Passive matrix driven micro-led print head and method of operation thereof

Abstract

The present application relates to a passive matrix driven micro light emitting diode print head, comprising: S micro light emitting diode chips, each of which comprises M micro light emitting diode arrays, each array comprising N micro light emitting diodes, wherein the cathodes of the N micro light emitting diodes of the ith array are connected to the ith cathode line (NL1, NL2, …, NL i, …, NLM), and the anodes of the jth micro light emitting diode of each array are connected to the jth anode line (PL1, PL2, …, PLj, …, PLN) respectively, wherein S, M, N, i, j are natural numbers, and 1≤i≤M, 1≤j≤N; and a driver comprising S cathode drive end groups and S anode drive end groups, wherein each cathode drive end group comprises M cathode drive ports connected to M cathode lines respectively, and each anode drive end group comprises N anode drive ports connected to N anode lines respectively, wherein the driver is configured to control the on-off of each micro light emitting diode by controlling the control signals of the cathode drive ends and each anode drive end. Furthermore, the present application also relates to a method for operating the micro light emitting diode print head. Through the present application, the chip area occupied by the driving circuit and the power consumption can be reduced.

Description

Technical Field

[0001] This invention relates to the field of printing technology, specifically to a passively matrix-driven micro LED printhead and its operating method. Background Technology

[0002] Printers are essential electronic devices in daily work and life. Printers are mainly divided into inkjet printers, laser printers, and light-emitting diode (LED) printers. Traditional laser printing imaging technology transmits data signals to a laser emitter, whose emitted light is reflected by a rotating prism and then imaged onto a photosensitive drum. LED printers, on the other hand, use a set of light-emitting diodes (LEDs) for scanning and photosensitive imaging. A dense array of LEDs acts as the light emitter, converting the electrical signals of the data information into light signals, which are then emitted onto the photosensitive drum to form an image. Compared to laser printers, LED printers do not require a complex optical path system, and they are smaller, consume less power, and are noiseless, thus becoming a research hotspot in recent years.

[0003] In current LED printheads, ordinary light-emitting diodes (LEDs) are typically used as light-emitting pixels. Each pixel is controlled by a separate driving circuit. However, too many driving circuits will occupy a large chip area and consume too much power, which is not conducive to the development trend of miniaturized and low-power chips. Summary of the Invention

[0004] Based on existing technology, the objective of this invention is to provide a passively matrix-driven micro LED printhead and its operating method, which can reduce the chip area and power consumption occupied by the driving circuit.

[0005] In a first aspect of the invention, this task is accomplished by a passively matrix-driven micro-LED printhead, the printhead comprising:

[0006] There are S miniature LED chips, each comprising M miniature LED arrays, and each array comprising N miniature LEDs. The cathodes of the N miniature LEDs in the i-th array are connected to the i-th cathode line (NL1, NL2, ..., NLi, ..., NLM), and the anodes of the j-th miniature LEDs in each array are connected to the j-th anode line (PL1, PL2, ..., PLj, ..., PLN). S, M, N, i, and j are natural numbers, and 1 ≤ i ≤ M, 1 ≤ j ≤ N.

[0007] The driver includes S cathode drive terminal groups and S anode drive terminal groups, wherein each cathode drive terminal group includes M cathode drive ports connected to M cathode lines respectively, and each anode drive terminal group includes N anode drive ports connected to N anode lines respectively, wherein the driver is configured to control the on / off state of each micro LED by controlling control signals of the cathode drive terminals and each anode drive terminal respectively.

[0008] In an extended embodiment of the invention, each micro LED printhead comprises Q x S micro LED chips and Q drivers, where Q is a natural number and Q is greater than or equal to 1.

[0009] In another extension of the invention, Q = 1 to 20, S = 1 to 30, M = 2 to 100, and N = 100. For example, Q = 4, S = 5, M = 21, and N = 24. It should be noted that other numbers are also conceivable under the teachings of this invention, such as Q = 30, S = 40, M = 128, N = 128; Q = 64, S = 64, M = 256, N = 256, etc.

[0010] In one extended embodiment of the invention, the cathode line is specified as a metal layer commonly electrically connected to the anodes of each array; and / or

[0011] The anode line is an upper-layer trace above the insulating layer of the circuit board, which is electrically connected to the anode of the same numbered micro LED chips in different arrays. The anode of the micro LED chip is a lower-layer trace below the insulating layer of the circuit board, and they are electrically connected to each other through through-hole contacts at corresponding positions.

[0012] In another extension of the invention, the upper trace and the lower trace are specified to be perpendicular to each other; or

[0013] The upper trace is inclined to the lower trace.

[0014] In another extended embodiment of the invention, the left 12 upper traces are used to control the first to 12th micro LEDs in the first array, and the right 12 upper traces are used to control the 13th to 24th micro LEDs in the first array.

[0015] In another preferred embodiment of the invention, the cathode lines of micro-light-emitting diode arrays with the same number from different micro-light-emitting diode chips are connected to the same cathode drive port of the micro-light-emitting diode chips.

[0016] In a preferred embodiment of the present invention, each miniature light-emitting diode comprises:

[0017] Substrate;

[0018] A passivation layer is disposed on the substrate and surrounds the epitaxial layer;

[0019] An epitaxial layer includes a first epitaxial layer, a second epitaxial layer, and a light-emitting layer disposed between the first epitaxial layer and the second epitaxial layer, wherein the first epitaxial layer is disposed above the light-emitting layer and the second epitaxial layer is disposed below the light-emitting layer;

[0020] A transparent conductive layer covers the passivation layer and is electrically connected to the first epitaxial layer through a first via on the passivation layer, wherein a second via is provided on the bottom side of the micro-light-emitting diode for leading out the anode of each micro-light-emitting diode;

[0021] The cathode, which is disposed on a transparent conductive layer; and

[0022] The anode is led out through the second through hole.

[0023] In an extended embodiment of the present invention, the material of the second epitaxial layer is a material layer of a second conductivity type comprising at least two or more elements of Ga, N, As, Al, In, and P, and the first epitaxial layer is a material layer of a first conductivity type comprising at least two or more elements of Ga, N, As, Al, In, and P, wherein the first conductivity type is different from the second conductivity type.

[0024] In another extension of the present invention, the light-emitting layer is specified to include a multi-quantum-well layer, wherein the multi-quantum-well layer is an InGaN / GaN multi-quantum-well layer, an InGaN / AlGaN multi-quantum-well layer, an InGaAs / AlGaAs multi-quantum-well layer, or an AlGaInP multi-quantum-well layer.

[0025] In another extension of the present invention, an electron blocking layer is provided on the first side of the light-emitting layer, wherein the first side refers to the side along which electrons migrate out of the light-emitting layer.

[0026] In another extension of the invention, the cathode is specified to be made of one or more alloys of the following metals: Ni, Al, Ti, Ni, Pt, Au.

[0027] In another extension of the present invention, the material of the passivation layer is specified as a SiO2 film, a Si3N4 film, or an Al2O3 film.

[0028] In another extension of the invention, the driver includes a decoder configured to convert an input signal into a control signal.

[0029] In another extension of the invention, the miniature LED printhead further includes a controller configured to provide input signals to the driver. The controller may be, for example, a field-programmable gate array (FPGA), application-specific integrated circuit (ASIC), software, firmware, etc., used to implement the control functions.

[0030] The present invention also provides a miniature light-emitting diode printer, which includes a miniature light-emitting diode printhead according to the present invention.

[0031] In a second aspect of the invention, the aforementioned task is also accomplished by a method for operating a micro LED printhead according to the invention, comprising the following steps:

[0032] The driver generates control signals based on the input signals, the control signals including a first signal for controlling the on / off state of the cathode wire and a second signal for controlling the on / off state of the corresponding anode wire; and

[0033] The miniature light-emitting diode performs corresponding operations based on the first and second signals.

[0034] In one extension of the invention, the corresponding operation is specified to include:

[0035] Glowing light;

[0036] It does not emit light; and

[0037] It emits light of a corresponding intensity based on the strength of the electric current.

[0038] The present invention has at least the following beneficial effects:

[0039] (1) By applying micro-light-emitting diodes (LEDs) to the printhead, the chip area and power consumption can be significantly reduced. A micro-light-emitting diode (LED) is a novel LED structure obtained by thinning, miniaturizing, and arraying the existing LED structure. It integrates arrayed micron-sized LED units onto an active addressing driver panel to achieve individual lighting and control of the LED units, thereby outputting the desired display image. The core structure of a micro-light-emitting diode is a PN junction diode, which is composed of direct bandgap semiconductor materials. When a forward bias voltage is applied to the upper and lower electrodes to allow current to flow, electrons and holes recombine in the active region, simultaneously emitting single-color photons. To converge and collimate the light, existing micro-light-emitting diodes typically have microlenses in the optical path.

[0040] (2) Applying the passive matrix (PM) driving method to the printhead can significantly reduce the number of signal lines and controllers, thereby reducing chip complexity, power consumption, crosstalk, etc. In addition, by connecting the cathode lines of the same numbered arrays of different micro LED chips to the same cathode drive port of the micro LED chips, the number of cathode lines can be reduced. This is because although the arrays of the same number of different chips are common cathodes, the arrays of the same number of different chips are not common anodes (the anodes of different chips are connected to different anode drive ports of the controller). Thus, individual control of each micro LED can still be achieved, but the number of cathode lines is reduced.

[0041] (3) By connecting the anode of each micro LED to the first epitaxial layer through the first through hole on the passivation layer and leading out the anode of each micro LED through the second through hole on the transparent conductive layer, the upper and lower space can be better utilized for wiring and crosstalk between the wires can be reduced. Attached Figure Description

[0042] Figure 1 A block diagram of a light-emitting diode printhead according to the present invention is shown;

[0043] Figure 2 A driving logic diagram of a single chip of a light-emitting diode printhead according to the present invention is shown;

[0044] Figure 3 A driving logic diagram of multiple chips in a light-emitting diode printhead according to the present invention is shown;

[0045] Figure 4 A layout diagram of a light-emitting diode printhead according to the present invention is shown;

[0046] Figure 5A The edge of the LED printhead according to the present invention is shown. Figure 4 A schematic diagram of the cross-section of line A; and

[0047] Figure 5B The edge of the LED printhead according to the present invention is shown. Figure 4 A schematic diagram of the cross-section of line B in the middle. Detailed Implementation

[0048] In the following description, the invention is described with reference to various embodiments. However, those skilled in the art will recognize that the embodiments may be practiced without one or more specific details or with other alternatives and / or additional methods, materials, or components. In other instances, well-known structures, materials, or operations are not shown or described in detail so as not to obscure the inventive points of the invention. Similarly, for illustrative purposes, specific quantities, materials, and configurations are set forth to provide a comprehensive understanding of embodiments of the invention. However, the invention is not limited to these specific details. Furthermore, it should be understood that the embodiments shown in the drawings are illustrative representations and are not necessarily drawn to scale.

[0049] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not explicitly or implicitly suggest that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0050] In this specification, references to "an embodiment" or "this embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. The phrase "in one embodiment" appearing throughout this specification does not necessarily refer to the same embodiment in all instances.

[0051] First, the overall architecture of the passively matrix-driven micro LED printhead according to the present invention is described, which includes the following components:

[0052] • There are Q x S miniature light-emitting diode (LED) chips, each of which includes M miniature LED arrays, and each array includes N miniature LEDs. The cathodes of the N miniature LEDs in the i-th array are connected to the i-th cathode line (NL1, NL2, ..., NLi, ..., NLM), and the anodes of the j-th miniature LEDs in each array are connected to the j-th anode line (PL1, PL2, ..., PLj, ..., PLN). S, M, N, i, and j are natural numbers, and 1 ≤ i ≤ M, 1 ≤ j ≤ N. Q is a natural number.

[0053] A driver comprising S cathode drive terminal groups and S anode drive terminal groups, wherein each cathode drive terminal group comprises M cathode drive ports connected to M cathode lines respectively, and each anode drive terminal group comprises N anode drive ports connected to N anode lines respectively, wherein the driver is configured to control the on / off state of each micro LED by controlling control signals of the cathode drive terminals and each anode drive terminal respectively.

[0054] Furthermore, the miniature LED printhead according to the invention may optionally include a field controller configured to provide input signals to the driver. Examples of such a controller include, for example, a field controller programmable gate array, an application-specific integrated circuit (ASIC), firmware, and software.

[0055] exist Figure 1 In the embodiment, Q = 1, S = 20; in Figure 2 In the embodiment, Q = 1, S = 5, M = 21, N = 24; in Figure 3 In the embodiment, Q = 4, S = 5, M = 21, N = 24. Figure 2 and Figure 3 In the embodiment, M = 21, N = 24; in Figure 4 In this embodiment, M = 21 and N = 24. It should be noted that the above numbers are for illustrative purposes only and not as limitations; other numbers may be used as needed in other application scenarios.

[0056] The passively matrix-driven miniature light-emitting diode printhead according to the present invention is illustrated below through specific embodiments. It should be noted that the specific figures in these embodiments are merely for illustrative purposes and not for limitation; other numbers may be used as needed in other application scenarios.

[0057] Figure 1 A block diagram of a light-emitting diode printhead 100 according to the present invention is shown. (As shown) Figure 1 As shown, the micro LED printhead 100 according to the present invention includes micro LED chips 101-1 to 101-20, a driver 102, and signal lines 103. Each micro LED 101-1 to 101-20 includes a micro LED array (not shown), which are grouped and controlled by the driver 102.

[0058] It should be noted that although the present invention shows each driver 102 controlling 5 micro LED chips 101-1 to 101-20, this is merely exemplary, and other numbers are conceivable under the teachings of this invention, such as each driver 102 controlling 8, 10, 16, 30, 100, 512, etc. micro LED chips.

[0059] It should also be noted that, in this invention, the term "chip" can refer to either a packaged structure formed by encapsulating a bare die or an unencapsulated die. The miniature light-emitting diode chips 101-1 to 101-20 can perform specific operations, such as emitting light, not emitting light, and adjusting brightness, etc., via control signals transmitted through signal lines 103. Signal lines 103 include an anode line (PL) and a cathode line (NL) (not shown).

[0060] Figure 2 A driving logic diagram of a single chip of a micro LED printhead 200 according to the present invention is shown.

[0061] like Figure 2 As shown, in this embodiment, each micro LED chip 101 is composed of 504 micro LEDs (or pixels), which are divided into 21 micro LED arrays 105-1 to 105-21, and each array includes 24 micro LEDs 106.

[0062] In this embodiment, the 24 micro-light-emitting diodes 106 in each of the 21 arrays 105-1 to 105-21 share a single cathode line NL. Each micro-light-emitting diode chip 101 has 21 cathode lines assigned to each of the 21 arrays, which are respectively connected to 21 cathode drive ports of the driver 102. Figure 2 The ports are numbered K1 to K21.

[0063] Simultaneously, the first micro-LEDs 106 in arrays 105-1 to 105-24 of the 21 arrays share a single anode line PL, the second micro-LEDs 106 in arrays 105-1 to 105-24 share a single anode line PL, and so on, up to the 24th micro-LED 106 in arrays 105-1 to 105-24 sharing a single anode line PL. Each micro-LED chip 101 has 24 anode lines respectively assigned to 24 groups of micro-LEDs 16 with the same number, which are respectively connected to the 24 anode drive ports of the driver 102. Figure 2 The ports are numbered D1 to D24. Thus, each driver 102 controls 504 micro-LEDs 106 in each micro-LED chip 101 via the aforementioned 21 cathode lines NL and 24 anode lines PL. Therefore, this invention significantly reduces the number of cathode and anode lines and the number of drivers required to control each micro-LED chip.

[0064] The four input ports CKIP / N, D0IP / N, D1IP / N, and D2IP / N on the right side of driver 102 are configured to receive control signals. These control signals are, for example, decoded by driver 102 into cathode and anode signals, specifying which anode and cathode drive ports are high and which are low, and optionally controlling their voltage and / or current magnitudes. For example, CKIP / N is a clock input that receives a clock signal to synchronize signal edges; D0IP / N, D1IP / N, and D2IP / N are, for example, encoded control information, representing the high and low levels of the anode and cathode drive terminals, respectively. For instance, the three control signals form a 45-bit binary number, with the first 21 bits representing the high and low levels of the 21 cathode lines and the last 24 bits representing the high and low levels of the 24 anode lines, such as bit "0" representing low and bit "1" representing high. Other signal formats are also conceivable. D0IP / N, D1IP / N, and D2IP / N can be either serial ports or parallel ports.

[0065] Figure 3 A plurality of chip drive logic diagrams of a miniature light-emitting diode printhead 300 according to the present invention are shown.

[0066] like Figure 3 As shown, in this embodiment, the micro LED printhead 300 includes four drivers 102-1 to 102-4, each controlling five micro LED chips 101-1 to 101-5. That is, each LED printhead 300 includes four drivers and 20 micro LED chips. Similar to the first embodiment, in this embodiment, each micro LED chip 101-1 to 101-5 includes 21 micro LED arrays 105-1 to 105-21, and each array includes 24 micro LEDs 106. It should be noted that the above numbers are merely exemplary. In other embodiments, the LED printhead may include other numbers of drivers and micro LED chips, and the micro LED chips may also include other numbers of arrays, and each array may also include other numbers of micro LEDs. Each driver 102-1 to 102-4 is electrically connected to the cathode of one of the 21 arrays of micro-LEDs in each of the micro-LED chips 101-1 to 101-5 via 21 cathode lines NL, and each driver 102-1 to 102-4 is electrically connected to the anode of one of the 24 micro-LEDs in each array of each of the micro-LED chips 101-1 to 101-5 via 24 anode lines PL.

[0067] In this embodiment, the 24 micro-light-emitting diodes 106 in each of the 21 arrays 105-1 to 105-21 share a single cathode line NL, wherein each micro-light-emitting diode chip 101 has 21 cathode driving ports respectively assigned to the 21 arrays. Figure 3 Ports are numbered K1-K21, and correspondingly, the driver has 21 cathode drive ports for 5 miniature LED chips 101. Figure 3 The ports are numbered K1 to K21. That is, the cathode drive ports K1 to K21 of all (in this case, 5) miniature LED chips 101 with the same numbering array 105-1 to 105-21 are all connected to the same corresponding cathode drive ports K1 to K21 of the driver 102.

[0068] Meanwhile, the first micro-LEDs 106 in arrays 105-1 to 105-24 of the 21 arrays share a single anode line PL, the second micro-LEDs 106 in arrays 105-1 to 105-24 share a single anode line PL, and so on, with the 24th micro-LED 106 in arrays 105-1 to 105-24 sharing a single anode line PL. Each micro-LED chip 101 has 24 anode drive ports. Figure 3 The middle ports are numbered D1-D24, and correspondingly, the driver has 120 anode drive ports for five miniature LED chips 101. Figure 3 The ports are numbered D1 to D120. That is, the anode drive ports D1 to D24 of the arrays 105-1 to 105-21 of all the miniature light-emitting diode chips 101 are connected to the same anode drive ports D1 to D120 of the driver 102.

[0069] Furthermore, the anode and cathode in this invention are merely exemplary. In other application scenarios, the anode and cathode can be interchanged. In the case of interchangeable anode and cathode, the number of anode lines and cathode lines and their corresponding ports should also be interchanged.

[0070] It is feasible for arrays of different chips with the same number to share the same cathode drive port of the driver because arrays of different chips do not share the same anode drive port of the driver (the anode lines of different chips are connected to different anode drive ports of the controller). This still allows for individual control of each micro LED, but reduces the number of cathode lines (from 5x21 to 21). This setup can be understood as arrays of different chips with the same number sharing the same cathode drive port of the driver (one array can be understood as one row), essentially concatenating rows of different chips with the same number into one large row. However, since different columns are controlled separately, individual control of each micro LED is still possible.

[0071] Thus, each driver controls 5x504 micro-LEDs 106 in 5 micro-LED chips 101 via the aforementioned 21 cathode lines NL and 120 anode lines PL. It is evident that this invention significantly reduces the number of cathode and anode lines, as well as the number of drivers, required to control the same number of micro-LEDs.

[0072] Furthermore, the micro LED printhead 300 also includes a controller 107, which is implemented herein as a field-programmable gate array (FPGA). It should be noted that, under the teachings of this invention, other forms of controllers are also conceivable, such as application-specific integrated circuits (ASICs), software, firmware, etc., for implementing control functions. The controller 107, for example, provides input signals to corresponding drivers 102-1 to 102-4, which selectively decode the signals to drive the corresponding micro LED chips, causing them to emit light, not emit light, or adjust their brightness.

[0073] The following describes the operation method of the miniature light-emitting diode printhead according to the present invention.

[0074] First, in step S1, the driver generates a control signal based on the input signal. The control signal includes a first signal (i.e., cathode signal) for controlling the on / off state of the cathode wire and a second signal (i.e., anode signal) for controlling the on / off state of the corresponding anode wire.

[0075] by Figure 4 For example, the control signals assigned to the driver 102 of the five miniature light-emitting diode chips include:

[0076] Cathode signals NS1 to NS21 are used to control the on / off state and / or brightness of the micro-LEDs in the same numbered array of all micro-LED chips. For example, cathode signal NS1 controls the on / off state and / or brightness of the micro-LEDs in the first array of 5 micro-LED chips, cathode signal NS2 controls the on / off state and / or brightness of the micro-LEDs in the second array of 5 micro-LED chips, and so on.

[0077] Anode signals PS1 to PS120, each anode signal is used to control the on / off state and / or brightness of the same numbered micro-LEDs in different arrays of micro-LED chips. For example, anode signal PS1 controls the on / off state and / or brightness of the first micro-LED in all arrays of the first micro-LED chip, anode signal PS2 controls the on / off state and / or brightness of the second micro-LED in all arrays of the first micro-LED chip, anode signal PS25 controls the on / off state and / or brightness of the first micro-LED in all arrays of the second micro-LED chip, and so on.

[0078] In step S2, the micro-LEDs operate accordingly based on the first signal (i.e., the cathode signal) and the second signal (i.e., the anode signal). If both the cathode signal and the anode signal are high, the micro-LED represented by that cathode signal and the anode signal is lit or displays a corresponding brightness. For example, when the cathode signal NS1 and the anode signal PS1 are high, the first micro-LED in the first array of the first micro-LED chip is lit or displays a corresponding brightness; when the cathode signal NS4 and the anode signal PS5 are high, the fifth micro-LED in the fourth array of the first micro-LED chip is lit or displays a corresponding brightness; when the cathode signal NS21 and the anode signal PS25 are high, the first micro-LED in the 21st array of the second micro-LED chip is lit or displays a corresponding brightness. And so on.

[0079] The formula for calculating the position of a miniature light-emitting diode that is lit up or displays a corresponding brightness is:

[0080] The micro LED chip number A = ((PS-1)|X) + 1;

[0081] The array number within the chip is B = NS;

[0082] The number of the miniature light-emitting diodes in the array is C = PS%X;

[0083] Where NS is the cathode signal number, PS is the anode signal number, X is the number of pixels in the array, "|" is the integer division operator (i.e., taking the integer part of the quotient), and "%" is the modulo division operator (i.e., taking the remainder of the quotient).

[0084] The corresponding operations may include, for example, emitting light; not emitting light; and emitting light of a corresponding intensity based on the current intensity. By setting an appropriate model, the operations may also include other operations, such as emitting or not emitting light for an entire row or array of pixels (i.e., miniature light-emitting diodes), adjusting the brightness of an entire row or array of pixels, etc.

[0085] Figure 4 A layout diagram of a miniature light-emitting diode printhead 400 according to the present invention is shown.

[0086] like Figure 4 As shown, the LED printhead 400 includes a miniature LED chip comprising 21 microLED arrays, each array containing 24 microLEDs 106. The cathodes of the 24 microLEDs 106 in each array are connected to a common cathode line NL, while each of the 24 microLEDs 106 in each array is connected to a corresponding anode line PL. For example, the leftmost 12 anode lines PL are connected to the anodes of the 1st to 12th microLEDs 106 in each array, while the rightmost 12 anode lines PL are connected to the anodes of the 13th to 24th microLEDs 106 in each array.

[0087] The LED printhead 400 is, for example, a multi-layer trace circuit board, specifically a double-layer trace circuit board. The upper trace 109 is disposed on the surface of the circuit board, and the lower trace 110 is disposed within the circuit board. The upper trace 109 and the lower trace 110 are separated from each other by an insulating layer and are electrically insulated, but are electrically connected at the through-hole contact 108. In this embodiment, the upper trace 109 is, for example, the anode line PL, while the lower trace 110 is the anode of the miniature LED 106. The specific wiring configuration of the cathode line NL and the anode line PL is described below.

[0088] Here, the cathode line NL is a cathode metal layer arranged on the upper side, which is shared by 24 miniature light-emitting diodes 106 in each array. The cathode metal layers of adjacent arrays can be separated from each other by etching and the gaps can be filled with insulators.

[0089] Here, the anode line PL is a trace that is electrically connected to the anode of the same numbered micro-LED in each array (which is the lower trace 110 under the circuit insulation layer), for example, through a through-hole contact 108 passing through the insulation layer. The anode line PL may have a contact portion, such as a contact point, at its end for electrical contact. The anode of the micro-LED 106 is the lower trace 110 arranged vertically, and the anode line PL is the upper trace 109 perpendicular to it, and they are electrically connected to each other at the anode of the same numbered micro-LEDs through the through-hole contact 108. In this embodiment, the Nth anode line PL (N is a natural number from 1 to 12) of the 12 anode lines from left to right is connected to the anode of the Nth micro-LED in each array, and so on, until the anode line PL has been connected to the same numbered micro-LEDs in all arrays (e.g., 21 arrays). In this embodiment, the Nth anode line PL (where N is a natural number from 1 to 12) of the 12 anode lines from right to left is connected to the anode of the (24-N+1)th micro-LED in each array, and so on, until the anode line PL has been connected to the same numbered micro-LEDs in all arrays (e.g., 21 arrays). A via contact 108 is provided at the intersection of the anode line, i.e., the upper trace 109, and the anode, i.e., the lower trace 110, to achieve electrical connection between them. This circuit layout with the two traces perpendicular to each other and the arrangement of the via contact at the intersection minimizes the total wiring area, as almost all space is utilized.

[0090] In other embodiments, other circuit layouts are also conceivable. For example, the anode of the micro-LED 106 may be a lower-level trace at an angle, while the anode line PL may be an upper-level trace at an angle to it, and they may be electrically connected at the anode of micro-LEDs with the same number. Alternatively, in other applications, the anode may be arranged as an upper-level trace, and the anode line as a lower-level trace.

[0091] Figure 5A and Figure 5B The edges of the LED printhead according to the present invention are shown respectively. Figure 4 Schematic diagram of the cross sections of lines A and B.

[0092] like Figure 5A and Figure 5B As shown, the miniature light-emitting diode 106 includes:

[0093] • Substrate 501, which may be a transparent substrate, such as a glass substrate. Examples of other substrates include GaAs, GaP, InP, SiC, ZnO, and sapphire substrates. In some embodiments, the substrate is about 700 micrometers thick.

[0094] A conductive layer 508 is disposed at the bottom of the epitaxial layer 502 to electrically connect the epitaxial layer 502 to the anode 508 through the second through-hole 506. The conductive layer 508 is made of, for example, metal, but other conductive materials are also conceivable.

[0095] A passivation layer 504 is disposed on the substrate 501 and surrounds the epitaxial layer 503. The passivation layer 504 may be formed, for example, by CVD deposition of SiO2 or ALD deposition of Al2O3 film to effectively reduce chip leakage current.

[0096] Epitaxial layer 502 includes a first epitaxial layer, a second epitaxial layer, and a light-emitting layer disposed between the first and second epitaxial layers. Epitaxial layer 502 comprises a first epitaxial layer, a light-emitting layer, and a second epitaxial layer deposited sequentially, wherein the light-emitting layer includes a multiple quantum well layer and an electron blocking layer. In one embodiment of the present invention, the first epitaxial layer is an N-type GaN layer or an N-type AlGaN layer, and the second epitaxial layer is a P-type GaN layer or a P-type AlGaN layer. That is, the material of the second epitaxial layer can be a material layer of a second conductivity type comprising at least two or more elements of Ga, N, As, Al, In, and P, and the first epitaxial layer can be a material layer of a first conductivity type comprising at least two or more elements of Ga, N, As, Al, In, and P. The multiple quantum well layer is an InGaN / GaN multiple quantum well layer, an InGaN / AlGaN multiple quantum well layer, or an InGaAs / AlGaAs multiple quantum well layer. The electron blocking layer is disposed on a first side of the light-emitting layer, where the first side refers to the side along which electrons migrate out of the light-emitting layer. In another embodiment of the present invention, the first epitaxial layer may also be a P-type GaN layer or a P-type AlGaN layer, and the second epitaxial layer may be an N-type GaN layer or an N-type AlGaN layer. As shown in the figure, the epitaxial layer 502 is stepped.

[0097] A transparent conductive layer 503 covers the passivation layer 504 and is electrically connected to the first epitaxial layer of the epitaxial layer 502 through a first through-hole 505 in the passivation layer 503. The transparent conductive layer 503 has second through-holes 506 between adjacent micro-LEDs 106 for leading out the anode 508 of each micro-LED 106. The first through-holes 505 and second through-holes 506 are at least partially filled with conductive material to form through-hole contacts. As can be seen from the figure, due to the presence of the first and second through-holes 505 and 506, multiple adjacent micro-LEDs 106 can be connected to a common cathode line through the transparent conductive layer 503, and each micro-LED 106 can be connected to a corresponding anode line through its anode 508. In this embodiment, the transparent conductive layers 503 of two adjacent micro-LEDs 106 are connected to each other and cover the area between the two adjacent micro-LEDs 106. The passivation layers 504 of two adjacent micro-LEDs 106 are connected to each other and cover the area between the two adjacent micro-LEDs 106, so as to electrically insulate the transparent conductive layer 503 disposed thereon from the other layers below. Furthermore, a cathode 507 is disposed on the transparent conductive layer between two adjacent micro-LEDs 106. This arrangement facilitates the common cathode of different micro-LEDs 106. Here, the positional relationship between the light-emitting mesa formed by the transparent conductive layer 503, the epitaxial layer 502, and the passivation layer 504 is as follows: the transparent conductive layer 503 covers the entire light-emitting mesa and the transition area between adjacent light-emitting mesa. In the transition area between two adjacent micro-LEDs 106, the positional relationship of each layer is as follows, from bottom to top: substrate 501, passivation layer 504, transparent conductive layer 503, cathode.

[0098] A cathode 507 is disposed on a transparent conductive layer 503. The cathode 507 can be connected to a cathode line NL. The cathode 507 and its connecting components can be made of materials such as graphene, ITO, aluminum-doped zinc oxide (AZO), or fluorine-doped tin oxide (FTO), or any combination thereof. In another embodiment of the invention, the cathode 507 and its connecting components can be made of a non-transparent or transparent conductive material, such as indium tin oxide (ITO).

[0099] • An anode 508 is disposed on a passivation layer 504 and led out through a second through-hole 506, wherein the anode 508 is electrically insulated from the transparent conductive layer 503 at the second through-hole 506. An anode 507 may be connected to an anode line PL. The anode 508 and its connecting components may be made of materials such as graphene, ITO, aluminum-doped zinc oxide (AZO), or fluorine-doped tin oxide (FTO), or any combination thereof. In another embodiment of the invention, the anode 508 and its connecting components may be made of a non-transparent or transparent conductive material, such as indium tin oxide (ITO).

[0100] Each micro-LED chip has a size not exceeding 1 cm, preferably not exceeding 20 micrometers. The micro-LED structures are formed in an array within the micro-LED chips, with resolutions such as 720*480, 640*480, 1920*1080, 1280*720, 2K, or 4K. The diameter of the micro-LED structures is in the nanometer range, for example, from 20 nm to 100 nm.

[0101] A miniature light-emitting diode (LED) chip includes an integrated circuit (IC) backplane and an array of miniature LEDs. The miniature LED array comprises multiple miniature LEDs. Each miniature LED can form at least a portion of a pixel element on the miniature LED chip.

[0102] In some embodiments, the IC backplane may be electrically connected to each microLED in the microLED array via individual metal interconnects. In some embodiments, each microLED may be electrically controlled individually by the IC backplane. In some embodiments, the IC backplane may be electrically connected to the electrodes of the microLED chip via metal interconnects. In some embodiments, a dielectric layer may be formed in the gaps between the microLEDs. In some embodiments, a dielectric layer may also be formed in the gaps between interconnects.

[0103] In some embodiments, each micro-LED in the micro-LED array may include a micrometer-scale mesa structure. In some embodiments, the micrometer-scale mesa structure may include, from bottom to top, a first type epitaxial layer, a light-emitting layer, and a second type epitaxial layer. That is, in the three-layer structure, the first type epitaxial layer is closest to the IC backplane; the light-emitting layer is located above the first type epitaxial layer and further away from the IC backplane; and the second type epitaxial layer is located above the light-emitting layer and furthest away from the IC backplane. In some embodiments, the light-emitting layer is formed of multiple stacked quantum well layers, particularly superlattice stacked quantum well layers. Preferably, the superlattice stacked quantum well layers include multiple pairs of quantum well layers stacked with quantum barrier layers. In some embodiments, the first type epitaxial layer is a semiconductor material having a first conductivity type and includes multiple semiconductor layers. The main substrate material of the first type epitaxial layer may be, but is not limited to, materials such as Ga, N, As, P, In, or Al. Furthermore, the first type epitaxial layer may include, from top to bottom, a waveguide layer, a confinement layer, a transition layer, and a window layer; additionally, an ohmic contact layer may be formed below the window layer. In some embodiments, the second epitaxial layer is a semiconductor material having a second conductivity type and includes multiple semiconductor layers. The main substrate material of the second epitaxial layer may be, but is not limited to, materials such as Ga, N, As, P, In, or Al. Furthermore, the first epitaxial layer may include, from top to bottom, a confinement layer and a waveguide layer; additionally, in some embodiments, an ohmic contact layer may be formed on the confinement layer.

[0104] In some embodiments, a top conductive layer may be formed on the top surface of the micro-LED array. In some embodiments, the top conductive layer may be shared by all micro-LEDs in the micro-LED array. In some embodiments, the light-emitting layer may include at least one quantum well layer. In some embodiments, the micro-LED array may include a single-layer micro-LED structure. In some embodiments, the micro-LED array may include a multi-layer vertically stacked micro-LED structure.

[0105] In some embodiments, the micro-LED array may include blue micro-LEDs. In some embodiments, the spacing between the micro-LED array, i.e., the minimum center-to-center distance between the micro-LEDs, may be between about 2 micrometers and about 50 micrometers. In some embodiments, the number of micro-LED pixels may be between thousands and millions.

[0106] While some embodiments of the invention have been described in this application, those skilled in the art will understand that these embodiments are merely illustrative. Numerous variations, alternatives, and improvements will arise in those skilled in the art under the teachings of this invention without departing from its scope. The appended claims are intended to define the scope of the invention and thereby cover the methods and structures within the scope of the claims themselves and their equivalents.

Claims

1. A passively matrix-driven micro LED printhead, comprising: There are S miniature LED chips, each miniature LED chip includes M miniature LED arrays, and each array includes N miniature LEDs. The cathodes of the N miniature LEDs in the i-th array are connected to the i-th cathode line (NL1, NL2, ..., NLi, ..., NLM), and the anodes of the j-th miniature LEDs in each array are connected to the j-th anode line (PL1, PL2, ..., PLj, ..., PLN). S, M, N, i, and j are natural numbers, and 1 ≤ i ≤ M, 1 ≤ j ≤ N. as well as The driver includes S cathode drive terminal groups and S anode drive terminal groups, wherein each cathode drive terminal group includes M cathode drive ports connected to M cathode lines respectively, and each anode drive terminal group includes N anode drive ports connected to N anode lines respectively, wherein the driver is configured to control the on / off state of each micro LED by controlling control signals of the cathode drive terminals and each anode drive terminal respectively.

2. The micro LED printhead according to claim 1, wherein each micro LED printhead comprises Q x S micro LED chips and Q drivers, wherein Q is greater than or equal to 1.

3. The micro LED printhead according to claim 2, wherein: Q = 1 to 20, S = 1 to 30, M = 2 to 100, N = up to 100.

4. The micro LED printhead according to any one of claims 1 to 3, wherein the cathode line is a metal layer commonly electrically connected to the anodes of each array; and / or The anode line is an upper-layer trace above the insulating layer of the circuit board, which is electrically connected to the anode of the same numbered micro LED chips in different arrays. The anode of the micro LED chip is a lower-layer trace below the insulating layer of the circuit board, and they are electrically connected to each other through through-hole contacts at corresponding positions.

5. The micro LED printhead according to claim 4, wherein the upper layer trace and the lower layer trace are perpendicular to each other; or The upper trace is inclined to the lower trace.

6. The micro LED printhead according to claim 4, wherein the left 12 upper traces are used to control the first to 12 micro LEDs in the first array, and the right 12 upper traces are used to control the 13th to 24th micro LEDs in the first array.

7. The micro LED printhead according to claim 1, wherein the cathode lines of the same numbered micro LED arrays of different micro LED chips are connected to the same cathode drive port of the micro LED chips.

8. The micro LED printhead according to claim 1, wherein each micro LED comprises: Substrate; A passivation layer is disposed on the substrate and surrounds the epitaxial layer; An epitaxial layer includes a first epitaxial layer, a second epitaxial layer, and a light-emitting layer disposed between the first epitaxial layer and the second epitaxial layer, wherein the first epitaxial layer is disposed above the light-emitting layer and the second epitaxial layer is disposed below the light-emitting layer; A transparent conductive layer covers the passivation layer and is electrically connected to the first epitaxial layer through a first via on the passivation layer, wherein a second via is provided on the bottom side of the micro-light-emitting diode for leading out the anode of each micro-light-emitting diode; The cathode, which is disposed on a transparent conductive layer; and The anode is led out through the second through hole.

9. The micro LED printhead of claim 8, wherein the transparent conductive layers of two adjacent micro LEDs are connected to each other and cover the area between the two adjacent micro LEDs.

10. The micro LED printhead of claim 9, wherein the passivation layers of two adjacent micro LEDs are connected to each other and cover the area between the two adjacent micro LEDs.

11. The micro LED printhead according to claim 8 or 9, wherein the cathode is further disposed on a transparent conductive layer between two adjacent micro LEDs.

12. The micro LED printhead according to claim 8, wherein the material of the second epitaxial layer is a material layer of a second conductivity type comprising at least two or more elements including Ga, N, As, Al, In, and P, and the first epitaxial layer is a material layer of a first conductivity type comprising at least two or more elements including Ga, N, As, Al, In, and P, wherein the first conductivity type is different from the second conductivity type.

13. The micro LED printhead according to claim 8, wherein the light-emitting layer comprises a multi-quantum well layer, wherein the multi-quantum well layer is an InGaN / GaN multi-quantum well layer, an InGaN / AlGaN multi-quantum well layer, an InGaAs / AlGaAs multi-quantum well layer, or an AlGaInP multi-quantum well layer.

14. The micro LED printhead according to claim 8, wherein an electron blocking layer is provided on the first side of the light-emitting layer, the first side referring to the side along which electrons migrate out of the light-emitting layer.

15. The micro LED printhead according to claim 8, wherein the cathode material is one or more alloys of the following metals: Ni, Al, Ti, Ni, Pt, Au.

16. The micro LED printhead according to claim 8, wherein the material of the passivation layer is a SiO2 film, a Si3N4 film, or an Al2O3 film, etc.

17. The miniature LED printhead of claim 1, wherein the driver includes a decoder configured to convert an input signal into a control signal.

18. The miniature LED printhead of claim 1 further includes a field controller configured to provide an input signal to the driver.

19. The micro LED printhead according to claim 15, wherein the controller comprises one of the following: a field controller programmable gate array, an application-specific integrated circuit, firmware, and software.

20. A miniature light-emitting diode printer comprising a miniature light-emitting diode printhead according to any one of claims 1 to 16.

21. A method for operating a miniature light-emitting diode printhead according to any one of claims 1 to 20, comprising the following steps: The driver generates control signals based on the input signals, the control signals including a first signal for controlling the on / off state of the cathode wire and a second signal for controlling the on / off state of the corresponding anode wire; and The miniature light-emitting diode performs corresponding operations based on the first and second signals.

22. The method of claim 21, wherein the corresponding operation comprises: Glowing light; It does not emit light; as well as It emits light of a corresponding intensity based on the strength of the electric current.

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