JP2006156427A - Light emitting apparatus, printer head, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low price organic EL light emitting apparatus which is superior in uniformity of film thickness of a light emitting part and also in, as a result, light emitting characteristic as the simplified organic EL element structure not requiring a separation wall in formation of the organic EL thin film using the printing method. <P>SOLUTION: In an active light emitting apparatus comprising a plurality of thin film transistors formed on a substrate and a light emitting element driven with such thin film transistors, a lower electrode of the light emitting element is allocated in the region not overlapping with the region where a plurality of thin film transistors are formed, this lower electrode is smaller than a light emitting layer of the light emitting element, and the lower electrode is connected with a plurality of thin film transistors at the lower part of the relevant lower electrode. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light emitting device using an organic electroluminescence element (hereinafter abbreviated as an organic EL device), a printer head using the same, and an electronic apparatus.

In recent years, display devices and electronic devices using organic electroluminescence (EL) elements, which are self-luminous elements, have been developed. In the organic EL element, the portion contributing to the light emission is an organic thin film, and the film thickness is usually about several tens to 100 nm. As a method for forming such an organic thin film, vapor deposition is generally used in the case of a low molecular organic material, but it is difficult to form a film uniformly in a large area by the vapor deposition method. Therefore, it has been studied to use a polymer material as the material of the organic thin film and apply it to the substrate using a liquid phase method. As an example of forming an organic thin film by a liquid phase method, for example, Patent Document 1 describes using a printing method in combination with another film forming method. Similarly, Patent Document 2 describes the use of an ink jet printing method.
JP 2001-155858 A JP 2000-353594 A

  However, when an organic thin film is formed by a liquid phase method, there are various problems. For example, in the screen printing method, it is difficult to obtain a film thickness of 1 μm or less on the organic functional layer. In addition, in the spin coating method and the dip coating method, an operation of removing an unnecessary portion of the film after film formation is added, so that material is wasted and the manufacturing process is complicated. Furthermore, in the most promising ink jet printing, it is necessary to provide a partition in order to prevent the coating materials in the adjacent printing regions from being mixed.

  FIG. 16 shows an example of an organic EL device using an ink jet method. An interlayer insulating film 240 is disposed on the thin film transistor 143 provided on the substrate P, and the pixel electrode 141 and the partition wall 150 are further provided thereon. The organic EL layer 140 is formed in the partition wall 150 by an ink jet printing method, and the common electrode 154 further covers it. In the organic EL device having such a configuration, it is convenient to selectively dispose the organic EL material, but it is difficult to obtain a uniform film thickness over a wide area. That is, the film thickness of the liquid material is thick at a position close to the partition wall in the drying process, and the film thickness uniformity of the entire organic EL device is difficult to obtain due to the non-uniformity of the ejected droplets.

  In an organic EL device having the same configuration, when the organic EL material is applied using the relief printing method, the height of the partition wall of 1 to several microns becomes an obstacle, and the application of the organic material is insufficient in the vicinity of the partition wall. Become. As a result, the light emission luminance of each light emitting element varies, and a short circuit is likely to occur. In addition, since a flat surface is difficult to obtain on a thin film transistor or where driving wiring is present, unevenness in the coating thickness of the organic material is likely to occur, resulting in variations in light emission luminance.

  The present invention has been made in view of the above-mentioned problems of the prior art, and provides a simple organic EL element configuration that does not require a partition in the formation of an organic EL thin film using a printing method. The object is to obtain an organic EL light emitting device with excellent thickness uniformity. As a result, another object is to provide an organic EL light emitting device having excellent light emission characteristics at low cost.

  In order to solve the above problems, the present invention provides a light emitting device including a plurality of thin film transistors formed on a substrate and a light emitting element driven by the thin film transistors, in a region that does not overlap with a region where the thin film transistor is formed. The lower electrode of the light emitting element is disposed, the size of the lower electrode is smaller than the size of the light emitting layer of the light emitting element, and the lower electrode and the thin film transistor are electrically connected under the lower electrode. It is characterized by.

  In such a light-emitting device, since the lower electrode of the light-emitting element is provided in a place where it does not overlap with a region where a thin film transistor (TFT) necessary for active driving is formed, the light-emitting element is not affected by unevenness of the TFT forming portion. Can be formed. Therefore, it is possible to obtain a light-emitting layer with good thickness uniformity and no luminance unevenness. In addition, since it is not necessary to increase the thickness of the insulating layer formed on the TFT to make it flat with the periphery, it is not necessary to lengthen the process or to add a special manufacturing method or a special material. Further, since the size of the lower electrode of the light emitting element is formed smaller than that of the light emitting layer and the connection with the driving TFT is performed under the electrode, no further insulation is required for the non-light emitting region of the light emitting element. That is, with a simple configuration, the size of the lower electrode itself becomes the light emitting region itself, and all locations other than the lower electrode can be non-light emitting regions. This eliminates the need for a further insulating layer covering necessary for insulating the peripheral portion of the pixel electrode and the wiring to the pixel electrode, or a partition wall for pixel separation. As a result, even when an organic layer is formed extensively by letterpress printing, an organic thin film with excellent film thickness uniformity that is not affected by the unevenness of the underlying layer can be obtained, and an excellent light emitting device can be provided. Furthermore, according to the present invention, the manufacturing process can be simplified by simplifying the structure of the light emitting element, which can contribute to cost reduction of the light emitting device.

The light emitting device according to the present invention is characterized in that the light emitting element is an electroluminescence element including a light emitting layer made of an organic thin film.
As described above, the present invention does not require extra insulation around the lower electrode and segmentation of pixels by partition walls. Therefore, the light-emitting device according to the present invention has a structure and film formation conditions suitable for a light-emitting element using an organic material. That is, in the low molecular organic EL by vapor deposition and the high molecular organic EL that can be applied by printing, it is not necessary to pay attention to separate film formation for each pixel in the process. In addition, the organic EL thin film in the EL device can be collectively formed. In particular, in a polymer organic EL that can use a printing method, a simple method such as a relief printing, a screen, or a die coating that is a normal printing method can be used.

The light emitting device of the present invention is characterized in that at least one of the organic thin films is formed by applying a liquid material in a planar manner.
As described above, in the organic EL element of the present invention, the organic thin film is formed by applying a liquid material in a planar manner to a predetermined region on the substrate using a simple printing method. However, since the lower electrode of the light emitting element is formed on a flat surface that avoids the uneven surface due to the driving TFT, a flat film with good film thickness uniformity can be obtained even by a normal printing method. In addition, since there are no partition walls around the pixel, a coating film with good flatness is formed by printing. Therefore, a highly reliable light-emitting element that is excellent in uniformity of light emission luminance and does not have a short circuit can be obtained. Further, in the application using the printing method, the liquid material is formed without being applied to an extra region. Therefore, it is possible to prevent the material from being wasted as in the case of using the spin coating method, leading to a reduction in material cost.

The light-emitting device according to the present invention is characterized in that at least one layer of the organic thin film is applied across a plurality of light-emitting elements.
The greatest advantage of the organic EL device formed by the printing method is the batch formation of elements. A wide area can be formed in a short time without unevenness of film thickness with adjacent pixels. Therefore, in an apparatus in which a plurality of organic EL elements are disposed on a substrate, if at least one of the thin films constituting the organic layer is formed simultaneously, the manufacturing process is shortened and the quality is improved. In addition, since the printing method can apply a necessary amount of a material to a necessary portion, the material is not wasted and other unnecessary portions are not soiled, so that a light emitting device with high reliability can be provided at low cost. In the present invention, since the lower electrode of the light emitting element is electrically connected under the electrode, the pixels can be reliably separated by such batch application.

In the light emitting device of the present invention, the light emitting layer of the light emitting element is preferably formed from light emitting layers having the same emission color.
The film forming method in the present invention is a planar material application using a printing method. Therefore, it is preferable to apply the same material over a wide area. Needless to say, the printer head described later may have a single emission color and is compatible with the printing method. Also, in the display field, there are many things that function satisfactorily even in area color and mono color display other than moving image display such as full-color television. The present invention is most suitable for such applications, and can provide a light emitting device excellent in uniformity of emission spectrum and emission luminance at low cost.

In the light emitting device of the present invention, the lower electrode of the light emitting element is formed on an insulating film covering a thin film transistor and a layer on which the driving wiring of the light emitting element is formed, and penetrates the insulating film under the lower electrode. The thin film transistor and the lower electrode are electrically connected through the contact hole.
After the driving TFT is formed, a second interlayer insulating film is coated thereon. In a normal semiconductor device, the source / drain electrode terminal is formed in a region immediately above these TFTs, and naturally the wiring also extends from here. For example, the TFT and the light emitting element are connected by forming a contact hole in the second interlayer insulating film in the vicinity of the drain electrode, and the drain electrode and the light emitting element are connected through this hole. However, extended wiring is again applied to the region where the light emitting region is formed, or the electrodes of the light emitting element are extended and connected. However, since these wiring portions are unnecessary for light emission, it is necessary to cover the insulating film again so that the wiring portions do not emit light. On the other hand, when such wiring extension is not performed, a light emitting region remains on the TFT forming region, and therefore the best light emitting characteristics cannot be obtained due to the influence of unevenness due to the TFT. Alternatively, in order to eliminate these irregularities, an electrode of a light emitting element must be formed after a thick interlayer insulating film is provided and sufficient flatness is ensured. Therefore, the depth and size of the contact hole must be increased.

  On the other hand, in the configuration of the present invention, the wiring is directly extended from the drain electrode of the driving TFT, and the connection is made through the contact hole provided under the electrode of the light emitting element formed on the second interlayer insulating film. The above-described re-insulation of the wiring becomes unnecessary. Also, since the thickness of the insulating film does not have to worry about unevenness due to the TFT, it is thin and easy to make a hole. As a result, it is possible to build a simple process with less burden on the manufacture of the light emitting device.

The present invention is characterized in that the thin film transistor is electrically connected by a conductive member or wiring extended from the source / drain electrode of the thin film transistor and a conductive member formed in the contact hole.
As described above, the electrode connection between the driving TFT and the light emitting element is performed by the conductive member or wiring material directly extending from the drain electrode of the TFT and the conductive member formed in the contact hole. Therefore, the conductive member that mediates the connection is selected from materials that have good connectivity to both the member that forms the drain electrode or the member that forms the wiring and the member that forms the electrode of the light emitting element, and has low conduction resistance. A highly reliable product can be selected. As a result, a light emitting device with favorable display quality and high reliability can be provided.

The present invention is characterized in that the conductive member formed in the contact hole contains the same material as the lower electrode.
As described above, it is desirable that the conductive material filled in the contact hole has a low resistance and high reliability. However, since excessive quality is not necessary, when the lower electrode material of the light emitting element can be used directly, the electrode including the contact hole under the lower electrode may be formed and simultaneously connected to the TFT. Further, when the reliability of the contact is insufficient, the connection may be made through a thin intermediary. With this configuration, a light emitting device with favorable display quality and high reliability can be provided.

A printer head according to the present invention includes the light emitting device described above. As described above, the light emitting device according to the present invention can be a light emitting device having a simple configuration and particularly excellent in luminance uniformity of a single color. Therefore, it is possible to provide a large amount and a low cost of a printer head excellent in mass productivity.
In the printer head according to the present invention, it is preferable that the lower electrode of the light emitting element is formed in a substantially circular shape and the light emitting point is circular. The light emitting spot shape of the light emitting device can be changed by freely changing the shape of the lower electrode. However, the head used in the printer is required to have no defects in the printed result of printed characters, images, and the like. Therefore, when the present invention is applied to a printer head, it is preferable that the electrode shape itself is substantially circular so that an oblique straight line can be expressed smoothly.

  An electronic apparatus according to the present invention includes a display device using the light emitting device according to the present invention. In addition, an electronic apparatus according to the present invention is an image forming apparatus including the light emitting device described above.

Example 1
[Light emitting device]
Embodiments of the present invention will be described below with reference to the drawings. The light-emitting device according to the present invention is an organic electroluminescence device (hereinafter abbreviated as an organic EL device) in which self-emitting elements made of an organic functional material are arranged on a substrate. This light-emitting device can be suitably used as display means for electronic devices, for example.

  FIG. 1 is a circuit configuration diagram of the organic EL device of this embodiment. FIG. 2 is a diagram showing a planar structure of each pixel region 71 provided in the organic EL device. FIG. 2A is a diagram showing a configuration of a pixel driving portion such as a TFT mainly in the pixel region 71. FIG. 2B shows an electrode after the pixel driving portion is covered with an interlayer insulating film 240. FIG. FIG. FIG. 3 is a diagram showing a cross-sectional configuration along the line AA in FIG.

  As shown in FIG. 1, the organic EL device 70 includes a plurality of scanning lines 131, a plurality of signal lines 132 extending in a direction intersecting the scanning lines 131, and the signal lines 132 on a transparent substrate. A plurality of common power supply lines 133 extending in parallel are wired, and a pixel region 71 is provided at each intersection of the scanning lines 131 and the signal lines 132.

  For the signal line 132, a data side driving circuit 72 including a shift register, a level shifter, a video line, an analog switch, and the like is provided. On the other hand, for the scanning line 131, a scanning side driving circuit 73 including a shift register, a level shifter, and the like is provided. Each pixel region 71 includes a switching TFT (thin film transistor) 142 having a gate electrode to which a scanning signal is supplied via a scanning line 131, and a signal line 132 via the switching TFT (thin film transistor) 142. A holding capacitor cap that holds the supplied image signal, a driving TFT 143 that opens and closes a gate by the image signal held by the holding capacitor cap, and a pixel electrode through which a driving current flows from the common power supply line 133 via the driving TFT 143 141 and an organic functional layer 140 sandwiched between the pixel electrode 141 and the common electrode 154 are provided. An element constituted by the pixel electrode 141, the common electrode 154, and the organic functional layer 140 is a light emitting element.

  Under such a configuration, when the scanning line 131 is driven and the switching TFT 142 is turned on, the potential of the signal line 132 at that time is held in the holding capacitor cap, and depending on the state of the holding capacitor cap, The on / off state of the driving TFT 143 is determined. When a current flows from the common power supply line 133 to the pixel electrode 141 through the channel of the driving TFT 143 and further flows through the light emitting unit 140 to the common electrode 154, the light emitting unit 140 changes the luminance according to the amount of the flowing current. To emit light.

  Next, looking at the planar structure of the pixel region 71 shown in FIG. 2A, the pixel region 71 has four sides of the pixel electrode 141 having a substantially rectangular shape in plan view, the signal line 132, the common feed line 133, and the scanning line 131. And an arrangement surrounded by scanning lines (not shown) for other pixel electrodes. Further, in the cross-sectional structure of the pixel region 71 shown in FIG. 3, the driving TFT 143 is provided on the substrate P, and the light emitting element is formed on the plurality of insulating films 230 and 240 formed to cover the driving TFT 143. 200 is formed. The light emitting element 200 is mainly composed of the organic functional layer 140, and has a configuration in which the organic functional layer 140 is sandwiched between the pixel electrode 141 and the common electrode 154.

  As shown in FIG. 3, the driving TFT 143 includes a channel region 143c via a source region 143a and a drain region 143b formed in the semiconductor film 210, a channel region 143c, and a gate insulating film 220 formed on the surface of the semiconductor layer. The gate electrode 143A is opposed to the gate electrode 143A. A first interlayer insulating film 230 is formed on the semiconductor film 210 and the gate insulating film 220 so as to cover them, and contact holes 232 and 234 that reach the semiconductor film 210 through the first interlayer insulating film 230. There is. The drain electrode 236 and the source electrode 238 are electrically connected to the drain region 143b and the source region 143a through these contact holes, respectively. A wiring and an insulating film (second interlayer insulating film) 240 covering the wiring are formed on the first interlayer insulating film 230, and one of the pixel electrodes 141 is formed in the contact hole 245 a penetrating the second interlayer insulating film 240. Are connected. Then, the pixel electrode 141 and the drain electrode 236 are conductively connected, so that the driving TFT 143 and the pixel electrode 141 are electrically connected.

  The light-emitting element 200 includes a pixel electrode 141, two organic layers, a hole injection layer (charge transport layer) 140A and a light-emitting layer 140B, which are applied to cover the pixel electrode and the second interlayer insulating film 240. And a common electrode 154 that further covers the light emitting layer 140B. The shape and size of the pixel electrode 141 are the same as the shape and size of the light emitting portion, and the connection with the driving transistor 143 is made through the contact hole 245a on the lower side of the pixel electrode 141.

  In the case of a so-called top emission type organic EL device, the substrate P is configured to extract light from the side on which the light emitting element 200 is disposed. Therefore, in addition to a transparent substrate such as glass, an opaque substrate can also be used. As the opaque substrate, for example, ceramics such as alumina, a metal sheet such as stainless steel that has been subjected to an insulation treatment such as surface oxidation, a thermosetting resin or a thermoplastic resin, and a film thereof (plastic film), etc. Can be mentioned.

  The pixel electrode 141 is formed of a light-transmitting conductive material such as ITO (indium tin oxide) in the case of the bottom emission type that extracts light through the substrate P, but in the case of the top emission type, the light transmission is performed. It is not necessary to be made of a conductive material and can be formed of a suitable conductive material such as a metal material. In addition, when the organic EL device is a bottom emission type, the position of the contact hole 245a blocks light emission, and therefore it is necessary to connect the pixel electrode 141 near the TFT 143 with a necessary minimum area.

  The common electrode (upper electrode) 154 is formed in a state of covering the upper surface of the light emitting layer 140B. As a material of the common electrode 154, in the case of the top emission type, a transparent conductive material is used. ITO is suitable as the transparent conductive material, but other translucent conductive materials may be used.

  A cathode protective layer may be formed on the upper layer side of the common electrode 154. By providing such a cathode protective layer, an effect of preventing the common electrode 154 from being corroded during the manufacturing process can be obtained. The cathode protective layer can be formed of an inorganic compound, for example, a silicon compound such as silicon oxide, silicon nitride, or silicon nitride oxide. By covering the common electrode 154 with a cathode protective layer made of an inorganic compound, entry of oxygen or the like into the common electrode 154 can be satisfactorily prevented. The cathode protective layer is formed to a thickness of about 10 nm to 300 nm.

  Since the organic EL device 70 of the present example having the above-described configuration can obtain a light emitting layer with good film thickness uniformity over a wide range, light emission without unevenness can be obtained. In addition, the manufacturing process can be shortened because the barrier rib is eliminated and the configuration is simple.

[Manufacture of light emitting devices]
Hereinafter, a method for manufacturing a light emitting device using the organic EL element according to the present invention will be described with reference to FIGS. In this embodiment, a method for manufacturing the organic EL device 70 having the configuration shown in FIGS. 1 to 3 using a flexographic printing machine will be described as an example. 4 and 5 illustrate only a single pixel region 71 for the sake of simplicity, it is assumed that each pixel has a common configuration. In the organic EL device according to the present invention, both a configuration for taking out light of the light emitting element from the substrate side (bottom emission) and a configuration for taking out light from the side opposite to the substrate (top emission) can be adopted. This embodiment will be described as a top emission type organic EL device.

  First, as shown in FIG. 4A, a driving TFT 143 is formed on a substrate P. In the top emission type, since the substrate may be opaque, a ceramic sheet such as alumina, a metal sheet such as stainless steel that has been subjected to an insulation treatment such as surface oxidation, a thermosetting resin, a thermoplastic resin, or the like may be used. it can. Moreover, the glass substrate conventionally used for the liquid crystal device etc. may be sufficient. Next, a manufacturing procedure of the driving TFT 143 is illustrated.

First, a base protective film (not shown) made of a silicon oxide film having a thickness of about 200 to 500 nm is formed on the substrate P by plasma CVD using TEOS (tetraethoxysilane), oxygen gas or the like as a raw material. Thereafter, the substrate temperature is heated to about 350 ° C., an amorphous silicon film having a thickness of about 30 to 70 nm is formed on the surface of the substrate P by plasma CVD, and the semiconductor film 210 is patterned using a known photolithography technique. Then, the semiconductor film 210 is subjected to a crystallization process such as laser annealing or solid phase growth to form a polysilicon film. In the laser annealing method, for example, a line beam having an excimer laser beam length of 400 mm can be used, and its output intensity is 200 mJ / cm ² . For the line beam, the line beam is scanned so that a portion corresponding to 90% of the peak value of the laser intensity in the short dimension direction overlaps for each scanning region.

  Next, a gate insulating film 220 made of a silicon oxide film or a nitride film having a thickness of about 60 to 150 nm is formed on the surface of the semiconductor film 210 and the substrate P by plasma CVD using TEOS, oxygen gas, or the like as a raw material. The semiconductor film 210 becomes the channel region and the source / drain region of the driving TFT 143 shown in FIG. 3, and at the same time, the semiconductor film becomes the channel region and the source / drain region of the switching TFT 142 at other positions. It also becomes. That is, in the process of manufacturing the driving TFT 143 shown in FIG. 4A, two types of transistors 142 and 143 are manufactured at the same time.

  Next, after forming a metal film such as aluminum, tantalum, molybdenum, titanium, or tungsten, or a conductive film made of a laminated film of these by sputtering or the like, the gate electrode 143A is formed by patterning. Subsequently, by implanting high-concentration phosphorus ions into the semiconductor film 210, source / drain regions 143a and 143b are formed in a self-aligned manner with respect to the gate electrode 143A. At this time, a channel region 143c is a portion which is shielded by the gate electrode 143A and no impurity is introduced. Thereafter, an interlayer insulating film 230 that covers the surface of the semiconductor film 210 and the substrate P is formed.

  Next, contact holes 232 and 234 penetrating the interlayer insulating film 230 are formed, and a drain electrode 236 and a source electrode 238 are formed through the contact holes 232 and 234 to obtain a driving TFT 143. Here, a common power supply line (wiring) and a scanning line (not shown) are also formed on the interlayer insulating film 230 so as to be connected to the source electrode 238. Further, a second interlayer insulating film 240 is formed so as to cover the upper surface of the interlayer insulating film 230 and each wiring, and the contact hole 245a reaching the wiring from the drain electrode 236 through the second interlayer insulating film 240 is penetrated. Set up. The contact hole 245a can be placed anywhere below the pixel electrode 141. Further, a plurality of locations may be provided in consideration of conductivity.

  Next, as shown in FIG. 4B, a pixel electrode 141 is formed by patterning using a known photolithography technique in a region that does not overlap with the driving TFT 143 and includes the contact hole 245a. Thereby, the pixel electrode 141 is formed at a position surrounded by the signal line, the common power supply line, and the scanning line as shown in FIG. The contact between the extended portion from the drain electrode 236 and the pixel electrode 141 proceeds simultaneously with the formation of the thin film of the electrode 141, and is established by filling the contact hole with an electrode material. Further, from the viewpoint of connection reliability, the connection may be made after metallization with a conductive material as an intermediary, for example, a different material. In the case of the top emission type, all of the drain electrode, the wiring, and the pixel electrode are made of metal, so that connection can be made without any problem. In the case of the bottom emission type, the pixel electrode is made of transparent indium tin oxide (ITO), indium zinc oxide (IZO) or the like, but is compatible with the metal wiring material.

  In the case of this embodiment (top emission type), the pixel electrode 141 does not need to be a transparent conductive film, and can be formed of a metal material. If the pixel electrode 141 is formed of a light-reflective metal film such as aluminum or silver, light incident on the pixel electrode can be reflected and emitted to the viewer side. In the present organic EL device 70, since the pixel electrode 141 functions as an anode, it is preferable that the pixel electrode 141 is formed of a material having a work function of 4.8 eV or more. For example, an ITO / Al laminated film, Au, Pt It is good to form with the metal film which consists of etc. Prior to the formation of the pixel electrode 141, a process for cleaning the surface of the second interlayer insulating film 240 (for example, an oxygen plasma process, a UV irradiation process, an ozone process, or the like) may be performed. Thereby, the adhesion between the pixel electrode 141 and the second interlayer insulating film 240 can be improved.

  Next, as shown in FIG. 4C, a liquid material 140a containing a hole injection layer forming material is selectively applied to an application position by a flexographic printing apparatus. As the hole injection layer forming material, for example, a polythiophene derivative, a polypyrrole derivative, or a doped body thereof can be used. Specifically, 3,4-polyethylenedioxythiophene / polystyrene sulfonic acid (PEDOT / PSS) dispersion, that is, 3,4-polyethylenedioxythiophene is dispersed in polystyrene sulfonic acid as a dispersion medium. An aqueous solution in which water is dispersed is used.

  After the application of the liquid material 140a, as shown in FIG. 5A, the substrate P is heated by a heating means (heater or the like) 300 installed on the lower surface of the substrate P, and the liquid material 140a is dried and solidified. As an example of the drying conditions, baking is performed at 200 ° C. for about 10 minutes in an air environment or a nitrogen gas atmosphere. Or you may accelerate | stimulate the removal of a solvent by installing in the pressure environment (under reduced pressure environment) lower than atmospheric pressure.

  Subsequently, as shown in FIG. 5B, a liquid material 140b containing a light emitting layer forming material and a solvent is selectively applied onto the hole injection layer 140A as described above. As this light emitting layer forming material, for example, a material containing a precursor of a conjugated polymer organic compound and a fluorescent dye for changing the light emission characteristics can be suitably used. The precursor of the conjugated polymer organic compound is formed into a thin film together with a fluorescent dye or the like, and then cured by heating to become a conjugated polymer organic EL layer.

  Such a conjugated polymer organic compound is solid and has strong fluorescence, and can form a homogeneous solid ultrathin film. In addition, the adhesion with the ITO electrode is high. Furthermore, before the heat curing, the precursor solution can be adjusted to an optimum viscosity for coating, and a thin film can be formed easily and in a short time.

  As the precursor, for example, PPV (polypara-phenylene vinylene) or a precursor thereof is preferable. Since the precursor of PPV or its derivative is soluble in water or an organic solvent and can be polymerized, a high-quality thin film can be obtained optically. Furthermore, PPV has strong fluorescence, and double-bonded π electrons are also nonpolar conductive polymers on the polymer chain, so that a high-performance light-emitting element can be obtained.

  The precursor of the PPV or PPV derivative is soluble in water as described above, and is polymerized by heating after film formation to form a PPV layer. The content of the precursor typified by the PPV precursor is preferably 0.01 to 10.0 wt%, more preferably 0.1 to 5.0 wt% with respect to the entire liquid material composition. If the amount of the precursor added is too small, it is insufficient to form a conjugated polymer film, and if it is too large, the viscosity of the liquid material composition will be high and may not be suitable for high-precision patterning by printing. .

  Furthermore, the light emitting layer forming material preferably contains at least one fluorescent dye. As a result, the light emission characteristics of the light emitting layer can be changed. For example, it becomes a means for improving the light emission efficiency of the light emitting layer or changing the light absorption maximum wavelength (light emission color).

  As the fluorescent dye, rhodamine or a rhodamine derivative that emits red light can be used when a red light emitting layer is formed. In the case of forming a green light emitting layer, quinacridone and its derivatives that emit green light can be used. Furthermore, when forming a blue light emitting layer, distyryl biphenyl and its derivatives which emit blue light can be used. Since these fluorescent dyes are low in molecular weight, they are soluble in a water / alcohol mixed solution, have good compatibility with PPV, and can easily form a light emitting layer. As for the above fluorescent dyes, only one kind of each color may be used, or two or more kinds may be mixed and used.

  These fluorescent dyes are preferably added in an amount of 0.5 to 10 wt%, more preferably 1.0 to 5.0 wt%, based on the solid precursor of the conjugated polymer organic compound. If the amount of the fluorescent dye added is too large, it will be difficult to maintain the weather resistance and durability of the light emitting layer. On the other hand, if the amount added is too small, the effect of adding the fluorescent dye as described above cannot be obtained sufficiently.

  The precursor and the fluorescent dye are preferably dissolved or dispersed in a polar solvent to form a liquid material, and this liquid material is preferably used for printing and coating. The polar solvent can easily dissolve or uniformly disperse the precursor, the fluorescent dye, and the like. Specific examples of such polar solvents include water, alcohols compatible with water such as methanol and ethanol, N, N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), dimethylimidazoline (DMI), Examples include organic solvents or inorganic solvents such as dimethyl sulfoxide (DMSO), xylene, cyclohexylbenzene, and 2,3-dihydrobenzofuran, and two or more of these solvents may be appropriately mixed.

  When the liquid material 140b including the light emitting layer forming material of each color is applied in this manner, the solvent in the liquid material 140b is evaporated in the same manner as in the previous step of forming the hole injection layer 140A. By this step, as shown in FIG. 5C, a solid light emitting layer 140B is formed on the hole injection layer 140A, and thereby an organic functional layer 140 composed of the hole injection layer 140A and the light emitting layer 140B is obtained. . In addition, about the evaporation of the solvent in the liquid material 140b containing a luminescent material, processing, such as a heating or pressure reduction, is performed as needed.

  Next, as shown in FIG. 5C, the common electrode 154 made of a transparent conductive material such as ITO is formed on the entire top surface of the substrate P or in a stripe shape. Since ITO has a large work function and poor electron injection property, a thin film such as magnesium or lithium is attached to the ITO interface to treat the cathode. ITO itself is formed by methods such as vapor deposition, ion plating, and sputtering. In this way, the light emitting element 200 is obtained. The light-emitting element 200 in this embodiment includes a pixel electrode (anode) 141, a hole injection layer 140A, a light-emitting layer 140B, and a common electrode (cathode) 154. In addition to this, a hole transport layer, an electron A transport layer and an electron injection layer may be provided.

  Note that, when the present invention is applied to the bottom emission structure, it is necessary to devise the wiring connecting the pixel electrode 141 and the drain electrode 236 and the position of the contact hole 245a. That is, it is necessary to install in a place where wiring and contact holes do not block light emission. It seems that the periphery and the vicinity of the pixel electrode 141 are appropriate positions.

  In the above embodiment, it is described that a flexographic printing machine is used for forming the organic functional layer. However, other than this, a droplet discharge method using a droplet discharge device, a slit coat (or curtain coat) method, a die coat method, etc. The coating method can also be used. In addition, the liquid material generation step and the film formation step may be performed in an air environment or in an inert gas atmosphere such as nitrogen gas. In addition, it is desirable that the adjustment of the liquid material and the printing process be performed in a clean room in an environment where particles and chemical cleanliness are maintained.

  As described above, the present invention makes the partition unnecessary by changing the structure of the lower electrode. Further, since the partition walls are eliminated, the organic thin films (140A and 140B) can be formed by printing and a light emitting layer having no film thickness variation over a wide range can be obtained. As a result, it is possible to obtain an organic EL device, for example, a display device, which has no luminance unevenness and excellent emission characteristics. Furthermore, since the light emitting region of the light emitting device of the present invention is determined by the shape and size of the pixel electrode, an organic EL device in which the shape of the light emitting point can be freely changed is realized.

[Printer for organic functional layer]
FIG. 6 is a configuration diagram of the flexographic printing apparatus used in the first embodiment. A flexographic printing apparatus 60A shown in FIG. 6 is a so-called doctor roll type flexographic printing apparatus, and a printing plate roll 61 that supports a flexographic printing plate 61a on its peripheral surface, and a liquid material is applied to the flexographic printing plate 61a. An anilox roll 62 to be performed and a doctor roll 63 for applying a liquid material to the peripheral surface of the anilox roll 62 are configured. In order to apply the liquid material to the substrate 11 by the flexographic printing apparatus 60A, first, the liquid material 13a is supplied between the doctor roll 63 and the anilox roll 62 while the three rolls 61 to 63 are rotated. Then, a small amount of the liquid material 13a is supplied to the peripheral surface of the anilox roll 62 from the gap between the doctor roll 63 and the anilox roll 62, and the liquid material 13a is applied from the anilox roll 62 to the flexographic printing plate 61a. When the substrate 11 is passed through a position close to the peripheral surface of the printing plate roll 61 in such an operating state, the liquid material 13a held on the surface of the flexographic printing plate 61a is transferred onto the substrate 11. According to this printing apparatus 60A, the liquid material 13a can be applied onto the substrate 11 in a pattern corresponding to the planar shape of the flexographic printing plate 61a.

  The flexographic printing apparatus 60B shown in FIG. 7 is a so-called doctor blade type flexographic printing apparatus, and includes a doctor blade 64 instead of the doctor roll 63 of the flexographic printing apparatus 60A shown in FIG. The flexographic printing apparatus 60B is similar to the flexographic printing apparatus 60A except that a doctor blade 64 having a tip portion disposed close to the peripheral surface of the anilox roll 62 is used when supplying the liquid material 13a to the peripheral surface of the anilox roll 62. Even when such a printing apparatus 60B is used, it is possible to apply the liquid material 13a on the substrate 11 in a predetermined plane pattern.

  A die coater (coating apparatus) 50 shown in FIG. 8 is mainly composed of a die 51 and a liquid material supply unit 52. The liquid material supply unit 52 includes, for example, a material container that stores the liquid material, and a pump that conveys the liquid material from the material container to the die 51. In addition, a valve for adjusting the flow rate of the liquid material and a buffer for keeping the supply pressure of the liquid material constant may be provided. With such a configuration, the die coater 50 is disposed in the die 51 from the liquid material supply unit 52 while the tip of the die 51 is disposed close to the substrate 11 and the substrate 11 is moved in the direction of the arrow in the figure. By supplying the liquid material to the nozzle portion 51a, a certain amount of the liquid material 13a can be applied on the substrate 11. Furthermore, the liquid material 13a can be applied on the substrate 11 in a predetermined plane pattern by combining the transport operation of the substrate 11 and the supply / stop operation of the liquid material from the die 51.

  FIG. 9 is a plan configuration diagram showing an example of an application form of the liquid material 13 a to the substrate 11. On the substrate 11 shown in FIG. 9A, an anode 12 constituting an organic EL element is formed in a rectangular shape in plan view, and a liquid material 13 a is applied so as to cover the anode 12. Further, on the substrate 11, there are areas (non-application areas) 13x and 13y where the liquid material 13a is not applied, and these non-application areas are electrically connected to, for example, the cathode 14 of the organic EL element. And a terminal part for connecting the organic EL element and an external circuit, and the like.

  Also, as shown in FIG. 9B, when a plurality of anodes 12 are arranged on the substrate 11 so as to form a plurality of organic EL elements, the liquid is collectively covered so as to cover the plurality of anodes 12. The material 13a is applied, and an organic thin film is formed so that the liquid material 13a does not touch the non-application areas 13x1 and 13x2 on both sides in the y direction of the application area.

  As described above, when forming the organic EL element on the substrate 11, the printing machine used in this example uses the organic thin film liquid material 13 a constituting the organic EL layer as the organic thin film in the region on the substrate 11. The organic thin film is formed by selectively applying only to the region where the film is to be formed. Therefore, unlike the case where patterning is performed after forming an organic thin film on the entire surface of the substrate, the organic EL device is manufactured using the material with high efficiency without removing and discarding the excess organic thin film. be able to. In addition, the liquid material is not applied in advance to the area on the substrate that does not require the organic thin film, so that even if a terminal or the like is formed in the same area, the connection reliability of the terminal may be impaired. Will not be damaged. Thus, the film formation by printing is suitable for an organic EL device having a high yield and high reliability.

  In the present invention, since the liquid material is applied using a commercially available coating apparatus as shown in FIGS. 6 to 8, it is possible to apply the liquid material to a large area substrate with good uniformity. it can. And since the organic thin film of a uniform film thickness can be formed, it can also contribute to the luminous efficiency improvement of an organic EL element.

(Example 2)
[Printer head]
Next, a printer head that can suitably use a light-emitting device using the organic EL element of Example 1 (hereinafter abbreviated as an organic EL device) will be described with reference to FIGS. Although this embodiment is described using a top emission type organic EL device, a bottom emission type organic EL device may be used.

  FIG. 10 is a diagram schematically showing a printer head to which the organic EL device according to the present invention is applied. FIG. 10A is a plan view, and FIG. 10B is a side view. The printer head 1 is used as an exposure unit of an image forming apparatus, which will be described later, and has a single color structure in which a plurality of organic EL elements 3 are arranged in one or several rows on an elongated rectangular element substrate 2. The light emitting element array 3a, the drive element 4 for driving the organic EL element 3, and the control circuit 5 for controlling these drive elements are integrally formed. Therefore, this corresponds to the simple case of the organic EL device having the two-dimensional arrangement described in the first embodiment. Even in the case of a one-dimensional array, the interval between pixels is reduced by arranging in a staggered arrangement as shown in FIG.

  Next, as shown in FIG. 10B, there is a sealing substrate 6 for sealing the organic EL element 3 on the surface of the element substrate 2, which is bonded by a transparent adhesive. . Since this embodiment is a top emission type, the sealing substrate 6 is made of a transparent substrate such as glass. Further, the printer head 1 includes a heat radiating plate 7 made of a metal such as aluminum on the back surface side of the element substrate 2. The heat radiating plate 7 prevents an increase in the ambient temperature of the organic EL element 3 and prevents a decrease in light emission efficiency and life of the organic EL element 3.

  As shown in FIG. 10A, power lines 8 and 9 are connected to the driving TFT 4 formed on the element substrate 2, and a power source (not shown) is connected via these power lines 8 and 9. Thus, a voltage is applied to the source of the driving TFT 4. The light emitting operation of the organic EL element 3 is controlled by the driving TFT 4 controlled by the control circuit 5. Further, the printer head 1 may be provided with a temperature measuring unit for measuring the temperature of the light emitting element array 3a or the vicinity thereof.

  Further details of each unit configuration of the printer head 1 will be described. FIG. 11 is a plan view showing the main configuration of the printer head 1. In FIG. 11, only the outer shape of the cathode 154 is shown, and the middle part is a view seen through the lower part. In addition, since sectional drawing becomes the same as that of FIG. 3, the corresponding number was attached | subjected using the parenthesis in FIG.

  In FIG. 11, the power supply line 8 is connected to the source electrode of the driving TFT 4, and the power supply line 9 is connected to the cathode 154 of the organic EL element 3 via the wiring 30. The second interlayer insulating film 240 (transparent in the figure) shown in FIG. 3 is formed so as to cover the driving TFT 4 and the driving wiring. In the present embodiment, the pixel electrode 141 has a substantially circular shape, and is connected to the wiring coming from the drain electrode of the driving TFT 4 below the electrode via a contact hole. On the pixel electrode 141 and its surrounding interlayer insulating film, an organic thin film composed of two layers of a hole injection layer and a light emitting layer is laminated, and these are applied so as to completely cover the pixel electrode 141 by the printing method described above. Is done. The application area may be substantially the same as the cathode 154. That is, the hole injection layer and the light emitting layer formed planarly by printing are formed in a stripe shape as shown in the figure, and further, the cathode 154 covers the top. The cathode 154 is connected to the power supply line 9 via the wiring 30 located on the interlayer insulating film or at a position away from the interlayer insulating film. In this embodiment, the light emission shape is the same circular spot as that of the pixel electrode 141, and the shape is optimal for the line printer head.

  FIG. 12 shows a staggered arrangement of light emitting portions. It is substantially the same as FIG. The difference is that since the light emitting portions are arranged in a staggered manner, the wiring extending from the drain electrode of the driving TFT 4 differs between the adjacent light emitting elements 3. That is, the connection wiring from the driving TFT 4 to the pixel electrode 141 of each light emitting element 3 is freely extended to the position of the pixel electrode 141 and then contacted at the lower part of the pixel electrode 141. In FIG. 12, the cathode 154 of the light emitting element 3 is not covered up to the top of the driving TFT 4. The two organic layers, the hole injection layer and the light-emitting layer, formed by printing are similarly in the same size as the cathode 154 or in a smaller band shape. Moreover, there is no problem even if the shape protrudes from the cathode. The cathode 154 is connected to the power supply line 9 via the wiring 30.

  In the printer head having such a configuration, the emission color is preferably a single color emission corresponding to the emission wavelength band of red. However, of course, an emission color corresponding to green or blue in the emission wavelength band may be adopted. In short, the emission color may be adapted to the best sensitivity wavelength region of the photoreceptor of the image forming apparatus described later.

  In addition, in the printer head of this embodiment, the power supply wirings 8 and 9 can be routed in the non-application area of the organic thin film, and the input terminal portion connected thereto can be provided. As described above, the printer head according to the present embodiment is capable of simple strip-like printed film formation when forming the hole injection layer and the light emitting layer, and the power line and the terminal portion arranged outside the organic thin film. Since the liquid material for forming the layer does not come into contact, the reliability of the power supply line and the terminal portion due to the residue of the organic thin film does not occur. Therefore, according to the present invention, a printer head having excellent reliability can be provided at low cost.

(Example 3)
[Image forming apparatus 1]
Next, an image forming apparatus provided with the printer head 1 of the present invention will be described. FIG. 13 is a diagram illustrating a configuration of an image forming apparatus which is an embodiment of the electronic apparatus according to the invention. In the image forming apparatus 80 shown in FIG. 13, the printer heads 81K, 81C, 81M, and 81Y of the above-described embodiment are exposed to four photosensitive drums (image carriers) 82K, 82C, 82M, and 82Y having the same configuration. These are arranged in each device and are called tandem systems.

  This image forming apparatus 80 includes a driving roller 83, a driven roller 84, and a tension roller 85, and an intermediate transfer belt 86 is stretched around these rollers so as to circulate in the direction of the arrow (counterclockwise) in FIG. It is a thing. Photoconductors 82K, 82C, 82M, and 82Y are arranged at predetermined intervals with respect to the intermediate transfer belt 86. These photoreceptors 82K, 82C, 82M, and 82Y have a photosensitive layer as an image carrier on their outer peripheral surfaces.

  Here, K, C, M, and Y in the above symbols mean black, cyan, magenta, and yellow, respectively, and indicate that the photoconductors are for black, cyan, magenta, and yellow, respectively. The meanings of these symbols (K, C, M, Y) are the same for the other members. The photoreceptors 82K, 82C, 82M, and 82Y are driven to rotate in the arrow direction (clockwise) in FIG. 13 in synchronization with the drive of the intermediate transfer belt 86.

  Around each photosensitive member 82 (K, C, M, Y), charging means (corona charger) 87 (K) for uniformly charging the outer peripheral surface of the photosensitive member 82 (K, C, M, Y), respectively. , C, M, Y) and the outer peripheral surface uniformly charged by the charging means 87 (K, C, M, Y) are synchronized with the rotation of the photosensitive member 82 (K, C, M, Y). And an organic EL printer head 81 (K, C, M, Y) of the present invention that sequentially performs line scanning.

  Further, a developing device 88 (K) that applies toner as a developer to the electrostatic latent image formed by the organic EL printer head 81 (K, C, M, Y) to form a visible image (toner image). , C, M, Y) and a primary transfer roller 89 (K, C, M, Y) for sequentially transferring the toner image developed by the developing device 88 (K, C, M, Y) to the intermediate transfer belt 86 as a primary transfer target. C, M, Y) and a cleaning device 90 (K, C, M, Y) for removing toner remaining on the surface of the photosensitive member 82 (K, C, M, Y) after being transferred. It has been.

  Each of the organic EL printer heads 81 (K, C, M, Y) is installed such that the direction of the light emission point is along the bus line of the photosensitive drum 82 (K, C, M, Y). The emission energy peak wavelength of each organic EL printer head 81 (K, C, M, Y) and the sensitivity peak wavelength of the photosensitive member 82 (K, C, M, Y) are set so as to substantially match. Yes. Each organic EL printer head 81 (K, C, M, Y) is supported and attached to the image forming apparatus 80 by a support member.

  The developing device 88 (K, C, M, Y) uses, for example, a non-magnetic one-component toner as a developer. The film thickness of the adhered developer is regulated by a regulating blade, and the developing roller is brought into contact with or pressed against the photoreceptor 82 (K, C, M, Y), whereby the photoreceptor 82 (K, C, M, A developer is attached in accordance with the potential level of Y) and developed as a toner image.

  The black, cyan, magenta, and yellow toner images formed by the four-color single-color toner image forming station are intermediated by the primary transfer bias applied to the primary transfer roller 89 (K, C, M, Y). Primary transfer is sequentially performed on the transfer belt 86. The toner images, which are sequentially superimposed on the intermediate transfer belt 86 and become full color, are secondarily transferred to the recording medium P such as paper by the secondary transfer roller 91 and further pass through the fixing roller pair 92 as a fixing unit. Is fixed on the recording medium P. Thereafter, the paper is discharged onto a paper discharge tray 94 formed on the upper part of the apparatus by a pair of paper discharge rollers 93.

  In FIG. 13, reference numeral 95 denotes a paper feeding cassette in which a large number of recording media P are stacked and held, 96 denotes a pickup roller for feeding the recording media P from the paper feeding cassette 95 one by one, and 97 denotes secondary transfer. A pair of gate rollers for defining the supply timing of the recording medium P to the secondary transfer portion of the roller 91; a secondary transfer roller 91 as a secondary transfer means for forming a secondary transfer portion with the intermediate transfer belt 86; A cleaning blade 98 serves as a cleaning unit that removes toner remaining on the surface of the intermediate transfer belt 86 after the secondary transfer. As described above, since the image forming apparatus of FIG. 12 uses the organic EL printer head 81 (K, C, M, Y) as the exposure means (writing means), for example, compared with the case where a laser scanning optical system is used. Therefore, it is possible to reduce the size of the apparatus.

[Image forming apparatus 2]
Next, an image forming apparatus according to another embodiment of the present invention will be described. FIG. 14 is a longitudinal side view showing another embodiment of the image forming apparatus. In FIG. 14, the image forming apparatus 100 includes image writing means (exposure means) provided with a developing device 101 having a rotary structure, a photosensitive drum 105 functioning as an image carrier, and the organic EL printer head as main constituent members. ) 107, an intermediate transfer belt 109, a paper conveyance path 114, a fixing roller heating roller 112, and a paper feed tray 118.

  The developing device 101 is configured such that the developing rotary 101a rotates in the direction of arrow A about a shaft 101b. The interior of the development rotary 101a is divided into four, and image forming units for four colors of yellow (Y), cyan (C), magenta (M), and black (K) are provided. Reference numerals 102a to 102d are arranged in the image forming units of the four colors, and the developing rollers 103a to 103d that rotate in the direction of arrow B are toner supply rollers that rotate in the direction of arrow C. 104a to 104d are regulating blades that regulate the toner to a predetermined thickness.

  In FIG. 14, reference numeral 105 denotes a photosensitive drum that functions as an image carrier as described above, 106 denotes a primary transfer member, and 108 denotes a charger. Reference numeral 107 denotes an image writer serving as an exposure means in the present invention, which comprises the organic EL printer head of the present invention. The photosensitive drum 105 is rotationally driven in the direction of arrow D, which is the opposite direction to the developing roller 102a, by a drive motor (not shown), for example, a step motor. The organic EL printer head constituting the image writing means 107 is disposed in a state where the alignment (optical axis alignment) is performed between this and the imaging lens (not shown) and the photosensitive drum 105. Yes.

  The intermediate transfer belt 109 is stretched between the driving roller 110a and the driven roller 110b. The drive roller 110 a is connected to the drive motor of the photosensitive drum 105 and transmits power to the intermediate transfer belt 109. That is, by driving the drive motor, the drive roller 110a of the intermediate transfer belt 109 is rotated in the direction of arrow E, which is the opposite direction to the photosensitive drum 105.

  The paper transport path 114 is provided with a plurality of transport rollers, paper discharge roller pairs 116, and the like, so that the paper is transported. An image (toner image) on one side carried on the intermediate transfer belt 109 is transferred to one side of the paper at the position of the secondary transfer roller 111. The secondary transfer roller 111 is brought into contact with and separated from the intermediate transfer belt 109 by a clutch. When the clutch is turned on, the secondary transfer roller 111 is brought into contact with the intermediate transfer belt 109 so that an image is transferred onto a sheet.

  The sheet on which the image has been transferred as described above is then subjected to a fixing process by a fixing device having a fixing heater H. The fixing device is provided with a heating roller 112 and a pressure roller 113. The sheet after the fixing process is drawn into the discharge roller pair 116 and proceeds in the direction of arrow F. When the paper discharge roller pair 116 rotates in the opposite direction from this state, the paper reverses its direction and advances on the duplex printing conveyance path 115 in the direction of arrow G. 117 is an electrical component box, 118 is a paper feed tray for storing paper, and 119 is a pickup roller provided at the outlet of the paper feed tray 118.

  For example, a low-speed brushless motor is used as a drive motor for driving the transport roller in the paper transport path. Further, a step motor is used for the intermediate transfer belt 109 because color misregistration correction or the like is necessary. Each of these motors is controlled by a signal from a control means (not shown).

  In the state shown in FIG. 14, a yellow (Y) electrostatic latent image is formed on the photosensitive drum 105, and a high voltage is applied to the developing roller 102a, whereby a yellow image is formed on the photosensitive drum 105. Is done. When all of the yellow back side and front side images are carried on the intermediate transfer belt 109, the development rotary 101a rotates 90 degrees in the direction of arrow A.

  The intermediate transfer belt 109 rotates once and returns to the position of the photosensitive drum 105. Next, two images of cyan (C) are formed on the photosensitive drum 105, and this image is carried on the yellow image carried on the intermediate transfer belt 109. Thereafter, the 90-degree rotation of the development rotary 101 and the one-rotation process after the image is carried on the intermediate transfer belt 109 are repeated in the same manner.

  For carrying four color images, the intermediate transfer belt 109 rotates four times, and then the rotation position is further controlled to transfer the image onto the sheet at the position of the secondary transfer roller 111. The paper fed from the paper feed tray 118 is transported by the transport path 114, and the above color image is transferred to one side of the paper at the position of the secondary transfer roller 111. The sheet on which the image is transferred on one side is reversed by the pair of discharge rollers 116 as described above, and waits on the conveyance path. Thereafter, the sheet is conveyed to the position of the secondary transfer roller 111 at an appropriate timing, and the above color image is transferred to the other side. The housing 120 is provided with an exhaust fan 121.

  The image forming apparatus including the organic EL printer head has been described as an example of the electronic apparatus of the present invention. However, the image forming apparatus including the printer head of the present invention is not limited to the above-described embodiment. Various modifications are possible.

(Other electronic devices)
FIG. 15 is a perspective view showing a mobile phone which is an electronic apparatus provided with the light emitting device of the above embodiment in a display unit. A cellular phone 1300 is mainly composed of a display unit 1301, an operation unit 1302, a reception unit 1303, and a transmission unit 1304, and the display unit 1301 includes the organic EL device according to the embodiment. is there. This mobile phone is an excellent mobile phone that is easy to read because a bright self-luminous display is obtained on the display unit.

It is a basic circuit block diagram of the organic electroluminescent apparatus which concerns on an Example. (A) is a top view which shows the structure of a pixel area | region, (b) is a top view which shows a pixel electrode. It is sectional drawing which follows the AA line of Fig.2 (a). It is process sectional drawing which shows the film-forming process which concerns on the Example of this invention. It is process sectional drawing (continuation) which shows the film-forming process based on the Example of this invention. It is a block diagram of the printing apparatus used for a film-forming process. It is a block diagram of the other printing apparatus used for a film-forming process. It is a block diagram of the other printing apparatus used for a film-forming process. It is a top view which shows the state of the film-forming which concerns on an Example. (A) is a top view of the printer head according to the embodiment, and (b) is a side view of the same. It is a top view which shows the partial structure of the printer head which concerns on an Example. It is a top view which shows the partial structure of the other printer head based on an Example. 1 is a configuration diagram of an image forming apparatus according to an embodiment. FIG. 6 is a configuration diagram of another image forming apparatus according to an embodiment. It is a perspective lineblock diagram showing an example of electronic equipment. It is a structure sectional view of the organic EL device by the conventional technology.

Explanation of symbols

  1 printer head, 2 element substrate (substrate), 3 organic EL element, 4 driving TFT, 5 control circuit, 6 sealing substrate, 7 heat sink, 11 substrate, 12 anode, 13 organic EL layer, 70 organic EL device, 71 pixel region, 72 data side drive circuit, 73 investigation side drive circuit, 131 scanning line, 132 signal line, 133 feeder line, 140 organic functional layer, 141 pixel electrode, 142 switching TFT, 143 drive TFT, 154 common electrode 200 light emitting element, 210 semiconductor film, 220 gate insulating film, 230 first interlayer insulating film, 236 drain electrode, 238 source electrode, 240 second interlayer insulating film, 245a contact hole.

Claims (11)

In a light emitting device including a plurality of thin film transistors formed on a substrate and a light emitting element driven by the thin film transistors,
The lower electrode of the light emitting element is disposed in a region that does not overlap the region where the thin film transistor is formed, the size of the lower electrode is smaller than the size of the light emitting layer of the light emitting element, and the lower electrode and the thin film transistor Making an electrical connection under the lower electrode,
A light emitting device characterized by the above.   The light-emitting device according to claim 1, wherein the light-emitting element is an electroluminescence element including a light-emitting layer made of an organic thin film.   3. The light emitting device according to claim 2, wherein at least one layer of the organic thin film is formed by planarly applying a liquid material.   4. The light emitting device according to claim 3, wherein at least one layer of the organic thin film is applied across a plurality of the light emitting elements.   5. The light-emitting device according to claim 1, wherein the light-emitting layer of the light-emitting element includes light-emitting layers having the same light emission color.   2. The lower electrode according to claim 1, wherein the lower electrode is formed on an insulating film that covers the thin film transistor and a layer in which the driving wiring of the light emitting element is formed, and is penetrated through the insulating film in contact with the lower electrode. A light-emitting device, wherein the thin film transistor and the lower electrode are electrically connected through a contact hole.   7. The light emitting device according to claim 6, wherein the thin film transistor is electrically connected to the thin film transistor by a conductive member or wiring extended from a source / drain electrode of the thin film transistor and a conductive member formed in the contact hole. apparatus.   8. The light emitting device according to claim 7, wherein the conductive member formed in the contact hole includes the same material as the lower electrode.   A printer head comprising the light emitting device according to claim 1.   10. The printer head according to claim 9, wherein the lower electrode of the light emitting element is formed in a substantially circular shape, and the light emitting point is circular. An electronic apparatus comprising the light emitting device according to any one of claims 1 to 8, or the printer head according to claim 9 or 10.

Images