OLED device capable of improving brightness based on micro lens

Abstract

The invention discloses an OLED device for improving brightness based on a micro lens. The OLED device comprises a light emitting unit; the light-emitting unit comprises a plurality of sub-pixel light-emitting units; the flat layer is positioned on the light-emitting unit; the first micro-lens group is located on the flat layer and comprises a plurality of sub-pixel micro-lens groups, the number of the sub-pixel micro-lens groups is the same as that of the sub-pixel light-emitting units, and each sub-pixel micro-lens group is located at the orthographic projection position of the corresponding sub-pixel light-emitting unit; and the third micro lens layer is positioned on the first micro lens group. Through the design of the micro-lens array formed by the first micro-lens group and the third micro-lens layer, light loss caused by total reflection is reduced, meanwhile, different sub-pixel micro-lens designs are introduced, and focusing of red, green and blue at the same position is achieved, so that the brightness can be improved, and the chromatic aberration can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical display devices, and in particular to an OLED device with improved brightness based on a microlens. Background Art

[0002] In recent years, with the development of display technology and miniaturization of optical devices, micro lenses, as one of the important optical components, have received widespread attention due to their advantages in improving display brightness and light efficiency.

[0003] Microlens arrays are typically composed of a series of tiny lenses, each lens corresponding to a pixel of the display. These microlenses can focus or diffuse the incoming light to improve the distribution of light. By adjusting the design of the microlenses, better light control can be achieved while maintaining high brightness, thereby improving display quality and efficiency.

[0004] In the research and development of OLED devices, many research teams have introduced microlens arrays to improve display brightness. This requires that the microlens preparation process be compatible with the OLED device process, and that suitable refractive index materials and micro-nano manufacturing processes be used to maximize brightness. However, currently, improving the display brightness of OLED devices through microlens arrays is limited by difficulties in microlens materials and processes. Brightness enhancement through microlenses is often limited by high-refractive materials, and research on high-refractive organic materials is relatively slow. Therefore, there is still much room for development in improving brightness through microlens array design. Summary of the invention

[0005] Technical purpose: In view of the defects in the prior art, the present invention discloses an OLED device based on microlenses to enhance brightness. The design of the microlens array formed by the first microlens group and the third microlens layer reduces the light loss caused by total reflection. At the same time, different sub-pixel microlens designs are introduced to achieve red, green and blue focusing at the same position, thereby improving brightness and improving color difference.

[0006] Technical solution: In order to achieve the above technical objectives, the present invention adopts the following technical solution.

[0007] An OLED device for improving brightness based on a microlens, comprising:

[0008] A light-emitting unit; the light-emitting unit comprises a plurality of sub-pixel light-emitting units;

[0009] A flat layer, located above the light-emitting unit;

[0010] A first microlens group is located on the flat layer and includes a plurality of sub-pixel microlens groups. The number of the sub-pixel microlens groups is the same as the number of the sub-pixel light-emitting units, and each sub-pixel microlens group is located at the positive projection position of the corresponding sub-pixel light-emitting unit;

[0011] The third microlens layer is located on the first microlens group.

[0012] Preferably, the microlens height relationship between the sub-pixel microlens groups satisfies: the larger the incident light wavelength corresponding to the sub-pixel microlens group, the smaller the microlens height of the sub-pixel microlens group, so that different incident lights in the light-emitting unit are focused at the same height position after being refracted by the first microlens group.

[0013] Preferably, the formula for achieving focusing at the same height position is:

[0014]

[0015] Among them, H m is the height of the first microlens group corresponding to the m sub-pixel light-emitting unit, λ m is the wavelength of light emitted by the m sub-pixel light-emitting unit; H n is the height of the first microlens group corresponding to the n sub-pixel light-emitting unit, λ n is the light emission wavelength of the n sub-pixel light emitting unit, A and B are the Cauchy dispersion constants of the material used for the third microlens layer; A′ and B′ are the Cauchy dispersion constants of the material used for the first microlens group.

[0016] Preferably, the light-emitting unit includes a red sub-pixel light-emitting unit, a blue sub-pixel light-emitting unit, and a green sub-pixel light-emitting unit, and the number of sub-pixel microlens groups is 3.

[0017] Preferably, each sub-pixel microlens group includes a first microlens layer and a second microlens layer located above the first microlens layer, and the refractive index of the second microlens layer is greater than that of the first microlens layer.

[0018] Preferably, the first microlens layer is a hemispherical microlens, and the material is an organic material.

[0019] Preferably, the material of the second microlens layer is an inorganic high-refractive material.

[0020] Preferably, each sub-pixel microlens group is hemispherical.

[0021] Preferably, the third microlens layer is a liquid optical adhesive layer with a low refractive index, and the low refractive index of the third microlens layer is less than or equal to 1.5.

[0022] Beneficial effects: (1) The design of microlens arrays of different thicknesses described in the present invention can be achieved by using conventional semiconductor material preparation processes. In addition, the design of multi-layer microlenses can also be achieved by using photolithography and atomic deposition methods, which are simple and easy to implement.

[0023] (2) The design of the microlens array formed by the first microlens group and the third microlens layer in the present invention introduces different sub-pixel microlens designs to achieve focusing of red, green and blue at the same position, thereby improving brightness and improving color difference; the design of multiple layers of high and low refractive microlenses changes the light path, greatly reducing the situation where light cannot be emitted due to total reflection, thereby achieving brightness improvement, which is more conducive to achieving a high-brightness near-eye display effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of a local structure of an OLED device including RGB sub-pixel units according to an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of spherical refraction according to an embodiment of the present invention;

[0026] Figure 3 A schematic diagram of a simulation structure of an embodiment of the present invention;

[0027] Figure 4 Schematic diagram of simulation results of an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0029] To further improve the display brightness of OLED devices, the improvement through the microlens array process is often limited by the material aspect, while in terms of technology, the device luminous brightness can be effectively improved by designing a reasonable design scheme using optical principles. The focusing ability of the microlens depends on its geometric size and refractive index, and these factors are closely related to the wavelength of light. Therefore, the present invention mainly designs different microlens geometric sizes for different wavelengths of red, green and blue. In addition, in order to further achieve the effect of improving brightness, a multi-layer composite microlens array design is also designed. An embodiment of the present invention is described below.

[0030] As attached Figure 1 As shown, an OLED device based on microlenses to enhance brightness in this embodiment includes:

[0031] Light-emitting unit; the light-emitting unit includes a plurality of sub-pixel light-emitting units. In the present embodiment, the light-emitting unit includes a red sub-pixel light-emitting unit 1, a blue sub-pixel light-emitting unit 2, and a green sub-pixel light-emitting unit 3;

[0032] The flat layer is located above the light-emitting unit and its main function is flattening, which is a preliminary preparation for the preparation of the hemispherical microlenses of the first microlens group; in addition, it can also increase the overall height of the first microlens group and increase the focal length of its microlenses.

[0033] The first microlens group is located on the flat layer and includes a plurality of sub-pixel microlens groups. The number of the sub-pixel microlens groups is the same as the number of the sub-pixel light-emitting units, and each sub-pixel microlens group is located at the positive projection position of the corresponding sub-pixel light-emitting unit. In this embodiment, there are three sub-pixel microlens groups. The microlens height relationship between the sub-pixel microlens groups satisfies: the larger the incident light wavelength corresponding to the sub-pixel microlens group, the smaller the microlens height of the sub-pixel microlens group, so that different incident lights in the light-emitting unit are focused at the same height position after being refracted by the first microlens group; the realization formula of focusing at the same height position is:

[0034]

[0035] Among them, H m is the height of the first microlens group corresponding to the m sub-pixel light-emitting unit, λ m is the wavelength of light emitted by the m sub-pixel light-emitting unit; H n is the height of the first microlens group corresponding to the n sub-pixel light-emitting unit, λ n is the wavelength of light emitted by the n-sub-pixel light-emitting unit, A and B are respectively the Cauchy dispersion constants of the material used for the third microlens layer, and the values ​​are related to the material properties; A′ and B′ are respectively the Cauchy dispersion constants of the material used for the first microlens group, and the values ​​are related to the material properties;

[0036] Each sub-pixel microlens group includes a first microlens layer and a second microlens layer located on the first microlens layer, and the refractive index of the second microlens layer is greater than that of the first microlens layer. The first microlens layer is a hemispherical microlens made of an organic material; the second microlens layer is made of an inorganic high-refractive material and covers the first microlens layer, and each sub-pixel microlens group is hemispherical; the refractive index of the second microlens layer is greater than that of the first microlens layer, so that the optical path is changed, thereby reducing the light loss caused by total reflection; in this embodiment, a red sub-pixel first microlens layer 9 and a red sub-pixel second microlens layer 10 are sequentially arranged above the positive projection of the red sub-pixel light-emitting unit 1, a blue sub-pixel first microlens layer 7 and a blue sub-pixel second microlens layer 8 are sequentially arranged above the positive projection of the blue sub-pixel light-emitting unit 2, and a green sub-pixel first microlens layer 5 and a green sub-pixel second microlens layer 6 are sequentially arranged above the positive projection of the green sub-pixel light-emitting unit 3;

[0037] The third microlens layer 11 is located on the first microlens group; the third microlens layer is a low refractive index LOCA layer, that is, a low refractive index liquid optical adhesive layer. The low refractive index of the third microlens layer is less than or equal to 1.5;

[0038] The present invention designs different microlens sizes (H / D) for different R, G, and B sub-pixels, and the design principle is as follows:

[0039] 1. Regarding microlens materials, for the same transparent medium, the refractive index of different wavelengths is also different. For most transparent media, the refractive index decreases with the increase of wavelength. This relationship can be described by the dispersion formula. For example, one form of the dispersion formula is the Cauchy dispersion formula, and its calculation formula is as follows:

[0040]

[0041] Where n(λ) is the refractive index of the transparent medium at wavelength λ, λ is the wavelength of light, and A and B are the dispersion constants of the transparent medium.

[0042] After the microlens material is determined, that is, the dispersion constants A and B are determined, the refractive index of light of different colors in the microlens material can be obtained according to the specific light wavelengths of R, G, and B. Once the refractive index n(λ) at different wavelengths is known, the focal length f(λ) at different wavelengths can be calculated according to the design of the lens (such as the curvature radius R, thickness t of the lens, and the refractive index n0 of the surrounding medium).

[0043] As attached Figure 2 As shown, for a single spherical refraction, the formula can be used to calculate the focal length using the optical path calculation formula for paraxial light:

[0044]

[0045] Wherein, n is the refractive index of the material used for the third microlens layer, n′ is the refractive index of the material used for the first microlens group, and r is the radius of the hemispherical microlens of the first microlens group.

[0046] According to the wavelength relationship between red, green and blue R >λ G >λ B , the refractive index n(λ of red, green and blue under the same lens material R ) <n(λ G ) <n(λ B ), when the radius of the microlens is constant, it can be seen that the shorter wavelength blue light has a shorter focal length and a greater degree of deflection than the longer wavelength red light; therefore, when designing the red, green and blue microlenses, different microlens heights H can be designed to achieve focusing of the red, green and blue lights at the same position, thereby improving brightness and improving chromatic aberration. Therefore, the microlens height relationship corresponding to the red, green and blue lights satisfies: H R <H G <H B , the heights of the three microlenses corresponding to the red, green and blue sub-pixels are determined according to the dispersion coefficients A and B of the microlens material used, and the relationship is:

[0047] f R -H R =f G -H G =f B -H B

[0048] Among them, f R 、f G 、f B are the focal lengths of the microlenses corresponding to red, green and blue light, respectively.

[0049] Combining the Cauchy dispersion formula and the focal length formula, we can get the red, green and blue sub-pixels corresponding to three types of microlenses, and the relationship between wavelength and height is:

[0050]

[0051] Wherein, A is the Cauchy dispersion constant of the material used for the first microlens group, which is related to the properties of the material used, and B is the Cauchy dispersion constant of the material used for the first microlens group, which is related to the properties of the material used;

[0052] Although the single-layer microlens currently used in OLED devices can reduce the loss of total reflected light and achieve the light gathering effect, when the light enters the optically sparse medium, there is still light greater than the critical angle, which causes part of the light to be totally reflected and unable to emit light. Therefore, in order to achieve more efficient light emission, the present invention designs a multi-layer microlens structure with different refractive indices, by preparing a second microlens layer on the surface of the first microlens layer, and the refractive index of the second microlens layer is greater than that of the first microlens layer, and then preparing a low-refractive-index LOCA layer on the upper layer of the second microlens layer. The first and second microlens layers are high-refractive-index convex lenses, thereby changing the optical path, reducing the incident angle entering the optically sparse medium, and less than the critical angle of total reflection, achieving a more efficient light emission effect. The first microlens layer is prepared by a thermal reflow method using an organic photoresist with a refractive index of n1 to obtain a hemispherical microlens with a radius of r; the second microlens layer is an inorganic high-refractive material with a refractive index of n2, and the second microlens layer is obtained by an atomic deposition method on top of the first microlens layer, with a thickness of t2; the LOCA layer uses an organic material with a low refractive index of n3 to cover the top of the second microlens layer, with a thickness of t3. The following is the design principle and simulation results analysis:

[0053] As attached Figure 3 As shown, for a certain sub-pixel microlens group, the refractive index of the first microlens layer is n1=1.56, and the radius is r=2um; the refractive index of the second microlens layer is n2=1.98, and the thickness is t2=0.5um. In addition, the refractive index of the third microlens layer above the sub-pixel microlens group is n3=1.37;

[0054] If there is no second microlens layer, light enters the LOCA layer directly from the first microlens, then the critical angle of total reflection is degrees; when there is a second microlens layer, the critical angle of total reflection is Spend;

[0055] If there is an incident light with an incident angle of θ1 = 70 degrees, if there is no second microlens layer, this light will be totally reflected and cannot be emitted. However, when there is a second microlens layer, according to the law of refraction, the incident angle degrees; according to the geometric relationship of the triangle, using the Pythagorean theorem and the cosine theorem, it is obtained that θ3 = 36.29 degrees, which is less than the critical angle of total reflection C2, and total reflection will not occur. Therefore, designing a second microlens layer with a higher refractive index can change the direction of the light path, thereby greatly reducing the light that is not emitted due to total reflection and achieving brightness improvement.

[0056] The FDTD simulation software is used to simulate the lens-free, single-layer convex lens layer and double-layer convex lens layer. The lens design is carried out according to the above parameters. Through simulation, the simulation results are shown in the attached Figure 4As shown in the figure, No Lens means no lens, that is, there is no first microlens group and only the third microlens layer; Single Lens means a single-layer convex lens layer, that is, the first microlens group only has the first microlens layer, no second microlens layer, and there is a third microlens layer; DoubleLens means a double-layer convex lens layer, that is, the situation described in the present invention, including the first microlens group and the third microlens layer; Figure 4 It can be seen that in the Double Lens case, the intensity of light emitted by the device is much higher than that in the No Lens and Single Lens conditions, which strongly proves the feasibility of this microlens design scheme for improving brightness.

[0057] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An OLED device based on microlenses to enhance brightness, characterized in that: include: Light emitting unit; The light-emitting unit includes a plurality of sub-pixel light-emitting units; A flat layer, located above the light-emitting unit; A first microlens group is located on the flat layer and includes a plurality of sub-pixel microlens groups. The number of the sub-pixel microlens groups is the same as the number of the sub-pixel light-emitting units, and each sub-pixel microlens group is located at the positive projection position of the corresponding sub-pixel light-emitting unit; The third microlens layer is located on the first microlens group.

2. The OLED device for improving brightness based on microlenses according to claim 1, characterized in that: The microlens height relationship between the sub-pixel microlens groups satisfies that the larger the incident light wavelength corresponding to the sub-pixel microlens group, the smaller the microlens height of the sub-pixel microlens group, so that different incident lights in the light-emitting unit are focused at the same height position after being refracted by the first microlens group.

3. The OLED device for improving brightness based on microlenses according to claim 2, characterized in that: The formula for focusing at the same height position is: Among them, H m is the height of the first microlens group corresponding to the m sub-pixel light-emitting unit, λ m is the wavelength of light emitted by the m sub-pixel light-emitting unit; H n is the height of the first microlens group corresponding to the n sub-pixel light-emitting unit, λ n is the light emission wavelength of the n sub-pixel light emitting unit, A and B are the Cauchy dispersion constants of the material used for the third microlens layer; A and B are the Cauchy dispersion constants of the material used for the first microlens group.

4. The OLED device for improving brightness based on microlenses according to claim 1, characterized in that: The light-emitting unit includes a red sub-pixel light-emitting unit, a blue sub-pixel light-emitting unit, and a green sub-pixel light-emitting unit, and there are three sub-pixel microlens groups.

5. The OLED device for improving brightness based on microlenses according to claim 1, characterized in that: Each sub-pixel microlens group includes a first microlens layer and a second microlens layer located on the first microlens layer, and the refractive index of the second microlens layer is greater than that of the first microlens layer.

6. The OLED device for improving brightness based on microlenses according to claim 5, characterized in that: The first microlens layer is a hemispherical microlens made of an organic material.

7. The OLED device for improving brightness based on microlenses according to claim 5, characterized in that: The material of the second microlens layer is an inorganic high-refractive material.

8. The OLED device for improving brightness based on microlenses according to claim 5, characterized in that: Each sub-pixel microlens group is hemispherical.

9. The OLED device for improving brightness based on microlenses according to claim 1, characterized in that: The third microlens layer is a liquid optical adhesive layer with a low refractive index, and the low refractive index of the third microlens layer is less than or equal to 1.5.

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