Method for prediction of photostabililty of an organic material using laser ablation-direct analysis in real time-mass spectrometry

Abstract

The present invention relates to a method for predicting the light resistance of an organic material within a short period of time using LA-DART-MS, comprising the steps of: irradiating a specimen containing an organic material with a laser beam; obtaining a mass spectrum of components that are desorbed and ionized from the specimen; and calculating a decomposition yield according to Equation 1 of the specification of the present invention from the mass spectrum. The method for predicting the light resistance of an organic material according to the present invention as described above makes it possible to predict light resistance within a significantly shorter period of time, from seconds to minutes, compared to conventional methods for measuring the light resistance of organic materials.

Description

Technology Field

[0001] The present invention relates to a method for predicting the light resistance of organic materials within a short period of time using LA-DART-MS. Background Technology

[0002] Photostability of organic materials relates to the degradation of the material by a light source. As a critical factor determining the long-life operation of a light-emitting system when organic materials are used in such systems, it is a property that must be considered importantly for application in devices such as displays.

[0004] When the light tolerance of organic materials with luminescent properties decreases, a phenomenon called photobleaching occurs, in which the luminescent properties are lost. Photobleaching refers to the phenomenon in which an organic material, after being excited by external energy, fails to exhibit normal emission and loses its luminescent properties due to the formation of new bonds within the material, structural decomposition, or reactions with other substances. When the light tolerance of an organic material decreases, decomposition products or insoluble particles caused by the light source may be formed. Since decomposition products can possess light absorption characteristics similar to those of the organic material, they interfere with the organic material's light absorption, and insoluble particles induce scattering of the light source, resulting in photobleaching.

[0006] The evaluation of lightfastness is generally performed by exposing the product to an evaluation light source similar to the light source used for organic materials for a long period of time, measuring changes in the absorption or emission spectrum, or measuring the reduction rate of absorbed or emitted photons, and subsequently analyzing the degree of degradation of the material and the structure of degradation products through offline GC and LC / MS analysis. However, this process of measuring lightfastness and identifying degradation products has the disadvantage that it requires a long time to predict the physical properties of the material and identify degradation products that cause the degradation of physical properties due to the long irradiation time (hundreds to thousands of hours) to the evaluation light source and the performance of offline analysis.

[0008] Therefore, in order to develop organic materials with excellent physical properties, the development of an analytical method capable of predicting lightfastness within a short period of time is required. The problem to be solved

[0009] The present invention relates to an analysis method capable of predicting the lightfastness of organic materials within a short period of time using LA-DART-MS. means of solving the problem

[0010] To solve the above problem, the present invention provides a method for predicting the photostability of an organic material as follows:

[0011] In a method for predicting the light resistance of organic materials using LA-DART-MS,

[0012] Step of irradiating a laser beam onto a specimen containing organic material (Step 1);

[0013] A step of obtaining the mass spectrum of components desorbed and ionized from the above specimen (step 2); and

[0014] A method comprising the step (step 3) of calculating the decomposition yield of the following mathematical formula 1 from the above mass spectrum,

[0015] Method for Predicting Light Resistance of Organic Materials:

[0016] [Mathematical Formula 1]

[0017] Decomposition yield = (Sum of peak intensities of fragment ions) / (Sum of peak intensities of (molecular ions + fragment ions))

[0019] The present invention is intended to evaluate light resistance among the physical properties of organic materials, and the subject of such organic materials is not particularly limited. In particular, light resistance is a physical property that must be considered important in luminescent materials; from this perspective, the organic materials of the present invention include organic luminescent materials having luminescent properties, and their light resistance is predicted.

[0021] The present invention predicts the light resistance of an organic material using LA-DART-MS instead of using an evaluation light source for evaluating the light resistance of a conventional organic material, characterized by obtaining a mass spectrum by ionizing components desorbed from the organic material by laser beam irradiation with an ion source, and then predicting the light resistance through spectrum analysis.

[0023] Although not theoretically limited, the decomposition of organic materials is similar when irradiated with an evaluation light source versus a laser beam; therefore, it is possible to predict the light resistance of organic materials in a shorter time from this correlation.

[0025] In particular, the present invention utilizes LA-DART-MS, which allows for the prediction of light tolerance within a short period of time compared to evaluating light tolerance using a conventional evaluation light source. As described below, in order to evaluate light tolerance using a conventional evaluation light source, organic materials must be exposed to the evaluation light source for hundreds to thousands of hours. However, by using LA-DART-MS as in the present invention, the mass spectra of the decomposed products can be obtained directly, and by analyzing them, light tolerance can be predicted. Consequently, there is an advantage in that the light tolerance of organic materials can be predicted within seconds to minutes.

[0026] The term "LA-DART-MS (Laser ablation-direct analysis in real-time-mass spectrometry)" used in this invention refers to an analytical method that performs molecular weight and structural analysis of a substance by irradiating a specimen with a laser beam to desorb the analyte, and then ionizing the desorbed analyte with a heated metastable helium gas beam and reactive ions generated therefrom from a DART ionization unit (DART ion source). A system for the LA-DART-MS is schematically illustrated in FIG. 1, and the present invention will be described in detail step-by-step below with reference to FIG. 1.

[0028] (Step 1)

[0029] Step 1 of the present invention is a step of irradiating a laser beam onto a specimen containing an organic material, thereby decomposing the organic material in a manner similar to when the organic material is irradiated by an evaluation light source.

[0031] First, for the above step 1, a system for LA-DART-MS is described. As shown in FIG. 1, 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).

[0033] In the DART ionization unit (10), a laser beam is irradiated from the laser unit (40) to ionize the analyte detached from the specimen (2) mounted on the specimen mounting unit (30) using the helium beam (He beam) of the DART ionization unit (10) and the reactive ions generated therefrom. Specifically, a helium beam is emitted from the emission port (11) of the DART ionization unit (10) to ionize the analyte detached from the specimen (2) mounted on the specimen mounting unit (30).

[0035] The mass spectrometry unit (20) receives the ionized analyte and performs molecular weight and structural analysis of the ionized analyte. The specimen mounting unit (30) is located between the discharge port (11) of the DART ionization unit (10) and the inlet (21) of the mass spectrometry unit (20). Since the analyte detached from the specimen (2) mounted on the specimen mounting unit (30) flows into the inlet of the mass spectrometry unit (20), the specimen mounting unit (30) is located below the path between the discharge port (11) of the DART ionization unit (10) and the inlet (21) of the mass spectrometry unit (20). The inlet (21) of the mass spectrometry unit (20) may be a hole or protruding pipe formed in the mass spectrometry unit (20) to allow analyte from outside the mass spectrometry unit (20) to flow into the internal space of the mass spectrometry unit (20) for analysis. For example, the inlet (21) of the mass spectrometry unit (20) may be an orifice or a transfer tube extending from the orifice.

[0037] The laser unit (40) irradiates a laser beam onto the specimen (2) to detach the analyte from the specimen. Additionally, while the analyst checks the mass spectrum in real time, the relative position of the laser unit (40), the irradiation angle of the laser beam, and the power can be adjusted so that the ion peak intensity of the analyte originating from the specimen (2) is maximized.

[0039] Additionally, the LA-DART-MS system (1) may include an interface unit (100) located in the path between the emission port (11) of the DART ionization unit (10) and the inlet (21) of the mass spectrometry unit (20). The interface unit (100) has a tube-shaped body with both ends open. One end of the interface unit (100) may overlap with or be positioned adjacent to the end portion of the emission port (11) of the DART ionization unit (10). The other end may be fitted onto the outer surface of the inlet (21) of the mass spectrometry unit (20), be in contact with the inlet (21) of the mass spectrometry unit (20), or be connected to the inlet (21) at a predetermined distance (about 2 mm). By using the interface unit (100), components that have been desorbed and ionized by a laser can be effectively collected, and transmission toward the mass spectrometer can be increased, thereby improving detection sensitivity and signal stability.

[0041] Using the LA-DART-MS system as described above, when a laser beam is irradiated onto a specimen (2) mounted on a specimen mounting unit (30), components that are detached from the specimen containing organic material are generated and ionized using a helium beam from a DART ionization unit (10) and reactive ions generated therefrom. A helium beam is emitted from the emission port (11) of the DART ionization unit (10), and the analyte detached from the specimen (2) mounted on the specimen mounting unit (30) is ionized. The ionized analyte is then introduced into a mass spectrometry unit (20), and the mass spectrum obtained from the analytes can be analyzed as described in Step 2 below.

[0043] The above laser beam can be appropriately adjusted depending on the organic material.

[0045] Specifically, the laser may be a continuous wave (CW) or a pulsed laser.

[0047] In addition, the power of the laser beam may be 0.001 mW to 10 W. If the power of the laser beam is less than 0.001 mW, the power of the laser beam is weak, so fewer components are detached from the specimen containing organic material, making mass spectrum analysis difficult; if the power of the laser beam is greater than 10 W, the power of the laser beam is too strong, causing damage or severe degradation to the specimen containing organic material, making mass spectrum analysis difficult. Preferably, the power of the laser beam may be 0.001 mW to 1 W.

[0049] In addition, the wavelength of the laser beam may be 200 nm to 3000 nm. The above is a range of absorption wavelengths of general organic materials that is analyzed, and can be appropriately adjusted by considering the absorption wavelength of the organic material to be analyzed.

[0051] In addition, the irradiation time of the laser beam can be extended from the time of irradiation of the laser beam until a specific peak is no longer observed in the mass spectrum described later. Preferably, the time sufficient to obtain an effective mass spectrum is 30 minutes or less, and more preferably 10 minutes or less. In particular, the irradiation time of the laser beam is significantly shorter than the hundreds to thousands of hours required when measuring light tolerance with a conventional evaluation light source, thereby enabling the prediction of light tolerance within a short period of time.

[0053] (Step 2)

[0054] Step 2 of the present invention is a step of obtaining the mass spectrum of the components that are desorbed and ionized from the specimen by step 1.

[0056] When a laser beam is irradiated onto a specimen containing organic material according to Step 1 above, the organic material is desorbed from the specimen, and a portion of the organic material is decomposed, generating decomposition products. Since the degree of decomposition of the organic material is related to light resistance, the present invention analyzes the mass spectrum to determine the extent of the organic material's decomposition.

[0058] Meanwhile, for the above mass spectrum, in order to directly detect components that are desorbed and ionized by an ion source during laser beam irradiation in step 1, a specimen containing organic material as described above is positioned between the discharge port (11) of the DART ionization unit (10) and the inlet (21) of the mass analysis unit (20), and more preferably, the specimen mounting unit (30) is positioned below the path between the discharge port (11) of the DART ionization unit (10) and the inlet (21) of the mass analysis unit (20).

[0060] In addition, through step 2 above, a mass spectrum can be obtained directly, and since the mass spectrum contains information about the decomposition products of organic matter, there is an advantage that analysis of the decomposition products, such as the molecular weight and structure analysis of the decomposition products, can also be performed quickly.

[0062] In the case of evaluating light tolerance using a conventional evaluation light source, not only must the organic material be exposed to the evaluation light source for a long time, but a sample pretreatment process must also be performed to confirm the molecular weight and structure of the decomposition products, and thus a long time is required. However, through Step 2 of the present invention, the mass spectrum of the components desorbed and ionized from the specimen can be obtained directly, and since a sample pretreatment process is not required, the analysis of the decomposition products of the organic material can be performed in a significantly shorter time compared to the conventional method.

[0064] (Step 3)

[0065] Step 3 of the present invention is the step of calculating the decomposition yield of Equation 1 from the mass spectrum obtained in Step 2.

[0067] Just as organic materials decompose when irradiated with an evaluation light source, organic materials decompose similarly when irradiated with a laser beam; therefore, the light resistance of organic materials can be predicted by analyzing the degree of such decomposition.

[0069] The above mathematical formula 1 calculates the degradation yield to analyze this, and is mathematically expressed as follows. In the following, "I" represents the intensity of each peak. The peaks detected in the mass spectrum include peaks of molecular ions of undegraded organic matter and peaks of fragment ions generated from the decomposition of organic matter; therefore, the degradation yield can be calculated through the above mathematical formula 1.

[0070] Degradation yield = Σ I (fragment ions) / Σ I (parent + fragment ions)

[0072] A lower decomposition yield obtained according to the above indicates that the organic material is decomposed less by the laser beam, and thus the light resistance of the organic material can be predicted to be excellent. Conversely, a higher decomposition yield indicates that the decomposition is greater, and thus the light resistance of the organic material can be predicted to be poor.

[0074] By applying the above, the relative light resistance between organic materials can be evaluated. For example, if one wishes to compare light resistance with a specific organic material, the decomposition yield can be measured for each of the specific organic material and other organic materials according to steps 1 to 3 above, and the light resistance can be compared by comparing them.

[0076] (Step 4)

[0077] The present invention may, if necessary, add a step of deriving a light resistance prediction equation for an organic material by performing linear regression analysis on the light resistance data (X) of the organic material and the decomposition yield (Y) obtained in step 3.

[0079] When a decomposition yield is obtained for each of the multiple organic materials through steps 1 to 3 described above, a relationship between the decomposition yield (Y) and the light resistance data (X) of the multiple organic materials can be derived through regression analysis, and the decomposition yield of another organic material can be obtained from this relationship to predict its light resistance.

[0081] Meanwhile, lightfastness data of multiple organic materials is obtained by exposing the organic materials to an evaluation light source for a long time and measuring changes in the absorption or emission spectrum or the reduction rate of absorbed or emitted photons, and subsequently, the degree of degradation of the material and the structure of the degradation products can be analyzed through offline GC and LC / MS analysis.

[0083] As described in the examples below, lightfastness data of a plurality of organic light-emitting materials in the present invention was obtained by exposing the organic light-emitting materials to an evaluation light source for 500 hours and measuring the number of photons in the absorption or emission wavelength range using a luminance meter, and it was confirmed that this has a correlation with the decomposition yield measured according to the present invention. Effects of the invention

[0084] As described above, the method for predicting the light resistance of an organic material according to the present invention makes it possible to predict light resistance in a shorter time compared to conventional methods for measuring the light resistance of organic materials. Brief explanation of the drawing

[0085] FIG. 1 schematically shows the apparatus used to predict light resistance in the present invention. Figure 2 shows the mass spectrum obtained for organic light-emitting material 1 in an embodiment of the present invention. Figure 3 is a graph showing the results of an embodiment of the present invention. Specific details for implementing the invention

[0086] Hereinafter, embodiments of the present invention will be described in more detail in the following examples. However, the following examples are merely illustrative of embodiments of the present invention, and the content of the present invention is not limited by the following examples.

[0088] Examples

[0089] Step 1) Test subject material

[0090] The following five compounds were selected as experimental subjects, and the substituents of each compound are as shown in Table 1 below.

[0091]

[0092] Organic light-emitting material 1 R1, R3, R5, R7= methyl / R2, R6 = ethyl formate / R4 = phenyl / X1, X2 = F Organic light-emitting material 2 R1, R3, R5, R7= methyl / R2, R6 = CN / R4 = phenyl / X1, X2 = F Organic light-emitting material 3 R1, R3, R7= cycloheptyl / R5= cyclohexyl / R2= CN / R6= H / R4= phenyl / X1, X2= F Organic light-emitting material 4 R1, R3, R5, R7= cyclohexyl / R2 = CN / R6 = H / R4 = phenyl / X1, X2 = F Organic light-emitting material 5 R1, R3, R5, R7=cyclohexyl / R2=CN / R6=H / R4=phenyl / X1, X2=CN

[0094] Step 2) Preparation of the Psalms

[0095] For each of the above 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 compressed using a pellet tool to prepare a specimen having a diameter of about 3 mm.

[0097] Step 3) Experimental Equipment

[0098] A 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 from the laser unit (40) is irradiated onto a specimen (2) in the specimen mounting unit (30), and the specimen mounting unit (30) is positioned below the path between the outlet (11) of the DART ionization unit (10) and the inlet (21) of the mass spectrometer (20).

[0100] Step 4) Laser beam irradiation and mass spectrum measurement

[0101] A laser was irradiated onto each of the above-prepared specimens, and the laser, ion source temperature, and mass spectrum measurement conditions were as follows.

[0102] - Laser power: 180 mW, continuous wave, blue laser beam (405 nm)

[0103] - Ion source temperature: 400℃

[0104] - Mass spectrometer: positive mode (ionization mode), FTMS (analyzer), 240,000 (resolution)

[0106] For each specimen, the intensity of parent ions and fragment ions was calculated based on the mass spectrum obtained for 1 minute after laser irradiation, and the decomposition yield was measured according to the above-described mathematical formula 1. The average value and error were calculated by obtaining three mass spectra for each specimen. Representatively, the mass spectrum for the organic light-emitting material 1 is shown in Figure 2.

[0108] Step 5) Measurement of lightfastness for the evaluation light source

[0109] Lightfastness was measured by exposing organic light-emitting materials to an evaluation light source for an extended period. Specifically, for each of the organic light-emitting materials 1 to 5, the materials were exposed to an evaluation light source (400 to 450 nm) for 500 hours, and the number of photons in the absorption or emission wavelength range was measured using a luminance meter. At this time, the rate of decrease over time relative to the initial value was obtained as data for lightfastness.

[0111] Step 6) Experimental Results

[0112] The above experimental results are shown in Fig. 3. In Fig. 3, the x-axis represents the lightfastness data for the evaluation light source obtained in Step 5, and the y-axis represents the decomposition yield obtained in Step 4.

[0114] As shown in Fig. 3, it can be confirmed that the higher the decomposition yield obtained in step 4 according to the present invention, the lower the light resistance, and conversely, the lower the decomposition yield, the better the light resistance.

[0116] In addition, if the graph of Fig. 3 is subjected to linear regression analysis, the relationship equation at the top right of Fig. 3 can be obtained, and after obtaining a decomposition yield such as that of Step 4 for other organic light-emitting materials, light resistance can be predicted by substituting it into the above relationship equation.

[0118] Therefore, the lightfastness of an organic light-emitting material can be predicted in a significantly shorter time (1 minute) than the 500 hours measured for lightfastness according to the evaluation light source of the organic light-emitting material. Explanation of the symbols

[0119] 1: LA-DART-MS System 2: Specimen 10: DART ionization unit 11: DART ionization unit outlet 20: Mass spectrometry unit 21: Inlet of the mass spectrometry unit 30: Sample mounting unit 40: Laser unit 100: Interface Unit

Claims

Claim 1 A method for predicting the lightfastness of an organic material using LA-DART-MS, comprising: a step of irradiating a specimen containing the organic material with a laser beam (Step 1); a step of obtaining a mass spectrum of components that are desorbed and ionized from the specimen (Step 2); a step of calculating a decomposition yield according to the following Equation 1 from the mass spectrum (Step 3); and a step of deriving a lightfastness prediction equation for the organic material by performing linear regression analysis on the lightfastness data (X) of the organic material and the decomposition yield (Y) obtained in Step 3 (Step 4): [Equation 1] Decomposition yield = (Total sum of peak intensities of fragment ions) / (Total sum of peak intensities of (molecular ions + fragment ions)) Claim 2 A prediction method according to claim 1, wherein the laser is a continuous wave (CW) or pulsed laser. Claim 3 A prediction method according to claim 1, wherein the power of the laser beam is 0.001 mW to 10 W. Claim 4 A prediction method according to claim 1, wherein the wavelength of the laser beam is 200 nm to 3000 nm. Claim 5 A prediction method according to claim 1, wherein the irradiation time of the laser beam is 30 minutes or less. Claim 6 A prediction method according to claim 1, wherein the irradiation time of the laser beam is 10 minutes or less. Claim 7 delete

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