JP2007237576A - Aligner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance utilization efficiency of light from an organic EL (electro luminescent) element sufficiently in an aligner. <P>SOLUTION: The aligner comprises a plurality of light emitting elements (organic EL elements) 14 arranged on a light source substrate 20, a hologram lens array LA1 having a plurality of hologram lenses L1, and a hologram lens array LA2 having a plurality of hologram lenses L1 and sandwiching the hologram lens array LA1 between respective hologram lenses of a plurality of light emitting elements 14. Each of the plurality of hologram lenses L1 is overlapping each of the plurality of light emitting elements 14 in the direction perpendicular to the light source substrate 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exposure apparatus and an image forming apparatus.

  There is an exposure apparatus that is used as a line-type optical head in an electrophotographic image forming apparatus and writes an electrostatic latent image on an image carrier (for example, a photosensitive drum). One type of exposure apparatus is a combination of a light emitting device in which a large number of organic EL (Electro Luminescent) elements are arranged and a selfoc lens array (SLA) in which a number of selfoc lenses are arranged. The organic EL element is an OLED (Organic Light Emitting Diode) element, “SELFOC” / “SELFOC” is a registered trademark of Nippon Sheet Glass Co., Ltd., and the SELFOC lens is a refractive index distribution type rod lens. In the exposure apparatus having this configuration, the light from the organic EL element is guided by the selfoc lens and reaches the image carrier to form an electrostatic latent image here. The SELFOC lens array is disclosed in, for example, Patent Document 1.

As another kind of the above-described exposure apparatus, there is a structure in which the above-described light emitting device and a microlens array (MLA) in which a large number of convex lenses are arranged are combined (see Patent Document 2 and Patent Document 3). . In the exposure apparatus having this configuration, a large number of convex lenses are superimposed on a large number of organic EL elements, and the light from the organic EL elements is guided by the convex lens corresponding to the organic EL elements to reach the image carrier, so that An electrostatic latent image is formed here.
JP-A-11-231212 JP 2004-195676 A Japanese Patent Application Laid-Open No. 2004-195677

In an exposure apparatus equipped with a Selfoc lens array, light from the organic EL element that is guided to the gradient index lens has an incident angle to the gradient index lens within a predetermined range (for example, about ± 20 degrees). Limited to light inside. That is, this exposure apparatus has a drawback that the utilization efficiency of light from the organic EL element cannot be sufficiently increased.
On the other hand, in an exposure apparatus including a microlens array, if the microlens array can be disposed sufficiently close to the organic EL element, the light use efficiency from the organic EL element can be sufficiently increased. However, it is difficult to dispose the microlens array sufficiently close to the organic EL element. For example, it is conceivable to arrange the microlens array in a light-emitting device with a sufficiently thin microlens array. For this purpose, it is necessary to secure a sufficient refractive power with a sufficiently thin convex lens, which is difficult.

  Therefore, the present invention provides an exposure apparatus and an image forming apparatus that can sufficiently increase the utilization efficiency of light from an organic EL element.

An exposure apparatus according to the present invention includes a plurality of light-emitting elements arranged on a light source substrate and a plurality of diffractive positive lenses that diffract the transmitted light to converge the light bundle of the light to form an image. A lens array; and a second lens array having a plurality of lenses and sandwiching the first lens array between each of the plurality of light emitting elements, wherein each of the plurality of diffraction positive lenses includes the light source substrate. It overlaps with each of these light emitting elements in the direction perpendicular | vertical to. The above “light emitting element” refers to an element whose light emission characteristics change according to electric energy. Examples of such elements include organic EL elements and inorganic EL elements. In other words, the diffractive positive lens is a diffractive optical element that functions as a positive lens.
In the above exposure apparatus, since the lens included in the first lens array is a diffractive positive lens, the first lens array is sufficiently thin and has sufficient diffractive power (a kind of optical power, corresponding to the refracting power in the refractive lens). Ability). Therefore, in the above-described exposure apparatus, it is possible to adopt a configuration in which a large amount of light from the light emitting element is transmitted through the diffractive positive lens overlapping the light emitting element. Since the light flux converges during this transmission, the incident angle of the light emitted from the light emitting element and transmitted through the positive diffraction lens, that is, a lot of light from the light emitting element, to the second lens array becomes small. This leads to an increase in light transmitted through the second lens array. Therefore, according to the above-described exposure apparatus, the utilization efficiency of light from the light emitting element can be sufficiently increased.

  In the above exposure apparatus, the lens is a diffractive positive lens that diffracts transmitted light to converge a bundle of light beams to form an image, and each of the plurality of lenses is perpendicular to the light source substrate. In the direction, each of the plurality of light emitting elements may overlap with each of the plurality of diffractive positive lenses. According to this aspect, it is possible to reduce the size of the exposure apparatus. Further, the chromatic aberration of the positive diffractive lens increases remarkably when the diffractive power is large, but according to this aspect, the diffractive power can be dispersed between the first lens array and the second lens array. Chromatic aberration can be reduced as compared with an embodiment in which only a lens array is used. This is particularly beneficial when an element that emits light in a wide band is used as the light emitting element. As such a light emitting element, an organic EL element can be illustrated.

  In the above exposure apparatus, each of the plurality of lenses is a gradient index rod lens that guides light by refraction and forms an erect image, and the second lens array includes the plurality of lenses, the plurality of lenses. The images formed by the lenses may be arranged so as to form one continuous image. According to this aspect, reflection on the incident surface of the rod lens is suppressed, and a lot of light from the light emitting element is guided to the rod lens. Furthermore, in this aspect, a transparent member may be provided that is in contact with the second lens array and fills a gap between the first lens array and the second lens array. In this aspect, among the interfaces existing on the optical path of much light from the light emitting element, the interface between the solid and the gas is reduced, and the interface between the solid and the solid is increased. Therefore, reflection at the interface is suppressed, and light utilization efficiency is improved.

  In the above-described exposure apparatus, the lens is a refractive positive lens that converges a light bundle of light by refracting transmitted light to form an image, and each of the lenses is in a direction perpendicular to the light source substrate. In this case, the light-emitting elements may overlap each of the plurality of light-emitting elements and each of the plurality of diffraction positive lenses. According to this aspect, a lot of light from the light emitting element is transmitted through the refractive positive lens of the second lens array. Moreover, since the light passing through the refractive positive lens enters the refractive positive lens before the beam bundle spreads so much, the light from the light emitting element enters the refractive positive lens that does not overlap the light emitting element. Phenomenon, that is, optical crosstalk can be suppressed.

In the above exposure apparatus, the phase distribution φ (r) of the diffractive positive lens when the distance from the optical axis is r may be expressed by Expression (1). However, C ₁ -C ₁₀ is a constant, C ₁ is -10 or more -0.1 or less. This aspect is suitable when an organic EL element that emits broadband red light is used as a light emitting element.

  The present invention also includes the above-described exposure apparatus or the exposure apparatus according to each aspect and an image carrier, and charges the image carrier, and the light from the exposure apparatus is charged on the charged surface of the image carrier. To form a latent image, to attach a toner to the latent image to form a visible image, and to transfer the visible image to another object. According to this image forming apparatus, a clear image can be formed because the exposure apparatus capable of sufficiently increasing the utilization efficiency of light from the light emitting element is used for image formation.

[Exposure equipment]
Hereinafter, exposure apparatuses according to first to fourth embodiments of the present invention will be described with reference to the accompanying drawings. However, in the drawings, the ratio of the dimensions of each part is appropriately changed from the actual one. The exposure apparatus according to each embodiment is a line type light that writes a latent image by irradiating light onto the surface (image forming surface) of an image carrier (for example, a photosensitive drum) in an image forming apparatus using an electrophotographic system. It is used as a head, and the plan view is a view seen from the image carrier side. In addition, “upper and lower” in the following description means upper and lower in the sectional views.

<First Embodiment>
FIG. 1 is a perspective view, FIG. 2 is a plan view, and FIG. 3 is a sectional view of an exposure apparatus 10 according to the first embodiment of the present invention. 3 is also a cross-sectional view taken along line AA in FIG. As shown in these drawings, in the exposure apparatus 10, a plurality of light-emitting elements 14 serving as light sources are arranged in a zigzag pattern in a longitudinal direction of the light source substrate 20 on a flat light source substrate 20. In the image forming apparatus, this arrangement direction is parallel to the irradiated line of the image carrier (or the generating line if the image carrier is a photosensitive drum).

  In the present embodiment, an organic EL element is used as the light emitting element 14. Accordingly, the light-emitting element 14 includes a light-emitting layer that is formed of an organic material and emits light according to an electric current, and an anode and a cathode that allow current to flow through the light-emitting layer with the light-emitting layer interposed therebetween. Specifically, it includes a light emitting functional layer 141 that emits broadband red light, an anode 142, and a common cathode 143. The light emitting functional layer 141 may be composed of only the light emitting layer, or may include various layers that transport and inject holes and electrons toward the light emitting layer in addition to the light emitting layer. The common cathode 143 is a cathode common to the plurality of light emitting elements 14.

  The light source substrate 20 includes a flat element substrate 21 made of a material having high light transmittance such as glass and plastic, and wiring for driving and controlling the plurality of light emitting elements 14 formed on the element substrate 21. It has a wiring layer 22 in which circuit elements such as transistors are arranged, and a transparent layer 23 formed on the wiring layer 22 from a material having a high light transmittance such as silicon dioxide. The thickness of the element substrate 21 is, for example, 500 μm. The thickness of the transparent layer 23 is an appropriate thickness of 1 μm or more and 100 μm or less (in this embodiment, 10 μm).

  In the wiring layer 22, a plurality of hologram lenses L1 are arranged in an array. That is, the wiring layer 22 is also the hologram lens array LA1. The hologram lens array LA1 is a first lens array that appears first in the optical path of light from the light source. The plurality of hologram lenses L1 overlap with the plurality of light emitting elements 14 in a direction perpendicular to the light source substrate 20, respectively. A method of using the wiring layer 22 as the hologram lens array LA1 is arbitrary. For example, it may be formed using a material (for example, a metal material or silicon oxide) laminated on the element substrate 21 in the step of forming the circuit element of the wiring layer 22, or a plurality of hologram lenses L1 are arranged. A film may be attached to the element substrate 21 as a part of the wiring layer 22.

  On the light source substrate 20, an insulating layer 15 in which a plurality of anodes 142 are disposed is formed. Each anode 142 is connected to a circuit element in the wiring layer 22. The insulating layer 15 is made of, for example, silicon oxide, and each anode 15 is made of a material having a sufficiently high light transmittance such as ITO (Indium Tin Oxide). A part of the upper surface of each anode 142 is exposed from the insulating layer 15, and a partition wall 16 is formed on the insulating layer 15 so as to surround the exposed surface of each anode 142. The partition 16 is made of polyimide, for example. The insulating layer 15 and the partition 16 define a plurality of recesses, and the light emitting functional layer 141 is formed in these recesses. A common cathode 143 is formed on the insulating layer 15, the partition wall 16 and the light emitting functional layer 141 so as to cover them. Therefore, the light used for irradiation is light emitted from the light emitting surface P that is the lower surface of the light emitting functional layer 141. The light emitting surface P is circular and has a diameter of about 40 μm, for example.

  A passivation layer 17 is formed on the common cathode 143 so as to cover the common cathode 143 and the insulating layer 15. The passivation layer 17 is formed from a material having excellent gas barrier properties such as silicon oxide. On the transparent layer 23, a bowl-shaped sealing substrate 30 is fixed with an adhesive (for example, an epoxy-based adhesive) 31 having excellent gas barrier properties in a face-down state so as to cover the passivation layer 17. . The sealing substrate 30 is for sealing the plurality of light emitting elements 14 and protecting them from the outside air, and is formed of an appropriate material having excellent sealing properties such as glass, plastic, ceramic, or metal. A cavity filled with an inert gas such as nitrogen or argon exists between the sealing substrate 30 and the passivation layer 17. A desiccant 32 for improving the sealing performance of the light emitting element 14 is present in the cavity. The desiccant 32 is fixed to the sealing substrate 30 by being applied to the sealing substrate 30, for example.

  On the lower surface of the light source substrate 20, a hologram lens array LA2 in which a plurality of hologram lenses L2 are arranged in an array is formed. The hologram lens array LA2 is a second lens array that appears second in the optical path of light from the light source. In a direction perpendicular to the light source substrate 20, the hologram lens array LA1 is sandwiched between the hologram lens array LA2 and the plurality of light emitting elements 14, and each of the plurality of hologram lenses L2 includes each of the plurality of light emitting elements 14. And overlaps each of the plurality of hologram lenses L1. That is, from the viewpoint of overlapping in the direction perpendicular to the light source substrate 20, the plurality of light emitting elements 14, the plurality of hologram lenses L1, and the plurality of hologram lenses L2 correspond one-to-one. Further, the optical axes of the hologram lens L1 and the hologram lens L2 corresponding to each other coincide with each other and pass through the center of the light emitting surface P of the light emitting element 14 corresponding to these hologram lenses.

  The method for forming the hologram lens array LA2 is arbitrary. For example, a plurality of hologram lenses L2 may be formed by etching a material (for example, silicon oxide) laminated on the element substrate 21, or a film on which the plurality of hologram lenses L2 are arranged is attached to the element substrate 21. May be attached.

  Here, the hologram lens will be described. The hologram lens is a kind of diffractive positive lens included in the diffractive optical element. The diffractive positive lens has a thin disk shape, and can diffract the transmitted light to converge the light flux of the light and form an image. The hologram lens is a kind of hologram (Holographic Optical Element). In summary, the hologram lens is a hologram that functions as a positive lens.

In the present embodiment, the hologram lens L1 and the hologram lens L2 are hologram lenses whose phase distribution φ (r) is expressed by equation (1) when the distance from the optical axis is r. In Expression (1), C _{1 to} C ₁₀ are constants, and in this embodiment, the light from the hologram lens array LA1 to the hologram lens array LA2 is determined to be parallel light. Further, C ₁ is −10 or more and −0.1 or less, and in the present embodiment, C ₁ = −5 for the hologram lens L1 and C ₁ = −2.5 for the hologram lens L2. In this embodiment, the hologram lens is designed so as to form an image with the first-order diffracted light. However, the hologram lens can be modified to form an image with the second-order or higher-order diffracted light. is there.

  FIG. 4 is a schematic diagram showing an optical action in the exposure apparatus 10. In this figure, a hologram lens L1 and a hologram lens L2 corresponding to one light emitting element 14 and an optical axis AX common to these hologram lenses are shown. As shown in this figure, the light bundle of light from the light emitting functional layer 141 of the light emitting element 14 spreads in the process in which these light passes through the anode 142 and the transparent layer 23. Therefore, some of these lights are incident on the hologram lens L1. However, since the distance between the light emitting functional layer 141 and the hologram lens array LA1 is sufficiently close, a large amount of light enters the hologram lens L1. That is, most of the above light beams pass through the hologram lens L1.

  The light incident on the hologram lens L 1 is diffracted and enters the element substrate 21. The traveling direction of the incident light is parallel to the optical axis AX. Therefore, much of this incident light is transmitted through the element substrate 21. That is, many of the above-mentioned light beams are bent at the hologram lens L 1 and do not spread on the element substrate 21. Therefore, all of the light transmitted through the element substrate 21 enters the hologram lens L2. That is, most of the above light beams pass through the corresponding hologram lens L2.

  The light incident on the hologram lens L2 is diffracted and emitted from the exposure apparatus 10. That is, many of the light beams are bent at the hologram lens L <b> 2 and converge outside the exposure apparatus 10. As a result, an image of the light emitting surface P is formed on the imaging surface outside the exposure apparatus 10. This image is, for example, 80 μm.

As described above, in the exposure apparatus 10, most of the light from the light emitting element 14 is transmitted through the hologram lens L1 corresponding to the light emitting element 14, and the light beam is bent and the spread thereof is suppressed during this transmission. Therefore, most of the light from the light emitting element 14 passes through the hologram lens array LA2. Therefore, according to the exposure apparatus 10, the utilization efficiency of light from the light emitting element 14 can be sufficiently increased.
Further, in the exposure apparatus 10, since the diffractive power is dispersed between the hologram lens L1 and the hologram lens L2, the chromatic aberration is smaller than when the total diffractive power of both lenses is applied to one hologram lens. . This is a beneficial effect particularly in a form in which an organic EL element that emits broadband light is used as a light emitting element as in the present embodiment.
By the way, the hologram lens forms an image using only light incident on the correct position at the correct angle and the correct phase, and other incident light does not form an image anywhere. For example, in the exposure apparatus 10, even if light enters a certain hologram lens from the light emitting element 14 that does not correspond to the hologram lens, the incident light does not form an image anywhere. This contributes to the formation of a clear image together with the two effects described above.
Further, according to the exposure apparatus 10, since it is not necessary to use a Selfoc lens array or a microlens array, the exposure apparatus 10 can be reduced in size and cost.

<Second Embodiment>
FIG. 5 shows a plan view of an exposure apparatus 40 according to the second embodiment of the present invention, and FIG. 6 shows a sectional view thereof. 6 is also a cross-sectional view taken along line AA in FIG. Unlike the exposure apparatus 10, the exposure apparatus 40 does not include the hologram lens array LA2. Therefore, the light emitted from the light emitting element 14 and transmitted through the hologram lens L1 is emitted from the element substrate 21 into gas (for example, air). Since this light is parallel light, most of it is emitted into the gas without being reflected by the emission surface of the element substrate (the interface between the element substrate 21 and the gas).

  Under the element substrate 21, a SELFOC lens array LA3 is disposed as a second lens array away from the element substrate 21. The relative arrangement of the SELFOC lens array LA3 and the element substrate 21 is fixed. In a direction perpendicular to the element substrate 21, the hologram lens array LA1 is sandwiched between the Selfoc lens array LA3 and the plurality of light emitting elements 14. In the SELFOC lens array LA3, a plurality of SELFOC lenses L3 having an optical axis perpendicular to the light source substrate 20 are arranged in two rows in a staggered manner in the same direction as the arrangement direction of the plurality of light emitting elements 14. The Selfoc lens L3 is a refractive index distribution type rod lens (cylindrical lens) that guides light by refraction and forms an erect image. The Selfoc lens array LA3 is formed on the imaging surface by a plurality of Selfoc lenses L3. The combined images are configured to form one continuous image.

  In the exposure device 40, light from the hologram lens L1 travels in the gas along the optical axis of each Selfoc lens L3, and reaches the Selfoc lens L3 overlapping the hologram lens L1. Then, most of the light reaching the Selfoc lens L3 is guided to the Selfoc lens L3 without being reflected by the incident surface (the interface between the gas and the Selfoc lens L3) of the Selfoc lens L3. An image is formed on the image plane. The diameter of this image is, for example, 50 μm.

  As described above, according to the exposure apparatus 40, much of the light from the light emitting element 14 is guided to the selfoc lens L3 and contributes to the image formation. Therefore, the same effect as that obtained by the exposure apparatus 10 can be obtained. An effect can be obtained. By the way, in reality, when light from one light emitting surface P forms an image through many Selfoc lenses L3, the image of the light emitting surface P is blurred. On the other hand, in the exposure apparatus 40, the number of Selfoc lenses L3 through which the light beam from one light emitting surface P passes is reduced. Therefore, according to the exposure apparatus 40, a clear image can be formed.

  FIG. 7 is a sectional view of an exposure apparatus 41 obtained by modifying the exposure apparatus 40. In the exposure apparatus 41, a transparent member 45 is disposed between the element substrate 21 and the Selfoc lens array LA3. The transparent member 45 is made of a material having a high light transmittance such as glass or plastic, and is sandwiched between and in contact with the element substrate 21 and the Selfoc lens array LA3. The light from each hologram lens L1 passes through the element substrate 21 and the transparent member 45, and reaches the Selfoc lens array LA3 without passing through the gas. That is, among the interfaces existing on the optical path of much light from the light emitting element 14, the interface between the solid and the gas decreases, and the interface between the solid and the solid increases. Therefore, reflection at the interface is suppressed, and the light use efficiency is improved to some extent (for example, about 10%).

  FIG. 8 is a cross-sectional view of an exposure apparatus 42 obtained by modifying the exposure apparatus 40. The exposure device 42 does not have the transparent layer 23 and includes a wiring layer 46 instead of the wiring layer 22. The wiring layer 46 is obtained by removing the function of the hologram lens array LA1 from the wiring layer 22. However, the portion of the wiring layer 46 that overlaps the light emitting surface P in the direction perpendicular to the element substrate 21 is made of a material having high light transmittance (for example, silicon oxide). In the exposure apparatus 42, a hologram lens array LA4 is formed on the lower surface of the element substrate 21 as a first lens array. The hologram lens array LA4 is sandwiched between the Selfoc lens array LA3 and the light emitting elements 14 in a direction perpendicular to the element substrate 21.

  In the hologram lens array LA4, a plurality of hologram lenses L4 whose phase distribution φ (r) is expressed by the above-described equation (1) are arranged in an array. Each hologram lens L4 overlaps each of the plurality of light emitting elements 14. That is, the hologram lens array LA4 is a lens array that appears first in the optical path of light from the light emitting element 14, and the plurality of hologram lenses L4 and the plurality of light emitting elements 14 are in view of overlapping in a direction perpendicular to the element substrate 21. There is a one-to-one correspondence. Further, the optical axis of the hologram lens L4 passes through the center of the light emitting surface P of the corresponding light emitting element 14. The method for forming the hologram lens array LA4 is the same as the method for forming the second lens array L2 of the exposure apparatus 10.

  In the exposure device 42, the light from the light emitting element 14 passes through the element substrate 21 and then reaches the hologram lens array LA4. Then, the light incident on the hologram lens L4 of the hologram lens array LA4 travels in the gas as parallel light, reaches the Selfoc lens array LA3, and contributes to image formation. Compared with the exposure apparatus 40, the light utilization efficiency of the light from the light emitting element 14 becomes low because the distance between the light emitting functional layer 141 and the hologram lens array LA4 is long. However, since the reflection at the interface is suppressed similarly to the exposure apparatus 40, the utilization efficiency is sufficiently high. Further, the exposure apparatus 42 has an advantage that it can be manufactured relatively easily because the structure of the layers above the element substrate 21 is the same as that of a general exposure apparatus.

  It is also possible to configure the exposure apparatus by combining the configuration of the exposure apparatus 41 and the configuration of the exposure apparatus 42. That is, in the exposure device 42, a material having a high light transmittance may be filled between the hologram lens array LA4 and the Selfoc lens array LA3. According to this configuration, the utilization efficiency of light from the light emitting element 14 is improved to some extent (for example, about 10%) as compared with the exposure apparatus 42.

<Third Embodiment>
FIG. 9 is a plan view of an exposure apparatus 50 according to the third embodiment of the present invention, and FIG. 10 is a sectional view thereof. 9 is also a cross-sectional view taken along line AA in FIG. Unlike the exposure apparatus 40, the exposure apparatus 50 includes a microlens array LA5 fixed to the element substrate 21 as a second lens array instead of the selfoc lens array LA3. The microlens array LA5 has a U-shaped cross section, and has a flat plate portion and a cylindrical portion extending upward from the peripheral end of this portion. The method of fixing the microlens array LA5 to the element substrate 21 is arbitrary, and in the present embodiment, the entire front end surface of the cylindrical portion and the lower surface of the element substrate 21 are bonded together by an adhesive 55. The flat portion is not in contact with the element substrate 21, and a space filled with gas (for example, air) is defined between the element substrate 21 and the microlens array LA5.

  In a direction perpendicular to the light source substrate 20, the hologram lens array LA1 is sandwiched between the microlens array LA5 and the plurality of light emitting elements 14. In the microlens array LA5, a plurality of microlenses L5 having an optical axis perpendicular to the light source substrate 20 are arranged in an array. The swelled portion in the flat plate-like portion of the microlens array LA5 is the microlens L5.

  The plurality of microlenses L5 overlap with the plurality of light emitting elements 14 and the plurality of hologram lenses L1, respectively. That is, the plurality of light emitting elements 14, the plurality of hologram lenses L 1, and the plurality of micro lenses L 5 are in a one-to-one correspondence from the viewpoint of overlapping in the direction perpendicular to the light source substrate 20. Further, the optical axis of the micro lens L5 coincides with the optical axis of the corresponding hologram lens L1, and passes through the center of the light emitting surface P of the corresponding light emitting element 14. In the present embodiment, the biconvex lens is used as the microlens L5. However, it may be modified so that another refractive positive lens (for example, a planoconvex lens) is used as the microlens L5.

  According to the exposure apparatus 50, much of the light from the light emitting element 14 is transmitted through the corresponding microlens L5 and contributes to image formation. Therefore, the same effect as that obtained by the exposure apparatus 10 can be obtained. In addition, since the light passing through the microlens L5 becomes parallel light before the light bundle spreads so much and enters the microlens L5, the microlens array and the light emitting functional layer are arranged close to each other. Even though it is a bottom emission type (a type in which light from the light emitting element is emitted from the element substrate side) that is difficult to do, optical crosstalk can be suppressed. The optical crosstalk in this embodiment is a phenomenon in which light from the light emitting element 14 is incident on the microlens L5 that does not overlap the light emitting element 14, and the suppression thereof results in the formation of a clear image. Contribute.

  FIG. 11 is a cross-sectional view of an exposure apparatus 51 obtained by modifying the exposure apparatus 50. Similar to the exposure apparatus 42, the exposure apparatus 51 does not have the transparent layer 23, includes a wiring layer 46 instead of the wiring layer 22, and includes a hologram lens array LA4. The hologram lens array LA4 is sandwiched between the microlens array LA5 and the plurality of light emitting elements 14 in a direction perpendicular to the element substrate 21.

  The plurality of hologram lenses L4 of the hologram lens array LA4 overlap the plurality of light emitting elements 14 and the plurality of microlenses L5, respectively. That is, the hologram lens array LA4 in the present embodiment is a first lens array, and the plurality of hologram lenses L4, the plurality of light emitting elements 14, and the plurality of microlenses L5 are from the viewpoint of overlapping in a direction perpendicular to the element substrate 21. There is a one-to-one correspondence. The optical axis of the hologram lens L4 coincides with the optical axis of the corresponding microlens L5 and passes through the center of the light emitting surface P of the corresponding light emitting element 14.

  In the exposure apparatus 51, the light from the light emitting element 14 passes through the element substrate 21 and then reaches the hologram lens array LA4. Then, the light incident on the hologram lens L4 of the hologram lens array LA4 travels in the gas as parallel light, reaches the microlens array LA5, and contributes to image formation. According to the exposure apparatus 51, the same effect as that obtained by the exposure apparatus 50 can be obtained.

<Fourth embodiment>
FIG. 12 shows a plan view of an exposure apparatus 60 according to the fourth embodiment of the present invention, and FIG. 13 shows a sectional view thereof. 13 is also a cross-sectional view taken along line AA in FIG. Similar to the exposure device 40, the exposure device 60 uses a hologram lens array having hologram lenses as the first lens array and the second lens array. However, the exposure apparatus 60 is a top emission type (a type in which light from a light emitting element is emitted from the opposite side of the element substrate), and differs from the exposure apparatus 40 in the following points.

  The exposure apparatus 60 includes a light emitting element 71 as a light source. The light emitting element 71 is an organic EL element, and includes a light emitting functional layer 711 that emits broadband red light, an anode 712, and a common cathode 713. The light emitting functional layer 711 may be composed of only the light emitting layer, or may include various layers that transport and inject holes and electrons toward the light emitting layer in addition to the light emitting layer. In the present embodiment, the upper surface of the light emitting functional layer 711 is the light emitting surface P. The common cathode 713 is a cathode common to the plurality of light emitting elements 14 and is made of a material having a sufficiently high light transmittance such as ITO (Indium Tin Oxide).

  The exposure apparatus 60 also includes a passivation layer 72 as a passivation layer that covers the common cathode and the insulating layer. The passivation layer 72 is formed from a material having excellent gas barrier properties and light transmission properties such as silicon dioxide. Further, the exposure apparatus 60 includes a sealing substrate 80 having the same shape and size as the sealing substrate 30 as a sealing substrate for sealing the plurality of light emitting elements 71 and protecting them from the outside air. The sealing substrate 80 is formed of a material excellent in sealing properties and light transmission properties such as glass or plastic. A cavity filled with an inert gas such as nitrogen or argon exists between the sealing substrate 80 and the passivation layer 72.

  On the inner surface of the sealing substrate 80, a hologram lens array LA6 is formed as a first lens array, and the desiccant 32 is fixed avoiding this. On the other hand, a hologram lens array LA7 is formed on the outer surface of the sealing substrate 80 as a second lens array. The hologram lens array LA6 and the hologram lens array LA7 can be formed by the same method as the hologram lens array LA2 of the exposure apparatus 10, respectively. As is clear from the above, the flat plate-like portion of the sealing substrate 80 is sandwiched between the hologram lens array LA6 and the hologram lens array LA7 that are parallel to each other.

  In the hologram lens array LA6, a plurality of hologram lenses L6 whose phase distribution φ (r) is expressed by the above-described equation (1) are arranged in an array. On the other hand, in the hologram lens array LA7, a plurality of hologram lenses L7 whose phase distribution φ (r) is expressed by the above-described equation (1) are arranged in an array. In the direction perpendicular to the light source substrate 70 to be described later, the plurality of hologram lenses L6 overlap with the plurality of hologram lenses L7, respectively, and the optical axes of the hologram lenses corresponding to each other coincide with each other in view of the overlap. .

  Each of the plurality of hologram lenses L7 overlaps each of the plurality of light emitting elements 71 and each of the plurality of hologram lenses L6, and the optical axis thereof passes through the center of the light emitting surface P of the corresponding light emitting element 71, respectively. . As is clear from the above, from the viewpoint of overlapping in the optical axis direction, the plurality of light emitting elements 71, the plurality of hologram lenses L6, and the plurality of hologram lenses L7 correspond one-to-one, and in the optical axis direction, The hologram lens array LA6 is sandwiched between the hologram lens array LA7 and the plurality of light emitting elements 71.

  In addition, the exposure apparatus 60 includes a light source substrate 70 as a light source substrate on which light sources are arranged. The light source substrate 70 is a flat element substrate 73 formed of an appropriate material such as glass, plastic, ceramic, or metal, and wiring for driving and controlling the plurality of light emitting elements 71 formed on the element substrate 73. And a wiring layer 74 in which circuit elements such as transistors are arranged. The thickness of the element substrate 73 is, for example, 500 μm.

  In the exposure device 60, the light bundle of light from the light emitting functional layer 141 spreads in the process in which these lights pass through the common cathode 713 and the passivation layer 72 and reach the hologram lens array LA6. Therefore, some of these lights are incident on the corresponding hologram lens L6. However, since the distance between the light emitting functional layer 141 and the hologram lens array LA6 is sufficiently close, a large amount of light enters the hologram lens L6. That is, most of the above light beams pass through the corresponding hologram lens L6.

  The light incident on the hologram lens L 6 is diffracted and enters the sealing substrate 80. The traveling direction of the incident light is parallel to the optical axis of the hologram lens L6. Therefore, much of this incident light is transmitted through the sealing substrate 80. That is, many of the above-mentioned light beams are bent at the hologram lens L 6 and do not spread on the sealing substrate 80. Therefore, all of the light transmitted through the sealing substrate 80 enters the hologram lens L7. That is, most of the above light beams pass through the corresponding hologram lens L7.

  The light incident on the hologram lens L7 is diffracted and emitted from the exposure apparatus 10. That is, many of the light beams are bent at the hologram lens L7 and converge outside the exposure apparatus 60. As a result, an image of the light emitting surface P is formed on the imaging surface outside the exposure apparatus 60.

  As is clear from the above, according to the exposure apparatus 60, the same effect as that obtained by the exposure apparatus 10 can be obtained. Further, according to the exposure apparatus 60, the hologram lens array LA6 is formed on the inner surface of the sealing substrate 80 and the hologram lens array LA7 is formed on the outer surface, and the sealing substrate 80 is bonded to the light source substrate 70. It is possible to adopt the manufacturing method of. That is, the exposure apparatus 60 has an advantage that it can be easily manufactured.

  FIG. 14 is a cross-sectional view of an exposure apparatus 61 obtained by modifying the exposure apparatus 60. The exposure device 61 includes a SELFOC lens array LA3 as a third lens array that appears third in the optical path of light from the light source. In the exposure device 61, the SELFOC lens array LA3 is arranged away from the hologram lens array LA7, and the relative arrangement of the two is fixed. The optical axes of the plurality of Selfoc lenses L3 in the Selfoc lens array LA3 are all perpendicular to the light source substrate 70.

The exposure device 61 includes a hologram lens array LA8 having a hologram lens L8 instead of the hologram lens L6 as a first lens array, and a hologram lens array LA9 having a hologram lens L9 instead of the hologram lens L7 as a second lens array. Is provided. The phase distribution φ (r) of the hologram lens L8 and the phase distribution φ (r) of the hologram lens L9 are each expressed by Expression (1). In each expression, the constants C _{1 to} C ₁₀ are determined so that the light emitted from the hologram lens L9 becomes parallel light.

  In the exposure device 61, the light to be irradiated is emitted from the light emitting element 71, diffracted by the hologram lens L8, and then diffracted by the hologram lens L9 to become parallel light. Then, the parallel light travels through the gas (for example, air) and enters the SELFOC lens L3. Therefore, according to the exposure apparatus 61, the effect similar to the effect acquired with the exposure apparatus 60 and the exposure apparatus 40 can be acquired. Moreover, according to the exposure apparatus 61, the diffraction force requested | required of each hologram lens can be made smaller. This contributes to reduction of chromatic aberration. Note that the exposure apparatus 61 may be modified to include a microlens array instead of the Selfoc lens array LA3.

  FIG. 15 is a cross-sectional view of an exposure apparatus 62 obtained by modifying the exposure apparatus 61. In the exposure device 62, the gap between the hologram lens array LA9 and the Selfoc lens array LA3 existing in the exposure device 61 is filled with a transparent member 81 formed of a material having a high light transmittance such as glass or plastic. . Further, in the exposure device 62, the gap between each light emitting element 71 and the hologram lens array LA8 existing in the exposure device 61 is filled with a transparent member 75 formed of a material having a high light transmittance such as glass or plastic. It has been.

  As described above, in the exposure apparatus 62, there is no gas layer between the light emitting element 71 and the Selfoc lens array LA3 in the optical path of the light that becomes the irradiation light. Accordingly, among the light from the light emitting element 71, the light that is irradiated reaches the Selfoc lens array LA3 without passing through the gas. That is, the reflection at the interface is suppressed for the light that becomes the irradiation light. Therefore, in the exposure device 62, the light use efficiency is improved. Note that the exposure device 62 may be modified so that only one of the transparent member 75 and the transparent member 81 is provided.

  Further, the exposure apparatus 61, its modification, the exposure apparatus 62, and its modification may be modified so that the number of lens arrays having hologram lenses is one. In this case, this lens array becomes the first lens array, and the SELFOC lens array LA3 or the microlens array becomes the second lens array. Of course, the phase distribution φ (r) of the hologram lens of the first lens array should be suitable for this configuration. Note that the Selfoc lens array LA3 or the microlens array can be grasped as the second lens array without undergoing such deformation. When grasping in this way, the hologram lens L8 and the hologram lens L9 are grasped as the first lens array.

In addition, the exposure apparatus according to each of the above-described embodiments and modifications thereof may be modified as described below.
For example, light that is not parallel light may be emitted from any hologram lens. In this case, the amount of light reflected by the incident surface of the latter lens increases, but the beam bundle still converges by the hologram lens. If the degree of convergence is appropriate, the latter lens A large amount of light is incident on the light, and the utilization efficiency of light from the light emitting element is sufficiently high. When the subsequent lens is a SELFOC lens, the angle of incidence on the SELFOC lens should be within a range of ± 20 degrees (preferably a range of ± 12.5 degrees).

For example, a hologram lens represented by the formula (1) in which the phase distribution φ (r) has a constant C ₁ of less than −10 may be used, or the phase distribution φ (r) may have a constant C ₁ of −0. A hologram lens represented by the formula (1) larger than .1 may be used. Further, for example, a hologram lens in which the phase distribution φ (r) when the distance from the optical axis is r can be expressed by equation (2) may be used. However, in the formula (2), C ₁ ~C ₂₀ are constants.

For example, a diffractive positive lens that is not a hologram may be used instead of the hologram lens. An example of such a diffractive positive lens is a binary optical element.
For example, an organic EL element that emits light in a narrow band may be used as the light emitting element, or an organic EL element that emits light other than red light may be used. Moreover, you may make it use light emitting elements (for example, inorganic EL element) other than an organic EL element.
For example, the number of columns of the plurality of light emitting elements may be 1 or 3 or more. The same applies to the SELFOC lens.

[Image forming apparatus]
FIG. 16 is a longitudinal sectional view of the image forming apparatus according to the embodiment of the present invention. This image forming apparatus is a tandem type full-color image forming apparatus using a belt intermediate transfer body system.

  In this image forming apparatus, four organic EL array exposure heads 10K, 10C, 10M, and 10Y having the same configuration have four photosensitive drums (image carriers) 110K, 110C, 110M, and 110Y having the same configuration. The exposure positions are respectively arranged. The organic EL array exposure heads 10K, 10C, 10M, and 10Y are exposure apparatuses according to the above-described embodiments or exposure apparatuses according to modifications thereof.

  As shown in FIG. 16, this image forming apparatus is provided with a driving roller 121 and a driven roller 122, and an endless intermediate transfer belt 120 is wound around these rollers 121 and 122, as indicated by arrows. Thus, the periphery of the rollers 121 and 122 is rotated. Although not shown, tension applying means such as a tension roller that applies tension to the intermediate transfer belt 120 may be provided.

  Around the intermediate transfer belt 120, photosensitive drums 110K, 110C, 110M, and 110Y having photosensitive layers on four outer peripheral surfaces are arranged at predetermined intervals. The subscripts K, C, M, and Y mean that they are used to form black, cyan, magenta, and yellow visible images, respectively. The same applies to other members. The photosensitive drums 110K, 110C, 110M, and 110Y are rotationally driven in synchronization with the driving of the intermediate transfer belt 120.

  Around each photosensitive drum 110 (K, C, M, Y), a corona charger 111 (K, C, M, Y), an organic EL array exposure head 10 (K, C, M, Y), and Developers 114 (K, C, M, Y) are disposed. The corona charger 111 (K, C, M, Y) uniformly charges the outer peripheral surface of the corresponding photosensitive drum 110 (K, C, M, Y). The organic EL array exposure head 10 (K, C, M, Y) writes an electrostatic latent image on the charged outer peripheral surface of the photosensitive drum. In each organic EL array exposure head 10 (K, C, M, Y), the arrangement direction of the plurality of OLED elements 14 is aligned with the bus (main scanning direction) of the photosensitive drum 110 (K, C, M, Y). Installed. The electrostatic latent image is written by irradiating the photosensitive drum with light from the plurality of OLED elements 14. The developing device 114 (K, C, M, Y) forms a visible image, that is, a visible image on the photosensitive drum by attaching toner as a developer to the electrostatic latent image.

  The black, cyan, magenta, and yellow developed images formed by the four-color single-color image forming station are sequentially transferred onto the intermediate transfer belt 120 to be superimposed on the intermediate transfer belt 120. As a result, a full-color visible image is obtained. Four primary transfer corotrons (transfer devices) 112 (K, C, M, Y) are arranged inside the intermediate transfer belt 120. The primary transfer corotron 112 (K, C, M, Y) is disposed in the vicinity of the photosensitive drum 110 (K, C, M, Y), and the photosensitive drum 110 (K, C, M, Y). The electrostatic image is electrostatically attracted from the toner image to transfer the visible image to the intermediate transfer belt 120 passing between the photosensitive drum and the primary transfer corotron.

  A sheet 102 as an object on which an image is to be finally formed is fed one by one from the sheet feeding cassette 101 by the pickup roller 103, and between the intermediate transfer belt 120 and the secondary transfer roller 126 in contact with the driving roller 121. Sent to the nip. The full-color visible image on the intermediate transfer belt 120 is secondarily transferred to one side of the sheet 102 by the secondary transfer roller 126 and fixed on the sheet 102 through the fixing roller pair 127 as a fixing unit. . Thereafter, the sheet 102 is discharged onto a paper discharge cassette formed in the upper part of the apparatus by a paper discharge roller pair 128.

  FIG. 17 is a longitudinal sectional view of another image forming apparatus according to the embodiment of the present invention. This image forming apparatus is a rotary developing type full-color image forming apparatus using a belt intermediate transfer body system. In the image forming apparatus shown in FIG. 17, a corona charger 168, a rotary developing unit 161, an organic EL array exposure head 167, and an intermediate transfer belt 169 are provided around a photosensitive drum (image carrier) 165. Yes.

  The corona charger 168 uniformly charges the outer peripheral surface of the photosensitive drum 165. The organic EL array exposure head 167 writes an electrostatic latent image on the charged outer peripheral surface of the photosensitive drum 165. The organic EL array exposure head 167 is the exposure apparatus according to each of the embodiments described above or an exposure apparatus according to a modification thereof, and the arrangement direction of the plurality of light emitting elements 14 is set to the bus line (main scanning direction) of the photosensitive drum 165. It is installed along. The electrostatic latent image is written by irradiating the photosensitive drum with light by the plurality of light emitting elements 14 described above.

  The developing unit 161 is a drum in which four developing units 163Y, 163C, 163M, and 163K are arranged at an angular interval of 90 °, and can rotate counterclockwise about the shaft 161a. The developing units 163Y, 163C, 163M, and 163K supply yellow, cyan, magenta, and black toners to the photosensitive drum 165, respectively, and attach the toner as a developer to the electrostatic latent image, thereby the photosensitive drum 165. A visible image, that is, a visible image is formed.

  The endless intermediate transfer belt 169 is wound around a driving roller 170a, a driven roller 170b, a primary transfer roller 166, and a tension roller, and is rotated around these rollers in a direction indicated by an arrow. The primary transfer roller 166 transfers the visible image to the intermediate transfer belt 169 that passes between the photosensitive drum and the primary transfer roller 166 by electrostatically attracting the visible image from the photosensitive drum 165.

  Specifically, in the first rotation of the photosensitive drum 165, an electrostatic latent image for a yellow (Y) image is written by the exposure head 167, and a developed image of the same color is formed by the developing unit 163Y. The image is transferred to the transfer belt 169. Further, in the next rotation, an electrostatic latent image for a cyan (C) image is written by the exposure head 167, and a developed image of the same color is formed by the developing device 163C. The intermediate transfer is performed so as to overlap the yellow developed image. Transferred to the belt 169. Then, during the four rotations of the photosensitive drum 9, the yellow, cyan, magenta, and black visible images are sequentially superimposed on the intermediate transfer belt 169. As a result, a full-color visible image is formed on the transfer belt 169. It is formed. When images are finally formed on both sides of a sheet as an object on which an image is to be formed, the same color images of the front and back surfaces are transferred to the intermediate transfer belt 169, and then the front and back surfaces are transferred to the intermediate transfer belt 169. A full-color visible image is obtained on the intermediate transfer belt 169 by transferring the visible image of the next color.

  The image forming apparatus is provided with a sheet conveyance path 174 through which a sheet passes. The sheets are picked up one by one from the paper feed cassette 178 by the pick-up roller 179, advanced through the sheet transport path 174 by the transport roller, and between the intermediate transfer belt 169 and the secondary transfer roller 171 in contact with the drive roller 170a. Pass through the nip. The secondary transfer roller 171 transfers the developed image onto one side of the sheet by electrostatically attracting a full-color developed image from the intermediate transfer belt 169 collectively. The secondary transfer roller 171 can be moved closer to and away from the intermediate transfer belt 169 by a clutch (not shown). The secondary transfer roller 171 is brought into contact with the intermediate transfer belt 169 when a full-color visible image is transferred onto the sheet, and is separated from the secondary transfer roller 171 while the visible image is superimposed on the intermediate transfer belt 169.

  The sheet on which the image has been transferred as described above is conveyed to the fixing device 172 and is passed between the heating roller 172a and the pressure roller 172b of the fixing device 172, whereby the visible image on the sheet is fixed. The sheet after the fixing process is drawn into the discharge roller pair 176 and proceeds in the direction of arrow F. In the case of double-sided printing, after most of the sheet passes through the paper discharge roller pair 176, the paper discharge roller pair 176 is rotated in the reverse direction and introduced into the double-sided printing conveyance path 175 as indicated by an arrow G. The Then, the visible image is transferred to the other surface of the sheet by the secondary transfer roller 171, the fixing process is performed again by the fixing device 172, and then the sheet is discharged by the discharge roller pair 176.

Since each of the image forming apparatuses uses the exposure apparatus according to each of the above-described embodiments or the exposure apparatus according to the modification as the optical head, a clear image can be formed over a long period of time.
As described above, the image forming apparatus to which the exposure apparatus according to each of the above-described embodiments or the exposure apparatus according to the modification can be applied has been exemplified. However, it can be applied to other electrophotographic image forming apparatuses. Such an image forming apparatus is within the scope of the present invention. For example, the present invention can be applied to an image forming apparatus that transfers a visible image directly from a photosensitive drum to a sheet without using an intermediate transfer belt, and an image forming apparatus that forms a monochrome image.

1 is a perspective view of an exposure apparatus 10 according to a first embodiment of the present invention. 2 is a plan view of the exposure apparatus 10. FIG. 1 is a sectional view of an exposure apparatus 10. 3 is a schematic diagram showing an optical action in the exposure apparatus 10. FIG. It is a top view of the exposure apparatus 40 which concerns on the 1st Embodiment of this invention. 2 is a cross-sectional view of an exposure apparatus 40. It is sectional drawing of the exposure apparatus 41 which concerns on the modification of the exposure apparatus 40. FIG. It is sectional drawing of the exposure apparatus which concerns on the modification of the exposure apparatus. It is a top view of the exposure apparatus 50 which concerns on the 3rd Embodiment of this invention. 2 is a cross-sectional view of an exposure apparatus 50. It is sectional drawing of the exposure apparatus 51 which concerns on the exposure apparatus 50 as a modification. It is a top view of the exposure apparatus 60 which concerns on the 4th Embodiment of this invention. 2 is a cross-sectional view of an exposure apparatus 60. FIG. It is sectional drawing of the exposure apparatus 61 which concerns on the modification of the exposure apparatus 60. FIG. It is sectional drawing of the exposure apparatus 62 which concerns on the modification of the exposure apparatus 61. FIG. 1 is a longitudinal sectional view of an image forming apparatus according to an embodiment of the present invention. It is a longitudinal cross-sectional view of another image forming apparatus according to an embodiment of the present invention.

Explanation of symbols

  10, 40, 41, 42, 50, 51, 60, 61, 62 ... exposure apparatus, 14, 71 ... light emitting element, 21, 20, 70 ... light source substrate, 21, 73 ... element substrate, 45, 75, 81 ... Transparent member, 110 ... photosensitive drum (image carrier), L1, L2, L4, L6-L9 ... hologram lens (diffractive positive lens), L3 ... selfoc lens (rod lens), L5 ... micro lens (refractive positive lens) ), LA1, LA2, LA4, LA6 to LA9: Hologram lens array, LA3: Selfoc lens array, LA5: Micro lens array.

Claims (7)

A plurality of light emitting elements arranged on a light source substrate;
A first lens array having a plurality of diffractive positive lenses that diffract the transmitted light to converge the light flux of the light to form an image;
A second lens array having a plurality of lenses and sandwiching the first lens array between each of the plurality of light emitting elements;
Each of the plurality of diffractive positive lenses overlaps each of the plurality of light emitting elements in a direction perpendicular to the light source substrate.
An exposure apparatus characterized by that. The lens is a diffractive positive lens that converges the light bundle of light by diffracting the transmitted light and forms an image,
Each of the plurality of lenses overlaps each of the plurality of light emitting elements and each of the plurality of diffraction positive lenses in a direction perpendicular to the light source substrate.
An exposure apparatus characterized by that. Each of the plurality of lenses is a gradient index rod lens that guides light by refraction to form an erect image,
In the second lens array, the plurality of lenses are arranged so that an image formed by the plurality of lenses forms one continuous image.
An exposure apparatus characterized by that. A transparent member that is in contact with the second lens array and fills a gap between the first lens array and the second lens array;
The exposure apparatus according to claim 3, wherein: The lens is a refractive positive lens that converges the light flux of the light by refracting the transmitted light to form an image,
Each of the lenses overlaps each of the plurality of light emitting elements and each of the plurality of diffraction positive lenses in a direction perpendicular to the light source substrate.
The exposure apparatus according to claim 1, wherein: For the diffractive positive lens, the phase distribution φ (r) when the distance from the optical axis is r is expressed by the equation (1).
The exposure apparatus according to claim 1, wherein:
Here, C _{1 to} C ₁₀ are constants, and C ₁ is −10 or more and −0.1 or less.

An exposure apparatus according to any one of claims 1 to 6,
An image carrier,
Charging the image carrier, irradiating the charged surface of the image carrier with light from the exposure device to form a latent image, attaching toner to the latent image to form a visible image, and An image forming apparatus, wherein a visible image is transferred to another object.

Images