JP2000127481A - Exposure device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exposure device corrected in the irregularity of latent image potential after the charge/exposure of a photosensitive body without requiring a special drive circuit. SOLUTION: In an exposure device having a light emitting element array wherein a plurality of light emitting elements each constituted of at least an anode layer 3, a cathode layer 6 and one or plurality of org. compd. layers 7 held between them are arranged on a substrate 1, by adjusting the spectral light emitting characteristics of the light emitting elements, the latent image potential after the charge/exposure of a photosensitive body exposed by the exposure device is uniformized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus and an image forming apparatus used for an electrophotographic apparatus such as a copying machine and a printer, and more particularly to an optical printer head.

[0002]

2. Description of the Related Art Conventionally, a laser beam system, an LED array system, and the like have been mainly used as an exposure system for writing a latent image on a photosensitive member.

[0003] However, in the case of the laser beam system, optical components such as a polygon mirror and a lens are required, so that it is difficult to reduce the size of the apparatus, and it is difficult to increase the speed.

In the case of the LED array system, since the substrate is expensive and an array cannot be formed on a single substrate, it is necessary to arrange the cut out chips. In this case, the light emission characteristics do not match between the chips. Therefore, there is a problem that the amount of emitted light differs between chips.

Generally, in order to correct the variation of the light emission characteristics of each light emitting element, after the LED array is created, the light emission amount distribution of all the elements is measured to create light amount correction data corresponding to each light emitting element. On the basis of this, light amount correction is performed by a light amount correction circuit (for example, current correction / pulse width correction, etc.) of the drive circuit, but there is a problem that the drive circuit and the like become complicated.

It is also conceivable to create a drive circuit for each element, modify the thin-film resistance substrate in the drive circuit by laser trimming or the like, and optimize the emission current. However, it is possible to reduce the cost by sharing the drive circuit. Since it cannot be applied to the time-division driving method which performs the following, it is not generally used.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and is high-speed, small-sized, low-cost, high-definition, and at the same time, does not require a special driving circuit.
An object of the present invention is to provide an exposure apparatus and an image forming apparatus, in particular, an optical printer head, in which a variation in latent image potential after exposure is corrected.

[0008]

According to the present invention, there is provided an exposure apparatus comprising a light emitting device comprising at least an anode layer and a cathode layer, and one or more organic compound layers sandwiched between the anode layer and the cathode layer. An exposure apparatus having a plurality of light-emitting body arrays, wherein a latent image potential after charging / exposure of a photoconductor exposed by the exposure apparatus is made uniform by adjusting spectral emission characteristics of each light-emitting element. It is characterized by the following.

Further, an image forming apparatus according to the present invention is characterized by having at least the above-mentioned exposure device and a photoreceptor exposed by the exposure device.

By adopting such a configuration, high speed,
Special peripheral drive for light quantity correction in order to make the latent image potential after charging / exposure of the photoreceptor uniform by adjusting the spectral emission characteristics of the light emitting element while at the same time being small, low cost and high definition It is possible to correct the variation in the latent image potential without requiring a circuit or the like.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 is a perspective view showing an example of a light emitting array which is an exposure apparatus of the present invention.

In FIG. 1, 1 is a substrate, 3 is an anode layer, 6
Denotes a cathode layer, and 7 denotes an organic compound layer composed of a hole transport layer 4 and an electron transport layer 5.

FIG. 2 is an enlarged view of the light emitting portion as viewed from the substrate 1 side, and the overlapping portion of the anode layer 3 and the cathode layer 6 corresponds to the light emitting portion 8.
Becomes Then, by applying a voltage between the anode layer 3 and the cathode layer 6, light emission is obtained from the light emitting portion. By changing the electrode width of the anode layer 3 or the cathode layer 6, a light emitting portion of an arbitrary size can be formed. It is possible to get.

As the substrate 1, any material can be used as long as the light emitting element can be formed on the surface. For example, it is preferable to use a transparent insulating substrate such as glass such as soda lime glass or a resin film.

As the material of the anode layer 3, a material having a large work function is desirable. For example, ITO, tin oxide, gold, platinum, palladium, selenium, iridium, copper iodide and the like can be used. On the other hand, it is desirable that the material of the cathode layer 6 has a small work function, for example, Mg / Ag, Mg, A
1, In, or an alloy thereof can be used.

The organic compound layer 7 may have a single-layer structure or a multi-layer structure. For example, as shown in FIG. 1, the hole transport layer 4 into which holes are injected from the anode layer 3. And an electron transporting layer 5 into which electrons are injected from the cathode layer 6, and either the hole transporting layer 4 or the electron transporting layer 5 becomes a light emitting layer. In addition, the phosphor layer containing the phosphor is
And the electron transport layer 5. In addition, a configuration in which the hole transport layer 4, the electron transport layer 5, and the fluorescent layer also serve as a mixed single layer configuration is also possible.

As the hole transport layer 4, for example, N, N '
-Bis (3-methylphenyl) -N, N'-diphenyl- (1,1'-biphenyl) -4,4'-diamine (TPD) can be used, and the following organic materials are also used. be able to.

[0019]

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[0020]

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[0021]

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[0022]

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[0023]

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Further, for example, an inorganic material such as a-Si or a-SiC may be used.

As the electron transport layer 5, for example, tris (8-quinolinol) aluminum (hereinafter Alq ₃ ) can be used, and the following materials can also be used.

[0026]

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[0027]

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[0028]

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[0029]

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The electron transporting layer 5 or the hole transporting layer 4 can be doped with a dopant as described below.

[0031]

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Preferably, a dielectric layer is provided between the anode layer 3 and the substrate 1. The dielectric layer can increase (lower) the reflection transmittance at a specific wavelength by laminating layers having different refractive indexes such as SiO ₂ and SiO. Alternatively, it is also possible to simply use a half mirror.

It is desirable to select a material for each layer that emits light in a spectrum that is sensitive to the photosensitive material such as the photosensitive drum to be used.

Hereinafter, a specific production example will be described.

In this example, a glass substrate was used as the transparent insulating substrate 1. Both surfaces of the glass substrate are sufficiently washed.

Next, a metal mask having a line width of 50 μm and a pitch of 80 μm is put on the substrate 1 to form an
O is formed to a thickness of 100 nm by a sputtering method.

At this time, after forming the entire surface, etching may be performed by a usual photolithography method to form a desired pattern.

Next, TPD is deposited as the hole transport layer 4 and Alq ₃ obtained by doping 5 wt% of Nile Red as the electron transport layer 5 is sequentially deposited by a vacuum deposition method at a thickness of 50 nm. The degree of vacuum at the time of vapor deposition is 2-3 × 10 ^-6 To.
rr, and the film formation rate was 0.2 to 0.3 nm / s.

Finally, a metal mask having a line width of 80 μm is covered so as to be orthogonal to the anode layer 3, and the cathode layer 6 is made of Mg.
And Ag are co-deposited at a deposition rate ratio of 10: 1 to obtain Mg / Ag
Form a 200 nm alloy of 10/1. At this time, the deposition rate was 1 nm / s.

When a driver for driving is connected to the luminous array thus obtained, and a positive voltage is applied to the ITO electrode serving as the anode layer and a negative voltage is applied to the Mg / Ag electrode serving as the cathode layer, a DC voltage is applied. Green light is obtained from the intersection of the MgO and Ag / Ag electrodes, and an image can be formed on the photoreceptor surface through the cell hook lens array.

FIG. 8 is a graph showing the spectral emission characteristics of the light emitting element array and the spectral sensitivity characteristics of the photosensitive member, wherein B is the spectral emission characteristic of this example, and A is that of the array in which the electron transport layer 5 is not doped with Nile Red. The spectral emission characteristics and those indicated by bold lines are the spectral sensitivity characteristics of the photoconductor. As shown in FIG. 8, in this example, the spectral emission characteristics are shifted in accordance with the spectral sensitivity characteristics of the photoconductor by doping the electron transport layer 5. In addition, C in FIG. 8 is a spectral emission characteristic after adjustment described later.

In this embodiment, a light emitting element array of 300 dpi is prepared, but a light emitting point of an arbitrary size can be obtained by changing the electrode width.

FIG. 5 is a graph showing an example of the light emission amount distribution of the light emitting element array manufactured as described above. FIG. 6 is a graph showing the potential distribution of the latent image after charging / exposure of the photosensitive member exposed by the light emitting element array. It is a graph which shows an example. As shown in FIG. 5, in this example, the amount of emitted light tends to be lower at the center of the array and higher at both ends. As a result, as shown in FIG. 6, the latent image potential of the photoconductor tends to be too low at the ends. This is probably due to the thickness distribution of the deposited film when depositing the organic compound layer, and the film thickness at the end was smaller than at the center, so the electric field intensity applied to the light emitting part at the end was at the center. This is considered to be due to the fact that the light emission amount increased. Although it is possible to improve the light emission amount distribution by improving the vapor deposition apparatus, other factors may also overlap to prevent complete uniformity.

In the present invention, by adjusting the spectral emission characteristics of each light emitting element, the latent image potential of the photosensitive member after charging / exposure is made uniform as shown in FIG.

Specifically, first, light is emitted in pixel units,
The light amounts of all the pixels are measured, and the measured data is used to shift the emission wavelength of the pixels of the high light amount pixels away from the high sensitivity region of the spectral sensitivity characteristic of the photosensitive member, and charge / expose the photosensitive member. The potential of the subsequent latent image is made uniform.

That is, a light beam is directly radiated to the light emitting surface by a laser beam or the like focused on the size of the light emitting pixel from the substrate side, and heat or light energy is applied to the organic compound layer to melt / recrystallize / decompose the organic compound layer. The spectral emission characteristics B are shifted to the spectral characteristics C as shown in FIG.
The center wavelength of the array should be shifted from the high sensitivity part of the spectral sensitivity characteristic of the photoconductor. As a result, the latent image potential of the photoconductor can be increased.

Contrary to this example, the same effect can be obtained by shifting the emission wavelength of the light emitting element having a low light emission amount so as to approach the high sensitivity region of the spectral sensitivity characteristic of the photosensitive member. Needless to say.

As an example of the image forming apparatus of the present invention, FIG. 3 shows a schematic configuration diagram of an image forming apparatus using an electrophotographic system.

Reference numeral 211 denotes a rotating drum type electrophotographic photosensitive member as an image carrier, 212 denotes a charging unit, 213 denotes a developing unit, 214 denotes a transfer unit, 215 denotes a fixing unit, and 216 denotes a cleaning unit.

As the exposure L, the exposure apparatus (not shown) of the present invention is used. A driving driver is connected to the exposure apparatus, and when a positive voltage is applied to the anode layer and a negative voltage is applied to the cathode layer to apply a DC voltage, green light is emitted from the light emitting unit, and an image can be formed on the photoconductor 211. Good images can be obtained.

The photosensitive member 211 is uniformly charged by the charging means 212. Exposure L is performed by an exposure device in accordance with a time-series electric digital pixel signal of target image information output to the charged surface of the photoconductor 211,
An electrostatic latent image corresponding to the target image information is formed on the peripheral surface of. The electrostatic latent image is developed as a toner image by developing means 213 using insulating toner. On the other hand, a transfer material p as a recording material is supplied from a paper feeding unit (not shown),
The photosensitive member 211 is introduced at a predetermined timing into a press-contact nip (transfer portion) T between the photosensitive transfer member 211 and the contact transfer unit contacted with a predetermined pressing force, and performs transfer by applying a predetermined transfer bias voltage. .

The transfer material P to which the toner image has been transferred is separated from the surface of the photosensitive member 211 and is fixed by a fixing means 2 such as a heat fixing method.
15, the toner image is fixed, and is discharged out of the apparatus as an image-formed product (print). Transfer material P
After the transfer of the toner image to the photosensitive member surface, the cleaning means 216 removes adhered contaminants such as residual toner and the like, and is cleaned and repeatedly used for image formation.

As another example of the image forming apparatus of the present invention, a schematic configuration diagram of a multicolor image forming apparatus using an electrophotographic system is shown in FIG.

C1 to C4 are charging means, D1 to D4 are developing means, E1 to E4 are exposure means of the present invention, S1 to S4 are developing sleeves, T1 to T4 are transfer blades, TR1 to TR4
2 is a roller, TF1 is a transfer belt, P is transfer paper, F1 is a fixing device, and 301 to 304 are rotary drum type electrophotographic photosensitive members.

The transfer paper P is transported in the direction of the arrow,
The transfer belt TF1 is guided over the transfer belt TF1 suspended by R1 and TR2, and moves to a black transfer position set so as to be sandwiched between the photosensitive member 301 and the transfer blade T1 by the transfer belt TF1. At this time, the photosensitive member 301 is arranged around the drum, and includes a charging unit C1, an exposure unit E1, and a developing unit D1.
Has a desired black toner image by the electrophotographic process by the developing sleeve S1, and the black toner image is transferred onto the transfer paper P.

The transfer paper P is transferred by the transfer belt TF1 to a cyan transfer position set between the photosensitive member 302 and the transfer blade T2, the photosensitive member 303 and the transfer blade T3.
Move to a magenta transfer position set so as to be sandwiched by the photosensitive member 304 and a yellow transfer position set so as to be sandwiched between the photosensitive member 304 and the transfer blade T4. The transfer of the cyan toner image, the magenta toner image, and the yellow toner image is performed by the means.

At this time, since each of the photoconductors 301 to 304 is rotating favorably, image registration can be performed well between recordings. The transfer paper P on which the multicolor recording has been performed by the above process is supplied to the fixing device F1 and fixed to obtain a desired multicolor image.

[0058]

As described above, according to the present invention,
By adjusting the spectral emission characteristics of the light emitting elements to equalize the latent image potential after charging / exposure of the photoreceptor, a special peripheral drive circuit or the like for light quantity correction is not required, and the light emission of each light emitting element is achieved. It is possible to correct variations in the amount of light.

Further, according to the present invention, since light amount correction can be performed easily and with high accuracy, it becomes more and more effective especially when the number of light emitting pixels is increased to increase the density.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an exposure apparatus of the present invention.

FIG. 2 is an enlarged view of a light emitting unit when the exposure apparatus of FIG. 1 is viewed from a substrate side.

FIG. 3 is a schematic configuration diagram illustrating an example of an image forming apparatus of the present invention.

FIG. 4 is a schematic configuration diagram illustrating another example of the image forming apparatus of the present invention.

FIG. 5 is a graph illustrating an example of a light emission amount distribution of an exposure apparatus before adjustment of spectral emission characteristics.

FIG. 6 is a graph showing an example of a latent image potential distribution after charging / exposure of an exposed photoconductor.

FIG. 7 is a graph showing a latent image potential distribution after charging / exposure of a photoreceptor exposed by the exposure apparatus of the present invention.

FIG. 8 is a graph showing spectral emission characteristics of a light emitting array and spectral sensitivity characteristics of a photosensitive member.

[Explanation of symbols]

 Reference Signs List 1 substrate 3 anode layer 4 hole transport layer 5 electron transport layer 6 cathode layer 7 organic compound layer 8 light emitting section

Continuation of the front page (72) Inventor Noboru Yukimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Izumi Narita 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. F term (reference) 2C162 AE08 AE21 AE28 AE40 AE66 AH05 FA04 FA17 FA23 FA50

Claims (5)

[Claims] 1. An exposure apparatus having a light-emitting array in which a plurality of light-emitting elements each having at least an anode layer and a cathode layer and one or more organic compound layers sandwiched therebetween are arranged on a substrate. An exposure apparatus, wherein the potential of a latent image after charging / exposure of a photosensitive member exposed by the exposure apparatus is made uniform by adjusting spectral emission characteristics of each light emitting element. 2. The method according to claim 1, wherein adjusting the spectral emission characteristic shifts an emission wavelength of the light emitting element having a high light emission amount so as to be away from a high sensitivity region of the spectral sensitivity characteristic of the photosensitive member. 2. The exposure apparatus according to 1. 3. The method according to claim 2, wherein adjusting the spectral emission characteristic shifts an emission wavelength of the light emitting element having a low light emission amount so as to approach a high sensitivity region of the spectral sensitivity characteristic of the photosensitive member. 3. The exposure apparatus according to 1 or 2. 4. A light emission characteristic is adjusted by directly irradiating a light emission surface with a beam focused on the size of a light emission pixel and changing the quality of an organic compound layer.
3. The exposure apparatus according to claim 1. 5. An image forming apparatus comprising at least the exposure apparatus according to claim 1 and a photoconductor exposed by the exposure apparatus.