合具体模式描述本公开的波长转换层。
模式I：喷墨打印法形成波长转换层并对盒组装
在本公开中，模式I是先通过喷墨打印方式形成与发光层分开的波长转换层，并随后将波长转换层与发光层对盒组装。
在模式I中，在一个独立于发光层的底板上形成波长转换层。在将波长转换层中各个子像素的波长转换单元或任选的透明单元与发光单元对准的情况下，将发光层与波长转换层的组装在一起形成显示面板。为了对盒形成显示面板，在发光层与波长转换层之间，在显示面板中央通常还需设置填料层和支撑柱结构，以及在周边的围堤层。
在对盒模式中，波长转换层优选直接形成在彩膜层上。即，彩膜层作 为波长转换层的底板，这样可以不必为了形成波长转换层提供额外的底板，使得波长转换单元与彩膜直接接触，既简化工艺和材料，又提高发光效率。这一组合也可以称为波长转换彩膜基板。当使用量子点作为下转换材料时，可称为量子点彩膜基板
图4示出了作为底板的彩膜层的示意图。彩膜层3具有透明基板31，并且在其上具有用于遮光的黑矩阵BM。在黑矩阵之间，形成所需的彩膜单元，如蓝、绿、红彩膜单元B-CF、G-CF、R-CF。
可以在透明基板31上，按照常规的工艺流程依次制备BM/B-CF/R-CF/G-CF，优选厚度为BM≤2μm，R/G/B CF≤3μm。由于彩膜单元稍厚于BM，因此一般情况下CF会部分叠盖于BM上。这可以确保BM与彩膜单元之间无漏光的缝隙。具体地，彩膜边缘可以以倾斜曲面方式搭接在BM的顶部。
关于与波长转换单元相应的彩膜单元的波谱选择，原则上说，透过率谱图需与波长转换材料例如QD受B-OLED激发后的谱图匹配良好。简单来说R-CF/G-CF需很好地滤除没有被波长转换材料吸收的蓝光，另外需覆盖下转换出来的激发峰范围。
以彩膜层为基板，可以形成波长转换层，并且由此得到的波长转换彩膜基板随后与发光层对盒组装，制成显示面板。
适当地选择彩膜层中的彩膜单元的滤光性能，以与波长转换单元的转换发光良好配合。图5示出了彩膜单元的滤光性与波长转换单元的发光性的配合的一个实例。图中的纵坐标对于彩膜单元来说是透光率，对波长转换单元来说是受激发后的光谱能量，横坐标为波长。图中，深色实线G-QD表示绿色波长转换层的光谱能量，浅色实线R-QD表示红色波长转换层的光谱能量，密虚线G-CF表示绿色彩膜单元的透光率，疏虚线R-CF表示红色彩膜单元的透光率。从图中可见，在480nm以下的光都被彩膜滤除。绿色彩膜允许在540nm左右的绿色转换光通过，而红色彩膜允许640nm左右的红色转换光通过。由此，在蓝色光照射下，波长转换彩膜基板可以良好地显示红光和绿光。如图所示，在绿色彩膜透过波长范围的绿色波长转换单元发光能量低。如前文所述，为了保证合适的亮度，绿色子像素面积可以最大，而蓝色子像素因为没有下转换损失可以面积最小。
如无特别说明，以上对彩膜的描述不但适用于模式I，也适用于模式II-IV。
在彩膜层上形成第二像素限定层PDL-2，其限定波长转换单元或透明单元的空间。随后，在PDL-2的壁围成的空间中形成波长转换单元或透明单元。
第二像素限定层PDL-2可以直接在BM上形成，并且在本模式中作为喷墨打印形成波长转换单元的堤坝层(Bank)。喷墨打印形成波长转换单元的工艺是采用含有波长转换材料的墨水(Ink)，将墨水打印到堤坝层之间的空间中，随后将墨水层固化(例如光固化)从而形成波长转换单元。喷墨打印例如QD的工艺是已知的。彩膜层也可以具有覆盖黑矩阵和/或彩膜单元的保护层，并且PDL-2以及波长转换单元形成在该保护层上。
为了有利地用于喷墨打印，堤坝层需具有疏液的表面，包括侧面和顶面，以降低墨水沿壁侧的攀爬。相对于侧面，顶面对疏液性的要求更高。优选地，PDL-2整体由具有疏液性的材料制备。疏液性材料的原料实例可以包括丙烯酸酯聚合物与多官能度单体的混合物，硅氧烷聚合物和丙烯酸单体的混合物，等等。疏液性可以用接触角来表征。
堤坝层的截面的特征四边形中，由于其形成在与衬底基板相反一侧的底板上，因此其靠近衬底基板的一侧为其特征四边形的第一边。优选其第二边与第三边的夹角和第二边与第四边的夹角中的每一个在80°至140°之间，更优选95°至120°之间。相应地，其第一边第三边的夹角和第一边与第四边的夹角中的每一个在40°至100°之间，优选60°至85°之间。截面可以为梯形(包括矩形)，并且当以彩膜层侧为梯形的底边侧时，侧边与底边的夹角在80°至140°之间，优选95°至120°之间。相应地，若以对盒后的发光层为底侧，则堤坝层的截面的侧边与底边的夹角在40°至100°之间，优选60°至85°之间。对于堤坝层来说，形状在此优选角度范围内时，其限定的通过喷墨打印形成的波长转换单元的光学能量利用率高。在此角度之外时，光能量损失增加。应当注意，此优选范围不仅考虑光学性能，而且也考虑到了这种角度的堤坝层的工艺实现难度。
在优选的角度范围内，在彩膜层上的堤坝层实际上是“倒梯形”。
虽然理想地想要形成梯形截面，但是由于堤坝层材料和工艺限制，实 际制成的产品中截面形状常常与标准梯形产生一些偏差。倒梯形的顶角常常不是尖锐角，而是圆角，甚至在实际生产中形成的“蘑菇形”的截面，如图6(a)所示。图6(a)示出了本公开的一个实例中对盒模式喷墨打印的波长转换彩膜基板的结构的显微照片。照片中显示了堤坝层、在堤坝层两侧的波长转换单元、和在堤坝层和波长转换单元上方的封装层、填料层等，具体地，图6(a)中，显示了一个“倒置”(即彩膜层在下方)的显示面板的局部。61为Encap-1层的一部分。其上的OLED单元和第一像素限定层为了制备SEM样品已被剥离，箭头处的浅凹陷即是对盒情况下第一像素限定层所在位置。62为填料层，63为第二封装层Encap-2，64为波长转换单元，65为PDL-2层(即堤坝层Bank)，66为彩膜单元，67为黑矩阵，68为基底。在图右侧波长转换单元出现分层的原因是工艺引起固化效率不同所导致的。蘑菇形截面的示意图可以如图6(b)所示，其两个上顶角圆滑化，并且在根部底切深度还有可能有所减少。在本公开中，采用与该蘑菇形外切的倒梯形来进行代表它。外切的倒梯形的顶边与蘑菇形的最高处平齐，底边为蘑菇形根部。图6(b)中以灰色线示出了代表该蘑菇形截面的梯形。因此，本公开的倒梯形设计范围也包含由这样的梯形所代表蘑菇形堤坝层。应当注意，在工艺允许的情况下，应尽量避免产品由梯形产生偏差，即，标准梯形是更为理想的。
此外，堤坝层的厚度优选为6-20μm，更优选10-16μm，即厚度可以为PDL-1的厚度(1-2μm)的3至20倍，更优选5至16倍。这样尺寸的梯形截面形状有利于减小关键尺寸偏差(CD bias)，同时降低墨水攀爬。该厚度设置范围对于现有含波长转换材料的墨水材料来说，是在平衡光学转化效率与亮度后的最佳范围。厚度过低时，波长转换材料如QD对发光的吸收率不足；而厚度过高时，波长转换量子效率在达到饱和值后会出现量子湮灭而下降。未来墨水配方如有进一步进步，厚度可以进一步减薄，但仍应保持在6μm以上。
图7(a)-7(e)示意性示出了模式I的波长转换彩膜基板的一些实施方案。波长转换彩膜基板包括彩膜层和波长转换层。图7(a)显示先在黑矩阵上形成PDL-2，限定出用于波长转换单元和透明单元的空间。图7(b)显示向上述空间中通过喷墨打印形成绿色、红色波长转换单元G-QD和R-QD和透 明单元T，分别位于绿色、红色和蓝色彩膜单元上。图7(c)显示随后可以形成第二封装层Encap-2。图7(d)显示在PDL-2上还可形成对盒所需的支撑柱结构(PS)。图7(e)示出了，在一些实施方案中，例如由于均匀性控制导致墨水容纳量发生差异时，波长转换层的顶面也可以略低于PDL-2的顶面。
在实际制备时，堤坝层需选用疏液材料，并且综合考虑到其与基板的粘附能力，因此其形状受到制备工艺的影响。
PDL-2层典型地可以通过曝光显影的方式图案化，即通过在掩模下光照进行紫外光固化后除去未固化的部分来形成PDL-2。此时，有颜色的PDL-2，例如黑色PDL-2，是优选的。当PDL-2有颜色且厚度较高时，靠近彩膜层的像素限定层材料接受的紫外光不足以使其固化，而在显影时容易被去除，形成底切(undercut)，进而造成梯形截面侧边与底边的夹角大于95°的前述优选范围内。
从光学性能的角度看，反射型的PDL-2也是优选的。反射型PDL-2可以是灰色堤坝层，其因含有散射粒子而显示灰色，或者是对于黄色波段具有更强反射效果的黄色堤坝层。灰色堤坝层可以提供适当的反射，并且便于通过控制曝光程度来制成倒梯形或正梯形。黄色堤坝层的优势则在于对于提高取光效率特别有利。反射型PDL-2还可以是通过光刻工艺在堤坝层上增加侧边金属来提升反射效果，例如金属Al及合金等。金属层的厚度可以为200-400nm，即可以提供充足的反射性，又不影响堤坝层的构型。利用反射型PDL-2及相应提升反射率升有助于提高光取出效果。第二像素限定层的侧边制备图形化反光金属层可以增加蓝光发光在波长转换单元中的光学波长转换路程。不过，通过光刻增加金属层的反射型PDL-2有时会降低图形化光刻的工艺窗口。
优选地，反射型的PDL-2的黄光波段反射率为50至70％，而蓝光波段反射率20至40％。当在波长转换单元周边使用这样的反射型的PDL-2时，大部分蓝光被吸收，同时大部分黄光得到反射，从而提高了取光效率。
发明人发现，PDL-2对色光的反射性能还与其厚度有关。例如，在不同高度下，堤坝层对各种颜色光的反射率可以是不同的。灰色堤坝层和黄色堤坝层都在波长较长的黄光区反射率高，而在波长较短的蓝光区反射率 低。对于灰色PDL-2堤坝层来说，在蓝光区厚度对于反射率几乎无影响，在黄光区，厚度越高，反射率越高。对于黄色PDL-2堤坝层来说，在黄光区，厚度越高，反射率越高，而在蓝光区，当其厚度越小，特别是小于6μm时，其蓝光区的反射能力反而越高。因此，大的PDL-2厚度是有利的，其保证在黄光区的高反射，并避免在蓝光区出现高反射。因此，从反射效果看，PDL-2的厚度不应小于6μm。
在此模式I中所述的PDL-2的选材、厚度等特征也适用于本公开的其他情况，包括但不限于模式II-IV。不过，与疏液性有关的特征仅适用于堤坝层，即模式I和III中的PDL-2。对于不同的堤坝层材料，其疏液性可以通过接触角表征。优选地，其对去离子水的接触角应≥90°，并且对丙二醇甲醚醋酸酯(PGMEA)的接触角应≥35°。
第二像素限定层的线宽通常为10-50μm，优选15至30μm。本公开中，以第二像素限定层最宽部分为其线宽。关键几何尺寸的宽度一般都采用最宽的宽度，以便于例如光刻工艺中临界尺寸的判定。其树脂可用常规的230℃工艺进行主固化。更优选地，使用可以低温固化(例如固化条件85至105℃)的、疏液的且有颜色的树脂制备PDL-2。
图8(a)-(f)示出了一些第二像素限定层的显微照片。图8(a)示出了一个正梯形的灰色堤坝层。图8(c)示出了一个倒梯形的灰色堤坝层。具有散射粒子的灰色堤坝层可以通过调节光固化参数比较方便地获得正梯形或倒梯形截面。图8(c)示出了一个近似于矩形的黄色堤坝层，其有利于增加红绿光反射和减少蓝光反射。图8(d)示出了一个蘑菇形的黑色堤坝层，其底切易于由光固化工艺形成。图8(e)示出了一个倒梯形的堤坝层，并且具有用于反射的金属侧边。图8(e)示出了一个倒梯形的堤坝层的一侧，并且具有用于反射的金属侧边，即其中明亮的边缘。图8(f)示出了一个具有用于反射的金属侧边的倒梯形的堤坝层的斜视图。
在模式I中，在彩膜层上形成PDL-2即堤坝层后，采用喷墨打印的方法，用含波长转换材料的墨水制备波长转换单元。
在疏液的堤坝层限定的空间中，通过喷墨打印法打印含波长转换材料的墨水并进行固化。典型地，含波长转换材料的墨水可以由波长转换材料(如QD粒子)和基质组成，且含波长转换材料的墨水中的基质是可光固化 的。固化后，含波长转换材料的墨水层转变为波长转换树脂薄膜。常规地，波长转换树脂薄膜的厚度范围可以在疏液堤坝层厚度(如6至20微米)的基础上扩充为6至30微米，其取决于堤坝层的疏液程度及打印墨水的体积。如上所述，优选波长转换树脂厚度在10至20μm。堤坝层的疏液性如前所述，可以优选为对去离子水的接触角≥90°，并且对丙二醇甲醚醋酸酯(PGMEA)的接触角≥35°。
图9示出了在一个实施方案中由倒梯形第二像素限定层限定的波长转换单元的45°角俯视SEM照片。图中，区域A是固化的波长转换单元的上表面，区域B是其截面。波长转换单元两侧是倒梯形堤坝层(即第二像素限定层)，更具体地，其是“蘑菇”形。其侧壁为C，截面为D，顶面为E，顶面向下倾斜的边缘为F。堤坝层中间围成的空间设置波长转换单元。图片右下角可以看到尚未填充墨水的由堤坝层限定的空间G。图中示出了借助倒梯形疏水性堤坝层下，可以良好地实施喷墨打印，用含转换材料的墨水良好填充堤坝层限定的空间并固化，形成波长转换单元。若以彩膜层为底侧观察，侧壁C与底边的夹角可以为80至140°，优选为呈倒梯形的95至120°。相应地，若以显示面板中的发光层为底侧观察，侧边与底边夹角可以为40至100度，优选为60至85°。
图10(a)示出了模式I的优选角度范围。应当理解，图10(a)-(d)中的梯形形状仅是示意性的，其表示相应模式的特征四边形。
在波长转换单元制备完成之后，可以再覆盖一层第二封装层Encap-2，如图5(c)所示。第二封装层覆盖第二像素限定层和波长转换单元的表面，以保护制得的波长转换单元。在本公开中，第二封装层是形成波长转换单元后保护波长转换单元的封装层，第一封装层是形成发光单元后保护发光单元的封装层。第二封装层是任选的。当采用足够高稳定性的波长转换材料或者足够好的层叠体整合工艺时，也可无需对波长转换单元进行封装。
Encap-2可以是通过低温工艺(≤180℃)制备的低应力、致密的无机薄膜，例如SiOx/SiNx/Al2O3等，具体可以使用CVD、ALD等制程。该膜层厚度小于1μm，优选小于0.5μm，且折射率范围1.7至2.0之间，优选1.75至1.85之间，用于保护波长转换树脂膜层，保持波长转换光学效率。这样的第二封装层厚度范围可以减小下文所述的光学盒厚，降低串扰。 而且，这样折射率的薄膜的致密性也更好，更有利于保护波长转换树脂膜层。这样的第二封装层也可以用于模式II。
随后，将包含彩膜层和波长转换层的波长转换彩膜基板与已制备好的发光层对盒组装。在两者之间，充入填料，任选地设置支撑柱结构，并且在显示面板周边包围封闭填料层的围堤层。
围堤层和填料可以在真空或氮气环境下涂布和填充。具体地，在真空或者氮气环境下，在发光层的出光面或波长转换层的入光面上，在外围涂布围堤层材料以及在面板的有效显示区(AA)中涂敷填料，随后两层贴近后高精度对位并实现对盒。
其中围堤层使用紫外(UV)光固化。工艺过程中，使用掩模遮罩有效显示区，避免影响显示特性。填料可以采用低温(≤100℃)热固化。围堤层厚度为15至50μm，优选20至40μm，更优选20至30微米。围堤层可以采用树脂，其中可以含有粒径或厚度受控的纤维或微球填充物。填料优选低温固化树脂(主固化温度≤100℃，优选≤90℃)，且固化后经100℃下烘烤2小时其气体释放(outgas)值≤100ppm。填料固化后其厚度范围为5至30um，优选10至15um。填料和围堤过薄会影响两侧部件的对盒性能，过厚则会影响显示面板的显示性能。特别的，在填料厚度增大时，波长转换单元的面积可以随之增加，且其与发光单元的发光面积的相差值与光学盒厚(波长转换单元入光面与发光单元的出光面之间的距离，即可以是填料层与封装层的厚度之和)成正相关性。即光学盒厚越大，波长转换单元的面积与发光单元的发光面积之差也越大，以避免像素间受激发光造成的串色的影响。光学盒厚也与像素设计及分辨率有相关性，分辨率越高、像素设计越小，所需的光学盒厚也越小。类似地，过厚的光学盒厚可能导致光折射对相邻子像素的串扰。
图11示意性显示了对盒后的QD-OLED显示面板的一个实施方案。将蓝色B-OLED发光层和图5(d)的具有支撑柱结构PS的QD波长转换彩膜基板对盒，其间填充填料Filler且周边有围堤层DAM，组装成本公开的显示面板的一个实施方案。图中，T表示透明单元，G-QD和R-QD表示绿色和红色QD波长转换单元，B-CF、G-CF和R-CF表示蓝绿红三种颜色的彩膜单元。图11着重说明填料和围堤层，并且为了清楚地说明各个 子像素，OLED描绘为被PDL-1完全隔开。但应理解，如上所述，相邻OLED中的发光材料层、阴极等也是可以越过PDL-1相互连接的。
本公开中的围堤层厚度可以与常规围堤层类似为30μm左右，填料层厚度(按发光单元与波长转换单元或透明单元的间距计)则可减薄至5至10μm，大大小于常规围堤-填料结构中的填料层厚度(20μm以上)，以制备更高分辨率和更小子像素的显示面板。
在本公开中，支撑柱结构既可以形成在第二像素限定层上，也可以形成在第一像素限定层上，并且在一些情况下，还可以没有支撑柱结构，仅依靠围堤层和填料维持OLED发光单元与波长转换单元或透明单元的间距。支撑柱可以与像素限定层直接接触，也可以不与其直接接触。此外，可以选择性地仅在一部分像素限定层上当设置支撑柱结构。支撑柱结构可以以相关技术中的一般方法制备，并且适当地设计其在显示面板中的分布密度。优先在更大开口面积的红色子像素和绿色子像素之间的像素限定层上制备支撑柱结构，这是由于可以兼顾绿色在光学上的高亮度敏感性和工艺窗口能力。一方面，人眼对绿色不敏感，因此对绿色子像素的亮度要求高；另一方面，绿色和红色子像素的物理尺寸大，可以提供为形成支撑柱结构提供更好的加工能力。
在所述显示面板中的每个子像素中，所述发光单元的出光面处于所述波长转换单元的入光面在所述发光层中的正投影中。优选地，发光单元的出光面小于波长转换单元的入光面。
图12显示了发光单元的出光面、波长转换单元的入光面和盒厚的关系。在图12中，下方的发光单元的出光面与上方的波长转换单元的下表面之间的厚度为盒厚，该厚度内可以包括填料层(Filler)和任选的封装层(Encap，如第一、第二封装层Encap-1和Encap-2)。设发光单元的出光面边缘与波长转换单元的入光面边缘的横向距离为a，盒厚为b，则a≤1.8b。更优选地，a/b不大于tan 60°(即图中α≤60°)。若a/b的值过大，则发光单元进入波长转换单元时的角度偏离竖直方向过大，在具有折射率差异的薄膜层叠体结构中的出光路径上容易发生全反射现象，影响发光效率。
此外，多个波长转换单元可以搭接在所述第二像素限定层靠近所述衬底基板的一侧表面。多个波长转换单元可以包括相邻设置的第一颜色波长 转换单元和第二颜色波长转换单元，所述第一颜色波长转换单元与所述第一颜色波长转换单元搭接在将两者隔开的所述第二像素限定层上的宽度不同。显示面板还可以包括：在所述波长转换单元远离所述发光层一侧的彩膜层，其中，所述彩膜层包括多个彩膜单元以及限定所述多个彩膜单元的黑矩阵，所述多个彩膜单元搭接在所述黑矩阵靠近所述衬底基板的一侧表面，并且波长转换单元在第二像素限定层上的所述搭接的宽度和与其同属于同一子像素的彩膜单元在黑矩阵上的所述搭接的宽度不同。
特别是，对于使用墨水打印的模式I，最终形成的所述波长转换单元搭接在所述第二像素限定层上的宽度优选为所述第二像素限定层的被搭接表面的宽度的10％以内。
在本公开中，搭接是指分别填充在黑矩阵、第一像素限定层和第二像素限定层(可以统称为单元限定层)中的彩膜单元、波长转换单元或发光层在它们的顶部反而覆盖这些单元限定层。如果单元限定层的顶面为平面，则搭接部分即是在顶面平面上的部分。搭接部分的边缘与顶面边缘的水平距离即为搭接宽度。
图11示出了彩膜单元搭接在黑矩阵的靠近衬底基板的一侧，波长转化单元搭接在第二像素限定层靠近衬底基板的一侧。两者的搭接宽度不同。图11中显示相邻的波长转换单元搭接在第二像素限定层上的宽度基本相同，但它们也可以是不同的，并且每个搭接宽度为第二像素限定层的被搭接表面的宽度的10％以内。在图11所示的实施方案中，被搭接表面即为PDL-2的下表面。
模式II：光刻法形成波长转换层并对盒组装
模式II与模式I相同之处至少在于发光层以及对盒工艺，与模式I的主要区别在于不是使用喷墨打印法而是使用光刻法形成波长转换单元。
与喷墨打印法不同，采用直接涂敷包含波长转换材料如QD的光阻树脂或光刻胶并利用光刻法对其进行图案化，来形成波长转换单元。
与模式I中相同，在形成波长转换单元之前，在彩膜层的黑矩阵BM上制备第二像素限定层PDL-2。不过，此处的PDL-2不再是用于喷墨打印的堤坝层。因此，其无需具有针对打印墨水的疏液性，也不再充当堤坝层。 但与堤坝层类似，堤坝层的截面的特征四边形中，由于其形成在与衬底基板相反一侧的底板上，因此其靠近衬底基板的一侧为其特征四边形的第一边。优选其第二边与第三边的夹角和第二边与第四边的夹角中的每一个在60°至120°之间，更优选90°至120°之间。相应地，其第一边与第三边的夹角和第一边与第四边的夹角中的每一个在60°至120°之间，优选60°至90°之间。截面可以为梯形(包括矩形)，并且当以彩膜层侧为梯形的底边侧时，侧边与底边的夹角在60°至120°之间，优选90°至120°之间。相应地，若以对盒后的发光层为底侧，则堤坝层的截面的侧边与底边的夹角在60°至120°之间，优选60°至90°之间。在此优选角度范围内时，其限定的通过光刻形成的波长转换单元的光学能量利用率高。在此角度之外时，光能量损失增加。
图10(b)示出了模式II的优选角度范围。
优选地，PDL-2的厚度为6至12μm。相对于含波长转换材料的墨水，树脂密度较高并且所占体积较小，因此其PDL-2的厚度与模式I相比可以略低，但是，其下限仍应为PDL-1的2倍以上，优选为6μm以上。
可以向形成有PDL-2的彩膜层上，整面涂敷含有波长转换材料的光阻树脂，也称为波长转换光刻胶，使其填充PDL-2限定的空间。随后，通过在掩模下照射、显影、刻蚀等光刻步骤，除去不需要的部分的波长转换光刻胶，在PDL-2限定的空间中的一部分中保留波长转换光刻胶，即实现图案化，从而形成波长转换单元。典型地，对红色波长转换单元、绿色波长转换单元以及透明单元，涂敷不同的光刻胶并且各自进行一次光刻工艺。
光刻胶显影后的烘焙固化温度优选≤180℃，以减少热处理对材料的影响。
透明单元可以用掺有散射粒子的光扩树脂形成，以确保各子像素显示视角的一致性。
优选地，波长转换单元的厚度与PDL-2的厚度相近，在6-12μm的范围内。两者厚度相近有利于后续整合工艺的窗口控制，有助于后续工艺的平坦化，从而保持光学表现的均一性和保持视角。
图13(a)-(b)示意性示出了在彩膜层上通过光刻法形成的波长转换单元和透明单元的实施方案。图13(a)中示出了，为了便于波长转换光刻胶的 充分填充，PDL-2呈正梯形(以彩膜层侧为底侧)。在本图中，示出了绿色单元的面积≥红色单元的面积≥蓝色单元的面积。此外，可以在PDL-2的顶部再形成支撑柱结构PS，且图中示出了仅在绿色和红色子像素之间设置PS。如上所述，这是由于可以兼顾工艺窗口能力以及G在光学上的高亮度敏感性。如图所示，通过涂敷光刻胶和随后的光刻工艺形成的波长转换单元和透明单元的厚度与PDL-2的厚度相近。与喷墨打印法相比，在光刻法中，通过PDL-2的厚度对波长转换单元的厚度进行调节更加简单。图13(b)示出了还可以在其上形成第二封装层Encap-2。
在制成波长转换彩膜基板后，可以以与模式I中所述类似的工艺，进行对盒等步骤，进一步制备显示面板。
应当理解，除了波长转换单元和PDL-2有所区别之外，模式I、II在大部分共有部分中可以使用相同的工艺参数。例如，可以使用相同的彩膜层、填料层和围堤层。
模式I和II都是制备本公开的显示面板的方法，包括：
在作为底板的彩膜层上形成第二像素限定层，
在第二像素限定层限定的空间中，通过喷墨打印含波长转换材料的墨水或通过涂敷和光刻含波长转换材料的光刻胶形成波长转换层，以制备波长转换彩膜基板，以及
将波长转换彩膜基板与发光层对盒组装成显示面板，其中，在波长转换彩膜基板与发光层之间设置填料层和围堤层。
优选地，在≤180℃的温度下，以低温工艺形成所述波长转换层，包括但不限于形成PDL-2、波长转换单元、以及Encap-2。
模式I类似，多个波长转换单元可以搭接在所述第二像素限定层靠近所述衬底基板的一侧表面。多个波长转换单元可以包括相邻设置的第一颜色波长转换单元和第二颜色波长转换单元，所述第一颜色波长转换单元与所述第一颜色波长转换单元搭接在将两者隔开的所述第二像素限定层上的宽度不同。显示面板还可以包括：在所述波长转换单元远离所述发光层一侧的彩膜层，其中，所述彩膜层包括多个彩膜单元以及限定所述多个彩膜单元的黑矩阵，所述多个彩膜单元搭接在所述黑矩阵靠近所述衬底基板的一侧表面，并且波长转换单元在第二像素限定层上的所述搭接的宽度和 与其同属于同一子像素的彩膜单元在黑矩阵上的所述搭接的宽度不同。
图13中示出了彩膜单元搭接在黑矩阵的靠近衬底基板的一侧，但未示出波长转化单元搭接在第二像素限定层上。
模式III：on-EL喷墨打印波长转换层
如本公开所述的on-EL是指在发光层上继续形成波长转换层和彩膜层来形成显示面板的方式，其无需进行对盒组装。
在模式III中，与模式I类似，采用喷墨打印的方式形成波长转换单元。与模式I的区别在于，以发光层而非彩膜层作为底板形成PDL-2和随后形成波长转换单元。
图14(a)-(e)示意性示出了通过on-EL及喷墨打印形成显示面板的过程。图14(a)示出了首先在发光层的PDL-1的位置处形成PDL-2。图14(b)示出了随后在PDL-2限定的空间中通过喷墨打印形成QD波长转换单元和透明单元T。图14(c)显示随后可以形成第二封装层。图14(d)显示随后形成包含黑矩阵的彩膜层。图14(e)显示最后形成反射型偏振片P和盖膜Cover。图14中，发光层中各图例与图2中所示的发光层相同。可以看到，on-EL模式中可以无需填充填料层。
在本模式中，PDL-2的截面形状的特征四边形中，由于其形成在与衬底基板一侧的底板上，因此其远离衬底基板的一侧为其特征四边形的第一边。优选其第二边与第三边的夹角和第二边与第四边的夹角中的每一个在80°至140°之间，优选95°至120°之间。截面可以为梯形。理想地，无论以on-EL方式还是对盒方式形成显示面板，从光学上考虑，PDL-2的形状的最优选角度都是类似的，为顶部略宽，底部略窄。然而，考虑到适用于喷墨打印工艺，此处的PDL-2仍为堤坝层并应考虑墨水的疏液和攀爬问题。在此情况下，与在模式I以彩膜层为底板的情况类似，PDL-2的侧边与底角的夹角在80°至140°之间，优选95°至120°之间，即对角度作了一定的让步。应当注意，此优选范围不仅考虑光学性能，而且也考虑到了这种角度的PDL-2的工艺实现难度。这一角度范围虽然未实现顶部略宽，底部略窄的波长转换单元，但在本制备模式下，仍获得了较佳的显示性能。
图10(c)示出了模式III的优选角度范围。
PDL-2的厚度优选为6-20μm，更优选10-16μm，即厚度可以为PDL-1的厚度(1-2μm)的3至20倍，更优选5至16倍。这样的梯形截面形状有利于减小关键尺寸偏差(CD bias)，同时降低墨水攀爬。该厚度设置范围对于现有含波长转换材料的墨水材料来说，是在平衡光学转化效率与亮度后的最佳范围。未来墨水配方如有进一步进步，厚度可以进一步减薄，但仍应保持在6μm以上。
图15(a)-(b)示出了本公开的一个实例中on-EL及喷墨打印形成的结构的显微照片。图15(a)显示了下方的正梯形的PDL-1、PDL-1上方的第一封装层、和第一封装层上方的倒梯形的PDL-2。PDL-2PDL-1两侧的发光单元厚度很薄，在此显微尺度下不可见。图15(b)则示出了倒梯形的PDL-2和在其左侧通过喷墨打印填充形成的波长转换单元，其右侧则还未进行喷墨打印填充。
模式III中也使用喷墨打印方式，因此，为了形成优选的底切，与模式I类似，有颜色的PDL-2，例如黑色PDL-2，是优选的。
同样，类似地，反射型的PDL-2也是优选的。反射型PDL-2可以是含有散射粒子的灰色堤坝层，或者对于黄色波段具有更强反射效果的黄色堤坝层。反射型PDL-2还可以是通过光刻工艺在堤坝层上增加侧边金属来提升反射效果，例如金属Al及合金等。金属层的厚度可以为200-400nm，即可以提供充足的反射性，又不影响堤坝层的构型。利用反射型PDL-2及相应提升反射率升有助于提高光取出效果。第二像素限定层的侧边制备图形化反光金属层可以增加蓝光发光在波长转换单元中的光学波长转换路程。反射型PDL-2的侧边与底边的夹角也在80°至140°之间，优选95°至120°之间。
对于不同的第二像素限定层材料，其疏液性可以通过接触角表征。优选地，其对去离子水的接触角应≥90°，并且对丙二醇甲醚醋酸酯(PGMEA)的接触角应≥35°。
第二像素限定层的线宽通常为10-50μm，优选15至30μm。不过在模式III中，应选择主固化温度不超过100℃的疏液树脂形成PDL-2，而不是如模式I中的常规的多至230℃的主固化温度。这归因于作为底板的发光层的耐热性比彩膜层差。
在疏液的堤坝层限定的空间中，通过喷墨打印法打印含波长转换材料的墨水并进行固化。典型地，含波长转换材料的墨水由波长转换材料(如QD粒子)和基质组成，且含波长转换材料的墨水中的基质是可光固化的。固化后，含波长转换材料的墨水层转变为波长转换树脂薄膜。常规地，波长转换树脂薄膜的厚度范围可以在疏液堤坝层厚度(如6至20微米)的基础上扩充为6至30微米，其取决于堤坝层的疏液程度及打印墨水的体积。优选波长转换树脂厚度在10至20μm。
在波长转换单元制备完成之后，可以再覆盖一层第二封装层。在模式III中，考虑到发光层的耐热性，优选通过超低温工艺(≤100℃)制备低应力、致密的无机薄膜即Encap-2膜层，例如SiOx/SiNx/Al2O3等，，具体可以使用CVD、ALD等制程。该膜层厚度小于1um，优选小于0.5um，且折射率范围1.7至2.0之间，优选1.75至1.85之间。
随后继续在Encap-2上制备图形化黑矩阵BM及各色彩膜R-CF/G-CF/B-CF，同样应使用超低温工艺(≤100℃)。彩膜层的厚度及光学要求与对盒路线中的要求中相同。
与对盒路线不同，在on-EL路线中，由于彩膜层并不作为负载PDL-2的底板，因此可以再在彩膜层上制备或者贴附一层反射型偏振片，优选在蓝光波段反射率略高的反射型偏振片(例如3M公司的DBEF薄膜或者光固化的宽谱液晶性反射偏光膜)。其上可以再贴附高透过率、防刮擦的盖膜(Cover film)材料或其他光学补偿膜片。
总体说来，在on-EL路线中，不设置填料层、围堤层和支撑柱结构，光学盒厚可以进一步降低。更小光学盒厚的on-EL式器件结构具有更大的产品化空间。不过，由于发光层的耐热性不如彩膜层，因此on-EL路线中对超低温工艺的要求较高。
此外，多个波长转换单元可以搭接在所述第二像素限定层远离所述衬底基板的一侧表面。多个波长转换单元可以包括相邻设置的第一颜色波长转换单元和第二颜色波长转换单元，所述第一颜色波长转换单元与所述第一颜色波长转换单元搭接在将两者隔开的所述第二像素限定层上的宽度不同。显示面板还可以包括：在所述波长转换单元远离所述发光层一侧的彩膜层，其中，所述彩膜层包括多个彩膜单元以及限定所述多个彩膜单元 的黑矩阵，所述多个彩膜单元搭接在所述黑矩阵靠近所述衬底基板的一侧表面，并且波长转换单元在第二像素限定层上的所述搭接的宽度和与其同属于同一子像素的彩膜单元在黑矩阵上的所述搭接的宽度不同。
特别是，对于使用墨水打印的模式III，最终形成的所述波长转换单元搭接在所述第二像素限定层上的宽度优选为所述第二像素限定层的被搭接表面的宽度的10％以内。
图14示出了波长转化单元搭接在第二像素限定层靠近衬底基板的一侧，但未示出彩膜单元搭接在黑矩阵上。
模式IV：on-EL光刻波长转换层
在模式IV中，与模式II类似，采用光刻法的方式形成波长转换单元。与模式II的区别在于，以发光层而非彩膜层作为底板形成PDL-2和随后形成波长转换单元。
图16示意性示出了通过on-EL及光刻形成的显示面板。其中，其产品的层结构与图14(e)所示的层结构类似。
在本模式中，PDL-2的截面形状的特征四边形中，由于其形成在与衬底基板一侧的底板上，因此其远离衬底基板的一侧为其特征四边形的第一边。优选其第二边与第三边的夹角和第二边与第四边的夹角中的每一个在60-100°之间。优选地，该夹角在70°至90°之间。截面可以为梯形或接近矩形。如上所述，PDL-2的形状的最优选角度为顶部略宽，底部略窄。PDL-2的侧边与底边的夹角在60-100°之间。优选地，该夹角在70°至90°之间，以形成开口大、底部小的空间，便于含波长转换材料的树脂涂敷。应当注意，此优选范围不仅考虑光学性能，而且也考虑到了这种角度的PDL-2的工艺实现难度。
图10(d)示出了模式II的优选角度范围。
图17示出了一个位于PDL-2所限定的子像素空间中的固化后的含QD波长转换材料的光刻胶层的显微照片。从图中可见，含QD的光刻胶树脂充分填充在PDL-2限定的空间中。PDL-2和QD单元形成在Encap-1上，并且上方又覆盖有Encap-2。
优选地，PDL-2的厚度为6至12μm。相对于含波长转换材料的墨水， 树脂密度较高并且所占体积较小，因此其PDL-2的厚度与模式II相比可以略低，但是，其下限仍应为PDL-1的2倍以上，优选为6μm以上。
与模式II类似地，采用光刻法在PDL-2限定的空间中形成波长转换单元或透明单元。与模式II的区别在于，光刻胶显影后的烘焙固化温度优选≤100℃，而不是对盒路线中的≤180℃。
同样，优选地，波长转换单元的厚度与PDL-2的厚度相近。
在模式IV中也可以形成第二封装层Encap-2。该第二封装层Encap-2与模式II中的区别在于使用超低温工艺(≤100℃)而非低温工艺(≤180℃)制备低应力、致密的无机薄膜，例如SiOx/SiNx/Al2O3等，具体可以使用CVD、ALD等制程。该膜层厚度小于1μm，优选小于0.5μm，且折射率范围1.7至2.0之间，优选1.75至1.85之间，用于保护波长转换树脂膜层，保持波长转换光学效率。超低温工艺制作的Encap-2膜层不耐刮蹭，需注意存放。
在超低温工艺中若使用真空沉积，可以将波长转换单元或透明单元在光刻过程的低温固化期间仍未充分释放的杂气进一步释放，有利于进一步提高波长转换单元或透明单元的质量。
与模式III中类似，可以继续在Encap-2上制备图形化黑矩阵BM及各色彩膜R-CF/G-CF/B-CF，以及任选的反射型偏振片、盖膜材料或其他光学补偿膜片。
具体地，随后继续在Encap-2上制备图形化黑矩阵BM及各色彩膜R-CF/G-CF/B-CF，同样应使用超低温工艺(≤100℃)。彩膜层的厚度及光学要求与对盒路线中的要求中相同。
与对盒路线不同，在on-EL路线中，可以再在彩膜层上制备或者贴附一层反射型偏振片，优选在蓝光波段反射率略高的反射型偏振片(例如3M公司的DBEF薄膜或者光固化的宽谱液晶性反射偏光膜)。其上可以再贴附高透过率、防刮擦的盖膜(Cover film)材料或其他光学补偿膜片。
模式III和IV都是制备本公开的显示面板的方法，包括：
在作为底板的发光层上形成第二像素限定层，
在第二像素限定层限定的空间中，通过喷墨打印含波长转换材料的墨水或通过涂敷和光刻含波长转换材料的光刻胶形成波长转换层，以及
在波长转换层上形成彩膜层，以形成显示面板。
优选地，在≤100℃的温度下，以超低温工艺形成所述波长转换层，包括但不限于形成PDL-2、波长转换单元、Encap-2、以及彩膜层。
模式IV类似，多个波长转换单元可以搭接在所述第二像素限定层远离所述衬底基板的一侧表面。多个波长转换单元可以包括相邻设置的第一颜色波长转换单元和第二颜色波长转换单元，所述第一颜色波长转换单元与所述第一颜色波长转换单元搭接在将两者隔开的所述第二像素限定层上的宽度不同。显示面板还可以包括：在所述波长转换单元远离所述发光层一侧的彩膜层，其中，所述彩膜层包括多个彩膜单元以及限定所述多个彩膜单元的黑矩阵，所述多个彩膜单元搭接在所述黑矩阵靠近所述衬底基板的一侧表面，并且波长转换单元在第二像素限定层上的所述搭接的宽度和与其同属于同一子像素的彩膜单元在黑矩阵上的所述搭接的宽度不同。
图16中，波长转换单元和彩膜单元均未发生搭接。
以上描述了制备本公开显示面板的四种模式和相关的一些优选工艺参数。应当理解，当未特别说明是，四种模式中的材料和工艺是可以替换使用的，只要不对性能造成不利影响即可。
实施例
实施例1
采用喷墨打印法和对盒组装法制备6个模式I的显示面板中第一颜色的子像素，这些显示面板的区别仅在于第二像素限定层的梯形侧边与底边夹角(即其特征四边形的第二边与第三、第四边的夹角)不同，分别为60°、70°、80°、100°、110°和120°。其中底边为发光层一侧的边，且夹角为梯形内角。随后测试这些显示面板的有效出光能量比例。测试结果示于图18中。有效出光能量比例是指观测到的透过波长转换单元的发光的经波长转换的光经能量回溯至发光单元的发光(在本实施例中为蓝色OLED发出的蓝光)，与射入该像素内发光能量的比值。有效出光能量比例小于100％，主要由于取光结构设计的原因，导致部分发光可能进入别的像素，或由同层介质导出等。
如图18所示，在模式I的结构中，当第二像素限定层的梯形侧边与底 边夹角为60°、70°和80°时，明显高于为100°、110°和120°时。这表明，当上述夹角在本公开的优选范围内时，获得具有优良效果的取光结构。
实施例2
采用光刻法和对盒组装法制备6个模式II的显示面板，这些显示面板的区别仅在于第二像素限定层的梯形侧边与底边夹角(即其特征四边形的第二边与第三、第四边的夹角)不同，分别为60°、70°、80°、100°、110°和120°。其中底边为发光层一侧的边，且夹角为梯形内角。随后测试这些显示面板的器件蓝光吸收比例。测试结果示于图19中。器件蓝光吸收率是指在多个子像素的局部区域内，去除漏出的发光比例后与该区域发光单元发出光(在本实施例中为蓝色OLED发出的蓝光)能量的比值。器件蓝光吸收率小于100％，主要由于取光结构设计的原因。
如图19所示，在模式II的结构中，当第二像素限定层的梯形侧边与底边夹角为60°、70°和80°时，明显高于为100°、110°和120°时。这表明，当上述夹角在本公开的优选范围内时，获得具有优良效果的取光结构。
从实施例1和2的对比也可看出，同样使用对盒组装法制备具有波长转换层的显示面板时，当其波长转换单元的制备工艺不同时，第二像素层的梯形侧边与底边夹角的优选范围完全不同。这清楚地说明，第二像素限定层的几何特征对于器件的光学性能具有重大影响。
通过设计包括具有特定形状的第二像素限定层和由其限定的波长转换单元的波长转换层，和与之配合的发光层及彩膜层，本公开提供了一种更加紧凑的取光结构，可以提高显示面板取光效率，从而改善发光效能和色域，提升关键的光学性能。
还提供了包含上述显示面板的显示装置，其可以具有优良的光学性能。
显然，本领域的技术人员可以对本公开实施例进行各种改动和变型而不脱离本公开的精神和范围。这样，倘若本公开的这些修改和变型属于本公开权利要求及其等同技术的范围之内，则本公开也意图包含这些改动和变型在内。

Claims (44)

  1. 一种显示面板，包括：
    衬底基板，
    在所述衬底基板一侧的发光层，和
    在所述发光层远离所述衬底基板一侧的波长转换层，
    其中，所述发光层包括多个发光单元以及限定所述多个发光单元的第一像素限定层，所述波长转换层包括多个波长转换单元以及限定所述多个波长转换单元的第二像素限定层，并且所述多个波长转换单元中的每个被配置为转换所述多个发光单元中的至少一者发出的光的波长，
    其中，在垂直于所述衬底基板的方向上，所述第二像素限定层的厚度为所述第一像素限定层的厚度的2倍以上。
  2. 根据权利要求1所述的显示面板，其中，
    所述波长转换单元中的每个的入光面的面积大于发出其所转换的光的所述发光单元的出光面的面积。
  3. 根据权利要求1所述的显示面板，其中，
    所述第二像素限定层在所述衬底基板的正投影落入所述第一像素限定层在所述衬底基板的正投影内。
  4. 根据权利要求1所述的显示面板，还包括：
    在所述发光层靠近所述波长转换层一侧的第一封装层，所述第一封装层包括第一无机层和在所述第一无机层远离所述发光层的一侧的第二无机层，所述第二无机层包括多个无机子层的层叠体，所述层叠体对其波长经所述波长转换单元转换的光的反射率强于对所述发光单元发出的光的反射率，并且对所述发光单元发出的光的透射率大于对其波长经所述波长转换单元转换的光的透射率。
  5. 根据权利要求4所述的显示面板，其中，
    在垂直于所述衬底基板的方向上，所述第一封装层的厚度为1至6μm。
  6. 根据权利要求1所述的显示面板，还包括：
    在所述波长转换单元远离所述发光层一侧的彩膜层，
    其中，所述彩膜层包括多个彩膜单元以及限定所述多个彩膜单元的黑矩阵。
  7. 根据权利要求6所述的显示面板，其中，
    所述黑矩阵在所述衬底基板的正投影落入所述第二像素限定层在所述衬底基板的正投影内。
  8. 根据权利要求1所述的显示面板，其中，
    在垂直于所述衬底基板的方向上，所述第一像素限定层的厚度为1-2μm，且所述第二像素限定层的厚度为6至20μm。
  9. 根据权利要求1所述的显示面板，其中，
    沿远离衬底基板的方向上，所述多个发光单元依次包括阳极、发光层、阴极，所述阴极远离衬底基板的一侧表面与所述波长转换单元靠近衬底基板的一侧表面之间的距离小于所述第二像素限定层的所述厚度，且大于所述第一像素限定层的所述厚度。
  10. 根据权利要求1所述的显示面板，其中，
    所述波长转换层还包括与多个波长转换单元同层设置的透明单元，所述透明单元与所述波长转换单元之间设置有第二像素限定层。
  11. 根据权利要求1所述的显示面板，其中，
    对于所述第一像素限定层的在垂直于所述衬底基板方向上的横截面形状，以通过所述横截面形状最远离所述衬底基板的点的平行于所述衬底基板的直线为第一边，以经过所述横截面形状与其在靠近所述衬底基板层一侧的相邻层之间的边界的两端的线段为第二边，以分别经过所述两端的向所述第一边延伸并与所述横截面形状外切的直线为第三边和第四边，在由所述第一、二、三、四边围成的四边形中，第二边与第三边的夹角和第二边与第四边的夹角中的每一个在20°至40°的范围内。
  12. 根据权利要求1所述的显示面板，其中，
    所述第一像素限定层与所述第二像素限定层材料不同。
  13. 根据权利要求1所述的显示面板，还包括：
    在所述发光层和所述波长转换层之间的填料层，和
    围堤层，所述围堤层与所述发光层和所述波长转换层包封所述填料层。
  14. 根据权利要求13所述的显示面板，其中，
    对于所述第二像素限定层的在垂直于所述衬底基板方向上的横截面形状，以通过所述横截面形状最靠近所述衬底基板的点的平行于所述衬底基板的直线为第一边，以经过所述横截面形状与其在远离所述衬底基板层一侧的相邻层之间的边界的两端的线段为第二边，以分别经过所述两端的向所述第一边延伸并与所述横截面形状外切的直线为第三边和第四边，在由所述第一、二、三、四边围成的四边形中，第一边与第三边的夹角和第一边与第四边的夹角中的每一个在60°至90°的范围内。
  15. 根据权利要求14所述的显示面板，其中，
    所述第二像素限定层的表面对去离子水的接触角≥90°，并且对丙二醇甲醚醋酸酯的接触角≥35°，并且
    在所述四边形中，第一边与第三边的夹角和第一边与第四边的夹角中的每一个在60°至85°的范围内。
  16. 根据权利要求13所述的显示面板，其中，
    所述围堤层厚度为15至50μm，填料层厚度为5至30微米。
  17. 根据权利要求13所述的显示面板，其中，
    所述多个波长转换单元搭接在所述第二像素限定层靠近所述衬底基板的一侧表面。
  18. 根据权利要求17所述的显示面板，其中，
    所述波长转换单元搭接在所述第二像素限定层上的宽度为所述第二像素限定层的被搭接表面的宽度的10％以内。
  19. 根据权利要求17所述的显示面板，其中，
    所述多个波长转换单元包括相邻设置的第一颜色波长转换单元和第二颜色波长转换单元，所述第一颜色波长转换单元与所述第一颜色波长转换单元搭接在将两者隔开的所述第二像素限定层上的宽度不同。
  20. 根据权利要求17所述的显示面板，还包括：
    在所述波长转换单元远离所述发光层一侧的彩膜层，
    其中，所述彩膜层包括多个彩膜单元以及限定所述多个彩膜单元的黑矩阵，
    所述多个彩膜单元搭接在所述黑矩阵靠近所述衬底基板的一侧表面，并且.
    波长转换单元在第二像素限定层上的所述搭接的宽度和与其同属于同一子像素的彩膜单元在黑矩阵上的所述搭接的宽度不同。
  21. 根据权利要求1所述的显示面板，其中，
    所述波长转换层与第一封装层接触，所述第一封装层与所述发光层接触。
  22. 根据权利要求21所述的显示面板，其中，
    对于所述第二像素限定层的在垂直于所述衬底基板方向上的横截面形状，以通过所述横截面形状最远离所述衬底基板的点的平行于所述衬底基板的直线为第一边，以经过所述横截面形状与其在靠近所述衬底基板层一侧的相邻层之间的边界的两端的线段为第二边，以分别经过所述两端的向所述第一边延伸并与所述横截面形状外切的直线为第三边和第四边，在由所述第一、二、三、四边围成的四边形中，第二边与第三边的夹角和第二边与第四边的夹角中的每一个在70°至90°的范围内。
  23. 根据权利要求21所述的显示面板，其中，
    所述第二像素限定层的表面对去离子水的接触角≥90°，并且对丙二醇甲醚醋酸酯的接触角≥35°，并且
    对于所述第二像素限定层的在垂直于所述衬底基板方向上的横截面形状，以通过所述横截面形状最远离所述衬底基板的点的平行于所述衬底基板的直线为第一边，以经过所述横截面形状与其在靠近所述衬底基板层一侧的相邻层之间的边界的两端的线段为第二边，以分别经过所述两端的向所述第一边延伸并与所述横截面形状外切的直线为第三边和第四边，在由所述第一、二、三、四边围成的四边形中，第二边与第三边的夹角和第二边与第四边的夹角中的每一个在95°至120°的范围内。
  24. 根据权利要求21所述的显示面板，其中，
    所述多个波长转换单元搭接在所述第二像素限定层远离所述衬底基板的一侧表面。
  25. 根据权利要求24所述的显示面板，其中，
    所述波长转换单元搭接在所述第二像素限定层上的宽度为所述第二像素限定层的被搭接表面的宽度的10％以内。
  26. 根据权利要求24所述的显示面板，其中，
    所述多个波长转换单元包括相邻设置的第一颜色波长转换单元和第二颜色波长转换单元，所述第一颜色波长转换单元与所述第一颜色波长转换单元搭接在将两者隔开的所述第二像素限定层上的宽度不同。
  27. 根据权利要求24所述的显示面板，还包括：
    在所述波长转换单元远离所述发光层一侧的彩膜层，
    其中，所述彩膜层包括多个彩膜单元以及限定所述多个彩膜单元的黑矩阵，
    所述多个彩膜单元搭接在所述黑矩阵远离所述衬底基板的一侧表面，并且
    波长转换单元在第二像素限定层上的所述搭接的宽度和与其同属于同一子像素的彩膜单元在黑矩阵上的所述搭接的宽度不同。
  28. 根据权利要求14、15、22和23中任一项所述的显示面板，其中，
    所述四边形为以所述第三边和第四边为侧边的梯形。
  29. 根据权利要求1所述的显示面板，其中，
    所述第二像素限定层为光反射型像素限定层或光吸收型像素限定层。
  30. 根据权利要求1所述的显示面板，其中，
    所述第二像素限定层包括散射粒子或所述第二像素限定层靠近所述波长转换单元的表面设置有金属。
  31. 根据权利要求1所述的显示面板，其中，
    所述波长转换单元是量子点下转换单元。
  32. 根据权利要求1所述的显示面板，其中，
    所述显示面板包括绿色子像素、红色子像素和蓝色子像素，每个子像素包含一个所述发光单元，
    其中，所述绿色子像素中所述发光单元的出光面积≥所述红色子像素中所述发光单元的出光面积≥所述蓝色子像素中所述发光单元的出光面积。
  33. 根据权利要求1所述的显示面板，其中，
    所述波长转换单元中的每个的入光面在所述衬底基板的正投影的边缘与发出其所转换的光的所述发光单元的出光面在所述衬底基板的正投影的边缘的距离a与所述OLED发光单元的出光面与所述背光下转换单元 的入光面的距离b满足a≤1.8b。
  34. 根据权利要求1所述的显示面板，其中，
    所述波长转换层包含第二封装层，所述第二封装层厚度小于1μm。
  35. 一种制备根据权利要求1所述的显示面板的方法，包括：
    提供衬底基板，
    形成在所述衬底基板一侧的发光层，以及
    形成在所述发光层远离所述衬底基板一侧的波长转换层，
    其中，所述发光层包括多个发光单元以及限定所述多个发光单元的第一像素限定层，所述波长转换层包括多个波长转换单元以及限定多个波长转换单元的第二像素限定层，并且所述波长转换单元中的每个被配置为转换所述多个发光单元中的至少一者发出的光的波长，
    其中，在垂直于所述衬底基板的方向上，所述第二像素限定层的厚度为所述第一像素限定层的厚度的2倍以上。
  36. 根据权利要求35所述的方法，其中，
    形成在所述发光层远离所述衬底基板一侧的波长转换层包括：
    在底板上形成所述第二像素限定层，
    在所述第二像素限定层限定的空间中，通过喷墨打印并固化含有波长转换材料的墨水，形成所述波长转换单元，
    并且将所述波长转换层与所述发光层对盒组装成所述显示面板，其中在所述波长转换层与所述发光层对盒之间设置填料层和围堰层。
  37. 根据权利要求35所述的方法，其中，
    形成在所述发光层远离所述衬底基板一侧的波长转换层包括：
    在底板上形成所述第二像素限定层，
    在所述第二像素限定层限定的空间中，通过涂敷并光刻含有波长转换材料的光刻胶，形成所述波长转换单元，
    并且将所述波长转换层与所述发光层对盒组装成所述显示面板，其中在所述波长转换层与所述发光层对盒之间设置填料层和围堰层。
  38. 根据权利要求35或36所述的方法，其中，
    所述底板是彩膜层。
  39. 根据权利要求35或36所述的方法，还包括：
    在形成所述波长转换单元之后，在≤180℃的温度下形成覆盖所述第二像素限定层和所述波长转换单元的第二封装层。
  40. 根据权利要求35所述的方法，其中，
    形成在所述发光层远离所述衬底基板一侧的波长转换层包括：
    在所述发光层上形成所述第二像素限定层，
    在所述第二像素限定层限定的空间中，通过喷墨打印并固化含有波长转换材料的墨水，形成所述波长转换单元。
  41. 根据权利要求35所述的方法，其中，
    形成在所述发光层远离所述衬底基板一侧的波长转换层包括：
    在所述发光层上形成所述第二像素限定层，
    在所述第二像素限定层限定的空间中，通过涂敷并光刻含有波长转换材料的光刻胶，形成所述波长转换单元。
  42. 根据权利要求40或41所述的方法，还包括：
    形成在所述波长转换层上的彩膜层。
  43. 根据权利要求40或41所述的方法，还包括：
    在形成所述波长转换单元之后，在≤100℃的温度下形成覆盖所述第二像素限定层和所述波长转换单元的第二封装层。
  44. 一种显示装置，所述显示装置包含根据权利要求1-34中任一项所述的显示面板。
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