JP2000077188A - Exposure device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized photosensitive material writing device of a reduced cost with can be operated at a high speed with high definition, and simultaneously, can efficiently use light emitted from a light emitting element. SOLUTION: This exposure device comprises, on a substrate 1, the array of light emitting elements, each of which is composed of at least an anode layer 3, a cathode layer 6 and one or a plurality of organic compound layers 8 sandwiched between the layers 3 and 6. The array of the light emitting elements includes micro lenses 2 and translucent reflection layers 7 on the substrate 1. A micro light resonator structure is configured between the translucent reflection layer 7 and the cathode layer 6. The exposure device has a light emitting peak within the half width range of a sensitivity to a wavelength of a photosensitive body which is exposed to light by the exposure device.

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.

[0004] In the case of the LED array system, since the substrate is expensive and an array cannot be formed with one substrate, it is necessary to arrange the cut chips. At that time, steps and intervals between chips become problems.

Further, a rod lens array is required to form an image on a photoreceptor. However, when an attempt is made to form an image of diffused light by a rod lens array, the light incidence efficiency of the rod lens array is low, and The emitted light cannot be used efficiently. Therefore, in order to obtain a required amount of light on the photoreceptor, the light emitting element must emit more light than necessary.

Further, since the emission wavelength of a normal organic light emitting device has a wide half-value width of about 100 nm, there is a light amount component which does not match the sensitivity peak of the photoreceptor, which is not efficient.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and provides an exposure apparatus and an image processing apparatus which is high-speed, small-sized, low-cost, and high-definition, and which can efficiently use the amount of light emitted from a light-emitting element. It is an object to provide a forming apparatus, in particular, an optical printer head.

[0008]

According to the present invention, there is provided an exposure apparatus comprising a light emitting element array comprising at least an anode layer and a cathode layer, and one or more organic compound layers sandwiched therebetween. An exposure apparatus comprising: the light-emitting element array has a microlens on a substrate, further has a translucent reflective layer, forming a micro-optical resonator structure between the translucent reflective layer and the cathode layer And a light emission peak within a half width range of sensitivity to the wavelength of the photoreceptor exposed by the exposure apparatus.

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,
It is possible to provide an exposure apparatus, specifically, an optical printer head, which is small, low-cost, high-definition, and can efficiently use emitted light.

[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 element array which is an exposure apparatus of the present invention.

In FIG. 1, 1 is a substrate, 2 is a microlens, 3 is an anode layer as a transparent electrode, 6 is a cathode layer, 7 is a translucent reflection layer, 8 is a hole transport layer 4 and an electron transport layer 5. An organic compound layer that is formed. By applying a voltage between the anode layer 3 and the cathode layer 6, light emission is obtained from a portion (light emitting portion) where the anode layer 3 and the cathode layer 6 intersect. By changing the electrode width of the cathode layer 3 or the cathode layer 6, it is possible to obtain a light emitting portion of an arbitrary size.

In the present invention, the substrate 1 has a micro lens 2. As shown in FIG. 1, the microlens 2
It is formed in one-to-one correspondence with the light emitting unit.

At this time, in order to use the emitted light efficiently, it is preferable that the opening area of the microlens 2 is larger than the area of the light emitting section. In order to efficiently obtain the amount of light, it is preferable that the focal length of the microlens 2 be shorter than the distance between the light emitting unit and the microlens 2 corresponding to the light emitting unit.

The microlens 2 is not limited to the one shown in FIG. 1, but may be any as long as it can collect light emitted from the light emitting section. Specifically, in FIG. 1, the microlens 2 is a microlens having a convex lens shape with respect to the light emitting portion, but may be a microlens having a concave lens shape. Further, in FIG. 1, the microlens 2 is formed on the same side of the substrate 1 as the side on which the organic compound layer 8 is formed.
It may be formed on the surface of the substrate 1 opposite to the side on which the organic compound layer 8 is formed.

The light emitting element array includes a translucent reflective layer 7.
And the cathode layer 6 to form a minute optical resonator structure. For this reason, the diffusion of light is suppressed, and the spread of the exposure spot can be reduced. Further, since the output at the peak wavelength can be enhanced at the same time as the half width of the emission wavelength is reduced, the amount of emitted light can be used efficiently.

Further, the light emitting element array has a light emission peak within a half width range of sensitivity to the wavelength of the photosensitive body to be exposed. Therefore, a good image can be obtained, the driving voltage can be reduced, and the life of the element can be prolonged.

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

The translucent reflection layer 7 is not particularly limited as long as it can increase or decrease the reflection transmittance at a specific wavelength. For example, a plurality of layers having different refractive indices depending on the material, thickness and the like are used. Laminated ones are preferred. As a material for forming the translucent reflection layer 7, for example, SiO ₂ , T
iO _{2 and the} like.

As a 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
l, Li, In, or an alloy thereof can be used.

The organic compound layer 8 may have a single layer structure or a multilayer 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 light emitting layer containing the fluorescent material 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 light emitting layer also serve as a mixed single layer configuration is possible.

The material of the organic compound layer 8 is desirably selected to emit light having a spectrum that is sensitive to the photosensitive material such as the photosensitive drum to be used.

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.

[0025]

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[0026]

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[0027]

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[0028]

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[0029]

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Further, inorganic materials such as a-Si and a-SiC may be used.

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

[0032]

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[0033]

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[0034]

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[0035]

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Further, the electron transport layer 5 or the hole transport layer 4 can be doped with a dopant as described below.

[0037]

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The thickness of each layer and the like are not particularly limited, but it is desirable to optimize the layer so that a spectrum matching the sensitivity of the photosensitive member can be obtained.

The light-emitting element array may be formed by stacking the cathode layer, the organic compound layer, the anode layer, and the translucent reflective layer on the substrate in the reverse order, and finally forming the microlenses. .

Hereinafter, an example of a manufacturing process of the light emitting element array of the present invention will be described with reference to FIG.

A) Production of micro lens 2 (FIG. 2)
(A) The microlens 2 can be formed by ion-exchanging the portion of the substrate 1 corresponding to the light emitting section.

First, both surfaces of the substrate 1 are sufficiently washed. Next, the entire substrate 1 is masked with an ion-impermeable film such as Ti. A row of openings is formed on Ti on the ion diffusion surface by photolithographic etching at a desired diameter and center interval. In order to perform an ion exchange treatment on this substrate, for example, Tl
A hemispherical microlens 2 is formed by immersing in a mixed molten salt of NO ₃ and KNO _3, a molten salt such as nitrate such as Ag ⁺ and Tl ^+, and a sulfate.

At this time, the refractive index distribution of the microlens 2 may be formed in several stages.

The method of forming the microlenses 2 is not particularly limited, and the microlenses 2 may be formed by a method using a photoresist, a replica method, or the like, as shown in Examples described later.

B) As shown in FIG. 2B, a translucent reflective layer 7 composed of a plurality of layers is formed on the surface on which the microlenses 2 are formed by a sputtering method.

C) As shown in FIG. 2B, the line width and pitch are adjusted so that the anode layer 3 is placed on the portion corresponding to the microlens 2, and a metal mask is placed thereon. The anode layer 3 is formed to a thickness of 3 mm.

D) As shown in FIG. 2D, the hole transport layer 4 and the electron transport layer 5 are sequentially deposited by a vacuum deposition method.

E) As shown in FIG. 2E, a metal mask having a desired line width is covered so as to overlap the rows of the microlenses 2, and the cathode layer 6 is formed.

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

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 having received the transfer of the toner image 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.

[0059]

EXAMPLES (Example 1) The light emitting element array shown in FIG. 1 was manufactured by the procedure shown in FIG.

The transparent insulating substrate 1 has microlenses 2 formed at portions corresponding to respective light emitting portions by an ion exchange method, and a dielectric layer 7, an anode layer 3, a hole transport layer 4, a light emitting An electron transport layer 5 also serving as a layer and a cathode layer 6 are laminated.

First, a method for forming the microlenses 2 on the substrate 1 will be described.

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

Next, the entire glass substrate is masked with a Ti film. An opening row having a diameter of 30 μm and a center interval of 80 μm is formed in Ti on the ion diffusion surface by photolithographic etching.

This substrate is subjected to TlNO for ion exchange.
₃ and KNO ₃ to form a hemispherical refractive index region (microlens) 2 having a diameter of about 70 μm.

Next, a method for forming a light emitting element array will be described.

On the surface on which the microlenses 2 are formed, a SiO ₂ layer 21 having a thickness of 93 nm and a TiO ₂ layer 22 having a thickness of 59 nm are alternately laminated by sputtering to form the translucent reflective layer 2.

Next, ITO is formed as the anode layer 3. As ITO is placed on the part corresponding to the micro lens 2,
ITO is formed to a thickness of 60 nm by a sputtering method while covering a metal mask having a line width of 50 μm and a pitch of 80 μm.

Next, TPD as the hole transport layer 4 and Alq ₃ as the electron transport layer 5 are sequentially deposited by vacuum evaporation at 40 nm and 50 nm, respectively. The degree of vacuum at the time of vapor deposition was 2-3 × 10 ⁻⁶ Torr, and the film formation rate was 0.2
0.3 nm / s.

Finally, a metal mask having a line width of 40 μm is placed so as to be orthogonal to the anode layer 2 so as to overlap the rows of the microlenses 2, and co-deposited as the cathode layer 6 with Mg and Ag at a deposition rate ratio of 10: 1. And an alloy having a Mg / Ag ratio of 10/1 to 2
It is formed to a thickness of 00 nm. At this time, the deposition rate was 1 nm / s.

The opening area of the microlens 2 is made larger than the area of the light emitting portion so that emitted light can be obtained efficiently.

To the light emitting element array obtained in this manner, an ITO electrode serving as an anode layer was added, and an M electrode serving as a cathode layer was added.
When a DC voltage is applied with the g / Ag electrode being negative,
Green light emission was obtained from the intersection of the ITO electrode and the Mg / Ag electrode.

The light emitting element array and the translucent reflection layer
A driving driver was connected to a light emitting element array (comparative example) having a different thickness of an organic compound layer or the like, and writing was performed on a photoconductor as a light source for electrophotography, and an image was actually output. FIG.
2 shows the sensitivity characteristics of the photoconductor and the emission spectrum of the light emitting element array.

As shown in FIG. 5, the light emitting element array of Example 1 had a light emission peak wavelength within the half width range of the sensitivity of the photoreceptor, and a good image could be obtained. On the other hand, in the light emitting element array of the comparative example, since the emission peak is not within the half width range of the sensitivity of the photoconductor, the potential of the photoconductor cannot be reduced to a desired potential, and the image is blurred and a good image is obtained. I couldn't get it.

Further, several kinds of light emitting element arrays having different light emission peak wavelengths were produced, and an image was output. In order to obtain a good image, the light emission peak wavelength was at least within the half width range of the sensitivity of the photosensitive member. It was necessary.
A good image can be obtained by increasing the drive voltage without having a light emission peak wavelength within the half width range of the sensitivity of the photoreceptor, but in this case, there is a problem that the element life is shortened. Not preferred.

By using the light emitting element array having the microlens and the optical resonator structure as described above, the diffusion of light can be suppressed, the spread of the exposure spot can be reduced, and the microlens can form an image on the photosensitive member. It has become possible. In addition, since the output at the peak wavelength can be enhanced at the same time as the half width of the emission wavelength is reduced, the amount of emitted light can be used efficiently.

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

(Embodiment 2) FIG. 6 is a sectional view of a light emitting element array of this embodiment.

The glass substrate serving as the substrate 1 has a micro lens 24 having a convex lens shape at a portion corresponding to each light emitting portion.
Is formed thereon, and a translucent reflective layer 7, an anode layer 3, a hole transport layer 4, an electron transport layer 5 also serving as a light emitting layer, and a cathode layer 6 are laminated thereon.

First, the micro lens 24 on the glass substrate
A method for creating a file will be described.

As the material for forming the lens, there are ordinary ultraviolet and far ultraviolet photoresists, and particularly, positive type deep ultraviolet such as polymethyl methacrylate, PMIPK, polyglycylmethyl acrylate and phenol novolak. Photoresist softens at a relatively low temperature,
It is desirable because the shape of the condenser lens can be easily formed.

The above-mentioned photoresist is laminated on a glass substrate by a method such as coating or the like, and the photoresist layer is patterned by a lift-off method or a dry etching method by a photolithography method so as to have a diameter of 70 μm and a center interval of 80 μm. Patterning is performed using a forming method. By annealing this patterned photoresist,
By softening and fluidizing, an arc-shaped micro lens 24 is formed.

Next, after forming the translucent reflective layer 7 in the same manner as in the first embodiment, a metal mask having a line width of 50 μm and a pitch of 80 μm is covered so as to correspond to the microlens 24, and ITO is used as the anode layer 3. 60n by sputtering
m.

Next, in the same manner as in Example 1, TPD is deposited as the hole transport layer 4 and Alq ₃ is deposited as the electron transport layer 5 by a vacuum deposition method. In addition, the degree of vacuum at the time of vapor deposition is 2-3 ×
10 ⁻⁶ , and the film formation rate was 0.2 to 0.3 nm / s.

Lastly, a metal mask having a line width of 40 μm is placed so as to overlap the rows of the microlenses 24, and Mg and Ag are co-deposited as the cathode layer 6 at a deposition rate ratio of 10: 1. / 1 alloy is formed to a thickness of 200 nm. At this time, the deposition rate was 1 nm / s.

A driving driver was connected to the light emitting element array thus obtained, and the light emitting element array was used as a light source for electrophotography. Green light emission is obtained from the intersection of the ITO electrode and the Mg / Ag electrode as in Example 1, and an image can be formed on the surface of the photosensitive drum through the translucent reflective layer 7 and the microlens 24. Images were obtained.

As described above, by providing the light emitting element array with the optical resonator structure, an optical printer head capable of obtaining a high-definition image with low power can be realized.

(Example 3) The organic LED array shown in FIG. 7 was manufactured according to the procedure shown in FIG.

A microlens 25 having a convex lens shape is formed on a glass substrate as a substrate 1 at a portion corresponding to each light emitting portion.
On the surface opposite to 5, a translucent reflective layer 7, an anode layer 3, a hole transport layer 4, an electron transport layer 5 also serving as a light emitting layer, and a cathode layer 6 are laminated.

First, the micro lens 25 on the glass substrate
A method for creating a file will be described. As shown in FIG. 8A, the microlenses 25 form an array having openings of 75 μm and center intervals of 80 μm by the replica method. Then, similarly to the first embodiment, the micro lens 25
The semi-transparent reflective layer 7 is formed on the opposite side.

As shown in FIG. 8B, the micro lens 2
A metal mask having a line width of 50 μm and a pitch of 80 μm is placed on the surface opposite to the surface on which 5 is formed so as to correspond to the microlenses 25, and ITO is formed to 60 nm as the anode layer 3 by sputtering.

Next, as shown in FIG.
Similarly to the above, TPD is deposited as the hole transport layer 4 and Alq ₃ is deposited as the electron transport layer 5 sequentially by a vacuum deposition method.

Finally, as shown in FIG. 8D, a metal mask having a line width of 40 μm is placed so as to overlap the rows of the microlenses 25, and Mg and Ag are used as the cathode layer 6.
Co-deposition at a deposition rate ratio of 0: 1, and Mg / Ag is 10/1
Is formed to a thickness of 200 nm.

By connecting a driving driver to the thus obtained organic LED array and using it as a light source for electrophotography, a good image could be obtained.

[0094]

As described above, according to the present invention,
It is possible to provide an exposure apparatus and an image forming apparatus, such as an optical printer head, which are high-speed, small-sized, low-cost, high-definition, and can efficiently use the amount of light emitted from the light-emitting element.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating an example of a manufacturing process of a light-emitting element array of the present invention.

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 showing the relationship between the spectral sensitivity of the photoconductor of Example 1 and the emission wavelength of the light-emitting element array.

FIG. 6 is a cross-sectional view illustrating a light emitting element array according to a second embodiment.

FIG. 7 is a cross-sectional view illustrating a light emitting element array according to a third embodiment.

FIG. 8 is a diagram illustrating a manufacturing process of a light-emitting element array in Example 3.

[Explanation of symbols]

1 substrate 2,24,25 microlens 3 anode layer 4 hole transport layer 5 electron-transporting layer 6 cathode layer 7 semitransparent reflective layer 8 organic compound layer 71 SiO ₂ layer 72 TiO ₂ layers

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H05B 33/14 33/24 (72) Inventor Akihiro 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yuichi Hashimoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yukio Nagase 3-30-2, Shimomaruko 3-chome, Ota-ku, Tokyo Canon Inc. (72) Invention Person Noboru Yukimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (10)

[Claims] 1. An exposure apparatus having a light-emitting element array comprising at least an anode layer and a cathode layer and one or more organic compound layers sandwiched between them on a substrate, wherein the light-emitting element The array has a microlens on the substrate, further has a translucent reflective layer, forms a micro-optical resonator structure between the translucent reflective layer and the cathode layer, and is exposed by the exposure apparatus. An exposure apparatus having an emission peak within a half-value width range of sensitivity to a wavelength of the photosensitive member. 2. The exposure apparatus according to claim 1, wherein the micro lens has a one-to-one correspondence with the light emitting unit. 3. The exposure apparatus according to claim 1, wherein the opening area of the microlens is larger than the area of the light emitting section. 4. The exposure apparatus according to claim 1, wherein a focal length of the micro lens is shorter than a distance between the light emitting unit and the micro lens corresponding to the light emitting unit. 5. The exposure apparatus according to claim 1, wherein the microlens is formed by performing ion exchange on a portion of the substrate corresponding to the light emitting section. 6. The exposure apparatus according to claim 1, wherein the microlens is a microlens having a convex lens shape with respect to the light emitting unit. 7. The exposure apparatus according to claim 1, wherein the microlenses are formed on the same side of the substrate as the side on which the organic compound layer is formed. 8. The exposure apparatus according to claim 1, wherein the microlens is formed on a surface of the substrate opposite to a surface on which the organic compound layer is formed. 9. The exposure apparatus according to claim 1, wherein the translucent reflection layer is in contact with the anode layer. 10. An image forming apparatus comprising at least the exposure apparatus according to claim 1 and a photoconductor exposed by the exposure apparatus.