OLED display panel and color coordinate adjusting method thereof

Abstract

The present application relates to the technical field of display, in particular to an OLED display panel and a color coordinate adjusting method thereof. The OLED display panel comprises an anode layer, a light emitting device module and a cathode layer arranged in sequence along a light emitting direction. The light emitting device module comprises multiple functional layers, and at least one of the functional layers is doped with piezoelectric material which is stretched and contracted along the light emitting direction under the action of an electric field. The film thickness of the functional layer doped with the piezoelectric material is increased or decreased with the stretching and contraction of the piezoelectric material under the action of the electric field, so that the color coordinate of the OLED display panel is changed. The present application dopes the piezoelectric material in one or more functional layers of the light emitting device module, so that the film thickness of the corresponding functional layer is automatically increased or decreased under the action of the electric field, and thus the color coordinate of the OLED display panel is changed to meet different color gamut requirements of different display products. The present application can be flexibly applied to different display products, and the film thickness does not need to be accurately controlled during the manufacturing process of the OLED display panel, so that the process efficiency is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of display, in particular to an OLED display panel and a color coordinate adjusting method thereof. BACKGROUND

[0002] Different display products have different color gamut requirements for OLED (Organic Light-Emitting Diode) panels. Currently commonly used color gamut standards include Adobe RGB, DCI-P3, NTSC, etc. Different color gamut standards and different color gamut coverages under the same color gamut standard have different requirements for the color coordinates (including R / G / B three-color color coordinates) of OLED panels.

[0003] At present, the way to make the color coordinates of OLED panels meet the requirements of related color gamut is to determine the required color coordinates according to the final display product to which the OLED panel needs to be applied, and to make the thickness of the related film layer a certain thickness when the OLED panel is manufactured, so that the color coordinates meet the requirements. However, by using this method, only OLED panels with fixed color coordinates can be obtained, and different color gamut requirements cannot be flexibly and efficiently met, which increases the difficulty of the process of OLED panels.

[0004] It should be noted that the information disclosed in the above background section is only used to strengthen the understanding of the background of the present application, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0005] Therefore, the present application provides an OLED display panel and a color coordinate adjusting method thereof, which can automatically adjust the thickness of the related film layer under the action of an electric field, so that the color coordinates of the OLED display panel change accordingly to meet different color gamut requirements, can be flexibly applied to different display products, and can improve the process efficiency of the OLED display panel.

[0006] One aspect of the present application provides an OLED display panel, which comprises an anode layer, a light-emitting device module and a cathode layer arranged in sequence along a light-emitting direction, the light-emitting device module comprises a plurality of functional layers, at least one of the functional layers is doped with a piezoelectric material that stretches and contracts along the light-emitting direction under the action of an electric field; as the piezoelectric material stretches and contracts under the action of the electric field, the film thickness of the functional layer doped with the piezoelectric material increases or decreases, so that the color coordinates of the OLED display panel change.

[0007] In some embodiments, the piezoelectric material is an organic piezoelectric material or an inorganic piezoelectric material; when the piezoelectric material is an organic piezoelectric material, the doping ratio R1 of the organic piezoelectric material in the corresponding functional layer is 0 < R1 ≤ 100%; when the piezoelectric material is an inorganic piezoelectric material, the doping ratio R2 of the inorganic piezoelectric material in the corresponding functional layer is 0 < R2 < 100%.

[0008] In some embodiments, when the piezoelectric material is an organic piezoelectric material, the organic piezoelectric material can be polyvinylidene fluoride but is not limited to this material; when the piezoelectric material is an inorganic piezoelectric material, the inorganic piezoelectric material can be a piezoelectric crystal or a piezoelectric ceramic but is not limited to this material.

[0009] In some embodiments, the electric field is an electric field applied between the anode layer and the cathode layer; or, the electric field is an external electric field applied on the functional layer doped with the piezoelectric material.

[0010] In some embodiments, the light-emitting device module comprises: a hole injection layer disposed on the anode layer; a hole transport layer disposed on the hole injection layer; a light-emitting layer disposed on the hole transport layer; an electron transport layer disposed on the light-emitting layer; and an electron injection layer disposed on the electron transport layer.

[0011] In some embodiments, the light-emitting device module further comprises: an electron blocking layer disposed between the hole transport layer and the light-emitting layer; and / or, a hole blocking layer disposed between the light-emitting layer and the electron transport layer.

[0012] In some embodiments, the OLED display panel further comprises: a light extraction layer disposed on the cathode layer.

[0013] Another aspect of the present application provides a color coordinate adjustment method of an OLED display panel, the OLED display panel comprising an anode layer, a light-emitting device module and a cathode layer disposed in sequence along a light-emitting direction, the light-emitting device module comprising a plurality of functional layers, at least one of the functional layers being doped with a piezoelectric material that stretches and contracts along the light-emitting direction under the action of an electric field; the color coordinate adjustment method comprising: obtaining a color coordinate change value and a current voltage value of the electric field; obtaining a film thickness change value of the functional layer doped with the piezoelectric material according to the color coordinate change value; obtaining a voltage change value of the electric field according to the film thickness change value, a piezoelectric coefficient of the piezoelectric material and a doping ratio of the piezoelectric material in the corresponding functional layer; and adjusting the current voltage value according to the voltage change value, so that the film thickness of the functional layer doped with the piezoelectric material increases or decreases by the film thickness change value, and the color coordinate of the OLED display panel changes by the color coordinate change value.

[0014] In some embodiments, the film thickness change value is linearly related to the coordinate change value; the voltage change value is positively proportional to the film thickness change value, and the voltage change value is inversely proportional to both the piezoelectric coefficient and the doping ratio.

[0015] In some embodiments, the voltage change value is obtained according to the following formula: Δv = c * Δx / (d * r), wherein Δv is the voltage change value, Δx is the film thickness change value, d is the piezoelectric coefficient, r is the doping ratio, and c is a conversion coefficient.

[0016] Compared with the prior art, the present application has at least the following beneficial effects:

[0017] The OLED display panel and the color coordinate adjusting method thereof according to the present application can realize automatic increase or decrease of the film thickness of the corresponding functional layer under the action of an electric field by doping the piezoelectric material in one or more functional layers of the light-emitting device module, so that the color coordinates of the OLED display panel are changed accordingly to meet different color gamut requirements, and the OLED display panel can be flexibly applied to different display products to save costs and greatly improve the process efficiency without the need for accurate control of the film thickness during the manufacturing process of the OLED display panel.

[0018] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0019] The drawings incorporated into the specification and forming a part thereof show embodiments consistent with the present application and, together with the specification, serve to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained from these drawings without creative labor for those skilled in the art.

[0020] Figure 1 FIG. 1 shows a structural schematic diagram of an OLED display panel in an embodiment of the present application;

[0021] Figure 2 and Figure 3 FIG. 2 shows two schematic diagrams of applying an electric field on the OLED display panel in an embodiment of the present application;

[0022] Figure 4 FIG. 3 shows a step schematic diagram of the color coordinate adjusting method of the OLED display panel in an embodiment of the present application. DETAILED DESCRIPTION

[0023] Example implementations will now be described more fully with reference to the accompanying drawings. Example implementations can be implemented in any

[0024] The accompanying drawings are included to provide a further understanding of principles of embodiments and no limitations on the present disclosure are intended to be derived therefrom. Like reference numerals refer to like elements in the drawings and description.

[0025] Moreover, the flow charts illustrated in the drawings are examples only and can not necessarily include all of the steps as a matter of course. For example, some steps can be split, some steps can be combined or partially combined, and the order of actual execution can be changed as a matter of course. It should be noted that the embodiments of the present disclosure and the features in different embodiments can be combined with each other without conflict.

[0026] Figure 1 The main structure of the OLED display panel in the embodiment is shown, and it is shown in FIG. 1 that the OLED display panel in the embodiment includes an anode layer 11, a light emitting device module 12 and a cathode layer 13 arranged in sequence along a light emitting direction E, and the light emitting device module 12 includes multiple functional layers, at least one of which is doped with a piezoelectric material (for example, a functional layer 122) that stretches and contracts along the light emitting direction E under the action of an electric field. Figure 1 The piezoelectric material in the functional layer 122 is shown by diagonal shading); as the piezoelectric material stretches and contracts under the action of an electric field, the film thickness of the functional layer (for example, the functional layer 122) doped with the piezoelectric material changes, so that the color coordinates of the OLED display panel change. Figure 1

[0027] The piezoelectric material has a piezoelectric phenomenon, which refers to the phenomenon that when the piezoelectric material is mechanically deformed, for example, stretched or compressed, an electric polarization phenomenon can be generated. The present disclosure utilizes the reverse phenomenon of the piezoelectric phenomenon, that is, the phenomenon that the piezoelectric material is elongated or shortened under the action of an electric field, and by doping the piezoelectric material in one or more functional layers of the light emitting device module 12, the piezoelectric material stretches and contracts when the electric field changes, so that the film thickness of the corresponding functional layer automatically changes. Specifically, when the electric field acting on the functional layer doped with the piezoelectric material is strengthened, the piezoelectric material is elongated, and the film thickness of the corresponding functional layer is increased; when the electric field is weakened, the piezoelectric material is shortened, and the film thickness of the corresponding functional layer is decreased.

[0028] ​The strength of the electric field can be achieved by regulating the voltage applied on the electrode. Figure 2 and Figure 3 Two schemes of applying electric field on the OLED display panel in the embodiment are shown. As shown in Figure 2 , the electric field can be the electric field applied between the anode layer 11 and the cathode layer 13, that is, the anode layer 11 and the cathode layer 13 provided by the OLED display panel can be used to form the electric field acting on the entire light emitting device module 12, and by regulating the voltage applied between the anode layer 11 and the cathode layer 13, the strength of the electric field is adjusted to realize the increase or decrease of the film thickness of the functional layer doped with piezoelectric material, so that the color coordinates of the OLED display panel are changed. The anode layer 11 can be formed of ITO (Indium Tin Oxide), and the material of the cathode layer 13 is, for example, Mg (magnesium): Ag (silver) with a mass ratio of 1:9.

[0029] As shown in Figure 3 , the electric field can also be an external electric field applied to the functional layer 122 doped with piezoelectric material, that is, by applying an external electric field to the functional layer 122 doped with piezoelectric material alone, the film thickness of the functional layer 122 is increased or decreased with the strength of the electric field, so that the color coordinates of the OLED display panel are changed. The functional layer doped with piezoelectric material can also be one or more other functional layers in the light emitting device module 12, and then the color coordinates of the OLED display panel can be regulated by applying an external electric field to the one or more other functional layers alone.

[0030] The color coordinates of the OLED display panel specifically include blue light color coordinates, red light color coordinates and green light color coordinates. The OLED display panel uses the principle of micro resonant cavity to emit light, and when the resonant cavity length is an integer multiple of the half wavelength of the emitted light, the light at the wavelength position is strengthened. The resonant cavity length is specifically the sum of the product of the refractive index and the film thickness of each functional layer of the light emitting device module 12. When the film thickness of the functional layer of the light emitting device module 12 changes, the resonant cavity length changes, resulting in a change in the wavelength of the emitted light.

[0031] Therefore, according to the light emitting principle of the OLED display panel, when the thickness of the organic film layer (i.e., each functional layer of the light emitting device module 12) changes, the R / G / B color coordinates of the OLED display panel will also change. Therefore, by doping piezoelectric material in one or more functional layers of the light emitting device module 12, the color coordinates of the OLED display panel can be flexibly regulated by the electric field.

[0032] Therefore, for the production line of the OLED display panel, the film thickness does not need to be accurately controlled, and only a proper amount of piezoelectric material needs to be doped in the related functional layer, thereby greatly improving the process efficiency; and the same OLED display panel can be flexibly applied to different display products to meet different color gamut requirements and save costs.

[0033] When the OLED display panel is applied to a specific display product, the OLED display panel can be controlled under a specific electric field according to the color gamut requirement, so that the related functional layer maintains a certain film thickness, and the color coordinates reach a specific value to meet the color gamut requirement of the specific display product.

[0034] The piezoelectric material can be an organic piezoelectric material or an inorganic piezoelectric material. The organic piezoelectric material can be polyvinylidene fluoride (PVDF), and the inorganic piezoelectric material can be a piezoelectric crystal or a piezoelectric ceramic. However, the organic piezoelectric material is not limited to polyvinylidene fluoride, and the inorganic piezoelectric material is not limited to piezoelectric crystals and piezoelectric ceramics. In other embodiments, a suitable piezoelectric material can be selected according to actual needs.

[0035] When the piezoelectric material is an organic piezoelectric material, the corresponding functional layer can be completely made of the organic piezoelectric material, or a certain proportion of the organic piezoelectric material can be doped in the organic material used to traditionally make the functional layer. That is, the doping proportion R1 of the organic piezoelectric material in the corresponding functional layer satisfies: 0 < R1 ≤ 100%. When the piezoelectric material is an inorganic piezoelectric material, a certain proportion of the inorganic piezoelectric material can be doped in the organic material used to traditionally make the functional layer. That is, the doping proportion R2 of the inorganic piezoelectric material in the corresponding functional layer satisfies: 0 < R2 < 100%.

[0036] The number of layers and distribution of the functional layer doped with the piezoelectric material can be determined as needed. Referring to FIG. 1, the functional layer doped with the piezoelectric material can be the hole injection layer 121, the hole transport layer 122, the electron transport layer 125, or the electron injection layer 126. Figure 1 As shown in FIG. 1, the light-emitting device module 12 specifically includes: a hole injection layer 121 disposed on the anode layer 11; a hole transport layer 122 disposed on the hole injection layer 121; a light-emitting layer 124 disposed on the hole transport layer 122; an electron transport layer 125 disposed on the light-emitting layer 124; and an electron injection layer 126 disposed on the electron transport layer 125. Further, an electron blocking layer 123 can be disposed between the hole transport layer 122 and the light-emitting layer 124, and / or a hole blocking layer can be disposed between the light-emitting layer 124 and the electron transport layer 125. Figure 1 In the embodiment shown in FIG. 1, only the electron blocking layer 123 is shown, but this is not limiting.

[0037] In the embodiment shown in FIG. 1, the OLED display panel includes the anode layer 11, the cathode layer 12, and the light-emitting device module 12. Figure 1The structure of the light emitting device module 12 shown is an example. According to requirements, piezoelectric material can be doped in any one or more of the hole injection layer 121, the hole transport layer 122, the electron blocking layer 123, the light emitting layer 124, the electron transport layer 125 and the electron injection layer 126, in any proportion, to achieve flexible adjustment of the color coordinates of the OLED display panel under electric field control.

[0038] In one embodiment, 10% piezoelectric ceramic is doped in the hole transport layer 122; when the voltage applied between the anode layer 11 and the cathode layer 13 is 4V, the blue light color coordinate (CIE-y) is 0.040; when the voltage applied between the anode layer 11 and the cathode layer 13 is increased to 4.7V, the film thickness of the hole transport layer 122 is increased by 20A, and the blue light color coordinate (CIE-y) is increased to 0.043.

[0039] Continuing to refer to Figure 1 The OLED display panel can further include a light extraction layer 14 disposed on the cathode layer 13. The anode layer 11, the cathode layer 13 and the light extraction layer 14 do not participate in the calculation of the resonant cavity length, and the influence of the change in their film thickness on the change in color coordinates is small. Therefore, piezoelectric material can be doped in any proportion in other functional layers in addition to the anode layer 11, the cathode layer 13 and the light extraction layer 14, to achieve flexible adjustment of the color coordinates of the OLED display panel through electric field control.

[0040] The present embodiment further provides a color coordinate adjustment method of an OLED display panel, which can be applied to the OLED display panel described in any of the above embodiments. The features and principles of the OLED display panel described in any of the above embodiments can be applied to the following color coordinate adjustment method embodiments. In the following color coordinate adjustment method embodiments, the features and principles of the OLED display panel that have been elucidated will not be described again.

[0041] In one embodiment, the OLED display panel is, for example Figure 1 the OLED display panel shown. Figure 4 The main steps of the color coordinate adjustment method of the OLED display panel are shown, in combination with Figure 1 and Figure 4As shown, the OLED display panel includes an anode layer 11, a light emitting device module 12 and a cathode layer 13 arranged in sequence along a light emitting direction E, the light emitting device module 12 includes a plurality of functional layers, and at least one functional layer (for example, functional layer 122) is doped with a piezoelectric material that stretches and contracts along the light emitting direction E under the action of an electric field; the color coordinate adjustment method specifically includes: step S410, obtaining a color coordinate change value and a current voltage value of the electric field; step S420, obtaining a film thickness change value of the functional layer doped with the piezoelectric material according to the color coordinate change value; step S430, obtaining a voltage change value of the electric field according to the film thickness change value, a piezoelectric coefficient of the piezoelectric material and a doping proportion of the piezoelectric material in the corresponding functional layer; and step S440, adjusting the current voltage value according to the voltage change value, so that the film thickness of the functional layer doped with the piezoelectric material (hereinafter referred to as a target functional layer) is increased or decreased by the film thickness change value, and the color coordinate of the OLED display panel is changed by the color coordinate change value.

[0042] The color coordinate change value refers to the color coordinate change value of a single color pixel of the OLED display panel, and can be obtained according to a current color coordinate value of the single color pixel obtained by measurement and a target color coordinate value of the single color pixel expected to be adjusted.

[0043] The film thickness change value and the coordinate change value are in a linear relationship. Specifically, the film thickness change value and the color coordinate change value are generally in a linear relationship near the median value of the color coordinate, and the specific relationship therebetween can be determined according to a material system by using existing technologies, which is not limited in the present application. According to the color coordinate change value, the required film thickness change value can be obtained, and generally the greater the color coordinate change value, the greater the required film thickness change value.

[0044] The voltage change value is in a positive proportional relationship with the film thickness change value, and is in an inverse proportional relationship with the piezoelectric coefficient and the doping proportion. Specifically, the greater the required film thickness change value, the greater the voltage change value acting on the target functional layer under the condition that other variables are constant, so as to greatly adjust the film thickness of the target functional layer by a large amplitude of voltage change. The higher the doping proportion of the piezoelectric material in the target functional layer, the greater the deformation amount of the target functional layer under a unit electric field intensity, and therefore the smaller the voltage adjustment amplitude required for the change of a certain film thickness when the doping proportion is higher. For a certain piezoelectric material, the piezoelectric coefficient is fixed, the higher the piezoelectric coefficient, the greater the deformation amount of the piezoelectric material under a unit electric field intensity, and therefore the smaller the voltage change value required for a certain film thickness change value when the piezoelectric coefficient is higher.

[0045] In some embodiments, the voltage change value is obtained according to the following formula: Δv = c * Δx / (d * r), where Δv is the voltage change value, Δx is the film thickness change value, d is the piezoelectric coefficient, r is the doping proportion, and c is a conversion coefficient.

[0046] Of course, the above formula is only a way of estimating the voltage variation value according to the film thickness variation value, piezoelectric coefficient, doping ratio and other variables, and combining with appropriate conversion coefficients. The specific and accurate voltage variation value can be determined by the actual device structure.

[0047] In summary, the OLED display panel and the color coordinate adjusting method thereof can automatically increase or decrease the film thickness of the corresponding functional layer under the action of the electric field by doping the piezoelectric material in one or more functional layers of the light-emitting device module of the OLED display panel, so that the color coordinates of the OLED display panel change accordingly to meet different color gamut requirements, can be flexibly applied to different display products, saves cost, and does not need to accurately control the film thickness in the manufacturing process of the OLED display panel, greatly improving the process efficiency.

[0048] The above is a further detailed description of the present application in combination with specific preferred embodiments, and the specific implementation of the present application cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, a number of simple deductions or substitutions can be made without departing from the concept of the present application, and all of them should be regarded as falling within the protection scope of the present application.

Claims

1. An OLED display panel, comprising, in sequence along a light emitting direction, an anode layer, a light emitting device module, a cathode layer, and a light extraction layer disposed on the cathode layer, characterized in that: the light emitting device module comprises a plurality of functional layers, and at least one of the functional layers is doped with a piezoelectric material that stretches and contracts along the light emitting direction under the action of an electric field; wherein the functional layers of the light emitting device module comprise: a hole injection layer disposed on the anode layer; a hole transport layer disposed on the hole injection layer; a light emitting layer disposed on the hole transport layer; an electron transport layer disposed on the light emitting layer; an electron injection layer disposed on the electron transport layer; an electron blocking layer and / or a hole blocking layer, the electron blocking layer being disposed between the hole transport layer and the light emitting layer, and the hole blocking layer being disposed between the light emitting layer and the electron transport layer; wherein the piezoelectric material is an organic piezoelectric material, and a doping ratio R1 of the organic piezoelectric material in the corresponding functional layer is 0 < R1 ≤ 100%, so that the organic piezoelectric material is doped in the organic material of the corresponding functional layer, or the corresponding functional layer is completely made of the organic piezoelectric material; as the piezoelectric material stretches and contracts under the action of the electric field, the film thickness of the functional layer doped with the piezoelectric material increases and decreases, so that the color coordinates of the OLED display panel change. When the piezoelectric material is an organic piezoelectric material, the organic piezoelectric material is polyvinylidene fluoride. When the piezoelectric material is an inorganic piezoelectric material, the inorganic piezoelectric material is a piezoelectric crystal or a piezoelectric ceramic. The electric field is an electric field applied between the anode layer and the cathode layer; or The electric field is an external electric field applied on the functional layer doped with the piezoelectric material. 2.The OLED display panel of claim 1, wherein, The light emitting device module comprises a plurality of functional layers, and at least one of the functional layers is doped with a piezoelectric material that stretches and contracts along the light emitting direction under the action of an electric field; wherein the functional layers of the light emitting device module comprise: a hole injection layer disposed on the anode layer; a hole transport layer disposed on the hole injection layer; a light emitting layer disposed on the hole transport layer; an electron transport layer disposed on the light emitting layer; an electron injection layer disposed on the electron transport layer; an electron blocking layer and / or a hole blocking layer, the electron blocking layer being disposed between the hole transport layer and the light emitting layer, and the hole blocking layer being disposed between the light emitting layer and the electron transport layer; 3.The OLED display panel of claim 1, wherein, wherein the piezoelectric material is an organic piezoelectric material, and a doping ratio R1 of the organic piezoelectric material in the corresponding functional layer is 0 < R1 ≤ 100%, so that the organic piezoelectric material is doped in the organic material of the corresponding functional layer, or the corresponding functional layer is completely made of the organic piezoelectric material; The color coordinate adjustment method comprises: 4.A method for adjusting color coordinates of an OLED display panel, the OLED display panel comprising, in sequence along a light emitting direction, an anode layer, a light emitting device module, a cathode layer, and a light extraction layer disposed on the cathode layer, characterized in that, obtaining a color coordinate change value and a current voltage value of the electric field; obtaining a film thickness change value of the functional layer doped with the piezoelectric material according to the color coordinate change value; ​ ​ ​ ​ According to the film thickness change value, piezoelectric coefficient of the piezoelectric material and doping proportion of the piezoelectric material in the corresponding functional layer, a voltage change value of the electric field is obtained; According to the voltage change value, the current voltage value is adjusted, so that the film thickness of the functional layer doped with the piezoelectric material increases or decreases by the film thickness change value, and the color coordinate of the OLED display panel changes by the color coordinate change value.

5. The color coordinate adjusting method of claim 4, wherein, The film thickness change value and the coordinate change value are in linear relationship. The voltage change value is in direct proportional relationship with the film thickness change value, and in inverse proportional relationship with the piezoelectric coefficient and the doping proportion.

6. The color coordinate adjusting method of claim 5, wherein, The voltage change value is obtained according to the following formula: Δv = c * Δx / (d * r), wherein Δv is the voltage change value, Δx is the film thickness change value, d is the piezoelectric coefficient, r is the doping proportion, and c is a conversion coefficient.

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