JP2006272685A - Line head and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a line head capable of efficiently forming a desired image while extending the life of a light emitting element.
A line head includes a first line portion having a first light emitting element arranged in a predetermined direction and a second line portion having a second light emitting element arranged in a predetermined direction. The area of the light emitting region 4A of the first light emitting element 3A is smaller than the area of the light emitting region 4B of the second light emitting element 3B, and the distance D1 between the light emitting regions 4A of the first light emitting element 3A in the first line portion L1 is the first. It is smaller than the distance D2 between the light emitting regions 4B of the second light emitting element 3B in the two line portions L2.
[Selection] Figure 3

Description

  The present invention relates to a line head and an image forming apparatus.

A line printer (image forming apparatus) is known as a printer using an electrophotographic system. In this line printer, devices such as a charger, a line-shaped printer head (line head), a developing device, and a transfer device are arranged close to the peripheral surface of the photosensitive drum as an exposed portion. It is. The line printer forms an electrostatic latent image by exposing the peripheral surface of the photosensitive drum charged by the charger by a selective light emitting operation of a light emitting element provided in the printer head, and develops the latent image. The toner image is developed with the toner supplied from the device, and the toner image is transferred to the paper with the transfer device (see Patent Documents 1 and 2).
JP 7-306481 A JP 2004-330472 A

  By the way, in the image forming apparatus as described above, it is desirable that a desired image can be efficiently formed while extending the life of the light emitting element.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a line head and an image forming apparatus capable of realizing a long lifetime of a light emitting element and efficiently forming a desired image.

  In order to solve the above problems, the present invention has a first line portion having a plurality of first light emitting elements arranged in a predetermined direction and a second line portion having a plurality of second light emitting elements arranged in the predetermined direction. The area of the light emitting region of the first light emitting element is smaller than the area of the light emitting region of the second light emitting element, and the distance between the light emitting regions of the first light emitting element in the first line portion is the second line portion. A line head smaller than the distance between the light emitting regions of the second light emitting element is provided.

  According to the present invention, each of the first light emitting element constituting the first line part and the second light emitting element constituting the second line part by switching the first line part and the second line part to emit light. Long service life can be realized. The first line portion is composed of a first light emitting element having a small light emitting region, and the distance (pitch) between the light emitting regions of the first light emitting element is small. A fine image can be formed. On the other hand, since the second line portion is constituted by the second light emitting element having a large light emitting area, an image corresponding to the light emitting area of the second light emitting element can be formed.

  Each of the first light emitting element and the second light emitting element can employ a configuration including an organic electroluminescence element. For example, when a light emitting diode (LED) is used as the light emitting element, it is necessary to arrange a large number of LEDs with high accuracy. However, by using an organic electroluminescence element (organic EL element) as the light emitting element, a light emitting region (light emission) Can be arranged with high accuracy. In addition, it is possible to suppress the occurrence of inconvenience such as luminance variation among the light emitting elements. Therefore, an image can be formed satisfactorily.

  The present invention also provides an image forming apparatus comprising the above-described line head and a photosensitive drum exposed by light emitted from the line head.

  According to the present invention, each of the first light emitting element constituting the first line part and the second light emitting element constituting the second line part by switching the first line part and the second line part to emit light. Long service life can be realized. The first line portion is composed of a first light emitting element having a small light emitting region, and the distance (pitch) between the light emitting regions of the first light emitting element is small. A fine image can be formed. On the other hand, since the second line portion is constituted by the second light emitting element having a large light emitting area, an image corresponding to the light emitting area of the second light emitting element can be formed.

  A configuration including a control device that emits light from either the first line portion or the second line portion in accordance with an image to be formed can be employed. According to this, when a high-definition image is to be formed, the first light-emitting element of the first line portion is caused to emit light, and when an image whose definition is relatively acceptable is formed, the second light-emitting element of the second line portion is caused to emit light. As described above, the first line portion and the second line portion can be used properly according to the image to be formed. In addition, the life of the light emitting element can be increased, and a desired image can be efficiently formed.

  The brightness of the second light emitting element is higher than the brightness of the first light emitting element, and the control device forms a predetermined image in a predetermined time using the first line portion, and uses the second line portion to A configuration in which the predetermined image is formed in a time shorter than the predetermined time can be employed. That is, by emitting high-luminance light from the second light-emitting element having a large light-emitting area, the control device can form an image at a high speed although it is low definition by using the second line portion. On the other hand, by using the first line portion, the control device can form a high-definition image although the speed is low. When a predetermined image is formed by using the second light emitting element, the lifetime of the second light emitting element can be extended because the luminance of the second light emitting element is high but the light emission time is short. In addition, when a predetermined image is formed using the first light emitting element, the lifetime of the first light emitting element can be extended because the luminance of the first light emitting element is long but the luminance is low.

  The present invention further includes a first line head having a plurality of first light emitting elements arranged in a predetermined direction, and a second line head having a plurality of second light emitting elements arranged in the predetermined direction. The area of the light emitting region is smaller than the area of the light emitting region of the second light emitting element, and the distance between the light emitting regions of the first light emitting element in the first line head is the distance of the second light emitting element in the second line head. Provided is an image forming apparatus smaller than the distance between light emitting areas.

  According to the present invention, the first light emitting element provided in the first line head and the second light emitting element provided in the second line head by switching the first line head and the second line head to emit light. Each can have a longer life. The first line head has a first light emitting element having a small light emitting region, and the distance (pitch) between the light emitting regions of the first light emitting element is small. A fine image can be formed. On the other hand, the second line head has a second light emitting element having a large light emitting area, and can form an image corresponding to the light emitting area of the second light emitting element.

  Each of the first light emitting element and the second light emitting element can employ a configuration including an organic electroluminescence element. For example, when a light emitting diode (LED) is used as a light emitting element, it is necessary to arrange a large number of LEDs with high accuracy. However, by using an organic electroluminescence element (organic EL element) as a light emitting element, a light emitting region is obtained. (Light emission points) can be arranged with high accuracy. In addition, it is possible to suppress the occurrence of inconvenience such as luminance variation among the light emitting elements. Therefore, an image can be formed satisfactorily.

  A configuration including a photosensitive drum exposed by light emitted from at least one of the first line head and the second line head can be employed. According to this, a desired image can be formed using the photosensitive drum.

  A configuration including a control device that emits light from either the first line head or the second line head according to an image to be formed can be employed. According to this, when a high-definition image is to be formed, the first light emitting element of the first line head is caused to emit light, and when an image having a relatively fine definition is to be formed, the second light emitting element of the second line head is caused to emit light. As described above, the first line head and the second line head can be used properly according to the image to be formed. Accordingly, a desired image can be efficiently formed while extending the life of the light emitting element.

  The luminance of the second light emitting element is higher than the luminance of the first light emitting element, and the control device forms a predetermined image in a predetermined time using the first line head, and uses the second line head to A configuration in which the predetermined image is formed in a time shorter than the predetermined time can be employed. That is, by emitting high-luminance light from the second light-emitting element having a large light-emitting area, the control device can form an image at a high speed although it is low definition using the second line head. On the other hand, by using the first line head, the control device can form a high-definition image at a low speed. When a predetermined image is formed by using the second light emitting element, the lifetime of the second light emitting element can be extended because the luminance of the second light emitting element is high but the light emission time is short. In addition, when a predetermined image is formed using the first light emitting element, the lifetime of the first light emitting element can be extended because the luminance of the first light emitting element is long but the luminance is low.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, an XYZ orthogonal coordinate system is set, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. The predetermined direction in the horizontal plane is the X-axis direction, the direction orthogonal to the X-axis direction in the horizontal plane is the Y-axis direction, and the direction orthogonal to each of the X-axis direction and the Y-axis direction (that is, the vertical direction) is the Z-axis direction. To do. Furthermore, the rotation directions around the X, Y, and Z axes are the θX, θY, and θZ directions, respectively.

<First Embodiment>
FIG. 1 is a schematic diagram illustrating a part of the image forming apparatus. In FIG. 1, an image forming apparatus 100 includes a line head 1, a lens array (optical imaging system) 31 that forms an image of light emitted from the line head 1, and light emitted from the line head 1 and passes through the lens array 31. The photosensitive drum 9 exposed by the light and the control device C that performs overall control of the operation of the image forming apparatus 100 are provided.

  FIG. 2 is a perspective sectional view of a line head module 101 including the line head 1 and the lens array 31 described above. In FIG. 2, the line head 1 and the lens array 31 are integrally held by a head case 52 in a state of being aligned with each other. The line head module 101 includes a line head 1 in which a plurality of light emitting elements (organic EL elements) are arranged and arranged, a lens array 31 in which lens elements that form an image of light from the line head 1 are arranged, a line head 1 and a lens. And a head case 52 that holds the outer periphery of the array 31. In the present embodiment, the lens array 31 is a SELFOC (registered trademark) lens array (product name of Nippon Sheet Glass Co., Ltd .; hereinafter, SELFOC (registered trademark) lens, SL, SELFOC (registered). (Trademark) lens array is referred to as SL array as appropriate). The line head module 101 causes the light emitted from the line head 1 to form an erecting equal-magnification image on the photosensitive drum 9.

  FIG. 3 is a diagram schematically showing the line head 1. The line head 1 includes a plurality of organic electroluminescence (EL) elements 3 that are light emitting elements. The line head 1 includes a long and thin rectangular substrate (element substrate) 2, and a plurality of organic EL elements 3 are arranged on the element substrate 2. In FIG. 3, the line head 1 includes a first line portion L1 having a plurality of organic EL elements 3 arranged in the X-axis direction and a second line portion L2 having a plurality of organic EL elements 3 arranged in the X-axis direction. Have. The first line portion L1 and the second line portion L2 are provided at a predetermined distance in the Y-axis direction. In the present embodiment, the first and second line portions L1 and L2 are each formed in one row. In the following description, the organic EL element 3 constituting the first line portion L1 is appropriately referred to as “first organic EL element 3A”, and the organic EL element 3 constituting the second line portion L2 is appropriately referred to as “second”. This is referred to as “organic EL element 3B”.

  Each of the plurality of first organic EL elements 3A constituting the first line portion L1 has a predetermined light emitting region (light emitting pixel) 4A that emits light. Each of the plurality of second organic EL elements 3B constituting the second line portion L2 also has a predetermined light emitting region (light emitting pixel) 4B that emits light. The light emitting areas 4 </ b> A and 4 </ b> B are set on the surface 2 </ b> S of the substrate 2. In FIG. 3, each of the light emitting regions 4A and 4B has a substantially circular shape in plan view, but may have another shape.

  The area of the light emitting region 4A of the first organic EL element 3A constituting the first line portion L1 is provided smaller than the area of the light emitting region 4B of the second organic EL element 3B constituting the second line portion L2. The areas of the light emitting regions 4A of the first organic EL elements 3A constituting the first line portion L1 are substantially equal to each other. Similarly, the areas of the light emitting regions 4B of the second organic EL elements 3B constituting the second line portion L2 are substantially equal to each other.

  Further, the distance (pitch) D1 between the light emitting regions 4A of the first organic EL elements 3A in the first line portion L1 is the distance (pitch) D2 between the light emitting regions 4B of the second organic EL elements 3B in the second line portion L2. Is provided smaller. Note that the distances D1 between the light emitting regions 4A of the first organic EL elements 3A constituting the first line portion L1 are substantially equal to each other. That is, the pitch (distance between the centers) of the light emitting regions 4A arranged in the X-axis direction is substantially constant. Similarly, the distances D2 between the light emitting regions 4B of the second organic EL elements 3B constituting the second line portion L2 are substantially equal to each other. That is, the pitch (distance between the centers) of the plurality of light emitting regions 4B arranged in the X-axis direction is substantially constant.

  As shown in FIG. 1, the surface 2S of the substrate 2 on the light emission side of the line head 1 and the photosensitive drum 9 are arranged to face each other, and the organic EL of each of the first and second line portions L1 and L2 is arranged. The arrangement direction of the elements 3A and 3B (Y-axis direction) and the rotation axis of the photosensitive drum 9 are arranged in parallel.

  FIG. 4 is a diagram showing an example of a TFT (Thin Film Transistor) as a switching element. The organic EL element 3 is driven in an active matrix by TFTs. That is, the line head 1 includes a plurality of scanning lines 105, a plurality of signal lines 102 extending in a direction perpendicular to the scanning lines 105, and a plurality of power supply lines extending in parallel to the signal lines 102. 103, and pixel regions X are provided near the intersections of the scanning lines 105 and the signal lines 102.

  The signal line 102 is connected to a data line driving circuit 106 including a shift register, a level shifter, a video line, and an analog switch. Further, a scanning line driving circuit 107 including a shift register and a level shifter is connected to the scanning line 105. In the present embodiment, drivers (driving elements) including TFTs, driving circuits such as the data line driving circuit 106 and the scanning line driving circuit 107 are all formed on the substrate 2 on which the organic EL elements 3 are formed. Yes. That is, the line head 1 is configured to include the driver with a so-called internal connection.

  Further, in each of the pixel regions X, a switching TFT 112 to which a scanning signal is supplied to the gate electrode via the scanning line 105 and a pixel signal shared from the signal line 102 via the switching TFT 112 are held. A capacitor 113, a driving TFT 123 to which a pixel signal held by the holding capacitor 113 is supplied to the gate electrode, and driving from the power line 103 when electrically connected to the power line 103 through the driving TFT 123 A pixel electrode 23 into which a current flows and a functional layer 110 sandwiched between the pixel electrode 23 and the cathode 50 are provided. The pixel electrode 23, the cathode 50, and the functional layer 110 constitute the organic EL element 3. The functional layer 110 is composed of a hole transport layer and a light emitting layer as will be described later.

  In the line head 1, when the scanning line 105 is driven and the switching TFT 112 is turned on, the potential of the signal line 102 at that time is held in the holding capacitor 113, and the driving line is driven according to the state of the holding capacitor 113. The on / off state of the TFT 123 is determined. Then, current flows from the power supply line 103 to the pixel electrode 23 through the channel of the driving TFT 123, and further current flows to the cathode 50 through the functional layer 110. The functional layer 110 emits light according to the amount of current flowing through it.

  The line head 1 can expose the photosensitive drum 9 by the active matrix driving of the organic EL element 3.

  The luminance in the light emitting region 4B of the second organic EL element 3B is higher than the luminance in the light emitting region 4A of the first organic EL element 3A. In general, the luminance of light emission of the organic EL element is determined by the value of current flowing through the functional layer 110, and is proportional to the current value in a normal use range. Therefore, in the present embodiment, the control device C is configured so that the luminance of the second organic EL element 3B in the second line portion L2 is higher than the luminance of the first organic EL element 3A in the first line portion L1. 1. A predetermined current is passed through each of the first and second organic EL elements 3A and 3B.

  FIG. 5 is a perspective view of an SL array as the lens array 31. The lens array (SL array) 31 includes a plurality of SL elements 31a. A black silicone resin 32 is filled in a gap between the SL elements 31a, and a frame 34 is disposed around the silicone resin 32.

  The SL element 31a has a parabolic refractive index distribution from the center to the periphery. For this reason, the light incident on the SL element 31a travels while meandering in the constant cycle. Therefore, if the length of the SL element 31a is adjusted, an image can be formed upright at an equal magnification.

  Returning to FIG. 2, the line head module 101 includes a head case 52 that supports the outer periphery of the line head 1 and the lens array 31. The head case 52 is formed in a slit shape by a rigid material such as Al. The cross section perpendicular to the longitudinal direction of the head case 52 has a shape in which both upper and lower ends are opened, and the upper half side walls 52a and 52a are arranged in parallel with each other, and the lower half side walls 52b and 52b are respectively provided. Is inclined toward the center of the lower end. Although not shown, the side walls at both ends in the longitudinal direction of the head case 52 are also arranged in parallel to each other. The above-described line head 1 is disposed inside the upper half side wall 52a of the head case 52.

  FIG. 6 is an enlarged view of a connecting portion (A portion in FIG. 2) of the line head. As shown in FIG. 6, a stepped base 53 is formed on the inner surface of the side wall 52 a of the head case 52 over the entire circumference. The line head 1 is disposed horizontally with the lower surface of the line head 1 abutting on the upper surface of the pedestal 53. In this embodiment, the line head 1 is a so-called bottom emission system, and light is extracted from the element substrate 2 side to the outside.

  In addition, sealing materials 54 a and 54 b are arranged over the entire periphery at the corner formed by the side wall 52 a of the head case 52 and the line head 1. A sealing material is also disposed in the gap between the inner surface of the side wall 52 a of the head case 52 and the side surface of the line head 1. Thereby, the line head 1 is hermetically bonded to the head case 52. Among them, the sealing material 54b disposed on the upper side in FIG. 6 of the line head 1 is made of an ultraviolet curable resin such as acrylic. Moreover, the sealing material 54a arrange | positioned below the line head 1 in FIG. 6 is comprised with thermosetting resins, such as an epoxy.

  Note that a getter agent may be contained in these sealing materials 54a and 54b. A getter agent means a desiccant or an oxygen scavenger and adsorbs moisture and oxygen. According to this configuration, moisture and oxygen can be reliably blocked by the sealing materials 54a and 54b. Therefore, it becomes possible to suppress moisture absorption and oxidation of the organic EL element formed on the line head, and it is possible to prevent the durability of the organic EL element from being lowered and the life from being shortened.

  Returning to FIG. 2, the lens array 31 is disposed in the slit-shaped opening formed in the lower end portion of the head case 52. Sealing materials 55a and 55b are arranged at the corner formed by the side wall 52b of the head case 52 and the lens array 31 over the entire circumference. A sealing material is also disposed in the gap between the inner surface of the side wall 52 a of the head case 52 and the side surface of the line head 1. Thereby, the lens array 31 is hermetically bonded to the head case 52. Among them, the sealing material 55a disposed on the upper side of the lens array 31 is made of a thermosetting resin such as epoxy. Further, the sealing material 55b disposed on the lower side of the lens array 31 is made of an ultraviolet curable resin such as acrylic. Furthermore, a getter agent may be contained in these sealing materials 55a and 55b.

  A chamber 56 is formed between the line head 1 and the lens array 31 inside the head case 52. As described above, since the line head 1 and the lens array 31 are hermetically joined to the head case 52, the chamber 56 is hermetically sealed. The interior of the chamber 56 is filled with an inert gas such as nitrogen gas or kept in a vacuum.

  Next, a detailed configuration of the organic EL element 3 in the line head 1 will be described with reference to FIG. In the case of a so-called bottom emission system in which light emitted from the light emitting layer 60 is emitted from the pixel electrode 23 side, the light emitted from the element substrate 2 side is taken out. Therefore, the element substrate 2 is transparent or semitransparent. Things are adopted. For example, glass, quartz, resin (plastic, plastic film) and the like can be mentioned, and a glass substrate is particularly preferably used.

  Further, in the case of a so-called top emission method in which light emitted from the light emitting layer 60 is emitted from the cathode (counter electrode) 50 side, the emitted light is extracted from the sealing substrate side that is the opposite side of the element substrate 2. Therefore, both a transparent substrate and an opaque substrate can be used. Examples of the opaque substrate include a thermosetting resin and a thermoplastic resin in addition to a ceramic sheet such as alumina and a metal sheet such as stainless steel that has been subjected to an insulation treatment such as surface oxidation. In the present embodiment, the bottom emission method is adopted, and therefore, transparent glass is used for the element substrate 2.

  A circuit unit 11 including a driving TFT 123 connected to the pixel electrode 23 and the like is formed on the element substrate 2, and the organic EL element 3 is provided thereon. The organic EL element 3 includes a pixel electrode 23 that functions as an anode, a hole transport layer 70 that injects / transports holes from the pixel electrode 23, a light-emitting layer 60 made of an organic EL material, and a cathode 50. It is comprised by having been formed in order. Under such a configuration, in the organic EL element 3, a current is passed through the functional layer including the hole transport layer 70 and the light emitting layer 60, whereby the holes injected from the hole transport layer 70 and the cathode 50. The electrons from the above are combined in the light emitting layer 60 to emit light.

  In the present embodiment, which is a bottom emission method, the pixel electrode 23 that functions as an anode is formed of a transparent conductive material, and specifically, ITO is suitably used. As a material for forming the hole transport layer 70, in particular, a dispersion of 3,4-polyethylenedioxythiophene / polystyrene sulfonic acid (PEDOT / PSS), that is, 3,4-polyethylenedioxy in polystyrene sulfonic acid as a dispersion medium. A dispersion in which thiophene is dispersed and further dispersed in water is preferably used. In addition, as a forming material of the positive hole transport layer 70, various things can be used, without being limited to the said thing. For example, those obtained by dispersing polystyrene, polypyrrole, polyaniline, polyacetylene or a derivative thereof in an appropriate dispersion medium such as the above-described polystyrene sulfonic acid can be used.

  As a material for forming the light emitting layer 60, a known light emitting material capable of emitting fluorescence or phosphorescence is used. In this embodiment, for example, a light emitting layer whose emission wavelength band corresponds to red is adopted, but of course, a light emission layer whose emission wavelength band corresponds to green or blue may be adopted. In this case, the photoconductor used has sensitivity in the light emitting region.

  Specific examples of the material for forming the light emitting layer 60 include (poly) fluorene derivative (PF), (poly) paraphenylene vinylene derivative (PPV), polyphenylene derivative (PP), polyparaphenylene derivative (PPP), and polyvinylcarbazole (PVK). ), Polythiophene derivatives, and polysilanes such as polymethylphenylsilane (PMPS) are preferably used. In addition, these polymer materials are doped with low molecular weight materials such as perylene dyes, coumarin dyes, rhodamine dyes, rubrene, perylene, 9,10-diphenylanthracene, tetraphenylbutadiene, nile red, coumarin 6, and quinacridone. It can also be used.

  The hole transport layer 70 and the light emitting layer 60 can be formed using a predetermined method such as a droplet discharge method (inkjet method), a spin coating method, or a dip method.

  The cathode 50 is formed so as to cover the light emitting layer 60. For example, Ca is formed to a thickness of about 20 nm, and Al is formed thereon to a thickness of about 200 nm to form an electrode having a laminated structure, and the Al is reflected. It also functions as a layer. Further, a sealing substrate (not shown) is stuck on the cathode 50 via an adhesive layer.

Further, as described above, the circuit unit 11 is provided below the organic EL element 3. The circuit unit 11 is formed on the element substrate 2. That is, a base protective layer 281 mainly composed of SiO ₂ is formed on the surface of the element substrate 2 as a base, and a silicon layer 241 is formed thereon. A gate insulating layer 282 mainly composed of SiO ₂ and / or SiN is formed on the surface of the silicon layer 241.

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

  Further, in the silicon layer 241, a low concentration source region 241b and a high concentration source region 241S are provided on the source side of the channel region 241a, while a low concentration drain region 241c and a high concentration drain are provided on the drain side of the channel region 241a. The region 241D is provided to form a so-called LDD (Lightly Doped Drain) structure. Among these, the high-concentration source region 241S is connected to the source electrode 243 through a contact hole 243a that opens over the gate insulating layer 282 and the first interlayer insulating layer 283. The source electrode 243 is configured as a part of a power supply line (not shown). On the other hand, the high-concentration drain region 241D is connected to the drain electrode 244 made of the same layer as the source electrode 243 through a contact hole 244a that opens through the gate insulating layer 282 and the first interlayer insulating layer 283.

  On the first interlayer insulating layer 283 on which the source electrode 243 and the drain electrode 244 are formed, for example, a planarizing film 284 mainly composed of an acrylic resin component is formed. The planarizing film 284 is formed of a heat-resistant insulating resin such as acrylic or polyimide, and is formed to eliminate surface irregularities due to the driving TFT 123, the source electrode 243, the drain electrode 244, and the like. Are known.

  A pixel electrode 23 made of ITO or the like is formed on the surface of the planarizing film 284 and connected to the drain electrode 244 through a contact hole 23a provided in the planarizing film 284. That is, the pixel electrode 23 is connected to the high concentration drain region 241D of the silicon layer 241 through the drain electrode 244.

  On the surface of the planarization film 284 on which the pixel electrode 23 is formed, the pixel electrode 23 and the above-described inorganic partition wall 25 are formed, and on the inorganic partition wall 25, an organic partition wall 221 is formed. On the pixel electrode 23, the hole transport layer 70 and the light emitting layer 60 are formed inside the opening 25 a formed in the inorganic partition wall 25 and the opening 221 a formed in the organic partition wall 221, that is, in the pixel region. Are stacked in this order from the pixel electrode 23 side, thereby forming a functional layer.

  Here, since the inorganic partition wall 25 is thin, light is normally transmitted therethrough. Therefore, the area of the light emitting pixel of the organic EL element 3 in the present invention is determined by the opening 221 a of the organic partition 221. Therefore, when the organic partition 221 is patterned by lithography technology or the like, by setting the appropriate shape, area, and position preset for each of the first line portions L1 and the second line portions L2 as described above, As described with reference to FIG. 3 and the like, the first and second organic EL elements 3A and 3B having the light emitting regions (light emitting pixels) 4A and 4B having a predetermined area can be formed at predetermined positions.

  Next, an image forming method using the image forming apparatus 100 as described above will be described. The image forming apparatus 100 uses the first line portion L1 and the second line portion L2 in the line head 1 in accordance with the image to be formed. That is, the control device C causes the first line portion L1 and the second line portion L2 to emit light according to the image to be formed, and exposes the photosensitive drum 9.

  When the image to be formed requires high definition, the control device C causes the first organic EL element 3A constituting the first line portion L1 to emit light. As described above, since the area of each light emitting region 4A of the first organic EL element 3A is small and the pitch D1 between the light emitting regions 4A is also small, the image forming apparatus 100 can form a high-definition image. When forming an image using the first organic EL element 3A, the control device C supplies a predetermined value of current to the first organic EL element 3A, and at a predetermined speed, the line head 1 and the photosensitive drum 9 And scan. Thereby, the control apparatus C can form a desired image in 1st time using the 1st line part L1.

  On the other hand, if the definition of the image to be formed is allowed to be relatively low, the control device C causes the second organic EL element 3B constituting the second line portion L2 to emit light. As described above, the area of the light emitting region 4B of each of the second organic EL elements 3B is large, and the control device C uses the second organic EL element 3B to form an image with respect to the second organic EL element 3B. By supplying a predetermined current and causing the second organic EL element 3B to emit light with a luminance higher than that of the first organic EL element 3A, the line head 1 and the photosensitive drum 9 are scanned at a relatively high speed. Even so, a desired image can be formed. As described above, the control device C can form a desired image in the second time shorter than the first time by using the second line portion L2.

  As shown in FIG. 1, the line head module 101 irradiates the photosensitive drum 9 serving as an exposed portion with light and exposes it. At this time, since the line head 1 and the lens array 31 are integrally held in the head case 52 in a state of being aligned with each other, the line head module 101 is simply aligned with the photosensitive drum 9 in use. Good. Therefore, in the image forming apparatus 100 provided with the line head module 101, the alignment with respect to the photosensitive drum 9 becomes easier as compared with the case where the line head 1 and the lens array 31 are prepared separately, resulting from poor alignment. Uneven exposure is reliably prevented.

  The photosensitive drum 9 is charged in advance by a charger. Then, the surface of the uniformly charged photoreceptor drum 9 is selectively neutralized by exposure by the line head 1 to form an electrostatic latent image. The electrostatic latent image is developed with toner supplied from a developing device, and the toner image is transferred onto a sheet by a transfer device, whereby printing is performed.

  The charge removal amount from the charged photosensitive drum 9 is determined by the exposure amount, that is, the sum of the exposure amounts by the respective organic EL elements 3. The change in the charge removal amount with respect to the exposure amount also varies depending on the charge amount with respect to the photosensitive drum 9, but if these are adjusted in advance, the change is basically determined by the sensitivity of the photosensitive drum 9.

  As explained above, the first organic EL element 3A and the second line portion L2 constituting the first line portion L1 are constituted by switching the first line portion L1 and the second line portion L2 to emit light. Each of the second organic EL elements 3B suppresses continuous use (light emission), and each of the first organic EL elements 3A constituting the first line portion L1 and the second organic EL elements 3B constituting the second line portion L2. Can extend the service life. The first line portion L1 is composed of the first organic EL element 3A having a small light emitting region 4A, and the distance (pitch) D1 between the light emitting regions 4A of the first organic EL element 3A is small. By using the line portion L1, a high-definition image can be formed. On the other hand, since the second line portion L2 is configured by the second organic EL element 3B having the large light emitting region 4B, an image corresponding to the light emitting region 4B of the second organic EL element 3B can be formed.

  Then, by emitting high-luminance light from the second organic EL element 3B having a large light emitting region 4B, the control device C uses the second line portion L2 to form an image at a high speed although it is low definition. be able to. On the other hand, the control device C can form a high-definition image at a low speed by using the first line portion L1. And when forming a predetermined image using the 2nd organic EL element 3B, since the light emission time is short although the brightness | luminance of 2nd organic EL element 3B is high, the lifetime of 2nd organic EL element 3B can be aimed at. . In addition, when a predetermined image is formed using the first organic EL element 3A, the first organic EL element 3A has a long light emission time but low luminance, so that the life of the first organic EL element 3A can be extended. .

  In the present embodiment, each of the first line portion L1 and the second line portion L2 is provided in one row, but of course, any plurality of rows can be provided. Then, by properly using the plurality of first line portions L1 (or second line portions L2), the first organic EL element 3A (second second) constituting each of the first line portions L1 (or second line portions L2). The lifetime of the organic EL element 3B) can be extended.

  In the present embodiment, the line head 1 is configured to include a light emitting region 4A having a first area and a light emitting region 4B having a second area. That is, in the present embodiment, the line head 1 is configured to include the light emitting regions 4A and 4B having two different areas, but of course, the light emitting regions having three or more different areas are included. It may be a configuration.

<Second Embodiment>
Next, a second embodiment will be described. In the following description, the same or equivalent components as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof is simplified or omitted.

  FIG. 8 is a plan view showing the second embodiment. In FIG. 8, the image forming apparatus 100 includes a plurality (here, two) of line heads 1 </ b> A and 1 </ b> B. Each of the first and second line heads 1A and 1B includes a plurality of organic EL elements 3A and 3B which are light emitting elements. The first line head 1A includes a plurality of first organic EL elements 3A arranged in the X-axis direction in FIG. The second line head 1B has a plurality of second organic EL elements 3B arranged in the X-axis direction. Each of the plurality of first organic EL elements 3A provided in the first line head 1A has a predetermined light emitting region (light emitting pixel) 4A that emits light. Each of the plurality of second organic EL elements 3B provided in the second line head 1B has a predetermined light emitting region (light emitting pixel) 4B that emits light. The light emitting area 4A is set on the surface 2S of the substrate 2A constituting the first line head 1A, and the light emitting area 4B is set on the surface 2S of the substrate 2B constituting the second line head 1B.

  The area of the light emitting region 4A of the first organic EL element 3A provided in the first line head 1A is smaller than the area of the light emitting region 4B of the second organic EL element 3B provided in the second line head 1B. Yes. Note that the areas of the light emitting regions 4A of the first organic EL elements 3A provided in the first line head 1A are substantially equal to each other. Similarly, the areas of the light emitting regions 4B of the second organic EL elements 3B provided in the second line head 1B are substantially equal to each other.

  Further, the distance (pitch) D1 between the light emitting regions 4A of the first organic EL elements 3A provided in the first line head 1A is set between the light emitting regions 4B of the second organic EL elements 3B provided in the second line head 1B. Is provided smaller than the distance (pitch) D2. Note that the distances D1 between the light emitting regions 4A of the first organic EL elements 3A provided in the first line head 1A are substantially equal to each other. That is, the pitch (distance between the centers) of the light emitting regions 4A arranged in the X-axis direction is substantially constant. Similarly, the distances D2 between the light emitting regions 4B of the second organic EL elements 3B provided in the second line head 1B are substantially equal to each other. That is, the pitch (distance between the centers) of the plurality of light emitting regions 4B arranged in the X-axis direction is substantially constant.

  The surfaces 2S of the substrates 2A and 2B on the light emission side of the first and second line heads 1A and 1B and the photosensitive drum 9 are arranged to face each other. At this time, the first and second lines The alignment direction (Y-axis direction) of the organic EL elements 3 of the heads 1A and 1B and the rotation axis of the photosensitive drum 9 are arranged in parallel.

  The image forming apparatus 100 uses the first line head 1A and the second line head 1B properly according to the image to be formed. That is, the control device C emits light from either the first line head 1A or the second line head 1B in accordance with the image to be formed, and exposes the photosensitive drum 9.

  When the image to be formed requires high definition, the control device C causes the first organic EL element 3A provided in the first line head 1A to emit light. As described above, since the area of each light emitting region 4A of the first organic EL element 3A is small and the pitch D1 between the light emitting regions 4A is also small, the image forming apparatus 100 can form a high-definition image. When forming an image using the first organic EL element 3A, the control device C supplies the first organic EL element 3A with a predetermined value of current, and the first line head 1A and the photosensitive member at a predetermined speed. The drum 9 is scanned. Thereby, the control apparatus C can form a desired image in 1st time using the 1st line head 1A.

  On the other hand, when the definition of the image to be formed is allowed to be relatively low, the control device C causes the second organic EL element 3B provided in the second line head 1B to emit light. As described above, the area of the light emitting region 4B of each of the second organic EL elements 3B is large, and the control device C uses the second organic EL element 3B to form an image with respect to the second organic EL element 3B. By supplying a predetermined current and causing the second organic EL element 3B to emit light with a luminance higher than that of the first organic EL element 3A, the second line head 1B and the photosensitive drum 9 can be driven at a relatively high speed. A desired image can be formed even by scanning with. Thus, the control device C can form a desired image in the second time shorter than the first time by using the second line head 1B.

  As described above, a configuration in which the array group of the first organic EL elements 3A and the array group of the second organic EL elements 3B are provided in separate line heads 1A and 1B is also possible. Even in such a configuration, by switching the first line head 1A and the second line head 1B to emit light, the first organic EL element 3A and the second line head 1B provided in the first line head 1A The second organic EL element 3B provided in the first line head 1B and the second organic EL element 3B provided in the first line head 1A are suppressed from being continuously used (light emission). The lifetime of each organic EL element 3B can be extended. The first line head 1A includes a first organic EL element 3A having a small light emitting area 4A. Since the distance (pitch) D1 between the light emitting areas 4A of the first organic EL element 3A is small, the first line By using the head 1A, a high-definition image can be formed. On the other hand, since the second line head 1B includes the second organic EL element 3B having the large light emitting region 4B, an image corresponding to the light emitting region 4B of the second organic EL element 3B can be formed.

  In the present embodiment, the first line head 1A has a plurality of first organic EL elements 3A arranged in one row, and the second line head 1B has a plurality of second organic EL elements 3B arranged in one row. Of course, any plurality of rows can be provided. Then, by properly using the plurality of first line heads 1A (or second line heads 1B), the first organic EL element 3A (or second line head 1B) provided in each of the first line heads 1A (or second line heads 1B). The lifetime of the second organic EL element 3B) can be extended.

  In addition, in this embodiment, it has the 1st line head 1A provided with the light emission area | region 4A which has a 1st area, and the 2nd line head 1B provided with the light emission area | region 4B which has a 2nd area. It is a configuration. That is, in the present embodiment, the configuration includes two types of line heads 1A and 1B each having two types of light emitting regions 4A and 4B having different areas, but of course light emission of three or more types of areas different from each other. A plurality of line heads each having a region may be provided.

<Tandem type image forming apparatus>
FIG. 9 is a diagram showing an example of an image forming apparatus to which the present invention is applied. In FIG. 9, an image forming apparatus 100A includes an organic EL array line head 101K, 101C, 101M, 101Y and four corresponding photosensitive drums 41K, 41C, 41M, 41Y having the same configuration. belongs to.

  The image forming apparatus 100A includes a driving roller 91, a driven roller 92, and a tension roller 93, and an intermediate transfer belt 90 is stretched around these rollers so as to circulate and drive in the direction of the arrow (counterclockwise) in FIG. It is. Photosensitive drums 41K, 41C, 41M, and 41Y are arranged at predetermined intervals with respect to the intermediate transfer belt 90. These photosensitive drums 41K, 41C, 41M, and 41Y have a photosensitive layer as an image carrier on the outer peripheral surface thereof.

  Here, K, C, M, and Y in the symbols mean black, cyan, magenta, and yellow, respectively, and indicate that the photoconductors are for black, cyan, magenta, and yellow, respectively. The meanings of these symbols (K, C, M, Y) are the same for the other members. The photosensitive drums 41K, 41C, 41M, and 41Y are driven to rotate in the arrow direction (clockwise) in FIG. 9 in synchronization with the driving of the intermediate transfer belt 90.

  Around each photosensitive drum 41 (K, C, M, Y), charging means (corona charger) 42 for uniformly charging the outer peripheral surface of the photosensitive drum 41 (K, C, M, Y), respectively. (K, C, M, Y) and rotation of the photosensitive drum 41 (K, C, M, Y) on the outer peripheral surface uniformly charged by the charging means 42 (K, C, M, Y) And an organic EL array line head 101 (K, C, M, Y) that sequentially performs line scanning.

  Here, as described above, the organic EL array line head 101 (K, C, M, Y) is integrally held together with the SL array (not shown) by the head case in a state of being aligned with each other. It is used as.

  Further, a toner as a developer is applied to the electrostatic latent image formed by the organic EL array line head 101 (K, C, M, Y) (line head module) to form a visible image (toner image). As a transfer means for sequentially transferring the developing device 44 (K, C, M, Y) and the toner image developed by the developing device 44 (K, C, M, Y) to the intermediate transfer belt 90 that is a primary transfer target. Primary transfer roller 45 (K, C, M, Y) and a cleaning device as a cleaning means for removing toner remaining on the surface of the photosensitive drum 41 (K, C, M, Y) after being transferred 46 (K, C, M, Y).

  Here, each organic EL array line head 101 (K, C, M, Y) is installed such that each array direction is along the bus line of the photosensitive drum 41 (K, C, M, Y). Then, the emission energy peak wavelength of each organic EL array line head 101 (K, C, M, Y) and the sensitivity peak wavelength of the photosensitive drum 41 (K, C, M, Y) are set to substantially coincide with each other. Has been.

  The developing device 44 (K, C, M, Y) uses, for example, a non-magnetic one-component toner as a developer. The film thickness of the developed developer is regulated by a regulating blade, and the developing roller is brought into contact with or pressed against the photosensitive drum 41 (K, C, M, Y), whereby the photosensitive drum 41 (K, C, M, A developer is attached in accordance with the potential level of Y) and developed as a toner image.

  The black, cyan, magenta, and yellow toner images formed by the four-color single-color toner image forming station are intermediated by the primary transfer bias applied to the primary transfer roller 45 (K, C, M, Y). Primary transfer is sequentially performed on the transfer belt 90. The toner images that are sequentially superimposed on the intermediate transfer belt 90 to become a full color are secondarily transferred to the recording medium P such as paper by the secondary transfer roller 66 and further pass through the fixing roller pair 61 that is a fixing unit. Then, the toner image is fixed on the recording medium P and then discharged onto a paper discharge tray 68 formed on the upper part of the apparatus by a pair of paper discharge rollers 62.

  Further, the image forming apparatus 100A includes a paper feed cassette 63 in which a large number of recording media P are stacked and held, a pickup roller 64 that feeds the recording media P from the paper feed cassette 63 one by one, and a secondary transfer roller. A pair of gate rollers 65 for defining the supply timing of the recording medium P to the secondary transfer portion 66, and a secondary transfer roller 66 as a secondary transfer means for forming a secondary transfer portion between the intermediate transfer belt 90 and And a cleaning blade 67 as a cleaning means for removing toner remaining on the surface of the intermediate transfer belt 90 after the secondary transfer.

<4-cycle image forming apparatus>
FIG. 10 is a diagram showing another example of an image forming apparatus to which the present invention is applied. In FIG. 10, an image forming apparatus 100B includes a developing device 161 having a rotary structure, a photosensitive drum 165 that functions as an image carrier, an image writing unit 167 that includes a line head module, an intermediate transfer belt 169, and a sheet conveyance device. A four-cycle system having a path 174, a fixing roller heating roller 172, and a paper feed tray 178.

  The developing device 161 is configured such that the developing rotary 161a rotates in the direction of arrow A about the shaft 161b. The inside of the development rotary 161a is divided into four, and image forming units for four colors of yellow (Y), cyan (C), magenta (M), and black (K) are provided. Reference numerals 162a to 162d are arranged in the image forming units for the four colors. The developing rollers rotate in the arrow B direction, and the toner supply rollers 163a to 163d rotate in the arrow C direction. Reference numerals 164a to 164d are regulating blades that regulate the toner to a predetermined thickness.

  Further, the image forming apparatus 100B includes a photosensitive drum 165 that functions as an image carrier, a primary transfer member 166, a charger 168, and a line head module 167 according to the present invention.

  The photosensitive drum 165 is rotationally driven in the direction of arrow D, which is the direction opposite to the developing roller 162a, by a drive motor (not shown), for example, a step motor. The line head module constituting the image writing unit 167 is arranged in a state where alignment (optical axis alignment) is performed between the line head module and the photosensitive drum 165.

  The intermediate transfer belt 169 is stretched between the driving roller 170a and the driven roller 170b. The driving roller 170 a is connected to the driving motor of the photosensitive drum 165 and transmits power to the intermediate transfer belt 169. That is, the drive roller 170a of the intermediate transfer belt 169 is rotated in the direction of arrow E which is the opposite direction to the photosensitive drum 165 by the drive motor.

  The paper transport path 174 is provided with a plurality of transport rollers, a pair of paper discharge rollers 176, and the like, so that the paper is transported. An image (toner image) on one side carried on the intermediate transfer belt 169 is transferred to one side of the paper at the position of the secondary transfer roller 171. The secondary transfer roller 171 is brought into contact with and separated from the intermediate transfer belt 169 by a clutch. When the clutch is turned on, the secondary transfer roller 171 is brought into contact with the intermediate transfer belt 169 so that an image is transferred onto a sheet.

  The sheet on which the image has been transferred as described above is then subjected to a fixing process by a fixing device having a fixing heater H. The fixing device is provided with a heating roller 172 and a pressure roller 173. The sheet after the fixing process is drawn into the discharge roller pair 176 and proceeds in the direction of arrow F. When the paper discharge roller pair 176 rotates in the reverse direction from this state, the paper reverses its direction and advances in the double-sided printing conveyance path 175 in the direction of arrow G. 177 is an electrical component box, 178 is a paper feed tray for storing paper, and 179 is a pickup roller provided at the outlet of the paper feed tray 178.

  For example, a low-speed brushless motor is used as a drive motor for driving the transport roller in the paper transport path. For the intermediate transfer belt 169, a step motor is used because color misregistration correction is required. Each of these motors is controlled by a signal from a control means (not shown).

  In the state shown in FIG. 10, a yellow (Y) electrostatic latent image is formed on the photosensitive drum 165, and a high voltage is applied to the developing roller 162a, whereby a yellow image is formed on the photosensitive drum 165. Is done. When the yellow back side and front side images are all carried on the intermediate transfer belt 169, the development rotary 161a rotates 90 degrees in the direction of arrow A.

  The intermediate transfer belt 169 rotates once and returns to the position of the photosensitive drum 165. Next, two images of cyan (C) are formed on the photosensitive drum 165, and this image is carried on the yellow image carried on the intermediate transfer belt 169. Thereafter, the 90-degree rotation of the development rotary 161 and the one-rotation process after the image is carried on the intermediate transfer belt 169 are repeated in the same manner.

  For carrying four color images, the intermediate transfer belt 169 rotates four times, and then the rotation position is further controlled to transfer the image onto the sheet at the position of the secondary transfer roller 171. The paper fed from the paper feed tray 178 is transported by the transport path 174, and the color image is transferred to one side of the paper at the position of the secondary transfer roller 171. The sheet on which the image is transferred on one side is reversed by the discharge roller pair 176 as described above, and stands by on the conveyance path. Thereafter, the sheet is conveyed to the position of the secondary transfer roller 171 at an appropriate timing, and the color image is transferred to the other side. The housing 180 is provided with an exhaust fan 181.

  In the image forming apparatuses 100A and 100B shown in FIGS. 9 and 10, the above-described image forming apparatus 100 can be applied. In these image forming apparatuses 100A and 100B, the lifetime of the organic EL element which is a light emitting element can be extended. In addition, since a line head embedded on the substrate can be used as a driver for driving each organic EL element, the degree of structural freedom of the image forming apparatuses 100A and 100B provided with the head can be increased. it can. The image forming apparatus of the present invention is not limited to the above embodiment, and various modifications can be made.

FIG. 2 is a schematic diagram for explaining the image forming apparatus according to the first embodiment. FIG. 3 is an enlarged perspective view of a main part of the image forming apparatus. It is a figure for demonstrating the line head which concerns on 1st Embodiment. It is a schematic diagram which shows the wiring structure of a line head. It is a perspective view of SL array. It is an enlarged view in the joint part of a line head. It is principal part side sectional drawing of a line head. It is a figure for demonstrating the line head which concerns on 2nd Embodiment. 1 is a diagram illustrating an example of an image forming apparatus. 1 is a diagram illustrating an example of an image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 (1A, 1B) ... Line head, 3 (3A, 3B) ... Light emitting element (organic EL element), 4A, 4B ... Light emitting area, 100 ... Image forming apparatus, L1 ... 1st line part, L2 ... 2nd line Part

Claims (10)

A first line portion having a plurality of first light emitting elements arranged in a predetermined direction;
A second line part having a plurality of second light emitting elements arranged in the predetermined direction,
The area of the light emitting region of the first light emitting element is smaller than the area of the light emitting region of the second light emitting element, and the distance between the light emitting regions of the first light emitting element in the first line portion is the same as that in the second line portion. A line head that is smaller than the distance between the light emitting regions of the second light emitting element.   The line head according to claim 1, wherein each of the first light emitting element and the second light emitting element includes an organic electroluminescence element.   An image forming apparatus comprising: the line head according to claim 1; and a photosensitive drum exposed by light emitted from the line head.   The image forming apparatus according to claim 3, further comprising a control device that emits light from either the first line portion or the second line portion in accordance with an image to be formed. The brightness of the second light emitting element is higher than the brightness of the first light emitting element,
5. The image according to claim 4, wherein the control device forms a predetermined image in a predetermined time using the first line portion, and forms the predetermined image in a time shorter than the predetermined time using the second line portion. Forming equipment. A first line head having a plurality of first light emitting elements arranged in a predetermined direction;
A second line head having a plurality of second light emitting elements arranged in the predetermined direction,
The area of the light emitting region of the first light emitting element is smaller than the area of the light emitting region of the second light emitting element, and the distance between the light emitting regions of the first light emitting element in the first line head is the same as that of the second line head. An image forming apparatus that is smaller than the distance between the light emitting regions of the second light emitting element.   The image forming apparatus according to claim 6, wherein each of the first light emitting element and the second light emitting element includes an organic electroluminescence element.   The image forming apparatus according to claim 6, further comprising a photosensitive drum exposed by light emitted from at least one of the first line head and the second line head.   The image forming apparatus according to any one of claims 6 to 8, further comprising a control device that emits light from either the first line head or the second line head in accordance with an image to be formed. The brightness of the second light emitting element is higher than the brightness of the first light emitting element,
10. The control device according to claim 6, wherein the control device forms a predetermined image in a predetermined time using the first line head, and forms the predetermined image in a time shorter than the predetermined time using the second line head. The image forming apparatus according to claim 1.

Images