JP2000188181A - Luminescence device, exposure device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apply high electric field, to provide high-intensity luminescence, to prevent the occurrence of a dark spot and to provide a stable luminescence output by arranging a positive electrode and a negative electrode on the same plane of a substrate, and arranging one or multiple organic compound layers on both electrodes. SOLUTION: A positive electrode 2 and a negative electrode 3 are provided on a substrate 1, and an organic compound layer 4 is provided on both electrodes 2, 3 to form a luminescence element. A transparent protective membrane may be formed on the organic compound layer 4, thereby the mixing of gas such as oxygen and water can be prevented, and durability can be increased. An insulating plate made of glass or a plastic film is used for the substrate 1. A hole transportation compound, a hole transportation emitter compound or an electron transportation compound can be used as the component for forming the organic compound layer 4. The luminescence on the organic compound layer 4 is obtained between the positive electrode 2 and the negative electrode 3 where electric field is operated, thus a luminescence pattern can be properly set by changing the distance both electrodes 2, 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device having a charge injection type light emitting element having an organic compound layer and directly converting the recombination energy of the injected charge by applying an electric field to light energy. The present invention relates to an exposure apparatus and an image forming apparatus, and more particularly to a light emitting device that can be applied as a display panel.

[0002]

2. Description of the Related Art The electroluminescence phenomenon of organic materials is known as pop (P).
ope) in an anthracene single crystal in 1963; Chem. Phys. 38 (19
63) 2042. Then in 1965,
Helfrich and Schneider (S
Chneider) has succeeded in observing relatively strong injection-type luminescence by using a solution electrode system having a high injection efficiency. Rev .. Lett. 14 (1965) 2
29.

[0003] Since then, research has been conducted to form an organic luminescent material with a conjugated organic host material and a conjugated organic activator having a condensed benzene ring.
No. 72,862, U.S. Pat. No. 3,173,050, U.S. Pat.
No.710167, J.A. Chem. Phys. 44 (19
66) 2902, J. Mol. Chem. Phys. 50 (19
69) 14364, J. Am. Chem. Phys. 58 (1
973) 1542, or Chem. Phys. Le
tt. 36 (1975) 345, etc. There, as organic host substances, naphthalene, anthracene, finanthrene, tetracene, pyrene, benzopyrene, chrysene, picene, carbazole, fluorene, biphenyl, terphenyl, triphenylene oxide,
Dihalobiphenyl, trans-stilbene and 1,4-
Examples include diphenylbutadiene, and examples of the organic activator include anthracene, tetracene, and pentacene. However, each of the organic light emitting substances there existed as a single layer having a thickness exceeding 1 μm, and a high electric field was required for light emission.

For this reason, for example, Thin Solid
・ Films ・ 94 (1982) 171, Polyme
r.24 (1983) 748, Jpn. J. Appl.
Phys. 25 (1986) L773, etc., research on thin film devices by the vacuum evaporation method has been promoted. Although such thinning was effective in reducing the driving voltage, a device having a high level of luminance at a practical level was obtained. I didn't get it.

In recent years, however, Tang et al. Have devised a light-emitting element in which two extremely thin layers (a charge transport layer and a light-emitting layer) are stacked by vacuum evaporation between an anode and a cathode, and have a high driving voltage at a low driving voltage. Brightness is realized, and Appl. Phys. L
ett. 51 (1987) 913 or U.S. Pat.
No. 56429. This type of stacked organic light-emitting device has been actively studied since then.
No. 194393, U.S. Pat. No. 4,539,507, U.S. Pat. No. 4,720,432, JP-A-63-264692, Appl. Phys. Lett. 55 (1989)
1467, JP-A-3-163188 and the like.

[0006] Jpn. J. Appl. Phys.
27 (1988) L269. L713 reports an organic light-emitting device having a three-layer structure in which the functions of carrier transport and light emission are separated from each other. According to this, when selecting a dye of a light-emitting layer that determines a light emission color, restrictions on carrier transport performance are relaxed. It is suggested that the degree of freedom in selection is considerably increased, and furthermore, there is a possibility that holes and electrons (or excitons) can be effectively confined in the central light emitting layer to improve luminous efficiency.

In general, a vacuum evaporation method is used to manufacture a stacked organic light-emitting device. For example, the preliminary proceedings 1006 (1989) and 5th
Proceedings of the 0th CSJ Academic Lecture Meeting 1041 (199
0), the casting method also gives
It has been reported that a device with considerable brightness can be obtained. Further, as shown in, for example, the 38th Preliminary Lecture Meeting of the Association of Correspondence Associations, 1086 (1991), a solution obtained by mixing polyvinyl carbazole as a hole transport compound, an oxadiazole derivative as an electron transport compound, and coumarin 6 as a light emitter. Mix 1 formed by dip coating
It has been reported that a layer-type organic light-emitting device can also obtain a considerably high luminous efficiency.

[0008] Thus, recent advances in organic light-emitting devices have suggested a remarkably wide range of applications.

[0009]

However, the history of such research is still short, and the research on the physical properties of the material and the research into the device have not been sufficiently performed. At present, there are problems in terms of durability, such as film defects during film formation, changes over time due to long-term use, and deterioration due to an atmosphere containing oxygen, moisture, and the like, and further higher luminance emission is required.

[0010] Also, the problem of diversification of emission wavelengths, etc., for precisely selecting emission hues of blue, green, and red in consideration of application to a full color display or the like has not been sufficiently solved.

FIG. 3 is a cross-sectional view showing an example of a conventional charge injection type light emitting element. This charge injection type light emitting element is formed on a light transmitting substrate 1. An anode 2, an organic compound layer 4 made of an organic compound, and a cathode 3 are sequentially laminated.

Such a charge injection type organic light emitting element converts the recombination energy of the injected charge directly into light energy by applying an electric field, and the light emission intensity is determined by the carrier (hole or electron) from the electrode. ) Strongly depends on the injection amount. Therefore, the electrodes (anode 2,
In order to increase the carrier injection amount from the cathode 3), it is necessary to increase the electric field applied between the electrodes.

However, in the element structure shown in FIG. 3 in which the anode 2, the organic compound layer 4, and the cathode 3 are sequentially laminated, the organic compound layer 4 is extremely thin. There is a problem that it is difficult to prevent the occurrence of dark spots due to dust and impurities at the time and film defects caused by irregularities on the surface of the substrate 1 causing dielectric breakdown.

Further, in order to change the light emission pattern in the conventional charge injection type light emitting device as shown in FIG. 3, the shape of the anode 2 or the cathode 3 must be formed in accordance with the set pattern. Lower and higher manufacturing costs.

Further, since the formed electrodes (anode 2 and cathode 3) are directly exposed to the outside air, corrosion and deterioration are promoted by a gas such as oxygen or water.

In view of the foregoing, the present invention has been made in view of the above-mentioned conventional problems, and it is possible to apply a high electric field and perform high-luminance light emission, while preventing generation of dark spots in an organic compound layer. It is an object of the present invention to provide a light emitting device, an exposure device, and an image forming device that can obtain a stable light emission output with high durability and can easily obtain an arbitrary light emission pattern.

[0017]

That is, the present invention comprises a substrate, an anode and a cathode disposed on the same surface of the substrate,
A light emitting device comprising a charge injection type light emitting element having one or more organic compound layers disposed on both electrodes, a substrate, and a light emitting device disposed on the same surface of the substrate. An exposure apparatus comprising: a charge injection type light emitting element having an anode and a cathode, and one or more organic compound layers disposed on both of the electrodes. An image forming apparatus comprising at least a photoconductor exposed by the apparatus.

With the above structure, in the charge injection type light emitting device of the present invention, an anode and a cathode are formed on the same surface of an insulating substrate, and an organic compound layer is formed on both electrodes. Here, an electric field due to the applied voltage is generated between the anode and the cathode, which is in a direction along the film layer surface of the organic compound layer,
The distance between the two electrodes can be set as appropriate, and can be set sufficiently wider than the thickness of the organic compound layer. For this reason, the limit point of the applied electric field can be increased with respect to the dielectric breakdown of the film defect of the organic compound layer.

In addition, since the organic compound layer is formed and covered on both electrodes, it can be isolated from the outside air, and it is possible to prevent the penetration of substances that promote deterioration such as oxygen and moisture.

Further, since the light emission in the organic compound layer is performed between the anode and the cathode where an electric field is applied, the light emission pattern can be appropriately set by changing the distance between the two electrodes.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention and showing a configuration of a charge injection type light emitting element used in the device of the present invention.

This light emitting element has a configuration in which an anode 2 and a cathode 3 are provided on a substrate 1 and an organic compound layer 4 is provided on both electrodes. The organic compound layer 4 is made of an organic compound and has a single hole transporting ability, electron transporting ability and photovoltaic ability, or a mixture of compounds having the respective properties. ing.

FIG. 2 shows a second embodiment of the present invention, and is a cross-sectional view showing the configuration of a charge injection type light emitting device used in the device of the present invention.

As shown in FIG. 2, the charge injection type light emitting element may have a structure in which a light-transmitting protective film 5 is provided on the organic compound layer 4. This can prevent gas such as oxygen and water from being mixed, and the light-transmitting protective film 5 reduces loss of light extraction. As a result, durability (lifetime) can be improved.

As the substrate 1, an insulating plate material such as glass or plastic film is used. If such an insulating plate material is made of a light-transmitting material, light can be obtained from both the upper and lower surfaces of the element. In addition, TFT is used for such insulating plate material.
A hybrid type may be incorporated by incorporating a photosensor (photodiode, phototransistor) and the like.

The material of the anode 2 preferably has a work function as large as possible. For example, nickel, gold, platinum, palladium, selenium, rhenium, iridium and alloys thereof, or tin oxide, indium tin oxide (ITO), iodine Copper oxide is preferred. Also, a dielectric polymer such as poly (3-methylthiophene), polyphenylene sulfide, or polypyrrole can be used.

On the other hand, the material of the cathode 3 preferably has a small work function, for example, silver, lead, tin, magnesium, aluminum, calcium, manganese, indium, chromium, or an alloy thereof. If a dielectric film layer is provided on the cathode 3 so as to cover it, the above-described materials used for the anode 2 can be used. LiF, NaF, M
Fluoride such as gF, CaF ₂ , SiO, SiO ₂ , Zr
Oxides such as O ₂ , ZnO, TiO, and TiO ₂ are used.

As a component constituting the organic compound layer 4, a hole transporting compound which has been studied in a photoreceptor of a so-called electrophotographic process, a hole transporting luminous compound represented by the following formulas 1 to 4, or the like, or If necessary, two or more kinds of electron-transporting compounds and electron-transporting illuminant compounds as shown in the following chemical formulas 5 and 6 can be used.

[0030]

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[0031]

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[0032]

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[0033]

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[0034]

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[0035]

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The organic compound layer 4 is formed as a thin film by vacuum-depositing the above-mentioned compound. For this purpose, a thin film may be formed in combination with an appropriate binder.

The binder can be selected from a wide range of various binder resins, for example, polyvinyl carbazole resin, polycarbonate resin, polyester resin,
Polyacrylate resin, butyral resin, polystyrene resin, polyvinyl acetal resin, diallyl phthalate resin, acrylic resin, methacrylic resin, phenolic resin, epoxy resin, silicone resin, polysulfone resin,
Examples include, but are not limited to, urea resins. In addition, various kinds of binder resins may be used alone or in combination of two or more kinds as a copolymer polymer.

The protective film 5 may be made of any material as long as it is a light-transmitting insulating material.
Examples include inorganic materials such as TiN and glass, and high molecular compounds such as epoxy resin and acrylic resin.

With the above configuration, in the charge injection type light emitting device of the present embodiment, the anode 2 and the cathode 3 are formed on the same surface of the insulating substrate 1 and the organic compound layer 4 are formed. Here, an electric field due to the applied voltage is generated between the anode 2 and the cathode 3, which is in a direction along the film layer surface of the organic compound layer 4, the distance between the two electrodes can be appropriately set, and the film of the organic compound layer 4 is formed. It can be set sufficiently wider than the thickness. For this reason, the limit point of the applied electric field can be increased with respect to the dielectric breakdown of the film defect of the organic compound layer 4,
The occurrence of dark spots can be prevented. Since the electric field can be increased, high luminance light emission can be achieved.

An organic compound layer 4 is provided on both electrodes 2 and 3.
Is formed and covered, it can be isolated from the outside air, and the intrusion of substances that promote deterioration such as oxygen and moisture can be suppressed. As a result, the durability of the element is increased, a stable light emission output is obtained, and the life can be extended.

By the way, light emission in the organic compound layer 4 is generated between the anode 2 and the cathode 3 where an electric field is acting.
By changing the distance between the two electrodes, the light emission pattern can be appropriately set, and an arbitrary light emission pattern can be easily obtained. Therefore, versatility is high and manufacturing cost can be reduced.

As described above, the charge injection type light emitting device of the present invention can achieve high luminance light emission by applying a high electric field, but can obtain stable light emission output with high durability. Can be used for display panels and the like that have strict requirements.

As an example of the image forming apparatus of the present invention, FIG. 4 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 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.

[0053]

EXAMPLES Examples of the charge injection type light emitting device according to the present invention and comparative examples thereof will be described below.

(Examples 1, 2 and Comparative Example 1)
The anode 2 and the cathode 3 are made of ITO and Al, respectively.
m was formed as the anode 2 and Al was further evaporated to a film thickness of 50 nm to form the cathode 3. At this time, the distance between both electrodes was 0.5 μm in this embodiment.

Then, 8 Alq ₃ was applied on both electrodes.
The organic compound layer 4 is formed by vacuum evaporation to a thickness of 0 nm,
The charge injection type light emitting device shown in FIG. 1 was manufactured.

In the second embodiment, a protective film 5 is formed on the organic compound layer 4 of the first embodiment. The organic compound layer 4 is formed in the same manner as in the first embodiment. A protective film 5 was formed by bonding insulating glass to the surface of the device, and the charge injection type light emitting device shown in FIG. 2 was manufactured.

On the other hand, Comparative Example 1 has a conventional laminated structure shown in FIG.
Is deposited to a thickness of 50 nm to form an anode 2. On the anode 2, Alq ₃ is deposited to a thickness of 50 nm to form an organic compound layer 4.
Then, Al was vapor-deposited to a thickness of 120 nm to form the cathode 3, and the charge injection type light emitting device of Comparative Example 1 was manufactured.

Next, the luminance of each of the device samples was measured. Table 1 shows the measurement results.

[0059]

[Table 1]

That is, when a voltage was applied to each element sample to emit light, Examples 1 and 2 had no dark spot from the beginning, and the change in luminance was small even after 100 hours. Many dark spots are seen from
After 100 hours, almost no light was emitted.

(Examples 3 and 4 and Comparative Example 2)
The anode 2 and the cathode 3 are also formed of Au in the same manner. On a glass plate serving as the substrate 1, Au is deposited to a thickness of 60 nm to form an anode 2, and further, Au is deposited to a thickness of 60 nm to form a cathode 3. However, at this time, the distance between both electrodes is 1 in this embodiment.
μm.

Then, an organic compound layer 4 was formed on both electrodes by co-evaporating Alq ₃ and the compound shown below to a thickness of 100 nm to produce the charge injection type light emitting device shown in FIG.

[0063]

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In the fourth embodiment, a protective film 5 is formed on the organic compound layer 4 of the third embodiment. The organic compound layer 4 is formed in the same manner as in the third embodiment. A protective film 5 was formed by bonding insulating glass to the surface of the device, and the charge injection type light emitting device shown in FIG. 2 was manufactured.

On the other hand, Comparative Example 2 has a conventional laminated structure as shown in FIG.
Au is deposited to a thickness of 50 nm to form an anode 2, the above compound is deposited to a thickness of 20 nm, Alq ₃ is deposited to a thickness of 20 nm to form an organic compound layer 4, and Au is further deposited to a thickness of 100 nm.
Then, the cathode 3 was formed by vapor deposition on m to form a charge injection type light emitting device of Comparative Example 2.

Next, the luminance of each of the device samples was measured. Table 2 shows the measurement results.

[0067]

[Table 2]

That is, when a voltage was applied to each element sample to emit light, Examples 3 and 4 had no dark spots from the beginning, and the change in luminance was small even after 100 hours. Many dark spots are seen from
After 100 hours, almost no light was emitted.

(Examples 5 and 6) In Example 5, the material was set in the same manner as in Example 2, but LiF was vacuum-deposited to a film thickness of 10 ° on the cathode 3 to form a dielectric layer. Except for this, it was manufactured under the same conditions and settings as in Example 2.

In the sixth embodiment, the material is set in the same manner as in the fourth embodiment, but LiF is vacuum-deposited on the cathode 3 to a thickness of 12 ° to form a dielectric layer. Except for this, it was manufactured under the same conditions and settings as in Example 4.

Next, the luminance of each of the device samples was measured. Table 3 shows the measurement results.

[0072]

[Table 3]

That is, when voltage was applied to each element sample to emit light, in Examples 5 and 6, there was no dark spot from the beginning, and the change in luminance was small even after 100 hours.

[0074]

As described above, according to the present invention,
Since the anode and the cathode are formed on the same surface of the insulating substrate, an electric field due to the applied voltage is generated between the anode and the cathode, which is in a direction along the film surface of the organic compound layer, and Can be set as appropriate, and can be set sufficiently wider than the thickness of the organic compound layer. For this reason, the limit point of the applied electric field can be increased with respect to the dielectric breakdown of the film defect of the organic compound layer, and the occurrence of a dark spot can be prevented. Since the electric field can be increased, high luminance light emission can be achieved.

In addition, since the organic compound layer is formed and covered on both electrodes, it can be isolated from the outside air, and it is possible to prevent entry of a substance which promotes deterioration such as oxygen and moisture. As a result, the durability of the element is increased, a stable light emission output is obtained, and the life can be extended.

Since the light emission in the organic compound layer is performed between the anode and the cathode where an electric field is applied, the light emission pattern can be appropriately set by changing the distance between the two electrodes. Can be easily obtained. Therefore, versatility is high and manufacturing cost can be reduced.

That is, according to the present invention, while high luminance emission can be achieved by applying a high electric field, a stable light emission output with high durability can be obtained. Etc. can be used.

[Brief description of the drawings]

FIG. 1 is a sectional view of a charge injection type light emitting device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a charge injection type light emitting device according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating an example of a conventional charge injection type light emitting device.

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

FIG. 5 is a schematic configuration diagram illustrating another example of the image forming apparatus of the present invention.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 anode 3 cathode 4 organic compound layer 5 protective film

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 33/14 (72) Inventor Akihiro 3-3-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Seiji Mashimo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Shinichi Urakawa 3-30-2 Shimomaruko 3-chome, Ota-ku, Tokyo F-term ( Reference) 2C162 AE28 AG11 FA16 FA23 3K007 AB02 AB07 AB11 BB00 CA01 CB01 CC00 DA01 DB03 EB00 FA01 FA02

Claims (11)

[Claims] 1. A charge injection type light emitting device comprising a substrate, an anode and a cathode disposed on the same surface of the substrate, and one or more organic compound layers disposed on both electrodes. A light-emitting device comprising an element. 2. The light emitting device according to claim 1, wherein a dielectric film is provided on the cathode. 3. The light emitting device according to claim 1, wherein a translucent or transparent protective film is provided on the organic compound layer. 4. The light emitting device according to claim 1, wherein the substrate comprises a substrate including at least one kind of semiconductor layer. 5. The light emitting device according to claim 1, wherein the substrate is a transparent insulating substrate. 6. A charge injection type light emitting device comprising: a substrate; an anode and a cathode disposed on the same surface of the substrate; and one or more organic compound layers disposed on the two electrodes. An exposure apparatus comprising an element. 7. The light emitting device according to claim 6, wherein a dielectric film is provided on the cathode. 8. The exposure apparatus according to claim 6, wherein a translucent or transparent protective film is provided on the organic compound layer. 9. The exposure apparatus according to claim 6, wherein the substrate is a substrate including at least one or more types of semiconductor layers. 10. The exposure apparatus according to claim 6, wherein the substrate is a transparent insulating substrate. 11. An exposure apparatus according to claim 6, wherein:
An image forming apparatus comprising at least a photoconductor exposed by the exposure apparatus.