JP4126531B2 - Image forming apparatus using organic EL array exposure head - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus using an organic EL array exposure head, and more particularly to an image forming apparatus using an organic EL array exposure head that prevents crosstalk between pixels.
[0002]
[Prior art]
Conventionally, various types using an organic EL array as an exposure head for an image forming apparatus have been proposed. The related items are as follows.
[0003]
In JP-A-10-55890, an organic EL array is collectively produced on an insulating substrate such as glass, combined with a separate driver IC, and a light emitting portion of the organic EL array is imaged on a photosensitive drum. A light rod lens array is used.
[0004]
In Japanese Patent Application Laid-Open No. 11-198433, a one-chip organic EL array having a plurality of rows is used, and an optical system for forming an image of the light emitting portion on a photosensitive drum is unknown. Note that the EL layer of the organic EL array is deposited by vapor deposition.
[0005]
In Japanese Patent Laid-Open No. 2000-77188, a microlens is formed on the top surface of the substrate by the in-place exchange method, or a microlens is formed on the back surface of the substrate by a method using a photoresist or a replica method, and is aligned with the microlens. An organic EL array having is deposited by vapor deposition.
[0006]
Japanese Patent Application Laid-Open No. 10-12377 relates to a method of manufacturing an active matrix organic EL display, in which an organic light emitting layer is formed on a glass substrate having a thin film transistor by an ink jet method.
[0007]
In Japanese Patent Laid-Open No. 2000-323276, a hole injection layer and an organic light emitting layer of an organic EL element are formed by providing a partition wall and applying the ink jet method.
[0008]
In Japanese Patent Laid-Open No. 2001-18441, a printer is configured by forming a light emitting layer and a TFT layer for controlling the light emission inside a photosensitive drum.
[0009]
[Problems to be solved by the invention]
In the above prior art, when the organic EL array is used for an exposure head of an electrophotographic printer or the like, a condensing rod lens array is used to condense the light beam from the light emitting portion of the organic EL array onto the photosensitive drum. In this case, the optical path length becomes long and the size increases, and the condensing rod lens is not arranged one-on-one with respect to each light emitting unit, so that periodic light amount unevenness occurs. The cost is inevitable due to the advanced manufacturing method.
[0010]
Also, in the case of using a microlens array, each microlens is arranged one-on-one with respect to each light emitting unit, but is not a pixel that does not correspond via a microlens that does not correspond to the light emitting unit, but is not adjacent to it There is a tendency that crosstalk incident on the position tends to occur, leading to a decrease in resolving power.
[0011]
The present invention has been made in view of such problems of the prior art, and its object is to reduce crosstalk of an organic EL array exposure head in which microlenses are arranged corresponding to individual elements of the organic EL array. Thus, it is an object of the present invention to provide a small exposure head and an image forming apparatus using the same, in which a light beam from each element is condensed on an image carrier such as a photoreceptor with sufficient resolution and contrast.
[0012]
[Means for Solving the Problems]
An image forming apparatus using the organic EL array exposure head of the present invention that achieves the above object comprises an array of organic EL elements arranged in a pixel shape in at least one column on a long substrate, and the organic EL On the light emitting side of the element array, an optical hole is provided to block the light emitted from the light emitting part of the organic EL element adjacent to the light condensing position of the light emitted from the light emitting part of each organic EL element. An organic EL array exposure head in which a partition is arranged and a positive lens is arranged in each hole position of the partition is provided as an exposure head for writing an image on the image carrier, and the periphery of the image carrier is charged. A tandem type color image forming apparatus in which at least two or more image forming stations are provided, each having an exposure head, a toner developing unit, and a transfer unit, and a transfer medium passes through each station. In the image forming apparatus,
The height of the surface on the exit side of the partition wall is higher than that of the positive lens, and
The work function of the positive lens material is Φ _L The work function of the partition wall material is Φ _B Φ the work function of the toner material _T And when
｜ Φ _T −Φ _L | ≦ 0.2 eV (1)
｜ Φ _T −Φ _B | ≧ 0.5 eV (2)
It is characterized by satisfying the relationship at the same time.
[0014]
Moreover, it is desirable that the linear expansion coefficients of the substrate and the partition wall are substantially equal.
[0015]
Moreover, as a partition, what was comprised by making the hole in a metal plate, what was comprised by making the hole by resin molding, etc. may be sufficient.
[0016]
Further, the partition wall and the substrate may be integrally formed.
[0018]
Moreover, it is desirable that the wall surface of the hole of the partition wall is light reflective or light absorbing.
[0019]
The positive lens can be made of resin. In that case, the positive lens can be formed in the hole of the partition wall by an ink jet method or formed by a molding method.
[0020]
The positive lens may be made of glass.
[0021]
The positive lens may be a ball lens.
[0022]
The organic EL element may be either one that emits emitted light to the anode side or one that emits emitted light to the cathode side.
[0023]
The organic EL element may be either a high molecular type or a low molecular type.
[0024]
In addition, it is desirable that the organic EL element is light emission controlled by a TFT provided on the substrate.
[0027]
In the present invention, the optical element that blocks the light emitted from the light emitting portion of the organic EL element adjacent to the light condensing position of the light emitted from the light emitting portion of each organic EL element from being mixed on the light emitting side of the array of organic EL elements. Since the partition wall provided with a typical hole is arranged, crosstalk between adjacent pixels is reduced, and sufficient resolution and contrast can be obtained.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an organic EL array exposure head of the present invention and an image forming apparatus using the same will be described below with reference to the drawings.
[0029]
FIG. 1 is a schematic plan view of one embodiment of an organic EL array exposure head according to the present invention, and FIG. 2 shows a cross-sectional view of one pixel of the array along the line AA ′ of FIG.
[0030]
The organic EL array exposure head 1 of this embodiment is arranged such that two rows of arrays 2 and 2 'are parallel and the pixels are arranged in a staggered manner, and each array 2 and 2' is arranged in a straight line. Each pixel 3 has the same configuration, and includes an organic EL element 4 and a TFT 5 that controls light emission of the organic EL element 4.
[0031]
FIG. 2 is a cross-sectional view including the organic EL element 4 and the TFT 5 of one pixel 3. This organic EL element 4 is an example in which emitted light is emitted from the cathode side.
[0032]
The organic EL element 4 emits light when electrons and holes are respectively injected from the cathode 10 and the anode 7 and recombined, and has a structure in which an electron transporting light emitting layer 9 and a hole injection layer 8 are laminated. It has become.
[0033]
Organic EL elements include those that extract light from the cathode and those that extract light from the anode, and those that extract light from the anode, that is, the substrate side, are generally used (examples described later). The part by restriction is large. Since the substrate is emitted from the substrate, the substrate is limited to a transparent member such as glass, and the drive circuit is a TFT that can be formed on the glass.
[0034]
On the other hand, the present embodiment is configured to extract light from the cathode side, and the cathode 10 is light transmissive. On the other hand, by making the anode 7 reflective rather than light transmissive, there is an effect that the amount of radiation to the cathode 10 side can be increased.
[0035]
The organic EL array exposure head 1 transmits a substrate 6 made of glass, silicon, etc., an anode 7 made of ITO or a magnesium / silver alloy, aluminum, etc., a hole injection layer 8, a light emitting layer 9, ITO or light. A cathode 10 that is a sufficiently thin metal electrode, an adhesive layer 11 made of a transparent resin, a microlens 13 that serves as a condensing element and a sealing member that prevents the light-emitting layer 9 from being deteriorated by contact with moisture, a microlens As shown in FIG. 1, one light emitting pixel 3 composed of partition walls 12 arranged between 13 has a structure arranged in, for example, two rows of arrays 2 and 2 ′.
[0036]
As will be described later, for example, when used in an exposure head of an electrophotographic color image forming apparatus, the photoconductor is configured to face the microlens 13, and each microlens 13 causes the light emitting pixels 3 to act. Are emitted in an array on the photosensitive member.
[0037]
As a basic manufacturing method and configuration of the organic EL array exposure head 1 of this embodiment, an organic EL array composed of organic EL elements 4 and TFTs 5 arranged in an array on a substrate 6, and light emitted from the organic EL element 4 The microlens 13 is collected separately from the array of microlenses 13 and is optically and mechanically coupled via the adhesive layer 11. The manufacturing method of the organic EL element 4 may be any known general method, and the films 7, 8, 9, and 10 are formed on the substrate 6 by a vacuum deposition method, a casting method, or the like. Alternatively, it can be formed by an ink jet method as described in JP-A-10-12377 or the like. As the microlens 13 and the adhesive layer 11, an ultraviolet curable resin is most easily used. However, the microlens 13 and the adhesive layer 11 are not limited as long as they have sufficient transmittance with respect to the emission wavelength and at the same time meet the manufacturing process. In particular, since the material of the light-emitting layer 9 dislikes ultraviolet irradiation, it is conceivable that a thermosetting resin is better.
[0038]
An example of a method for producing an organic EL array will be described. First, a TFT 5 is produced on a substrate 6. Various methods for manufacturing TFT 5 are known. For example, a silicon oxide film is first deposited on the substrate 6, and an amorphous silicon film is further deposited. Next, the amorphous silicon film is crystallized by irradiating it with an excimer laser beam to form a polysilicon film serving as a channel. After patterning the polysilicon film, a gate insulating film is deposited, and a gate electrode made of tantalum nitride is formed. Subsequently, the source / drain portions of the N-channel TFT are formed by phosphorus ion implantation, and the source / drain portions of the P-channel TFT are formed by boron ion implantation. After activating the ion-implanted impurity, the first interlayer insulating film is deposited, the first contact hole is opened, the source line is formed, the second interlayer insulating film is deposited, the second contact hole is opened, and the metal pixel electrode is formed. The array of TFTs 5 is completed sequentially (see, for example, “8th Electronic Display Forum (2001.18)“ polymer organic EL display ”). Here, this metal pixel electrode serves as the anode 7 of the organic EL element 4 and also serves as a reflective layer of the organic EL element 4 and is formed of a metal thin film electrode such as Mg, Ag, Al, Li or the like. The
[0039]
Next, the ink composition for the hole injection layer is discharged from the head of the ink jet printing apparatus, and patterning is applied on the anode 7 of each pixel. After coating, the solvent is removed and heat treatment is performed to form the hole injection layer 8.
[0040]
Here, the ink jet system referred to in the present invention is a piezo jet system that ejects an ink composition using mechanical energy such as a piezoelectric element, and generates bubbles using the thermal energy of a heater. Any of the thermal methods for discharging the ink composition on the basis of the above (published “Fine Imaging and Hardcopy” 1999.1.7 (Corona) .43). FIG. 3 shows a configuration example of a piezo jet head. The inkjet head 21 includes, for example, a stainless steel nozzle plate 22 and a diaphragm 23, and both are joined via a partition member (reservoir plate) 24. A plurality of ink chambers 25 and liquid reservoirs (not shown) are formed between the nozzle plate 22 and the vibration plate 23 by the partition member 24. The interiors of the ink chamber 25 and the liquid reservoir are filled with the ink composition, and the ink chamber 25 and the liquid reservoir communicate with each other through a supply port. Further, the nozzle plate 22 is provided with a nozzle hole 26 for ejecting the ink composition from the ink chamber 25 into a jet shape. On the other hand, the ink jet head 21 is formed with an ink introduction hole for supplying the ink composition to the liquid reservoir. A piezoelectric element 28 is bonded to the surface of the vibration plate 23 opposite to the surface facing the ink chamber 25 so as to correspond to the position of the ink chamber 25. The piezoelectric element 28 is located between the pair of electrodes 29 and bends so that the piezoelectric element 28 protrudes outward when energized. As a result, the volume of the ink chamber 25 increases. Therefore, the ink composition corresponding to the increased volume in the ink chamber 25 flows from the liquid reservoir through the supply port. Next, when energization to the piezoelectric element 28 is released, both the piezoelectric element 28 and the diaphragm 23 return to their original shapes. As a result, the space 25 also returns to its original volume, so that the pressure of the ink composition inside the ink chamber 25 increases, and the ink composition is ejected from the nozzle hole 26 toward the substrate on which the partition wall 9 is provided.
[0041]
After the hole injection layer 8 is formed on the anode 7, the ink composition for the light emitting layer is discharged from the head of the ink jet printing apparatus, and patterning coating is performed on the hole injection layer 8 of each pixel. After coating, the solvent is removed and heat treatment is performed to form the light emitting layer 9.
[0042]
The order of the hole injection layer 8 and the light emitting layer 9 may be reversed. It is desirable to arrange a layer that is more resistant to moisture on the surface side (the side farther from the substrate 6).
[0043]
In addition, the hole injection layer 8 and the light emitting layer 9 can be formed by a known spin coating method, dip method, or vapor deposition method, instead of forming the ink composition by applying the ink jet method as described above. . In particular, when the organic EL material is a high-molecular organic EL material, the ink jet method is suitable, and when the organic EL material is a low-molecular organic EL material, a vapor deposition method is suitable.
[0044]
As for the material used for the light emitting layer 9 and the material used for the hole injection layer 8, for example, Japanese Patent Application Laid-Open No. 10-12377 for the high molecular organic EL material, and for example Japanese Patent Application Laid-Open No. 11-138899 for the low molecular organic EL material. Various known items can be used, and details are omitted.
[0045]
After the hole injection layer 8 and the light emitting layer 9 are formed in order on the anode 7 of each pixel, a transparent electrode to be the cathode 10 of the organic EL element 4 is deposited on the entire surface of the substrate 6 by vacuum deposition. Examples of the material for the transparent electrode include a tin oxide film, an ITO film, a composite oxide film of indium oxide and zinc oxide, and a photolithography method, a sputtering method, a pyrosol method, and the like can be employed in addition to the vacuum deposition method.
[0046]
The microlens array in which the partition walls 12 are arranged between the microlenses 13 on the organic EL array thus manufactured is in an alignment state in which each microlens 13 has a one-to-one correspondence with each organic EL element 4. Then, they are optically and mechanically bonded by the adhesive layer 11.
[0047]
In the configuration of FIG. 2, since the emitted light is emitted to the cathode 10 side, that is, the side opposite to the substrate 6, the substrate 6 may be opaque and the driving circuit does not need to be the TFT 5. A configuration in which the organic EL element 4 is laminated on a drive circuit formed by a general silicon process is also possible.
[0048]
Now, the partition 12 will be described. When a voltage is applied between the cathode 10 and the anode 7 under the control of the TFT 5, the light emitting layer 9 emits light. The emitted light is radiated isotropically in all directions from the light emitting layer 9, but if the anode 7 is non-light transmissive, it is transmitted through the cathode 10 and mainly emitted upward in FIG. A component having a small angle with respect to the normal line of the light emitting layer 9 reaches the microlens 13 as it is, and is directly emitted through the microlens 13 to be condensed at a predetermined position. On the other hand, a component having a large angle with respect to the normal line of the light emitting layer 9 is directed to the partition wall 12 between the microlenses 13. When the partition wall 12 is formed by, for example, a metal plate having holes 14 for holding a large number of microlenses 13 in an array, the wall surface of the hole 14 of the partition wall 12 is light-reflective so that it is reflected once. Alternatively, it is reflected multiple times between the wall surfaces of the holes 14 of the partition wall 12 and reaches and exits the microlens 13, and at least a part of the light is collected through the direct microlens 13. Condensed near the condensing position. Therefore, in this case, since a component having a large angle with respect to the normal line of the light emitting layer 9 is also used as the light condensed in an array, it is a high efficiency, low power, long life (the biggest problem in organic EL). .) Exposure head.
[0049]
When the partition wall 12 is made of a light absorbing material such as a black resist or a resin in which carbon powder is dispersed, a component having a large angle with respect to the normal line of the light emitting layer 9 is absorbed by the wall surface of the hole 14. Therefore, the component having a large angle can be eliminated more reliably.
[0050]
In the case where the partition wall 12 is either light reflective or light absorbing, the degree of overlap (occurs of crosstalk) with the light emitted from the adjacent adjacent pixels on the photosensitive member is greater than when the partition wall 12 is not provided. The effect of being significantly reduced is high.
[0051]
In the configuration in which emitted light is emitted from the cathode 10 side of the organic EL element 4 in FIG. 2 described above, only the sealing member (microlens 13) separates the organic EL element 4 from the outside, so that the organic EL element can be thinned. The amount of light extracted from the element 4 can be improved. Further, the distance between the light emitting portion of the organic EL element 4 and the microlens 13 or the partition wall 12 can be shortened, and the prevention of crosstalk between the pixels becomes easier.
[0052]
As the partition wall 12, there are a metal plate in which a large number of holes 14 are formed in an array as described above, and a resin plate in which a large number of holes 14 are formed in an array by molding. In this case, it is desirable to use a substrate having a linear expansion coefficient substantially equal to that of the substrate 6. If it does so, even if temperature changes, the light emission point of the organic EL element 4 and the micro lens 13 in the partition 12 will not shift | deviate, and the temperature stability of the condensing point array of the exposure head 1 will become high. In addition, when the partition 12 is produced by resin molding, there is an advantage that manufacture is easy, and low cost and light weight are achieved.
[0053]
In the above description, the organic EL array and the micro lens array in which the partition walls 12 are arranged between the lenses are separately manufactured and bonded by the adhesive layer 11. However, the partition walls 12 are configured integrally with the substrate 6. May be. For example, holes 14 having a certain depth for arranging the pixels 3 on the surface of the substrate 6 are formed in an array, the function between the holes 14 is assigned to the portion between the holes 14, and the TFT 5 or organic EL element is formed at the bottom of each hole 14. 4 (anode 7, hole injection layer 8, light emitting layer 9, cathode 10) are stacked, and microlens 13 is disposed on organic EL element 4. In this case, when the substrate 6 itself is made light reflective or light absorbent, or the substrate 6 is made of a transparent material such as glass, the inner surface of the hole 14 formed on the surface of the substrate 6 is made light reflective or light absorbent. For example, a light reflecting film or a light absorbing film may be applied. Thus, when the partition 12 is integrally formed with the substrate 6, there is an advantage that the positional accuracy of the light emitting portion of the organic EL element 4, the microlens 13, and the partition 12 is improved.
[0054]
As the microlens 13 provided on the partition wall 12, various types are conceivable. As shown in FIG. 4, a transparent ink composition for microlens, for example, an ultraviolet curable type, is provided in the hole 14 provided in the partition wall 12. The resin monomer can be ejected from the head 21 of the ink jet printing apparatus 20 and subjected to patterning application, cured after application, and formed into a convex microlens that bulges on the upper surface of the hole 14. In this case, the radius of curvature of the convex surface of the microlens 13, that is, the focal length is determined by the ejection amount of the ink composition, the diameter of the hole 14, the surface tension of the transparent ink composition for microlens, and the water repellency with respect to the inner surface of the hole 14. Although it depends on the degree and the amount of shrinkage when the ink composition is cured, there is a merit that the lens surface accuracy is high and a microlens array can be easily produced without a mold. In addition, the member 15 arrange | positioned at the bottom of the hole 14 of FIG. 4 is a backing member, and is removed after hardening of an ink composition. However, when the partition wall 12 is formed integrally with the substrate 6, the member 15 is the substrate 6, the TFT 5 or the organic EL element 4 disposed there.
[0055]
Moreover, the microlens 13 formed in the hole 14 of the partition 12 can also be produced from glass or transparent resin by a molding method (replica method). In this case, the stability of the shape of the microlens 13 is high, and the degree of freedom in shape is also high.
[0056]
Further, as the microlens 13, a ball (spherical) lens 13 ′ made of glass or resin as shown in FIG. 5A or a hemispherical lens 13 ″ as shown in FIG. 5B may be used. These may be dropped into the hole 14 of the partition wall 12 and fixed with the adhesive 16.
[0057]
Incidentally, the height relationship between the lens surface of the microlens 13 disposed in the hole 14 of the partition wall 12 and the upper surface of the partition wall 12 is as shown in FIGS. 2, 4, and 5 (a). There are a case where the lens surface of the microlens 13 is made higher than the upper surface and a case where the partition wall 12 is made higher than the lens surface of the microlens 13 as shown in FIG. In the latter case, the partition wall 12 serves as a protective member and can protect the microlens 13 from scratches and damage. In the former case, the microlens 13 can be easily manufactured by the ink jet method as shown in FIG.
[0058]
Next, FIG. 6 shows an embodiment in which emitted light is emitted from the anode side of the organic EL element 4. 6 is a cross-sectional view of one pixel of the array along the line AA ′ in FIG.
[0059]
In the organic EL array exposure head 1, an organic EL element 4 is formed on a transparent substrate 6 such as glass in the same manner as in FIG. 2, an anode 7 made of a substantially transparent material such as ITO, a hole injection layer 8, Sealing that is formed as a light emitting layer 9, a cathode 10 that is an electrode made of ITO, an alloy of magnesium or silver, aluminum or the like, and prevents the light emitting layer 9 from being deteriorated by being exposed to moisture by an adhesive layer 17 thereon. The member 18 is bonded to produce an organic EL array.
[0060]
The manufacturing method of this organic EL element 4 may be any of the known general ones as in the case of FIG. 2, and the films 7, 8, 9, 10 are formed on the substrate 6 by vacuum deposition, casting, or the like. Be filmed. Alternatively, it can be formed by an ink jet method as described in JP-A-10-12377 or the like.
[0061]
In this configuration of the organic EL array thus produced, each microlens 13 has a microlens array in which partition walls 12 are arranged between the microlenses 13 on the substrate 6 side, as in FIG. The organic EL element 4 is optically and mechanically bonded by the adhesive layer 11 in an alignment state corresponding to the organic EL element 4 on a one-to-one basis.
[0062]
In the configuration of FIG. 6, since the emitted light is emitted to the anode 7 side, that is, the substrate 6 side, the substrate 6 must be transparent. Therefore, the driving circuit needs to use the TFT 5.
[0063]
Even in this configuration, when a voltage is applied between the cathode 10 and the anode 7 under the control of the TFT 5, the light emitting layer 9 emits light. The emitted light is emitted isotropically in all directions from the light emitting layer 9, but if the cathode 10 is non-light-transmitting, it is transmitted through the anode 7 and the substrate 6 and mainly emitted downward in FIG. . A component having a small angle with respect to the normal line of the light emitting layer 9 reaches the microlens 13 as it is, and is directly emitted through the microlens 13 to be condensed at a predetermined position. On the other hand, a component having a large angle with respect to the normal line of the light emitting layer 9 is directed to the partition wall 12 between the microlenses 13. When the hole 14 of the partition wall 12 is light-reflective, the light reaches the microlens 13 after being reflected once or subjected to multiple reflection between the wall surfaces of the hole 14, and at least a part of the hole 14 is directly micro-reflected. The light is condensed near the condensing position of light condensed through the lens 13. Therefore, in this case, since a component having a large angle with respect to the normal line of the light emitting layer 9 is also used as the light condensed in an array, it is a high efficiency, low power, long life (the biggest problem in organic EL). .) Exposure head. When the partition wall 12 is light-absorbing, a component having a large angle with respect to the normal line of the light emitting layer 9 is absorbed by the partition wall 12, so that the component having a large angle can be more reliably eliminated. Therefore, in any case, compared to the case without the partition wall 12, an effect of significantly reducing the degree of overlapping (occurrence of crosstalk) with the light emitted from the adjacent adjacent pixels on the photosensitive member can be obtained. .
[0064]
6 has a feature that the material selection and the manufacturing method are easy because the emission light is emitted to the anode 7 side of the transparent substrate 6 like the conventional organic EL element. Since the emitted light is incident on the microlens 13 and the partition wall 12 through the distance between the light emitting portion of the organic EL element 4 and the microlens 13 or the partition wall 12 tends to be long, the amount of light taken out from the organic EL element 4 is reduced. The crosstalk between pixels tends to increase. In order to alleviate these, it is necessary to either use a sufficiently thin substrate 6 or to cut the substrate 6 to make it thin after an organic EL array is manufactured. Currently, a substrate having a thickness of about 0.3 mm can be used as the substrate 6, and a technique of thinning to about 0.1 mm by polishing is also becoming generally available. In the case where the mechanical strength after handling or products in the polishing process is insufficient, this can be avoided by a configuration in which a portion having a frame thickness is left on the substrate 6.
[0065]
In the case of the configuration in which the emitted light is emitted to the anode 7 side in FIG. 6, the partition wall 12 and the microlens 13 can be applied in the same manner as in FIG.
[0066]
Now, the organic EL array exposure head 1 in which the partition wall is provided between the microlenses and the crosstalk is reduced according to the present invention as described above is a predetermined distance from the organic EL array exposure head 1 as shown in a side view in FIG. On the surface S separated by L, the luminous flux from each organic EL light emitting unit 4 is condensed in the same arrangement pattern as the pixel 3 arrangement of the organic EL array exposure head 1. Therefore, by relatively moving this surface S in the direction orthogonal to the longitudinal direction of the organic EL array exposure head 1 and controlling the light emission of each organic EL element 4 of the organic EL array exposure head 1 by the TFT 5, A predetermined pattern can be recorded on the surface S.
[0067]
Therefore, in the present invention, the organic EL array exposure head 1 of the present invention as described above is used for an exposure head of an electrophotographic color image forming apparatus, for example. FIG. 8 shows a tandem in which four similar organic EL array exposure heads 1K, 1C, 1M, and 1Y according to the present invention are respectively arranged at exposure positions of corresponding four photosensitive drums 41K, 41C, 41M, and 41Y. 1 is a front view showing an overall schematic configuration of an example of a color image forming apparatus of a system. As shown in FIG. 8, this image forming apparatus is tensioned by a driving roller 51, a driven roller 52, and a tension roller 53, and is intermediately transferred by being circulated in the direction indicated by an arrow (counterclockwise). Photosensitive members 41K, 41C, 41M, and 41Y each having a photosensitive layer are disposed on the outer peripheral surface as four image carriers that are provided with a belt 50 and are disposed at a predetermined interval with respect to the intermediate transfer belt 50. “K”, “C”, “M”, and “Y” added after the symbols mean black, cyan, magenta, and yellow, respectively, and indicate that the photoconductors are for black, cyan, magenta, and yellow, respectively. The same applies to other members. The photoconductors 41K, 41C, 41M, and 41Y are driven to rotate in the direction indicated by the arrow (clockwise) in synchronization with the driving of the intermediate transfer belt 50, but around each photoconductor 41 (K, C, M, Y). Are respectively charging means (corona charger) 42 (K, C, M, Y) for uniformly charging the outer peripheral surface of the photoconductor 41 (K, C, M, Y) and this charging means 42 (K, The organic EL array exposure as described above according to the present invention, in which the outer peripheral surface uniformly charged by C, M, Y) is sequentially scanned in line in synchronization with the rotation of the photoconductor 41 (K, C, M, Y). A toner as a developer is applied to the electrostatic latent image formed by the head 1 (K, C, M, Y) and the organic EL array exposure head 1 (K, C, M, Y) to form a visible image. Developing with the developing device 44 (K, C, M, Y) as a (toner image) and the developing device 44 (K, C, M, Y) A primary transfer roller 45 (K, C, M, Y) as transfer means for sequentially transferring the toner image to the intermediate transfer belt 50 as a primary transfer target, and a photoreceptor 41 (K, C, M, And a cleaning device 46 (K, C, M, Y) as a cleaning means for removing the toner remaining on the surface of Y).
[0068]
Here, as shown in FIG. 7, each organic EL array exposure head 1 (K, C, M, Y) is an inkjet system in the hole 14 of the partition wall 12 at a position corresponding to the light emitting portion of each organic EL element 4. The microlens 13 having a predetermined focal length is formed at a distance of a predetermined distance L from the surface of the corresponding photoconductor 41 (K, C, M, Y), and the organic EL array exposure head 1 (K, C, M, Y) are arranged so that the array direction of the photosensitive drums 41 (K, C, M, Y) is along the bus. The light emission energy peak wavelength of each organic EL array exposure head 1 (K, C, M, Y) and the sensitivity peak wavelength of the photoconductor 41 (K, C, M, Y) are set to substantially coincide with each other. Yes.
[0069]
The developing device 44 (K, C, M, Y) uses, for example, a non-magnetic one-component toner as a developer, and the one-component developer is conveyed to the developing roller by a supply roller, for example, and adheres to the surface of the developing roller. The film thickness of the developed developer is regulated by a regulation blade, and the potential of the photoreceptor 41 (K, C, M, Y) is adjusted by bringing the developing roller into contact with or pushing the photoreceptor 41 (K, C, M, Y). The toner image is developed by attaching a developer according to the level.
[0070]
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 45 (K, C, M, Y). The toner image, which is sequentially primary transferred onto the transfer belt 50 and sequentially superposed on the intermediate transfer belt 50 to become a full color, is secondarily transferred to a recording medium P such as paper by a secondary transfer roller 66, and serves as a fixing unit. The toner is fixed on the recording medium P by passing through the fixing roller pair 61, and is discharged onto a paper discharge tray 68 formed in the upper part of the apparatus by a paper discharge roller pair 62.
[0071]
In FIG. 8, 63 is a paper feed cassette in which a large number of recording media P are stacked and held, 64 is a pickup roller for feeding the recording media P from the paper feed cassette 63 one by one, and 65 is a secondary transfer roller. A pair of gate rollers for defining the supply timing of the recording medium P to the secondary transfer portion 66, a secondary transfer roller 66 as a secondary transfer means for forming a secondary transfer portion with the intermediate transfer belt 50, 67 Is a cleaning blade as a cleaning means for removing the toner remaining on the surface of the intermediate transfer belt 50 after the secondary transfer.
[0072]
When the organic EL array exposure head 1 of the present invention is used in the exposure head of such an electrophotographic image forming apparatus, the developer toner adheres to the lens surface of the microlens 13 and becomes dirty, resulting in uneven exposure. Cause deterioration of the image. Therefore, the work function Φ of the material used for the microlens 13 of the organic EL array exposure head 1 _L And the work function Φ of the material of the partition wall 12 _B And the work function of the toner material Φ _T It is desirable to select those materials so that and satisfy the following relationship simultaneously.
[0073]
｜ Φ _T −Φ _L | ≦ 0.2 eV (1)
｜ Φ _T −Φ _B | ≧ 0.5 eV (2)
If a combination of materials that satisfies the above conditions is used, the toner that stains the organic EL array exposure head 1 adheres exclusively to the partition wall 12 around the microlens 13 and does not adhere to the lens surface. The lens surface can be prevented from being stained with toner.
[0074]
The organic EL array exposure head of the present invention and the image forming apparatus using the same have been described based on the embodiments. However, the present invention is not limited to these embodiments, and various modifications are possible.
[0075]
【The invention's effect】
As is apparent from the above description, according to the organic EL array exposure head of the present invention and the image forming apparatus using the same, the light emitted from the light emitting portion of each organic EL element is placed on the light emitting side of the organic EL element array. Since the partition wall provided with the optical hole which blocks the light emitted from the light emitting part of the organic EL element adjacent to the light condensing position is disposed, the crosstalk between the adjacent pixels is reduced and sufficient. Resolution and contrast can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of one embodiment of an organic EL array exposure head according to the present invention.
FIG. 2 is a cross-sectional view of one pixel of an embodiment in which emitted light is emitted from the cathode side of the organic EL element.
FIG. 3 is a diagram illustrating a configuration example of a piezo jet head in an ink jet method.
FIG. 4 is a view for explaining a state where microlenses are formed in a hole of a partition wall by an ink jet method.
FIG. 5 is a diagram for explaining that a ball lens and a hemispherical lens are dropped into a partition hole to form a microlens.
FIG. 6 is a cross-sectional view of one pixel of an embodiment in which emitted light is emitted from the anode side of the organic EL element.
FIG. 7 is a side view showing a state of light collection by the organic EL array exposure head according to the present invention.
FIG. 8 is a front view showing an overall schematic configuration of an example of a tandem color image forming apparatus in which the organic EL array exposure head of the present invention is arranged.
[Explanation of symbols]
1 ... Organic EL array exposure head
1 (K, C, M, Y): Organic EL array exposure head
2, 2 '... array
3 ... Luminescent pixels
4 ... Organic EL element
5 ... TFT
6 ... Glass substrate
7 ... Anode
8 ... Hole injection layer
9 ... Light emitting layer
10 ... Cathode
11 ... Adhesive layer
12 ... Bulkhead
13 ... Microlens
13 '... Ball lens
13 "... hemispherical lens
14 ... hole
15 ... Backing member
16 ... Adhesive
17 ... Adhesive layer
18 ... Sealing member
20 ... Inkjet printer
21 ... Head
22 ... Nozzle plate
23 ... Diaphragm
24 ... Partition member (reservoir plate)
25. Ink chamber
26 ... Nozzle hole
28: Piezoelectric element
29 ... Electrode
41 (K, C, M, Y) ... photosensitive drum
42 (K, C, M, Y): Charging means (corona charger)
44 (K, C, M, Y) ... developing device
45 (K, C, M, Y) ... primary transfer roller
46 (K, C, M, Y) ... Cleaning device
50. Intermediate transfer belt
51. Driving roller
52. Followed roller
53 ... Tension roller
61. Fixing roller pair
62 ... Paper discharge roller pair
63: Paper cassette
64 ... Pickup roller
65 ... Gate roller pair
66. Secondary transfer roller
67 ... Cleaning blade
68 ... Output tray
S ... surface
P ... Recording medium

Claims (17)

An organic EL element array arranged in a pixel shape in at least one column is provided on a long substrate, and the light emitted from the light emitting portion of each organic EL element is collected on the light emitting side of the organic EL element array. Partitions provided with optical holes that block light emitted from the light emitting part of the organic EL element adjacent to the light position are disposed , and positive lenses are disposed at the respective hole positions of the partition walls. An organic EL array exposure head is provided as an exposure head for writing an image on the image carrier, and at least two image forming stations each having a charging unit, the exposure head, a toner developing unit, and a transfer unit arranged around the image carrier. In a tandem color image forming apparatus that performs color image formation by providing two or more transfer media through each station,
The height of the surface on the exit side of the partition wall is higher than that of the positive lens, and
When the work function of the positive lens material is Φ _L , the work function of the partition wall material is Φ _B , and the work function of the toner material is Φ _T ,
| Φ _T −Φ _L | ≦ 0.2 eV (1)
| Φ _T −Φ _B | ≧ 0.5 eV (2)
An image forming apparatus satisfying the above relationship at the same time. The image forming apparatus according to claim 1, wherein the linear expansion coefficient of the substrate and the partition wall are substantially equal. The partition wall, the image forming apparatus according to claim 1 or 2, characterized in that constructed pierced metal plate. The partition wall, the image forming apparatus according to claim 1 or 2, characterized in that constructed pierced by resin molding. The partition wall and the substrate is image forming apparatus according to claim 1 or 2, characterized in that it is integrally constructed. The image forming apparatus according to any one of claims 1 to 5, wherein the walls of said hole of said partition wall is a light reflective. The image forming apparatus according to any one of claims 1-5, characterized in that the wall of the hole of the partition wall is light absorbing. The positive lens is the image forming apparatus according to claim 1, characterized in that it consists of a resin. 9. The image forming apparatus according to claim 8, wherein the positive lens is formed in the hole of the partition wall by an ink jet method . 9. The image forming apparatus according to claim 8, wherein the positive lens is formed in the hole of the partition wall by a molding method . The positive lens is the image forming apparatus according to claim 1, characterized in that it consists of glass. The positive lens is the image forming apparatus according to claim 1, characterized in that it consists of a ball lens. The organic EL device is an image forming apparatus according to any one of claims 1, wherein 12 to be those which emits luminescent light to the anode side. The organic EL device is an image forming apparatus according to any one of claims 1, wherein 12 to be those which emits luminescent light to the cathode side. The organic EL device is an image forming apparatus according to any one of claims 1, wherein 14 to be a polymer electrolyte. The organic EL device is an image forming apparatus according to any one of claims 1, wherein 14 to be a low molecular weight type. The organic EL device is an image forming apparatus of any one of claims 1 to 16, characterized in that the light emission control with a TFT provided on the substrate is performed.

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