KR100652863B1 - Silica-Polyimide Hybrid and Method for making the same - Google Patents

Abstract

A silica-polyimide hybrid is disclosed wherein 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS) are applied to a colorless transparent polyimide. Thermal stability and optical properties are better than the existing polyimide, and when AZO is sputtered as the substrate of the organic electroluminescent device, the optical and electrical properties can be improved more remarkably than the conventional polyimide.

Hybrid, 6FDA, OLED, AZO, Polyimide, Achromatic

Description

Silica-Polyimide Hybrid and Method for making the same             

1 is a structure of silica-polyimide for an organic electroluminescent device substrate prepared in the present invention.

2 is a schematic of the synthesis of silica-polyimide of the present invention.

3 shows the FT-IR spectrum of 6FDA-TFDB polyimide and silica-polyimide film.

Figure 4 shows the transmission by the ultraviolet spectroscopy of 6FDA-TFDB polyimide and hybrid 1-3, hybrid 1-4, hybrid 2-2.

Figure 5a shows the tan delta data of 6FDA-TFDB polyimide and hybrid 1-3, hybrid 1-4.

5b shows tan delta data of 6FDA-TFDB polyimide and hybrid 2-1 and hybrid 2-2.

FIG. 6 shows the transmittance by UV spectroscopy of AZO sputtered films and thin films made of ITO-glass in each of glass, 6FDA-TFDB polyimide, and hybrids 1-4.

FIG. 7 shows the X-ray diffraction change of the film sputtered with AZO on 6FDA-TFDB polyimide, hybrid 1-3, hybrid 1-4, and glass substrate, respectively.

The present invention relates to a silica-polyimide hybrid for an organic electroluminescent device having excellent optical and thermal properties and a method of manufacturing the same.

The organic electroluminescent device, which is one of the most popular thin film display technologies, combines the light injected from the anode and the electron injected from the cathode to emit light. The organic electroluminescent device has the advantage of faster response speed than other displays and the light emitting form, so it has excellent brightness, light and thinness, and has an advantage of facilitating the manufacturing process according to the light emitting material used (H. Lim, WJ Cho, CS Ha, Vol. 12, No. 6, 18-34.

These advantages can be used in the form of a number of displays, the most popular of these is the study of flexible organic electroluminescent devices. This research uses the electroluminescent device substrate as a polymer, making it lighter than conventional electroluminescent devices, making it easy to carry and allowing the manufacture of rollable displays.

In order for this to be commercialized, many parts such as fatigue-resistant electrodes, light emitting materials, holes, and electron transfer materials must be studied, but above all, research on flexible display substrates must be conducted.

In the case of the substrate of the electroluminescent device, sufficient thermal stability and colorless and transparent optical properties are required when depositing the anode material thereon. Currently, polymers such as polyethylene terephthalate (PET), polycarbonate (PC), polypropylene adipate (PPA), and polyimide (PI) are mainly studied (H. Lim, WJ Cho, CS Ha, S). Ando, YK Kim, CH Park and K. Lee, Adv. Mater ., 18, 14 (2002)).

However, most polymers have many difficulties in being used as a substrate of an electroluminescent device requiring a deposition temperature of 250 ° C. or higher. In addition, the moisture absorption rate and the oxygen absorption rate are important factors for maintaining the lifespan and efficiency of the electroluminescent device, and the polymers do not satisfy the values of glass substrates used in the past (A. Sugimoto, H. Ochi , S. Fujimura, A. Yoshida, T. Miyadera and M. Tsuchida, IEEE J. SELECTED TOPICS IN QUANTUM ELECTRONICS , 10, 1, 107-114).

Among them, polyimide has a strong thermal property and has sufficient advantages to be used as a flexible substrate, but due to the polyimide-specific structure, it has a yellow color and thus is insufficient to satisfy the property of a colorless substrate.

In addition, when the polymer substrate is used, since the cathode material is an inorganic material, there is a difficulty in that the cathode material is not deposited well due to the difference in the interfacial adhesion between the organic polymer.

Indium oxide (ITO) is typically used as a cathode material of organic electroluminescent devices (I. Hamberg and CG Granqvist, J. Appl. Phys. , 60, R123 (1986), H. Kim, CM Gilmore). , A. Pique, JS Horwitz.H. Mattoussi, H. Murata, ZH Kafafi, and DB Chrisey, J. Appl. Phys. , 86, 6451 (1999)). This material has excellent electrical and optical properties, and is used in various electric material fields as well as display electrodes.

However, this electrode material also has the disadvantage of being easy to oxidize and high price due to the low amount of indium on the earth. Recently, aluminum-added zinc oxide (AZO) has been studied as an alternative transparent electrode material. This anode material is slightly lower in electrical properties than conventional ITO, but has excellent optical properties, is resistant to active hydrogen environment, does not oxidize well, and is much cheaper than ITO due to its high amount of abundant earth (H. Kim, JS Horwitz, WH Kim). , AJ Makinen, ZH Kafafi, DB Chrisey, Thin Solid Films, 420 -421 (2002) 539.543).

It is an object of the present invention to provide a colorless and transparent silica-polyimide hybrid having better thermal stability and optical properties than conventional polyimide.

Another object of the present invention is to provide a silica-polyimide hybrid substrate having improved electrical and optical properties by imparting inorganic properties to polyimide, which is an organic material, to improve adhesion to an anode material, which is an inorganic material.

It is still another object of the present invention to provide a silica-polyimide hybrid substrate having improved device stability through a new anode material called AZO instead of the existing anode material ITO.

Other objects and features of the present invention will be clearly understood through the preferred embodiments described below.

The inventors of the present invention synthesized a flexible organic electroluminescent device substrate material having excellent thermal properties, colorless and transparent by introducing a heat-resistant, colorless and transparent polyimide in order to solve the above-mentioned conventional problems, the 3-aminopropyl Introduced silica-polyimide hybrid system using triethoxysilane (aminoTEStriethoxysilane (APTES) and tetraethoxysilane (TEOS) to impart inorganic properties to organic polyimide, thereby interfacial adhesion with inorganic cathode material Improved sex.

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

According to the present invention, the dianhydride required for synthesizing colorless transparent polyimide is 2,2'-bis- (3,4-carboxyphenyl) hexafluoropropane dianhydride. (hexafluoropropane dianhydride; 6FDA) and diamine was used as 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl; TFDB) was used to synthesize the original polyimide, and 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS) were used to prepare the silica-polyimide hybrid.

Targets of aluminum-added zinc oxide (AZO) for sputtering were those made of aluminum 10w / w and zinc oxide 90w / w.

First, in order to synthesize a polyimide, the above monomers are used to add an equivalent mole of diamine dianhydride to react with N, N-dimethylacetamide (DMAc) under a nitrogen stream to form a polyamic acid. The temperature is reacted at room temperature, preferably at 60 ° C and more preferably about 40 ° C at room temperature.

The polyamic acid thus prepared may be thermally cured and imidized, or imidized by a chemical method using a catalyst.

In this example, the polyimide of Chemical Formula 1 is produced by thermosetting method.

On the other hand, it is possible to produce a colorless transparent polyimide using the other monomers through the same process, which is represented by the formula (2) to (8).

As dianhydride, BHDA can be applied in addition to 6FDA, and in addition to TFDB, 1,4 (4) -APB, 1,3 (4) -APB, 4,4-BAPS (4APPS), 3ADF, and DDSO ₂ , 4BDAF or 3,3'-ODA can be applied.

The silica-polyimide hybrid is made of polyamic acid under the above conditions by matching the number of functional groups by moles of dianhydride and the number of functional groups by moles of diamine and APTES, and by adding TEOS and distilled water to silica-polya The mixed acid is prepared and then the silica-polyimide shown in FIG. 1 is produced through a thermosetting method.

In FIG. 1, black bars are replaced for the convenience of the display by replacing the chemical formula at the top.

The AZO film was prepared by sputtering AZO on the thus prepared polyimide and silica-polyimide.

Experimental Example 1

0.64046 g of TFDB is dissolved in 8 ml of DMAc and stirred under a stream of nitrogen. To this is added 0.8885 g of 6FDA. After the addition, the reaction is carried out at room temperature under nitrogen stream for 12 hours. 6FDA-TFDB polyimide was made by thermal curing at 80 ° C. for 6 hours at 100 ° C., 1 hour at 100 ° C., 1 hour at 150 ° C., 1 hour at 200 ° C., and 1 hour at 250 ° C. The temperature rise time for each step of thermal curing is 1 hour.

Experimental Example 2

2 is a flowchart illustrating a process of generating a silica-polyimide hybrid according to an embodiment of the present invention.

First, the diamine of a hybrid polyimide is dissolved in 8 ml of DMAc by the corresponding amount, and stirred for about 1 hour under a nitrogen stream (step S21).

0.8885 g of 6FDA is added thereto (step S22).

After stirring the solution for 1.5 hours, APTES of the hybrid polyimide was added to the solution by the corresponding amount, followed by stirring for 12 hours under a stream of nitrogen (step S23).

TEOS and distilled water were added to the prepared solution by a corresponding amount, and stirred for 6 hours under the same conditions to prepare silica-polyamic acid (step S24).

At this time, as shown in Table 1, various kinds of polyimides of different kinds according to APTES and silica content are prepared.

Thereafter, a silica-polyimide hybrid is produced through a thermosetting step similar to Experimental Example 1 (step S25) (step S26).

Referring to FIG. 1, it was confirmed that the peak of the hydroxy group disappeared and the imide structure peak appeared in the synthesis of polyimide. In the silica-polyimide hybrid, the intensity of the peak of Si-O-Si was increased as the content of silica increased. It can be seen that is counted. This confirmed that the polyimide and silica-polyimide hybrid was successfully synthesized.

3 shows the FT-IR spectrum of 6FDA-TFDB polyimide and silica-polyimide film.

Through the UV spectroscopic measurement results of Figure 3 it can be seen that the silica-polyimide hybrid has improved transmittance according to the silica content than the conventional polyimide. This is due to the reduction of the intermolecular and intramolecular charge transfer complex generation of the silica-polyimide hybrid film. As the silica molecules increase the free volume between the polymers in the film, the following increase in permeability occurs.

5a and 5b are measured the dynamic thermo-mechanical properties of the silica-polyimide hybrid through a rheometer, this data also shows that the glass transition temperature increases with increasing silica content as shown in FIG. I can see it. This is because silica molecules act as a bridge between polymers, that is, crosslinks, thereby improving thermal properties than conventional polyimides.

It can be seen that the hybrid 2 of FIG. 5b is more improved than the hybrid 1 of FIG. 5a even though the silica content is the same, which is due to the difference in A / T (APTES / TEOS) ratio. Since the content of APTES is large, the degree of crosslinking is lower than that of Hybrid 2. Thus, the improvement of the properties is shown.

Application example

Prepared polyimide (6FDA-TFDB PI) and silica-polyimide hybrid (Silica-6FDA-TFDB PI hybrid) using a radio wave (13.56MHz) magnetron sputtering to a substrate temperature of 250 ℃ and the substrate and The distance from the target was 60 mm, the oxygen partial pressure was 10-7 Torr, the argon partial pressure was 2.6 mTorr, and sputtered at 100 watts for 10 minutes to prepare an AZO film having a thickness of about 300 nm.

Figure 4 shows the transmission by the ultraviolet spectroscopy of 6FDA-TFDB polyimide and hybrid 1-3, hybrid 1-4, hybrid 2-2.

The UV spectroscopy data of FIG. 4 show the difference in transmittance between AZO-polyimide and AZO-hybrid 1-4. The hybrid film has higher transmittance when forming AZO film than conventional polyimide. This shows that the hybrid film is better deposited than the existing polyimide under the same deposition conditions.

In addition, referring to Table 2, hybrid 1-4 calculates the average transmittance value in the visible light region (400-700 nm) that can be seen on the display, such as other films sputtered on glass, for example, AZO-glass or It can be seen that there is little difference from commercially available ITO-glass. In addition, when comparing ITO deposited film with AZO deposited film, AZO film shows better transmittance.

In addition, referring to [Table 2], it can be seen that the sheet resistance value decreases as the content of silica increases in the hybrid rather than the polyimide. This means that under the same sputtering conditions as mentioned in FIG. 4, the hybrid produces a better structure, which can be seen in the X-ray diffractometer of FIG.

In addition, ITO compared with AZO, the better the sheet resistance value, showing that AZO as an alternative anode material of ITO in electrical properties.

The data of the X-ray diffraction apparatus of FIG. 6 may support the improvement of the sheet resistance mentioned above. The better the deposition and the better structure of the AZO film, the better the electrical properties and the stronger the intensity of the (002) plane peak (Xiao-Tao Hao, Xiang-Dong Liu, Materials Science and Engineering, B90 (2002)). 50-54), in Figure 6 it can be seen that the peak intensity of the hybrid film of polyimide is stronger.

These electrical and optical properties can be explained comprehensively through the figure of merit, which is important data indicating the utility and stability of transparent conducting electrodes such as ITO and AZO. When comparing the values of AZO-polyimide and AZO-hybrid through [Table 2], it can be seen that the value of AZO-hybrid is significantly improved. In addition, it can be confirmed that even better compared with the value of the ITO-polyimide.

Although the above has been described with reference to the preferred embodiments of the present invention, various changes and modifications can be made without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be limited to the above embodiments, but should be determined by the claims described below.

As described in detail above, the newly synthesized silica-polyimide hybrid has better thermal stability and optical properties than conventional polyimide, and is more remarkable than conventional polyimide when sputtering AZO as a substrate of an organic electroluminescent device. You can see the effect of improving the.

In addition, when AZO is used instead of ITO, it can be confirmed that the optical and electrical properties required as the anode material of the organic electroluminescent device are very excellent.
Such materials can be applied not only to organic electroluminescent devices but also to OTFTs and semiconductor substrates.

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Claims (6)

3-aminopropyltriethoxysilane (APTES) was added to the colorless transparent polyimide, followed by stirring. Distilled water and tetraethoxysilane (TEOS) were added to form silica-polyamic acid. Silica-polyimide hybrid characterized by. 2. The silica-polyimide hybrid according to claim 1, wherein the colorless transparent polyimide is dissolved in diamine in DMAc and stirred under a stream of nitrogen, and dianhydride is added to the stirred diamine. A silica-polyimide hybrid substrate produced by sputtering aluminum-added zinc oxide (AZO) to the silica-polyimide hybrid of claim 1. Dissolving diamine in DMAc and stirring under a stream of nitrogen, adding dianhydride to the stirred diamine and stirring to produce a colorless transparent polyimide solution; Adding 3-aminopropyltriethoxysilane (APTES) to the polyimide solution and stirring under nitrogen stream; Adding distilled water and tetraethoxysilane (TEOS) to the stirred solution and stirring to produce silica-polyamic acid; And Silica-polyimide hybrid manufacturing method comprising the step of thermally curing the silica-polyamic acid. The dianhydride of claim 4, wherein the dianhydride forming the polyimide is either 6FDA or BHDA, and the diamine is TFDB, 1,4 (4) -APB, 1,3 (4) -APB, 4,4- A method for preparing a silica-polyimide hybrid, which is any one selected from BAPS (4APPS), 3ADF, DDSO ₂ , 4BDAF, and 3,3'-ODA. The dianhydride of claim 2, wherein the dianhydride forming the polyimide is either 6FDA or BHDA, and the diamine is TFDB, 1,4 (4) -APB, 1,3 (4) -APB, 4,4- Silica-polyimide hybrid, which is any one selected from BAPS (4APPS), 3ADF, DDSO ₂ , 4BDAF and 3,3'-ODA.

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