JP2012086521A - Exposure head and image forming apparatus - Google Patents

Abstract

In an exposure head in which a light shielding member having a light guide hole opened in an organic EL element is arranged on a substrate on which an organic EL element is arranged, it is possible to suppress the occurrence of ghost. A light emitting substrate on which the organic EL element is disposed, a support substrate on which the light emitting substrate is disposed in the first direction, a light shielding member in which a light guide hole opening to the organic EL element is disposed, and light emitted from the organic EL element. A lens for imaging light passing through the light guide hole and a drive circuit for driving the organic EL element. When the light emitting substrate is viewed in plan through the light guide hole, the support substrate is shielded by the light emitting substrate. In addition, the drive circuit has a region that is not shielded by the light shielding member.
[Selection] Figure 4

Description

  The present invention relates to an exposure head that forms an image of light emitted from an organic EL element with a lens.

  Patent Document 1 describes an exposure head in which a lens is disposed on an LED chip on which an LED (Light Emitting Diode) is formed, and light from a light emitting element (LED) is imaged by the lens. Further, in this exposure head, when light from other than the facing light emitting element enters the lens, a so-called ghost may be caused. Therefore, a light shielding member is provided to suppress this. In other words, the light blocking member is disposed between the light emitting element and the lens, and has a light guide hole that opens from the light emitting element toward the lens, so that light that does not pass through the light guide hole is directed to the lens. By limiting the incidence, the occurrence of ghost is suppressed.

JP 2009-029106 A

  By the way, it is possible to use the silicon substrate etc. which formed the organic EL (Electro-Luminescence) element as a light emitting element instead of the above LED chips. However, such an organic EL element has a smaller amount of light than an LED. For this reason, there is a possibility that a ghost generated due to the following reason may have an influence that cannot be ignored. In other words, a light shielding member is provided between the substrate on which the organic EL element is formed and the lens. If light enters between the substrate and the light shielding member for some reason, this light is transmitted between the substrate and the light shielding member. The reflection may be repeated until the light guide hole is reached. In some cases, a ghost is generated when the light reaching the light guide hole is imaged by the lens.

  The present invention has been made in view of the above problems, and in an exposure head in which a light shielding member having a light guide hole opened in the organic EL element is provided on a substrate on which the organic EL element is provided, ghosting is generated. The purpose is to provide a technology that can be suppressed.

  In order to achieve the above object, an exposure head according to the present invention includes a light emitting substrate on which an organic EL element is disposed, a support substrate on which the light emitting substrate is disposed in a first direction, and a lead opening to the organic EL element. A light-shielding member having a light hole, a lens that forms an image of light emitted from the organic EL element and passing through the light guide hole, and a drive circuit that drives the organic EL element. When the light emitting substrate is viewed in plan, the support substrate is shielded by the light emitting substrate, and the drive circuit has a region that is not shielded by the light shielding member.

  In order to achieve the above object, an image forming apparatus according to the present invention includes a light emitting substrate on which an organic EL element is disposed, a support substrate on which the light emitting substrate is disposed in a first direction, and a light guide opening to the organic EL element. A light-shielding member in which a hole is disposed; a lens that forms an image of light emitted from the organic EL element and passing through the light-guiding hole; and a drive circuit that drives the organic EL element. When the substrate is viewed in plan, it is shielded by the light emitting substrate, and the drive circuit connects the exposure head that is not partially shielded by the light shielding member when the light emitting substrate is viewed in plan through the light guide hole and the lens of the exposure head. The image forming apparatus includes a latent image carrier on which a latent image is formed by the imaged light, and a developing unit that develops the latent image.

  In the invention configured as described above (exposure head, image forming apparatus), a light-shielding member provided with a light guide hole that opens to the organic EL element is provided on the light emitting substrate on which the organic EL element is provided. . Therefore, the light that has repeatedly reflected between the light emitting substrate and the light shielding member may reach the light guide hole. On the other hand, in this invention, when the light emitting substrate is viewed in plan through the light guide hole, the drive circuit has a region that is not shielded by the light shielding member. Therefore, the light traveling toward the light guide hole while repeating reflection between the substrate and the light shielding member can be scattered by the region of the drive circuit, and the incidence of this light on the lens can be suppressed. As a result, it is possible to suppress the occurrence of ghosts.

  Moreover, in the present invention, it is not necessary to provide a member for each function by configuring the driving circuit to have both the driving function and the light scattering function of the organic EL element. Therefore, it is possible to save the space of the layout of each functional unit in the exposure head.

  Further, when the light emitting substrate is viewed in plan in the optical axis direction of the lens, the periphery of the drive circuit and the periphery of the light guide hole may intersect. By arranging the drive circuit in this manner, the light traveling toward the light guide hole while repeating reflection between the substrate and the light shielding member can be more reliably scattered by the drive circuit. Can be more effectively suppressed. As a result, it is possible to more reliably suppress the occurrence of ghosts.

  Various shapes can be adopted for the shape of the light guide hole and the arrangement of the drive circuit corresponding thereto. Therefore, the light guide hole has a long shape in the first direction, and the drive circuit is guided between the periphery of the drive circuit in the first direction and the second direction perpendicular to the optical axis of the lens. You may comprise so that a light hole may be arranged. Further, at this time, the light guide hole may be a rectangle having a long side extending in the first direction.

  A plurality of substrates on which organic EL elements are arranged can be provided. At this time, for the reason described in detail later, the ends of the substrate and the second substrate in the first direction may be configured to have sides extending in the third direction intersecting the first direction at an acute angle. It may be appropriate. In such a case, the configuration in which the drive circuit has a side extending in the third direction is advantageous in that the drive circuit can be made larger and the light scattering function of the drive circuit can be exhibited more effectively. is there.

  Various specific configurations of the substrate can be employed. Therefore, the substrate may be a single crystal silicon substrate.

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 side view which shows an example of the line head which can apply this invention. The partial top view which shows the structure of a light emitting element group and a drive circuit. The figure which shows the other example of the line head which can apply this invention. The figure which shows the other example of the line head which can apply this invention. The figure which shows the other example of the line head which can apply this invention. The partial top view which shows another structure of a light emitting element group and a drive circuit. 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.

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 partially exploded plan view of the line head 29, FIG. 2 is a partially exploded perspective view of the line head 29, and FIG. 3 is a partial side view of the line head 29. This line head 29 forms the spot SP on the exposed surface ES such as the surface of the photosensitive drum by imaging the light from the light emitting element E by the imaging optical systems LS1 and LS2, and in the longitudinal direction LGD. The entire structure is long 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. In addition, the optical axis direction Doa of the imaging optical systems LS1 and LS2 is also appropriately shown in FIGS. 1 to 3 and the following drawings. Here, the optical axis direction Doa is parallel to the optical axis OA of the imaging optical systems LS1 and LS2, and is a direction in which the light emitting element E emits light. 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.

  The line head 29 uses an organic EL element formed by a semiconductor process on a light source chip 291 made of single crystal silicon as the light emitting element E. In addition, the organic EL element which comprises the light emitting element E is sealed with the sealing film not shown. In the light source chip 291, one light emitting element group EG is composed of a plurality of light emitting elements E, and a plurality (10 in FIG. 1 and FIG. 2) of light emitting element groups EG are arranged in a zigzag pattern in two rows in the longitudinal direction LGD. Are lined up. In other words, in the light source chip 291, a pair of two light emitting element groups EG that are spaced apart by 6.7 [mm] in the width direction LTD and shifted by 2.03 [mm] in the longitudinal direction LGD has an equal pitch in the longitudinal direction LGD ( = 2.03 [mm] x 2).

  At this time, the two light emitting element groups EG constituting the pair are arranged in parallel in an oblique direction Dsk that intersects the longitudinal direction LGD at an angle of 76 ° (acute angle). In correspondence with such an arrangement of the light emitting element groups EG, both ends in the longitudinal direction LGD of the light source chip 291 are cut in parallel to the oblique direction Dsk, and the light source chip 291 has a parallelogram shape. In addition, the length of the both ends of the light source chip 291 in the width direction LTD is 20.3 [mm].

  Here, the reason why both end sides in the longitudinal direction LGD of the light source chip 291 are cut in the oblique direction Dsk is that the line head 29 is lengthened. This is because, by arranging a plurality of light source chips 291 in the longitudinal direction LGD, it is possible to arrange as many light emitting element groups EG that constitute the pair as required in the longitudinal direction LGD. This is because the length can be easily increased. The plurality of light source chips 291 arranged in the longitudinal direction LGD to be elongated are bonded to the surface of the light source substrate 292. At this time, for example, when the light source substrate 292 is a glass substrate, the light source chip 291 can be bonded to the light source substrate 292 by COG (chip on glass). Incidentally, each light emitting element E of the plurality of light source chips 291 emits light with the same or substantially the same emission spectrum.

  On the optical axis direction Doa side of the plurality of light source chips 291, a thin flat light-shielding plate 293 that is long in the longitudinal direction LGD is provided. The light shielding plate 293 is supported on both sides in the width direction LTD by spacers S293 interposed between the light source chips 291 and is separated from the light source chip 291 in the optical axis direction Doa. In the light shielding plate 293, a light guide hole 2931 having a size smaller than that of the light source chip 291 and opening from the optical axis direction Doa to the light emitting element group EG is provided for each light emitting element group EG. Each light guide hole 2931 has a circular shape with a diameter of 3 [mm].

  Further, two lens arrays 294 and 295 are provided on the light shielding plate 293 on the optical axis direction Doa side. The lens array 294 is supported on both sides in the width direction LTD by spacers S294 inserted between the light source chips 291 and is separated from the light shielding plate 293 in the optical axis direction Doa. The lens array 295 is supported on both sides in the width direction LTD by spacers S295 interposed between the lens array 294 and is separated from the lens array 294 in the optical axis direction Doa. In each lens array 294, 295, lenses LS1, LS2 facing the light emitting element group EG from the optical axis direction Doa are formed for each light emitting element group EG. Each lens LS1, LS2 is convex with respect to the light emitting element group EG and has a circular shape with a diameter of 3.6 [mm].

  Thus, the light emitting element group EG, the light guide hole 2931, the lens LS1, and the lens LS2 are arranged in this order in the optical axis direction Doa. 3, the light emitted from each light emitting element E of the light emitting element group EG enters the lenses LS1, LS2 after passing through the light guide hole 2931, and the lenses LS1, An image is formed by an imaging optical system composed of LS2. Note that the imaging optical systems LS1 and LS2 form an image with an imaging magnification of -1 times, and have imaging characteristics of inversion equal magnification.

  In this embodiment, the drive circuit DC that drives each light emitting element E of the light emitting element group EG is formed in the light source chip 291 by a semiconductor process. Next, the drive circuit DC will be described together with the configuration of the light emitting element group EG.

  FIG. 4 is a partial plan view showing the configuration of the light emitting element group and the drive circuit, and shows a case where the light emitting element group EG and the drive circuit DC are viewed in plan from the optical axis direction Doa via the light guide hole 2931. In FIG. 4, the lenses LS1 and LS2 are shown together to show the positional relationship between the light guide hole 2931 and the light emitting element group EG and the lenses LS1 and LS2. In this embodiment, the light source chip 291 is larger than the light guide hole 2931, and the light source substrate 292 is hidden under the light source chip 291 and shielded by the light source chip 291 in the plan view of FIG.

  The light emitting element group EG is composed of 98 light emitting elements E arranged in a staggered manner in two rows in the longitudinal direction LGD. The arrangement pitch of these light emitting elements E is 0.02 [mm], which corresponds to 1200 dpi (dot per inch). Thus, 0.11 [mm] from the virtual straight line VL on both sides in the width direction LTD of the virtual straight line VL (longitudinal center line VL of the light guide hole 2931) passing through the center of the light guide hole 2931 and parallel to the longitudinal direction LGD. The 49 light-emitting elements E are linearly arranged in the longitudinal direction LGD at the position. Each light emitting element E has a circular shape with a diameter of 0.04 [mm].

  In addition, drive circuits DC are provided on both sides of the light emitting element group EG in the width direction LTD. Each drive circuit DC has a parallelogram shape in which both ends in the width direction LTD are parallel to the longitudinal direction LGD and both ends in the longitudinal direction LGD are parallel to the oblique direction Dsk. It is formed so as to overlap the inside of the light guide hole 2931. That is, in the plan view of FIG. 4, a region of the drive circuit DC that overlaps the inside of the light guide hole 2931 is not shielded by the light shielding plate 293 and is viewed from the light guide hole 2931. In particular, in this embodiment, the peripheral edge of the drive circuit DC and the peripheral edge of the light guide hole 2931 intersect in plan view (planar perspective) from the optical axis direction Doa. In other words, each drive circuit DC is in the oblique direction Dsk. The light guide hole 2931 extends from the inner side to the outer side beyond the periphery (FIGS. 1 to 4). Each drive circuit DC is formed 0.31 [mm] away from the longitudinal center line VL of the light guide hole 2931 in the width direction LTD.

  The drive circuit DC on one side in the width direction LTD of the light emitting element group EG is electrically connected to each light emitting element E on one side of the longitudinal center line VL of the light guide hole 2931, and the width direction of the light emitting element group EG. The drive circuit DC on the other side of the LTD is electrically connected to each light emitting element E on the other side of the longitudinal center line VL of the light guide hole 2931. Each drive circuit DC applies a drive signal to the connected light emitting element E to cause the light emitting element E to emit light.

  As described above, in the line head 29 of this embodiment, the light emitting element E has an opening smaller than the light source chip 291 with respect to the light source chip 291 (substrate) on which the light emitting element E (organic EL element) is formed. A light shielding plate 293 (light shielding member) in which a light guide hole 2931 is formed is provided. Therefore, the light repeatedly reflected between the light source chip 291 and the light shielding plate 293 sometimes reaches the light guide hole 2931. On the other hand, in this embodiment, when the light source chip 291 is viewed in plan through the light guide hole 2931, the drive circuit DC has a region that is not shielded by the light shielding plate 293. In other words, the light guide hole A drive circuit DC is formed in the light source chip 291 so as to overlap the inside of the 2931. Therefore, the light (for example, the light SL in FIG. 3) traveling toward the light guide hole 2931 while repeatedly reflecting between the light source chip 291 and the light shielding plate 293 is guided by the drive circuit DC (light scattering member). Scattering by the region inside the hole 2931 can suppress the incidence of this light on the lenses LS1 and LS2. As a result, it is possible to suppress the occurrence of ghosts.

  In addition, in this embodiment, since the drive circuit DC has both the drive function and the light scattering function of the light emitting element E, it is not necessary to provide a member for each function. Therefore, it is possible to save the space of the layout of each functional unit in the line head 29.

  Further, in the above embodiment, when the light source chip 291 is viewed in plan in the optical axis direction Doa, the periphery of the drive circuit DC and the periphery of the light guide hole 2931 intersect, in other words, the drive circuit DC is guided. When the light source chip 291 is viewed in plan through the light hole 2931, it is arranged from the inside of the light guide hole 2931 to the periphery. By arranging the drive circuit in this way, the light traveling toward the light guide hole 2931 while being repeatedly reflected between the light source chip 291 and the light shielding plate 293 can be more reliably scattered by the drive circuit DC, Incidence of this light to the lenses LS1 and LS2 can be more effectively suppressed. As a result, it is possible to more reliably suppress the occurrence of ghosts.

  Further, in the above embodiment, both ends of the light source chip 291 in the longitudinal direction LGD have sides extending in the direction Dsk at both ends of the longitudinal direction LGD of the drive circuit DC corresponding to the fact that both ends of the light source chip 291 are cut in the oblique direction Dsk. (In other words, the drive circuit DC is extended in the oblique direction Dsk). Therefore, the drive circuit DC can be made large. That is, for example, in a configuration in which the drive circuit DC is drawn straight in a direction orthogonal to the longitudinal direction LGD (width direction LTD), the size of the drive circuit DC is within a range where the drive circuit DC does not reach the end of the light source chip 291 in the longitudinal direction LGD. It is necessary to accommodate it. On the other hand, both ends of the drive circuit DC in the longitudinal direction LGD are formed in an oblique direction Dsk parallel to the edges of the light source chip 291 in the longitudinal direction LGD (in other words, the drive circuit DC is extended). Thus, the drive circuit DC can be made larger by removing such a restriction on the size of the drive circuit DC. Therefore, the configuration of the above embodiment is advantageous when the drive circuit DC is made large and the light scattering function of the drive circuit DC is more effectively exhibited.

Second Embodiment Next, a second embodiment will be described. In the following description of the second embodiment, the description of the configuration common to the first embodiment is omitted as appropriate, but the same effect can be achieved by providing the configuration common to the first embodiment. Needless to say.

  5, 6 and 7 are diagrams showing another example of a line head to which the present invention can be applied. In particular, FIG. 5 is a partially exploded plan view of the line head 29, FIG. 6 is a partially exploded perspective view of the line head 29, and FIG. 7 is a partial side view of the line head 29. FIG. 8 is a partial plan view showing another configuration of the light emitting element group and the drive circuit, and shows a case where the light emitting element group EG and the drive circuit DC are viewed in plan from the optical axis direction Doa through the light guide hole 2931. Yes. Further, in FIG. 8, the lenses LS1 and LS2 are shown together to show the positional relationship between the light guide hole 2931 and the light emitting element group EG and the lenses LS1 and LS2.

  As shown in FIGS. 5 and 6, in each of the plurality of light source chips 291, ten light emitting element groups EG arranged in a zigzag pattern in two rows in the longitudinal direction LGD are formed. Each light source chip 291 has a rectangular shape in which both ends in the longitudinal direction LGD are cut in an oblique direction Dsk, and both ends in the width direction LTD are cut in a direction orthogonal or substantially orthogonal to the oblique direction Dsk.

  Each light emitting element group EG formed on the light source chip 291 is composed of 196 light emitting elements E (organic EL elements) arranged in the longitudinal direction LGD at a pitch of 0.011 [mm] (corresponding to 2400 dpi). It has a length of 2.05 [mm] in the longitudinal direction LGD (FIG. 8). More specifically, the light emitting element group EG has a configuration in which 49 light emitting elements E arranged in a straight line in the longitudinal direction LGD are arranged in four rows in the width direction LTD. Each light emitting element E has a circular shape with a diameter of 0.02 [mm].

  A light guide hole 2931 having a size smaller than that of the light source chip 291 and opening from the optical axis direction Doa to the light emitting element group EG is emitted from the light shielding plate 293 facing the plurality of light source chips 291 from the optical axis direction Doa side. It is provided for each element group EG. Each light guide hole 2931 is long (3.4 [mm]) in the longitudinal direction LGD and short (1.4 [mm]) in the width direction LTD (long length extending in the longitudinal direction LGD). (Rectangular shape having sides) (FIG. 8). At this time, the light shielding plate 293 is positioned with respect to the lens arrays 294 and 295 so that the geometric center of gravity of each of the light guide hole 2931 and the light emitting element group EG (the intersection of the dashed line in FIG. 8) coincides.

  In each of the lens arrays 294 and 295 facing the light shielding plate 293 from the optical axis direction Doa side, lenses LS1 and LS2 facing the light emitting element group EG from the optical axis direction Doa are formed for each light emitting element group EG. Each lens LS1, LS2 is convex with respect to the light emitting element group EG and has a circular shape with a diameter of 3.6 [mm]. In the second embodiment, the optical axes OA of the lenses LS1 and LS2 are located inside the width direction LTD with respect to the light emitting element group EG and the light guide hole 2931. As a result, the light emitting element group EG and the light guide hole 2931 are located on both outer sides in the width direction LTD of the region Roa between the optical axes OA arranged in the width direction LTD. Then, the lenses LS1 and LS2 (imaging optical system) arranged in this way form the spot SP by imaging the light from the light emitting element group EG with a negative imaging magnification (−1).

  In this way, the imaging optical systems LS1 and LS2 are shifted inward in the width direction LTD, and the magnifications of the imaging optical systems LS1 and LS2 are made negative, thereby forming 2 side by side in the width direction LTD. It is possible to reduce the distance Δsp between the two spots SP. As a result, the line head 29 is more suitable for image formation in an image forming apparatus described later. That is, in the image forming apparatus, the portion exposed by the spot SP is transported to the development position downstream in the width direction LTD (sub scanning direction SD) and undergoes toner development. At this time, if the time from exposure by the spot SP to toner development (exposure development time) differs greatly between the spots SP, there is a risk of causing printing unevenness such as different amounts of adhering toner. On the other hand, by reducing the distance Δsp between the spots SP, the difference in exposure and development time between the spots SP can be reduced, and the occurrence of such printing unevenness can be suppressed.

  Incidentally, drive circuits DC are provided on both sides of the light emitting element group EG in the width direction LTD. Both ends of the drive circuit DC in the longitudinal direction LGD are parallel to the oblique direction Dsk. The end of the drive circuit DC in the width direction LTD on the light emitting element group EG side is parallel to the longitudinal direction LGD, while the end of the drive circuit DC in the width direction LTD on the opposite side of the light emitting element group EG is in the oblique direction Dsk. It is orthogonal or substantially orthogonal. Thus, the drive circuit DC has a trapezoidal shape. The drive circuit DC is formed so as to overlap the light guide hole 2931 in the plan view of FIG. In particular, in this embodiment, the peripheral edge of the light guide hole 2931 is positioned between both ends (peripheries) in the width direction LTD of the drive circuit DC in a plan view (plan view) from the optical axis direction Doa. The circuit DC extends in the oblique direction Dsk from the inside of the light guide hole 2931 to the outside beyond the peripheral edge (FIGS. 5 to 8).

  The drive circuit DC on one side in the width direction LTD of the light emitting element group EG is electrically connected to each light emitting element E on one side of the longitudinal center line VL of the light guide hole 2931, and the width direction of the light emitting element group EG. The drive circuit DC on the other side of the LTD is electrically connected to each light emitting element E on the other side of the longitudinal center line VL of the light guide hole 2931. Each drive circuit DC applies a drive signal to the connected light emitting element E to cause the light emitting element E to emit light.

  As described above, also in the second embodiment, the light source chip 291 (substrate) on which the light emitting element E (organic EL element) is formed has a size smaller than that of the light source chip 291 and opens to the light emitting element E. A light shielding plate 293 (light shielding member) in which a light hole 2931 is formed is provided. Therefore, the light repeatedly reflected between the light source chip 291 and the light shielding plate 293 sometimes reaches the light guide hole 2931. On the other hand, in the second embodiment, when the light source chip 291 is viewed in plan through the light guide hole 2931, the drive circuit DC has a region that is not shielded by the light shielding plate 293. A drive circuit DC is formed in the light source chip 291 so as to overlap the inside of the hole 2931. Therefore, the light (for example, the light SL in FIG. 3) traveling toward the light guide hole 2931 while repeatedly reflecting between the light source chip 291 and the light shielding plate 293 is guided by the drive circuit DC (light scattering member). Scattering by the region inside the hole 2931 can suppress the incidence of this light on the lenses LS1 and LS2. As a result, it is possible to suppress the occurrence of ghosts.

Next, an example of an image forming apparatus to which the line head 29 described in the first and second embodiments can be applied will be described. FIG. 9 is a diagram illustrating an example of an image forming apparatus to which the above-described line head can be applied. FIG. 10 is a block diagram showing an electrical configuration of the apparatus of FIG. 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. 9, 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 the 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. 9, 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. 9), 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. 9) 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, the drive circuit DC emits each light emitting element E in response to the supply of the drive signal corresponding to 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. 9 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 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, 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 corresponds to the “first direction” of the present invention, the width direction LTD corresponds to the “second direction” of the present invention, and the oblique direction Dsk corresponds to the “third direction” of the present invention. Equivalent to. The light source chip 291 corresponds to the “light emitting substrate” of the present invention, the light source substrate 292 corresponds to the “supporting substrate” of the present invention, the light shielding plate 293 corresponds to the “light shielding member” of the present invention, and the light guide hole. 2931 corresponds to the “light guide hole” of the present invention, the lenses LS1 and LS2 correspond to the “lens” of the present invention, and the drive circuit DC corresponds to the “drive circuit” 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. Therefore, the configuration of the light shielding member is not limited to the above-described one. For example, a light shielding member can be configured by arranging a plurality of light shielding plates in the optical axis direction Doa as described in Japanese Patent Application Laid-Open No. 2008-307885. . Even in such a configuration, a ghost is generated by forming the drive circuit DC in the light source chip 291 so as to overlap the light guide hole 2931 when the light source chip 291 is viewed in plan through the light guide hole 2931. Can be suppressed.

  The base material of the light source chip 291 is not limited to single crystal silicon, and high temperature polysilicon, low temperature polysilicon, or the like can be used.

  Further, a modification in which an IC (Integrated Circuit) is mounted on the front surface / back surface of the light source chip 291 is also possible.

  Further, various modifications can be made to the imaging optical systems LS1 and LS2, and for example, a modification such as an image side telecentric configuration is possible.

  In the above-described embodiment, the detailed configuration of the lens arrays 294 and 295 is not particularly described. For example, a configuration in which the lenses LS1 and LS2 are formed of a resin in a glass substrate shape can be employed.

  Further, the shape of the light source chip 291, the arrangement mode of the light emitting element groups EG in the light source chip 291, and the arrangement mode of the plurality of light emitting elements E constituting each light emitting element group EG can be appropriately changed.

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 29 ... Line head, 291 ... Light source chip, 292 ... Light source board, 293 ... Light-shielding plate, 2931 ... Light guide hole, 294 ... Lens array, 295 ... Lens array, LS1 ... Lens, LS2 ... Lens, DC: driving circuit, E: light emitting element, EG: light emitting element group, LGD: longitudinal direction, LTD: width direction, Dsk: oblique direction

Claims (7)

A light emitting substrate on which an organic EL element is disposed;
A support substrate in which the light emitting substrate is arranged in a first direction;
A light shielding member provided with a light guide hole that opens to the organic EL element;
A lens for imaging light emitted from the organic EL element and passing through the light guide hole;
A drive circuit for driving the organic EL element;
With
When the light emitting substrate is viewed in plan through the light guide hole,
The exposure head according to claim 1, wherein the support substrate is shielded by the light emitting substrate, and the drive circuit has a region not shielded by the light shielding member.   2. The exposure head according to claim 1, wherein a peripheral edge of the drive circuit and a peripheral edge of the light guide hole intersect when the light emitting substrate is viewed in plan in the optical axis direction of the lens.   The light guide hole has a shape that is long in the first direction, and the drive circuit has a peripheral edge of the drive circuit in the first direction and a second direction perpendicular to the optical axis of the lens. The exposure head according to claim 2, wherein a periphery of the light guide hole is disposed between the exposure heads.   The exposure head according to claim 3, wherein the light guide hole is a rectangle having a long side extending in the first direction.   The edge of the said 1st direction of the said board | substrate is extended in the 3rd direction which cross | intersects the said 1st direction at an acute angle, The said drive circuit has the edge | side extended in the said 3rd direction. Exposure head.   6. The exposure head according to claim 1, wherein the substrate is a single crystal silicon substrate. A light emitting substrate on which the organic EL element is disposed, a support substrate on which the light emitting substrate is disposed in the first direction, a light shielding member in which a light guide hole opening to the organic EL element is disposed, and light emitted from the organic EL element A lens that forms an image of light passing through the light guide hole, and a drive circuit that drives the organic EL element, and the support substrate is a plan view of the substrate when viewed through the light guide hole. An exposure head that is shielded by a light emitting substrate, and the drive circuit is not partially shielded by the light shielding member when the light emitting substrate is viewed in plan through the light guide hole;
A latent image carrier on which a latent image is formed by light formed by the lens of the exposure head;
A developing unit for developing the latent image;
An image forming apparatus comprising:

Images