JP2003171524A - Luminescent polymer composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a luminescent polymer composition capable of obtaining an organic electroluminescence element having a high luminescence efficiency and excellent durability, and capable of easily forming an organic material layer by a wet method. <P>SOLUTION: This luminescent polymer composition comprises a copolymer (A) comprising 50-99 mol% structural unit derived from a tertiary aromatic amine derivative and 50-1 mol% structural unit derived from an oxadiazole derivative, and a tetraphenyl butadiene (B). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a luminescent polymer composition which can be suitably used as an organic electroluminescent material.

[0002]

2. Description of the Related Art Organic electroluminescent devices are
Being thin, capable of being driven by a DC voltage, having a wide viewing angle and high visibility because it is a self-luminous element, and having excellent characteristics such as fast response speed Therefore, it is expected as a next-generation display element, and its research is actively conducted. Conventionally,
The organic electroluminescent element has a single layer structure in which a light emitting layer made of an organic material is formed between an anode and a cathode, a structure having a hole transport layer between the anode and the light emitting layer, and a cathode. Multilayered structures such as those having an electron transport layer between the light emitting layer and the like are known, and these organic electroluminescent elements each have an electron injected from a cathode and a hole injected from an anode. However, the light is emitted by recombination in the light emitting layer.

In such an organic electroluminescence device, as a method of forming an organic material layer such as a light emitting layer and a hole transport layer, a dry method of forming an organic material by vacuum vapor deposition, or a solution in which the organic material is dissolved is applied. There is known a wet method of forming by drying after drying. Among these, the dry method has a complicated process, and it is difficult to cope with mass production, and there is a limit in forming a layer having a large area. On the other hand, in the wet method, the process is relatively simple and can be applied to mass production, and an organic material layer having a large area can be easily formed. It is advantageous as compared with the dry method.

On the other hand, the organic material layer constituting the organic electroluminescence device is required to have high durability and high luminous efficiency, and is conventionally made of various materials. Is known, and recently, an organic material layer containing a phosphorescent organic iridium compound or an organic osmium compound as a light emitting molecule has been proposed (WO 00/70).
655 publication). This organic material layer is made of only an organic iridium compound or an organic osmium compound, or these compounds and 4,4′-N, N′-dicarbazole biphenyl or 4,4′-bis [N- (1- And a hole transport material such as naphthyl) -N-phenyl-amino) biphenyl. However, since this organic material layer is formed by a dry method, it is difficult to cope with mass production and to form a large-area organic material layer.

[0005]

The present invention has been made based on the above circumstances, and its purpose is to:
It is an object of the present invention to provide a luminescent polymer composition which can obtain an organic electroluminescence device having high luminous efficiency and excellent durability and which can easily form an organic material layer by a wet method.

[0006]

The present invention provides a structural unit of 50 to 99 mol% derived from a tertiary aromatic amine derivative and a structural unit of 50 to 1 derived from an oxadiazole derivative.
A luminescent polymer composition containing a copolymer consisting of mol% and tetraphenylbutadiene, and a hole transporting polymer obtained by polymerizing a tertiary aromatic amine derivative and oxadiazole are polymerized. And a polymer component comprising an electron-transporting polymer having a ratio of the hole-transporting polymer and the electron-transporting polymer of 50:50 to 99: 1 in terms of a molar ratio converted into a monomer, and tetraphenylbutadiene. A luminescent polymer composition containing the same is provided.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. The luminescent polymer composition of the present invention contains, as a polymer component, any of the following components (A-1) to (A-3) and also a component (B) comprising a phosphorescent agent. Is. Component (A-1): a polymer component comprising a copolymer composed of a structural unit derived from a tertiary aromatic amine derivative and a structural unit derived from oxadiazole, (A-2) component: a tertiary aromatic Polymer component (A-3) consisting of a hole-transporting polymer obtained by polymerizing a group amine derivative and an electron-transporting polymer obtained by polymerizing an oxadiazole: a tertiary aromatic amine derivative Component consisting of hole transporting polymer and electron transporting monomer

[Component (A-1)] The component (A-1) is a polymer component composed of a copolymer of a tertiary aromatic amine derivative and oxadiazole. It may be any of a random copolymer, a block copolymer and an alternating copolymer of a tertiary aromatic amine derivative and oxadiazole.

As the tertiary aromatic amine derivative, it is particularly preferable to use a carbazole derivative, and specific examples thereof include N-vinylcarbazole, 3,6-dimethyl-9-vinylcarbazole and 3,6-diethyl-. 9-
Examples thereof include vinylcarbazole, 3-methyl-9-vinylcarbazole, 3-ethyl-9-vinylcarbazole and the like. Among these, N-vinylcarbazole,
3,6-Dimethyl-9-vinylcarbazole is preferred.

As the oxadiazole derivative, 2-β
-Naphthyl-5- (4-vinylphenyl) -1,3,4
-Oxadiazole, 2-α-naphthyl-5- (4-vinylphenyl) -1,3,4-oxadiazole, 2-
Phenyl-5- (4-vinylphenyl) -oxadiazole, 2-phenyl-5- (4-vinyl-p-biphenylyl) -1,3,4-oxadiazole, 2- (p-biphenyl) -5 -(4-vinylphenyl) -oxadiazole, 2- (p-biphenyl) -5- (4-propenylphenyl) -1,3,4-oxadiazole, 2
-T-butoxyphenyl-5- (4- (4-vinylphenyl) -p-biphenylyl) -1,3,4-oxadiazole or these oxadiazole derivatives substituted with an acryloyl group or a methacryloyl group, etc. Is mentioned. Among these, 2-β-naphthyl-5-
(4-vinylphenyl) -1,3,4-oxadiazole, 2- (p-biphenyl) -5- (4-vinylphenyl) -1,3,4-oxadiazole, 2- (p-biphenyl) ) -5- (4-Propenylphenyl) -1,
3,4-oxadiazole is preferred.

In the copolymer used as the component (A-1), the molar ratio of the structural units derived from the tertiary aromatic amine derivative to the structural units derived from oxadiazole is 50:50. ˜99: 1, preferably 65:35 to 95: 5. When the proportion of the structural unit derived from the tertiary aromatic amine derivative is too small,
If the amount of injected holes is reduced and the proportion of structural units derived from the tertiary aromatic amine derivative is too large, the injected amount of holes becomes excessive and the balance of recombination with electrons is lost. Not preferable.

The copolymer used as the component (A-1) has a polystyrene-reduced weight average molecular weight of 2,000 to 1,50 by gel permeation chromatography.
It is preferably 50,000, particularly preferably 5,000 to 500,000. When the weight average molecular weight is less than 2,000, the resulting luminescent polymer composition tends to have insufficient heat resistance, stability in a thin film state and mechanical strength. On the other hand, this weight average molecular weight is 1,
When it exceeds 500,000, the resulting luminescent polymer composition tends to have a remarkably high solution viscosity, resulting in poor handleability in the production of an organic electroluminescence device, and solution stringability. Is caused, which is not preferable. The total proportion of unreacted tertiary aromatic amine derivative and oxadiazole contained in the copolymer used as the component (A-1) is preferably 5% by weight or less.

Such a copolymer is obtained by copolymerizing a tertiary aromatic amine derivative and oxadiazole in the presence of a cationic polymerization catalyst, a radical polymerization catalyst or an anionic polymerization catalyst in an appropriate polymerization solvent. Obtained by Here, as the polymerization solvent, halogenated hydrocarbons such as methylene chloride and chlorobenzene, aromatic hydrocarbons such as toluene and benzene, ether solvents such as dibutyl ether, diphenyl ether, dioxane and tetrahydrofuran, acetonitrile, nitrobenzene, N -Highly polar solvents such as methylpyrrolidone and dimethylacetamide can be used. As the cationic polymerization catalyst, or the like can be used _{HI-ZnI 2, I 2,} I 2 -HI. As the radical polymerization catalyst, azobisisobutyronitrile, azobis-1-acetoxy-1-phenylene ethane or the like can be used. As the anionic polymerization catalyst, alkyllithium or the like can be used. The proportion of the polymerization catalyst used is 0.0001 to 0.5 mol per 1 mol of the total amount of the tertiary aromatic amine derivative and oxadiazole. The reaction temperature is, for example, -150 when a cationic polymerization catalyst is used.
It is -50 degreeC, when using a radical polymerization catalyst, it is 60-200 degreeC, and when using an anionic polymerization catalyst, it is 0-100 degreeC, for example.

[Component (A-2)] The component (A-2) is a hole-transporting polymer obtained by polymerizing a tertiary aromatic amine derivative and an electron-transporting polymer obtained by polymerizing oxadiazole. It is a polymer component consisting of Specific examples of the tertiary aromatic amine derivative for obtaining the hole transporting polymer and the oxadiazole for obtaining the electron transporting polymer include the copolymers used as the above-mentioned component (A-1). The same thing as the monomer for obtaining can be mentioned.

The hole-transporting polymer has a polystyrene-reduced weight average molecular weight of 5,000 to 1,000,000 by gel permeation chromatography, especially 1
It is preferably from 50,000 to 1,000,000. When the weight average molecular weight is less than 5,000, the resulting luminescent polymer composition tends to have insufficient heat resistance, stability in a thin film state, and mechanical strength. On the other hand, the weight average molecular weight is 1,000,00.
When it exceeds 0, the resulting luminescent polymer composition is
The solution viscosity is liable to be extremely high, the handling property is lowered in the production of the organic electroluminescence element, and the stringing property of the solution is generated, which is not preferable.

The electron transporting polymer preferably has a polystyrene reduced weight average molecular weight of 1,000 to 1,000,000 as determined by gel permeation chromatography. When the weight average molecular weight is less than 1,000, the resulting polymer tends to have insufficient heat resistance, stability and mechanical strength, while the weight average molecular weight is less than 1,000,000. When it exceeds, the resulting luminescent polymer composition tends to have a remarkably high solution viscosity, and in the production of the organic electroluminescence device, the handling property is lowered, and the stringing property of the solution occurs, Not preferable.

The ratio of the hole transporting polymer to the electron transporting polymer in the component (A-2) is 50:50 to 99: 1 in terms of monomer, preferably 70:50.
It is set to 30 to 99: 1. When the proportion of the hole transporting polymer is too small, the hole injection amount decreases, while when the proportion of the hole transporting polymer is too large, the hole injection amount increases and the Is unfavorable because it will lose the balance.

The hole-transporting polymer and the electron-transporting polymer can be prepared by a cationic polymerization method in an appropriate polymerization solvent.
It can be produced by a radical polymerization method or an anionic polymerization method.

In the case of producing a polymer by the cationic polymerization method, the polymerization solvent includes halogenated hydrocarbons represented by methylene chloride, chlorobenzene, etc., ether solvents such as dibutyl ether, diphenyl ether, dioxane, tetrahydrofuran, acetonitrile, etc. A highly polar solvent such as nitrobenzene can be used. As a cationic polymerization catalyst, HI-ZnI
A catalyst such as ₂ , I ₂ , I ₂ -HI can be used,
In addition, a catalyst composed of a combination of a Lewis acid and a base such as a metal halide / ether complex can be used. The ratio of such cationic polymerization catalyst used is 0. 1 with respect to 1 mol of N-vinylcarbazole initially polymerized.
It is from 01 to 0.00001 mol. The reaction temperature is
For example, it is −150 to 50 ° C.

When the polymer is produced by the radical polymerization method, the polymerization solvent is an amide solvent such as dimethylformamide, dimethylacetamide or N-methylpyrrolidone, or a hydrocarbon solvent such as benzene, toluene, xylene, hexane or cyclohexane. , Γ-butyrolactone, esters such as ethyl lactate, ketone solvents such as cyclohexylbenzophenone and cyclohexanone, and the like can be used. As the radical polymerization catalyst, peroxide, 4-methylsulfonyloxy-2,
2 ', 6,6'-Tetramethyl-1-piperidine-N-
With N-oxy radicals such as oxide, 2,2 ', 5,5'-tetramethylpyrrolidine oxide, 4-oxo-2,2', 6,6'-tetramethyl-1-piperidine-N-oxide Combination type and sulfide type catalysts can be used. The radical polymerization catalyst is used in an amount of 0.0001 to 1 mol of the monomer.
It is 0.5 mol. The reaction temperature is, for example, 60 to 2
It is 00 ° C.

In the case of producing a polymer by the anionic polymerization method, an aromatic hydrocarbon such as toluene and benzene, an aliphatic hydrocarbon such as hexane and heptane, an ether compound such as tetrahydrofuran and the like can be used as a polymerization solvent. . As the anionic polymerization catalyst, an alkali metal compound such as naphthalene potassium and butyl lithium, or an alkaline earth metal compound such as an art type complex of barium and aluminum can be used. Of these, butyllithium and naphthalenelithium are preferable. The proportion of such anionic polymerization catalyst used is 0.0001 to 0.1 mol per mol of the monomer.
The reaction temperature is, for example, 0 to 100 ° C.

[Component (A-3)] It contains the hole-transporting polymer and the same electron-transporting monomer used in the synthesis of the electron-transporting polymer. The hole-transporting polymer and the electron-transporting monomer are in a molar ratio of 50:50 to 99: 1 in terms of monomer, preferably 70:
It is set to 30 to 99: 1.

[Component (B)] The use ratio of tetraphenylbutadiene is 0.1 with respect to 100 parts by weight of the polymer component.
The amount is preferably -30 parts by weight, more preferably 0.5-10 parts by weight. When this proportion is less than 0.1 parts by weight, the light emission is not sufficient, while when this proportion exceeds 30 parts by weight, concentration quenching may occur, which is not preferable.

In the luminescent polymer composition of the present invention,
Usually, it is prepared as a composition solution by dissolving the above-mentioned polymer component and the phosphorescent agent in an appropriate organic solvent, and the composition solution is applied to the surface of the substrate on which the organic material layer is to be formed to obtain a composition solution. The organic material layer in the organic electroluminescent element can be formed by performing an organic solvent removal treatment on the obtained coating film. The organic material layer thus obtained may be applied as a light emitting layer or a hole transporting layer.

In the above, the organic solvent for preparing the composition solution is not particularly limited as long as it can dissolve the polymer component and the phosphorescent agent used, and specific examples thereof include chloroform and chlorobenzene. , Halogenated hydrocarbons such as tetrachloroethane, amide solvents such as dimethylformamide, N-methylpyrrolidone, ethyl lactate, pegmia, ethylethoxypropionate,
Examples thereof include cyclohexanone and methyl amyl ketone. These organic solvents can be used alone or in combination of two or more. Among these, it is preferable to use one having an appropriate evaporation rate, specifically, an organic solvent having a boiling point of about 70 to 200 ° C., in that a thin film having a uniform thickness can be obtained. The proportion of organic solvent used is
Depending on the type of polymer component and phosphorescent agent,
Usually, it is a ratio such that the total concentration of the polymer component and the phosphorescent agent in the composition solution is 0.1 to 10% by weight. Further, as a means for applying the composition solution, for example, a spin coating method, a dipping method, a roll coating method, an ink jet method, a printing method or the like can be used. The thickness of the organic material layer formed is not particularly limited, but is usually 10 to 1000 nm, preferably 30 to 2 nm.
It is selected in the range of 00 nm.

According to such a luminescent polymer composition,
It is possible to obtain an organic electroluminescence device having high luminous efficiency and excellent durability, and moreover, an organic material layer can be easily formed by a wet method.

[0027]

EXAMPLES Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.

(1) Synthesis of Polymer: <Synthesis Example 1> In a 1000 mL two-neck round bottom flask, under nitrogen atmosphere, 0.85 mol of N-vinylcarbazole,
2-biphenyl-5 (p-vinylphenyl) -1,3
0.15 mol of 4-oxadiazole (V-PBD) and 0.02 mol of azobisisobutyronitrile were added, and dimethylformamide in an amount which was 3 times as much as the weight of the monomer was added. The radical polymerization of the monomer was performed under the condition of time. Then, a large amount of methanol was poured into the obtained reaction solution to solidify the reaction product. Further, by repeating the reprecipitation purification, the proportion of unreacted monomer contained in the reaction product was reduced to 1% by weight or less. When the obtained copolymer was analyzed, it was found that the structural unit derived from N-vinylcarbazole was 84.5 mol%,
It was confirmed that the copolymer was composed of 14.95 mol% of structural units derived from V-PBD, and the weight average molecular weight was measured by gel permeation chromatography and found to be 58,000 in terms of polystyrene. Hereinafter, this copolymer is referred to as "polymer (1)". <Synthesis Example 2> In Synthesis Example 1, the amount of N-vinylcarbazole used was 1.0 mol, and 2-biphenyl-5 (p-
Vinylphenyl) -1,3,4-oxadiazole (V
-PBD) same as in Synthesis Example 1 except that the amount used was 0 mol.
Polymerization was performed in this manner. The polymer obtained has a molecular weight of 18
It was 000. Hereinafter, this polymer is referred to as "polymer (2)". <Synthesis Example 3> In Synthesis Example 1, the amount of N-vinylcarbazole used was 0 mol, and 2-biphenyl-5 (p-vinylphenyl) -1,3,4-oxadiazole (VP
Same as Synthesis Example 1 except that the amount of BD) used was 1.0 mol.
Polymerization was performed in this manner. The polymer obtained has a molecular weight of 35.
It was 000. Hereinafter, this copolymer is referred to as "polymer (3)".

Example 1 Cyclohexanone was added to 1 g of the polymer (1) obtained in Synthesis Example 1 and 0.01 g of tetraphenylbutadiene to give a solid concentration of 5% by weight, which was then filtered with a 2.5 μm filter to emit light. The coating liquid for layer formation (1) was used. Example 2 The polymer (2) obtained in Synthesis Example 2 and the polymer (3) obtained in Synthesis Example 3 were converted into polymer (2): polymer (3).
= 100% of a polymer component mixed at a molar ratio of 2: 1 and 0.5 g of tetraphenyl butadiene to make a solid concentration of 5% by weight, and then filtered with a filter of 2.5 μm to form a light emitting layer. It was designated as liquid (2). Example 3 Polymer (2) obtained in Synthesis Example 2 and 2-biphenyl-
5 (p-vinylphenyl) -1,3,4-oxadiazole, polymer (2): 2-biphenyl-5 (p-vinylphenyl) -1,3,4-oxadiazole = 7: 3
100 g of the polymer components and 0.5 g of tetraphenylbutadiene mixed at a (molar ratio) were added to make a solid concentration of 5% by weight, and then filtered with a filter of 2.5 μm to form a coating solution for forming a light emitting layer (2). And Test Example A 5 cm square glass substrate with an ITO film formed on the surface was coated with an aromatic polymer (trade name PED manufactured by Bayer Co., Ltd.).
After applying a 5% by weight solution of OT P8000),
After heating at 0 ° C. for 30 minutes, the coating solution for forming a light emitting layer is applied by a spin coater to form a coating layer having a thickness of 70 μm.
This was heated at 120 ° C. for 10 minutes to form a light emitting layer. Vasophenanthroline and Cs were vapor-deposited on the obtained light emitting layer so that the molar ratio was 3: 1, and then an aluminum electrode (cathode) was further formed at 1500 angstrom. For the organic EL device manufactured in this way, I
A TO film was used as an anode, an aluminum film was used as a cathode, and a direct current voltage of 25 V was applied to cause the light emitting layer to emit light. As a result, the light emission starting voltage is 8 V, the maximum luminance is 4000 cd / m ² , and the light emitting efficiency is 2 cd.
/ A, 1 lm / W. Further, the durability of the organic EL device manufactured in the same manner as above was evaluated as follows. The results are shown in Table 1.

[0030]

[0031]

[Table 1]

[0032]

According to the present invention, an organic electroluminescence device having high luminous efficiency and excellent durability can be obtained, and further, the organic material layer can be easily formed by a wet method. A polymer composition can be provided.

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Claims (4)

[Claims] 1. A copolymer comprising (A) 50 to 99 mol% of a structural unit derived from a tertiary aromatic amine derivative and 50 to 1 mol% of a structural unit derived from an oxadiazole derivative, and (B). A luminescent polymer composition containing tetraphenyl butadiene. 2. A hole-transporting polymer obtained by polymerizing (A) a tertiary aromatic amine derivative and an electron-transporting polymer obtained by polymerizing an oxadiazole derivative,
The hole transporting polymer and the electron transporting polymer are in a molar ratio of 50:50 to 9 in terms of monomers.
A luminescent polymer composition comprising a polymer component of 9: 1 and (B) tetraphenylbutadiene. 3. A component comprising (A) a hole-transporting polymer obtained by polymerizing a tertiary aromatic amine derivative and an oxadiazole derivative, and (B) tetraphenylbutadiene. And a luminescent polymer composition. 4. The light-emitting property according to claim 1, wherein tetraphenyl butadiene is contained in an amount of 0.1 to 30 parts by weight based on 100 parts by weight of the copolymer or polymer component. Polymer composition.