JP4821282B2 - LED array head and image recording apparatus - Google Patents

Description

  The present invention relates to an LED array head including a plurality of LEDs and an image recording apparatus.

  Conventionally, an LED array used for an LED array head or the like as a light emitting device is connected to a printed board by a bonding wire. At the bonding portion of the bonding wire on the LED array, the light from the light emitting point of the LED is reflected on the bonding wire ball or wire, and scattered light or stray light is likely to be generated.

  Due to the scattered light and stray light, the photosensitive member is exposed with an exposure amount that is greater than the original exposure amount.

  For this reason, for example, in Patent Document 1, a second bond is made to the pad on the LED array, and the first bond is made to the LED array mounting substrate, so that the wire loop height is lowered by a so-called stitch bond, and the problem of stray light occurs. However, since stitch bonding requires a wide pad area and pad surface strength, it is necessary to increase the width and length of the LED array and increase the pad strength. Therefore, when the width of the LED array is only about 125 μm, the pad area is small, and the bonding part protrudes from the pad during bonding, causing an electrical short circuit or breaking the pad.

Moreover, in patent document 2, the mask which has a pinhole is arrange | positioned between the microcapsule in which image information is actualized by development, and LED, and the output light from LED passes through a pinhole and irradiates a microcapsule. As described above, stray light is prevented, but the mechanism is complicated and high assembly accuracy is required, and the number of manufacturing steps is also increased.
JP-A-5-183191 Japanese Patent Laid-Open No. 10-10747

  In view of the above facts, an object of the present invention is to prevent stray light and to provide a small LED array head and an image recording apparatus.

The invention according to claim 1 is an elongated printed circuit board, an LED array disposed on the printed circuit board and provided with a plurality of LEDs, and a first electrode pad disposed on an upper surface of the LED array A second electrode pad disposed on the printed circuit board; an insulating connecting member disposed between the first electrode pad and the second electrical pad; and mounted on the printed circuit board; One end portion embedded in the connection member and connected to the first electrode pad and the other end portion connected to the second electrode pad are formed to protrude from the connection member and have elasticity. And when the connection member is attached to the printed circuit board, one end of the conducting body presses the first electrode pad and contacts the first electrode pad, and the other end of the conducting body Part of the second electrode pack. The presses, characterized in that contact with the second electrode pad.

According to the first aspect of the present invention, an insulating connecting member is disposed between the first electrode pad and the second electric pad, the conductive member is embedded in the connecting member, and the end of the conductive member protruding from the connecting member The first electrode pad and the second electric pad can be electrically connected by bringing the portion into contact with the first electrode pad and the second electric pad, respectively. Further, the conductive body has a spring property, and the end of the conductive body is brought into contact with the first electrode pad or the second electrode pad in a state where the first electrode pad or the second electrode pad is pressed. The first electrode pad and the second electrode pad can be easily conducted simply by mounting the relay member on the substrate.

The invention according to claim 2 is characterized in that a plurality of holes are formed in the printed circuit board, and a plurality of protrusions fitted into the holes are provided on the lower surface of the connection member. To do.

According to the second aspect of the present invention , the connecting member is attached to the printed circuit board only by fitting the projection of the connecting member into the hole of the printed circuit board. Moreover, since it is not necessary to position the conducting body with the first electrode pad and the second electrode pad, workability is improved.

According to a third aspect of the present invention, in the LED array head according to the first or second aspect , the LED arrays are staggered on the substrate, and the LEDs disposed on the adjacent LED arrays and the first electrode pads are arranged. It is characterized by facing.

In the invention according to claim 3 , the LED arrays are arranged in a staggered manner on the substrate, and the LEDs arranged in the adjacent LED arrays are opposed to the first electrode pads, so that the LEDs and the first electrode pads are closer to each other. Will be placed at the position. For this reason, the effect of the invention of Claim 1 or 2 can be acquired more effectively.

According to a fourth aspect of the present invention, in the image recording apparatus, the LED array head according to any one of the first to third aspects is provided.

In the invention described in claim 4, by providing the LED array head according to any one of claim 1 to 3 the effect substantially the same effects described in any one of claims 1 to 3 Obtainable.

  Since the present invention has the above-described configuration, generation of scattered light and stray light can be prevented. In addition, since it is not necessary to perform stitch bonding on the first electrode pad as a countermeasure against stray light, the pad strength of the first electrode pad on the LED array can be reduced, and the size of the first electrode pad can be reduced. For this reason, since the LED chip becomes smaller and the number of wafers taken per wafer increases, the cost of the LED chip can be reduced, and a small LED array can be manufactured, and the image recording apparatus can be downsized. it can. Furthermore, since it is not necessary to perform stitch bonding on the first electrode pad as a countermeasure against stray light, the production direct rate is improved. That is, since the bonding force to the first electrode pad is reduced, damage such as cracks to the LED array is reduced, and an improvement in product yield can be expected.

  FIG. 1 shows an image recording apparatus 10 to which an LED array head 20 according to an embodiment of the present invention is applied. The image recording apparatus 10 is a so-called tandem type image recording apparatus. The image recording apparatus 10 includes an intermediate transfer belt 12 that is stretched substantially horizontally. Under the intermediate transfer belt 12, four image recording units 14 corresponding to different development colors are arranged. .

  A paper tray 11 is provided below the image recording unit 14, and a conveyance path 13 extending upward from the paper feeding side of the paper tray 11 includes a secondary transfer unit 15 that contacts the intermediate transfer belt 12 and a fixing device. It passes through the fixing unit 17 and reaches the discharge port, and the outside of the discharge port is a discharge tray 19.

  Each image recording unit 14 includes a photoreceptor 16, a charger 18, an LED array head 20, a developing device 40, and a cleaner 42.

  The photoconductor 16 has a light receiving surface 16A whose outer peripheral surface is cylindrical, and an electrostatic latent image can be formed on the light receiving surface 16A. The light receiving surface 16 </ b> A is in contact with the intermediate transfer belt 12 on the downstream side (hereinafter simply referred to as “downstream side”) of the photosensitive drum rotation direction (arrow R direction) with respect to the developing device 40.

  The charger 18 is a conductive roller, and a metal cored bar is covered with an elastic layer made of a synthetic resin so that a negative voltage is applied to the cored bar by a power source (not shown). It has become. An LED array head 20 is disposed downstream of the charger 18 and irradiates the light receiving surface 16A (photosensitive layer) of the photoconductor 16 with a light image. As a result, the photosensitive member 16 charged by the charger 18 is exposed to form an electrostatic latent image.

  Further, a developing device 40 is disposed on the downstream side of the LED array head 20. The developing device 40 is filled with a two-component developer in which toner and carrier are mixed, and the toner and carrier filled in the developing device 40 are agitated, frictionally charged, and mixed without unevenness. ing. Thereby, the toner is electrostatically adhered to the carrier.

  Then, the magnetic powder carrier is adsorbed by the magnetic force of the magnet roller 44 disposed facing the photoconductor 16. The toner adhering to the carrier on the magnet roller 44 is electrostatically applied to the photoconductor 16 by the potential difference (development potential) between the potential (−200 V) at which the photoconductor 16 is exposed and the development bias potential (−550 V). It comes to be attached.

  As a result, the developing device 40 causes the toner to adhere to the electrostatic latent image formed on the photoreceptor 16 and develops it to form a toner image. Then, the toner image is transferred onto the intermediate transfer belt 12, and finally, the toner images of all colors are superimposed on the intermediate transfer belt 12.

  On the other hand, the cleaner 42 disposed on the downstream side of the developing device 40 is in contact with the light receiving surface 16A of the photoconductor 16 to remove deposits (waste toner, waste carrier, etc.) attached to the photoconductor 16. .

  The LED array head according to the first embodiment of the present invention will be described.

  As shown in FIG. 2, the LED array head 20 includes a long printed board 22. A circuit for supplying various signals for controlling driving of the LED array head 20 (each LED 28) is formed on the printed circuit board 22, and image data for one line can be sequentially processed.

  In addition, LED arrays (also referred to as LED chips) 26 and 27 are alternately arranged in two rows on the printed circuit board 22 so that the ends in the longitudinal direction partially overlap. In addition, a plurality of LEDs 28 arranged one-dimensionally along the longitudinal direction of the LED arrays 26 and 27 are provided on the upper surfaces of the LED arrays 26 and 27, and the number of pixels (dots) corresponding to the resolution is the same. Is provided.

  On the other hand, a lens holder 23 is provided at a position opposed to the printed circuit board 22, and a rod lens array (SLA) 30 as a condenser lens (optical system) is formed along the same direction as the longitudinal direction of the printed circuit board 22. It is arranged. With this rod lens array 30, the light from the LEDs 28 of the LED arrays 26 and 27 is imaged on the photosensitive member 16.

  In the present embodiment, self-scanning LED (SLED) arrays are used as the LED arrays 26 and 27. Since the SLED array can selectively emit light by using two signal lines at the on / off timing of the switch, the data line can be shared and the wiring can be simplified. As the SLED array, for example, one disclosed in JP-A-8-216448 can be applied.

  In this self-scanning LED, the number of first electrode pads 32 (see FIG. 3) for electrically connecting the LED arrays 26 and 27 to the printed circuit board 22 can be significantly reduced as compared with the conventional LED array. For this reason, the 1st electrode pad 32 can be concentrated on the edge part of the arrangement direction of LED28 in LED array 26,27.

  Therefore, as shown in FIG. 3, the first electrode pads 32 are disposed on both ends in the longitudinal direction of the LED arrays 26 and 27, and the first electrode pads 32 are arranged on the printed circuit board 22 at positions corresponding to the first electrode pads 32. A two-electrode pad 24 is provided.

  Thus, by making the number of the first electrode pads 32 significantly smaller than that of the conventional LED array, the LED arrays 26 and 27 can be miniaturized, so that the number of chips taken from one wafer can be greatly increased. Thus, the cost per chip can be reduced.

  Here, as shown in FIGS. 3 and 4, between the first electrode pad 32 and the second electrode pad 24, a resin-made relay member 50 having a square cross section is formed on the printed circuit board 22. It is fixed with. The vertical surface 50A of the relay member 50 can be in surface contact with the side surface 27A of the LED array 27, and the vertical surface 50B opposite to the vertical surface 50A can be in surface contact with the side surface of the second electrode pad 24. It has become.

  The vertical surface 50A and the vertical surface 50B of the relay member 50 are connected by an inclined surface portion 50C. One end portion of the slope portion 50C is substantially the same as the height of the first electrode pad 32, and the other end portion is substantially the same as the height of the second electrode pad 24. The electrode pads 24 are connected on a continuous surface.

  Then, in a state where the relay member 50 is fixed on the printed circuit board 22, a paste-like metal 52 (gold, silver, or the like) is applied in a planar shape along the inclined surface portion 50 </ b> C of the relay member 50, and the metal 52 Is extended to the first electrode pad 32 and the second electrode pad 24 to electrically connect the first electrode pad 32 and the second electrode pad 24.

  By the way, since there is no LED 28 at the position where the first electrode pad 32 is disposed, the LED array 27 (or the LED array 26) is used to perform exposure without a gap along the axial direction of the photosensitive member 16 (see FIG. 1). ) Of the LED array 26 (or LED array 27) facing each other is required to be disposed opposite to the portion where the first electrode pad 32 is disposed.

  For this reason, the first electrode pad 32 of the LED array 27 is disposed at a position close to the LED 28 of the adjacent LED array 26. For example, as shown in FIG. 9, the first electrode pad 32 and the second electrode When the pad 24 is connected by the bonding wire 35, the light from the light emitting point of the LED 28 of the LED array 26 is transmitted to the wire 35 </ b> A of the bonding wire 35 at the joint portion of the bonding wire 35 with the first electrode pad 32 on the LED array 27. The first electrode pad 32 of the LED array 26 is the same as the LED array 27, but only the LED array 27 side will be described for convenience. Do).

  However, in this embodiment, as shown in FIGS. 3 and 4, the relay member 50 is disposed between the first electrode pad 32 and the second electrode pad 24, and along the inclined surface portion 50 </ b> C of the relay member 50, Since the paste-like metal 52 is applied in a plane and the first electrode pad 32 and the second electrode pad 24 are electrically connected, the first electrode pad 32 is compared with the case where the bonding wire 35 is used for connection. The amount of protrusion from the upper surface of the plate becomes low.

  For this reason, the paste-like metal 52 is outside the light-emitting area of the LEDs 28 arranged in the LED array 26 (the area indicated by the so-called directivity angle θ (light spread angle with respect to the optical axis of the LED)). The light from the light emitting point is not reflected, and the generation of scattered light and stray light due to the light from the light emitting point of the LED 28 can be prevented.

  Here, FIGS. 5A and 5B schematically show the experimental results obtained by photographing the light after passing through the rod lens array 30 through the CCD with the LED 28 emitting light. In the comparative example, FIGS. As shown in FIG. 5 (A), stray light (white elliptical point) is generated, whereas in the example of this embodiment, stray light is generated as shown in FIG. 5 (B). It was confirmed that it was not.

  That is, as a countermeasure against stray light, it is not necessary to perform STCB, so-called stitch bonding, on the first electrode pad 32. In the stitch bond, since the bonding force to the first electrode pad 32 is larger than other bonding methods, it is necessary to increase the pad strength, and there is a problem that the pad area becomes large.

  Therefore, as in the present embodiment, the paste-like metal 52 is applied in a planar shape along the inclined surface portion 50C of the relay member 50, and the first electrode pad 32 and the second electrode pad 24 are electrically connected. By doing so, the pad strength of the first electrode pad 32 on the LED array 27 can be reduced, and the size of the first electrode pad 32 can be reduced.

  Therefore, the small LED arrays 26 and 27 can be manufactured, and the image recording apparatus 10 can be downsized. Specifically, the dimension in the short direction of the LED arrays 26 and 27 can be 130 μm (generally 300 μm) or less.

  Further, since it is not necessary to perform stitch bonding on the first electrode pad 32 as a countermeasure against stray light, the production direct rate is improved. That is, since damage such as cracks due to bonding to the LED arrays 26 and 27 does not occur, an improvement in product yield can be expected.

  In this embodiment, the relay member 50 is disposed between the first electrode pad 32 and the second electrode pad 24, and the paste-like metal 52 is applied along the slope portion 50C of the relay member 50. Although it is configured to be outside the light emitting region of the LEDs 28 arranged in the LED array 26, the light shielding insulator 60 may be further covered on the first electrode pad 32 side.

  Here, the resin-made relay member 50 is disposed between the first electrode pad 32 and the second electrode pad 24. However, the relay member 50 is not necessarily required, and the side wall 27A of the LED array 27 and the prints are printed. Of course, the paste-like metal 52 may be directly applied along the upper surface of the substrate 22 to connect the first electrode pad 32 and the second electrode pad 24.

  In addition, for example, the effect of the present invention can be enhanced by providing a step in the height of the light emitting point on the LED array 26 facing the first electrode pad 32 on the LED array 27.

  Further, a shape such as the relay member 50 may be formed by injecting and solidifying epoxy, silicon, or the like with a dispenser or the like. By forming the relay member 50 by using a dispenser or the like in this manner, injection can be performed even if the gap between the first electrode pad 32 and the second electrode pad 24 is small. Can do.

  Furthermore, a connection member 54 shown in FIGS. 6 to 8 may be used. The connecting member 54 has substantially the same shape as the relay member 50 and is slightly higher than the relay member 50. A projecting portion 56 projects from the lower portion of the connecting member 54, and a hole 58 into which the projecting portion 56 can be fitted is formed in the printed board 22. As a result, the connecting member 54 is attached to the printed circuit board 22 simply by fitting the protrusion 56 of the connecting member 54 into the hole 58 of the printed circuit board 22, and the workability is good.

  Then, a wire 55 is embedded in the connection member 54, and an end portion of the wire 55 is exposed from the connection member 54 so as to be able to contact the first electrode pad 32 and the second electrode pad 24. .

  Here, the wire 55 is made of a material having elasticity such as gold, silver, stainless steel, tungsten, or beryllium steel, and the first electrode pad 32 or the second electrode is pressed with the first electrode pad 32 and the second electrode pad 24 being pressed. It is made to contact | abut to the pad 24. FIG.

  Accordingly, the first electrode pad 32 and the second electrode pad 24 can be easily conducted simply by mounting the connection member 54 on the printed circuit board 22, and it is not necessary to solder both ends of the wire 55. Workability is improved.

1 is a schematic configuration diagram illustrating a configuration of an image recording apparatus to which an LED array head according to an embodiment of the present invention is applied. It is a perspective view explaining the relationship between the LED array head which concerns on embodiment of this invention, and a photoreceptor. It is a top view which shows the LED array head which concerns on embodiment of this invention. It is sectional drawing which shows the connection method of the LED array and printed circuit board which concern on embodiment of this invention. (A) is a schematic diagram which shows the state in which the stray light by the light from the light emission point of LED has arisen, (B) is a schematic diagram corresponding to (A) which shows the result of an Example. It is a perspective view which shows the other connection method of the LED array which concerns on embodiment of this invention, and a printed circuit board. It is sectional drawing of FIG. FIG. 7 is a plan view of FIG. 6. It is sectional drawing which shows the comparative example of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image recording device 20 LED array head 24 2nd electrode pad 26 LED array 27 LED array 32 1st electrode pad 50 Relay member 52 Metal 54 Connection member 55 Wire (conductor)
60 Shading insulator

Claims (4)

A long printed circuit board;
An LED array disposed on the printed circuit board and provided with a plurality of LEDs;
A first electrode pad disposed on an upper surface of the LED array;
A second electrode pad disposed on the printed circuit board;
An insulative connection member disposed between the first electrode pad and the second electric pad and mounted on the printed circuit board;
One end portion embedded in the connection member and connected to the first electrode pad and the other end portion connected to the second electrode pad are formed to protrude from the connection member and have elasticity. Body,
With
When the connection member is attached to the printed circuit board, one end portion of the conductive body presses the first electrode pad to contact the first electrode pad, and the other end portion of the conductive body is the second electrode. An LED array head that presses an electrode pad and contacts the second electrode pad . The LED array head according to claim 1 , wherein a plurality of holes are formed in the printed circuit board, and a plurality of protrusions fitted into the holes are provided on a lower surface of the connection member . The LED array head according to claim 1, wherein the LED arrays are arranged in a staggered manner on the substrate, and the LEDs arranged in adjacent LED arrays are opposed to the first electrode pads . An image recording apparatus comprising the LED array head according to claim 1.

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