JP2011161631A - Exposure head and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for suppressing the strength of ghost light. <P>SOLUTION: The exposure head includes a reflected light attenuating member disposed between the first and second light emitting chips of a substrate. The optical length of a first imaging optical system has the following relations: h1<h4<h3 and h2<h4<h3, wherein h1 is the length of the first light emitting chip in the direction of an optical axis, h2 is the length of the second light emitting chip in the direction of the optical axis, h3 is a distance between the substrate and a light shielding portion in the direction of the optical axis, and h4 is the length of the reflected light attenuating member in the direction of an optical axis. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exposure technique for imaging light from a plurality of light emitting chips arranged on a substrate by an imaging optical system.

  Patent Document 1 proposes an exposure head that includes a lens array in which a plurality of lenses are arranged in a staggered manner, and a substrate on which a light source is disposed so as to face each lens. That is, in the exposure technique using this exposure head, the imaging optical system composed of lenses forms an image of light from the light source, so that a light spot is irradiated onto the exposed surface, and the exposed surface becomes Exposed.

  Patent Document 2 proposes that an exposure head is configured using a chip-like LED array (light emitting chip) in which a light emitting section such as an LED (Light Emitting Diode) is formed. Therefore, it is conceivable to use the light emitting part of the light emitting chip as the light source of the exposure head of Patent Document 1. Specifically, the exposure head is configured such that a plurality of light emitting chips are arranged on a substrate, and light from the light emitting portion of each light emitting chip is imaged by an imaging optical system.

  By the way, in the configuration in which the light emitting portion is arranged facing each of the plurality of imaging optical systems, ghost light may be generated as follows. That is, each light emitting unit emits most of the light toward the opposing imaging optical system. However, a part of the light emitted from the light emitting unit becomes stray light without going to the imaging optical system facing the light emitting unit. When stray light from the light emitting part is incident on an imaging optical system that does not face the light emitting part and is imaged, ghost light may be generated on the exposed surface.

  In order to cope with such a problem, the exposure head described in Patent Document 1 includes a light shielding member. The light shielding member is disposed between the substrate (where the light source is disposed) and the lens array, and has a light guide hole penetrating from the light emitting portion toward the lens facing the light emitting portion. For this reason, stray light that does not travel from the light emitting portion to the light guide hole is reflected by the bottom surface (the surface facing the substrate) of the light shielding member, and thus does not directly enter the imaging optical system. Thus, in the exposure head of Patent Document 1, the generation of ghost light is suppressed.

JP 2008-093882 A Japanese Patent Laid-Open No. 06-278314

  By the way, a space can be provided between the substrate (with the light source disposed) and the above-described light shielding member. In particular, when the light emitting chip is disposed on the substrate to constitute an exposure head, In order to avoid interference with the light shielding member, it is desirable to provide a considerable distance (at least larger than the thickness of the light emitting chip) between the substrate and the light shielding member. However, when a space is provided between the light shielding member and the substrate in this way, a part of the stray light reflected on the bottom surface (surface on the substrate side) of the light shielding member is re-directed on the substrate after changing the direction to the substrate side. The reflection such as being reflected toward the light shielding member is repeated between the substrate and the light shielding member. Then, it is considered that the stray light that has been repeatedly reflected in this way finally reaches the light guide hole of the light shielding member and enters the imaging optical system to cause ghost light.

  However, since the intensity of stray light is attenuated each time it is reflected, it can be expected that if the number of reflections of stray light between the substrate and the light shielding member is large, the ghost light will be weakened to a negligible level. However, in order to prevent interference between the light emitting chip and the light shielding member, if a large gap is provided between the substrate and the light shielding member, the number of stray light reflections between the substrate and the light shielding member is small, so that the strength is relatively maintained. The stray light may reach the light guide hole and the ghost light may appear strongly.

  The present invention has been made in view of the above problems, and forms an image of light from a light emitting chip disposed on a substrate by an imaging optical system, and a light shielding member is provided between the substrate and the imaging optical system. Another object of the present invention is to provide a technique for suppressing the intensity of ghost light caused by stray light reflected by a light shielding member.

In order to achieve the above object, an exposure head according to the present invention comprises a substrate, a first light emitting element, and a second light emitting element disposed in a first direction of the first light emitting element. A first light emitting chip disposed on the substrate, a third light emitting element, and a fourth light emitting element disposed in a first direction of the third light emitting element. A second light emitting chip disposed in a second direction different from the first direction of the first light emitting chip, and the first light emitting element and the first light transmitting the light emitted from the second light emitting element. A light-shielding portion having a hole and a second hole through which light emitted from the third light-emitting element and the fourth light-emitting element passes, and the first light-emitting element and the first light-emitting element that exit from the first light-emitting element A first imaging optical system that forms an image of light that has passed through the hole, and light that has passed through the second hole through the third and fourth light emitting elements. A second imaging optical system that forms an image; and an optical unit that is disposed between the first light emitting chip and the second light emitting chip of the substrate, and is in the optical axis direction of the first imaging optical system Is the following relationship h1 <h4 <h3
h2 <h4 <h3
h1: Length of the first light emitting chip in the optical axis direction h2: Length of the second light emitting chip in the optical axis direction h3: Distance in the optical axis direction between the substrate and the light shielding portion h4: Light of the reflected light attenuating member And a reflected light attenuating member having a length in the axial direction.

In order to achieve the above object, an image forming apparatus according to the present invention includes a substrate, a first light emitting element, and a second light emitting element disposed in a first direction of the first light emitting element. A first light emitting chip disposed on the substrate, a third light emitting element, and a fourth light emitting element disposed in a first direction of the third light emitting element. A second light emitting chip disposed in a second direction different from the first direction, a first hole through which light emitted from the first light emitting element and the second light emitting element passes, and a third light emitting element A light-shielding portion having a second hole through which light emitted from the first light-emitting element and the fourth light-emitting element pass, and image light emitted from the first light-emitting element and the second light-emitting element through the first hole. First imaging optical system and second imaging optical system for imaging light that has exited from the third light emitting element and the fourth light emitting element and passed through the second hole An optical unit comprising, and, the first light emitting chip and related length of the arranged by the optical axis of the first imaging optical system in the following between the second light emitting chip of the substrate h1 <h4 <h3
h2 <h4 <h3
h1: Length in the optical axis direction of the first light emitting chip h2: Length in the optical axis direction of the second light emitting chip h3: Distance in the optical axis direction between the substrate and the light shielding portion h4: The above-mentioned of the reflected light attenuating member An exposure head having a reflected light attenuating member having a length in the optical axis direction, a latent image carrier on which light from the exposure head is irradiated to form a latent image, and a latent image formed on the latent image carrier And a developing section for developing the image.

  The invention thus configured (exposure head, image forming apparatus) includes a reflected light attenuating member disposed between the first light emitting chip and the second light emitting chip of the substrate. That is, the length h4 of the reflected light attenuating member in the optical axis direction is longer than the length h1 of the first light emitting chip in the optical axis direction and the length h2 of the second light emitting chip in the optical axis direction. The distance between the light shielding part and the reflected light attenuating member is short (compared to the distance h3 between the light shielding part and the substrate in the optical axis direction). And by reflecting the stray light between the light shielding part having such a short interval and the reflected light attenuating member, the number of reflections of the stray light can be increased and the stray light can be effectively attenuated. As a result, it is possible to suppress the intensity of ghost light caused by stray light reflected by the light shielding portion.

  The first light-emitting chip includes a fifth light-emitting element, and light emitted from the fifth light-emitting element passes through a third hole formed in the light shielding portion and is formed in the optical unit. The exposure head may be configured so as to be imaged by the imaging optical system.

  By the way, in the present invention, the length h4 of the reflected light attenuating member in the optical axis direction is longer than the length h1 of the first light emitting chip in the optical axis direction and the length h2 of the second light emitting chip in the optical axis direction. . That is, the reflected light attenuating member protrudes closer to the light shielding part than the first light emitting chip and the second light emitting chip. In such a configuration, the light emitted from the light emitting portion is reflected by the side surface of the reflected light attenuating member and becomes stray light. Further, the stray light passes through the light guide hole and then enters the imaging optical system to cause ghost light. It is possible.

  Thus, the exposure head may be configured so that the reflected light attenuating member has protrusions on the side surface facing the first light emitting chip and the side surface facing the second light emitting chip. By providing the protrusion, the stray light incident on the side of the reflected light attenuating member can be reflected to the substrate side by the protrusion, so that the generation of ghost light due to the stray light reflected on the side of the reflected light attenuating member can be suppressed. It becomes.

  In this case, specifically, the reflected light attenuating member is formed by laminating a first flat plate and a second flat plate whose length in the second direction is longer than that of the first flat plate. What is necessary is just to comprise an exposure head.

  The substrate may be made of glass. This is because glass has a small coefficient of linear expansion, so that even when temperature fluctuations occur, positional deviation of the light emitting chip is suppressed, and a stable exposure operation can be realized.

  Further, the first light emitting chip and the second light emitting chip may be LED chips. This is because the LED has a long life and can realize a stable exposure operation over a long period.

The top view which shows an example of the line head which can apply this invention. The partial perspective view of a line head. The partial step sectional view showing an example of the line head to which the present invention is applicable. The figure which expanded the substantially rectangular part of the broken line in FIG. The AA partial fragmentary sectional view of the line head in a 2nd embodiment. 1 is a diagram illustrating an example of an image forming apparatus to which a line head can be applied. FIG. 7 is a block diagram showing an electrical configuration of the apparatus of FIG. 6.

First Embodiment FIGS. 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 elements and the lenses included in the line head 29 as viewed from the optical axis direction Doa of the imaging optical system formed by the lenses, and FIG. 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 the section is viewed from the longitudinal direction LGD of the line head 29. Corresponds to the case. In FIG. 1, the lenses LS1 and LS2 are indicated by alternate long and short dash lines. This is because the light emitting element E and the lenses LS1 and LS2 are in different positions in the optical axis direction Doa.

  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 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 a line. It is parallel or substantially parallel to the width direction LTD of the head 29. 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.

  In the line head 29, a plurality of (10 in the example of FIG. 1) light emitting elements E are arranged in a straight line in the longitudinal direction LGD to form one light emitting element group EG. Further, a plurality of light emitting element groups EG are arranged in the longitudinal direction LGD in two rows and staggered. In other words, this arrangement mode can be explained as follows. That is, a light emitting element group EG is arranged at a distance of 2 × Dg in the longitudinal direction LGD, and one light emitting element group row GRa (GRb) is configured from a plurality of light emitting element groups EG linearly arranged in the longitudinal direction LGD. The Further, the two light emitting element group rows GRa and GRb are arranged with a distance Dt in the width direction LTD and are shifted from each other by a distance Dg in the longitudinal direction LGD.

  Each light emitting element E is an LED element formed on the LED chips CPa and CPb. These LED chips CPa and CPb are obtained by dicing a semiconductor wafer on which LED elements are formed at predetermined positions (dies), and one LED chip CPa (CPb) has three pieces arranged linearly in the longitudinal direction LGD. LED elements for the light emitting element group EG are formed. 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. Each LED element is configured to receive a drive signal and emit light beams having the same emission spectrum.

  A plurality of LED chips CPa and CPb are arranged in the longitudinal direction LGD in a two-row zigzag manner (FIGS. 1 and 2) and bonded to the surface 293-h of the head substrate 293 (FIGS. 2 and 3). Incidentally, the head substrate 293 is made of glass. That is, since the head substrate 293 has a function of fixedly supporting the LED chips CPa and CPb, when the head substrate 293 undergoes temperature deformation, the positions of the LED chips CPa and CPb change, There is a possibility that a stable exposure operation cannot be performed. Therefore, in this line head 29, the head substrate 293 is made of glass having a small linear expansion coefficient, so that the positional deviation of the LED chips CPa and CPb can be suppressed even when temperature fluctuation occurs, and a stable exposure operation is realized. I am trying.

  One imaging optical system is opposed to each of the plurality of light emitting element groups EG arranged as described above. This imaging optical system includes two lenses LS1 and LS2 that are convex on the light emitting element group EG side. 2 and 3, members 2971 and 2972 are shown between the light emitting element group EG and the imaging optical systems LS1 and LS2. This will be described after the description of the imaging optical system. .

  In this line head 29, a lens array LA1 in which a plurality of lenses LS1 are arranged in a two-row zigzag, and a plurality of lenses LS1, LS2 are arranged to face each of the plurality of light emitting element groups EG arranged in a two-row zigzag. Lens array LA2 in which two lenses LS2 are arranged in a staggered manner in two rows. In other words, in the lens array LA1 (LA2), the lenses LS1 (LS2) are arranged at a distance of 2 × Dg in the longitudinal direction LGD, and one line of lenses is arranged from the plurality of lenses LS1 (LS2) linearly arranged in the longitudinal direction LGD. A line is composed. Further, the two lens rows are arranged with a distance Dt in the width direction LTD and are shifted from each other by a distance Dg in the longitudinal direction LGD.

  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, the lens arrays LA1 and LA2 arranged at a predetermined interval face the head substrate 293 in the optical axis direction Doa. As a result, the imaging optical systems LS1 and LS2 having the optical axis OA parallel to the optical axis direction Doa face the light emitting element group EG, and the light emitted from each light emitting element E of the light emitting element group EG is imaged. The light passes through the optical systems LS1 and LS2 and the support glass SS in this order, and is irradiated onto the exposed surface ES (broken line in FIG. 3). As a result, the light from each light emitting element E of the light emitting element group EG is imaged from the imaging optical systems LS1 and LS2 and irradiated to the exposed surface ES as spots ST, and the exposed surface ES is composed of a plurality of spots ST. A spot group SG is formed. Here, the imaging optical systems LS1 and LS2 are reduction reversal optical systems in which the absolute value of the imaging magnification is less than 1 and an inverted image is formed (imaging magnification is negative).

  Thus, an optical unit is constituted by the lens array LA1 and the lens array LA2. In the optical unit, the lens array LA1 and the lens array LA2 are arranged so that the optical axes of the lens LS1 formed on the lens array LA1 and the lens LS2 formed on the lens array LA2 coincide. . An imaging optical system is configured by LS1 and the lens LS2 having the same optical axis.

  As can be seen from the above description, in the line head 29 of the first embodiment, dedicated imaging optical systems LS1 and LS2 are arranged for each of the plurality of light emitting element groups EG. In such a line head 29, it is desirable that the light from the light emitting element group EG is incident only on the imaging optical system provided in the light emitting element group EG, and not incident on other imaging optical systems. . Therefore, a light shielding member 297 (FIG. 2) is provided between the surface 293-h of the head substrate 293 and the lens array LA1.

  The light shielding member 297 functions to limit a light beam from the light emitting element group EG toward the imaging optical systems LS1 and LS2 facing the light emitting element group EG. Specifically, the light shielding member 297 includes a light shielding flat plate 2971 and a main body member 2972 (FIGS. 2 and 3). The light shielding plate 2971 is formed with a small-diameter hole BR1 extending from the light emitting element group EG to the imaging optical systems LS1 and LS2 opposed to the light emitting element group EG in the optical axis direction Doa. The main body member 2972 is formed with a large-diameter hole BR2 extending from the light emitting element group EG to the imaging optical systems LS1 and LS2 facing the light emitting element group EG in the optical axis direction Doa. The light shielding flat plate 2971 and the main body member 2972 can be made of metal, ceramic, resin, or the like.

  The small diameter hole BR1 and the large diameter hole BR2 are both cylindrical holes, and the large diameter hole BR2 has a larger diameter than the small diameter hole BR1. Then, the upper surface of the light shielding flat plate 2971 is placed on the bottom surface of the main body member 2972 so that the central axis (or geometric gravity center axis) of the small diameter hole BR1 and the central axis (or geometric gravity center axis) of the large diameter hole BR2 match or substantially match. Bonded with adhesive or the like. Thereby, the light shielding flat plate 2971 and the main body member 2972 are positioned with respect to each other so that the peripheral edge of the small diameter hole BR1 protrudes from the peripheral edge of the large diameter hole BR2.

  The light shielding member 297 having the above configuration is disposed between the head substrate 293 and the lens array LA1. At this time, the light shielding member 297 faces the head substrate 293 via the spacer 296 disposed on the head substrate 293. That is, elongated rectangular parallelepiped spacers 296 that are elongated in the longitudinal direction LGD are arranged on both sides in the width direction LTD with respect to the two-row staggered arrangement of the LED chips CPa and CPb. 296, 296. In this manner, by supporting the light shielding member 297 (the bottom surface thereof) at a certain distance from the head substrate surface 293-h, the LED chips CPa, CPb bonded to the head substrate 293-h and the light shielding member 297 are supported. Interference is prevented.

  Thus, the light shielding plate 2971 and the main body member 2972 are arranged in this order in the direction (optical axis direction Doa) from the light emitting element group EG toward the imaging optical systems LS1, LS2. Of the light emitted from the light emitting element group EG, the light incident on the small diameter hole BR1 without being blocked by the bottom surface of the light shielding plate 2971 is imaged by the imaging optical system after passing through the large diameter hole BR2. A spot ST is formed on the exposed surface ES. Thus, in the light shielding member 297, the light guide hole is constituted by the small diameter hole BR1 and the large diameter hole BR2. Incidentally, at least the bottom surface of the light shielding flat plate 2971 is preferably black-plated. Thereby, the intensity of stray light shielded by the light shielding flat plate 2971 can be effectively attenuated.

  Incidentally, as described above, in order to prevent interference between the light shielding member 297 and the LED chips CPa and CPb on the head substrate 293, a space is provided between the light shielding member 297 and the head substrate 293. And in such a structure, there existed a possibility that the ghost light resulting from the stray light reflected by the light shielding member 297 might appear strongly. Therefore, the line head 29 of this embodiment includes a reflected light attenuation member 295. The reflected light attenuating member 295 will be described with reference to FIG. 4 in addition to FIGS. Here, FIG. 4 corresponds to an enlarged view of the substantially rectangular portion of the broken line in FIG. 3, and the upper part of FIG. 4 shows a configuration including a reflected light attenuating member, and the lower part of FIG. 4 includes a reflected light attenuating member. Shows no configuration. In the following, the configuration of the present embodiment including the reflected light attenuating member is described using the upper part of FIGS. 2, 3, and 4, and then the function of the reflected light attenuating member is described using the upper and lower stages of FIG. .

  First, the configuration of the reflected light attenuating member 295 will be described using the upper part of FIGS. 2, 3, and 4. The reflected light attenuating member 295 is a rod-like or flat plate-like member having a length in the longitudinal direction LGD that is about the same as the entire two-row staggered arrangement of the LED chips CPa, CPb, and can be made of metal, ceramic, resin, or the like. it can. The reflected light attenuating member 295 includes a plurality of LED chips CPa arranged linearly in the longitudinal direction LGD to form the light emitting element group row GRa and a plurality arranged linearly in the longitudinal direction LGD to form the light emitting element group row GRb. Between the LED chip CPb. In other words, the LED chip CPa is arranged on one side of the reflected light attenuating member 295 in the width direction LTD, and the LED chip CPb is arranged on the other side of the reflected light attenuating member 295 in the width direction LTD.

Further, the thickness h1 of the LED chip CPa, the thickness h2 (= h1) of the LED chip CPb, and the distance h3 (> h1 = h2) between the head substrate surface 293-h and the bottom surface 2971-t of the light shielding plate 2971 are reflected. The thickness h4 of the light attenuating member 295 has the following relationship:
h3>h4> h1 = h2
have. That is, the thickness h4 of the reflected light attenuating member 295 is larger than the thicknesses h1 and h2 of the LED chips CPa and CPb and smaller than the distance h3 between the head substrate 293 and the light shielding member 297.

In other words, the length h1 of the optical axis direction Doa of the LED chip CPa, the length h2 of the optical axis direction Doa of the LED chip CPb, the distance h3 of the optical axis direction Doa between the head substrate surface 293 and the light shielding member 297, The length h4 of the reflected light attenuating member 295 in the optical axis direction Doa has the following relationship: h1 <h4 <h3
h2 <h4 <h3
Meet.

  Also, the bottom surface 2971-t of the light shielding member 297 faces the reflected light attenuating member 295 disposed between the LED chip CPa and the LED chip CPb from the optical axis direction Doa. Here, the bottom surface 2971-t of the light shielding member 297 is a surface physically present in the light shielding plate 2971 of the light shielding member 297 other than the small-diameter hole BR1. Then, in the cross section in the width direction LTD, the reflected light attenuating member 295 has a width W295 wider than the width W2971 of the light shielding member bottom surface 2971-t facing this.

  Next, the function of the reflected light attenuating member 295 will be described using the upper and lower stages of FIG. If some of the light beams emitted from the light emitting element E of the chip CPb enter the small-diameter hole BR1 as it is (solid line in the figure), they do not enter the small-diameter hole BR1 and are reflected by the light shielding member bottom surface 2971-t. Some of them are shown (broken line in the figure). Then, as shown by the broken line in the figure, the stray light reflected by the light shielding member bottom surface 2971-t is separated from the light shielding member bottom surface 2971-t and the member facing it (the reflected light attenuation member 295 in the upper part of the figure, and the lower part of the figure). While reflection is repeated between the head substrates 293), the light enters the small-diameter hole BR1 and may cause ghost light.

  Therefore, in this embodiment, the reflected light attenuation member 295 is provided. That is, the reflected light attenuating member 295 absorbs part of the light incident on the member surface. Thereby, since the light quantity of reflected light becomes smaller than the light quantity of incident light, the light quantity of stray light can be effectively attenuated by repeating the reflection by this member.

  Thus, since the stray light intensity decreases with each reflection, the ghost light intensity is suppressed if the number of stray light reflections is large. Therefore, it should be further noted that the number of reflections of stray light differs between the configuration in which the reflected light attenuation member 295 is provided (the upper part of the figure) and the configuration in which the reflected light attenuation member 295 is not provided (the lower part of the figure). .

  In the configuration in which the reflected light attenuating member 295 is not provided, a relatively large distance h3 is provided between the light shielding member bottom surface 2971-t and the head substrate 293 which is a member facing the light shielding member bottom surface 2971-t. Therefore, the stray light will reach the small diameter hole BR1 only by reflecting a relatively small number of times. On the other hand, in the configuration in which the reflected light attenuating member 295 is provided, the distance between the light shielding member bottom surface 2971-t and the member (reflected light attenuating member 295) facing this is reduced by the thickness h4 of the reflected light attenuating member 295 (reflected). (Compared with a configuration in which the light attenuation member 295 is not provided). Accordingly, the stray light repeats many reflections between the reflected light attenuating member 295 and the light shielding member bottom surface 2971-t having a relatively narrow interval h5 (= h3−h4 <h3) before reaching the small diameter hole BR1. It becomes. By repeating many reflections in the stray light in this manner, the intensity of the stray light when it reaches the small-diameter hole BR1 can be effectively attenuated.

  As can be understood from these descriptions, the reflected light attenuating member 295 functions to suppress the intensity of ghost light caused by stray light reflected by the bottom surface 2971-t of the light shielding member 297. Here, the function of the reflected light attenuating member 295 has been described by taking up the stray light from the LED chip CPb, but it goes without saying that the reflected light attenuating member 295 also performs the same function for the stray light from the LED chip CPa. Yes.

  In summary, the line head 29 of the present embodiment includes the reflected light attenuation member 295 disposed between the LED chip CPa and the LED chip CPb. The thickness h4 of the reflected light attenuating member 295 is larger than the thicknesses h1 and h2 of the LED chips CPa and CPb. In other words, the light shielding member (compared to the distance h3 between the light shielding member 297 and the head substrate 293). The distance between 297 and the reflected light attenuating member 295 is small. Then, by reflecting the stray light between the light shielding member 297 and the reflected light attenuating member 295 having such a small interval, the number of stray light reflections can be increased and the stray light can be effectively attenuated. As a result, the intensity of ghost light caused by stray light reflected by the light shielding member 297 can be suppressed.

Second Embodiment Meanwhile, in the above-described line head 29, the thickness h4 of the reflected light attenuating member 295 is larger than the thicknesses h1 and h2 of the LED chips CPa and CPb. That is, the reflected light attenuating member 295 protrudes closer to the light shielding member 297 than the LED chips CPa and CPb. In such a configuration, the light beam emitted from the light emitting element E is reflected on the side surfaces (both side surfaces facing the light emitting chips CPa and CPb) of the reflected light attenuating member 295 to become stray light, and this stray light passes through the small-diameter hole BR1. Then, it is conceivable that the light enters the imaging optical systems LS1 and LS2 to cause ghost light. Therefore, it may be configured as shown in FIG.

  FIG. 5 is a partial step sectional view taken along line AA of the line head according to the second embodiment. Moreover, in the same figure, as shown in the inside of a circle, the partial enlarged view is written together. Since the difference between the second embodiment and the first embodiment is only the configuration of the reflected light attenuating member 295, the difference will be mainly described below, and the description of the common parts will be omitted. In the second embodiment, it is needless to say that the same effects as those of the first embodiment can be obtained by providing the same configuration as that of the first embodiment.

  As shown in FIG. 5, the reflected light attenuating member 295 has two types of flat plates 2951 and 2952 having different widths and thicknesses laminated in a range PR protruding from the LED chips CPa and CPb to the light shielding member 297 side. Specifically, the thin flat plate 2952 is thinner than the thick flat plate 2951 and has a width wider than the thick flat plate 2951 in the width direction LTD (in other words, the thin flat plate 2952 is wider than the thick flat plate 2951 in the width direction). Long to LTD). In the width direction LTD, a plurality of thin flat plates 2952 and thick flat plates 2951 are alternately stacked with both ends of the thin flat plate 2952 protruding from the thick flat plate 2951. Thereby, in the range PR, both ends of the thin flat plate 2952 protrude toward the LED chips CPa and CPb.

  As described above, the reflected light attenuating member 295 according to the second embodiment projects both ends of the thin flat plate 2952 and has the protruding portions on the respective sides of the LED chips CPa and CPb. As shown, the stray light incident on the side surface of the stray light absorbing member 295 (the side surface of the thick flat plate 2951) can be reflected to the head substrate 293 side by the protruding portion (the bottom surface of the thin flat plate 2952). As a result, generation of ghost light due to stray light reflected by the side surface of the reflected light attenuating member 295 can be suppressed.

Third Embodiment FIG. 6 is a diagram showing an example of an image forming apparatus to which the above-described line head can be applied. FIG. 7 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. 6, in order to make the drawing easier to see, reference numerals are given only to the respective components constituting the image forming station 2 </ b> C, and description of the reference numerals to be attached to the other image forming stations 2 </ b> Y, 2 </ b> M, and 2 </ b> K is omitted. Further, 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. 6, 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. 6), and is at 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. 6) of the photosensitive drum 21 in the order of these.

  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, each light emitting element E emits light based on the video data VD. 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. 6 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 the main motor, and functions as a belt driving roller for driving 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, and the photosensitive drum 21 corresponds to the “latent image carrier” of the present invention. The head substrate 293 corresponds to the “substrate” of the present invention, the LED chips CPa and CPb correspond to the “first light emitting chip” and the “second light emitting chip” of the present invention, and the small-diameter hole BR1 or The large-diameter hole BR2 cooperates to function as the “first hole” and “second hole” in the present invention, and the light shielding member 297 corresponds to the “light shielding portion” in the present invention, and the imaging optical system LS1. , LS2 correspond to the “first imaging optical system” and the “second imaging optical system” of the present invention. Further, the thick flat plate 2951 corresponds to the “first flat plate” of the present invention, and the thin flat plate 2952 corresponds to the “second flat plate” 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 is adopted. Also good.

  Moreover, in the said embodiment, although small diameter hole BR1 of the light shielding member was comprised by the column shape, the shape of small diameter hole BR1 is not restricted to this. Therefore, for example, the small-diameter hole BR1 may be formed in an elliptic cylinder shape.

  Moreover, in the said embodiment, although the large diameter hole BR2 of the light shielding member was comprised by the column shape, the shape of the large diameter hole BR2 is not restricted to this. Therefore, for example, the large-diameter hole BR2 may be configured in an elliptic cylinder shape.

  Moreover, in the said embodiment, although it did not mention in particular about the raw material of the reflected light attenuation | damping member 295, various variations can be considered also about this. Specifically, the reflected light attenuating member 295 can be made of iron, ceramic, resin, or the like, and the surface thereof can be black-plated, or conversely, the surface can be glossy.

  The dimensional relationship of the reflected light attenuating member 295 is not limited to the dimensions illustrated in the above embodiment, and can be changed as necessary.

  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.

  Moreover, in the said embodiment, in the light emitting element group EG, although the several light emitting element E was located in a line with the longitudinal direction LGD, the arrangement | sequence aspect of the light emitting element E in the light emitting element group EG is not restricted to this. Therefore, for example, as described in Japanese Patent Application No. 2006-213299, the light emitting elements E can be arranged in a staggered pattern.

  Moreover, in the said embodiment, although the several light emitting element group EG was located in 2 rows zigzag in the longitudinal direction LGD, the arrangement | sequence aspect of a light emitting element group is not restricted to this. Therefore, for example, as described in Japanese Patent Application No. 2006-213299, the light-emitting elements E can be arranged in a three-row zigzag pattern.

  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.

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 21 ... Photosensitive drum, 29 ... Line head, 293 ... Head substrate 293, 293-h ... Head substrate surface 293-h, 295 ... Reflected light attenuation member, 2951 ... Thick plate, 2952 ... Thin plate 296: spacer, 297: light shielding member, 2971: light shielding flat plate, 2971-t: bottom surface of light shielding member (light shielding flat plate), 2972: body member 2972, BR1: small diameter hole, BR2: large diameter hole, E: light emitting element, EG ... light emitting element group, LA1 ... lens array, LA2 ... lens array, LS1 ... lens, LS2 ... lens, LGD ... longitudinal direction, LTD ... width direction, OA ... optical axis, Doa ... optical axis direction

Claims (7)

A substrate,
A first light emitting chip disposed on the substrate having a first light emitting element and a second light emitting element disposed in a first direction of the first light emitting element;
A third light emitting element; and a fourth light emitting element disposed in the first direction of the third light emitting element, and the first direction of the first light emitting chip of the substrate. A second light emitting chip disposed in a second direction different from
A first hole through which light emitted from the first light emitting element and the second light emitting element passes; and a second hole through which light emitted from the third light emitting element and the fourth light emitting element passes. And a light-shielding portion having
A first imaging optical system that forms an image of light that has exited from the first light emitting element and the second light emitting element and passed through the first hole, and the third light emitting element and the fourth light emitting element. An optical unit comprising: a second imaging optical system that forms an image of light that has exited the element and passed through the second hole;
The length in the optical axis direction of the first imaging optical system is arranged between the first light emitting chip and the second light emitting chip of the substrate, and the following relationship is established: h1 <h4 <h3
h2 <h4 <h3
h1: Length of the first light emitting chip in the optical axis direction h2: Length of the second light emitting chip in the optical axis direction h3: Distance in the optical axis direction between the substrate and the light shielding portion h4 A reflected light attenuating member having a length in the optical axis direction of the reflected light attenuating member;
An exposure head comprising: The first light emitting chip includes a fifth light emitting element,
The light emitted from the fifth light emitting element passes through a third hole formed in the light shielding portion and is imaged by a third imaging optical system formed in the optical unit. The exposure head described.   The exposure head according to claim 1, wherein the reflected light attenuating member has a protrusion on a side surface facing the first light emitting chip and a side surface facing the second light emitting chip.   The exposure according to claim 3, wherein the reflected light attenuating member is formed by laminating a first flat plate and a second flat plate having a length in the second direction longer than the first flat plate. head.   The exposure head according to claim 1, wherein the substrate is made of glass.   The exposure head according to claim 1, wherein the first light emitting chip and the second light emitting chip are LED chips. A first light emitting chip, a third light emitting element, having a substrate, a first light emitting element, and a second light emitting element disposed in a first direction of the first light emitting element. A second direction different from the first direction of the first light emitting chip of the substrate having a fourth light emitting element disposed in the first direction of the element and the third light emitting element; A second light emitting chip disposed on the first light emitting element, a first hole through which light emitted from the first light emitting element and the second light emitting element passes, and the third light emitting element and the fourth light emitting element. A light-shielding portion having a second hole through which the light emitted from the first light-emitting element passes through the first light-emitting element and the first light-emitting element, and the first light-emitting element that forms an image of the light that has passed through the first hole. A second image forming an image of the light that has exited from the imaging optical system and the third and fourth light emitting elements and passed through the second hole; An optical unit including an imaging optical system, and the length of the first imaging optical system in the optical axis direction disposed between the first light emitting chip and the second light emitting chip of the substrate. Next relationship h1 <h4 <h3
h2 <h4 <h3
h1: Length of the first light emitting chip in the optical axis direction h2: Length of the second light emitting chip in the optical axis direction h3: Distance in the optical axis direction between the substrate and the light shielding portion h4 An exposure head comprising a reflected light attenuating member having a length in the optical axis direction of the reflected light attenuating member;
A latent image carrier on which a latent image is formed by irradiation with light from the exposure head;
A developing unit for developing the latent image formed on the latent image carrier;
An image forming apparatus comprising:

Images