Photostability Prediction Method of Organic Material Using La-Dart-MS

Abstract

The present disclosure relates to a method for predicting photostability of an organic material within a short time using LA-DART-MS, the method including the steps of: irradiating a specimen containing an organic material with a laser beam; obtaining a mass spectrum of components desorbed and ionized from the specimen; and calculating a degradation yield of the mathematical expression 1 according to the present disclosure from the mass spectrum. The method for predicting photostability of an organic material according to the present disclosure as described above can predict photostability within seconds to minutes, which is a remarkably short time, as compared with a conventional method for measuring photostability of an organic material.

Claims

1. A method for predicting photostability of an organic material using laser ablation-direct analysis in real time-mass spectrometry (LA-DART-MS), comprising the steps of: irradiating a specimen containing an organic material with a laser beam and ionizing with a helium beam from an ablation-direct analysis in real time (DART) ionization unit to obtain components desorbed and ionized from the specimen (step 1); obtaining a mass spectrum of the components desorbed and ionized from the specimen by a mass spectrometer (step 2); and calculating a degradation yield using the following Mathematical Expression 1 from the mass spectrum (step 3): [Mathematical Expression 1] Degradation yield = (Sum of peak intensities of fragment ions) / (Sum of peak intensities of (molecular ions + fragment ions)).

2. The prediction method according to claim 1, wherein the laser beam is a continuous wave (CW) or a pulsed laser.

3. The prediction method according to claim 1, wherein a power of the laser beam is 0.001 mW to 10 W.

4. The prediction method according to claim 1, wherein a wavelength of the laser beam is 200 nm to 3000 nm.

5. The prediction method according to claim 1, wherein an irradiation time of the laser beam is 30 minutes or less.

6. The prediction method according to claim 1, wherein an irradiation time of the laser beam is 10 minutes or less.

7. The prediction method according to claim 1, which further comprises linearly regression-analyzing photostability data (X) of the organic material and the degradation yield (Y) obtained in step 3 to derive a prediction expression of the photostability of the organic material (step 4).

8. The prediction method according to claim 1, wherein the specimen containing the organic material is located between an outlet of the DART ionization unit and an inlet of the mass spectrometer.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0047] FIG. 1 schematically shows an apparatus used for predicting photostability in the present disclosure;

[0048] FIG. 2 shows the mass spectrum obtained for organic light emitting material 1 in Example of the present disclosure; and

[0049] FIG. 3 graphically shows the results of Examples of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] Hereinafter, embodiments of the present disclosure will be described in more detail by way of examples. However, the following examples are only provided for illustrative purposes, and the contents of the present disclosure are not limited by these examples.

Example

Step 1) Experimental Material

[0051] The following five compounds were used as experimental materials, and the substituents of each compound are shown in Table 1 below.

##STR##

TABLE-US-00001 Organic light emitting material 1 R.sub.1, R.sub.3, R.sub.5, R.sub.7 = methyl / R.sub.2, R.sub.6 = ethyl formate / R.sub.4 = phenyl / X.sub.1, X.sub.2 = F Organic light emitting material 2 R.sub.1, R.sub.3, R.sub.5, R.sub.7 = methyl / R.sub.2, R.sub.6 = CN / R.sub.4 = phenyl / X.sub.1, X.sub.2 = F Organic light emitting material 3 R.sub.1, R.sub.3, R.sub.7 = cycloheptyl / R.sub.5 = cyclohexyl / R.sub.2 = CN / R.sub.6 = H / R.sub.4 = phenyl / X.sub.1, X.sub.2 = F Organic light emitting material 4 R.sub.1, R.sub.3, R.sub.5, R.sub.7 = cyclohexyl / R.sub.2 = CN / R.sub.6 = H / R.sub.4 = phenyl / X.sub.1, X.sub.2 = F Organic light emitting material 5 R.sub.1, R.sub.3, R.sub.5, R.sub.7 = cyclohexyl / R.sub.2 = CN / R.sub.6 = H / R.sub.4 = phenyl / X.sub.1, X.sub.2 = CN

Step 2) Preparation of Specimen

[0052] For each of the organic light emitting materials 1 to 5, 0.5 mg of the organic light emitting material in powder form was loaded onto an aluminum plate, and then crimped using a pellet tool to prepare a specimen having a diameter of about 3 mm.

Step 3) Experimental Instrument

[0053] The LA-DART-MS system as shown in FIG. 1 was used. Specifically, the LA-DART-MS system 1 includes a DART ionization unit 10, a mass spectrometer 20, a specimen mounting unit 30, and a laser unit 40. A laser beam was set to irradiate to a specimen 2 of the specimen mounting unit 30 from the laser unit 40, and the specimen mounting unit 30 was located below the path between the outlet 11 of the DART ionization unit 10 and the inlet 21 of the mass spectrometer 20.

Step 4) Laser Beam Irradiation and Mass Spectrum Measurement

[0054] Each of the prepared specimens was irradiated with a laser, and the laser, ion source temperature, and mass spectrum measurement conditions were as follows. [0055] Laser power: 180 mW, continuous wave, blue laser beam (405 nm) [0056] Ion source temperature: 400° C. [0057] Mass spectrometer: positive mode (ionization mode), FTMS (analyzer), 240,000 (resolution)

[0058] After laser irradiation for each specimen, the intensities of parent ions and fragment ions were calculated based on the mass spectrum obtained for 1 minute, and then the degradation yield was measured according to the mathematical expression 1. Three mass spectra were obtained for each specimen, and the average value and error were calculated. Typically, the mass spectrum of the organic light emitting material 1 is shown in FIG. 2.

Step 5) Measurement of Photostability for Evaluation Light Source

[0059] The photostability was measured by a method in which an organic light emitting material was exposed to an evaluation light source for a long time. Specifically, each of the organic light emitting materials 1 to 5 was exposed to an evaluation light source (400 to 450 nm) for 500 hours, and the number of photons in the absorption or emission wavelength region was measured with a luminance meter. At this time, a ratio that decreases with time compared to the initial value was obtained as the photostability data.

Step 6) Experimental Results

[0060] The experimental results are shown in FIG. 3. In FIG. 3, the x-axis is photostability data for the evaluation light source obtained in step 5, and the y-axis means the degradation yield obtained in step 4.

[0061] As shown in FIG. 3, it can be confirmed that the higher the degradation yield obtained in step 4 according to the present disclosure, the lower the photostability, and conversely, the lower the degradation yield, the better the photostability.

[0062] Further, when the graph of FIG. 3 is linearly regression-analyzed, the relational expression in the right upper end of FIG. 3 can be obtained, and after obtaining the same degradation yield as in step 4 for other Organic light emitting materials, the photostability can be estimated by substituting for the above relational expression.

[0063] Accordingly, the photostability of the organic light emitting material can be predicted within a significantly shorter time (1 minute) than 500 hours, which is the measurement time of light resistance according to the evaluation light source of the organic light emitting material.

EXPLANATION OF SYMBOLS

[0064] 1: LA-DART-MS system [0065] 2: specimen [0066] 10: DART ionization unit [0067] 11: outlet of DART ionization unit [0068] 20: mass spectrometer [0069] 21: inlet of mass spectrometer [0070] 30: specimen mounting unit [0071] 40: laser unit [0072] 100: interface unit