An inkjet printing compensation control method

Abstract

The present application relates to inkjet printing, in particular to a kind of inkjet printing compensation control method, the displacement between the actual position of ink drop and ink drop target position is obtained, the printing parameters of nozzle are compensated when calculating inkjet difference;The pressure sensor in ink sac is calibrated, and the basic calibration coefficient under the calibration temperature is obtained, and the basic calibration coefficient is corrected according to the temperature difference between current ambient temperature and calibration temperature;The reference voltage source voltage and output voltage of pressure sensor are collected, and the ink sac pressure value is calculated in combination with real-time calibration coefficient;The ink sac pressure value is compared with the preset pressure value, if there is deviation between the two, then increase / decrease the pressure inside ink sac;The average value of the projection area of all ink drops is obtained, the corresponding nozzle voltage is matched as the actual inkjet voltage, and the printing parameters of nozzle are compensated;The present application can effectively overcome the defects of the coordinated control of ink drop landing point time difference compensation, ink sac pressure calibration regulation and control and nozzle voltage self-adaptive adjustment.

Description

Technical Field

[0001] This invention relates to inkjet printing, and more specifically to an inkjet printing compensation control method. Background Technology

[0002] Organic light-emitting diodes (OLEDs) have become the mainstream technology in the display field due to their outstanding advantages such as self-illumination, high contrast, and flexibility. Compared with traditional vacuum evaporation processes, inkjet printing for OLED fabrication does not require precision metal masks, and has advantages such as high material utilization, simplified processes, low production costs, and suitability for mass production of large-size panels. It is gradually becoming the core technology route for the industrialization of printed OLEDs.

[0003] However, existing OLED inkjet printing processes still have many technical shortcomings. The printing process is susceptible to factors such as mechanical transmission errors, ambient temperature fluctuations, and unstable ink sac pressure, often resulting in issues like droplet placement misalignment and jetting timing errors, making it difficult to accurately match pixel array layout requirements. Simultaneously, changes in ambient temperature can cause pressure sensor drift, making it impossible to accurately calibrate and control ink sac pressure in real time, further degrading the consistency of droplet volume and jetting state across different nozzles. Furthermore, traditional printing methods lack an adaptive nozzle voltage adjustment mechanism based on droplet projection area, failing to dynamically correct printing parameters according to the actual droplet morphology. This can easily lead to uneven OLED pixel film formation and the "coffee ring effect," ultimately affecting luminous uniformity and device yield.

[0004] Existing technologies mostly employ fixed printing parameters and open-loop ink sac pressure control, failing to achieve coordinated control of ink droplet landing time difference compensation, ink sac pressure calibration and regulation, and nozzle voltage adaptive adjustment. This makes it difficult to meet the process requirements of high-precision and high-consistency OLED inkjet printing, thus restricting the improvement of printed OLED panel yield and large-scale mass production applications. Therefore, it is urgent to propose an inkjet printing compensation control method adapted to OLED fabrication. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] In view of the above-mentioned shortcomings of the prior art, the present invention provides an inkjet printing compensation control method, which can effectively overcome the defects of the prior art in that it does not achieve coordinated control of ink droplet landing time difference compensation, ink bladder pressure calibration and regulation and nozzle voltage adaptive adjustment.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] An inkjet printing compensation control method includes the following steps:

[0010] S1. Pre-printing on the test substrate;

[0011] S2. Obtain the displacement between the actual position of the ink droplet and the target position of the ink droplet, calculate the inkjet difference, and compensate the printing parameters of the nozzle.

[0012] S3. Calibrate the pressure sensor inside the ink sac to obtain the basic calibration coefficient at the calibration temperature. Correct the basic calibration coefficient based on the temperature difference between the current ambient temperature and the calibration temperature to obtain the real-time calibration coefficient.

[0013] S4. Collect the reference voltage source voltage and output voltage of the pressure sensor, and calculate the ink bladder pressure value by combining the real-time calibration coefficient.

[0014] S5. Compare the ink sac pressure value with the preset pressure value. If there is a deviation, increase / decrease the internal pressure of the ink sac.

[0015] S6. Obtain the average projected area of ​​all ink droplets, match the corresponding nozzle voltage as the actual inkjet voltage, and compensate the printing parameters of the nozzle.

[0016] Preferably, in S2, when obtaining the displacement between the actual position of the ink droplet and the target position of the ink droplet and calculating the inkjet difference, the following steps are included:

[0017] Obtain the displacement between the actual position of the ink droplet and the target position of the ink droplet. Based on the displacement and the printing speed of the nozzle in the printing direction, calculate the ink ejection time difference of the nozzle.

[0018] Preferably, obtaining the displacement between the actual position of the ink droplet and the target position of the ink droplet includes:

[0019] Obtain the offset between the actual position of the ink droplet and the center position of the corresponding marking area. Based on the offset and the angle between the printing direction and the offset direction, determine the displacement between the actual position of the ink droplet and the target position of the ink droplet.

[0020] Preferably, in S2, the printing parameters of the nozzle are compensated, including:

[0021] Based on the inkjet timing and the preset inkjet start time of the nozzle, the compensated inkjet start time of the nozzle is determined to compensate for the printing parameters of the nozzle.

[0022] Preferably, in step S3, the pressure sensor inside the ink sac is calibrated to obtain a basic calibration coefficient at the calibration temperature. The basic calibration coefficient is then corrected based on the temperature difference between the current ambient temperature and the calibration temperature to obtain a real-time calibration coefficient, including:

[0023] S31. Perform fixed-point linearization calibration on the pressure sensor inside the ink sac to obtain the basic calibration coefficient C at the calibration temperature. Basic calibration;

[0024] S32. Real-time acquisition of the current ambient temperature, and adjustment of the basic calibration coefficient C based on the temperature difference ΔT between the current ambient temperature and the calibration temperature. Basic calibration Corrections are made to obtain the real-time calibration coefficient C. Live calibration :

[0025] .

[0026] Preferably, in step S4, the reference voltage source voltage and output voltage of the pressure sensor are acquired, and the ink sac pressure value is calculated by combining the real-time calibration coefficient, including:

[0027] S41. Synchronously acquire the reference voltage source voltage V of the pressure sensor. ref Output voltage V out Combined with real-time calibration coefficient C Live calibration Calculate the ink sac pressure value P:

[0028] ;

[0029] S42. If the calculated ink sac pressure value P is a positive number, then take the opposite number of the ink sac pressure value P to obtain the corrected ink sac pressure value P.

[0030] Preferably, in step S5, the ink sac pressure value is compared with a preset pressure value. If there is a deviation, the internal pressure of the ink sac is increased / decreased, including:

[0031] The ink sac pressure value P is compared with the preset pressure value. When there is a deviation between the two, closed-loop adjustment is performed by increasing / decreasing the air / liquid supply pressure inside the ink sac to make the pressure inside the ink sac approach and stabilize near the preset pressure value.

[0032] Preferably, in step S6, the average projected area of ​​all ink droplets is obtained, the corresponding nozzle voltage is matched as the actual inkjet voltage, and the printing parameters of the nozzle are compensated, including:

[0033] S61. Establish the mapping relationship between the projected area of ​​the ink droplet and the nozzle voltage;

[0034] S62. Obtain the average projected area of ​​all ink droplets;

[0035] S63. Based on the mapping relationship between the projected area of ​​ink droplets and the nozzle voltage, match the corresponding nozzle voltage to the average projected area of ​​all ink droplets as the actual inkjet voltage to compensate for the printing parameters of the nozzle.

[0036] Preferably, in step S6, the average projected area of ​​all ink droplets is obtained, the corresponding nozzle voltage is matched as the actual inkjet voltage, and the printing parameters of the nozzle are compensated, including:

[0037] Obtain the variation range between the actual volume and the ideal volume of each ink droplet, and close the nozzle corresponding to the ink droplet whose variation range is greater than a preset threshold.

[0038] Preferably, obtaining the actual volume of each ink droplet includes:

[0039] The actual volume of each ink droplet is determined based on its projected area on the test substrate and its contact angle.

[0040] (III) Beneficial Effects

[0041] Compared with the prior art, the inkjet printing compensation control method provided by the present invention has the following beneficial effects:

[0042] 1) Accurately compensates for inkjet jet time difference, improving printing positioning accuracy.

[0043] By obtaining the displacement between the actual position of the ink droplet and the target position of the ink droplet through pre-printing, and calculating the ink jet difference time in combination with the printing speed, the ink jet start time of the nozzle is corrected to achieve accurate compensation of printing parameters. At the same time, by identifying the offset and angle between the ink droplet and the center of the corresponding marking area, the displacement deviation is accurately determined, breaking the limitations of ink droplet landing point offset and jet timing misalignment in traditional printing. This effectively solves the problem of inaccurate positioning in OLED pixel array printing, ensuring that the ink droplet accurately lands at the target pixel position, providing a guarantee for the high resolution and high pixel density of OLED panels, and greatly improving the printing positioning accuracy and pixel arrangement consistency.

[0044] 2) Temperature compensation calibration ensures steady-state and controllable ink cartridge pressure.

[0045] The pressure sensor inside the ink sac undergoes fixed-point linearization calibration. The calibration coefficient is corrected by combining the temperature difference between the current ambient temperature and the calibration temperature. The ink sac pressure value is then calculated by collecting the reference voltage source voltage and output voltage of the pressure sensor. Based on the preset pressure value, the pressure of the ink sac is controlled in a closed loop. This design effectively offsets the pressure sensor detection drift caused by ambient temperature fluctuations, avoids problems such as ink breakage, ink dripping, and ink splatter caused by excessive or insufficient ink sac pressure, achieves real-time and precise control of ink sac pressure, ensures the stability of ink droplet ejection, and provides support for the quality of ink droplet formation in OLED printing.

[0046] 3) Adaptive matching of nozzle voltage improves inkjet consistency and device yield.

[0047] By establishing a mapping relationship between the projected area of ​​ink droplets and the nozzle voltage, and matching the actual inkjet voltage with the average projected area of ​​all ink droplets, and simultaneously detecting the deviation between the actual volume and the ideal volume of the ink droplets, nozzles exceeding the threshold are shut down. This design achieves adaptive adjustment of the nozzle voltage, effectively improving the problem of inconsistent ink droplet volume and jetting state among different nozzles, reducing defects such as uneven OLED pixel film formation and the coffee ring effect. At the same time, by shutting down abnormal nozzles, the impact of poor inkjet printing on panel quality is avoided, significantly improving the inkjet consistency of OLED printing, and thus improving the luminous uniformity and product yield of OLED devices. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0049] Figure 1 This is a schematic diagram of the process of the present invention;

[0050] Figure 2 This is a schematic diagram of the process for real-time and precise calibration and control of ink sac pressure in this invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0052] The specific process of the inkjet printing compensation control method provided by this invention is described below with reference to specific examples (e.g., Figure 1 (as shown) and technical effects.

[0053] S1. Pre-printing is performed on the test substrate.

[0054] S2. Obtain the displacement between the actual position of the ink droplet and the target position of the ink droplet, calculate the inkjet difference, and compensate the printing parameters of the nozzle.

[0055] 1) In S2, the displacement between the actual position and the target position of the ink droplet is obtained. When calculating the inkjet difference, this includes:

[0056] Obtain the displacement between the actual position of the ink droplet and the target position of the ink droplet. Based on the displacement and the printing speed of the nozzle in the printing direction, calculate the ink ejection time difference of the nozzle.

[0057] Specifically, obtaining the displacement between the actual position of the ink droplet and the target position of the ink droplet includes:

[0058] Obtain the offset between the actual position of the ink droplet and the center position of the corresponding marking area. Based on the offset and the angle between the printing direction and the offset direction, determine the displacement between the actual position of the ink droplet and the target position of the ink droplet.

[0059] 2) In S2, the printing parameters of the nozzles are compensated, including:

[0060] Based on the inkjet timing and the preset inkjet start time of the nozzle, the compensated inkjet start time of the nozzle is determined to compensate for the printing parameters of the nozzle.

[0061] The above technical solution obtains the displacement between the actual position of the ink droplet and the target position of the ink droplet through pre-printing, calculates the ink jet difference time in combination with the printing speed, and then corrects the ink jet start time of the nozzle to achieve accurate compensation of printing parameters. At the same time, by identifying the offset and angle between the ink droplet and the center of the corresponding marking area, the displacement deviation is accurately determined, breaking the limitations of ink droplet landing point offset and jet timing misalignment in traditional printing. It effectively solves the problem of inaccurate positioning in OLED pixel array printing, ensuring that the ink droplet accurately lands at the target pixel position, providing a guarantee for the preparation of high resolution and high pixel density OLED panels, and greatly improving the printing positioning accuracy and pixel arrangement consistency.

[0062] S3. Calibrate the pressure sensor inside the ink sac to obtain the basic calibration coefficient at the calibration temperature. Correct the basic calibration coefficient based on the temperature difference between the current ambient temperature and the calibration temperature to obtain the real-time calibration coefficient. Figure 2 As shown, it includes:

[0063] S31. Perform fixed-point linearization calibration on the pressure sensor inside the ink sac to obtain the basic calibration coefficient C at the calibration temperature. Basic calibration ;

[0064] S32. Real-time acquisition of the current ambient temperature, and adjustment of the basic calibration coefficient C based on the temperature difference ΔT between the current ambient temperature and the calibration temperature. Basic calibration Corrections are made to obtain the real-time calibration coefficient C. Live calibration :

[0065] .

[0066] S4. Acquire the reference voltage source voltage and output voltage of the pressure sensor, and calculate the ink sac pressure value by combining it with the real-time calibration coefficient, such as... Figure 2As shown, it includes:

[0067] S41. Synchronously acquire the reference voltage source voltage V of the pressure sensor. ref Output voltage V out Combined with real-time calibration coefficient C Live calibration Calculate the ink sac pressure value P:

[0068] ;

[0069] S42. If the calculated ink sac pressure value P is a positive number, then take the opposite number of the ink sac pressure value P to obtain the corrected ink sac pressure value P.

[0070] S5. Compare the ink sac pressure value with the preset pressure value. If there is a discrepancy, increase / decrease the internal pressure of the ink sac. Figure 2 As shown, it includes:

[0071] The ink sac pressure value P is compared with the preset pressure value. When there is a deviation between the two, closed-loop adjustment is performed by increasing / decreasing the air / liquid supply pressure inside the ink sac to make the pressure inside the ink sac approach and stabilize near the preset pressure value.

[0072] The above technical solution performs point-to-point linearization calibration of the pressure sensor inside the ink sac, corrects the calibration coefficient by combining the temperature difference between the current ambient temperature and the calibration temperature, calculates the ink sac pressure value by collecting the reference voltage source voltage and output voltage of the pressure sensor, and performs closed-loop control of the ink sac pressure based on the preset pressure value. This design effectively offsets the pressure sensor detection drift caused by ambient temperature fluctuations, avoids problems such as ink interruption, ink dripping, and ink splatter caused by excessive or insufficient ink sac pressure, achieves real-time and precise control of ink sac pressure, ensures the stability of ink droplet ejection, and provides support for the quality of ink droplet formation in OLED printing.

[0073] S6. Obtain the average projected area of ​​all ink droplets, match the corresponding nozzle voltage as the actual inkjet voltage, and compensate the nozzle printing parameters, including:

[0074] S61. Establish the mapping relationship between the projected area of ​​the ink droplet and the nozzle voltage;

[0075] S62. Obtain the average projected area of ​​all ink droplets;

[0076] S63. Based on the mapping relationship between the projected area of ​​ink droplets and the nozzle voltage, match the corresponding nozzle voltage to the average projected area of ​​all ink droplets as the actual inkjet voltage to compensate for the printing parameters of the nozzle.

[0077] In S6, the average projected area of ​​all ink droplets is obtained, the corresponding nozzle voltage is matched as the actual inkjet voltage, and the nozzle printing parameters are compensated, including:

[0078] Obtain the variation range between the actual volume and the ideal volume of each ink droplet, and close the nozzle corresponding to the ink droplet whose variation range is greater than a preset threshold.

[0079] Specifically, the actual volume of each ink droplet is obtained, including:

[0080] The actual volume of each ink droplet is determined based on its projected area on the test substrate and its contact angle.

[0081] The above technical solution establishes a mapping relationship between the projected area of ​​ink droplets and the nozzle voltage, and matches the actual inkjet voltage with the average projected area of ​​all ink droplets. At the same time, it detects the deviation between the actual volume and the ideal volume of the ink droplets and closes nozzles that exceed the threshold. This design achieves adaptive adjustment of the nozzle voltage, effectively improving the problem of inconsistent ink droplet volume and jetting state among different nozzles, reducing defects such as uneven OLED pixel film formation and coffee ring effect. Meanwhile, by closing abnormal nozzles, it avoids the impact of poor inkjet on panel quality, significantly improving the inkjet consistency of OLED printing, and thus improving the luminous uniformity and product yield of OLED devices.

[0082] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for inkjet printing compensation control, characterized in that: Includes the following steps: S1. Pre-printing on the test substrate; S2. Obtain the displacement between the actual position of the ink droplet and the target position of the ink droplet, calculate the inkjet difference, and compensate the printing parameters of the nozzle. S3. Calibrate the pressure sensor inside the ink sac to obtain the basic calibration coefficient at the calibration temperature. Correct the basic calibration coefficient based on the temperature difference between the current ambient temperature and the calibration temperature to obtain the real-time calibration coefficient. S4. Collect the reference voltage source voltage and output voltage of the pressure sensor, and calculate the ink bladder pressure value by combining the real-time calibration coefficient. S5. Compare the ink sac pressure value with the preset pressure value. If there is a deviation, increase / decrease the internal pressure of the ink sac. S6. Obtain the average projected area of ​​all ink droplets, match the corresponding nozzle voltage as the actual inkjet voltage, and compensate the printing parameters of the nozzle.

2. The inkjet printing compensation control method according to claim 1, characterized in that: In S2, the displacement between the actual position and the target position of the ink droplet is obtained. When calculating the inkjet difference, the following is included: Obtain the displacement between the actual position of the ink droplet and the target position of the ink droplet. Based on the displacement and the printing speed of the nozzle in the printing direction, calculate the ink ejection time difference of the nozzle.

3. The inkjet printing compensation control method according to claim 2, characterized in that: The process of obtaining the displacement between the actual position of the ink droplet and the target position of the ink droplet includes: Obtain the offset between the actual position of the ink droplet and the center position of the corresponding marking area. Based on the offset and the angle between the printing direction and the offset direction, determine the displacement between the actual position of the ink droplet and the target position of the ink droplet.

4. The inkjet printing compensation control method according to claim 2, characterized in that: S2 compensates for the nozzle printing parameters, including: Based on the inkjet timing and the preset inkjet start time of the nozzle, the compensated inkjet start time of the nozzle is determined to compensate for the printing parameters of the nozzle.

5. The inkjet printing compensation control method according to claim 1, characterized in that: In S3, the pressure sensor inside the ink sac is calibrated to obtain the basic calibration coefficient at the calibration temperature. The basic calibration coefficient is then corrected based on the temperature difference between the current ambient temperature and the calibration temperature to obtain the real-time calibration coefficient, including: S31. Perform fixed-point linearization calibration on the pressure sensor inside the ink sac to obtain the basic calibration coefficient C at the calibration temperature. Basic calibration ; S32. Real-time acquisition of the current ambient temperature, and adjustment of the basic calibration coefficient C based on the temperature difference ΔT between the current ambient temperature and the calibration temperature. Basic calibration Corrections are made to obtain the real-time calibration coefficient C. Live calibration : 。 6. The inkjet printing compensation control method according to claim 5, characterized in that: The S4 acquires the reference voltage source voltage and output voltage of the pressure sensor, and calculates the ink sac pressure value by combining it with the real-time calibration coefficient, including: S41. Synchronously acquire the reference voltage source voltage V of the pressure sensor. ref Output voltage V out Combined with real-time calibration coefficient C Live calibration Calculate the ink sac pressure value P: ； S42. If the calculated ink sac pressure value P is a positive number, then take the opposite number of the ink sac pressure value P to obtain the corrected ink sac pressure value P.

7. The inkjet printing compensation control method according to claim 6, characterized in that: In S5, the ink sac pressure value is compared with the preset pressure value. If there is a discrepancy, the internal pressure of the ink sac is increased / decreased, including: The ink sac pressure value P is compared with the preset pressure value. When there is a deviation between the two, closed-loop adjustment is performed by increasing / decreasing the air / liquid supply pressure inside the ink sac to make the pressure inside the ink sac approach and stabilize near the preset pressure value.

8. The inkjet printing compensation control method according to claim 1, characterized in that: In S6, the average projected area of ​​all ink droplets is obtained, the corresponding nozzle voltage is matched as the actual inkjet voltage, and the printing parameters of the nozzles are compensated, including: S61. Establish the mapping relationship between the projected area of ​​the ink droplet and the nozzle voltage; S62. Obtain the average projected area of ​​all ink droplets; S63. Based on the mapping relationship between the projected area of ​​ink droplets and the nozzle voltage, match the corresponding nozzle voltage to the average projected area of ​​all ink droplets as the actual inkjet voltage to compensate for the printing parameters of the nozzle.

9. The inkjet printing compensation control method according to claim 1, characterized in that: In S6, the average projected area of ​​all ink droplets is obtained, the corresponding nozzle voltage is matched as the actual inkjet voltage, and the nozzle printing parameters are compensated, including: Obtain the variation range between the actual volume and the ideal volume of each ink droplet, and close the nozzle corresponding to the ink droplet whose variation range is greater than a preset threshold.

10. The inkjet printing compensation control method according to claim 9, characterized in that: The process of obtaining the actual volume of each ink droplet includes: The actual volume of each ink droplet is determined based on its projected area on the test substrate and its contact angle.

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