JP5055927B2 - Light emitting unit and printing apparatus - Google Patents

Description

  The present invention relates to a light emitting unit and a printing apparatus that use a light emitting element as a light source, and more particularly to a light emitting unit and a printing apparatus that use an organic EL element as a light source.

2. Description of the Related Art Conventionally, an EL light emitting unit using an organic EL element as a light source is known, and is used for an exposure device in a printing apparatus, for example. As a technique related to this, for example, Patent Document 1 discloses an exposure apparatus and an image forming apparatus including an organic EL element. In the technique disclosed in Patent Document 1, an organic EL element and a photoconductor are installed at a certain distance through a lens, and static light is placed on the photoconductor by focused light from the organic EL element. An electrostatic latent image is formed.
JP 2004-327217 A

  By the way, a printing apparatus that uses an EL light emitting unit that uses an organic EL element as a light source for exposure has a problem peculiar to the organic EL element. In other words, in order to obtain a light amount necessary for a photoconductor in a printing apparatus or the like, when using an organic EL element whose emission intensity is originally weak, the exposure time must be lengthened, resulting in a slow printing time. End up. Here, if the instantaneous emission intensity of the organic EL element is increased in order to shorten the printing time, the printing time can be shortened, but the life of the organic EL element is shortened by overcurrent control. The technique disclosed in Patent Document 1 does not solve such a problem.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a light emitting unit and a printing apparatus that can obtain a sufficient amount of light for exposure in a printing apparatus or the like.

In order to achieve the above object, the light emitting unit according to the first aspect of the present invention comprises:
A plurality of light emitting elements formed on a substrate and emitting light in an upward or downward direction;
A waveguide that condenses light emitted from the light emitting element in the lateral direction and exits from the exit end face ;
An insulating layer provided between the light emitting element and the waveguide;
A clad part having a refractive index lower than that of the waveguide;
I have a,
The waveguide includes an inclined surface that is inclined at a predetermined angle with respect to the light emitting surface of the light emitting element at an interface with the cladding portion at a position corresponding to the light emitting surface of the light emitting element, and one end of the inclined surface. A first waveguide portion provided with a first reflective film on a horizontal plane parallel to a light emitting surface of the light emitting element at an interface with the clad portion at a position facing the emission end face; And a second waveguide part provided with no reflective film at an interface with the cladding part from one end on the exit end face side to the exit end face .

It is preferable that a second reflective film is provided between the first waveguide portion of the waveguide and the insulating layer .

It is preferable that the first reflective film is provided on an upper surface and a side surface of the first waveguide portion .

  The light emitting elements are preferably arranged in the main scanning direction, respectively, and the light emitting surface of the light emitting elements is preferably wider in the direction perpendicular to the main scanning direction than in the main scanning direction.

  The light emitting unit can be applied to a printing apparatus.

  According to the present invention, a sufficient amount of light for exposure in a printing apparatus or the like can be obtained.

  Hereinafter, an EL light emitting unit according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating an example of a configuration of a printing apparatus using an EL light emitting unit according to the present embodiment. First, as shown in FIG. 1, a printing apparatus using an EL light emitting unit according to the present embodiment includes a photosensitive drum 1, an EL light emitting unit 2A according to the present embodiment, and a rod lens array 2B. The image forming apparatus includes a unit 2, a charging roller 3, an eraser light source photoconductor 4, a cleaning member 5, a developing device 6 including a developing roller 6 a, a transfer roller 8, a fixing roller 9, and a conveyance belt 11. . Note that reference numeral 7 denotes printing paper.

  The photoreceptor drum 1 is a negatively charged OPC (Organic Photo Conductor) photoreceptor (organic photoreceptor). In view of this, the charging roller 3 is a negative charger. The developing device 6 is a developing device for developing with negatively charged toner. The EL light emitting unit 2A is configured by arranging a plurality of organic EL elements in an array, as will be described in detail later.

  By the way, in the printing apparatus shown in FIG. 1, printing is roughly performed by the following processes. First, when the charging roller 3 comes into contact with the surface of the rotating photosensitive drum 1, the contacted surface of the photosensitive drum 1 is uniformly charged with a negative potential. Subsequently, the EL light emitting section 2A irradiates the photosensitive drum 1 with light through the rod lens array 2B, and an electrostatic latent image is formed on the photosensitive drum 1. Thereafter, toner is attached to the electrostatic latent image by the developing device 6. Then, the toner attached to the electrostatic latent image is transferred to the printing paper 7 by the transfer roller 8. Hereinafter, such a printing process will be described in detail.

  First, the photosensitive drum 1 is initialized to a negative potential supplied from a charging power source (not shown) and relatively close to or equal to a developing voltage output from a developing device 6 described later. A charging voltage is applied by the charging roller 3. As a result, the peripheral surface of the photosensitive drum 1 is uniformly negatively charged and is initialized in terms of potential (becomes an initialized charging state).

  Then, optical writing (exposure) according to the printing information is performed on the photosensitive drum 1 whose peripheral surface is in the initialized charging state by the EL light emitting unit 2A. As a result, the initialization charging portion that remains in the initialization charged state because no exposure is performed, and the exposure charging voltage of about −50 (V) that is a negative potential relatively higher than the initialization charging portion by the exposure. Is formed on the peripheral surface of the photosensitive drum 1.

  Here, the toner charged in the developing unit 6 and charged to a weak negative potential is rotated and conveyed by the developing roller 6a to the opposing portion between the developing roller 6a and the photosensitive drum 1. At this time, the developing roller 6a is applied with a developing voltage of about -250 (V), which is lower than the exposure charging unit, from a power source (not shown). Therefore, the exposure charging unit of about −50 (V) of the electrostatic latent image on the photosensitive drum 1 has a potential of about 200 (V) higher than the development voltage, and the initialization charging unit Is a voltage whose absolute value is sufficiently smaller than 200 (V).

  Due to the difference in potential difference from the developing voltage in these electrostatic latent images, the exposure charging portion in the electrostatic latent image that has a positive polarity relative to the developing roller 6a is charged negatively. On the other hand, a toner image does not adhere to the initialization charging portion because an electric field that attracts the toner electrostatically does not occur in the initialization charging portion. The toner image is conveyed to a transfer portion where the photosensitive drum 1 and the transfer roller 8 face each other by the rotation of the photosensitive drum 1.

  The toner adhesion amount (developed image density) in the toner image formed as described above is generated according to the exposure amount of the photosensitive drum 1 by the EL light emitting unit 2A. Is determined by the potential difference between the potential on the peripheral surface of the toner and the developing voltage.

  By the way, as described above, when the toner image is transported to the transfer unit, the printing paper 7 is transported to the transfer unit by the transport belt 11. In the transfer unit, the toner image is transferred onto the printing paper 7 by the transfer roller 8. The printing paper 7 to which the toner image is transferred in this way is further conveyed downstream, and after the toner image is thermally fixed by the fixing roller 9, the printing paper 7 is discharged to the outside of the printing apparatus. The

  Hereinafter, the basic structure of the EL light emitting unit 2A will be described with reference to FIGS. Here, the EL light emitting unit 2A includes an organic EL element 20A that mainly emits light, a light guide unit 50 that sets the traveling direction of light emitted by the organic EL element 20A to a predetermined direction, and emits the light. It mainly comprises a drive circuit unit 40 that electrically controls light emission of the organic EL element 20A.

  The organic EL element 20A is formed on a substrate 21 such as glass as shown in FIG. 2, and is sealed by a sealing substrate 28 such as glass. Specifically, as the organic EL element 20A on the substrate 21, a light-reflective anode electrode 23, a hole transport layer (HTL) 24, a light-emitting layer 25, an electron transport layer (ETL) 26, and a light-transmissive cathode The electrode 27 is formed in this order. Here, the hole transport layer 24, the light emitting layer 25, and the electron transport layer (ETL) 26 are organic EL layers made of an organic compound. The organic EL layer is not limited to the above, and may be, for example, a hole transport layer and an electron transport light emitting layer, or only a hole transport / electron transport light emitting layer, or a hole transport light emitting layer and an electron transport layer. In addition, a carrier transport layer may be appropriately interposed therebetween, or a combination of other carrier transport layers may be used.

  The anode electrode 23 is made of a reflective metal layer such as an aluminum alloy provided on the lower layer side and a transparent electrode material such as tin-doped indium oxide (ITO) or zinc-doped indium oxide provided on the upper layer side. It may be a laminated structure with a transparent conductive metal oxide layer or a single layer of a reflective metal layer such as an aluminum alloy.

  The cathode electrode 27 is a laminated structure of an electron injection layer having a low work function such as barium, magnesium, lithium, etc. provided on the lower layer side, and a transparent conductive metal oxide layer similar to the above provided on the upper layer side. It may be.

  Then, by applying a predetermined voltage between the anode electrode 23 and the cathode electrode 27, holes are injected from the anode electrode 23 and electrons are injected from the cathode electrode 27 into the light emitting layer 25. In the light emitting layer 25, holes and electrons recombine to emit light. The light hν100 generated by this light emission passes through the light-transmitting cathode electrode 27 and is completely diffused and radiated upward.

  By the way, in the present embodiment, the exposure unit 2 composed of the EL light emitting unit 2A and the rod lens array 2B causes a small-diameter light on the photosensitive drum 1 that is separated from the exposure unit 2 by a millimeter order distance. Create a light beam that forms spots and resolves each dot. Hereinafter, the detailed configuration of the exposure unit 2 will be described with reference to FIG.

  In the EL light emitting section 2A, a plurality of the organic EL elements 20A are arranged in an array. Here, the organic EL element 20 </ b> A exists between the substrate 21 and the sealing substrate 28, and the light whose traveling direction is controlled by the light guide unit 50 is the light of the substrate 21. The light is emitted from the emission region 33 to the outside of the substrate 21. Therefore, although the organic EL element 20A is not shown in FIG. 3, since the organic EL element 20A and the light emitting region 33 have a one-to-one correspondence, the arrangement of the organic EL elements 20A is as follows. It can be easily guessed from the figure.

  That is, a plurality of EL light emitting sections 2A are arranged in the main scanning direction of the exposure scanning on the photosensitive drum 1 shown in FIG. 1 (the width direction of the photosensitive drum 1, that is, the width direction of the printing paper 7). The organic EL element 20A is disposed to form an organic EL array. If the printing apparatus is a printing apparatus capable of printing at a printing density of 1200 dpi (dots / inch) to the full width using, for example, A4 size printing paper in the vertical direction, this organic EL array is approximately 14,000 pieces. The organic EL element is provided. A pulse voltage in accordance with print information output from a host device (not shown) is applied to each of the organic EL elements 20A. That is, each organic EL element 20A is selectively controlled to emit light.

  Each organic EL element 20A is electrically connected to the host device (not shown) by control cables 31A and 31B shown in FIG. Here, the connection method between the control cables 31A and 31B and the organic EL element 20A may be any connection method as long as it can drive the organic EL element 20A.

  Incidentally, the organic EL element 20A provided between the substrate 21 and the sealing substrate 28 is sealed around a sealing material 29 as shown in FIG.

  As described above, in the EL light emitting section 2A, a plurality of emission end faces 80 are provided in a line on the surface facing the rod lens array 2B and between the substrate 21 and the sealing substrate 28. ing. The emission end surface 80 is a region for emitting light emitted from the organic EL element 20A to the outside of the EL light emitting unit 2A, and is located on one end surface in the lateral direction of the EL light emitting unit 2A.

  Hereinafter, the detailed structure of the EL light emitting unit 2A according to the first embodiment will be described with reference to FIG.

  As shown in FIG. 4, the organic EL element 20 </ b> A is formed on the substrate 21 and sealed with the sealing substrate 28.

  Here, a clad optical layer 70 is formed on the sealing substrate 28 by resin coating as shown in FIG. A plurality of the light guide portions 50 are formed in the clad optical layer 70 (refractive index 1.5) so as to correspond to the respective organic EL elements 20A.

  The organic EL element 20A is formed on the substrate 21, and the drive circuit unit 40 is electrically connected to the organic EL element 20A.

  The light guide 50 includes a waveguide 57 including a waveguide A portion 55 and a waveguide B portion 56 formed in the clad optical layer 70, and a reflection film 59 that reflects light. The waveguide 57 is filled with a core optical resin (refractive index 1.6 or 1.7; details will be described later), and a reflective film 59 is provided on a part of the upper surface and side surfaces, and a part of the lower surface. A reflective film 60 is provided. The waveguide B portion 56 may be a quadrangular prism or a cylinder.

  As shown in FIG. 4, the waveguide 57 includes a waveguide A portion 55 and a waveguide A portion 56.

  The waveguide A portion 55 includes a portion corresponding to the surface facing the organic EL element 20A, and the upper surface is the organic EL light emitting surface 61 (the surface from which the light emission in the organic EL element 20A is emitted). A portion inclined at a predetermined angle with respect to the surface facing the waveguide 57 and a portion parallel to the organic EL light emitting surface 61, and the reflection film 59 or the reflection film 60 is formed. Corresponds to the part that has been.

  The waveguide B part 56 corresponds to a part of the waveguide 57 excluding the waveguide A part 55, where the reflective film 59 or the reflective film 60 is not formed, and the periphery is clad optical. Surrounded by layer 70.

  Here, the upper surface of the waveguide A portion 55 is parallel to the organic EL light emitting surface 61 and an inclined surface 55a inclined at a predetermined angle with respect to the organic EL light emitting surface 61 as shown in FIG. It has a horizontal surface 55b which is a surface.

  Further, as will be described in detail later, the waveguide 57 is formed by filling the recess with the recess in the recess imprinted in the clad optical layer 70 with the core optical resin.

  The drive circuit unit 40 includes a source electrode 41, a drain electrode 42, a gate electrode 43, a semiconductor 44, a gate insulating layer 45, and an interlayer insulating layer 46.

  The drive circuit unit 40 is not a feature of the present invention and will not be described in detail. However, in the present embodiment, the source electrode 42, the drain electrode 41, and the gate electrode in the drive circuit unit 40 are omitted. By outputting an image signal to the TFT transistor having 43, the light emitting section 2A emits light appropriately in a line shape, and a two-dimensional electrostatic latent image is formed on the surface of the photosensitive drum 1 rotating by repeating this operation. Form an image.

  That is, the organic EL element 20A is controlled to emit light by controlling the current value of the current that the TFT transistor passes through the organic EL element 20A. Here, for example, the cathode electrode 27 is fixed at zero volts, and the anode electrode 23 is electrically connected to the TFT transistor. The reflective layer 22 is a member that reflects incident light toward the reflective film 59, and may be formed by patterning together with the gate electrode 43 using a gate metal, or may not be formed separately. The anode electrode 23 can be replaced by providing light reflectivity.

  By the way, the cathode electrode of the organic EL element is generally easily oxidized by oxygen and moisture. Therefore, in order to prevent the oxidation of the cathode electrode of the organic EL element, for example, the following sealing treatment is performed so that the organic EL element does not directly contact moisture including the outside air.

  That is, a transparent sealing film 34 is formed on the organic EL element 20A and the drive circuit unit 40 as shown in FIG. In other words, the organic EL element 20 </ b> A and the drive circuit unit 40 are sealed by the sealing film 34. Further, a planarizing layer 35 is formed on the sealing film 34 with UV curable epoxy resin (refractive index 1.5) as shown in FIG. That is, the planarization process of the organic EL element 20 </ b> A and the drive circuit unit 40 is performed by the planarization layer 35 having the same refractive index as that of the clad optical layer 70. As described above, the periphery of the waveguide B portion 56 is surrounded by the clad optical layer 70 and the planarizing layer 35 having a lower refractive index than the waveguide B portion 56, and the waveguide B portion 56 is the core. An optical fiber structure is formed using the clad optical layer 70 and the planarizing layer 35 as clad portions.

  The anode electrode 23, the HTL 24, the light emitting layer 25, the ETL 26, and the cathode electrode 27 are formed between the substrate 21 and the sealing substrate 28, that is, inside the glass. Such a structure is not a structure for improving the light extraction efficiency, but the waveguide 57 can be a simple structure. Such a structure also has an advantage that the organic EL element 20A that is easily affected by oxygen and moisture can be hermetically sealed so as not to come into contact with outside air that may contain oxygen and moisture.

  Under the structure described above, the light emitted from the organic EL element 20A is the core optical resin of the waveguide 57 by the reflective film 59, the reflective film 60, and the reflective layer 22 in the waveguide A section 55. Reflected in. At this time, since the inclined surface 55a is inclined, the light is reflected so as to be condensed on the waveguide B portion 56 side. On the other hand, in the waveguide B portion 56, the light incident from the waveguide A portion 55 side is reflected by the difference in refractive index between the core optical resin and the clad optical layer 70 and the planarizing layer 35. The light is condensed on the exit end face 80 side.

  That is, in the waveguide B portion 56, a material having a high refractive index (the core optical resin) is applied in order to apply the principle that when light is applied to an interface with a substance having a different refractive index, the light is totally reflected. And a peripheral material having a low refractive index (the cladding optical layer 70 and the planarizing layer 35) as a cladding, and light in the material having a high refractive index (the core optical resin) is transmitted to the cladding optical layer 70 and The light is propagated by repeated total reflection at the interface with the flattening layer 35. Thus, the light reflected and collected by the waveguide 57 is radiated from the emission end face 80 toward the rod lens array 2B.

  Hereinafter, points to be noted when constructing the organic EL element 20A and the light guide unit 50 will be described. In the EL light emitting section 2A, as described above, a plurality of organic EL elements 20A are actually constructed in a line in the main scanning direction of exposure scanning on the photosensitive drum 1 shown in FIG. An array is formed.

  First, when the organic EL element 20A is constructed on the substrate 21, the shape when the organic EL element 20A (organic EL light emitting surface 61) is viewed from the sealing substrate 28 side is the sub-scanning direction. A rectangle with the (paper transport direction) as the longitudinal direction is formed. For this reason, even if the width of the organic EL light emitting surface 61 is a narrow pitch, the organic EL light emitting surface 61 can be increased. Thereby, the light emission area in the said organic EL element 20A can be enlarged. The intensity of the emitted light per unit area at the emission end face 80 is (area of the organic EL light emitting surface 61 of the organic EL element 20A) / (area of the emission end face 80). The light imparted with directivity by the inclined waveguide A portion 55 and the waveguide B portion 56 having the core and the clad can suppress the area of the emission end face 80 to be small. The intensity of the emitted light per unit area can be emitted.

  When forming the light guide 50, first, a wedge-shaped mold having the same type as that of the waveguide 57 shown in FIG. 5 is applied to the uncured clad optical layer 70 deposited on the sealing substrate 28. Then, the resin is cured to form concave portions imprinted in an array on the clad optical layer 70 formed on the sealing substrate 28. In this imprinting, the wedge-shaped waveguide 57 is imprinted in a concave so that the waveguide 57 has a one-to-one correspondence with the organic EL element 20A.

  Further, the waveguide A portion 55 is provided by forming the reflective film 59 on a part of the inner surface of the waveguide 57 formed by being imprinted concavely on the clad optical layer 70. At this time, the reflective film 59 is not formed by masking a portion where the reflective film 59 is not formed. Thus, the portion of the waveguide 57 where the reflective film 59 is not formed becomes the waveguide B portion 56.

  Then, a core optical resin (for example, polycarbonate: refractive index 1.6) is filled in the waveguide 57 formed by being imprinted concavely on the clad optical layer 70 and flattened. Thereafter, the sealing substrate 28 provided with the light guide 50 and the substrate 21 provided with the organic EL element 20A so that the light guide 50 and the organic EL element 20A face each other. Paste together. The reflective film 60 may be formed on the waveguide 57 before being attached, or may be formed on the planarizing layer 35.

  The array of the organic EL elements 20A is formed in the EL light emitting portion 2A by the formation process as described above. In addition to the method of bonding the organic EL element 20A and the light guide unit 50 after forming them in separate steps as described above, after forming the organic EL element 20A, the organic EL element 20A Of course, a method of laminating the light guide unit 50 may be adopted.

  Hereinafter, the output efficiency (end face output efficiency) from the output end face 80 of the organic EL element 20A and the light incidence of the rod lens array 2B when the output light quantity from the waveguide A section 55 is set as a reference (100%). The simulation result of the light incidence efficiency (rod lens surface efficiency) on the surface will be described with reference to the result list shown in FIG.

  The rod lens array 2B has a parabolic refractive index distribution from the center to the periphery. Usually, the rod lens array 2B is used by arranging cylindrical rod lenses regularly and precisely in one or two rows and sandwiched between two frame plates. Various rod lenses exist depending on optical parameters (working distance l0, incident angle θo, conjugate length TC, etc.), but a normal rod lens has a lens diameter of 0.5 to 1 mm and an incident angle θo of about 20 °. The working distance l0 is about 2 to 5 mm.

  Here, in this simulation, a rod lens having typical optical parameters having the following values was assumed. That is, as shown in FIGS. 6A and 6B, the rod lens array 2B is composed of two rows, the lens diameter is 0.5 mm, the incident angle is θo = 20 °, and the working distance lo is 2.5 mm. Was assumed. The amount of light that can be captured by the rod lens array 2B is assumed to be the amount of light incident on a circular photoreceptor having a diameter of 2 mm.

  Further, in the simulation, the size of the organic EL light-emitting surface 61 is 10 × 200 μm, the emission opening in the waveguide B portion 56 is 10 × 10 μm, and the waveguide length of the waveguide B portion 56 is 2 mm. .

  Then, as shown in FIG. 7, assuming the following three types of waveguides as the waveguide 57, a simulation for obtaining the end face output efficiency and the rod lens surface efficiency is performed.

Waveguide (1);
When the refractive index of the core optical resin is 1.7 and the refractive indexes of the cladding optical layer 70 and the planarizing layer 35 are 1.5, the end face output efficiency is about 80%, and the surface of the rod lens array 2B. The efficiency is about 15%.

Waveguide (2);
When the refractive index of the core optical resin is 1.6 and the refractive indexes of the cladding optical layer 70 and the planarizing layer 35 are 1.5, the end face output efficiency is about 40% and the surface of the rod lens array 2B. The efficiency is about 20%.

Waveguide (3);
In the waveguide using the reflection film instead of the refractive index difference over the entire waveguide, the end face output efficiency is about 10%.

  The following matters can be understood from the simulation results.

  (A) The end face output efficiency is better in the waveguide using the refractive index difference than in the waveguide using the reflective film.

  (B) In the waveguide using the refractive index difference, the larger the refractive index difference, the better the end face output efficiency.

  (C) In a waveguide using a refractive index difference, the smaller the refractive index difference, the narrower the directivity, so the surface efficiency of the rod lens array 2B is better.

  Therefore, in the simulation, it can be said that the waveguide having the parameter set in the “waveguide (2)” is the most efficient waveguide. Thus, in this embodiment, the directivity is controlled by adjusting the length of the waveguide and the refractive index difference between the core (core optical resin) and the clad (the clad optical layer 70 and the planarization layer 35). The efficiency of taking out the light emitted from the organic EL element to the outside can be optimized.

  Note that the relative refractive index difference between the core and the clad in the single-mode optical fiber is usually as small as about 0.3%. Therefore, when a light source having a narrow directivity, such as laser light, is used as the light source, and the incident angle of the light emitted from the light source to the optical fiber is larger than the total reflection angle, the light is only reflected on the core by total reflection. Propagate while passing. The point in the structure of such an optical fiber is that the relative refractive index difference between the core and the clad is small. Thereby, since the total reflection angle becomes large, the light travels almost straight.

  However, when an organic EL element is used as the light source, the light emitted from the organic EL element is diffused light, so that the straightness is improved with a very small relative refractive index difference in a normal optical fiber as described above. Light leakage from the core will increase. Therefore, in the present embodiment, by setting the relative refractive index difference to about 10%, light leakage is reduced and irradiation directivity is narrowed.

  By the way, the dimensions of the main parts of the organic EL element 20A shown in FIG. 4 are as shown in FIG. That is, the length of the waveguide A portion 55 in the sub-scanning direction (paper transport direction) is 215 μm (of which the slope 55 a is 200 μm and the horizontal surface 55 b is 15 μm), and the waveguide B portion 56 is in the sub-scanning direction ( The length in the paper conveyance direction) is 2000 μm. Here, the height of the horizontal surface 55b (the length in the direction perpendicular to the main scanning direction and the sub-scanning direction) is 7 μm.

  Furthermore, the height of the sealing substrate 28 is 700 μm, the height of the cladding optical layer 70 is 20 μm, the height of the substrate 21 is 700 μm, and the height at the highest portion of the planarizing layer 35 is high. The thickness is 3 μm.

  Note that the HTL 24, the light emitting layer 25, and the ETL 26 are collectively expressed as one layer in FIG. 8 as the light emitting layer 200 for convenience of paper size. Further, the specific numerical values of the dimensions of the respective parts shown in FIG. 8 are merely examples, and it is needless to say that the numerical values are not limited thereto.

  As described above, according to the present embodiment, it is possible to obtain a sufficient amount of light for exposure in a printing apparatus or the like while being an EL light emitting unit using an organic EL element having a simple waveguide structure, and It is possible to provide an EL light emitting unit that can be completely sealed so that the light emitting unit in an organic EL element that is easily affected by moisture is not exposed to the outside air.

  Specifically, according to the EL light emitting unit according to the present embodiment, the influence of moisture is obtained by adopting a structure in which light from the organic EL light emitting surface 61 is reflected and collected by the waveguide 57 and emitted. The light-emitting material of the organic EL that is easily received can be completely sealed with glass so as not to be exposed to the outside air, and a sufficient light amount can be obtained by a simple waveguide structure.

  Further, according to the EL light emitting unit according to the present embodiment, as described above, the length of the waveguide 57 and the refractive index difference between the core (core optical resin) and the clad (cladding optical layer 70) are adjusted. Since the directivity can be controlled by this, it is possible to optimize the efficiency of extracting the light emitted from the organic EL element to the outside.

  As described above, the light-emitting material of the organic EL element is easily affected by moisture, and needs to have a certain distance from the outside air. Therefore, in the present embodiment, the light emitted from the organic EL element 20A is guided to the emission end face 80 by the waveguide 57, thereby placing the organic EL element 20A at a certain distance from the outside air. It was possible to provide in the position.

  As mentioned above, although this invention was demonstrated based on one Embodiment, this invention is not limited to embodiment mentioned above, Of course, a various deformation | transformation and application are possible within the range of the summary of this invention. is there.

  Further, the above-described embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be extracted as an invention.

  For example, in each of the above embodiments, the organic EL light emitting surface 61 has a top emission structure provided on the upper side of the organic EL element 20A. However, the organic EL light emitting surface 61 has a bottom emission structure, and the organic EL element 20A has a lower emission side. An organic EL light emitting surface 61 is provided, the waveguide 57 is formed so that the waveguide A portion 55 is disposed below the organic EL element 20A, and a cladding portion is provided around the waveguide 57, and the EL You may make it radiate | emit light from the said output end surface 80 of the horizontal direction of the light emission part 2A.

1 is a diagram illustrating a configuration example of a printing apparatus using an EL light emitting unit according to an embodiment of the present invention. The figure which shows the structure of the light emission part in an organic EL element. FIG. 2 is a diagram illustrating an appearance of an exposure unit of a printing apparatus using an EL light emitting unit according to an embodiment of the present invention. The figure which shows the structure of the organic EL element in the EL light emission part which concerns on one Embodiment of this invention. The figure which shows the shape of the waveguide in the light guide part of the organic EL element which the EL light emission part which concerns on one Embodiment of this invention has. (A), (B) is a figure which shows the typical optical parameter of the rod lens assumed in simulation. The figure which shows a simulation result. The figure which shows the dimension of each main part in the organic EL element which concerns on one Embodiment of this invention.

Explanation of symbols

    DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 3 ... Charge roller, 4 ... Eraser light source photoconductor, 5 ... Cleaning member, 6 ... Developing device, 6a ... Developing roller, 7 ... Printing paper, 8 ... Transfer roller, 9 ... Fixing roller, 11 ... Transport belt, 20A ... organic EL element, 21 ... substrate, 22 ... reflective layer, 23 ... anode electrode, 24 ... hole transport layer, 25 ... light emitting layer, 26 ... electron transport layer, 27 ... cathode electrode, 28 ... sealing Substrate, 29 ... Sealing material, 20A ... EL element, 31A, 31B ... Control cable, 34 ... Sealing film, 35 ... Flattening layer, 40 ... Drive circuit section, 41 ... Source electrode, 42 ... Drain electrode, 43 ... Gate Electrode 44 ... Semiconductor 45 ... Gate insulation layer 46 ... Interlayer insulation layer 50 ... Light guide part 55 ... Waveguide A part 56 ... Waveguide B part 57 ... Waveguide 59 ... Anti Projection film, 61 ... organic EL light emitting surface, 70 ... cladding optical layer, 80 ... emission end face.

Claims (5)

A plurality of light emitting elements formed on a substrate and emitting light in an upward or downward direction;
A waveguide that condenses light emitted from the light emitting element in the lateral direction and exits from the exit end face ;
An insulating layer provided between the light emitting element and the waveguide;
A clad part having a refractive index lower than that of the waveguide;
I have a,
The waveguide includes an inclined surface that is inclined at a predetermined angle with respect to the light emitting surface of the light emitting element at an interface with the cladding portion at a position corresponding to the light emitting surface of the light emitting element, and one end of the inclined surface. A first waveguide portion provided with a first reflective film on a horizontal plane parallel to a light emitting surface of the light emitting element at an interface with the clad portion at a position facing the emission end face; And a second waveguide part provided with no reflective film at an interface with the cladding part from one end on the exit end face side to the exit end face . 2. The light emitting unit according to claim 1 , wherein a second reflective film is provided between the first waveguide part of the waveguide and the insulating layer . The light emitting unit according to claim 1, wherein the first reflective film is provided on an upper surface and a side surface of the first waveguide unit.   2. The light emitting unit according to claim 1, wherein the light emitting elements are respectively arranged in a main scanning direction, and a light emitting surface of the light emitting element is wider in a direction orthogonal to the main scanning direction than in the main scanning direction. .   A printing apparatus comprising the light emitting unit according to claim 1.

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