JP2007310157A - Photoreceptor drum, method for manufacturing the same, printing engine and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress degradation of an electrostatic latent image formed on a surface of a photoreceptor drum by increase of the diameter of writing light emitted by light emitting pixels. <P>SOLUTION: The photoreceptor drum 30 rotated in a secondary scanning direction receives light emitted from light emitting pixels 10 arrayed on a substrate at photosensitive portions 31 formed on a surface of a conductive cylindrical member to form an electrostatic latent image, wherein the photosensitive portions 31 are enclosed in a non-photosensitive portion 29 incapable of forming an electrostatic latent image, and the array pitch of the photosensitive portions 31 in a main scanning direction is equal to the array pitch of the light emitting pixels 10 in the main scanning direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image by irradiating a photosensitive drum with light emitted from light emitting pixels arranged on a substrate to form an electrostatic latent image.

  The image forming apparatus includes a photosensitive drum having a photosensitive layer on a surface of a cylindrical member, and a line head in which a large number of light emitting pixels are regularly arranged along the longitudinal direction of the photosensitive drum. While rotating the photosensitive drum around the axis, the light emitting elements of the line head are selectively made to emit light individually based on the image data, and the emitted light (hereinafter referred to as “writing light”) is the photosensitive member. An electrostatic latent image is formed by irradiating a photosensitive layer on the drum surface to form an image, and after developing the electrostatic latent image, the image is transferred to a medium such as paper. Therefore, the quality of the image formed on the medium is greatly influenced by the identity between the image data and the electrostatic latent image formed on the photosensitive drum. Thus, various proposals for improving the identity have been made.

  For example, in Patent Document 1, the positional relationship between the photosensitive drum and the line head, and the gap between the photosensitive drum and the developing unit are maintained with high accuracy and the deformation of the photosensitive drum itself is prevented, so that the focal position of the writing light is increased. Is disposed on the surface of the photosensitive drum, a photosensitive drum position regulating member for regulating the relative position between the photosensitive drum and the line head is disposed.

  Further, in Patent Document 2, when driving a photosensitive drum by a motor, density unevenness (banding) due to deterioration in exposure position accuracy due to rotation error (peripheral speed fluctuation) caused by the pitch of a gear directly connected to the photosensitive drum. ), Multiple exposure is performed by a line head in which a plurality of light emitting elements are arranged in the sub-scanning direction.

Japanese Patent Laid-Open No. 11-143159 Japanese Patent Laying-Open No. 2005-070484

  However, since the photosensitive drum and the image forming apparatus having the above structure irradiate the photosensitive drum without changing the writing light, the diameter of the writing light (the section perpendicular to the optical axis of the writing light is not necessarily circular, The dimension of the cross section is referred to as “diameter” for the sake of convenience.) The phenomenon that the above-mentioned identity is impaired by increasing the diameter of the light emitting pixel cannot be dealt with.

  In order to solve the above-described problems, the photosensitive drum according to the present invention is formed on the surface of the conductive cylindrical member while rotating the light emitted from the light emitting pixels aligned on the substrate in the sub-scanning direction. A photosensitive drum that receives an electrostatic latent image to form an electrostatic latent image, and the photosensitive portion is surrounded by a non-photosensitive portion that cannot form the electrostatic latent image. The arrangement pitch in the main scanning direction is the same as the arrangement pitch of the light emitting pixels in the main scanning direction.

  Rather than making the entire surface of the photosensitive drum a photosensitive part, the photosensitive part surrounded by the non-photosensitive part is arranged at the same arrangement pitch as the light emitting pixels so that the periphery is surrounded by the non-photosensitive part. A photosensitive portion having a center line coinciding with the opposed light emitting pixels can be disposed. Then, by adjusting the width from the center line, light of an arbitrary area can be received without being influenced by the phenomenon in which the light emitted from the light emitting pixel expands. Therefore, with this configuration, it is possible to suppress the reception of excess light generated by expanding the light emitted from the light emitting pixels, and a sharp electrostatic latent image can be formed on the surface of the photosensitive drum.

  Preferably, the shape of the photosensitive portion is substantially similar to the shape of the light emitting pixel.

  The light emitted from the light emitting pixels expands as it travels, and on the surface of the photosensitive drum, the light emitting pixels have a similar shape in which the shape of the light emitting pixels is uniformly expanded in the entire circumferential direction. Therefore, by making the shape of the corresponding photosensitive portion similar to the shape of the light emitting pixel, light emitted from the light emitting pixel can be used effectively, and a sharper electrostatic latent image can be formed on the surface of the photosensitive drum.

  Preferably, the shape of the photosensitive portion is a stripe shape that makes a round around the surface of the photosensitive drum in the sub-scanning direction while being spaced apart from each other.

  The photosensitive drum forms an electrostatic latent image while rotating in the sub-scanning direction. However, if the photosensitive portion is striped, the relative positional relationship with the light emitting pixels is not affected by the above-described rotational movement and is always constant. Can be kept in a state. Therefore, with such a configuration, a sharp electrostatic latent image can be formed on the surface of the photosensitive drum while suppressing an increase in cost.

  In order to solve the above-mentioned problems, a print engine according to the present invention includes the above-described photosensitive drum.

  Preferably, a mechanism for aligning the positions of the light emitting pixels and the photosensitive portion is further provided.

  The photosensitive drum forms an electrostatic latent image while rotating in the sub-scanning direction. With such a configuration, the relative positional deviation between the light emitting pixel and the photosensitive portion due to the rotational movement described above is corrected, and the position of the photosensitive drum is corrected. Can always be kept in a constant state. Therefore, with such a configuration, the degree of freedom in setting the shape of the photosensitive portion is increased, and a sharper electrostatic latent image can be formed on the surface of the photosensitive drum.

  In order to solve the above problems, an image forming apparatus according to the present invention includes the above-described print engine.

  With such a configuration, a sharper electrostatic latent image can be formed on the surface of the photosensitive drum, so that a sharper image can be formed on the recording medium.

  In order to solve the above-described problems, a method for manufacturing a photosensitive drum according to the present invention includes a photosensitive drum formed on the surface of a conductive cylindrical member with light emitted from light emitting pixels aligned on a substrate. A photosensitive drum manufacturing method for forming an electrostatic latent image by receiving light at a portion, wherein a photosensitive layer capable of forming an electrostatic latent image by receiving a predetermined range of light on the surface of the cylindrical member is formed. And forming the electrostatic latent image on the surface of the photosensitive drum by forming a light shielding layer capable of shielding the light in the predetermined range in a partial region of the surface of the photosensitive layer. And regularly forming a photosensitive portion and a non-photosensitive portion where the electrostatic latent image cannot be formed.

  According to this manufacturing method, the photosensitive drum having the above-described configuration can be manufactured only by adding the process of forming the non-photosensitive portion to the conventional manufacturing process of the photosensitive drum. Therefore, the photosensitive drum capable of forming the above-described sharp electrostatic latent image can be manufactured while suppressing an increase in manufacturing cost.

  Preferably, the light-shielding layer is formed by selectively removing the photosensitive material applied to the surface of the photoreceptor layer from the region where the photosensitive portion is to be formed by photolithography, and then curing the photosensitive material. Features.

  Since the photosensitive material can be patterned with high definition by photolithography, the degree of freedom in setting the shape of the photosensitive portion can be improved. Therefore, according to such a manufacturing method, a photosensitive drum capable of forming a sharper electrostatic latent image can be manufactured while suppressing an increase in manufacturing cost.

  In order to solve the above-described problems, a method for manufacturing a photosensitive drum according to the present invention includes a photosensitive drum formed on the surface of a conductive cylindrical member with light emitted from light emitting pixels aligned on a substrate. A photosensitive drum manufacturing method for forming an electrostatic latent image by receiving light at a portion, comprising the step of forming the photosensitive portion only in a predetermined region on the surface of the cylindrical member.

  Since the photosensitive drum obtained by such a manufacturing method does not have a light-shielding layer in the non-photosensitive portion, the surface step can be suppressed. Therefore, it is possible to freely set the distance between the established unit magnification image lens that transmits the light emitted from the light emitting pixel and the photosensitive part without being affected by the non-photosensitive part, so that the electrostatic latent image is sharper. Can be obtained. Further, since unnecessary steps on the surface of the photosensitive member are eliminated, the toner remaining on the photosensitive member can be cleaned cleanly before the next writing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings shown below, the dimensions and ratios of the components are appropriately different from the actual ones in order to make the components large enough to be recognized on the drawings.
(First embodiment)

  The present invention relates to a photosensitive drum. The photosensitive drum has a function of forming an electrostatic latent image by receiving light emitted from a line head in which a large number of light emitting pixels are regularly arranged. Therefore, before describing an embodiment of the photosensitive drum, a line head will be described first.

  FIG. 1A schematically shows a configuration of a light emitting pixel 10 and the like disposed on a line head 32 (see FIG. 1B) of an image forming apparatus in which the photosensitive drum of the present embodiment is used. It is. An EL element using an electroluminescence (hereinafter referred to as “EL”) phenomenon that emits light when a current flows by application of a voltage is used as the light emitting pixel 10. The horizontal direction in FIG. 1, that is, the X direction is the main scanning direction, and the respective light emitting pixels 10 are arranged in a staggered manner along the direction at a predetermined interval. The light emitting pixel 10 is composed of a functional layer including at least a light emitting layer (a layer of a substance that causes the EL phenomenon) sandwiched between a pixel electrode 20 that is a first electrode and a second electrode (not shown). . When a voltage is applied to the pixel electrode 20, a current flows through the light emitting layer, and light is emitted by the EL phenomenon.

  A driving thin film transistor (hereinafter referred to as “TFT”) 12 applies the voltage to the light emitting pixel 10 by driving the pixel electrode 20. The source electrode 18 of the driving TFT 12 is electrically connected to a storage capacitor (not shown) via the source wiring 22, and the gate wiring 14 is electrically connected to a switching TFT (not shown). The drain electrode 16 is electrically connected to the pixel electrode 20. When a signal voltage is applied from the switching TFT via the gate wiring 14, the driving TFT 12 is turned on. When a voltage is applied to the pixel electrode 20, a current flows through the storage capacitor described above, and the light emitting pixel 10 emits writing light. Exit.

  FIG. 1B is a diagram schematically showing the entire line head 32. The light emitting pixels 10 and the driving TFTs 12 are arranged in a staggered pattern in the main scanning direction on the substrate. A line head control circuit (hereinafter referred to as “control circuit”) 25 made up of switching TFTs and the like is arranged along the arrangement of the light emitting pixels 10 described above. When forming an image using the line head, the control circuit 25 controls each light-emitting pixel 10 based on image data processed by a CPU of an image forming apparatus (not shown) to emit light toward the photosensitive drum. Is emitted.

  As described above, the second electrode 27 sandwiches the light emitting layer together with the pixel electrode 20 and has a function of flowing current through the light emitting layer. Since each pixel 10 has a common potential, it is a single plate that is not divided for each pixel. Then, the grounding portion 26 is electrically connected to the grounding portion of the image forming apparatus main body.

  The alignment light emitting pixels 40 are arranged one by one on both ends of the substrate, and are used for alignment of the photosensitive drum 30 (see FIG. 2) and the line head 32 which will be described later. Since the alignment light emitting pixels 40 and the light emitting pixels 10 arranged in a zigzag pattern for forming electrostatic latent images are formed in the same photolithography process, the relative positional relationship is always constant. Then, like the light emitting pixel 10 for image formation, light is emitted by the driving TFT 12 and the control circuit 25.

  Line heads using EL elements as light emitting pixels include a bottom emission method in which writing light is extracted from the substrate side and a top emission method in which light is extracted from the side opposite to the substrate. The photosensitive drum 30 of this embodiment (FIG. 2 ( c)) corresponds to both methods. In the case of the bottom emission method, the substrate of the line head 32 uses a light-transmitting material such as glass. In the case of the top emission method, a light-shielding material such as metal or ceramic can be used for the substrate, but the second electrode 27 needs to have a light-transmitting property. In that case, a thin film having a thickness of about 10 nm made of a metal such as Ba or MgAg or an alloy and a conductive light-transmitting material such as ITO (indium tin oxide) are used in combination to achieve both light transmission and conductivity.

  FIG. 2 is a diagram schematically showing the photosensitive drum 30 and the line head 32 of the present embodiment. FIG. 2A shows the arrangement of the light emitting pixels 10 on the line head 32. FIG. 2B shows a state where the surface of the photosensitive drum 30 on which the photosensitive portion 31 is formed, that is, the side surface of the cylinder is horizontally developed to be planar. As shown in the drawing, on the line head 32, the light emitting pixels 10 are continuously arranged in a staggered manner in the main scanning direction. The arrangement pattern of the photosensitive portions 31 on the surface of the photosensitive drum is a continuous arrangement pattern of the above-described light emitting pixels. The shape of each photosensitive portion 31 is the same as that of the light emitting pixel. As shown in FIG. 2B, the arrangement pattern of the photosensitive portions 31 is a pattern obtained by continuously arranging the arrangement patterns of the light emitting pixels 10 shown in the broken lines in FIG. 2A in the sub-scanning direction. A region where the photosensitive portion 31 is not formed on the surface of the photosensitive drum is a non-photosensitive portion 29, and an electrostatic latent image is not formed even when light emitted from the light emitting pixels 10 is irradiated.

  FIG. 2C shows a photosensitive drum having a surface on which a photosensitive portion 31 surrounded by a non-photosensitive portion 29 is formed, as shown in FIG. A photosensitive portion having the same arrangement pitch in the main scanning direction as the arrangement pitch of the light emitting pixels 10 and the same shape surrounds the photosensitive drum. The arrangement pitch in the sub-scanning direction is determined by the timing at which the light emitting pixels emit light and the rotational speed of the photosensitive drum. In FIG. 2C, the arrangement pitch in the main scanning direction and the arrangement pitch in the sub-scanning direction of the photosensitive portions on the surface of the photosensitive drum are substantially the same, but the present invention is not limited to this mode.

  FIG. 3 shows the photosensitive drum 30 according to the present embodiment together with a line head module 100 including a line head 32 and the like. Together with an intermediate transfer belt described later (see FIG. 8), an engine of the image forming apparatus is configured.

  The line head 32 is sandwiched between a sealing plate 34 made of a translucent material and a heat radiating plate 33 made of a metal such as Al, and is formed by bundling a plurality of erecting equal-magnification imaging lenses. It faces the photosensitive drum 30 via 35. Then, a line-shaped image is continuously formed by the light emission of each light emitting pixel 10.

  The sealing plate 34 protects the light emitting pixels 10 and the like from contact and the like, and is essential in the top emission method in which light is emitted from the side opposite to the substrate. The heat radiating plate 33 functions to stably operate the light emitting pixel 10 or the control circuit 25 of the light emitting pixel (see FIG. 1B) by diffusing heat generated by energization of the light emitting pixel.

  The lens unit 35 is a bundle of erecting equal-magnification image lenses, and irradiates the surface of the photosensitive drum 30 with an erecting equal-magnification image of a line-shaped image formed by the light emitting pixels 10 on the line head 32. . The line head panel 100 and the lens unit 35 constitute a line head module 100.

  The photosensitive drum 30 is formed with a photosensitive portion 31 and a non-photosensitive portion 29 in the form shown in FIG. 2C on the entire surface excluding a part near both ends of the cylindrical member. An alignment mark 38 is formed in the vicinity of both ends. The interval between the alignment marks 38 is the same as the interval between the alignment light emitting pixels 40 on the line head 32. The photosensitive drum 30 and the line head 32 are set so that the alignment mark 38 and the alignment light-emitting pixel 40 face each other with the half mirror 36 interposed therebetween. A specific alignment mechanism will be described later.

  Actual electrostatic latent image formation is performed as follows. First, the photosensitive drum 30 is aligned before the rotation starts, that is, before the light emitting pixels 10 on the line head 32 start to emit light, and the row of photosensitive portions 31 formed in a staggered pattern is arranged in the lens unit 35. Is exactly opposed to the light emitting pixel 10.

  Then, the light emission pixel 10 on the line head 32 starts light emission based on the image data to be formed, and at the same time, the rotation starts in accordance with the light emission arrangement pitch of the light emission pixels 10. Therefore, the corresponding photosensitive portion when the light emitting pixel 10 emits light accurately faces the light emitting pixel. As a result, an image identical to the electrostatic latent image formed on the surface of the conventional photosensitive drum is formed on each photosensitive portion.

  As described above, the light emitted from each light emitting pixel 10 formed in the line head 32 is irradiated onto the surface of the photosensitive drum 30 by the lens unit 35. The lens unit 35 is a bundle of SELFOC (registered trademark) lenses. A SELFOC (registered trademark) lens is a glass fiber whose component is adjusted so that the refractive index changes depending on the distance from the central axis (optical axis), and is cut to a predetermined length. It has the property of forming an erect real image at the same magnification. Therefore, the light emitted from each light emitting pixel 10 is theoretically irradiated on the surface of the photosensitive drum 30 in the same area as the light emitting pixel.

  However, an actual SELFOC (registered trademark) lens is enlarged and irradiated by an error such as a refractive index distribution in the glass fiber or a size and shape. For example, when the diameter of the light emitting pixel is 50 μm, the surface of the photosensitive drum 30 has a diameter of 80 to 90 μm. Therefore, when the entire surface of the photosensitive drum is a photosensitive portion, an electrostatic latent image is also formed in a region not facing the light emitting pixel, that is, the non-photosensitive portion in the present embodiment. As a result, the electrostatic latent image actually formed on the surface is a blurred image as compared with the image derived from the size and distribution of the light emitting pixels.

  However, according to the photosensitive drum 30 of the present embodiment, the region that does not face the light emitting pixels 10 is the non-photosensitive portion 29. Therefore, a sharp electrostatic charge is formed on the surface of the photosensitive drum regardless of the expansion of the writing light. A latent image can be formed. As a result, an image formed on a recording medium such as paper, which is the final object, can be further sharpened.

In the present embodiment, the shape of the photosensitive portion 31 is made to coincide with the shape of the light emitting pixel 10, but the effect of the present invention can be obtained even if both the shapes are not made to coincide completely. The arrangement pitch in the main scanning direction of the center point of each photosensitive portion 31 coincides with the arrangement pitch of the light emitting pixels 10, and the arrangement pitch in the sub-scanning direction of the central point of each photosensitive portion 31 is the emission pixel 10. If the light emission timing and the rotational speed of the photosensitive drum 30 are matched, the same effect as that of this embodiment can be obtained even if the shape of the photosensitive portion 31 is similar to the shape of the light emitting pixel 10. For example, when the arrangement of the light emitting pixels 10 is dense, there may be a mode in which a sharper electrostatic latent image is obtained by making the shape of the photosensitive portion 31 smaller than the shape of the light emitting pixels 10. Further, the shapes of the light emitting pixel 10 and the photosensitive portion 31 are not limited to a circular shape, and the effect of the present invention can be obtained even in a rectangular shape.
(Alignment)

  In the present invention, since the photosensitive portion 31 capable of forming an electrostatic latent image is formed only in a partial region of the surface of the photosensitive drum 30, the relative positions of the light emitting pixels 10 and the photosensitive portion 31 are accurately aligned. It is necessary to face each other. FIG. 4 schematically shows an example of the alignment mechanism. As described above, the alignment marks 38 are formed on both sides of the region where the photosensitive portion 31 is formed on the surface of the photosensitive drum 30. On the other hand, an alignment light emitting pixel 40 is formed at a position facing the alignment mark 38 of the line head 32 with the half mirror 36 interposed therebetween.

  Before the image formation, first, the photosensitive drum 30 is rotated to a position where the alignment mark 38 roughly faces the alignment light emitting pixel 40 and stops. Next, alignment light 41 emitted from the alignment light-emitting pixel 40 is applied to the alignment mark 38. A part of the alignment light 41 reflected by the alignment mark 38 is irradiated to the imaging device 42 as image data of the alignment mark 38 by the half mirror 36. The image data is transmitted to the control unit 44, and the control unit 44 stores the difference between the two data and the difference between them when compared with the image data stored inside, when the photosensitive drum 30 is in the correct position. The amount of movement of the photosensitive drum 30 necessary to achieve this is calculated. Then, the drive control unit 48 moves the photosensitive drum 30 based on the calculated movement amount.

For the movement in the rotation direction, a motor used for rotation at the time of forming the electrostatic latent image can be used. On the other hand, it is necessary to provide a separate dedicated movement mechanism for movement in other directions, for example, movement in the vertical axis direction. However, since the photosensitive drum 30 rotates in the sub-scanning direction when forming the electrostatic latent image, the positional deviation from the line head 32 is likely to occur in the rotating direction. On the other hand, the occurrence of misalignment in the axial direction or the like can be suppressed for a long time if it is adjusted during assembly. Therefore, in the present embodiment, the axial movement mechanism can be omitted. In addition, it is possible to perform the alignment by fixing the photosensitive drum 30 and moving the line head module 100.
(Formation of non-photosensitive part)

  A means for forming a photosensitive portion surrounded by a non-photosensitive portion on the surface of the photosensitive drum is formed by forming a light-sensitive layer on a region to be a non-photosensitive portion after forming a layer made of a photosensitive member over the entire surface of the photosensitive drum. And a method of forming a layer made of the photosensitive member only in a region where a photosensitive portion on the surface of the photosensitive drum is to be formed. In the present embodiment, the former method is used. The outline of the process will be described below.

  First, a photoresist containing a light-shielding material is applied to a photoreceptor drum having a photoreceptor layer formed on the entire surface. The resist can be implemented by either a positive type or a negative type, but considering the pattern used for exposure, a positive type in which a portion irradiated with light is removed by development is preferable. The resist is obtained by dissolving a photosensitive resin in a solvent. The photosensitive resin is preferably a mixed / condensed product containing a general novolac resin as a main component, and the solvent is also preferably a general organic solvent such as ethyl carbitol. As the light-shielding material, metal oxides, pigments, carbon fine particles, and the like can be applied. Since the general spin coating cannot be applied to the resist, a technique such as spray coating or dip coating is preferable.

  Next, the resist is patterned by exposure and development to leave the resist only in the region to be the non-photosensitive portion. When exposure is performed with general ultraviolet rays, the light-emitting elements used in the above-described line head are inappropriate because of their different wavelengths, and a dedicated ultraviolet light source is required. However, a photomask used for forming the above-described line head, in particular, a photomask used for patterning a light emitting pixel can be used. Further, a developer generally used for the above-described novolak resin may be used. Before the exposure, it is preferable to remove the solvent to some extent by heating for several minutes as a pre-bake at a temperature of less than 100 degrees.

  Finally, the resist left only in the region to be the non-photosensitive portion is baked to form a light shielding layer. The baking is performed at a temperature of about 200 ° C., and the resist is completely cured so that it can be used as a photosensitive drum.

The thickness of the light shielding layer, that is, the resist is preferably 1 μm or less after baking. If the level difference is 1 μm or less, the function as the photosensitive drum is not adversely affected. In addition, the light-shielding layer does not need to shield all visible light, and can function as long as the writing light from the light emitting pixels of the line head can be shielded.
(Second Embodiment)

5 to 7 show a photosensitive drum and the like according to the second embodiment of the present invention. As in the first embodiment, before describing the embodiment of the photosensitive drum, the line head will be described first.
FIG. 5A schematically shows the configuration of the light emitting pixels of the line head 32 (see FIG. 5B) corresponding to the photosensitive drum 30 of the present embodiment. Similar to the first embodiment, an EL element is used as the light emitting pixel 10, and only the arrangement pattern is different. The pixel electrodes 20 driven by the driving TFTs 12 are not staggered but are arranged in a line in the main scanning direction. The sizes of the pixel electrode 20 and the light emitting pixel 10 are also slightly smaller than those in the first embodiment, and a predetermined space is left between the light emitting pixels 10 when viewed in the sub-scanning direction.

  FIG. 5B is a diagram schematically showing the entire line head 32 corresponding to the photosensitive drum of the present embodiment. The light emitting pixels 10 are arranged in a line as described above.

  FIG. 6 is a diagram schematically showing the surface of the photosensitive drum 30 and the line head 32 of the present embodiment. FIG. 6A shows the line head 32, and FIG. 6B shows a state where the surface of the photosensitive drum 30 is developed.

  As shown in FIG. 6A, the light emitting pixels 10 are arranged at equal intervals in the main scanning direction with a predetermined space on the substrate of the line head 32. The intervals between the center points of the respective light emitting pixels 10 are equal.

  Further, as shown in FIG. 6B, the photosensitive portion 31 is formed in a stripe shape that goes around the surface of the photosensitive drum 30 in the sub-scanning direction. A stripe-shaped non-photosensitive portion 29 is also formed between the photosensitive portions 31. The intervals between the center lines of the photosensitive portions 31 are equal. The arrangement pitch of the photosensitive portions 31, that is, the distance between the center lines of the respective photosensitive portions 31 is formed to be equal to the arrangement pitch of the light emitting pixels 10, that is, the distance between the respective light emitting pixels 10.

  FIG. 7 shows a state in which the line head module 100 including the line head 32 shown in FIG. When the two elements are combined, adjustment is made so that the optical axis of the writing light is positioned on the center line of the photosensitive portion 31. As a result, even if the photosensitive drum 30 rotates, the mode of the photosensitive portion 31 at the position facing the light emitting pixels 10 does not change. The center of the light emitting pixel 10, that is, the optical axis of the writing light of the light emitting pixel 10 is located on the center line of the opposing photosensitive portion 31. Similarly, the non-photosensitive portion 29 is always located at a position facing the space between the light emitting pixels 10.

  As described in the first embodiment, an erecting equal-magnification image of the image formed by each light emitting pixel 10 on the line head 32 is formed on the surface of the photosensitive drum 30. At this time, since the lens unit 35 in the line head module 100 cannot form a complete equal-magnification image, the diameter of the image formed on the surface of the photosensitive drum 30 is larger than the diameter of the light emitting pixel 10. The enlarged area is an area that was not intended to be irradiated with writing light. When the area is exposed to form an electrostatic latent image, a blurred image is formed as a whole. However, when the periphery of the photosensitive portion 31 that circulates around the photosensitive drum 30 is surrounded by the non-photosensitive portion 29 and the optical axis of the light emitting pixel 10 and the center line of the photosensitive portion 31 coincide with each other as in the present embodiment, the lens unit described above. Deterioration of the image due to 35 can be suppressed. That is, by adjusting the ratio of the photosensitive portion 31 and the non-photosensitive portion 29 on the surface of the photosensitive drum 30 so that the region that was not intended for the writing light irradiation described above becomes the non-photosensitive portion 29, It is possible to avoid the formation of an electrostatic latent image in an unintended region, and it is possible to suppress image deterioration due to the expansion of the optical axis of writing light.

  A feature of this embodiment is that the relative position between the light emitting pixel 10 and the photosensitive portion 31 does not change even when the photosensitive drum 30 rotates in the sub-scanning direction. Unlike the circular shape (spot shape) as in the first embodiment, the shape of the photosensitive portion 31 is a stripe shape that circulates around the photosensitive drum 30 with a constant width. The photosensitive portion 31 is always present at a position facing 10. Therefore, in this embodiment, it is only necessary to deal with changes in the axial direction of the photosensitive drum 30, and the necessity of performing the alignment operation as described above (see FIG. 4) for each image formation is reduced. However, axial misalignment can also occur over long periods of use. Therefore, although the description of the alignment mechanism is omitted in the above description, the alignment mechanism can be mounted in the image forming apparatus including the photosensitive drum 30 according to the present embodiment as in the first embodiment. preferable.

In the present embodiment, the diameter of the light emitting pixel 10 and the width of the photosensitive portion 31 are not necessarily the same. If the arrangement pitch of the two elements in the axial direction is the same, an image can be formed on the surface of the photosensitive drum 30 even if the diameter of the light emitting pixel 10 and the width of the photosensitive portion 31 are different. The ratio of the photosensitive portion 31 and the non-photosensitive portion 29 on the surface of the photosensitive drum 30 may be adjusted according to the degree of expansion of the light beam caused by the lens unit 35 to form an optimal electrostatic latent image.
(Image forming device)

  Next, an image forming apparatus including the photosensitive drum according to the present invention will be described. FIG. 8 shows the configuration of a tandem type full-color image forming apparatus using the belt intermediate transfer system, which includes the photosensitive drum 30 according to the present invention. Note that the subscripts K, C, M, and Y correspond to black, cyan, magenta, and yellow, respectively. The same applies to other components.

  As shown in the figure, this image forming apparatus is provided with a driving roller 171 and a driven roller 172. An endless intermediate transfer belt 170 is wound around these rollers and rotates around the driving roller 171 and the driven roller 172 as indicated by arrows. Around the intermediate transfer belt 170, the four photosensitive drums 30K, C, M, and Y according to any one of the first and second embodiments are similarly arranged at predetermined intervals. The light emitting pixels described in the first or second embodiment are arranged to face each of the line head modules 100K, C, M, and Y arranged in the main scanning direction.

  Around each photosensitive drum 30K, C, M, Y, there is a corona charger 161K, C, M, Y, a line head module 100K, C, M, Y, and a developer 164K, C, M, Y, Is arranged. The corona chargers 161K, C, M, and Y charge the photosensitive portions formed on the surfaces of the corresponding photosensitive drums 30K, C, M, and Y. The line head modules 100K, C, M, and Y emit light from a plurality of light emitting pixels, each of which is controlled independently. The emitted light irradiates the surfaces of the photosensitive drums 30K, C, M, and Y in a state where the diameter of the light beam is enlarged. The photoconductive drums 30K, 30C, 30M, and 30Y fix an image that changes with time, which is emitted from the line head module 100, on the charged photoconductor to form an electrostatic latent image. Then, the fixed electrostatic latent image is transferred to a recording medium via an intermediate transfer belt 170 described later, thereby forming an image on the recording medium.

  As described in the first and second embodiments, the photosensitive drum 30 according to the present invention is different from the conventional photosensitive drum in that the entire area on the surface is not the photosensitive portion 31. On the surface, the periphery is surrounded by a non-photosensitive portion 29 where an electrostatic latent image cannot be formed, and a photosensitive portion 31 whose arrangement pitch in the main scanning direction is the same as the arrangement pitch in the main scanning direction of the light emitting pixels 10. Is formed. The shape of the photosensitive portion 31 is determined according to the shape of the light emitting pixel 10 and the like, and the light irradiated to the non-photosensitive portion 29 around the photosensitive portion 31 does not form an electrostatic latent image. Therefore, even if the light emitted from the line head module 100 irradiates the surface of the photosensitive drum 30 in a state where the diameter is enlarged, an electrostatic latent image similar to the case where the enlargement does not occur on the surface is formed. It is formed.

  The electrostatic latent image formed on the photosensitive drum 30 is transferred to a medium as described below, as in the conventional image forming apparatus.

First, the developing units 164K, C, M, and Y form a visible image, that is, a visible image on the photosensitive drums 30K, C, M, and Y by attaching toner as a developer to the electrostatic latent image. . The black, cyan, magenta, and yellow single-color visible images are sequentially primary-transferred onto the intermediate transfer belt 170 to be superimposed on the intermediate transfer belt 170 to form a full-color visible image.
Inside the intermediate transfer belt 170, primary transfer corotrons (transfer devices) 162K, C, M, and Y are arranged. The primary transfer corotrons 162K, C, M, and Y are disposed in the vicinity of the photosensitive drums 30K, C, M, and Y, respectively, and electrostatic images are electrostatically attracted from the photosensitive drums 30K, C, M, and Y. As a result, the visible image is transferred to the intermediate transfer belt 170 that passes between the photosensitive drums 30K, C, M, and Y and the primary transfer corotrons 162K, C, M, and Y.

  Finally, the recording paper 152 as a recording medium on which an image is to be formed is unloaded one by one from the paper feeding cassette 151 by the pickup roller 153, and the intermediate transfer belt 170 in contact with the driving roller 171 and the secondary transfer belt 171. Sent to the nip between rollers 176. The full-color visible image on the intermediate transfer belt 170 is secondarily transferred to one side of the recording paper 152 by the secondary transfer roller 176 and passes through the fixing roller pair 177 serving as a fixing unit. It is fixed. Thereafter, the recording paper 152 is discharged by a paper discharge roller pair 178 onto a paper discharge cassette (not shown) provided on the image forming apparatus.

  As described above, the image forming apparatus according to the present invention includes the photosensitive drum described in the first or second embodiment as a target on which an electrostatic latent image is formed, so that the line head module emits light. In spite of irradiating the surface of the photosensitive drum in a state where the diameter of the light beam of the writing light is enlarged, a sharp image substantially the same as that in the case where the enlargement does not occur is formed on the recording medium.

FIG. 2A is a diagram schematically illustrating a configuration of a light emitting pixel and the like according to the first embodiment. FIG. 2B is a diagram schematically illustrating the entire line head. FIG. 2 is a schematic diagram illustrating a photosensitive drum and a line head according to the first embodiment. FIG. 2 is a diagram illustrating a photosensitive drum and a line head module according to the first embodiment. The figure which shows the mechanism of position alignment typically. (A) is a figure which shows typically the structure of the light emitting pixel of 2nd Embodiment. FIG. 5B is a diagram schematically illustrating a line head corresponding to the photosensitive drum of the second embodiment. The figure which shows typically the surface of the photoconductive drum and line head of 2nd Embodiment. FIG. 6 is a diagram illustrating a photosensitive drum and a line head module according to a second embodiment. 1 is a diagram illustrating a configuration of an image forming apparatus including a photosensitive drum according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Light emitting pixel, 12 ... Driving TFT, 14 ... Gate wiring, 16 ... Drain electrode, 18 ... Source electrode, 20 ... Pixel electrode, 22 ... Source wiring, 25 ... Control circuit, 26 ... Grounding part, 27 ... Second 29 ... non-photosensitive part, 30 ... photosensitive drum, 31 ... photosensitive part, 32 ... line head, 33 ... heat sink, 34 ... sealing plate, 35 ... lens unit, 36 ... half mirror, 38 ... alignment Marks 40... Alignment light emitting pixels 41... Alignment light 42. Imaging device 44. Control unit 48. Drive control unit 100. Line head module 151 151 Paper feed cassette 152 152 Recording paper 153 Pickup roller 161... Corona charger 162. Primary transfer corotron 164 developing device 170 intermediate transfer belt 171 drive roller 172 driven roller 17 ... secondary transfer roller, 177 ... fixing roller pair, 178 ... discharge rollers.

Claims (9)

Photosensitivity for forming an electrostatic latent image by receiving light emitted from light emitting pixels arranged in alignment on a substrate in a sub-scanning direction and receiving light at a photosensitive portion formed on the surface of a conductive cylindrical member. A body drum,
The photosensitive portion is surrounded by a non-photosensitive portion where the electrostatic latent image cannot be formed,
The photosensitive drum, wherein an arrangement pitch of the photosensitive portions in the main scanning direction is the same as an arrangement pitch of the light emitting pixels in the main scanning direction.   The photosensitive drum according to claim 1, wherein a shape of the photosensitive portion is substantially similar to a shape of the light emitting pixel.   2. The photosensitive drum according to claim 1, wherein the shape of the photosensitive portion is a stripe shape that makes a round in the sub-scanning direction with a space between the surfaces of the photosensitive drum.   A printing engine comprising the photosensitive drum according to claim 1.   The print engine according to claim 4, further comprising a mechanism for aligning the positions of the light emitting pixels and the photosensitive portion.   An image forming apparatus comprising the print engine according to claim 4. A method of manufacturing a photosensitive drum, wherein light emitted from light emitting pixels arranged in alignment on a substrate is received by a photosensitive portion formed on a surface of a conductive cylindrical member to form an electrostatic latent image,
Forming a photosensitive layer capable of forming an electrostatic latent image by receiving a predetermined range of light on the cylindrical member surface;
A photosensitive part capable of forming the electrostatic latent image on the surface of the photosensitive drum by forming a light shielding layer capable of shielding the light in the predetermined range in a partial region of the surface of the photosensitive layer; And a step of regularly forming non-photosensitive portions where the electrostatic latent image cannot be formed.   The light shielding layer is formed by selectively removing a photosensitive material applied to the surface of the photosensitive layer from a region where the photosensitive portion is to be formed by photolithography, and then curing the photosensitive material. A method for producing a photosensitive drum according to claim 7. A method of manufacturing a photosensitive drum, wherein light emitted from light emitting pixels arranged in alignment on a substrate is received by a photosensitive portion formed on a surface of a conductive cylindrical member to form an electrostatic latent image,
A method for producing a photosensitive drum, comprising the step of forming the photosensitive portion only in a predetermined region on the surface of the cylindrical member.

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