Electron transport materials using oxadiazole derivatives having a parylene structure

Abstract

To provide a novel and useful organic semiconductor material that utilizes parylene, and a method for producing the same.SOLUTION: An electron transport material comprises an oxadiazole derivative having a parylene structure.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to organic semiconductor materials utilizing polymers. More specifically, it relates to an electron transport material comprising one or more oxadiazole derivatives having a parylene structure as constituent materials, a method for producing oxadiazole derivatives having a parylene structure, and an electron transport system using the electron transport material. [Background technology]

[0002] social background Organic molecules have a closed-shell electron configuration with no unpaired electrons, resulting in a large HOMO-LUMO energy gap. Therefore, organic molecules were considered insulators. Consequently, materials used in electronics, such as semiconductors, were predominantly inorganic, including silicon and metals. However, it was discovered that molecules with broad conjugated systems allow for carrier movement, and their electrical properties became clearer. (Non-Patent Literature 1) Since then, the development of electronic devices using organic semiconductors has been actively pursued. Among these, organic electroluminescent (EL) elements, which have seen the most practical application, are attracting attention as next-generation flat-panel displays with many advantages, including high-efficiency light emission, planar emission, lightweight and thin design, flexibility, high responsiveness, and environmental resistance. (Non-Patent Literature 2)

[0003] Organic semiconductors are classified into p-type and n-type semiconductors. Triphenylamine derivatives, bisbenzothiophene derivatives, and triphenylene derivatives, as shown in [Chemical Formula 1-3], are electron-rich and therefore possess p-type semiconductor properties (Non-Patent Documents 3-5), while oxadiazole derivatives, phenanthroline derivatives, and triazole derivatives, as shown in [Chemical Formula 1-4], contain electron-deficient atoms such as imine nitrogen atoms and are known to possess n-type semiconductor properties (Non-Patent Documents 6-8). [ka] Structure of p-type organic semiconductor [ka] Structure of n-type organic semiconductor

[0004] Examples of previous research Due to their high electron affinity, 2,5-diaryl-1,3,4-Oxadiazole (OXD) derivatives possess excellent electron injection and transport capabilities, as well as superior thermal and chemical stability and high photoluminescence quantum yield. Therefore, they are widely used as electron transport materials in electroluminescent (EL) devices. (Non-Patent Literature 9)

[0005] Chihaya Adachi et al. reported that 2-(4-tert-Butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole (PBD) possesses properties as an electron transport material. (Non-Patent Literature 6) However, PBD is prone to crystallization, which posed problems with the stability of thin films. Since then, the development of electron transport materials using OXD derivatives has become widespread. Among these are 1,3-Bis[5-(4-tert-butylphenyl)-2-[1,3,4]oxadiazolyl]benzene (OXD-7) (Non-Patent Literature 10), also reported by Adachi et al., and 2,2',2''-(1,3,5-benzenetriyl)tris[5-[4-(1,1-dimethylethyl)phenyl]-1,3,4-oxadiazole (TPOB) (Non-Patent Literature 11), reported by Yasuhiko Shirota et al. These molecules are known to possess electron transport and hole-blocking properties, as well as high thermal stability. Currently, the mainstream method for fabricating organic LED films involves stacking these low-molecular-weight materials using vacuum deposition.

[0006] technical challenges Low molecular weight organic EL devices are fabricated by vacuum evaporation. The vacuum evaporation method enables film thickness control at the nanolevel and is a dry process, so lamination is also possible. However, low molecular weight organic EL devices often have a complex multilayer structure. On the other hand, by incorporating various functions into the molecule, it is possible to reduce the number of layers of the device using a polymer material. As a method for forming a film of a polymer material, there is a coating method, but film thickness control is more difficult than the vacuum evaporation method, and control of solubility such as selection of a coating solvent is required for lamination. Therefore, a polymer material with high solvent resistance is required.

Prior Art Documents

Non-Patent Documents

[0007]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Non-Patent Document 6

Non-Patent Document 7

Non-Patent Document 8

Non-Patent Document 9

Non-Patent Document 10

Non-Patent Document 18

Non-Patent Document 19

Non-Patent Document 20

[0008] Purpose and Significance of the Invention This invention relates to Poly(p-xylylene) (parylene).

[0009] In other words, it was expected that by synthesizing parylene with substituents that have semiconducting properties, it would be possible to synthesize organic semiconductor materials that do not dissolve in coating solvents. Parylene is a paraxylene-based polymer polymerized by chemical vapor deposition (CVD). Parylene has high mechanical strength and excellent chemical stability, and its unique polymerization method makes it easy to produce uniform and defect-free films and control the film thickness. Furthermore, since the first synthesis of parylene precursor [2,2]-paracycrophane by Pellegrin in 1899 (Non-Patent Literature 12), various structures with substituents have been reported (Non-Patent Literature 13, 14). However, there have been few reports on organic semiconductors using parylene, and the field remains underdeveloped.

[0010] This invention aims to introduce an oxadiazole derivative into parylene and evaluate its properties. By using an oxadiazole derivative, which is one of the electron transport materials, as a substituent, it is possible to impart electron transport properties to parylene, thereby enabling the fabrication of electron transport materials with high solvent resistance. This idea was explored through diligent academic research, leading to the completion of this invention. [Means for solving the problem]

[0011] The present invention is an electron transport material comprising an oxadiazole derivative having a parylene structure. An electron transport material characterized in that the oxadiazole derivative is represented by the following formula (X), (Y), or (Z). This provides... [ka] (n is a number representing the degree of polymerization) [ka] (n is a number representing the degree of polymerization) [ka] (n is a number representing the degree of polymerization)

[0012] Furthermore, the present invention relates to an electron transport material comprising one or more oxadiazole derivatives having a parylene structure as constituent materials. An electron transport material characterized in that the oxadiazole derivative is represented by the following formula (X), (Y), or (Z). This provides... [ka] (n is a number representing the degree of polymerization) [ka] (n is a number representing the degree of polymerization) [ka] (n is a number representing the degree of polymerization)

[0014] Furthermore, the present invention provides a method for producing an oxadiazole derivative having a parylene structure, comprising the following steps (1), (2), (3), and (4). Step (1): A step to produce 4-Carboxylic acid-[2,2]-paracyclophane from 4-Methoxycarbonyl-[2,2]-paracyclophane. [ka] Step (2): A step to produce 4-(2-Phenyl-1,3,4-Oxadiazole)-[2,2]-paracyclophane (monomer 1) from 4-Carboxylic acid-[2,2]-paracyclophane. [ka] Step (3): A step to produce 4-[2-(4-trifluoromethylphenyl)-1,3,4-Oxadiazole]-[2,2]-paracyclophane (monomer 2) from 4-Carboxylic acid-[2,2]-paracyclophane. [ka] Step (4): A step to produce 4-[2-(3,5-bistrifluoromethylphenyl)-1,3,4-Oxadiazole]-[2,2]-paracyclophane (monomer 3) from 4-Carboxylic acid-[2,2]-paracyclophane. [ka] Step (5): A step to produce polymers X, Y, and Z from monomers 1, 2, and 3 by CVD. [ka] (n is a number representing the degree of polymerization) [ka] (n is a number representing the degree of polymerization) [ka] (n is a number representing the degree of polymerization)

[0015] Furthermore, the present invention provides an electron transport system using any of the aforementioned electron transport materials. [Effects of the Invention]

[0016] The present invention provides novel and useful organic semiconductor materials utilizing parylene and methods for producing the same. [Brief explanation of the drawing]

[0017] [Figure 1-1] Figure 1-1 shows monomer 1. [Figure 1-2] Figure 1-2 shows monomer 2. [Figure 1-3] Figure 1-3 shows monomer 3. [Figure 1-4] Figure 1-4 shows polymer 1. [Figure 1-5] Figure 1-5 shows polymer 2. [Figure 1-6] Figures 1 - 6 are Polymer 3. [Figure 2-1] Mass spectra of PCP-COOH [Figure 2-2] 1H-NMR spectra of PCP-OXD-Ph in CDCl3 [Figure 2-3] 13C-NMR spectra of PCP-OXD-Ph in CDCl3 [Figure 2-4] Mass spectra of PCP-OXD-Ph [Figure 2-5] 1H-NMR spectra of PCP-OXD-CF3 in CDCl3 [Figure 2-6] 13C-NMR spectra of PCP-OXD-CF3 in CDCl [Figure 2-7] Mass spectra of PCP-OXD-CF3 [Figure 2-8] 1H-NMR spectra of PCP-OXD-bisCF3 in CDCl3 [Figure 2-9] 13C-NMR spectra of PCP-OXD-bisCF3 in CDCl [Figure 3-1] [[ID=CO2]]AFM image of PPX-OXD-Ph and PPX-OXD-CF3 [Figure 3-2] FT-IR spectra of PCP-OXD-Ph and PPX-OXD-Ph [Figure 3-3] FT-IR spectra of PCP-OXD-CF3 and PPX-OXD-CF3 [Figure 3-4] Simulated molecular geometries of PCP-OXD-Ph [Figure 3-5] Molecular orbital of PCP-OXD-Ph [Figure 3-6] Simulated molecular geometries of PPX-OXD-Ph [Figure 3-7] Simulated molecular geometries of PCP-OXD-CF3 [Figure 3-8] Molecular orbital of PCP-OXD-CF3 [Figure 3-9] Simulated molecular geometries of PPX-OXD-CF3 [Figure 3-10] Caluculated UV-vis adsorption spectra of PCP-OXD-Ph [Figure 3-11] Caluculated UV-vis adsorption spectra of PPX-OXD-Ph [Figure 3-12] Caluculated UV-vis adsorption spectra of PCP-OXD-CF3 [Figure 3-13] Caluculated UV-vis adsorption spectra of PPX-OXD-CF3 [Figure 3-14] Caluculated energy levers of PCP-OXD-Ph(←) and PPX-OXD-Ph(→) [Figure 3-15] Caluculated energy levers of PCP-OXD-CF3(←) and PPX-OXD-CF3(→) [Figure 3-16] UV-visible absorption spectrum of PCP-OXD-Ph and PPX-OXD-Ph [Figure 3-17] UV-visible absorption spectrum of PCP-OXD-CF3 and PPX-OXD-CF3 [Figure 3-18] DSC results of PCP-OXD-Ph and PPX-OXD-Ph [Figure 3-19] DSC results of PCP-OXD-CF3 and PPX-OXD-CF3 [Figure 3-20]TGA results of PPX-OXD-Ph and PPX-OXD-CF3 [Figure 3-21] Contact angle image of PPX-OXD-Ph [Figure 3-22] Contact angle image of PPX-OXD-CF3 [Figure 3-23] Cyclic voltammograms (scan rate 0.05V / s) [Figure 3-24] Differential pulse voltammograms [Figure 3-25] XRD patterns of PPX-OXD-Ph [Figure 3-26] XRD patterns of PPX-OXD-CF3 [Figure 3-27] PYSA results of PPX-OXD-Ph [Figure 3-28] PYSA results of PPX-OXD-CF3 [Figure 3-29] AFM images of PPX-OXD-Ph before and after immersion in DCM [Figure 3-30] AFM images of PPX-OXD-CF3 before and after immersion in DCM [Modes for carrying out the invention]

[0018] Outline of the method for carrying out the invention The guideline for this invention is to synthesize parylene into which an OXD derivative has been introduced and to investigate its physical properties. In this study, the monomer [2,2]-paracycrophane into which an OXD derivative had been introduced was synthesized, and parylene of the following [Chemical Formulas 1-5] and [Chemical Formulas 1-6] was polymerized by CVD. The physical properties of the resulting parylene, such as thermal and electrical properties, were measured and their characteristics were evaluated. Furthermore, by synthesizing parylene with different substituents, the differences in properties due to substituents will be evaluated. [ka] Structure of PPX-OXD-Ph [ka] Structure of PPX-OXD-CF3

[0019] Furthermore, parylene in [Chemical Formula 1-7] is polymerized as described in the examples. [ka]

[0020] Theoretical background of the invention Chemical vapor deposition (CVD) method CVD (Chemical Vapor Deposition) is a vapor deposition method for forming thin films, using a gas-phase chemical reaction to create a film on a substrate. It involves reacting raw material gases under vacuum conditions using heat, light, or plasma, and allowing the gases to adsorb onto the substrate surface, thus forming the film. When forming a parylene film, heating the raw material (dimer) under vacuum conditions vaporizes it into a dimer gas. This gas then undergoes thermal decomposition, causing the dimer to cleave and become monomers. These monomers then polymerize on the substrate surface, forming a thin-film polymer.

[0021] Atomic force microscope (AFM) The attractive or repulsive force acting between the probe and the sample surface is converted into the displacement of the cantilever. When the probe experiences an attractive force, the cantilever is displaced toward the sample; when it experiences a repulsive force, it is displaced in the opposite direction from the sample. Laser light is shone onto the back of this cantilever, and the displacement is detected by the reflected light. By controlling the distance between the probe and the sample while moving horizontally to keep this displacement constant, the surface shape is imaged.

[0022] Fourier transform infrared spectroscopy (FT-IR) method When infrared light is shone on a molecule, if the vibration period of the infrared light matches the vibration period of the atom, individual atoms and atomic groups absorb energy according to their respective periods, and their vibrations change from the ground state to an excited state. This absorption appears as absorption in the infrared spectrum. Since molecules have unique vibrations depending on their structure, analyzing the spectrum can provide information about the molecular structure and the state of the material.

[0023] Ultraviolet-visible spectroscopy (UV-vis) method This analytical method utilizes the absorption of light due to electronic transitions in the sample. The sample is irradiated with ultraviolet and visible light, and the transmitted light intensity is measured to determine the absorption spectrum of the sample. The transmittance T and absorbance A are calculated from the transmitted light intensity using the following formulas.

number

[0024] absorbance The absorbance A is given by the following equation, known as the Lambert-Beer law:

number

[0025] Differential Scanning Calorimetry (DSC) The temperature difference between a reference substance and a sample being measured is measured when they are heated simultaneously. From this, endothermic and exothermic reactions due to phase transitions such as crystallization and melting of the sample can be measured. If the furnace temperature is increased at a constant rate, both the reference substance and the sample being measured will rise at the same rate. If an endothermic reaction occurs in the sample being measured, the temperature rise of the sample will stop during the reaction, and a temperature difference will be created between it and the reference substance. Since the amount of heat flowing into the sample per unit time is proportional to the temperature difference between the sample being measured and the reference substance, the amount of heat for the reaction can be determined by integrating the temperature difference with respect to time.

[0026] Cyclic voltammetry (CV) By immersing an electrode in a stationary sample solution and repeatedly sweeping the potential, the change in response current can be measured. By analyzing the resulting current-potential curve (cyclic voltagram), information such as the oxidation-reduction potential, the reaction rate of the electrode, the diffusion constant of the reactants, and the HOMO / LUMO of organic compounds can be obtained.

[0027] X-ray diffraction (XRD) method When X-rays are irradiated onto a crystal, the X-rays are scattered by the electrons of each atom in the crystal (scattered X-rays). Scattered X-rays interfere with each other and reinforce each other in specific directions. The direction in which scattered X-rays reinforce depends on the path difference due to the spacing between adjacent planes. Given the atomic spacing (lattice plane spacing) d and the angle of incidence as θ, the path difference between the first and second planes is 2dsinθ. When the path difference is an integer multiple of the wavelength λ of the incident X-rays, reinforcement occurs, and Bragg's law, as given by the following equation, holds true.

number

[0028] Photoelectron yield spectroscopy (PYSA) in air When ultraviolet light is irradiated onto a material surface, electrons are emitted. These electrons are called photoelectrons, and the number emitted varies depending on the energy of the ultraviolet light. The PYSA instrument is a surface analysis instrument that counts photoelectrons in the atmosphere using a counter tube called an open counter. White ultraviolet light emitted from the light source is spectrally separated by a spectrometer, and monochromatic ultraviolet light is irradiated onto the sample. By operating the spectrometer and increasing the energy of the ultraviolet light, photoelectrons are emitted from the sample material when the energy exceeds the work function. Therefore, by finding the threshold energy at which photoelectron emission begins, the work function or ionization potential can be determined. [Examples]

[0029] Experimental method synthesis 4-carboxylic acid-[2,2]-paracyclophane (PCP-COOH) (Non-patent Document 16) [ka]

[0030] 20 mL of dichloromethane (super-dehydrated) and aluminum chloride (1.28 g, 9.60 mmol, 1.9 eq) were added to a 100 mL round-bottom flask and cooled to -10°C under a nitrogen atmosphere. Oxalyl dichloride (0.8 mL, 9.13 mmol, 1.9 eq) was added dropwise and stirred for 5 minutes, then [2,2]-paracyclophane (1.02 g, 4.82 mmol) was added and stirred for 30 minutes. Ice and dichloromethane were added, liquid-liquid extraction was performed and the organic layer was extracted. Dehydration was performed using magnesium sulfate to remove the solvent, then 20 mL of chlorobenzene was added and refluxed for 3 days. After solvent removal, a mixed solvent of methanol and dichloromethane (3:1) was added, stirred overnight at room temperature, and then refluxed for 2 days. After solvent removal, the solution was purified by column chromatography (silica, solvent: dichloromethane). The obtained solid was placed in a test tube, and 4 mL of 5.6 M sodium hydroxide aqueous solution and 20 mL of THF were added. After refluxing overnight, water was added and refluxed for 3 days. The mixture was filtered, acetic acid was added to the filtrate, the precipitate was collected by filtration and dried to obtain the target product. The yield was 0.62 g, and the yield was 50.8%.

[0031] HR-ESI-TOF-MS:m / z 253.1172 (calad:m / z 253.1223)

[0032] The mass spectra of PCP-COOH are shown in Figure 2-1.

[0033] 4-(2-Phenyl-1,3,4-Oxadiazole)-[2,2]-paracyclophane (PCP-OXD-Ph) (Non-patent Documents 17-19) [ka]

[0034] In a 50 mL eggplant-shaped flask, Benzoyl hydrazine (0.20 g, 1.47 mmol, 1.2 eq) was placed inside a glove box, taken out of the glove box, PCP-COOH (0.30 g, 1.19 mmol) was added, nitrogen substitution was carried out, 10 mL of phosphoryl chloride was added, and reflux was carried out overnight. Then, ice was added to the reaction solution, liquid separation was performed with dichloromethane, and the organic layer was extracted. After removing the solvent, column chromatography (silica, solvent: dichloromethane) was carried out, the solvent was removed, and the target product was obtained by sublimation purification. The yield was 0.26 g and the yield rate was 62.5%.

[0035] 1H NMR: (400 MHz, CDCl3) δ[ppm] =8.18 (m, 2H, H Ph-OXD , J=2.44Hz), 7.58(m, 3H, H Ph-OXD , J=2.23), 7.18 (d, 1H, H Ar , J=1.62Hz), 6.73-6.40 (m, 6H, H Ar , J=8.68Hz), 3.24-2.97(m, 8H,H PC , J=5.80) 13C NMR:(101 MHz, CDCl3) δ[ppm] =165.0(C OXD ), 164.2(C OXD ), 140.5(C Ar ), 139.8(C Ar ), 139.4(C Ar ), 136.4(C Ar ), 135.6(C Ar ), 133.2(C Ar ), 133.1(C Ar ), 132.2(C Ar ), 131.7(C Ar ), 130.8(C Ph ), 129.1(C Ph ), 126.9(C Ph ), 124.1(C Ph ), 35.5(CH2), 35.2(CH2), 35.0(CH2), 34.4(CH2). HR-ESI-TOF-MS:m / z 353.1645 (calad:m / z 353.1648)

[0036] 1 Figure 2-2 shows the 1H-NMR spectra of PCP-OXD-Ph in CDCl3. 13 The 1C-NMR spectra of PCP-OXD-Ph in CDCl3 are shown in Figure 2-3. The mass spectra of PCP-OXD-Ph are shown in Figure 2-4.

[0037] 4-[2-(4-trifluoromethylphenyl)-1,3,4-Oxadiazole]-[2,2]-paracyclophane (PCP-OXD-CF3) [ka]

[0038] 4-(trifluoromethyl)-Benzoylhydrazine (0.30 g, 1.43 mmol, 1.2 eq) was placed in a 50 mL round-bottom flask in a glove box. After removing the flask from the glove box, PCP-COOH (0.30 g, 1.19 mmol) was added, nitrogen purging was performed, and 10 mL of phosphoryl chloride was added. The mixture was refluxed overnight. Ice was then added to the reaction solution, and the mixture was separated with dichloromethane to extract the organic layer. After solvent removal, column chromatography (silica, solvent: ethyl acetate) was performed, the solvent was removed, and the target product was obtained by sublimation purification. The yield was 0.28 g, and the yield was 56%.

[0039] 1H NMR: (400 MHz, CDCl3) δ[ppm] =8.31 ​​(d, 2H, H Ph-OXD, J=8.10Hz), 7.84(d, 2H, H Ph-OXD , J=8.20Hz), 7.18 (d, 1H, H Ar , J=1.80), 6.74-6.39 (m, 6H, H Ar, J=7.59Hz), 3.25-2.99(m, 8H, H PC (J=4.31Hz) 13C NMR:(101 MHz, CDCl3) δ[ppm] =165.5(C OXD ), 163.1(CF3), 140.6(C Ar ), 139.8(C Ar ), 139.4(C Ar ), 136.5(C Ar ), 135.9(C Ar ), 133.2(C Ar ), 133.1(C Ar ), 132.2(C Ar ), 131.7(C Ar ), 130.8(C Ph ), 127.2(C Ph ), 126.2(C Ph ), 126.1(C Ph ), 35.5(CH2), 35.2(CH2), 35.0(CH2), 34.4(CH2). HR-ESI-TOF-MS:m / z 421.1461 (calad:m / z 421.1552)

[0040] 1 The 1H-NMR spectra of PCP-OXD-CF3 in CDCl3 are shown in Figure 2-5. 13 The 1C-NMR spectra of PCP-OXD-CF3 in CDCl are shown in Figure 2-6. The mass spectra of PCP-OXD-CF3 are shown in Figure 2-7.

[0041] 4-[2-(3,5-bistrifluoromethylphenyl)-1,3,4-Oxadiazole]-[2,2]-paracyclophane (PCP-OXD-bisCF3)

[0042] [ka]

[0043] 3,5-(bistrifluoromethyl)-Benzoylhydrazine (0.40 g, 1.43 mmol, 1.2 eq) was placed in a 50 mL round-bottom flask in a glove box. After removing it from the glove box, PCP-COOH (0.30 g, 1.19 mmol) was added, nitrogen purging was performed, and 10 mL of phosphoryl chloride was added. The mixture was refluxed overnight. Ice was then added to the reaction solution, and the mixture was separated with dichloromethane to extract the organic layer. After solvent removal, column chromatography (silica, solvent: ethyl acetate) was performed, the solvent was removed, and the target product was obtained by sublimation purification. The yield was 0.12 g, and the yield was 21%.

[0044] 1H NMR:(400 MHz, CDCl3) δ[ppm] =8.60 (s, 2H, HPh-OXD), 8.08(s, 1H, HPh-OXD), 7.18 (s, 1H, HAr), 6.76-6.38 (m, 6H, HAr), 3.26-3.06(m, 8H, HPC) 13C NMR:(101 MHz, CDCl3) δ[ppm] =165.8(COXD), 161.9(CF3), 140.9(CAr), 139.8(CAr), 139.5(CAr), 136.5(CAr), 136.2(CAr), 133.2(CAr), 133.2(CAr), 132.9(CAr), 132.2(CAr), 130.7(CPh), 126.8(CPh), 126.2(CPh), 126.3(CPh), 35.7(CH2), 35.3(CH2), 35.1(CH2), 34.5(CH2)

[0045] 1 Figure 2-8 shows the 1H-NMR spectra of PCP-OXD-bisCF3 in CDCl3. 13 The 1C-NMR spectra of PCP-OXD-bisCF3 in CDCl3 are shown in Figure 2-9.

[0046] Film forming 150 mg each of PCP-OXD-Ph and PCP-OXD-CF3 were used to deposit films on Si wafers, quartz glass, aluminum films, and ITO substrates. The deposition conditions were a vaporizer temperature of 650°C, a furnace temperature of 175°C, and a chamber pressure of 30 mtorr.

[0047] <Results and Discussion> AFM measurement The surface morphology of the PPX-OXD-Ph film and the PPX-OXD-CF3 film on a Si wafer was measured by AFM. The results are shown in Figure 3-1. Figure 3-1: AFM image of PPX-OXD-Ph and PPX-OXD-CF3

[0048] The average roughness of the PPX-OXD-Ph film and the PPX-OXD-CF3 film was 1.43 nm and 1.00 nm, respectively, with maximum height differences of 12.13 nm and 25.81 nm, respectively. The PPX-OXD-Ph film showed no significant surface irregularities and formed a uniform film. The PPX-OXD-CF3 film had some particle adhesion, but the rest of the film was uniform.

[0049] IR measurement IR measurements were performed on PCP-OXD-Ph and PPX-OXD-Ph films, and PCP-OXD-CF3 and PPX-OXD-CF3 films. The results are shown in Figures 3-2 and 3-3 below. Figure 3-2: FT-IR spectra of PCP-OXD-Ph and PPX-OXD-Ph Figure 3-3: FT-IR spectra of PCP-OXD-CF3 andPPX-OXD-CF3

[0050] In PCP-OXD-Ph and PPX-OXD-Ph films, the 3000 cm² originates from the CH stretching vibration of the benzene ring. -1 Nearby peak, 1500 cm, originating from C=C stretching vibrations of the benzene ring. -1 Nearby peak, 1450 cm, originating from the C=N stretching vibration of oxadiazole. -1Nearby peak, 1050 cm, originating from COC stretching vibration of oxadiazole. -1 Nearby peaks were observed. In addition, in the PCP-OXD-CF3 and PPX-OXD-CF3 films, in addition to these peaks, a peak of 1300 cm originating from CF stretching vibration was observed. -1 A nearby peak was identified. (Non-patent document 20)

[0051] 3-3 TD-DFT calculation DFT calculations were performed for PCP-OXD-Ph, PPX-OXD-Ph, PCP-OXD-CF3, and PPX-OXD-CF3. Figures 3-4 to 3-9 show the appearance of the structural optimization and molecular orbitals obtained by DFT calculations. Figure 3-4: Simulated molecular geometries of PCP-OXD-Ph Figure 3-5:Molecular orbital of PCP-OXD-Ph Figure 3-6: Simulated molecular geometries of PPX-OXD-Ph Figure 3-7: Simulated molecular geometries of PCP-OXD-CF3 Figure 3-8: Molecular orbital of PCP-OXD-CF3 Figure 3-9: Simulated molecular geometries of PPX-OXD-CF3

[0052] The predicted molecular orbitals indicate that the oxadiazole portion is electron-deficient compared to the cyclophane portion. Therefore, it is suggested that the OXD derivative possesses electron-transporting properties.

[0053] Next, the UV-vis absorption spectra and molecular orbital energy levels obtained by TD-DFT calculations are shown in Figures 3-10 to 3-15. Figure 3-10: Calculated UV-vis adsorption spectra of PCP-OXD-Ph Figure 3-11: Calculated UV-vis adsorption spectra of PPX-OXD-Ph Figure 3-12: Calculated UV-vis adsorption spectra of PCP-OXD-CF3 Figure 3-13: Calculated UV-vis adsorption spectra of PPX-OXD-CF3 Figure 3-14: Calculated energy levers of PCP-OXD-Ph(←) and PPX-OXD-Ph(→) Figure 3-15: Calculated energy levers of PCP-OXD-CF3(←) and PPX-OXD-CF3(→)

[0054] PCP-OXD-Ph and PCP-OXD-CF3 showed peaks at 303 nm and 310 nm, respectively, while PPX-OXD-Ph and PPX-OXD-CF3 showed peaks at 293 nm and 292 nm, respectively. The polymers showed peaks at shorter wavelengths than the monomers. Therefore, it can be inferred that the band gap is higher for polymers. Furthermore, from the energy level diagram, it can be seen that the HOMO·LUMO energies are lower for both monomers and polymers that have CF3 groups.

[0055] 3-3 UV-Vis measurement UV-vis measurements were performed on PCP-OXD-Ph and PCP-OXD-CF3 (solvent: dichloromethane), as well as on PPX-OXD-Ph films and PCP-OXD-CF3 on quartz glass. The results are shown in Figures 3-16 to 3-17. Figure 3-16:UV-visible absorption spectrum of PCP-OXD-Ph and PPX-OXD-Ph Figure 3-17: UV-visible absorption spectrum of PCP-OXD-CF3 and PPX-OXD-CF3

[0056] The peaks for PCP-OXD-Ph and PCP-OXD-CF3 were at 307 nm and 309 nm, respectively. This is consistent with the UV-vis absorption spectra obtained by TD-DFT calculations. Although no peaks appeared for PPX-OXD-Ph and PPX-OXD-CF3 due to their thin film nature, their rise wavelengths were similar to those of PCP-OXD-Ph and PCP-OXD-CF3, suggesting that the polymer was deposited on the substrate.

[0057] 3-4 DSC measurement DSCs were measured for PCP-OXD-Ph and PPX-OXD-Ph films, and PCP-OXD-CF3 and PPX-OXD-CF3 films. The results are shown in Figures 3-18 to 3-19. Figure 3-18: DSC results of PCP-OXD-Ph and PPX-OXD-Ph Figure 3-19: DSC results of PCP-OXD-CF3 and PPX-OXD-CF3

[0058] PCP-OXD-Ph melted at 137.3°C, but no melting was observed in the PPX-OXD-Ph film at around this temperature. Therefore, it was found that the PPX-OXD-Ph film has improved thermal stability compared to PCP-OXD-Ph. Furthermore, PCP-OXD-Ph-CF melted at 165.1°C, indicating higher thermal stability than PCP-OXD-Ph.

[0059] 3-5 TGA measurement The TG of the PPX-OXD-Ph film and the PPX-OXD-Ph film was measured. The results are shown in Figure 3-20. Figure 3-20: TGA results of PPX-OXD-Ph and PPX-OXD-CF3

[0060] The PPX-OXD-Ph film and the PPX-OXD-CF3 film exhibited little mass loss up to around 470°C, and the TGA results also indicated high thermal stability.

[0061] 3-6 Contact angle measurement When the PPX-OXD-Ph film and the PPX-OXD-Ph-CF3 film were deposited on a silicon wafer and their contact angles were measured, it was found that the wettability was similar, with the PPX-OXD-Ph film measuring 81.5° and the PPX-OXD-CF3 film measuring 83.1°. Figures 3-21 to 3-22 show the appearance of water droplets dropped onto each film. Figure 3-21: Contact angle image of PPX-OXD-Ph Figure 3-22: Contact angle image of PPX-OXD-CF3

[0062] 3-7 CV measurement and DPV measurement CV and DPV measurements were performed on PCP-OXD-Ph and PCP-OXD-CF3. Tetrabutylammonium tetrafluoroborate (TBABF4) was used as the supporting electrolyte, and DMF was used as the solvent. Measurements were also performed using carbon and platinum working electrodes, respectively. The results are shown in Figures 3-23 to 3-24. Figure 3-23: Cyclic voltammograms (scan rate 0.05V / s) Figure 3-24: Differential pulse voltammograms

[0063] Furthermore, the LUMO for each peak was calculated using the following formula.

number

[0064] LUMO by Differential pulse voltammograms [Table 3-2]

[0065] PCP-OXD-CF3 showed a lower LUMO than PCP-OXD-Ph. This is consistent with the results of TD-DFT calculations. Furthermore, since the LUMO of OXD derivatives of typical electron transport materials is -2.5 to -2.9 eV (Non-Patent Documents 21 to 22), it is expected to possess electron transport properties.

[0066] 3-8 XRD measurement XRD was performed on PPX-OXD-Ph and PPX-OXD-CF3 films. The results are shown in Figures 3-25 to 3-26. Figure 3-25: XRD patterns of PPX-OXD-Ph Figure 3-26: XRD patterns of PPX-OXD-CF3

[0067] The peaks for the PPX-OXD-Ph and PPX-OXD-CF3 films are broad, confirming that these films are amorphous and lack crystalline properties.

[0068] 3-9 PYSA Measurement PYSA measurements were performed using PPX-OXD-Ph and PPX-OXD-CF3 films on an ITO substrate. The results are shown in Figures 3-27 to 3-28. The horizontal axis represents the irradiation light energy, and the vertical axis represents the amount of photoelectrons emitted. Figure 3-27:PYSA results of PPX-OXD-Ph Figure 3-28:PYSA results of PPX-OXD-CF3

[0069] Furthermore, the work functions of PPX-OXD-Ph and PPX-OXD-CF3 were 5.24 eV and 5.31 eV, respectively, with PPX-OXD-Ph-CF having a higher value. The work function of typical electron transport materials is 5.2 to 5.9 eV (Non-Patent Literature 23). From these results, it can be expected that PPX-OXD-Ph and PPX-OXD-CF3 possess electron transport properties.

[0070] 3-10 Solvent Test The solvent resistance of PCP-OXD-Ph and PPX-OXD-CF3 films on silicon wafers was investigated by immersing them in dichloromethane, washing them with methanol, drying them, and then observing their surface morphology using AFM. The results are shown in Figures 3-29 to 3-30. Figure 3-29: AFM images of PPX-OXD-Ph before and after immersion in DCM Figure 3-30: AFM images of PPX-OXD-CF3 before and after immersion in DCM

[0071] Since there was no significant change in average roughness before and after immersion, it was confirmed that the materials had high chemical stability. [Industrial applicability]

[0072] In this invention, two types of monomer [2,2]-paracycrophane were synthesized by introducing an OXD derivative, and parylene film formation by CVD was confirmed by AFM, IR, and UV-vis measurements. These parylenes, PPX-OXD-Ph and PPX-OXD-CF3, were confirmed to have high thermal and chemical stability. Furthermore, it was suggested that they possess electron transport properties.

[0073] The present invention provides novel and useful organic semiconductor materials utilizing parylene and methods for producing the same.

Claims

1. An electron transport material comprising an oxadiazole derivative having a parylene structure, characterized in that the oxadiazole derivative is represented by the following formula (X), (Y), or (Z). 【Chemistry 1-1】 (n is a number representing the degree of polymerization) 【Chemistry 2-1】 (n is a number representing the degree of polymerization) 【Chemistry 3-1】 (n is a number representing the degree of polymerization)

2. An electron transport material comprising one or more oxadiazole derivatives having a parylene structure as constituent materials, characterized in that the oxadiazole derivative is represented by the following formula (X), (Y), or (Z). 【Chemistry 1-2】 (n is a number representing the degree of polymerization) 【Chemistry 2-2】 (n is a number representing the degree of polymerization) 【Chemistry 3-2】 (n is a number representing the degree of polymerization)

3. A method for producing an oxadiazole derivative having a parylene structure, comprising the following steps (1), (2), (3), and (4). Step (1): A step to produce 4-Carboxylic acid-[2,2]-paracyclophane from 4-Methoxycarbonyl-[2,2]-paracyclophane. 【Chemistry 4】 Step (2): A step to produce 4-(2-Phenyl-1,3,4-Oxadiazole)-[2,2]-paracyclophane (monomer 1) from 4-Carboxylic acid-[2,2]-paracyclophane. 【Transformation 5】 Step (3): A step to produce 4-[2-(4-trifluoromethylphenyl)-1,3,4-Oxadiazole]-[2,2]-paracyclophane (monomer 2) from 4-Carboxylic acid-[2,2]-paracyclophane. 【Transformation 6】 Step (4): A step to produce 4-[2-(3,5-bistrifluoromethylphenyl)-1,3,4-Oxadiazole]-[2,2]-paracyclophane (monomer 3) from 4-Carboxylic acid-[2,2]-paracyclophane. 【Transformation 7】 Step (5): A step to produce polymers X, Y, and Z from monomers 1, 2, and 3 by CVD. 【Transformation 8】 (n is a number representing the degree of polymerization) 【Chemistry 9】 (n is a number representing the degree of polymerization) 【Chemistry 10】 (n is a number representing the degree of polymerization)

4. An electron transport system using the electron transport material according to either Claim 1 or 2.

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