JP2007288071A - Organic electroluminescent element, method of manufacturing the same, and display device and exposure device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent element which operates stably with uniform light-emitting performance and is excellent in lifetime properties. <P>SOLUTION: The organic electoluminescent element comprises an anode, a cathode, and a plurality of functional layers formed between the anode and the cathode, wherein the functional layers include a light-emitting function layer composed of at least one kind of organic semiconductor, and at least one kind of transition-metal oxide layer interposed between the cathode and the light-emitting function layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic electroluminescent device and a method for manufacturing the same, and is particularly used for a display for a mobile phone, a display device, various light sources, and the like, and is driven in a wide luminance range from low luminance to high luminance for a light source. The present invention relates to an organic electroluminescent device that is an electroluminescent device.

  An organic electroluminescent element is a light-emitting device that utilizes the electroluminescence phenomenon of a solid fluorescent material, and is partially put into practical use as a small display.

  Organic electroluminescent devices can be classified into several groups depending on the material used for the light emitting layer. One typical example is a low molecular weight organic electroluminescent device using a low molecular weight organic compound in the light emitting layer, which is mainly produced by vacuum deposition. The other is a polymer organic electroluminescent device using a polymer compound in the light emitting layer.

  The polymer organic electroluminescent device uses a solution in which the material constituting each functional layer is dissolved, so that wet methods such as a spin coating method, an ink jet method, a flood printing method, a gap coating method, a spray method, an LB method, and a printing method are used. The film can be formed by a coating method, and has attracted attention as a technology that can be expected to reduce costs and increase the area from a simple process.

  A typical polymer organic electroluminescent device is produced by laminating a plurality of functional layers such as a charge injection layer and a light emitting layer between an anode and a cathode. Below, the structure of the typical polymer organic electroluminescent element and its preparation procedure are demonstrated.

  For example, as shown in FIG. 18, first, PEDOT: PSS (mixture of polythiophene and polystyrenesulfonic acid: hereinafter referred to as PEDT) as a charge injection layer 126 on a glass substrate 100 on which ITO (indium tin oxide) as an anode 111 is formed. A thin film is formed by spin coating or the like. PEDT is a material that has become a de facto standard as a charge injection layer, and functions as a hole injection layer by being disposed on the anode side. 125 seems to be a buffer.

  On the PEDT layer, polyphenylene vinylene (hereinafter referred to as PPV) and a derivative thereof, or polyfluorene and a derivative thereof are formed as the light emitting layer 112 by a spin coating method or the like. A metal electrode 113 as a cathode is formed on these light emitting layers by vacuum deposition sputtering or wet coating to complete the device.

As described above, the polymer organic electroluminescent device has an excellent feature that it can be produced by a simple process, and is expected to be applied to various applications. This is a problem to be solved in that it cannot be performed and when the driving is performed for a long time, the lifetime is not sufficient.
In particular, when used as an exposure light source in an exposure head or the like, high luminance characteristics are required, and further improvement in controllability is required for controllability of the pixel region, pixel area, and light emission characteristics in the pixel. Have been intensively studied.

  The decrease in the emission intensity of polymer organic electroluminescent devices, that is, the deterioration progresses in proportion to the product of the energization time and the current flowing through the device, but the details have not been clarified yet and earnest research is ongoing. It is being done.

  Various speculations have been made about the cause of the decrease in the emission intensity, but the degradation of PEDT is considered as one of the main ones. As described above, PEDT is a mixture of two polymer substances, polystyrene sulfonic acid and polythiophene, the former being ionic and the latter having local polarity in the polymer chain. Due to the Coulomb interaction resulting from such charge anisotropy, the two are loosely coupled, thereby exhibiting excellent charge injection characteristics.

  In order for PEDT to exhibit excellent properties, close interaction between the two is indispensable. In general, however, a mixture of polymer substances tends to cause phase separation due to a subtle difference in solubility in a solvent. This is no exception for PEDT. The occurrence of phase separation means that the loose bond between the two macromolecules can be removed relatively easily and is unstable when the PEDT is driven in an organic electroluminescent device. This indicates that components that did not contribute to bonding, particularly ionic components, as a result of phase separation, may be diffused by the electric field accompanying current flow, and may have undesirable effects on other functional layers. ing. Thus, although PEDT has excellent charge injection characteristics, it cannot be said that it is a stable substance.

Based on the results of various experiments, the present inventors have responded to the concerns related to PEDT as described above by forming molybdenum oxide MoO ₃ instead of PEDT between the anode and the light emitting layer. It has been proposed that injection characteristics can be obtained (Patent Document 1).
JP 2005-203340 A

In the above structure, a MoO ₃ film having a thickness of about 20 nm is used on the anode, and a functional layer such as a light emitting layer is formed thereon. On the cathode side, an intermediate layer that is in contact with a metal such as Ba, Ca, Mg, Li, or Cs, or an organic material layer made of a fluoride or oxide of these metals such as LiF or CaO, is formed thereon. In many cases, a laminated structure of a metal composed of an electrode layer made of a metal material such as Ag, Al, Mg, or In is used.
Since a highly reactive material is used for the intermediate layer in this way, it may be necessary to interpose a barrier layer for blocking the inflow of reactive substances between the light emitting layer and this may cause a voltage drop. Sometimes it was the cause. For this reason, it is difficult to adjust the balance of carriers and it is difficult to emit light in the middle of the light emitting layer.

  In addition, since organic semiconductors have a low mobility, it is said that good light emission cannot be obtained in an organic electroluminescent element unless the film is made as thin as about 100 nm. If this occurs, electric field concentration may occur. In such a situation, if light emission continues, an electric field is applied intensively in a thin film area, and if light is emitted at a biased position rather than in the middle of the light emitting layer, deterioration rapidly proceeds. There was a problem that the life could not be maintained.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an organic electroluminescent device that operates stably with uniform light emission characteristics and has excellent life characteristics.

The present invention comprises an anode and a cathode, and a plurality of functional layers formed between the anode and the cathode, wherein the functional layer comprises a layer having a light emitting function made of at least one organic semiconductor, and the cathode And at least one transition metal oxide layer between the layer having a light emitting function.
With this configuration, even if the cathode material is a highly reactive material, it acts as a barrier layer, and the reactive substance does not flow from the cathode side and does not cause deterioration of the light emitting layer. In addition, when a transition metal oxide such as MoO ₃ is applied to an organic electroluminescent element, charge injection is efficiently performed. Further, when used in a thin film of 1 μm or less, an electric field applied between both electrodes is directly applied to the light emitting layer without causing a voltage drop, and high luminance characteristics can be obtained. In addition, since transition metal oxides have properties such as electron injection capability, electron transport properties, and hole blocking properties, high functions can be obtained with a single layer, and the device can be made thinner. Therefore, good electron injection can be realized and the light emitting region can be controlled. Therefore, for example, by controlling the light emitting region so as to be in the middle of the light emitting layer, which was not easy in the prior art, the device efficiency can be further improved and the device life can be improved.

The present invention includes the organic electroluminescent element, wherein the transition metal oxide layer has a thickness of 1 nm to 1 μm.
If it exceeds 1 μm, the transmittance becomes high, and it becomes difficult to secure a transmittance of 70%. In consideration of the film formation time, it is preferably 500 nm or less. In the case of a thin film, even if it is not in the form of a film, if the film has an average thickness of about 1 nm, the same effect as described above can be obtained even if it is spongy. In the case of a film thinner than 1 nm, a sufficient effect as a metal oxide cannot be obtained.

The present invention includes the organic electroluminescent element, wherein the transition metal oxide layer has a transmittance of 70% or more.
With this configuration, a sufficient amount of emitted light can be maintained. When the transmittance is less than 70%, there is a problem that the amount of emitted light decreases.

  According to the present invention, in the organic electroluminescent element, the layer having the light emitting function includes a polymer compound.

  In the organic electroluminescent element, the present invention includes a polymer compound in which the layer having the light emitting function includes a fluorene ring. Here, the polymer compound containing a fluorene ring refers to a compound in which a desired group is bonded to the fluorene ring to form a polymer. Polymer compounds having various groups bonded thereto are commercially available.

According to the present invention, in the organic electroluminescent element, the transition metal oxide layer has a work function of 4 to 6 eV.
With this configuration, a good ohmic contact can be formed. When the work function is less than 4 eV, the reactivity tends to be high, it is difficult to reduce the influence of the reactive substance that is the feature of the present invention, and good light emission cannot be obtained, and the detailed mechanism is clear However, if it exceeds 6 eV, a good light emission cannot be obtained because the work function difference from the cathode increases.

According to the present invention, in the organic electroluminescent element, the transition metal oxide layer has a specific resistance of 10,000 Ωm or less.
With this configuration, a voltage drop due to the transition metal oxide layer itself is small, and light emission with high luminance is possible.

According to the present invention, in the organic electroluminescent element, the transition metal oxide layer includes a molybdenum oxide layer.
Although the molybdenum oxide layer is a metal oxide, its specific resistance is small, so that there is no voltage drop and highly reliable light emission is possible. In addition, since a good contact property can be obtained without using a reactive substance for the cathode, the cathode may have a single layer structure, and a thinner film can be achieved. In addition, since the barrier property is high and a smooth surface can be obtained, the uniformity of the light emitting layer can be obtained. Here, molybdenum oxide (MOx) is not limited to MO ₃ , but those having different valences are also effective.

According to the present invention, in the organic electroluminescent element, the transition metal oxide layer includes a vanadium oxide layer. Here, vanadium oxide (VxOy) is not limited to V ₂ O ₅ , but those having different valences are also effective.

According to the present invention, in the organic electroluminescent element, the transition metal oxide layer includes a tungsten oxide layer. Here, tungsten oxide (WOx) is not limited to WO _3, and those having different valences are also effective.

  According to the present invention, in the organic electroluminescent element, the transition metal oxide layer is formed so as to be in contact with the cathode via an intermediate layer.

  According to the present invention, in the organic electroluminescent device, the intermediate layer includes at least one of barium, calcium, lithium, cesium, or an oxide / halide thereof. As the halide, fluorides such as lithium fluoride and calcium fluoride are particularly desirable. Halides, particularly fluorides, are difficult to oxidize and are stable, prevent transition metal oxides from escaping oxygen, and maintain a stable and highly reliable structure. Carbon dioxide is also applicable.

In the organic electroluminescent device, the layer having the light emitting function includes polyfluorene represented by the following general formula (I) and derivatives thereof (R1 and R2 each represent a substituent).
.

  According to the present invention, in the organic electroluminescent element, the layer having the light emitting function includes a phenylene vinylene group.

In the organic electroluminescent device, the layer having the light emitting function includes polyphenylene vinylene represented by the following general formula (II) and derivatives thereof (R3 and R4 each represent a substituent).

  According to the present invention, in the organic electroluminescent element, the intermediate layer is composed of a polymer layer.

  According to the present invention, in the organic electroluminescent element, an anode that is one electrode of the pair of electrodes is formed on a light-transmitting substrate, and the functional layer is formed on the anode. The transition metal oxide on the layer having the light emitting function so as to face the hole injecting layer through the layer having the light emitting function and the layer having the light emitting function. This includes a cathode formed as the other electrode of the set of electrodes formed through a layer.

  According to the present invention, in the organic electroluminescent element, an anode which is one electrode of the pair of electrodes is formed on a substrate, and the functional layer is a hole injection formed on the anode. A layer having a light emitting function, and a layer having a light emitting function, on the layer having the light emitting function so as to face the hole injection layer via the layer having the light emitting function, with the transition metal oxide layer interposed therebetween. The cathode which is the other electrode of the set of electrodes formed as described above is formed as a transparent electrode that transmits light emitted from the layer having the light emitting function.

  The present invention comprises an anode and a cathode, and a plurality of functional layers formed between the anode and the cathode, wherein the functional layer comprises a layer having a light emitting function made of at least one organic semiconductor, and the cathode And at least one transition metal oxide layer between the layer having a light emitting function and at least one transition metal oxide layer between the anode and the layer having a light emitting function.

  Moreover, this invention is a manufacturing method of the said organic electroluminescent element, Comprising: The said functional layer contains the transition metal oxide layer, and includes the process of forming a cathode on the said transition metal oxide layer.

Moreover, this invention is a manufacturing method of the said organic electroluminescent element, Comprising: The process of forming the said cathode into a film by the sputtering method on the said transition metal oxide layer is included.
The sputtering method can easily form a dense film, but has a large damage to the base substrate. However, the use of a transition metal oxide can reduce the damage caused by sputtering.

Moreover, this invention is a manufacturing method of the said organic electroluminescent element, Comprising: The process of forming the said cathode into a film by CVD method on the said transition metal oxide layer is included.
Since the CVD method can form a film having good step coverage, a reliable organic electroluminescent element can be formed.

  In the present invention, the organic electroluminescent elements may be two-dimensionally arranged to constitute a display device.

  In the present invention, the organic electroluminescent elements may be arranged in a line to form a light emitting unit to constitute an exposure apparatus.

  Further, in the present invention, the layer having a light emitting function made of at least one kind of organic semiconductor, the electrode for injecting electrons into the layer having the light emitting function, and the electrode and the layer having the light emitting function are disposed. Having at least one transition metal oxide layer;

  Note that the layer having a light emitting function is not limited to a layer having only a light emitting function, but a layer having other functions such as a charge transport function, a charge injection function, and a charge blocking function. Shall be included. In the following embodiments, the light emitting layer is simplified.

  According to the organic electroluminescent device of the present invention, the transition metal oxide layer is arranged between the light emitting layer and the cathode, and the carrier balance can be adjusted. For example, light emission is realized in the middle of the light emitting layer. In addition, it is possible to suppress the destruction of the interface and to suppress the thermal deactivation of excitons, so that the operation is stable and the life characteristics are excellent.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a configuration diagram of a polymer organic electroluminescent element in an embodiment of the present invention.

  In this embodiment mode, a molybdenum oxide layer 117 is provided between the light-emitting layer 112 and the cathode 113, and the light-transmitting substrate 111 is formed over the light-transmitting anode 111. Further, molybdenum oxide, which is a metal oxide thin film, is formed as the charge injection layer 115, and a molybdenum oxide layer is formed thereon as a metal oxide thin film as the buffer layer 116 having an electron blocking function, and a polymer material as the light emitting layer 112 is formed. Are sequentially stacked, and a cathode 113 is formed thereon. This molybdenum oxide layer had a thickness of 40 nm, a work function of 5.4 eV, and a transmittance of 80%.

  That is, as shown in FIG. 1, the organic electroluminescent element of this embodiment includes a substrate 100 made of a light-transmitting glass material, and ITO (indium tin oxide) as an anode 111 formed on the substrate 100. Oxide), a metal oxide thin film as a charge injection layer 115 formed thereon, a light emitting layer 112 made of a polymer material, a molybdenum oxide layer as a buffer layer 116, Ag, Al, Mg, In, etc. And a cathode 113 made of a metal material.

  When a DC voltage or a DC current is applied with the anode 111 of the organic electroluminescent element as a positive electrode and the cathode 113 as a negative electrode, holes are injected into the light emitting layer 112 from the anode 111 through the charge injection layer 115. At the same time, electrons are injected from the cathode 113 through the buffer layer 116. In the light emitting layer 112, the holes and electrons injected in this manner are recombined, and a light emission phenomenon occurs when excitons generated along with the recombination shift from the excited state to the ground state. .

  According to the organic electroluminescent element of the present embodiment, since the barrier effect is high due to the molybdenum oxide layer, uniform light emission characteristics can be obtained.

Next, the manufacturing process of the organic electroluminescent element of this invention is demonstrated.
First, an ITO thin film is formed on the glass substrate 100 by sputtering, and then a MoO ₃ layer as a metal oxide thin film is formed by vacuum deposition, and these are patterned by photolithography (as it is because of the MoO ₃ sandwich structure). The ITO thin film is formed on the glass substrate 100 by sputtering, and this is patterned by photolithography. Subsequently, a metal oxide thin film is formed by vacuum deposition, and these are patterned by photolithography or a mask, thereby forming an anode. 111 and charge injection layer 115 are formed.

Then, the light emitting layer 112 is formed on the charge injection layer 115 by screen printing.
Thereafter, a buffer layer 116 made of MoO ₃ is formed by vacuum evaporation.

  Finally, the cathode 113 is formed.

As described above, according to the method of the present invention, since the light emitting layer 112 is formed by screen printing on the molybdenum oxide layer as the charge injection layer 115, it is easy to manufacture and can be miniaturized and highly integrated. is there. In this embodiment, the light emitting layer is formed prior to the formation of the MoO ₃ layer as the buffer layer, but this molybdenum oxide layer also functions as an electron injection layer. Although another functional layer can be interposed, it is desirable that the light emitting layer be screen-printed on a metal oxide layer such as a molybdenum oxide layer.

The molybdenum oxide thin film in this embodiment is an amorphous thin film formed by vacuum deposition. In this embodiment mode, molybdenum oxide is mainly represented as molybdenum 3 oxide (MoO ₃ ), which is stable among molybdenum oxides. However, the environment during vacuum deposition is a reducing atmosphere, and heating sublimation therein. The molybdenum oxide undergoes reduction in the process of being deposited on the substrate. The reduced molybdenum oxide produces some oxides with a smaller oxidation number in addition to hexavalent MoO ₃ . They are, for example, tetravalent MoO ₂ and trivalent Mo ₂ O ₃ . That is, in this embodiment, the molybdenum oxide is MoO ₃ , but it goes without saying that it effectively includes MoO ₂ and Mo ₂ O ₃ . Since receiving is equivalent to receiving electrons, an oxide having a reduced valence is more likely to release electrons than an oxide having a higher valence, that is, more likely to receive holes. This is equivalent to having a higher energy level.

Next, examples of the present invention will be described.
The structure is the same as that shown in FIG. 1, and will be described with reference to FIG.
The organic electroluminescent element of Example 1 includes a glass substrate 100 made of glass called Corning 7029 # with a thickness of 1 mm, and an anode 111 made of an ITO thin film with a thickness of 20 nm formed as an upper layer. The charge injection layer 115 made of a molybdenum oxide thin film with a thickness of 40 nm formed on the anode 111 and 7-diyl) -alt-co- (N, N′-diphenyl) -N, N′di (p -butyl-oxyphenyl) -1,4-diaminobenzene)] and poly [9,9-dioctylfluorenyl-2,7-diyl) -co-1,4-benzo which is a polyfluorene compound having a thickness of 80 nm -{2,1'-3} -thiadiazole] Poly [9,9-dioctylfluorenyl-2,7-diyl) -co-1,4-benzo- {2,1'-3} -thiadiazole)] poly [( 9,9-Dioctylfluorenyl-2,7-diyl) -co- (1,4-benzo- {2,1'-3} -thiadiazole)] Poly [(9,9-dioctylfluorenyl-2,7- diyl) -co- (1,4-benzo- {2,1'-3} -thiadiazole)] and a shape formed on the light-emitting layer 112 A buffer layer 116 made of a molybdenum oxide thin film having a thickness of 40 nm and a cathode 113 made of a calcium (Ca) layer 113a having a thickness of 20 nm and an aluminum (Al) layer 113b having a thickness of 100 nm are formed.
This luminescent material can be purchased from, for example, Nippon Sebel Hegner.

According to this configuration, the buffer layer 116 made of MoO ₃ is interposed between the light emitting layer 112 and the cathode 113, thereby reducing a voltage drop, excellent electron injection capability, and electron transport properties. Because it has a hole blocking property, it can be adjusted so that light emission region is controlled and light emission occurs at the center of the light emitting layer, so that a high brightness and long life organic electroluminescent device is formed. Is possible. Further, a MoO ₃ layer as an electron injection layer is also provided on the lower layer side of the light emitting layer, so that the base of the pixel regulating layer 114 can be smoothed, and even if the thickness of the pixel regulating layer is reduced accordingly. As a result, sufficient insulation can be maintained, and the step difference caused by the pixel regulation layer can be reduced. As a result, the film thickness distribution of the layer having a light emitting function can be made more uniform. It becomes. Also, there was no short circuit of the pixels. Here, the pixel regulation layer may be a light shielding material instead of an insulating material. Moreover, even if it has both the light-shielding property and the insulating property, the light emission region can be well regulated, and the pixels can be defined. According to the present invention, the buffer layer 116 made of the MoO ₃ layer is disposed between the light emitting layer 112 and the cathode 113, and the surface is flattened and smoothed by the thick MoO ₃ layer. The layer 112 is formed by a screen printing method.

Here, the buffer layer 116 is composed of a MoO ₃ layer, which is a transition metal oxide layer, and functions as an electron injection layer. The second electrode, that is, the cathode 113 is composed of a barium electrode 113a having a film thickness of about 3 nm and an aluminum electrode 113b having a film thickness of 150 nm formed thereon.

  According to this configuration, the base at the time of forming the light emitting layer is smoothed to Ra 20 nm or less, and screen printing is performed thereon. In this way, a highly accurate light emitting layer pattern can be formed. In addition, even if the thickness of the pixel regulation layer is reduced, sufficient insulation can be maintained, and a step caused by the pixel regulation layer can be reduced. As a result, a layer having a light emitting function The film thickness distribution can be made more uniform. Also, there was no short circuit of the pixels. The result of measuring the light emission characteristics at this time is shown in FIG. Here, the horizontal axis represents position, and the vertical axis represents emission intensity. As is apparent from this figure, it has a rectangular emission spectrum and shows good emission characteristics. Here, the pixel regulation layer may be a light shielding material instead of an insulating material. Moreover, even if it has both the light-shielding property and the insulating property, the light emission region can be well regulated, and the pixels can be defined.

Next, in this organic electroluminescent element, a sample was prepared by changing the film thickness in order to observe the characteristic change due to the film thickness of the MoO ₃ layer. Here, the light emitting layer 112 was formed by screen printing.
For each sample, an ITO film is formed on the surface of the light-transmitting glass substrate 100 by a sputtering method, the first electrode 111 is formed, and then the MoO ₃ layer 115 is formed to have a desired film thickness by a vacuum deposition method. A film is formed, a silicon nitride film is formed by a CVD method using high-density plasma, and an opening is formed by photolithography to form a pixel regulation layer 114. Then, the light emitting layer 112 is formed. As the light emitting layer, a polymer layer is mixed with a solvent and formed by a screen printing method. The material will be described later. Then, a metal oxide layer 116 and a cathode 113 are formed.

  In the present invention, the layer 112 having a light emitting function made of at least one organic semiconductor, the electrode 113 for injecting electrons into the layer having the light emitting function, and the electrode and the layer having the light emitting function are disposed. By having at least one kind of transition metal oxide layer 116, electrons are more efficiently injected into the light emitting layer.

  In the present invention, a layer having a light emitting function made of at least one organic semiconductor, an electrode for injecting electrons into the layer having the light emitting function, and the electrode and the layer having the light emitting function are disposed. By having at least one kind of transition metal oxide layer, it is possible to provide an electroluminescent element with high efficiency and high reliability. When applying the electric field, an electric field generated by an external magnetic field may be used.

(Embodiment 2)
FIG. 3 is a schematic cross-sectional view showing the configuration of the organic electroluminescent element of the optical head provided in the exposure unit of the image forming apparatus according to Embodiment 2 of the present invention. In this electroluminescent element, the entire surface of the pixel regulating layer 114 is covered with a MoO ₃ layer as a transition metal oxide layer 115, and the surface roughness of the MoO ₃ layer is set to Ra: 15 nm. After performing the above, the first embodiment is different from the first embodiment in that a layer 112 having a light emitting function is formed on the upper layer by screen printing. Others are formed in the same manner as in the above embodiment.

According to this configuration, the MoO ₃ layer (116) is formed on the light emitting layer 112. Further, since the region from the light emitting region to the pixel regulating layer 112 is covered, the layer having a light emitting function is formed on a smoother surface, and a uniform film thickness distribution can be obtained. And a MoO ₃ layer (115) that can achieve a longer life is formed on the pixel regulation layer 114 and covers the area from the light emitting area to the pixel regulation layer 114. Therefore, the layer having a light emitting function is formed on a smoother surface, a uniform film thickness distribution can be obtained, and a longer life can be achieved.

  The results of measuring the light emission characteristics at this time are shown in FIG. Here, the horizontal axis represents position, and the vertical axis represents emission intensity. As is apparent from this figure, the light emission position is the center of the light emitting layer, and it has a rectangular light emission spectrum and shows good light emission characteristics. Compared with the first embodiment shown in FIG. 2, the emission spectrum is slightly steeper.

(Embodiment 3)
FIG. 5 is a cross-sectional view showing the configuration of the optical head provided in the exposure unit of the image forming apparatus according to Embodiment 3 of the present invention, in which a photodetecting element is formed below the electroluminescent element and is integrated. Is configured. The electroluminescent element 110 as a light source and its periphery are shown, and the relationship of the vertical arrangement of each layer constituting the light detecting element 120 is shown. FIG. 6 is a top view of the main part. In this embodiment, a light detection element 120 and an electroluminescent element as a light source are stacked on a glass substrate 100, and a plurality of light emitting element units are one-dimensionally arranged and integrated to form a monolithic device. It is configured. In the present embodiment, as shown in FIG. 6, the light emitting layer of this electroluminescent element is divided and arranged for each unit by screen printing. This electroluminescent element is a layer having a light emitting function, that is, a light emitting layer composed of an anode as the first electrode 111, a cathode as the second electrode 113, and at least one organic semiconductor formed between these electrodes. And a layer 112 of the MoO ₃ layer 115 having a thickness of 40 nm as the transition metal oxide layer 115 between the electrode and the layer having the light emitting function, and a silicon nitride film having a thickness of 50 nm as an upper layer. A pixel regulation layer 114 and a buffer layer 116 composed of a MoO ₃ layer are provided, and the thickness of the MoO ₃ layer as the transition metal oxide layer 115 is set to a thickness of 40 nm, which has not been considered in the past. Thus, the surface is flattened and smoothed with a thick MoO ₃ layer so that Ra = 20 nm or less, and then screen printing is performed to obtain the light emitting layer 11. The second pattern (see FIG. 6) is configured to favorably regulate the area of the light emitting region.

  Here, the silicon nitride film as the pixel regulation layer 114 is formed to a thickness of about 50 nm by a low temperature CVD method using high density plasma. Then, a resist pattern is formed by photolithography, and etching for forming an opening is performed. After anisotropic etching is performed first, isotropic etching is performed to form a smooth edge pattern. At this time, the angle between the pattern edge and the ground is set to about 3 to 10 degrees.

In this optical head, as shown in FIG. 6, an electroluminescent element 110 is laminated on an upper layer of a thin film transistor (TFT) constituting a light detecting element 120 formed on a substrate. Since the anode as the first electrode 111 located on the light detection element 120 side is formed so as to cover the entire photoelectric conversion portion of the light detection element 120, the first electrode of the electroluminescent element is the light detection element. It faces the whole photoelectric conversion part. With this configuration, the first electrode effectively acts as the gate electrode of the light detection element, and the channel characteristic of the light detection element is reliably controlled by the potential of the first electrode, which is a stable potential, and stable light emission characteristics. It is possible to provide an optical head having Further, a cathode as the second electrode 113 provided so as to face the first electrode with the light emitting layer interposed therebetween is formed on the upper layer side through a buffer layer 116 made of a MoO ₃ layer.

Further, this optical head, the outer edge of the island region 121 of the polycrystalline silicon constituting the element region of the photodetector element 120 is formed such that the outside of the light emission region A _LE of the electroluminescent element. Thus, here namely the island region 121 of the light detecting element 120 result in the formation of the step, formed to the outer edge of the element region A _R is the outside of the light emission region A _LE of the electroluminescent element, There is no step in the region corresponding to the light emitting region of the electroluminescent element, and the base of the light emitting layer forms a flat surface. Therefore, in the light emitting region that is the effective region of the optical head, the light emitting layer of the optical head is Uniformly formed.

In order to the MoO ₃ layer to the desired surface condition, by adjusting the film forming conditions such as film formation at low temperatures, it can be realized. It can also be easily realized by adjusting the surface roughness by forming a pixel regulating layer and performing surface treatment such as plasma treatment after patterning or simultaneously with patterning.

As shown in FIG. 5, the optical head using the organic electroluminescent element of the present embodiment has a light detecting element 120 on a glass substrate 100 on which a base coat layer 101 for planarization is formed. A thin film transistor as a switching transistor 130 for sequentially laminating the electroluminescent element 110 and driving the electroluminescent element while correcting the driving current or the driving time according to the output of the photodetecting element 120 A drive circuit (140) as a chip IC connected to the thin film transistor is mounted. The photodetector element 120 is the source region 121S by doping the desired concentration at a channel region formed of the island region A _R of polycrystalline silicon layer formed on the base coat layer 101 surface of a strip-shaped i layer, a drain A source made of a polycrystalline silicon layer formed through a through hole so as to penetrate the first insulating film 122 and the second insulating film 123 made of a silicon oxide film formed in the region 121D. And drain electrodes 125S and 125D. Further, an electroluminescent element 110 is formed on the upper layer through a silicon nitride film as a protective layer 124, and ITO (indium tin oxide) 111 serving as an anode, a protective film 124, a light emitting layer 112, a cathode Each layer is formed in the order of 113.

On the other hand, each layer constituting the photodetecting element 120 is formed in the same manufacturing process as the selection transistor 130 as a driving transistor. In other words, the source regions 132S and 132D are formed in the same process as the semiconductor island of the photodetecting element across the channel region 131C, the source / drain electrodes 134S and 134D that are in contact therewith are stacked, and the gate electrode 133 and the selection transistor The thin film transistor is configured.
Each of these layers is formed through a usual semiconductor process such as formation of a semiconductor thin film by a CVD method, patterning by photolithography, impurity ion implantation, and formation of an insulating film.

  Here, the glass substrate 100 is a single plate of colorless and transparent glass. Examples of the glass substrate 100 include transparent or translucent soda-lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, quartz glass, and other inorganic oxide glasses, inorganic fluorides Inorganic glass such as glass can be used.

Other materials can be used as the glass substrate 100, for example, transparent or translucent polyethylene terephthalate, polycarbonate, polymethyl methacrylate, polyether sulfone, polyvinyl fluoride, polypropylene, polyethylene, polyacrylate, amorphous polyolefin. Polymer films using polymer materials such as fluororesin polysiloxane and polysilane, or transparent or translucent chalcogenoid glasses such as As ₂ S ₃ , As ₄₀ S ₁₀ , S ₄₀ Ge ₁₀ , ZnO, Nb _When extracting light emitted from a material such as metal oxide and nitride, such as ₂ O, Ta ₂ O ₅ , SiO, Si ₃ N ₄ , HfO ₂ , TiO ₂ , or light emitting region without passing through the substrate , Opaque silicon, germanium, silicon carbide, gallium arsenide, A semiconductor material such as gallium phosphide, or the above-mentioned transparent substrate material containing a pigment or the like, a metal material whose surface is subjected to insulation treatment, and the like can be appropriately selected and used, and a laminated substrate in which a plurality of substrate materials are laminated is used. You can also.

  On the surface of the substrate such as the glass substrate 100 or inside the substrate, a circuit composed of a resistor, a capacitor, an inductor, a diode, a transistor and the like for driving the electroluminescent device 110 is integrated as described later. Also good.

  Further, depending on the application, a material that transmits only a specific wavelength, a material that converts light into a specific wavelength having a light-light conversion function, or the like may be used. The substrate is preferably insulative, but is not particularly limited, and may have conductivity depending on a range or use that does not hinder driving of the electroluminescent element 110.

A base coat layer 101 is formed on the glass substrate 100. The base coat layer 101 is composed of, for example, a first layer made of SiN and a second layer made of SiO ₂ . Each layer of SiN and SiO ₂ can be formed by vapor deposition or the like, but is preferably formed by sputtering.

On the base coat layer 101, the selection transistor 130 of the electroluminescent element 110 and the light detection element 120 are formed using a polycrystalline silicon layer formed in the same process. The driving circuit for the electroluminescent element 110 is composed of circuit elements such as a resistor, a capacitor, an inductor, a diode, and a transistor. In consideration of downsizing of the optical head, it is desirable to use a thin film transistor. In the third embodiment, the light detection element 120 is located between the electroluminescent element 110 including the light emitting layer 112 and the glass substrate 100 which is the light output surface as is apparent from FIG. element region _{a R} of the detecting element 110 is larger than the light emission region _{a LE.} Further, since the light emission region A _LE exists inside the light detection element 120, a material that does not transmit light cannot be used for the light detection element 120. Therefore, in order not to disturb the light output from the light emitting layer 112, it is necessary to use a material having transparency for the light detection element 120. As a material of the photodetecting element 120 having transparency, it is desirable to select, for example, polycrystalline silicon.

In Embodiment 3, after a uniform semiconductor layer is formed over the base coat layer 101, the semiconductor layer is etched to form the selection transistor 130 and the photodetecting element 120 from the same layer. . The process of forming the selection transistor 130 and the metal layer of the photodetecting element 120 independent from each other in the form of islands from the same metal layer is advantageous in reducing the number of manufacturing steps and the manufacturing cost. Note in the photodetector element 120, the element region A _R for receiving the light output from the light emission region A _LE is the surface of the polycrystalline silicon or amorphous silicon that is configured in an island shape having a light-detecting element 120.

On the selection transistor 130 and the light detection element 120 for applying an electric field to the light emitting layer 112 of the electroluminescent element 110, the first insulating layer 122 and the second insulating layer 123 made of this silicon oxide film are protected. The layer 124 acts as a gate insulating film between the layer 111 and the ITO 111 serving as the anode of the electroluminescent element, and the drop width from the ITO potential is determined by the voltage drop due to the film thickness. The first insulating layer 122, the second insulating layer 123, and the protective layer 124 constituting the gate insulating film 3 are made of, for example, SiO _{2 and} are formed by vapor deposition, sputtering, or the like.

  A gate electrode 133 is formed on the surface of the first insulating layer 122 as a gate insulating film directly above the selection transistor 130. For example, Cr is used as the material of the gate electrode 133. The gate electrode 133 is formed by vapor deposition, sputtering, or the like.

  A second insulating layer 123 is formed on the substrate surface on which the gate electrode 133 is formed. The second insulating layer 123 is formed over the entire surface of the stacked body that has been formed so far. The second insulating layer 123 is made of, for example, SiN or the like, and is formed by a vapor deposition method, a sputtering method, or the like.

  On the second insulating layer, a drain electrode 125D as a light detection element output electrode, a source electrode 125S as a light detection element ground electrode, a source electrode 134S, and a drain electrode 134D are formed. The drain electrode 125D as the light detection element output electrode and the source electrode 125S as the light detection element ground electrode are connected to the source / drain regions 121S and 121D of the light detection element 120, and an electric signal output from the light detection element 120. Transmission and grounding of the light detection element 120. The source electrode 134S and the drain electrode 134D are connected to the source / drain regions 132S and 132D of the selection transistor 130, and the gate electrode 133 described above is applied with a predetermined potential difference between the source electrode 134S and the drain electrode 134D. By applying a predetermined potential, the selection transistor 130 has a function as a switching element, and operates as a circuit for driving the electroluminescent element 110 as a light emitting element.

  For example, a metal such as Cr is used as the material of the drain electrode 125D as the light detection element output electrode, the source electrode 125S as the light detection element ground electrode, the source electrode 134S, and the drain electrode 134D.

  As shown in FIG. 5, the drain electrode 125 </ b> D as the light detection element output electrode and the light detection element ground electrode pass through the first insulating film 122 and the second insulating layer 123 and are connected to the end of the light detection element 120. Similarly, the source electrode 134S and the drain electrode 134D penetrate the first insulating film 122 and the second insulating layer 123 and are connected to the end portion of the selection transistor 130.

  Therefore, prior to the formation of the drain electrode 125D as the light detection element output electrode, the source electrode 125S as the light detection element ground electrode, the source electrode 134S, and the drain electrode 134D, the first insulating film 122 and the second insulating layer 123 are formed. On the other hand, the drain electrode 125D as the light detection element output electrode and the source electrode 125S as the light detection element ground electrode and the through hole for connecting the light detection element 120, the source electrode 134S and the drain electrode 134D, and the selection transistor 130 are connected. It is necessary to provide a through hole for this purpose. The through holes are formed on the surface of the photodetecting element 120 and the surface of the selection transistor 130, that is, the contact surface between the photodetecting element 120 and the drain electrode 125D serving as the photodetecting element output electrode and the source electrode 125S serving as the photodetecting element ground electrode. The depth is such that the contact surface of 130 with the source electrode 134S and the drain electrode 134D is exposed, and is provided by etching or the like directly above the ends of the photodetection element 120 and the selection transistor 130. For the etching, a halogen-based etching gas is used. Etching gas is introduced and patterned by photolithography while the surface is covered with a resist pattern having openings. (Through holes are opened in the first insulating film 122 and the second insulating layer 123.) At this time, an etching gas that does not cause a chemical reaction with the materials constituting the light detection element 120 and the selection transistor 130 is selected. To do.

  Processing to expose the contact surface between the source electrode 125S as the photodetection element output electrode and the source electrode 125S as the photodetection element ground electrode and the photodetection element 120 and the contact surface between the source electrode 134S and the drain electrode 134D and the selection transistor 130 is completed. After that, the drain electrode 125D as the light detection element output electrode, the source electrode 125S as the light detection element ground electrode, the source electrode 134S, and the drain electrode 134D are formed.

  The source electrode 134S and the drain electrode 134D are formed by forming a metal layer serving as a sensor electrode on the surface of the second insulating layer 123, the surface of the through hole and the both sensor electrodes, the surface of the light detection element 120, and the contact surface of the selection transistor 130. After uniformly forming on the surface, this metal layer is etched using a resist pattern formed by photolithography as a mask, and the metal layer is used as a drain electrode 125D as a light detection element output electrode and as a light detection element ground electrode. It is obtained by dividing the source electrode 125S, the source electrode 134S, and the drain electrode 134D.

  After the drain electrode 125D as the light detection element output electrode, the source electrode 125S as the light detection element ground electrode, the source electrode 134S, and the drain electrode 134D are formed, the protective film 124 is formed. The protective film 124 is made of, for example, SiN and is formed by vapor deposition, sputtering, or the like.

An anode 111 is formed on the protective film 124. The anode 111 is made of, for example, ITO (indium tin oxide). As the constituent material of the anode 111, IZO (zinc-doped indium oxide), ATO (Sb-doped SnO ₂ ), AZO (Al-doped ZnO), ZnO, SnO ₂ , In ₂ O _{3 and the} like are used in addition to ITO. be able to. As shown in FIG. 5, the anode 111 is formed on the surface of the protective film 124 that is directly above the photodetecting element 120. As shown in FIG. 5, the anode 111 penetrates the protective film 124 and is connected to the end of the drain electrode 134D. Therefore, before forming the anode 111, it is necessary to provide a through hole for connecting the anode 111 and the drain electrode 134D to the protective film 124. This through hole has a depth until the surface of the drain electrode 134D, that is, the contact surface between the drain electrode 134D and the anode 111 is exposed, and is provided directly above the end of the drain electrode 134D by etching or the like. It is done. After this etching process is performed, a layer of the anode 111 is formed. The anode 111 can be formed by vapor deposition or the like, but is preferably formed by sputtering. In Embodiment 3, ITO is used as the anode 111.

After the anode 111 is formed, a silicon nitride film 114 as a pixel restricting layer is formed. It is desirable that the silicon nitride film 114 as the pixel regulation layer has a high insulating property, a strong resistance to dielectric breakdown, a good film forming property, and a high patterning property. In the third embodiment, silicon nitride or aluminum nitride is used as a material constituting the silicon nitride film 114 as the pixel restricting layer. A silicon nitride film 114 as a pixel restricting layer is provided between a light emitting layer 112 and an anode 111, which will be described later, and insulates the light emitting layer 112 outside the light emitting region _ALE from the anode 111. The place where light is emitted is regulated. Therefore, the region of the light emitting layer 112 that overlaps the silicon nitride film 114 as the pixel restricting layer is a non-light emitting region, and the region that does not overlap the silicon nitride film 114 as the pixel restricting layer is the light emitting region _ALE . Silicon nitride film as the pixel regulating layer 114 restricts so that the light emission region _{A LE} of the light emitting layer 112 is smaller than the element region _{A R} of the light-detecting element 120, and the light emission region _{A LE} photodetection element 120 configured to be placed inside the element region a _R.

After the silicon nitride film 114 as the pixel regulating layer is formed, the light emitting layer 112 is formed by a screen printing method. The light emitting layer 112 is formed of an inorganic light emitting material, or a high molecular weight or low molecular weight organic light emitting material described in detail below. As the inorganic light emitting material for forming the light emitting layer 112, titanium / potassium phosphate, barium / boron oxide, lithium / boron oxide, or the like can be used. As the polymer organic light emitting material constituting the light emitting layer 112, a material having fluorescence or phosphorescence characteristics in the visible region and good film forming property is desirable. For example, polymers such as polyparaphenylene vinylene (PPV) and polyfluorene are used. A light emitting material or the like can be used. In addition to Alq ₃ and Be-benzoquinolinol (BeBq ₂ ), low molecular organic light emitting materials constituting the light emitting layer 112 include 2,5-bis (5,7-di-t-pentyl-2). -Benzoxazolyl) -1,3,4-thiadiazole, 4,4'-bis (5,7-benzyl-2-benzoxazolyl) stilbene, 4,4'-bis [5,7-di- (2-Methyl-2-butyl) -2-benzoxazolyl] stilbene, 2,5-bis (5,7-di-t-benzyl-2-benzoxazolyl) thiophine, 2,5-bis ( [5-α, α-dimethylbenzyl] -2-benzoxazolyl) thiophene, 2,5-bis [5,7-di- (2-methyl-2-butyl) -2-benzoxazolyl]- 3,4-diphenylthiophene, 2,5-bis (5-methyl-2 -Benzoxazolyl) thiophene, 4,4'-bis (2-benzoxazolyl) biphenyl, 5-methyl-2- [2- [4- (5-methyl-2-benzoxazolyl) phenyl] Benzoxazoles such as vinyl] benzoxazolyl, 2- [2- (4-chlorophenyl) vinyl] naphtho [1,2-d] oxazole, 2,2 ′-(p-phenylenedivinylene) -bisbenzothiazole Such as benzothiazole, 2- [2- [4- (2-benzimidazolyl) phenyl] vinyl] benzimidazole, 2- [2- (4-carboxyphenyl) vinyl] benzimidazole, etc. Whitening agent, tris (8-quinolinol) aluminum, bis (8-quinolinol) magnesium, bis (benzo [f] -8-quino Nor) zinc, bis (2-methyl-8-quinolinolate) aluminum oxide, tris (8-quinolinol) indium, tris (5-methyl-8-quinolinol) aluminum, 8-quinolinol lithium, tris (5-chloro-8- Quinolinol) gallium, bis (5-chloro-8-quinolinol) calcium, poly [zinc-bis (8-hydroxy-5-quinolinyl) methane] and other 8-hydroxyquinoline metal complexes and dilithium ependridione Metal chelated oxinoid compounds, 1,4-bis (2-methylstyryl) benzene, 1,4- (3-methylstyryl) benzene, 1,4-bis (4-methylstyryl) benzene, distyrylbenzene, 1 , 4-Bis (2-ethylstyryl) benzene, 1,4-bis (3-ethyl) Styryl) benzene, 1,4-bis (2-methylstyryl) 2-methylbenzene and other styrylbenzene compounds, 2,5-bis (4-methylstyryl) pyrazine, 2,5-bis (4-ethylstyryl) ) Pyrazine, 2,5-bis [2- (1-naphthyl) vinyl] pyrazine, 2,5-bis (4-methoxystyryl) pyrazine, 2,5-bis [2- (4-biphenyl) vinyl] pyrazine, Distil pyrazine derivatives such as 2,5-bis [2- (1-pyrenyl) vinyl] pyrazine, naphthalimide derivatives, perylene derivatives, oxadiazole derivatives, aldazine derivatives, cyclopentadiene derivatives, styrylamine Derivatives, coumarin derivatives, aromatic dimethylidin derivatives and the like are used. Furthermore, anthracene, salicylate, pyrene, coronene and the like are also used. Alternatively, a phosphorescent material such as fac-tris (2-phenylpyridine) iridium can be used. The light emitting layer 112 made of a high molecular weight material or a low molecular weight material can be obtained by forming a layer in which a material is dissolved in a solvent such as toluene or xylene by spin coating and volatilizing the solvent in the solution. .

  In Embodiment 3, the light-emitting layer 112 is described as a single layer for convenience, but the light-emitting layer 112 is sequentially formed from the anode 111 side with the hole transport layer / electron block layer / the above-described organic light-emitting material layer (both The light-emitting layer 112 may have a two-layer structure of an electron transport layer / organic light-emitting material layer (both not shown) in order from the cathode 113 side, or may be positive in order from the anode 111 side. 2 layer structure of hole transport layer / organic light emitting material layer (both not shown), or hole injection layer / hole transport layer / electron blocking layer / organic light emitting material layer / hole blocking layer / A seven-layer structure (both not shown) such as an electron transport layer / electron injection layer may be used. Alternatively, the light emitting layer 112 may have a single layer structure made of only the organic light emitting material described above. As described above, the light-emitting layer 112 in Embodiment Mode 3 includes a case where the light-emitting layer 112 has a multilayer structure having functional layers such as a hole transport layer, an electron block layer, and an electron transport layer. The same applies to other embodiments described later.

The hole transport layer in the functional layer described above preferably has a high hole mobility, is transparent and has good film-forming properties, and besides TPD, porphine, tetraphenylporphine copper, phthalocyanine, copper phthalocyanine, titanium phthalocyanine oxide, etc. Or 1,1-bis {4- (di-P-tolylamino) phenyl} cyclohexane, 4,4 ′, 4 ″ -trimethyltriphenylamine, N, N, N ′, N′-tetrakis ( P-tolyl) -P-phenylenediamine, 1- (N, N-di-P-tolylamino) naphthalene, 4,4′-bis (dimethylamino) -2-2′-dimethyltriphenylmethane, N, N, N ′, N′-tetraphenyl-4,4′-diaminobiphenyl, N, N′-diphenyl-N, N′-di-m-tolyl-4,4′-diaminobiphe Aromatic tertiary amines such as Nyl, N-phenylcarbazole, 4-di-P-tolylaminostilbene, 4- (di-P-tolylamino) -4 ′-[4- (di-P—) Stilbene compounds such as (tolylamino) styryl] stilbene, triazole derivatives, oxazizazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, annealed amine derivatives, amino-substituted chalcones Derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, silazane derivatives, polysilane aniline copolymers, polymer oligomers, styrylamine compounds, aromatic dimethylidin compounds, Poly-3,4 ethylene glycol Organic materials such as polythiophene derivatives such as xylthiophene (PEDT), tetradihexylfluorenylbiphenyl (TFB), and poly-3-methylthiophene (PMeT) are used. Further, a polymer-dispersed hole transport layer in which an organic material for a low-molecular hole transport layer is dispersed in a polymer such as polycarbonate is also used. There is also a _{MoO 3, V 2 O 5,} WO 3, TiO 2, SiO, also be an inorganic oxide such as MgO. These hole transport materials can also be used as an electron block material.

  Examples of the electron transport layer in the functional layer described above include oxadiazole derivatives such as 1,3-bis (4-tert-butylphenyl-1,3,4-oxadiazolyl) phenylene (OXD-7), and anthraquinodimethane derivatives. , Diphenylquinone derivatives, polymer materials composed of silole derivatives, bis (2-methyl-8-quinolinolate)-(para-phenylphenolate) aluminum (BAlq), bathopproin (BCP), and the like are used. Moreover, the material which can comprise these electron carrying layers can also be used as a hole block material.

  After the light emitting layer 112 is formed, the cathode 113 is formed after the film thickness of 40 nm and the molybdenum oxide layer 116 are formed by a vacuum evaporation method. The cathode 113 can be obtained, for example, by forming a layer of metal such as Al by vapor deposition or the like. As the cathode 113 of the organic electroluminescent element 110, a metal or alloy having a low work function, for example, a metal such as Ag, Al, In, Mg, Ti, a Mg alloy such as Mg-Ag alloy, Mg-In alloy, An Al alloy such as an Al—Li alloy, an Al—Sr alloy, an Al—Ba alloy, or the like is used. Alternatively, a first electrode layer in contact with a metal such as Ba, Ca, Mg, Li, or Cs, or an organic material layer made of a fluoride or oxide of these metals such as LiF or CaO, and Ag formed thereon It is also possible to use a laminated structure of a metal made of a second electrode made of a metal material such as Al, In or the like. Here, it is desirable that the work function of the molybdenum oxide layer interposed between the light emitting layer and the cathode has a work function larger than that of the cathode material. Here, the transmittance of the molybdenum oxide layer is 80%. However, by setting the transmittance to 70% or more, it can be applied to a top emission type light-emitting element.

  The optical head using the organic electroluminescent element of Embodiment 3 as shown in FIG. 5 employs a method of outputting light from the selection transistor 130 side of the organic electroluminescent element. The structure of an organic electroluminescent element is called bottom emission. Since the bottom emission structure extracts light from the glass substrate 100 side, the light detection element 120 needs to be made of a highly transparent material, for example, polycrystalline silicon (polysilicon), as described above. The photo-detecting element 120 made of polycrystalline silicon has a problem that the photocurrent generation capability is lower than that made of amorphous silicon, but for example, a capacitor (not shown) is made organic. The problem can be solved by providing a processing circuit that is provided in the vicinity of the electroluminescent element 110 and stores a charge based on the current output from the photodetecting element 120 in a capacitor for a predetermined period of time and then performs voltage conversion. it can. In the case of the bottom emission structure, since the electrode (anode) on the side from which light is extracted can be easily made transparent, there is an advantage that manufacture is simplified.

  FIG. 6 is a configuration plan view showing the configuration in the vicinity of the light detection element of the optical head using the organic electroluminescent element in the third embodiment of the present invention.

As shown in FIG. 6, the optical head using the organic electroluminescent element of Embodiment 3 is configured by arranging a plurality of electroluminescent elements 110 in the main scanning direction (direction of the element row). One light detection element 120 is arranged corresponding to one light emitting region (light emitting region A _LE ). By setting it as such a structure, the light-emission light quantity of each organic electroluminescent element 110 can be measured independently with the photon detection element 120. FIG. That is, it becomes possible to measure the light quantity of the plurality of organic electroluminescent elements 110 at the same time, and the measurement time can be greatly shortened.

In FIG. 6, the light detection element 120, the drain electrode 125 </ b> D as the light detection element output electrode, the source electrode 125 </ b> S as the light detection element ground electrode, the light emission area A _LE , the element area A _R , and the ITO serving as the anode of the light emitting layer 112. (indium tin oxide) 111, interrelationship of the contact hole _{H D} and the drain electrode 134D are shown. The light detection element 120 is connected to a drain electrode 125D as a light detection element output electrode and a source electrode 125S as a light detection element ground electrode. The drain electrode 125D as the light detection element output electrode is an electrode that transmits an electric signal output from the light detection element 120 for light correction to a correction circuit (not shown). A feedback signal generated by the correction circuit is determined based on the electrical signal, and processing necessary for light correction is performed based on the feedback signal. In the third embodiment, the light emission amount of each electroluminescent element 110 is corrected based on this feedback signal, and the current value for driving each electroluminescent element 110 is controlled by a driver circuit (not shown). Yes. As described above, in Embodiment 3, the amount of emitted light is controlled based on the output of the light detection element 120, but so-called PWM control is performed to control the drive time of each electroluminescent element 110 based on the feedback signal. You may comprise as follows.

  The source electrode 125S as the light detection element ground electrode is an electrode for grounding the light detection element 120. ITO (indium tin oxide) 111 which is an anode of the electroluminescent element 110 as a light emitting element is connected to the drain electrode 134D of the selection transistor 130, and the electroluminescent element 110 is connected via the drain electrode 134D. It is controlled by the selection transistor 130.

As shown in FIGS. 5 and 6, the optical head using the organic electroluminescent element according to the third embodiment mainly includes a light detecting element 120 made of polycrystalline silicon (polysilicon) formed in an island shape. arranged in rows in the scanning direction, than the light emission region a _LE at the bottom of each organic electroluminescent light emitting layer 112 where the light emission region a _LE by silicon nitride film 114 serving as the pixel regulating layer in cents element 110 is limited it can be seen that also arranged a light-detecting element 120 having a large element region a _R. By making the element region A _R (island-like portion of polycrystalline silicon formed in an island shape) of the light detection element 120 larger than the light emission region A _LE, a local change in the layer thickness of the light-emitting layer 112 is suppressed. Thus, the bias of the current flowing through the light emitting layer 112 can be suppressed. Therefore, it is possible to manufacture an optical head that achieves a uniform light emission distribution and improved lifetime.

Furthermore, since the element region A _R of the light-detecting element 120 configured in an island shape to be mounted on the optical head of the third embodiment larger than the light emitting area or the light emission region A _LE, the output light from the light-emitting layer It can be efficiently converted into an electrical signal used for light correction.

  Next, a light amount correction circuit used in the optical head of the present invention will be described. As shown in an equivalent circuit in FIG. 7, the light amount correction circuit is formed by being integrated on the glass substrate 100 described above so as to be connected to the driving IC 150 provided with the charge amplifier and the input terminal of the driving IC 150. The correction circuit unit C includes the switching transistor 130, the photodetection element 120, and the capacitor 140 that is connected in parallel to the photodetection element and charges the output current of the photodetection element. Composed. Although not shown in the cross-sectional view of FIG. 5, the capacitor 140 is a conductive film formed in the same process so as to be connected to the source electrode 134S and the drain electrode 134D of the light detection element. It is formed by sandwiching the second insulating films 122 and 123.

Here, the photodetection element is photoelectrically converted in the polycrystalline silicon layer 121i by the light from the electroluminescent element, and the current flowing from the source region to the drain region is taken out as a photocurrent. Is detected. However, as described above, the ITO electrode 111 that is the anode of the electroluminescent element 110 is used as a gate electrode, and an electric field is applied to the polycrystalline silicon layer 121i that is the channel region of the photodetecting element by the potential of the gate electrode. As a result, the drain current _ID flows. Since the drain current _ID is added to the photoelectric conversion current, the photoelectric conversion current output from the drain electrode 125D as a sensor output to the correction circuit unit C (see FIG. 7) is converted into the actual photoelectric conversion current. The current _ID is added. For this reason, there exists a problem that the light quantity detection accuracy falls. The result of measuring the relationship between the gate voltage Vg and the drain current ID is shown by a solid line in FIG. As is apparent from this figure, it is desirable to use the thin film transistor in a region where the drain current is 0, that is, a region where the transistor operation is turned off (OFF region).

Desirably, the thin film transistor can be used in the OFF region and almost no dark current can be obtained by shifting the gate potential in the minus direction as shown by the broken line in FIG.
Further, the channel is controlled by the gate electric field when the entire polycrystalline silicon layer 121i, which is the channel region of the thin film transistor that constitutes the photodetecting element, is completely covered with the ITO electrode that is the anode of the electroluminescent element. It is more effective.
In the present invention, since it is extremely important to detect the output of the light detection element with high accuracy, it is important to detect the thin film transistor constituting the light detection element in the OFF state.
In addition, the state in which the entire polycrystalline silicon layer that becomes the channel region 121i of the thin film transistor that constitutes the photodetecting element is completely covered with the ITO electrode that is the anode of the electroluminescent element controls the channel by the gate electric field. It is more effective.

The output of the photodetecting element is obtained by taking out a current charged in the capacitor 140 for a desired number of lighting times by switching the selection transistor 130 as shown in the timing charts of FIGS. Highly accurate light quantity detection is possible. Here, FIG. 9A is a diagram showing the state of charge, FIG. 9B is a diagram showing the operation of the selection transistor, and FIG. 9C is a diagram showing the lighting timing of the electroluminescent element, 9D is a diagram showing the potential of the capacitive element 140, FIG. 9E is a diagram showing the output voltage of the operational amplifier, FIG. 9F is a diagram showing a data read operation, and FIG. ) Is a diagram showing a light amount detection signal.
In addition, since it is very important to detect the output of the light detection element with high accuracy, it is important to detect the thin film transistor constituting the light detection element in an OFF state. Therefore, a desired detection accuracy can be obtained by adjusting the gate potential of the light detection element.

First, the selection transistor 130 is turned on, and the capacitor 140 is charged with the initial voltage V _ref (S1: reset step).
When the selection transistor 130 is turned off, the charge charged in the capacitor element 140 is reduced by the photocurrent flowing through the light detection element 120 (S2: lighting step).
In this state, the switch SW of the charge amplifier 150 is turned OFF, and the charge amplifier is in a measurable state (S3: measurement start step).
Then, the selection transistor 130 is turned on, and the charge lost in the capacitor element 140 is supplied from the capacitor element C _ref of the charge amplifier. As a result, the output voltage V _r0 of the operational amplifier of the charge amplifier 150 increases. Also during this period, the photocurrent of the photodetecting element flows and _Vr0 increases (S4: charge transfer step).
Then, the selection transistor 130 is turned off and V _r0 is determined. This voltage is taken in by the AD converter, and the photometric operation is completed (S5: read step).

As a modification of the third embodiment of the present invention, as shown in FIG. 10, a light shielding film 104 made of a chrome thin film is formed on the back surface side of the glass substrate, and the second light emission region A _LE1 is defined by this opening. is doing. By forming the second light emitting region _ALE1 smaller than the opening of the silicon nitride film 114 as the pixel defining portion described in the third embodiment, a step portion of the light emitting layer caused by the silicon nitride film 114 is formed. It can be excluded from the light emission region, and the light emitting layer can be made more uniform. Other configurations are the same as those in the third embodiment.

In the above optical head, the anode as the first electrode 111 of the electroluminescent element may be formed so as to have the same width as the channel region 121i.
With this configuration, the gate electric field is applied with high efficiency, and the light emitting layer itself of the electroluminescent element is formed on a flat surface. It can be avoided. At this time, since the light emitting region does not become a light emitting region on the source / drain region, the light emitting region and the light emitting region can be substantially matched, and a fine line light emitting region can be obtained. Therefore, it is possible to avoid crosstalk when the pitch is increased due to miniaturization. Thus, since a small exposure spot (line) can be obtained in the sub-scanning direction, it is effective for multi-value reproduction based on area modulation.
The exposure head and the photoconductor move relative to each other in the sub-scanning direction, and the exposure area changes with this relative movement. Considering only from the aspect of area modulation, it is ideal that the exposure spot shape is a single line having no width in the sub-scanning direction. However, the light emission luminance in this case must be infinite. That is, in this case, since the light emitting area in the sub-scanning direction becomes small, the light emitting area becomes small, and the exposure condition becomes strict in terms of energy, so it is necessary to increase the luminance.

(Embodiment 4)
Next, FIG. 11 of the present invention is a cross-sectional view in the case where the organic electroluminescent element used in the optical head has a top emission structure. In contrast to the bottom emission structure, the top emission structure is a type in which light output from the light emitting layer 112 is output to the cathode side above the light emitting layer 112. In the configuration of FIG. 11, a reflective layer 105 made of metal is provided on the glass substrate 100, and the light output is on the cathode side.
Here, since light is extracted to the cathode side, the transmittance of the molybdenum oxide layer 116 interposed between the light emitting layer and the cathode is preferably 70% or more.

  When this structure is adopted, as shown in the figure, among the light generated in the light emitting layer 112 of the organic electroluminescent element 110, the light (not shown) is emitted by the light emitted in the direction opposite to the light detecting element 120. (See 28Y to 28K in FIG. 13 to be described later). On the other hand, the light generated in the light emitting layer 112 is also emitted in the direction opposite to the direction used for exposure, that is, the light detection element 120 side, and this light is received by the light detection element 120.

  When the top emission structure is adopted, it is not necessary for the light used for exposure to pass through the photodetecting element 120. Therefore, the photodetecting element 120 does not need to dare to use highly transparent polycrystalline silicon, and has a high photocurrent generation capability. The photodetecting element 120 may be composed of amorphous silicon (amorphous silicon).

  Now, in order to implement the top emission structure, the cathode needs to be made of a transparent metal material, which is technically difficult. Therefore, as shown in FIG. 11, a very thin metal layer (thin film cathode) 113a such as Al or Ag and a transparent electrode 113b such as ITO are laminated and used as a cathode. Since the metal layer 113a is very thin, it is possible to realize a cathode with a light-transmitting property. The top emission structure requires a larger number of manufacturing steps than the bottom emission structure, and thus the manufacturing cost increases. However, an optical head with good light emission efficiency can be configured.

  The configuration and operation of the electroluminescent element 110 and the photodetecting element 120 constituting the optical head have been described above in detail. Although the light emitting element (electroluminescent element) row in the optical head has been described as one row in the third embodiment, it may be constituted in a plurality of rows so as to substantially increase the amount of emitted light.

  Of course, the above-described structures of the electroluminescent element 110 and the light detecting element 120 can be applied two-dimensionally to a display device.

As a modification of the fourth embodiment of the present invention, as shown in FIG. 12, a light shielding film 106 made of a chrome thin film is formed on the back surface side of the glass substrate, and the second light emitting area A _LE1 is defined by this opening. is doing. By forming the second light emitting region _ALE1 smaller than the opening of the silicon nitride film 114 as the pixel defining portion described in the third embodiment, a step portion of the light emitting layer caused by the silicon nitride film 114 is formed. It can be excluded from the light emission region, and the light emitting layer can be made more uniform. Other configurations are the same as those in the third embodiment.

(Embodiment 5)
FIG. 13 is a diagram showing a configuration of an image forming apparatus 21 equipped with an optical head using the organic electroluminescent element of the present invention. In FIG. 13, an image forming apparatus 21 has four color developing stations arranged vertically in a stepwise manner in a vertical direction in a yellow developing station 22Y, a magenta developing station 22M, a cyan developing station 22C, and a black developing station 22K. Is provided with a paper feed tray 24 in which the recording paper 23 is accommodated, and a recording paper transport serving as a transport path for the recording paper 23 supplied from the paper feed tray 24 at locations corresponding to the developing stations 22Y to 22K. The path 25 is arranged in the vertical direction from the top to the bottom.

  The developing stations 22Y to 22K form yellow, magenta, cyan, and black toner images in order from the upstream side of the recording paper conveyance path 25. The yellow developing station 22Y includes a photoconductor 28Y and a magenta developing station 22M. The photosensitive member 28M and the cyan developing station 22C include the photosensitive member 28C, the black developing station 22K includes the photosensitive member 28K, and each developing station 22Y to 22K includes a series of electrophotographic systems such as a developing sleeve and a charger (not shown). The member which implement | achieves the image development process in is included.

  Further, exposure devices 33Y, 33M, 33C, and 33K for exposing the surfaces of the photoreceptors 28Y to 28K to form electrostatic latent images are disposed below the developing stations 22Y to 22K. The optical head shown in the third embodiment is mounted on the exposure apparatuses 33Y, 33M, 33C, and 33K.

  The developing stations 22Y to 22K are different in the color of the filled developer, but the configuration is the same regardless of the developing color. Therefore, the developing stations are excluded unless particularly necessary to simplify the following description. 22, the photosensitive member 28, and the exposure device 33 will be described without specifying specific colors.

  FIG. 14 is a configuration diagram showing the periphery of the developing station 22 in the image forming apparatus 21 according to the fourth embodiment of the present invention. In FIG. 14, the developer station 22 is filled with a developer 26 which is a mixture of carrier and toner. Reference numerals 27a and 27b denote stirring paddles for stirring the developer 26. The toner in the developer 26 is charged to a predetermined potential by friction with the carrier by the rotation of the stirring paddles 27a and 27b, and the interior of the developing station 22 is also charged. By circulating, the toner and the carrier are sufficiently stirred and mixed. The photoreceptor 28 is rotated in the direction D3 by a driving source (not shown). A charger 29 charges the surface of the photoreceptor 28 to a predetermined potential. 30 is a developing sleeve, and 31 is a thinning blade. The developing sleeve 30 has a mag roll 32 having a plurality of magnetic poles formed therein. The layer thickness of the developer 26 supplied to the surface of the developing sleeve 30 is regulated by the thinning blade 31 and the developing sleeve 30 is rotated in a direction D4 by a driving source (not shown). The developer 26 is supplied to the surface of the developing sleeve 30 by the action, and an electrostatic latent image formed on the photoconductor 28 is developed by an exposure device to be described later, and the developer 26 that has not been transferred to the photoconductor 28 is developed in the developing station. 22 is collected inside.

  Reference numeral 33 denotes the exposure apparatus already described. In the image forming apparatus 21 to which the exposure apparatus 33 equipped with the optical head using the organic electroluminescent element of the third embodiment is applied, the exposure apparatus 33 forms a latent image stably over a long period of time as described above. Therefore, the product life is long and the exposure apparatus 33 equipped with the optical head of Embodiment 3 can always form a high-quality image because an electrostatic latent image of a desired shape can be obtained over a long period of time.

  In the exposure apparatus 33 according to the fourth embodiment, organic electroluminescent elements are linearly arranged at a resolution of 600 dpi (dot / inch), and the photosensitive member 28 charged to a predetermined potential by the charger 29 is used. An electrostatic latent image of maximum A4 size is formed by selectively turning on / off the organic electroluminescent element according to the image data. Only the toner of the developer 26 supplied to the surface of the developing sleeve 30 adheres to the electrostatic latent image portion, and the electrostatic latent image is visualized.

  A transfer roller 36 is provided at a position facing the recording paper conveyance path 25 with respect to the photoreceptor 28, and is rotated in the direction D5 by a driving source (not shown). A predetermined transfer bias is applied to the transfer roller 36, and the toner image formed on the photoconductor 28 is transferred to the recording paper conveyed through the recording paper conveyance path 25.

  Hereinafter, the description will be continued returning to FIG.

  As described above, the image forming apparatus 21 according to the fourth embodiment is a tandem color image forming apparatus in which a plurality of developing stations 22Y to 22K are arranged in a stepwise manner in the vertical direction, and is equivalent to a color inkjet printer. It aims at the size of. Since a plurality of units are arranged in the developing stations 22Y to 22K, in order to reduce the size of the image forming apparatus 21, the developing stations 22Y to 22K themselves are reduced in size and are arranged around the developing stations 22Y to 22K. It is necessary to reduce the members involved in the image process and to reduce the arrangement pitch of the developing stations 22Y to 22K as much as possible.

  In consideration of user convenience when installing the image forming apparatus 21 on the desktop in an office or the like, in particular, accessibility to the recording paper 23 at the time of paper feeding or paper ejection, from the bottom surface of the image forming apparatus 21 to the paper feed port 65. The height is preferably 250 mm or less. In order to realize this, it is necessary to suppress the height of the entire developing stations 22Y to 22K to about 100 mm in the entire configuration of the image forming apparatus 21.

  However, the existing LED head, for example, has a thickness of about 15 mm, and if it is disposed between the developing stations 22Y to 22K, it is difficult to achieve the target. According to the examination results of the present inventors, when the thickness of the exposure device 33 is 7 mm or less, the height of the entire development station is 100 mm or less even if the exposure devices 33Y to 33K are arranged in the gaps between the development stations 22Y to 22K. It is possible to suppress.

  A toner bottle 37 stores yellow, magenta, cyan, and black toners. A toner transport pipe (not shown) is provided from the toner bottle 37 to each of the developing stations 22Y to 22K, and supplies toner to each of the developing stations 22Y to 22K.

  A paper feed roller 38 is rotated in the direction D1 by controlling an electromagnetic clutch (not shown), and feeds the recording paper 23 loaded in the paper feeding tray 24 to the recording paper transport path 25.

  A registration paper 39 and a pair of pinch rollers 40 are provided as a nip conveyance means on the inlet side in the recording paper conveyance path 25 positioned between the paper supply roller 38 and the transfer portion of the most upstream yellow developing station 22Y. The registration roller 39 and the pinch roller 40 pair temporarily stop the recording paper 23 conveyed by the paper supply roller 38 and convey it in the direction of the yellow developing station 22Y at a predetermined timing. This temporary stop restricts the leading edge of the recording paper 23 in parallel with the axial direction of the registration roller 39 and pinch roller 40 pair, thereby preventing the recording paper 23 from skewing.

  Reference numeral 41 denotes a recording paper passage detection sensor. The recording paper passage detection sensor 41 is constituted by a reflective sensor (photo reflector), and detects the leading edge and the trailing edge of the recording paper 23 based on the presence or absence of reflected light.

  When the rotation of the registration roller 39 is started (the power transmission is controlled by an electromagnetic clutch (not shown) and the rotation is turned ON / OFF), the recording paper 23 is conveyed along the recording paper conveyance path 25 in the direction of the yellow developing station 22Y. However, starting from the rotation start timing of the registration roller 39, the writing timing of the electrostatic latent images by the exposure devices 33Y to 33K disposed in the vicinity of the developing stations 22Y to 22K is independently controlled.

  A fixing device 43 is provided as a nip conveying means on the outlet side in the recording paper conveyance path 25 located further downstream of the most downstream black developing station 22K. The fixing device 43 includes a heating roller 44 and a pressure roller 45. The heating roller 44 is a multi-layered roller composed of a heating belt, a rubber roller, and a core material (both not shown) in order from the surface. Among them, the heat generating belt is a belt having a three-layer structure, and is composed of a release layer, a silicon rubber layer, and a base material layer (both not shown) from the side closer to the surface. The release layer is made of a fluororesin having a thickness of about 20 to 30 micrometers and imparts release properties to the heating roller 44. The silicon rubber layer is made of silicon rubber having a thickness of about 170 micrometers and gives the pressure roller 45 appropriate elasticity. The base material layer is made of a magnetic material that is an alloy of iron, nickel, chromium, or the like.

  A back core 26 includes an exciting coil. Inside the back core 46, an excitation coil in which a predetermined number of copper wires (not shown) whose surfaces are insulated is bundled in the direction of the rotation axis of the heating roller 44, and at both ends of the heating roller 44, the heating roller It circulates along the circumferential direction of 44. When an alternating current of about 30 kHz is applied to the exciting coil from an exciting circuit (not shown) that is a semi-resonant inverter, a magnetic flux is generated in a magnetic path constituted by the back core 46 and the base layer of the heating roller 44. Due to this magnetic flux, an eddy current is formed in the base material layer of the heat generating belt of the heating roller 44 and the base material layer generates heat. The heat generated in the base material layer is transmitted to the release layer through the silicon rubber layer, and the surface of the heating roller 44 generates heat.

  Reference numeral 47 denotes a temperature sensor for detecting the temperature of the heating roller 44. The temperature sensor 47 is a ceramic semiconductor obtained by sintering at a high temperature using a metal oxide as a main raw material, and it is possible to measure the temperature of a contacted object by applying a change in load resistance according to the temperature. it can. The output of the temperature sensor 47 is input to a control device (not shown). The control device controls the power output to the exciting coil inside the back core 46 based on the output of the temperature sensor 47, and the surface temperature of the heating roller 44 is about 170 °. Control to be C.

  When the recording paper 23 on which the toner image is formed is passed through the nip formed by the heating roller 44 and the pressure roller 45 that are controlled in temperature, the toner image on the recording paper 23 is connected to the heating roller 44. The toner image is fixed on the recording paper 23 by being heated and pressurized by the pressure roller 45.

  A recording paper trailing edge detection sensor 48 monitors the discharge state of the recording paper 23. Reference numeral 52 denotes a toner image detection sensor. The toner image detection sensor 52 is a reflective sensor unit that uses an electroluminescent element (both visible light) as a plurality of light emitting elements having different emission spectra and a single light receiving element (light detecting element). The image density is detected by utilizing the fact that the absorption spectrum differs depending on the image color between the background and the image forming portion. Further, since the toner image detection sensor 52 can detect not only the image density but also the image forming position, in the image forming apparatus 21 according to the third embodiment, two toner image detection sensors 52 are provided in the width direction of the image forming apparatus 21 to perform recording. The image formation timing is controlled based on the detection position of the image displacement amount detection pattern formed on the paper 23.

  53 is a recording paper transport drum. The recording paper transport drum 53 is a metal roller whose surface is covered with rubber having a thickness of about 200 micrometers, and the recording paper 23 after fixing is transported along the recording paper transport drum 53 in the direction D2. At this time, the recording sheet 23 is cooled by the recording sheet conveying drum 53 and is bent and conveyed in the direction opposite to the image forming surface. As a result, curling that occurs when a high density image is formed on the entire surface of the recording paper can be greatly reduced. Thereafter, the recording paper 23 is conveyed in the direction D6 by the kicking roller 55 and discharged to the paper discharge tray 59.

  Reference numeral 54 denotes a face-down paper discharge unit. The face-down paper discharge unit 54 is configured to be rotatable about the support member 56. When the face-down paper discharge unit 54 is opened, the recording paper 23 is discharged in the direction D7. In the closed state, the face-down paper discharge unit 54 is formed with ribs 57 along the transport path on the back surface so as to guide the transport of the recording paper 23 together with the recording paper transport drum 53.

  Reference numeral 58 denotes a drive source, and a stepping motor is employed in the third embodiment. By the drive source 58, peripheral portions of the developing stations 22Y to 22K including the paper feed roller 38, the registration roller 39, the pinch roller 40, the photoconductors (28Y to 28K), and the transfer rollers (36Y to 36K), the fixing device 43, The recording paper transport drum 53 and the kicking roller 55 are driven.

  A controller 61 receives image data from a computer (not shown) via an external network and develops and generates printable image data.

  Reference numeral 62 denotes an engine control unit. The engine control unit 62 controls the hardware and mechanism of the image forming apparatus 21, forms a color image on the recording paper 23 based on the image data transferred from the controller 61, and performs overall control of the image forming apparatus 21. Yes.

  63 is a power supply unit. The power supply unit 63 supplies power of a predetermined voltage to the exposure apparatuses 33Y to 33K, the drive source 58, the controller 61, and the engine control unit 62, and supplies power to the heating roller 44 of the fixing device 43. The power supply unit also includes a so-called high-voltage power supply system such as charging of the surface of the photosensitive member 28, a developing bias applied to the developing sleeve (see reference numeral 30 in FIG. 11), and a transfer bias applied to the transfer roller 36. .

  The power supply unit 63 includes a power supply monitoring unit 64 so that at least the power supply voltage supplied to the engine control unit 62 can be monitored. This monitor signal is detected by the engine control unit 62 to detect a drop in power supply voltage that occurs when the power switch is turned off or a power failure occurs.

  In the above description, the case where the present invention is applied to a color image forming apparatus has been described. However, the present invention can also be applied to a single color image forming apparatus such as black. When applied to a color image forming apparatus, the development colors are not limited to four colors of yellow, magenta, cyan and black.

  Since the image forming apparatus 21 of the present invention is equipped with exposure apparatuses 33Y to 33K having a uniform light emission distribution and excellent durability, the image forming apparatus 21 is excellent in image quality and durability.

(Embodiment 6)
Next, a display device using the organic electroluminescent element of the present invention will be described. In the display device of this embodiment, a light emitting layer is formed by an inkjet method on a transition metal oxide layer having an ionization potential of about 5.6 eV through a TFB (not shown) as a buffer layer. FIG. 16 is an equivalent circuit diagram of the active matrix display device, FIG. 16 is an explanatory layout diagram, and FIG. 17 is an upper surface explanatory diagram. The active matrix display device includes a drive circuit formed in each pixel. is there.

  As shown in an equivalent circuit diagram in FIG. 15 and a layout explanatory diagram in FIG. 16, the display device 140 includes an organic electroluminescent element (electroluminescent) 110 and a switching transistor 130 that form pixels, and a photodetecting element. A plurality of drive circuits consisting of two current transistors 120 (T1, T2) and a capacitor C are arranged in the vertical and horizontal directions, and the gate of the first TFT (T1) of each drive circuit arranged in the horizontal direction. An electrode is connected to the scanning line 143 to give a scanning signal, and a drain electrode of the first TFT of each driving circuit arranged in the vertical direction is connected to the data line to supply a light emission signal. A driving power source (not shown) is connected to one end of the electroluminescent element (electroluminescent), and one end of the capacitor C is grounded. Reference numeral 143 denotes a scanning line, 144 denotes a signal line, 145 denotes a common power supply line, 147 denotes a scanning line driver, 148 denotes a signal line driver, and 149 denotes a common power supply line driver.

  FIG. 17 is an explanatory top view of this display device. A transition comprising an anode (ITO) 111, a molybdenum oxide layer having an ionization potential of 5.6 eV, etc. on a glass substrate 100 on which a driving thin film transistor (not shown) is formed. A metal oxide layer 115, a charge blocking layer 116, a light emitting layer 112, and a cathode 113 are formed to form an organic electroluminescent element. As a structure, the anode and the charge injection layer are formed separately, the light emitting layer to the pixel regulating layer 114 are formed from the buffer layer, and the cathode is formed in a stripe shape. In this driving thin film transistor, for example, an organic semiconductor layer (polymer layer) is formed on a glass substrate 100, which is covered with a gate insulating film, a gate electrode is formed thereon, and a through electrode formed on the gate insulating film. Source / drain electrodes are formed through holes. Then, a polyimide film or the like is applied thereon to form an insulating layer (flat layer), and an anode (ITO) 111, a molybdenum oxide layer, an electron blocking layer, an organic semiconductor layer such as a light emitting layer, and a cathode 115 are formed thereon. It has the structure which formed and formed the organic electroluminescent element. In FIG. 17, although capacitors and wirings are omitted, these are also formed on the same glass substrate. A plurality of pixels composed of such TFTs and organic electroluminescent elements are formed in a matrix on the same substrate to constitute an active matrix display device.

  At the time of manufacture, as shown in FIG. 16, a light emitting layer is formed by an ink jet method in an opening 153 formed by a pixel regulating layer 114 formed of an insulating layer.

That is, in manufacturing, the pixel regulation layer 114 is formed on the scanning line 143, the signal line 144, the switching TFT 130, the pixel electrode 111, and the like formed on the glass substrate 100, and then an opening is provided.
Then, a transition metal oxide layer is formed on the entire surface by vapor deposition.
Thereafter, TFB is applied as necessary by an inkjet method. This TFB layer may be applied to the entire surface in the same manner as the transition metal oxide layer, or may be applied only to a portion corresponding to the opening.
Then, after a drying process, a polymer organic EL material corresponding to a desired color (any of RGB) is applied to a position corresponding to the opening by an inkjet method.
Finally, a cathode (not shown) is formed in the region where the display pixel 141 is disposed.

  According to this configuration, a display device that can be driven at high speed and has high reliability can be provided.

  Next, an example of a lighting device in which a plurality of electroluminescent elements 1 are two-dimensionally arranged will be described with reference to FIG. With respect to the electroluminescent elements 110 arranged two-dimensionally, for example, a configuration in which all the electroluminescent elements 1 are simultaneously turned on / off can be realized very easily. However, even in such a configuration where the light is turned on / off all at once, at least one electrode (for example, a pixel electrode made of ITO (see the anode 111 in FIG. 1)) is one unit of each electroluminescent element. It is desirable to have a separate structure. This is because even if the display pixel 141 is defective due to some factor, the defect remains in the display pixel 141, so that the manufacturing yield of the entire lighting device can be improved. The lighting device having such a configuration can be applied to a general lighting fixture in a home, for example. In this case, since the lighting device can be configured to be extremely thin, it can be easily installed not only on the ceiling but also on the wall surface.

  In addition, the electroluminescent device 1 arranged in a two-dimensional manner can easily control the light emission pattern by supplying arbitrary data, and the electroluminescent device 1 according to the present invention includes: Since the light emitting region can be configured with a size of, for example, about 40 μm square, an application can be configured in which data is supplied to the lighting device and also used as a panel type display device. Of course, in this case, the display pixel 141 needs to be painted in red, green, and blue depending on the position, but according to the ink jet method, it is possible to increase the number of colors very easily.

  Conventionally, when a lighting device and a display device are compared, the light emission luminance of the lighting device is larger. However, since the electroluminescent device 110 according to the present invention has extremely high light emission luminance, the lighting device and the display device can be used together. In this case, the illumination device and the display device require a mechanism for adjusting the light emission luminance due to the difference in function (that is, the use mode). For this mechanism, for example, the configuration shown in the third embodiment is adopted. This can be realized by controlling the drive current to adjust the light emission luminance of each electroluminescent element 1. That is, when used as a lighting device, all the electroluminescent elements 1 are driven with a larger current, and when used as a display device, the current value is small and controlled according to the gradation (that is, image data). Each electroluminescent element 1 may be driven. In such an application, the power source for functioning as a lighting device and the power source for functioning as a display device may be a single power source. In the case where the number of gray levels when using as a display device is large, the power source (not shown) connected to the common power supply line 145 shown in FIGS. 15 and 16 is switched according to the use mode. It is desirable to use a simple configuration. Of course, even in a mode of use as a lighting device, in a mode where brightness control is necessary (that is, a lighting device having a dimming function), it is easily handled by current value control according to the gradation described above. be able to. Moreover, since the electroluminescent element 1 of the present invention can be formed not only on the glass substrate 2 but also on a resin substrate such as PET, it can be applied as various illumination devices.

  Note that the thin film transistor may be an organic transistor. A structure in which an organic electroluminescent element is stacked on a thin film transistor or a structure in which a thin film transistor is stacked on an organic electroluminescent element is also effective.

  In addition, in order to obtain a high-quality electroluminescent display device, an electroluminescent substrate on which an organic electroluminescent element is formed and a TFT substrate on which a TFT, a capacitor, wiring, and the like are formed are electroluminescent. The electrodes on the cent substrate and the electrodes on the TFT substrate may be bonded together using a connection bank.

  In the above description, the organic electroluminescent element is driven by DC, but may be driven by AC voltage, AC current, or pulse wave.

The organic electroluminescent device of the present invention is a material having a buffer layer having an absolute value of energy value representing the electron affinity of the buffer layer (hereinafter referred to as electron affinity) smaller than the electron affinity of the layer having the light emitting function. It is desirable to use
With this configuration, the loss of charge can be blocked, and the charge can effectively contribute to light emission in the light emitting layer.

  In addition, as the oxide used as the charge injection layer here, chromium (Cr), tungsten (W), vanadium (V), niobium (Nb), tantalum (Ta), titanium (Ti), zirconium (Zr), Hafnium (Hf), scandium (Sc), yttrium (Y), thorium (Tr), manganese (Mn), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), nickel (Ni), Copper (Cu), zinc (Zn), cadmium (Cd), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), Examples include oxides such as antimony (Sb), bismuth (Bi), and so-called rare earth elements from lanthanum (La) to lutetium (Lu). Among these, aluminum oxide (AlO), copper oxide (CuO), and silicon oxide (SiO) are particularly effective for extending the life.

  In addition, there are very many types of nitrides, and many of them are used as functional materials. Films can be formed mainly by sputtering or CVD. Various compounds are known, ranging from those used as semiconductors to those with very high insulation properties. However, as a result of various experiments, the film thickness of highly insulating compounds is about 5 nm during film formation. It was found that carrier injection becomes possible by making the following. Specific examples of the compound include the following, and titanium nitride (TiN) is preferable. TiN is known as a very robust material and is stable to heat.

  In addition, gallium nitride (GaN), indium nitride (InN), aluminum nitride (AlN), boron nitride (BN), silicon nitride (SiN), magnesium nitride (MgN), molybdenum nitride (MoN), calcium nitride (CaN) Niobium nitride (NbN), tantalum nitride (TaN), vanadium nitride (BaN), zinc nitride (ZnN), zirconium nitride (ZrN), iron nitride (FeN), copper nitride (CuN), barium nitride (BaN), nitride Lanthanum (LaN), chromium nitride (CrN), yttrium nitride (YN), lithium nitride (LiN), titanium nitride (TiN), and composite nitrides thereof are also applicable.

In the organic electroluminescent device of the present invention, the charge injection layer may contain an oxynitride, preferably a transition metal oxynitride.
For example, ruthenium (Ru) oxynitride crystal Ru4Si ₂ O ₇ N _{2 and the} like are extremely heat-resistant (1500 ° C.) and stable, and therefore can be applied as a charge injection layer by forming a thin film. . In this case, the film can be formed by performing a heat treatment after forming the film by a sol-gel method.

In addition, barium sialon (BaSiAlON), calcium sialon (CaSiAlON), cerium sialon (CeSiAlON), lithium sialon (LiSiAlON), magnesium sialon (MgSiAlON), scandium sialon (ScSiAlON), yttrium sialon (YSiAlON), erbium sialon (E) Further, sialons containing elements of group IA, IIA, IIIB such as neodymium sialon (NdSiAlON), or oxynitrides such as multi-element sialon are applicable. These can be formed by CVD, sputtering, or the like. In addition, lanthanum silicon oxynitrate (LaSiON), lanthanum europium silicon oxynitride (LaEuSi ₂ O ₂ N ₃ ), silicon oxynitride (SiON ₃ ), and the like are also applicable. Since these are mostly insulators, it is necessary to reduce the film thickness to about 1 nm to 5 nm. These compounds have a large exciton confinement effect and may be formed on the side where electrons are injected.

In the organic electroluminescent device of the present invention, the charge injection layer may include a composite oxide containing a transition metal. Although the reason is not clear, when the composite oxide containing a transition metal is used for the charge injection layer, the emission intensity can be greatly improved.
In addition, there are a great many types of complex oxides, and many of them have electronically interesting properties. Specific examples include the following compounds, but these are merely examples.

For example, barium titanate (BaTiO ₃ ), strontium titanate (SrTiO ₃ ), calcium titanate (CaTiO ₃ ), potassium niobate (KNbO ₃ ), bismuth iron oxide (BiFeO ₃ ), lithium niobate (LiNbO ₃₎ ), sodium vanadate (Na ₃ VO _4), vanadium iron (FeVO _3), titanate vanadium (TiVO _3), chromic acid vanadium (CRVO _3), vanadium, nickel (NiVO _3), magnesium vanadate (MgVO ₃ ), calcium vanadate (Cavo _3), vanadium lanthanum (LaVO _3), molybdate vanadium (VMoO _5), molybdate vanadium (V ₂ MoO _8), lithium vanadate (LiV ₂ O _5), magnesium silicate (Mg ₂ SiO ₄ ), magnesium silicate (MgSiO ₃ ), zirconium titanate (ZrTiO ₄ ), strontium titanate (SrTiO ₃ ), lead magnesium acid (P bMgO ₃ ), lead niobate (PbNbO ₃ ), barium borate (BaB ₂ O ₄ ), lanthanum chromate (LaCrO ₃ ), lithium titanate (LiTi ₂ O ₄ ), lanthanum cuprate (LaCuO ₄ ), titanate Zinc (ZnTiO ₃ ), calcium tungstate (CaWO ₄ ), and the like are possible.

Although any of these can be used to carry out the present invention, barium titanate (BaTiO ₃ ) is preferably used. BaTiO ₃ is a typical dielectric and is a complex oxide with high insulating properties, but it is possible to inject carriers when used in thin films based on the results of various experiments. I understood. BaTiO ₃ and strontium titanate (SrTiO ₃ ) are stable as compounds and have a very large dielectric constant, so that efficient carrier injection can be performed. For film formation, a sputtering method, a sol-gel method, a CVD method, or the like can be selected as appropriate.

Moreover, the organic electroluminescent element of this invention contains what includes the said buffer layer arrange | positioned between the charge injection layer arrange | positioned at the hole injection side, and the layer which has a light emission function.
With this configuration, the escape of electrons can be blocked, and the electrons can effectively contribute to light emission in the layer having a light emitting function.

  The electroluminescent element of the present invention can be applied to a copying machine, a printer, a multifunction printer, a facsimile, etc. as an optical head and an image forming apparatus.

Cross-sectional schematic diagram of organic electroluminescent element 110 according to Embodiment 1 of the present invention The figure which shows the luminescent property of the organic electroluminescent element Cross-sectional schematic diagram of organic electroluminescent element 110 according to Embodiment 2 of the present invention The figure which shows the luminescent property of the organic electroluminescent element The figure which shows the principal part cross section of the optical head as described in Embodiment 3 of this invention. Plane explanatory diagram of the optical head Equivalent circuit diagram of a light amount detection circuit of an optical head using the organic electroluminescent element according to the third embodiment of the present invention The figure which shows the characteristic of the photon detection element of the optical head using the organic electroluminescent element as described in Embodiment 3 of this invention. The figure which shows the light quantity detection flow of the optical head using the organic electroluminescent element as described in Embodiment 3 of this invention. Sectional drawing which shows the modification of the optical head using the organic electroluminescent element as described in Embodiment 3 of this invention. Sectional drawing at the time of comprising the organic electroluminescent element of Embodiment 4 of this invention with a top emission structure Sectional drawing which shows the modification of the optical head as described in Embodiment 4 of this invention. Configuration diagram of an image forming apparatus 21 using the optical head according to the fifth embodiment of the present invention. Configuration diagram showing the periphery of the developing station 22 in the image forming apparatus 21 according to the fifth embodiment of the present invention. Top view of the display device according to Embodiment 6 of the present invention. Cross-sectional schematic diagram of organic electroluminescent element 110 of a conventional example The figure which shows the luminescent property of the organic electroluminescent element Cross-sectional schematic diagram of organic electroluminescent element 110 of a conventional example

Explanation of symbols

100 glass substrate 101 overcoat layer 110 electroluminescent device 111 anode 112 light-emitting layer 113 cathode 114 pixel regulating layer 115 metal oxide layer _(MoO 3)
120 Photodetector 121 Polycrystalline silicon layer 121S, D source / drain region 121i Channel region 122 First insulating layer 123 Second insulating layer 124 Protective layer 125S, D source / drain electrode 130 Drive transistor 131 Active layers 132S, D Source / drain region 133 Gate electrode 134S, D Source / drain electrode 21 Image forming apparatus 22 Developing station 22Y Developing station 22M Developing station 22C Developing station 22K Developing station 23 Recording paper 24 Paper feed tray 25 Recording paper transport path 26 Developer 27a Stirring Paddle 27b stirring paddle 28 photoconductor 28Y photoconductor 28M photoconductor 28C photoconductor 28K photoconductor 29 charger 30 developing sleeve 31 thinning blade 32 mag roll 33 exposure device 33Y dew Device 33M Exposure device 33C Exposure device 33K Exposure device 36 Transfer roller 37 Toner bottle 38 Paper feed roller 39 Registration roller 40 Pinch roller 41 Recording paper passage detection sensor 43 Fixing device 44 Heating roller 45 Pressure roller 46 Back core 47 Temperature sensor 48 Recording Paper trailing edge detection sensor 52 Toner image detection sensor 53 Recording paper transport drum 54 Face down discharge section 55 Kicking roller 56 Support member 57 Rib 58 Drive source 59 Paper discharge tray 61 Controller 62 Engine control section 63 Power supply section 64 Power supply monitoring section 65 Paper feed slot

Claims (25)

An anode and a cathode, and a plurality of functional layers formed between the anode and the cathode,
The functional layer includes an organic electroluminescence layer including a layer having a light emitting function made of at least one organic semiconductor and at least one transition metal oxide layer between the cathode and the layer having the light emitting function. Cent element. The organic electroluminescent device according to claim 1,
The organic electroluminescent element whose thickness of the said transition metal oxide layer is 1 nm or more and 1 micrometer or less. The organic electroluminescent device according to claim 1,
The organic electroluminescent element whose transmittance | permeability of the said transition metal oxide layer is 70% or more. The organic electroluminescent device according to claim 1,
The transition metal oxide layer is an organic electroluminescent device having a work function of 4 to 6 eV. The organic electroluminescent device according to claim 1,
The transition metal oxide layer is an organic electroluminescent device having a specific resistance of 10,000 Ωm or less. The organic electroluminescent device according to claim 1,
The transition metal oxide layer is an organic electroluminescent device including a molybdenum oxide layer. The organic electroluminescent device according to claim 1,
The transition metal oxide layer is an organic electroluminescent device including a vanadium oxide layer. The organic electroluminescent device according to claim 1,
The transition metal oxide layer is an organic electroluminescent device including a tungsten oxide layer. The organic electroluminescent device according to claim 1,
The organic electroluminescent element in which the layer having the light emitting function contains a polymer compound. The organic electroluminescent device according to claim 1,
The organic electroluminescent element in which the layer having the light emitting function contains a polymer compound containing a fluorene ring. An organic electroluminescent device according to any one of claims 6 to 8,
The organic electroluminescent device, wherein the transition metal oxide layer is formed in contact with the cathode via an intermediate layer. The organic electroluminescent device according to claim 11,
The said intermediate | middle layer is an organic electroluminescent element containing at least one of barium, calcium, lithium, cesium, or these oxides or halides. The organic electroluminescent device according to claim 10, wherein
The organic electroluminescent device, wherein the layer having a light emitting function contains polyfluorene represented by the following general formula (I) and derivatives thereof (R1 and R2 each represent a substituent).
The organic electroluminescent device according to claim 10, wherein
The organic electroluminescent element in which the layer having the light emitting function contains a phenylene vinylene group. The organic electroluminescent device according to claim 14, wherein
The organic electroluminescent element characterized in that the layer having a light emitting function contains polyphenylene vinylene represented by the following general formula (II) and derivatives thereof (R3 and R4 each represent a substituent).
The organic electroluminescent device according to claim 11,
The intermediate layer is an organic electroluminescent device composed of a polymer layer. An organic electroluminescent device according to any one of claims 1 to 16,
The anode which is one electrode of the set of electrodes is formed on a translucent substrate,
The functional layer includes a hole injection layer formed on the anode;
A layer having a light emitting function;
Of the set of electrodes formed via the transition metal oxide layer on the layer having the light emitting function so as to face the hole injection layer through the layer having the light emitting function The organic electroluminescent element in which the cathode which is the other electrode was formed. An organic electroluminescent device according to any one of claims 1 to 16,
The anode which is one electrode of the set of electrodes is formed on the substrate,
The functional layer includes a hole injection layer formed on the anode;
A layer having a light emitting function;
Of the set of electrodes formed via the transition metal oxide layer on the layer having the light emitting function so as to face the hole injection layer through the layer having the light emitting function The organic electroluminescent element formed as a transparent electrode which the cathode which is the other electrode permeate | transmits the light radiated | emitted from the layer which has the said light emission function. An anode and a cathode, and a plurality of functional layers formed between the anode and the cathode,
The functional layer is composed of at least one organic semiconductor layer having a light emitting function, the layer having the light emitting function, and at least one transition metal oxide layer disposed between the cathode and the anode. And an organic electroluminescent device. A method for producing an organic electroluminescent element according to any one of claims 1 to 19,
An anode and a cathode, and a plurality of functional layers formed between the anode and the cathode,
A method for producing an organic electroluminescent element, comprising: a step in which the functional layer includes a transition metal oxide layer, and the cathode is formed on the transition metal oxide layer. It is a manufacturing method of the organic electroluminescent element according to claim 20,
The step of forming the cathode is a method of manufacturing an organic electroluminescent element, which is a step of forming a film by a sputtering method. It is a manufacturing method of the organic electroluminescent element according to claim 20,
The method of manufacturing an organic electroluminescent element, wherein the step of forming the cathode is a step of forming a film by a CVD method.   20. A display device using the organic electroluminescent element according to claim 1, wherein the organic electroluminescent element is two-dimensionally arranged.   20. An exposure apparatus using the organic electroluminescent element according to claim 1, wherein the organic electroluminescent element is arranged in a line to form a light emitting unit. A layer having a light emitting function composed of at least one organic semiconductor;
An electrode for injecting electrons into the layer having the light emitting function;
An organic electroluminescent device having at least one transition metal oxide layer disposed between the electrode and the layer having a light emitting function.