JPH0820614A - Copolymer, its production and luminous element using the same - Google Patents

Abstract

PURPOSE:To obtain a copolymer providing a luminous element which contains a red luminous coloring matter having strong fluorescent intensity. is firmly stuck to a substrate without using a resin and has high efficiency by copolymerizing a vinylcarbazole with a specific phenoxazone derivative/a styryl derivative. CONSTITUTION:This copolymer comprises 99.99-50mol% of a structural unit of formula I and 0.01-50mol% of a structural unit of formula II (R1 is H or methyl; R is group of formula III, IV or V; R2 and R3 are each an alkyl, dulolidine ring, etc.; R4 is an alkyl, an aryl, etc.; X is O or S; Y is O or dicyanomethylene) and has 5,000-1,000,000 of weight-average molecular weight calculated as polystyrene. The copolymer is obtained by copolymerizing one or more compounds of a phenoxazone derivative of formula VI or formula VII and a styryl derivative of formula VIII with N-vinylcarbazole. The copolymer and an electron transporting material are made to exist between an anode and a cathode to give the objective luminous element in an electric field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel copolymer, a method for producing the same, and a luminescent material such as a fluorescent coating material and an electroluminescence (EL) device.

[0002]

2. Description of the Related Art In recent years, active research has been conducted on devices utilizing the EL performance of organic compounds. This is because the fluorescence of the organic compound is strong and there are various emission colors. In particular, many devices using low molecular weight organic compounds have been studied. For example, Tan and Vance Like (CW
Tang, SAVanslyke) obtained green light emission using an oxine complex (Alq) (Applied Physics Letter, Vol. 51, p. 21, 1987 Appl.Phy.
S. Lett., 51 (12), 21 (1987)). However, it does not have sufficient conditions for practical use. For example, a thin film of a diamine derivative (TPD) used as a hole transport layer has poor physical or thermal durability and has a drawback that the thin film is deteriorated during driving or storage of the device. . In addition, the emission color of Alq, which is a light emitting material, was green. However, in practice, it is necessary to produce the three primary colors or white. As a modification of this element, A
A device in which a fluorescent dye is doped in lq is known (J.
Appl. Phys., 65, 3610 (1989)). Of these, the device doped with DCM has a red emission color, but the hole transport layer is not improved, and thus the durability is still low.

On the other hand, JP-A-4-212286 reports an organic EL device in which a compound having a hole transport layer, a fluorescent substance and a compound having an electron transport layer are mixed.
However, this device was not satisfactory in terms of luminous efficiency. In order to obtain high luminous efficiency in an organic EL device, it is necessary to efficiently take out holes and electrons from the electrode, efficiently transport them to the emission center, and further efficiently inject them into the emission center. Polyvinylcarbazole (PVCz) is known as one of the high-molecular hole transport materials. Japanese Patent Laid-Open No. 3-137186 discloses an example of using this PVCz as a hole transport layer. However, the potential barrier with the light emitting layer is one of the factors that reduce the efficiency. In addition, the above-mentioned JP-A-4-
212286 discloses an example in which a fluorescent dye is mixed with PVCz. When holes or electrons move from one molecule to another, the shorter the intermolecular distance between them, the more efficiently they move. That is, it is preferable that the hole transport material and the light emitting material are close to each other, and it is particularly preferable that the hole transport material and the light emitting material are connected to each other by a chemical bond.

Therefore, as a result of intensive studies to solve these problems and to find an organic EL device which emits red light and has high emission efficiency and high durability, a phenoxazone derivative and / or a styryl derivative and vinylcarbazole were copolymerized. The present inventors have completed the present invention by finding that the organic electroluminescence device using the novel copolymer is highly efficient and has excellent durability.

[0005]

Means for Solving the Problems The present invention includes the following (1) to
It has a configuration consisting of item (4). (1) General formula (1)

[Chemical 19] The structural unit represented by 99.99 to 50 mol% and one or more kinds of general formula (2)

Embedded image The structural unit represented by is contained in an amount of 0.01 to 50 mol% and has a polystyrene-reduced weight average molecular weight of 5,000 to 1,000.
A copolymer that is 10,000. [However, in the general formula (2), R ₁ represents hydrogen or a methyl group, and R represents the general formula (3).

[Chemical 21] , General formula (4)

[Chemical formula 22] Or general formula (5)

[Chemical formula 23] {However, in the general formulas (3), (4) and (5), R ₂ and R ₃ each independently represent an alkyl group or an aryl group, or form a julolidine ring, and R ₄ Represents an alkyl group or an aryl group, or
Alternatively, it constitutes a piperidine ring, X represents O or S, and Y represents O or a dicyanomethylene group}]. (2) General formula (6)

[Chemical formula 24] Or general formula (7)

[Chemical 25] And a phenoxazone derivative represented by the general formula (8)

[Chemical formula 26] By copolymerizing one or more compounds of the styryl derivatives represented by and N-vinylcarbazole,
Contains 99.99 to 50 mol% of the structural unit represented by the general formula (1) and 0.01 to 50 mol% of one or more types of the structural unit represented by the general formula (2), and has a polystyrene-converted weight average molecular weight of A method for producing a copolymer having a molecular weight of 5,000 to 1,000,000. {However, in the general formulas (6), (7) and (8), R1, R2, R3, X and Y are as described above}. (3) The structural unit represented by the general formula (1) is 99.99
To 50 mol% and 0.01 to 50 mol% of the structural unit represented by one or more kinds of general formula (2), and a polystyrene-converted weight average molecular weight of 5,000 to 1,000,000. An electroluminescent device containing: (4) The electroluminescent device as described in the item (3), wherein the copolymer and the electron transport material are interposed between the anode and the cathode.

The method for producing the copolymer of the present invention is not particularly limited as long as it is a method in which the monomers used in the production method of the present invention are polymerized. Examples of this polymerization method include radical polymerization and cationic polymerization, which can be produced under known reaction conditions by utilizing these polymerization reactions. Examples of the initiator used in the radical polymerization include azo type compounds such as azobisisobutyronitrile (AIBN), peroxide type compounds such as benzoyl peroxide, and dithiocarbamate type compounds such as tetraethylthiuram disulfide. Using these initiators, a known method such as solution polymerization, emulsion polymerization, suspension polymerization or bulk polymerization is used, and the temperature is 30 to 100 ° C., preferably 50 to
The copolymer of the present invention can be obtained by carrying out the reaction at 80 ° C. for 0.5 to 100 hours, preferably 1 to 40 hours. Examples of the catalyst used in the cationic polymerization include Lewis acid type such as trifluoroborate or tin tetrachloride, inorganic acid type such as sulfuric acid or hydrochloric acid, and cation exchange resin. Using these catalysts, temperature-1
00-50 ° C, preferably -50-30 ° C, 0.5-
The copolymer of the present invention can be obtained by carrying out the reaction for 100 hours, preferably for 1 to 40 hours.

The molecular weight of the copolymer of the present invention is 5,000 to 1.0 in terms of polystyrene equivalent weight average molecular weight measured by gel permeation chromatography (GPC).
It is in the range of 0,000, more preferably 10,000
It is 0 to 500,000.

Specific examples of the fluorescent dye monomer used in the synthesis of the copolymer of the present invention include the following formulas (9) to (2).
The compound shown by 1) can be mentioned.

[Chemical 27]

[Chemical 28]

[Chemical 29]

Embedded image

[Chemical 31]

Embedded image

[Chemical 33]

Embedded image

Embedded image

Embedded image

Embedded image

[Chemical 38]

[Chemical Formula 39] Of these, the compounds represented by formulas (9) to (13) are particularly preferable.

The composition ratio of the copolymer of the present invention is 0.01 in the portion represented by the general formula (2) which is a portion having a light emitting function.
˜50 mol%, more preferably 0.05 to 10 mol%. Further, the copolymer of the present invention can variously change the brightness and saturation of the emission color by changing the structure of the fluorescent dye portion. For example, the copolymer obtained from the monomer represented by the formula (14) emits orange light,
The copolymer obtained from the monomer represented by the formula (12) emits red light. Further, when the composition ratio of the fluorescent dye portion is extremely smaller than that of the carbazole portion, violet emission derived from the carbazole portion is observed. Therefore, the copolymer of the present invention is useful as a red component of a full-color display. The copolymer of the present invention is obtained by chemically bonding the polyvinyl carbazole moiety having an excellent hole transporting ability and the fluorescent dye moiety having high luminous efficiency. Therefore, holes were very efficiently transported to the fluorescent dye portion, which is the emission center, and as a result, highly efficient light emission was achieved. Further, since the copolymer of the present invention has a high glass transition point, it can maintain a very clean amorphous film for a long time when formed into a thin film. Therefore, the element of the present invention has excellent durability.

The EL device using the copolymer of the present invention has various configurations, but basically, the above-mentioned copolymer is sandwiched between a pair of electrodes (anode and cathode), If necessary, a hole transport layer and an electron transport layer may be interposed therebetween. In addition, it is preferable that all of the elements having the above-mentioned constitution are supported by a substrate, and there is no particular limitation on the substrate, and those conventionally used for EL elements such as glass, transparent plastic, quartz, etc. Can be used. The copolymer of the present invention is useful as a light emitting layer of these EL devices. The light emitting layer can be formed by thinning it by a known method such as a coating method. In addition, the light emitting layer does not require a binder such as a resin and can be formed into a thin film by a spin coating method after being dissolved in a solvent to form a solution, which is industrially advantageous.

The thickness of the thin film of the light emitting layer thus formed is not particularly limited and can be appropriately selected depending on the situation, but is usually selected in the range of 2 nm to 5,000 nm. As the anode in this EL element,
A material having a high work function (4 eV or more), an alloy, an electrically conductive compound or a mixture thereof as an electrode material is preferably used. Specific examples of such an electrode material include metals such as Au, CuI, ITO, SnO ₂ and ZnO.
Dielectric transparent materials such as The anode is prepared by subjecting these electrode materials to a method such as vapor deposition or sputtering.
It can be produced by forming a thin film. When the emitted light is taken out from this electrode, it is desirable that the transmittance is higher than 10%, and the sheet resistance as the electrode is preferably several hundred Ω / square or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 nm to 1 μm, preferably 10 to 200 nm. On the other hand, as the cathode, those having an electrode substance of a metal, an alloy, an electrically conductive compound and a mixture thereof having a low work function (4.3 eV or less) are used. Specific examples of such an electrode material include sodium, sodium-potassium alloy, aluminum, magnesium, lithium, lithium alloy, magnesium alloy, aluminum alloy, magnesium / silver mixture, and indium. The cathode can be produced by forming a thin film of these electrode substances by a method such as vapor deposition or sputtering. The sheet resistance as an electrode is preferably several hundreds Ω / square or less, and the film thickness is usually selected in the range of 10 nm to 1 μm, preferably 50 to 200 nm.

The EL device using the copolymer of the present invention may have various constitutions as described above. However, since the copolymer of the present invention itself has a hole transporting ability, a hole transporting layer is particularly preferable. Is not required, which is industrially advantageous. However, if necessary, a hole transport layer may be provided between the anode and the copolymer layer, or another hole transport material may be mixed with the copolymer layer. The hole-transporting material used is a compound which is arranged between two electrodes to which an electric field is applied and which can appropriately transfer the holes to the light-emitting layer when the holes are injected from the anode. The hole transporting material is not particularly limited as long as it has the above-mentioned preferable properties, and it is conventionally used as a charge transporting material for holes in photoconductive materials and the hole of EL elements. Any known material used for the transport layer may be selected and used.

The electron transporting material in the EL device of the present invention has a function of transmitting the electrons injected from the cathode to the light emitting material. There is no particular limitation on such an electron transporting material, and any one of conventionally known compounds can be selected and used. As a preferable example of the electron transport material,

[Chemical 40] Derivatives of diphenylquinone (Journal of the Electrophotographic Society, 30, 3
(Described in (1991)) or chemical formula 41, chemical formula 42

Embedded image

Embedded image Compounds such as those described in J. Apply. Phys., 27, 269 (1988) and oxadiazole derivatives (Nikkei, 1991 (1)
1): 1540, Jpn.J.Appl.Phys., 27, L713 (1988), Appl.Ph
ys.Lett., 55,1489 (1989) etc.), triazole derivatives (Jpn.J.Appl.Phys., 32, L917 (1993) etc.), thiadiazole derivatives (43rd high) Molecular Society of Japan, IIIP1a007, etc.), thiophene derivatives (described in JP-A-4-212286, etc.), metal complexes derived from quinoline derivatives such as Alq, and polymers of quinoxaline derivatives (Jpn.J. Ap
pl.Phys., 33, L250 (1994) etc.), 2,5-
Examples thereof include bis (5′-tertiarybutyl-2-benzoxazolyl) thiophene (BBOT).

When the electron transport material is used, it can be mixed with the copolymer of the present invention or can be used as one component of the layer laminated on the copolymer layer of the present invention. When mixed with the copolymer of the present invention, the composition ratio may be arbitrary, preferably 1 to 80% by weight, particularly preferably 10%.
To 60% by weight. When used as one component of the laminated layers, it may be used as a single thin film or may be used as a layer mixed with other materials. Examples of the mixture include not only the copolymer of the present invention but also the hole transport material, the fluorescent dye, the electron transport material, the binder polymer and the like.

Next, an example of a suitable method for producing an EL device using the copolymer of the present invention will be described for each device having each constitution. First, a method of manufacturing an EL device composed of an anode / the copolymer layer of the present invention / a cathode will be described. First, a thin film of a desired electrode substance, for example, a substance for an anode, of 1 μm or less, preferably on a suitable substrate. 10-200 nm
After forming the anode by a method such as vapor deposition or sputtering so as to have a film thickness within the range, a thin film of the copolymer of the present invention is formed thereon to provide a light emitting layer. Examples of the method for forming a thin film of the light emitting material include a dip coating method, a spin coating method, a casting method and a vapor deposition method. However, it is easy to obtain a homogeneous film without destroying the copolymer of the present invention. Further, the dipping coating method, the spin coating method, or the casting method is preferable from the viewpoint that it is difficult to form pinholes. When a thin film of the copolymer is adopted by, for example, a spin coating method, the copolymer is dissolved in a solvent (for example, THF, DMF, NMP, DMSO, toluene, benzene, chloroform, etc.) and a spinner is used. Coating on the substrate while rotating the substrate. Next, after forming this copolymer layer, a thin film of a substance for a cathode is formed thereon by a method of 1 μm or less, for example, vapor deposition or sputtering, and a cathode is provided to obtain a desired EL element. In the production of this EL element, the production order may be reversed and the cathode, the light emitting layer and the anode may be produced in this order.

Next, a method of manufacturing an EL device composed of anode / copolymer layer of the present invention / electron transport layer / cathode will be described. First, after forming the anode in the same manner as in the case of the EL device, On top of that, a copolymer thin film is formed according to the above spin coating conditions to provide a polymer layer. Next, a thin film made of an electron transporting material is formed on this polymer layer by a vapor deposition method or a coating method, an electron transporting layer is provided, and then a cathode is formed thereon as in the case of manufacturing the EL element. By providing the above, a desired EL element can be obtained. In addition,
Also in the fabrication of this EL element, the fabrication order is reversed,
It is also possible to fabricate a cathode, an electron injection layer, a light emitting layer and an anode in this order. Further, a method of manufacturing an EL device comprising an anode / (copolymer of the present invention + electron transport material) layer / cathode will be described. An anode is provided in the same manner as in the case of the EL device described above, and then the present invention is used. Of the above copolymer and electron transport material are mixed by spin coating (copolymer + electron transport material)
A desired EL element is obtained by providing a layer and finally providing a cathode in the same manner as described above. Also in the production of this EL element, the production order may be reversed to produce the cathode, the light emitting layer, the hole injection layer, and the anode in this order. When a DC voltage is applied to the EL device thus obtained, a voltage of about 3 to 40 V is applied, and light emission can be observed from the transparent or semitransparent electrode side. Further, it also emits light by applying an AC voltage. The waveform of the alternating current applied may be arbitrary.

Next, the light emission mechanism of the EL device will be described by taking the case of the structure of anode / (copolymer of the present invention + electron transport material) layer / cathode as an example. When a voltage is applied between the electrodes, holes are injected from the anode into the carbazole portion of the copolymer by an electric field. The injected holes are transported to the fluorescent dye portion through the carbazole portion of the copolymer. On the other hand, electrons are injected from the cathode into the electron transport material by an electric field, and further transported to the fluorescent dye portion of the copolymer,
Recombines with holes. When this recombination occurs, the fluorescent dye portion is excited and emits light when returning to the ground state.

[Embodiment] The present invention will be described in more detail based on an embodiment.

(Example 1) Copolymerization of N-vinylcarbazole and phenoxazone monomer 25 mg of the compound represented by the formula (9) and 500 mg of N-vinylcarbazole were dissolved in 20 ml of benzene, and degassing was sufficiently performed. Then, 10 mg of AIBN was added, and the mixture was stirred at 60 ° C. for 5 hours.
After cooling, this solution was added dropwise to a mixed solution of 300 ml of methanol and 200 ml of acetone. The precipitated solid was collected by filtration, dissolved in 10 ml of THF, and again 300 ml of methanol and 200 ml of acetone.
Was added dropwise to the mixed solution. The solid obtained after repeating this operation three times was dried under reduced pressure to obtain the copolymer of the present invention.
320 mg was obtained. This copolymer contains 95 mol% of the structure represented by the formula (1) and 5 mol% of the structure represented by the formula (2).
It contained and the weight average molecular weight was 32,000. This compound emitted orange fluorescence upon irradiation with ultraviolet rays.

Example 2 Copolymerization of N-Vinylcarbazole and Phenoxazone Monomer The compound represented by the formula (9) used in Example 1 is represented by the formula (1)
Polymerization was carried out in the same manner except that the compound represented by 7) was replaced. The obtained copolymer of the present invention contains 94 mol% of the structure represented by the formula (1) and 6 mol% of the structure represented by the formula (2).
It contained and the weight average molecular weight was 29,000. This compound emitted red fluorescence upon irradiation with ultraviolet rays.

(Example 3) Copolymerization of N-vinylcarbazole and styryl monomer The compound represented by the formula (9) used in Example 1 was converted to the formula (2)
Polymerization was carried out in the same manner except that the compound represented by 0) was used instead. The obtained copolymer has a structure represented by the formula (1):
7 mol% and 3 mol% of the structure represented by the formula (2) are contained,
The weight average molecular weight was 31,000. This compound emitted red-orange fluorescence upon irradiation with ultraviolet rays.

(Embodiment 4) 25 mm × 75 mm × 1.1
A transparent support substrate was prepared by depositing ITO with a thickness of 50 nm on a glass substrate having a thickness of 50 mm (manufactured by Tokyo Sanyo Vacuum Co., Ltd.). This transparent support substrate was fixed on a commercially available spinner (manufactured by Kyoei Semiconductor Co., Ltd.), and 0.5 parts by weight of the copolymer obtained in Example 1 and 2- (4-biphenyl) were used.
After spin coating at 6000 rpm with a toluene solution of 0.5 parts by weight of -5- (4-butylphenyl) -1,3,4-oxadiazole (PBD), the substrate was coated with 10 ^-1.
It dried at 50 degreeC under reduced pressure of Pa, and formed the light emitting layer.
The film thickness was 50 nm. Next, the substrate on which the light emitting layer was formed was fixed to a substrate holder of a commercially available vapor deposition device (manufactured by Vacuum Kiko Co., Ltd.), an aluminum mask was placed on the light emitting layer, and then a vacuum chamber was set to 2 × 10. ^After reducing the pressure to ^-4 Pa, magnesium is evaporated from the graphite crucible at a deposition rate of 1.2 to 2.4 nm / sec, and silver is simultaneously evaporated from the other crucible at 0.1 to 0.2 nm / sec. Deposited at a rate. Under the above conditions, a mixed metal electrode of magnesium and silver was laminated on the light emitting layer to a thickness of 200 nm to form a counter electrode,
A device was created. A uniform and stable red-orange surface emission was observed when a DC voltage was applied to this device with an ITO electrode as an anode and a mixed metal electrode of magnesium and silver as a cathode in the atmosphere.

(Embodiment 5) After the light emitting layer was formed in the same manner as in Embodiment 4 without adding the PBD used in Embodiment 4, the substrate was fixed to the substrate holder of the vapor deposition apparatus and the vacuum chamber was set to 2 × 10.
^After reducing the pressure to ⁻⁴ Pa, tris (8-hydroxyquinolino) aluminum was vapor-deposited as an electron transport layer to a thickness of 50 nm from a quartz crucible. Vapor deposition rate is 0.1-0.2n
It was m / sec. Thereafter, similarly to Example 4, a mixed metal electrode of magnesium and silver was vapor-deposited on the electron transport layer to a thickness of 200 nm to form a device. An ITO electrode is used as an anode on this element,
When a DC voltage was applied in the atmosphere using the mixed metal electrode as a cathode, uniform and stable red surface emission was observed.

(Example 6) After forming a light emitting layer by the same method as in Example 4, the substrate was fixed to a substrate holder of a vapor deposition apparatus,
The vacuum layer was depressurized to 2 × 10 ^-4 Pa, and then tris (8-hydroxyquinolino) aluminum was deposited as an electron transport layer to a thickness of 50 nm from a quartz crucible. The deposition rate is 0.
It was 1 to 0.2 nm / sec. Thereafter, similarly to Example 4, a mixed metal electrode of magnesium and silver was vapor-deposited on the electron transport layer to a thickness of 200 nm to form a device. ITO for this element
When a DC voltage was applied in the atmosphere using the electrode as an anode and the mixed metal electrode as a cathode, uniform and stable red surface emission was observed.

(Comparative Example 1) A transparent support substrate was prepared in the same manner as in Example 4 using a toluene solution in which 1.5 parts by weight of Nile Red, 50 parts by weight of N-polyvinylcarbazole and 50 parts by weight of PBD were dissolved as a light emitting material. A light emitting layer was formed on the top. The film thickness was 50 nm. Then, a mixed metal electrode of magnesium and silver was formed on the light emitting layer in the same manner as in Example 4.
A device was prepared by vapor deposition of 00 nm. When a DC voltage was applied to this device in the atmosphere using an ITO electrode as an anode and a mixed metal electrode as a cathode, an orange surface emission was observed, but it was a shade and the emission was attenuated immediately after the voltage was applied.

[0025]

EFFECT OF THE INVENTION The copolymer of the present invention produced by the production method of the present invention has a red luminescent dye having a high fluorescence intensity and is therefore suitable as one component of the luminescent layer of an EL device. In addition, since it has a carbazole moiety with excellent charge transportability,
Suitable as a charge transport layer of the device. Since the charge-transporting carbazole moiety and the light-emitting dye moiety are chemically bonded, charge transfer occurs efficiently. Further, since it has a strong binding property itself, it does not require a resin and firmly adheres to the substrate. By using these, a highly efficient light emitting device such as a full color display can be produced.

Claims (4)

[Claims] 1. A compound represented by the general formula (1): The structural unit represented by 99.99 to 50 mol% and one or more kinds of general formula (2) The structural unit represented by is contained in an amount of 0.01 to 50 mol% and has a polystyrene-reduced weight average molecular weight of 5,000 to 1,000.
A copolymer that is 10,000. [However, in the general formula (2), R ₁ represents hydrogen or a methyl group, and R represents the general formula (3) , The general formula (4): Or general formula (5) {However, in the general formulas (3), (4) and (5), R ₂ and R ₃ each independently represent an alkyl group or an aryl group, or form a julolidine ring, and R ₄ Represents an alkyl group or an aryl group, or
Alternatively, it constitutes a piperidine ring, X represents O or S, and Y represents O or a dicyanomethylene group}]. 2. A general formula (6): Or general formula (7) And a phenoxazone derivative represented by the general formula (8): By copolymerizing one or more compounds of the styryl derivatives represented by and N-vinylcarbazole,
General formula (1) The structural unit represented by 99.99 to 50 mol% and one or more kinds of the general formula (2): The structural unit represented by is contained in an amount of 0.01 to 50 mol% and has a polystyrene-reduced weight average molecular weight of 5,000 to 1,000.
A method for producing a copolymer which is 10,000. [However, in the general formula (2), R ₁ represents hydrogen or a methyl group, and R represents the general formula (3) , The general formula (4): Or the general formula (5) {However, in the general formulas (3), (4) and (5), R ₂ and R ₃ each independently represent an alkyl group or an aryl group, or form a julolidine ring, and R ₄ Represents an alkyl group or an aryl group, or
Alternatively, it constitutes a piperidine ring, X represents O or S, and Y represents O or a dicyanomethylene group}]. 3. A compound represented by the general formula (1): The structural unit represented by 99.99 to 50 mol% and one or more kinds of the general formula (2) The structural unit represented by is contained in an amount of 0.01 to 50 mol% and has a polystyrene-reduced weight average molecular weight of 5,000 to 1,000.
An electroluminescent device containing a copolymer of 10,000.
[However, in the general formula (2), R ₁ represents hydrogen or a methyl group, and R represents the general formula (3) , The general formula (4): Or the general formula (5) {However, in the general formulas (3), (4) and (5), R ₂ and R ₃ each independently represent an alkyl group or an aryl group, or form a julolidine ring, and R ₄ Represents an alkyl group or an aryl group, or
Alternatively, it constitutes a piperidine ring, X represents O or S, and Y represents O or a dicyanomethylene group}]. 4. The electroluminescent device according to claim 3, wherein the copolymer and the electron transport material are interposed between the anode and the cathode.