KR20000000628A - Fully conjugated organic electoluminescence polymer composition and process for producing the same - Google Patents

Abstract

PURPOSE: A fully conjugated organic electroluminescence polymer composition is provided which contains fluorinated aryl group having strong electron affinity to increase luminescence efficiency. CONSTITUTION: The polymer composition represented by formula 1 is produced by reacting the compound having fluorinated aryl group (formula II) and the compound represented by formula 3.

Description

Fully Conjugated Organic Electroluminescent Polymer Composition Containing Fluorinated Aryl Group and Manufacturing Method Thereof

Field of invention

The present invention relates to a light emitting polymer composition. More specifically, the present invention relates to a light emitting polymer composition having a fluorinated aryl group having electron affinity.

Background of the Invention

As the information and communication industry develops, as display interest increases, display technologies are gradually developed. In order to meet the increasing demands of customers, technologies related to the display's basic performance such as driving voltage, power consumption, responsiveness, brightness, contrast, display color and lifetime should be further improved.

Liquid crystal display (LCD), which is currently commercially available, has the advantages of low power consumption and light weight, and significant technological development such as colorization and screen enlargement has been made through steady research and development, but the device structure and driving system are complicated. Problems such as viewing angle.

The EL (Electroluminescence) display, which is attracting attention as a next-generation display, has various advantages such as fast response speed and self-luminous type, which does not require back light, and has excellent brightness and no viewing angle dependence. There is much research going on.

Organic electroluminescence and inorganic electroluminescence are classified according to whether the electroluminescent element is made of an organic material or an inorganic material. In the case of an electroluminescent device made of an inorganic material, a driving voltage is required to be AC 200V or more, and the manufacturing method of the device is made by vacuum deposition, which makes it difficult to enlarge the size and has a high cost. On the other hand, the organic electroluminescent display device can be manufactured to have a thin display panel thickness of about several millimeters, and the low voltage driving and the direct voltage driving can be used to facilitate the IC of the circuit, thereby reducing the size and power consumption of the device. It is easy to synthesize various types of materials and has the advantage that color tuning is possible. However, since the mechanical strength is low and crystallization by heat occurs, the organic electroluminescent device having a polymer structure that compensates for this is being advanced.

On the other hand, the use of a polymer organic material as a light emitting material is capable of manufacturing a flexible display such as a flat panel display as well as a curved display, and can reduce the manufacturing cost by simplifying the manufacturing process.

Recently, the development of organic electroluminescent materials capable of increasing luminous efficiency at home and abroad has been actively progressed. Existing light-emitting polymers containing alkoxy or phenyl groups are not easy to move electrons and have a lot of holes, and thus the light-emitting efficiency is improved because the introduced holes move directly to the cathode without bonding with electrons in the light-emitting polymer. Falls.

In addition, the light emitting polymer having a cyano (-CN) group increases the luminous efficiency by inducing a balanced encounter between electrons and holes, but has a disadvantage in that the luminous color is limited to red. In the present invention, in order to solve the above problems, it is to prepare a light emitting polymer having a fluorinated aryl group that has a strong electron affinity property can increase the luminous efficiency of the polymer material.

An object of the present invention is to provide a light emitting polymer having strong electron affinity.

Another object of the present invention is to provide a light emitting polymer that induces the inflow of balanced electrons and holes in the electroluminescent device.

Still another object of the present invention is to provide a light emitting polymer having a green light emission color.

Still another object of the present invention is to form a uniform thin film free of pinholes or other defects, and to provide a light emitting polymer having excellent adhesion to a substrate.

The above and other objects of the present invention can be achieved by the present invention described below.

1 is a synthetic route of a fully conjugated polymer containing fluorinated aryl groups.

2 is 2-{[2,3,4,5,6-pentafluorobenzene] -2,3,5,6-tetrafluorophenyl} -1,4-phenylenedimethylene-bis of Example 1 1H-NMR spectrum of (tetrahydrothiophenium bromide).

3 is a device structure of the third embodiment and the fourth embodiment.

4 is a UV absorption spectrum and PL spectrum of the electroluminescent polymer thin film of the present invention.

5 is an EL spectrum measured from the single-layer and double-layer EL elements provided in Examples 3 and 4. FIG.

6 is an I-V curve measured from the single-layer and double-layer EL elements provided in Examples 3 and 4. FIG.

7 is an L-V curve measured from the single-layer and double-layer EL elements provided in Examples 3 and 4. FIG.

8 is a L-I curve of the polymer thin film and other light emitting polymer thin films provided in the present invention.

It is well known that the driving voltage in the organic light emitting polymer is the movement of holes, and the electron is the dominant light emitting efficiency. The inflow of holes in the light emitting polymer is easy while the inflow of electrons is difficult. The introduced electrons and holes meet in the light emitting polymer to form an exciton, and when the exciton is inactivated, the light of the wavelength corresponding to the band gap of the light emitting material is emitted. It is a principle.

That is, the maximum luminous efficiency can be exhibited when the amount of holes introduced and the amount of electrons are in balance with each other.

The most representative method of improving the luminous efficiency of organic electroluminescent materials is the energy barrier that electrons must pass through using a cathode having a small work function or a polymer having a high electron affinity. There is a way to reduce the height. In order to increase the electron affinity of the polymer material, the conjugated polymer chain is substituted with an electron affinity substituent to lower the height of the lower unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) under vacuum of the light emitting polymer. It is to reduce the height of the energy barrier that the electrons must overcome. Electron affinity substituents published to date include -CN, -CF ₃ and the like.

However, they are limited to the red color of the electroluminescent color. The fluorinated aryl group, a new electron substituent, has a strong electron affinity, and when it is substituted into the light emitting polymer, it helps the inflow of balanced electrons and holes to improve the efficiency of electroluminescence. In addition, a green emission color can be obtained.

The present invention is an organic electroluminescent polymer represented by the following structural formula (I):

R ₁ in the formula (I) , Aliphatic alkoxy, (CH ₂ ) _n CH ₃ (n is an integer from 0 to 15) or CH ₂ CHCH ₃ (CH ₂ ) _m CH ₃ (m is an integer from 1 to 15), R ₂ is H, or And p is an integer of 5 to 100.

Synthesis of the organic electroluminescent polymer of the present invention first prepares a compound represented by the following structural formula (II):

Reacting a compound represented by the following formula (III) with a compound of the above formula (II):

To prepare a monomer represented by the following structural formula (IV):

Polymerizing the compound represented by the above formula (IV) to obtain a precursor, dissolving it in a solvent and preparing a thin film by spin coating method to obtain a final electroluminescent polymer represented by the above formula (I) through heat removal. :

R ₁ in the formulas (II), (III) and (IV) , Aliphatic alkoxy, (CH ₂ ) _n CH ₃ (n is an integer from 0 to 15) or CH ₂ CHCH ₃ (CH ₂ ) _m CH ₃ (m is an integer from 1 to 15), R ₂ is H, or R ₃ is aliphatic alkoxy, (CH ₂ ) nCH ₃ (n is an integer from 3 to 15) or CH ₂ CHCH ₃ (CH ₂ ) _m CH ₃ (m is an integer from 1 to 15).

The light emitting polymer of the present invention has excellent solubility in a general organic solvent in a precursor state, and a polymer thin film produced by spin coating or casting in a solution state forms a uniform thin film without pinholes or other defects. Very good adhesion to the substrate.

In addition, it has a stable thermal stability up to 400 ℃ after heat treatment, it is possible to manufacture a double layer and a multi-layer light emitting device by using an insoluble insoluble in other solvents after heat treatment.

A single layer type device is fabricated using the conjugated polymer having a fluorinated aryl group of the present invention. In addition, a device is fabricated by layering the polymer prepared in the present invention with poly [1,4-phenylenevinylene] (PPV), which is a light emitting polymer known in the art. Measure the properties.

The present invention provides a light-emitting polymer comprising a fluorinated aryl group using fluorinated aryl substituents, which have a strong electron affinity, thereby helping to inject balanced electrons and holes to increase luminous efficiency and improved maximum luminance.

The present invention is described in detail by the following examples, but the following examples are merely illustrative of specific embodiments of the present invention and are not intended to limit or limit the protection scope of the present invention.

Example

1. 2-{[2,3,4,5,6-pentafluorobenzene] -2,3,5,6-tetrafluorophenyl} -1,4-phenylenedimethylene-bis (tetrahydrothiopheny Umbromide) (2-{[2,3,4,5,6-pentafluorobenzene] -2,3,5,6

-tetrafluorophenyl} -1,4-phenylenedimethylene-bis (tetrahydrothiophenium bromide)

(1) 1- [4- (2,5-dimethylphenyl) -2,3,5,6-tetrafluorophenyl] -2,3,4,5,6-pentafluorobenzene (1- [4 -(2,5-dimethylphenyl) -2,3,5,6-tetrafluorophenyl] -2,3,4,5,6-pentafluorobenzene)

2-bromoxylene (10 g) was dissolved in anhydrous THF (30 mL), and then 2 equivalents of Mg (3 g) were added to react for 3 hours. The reaction solution was added to a reactor in which decafluorobiphenyl (27 g) was dissolved in THF (10 mL), followed by reaction for 8 hours, and then yielded 1- [4- (2,5-dimethylphenyl)-with a yield of 70%. 2,3,5,6-tetrafluorophenyl] -2,3,4,5,6-pentafluorobenzene was obtained.

(2) 1- {4- [2,5-bis (bromomethyl) phenyl] -2,3,5,6-tetrafluorophenyl} -2,3,4,5,6-pentafluorobenzene (1- {4- [2,5-bis (bromomethyl) phenyl] -2,3,5,6-tetrafluorophenyl} -2,3,4,5,6-pentafluorobenzene)

1- [4- (2,5-dimethylphenyl) -2,3,5,6-tetrafluorophenyl] -2,3,4,5,6-pentafluorobenzene (9.45 g) After dissolving in tetrachloride (60 ml), N-bromosuccinimide (8.806 g) was added, and benzoylperoxide was added as a catalyst.

After the reaction at 80 ° C. for 4 hours, the time when the reacted succinimide floats on the solution due to the density difference is used as the end point of the reaction. After the reaction, the succinimide was removed and recrystallized from methanol to yield 40% of 1- {4- [2,5-bis (bromomethyl) phenyl] -2,3,5,6-tetrafluorophenyl} -2. , 3,4,5,6-pentafluorobenzene was obtained.

(3) 2-{[2,3,4,5,6-pentafluorobenzene] -2,3,5,6-tetrafluorophenyl} -1,4-phenylenedimethylene-bis (tetrahydrothio Phenium bromide) (2-{[2,3,4,5,6-pentafluorobenzene] -2,3,5,6

-tetrafluorophenyl} -1,4-phenylenedimethylene-bis (tetrahydrothiophenium bromide)

The 1- {4- [2,5-bis (bromomethyl) phenyl] -2,3,5,6-tetrafluorophenyl] (2 g) was dissolved in methanol (20 mL), followed by excess tetrahydrothio. Fin (tetrahydrothiophene) (2 ml) was added and allowed to react at room temperature for 24 hours. After the reaction, excess methanol and tetrahydrothiophene were removed with a vacuum pump, and then solidified in acetone to yield 90% of the compound represented by the following structural formula (IVa), 2-{[2,3,4,5,6 -Pentafluorobenzene] -2,3,5,6-tetrafluorophenyl} -1,4-phenylenedimethylene-bis (tetrahydrothiophenium bromide) was obtained.

2. Preparation of Polymer Having Fluorinated Aryl Group

The monomer 2-{[2,3,4,5,6-pentafluorobenzene] -2,3,5,6-tetrafluorophenyl}-

1,4-phenylenedimethylene-bis (tetrahydrothiophenium bromide) (0.6 g) was dissolved in methanol (0.8 mL) and NaOH (0.7 mL) at 1 N concentration was added at 0 ° C. Immediately after polymerization, excess methanol was added and reacted at 60 ° C. for 12 hours. The precursor polymer (0.1 g) obtained here was dissolved in 3 ml of dichloroethane, and a thin film was obtained with a thickness of 100 nm by spin coating. The final polymer represented by the following structural formula (Ia) was obtained through heat removal at 200 ° C. under vacuum.

Wherein p is an integer from 5 to 100.

3. Fabrication of EL device of single layer homo system type

Using a fully conjugated polymer substituted with a fluorinated aryl group prepared in Example 2, an EL device of a homogeneous single layer type was manufactured as shown in FIG. The fabrication process of the EL device is to clean the transparent electrode substrate obtained by coating ITO (indium-tin oxide) on the glass substrate, and then pattern the ITO into a desired shape by using photoresist resin and etchant. ), And again washed, and spin-coated an organic light emitting polymer solution prepared by dissolving in 1,2-dichloroethane thereon and completely removing the solvent in a vacuum oven after heat treatment to remove the polymer thin film. Formed. The polymer solution was spin coated by filtering with a 0.2 μm filter, and the thickness of the polymer thin film can be freely controlled by using the concentration of the polymer solution and the speed of spin. The metal electrode was formed by depositing aluminum having a purity of 99.999% while maintaining a vacuum degree of 4 × 10 ⁻⁶ torr or less using a vacuum evaporator. During deposition, the film thickness and the growth rate of the film were controlled by using a crystal sensor, the emission area was 6 mm 2, and the driving voltage was a direct bias voltage.

4. Fabrication of double layer system EL device

The polymer prepared in Example 2 and PPV, which is a conventionally known light emitting polymer, were fabricated as a layered EL device as shown in FIG. The thickness of the PPV was 50 nm, and all fabrication processes of the EL device were fabricated in the same manner as in Example 3.

5. Evaluation of Electro-optical Properties of EL Devices Fabricated in Single-Layer Homogenous Forms

After spin coating the polymer solution prepared in Example 2 to form a polymer thin film, UV absorption peak and PL were measured. Each measurement result is shown in FIG. The UV maximum absorption peak was 395 nm, and the PL maximum peak in the PL spectrum when the excitation wavelength was 390 nm was measured at 520 nm, which is a green region.

The EL spectrum results of the EL device fabricated in Example 3 are shown in FIG. The applied DC voltage was 25V, and the current density flowing at that time was 1.5 × 10 ² (mA / cm 2), and the EL maximum peak was measured at 525 nm in the green region. The results of comparing the luminous efficiency between the well-known light-emitting polymer MEH-PPV and the polymer prepared in the present invention are shown in FIGS. 5, 6 and 7.

As shown in Table 1 below, the EL luminous efficiency when the EL device was manufactured using MEH-PPV was 1.5 × 10 ⁻⁴ (%), and 3.4 × 10 for the EL device using the polymer prepared in the present invention. ^-3 (%) showed about 20 times improved luminous efficiency. That is, it can be seen that the fluorinated aryl group substituents help to balance the injection of electrons and holes to increase the luminous efficiency.

6. Evaluation of Electro-optical Characteristics of EL Devices Fabricated in Double Layer System

The results of evaluating the characteristics of the EL device fabricated in Example 4 are as in FIGS. 5, 6, and 7. The threshold voltage was lower than that of the monolayer, and the maximum luminance and the EL wavelength showed the same results. It can be seen that PPV was used as the hole transport layer in the layer type device.

On the other hand, as shown in Table 1 below, the EL luminous efficiency is 2.0 × 10 ^-2 (%) showed a result more than 100 times compared to MEH-PPV, which is not the light emission occurs between the electrode and the light emitting polymer, the present invention Holes and electrons collide between the light-emitting polymer containing a fluorinated aryl group and PPV, produced in the present invention. In this case, the ratio of non-radiative decay is smaller than that of light emission at the electrode interface. Can be.

Table 1

EL element configuration (anode / EL polymer / cathode) Light emitting efficiency of EL device (%) Applied Voltage [Electric Field (V / m)] ITO / HEM-PPV / Al 1.5 × 10 ^-4 2.8 × 10 ⁷ ITO / PPFPV / Al 3.4 × 10 ^-3 1.2 × 10 ⁸ ITO / PPV / PPFPV / Al 2.0 × 10 ^-2 7.1 × 10 ⁷

The present invention includes a fluorinated aryl group having strong electron affinity properties, thereby inducing balanced inflow of electrons and holes from the electrode, thereby increasing the luminous efficiency of the electroluminescent device and improving the maximum luminance. Has In addition, it has an effect of providing a light emitting polymer having a green light emission color, forming a uniform thin film without pin holes or other defects, and having excellent adhesion to a substrate.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims (5)

An electroluminescent polymer comprising a fluorinated aryl group and represented by the following structural formula (I) which is fully conjugated: In the structural formula (I), R ₁ , Aliphatic alkoxy, (CH ₂ ) _n CH ₃ (n is an integer from 0 to 15) or CH ₂ CHCH ₃ (CH ₂ ) _m CH ₃ (m is an integer from 1 to 15), R ₂ is H, or And p is an integer of 5 to 100. Providing a compound represented by the following structural formula (II) having a fluorinated aryl group; And Reacting a compound represented by formula (III) with a compound of formula (II): Method for producing a fully conjugated organic electroluminescent polymer containing a fluorinated aryl group represented by the following structural formula (I) provided in claim 1 characterized in that it comprises a step: Electroluminescence comprising a thin film formed from a polymer solution prepared by dissolving a fully conjugated organic electroluminescent polymer material having a fluorinated aryl group in an organic solvent as a single layer system. display. An electroluminescent display comprising a thin film in which a full conjugated organic electroluminescent polymer having a fluorinated aryl group and another luminescent polymer are formed in a double layer system. 5. The method of claim 4, wherein the other light emitting polymer is poly [2-methoxy-5- (2'-ethylhexyloxy) -1,4-phenylene vinylene] (MEH-PPV). Luminous display.