JP2006190715A - Organic EL device and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the accumulation of electric charges in an organic EL element, to suppress a decrease in lifetime and light emission, and to perform display without shortening an effective light emission time.
An organic EL device having at least a light emitting layer 60 between an anode 23 and a cathode 50 facing each other, comprising an anode buffer layer 70 between the anode and the light emitting layer, and the cathode and the light emitting layer. The cathode buffer layer 52 is provided between them, and light emission can always be obtained in both positive and negative biases when voltages having different polarities are alternately applied. The anode buffer layer and the cathode buffer layer are preferably a polymer compound containing ethylenedioxythiophene. Moreover, it is desirable to use the same material for the anode buffer layer and the cathode buffer layer.
[Selection] Figure 5

Description

  The present invention relates to an organic EL device and an electronic apparatus.

  Generally, a light emitting element constituting an organic EL device has a structure in which an organic light emitting material is formed as a thin film between an anode and a cathode. Then, electrons and holes injected from both electrodes are recombined in the light emitting layer, and the excited energy is emitted as light emission.

  In such a light emitting device, the organic compound layer is usually formed as a thin film having a thickness of less than 1 μm. Further, since the light emitting element is a self-luminous element in which the organic compound layer itself emits light, a backlight as used in a conventional liquid crystal display is not necessary. Therefore, it is a great advantage that the light-emitting element can be manufactured to be extremely thin and light. By making the organic compound layer a uniform ultrathin film with a thickness of about 100 nm, selecting an electrode material that reduces the carrier injection barrier for the organic compound layer, and introducing a heterostructure (laminated structure), 5.5 There is a report that sufficient luminance of 100 cd / m 2 has been achieved at V (Non-patent Document 1).

  However, in such a light-emitting element, when direct current driving in which a bias in a constant direction is always applied is used, charges are accumulated in the element, resulting in a problem that the light emission life and luminance are reduced.

  In this regard, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-114506 (Patent Document 1) and the like, the driving voltage applied to the light emitting element at the time of light emission, that is, the forward bias, and the polarity is opposite to this voltage. There have been reports using AC driving in which reverse bias is applied alternately.

This is because, by alternately applying voltages with different polarities to the organic compound layer by alternating current driving, charge accumulation inside the element is alleviated, so that it is possible to suppress a decrease in light emission lifetime and luminance. It is.
Appl. Phys. Lett., 51, 913 (1987). JP 2004-114506 A

  However, when driving a light emitting element by AC driving, the light emitting element usually has a laminated structure including an anode, a light emitting layer, and a cathode, so that a positive voltage is applied from the anode side and a negative voltage is applied to the cathode side. The light emission can be obtained only when the voltage is applied, that is, when the forward bias is applied. That is, when a reverse bias is applied using AC driving, the light emitting element does not emit light.

In order to solve the above problems, the present invention provides an anode buffer layer between an anode and a light emitting layer, a cathode buffer layer between a cathode and a light emitting layer, and forward bias voltage and reverse bias voltage having different polarities from the anode. Drive means for alternately applying to the cathode, wherein the anode buffer layer and the cathode buffer layer are made of the same material.
At this time, the charge transport characteristics of the anode buffer layer and the cathode buffer layer and the charge injection characteristics between the light emitting layers are equal, and the light emission characteristics when the forward bias is applied and the light emission characteristics when the reverse bias is applied are approximately symmetrical.

Further, the difference between the work function of the material used for the anode and the work function of the material used for the cathode is preferably smaller than 0.5 eV, and the smaller the work function difference is, the more desirable.
At this time, the difference in charge injection characteristics between the anode and the anode buffer layer and between the cathode and the cathode buffer layer is small, and the light emission characteristics when applying a forward bias and the light emission characteristics when applying a reverse bias are approximately symmetrical. .

  The anode buffer layer and the cathode buffer layer are preferably made of a conductive material, particularly preferably a conductive polymer.

  The conductive material is preferably made of a polymer compound containing ethylenedioxythiophene.

  The conductive material may be PEDOT / PSS.

Further, it is desirable that sheet resistance values of the anode buffer layer and the cathode buffer layer are smaller than 100 Ωcm.
When the sheet resistance value is larger than this range, it becomes difficult to inject charges and the light emission characteristics are deteriorated.

In the driving means, it is desirable that the absolute value of the forward bias voltage and the absolute value of the reverse bias voltage are equal. Furthermore, it is desirable that the time for applying the forward bias and the time for applying the reverse bias are equal.
By adopting this driving means, charge accumulation inside the light emitting element is efficiently eliminated, and a decrease in light emission lifetime and luminance can be suppressed. Furthermore, flickering due to the difference in luminance between forward bias application and reverse bias application can be suppressed.

  As described above, since light emission is always obtained in both forward bias and reverse bias when voltages of different polarities are applied alternately, display can be performed without shortening the effective light emission time. Is possible. Therefore, the problem that the display is dark can be solved.

On the other hand, an electronic apparatus according to the present invention includes the above-described organic EL device.
According to this configuration, an electronic device having good display characteristics can be provided.

  The present invention will be described in detail below. This embodiment shows a part of the present invention and does not limit the present invention, and can be arbitrarily changed within the scope of the technical idea of the present invention. Moreover, in each figure shown below, in order to make each layer and each member the size which can be recognized on drawing, the scale is varied for each layer and each member.

[Organic EL device]
First, an embodiment of the organic EL device of the present invention will be described.

(Equivalent circuit)
FIG. 1 is a schematic diagram showing a wiring structure of the organic EL device of the present embodiment. In FIG. 1, reference numeral 1 denotes the organic EL device. This organic EL device 1 is of an active matrix type using a thin film transistor (TFT) as a switching element, and has a plurality of scanning lines 101 and a plurality of signal lines 102 extending in a direction perpendicular to each scanning line 101. And a plurality of power supply lines 103 extending in parallel to each signal line 102, and a pixel region X is formed near each intersection of the scanning line 101 and the signal line 102. A data line driving circuit 100 including a shift register, a level shifter, a video line, and an analog switch is connected to the signal line 102. Further, a scanning line driving circuit 80 including a shift register and a level shifter is connected to the scanning line 101.

  Further, in each pixel region X, a switching TFT 112 to which a scanning signal is supplied to the gate electrode via the scanning line 101, and a storage capacitor for holding a pixel signal supplied from the signal line 102 via the switching TFT 112. 113, a driving TFT 123 to which a pixel signal held by the holding capacitor 113 is supplied to a gate electrode, and a driving current from the power supply line 103 when electrically connected to the power supply line 103 via the driving TFT 123 And a functional layer 110 sandwiched between the pixel electrode 23 and the common cathode (electrode) 50 are provided. The pixel electrode 23, the common cathode 50, and the functional layer 110 constitute a light emitting element, that is, an organic EL element.

  According to the organic EL device 1 having such a configuration, when the scanning line 101 is driven and the switching TFT 112 is turned on, the potential of the signal line 102 at that time is held in the holding capacitor 113, and The on / off state of the driving TFT 123 is determined according to the state. Then, a current flows from the power supply line 103 to the pixel electrode 23 through the channel of the driving TFT 123, and further a current flows to the common cathode 50 through the functional layer 110. Then, the functional layer 110 emits light according to the amount of current flowing therethrough.

  Next, specific modes of the organic EL device 1 of the present embodiment will be described with reference to FIGS. FIG. 2 is a plan view schematically showing the configuration of the organic EL device 1.

(Plane configuration)
As shown in FIG. 2, the organic EL device 1 according to the present embodiment includes a substrate 20 having optical transparency and electrical insulation, and a pixel electrode connected to a switching TFT (not shown) in a matrix on the substrate 20. A pixel electrode area (not shown) arranged in a shape, a power supply line arranged around the pixel electrode area and connected to each pixel electrode, and at least a substantially rectangular shape in plan view located on the pixel electrode area The pixel portion 3 (inside the one-dot chain line frame in FIG. 2) is provided. In the present embodiment, the pixel unit 3 includes an actual display area 4 (within the two-dot chain line in the figure) in the center and a dummy area 5 (one-dot chain line and two-dot chain line) arranged around the actual display area 4. Between the two areas).

In the actual display area 4, light emitting elements R, G, and B each having a pixel electrode are regularly arranged in the AB direction and the CD direction.
Further, scanning line driving circuits 80 and 80 are arranged on both sides of the actual display area 4 in FIG. The scanning line driving circuits 80 and 80 are provided on the lower layer side of the dummy region 5.

  Further, an inspection circuit 90 is disposed above the actual display area 4 in FIG. 2, and the inspection circuit 90 is disposed on the lower layer side of the dummy area 5. This inspection circuit 90 is a circuit for inspecting the operating state of the organic EL device 1 and includes, for example, inspection information output means (not shown) for outputting the inspection result to the outside, and is displayed during manufacture or at the time of shipment. It is configured to be able to inspect the quality and defects of the apparatus.

  The driving voltages of the scanning line driving circuit 80 and the inspection circuit 90 are applied from a predetermined power supply unit via the driving voltage conducting unit 310 (see FIG. 3) and the driving voltage conducting unit 340 (see FIG. 4). In addition, the drive control signal and the drive voltage to the scanning line drive circuit 80 and the inspection circuit 90 are supplied from a predetermined main driver that controls the operation of the organic EL device 1 and the drive control signal conduction unit 320 (see FIG. 3) and Transmission and application are performed via the drive voltage conduction unit 350 (see FIG. 4). The drive control signal in this case is a command signal from a main driver or the like related to control when the scanning line drive circuit 80 and the inspection circuit 90 output signals.

(Cross section configuration)
3 is a cross-sectional view taken along line AB in FIG. 2, FIG. 4 is a cross-sectional view taken along line CD in FIG. 2, and FIG. 6 is an enlarged cross-sectional view of the main part of FIG. FIG. 5 is a simplified view of the element portion of FIG. As shown in FIGS. 3 and 4, the organic EL device 1 is formed by bonding a substrate 20 and a sealing substrate 30 through a sealing resin 40. In a region surrounded by the substrate 20, the sealing substrate 30, and the sealing resin 40, a getter agent 45 that absorbs moisture and oxygen is attached to the inner surface of the sealing substrate 30. The space is filled with nitrogen gas to form a nitrogen gas filled layer 46. Under such a configuration, moisture and oxygen are prevented from penetrating into the organic EL device 1, thereby extending the lifetime of the organic EL device 1.

In the case of a so-called top emission type organic EL device, the substrate 20 is configured to extract emitted light from the sealing substrate 30 side that is the opposite side of the substrate 20, so that both a transparent substrate and an opaque substrate can be used. it can. Examples of the opaque substrate include a thermosetting resin and a thermoplastic resin in addition to a ceramic sheet such as alumina and a metal sheet such as stainless steel that has been subjected to an insulation treatment such as surface oxidation.
In the case of a so-called bottom emission type organic EL device, since the emitted light is extracted from the substrate 20 side, a transparent or semi-transparent substrate 20 is employed. For example, glass, quartz, resin (plastic, plastic film) and the like can be mentioned, and a glass substrate is particularly preferably used. In the present embodiment, a bottom emission type in which emitted light is extracted from the substrate 20 side, and thus a transparent or translucent substrate 20 is used.

  As the sealing substrate 30, for example, a plate-like member having electrical insulation can be employed. Further, the sealing resin 40 is made of, for example, a thermosetting resin or an ultraviolet curable resin, and is preferably made of an epoxy resin which is a kind of thermosetting resin.

Further, as shown in FIG. 5, a circuit unit 11 including a driving TFT 123 for driving the pixel electrode 23 and the like is provided on the substrate 20. The circuit unit 11 is formed on the substrate 20. That is, a base protective layer 281 mainly composed of SiO ₂ is formed on the surface of the substrate 20 as a base, and a silicon layer 241 is formed thereon. A gate insulating layer 282 mainly composed of SiO ₂ and / or SiN is formed on the surface of the silicon layer 241.

In the silicon layer 241, a region overlapping with the gate electrode 242 with the gate insulating layer 282 interposed therebetween is a channel region 241a. The gate electrode 242 is a part of the scanning line 101 (not shown). On the other hand, a first interlayer insulating layer 283 mainly composed of SiO ₂ is formed on the surface of the gate insulating layer 282 that covers the silicon layer 241 and on which the gate electrode 242 is formed.

  Further, in the silicon layer 241, a low concentration source region 241b and a high concentration source region 241S are provided on the source side of the channel region 241a, while a low concentration drain region 241c and a high concentration drain are provided on the drain side of the channel region 241a. The region 241D is provided to form a so-called LDD (Light Doped Drain) structure. Among these, the high-concentration source region 241S is connected to the source electrode 243 through a contact hole 243a that opens over the gate insulating layer 282 and the first interlayer insulating layer 283. The source electrode 243 is configured as a part of the power supply line 103 described above (see FIG. 1, extending in the direction perpendicular to the paper surface at the position of the source electrode 243 in FIG. 6). On the other hand, the high-concentration drain region 241D is connected to the drain electrode 244 made of the same layer as the source electrode 243 through a contact hole 244a that opens through the gate insulating layer 282 and the first interlayer insulating layer 283.

The upper layer of the first interlayer insulating layer 283 on which the source electrode 243 and the drain electrode 244 are formed is covered with a second interlayer insulating layer 284 mainly composed of, for example, an acrylic resin component. The second interlayer insulating layer 284 can be made of a material other than an acrylic insulating film, such as SiN or SiO ₂ . A pixel electrode 23 made of ITO is formed on the surface of the second interlayer insulating layer 284 and is connected to the drain electrode 244 through a contact hole 23a provided in the second interlayer insulating layer 284. Yes. That is, the pixel electrode 23 is connected to the high concentration drain region 241D of the silicon layer 241 through the drain electrode 244.
The layers from the substrate 20 to the second interlayer insulating layer 284 described above constitute the circuit unit 11.

  Note that TFTs (driving circuit TFTs) included in the scanning line driving circuit 80 and the inspection circuit 90 (see FIG. 2), that is, for example, an N-channel type that constitutes an inverter included in the shift register among these driving circuits or The P-channel TFT has the same structure as the driving TFT 123 except that it is not connected to the pixel electrode 23.

The surface of the second interlayer insulating layer 284 on which the pixel electrode 23 is formed is composed of the pixel electrode 23, a lyophilic control layer 25 mainly composed of a lyophilic material such as SiO ₂ , an acrylic resin, a polyimide resin, or the like. The organic bank layer 221 is covered. In addition, “lyophilic” of the lyophilic control layer 25 in the present embodiment means that the lyophilic property is higher than at least materials such as acrylic resin and polyimide resin constituting the organic bank layer 221. And The opening 25a provided in the lyophilic control layer 25 and the inside of the opening 221a provided in the organic bank layer 221 constitute a pixel region. A BM (black matrix) (not shown) in which metallic chromium is formed by sputtering or the like is positioned between the organic bank layer 221 and the lyophilic control layer 25 at the boundary between the color display regions (pixel regions). Is formed.

(Light emitting element)
Light emitting elements (organic EL elements) R, G, and B are provided above the pixel electrode 23 in each pixel region. The light emitting elements R, G, and B include a pixel electrode 23 that functions as an anode, an anode buffer layer 70, a light emitting layer 60 (60R, 60G, 60B) made of an organic EL material, and a cathode buffer layer 52 common cathode 50. It is comprised by having been formed in order. In the light emitting elements R, G, and B having such a configuration, when a positive bias is applied, the holes injected from the anode buffer layer 70 and the electrons injected from the cathode buffer layer 52 are emitted from the light emitting layer 60. By combining with each other, red, green, or blue light is emitted. When reverse bias is applied, electrons injected from the anode buffer layer 70 and holes injected from the cathode buffer layer 52 are combined in the light emitting layer 60 so that red, green, or blue light is emitted. It has become.

  The pixel electrode 23 functioning as an anode is formed of a transparent conductive material because it is a bottom emission type in this example. ITO is suitable as the transparent conductive material, but other than this, for example, indium oxide / zinc oxide based amorphous transparent conductive film (Indium Zinc Oxide: IZO / registered trademark)) (Idemitsu Kosan) Etc.) can be used. In the present embodiment, ITO is used. In the case of the top emission type, it is not necessary to use a material having a light transmission property. For example, Al or the like may be provided on the lower layer side of ITO and used as a reflection layer.

  As a material for forming the anode buffer layer 70, in particular, a dispersion of 3,4-polyethylenedioxythiophene / polystyrene sulfonic acid (PEDOT / PSS), that is, 3,4-polyethylenedioxythiophene in polystyrene sulfonic acid as a dispersion medium. Is preferably used, which is further dissolved in a polar solvent such as water or isopropyl alcohol.

  The sheet resistance value of the anode buffer layer 70 is desirably smaller than 100 Ωcm. In the present embodiment, a sheet resistance value of 0.1 Ωcm or less is preferably used.

  As a material for forming the light emitting layer 60, a known light emitting material capable of emitting fluorescence or phosphorescence is used. In the present embodiment, the emission wavelength bands are formed corresponding to the three primary colors of light in order to perform full color display. That is, one pixel is composed of three light emitting layers, a light emitting layer 60R corresponding to red, a light emitting layer 60G corresponding to green, and a light emitting layer 60B corresponding to blue. As a result, the organic EL device 1 performs full color display as a whole.

Specific examples of the material for forming the light emitting layer 60 include (poly) fluorene derivative (PF), (poly) paraphenylene vinylene derivative (PPV), polyphenylene derivative (PP), polyparaphenylene derivative (PPP), and polyvinylcarbazole (PVK). ), Polythiophene derivatives, and polysilanes such as polymethylphenylsilane (PMPS) are preferably used. In addition, these polymer materials include polymer materials such as perylene dyes, coumarin dyes, rhodamine dyes, rubrene, perylene, 9,10-diphenylanthracene, tetraphenylbutadiene, Nile red, coumarin 6, and quinacridone. It can also be used by doping a low molecular weight material such as.
The “polymer” means a polymer having a molecular weight higher than that of a so-called “low molecule” having a molecular weight of about several hundreds. The above-mentioned polymer material includes a polymer generally called a polymer and having a molecular weight of 10,000 or more. In addition, a low polymer called an oligomer having a molecular weight of 10,000 or less is included.

  In this embodiment, MEHPPV (poly (3-methoxy 6- (3-ethylhexyl) paraphenylenevinylene) is used as a material for forming the red light emitting layer 60R, and polydioctylfluorene and F8BT are used as the material for forming the green light emitting layer 60R. Polydioctylfluorene is used as a material for forming the blue light-emitting layer 60R in the mixed solution of (dioctylfluorene and benzothiadiazole alternating copolymer). For example, the thickness of the blue light emitting layer 60B is preferably about 60 to 70 nm, although there is no limitation and the preferred thickness varies for each color.

  As the constituent material of the cathode buffer layer 52, in the same manner as the anode buffer layer 70, in particular, a dispersion of 3,4-polyethylenedioxythiophene / polystyrene sulfonic acid (PEDOT / PSS), that is, 3 in polystyrene sulfonic acid as a dispersion medium. , 4-polyethylenedioxythiophene dispersed therein and further dissolved in a polar solvent such as water or isopropyl alcohol is preferably used.

  The sheet resistance value of the cathode buffer layer 52 is preferably smaller than 100 Ωcm, and in this embodiment, a sheet resistance value of 0.1 Ωcm or less is suitably used.

  Moreover, it is preferable that the constituent materials and film forming conditions of the cathode buffer layer 52 and the anode buffer layer 70 are the same.

As shown in FIGS. 2 to 4, the common cathode 50 has an area larger than the total area of the actual display region 4 and the dummy region 5 and is formed so as to cover each.
The common cathode 50 is not particularly limited as long as it is a chemically stable conductive material, and an arbitrary material such as a metal or an alloy can be used. In particular, it is desirable that the difference from the work function of the material used for the previous pixel electrode 23 is smaller than 0.5 eV. Specifically, Au (gold), Ni (nickel), Pd (palladium), Cu (copper), etc. Are preferably used. The thickness of the common cathode 50 is preferably about 100 nm to 500 nm, particularly about 200 nm. If the thickness is less than 100 nm, the protective function may not be sufficiently obtained. If the thickness exceeds 500 nm, the thermal load during production increases, and the light emitting layer 60 may be adversely affected such as deterioration or alteration. In the present embodiment, the cathode 50 is made of Au. In particular, in the case of a top emission type organic EL device, it is possible to form a sufficiently thin cathode 50 so as to have a light-transmitting property, or a conductive material such as ITO having a light-transmitting property. It is also possible to form the cathode 50 using a material.

  In the organic EL device 1 having such a configuration, light emission is always obtained regardless of whether voltages having different polarities are alternately applied by the anode buffer layer and the cathode buffer layer. Accordingly, it is possible to suppress the lifetime and light emission decrease due to the accumulation of electric charges and perform display without shortening the effective light emission time.

[Method for Manufacturing Organic EL Device]
Next, an example of a method for manufacturing the organic EL device 1 according to this embodiment will be described with reference to FIGS. Each cross-sectional view shown in FIGS. 6 and 7 corresponds to the cross-sectional view taken along the line AB in FIG. 2 and is shown in the order of each manufacturing process.
First, as shown in FIG. 6A, the pixel electrode 23 is formed on the surface of the circuit unit 11 on the substrate 20. Specifically, first, a conductive film made of a conductive material such as ITO is formed so as to cover the entire surface of the substrate 20. At that time, the contact hole 23a of the second interlayer insulating layer 284 is filled with a conductive material to form a contact. The pixel electrode 23 is formed by patterning this conductive film, and is electrically connected to the drain electrode 244 of the driving TFT 123 through a contact. At the same time, a dummy pattern 26 in the dummy area is also formed. 3 and 4, the pixel electrode 23 and the dummy pattern 26 are collectively referred to as the pixel electrode 23.

  The dummy pattern 26 is formed in an island shape like the pixel electrode 23 formed in the actual display area, but is not connected to the lower metal wiring via the second interlayer insulating layer 284. . Of course, the shape may be different from that of the pixel electrode 23 formed in the display area. In this case, the dummy pattern 26 includes at least the one located above the drive voltage conducting portion 310 (340).

  Next, as shown in FIG. 6B, a lyophilic control layer 25 that is an insulating layer is formed on the pixel electrode 23, the dummy pattern 26, and the second interlayer insulating layer 284. In the pixel electrode 23, the lyophilic control layer 25 is formed so as to partially open, and holes can be transferred from the pixel electrode 23 in the opening 25a (see also FIG. 3). Subsequently, in the lyophilic control layer 25, a BM (not shown) is formed in a concave portion formed between two different pixel electrodes 23. Specifically, a film is formed on the concave portion of the lyophilic control layer 25 by sputtering using metallic chromium.

Next, as shown in FIG. 6C, an organic bank layer 221 is formed so as to cover a predetermined position of the lyophilic control layer 25, specifically, the BM. As a specific method for forming the organic bank layer 221, for example, an organic layer is formed by applying a resist such as acrylic resin or polyimide resin dissolved in a solvent by various coating methods such as a spin coating method or a dip coating method. To do. The constituent material of the organic layer may be any material as long as it does not dissolve in the ink solvent described later and is easily patterned by etching or the like.
Subsequently, the organic layer is patterned using a photolithography technique and an etching technique, and a bank opening 221a is formed in the organic layer, thereby forming an organic bank layer 221 having a wall surface in the opening 221a. In this case, the organic bank layer 221 includes at least a layer positioned above the drive control signal conducting unit 320.

  Next, a region showing lyophilicity and a region showing liquid repellency are formed on the surface of the organic bank layer 221. In the present embodiment, each region is formed by plasma processing. The plasma treatment includes a preliminary heating step, and an ink repellency step in which the upper surface of the organic bank layer 221 and the wall surface of the opening 221a, and the electrode surface 23c of the pixel electrode 23 and the upper surface of the lyophilic control layer 25 are made lyophilic. And an ink repellent process for making the upper surface of the organic bank layer and the wall surface of the opening liquid repellent, and a cooling process.

That is, the base material (substrate 20 including a bank or the like) is heated to a predetermined temperature, for example, about 70 to 80 ° C., and then plasma treatment using oxygen as a reactive gas at atmospheric pressure as an ink-philic process (O ₂ plasma treatment) I do. Next, as an ink repellent process, plasma treatment (CF ₄ plasma treatment) using methane tetrafluoride as a reaction gas under atmospheric pressure is performed, and then the substrate heated for the plasma treatment is cooled to room temperature. In addition, lyophilicity and liquid repellency are imparted to predetermined locations.

In this CF ₄ plasma treatment, the electrode surface 23c of the pixel electrode 23 and the lyophilic control layer 25 are somewhat affected, but the structure of the ITO that is the material of the pixel electrode 23 and the lyophilic control layer 25. Since materials such as SiO ₂ and TiO ₂ have poor affinity for fluorine, the hydroxyl group imparted in the ink-philic process is not replaced with the fluorine group, and the lyophilic property is maintained.

  Next, the anode buffer layer 70 is formed by an anode buffer layer forming step. In this anode buffer layer forming step, an inkjet method is particularly preferably employed as the droplet discharge method. That is, by the ink jet method, the anode buffer layer forming material is selectively disposed on the electrode surface 23c and applied. Thereafter, drying treatment and heat treatment are performed to form the anode buffer layer 70 on the electrode 23. As a material for forming the anode buffer layer 70, a material obtained by dissolving the PEDOT / PSS in a polar solvent such as water or isopropyl alcohol is used.

  Here, in forming the anode buffer layer 70 by the ink jet method, first, an anode buffer layer forming material is filled in the ink jet head (not shown), and while relatively moving the ink jet head and the base material (substrate 20), The discharge nozzle of the inkjet head is made to face the electrode surface 23c located in the opening 25a formed in the lyophilic control layer 25. Then, a droplet whose liquid amount per droplet is controlled is discharged from the discharge nozzle to the electrode surface 23c. Next, the discharged droplets are dried and the anode buffer layer 70 is formed by evaporating the dispersion medium and solvent contained in the hole injection layer material.

At this time, the droplet discharged from the discharge nozzle spreads on the electrode surface 23c that has been subjected to the lyophilic treatment, and fills the opening 25a of the lyophilic control layer 25. On the other hand, droplets are repelled and do not adhere to the upper surface of the organic bank layer 221 that has been subjected to ink repellent treatment. Therefore, even if the liquid droplet is displaced from a predetermined discharge position and a part of the liquid droplet is applied to the surface of the organic bank layer 221, the surface is not wetted by the liquid droplet, and the repelled liquid droplet is not lyophilic. It is drawn into the opening 25 a of the property control layer 25. The firing temperature is preferably in the range of 100 ° C. to 200 ° C., more preferably about 100 ° C. If the temperature is lower than 100 ° C., the forming material is not sufficiently cured, and if the forming material for the light emitting layer is provided thereon, the forming materials may be mixed with each other. Moreover, there is a possibility that the contained solvent cannot be completely removed. On the other hand, if the temperature exceeds 200 ° C., the forming material may be deteriorated and deteriorated by heat. Further, it is desirable to use the same forming material as that of the cathode buffer layer 52 described later, and it is also preferable that the film forming method, particularly the firing temperature, be the same. In this regard, if PEDOT / PSS is employed as the conductive material, it can be fired under conditions of about 100 ° C. × 10 minutes.
In addition, after this anode buffer layer formation process, it is preferable to carry out in inert gas atmospheres, such as nitrogen atmosphere and argon atmosphere, in order to prevent oxidation and moisture absorption of various formation materials and the formed element.

  Next, as shown in FIG. 7D, the light emitting layer 60 is formed by the light emitting layer forming step. In this light emitting layer forming step, as in the formation of the anode buffer layer 70, an ink jet method that is a droplet discharge method is suitably employed. That is, the light emitting layer forming material is ejected onto the anode buffer layer 70 by an ink jet method, and then a drying process and a heat treatment are performed, thereby forming the light emitting layer 60 in the opening 221a formed in the organic bank layer 221. . The light emitting layer 60 is formed for each color. Note that by using the ink jet method (droplet discharge method), the material for forming the light emitting layer 60 can be selectively disposed only in a predetermined position, that is, the pixel region, and the discharge amount can be set at each position. It is also possible to change. Further, in the light emitting layer forming step, a nonpolar solvent that is insoluble in the hole injection layer 70 is used as a solvent used for the light emitting layer forming material in order to prevent re-dissolution of the anode buffer layer 70.

  Next, as shown in FIG. 7E, the cathode buffer layer 52 is formed. In the step of forming the cathode buffer layer 52, first, the cathode buffer layer 52 is formed so as to cover the light emitting layer 60 and the organic bank layer 221. The cathode buffer layer 52 is formed by applying a liquid containing the constituent material of the cathode buffer layer 52. When the PEDOT / PSS is used as a material for forming the cathode buffer layer 52, 3,4-polyethylenedioxythiophene is dispersed in polystyrene sulfonic acid as a dispersion medium, and this is further mixed with a polar solvent such as water or isopropyl alcohol. Dissolve in.

  As described above, when a polar substance is employed as the dispersion medium or the solvent, it is possible to suppress re-dissolution of the light emitting layer 60 with respect to the applied liquid material. When the light emitting layer 60 is exceptionally eluted into the polar substance, a nonpolar substance such as toluene, xylene, benzene, hexane, cyclohexane, tetradecane, or isooctane may be used as the dispersion medium or solvent.

  Then, the liquid material produced as described above is applied to the surfaces of the light emitting layer 60 and the organic bank layer 221. A spin coating method or the like can be employed as the coating method, but an ink jet method can also be employed in the same manner as the light emitting layer 60 and the anode buffer layer 70. Further, the coated liquid material is dried and baked to form a film of the cathode buffer layer 52. The film forming temperature of the cathode buffer layer 52 is desirably 150 ° C. or lower. This is because if the heat treatment is performed at a temperature exceeding 150 ° C., the function of the light emitting layer 60 composed of an organic substance may be deteriorated. In this respect, if PEDOT / PSS is adopted as the conductive material, it is possible to perform baking under conditions of about 100 ° C. × 10 minutes, and damage to the light emitting layer 60 can be suppressed.

  Next, the cathode 50 is formed. The cathode 50 is not limited as long as it is a conductive material that can be stably used in the air, but a material having a small work function difference from the anode is desirable. If ITO is used for the anode, Au (gold) can be used.

Thereafter, as shown in FIG. 7F, the surface of the substrate 20 is sealed with the sealing substrate 30. In this sealing step, the sealing substrate 30 with the getter agent 45 attached inside is bonded to the substrate 20 with the sealing resin 40. This sealing step is preferably performed in an inert gas atmosphere such as nitrogen, argon or helium. As a result, the inert gas is hermetically sealed in the space surrounded by the substrate 20, the sealing substrate 30, and the sealing resin 40.
Thus, the organic EL device 1 according to this embodiment is formed.

  As described in detail above, in the organic EL device and the manufacturing method thereof according to this embodiment, the anode buffer layer 70 and the cathode buffer layer 52 are made of a conductive polymer. According to this configuration, light emission is always obtained in both forward and reverse bias when voltages of different polarities are applied alternately. Accordingly, it is possible to suppress the lifetime and light emission decrease due to the accumulation of electric charges and perform display without shortening the effective light emission time.

[Electronics]
Next, the electronic device of the present invention will be described with reference to FIG. FIG. 8 is a perspective view of a mobile phone provided with the organic EL device of the present embodiment. In FIG. 8, reference numeral 1000 indicates a mobile phone body, and reference numeral 1001 indicates a display unit. Since the mobile phone 1000 includes the display unit 1001 including the organic EL device according to the present embodiment, it can exhibit good display characteristics.

  In addition, this invention is not limited to the above-mentioned embodiment, It can implement in various deformation | transformation in the range which does not deviate from the meaning of this invention. For example, although the polymer material is used for the light emitting layer 60 in the above embodiment, a low molecular material can be used instead. Further, the configuration of the circuit unit 11 described above is only an example, and other configurations can be adopted.

An anode electrode made of ITO was formed on the upper surface of the glass substrate, an anode buffer layer made of PEDOT / PSS was formed on the upper surface, and then baked on a hot plate at 100 ° C. for 10 minutes. A light emitting layer was formed on the upper surface using a mixed solution of polydioctylfluorene and F8BT (an alternating copolymer of dioctylfluorene and benzothiadiazole).
A cathode buffer layer made of PEDOT / PSS was formed on the upper surface of the light emitting layer, and then baked on a hot plate at 100 ° C. for 10 minutes.
The sheet resistance values of PEDOT / PSS used for the anode buffer layer and the cathode buffer layer were both 0.02 Ωcm.
Gold serving as a cathode was formed on the upper surface of the cathode buffer layer by vacuum evaporation of 2000 mm. For vacuum deposition, a vacuum deposition apparatus arranged in a glove box in a nitrogen atmosphere was used. The degree of vacuum at the start of deposition is about 4 × 10 ⁻⁶ torr.
Thereafter, the whole was sealed with a sealing substrate.
In the organic EL device thus formed, when a forward bias was applied between ITO and Au, that is, when a bias was applied so that ITO became an anode and Au became a cathode, light was emitted well at a voltage of 10 V or less. Further, when a reverse bias was applied between ITO and Au, that is, when a bias was applied so that ITO was a cathode and Au was an anode, light was emitted well at a voltage of 10 V or less.

[Comparative Example 1]
The layers up to the light emitting layer were formed in the same manner as in Example 1.
A cathode buffer layer made of PEDOT / PSS was formed on the upper surface of the light emitting layer, and then baked on a hot plate at 100 ° C. for 10 minutes.
The resistance value of PEDOT / PSS used for the anode buffer layer was 0.02 Ωcm, and the resistance value of PEDOT / PSS used for the cathode buffer layer was 1 × 10 ⁵ Ωcm.
In the organic EL device thus formed, light emission was observed at a voltage of about 13 V when a forward bias was applied between ITO and Au. However, when a reverse bias was applied between ITO and Au, no light emission was observed even at 18V.

It is a schematic diagram which shows the wiring structure of the organic electroluminescent apparatus of embodiment. It is a top view which shows typically the structure of the organic electroluminescent apparatus of embodiment. It is side surface sectional drawing which follows the AB line | wire of FIG. It is side surface sectional drawing which follows the CD line of FIG. It is a principal part expanded sectional view of FIG. It is sectional drawing explaining the manufacturing method of an organic electroluminescent apparatus in order of a process. It is sectional drawing explaining the manufacturing method of an organic electroluminescent apparatus in order of a process. It is a perspective view of a mobile phone provided with the organic EL device of the embodiment.

Explanation of symbols

23 anode 50 cathode 52 cathode buffer layer 60 light emitting layer 70 cathode buffer layer

Claims (10)

An organic EL device having at least a light emitting layer between an opposing anode and cathode,
An anode buffer layer between the anode and the light emitting layer;
A cathode buffer layer between the cathode and the light emitting layer;
Driving means in which forward bias voltage and reverse bias voltage of different polarities are alternately applied to the anode and the cathode, and
The organic EL device, wherein the anode buffer layer and the cathode buffer layer are made of the same material.   2. The organic EL device according to claim 1, wherein a difference between a work function of a material used for the anode and a work function of a material used for the cathode is smaller than 0.5 eV.   The organic EL device according to claim 1, wherein the anode buffer layer and the cathode buffer layer are made of a conductive material.   The organic EL device according to any one of claims 1 to 3, wherein the anode buffer layer and the cathode buffer layer are made of a conductive polymer.   The organic EL device according to any one of claims 1 to 4, wherein the anode buffer layer and the cathode buffer layer are made of a polymer compound containing ethylenedioxythiophene.   The organic EL device according to any one of claims 1 to 5, wherein the anode buffer layer and the cathode buffer layer are made of PEDOT / PSS.   7. The organic EL device according to claim 1, wherein sheet resistance values of the anode buffer layer and the cathode buffer layer are smaller than 100 Ωcm.   8. The organic EL device according to claim 1, wherein an absolute value of the forward bias voltage is equal to an absolute value of the reverse bias voltage.   9. The organic EL device according to claim 1, wherein a time for applying the forward bias voltage is equal to a time for applying the reverse bias voltage. An electronic apparatus comprising the organic EL device according to claim 1.

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