JP2004066758A - Exposure head and imaging apparatus employing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an exposure head having light emitting parts, e.g. organic EL light emitting elements, arranged in array on a transparent substrate in which detection accuracy of the quantity of light can be enhanced by disposing a means for detecting the quantity of light on the end face of the transparent substrate and guiding a light beam reflected totally on the exit side surface of the transparent substrate to the means for detecting the quantity of light thereby detecting the quantity of light emitted from the light emitting element efficiently. <P>SOLUTION: The exposure head is arranged such that a light beam from a light emitting part 63 transmits the transparent substrate 62 and exits to the image carrier side. The transparent substrate 62 has a surface for forming the light emitting part 63 and a light beam exiting surface substantially parallel therewith. A means 100 for detecting the quantity of light beam being emitted from the light emitting part 63 is provided at a position of the transparent substrate 62 other than the surface for forming the light emitting part 63 and the light beam exiting surface. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure head and an image forming apparatus using the same, for example, an exposure head in which light-emitting portions made of organic EL elements are arranged in an array on a transparent substrate, and miniaturized image forming using the same. It concerns the device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a printer, and a facsimile using an electrophotographic method, a laser scanning optical system is generally used as an optical writing unit (exposure unit).
[0003]
In such a situation, Japanese Patent Application Laid-Open No. H11-138899 proposes a method in which organic EL light emitting elements are integrated on a single chip to eliminate variations in light emitting characteristics and reduce cost.
[0004]
In Japanese Patent Application Laid-Open No. 2000-238333, an exposure head is configured by arranging an organic EL light emitting element and a light amount sensor for measuring the light emission amount on the same substrate to prevent density unevenness due to a decrease in light emission amount. Things have been suggested.
[0005]
[Problems to be solved by the invention]
As shown in these conventional examples, the light emitted from the light emitting portion of the organic EL element enters the transparent substrate and exits from the transparent substrate surface opposite to the surface on which the light emitting portion is provided. At this time, as shown in FIG. 16, when a light beam is emitted from the light emitting unit 63 through the transparent substrate 62, the emitted light beam from the light emitting unit 63 is emitted light a from the emission side surface 102 of the transparent substrate 62. , And is split into light reflected by the surface 102. Moreover, light reflection at the surface 102 of the exit side, the light beam b to total reflection is incident on the surface 102 of the exit side at the critical angle theta _C or higher, is divided into light c reflected below the critical angle theta _C. Since the reflectance at the total reflection is 100%, the reflectance at the critical angle θ _C or less is usually 10% or less, the intensity of the light beam c is much smaller than that of the light beam b. The light beam b is reflected on the emission side surface 102 and then enters the opposite surface 101 provided with the light emitting portion 63. If the opposite surface 101 is parallel to the emission side surface 102, the light beam b on the opposite side is emitted. also incident at the critical angle theta _C or more with respect to the surface 101, is totally reflected again. The light beam b repeatedly undergoes total reflection on the surfaces 101 and 102 on both sides of the transparent substrate 62 in this manner, and almost all of the light beam b exits from the end surface 103 of the transparent substrate 62.
[0006]
In the case of the conventional Japanese Patent Application Laid-Open No. 2000-238333, the light amount sensor for measuring the light emission amount from the light emitting unit is arranged on the same surface as the light emitting unit. There is a problem that the detection is insufficient and high-precision detection cannot be performed, and density unevenness and the like cannot be prevented with high precision.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the related art, and has as its object to detect a light amount in an exposure head in which light-emitting portions such as organic EL light-emitting elements are arranged in an array on a transparent substrate. By installing the means on the end surface of the transparent substrate and guiding the light totally reflected on the emission side surface of the transparent substrate to the light amount detecting means, the light amount of the light emitting element is efficiently detected and the light amount detection accuracy is improved. is there.
[0008]
[Means for Solving the Problems]
According to the exposure head of the present invention that achieves the above object, a light emitting portion is formed in an array on a transparent substrate, and a modulated light beam from the light emitting portion is projected on the image carrier to form a predetermined pattern on the image carrier. An exposure head, wherein the light beam from the light emitting unit is transmitted through the transparent substrate and is emitted to the image carrier side,
The transparent substrate is formed of a substantially flat surface in which a surface on which the light emitting portion is formed and a surface from which light is emitted are substantially parallel to each other, and a position other than the surface on which the light emitting portion is formed and the surface on which the light is emitted of the transparent substrate. And a light amount detecting means for detecting a light amount of a light beam emitted from the light emitting section.
[0009]
In this case, it is particularly effective if the light emitting section is a light emitting section of an organic EL light emitting element.
[0010]
Further, it is possible to provide a light amount detecting means on an end surface of the transparent substrate in the sub-scanning direction.
[0011]
Alternatively, it is possible to provide a light amount detecting means on the end surface of the transparent substrate in the main scanning direction.
[0012]
In this case, it is desirable to provide the light amount detecting means on both end surfaces of the transparent substrate in the main scanning direction.
[0013]
Further, light amount detecting means may be provided at a plurality of positions on the end face of the transparent substrate.
[0014]
Further, it is desirable that the end face of the transparent substrate on which the light amount detecting means is not provided is made light-reflective.
[0015]
Further, it is desirable that the light amount of the light emitting unit is corrected based on a light amount detection signal detected by a single light amount detection unit or a light amount detection signal obtained by summing the light amount detection signals detected by a plurality of light amount detection units.
[0016]
Further, it is desirable to have storage means for storing a correction coefficient for correcting the amount of light emitted from the light emitting section.
[0017]
According to the present invention, at least two or more image forming stations including a charging unit, any one of the above-described exposure heads, a toner developing unit, and a transfer unit are provided around an image carrier, and a transfer medium passes through each station. And a tandem type color image forming apparatus for forming a color image.
[0018]
In this case, it is effective to apply the exposure head of the present invention in a case where a heating and fixing unit for heating and fixing the toner image transferred from the transfer medium onto the recording medium is provided.
[0019]
The storage unit for storing the correction coefficient for correcting the amount of light emitted from the light emitting unit of the exposure head may be provided not in the exposure head but in the image forming apparatus main body.
[0020]
In the present invention, the transparent substrate is formed of a substantially flat surface in which the surface on which the light emitting portion is formed and the surface on which the light is emitted are substantially parallel to each other, and other than the surface of the transparent substrate on which the light emitting portion is formed and the surface on which the light is emitted. Since the light amount detecting means for detecting the light amount of the light beam emitted from the light emitting unit is provided at the position, it is possible to detect the light which is totally reflected inside the transparent substrate and guided at the position of the light amount detecting means. As a result, the amount of detected light increases, and highly accurate light amount measurement becomes possible. As a result, even if the light emitting characteristics of each light emitting unit vary, and even if each light emitting unit deteriorates, it is possible to control to obtain a uniform light emission amount distribution. Further, the number of light amount detecting means arranged corresponding to each light emitting unit can be remarkably reduced, so that the configuration of the exposure head can be simplified and the price can be reduced.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an image forming apparatus of the present invention and an exposure head used therein will be described with reference to the drawings.
[0022]
FIG. 1 is a schematic sectional view showing the overall configuration of an embodiment of an image forming apparatus using an exposure head (image writing means) of the present invention. In this embodiment, an intermediate transfer belt is used as a transfer belt.
[0023]
In FIG. 1, an image forming apparatus 1 of the present embodiment is mounted on a housing main body 2, a first opening / closing member 3 mounted on a front surface of the housing main body 2 so as to be openable and closable, on an upper surface of the housing main body 2. A second opening / closing member (also serving as a paper discharge tray) 4, and a first opening / closing member 3 having an opening / closing lid 3 ′ attached to the front surface of the housing body 2 so as to be openable and closable. The opening / closing lid 3 ′ can be opened / closed in conjunction with the first opening / closing member 3 or independently.
[0024]
An electrical component box 5 containing a power supply circuit board and a control circuit board, an image forming unit 6, a blower fan 7, a transfer belt unit 9, and a paper feed unit 10 are provided in the housing body 2, and a first opening / closing member is provided. A secondary transfer unit 11, a fixing unit 12, and a recording medium transporting unit 13 are provided in 3. The consumables in the image forming unit 6 and the paper supply unit 10 are configured to be detachable from the main body. In this case, the consumables including the transfer belt unit 9 can be removed and repaired or replaced. It has become.
[0025]
A first opening / closing member 3 is attached to the housing main body 2 so as to be openable and closable on both sides of a front lower portion of the housing main body 2 via a rotating shaft 3b.
[0026]
In the present embodiment, as will be described later, each unit can be attached and detached by accessing only from the front of the apparatus, so that the apparatus can be compactly installed indoors.
[0027]
In FIG. 1, a transfer belt unit 9 includes a drive roller 14 disposed below the housing body 2 and driven to rotate by a drive source (not shown), a driven roller 15 disposed obliquely above the drive roller 14, An intermediate transfer belt 16 that is stretched between two rollers 14 and 15 and is driven to circulate in the direction of the arrow shown in the figure, and a cleaning unit 17 that comes into contact with and separates from the surface of the intermediate transfer belt 16 are provided. An intermediate transfer belt 16 is disposed in a direction inclined leftward in FIG. As a result, the belt surface 16a in which the belt conveyance direction when the intermediate transfer belt 16 is driven is directed downward is located below. In the present embodiment, the belt surface 16a is a belt tension surface (surface pulled by the driving roller 14) during belt driving.
[0028]
The driving roller 14 and the driven roller 15 are rotatably supported by a support frame 9a, and a rotating portion 9b is formed at a lower end of the supporting frame 9a. The support frame 9a is rotatably mounted on the housing main body 2 by being fitted to a shaft (rotation fulcrum) 2b. A lock lever 9c is rotatably provided at the upper end of the support frame 9a, and the lock lever 9c can be locked by a lock shaft 2c provided on the housing body 2.
[0029]
The drive roller 14 also serves as a backup roller for the secondary transfer roller 19 that constitutes the secondary transfer unit 11. In addition, the driven roller 15 is also used as a backup roller of the cleaning unit 17. The cleaning unit 17 is provided on the belt surface 16a facing downward in the transport direction.
[0030]
A primary transfer member 21 composed of a leaf spring electrode is provided on the back surface of the belt surface 16a of the intermediate transfer belt 16 facing downward in the transport direction, facing the image carrier 20 of each of the image forming stations Y, M, C, and K described later. The transfer bias is applied to the primary transfer member 21 by the elastic force.
[0031]
On the support frame 9 a of the transfer belt unit 9, a test pattern sensor 18 is installed near the drive roller 14. The test pattern sensor 18 is a sensor for positioning each color toner image on the intermediate transfer belt 16, detecting the density of each color toner image, and correcting a color shift and an image density of each color image.
[0032]
The image forming unit 6 includes a plurality of (four in this embodiment) image forming stations Y (for yellow), M (for magenta), C (for cyan), and K (for black) that form images of different colors. In each of the image forming stations Y, M, C, and K, an image carrier 20 composed of a photosensitive drum and a charging unit 22, an image writing unit 23, and a developing unit are provided around the image carrier 20. Means 24. The charging unit 22, the image writing unit 23, and the developing unit 24 are given the drawing numbers only for the image forming station Y, and the drawing numbers are omitted because the other image forming stations have the same configuration. The arrangement order of the image forming stations Y, M, C, and K is arbitrary.
[0033]
Then, the image carriers 20 of the image forming stations Y, M, C, and K are brought into contact with the belt surface 16a of the intermediate transfer belt 16 that faces downward in the transport direction. As a result, each of the image forming stations Y, M , C, and K are also disposed in a direction inclined leftward in FIG. The image carrier 20 is driven to rotate in the transport direction of the intermediate transfer belt 16 as shown by the arrow in the figure.
[0034]
The charging means 22 is composed of a conductive brush roller connected to a high-voltage generation source, and the outer circumference of the brush is applied in a direction opposite to that of the image carrier 20 which is a photosensitive member and at a peripheral speed of two to three times. The surface of the image carrier 20 is uniformly charged by the rotation. Further, when such a conductive brush roller is used in an image forming apparatus having a cleaner-less configuration as in this embodiment, a bias having the same polarity as the charged polarity of the toner is applied to the brush roller during non-image formation. Then, the transfer residual toner adhered to the brush roller is discharged to the image carrier 20, transferred to the intermediate transfer belt 16 in the primary transfer unit, and collected by the cleaning unit 17 of the intermediate transfer belt 16. .
[0035]
By using such a charging unit 22, the surface of the image bearing member can be charged with an extremely small current, so that the inside and outside of the apparatus are not contaminated with a large amount of ozone as in the corona charging system. Further, since the contact with the image carrier 20 is soft, the transfer residual toner, which is generated when the roller charging method is used, does not easily adhere to the charging roller, thereby ensuring stable image quality and apparatus reliability. can do.
[0036]
As described later, the image writing unit 23 uses an organic EL array exposure head in which organic EL light emitting elements are arranged in a row in the axial direction of the image carrier 20. The organic EL array exposure head has an advantage that it has a shorter optical path length than a laser scanning optical system, is compact, can be disposed close to the image carrier 20, and can be downsized as a whole. In this embodiment, the image carrier 20, the charging unit 22, and the image writing unit 23 of each of the image forming stations Y, M, C, and K are unitized as one image carrier unit 25 and supported together with the transfer belt unit 9. The organic EL array exposure head can be replaced with the frame 9a to maintain the positioning of the organic EL array exposure head with respect to the image carrier 20, and when the image carrier unit 25 is exchanged, the organic EL array exposure head is also exchanged.
[0037]
Next, the details of the developing unit 24 will be described using the image forming station K as a representative. In the present embodiment, each of the image stations Y, M, C, and K is disposed in an oblique direction, and the image carrier 20 contacts the downwardly facing belt surface 16 a of the intermediate transfer belt 16 in the transport direction. The toner storage container 26 is disposed obliquely downward. Therefore, a special configuration is adopted as the developing unit 24.
[0038]
That is, the developing unit 24 includes a toner storage container 26 that stores toner (hatched portion in the figure), a toner storage unit 27 formed in the toner storage container 26, and a toner disposed in the toner storage unit 27. The agitating member 29, a partition member 30 defined above the toner storage section 27, a toner supply roller 31 disposed above the partition member 30, and abut on the toner supply roller 31 provided on the partition member 30. The developing roller 33 includes a developing roller 33 disposed in contact with the toner supply roller 31 and the image carrier 20, and a regulating blade 34 in contact with the developing roller 33.
[0039]
The image carrier 20 is rotated in the transport direction of the intermediate transfer belt 16, and the developing roller 33 and the supply roller 31 are driven to rotate in a direction opposite to the rotation direction of the image carrier 20, as indicated by arrows in the drawing. The stirring member 29 is driven to rotate in a direction opposite to the rotation direction of the supply roller 31. The toner stirred and carried by the stirring member 29 in the toner storage unit 27 is supplied to the toner supply roller 31 along the upper surface of the partition member 30, and the supplied toner rubs against the blade 32 and is supplied to the toner supply roller 31. It is supplied to the surface of the developing roller 33 by the mechanical adhesion to the surface irregularities and the adhesion by the friction band power. The toner supplied to the developing roller 33 is regulated to a predetermined thickness by the regulating blade 34, and the thinned toner layer is conveyed to the image carrier 20 so that the developing roller 33 contacts the image carrier 20. The latent image portion of the image carrier 20 is developed in the nip portion and the vicinity thereof.
[0040]
In this embodiment, the developing roller 33, the toner supply roller 31, and the contact portion between the developing roller 33 and the regulating blade 34 on the side facing the image carrier 20 are not buried in the toner in the toner storing section 27. With this configuration, it is possible to prevent the fluctuation of the contact pressure of the regulating blade 34 against the developing roller 33 due to the decrease of the stored toner, and the excess toner scraped off from the developing roller 33 by the regulating blade 34 falls into the toner storing section 27. Therefore, filming of the developing roller 33 can be prevented.
[0041]
Further, the contact portion between the developing roller 33 and the regulating blade 34 is positioned below the contact position between the supply roller 31 and the developing roller 33, and the surplus portion supplied to the developing roller 33 by the supply roller 31 and not transferred to the developing roller 33. A path is provided for returning the toner and the excess toner regulated and removed from the developing roller 33 by the regulating blade 34 to the toner storing section 27 below the developing unit, and the toner returned to the toner storing section 27 is stored in the toner storing section 27 by the stirring member 29. Is supplied to the toner introduction section near the supply roller 31 by the stirring member 29 again. Therefore, the surplus toner is dropped to the lower portion without congestion in the rubbing portion between the supply roller 31 and the developing roller 33 and the contact portion between the developing roller 33 and the regulating blade 34 to agitate the toner in the toner storage portion 27. It is possible to prevent the deterioration of the toner in the developing unit from gradually progressing, and a sharp change in image quality from occurring immediately after the replacement of the developing unit.
[0042]
The paper supply unit 10 includes a paper supply unit including a paper supply cassette 35 on which recording media P are stacked and held, and a pickup roller 36 for feeding the recording media P from the paper supply cassette 35 one by one. I have.
[0043]
Inside the first opening / closing member 3, a pair of registration rollers 37 that regulates the timing of feeding the recording medium P to the secondary transfer section, and a secondary transfer unit that is pressed against the drive roller 14 and the intermediate transfer belt 16. The image forming apparatus includes a secondary transfer unit 11, a fixing unit 12, a recording medium conveying unit 13, a pair of paper discharge rollers 39, and a conveying path 40 for double-sided printing.
[0044]
The fixing unit 12 is provided with a heating roller 45 that is rotatable with a built-in heating element such as a halogen heater, a pressure roller 46 that presses and urges the heating roller 45, and is slidably provided on the pressure roller 46. And a heat-resistant belt 49 stretched between the pressure roller 45 and the belt stretching member 47. The color image secondary-transferred onto the recording medium is formed by the heating roller 45 and the heat-resistant belt 49. Is fixed on the recording medium at a predetermined temperature in the nip formed by the above. In this embodiment, the fixing unit 12 can be disposed in a space formed obliquely above the intermediate transfer belt 16, in other words, in a space opposite to the image forming unit 6 with respect to the intermediate transfer belt 16. Thus, heat transfer to the electrical component box 5, the image forming unit 6, and the intermediate transfer belt 16 can be reduced, and the frequency of performing the color misregistration correction operation for each color can be reduced.
[0045]
The outline of the operation of the entire image forming apparatus of the present embodiment as described above is as follows.
(1) When a print command signal (image forming signal) from a not-shown host computer or the like (a personal computer or the like) is input to a control circuit in the electrical component box 5, each of the image forming stations Y, M, C, and K is sent. The image carrier 20, the rollers of the developing unit 24, and the intermediate transfer belt 16 are driven to rotate.
(2) The surface of the image carrier 20 is uniformly charged by the charging unit 22.
(3) In the image forming stations Y, M, C, and K, the surface of the image carrier 20 that is uniformly charged is selectively exposed by the image writing unit 23 in accordance with the image information of each color. Is formed.
(4) The developing unit 24 develops the toner images of the electrostatic latent images formed on the respective image carriers 20.
(5) To the primary transfer member 21 of the intermediate transfer belt 16, a primary transfer voltage having a polarity opposite to the charging polarity of the toner is applied, and the toner image formed on the image carrier 20 is transferred to the intermediate transfer belt 16 at the primary transfer portion. Are sequentially transferred onto the intermediate transfer belt 16 in an overlapping manner.
(7) The recording medium P stored in the paper feed cassette 35 is fed to the secondary transfer roller 19 via the registration roller pair 37 in synchronization with the movement of the intermediate transfer belt 16 on which the primary image has been primarily transferred. .
(8) The primary transfer image is synchronously merged with the recording medium at the secondary transfer portion, and is pressed against the drive roller 14 of the intermediate transfer belt 16 by a pressing mechanism, and is opposite to the primary transfer image. The primary transfer image formed on the intermediate transfer belt 16 with the polarity bias applied is secondarily transferred to a synchronously fed recording medium.
(9) The transfer residual toner in the secondary transfer is conveyed in the direction of the driven roller 15 and is scraped off by the cleaning means 17 arranged opposite to the roller 15, and the intermediate transfer belt 16 is refreshed. Again, the above cycle can be repeated.
(10) The toner image on the recording medium is fixed by passing the recording medium through the fixing unit 12, and thereafter, the recording medium is directed to a predetermined position (or to the discharge tray 4 in the case of non-double-sided printing, In this case, the sheet is conveyed toward the double-sided printing conveyance path 40).
[0046]
Next, replacement of consumables and jam processing will be described with reference to FIGS. FIG. 2 shows that the first opening / closing member 3 is rotated together with the opening / closing lid 3 ′ about the rotation shaft 3 b as a fulcrum to expose the fixing unit 12 and the secondary transfer unit 11. The lock lever 9c provided on the upper portion of the frame 9a is rotated to disengage the engagement with the locking shaft 2c, and the frame 9a is rotated rightward with the rotation shaft 2b as a fulcrum, so that the transfer supported by the frame 9a is performed. FIG. 3 shows a state in which the belt unit 9 and the image carrier unit 25 are exposed, and the developing means 24 supported on the housing main body 2 side is also exposed by such an operation. In this state, as shown in FIG. The image carrier unit 25 and the transfer belt unit 9 can be detached from the frame 9a so that they can be exchanged, and the developing means 24 can be independently and selectively exchangeable. Further, it is possible to perform jam clearance for paper jammed in the transport path.
[0047]
Next, an image carrier unit (image carrier cartridge) 25 in which the image carrier 20, the charging unit 22, and the image writing unit 23 of each of the image forming stations Y, M, C, and K are integrated will be described with reference to FIGS. This will be described with reference to FIG. FIG. 4 is a perspective view of the image carrier unit 25 viewed from the developing unit 24 side, and FIG. 5 is a sectional view thereof. The image carrier unit 25 includes four images of image forming stations Y, M, C, and K in a case 50 made of an opaque metal plate or the like having an open side in contact with the intermediate transfer belt 16. A carrier (photosensitive drum) 20 is rotatably supported, and a conductive brush roller of a charging unit 22 is supported so as to rotate at a predetermined position of each image carrier 20. The image writing means 23 composed of an organic EL array exposure head is positioned on each image carrier 20 and supported in parallel with the image carrier 20 on the downstream side. An opening 51 is provided on the wall surface of the case 50 on the downstream side of the image writing unit 23 so as to contact the developing roller 33 of the developing unit 24 corresponding to each image carrier 20. A shielding part 52 of the case 50 is left between each opening 51 and the image writing means 23, and a shielding part 53 of the case 50 is left between the charging means 22 and the image writing means 23. I have. As will be described later, the shielding portions 52 and 53, particularly the shielding portion 52 between the opening 51 and the image writing unit 23, emit ultraviolet light from outside to the light emitting unit made of the organic EL material in the image writing unit 23. Preventing it from reaching.
[0048]
FIG. 6 shows a cross-sectional view of the image writing unit 23. The image writing means 23 includes a gradient index rod lens array 65 formed by stacking a gradient index rod lens 65 ′ (FIG. 8) at the center so as to communicate with the inside and outside facing the image carrier 20. An opaque housing 60 mounted, an organic EL light emitting element array 61 mounted facing the rear surface of the gradient index rod lens array 65 in the housing 60, and an organic EL light emission therein from the rear surface of the housing 60. An opaque cover 66 for shielding the element array 61 is provided. The cover 66 is pressed against the rear surface of the housing 60 by a fixed leaf spring 67 so that the inside of the housing 60 is airtightly sealed.
[0049]
FIG. 7 is a cross-sectional view of an example of the vicinity of the light emitting portion 63 of the organic EL light emitting element array 61 of the image writing means 23 in FIG. On the substrate 62, a TFT (thin film transistor) 71 made of polysilicon having a thickness of 50 nm for controlling the light emission of each light emitting unit 63 is provided on the margin corresponding to each of the two rows of the light emitting units 63 in a staggered arrangement, for example. An insulating film 72 made of SiO ₂ having a thickness of about 100 nm is formed on the glass substrate 62 except for the contact hole on the TFT 71, and the thickness of the insulating film 72 is set at the position of the light emitting unit 63 so as to be connected to the TFT 71 via the contact hole. An anode 73 made of 150 nm ITO is formed. Next, another insulating film 74 made of SiO ₂ having a thickness of about 120 nm is formed in a portion corresponding to a position other than the light emitting portion 63, and a hole 76 corresponding to the light emitting portion 63 is formed thereon to a thickness of 2 μm. A bank 75 made of polyimide is provided. A hole injection layer 77 having a thickness of 50 nm and a light emitting layer 78 having a thickness of 50 nm are formed in the hole 76 of the bank 75 in this order from the anode 73 side. A first cathode layer 79a made of Ca with a thickness of 100 nm and a second cathode layer 79b made of Al with a thickness of 200 nm are sequentially formed so as to cover the upper surface of 78, the inner surface of the hole 76, and the outer surface of the bank 75, The light-emitting portion 63 of the organic EL light-emitting element array 61 is covered with a cover glass 64 having a thickness of about 1 mm via an inert gas 80 such as nitrogen gas. Light emission from the light emitting section 63 is performed on the glass substrate 62 side.
[0050]
As the material used for the light emitting layer 78 and the material used for the hole injection layer 77, for example, various materials known in JP-A-10-12377, JP-A-2000-323276 and the like can be used, and the details are omitted.
[0051]
FIG. 8 shows an example of a mechanism for accurately positioning the image writing means 23 with respect to each image carrier (photosensitive drum) 20 attached to the image carrier unit 25. The image carrier 20 is rotatably attached to the case 50 of the image carrier unit 25 with its axis, while the organic EL light emitting element array 61 is held in a long housing 60 as shown in FIG. Have been. The positioning pins 69 provided at both ends of the long housing 60 are fitted into the opposite positioning holes of the case 50, and the fixing screws are inserted into the screw holes of the case 50 through the screw insertion holes 68 provided at both ends of the long housing 60. By screwing and fixing, each image writing means 23 is fixed at a predetermined position.
[0052]
With the above configuration, for example, as shown in FIGS. 2 and 3, the developing unit 24 is removed from the image carrier unit 25 and the image carrier unit 25 is exposed to external light for replacement of consumables and jam clearance. , Fluorescent light and ultraviolet rays from the sun enter the case 50 through the opening 51 of the image carrier unit 25, but the shielding portion 52 of the case 50 is left between the opening 51 and the image writing unit 23. Therefore, the ultraviolet rays are directly incident on the exposure position, reflected by the image carrier 20 at that position, and emitted by the organic EL light emitting element array 61 in the image writing means 23 via the gradient index rod lens array 65. It is prevented from reaching the part 63. Ultraviolet rays entering from the opening of the case 50 in contact with the intermediate transfer belt 16 are also shielded by the charging unit 22 and the shielding portion 53 of the case 50 between the charging unit 22 and the image writing unit 23. The ultraviolet rays are prevented from reaching the light emitting section 63 at the same time. When the inner surface of the case 50 is painted black to absorb ultraviolet rays, the above-mentioned ultraviolet ray shielding action becomes more reliable.
[0053]
On the other hand, since the housing 60 of the image writing means 23 is opaque and its back surface is covered with an opaque cover 66, fluorescent light and ultraviolet rays from the sun which enter the back surface of the organic EL light emitting element array 61 are also organic. It is prevented from reaching the light emitting section 63 of the EL light emitting element array 61.
[0054]
Therefore, even if the image carrier unit 25 is exposed to ultraviolet light for replacement of consumables or jam clearance, the ultraviolet light is not applied to the light emitting portion 63 of the organic EL light emitting element array 61 in the image writing means 23 integrated therewith. And the organic EL element is prevented from being deteriorated by ultraviolet rays.
[0055]
Now, a description will be given of the light amount detecting means for detecting the amount of light emitted from the light emitting section 63 of each organic EL light emitting element in the image writing means 23 described above. FIG. 9 is a cross-sectional view of the glass substrate 62 of the organic EL light emitting element array 61 of the image writing unit 23 in the sub-scanning direction. Only one light emitting part 63 of the organic EL light emitting element array 61 is shown. . Here, the sub-scanning direction means a direction orthogonal to the rotation axis of the image carrier 20, and the main scanning direction described later means a direction parallel to the rotation axis of the image carrier 20. FIG. 10 shows a perspective view thereof.
[0056]
As described with reference to FIG. 16, when light is emitted from the light emitting unit 63 through the transparent substrate 62, the light emitted from the light emitting unit 63 is mainly emitted from the emission-side surface 102 of the transparent substrate 62. and a, is divided into a light b which total reflection is incident on the surface 102 of the exit side at the critical angle theta _C or higher. Among them, the central portion of the emission light a is used for exposing the image carrier 20 via the gradient index rod lens array 65 (FIGS. 6 and 8). On the other hand, light b repeats total reflection on both sides 101 and 102 of the transparent substrate 62 and becomes useless light. Here, a light amount sensor 100 including a light receiving element such as a photodiode is attached to a predetermined position (substantially the center in FIG. 10) of the end surface 103 of the glass substrate 62 of the organic EL light emitting element array 61 in the sub-scanning direction. The light b from the light emitting unit 63 guided in the transparent substrate 62 by the total reflection enters the light amount sensor 100, so that the relative light amount of the light emitted from the light emitting unit 63 can be detected. FIG. 11 is a cross-sectional view of the image writing unit 23 similar to FIG. 6 in this case. FIG. 12 is a cross-sectional view of the image writing unit 23 in FIG. FIG. 2 shows a cross-sectional view of a part reaching the sensor 100.
[0057]
A light reflection layer 91 made of metal or the like is arranged on another end surface 104 in the sub-scanning direction opposite to the surface on which the light amount sensor 100 is installed, and reflects the light guided to the end surface 104 so as to reflect the light amount. It is desirable to increase the amount of light incident on the light amount sensor 100 by returning the same to the end face 103 where the sensor 100 is installed by similar repeated reflection.
[0058]
Next, based on the light amount data detected by the light amount sensor 100, the light emission amount of each light emitting unit 63 of the organic EL light emitting element array 61 is stably controlled to a constant amount, and the density unevenness of each light emitting unit 63 is controlled. An example of a method for preventing the problem will be described.
[0059]
First, when the image carrier unit 25 is shipped, the amount of light that is exposed from the organic EL light emitting element array 61 of each image writing unit 23 to the position of the image carrier 20 via the gradient index rod lens array 65 is determined for each light emitting unit 63. To be measured. For this purpose, the image writing means 23 is attached to the inspection jig. The inspection jig is provided with a light amount detector that detects the amount of light emitted from the light emitting section 63 of each light emitting element of the organic EL light emitting element array 61 at a corresponding image plane position of the image carrier 20. As this light amount detector, even if one detector is sequentially moved along the organic EL light emitting element array 61 and the light emission amount of each light emitting unit 63 is sequentially detected, the same number of light emitting units 63 are detected. A detector may be provided. Then, each light emitting unit 63 emits light in order, and the value Ph _n (n represents the nth light emitting unit 63) detected by the light amount sensor 100 of the image writing unit 23 and the light amount detector of the inspection jig. obtain the value Pg _n. Then, to calculate the correction coefficient _Pg n / Ph _n for each light emitting unit 63.
[0060]
Performed for the light emitting portion 63 of all the light emitting elements of the calculation of the measurement and the correction coefficient of the amount of light, obtaining a correction coefficient Pg n _/ Ph _n of all of the light emitting element.
[0061]
In this way, the correction coefficient Pg n _/ Ph _n obtained, as shown in the block diagram in FIG. 13 and stored in the in the memory 124 which is arranged in the image writing means 23. The emission light amount correction of the light-emitting portion 63 using the correction coefficient Pg n _/ Ph _n stored in the memory 124, performed in the image forming apparatus 1 of FIG. 1. An example of the method will be described.
[0062]
The individual light emitting portions 63 of the organic EL light emitting element array 61 of each image writing means 23 are caused to emit light through the control circuit 122 and the drive circuit 123 based on the data of the initial value stored in the memory 124. The measured value at this time is measured by the light amount sensor 100. As to the measurement values, by multiplying the correction coefficient Pg n _/ Ph _n which had been stored in the memory 124, the light quantity at the image plane position of each light emitting unit 63 is calculated.
[0063]
The calculated light quantity is compared with a target light quantity given by the main body controller 121 disposed in the electric component box 5 of the main body, and based on the difference, the calculated light quantity becomes the target light quantity. By controlling a current or the like flowing through each light emitting element of the EL light emitting element array 61, the light emitting amount of each light emitting unit 63 is adjusted to be a target light amount. Such an adjustment operation is repeated for all the light emitting elements, and the light amounts of all the light emitting elements are adjusted to the target values.
[0064]
This light quantity correction operation can be performed based on a command from the main body controller 121 at any time, such as immediately after the image forming apparatus 1 is started, before printing is started, or between sheets.
[0065]
Incidentally, at the time of shipment image carrier unit 25, instead of storing in the memory 124 to seek the correction coefficient Pg n _/ Ph _n as described above, the corresponding amount of light emitted from the light emitting portion 63 of each light emitting element of the image carrier 20 in the image plane position by emitting the light emitting portion 63 so that the target amount of the light, i.e., Pg _n is caused to emit light to a predetermined value, stores the value Ph _n detected by the light amount sensor 100 at that time You may make it do. In this case, each light emitting section 63 is caused to emit light based on the initial value data stored in the memory 124, and the measured value at that time is obtained by the light amount sensor 100. The measured value is compared with Ph _n stored in the memory 124, and a current or the like flowing to each light emitting element of the organic EL light emitting element array 61 is controlled so as to eliminate the difference. The emitted light amount is adjusted to be a target light amount.
[0066]
In, were to be arranged memory 124 for storing the value Ph _n detected by the light amount sensor 100 while emitting the correction coefficient Pg n _/ Ph _n or target light quantity of the light-emitting portion 63 to the image writing means 23 or more However, it may be connected to the main body controller 121 in the electric component box 5 of the main body and arranged on the main body side.
[0067]
Thus, the image writing means 23 or the apparatus body, by storing the value Ph _n when that emits light by a correction coefficient Pg n _/ Ph _n or target light quantity of each light emitting unit 63, the light-emitting portions 63 Even if the light emitting characteristics of the organic EL light emitting element vary, or even if the organic EL light emitting element is degraded by the ultraviolet light of the external light or the heating from the heat source of the fixing unit 12, it is possible to control to obtain a uniform light emitting amount distribution. it can.
[0068]
In the above embodiment, one light amount sensor 100 is arranged as the light amount sensor 100 on the end surface 103 of the glass substrate 62 of the organic EL element array 61 in the sub-scanning direction. May be arranged. In the example of FIG. 14, two light quantity sensors 100 _{1 to} 100 ₄ are arranged on both end faces 103 and 104 in the sub-scanning direction.
[0069]
As shown in FIGS. 10 and 14, when the light quantity sensors 100 and 100 _{1 to} 100 ₄ are arranged on the end faces 103 and 104 in the sub-scanning direction of the glass substrate 62, the light quantity sensors 100 and 100 _{1 to} 100 _{4 use the} light emitting unit 63. Since it can be arranged at a position closer to the camera, there is an advantage that the amount of detected light can be increased. When a plurality of light quantity sensors 100 _{1 to} 100 ₄ are used, as the detection value Ph _n , a value obtained by adding the detection values of the respective light quantity sensors 100 _{1 to} 100 ₄ is used as Ph _n or the closest light quantity the detection value of the sensor ₁₀₀ 1 to 100 ₄ and various modifications are possible, such as use as Ph _n.
[0070]
Further, the light amount sensor 100 may be disposed on an end surface of the glass substrate 62 of the organic EL light emitting element array 61 in the main scanning direction. In the example of FIG. 15, two light amount sensors 100 ₁ and 100 ₂ are arranged on both end surfaces 105 and 106 of the glass substrate 62 of the organic EL light emitting element array 61 in the main scanning direction. With such an arrangement, when the value obtained by adding the detection values of the _two light amount sensors 100 ₁ and 100 ₂ is used as Ph _n , the light emitting units 63 at all positions can be detected with a substantially uniform detected light amount. It becomes possible. Also in this case, modifications such as using the detection values of the closest light amount sensors 100 ₁ and 100 ₂ as Ph _n are possible. Of course, it is also possible to place only the light intensity sensor 100 ₁ or 100 ₂ only one end face 105 or 106 in the main scanning direction.
[0071]
As described above, when the light amount sensors 100 ₁ and 100 ₂ are disposed on the end surfaces 105 and 106 of the glass substrate 62 in the main scanning direction, the size of the line-shaped image writing unit 23 in the sub scanning direction may be reduced. Thus, a small line head (exposure head) 23 can be formed.
[0072]
As described above, the exposure head and the image forming apparatus using the same according to the present invention have been described based on some embodiments. However, the present invention is not limited to these embodiments, and various modifications are possible.
[0073]
【The invention's effect】
As is clear from the above description, according to the exposure head of the present invention and the image forming apparatus using the same, the transparent substrate has a substantially flat surface in which the surface on which the light emitting portion is formed and the surface on which the light is emitted are substantially parallel. Since the light amount detecting means for detecting the light amount of the light emitted from the light emitting portion is provided at a position other than the surface on which the light emitting portion is formed and the light emitting surface of the transparent substrate, the position of the light amount detecting means This makes it possible to detect light guided by being totally reflected in the transparent substrate, and to increase the amount of detected light, thus enabling highly accurate light amount measurement. As a result, even if the light emitting characteristics of each light emitting unit vary, and even if each light emitting unit deteriorates, it is possible to control to obtain a uniform light emission amount distribution. Further, the number of light amount detecting means arranged corresponding to each light emitting section can be significantly reduced, so that the configuration of the exposure head can be simplified and the price can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an overall configuration of an embodiment of an image forming apparatus using an exposure head (image writing unit) of the present invention.
FIG. 2 is a diagram illustrating a state in which a fixing unit, a secondary transfer unit, a transfer belt unit, an image carrier unit, and a developing unit are exposed in the apparatus of FIG.
FIG. 3 is a diagram showing a state in which the image carrier unit and the transfer belt unit have been removed and made replaceable in the state of FIG. 2;
FIG. 4 is a perspective view of an image carrier unit used in the apparatus of FIG. 1 as viewed from a developing unit side.
FIG. 5 is a sectional view of the image carrier unit of FIG. 4;
FIG. 6 is a sectional view of an image writing unit used in the image carrier unit of FIG. 4;
7 is a cross-sectional view of an example of the vicinity of a light emitting portion of the organic EL light emitting element array of the image writing means of FIG. 6;
FIG. 8 is a perspective view showing an example of a mechanism for accurately positioning an image writing unit with respect to each image carrier attached to the image carrier unit.
FIG. 9 is a sectional view of the glass substrate of the organic EL light emitting element array in the sub-scanning direction.
FIG. 10 is a perspective view of FIG. 9;
FIG. 11 is a sectional view of the image writing means in the case of FIGS. 9 and 10;
12 is a cross-sectional view of a portion from the vicinity of a light emitting portion of the organic EL light emitting element array of the image writing means of FIG. 11 to a light amount sensor.
FIG. 13 is a block diagram of a control unit for correcting a light emission amount of each light emitting unit.
FIG. 14 is a perspective view showing a modification of the arrangement position and the number of light amount sensors.
FIG. 15 is a perspective view showing another modified example of the arrangement position and the number of the light amount sensors.
FIG. 16 is a diagram for explaining a behavior of a light beam emitted from a light emitting unit of the organic EL light emitting element.
[Explanation of symbols]
P: Recording medium 1: Image forming apparatus 2: Housing body 2b: Rotating shaft (rotating fulcrum)
2c: locking shaft 3: first opening / closing member 3 'opening / closing lid 3b: rotating shaft 4: second opening / closing member 5: electrical component box 6: image forming unit 7: blowing fan 9: transfer belt unit 9a Support frame 9b Rotating part 9c Lock lever 10 Paper feed unit 11 Secondary transfer unit 12 Fixing unit 13 Recording medium transport means 14 Drive roller 15 Driven roller 16 Intermediate transfer belt 16a Intermediate transfer belt Belt surface 17 whose belt conveyance direction is downward during driving Cleaning means 18 Test pattern sensor 19 Secondary transfer roller 20 Image carrier 21 Primary transfer member 22 Charging means 23 Image writing means 24 Development Means 25: Image carrier unit (image carrier cartridge)
26 toner storage container 27 toner storage section 29 toner stirring member 30 partition member 31 toner supply roller 32 blade 33 developing roller 34 regulating blade 35 paper feed cassette 36 pickup roller 37 registration roller pair 39 .., A discharge roller pair 40, a double-sided printing conveyance path 45, a heating roller 46, a pressure roller 47, a belt stretching member 49, a heat-resistant belt 50, a case 51, an opening 52, a shielding part 53, a shielding part 60, a housing 61 Organic EL light emitting element array 62 Glass substrate 63 Light emitting section 64 Cover glass 65 Refractive index rod lens array 65 'Refractive index rod lens 66 Cover 67 Fixed leaf spring 68 Screw insertion hole 69 Positioning pin 71: TFT (thin film transistor)
72 insulating film 73 anode 74 insulating film 75 bank 76 bank hole 77 hole injection layer 78 light emitting layer 79a cathode first layer 79b cathode second layer 80 inert gas 91 light reflection Layers 100, 100 ₁ , 100 ₂ , 100 ₃ , 100 ₄ ... Light amount sensor 101... Surface 102 provided with a light emitting portion of the transparent substrate 102... Surface 103 on the emission side of the transparent substrate 103. Other end faces 105 and 106 of the substrate in the sub-scanning direction End faces 121 of the transparent substrate in the main scanning direction 121 Main body controller 122 Control circuit 123 Drive circuit 124 Memory

Claims (12)

An exposure head in which light emitting units are formed in an array on a transparent substrate, and the modulated light from the light emitting units is projected onto an image carrier to form a predetermined pattern on the image carrier. The light beam is transmitted through the transparent substrate and is emitted to the image carrier side in an exposure head,
The transparent substrate is formed of a substantially flat surface in which a surface on which the light emitting portion is formed and a surface from which light is emitted are substantially parallel to each other. A light amount detecting means for detecting a light amount of a light beam emitted from the light emitting section. 2. The exposure head according to claim 1, wherein the light emitting section is a light emitting section of an organic EL light emitting element. The exposure head according to claim 1, wherein the light amount detection unit is provided on an end surface of the transparent substrate in a sub-scanning direction. The exposure head according to claim 1, wherein the light amount detection unit is provided on an end surface of the transparent substrate in a main scanning direction. 5. The exposure head according to claim 4, wherein the light amount detection means is provided on both end surfaces of the transparent substrate in the main scanning direction. The exposure head according to claim 1, wherein the light amount detection unit is provided at a plurality of positions on an end surface of the transparent substrate. The exposure head according to claim 1, wherein an end surface of the transparent substrate on which the light amount detection unit is not provided is light-reflective. Light amount correction of the light emitting unit is performed based on a light amount detection signal detected by a single light amount detection unit or a light amount detection signal obtained by summing light amount detection signals detected by a plurality of the light amount detection units. The exposure head according to any one of claims 1 to 7, wherein The exposure head according to claim 1, further comprising a storage unit configured to store a correction coefficient for correcting a light emission amount of the light emitting unit. At least two image forming stations including a charging unit, an exposure head according to any one of claims 1 to 9, a toner developing unit, and a transfer unit are provided around the image carrier, and a transfer medium passes through each station. A tandem-type color image forming apparatus for forming a color image. 10. The color image forming apparatus according to claim 9, further comprising a heat fixing unit that heats and fixes the toner image transferred from the transfer medium onto the recording medium. The color image forming apparatus according to claim 10, further comprising a storage unit configured to store a correction coefficient for correcting a light emission amount of the light emitting unit of the exposure head.

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