JP2006043988A - Exposure head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure head which can suppress a mounting area. <P>SOLUTION: The exposure head includes an array substrate which has a plurality of EL elements arranged in an array shape at one face side and is constituted to make an ejected light from the organic EL elements discharged to the other face, and a plurality of circuit chips which include driving circuits for the organic EL elements and are arranged in series along a longitudinal direction of the array substrate so that a formation face of the driving circuits is opposed to the one face of the array substrate. The plurality of circuit chips are bump-connected to the array substrate. A plurality of array substrate side electrode pads set at the array substrate to be respectively abutted with a plurality of bumps, and a plurality of circuit chip side electrode pads (36a and 36b) set at the plurality of circuit chips to be abutted with the plurality of bumps, respectively are arranged in a staggering form along the longitudinal direction of the array substrate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exposure head or the like that forms a latent image on a photoconductor in an electrophotographic printer or copying machine by a multiple exposure method.

  In the field of image forming apparatuses, various methods have been proposed that employ an organic EL as a light source for exposing a photoreceptor (for example, see Patent Document 1).

  FIG. 16 is a diagram illustrating the configuration of an organic EL array print head that employs an organic EL as a light source. As shown in FIG. 16, an organic EL array substrate 300 having an organic EL array 200 and a plurality of driver ICs 400 for controlling light emission of each organic EL are arranged on a chip-on-board (hereinafter, COB) substrate 100. . The bonding wires 500 are electrically connected between the COB substrate 100 and the driver IC 400 and between the driver IC 400 and the organic EL array substrate 300. As described above, by using the organic EL as a light source for exposing the photoconductor, it is possible to manufacture a single organic EL array substrate 300 in a lump, and a conventional mounting in which a large number of LED chips are arranged in a straight line. Compared to the method, the cost and density can be reduced.

JP-A-9-226171

  However, as described above, when the organic EL array substrate and the plurality of driver ICs are disposed on the COB substrate in a planar manner, the mounting area becomes large, and the COB substrate must be enlarged. Arise. Further, in order to electrically connect the organic EL array substrate and each driver IC, a wire bonding process is indispensable, and each organic EL light emitting portion in the organic EL substrate and each terminal to be wire bonded are connected. There is a problem that the wiring between them becomes complicated and complicated. Such a problem is particularly noticeable when multiple exposures are performed by arranging a plurality of rows of organic EL light emitting units in the sub-scanning direction.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an exposure head that can reduce the mounting area.

  The present invention is an exposure head used for forming a latent image on a photoconductor in a printing apparatus, and has a plurality of organic EL elements arranged in an array on one surface side. The array substrate includes an array substrate configured to emit emitted light to the other surface and a drive circuit for the organic EL element, with the formation surface of the drive circuit facing one surface of the array substrate. A plurality of circuit chips arranged in series along the longitudinal direction of the array substrate and bump-connected to the array substrate, and a plurality of array substrate-side electrode pads provided on the array substrate to contact each of the plurality of bumps And a plurality of circuit chip side electrode pads provided on each of the plurality of circuit chips to come into contact with each of the plurality of bumps, respectively, along the longitudinal direction of the array substrate. Are arranged in a staggered Te, is the exposure head.

  According to such a configuration, each organic EL element and the circuit chip can be electrically connected without using wire bonding, and the mounting area can be reduced. In particular, by arranging the electrode pads in a staggered manner, the mounting area can be reduced as compared with, for example, a two-dimensional array arranged at equal intervals, so the width of the entire exposure head (perpendicular to the longitudinal direction). (Length in the direction) can be reduced.

  Preferably, in the array substrate, the plurality of organic EL elements are formed in a substantially central region along the longitudinal direction of the array substrate, and the plurality of array substrate-side electrode pads are formed around the region, In each of the plurality of circuit chips, the drive circuit is formed in a substantially central region along the longitudinal direction of the array substrate, the circuit chip side electrode pad is formed around the region, and the drive circuit The array substrate and each of the plurality of circuit chips are arranged so as to face each other directly above the plurality of organic EL elements.

  By adopting such a configuration, it is possible to prevent the driving circuit and / or the organic EL element from being damaged due to the pressing force when the array substrate and the circuit chip are bump-connected, and causing problems such as breakage.

  Embodiments according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic diagram illustrating the overall configuration of the organic EL array exposure head 1. 1A is a plan view (top view), and FIG. 1B is a cross-sectional view taken along line BB in FIG. 1A. The organic EL array exposure head 1 of the present embodiment is formed so that its entire length is slightly longer than the printing width in the main scanning direction. Further, since the cross-sectional size of the head 1 is extremely small, the scale is somewhat changed from the actual one in FIG. 1 for easy understanding of the configuration. Details of each part will be described later with reference to enlarged views.

  As shown in FIG. 1, an organic EL array exposure head 1 according to this embodiment is used for forming a latent image on a photosensitive member by a multiple exposure method in an electrophotographic printer (or a copying machine). The main component includes a connector 2, a frame 3, a condenser lens array 4, a driver IC 7 and an organic EL array 8. Reference numeral 24 denotes a sealant.

  The connector 2 is to be connected to a printer controller (not shown) on the printer side, and includes a control signal line that is wiring for receiving print data, and a power supply line that is wiring for supplying power. Including.

  The organic EL array (array substrate) 8 is formed by forming a plurality of organic EL light emitting sections (organic EL elements) in an array on one surface of a glass substrate. The organic EL array 8 is configured such that emitted light from each organic EL element is emitted to the other surface side of the glass substrate through the glass substrate.

  The driver IC (circuit chip) 7 is for controlling each organic EL light emitting unit (hereinafter abbreviated as a light emitting unit), and a predetermined number is mounted on the other surface of the glass substrate of the organic EL array 8. Yes. More specifically, the driver ICs 7 are arranged in series along the longitudinal direction (extending direction) of the organic EL array 8 so that the circuit formation surface faces one surface of the organic EL array 8.

  The condensing lens array 4 includes a large number of condensing lenses, and is configured such that each lens is disposed almost immediately above each light emitting portion of the organic EL array 8.

  FIG. 2 is a block diagram illustrating the configuration of the control circuit of the organic EL array exposure head according to the present embodiment. As shown in FIG. 2, in the organic EL array exposure head 1, a predetermined number of driver ICs 7 are mounted on the other surface of the organic EL array 8 along the main scanning direction. Each driver IC 7 is configured to control / drive one block allocated to each of the number of pixels in the main scanning direction and the organic EL array arranged in a staggered manner in the sub-scanning direction. The driver IC 7 of this embodiment includes a control circuit and a drive circuit.

  A data control line (signal line) 57 is a signal for daisy chain connecting a predetermined number of driver ICs 7 in the main scanning direction, and sending print data sent from the printer controller to the driver ICs 7 assigned to each line. Line.

  The power line 58 is for supplying power to each driver IC 7. As shown in FIG. 2, the data control line 57 and the power supply line 58 are both daisy chain connected to the driver IC 7, but the data control line 57 and the power supply line 58 are also provided inside the driver IC 7. Are wired as shown, and can be easily patterned without crossing the single-sided wiring on the glass substrate. The data control line 57 and the power supply line 58 are formed by forming a conductive film such as ITO on a glass substrate and patterning it. Note that aluminum or gold plating may be applied to reduce the wiring resistance.

  FIG. 3 is a plan view schematically illustrating the component configuration by enlarging the A portion of the organic EL array exposure head 1 shown in FIG. As shown in FIG. 3A, the condensing lens array 4 is disposed immediately above the organic EL array 8, and includes a condensing lens group 14a that condenses the light emitted from each organic EL element. The light shielding material 9 shields leakage light from the light emitting elements around the organic EL element. The condenser lens array 4 is provided with a positioning pad 10 for positioning when assembling with the organic EL array 8. As shown in FIG. 3B, the organic EL array 8 includes an organic EL array exposure head 1 having a number of pixels in the main scanning direction and a plurality of lines of organic EL elements arranged in a staggered pattern in the sub-scanning direction. It is formed on the glass substrate 60. As shown in FIG. 3C, the driver ICs 7 are mounted side by side along the extending direction of the organic EL array 8.

  Here, as shown in FIGS. 3B and 3C, in this embodiment, the driver ICs 7 are arranged on one surface of the organic EL array 8 and outside the organic EL element arrangement region. A wiring group 70 is provided in association with each boundary position. As shown in the figure, in this example, one set of wiring groups 70 is formed at each boundary position at both ends in the longitudinal direction of each driver IC 7. Although details will be described later, one of the adjacent driver ICs 7 is bump-connected to one end side of the wiring group 70, and the other is bump-connected to the other end side of the wiring group 70. That is, in this example, two adjacent driver ICs 7 are each provided with a set of wiring groups 70 at both ends in the longitudinal direction, and one of these wiring groups 70 together with the internal wiring group built in the driver IC 7 is described above. The data control line 57 (that is, the signal path) is configured, and the other constitutes the power supply line 58 (that is, the signal path) together with the internal wiring group incorporated in the driver IC 7.

  FIG. 4 is an enlarged view of the portion B shown in FIG. 3 of the organic EL array exposure head 1 and shows details of the structure of the condenser lens array 4. The condensing lens array 4 is provided with positioning pads (condensing lens assembly side targets) 10 a and 10 b for positioning at the time of bonding to the organic EL array 8.

  A light shielding material 9 is provided on one surface of the condenser lens array 4. The condenser lens array 4 includes a plurality of condenser lenses 13 corresponding to the number of pixels in the main scanning direction and arranged in a staggered manner in the sub scanning direction. Each is embedded in the light hole 27.

  A condensing lens similar to the condensing lens 13 is also provided in the boundary region of each driver IC 7. Specifically, the condensing lens group 14a is located immediately above the organic EL element to be driven by a driver IC 7 (not shown) disposed on the left side of the boundary indicated by a one-dot chain line in the drawing. . Similarly, the condensing lens group 14b is located immediately above the organic EL element to be driven by a driver IC 7 (not shown) disposed on the right side of the boundary indicated by a one-dot chain line in the drawing. The detailed structure of the condenser lens array 4 will be described later.

  FIG. 5 is an enlarged view of the portion C shown in FIG. 3 of the organic EL array exposure head 1, and shows details of the structure of the organic EL array 8.

  The positioning pad 11a is prepared corresponding to the driver IC 7 mounted on the left side in the drawing, and the positioning pad 11b is prepared corresponding to the driver IC 7 mounted on the right side in the drawing.

  Reference numeral 15 denotes a power supply pad on the glass substrate 60 side. The power supply pad 15a is connected to the driver IC 7 mounted on the left side, and the power supply pad 15b is connected to the driver IC 7 mounted on the right side. As shown in the figure, in this example, there are 10 sets of these power supply pads, which are distributed to the power supply potential side (VDD) and the ground side (GND), and are supplied to the power supply line pads 19 of a predetermined number of driver ICs 7 in the main scanning direction. Connected. The left and right power supply line pads of the driver IC 7 are connected inside the IC (not shown).

  Reference numeral 16 denotes an anode wiring pad on the glass substrate 60 side of the joint portion of the driver IC 7. The anode wiring pad 16a controls the organic EL element driven by the driver IC 7 that controls the left block, and the anode wiring pad 16b controls the organic EL element driven by the driver IC 7 that controls the right block. Is.

  Reference numeral 17 denotes an anode side electrode. The anode side electrode 17a is prepared for the driver IC 7 mounted on the left side, and the anode side electrode 17b is prepared for the driver IC 7 mounted on the right side.

  Reference numeral 18 denotes a data control line pad. The data control line pad 18a is prepared for the driver IC mounted on the left side, and the data control line pad 18b is prepared for the driver IC mounted on the right side.

  The data control lines 57 shown in FIG. 2 are connected to the data control line pads 21 of a predetermined number of driver ICs 7 in the main scanning direction (see FIG. 6). The left and right data control line pads of the driver IC 7 are connected inside the driver IC 7 and connected to the control circuit 56 inside the circuit unit 22 of the driver IC 7 (see FIG. 11).

  Reference numeral 32 denotes an anode electrode (ITO) pad. The anode electrode pad 32a is prepared for the driver IC 7 mounted on the left side, and the anode electrode pad 32b is prepared for the driver IC 7 mounted on the right side. In this example, each anode electrode pad is arranged above and below each anode electrode. This is done to reduce the wiring density on the glass substrate and facilitate wiring.

  Reference numeral 40 denotes a cathode side wiring pad. The cathode side wiring pad 40a is prepared for a driver IC mounted on the left side, and the cathode side wiring pad 40b is prepared for a driver IC mounted on the right side. The cathode side wiring pad is composed of a plurality of pads excluding the data control line pad 18 in the data control line pad 18.

  The anode wiring pad 16a, the anode wiring pad 16b, the anode wiring pad 32a, and the anode wiring pad 32b described above correspond to “array substrate side electrode pads”. These are provided on each of the organic EL arrays 8 (array substrate) so as to come into contact with bumps described later, and are arranged in a staggered manner along the longitudinal direction of the organic EL array 8 as shown in the figure. . Further, as shown in the figure, the organic EL array 8 has each organic EL element formed in a substantially central region along the longitudinal direction of the organic EL array 8, and the anode wiring pads (on the array substrate side) around the region. Electrode pad) is formed.

  FIG. 6 is an enlarged view of the portion D shown in FIG. 3 of the organic EL array exposure head 3, and shows details of the driver IC 7 which is adjacent to each other.

  Reference numeral 7a is a driver IC located on the left side, and reference numeral 7b is a driver IC located on the right side.

  Reference numeral 12 denotes a positioning pad on the driver IC side. The positioning pad 12a is used together with the positioning pad 11a for positioning with the organic EL array shown in FIG. 5, and the positioning pad 12b is used with the positioning pad 11b for positioning with the organic EL array shown in FIG.

  Reference numeral 19 denotes a power supply line pad on the driver IC side, which is bump-bonded to the power supply line pad 15 on the glass substrate side in FIG. The power line pad 19a is a pad on the driver IC side of the driver IC 7 located on the left side, and the power line pad 19b is a pad on the driver IC side of the driver IC 7 located on the right side.

  Reference numeral 20 denotes an anode wiring pad at a joint portion of the driver IC 7, and is bump-bonded to the anode wiring pad 16 on the glass substrate side of the joint portion of the driver IC 7 shown in FIG. The anode wiring pad 20a is for the driver IC 7 located on the left side, and the anode wiring pad 20b is for the driver IC 7 located on the right side.

  Reference numeral 21 denotes a data control line pad on the driver IC side, which is pump-bonded to the data control line pad 18 shown in FIG. The data control line pad 21a is for the driver IC located on the left side, and the data control line pad 21b is for the driver IC located on the right side.

  Reference numeral 22 denotes a circuit unit of the driver IC 7. The circuit unit 22a is for the driver IC located on the left side, and the circuit unit 22b is for the driver IC located on the right side.

  Reference numeral 36 denotes an anode wiring pad on the driver IC side, which is bump-bonded to the anode electrode pad 32 shown in FIG. The anode wiring pad 36a is on the driver IC side located on the left side, and the anode wiring pad 36b is on the driver IC side located on the right side.

  Reference numeral 38 denotes a cathode wiring pad on the driver IC side, and is bump-bonded to the cathode side wiring pad 40 shown in FIG. The cathode wiring pad 38a is on the driver IC side located on the left side, and the cathode wiring pad 38b is on the driver IC side located on the right side.

  The anode wiring pad 20a, the anode wiring pad 20b, the anode wiring pad 36a, and the anode wiring pad 36b described above correspond to “circuit chip side electrode pads”. These are provided in each of the driver ICs 7 (circuit chips) so as to come into contact with bumps described later, and are arranged in a staggered manner along the longitudinal direction of the organic EL array 8 (array substrate) as shown in the figure. Has been. Further, as shown in the figure, each driver IC 7 includes circuit portions 22a and 22b (drive circuit) formed in a substantially central region along the longitudinal direction of the organic EL array 8 (array substrate). A wiring pad (circuit chip side wiring pad) is formed.

  FIG. 7 is a more detailed cross-sectional view of the organic EL array exposure head 1 and shows a cross section in the direction of the BB line shown in FIG. As shown in the drawing, the organic EL array exposure head 1 includes an exposure head module 5 and a head support frame (frame) 3. Here, the exposure head module 5 is a complex composed of the condenser lens array 4, the organic EL array 8 and the IC driver 7, and is fixed to the frame 3 by the sealant 24. The frame 3 is also used as a radiator for the driver IC 7. Reference numeral 4 denotes a condenser lens array, reference numeral 8 denotes an organic EL array, and reference numeral 23 denotes a sealant.

  FIG. 8 is an enlarged cross-sectional view of the portion F shown in FIG. 7 of the organic EL array exposure head 1 and shows the exposure head module 5. The light emitted from the light emitting unit 25 formed in the organic EL array 8 passes through the optical path 26 and reaches the light hole 27. Of the light, the light passing through the light hole 27 immediately above the light emitting unit 25 passes through the condenser lens 13 and becomes a substantially parallel light beam, which is connected to a photoconductor (not shown). However, the light reaching the light hole 27 that is not directly above the light emitting unit 25 is blocked by the light blocking unit 9 and does not reach the condenser lens 13 disposed there. Reference numeral 4 denotes a condenser lens array, reference numeral 7 denotes a driver IC, reference numeral 8 denotes an organic EL array, reference numeral 23 denotes a sealant, reference numeral 28 denotes an adhesive, and reference numeral 29 denotes a bump joint.

  FIG. 9 is an enlarged view of the G section shown in FIG. 8 of the exposure head module, and illustrates the layer configuration of the periphery of the light emitting section 25 of the organic EL array 8 and the driver IC 7. A drive circuit 55 and a control circuit 56 are disposed on the substrate of the driver IC 7, and the surface thereof is covered with the insulating layer 30. A hygroscopic agent 31 is disposed in the gap between the driver IC 7 and the organic EL array 8. The cathode electrode (AL) 35 constitutes an organic EL element, and a light emitting layer 34, a hole transport layer 33, and an anode electrode (ITO) 17 are laminated thereon. The insulating layer 44 is disposed around the light emitting unit 25. The glass substrate 60 supports the organic EL light emitting element, and also serves as a sealing material that protects the element from the outside. In this example, on the opposite side, one surface side of the driver IC 7 also functions as a sealing material.

  FIG. 10 is a diagram for explaining the configuration of the exposure head module 5, and FIG. 11 is a diagram for explaining each component of the exposure head module 5. 10 and 11, in order to facilitate understanding of the description, some of the light emitting portions (the light emitting layer 34 and the condenser lens 13 shown in the drawing) are illustrated, and most of the light emitting portions and the like are illustrated. Omitted.

  The exposure head module 5 includes a driver IC 7, a hygroscopic agent 31, an organic EL array 8, and a condenser lens array 4. 12A and 12B are diagrams for explaining the structure of the condenser lens array 4. FIG. 12A is a diagram showing the relationship between the light holes 27, and FIG. FIG.

  A plurality of through-holes having the same pattern as the arrangement pattern of the light emitting units 25 formed in the organic EL array 8 are formed on the surface of the condenser lens array 4. As shown in FIG. 12, the diameter of the through hole (light emitting portion side light hole 27a) on the side to be bonded to the array assembly 4, that is, the light incident side is equal to the light emitting side through hole (lens press-fit side light guide). It is set to be larger than the diameter of the hole 27b).

  Further, the condenser lens 13 is press-fitted into the through-hole on the light emission side (the optical hole 27b on the lens press-fitting side). On the other hand, the light shielding material 9 constituting the condensing lens array 4 is composed of a glass cloth base epoxy resin black laminate (FRP) having substantially the same characteristics as the thermal expansion of the condensing lens 13, and the light on the lens press-fitting side. The diameter of the hole 27b is set to be slightly smaller than the diameter of the condenser lens 13 to such an extent that the condenser lens 13 can be held. The light guide hole 27 is designed so that only the light from the light emitting unit 25 located immediately below it is emitted through the condenser lens, and the light from the adjacent light emitting unit is shielded from passing therethrough. According to the condensing lens array 4 having such a configuration, since the diameter of the condensing lens 13 can be increased, the light emitted from the light emitting unit can be further condensed, and as a result, the amount of emitted light can be increased. can do. Further, if the diameter of the condenser lens 13 is increased, the spherical aberration of the lens can be suppressed, which is also advantageous in this respect. Further, when a drum-shaped lens is used as the condenser lens 13, spherical aberration can be further suppressed.

  FIG. 13 is a diagram for explaining a production process of the organic EL array 8 shown in FIG. In addition, in order to facilitate understanding of the invention, FIG. 13 also illustrates a part of the light emitting portions (the light emitting layer 34 and the like shown in the drawing) and omits most of the light emitting portions and the like. .

  The organic EL array 8 is generated through steps I → J → K → L shown in FIG. More specifically, first, in the step I, the glass substrate side wiring electrode pad 43, the anode electrode transparent electrode 17, and the cathode side wiring electrode pad 40, which are transparent electrode (ITO) films, are formed on the glass substrate 60 by sputtering or the like. A pattern is generated.

  In the J process, an insulating layer (polyimide or the like) 44 is printed on the glass substrate 60 patterned with ITO, and in the K process, an organic EL light emitting layer made of a polymer material or a low molecular material is formed. Is done. This organic EL light emitting layer is composed of a light emitting layer 34, a hole transport layer 33, an electron transport layer (not shown), and the like, and each layer is formed using a material suitable for each. Finally, in the L step, the cathode electrode 35, the anode electrode aluminum pad 32, and the electrode pad 59 using a material such as aluminum (Al) are formed by vapor deposition or the like.

  The organic EL array 8 formed in this way is fixed to the condenser lens array 4 with an adhesive such as a thermosetting resin (see FIG. 11). At the time of such fixing, a positioning pad 10 provided on the condenser lens array 4 and a positioning pad 11 provided on the organic EL array 8 are used (see FIGS. 4 and 5). Secured.

  Next, the organic EL array 8 and the driver IC 7 are bonded and fixed by bumps 42, 37, and 39 (see FIG. 11). When performing such fixing, the positioning pad 10 provided on the condenser lens array 4 and the positioning pad 12 provided on the driver IC 7 are used (see FIGS. 5 and 6), thereby ensuring high fixing position accuracy. Is done. During bump bonding, a hygroscopic agent 31 is inserted between the driver IC 7 and the organic EL array 8 (see FIG. 11). The hygroscopic agent 31 is for protecting the hole transport layer 33 and the light emitting layer 34 from deterioration due to humidity, and a desiccite or the like is used.

  Here, the driver IC 7 (see FIG. 11) will be described in detail. First, the drive circuit 55 and the control circuit 56 constitute the circuit unit 22 of the driver IC shown in FIG. The drive circuit 55 and the control circuit 56 are disposed away from the place where the bump pad is placed in order to avoid element destruction due to pressure at the time of bump bonding.

  The wiring electrode pad 41 constitutes the power supply line pad 19 and the data control line pad 21 shown in FIG. A wiring electrode bump 42 is formed on the wiring electrode pad 41. The wiring electrode bumps 42 are formed of an electrically conductive material (such as gold) for connecting and fixing to the electrode aluminum pads 59 of the organic EL array 8.

  The anode wiring pad 36 constitutes the anode wiring pad 20 and the anode wiring pad 36 at the joint portion of the driver IC shown in FIG. An anode wiring bump 37 is formed on the anode wiring pad 36. The anode wiring pad 36 is formed of an electrically conductive material (such as gold) for bonding and fixing to the electrode aluminum pad 32 of the organic EL array 8.

  The cathode wiring pad 38 constitutes the cathode wiring pad 38 shown in FIG. Cathode wiring bumps 39 are formed on the cathode wiring pads 38. The cathode wiring pad 38 is formed of an electrically conductive material (such as gold) for bonding and fixing to the electrode aluminum pad 35 of the organic EL array 8.

  After the organic EL array 8 having such a configuration and the driver IC 7 are bonded together by the bumps 42, 37, and 39, the periphery of the bonded portion between the organic EL array 8 and the driver IC 7 is quickly solidified with the sealant 23. By forming the exposure head module 5 in this way, the light emitted from the light emitting layer 34 becomes a substantially parallel light beam by the condenser lens 13 through the light hole 27 directly below, and forms an image on the surface of the photoreceptor (not shown).

<Control mode of light emission>
FIG. 14 is a diagram illustrating a configuration of a light emitting element control circuit according to the present embodiment. In the following, a control mode of the light emitting unit 25 controlled by one driver IC 7 will be described as an example, but this mode is merely an example, and how the light emitting unit 25 is controlled can be changed as appropriate.

  A plurality of light emitting sections 25 formed in the organic EL array 8 are arranged in the main scanning direction Y as shown by reference numeral 48 in FIG. 14 and arranged in eight rows in the sub scanning direction X. The data output timing control means 45 is realized by a printer controller (not shown), and performs processing such as color separation, gradation processing, development of image data into a bitmap, and color misregistration adjustment based on image data to be formed. On the other hand, the image data for each line is output to each storage means 47. The data output timing control means 45 may be realized by a printer controller or may be realized by the circuit unit 22 of the driver IC 7.

  The storage unit 47 includes shift registers 47a to 47h. These shift registers are divided into shift registers 47a, 47c, 47e, 47g belonging to the first group and shift registers 47b, 47d, 47f, 47h belonging to the second group. The shift registers 47a, 47c, 47e, and 47g belonging to the first group hold image data, output to the light emitting unit, and transfer to the next-stage shift register.

Similarly to the shift registers belonging to the first group, the shift registers 47b, 47d, 47f and 47h belonging to the second group also hold image data, output to the light emitting unit, and transfer to the next-stage shift register. Similarly to the shift register, the light emitting unit lines are divided into light emitting unit lines 48a, 48c, 48e, 48g belonging to the first group and light emitting unit lines 48b, 48d, 48f, 48h belonging to the second group. . The storage means 47 is provided with a shift register group for transferring image data for I lines in the main scanning direction Y, but is omitted in FIG. 14 to prevent the drawing from becoming complicated. . The storage unit 47 may also be realized by the circuit unit 22 of the driver IC 7 in the same manner as the data output timing control unit 45.

  The operation of the light emitting element control circuit will be described. First, the data output timing control means 46 outputs image data from the control line 50 to the first group of shift registers and from the control line 49 to the second group of shift registers. Image data is output.

  The image data stored in each shift register is output from the data output timing control means 46 to the corresponding light emitting unit according to the timing signals 46a to 46h supplied to each shift register.

  Specifically, first, when the timing signal 46a is supplied from the data output timing control means 46 to the shift register 47a, the image data is output from the shift register 47a to the first line 48a of the light emitting units of the first group, and the photosensitive data is detected. The first pixel line is exposed at a spot position on the body (not shown). Similarly, when the timing signal 46b is supplied from the data output timing control means 46 to the shift register 47b, the image data is output from the shift register 47b to the first line 48b of the light emitting unit of the first group, and a photoconductor (not shown). ) The second pixel line is exposed at the upper spot position.

  Next, when the image carrier moves by the pixel pitch in the sub-scanning direction, the image data stored in the shift register 47a is transferred to the shift register 47c. Similarly, the image data stored in the shift register 47b is transferred to the shift register 47d. When the timing signal 46c and the timing signal 46d are supplied from the data output timing control means 46 to the shift register 47c and the shift register 47d, the image data is output from the shift register 47c and the shift register 47d to the light emitting unit lines 48c and 48d, respectively. Is done. At this time, the same pixel is exposed on the first pixel line and the second pixel line at the spot position. Thereafter, similarly, the image carrier is moved, the image data is transferred to each shift register, and the image data is output to the light emitting unit, and multiple exposure is performed on the same pixel.

  As described above, even when the light emitting units are arranged in a staggered manner and the interval in the sub scanning direction between the spot positions formed by the light emitting units on the image carrier is set to an integral multiple of the pixel density in the sub scanning direction, 1 Pixels can be multiple exposed. That is, even when the light emitting units are arranged in a staggered manner, the storage means of each pixel column and the light emitting unit column can correspond one-to-one. For this reason, by combining the timing for transferring the image data stored in the shift register to the next-stage shift register and the timing for causing the light emitting section line to emit light based on the image data of the pixel column stored in the shift register. Therefore, the circuit configuration can be simplified and the operation speed can be increased.

  Further, when the light emitting portions are arranged in a staggered pattern, the light emitting portion lines 48 are caused to emit light sequentially at intervals of 1 dot line pitch in the order of 48a → 48b → 48c → 48d → 48e → 48f → 48g → 48h. Is also possible. In addition, by using four exposure heads as described above, a so-called tandem image forming apparatus that forms an image with four colors of cyan (C), magenta (M), yellow (Y), and black (K). Of course, it may be applied.

  FIG. 15 is a diagram illustrating a configuration of a drive circuit that drives the light emitting unit with an active matrix. The power supply line 51 is connected to the source Sb of the driving transistor Tr2. On the other hand, the anode terminal A of the organic EL element constituting the light emitting unit is connected to the drain Db of the driving transistor Tr2, and the cathode terminal K is connected to the ground GND. The scanning line 53 is connected to the gate Ga of the switching transistor Tr1, and the capacitance line 52 is connected to the source Sa of the switching transistor Tr1. Further, the drain Da of the switching transistor Tr1 is connected to the gate Gb of the driving transistor Tr2 and one electrode of the storage capacitor Ca. The other electrode of the storage capacitor Ca is connected to the source Sb of the driving transistor Tr2.

  The operation of the driving circuit will be described. First, when the scanning line 53 is energized in a state where the voltage of the power supply line 51 is applied to the drain Da of the switching transistor Tr1 via the storage capacitor Ca, the switching transistor Tr1 Switch from off to on. By such a switching operation, the gate voltage of the driving transistor Tr2 is lowered, and the driving transistor Tr2 is switched from off to on. As a result, the organic EL element operates to emit light with a predetermined light amount, and the storage capacitor Ca is charged by the potential difference between the power supply line 51 and the capacitor line 52.

  Thereafter, even if the switching transistor Tr1 is switched from on to off, the driving transistor Tr2 maintains the on state by the electric charge charged in the storage capacitor Ca, so that the organic EL element maintains the light emitting state. As a result, even when the switching transistor Tr1 is switched from on to off in order to transfer the image data to the shift register, the organic EL element continuously maintains the light emitting operation, and high-luminance pixel exposure is performed. It becomes possible.

  As described above, according to the exposure head of the present embodiment, each organic EL element and the IC driver (circuit chip) can be electrically connected without using wire bonding, and the mounting area can be reduced. Is possible. In particular, by arranging the anode wiring pads (array substrate side electrode pads, circuit chip side electrode pads) in a staggered manner, the mounting area can be reduced as compared with, for example, a two-dimensional array arranged at equal intervals. As a result, the width of the entire exposure head (the length in the direction orthogonal to the longitudinal direction) can be reduced.

  In addition, by adopting a configuration in which each organic EL array (array substrate) and each driver IC (circuit chip) are arranged so that each driver IC is directly opposite to the organic EL element, by the pressing force at the time of bump connection It is possible to avoid the occurrence of problems such as breakage due to stress applied to the drive circuit and / or the organic EL element in the driver IC.

  In addition, this invention is not limited to the content of the said embodiment, A various deformation | transformation implementation is possible within the range of the summary of this invention.

It is the schematic explaining the whole structure of an organic EL array exposure head. It is a block diagram explaining the structure of the control circuit of an organic EL array exposure head. It is a top view which expands the A section shown in the said FIG. 1 of the organic electroluminescent array exposure head, and roughly demonstrates a component structure. FIG. 4 is an enlarged view of a portion B shown in FIG. 3 of the organic EL array exposure head, and shows details of the structure of the condenser lens array. FIG. 4 is an enlarged view of a portion C shown in FIG. 3 of the organic EL array exposure head, and shows details of the structure of the organic EL array. FIG. 4 is an enlarged view of a portion D shown in FIG. 3 of the organic EL array exposure head, and shows details of driver ICs that are adjacent to each other. FIG. 2 is a more detailed cross-sectional view of the organic EL array exposure head, showing a cross section in the BB line direction shown in FIG. It is an expanded sectional view of the F section shown in the above-mentioned FIG. 7 of the organic EL array exposure head, and shows the exposure head module. FIG. 9 is an enlarged view of the G section shown in FIG. 8 of the exposure head module, and illustrates the layer configuration of the periphery of the light emitting section of the organic EL array and the driver IC. It is a figure for demonstrating the structure of an exposure head module. It is a figure for demonstrating each component of an exposure head module. It is a figure for demonstrating the structure of a condensing lens array. It is a figure for demonstrating the production | generation process of the organic electroluminescent array shown in FIG. It is a figure which shows the structure of the light emitting element control circuit which concerns on this embodiment. It is a figure which shows the structure of the drive circuit which drives a light emission part by an active matrix. It is the figure which illustrated the structure of the organic EL array print head which employ | adopted organic EL as a light source.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Organic EL array exposure head, 2 ... Connector, 3 ... Frame, 4 ... Condensing lens array, 7 ... Driver IC7, 8 ... Organic EL array, 16a, 16b, 32a, 32b ... Anode wiring pad (array substrate side electrode) Pads), 20a, 20b, 36a, 36b ... anode wiring pads (circuit chip side electrode pads)

Claims (2)

An exposure head used for forming a latent image on a photoconductor in a printing apparatus,
An array substrate configured to have a plurality of organic EL elements arranged in an array on one side and to emit light emitted from the organic EL elements to the other side;
It includes a drive circuit for the organic EL element, and is arranged in series along the longitudinal direction of the array substrate so that the formation surface of the drive circuit faces one surface of the array substrate, and is bump-connected to the array substrate A plurality of circuit chips;
Including
A plurality of array substrate side electrode pads provided on the array substrate to contact each of the plurality of bumps, and a plurality of circuits provided to each of the plurality of circuit chips to contact each of the plurality of bumps An exposure head in which chip-side electrode pads are arranged in a staggered manner along the longitudinal direction of the array substrate. In the array substrate, the plurality of organic EL elements are formed in a substantially central region along the longitudinal direction of the array substrate, and the plurality of array substrate side electrode pads are formed around the region,
In each of the plurality of circuit chips, the drive circuit is formed in a substantially central region along the longitudinal direction of the array substrate, and the circuit chip side electrode pad is formed around the region,
2. The exposure head according to claim 1, wherein the array substrate and each of the plurality of circuit chips are arranged such that the drive circuit faces directly above the plurality of organic EL elements.

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