KR101779162B1 - Method for testing an organic light emitting diode panel - Google Patents

Abstract

The present invention relates to a method of inspecting the quality of an organic light emitting diode panel, and more particularly, to a method of inspecting an organic light emitting diode panel using a noise measurement method, before or after an encapsulating process for an organic light emitting diode The present invention also provides an organic light emitting diode panel inspection method capable of checking the quality of an organic light emitting diode panel. To this end, a method of inspecting an organic light emitting diode panel according to the present invention includes: storing a lookup table including information on a correlation between a noise characteristic and a life span of the organic light emitting diode panel; And measuring the noise of the organic light emitting diode panel on which the deposition process has been performed and comparing the result with the lookup table to determine whether the organic light emitting diode panel is defective.

Description

TECHNICAL FIELD [0001] The present invention relates to an organic light emitting diode (OLED) panel,

The present invention relates to a method for checking the quality of an organic light emitting diode panel.

2. Description of the Related Art In recent years, various flat panel displays (FPDs) have been developed to reduce weight and volume, which are disadvantages of cathode ray tubes. Such flat panel display devices include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), and an electroluminescence device.

In particular, the organic light emitting diode display device uses a self-luminous element which emits light by itself, and thus has a high response speed and a high luminous efficiency and luminance And a large viewing angle.

1 is a diagram for explaining the principle of light emission of a general organic light emitting diode display device.

The organic light emitting diode display has an organic light emitting diode (OLED) as shown in FIG. The organic light emitting diode includes an anode electrode, a cathode electrode, and organic compound layers (HIL, HTL, EML, ETL, EIL) formed between the electrodes.

That is, the organic light emitting diode display device arranges a plurality of subpixels including the organic light emitting diode as described above in a matrix form, selects the subpixels by selectively turning on the TFT as the active device through the scan pulse, And controls the brightness of the selected subpixels according to the gradation of the digital video data.

In the OLED panel having the above-described organic light emitting diode, the characteristics of the OLED panel are different according to the change of the electrode surface, the thickness of the thin films, and the doping amount during the fabrication process. This is because the current density- JVL ') characteristics. Therefore, in the past, during the mass production process of the organic light emitting diode display device, the device evaluation process for the OLED panel was performed using the JVL characteristic change.

However, when the characteristics of the JVL are very small, it is difficult to evaluate the normal operation of the OLED panel using the change in the JVL characteristics. Especially, when the organic material used contains impurities or has a very low vapor pressure, If the chamber is contaminated, a drastic reduction in service life occurs without significant changes in JVL. Therefore, quality control items of OLED panels under mass production process should be combined with JVL measurement and life measurement.

However, the present lifetime measuring method takes a considerable time (usually several hours to several hundred hours) because of the long measuring time, which is a great problem because it is impossible to quickly respond to feedback during the mass production process.

That is, the total organic film thickness between the anode and the cathode of the OLED is generally as thin as 1000 to 2000 Å, and the dopant participating in luminescence is doped to only about 1 to 10 wt% in the light emitting layer having a thickness of 200 to 400 Å. Impregnation of impurities can significantly affect the lifetime of the actual device. This phenomenon does not usually appear as a JVL characteristic, and it is necessary to measure the lifetime of the manufactured specimen. However, this lifetime measurement usually takes several hours to several hundred hours depending on the initial brightness.

In addition, the change in the thickness of the thin film during the deposition process can be finely changed according to the frequency of the oscillator used, and the surface treatment conditions of the ITO using the plasma are also slightly changed. It can also lead to change. Therefore, it is very difficult to measure these physical changes in real time during the mass production process.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems and it is an object of the present invention to provide a method of inspecting an organic light emitting diode panel using a noise measurement method before or after an encapsulating process for an organic light emitting diode panel, The present invention provides an organic light emitting diode panel inspection method capable of inspecting the quality of a diode panel.

According to another aspect of the present invention, there is provided a method of inspecting an organic light emitting diode panel, comprising: storing a lookup table including information on a correlation between noise characteristics and lifetime of the organic light emitting diode panel; And measuring the noise of the organic light emitting diode panel on which the deposition process has been performed and comparing the result with the lookup table to determine whether the organic light emitting diode panel is defective.

According to the above-mentioned solution, the present invention provides the following effects.

That is, according to the present invention, an inspection process of the organic light emitting diode panel using the noise measurement method is performed before or after the sealing process of the organic light emitting diode panel after the deposition process, and the quality of the organic light emitting diode panel is inspected, It is possible to monitor the quality of the OLED panel in real time, thereby providing a stable OLED panel by rapidly processing the mass production process and mass production management.

Further, the present invention may be utilized for analyzing the cause of the degradation of the OLED panel.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining the principle of light emission of a general organic light emitting diode display device. FIG.
BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic light emitting diode (OLED) panel.
FIG. 3 is a flowchart illustrating a method of manufacturing an organic light emitting diode panel to which the organic light emitting diode panel inspection method according to the present invention is applied.
4 is a view illustrating an organic light emitting diode panel to which the organic light emitting diode panel inspection method according to the present invention is applied.
5 is a circuit diagram for analyzing NF characteristic change applied to the organic light emitting diode panel inspection method according to the present invention.
FIGS. 6 to 10 are diagrams illustrating the results of examining lifetime characteristics of each color of the organic light emitting diode panel by the organic light emitting diode panel inspection method according to the present invention. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram of a manufacturing line of an organic light emitting diode panel to which an organic light emitting diode panel inspection method according to the present invention is applied. 3 is a flowchart illustrating a method of manufacturing an organic light emitting diode (OLED) panel according to an exemplary embodiment of the present invention. Referring to FIG. 4 is a view illustrating an organic light emitting diode panel to which the organic light emitting diode panel inspection method according to the present invention is applied. 5 is a circuit diagram for analyzing N-F characteristic change applied to the organic light emitting diode panel inspection method according to the present invention.

An organic light emitting diode (hereinafter, simply referred to as 'OLED') has a specific noise level, that is, a noise power spectral density, in accordance with a frequency, The present invention relates to a method of inspecting an organic light emitting diode panel using a correlation between noise and frequency (hereinafter, simply referred to as a 'noise measurement method'). ). Hereinafter, an OLED panel will be described as an object of inspection for the sake of convenience of description, but specifically, it means one OLED element. More specifically, the test OLED 200 shown in FIG. That is, the noise measurement method is performed on the OLED extracted as the sample. If there are a plurality of such samples, the noise measurement method is performed for the entire OLED panel.

In the OLED, when an organic light emitting material is inserted between two electrodes and a voltage is applied to each electrode, holes and electrons injected from the anode and the cathode form an exciton in the light emitting layer through the charge transport layer , And then self-emit light by self-recombination process. At this time, depending on the organic material used in the light emitting layer, red, green, and blue light can be emitted to realize a full color without a color filter.

Such an OLED is formed of a thin organic thin film within 200 nm, and it is possible to realize a monolithic or bidirectional ultra thin display depending on the configuration of the electrode used.

In addition, since the response speed is 1000 times faster than that of the LCD, and a wide viewing angle and afterimage are left, many studies are being actively conducted.

Particularly, the development of phosphorescent materials and the development of materials with high charge mobility have drastically lowered the power consumption, and organic light emitting diode (OLED) display devices using OLEDs are the next generation displays to replace liquid crystal displays And it is already replacing many LCDs in small displays for mobile.

Hereinafter, an organic light emitting diode panel inspection method according to the present invention will be described in detail with reference to FIGS.

As shown in FIG. 2, the mass production equipments of the production line for mass production of the organic light emitting diode panel are roughly composed of a substrate preprocessing unit, a plurality of evaporation units and an encapsulation unit, A buffer chamber is provided to allow the substrate for the next process to wait.

First, in order to manufacture an organic light emitting diode panel, a substrate pretreatment process is performed through a substrate pretreatment unit (302).

That is, the transparent substrate is coated with a positive electrode material. Indium tin oxide (ITO) is widely used as an anode material. In general, UV-ozone cleaning, O ₂ , N ₂ , and Ar gas plasma treatment are performed for the surface modification of the cathode material. This not only decomposes and cleans organic materials in the ITO surface layer that have not been removed by the solvent treatment, but also functions to lower the hole injection barrier from ITO to the organic layer by increasing the work function.

The substrate prepared as described above is put into a deposition unit and a deposition process is performed (304). That is, a HIL (Hole Injection Layer) is deposited on the substrate after the pretreatment process.

As the hole injection layer, copper phthalocyanine (CuPc) is mainly deposited to a thickness of about 10 nm to 30 nm.

Then, a hole transport layer (HTL) is deposited. As the hole transport layer, 4,4'-bis [N- (1-naphthyl) -N-pentylamino] biphenyl (4,4'- NPB) is deposited to a thickness of about 30 nm to 100 nm.

And an emission layer (EML) is formed thereon. At this time, depending on the organic material used as the dopant, red, green, and blue are formed. Alq ₃ (8-hydroxyquinolatealuminum) doped with 1 to 3 wt% of MQD (N-methylquinacridone) is an example of a green light emitting layer.

Then, an electron transport layer (ETL) and an electron injection layer (EIL) are continuously deposited.

Next, a metal such as Al is deposited to form a cathode.

Next, an encapsulation process is performed in the encapsulation unit to complete the OLED panel of the organic light emitting diode display device (306). At this time, the completed OLED panel is divided into a display area 140 in which an image is displayed and a non-display area 130 in which no image is displayed, as shown in FIG.

That is, the OLED panel is formed by sealing the lower substrate 110 with the plurality of organic light emitting diodes 100 sealed together with the upper substrate 120, and the organic light emitting diode is formed in the display region 140 It is an area.

The non-display area 130 is formed with a plurality of pads (not shown) so that the data driver IC or the gate driver ICs can be electrically connected to the OLED panel.

At least two test OLEDs 200 formed through the same process as the OLEDs formed in the display region are formed in the non-display region 130. Such a test OLED is formed for the test for inspecting the characteristics of the OLED formed in the display region and formed through the same process as the OLED formed in the display region. In addition to the inspection process according to the present invention, such a test OLED can be used in various inspection processes for inspection of characteristics of an OLED panel.

That is, the inspection process is performed through the inspection unit of the OLED panel fabricated through the processes 302 to 306 as described above. This inspection process is performed by the noise measurement method as described above.

However, the noise measurement method (inspection process) is not necessarily performed before the encapsulation process 306 is completed, but may be performed after the sealing process. That is, the noise measurement method monitors the presence or absence of a stacked device structure being fabricated in real time by simply measuring the noise (NF) with respect to the OLED panel before or after the encapsulation process 306 is completed can do.

Therefore, the noise measurement method (inspection process) can be performed before or after the OLED panel fabrication, before or after the sealing process, or after the scribing & breaking process.

On the other hand, the anomaly of the OLED panel that can be inspected in the inspection process to be described below may be as follows. That is, the occurrence of an anomaly in an OLED panel can be divided into a case of coming from a substrate and a case occurring during a deposition process.

First, in the case of coming from the substrate, when the material exists on the surface of the ITO before the deposition or when the surface roughness of the ITO is large, the foreign material acts as a leakage current source, which affects the efficiency and lifetime of the device, Changes in the ITO surface treatment conditions also affect the properties of the OLED panel by causing changes in the work function of ITO.

On the other hand, a problem that may arise during the deposition process is that if the impurities are initially contained in the organic material by mainly impurity impregnation, the organic material remains in the source during the continuous deposition process of the organic material, May be caused by increased source temperature, by organic decomposition, and by contamination inside the deposition chamber.

The total organic film thickness between the anode and the cathode of the OLED is generally as thin as 1000 to 2000 Å and dopants participating in luminescence are doped to only about 1 to 10 wt% in the light emitting layer having a thickness of 200 to 400 Å. The presence of impurities has a significant effect on the luminescence stability, even if the amount is very small.

In addition to the impurities, there are variations in the thickness of each organic film layer, but usually a single organic film is deposited on each organic film layer before the device is fabricated, the thickness is measured and corrected in advance, It is not a big problem to monitor the thickness continuously.

However, as the organic material is deposited on the vibrator, a minute thickness change may occur due to the frequency change. On the other hand, in the case of a large-area panel, the characteristics of the OLED device at the center and the edge of the substrate are slightly different from each other. This is because most of the organic film comes from the uniformity of the organic film, Thereby obtaining a uniform thin film as a whole.

AFM (Atomic Force Microscopy), α-step, ellipsometry, etc. are mainly used for thickness correction and SEM (Scanning Electron Microscope) is also used.

Meanwhile, the present invention is characterized in that the quality of the OLED panel is inspected using the noise (N-F) measurement method during the inspection step 308 as described above.

That is, the method of measuring the noise (NF) is introduced because the OLED panel is very sensitive to the defect sites, non-uniformity, and velocity fluctuation of the surface and the interface, and it is very possible to study the internal mechanism of the device It is a sensitive method.

In the noise (N-F) measuring method applied to the present invention, a constant current (or a constant voltage) is applied to a measuring device (test OLED 200) to measure a change amount of current with time. Then, a function (change amount of current) about the time obtained through the measurement is expressed as a function relating to frequency through a Fourier transform. At this time, the noise level, i.e., the noise power spectral density, is expressed by Equation (1) below, and the meaning of each portion is as follows.

In Equation (1), 1 / f Gaussian noise represents the bulk characteristic of the device. This is related to the mobility of the charge. Scattering occurs due to defects that increase internally as the degradation progresses. This causes more fluctuation in the charge flow and affects the lifetime of the device.

Excessive frequency noise is also related to changes in carrier numbers. This is due to deterioration of the interface, Generation & Furnish of the trap, defects of the surface and interface, and the like. This noise increases more rapidly as the device is stressed.

Generally, such noise may include a white noise, a pink noise, a red noise, a brown noise, a thermal noise, a shot noise, .

That is, in the noise measurement method, NF is used as a characteristic evaluation means of the OLED panel by using the fact that the charge is moved to the OLED and the NF (Noise Power Spectral Density-Frequency) characteristic changes even in the minute change inside.

The noise measuring method as described above will be described in more detail as follows. That is, in order to check the quality of the OLED panel using the noise measurement method, a look-up table for the N-F characteristic to be used for the quality inspection must first be generated and secured.

Therefore, the device structure required for the product in terms of efficiency and lifetime is secured in a state where both the vacuum degree of the deposition chamber and the state of the organic material are stabilized before or after the sealing process. That is, an OLED panel in which a high-quality OLED is formed to be tested for generation of a look-up table is obtained.

A library for the N-F characteristic variation tendency according to the gas flow rate, the processing time, and the applied power at the time of the plasma surface treatment for the OLED panel (or OLED)

Further, in the OLED panel obtained above, the thickness of each layer is slightly changed to secure a library for the N-F characteristic change tendency according to the thickness variation of each layer.

Further, in the OLED panel obtained above, a library for the N-F characteristic change tendency according to the doping amount change of the light emitting layer is secured.

Also, a criterion for the allowable N-F value is determined through the above processes.

That is, the present invention is to inspect the quality of the OLED panel during the mass production process through the NF characteristic. After securing the OLED panel in an ideal state that can be compared with the OLED panel during the mass production process, Are stored in a look-up table.

Thereafter, in the actual mass production process, by comparing the noise measurement result made with respect to the OLED panel through the processes 302 to 306 as described above with the lookup table stored in the above, the quality inspection Can be monitored. At this time, since the noise measurement method can be performed in a very short time, it does not affect the tack time of the entire OLED panel manufacturing process.

That is, in the noise measuring method as described above, when the OLED panel is in mass production in the inspection unit, the NF measurement is performed on the incoming OLED panel, and the inspection unit compares the measured NF result and the data stored in the lookup table If the measured values exceed the predetermined reference value, it can be judged to be defective. When an OLED panel judged to be defective is generated, the manager or the inspection unit stops the manufacturing process of the OLED panel and performs the action accordingly, thereby preventing the occurrence of defect of the OLED panel in real time or in advance.

Meanwhile, in order to apply the noise measurement method to a new OLED panel, the NF characteristics of the OLED panel are repeatedly changed as the thickness of the thin film is changed, And a lookup table suitable for the OLED panel should be created.

That is, the present invention uses NF as a characteristic evaluation means of an OLED device by using a change in NF (Noise Power Spectral Density-Frequency) characteristic even in a minute change of an internal charge in an OLED element. The checks before the method and the noise measurement procedure are as follows.

5, a DC source is connected to a DUT (a measurement element in a metal shield, that is, a test OLED), a DUT is connected to a current-voltage amplifier, a current-voltage amplifier (current- To a signal analyzer.

Next, the DUT is disconnected and the white noise level of the circuit itself, including the amplifier stage, is measured.

Next, the white noise level according to the sensitivity is measured, and the amplification factor is adjusted so that the noise of the device is kept larger than the noise of the circuit itself.

Next, connect a resistor to the DUT to make sure that the thermal white noise level meets the general reference value. At this time, the reference value is expressed by the following equation (2).

Next, the NF (Noise Power Spectral Density-Frequency) of the device is measured and analyzed.

FIGS. 6 to 10 are views illustrating life characteristics of each color of the organic light emitting diode panel according to an exemplary embodiment of the present invention.

That is, the present invention examines the lifetime of the OLED panel using the noise-frequency characteristics of the device, and test results for examining the correlation between the lifetime of the OLED panel and the noise-frequency characteristics of the device are shown in FIGS. 6 to 10 Respectively. To be more specific, the various graphs and the results shown in Figs. 6 to 10 can be applied to the generation of the lookup table as described above. Therefore, after the lookup table is formed using the results of FIGS. 6 to 10, the quality of the OLED panel during the actual mass production process may be determined through comparison with the lookup table.

Meanwhile, as described above, the noise measurement method is performed for an OLED panel, specifically, for one OLED. In the following, the validity of the noise measurement for each RGB will be examined.

First, Device 1 and Device 2 having the same structure are fabricated to investigate the change of N-F characteristic according to the lifetime of the Red element in the OLED according to the first embodiment. At this time, Device1 is a defective OLED and Device2 is a good OLED.

In the examination of the following, first, a 2mm X 2mm in size of ITO over O ₂ after the plasma treatment the electron injection layer (HIL), an electron transport layer (HTL), emitting layer (EML), an electron transport layer (ETL), an electron injection layer (EIL) Al was deposited as Cathode after deposition.

A constant current of 2 mA was applied to the fabricated device of the same structure. At this time, the sensitivity of the Current-Voltage Amplifier was set to 20 μA / V.

Experimental results show that the device with poor lifetime (Device1) has a high noise level, and the system noise is about 5.0E-21 [A ² / Hz]. This is consistent with the result that the normal system noise results in white noise. The results at this time are shown in FIGS. 6 (a), 6 (b) and 9, respectively.

Next, Device 3 and Device 4 having the same structure were fabricated to investigate the change of N-F characteristic according to the lifetime of Green device in the second embodiment. The manufacturing method and manufacturing conditions of the device were the same as those of the first embodiment.

A constant current of 2 mA was applied to the fabricated device of the same structure. At this time, the sensitivity of the Current-Voltage Amplifier was set to 100 μA / V. As in the first embodiment, the device 3 having a poor lifetime has a high noise level, and the system noise is about 5.0E-21 [A ² / Hz], which is similar in the entire frequency range. The results at this time are shown in Figs. 7 (a), (b) and 10, respectively.

Finally, Device 5 and Device 6 having the same structure were fabricated in order to investigate the change of N-F characteristic according to the lifetime of Blue device in the third embodiment. The manufacturing method and manufacturing conditions of the device were the same as those of the first embodiment.

A constant current of 2 mA was applied to the fabricated device of the same structure. At this time, the sensitivity of the Current-Voltage Amplifier was set to 20 μA / V. As in the case of the first embodiment, the device 5 having a poor lifetime has a high noise level, and the system noise is about 5.0E-21 [A ² / Hz], which is similar in the entire frequency range. The results at this time are shown in Figs. 8 (a), 8 (b) and 9, respectively.

In order to investigate the change of NF characteristics according to the lifetime of the above examples, a constant current of 2 mA was applied to the noise measurement. As a result, it was found that devices having poor lifespan (Devce 1, 3, 5) Noise level showed high tendency. Therefore, the present invention is characterized by monitoring the change of the characteristics of the OLED panel in real time when manufacturing the OLED panel using the look-up table secured by the N-F measurement as described above.

That is, as a result of the above-described test results, noise levels are higher in OLEDs having poor lifetimes, that is, OLEDs having a high probability of being defective. As a result, The panel is inspected to check the quality of the OLED panel.

Therefore, if it is determined that an abnormality has occurred after performing the inspection through the noise measurement method as described above, the production can be stopped immediately and the measure can be quickly performed.

The features of the present invention as described above can be summarized as follows.

That is, the present invention provides a method of monitoring the presence or absence of a stacked element structure fabricated in real time by simply measuring the noise (NF) with respect to the OLED panel before or after the completion of the encapsulation process .

In other words, the present invention monitors the change in the characteristics of the OLED that occurs during the deposition in the production of the OLED panel through noise (N-F, noise power spectral density-frequency) measurement.

In the above, noise measurement can measure the rate of change by applying a constant voltage or a constant current.

For the above process, the present invention firstly secures the element structure required for the product in terms of efficiency and lifetime in a state where both the conditions of the deposition chamber and the organic material are stabilized. In the OLED device, (Look-up table) for changes in NF according to changes in surface treatment (gas flow rate, treatment time, and applied power during plasma treatment), and then sets the NF range corresponding to the product demand level.

Thereafter, the NF value set in the above-described mass production process is set as a management item, and the value is compared with the actually measured noise value to judge whether the OLED panel is defective or not, can do.

The NF measurement condition for securing the reference value of the lookup table uses values of a constant voltage (-50 V to 50 V range) or a constant current (-10 A to 10 A range), and a sensitivity for amplifying a minute current is 1 pA / V Or more can be used.

On the other hand, the N-F measurement of the OLED panel can be performed in any process after the cathode deposition.

At this time, the N-F measurement can measure all of the entire panel or can selectively measure it.

Further, in monitoring the change in the characteristics of the OLED panel by measuring N-F, it is possible to agitate the OLED panel by applying a current to the OLED panel for a predetermined time, and then to monitor the device characteristics through the N-F change after the current application.

In the above, the applied current for the device aging is both AC and DC, and a current of 0.1 mA / cm ² or more can be applied.

The current application time for aging the device may be 10 seconds or more.

The N-F measuring condition may be a value of a constant voltage (-50 V to 50 V) or a constant current (-10 A to 10 A), and a sensitivity of 1 pA / V or more may be used for amplifying a minute current.

The N-F measurement as described above may be used as a method of verifying the equipment state after maintenance of the equipment. That is, if the noise is measured by the equipment that has been maintained for the OLED panel judged to be of good quality and the result is good quality, the performance of the equipment may be judged to be normal, but the result is not good If so, then the equipment may be tested for performance because it is defective.

In the meantime, the present invention is not applied to an actual panel on a frequency basis. As described above, after applying a constant current (or a constant voltage), a function (a change amount of a current) concerning a time obtained through measurement is converted into a Fourier transform ) As a function of frequency.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

100: OLED 110: Lower substrate
120: upper substrate 130: non-display area
140: Display area 200: Test OLED

Claims (9)

Storing a lookup table including information on a correlation between noise characteristics and lifetime of the organic light emitting diode panel; And
Measuring the noise of the organic light emitting diode panel on which the deposition process has been performed and comparing the result with the lookup table to determine whether the organic light emitting diode panel is defective,
The look-up table may include at least one of a change in thickness of the organic light emitting diode layer formed on the organic light emitting diode panel, a change in doping amount, a change in gas flow rate in the surface treatment, Wherein the organic light emitting diode panel is set by using a relationship between noise and frequency for one. The method according to claim 1,
And applying a constant voltage or a constant current to the organic light emitting diode panel for measuring the noise to measure the change ratio with time. The method according to claim 1,
Wherein the noise measurement converts a rate of change with respect to time of the organic light emitting diode panel to a rate of change with respect to frequency. delete The method according to claim 1,
In the noise measurement,
Wherein a cathode is deposited on the organic light emitting diode panel by the deposition process. The method according to claim 1,
Further comprising the step of aging the organic light emitting diode panel by applying a current to the organic light emitting diode panel for a predetermined period of time before the noise measurement process. The method according to claim 6,
Wherein the current applied when the organic light emitting diode panel is aged may be AC or DC and a current of 0.1 mA / cm ² or more is applied for 10 seconds or more. The method according to claim 1,
Wherein the constant voltage used for the noise measurement is -50V to 50V. The method according to claim 1,
Wherein the constant current used for the noise measurement is -10A to 10A.

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