KR100411184B1 - Highly luminescent polymer and red electroluminescent device - Google Patents

Abstract

The present invention relates to a high efficiency red organic light emitting polymer and an electroluminescent device using the same. More specifically, pyranmalonitrile is newly introduced into the main chain of poly ( p -phenylenevinylene), thereby providing electrons to the light emitting layer. A red organic light emitting polymer represented by the following Formula 1 and an electroluminescent device using the red organic light emitting polymer which facilitate the injection of red light by increasing the luminous efficiency and extending the conjugated bond length by a cyano group will be.

In Formula 1, R represents a linear or crushed alkyl group having 3 to 20 carbon atoms, and n is an integer ranging from 4 to 20.

Description

Highly efficient red organic light emitting polymer and electroluminescent device using same {Highly luminescent polymer and red electroluminescent device}

The present invention relates to a high efficiency red organic light emitting polymer and an electroluminescent device using the same. More specifically, pyranmalonitrile is newly introduced into the main chain of poly ( p -phenylenevinylene), thereby providing electrons to the light emitting layer. A red organic light emitting polymer represented by the following Formula 1 and an electroluminescent device using the red organic light emitting polymer which facilitate the injection of red light by increasing the luminous efficiency and extending the conjugated bond length by a cyano group will be.

Formula 1

In Formula 1, R represents a linear or crushed alkyl group having 3 to 20 carbon atoms, and n is an integer ranging from 4 to 20.

The semiconductor industry using silicon semiconductors has developed remarkably over the past few decades, and organic semiconductors have also developed remarkably. Recently, due to the development of the optical communication and multimedia fields, optoelectronic materials are becoming the center of the information communication industry. Due to the development of information and communication, display technology is also developing day by day. The liquid crystal display currently used typically has the advantage of being lighter than conventional CRTs, but has a disadvantage in that a viewing angle is limited and a back light is required. On the contrary, a display using an organic light emitting diode (OLED) is a display using a self-luminous phenomenon, and has a large viewing angle, lighter and thinner than a liquid crystal display, can be miniaturized, and has a fast response speed. . Electroluminescent devices can be classified into inorganic light emitting devices and organic light emitting devices, and inorganic light emitting devices can be composed of GaN, ZnS and the like, and are currently commercially available. However, the inorganic light emitting device has a driving voltage of 200 V or more, and it is difficult to increase the size of the device and the price is also high. In 1987, Eastman Kodak Co. announced a multi-layered organic light emitting device that emits green light using aluminum complex (Alq ₃ ), an organometallic compound consisting of a conjugated double bond, as a light emitting material by Tang et al. This organic light emitting device has a quantum efficiency (quantum number of emitted light / number of injected electrons x 100, external quantum efficiency) of 1% and luminance of 1000 cd / mm 2 at 10 V or less. Since the efforts of many research groups, color tuning is easy and remarkable developments have been made in the field of organic light emitting devices having high quantum efficiency. However, there is a disadvantage that the luminous efficiency decreases due to rearrangement (crystallization, etc.) of organic materials, which are device components, due to deterioration of mechanical properties and heat generated during operation of the device. This disadvantage can be overcome by replacing with a polymeric material having a conjugated double bond.

Since the electroluminescent device using poly ( p -phenylenevinylene) (PPV) having conjugated double bond was developed by Friend of Cambridge University in England in 1990, research on organic polymers has been actively conducted. Red, green, and blue organic light emitting polymers for emitting light have been developed, and a polymer light emitting diode (LED) having excellent quantum efficiency having a multilayer structure has been developed.

The color of light emitted from the organic light emitting polymer is determined by a band gap, which is a difference between HOMO and LUMO energy levels. In addition, the factors governing the driving voltage and quantum efficiency of the polymer light emitting diode (PLED) are the difference between the work function and homo level of the anode injecting holes, electrons ( It is determined by the difference between the work function of the cathode and the Lumo energy level. The homo level of most organic light emitting polymers has a small energy difference from the work function of indium tin oxide (ITO), which is a typical anode material. Hard. Therefore, the hole injection rate (or amount) and electron injection rate (or amount) are not balanced, and thus the first injected hole is tunneled to the cathode, resulting in ohmic current, resulting in low quantum efficiency and heat generation. This shortens the lifetime of the device. In order to balance the hole and electron injection, various research groups have introduced functional groups such as cyano (CN) and oxadiazole, which have strong electron affinity, into the polymer main chain or side chain to lower the lumo level to facilitate the injection of electrons. In addition, the homo level is also lowered to balance hole injection and electron injection, resulting in a significant improvement in quantum efficiency for luminescence. However, the light emitting device having such a structure has a disadvantage in that an operating voltage increases. Efforts have been made to increase the quantum efficiency by forming a multi-layer EL device by coating a thin film between the light emitting layer and the anode with a strong electron affinity, or by blending these materials with the light emitting material. However, there is a disadvantage in that the life of the device is shortened by rearrangement or phase separation of materials mixed with generation of space charge. Polyalkylthiophenes and dialkoxy CN-PPVs are representative red organoluminescent polymers. Polyalkyl thiophene maximum emission peaks of emitting red light of 620~650 nm, but has a low efficiency ^(10-5%). The peak emission peak of dialkoxy CN-PPV (Cavendish Display Technology, Inc.) emits light in the red region of 695 nm, and the multilayer structure EL device comprising the light emitting polymer The efficiency is very high.

The inventors of the present invention researched to develop a red organic light emitting polymer having excellent color purity, and as a result synthesized a red organic light emitting polymer having a novel structure in which pyranmalonitrile was introduced into the main chain of poly ( p -phenylenebininene). By introducing cyano groups, the conjugated bond length is extended to shift the emission color to the red region, and the electron acceptor effect of the cyano group facilitates the injection of electrons from the cathode to the emission layer, thereby increasing the emission efficiency. The invention was completed.

Accordingly, an object of the present invention to provide a red organic light emitting polymer having a novel structure represented by the formula (1).

In addition, another object of the present invention to provide an electroluminescent device comprising a red organic light emitting polymer represented by the formula (1).

1 is a ¹ H-NMR spectrum of a 1,4-bis-dodecyloxy-2,5-divinylbenzene monomer.

Figure 2 is a ¹ H-NMR spectrum of 2- {2,6-bis- [2- (4-bromo-phenyl) -vinyl] -pyran-4-ylidene} -malonitrile monomer.

3 is (a) ¹ H-NMR (b) FT-IR spectrum of an organic light emitting polymer (PM-PPV).

4 is a structure of an electroluminescent device having (a) single layer and (b) double layer structure using an organic light emitting polymer (PM-PPV).

5 is (a) UV-visible and (b) PL spectra of the organic light emitting polymer (PM-PPV).

6 is an EL spectrum of an electroluminescent device having (a) single layer or (b) multilayer structure using an organic light emitting polymer (PM-PPV).

7 is a voltage-current, voltage-EL intensity characteristic curve and current-EL quantum efficiency curve of a single layer electroluminescent device using organic light emitting polymer (PM-PPV).

8 is a voltage-current, voltage-EL intensity characteristic curve and current-EL quantum efficiency curve of a double layer electroluminescent device using organic light emitting polymer (PM-PPV) and PPV.

FIG. 9 is a comparison of current-external quantum efficiency characteristic curves of monolayer and bilayer electroluminescent devices of organic light emitting polymer (PM-PPV).

A high efficiency red organic light emitting polymer represented by the following Chemical Formula 1 and an electroluminescent device using the same are featured.

[Formula 1]

In Formula 1, R represents a linear or crushed alkyl group having 3 to 20 carbon atoms, and n is an integer ranging from 4 to 20.

Referring to the present invention in more detail as follows.

Red organic light emitting polymers must form effective conjugated bonds in repeat units. Thus, in the present invention, in order to achieve an effective conjugated double bond, pyranmalonitrile group was introduced into the polymer backbone, and the introduction of cyano group lowered the lumo energy level of the polymer and lowered the homo level to effectively recombine electrons and holes. (recombination) can be achieved. As a result, the efficiency of the electroluminescent device having a single layer structure was increased, and the efficiency of the electroluminescent device was further increased by using PPV through a thiophenoxy precursor polymer as a major transport layer.

In the organic light emitting polymer represented by Chemical Formula 1, the phenyl group introduced with OR is connected to 2- and 5-positions in the main chain.

Meanwhile, the organic light emitting polymer represented by Chemical Formula 1 according to the present invention may be represented by the following Chemical Formula 1, 2- {2,6-bis- [2- (bromoaryl) -vinyl] represented by the following Chemical Formula 2. -Pyran-4-ylidene} -malonitrile and an aromatic divinylbenzene substituted with an alkoxy group represented by the following formula (3) is prepared by a Heck coupling reaction under a Pd (0) catalyst.

In Scheme 1: R and n are as defined above, respectively.

In addition, 2- {2,6-bis- [2- (bromoaryl) -vinyl] -pyran-4-ylidene having two halogens represented by Formula 2 used in the preparation method according to Scheme 1 above }-Malonitrile monomers synthesize 2,6-dimethyl pyran malonitrile and haloarylaldehyde derivatives by condensation reaction under a piperidine catalyst.

In addition, the aromatic divinylbenzene monomer substituted with the alkoxy group represented by Chemical Formula 3 is generally known in the art for preparing dialkoxy dicarbaldehyde, and witlid (yilid) of this and methyltriphenylphosphine salt. Wittig) by the condensation reaction, the yield can be obtained at 75% or more.

The organic light emitting polymer represented by Chemical Formula 1 according to the present invention has a long chain alkoxy group (-OR) introduced into the side branch, so that it has excellent solubility in a general organic solvent and excellent ability to form a thin film without defects.

On the other hand, the present invention includes an electroluminescent device having a single layer or a multilayer structure in which the organic light emitting polymer represented by Formula 1 or a mixture containing the organic light emitting polymer is a light emitting layer. That is, the organic light emitting polymer represented by the formula (1) or a mixture containing the compound to be a light emitting layer to produce a light emitting diode (LED) having a structure of anode / light emitting layer / cathode, and to increase the light emitting efficiency In order to fabricate a photodiode having a structure of anode / PPV / light emitting layer / cathode coated with PPV through a thiophenoxy precursor polymer with a hole injection layer. The specific structure of the light emitting diode will be shown in the following examples. The turn-on voltage of a single layer EL device using the organic light emitting polymer represented by Chemical Formula 1 as a light emitting layer is 7.5 V, emits red color, and the quantum efficiency is 0.003%. The quantum efficiency is 15 times higher than the conventional MEH-PPV (0.0002%). The turn-on voltage of a bilayer bilayer EL device using PPV as the hole injection layer is 5.5 V, about 2 V lower than the monolayer LED, quantum efficiency is 0.05%, 250 times greater than MEH-PPV, and single layer emission. It's about 17 times higher than a diode.

The present invention described above will be described in more detail based on the following examples, but the present invention is not limited by the embodiments.

Preparation Example: Preparation of Monomer

Preparation Example 1 Preparation of 1,4-bis-dodecyloxy-benzene

16.82 g (0.30 mol) of potassium hydroxide was dissolved in 200 mL of methanol followed by 16.52 g (0.15 mol) of hydroquinone. 74.77 g (0.30 mol) of 1-bromododecane was added to the solution and refluxed under a nitrogen atmosphere for 24 hours. After cooling the reaction solution to room temperature, the precipitate was filtered. The filtered precipitate was washed with methanol and distilled water. The precipitate was dried and then recrystallized from methanol to give a white solid compound in the yield of 78.3%.

Melting point: 72-73 캜. MS [M ⁺ ]: m / z 447. ¹ H-NMR (CDCl ₃ , ppm): δ6.83 (s, 4H), 3.92 to 3.90 (t, J = 6.6, 4H), 1.79 to 1.74 (m, 4H), 1.48-1.42 (m, 4H), 1.35-1.28 (m, 32H), 0.91-0.99 (t, J = 6.6, 6H). ¹³ C-NMR (CDCl ₃ , ppm): δ 153.18, 115.34, 68.62, 31.92, 29.66, 29.64 29.60, 29.59, 29.42, 29.40, 29.35, 26.06, 22.69, 14.12. Anal. Calcd. for C ₃₀ H ₅₄ O ₂ : C, 80.65; H, 12.18. Found: C, 80.68; H, 12.15.

Preparation Example 2 Preparation of 1,4-bis-bromomethyl-2,5-bis-dodecyloxy-benzene

To 44.67 g (0.10 mol) of 1,4-bis-dodecyloxy-benzene and 30.00 g (1.0 mol) of paraformaldehyde mixture, HBr (30%) acetic acid solution was slowly added under nitrogen atmosphere. The mixture was stirred at 80-90 ° C. for 12 hours. After the reaction solution was cooled to room temperature, 100 mL of water was slowly added, followed by 250 mL of chloroform. The organic layer was washed with water and aqueous sodium hydrogen carbonate solution. The organic layer was dried over anhydrous MgSO ₄ , filtered, evaporated and recrystallized with chloroform / methanol to give a white solid in a yield of 63.3%.

Melting point: 95-96 캜. MS [M ⁺ ]: m / z 633. ¹ H-NMR (CDCl ₃ , ppm): δ6.86 (s, 4H), 4.54 (s, 4H), 4.00 to 3.98 (t, J = 6.5, 4H) , 1.85 to 1.79 (m, 4H), 1.53 to 1.47 (m, 4H), 1.37 to 1.28 (m, 32H), 0.91 to 0.87 (t, J = 6.9, 6H). ¹³ C-NMR (CDCl ₃ , ppm): δ 150.64, 127.49, 114.61, 68.98, 31.92, 29.67, 29.64, 29.59, 29.56, 29.35, 29.32, 28.75, 26.07, 22.69, 14.12. Anal. Calcd. for C ₃₂ H ₅₆ Br ₂ O ₂ : C, 60.76; H, 8.92. Found: C, 60.78; H, 8.91.

Preparation Example 3 Preparation of 4-Acetoxymethyl-2,5-bis-dodecyloxy-benzyl ester

27.20 g (0.043 mol) of 1,4-bis-bromomethyl-2,5-bis-dodecyloxy-benzene, 21.32 g (0.260 mol) of sodium acetate and 13.26 g (0.130 mol) in 250 mL of acetic acid Acetic anhydride was added thereto, and the mixture was refluxed for 24 hours under a nitrogen atmosphere. After the reaction solution was cooled to room temperature, 200 mL of chloroform was added to the reaction solution. The organic layer was separated, washed with water, aqueous sodium bicarbonate, brine, and the like, dried over anhydrous MgSO ₄ , filtered and evaporated, and recrystallized with chloroform / methanol to obtain a white solid in a yield of 98.5%.

Melting point: 83-84 캜. ^{MS [M +]: m /} z 591. 1 H-NMR (CDCl 3, ppm): δ6.88 (s, 2H), 5.14 (s, 4H), 3.96~3.93 (t, J = 6.5, 4H) 2.10 (s, 6H), 1.79-1.74 (m, 4H), 1.49-1.41 (m, 4H), 1.31-1.27 (m, 32H), 0.90-0.77 (t, J = 6.8, 6H). ¹³ C-NMR (CDCl ₃ , ppm): δ 150.77, 125.07, 113.77, 69.01, 61.67, 31.89, 29.65, 29.61, 29.59, 29.37, 29.33, 26.04, 22.67, 21.06, 14.11. Anal. Calcd. for C ₃₆ H ₆₂ 0 ₆ : C, 73.18; H, 10.58. Found: C, 73.13; H, 10.66.

Preparation Example 4 Preparation of (2,5-bis-dodecyloxy-4-hydroxymethyl-phenyl) -methanol

9.30 g (0.23 mol) of sodium hydroxide was dissolved in 250 mL of methanol, followed by 23.04 g (0.039 mol) of acetic acid 4-acetoxymethyl-2,5-bis-dodecyloxy-benzyl ester. It was refluxed for time. After cooling the reaction solution to room temperature, the solid compound formed was filtered and washed with methanol and water. The washed solid compound was recrystallized from methanol to give a white solid in 90.6% yield.

Melting point: 109-110 ° C. MS [M ⁺ ]: m / z 507. ¹ H-NMR (CDCl ₃ , ppm): δ6.85 (s, 2H), 4.68 to 4.67 (d, J = 6.5, 4H), 4.00 to 3.97 (t, J = 6.5, 4H), 2.37-2.35 (t, J = 6.5, 2H), 1.81-1.76 (m, 4H), 1.49-1.40 (m, 4H), 1.35-1.27 (m, 32H), 0.90-0.87 (t, J = 6.7, 6H). ¹³ C-NMR (CDCl ₃ , ppm): δ 150.64, 129.04, 112.32, 68.74, 62.20, 31.92, 29.65, 29.62, 29.59, 29.57, 29.41, 29.37, 29.34, 26.15, 22.69, 14.11.Anal. Calcd. for C ₃₂ H ₅₈ O ₄ : C, 75.84; H, 11.54. Found: C, 75.88; H, 11.63.

Preparation Example 5 Preparation of 2,5-bis-dodecyloxy-benzene-1,4-dicarbaaldehyde

16.72 g (0.033 mol) of (2,5-bis-dodecyloxy-4-hydroxymethyl-phenyl) -methanol and 28.00 g of celite were mixed in 250 mL of dichloromethane, followed by 28.07 at 0 ° C. g (0.13 mol) of pyridinium chlorochromate (PCC) was added in the solid state. The degree of completion of the reaction was confirmed by thin layer chromatography (mobile phase: ethyl acetate / n-hexane = 3/7). If no reaction was found, 200 mL of diethyl ether was added to the reaction. The organic solvent of the organic layer from which the dark brown precipitate was removed was removed. The obtained solid was purified by column chromatography (mobile phase: ethyl acetate / n-hexane = 3/7) to give a green yellow solid in a yield of 75.8%.

Melting point: 90-91 캜. MS [M ⁺ ]: m / z 503. ¹ H-NMR (CDCl ₃ , ppm): δ 10.5 (s, 2H), 7.43 (s, 2H), 4.09 to 4.07 (t, J = 6.3, 4H) , 1.86 to 1.80 (m, 4H), 1.50 to 1.44 (m, 4H), 1.35 to 1.26 (m, 32H), 0.89 to 0.86 (t, J = 6.8, 6H). ¹³ C-NMR (CDCl ₃ , ppm): δ 189.49, 155.19, 129.21, 115.53, 69.18, 31.89, 29.62, 29.60, 29.55, 29.52, 29.32, 29.29, 29.02, 25.98, 22.66, 14.11. Anal. Calcd. for C ₃₂ H ₅₄ O ₄ : C, 76.45; H, 10.83. Found: C, 76.37; H, 11.01.

Preparation Example 6 Preparation of 1,4-bis-dodecyloxy-2,5-divinylbenzene

Methyltriphenylphosphonium bromide was added to 50 mL of anhydrous THF under nitrogen atmosphere to form a suspension, and then maintained at 0 ° C. 18.3 mL of normal butyllithium solution (2.0 mmol, 1.2 M normal hexane solution) was slowly added to the suspension prepared at 0 ° C., and then stirred for 30 minutes at room temperature. Is formed). Then, 5.003 g of 2,5-bis-dodecyloxy-benzene-1,4-dicarbaaldehyde solution dissolved in 50 mL of anhydrous THF was slowly added to the reaction solution described above. After all additions, the reaction solution was refluxed slightly for 4 hours. After the reaction, 200 mL of diethyl ether and 100 mL of water were added thereto. The organic layer was separated and the aqueous layer was extracted three times with 30 mL of diethyl ether. All organic layers were combined and washed several times with brine and water. The organic layer was dried over anhydrous MgSO ₄ , filtered, evaporated and recrystallized with THF / methanol to give a solid compound in a yield of 80.6%. The ¹ H-NMR spectrum of this compound is shown in FIG.

MS [M ⁺ ]: 498. ¹ H-NMR (CDCl ₃ , ppm): δ 7.07-7.02 (dd, J = 6.7 and J = 11.1, 2H), 6.99 (s, 2H), 5.75-5.71 (dd , J = 1.4 and J = 16.3, 2H), 5.27-5.24 (dd, J = 1.4 and J = 9.8, 2H), 3.98-3.95 (t, J = 6.5, 4H), 1.81-1.77 (m, 4H) , 1.49 to 1.45 (m, 4H), 1.36 to 1.27 (m, 32H), 0.90 to 0.87 (t, J = 6.8, 6H) 6.73 (s, 2H). ¹³ C-NMR (CDCl ₃ , ppm): δ 150.62, 131.53, 113.99, 110.49, 69.31, 31.92, 29.67, 29.64, 29.60, 29.59, 29.44, 29.41, 29.36, 26.14, 22.69, 14.12. Anal. Calcd. for C ₃₄ H ₅₈ O ₂ : C, 81.87; H, 11.72. Found: C, 81.85; H, 11.77.

Preparation Example 7 Preparation of 2- {2,6-bis- [2- (4-bromo-phenyl) -vinyl] -pyran-4-ylidene} -malonitrile

Dissolve 1.85 g (10.00 mmol) of 4-bromobenzaldehyde and 0.861 g (5.00 mmol) of 2,6-dimethyl pyranmalonitrile in 10 mL of purified acetonitrile, add 10 drops of piperidine, and then add nitrogen. It was refluxed for 24 hours under the atmosphere. Thirty minutes after the start of reflux, a yellowish solid began to form. After the reaction was cooled to room temperature and precipitated. The precipitate was washed with 20 mL acetonitrile. The filtered yellow solid was recrystallized from methanol to give a yellow solid compound in 75.3% yield. The <^1> H-NMR spectrum of this compound is shown in FIG.

MS [M ⁺ ]: 506. ¹ H-NMR (CDCl ₃ , ppm): δ 7.61-7.58 (d, J = 8.5, 4H), 7.47-7.44 (d, J = 8.8, 4H), 7.48-7.43 (t, J = 15.7, 2H), 6.80-6.75 (t, J = 15.9, 1H), 6.73 (s, 2H). Anal. Calcd. for C ₂₄ H ₁₄ Br ₂ N ₂ O: C, 56.95; H, 2.79; N, 5.53. Found: C, 56.94; H, 2.73; N, 5.49.

Example 1 Preparation of Organic Luminescent Polymer (PM-PPV)

The organic light emitting polymer was prepared by Heck coupling reaction (Heck coupling reaction, Heck, RF Org.Reactions 1982, 27 , 345). 1,4-bis-dodecyloxy-2,5-divinylbenzene 0.5 mmol, 2- {2,6-bis- [2- (4-bromo-phenyl) -vinyl] -pyran-4-ylidene }-10 mL of dimethylformamide was added to a mixture of 0.50 mmol of malonitrile, 4.5 mg (0.020 mmol) of Pd (OAc) ₂ and 0.0305 g (0.100 mmol) of tri-o-tolylphosphine, followed by 0.31 mL of tributylamine. Was added. The reaction solution was stirred at 140 ° C. under a nitrogen atmosphere for 24 hours. The hot reaction solution was poured into 400 mL of methanol to form a precipitate. The precipitate formed was filtered off and dissolved again in 100 mL of chloroform, 300 mL of ultrapure water was added, and stirred for 1 hour. After pouring out the water layer well, the solvent was completely removed from the remaining organic layer. Again saturated with a small amount of THF and poured into 400 mL of methanol to form a reprecipitate. The precipitate was filtered off and dried in vacuo to yield a red polymer with a yield of 75%. 3 (a) and (b) are ¹ H-NMR and FT-IR spectra of the organic light emitting polymer (PM-PPV), respectively.

Example 2 Fabrication of Electroluminescent Device (EL device)

The electroluminescent device manufactured using the organic light emitting polymer (PM-PPV) prepared in Example 1 may have a single layer or a bilayer structure as shown in FIG. 4 (a). consist of.

(1) Fabrication of electroluminescent device with single layer structure

After the ITO-coated glass plate was patterned into a desired shape, the foreign substances were washed clean. The light emitting polymer solution was dissolved in a chloroform solvent at a concentration of 15 mg / mL, and then filtered using a 0.45 μm membrane filter and a syringe to remove fine dust and foreign substances present in the light emitting polymer solution. The light-emitting polymer solution was spin-coated at 1500 rpm on a clean patterned ITO glass plate. The thin film was dried in vacuo for 2 hours, and then an aluminum electrode was vacuum deposited thereon at 10 ⁻⁵ torr or lower. The thickness of the aluminum film was 100-150 nm, and the thickness of the aluminum film was measured using a crystal sensor of Sigma, and the area of the aluminum film was fixed at 4 mm 2 using a mask.

After mixing PVK and PM-PPV in a 1: 1 ratio, the solution is dissolved in chloroform to a concentration of 15 mg / mL, and then filtered using a 0.45 μm membrane filter and a syringe to remove fine dust and foreign substances present in the light emitting polymer solution. It was. The light emitting polymer solution was spin-coated at 1500 rpm on a clean patterned ITO glass plate. The thin film was dried in vacuo for 2 hours and the aluminum film was coated in the same way.

(2) Bilayer Electroluminescent Device Fabrication

As in the monolayer fabrication process, the PPV precursor solution was spin coated at 1500 rpm on the patterned ITO and reacted at 240 ° C. for 2 hours under vacuum to prepare a thin PPV film. The red light-emitting polymer solution prepared by the above method was spin-coated on an ITO plate coated with PPV. After the thin film was dried for 2 hours, an aluminum film was coated in the same manner as above.

Example 3 Optical Characteristics

After forming a thin film by spin coating the organic light-emitting polymer (PM-PPV) solution prepared in Example 1 on a quartz plate (UV-visible) and the absorption (UV-visible) and photoluminescence (PL) spectrum was measured. Absorption spectra were used by Model 8453 of Hewlett-Packard Corporation, and fluorescence spectrometers of PTI Corporation. The absorption spectrum and emission spectrum of the light emitting polymer are shown in FIG. 5.

The organic light emitting polymer (PM-PPV) exhibited a maximum absorption peak at 465 nm and an absorption edge wavelength of 640 nm (1.94 eV). The maximum peak of the PL spectrum emitted red light at 657 nm.

Example 4 EL spectrum and current-voltage-EL intensity characteristic curve and current-EL quantum efficiency characteristic

(1) single layer electroluminescent device

The EL spectrum of the single layer type electroluminescent device manufactured as shown in FIG. 4 (a) using the organic light emitting polymer (PM-PPV) prepared in Example 1 is shown in FIG. 6 (a). The peak emission peak of PM-PPV emitted light in the red region at 646 nm. 7 shows the current-voltage-EL intensity characteristic curve and the current-EL quantum efficiency characteristic curve, and the ON voltage was 7.5V. The quantum efficiency is 0.003%, which is 15 times larger than MEH-PPV, and the light emission can be easily observed in a lighted room. The reason for having higher efficiency than MEH-PPV is that homo and lumo energy levels are lowered due to the electron acceptor phenomenon of the cyano group of the polymer, so that the hole and electron injection are balanced.

The EL spectrum of the single layer electroluminescent device using PM-PPV mixed with PVK is shown in Fig. 6 (b). The maximum luminescence peak emitted light in the red region at 633 nm.

(2) Bilayer Electroluminescent Device

The EL spectrum of the double layer electroluminescent device manufactured as shown in FIG. 4 (a) using the organic light emitting polymer (PM-PPV) prepared in Example 1 is as shown in FIG. 6 (b). The peak emission peak of PM-PPV emitted light in the red region at 643 nm. 8 shows a current-voltage-EL intensity characteristic curve and a current-EL quantum efficiency characteristic curve of a double layer electroluminescent device, and the ON voltage is 5.5 V, which is 2 V lower than that of the single layer electroluminescent device. The quantum efficiency is 0.003%, which is 250 times higher than MEH-PPV, about 17 times higher than that of the single-layer electroluminescent device, and light emission can be easily observed in a lighted room. The reason why the double layer electroluminescent device exhibits a lower ON voltage and higher efficiency than the single layer electroluminescent device is because PPV serves as an effective hole transport layer and the cyano group of the polymer facilitates the injection of electrons.

The emission color shifted to 50 nm blue compared to dialkoxy CN-PPV of CDT (Cavendish Display Technology). And shifted to the red region rather than the well-known Eastman Kodak co. DCM derivative (585-597 nm). As a result of measuring the color coordinates, it can be seen that the NTSC standard red coordinates are closer to those of CDT's CN-PPV and Eastman Kodak's DCM derivatives as shown in Table 1 below.

Driving voltage Luminescence x y - NTSC standard red coordinates 0.67 0.33 8 V PM-PPV (Dual Layer Electroluminescent Device) 0.69 0.31 9 V PM-PPV (Dual Layer Electroluminescent Device) 0.69 0.31 10 V PM-PPV (Dual Layer Electroluminescent Device) 0.69 0.31 - CN-PPV (CDT) 0.63 0.32 - DCM (Eastman Kodak) 0.62 0.36

Comparative Example

FIG. 9 is a single-layer structure manufactured as shown in FIG. 4 (a) using the current-external quantum efficiency characteristic curve and MEH-PPV of PM-PPV monolayer and double layer electroluminescent devices. Shows a comparison of the current-external quantum efficiency characteristic curves of the electroluminescent device. PM-PPV has an external quantum efficiency of 0.003% for single layer and 0.05% for double layer, which is much higher than 0.0002% of MEH-PPV.

As described above, the red organic light emitting polymer according to the present invention is 50 nm blue compared to the dialkoxy CN-PPV of CDT (Cavendish Display Technology), Eastman Kodak co. (Eastman Kodak co.) DCM derivative (585-597) The color purity for red was improved by moving to the red region rather than to nm).

In the case of the electroluminescent device having a single layer structure, the efficiency is higher than that of a general PPV, and the electroluminescent device having a double layer structure using the PPV as the hole transport layer is highly improved. Peaks in the EL spectrum appear in the range of 633 to 645 nm, all emitting light in the red region.

When the red light-emitting material is mixed with poly-N-vinylcarbazole (PVK) to form an electroluminescent device, it also shows high efficiency (more than 0.003%). The location of the peaks of the EL spectrum according to the ratio of PVK appears in the range of 630 to 640 nm, again all emitting light in the red region.

In addition, because of the side alkoxy group, it has high solubility in general solvents and excellent film forming ability.

Claims (2)

The red organic light emitting polymer, characterized in that represented by the formula (1). [Formula 1] In Formula 1, R represents a linear or crushed alkyl group having 3 to 20 carbon atoms, and n is an integer ranging from 4 to 20. An organic electroluminescent device having a single layer or multilayer structure in which an organic light emitting polymer represented by Formula 1 or a mixture containing the organic light emitting polymer is a light emitting layer. [Formula 1] In Formula 1, R represents a linear or crushed alkyl group having 3 to 20 carbon atoms, and n is an integer ranging from 4 to 20.