JP2012125967A - Exposure head, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an electrical short circuit between the electrical wiring of a transparent substrate for supporting a substrate and a drive unit, in the configuration where a light emitting element and the drive unit for driving the element are arranged on the same substrate.SOLUTION: An exposure head includes: a first light transmissive substrate with wiring; a second substrate, which has the light emitting element, and also which is supported by the first substrate while directing the light emitting element to the first substrate; the drive unit, which is arranged at the second substrate, and which drives the light emitting element; and an insulating member arranged between the wiring of the first substrate and the drive unit of the second substrate.

Description

  The present invention relates to an exposure head that includes a substrate on which an organic EL is disposed and performs exposure using light from the organic EL. In particular, the substrate on which the organic EL is disposed is supported by a light-transmitting substrate and emitted from the organic EL. The present invention relates to an exposure head that performs exposure with light transmitted through a light-transmitting substrate.

  Patent Document 1 describes an optical printer head using an LED array chip on which an LED (Light Emitting Diode) as a light emitting element is formed. The optical printer head is provided with a transparent substrate on which terminal electrodes and other electric wirings are formed. The LED array chip is supported by being bonded to the transparent substrate via the terminal electrodes. Then, the LED emits light according to a signal input to the LED array chip via the terminal electrode. At this time, the LED array chip is bonded in a state where the LED is directed to the transparent substrate, and the light emitted from the LED passes through the transparent substrate and is then subjected to exposure of the photoreceptor and the like.

JP 2000-135814 A

  By the way, the drive part which drives a light emitting element (LED) can be formed in the same board | substrate (LED array chip) with a light emitting element. However, in such a configuration, since the drive unit provided on the substrate faces the transparent substrate, the drive unit and the electrical wiring of the transparent substrate may be electrically short-circuited.

  The present invention has been made in view of the above problems. In a configuration in which a light emitting element and a drive unit for driving the light emitting element are provided on the same substrate, the electrical wiring between the electrical wiring of the transparent substrate that supports the substrate and the drive unit is provided. The purpose is to provide technology to prevent short circuit.

  In order to achieve the above object, an exposure head according to the present invention includes a light-transmitting first substrate on which wiring is arranged, a light emitting element, and the light emitting element facing the first substrate. A second substrate supported by the first substrate; a driving unit disposed on the second substrate for driving the light emitting element; and a wiring between the first substrate and a driving unit for the second substrate. And an insulating member.

  In order to achieve the above object, an image forming apparatus according to the present invention has a light-transmitting first substrate on which wiring is arranged, a light emitting element, and the light emitting element is directed to the first substrate. A second substrate supported by the first substrate in a state, a driving unit disposed on the second substrate and driving the light emitting element, and between the wiring of the first substrate and the driving unit of the second substrate An exposure head having an insulating member disposed, and a latent image carrier on which a latent image is formed by exposure by the exposure head.

  In the invention thus configured (exposure head, image forming apparatus), an insulating member is disposed between the wiring of the first substrate and the driving unit of the second substrate. Therefore, the wiring of the first substrate and the driving unit of the second substrate are insulated by the insulating member, and an electrical short circuit between them is prevented.

  At this time, the insulating member is light transmissive and is disposed between the light emitting element and the first substrate, and the light emitted from the light emitting element is transmitted through the insulating member and then transmitted through the first substrate. It may be configured. In this manner, by using the light-transmissive insulating member, the insulating member can be extended between the light-emitting element and the first substrate without blocking light from the light-emitting element with the insulating member. As a result, it is possible to more reliably prevent an electrical short circuit between the driving unit that drives the light emitting element and the wiring of the first substrate.

  An organic EL can be used as the light emitting element. In this case, when the organic EL is sealed on the second substrate and a sealing member that transmits light from the organic EL is disposed, deterioration of the organic EL can be suppressed. However, if air is interposed between the sealing member and the insulating member, a lot of light is scattered at the interface between the sealing member and the air, and the utilization efficiency of light from the light emitting element is lowered. Therefore, the insulating member is preferably filled between the sealing member and the first substrate so as to have a refractive index larger than that of air. As a result, air is arranged to suppress light scattering at the interface of the sealing member, and the utilization efficiency of light from the light emitting element can be improved.

  Furthermore, the refractive index of the insulating member may be larger than the refractive index of the sealing member. Thereby, the scattering of the light at the interface of the sealing member can be reliably suppressed, and the decrease in the utilization efficiency of the light from the light emitting element can be improved more efficiently.

  As the insulating member, a light transmissive resin can be used.

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 width direction fragmentary sectional view which shows the silicon substrate of the state mounted in the head substrate. The top view which shows an example of the arrangement | positioning form of each wiring in a head substrate back surface. 1 is a diagram illustrating an example of an image forming apparatus to which a line head can be applied. The block diagram which shows the electric constitution of the apparatus of FIG. The figure which shows the modification of the filling method of transparent resin.

  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 293 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 pattern in the longitudinal direction LGD at the light emitting element pitch Pe are grouped to form a light emitting element group EG, and the plurality of light emitting element groups EG They 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 are mounted face-down on the back surface 293-t of the glass head substrate 293. As a result, a plurality of light emitting element groups EG facing the back surface 293-t of the head substrate 293 are arranged in a staggered manner in two rows at a pitch Dg in the longitudinal direction LGD, and each light emitting element 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. The chip CP includes a silicon substrate SS having a rectangular shape that is long in the longitudinal direction LGD and short in the width direction LTD. On the silicon substrate SS, an organic EL as the light emitting element E, a driving circuit DC for driving the light emitting element E, a transfer circuit for transferring data to the driving circuit DC, wiring, and the like are integrated and formed by a semiconductor process. .

  More specifically, in the silicon substrate SS, four sets of light emitting element groups EG are linearly arranged in the longitudinal direction LGD, and each of the both sides of the width direction LTD is sandwiched between the light emitting element groups EG. A plurality of terminals Ta are formed linearly in the 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. The silicon substrate SS is formed with a light-transmitting sealing thin film SL that seals the light-emitting element E in order to block the light-emitting element E, which is an organic EL, from moisture or oxygen (moisture or 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. However, the terminal Ta is not covered with the sealing thin film SL, and the electrical connection of the terminal Ta is ensured.

The sealing thin film SL is preferably a strong film of an inorganic material having gas barrier properties. Specifically, silicon nitride (Si ₃ N ₄ , refractive index: 2.00), silicon dioxide (SiO ₂ , refractive index: 1.54), aluminum oxide (alumina, AL ₂ O ₃ , refractive index: 1. 77) can be used. Here, the value of the refractive index is a value for the wavelength 650 [nm]. Although these materials sufficiently block moisture and the like even in a thin film, defects are likely to occur if they are too thin, and cracks are likely to occur if they are too thick, so thicknesses of several tens [nm] to several hundreds [nm] Is preferred. The sealing thin film SL is formed by plasma coating, sputtering, or the like. However, since the organic EL is weak against heat, it is preferable to use a film forming process with little temperature rise.

  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. Then, each driving circuit DC drives the light emitting element E to emit light according to data input via the terminal Ta.

  The silicon substrate SS configured as described above is flip-chip mounted on the back surface 293-t of the light-transmissive head substrate 293 (glass substrate) (FIG. 5). FIG. 5 is a partial cross-sectional view in the width direction showing the silicon substrate mounted on the head substrate. As shown in the figure, the silicon substrate SS is mounted face-down on the back surface 293-t of the head substrate 293 with the surface on which the light emitting element E is formed facing the back surface 293-t of the head substrate 293.

  More specifically, a plurality of terminals Tb are formed on the back surface 293-t of the head substrate 293 in one-to-one correspondence with the terminals Ta. A bump BP of a metal wire such as gold provided on the terminal Ta of the silicon substrate SS is pressure-bonded to the terminal Tb of the head substrate back surface 293-t. Thus, the terminal Ta of the silicon substrate SS and the terminal Tb of the head substrate back surface 293-t are electrically connected, and the silicon substrate SS is supported by the head substrate 293. Incidentally, it is preferable that the surface of the terminal Tb on the back surface 293-t of the head substrate is plated with gold.

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. 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 ensure the flatness of the head substrate 293 by setting the thickness to 0.3 [mm] to 1.5 [mm]. Further, since the head substrate 293 is made of glass having a small linear expansion coefficient of 3 to 8 × 10 ⁻⁶ , the linear expansion coefficient is the same as that of the lens arrays LA1 and LA2, and the relative position change due to the temperature change is suppressed. Stable exposure is possible regardless of the above.

  By the way, when operating the drive circuit DC so that the light emitting element emits light appropriately, power is supplied to the drive circuit DC, and further, a control signal for controlling light emission of the light emitting element E by the drive circuit DC is supplied to the drive circuit DC. It is necessary to supply. Therefore, in this embodiment, these wirings are provided on the back surface 293-t of the head substrate 293. Next, the arrangement of these wirings will be described.

  FIG. 6 is a plan view showing an example of an arrangement form of each wiring on the back surface of the head substrate. The figure shows a plan view from the normal direction of the head substrate back surface 293-t (which coincides with the optical axis direction Doa), and understands the correspondence between each wiring on the head substrate back surface 293-t and the chip CP. For ease of illustration, the chip CP and its constituent members (light emitting elements E) are shown together with broken lines. Note that since the terminal Ta of the chip CP overlaps the terminal Tb of the back surface 293-t of the head substrate, the notation of the terminal Tb is used instead of the notation of the terminal Ta.

  Further, in the terminal row composed of the terminals Tb linearly arranged in the longitudinal direction LGD, a space between the first terminal row and the light emitting element group EG is denoted by reference symbol A1, and the second terminal row and the light emission. A space between the element group EG is denoted by reference symbol A2, a space between the third terminal row and the light emitting element group EG is denoted by reference symbol A3, and the fourth terminal row and the light emitting element group EG A space A is designated by A4. Such notation is also used as appropriate in the following drawings.

  As described above, in the chip CP, the drive circuit DC is formed between the terminal Ta and the light emitting element group EG. Accordingly, the spaces A1 to A4 on the back surface 293-t of the head substrate are located directly above or substantially above the drive circuit DC. In the example of the wiring mode shown below, the line head 29 is slimmed down by effectively utilizing the spaces A1 to A4 provided on the drive circuit DC. Details are as follows.

  On the back surface 293-t of the head substrate, there are bus lines Lb1 and Lb2 through which control signals flow, cascade lines Lc1 and Lc2, which electrically connect chips CP adjacent in the longitudinal direction LGD, power supply lines VEL1 and VLE2, a ground line GND, and the like. Is provided. Further, in correspondence with the fact that a plurality of chips CP are arranged in a zigzag manner with two rows in the longitudinal direction LGD, in the example shown in FIG. 6, a row consisting of the chips CP constituting the first row and a second row are constituted. The wiring lines of the bus line, the cascade line, and the power source are divided by the row composed of the chips CP.

  Specifically, a bus line Lb1 mainly passing through the spaces A1 and A2 is provided for each chip CP in the first row, and the terminals Ta of these chips CP are connected to each other by the bus line Lb1. ing. In the first row, the chips CP adjacent to each other in the longitudinal direction LGD are electrically connected to each other by a cascade line Lc1 that mainly passes through the space A2. Further, for each chip CP in the first row, a power line VEL1 that mainly passes through the space A1 is provided, and a terminal Ta of each chip CP is connected to a common power line VEL1.

  On the other hand, a bus line Lb2 mainly passing through the spaces A3 and A4 is provided for each chip CP in the second row, and the terminals Ta of these chips CP are connected to each other by the bus line Lb2. In the second row, the chips CP adjacent in the longitudinal direction LGD are electrically connected to each other by a cascade line Lc2 that mainly passes through the space A3. Further, a power line VEL2 that mainly passes through the space A4 is provided for each chip CP in the second row, and a terminal Ta of each chip CP is connected to a common power line VEL2.

  The ground line GND is shared by the chips CP in the first and second rows. Specifically, the ground line GND is disposed so as to pass between the chip CP in the first row and the chip CP in the second row, and the terminal Ta of the chip CP in the first row and the second row is connected to this ground. It is connected to the line GND.

  As described above, in this embodiment, there are provided two substrates, the chip CP on which the light emitting element E is formed in the longitudinal direction LGD and the light transmissive head substrate 293. In the chip CP, a terminal Ta is arranged so as to sandwich the light emitting element group EG in the width direction LTD, and a terminal Tb is also arranged in the width direction LTD on the head substrate 293. Then, the terminal Ta and the terminal Tb are connected to each other, so that the chip CP is supported by the head substrate 293. In other words, the line head 29 is connected to these chips CP (silicon substrate SS). The head substrate 293 is stacked.

  Then, a light transmissive transparent resin TP is filled between the silicon substrate SS (chip CP) and the head substrate 293 (FIG. 5). The transparent resin TP is made of an insulating material and functions as the “insulating member” of the present invention. The transparent resin TP is provided so as to completely fill the space between each chip CP and the head substrate 293 except for the region where the bumps BP are formed, whereby the silicon substrate SS and the head substrate 293 are filled. Air is excluded from the gap, and each part of the silicon substrate SS and each part of the head substrate 293 are electrically insulated in regions other than the bumps BP. More specifically, the wirings Lb1, Lb2, Lc1, Lc2, VEL1, VEL2, etc. on the back surface 293-t of the head substrate and the drive circuit DC on the chip CP are opposed to each other in the optical axis direction Doa. Are electrically insulated by a transparent resin TP filled therebetween.

  The transparent resin TP is provided so as to cover the sealing thin film SL on the surface of the silicon substrate SS. Further, the transparent resin TP is filled between the silicon substrate SS and the head substrate 293, and is also filled into a gap Δcp between two silicon substrates SS adjacent in the width direction LTD. Further, the transparent resin TP protruding from the end of the silicon substrate SS is provided so as to go from the side of the silicon substrate SS to the back surface. And in this embodiment, the refractive index of transparent resin TP is larger than the refractive index of air, and is below the refractive index of sealing thin film SL.

As such a transparent resin TP, a general ultraviolet (UV) curable resin can be used, and an anaerobic adhesive, a two-component mixed adhesive, or a thermosetting adhesive can be used. When an adhesive other than the ultraviolet curable resin is used, there is an advantage that there is no possibility that the organic EL is deteriorated by ultraviolet rays irradiated to cure the transparent resin TP. Moreover, as a material of transparent resin TP, an epoxy resin (refractive index 1.55-1.6), an acrylic resin (refractive index 1.49), and a silicon resin (1.4-1.45) are suitable. In particular, when silicon nitride (Si ₃ N ₄ ) having a high refractive index is used, a material having a high refractive index (refractive index of 1.6 to 1.65) among the epoxy resins is preferably used for the transparent resin TP.

  As a method for filling such a resin, a method similar to the underfill generally used in flip chip mounting can be used. That is, after the bump BP of the silicon substrate SS and the electrode of the head substrate 293 are pressure-bonded, the transparent resin TP is poured from the gap between the silicon substrate SS and the head substrate 293 using surface tension. At this time, by keeping the viscosity of the transparent resin TP low, the transparent resin TP can be spread quickly on the surface of the silicon substrate SS. Further, by setting the viscosity of the transparent resin TP to 1000 [mPa · s] or less, preferably 100 [mPa · s] or less, it is possible to fill the transparent resin TP while suppressing entrainment of bubbles. Note that the gap filled with the transparent resin TP is determined by the height of the bump BP or the height at which the bump BP is crushed. A typical gold stud bump has a height of around 50 [μm], and when it is crimped and pressed, it collapses to about half of the height, so that a gap of about 20 [μm] is secured. Therefore, a resin having a low viscosity can sufficiently penetrate. In this embodiment, since the head substrate 293 is transparent, the transparent resin TP can be cured by irradiating light through the head substrate 293 after infiltrating the transparent resin TP.

  At this time, the transparent resin TP to be filled only needs to have transparency according to the wavelength to be used. For example, a photoconductor used in electrophotography has a high sensitivity to light of red to near-infrared wavelength (600 to 800 [nm]). Therefore, the transparent resin TP used in this embodiment has transparency to this wavelength. There is no problem even if it is slightly colored yellow when visually observed. Further, the internal transmittance of the resin shows a value per 10 [mm] of the transmission thickness, but in this embodiment, since the thickness of the transparent resin TP is thin, the value indicated as the internal transmittance is low. But in practice there are few problems. In general, since the absorption rate is proportional to an exponential function of thickness, for example, even if the internal transmittance at 10 [mm] thickness is 10 [%], the transmittance is about 99 [%] at a thickness of 50 [μm]. become. Thus, there is little problem if the transmission loss is 1%. Therefore, even if it looks yellow like a normal epoxy resin, there is no problem because the transmittance at a necessary wavelength is surely 10% or more.

  Since it is configured as described above, light emitted from the light emitting element E upon being driven by the drive circuit DC is transmitted through the sealing thin film SL, the transparent resin TP, and the head substrate 293 in this order, and then subjected to exposure. . In this embodiment, since the transparent resin TP having a refractive index larger than that of air is filled between the silicon substrate SS and the head substrate 293, the amount of light reflected by the back surface 293-t of the head substrate 293 is suppressed. It is possible to improve the light use efficiency. Moreover, the problem that the light reflected by the back surface 293-t of the head substrate 293 becomes stray light and causes ghost is also suppressed. Further, by filling the transparent resin TP between the silicon substrate SS and the head substrate 293, foreign matter can be prevented from entering directly above the light emitting element E of the silicon substrate SS, and the light emitted from the light emitting element E is foreign matter. Occurrence of the problem that the light utilization efficiency decreases due to scattering by the light is suppressed.

  As described above, in this embodiment, the wiring Lb1, Lb2, Lc1, Lc2, VEL1, VEL2, etc. of the head substrate 293 (first substrate) and the driving circuit DC (driving unit) of the chip CP (second substrate) ) Is filled with an insulating transparent resin TP. Therefore, the wirings Lb1, Lb2, Lc1, Lc2, VEL1, VEL2, etc. of the head substrate 293 are insulated from the drive circuit DC by the transparent resin TP, and an electrical short circuit between them is prevented.

  Further, in this embodiment, the transparent resin TP provided as an insulating member is light transmissive and extends between the light emitting element group EG and the head substrate 293, and each light emitting element of the light emitting element group EG is provided. The light emitted from E is transmitted through the transparent resin TP and then transmitted through the head substrate 293. As described above, by using the light-transmitting transparent resin TP as the insulating member, the insulating member can be extended between the light emitting element and the head substrate 293 without blocking the light from the light emitting element E by the insulating member. As a result, it is possible to more reliably prevent an electrical short circuit between the drive circuit DC that drives the light emitting element E and the wirings Lb1, Lb2, Lc1, Lc2, VEL1, VEL2, etc. of the head substrate 293.

  In particular, in a configuration using an organic EL as the light emitting element E, it is particularly preferable to reliably prevent an electrical short circuit as described above. In other words, the driving voltage of a normal red to infrared LED is 2 to 3 [V], whereas the driving voltage of an organic EL reaches a high voltage of 5 to 20 [V]. This is because short-circuiting is likely to occur and more reliable insulation is required.

  Further, as shown in FIGS. 5 and 6, a large number of wirings are provided at a narrow pitch in the space on the head substrate 293 corresponding to the region between the light emitting element E (light emitting portion) and the terminal of the silicon substrate SS. It has been. A drive circuit DC for driving the light emitting element E is provided on the silicon substrate facing the substrate. Therefore, in the configuration described above, there is a higher risk of short circuit between these wirings and the drive circuit DC than when there is no wiring on the head substrate 293 or when a resist film is provided like a glass epoxy substrate, It is effective to add an insulating function to the transparent resin TP.

  Further, the sealing thin film SL is provided on the silicon substrate SS, but at least in the vicinity of the terminal, the sealing thin film SL is not provided in order to ensure electrical connection. Further, even when a protective film is provided on the above wiring in the head substrate 293, a protective film cannot be provided in the vicinity of the terminals. Therefore, it is particularly preferable to fill the insulating transparent resin TP in the vicinity of these terminals.

Incidentally, it is preferable that the transparent resin TP has a volumetric low efficiency of at least 10 ⁹ Ω · cm in order to reliably exhibit insulation. In particular, when the transparent resin TP is formed as a thin film as described above, the transparent resin TP preferably has a low volume efficiency of 10 ¹² Ω · cm or more.

  In this embodiment, the chip CP is provided with a sealing thin film SL that seals the organic EL that is the light emitting element E and transmits light from the organic EL, thereby suppressing deterioration of the organic EL. It is possible. However, if air is interposed between the sealing thin film SL and the transparent resin TP, a lot of light is scattered at the interface between the sealing thin film SL and the air, and the utilization efficiency of light from the light emitting element E is lowered. On the other hand, in this embodiment, the transparent resin TP is filled between the sealing thin film SL and the head substrate 293 and has a refractive index higher than that of air. Thereby, air is arranged to suppress light scattering at the interface of the sealing thin film SL, and the utilization efficiency of light from the light emitting element E is improved.

  In this embodiment, transparent resin TP is used as a filling member. Therefore, since the transparent resin TP also functions as an adhesive for bonding the silicon substrate SS and the head substrate 293, the mechanical strength of the line head 29 can be improved by firmly fixing the silicon substrate SS and the head substrate 293. it can.

  In this embodiment, the transparent resin TP is filled between the silicon substrate SS and the head substrate 293, and is also filled in the gap Δcp between two adjacent silicon substrates SS. Thereby, these two silicon substrates SS can be firmly fixed to the head substrate 293, and the mechanical strength of the line head 29 can be improved. In addition, by enlarging the transparent resin TP in the gap Δcp of the silicon substrate SS and the surrounding portion in this way, it becomes possible to increase the sealing distance from the outside world to the light emitting part, and in the event of moisture intrusion Even if it begins, sealing performance improves more by earning approach time.

  In this embodiment, a glass head substrate 293 is used, and a transparent resin TP having a refractive index very close to the refractive index of glass (about 1.5) is used between the head substrate 293 and the silicon substrate SS. Buried. Therefore, the reflection of light at the interface between the transparent resin TP and the head substrate 293 is suppressed, and in this respect also, the light use efficiency is improved.

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. The head substrate 293 corresponds to the “first substrate” of the present invention, the sealing thin film SL corresponds to the “sealing member” of the present invention, and the silicon substrate SS or the chip CP corresponds to the “second substrate” of the present invention. The wiring Lb1, Lb2, Lc1, Lc2, VEL1, VEL2, etc. are conceived as the “wiring” of the present invention, the drive circuit DC is conceived as the “driving part” of the present invention, and the transparent resin TP is the main substrate. It corresponds to the “insulating member” of the 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, for example, the refractive index of the transparent resin TP and the refractive index of the head substrate 293 can be configured to be equal. As a result, light reflection at the interface between the transparent resin TP and the head substrate 293 can be suppressed, and light utilization efficiency can be improved.

  The sealing thin film SL is sufficiently effective even if it is composed of a single inorganic layer as described above, but in order to avoid the cracks as described above more reliably, an inorganic layer and an organic layer It is effective to form the sealing thin film SL by alternately stacking layers. As the organic layer, resins that are stable with respect to the environment and temperature, such as acrylic, epoxy, and silicon, are suitable. Further, by forming the organic film relatively thick as several [μm], the unevenness caused by the light emitting element E, the wiring, or the drive circuit DC is flattened, and there is a step in the inorganic layer formed on the organic film. It can be prevented from occurring. As a result, the generation of defects in the sealing thin film SL due to this step can be suppressed. Further, the organic layer also functions as a buffer layer for preventing cracks due to shrinkage of the film itself when forming the inorganic layer. Moreover, since the refractive index of the material used for the organic film is about 1.4 to 1.6, the difference in refractive index from the inorganic layer is small, and the reflection of light at the interface with the inorganic layer is small.

  Further, the filling method of the transparent resin TP is not limited to the above, and for example, a direction as shown in FIG. 8 can be adopted. Here, FIG. 8 is a figure which shows the modification of the filling method of transparent resin. In this filling method, a transparent resin is placed on the back surface 293-t of the head substrate 293 before mounting the silicon substrate SS (the state (A) in the figure), and the silicon substrate SS is mounted when the silicon substrate SS is mounted. The transparent resin TP is spread with SS (state (B) in the figure). In this case, a transparent resin TP having a relatively high viscosity can be used.

  Further, the refractive index of the transparent resin TP is not limited to the above. Therefore, the refractive index of the transparent resin TP may be larger than the refractive index of the sealing thin film SL. Thereby, the scattering of the light at the interface of the sealing thin film SL can be reliably suppressed, and the decrease in the utilization efficiency of the light from the light emitting element E can be improved more efficiently.

  Further, the arrangement of the wirings Lb1, Lb2, Lc1, Lc2, VEL1, VEL2, etc. is not limited to the above, and various changes can be made.

  Further, the arrangement mode of the light emitting element group EG and the lenses LS1, LS2 is not limited to the above, and other arrangement modes such as a three-row zigzag pattern can be adopted. Further, the number and arrangement of the light emitting elements E constituting the light emitting element group EG can be changed as appropriate.

  22 ... photosensitive drum, 29 ... line head, 293 ... head substrate, 295 ... light shielding member, SS ... silicon substrate, CP ... chip, SL ... sealing thin film, TP ... transparent resin (insulating member), Lb1, Lb2 ... bus Line, Lc1, Lc2 ... Cascade line, VEL1, VEL2 ... Power supply line, DC ... Drive circuit, E ... Light emitting element (organic EL)

Claims (7)

A light-transmissive first substrate on which wiring is arranged;
A second substrate having a light emitting element and supported by the first substrate in a state where the light emitting element faces the first substrate;
A driving unit disposed on the second substrate to drive the light emitting element;
An insulating member disposed between the wiring of the first substrate and the driving unit of the second substrate;
An exposure head comprising:   The insulating member is light transmissive and is disposed between the light emitting element and the first substrate, and light emitted from the light emitting element is transmitted through the insulating member and then transmitted through the first substrate. The exposure head according to claim 1.   The exposure head according to claim 2, wherein the light emitting element is an organic EL, and a sealing member that seals the organic EL and transmits light from the organic EL is disposed on the second substrate.   The exposure head according to claim 3, wherein the insulating member is filled between the sealing member and the first substrate and has a refractive index higher than that of air.   The exposure head according to claim 4, wherein a refractive index of the insulating member is larger than a refractive index of the sealing member.   The exposure head according to claim 1, wherein the insulating member is a light transmissive resin. A second substrate having a light-transmitting first substrate on which wiring is arranged and a light-emitting element, and being supported by the first substrate in a state where the light-emitting element faces the first substrate; An exposure head having an insulating member disposed between the wiring of the first substrate and the driving unit of the second substrate;
A latent image carrier that is exposed by the exposure head to form a latent image; and
An image forming apparatus comprising:

Images