JP2011235513A - Exposure head, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of suppressing damage of a bonding wire caused by contact with a light shielding member, in an exposure head in which the light shielding member is disposed between a light emitting chip and an imaging optical system, while effectively exhibiting the crosstalk suppressing function of the light shielding member.SOLUTION: The exposure head includes the light shielding member having a first light shielding plate and a second light shielding plate, wherein the first light shielding plate includes a first aperture from a first light emitting element toward a first imaging optical system, and the second light shielding plate is opposed to the bonding wire across the first aperture. A distance t1 from a substrate to the second light shielding plate and a distance t2 from the substrate to the first light shielding plate satisfy a relational expression of t1>t2.

Description

  The present invention relates to an exposure technique using an exposure head that forms an image of light from a light emitting chip by an imaging optical system.

  Patent Document 1 proposes that an exposure head is configured using an LED chip formed with a plurality of LED (Light Emitting Diode) elements arranged in the main scanning direction. Specifically, in this exposure head, LED chips are arranged on a flat glass substrate, and a plurality of imaging optical systems (microlenses) are opposed to each LED chip (see Patent Document 1). FIG. 14 etc.). Each light emitting element (LED element) formed on the LED chip emits light toward an opposing imaging optical system, and thus the exposed surface is exposed by the light imaged by the imaging optical system. .

  Incidentally, in a configuration in which a plurality of imaging optical systems are arranged in the main scanning direction, the light from the light emitting element is incident on an imaging optical system adjacent to the imaging optical system other than the imaging optical system facing the light emitting element. Talk may occur. Therefore, in Patent Document 1, a light shielding member is provided between the LED chip and the imaging optical system in order to suppress the occurrence of crosstalk. In this light shielding member, a light guide hole that opens from the light emitting element toward the imaging optical system facing the light emitting element is provided for each imaging optical system. That is, the space from the light emitting element toward the imaging optical system is partitioned by the inner wall of the light guide hole for each imaging optical system, thereby suppressing the occurrence of crosstalk.

JP 2009-000827 A

  By the way, as described above, in an exposure head in which a light emitting chip such as an LED chip is disposed on a substrate, a bonding wire is connected to the light emitting chip, and a drive signal is given to the light emitting element through the bonding wire. Can do. However, the exposure head in which the light shielding member is disposed between the light emitting chip and the imaging optical system has the following problems. That is, in order to effectively exhibit the crosstalk suppressing function of the light shielding member, it is preferable to make the light shielding member and the light emitting chip as close as possible. However, when the light shielding member is brought close to the light emitting chip, the light shielding member and the bonding wire come into contact with each other, and the bonding wire may be damaged.

  The present invention has been made in view of the above problems, and in an exposure head in which a light shielding member is disposed between a light emitting chip and an imaging optical system, while effectively exerting a crosstalk suppressing function of the light shielding member, An object of the present invention is to provide a technique capable of suppressing damage to a bonding wire caused by contact with a light shielding member.

  In order to achieve the above object, an exposure head according to the present invention is a substrate that supports a light emitting chip in which a first light emitting element and a second light emitting element that emit light in response to a drive signal are arranged in a first direction. And an imaging optical system that forms an image of the light emitted from the first light emitting element, and a light emitting chip connected to the light emitting chip from a second direction orthogonal or substantially orthogonal to the first direction, and driven by the first light emitting element. A bonding wire for supplying a signal; a first light-shielding plate disposed between the substrate and the imaging optical system; and a second light-shielding plate disposed between the first light-shielding plate and the imaging optical system. A light shielding member having a light shielding plate, the first light shielding plate having a first opening from the first light emitting element toward the first imaging optical system, and the second light shielding plate having a first light shielding plate. A second light shielding plate having a second opening opposite to the first opening and having a smaller diameter in the second direction than the first opening. The distance t1 from the substrate to the second light shielding plate and the distance t2 from the substrate to the first light shielding plate satisfy the relational expression t1> t2, facing the bonding wire across the first opening. It is said.

  In order to achieve the above object, an image forming apparatus according to the present invention includes a latent image carrier, an exposure head that exposes the latent image carrier, and a development that develops a latent image formed on the latent image carrier by the exposure head. The exposure head includes a first light emitting element that emits light in response to a drive signal and a substrate that supports the light emitting chip in which the second light emitting element is disposed in the first direction; An imaging optical system that forms an image of light emitted from the element, and a bonding wire that is connected to the light-emitting chip from a second direction orthogonal or substantially orthogonal to the first direction and supplies a drive signal to the first light-emitting element And a light shielding member having a first light shielding plate disposed between the substrate and the imaging optical system, and a second light shielding plate disposed between the first light shielding plate and the optical member, And the first light shielding plate has a first opening from the first light emitting element toward the imaging optical system. The second light-shielding plate includes a second opening that has a smaller diameter in the second direction than the first opening and faces the first opening, and the second light-shielding plate has the first opening. The distance t1 from the substrate to the second light shielding plate and the distance t2 from the substrate to the first light shielding plate satisfy the relational expression t1> t2.

  In the invention configured as described above (exposure head, image forming apparatus), the light emitting chip in which the first light emitting element and the second light emitting element are arranged in the first direction is supported by the substrate, and the first A bonding wire for supplying a driving signal to the light emitting element is connected to the light emitting chip. Then, the light emitted from the first light emitting element upon receiving the drive signal is imaged by the first imaging optical system.

  A light shielding member is provided between the substrate that supports the light emitting chip and the imaging optical system. More specifically, the light shielding member includes a first light shielding plate disposed between the substrate and the imaging optical system, and a second light shielding plate disposed between the first light shielding plate and the optical member. Have Among these light shielding plates, the first light shielding plate has a first opening from the first light emitting element toward the imaging optical system. Further, the second light shielding plate includes a second opening that has a smaller diameter in the second direction than the first opening and faces the first opening. Therefore, the light from the first light emitting element enters the imaging optical system after passing through the first opening and the second opening in this order. Thus, according to the present invention, an aperture is provided for each imaging optical system, and the imaging optical system is configured so that light that has passed through the corresponding aperture is incident, thereby preventing the occurrence of the above-described crosstalk. Suppressed.

  Further, according to the present invention, the second light shielding plate faces the bonding wire across the first opening, and the distance t1 from the substrate to the second light shielding plate and from the substrate to the first light shielding plate. The distance t2 satisfies the relational expression t1> t2. Accordingly, the contact between the bonding wire and the light shielding member can be suppressed while bringing the first light shielding plate close to the light emitting chip, and the contact with the light shielding member is effectively performed while the crosstalk suppressing function of the light shielding member is effectively exhibited. It is possible to suppress the damage of the bonding wire due to the above.

  The light emitting chip may have a second light emitting element disposed at a position facing the first light shielding plate. At this time, a bonding wire for supplying a drive signal to the second light emitting element may be configured not to be connected to the light emitting chip.

  In addition, it is particularly suitable to apply the present invention to an exposure head in which a driver IC that generates a drive signal is disposed on a substrate and a bonding wire is connected to the driver IC. In other words, in such a configuration, since the bonding wire is bridged from the light emitting chip to the driver IC, the bonding wire passes through a position relatively away from the substrate, and contact between the bonding wire and the light shielding member occurs. Cheap. Therefore, by applying the present invention, it is preferable to suppress the bonding wire damage due to the contact with the light shielding member while effectively exhibiting the crosstalk suppressing function of the light shielding member.

  Further, the substrate is a glass epoxy substrate, and the glass epoxy substrate supplies a control signal for controlling light emission of the first light emitting element to the driver IC, and the driver IC is configured to generate a drive signal based on the control signal. May be. At this time, a wiring for connecting the glass epoxy substrate and the driver IC may be provided, and the control signal may be supplied to the driver IC through the wiring.

The top view which shows an example of the line head which can apply this invention. The fragmentary perspective view of the line head which can apply this invention. The partial step sectional view showing an example of the line head to which the present invention is applicable. The top view which looked at the 2nd light-shielding plate from the optical axis direction. The top view which looked at the 1st light-shielding plate from the optical axis direction. The fragmentary sectional view which shows the arrangement | positioning relationship between a head substrate surface and a light-shielding member. 1 is a diagram illustrating an example of an image forming apparatus to which a line head can be applied. The block diagram which shows the electric constitution of the apparatus of FIG. The figure which shows an example of the line head concerning another embodiment.

First Embodiment As will be described in detail later, the line head 29 of the present embodiment forms an image of light emitted from the light emitting element E by the imaging optical systems LS1 and LS2. A light shielding member 297 having openings AP1 and AP2 is disposed between the light emitting element E and the imaging optical systems LS1 and LS2. Light emitted from the light emitting element E passes through the openings AP1 and AP2. After passing, the light enters the imaging optical systems LS1 and LS2. Based on these, the details of the line head 29 of the present embodiment will be described.

  1, 2 and 3 are diagrams showing an example of a line head to which the present invention can be applied. In particular, FIG. 1 is a plan view of the positional relationship between the light emitting element E provided in the line head 29 and the apertures AP1 and AP2 as viewed from the optical axis direction Doa of the imaging optical system, and FIG. 3 is a partial perspective view, and FIG. 3 is a partial step sectional view taken along line AA (stepped two-dot chain line in FIG. 1) of the line head 29, and is viewed from the longitudinal direction LGD of the line head 29. It corresponds to the case. In FIG. 1, the openings AP1 and AP2 are indicated by alternate long and short dash lines. This is because the light emitting element E and the openings AP1 and AP2 are in different positions in the optical axis direction Doa. Although not shown in FIG. 1, one imaging optical system LS1, LS2 is opposed to each aperture AP2. The line head 29 includes two lens arrays LA1 and LA2, but the lens array LA2 is not shown in FIG.

  The line head 29 has an overall configuration that is long in the longitudinal direction LGD and short in the width direction LTD. 1 to 3 and the following drawings show the longitudinal direction LGD and the width direction LTD of the line head 29 as necessary. Further, the optical axis direction Doa of the imaging optical system formed by the lens is also appropriately shown in FIGS. 1 to 3 and the following drawings. Note that these directions LGD, LTD, and Doa are orthogonal or substantially orthogonal to each other. Further, in the following, the arrow side in the optical axis direction Doa is expressed as “front” or “upper” and the opposite side to the arrow in the optical axis direction Doa is expressed as “back”, “lower”, or “bottom” as necessary. To do.

  As will be described later, when the line head 29 is applied to the image forming apparatus, the line head 29 is exposed to an exposed surface ES (photosensitive drum) that moves in the sub-scanning direction SD that is orthogonal or substantially orthogonal to the main scanning direction MD. The surface) is exposed. In addition, the main scanning direction MD of the exposed surface ES is parallel or substantially parallel to the longitudinal direction LGD of the line head 29, and the sub-scanning direction SD of the exposed surface ES is parallel or substantially parallel to the width direction LTD of the line head 29. is there. Therefore, as necessary, the main scanning direction MD and the sub-scanning direction SD are also illustrated together with the longitudinal direction LGD and the width direction LTD.

  The head substrate 293 provided in the line head 29 is a glass epoxy substrate on which a predetermined wiring pattern (wiring layer) is formed, and has a flat plate shape that is long in the longitudinal direction LGD. On the surface 293-h of the head substrate 293, a plurality of LED chips CPa and CPb are arranged in a staggered manner in two rows in the longitudinal direction LGD (FIGS. 1 and 2) and bonded to the surface 293-h of the head substrate 293. (FIGS. 2 and 3). In other words, a plurality of LED chips CPa arranged linearly in the longitudinal direction LGD and a plurality of LED chips CPb arranged linearly in the longitudinal direction LGD are arranged at different positions in the width direction LTD. Then, it is bonded to the surface 293-h of the head substrate 293.

  Each of the LED chips CPa and CPb has a substantially rectangular shape elongated in the longitudinal direction LGD in plan view from the optical axis direction Doa, and a semiconductor wafer on which the LED element as the light emitting element E is formed is diced. Things (die). Specifically, in each of the LED chips CPa and CPb, a plurality of light emitting elements E are linearly arranged at the light emitting element pitch Pe in the longitudinal direction LGD. These light emitting elements E emit light beams having the same emission spectrum upon receiving a drive signal (drive voltage). As described above, by using the LED having a relatively long life as the light emitting element E, it is possible to realize a stable exposure operation over a long period.

  Thus, on the head substrate surface 293-h, a plurality of light emitting elements E arranged linearly in the longitudinal direction LGD are arranged in two rows in the width direction LTD. The light shielding member 297 is opposed to the head substrate surface 293-h with a gap from the optical axis direction Doa. The light shielding member 297 has a structure in which a first light shielding plate BR1 having a thickness of 2.31 [mm] and a second light shielding plate BR2 having a thickness of 0.1 [mm] are stacked in the optical axis direction Doa. The supporting member is supported with respect to the head substrate 293.

  FIG. 4 is a plan view of the second light shielding plate viewed from the optical axis direction, and FIG. 5 is a plan view of the first light shielding plate viewed from the optical axis direction. 4 and 5 are added to FIGS. 1 to 3 and the details of the light shielding member 297 will be described. The first light shielding plate BR1 includes a frame FR extending in the longitudinal direction LGD and a partition wall AW protruding from the frame FR in the width direction LGD. Specifically, on both sides of the width direction LTD of the frame FR having a width of 2.09 [mm], a plurality of partition walls AW are arranged in the longitudinal direction LGD with a distance Pg (FIG. 1) therebetween. Further, the first light shielding plate BR1 includes a side wall SW having a width of 0.4 [mm] that closes a space between the partition walls AW from the outside in the width direction LTD. Thus, in the first light shielding plate BR1, the first opening AP1 surrounded by the frame FR, the two partition walls AW, AW, and the side wall SW is formed, and the plurality of first openings AP1 are staggered in the longitudinal direction LGD. Line up with. Each of the first openings AP1 has a rectangular shape with a length of 3.51 [mm] having a long length in the width direction LTD, and is provided with rounds at each corner. The first light-shielding plate BR1 having the above configuration has a width of 10 [mm].

  The second light shielding plate BR2 has a configuration in which a plurality of second openings AP2 are arranged in a zigzag pattern in the longitudinal direction LGD. This second opening AP2 is formed so as to face (oppose) each first opening AP1 of the first light shielding plate BR1, and the LED chip on the head substrate surface 293-h via the first opening AP. Open to CPa and CPb. The second opening AP2 has a circular shape having a diameter of 1.25 [mm]. The distance in the width direction LTD between the rows of the plurality of second openings AP2 arranged in two rows in a staggered manner is 3.54 [mm], and the distance from each row in the width direction LTD to the end of the second light shielding plate BR2. Is 3.18 [mm]. The second light shielding plate BR2 having such a configuration has a width of 10 [mm].

  The first and second light shielding plates BR1 and BR2 are laminated to form a light shielding member 297. At this time, the second opening AP2 of the second light shielding plate BR2 has a smaller diameter in both the longitudinal direction LGD and the width direction LTD than the first opening AP1 of the first light shielding plate BR1. Therefore, the second opening AP2 is completely contained in the first opening AP1 in a plan view from the optical axis direction Doa. Thus, in the light shielding member 297, first and second apertures AP1 and AP2 are formed from the light emitting element E toward the imaging optical systems LS1 and LS2, which will be described later, and the light from the light emitting element E is the first and second apertures. After passing through AP 1 and AP 2 in this order, they enter the imaging optical systems LS 1 and LS 2.

  The above is the detailed configuration of the light shielding member 297. The light shielding member 297 is opposed to a plurality of imaging optical systems LS1 and LS2 arranged in a zigzag pattern in the longitudinal direction LGD. This imaging optical system is composed of two lenses LS1 and LS2 formed so as to face each second aperture AP2 of the second light shielding plate BR2, and the second aperture AP1 and the first aperture AP2 are formed. Via the LED chips CPa and CPb. Subsequently, the lenses LS1 and LS2 constituting the imaging optical system will be described in detail.

  The line head 29 is provided with a lens array LA1 in which a plurality of lenses LS1 are arranged in a staggered manner in two rows and a lens array LA2 in which a plurality of lenses LS2 are arranged in a staggered manner in two rows. That is, in the lens array LA1 (LA2), the lenses LS1 (LS2) are arranged for each distance Pg (= 2 × Dg) in the longitudinal direction LGD, and a plurality of lenses LS1 (LS2) linearly arranged in the longitudinal direction LGD are used. One lens row is formed, and further two lens rows are arranged with a distance Dt in the width direction LTD and are shifted from each other by a distance Dg (= Pg / 2) in the longitudinal direction LGD.

  Here, the inter-lens distance Pg in the longitudinal direction LGD is the distance in the longitudinal direction LGD between the optical axes of two lenses adjacent in the longitudinal direction LGD in the lens row, and the distance Dg is a half of the distance Pg. Is the length of In addition, the distance Dt between the lens rows in the width direction LTD is a virtual straight line extending in the longitudinal direction LGD through the optical axes of the plurality of lenses constituting one lens row and the light of the plurality of lenses constituting the other lens rows. A distance in the width direction LTD between a virtual straight line extending in the longitudinal direction LGD through the axis.

  The optical axis is defined as follows. In many cases, the imaging optical system has a plane symmetry (mirror symmetry) with respect to a symmetry plane perpendicular to the main scanning direction MD (longitudinal direction LGD) and a symmetry plane perpendicular to the sub-scanning direction SD (width direction LTD). Is plane symmetric (mirror symmetry). As described above, the imaging optical system has the first symmetry plane perpendicular to the main scanning direction MD and the second symmetry plane perpendicular to the sub-scanning direction SD perpendicular to the main scanning direction MD. And the intersection line of the second symmetry plane is determined. When the imaging optical system is rotationally symmetric, the intersection line of the first symmetric surface and the second symmetric surface coincides with the optical axis. If the imaging optical system is not rotationally symmetric, strictly speaking, the optical axis of the imaging optical system may not be defined. In such a case, the above-described intersection line may be handled as the optical axis.

  Incidentally, the lens array LA1 (LA2) can be configured by forming a resin lens LS1 (LS2) on a light-transmitting glass flat plate. In addition, in this embodiment, in view of the difficulty in producing a lens array that is long in the longitudinal direction LGD with an integral configuration, a resin lens LS1 (LS2) is provided on a relatively short glass plate. A short lens array LA1 (LA2) is formed by forming two rows in a staggered pattern, and a plurality of short lens arrays LA1 (LA2) are arranged in the longitudinal direction LGD to form a long lens array in the longitudinal direction LGD. is doing.

  More specifically, a plurality of spacers SP1 are linearly arranged in the longitudinal direction LGD at both ends in the width direction LTD of the head substrate surface 293-h. A plurality of lens arrays LA1 are arranged in the longitudinal direction LGD with the spacers SP1 and SP1 extending in the width direction LTD to form one long lens array. In addition, a plurality of spacers SP2 are linearly arranged in the longitudinal direction LGD at both ends in the width direction LTD on the surface of the long lens array composed of the lens array LA1. A plurality of lens arrays LA2 are arranged in the longitudinal direction LGD in a state where the spacers SP2 and SP2 are installed in the width direction LTD to form one long lens array. Further, a plate-like support glass SS is bonded to the surface of the long lens array composed of the lens array LA2, and the plurality of lens arrays LA2 are not only supported by each spacer SP2, but also by the support glass SS from the opposite side of the spacer SP2. Is also supported. The support glass SS also has a function of covering the lens array LA2 so that each lens array LA2 is not exposed to the outside.

  Thus, an imaging optical system is configured by the two lenses LS1 and LS2 of the lens arrays LA1 and LA2. At this time, the lens arrays LA1 and LA2 are arranged so that the optical axes of the imaging optical systems LS1 and LS2 pass through the center of the second aperture AP2 of the light shielding member 297 (geometric center of gravity in plan view from the optical axis direction Doa). It is positioned. Thus, the imaging optical systems LS1, LS2 face the light emitting element E through the first and second openings AP1, AP2 of the light shielding member 297. Therefore, of the light emitted from the light emitting element E, the light that has passed through the first and second apertures AP1 and AP2 is imaged by the imaging optical systems LS1 and LS2. Incidentally, the imaging optical systems LS1 and LS2 are reduction inversion optical systems that form an inverted image (the imaging magnification is negative) with an absolute value of the imaging magnification being less than 1.

  By the way, in order to cause each light emitting element E to emit light, it is necessary to give a drive signal to the light emitting element E. Therefore, this embodiment has the following configuration. That is, as shown in FIG. 3, driver ICs 295 are arranged on both sides of the width direction LTD of the LED chips CPa and CPb on the surface of the head substrate 293-h. The input terminal of the driver IC 295 is connected to the wiring pattern of the head substrate 293 by the wiring WR. On the other hand, the output terminal of the driver IC 295 is connected to the LED chips CPa and CPb by the bonding wire BW. The driver IC 295 generates a drive signal based on the video data VD (control signal) received from the head substrate 293 via the wiring WR, and sends the drive signal to the LED chips CPa and CPb via the bonding wire BW. The light is supplied to the light emitting element E.

  Further, as shown in FIG. 1, the bonding wires BW are not connected to all the light emitting elements E, but are connected only to some selected light emitting elements E. Specifically, the bonding wires BW are connected to the ten light emitting elements E facing the second opening AP2 from one side in the width direction LTD. Therefore, on the head substrate surface 293-h, the light emitting element groups EG composed of the ten light emitting elements E to which wire bonding is performed are arranged in a zigzag pattern in the longitudinal direction LGD. Then, only the light emitting element E to which wire bonding is performed receives the drive signal and emits light, and the other light emitting elements E do not emit light.

  Thus, on the head substrate surface 293-h, in addition to the LED chips CPa and CPb, bonding wires BW connected to these are arranged. In this embodiment, the head substrate surface 293-h and the light shielding member are arranged so as to satisfy a predetermined arrangement relationship. FIG. 6 is a partial cross-sectional view showing the positional relationship between the head substrate surface and the light shielding member. Next, the arrangement relationship will be described with reference to FIGS. 3 and 6.

  As shown in FIG. 6, in the line head 29, a partition wall AW is provided so as to partition the space SC from the light emitting element group EG to the lens LS1 facing it in the longitudinal direction LGD, and the first opening AP1 is formed. Is formed. In other words, the spaces SC and SC adjacent to each other in the longitudinal direction LGD are partitioned by the partition wall AW to form the first opening AP1. The bonding wires BW connected to each light emitting element group EG are curved in a mountain shape, and a part of the top of the bonding wire BW enters the first opening AP1 (FIGS. 3 and 6). In addition, above the opening AP1, a facing surface FS corresponding to the bottom surface of the second light shielding plate BR2 is opposed to the bonding wire BW (the top) thereof with the first opening AP1 interposed therebetween. Each light emitting element E of the light emitting element group EG emits light upon receiving a drive signal from the bonding wire BW, and the light passes through the first opening AP1 partitioned by the partition wall AW. It is squeezed by the second aperture AP2 and enters the lens LS1.

  As shown in FIG. 1, a plurality of light emitting elements E are linearly arranged on the LED chips CPa and CPb. For this reason, the light emitting element E is also disposed in a range of the LED chips CPa and CPb facing the partition wall AW. However, the bonding wires BW for giving drive signals to these light emitting elements E are not connected to the LED chips CPa and CPb.

  Then, a distance t1 from the head substrate 293 (surface 293-h) to the facing surface FS in the optical axis direction Doa and an optical axis direction Doa from the head substrate 293 (surface 293-h) to the partition wall AW. The distance t2 satisfies the following relational expression, t1> t2. More specific numerical values are as follows. As shown in FIG. 3, since the LED chips CPa and CPb have a height of 0.39 [mm] and the distance from the LED chips CPa and CPb to the partition wall AW is 0.34 [mm], the distance t2 = 0.39 + 0.34 = 0.73 [mm]. On the other hand, since the distance from the bottom surface of the partition wall AW to the opposing surface FS is 2.31 [mm], the distance t1 = 0.73 + 2.31 = 3.04 [mm] (> 0.73 [mm] = t2 ).

  As described above, in this embodiment, the light shielding member 297 is provided between the head substrate 293 that supports the LED chips CPa and CPb and the imaging optical systems LS1 and LS2. More specifically, the light shielding member 297 includes a first light shielding plate BR1 disposed between the head substrate 293 and the imaging optical systems LS1 and LS2, and a space between the first light shielding plate BR1 and the imaging optical systems LS1 and LS2. And a second light shielding plate BR2. Of these light shielding plates BR1, BR2, the first light shielding plate BR1 is provided with a first opening AP1 from the light emitting element E toward the imaging optical system LS1. The second light shielding plate BR2 is provided with a second opening AP2 having a smaller diameter in the width direction LTD than the first opening AP1 and facing the first opening AP1. Therefore, the light from the light emitting element E enters the imaging optical systems LS1 and LS2 after passing through the first aperture AP1 and the second aperture AP2 in this order. As described above, in this embodiment, the apertures AP1 and AP2 are provided for each of the imaging optical systems LS1 and LS2, and the light passing through the corresponding apertures AP1 and AP2 is incident on the imaging optical systems LS1 and LS2. With this configuration, the occurrence of the above-described crosstalk is suppressed.

  Further, in the present invention, the second light shielding plate BR2 faces the bonding wire BW across the first opening AP1, and further, the distance t1 from the head substrate 293 to the second light shielding plate BR2 and the head 293 substrate to the first The distance t2 to one light shielding plate BR1 satisfies the relational expression t1> t2. Therefore, the contact between the bonding wire BW and the light shielding member 297 can be suppressed while bringing the first light shielding plate BR1 close to the LED chips CPa and CPb, and the crosstalk suppressing function of the light shielding member 297 is effectively exhibited. Further, damage to the bonding wire BW due to contact with the light shielding member 297 can be suppressed.

  As described above, it is particularly preferable to apply the present invention to the line head 29 in which the driver IC 295 that generates the drive signal is disposed on the head substrate 293 and the bonding wire BW is connected to the driver IC 295. Become. That is, in such a configuration, since the bonding wire BW is bridged from the LED chips CPa and CPb to the driver IC 295, the bonding wire BW passes through a position relatively away from the head substrate 293, and the bonding wire BW And the light shielding member 297 are likely to contact each other. Therefore, by applying the present invention, it is preferable to suppress damage to the bonding wire BW due to contact with the light shielding member 297 while effectively exhibiting the crosstalk suppressing function of the light shielding member 297.

Second Embodiment FIG. 7 is a diagram showing an example of an image forming apparatus to which the above-described line head can be applied. FIG. 8 is a block diagram showing an electrical configuration of the apparatus of FIG. In the third embodiment, an example of an image forming apparatus including the above-described line head 29 will be described with reference to these drawings. The image forming apparatus 1 includes four image forming stations 2Y (for yellow), 2M (for magenta), 2C (for cyan), and 2K (for black) that form images of different colors. The image forming apparatus 1 includes a color mode in which four color toners of yellow (Y), magenta (M), cyan (C), and black (K) are overlapped to form a color image, and black (K). A monochrome mode in which a monochrome image is formed using only toner can be selectively executed.

  In this image forming apparatus, when an image forming command is given from an external device such as a host computer to a main controller MC having a CPU, a memory, etc., the main controller MC provides a control signal to the engine controller EC and also supports the image forming command. The video data VD to be transmitted is supplied to the head controller HC. At this time, every time the main controller MC receives the horizontal request signal HREQ from the head controller HC, the main controller MC supplies video data VD for one line to the head controller HC in the main scanning direction MD. The head controller HC also sets the line heads 29 of the image forming stations 2Y, 2M, 2C, and 2K for each color based on the video data VD from the main controller MC, the vertical synchronization signal Vsync from the engine controller EC, and the parameter values. Control. Accordingly, the engine unit ENG executes a predetermined image forming operation, and forms an image corresponding to the image forming command on a sheet-like recording medium RM such as copy paper, transfer paper, paper, and an OHP transparent sheet.

  Each of the image forming stations 2Y, 2M, 2C, and 2K has the same structure and function except for the toner color. Therefore, in FIG. 7, in order to make the drawing easier to see, reference numerals are given only to the components constituting the image forming station 2 </ b> C, and description of reference numerals to be attached to the other image forming stations 2 </ b> Y, 2 </ b> M, and 2 </ b> K is omitted. In the following description, the structure and operation of the image forming station 2C will be described with reference to the reference numerals attached to FIG. 7, but the structure and operation of the other image forming stations 2Y, 2M, and 2K also differ in toner color. It is the same except that.

  The image forming station 2C is provided with a photosensitive drum 21 on which a cyan toner image is formed. The photosensitive drum 21 is arranged so that the rotation axis thereof is parallel or substantially parallel to the main scanning direction MD (direction perpendicular to the paper surface of FIG. 7), and a predetermined speed in the direction of arrow D21 in FIG. Is driven to rotate. As a result, the surface of the photosensitive drum 21 moves in the sub-scanning direction SD that is orthogonal or substantially orthogonal to the main scanning direction MD.

  Around the photosensitive drum 21, a charger 22 that is a corona charger that charges the surface of the photosensitive drum 21 to a predetermined potential, and an electrostatic latent image is formed by exposing the surface of the photosensitive drum 21 according to an image signal. A line head 29 for forming the electrostatic latent image, a developing device 24 for visualizing the electrostatic latent image as a toner image, a first squeeze unit 25, a second squeeze unit 26, and the surface of the photosensitive drum 21 after transfer. The cleaning units for cleaning are arranged along the rotation direction D21 (clockwise in FIG. 7) of the photosensitive drum 21 in this order.

  In this embodiment, the charger 22 includes two corona chargers 221 and 222, and the corona charger 221 is disposed upstream of the corona charger 222 in the rotation direction D 21 of the photosensitive drum 21. In addition, the two corona chargers 221 and 222 are configured to be charged in two stages. Each of the corona chargers 221 and 222 has the same configuration and does not contact the surface of the photosensitive drum 21 and is a scorotron charger.

  The line head 29 forms an electrostatic latent image on the surface of the photosensitive drum 21 charged by the corona chargers 221 and 222 based on the video data VD. That is, when the head controller HC transmits the video data VD to the line head 29, a drive signal corresponding to the video data VD is supplied to each light emitting element E via the bonding wire BW, and each light emitting element E emits light. As a result, the surface of the photosensitive drum 21 is exposed to form an electrostatic latent image corresponding to the image signal. The specific configuration of the line head 29 is as already described.

  Toner is applied from the developing device 24 to the electrostatic latent image formed in this manner, and the electrostatic latent image is developed with the toner. The developing device 24 of the image forming apparatus 1 has a developing roller 241. The developing roller 241 is a cylindrical member, and is provided with an elastic layer such as polyurethane rubber, silicon rubber, NBR, or PFA tube on the outer periphery of an inner core made of metal such as iron. The developing roller 241 is connected to a developing motor and is rotated counterclockwise on the paper surface of FIG. 7 to rotate with respect to the photosensitive drum 21. Further, the developing roller 241 is electrically connected to a developing bias generator (constant voltage power source) (not shown) so that the developing bias is applied at an appropriate timing.

  An anilox roller is provided to supply the liquid developer to the developing roller 241, and the liquid developer is supplied from the developer storage unit to the developing roller 241 via the anilox roller. As described above, the anilox roller has a function of supplying the liquid developer to the developing roller 241. This anilox roller is a roller in which a concave pattern is formed by spiral grooves or the like engraved finely and uniformly on the surface so as to easily carry the liquid developer. Similar to the developing roller 241, a metal cored bar wrapped with a rubber layer such as urethane or NBR, or a PFA tube is used. The anilox roller is connected to a developing motor and rotates.

  The liquid developer stored in the developer storage section is volatile at room temperature at a low concentration (1-2 wt%) and low viscosity using Isopar (trademark: Exon) as a liquid carrier, which is generally used conventionally. Not a volatile liquid developer having a solid particle having a mean particle size of 1 μm, in which a colorant such as a pigment is dispersed in a non-volatile resin having a high concentration and high viscosity at room temperature, an organic solvent, silicon oil, mineral oil or A liquid developer having a high viscosity (about 30 to 10,000 mPa · s) added to a liquid solvent such as edible oil together with a dispersant and having a toner solid content concentration of about 20% is used.

  As described above, the developing roller 241 supplied with the liquid developer rotates simultaneously with the anilox roller and rotates so as to move in the same direction as the surface of the photosensitive drum 21 and is carried on the surface of the developing roller 241. The liquid developer thus conveyed is conveyed to the development position. In order to form a toner image, the rotation direction of the developing roller 241 needs to be rotated so that the surface thereof moves in the same direction as the surface of the photosensitive drum 21, but is opposite to the anilox roller. It may be configured to move in either the direction or the same direction.

  In the developing device 24, a toner compression corona generator 242 is disposed opposite to the developing roller 241 immediately before the developing position in the rotation direction of the developing roller 241. The toner compression corona generator 242 is an electric field applying means for increasing the charging bias on the surface of the developing roller 241 and is electrically connected to a toner charge generator (not shown) configured with a constant current power source. When a toner charge bias is applied to the toner compression corona generator 242, an electric field is applied to the liquid developer toner conveyed by the developing roller 241 at a position close to the toner compression corona generator 242. Then, charging and compression are performed. For the toner charging and compression, a compaction roller that is charged by contact may be used instead of corona discharge by applying electrolysis.

  Further, the developing device 24 configured as described above can reciprocate between a developing position for developing the latent image on the photosensitive drum 21 and a retracted position away from the photosensitive drum 21. Therefore, when the developing device 24 is moved to the retracted position and positioned, supply of new liquid developer to the photosensitive drum 21 is stopped in the cyan image forming station 2C.

  A first squeeze portion 25 is disposed on the downstream side of the developing position in the rotation direction D <b> 21 of the photosensitive drum 21, and a second squeeze portion 26 is disposed on the downstream side of the first squeeze portion 25. These squeeze portions 25 and 26 are provided with squeeze rollers 251 and 261, respectively. Then, the squeeze roller 251 rotates in response to the rotational driving force from the main motor while contacting the surface of the photosensitive drum 21 at the first squeeze position to remove excess developer in the toner image. Further, in the rotation direction D21 of the photosensitive drum 21, the squeeze roller 261 rotates in response to the rotational driving force from the main motor while contacting the surface of the photosensitive drum 21 at the second squeeze position downstream of the first squeeze position. Then, excess liquid carrier and fog toner in the toner image are removed. In this embodiment, a squeeze bias generator (constant voltage power supply) (not shown) is electrically connected to the squeeze rollers 251 and 261 in order to increase the squeeze efficiency, and the squeeze bias is applied at an appropriate timing. It is configured to be. In this embodiment, the two squeeze portions 25 and 26 are provided. However, the number and arrangement of the squeeze portions are not limited to this, and for example, one squeeze portion may be disposed.

  The toner image that has passed through these squeeze positions is primarily transferred to the intermediate transfer member 31 of the transfer unit 3. The intermediate transfer member 31 is an endless belt as an image carrier that can temporarily carry a toner image on its surface, more specifically, on its outer peripheral surface. The intermediate transfer member 31 includes a plurality of rollers 32, 33, 34, 35, and 36. It is being handed over. Among these, the roller 32 is connected to a main motor, and functions as a belt driving roller that drives the intermediate transfer member 31 in the direction of the arrow D31 in FIG. In the present embodiment, an elastic layer is provided on the surface of the intermediate transfer body 31 in order to improve the adhesion with the recording paper RM and improve the transferability of the toner image onto the recording paper RM. A toner image is supported.

  Here, of the rollers 32 to 36 over which the intermediate transfer body 31 is stretched, only the belt driving roller 32 is driven by the main motor, and the other rollers 33 to 36 are driven without a driving source. It is a roller. Further, the belt driving roller 32 winds the intermediate transfer member 31 on the downstream side of the primary transfer position TR1 and the upstream side of the secondary transfer position TR2 described later in the belt moving direction D31.

  The transfer unit 3 includes a primary transfer backup roller 37, and the primary transfer backup roller 37 is disposed to face the photosensitive drum 21 with the intermediate transfer member 31 interposed therebetween. At the primary transfer position TR1 where the photosensitive drum 21 and the intermediate transfer member 31 are in contact, the outer peripheral surface of the photosensitive drum 21 is in contact with the intermediate transfer member 31 to form the primary transfer nip portion NP1c. Then, the toner image on the photosensitive drum 21 is transferred to the outer peripheral surface of the intermediate transfer member 31 (the lower surface at the primary transfer position TR1). Thus, the cyan toner image formed by the image forming station 2C is transferred to the intermediate transfer member 31. Similarly, the toner images are transferred at the other image forming stations 2Y, 2M, and 2K, so that the toner images of the respective colors are sequentially superimposed on the intermediate transfer member 31 to form a full-color toner image. On the other hand, when a monochrome toner image is formed, the toner image is transferred to the intermediate transfer member 31 only in the image forming station 2K corresponding to the black color.

  The toner image transferred to the intermediate transfer member 31 in this way is conveyed to the secondary transfer position TR2 via the winding position around the belt driving roller 32. At the secondary transfer position TR2, the secondary transfer roller 42 of the secondary transfer unit 4 is disposed opposite to the roller 34 around which the intermediate transfer body 31 is wound, with the intermediate transfer body 31 interposed therebetween. The surface 31 and the surface of the transfer roller 42 are in contact with each other to form the secondary transfer nip portion NP2. That is, the roller 34 functions as a secondary transfer backup roller. The rotation shaft of the backup roller 34 is supported elastically by a pressing portion 345 which is an elastic member such as a spring and can be moved toward and away from the intermediate transfer member 31.

  At the secondary transfer position TR2, the single-color or multi-color toner images formed on the intermediate transfer member 31 are transferred from the pair of gate rollers 51 to the recording medium RM conveyed along the conveyance path PT. Further, the recording medium RM on which the toner image is secondarily transferred is sent from the secondary transfer roller 42 to the fixing unit 7 provided on the transport path PT. In the fixing unit 7, heat or pressure is applied to the toner image transferred to the recording medium RM to fix the toner image on the recording medium RM. In this way, a desired image can be formed on the recording medium RM.

Others As described above, in the above embodiment, the line head 29 corresponds to the “exposure head” of the present invention, the photosensitive drum 21 corresponds to the “latent image carrier” of the present invention, and the developing device 24 corresponds to the present invention. Corresponds to the “developing part”. The longitudinal direction LGD or the main scanning direction MD corresponds to the “first direction” of the present invention, and the width direction LTD or the sub-scanning direction SD corresponds to the “second direction” of the present invention. The LED chips CPa and CPb correspond to the “light emitting chip” of the present invention, the imaging optical systems LS1 and LS2 correspond to the “imaging optical system” of the present invention, and the first aperture AP1 corresponds to the “first” The second opening AP2 corresponds to the “second opening” of the present invention.

  The present invention is not limited to the above-described embodiment, and various modifications can be made to the above-described one without departing from the spirit of the present invention. For example, the configuration of the light shielding member 297 is not limited to the above-described one, and specifically, a configuration in which a plurality of light shielding plates described in Japanese Patent Application Laid-Open No. 2008-30785 are arranged in the optical axis direction Doa may be adopted. good.

  Moreover, in the said embodiment, the shape of 1st opening AP1 and 2nd opening AP2 of a light-shielding member can also be changed as needed. That is, if the second opening AP2 is specifically described by taking an example, the second opening AP2 can be changed to an elliptical shape as necessary as shown below.

  FIG. 9 is a diagram showing an example of a line head according to another embodiment. In particular, the positional relationship between the light emitting element E and the apertures AP1 and AP2 included in the line head 29 is determined in the optical axis direction Doa of the imaging optical system. It is the top view seen from. As shown in the figure, this second embodiment is different from the above-described embodiment in that the second opening AP2 has an elliptical shape with the width direction LTD as the long direction. However, in other respects, the embodiment of FIG. 9 has the same configuration as the above-described embodiment, and can achieve the same effects.

  In addition to the LED elements described above, a light source such as organic EL (Electro-Luminescence) can be used as the light emitting element E.

  In the above embodiment, the plurality of lenses LS1 (LS2) are arranged in a zigzag pattern in the longitudinal direction LGD, but the lens arrangement is not limited to this. Therefore, for example, as described in Japanese Patent Application No. 2006-213299, lenses can be arranged in a three-row zigzag pattern.

  In the above embodiment, the light emitting elements E are desired to be arranged in a straight line in the LED chips CPa and CPb, but these may be arranged in a staggered pattern.

  In the above embodiment, a voltage signal is applied to the light emitting element E as a drive signal. However, a current signal may be applied to the light emitting element E to cause the light emitting element E to emit light.

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 21 ... Photosensitive drum, 29 ... Line head, 293 ... Head substrate, 293-h ... Head substrate surface, 295 ... Driver IC, CPa, CPb ... LED chip, BW ... Bonding wire, 297 ... Light shielding Member, AW ... partition wall, FS ... opposing surface, LA1 ... lens array, LA2 ... lens array, LS1 ... lens, LS2 ... lens, LGD ... longitudinal direction, LTD ... width direction, Doa ... optical axis direction, OA ... optical axis

Claims (6)

A substrate that supports a light emitting chip in which a first light emitting element and a second light emitting element that emit light in response to a drive signal are arranged in a first direction;
An imaging optical system that forms an image of the light emitted by the first light emitting element;
A bonding wire connected to the light emitting chip from a second direction orthogonal or substantially orthogonal to the first direction and supplying the drive signal to the first light emitting element;
A first light shielding plate disposed between the substrate and the imaging optical system; and a second light shielding plate disposed between the first light shielding plate and the imaging optical system. A light shielding member;
With
The first light shielding plate includes a first opening from the first light emitting element toward the first imaging optical system,
The second light shielding plate includes a second opening having a smaller diameter in the second direction than the first opening and facing the first opening,
The second light shielding plate faces the bonding wire across the first opening,
An exposure head, wherein a distance t1 from the substrate to the second light shielding plate and a distance t2 from the substrate to the first light shielding plate satisfy a relational expression t1> t2.   The exposure head according to claim 1, wherein a bonding wire that supplies the driving signal to the second light emitting element is not connected to the light emitting chip.   The exposure head according to claim 1, wherein a driver IC that generates the driving signal is disposed on the substrate, and the bonding wire is connected to the driver IC.   The substrate is a glass epoxy substrate, and the glass epoxy substrate supplies a control signal for controlling light emission of the first light emitting element to the driver IC, and the driver IC generates the drive signal based on the control signal. The exposure head according to claim 3.   The exposure head according to claim 4, further comprising: a wiring that connects the glass epoxy substrate and the driver IC, and the control signal is supplied to the driver IC through the wiring. A latent image carrier;
An exposure head for exposing the latent image carrier;
A developing unit for developing the latent image formed on the latent image carrier by the exposure head;
With
The exposure head is
A substrate that supports a light emitting chip in which a first light emitting element and a second light emitting element that emit light in response to a drive signal are arranged in a first direction;
An imaging optical system that forms an image of the light emitted by the first light emitting element;
A bonding wire connected to the light emitting chip from a second direction orthogonal or substantially orthogonal to the first direction and supplying the drive signal to the first light emitting element;
A first light shielding plate disposed between the substrate and the imaging optical system; and a second light shielding plate disposed between the first light shielding plate and the imaging optical system. A light shielding member;
With
The first light shielding plate includes a first opening from the first light emitting element toward the first imaging optical system,
The second light shielding plate includes a second opening having a smaller diameter in the second direction than the first opening and facing the first opening,
The second light shielding plate faces the bonding wire across the first opening,
An image forming apparatus, wherein a distance t1 from the substrate to the second light shielding plate and a distance t2 from the substrate to the first light shielding plate satisfy a relational expression t1> t2.

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