JP2012086520A - Exposure head and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique which can suppress the occurrence of a ghost, in an exposure head in which a light-transmissive substrate is arranged between an organic EL and a light shielding member.SOLUTION: The exposure head includes: a silicon substrate on which the organic EL and a sealing member for sealing the organic EL are arranged; the light-transmissive substrate which covers the organic EL and the sealing member on the silicon substrate and transmits light emitted by the organic EL; a light shielding member in which holes are arranged. each of the holes having an opening part opened to the organic EL and allowing the light transmitted by the light-transmissive substrate and made incident on the opening part from the organic EL to pass, and in which the opening parts are arranged on the inside of the silicon substrate in such a manner that the opening part becomes smaller than the silicon substrate as viewed from the direction of the holes; and an optical system which image-forms the light passing through the holes of the light-shielding member.

Description

  The present invention relates to an exposure head that forms an image of light emitted from an organic EL by an imaging optical system.

  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 the light emitting element (LED) is imaged by an optical system. Further, in this exposure head, when light from other than the facing light emitting element enters the optical system, there is a possibility that so-called ghost may be caused. In Patent Document 1, in order to suppress this, a light shielding member having a hole (light guide hole) penetrating from the light emitting element toward the optical system is disposed between the light emitting element and the optical system. The hole of the light shielding member has an opening that opens toward the light emitting element, and light emitted from the organic EL enters the optical system after passing through the opening and passing through the hole. In this way, the occurrence of ghost is suppressed by limiting the incidence of light that does not enter the aperture to the imaging optical system.

JP 2009-029106 A

  By the way, it can be considered to use a silicon substrate or the like in which organic EL (Electro-Luminescence) is formed as a light emitting element instead of the LED chip as described above. However, since the characteristics of the organic EL deteriorate due to moisture or the like, it is necessary to seal the organic EL with a sealing member and shield it from the outside air. Furthermore, it is preferable to cover the organic EL and the sealing member with a light-transmitting substrate such as a glass substrate so that the sealing is not broken. That is, in this case, the organic EL and the sealing member are covered with the glass substrate, and the light emitted from the organic EL passes through the sealing member and the light-transmitting substrate and enters the opening of the hole of the light shielding member.

  However, in such a configuration, stray light traveling toward the opening of the hole of the light shielding member passes through the light transmissive substrate so as to pass through the side of the silicon substrate and then enters the opening. There was a risk of causing ghosts.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a technique capable of suppressing the occurrence of ghost in an exposure head in which a light-transmitting substrate is disposed between an organic EL and a light shielding member. To do.

  In order to achieve the above object, the exposure head according to the present invention covers a silicon substrate on which an organic EL and a sealing member for sealing the organic EL are disposed, an organic EL of the silicon substrate, and a sealing member, A light-transmitting substrate through which light emitted from the organic EL transmits, and an opening that opens to the organic EL, and a hole through which light that passes through the light-transmitting substrate from the organic EL and enters the opening is arranged. And a light shielding member having an opening smaller than the silicon substrate as viewed from the direction of the hole and disposed inside the silicon substrate, and an optical system for imaging light passing through the hole of the light shielding member. Yes.

  In order to achieve the above object, an image forming apparatus according to the present invention covers a silicon substrate on which an organic EL and a sealing member that seals the organic EL are disposed, an organic EL of the silicon substrate, and a sealing member. At the same time, a light-transmitting substrate through which light emitted from the organic EL is transmitted, and an opening having an opening opening in the organic EL, through which the light that passes through the light-transmitting substrate from the organic EL and enters the opening pass are arranged. And an exposure head having an optical system that forms an image of light passing through the hole of the light shielding member, a light shielding member that is smaller in size than the silicon substrate and disposed inside the silicon substrate when viewed from the direction of the hole, And a latent image carrier on which a latent image is formed by light formed by the system.

  In the invention configured as described above (exposure head, image forming apparatus), the organic EL and the sealing member disposed on the silicon substrate are covered with the light transmissive substrate. And the light which permeate | transmitted the light transmissive board | substrate from organic EL is imaged by an optical system, after passing the hole of a light shielding member. Therefore, for the same reason as described above, stray light traveling toward the opening of the hole of the light shielding member passes through the light transmissive substrate so as to pass through the side of the silicon substrate, and then enters the opening. This could cause ghosts. On the other hand, in the present invention, the opening of the hole is smaller than the silicon substrate when viewed from the direction of the hole of the light shielding member, and is arranged inside the silicon substrate. Therefore, most of the stray light traveling toward the opening of the hole of the light shielding member is reflected by the silicon substrate and does not enter the light transmissive substrate. Thus, in the present invention, it is possible to suppress the occurrence of ghost.

  Moreover, you may comprise so that the drive circuit which distribute | arranges to a silicon substrate and drives organic EL may be provided. In this manner, by integrating the organic EL and the drive circuit on the silicon substrate, it is not necessary to provide a member constituting the drive circuit other than the silicon substrate, and it becomes easy to save the space of the exposure head.

  At this time, more specifically, the drive circuit and the organic EL may be stacked on the silicon substrate. Furthermore, a wiring for supplying a signal for driving the organic EL to the driving circuit may be arranged on the silicon substrate.

  Further, the absolute value of the imaging magnification of the optical system may be less than 1. As will be described later, in the case of such a configuration, the drive circuit can be formed large and the drive capability of the drive circuit can be easily improved.

  Further, a glass substrate can be used as the light transmissive substrate.

The figure which shows an example of the line head which can apply this invention. The figure which shows arrangement | positioning of the light emitting element in the line head of FIG. The partial top view of the chip | tip seen from the optical axis direction. The figure which shows partially the cross section of the width direction of the chip | tip seen from the longitudinal direction LGD. The figure explaining the effect of 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. The figure which shows the modification of a chip | tip. The figure which shows the modification of a chip | tip. The figure which shows the modification of the arrangement | sequence aspect of the light emitting element which comprises a light emitting element group. The figure which shows the modification of the arrangement | positioning relationship between an imaging optical system and a light emitting element group.

  FIG. 1 is a diagram showing an example of a line head to which the present invention can be applied. In particular, the cross-section of the line head 29 (A-A cross section shown in FIG. 2) is partially shown from the longitudinal direction LGD. ing. As shown by a broken line in FIG. 1, the line head 29 forms an image of light from the light emitting element formed on the chip CP by the imaging optical systems LS1 and LS2, and forms an exposed surface ES such as the surface of the photosensitive drum. The spot SP is formed. FIG. 2 is a diagram showing the arrangement of the light emitting elements in the line head of FIG. 1, particularly when the configuration of the head substrate 293 that supports the chip CP on which the light emitting element E is formed is viewed from the optical axis direction Doa. Partially shown. In addition, in FIG. 1 and the figure demonstrated later, the hatching of the dot is suitably given with respect to the cross section of the member comprised with optically transparent materials, such as glass. In FIG. 2, members (LS1, LS2, D1) other than the members arranged on the head substrate 293 are indicated by one-dot / two-dot chain lines, but this is the light-emitting element E and each member (LS1, LS2,. This is to make it easier to understand the correspondence with D1).

  The line head 29 has an overall configuration that is long in the longitudinal direction LGD and short in the width direction LTD. Therefore, in FIG. 1 and the drawings described later, the longitudinal direction LGD and the width direction LTD of the line head 29 are shown as necessary. In addition, the optical axis direction Doa of the imaging optical systems LS1 and LS2 is also shown as appropriate. 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 elements formed on the chip CP emit 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 includes a head substrate that supports the chip CP and lens arrays LA1 and LA2 on which lenses LS1 and LS2 are formed. In the chip CP, a plurality of (16) light emitting elements E arranged in a zigzag manner in two rows in the longitudinal direction LGD at the light emitting element pitch Pe are grouped to form a light emitting element group EG, and a plurality (three) of light emitting elements are formed. The element groups EG are linearly arranged at a predetermined pitch (Dg × 2) in the longitudinal direction LGD. A plurality of chips CP are arranged in a zigzag pattern in two rows in the longitudinal direction LGD and fixed to the back surface 293-t of the glass head substrate 293. As a result, on the back surface 293-t of the head substrate 293, a plurality of light emitting element groups EG are arranged in a staggered manner in two rows in a longitudinal direction LGD with a pitch Dg, and from the light emitting elements E of the light emitting element group EG. The light passes through the head substrate 293 and is emitted from the head substrate surface 293-h.

  On the surface 293-h of the head substrate 293, spacers AS1 are arranged on both sides in the width direction LTD, and a lens array LA1 is installed on these spacers AS1 in the width direction LTD. On the back surface of the lens array LA1, a plurality of lenses LS1 are arranged in a zigzag pattern in the longitudinal direction LGD corresponding to the arrangement of the light emitting element groups EG. Accordingly, one lens LS1 is opposed to one light emitting element group EG. Incidentally, the lens LS1 has a convex shape with respect to the light emitting element group EG and is made of resin.

  Further, spacers AS2 are arranged on both sides of the width direction LTD on the surface of the lens array LA1, and the lens array LA2 is installed in the width direction LTD on these spacers AS2. On the back surface of the lens array LA2, a plurality of lenses LS2 are arranged in a zigzag pattern in the longitudinal direction LGD corresponding to the arrangement of the light emitting element groups EG. As a result, one lens LS2 is opposed to one light emitting element group EG. Incidentally, the lens LS2 has a convex shape with respect to the light emitting element group EG and is made of resin.

  Further, the line head 29 includes a light shielding member 295 between the head substrate 293 and the lens array LA1. The light shielding member 295 has five light shielding plates FP1 to FP5 arranged in the optical axis direction Doa. More specifically, the light shielding member 295 is provided with two spacers arranged on the head substrate surface 293-h with an interval in the width direction LTD, and a light shielding plate FP1 is installed on these spacers. ing. Further, the light shielding member 295 is provided with two spacers arranged on the surface of the light shielding flat plate FP1 with an interval in the width direction LTD. The light shielding flat plate FP2 is installed on these spacers, and other light shielding is similarly performed. The flat plates FP3 to FP5 are also stacked via spacers.

  In the light shielding plate FP1, a light guide hole D1 having a circular shape centered on the optical axis OA of the lenses LS1 and LS2 and penetrating in the optical axis direction Doa is formed for each light emitting element group EG. Thus, on the light shielding flat plate FP1, a plurality of light guide holes D1 are arranged in a zigzag pattern in the longitudinal direction LGD corresponding to the arrangement of the light emitting element groups EG. Similarly, for each of the other light shielding flat plates FP2 to FP5, light guide holes D2 to D5 are arranged in a zigzag pattern in the longitudinal direction LGD corresponding to the arrangement of the light emitting element groups EG. The diameter of the light guide hole D1 closest to the head substrate 293 is smaller than the diameters of the other light guide holes D2 to D5.

  Thus, the light guide holes D1 to D5 and the lenses LS1 and LS2 arranged in a line in the optical axis direction Doa face each light emitting element group EG. Accordingly, among the light emitted from each light emitting element E of the light emitting element group EG, the light that has passed through the light guide holes D1 to D5 is incident on the lenses LS1 and LS2 and is imaged. The imaging optical systems LS1 and LS2 have inversion / reduction imaging magnification (that is, the imaging magnification is a negative value and an absolute value is less than 1).

  The above is the schematic configuration of the line head 29. Next, a detailed configuration of the chip CP included in the line head 29 will be described with reference to FIGS. 3 and 4. Here, FIG. 3 is a partial plan view of the chip as seen from the optical axis direction. FIG. 4 is a diagram partially showing a cross-section in the width direction of the chip viewed from the longitudinal direction LGD. In FIG. 3, the members (D1) other than the members arranged on the chip CP are indicated by one-dot / two-dot chain lines, but this means that the light-emitting element E formed on the chip CP and each member (D1) This is to make it easier to understand the correspondence between

  The chip CP includes a silicon substrate SS having a rectangular shape having a length L1 in the longitudinal direction LGD and a width L2 (<L1) in the width direction LTD. For this silicon substrate SS, an organic EL as the light-emitting element E, a drive circuit DC that drives the light-emitting element E, a transfer circuit TC that transfers data to the drive circuit DC, and wiring that connects the drive circuit and the transfer circuit TC WL and the like are integrated and formed by a semiconductor process.

  More specifically, in the silicon substrate SS, three sets of light emitting element groups EG are formed side by side in the longitudinal direction LGD. Each light emitting element E of these light emitting element groups EG is a so-called top emission type organic EL, and emits light with an equal or substantially equal emission spectrum. A sealing thin film SL that seals the light emitting element E is formed on the silicon substrate SS in order to block the light emitting element E, which is an organic EL, from moisture and the like. At this time, in order to prevent moisture from entering between the sealing thin film SL and the silicon substrate SS, it is preferable to form the sealing thin film SL around the light emitting element E with a certain margin. Specifically, a margin of about 0.5 [mm] to 2 [mm] is appropriate. Note that, as in the present embodiment, by arranging a plurality of light emitting element groups EG in a discrete manner, the distance from the end of the chip CP to the light emitting element group EG can be secured, and the light emitting element group EG to the chip CP can be secured. The sealing thin film SL can be provided with a sufficient margin between the ends.

  In the silicon substrate SS, the drive circuit DC disposed so as to overlap the light emitting element E is formed in the lower layer of each light emitting element E (that is, the light emitting element E and the drive circuit DC are stacked). In other words, the drive circuits DC arranged in a zigzag pattern in the longitudinal direction LGD at the light emitting element pitch Pe are formed in the lower layer of the light emitting element group EG. Thus, the strip-like drive circuit DC that is long in the width direction LTD is extended from each light emitting element E to the outside of the width direction LTD. Thus, by using the top emission type organic EL as the light emitting element E, the light emitting element E can be formed directly above the drive circuit DC. For this reason, it is not necessary to provide a space between the light emitting elements E in order to secure the arrangement area of the drive circuit DC, and the light emitting elements E can be arranged at high density. The driving circuit DC is composed of a transistor that drives the light emitting element E and a capacitor that holds a voltage applied to an input terminal of the transistor.

  Further, transfer circuits TC extending in the longitudinal direction LGD are formed on both sides of the light emitting element group EG in the width direction LTD, and each drive circuit DC and the transfer circuit TC are electrically connected by the wiring WL. Further, terminals TM are formed on the silicon substrate for exchanging signals with the outside. Accordingly, when the transfer circuit TC supplies the data input from the terminal TM to the drive circuit DC via the wiring WL, the drive circuit DC causes the light emitting element E to emit light according to the data.

  The silicon substrate SS configured as described above is bonded to the back surface of a glass head substrate 293 (glass substrate) by COG (chip on glass). Thus, by bonding the silicon substrate SS to the head substrate 293, the deformation of the silicon substrate SS is suppressed by the head substrate 293, and the sealing of the light emitting element E can be suppressed from being broken by the deformation of the silicon substrate SS. In particular, when the head substrate 293 has a function of suppressing deformation of the silicon substrate SS, it is not necessary to separately provide a member such as a cover glass for the function, and the entire line head 29 can be thinned. Further, there is an advantage that the wiring provided on the head substrate 293 and the wiring electrode provided on the silicon substrate SS can be easily connected. In the configuration in which the silicon substrate SS is bonded to the head substrate 293, the light emitting element E of the silicon substrate SS can be positioned with reference to the head substrate 293. However, in order to take advantage of this advantage, It is preferable to maintain the strength of the head substrate 293 by setting the thickness to 0.3 [mm] to 1.5 [mm].

  In this embodiment, the relationship between the opening portion of the light guide hole D1 opening in the light emitting element group EG formed in the silicon substrate SS and the silicon substrate SS is set as follows. That is, when viewed from the optical axis direction Doa (the direction of the light guide hole D1), the opening of the light guide hole D1 is smaller than the silicon substrate SS, and the entire opening of the light guide hole D1 is located inside the silicon substrate SS. is doing. In other words, when viewed from the optical axis direction Doa, the diameter Rd of the opening of the light guide hole D1 is shorter than the long side length L1 and the short side length L2 of the silicon substrate SS. The silicon substrate SS protrudes outward from the entire opening. And as a result of having comprised in this way, there exist the following effects.

  FIG. 5 is a diagram for explaining the effect of the embodiment, and partially shows a cross section of the line head 29 in the width direction LTD. In the “comparative form” shown in the lower part of the figure, the length L2 of the silicon substrate SS is smaller than the diameter Rd of the opening of the light guide hole D1, and the opening of the light guide hole D1 is viewed from the optical axis direction Doa. It protrudes outside the silicon substrate SS. As a result, the stray light LT traveling toward the opening of the light guide hole D1 passes through the head substrate 293 so as to pass through the side of the silicon substrate SS, and then enters the opening. Therefore, when this stray light LT is incident on the imaging optical systems LS1 and LS2, there is a possibility that a ghost is caused. On the other hand, in this embodiment, when viewed from the optical axis direction Doa (the direction of the light guide hole D1), the opening of the light guide hole D1 is smaller than the silicon substrate SS and is disposed inside the silicon substrate SS. Therefore, as shown in the “embodiment” of FIG. 5, most of the stray light LT traveling toward the opening of the light guide hole D1 of the light shielding member is reflected by the silicon substrate SS and does not enter the head substrate 293. . Thus, in this embodiment, the occurrence of ghost can be suppressed.

  In the above-described embodiment, since the light emitting element E (organic EL) and the drive circuit DC are integrated on the silicon substrate SS, it is not necessary to provide members constituting the drive circuit DC other than the silicon substrate SS, and the line head 29 It becomes easy to save the space.

  In the above embodiment, the absolute value of the imaging magnification of the imaging optical system is less than 1. Therefore, it is easy to improve the performance of the drive circuit DC. That is, the pitch Pe of two adjacent light emitting elements E, the pitch Psp of two spots SP formed by the light emitting elements E emitting light, and the imaging magnification β of the imaging optical system are Pe / | Although β | = Psp is satisfied, Pe> Psp is satisfied under the condition of | β | <1. That is, the pitch Pe of the light emitting elements E is larger than the pitch Psp of the spots SP. This means that high resolution can be obtained even if the light emitting elements E are arranged at a relatively large pitch Pe. Therefore, while maintaining high resolution, the arrangement pitch of the drive circuits DC provided for the light-emitting elements E can be increased as well, and the drive circuit DC is enlarged to improve the performance of the drive circuit DC. Is easy.

Configuration of Image Forming Apparatus Next, an example of an image forming apparatus to which the line head 29 described in the above embodiment can be applied will be described. FIG. 6 is a diagram illustrating 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. 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 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, 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. 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. Further, the sealing thin film SL corresponds to the “sealing member” of the present invention, the silicon substrate SS corresponds to the “silicon substrate” of the present invention, and the head substrate 293 corresponds to the “light transmissive substrate” of the present invention. The light guide hole D1 corresponds to the “hole” of the present invention, the light shielding member 295 corresponds to the “light shielding member” of the present invention, and the imaging optical systems LS1 and LS2 correspond to the “optical system” of the present invention. The drive circuit DC corresponds to the “drive circuit” of the present invention, and the wiring WL corresponds to the “wiring” 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 chip CP can be modified to the one shown in FIG. 8 or FIG. Here, FIG. 8 and FIG. 9 are diagrams showing modifications of the chip, and partially show a cross section in the width direction of the chip as viewed from the longitudinal direction LGD. In the modification shown in FIGS. 8 and 9, the silicon substrate SS is bonded to the cover glass 294 by bonding means (not shown) such as COG, and one chip CP is constituted by the silicon substrate SS and the cover glass 294. Yes. In the modification shown in FIG. 8, the chip CP is supported by the head substrate 293 by bonding the front surface of the cover glass 294 to the head substrate back surface 293-h. In the modification shown in FIG. 9, the chip CP is supported by the head substrate 293 by bonding the back surface 293-t of the silicon substrate SS to the head substrate surface 293-h.

  Further, various modifications can be made to the arrangement of the light emitting elements E constituting the light emitting element group EG, for example, as shown in FIGS. 10A and 10B. Here, FIG. 10 is a diagram showing a modified example of the arrangement of the light emitting elements constituting the light emitting element group. In the drawing, four sets of six light emitting elements E (light emitting element rows) arranged linearly in the longitudinal direction LGD are provided in the width direction LTD to constitute one light emitting element group EG. In FIG. 10A, the drive circuit DC is formed at a position off the light emitting element group EG on both sides in the width direction LTD. On the other hand, in FIG. 10B, the drive circuit DC is divided into two parts. Specifically, the drive circuit DC is divided into a large transistor Tr that supplies a drive signal to the light emitting element E and other parts. The large transistor Tr is stacked on the light emitting element E, and the parts other than the large transistor Tr are arranged at positions away from the light emitting element group EG in the width direction LTD.

  Further, as shown in FIG. 11, the light emitting element group EG may be decentered outside the width direction LTD with respect to the optical axis OA of the imaging optical systems LS1 and LS2. Here, FIG. 11 is a diagram showing a modification of the arrangement relationship between the imaging optical system and the light emitting element groups. Specifically, in FIG. 11, the normal line GC of the silicon substrate SS passing through the geometric center of gravity of the light emitting element group EG is decentered by an eccentric amount Δd outside the width direction LTD with respect to the optical axis OA. As a result, since the two silicon substrates SS are separated from each other in the width direction LTD, each silicon substrate SS can be enlarged to sufficiently secure a region for forming the drive circuit DC. As a result, the capacity of the drive circuit DC can be improved by increasing the size of the drive circuit DC.

  Furthermore, the distance Δsp between the spots SP can be shortened by using the imaging optical systems LS1 and LS2 having reversal characteristics after decentering the light emitting element group EG in this way. Therefore, the following effects can be obtained. 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, it is possible to reduce the difference in exposure and development time between the spots SP, thereby suppressing the occurrence of such printing unevenness. .

  In addition to the above, the configuration of FIG. 11 also has the following effects. That is, when a line-shaped latent image parallel to the main scanning direction MD is formed by the imaging optical systems at different positions in the sub-scanning direction SD, the imaging optical systems LS1, LS2 upstream of the sub-scanning direction SD. The spot SP is formed by the above, and then the spot SP is formed by the imaging optical systems LS1 and LS2 on the downstream side in the sub-scanning direction SD after a predetermined time ΔT, so that the portion exposed by each spot SP is aligned in the main scanning direction MD. Arrange them in parallel. At this time, the speed of the surface of the photosensitive drum 21 fluctuates during the predetermined time ΔT, thereby causing a step in the line latent image. On the other hand, by reducing the distance Δsp between the spots SP, the time ΔT can be shortened and the step of the line latent image due to the speed fluctuation on the surface of the photosensitive drum 21 can be suppressed.

  When the line head 29 is attached to the photosensitive drum 21 so as to be shifted in the sub-scanning direction SD, the surface of the photosensitive drum 21 is cylindrical, so that each imaging optical system The distance to the surface of the photosensitive drum 21 is different. As a result, the size of the spot SP formed by each imaging optical system is also different, which may cause a density difference in the formed image. On the other hand, by reducing the distance Δsp between the spots SP, it is possible to suppress the difference in size of the spots SP and to suppress such a density difference.

  The configuration of the light shielding member 295 is not limited to the configuration in which the plurality of light shielding plates FP1 to FP5 are stacked as described above, and various modifications are possible. Therefore, a light guide hole penetrating in the optical axis direction Doa may be formed in one thick plate member, and this thick plate member may be used as the light shielding member 295.

  Further, the materials and the like of the respective parts (head substrate 293, lenses LS1, LS2, etc.) constituting the line head 29 are not limited to those described above, and materials other than those described above can be used.

  DESCRIPTION OF SYMBOLS 22 ... Photosensitive drum, 29 ... Line head, 293 ... Head board | substrate, 295 ... Light-shielding member, OA ... Optical axis, FP1-FP5 ... Light-shielding flat plate, D1-D5 ... Light guide hole, LS1, LS2 ... Lens, CP ... Chip SS ... Silicon substrate, DC ... Drive circuit, WL ... Wiring

Claims (7)

A silicon substrate on which an organic EL and a sealing member for sealing the organic EL are disposed;
A light-transmitting substrate that covers the organic EL and the sealing member of the silicon substrate and transmits light emitted from the organic EL;
The organic EL has an opening, and a hole through which the light transmitted from the organic EL through the light-transmitting substrate and incident on the opening passes is disposed, and the hole is viewed from the direction of the hole. A light shielding member having an opening smaller than the silicon substrate and disposed inside the silicon substrate;
An optical system for imaging light passing through the hole of the light shielding member;
An exposure head comprising:   The exposure head according to claim 1, further comprising a drive circuit disposed on the silicon substrate and driving the organic EL.   The exposure head according to claim 2, wherein the drive circuit and the organic EL are stacked on the silicon substrate.   4. The exposure head according to claim 2, wherein a wiring for supplying a signal for driving the organic EL to the driving circuit is disposed on the silicon substrate.   The exposure head according to any one of claims 2 to 4, wherein an absolute value of an imaging magnification of the optical system is less than 1.   The exposure head according to claim 1, wherein the light transmissive substrate is a glass substrate. A silicon substrate on which an organic EL and a sealing member for sealing the organic EL are disposed, a light-transmitting substrate that covers the organic EL and the sealing member of the silicon substrate and transmits light emitted from the organic EL; A hole that has an opening that opens in the organic EL and through which the light that passes through the light-transmitting substrate from the organic EL and enters the opening passes, and the opening as viewed from the direction of the hole An exposure head having a light shielding member that is smaller than the silicon substrate and disposed inside the silicon substrate, and an optical system that images light passing through the hole of the light shielding member;
A latent image carrier on which a latent image is formed by light imaged by the optical system of the exposure head;
An image forming apparatus comprising:

Images