JP2007080910A - Organic electroluminescent element, exposure device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent element in which emission intensity distribution in a light emitting face is uniform even if a light emitting layer is formed by using a wet process; and to provide an exposure device where emission intensity distribution of the organic electro luminescent elements is uniform, and an image forming device of high image quality, which uses the exposure device. <P>SOLUTION: The element is provided with a glass substrate 2, a first electrode 3 formed on the glass substrate 2, an insulating layer 4 formed to cover a part of at least the first electrode 3, the light emitting layer 8, and a second electrode 9 which is brought into contact with the light emitting layer 8 and which is arranged to face the first electrode 3. An intermediate layer 5 in prescribed thickness is disposed between the first electrode 3 and the light emitting layer 8, and between the insulating layer 4 and the light emitting layer 8. The intermediate layer 5 is constituted of an inorganic layer 6 formed by using a dry process, and an organic layer 7 formed by using the wet process. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic electroluminescent element which is an electroluminescent element used for various light sources, an exposure apparatus using the organic electroluminescent element as a light source, and an image forming apparatus equipped with the exposure apparatus.

  An organic electroluminescent element is a light emitting device utilizing the electroluminescence phenomenon of a solid fluorescent material, and has already been put into practical use as a small display.

  Organic electroluminescent devices can be classified into several groups based on the difference in materials used for the light emitting layer. One typical example is a low molecular weight organic electroluminescent device using a low molecular weight organic compound in a light emitting layer, which is mainly produced by using a vacuum deposition method. The other is a polymer organic electroluminescent device using a polymer compound in the light emitting layer.

  A polymer organic electroluminescent device uses a solution in which materials constituting each functional layer are dissolved to form a film by a spin coating method, an ink jet method, a slit coating method, a dip coating method, a printing method, etc. A film forming process having a simple characteristic that is a feature of a process for producing a polymer electroluminescent element using a means for applying a liquid material to a thin film is called a “wet process.” In contrast, a vacuum deposition method is used. The film forming process represented by sputtering method, CVD method, etc. is referred to as “dry process”.) As a technology that can be expected to reduce the cost and increase the area from the simple process. Attention has been paid.

  FIG. 9 is a cross-sectional view showing the structure of a conventional polymer organic electroluminescent device.

  Hereinafter, the structure of a conventional organic electroluminescent element and the production procedure thereof will be described with reference to FIG.

  In the following description, the polymer organic electroluminescent element is simply referred to as “organic electroluminescent element”. In addition, when it is necessary to distinguish between them, the distinction between high molecules and low molecules will be shown.

  A typical organic electroluminescent element 11 is produced by laminating a plurality of functional layers such as a charge injection layer (PEDOT layer 10 described later) and a light emitting layer 18 between an anode 13 and a cathode 19.

  First, an ITO (indium tin oxide) film is formed as the anode 13 and then patterned into a predetermined shape by etching, and an electric charge is injected onto the glass substrate 12 in which an insulating layer 14 is disposed so as to obtain a desired light emission shape. PEDOT: PSS (mixture of polythiophene and polystyrene sulfonic acid: hereinafter referred to as PEDOT) as a layer is formed into a film by a spin coating method which is a wet process. The PEDOT layer 10 is a material that has become a de facto standard as a charge injection layer, and functions as a hole injection layer by being disposed on the anode 13 side.

  On the PEDOT layer 10, for example, polyphenylene vinylene (hereinafter referred to as PPV) and a derivative thereof, or polyfluorene and a derivative thereof are formed by a spin coating method or the like, which is a wet process. Then, a metal electrode as a cathode 19 is formed on these light emitting layers 18 by vacuum deposition to complete the device.

Now, with respect to the conventional organic electroluminescent device, as an idea for improving the reliability of the low-molecular organic electroluminescent device, for example, an intermediate layer made of silicon as a main material as disclosed in Patent Document 1 is used. Technologies to be introduced have been proposed. However, since the intermediate layer made of these materials has a high first ionization potential, a significant potential gap is generated between the electrodes. As a result, the intermediate layer has an extremely high electric resistance, and it is necessary to reduce its thickness as much as possible in order to inject charges at a low voltage. In addition, although these intermediate layers have actions such as improving the surface roughness of the substrate and preventing diffusion of impurities from the electrode surface into the functional layer, they essentially act as a charge barrier layer, The luminous efficiency of the device could not be improved.
JP 2002-280186 A

  The PPV and polyfluorene described above are typical materials for the light emitting layer 18 used in the polymer organic electroluminescent element 11, and are usually applied after being dissolved in an organic solvent such as toluene or xylene. . As described above, the organic electroluminescent element 11 can be manufactured by a simple method called a wet process in which many of the functional layers are produced. However, when the material solution is applied to the glass substrate 12, the glass substrate 12 itself and the glass substrate There is a problem that uniform film formation is not performed due to the difference in wettability between the anode 13 and the insulating layer 14 disposed on the substrate 12. This problem is represented by a polymer organic electroluminescent element, unlike a low molecular electroluminescent element in which uniform film formation is performed regardless of the surface state of the glass substrate 12 by a dry process such as a vacuum deposition method. This is a problem peculiar to an organic electroluminescent device manufactured using a wet process.

  Such a problem will be described in detail below with an example.

  In general, the surface of ITO constituting the anode 13 is hydrophilic, whereas many insulating materials constituting the insulating layer 14 are made of an organic material such as acrylic or polyimide, and the surface is often oleophilic. . When the above-described PEDOT layer 10 is formed by coating on a surface where portions having different surface characteristics are mixed, due to the difference in wettability of the coated surface, particularly at the boundary portion between ITO and the insulating layer 14 constituting the anode 13. Non-uniform film thickness is strongly generated.

  The non-uniformity of the film thickness that occurs when the PEDOT layer 10 is formed by coating is not improved by other functional layers that are subsequently applied over the PEDOT layer 10, and as a result, organic electroluminescence The light emitting surface of the nescent element 11 may be shaped like a wave of the water surface within the light emitting surface, for example, when the film thickness decreases toward the periphery, or vice versa. In particular, the latter often occurs when a solution of a polymer organic electroluminescent material is dropped onto the anode 13 surrounded by the insulating layer 14 using an inkjet method which is one of wet processes.

  The non-uniformity of the film thickness appears as non-uniformity of the electric field applied in the film thickness direction of the light emitting surface when the organic electroluminescent element 11 is driven. Cause problems such as non-lighting.

  These problems remain as they are even when the organic electroluminescent element 11 is applied to a light emitting device or the like. In addition to shortening the lifetime and not lighting, the luminance unevenness in the light emitting surface is particularly affected in the case of an exposure apparatus using the organic electroluminescent element 11 as a light source. If the light source used in the exposure apparatus has uneven brightness in the light emitting surface, the details will be described later. However, the surface potential distribution of the photoconductor becomes non-uniform when the exposure is performed, resulting in non-uniform toner adhesion and sharpness. In this case, correct print output cannot be obtained.

  In the present invention, even when an organic electroluminescent device is manufactured using a wet process, the organic electroluminescent device having a uniform emission intensity distribution in the light emitting surface, and the light intensity of each organic electroluminescent device is uniform. An object of the present invention is to provide a simple exposure apparatus and a high-quality image forming apparatus using the exposure apparatus.

  The organic electroluminescent device of the present invention has been made in view of the above problems, and is formed to cover a substrate, a first electrode formed on the substrate, and at least a part of the first electrode. An insulating layer, a light emitting layer formed on the insulating layer and the first electrode, and a second electrode disposed in contact with the light emitting layer and facing the first electrode. An intermediate layer having a predetermined thickness is disposed between the electrode and the light-emitting layer and between the insulating layer and the light-emitting layer. The intermediate layer is formed by using a dry process and an inorganic material layer formed by using a wet process and an organic material formed by using a wet process. It is composed of layers.

  According to the present invention, the portion of the wettability mixed on the substrate is uniformly covered by the intermediate layer, the wettability can be made uniform, and the film of the light emitting layer material applied on the upper surface by a wet process It is possible to obtain an element that can be stably operated with uniform thickness and no unevenness in light emission. Moreover, since a simple process called a wet process can be used, an organic electroluminescent element can be manufactured at low cost. By applying this organic electroluminescent element to an exposure apparatus, a high-definition exposure apparatus can be provided at low cost, and an image forming apparatus equipped with this exposure apparatus can be provided at low cost and the image quality of the image forming apparatus can be improved. Can be improved.

  An organic electroluminescent element of the present invention includes a substrate, a first electrode formed on the substrate, an insulating layer formed so as to cover at least a part of the first electrode, and the insulating layer and A light-emitting layer formed on the first electrode; and a second electrode disposed in contact with the light-emitting layer and facing the first electrode, and insulating between the first electrode and the light-emitting layer An intermediate layer having a predetermined thickness is disposed between the layer and the light-emitting layer, and the intermediate layer is constituted by an inorganic layer formed using a dry process and an organic layer formed using a wet process. This intermediate layer uniformly covers portions with different wettability mixed on the substrate, can make the wettability uniform, and the thickness of the light emitting layer material applied on the upper surface by a wet process becomes uniform. . Thus, since the individual organic electroluminescent elements can have uniform light emission intensity up to the periphery of the light emitting surface, it is possible to obtain an organic electroluminescent element capable of stable operation without light emission unevenness. When the inorganic layer in the intermediate layer is formed by a dry process, the inorganic layer is formed on the surfaces of the first electrode and the insulating layer that have different wettability, but regardless of the wettability of the substrate surface due to the nature of the dry process. The inorganic layer can be formed with a uniform thickness. In addition, since a simple process called a wet process can be used for forming the organic layer in the intermediate layer, the organic electroluminescent element can be manufactured at low cost.

  In the present invention, the inorganic layer constituting the intermediate layer is configured to be in contact with the first electrode and the insulating layer. This makes it possible to impart uniform wettability to the surfaces of the first electrode and the insulating layer having different wettability.

  In the present invention, the inorganic layer in the intermediate layer is composed of any one of oxide, nitride, oxynitride, and composite oxide. These materials are suitable for forming a film using a dry process such as vacuum deposition, sputtering, or CVD, and can form a uniform film on a substrate having portions with different wettability. Therefore, an electroluminescent element having uniform light emission characteristics can be realized.

  In the present invention, the inorganic layer in the intermediate layer is composed of an oxide of molybdenum, tungsten, or vanadium. Molybdenum oxide, tungsten oxide, vanadium oxide, and the like are sufficiently stable, have high conductivity, can perform efficient carrier injection, and have high light transmittance. That is, the intermediate layer of the present invention contributes not only to improving the wettability but also to improving the charge injection characteristics of the organic electroluminescent device. As a result, the luminous efficiency of the organic electroluminescent device can be increased, and the lifetime of the device can be improved.

  In the present invention, the organic material layer constituting the intermediate layer is configured to be in contact with the light emitting layer. The organic material layer is formed so as to cover the inorganic material layer. Since the wettability of the substrate surface is made uniform by the inorganic material layer prior to the formation of the organic material layer, the organic material layer can be formed extremely uniformly. Since the organic layer has very close wettability to the material of the light emitting layer to be formed next, the light emitting layer of the organic electroluminescent element can be formed uniformly.

  In the present invention, when the thickness of the organic material layer constituting the intermediate layer is L1 and the thickness of the light emitting layer is L2, L1 satisfies the relationship of (L2 / 20) <L1 <(L2 / 3). It is configured. Accordingly, even when an inorganic material having high insulating properties is introduced as the intermediate layer, the driving voltage does not increase, and dielectric breakdown of the element can be prevented. Even if the inorganic substance is colored, the light emitted from the light emitting layer is not lost by absorption because the film thickness is thin. Furthermore, it is possible to achieve a surface state in which wettability suitable for formation of the light emitting layer performed next to the intermediate layer is made uniform, and a uniform light emitting layer thickness can be obtained.

  In the present invention, the light emitting layer is formed by a wet process using a polymer material. Since the wettability of the solution of the polymer material constituting the light emitting layer dissolved in the solvent and the organic material layer constituting the intermediate layer is very close, the light emitting layer of the organic electroluminescent element should be uniformly formed by a wet process. Is possible.

  In the exposure apparatus of the present invention, the above-described organic electroluminescent elements are arranged in a row, and each organic electroluminescent element can be controlled to be turned on / off independently. Since the organic electroluminescent element of the present invention has a uniform light emission intensity up to the periphery of the light emitting surface, it is possible to form a stable latent image by an exposure apparatus using this organic electroluminescent element. Become. In addition, since the organic electroluminescent device of the present invention can be manufactured by a simple wet process, an exposure apparatus can be provided at a low cost.

  The image forming apparatus of the present invention includes the above-described exposure apparatus, a photoreceptor on which an electrostatic latent image is formed by the exposure apparatus, and a developing unit that visualizes the electrostatic latent image formed on the photoreceptor. It is what has. The intensity distribution of the light irradiated onto the photoconductor by the exposure apparatus of the present invention is also uniform, and the surface potential distribution of the photoconductor and the toner adhesion state are uniformized by exposure. Therefore, the image forming apparatus of the present invention High-definition and faithful print output can be obtained.

  Hereinafter, specific contents of the present invention will be described with reference to examples.

Example 1
FIG. 1 is a configuration diagram of an organic electroluminescent element in Example 1 of the present invention.

  In FIG. 1, 1 is an organic electroluminescent element. Reference numeral 2 denotes a translucent glass substrate for supporting the organic electroluminescent element 1. The details of the process of manufacturing the organic electroluminescent element 1 in Example 1 will be described later. In Example 1, the anode 3 made of translucent ITO, for example, as the first electrode on the glass substrate 2 is used. Are formed, and at least a part thereof is covered with the insulating layer 4. An inorganic layer 6 constituting the intermediate layer 5 is formed on the entire upper surface by a dry process, and then an organic layer 7 constituting the intermediate layer 5 is formed by a wet process. Further, a polymer material layer as the light emitting layer 8 is formed by a wet process, and finally a cathode 9 as a second electrode as a counter electrode is formed by a vacuum deposition method.

  When a direct current voltage or direct current is applied with the anode 3 of the organic electroluminescent element 1 as a positive electrode and the cathode 9 as a negative electrode, holes are injected into the light emitting layer 8 from the anode 3 through the intermediate layer 5. At the same time, electrons are injected from the cathode 9. In the light emitting layer 8, the holes and electrons injected in this way are recombined, and a light emission phenomenon occurs when excitons generated along with this recombine from the excited state to the ground state.

  Hereinafter, the details of the manufacturing process of the organic electroluminescent element 1 of Example 1 will be described with reference to FIG.

  First, steps from the formation of the anode 3 on the glass substrate 2 to the formation of the insulating layer 4 will be described.

  An ITO thin film having a thickness of about 150 to 200 nm is formed on the glass substrate 2 by sputtering, an electrode pattern having a predetermined shape is formed by using a photolithography method and an etching method, and the anode 3 is formed. Subsequently, an insulating material made of photosensitive polyimide having a thickness of about 1 μm is applied to the entire surface by a spin coating method, and patterned into a predetermined shape by a photolithography method to form the insulating layer 4. The patterning of the insulating layer 4 is performed so as to cover the boundary portion between the anode 3 and the glass substrate 2 and regulates the shape of the light emitting surface.

  The reason why the light emitting surface is regulated by the insulating layer 4 varies depending on the application. For example, when an exposure apparatus is assumed, it is performed to accurately determine the position and shape of the light emitting surface. Of course, the organic electroluminescent element 1 emits light from the overlapping portion of the anode 3 and the cathode 9 facing each other according to the principle described above, and thus the light emitting surface can be regulated by the shape of the anode 3 and the cathode 9. In the exposure apparatus, the individual light emitting surfaces are very small. Therefore, in order to restrict the light emitting surfaces only by the electrodes such as the anode 3 and the cathode 9, the individual electrode lines become too thin, resulting in an increase in resistance. Arise. Therefore, a method is generally used in which an electrode having a certain width is produced so that the resistance value does not increase, and then a part thereof is regulated by the insulating layer 4 to regulate the light emitting surface.

  An intermediate layer 5 is formed on the glass substrate 2 on which the anode 3 and the insulating layer 4 have been produced. The intermediate layer 5 includes an inorganic layer 6 and an organic layer 7 as will be described in detail below.

  The process for forming the intermediate layer 5 will be described below.

  The inorganic layer 6 constituting the intermediate layer 5 is formed by, for example, a dry process such as a vacuum deposition method, and is configured to be in contact with both the anode 3 and the insulating layer 4 as illustrated. The inorganic layer 6 is formed on the surfaces of the anode 3 and the insulating layer 4 having different wettability, but can be formed with a uniform thickness regardless of the wettability of the substrate surface due to the characteristics of the dry process.

  In Example 1, a layer made of molybdenum oxide having a thickness of 10 nm was formed as the inorganic layer 6 by a vacuum deposition method which is a dry process. The formation of the film by the inorganic layer 6 may be performed on the entire surface of the glass substrate 2 or may be formed on a part of the glass substrate 2 using a mask during vacuum deposition. In any case, in order to obtain the effect of the present invention, at least the boundary portion between the anode 3 and the insulating layer 4 needs to be covered with a molybdenum oxide layer.

  After the inorganic layer 6 is formed, the organic layer 7 is formed by coating. The organic layer 7 is formed by a wet process such as a spin coating method, and the organic layer 7 is configured to be in contact with the light emitting layer 8 as illustrated. Yes. In forming the organic layer 7, the entire coated surface or at least the boundary between the anode 3 and the insulating layer 4 is covered with the molybdenum oxide layer, which is the inorganic layer 6 described above. Is possible. That is, when the organic layer 7 is formed, the coated surface is already covered with a uniform inorganic film by the inorganic layer 6, so that it is possible to form the organic layer 7 with high uniformity even by a wet process.

  The organic material layer 7 may be slightly non-uniform in film thickness because the wettability is different although the surface on which the organic material layer 7 is coated is covered with the inorganic material layer 6. However, since the organic layer 7 is formed very thin as will be described later, even if some non-uniformity occurs in the film thickness, the uniformity of light emission is not substantially affected.

  In Example 1, poly [9,9-dioctylfluorenyl-2,7-diyl) -co-1,4-benzo- {2,1′-3} -thiadiazole] (Poly [9] is used as the material for the organic layer 7. 9,9-dioctylfluorenyl-2,7-diyl] -co-1,4-benzo- {2,1'-3} -thiazole)]). This is formed as a thin film having a thickness of 10 nm by a spin coating method which is a wet process.

  This material also functions as an electron blocking layer in combination with MEH-PPV, which is a material of the light emitting layer 8 described later, and in order to prevent electrons injected from the cathode 9 from slipping through the anode 3, an organic electroluminescent material is used. There is an effect of improving the luminous efficiency of the element 1.

  In order to form the organic layer 7 in a thin film having a thickness of 10 nm, it is desirable to lower the viscosity by lowering the concentration of the solution used in the spin coating method. In Example 1, the concentration of the solution is set to 0.5% in order to form the organic layer 7 as thin as 10 nm. However, this concentration is a representative value and is not limited to this value. The film thickness of the organic layer 7 is affected by the concentration of the solution, the molecular weight of the organic substance, the type of solvent, the number of rotations during spin coating, the spin coating atmosphere, and the like. If the viscosity of the solution is high due to the fact that the concentration of the solution is somewhat high or the dissolved organic substance has a large molecular weight, it is possible to form a thin film to some extent by increasing the number of revolutions during spin coating. It is.

  The above-mentioned solution concentration of 0.5% is a typical value assuming a molecular weight of the material constituting the organic layer 7 of around 200,000 and a general spin coating condition of 1000 to 5000 rpm. is there. The average molecular weight of this material is about 100,000 to 500,000, preferably around 200,000. It is possible to easily obtain a film thickness of 10 nm by making such an organic substance a solution in the range of about 0.1 to 2.0% and adjusting the conditions such as the spin coater rotation speed when applying the spin coating method. it can.

  As described above, the light emitting layer 8 is applied by using a wet process by forming the intermediate layer 5 by forming a two-layer film composed of the inorganic layer 6 formed by the dry process and the organic layer 7 formed by the wet process. In doing so, the electroluminescent device 1 having a uniform thickness distribution of the light emitting layer 8 can be manufactured.

  Next, a process for forming the light emitting layer 8 will be described.

  The light emitting layer 8 is applied to the upper surface of the intermediate layer 5 (the organic material layer 7 constituting the intermediate layer 5) by a wet process. The surface on which the light emitting layer 8 is formed is already a uniform wettability film called the organic material layer 7. Since the wettability of the solution in which the material of the light emitting layer 8 is dissolved and the wettability of the film formed by the organic material layer 7 are very close, the light emitting layer 8 is very highly uniform. can do.

  In applying and forming the light emitting layer 8 made of a polymer material by a spin coating method which is a wet process, in Example 1, MEH-PPV dissolved in toluene is used as the polymer organic electroluminescent material, and the film thickness is 120 nm. It is said. MEH-PPV is very common as a polymer organic electroluminescent material, and can be purchased from, for example, Nippon Sebel Hegner.

  In Example 1, the light emitting layer 8 is a single layer film made of MEH-PPV, but it may be a laminated film made of several materials. For example, in order to confine the charge injected into the MEH-PPV layer and improve the recombination efficiency, it is desirable to add a layer made of a material having an electron blocking function or a hole blocking function, which leads to improvement of device characteristics. is there.

  Further, the material itself is not limited to MEH-PPV. Currently, polymer organic electroluminescent materials having various characteristics and luminescent colors have been proposed, and the light emitting layer 8 can be configured by appropriately selecting from these materials.

  Finally, the cathode 9 is formed. In Example 1, a barium and silver laminated electrode is used. Barium helps to inject electrons from the cathode 9 and is effective in reducing the driving voltage of the organic electroluminescent device. For the same purpose, compounds such as calcium and lithium fluoride may be used.

  As described above, since the wettability of the organic layer 7 on which the substrate surface on which the organic layer 7 is applied is covered with the inorganic layer 6 is different, there is a possibility that the film thickness may be slightly uneven. However, the organic material layer 7 is formed as thin as 10 nm as described above. Specifically, when the film thickness of the organic material layer 7 is L1 and the film thickness of the light emitting layer 8 is L2, L1 is (L2 / 20). ) <L1 <(L2 / 3) so that the electric field intensity distribution in the light emitting surface due to the film thickness distribution is extremely small even if there is some non-uniformity. It does not affect the uniformity of the top emission.

  There is an optimum range for the ratio of the thickness of the organic layer 7 to the thickness of the light emitting layer 8. The relationship between the film thickness of the light emitting layer 8 and the film thickness of the organic layer 7 will be described below using (Table 1).

  As shown in Table 1, when the ratio of the thickness of the organic layer 7 to the thickness of the light emitting layer 8 is 1/30 or less, the thickness of the light emitting layer 8 is assumed assuming that the thickness of the organic layer 7 is 10 nm. Becomes as large as 300 nm. As a result, the total thickness of the organic electroluminescent element 1 becomes too thick, and the applied voltage required for lighting becomes high, so that the power efficiency of the organic electroluminescent element 1 is remarkably lowered. If the thickness of the light emitting layer 8 is limited to about 100 nm in order to avoid an increase in applied voltage, the thickness of the organic material layer 7 is now about 3 nm, and it is difficult to obtain a uniform film using a wet process. .

  On the other hand, when the ratio of the film thickness of the organic material layer 7 to the light emitting layer 8 is 1/3 or more, assuming that the film thickness of the organic material layer 7 is 10 nm, the light emitting layer 8 has a film thickness of 30 nm at most. As a result of the total thickness of the cent element 1 being reduced, dielectric breakdown is likely to occur. On the other hand, if the thickness of the light emitting layer 8 is secured to about 100 nm, the thickness of the organic layer 7 becomes too thick at 30 nm or more, and uniform film formation on the inorganic layer 7 becomes difficult.

  For this reason, the film thickness ratio of the organic layer 7 to the light emitting layer 8 should be selected from the range of about 1 / 20-1 / 3, and preferably about 1/10.

  Now, the emission intensity distribution radiated from the light emitting surface of the organic electroluminescent device 1 manufactured in this way will be described in comparison with the case of a device using PEDOT which is a conventional technique.

  FIG. 2A shows an organic electroluminescent element based on a conventional technique using PEDOT and a PPV material (an organic electroluminescent element lacking the intermediate layer 5, hereinafter referred to as a PEDOT element), and FIG. It is explanatory drawing which shows the emitted light intensity distribution of the organic electroluminescent element (The organic electroluminescent element which has the intermediate | middle layer 5, and henceforth an intermediate | middle layer element) in Example 1 of this invention. The range indicated by “A” in both figures is a light emitting surface, and both sides thereof are non-light emitting surfaces regulated by an insulating layer.

  As is clear from FIG. 2B, the intermediate layer element has a sudden increase in emission intensity in the peripheral portion of the light emitting surface, while maintaining a uniform emission intensity over most of the light emitting surface. In the PEDOT element shown in FIG. 2 (a), the amount of light around the light emitting surface is small, and the intensity distribution has a mountain shape, and there is almost no range having uniform light emission intensity.

  The cause of the difference in the emission intensity distribution is the nonuniformity of the film thickness distribution in the light emitting surface.

  FIG. 3A is a cross-sectional view of the layer structure of the PEDOT element based on the prior art, and FIG. 3B is a cross-sectional view of the layer structure of the intermediate layer element based on the present invention. 3A and 3B, P1 indicates a position on the insulating layer, P2 indicates a position near the light emitting surface, and P3 indicates a position near the center of the light emitting surface.

  Hereinafter, the mechanism by which the film thickness in the light emitting surface becomes non-uniform will be described with reference to FIGS.

  First, in the PEDOT element based on the prior art shown in FIG. 3A, when the PEDOT layer 10 is formed, the surface of the glass substrate 12 is mixed with an oleophilic insulating layer 14 and an anode 13 composed of hydrophilic ITO. The PEDOT layer 10 applied by spin coating is good in wettability with the hydrophilic anode 13, but is not good in wetness with the lipophilic insulating layer 14. Try to move to. However, these phenomena occur only in a very short time from when the PEDOT layer 10 is applied by the spin coating method to when the solvent is dried, and as a result, a non-uniform film thickness is fixed. That is, in the peripheral portion of the light emitting surface shown by P2, the film thickness becomes thicker than the element central portion P3 by PEDOT moving from the lipophilic insulating layer 4 shown by P1, and gradually toward the central portion of the light emitting surface. It has a “mortar-shaped” film thickness distribution that becomes thinner.

  By forming the PEDOT layer 10, the coated surface is covered with a uniform wettability film called the PEDOT layer 10, so that the film thickness of the PPV material constituting the light emitting layer 18 to be coated thereafter is uniform. Further, since the subsequent formation of the cathode 19 is performed by a vacuum vapor deposition method, a uniform film thickness is obtained in principle. However, since the non-uniformity of the film thickness generated at the element peripheral portion P2 due to the application of the PEDOT layer 10 is not eliminated in the subsequent process, the total film thickness as the organic electroluminescent element 11 is within the light emitting surface. It will have a non-uniform distribution. This means that the electric field strength is nonuniform in the light emitting surface when energized.

  On the other hand, in the intermediate layer element according to the present invention shown in FIG. 3B, an intermediate layer is formed on the glass substrate 2 in which the lipophilic insulating layer 4 and the hydrophilic anode 3 are mixed prior to the application of the light emitting layer 8. Layer 5 is formed. By forming the intermediate layer 5, at least the boundary between the insulating layer 4 and the anode 3 and the surface of the anode 3 are covered with a film having uniform wettability. Moreover, as described above, the intermediate layer 5 constituted by the inorganic layer 6 and the organic layer 7 has high uniformity in film thickness. Therefore, since the light emitting layer 8 formed by the wet process next to the intermediate layer 5 is applied to a surface having uniform wettability, the film thickness becomes uniform.

  By forming the intermediate layer 5 in this way, the film thickness of the light emitting layer 8 of the organic electroluminescent element 1 can be made uniform, and excellent organic electroluminescence with uniform light emission intensity to the periphery of the light emitting surface. A luminescent element can be obtained.

  In Example 1, molybdenum oxide was used as the inorganic material layer 6 constituting the intermediate layer 5. However, this is because molybdenum oxide is sufficiently stable, has high conductivity, and can perform efficient carrier injection. In addition, the light transmittance is high. Tungsten or vanadium oxide can be used as a material capable of obtaining the same effect from the viewpoint of material characteristics.

  Further, even if the inorganic layer 6 constituting the intermediate layer 5 is made of any of oxide, nitride, oxynitride, and composite oxide, the same effect as the above-described molybdenum oxide layer can be obtained. .

  Examples of oxides include chromium (Cr), tungsten (W), vanadium (V), niobium (Nb), tantalum (Ta), titanium (Ti), zirconium (Zr), hafnium (Hf), scandium (Sc), Yttrium (Y), Thorium (Tr), Manganese (Mn), Iron (Fe), Ruthenium (Ru), Osmium (Os), Cobalt (Co), Nickel (Ni), Copper (Cu), Zinc (Zn), Cadmium (Cd), Aluminum (Al), Gallium (Ga), Indium (In), Silicon (Si), Germanium (Ge), Tin (Sn), Lead (Pb), Antimony (Sb), Bismuth (Bi) or And oxides of so-called rare earth elements from lanthanum (La) to lutetium (Lu).

  As nitrides, gallium nitride (GaN), indium nitride (InN), aluminum nitride (AlN), boron nitride (BN), silicon nitride (SiN), magnesium nitride (MgN), molybdenum nitride (MoN), calcium nitride (CaN), niobium nitride (NbN), tantalum nitride (TaN), vanadium nitride (BaN), zinc nitride (ZnN), zirconium nitride (ZrN), iron nitride (FeN), copper nitride (CuN), barium nitride (BaN) ), Lanthanum nitride (LaN), chromium nitride (CrN), yttrium nitride (YN), lithium nitride (LiN), titanium nitride (TiN), and composite nitrides thereof.

Examples of the oxynitrides include barium sialon (BaSiAlON), calcium sialon (CaSiAlON), cerium sialon (CeSiAlON), lithium sialon (LiSiAlON), magnesium sialon (MgSiAlON), scandium sialon (ScSiAlON), and yttrium sialon (YSiAlON). ), Sialon containing elements of group IA, IIA, IIIB such as erbium sialon (ErSiAlON), neodymium sialon (NdSiAlON), or oxynitrides such as multi-element sialon, and lanthanum silicon oxynitrate (LaSiON), Lanthanum europium silicon nitride (LaEuSi ₂ O ₂ N ₃ ), silicon oxynitride (SiON ₃ ), and the like are also applicable.

Further, examples of the composite oxide described above include barium titanate (BaTiO ₃ ), strontium titanate (SrTiO ₃ ), calcium titanate (CaTiO ₃ ), potassium niobate (KNbO ₃ ), and bismuth iron oxide (BiFeO _3). ), lithium niobate (LiNbO _3), sodium vanadate _(Na 3 _VO 4), vanadium iron (FeVO _3), titanate vanadium (TiVO _3), chromic acid vanadium (CRVO _3), vanadium, nickel (NiVO ₃ ), Magnesium vanadate (MgVO ₃ ), calcium vanadate (CAVO ₃ ), lanthanum vanadate (LaVO ₃ ), vanadium molybdate (VMoO ₅ ), vanadium molybdate (V ₂ MoO ₈ ), lithium vanadate (LiV) ₂ O ₅ ), magnesium silicate (Mg ₂ SiO ₄ ), magnesium silicate (MgSiO ₃ ), zirconium titanate (ZrTiO ₄ ), strontium titanate (SrTiO ₃ ), lead magnesium oxide (PbMgO ₃ ), lead niobate (PbNbO) ₃ ), barium borate (BaB ₂ O ₄ ), lanthanum chromate (LaCrO ₃ ), lithium titanate (LiTi ₂ O ₄ ), lanthanum cuprate (LaCuO ₄ ), zinc titanate (ZnTiO ₃ ), calcium tungstate (CaWO ₄ ) and the like.

  In addition, the said compound is a part of what can be applied to the last, and in the said compound, the compound from which a valence differs easily exists, and what takes the form of the compound from which a valence differs from what was illustrated is also contained.

  The above-mentioned compounds include those with high insulation properties. However, even if the material is generally an insulator, it can be energized by reducing the film thickness to about 1 nm to 5 nm. The present invention can be applied as the inorganic layer 6 constituting the intermediate layer 5 shown in the present invention. Moreover, even for the above-mentioned compounds that are colored, the problem can be avoided by setting the thickness of the film to be formed to several nm, and the effects of the present invention can be achieved.

  In addition, the light emitting layer 8 of the organic electroluminescent element 1 described above is not limited to a layer having only a light emitting function, but has other functions such as a charge transport function, or those A laminated film made of a plurality of materials including may be used.

  Further, in Example 1, the molybdenum oxide layer as the inorganic layer 6 was formed by using the vacuum evaporation method, but of course, other dry processes as described above including the sputtering method may be used. For example, molybdenum oxide and vanadium oxide have sublimability and can be formed by a general vacuum deposition method, but tungsten oxide needs to be formed by a sputtering method. In addition, many of the other oxides described above cannot be applied with the vacuum deposition method, and it is preferable to use the sputtering method for these.

  Similarly, the organic layer 7 is not limited to the material used in Example 1. The optimum selection should be made as appropriate in consideration of compatibility with the material of the light emitting layer 8 including wettability.

  Now, an example in which such an organic electroluminescent element having a uniform emission intensity distribution is applied to an exposure apparatus will be described in detail below.

  FIG. 4 is a block diagram of the exposure apparatus in Embodiment 1 of the present invention. Hereinafter, the structure of the exposure apparatus will be described in detail with reference to FIG.

  In FIG. 4, an exposure device 33 is mounted on an image forming apparatus (not shown), and is a member that forms an electrostatic latent image on the surface of the photoreceptor 28. The formation process of the electrostatic latent image on the photoreceptor 28 and the configuration and operation of the image forming apparatus will be described in detail later.

  Reference numeral 2 denotes the glass substrate already described, and the organic electroluminescent element 1 is formed on the surface A of the glass substrate 2 as an exposure light source at a resolution of 600 dpi (dot / inch) in a direction perpendicular to the drawing (main scanning direction). Has been.

  Reference numeral 71 denotes a lens array in which rod lenses (not shown) made of plastic or glass are arranged in a row, and the emitted light of the organic electroluminescent element 1 formed on the surface A of the glass substrate 2 is erect. An image of the same magnification is formed on the surface of the photoreceptor 28 where a latent image is formed. The positional relationship of the glass substrate 2, the lens array 71, and the photoconductor 28 is adjusted so that one focus of the lens array 71 is the surface A of the glass substrate 2 and the other focus is the surface of the photoconductor 28. . That is, when the distance L1 from the surface A to the surface closer to the lens array 71 and the distance L2 from the other surface of the lens array 71 to the surface of the photosensitive member 28 are set, L1 = L2.

  Reference numeral 72 denotes a relay substrate in which a circuit is configured by electronic components on a glass epoxy substrate, for example. 73 a is a connector A, 73 b is a connector B, and at least a connector A 73 a and a connector B 73 b are mounted on the relay board 72. The relay substrate 72 temporarily relays image data, light amount correction data, and other control signals supplied from the outside to the exposure apparatus 33 via a cable 76 such as a flexible flat cable, etc., via a connector B 73b, and these signals are glass. Pass to substrate 2.

  Since it is difficult to directly mount the connector on the surface of the glass substrate 2 in consideration of bonding strength and reliability in various environments where the exposure apparatus 33 is placed, the connector A 73a of the relay substrate 72 and the glass are used in the first embodiment. FPC (flexible printed circuit) is adopted as a connection means with the substrate 2 (not shown, details will be described later), and the glass substrate 2 and FPC are bonded in advance using, for example, ACF (anisotropic conductive film). For example, it is configured to be directly connected to, for example, an ITO electrode formed on the substrate 2.

  On the other hand, the connector B 73b is a connector for connecting the exposure apparatus 33 to the outside. In general, connection by ACF or the like often has a problem of bonding strength, but by providing the connector B 73b for connecting the exposure apparatus 33 on the relay substrate 72 in this way, the interface directly accessed by the user. Sufficient strength can be secured.

  Reference numeral 74a denotes a casing A which is formed by bending a metal plate, for example. An L-shaped portion 75 is formed on the side of the housing A 74 a facing the photoreceptor 28, and the glass substrate 2 and the lens array 71 are disposed along the L-shaped portion 75. By aligning the end surface of the housing A 74a on the photosensitive member 28 side with the end surface of the lens array 71 and further supporting one end of the glass substrate 2 by the housing A 74a, the L-shaped portion 75 of the L-shaped portion 75 is supported. If the molding accuracy is ensured, the positional relationship between the glass substrate 2 and the lens array 71 can be accurately adjusted. As described above, since the casing A 74a is required to have dimensional accuracy, the casing A 74a is preferably made of metal. Further, by making the casing A 74a made of metal, it is possible to suppress the influence of noise on electronic components such as a control circuit formed on the glass substrate 2 and an IC chip surface-mounted on the glass substrate 2. It is.

  74b is a casing B obtained by molding a resin. A notch (not shown) is provided in the vicinity of the connector B 73b of the housing B 74b, and the user can access the connector B 73b from this notch. The image data, the light amount correction data, the control signal such as the clock signal and the line synchronization signal, the driving power source of the control circuit, and the light emitting element are supplied from the outside of the exposure apparatus 33 to the exposure apparatus 33 through the cable 76 connected to the connector B 73b. Drive power for the organic electroluminescent element is supplied.

  FIG. 5A is a top view of the glass substrate 2 according to the exposure apparatus 33 of Embodiment 1 of the present invention, and FIG. 5B is an enlarged view of the main part thereof. Hereinafter, the configuration of the glass substrate 2 in Example 1 will be described in detail with reference to FIG.

  In FIG. 5, a glass substrate 2 is a rectangular substrate having a thickness of about 0.7 mm and having at least a long side and a short side, and a plurality of organic electroluminescent elements are arranged in the long side direction (main scanning direction). 1 is formed in a row. In Example 1, the organic electroluminescent element 1 necessary for exposure of at least A4 size (210 mm) is arranged in the long side direction of the glass substrate 2, and the long side direction of the glass substrate 2 is the drive control unit 78 described later. It is 250 mm including the arrangement space. In the first embodiment, the glass substrate 2 is described as a rectangle for the sake of simplicity. However, a notch is provided in a part of the glass substrate 2 for positioning when the glass substrate 2 is attached to the housing A 74a. May be accompanied by various deformations.

  A drive 78 receives a control signal (a signal for driving the organic electroluminescent element 1) supplied from the outside of the glass substrate 2, and controls driving of the organic electroluminescent element 1 based on the control signal. An IC chip (source driver) that controls the driving of the organic electroluminescent element 1 based on an interface unit that receives a control signal from the outside of the glass substrate 2 and a control signal received through the interface unit as will be described later ) Is included.

  Reference numeral 80 denotes an FPC (flexible printed circuit) as an interface means for connecting the connector A 73a of the relay substrate 72 and the glass substrate 2, and is directly connected to a circuit pattern (not shown) provided on the glass substrate 2 without using a connector or the like. ing. As already described, image data, light amount correction data, control signals such as clock signals and line synchronization signals, drive power for the control circuit, and drive power for the organic electroluminescent element 1 are supplied to the exposure apparatus 33 from the outside. Then, after passing through the relay substrate 72 shown in FIG. 4, it is supplied to the glass substrate 2 through the FPC 80.

  In Example 1, 5120 organic electroluminescent elements 1 as a light source of the exposure apparatus 33 are formed in a row at a resolution of 600 dpi in the main scanning direction, and each of the organic electroluminescent elements 1 is respectively Lighting / extinguishing is controlled independently by a TFT circuit described later.

  A source driver 81 is supplied as an IC chip for controlling the driving of the organic electroluminescent element 1 and is flip-chip mounted on the glass substrate 2. Considering that surface mounting is performed on the glass surface, the source driver 81 employs a bare chip product. The source driver 81 is supplied with control-related signals such as a power supply, a clock signal, and a line synchronization signal and light amount correction data (for example, 8-bit multi-value data) from the outside of the exposure apparatus 33 via the FPC 80. The source driver 81 is a drive parameter setting means for the organic electroluminescent element 1. More specifically, the source driver 81 is a drive current value of each organic electroluminescent element 1 based on the light amount correction data passed through the FPC 80. Is for setting.

  In the glass substrate 2, the joint portion of the FPC 80 and the source driver 81 are connected through, for example, an ITO circuit pattern (not shown) having a metal formed on the surface, and the FPC 80 is connected to the source driver 81 as drive parameter setting means. Control signals such as light quantity correction data, a clock signal, and a line synchronization signal are input via the control signal. Thus, the FPC 80 as the interface means and the source driver 81 as the drive parameter setting means constitute the drive control unit 78.

  Reference numeral 82 denotes a TFT (Thin Film Transistor) circuit formed on the glass substrate 2. The TFT circuit 82 includes a shift controller, a data latch unit, and the like, a gate controller that controls the timing of turning on / off the organic electroluminescent element 1, and a driving circuit that supplies a driving current to each organic electroluminescent element 1 ( Hereinafter referred to as a pixel circuit). One pixel circuit is provided for each organic electroluminescent element 1 and is arranged in parallel with a light emitting element array formed by the organic electroluminescent element 1. A drive current value for driving each organic electroluminescent element 1 is set in the pixel circuit by the source driver 81 which is a drive parameter setting means.

  The TFT circuit 82 is supplied with a control signal such as a power supply, a clock signal, and a line synchronization signal and image data (1-bit binary data) from the outside of the exposure apparatus 33 via the FPC 80. The TFT circuit 82 supplies these power supplies. And the lighting / extinguishing timing of each organic electroluminescent element 1 is controlled based on the signal.

  84 is sealing glass. When the organic electroluminescent device 1 is affected by moisture, the light emitting region shrinks (shrinking) with time, or a minute non-light emitting portion (dark spot) in the light emitting region expands. Since it deteriorates extremely, the sealing for interrupting | blocking a water | moisture content is required. In Example 1, the solid sealing method in which the sealing glass 84 is attached to the glass substrate 2 via an adhesive is employed. However, in order to adsorb moisture in the sealing region, the sealing glass 84 and the glass substrate 2 You may arrange | position the desiccant which is not illustrated in between. In general, the sealing region is required to be several mm to several cm in the sub-scanning direction from the light emitting element array formed by the organic electroluminescent element 1. In Example 1, 2000 μm is secured as a sealing margin.

  Reference numeral 77 denotes a light quantity sensor unit in which a plurality of light quantity sensors made of amorphous silicon or the like are arranged along the glass substrate 2 in the main scanning direction. The amount of light emitted from each organic electroluminescent element 1 is measured by the light amount sensor unit 77. The output of the light quantity sensor unit 77 is once taken into the TFT circuit 82 by a wiring (not shown) and subjected to signal processing such as amplification and analog-digital conversion by a signal processing means (not shown), and then FPC 80, relay board 72 (see FIG. 4), cable It is output to the outside of the exposure apparatus 33 via 76 (see FIG. 4).

  This signal is received and signal-processed by a controller (not shown) of the image forming apparatus to generate light amount correction data (for example, 8 bits). The light amount sensor unit 77 measures each organic electrometer. This is the total amount of light emitted from the luminescent element 1, and not the light emission luminance distribution in the light emitting region. Therefore, although the total light emission amount of the organic electroluminescent element 1 can be recovered by correction based on the light amount correction data, it is difficult to recover the light emission intensity distribution in the light emission region that has changed due to deterioration over time, for example.

  In Example 1, since the emission intensity distribution of the organic electroluminescent element 1 is uniform as already described, the deterioration of the organic electroluminescent element 1 occurs uniformly, and even when the deterioration occurs. The light emission luminance distribution in the light emitting region does not change.

  For this reason, the exposure apparatus 33 using the organic electroluminescent element 1 of Example 1 measures the emitted light amount of each organic electroluminescent element 1 by the light amount sensor unit 77 as described above, and measures the emitted light amount. For example, by resetting the drive current for driving the organic electroluminescent element 1 based on the above, it is possible to reliably recover both the total light emission amount of the organic electroluminescent element 1 and the light emission luminance distribution in the light emission region. There is an extremely remarkable effect that can be done.

  In the first embodiment, the FPC 80 serving as the interface means that constitutes the drive control unit 78 and the source driver 81 serving as the drive parameter setting means are placed on the extension line (EL_dir) of the light emitting element array formed by the organic electroluminescent element 1. I made it.

  With such an arrangement, the drive control unit 78 is arranged at a position that does not overlap the light emitting element array at an arbitrary position in the long side direction (main scanning direction) of the glass substrate 2. At the same time, in this configuration, at any position in the long side direction (main scanning direction) of the glass substrate 2, the drive control unit 78 does not overlap with the TFT circuit 82 (including the pixel circuit) formed in parallel with the light emitting element array. Will be placed. With such an arrangement, the size of the glass substrate 2 can be reduced.

  FIG. 6 is an explanatory view showing a situation in which the photosensitive member 28 is exposed by the exposure device 33 to which the organic electroluminescent element 1 of Example 1 of the present invention is applied.

  In FIG. 6, reference numeral 20 denotes a propagation path of light emitted from the organic electroluminescent element 1. The organic electroluminescent element 1 is formed on the surface A (see FIG. 4) of the glass substrate 2, and the lower surface of the glass substrate 2 is a light extraction surface.

  Hereinafter, the latent image forming process by the exposure apparatus 33 according to the first embodiment will be described in detail with reference to FIG.

  In FIG. 6, for simplification of explanation, only portions necessary for explanation are extracted and described, and the glass substrate 2, the lens array 71 and the like are appropriately supported by the casing A 74a shown in FIG. In the following description, it is assumed that the positional relationship with the photosensitive member 28 is also properly maintained.

  In the first embodiment, the lens array 71 described above is used as an optical system for forming an erecting equal-magnification image on the photoreceptor 28, but this optical system is output from the organic electroluminescent element 1. Any material can be used as long as the incident light can be appropriately imaged on the photosensitive member 28. For example, a microlens array or a planar optical system may be used. The luminescent element 1 may be formed to constitute a so-called lensless contact exposure system.

  The organic electroluminescent element 1 illustrated in FIG. 6 is one of the 5120 organic electroluminescent elements 1 arranged on the glass substrate 2 with a resolution of 600 dpi. In actual exposure, the organic electroluminescent elements 1 arranged in large numbers are controlled in cooperation as described with reference to FIG. 5 to create a two-dimensional printed image.

  The entire so-called electrophotographic process in which a latent image is formed on the photoreceptor 28, developed to transfer a toner image that has been visualized onto a sheet of paper, and then heat-fixed will be described later. Now, the process from when the light from the organic electroluminescent element 1 forms an image on the photosensitive member 28 and an electrostatic distribution called a latent image is formed until the toner is attached will be described. .

  First, the surface of the photosensitive member 28 is charged using a charging means (not shown) such as a scorotron charger or a roller charger. Next, the radiated light from the organic electroluminescent element 1 is propagated using the lens array 71 and then imaged on the surface of the photoreceptor 28. At this time, since the lens array 71 is an erecting equal-magnification lens, the radiated light from the organic electroluminescent element 1 passes through the propagation path 20 and remains on the photoconductor 28 while maintaining the light emitting surface shape and the light emission intensity distribution. Tie the statue. That is, the light emission intensity distribution described with reference to FIG. 2 is reflected on the photoconductor 28 as it is.

  The region receiving light on the photoconductor 28 releases the electric potential so as to form an invisible electrostatic image, that is, a latent image. This is because the photoreceptor 28 is made of a material having photoconductivity. When the light is irradiated, the conductivity of only that portion increases, and as a result, the charge of the portion receiving the light passes through the conductive portion formed on the back surface of the photoreceptor 28 and is released to the ground. . At this time, the degree of release of the surface charge on the photoconductor 28 depends on the intensity of the irradiated light under a certain time, and the surface potential approaches the ground potential as the strong light hits. Therefore, the latent image has a shape reflecting the intensity distribution of the irradiated light, that is, the emission intensity distribution of the organic electroluminescent element 1.

  After the latent image is formed, toner is adhered to the surface of the photoreceptor 28 by a developing means (not shown). The toner is charged in advance, and by applying a predetermined bias potential to a developing means (not shown), the toner interacts with the surface potential of the photoreceptor 28, and the photoreceptor 28 responds to the Coulomb force based on the surface potential. It adheres to the part where the latent image is formed. Also at this time, the degree of adhesion of the toner onto the photoreceptor 28 depends on the state of the latent image, that is, depends on the light emission intensity distribution of the organic electroluminescent element 1.

  As described above, the light emission intensity distribution of the organic electroluminescent element 1 which is the light source of the exposure device 33 finally determines the adhesion state of the toner on the photosensitive member 28, and this is directly reflected in the printing result. .

  Now, in the exposure apparatus 33 that performs such an operation, the difference in the case where the emission intensity distribution of the organic electroluminescent element 1 is as shown in FIGS. 2A and 2B will be described below. 6 will be described with reference to FIG.

  In the case of the emission intensity distribution of FIG. 2B (that is, in the case of the organic electroluminescent device of the present invention), the emission intensity distribution is strong and flat, so that the latent image on the photoreceptor 28 is in a sufficiently wide range. The potential drops. However, in the case of the emission intensity distribution shown in FIG. 2A (that is, in the case of an organic electroluminescent device based on the prior art), a potential drop is sufficiently observed in the central portion of the latent image, but suddenly moves away from the central portion. Further, since the irradiation light becomes weak, the potential of the photoreceptor 28 is not sufficiently lowered.

  When toner is attached to these latent images by developing means (not shown), a sufficient amount of toner is contained in the latent image obtained from the organic electroluminescent element 1 having a light emission intensity distribution as shown in FIG. In contrast, in the case of a latent image obtained from the organic electroluminescent element 1 having a light emission intensity distribution as shown in FIG. 2A, the toner adhesion amount on the photosensitive member 28 is reduced.

  When this is seen in the print result, in the case of the emission intensity distribution of FIG. 2B, so-called solid black is reproduced at a high density, whereas in the case of the emission intensity distribution of FIG. Since the amount of toner adhering to the body 28 is insufficient, it cannot be completely black. That is, only the output with a small contrast ratio can be obtained from the printing result from FIG.

  Now, the organic electroluminescent element 1 in Example 1 of the present invention realizes the uniform thickness of the light emitting layer formed on the intermediate layer by the wet process by arranging the intermediate layer as described above. ing. That is, since the film thickness around the light emitting surface is the same as that at the center of the light emitting surface, the light emission intensity pattern of FIG. This means that a clear print output with a sufficient contrast ratio can be obtained by using the exposure apparatus 33 according to the present invention.

  Thus, in the organic electroluminescent element 1 which forms a light emitting layer using a wet process, the intermediate layer for improving the wettability is disposed between the insulating layer and the light emitting layer, so that the subsequent wet process is performed. The film thickness of the light emitting layer by the process can be made uniform, and as a result, an excellent organic electroluminescent device 1 in which the light emission intensity distribution is uniform in the light emitting surface can be obtained. Further, by using the organic electroluminescent element 1 having such excellent light emission intensity distribution characteristics for the exposure device 33, the potential distribution on the photoconductor 28 at the time of forming the latent image is improved, and the contrast ratio is high. Thus, it is possible to realize the exposure apparatus 33 that makes a correct print output.

  Furthermore, as already described, since the organic layer and the light emitting layer constituting the intermediate layer are formed by a simple wet process, the cost of manufacturing equipment can be reduced, and the time required for film formation can be shortened. The exposure apparatus 33 can be provided at a low cost.

  FIG. 7 is a block diagram of an image forming apparatus equipped with an exposure device 33 to which the organic electroluminescent element 1 of Example 1 of the present invention is applied.

  In FIG. 7, an image forming apparatus 21 has four color developing stations, a yellow developing station 22Y, a magenta developing station 22M, a cyan developing station 22C, and a black developing station 22K, arranged in a stepwise manner in the vertical direction. Is provided with a paper feed tray 24 in which the recording paper 23 is accommodated, and a recording paper transport serving as a transport path for the recording paper 23 supplied from the paper feed tray 24 at locations corresponding to the developing stations 22Y to 22K. The path 25 is arranged in the vertical direction from the top to the bottom.

  The developing stations 22Y to 22K form yellow, magenta, cyan, and black toner images in order from the upstream side of the recording paper conveyance path 25. The yellow developing station 22Y includes a photoconductor 28Y and a magenta developing station 22M. The photosensitive member 28M and the cyan developing station 22C include the photosensitive member 28C, the black developing station 22K includes the photosensitive member 28K, and each developing station 22Y to 22K includes a series of electrophotographic systems such as a developing sleeve and a charger (not shown). The member which implement | achieves the image development process in is included.

  Further, exposure devices 33Y, 33M, 33C, and 33K for exposing the surfaces of the photoreceptors 28Y to 28K to form electrostatic latent images are disposed below the developing stations 22Y to 22K.

  The developing stations 22Y to 22K are different in the color of the filled developer, but the configuration is the same regardless of the developing color. Therefore, the developing stations are excluded unless particularly necessary to simplify the following description. 22, the photosensitive member 28, and the exposure device 33 will be described without specifying specific colors.

  FIG. 8 is a configuration diagram illustrating the periphery of the developing station 22 in the image forming apparatus 21 according to the first exemplary embodiment of the present invention. In FIG. 8, the developing station 22 is filled with a developer 26 which is a mixture of carrier and toner. Reference numerals 27a and 27b denote stirring paddles for stirring the developer 26. The toner in the developer 26 is charged to a predetermined potential by friction with the carrier by the rotation of the stirring paddles 27a and 27b, and the interior of the developing station 22 is also charged. By circulating, the toner and the carrier are sufficiently stirred and mixed. The photoreceptor 28 is rotated in the direction D3 by a driving source (not shown). A charger 29 charges the surface of the photoreceptor 28 to a predetermined potential. 30 is a developing sleeve, and 31 is a thinning blade. The developing sleeve 30 has a mag roll 32 having a plurality of magnetic poles formed therein. The layer thickness of the developer 26 supplied to the surface of the developing sleeve 30 is regulated by the thinning blade 31 and the developing sleeve 30 is rotated in a direction D4 by a driving source (not shown). The developer 26 is supplied to the surface of the developing sleeve 30 by the action, and an electrostatic latent image formed on the photoconductor 28 is developed by an exposure device to be described later, and the developer 26 that has not been transferred to the photoconductor 28 is developed in the developing station. 22 is collected inside.

  Reference numeral 33 denotes the exposure apparatus already described. In the image forming apparatus 21 to which the exposure apparatus 33 according to the first embodiment is applied, as described above, the organic electroluminescent element 1 according to the first embodiment has a very uniform emission intensity distribution in each organic electroluminescent element 1. Therefore, since the exposure apparatus 33 of Example 1 can obtain an electrostatic latent image of a desired shape over a long period of time, the image forming apparatus 21 equipped with the exposure apparatus 33 can always form a high-quality image.

  The exposure apparatus 33 according to the first embodiment has organic electroluminescent elements arranged linearly with a resolution of 600 dpi (dot / inch). An electrostatic latent image of maximum A4 size is formed by selectively turning ON / OFF the organic electroluminescent element according to data. Only the toner of the developer 26 supplied to the surface of the developing sleeve 30 adheres to the electrostatic latent image portion, and the electrostatic latent image is visualized. This visualization process has already been described in detail with reference to FIG.

  A transfer roller 36 is provided at a position facing the recording paper conveyance path 25 with respect to the photoreceptor 28, and is rotated in the direction D5 by a driving source (not shown). A predetermined transfer bias is applied to the transfer roller 36, and the toner image formed on the photoconductor 28 is transferred to the recording paper conveyed through the recording paper conveyance path 25.

  Hereinafter, the description will be continued returning to FIG.

  As described above, the image forming apparatus 21 according to the first exemplary embodiment is a tandem type color image forming apparatus in which a plurality of developing stations 22Y to 22K are arranged in a stepwise manner in the vertical direction, and is equivalent to a color inkjet printer. It aims at size. Since a plurality of units are arranged in the developing stations 22Y to 22K, in order to reduce the size of the image forming apparatus 21, the developing stations 22Y to 22K themselves are reduced in size and are arranged around the developing stations 22Y to 22K. It is necessary to reduce the members involved in the image process and to reduce the arrangement pitch of the developing stations 22Y to 22K as much as possible.

  In consideration of user convenience when installing the image forming apparatus 21 on the desktop in an office or the like, in particular, accessibility to the recording paper 23 at the time of paper feeding or paper ejection, from the bottom surface of the image forming apparatus 21 to the paper feed port 65. The height is preferably 250 mm or less. In order to realize this, it is necessary to suppress the height of the entire developing stations 22Y to 22K to about 100 mm in the entire configuration of the image forming apparatus 21.

  However, the existing LED head, for example, has a thickness of about 15 mm, and if it is disposed between the developing stations 22Y to 22K, it is difficult to achieve the target. According to the examination results of the present inventors, when the thickness of the exposure device 33 is 7 mm or less, the height of the entire development station is 100 mm or less even if the exposure devices 33Y to 33K are arranged in the gaps between the development stations 22Y to 22K. It is possible to suppress.

  A toner bottle 37 stores yellow, magenta, cyan, and black toners. A toner transport pipe (not shown) is provided from the toner bottle 37 to each of the developing stations 22Y to 22K, and supplies toner to each of the developing stations 22Y to 22K.

  A paper feed roller 38 is rotated in the direction D1 by controlling an electromagnetic clutch (not shown), and feeds the recording paper 23 loaded in the paper feeding tray 24 to the recording paper transport path 25.

  A registration paper 39 and a pair of pinch rollers 40 are provided as a nip conveyance means on the inlet side in the recording paper conveyance path 25 positioned between the paper supply roller 38 and the transfer portion of the most upstream yellow developing station 22Y. The registration roller 39 and the pinch roller 40 pair temporarily stop the recording paper 23 conveyed by the paper supply roller 38 and convey it in the direction of the yellow developing station 22Y at a predetermined timing. This temporary stop restricts the leading edge of the recording paper 23 in parallel with the axial direction of the registration roller 39 and pinch roller 40 pair, thereby preventing the recording paper 23 from skewing.

  Reference numeral 41 denotes a recording paper passage detection sensor. The recording paper passage detection sensor 41 is constituted by a reflective sensor (photo reflector), and detects the leading edge and the trailing edge of the recording paper 23 based on the presence or absence of reflected light.

  When the rotation of the registration roller 39 is started (the power transmission is controlled by an electromagnetic clutch (not shown) and the rotation is turned ON / OFF), the recording paper 23 is conveyed along the recording paper conveyance path 25 in the direction of the yellow developing station 22Y. However, starting from the rotation start timing of the registration roller 39, the writing timing of the electrostatic latent images by the exposure devices 33Y to 33K disposed in the vicinity of the developing stations 22Y to 22K is independently controlled.

  A fixing device 43 is provided as a nip conveying means on the outlet side in the recording paper conveyance path 25 located further downstream of the most downstream black developing station 22K. The fixing device 43 includes a heating roller 44 and a pressure roller 45. The heating roller 44 is a multi-layered roller composed of a heating belt, a rubber roller, and a core material (both not shown) in order from the surface. Among them, the heat generating belt is a belt having a three-layer structure, and is composed of a release layer, a silicon rubber layer, and a base material layer (both not shown) from the side closer to the surface. The release layer is made of a fluororesin having a thickness of about 20 to 30 μm and imparts release properties to the heating roller 44. The silicon rubber layer is made of silicon rubber having a thickness of about 170 μm and gives the pressure roller 45 a suitable elasticity. The base material layer is made of a magnetic material that is an alloy of iron, nickel, chromium, or the like.

  A back core 26 includes an exciting coil. Inside the back core 46, an excitation coil in which a predetermined number of copper wires (not shown) whose surfaces are insulated is bundled in the direction of the rotation axis of the heating roller 44, and at both ends of the heating roller 44, the heating roller It circulates along the circumferential direction of 44. When an alternating current of about 30 kHz is applied to the exciting coil from an exciting circuit (not shown) that is a semi-resonant inverter, a magnetic flux is generated in a magnetic path constituted by the back core 46 and the base layer of the heating roller 44. Due to this magnetic flux, an eddy current is formed in the base material layer of the heat generating belt of the heating roller 44 and the base material layer generates heat. The heat generated in the base material layer is transmitted to the release layer through the silicon rubber layer, and the surface of the heating roller 44 generates heat.

  Reference numeral 47 denotes a temperature sensor for detecting the temperature of the heating roller 44. The temperature sensor 47 is a ceramic semiconductor obtained by sintering at a high temperature using a metal oxide as a main raw material, and it is possible to measure the temperature of a contacted object by applying a change in load resistance according to the temperature. it can. The output of the temperature sensor 47 is input to a control device (not shown). The control device controls the power output to the exciting coil inside the back core 46 based on the output of the temperature sensor 47, and the surface temperature of the heating roller 44 is about 170 °. Control to be C.

  When the recording paper 23 on which the toner image is formed is passed through the nip formed by the heating roller 44 and the pressure roller 45 that are controlled in temperature, the toner image on the recording paper 23 is connected to the heating roller 44. The toner image is fixed on the recording paper 23 by being heated and pressurized by the pressure roller 45.

  A recording paper trailing edge detection sensor 48 monitors the discharge state of the recording paper 23. Reference numeral 52 denotes a toner image detection sensor. The toner image detection sensor 52 is a reflective sensor unit that uses a plurality of light emitting elements (both visible light) having different emission spectra and a single light receiving element, and changes the image color between the background of the recording paper 23 and the image forming portion. Accordingly, the image density is detected by utilizing the fact that the absorption spectrum is different. Further, since the toner image detection sensor 52 can detect not only the image density but also the image forming position, the image forming apparatus 21 according to the first exemplary embodiment is provided with two toner image detection sensors 52 in the width direction of the image forming apparatus 21, and recording paper. The image formation timing is controlled based on the detection position of the image position deviation amount detection pattern formed on the image 23.

  53 is a recording paper transport drum. The recording paper transport drum 53 is a metal roller whose surface is covered with rubber having a thickness of about 200 μm, and the recording paper 23 after fixing is transported along the recording paper transport drum 53 in the direction D2. At this time, the recording sheet 23 is cooled by the recording sheet conveying drum 53 and is bent and conveyed in the direction opposite to the image forming surface. As a result, curling that occurs when a high density image is formed on the entire surface of the recording paper can be greatly reduced. Thereafter, the recording paper 23 is conveyed in the direction D6 by the kicking roller 55 and discharged to the paper discharge tray 59.

  Reference numeral 54 denotes a face-down paper discharge unit. The face-down paper discharge unit 54 is configured to be rotatable about the support member 56. When the face-down paper discharge unit 54 is opened, the recording paper 23 is discharged in the direction D7. In the closed state, the face-down paper discharge unit 54 is formed with ribs 57 along the transport path on the back surface so as to guide the transport of the recording paper 23 together with the recording paper transport drum 53.

  Reference numeral 58 denotes a drive source. In the first embodiment, a stepping motor is employed. By the drive source 58, peripheral portions of the developing stations 22Y to 22K including the paper feed roller 38, the registration roller 39, the pinch roller 40, the photoconductors (28Y to 28K), and the transfer rollers (36Y to 36K), the fixing device 43, The recording paper transport drum 53 and the kicking roller 55 are driven.

  A controller 61 receives image data from a computer (not shown) via an external network and develops and generates printable image data.

  Reference numeral 62 denotes an engine control unit. The engine control unit 62 controls the hardware and mechanism of the image forming apparatus 21, forms a color image on the recording paper 23 based on the image data transferred from the controller 61, and performs overall control of the image forming apparatus 21. Yes.

  63 is a power supply unit. The power supply unit 63 supplies power of a predetermined voltage to the exposure apparatuses 33Y to 33K, the drive source 58, the controller 61, and the engine control unit 62, and supplies power to the heating roller 44 of the fixing device 43. The power supply unit also includes a so-called high-voltage power supply system such as charging of the surface of the photosensitive member 28, a developing bias applied to the developing sleeve (see reference numeral 30 in FIG. 8), and a transfer bias applied to the transfer roller 36. .

  The power supply unit 63 includes a power supply monitoring unit 64 so that at least the power supply voltage supplied to the engine control unit 62 can be monitored. This monitor signal is detected by the engine control unit 62 to detect a decrease in power supply voltage that occurs when the power switch is turned off or a power failure occurs.

  In the above description, the case where the present invention is applied to a color image forming apparatus has been described. However, the present invention can also be applied to a single color image forming apparatus such as black. When applied to a color image forming apparatus, the development colors are not limited to four colors of yellow, magenta, cyan and black.

  The organic electroluminescent device according to the present invention has a uniform light emission intensity distribution in the light emitting surface, and thus is useful in a wide range of applications including exposure apparatuses, flat panel displays, display devices, and other light sources. . The exposure apparatus using the organic electroluminescent device according to the present invention has a uniform light emission intensity distribution in the light emitting surface, so that exposure faithful to image data is possible, and electrophotography such as printers and copiers. The present invention can be applied to an apparatus or a photo printer that directly exposes photographic paper based on image data.

Configuration diagram of organic electroluminescent element in Example 1 of the present invention (A) is explanatory drawing which shows the light emission intensity distribution of the organic electroluminescent element based on a prior art, (b) is explanatory drawing which shows the light emission intensity distribution of the organic electroluminescent element in Example 1 of this invention. (A) is sectional drawing of the layer structure of the PEDOT element based on a prior art, (b) is sectional drawing of the layer structure of the intermediate | middle layer element based on this invention FIG. 1 is a block diagram of an exposure apparatus in Embodiment 1 of the present invention. (A) is a top view of the glass substrate which concerns on the exposure apparatus of Example 1 of this invention, (b) is the principal part enlarged view. Explanatory drawing which shows the condition which has exposed the photoreceptor with the exposure apparatus which applied the organic electroluminescent element of Example 1 of this invention 1 is a configuration diagram of an image forming apparatus equipped with an exposure device 33 to which an organic electroluminescent element of Example 1 of the present invention is applied. 1 is a configuration diagram showing the periphery of a developing station in an image forming apparatus according to Embodiment 1 of the present invention. Sectional drawing which shows the structure of the conventional polymer organic electroluminescent element

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic electroluminescent element 2 Glass substrate 3 Anode 4 Insulating layer 5 Intermediate layer 6 Inorganic layer 7 Organic layer 8 Light emitting layer 9 Cathode 10 PEDOT layer 11 Organic electroluminescent element 12 Glass substrate 13 Anode 14 Insulating layer 18 Light emitting layer 19 Cathode 21 Image forming device 22, 22Y, 22M, 22C, 22K Developing station 28, 28Y, 28M, 28C, 28K Photosensitive member 33, 33Y, 33M, 33C, 33K Exposure device 71 Lens array 78 Drive controller 81 Source driver 82 TFT circuit 84 Sealing glass

Claims (9)

A substrate, a first electrode formed on the substrate, an insulating layer formed to cover at least a part of the first electrode, and formed on the insulating layer and the first electrode A light-emitting layer and a second electrode disposed in contact with the light-emitting layer and facing the first electrode; an intermediate between the first electrode and the light-emitting layer and between the insulating layer and the light-emitting layer; An organic electroluminescent device characterized in that a layer is disposed, and the intermediate layer is composed of an inorganic layer formed using a dry process and an organic layer formed using a wet process. 2. The organic electroluminescent device according to claim 1, wherein the inorganic layer is configured to be in contact with the first electrode and the insulating layer. 2. The organic electroluminescent device according to claim 1, wherein the inorganic layer is composed of any one of an oxide, a nitride, an oxynitride, and a composite oxide. 2. The organic electroluminescent device according to claim 1, wherein the inorganic layer is made of an oxide of molybdenum, tungsten, or vanadium. The organic electroluminescent device according to claim 1, wherein the organic material layer is configured to be in contact with the light emitting layer. When the thickness of the organic layer is L1 and the thickness of the light emitting layer is L2, L1 is configured to satisfy the relationship of (L2 / 20) <L1 <(L2 / 3). The organic electroluminescent device according to claim 1. 2. The organic electroluminescent device according to claim 1, wherein the light emitting layer is formed by a wet process using a polymer material. An exposure apparatus in which the organic electroluminescent elements according to any one of claims 1 to 7 are arranged in a line, and each organic electroluminescent element can be controlled to be turned on / off independently. 9. An image forming apparatus comprising: an exposure apparatus according to claim 8; a photoconductor on which an electrostatic latent image is formed by the exposure apparatus; and a developing unit that visualizes the electrostatic latent image formed on the photoconductor. apparatus.

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