Patent Application
20060176538
The present application claims priority to Japanese Patent Application Nos. 2005-032777 filed in Japan on Feb. 9, 2005; 2005-087923 filed in Japan on Mar. 25, 2005; 2005-087927 filed in Japan on Mar. 25, 2005; and 2005-094778 filed in Japan on Mar. 29, 2005; which are hereby expressly incorporated by reference in their entireties.
The present invention relates to an image forming apparatus (image printing apparatus) in which a latent image is formed on an image carrier by light emitted from light emitting elements.
In general, an image forming apparatus includes an image carrier and a head facing the surface of the image carrier. A photoreceptor drum is generally used as the image carrier. A plurality of light emitting elements formed of a light emitting material, such as an organic EL (electroluminescent) material, is formed on a surface of the head facing the photoreceptor drum. A latent image is formed on the surface of the photoreceptor drum by light emitted from each light emitting element.
In the image forming apparatus according to the related art, when light emitted from each light emitting element reaches the surface of the photoreceptor drum to form a latent image (hereinafter, referred to as a ‘spot image’) in each region on the surface, a large variation in the area or shape of the latent image may occur. When a large variation occurs in the area or shape of the spot image, it is difficult to form a high-resolution latent image composed of fine pixels. The large variation in the area or shape of the spot image may occur due to a difference in distances between the surface of the photoreceptor drum and the light emitting elements. In order to solve this problem, JP-A-7-178956 discloses a structure in which a guide member coming into contact with the surface of a photoreceptor drum is fixed to a head, and JP-A-5-27563 discloses a structure in which end surfaces of light emitting elements come into contact with the surface of a photoreceptor drum.
However, in these structures, there is a fear that the head may be elastically deformed by friction force acting on the head (including the guide member and the light emitting elements) from the photoreceptor drum, which is generated by the rotation of the photoreceptor drum, and then restored to the original shape thereof when the stress of the head exceeds a threshold value, that is, the head may be vibrated. When the photoreceptor drum is driven at high speed, the vibration of the head becomes more remarkable. When the head is vibrated, a gap between the photoreceptor drum and each light emitting element is changed, which results in a large variation in the area or shape of the spot image with the passage of time. In addition, in these structures, there is a fear that the surfaces of the head and the photoreceptor drum may be rapidly worn away by friction therebetween, resulting in a large variation in gap between each light emitting element and the photoreceptor drum. That is, there is a fear that the area or shape of the spot image may be greatly varied with the passage of time.
An advantage of some aspects of the invention is that it provides an image forming apparatus capable of reducing a variation in the area or shape of a spot image.
According to an aspect of the invention, an image forming apparatus includes an image carrier that has an image carrier surface moving in a direction; a supporting member that faces the image carrier; a plurality of light emitting elements which are provided on a surface of the supporting member facing the image carrier and emit light to form a latent image on the image carrier; a roller which is arranged on the surface of the supporting member facing the image carrier such that a rotational shaft thereof extends in a direction traversing an image carrier surface; and an urging unit which urges the supporting member against the image carrier so that the roller comes into contact with the image carrier. According to this structure, since the supporting member is urged against the image carrier so that the roller comes into contact with the image carrier, a gap between the image carrier and the light emitting elements formed on the supporting member is maintained at a predetermined value. In addition, since the roller having a rotational shaft extending in the direction traversing the image carrier surface comes into contact with the image carrier, the roller rotates with the movement of the image carrier surface. Therefore, it is possible to prevent the vibration of the roller and the supporting member or the light emitting elements formed on the supporting member, and to reduce the degree of abrasion of a contact portion between the image carrier and the head. Thus, it is possible to reduce a variation in the area or shape of a spot image. In addition, even when a foreign material is caught between the image carrier and the roller, it can be rapidly removed therebetween by the rotation of the roller. Accordingly, it is possible to prevent the damage of the image carrier surface due to the foreign material being continuously stuck to the image carrier surface. These effects contribute to forming (printing) a stable and high-quality image.
Further, in the above-mentioned structure, it is preferable that the urging unit include a plurality of elastic members that is provided on a surface of the supporting member opposite to the image carrier to press the supporting member against the image carrier. According to this structure, it is possible to uniformly urge the supporting member against the image carrier with a simple structure.
Furthermore, in the above-mentioned structure, it is preferable that the urging unit include a frame member which has surfaces facing side surfaces of the supporting member; and elastic members which are provided between the side surfaces of the supporting member and the frame member. According to this structure, it is possible to reduce a space on the side of the supporting member opposite to the image carrier. In addition, in this structure, the urging unit may include elastic members which press the frame member against the image carrier. According to this structure, it is possible to reliably urge the supporting member against the image carrier.
Moreover, in the above-mentioned structure, preferably, a groove is formed in the surface of the supporting member facing the image carrier so as to extend in a direction traversing the image carrier surface, and the roller is accommodated in the groove such that an outer circumferential surface thereof partially protrudes, toward the image carrier, from the surface of the supporting member facing the image carrier. According to this structure, since a portion of the roller is accommodated in the groove, the thickness of the head including the supporting member, the roller, and the light emitting elements can be reduced. However, in this structure, the supporting member may be bent toward the roller to cause the bottom of the groove to come into contact with the roller. In this case, the rotation of the roller may be interrupted by friction caused by the contact therebetween. Therefore, it is preferable that an auxiliary roller be arranged in the bottom of the groove such that an outer circumferential surface thereof comes into contact with the outer circumferential surface of the roller. According to this structure, since the auxiliary roller rotates with the rotation of the roller, it is possible to smoothly rotate the roller. When the auxiliary is not provided, it is possible to smoothly rotate the roller by reducing a friction coefficient of the image carrier surface facing the roller of the supporting member or by forming the supporting member with a high-rigidity material to prevent the deformation thereof.
Further, in the above-mentioned structure, it is preferable that a plurality of the rollers be arranged in the supporting member so as to be opposite to each other with the plurality of light emitting elements interposed therebetween. According to this structure, it is possible to uniformly press the supporting member against the image carrier, and thus to maintain a uniform gap between the light emitting elements and the image carrier. In this structure, it is also preferable that the plurality of light emitting elements be arranged in the direction traversing the image carrier surface, and that the rollers be arranged so as to face the surface of the image carrier over the whole width of the image carrier. According to this structure, it is possible to maintain a uniform gap between the light emitting elements and the image carrier, and to shield light emitted from the light emitting elements by using the roller positioned at both sides of each light emitting element. Therefore, even when the light emitted from the light emitting elements is diffused, it is possible to selectively radiate light emitted from the light emitting elements onto a region of the image carrier interposed between the rollers.
Furthermore, in the above-mentioned structure, it is preferable that the image forming apparatus further include optical elements which are provided between the image carrier and the light emitting elements. For example, condensing lenses for condensing light emitted from the light emitting elements are provided between the image carrier and the light emitting elements. According to this structure, it is possible to effectively emit light from the light emitting elements to the image carrier. In this structure, since the are of a spot image (the area of a region where light emitted from the light emitting element is incident) is markedly changed according to a gap between the image carrier and the light emitting element, an error of the gap between the image carrier and the light emitting element allowable to form a spot image having a predetermined area on the image carrier surface is small, compared with a structure in which the lenses are not provided. According to this aspect, as described above, since it is possible to maintain a substantially uniform gap between the image carrier and the light emitting element, the structure in which the lenses are provided between the light emitting element and the image carrier also makes it possible to accurately form a desired spot image on the image carrier surface.
According to another aspect of the invention, an image forming apparatus includes an image carrier which has a curved image carrier surface moving in a direction (sub-scanning direction); a transmissive sliding member which has a sliding surface coming into surface contact with the image carrier surface, the sliding surface having a curvature substantially equal to that of the image carrier surface; and light emitting elements which are fixed to a surface of the sliding member opposite to the image carrier and which emit light to the image carrier surface to form a latent image on the image carrier. In this structure, the image carrier surface means the surface of the image carrier on which light emitted from the light emitting elements is incident. For example, the image carrier surface is an outer circumferential surface of a cylinder or hollow cylinder or an inner circumferential surface of a hollow cylinder. According to this structure, the light emitting elements are fixed on one surface of the sliding member, and the sliding surface of the sliding member, having a curvature substantially equal to that of the image carrier surface, comes into contact with the image carrier surface. Therefore, as compared with the structure in which the surface of the guide member or the end surface of the light emitting element comes into line contact with the surface of the image carrier, it is possible to accurately arrange the sliding member in a desired posture and at a desired position, and to accurately maintain the desired posture and position of the sliding member by preventing the vibration of the head. That is, it is possible to adjust the gap between the light emitting elements and the image carrier with high accuracy. Thus, the above-mentioned structure makes it possible to reduce a variation in the area or shape of a spot image. As a result, a high-quality image can be stably formed (printed).
Further, in the above-mentioned structure, preferably, the sliding member is arranged on the outside of the image carrier such that the sliding surface thereof comes into surface contact with the image carrier surface, which is an outer circumferential surface of a substantially cylindrical member (that is, a surface of the cylindrical member opposite to a center line thereof). According to this structure, it is possible to easily arrange the sliding member.
Furthermore, in the above-mentioned structure, preferably, the image carrier surface is an inner circumferential surface of a substantially cylindrical member, and the sliding member is arranged on the inside of the image carrier such that the sliding surface thereof comes into surface contact with the image carrier surface. According to this structure, it is possible to reduce a space require for arranging the sliding member.
Moreover, in the above-mentioned structure, it is preferable that the image forming apparatus further include an urging unit which urges the sliding member against the image carrier. According to this structure, it is possible to reliably maintain the posture or position of the sliding member with respect to the image carrier. In this aspect, elastic members, such as springs or rubber, are used for the urging unit. In this structure, the sliding member may be directly urged by the elastic members, or it may be indirectly urged against the image carrier by pressing a member fixed to the sliding member.
Further, in the above-mentioned structure, it is preferable that the light emitting elements be formed on the surface of the sliding member opposite to the sliding surface thereof and that a sealing member be formed on the surface of the sliding member opposite to the sling surface thereof so as to cover the light emitting elements. That is, in a structure in which a transmissive board having the light emitting element formed thereon transmits light emitted from the light emitting elements (a so-called bottom emission type), the board having the light emitting elements formed thereon can be used as the sliding member. According to this structure, it is possible to reduce the number of components and thus to achieve a reduction in manufacturing costs and a decrease in the number of manufacturing processes, compared with a structure in which the sliding member and the board having the light emitting elements formed thereon are composed of different members. Further, in this structure, preferably, a sealing member is formed on the surface of the sliding member opposite to the sliding surface so as to cover the light emitting elements. This structure makes it possible to prevent the deterioration of the light emitting elements due to permeation of air or water.
Furthermore, in the above-mentioned structure, it is preferable that the sliding member have an inclined surface which is positioned between the sliding surface and a side surface thereof located on the upstream side in a rotational direction of the image carrier and that the inclined surface be tilted such that an elevation angle with respect to the image carrier surface is an acute angle. In the structure in which the sliding surface and the side surface of the sliding member positioned on the upstream side in the rotational direction of the image carrier intersect each other at an acute angle, the image carrier surface may be damaged by collision with the edge of the sliding member. In contrast, according to this aspect, since the inclined surface is provided between the side surface and the sliding surface of the sliding member, it is possible to prevent the damage of the image carrier surface due to collision with the sliding member.
Moreover, in the above-mentioned structure, it is preferable that the image forming apparatus further include lenses which are provided between the image carrier surface and the light emitting elements to condense light emitted from the light emitting elements. According to this structure, it is possible to improve the utilization efficiency of light emitted from the light emitting elements. That is, it is possible to more reduce the amount of light required for forming a latent image on the image carrier, compared with the structure in which the lenses are not provided. Thus, it is possible to reduce power consumption and to prevent the deterioration of the light emitting elements.
Further, in the above-mentioned structure, preferably, the sliding member has, on the surface thereof facing the image carrier surface, a first portion in which the light emitting elements are formed and second portions which are positioned at both sides of the first portion in a direction traversing the image carrier surface and which protrude from the first portion toward the image carrier surface. In addition, preferably, the sliding surface is surfaces of the second portions facing the image carrier surface. According to this structure, the light emitting elements and the image carrier surface are separated from each other at a gap corresponding to a step difference between the first and second portions, which makes it possible to prevent the damage or deterioration of the light emitting elements due to contact with the image carrier surface.
Furthermore, in the above-mentioned structure, preferably, the image forming apparatus further includes a substrate which has the light emitting elements formed on a surface thereof facing the image carrier surface, and the sliding member is fixed to the substrate so as to be interposed between the light emitting elements and the image carrier. According to this structure, the substrate and the light emitting elements formed thereon are fixed on one surface of the sliding member, and the sliding surface of the sliding member, having a curvature substantially equal to that of the image carrier surface, comes into surface contact with the image carrier surface. Therefore, as compared with the structure in which the surface of the guide member or the end surface of the light emitting element comes into line contact with the surface of the image carrier, it is possible to accurately arrange the sliding member and the substrate in desired postures and at desired positions, and to accurately maintain the desired postures and positions of the sliding member and substrate by preventing the vibration of the head. That is, it is possible to adjust the gap between the light emitting elements and the image carrier with high accuracy. Thus, in this structure, it is preferable that the sliding member be composed of a sealing member for covering the light emitting elements together with the substrate. The sealing member seals the light emitting elements to protect them from the air.
Moreover, according to still another aspect of the invention, an image forming apparatus includes an image carrier which has an image carrier surface moving in a predetermined direction; a main substrate; light emitting elements which are formed on the main substrate and emit light to form a latent image on the image carrier surface; and a sealing substrate which overlaps the main substrate to seal the light emitting elements. In the image forming apparatus, the main substrate or the sealing substrate constitutes a contact surface coming into contact with the image carrier surface. Cylindrical optical waveguides, each having an end surface constituting a portion of the contact surface, are provided in the substrate constituting the contact surface. The other end surfaces of the optical waveguides cover the light emitting elements. Each optical waveguide guides light incident on the other end surface thereof to the one end surface by specularly reflecting the light from an outer circumferential surface thereof. In the image forming apparatus according to this aspect, the optical waveguides are provided in the substrate facing the image carrier, and the one end surface of each optical waveguide constitutes a portion of the contact surface coming into contact with the image carrier surface. Therefore, the other end surface of each optical waveguide is closer to the light emitting element than the one end surface thereof. In addition, the other end surfaces of the optical waveguides cover the light emitting elements. Most of light components emitted from the light emitting element to the substrate are incident on the other end surface of the cylindrical optical waveguide. The incident light is guided to the one end surface of the optical waveguide without leaking to the outside of the outer circumferential surface of the optical waveguide. Thus, a spot image having the same shape and size as those of the end surface of the optical waveguide is formed on the contact surface.
In general, when the light emitting element formed of a light emitting material, such as an organic EL material, contacts the air, the life span thereof is considerably shortened. Therefore, sealing the light emitting elements is indispensable. The sealing is performed by overlapping the sealing substrate with the main substrate having the light emitting elements formed thereon. Light emitted from the light emitting elements reaches the surface of the image carrier through one of the substrates. The light emitting elements are surface-emitting elements, and light emitted from a light emitting surface (light emitting layer) is diffused while traveling. Meanwhile, in order to ensure a sealing function, the main substrate and the sealing substrate need to have predetermined thicknesses. In general, light emitted from the light emitting surface is largely diffused at a point of time when it is emitted from the substrate. For example, when the light emitting surface has a diameter of 50 μm and a distance from the light emitting surface to the light emission surface of the substrate is 50 μm, a spot image having a diameter of about 100 μm is formed on the light emission surface. When a spot image having a large diameter is formed, the brightness of the spot image is lowered. In order to improve the brightness of the spot image while maintaining the size thereof, it is necessary to improve the brightness of the light emitting surface. For example, in the above-mentioned structure, in order to raise the brightness level of the spot image to the brightness level of the light emitting surface, it is necessary to raise the brightness of the light emitting surface by four times, which causes the life span of the light emitting element to be shortened. In addition, the larger the diameter of the spot image is, the lower the resolution of the spot image becomes.
When a latent image is formed, the surface of the image carrier moves. Therefore, in contact exposure in which the head comes into contact with the image carrier, a portion of the head coming into contact with the image carrier is worn away. When the contact portion of the head is worn away, an optical path from the light emitting element to the surface of the image carrier varies. As described above, in general, the variation of the optical path causes a change of the size a spot image. That is, a variation in the area or shape of a spot image occurs due to abrasion.
In contrast, in the image forming apparatus according to this aspect, light emitted from the light emitting element is guided, without leaking to the outside of the outer circumferential surface of the optical waveguide, to form a spot image, which makes it possible to achieve a high-definition spot image. In addition, since a spot image having the same size and shape as those of the end surface of the optical waveguide is formed on the contact surface, it is possible to reduce a variation in the area or shape of a spot image. Further, even when the optical waveguide is shortened due to the abrasion of the contact portion, the shape and size of the spot image formed on the contact surface are hardly varied, since the optical waveguide is a cylindrical member which guides light by specularly reflecting the light from the outer circumferential surface thereof and the central axis thereof extends in a direction where the contact surface recedes due to abrasion. Thus, it is possible to reduce a variation in the area or shape of the spot image, and thus to stably form a high-definition spot image. As can be seen from the above description, according to the image forming apparatus of this aspect, regardless of the contact exposure in which the head comes into contact with the image carrier, it is possible to guide light emitted from the light emitting elements without largely diffusing light in a transmissive substrate, and thus stably form a high-definition spot image. As a result, it is possible to stably form (printing) a high-quality image.
Further, in the above-mentioned structure, it is preferable that the optical waveguides are provided so as to pass through the substrate constituting the contact surface. This structure more reliably prevents the diffusion of light emitted from the light emitting elements.
Furthermore, in the above-mentioned structure, preferably, a concave portion is formed in a surface of the substrate constituting the contact surface which faces the image carrier, and an optical waveguide plate is fixed in the concave portion. In addition, preferably, the optical waveguides are formed in the optical waveguide plate. According to this structure, it is possible to more reduce the number of manufacturing processes and manufacturing costs, compare with the structure in which the optical waveguides are formed so as to pass through the substrate constituting the contact surface. As will be described below, this structure can ensure a sealing function. A member having the optical waveguides formed therein may be deformed due to a difference between thermal shrinkage (expansion) of the optical waveguides and thermal shrinkage (expansion) of peripheral portions thereof. In the structure in which the optical waveguides are formed so as to pass through the substrate, a bonding surface of the optical waveguide and the peripheral portion thereof extends from an internal space on the light emitting side to an external space. When a gap is formed along the bonding surface due to the deformation, the sealing function is deteriorated. In contrast, in the structure in which the optical waveguide plate is fixed in the concave portion, the optical waveguides are formed in a member other than the substrate. Therefore, even when a gap is formed along the bonding surface between the optical waveguide and a peripheral portion thereof, the sealing function is not deteriorated since the bonding surface does not extend to the internal space. In addition, since the optical waveguides are formed in the optical waveguide plate, not in the main substrate and the sealing substrate, it is possible to reduce a possibility that the main substrate or the sealing substrate will be deformed due to the difference.
Moreover, in the above-mentioned structure, it is preferable that the substrate constituting the contact surface be the sealing substrate. A method of cutting the substrate can be used to the optical waveguides in the substrate. However, in this aspect, when the method is used, it is preferable to cut the sealing member, not the main substrate requiring a high degree of utilization efficiency of light. Therefore, the utilization efficiency of the mains substrate is not lowered, which is effective in the mass production.
Further, in the above-mentioned structure, it is preferable that the substrate constituting the contact surface be the main substrate. According to this structure, it is possible to more reduce a distance from the light emitting layer to the optical waveguide, compared with the structure in which the substrate constituting the contact surface is the sealing substrate. This structure contributes to an improvement in brightness.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
In the drawings used for describing the following preferred embodiments of the invention, scales and dimensions of components are different from actual scales and dimensions thereof.
First Embodiment
The light emitting device 33 emits light to form a latent image on the photoreceptor drum 110. As shown in
Meanwhile, each roller 35 is composed of a cylindrical black member having a diameter of about 1 mm to 2 mm, and is formed of a resin material, such as plastic. The total length of the roller 35 is equal to or larger than the width of the photoreceptor drum 110 (dimensions in the drum axis direction X).
Further, grooves 311 are formed in a surface of the supporting member 31 opposite to the photoreceptor drum 110 at both sides of the light emitting device 33. Each groove 311 is a concave portion having a width larger than the diameter of the roller 35 (about 1 mm to 2 mm), and extends in the drum axis direction X, corresponding to the arrangement of the light emitting device 33. Each roller 35 is provided in the groove 311. Therefore, the rotational axis of the roller 35 extends a direction traversing the surface of the photoreceptor drum 110 (that is, a direction parallel to the drum axis direction X). In addition, as described above, since the total length of the roller 35 is equal to or larger than the width of the photoreceptor drum 110, the roller 35 is opposite to the entire surface of the photoreceptor drum 110 in the widthwise direction.
As shown in
As shown in
For example, a coil spring having one end fixed to the supporting member 31 and the other end fixed to the case 50 is used as the elastic body 41. However, the elastic body 41 may have any other shapes. That is, any members can be used as long as they can urge the supporting member 31 against the photoreceptor drum 110. For example, various members, such as a leaf spring and rubber interposed between the supporting member 31 and the case 50, can be used as the elastic bodies 41.
As represented by arrow F1 in
As described above, in the first embodiment, the elastic bodies 41 press the supporting member 31 to allow the roller to come into contact with the surface of the photoreceptor drum 110. Therefore, even when errors occur in the dimensions of the head 10 and the photoreceptor drum 110 or in the mounting positions thereof, or even when surface deflection occurs in the surface of the photoreceptor drum 110 due to insufficient circularity of the cross section of the photoreceptor drum 110 or an error in the drum axis direction X, each light emitting element 332 follows the surface of the photoreceptor drum 110. Therefore, it is possible to maintain a predetermined gap between the light emitting elements 332 and the photoreceptor drum 110.
Further, the rollers 35 of the head 10 come into contact with the surface of the photoreceptor drum 110 and rotate with the revolution of the photoreceptor drum 110, which makes it possible to solve various problems due to contact between the head 10 and the photoreceptor drum 110.
For example, the related art has a problem in that the head vibrates due to contact with the photoreceptor drum. However, in the first embodiment, friction force generated from the photoreceptor drum 110 is hardly applied to the head 10, making it possible to prevent the vibration of the head 10 due to the rotation of the photoreceptor drum 110. Therefore, it is possible to keep a predetermined gap between the light emitting elements 332 and the photoreceptor drum 110 with high accuracy. In addition, this structure has an advantage of reducing the friction of a contact portion between the head 10 and the photoreceptor drum 110, compared with the structure in which the photoreceptor drum rotates with its surface coming into contact with the head. Therefore, it is possible to prevent a variation in the gap between the light emitting element 332 and the photoreceptor drum 110 with the passage of time, and thus to maintain a uniform gap therebetween.
In general, a variation in the area or shape of a spot image formed on the surface of the photoreceptor drum may be caused by, for example, an error in the dimensions of the head or the photoreceptor drum or an error in the mounting positions thereof. In contrast, the structure according to the first embodiment can absorb these errors, which makes it possible to maintain a predetermined gap between the light emitting element 332 and the photoreceptor drum 110.
As described above, according to the first embodiment, it is possible to reduce a variation in the area or shape of the spot image formed on the surface of the photoreceptor drum 110. In addition, according to the first embodiment, a predetermined amount of light is radiated onto a region where the spot image is formed, and thus a clear spot image can be obtained. Further, according to the first embodiment, even when a foreign matter is caught between the roller 35 and the photoreceptor drum 110, the foreign matter can be rapidly removed by the rotation of the roller 35, which prevents the surface of the photoreceptor drum 110 from being damaged due to the foreign matter.
Furthermore, according to the first embodiment, a plurality of elastic bodies 41 is evenly arranged on the upper surface of the supporting member 31. This structure makes it possible to uniformly press, for example the supporting member 31, compared with a structure in which the elastic bodies 41 are unevenly arranged in a predetermined region on the upper surface of the supporting member 31. Therefore, it is possible to maintain a uniform gap between the light emitting elements 332 and the photoreceptor drum 110.
As shown in
Moreover, according to the first embodiment, the rollers 35 arranged at both sides of the light emitting elements 332 have a light shielding property. According to this structure, light which has been emitted from the light emitting elements 332 and then has been diffused at a wide angle is shielded by the roller 35. Therefore, it is possible to selectively radiate light from the light emitting elements 332 onto only a region on the surface of the photoreceptor drum 110 between the rollers 35 (a region R shown in
Second Embodiment
A plurality of elastic bodies 42 is provided between the inner circumferential surface of the frame member 53 and the side surface of supporting member 31. An end of each elastic body 42 is fixed to the inner circumferential surface of the frame member 53, and the other end thereof is fixed to the side surface of the supporting member 31. More specifically, as shown in
Further, a plurality of elastic bodies 43 is arranged on a surface of the frame member 53 opposite to the photoreceptor drum 10. The elastic bodies 43 are members for urging the frame member 53 against the photoreceptor drum 110, and are provided between the case 50 of the image forming apparatus and the frame member 53. In the second embodiment, six elastic bodies 43 are arranged around four corners of the frame member 53 and in a central portion thereof in the longitudinal direction. The elastic bodies 42 and 43 are the same components as the elastic bodies 41 of the first embodiment. For example, coil springs or leaf springs are used as the elastic bodies 42 and 43.
In the above-mentioned structure, when the elastic bodies 43 urge the frame member 53 against the photoreceptor drum 110, the elastic bodies 42 are extended. Then, the supporting member 31 is urged against the photoreceptor drum 110 by elastic force generated by the elastic bodies 42. Therefore, in the second embodiment, the rollers 35 is also pressed against the photoreceptor 110, and thus the same effects as those in the first embodiment can be obtained. The frame member 53 can have any shapes as long as it has a portion opposite to the side surface of the supporting member 31. Therefore, the shape of the frame member 53 is not limited to that shown in
In the above-mentioned structure, the elastic bodies 43 press the frame member 53 against the photoreceptor drum 110. However, as shown in
Modifications of First and Second Embodiments
Various modifications of the above-mentioned embodiments can be made. The modifications thereof will be described in detail. The following modifications may be appropriately combined.
First Modification
In the above-mentioned embodiments, the head 10 is arranged so as to face the outer circumferential surface of the cylindrical photoreceptor drum 110. However, as shown in
Second Modification
In the above-mentioned embodiments, the cylindrical photoreceptor drum 110 is used as an image carrier. However, as shown in
Third Embodiment
As described in the first embodiment, when the bottom 312 of the groove 311 formed in the supporting member 31 comes into contact with the roller 35, the rotation of the roller 35 is interrupted. In order to solve the problem, in the first embodiment, the bottom 312 of the groove 311 having a small friction coefficient is used. However, the structure shown in
Fourth Modification
In the above-mentioned embodiments, the light emitting device 33 is opposite to the photoreceptor drum 110 without any members interposed therebetween (that is, any members are not provided between the light emitting device 33 and the photoreceptor drum 110). However, optical members may be provided between the light emitting device 33 and the photoreceptor drum 110. For example, an optical waveguide (for example, an optical fiber) for guiding light emitted from the light emitting elements 332 to the surface of the photoreceptor drum 110 or a lens (for example, a condensing lens array) for condensing light emitted from the light emitting elements 332 may be provided between the light emitting device 33 and the photoreceptor drum 110.
Further, as shown in
In the structure in which light emitted from the light emitting elements 332 is condensed by the microlenses 74, even when a distance between the light emitting element 332 and the photoreceptor drum 110 varies slightly, a variation in the diameter of a spot region on the surface of the photoreceptor drum 110 where light emitted from the light emitting element 332 is incident becomes remarkable. According to the fourth modification, the roller 35 makes it possible to maintain a uniform gap between the light emitting device 33 and the photoreceptor drum 110 with high accuracy. Therefore, in the structure capable of improving the utilization efficiency of light by using the microlenses 74, it is also possible to accurately form a predetermined latent image on the surface of the photoreceptor drum 110. That is, the effects of maintaining a uniform gap between the light emitting device 33 and the photoreceptor drum 110 can be more reliably obtained by the structure in which optical components, such as the microlenses 74, are arranged between the light emitting device 33 and the photoreceptor drum 110, as shown in
Fifth Modification
In the above-mentioned embodiments, two rollers 35 are arranged at both sides of the light emitting device 33. However, the number of rollers 35 and the positions thereof can be changed. In the first embodiment, the light-shielding rollers 35 prevent the diffusion of light emitted from the light emitting elements 332. The roller 35 may be formed of a transmissive material, or the total length of the roller 35 may be smaller than the width of the photoreceptor drum 110 as long as the diffusion of light emitted from the light emitting elements 332 does not matter particularly (for example, a member for shielding diffused light is separately provided from the roller 35, or the diffusion of light is suppressed by an optical component such as a lens). In addition, as shown in
Third Embodiment
As shown in
The substrate 31a shown in
Next,
Meanwhile, the inclined surface 45a is positioned between the sliding surface 41a and a side surface 47a located at the upstream side of the substrate 31a in a rotational direction A of the photoreceptor drum 110. As shown in
As described above, in the third embodiment, the sliding surface 41a having a curvature substantially equal to that of the outer circumferential surface 21 of the photoreceptor drum 110 comes into contact with the outer circumferential surface 21 of the photoreceptor drum 110. Therefore, it is possible to accurately maintain a predetermined distance between the light emitting elements 38 and the outer circumferential surface 21 of the photoreceptor drum 110, compared with the structure in which the drum opposing surface Sa1 is flat. This effect will be described below.
As a structure compared with the third embodiment, a head 10x including a substrate 31b having a flat drum opposing surface Sa1 is considered, as shown in
In contrast, in the third embodiment, the surface contact between the sliding surface 41a and the outer circumferential surface 21 of the photoreceptor drum 110 enables a stable posture or position of the head 10a with respect to the photoreceptor drum 110. That is, the surface contact therebetween effectively prevents the inclination of the head 10a as shown in
Further, in the third embodiment, since a portion of the drum opposing surface Sa1 of the substrate 31a arranged on the upstream side thereof in the rotational direction A of the photoreceptor drum 110 serves as the inclined surface 45a, it is possible to prevent the damage of the outer circumferential surface 21 due to collision between the drum opposing surface Sa1 and the outer circumferential surface 21 of the photoreceptor drum 110. For example, a structure in which the drum opposing surface Sa1 (that is, for example, as shown in
Fourth Embodiment
In the fourth embodiment, the sliding surface 41c having a curvature substantially equal to that of the inner circumferential surface 22 of the photoreceptor drum 110 comes into surface contact with the inner circumferential surface 22. Therefore, it is possible to maintain a predetermined distance between the light emitting elements 38 and the inner circumferential surface 22 of the photoreceptor drum 110 with high accuracy, similar to the third embodiment. Further, in the fourth embodiment, since the head 10b is accommodated inside the photoreceptor drum 110, it is possible to reduce a space required for arranging the head, compared with the third embodiment in which the head 10a is arranged outside the photoreceptor drum 110.
Fifth Embodiment
In the third embodiment, the sliding surface 41a is formed on the entire surface of the substrate 31a in the longitudinal direction (drum axis direction X) thereof. In contrast, in the fifth embodiment, only both ends of the substrate having the light emitting elements 38 formed thereon in the longitudinal direction (drum axis direction) serve as the sliding surface. In the fifth embodiment, the same components as those in the third embodiment have the same reference numerals, and a description thereof will be omitted.
The substrate 50a includes a first portion 51 having a plurality of light emitting elements 38 on a surface opposite to the photoreceptor drum 110 and second portions 52 arranged at both ends thereof in the longitudinal direction. Surfaces of the second portions 52 opposite to the photoreceptor drum 110 protrude from the surface of the first portion having the light emitting elements 38 formed thereon toward the photoreceptor drum 110. Therefore, as shown in
In the fifth embodiment, as shown in
In the fifth embodiment, the head 10c is opposite to the outer circumferential surface 21 of the photoreceptor drum 110. However, the head 10c may be opposite to the inner circumferential surface 22 of the photoreceptor drum 110, as in the fourth embodiment. In this structure, the sliding surface 521 of the second portion 52 of the substrate 50a opposite to the inner circumferential surface 22 of the photoreceptor drum 110 is a curved surface (convex surface) which has a curvature substantially equal to that of the inner circumferential surface 22 and protrudes toward the photoreceptor drum 110. In addition, in FIGS. 21 to 23, parts of the second portions 52 opposite to the photoreceptor drum 110 serve as the sling surface 521. However, an inclined surface 45, which is the same as that in the third or fourth embodiment, may be formed in the second portion 52.
In FIGS. 21 to 23, the top-emission-type head 10c is used. However, the fifth embodiment can be applied to a bottom-emission-type head. That is, when both ends (second portions 52) of the drum opposing surface Sa1 of the substrate shown in
Further, in FIGS. 21 to 23, the substrate 50a is formed of a single plate. However, similar to the third embodiment or the fourth embodiment, a base member formed by laminating a plurality of substrates may be used. In addition, as shown in
Sixth Embodiment
In the third embodiment, a plurality of elastic bodies 631 is arranged on the surface of the head 10a opposite to the photoreceptor drum 110. In contrast, in the sixth embodiment, elastic bodies arranged on the side surfaces of the head 10a urge the head 10a against the photoreceptor drum 110. In the sixth embodiment, the same components as those in the third embodiment have the same reference numerals, and a description thereof will be omitted.
A plurality of elastic bodies 632 is provided between the inner circumferential surface of the frame member 65 and the side surface of the head 10a. Each elastic body 632 has one end fixed to the inner circumferential surface of the frame member 65 and the other end fixed to the side surface of the head 10a. More specifically, as shown in
Further, a plurality of elastic bodies 633 is arranged on a surface of the frame member 65 opposite to the photoreceptor drum 10. The elastic bodies 633 are members for urging the frame member 65 against the photoreceptor drum 110, and are provided between the case 60 of the image forming apparatus and the frame member 65. In the sixth embodiment, six elastic bodies 633 are arranged around four corners of the frame member 65 and in a central portion thereof in the longitudinal direction. The elastic bodies 632 and 633 are the same components as the elastic bodies 631 of the third embodiment. For example, coil springs or leaf springs are used as the elastic bodies 632 and 633.
In the above-mentioned structure, when the elastic bodies 633 press the frame member 65 against the photoreceptor drum 110, the elastic bodies 632 are extended. Then, the head 10a is urged against the photoreceptor drum 110 by elastic force generated by the elastic bodies 632. Therefore, the sixth embodiment can obtain the same effects as those in the third embodiment.
In the above-mentioned structure, the elastic bodies 633 press the frame member 65 against the photoreceptor drum 10. However, as shown in
In FIGS. 24 to 26, the head 10a according to the third embodiment is urged. However, the fourth embodiment or the fifth embodiment can adopt the structure in which the head 10a is urged against the photoreceptor drum 110 by the components of the sixth embodiment, such as the frame member 65 and the elastic bodies 632.
Modifications of Third to Sixth Embodiments
Various modifications of the third to sixth embodiments can be made. The modifications thereof will be described in detail. The following modifications may be appropriately combined.
First Modification
In the third, fourth, and sixth embodiments, the surface of the head opposite to the photoreceptor drum 110 includes an inclined surface. However, the inclined surface is not necessarily needed. For example, in the third or sixth embodiment, as shown in
Second Modification
In the third to sixth embodiments, optical components may be provided between the light emitting elements 38 and the photoreceptor drum 110. For example, an optical waveguide (for example, an optical fiber) for guiding light emitted from the light emitting elements 38 to the surface of the photoreceptor drum 110 or a lens for condensing light emitted from the light emitting elements 38 may be provided between the light emitting elements 38 and the photoreceptor drum 110.
A resin material having a different reflective index from those of the substrate 31h and the board 56a is filled up into spaces formed by the concave portions 31h1 of the substrate 31h and the concave portions 56a1 of the substrate 56a, thereby forming the microlenses 55a, which are double-sided convex lenses. The microlenses 55a condense light emitted from the corresponding light emitting elements 38, so that an image is formed on the surface of the photoreceptor drum 110. The shape and arrangement of the microlenses 55a are not limited to those shown in
In the structure in which light emitted from the light emitting elements 38 is condensed by the microlenses 55a, even when a distance between the light emitting elements 38 and the photoreceptor drum 110 varies slightly, a variation in the area of a spot on the surface of the photoreceptor drum 110 where light emitted from the light emitting element 38 is incident becomes remarkable. According to this modification, the surface contact between the photoreceptor drum 110 and the sliding surface having a curvature substantially equal to that of the surface of the photoreceptor drum 110 makes it possible to maintain a uniform distance between the light emitting elements 38 and the photoreceptor drum 110 with high accuracy. Therefore, in the structure capable of improving the utilization efficiency of light by using the microlenses 55a, it is also possible to accurately form a predetermined latent image on the surface of the photoreceptor drum 110. That is, the effects of maintaining the uniform distance between the light emitting elements 38 and the photoreceptor drum 110 can be more reliably obtained by the structure in which optical components, such as microlenses, are arranged between the light emitting elements 38 and the photoreceptor drum 110, as shown in
Seventh Embodiment
As shown in
The substrate 32 shown in
Next,
Meanwhile, the inclined surface 45d is positioned between the sliding surface 41d and a side surface 47d located at the upstream side of the sealing member 36d in a rotational direction A of the photoreceptor drum 110. As shown in
The above-mentioned sealing member 36d is formed by a method (injection molding) of hardening an ultraviolet-curable or thermosetting resin material filled into a mold by heating or radiation of ultraviolet rays and of taking it out or by a method of mechanically or chemically polishing a board which is formed substantially in a rectangular shape so as to cover the element forming surface Sa2 of the substrate 32. The former shaping method has an advantage that an inexpensive sealing member 36d can be produced in large quantities. In addition, the substrate 32 is fit into a groove formed by mechanically or chemically polishing the surface of the sealing member 36d opposite to the drum opposing surface Sa1 and is then fixed to the sealing member 36d by an adhesive.
As described above, in the seventh embodiment, the sliding surface 41d having a curvature substantially equal to that of the outer circumferential surface 21 of the photoreceptor drum 110 comes into surface contact with the outer circumferential surface 21 of the photoreceptor drum 110. Therefore, it is possible to accurately maintain a predetermined distance between each light emitting element 38 and the outer circumferential surface 21 of the photoreceptor drum 110, compared with the structure in which the drum opposing surface Sa1 is flat. This effect will be described below.
As a structure compared with the seventh embodiment, a head 10y including a sealing member 36 having a flat drum opposing surface Sa1 is considered, as shown in
In contrast, in the seventh embodiment, the surface contact between the sliding surface 41d and the outer circumferential surface 21 of the photoreceptor drum 110 enables the stale posture or position of the head 10d with respect to the photoreceptor drum 110. That is, the surface contact therebetween effectively prevents the inclination of the head 10d as shown in
Further, in the seventh embodiment, since a portion of the drum opposing surface Sa1 of the sealing member 36d arranged on the upstream side thereof in the rotational direction A of the photoreceptor drum 110 is the inclined surface 45d, it is possible to prevent the damage of the outer circumferential surface 21 due to collision between the drum opposing surface Sa1 and the outer circumferential surface 21 of the photoreceptor drum 110. For example, a structure in which the drum opposing surface Sa1 does not include the inclined surface 45d (that is, for example, as shown in
In the above-mentioned embodiment, the top-emission-type head 10d is used. However, as described above, the structure in which the sliding surface comes into surface contact with the photoreceptor drum 110 can be applied to a bottom-emission-type head, as shown in
The substrate needs to have high flatness in order to form the light emitting elements 38 thereon. For example, the substrate is more expensive than the sealing member not requiring high flatness. Therefore, from the viewpoint of a reduction in manufacturing costs, it is preferable that the substrate have a small size. In addition, when a plurality of substrates is manufactured by dividing a large board (a so-called mother glass), the larger the number of substrates obtained from one board is, the lower the manufacturing costs thereof becomes. Therefore, from this point of view, it is preferable that the substrate have a small size. Meanwhile, as shown in
In contrast, in the seventh embodiment shown in FIGS. 30 to 33, since the sealing member 36d, not the substrate 32, comes into contact with the photoreceptor drum 110, it is possible to reliably ensure a sufficient area of the sliding surface coming into contact with the photoreceptor drum 110, regardless of the size of the substrate 32. For example, in the structure shown in
Further, in the structure shown in
Eighth Embodiment
In the eighth embodiment, the sliding surface 41e having a curvature substantially equal to that of the inner circumferential surface 22 of the photoreceptor drum 110 comes into surface contact with the inner circumferential surface 22. Therefore, the same effects as those in the seventh embodiment can be obtained. Further, in the eighth embodiment, since the head 10e is accommodated inside the photoreceptor drum 110, it is possible to reduce a space required for arranging the head, compared with the seventh embodiment in which the head 10d is arranged outside the photoreceptor drum 110.
Ninth Embodiment
In the seventh embodiment, a plurality of elastic bodies 631 is arranged on the surface of the head 10d opposite to the photoreceptor drum 110. In contrast, in the ninth embodiment, elastic bodies arranged on the side surfaces of the head 10d urge the head 10d against the photoreceptor drum 110. In the ninth embodiment, the same components as those in the seventh embodiment have the same reference numerals, and a description thereof will be omitted.
A plurality of elastic bodies 632 is provided between the inner circumferential surface of the frame member 65 and the side surface of the head 10d. Each elastic body 632 has one end fixed to the inner circumferential surface of the frame member 65 and the other end fixed to the side surface of the head 10d. More specifically, as shown in
Further, a plurality of elastic bodies 633 is arranged on a surface of the frame member 65 opposite to the photoreceptor drum 110. The elastic bodies 633 are members for urging the frame member 65 against the photoreceptor drum 110, and are provided between the case 60 of the image forming apparatus and the frame member 65. In the ninth embodiment, six elastic bodies 633 are arranged around four corners of the frame member 65 and in a central portion thereof in the longitudinal direction. The elastic bodies 632 and 633 are the same components as the elastic bodies 631 of the seventh embodiment. For example, coil springs or leaf springs are used as the elastic bodies 632 and 633.
In the above-mentioned structure, when the elastic bodies 633 press the frame member 65 against the photoreceptor drum 110, the elastic bodies 632 are extended. Then, the head 10d is urged against the photoreceptor drum 110 by elastic force generated by the elastic bodies 632. Therefore, the ninth embodiment can obtain the same effects as those in the seventh embodiment.
In the above-mentioned structure, the elastic bodies 633 press the frame member 65 against the photoreceptor drum 110. However, as shown in
In FIGS. 38 to 40, the head 10d according to the seventh embodiment is urged. However, similar to the eighth embodiment, the head 10d is urged against the photoreceptor drum 110 by the components of the ninth embodiment, such as the frame member 65 and the elastic bodies 632.
Modifications of Seventh to Ninth Embodiments
Various modifications of the seventh to ninth embodiments can be made. The modifications thereof will be described in detail. The following modifications may be appropriately combined.
First Modification
In the seventh to ninth embodiments, the drum opposing surface Sa1 includes an inclined surface. However, the inclined surface is not necessarily needed. For example, in the seventh or ninth embodiment, as shown in
Second Modification
In the seventh to ninth embodiments, optical components may be provided between the light emitting elements 38 and the photoreceptor drum 110. For example, an optical waveguide (for example, an optical fiber) for guiding light emitted from the light emitting elements 38 to the surface of the photoreceptor drum 110 or a lens for condensing light emitted from the light emitting elements 38 may be provided between the light emitting elements 38 and the photoreceptor drum 110.
A resin material having a different reflective index from those of the sealing member 36c and the board 56b is filled up into spaces formed by the concave portions 36c1 of the sealing member 36c and the concave portions 56b1 of the substrate 56b, thereby forming the microlenses 55b, which are double-sided convex lenses. The microlenses 55b condense light emitted from the corresponding light emitting elements 38, so that an image is formed on the surface of the photoreceptor drum 110. The shape and arrangement of the microlenses 55b are not limited to those shown in
In the structure in which light emitted from the light emitting elements 38 is condensed by the microlenses 55b, even when a distance between the light emitting elements 38 and the photoreceptor drum 110 varies slightly, a variation in the area of a spot on the surface of the photoreceptor drum 110 where light emitted from the light emitting element 38 is incident becomes remarkable. According to this modification, the surface contact between the photoreceptor drum 110 and the sliding surface having a curvature substantially equal to that of the surface of the photoreceptor drum 110 makes it possible to maintain a uniform distance between the light emitting elements 38 and the photoreceptor drum 110 with high accuracy. Therefore, in the structure capable of improving the utilization efficiency of light by using the microlenses 55b, it is also possible to accurately form a predetermined latent image on the surface of the photoreceptor drum 110. That is, the effects of maintaining the uniform distance between the light emitting elements 38 and the photoreceptor drum 110 can be more reliably obtained by the structure in which optical components, such as the microlenses 55b, are arranged between the light emitting elements 38 and the photoreceptor drum 110, as shown in
Third Modification
In the first to ninth embodiments, the light emitting element includes the light emitting layer formed of an organic EL material. However, functions related to the above-mentioned embodiments or modifications may be realized by using a head having light emitting elements arranged therein, each including a light emitting layer formed of an inorganic EL material, or a head having light emitting diodes (LEDs) as light emitting elements. That is, elements which emit light when electric energy is applied as well as the light emitting elements each including a light emitting layer formed of an organic EL material can be used.
Tenth to Thirteenth Embodiments
Hereinafter, the tenth to thirteenth embodiments according to the invention will be described in detail. In the following drawings used for the description, only the main parts are hatched. In addition, the image forming apparatuses of the tenth to thirteenth embodiments differ from each other in the structure of the head 10, and thus a description of the above-mentioned embodiments will be made, centered on the structure of the head 10. In the tenth embodiment, the head 10 is denoted by reference numeral 200. In the eleventh embodiment, the head 10 is denoted by reference numeral 300. In the twelfth embodiment, the head 10 is denoted by reference numeral 201. In the thirteenth embodiment, the head 10 is denoted by reference numeral 301.
Tenth Embodiment
Further, the sealing substrate 230 overlaps the main substrate 220 having the light emitting elements 205 formed thereon so as to seal the light emitting elements 205 together with the main substrate 220. The sealing protects the light emitting elements 205 from the air (in particular, water and oxygen) and thus prevents the deterioration thereof. A transmissive adhesive 290 is used to fix the sealing substrate 230 to the main substrate 220. For example, a thermosetting adhesive or an ultraviolet-curable adhesive is used as the adhesive 290.
The sealing method used for this technical field includes a film sealing method in which the entire surface of the sealing substrate 230 is bonded to the main substrate 220 by the adhesive 290 and a gap sealing method in which the periphery of the sealing substrate 230 is bonded to the main substrate 220 by the adhesive 290 to form spaces defined by the sealing substrate 230 and the main substrate 220 around the light emitting elements 205. A drying agent is arranged in the spaces in the gap sealing method. In the tenth embodiment, the film sealing method is used, but the gap sealing method can be used.
The sealing substrate 230 is formed by arranging a plurality of optical waveguides 235 in a plate 231. The plate 231 is formed of, for example, glass, metal, ceramic, or plastic. Each optical waveguide 235 is provided so as to pass through the front and rear surfaces of the sealing substrate 230, and the central axis thereof extends in the thickness direction of the sealing substrate 230. In addition, the outer circumferential surface of each optical waveguide 235 is covered with the plate 231. One end surface of the optical waveguide 235 facing the light emitting element 205 serves as a portion of the rear surface of the sealing substrate 230, and the other end surface thereof serves as a portion of the front surface (the light emission surface S200) of the sealing substrate 230. The one end surface of the optical waveguide 235 facing the light emitting element 205 covers the light emitting layer 210 of the corresponding light emitting element 205, as viewed from the light emission surface S200.
Further, the optical waveguides 235 are formed of a transmissive material. The material has a refractive index which is equal to that of the adhesive 290 and is higher than that of a material forming the plate 231.
In addition, the optical waveguides 235 are fixed to the plate 231. Any methods can be used to fix the optical waveguides 235 to the plate, but attentions should be paid when using a method in which the outer circumferential surface of the optical waveguide 235 does not contact the plate 231. In this case, a method of fixing the optical waveguides 235 to the plate 231 using an adhesive is considered. In this method, an adhesive needs to have a refractive index lower than that of a material forming the optical waveguide 235. That is, the outer circumferential surfaces of the optical waveguides 235 must be covered with a material having a refractive index lower than that of the material.
When the light components traveling in the optical waveguide 235 reach the outer circumferential surface of the optical waveguide 235, most of them are specularly reflected therefrom. That is, the optical waveguide 235 functions as a core of an optical fiber having a large diameter to guide the incident light. The reason why the specular reflection occurs is that an angle between the outer circumferential surface of the optical waveguide 235 and the traveling direction of light reached the outer circumferential surface is generally very small. In order words, this is because, in general, the incident angle of light on the outer circumferential surface of the optical waveguide 235 is very large. More specifically, the reason is as follows.
Since the refractive index of the material forming the optical waveguide 235 is higher than that of a material covering the outer circumferential surface thereof (for example, an adhesive or a material forming the plate 231), most of the light components traveling in the optical waveguide 235 are specularly reflected. However, in order for the specular reflection, the incident angle should be larger than a threshold angle which is determined on the basis of the ratio of two reflective indexes. Therefore, as described above, since the incident angle of light with respect to the outer circumferential surface is generally very large, most of the light components reached the outer circumferential surface are specularly reflected therefrom as long as a material having an excessive threshold angle is not used. Therefore, it is preferable to select a material forming the optical waveguides 235 and a material covering the outer circumferential surfaces thereof such that a large number of light components are specular reflected.
In this way, light travels in the optical waveguide 235 and is then emitted from the end surface of the optical waveguide 235 on the side of the light emission surface S200. Therefore, a spot image (an optical image) is formed on the light emission surface S200.
Furthermore, even when the thickness of the sealing substrate 230 is reduced due to the abrasion of a contact portion and thus the optical waveguide 235 is shortened, the shape and size of the end surface of the optical waveguide 235 exposed from the light emission surface S200 are hardly varied, since the optical waveguide 235 is a cylindrical member which guides light by the specular reflection from the outer circumferential surface thereof and the central axis thereof extends in a direction where the contact surface recedes due to abrasion. Thus, the shape and size of the spot image formed on the light emission surface S200 are also hardly changed.
As described above, according to the image forming apparatus of the tenth embodiment, in disregard of contact exposure in which the head 200 comes into contact with the image carrier 110a, it is possible to guide light emitted from the light emitting layer 210 to the sealing substrate 230 without leakage and thus to stably form a high-definition image. That is, it is possible to reduce a variation in the area or shape of a spot image. This effect contributes to an improvement in the quality of printing and stabilization. In addition, since the optical waveguides are formed in the sealing substrate not requiring surface accuracy as high as the main substrate, an image forming apparatus can be more easily manufactured than an image forming apparatus having a head in which the optical waveguides are formed in the main substrate.
Next, an example of a method of manufacturing the head 200 will be described.
As described above, in this manufacturing method, a process for cutting the substrate is needed. However, the sealing substrate, not the main substrate, is cut. Therefore, the utilization efficiency of the main substrate requiring a high degree of utilization efficiency is not lowered, which is effective in the mass production.
Eleventh Embodiment
A surface of the main substrate 320 opposite to the surface thereof having the light emitting elements 305 formed thereon is a light emission surface S300. The light emission surface S300 corresponds to the contact surface S10 of
The main substrate 320 is formed by arranging optical waveguides 323 in a plate 321 so as to correspond to light emitting elements 305. Each optical waveguide 323 overlaps the corresponding light emitting element 305. The plate 321 is formed of, for example, glass, quartz, or plastic. Each optical waveguide 323 is provided so as to pass through the front and rear surfaces of the main substrate 320, and the central axis thereof extends in the thickness direction of the main substrate 320. In addition, the outer circumferential surface of each optical waveguide 323 is covered with the plate 321. One end surface of the optical waveguide 323 facing the light emitting element 305 serves as a portion of the rear surface of the main substrate 320, and the other end surface thereof serves as a portion of the front surface (the light emission surface S300) of the main substrate 320.
The one end surface of the optical waveguide 323 facing the light emitting element 305 covers the light emitting layer 210 of the corresponding light emitting element 305, as viewed from the light emission surface S300. Further, the optical waveguides 323 are formed of a transmissive material. The material has a refractive index which is higher than that of a material forming the plate 321. That is, the optical waveguides 323 are fixed to the plate 321, and the outer circumferential surfaces thereof are covered with a material having a refractive index lower than that of the material.
The image forming apparatus of the eleventh embodiment can obtain the same effects as those obtained from the image forming apparatus of the tenth embodiment. However, since the optical waveguides are formed in the main substrate, the effects obtained by forming the optical waveguides in the sealing substrate are not obtained.
Further, in the image forming apparatus according to the eleventh embodiment, since the optical waveguides 323 are formed in the main substrate 320, a distance between the light emitting layer and the optical waveguide is smaller than that in the image forming apparatus according to the tenth embodiment. This contributes to an improvement in the brightness of a spot image.
Twelfth Embodiment
The sealing substrate 238 is a plate member having a groove 239 in one surface (front surface) thereof opposite to the other surface (rear surface) thereof facing the light emitting elements 205. The groove 239 has a flat bottom. The sealing substrate is generally formed of, for example, glass, metal, ceramic, or plastic. However, since the sealing substrate 238 needs to transmit light emitted from the light emitting layer 210, the sealing substrate 238 is formed of a transmissive material. In addition, the refractive index of a material forming the sealing substrate 238 is equal to or higher than that of the adhesive 290.
The optical waveguide plate 236 is fixed to the sealing substrate 238 such that the rear surface thereof comes into contact with the bottom of the groove 239. Any methods can be used to fix the optical waveguide plate 236 to the sealing substrate 238 as long as a light shielding material is not interposed between the rear surface of the optical waveguide plate 236 and the bottom of the groove 239. The optical waveguide plate 236 is formed by arranging a plurality of optical waveguides 233 in a plate 237 having rectangular front and rear surfaces.
Each optical waveguide 233 for guiding light emitted from the light emitting layer 210 is provided so as to pass through the front and rear surfaces of the optical waveguide plate 236, and the central axis thereof extends in the thickness direction of the optical waveguide plate 236. In addition, the outer circumferential surface of each optical waveguide 233 is covered with the plate 237. One end surface of the optical waveguide 233 facing the light emitting element 205 serves as a portion of the rear surface of the optical waveguide plate 236, and the other end surface thereof serves as a portion of the front surface (the light emission surface S201) of the optical waveguide plate 236. The one end surface of the optical waveguide 233 facing the light emitting element 205 covers the light emitting layer 210 of the corresponding light emitting element 205, as viewed from the light emission surface S201.
Further, the optical waveguides 233 are formed of a transmissive material. The material has a refractive index which is equal to or higher than that of a material forming the sealing substrate 238 and which is higher than that of a material forming the plate 237. In addition, the optical waveguides 233 are fixed to the plate 237. Any methods can be used to fix the optical waveguides 233 to the plate 237, but attentions should be paid when using a method in which the outer circumferential surface of the optical waveguide 233 does not contact the plate 237. In this case, a method of fixing the optical waveguides 233 to the plate 237 using an adhesive is considered. In this method, it is necessary to use an adhesive having a refractive index lower than that of a material forming the optical waveguide 233. That is, the outer circumferential surfaces of the optical waveguides 233 must be covered with a material having a refractive index lower than that of the material.
The width, length, and depth of the groove 239 are set such that the optical waveguide plate 236 is flush with the sealing substrate 238 except for the groove 239. That is, the width, length, and depth of the groove 239 depend on the width, length, and thickness of the optical waveguide plate 236. The width and length of the optical waveguide plate 236 are set to the minimum values capable of causing a plurality of optical waveguides 233 to be arranged in the optical waveguide plate 236. That is, the width and length of the optical waveguide plate 236 depend on the arrangement of the light emitting elements 205. More specifically, the width of the groove 239 is about several hundreds of micrometers.
The thickness of the optical waveguide plate 236 depends on the thickness of the sealing substrate 238.
Since the optical waveguide 233 functions to guide light emitted from the light emitting layer 210, it is preferable that the end surface thereof facing the light emitting element 205 be close to the light emitting element 205. Therefore, it is preferable that a thick optical waveguide plate 236 be used to improve the utilization efficiency of light emitted from the light emitting layer 210. However, in order to increase the thickness of the optical waveguide plate 236, it is necessary to reduce the thickness of a portion of the sealing substrate 238 where the groove 239 is formed. In this case, the rigidity of the sealing substrate 238 should be considered. In this structure, the width of the groove 239 is about several hundreds of micrometers, but the width of the sealing substrate 238 (the length of a short side in
Since a portion of the sealing substrate 238 covering the light emitting elements 205 has a relatively small thickness, all the light components incident on the sealing substrate 238 reach the front surface of the sealing substrate 238 (the bottom of the groove 239). More specifically, the light components reach the end surfaces of the optical waveguides 233 facing the light emitting elements 205. Since the refractive index of a material forming the optical waveguides 233 is equal to or higher than that of a material forming the sealing substrate 238, it is easy for all light components reached the one end surface to be incident on the optical waveguide 233. Therefore, most of the reached light components are incident on the optical waveguides 233 and then travel in the optical waveguides 233.
When the light components traveling in the optical waveguide 233 reach the outer circumferential surface of the optical waveguide 233, most of them are specularly reflected therefrom. That is, the optical waveguide 233 functions as a core of an optical fiber having a large diameter to guide the incident light. The reason why the specular reflection occurs is the same as described in the tenth embodiment. Preferably, a material forming the optical waveguides 233 and a material covering the outer circumferential surfaces of the optical waveguides 233 are selected such that a sufficient amount of light can be specularly reflected.
In this way, light travels in the optical waveguide 233 and is then emitted from the end surface of the optical waveguide 233 on the side of the light emission surface S201. Therefore, a spot image (an optical image) is formed on the light emission surface S201, as shown in
Furthermore, even when the thicknesses of the optical waveguide plate 236 and the sealing substrate 238 are reduced due to the abrasion of a closely adhering portion and thus the optical waveguide 233 is shortened, the shape and size of the end surface of the optical waveguide 233 exposed from the light emission surface S201 are hardly changed, since the optical waveguide 233 is a cylindrical member which guides light by the specular reflection from the outer circumferential surface thereof and the central axis thereof extends in a direction where the contact surface recedes due to abrasion. Thus, the shape and size of the spot image formed on the light emission surface S200 are also hardly changed.
As described above, according to the image forming apparatus of the twelfth embodiment, in disregard of contact exposure in which the head 201 comes into contact with the image carrier 110a, it is possible to guide light emitted from the light emitting layer 210 to the sealing substrate 238 without leakage and thus to stably form a high-definition image. That is, it is possible to reduce a variation in the area or shape of a spot image. This effect contributes to an improvement in the quality of printing and stabilization. In addition, light emitted from the light emitting layer 210 is hardly reflected not only from an interface between the adhesive 290 and the sealing substrate 238 but also from an interface between the sealing substrate 238 and the optical waveguide 233, which makes it possible to improve the utilization efficiency of light emitted from the light emitting layer 210.
Further, one groove 239 is formed in the sealing substrate 238. Therefore, it is possible to easily manufacture a sealing substrate, compared with the structure in which the optical waveguides passing through the sealing substrate are directly formed in the sealing substrate. In addition, it is possible to reduce manufacturing costs, compared with the structure in which the entire surface of the sealing substrate is cut.
Furthermore, since the optical waveguide plate 236 having the optical waveguides 233 formed therein does not need to have a sealing function, there is no restriction to select a material forming the plate 237. In addition, the optical waveguide plate 236 is smaller than the sealing substrate 238 in size. Therefore, it is possible to easily form the optical waveguides 233, compared with the structure in which the optical waveguides passing through the sealing substrate is directly formed in the sealing substrate.
Moreover, in the head 201, a surface of the sealing substrate 238 facing the main substrate 220 has no seam, which makes it possible to reliably maintain the sealing function. In addition, the optical waveguides 233 are formed in the optical waveguide plate 236, not in the sealing substrate 238 or the main substrate 220. Therefore, the optical waveguide plate 236, not the main substrate and the sealing substrate, is directly deformed due to a difference between thermal shrinkage (expansion) of the optical waveguide 233 and thermal shrinkage (expansion) of a circumferential portion thereof (the plate 237 or adhesive). That is, the deformation of the main substrate or the sealing member due to the optical waveguides 233 does not occur.
Next, an example of a method of manufacturing the head 201 will be described.
As described above, in this manufacturing method, a process for cutting the substrate is needed. However, the sealing substrate 238 and the plate 237, not the main substrate 220, are cut. Therefore, the utilization efficiency of the main substrate requiring a high degree of utilization efficiency is not lowered, which is effective in the mass production.
In this manufacturing method, the optical waveguide plate 236 is provided in the groove 239 of the sealing substrate 238 before the sealing substrate 238 is fixed to the main substrate 220. However, the optical waveguide plate 236 may be provided in the groove 239 of the sealing substrate 238 after the sealing substrate 238 is fixed to the main substrate 220.
Thirteenth Embodiment
The plate 231 differs from the sealing substrate 238 shown in
The light emitting elements 305 are covered with the main substrate 328 and are further covered with a flat optical waveguide plate 326 which is provided in the groove 329 of the main substrate 328 and is fixed to the main substrate 328. The main substrate 328 should be formed of a transmissive material, such as glass, quartz, or plastic. The optical waveguide plate 326 is fixed to the main substrate 328 by the same method as that used for fixing the optical waveguide plate 236 to the sealing substrate 238 in
The groove 329 is formed in one surface (front surface) of the main substrate 328 opposite to the other surface (rear surface) thereof facing the light emitting elements 305. The groove 329 has a flat bottom, and the rear surface of the optical waveguide plate 236 comes into contact with the bottom. Similar to the groove 239, the width, length, and depth of the groove 329 are set such that the surface (the light emission surface S301) of the optical waveguide plate 326 is flush with the surface of the main substrate 328 except for the groove 329. That is, the width, length, and depth of the groove 329 depend on the width, length, and thickness of the optical waveguide plate 326. In addition, the width, length, and thickness of the optical waveguide plate 326 are set, similar to the optical waveguide plate 236.
A cylindrical optical waveguide 323 is formed in each light emitting element 305 in a portion of the optical waveguide plate 326 overlapping the light emitting element 305. Each optical waveguide 323 for guiding light emitted from the light emitting layer 210 is provided so as to pass through the front and rear surfaces of the optical waveguide plate 326, and the central axis thereof extends in the thickness direction of the optical waveguide plate 326. In addition, the outer circumferential surface of each optical waveguide 323 is covered with the plate 327. One end surface of the optical waveguide 323 facing the light emitting element 305 serves as a portion of the rear surface of the optical waveguide plate 326, and the other end surface thereof serves as a portion of the front surface (the light emission surface S301) of the optical waveguide plate 326. The one end surface of the optical waveguide 323 facing the light emitting element 305 covers the light emitting layer 210 of the corresponding light emitting element 305, as viewed from the light emission surface S301.
Further, the optical waveguides 323 are formed of a transmissive material. The material has a refractive index which is equal to or higher than that of a material forming the main substrate 328 and which is higher than that of a material forming the plate 327. The outer circumferential surface of each optical waveguide 233 should be covered with a material having a refractive index lower than that of the material in any methods.
Since a portion of the main substrate 328 covering the light emitting elements 305 has a relatively small thickness, all the light components incident on the main substrate 328 reach the front surface of the main substrate 328 (the bottom of the groove 329). More specifically, the light components reach the end surfaces of the optical waveguides 323 facing the light emitting elements 305. Since the refractive index of a material forming the optical waveguides 323 is equal to or higher than that of a material forming the main substrate 328, it is easy for all the light components reached the end surface to be incident on the optical waveguide 323. Therefore, most of the reached light components are incident on the optical waveguide 323 and then travel in the optical waveguide 323. Since the optical waveguide 323 functions as a core of an optical fiber having a large diameter, most of the light incident on the optical waveguide 323 travels in the optical waveguide 323 and is then emitted from the end surface of the optical waveguide 323 on the side of the light emission surface S301.
The image forming apparatus of the thirteenth embodiment can obtain the same effects as those obtained from the image forming apparatus of the twelfth embodiment. However, since the optical waveguides are formed in the main substrate, the effects obtained by forming the optical waveguides in the sealing substrate are not obtained.
Further, in the image forming apparatus according to the thirteenth embodiment, since the optical waveguides 323 are formed in the main substrate 328, a distance between the light emitting layer and the optical waveguide is smaller than that in the image forming apparatus according to the twelfth embodiment. This contributes to an improvement in the brightness of a spot image.
Modifications of Tenth to Thirteenth Embodiments
Various modifications of the above-mentioned tenth to thirteenth embodiments can be made. The modifications thereof will be described in detail. The following modifications may be appropriately combined.
First Modification
In the tenth to thirteenth embodiments, a cylindrical optical waveguide is used, but the shape of the optical waveguide is not limited thereto. For example, the optical waveguide may be formed in a prismatic shape or a pillar shape having a hemispherical end surface. That is, the optical waveguide can have any pillar shapes.
Second Modification
In the tenth to thirteenth embodiments, organic EL elements are used as light emitting elements. However, inorganic EL elements may be used as light emitting elements.
Third Modification
In the tenth to thirteenth embodiments, the optical waveguide serving as an optical fiber is used. An optical fiber array composed of a bundle of optical fibers may be used as the optical waveguide. In this case, one end surface of the fiber array constitutes a portion of a light emission surface (contact surface), and the other end surface thereof covers the light emitting layer 210. Light incident on one end of the optical fiber travels toward the other end of the optical fiber while being specularly reflected from the inner circumferential surface of the optical fiber. The one end of each optical fiber constitutes a portion of the one end surface of the fiber array, and the other end thereof constitutes a portion of the other end surface of the fiber array.
Overall Structure of Image Forming Apparatus
In this image forming apparatus, four heads 10K, 10C, 10M, and 10Y having the same structure are arranged at exposure positions of four photoreceptor drums (image carriers) 110K, 110C, 110M, and 110Y having the same structure. The heads 10K, 10C, 10M, and 10Y correspond to any one of the heads of the image forming apparatuses according to the above-described embodiments, and are organic EL array exposure heads in which organic EL elements, each including a light emitting layer formed of an organic EL material, are arranged as light emitting elements.
As shown in
The four photoreceptor drums 110K, 110C, 110M, and 110Y are disposed at predetermined intervals around the intermediate transfer belt 120. Each photoreceptor drum has a photosensitive layer on the outer peripheral surface thereof. These photoreceptor drums correspond to the photoreceptor drums (image carriers) of the image forming apparatuses according to the above-described embodiments, and suffixes ‘K’, ‘C’, ‘M’, and ‘Y’ added to reference numerals indicate black, cyan, magenta, and yellow which are used for forming a toner image, respectively. This is similarly applied to other members. The photoreceptor drums 110K, 110C, 110M, and 110Y are rotated in synchronism with the driving of the intermediate transfer belt 120.
A corona charger 111 (K, C, M, and Y), the head 10 (K, C, M, and Y), and a developing device 114 (K, C, M, and Y) are arranged around each photoreceptor drum 110 (K, C, M, and Y). The corona charger 111 (K, C, M, and Y) uniformly charges the outer peripheral surface of the corresponding photoreceptor drum 110 (K, C, M, and Y). The head 10 (K, C, M, and Y) writes a latent image on the charged outer peripheral surface of the photoreceptor drum. Each head 10 (K, C, M, and Y) is arranged such that a plurality of light emitting elements is arranged along a bus (the main scanning direction) of the photoreceptor drum 110 (K, C, M, and Y). The writing of the latent image is performed by radiating light emitted from the plurality of light emitting elements on the photoreceptor drum. The developing device 114 (K, C, M, and Y) applies toner, as a developer, onto the latent image to form a toner image, that is, a visible image on the photoreceptor drum.
Black, cyan, magenta, and yellow toner images formed by single-color toner image forming stations for the four colors are sequentially primarily transferred onto the intermediate transfer belt 120 so as to be superimposed on the intermediate transfer belt 120, thereby forming a full-color toner image. Four primary transfer corotrons (transfer devices) 112 (K, C, M, and Y) are arranged inside the intermediate transfer belt 120. The primary transfer corotrons 112 (K, C, M, and Y) are arranged in the vicinities of the photoreceptor drums 110 (K, C, M, and Y), respectively, and electrostatically attract the toner images from the photoreceptor drums 110 (K, C, M, and Y) to transfer the toner images onto the intermediate transfer belt 120 passing between the photoreceptor drums and the primary transfer corotrons.
Finally, sheets 102, which are image forming targets, are fed one by one from a paper feed cassette 101 to a nip between a secondary transfer roller 126 and the intermediate transfer belt 120 coming into contact with the driving roller 121 by a pick-up roller 103. The full-color toner image on the intermediate transfer belt 120 are collectively secondary-transferred onto one surface of the sheet 102 by the secondary transfer roller 126 and are then fixed on the sheet 102 by a pair of fixing rollers 127 serving as a fixing unit. Then, the sheet 102 is discharged onto a paper discharge cassette formed on the upper side of the apparatus by a pair of paper discharge rollers 128.
The corona charger 168 uniformly charges the outer peripheral surface of the photoreceptor drum 165. The head 167 writes a latent image on the charged outer peripheral surface of the photoreceptor drum 165. The photoreceptor drum 165 corresponds to any one of the photoreceptor drums (image carriers) of the image forming apparatuses according to the above-described embodiments. The head 167 corresponds to any one of the heads of the image forming apparatuses according to the above-described embodiments, and is an organic EL array exposure head in which organic EL elements, each including a light emitting layer formed of an organic EL material, are arranged as light emitting elements. The head 167 is provided such that a plurality of light emitting elements is arranged along a bus (the main scanning direction) of the photoreceptor drum 165. The writing of the latent image is performed by radiating light emitted from the plurality of light emitting elements on the photoreceptor drum 165.
The developing unit 161 is a drum including four developing devices 163Y, 163C, 163M, and 163K arranged at right angles to each other, and can be rotated on a shaft 161a in the counterclockwise direction. The developing devices 163Y, 163C, 163M, and 163K respectively supply yellow, cyan, magenta, and black toners to the photoreceptor drum 165 to attach the toners, as developing agents, onto the latent image, thereby forming a toner image, that is, a visible image on the photoreceptor drum 165.
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 circulates around these rollers in the direction of arrow shown in
More specifically, at the first rotation of the photoreceptor drum 165, a latent image for a yellow (Y) image is written by the head 167, and a toner image having the same color is formed by the developing device 163Y and is then transferred onto the intermediate transfer belt 169. At the next rotation thereof, a latent image for a cyan (C) image is written by the head 167, and a toner image having the same color is formed by the developing device 163C and is then transferred onto the intermediate transfer belt 169 so as to overlap the yellow toner image. When the photoreceptor drum 165 makes four rotations in this way, yellow, cyan, magenta, and black toner images sequentially overlap each other on the intermediate transfer belt 169, thereby forming a full-color toner image on the intermediate transfer belt 169. Finally, when images are formed on both surfaces of a sheet, which is an image forming target, a toner image having a color common to the front and rear surfaces is transferred onto the intermediate transfer belt 169, and then a toner image having the next color common to the front and rear surfaces is transferred thereon, thereby forming a full-color toner image on the intermediate transfer belt 169.
A sheet transfer path 174 through which sheets pass is provided in the image forming apparatus. The sheets are fed one by one from the paper feed cassette 178 by the pick-up roller 179 and are then transferred along the sheet transfer path 174 by a transfer roller. Then, the sheets pass through a nip between a secondary transfer roller 171 and the intermediate transfer belt 169 coming into contact with the driving roller 170a. The secondary transfer roller 171 collectively and electrostatically attracts the full-color toner image from the intermediate transfer belt 169 to transfer the toner image onto one surface of the sheet. The secondary transfer roller 171 approaches or is separated from the intermediate transfer belt 169 by a clutch (not shown). When a full-color toner image is transferred onto a sheet, the secondary transfer roller 171 abuts on the intermediate transfer belt 169. On the other hand, when the toner images are superposed on the intermediate transfer belt 169, the secondary transfer roller 171 is separated therefrom.
In this way, the sheet having an image thereon is transferred to a fixing device 172 and passes between a heating roller 172a and a pressing roller 172b of the fixing device 172, thereby fixing a toner image on the sheet. The sheet having the fixed toner image is transferred to the pair of paper discharge rollers 176 to be carried in the direction of arrow F. In a case in which printing is performed on both sides of a sheet, after most of the sheet passes through the paper discharge rollers 176, the pair of paper discharge rollers 176 is reversely rotated to transfer the sheet in a double-sided printing transfer path 175 as represented by an arrow G. Subsequently, a toner image is transferred onto the other surface of the sheet by the secondary transfer roller 171, and is then fixed by the fixing device 172. Then, the sheet is discharged to the outside by the pair of paper discharge rollers 176.
In the image forming apparatuses shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-032777 | Feb 2005 | JP | national |
| 2005-087923 | Mar 2005 | JP | national |
| 2005-087927 | Mar 2005 | JP | national |
| 2005-094778 | Mar 2005 | JP | national |
