JP2000100569A - Luminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a luminescent element allowing blue luminescence having a peak in a shorter-wavelength region. SOLUTION: This luminescent element has a material governing luminescence between a positive electrode and a negative electrode, it luminesces with electric energy, and it contains the alkali metal complex expressed by the formula, where X is selected from among O, S, NR9. R1-R8 may be the same or different, and they are selected from among hydrogen, an alkyl group, a cycloalkyl group, an arakyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, the hydroxy group, the mercapto group, an alkoxy group, a condensed ring formed between adjacent substitutional groups, a heterocyclic ring, an aliphatic ring, a single bond for connection to other skeleton, an ether linkage, an amino group, an amide bond, an ester bond and a sulfide bond. R9 is selected from among hydrogen, an alkyl group, an aryl group and a heterocyclic group. M is selected from among Li, Na, K, Rb and Sc.

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.

As a host material of the light emitting layer, tris (8
(Quinolinolato) aluminum and other metal chelated oxinoid compounds, diarylbutadiene derivatives, stilbene derivatives, benzoxazole derivatives, benzothiazole derivatives (Japanese Patent Application Laid-Open No. 63-264692) and the like.

On the other hand, as dopant materials as guest materials, fluorescent coumarin dyes such as 7-dimethylamino-4-methylcoumarin, dicyanomethylenepyran dye, and the like, which are known to be useful as laser dyes, 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 (JP-A-63-264892), tetracene, pentacene (JP-A-2-261889), quinacridone compounds, quinazoline compounds Kaihei 5-70773
Japanese Patent Application Laid-Open No. 5-222360), pyrrolopyridine compound, furopyridine compound (JP-A-5-222360), 1,2,5-thiadiazolopyrene derivative (JP-A-5-222361), and perinone derivative (JP-A-5-279662). , Pyrrolopyrrole compounds (JP-A-5-320363)
), Squarylium compounds (JP-A-6-9325)
No. 7), a biolanthrone compound (JP-A-7-902)
No. 59), phenazine derivatives (JP-A-7-1022)
No. 50), an acridone compound (JP-A-8-6787)
No. 3), diazaflavin derivatives (JP-A-9-780)
No. 58) is known.

[0006]

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. Among the three primary colors required for a full-color display, a high-performance light-emitting material has been found for green light emission, but a light-emitting material having sufficient characteristics for blue light has not been obtained. An object of the present invention is to solve the problem of the related art and to provide a light emitting element capable of emitting blue light having a peak in a shorter wavelength region.

[0007]

SUMMARY OF THE INVENTION The present invention provides an element which emits light by electric energy, in which a substance responsible for light emission is present between a positive electrode and a negative electrode, wherein the element is an alkali represented by the general formula (1). A light-emitting element including a metal complex.

[0008]

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[0009]

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 in the present invention is not particularly limited as long as it can efficiently inject electrons into a substance which efficiently emits light or a substance adjacent to the substance which emits light (for example, an electron transport 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,
Inorganic substances such as titania and silicon nitride, and polymers such as polyvinyl alcohol and vinyl chloride can be laminated.
These electrodes are also manufactured by resistance heating method, electron beam evaporation method, sputtering method, ion plating method,
There is no particular limitation as long as conduction can be achieved by a coating method or the like.

In the present invention, the structure of the substance that controls light emission 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 multi-layer structure of 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.

The light-emitting material may be either a host material alone or a combination of a host material and a dopant material. 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 transporting 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 material has an appropriate ionization potential, has a high hole mobility, is excellent in stability, and hardly generates impurities serving as traps during production and use. As a substance satisfying such conditions,
Although not particularly limited, TPD, m-MTDA
TA, heterophenyl compounds represented by triphenylamine derivatives such as α-NPD, biscarbazolyl derivatives, pyrazoline derivatives, stilbene compounds, hydrazone compounds and phthalocyanine derivatives, polyvinylcarbazole,
Known hole transport materials such as polysilanes 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 according to the present invention contains an alkali metal complex represented by the following general formula (1). The alkali metal complex may be used as a dopant material, but is preferably used as a host material.

[0015]

Embedded image Here, X is selected from O, S, and NR ₉ . R _{1 to} R
₈ may be the same or different, respectively, hydrogen, alkyl group, cycloalkyl group, 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, amino group,
Nitro group, silyl group, siloxanyl group, condensed ring formed between adjacent substituents, heterocyclic ring and aliphatic ring, and single bond, ether bond, amino group, amide bond for connection with other skeleton , An ester bond or a sulfide bond. R ₉ is hydrogen, an alkyl group, an aryl group,
Selected from among heterocyclic groups. M is Li, Na, K, R
b or Sc.

Among these substituents, the alkyl group refers to 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. Further, 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 refers to a cyclic structural group having an atom other than carbon, such as a furanyl group, a thiophenyl group, an oxazolyl group, a pyridyl group, a quinolinyl group, and a carbazolyl group, which may be unsubstituted or substituted. Absent. Halogen refers to fluorine, chlorine, bromine and iodine. Haloalkanes, haloalkenes, and haloalkynes are those in which some or all of the aforementioned alkyl, alkenyl, and alkynyl groups, such as trifluoromethyl, have been substituted with the aforementioned halogens, and the rest are unsubstituted. It may be replaced. The carbonyl group, ester group, carbamoyl group, and amino group include aliphatic hydrocarbons, alicyclic hydrocarbons,
Aromatic hydrocarbons, including those substituted with heterocycles,
Further, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, and heterocycles may be unsubstituted or substituted.
The silyl group indicates a silicon compound group such as a trimethylsilyl group, which may be unsubstituted or substituted. The siloxanyl group refers to a silicon compound group via an ether bond such as a trimethylsiloxanyl group, which may be unsubstituted or substituted.

Specific examples include alkali metal complexes having the following compounds as ligands. Of course, the compounds that can be used in the present invention are not limited to these.

[0018]

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Embedded image By using an alkali metal as the central metal, the metal complex can provide a light-emitting element having a peak in a shorter wavelength region and having excellent blue light-emitting properties, as compared with the case where another metal is used. Of the alkali metals, it is preferable to use lithium from the viewpoint of the stability of the complex.

The lithium complex can be synthesized by mixing lithium hydroxide or lithium acetate with a ligand. Needless to say, the above-described synthesis method is merely an example, and the present invention is not limited to this.

The host material does not need to be limited to one kind of alkali metal complex, but may be a mixture of a plurality of alkali metal complexes or a mixture of one or more known host materials with an alkali metal complex. Good. Specifically, condensed ring derivatives such as anthracene and pyrene, which have long been known as light emitters, metal chelated oxinoid compounds such as tris (8-quinolinolato) aluminum, bisstyrylanthracene derivatives and distyrylbenzene derivatives Bisstyryl derivative, tetraphenylbutadiene derivative, coumarin derivative, oxadiazole derivative, pyrrolopyridine derivative, perinone derivative, cyclopentadiene derivative, oxadiazole derivative, thiadiazolopyridine derivative, polymer system, polyphenylenevinylene derivative, polyparaphenylene Derivatives and polythiophene derivatives can be used, but are not particularly limited.

The dopant material to be added to the light emitting material is not particularly limited, but a known dopant material can be used. Specifically, conventionally known,
Condensed ring derivatives such as perylene and rubrene, quinacridone derivatives, phenoxazone 660, DCM1, perinone,
Coumarin derivatives, pyromethene derivatives, cyanine dyes and the like can be used as they are.

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 necessary to have a high electron injection efficiency and to efficiently transport the injected electrons. Is desirable. For that purpose, electron affinity is large, and electron mobility is large,
Further, it is required that the substance be excellent in stability and hardly generate impurities serving as traps during production and use. Materials satisfying such conditions include lithium complexes, quinolinol derivative metal complexes represented by tris (8-quinolinolato) aluminum, tropolone metal complexes,
Flavonol metal complexes, perylene derivatives, perinone derivatives, naphthalene, coumarin derivatives, oxadiazole derivatives, aldazine derivatives, bisstyryl derivatives, pyrazine derivatives, phenanthroline derivatives, silole derivatives, and the like are not particularly limited. 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 of forming the substance that controls light emission is not particularly limited, such as resistance heating evaporation, electron beam evaporation, sputtering, molecular lamination, and coating. However, resistance heating evaporation and electron beam evaporation are usually used. Preferred in terms of surface. The thickness of the layer cannot be limited because it depends on the resistance of the substance that controls light emission, 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 in the present invention refers to 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.

[0030]

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 (15 Ω / □, electron beam vapor-deposited product, manufactured by Asahi Glass Co., Ltd.) on which a 150 nm ITO transparent conductive film was deposited was used for 30
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 ⁻⁶ Pa or less. First, 4,4′-bis (N- (m-tolyl) -N-phenylamino) biphenyl was used as a hole transport material at a rate of 0.3 nm / sec by a resistance heating method.
Then, {2- (2-benzoxazolyl) phenolate} lithium was deposited to a thickness of 100 nm as a light emitting layer.
The thickness was laminated. Next, a mask is attached so that a 5 × 5 mm square element can be formed.
A 5 × 5 mm square device was prepared by forming a cathode by vapor deposition in nm. 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.

The emission peak wavelength of this light emitting device is 458n
m.

Comparative Example 1 A light-emitting material was produced in the same manner as in Example 1 except that {2- (2-benzoxazolyl) phenolate} zinc was used. The light emission peak wavelength of this light emitting device was 486 nm. As compared with Example 1, the emission peak wavelength of Comparative Example 1 was obtained on the longer wavelength side as much as 28 nm.

Example 2 A light-emitting material was produced in the same manner as in Example 1, except that {2- (2-benzthiazolyl) phenolate} lithium was used. The light emission peak wavelength of this light emitting device was 490 nm. Comparative example 2 It produced similarly to Example 1 except having used {2- (2-benzthiazolyl) phenolate} zinc as a light emitting material. The light emission peak wavelength of this light emitting device was 524 nm. As compared with Example 2, the emission peak wavelength of Comparative Example 2 was as long as 34 nm on the longer wavelength side.

[0035]

By using the metal complex of the present invention, a light emitting device capable of emitting blue light having a peak in a shorter wavelength region can be provided.

Claims (5)

[Claims] An element which emits light by electric energy, wherein a substance which controls light emission is present between a positive electrode and a negative electrode, wherein the element contains an alkali metal complex represented by the general formula (1). A light emitting element. Embedded image (Wherein, X is O, S, .R ₁ ~ selected from among NR ₉
R ₈ may be the same or different, and may be hydrogen, alkyl, cycloalkyl, aralkyl, alkenyl, cycloalkenyl, alkynyl, hydroxyl, mercapto, alkoxy, alkylthio, arylether, 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, siloxanyl group, adjacent substitution Condensed ring, heterocyclic and aliphatic ring formed between the group, and a single bond, an ether bond for connection with another skeleton,
It is selected from an amino group, an amide bond, an ester bond, and a sulfide bond. R ₉ is selected from hydrogen, an alkyl group, an aryl group, and a heterocyclic group. M is Li, Na, K,
It is selected from Rb and Sc. ) 2. The light emitting device according to claim 1, wherein M is Li in the alkali metal complex represented by the general formula (1). 3. The light emitting device according to claim 1, wherein said alkali metal complex is a light emitting material. 4. The light emitting device according to claim 1, wherein said light emitting device constitutes a display for displaying in a matrix and / or segment system. 5. The light emitting device according to claim 1, wherein the light emitting device is a backlight.