JP2014082169A - Organic el element, light-emitting device, image forming apparatus, display device, imaging device, and method of manufacturing the organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a long-life organic EL element capable of stabilizing a carrier injection property on an electrode surface.SOLUTION: An organic EL element comprises: a first electrode 2 containing titanium; a second electrode 4; and an organic compound layer 3 formed between the first electrode 2 and the second electrode 4. On a surface of the first electrode 2, a titanium oxide is formed. An area ratio of a region where an electric resistance value in a direction vertical to the first electrode 2 is 2.0×10Ω or less, in an arbitrary region in the first electrode 2, is 1.0% or less.

Description

  The present invention relates to an organic EL element, a light-emitting device using the same, an image forming apparatus, a display device or an imaging device, and a method for manufacturing an organic EL element.

  In recent years, it has been studied to use an organic EL element as a display element of a display device. The organic EL element includes a pair of electrodes and an organic compound layer including at least a light emitting layer. The organic EL element is formed in the order of one electrode, the organic compound layer, and the other electrode.

  If the organic compound layer and the other electrode are formed with dirt or impurities attached to the surface of one electrode of the organic EL element, a non-light-emitting portion is formed in the organic EL element or light emission is stabilized. Problems such as missing.

  In Patent Document 1, in order to remove dirt and impurities on the anode surface in a short time and oxidize the anode, the anode is patterned by dry etching, and the anode is subjected to UV ozone treatment or oxygen plasma treatment. It is described that it is carried out consistently under reduced pressure.

JP-A-10-302965

  In general, since the surface of the electrode is grain-like, the UV ozone treatment and oxygen plasma treatment described in Patent Document 1 do not uniformly form an oxide film having the same composition on the surface of the electrode. Have difficulty. For this reason, carrier injection properties differ on the electrode surface, a portion where current concentrates on the electrode surface, and the organic compound layer in the portion tends to deteriorate. And a long-life organic EL element cannot be obtained.

  An object of the present invention is to provide a long-life organic EL device.

The present invention is an organic EL device comprising a first electrode containing titanium, a second electrode, and an organic compound layer formed between the first electrode and the second electrode, A region in which titanium oxide is formed on the surface of one electrode, and an electric resistance value in a direction perpendicular to the first electrode in an arbitrary region in the first electrode is 2.0 × 10 ⁹ Ω or less The area ratio is 1.0% or less.

  ADVANTAGE OF THE INVENTION According to this invention, a long life organic EL element can be provided.

1 is a schematic diagram illustrating an example of a display device according to Embodiment 1 of the present invention. Schematic diagram illustrating an example of a method for manufacturing a display device according to the first embodiment of the present invention. The schematic diagram which shows an example of the measuring method of the electrical resistance value by Conductive-AFM method The figure which shows the electric current image of Ti electrode obtained by Conductive-AFM method FIG. 3 is a schematic cross-sectional view illustrating an example of an imaging apparatus including the display device according to the first embodiment. FIG. 6 is a schematic cross-sectional view illustrating an example of an image forming apparatus including the light emitting device according to the second embodiment. Schematic diagram illustrating an example of a light-emitting device according to Embodiment 2 The electrical resistance value in the direction perpendicular to the first electrode containing Ti in the area per 1.0 μm × 1.0 μm of the first electrode containing Ti in Examples and Comparative Examples is 2.0 × 10 ⁹ Ω or less. It shows the area ratio of a portion, the relationship between the relative luminance L _{150 / L} 0 _(drive start (relative luminance of 150 hours after the drive to the luminance of the drive 0 hour) time point) The figure which shows the measurement result by the X-ray photoelectron spectrometer of the 1st electrode containing Ti in an Example and a comparative example.

  Hereinafter, the present invention will be described with reference to the drawings by way of embodiments. In addition, the well-known or well-known technique of the said technical field is applied regarding the part which is not illustrated or described especially in this specification. The embodiment described below is one embodiment of the invention and is not limited thereto.

(Embodiment 1)
This embodiment relates to a display device including the organic EL element of the present invention. FIG. 1A is a schematic perspective view showing a display device according to the present embodiment. The display device according to the present embodiment includes a plurality of pixels 100 including organic EL elements. The plurality of pixels 100 are arranged in a matrix and form a display area 101. Note that a pixel means a region corresponding to a light emitting region of one light emitting element. In the display device of this embodiment, the light emitting element is an organic EL element, and one color organic EL element is disposed in each pixel 100. Examples of the emission color of the organic EL element include red, green, blue, yellow, cyan, magenta, and white. In the display device of this embodiment, a plurality of pixel units each including a plurality of pixels having different emission colors (for example, a pixel that emits red, a pixel that emits green, and a pixel that emits blue) are arranged. The pixel unit is a minimum unit that enables light emission of a desired color by mixing colors of pixels.

  FIG. 1B is a partial schematic cross-sectional view taken along the line A-A ′ of FIG. The pixel 100 includes an organic compound layer 1 on a substrate 1, an organic compound layer 3 including a light emitting layer, a second electrode (cathode) 4, and a color filter that transmits a specific color. It has an EL element. In FIG. 1B, the light emitting layer of the organic compound layer 3 emits white, and each organic EL element (pixel 100) has a color filter 6R that transmits red, a color filter 6G that transmits green, and a blue color. An example having any of the color filters 6B to transmit is shown. Therefore, the organic EL element (pixel) having the color filter 6R emits red light, the organic EL element (pixel) having the color filter 6G emits green light, and the organic EL element (pixel) having the color filter 6B. Emits blue light.

  Instead of using a color filter, instead of the white light emitting layer that is commonly formed in the organic EL element, a configuration in which the light emitting layer that emits light of each color is patterned for each organic EL element may be used.

  In this embodiment, the first electrode 2 is a light-reflective electrode, the second electrode 4 is a light-transmissive electrode, and light emitted from the light-emitting layer is emitted from the second electrode 4, that is, from the side opposite to the substrate 1. A top emission type display device to be ejected will be described. However, the present invention can also be applied to a bottom emission type display device in which light is emitted from the substrate 1 side. Further, the present invention can also be adopted in a configuration in which the first electrode 2 is a cathode and the second electrode 4 is an anode.

  The organic EL element is covered with a sealing film 5 in order to prevent moisture and gas from entering the organic EL element from the outside. Further, the sealing film 5 is formed between the color filter 6R (6G, 6B) and the organic EL element. Moreover, the sealing film 5 is formed in common with each organic EL element.

  The first electrode 2 is formed separately from the first electrode 2 of the adjacent pixel, and the organic compound layer 3 and the second electrode 4 are formed in common for all the pixels. However, the 1st electrode 2 may be formed in common with all the pixels, and the 2nd electrode 4 may be isolate | separated for every pixel.

The first electrode 2 is an electrode containing Ti. Then, a titanium oxide film is formed on the surface of the first electrode 2 by a surface oxidation treatment described later. Furthermore, the area ratio of the region where the electrical resistance value in the direction perpendicular to the first electrode 2 in any region in the first electrode 2 is 2.0 × 10 ⁹ Ω or less is 1.0% or less. . For this reason, the location where the current concentrates on the surface of the first electrode 2 is suppressed, and even when the organic EL element is driven for a long time, the local deterioration of the organic compound layer is suppressed and the decrease in the emission luminance is suppressed. Can lead to longer service life. In addition, the electrical resistance value of the 1st electrode 2 is demonstrated using an Example and a comparative example.

The arbitrary region is a region for measuring a current value or an electric resistance value, and the target region may be the entire first electrode 2 or a part of the first electrode 2. In addition, the target area may be one place or a plurality of places in the first electrode. Further, the total area of the target regions may be any area, but is preferably 0.5 μm ² or more from the viewpoint of the reliability of the measurement result. When the area of the first electrode 2 of one organic EL element is less than 0.5 μm ² , the first electrode 2 of another organic EL element is added to the target region, and the total area is 0.5 μm ² or more. The target area may be selected so that

  Next, each member will be specifically described.

  As the substrate 1, an insulating substrate such as quartz, glass, or plastic, a metal substrate, a silicon substrate, or the like can be used. In addition, a control circuit (not shown) for controlling light emission of an organic EL element including a switching element such as a transistor or an MIM element is formed on the insulating substrate or the silicon substrate. In that case, the substrate 1 may have a flattening film for flattening the unevenness of the switching elements.

  The first electrode 2 may be made of any material as long as it has a metal whose electrical conductivity is changed by an oxidation process described later. Specific examples of the material include transition metals, and more specifically, titanium (Ti), tungsten (W), molybdenum (Mo), and the like can be used. In particular, a material containing Ti is widely used for a barrier metal or the like in a semiconductor process, and can be suitably used as the first electrode 2 from the viewpoint of workability. When the first electrode 2 contains Ti, the surface of the first electrode 2 is oxidized, so that the first electrode 2 has a laminated structure of a titanium oxide layer and a titanium layer from the side close to the organic compound layer 3.

  Further, the first electrode 2 has a structure in which a metal (specifically, Ti, W, Mo) whose electric conductivity changes due to an oxidation process is provided on the surface of the first electrode 2. As long as it is made, the laminated structure by a different metal may be sufficient. For example, the configuration of the first electrode 2 may be a stacked configuration of a titanium oxide layer and an aluminum layer from the side close to the organic compound layer 3. In this case, a titanium layer or an aluminum oxide layer may be provided between the titanium oxide layer and the aluminum layer. When the first electrode 2 has a laminated structure of different metal materials, the coverage is improved and the metal layer on the organic compound layer 3 side is formed so that the metal layer closer to the substrate 1 side is not exposed on the surface. It is preferable.

  The organic compound layer 3 only needs to include at least a light emitting layer. Furthermore, the organic compound layer 3 may have a plurality of functional layers such as a hole transport layer and an electron transport layer. The light emitting layer may be composed of only a light emitting material, or may be a mixed layer of a light emitting dopant material and a host material. The light emitting layer may contain an assist dopant material in addition to the light emitting dopant material and the host material. In the present invention, the host material means a material having the highest weight concentration among the components in the light emitting layer. Further, the light emitting material and the light emitting dopant material may be either a fluorescent material or a phosphorescent material.

  As a material used for the hole transport layer, a phthalocyanine derivative, a triphenyldiamine derivative, an oxodiazole derivative, a polyphylyl derivative, a stilbene derivative, or the like can be used. In addition, oxides such as molybdenum oxide and tungsten oxide, organic substances such as 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), and mixtures thereof can be used. . The hole transport layer is composed of a single layer or a plurality of layers of an organic compound having a hole injection property and a hole transport property. Further, if necessary, as a hole transport layer, in order to suppress movement of electrons from the light emitting layer to the first electrode 2 side, a function as an electron blocking layer can be provided.

  Examples of the material used for the electron transport layer include aluminum quinolinol derivatives, oxadiazole derivatives, triazole derivatives, phenylquinoxaline derivatives, silole derivatives, phenanthroline derivatives, and the like. In addition, alkali metals, alkaline earth metals, rare earth metals, and compounds thereof can be used. Moreover, the mixture of the illustrated material can also be used suitably. It consists of a single layer or a plurality of layers of an organic compound having electron injection properties and electron transport properties. In addition, the electron transport layer can also have a function as a hole blocking layer.

  In addition, the hole transport layer and the electron transport layer can also have a function as an exciton blocking layer for suppressing diffusion of excitons generated in the light emitting layer.

  The second electrode 4 is made of a transparent oxide conductive layer such as tin oxide, indium oxide, indium tin oxide, or indium zinc oxide, or a single metal such as Al, Ag, Cr, Ti, Mo, W, Au, Mg, or Cs. A metal layer made of such an alloy can be used. Furthermore, the 2nd electrode 4 may be comprised by the laminated film of a transparent oxide conductive layer and a metal layer, or the laminated film of a some metal layer.

  The sealing film 5 has a function of preventing oxygen and moisture from entering the organic EL element, and an inorganic material such as silicon nitride, silicon oxide, or alumina oxide can be used. Moreover, the sealing film 5 may be comprised by the laminated film which consists of two or more layers of inorganic materials, and may be comprised by the laminated film of the inorganic material and the resin material.

  Any structure may be used as long as the organic EL element is sealed, and a sealing cap may be used instead of the sealing film 5. As the sealing cap, a cap-shaped member such as glass or plastic can be used. In addition, the sealing cap may be configured by a plate-like member such as a glass plate and a sealant disposed around the display area 101 in order to bond the member and the substrate 1. The space between the sealing cap and the second electrode 4 may be filled with a gas such as nitrogen or argon, or may be filled with a resin material such as an acrylic resin. A desiccant may be disposed in the space.

  Known materials can be used for the color filters 6R, 6G, and 6B. Further, as shown in FIG. 1B, the color filters 6R, 6G, and 6B may be formed by patterning on the sealing film 5, or the color filters 6R, 6G, and 6B may be formed on a color filter substrate (not shown). May be formed and bonded onto the sealing film 5. A black matrix may be formed between the color filters 6R, 6G, and 6B patterned for each pixel.

Next, the manufacturing method of the organic EL element used for the display apparatus of this embodiment is demonstrated using FIG. This method of manufacturing an organic EL element includes a step of forming a first electrode 2 containing titanium on a substrate 1, a step of subjecting the first electrode 2 to surface oxidation treatment, and an organic compound on the first electrode 2 subjected to surface oxidation treatment. A step of forming the layer 3 and a step of forming the second electrode 4 on the organic compound layer 3. Then, in the step of surface oxidation treatment, the area ratio of the region in which the electric resistance value in the direction perpendicular to the surface of the first electrode 2 in an arbitrary region in the first electrode 2 is 2.0 × 10 ⁹ Ω or less is The surface of the first electrode 2 is oxidized so as to be 1.0% or less.

  First, as shown in FIG. 2A, the first electrode 2 containing titanium is formed on the substrate 1. The first electrode 2 is formed so as to be connected to a switching element (not shown) formed on the substrate 1 via a contact portion (not shown). The first electrode 2 is formed by sputtering or vacuum vapor deposition, and then patterned for each pixel (organic EL element) by photolithography.

  Next, as shown in FIG. 2B, the surfaces of the substrate 1 and the first electrode 2 are cleaned. As a cleaning method, two-fluid cleaning, shower rinsing, or the like can be used. Further, they can be used in combination. Further, an air knife can be further used as necessary. In this cleaning process, dust (glass) and the like on the substrate 1 and the first electrode 2 are removed.

After the cleaning, as shown in FIG. 2C, the substrate 1 is dehydrated by heating in vacuum. The pressure of the atmosphere during heating is preferably 1.0 × 10 ⁻³ Pa or less. Furthermore, the heating temperature is preferably 120 ° C. or higher, more preferably 150 ° C. or higher, so that the substrate surface temperature promotes desorption of moisture. The heating means may be any means as long as it can uniformly heat the substrate 1, such as a halogen heater, a sheath heater, or a combination of a heating source and a plate material.

  Next, as shown in FIG. 2D, the first electrode 2 is subjected to surface oxidation treatment. This surface oxidation treatment is performed for the purpose of reducing the carrier injection barrier with respect to the organic compound layer 3 formed on the first electrode 2 and improving the carrier injection property. As the surface oxidation treatment method, UV ozone treatment, oxygen plasma treatment, thermal oxidation treatment, or the like can be used. In particular, the UV ozone treatment is preferable because it has a high ability to remove organic substances (resist residues used in photolithography) on the surface of the first electrode 2 in addition to the ability to oxidize the surface.

Since the surface of the first electrode 2 is grained or has a different crystal structure in the in-plane direction, oxide films with different oxidation numbers are formed on the surface due to the influence of the mean free path of the processing method. Is done. For example, when a Ti film is described as an example, it is known that when the Ti film is oxidized, a low-order oxide of TiOx (1 <x <2) is formed in addition to TiO ₂ . TiO ₂ is a typical insulating film, has a low electric conductivity, and current does not flow easily. On the other hand, a low-order oxide such as TiOx has a higher electrical conductivity than TiO ₂ , and a current flows easily.

When TiO ₂ and TiO x are mixed on the surface of the first electrode 2, a difference occurs in electrical resistance in the vertical direction on the surface of the first electrode 2. If the surface of the first electrode 2 has a small electric resistance (region having a high electric conductivity), the current concentrates on the region, so that when the organic EL element is driven for a long time, It becomes a factor which degrades the organic compound layer 3 to be formed.

  The electrical resistance in the direction perpendicular to the electrode surface of the first electrode 2 containing Ti subjected to the surface oxidation treatment can be examined using a Conductive-AFM method. As shown in FIG. 3, the Conductive-AFM method applies a voltage between the first electrode 2 and the cantilever 12 while measuring the surface shape of the first electrode 2 with the cantilever 12, and is perpendicular to the first electrode 2. The current value in the direction can be measured by the measuring instrument 10 via the amplifier 11. The measurement sample (in this case, the substrate 1 on which the first electrode 2 is formed) is supported by the conductive support 13 and is electrically connected to the first electrode 2 via the conductive tape 14. ing. The electric resistance value can be calculated from the measured current value, and the distribution of the electric resistance value on the surface of the first electrode 2 can be calculated.

  When the in-plane current value of the first electrode 2 containing Ti is measured by the conductive-AFM method, a current image as shown in FIG. 4 is obtained. Note that FIG. 4 shows a Ti-containing first electrode obtained under the conditions of a measurement region of 1.0 μm × 1.0 μm (measurement pitch 256 × 256) in the first electrode 2 containing Ti and a measurement bias of −2V. 2 is a current image of the surface of one electrode 2. In FIG. 4, a portion where a current exceeding a certain threshold flows is displayed in black. Others are displayed in gray. Thus, the current value is distributed in the in-plane direction, and it is considered that a TiOx film having high electrical conductivity exists in the black portion in the measurement region in FIG. In this black spot, the current concentrates, so that the organic compound layer 3 is deteriorated.

For this reason, in this invention, in order to suppress the dispersion | variation in the electric current value in such an in-plane direction, ozone treatment is performed on condition of the following. That is, in the UV ozone treatment, the surface of the first electrode 2 is irradiated with UV light with an integrated illuminance of 6700 mJ / cm ² or more. Under this condition, the area ratio of the region in which the electric resistance value in the direction perpendicular to the first electrode 2 in an arbitrary region in the first electrode 2 is 2.0 × 10 ⁹ Ω or less is 1. It can be 0% or less. That is, the current concentration region is reduced by reducing the abundance ratio of the low-order oxide of TiOx. As a result, deterioration of the organic compound layer can be suppressed, and a long-life organic EL element can be obtained.

  In addition, since the same subject arises also in W and Mo in which the electronic state is similar to Ti, conditions such as the integrated illuminance as described above are necessary in the surface oxidation treatment.

In addition, the measurement of the electric resistance value by the Conductive-AFM method may be performed by extracting the substrate 1 after the surface oxidation treatment during the manufacturing process and inspecting the organic compound layer 3 or the second electrode 4 after the display device is manufactured. You may peel and test | inspect. Moreover, although the measurement area | region in the 1st electrode 2 was 1.0 micrometer x 1.0 micrometer, you may measure in area | regions of what area. However, at least the area of the measurement region is preferably 0.5 μm ² or more from the viewpoint of the reliability of the measurement result.

  As the UV light source used for the UV ozone treatment, a low-pressure mercury lamp is preferable, and a synthetic quartz lamp tube is particularly preferable. When a low-pressure mercury lamp is used as a UV light source, the light source has emission spectra near 185 nm and 254 nm, generates ozone with light near 185 nm, decomposes ozone with light near 254 nm, and generates active oxygen. It is known. For this reason, the surface of the 1st electrode 2 can be oxidized efficiently. Further, the UV lamp tube may be provided with a reflecting plate for imparting directivity to the UV light.

  The gas used as the ozone generation source for the UV ozone treatment may be any gas containing oxygen, and oxygen gas, dry air, or the like can be used. In particular, the lower the dew point of dry air or oxygen, the better and is preferably −60 ° C. or lower.

  In order to promote dehydration from the substrate 1, the substrate 1 may be heated during the UV ozone treatment. In this case, it is desirable to heat from the side opposite to the surface on which the first electrode 2 of the substrate 1 is formed. Note that this heat treatment may double as the dehydration treatment shown in FIG. Moreover, the atmosphere of UV ozone treatment may be under reduced pressure or atmospheric pressure.

  Next, as shown in FIG. 2E, an organic compound layer 3 is formed on the first electrode 2 subjected to the surface oxidation treatment. The light emitting layer and each functional layer of the organic compound layer 3 are formed using a vacuum deposition method, a coating method, or the like.

  Next, as shown in FIG. 2 (f), the second electrode 4 is formed on the organic compound layer 3. The second electrode 4 is formed using a sputtering method or a vacuum evaporation method. Thereafter, the sealing film 5 and the color filters 6R, 6G, and 6B are formed using a known method (not shown).

  The display device of this embodiment is used for a display unit of a television receiver or a personal computer. In addition, it may be used for a display unit or an electronic viewfinder of an imaging apparatus such as a digital camera or a digital video camera.

  As shown in FIG. 5, the imaging apparatus includes an imaging element 93 such as a low-pass filter 91, an infrared cut filter 92, and a CMOS sensor in a housing 90. The display device 94 according to the present embodiment is arranged in the housing 90 of the imaging device, and can display an image captured by the image sensor 93 and imaged by the image processing circuit. In FIG. 5, the imaging apparatus has a lens 95 provided outside the housing 90, and the lens 95 and the housing 90 are detachable. However, the display device of this embodiment can also be applied to an imaging device in which the housing 90 and the lens are provided integrally.

  Furthermore, the display device of the present embodiment may be used for a display unit of a mobile phone, a display unit of a portable game machine, or the like, and further, a display unit of a portable music player, a display of a personal digital assistant (PDA). May be used for a display part of a car navigation system.

(Embodiment 2)
The organic EL element of the present invention can be applied to devices other than the display device as in the first embodiment. In the present embodiment, an example in which the organic EL element of the present invention is applied to a light emitting device is shown. In particular, the light emitting device of this embodiment can be used as an exposure light source of an image forming apparatus as shown in FIG. The image forming apparatus includes a light emitting device, a photoconductor on which a latent image is formed by the light emitting device, and a charging unit that charges the photoconductor.

  The light emitting device of this embodiment has a plurality of light emitting regions 400 each including an organic EL element. In FIG. 7A, the plurality of light emitting regions 400 are arranged in a staggered pattern, and in FIG. 7B, the plurality of light emitting regions 400 are arranged in one row. Examples of the emission color of the organic EL element include red, green, blue, yellow, cyan, magenta, white, and the like, and the configuration of the organic EL element may be appropriately adopted according to the photosensitive characteristics of the photoreceptor.

  FIG. 7C is a partial schematic cross-sectional view taken along the line B-B ′ of FIG. The light emitting region 400 is formed of an organic EL element including a first electrode (anode) 2, an organic compound layer 3 having a light emitting layer, and a second electrode (cathode) 4 on the substrate 1. Unlike Embodiment 1, the organic EL element used in this embodiment does not have a color filter. In addition, a control circuit (not shown) for controlling light emission of the organic EL element is formed on the substrate 1.

  The first electrode 2 is formed separately from the first electrode 2 of the adjacent pixel, and the organic compound layer 3 and the second electrode 4 are formed in common for all the pixels. Each organic EL element is sealed with a sealing film 5 so that external oxygen and moisture do not enter.

Similarly to the organic EL element used in the first embodiment, the first electrode 2 of the organic EL element used in the light emitting device according to the present embodiment is configured by an electrode containing titanium. Then, a titanium oxide film is formed on the surface of the first electrode 2 by the oxidation treatment described above. Furthermore, the area ratio of the region where the electric resistance value in the direction perpendicular to the surface of the first electrode 2 in any region in the first electrode 2 is 2.0 × 10 ⁹ Ω or less is 1.0% or less. ing. For this reason, a long-life organic EL element can be obtained.

  Next, an image forming apparatus including the light emitting device of this embodiment as an exposure light source will be described. The image forming apparatus shown in FIG. 6 includes a color mode in which four color toners of yellow (Y), magenta (M), cyan (C), and black (K) are superimposed to form a color image, and black (K). A monochrome mode in which a monochrome image is formed using only toner can be selectively executed. FIG. 6 is a cross-sectional view of the main part in the sub-scanning direction. In the image forming apparatus, when code data Dc is input from an external device such as a personal computer to a print controller (not shown), the code data Dc is converted into image data (dot data) Di. The image data Di is input to exposure units 70Y, 70M, 70C, and 70K built in the image forming apparatus. The exposure units 70Y, 70M, 70C, and 70K are controlled based on the image data Di.

  The exposure unit 70Y includes the light emitting device of the present embodiment and a lens that collects the light emitted from the light emitting device and irradiates the surface of the photosensitive drum 85Y with the exposure light. Further, the exposure unit 70Y may have a light absorbing member so that light is not irradiated to other than a predetermined position on the surface of the photosensitive drum 85Y.

  In addition to the exposure units 70Y, 70M, 70C, and 70K, a print controller, a transfer belt 81, a paper feed unit 82, a fixing roller 83, and a pressure roller 84 are disposed in the housing 80 of the image forming apparatus. Further, photosensitive drums 85Y, 85M, 85C, 85K, charging rollers 86Y, 86M, 86C, 86K, developing devices 87Y, 87M, 87C, 87K, and transfer rollers 88Y, 88M, 88C, 88K are arranged in the housing 80. ing. The paper feed unit 82 is configured to be detachable.

  The image forming operation is as follows. In the following, a case where a yellow (Y) image is latent is described. However, a sheet is conveyed by the transfer belt 81, and magenta (M), cyan (C), and black (K) images are yellow ( The image is sequentially formed in the same manner as the image formation of Y).

  First, based on a signal from the print controller, the photosensitive drum 85Y, which is an electrostatic latent image carrier, is rotated clockwise by a motor (not shown). With this rotation, each photosensitive surface of the photosensitive drum 85Y rotates with respect to each exposure light. Below the photosensitive drum 85Y, a charging roller 86Y for charging the surface of the photosensitive drum 85Y with a desired pattern is provided in contact with the surface. The exposure unit 70Y irradiates exposure light onto the surface of the photosensitive drum 85Y that is uniformly charged by the charging roller 86Y.

  The exposure light emitted from the exposure unit 70Y is adjusted in irradiation position, irradiation timing, irradiation time, irradiation intensity, and the like based on the image data Di, and an electrostatic latent image is formed on the surface of the photosensitive drum 85Y by the exposure light. . The electrostatic latent image is developed as a toner image by a developing unit 87Y disposed so as to be in contact with the photosensitive drum 85Y downstream of the exposure light irradiation position in the rotation direction of the photosensitive drum 85Y.

  The toner image developed by the developing unit 87Y is transferred onto a sheet as a transfer material by a transfer roller 88Y disposed below the photosensitive drum 85Y so as to face the photosensitive drum 85Y. The paper is stored in a paper cassette in the paper supply unit 82, but paper can also be fed by a manual tray. A paper feed roller is disposed at the end of the paper cassette, and feeds the paper in the paper cassette into the transport path.

  The sheet having the toner image transferred thereon as described above is conveyed to the fixing device by the transfer belt 81. The fixing device includes a fixing roller 83 having a fixing heater (not shown) therein and a pressure roller 84 disposed so as to be in pressure contact with the fixing roller 83. The fixing device fixes the toner image on the paper by heating the conveyed paper while being pressed by the fixing roller 83 and the pressure roller 84.

Example 1
A display device having the configuration shown in FIG. 1 was produced. This example corresponds to the first embodiment.

  First, a control circuit (not shown) including a switching element or the like was formed on a silicon substrate. And the interlayer insulation film which consists of silicon oxide was formed on it, and the board | substrate 1 was produced. Next, as shown in FIG. 2A, a Ti film having a thickness of 40 nm was formed on the substrate 1 by sputtering. Subsequently, the Ti film was patterned for each pixel to form the first electrode (anode) 2.

Next, as shown in FIG. 2B, the substrate 1 was cleaned using two-fluid cleaning, shower rinsing, and an air knife. Thereafter, as shown in FIG. 2C, the substrate 1 was put into a vacuum drying apparatus, and a dehydration process was performed. In this dehydration step, the substrate 1 was heated continuously for 2.0 hours from the first electrode 2 side using radiant heat from a plate material heated by a halogen heater set at 160 ° C. The pressure in the apparatus was 5.0 × 10 ⁻⁴ Pa.

  Next, as shown in FIG. 2D, UV ozone treatment was performed on the entire surface of the substrate 1 in order to oxidize the surface of the first electrode 2. In the UV ozone treatment, ozone is generated by flowing dry air containing oxygen under reduced pressure while heating from the opposite side of the substrate 1 to the first electrode 2 using a UV ozone treatment device. I went there.

  The dew point of dry air was -70 ° C. While introducing this dry air at 10 slm, the exhaust speed was adjusted on the exhaust line side so that the internal pressure of the apparatus was 1.0 kPa. Further, the heating was performed from the opposite side (back surface) of the substrate 1 to the first electrode 2 with the set temperature of the heating plate being 88.3 ° C. The back surface of the substrate 1 and the heating plate were arranged in close contact with each other. A quartz glass plate was placed between the UV lamp tube and the substrate 1 so as to face the substrate 1. The UV lamp tube used was EUV200NS-46 manufactured by Sen Special Light Company. The distance between the surface of the quartz glass on the substrate 1 side and the surface of the first electrode 2 on the substrate 1 was 40 mm. Under this UV ozone treatment condition, the UV lamp tube was turned on for 10 minutes, ozone was generated in the UV treatment apparatus, and the surface of the first electrode 2 on the substrate 1 was oxidized. These conditions are shown in Table 1. Samples 1 and 2 respectively show two organic EL elements among the plurality of organic EL elements of the display device manufactured in this example, and the conditions are the conditions of the UV ozone treatment at the positions of Samples 1 and 2. Represents.

  In Table 1, the integrated illuminance on the substrate 1 of each sample when irradiated with UV light for 10 minutes was obtained as follows. In other words, instead of the substrate 1, the UV illuminance meter 25 / 36-3 manufactured by Sen Special Light Source Co., Ltd. was installed at the same height as the substrate 1 and the position of each sample, and UV ozone treatment under the same conditions as in this example was performed. The integrated illuminance at that time was measured. The measurement was performed in a mode for measuring around a central wavelength of 254 nm. Note that, under the UV ozone treatment conditions of this example, the surface temperature of the first electrode 2 provided on the substrate 1 when the UV ozone treatment for 10 minutes was completed was 157.0 ° C. The surface temperature was measured with a thermocouple installed on the substrate 1 under the UV ozone treatment conditions of this example.

  Next, as shown in FIG. 2E, an organic compound layer 3 including a white light emitting layer was formed on the entire surface of the substrate 1 having the first electrode 2 subjected to surface oxidation treatment by a vacuum deposition method. The film thickness of the organic compound layer 3 was a stacked structure of 15 nm hole injection layer / 10 nm hole transport layer / 21 nm white light emitting layer / 21 nm electron transport layer / 39 nm electron injection layer.

  Next, as shown in FIG. 2F, indium zinc oxide was formed to a thickness of 500 nm as the second electrode 4 by sputtering.

  Then, a silicon nitride sealing film 5 was formed on the second electrode 4 at 4.0 μm. Further, color filters 6R, 6G, and 6B in which pigments are dispersed in a negative acrylic photosensitive material are formed on each pixel by patterning. The thickness of each color filter was 2.0 μm.

(Example 2)
In this example, the conditions for the UV ozone treatment are different from those in Example 1. The conditions are shown in Table 1. Specifically, this example differs from Example 1 in that the set temperature of the heating plate is set to 112.6 ° C. Further, the integrated illuminance at the positions of the organic EL elements (samples 3 to 5) manufactured in this example is different from that at the positions of samples 1 and 2. In the UV ozone treatment conditions of this example, the surface temperature of the first electrode 2 provided on the substrate 1 when the UV ozone treatment for 10 minutes was completed was 168.0 ° C. Except for this condition, the second embodiment is the same as the first embodiment.

(Comparative example)
In this comparative example, the conditions for the UV ozone treatment are different from those in Example 1. The conditions are shown in Table 1. Specifically, the integrated illuminance at the position of the organic EL element (sample 6) manufactured in this comparative example is different from that at the positions of samples 1 and 2. Except for this condition, the second embodiment is the same as the first embodiment.

<Evaluation of deterioration characteristics of Examples 1 and 2 and Comparative Example>
The luminance degradation characteristics of samples 1 to 6 during long-term driving were evaluated. This luminance deterioration characteristic was implemented by driving at a constant voltage by adjusting the voltage so that the light emission luminance was 100 cd / m ² . In addition, the display devices manufactured in Examples 1 and 2 and the comparative example were placed in a PWL-4KP thermostatic chamber manufactured by Espec, and temperature control was performed so that the surface temperature of the organic EL display device during long-term driving was 40 ° C. . Moreover, the brightness | luminance during a long-term drive was measured using Konica Minolta CA-2000.

Samples 1 to 5 showed deterioration of 94% to 98% at L ₁₅₀ / L ₀ (relative luminance after driving 150 hours with respect to luminance (initial luminance) at the start of driving), respectively. The results are summarized in Table 2 and FIG.

When L ₁₅₀ / L ₀ is 90.6% or more, there is no problem in the long-term driving test of the organic EL element. The indicator of 90.6% was derived as follows. First, the display device performs white display with all the pixels for 5 hours, and then performs the other pixel display with black display for 25 hours while the central pixel of the display device remains in white display. When this drive is alternately performed for 150 hours (alternately 5 times), the luminance difference between the central pixel always displaying white and the pixels in other regions is within 1.5%, so the degradation is greatest. This is the luminance value of the pixel (organic EL element). If the luminance difference is within 1.5%, the luminance unevenness in the display device is not visually recognized.

  Note that, under the measurement conditions at the time of evaluation, the display device of this example caused a change in light emission efficiency and a decrease in luminance with a change in current during driving. From this, it is considered that a change in current in the first electrode 2 suggests that the organic compound layer 3 is deteriorated.

On the other hand, in Sample 6, L ₁₅₀ / L ₀ was 82%, and in the display device manufactured in the comparative example, luminance unevenness was visually recognized.

<Measurement of electrical resistance value of surface of first electrode 2 of Examples 1 and 2 and Comparative Example>
Next, the current image was acquired for the surface of the 1st electrode 2 of the samples 1 thru | or 6 using Conductive-AFM mode in SPA-400 by SII Nanotechnology. SI-DF3R manufactured by SII Nanotechnology, Inc. used for simultaneous current AFM measurement by SII Nanotechnology was used as the cantilever. In SI-DF3R, the back coating material was Al, and the probe tip coating material was Rh. The applied voltage at the time of acquiring the current image was set to -2.0V.

With this measurement method, current images of the surfaces of the first electrodes 2 of Samples 1 to 5 were acquired. As a result, in the area per 1.0 μm × 1.0 μm, the area ratio of the portion where the electric resistance value in the vertical direction of the first electrode 2 is 2.0 × 10 ⁹ Ω or less is 0.558% to 0.001. It was 751% of range.

On the other hand, when the current image of the surface of the first electrode 2 of the sample 6 was acquired, the electric resistance value in the vertical direction of the first electrode 2 was 2.0 × 10 ^{9 in} the area per 1.0 μm × 1.0 μm. The area ratio of the portion that is Ω or less was in the range of 1.055%. These results are shown in Table 2.

In the comparative example, the integrated illuminance is smaller than 6700 mJ / cm ² , and the surface oxidation treatment of the first electrode 2 of the sample 6 is insufficient, so it is considered that the current concentration area is increased. For this reason, it is estimated that the brightness | luminance fall as mentioned above is invited.

<Measurement of Work Function of First Electrode 2 of Examples 1 and 2 and Comparative Example>
Next, the work functions of the first electrodes 2 of Samples 1 to 6 were measured using AC-2 manufactured by Riken Keiki Co., Ltd. In addition, the measurement light quantity in AC-2 was 730 nW. The work function of the first electrode 2 of Samples 1 to 5 was in the range of 5.05 eV to 5.20 eV. On the other hand, the work function of the first electrode 2 of Sample 6 was 4.95 eV.

  The work function is related to the carrier injection property, and it can be said that the first electrode 2 of the samples 1 to 5 is superior to that of the sample 6 from the viewpoint of the hole injection property.

<Measurement of oxidation state of first electrode 2 of Examples 1 and 2 and Comparative Example>
Next, the oxidation state of the first electrode 2 of the organic EL elements of Samples 1 to 6 was evaluated using an X-ray photoelectron spectrometer manufactured by ULVAC-PHI. As the evaluation method, and a main peak of the O1s spectrum having a TiO ₂ of the Ti2p spectrum of the first electrode 2 of the Ti film were compared for each sample. In the Ti2p spectrum, a peak mainly attributable to TiO ₂ is observed in the vicinity of 460 eV. In the O1s spectrum, a main peak is observed in the vicinity of 529 eV. In the O1s spectrum, since a sub peak appears in the vicinity of 531 eV, waveform separation was performed using a Lorentz function and a Gaussian function, and a main peak value was calculated. The main peak in each spectrum indicates the amount of Ti that has been oxidized mainly containing a large amount of TiO _2. It can be said that the higher the both peaks, the more the Ti film is oxidized.

  In FIG. 9, the result of the X-ray photoelectron spectroscopy of the 1st electrode 2 of the samples 1 thru | or 6 is shown. In addition, the gray rhombus plot at the lower left in FIG. 9 is a measurement result of the Ti film not subjected to the surface oxidation treatment. From FIG. 9, the first electrode 2 (white circle plot) of Samples 1 to 5 has a peak top value in the Ti2p spectrum and the O1s spectrum as compared with the first electrode 2 (black triangle plot) of Sample 6. large. From this, it was found that the first electrode 2 of samples 1 to 5 was more oxidized than the first electrode 2 of sample 6. The progress of oxidation means that there is a low probability that a low-order oxide in which x of TiOx is 1 <x <2 is present, and the measurement result of the electric resistance value and the measurement of the work function described above. It agrees with the result.

2 First electrode 3 Organic compound layer 4 Second electrode

Claims (9)

An organic EL element having a first electrode containing titanium, a second electrode, and an organic compound layer formed between the first electrode and the second electrode,
Titanium oxide is formed on the surface of the first electrode,
An area ratio of a region in which an electric resistance value in a direction perpendicular to the first electrode in an arbitrary region in the first electrode is 2.0 × 10 ⁹ Ω or less is 1.0% or less, Organic EL element to be used.   2. The organic EL element according to claim 1, wherein the first electrode includes a titanium oxide layer and a titanium layer in this order from a side close to the organic compound layer.   A light emitting device comprising: the organic EL element according to claim 1; and a control circuit that controls light emission of the organic EL element.   An image forming apparatus comprising: the light emitting device according to claim 3; a photoconductor on which a latent image is formed by the light emitting device; and a charging unit that charges the photoconductor. A display device having a plurality of organic EL elements that emit different colors and a control circuit that controls light emission of the organic EL elements,
A display device, wherein the organic EL element is the organic EL element according to claim 1.   An imaging apparatus comprising: the display device according to claim 5; and an imaging element. An organic EL having a first electrode containing titanium, a second electrode, and an organic compound layer formed between the first electrode and the second electrode, and light is emitted from the second electrode. A method for manufacturing an element, comprising:
Forming a first electrode containing titanium;
Subjecting the first electrode to a surface oxidation treatment;
Forming an organic compound layer on the surface-treated first electrode;
Forming the second electrode on the organic compound layer,
In the surface oxidation treatment step, an area ratio of a region in which an electric resistance value in a direction perpendicular to the first electrode in an arbitrary region in the first electrode is 2.0 × 10 ⁹ Ω or less is 1.0. %. The method for producing an organic EL element, wherein the surface of the first electrode is oxidized so as to be not more than%.   8. The method of manufacturing an organic EL element according to claim 7, wherein the surface oxidation treatment uses UV ozone treatment. 9. The method of manufacturing an organic EL element according to claim 8, wherein in the UV ozone treatment, the surface of the first electrode is irradiated with UV light at an integrated illuminance of 6700 mJ / cm ² or more.