JP2007066916A - Organic electroluminescent element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent element enabled to lower element drive voltage, improve life characteristics and stability of chromaticity at the time of continuous drive, and with resistance rise suppressed as much as possible. <P>SOLUTION: The organic electroluminescent element is formed by having an organic luminescent layer prepared between an anode and a cathode. The anode is to be processed by halogen. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence element used for various displays, display devices, liquid crystal backlights, and the like, and a method for producing the same.

  An electroluminescent element is a light emitting device that uses electroluminescence of a solid phosphor material. At present, an inorganic electroluminescent element using an inorganic material as a light emitter has been put to practical use, and a backlight of a liquid crystal display or a flat panel display is used. Some applications are being developed. However, since the inorganic electroluminescence element has a high voltage for emitting light of 100 V or more and is difficult to emit blue light, it is difficult to achieve full color using RGB three primary colors.

On the other hand, research on electroluminescent devices using organic materials has been attracting attention for a long time, and various studies have been made. However, since the luminous efficiency is very low, full-scale practical research has not been achieved. However, in 1987, Kodak's C.I. W. Tang et al. Proposed an organic electroluminescence having a function-separated layered structure in which an organic material is divided into two layers, a hole transport layer and an organic light emitting layer. In this case, although it has a low voltage of 10 V or less, 1000 cd / It was revealed that a high emission luminance of m ² or more can be obtained. Since then, organic electroluminescence devices have begun to attract attention and active research has been conducted.

As a result of such research and development, the organic electroluminescence device can emit surface light with a high luminance of about 100 to 100,000 cd / m ² at a low voltage of about 10 V, and can be blue by selecting the type of fluorescent material. From red to red is now possible.

  However, when considering application development as a full-color display and a light-emitting element for illumination, it is necessary to lower the element driving voltage to further increase the efficiency. In order to realize such a low device driving voltage, it is necessary to increase the efficiency of injection of holes from the anode and electrons from the cathode into the organic light emitting layer. As a method for increasing the hole injection efficiency from the anode, there is a method of increasing the work function of the metal of the anode and reducing the energy barrier with the hole transport layer.

  Here, in the case of ITO (indium tin oxide) that is generally used as an anode metal, it is considered that the work function is about 6.0 eV in principle, but when cleaning is performed with an organic solvent or the like that is normally performed. Shows only a work function of about 4.7 to 4.8 eV. This is considered to be because dirt such as a residual carbon component due to an organic solvent or the like remains on the surface of the anode. For this reason, after the cleaning process, UV ozone cleaning or oxygen plasma processing may be performed.

On the other hand, as a method for increasing the work function of the anode metal, methods for treating the surface of the anode with an acid have been attempted in Japanese Patent Application Laid-Open Nos. 4-14795 and 9-120890. That is, in JP-A-4-14795, the surface of the anode is acid-treated, and then washed and dried with an organic solvent, so that the work function of the anode is increased by about 0.1 to 0.3 eV than before the acid treatment. Thus, the drive voltage of the element is lowered by increasing the work function of the anode. In JP-A-9-120890, the surface of the anode is polished, then acid-treated, and further washed and dried with an organic solvent to flatten the anode surface and form pores on the outermost surface. The drive voltage of the element is lowered and the life is improved.
JP-A-4-14795 JP-A-9-120890 JP 2001-319777 A

  However, in what is disclosed in Japanese Patent Application Laid-Open Nos. 4-14795 and 9-120890, the anode is acid-treated and then washed with an organic solvent or the like. Residual carbon content remained, and the effect of increasing the work function was insufficient. In addition, when the organic electroluminescence element is continuously driven, there is a problem that the luminance decreases and the resistance of the element increases. Japanese Patent Laid-Open No. 2001-319777 discloses that after the anode is acid-treated, an organic light emitting layer or the like is formed without cleaning, thereby increasing the work function of the anode and lowering the element driving voltage. A possible element has been proposed. However, in this element, the life characteristics are insufficient, and there is room for improvement.

  The present invention has been made in view of the above points. The work function of the anode is increased to increase the hole injection efficiency, the device driving voltage can be lowered, and the life characteristics and color during continuous driving can be reduced. It is an object of the present invention to provide an organic electroluminescence device that can improve the stability of the temperature and suppress the increase in resistance as much as possible, and a method for manufacturing the same.

  The organic electroluminescence device according to claim 1 of the present invention is an organic electroluminescence device formed with an organic light emitting layer between an anode and a cathode, wherein the anode is treated with a halogen. Is.

  The invention of claim 2 is characterized in that, in claim 1, the work function of the anode is increased by 0.5 eV or more by the treatment with halogen than before the treatment.

  The invention of claim 3 is characterized in that, in claim 1 or 2, the halogen used for the treatment of the anode is selected from fluorine, chlorine, bromine and iodine.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the anode treatment is a plasma treatment in the presence of a halogen gas.

  According to a fifth aspect of the present invention, there is provided a method for producing an organic electroluminescent device comprising: laminating an organic light emitting layer on an anode; and laminating a cathode on the organic light emitting layer to produce an organic electroluminescent device. After the treatment, the organic light emitting layer and the cathode are laminated.

  The invention of claim 6 is characterized in that, in claim 5, the anode is plasma-treated before being treated with halogen.

  According to the present invention, the work function of the anode is increased to increase the hole injection efficiency, the device driving voltage can be lowered, the life characteristics during continuous driving and the stability of chromaticity can be improved, and the resistance can be improved. It is possible to provide an organic electroluminescence device that suppresses the increase as much as possible and a method for manufacturing the same.

  Hereinafter, the best mode for carrying out the present invention will be described.

  As shown in FIG. 1, the organic electroluminescence device according to the present invention is provided by laminating an anode 6, a hole transport layer 4, an organic light emitting layer 3, an electron transport layer 2, and a cathode 1 in this order on a substrate 7. It is formed by. When a positive voltage is applied to the anode 6 and a negative voltage is applied to the cathode 1, electrons injected into the organic light emitting layer 3 through the electron transport layer 2 and injected into the organic light emitting layer 3 through the hole transport layer 4. The holes are recombined in the organic light emitting layer 3 to emit light.

  In the present invention, the work function of the anode 6 is increased by treating the surface of the anode 6 with halogen and forming the halogen-treated layer 5b on the surface of the anode 6. The hole injection efficiency from the anode 6 can be increased, and the device drive voltage can be lowered.

  Examples of the halogen used for the treatment of the anode 6 include fluorine, chlorine, bromine and iodine. These may be used alone or in combination of two or more. Among these, bromine is most preferred. As a method for treating the anode 6 with halogen, the anode 6 is immersed in a halogen-containing solution for a predetermined time or exposed to the vapor for a predetermined time. The anode 6 is immersed in a liquid halogen for a predetermined time and then dried. A method of exposing the anode 6 to the halogen gas for a predetermined time, a method of plasma-treating the anode 6 in the presence of the halogen gas, and the like can be employed. The treatment time with halogen varies depending on the type of halogen used, the treatment method, and the like, but is usually about 1 second to 1 hour.

  When acid treatment is performed in order to increase the work function of the anode 6, the surface of the anode 6 may be etched to disturb the surface shape of the anode 6, which may adversely affect the characteristics and life of the organic electroluminescence element. However, the treatment with halogen hardly affects the surface shape of the anode 6, and even when a material that is easily etched with an acid, such as IZO, is used for the anode 6, the desired performance can be exhibited. It will be easier. In addition, the organic light emitting layer 3 and the like can be formed on the anode 6 in a state where the anode 6 is treated with halogen and the halogen-treated layer 5b is provided on the surface of the anode 6. It is not necessary to wash with water or an organic solvent after the treatment. Therefore, after the anode 6 is treated with halogen, the organic electroluminescent element is manufactured by performing the processing for forming the organic light-emitting layer 3 and the like on the anode 6 without washing with water or an organic solvent. It is possible to minimize the contamination of residual carbon or the like due to an organic solvent on the surface, and to obtain a high effect of increasing the work function of the anode 6.

  As described above, when the surface of the anode 6 is subjected to halogen treatment to increase the work function of the anode 6, in the present invention, the work function of the surface of the anode 6 becomes 0.5 eV or more larger than the work function before the processing. It is necessary to be. If the work function of the anode 6 is not increased by 0.5 eV or more, the effect of increasing the hole injection efficiency by increasing the work function of the anode 6 becomes insufficient, and the purpose of lowering the element drive voltage is sufficient. Can not be achieved. Since the work function of the anode 6 is preferably as large as possible, there is no particular upper limit for increasing the work function. However, there is a limit to increasing the work function of the anode 6 by halogen treatment, so the work function should be increased. Is substantially about 1.3 eV.

  In the present invention, the surface of the anode 6 is cleaned prior to the halogen treatment of the surface of the anode 6 as described above. This cleaning treatment is preferably performed by dry cleaning, and examples of dry cleaning include ultraviolet cleaning by low-pressure mercury lamp irradiation, ultraviolet cleaning by excimer lamp irradiation, atmospheric pressure plasma cleaning, and vacuum plasma cleaning. The surface of the anode 6 can be cleaned using one method selected from the above or a combination of a plurality of methods. In general, the surface of the anode 6 is often contaminated with contaminants in the air. Therefore, wet cleaning such as alkali cleaning or organic solvent cleaning is performed before the dry cleaning process. preferable.

  The conditions for this cleaning process may be appropriately selected from the wavelength and power of the ultraviolet light source, the power of plasma, etc. In the present invention, the wettability of the processed surface of the anode 6 is the contact angle with water after the completion of this cleaning process. It is necessary that the angle is 10 ° or less, more preferably 7 ° or less. By cleaning the surface of the anode 6 in this way and improving the wettability of the surface of the anode 6, the halogen treatment described above is performed when the surface of the anode 6 is subjected to the halogen treatment described above. The layer 5b in which the halogen exists can be firmly provided on the surface of the anode 6, and the effect of increasing the work function of the anode 6 can be obtained highly. The contact angle of the surface of the anode 6 obtained by the cleaning treatment is preferably as low as possible, and ideally 0 ° is desirable, but practically about 0.1 ° is the lower limit of the contact angle.

  Further, the effect of improving the wettability of the surface of the anode 6 by the cleaning treatment is maintained even after the halogen treatment, and the contact angle of the surface of the anode 6 with water is kept at 10 ° or less. Therefore, this high wettability forms a bonded interface having high and uniform adhesion between the anode 6 and the layer having a hole transport function such as the hole transport layer 4 formed on the surface of the anode 6. Therefore, it is possible to realize a good interface bonding state which is important in the characteristics of the organic electroluminescence element, and to obtain an organic electroluminescence element having high emission efficiency and a long lifetime.

  Next, the organic layer and electrode which comprise the organic electroluminescent element of this invention are demonstrated. However, the organic electroluminescence device of the present invention uses the anode 6 having a work function increased by 0.5 eV or more by performing a treatment with a halogen after washing so that the contact angle with water is 10 ° or less. In regard to the configuration of the organic light emitting layer 3 formed on the anode 6, known ones that have been conventionally used in the production of organic electroluminescence elements can be used as appropriate. Needless to say, the present invention is not limited to the following.

First, the anode 6 is an electrode for injecting holes into the element as described above, and it is preferable to use an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a large work function. It is preferable to use a function of 4 eV or more. Specific examples of the material of the anode 6 include metals such as gold, conductive transparent materials such as CuI, ITO (indium tin oxide), SnO ₂ , ZnO, and IZO (indium zinc oxide). Of these, ITO and IZO are more preferable. The anode 6 can be produced by forming these electrode materials into a thin film on the surface of a substrate 7 formed of a transparent material such as glass or transparent resin by a method such as vacuum deposition or sputtering. Is. In addition, when light emitted from the organic light emitting layer 3 is transmitted through the anode 6 and irradiated to the outside, the light transmittance of the anode 6 is preferably formed on a transparent electrode of 10% or more. Furthermore, the sheet resistance of the anode 6 is preferably several hundred Ω / □ or less, and particularly preferably 100 Ω / □ or less. Here, the film thickness of the anode 6 varies depending on the material in order to control the light transmittance, sheet resistance, and other characteristics of the anode 6 as described above, but is set to a range of 500 nm or less, preferably 10 to 200 nm. It is good.

On the other hand, the cathode 1 which is an electrode for injecting electrons into the organic light emitting layer 3 is preferably made of an electrode material made of a metal, an alloy, an electrically conductive compound and a mixture thereof having a small work function, and the work function is It is preferably 5 eV or less. Examples of the electrode material of the cathode 1 include sodium, sodium-potassium alloy, lithium, magnesium, aluminum, magnesium-silver mixture, magnesium-indium mixture, aluminum-lithium alloy, Al / Al ₂ O ₃ mixture, Al / LiF. A mixture etc. can be mentioned. The cathode 1 can be produced by, for example, forming these electrode materials into a thin film by a method such as vacuum deposition or sputtering. In addition, when the light emitted from the organic light emitting layer 3 is transmitted through the cathode 1 and irradiated outside, the light transmittance of the cathode 1 is preferably set to 10% or more. In this case, the thickness of the cathode 1 varies depending on the material in order to control the characteristics such as the light transmittance of the cathode 1 as described above, but is usually 500 nm or less, preferably 100 to 200 nm. .

  The light emitting material or doping material that can be used for the organic light emitting layer 3 includes anthracene, naphthalene, pyrene, tetracene, coronene, perylene, phthaloperylene, naphthaloperylene, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxadiazole, bisbenzoxazoline, Bisstyryl, cyclopentadiene, quinoline metal complex, tris (8-hydroxyquinolinato) aluminum complex, tris (4-methyl-8-quinolinato) aluminum complex, tris (5-phenyl-8-quinolinato) aluminum complex, aminoquinoline metal Complex, benzoquinoline metal complex, tri- (p-terphenyl-4-yl) amine, 1-aryl-2,5-di (2-thienyl) pyrrole derivative, pyran, quinacridone, rubrene, Styryl benzene derivatives, there is a distyryl arylene derivatives, and various fluorescent pigments, etc., but not limited thereto. It is also preferable to include 90 to 99.5 parts by mass of a light emitting material selected from these compounds and 0.5 to 10 parts by weight of a doping material. The organic light emitting layer 3 has a thickness of 0.5 to 500 nm, more preferably 0.5 to 200 nm.

  The hole transport material constituting the hole transport layer 4 has the ability to transport holes, has a hole injection effect from the anode 6, and has an excellent hole injection effect for the organic light emitting layer 3 or the light emitting material. And a compound that prevents movement of electrons to the hole transport layer 4 and has an excellent ability to form a thin film. Specifically, phthalocyanine derivatives, naphthalocyanine derivatives, porphyrin derivatives, N, N′-bis (3-methylphenyl)-(1,1′-biphenyl) -4,4′-diamine (TPD), 4,4 ′ -Aromatic diamine compounds such as bis [N- (naphthyl) -N-phenyl-amino] biphenyl (α-NPD), oxazole, oxadiazole, triazole, imidazole, imidazolone, stilbene derivative, pyrazoline derivative, tetrahydroimidazole, poly Arylalkane, butadiene, 4,4 ′, 4 ″ -tris (N- (3-methylphenyl) N-phenylamino) triphenylamine (m-MTDATA), and polyvinylcarbazole, polysilane, polyethylene dioxide thiophene (PEDOT) Polymer such as conductive polymer Examples include, but are not limited to, materials.

  The electron transport material constituting the electron transport layer 2 has the ability to transport electrons, has an electron injection effect from the cathode 1, and has an excellent electron injection effect for the organic light emitting layer 3 or the light emitting material. And a compound that prevents migration of holes to the electron transport layer 2 and has an excellent thin film forming ability. Specifically, fluorene, bathophenanthroline, bathocuproine, anthraquinodimethane, diphenoquinone, oxazole, oxadiazole, triazole, imidazole, anthraquinodimethane, etc. and their compounds, metal complex compounds or nitrogen-containing five-membered ring derivatives is there. Specifically, examples of the metal complex compound include tris (8-hydroxyquinolinate) aluminum, tri (2-methyl-8-hydroxyquinolinate) aluminum, tris (8-hydroxyquinolinato) gallium, bis ( 10-hydroxybenzo [h] quinolinato) beryllium, bis (10-hydroxybenzo [h] quinolinato) zinc, bis (2-methyl-8-quinolinato) (o-cresolate) gallium, bis (2-methyl-8-quinolinato) ) (1-naphtholato) aluminum, but is not limited thereto. The nitrogen-containing five-membered ring derivative is preferably an oxazole, thiazole, oxadiazole, thiadiazole or triazole derivative. Specifically, 2,5-bis (1-phenyl) -1,3,4-oxazole, 2,5-bis (1-phenyl) -1,3,4-thiazole, 2,5-bis (1 -Phenyl) -1,3,4-oxadiazole, 2- (4′-tert-butylphenyl) -5- (4 ″ -biphenyl) 1,3,4-oxadiazole, 2,5-bis ( 1-naphthyl) -1,3,4-oxadiazole, 1,4-bis [2- (5-phenylthiadiazolyl)] benzene, 2,5-bis (1-naphthyl) -1,3,4 -Triazole, 3- (4-biphenylyl) -4-phenyl-5- (4-t-butylphenyl) -1,2,4-triazole, and the like, but is not limited thereto. Polymer materials used in polymer organic electroluminescent devices It can be use. For example, polyparaphenylene and its derivatives, fluorene and its derivatives.

  FIG. 2 shows another embodiment of the organic electroluminescence device. The anode 6 is composed of an inorganic oxide layer 6a made of either ITO (indium oxide) or IZO (indium zinc oxide) and a metal thin film 6b. The inorganic oxide layer 6a is arranged on the organic light emitting layer 3 side. The metal thin film 6b preferably has a lower specific resistance than the inorganic oxide layer 6a. Therefore, the metal thin film 6b can be formed of a metal selected from Au, Ag, Cu, Pt, and Al. The thickness of the metal thin film 6b is preferably set to 10 nm or less. When the emitted light is extracted from the anode 6, the metal thin film 6b preferably has a high transmittance. However, in order to ensure the transparency of the metal thin film 6b, it is desirable to set the thickness to 10 nm or less. is there.

  By providing the metal thin film 6b on the anode 6 as described above, the metal thin film 6b can be used as an auxiliary electrode having a small sheet resistance. For example, a bus electrode in the case where a large number of organic electroluminescent elements are arranged in a matrix. The metal thin film 6b can be used. The thickness of the metal thin film 6b is preferably as thin as possible in order to obtain a high extraction rate when light emission is extracted through the anode 6. However, since the thickness of the metal thin film 6b is required to be higher than a level at which conduction can be obtained as an auxiliary electrode such as a bus electrode. The thickness is desirably 0.1 nm or more.

  Next, the present invention will be specifically described with reference to examples.

Example 1
An ITO glass substrate (manufactured by Sanyo Vacuum Co., Ltd.) on which an anode 6 having a sheet resistance of 7Ω / □ was formed by sputtering ITO (indium-tin oxide) on a glass substrate 7 having a thickness of 0.7 mm was used. First, this was ultrasonically washed with acetone, pure water and isopropyl alcohol for 15 minutes, respectively, and then dried.

  Next, vacuum plasma cleaning was performed for 1 minute on the surface of the ITO anode 6 with oxygen plasma generated under conditions of 2 Pa and RF 10 W in a gas atmosphere having an argon / oxygen volume ratio of 3/1.

  Subsequently, the surface of the anode 6 was treated with bromine by exposing the ITO glass substrate to steam of bromine water (manufactured by Kanto Chemical Co., Ltd., concentration 1.0 wt%) for 10 minutes at room temperature.

Next, the ITO glass substrate treated with bromine was set in a vacuum deposition apparatus without washing, and 4,4′− under vacuum conditions of 133.322 × 10 ⁻⁶ Pa (1 × 10 ⁻⁶ Torr). Bis [N- (naphthyl) -N-phenyl-amino] biphenyl (α-NPD) (manufactured by Dojindo Laboratories) was deposited at a deposition rate of 1 to 2 liters / s, and a hole transport layer having a thickness of 400 liters 4 was formed.

  Next, a tris (8-hydroxyquinolinate) aluminum complex (“Alq3” manufactured by Dojindo Laboratories Co., Ltd.) was deposited at a deposition rate of 1 to 2 liters / s, and the organic light-emitting layer 3 and electron transport having a thickness of 400 liters. Layer 2 was formed.

  Thereafter, LiF was first deposited at a thickness of 5 mm at a deposition rate of 0.5 to 1.0 mm, and then Al was deposited at a thickness of 1500 mm at a deposition rate of 10 mm / s to form the cathode 1.

  Next, the ITO glass substrate on which each layer was formed was put in a glove box in a dry nitrogen atmosphere having a dew point of −76 ° C. or less and transported without being exposed to the air. On the other hand, a barium oxide powder as a water absorbing agent is put in a bag having air permeability, and this is adhered to a glass sealing plate with an adhesive, and an outer peripheral portion of the sealing plate is made of an ultraviolet curable resin in advance. A sealing agent is applied, and a sealing plate is bonded to the ITO glass substrate 7 on which each of the layers 1 to 6 is formed in the glove box with the sealing agent, and the sealing agent is cured by UV irradiation, as shown in FIG. A layered organic electroluminescence device was obtained.

(Example 2)
Instead of treating with bromine water vapor, the surface of the anode 6 is treated with chlorine by exposing the ITO glass substrate to chlorine water (Kanto Chemical Co., Ltd., concentration: 0.3 wt%) for 10 minutes at room temperature. An organic electroluminescent element was obtained in the same manner as in Example 1 except that the above was done.

(Example 3)
Instead of performing vacuum plasma cleaning with oxygen plasma, an excimer lamp (“UER20-172A” manufactured by Ushio Electric Co., Ltd.) was used, and UV irradiation ozone cleaning was performed for 1 minute under the condition of 10 mW / cm ^2. Obtained an organic electroluminescence device in the same manner as in Example 1.

Example 4
Instead of performing vacuum plasma cleaning with oxygen plasma, UV irradiation ozone cleaning was performed for 10 minutes under the condition of 13 W using a low pressure mercury lamp (“NL-UV253” manufactured by Nippon Laser Electronics Co., Ltd.). In the same manner as in Example 1, an organic electroluminescence element was obtained.

(Example 5)
On a glass substrate 7 having a thickness of 0.7 mm, IZO (indium-zinc oxide) was sputtered to produce an anode 6 having a thickness of 2000 mm and a sheet resistance of 15Ω / □. An organic electroluminescence device was obtained in the same manner as in Example 1 except that this IZO glass substrate was used.

(Example 6)
A metal thin film 6b having a thickness of 5 mm is formed on a glass substrate 7 having a thickness of 0.7 mm by sputtering gold, and then an IZO (indium-zinc oxide) film is further sputtered thereon to form an inorganic oxide layer having a thickness of 1000 mm. By forming 6a, an anode 6 having a sheet resistance of 15Ω / □ made of a laminate of the inorganic oxide layer 6a and the metal thin film 6b was produced.

  An organic electroluminescence device having a layer structure shown in FIG. 2 was obtained in the same manner as in Example 1 except that this IZO glass substrate laminated with gold was used.

(Example 7)
In the same manner as in Example 1, the surface of the anode 6 of the ITO glass substrate was subjected to plasma cleaning treatment and bromine treatment, and then the ITO glass substrate was set in a vacuum deposition apparatus, and α-NPD was added to 1 to 2 mm under the same conditions as in Example 1. The hole transport layer 4 having a thickness of 300 mm was formed by vapor deposition at a vapor deposition rate of / s.

  Then, on the hole transport layer 4, a yellow light-emitting layer is laminated with α-NPD doped with 1% by mass of rubrene (manufactured by Acros) at a thickness of 100 mm, and then a blue light-emitting layer is used as a distyryl biphenyl derivative A DPA derivative (BCzVBi) doped with 12% by mass of a carbazolyl group at (DPVBi) was laminated at a thickness of 500 mm to form a two-layer organic light emitting layer 3.

  After that, Vasophenanthroline (manufactured by Dojindo Laboratories Co., Ltd.) and Cs are co-evaporated at a molar ratio of 1: 1 to a thickness of 200 mm to form the electron transport layer 2, and subsequently, Al is evaporated at a rate of 10 mm / s. The cathode 1 was formed by vapor deposition with a thickness of 1500 mm at a speed. Thereafter, a white light-emitting organic electroluminescence device was obtained in the same manner as in Example 1.

(Comparative Example 1)
In Example 1, an organic electroluminescence element was obtained in the same manner as in Example 1 except that the ITO glass substrate was not brominated.

(Comparative Example 2)
In Example 1, an organic electroluminescence element was obtained in the same manner as in Example 1 except that the ITO glass substrate was not cleaned with plasma.

(Comparative Example 3)
In Example 7, the organic electroluminescent element was obtained like Example 7 except not having brominated the ITO glass substrate.

(Comparative Example 4)
In Example 7, the organic electroluminescent element was obtained like Example 7 except not having wash | cleaned the ITO glass substrate by the plasma.

The organic electroluminescence elements prepared in Examples 1 to 7 and Comparative Examples 1 to 4 were connected to a power source (KEYTHLEY 236 model), and the luminance of the elements was measured with a luminance meter (“LS-110, manufactured by Minolta Co., Ltd.). )). At this time, the voltage at which the luminance became 1 cd / m ² was measured as the light emission start voltage, the luminance when 6 V was applied was measured, and the 6 V current density was measured.

  In addition, the contact angle between the work function and water was measured for the anode before the halogen treatment or the acid treatment and the anode immediately before the device was processed into an organic electroluminescence element. The work function is measured by an ultraviolet photoelectron analyzer (“AC-1” manufactured by Riken Keiki Co., Ltd.), and the contact angle with water is measured by an automatic contact angle meter (“CA-W150” manufactured by Kyowa Interface Science Co., Ltd.). ).

Further, the device was continuously driven at a constant current of 10 mA / cm ² to conduct a life test, a half life until the luminance was reduced by half was measured, and a change in drive voltage after the half life was measured. These results are shown in Table 1.

  As can be seen from Table 1, in each of the examples, the wettability of the anode before the device formation of the organic electroluminescence element is high, and the work function of the anode is increased by 0.5 eV or more by treatment with halogen or acid. In addition, it is confirmed that the emission starting voltage is lower and the luminance is higher than those of the comparative examples, the half-life is longer, and the resistance increase is small.

For the white light-emitting organic electroluminescence elements of Example 7 and Comparative Example 3, the chromaticity coordinates at 100 cd / m ² before and after the life test were measured with “Multi-Channel Analyzer PMA-10” manufactured by Hamamatsu Photonics. The results are shown in Table 2.

  As seen in Table 2, it is confirmed that the example 7 has higher chromaticity stability than the comparative example 3.

It is sectional drawing which shows an example of embodiment of this invention. It is sectional drawing which shows another example of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cathode 2 Electron transport layer 3 Organic light emitting layer 4 Hole transport layer 5b Halogen-treated layer 6 Anode 6a Inorganic oxide layer 6b Metal thin film 7 Substrate

Claims (6)

  An organic electroluminescence element formed by providing an organic light emitting layer between an anode and a cathode, wherein the anode is treated with a halogen.   2. The organic electroluminescence device according to claim 1, wherein the anode has a work function of 0.5 eV or more larger than that before the treatment by treatment with halogen.   3. The organic electroluminescence device according to claim 1, wherein the halogen used for the treatment of the anode is selected from fluorine, chlorine, bromine and iodine.   4. The organic electroluminescence device according to claim 1, wherein the treatment of the anode is a plasma treatment in the presence of a halogen gas.   An organic light-emitting layer is laminated on the anode, and a cathode is laminated on the organic light-emitting layer to produce an organic electroluminescence device. The organic light-emitting layer and the cathode are laminated after the surface of the anode is treated with halogen. A method for manufacturing an organic electroluminescence element.   6. The method of manufacturing an organic electroluminescent element according to claim 5, wherein the anode is subjected to plasma treatment before treatment with halogen.

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