JP2000323278A - Light emitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitter with high light emitting efficiency and luminance, and superior in color purity by including an organic phosphor having an imidazole skeleton. SOLUTION: This emitter includes an organic phosphor having an imidazole structure expressed by the formula. In the formula, R1 may be either same or different respectively and selected from hydrogen, an alkyl group, a cycloalkyl group, an aralkyl group, an alkenyl group, a cycloalkenyl group, etc., X1 is a bond unit and selected from a substituted or non-substituted aromatic ring, heterocycle, a saturated fat chain, etc., Y1 is selected from a single or a combination of either of single bond, an alkyl chain, an alkylene chain, an ether chain, etc., and Ar is selected from a substituted or non-substituted aromatic ring, heterocycle, etc. The substitutional groups expressed by X1, Y1, Ar are selected from those expressed by R1 and (n) expresses a natural number. The organic phosphor is preferably a light emitting material having a guest material doped in a host material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an element capable of converting electric energy into light, and relates to a display element, a flat panel display, a backlight, lighting, an interior, a sign, a sign, an electrophotographic device, an optical signal generator, and the like. The present invention relates to a light emitting element that can be used in the field of (1).

[0002]

2. Description of the Related Art In recent years, active research has been conducted on organic thin-film light emitting devices that emit light when electrons injected from a negative electrode and holes injected from a positive electrode recombine in an organic phosphor sandwiched between both electrodes. I have. This element is characterized by thinness, high luminance light emission under a low driving voltage, and multicolor light emission by selecting a fluorescent material.

[0003] It is known from Kodak's C.I. W. Tang et al. (Appl. Phys. Lett. 51 (12)
21, p. 913, 1987). A typical configuration of the organic laminated thin-film light emitting device presented by Kodak Company is a hole transporting diamine compound and a light emitting layer on an ITO glass substrate,
Tris (8-quinolinolato) aluminum, which also has an electron transporting property, and Mg: Ag were sequentially provided as a negative electrode, and green light emission of 1000 candela / m 2 was possible at a driving voltage of about 10V. The current organic laminated thin-film light-emitting device has a different configuration, such as a device provided with an electron transport layer, in addition to the above-described device components, but basically follows the configuration of Kodak. I have.

[0004] The light emitting layer is composed of only a host material,
A host material is doped with a guest material.
The light emitting material is required to have three primary colors, but the research on the green light emitting material has been most advanced so far. At present, intensive studies have been made on red light emitting materials and blue light emitting materials with the aim of improving the characteristics. In particular, a blue light-emitting material that can emit light with high luminance and good color purity is desired.

As the host material, the above-mentioned tris (8-
Metal complexes of quinolinol derivatives including quinolinolato) aluminum, benzoxazole derivatives, stilbene derivatives, benzothiazole derivatives, thiadiazole derivatives, thiophene derivatives, tetraphenylbutadiene derivatives, cyclopentadiene derivatives, oxadiazole derivatives, oxadiazole derivative metal complexes And benzazole derivative metal complexes.

As an example of a blue light-emitting host material having relatively good performance, a metal complex obtained by combining a quinolinol derivative with a different ligand (Japanese Patent Laid-Open No. 5-21)
4332, JP-A-6-172751),
Bisstyrylbenzene derivatives (JP-A-4-117485)
And JP-A-5-17765), but the color purity is not particularly sufficient.

On the other hand, as a dopant material as a guest material, a fluorescent coumarin dye such as 7-dimethylamino-4-methylcoumarin, a dicyanomethylenepyran dye, which is known to be useful as a laser dye, Dicyanomethylenethiopyran dye, polymethine dye, cyanine dye, oxobenzanthracene dye, xanthene dye, rhodamine dye, fluorescein dye,
Pyrylium dye, carbostyril dye, perylene dye,
Acridine dye, bis (styryl) benzene dye, pyrene dye, oxazine dye, phenylene oxide dye,
Perylene, tetracene, pentacene, quinacridone compound, quinazoline compound, pyrrolopyridine compound, furopyridine compound, 1,2,5-thiadiazolopyrene derivative, perinone derivative, pyrrolopyrrole compound, squarylium compound, biolanthrone compound, phenazine derivative, acridone compound, diazaflavin Derivatives and the like are known.

[0008]

However, the luminescent materials (host materials and dopant materials) used in the prior art include those having low luminous efficiency and high power consumption, and those having low durability of the compound and short element life. There were many. In addition, red, green, and blue light emission of three primary colors is required as a full-color display. However, in red and blue light emission, few light emission wavelengths are satisfied, and few light emission peaks have a wide emission peak width and good color purity. In particular, for blue light emission, a material having excellent durability and sufficient luminance and color purity characteristics is required.

An object of the present invention is to solve the problems of the prior art and to provide a light emitting device having high luminous efficiency, high luminance and excellent color purity.

[0010]

According to the present invention, there is provided an element which emits light by electric energy in which a substance responsible for light emission exists between a positive electrode and a negative electrode, and the element is represented by the following general formula (1). A light-emitting element including an organic phosphor having an imidazole skeleton.

[0011]

Embedded image

(Wherein R1 may be the same or different and each represents hydrogen, an alkyl group, a cycloalkyl group, an aralkyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a mercapto group, an alkoxy group, an alkylthio group, Aryl ether group, aryl thioether group, aryl group, heterocyclic group, halogen, haloalkane, haloalkene, haloalkyne, cyano group, aldehyde group, carbonyl group, carboxyl group, ester group, carbamoyl group, amino group, nitro group, silyl group, X1 is a bonding unit and is a substituted or unsubstituted aromatic ring, substituted or unsubstituted heterocyclic ring, substituted or unsubstituted saturated ring, substituted or unsubstituted saturated aliphatic chain, substituted or unsubstituted saturated aliphatic chain, Unsubstituted unsaturated fatty chains or single bond .Y1 selected from the group consisting of a single bond,
It is selected from an alkyl chain, an alkylene chain, a cycloalkyl chain, an aryl chain, a heterocyclic chain, an ether chain, or a thioether chain alone or in combination. Ar is selected from a substituted or unsubstituted aromatic ring, a substituted or unsubstituted heterocyclic ring, or a mixed ring structure of a substituted or unsubstituted aromatic ring and a heterocyclic ring. X1, Y1,
The substituent represented by Ar can be selected from those represented by R1. n represents a natural number. )

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A positive electrode according to the present invention is made of a conductive metal oxide such as tin oxide, indium oxide, indium tin oxide (ITO), or gold, silver, chromium, if it is transparent to extract light. Metals such as, for example, inorganic conductive substances such as copper iodide and copper sulfide, and conductive polymers such as polythiophene, polypyrrole, and polyaniline are not particularly limited, but it is particularly preferable to use ITO glass or Nesa glass. The resistance of the transparent electrode is not limited as long as a current sufficient for light emission of the element can be supplied, but is preferably low from the viewpoint of power consumption of the element. For example, an ITO substrate having a resistance of 300Ω / □ or less functions as an element electrode, but a substrate having a resistance of about 20Ω / □ or less should be used because a substrate of about 10Ω / □ can be supplied at present. Is particularly desirable. The thickness of the ITO can be arbitrarily selected according to the resistance value.
It is often used between ３００300 nm. Further, as the glass substrate, soda lime glass, non-alkali glass or the like is used, and the thickness only needs to be sufficient to maintain the mechanical strength.
As for the material of the glass, alkali-free glass is preferable because it is better that ions eluted from the glass are small,
Soda lime glass provided with a barrier coat such as SiO ₂ is also commercially available and can be used. The method of forming the ITO film is not particularly limited, such as an electron beam evaporation method, a sputtering method, and a chemical reaction method.

The negative electrode of the present invention efficiently converts electrons,
The substance is not particularly limited as long as it can be injected into a substance which controls light emission or a substance adjacent to the substance which controls light emission (for example, an electron transporting layer). Generally, platinum, gold, silver, copper, iron, tin, aluminum, indium, lithium, sodium, potassium, calcium, magnesium and the like can be mentioned. In order to improve the device characteristics by increasing the electron injection efficiency, lithium, sodium, potassium, calcium, magnesium or an alloy containing these low work function metals is effective. However, these low work function metals are generally unstable in the atmosphere, and platinum, gold,
Metals such as silver, copper, iron, tin, aluminum and indium, or alloys using these metals, and silica,
It is preferable to laminate an inorganic substance such as titania and a polymer such as polyvinyl alcohol and vinyl chloride. These electrodes are also manufactured by resistance heating method evaporation, electron beam evaporation method,
There is no particular limitation as long as electrical continuity such as a sputtering method, an ion plating method, and a coating method can be achieved.

The structure of the substance that controls light emission in the present invention is as follows:
1) a hole transporting material / a light emitting material, 2) a hole transporting material / a light emitting material / an electron transporting material, 3) a light emitting material / an electron transporting material, and 4) a form in which a combination of the above substances is mixed.
Any of these may be used. That is, in addition to the multilayered structures 1) to 3), a layer containing a luminescent material alone or a luminescent material and a hole transporting material, or a layer containing a luminescent material, a hole transporting material and an electron transporting material as in 4) is further provided. It may just be provided.

In the present invention, the luminescent material may be a host material alone or a combination of a host material and a dopant material.
Any of them may be used. In addition, the dopant material may be included in the entire host material, partially, or may be included. The dopant material may be stacked, dispersed, or the like.

The hole transport material in the present invention is required to efficiently transport holes from the positive electrode between the electrodes to which an electric field is applied, and has a high hole injection efficiency. Good transport is desirable. For that purpose, it is required that the ionization potential be small, the hole mobility be large, the stability be further improved, and impurities serving as traps be hardly generated during production and use. The substance satisfying such conditions is not particularly limited, but is a biscarbazolyl derivative,
Known triphenylamine derivatives such as TPD, m-MTDATA, α-NPD, pyrazoline derivatives, stilbene compounds, hydrazone compounds, heterocyclic compounds represented by oxadiazole derivatives and phthalocyanine derivatives, polyvinyl carbazole, polysilane and the like Hole transport materials can be used. These hole transport materials may be used alone or may be laminated or mixed with different hole transport materials.

The luminescent material of the present invention contains an organic phosphor having an imidazole skeleton represented by the following general formula (1).

[0019]

Embedded image

Here, R1 in the general formula (1) may be the same or different, and may be hydrogen, an alkyl group, a cycloalkyl group, an aralkyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a mercapto group, an alkoxy group. Group, alkylthio group, arylether group, arylthioether group, aryl group, heterocyclic group, halogen,
It is preferably selected from haloalkanes, haloalkenes, haloalkynes, cyano groups, aldehyde groups, carbonyl groups, carboxyl groups, ester groups, carbamoyl groups, amino groups, nitro groups, silyl groups, and siloxanyl groups.

X1 is a bonding unit, which is a substituted or unsubstituted aromatic ring, a substituted or unsubstituted heterocyclic ring, a substituted or unsubstituted saturated ring, a substituted or unsubstituted saturated aliphatic chain, a substituted or unsubstituted unsubstituted unsubstituted aliphatic chain. Selected from saturated fatty chains or single bonds, wherein Y1 is a single bond, an alkyl chain, an alkylene chain, a cycloalkyl chain, an aryl chain, a heterocyclic chain, an ether chain, or a thioether chain; It is preferable to be selected from the following. Ar is preferably selected from a substituted or unsubstituted aromatic ring, a substituted or unsubstituted heterocyclic ring, or a mixed ring structure of a substituted or unsubstituted aromatic ring and a heterocyclic ring. Further, the substituents that can be used in each configuration of X1, Y1, and Ar can be selected from those represented by R1. n represents a natural number.

Among these substituents, the alkyl group means a saturated aliphatic hydrocarbon group such as a methyl group, an ethyl group, a propyl group and a butyl group, which may be unsubstituted or substituted. The cycloalkyl group is, for example, a saturated alicyclic hydrocarbon group such as cyclopropyl, cyclohexyl, norbornyl, and adamantyl, which may be unsubstituted or substituted. The aralkyl group refers to an aromatic hydrocarbon group via an aliphatic hydrocarbon such as a benzyl group and a phenylethyl group, and the aliphatic hydrocarbon and the aromatic hydrocarbon may be unsubstituted or substituted. I don't care. The alkenyl group refers to an unsaturated aliphatic hydrocarbon group containing a double bond such as a vinyl group, an allyl group and a butadienyl group, which may be unsubstituted or substituted. The cycloalkenyl group refers to an unsaturated alicyclic hydrocarbon group containing a double bond such as a cyclopentenyl group, a cyclopentadienyl group, and a cyclohexene group, which may be unsubstituted or substituted. . The alkynyl group means an unsaturated aliphatic hydrocarbon group containing a triple bond such as an acetylenyl group, which may be unsubstituted or substituted. The alkoxy group refers to an aliphatic hydrocarbon group via an ether bond such as a methoxy group, and the aliphatic hydrocarbon group may be unsubstituted or substituted. The alkylthio group is obtained by substituting the oxygen atom of the ether bond of the alkoxy group with a sulfur atom. Further, the aryl ether group refers to an aromatic hydrocarbon group via an ether bond such as a phenoxy group, and the aromatic hydrocarbon group may be unsubstituted or substituted. Also,
The arylthioether group is a group in which an oxygen atom of an ether bond of the arylether group is substituted with a sulfur atom. The aryl group refers to, for example, an aromatic hydrocarbon group such as a phenyl group, a naphthyl group, a biphenyl group, a phenanthryl group, a terphenyl group, and a pyrenyl group, which may be unsubstituted or substituted. Further, the heterocyclic group is, for example, a furyl group, a thienyl group, an oxazolyl group,
It represents a cyclic structural group having an atom other than carbon, such as a pyridyl group, a quinolyl group, and a carbazolyl group, which may be unsubstituted or substituted. Halogen refers to fluorine, chlorine, bromine and iodine. Haloalkanes, haloalkenes, and haloalkynes are those in which part or all of the aforementioned alkyl group, alkenyl group, and alkynyl group such as a trifluoromethyl group have been substituted with the aforementioned halogen, and the remaining part is unsubstituted. It may be replaced. Aldehyde, carbonyl, ester, carbamoyl, and amino groups include those substituted with aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, heterocycles, and the like. The cyclic hydrocarbon, aromatic hydrocarbon and heterocyclic ring may be unsubstituted or substituted. The silyl group means a silicon compound group such as a trimethylsilyl group, which may be unsubstituted or substituted. The siloxanyl group means a silicon compound group via an ether bond such as a trimethylsiloxanyl group, which may be unsubstituted or substituted.

Among the organic phosphors having an imidazole skeleton represented by the general formula (1) in the present invention, those having a benzoimidazole skeleton in which Ar is a benzene ring are preferably used because of easy synthesis. Specific examples include an organic phosphor having a benzimidazole skeleton represented by the following general formula (2).

[0024]

Embedded image

Here, R2 to R6 in the general formula (2) may be the same or different, and include hydrogen, an alkyl group, a cycloalkyl group, an aralkyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group and a mercapto group. ,
Alkoxy group, alkylthio group, aryl ether group,
Arylthioether group, aryl group, heterocyclic group, halogen, haloalkane, haloalkene, haloalkyne, cyano group, aldehyde group, carbonyl group, carboxyl group, ester group, carbamoyl group, amino group, nitro group, silyl group, siloxanyl group, adjacent It is preferable to be selected from the ring structures formed between the substituents.

X2 is a bonding unit, which is a substituted or unsubstituted aromatic ring, a substituted or unsubstituted heterocyclic ring, a substituted or unsubstituted saturated ring, a substituted or unsubstituted saturated aliphatic chain, a substituted or unsubstituted unsubstituted unsubstituted aliphatic chain. Selected from saturated fatty chains or single bonds, wherein Y2 is a single bond, an alkyl chain, an alkylene chain, a cycloalkyl chain, an aryl chain, a heterocyclic chain, an ether chain, or a thioether chain; It is preferable to be selected from the following. n represents a natural number.

The substituents that can be used in each of these structures of X2 and Y2 are the same as those described above, and the ring structure formed between adjacent substituents is unsubstituted and substituted. It doesn't matter.

In the organic phosphor having a benzimidazole skeleton represented by the general formula (2) in the present invention, Y3 is preferably an alkyl chain because of easy synthesis.

Specific examples of the organic phosphor having an imidazole skeleton include the following structures.

[0030]

Embedded image

[0031]

Embedded image

[0032]

Embedded image

[0033]

Embedded image

The organic phosphor having an imidazole skeleton may be used as a dopant material, but is preferably used as a host material because of its excellent electron transporting ability.

The host material of the light-emitting material is not limited to one kind of organic phosphor having an imidazole skeleton, and a mixture of organic phosphors having a plurality of azole skeletons may be used.
One or more kinds of known host materials may be used as a mixture with an organic phosphor having an imidazole skeleton. Known host materials are not particularly limited, but fused ring derivatives such as anthracene, phenanthrene, pyrene, perylene, and chrysene, which have long been known as light emitters,
Metal complexes of quinolinol derivatives including tris (8-quinolinolato) aluminum, benzoxazole derivatives, stilbene derivatives, benzothiazole derivatives, thiadiazole derivatives, thiophene derivatives, tetraphenylbutadiene derivatives, cyclopentadiene derivatives, oxadiazole derivatives, bisstyryl Bisstyryl derivatives such as anthracene derivatives and distyrylbenzene derivatives, metal complexes combining quinolinol derivatives with different ligands, oxadiazole derivative metal complexes, benzazole derivative metal complexes, coumarin derivatives, pyrrolopyridine derivatives, perinone derivatives, thiadia Zolopyridine derivatives, polyphenylene vinylene derivatives in polymer systems,
Polyparaphenylene derivatives and polythiophene derivatives can be used.

The dopant material to be added to the light emitting material is not particularly limited. Specifically, phenanthrene, anthracene, pyrene, tetracene, pentacene, perylene, naphthopyrene, dibenzopyrene, and rubrene, which are conventionally known, are used. Condensed ring derivatives such as benzoxazole derivatives, benzothiazole derivatives, benzimidazole derivatives, benztriazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, imidazole derivatives, thiadiazole derivatives, triazole derivatives, pyrazoline derivatives, stilbene derivatives, thiophene derivatives , Tetraphenylbutadiene derivatives, cyclopentadiene derivatives, bisstyryl anthracene derivatives, bisstyryl derivatives such as distyrylbenzene derivatives, diaza Ndasen derivatives, furan derivatives,
Benzofuran derivatives, phenylisobenzofuran, dimesitylisobenzofuran, di (2-methylphenyl) isobenzofuran, di (2-trifluoromethylphenyl) isobenzofuran, isobenzofuran derivatives such as phenylisobenzofuran, dibenzofuran derivatives, 7
-Dialkylaminocoumarin derivative, 7-piperidinocoumarin derivative, 7-hydroxycoumarin derivative, 7-methoxycoumarin derivative, 7-acetoxycoumarin derivative, 3-benzthiazolyl coumarin derivative, 3-benzimidazolyl coumarin derivative, 3- Coumarin derivatives such as benzoxazolyl coumarin derivatives, dicyanomethylenepyran derivatives, dicyanomethylenethiopyran derivatives,
Polymethine derivatives, cyanine derivatives, oxobenzanthracene derivatives, xanthene derivatives, rhodamine derivatives, fluorescein derivatives, pyrylium derivatives, carbostyril derivatives, acridine derivatives, bis (styryl)
Benzene derivatives, oxazine derivatives, phenylene oxide derivatives, quinacridone derivatives, quinazoline derivatives,
Pyrrolopyridine derivatives, furopyridine derivatives, 1,2,2
A 5-thiadiazolopyrene derivative, a perinone derivative, a pyrrolopyrrole derivative, a squarylium derivative, a biolanthrone derivative, a phenazine derivative, an acridone derivative, a diazaflavin derivative, and the like can be used as they are, but an isobenzofuran derivative is particularly preferably used.

As the electron transporting material in the present invention,
It is necessary to efficiently transport electrons from the negative electrode between the electrodes to which an electric field is applied, and it is desirable that the electron injection efficiency is high and the injected electrons are transported efficiently. For this purpose, it is required that the material has a high electron affinity, a high electron mobility, a high stability, and a small amount of impurities serving as traps during production and use. Materials satisfying such conditions include quinolinol derivative metal complexes represented by 8-hydroxyquinoline aluminum, tropolone metal complexes, flavonol metal complexes, perylene derivatives, perinone derivatives, naphthalene,
There are coumarin derivatives, oxadiazole derivatives, aldazine derivatives, bisstyryl derivatives, pyrazine derivatives, phenanthroline derivatives, and the like, but are not particularly limited. The organic phosphor having an imidazole skeleton according to the present invention also has an excellent electron transporting ability, and thus can be suitably used as an electron transporting material. These electron transporting materials may be used alone or may be laminated or mixed with different electron transporting materials.

The above materials used for the hole transporting layer, the light emitting layer and the electron transporting layer can be used alone to form the respective layers. As the polymer binder, polyvinyl chloride, polycarbonate, polystyrene, poly (N- (Vinyl carbazole), polymethyl methacrylate, polybutyl methacrylate, polyester, polysulfone, polyphenylene oxide, polybutadiene, hydrocarbon resin, ketone resin, phenoxy resin, polyamide, ethyl cellulose, vinyl acetate, ABS resin, polyurethane resin, and other solvent-soluble resins. It can also be used by dispersing it in a curable resin such as a phenol resin, a xylene resin, a petroleum resin, a urea resin, a melamine resin, an unsaturated polyester resin, an alkyd resin, an epoxy resin, or a silicone resin.

The method for forming the substance which controls light emission in the present invention is not particularly limited, such as resistance heating evaporation, electron beam evaporation, sputtering, molecular lamination, and coating. Beam evaporation is preferred in terms of properties. The thickness of the layer depends on the resistance of the substance that controls light emission and cannot be limited, but is selected from the range of 10 to 1000 nm.

The electric energy in the present invention mainly refers to a direct current, but it is also possible to use a pulse current or an alternating current. The current value and voltage value are not particularly limited,
In consideration of the power consumption and life of the device, it is necessary to obtain the maximum brightness with the lowest possible energy.

It is preferable that the light emitting device of the present invention constitutes a display for displaying by a matrix or segment system or a combination of both.

The matrix according to the present invention is a matrix in which pixels for display are arranged in a lattice, and displays a character or an image by a set of pixels. The shape and size of the pixel depend on the application. For example, for the display of images and characters on personal computers, monitors, televisions, and the like, generally square pixels with a side of 300 μm or less are used, and in the case of a large display such as a display panel, pixels with a side on the order of mm are used. Become. In the case of monochrome display, pixels of the same color may be arranged, but in the case of color display, red, green and blue pixels are displayed side by side. In this case, there are typically a delta type and a stripe type. Note that the light-emitting element of the present invention can emit red, green, and blue light, so that multi-color or full-color display can be performed by using the display method. The matrix may be driven by either a line-sequential driving method or an active matrix. The line-sequential driving has the advantage of a simpler structure, but the active matrix is sometimes superior in consideration of the operating characteristics. Therefore, it is necessary to use this depending on the application.

In the segment type according to the present invention, a pattern is formed so as to display predetermined information, and a predetermined area emits light. For example, there are a time display and a temperature display on a digital clock or a thermometer, an operation state display of an audio device, an electromagnetic cooker, or the like, and a panel display of an automobile. The matrix display and the segment display may coexist in the same panel.

The light emitting device of the present invention is also preferably used as a backlight. The backlight in the present invention,
It is mainly used for improving the visibility of a display device that does not emit light, and is used for a liquid crystal display device, a clock, an audio device, an automobile panel, a display panel, a sign, and the like. In particular, as for the backlight for liquid crystal display devices, particularly for personal computer applications where thinning is an issue, the present invention is considered to be difficult because the conventional type is made of a fluorescent lamp or a light guide plate, and it is difficult to make it thin. Is characterized by its thinness and light weight.

[0045]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 A glass substrate on which an ITO transparent conductive film was deposited to a thickness of 150 nm (made by Asahi Glass Co.,
The wafer was cut into a size of 40 mm and etched. The obtained substrate was subjected to ultrasonic cleaning with acetone and semicocrine 56 for 15 minutes each, and then with ultrapure water. Subsequently, the substrate was subjected to ultrasonic cleaning with isopropyl alcohol for 15 minutes, immersed in hot methanol for 15 minutes, and dried. This substrate was subjected to UV-ozone treatment for 1 hour immediately before producing the element, placed in a vacuum evaporation apparatus, and evacuated until the degree of vacuum in the apparatus became 5 × 10 ⁻⁵ Pa or less. First, 130 nm of 4,4'-bis (N- (m-tolyl) -N-phenylamino) biphenyl was deposited as a hole transporting material by a resistance heating method. Next, EM1 shown below was laminated to a thickness of 30 nm as a light emitting material. Next, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline was laminated to a thickness of 70 nm as an electron transporting material. Then lithium is added to 0.5
5 nm, aluminum is evaporated to 200 nm to form a cathode,
A device having a size of 5 mm square was manufactured. The film thickness referred to here is a value displayed on a crystal oscillation type film thickness monitor corrected by a value measured by a surface roughness meter. From this light emitting device, blue light emission with good color purity was obtained.

[0047]

Embedded image

Comparative Example 1 Bis (2-methylquinolinolate) (2
A light emitting device was produced in exactly the same manner as in Example 1 except that (pyridinolate) aluminum (III) was used. From this light-emitting element, only green light was emitted, and the color purity was poor.

Example 2 A light emitting device was manufactured in exactly the same manner as in Example 1 except that EM2 shown below was used as a light emitting material. Blue light emission with good color purity was obtained from this light emitting device.

[0050]

Embedded image

Example 3 A light emitting device was manufactured in exactly the same manner as in Example 1 except that EM3 shown below was used as a light emitting material. Blue light emission with good color purity was obtained from this light emitting device.

[0052]

Embedded image

Example 4 Copper phthalocyanine was used as a hole transport material at 20 nm,
A light emitting device was manufactured in exactly the same manner as in Example 1 except that 3 ′ bis (ethylcarbazole) was used at 130 nm. Blue light emission with good color purity was obtained from this light emitting device.

Example 5 Using EM1 as a host material as a light emitting material, 1,3-
Dimesityl isobenzofuran is used as a dopant material, and the concentration of the dopant is set to 30 wt.
A light emitting device was produced in exactly the same manner as in Example 1 except that co-evaporation was performed to a thickness of. Blue light emission with good color purity was obtained from this light emitting device.

Comparative Example 2 Bis (2-methylquinolinolate) as a host material
A light emitting device was produced in exactly the same manner as in Example 5, except that (2-pyridinolate) aluminum (III) was used.
From this light-emitting element, only green light was emitted. Light emission from the dopant material was not obtained, and the color purity was poor.

Example 6 A light emitting device was manufactured in the same manner as in Example 5, except that 1,3-di (2-methylphenyl) isobenzofuran was used as a dopant material. Blue light emission with good color purity was obtained from this light emitting device.

[0057]

According to the present invention, it is possible to provide a light emitting device having high luminous efficiency and excellent color purity. It is particularly effective for blue light emission.

Claims (6)

[Claims] An element which emits light by electric energy, in which a substance responsible for light emission exists between a positive electrode and a negative electrode, wherein the element has an imidazole skeleton represented by the following general formula (1): A light-emitting element comprising: Embedded image (Where R1 may be the same or different,
Hydrogen, an alkyl group, a cycloalkyl group, an aralkyl group,
Alkenyl group, cycloalkenyl group, alkynyl group, hydroxyl group, mercapto group, alkoxy group, alkylthio group,
Aryl ether group, aryl thioether group, aryl group, heterocyclic group, halogen, haloalkane, haloalkene, haloalkyne, cyano group, aldehyde group, carbonyl group, carboxyl group, ester group, carbamoyl group,
It is selected from an amino group, a nitro group, a silyl group, and a siloxanyl group. X1 is a bonding unit, which is a substituted or unsubstituted aromatic ring, a substituted or unsubstituted heterocyclic ring, a substituted or unsubstituted saturated ring, a substituted or unsubstituted saturated aliphatic chain, a substituted or unsubstituted unsaturated aliphatic chain, Alternatively, it is selected from single bonds. Y1 is a single bond, an alkyl chain, an alkylene chain, a cycloalkyl chain, an aryl chain, a heterocyclic chain,
It is selected from an ether chain or a thioether chain alone or in combination. Ar is a substituted or unsubstituted aromatic ring, a substituted or unsubstituted heterocyclic ring,
Alternatively, it is selected from a mixed ring structure of a substituted or unsubstituted aromatic ring and a heterocyclic ring. The substituents represented by X1, Y1, and Ar can be selected from those represented by R1. n
Represents a natural number. ) 2. The light emitting device according to claim 1, wherein the organic phosphor having an imidazole skeleton is represented by the following general formula (2). Embedded image (Where R2 to R6 may be the same or different, and each may be hydrogen, alkyl, cycloalkyl, aralkyl, alkenyl, cycloalkenyl, alkynyl, hydroxyl, mercapto, alkoxy, alkylthio, aryl Ether group, arylthioether group,
Aryl group, heterocyclic group, halogen, haloalkane, haloalkene, haloalkyne, cyano group, aldehyde group, carbonyl group, carboxyl group, ester group, carbamoyl group, amino group, nitro group, silyl group, siloxanyl group, And a ring structure formed therebetween. X2 is a bonding unit, which is a substituted or unsubstituted aromatic ring, a substituted or unsubstituted heterocyclic ring, a substituted or unsubstituted saturated ring, a substituted or unsubstituted saturated aliphatic chain,
It is selected from a substituted or unsubstituted unsaturated aliphatic chain or a single bond. Y2 is selected from a single bond, an alkyl chain, an alkylene chain, a cycloalkyl chain, an aryl chain, a heterocyclic chain, an ether chain, or a thioether chain, alone or in combination. The substituent represented by X2 can be selected from those represented by R2 to R6. n represents a natural number. ) 3. An organic phosphor having an imidazole skeleton according to claim 2, wherein Y2 in the general formula (2) is an alkyl chain. 4. The light emitting device according to claim 1, wherein said organic phosphor is a light emitting material. 5. The light emitting device according to claim 4, wherein the light emitting material is a host material doped with a guest material. 6. The light emitting device according to claim 1, wherein said organic phosphor is an electron transporting material.