Pixel unit, manufacturing method thereof and display panel

Abstract

The invention relates to a pixel unit, a manufacturing method thereof and a display panel. The light-emitting chips form a single pixel, each light-emitting chip is provided with a reflecting layer used for reflecting light rays emitted by the light-emitting chip, and the reflecting layers are designed to reflect incident light rays with the incident angle smaller than a preset incident angle so as to limit the light rays emitted by the light-emitting chips within a preset angle range; wherein the preset incident angle does not exceed 55 degrees, and the preset angle range does not exceed 110 degrees. The light-emitting angle is limited through the reflecting layers of the light-emitting chips, optical crosstalk between the light-emitting chips is reduced, and therefore a good display effect is achieved.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to a pixel unit and a manufacturing method thereof and a display panel. Background Art

[0002] With the development of display technology and the improvement of user needs, fine-pitch displays with higher definition and brightness have become one of the main high-end display products. For example, Micro LED (Micro Light Emitting Diode) miniaturizes LED (Light Emitting Diode) and can reduce the pixel distance from millimeters to microns.

[0003] In display technology, pixels are usually composed of red, green and blue sub-pixels, and each sub-pixel is usually composed of a light-emitting chip. As the pixel pitch decreases, the distance between each light-emitting chip is very close, so the light between adjacent light-emitting chips of different colors will affect each other, that is, the cross-light phenomenon occurs, resulting in a decrease in display effect.

[0004] Therefore, how to reduce the cross-talk phenomenon between light-emitting chips in display products is an urgent problem to be solved. Summary of the invention

[0005] In view of the deficiencies of the above-mentioned related technologies, the purpose of the present application is to provide a pixel unit and a manufacturing method thereof and a display panel, aiming to solve the problem of crosstalk between light-emitting chips in display products affecting the display effect.

[0006] A pixel unit, comprising:

[0007] A plurality of light-emitting chips constitute a single pixel, each of the light-emitting chips being provided with a reflective layer for reflecting the light emitted by the light-emitting chip, the reflective layer being designed to reflect incident light having an incident angle less than a preset incident angle, so as to limit the light emitted by the light-emitting chip to within a preset angle range; wherein the preset incident angle does not exceed 55°, and the preset angle range does not exceed 110°.

[0008] The pixel unit limits the light emission angle through the reflective layer of the light emitting chip, reduces the crosstalk between the light emitting chips in the pixel, and thus has a better display effect.

[0009] Optionally, the reflective layer is a Bragg reflective layer, and a reflection spectrum of the Bragg reflective layer satisfies the following conditions:

[0010] When the incident angle is 0°, the high-reflection band with a reflectivity higher than a predetermined threshold includes the light-emitting wavelength of the light-emitting chip; as the incident angle increases, the reflection spectrum blue-shifts, and after the incident angle is greater than the preset incident angle, the range of the high-reflection band shifts and no longer includes the light-emitting wavelength.

[0011] By utilizing the blue shift phenomenon of the Bragg reflector layer, low reflection of light incident at large angles and high reflection of light incident at small angles are achieved, thereby achieving the purpose of controlling the light output angle of the light-emitting chip, thereby reducing the problem of crosstalk between light-emitting chips. No additional structure is required, and the Bragg reflector layer is a structure that is usually set up. Therefore, in some implementation processes, no additional structure needs to be added, the process changes are small, and the cost required is low.

[0012] Optionally, the pixel unit is an independently packaged device, and the pixel unit also includes: a routing layer connected to each of the light-emitting chips, arranged on one side of the light-emitting chip, the routing layer including a plurality of first pad areas connected one-to-one with the first pole of the light-emitting chip, and a second pad area connected to the second pole of each of the light-emitting chips.

[0013] The pixel unit is packaged as an independent device and has a larger size than a single light-emitting chip. It is easier to process further, reduces the difficulty of subsequent processes, and is also beneficial to the application of back-end manufacturers.

[0014] Based on the same inventive concept, the present application also provides a method for manufacturing a pixel unit, comprising:

[0015] providing a substrate;

[0016] A plurality of light-emitting chips required for forming a pixel are provided, each of the light-emitting chips is provided with a reflective layer for reflecting the light emitted by the light-emitting chip, and the reflective layer is designed to reflect incident light with an incident angle less than a preset incident angle, so as to limit the light emitted by the light-emitting chip to a preset angle range; wherein the preset incident angle does not exceed 55°, and the preset angle range does not exceed 110°;

[0017] The plurality of light emitting chips are disposed on the substrate.

[0018] The pixel unit manufactured by the above method limits the light output angle through the reflective layer of the light emitting chip, reduces the crosstalk between the light emitting chips in the pixel, and thus has a better display effect.

[0019] Based on the same inventive concept, the present application also provides a display panel, including a circuit substrate and a plurality of the above-mentioned pixel units arranged on the circuit substrate.

[0020] Since the light emitting chip used in the above display panel has a smaller light emission angle, the cross-light problem of the display panel is smaller and the display effect is better. In some implementation processes, no additional structure needs to be added, the process changes are small, and the cost required is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of a reflection spectrum of a Bragg reflection layer with a blue shift phenomenon provided in an embodiment of the present application;

[0022] Figure 2 A schematic diagram of a reflection spectrum of the Bragg reflection layer of the blue light emitting chip provided in an embodiment of the present application;

[0023] Figure 3 A schematic diagram of light emission angles provided in an embodiment of the present application;

[0024] Figure 4 A schematic diagram of the optical path of the light-emitting chip provided in an embodiment of the present application;

[0025] Figure 5 A schematic diagram of a pixel unit packaged as an independent device provided in an embodiment of the present application;

[0026] Figure 6 A schematic diagram of the wiring layer layout of a pixel unit provided in an embodiment of the present application;

[0027] Figure 7 A schematic diagram of a pixel unit with a light-blocking structure provided in an embodiment of the present application;

[0028] Figure 8 A schematic diagram of the basic process of the method for manufacturing a pixel unit provided in an embodiment of the present application;

[0029] Fig. 9 A schematic diagram of a process for manufacturing a pixel unit according to an embodiment of the present application;

[0030] Fig.10 A schematic diagram of a process for packaging a pixel unit as an independent device provided in an embodiment of the present application;

[0031] Fig.11 A schematic diagram of the manufacturing process of the light-emitting chip provided in an embodiment of the present application;

[0032] Description of reference numerals:

[0033] 101-substrate; 102-adhesion layer; 103-flat layer; 104-blue light emitting chip; 105-green light emitting chip; 106-red light emitting chip; 107-routing layer; 1071-first pad area; 1072-second pad area; 108-black encapsulation layer; 109-light blocking structure; 201-growth substrate; 202-buffer layer; 203-N-type semiconductor layer; 204-active layer; 205-P-type semiconductor layer; 206-transparent conductive layer; 207-ohmic contact electrode; 208-Bragg reflection layer; B-high reflection band; L1-light with an incident angle greater than 45°; L2, L3-light with an incident angle less than 45°. DETAILED DESCRIPTION

[0034] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thoroughly and comprehensively understood.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0036] The light between adjacent light-emitting chips of different colors will affect each other, that is, the cross-light phenomenon will occur, resulting in a decrease in display effect. Based on this, the present application hopes to provide a solution that can solve the above technical problems, and its details will be described in subsequent embodiments.

[0037] Example:

[0038] This embodiment provides a pixel unit, which includes a plurality of light-emitting chips constituting a single pixel, and each light-emitting chip can be used as a sub-pixel. In practical applications, the light-emitting chips in a single pixel may include three light-emitting chips capable of emitting red, green and blue respectively, and the light-emitting chip of each color is used as a sub-pixel, that is, one pixel includes sub-pixels of red, green and blue. Exemplarily, the light-emitting chip may be a Micro LED chip, a Mini LED (Mini Light Emitting Diode, sub-millimeter light-emitting diode) chip, etc.

[0039] In the related art, light crosstalk between adjacent light emitting chips of different colors can be prevented by setting a light blocking structure 109 outside the light emitting chip or in the display device, but this also leads to an increase in production processes and costs during the production of the display device.

[0040] The light-emitting chip used in the pixel unit in this embodiment includes a reflective layer, which can reflect the light emitted by the light-emitting chip. It can be understood that the reflective layer is arranged on the non-light-emitting surface of the light-emitting chip. In practical applications, the reflective layer can be made of an insulating material. When it is arranged on the surface of the light-emitting chip, it can also insulate and protect the light-emitting chip. In some embodiments, the reflection of the reflective layer is not full-band, it can only reflect a certain range of bands, or only have a high reflectivity within a certain band range, but it should be understood that the reflective layer can at least reflect the light emitted by the light-emitting chip. The reflective layer of this embodiment is designed to reflect incident light with an incident angle less than a preset incident angle, so as to limit the light emitted by the light-emitting chip to a preset angle range. In other words, it has a higher reflectivity for incident light less than the preset incident angle, and a lower reflectivity for incident light greater than the preset incident angle. It is understandable that for some reflective layers, their reflective effect is also related to the wavelength of light. For example, for light of different wavelengths, the reflectivity is also different. The incident light that can be reflected by the reflective layer includes at least the light emitted by the light-emitting chip corresponding to the reflective layer, thereby limiting the light emitted by the corresponding light-emitting chip. The light-emitting chip corresponding to the reflective layer is the light-emitting chip to which it is set. For light-emitting chips of different colors, the reflective layers thereon may be different.

[0041] It can be understood that incident light with an angle smaller than the preset incident angle will be blocked by the reflective layer; the lateral light has a small incident angle relative to the reflective layer of the side wall of the light-emitting chip, and is reflected back into the light-emitting chip by the reflective layer, and may be emitted after multiple reflections, thereby limiting the intensity of the lateral emitted light; and the light with a large incident angle relative to the bottom of the light-emitting chip (the side opposite to the light-emitting surface) is not easily reflected, and the large-angle light emission is also reduced. For the light relatively perpendicular to the light-emitting surface, the incident angle relative to the reflective layer of the side wall of the light-emitting chip is large, and it is easy to emit; and the incident angle relative to the reflective layer at the bottom of the light-emitting chip is small, and it is also easy to be reflected and emitted. Therefore, by selecting a reflective layer with the above-mentioned properties, this embodiment makes the light emitted by the light-emitting chip concentrated within the range corresponding to the preset incident angle, so the preset angle range of the light-emitting chip is usually about 2 times the preset incident angle.

[0042] In this embodiment, the preset incident angle does not exceed 55°, and the preset angle range of the light-emitting chip does not exceed 110°. Compared with the 120-135° light-emitting angle of the traditional light-emitting chip, this embodiment concentrates the light more in the central area; the light emitted at a large angle is weaker, which reduces the crosstalk to adjacent light-emitting chips of different colors. In addition, the pixel unit of this embodiment uses the reflective performance of the reflective layer of the light-emitting chip itself to achieve the control of the light-emitting angle, without the need to make additional structures, and its process is simpler, which is conducive to cost control.

[0043] In some embodiments, the reflectivity of the reflective layer to incident light with an incident angle less than a preset incident angle is not less than 90%. The above reflectivity requirement can achieve more effective control of the light output angle in the application. Of course, in practical applications, in order to better limit the light emitted by the light-emitting chip, the reflectivity of the incident light with an incident angle less than the preset incident angle can be as high as possible, for example, the reflectivity is greater than 95%, 98%, 99%, etc. The reflectivity of the reflective layer to incident light with an incident angle not less than the preset incident angle is not greater than 10%, and the reflectivity of the incident light with an incident angle greater than the preset incident angle can be as low as possible, for example, the reflectivity is less than 8%, 5%, etc.

[0044] It should be noted that, unless otherwise specified, the reflectivity is the reflectivity when the incident angle is 0°. In some embodiments, the reflective layer is a Bragg reflective layer 208 (also known as Distributed Bragg Reflection, a distributed Bragg reflector, or DBR for short). The Bragg reflective layer 208 is a periodic structure composed of two materials with different refractive indices arranged alternately in an ABAB manner. The optical thickness of each layer is one-quarter of the central reflection wavelength, and its reflection spectrum is distributed in a band shape, with a maximum reflectivity of more than 99%. Usually, the structure of the Bragg reflective layer 208 can be expressed as G(HL)pHA, where G represents the substrate and the refractive index is n s , A represents air, and its refractive index is n 0 , HL are the center wavelength λ 0 A quarter thickness of high refractive index material and a quarter thickness of low refractive index material, with refractive indices n H and n L , then the number of layers of the Bragg reflector 208 is 2p+1. According to the matrix optical theory, it can be deduced that when the incident light is normal (the incident angle is 0°), the reflectivity R of the Bragg reflector 208 is as follows:

[0045]

[0046] The bandwidth frequency difference Δf of the reflection spectrum of the Bragg reflection layer 208 0 It is determined by the refractive index of the two materials, as shown in Equation 2:

[0047]

[0048] In formula 2, f 0 is the central wavelength λ of the Bragg reflection layer 208 0 Corresponding frequency. It can be seen from the above two formulas that the reflectivity of the Bragg reflector 208 film system will increase with the increase of the number of periods and the refractive index difference of the material. When selecting the dielectric material, in order to realize the Bragg reflector 208 with a wide reflection band, the central wavelength when the reflectivity is the highest can be changed. The central wavelength directly determines the thickness of the film system. Exemplarily, the materials of the common Bragg reflector 208 include but are not limited to compound semiconductors such as AlGaAs, AlGaInN, or dielectric materials such as hafnium oxide, tantalum oxide, titanium oxide, and silicon oxide. The Bragg reflector 208 of the compound semiconductor can be grown by MOCVD (Metal-organic Chemical Vapor Deposition) or MBE (Molecular beam epitaxy), and the Bragg reflector 208 of the dielectric material can be grown by electron beam evaporation or prepared by uniform glue spin coating.

[0049] Each Bragg reflection layer 208 includes two dielectric materials alternately stacked with the same layer thickness, and the refractive index of the two dielectric materials is different. In this embodiment, the layer thickness of the dielectric material between the light-emitting chips with different light-emitting wavelengths is different, that is, the light-emitting chips with different light-emitting wavelengths in this embodiment can be provided with Bragg reflection layers 208 of different structures, so that the wavelength band with higher reflectivity corresponds to the light-emitting wavelength of the light-emitting chip. In some embodiments, the reflection layer can also be a composite structure formed by multiple Bragg reflection layers 208.

[0050] In this embodiment, the reflection spectrum of the Bragg reflection layer 208 of the light emitting chip satisfies the following conditions:

[0051] When the incident angle is 0°, the high reflection band B with a reflectivity higher than a predetermined threshold includes the emission wavelength of the light-emitting chip; as the incident angle increases, the reflection spectrum blue-shifts, and when the incident angle is greater than the preset incident angle, the range of the high reflection band B shifts and no longer includes the emission wavelength. Among them, the high reflection band B is the range of all wavelengths with a reflectivity higher than a predetermined threshold, and the emission wavelength of the light-emitting chip is within this range. . Exemplarily, the predetermined threshold can be 90% as mentioned above, or it can be set to a stricter value such as 95%, 98%, 99%, etc.

[0052] For easier understanding, see Figure 1, which is a reflection spectrum of a Bragg reflection layer 208, wherein the horizontal axis represents the wavelength of the light, and the vertical axis represents the reflectivity of the Bragg reflection layer 208 for the light of the wavelength. In practical applications, the Bragg reflection layer 208 can be designed according to actual needs. For light-emitting chips with different light-emitting wavelengths, different Bragg reflection layers 208 can be designed to provide higher reflectivity for different light-emitting wavelengths.

[0053] like Figure 1 In the example, in the wavelength range of about 400-550nm, its reflectivity is close to 100%, forming a high-reflection band B; while the reflectivity of other surrounding bands is significantly lower than the high-reflection band B. It can be understood that the high-reflection band B is a relative concept, which means that the reflectivity of the wavelengths in this area is higher than that of the remaining wavelengths and the reflectivity is not less than a predetermined threshold. Accordingly, the reflectivity of the remaining bands outside the high-reflection band B can be further set to no more than 10%, or 8%, 5%, etc.

[0054] like Figure 1 It can be seen from the illustrated reflection spectrum that the reflectivity does not change suddenly with the change of wavelength. At the boundary of the high reflection band B, the reflectivity decreases at a faster rate. In addition, the reflectivity outside the high reflection band B is not a simple monotonically decreasing law, but there is a certain degree of up and down fluctuation. However, it can be seen that the reflectivity of the wavelength in the high reflection band B is generally high, while the reflectivity outside the high reflection band B is generally low and shows a trend of oscillating decline. It should be noted that at the boundary of the high reflection band B, there is a certain transition change area, and the reflectivity has a certain fluctuation. Therefore, in practical applications, the reflectivity referred to in this application should be understood as the overall situation, for example, the reflectivity is not greater than 10% means that the average reflectivity is not greater than 10%, for example, the average reflectivity after the incident angle is greater than the preset incident angle is not greater than 10%. Of course, in order to achieve a better reflection effect in practical applications, when designing the Bragg reflection layer 208, the reflectivity of each wavelength can be made to meet the requirements as much as possible.

[0055] See also Figure 1The dotted line portion in the figure reflects the reflection spectrum of the same Bragg reflection layer 208 when the incident angle is a preset incident angle (here, 55° is assumed as an example). The reflection spectrum of the Bragg reflection layer 208 used in this embodiment will undergo a blue shift as the incident angle increases. The reflection spectrum when the incident angle is the preset incident angle is shifted to the left (in the direction shown in the figure) as a whole compared to the reflection spectrum when the incident angle is 0°. At the same time, the bandwidth of the high reflection band B also decreases. If the incident angle is further increased, the blue shift phenomenon is more obvious, and the reflection spectrum as a whole shifts further to the left. In some examples, the bandwidth of the high reflection band B may not decrease, and this application does not limit this. Exemplarily, when the wavelength corresponding to the incident light is about 450nm, when its incident angle is 0°, referring to the corresponding reflection curve, it can be seen that its wavelength is in the high reflection band B, and the Bragg reflection layer 208 has a high reflectivity to it; and when its incident angle gradually increases to the preset incident angle, due to the blue shift of the reflection spectrum, the high reflection band B also shifts until the incident light is no longer in the high reflection band B, that is, the Bragg reflection layer 208 can achieve high reflection at a small incident angle and low reflection at a large incident angle for light with a wavelength of about 450nm.

[0056] In conventional light-emitting chips, the blue shift phenomenon of the Bragg reflector layer 208 is avoided as much as possible. For this reason, many optimization methods for the Bragg reflector layer 208 are proposed in the related art to reduce the impact of the blue shift phenomenon. However, the present embodiment sets the Bragg reflector layer 208 and utilizes its blue shift characteristics to achieve low reflection of light incident at large angles and high reflection of light incident at small angles, thereby achieving the purpose of controlling the light output angle of the light-emitting chip, thereby reducing the problem of crosstalk between light-emitting chips. For light-emitting chips, the Bragg reflector layer 208 is a structure that is usually set, so the above-mentioned implementation method does not need to add additional structures in the current process flow, the process changes are small, and the cost required is low.

[0057] In some embodiments, the light-emitting chips of the pixel unit include a blue light-emitting chip 104, a green light-emitting chip 105, and a red light-emitting chip 106; wherein, the high reflection band B of the Bragg reflection layer 208 of the blue light-emitting chip 104 is in the wavelength range of 400-500nm, for example, it can be 450-500nm, etc.; the high reflection band B of the Bragg reflection layer 208 of the green light-emitting chip 105 is in the wavelength range of 500-560nm, for example, it can be 530-560nm; the high reflection band B of the Bragg reflection layer 208 of the red light-emitting chip 106 is in the wavelength range of 600-650nm, for example, it can be 620-650nm. For each Bragg reflection layer 208, the reflectivity of wavelengths outside the above wavelength range can also be set to be lower, for example, the reflectivity of the Bragg reflection layer 208 of the blue light emitting chip 104 is not higher than 10%, 8% or 5% when the wavelength is less than 400nm and greater than 500nm; the green light emitting chip 105 and the red light emitting chip 106 are similar and will not be described in detail. In practical applications, the wavelength range of the high reflection band B can be designed according to the blue shift of the Bragg reflection layer 208. If the light output angle is to be smaller, a Bragg reflection layer 208 with a smaller wavelength range of the high reflection band B can be used, so that the high reflection band B is shifted earlier to the wavelength outside the corresponding wavelength of the light emitting chip; conversely, if the light output angle is to be larger, a Bragg reflection layer 208 with a larger wavelength range of the high reflection band B can be used.

[0058] As an example, see Figure 2 As shown in the reflection spectrum, the reflectivity of the Bragg reflection layer 208 used by the blue light emitting chip 104 at a wavelength of 400-500nm is greater than 98%, while the reflectivity at wavelengths less than 400nm and greater than 500nm is very small, not exceeding 10% on average. Assuming that the emission wavelength of the blue light emitting chip 104 in the example is about 470nm, the dotted line portion in the figure is the reflection spectrum when the incident angle is 45°. When the light emitted by the blue light emitting chip 104 is incident at an incident angle of less than 45°, the reflectivity of the Bragg reflection layer 208 is high, and when the light emitted by the blue light emitting chip 104 is incident at an incident angle of more than 45°, the reflectivity of the Bragg reflection layer 208 is low, and at a larger incident angle, the reflectivity of the Bragg reflection layer 208 to the light emitted by the blue light emitting chip 104 does not exceed 10% on average. Similarly, the Bragg reflection layer 208 on the green light emitting chip 105 and the red light emitting chip 106 is designed based on the emission wavelength of the green light emitting chip 105 and the red light emitting chip 106 and the preset incident angle. The blue shift phenomenon of the Bragg reflection layer 208 is utilized so that the reflectivity of the Bragg reflection layer 208 to the light emitted by the light emitting chip changes with the angle, thereby achieving the effect of limiting the light emission angle of the light emitting chip. The specific reflection spectrum is designed according to actual needs and will not be elaborated here.

[0059] It is understandable that the smaller the light emission angle of the light emitting chip is, the smaller the crosstalk between adjacent light emitting chips is. In practical applications, the light emission angle of the light emitting chip can also be set to a lower range such as 100°, 90°, 80°, etc. Figure 3 As shown, the range of light intensity greater than 0.5 is taken as the effective light emission range (the maximum light emission intensity is set to 1), and the light emission angle of a conventional light emitting chip is about 135°; and in an example of this embodiment, the preset incident angle can be 45°, that is, the reflective layer is designed to have a higher reflectivity at an incident angle of 0-45°, and a lower reflectivity at an incident angle of 45-90°, thereby limiting the light emission angle of the light emitting chip to about 90° and reducing crosstalk between adjacent light emitting chips.

[0060] like Figure 4 As shown, the optical path of the light emitting chip is schematically shown, with the above-mentioned blue light emitting chip 104 and Figure 2 The reflection spectrum of the Bragg reflector 208 is taken as an example; for ease of understanding, the specific structure of the blue light emitting chip 104 and the Bragg reflector 208 disposed on its surface are omitted in the figure. The light L1 with an incident angle greater than 45° relative to the side and the light L2 with an incident angle less than 45° (assuming that it is not reflected, the path is the arrow with a dotted line in the figure) are both light emitted by the blue light emitting chip 104 with a wavelength of about 470nm, and the same is true for the light L3 with an incident angle less than 45° relative to the bottom (the lower side of the direction shown in the figure). It can be understood that the upper side of the figure is the light emitting side of the blue light emitting chip 104, and the Bragg reflector 208 in this example has a low reflectivity for the light L1 with an incident angle greater than 45°, so most of the light L1 with an incident angle greater than 45° can be emitted through the side. The Bragg reflection layer 208 has a low reflectivity for the light L2 with an incident angle less than 45°, so that a large amount of it is reflected back to the inside of the blue light emitting chip 104 from the side. The light L2 with an incident angle less than 45° may be emitted after multiple reflections, but its intensity is lost during the multiple reflections, or it is reflected to other angles, so that the lateral large-angle light intensity is weakened. The light L3 with an incident angle less than 45° relative to the bottom surface is reflected in large quantities on the bottom surface, and these lights are also relatively concentrated directly above the blue light emitting chip 104. This example makes the light intensity relatively concentrated in a smaller angle range, and limits the light output angle of the blue light emitting chip 104 to no more than 90°.

[0061] The pixel unit of this embodiment can be a single pixel in a pixel array set on the display panel. For example, a plurality of light-emitting chips are arranged in an array on the display panel, wherein each three adjacent light-emitting chips of different colors constitute a pixel unit. Since the light-emitting chip used has a smaller light output angle, the display panel has a smaller cross-light problem and a better display effect.

[0062] The pixel unit of this embodiment may also be an independent packaged device formed in units of pixels. As an example, see Figure 5 , the pixel unit is packaged as a single device. Following the above example, the pixel unit also includes a wiring layer 107 connected to each light-emitting chip. The wiring layer 107 is arranged on one side of the light-emitting chip. The wiring layer 107 includes a plurality of first pad areas 1071 connected to the first pole of the light-emitting chip in a one-to-one correspondence, and a second pad area 1072 connected to the second pole of each light-emitting chip. The first pad area 1071 and the second pad area 1072 can be used as pads for external bonding of the pixel unit. The second pad area 1072 serves as a common end. Through the first pad area 1071, each light-emitting chip in the pixel unit can be controlled separately. This embodiment takes a single pixel unit including a red light-emitting chip 106, a green light-emitting chip 105 and a blue light-emitting chip 104 as an example, see Figure 6 , the wiring layer 107 includes three first pad areas 1071 connected to the first electrodes of the three light-emitting chips respectively, and these first pad areas 1071 are independent of each other. The wiring layer 107 also includes a second pad area 1072 connected to the second electrode of each light-emitting chip at the same time. Generally, one second pad area 1072 is provided in each light-emitting chip packaging structure. The first pad area 1071 and the second pad area 1072 can be distributed at the four corners of the pixel unit and connected to the electrode of the light-emitting chip through the connection path in the wiring layer 107. It can be seen that the pixel unit of this embodiment can be formed as an independent packaged device, but each light-emitting chip can still be independently lit and brightness controlled.

[0063] In some embodiments, in order to facilitate the arrangement of the routing layer 107, a flat layer 103 may be further arranged between each light-emitting chip. The flat layer 103 may be arranged around the light-emitting chip, covering the light-emitting chip from the side. The flat layer 103 fills the area between the light-emitting chips and raises the plane around the light-emitting chip. When making the routing layer 107, the height difference between the light-emitting chip and the surrounding structure is smaller, which facilitates the metal climbing of the routing layer 107. The thickness of the flat layer 103 may be set to be consistent with or similar to the height of the light-emitting chip. For example, the difference between the thickness of the flat layer 103 and the height of the light-emitting chip may be set to within 1um. In other examples, 2um and 3um may also be selected, which may be set according to actual process requirements.

[0064] See also Figure 7In some examples, in order to avoid crosstalk between light-emitting chips, a light-blocking structure 109 is provided in the light-emitting direction of the light-emitting chip. The light-blocking structure 109 can be a black glue layer, and an opening for light emission is provided on the black glue layer, and the part outside the opening is blocked by the black glue to avoid large-angle light emission and block the large-angle light of crosstalk to improve the display effect. The light-blocking structure 109 can also be in the form of a retaining wall or a grille provided between the light-emitting chips. The pixel unit in this embodiment adopts a light-emitting chip with a small-angle light emission, and the crosstalk between each light-emitting chip is weakened. In some implementations, the light-blocking structure 109 for preventing adjacent light-emitting chips from crosstalk may no longer be provided in the light-emitting direction of the light-emitting chip. The provision of the light-blocking structure 109 in the pixel unit increases the packaging step, and the cost is correspondingly higher. This embodiment can save the provision of the light-blocking structure 109 and reduce the packaging cost.

[0065] like Figure 5 In the example of, an encapsulation layer may be provided in the light emitting direction of the light emitting chip, and the encapsulation layer may be composed of a light-transmitting material. The encapsulation layer may form an encapsulation protection for the light emitting side of the light emitting chip. The encapsulation layer of the light emitting chip may include, but is not limited to, a light-transmitting substrate 101 and an adhesive layer 102 provided between the substrate 101 and the light emitting chip. When manufacturing the pixel unit, the light emitting chip may be fixed to the substrate 101 through the adhesive layer 102. The adhesive layer 102 may be provided on the entire surface of the substrate 101. In addition to fixing the light emitting chip, the flat layer 103 may also be provided more stably through the adhesive layer 102. In some examples, the substrate 101 of the pixel unit may also be removed.

[0066] The pixel unit may further include a black encapsulation layer 108 disposed on a side of the wiring layer 107 away from the light emitting chip, and the black encapsulation layer 108 is provided with a through hole to expose the first pad area 1071 and the second pad area 1072. The black encapsulation layer 108 not only forms an encapsulation protection for the side where the wiring layer 107 is disposed, but also can serve as a black background color of the pixel unit, so that the pixel unit can have a better contrast.

[0067] This embodiment also provides a method for manufacturing a pixel unit, see Figure 8 , the manufacturing method of the pixel unit includes but is not limited to:

[0068] S101, providing a substrate;

[0069] S102, providing a plurality of light-emitting chips required to form a pixel;

[0070] It is understandable that these light-emitting chips are arranged in the form of pixels, that is, the selection of their colors and the arrangement on the substrate are configured according to the needs of the pixels; for example, the red light-emitting chip 106, the green light-emitting chip 105 and the blue light-emitting chip 104 are arranged adjacent to each other in sequence at a predetermined interval. It should be noted that each light-emitting chip is provided with a reflection layer for reflecting the light emitted by the light-emitting chip, and the reflection layer is designed to reflect the incident light with an incident angle less than a preset incident angle, so as to limit the light emitted by the light-emitting chip to a preset angle range; wherein the preset incident angle does not exceed 55°, and the preset angle range does not exceed 110°.

[0071] S103, placing the plurality of light-emitting chips on a substrate;

[0072] The light emitting chip can be disposed on the substrate by transfer or the like.

[0073] In some embodiments, the pixel unit can be made as an independent device, such as Fig. 9 As shown, after a plurality of light-emitting chips are arranged on the substrate, the following steps may also be included but are not limited to:

[0074] S104, placing a filling material between the light-emitting chips to form a flat layer, so as to reduce the height difference between the light-emitting chip and the surrounding structure;

[0075] S105, setting a routing layer on the flat layer;

[0076] The wiring layer 107 includes a plurality of first pad regions 1071 connected to the first poles of the light emitting chips in a single pixel in a one-to-one correspondence, and a second pad region 1072 connected to the second poles of the light emitting chips in the single pixel;

[0077] S106, dividing the plurality of light-emitting chips into units of single pixels to form independent devices;

[0078] In addition, the present embodiment further provides a display panel, which includes a circuit substrate 101 and a plurality of pixel units arranged on the circuit substrate 101, and these pixel units are the aforementioned pixel units of the present embodiment. It should be noted that these pixel units can be a plurality of adjacent light-emitting chips directly arranged on the circuit substrate 101, or can be pre-packaged independent devices. The display panel of the present embodiment adopts the aforementioned pixel unit, and limits the light output angle through the reflective layer of the light-emitting chip, thereby reducing the crosstalk between the light-emitting chips, thereby having a better display effect. In some implementation processes, the display panel of the present embodiment can also omit the light-blocking structure 109, thereby reducing the production cost.

[0079] For a better understanding, the following takes a pixel unit packaged as an independent device as an example and combines its specific manufacturing process to further illustrate the solution of this embodiment. Figure 7 As shown, the process of making a pixel unit includes but is not limited to:

[0080] S201: Provide a substrate 101, and arrange an adhesion layer 102 on one surface of the substrate 101. The substrate 101 may be made of a light-transmitting material such as sapphire.

[0081] S202, transfer the light-emitting chip to the substrate 101. The light-emitting chip in this example adopts a Micro LED chip, which can be transferred to the substrate 101 by mass transfer. In a single production process, a light-emitting chip with multiple pixel units can be transferred to a single substrate 101, and after the production is completed, it can be cut to form an independent pixel unit device. In this example, the blue light-emitting chip 104, the green light-emitting chip 105 and the red light-emitting chip 106 are transferred to the substrate 101 in turn, and the three adjacent light-emitting chips are used as a pixel.

[0082] S203, a flat layer 103 is made on the substrate 101, and the flat layer 103 is arranged around each light-emitting chip to cover the light-emitting chip from the side. When the flat layer 103 is arranged, it can be slightly higher than the light-emitting chip and completely cover the light-emitting chip, and then an opening is formed at the light-emitting chip in a patterned manner to expose the electrode of the light-emitting chip.

[0083] S204, depositing conductive metal on the substrate 101 to form a wiring layer 107. When depositing the conductive metal, the conductive metal can be deposited on the entire surface of the light-emitting chip and the flat layer 103, and then a wiring pattern is formed by patterning. An example of a wiring pattern can be found in Figure 5 , I will not go into details here.

[0084] S205. A black encapsulation layer 108 is set on one side of the routing layer 107. The black encapsulation layer 108 can be a black glue material, which can be first coated on this side of the routing layer 107, and then the black encapsulation layer 108 corresponding to the first pad area 1071 and the second pad area 1072 is removed by patterning means to expose the first pad area 1071 and the second pad area 1072.

[0085] By cutting the substrate 101, a plurality of independently packaged pixel units can be obtained. The pixel units thus formed can be used as independent devices. Compared with a single light-emitting chip, they have a larger size, are easier to further process, reduce the difficulty of subsequent processes, and are also conducive to the application of back-end manufacturers.

[0086] Also as an example, see Figure 8 , illustrating a manufacturing process of a light-emitting chip, the manufacturing process includes but is not limited to:

[0087] S301, providing a growth substrate 201, and growing an epitaxial layer on the growth substrate 201. The epitaxial layer includes an N-type semiconductor layer 203, an active layer 204, and a P-type semiconductor layer 205 in sequence, wherein the portion of the N-type semiconductor layer 203 close to the growth substrate 201 may include a buffer layer 202, and the buffer layer 202 provides better lattice matching for subsequent growth. The N-type semiconductor layer 203 and the P-type semiconductor layer 205 may be made of gallium nitride material or other semiconductor materials. In practical applications, the materials of light-emitting chips of different luminous colors may also be different, and can be selected according to needs.

[0088] S302, etching the epitaxial layer to form a mesa; in this process, the P-type semiconductor layer 205 and the active layer 204 at the mesa are etched to expose the N-type semiconductor layer 203 below. In practical applications, the N-type semiconductor layer 203 at the mesa can also be etched to a certain thickness. In addition, a transparent conductive layer 206 is provided on the P-type semiconductor layer 205 and patterned. The transparent conductive layer 206 can be made of a transparent conductive metal such as indium tin oxide.

[0089] S303 , dividing the epitaxial layer into a plurality of independent epitaxial structures, and etching from a direction perpendicular to the growth substrate 201 until the underlying growth substrate 201 is exposed.

[0090] S304, fabricating an ohmic contact electrode 207, wherein the ohmic contact electrode 207 includes an N pole and a P pole, wherein the ohmic contact electrode 207 of the N pole is connected to the exposed N-type semiconductor layer 203 at the table, and the ohmic contact electrode 207 of the P pole is connected to the P-type semiconductor layer 205 at the side of the epitaxial layer away from the growth substrate 201. In some implementations, the execution order of step S303 and step S304 can be exchanged, that is, the ohmic contact electrode 207 can be fabricated first, and then the epitaxial layer can be divided into multiple independent epitaxial structures.

[0091] S305, forming a Bragg reflector layer 208 on the surface of the light emitting chip. It should be understood that the reflectivity of the Bragg reflector layer 208 of this example to the target incident light less than the preset incident angle is higher than the reflectivity of the reflector layer to the target incident light greater than the preset incident angle. The Bragg reflector layer 208 is designed in advance based on the light emission wavelength of the light emitting chip. For example, the required performance parameters can be input into the corresponding design software, and an effective design scheme of the Bragg reflector layer 208 can be determined through the design software. When forming the Bragg reflector layer 208, the material, thickness and other aspects are selected according to the determined design scheme, so that the prepared Bragg reflector layer 208 has the above-mentioned characteristics. The Bragg reflector layer 208 covers the surface of the light emitting chip, but an opening is formed in the area corresponding to the ohmic contact electrode 207, and a pad connected to the ohmic contact electrode 207 can be further made at this position.

[0092] The above example can produce a light-emitting chip with a Bragg reflection layer 208. In the present application, the light-emitting angle of the light-emitting chip is limited by the different reflectivities of the Bragg reflection layer 208 to target incident light at different incident angles. The light-emitting angle of the light-emitting chip is small, and the light crosstalk in the pixel is weakened, which is beneficial to improving the display effect.

[0093] It should be understood that the application of the present application is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to this application.

Claims

1. A pixel unit, It is characterized in that include: A plurality of light-emitting chips constitute a single pixel, each of the light-emitting chips being provided with a reflective layer for reflecting the light emitted by the light-emitting chip, the reflective layer being designed to reflect incident light having an incident angle less than a preset incident angle, so as to limit the light emitted by the light-emitting chip to within a preset angle range; wherein the preset incident angle does not exceed 55°, and the preset angle range does not exceed 110°.

2. The pixel unit according to claim 1, It is characterized in that The reflectivity of the reflective layer to the incident light whose incident angle is smaller than the preset incident angle is not less than 90%.

3. The pixel unit according to claim 1, It is characterized in that The reflective layer is a Bragg reflective layer, and the reflective spectrum of the Bragg reflective layer satisfies the following conditions: When the incident angle is 0°, the high-reflection band with a reflectivity higher than a predetermined threshold includes the light-emitting wavelength of the light-emitting chip; as the incident angle increases, the reflection spectrum blue-shifts, and after the incident angle is greater than the preset incident angle, the range of the high-reflection band shifts and no longer includes the light-emitting wavelength.

4. The pixel unit according to claim 3, It is characterized in that Each of the Bragg reflection layers comprises two dielectric materials alternately stacked with the same layer thickness, and the two dielectric materials have different refractive indices; the layer thickness of the dielectric material is different between the light-emitting chips with different light-emitting wavelengths.

5. The pixel unit according to claim 4, It is characterized in that The plurality of light emitting chips include a blue light emitting chip, a green light emitting chip and a red light emitting chip; The high reflection band of the Bragg reflection layer of the blue light emitting chip is within the wavelength range of 400-500nm; The high reflection band of the Bragg reflection layer of the green light emitting chip is within the wavelength range of 500-560nm; The high reflection band of the Bragg reflection layer of the red light emitting chip is within the wavelength range of 600-650nm.

6. The pixel unit according to any one of claims 1 to 5, It is characterized in that The pixel unit is an independently packaged device, and the pixel unit also includes: a routing layer connected to each of the light-emitting chips, arranged on one side of the light-emitting chip, the routing layer including a plurality of first pad areas connected one-to-one with the first pole of the light-emitting chip, and a second pad area connected to the second pole of each of the light-emitting chips.

7. The pixel unit according to claim 6, It is characterized in that Also includes: A black packaging layer is provided on a side of the wiring layer away from the light emitting chip, and the black packaging layer is provided with through holes to expose the first pad area and the second pad area.

8. A method for manufacturing a pixel unit, It is characterized in that include: providing a substrate; A plurality of light-emitting chips required for forming a pixel are provided, each of the light-emitting chips is provided with a reflective layer for reflecting the light emitted by the light-emitting chip, and the reflective layer is designed to reflect incident light with an incident angle less than a preset incident angle, so as to limit the light emitted by the light-emitting chip to a preset angle range; wherein the preset incident angle does not exceed 55°, and the preset angle range does not exceed 110°; The plurality of light emitting chips are disposed on the substrate.

9. The method for manufacturing a pixel unit according to claim 8, It is characterized in that After the plurality of light emitting chips are arranged on the substrate, the method further comprises: Disposing a filling material between the light-emitting chips to form a flat layer, so as to reduce the height difference between the light-emitting chip and the surrounding structure; A wiring layer is arranged on the flat layer, wherein the wiring layer includes a plurality of first pad regions connected to the first poles of the light emitting chips in a single pixel in a one-to-one correspondence, and a second pad region connected to the second poles of the light emitting chips in the single pixel; The plurality of light emitting chips are divided into individual pixels to form independent devices.

10. A display panel, It is characterized in that The invention comprises a circuit substrate and a plurality of pixel units according to any one of claims 1 to 7 arranged on the circuit substrate.

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