JP2001244078A - Organic light emitting device and method for forming image by using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical resonator organic light emitting device excellent in drive durability, a light emitting device array for exposure light source, and a method for forming color images with accurate color reproducibility by using either one of the above devices. SOLUTION: This invention provides optical resonator organic light emitting device consisting of an optical transparent substrate, a dielectric multi-layer film formed on the substrate, a transparent electrode, an organic chemical compound layer which includes at least an organic light emitting layer containing ortho-metallation complex and a back electrode, and a light emitting device array for exposure light sources made by arranging plural organic light emitting devices of picture element size of 10-500 μm at intervals of 1-50 μm. A method for forming images is also provided by exposing sensitive material using either one of the above devices to develop the material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an organic light emitting device, an organic light emitting device array, and an image forming method using any one of them.

[0002]

2. Description of the Related Art Organic light-emitting devices are expected to be used in various applications such as displays, backlights for LCDs, light sources for illumination, light sources for optical communication, and read / write heads for information files. Development is underway. An organic light-emitting device generally includes an organic compound layer having a thickness of 1 μm or less and two electrodes sandwiching the organic compound layer. In such an organic light emitting device, when a voltage is applied between both electrodes, electrons generated from one electrode (cathode) and holes generated from the other electrode (anode) are recombined in the organic compound layer. A self-luminous element that emits light by exciting a light emitting material.

[0003] Organic light-emitting devices are used in the range from visible light to near-infrared light (for example, red (R),
When used as a writing light source for a photosensitive material having spectral sensitivity in green (G) and blue (B), the half width of the emission spectrum in the central region (in this case, green (G)) is very important. is there. That is, when a normal green (G) light emitting organic light emitting element having a wide half width is used, a part of the red (R) and blue (B) regions is also exposed, and the obtained image becomes turbid (in the case of a negative photosensitive material). )
And color loss (in the case of a positive photosensitive material). Further, since the organic light-emitting element is a completely diffused light source similarly to the inorganic LED, there is a problem that a large amount of light is lost when used as an exposure light source for a printer. Therefore, it has been desired to develop an organic light-emitting element having a narrow half-width of an emission spectrum and excellent emission directivity, and some proposals have been made. For example, Japanese Patent Application Laid-Open No. Hei 9-80883 discloses that a micro optical resonator is formed in an element by sandwiching an organic compound layer between a dielectric multilayer thin film mirror and a metal mirror, and that the resonance wavelength is a short wavelength of the peak wavelength of the EL spectrum. It is described that an optical resonator-type organic light-emitting device having high directivity and a narrow half-value width of an emission spectrum can be obtained by setting to the side. By using such an optical resonator type organic light emitting element, it has become possible to obtain an excellent color image without color turbidity or color omission.

In the above-mentioned optical resonator type organic light emitting device,
Generally, the optical length is set to about 1.5 times the target resonance wavelength so as to resonate in a single mode. However, in this case I
The thickness of the electrode made of TO (Indium Tin Oxide) must be reduced, and the surface resistance inevitably increases. In particular, when the luminous efficiency of the element is low, the driving durability is significantly reduced. There is a need to develop a technology that can improve this.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical resonator type organic light emitting device having excellent driving durability, an organic light emitting device array for an exposure light source, and high color reproducibility by using any of them. An object of the present invention is to provide an image forming method capable of obtaining a color image by using the method.

[0006]

Means for Solving the Problems As a result of intensive studies in view of the above object, the present inventors have found that tris (2-
The present inventors have found that an optical resonator type organic light-emitting device containing a (phenylpyridine) iridium complex exhibits not only high luminous efficiency but also excellent driving durability, and reached the present invention.

That is, the optical resonator type organic light emitting device of the present invention comprises a light transmitting substrate, a dielectric multilayer film formed thereon, a transparent electrode, an organic compound layer including at least one organic light emitting layer, and a back electrode. Wherein the organic compound layer contains an orthometalated complex such as a tris (2-phenylpyridine) iridium complex.

[0008] In the organic light-emitting device of the present invention, the ortho-metalated complex is preferably an iridium complex.
Further, the organic light emitting element array for an exposure light source of the present invention is formed by arranging a plurality of the organic light emitting elements with a pixel size of 10 to 500 μm and an interval of 1 to 50 μm. The image forming method of the present invention is characterized in that a photosensitive material is exposed using the organic light emitting device or the organic light emitting device array, and an image is obtained by developing the photosensitive material.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [1] Optical Resonator-Type Organic Light-Emitting Device The optical resonator-type organic light-emitting device of the present invention comprises a light-transmitting substrate, a dielectric multilayer film formed thereon, a transparent electrode, and at least one layer. An organic compound layer including an organic light emitting layer; and a back electrode, wherein the organic compound layer contains an orthometalated complex. Usually, the transparent electrode is the anode and the back electrode is the cathode, but vice versa. The dielectric multilayer film is composed of two dielectric materials having different refractive indexes (for example, TiO ₂ and SiO ₂ , SiN _X and SiO ₂ , Ta ₂ O ₅ and SiO _2).
2 ) are alternately laminated and placed on the transparent electrode side surface of the light transmitting substrate. The dielectric multilayer has an optical thickness equal to 1/4 of the desired resonance wavelength.

The optical length (L) of the optical resonator type organic light-emitting device of the present invention is expressed by the following formula in which the optical length between the back electrode and the dielectric multilayer film is taken into consideration with the amount of light penetrating into the dielectric multilayer film. Is done. Note that the reflectivity of the dielectric multilayer film is preferably 60% or more, and more preferably 80% or more.

(Equation 1) _Where λ is the resonance wavelength, n _eff is the effective refractive index of the dielectric multilayer, Δn is the refractive index difference between the two types of layers in the dielectric multilayer, n
refractive index and film thickness of the _i and d _i is the organic compound layer and the transparent electrode, theta
Is the angle between the light incident on each of the layers in the organic compound layer or on each of the interfaces between the organic compound layer and the transparent electrode and the normal line at the interface. In the above equation, the first term is substantially determined by the constituent elements of the dielectric multilayer film. Therefore, in order to resonate light having a certain wavelength λ, the optical length L must be adjusted by the second term. Since the refractive index of the second term is material-specific,
Specifically, the optical length L is controlled by changing the film thickness of the organic compound layer and the transparent electrode.

In order to resonate light having a wavelength λ, the optical length L must be an integer (m) times (λ / 2). When the integer m is set large, the thickness of the transparent electrode can be set large, and the surface resistance can be reduced. In the present invention, the thickness of the transparent electrode is preferably 40 nm or more, more preferably 100 nm or more. The surface resistance of the transparent electrode is preferably 30Ω / □ or less, more preferably 10Ω / □ or less, and particularly preferably 5Ω / □ or less. That is, the smaller the surface resistance of the transparent electrode, the better. Although the film thickness increases as the surface resistance decreases, it is acceptable up to about 600 nm. If the film thickness exceeds 600 nm, it takes a long time to form the film, which is not practical. On the other hand, if the optical length L is too large, many low-order mode emission peaks appear on the longer wavelength side than the target resonance wavelength, and the efficiency decreases, which is not preferable. Therefore, in the present invention, it is preferable that the optical length L is 1.5 times (m = 3) or more and 3 times (m = 6) or less of the target resonance wavelength λ.

If the light emission in the lower order mode caused by increasing the optical length L overlaps with the spectral sensitivity region of the photosensitive material, light fogging may occur and the resulting image may be mixed or missing.
For example, when a photosensitive material having spectral sensitivity in the RGB region is exposed using three organic light-emitting devices of the optical resonator type, this phenomenon becomes more problematic for the short-wavelength B element. This is because, in the B element, the emission peak of the lower mode tends to overlap the spectral sensitivity region of R. For this reason, it is preferable to use a filter to cut low-order mode light other than light necessary for exposure. The filter used in the present invention is not particularly limited as long as it can be installed between the organic light emitting device and the photosensitive material. When an optical system such as a selfoc lens is arranged between the organic light emitting element and the photosensitive material, the filter may be installed on either side. The filter is preferably provided in the light transmitting substrate of the organic light emitting device and / or on the surface of the light transmitting substrate opposite to the dielectric multilayer film. Specific examples of the filter that can be used in the present invention include a dielectric multilayer film in which materials having different refractive indices are stacked, a film of an inorganic or organic pigment or dye formed by a vacuum evaporation method or a coating method, a light-transmitting substrate. And the like in which a pigment or a dye is contained in the above material.

In the present invention, a plurality of organic light emitting devices that emit light of different wavelengths may be arranged on the same substrate.
In that case, control each optical length well,
It is preferable to use a single type of filter to cut low-order mode light harmful to the photosensitive material. If one type of filter is used, it can be arranged on the entire surface of the substrate, processing is very simple, and the production of the light source for exposure becomes easy.

The optical resonator type organic light emitting device of the present invention has an organic compound layer containing an orthometalated complex. The orthometalated complex used in the present invention is described in "Basic and Application of Organometallic Chemistry" by Akio Yamamoto, pp. 150 and 232, Shokabosha (1982), "Photochemistry and Photop" by H. Yersin.
hysics of Coordination Compounds, '' p. 71-77 and 13
It is a generic term for compounds described in pages 5 to 146, Springer-Verlag (1987) and the like. The ligand forming the ortho-metalated complex is not particularly limited, and various ligands can be used, but 2-phenylpyridine derivative, 7,8-benzoquinoline derivative, 2- (2-thienyl) pyridine derivative, 2 It is preferably a-(1-naphthyl) pyridine derivative and / or a 2-phenylquinoline derivative. Further, other ligands may be included in addition to the ligands essential for the formation of the ortho-metalated complex. Metals that form orthometalated complexes include
Ir, Pd, Pt and the like can be used, but iridium (Ir) is particularly preferred. The ortho-metalated complex used in the present invention preferably emits light from triplet excitons from the viewpoint of improving luminous efficiency.

The amount of the orthometalated complex in the organic compound layer can be selected in a wide range, for example, 0.1 to 99% by weight, preferably 1 to 20% by weight. The orthometalated complex is preferably used for the organic light emitting layer, and is preferably added as a dopant.

In the optical resonator type organic light-emitting device of the present invention, a specific structure of laminating on a substrate having a dielectric multilayer film is as follows: anode (usually transparent electrode) / organic light-emitting layer / cathode (usually back electrode) , Anode / organic light emitting layer / electron transport layer /
Cathode / anode / hole transport layer / organic light emitting layer / electron transport layer /
Cathode, anode / hole transport layer / organic light-emitting layer / cathode, and a configuration in which these are stacked in reverse order, and the like. A hole injection layer, an electron injection layer, or the like may be provided, or a plurality of hole transport layers, organic light-emitting layers, electron transport layers, or the like may be provided. A conductive polymer layer may be provided between the anode and the light emitting layer in contact with the anode. Further, a sealing layer for preventing entry of moisture or the like may be provided. Further, it is preferable to provide a block layer on the surface of the light emitting layer on the cathode side so that holes do not pass through the cathode.

The organic compound layer included in the light emitting device of the present invention can be formed by a known method such as a vacuum evaporation method, a sputtering method, a dipping method, a spin coating method, a casting method, a bar coating method, a roll coating method and the like. it can. Multi-layer coating is also possible by using different solvents. The inorganic layer (anode, cathode, etc.) can be formed by a known method such as a vacuum evaporation method, a sputtering method, and an ion plating method. The electrode is preferably patterned by chemical etching using photolithography or the like, physical etching using a laser or the like, or the like. Patterning may be performed by stacking masks and performing vacuum deposition or sputtering.

Hereinafter, each component of the optical resonator type organic light emitting device of the present invention will be described in detail. (A) Light Transmitting Substrate In the present invention, a plastic substrate can be used as the light transmitting substrate in addition to a normal glass substrate. The plastic used as the substrate is preferably excellent in heat resistance, dimensional stability, solvent resistance, electrical insulation and workability, and has low air permeability and low moisture absorption. Such plastic materials include polyethylene terephthalate,
Examples thereof include polybutylene terephthalate, polyethylene naphthalate, polystyrene, polycarbonate, polyether sulfone, polyarylate, allyl diglycol carbonate, polyimide, and polycycloolefin.

It is preferable to provide a moisture permeation preventing layer (gas barrier layer) on the surface of the substrate on the electrode side, the surface on the side opposite to the electrode, or both. As a material constituting the moisture permeation preventing layer, an inorganic substance such as silicon nitride, silicon oxide, or alkali-free glass is preferable. The moisture permeation preventing layer can be formed by a high frequency sputtering method or the like. Further, a hard coat layer or an undercoat layer may be provided as necessary.

(B) Electrode As the material of the anode used in the present invention, tin oxide, ITO (I
A known material such as ndium tin oxide (IZO) or indium zinc oxide (IZO) may be used, and a metal thin film such as gold or platinum having a large work function can also be used. Organic materials such as polyaniline, polythiophene, polypyrrole, and derivatives thereof can also be used. Further, the transparent conductive film described in detail in "New Development of Transparent Conductive Film" (edited by Yutaka Sawada, published by CMC, 1999) can also be applied to the present invention.

As a cathode material, Li, K, C having a low work function are used.
It is preferable to use an alkali metal such as e or an alkaline earth metal such as Mg or Ca from the viewpoint of electron injection properties. Further, Al or the like, which is hardly oxidized and stable, is also preferable. A layer containing two or more kinds of materials may be used in order to achieve both stability and electron injecting property. Such materials are described in JP-A Nos. 2-15595 and 5-1.
It is described in detail in 21172 and the like.

(C) Hole Injecting Layer The hole injecting material used for the hole injecting layer is not particularly limited, but a P-type inorganic semiconductor, a porphyrin-based compound (eg, copper phthalocyanine) or the like can be used, and a P-type inorganic semiconductor is preferable. By providing a hole injection layer made of a P-type inorganic semiconductor, driving can be performed at a low voltage, and the driving durability of the element is further improved. Examples of the P-type inorganic semiconductor include Si _1-x C _x (0 ≦ x ≦ 1), CuI, CuS, GaAs, ZnTe, Cu
₂ O, Cu ₂ S, CuSCN, CuF, CuCl, CuBr, CuInSe ₂ , CuIn
S ₂ , CuAlSe ₂ , CuGaSe ₂ , CuGaS ₂ , GaP, NiO, CoO, FeO,
Bi ₂ O ₃ , MoO ₂ , Cr ₂ O _{3 and the} like can be mentioned. These may be used alone or in combination of two or more.

(D) Hole transporting layer The hole transporting material used for the hole transporting layer is poly-N
-Vinyl carbazole derivatives, polyphenylene vinylene derivatives, polyphenylene, polythiophene, polymethylphenylsilane, polyaniline, triazole derivatives,
Oxadiazole derivative, imidazole derivative, polyarylalkane derivative, pyrazoline derivative and pyrazolone derivative, phenylenediamine derivative, arylamine derivative, amino-substituted chalcone derivative, oxazole derivative, carbazole derivative, styryl anthracene derivative, fluorenone derivative, hydrazone derivative, stilbene derivative , Porphyrin derivatives (phthalocyanine etc.),
Aromatic tertiary amine compounds and styrylamine compounds, butadiene compounds, benzidine derivatives, polystyrene derivatives, triphenylmethane derivatives, tetraphenylbenzene derivatives, starburst polyamine derivatives, and the like can be used.

(E) Organic Light-Emitting Layer The light-emitting material used in the present invention is not particularly limited as long as it can emit fluorescence upon being excited. Azole compounds,
Perinone compounds, pyrrolopyrrole compounds, biphenyl compounds, naphthalene compounds, anthracene compounds, fluorene compounds, fluoranthene compounds, tetracene compounds, pyrene compounds, coronene compounds, quinolone compounds and azaquinolone compounds, pyrazoline derivatives and pyrazolone derivatives, rhodamine compounds, chrysene compounds, phenanthrene Compound, cyclopentadiene compound, stilbene compound, diphenylquinone compound, styryl compound,
Distyrylbenzene compounds, butadiene compounds, dicyanomethylenepyran compounds, dicyanomethylenethiopyran compounds, fluorescein compounds, pyrylium compounds, thiapyrylium compounds, selenapyrylium compounds, telluropyrylium compounds, aromatic aldadienes, oligophenylene compounds, xanthene compounds and thioxanthenes Compounds, cyanine compounds, acridine compounds, acridone compounds, quinoline compounds, metal complexes of 8-hydroxyquinoline compounds, benzoquinolinol beryllium complexes,
Metal complexes of 2,2'-bipyridine compounds, complexes of Schiff bases with Group III metals, metal complexes of oxadiazole compounds, rare earth complexes and the like can be used. Further, a high molecular light emitting material may be used as the light emitting material. Examples thereof include a π-conjugated polymer (poly-p-phenylene vinylene derivative, polyfluorene derivative, polythiophene derivative, etc.), a low molecular dye and tetraphenyldiamine, A polymer in which triphenylamine or the like is introduced into a main chain or a side chain may be used. These light-emitting materials may be used alone or as a mixture of two or more, or may be doped into the above-described electron transport material or hole transport material to form a light-emitting layer.

(F) Electron transport layer Electron transport materials used in the electron transport layer include oxadiazole derivatives, triazole derivatives, triazine derivatives, nitro-substituted fluorenone derivatives, thiopyrandioxide derivatives, diphenylquinone derivatives, and perylenetetracarboxyl derivatives. , Anthraquinodimethane derivatives,
Examples include a fluorenylidenemethane derivative, an anthrone derivative, a perinone derivative, an oxine derivative, and a quinoline complex derivative.

(G) Electron Injection Layer In the present invention, it is preferable to provide an insulating layer thin film as an electron injection layer between the cathode and the organic light emitting layer or the electron transport layer. As the insulating layer thin film, known aluminum oxide,
A thin layer of about 0.01 to 10 nm such as lithium fluoride and cesium fluoride can be preferably used.

(H) Conductive polymer layer By providing the conductive polymer layer, the thickness of the organic compound layer can be increased without substantially increasing the driving voltage, and the occurrence of luminance unevenness and short circuit can be reduced. This is preferable because the optical length can be adjusted and the optical length can be adjusted. As the conductive polymer forming the conductive polymer layer, polyaniline derivatives, polythiophene derivatives and polypyrrole derivatives described in WO 98/05187 and the like are preferable. These may be used in the state of being mixed with a protonic acid (for example, camphor sulfonic acid, p-toluene sulfonic acid, styrene sulfonic acid, polystyrene sulfonic acid, etc.), and if necessary, other polymers (polymethyl methacrylate (PMMA) ), Poly-N-vinylcarbazole (PVCz) and the like. The surface resistance of the conductive polymer layer is preferably 10,000 Ω / □ or less, the film thickness is preferably 10 to 1000 nm, and 20 to 20 nm.
More preferably, it is 0 nm.

(I) Sealing Layer An organic light-emitting device is generally provided with a sealing layer for preventing intrusion of moisture or oxygen. As a sealing material for forming the sealing layer, a copolymer of tetrafluoroethylene and at least one comonomer, a fluorinated copolymer having a cyclic structure in the copolymer main chain, polyethylene, polypropylene, polymethyl methacrylate, Polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, a copolymer of chlorotrifluoroethylene and dichlorodifluoroethylene, a water-absorbing substance having a water absorption of 1% or more and a moisture-proof substance having a water absorption of 0.1% or less Mixtures of metals, metals (In, Sn, Pb, Au, Cu, Ag,
Al, Ti, Ni, etc.), metal oxides (MgO, SiO, SiO ₂ , Al
₂ O ₃ , GeO, NiO, CaO, BaO, Fe ₂ O ₃ , Y ₂ O ₃ , TiO ₂ etc., metal fluorides (MgF ₂ , LiF, AlF ₃ , CaF ₂ etc.), liquid fluorinated carbon (per Fluoroalkane, perfluoroamine,
Perfluoroether, etc.) and those obtained by dispersing an adsorbent for adsorbing moisture and oxygen on the liquid fluorinated carbon can be used.

[2] Organic light emitting element array for exposure light source The organic light emitting element array for exposure light source of the present invention is formed by arranging a plurality of the organic light emitting elements of the present invention. Although the organic light emitting device of the present invention can be used with a single pixel, it is preferable to use the organic light emitting device as a dot array provided in a plurality of rows for each emission color. Each emission color may be one line or a plurality of lines. The size of one pixel is 10 to 500 μm, preferably 50 to 300 μm. The interval between the pixels is 1 to 50 μm. In particular, each pixel is preferably separated by a light-shielding material of preferably 3 to 50 μm, more preferably 5 to 20 μm.

[3] Image Forming Method In the image forming method of the present invention, an image is obtained by exposing a photosensitive material using the organic light emitting device or the organic light emitting device array of the present invention and developing the photosensitive material. . The photosensitive material that can be exposed by the organic light-emitting device or the organic light-emitting device array of the present invention includes silver halide photosensitive materials and silver described in “Known Technique No. 5” (Aztec Co., Ltd., published on March 22, 1991). Trigger type photosensitive material, non-silver photosensitive material (for example, "Sycolor" manufactured by Cycolor System Co., Ltd.)
Etc.). As a silver halide photosensitive material,
Not only color photographic materials such as normal color negative films for photography, color reversal films, color printing materials, instant films, heat-developable color photographic materials, but also black and white negative films for photography, black and white printing materials,
Almost all materials, such as heat-developable black-and-white photosensitive materials, are applicable.

Exposure is performed by applying a DC voltage (usually a pulse voltage of 2 to 30 volts, which may include an AC component if necessary) or a pulse current between an anode and a cathode of the organic light emitting device. It is preferable to use it. In the present invention, considering the writing time for one screen, 1
The exposure time of the pixel (light emission time of the element) is preferably from 10 ^-7 to 1 second, and more preferably from 10 ^-6 to 10 ^-1 second.
The exposure amount is adjusted by an intensity modulation method, a time modulation method, or the like. The intensity modulation method is a method of controlling light emission intensity by controlling a current flowing through an element to adjust an exposure amount. The time modulation method is a method in which an element is illuminated at a constant intensity and the exposure amount is adjusted by changing the irradiation time. Further, the exposure amount may be adjusted by a method in which the element emits light in a pulse shape and the exposure amount is controlled by counting pulses, that is, a pulse modulation method.

An image is obtained by developing the exposed photosensitive material. The details of the photosensitive material and the development processing that can be used in the present invention are described in "Theory of Photographic Process (Theory).
Theory of The Photographic Process ”, 4th edition, 353
Pp. 372 (James, 1977), "Dye Diffusion Systems in Color Photog
raphy) "(Van de Sande), Ang
ew. Chem. Int. Ed. Engl., 22, 191 (1983), "Imaging Systems", pp. 86-103 (Jacobson & J
acobson, Focal Press, 1976), and "Revised Photographic Engineering Fundamentals" (edited by the Photographic Society of Japan, published by Corona, 1998).

[0033]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. Example 1 On a 5.0 cm square glass substrate, each film thickness was 1/4 of the resonance wavelength.
Six dielectric thin films of TiO ₂ and SiO ₂ were laminated in this order so as to have an optical length corresponding to the above, thereby forming a dielectric multilayer film. On top of this, a 60 nm thick ITO film was formed by DC magnetron sputtering.
Was formed and patterned to form an anode. The surface resistance of the anode was 90Ω / □. After IPA cleaning and oxygen plasma treatment, 4,4'-bis [N- (1-naphthyl)
-N-phenylamino] biphenyl (NPD) hole transport layer (40 nm thick), quinacridone-doped 4,4'-bis (N-carbazole) biphenyl (CBP) doped 1 wt% (thickness) 20nm), 2,9-dimethyl-4,7-diphenyl-
Layer consisting of 1,10-phenanthroline (BCP) (film thickness 6n
m), tris (8-hydroxyquinoline) aluminum (Al
The electron transport layer (thickness: 20 nm) consisting of q) and the electron injection layer (thickness: 1 nm) consisting of LiF are vacuum-deposited in order, and an Al cathode (thickness: 150 nm) is further vacuum-deposited using a mask and filled with nitrogen. Sealing was performed using glass and a UV curable adhesive in the completed glove box, to produce a light-emitting element 1A for comparison. The optical length of the element is SiO ₂ provided between the ITO film and the dielectric reflection mirror so that it becomes 1.5 times the emission peak wavelength of 537 nm.
Adjusted by spacer. Further, organic light emitting devices 1B to 1F of the present invention were manufactured in the same manner as the method of manufacturing the light emitting device 1A, except that each of the quinacridones was doped with 6% by weight of each of the orthometalated complexes shown in Table 1.

A DC current (constant current) for obtaining an initial luminance of 2000 cd / m ² was applied to each of the obtained comparative light emitting element 1A and the organic light emitting elements 1B to 1F of the present invention, and the luminance after 10 minutes was measured. did. Table 1 shows the results together with the drive current value (mA / cm ² ).
Shown in

[0035]

[Table 1]

From Table 1, it can be seen that the comparative light-emitting element 1A containing no ortho-metalated complex did not emit any light 10 minutes after the application of a direct current for obtaining an initial luminance of 2000 cd / m ² . Organic light emitting device of the present invention using complex
It can be seen that 1B to 1F can be driven with a low current and emit light with sufficient luminance even after 10 minutes. That is, the organic light emitting device of the present invention has excellent luminous efficiency and high driving durability.

Example 2 An anode was formed by forming and patterning ITO with a thickness of 330 nm, and the optical length was 537 nm, which is the emission peak wavelength.
An organic light-emitting element 2A for comparison and an organic light-emitting element 2B of the present invention were produced in the same manner as in the method for producing the light-emitting elements 1A and 1B, except that the ratio was adjusted to 2.5 times with a SiO ₂ spacer. The surface resistance of the anode was 5Ω / □.
Next, to the obtained light emitting elements 2A and 2B, respectively, 2000 cd / m
Apply DC current (constant current) to obtain the initial brightness of ²
The luminance after one minute was measured. As a result, the comparative light emitting element 2A
While the luminance of 1580 cd / m ² was exhibited, the light emitting device 2B of the present invention exhibited a high driving durability of 1820 cd / m ² .

Example 3 A hole injection layer (thickness: 50 nm) made of P-type inorganic semiconductor CuI was formed between the anode and the hole transport layer by vacuum evaporation, and the optical length was 537 nm, which is the emission peak wavelength. An organic light-emitting element 3A for comparison and an organic light-emitting element 3B of the present invention were respectively produced in the same manner as in the production method of the light-emitting elements 1A and 1B, except that the adjustment was made with a SiO ₂ spacer so as to increase the number by _two times. Next, each of the obtained light emitting elements 3A and 3B
A direct current (constant current) for obtaining an initial luminance of cd / m ² was applied, and the luminance was measured 10 minutes later. As a result, the comparative light emitting element
3A had a luminance of 450 cd / m ² , whereas the light-emitting element 3B of the present invention showed a high driving durability of 1470 cd / m ² . In the present invention, the driving stability of the organic light emitting device is further improved by providing a hole injection layer made of a P-type inorganic semiconductor such as CuI.

Example 4 A conductive polymer layer (100 nm thick) made of poly (ethylenedioxythiophene) polystyrene sulfonate ("Baytron P" manufactured by Bayer AG) was used instead of the hole injection layer made of CuI. Except that the light emitting elements 3A and 3B
In the same manner as in the production method described above, a comparative organic light-emitting element 4A and an organic light-emitting element 4B of the present invention were produced. The conductive polymer layer was formed by spin-coating Baytron P, followed by vacuum drying at 150 ° C. for 2 hours. Next, the obtained light emitting elements 4A and 4B
Then, a DC current (constant current) for obtaining an initial luminance of 2000 cd / m ² was applied, and the luminance after 10 minutes was measured. As a result, the comparative light emitting device 4A had a luminance of 320 cd / m ² , whereas the light emitting device 4B of the present invention showed a high driving durability of 1340 cd / m ² .

Example 5 The light-emitting devices 2A, 2B, 3A, 3B, 4A and
Expose Fuji Color Paper (Fuji Photo Film Co., Ltd.) using 4B, color develop and desilver using Fuji Color Paper Processing Chemical Kit CP40FAII (Fuji Photo Film Co., Ltd.), wash with water, and dry I got For exposure, a selfoc lens was installed between the glass substrate of the light emitting element and the emulsion surface of Fuji Color Paper, the focal length was adjusted, the constant current driving time per pulse was 50 μs, and the brightness was 10
000 cd / m ² and the number of pulses was changed (that is, the exposure amount was changed). Note that a 50 μs current OF
F time was set. When the color reproducibility of the obtained image was examined, good magenta color was obtained for each light emitting element regardless of the image density. Next, when a continuous pulse was applied to these light emitting devices under the above conditions to evaluate the durability, the organic light emitting device of the present invention was evaluated.
It was found that 2B, 3B and 4B had higher durability than the comparative organic light emitting devices 2A, 3A and 4A and exhibited excellent color reproducibility.

[0041]

As described in detail above, the optical resonator type organic light emitting device of the present invention containing the orthometalated complex in the organic compound layer exhibits high luminous efficiency and excellent driving durability. According to the image forming method of the present invention using the organic light emitting device, a color image can be obtained with high color reproducibility.

Claims (4)

[Claims] An optical resonator type organic light emitting device having a light transmitting substrate and a dielectric multilayer film formed thereon, a transparent electrode, an organic compound layer including at least one organic light emitting layer, and a back electrode. An optical resonator type organic light emitting device, wherein the organic compound layer contains an orthometalated complex. 2. The optical resonator type organic light emitting device according to claim 1, wherein the ortho-metalated complex is an iridium complex. 3. An organic light-emitting element array for an exposure light source, comprising a plurality of the organic light-emitting elements according to claim 1 or 2 having a pixel size of 10 to 500 μm and an interval of 1 to 50 μm. 4. An image is obtained by exposing a photosensitive material using the organic light emitting device according to claim 1 or 2 or an organic light emitting device array according to claim 3, and developing the photosensitive material. Image forming method.