JP2003261634A - Block copolymer, electrochemiluminescent device using the same, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an LEC from a polymer mixture using a block copolymer in which the microscopic dispersion of a luminescent polymer and a polymer electrolyte in an organic layer is kept good and stable. The present invention provides an inexpensive block copolymer used for this purpose. SOLUTION: (A block copolymer (C) in which a luminescent polymer block (A) and an ion-conductive polymer block (B) are copolymerized at their ends, and an organic thin film layer 1 is made of metal or A light emitting device sandwiched between a metal oxide anode electrode 2 and a metal or metal oxide cathode electrode 3,
An electrochemical light emitting device, wherein the organic thin film layer 1 is made of the copolymer (C). .

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a light emitting device,
More specifically, it relates to a surface light emitting device including an organic light emitting layer. In particular, the present invention uses a macroinitiator having a radical polymerization initiation group at the molecular chain end of the polymer solid electrolyte material,
The present invention relates to a method for synthesizing a block copolymer composed of a luminescent polymer block and an ion conductive block. Furthermore, the present invention relates to an electrochemical light emitting device (LEC) using a block copolymer composed of an ion conductive block and a light emitting polymer block composed of a vinyl monomer.

[0002]

2. Description of the Related Art In recent years, with the spread of mobile devices such as mobile terminals, there has been an increasing demand for thin, compact and lightweight display elements with low power consumption. A backlight type liquid crystal display element (LC
Instead of D), an organic electroluminescence element (O
EL) is attracting attention. The OEL is a laminated surface emitting device and has a structure in which a hole transporting organic layer and an electron conducting organic layer are laminated between a transparent electrode which is an anode electrode and a cathode electrode, and is often a luminescent dye. Is further doped. In many cases, in order to lower the barrier against carrier injection from the electrode, a buffer layer is inserted in the portion in contact with the electrode.

By applying a DC voltage, holes are injected from the anode electrode into the organic layer, and the holes move toward the cathode electrode along the highest occupied level (HOMO) of the organic layer. On the other hand, electrons are injected from the cathode electrode into the organic layer, and the electrons move toward the anode electrode along the lowest unoccupied level (LUMO). Recombination of holes and electrons occurs in the organic layer, and the energy is extracted to the outside as light. In this device, the control of the film thickness is extremely important for the light emission characteristics, and the device is often formed by using the vacuum evaporation method.

On the other hand, an electrochemical light emitting device (LEC) has been proposed as an organic light emitting device having a mechanism different from that of OEL. It has a structure in which an electrolyte and a luminescent organic substance are sandwiched between electrodes, and the anion radicals injected into the electrolyte from the anode electrode and the cation radicals injected from the cathode electrode move in the electrolyte and disappear. The energy of doing is extracted as light.

Literature Pei, Q. Yu, G .; ; Zha
ng, C.I. Yang, Y .; Heeger, A .;
J. Science 1995, 269, 1086.
[1] discloses an all-solid-state LEC using a solid electrolyte. This LEC is a soluble luminescent polymer p
oly [5- (2'-ethylhexyloxy)-
2-methoxy-1,4-phenylene v
It has a structure in which a mixture of inylene] (MEH-PPV) and polyethylene oxide (PEO) to which a Li salt is added is sandwiched between electrodes. PEO containing Li salt functions as a solid electrolyte. Here, the layer of the mixture sandwiched between the electrodes is manufactured by the solution casting method, which is a cheaper process than the vacuum evaporation method.

As pointed out in the literature [1], in the LEC, the film thickness dependence of the light emission characteristics is smaller than that of the OEL, and the element has both polarities, and the element structure is compared with the laminated structure of OEL. It will be even simpler.

Japanese Unexamined Patent Publication No. 9-309173 discloses an ion conductive laminate which is a laminate having an ion conductive material and a low ion conductive layer or non-conductive layer property.

Further, in Japanese Unexamined Patent Publication No. 10-150234, an organic element including an organic material layer and a second electrode layer provided on the organic material layer has an interface contour shape between adjacent layers. An electronic device used as an organic thin film element having a Hausdorff dimension of 1.5 to 2.0 is disclosed.

Further, in Japanese Unexamined Patent Publication No. 8-190801, a luminescent medium containing an electrochemiluminescent substance is arranged between opposing electrodes, and ions generated in one electrode diffuse to reach the other electrode. The LEC is disclosed in which the distance between the electrodes is set so that the shortest time until the temperature becomes equal to or less than the average life of the ions in the light emitting medium.

In Japanese Patent Publication No. 2000-506916,
As a material for photoluminescence and electroluminescence, a polyfluorene compound having a polar group is disclosed.

However, the luminescent material and the electrolyte used for LEC are generally incompatible. In such a case, a macroscopic phase-separated structure in which each component forms a domain with a scale of several μm or more is widely observed.
hi, C.I. Cecchetto, E .; Franco
is, B. Synth. Met. 1999, 102,
It is as pointed out in 916 [2].

The size and shape of the macroscopically phase-separated domains are often non-uniform and significantly change depending on the film thickness and the drying conditions. Therefore, strict control of manufacturing conditions is required to obtain uniform devices. Yes, this is not an easy task.

On the other hand, in the case of block copolymers in which incompatible polymers are covalently bonded to each other at their ends, reference Ba
tes, F.F. S. Fredrickson, G .;
H. Annu. Res. Phys. Chem. 199
No. 0 (41) 525, a microphase-separated structure of the order of nm, which is usually determined by the molecular structure, is formed.

Therefore, it is expected that the use of the block copolymer of the luminescent polymer material and the polymer electrolyte will facilitate the production of a microscopically uniform device. The block copolymer does not significantly change the size of the phase separation domain depending on the conditions of solution casting, and maintains a structure in which each component is microscopically and uniformly dispersed. Therefore, in the above-mentioned document [2], poly at the end of PEO is
(P-phenylene vinylene) (PP
A material to which the monomer or oligomer of V) is added is being investigated. Here, the hydroxyl group at the PEO terminal and the halogenated PPV monomer α-chloro-α'-buty
lsulfinyl-p-xylene or α, α'-
It is said that the reaction product was obtained in a yield of 15-20% by reacting dichloro-p-xylene.

[0015]

DISCLOSURE OF THE INVENTION The present invention uses a block copolymer capable of maintaining good and stable microscopic dispersion of a luminescent polymer and a polyelectrolyte in an organic layer rather than a polymer mixture. And a block copolymer used for this purpose at a low cost.

[0016]

The present invention provides a block copolymer (C) obtained by copolymerizing a luminescent polymer block (A) and an ion conductive polymer block (B) at their ends.
Regarding

The present invention also relates to the above block copolymer (C), wherein the luminescent polymer block (A) is a vinyl polymer obtained by polymerizing a luminescent vinyl monomer.

The present invention also relates to the above block copolymer (C), which is characterized by being doped with a low molecular weight light emitting material.

In the present invention, the block copolymer (C) is characterized in that the ion conductive polymer block (B) is composed of a metal salt-containing polyalkylene oxide.
Regarding

In the present invention, the block copolymer is
The present invention relates to the above block copolymer (C), wherein the luminescent vinyl monomer is copolymerized with an ion conductive polymer having a radical polymerization initiation group at the terminal as a macroinitiator.

Further, the present invention is a light emitting device comprising an organic thin film layer 1 sandwiched between a metal or metal oxide anode electrode 2 and a metal or metal oxide cathode electrode 3, wherein the organic thin film layer 1 is the above-mentioned. And an electrochemical light emitting device comprising the copolymer (C).

The present invention also relates to the above-mentioned method for producing an electrochemical light-emitting device, characterized in that the organic thin film layer 1 is formed by casting from a uniform solution of the block copolymer (C). .

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The luminescent biopolymer block (A) of the present invention is preferably a polymer having a functional group having a luminescent property in its side chain or main chain. For example, polyvinyl carbazole, polyvinyl anthracene, polyvinyl fluorenone, polyquinoline and the like are preferable, and vinyl polymer obtained by polymerizing a light emitting vinyl monomer such as vinyl carbazole, vinyl anthracene and vinyl fluorenone is particularly preferable.

The ion conductive polymer block (B) is preferably a metal salt-containing polyalkylene oxide.
The polyalkylene oxide is preferably polyethylene oxide or polypropylene oxide, and polyethylene oxide is particularly preferably used.

The metal salt is LiClO having a low lattice energy.
₄ , Li salts such as LiPF ₆ are particularly preferably used. The amount of the metal salt is about 5 to 30%, particularly preferably 15 to 25%, based on the weight of the polyalkylene oxide.
Is used. In order to improve ionic conductivity,
A plasticizer for the ion conductive polymer block (B) can be added as appropriate.

The molecular weight of the block copolymer is approximately 100.
0 or more is used. Preferably 5000-10000
It is 0.

The ratio of A block to B block is preferably 20/80 to 80/20 by weight.

In the present invention, it is preferable that the organic thin film layer 1 is doped with a low molecular weight light emitting material. As a dopant, organic low molecular weight dyes such as rhodamine and coumarin,
Metal complexes such as metal phthalocyanine and metal porphyrin are preferably used.

In the present invention, the organic thin film layer 1 is preferably formed by casting from a homogeneous solution containing the block copolymer (C) and, if necessary, a low molecular weight luminescent material and a metal salt in a predetermined amount.

Tetrahydrofuran, chloroform, pyridine and the like are used as the solvent, and pyridine is particularly preferably used.

The uniform solution is an indium tin oxide film (I
It is cast on the surface of the electrode (1) such as TO), preferably in a water-free atmosphere, and dried to obtain a solid thin film.

The other electrode (2) is formed on the thin film cast on the electrode by vacuum deposition or the like.
By applying a predetermined voltage between the electrodes 1 and 2, it can be operated as a light emitting element.

In the block copolymer for forming the organic thin film layer of the present invention, a luminescent vinyl monomer is copolymerized with an ion conductive polymer having a radical polymerization initiation group at one end or both ends as a macroinitiator. It is preferable.

The light emitting block polymer in the present invention can be produced, for example, as follows.
That is, the radical polymerization is carried out by a conventional method in a suitable solvent containing a macroazo initiator composed of a polyalkylylene oxide having a radical polymerization initiation group at one or both ends and a luminescent vinyl monomer in an appropriate solvent in an inert gas atmosphere. It is a thing.

The weight ratio of the macro azo initiator to the vinyl monomer in the polymerization system is 5/95 to 80/2.
0, preferably 10/90 to 60/40, and more preferably 20/80 to 40/60.

Examples of the light emitting vinyl monomer include vinylcarbazole (CVz) and vinylanthracene. Of these, vinylcarbazole is particularly preferably used.

The polymerization reaction is preferably carried out in the presence of an organic solvent. Examples of the organic solvent include hydrocarbons such as toluene, xylene, benzene, cyclohexane and n-hexane, halogenated compounds such as methylene chloride, chloroform and carbon tetrachloride, N, N-dimethylformamide, N-methylpyrrolidone and dimethyl. Examples include polar solvents such as sulfoxide. Of these, toluene, benzene and n-hexane are particularly preferable, and toluene is particularly preferable.

The polymerization reaction is preferably carried out in an inert gas atmosphere or vacuum. Examples of the inert gas include nitrogen gas and argon gas. The polymerization temperature is not particularly limited, but if it is too low, the decomposition / cleavage of the azo group is small, so that the progress of the polymerization slows or may be stopped.If it is too high, the decomposition of the azo group becomes too much. Since it becomes difficult to control the polymerization reaction system with the evaporation of the solvent or the like, it is usually 20 to 150 ° C., preferably 40 to 150 ° C.
It is appropriately selected from the range of 100 ° C.

The reaction time varies depending on the reaction conditions such as the reaction temperature, the reaction product, and the concentration, but is usually 2 to 24.
It is appropriately selected from the time range. Thus, an AB diblock copolymer composed of the light emitting polymer block (A) and the ion conductive polymer (B) or an ABA triblock copolymer is obtained.

[0040]

Example 1 Synthesis of PEO-PVCz (C) Vinylcarbazole (manufactured by Hiroshima Wako) was purified by recrystallization in n-hexane. Polyethylene oxide macroazo initiator (Hiroshima Wako, trade name VPE-0601)
Was used as is. In a 100 mL three-necked flask equipped with a nitrogen introduction tube and a reflux tube, 3.03 g of a polyethylene oxide macroazo initiator was dissolved in 30 mL of toluene at 0 ° C for 2 hours. 5.0 g of vinylcarbazole was added to the solution, and a polymerization reaction was carried out at 80 ° C. for 4 hours.
After completion of the reaction, the reaction solution was poured into a large amount of diethyl ether to precipitate a white polymer. This was dried overnight at 40 ° C. under reduced pressure, and 7.85 g (yield 97%) of PEO-P was obtained.
A VCz block copolymer was obtained. The molecular weight of the block copolymer estimated by gel permeation chromatography (GPC) was about 60,000.

82 mg of the above block copolymer (C)
Was dissolved in 4 mL of pyridine to obtain a uniform solution (S). 18 mg of LiClO ₄ was dissolved in this solution S. A mixed solution of a glass substrate with an ITO film made of E ・ H ・ C having a surface resistance of 10 Ω / □ and a volume ratio of pure water, 30% hydrogen peroxide solution and 25% ammonia water to 5/1/1. In 80
It was washed at 0 ° C for 20 minutes. Then, the substrate is washed with pure water and dried, and the surface of the substrate is coated with the solution S at 1000 rpm.
Was spin-coated to form a thin film. The thin film was dried in a vacuum chamber at 80 ° C. for about 24 hours. The internal structure of the produced thin film was cut into an ultrathin section, and its cross section was observed using a transmission electron microscope (TEM). It had a structure in which the PVCz microdomains that appeared dark in the TEM image were uniformly dispersed.

An Al layer was formed by vapor deposition as the other electrode on the surface of the thin film on the ITO electrode. The degree of vacuum during deposition of the Al layer was maintained at about 3 × 10 ⁻³ Pa or less. After the electrodes were formed, the ITO film portion and the Al electrode portion were each connected to an external terminal with a silver paste, and then the laminated film was sealed with an ultraviolet curing acrylic resin. When a DC voltage of 12 V was applied to the above device using the ITO film as a positive electrode and the Al layer as a negative electrode, light was emitted at 4 cd / m ² .

Example 2 An element was prepared in the same manner as in Example 1 except that coumarin was added to S in an amount of 2 mol% based on the polyvinylcarbazole block in C. Applying a DC voltage of 12V to this device gave a result of 38 cd / m
It emitted light at 2.

[0044]

According to the present invention, it is possible to manufacture a novel planar light emitting device in which the microscopic dispersion of the light emitting polymer and the polymer electrolyte is kept good and stable.

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Claims (7)

[Claims] 1. A block copolymer (C) obtained by copolymerizing a luminescent polymer block (A) and an ion conductive polymer block (B) at their ends. 2. The block copolymer (C) according to claim 1, wherein the luminescent polymer block (A) is a vinyl polymer obtained by polymerizing a luminescent vinyl monomer. 3. The block copolymer (C) according to claim 1, which is doped with a low-molecular light emitting material. 4. The block copolymer (C) according to claim 1, wherein the ion-conductive polymer block (B) is composed of a metal salt-containing polyalkylene oxide. 5. The block copolymer is obtained by copolymerizing a luminescent vinyl monomer with an ion conductive polymer having a radical polymerization initiation group at a terminal as a macroinitiator. The block copolymer (C) according to any one of 1 to 4. 6. A light-emitting device comprising an organic thin film layer 1 sandwiched between a metal or metal oxide anode electrode 2 and a metal or metal oxide cathode electrode 3, wherein the organic thin film layer 1 is formed.
5. An electrochemiluminescent device comprising the copolymer (C) according to any one of 5 to 6. 7. The method for producing an electrochemical light emitting device according to claim 6, wherein the organic thin film layer 1 is formed by casting from a uniform solution of the block copolymer (C).