KR100441200B1 - Poly phenylene vinylene polymer and the preparation thereof - Google Patents

Abstract

The present invention relates to novel polyphenylene vinylene (PPV) polymers, and more particularly to a PPV polymer substituted with germanium, a method of preparation and an electroluminescent device comprising the polymer. The polymer according to the present invention is a polyphenylene vinylene polymer including a structure in which one or more germanyl groups are substituted in a benzene ring, and the phenylene vinylene group as the repeating unit may have a structure represented by the following Chemical Formula 1 or Formula 2.

(Formula 1)

(Formula 2)

(In Formula 1 or 2, R ₁ , R ₂ , R ₃ are each a linear or branched alkyl group of C ₁ -C ₂₀ )

The PPV polymer substituted with the germanyl group according to the present invention emits green light having substantially the same wavelength as that of the conventional PPV, and has a superior luminous efficiency than that of PPV. Also, when a long alkyl group is used, the final polymer is organically soluble and excellent in workability. Do.

Description

Polyphenylene vinylene polymer substituted with germanyl group and its manufacturing method {POLY PHENYLENE VINYLENE POLYMER AND THE PREPARATION THEREOF}

The present invention relates to novel polyphenylene vinylene (PPV) polymers that can be used in electroluminescent devices, and more particularly, to a PPV polymer substituted with germanium, a manufacturing method and an electroluminescent device comprising the polymer.

Recently, research in the field of electroluminescent devices has been actively conducted with the aim of flattening, lightening, thinning and high resolution of a display. As a material of the polymer electroluminescent device, π-conjugated polymer having a conjugated double bond is most widely used. For the practical use of the polymer electroluminescent device, development of a light emitting material having excellent processability and high luminous efficiency has been developed. It is essential.

As materials of light emitting devices, inorganic materials focusing on Group 3 and Group 5 elements have been mainly used, but have the disadvantages of poor processability, difficulty in making a large area, high driving voltage, and difficulty in obtaining blue region light. . On the other hand, the polymer light emitting material is relatively easy to process and color control, low driving voltage, fast response speed, light weight and large size can be compared to the conventional inorganic light emitting device has a number of advantages.

Among these, PPV and its derivatives are the most widely used light emitting materials for polymer light emitting devices, and are known as light emitting materials that show the closest commercialization properties due to high light emission efficiency and chemical stability. Patent application has been applied that can be used as a light emitting material of the light emitting device (US Patent No. 5 247 190). The PPV used as the light emitting layer in the patent is synthesized through a high temperature heat treatment process of about 200 ℃ or more after preparing a thin film of the polymer dissolved in water.

However, unsubstituted PPV is synthesized through a water-soluble prepolymer and emits green light. However, in the case of a device manufactured using PPV as a light emitting layer, there is a problem in that luminous efficiency is low.

Therefore, there is a continuing need for polymers having higher luminous efficiency and light emitting element and improved processability.

It is an object of the present invention to provide a novel PPV derivative and a method of manufacturing the same, which emit light of green light, such as PPV, and have higher luminous efficiency and brightness, and have improved processability, so as to solve the above problems.

It is also an object of the present invention to provide an electroluminescent device having improved properties comprising the above PPV derivative.

1 is a UV and photoluminescence (PL) spectrum of TEG-PPV prepared according to an embodiment of the present invention.

2 is a schematic cross-sectional view of an electroluminescent device fabricated comprising the polymer according to the invention.

Figure 3 is an electroluminescence (EL) spectrum of a single layer light emitting device comprising TEG-PPV prepared according to one embodiment of the present invention.

Figure 4 is a graph showing the voltage-current and voltage-luminance of a single layer device comprising TEG-PPV prepared according to one embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

100: transparent substrate

110: indium-tin-oxide (ITO) electrode

120: hole transporting layer (Hole Transporting layer)

130: polymer light emitting layer according to the present invention

140: Electron transporting layer

150: metal electrode

In order to achieve the above object, the present inventors have intensively researched and found that when the germanyl group having an alkyl group is introduced into the benzene ring of PPV, the problem can be solved. In other words, germanium is a semimetal element with semiconducting properties, and its electrical effect is almost the same as that of hydrogen, and when germanium is substituted for PPV polymer, it has a homo-lumo band gap similar to that of conventional PPV. The present invention has been completed with the idea that the properties will be superior to PPV.

The present invention provides a polyphenylene vinylene polymer comprising a structure in which at least one germanyl group is substituted for a benzene ring in a phenylene vinylene group as a repeating unit. In this case, the phenylene vinylene group which is a repeating unit of the polymer may have a structure of Formula 1 or a structure of Formula 2 below.

Wherein R ₁ , R ₂ and R ₃ are each a C ₁ -C ₂₀ linear or branched alkyl group.

Wherein R ₁ , R ₂ and R ₃ are each a C ₁ -C ₂₀ linear or branched alkyl group.

The present invention also provides a copolymer comprising the compound having the structure of Formula 1 or Formula 2 as one of the repeating units.

The copolymer includes a copolymer having a structure of Formula 3 or Formula 4 below.

(In Formula 3 or Formula 4, 1 <x <99, 1 <y <99, x + y = 100, R ₁ , R ₂ , R ₃ is a C ₁ -C ₂₀ linear or branched alkyl group, R ₄ , R ₅ is H or C ₁ -C ₂₀ linear or branched alkoxy group Wherein R ₆ is a linear or branched alkoxy group of C ₁ -C ₂₀ )

The present invention also provides an electroluminescent device comprising a polymer having a compound having the structure of Formula 1 or Formula 2 as a repeating unit.

The present invention also provides a method for preparing a halogenated trialkylgeryl group, comprising: substituting a trialkylgeryl group for a dihaloxylene by a Grignard reaction; Reacting the resultant with N-bromosuccinimide (NBS) or N-chlorosuccinimide (NCS) to obtain bis (trialkylgeryl) bis (haloalkyl) benzene; Reacting the obtained product with tetrahydrothiophene to obtain a monomer of sulfonium salt; And the monomer obtained by adding a base in an aqueous solution to obtain a prepolymer, and heat treatment in a vacuum to provide a method for producing a polyphenylene vinylene polymer substituted with a germanyl group.

The present invention is shown in the following Scheme 1, Scheme 2 and Scheme 3 of several examples of the method for producing a polymer according to the present invention.

(Wherein R ₁ , R ₂ , R ₃ = C ₁ -C ₂₀ linear or branched alkyl group, X is Cl or Br, i) THF / Mg, R ₁ R ₂ R ₃ Ge-X, ii) NBS or NCS / CCl ₄ , iii) Tetrahydrothiophene / MeOH, iv) NaOH / H ₂ O, v) 230 ° C., vacuum)

Wherein R ₁ , R ₂ , R ₃ are each a C ₁ -C ₂₀ linear or branched alkyl group, X is Cl or Br, i) THF / Mg, R ₁ R ₂ R ₃ Ge-X, Ii) NBS or NCS / CCl ₄ , i) Tetrahydrothiophene / MeOH, i) NaOH / H ₂ O, v) 230 ° C., vacuum)

Wherein R ₁ , R ₂ , and R ₃ are each a C ₁ -C ₂₀ linear or branched alkyl group, i) THF / Mg, R ₁ R ₂ R ₃ Ge-X, ii) NBS / CCl ₄ , Tetrahydrothiophene / Methanol (iv) NaOH / MeOH, v) 230 ° C., vacuum)

As described above, after the synthesis of a prepolymer soluble in the organic solvent from a sulfonium salt substituted with a germanyl group, the obtained prepolymer may be processed in the form of a film and then heat treated to prepare a method, but the length of the alkyl group In the case of long, the organic polymer can be directly dissolved through a dehydrohalogenation reaction known as Gilch reaction as in Scheme 4 and Scheme 5 below.

(Wherein R ₁ , R ₂ , R ₃ are each a C ₁ -C ₂₀ linear or branched alkyl group, X is Cl or Br, vi) is t-BuOK / THF)

(Wherein R ₁ , R ₂ , R ₃ are each a C ₁ -C ₂₀ linear or branched alkyl group, X is Cl or Br, vi) is t-BuOK / THF)

Hereinafter, the configuration of the present invention through the embodiment of the present invention in more detail.

Example 1: Preparation of 2-triethylgeryl-para-xylene

7.01 g (37.9 mmol) of 2-bromo-para-xylene dissolved in 20 ml of dry THF was slowly added to a clean piece of magnesium (3.7 g, 151.6 mmol) to make a Grignard reagent. When magnesium was completely dissolved, chlorotriethylgermanium (8.9 g, 45.5 mmol) was added, and the reaction was carried out at 70 ^° C. for about 3 hours.

Diluted hydrochloric acid solution was added to terminate the reaction, followed by extraction with diethyl ether. The extracted organic layer was distilled under vacuum to obtain 4.5 g (45%) of 2-triethylgeryl-para-xylene.

¹ H-NMR (CDCl ₃ , 200 MHz): δ7.24 (1H, s), 7.20 (2H, s), 2.38 (3H, s), 2.33 (3H, s), 1.08 (15H, Br)

¹³ C-NMR (CDCl ₃ , 200 MHz): δ 141.7, 139.5, 139.0, 137.2, 136.8, 135.4, 22.6, 21.3, 10.6, 6.55

Elemental Analysis-Measured Values: C (64.84 wt%), H (9.66 wt%)

Theoretical values: C (63.46 wt%), H (9.13 wt%)

Example 2: Preparation of 2-triethylgeryl-1,4-bis (bromomethyl) benzene

2.7 g (9.0 mmol) of 2-triethylgeryl-para-xylene, 3.2 g (17.9 mmol) of N-bromosuccinimide (NBS) and a small amount of benzoyl peroxide (BPO) prepared in Example 1 were dried. 40 ml of carbon tetrachloride was added and refluxed for 3 hours in a nitrogen atmosphere. Succinimide produced as a by-product after the reaction was removed using a filter paper. The liquid residue obtained after distilling off the solvent of the remaining solution was subjected to column chromatography to obtain 3.3 g (43%) of 2-triethylgeryl-1,4-bis (bromomethyl) benzene in the form of a colorless oil. Separated.

¹ H-NMR (CDCl ₃ , 200 MHz): δ 7.43 (1H, s), 7.40 (2H, s), 4.50 (2H, s), 4.47 (2H, s), 1.06 (15H, m)

¹³ C-NMR (CDCl ₃ , 200 MHz): δ 143.4, 139.5, 137.2, 131.2, 129.7, 34.1, 33.24 8.97, 5.42

Elemental Analysis-found C: 39.51 wt%, H: 5.46 wt%

Theoretic C: 39.78 wt%, H: 5.25 wt%

Example 3: Preparation of 2-triethylgeryl-1,4-bisxylene (tetrahydrothiophenium bromide)

3.0 g (7.1 mmol) of 2-triethylgeryl-1,4-bis (bromomethyl) benzene and 3.8 g (42.6 mmol) of tetrahydrothiophene prepared in Example 2 were dissolved in 20 ml of methanol solution for 24 hours. Was reacted at 50 ° C. After the reaction, methanol and excess tetrahydrothiophene were removed and cold acetone was added to the remaining solution to obtain a white solid precipitate. The precipitate was filtered and dried in vacuo to yield 3.6 g (85%) of 2-triethylgeryl-1,4-bisxylene (tetrahydrothiophenium bromide).

¹ H-NMR (D ₂ O, 200 MHz): δ 7.58 (1H, s), 7.51 (2H, s), 4.58 (2H, s), 4.49 (2H, s), 3.75-3.20 (8H, m) , 2.55-2.10 (8H, m), 1.25-0.80 (15H, m)

Elemental Analysis-found C: 42.41, H: 6.31

Theoretical C: 44.11, H: 6.39

Example 4: Preparation of Poly (2-triethylgeryl-1,4-phenylenevinylene) (TEG-PPV)

1.5 g (2.5 mmol) of the clean monomer synthesized in Example 3 was dissolved in 5 ml of methanol, and nitrogen was blown for 5 minutes to remove oxygen from the solution and the temperature of the reaction vessel was adjusted to 0 ° C. 2.5 ml of cold NaOH aqueous solution having 1.0 M concentration was added dropwise to the vessel containing the monomers. After reacting at 0 ° C. for 30 minutes, the temperature was raised to room temperature and stirred for 5-6 hours. First, a water-soluble prepolymer that was dissolved in water was formed, and then a substitution reaction was gradually performed with methanol used as a solvent to obtain an organic soluble prepolymer, which was rinsed several times with clean methanol and filtered. The obtained prepolymer was dissolved in toluene, filtered with a syringe filter, and the solution was spin coated onto a glass substrate. The coated prepolymer film was heat-treated at 230 ° C. for 10 hours in a vacuum state to obtain poly [(2-triethylgeryl) -1,4-phenylenevinylene] ([poly (2 -triethylgermyl -1,4-phenylenevinylene)] (TEG-PPV) was obtained.

The molecular weight of the resulting prepolymer was measured using gas phase chromatography (GPC). The measured molecular weight was between 30,000-100,000 and the dispersion was between 2.5-3.5 according to the conditions such as monomer concentration and polymerization temperature. The elimination reaction TEG-PPV showed a maximum absorption at about 400 nm and an absorption edge at about 515 nm. When excited with light of 400 nm wavelength generated from the xenon lamp, it exhibited a maximum photoluminescence (PL) spectrum in the green region of about 515 nm.

1 shows the UV-vis absorption spectrum and the PL spectrum of TEG-PPV.

Example 5 Fabrication of Electroluminescent Device

A single layer electroluminescent device (ITO / TEG-PPV / Al) was fabricated using TEG-PPV as a light emitting layer and ITO and Al coated on glass as a cathode and an anode, respectively. A schematic cross-sectional view of the fabricated electroluminescent device is shown in FIG. 2.

The electroluminescence (EL) spectrum showed a luminescence spectrum similar to that of the photoluminescence (PL) spectrum and emitted green light at about 550 nm. 3 shows the EL spectrum of a light emitting device fabricated using TEG-PPV as a light emitting layer. The current-voltage characteristic of the light emitting diode fabricated in FIG. 4 is illustrated, and the current-voltage curve shows a typical diode characteristic in which the current increases in proportion to the increase in voltage. It was confirmed that it emits bright green light from about 13 V. The intensity of luminescence was measured with an illuminometer and the maximum luminance was 300 cd / m ² at 22 V. Under the same conditions, the maximum luminance of the single-layer light emitting device fabricated using PPV as the light emitting layer was about 20-30 cd / m ² , and the germanium-substituted PPV synthesized according to the present invention showed an extremely high luminance.

The above embodiment is illustrative of a suitable embodiment of the present invention, it is obvious that the present invention is not limited by the above embodiment.

As described above, the germanyl-substituted PPV polymer and copolymer according to the present invention have the same light emitting area as PPV, and the luminous efficiency is superior to that of PPV, and a polymer which is soluble in an organic solvent when using a long alkyl group is prepared. It is excellent in workability. In addition, the electroluminescent device manufactured by using the PPV polymer substituted with germyl group as the light emitting layer also emits bright green light, and the performance is much better than the electroluminescent device manufactured using the conventional PPV as the light emitting layer.

Claims (6)

In the polymer which uses a phenylene vinylene group as a repeating unit, Polyphenylene vinylene polymer containing a germanyl group having a structure of the following formula (R ₁ , R ₂ , R ₃ are each a C ₁ -C ₂₀ linear or branched alkyl group) According to claim 1, A phenylene vinylene group as the repeating unit has a structure represented by the following formula (1). (Formula 1) Wherein R ₁ , R ₂ and R ₃ are each a C ₁ -C ₂₀ linear or branched alkyl group. According to claim 1, A phenylene vinylene group as the repeating unit has a structure represented by the following formula (2). (Formula 2) (R ₁ , R ₂ , R ₃ are each a C ₁ -C ₂₀ linear or branched alkyl group) A copolymer comprising the compound having the structure of Formula 3 or Formula 4 as one of the repeating units. [Formula 3] [Formula 4] (In Formula 3 or Formula 4, 1 <x <99, 1 <y <99, x + y = 100, R ₁ , R ₂ , R ₃ is a C ₁ -C ₂₀ linear or branched alkyl group, R ₄ , R ₅ is H or C ₁ -C ₂₀ linear or branched alkoxy group Wherein R ₆ is a C ₁ -C ₂₀ linear or branched alkoxy group.) An electroluminescent device comprising a polymer having a compound having the structure of Formula 1 or Formula 2 as a repeating unit. Substituting a trialkylgeryl group for dihaloxylene through a Grignard reaction; Then reacting the substituted product with N-bromosuccinimide (NBS) or N-chlorosuccinimide (NCS) to obtain bis (trialkylgeryl) bis (haloalkyl) benzene; Then reacting the obtained product with tetrahydrothiophene to obtain a monomer of sulfonium salt; And Thereafter, the obtained monomer is added with a base in an aqueous solution to obtain a prepolymer, followed by heat treatment in vacuo, and a method for producing a polyphenylene vinylene polymer substituted with a germanyl group.