JP2004074455A - Exposure head and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure head in which a leakage of stray light from a transparent substrate for mounting an EL light emitting element or reentrance of light into the transparent substrate is prevented. <P>SOLUTION: A light beam emitted from the light emitting part of an EL light emitting element array 61 passes through a glass substrate 62 and exits to the image carrier 20 side. In the glass substrate 62, the plane for forming the light emitting part is substantially parallel with the light beam exiting plane. A housing 60 is arranged to cover the glass substrate 62 in the main scanning direction as well as in the subscanning direction. Four sides of the glass substrate 62 facing the end face in the thickness direction is coated with black paint in order to prevent the leakage of the stray light from the glass substrate 62 or reentrance of a light into the glass substrate 62. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exposure head in which an organic EL array exposure head is integrally mounted on an image carrier cartridge as exposure means, and an image forming apparatus using the same.
[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.
[0003]
Recently, an image forming apparatus using an organic EL light emitting element array as optical writing means has been developed. As an example, Japanese Patent Application Laid-Open No. 2002-19176 proposes holding an organic EL light emitting element and a rod lens array with a cover for preventing light leakage. Japanese Patent Application Laid-Open No. H11-138899 proposes a device in which organic EL light emitting elements are integrated on a single chip to eliminate variations in light emitting characteristics and reduce cost.
[0004]
FIG. 8 is an explanatory diagram illustrating an example of the progress of a light beam emitted from the organic EL light emitting element. In FIG. 8, a light beam emitted from an organic EL light emitting element 90 is incident on a transparent substrate 91, and emitted light Rp is emitted from a surface opposite to a surface on which the organic EL light emitting device 90 is arranged. Reference numerals 92 and 93 denote frames disposed on the longitudinal end surfaces of the transparent substrate 81.
[0005]
When the light beam exits from the transparent substrate 81, the light beam whose incident angle on the exit surface is equal to or larger than the critical angle is totally reflected on the exit surface. Most of the light rays once totally reflected are emitted from the end face of the transparent substrate 91 while repeating the total reflection in the transparent substrate 91.
[0006]
[Problems to be solved by the invention]
Light rays emitted from the end face become stray light Rt in the exposure head. A part of the stray light Rt passes through the optical system and exposes an unnecessary part on the image plane, thereby deteriorating the image quality.
[0007]
For driving the organic EL light emitting element 90, a TFT (Thin Film Transistor thin film transistor) formed on the transparent substrate 81 can be used. The TFT has a characteristic that its electric characteristics change when irradiated with light. For this reason, when the light beam emitted from the end face of the transparent substrate 91 is incident as the re-incident light beam Rs and is irradiated on the TFT, the driving condition of the EL light emitting element 90 changes, and the amount of emitted light is disturbed. was there.
[0008]
The present invention has been made in view of such problems of the prior art, and an object of the present invention is to prevent stray light from a transparent substrate on which an organic EL light emitting element is mounted and light from re-entering the transparent substrate. An object of the present invention is to provide a head and an image forming apparatus using the same.
[0009]
[Means for Solving the Problems]
The exposure head of the present invention that achieves the above object is an exposure head that is arranged at an exposure position of an image carrier,
The exposure head includes at least a transparent substrate, an organic EL light emitting element array having light emitting portions formed in rows on the transparent substrate, and an imaging optical system arranged on a front surface of the organic EL light emitting element array. Prepare,
The light beam output from the light emitting unit passes through the transparent substrate and exits to the image carrier side, and the transparent substrate has a surface on which the light emitting unit is formed and a surface on which the light beam exits are substantially parallel. And
A member covering the transparent substrate is formed of an opaque member, and the opaque member is formed of a light-absorbing member on all surfaces facing the thickness direction end surface around the transparent substrate. Therefore, it is possible to prevent stray light from leaking out of the optical system from the transparent substrate, and prevent light emitted from the end face from re-entering the transparent substrate. Therefore, it is possible to prevent the light emission amount of the organic EL light emitting element from being disturbed and to prevent the image quality from deteriorating.
[0010]
Further, the present invention is characterized in that the light absorptivity of the light absorbing member is larger than the light absorptivity of the transparent substrate and 0.5 or less. Therefore, the amount of light absorbed by the light-absorbing member increases, and stray light and re-incident light can be effectively absorbed.
[0011]
Further, the present invention is characterized in that the light absorbing member is constituted by a black member. For this reason, since it has light absorbency at all wavelengths, light can be absorbed regardless of the emission wavelength of the organic EL light emitting element.
[0012]
Further, the invention is characterized in that the transparent substrate is optically sealed with the opaque member. Therefore, total reflection at the end surface of the transparent substrate can be prevented, and light can be efficiently absorbed.
[0013]
Further, the invention is characterized in that a TFT for driving the light emitting section is formed on the transparent substrate. For this reason, it is possible to prevent a disturbance in the amount of emitted light due to a change in the driving condition of the organic EL light emitting element.
[0014]
Further, according to the present invention, an exposure head according to any one of claims 1 to 5 is mounted on an image carrier cartridge, and charging means, exposure means, developing means, and transfer means are arranged around the image carrier. In this state, an image forming apparatus is configured to transfer the toner image formed on the image carrier to a transfer medium. For this reason, it is possible to provide an image forming apparatus in which the image quality does not deteriorate.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an image forming apparatus of the present invention and an image carrier cartridge used therein will be described with reference to the drawings.
[0016]
FIG. 3 is a schematic cross-sectional view showing the overall configuration of an embodiment of the image forming apparatus to which the present invention is applied. In this embodiment, an intermediate transfer belt is used as a transfer belt.
[0017]
3, the image forming apparatus 1 of the present embodiment is mounted on a housing main body 2, a first opening / closing member 3 mounted on the front surface of the housing main body 2 so as to be openable and closable, on the upper surface of the housing main body 2. A second opening / closing member (also serving as a paper discharge tray) 4. Further, the first opening / closing member 3 is provided with an opening / closing lid 3 ′ which is attached to the front surface of the housing body 2 so as to be openable and closable, and the opening / closing lid 3 ′ is interlocked with the first opening / closing member 3 or independently. It can be opened and closed.
[0018]
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.
[0019]
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.
[0020]
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. In the present embodiment, each unit can be attached and detached by accessing only from the front of the apparatus, so that the apparatus can be installed compactly in a room.
[0021]
In FIG. 3, 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 indicated by an arrow in the figure is provided with a cleaning unit 17 that is brought into contact with and separated from the surface of the intermediate transfer belt 16.
[0022]
The driven roller 15 and the intermediate transfer belt 16 are 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.
[0023]
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.
[0024]
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.
[0025]
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.
[0026]
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.
[0027]
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.
[0028]
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.
[0029]
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.
[0030]
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.
[0031]
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.
[0032]
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. .
[0033]
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.
[0034]
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.
[0035]
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.
[0036]
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.
[0037]
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. It has a stirring member 29 and a partition member 30 partitioned and formed above the toner storage section 27.
[0038]
Further, the toner supply roller 31 disposed above the partition member 30, the blade 32 provided on the partition member 30 and abutting on the toner supply roller 31, and the blade 32 abutting on the toner supply roller 31 and the image carrier 20. , And a regulating blade 34 that is in contact with the developing roller 33 are provided.
[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.
[0040]
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.
[0041]
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.
[0042]
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.
[0043]
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 surplus toner regulated and removed from the developing roller 33 by the regulating blade 34 to the toner storing section 27 below the developing unit.
[0044]
The toner returned to the toner storage unit 27 is stirred by the stirring member 29 with the toner in the toner storage unit 27, and is again supplied to the toner introduction unit near the supply roller 31 by the stirring member 29.
[0045]
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.
[0046]
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.
[0047]
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.
[0048]
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 secondarily transferred to the recording medium is fixed on the recording medium at a predetermined temperature at a nip formed by the heating roller 45 and the heat-resistant belt 49.
[0049]
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.
[0050]
The outline of the operation of the entire image forming apparatus of the present embodiment as described above is as follows.
[0051]
(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.
[0052]
(2) The surface of the image carrier 20 is uniformly charged by the charging unit 22.
[0053]
(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.
[0054]
(4) The developing unit 24 develops the toner images of the electrostatic latent images formed on the respective image carriers 20.
[0055]
(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.
[0056]
(6) 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. .
[0057]
(7) The primary transfer image is synchronized with the recording medium at the secondary transfer portion, and is pressed by the pressing mechanism toward the drive roller 14 of the intermediate transfer belt 16, 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.
[0058]
(8) 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 unit 17 arranged opposite to the roller 15, and the intermediate transfer belt 16 is refreshed. Again, the above cycle can be repeated.
[0059]
(9) The toner image on the recording medium is fixed by passing the recording medium through the fixing unit 12, and then the recording medium is directed to a predetermined position (or, if it is not double-sided printing, toward the paper output tray 4 and double-sided printing is performed). In this case, the sheet is conveyed toward the double-sided printing conveyance path 40).
[0060]
FIG. 4 is a partial cross-sectional view near the image carrier 20 of FIG. 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.
[0061]
A conductive brush roller of a charging unit 22 is supported so as to rotate at a predetermined position of each image carrier 20, and an image writing unit 23 including an organic EL array exposure head is provided downstream of the charging unit 22. Each image carrier 20 is positioned and supported in parallel with the image carrier 20.
[0062]
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.
[0063]
The shielding portions 52 and 53, particularly the shielding portion 52 between the opening 51 and the image writing unit 23, prevent ultraviolet rays from reaching the light emitting unit made of the organic EL material in the image writing unit 23 from the outside. Reference numeral 82 denotes a cleaning pad that wipes off the refractive index distribution type rod lens array 65 that covers the organic EL light emitting element array 61 from the front surface when it becomes dirty. The cleaning pad 82 is reciprocated by a handle (not shown).
[0064]
FIG. 5 is a schematic perspective view showing the image writing means 23 in an enlarged manner. FIG. 5 shows details of the exposure head 70 provided in the image writing means 23. A mechanism for accurately positioning the image writing means 23 with respect to each image carrier (photoconductor drum) 20 attached to the image carrier unit 25 is shown. The image carrier 20 is rotatably mounted in the case 50 of the image carrier unit 25 with its axis as shown in FIGS.
[0065]
On the other hand, the organic EL light emitting element array 61 is held in a long housing 60. 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.
[0066]
The image writing unit 23 has the light emitting unit 63 of the organic EL light emitting element array 61 mounted on a glass substrate 62 and is driven by a TFT 71 formed on the same glass substrate 62. The gradient index rod lens array 65 constitutes an imaging optical system, and has a stack of gradient index rod lenses 65 ′ arranged on the front surface of the light emitting unit 63.
[0067]
Numeral 60 denotes a housing which will be described in detail later, and numeral 66 denotes a cover. The housing 60 covers the periphery of the glass substrate 62, and the side facing the image carrier 20 is open. In this way, light rays are emitted from the gradient index rod lens 65 ′ to the image carrier 20. A light-absorbing member (paint) is provided on a surface of the housing 60 facing the end surface of the glass substrate 62.
[0068]
FIG. 6 is a sectional view of the image writing unit 23 in the sub-scanning direction. The image writing means 23 includes an organic EL light emitting element array 61 attached to the rear surface of the gradient index rod lens array 65 in the housing 60 and an organic EL light emitting element array therein from the back of the housing 60. An opaque cover 66 that shields 61 is provided.
[0069]
Further, the cover 66 is pressed against the rear surface of the housing 60 by the fixed leaf spring 67 to hermetically seal the inside of the housing 60 with light. That is, the glass substrate 62 is optically sealed by the housing 60 by the fixed leaf spring 67. For this reason, total reflection at the end surface of the glass substrate 62 can be prevented, and light can be efficiently absorbed. The fixed leaf spring 67 is provided at a plurality of positions in the longitudinal direction of the housing 60.
[0070]
In FIG. 6, a housing 60 made of an opaque member is made of a material that absorbs light, for example, a synthetic resin such as black polystyrene, or anodized aluminum. Further, a black paint is applied to the thickness direction end surfaces on both sides of the glass substrate 62, that is, the surface of the housing 60 facing the thickness direction end surface in the sub-scanning direction, to enhance the light absorption characteristics.
[0071]
FIG. 1 is a sectional view of the image writing unit 23 in the main scanning direction. As shown in FIG. 1, the light beam output from the light emitting unit of the organic EL light emitting element array 61 passes through the glass substrate 62 and is emitted to the image carrier 20 side. The glass substrate 62 has a surface on which the light emitting portion is formed and a surface on which light rays are emitted are substantially parallel to each other.
[0072]
The housing 60 shown in FIG. 6 is configured to cover not only the sub-scanning direction of the glass substrate 62 but also the main scanning direction. The black paint is also applied to the surfaces of the glass substrate 62 facing the thickness direction end surfaces on both sides in the main scanning direction.
[0073]
In this way, the housing 60 is formed of black members on all surfaces facing the four circumferential end surfaces of the glass substrate 62. For this reason, since it has light absorbency at all wavelengths, light can be absorbed regardless of the emission wavelength of the organic EL light emitting element.
[0074]
In the present invention, the glass substrate 62 is covered with a housing 60 formed of a member made of an opaque material. And so on. Therefore, it is possible to prevent stray light from leaking out of the optical system from the glass substrate. Further, it is possible to prevent light from re-entering the glass substrate.
[0075]
Therefore, even when the TFT is formed on the glass substrate, it is possible to prevent the light from re-entering the TFT and irradiating the TFT, thereby preventing the driving conditions of the organic EL light emitting element from being changed and the emitted light amount from being disturbed. Further, it is possible to provide an image forming apparatus in which the image quality does not deteriorate.
[0076]
In the housing 60 of the present invention, the light absorptance is higher than the absorptivity of the glass substrate 62 and is equal to or less than a predetermined value, for example, 0.5 or less. In this case, it is possible to prevent the stray light from leaking and re-entering the glass substrate 62.
[0077]
FIG. 2 is an explanatory diagram illustrating an example of measuring a light absorption characteristic of a member used for the housing 60. In FIG. 2, the light source 72 having a wavelength included in the emission wavelength distribution of the organic EL used in the present invention irradiates the test piece 60a of the member with parallel light Rx having an incident angle of 45 degrees.
[0078]
The total light reflectance is measured from the reflected light Ry at this time. The amount of light emitted from the light source 72 is also measured separately, and the amount of light Rz absorbed by the test piece 60a is determined from the relationship between the amount of emitted light and the total light reflectance. The ratio between the amount of absorbed light and the amount of emitted light is the light absorption of the test piece 60a. In addition, the total light reflectance of the test piece 60a is measured by this method or a method according to JIS because it is specified in JIS “Method for testing optical properties of plastic K7105”.
[0079]
FIG. 7 is a sectional view showing an example of the vicinity of the light emitting section 63 of the organic EL light emitting element array 61 of the image writing means 23 of FIG. The organic EL light emitting element array 61 includes, for example, two rows of TFTs (thin film transistors) 71 made of polysilicon having a thickness of 50 nm for controlling light emission of each light emitting unit 63 on a glass substrate 62 having a thickness of 0.5 mm, for example. Are provided on the margins corresponding to the respective light emitting portions 63.
[0080]
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.
[0081]
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. Is provided.
[0082]
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, and the upper surface of the light emitting layer 78, the inner surface of the hole 76, and the bank are formed. A first cathode layer 79a made of Ca and having a thickness of 100 nm and a second cathode layer 79b made of Al having a thickness of 200 nm are formed in this order so as to cover the outer surface of the cathode 75.
[0083]
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 a nitrogen gas. Light emission from the light emitting section 63 is performed on the glass substrate 62 side.
[0084]
As the material used for the light emitting layer 78 and the material used for the hole injection layer 77, various materials known in, for example, JP-A-10-12377 and JP-A-2000-323276 can be used, and detailed description is omitted. I do.
[0085]
When a black paint that absorbs ultraviolet light is applied to the inner surface of the case 50, the ultraviolet shielding effect on the organic EL light emitting element array 61 can be more reliably performed, and deterioration of the organic EL light emitting element can be prevented. . The housing 60 of the image writing means 23 is formed of an opaque member, and its back surface is covered with an opaque cover 66. For this reason, it is also possible to prevent fluorescent light or ultraviolet rays from the sun, which are incident on the back surface of the organic EL element array 61, from reaching the light emitting section 63 of the organic EL element array 61.
[0086]
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.
[0087]
【The invention's effect】
As is clear from the above description, according to the exposure head of the present invention, it is possible to prevent stray light from leaking out of the optical system from the glass substrate. Further, it is possible to prevent light emitted from the end face from re-entering the glass substrate. Therefore, an image forming apparatus using this exposure head can form a high-quality image without deterioration in image quality.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of an exposure head according to the present invention in a main scanning direction.
FIG. 2 is an explanatory diagram of an example of measuring a light absorption characteristic of a light absorbing member. 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. 1.
FIG. 3 is a schematic cross-sectional view illustrating the entire configuration of an embodiment of the image forming apparatus of the present invention.
FIG. 4 is an enlarged sectional view showing a part of FIG. 3;
FIG. 5 is a perspective view showing an example of an exposure head.
FIG. 6 is a sectional view of an image writing unit used in the image carrier unit.
FIG. 7 is a cross-sectional view illustrating an example of the vicinity of a light emitting portion of the organic EL light emitting element array.
FIG. 8 is an explanatory diagram showing an example of the progress of a light beam emitted from an 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 54, and a shielding film 60. ... Housing 60a ... Test piece 61 ... Organic EL light-emitting element array 62 ... Glass substrate 63 ... Light-emitting portion 64 ... Cover glass 65 ... Refractive index distribution type rod lens array 65 '... Refractive index distribution type rod lens 66 ... Cover 67 ... Fixing plate Spring 68 Screw insertion hole 69 Positioning pin 70 Exposure head 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 82 cleaning Pad 90: Organic EL element 91: Transparent substrate 92: Frame 93: Frame

Claims (6)

An exposure head disposed at an exposure position of the image carrier,
The exposure head includes at least a transparent substrate, an organic EL light emitting element array having light emitting portions formed in rows on the transparent substrate, and an imaging optical system arranged on a front surface of the organic EL light emitting element array. Prepare,
The light beam output from the light emitting unit passes through the transparent substrate and exits toward the image carrier, and the transparent substrate is formed of a surface on which the light emitting unit is formed and a surface on which the light exits are substantially parallel to each other. And
An exposure head, wherein a member covering the transparent substrate is formed of an opaque member, and the opaque member is formed of a light-absorbing member on all surfaces facing the end face in the thickness direction around the transparent substrate. 2. The exposure head according to claim 1, wherein the light absorptivity of the light absorbing member is larger than the light absorptivity of the transparent substrate and 0.5 or less. 3. The exposure head according to claim 1, wherein the light absorbing member is formed of a black member. 4. The exposure head according to claim 1, wherein the transparent substrate is optically sealed with the opaque member. The exposure head according to claim 1, wherein a TFT for driving the light emitting unit is formed on the transparent substrate. 6. The image forming apparatus according to claim 1, wherein the exposure head is mounted on an image carrier cartridge, and a charging unit, an exposure unit, a developing unit, and a transfer unit are arranged around the image carrier. An image forming apparatus wherein a toner image formed on a carrier is transferred to a transfer medium.

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