JP2008185668A - Light-shielding member, line head using the same, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-shielding member having two or more functions, a line head in which the light-shielding member is used for forming superior spots, and an image forming apparatus in which the line head is used and the image quality of which deteriorates less. <P>SOLUTION: The light guide pore 2971 of the light-shielding member 297 to be arranged between a light emitting element group 295 and a microlens ML has different cross-sectional areas S1, S2, S3. The cross-sectional area S2 of the middle position is made smaller than the cross-sectional area S1 on the side of the light-emitting element group 295 and the cross-sectional area S3 on the side of an imaging lens. Thus, even if an optical system including the light-emitting element group 295 and the microlens ML constitutes a reduced optical system, the light-shielding member 297 having two or more functions, corresponding to different cross-sectional areas in portions where the cross-sectional areas of the light guide pore 2971 are S1, S2 and S3 can be obtained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light shielding member, a line head that scans a light beam onto a surface to be scanned using the light shielding member, and an image forming apparatus.

As a line head that scans a surface to be scanned with a light beam, for example, as described in Patent Document 1, a light emitting element group (same as above) configured by arranging a plurality of LEDs (Light Emitting Diodes) as light emitting elements. The thing using the "LED array chip" in patent document 1 is proposed. In the line head described in Patent Document 1, a plurality of light emitting element groups are arranged side by side, and a plurality of imaging lenses are arranged to face each other with respect to the plurality of light emitting element groups.
Furthermore, the space between the LED array chip and the imaging lens is surrounded in a box shape by a light shielding plate or the like that is a light shielding member, and light from the LED array chip leaks to the adjacent space or outside to improve the print quality. There is known a configuration that reduces the development that deteriorates, that is, so-called crosstalk.

Japanese Patent No. 2510423 (page 4, FIGS. 1 and 2)

The light beam emitted from the light emitting element is imaged by an imaging lens facing the light emitting element group, and a spot is formed on the surface to be scanned.
Here, the light shielding member provided between the light emitting element and the imaging lens is required to have various functions in addition to the configuration for reducing crosstalk.
For example, the light beam reflected by the light-shielding member goes to a position far from the position where the image is originally formed and generates a ghost that is so-called stray light. A function for suppressing this ghost is mentioned. Further, there are a function as a diaphragm for defining a light beam incident on the imaging lens, a function for determining the position of the imaging lens, and the like.
In order to give these functions to one light shielding member, it is necessary to process the light shielding member into a shape corresponding to each function, and it is not easy to process the light shielding member.
An object of the present invention is to provide a light-shielding member having a plurality of functions, a line head using the light-shielding member using the light-shielding member, and an image forming apparatus using the same with little deterioration in image quality.

The light-shielding member of the present invention is used in a line head including a light-emitting element group having a plurality of light-emitting elements and a plurality of imaging lenses, and has one surface facing the light-emitting element group and the other surface facing the plurality of light-emitting elements. A light shielding member disposed to face the imaging lens, the light shielding member having a light guide hole penetrating from the one surface to the other surface in a one-to-one relationship with the light emitting element group; The areas are S1, S2, and S3 from the light emitting element group side, and S1, S2, and S3 have the following relationship.
S2 <S1, S2 <S3

  According to this invention, the light guide hole of the light shielding member disposed between the light emitting element group and the imaging lens has different cross-sectional areas S1, S2, and S3. The intermediate cross-sectional area S2 is smaller than the cross-sectional area S1 on the light emitting element group side and the cross-sectional area S3 on the imaging lens side. Therefore, even if the optical system including the light emitting element group and the imaging lens constitutes a reduction optical system, the light guide hole has a plurality of functions corresponding to the cross-sectional areas in the sections S1, S2, and S3. A light shielding member is obtained.

In the present invention, the light shielding member includes a plurality of light shielding plates having a hole between the light emitting element group and the imaging lens, and the plurality of light shielding plates have a hole having the cross-sectional area S1. A light-shielding plate, a light-shielding plate in which a hole of the cross-sectional area S2 is formed, and a light-shielding plate in which a hole of the cross-sectional area S3 is formed, and the holes are laminated to form the light guide hole It is preferable.
In this invention, the light guide hole is formed by laminating the light shielding plates including the light shielding plate in which holes having different cross-sectional areas are formed. Therefore, the cross-sectional area at an arbitrary position of the light guide hole is controlled by the stacking order of the light shielding plates. Further, since the light shielding member is formed by laminating light shielding plates that are easily punched, the processing speed is high and the cost is reduced.

The line head of the present invention is a line head that forms a spot by forming an image of a light beam on a surface to be scanned, and includes a plurality of substrates and light emitting elements, and a plurality of discretely arranged on the substrate. And a light beam emitted from a plurality of the light emitting elements belonging to the light emitting element group facing each other, and the light emitting element group, and the light emitting element group A plurality of imaging lenses that form an image on the substrate, one surface of which is opposed to the substrate and the other surface thereof is opposed to the plurality of imaging lenses. A light-shielding member having a plurality of light guide holes penetrating from the one surface to the other surface, and the imaging lens reduces the light-emitting element group and reduces the light-emitting element group. An optical system that forms an image on a scanning surface has a cross-sectional area of S1, S2, and S3 from the light emitting element group side, and S1, S2, and S3 have the following relationship: And
S2 <S1, S2 <S3

  According to this invention, the light guide hole of the light shielding member disposed between the light emitting element group and the imaging lens has different cross-sectional areas S1, S2, and S3. The intermediate cross-sectional area S2 is smaller than the cross-sectional area S1 on the light emitting element group side and the cross-sectional area S3 on the imaging lens side. Therefore, when the optical system including the light emitting element group and the imaging lens is a reduction optical system, the light shielding member having a plurality of functions corresponding to the cross-sectional areas at the portions where the cross-sectional areas of the light guide holes are S1, S2, and S3. Is obtained.

In the present invention, the light shielding member includes a plurality of light shielding plates having a hole between the light emitting element group and the imaging lens, and the plurality of light shielding plates have a hole having the cross-sectional area S1. A light-shielding plate, a light-shielding plate in which a hole of the cross-sectional area S2 is formed, and a light-shielding plate in which a hole of the cross-sectional area S3 is formed, and the holes are laminated to form the light guide hole It is preferable.
In this invention, the light guide hole is formed by laminating the light shielding plates including the light shielding plate in which holes having different cross-sectional areas are formed. Therefore, it is possible to obtain a line head including a light shielding member in which the cross-sectional area at an arbitrary position of the light guide hole is controlled according to the stacking order of the light shielding plates. Moreover, since the light shielding member formed by laminating the light shielding plates that can be easily perforated is provided, a line head with reduced cost can be obtained.

In the present invention, it is preferable that the hole of the cross-sectional area S1 is a ghost prevention part, the hole of the cross-sectional area S2 is a diaphragm part, and the hole of the cross-sectional area S3 is a lens positioning part.
In the present invention, the light shielding member includes a ghost preventing portion, a diaphragm portion, and a lens positioning portion. Therefore, with these functions, a line head can be obtained in which a light beam emitted from the light emitting element forms an image on the surface to be scanned at a predetermined position and size, and a good spot is formed.

In the present invention, the substrate is a transparent substrate capable of transmitting the light beam disposed so that a front surface thereof faces the light shielding member, and the light emitting element is disposed on a back surface of the transparent substrate. It is preferable that the organic EL is provided.
In the present invention, when the organic EL is used for the light emitting element, the above-described effects can be obtained.

In this invention, it is preferable that the said board | substrate is arrange | positioned so that the front surface may oppose the said light-shielding member, and the said light emitting element is LED provided in the said front surface of the said board | substrate.
In the present invention, when the LED is used for the light emitting element, the above-described effects can be obtained.

  The image forming apparatus according to the present invention includes a latent image carrier whose surface is conveyed in the sub-scanning direction, and a spot formed on the surface of the latent image carrier using the surface of the latent image carrier as a surface to be scanned. And an exposure unit having the same configuration as the line head.

  According to the present invention, since the exposure means having the same configuration as the line head having the above-described effect is provided, the occurrence of crosstalk and ghost is suppressed, and the optical system is also properly arranged. Therefore, an image is formed from the spot imaged at the original position, and an image forming apparatus with little deterioration in image quality can be obtained.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram illustrating an image forming apparatus 1 according to an embodiment and a line head 29 as an exposure unit.
FIG. 2 is a diagram showing an electrical configuration of the image forming apparatus 1 and the line head 29 of FIG.

The image forming apparatus 1 includes a color mode in which four color toners of black (K), cyan (C), magenta (M), and yellow (Y) are superimposed to form a color image, and only black (K) toner. It is possible to selectively execute a monochrome mode for forming a monochrome image using.
In FIG. 1, the image forming apparatus 1 includes a line head 29 for forming an image corresponding to each color. FIG. 1 is a diagram corresponding to the execution of the color mode.

  In FIG. 2, in the image forming apparatus 1, when an image forming command is given from an external device such as a host computer to a main controller MC having a CPU, a memory, etc., the main controller MC gives a control signal to the engine controller EC. At the same time, the video data VD corresponding to the image formation command is given to the head controller HC. The head controller HC controls the line head 29 for each color based on the video data VD from the main controller MC, the vertical synchronization signal Vsync from the engine controller EC, and parameter values. As a result, the engine unit EG executes a predetermined image forming operation, and forms an image corresponding to the image forming command on a sheet such as a copy sheet, a transfer sheet, a sheet, and an OHP transparent sheet.

In FIG. 1, the image forming apparatus 1 includes a housing body 3. In the housing main body 3, an electrical component box 5 is provided that contains a power circuit board, a main controller MC, an engine controller EC, and a head controller HC.
An image forming unit 7, a transfer belt unit 8, and a paper feeding unit 11 are also disposed in the housing body 3.
Further, a secondary transfer unit 12, a fixing unit 13, and a sheet guide member 15 are disposed in the housing body 3.
Note that the paper feed unit 11 and the transfer belt unit 8 can be removed and repaired or exchanged.

  The image forming unit 7 includes four image forming stations Y (for yellow), M (for magenta), C (for cyan), and K (for black) that form a plurality of different color images. Each of the image forming stations Y, M, C, and K is provided with a photosensitive drum 21 as a latent image carrier on which the respective color toner images are formed. Each photosensitive drum 21 is connected to a dedicated drive motor and is driven to rotate at a predetermined speed in the direction of rotation D21 indicated by an arrow in the drawing. As a result, the surface 211 as the scanning surface of the photosensitive drum 21 is conveyed in the sub-scanning direction.

A charging unit 23, a line head 29, a developing unit 25, and a photoconductor cleaner 27 are disposed around the photoconductive drum 21 along the rotation direction. Thus, a charging operation, an electrostatic latent image forming operation, a toner developing operation, and a cleaning operation are executed, respectively.
When the color mode is executed, the toner images formed by all the image forming stations Y, M, C, and K are superimposed on the transfer belt 81 of the transfer belt unit 8 to form a color image, and when the monochrome mode is executed. A monochrome image is formed using only the toner image formed at the image forming station K.
In FIG. 1, the image forming stations of the image forming unit 7 have the same configuration, and therefore, for convenience of illustration, only some image forming stations are denoted by reference numerals, and the other image forming stations are omitted. .

  The charging unit 23 includes a charging roller whose surface is made of elastic rubber. The charging roller is configured to rotate in contact with the surface 211 of the photosensitive drum 21 at the charging position, and the peripheral speed in the driven direction with respect to the photosensitive drum 21 as the photosensitive drum 21 rotates. Rotate following. The charging roller is connected to a charging bias generating unit (not shown), and receives the charging bias from the charging bias generating unit, and the photosensitive drum 21 is in a charging position where the charging unit 23 and the photosensitive drum 21 come into contact with each other. The surface 211 is charged.

The line head 29 irradiates light onto the surface 211 of the photosensitive drum 21 charged by the charging unit 23 to form an electrostatic latent image on the surface 211.
Hereinafter, the control of the line head 29 will be described in detail with reference to FIG.
In the embodiment, the image data included in the image formation command is input to the image processing unit 51 of the main controller MC. Various image processing is performed on the image data to create video data VD for each color, and the video data VD is given to the head controller HC via the main-side communication module 52. In the head controller HC, the video data VD is given to the head control module 54 via the head side communication module 53. As described above, the head controller module 54 is supplied with the signal indicating the parameter value related to the electrostatic latent image formation and the vertical synchronization signal Vsync from the engine controller EC. Based on these signals, video data VD, and the like, the head controller HC creates a signal for controlling element driving for the line head 29 of each color, and outputs the signal to each line head 29. Thus, the operation of the light emitting element 2951 (not shown) is appropriately controlled in each line head 29, and an electrostatic latent image corresponding to the image formation command is formed.
The configuration of the line head 29 including the light emitting element 2951 will be described in detail later.

  In FIG. 1, the developing unit 25 has a developing roller 251 that carries toner on its surface. The charged toner is developed at a developing position where the developing roller 251 and the photosensitive drum 21 come into contact with each other by a developing bias applied to the developing roller 251 from a developing bias generating unit (not shown) electrically connected to the developing roller 251. The electrostatic latent image formed by the line head 29 by moving from the roller 251 to the photosensitive drum 21 is manifested to become a toner image.

  The toner image that has been made visible at the development position in this way is conveyed in the rotational direction D21 of the photosensitive drum 21, and then the primary transfer position TR1 where the transfer belt 81, which will be described in detail later, and each photosensitive drum 21 come into contact with each other. 1 is primarily transferred to the transfer belt 81.

  In the embodiment, the photoreceptor cleaner 27 is provided in contact with the surface 211 of the photoreceptor drum 21 on the downstream side of the primary transfer position TR1 in the rotation direction D21 of the photoreceptor drum 21 and on the upstream side of the charging unit 23. It has been. The photoconductor cleaner 27 is in contact with the surface 211 of the photoconductor drum 21 to remove the toner remaining on the surface 211 of the photoconductor drum 21 after the primary transfer.

  In the embodiment, the photosensitive drum 21, the charging unit 23, the developing unit 25, and the photosensitive cleaner 27 of each of the image forming stations Y, M, C, and K are unitized as a photosensitive cartridge. Each photoconductor cartridge is provided with a nonvolatile memory for storing information related to the photoconductor cartridge. Then, wireless communication is performed between the engine controller EC and each photoconductor cartridge. In this way, information on each photoconductor cartridge is transmitted to the engine controller EC, and information in each memory is updated and stored.

  The transfer belt unit 8 includes a driving roller 82, a driven roller 83 (hereinafter referred to as a blade facing roller) disposed on the left side of the driving roller 82 in FIG. A transfer belt 81 that is circulated and driven in the transport direction). Further, the transfer belt unit 8 is disposed on the inner side of the transfer belt 81 so as to be opposed to each of the photosensitive drums 21 included in the image forming stations Y, M, C, and K when the photosensitive cartridge is mounted. Four primary transfer rollers 85 (85Y, 85M, 85C, 85K) are provided. These primary transfer rollers 85 are electrically connected to a primary transfer bias generator (not shown). As will be described in detail later, when the color mode is executed, as shown in FIG. 1, all the primary transfer rollers 85 (85Y, 85M, 85C, 85K) are moved to the image forming stations Y, M, C, K side. By positioning, the transfer belt 81 is pushed and brought into contact with the photosensitive drum 21 of each of the image forming stations Y, M, C, and K, and primary transfer is performed between the photosensitive drum 21 and the transfer belt 81. A position TR1 is formed. Then, by applying a primary transfer bias from the primary transfer bias generating unit to the primary transfer roller 85 at an appropriate timing, the toner images formed on the surface 211 of each photosensitive drum 21 are respectively corresponding. A color image is formed by transferring to the surface of the transfer belt 81 at the primary transfer position TR1.

  On the other hand, when the monochrome mode is executed, among the four primary transfer rollers 85, the color primary transfer rollers 85Y, 85M, and 85C are separated from the image forming stations Y, M, and C facing each other, and the monochrome primary transfer is performed. By bringing only the roller 85K into contact with the image forming station K, only the image forming station K in the monochrome mode is brought into contact with the transfer belt 81. As a result, the primary transfer position TR1 is formed only between the monochrome primary transfer roller 85K and the image forming station K. Then, by applying a primary transfer bias from the primary transfer bias generator to the monochrome primary transfer roller 85K at an appropriate timing, the toner image formed on the surface 211 of each photosensitive drum 21 is converted into a primary image. The image is transferred onto the surface of the transfer belt 81 at the transfer position TR1 to form a monochrome image.

  Further, the transfer belt unit 8 includes a downstream guide roller 86 disposed downstream of the monochrome primary transfer roller 85K and upstream of the driving roller 82. Further, the downstream guide roller 86 includes the monochrome primary transfer roller 85K and the photosensitive drum 21 at the primary transfer position TR1 formed by the monochrome primary transfer roller 85K being in contact with the photosensitive drum 21 of the image forming station K. Are configured to abut against the transfer belt 81 on the common inscribed line.

  The paper feed unit 11 includes a paper feed unit having a paper feed cassette 77 capable of stacking and holding sheets and a pickup roller 79 for feeding sheets one by one from the paper feed cassette 77. The sheet fed from the sheet feeding unit by the pickup roller 79 is fed to the secondary transfer position TR2 along the sheet guide member 15 after the sheet feeding timing is adjusted by the registration roller pair 80.

The secondary transfer unit 12 includes a secondary transfer roller 121 and a driving roller 82.
The drive roller 82 circulates and drives the transfer belt 81 in the direction of the arrow D81 in the figure, and also serves as a backup roller for the secondary transfer roller 121. A rubber layer having a thickness of about 3 mm and a volume resistivity of 1000 kΩ · cm or less is formed on the peripheral surface of the drive roller 82, and a secondary transfer bias (not shown) is generated by grounding through a metal shaft. This is a conductive path of a secondary transfer bias supplied from the part via the secondary transfer roller 121. As described above, by providing the driving roller 82 with a rubber layer having high friction and shock absorption, when the sheet enters the secondary transfer position TR2 which is a contact portion between the driving roller 82 and the secondary transfer roller 121. It is difficult for the impact to be transmitted to the transfer belt 81, and deterioration of image quality can be prevented.
The secondary transfer roller 121 is provided so as to be able to come into contact with and separate from the transfer belt 81, and is driven to come into contact with a secondary transfer roller drive mechanism (not shown).
The image transferred to the transfer belt 81 is secondarily transferred to the sheet fed to the secondary transfer position TR2.

The fixing unit 13 includes a heating roller 131 that includes a heating element such as a halogen heater and is rotatable, and a pressure unit 132 that presses and biases the heating roller 131.
The pressure unit 132 includes two rollers 1321 and 1322 and a pressure belt 1323 stretched between them.
The sheet on which the image has been secondarily transferred is guided by the sheet guide member 15 to a nip portion formed by the heating roller 131 and the pressure belt 1323 of the pressure portion 132, and the image is heated at a predetermined temperature in the nip portion. It is fixed.
By pressing the belt tension surface stretched by the two rollers 1321 and 1322 on the surface of the pressure belt 1323 against the peripheral surface of the heating roller 131, the nip portion formed by the heating roller 131 and the pressure belt 1323 is wide. It is configured to be taken.
The sheet subjected to the fixing process is conveyed to a paper discharge tray 4 provided on the upper surface of the housing body 3.

In the image forming apparatus 1, a cleaner unit 71 is disposed to face the blade facing roller 83. The cleaner unit 71 includes a cleaner blade 711 and a waste toner box 713.
The cleaner blade 711 removes foreign matters such as toner and paper dust remaining on the transfer belt 81 after the secondary transfer by bringing the tip of the cleaner blade 711 into contact with the blade facing roller 83 via the transfer belt 81. The foreign matter removed in this way is collected in a waste toner box 713. Further, the cleaner blade 711 and the waste toner box 713 are integrally formed with the blade facing roller 83.

Hereinafter, the line head 29 in the embodiment will be described in detail with reference to the drawings.
FIG. 3 is a perspective view showing an outline of the line head 29 according to the embodiment of the present invention. 4 is a cross-sectional view of the line head 29 in the sub-scanning direction YY.
1 and 3, the line head 29 includes a light emitting element group 295 including a plurality of light emitting elements 2951 arranged in the axial direction of the photosensitive drum 21 (direction perpendicular to the paper surface of FIG. 1). It is spaced from the photosensitive drum 21. Then, light is emitted from the light emitting elements 2951 to the surface 211 that is the surface to be scanned of the photosensitive drum 21 charged by the charging unit 23 to form an electrostatic latent image on the surface 211.

  In FIG. 3, the line head 29 in the embodiment includes a case 291 having the main scanning direction XX as a longitudinal direction, and positioning pins 2911 and screw insertion holes 2912 are provided at both ends of the case 291. The positioning head 2911 is fitted into a positioning hole that covers the photosensitive drum 21 and is formed in a photosensitive cover (not shown) that is positioned with respect to the photosensitive drum 21, so that the line head 29 is inserted into the photosensitive drum. 21 is positioned. Further, the line head 29 is positioned and fixed with respect to the photosensitive drum 21 by screwing and fixing a fixing screw into a screw hole (not shown) of the photosensitive member cover via the screw insertion hole 2912.

3 and 4, the case 291 holds the microlens array 299 in which the imaging lenses are arranged at a position facing the surface 211 of the photosensitive drum 21, and in the order close to the microlens array 299. Thus, a light shielding member 297 as a light shielding portion and a glass substrate 293 as a substrate are provided. The glass substrate 293 is a transparent substrate.
A plurality of light emitting element groups 295 are provided on the back surface 2932 of the glass substrate 293 (the surface opposite to the front surface 2931 facing the light shielding member 297 of the two surfaces of the glass substrate 293). As shown in FIG. 3, the plurality of light emitting element groups 295 are two-dimensionally and discretely arranged on the back surface 2932 of the glass substrate 293 so as to be separated from each other by a predetermined distance in the main scanning direction XX and the sub-scanning direction YY. Has been. Here, each of the plurality of light emitting element groups 295 is configured by two-dimensionally arranging a plurality of light emitting elements 2951 as shown in a circled portion in FIG.
In the embodiment, an organic EL is used as the light emitting element. That is, in the embodiment, the organic EL is arranged as the light emitting element 2951 on the back surface 2932 of the glass substrate 293. A light beam emitted from each of the plurality of light emitting elements 2951 toward the photosensitive drum 21 is directed to the light shielding member 297 through the glass substrate 293.
The light emitting element may be an LED. In this case, the substrate may not be a glass substrate, and the LED can be provided on the front surface 2931.

3 and 4, the light shielding member 297 is provided with a plurality of light guide holes 2971 on a one-to-one basis with respect to the plurality of light emitting element groups 295. The light guide hole 2971 is provided as a substantially cylindrical hole penetrating the light shielding member 297 with a line parallel to a perpendicular to the glass substrate 293 (indicated by a one-point difference line in the figure) as a central axis.
The light guide hole 2971 is formed by laminating a plurality of light shielding plates 2972 having holes 2993, 2974, and 2975 having different cross-sectional areas. When the cross-sectional area of the hole 2975 is S1, the cross-sectional area of the hole 2974 is S2, and the cross-sectional area of the hole 2973 is S3, the following relationship is established.
S2 <S1, S2 <S3
3 and 4, light emitted from the light emitting elements 2951 belonging to the light emitting element group 295 is guided to the microlens array 299 through the light guide holes 2971 corresponding to the light emitting element groups 295 on a one-to-one basis. The light beam that has passed through the light guide hole 2971 provided in the light shielding member 297 is imaged as a spot on the surface 211 of the photosensitive drum 21 by the microlens array 299 as indicated by a two-dot chain line. Become.

  As shown in FIG. 4, the back cover 2913 is pressed against the case 291 through the glass substrate 293 by the fixing device 2914. That is, the fixing device 2914 has an elastic force that presses the back cover 2913 toward the case 291, and presses the back cover 2913 with the elastic force, so that the inside of the case 291 is light-tight (that is, inside the case 291). From the outside of the case 291 so that no light leaks from the case 291). As shown in FIG. 3, a plurality of fixing devices 2914 are provided in the longitudinal direction of the case 291. The light emitting element group 295 is covered with a sealing member 294.

FIG. 5 is an exploded view of the light shielding member 297 into a light shielding plate 2972.
In FIG. 5, each light shielding plate 2972 can be aligned by aligning the positions of the alignment holes 2976 with protrusions and bonding them together.
Each light shielding plate 2972 can be aligned not only by the alignment hole 2976 but also by being housed in the case 291 shown in FIGS.

In the embodiment, for example, the thickness of the light shielding plate 2972 is about 0.10 mm. Then, 10 light shielding plates 2972 are laminated to form a light shielding member 297. Formation of the hole in the light shielding plate 2972 can be performed by etching or pressing. Although the diameters of these holes are different, they are about 0.85 mm, and the distance between the holes is 0.10 mm to 0.16 mm. As is well known, if the distance between the holes is about 1.5 times the plate thickness, a plurality of holes can be extracted by press working.
As a material for forming the light shielding plate 2972, synthetic resin, ceramic, or the like can be used in addition to metal. In the case of a synthetic resin or ceramic, it can be formed by molding.

FIG. 6 is a perspective view showing an outline of the microlens array 299. FIG. 7 is a cross-sectional view of the microlens array 299 in the main scanning direction.
The microlens array 299 includes a glass substrate 2991 and a plurality of lens pairs configured by two lenses 2993A and 2993B arranged one-on-one so as to sandwich the glass substrate 2991. These lenses 2993A and 2993B can be formed of resin.

  In FIG. 7, a plurality of lenses 2993A are arranged on the front surface 2991A of the glass substrate 2991, and a plurality of lenses 2993B are arranged on the back surface 2991B of the glass substrate 2991 so as to correspond to the plurality of lenses 2993A on a one-to-one basis. Yes. Further, the two lenses 2993A and 2993B constituting the lens pair share a common optical axis OA indicated by a one-dot chain line in the drawing. The plurality of lens pairs are arranged one-on-one in the plurality of light emitting element groups 295. In this specification, an optical system including lenses 2993A and 2993B forming a one-to-one pair and a glass substrate 2991 sandwiched between the lens pairs is referred to as a “microlens ML”. The microlens ML as an imaging lens is two-dimensionally arranged at a predetermined distance from each other in the main scanning direction XX and the sub-scanning direction YY corresponding to the arrangement of the light emitting element groups 295.

FIG. 8 is a diagram showing an arrangement of a plurality of light emitting element groups 295.
In the embodiment, one light emitting element group 295 is configured by arranging two light emitting element rows L2951 arranged in the main scanning direction XX at predetermined intervals and arranging two light emitting element rows L2951 in the sub scanning direction YY. . That is, eight light emitting elements 2951 corresponding to the position of the outer diameter of one microlens ML indicated by a two-dot chain line in FIG. The plurality of light emitting element groups 295 are arranged as follows.

  The light emitting element group 295 is two-dimensionally arranged such that three light emitting element group rows L295 (group row) configured by arranging a predetermined number (two or more) of light emitting element groups 295 in the main scanning direction XX are arranged in the sub scanning direction YY. Is arranged. Further, all the light emitting element groups 295 are arranged at different main scanning direction positions. Further, the plurality of light emitting element groups 295 are arranged so that the sub scanning direction positions of the light emitting element groups (for example, the light emitting element group 295C1 and the light emitting element group 295B1) whose main scanning direction positions are adjacent to each other are different. The main scanning direction position and the sub scanning direction position mean the main scanning direction component and the sub scanning direction component at the position of interest, respectively. Further, in this specification, “geometric centroid of light emitting element group” means the geometric centroid of the positions of all the light emitting elements 2951 belonging to the same light emitting element group 295.

  Corresponding to the arrangement of the light emitting element groups 295, the light shielding hole 297 is provided in the light shielding member 297, and the microlens ML is arranged. That is, in the embodiment, the geometric gravity center position E0 (FIG. 9) of the light emitting element group 295, the central axis of the light guide hole 2971, and the optical axis OA of the microlens ML are configured to substantially coincide with each other. . The light beam emitted from the light emitting element 2951 of the light emitting element group 295 enters the microlens array 299 through the corresponding light guide hole 2971 and is spotted on the surface 211 of the photosensitive drum 21 by the microlens array 299. Is imaged.

Hereinafter, how the light beam emitted from the light emitting element group 295 travels through the light guide hole 2971 will be described.
FIG. 9 is a cross-sectional view of the vicinity of the light shielding member 297 in the embodiment.

  In FIG. 9, a plurality of light emitting element groups 295 are discretely arranged on the back surface 2932 of the glass substrate 293. A plurality of microlenses ML corresponding to the plurality of light emitting element groups 295 on a one-to-one basis are arranged. Further, the light shielding member 297 is arranged so that one surface thereof faces the front surface 2931 of the glass substrate and the other surface thereof faces the microlens array 299. The light shielding member 297 is provided with a plurality of light guide holes 2971 corresponding to the plurality of light emitting element groups 295 on a one-to-one basis from one surface of the light shielding member 297 to the other surface.

In addition, the locus of the light beam that passes through the light guide hole 2971 among the light beams emitted from the light emitting element group 295 is shown. The locus of the light beam emitted from the geometric gravity center position E0 of the light emitting element group 295 is indicated by a two-dot chain line, and the locus of the light beam emitted from a position E1 farthest from the geometric gravity center position E0 is indicated by a dotted line. A one-dot chain line indicates each principal ray.
As indicated by the locus, the light beam emitted from each position enters the back surface 2932 of the glass substrate 293 and then exits from the front surface 2931 of the glass substrate 293. Then, the light beam emitted from the front surface 2931 of the glass substrate 293 passes through the light guide hole 2971 and passes through the microlens array 299, and is a photoconductor that is the scanned surface shown in FIGS. It reaches the surface 211 of the drum 21.

The optical system according to the embodiment is a so-called reduction optical system that forms an image by reducing the light emitting element group 295 on the surface 211 of the photosensitive drum 21 shown in FIGS.
Further, the light beam emitted from the geometric gravity center position E0 of the light emitting element group 295 forms an image at an image forming position that is an intersection of the surface 211 of the photosensitive drum 21 and the optical axis OA of the microlens ML shown in FIG. Is done. As described above, this is because, in the embodiment, the geometric gravity center position E0 of the light emitting element group 295 is on the optical axis OA of the microlens ML. Further, the light beam emitted from the position E1 is imaged at a position on the opposite side across the optical axis OA of the microlens ML in the main scanning direction XX shown in FIG. That is, the microlens ML is a so-called inverted optical system having reversal characteristics.
Further, since it is a reduction optical system, on the surface 211 of the photosensitive drum 21, the distance between the imaging position of the light beam emitted from the geometric gravity center position E0 and the imaging position of the light beam emitted from the position E1 is: The distance is shorter than the distance between the geometric gravity center position E0 and the position E1 in the light emitting element group 295.
In the embodiment, the microlens ML functions as the “imaging lens” in the present invention.

The seven light shielding plates 2972 on the glass substrate 293 side have holes 2975 having a cross-sectional area of S1, and function as ghost prevention portions 2985. The ghost is generated when the light beam reflected by the inner surface of the light guide hole 2971 enters the microlens array 299. In particular, the light beam reflected by the inner surface of the light guide hole 2971 near the glass substrate 293 has a large incident angle to the microlens ML, and tends to go to a position away from the original image forming position and become a ghost.
By reducing the cross-sectional area S1 of the hole 2975, the incident angle and the reflection angle on the inner surface of the light guide hole 2971 on the glass substrate 293 side are increased. Therefore, the incident angle to the microlens ML is reduced, and the ghost due to internal reflection is reduced.

On the microlens ML side of the seven laminated light shielding plates 2972, a light shielding plate 2972 whose hole 2974 has a cross-sectional area S2 is laminated. This light shielding plate 2972 functions as a diaphragm portion 2984.
The aperture 2984 defines a light beam incident on the microlens ML. The diaphragm unit 2984 can adjust the light amount, the depth of focus, and the like.

On the microlens ML side, two light shielding plates 2972 in which the cross-sectional area of the hole 2993 is S3 are stacked. Of the two sheets, the light shielding plate closest to the microlens ML functions as the lens positioning portion 2983.
For example, referring to FIG. 9, the distance between the microlens array 299 and the light emitting element group 295 is defined by determining the positions of the light shielding member 297 and the microlens array 299 by the lens positioning unit 2983. Further, by determining the position in the front-rear and left-right directions with respect to the paper surface, the geometric gravity center position E0 of the light-emitting element group 295 is positioned on the optical axis OA of the microlens ML, and the optical axis OA of the corresponding microlens ML and the light guide. The central axis of the hole 2971 can be matched.

FIG. 10 is a diagram showing a spot forming operation by the line head 29.
Hereinafter, a spot forming operation by the line head in the embodiment will be described with reference to FIGS. 2, 8, and 10. In order to facilitate understanding of the invention, here, a case where a plurality of spots are formed side by side on a straight line extending in the main scanning direction XX will be described. In the embodiment, a plurality of light emitting elements are caused to emit light at a predetermined timing by the head control module 54 while transporting the surface 211 of the photosensitive drum 21 in the sub scanning direction YY, so that a plurality of light emitting elements are aligned on a straight line extending in the main scanning direction XX. Are formed side by side.

  In FIG. 8, in the line head 29 of the embodiment, six light emitting element rows L2951 are arranged side by side in the sub-scanning direction YY corresponding to each position of the sub-scanning direction positions Y1 to Y6. In the embodiment, the light emitting element rows L2951 at the same sub scanning direction position emit light at substantially the same timing, and the light emitting element rows L2951 at different sub scanning direction positions emit light at different timings. More specifically, the light emitting element rows L2951 are caused to emit light in the order of the sub-scanning direction positions Y1 to Y6. A plurality of spots are arranged on a straight line extending in the main scanning direction XX of the surface 211 by causing the light emitting element array L2951 to emit light in the order described above while transporting the surface 211 of the photosensitive drum 21 in the sub scanning direction YY. Form.

Such an operation will be described with reference to FIGS. First, the light emitting elements 2951 of the light emitting element row L2951 in the sub scanning direction position Y1 belonging to the most upstream light emitting element groups 295A1, 295A2, 295A3,. Then, the plurality of light beams emitted by the light emission operation are enlarged while being inverted by the microlens ML which is the “imaging lens” having the above-described inversion enlargement characteristics, and formed on the surface 211 of the photosensitive drum 21. Is done. That is, a spot is formed at the position of the “first” hatching pattern in FIG.
In the figure, white circles represent spots that have not yet been formed and are to be formed in the future. In the same figure, the spots labeled with reference numerals 295C1, 295B1, 295A1, and 295C2 indicate spots formed by the light emitting element groups 295 corresponding to the reference numerals assigned thereto.

  Next, the light emitting elements 2951 of the light emitting element row L2951 in the sub-scanning direction position Y2 belonging to the light emitting element groups 295A1, 295A2, 295A3,. The plurality of light beams emitted by the light emission operation are enlarged while being inverted by the microlens ML and imaged on the surface 211 of the photosensitive drum 21. That is, in FIG. 10, a spot is formed at the position of the “second” hatching pattern. Here, while the conveyance direction of the surface 211 of the photosensitive drum 21 is the sub-scanning direction YY, the light emitting element rows L2951 on the downstream side in the sub-scanning direction YY are sequentially arranged (that is, the sub-scanning direction positions Y1, Y2). The reason for emitting light is that the microlens ML has a reversal characteristic.

  Next, the light emitting elements 2951 of the light emitting element array L2951 in the sub scanning direction position Y3 belonging to the second light emitting element groups 295B1, 295B2, 295B3,... From the upstream side in the sub scanning direction YY are caused to emit light. Then, the plurality of light beams emitted by the light emission operation are inverted and magnified by the microlens ML and imaged on the surface 211 of the photosensitive drum 21. That is, a spot is formed at the position of the “third” hatching pattern in FIG.

  Next, the light emitting elements 2951 of the light emitting element array L2951 in the sub-scanning direction position Y4 belonging to the light emitting element groups 295B1, 295B2, 295B3,. The plurality of light beams emitted by the light emission operation are enlarged while being inverted by the microlens ML and imaged on the surface 211 of the photosensitive drum 21. That is, a spot is formed at the position of the “fourth” hatching pattern in FIG.

  Next, the light emitting elements 2951 of the light emitting element row L2951 in the sub scanning direction position Y5 belonging to the light emitting element groups 295C1, 295C2, 295C3,. The plurality of light beams emitted by the light emission operation are enlarged while being inverted by the microlens ML and imaged on the surface 211 of the photosensitive drum 21. That is, a spot is formed at the position of the “fifth” hatching pattern in FIG.

  Finally, the light emitting elements 2951 of the light emitting element row L2951 in the sub-scanning direction position Y6 belonging to the light emitting element groups 295C1, 295C2, 295C3,. The plurality of light beams emitted by the light emission operation are enlarged while being inverted by the microlens ML and imaged on the surface 211 of the photosensitive drum 21. That is, a spot is formed at the position of the “sixth” hatching pattern in FIG. In this way, by performing the first to sixth light emitting operations, a plurality of spots are formed side by side on a straight line extending in the main scanning direction XX.

According to such an embodiment, there are the following effects.
(1) The light guide hole 2971 of the light shielding member 297 disposed between the light emitting element group 295 and the microlens ML has different cross-sectional areas S1, S2, and S3. The intermediate cross-sectional area S2 is smaller than the cross-sectional area S1 on the light emitting element group 295 side and the cross-sectional area S3 on the imaging lens side. Therefore, even if the optical system including the light emitting element group 295 and the microlens ML constitutes a reduction optical system, the cross-sectional area of the light guide hole 2971 has a plurality of functions corresponding to the cross-sectional areas at the portions S1, S2, and S3. Thus, the light shielding member 297 having the above can be obtained.

  (2) A light guide hole 2971 is formed by laminating a light shielding plate 2972 including a light shielding plate 2972 in which holes 2993, 2974, and 2975 having different cross-sectional areas are formed. Therefore, the cross-sectional area at an arbitrary position of the light guide hole 2971 can be controlled by the stacking order of the light shielding plates 2972. Further, since the light shielding member 297 is formed by laminating light shielding plates that are easily punched, the processing speed is high and the cost can be reduced.

  (3) The light guide hole 2971 of the light shielding member 297 disposed between the light emitting element group 295 and the microlens ML has different cross-sectional areas S1, S2, and S3. The intermediate cross-sectional area S2 is smaller than the cross-sectional area S1 on the light emitting element group 295 side and the cross-sectional area S3 on the imaging lens side. Therefore, when the optical system including the light emitting element group 295 and the micro lens ML is a reduction optical system, the light guide hole 2971 has a plurality of functions corresponding to the cross sectional area at the portions S1, S2, and S3. The line head 29 provided with the light shielding member 297 can be obtained.

  (4) A light guide hole 2971 is formed by laminating a light shielding plate 2972 including a light shielding plate 2972 in which holes 2993, 2974, and 2975 having different cross-sectional areas are formed. Therefore, it is possible to obtain the line head 29 including the light shielding member in which the cross-sectional area at an arbitrary position of the light guide hole 2971 is controlled by the stacking order of the light shielding plates 2972. Further, since the light shielding member 297 formed by laminating the light shielding plates 2972 that can be easily perforated is provided, the line head 29 with reduced cost can be obtained.

  (5) The light shielding member 297 includes a ghost prevention unit 2985, a diaphragm unit 2984, and a lens positioning unit 2983. Therefore, with these functions, the light beam emitted from the light emitting element 2951 forms an image on the surface 211 at a predetermined position and size, and the line head 29 in which a good spot is formed can be obtained.

  (7) When organic EL is used for the light emitting element 2951, the above-described effects can be obtained.

  (8) When an LED is used for the light emitting element 2951, the above-described effects can be obtained.

  (9) Since the exposure unit having the same configuration as that of the line head 29 having the above-described effect is provided, the occurrence of crosstalk and ghost is suppressed, and the optical system is also appropriately arranged. Therefore, an image is formed from the spot imaged at the original position, and the image forming apparatus 1 with little deterioration in image quality can be obtained.

(Modification)
FIG. 11 is a cross-sectional view in the vicinity of a light shielding member 297 according to a modification. The configuration is the same as that of the embodiment except for the configuration of the light shielding member 297.

In FIG. 11, the hole 2975 of the light shielding plate 2972 facing the glass substrate 293 has a smaller cross-sectional area S1 than that of the embodiment. By reducing the cross-sectional area S1 of the hole 2975, the light beam directed toward the inner surface of the light guide hole 2971 on the glass substrate 293 side is reduced, and ghost due to inner surface reflection is reduced.
Further, the cross-sectional area S2 of the hole 2974 is large, and the cross-sectional area S3 of the hole 2973 of the light shielding plate 2972 facing the microlens array ML is the same as in the embodiment. In the modification, the hole provided in the second light shielding plate from the microlens ML side is small. The size of the holes of the other light shielding plates 2972 including this hole is a size that does not interfere with the light beam directly incident on the microlens ML from the light emitting element group 295 via the diaphragm portion 2984.
Specifically, as shown in FIG. 11, the holes of the light shielding plates 2972 are formed by lines connecting the light beam emitting side openings of the holes 2974 of the diaphragm 2984 and the light emitting elements of the light emitting element group 295. It only needs to be large. For example, the light emitting element at the position E1 and the opening on the right side with respect to the paper surface of the diaphragm portion 2984 are shown by straight dotted lines, but each hole is larger than the dotted line.
The holes other than the hole 2974 are not limited to those shown in FIG. 11, but may have a size that does not hinder the light beam directly incident on the microlens ML from the light emitting element group 295 via the diaphragm unit 2984.

The present invention is not limited to the above-described embodiments and modifications, and various modifications other than those described above can be made without departing from the spirit of the present invention.
For example, the transparent substrate is made of glass, but it goes without saying that the material of the transparent substrate is not limited to glass. That is, the transparent substrate can be made of a material that can transmit a light beam.

  In addition, a light absorption layer having a light absorption property may be provided on the inner surface of the light guide hole 2971. As the light absorption layer, a black coating such as a matte black paint layer, a chromium plating layer, a zinc plating layer, a nickel plating layer, a nickel-phosphorous plating layer, a copper oxide layer, a black anodized layer, or diamond-like carbon may be used. it can.

  Moreover, in the said embodiment and modification, as shown in FIG. 8, the several light emitting element group 295 is arrange | positioned. That is, one light emitting element group 295 is configured by arranging two light emitting element rows L2951 arranged in the main scanning direction XX at predetermined intervals and arranged in two rows in the sub scanning direction YY. However, the number of the light emitting elements 2951 constituting the light emitting element group 295 and the arrangement method of the plurality of light emitting elements 2951 are not limited thereto, and can be changed as appropriate. However, as described above, the arrangement of the plurality of light emitting elements 2951 is preferable in that a favorable spot formation can be easily realized by adopting the above-described symmetrical arrangement.

  In the embodiment and the modification, the light emitting element group row L295 (group row) configured by arranging a predetermined number (two or more) of light emitting element groups 295 in the main scanning direction XX is arranged in three rows in the sub scanning direction YY. In addition, the light emitting element groups 295 are two-dimensionally arranged. However, the arrangement of the plurality of light emitting element groups 295 is not limited to this, and can be changed as appropriate.

  Moreover, in the said embodiment and modification, using the line head concerning this invention, several spots are formed in a line in the main scanning direction XX as shown in FIG. However, the spot forming operation is an example of the operation of the line head according to the present invention, and the operation that can be executed by the line head is not limited thereto. That is, the formed spots do not need to be formed in a straight line along the main scanning direction XX. For example, the spots may be formed side by side with a predetermined angle in the main scanning direction XX, You may form in a waveform.

  In each of the above embodiments and modifications, the present invention is applied to a color image forming apparatus. However, the application image of the present invention is not limited to this, and monochrome image formation for forming a so-called monochromatic image is performed. The present invention can also be applied to an apparatus.

1 is a diagram illustrating an image forming apparatus and a line head according to an embodiment of the present invention. 1 is a diagram illustrating an electrical configuration of an image forming apparatus and a line head. The perspective view which shows the outline of a line head. Sectional drawing of the subscanning direction of a line head. The figure which decomposed | disassembled the light-shielding member into the light-shielding plate. The perspective view which shows the outline of a microlens array. Sectional drawing of the main scanning direction of a micro lens array. The figure which shows arrangement | positioning of a several light emitting element group. Sectional drawing of the shading member vicinity. The figure which shows the spot formation operation | movement by a line head. Sectional drawing of the shading member vicinity concerning a modification.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 21 ... Photosensitive drum as latent image carrier, 211 ... Surface as scanning surface, 29 ... Line head as exposure means, 293 ... Glass substrate as substrate, 2931 ... Front surface , 2932... Back surface, 295. , 2293..., Anti-ghost section, 2984... Aperture section, 2983... Lens positioning section, 299... Micro lens array as a collection of imaging lenses Gathering.

Claims (8)

Used in a line head having a light emitting element group having a plurality of light emitting elements and a plurality of imaging lenses, one surface of which is opposed to the light emitting element group and the other surface thereof is opposed to the plurality of imaging lenses. A light-shielding member disposed in
A light guide hole penetrating from the one surface to the other surface in a one-to-one relationship with the light emitting element group,
The cross-sectional area of the light guide hole is from the light emitting element group side,
S1, S2, S3,
S1, S2 and S3 have the following relationship: S2 <S1, S2 <S3
A light-shielding member. The light shielding member according to claim 1,
The light shielding member includes a plurality of light shielding plates having holes between the light emitting element group and the imaging lens,
The plurality of light shielding plates are:
A light shielding plate in which a hole of the cross-sectional area S1 is formed;
A light shielding plate in which a hole of the cross-sectional area S2 is formed;
A light shielding plate in which a hole of the cross-sectional area S3 is formed,
The light shielding member, wherein the holes are stacked so as to form the light guide hole. A line head that forms a spot by imaging a light beam on a surface to be scanned;
A substrate,
A plurality of light emitting element groups, and a plurality of light emitting element groups arranged discretely on the substrate;
A plurality of light beams emitted from a plurality of the light emitting elements belonging to the light emitting element groups facing each other are arranged on the scanning surface in a one-to-one relationship with the light emitting element groups. An imaging lens;
It is arranged so that one surface thereof faces the substrate and the other surface faces the plurality of imaging lenses, and further, penetrates from the one surface to the other surface on a one-to-one basis with respect to the plurality of light emitting element groups. A light shielding member having a plurality of light guide holes provided,
The imaging lens has an optical system that reduces the light emitting element group and forms an image on the scanned surface,
The cross-sectional area of the light guide hole is from the light emitting element group side,
S1, S2, S3,
S1, S2 and S3 have the following relationship: S2 <S1, S2 <S3
A line head characterized by that. The line head according to claim 3,
The light shielding member includes a plurality of light shielding plates having holes between the light emitting element group and the imaging lens,
The plurality of light shielding plates are:
A light shielding plate in which a hole of the cross-sectional area S1 is formed;
A light shielding plate in which a hole of the cross-sectional area S2 is formed;
A light shielding plate in which a hole of the cross-sectional area S3 is formed,
The line head is characterized in that the holes are laminated to form the light guide hole. In the line head according to claim 3 or 4,
The hole of the cross-sectional area S1 is a ghost prevention part,
The hole of the cross-sectional area S2 is a throttle part,
The line head, wherein the hole of the cross-sectional area S3 is a lens positioning portion. In the line head according to any one of claims 3 to 5,
The substrate is a transparent substrate capable of transmitting the light beam disposed so that a front surface thereof faces the light shielding member,
The light-emitting element is an organic EL provided on the back surface of the transparent substrate. In the line head according to any one of claims 3 to 5,
The substrate is disposed such that a front surface thereof faces the light shielding member,
The line head, wherein the light emitting element is an LED provided on the front surface of the substrate. A latent image carrier whose surface is conveyed in the sub-scanning direction;
An exposure unit having the same configuration as the line head according to any one of claims 3 to 7, wherein a spot is formed on the surface of the latent image carrier using the surface of the latent image carrier as a surface to be scanned. An image forming apparatus.

Images